JP5227873B2 - Brake device - Google Patents

Description

  The present invention relates to a brake device.

  As a type of brake device, one disclosed in Patent Document 1 is known. As shown in FIG. 4 of Patent Document 1, in the brake device, the negative pressure P of the booster (vacuum booster) detected by the negative pressure sensor is read in Step S12, and then the negative pressure detected in Step S14. From the pressure P, the dead center fluid pressure (assistance limit master cylinder fluid pressure), which is the booster assist limit, is estimated. In step S14, the map shown in FIG. 6 of Patent Document 1 is referred to by the detected negative pressure P of the booster, and the dead point hydraulic pressure (assistance limit master cylinder hydraulic pressure) corresponding to the detected negative pressure P is estimated. This map is created by plotting the dead point fluid pressure according to the negative pressure of the booster. Next, the brake fluid pressure (master cylinder fluid pressure) of the master cylinder detected by the fluid pressure sensor in step S16 is read. Next, in step S18, it is determined whether or not the detected master cylinder hydraulic pressure exceeds the estimated dead center hydraulic pressure. Here, if master cylinder hydraulic pressure> estimated dead center hydraulic pressure, the process proceeds to step S22, and the pump is driven to increase the brake hydraulic pressure of the wheel cylinder by the pump. If master cylinder hydraulic pressure ≦ estimated dead center hydraulic pressure, a normal booster assisting operation is performed in step S20, and this processing cycle is completed.

JP 2000-127949 A

  In the brake device described above, the dead center fluid pressure (assistance limit master cylinder fluid pressure) corresponding to the detected negative pressure P of the booster 12 is estimated using the map shown in FIG. In this brake device, the booster 12 has characteristic variations due to mechanical variations. That is, due to this variation, there is a possibility that the actual dead-point fluid pressure of the booster 12 varies from booster 12 to booster 12 even at the same negative pressure value. Then, when only one type of the map is used and the map is applied to a large number of brake devices, the dead center fluid pressure estimated using the map is the actual dead center fluid pressure of the booster 12. There was a risk of divergence.

  Further, even with the same booster 12, there is a possibility that the actual dead-point fluid pressure of the booster 12 may change due to changes over time. Then, at the beginning of use of the brake device, the dead-point fluid pressure estimated using the map coincided with the actual dead-point fluid pressure of the booster 12, but there was a risk that it would deviate when the use period was prolonged. .

  In any case, if the estimated dead center fluid pressure deviates from the actual dead center fluid pressure of the booster 12, the pump 48 is actually operated even if the booster 12 has not reached the assisting limit, However, the pump 48 may not be operated even though the assist limit has been reached (because the start point of the assist control is shifted), the brake device may not be able to fully exhibit the desired brake performance. It was.

  In view of this, the present invention provides a brake device that can correct the reference value corresponding to the negative pressure-assistance limit master cylinder pressure characteristic of the vacuum booster appropriately, thereby reducing the influence of the characteristic variation as much as possible. The purpose is to suppress the brake device so that the desired braking performance is fully exhibited.

  In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that a master cylinder for forming a brake fluid pressure corresponding to the operation of the brake operation member, and a negative pressure is supplied and the negative pressure is used. A vacuum booster that assists the operating force of the brake operating member and outputs it to the master cylinder, a wheel cylinder that receives the brake fluid pressure supplied from the master cylinder and applies a braking force to each wheel of the vehicle, and a master A hydraulic pump connected to a hydraulic path connecting the cylinder and the wheel cylinder, driven by the output of the electric motor to form a brake fluid pressure and supply the wheel cylinder independently of the master cylinder, and a negative pressure chamber negative vacuum chamber Negative pressure acquisition means for acquiring pressure, master cylinder pressure acquisition means for acquiring the pressure of the master cylinder, and stepping on the brake operation member A discriminating means for determining whether or not the actual boost limit of the vacuum booster has been exceeded when the brake operating member is stepped on from the change in the negative pressure in the negative pressure chamber after the release point, and a master corresponding to the boost limit of the vacuum booster When the master cylinder pressure acquired by the correction means for correcting the reference value according to the assisting limit pressure, which is the pressure limit of the cylinder, based on the determination result of the determination means, and the master cylinder pressure acquisition means is equal to or higher than the reference value, Drive means for driving the pump.

  In addition, the structural feature of the invention according to claim 2 is that, in claim 1, the correcting means uses an arbitrary negative pressure in the negative pressure chamber as a reference value of the assist limit pressure, and the vacuum booster at the negative pressure. A storage means for storing a negative pressure-assistant limit pressure map indicating a relationship with the assist limit pressure, which is the pressure of the master cylinder corresponding to the assist limit, is provided, and the negative pressure-assist limit pressure map and the depression of the brake operation member are provided. The negative pressure-assistance limit pressure map is corrected based on the data consisting of the negative pressure and master cylinder pressure acquired at the time of release and the determination result of whether or not the actual boost limit of the vacuum booster was exceeded when the brake operation member was depressed. The new negative pressure-assistance limit pressure map corrected by the correcting means is updated by the updating means for storing in the storage means.

  Further, the structural feature of the invention according to claim 3 is that, in claim 2, the correction means determines that the data at the time of releasing the depression of the brake operation member indicates the actual assist limit of the vacuum booster when the brake operation member is depressed. If it is determined that the pressure has been exceeded and is located below the negative pressure-assistance limit pressure map, the negative pressure of the negative pressure chamber when the brake operation member is released is derived, which is derived from the negative pressure-assistance limit pressure map. The deviation between the assist limit pressure corresponding to the pressure and the master cylinder pressure at the time of release of the depression is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved downward by the correction amount.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the correction means is configured so that the negative pressure in the negative pressure chamber is reduced after the brake pedal is released. Once it has increased and returned to its original value, it is determined that the depression has been released after the brake operation member has been depressed beyond the actual boost limit of the vacuum booster. It is determined that the actual boost limit of the vacuum booster was exceeded when the operating member was depressed.

  According to a fifth aspect of the present invention, in any one of the second to fourth aspects, the correction means is configured such that the data when the brake operation member is released is stored when the brake operation member is released. The brake operating member is determined to have not exceeded the actual assist limit of the vacuum booster and is located above the negative pressure-assistant limit pressure map, and is derived from the negative pressure-assistant limit pressure map. The difference between the assist limit pressure corresponding to the negative pressure in the negative pressure chamber when releasing the depression and the master cylinder pressure when releasing the depression is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved upward by the correction amount It is to correct by doing.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the correcting means is configured to reduce the negative pressure in the negative pressure chamber after the release of the brake operation member. If it decreases, it is determined that the depression of the brake operation member has been released after the brake operation member has been depressed without exceeding the actual assist limit of the vacuum booster. Sometimes it is determined that the actual boost limit of the vacuum booster has not been exceeded.

  According to a seventh aspect of the present invention, in any one of the third to sixth aspects, the correction means stores a plurality of derived correction amounts and performs correction based on the plurality of correction amounts. The amount is derived, and the negative pressure-assistance limit pressure map is corrected based on the derived correction amount.

  Further, the structural feature of the invention according to claim 8 is that, in any one of claims 2 to 7, the data including the negative pressure and the master cylinder pressure acquired when the brake operation member is released is negative pressure − If it is located outside the predetermined range based on the assist limit pressure map, the correction means prohibits the derivation of the correction amount and does not perform the correction.

  According to a ninth aspect of the present invention, a negative pressure supply state detecting means for detecting normality / abnormality of the negative pressure supply state of the negative pressure source according to any one of the first to eighth aspects. If the negative pressure supply state detection means detects that the negative pressure supply state is abnormal, the correction means prohibits derivation of the correction amount and does not perform correction.

  In the invention according to claim 1 configured as described above, the reference value of the negative pressure-assist limit pressure characteristic is the actual value of the vacuum booster when the brake operating member is depressed from the negative pressure change when the brake operating member is depressed. It is determined whether or not the assist limit has been exceeded, and correction is performed using data consisting of the negative pressure and the master cylinder pressure acquired when the brake operation member is released. Therefore, the assisting limit pressure for determination for determining the start of control (start of driving of the hydraulic pump) is appropriately set based on the negative pressure-assisting limit pressure reference value appropriately corrected by the actual negative pressure assisting limit result. The assist control can be started at an appropriate timing. That is, it is possible to suppress the influence of the characteristic variation of the vacuum booster as much as possible, and to make the brake device sufficiently exhibit the desired brake performance.

In the invention according to claim 2 configured as described above, in claim 1, the correcting means uses an arbitrary negative pressure in the negative pressure chamber as the reference value of the assist limit pressure, and the vacuum booster at the negative pressure. A storage means for storing a negative pressure-assistance limit pressure map indicating a relationship with the assist limit pressure, which is the pressure of the master cylinder corresponding to the assist limit, is provided, and the correction means includes a negative pressure-assistance limit pressure map, a brake Negative pressure-assistance based on data consisting of negative pressure and master cylinder pressure acquired when depressing the operating member, and the determination result of whether or not the actual boost limit of the vacuum booster was exceeded when the brake operating member was depressed The limit pressure map is corrected. Then, the new negative pressure-assistance limit pressure map corrected by the correction unit is stored in the storage unit.
As a result, the negative pressure-assistance limit pressure map is determined whether or not the actual boost limit of the vacuum booster was exceeded when the brake operation member was depressed, and the negative pressure and master acquired when the brake operation member was released. It is corrected using data consisting of cylinder pressure. Therefore, if only one type of negative pressure-assisted limit pressure map is used and the map is applied to a large number of braking devices, the map is initially different from the actual negative pressure-assisted limit pressure characteristic of the vacuum booster. Even so, the correction according to the present invention can be corrected so that the initial map has the actual negative pressure-assist limit pressure characteristic. In addition, although the negative pressure-assistance limit pressure map was consistent with the actual negative pressure-assistance limit pressure relationship of the vacuum booster, even if the actual negative pressure-assistance limit pressure characteristic changed due to changes over time, this By the correction according to the invention, the initial map can be corrected so as to have an actual negative pressure-assistance limit pressure characteristic. In this way, even if the negative pressure-assistance limit pressure characteristics of the vacuum booster vary or is generated afterwards, the negative pressure-assistance limit pressure map corresponding to that characteristic can be corrected appropriately. The pressure-assistance limit pressure map can be prevented from deviating from the actual negative pressure-assistance limit pressure relationship. Therefore, the assisting limit pressure for determination can be appropriately derived based on the negative pressure-assisting limit pressure map appropriately corrected without being calculated at the time of deriving.

  In the invention according to claim 3 configured as described above, in claim 2, the correction means is configured such that the data at the time of releasing the depression of the brake operation member indicates the actual assist limit of the vacuum booster when the brake operation member is depressed. If it is determined that the pressure has been exceeded and is located below the negative pressure-assistance limit pressure map, the negative pressure of the negative pressure chamber when the brake operation member is released is derived, which is derived from the negative pressure-assistance limit pressure map. The deviation between the assist limit pressure corresponding to the pressure and the master cylinder pressure at the time of releasing the depression is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved downward by the correction amount to correct. As a result, even if the actual negative pressure-assistance limit pressure characteristic is shifted downward from the negative pressure-assistance limit pressure map stored in the storage means or afterwards, the negative pressure-assistance is deviated. The limit pressure map can be corrected appropriately.

  In the invention according to Claim 4 configured as described above, in any one of Claims 1 to 3, the correction means is configured to reduce the negative pressure in the negative pressure chamber after the release of the brake operation member. Once it has increased and returned to its original value, it is determined that the depression has been released after the brake operation member has been depressed beyond the actual boost limit of the vacuum booster. It is determined that the actual boost limit of the vacuum booster was exceeded when the operating member was depressed. Thus, based on the negative pressure that has been detected in the past, it is determined that the data at the time of release of the brake operation member exceeds the actual assist limit of the vacuum booster when the brake operation member is depressed. be able to. Therefore, since it is not necessary to provide another detection means, the determination can be performed reliably without causing an increase in cost, a complicated structure, and an increase in size.

  In the invention according to claim 5 configured as described above, in any one of claims 2 to 4, the correction means is configured such that the data when the brake operation member is released is stored when the brake operation member is released. The brake operating member is determined to have not exceeded the actual assist limit of the vacuum booster and is located above the negative pressure-assistant limit pressure map, and is derived from the negative pressure-assistant limit pressure map. The difference between the assist limit pressure corresponding to the negative pressure in the negative pressure chamber when releasing the depression and the master cylinder pressure when releasing the depression is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved upward by the correction amount To correct it. As a result, even if the actual negative pressure-assistance limit pressure characteristic is shifted upward from the negative pressure-assistance limit pressure map stored in the storage means or afterwards, the negative pressure-assist The limit pressure map can be corrected appropriately.

  In the invention according to Claim 6 configured as described above, in any one of Claims 1 to 5, the correction means is configured to reduce the negative pressure in the negative pressure chamber after the release of the depression of the brake operation member. If it decreases, it is determined that the depression of the brake operation member has been released after the brake operation member has been depressed without exceeding the actual assist limit of the vacuum booster. Sometimes it is determined that the actual boost limit of the vacuum booster has not been exceeded. As a result, based on the negative pressure that has been detected in the past, it is determined that the data at the time of release of the brake operation member did not exceed the actual assistance limit of the vacuum booster when the brake operation member was depressed. can do. Therefore, since it is not necessary to provide another detection means, the determination can be performed reliably without causing an increase in cost, a complicated structure, and an increase in size.

  In the invention according to claim 7 configured as described above, in any one of claims 3 to 6, the correction means stores a plurality of derived correction amounts, and based on the plurality of correction amounts. A correction amount is derived, and the negative pressure-assistance limit pressure map is corrected based on the derived correction amount. As a result, a highly accurate and reliable correction amount can be derived, and as a result, the negative pressure-assistance limit pressure map can be accurately corrected with high reliability.

  In the invention according to claim 8 configured as described above, in any one of claims 2 to 7, the data including the negative pressure and the master cylinder pressure acquired when the brake operation member is released is negative pressure− If it is located outside a predetermined range based on the assist limit pressure map, the correction means prohibits derivation of the correction amount and does not perform correction. As a result, by appropriately selecting and using only the highly reliable data, it is possible to correct the map to be accurate, and as a result, more accurate control can be performed.

  In the invention according to claim 9 configured as described above, in any one of claims 1 to 8, negative pressure supply state detecting means for detecting normality / abnormality of the negative pressure supply state of the negative pressure source. If the negative pressure supply state detection means detects that the negative pressure supply state is abnormal, the correction means prohibits derivation of the correction amount and does not perform correction. As a result, by excluding the low-reliability data in advance, it is possible to correct the map with high accuracy without performing wasteful control for processing the low-reliability data, and thus more accurate control. Can be done.

1 is a schematic diagram showing an embodiment of a vehicle to which a hydraulic brake device according to the present invention is applied. It is a schematic diagram which shows the structure of the hydraulic brake apparatus shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. It is a figure for demonstrating the action | operation of the vacuum booster shown in FIG. FIG. 2 is a diagram for explaining the operation of the vacuum booster shown in FIG. 1, wherein an upper stage, a middle stage, and a lower stage show a negative pressure, a master cylinder pressure, and a pedal depression force, respectively. (For example, it is assumed that Pmc (3) is not exceeded), and the depression of the right brake pedal 21 exceeds the assisting limit pressure (for example, Pmc (3)). Show. It is a control block diagram which shows the structure of the control apparatus shown in FIG. 1, FIG. It is a figure which shows a negative pressure-assistance limit pressure map (initial map). It is a figure which shows the relationship between the operating force of a brake pedal, and a master cylinder pressure for every negative pressure. It is a figure which shows the relationship of the target differential pressure (DELTA) P which is the difference of an actual brake fluid pressure and a target brake fluid pressure while showing the relationship between the operating force of a brake pedal and a master cylinder pressure in an actual brake fluid pressure and a target brake fluid pressure. It is a figure which shows the relationship between the master cylinder pressure and target differential pressure (DELTA) P for every negative pressure. It is a flowchart of the control program (assistance control) performed with the control apparatus shown in FIG. FIG. 16 is a flowchart of an end processing routine shown in FIG. 15. FIG. It is a flowchart of the pressure increase control routine shown in FIG. It is a flowchart of the control program (negative pressure-assistance limit pressure map correction | amendment) performed with the control apparatus shown in FIG. It is a flowchart of a cancellation | release operation start determination routine. It is a flowchart of the modification of cancellation | release operation start determination routine. It is a flowchart of the modification of cancellation | release operation start determination routine. It is a flowchart of a negative pressure increase determination routine. It is a flowchart of a negative pressure reduction determination routine. 5 is a flowchart of a region I determination / correction routine. 5 is a flowchart of a region II determination / correction routine. It is a figure explaining the case where a negative pressure-assistance limit pressure map is corrected below. It is a figure explaining the case where the negative pressure-assistance limit pressure map is corrected upward. It is a flowchart of the modification of the control program (negative pressure-assistance limit pressure map correction | amendment) performed with the control apparatus shown in FIG. It is a flowchart of the modification of the area | region I determination and correction routine. It is a figure for demonstrating the effect | action of the modification of an area | region I determination / correction | amendment routine. It is a flowchart of the control program (map correction is prohibited when the negative pressure source is abnormal) executed by the control device shown in FIG.

  Hereinafter, an embodiment of a vehicle to which a control device for a brake device according to the present invention is applied will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the vehicle, and FIG. 2 is a schematic diagram showing the configuration of the brake device. The vehicle M is a front-wheel drive vehicle and is of a type in which the driving force of the engine 11 that is a drive source mounted on the front part of the vehicle body is transmitted to the front wheels instead of the rear wheels. The vehicle M is not a front wheel drive vehicle, but may be a vehicle of another drive system, such as a rear wheel drive vehicle or a four wheel drive vehicle.

  The vehicle M includes an engine 11, a transmission 12, a differential 13, and left and right drive shafts 14a and 14b. The driving force of the engine 11 is changed by the transmission 12 and is driven through the differential 13 and the left and right drive shafts 14a and 14b. It is transmitted to the left and right front wheels Wfl and Wfr, respectively. The engine 11 includes an intake pipe 11a through which air flows into the combustion chamber of the engine 11, and the amount of air passing through the intake pipe 11a is adjusted in the intake pipe 11a by adjusting the opening / closing amount of the intake pipe 11a. A throttle valve 15a is provided.

  The throttle valve 15a is not a wire type in which the accelerator pedal 16 and the throttle valve 15a are connected by a wire, but an electronic control type. That is, the throttle valve 15a is opened and closed by driving a motor 15b according to a command from an engine ECU (electronic control unit) 17, the opening / closing amount of the throttle valve 15a is detected by a throttle opening sensor 15c, and a detection signal is transmitted to the engine ECU 17. The feedback control is performed so as to obtain a command value from the engine ECU 17. The engine ECU 17 basically receives the depression amount of the accelerator pedal 16 detected by the accelerator opening sensor 16a, and transmits a command value corresponding to the opening / closing amount of the throttle valve 15a corresponding to the depression amount to the motor 15b. Further, the engine ECU 17 receives the detected state of the engine 11 and transmits a command value corresponding to the opening / closing amount of the throttle valve 15a determined in consideration of the state to the motor 15b.

  The transmission 12 is an automatic transmission that shifts the driving force of the engine 11 and outputs it to driving wheels, and has a plurality of forward speeds (for example, 4th speed) and one reverse speed. The transmission 12 performs a shift based on the vehicle load and the vehicle speed within a range of the shift stage corresponding to the range selected by the driver.

  Further, the vehicle M includes a hydraulic brake device (brake device) A that brakes the vehicle M. The hydraulic brake device A includes wheel cylinders WCfl, WCfr, WCrl, WCrr, a brake pedal 21 as a brake operation member, a vacuum booster 22, a master cylinder 23, a reservoir tank 24, a brake actuator 25 as an automatic hydraulic pressure generator, And a brake ECU 26 which is a control device of the brake device.

  Each wheel cylinder WCfl, WCfr, WCrl, WCrr regulates the rotation of each wheel Wfl, Wfr, Wrl, Wrr, and is provided in each caliper CLfl, CLfr, CLrl, CLrr. When each wheel cylinder WCfl, WCfr, WCrl, WCrr is supplied with the basic hydraulic pressure as the first hydraulic pressure, the auxiliary hydraulic pressure as the second hydraulic pressure, or the control hydraulic pressure as the third hydraulic pressure, each wheel cylinder WCfl. , WCfr, WCrl, WCrr pistons (not shown) press a pair of brake pads (not shown) that are friction members, and a disk rotor DRfl that is a rotating member that rotates integrally with the wheels Wfl, Wfr, Wrl, Wrr. , DRfr, DRrl, DRrr are sandwiched from both sides to restrict the rotation. In this embodiment, the disc type brake is adopted, but a drum type brake may be adopted.

  The vacuum booster 22 assists by boosting the operating force of the brake pedal 21 according to the operating force of the brake pedal 21 by the action of the negative pressure that is the pressure from the engine 11 that is a negative pressure supply device (negative pressure source). A hydraulic pressure (hydraulic pressure formed by the force generated in the power piston) is formed, and the auxiliary hydraulic pressure is applied to the wheel cylinders WCfl, WCfr, WCrl, WCrr, and the wheels Wfl, Wfr, Wrl, This is a device that can generate the second friction braking force in Wrr.

  Specifically, as shown in FIGS. 3 to 8, the vacuum booster 22 (60) includes a housing 61 and a power piston 62 including a movable partition wall 62a and a valve body 62b. The movable partition wall 62a partitions the front negative pressure chamber (constant pressure chamber) R1 and the rear variable pressure chamber R2.

  The housing 61 is connected to a connection pipe 22f for communicating the negative pressure chamber R1 and a negative pressure source (for example, the intake pipe 11a of the engine 11). The connection pipe 22f is provided with a check valve 22f1 that allows only a gas flow from the vacuum booster 22 to the intake pipe 11a. Thereby, the negative pressure from the negative pressure source is supplied to the negative pressure chamber R1, and the negative pressure chamber R1 is basically maintained at the negative pressure of the negative pressure source.

  The rear end of the master cylinder 23 is in contact with and fixed to the front surface of the housing 61. A distal end portion of an output shaft 68 which will be described later is coupled so as to interlock with a piston (not shown) of the master cylinder 23. The movable partition wall 62a of the power piston 62 includes a metal-made annular plate (not shown) and a rubber-made annular diaphragm (not shown). The housing 61 has a front-rear direction (an axial direction of the power piston 62). It is installed to be movable.

  The valve body 62b of the power piston 62 is a resin-made hollow body connected to the inner peripheral portion of the movable partition wall 62a, and is airtight and forward and backward in the rear portion of the housing 61 at an intermediate portion formed in a cylindrical shape. It is assembled to be movable. The valve body 62 b is urged rearward by a return spring 63 interposed between the front portion of the housing 61.

  The valve body 62b is formed with a stepped shaft hole 62b1 penetrating in the front-rear direction. A communication hole 62b2 is formed in the intermediate step portion 62c of the shaft hole 62b1 so as to penetrate the intermediate step portion 62c in the front-rear direction and to communicate the rear of the intermediate step portion 62c with the negative pressure chamber R1. A pair of grooves 62b3 and 62b4 are formed along the front-rear direction on the inner wall surface of the intermediate step portion 62c of the shaft hole 62b1. Further, a communication hole 62b5 is formed in the intermediate step part 62c of the shaft hole 62b1 so as to penetrate the groove 62b4 and the variable pressure chamber R2 in the radial direction.

  An annular negative pressure valve seat 62b6 that is detachably seated on the negative pressure valve portion 66a of the valve body 66 is formed at the rear end of the intermediate step portion 62c, and the negative pressure valve seat 62b6 and the negative pressure valve portion 66a provide a negative pressure valve seat 66b. A negative pressure valve that communicates and blocks between the pressure chamber R1 and the variable pressure chamber R2 is configured.

  The input shaft 64, the plunger 65, and the valve body 66 are coaxially assembled in the shaft hole 62b1 of the valve body 62b. A reaction member 67 and an output shaft (output member) 68 are coaxially assembled to the front portion of the valve body 62b.

  The input shaft 64 can be moved back and forth with respect to the valve body 62b, and is connected to the receiving connection portion 65a of the plunger 65 in a joint shape by a spherical tip portion 64a. The rear end portion of the input shaft 64 is connected to the brake pedal 21 and is configured to receive a pedal force acting on the brake pedal 21 as an input Fi toward the front.

  The plunger 65 can advance and retreat in the front-rear direction within the intermediate step portion 62c of the shaft hole 62b1 of the valve body 62b. The plunger 65 has a movement range in the front-rear direction relative to the valve body 62b defined by a key member (not shown). The plunger 65 is formed with a communication hole 65b penetrating in the radial direction and communicating with a pair of grooves 62b3 and 62b4 formed in the valve body 62b.

  The distal end surface of the plunger 65 is in contact with the rear surface of the reaction member 67 (including those that can contact), and is a portion that partially receives the reaction force of the output Fo from the reaction member 67. An annular atmospheric valve seat 65c is formed at the rear end of the plunger 65 so as to be separable from the annular atmospheric valve portion 66b, and the variable pressure chamber R2 is formed by the atmospheric valve seat 65c and the annular atmospheric valve portion 66b. There is an atmospheric valve that communicates and shuts off the atmosphere.

  The reaction member 67 is a reaction rubber disc whose central portion on the rear surface can bulge and deform backward. The reaction member 67 is housed in a deformable space between the output shaft 68 and the valve body 62b, and is engaged (contacted) with the rear surface of the rear end of the output shaft 68 over the entire front surface. It is assembled to the front end of the. The reaction member 67 can always contact or contact the front end surface of the plunger 65 at its rear surface, and contact the annular front end surface of the valve body 62b.

  The output shaft 68 is assembled to the front portion of the valve body 62b together with the reaction member 67 so as to be movable in the front-rear direction. The distal end portion of the output shaft 68 abuts against the piston of the master cylinder 23 so as to be able to be pushed, and a reaction force received from the piston of the master cylinder 23 is transmitted to the reaction member 67 via the output shaft 68 during braking operation. It has become.

  The negative pressure valve portion 66a and the atmospheric valve portion 66b (valve element 66) are urged by the compression spring 69 toward the negative pressure valve seat 62b6 and the atmospheric valve seat 65c (toward the front).

  The operation of the thus configured vacuum booster 22 will be described with reference to FIGS. In FIG. 9, the depression of the brake pedal 21 shown on the left side indicates a case where the assisting limit pressure (for example, Pmc (3)) is not exceeded, and the depression of the brake pedal 21 shown on the right side is the assisting limit pressure. (For example, it is assumed that Pmc (3) is exceeded).

  First, the case of the left side will be described. As shown in FIG. 3, when the brake pedal 21 is not depressed (when released, until the depression is started at time t1), the atmospheric valve between the plunger 65 and the valve body 66 is closed to introduce the atmospheric air. Blocked. On the other hand, the negative pressure valve between the valve body 62b and the valve body 66 is open. For this reason, the variable pressure chamber R2 and the negative pressure chamber R1 communicate with each other via the communication hole 62b5, the groove 62b4, the communication hole 65b, the groove 62b3, and the communication hole 62b2. In pressure.

  When the depression of the brake pedal 21 is started at time t1, the vacuum booster 22 causes the plunger 65 to advance the valve body 62b when the input shaft 64 is pushed by the depression of the brake pedal 21, as shown in FIG. And move to the output side (forward). In accordance with the movement of the plunger 65, the negative pressure valve is first closed, and the negative pressure chamber R1 and the variable pressure chamber R2 are shut off. Subsequently, the atmosphere valve is opened, and the atmosphere is introduced into the variable pressure chamber R2 in a negative pressure state through the communication hole 62b5 and the groove 62b4. Then, an atmospheric pressure difference is generated between the variable pressure chamber R2 and the negative pressure chamber R1, and the valve body 62b moves to the output side due to the differential pressure.

  When the brake pedal 21 (input shaft 64) is held at or below the assisting limit pressure Pmc (3) of the vacuum booster 22 between time t2 and time t3, as shown in FIG. The reaction force from the master cylinder 23 to the output shaft 68 balances the resultant force of the pressure of the plunger 65 which is the direct depression pressure of the driver and the pressure generated by the differential pressure between the variable pressure chamber R2 and the negative pressure chamber R1. This balanced position is a position where both the plunger 65 and the valve body 62b are in contact with the valve body 66. Therefore, the inflow of air into the variable pressure chamber R2 is stopped, and a state where a constant force is applied to the master cylinder 23 is maintained.

  Thereafter, when the depression of the brake pedal 21 is released from the state shown in FIG. 5 and the brake pedal 21 (input shaft 64) is returned at time t3, the plunger 65 is input prior to the valve body 62b as shown in FIG. Since it moves to the side (rear), the negative pressure valve opens while the atmospheric valve is closed. For this reason, the variable pressure chamber R2 and the negative pressure chamber R1 are communicated, and the air in the variable pressure chamber R2 is introduced into the negative pressure chamber R1. The negative pressure in the variable pressure chamber R2 drops for a moment (atmospheric pressure increases), but immediately when the negative pressure in the negative pressure chamber R1 becomes lower than the negative pressure of the negative pressure source (increases the atmospheric pressure), a check valve (check valve) immediately Since 22f1 is opened, the negative pressure in the negative pressure chamber R1 is returned to the pressure of the negative pressure source. From the time t3 until the depression is completed (time t4), the above-described negative pressure decrease and increase are repeated.

  Next, the case of the right side will be described. From the time when the brake pedal 21 starts to be depressed to the time when the assist limit pressure is exceeded (from time t11 to time t12), it is the same as from time t1 to time t2 described above.

  As shown in FIG. 7, when the pedal 65 is depressed and held between time t12 and time t13, the plunger 65 precedes the valve body 62b and the atmospheric valve is opened, and the atmosphere is introduced into the variable pressure chamber R2. However, the variable pressure chamber R2 rises to atmospheric pressure at the assisting limit point, and the force due to the differential pressure with the negative pressure chamber R1 does not increase any more. Therefore, the valve body 62b (valve body 66) cannot move to the position where the atmospheric valve is closed, the plunger 65 precedes the valve body 62b, and the variable pressure chamber R2 remains in communication with the atmosphere.

  Thereafter, when the brake pedal 21 is returned from the state shown in FIG. 7 at time t13, the negative pressure chamber R1 and the variable pressure chamber R2 are blocked by the negative pressure valve until the assist limit is reached, as shown in FIG. The valve remains open. For this reason, when the valve body 62b moves to the input side (rear), the movable partition wall 62a also moves to the input side, so the volume of the negative pressure chamber R1 increases, but the negative pressure chamber R1 is blocked from the variable pressure chamber R2. Therefore, the pressure in the negative pressure chamber R1 decreases due to the increase in volume, and the apparent negative pressure increases. At this time, since the check valve 22f1 is closed, the negative pressure in the negative pressure chamber R1 rises above the negative pressure of the negative pressure source (the negative pressure before the movable partition wall 62a starts moving to the input side). On the other hand, the volume of the variable pressure chamber R2 is reduced, but the air corresponding to the volume is discharged to the air inlet 62d through the air valve because the air valve is open.

  Thereafter, when the brake pedal 21 is returned and becomes below the assist limit of the vacuum booster 22 (time t14), the atmospheric valve is closed and the negative pressure valve is opened, so that the variable pressure chamber R2 and the negative pressure chamber R1 communicate with each other. The atmosphere of R2 flows into the negative pressure chamber R1, and the negative pressure in the negative pressure chamber R1 once decreases, and is immediately returned to the negative pressure of the negative pressure source by the action of the check valve 22f1.

  The hydraulic brake device A also detects a negative pressure supplied to the vacuum booster 22, that is, a negative pressure in the intake pipe 11a of the engine 11 (a negative pressure in the connection pipe 22f) (negative pressure detection means). ) 22f2 and this detection signal is transmitted to the brake ECU 26. The negative pressure sensor 22f2 may be provided so as to directly detect the negative pressure in the negative pressure chamber R1.

  The master cylinder 23 converts the input from the push rod 22g into a hydraulic pressure (basic hydraulic pressure + auxiliary hydraulic pressure) and supplies it to the wheel cylinders WCfl, WCfr, WCrl, WCrr. That is, the master cylinder 23 generates a resultant force (brake operating force boosted by the vacuum booster 22) between the operating force (depression force) of the brake pedal 21 by the driver and the force generated in the power piston 22b of the vacuum booster 22 by the operation. It is input and converted into a hydraulic pressure consisting of a basic hydraulic pressure and an auxiliary hydraulic pressure and output. The basic hydraulic pressure is a hydraulic pressure component formed by the operating force (stepping force) of the brake pedal 21, and the auxiliary hydraulic pressure is a hydraulic pressure component formed by the force generated in the power piston 22b. A first friction braking force is generated on the wheels Wfl, Wfr, Wrl, Wrr by the basic hydraulic pressure.

  The reservoir tank 24 stores brake fluid and replenishes the master cylinder 23 with the brake fluid.

  The brake actuator 25 is provided between the master cylinder 23 and each wheel cylinder WCfl, WCfr, WCrl, WCrr, and automatically generates a control hydraulic pressure regardless of whether the brake pedal 21 is operated or not. This is a device that can be applied to WCfr, WCrl, WCrr and generate a third friction braking force on the corresponding wheels Wfl, Wfr, Wrl, Wrr.

  The configuration of the brake actuator 25 will be described in detail with reference to FIG. The brake actuator 25 is composed of a plurality of systems that are hydraulic circuits that operate independently. Specifically, the brake actuator 25 has a first system 25a and a second system 25b that are X pipes. The first system 25a communicates the first hydraulic chamber 23a of the master cylinder 23 with the left rear wheel Wrl and the wheel cylinders WCrl and WCfr of the right front wheel Wfr, respectively, and controls the braking force of the left rear wheel Wrl and the right front wheel Wfr. It is a system concerning. The second system 25b communicates the second hydraulic chamber 23b of the master cylinder 23 with the left front wheel Wfl and the wheel cylinders WCfl and WCrr of the right rear wheel Wrr, respectively, and controls the braking force of the left front wheel Wfl and the right rear wheel Wrr. It is a system concerning.

  The first system 25a includes a differential pressure control valve 41, a left rear wheel hydraulic pressure control unit 42, a right front wheel hydraulic pressure control unit 43, and a first pressure reducing unit 44.

  The differential pressure control valve 41 is a normally open linear electromagnetic valve interposed between the master cylinder 23 and the upstream portion of the left rear wheel hydraulic pressure control unit 42 and the upstream portion of the right front wheel hydraulic pressure control unit 43. . The differential pressure control valve 41 is controlled to be switched between a communication state (non-differential pressure state) and a differential pressure state by the brake ECU 26. Although the differential pressure control valve 41 is not energized and normally communicated, the hydraulic pressure on the wheel cylinders WCrl, WCfr side is changed to the hydraulic pressure on the master cylinder 23 side by energizing to the differential pressure state (closed side). The pressure can be kept higher than the predetermined control differential pressure. This control differential pressure is regulated by the brake ECU 26 in accordance with the control current. As a result, a control hydraulic pressure corresponding to the control differential pressure is formed on the premise of pressurization by the pumps 44a and 54a.

  The left rear wheel hydraulic pressure control unit 42 is capable of controlling the hydraulic pressure supplied to the wheel cylinder WCrl, and is a two-port two-position switching type normally open electromagnetic on-off valve 42a and a two-port two-position switching type. And a pressure reducing valve 42b which is a normally closed electromagnetic on-off valve. The pressure increasing valve 42a is interposed between the differential pressure control valve 41 and the wheel cylinder WCrl, and can communicate or block the differential pressure control valve 41 and the wheel cylinder WCrl in accordance with a command from the brake ECU 26. . The pressure reducing valve 42b is interposed between the wheel cylinder WCrl and the pressure regulating reservoir 44c, and can communicate or block the wheel cylinder WCrl and the pressure regulating reservoir 44c in accordance with a command from the brake ECU 26. As a result, the hydraulic pressure in the wheel cylinder WCrl can be increased, held and reduced.

  The right front wheel hydraulic pressure control unit 43 can control the hydraulic pressure supplied to the wheel cylinder WCfr, and includes a pressure increasing valve 43a and a pressure reducing valve 43b, like the left rear wheel hydraulic pressure control unit 42. The pressure increasing valve 43a and the pressure reducing valve 43b are controlled by a command from the brake ECU 26 so that the hydraulic pressure in the wheel cylinder WCfr can be increased, held and reduced.

  The first pressure reducing unit 44 includes a pump (hydraulic pump) 44a, a pump motor (electric motor) 44b, and a pressure regulating reservoir 44c. The pump 44a pumps up the brake fluid in the pressure regulating reservoir 44c and supplies the brake fluid between the differential pressure control valve 41 and the pressure increasing valves 42a and 43a. The pump 44a is driven by a pump motor 44b that is driven in accordance with a command from the brake ECU 26.

  The pressure regulating reservoir 44c is a device that temporarily accumulates brake fluid extracted from the wheel cylinders WCrl and WCfr via the pressure reducing valves 42b and 43b. The pressure regulating reservoir 44c is in communication with the master cylinder 23. When the brake fluid in the pressure regulating reservoir 44c is equal to or less than a predetermined amount, the brake fluid is supplied from the master cylinder 23 while the predetermined amount. In the case of more, the supply of brake fluid from the master cylinder 23 is stopped.

  Thereby, when the differential pressure state is formed by the differential pressure control valve 41 and the pump 44a is driven (for example, in the case of side slip prevention control, traction control, etc.), the brake fluid supplied from the master cylinder 23 is removed. The pressure can be supplied to the upstream side of the pressure increasing valves 42a and 43a via the pressure regulating reservoir 44c.

  The second system 25b includes a differential pressure control valve 51, a left front wheel hydraulic pressure control unit 52, a right rear wheel hydraulic pressure control unit 53, and a second pressure reducing unit 54.

  The differential pressure control valve 51 is a normally open linear electromagnetic valve interposed between the master cylinder 23 and the upstream portion of the left front wheel hydraulic pressure control unit 52 and the upstream portion of the right rear wheel hydraulic pressure control unit 53. . Similar to the differential pressure control valve 41, the differential pressure control valve 51 is a pressure that is higher by a predetermined control differential pressure than the hydraulic pressure on the wheel cylinder WCfl, WCrr side by the brake ECU 26 relative to the hydraulic pressure on the master cylinder 23 side. Can be retained.

  The left front wheel hydraulic pressure control unit 52 and the right rear wheel hydraulic pressure control unit 53 can control the hydraulic pressure supplied to the wheel cylinders WCfl and WCrr, respectively. The pressure increase valve 52a and the pressure reduction valve 52b are comprised from the pressure increase valve 53a and the pressure reduction valve 53b. The pressure-increasing valve 52a and the pressure-reducing valve 52b, and the pressure-increasing valve 53a and the pressure-reducing valve 53b are respectively controlled by commands of the brake ECU 26 so that the hydraulic pressure in the wheel cylinder WCfl and the wheel cylinder WCrr can be increased, held, and reduced, respectively. It has become.

  Similar to the first pressure reducing unit 44, the second pressure reducing unit 54 includes a pump (hydraulic pump) 54a, a pump motor 44b (shared with the first pressure reducing unit 44), and a pressure regulating reservoir 54c. The pump 54a pumps up the brake fluid in the pressure regulating reservoir 54c similar to the pressure regulating reservoir 44c, and supplies the brake fluid between the differential pressure control valve 51 and the pressure increasing valves 52a and 53a. The pump 54a is driven by a pump motor 44b that is driven in accordance with a command from the brake ECU 26.

  In the brake actuator 25 configured in this way, all the solenoid valves are de-energized during normal braking, and the brake hydraulic pressure corresponding to the operating force of the brake pedal 21, that is, the basic hydraulic pressure + auxiliary hydraulic pressure. Can be supplied to each wheel cylinder WC **. In addition, ** is a subscript corresponding to each ring and is any one of fl, fr, rl, and rr, and indicates left front, right front, left rear, and right rear. The same applies to the following description and drawings.

  Further, when the brake actuator 25 drives the pump motor 44b, that is, the pumps 44a and 54a and excites the differential pressure control valves 41 and 51, the control hydraulic pressure is added to the basic hydraulic pressure + auxiliary hydraulic pressure from the master cylinder 23. Brake fluid pressure can be supplied to each wheel cylinder WC **.

  Further, the brake actuator 25 can individually adjust the hydraulic pressure of the wheel cylinder WC ** by controlling the pressure increasing valves 42a, 43a, 52a, 53a and the pressure reducing valves 42b, 43b, 52b, 53b. . Thus, according to instructions from the brake ECU 26, for example, well-known anti-skid control, front / rear braking force distribution control, skid prevention control (specifically, understeer suppression control, oversteer suppression control), traction control, inter-vehicle distance control, etc. Can be achieved.

  Further, the brake actuator 25 is provided with a pressure sensor (master cylinder pressure detecting means) 25a1 for detecting a master cylinder pressure which is a brake fluid pressure in the master cylinder 23, and this detection signal is transmitted to the brake ECU 26. It is like that. In the present embodiment, the pressure sensor 25a1 is provided between the master cylinder 23 and the differential pressure control valve 41 in the first system 25a, but is provided at an equivalent position in the second system 25b. Also good.

  Further, as shown in FIGS. 1 and 2, the hydraulic brake device A includes a pedal stroke sensor 21 a that detects the stroke amount of the brake pedal 21. This detection signal is transmitted to the brake ECU 26. The stroke amount of the brake pedal 21 indicates the operation state of the brake pedal 21, and the pedal stroke sensor 21a is a brake operation state detection means.

  Further, the hydraulic brake device A includes wheel speed sensors Sfl, Sfr, Srl, Srr as shown in FIG. Wheel speed sensors Sfl, Sfr, Srl, Srr are provided in the vicinity of each wheel Wfl, Wfr, Wrl, Wrr, and brake a pulse signal having a frequency according to the rotation of each wheel Wfl, Wfr, Wrl, Wrr. It is output to the ECU 26.

  The brake ECU 26 has a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. When the CPU executes a program corresponding to the flowcharts of FIGS. 15 to 25 and the negative pressure supplied to the vacuum booster 22 is insufficient with respect to the predetermined pressure for exerting the predetermined braking force, the brake actuator The target brake fluid pressure corresponding to the operation of the brake pedal 21 is supplied to the wheel cylinder WC ** by compensating for the shortage by controlling 25.

  The brake ECU 26 is a control device that controls the hydraulic brake device A. As shown in FIG. 10, the brake ECU 26 includes a negative pressure acquisition unit (negative pressure acquisition means) 26a that acquires the negative pressure supplied to the vacuum booster 22 from the negative pressure sensor 22f2, and the pressure of the master cylinder 23 as the master cylinder. A master cylinder pressure acquisition unit (master cylinder pressure acquisition means) 26b that is acquired from the pressure sensor 25a1 is provided. The brake ECU 26 has a negative pressure − indicating a relationship between an arbitrary negative pressure supplied to the vacuum booster 22 and an assist limit pressure which is a pressure of the master cylinder 23 corresponding to the assist limit of the vacuum booster 22 at the negative pressure. It has the 1st memory | storage part (1st memory | storage means) 26c in which the assistance limit pressure map is memorize | stored.

  The negative pressure-assistance limit pressure map stored in advance in the first storage unit 26c is an initial map as shown in FIG. The initial map is a design value and can be obtained by simulation or based on actual experimental values. The negative pressure-assistance limit pressure map can be obtained from the relationship between the master cylinder pressure and the operating force F1 for each negative pressure shown in FIG.

  When the operating force F1 of the brake pedal 21 increases to a certain value, the vacuum booster 22 causes the pressure in the variable pressure chamber R2 to reach atmospheric pressure (even if the outside air is introduced into the variable pressure chamber R2, the negative pressure chamber R1 and the variable pressure chamber R2). Therefore, the force F2 generated in the power piston 22b is not further formed (increased). That is, until the pressure in the variable pressure chamber R2 reaches atmospheric pressure, a resultant force obtained by adding the force F2 generated in the power piston 22b to the operating force F1 of the brake pedal 21 is output from the vacuum booster 22. On the other hand, after the reaching time point, a resultant force obtained by adding only the increment of the operating force F1 of the brake pedal 21 to the force F2 at the reaching time point is output from the vacuum booster 22. The time when the pressure in the variable pressure chamber R2 reaches the atmospheric pressure is the time when the vacuum booster 22 reaches the assisting limit. In other words, the assist limit is a limit (limit) at which the vacuum booster 22 can no longer perform the assist function, and is determined by the negative pressure that is the pressure difference between the atmospheric pressure and the negative pressure chamber R1.

  From this, by obtaining the master cylinder pressure corresponding to the assist limit of the vacuum booster 22 by changing the operating force F1 at an arbitrary negative pressure, the assist limit pressure at the negative pressure can be calculated. For example, the assist limit pressure when the negative pressure is Pnn (negative pressure for obtaining the target brake fluid pressure of the brake device of the present embodiment) is Pmc (n), and the negative pressure is Pn3 smaller than Pnn. The assist limit pressure is Pmc (3), the assist limit pressure when the negative pressure is Pn2 smaller than Pn3 is Pmc (2), and the assist limit pressure when the negative pressure is Pn1 smaller than Pn2 is Pmc (1). It is. When the negative pressure is 0, the assist limit is not generated and the operating force F1 becomes the master cylinder pressure as it is, so there is no assist limit pressure and the assist cannot be performed in all regions.

  Since the negative pressure calculated in this way and the assist limit pressure in the negative pressure can be associated one-to-one, the negative pressure-assist limit pressure shown in FIG. 11 is obtained from a plurality of associated data (negative pressure, assist limit pressure). You can get a map. The assist limit pressure is a master cylinder pressure corresponding to the assist limit of the vacuum booster 22 by changing the operation force F1 at an arbitrary negative pressure.

  Further, the brake ECU 26 calculates the assist limit pressure obtained from the negative pressure acquired by the negative pressure acquisition unit 26a and the negative pressure-assistance limit pressure map stored in the first storage unit 26c as the determination assist limit pressure. And a determination assisting limit pressure calculating unit (determination assisting limit pressure calculating means) 26d. The assisting limit pressure for determination is a determination value used when determining whether to start assisting control based on the master cylinder pressure.

  Further, the brake ECU 26 drives the pumps 44a and 54a when the master cylinder pressure acquired by the master cylinder pressure acquisition unit 26b is equal to or higher than the determination assisting limit pressure calculated by the determination assisting limit pressure calculating unit 26d. By applying the brake fluid pressure formed by driving to the master cylinder pressure formed according to the operation of the brake pedal 21, the target brake fluid pressure according to the operation of the brake pedal 21 is supplied to the wheel cylinder WC **. An assist control unit (assistance control means) 26e that performs assist control is provided.

  There is a relationship as shown in FIG. 13 between the operating force F1 of the brake pedal 21 and the wheel cylinder pressure (master cylinder pressure). When the negative pressure is sufficiently supplied to the vacuum booster 22, the target brake fluid pressure of the wheel cylinder WC ** is as shown by a one-dot broken line in FIG. This target brake fluid pressure has an assist limit as described above. The assist limit in this case is that the wheel cylinder pressure (= master cylinder pressure) is Pwc (n) when the operating force F1 is F1 (n). On the other hand, when the vacuum pressure is reduced in the vacuum booster 22 as compared with the case described above (when the negative pressure is Pn2) and the assist limit is lowered, the actual brake fluid supplied to the wheel cylinder WC **. The pressure (actual brake fluid pressure) is indicated by a solid line in FIG. The assist limit in this case is Pwc (2) where the wheel cylinder pressure (= master cylinder pressure) is smaller than Pwc (n) when the operating force F1 is F1 (2) smaller than F1 (n). When the brake pedal 21 is operated, the base cylinder pressure and the auxiliary hydraulic pressure are output from the master cylinder 23. However, when the operating force F1 is smaller than F1 (2) corresponding to the assist limit, the auxiliary fluid is output. Only a desired amount (auxiliary fluid pressure corresponding to the target brake fluid pressure) is generated as the pressure. When the pressure is large, the assist fluid pressure can be generated only at a value smaller than the desired amount. Therefore, in the case of being large, the shortage of the auxiliary hydraulic pressure is defined as the target differential pressure ΔP, and the shortage of the auxiliary hydraulic pressure is supplemented with the control hydraulic pressure.

  FIG. 14 shows the relationship between the actual master cylinder pressure and the target differential pressure ΔP for each negative pressure. As described above, the target differential pressure ΔP is the difference between the target brake hydraulic pressure and the actual master cylinder pressure at an arbitrary negative pressure. In the relationship shown in FIG. 14, until the master cylinder pressure (wheel cylinder pressure) reaches a value (Pwc (2) when the negative pressure is Pn2) corresponding to the assist limit of the actual brake hydraulic pressure with respect to an arbitrary negative pressure. Can be supported by the vacuum booster 22, so the target differential pressure ΔP is zero. The master cylinder pressure (wheel cylinder pressure) is a value that corresponds to the assist limit of the actual brake fluid pressure with respect to an arbitrary negative pressure (Pwc (2) when the negative pressure is Pn2), and reaches the assist limit of the target brake fluid pressure. Until the corresponding value Pwc (n) is reached, the target differential pressure ΔP is a value that increases in proportion to the master cylinder pressure. Then, after the master cylinder pressure (wheel cylinder pressure) is a value Pwc (n) corresponding to the assist limit of the target brake fluid pressure, the target differential pressure ΔP is a constant value.

  Further, as the negative pressure decreases, ΔP with respect to the master cylinder pressure Pwc (n) corresponding to the assist limit at the target brake fluid pressure increases. This is because the shortage of the auxiliary hydraulic pressure increases, and it is necessary to increase the amount of replenishment with the control hydraulic pressure. In FIG. 14, when the negative pressure is Pn1 smaller than Pn2, the relationship at that time (the relationship between the master cylinder pressure and the target differential pressure ΔP) is located above the relationship when the negative pressure is Pn2. When the negative pressure is Pn3 larger than Pn2, the relationship at that time is positioned below the relationship when the negative pressure is Pn2. Furthermore, when the master cylinder pressure is less than Pwc (n), the inclinations are the same.

  The relationship shown in FIG. 14 is set so that after the assist limit of the vacuum booster 22 has been reached, the relationship in which the wheel cylinder pressure increases linearly with the same gradient as before the assist limit is reached with respect to the operating force F1. Yes. Further, the relationship shown in FIG. 14 is a design value and is stored in advance in the brake ECU 26.

  On the other hand, the brake ECU 26 obtains the negative pressure-assistance limit pressure map and the release of the depression of the brake pedal 21, which is determined whether or not the actual assistance limit of the vacuum booster 22 has been exceeded when the brake pedal 21 is depressed. The data including the negative pressure and the master cylinder pressure are compared with each other at the acquired negative pressure, and the negative pressure-assistance limit pressure map is corrected based on the comparison result.

  That is, the brake ECU 26 includes a negative pressure and master cylinder pressure deriving unit (hereinafter referred to as deriving unit) 26f, a data determining unit 26g, a comparing unit 26h, a correction amount deriving unit 26i, and a map deriving unit when the depression is released. 26j and a map update unit 26k.

  The deriving unit 26f derives the negative pressure of the negative pressure chamber R1 and the master cylinder pressure of the master cylinder 23 when the depression of the brake pedal 21 being depressed is released (when the depression of the depression is started). The deriving unit 26f includes a determination unit that determines that the depression of the brake pedal 21 has been released (depression has been started). The determination unit inputs the master cylinder pressure from the master cylinder pressure acquisition unit 26b, and when the master cylinder pressure has increased or is substantially constant until now, the depression of the brake pedal 21 is released (depression release). Is started). Then, the derivation unit 26f acquires (stores) the negative pressure in the negative pressure chamber R1 and the master cylinder pressure of the master cylinder 23 at the time when the determination unit determines that the depression of the brake pedal 21 has been released. The negative pressure in the negative pressure chamber R1 and the master cylinder pressure in the master cylinder 23 are referred to as data when the depression is released.

  Note that the determination unit acquires the stroke amount of the brake pedal 21 from the pedal stroke sensor 21a instead of the master cylinder pressure, and if the stroke amount has been increased or substantially constant until then, the brake pedal 21 is reduced. It may be determined that the stepping of is released.

  The data discriminating unit 26g discriminates whether or not the data including the negative pressure and the master cylinder pressure acquired when the brake pedal 21 is depressed has exceeded the actual assisting limit of the vacuum booster 22 when the brake pedal 21 is depressed. Is. That is, the data determination unit 26g determines whether or not the actual assisting limit of the vacuum booster 22 has been exceeded when the brake pedal 21 is depressed based on the fluctuation of the negative pressure in the negative pressure chamber R1 after the depression of the brake pedal 21 is released. To determine.

  Specifically, the data discriminating unit 26g performs braking beyond the actual assisting limit of the vacuum booster 22 once the negative pressure in the negative pressure chamber R1 once increases and returns after the release of the brake pedal 21 is released. By determining that the depression of the brake pedal 21 is released after the pedal 21 is depressed, the data when the depression of the brake pedal 21 exceeds the actual assist limit of the vacuum booster 22 when the brake pedal 21 is depressed. It is determined that

  As can be understood from the operation of the vacuum booster 22, the brake pedal 21 is depressed beyond the actual assisting limit of the vacuum booster 22, and the brake pedal 21 is returned from the state where the depression is maintained in that state. This is because the negative pressure in the negative pressure chamber R1 once increases and then returns to the original negative pressure when the release of the depression is started.

  On the other hand, if the negative pressure in the negative pressure chamber decreases after the brake pedal 21 is released, the data discriminating unit 26g does not exceed the actual assisting limit of the vacuum booster 22 and after the brake pedal 21 is depressed. By determining that the depression is released, it is determined that the data when the depression of the brake pedal 21 is released is the data that did not exceed the actual assist limit of the vacuum booster 22 when the brake pedal 21 was depressed.

  As can be understood from the operation of the vacuum booster 22, the brake pedal 21 is depressed without exceeding the actual assisting limit of the vacuum booster 22, and the brake pedal 21 is returned from the state where the depression is maintained in that state. This is because the negative pressure in the negative pressure chamber R1 is once reduced and then returned to the original negative pressure when the depression is started.

  The comparison unit 26h was determined whether or not the actual assist limit of the vacuum booster 22 was exceeded when the brake pedal 21 was depressed, and the negative pressure-assistance limit pressure map stored in the first storage unit 26c. The negative pressure acquired when the brake pedal 21 is released and the data including the master cylinder pressure are compared with each other in the acquired negative pressure.

  At this time, the comparison unit 26h performs the comparison in the following case, and does not perform the comparison in other cases. In the first case, it is determined that the data at the time when the brake pedal 21 is released is over the actual assisting limit of the vacuum booster 22 when the brake pedal 21 is depressed, and the negative pressure-assisting limit pressure is determined. In the second case, it was determined that the data when the brake pedal 21 was released did not exceed the actual assist limit of the vacuum booster 22 when the brake pedal 21 was depressed. This is the case where it is located above the negative pressure-assistance limit pressure map.

  The correction amount deriving unit 26i derives the correction amount of the negative pressure-assistance limit pressure map based on the comparison result by the comparison unit 26h. Specifically, in any of the first and second cases, the correction amount deriving unit 26i is derived from the negative pressure-assistance limit pressure map, and the negative pressure chamber R1 when the brake pedal 21 is released is released. The deviation between the assist limit pressure corresponding to the negative pressure and the master cylinder pressure when the depression is released is derived as a correction amount.

  The map deriving unit 26j uses the correction amount derived by the correction amount deriving unit 26i, and the negative pressure compared by the comparison unit 26h based on the positional relationship between the data compared by the comparison unit 26h and the negative pressure-assistance limit pressure map. -A new negative pressure-assist limit pressure map is derived from the assist limit pressure map. That is, the negative pressure-assistance limit pressure map compared by the comparison unit 26h is corrected to a new negative pressure-assistance limit pressure map. Specifically, in the first case, the map deriving unit 26j moves the negative pressure-assistance limit pressure map compared by the comparison unit 26h downward by the correction amount derived by the correction amount deriving unit 26i. This corrects to a new negative pressure-assistance limit pressure map. In the second case, the map deriving unit 26j moves the negative pressure-assistance limit pressure map compared by the comparing unit 26h upward by the correction amount derived by the correction amount deriving unit 26i, thereby creating a new negative pressure. -Correct to assist limit pressure map.

  The map updating unit 26k stores the new negative pressure-assistance limit pressure map derived (corrected) by the map deriving unit 26j in the first storage unit 26c as a negative pressure-assistance limit pressure map.

  Next, the operation of the hydraulic brake device configured as described above will be described with reference to the flowcharts of FIGS. First, referring to the flowcharts of FIGS. 15 to 17, when the master cylinder pressure acquired in step 102 is equal to or higher than the assisting limit pressure for determination calculated in step 106, the pumps 44 a and 54 a are driven and driven. Assistance control for supplying the target brake fluid pressure according to the operation of the brake pedal 21 to the wheel cylinder WC ** by pressurizing the formed brake fluid pressure to the master cylinder pressure formed according to the operation of the brake pedal 21 Will be described.

  For example, when an ignition switch (not shown) of the vehicle is in an on state, the brake ECU 26 executes a program corresponding to the above flowchart every predetermined short time (for example, 10 milliseconds). The brake ECU 26 acquires a master cylinder pressure signal indicating the master cylinder pressure from the master cylinder pressure sensor 25a1 (step 102), and acquires a negative pressure signal indicating the negative pressure from the negative pressure sensor 22f2 (step 104). Then, the brake ECU 26 calculates the assist limit pressure obtained from the negative pressure acquired in step 104 and the negative pressure-assistance limit pressure map stored in the first storage unit 26c as a determination assist limit pressure (step). 106).

  Subsequently, the brake ECU 26 determines whether or not the vacuum booster 22 is in a state capable of assisting (step 108). Specifically, the brake ECU 26 determines that the vacuum booster 22 is not in a state in which it can assist if the master cylinder pressure acquired in step 102 is equal to or greater than the assisting limit pressure for determination calculated in step 106 (“ On the contrary, if it is less than the determination assisting limit pressure, it is determined that the vacuum booster 22 is in a state capable of assisting (determined as “NO”). Here, the state in which assistance is possible refers to a state in which assistance is possible by the action of the negative pressure supplied to the vacuum booster 22.

  If the vacuum booster 22 is in a state where it can be assisted, the brake ECU 26 determines “NO” in step 108 and performs an end process (step 110). Specifically, the brake ECU 26 executes an end process of the pressure increase control in accordance with an end process that is a subroutine shown in the flowchart of FIG. In this end processing routine, in step 202, a signal for turning it off is output to the solenoid of the differential pressure control valve 41 (or 51), and the differential pressure control valve 41 (or 51) is turned off. In step 204, a signal for turning it off is output to the pump motor 44b, the pump motor 44b is turned off, and the drive of the pump 44a (or / and 54a) is stopped. This completes one execution of this end processing routine, and thereby ends one execution of the assist control routine shown in FIG. Note that the end processing of the pressure increase control shown in FIG. 16 has not only the operation of the end processing for ending the pressure increase control, but also the operation of the normal brake from the start of the depression of the brake pedal 21 until the assist limit is reached. In the normal brake process, the hydraulic pressure from the master cylinder 23 is supplied to the wheel cylinder WC ** as it is, so that the differential pressure control valve 41 (or / and 51) is not opened before and after the differential pressure control valve 41 (or 51). It is to be.

  On the other hand, if the vacuum booster 22 is not in a state where it can assist, the brake ECU 26 determines “YES” in step 108 and performs assist control (step 112). In the assist control, the pumps 44 a and 54 a are driven, and the brake fluid pressure formed by the driving is increased to the master cylinder pressure formed according to the operation of the brake pedal 21, so that the target according to the operation of the brake pedal 21 is achieved. This is control for supplying brake fluid pressure to the wheel cylinder WC ** (assist control means).

  Specifically, the brake ECU 26 executes assist control in accordance with pressure increase control that is a subroutine shown in the flowchart of FIG. In step 302, the brake ECU 26 actually generates the hydraulic pressure to be increased to the current master cylinder pressure based on the current values of the master cylinder pressure and the negative pressure, that is, the target brake hydraulic pressure of the wheel cylinder WC **. A target differential pressure ΔP, which is a difference from the existing wheel cylinder pressure (= master cylinder pressure), is calculated.

  Then, the brake ECU 26 determines a current value I to be supplied to the solenoid of the differential pressure control valve 41 (or / and 51) according to the determined target differential pressure ΔP (step 306). The relationship between the target differential pressure ΔP and the solenoid current value I is stored in the storage unit (ROM) of the brake ECU 26, and the solenoid current value I corresponding to the target differential pressure ΔP is determined according to the relationship. Subsequently, the brake ECU 26 controls the differential pressure control valve 41 (or 51) by causing the solenoid of the differential pressure control valve 41 (or 51) to supply current with the determined solenoid current value I. (Differential pressure control).

Thereafter, the brake ECU 26 outputs a signal for turning it ON to the pump motor 44b (step 308). Thereby, the pump 44a (or / and 54a) pumps the hydraulic fluid from the pressure regulating reservoir 44c (or / and 54c) and discharges the hydraulic fluid to each wheel cylinder WC **. As a result, each wheel cylinder WC * * A hydraulic pressure higher than the master cylinder pressure by the target differential pressure ΔP is generated.
This completes one execution of this pressure increase control routine, thereby ending one execution of the assist control routine shown in FIG.

  On the other hand, the brake ECU 26 corrects and updates the negative pressure-assistance limit pressure map used in the assist control described above. The correction update process will be described with reference to FIGS.

  The brake ECU 26 determines whether or not the actual boost limit of the vacuum booster 22 has been exceeded when the brake pedal 21 is depressed, and the negative pressure acquired when the brake pedal 21 is depressed. And the data including the master cylinder pressure are compared at the obtained negative pressure, and the negative pressure-assistance limit pressure map is corrected based on the comparison result (correction means).

  In the flowchart shown in FIG. 18, the brake ECU 26 acquires the master cylinder pressure from the master cylinder pressure sensor 25 a 1 every predetermined short time (for example, 10 milliseconds) over the entire operation stroke of the brake pedal 21. , MC1 (step 402). The brake ECU 26 applies the negative pressure in the negative pressure chamber R1 of the vacuum booster 22 (which may be the negative pressure supplied to the vacuum booster 22) from the negative pressure sensor 22f2 for a predetermined short time over the entire operation stroke of this time. Acquired every (for example, 10 milliseconds) and stored as negative pressure 1 (step 404). The MC1 and the negative pressure 1 stored in this way are stored as one data in association with those acquired at the same time.

  The brake ECU 26 derives the negative pressure of the negative pressure chamber R1 and the master cylinder pressure of the master cylinder 23 when the depression of the brake pedal 21 that is being depressed is released (when the release of the depression is started) in the current operation stroke. (get. First, the brake ECU 26 determines that the depression of the brake pedal 21 has been released (the release of the depression has been started) (step 406).

  At this time, the brake ECU 26 inputs the master cylinder pressure from the master cylinder pressure acquisition unit 26b, and if the master cylinder pressure has been increased or substantially constant until then, the depression of the brake pedal 21 is released. (Same as the above determination unit). Specifically, the brake ECU 26 executes a release operation start determination routine shown in FIG. This release operation start determination routine is repeatedly executed every predetermined short time (for example, 10 milliseconds).

  When the master cylinder pressure (MC pressure) acquired this time is smaller than the master cylinder pressure (MC pressure) acquired last time, the brake ECU 26 determines “YES” in step 502 and determines that the release operation has started ( Step 504). On the other hand, when the master cylinder pressure (MC pressure) acquired this time is equal to or higher than the master cylinder pressure (MC pressure) acquired last time, the brake ECU 26 determines “NO” in step 502 and the release operation is started. It is determined that there is not (step 508). In steps 506 and 510, the brake ECU 26 updates the master cylinder pressure acquired this time to the master cylinder pressure acquired last time. In addition, after the time point when it is determined that the release operation has been started, the determination that the depression of the brake pedal 21 has been released (step release has been started) until the next operation process is started (step release). 406) is not performed.

  If the brake ECU 26 determines in step 406 that the depression of the brake pedal 21 has been released, the brake ECU 26 acquires the negative pressure in the negative pressure chamber R1 and the master cylinder pressure in the master cylinder 23 at the time of release, and the negative pressure 1, Store as MC1 (step 408). The stored negative pressure (negative pressure 1) of the negative pressure chamber R1 and the master cylinder pressure (MC1) of the master cylinder 23 are referred to as data when the depression is released. Note that if the brake ECU 26 determines in step 406 that the depression of the brake pedal 21 has not been released, the process of steps 402 to 406 is repeatedly executed.

  In addition, you may make it perform the cancellation | release operation start determination process along the flowchart of FIG. 20 instead of the cancellation | release operation start determination process along the flowchart of FIG. The flowchart shown in FIG. 20 differs from the flowchart shown in FIG. 19 in that the master cylinder pressure acquired two times before and the master cylinder pressure acquired last time are also compared. Only the differences will be described in detail. In step 520, the master cylinder pressure acquired last time is compared with the master cylinder pressure acquired last time. That is, when the master cylinder pressure acquired this time is smaller than the master cylinder pressure acquired last time and the master cylinder pressure acquired last time is lower than the master cylinder pressure acquired last time, the brake ECU 26 determines that “ "YES" is determined, and it is determined that the release operation has been started (step 504). In other cases, it is determined that the release operation has not been started (step 508). In this way, not only the master cylinder pressure acquired this time but also the master cylinder pressure acquired last time (so-called double reading filter processing) can be used to determine the release operation start. Thereby, erroneous data caused by noise or the like can be removed from the detected master cylinder pressure, and erroneous determination of the release operation start can be suppressed. In steps 522 and 524, the brake ECU 26 updates the master cylinder pressure acquired last time to the master cylinder pressure acquired last time.

  Furthermore, instead of the release operation start determination process according to the flowchart of FIG. 20, the release operation start determination process according to the flowchart of FIG. 21 may be executed. The flowchart shown in FIG. 21 considers the threshold KM when comparing the master cylinder pressure acquired last time with the master cylinder pressure acquired this time, and the master cylinder pressure acquired last time and the master cylinder pressure acquired last time. 20 is different from the flowchart shown in FIG. Only the differences will be described in detail. Instead of the process at step 502 in FIG. 20, the process at step 530 in FIG. 21 is executed. That is, the master cylinder pressure acquired last time is compared with the value obtained by adding the threshold KM to the master cylinder pressure acquired this time. Instead of the process at step 520 in FIG. 20, the process at step 532 in FIG. 21 is executed. That is, the master cylinder pressure acquired two times before is compared with the value obtained by adding the threshold KM to the master cylinder pressure acquired last time. The threshold value KM is set in consideration of the detection fluctuation of the master cylinder pressure sensor 25a1. For example, the threshold value KM is set to a value larger than the detection fluctuation. As a result, it is possible to suppress erroneous determination of the start of the release operation due to noise that cannot be dealt with even by the twice reading filter processing, and it is also possible to suppress erroneous determination due to detection fluctuation of the master cylinder pressure sensor 25a1.

  Next, the brake ECU 26 determines whether or not the data including the negative pressure and the master cylinder pressure acquired when the brake pedal 21 is depressed exceeds the actual assist limit of the vacuum booster 22 when the brake pedal 21 is depressed. (Data discrimination unit 26g). That is, the brake ECU 26 uses the brake pedal 21 to generate the data including the negative pressure and the master cylinder pressure acquired when the brake pedal 21 is released based on the fluctuation of the negative pressure in the negative pressure chamber R1 after the brake pedal 21 is released. It is determined whether or not the actual assistance limit of the vacuum booster 22 was exceeded at the time of stepping on 21.

  Specifically, the brake ECU 26 determines “YES” in step 410 if the negative pressure in the negative pressure chamber R1 increases once and returns to the original level after the depression of the brake pedal 21 (depression start time). It is determined that the depression is released after the brake pedal 21 is depressed beyond the actual assist limit of the vacuum booster 22. Then, the brake ECU 26 determines that the data when the depression of the brake pedal 21 is released is the data that has exceeded the actual assist limit of the vacuum booster 22 when the brake pedal 21 is depressed (step 412). As can be understood from the operation of the vacuum booster 22, the brake pedal 21 is depressed beyond the actual assisting limit of the vacuum booster 22, and the brake pedal 21 is returned from the state where the depression is maintained in that state. This is because the negative pressure in the negative pressure chamber R1 once increases and then returns to the original negative pressure when the release of the depression is started.

  In step 410, the brake ECU 26 executes a negative pressure increase determination routine shown in FIG. This negative pressure increase determination routine is repeatedly executed every predetermined short time (for example, 10 milliseconds). If the negative pressure acquired this time is larger than the negative pressure acquired last time, the brake ECU 26 determines “YES” in step 602 and determines that the negative pressure has increased (increased) (step 604). On the other hand, if the negative pressure acquired this time is equal to or lower than the negative pressure acquired last time, the brake ECU 26 determines “NO” in step 602 and determines that the negative pressure has not increased (increased) (step 608). ). In step 606 and 610, the brake ECU 26 updates the negative pressure acquired this time to the negative pressure acquired last time.

  On the other hand, the brake ECU 26 determines “NO” or “YES” in steps 410 and 418 if the negative pressure in the negative pressure chamber decreases after the brake pedal 21 is released, and the vacuum booster 22 is actually operated. It is determined that the depression is released after the brake pedal 21 is depressed without exceeding the assist limit. Then, it is determined that the data when the depression of the brake pedal 21 is released is the data that did not exceed the actual assist limit of the vacuum booster 22 when the brake pedal 21 was depressed (step 420). As can be understood from the operation of the vacuum booster 22, the brake pedal 21 is depressed without exceeding the actual assisting limit of the vacuum booster 22, and the brake pedal 21 is returned from the state where the depression is maintained in that state. This is because the negative pressure in the negative pressure chamber R1 is once reduced and then returned to the original negative pressure when the depression is started.

  In step 418, the brake ECU 26 executes a negative pressure decrease determination routine shown in FIG. This negative pressure decrease determination routine is repeatedly executed every predetermined short time (for example, 10 milliseconds). If the negative pressure acquired this time is smaller than the negative pressure acquired last time, the brake ECU 26 determines “YES” in step 612 and determines that the negative pressure has decreased (step 614). On the other hand, when the negative pressure acquired this time is equal to or higher than the negative pressure acquired last time, the brake ECU 26 determines “NO” in step 612 and determines that the negative pressure has not decreased (step 618). In Steps 616 and 620, the brake ECU 26 updates the negative pressure acquired this time to the negative pressure acquired last time.

  Next, the brake ECU 26 determines whether or not the negative pressure / assistance limit pressure map stored in the first storage unit 26c and the actual assist limit of the vacuum booster 22 have been exceeded when the brake pedal 21 is depressed. In addition, the negative pressure acquired when the brake pedal 21 is released and the data including the master cylinder pressure are compared with each other in the acquired negative pressure (comparison unit 26h).

  Specifically, the brake ECU 26 is determined to have exceeded the actual assist limit of the vacuum booster 22 when the brake pedal 21 is depressed and the negative pressure-assistance limit pressure map stored in the first storage unit 26c. The data at the time of releasing the depression (negative pressure 1, MC1) is compared (step 414). At this time, it is determined whether or not the data at the time when the depression is released belongs to the region I (that is, whether or not the data is located below the negative pressure-assistance limit pressure map).

  That is, the brake ECU 26 executes a region I determination / correction routine shown in FIG. In step 702, the brake ECU 26 substitutes the negative pressure 1 acquired at the time of depressing into the formula MCA = A × negative pressure-α indicating the negative pressure-assistance limit pressure map stored in the first storage unit 26c, The master cylinder pressure at pressure 1 (in the negative pressure at the time of releasing the depression) is derived. In the case where the above expression is a linear function, A is a slope and α is an intercept (initial maps (pre-correction maps in FIGS. 26 and 27)). In step 704, the brake ECU 26 determines in step 702 the master cylinder pressure MCA in the negative pressure 1 that is the negative pressure at the time of depressing derived from the negative pressure-assistance limit pressure map in step 702, and the master cylinder pressure MC1 acquired at the time of depressing. And compare. When the MC1 is smaller than the MCA, the brake ECU 26 determines that the data when the depression is released belongs to the region I. When MC1 is larger than the MCA, the data when the depression is released is other than the region I (region II). It belongs to.

  Here, in the case where the negative pressure-assistance limit pressure map stored in the first storage unit 26c matches the actual characteristics of the vacuum booster 22, the step that has exceeded the actual assist limit of the vacuum booster 22 The master cylinder pressure of the data at the time of release is located above the negative pressure-assistance limit pressure map in the negative pressure at the time of release of depression, and is not located below. On the contrary, the master cylinder pressure of the data at the time of releasing the depression that does not exceed the actual assisting limit of the vacuum booster 22 is positioned below the negative pressure-assisting limit pressure map in the negative pressure at the time of releasing the depression. Never be located.

  However, when the characteristics of the actual vacuum booster 22 are shifted downward with respect to the negative pressure-assistance limit pressure map stored in the first storage unit 26c, the actual assist limit of the vacuum booster 22 has been exceeded. There is a case where the master cylinder pressure of the data at the time of depressing is located below the negative pressure-assistance limit pressure map stored in the negative pressure at the time of depressing. This is because the actual characteristics of the vacuum booster 22 are shifted downward with respect to the negative pressure-assistance limit pressure map stored in the first storage unit 26c.

  By utilizing this fact, as shown in FIG. 26, the vacuum booster 22 is operated when the brake pedal 21 is depressed with respect to the negative pressure-assistance limit pressure map (initial map) stored in the first storage unit 26c. If the depression release data (negative pressure 1, MC1) determined to have exceeded the actual assistance limit belongs to the region I (that is, if it is located below the negative pressure-assistance limit pressure map). It can be seen that the negative pressure-assistance limit pressure map stored in the first storage unit 26c remains positioned above the actual vacuum booster 22 characteristics. Therefore, the negative pressure-assistance limit pressure map stored in the first storage unit 26c may be corrected by a deviation from the actual characteristics of the vacuum booster 22.

  Then, in step 416 shown in FIG. 18, the brake ECU 26 corrects the negative pressure-assistance limit pressure map stored in the first storage unit 26c so that it passes the data when the depression is released (negative pressure 1, MC1). To do. Specifically, in step 706 shown in FIG. 24, the brake ECU 26 derives the correction amount of the negative pressure / assistance limit pressure map based on the comparison result described above. The brake ECU 26 derives from the negative pressure-assistance limit pressure map, the master cylinder pressure (assistance limit pressure) MCA corresponding to the negative pressure in the negative pressure chamber R1 when the brake pedal 21 is released, and the master when the depression is released. A deviation (MCA-MC1) from the cylinder pressure MC1 is derived as a correction amount.

  Further, the brake ECU 26 determines in step 706 the above-described negative pressure-assisting limit pressure based on the derived correction amount and the positional relationship between the compared depression release data and the negative pressure-assistance limit pressure map. A new negative pressure-assistance limit pressure map is derived from the map. Specifically, a value obtained by adding a deviation (MCA-MC1) to α before correction is set as a new α, so that the negative pressure-assistance limit pressure map is moved downward by the derived correction amount. Correction is made to a negative pressure-assistance limit pressure map (a corrected map indicated by a one-dot broken line in FIG. 26).

  In addition, the brake ECU 26 determines that the actual assist limit of the vacuum booster 22 has not been exceeded when the brake pedal 21 is depressed and the negative pressure / assistance limit pressure map stored in the first storage unit 26c. The time data (negative pressure 1, MC1) is compared (step 422). At this time, it is determined whether or not the data at the time of releasing the depression belongs to the region II (that is, whether or not the data is located above the negative pressure-assisting limit pressure map).

  That is, the brake ECU 26 executes a region II determination / correction routine shown in FIG. In step 712, the brake ECU 26 obtains the negative value acquired at the time of depressing to the expression MCA = A × negative pressure-α indicating the negative pressure-assistance limit pressure map stored in the first storage unit 26c, as in step 702. Substituting pressure 1, the master cylinder pressure at negative pressure 1 is derived. In step 714, the brake ECU 26 determines in step 712 the master cylinder pressure MCA at the negative pressure 1 that is the negative pressure at the time of depressing derived from the negative pressure-assistance limit pressure map in step 712, and the master cylinder pressure MC1 acquired at the time of depressing the depressing. And compare. When the MC1 is larger than the MCA, the brake ECU 26 determines that the data when the depression is released belongs to the region II, and when MC1 is smaller than the MCA, the data when the depression is released is other than the region II (region I). It belongs to.

  Here, when the characteristic of the actual vacuum booster 22 is shifted upward with respect to the negative pressure-assistance limit pressure map stored in the first storage unit 26c, the actual assist limit of the vacuum booster 22 is exceeded. There may occur a case where the master cylinder pressure of the data at the time of release of depression that is not present is located above the negative pressure-assistance limit pressure map stored in the negative pressure at the time of release of depression. This is because the actual characteristics of the vacuum booster 22 are shifted upward with respect to the negative pressure-assistance limit pressure map stored in the first storage unit 26c.

  By using this fact, as shown in FIG. 27, the vacuum booster 22 is applied to the negative pressure-assistance limit pressure map (pre-correction map) stored in the first storage unit 26c when the brake pedal 21 is depressed. If the data at the time of release of the depression (negative pressure 1, MC1) determined that the actual assisting limit was not exceeded does not belong to the region II (that is, it is located above the negative pressure-assisting limit pressure map) In other words, it can be seen that the negative pressure-assistance limit pressure map stored in the first storage unit 26c remains below the actual characteristics of the vacuum booster 22. Therefore, the negative pressure-assistance limit pressure map stored in the first storage unit 26c may be corrected by a deviation from the actual characteristics of the vacuum booster 22.

  Then, in step 424 shown in FIG. 18, the brake ECU 26 corrects the negative pressure / assistance limit pressure map stored in the first storage unit 26c so that it passes the data when the depression is released (negative pressure 1, MC1). To do. Specifically, in step 716 shown in FIG. 25, the brake ECU 26 derives the correction amount of the negative pressure / assistance limit pressure map based on the comparison result described above. The brake ECU 26 derives from the negative pressure-assistance limit pressure map, the master cylinder pressure (assistance limit pressure) MCA corresponding to the negative pressure in the negative pressure chamber R1 when the brake pedal 21 is released, and the master when the depression is released. A deviation (MC1-MCA) from the cylinder pressure MC1 is derived as a correction amount.

  Further, the brake ECU 26 determines in step 716 the negative pressure-assisting limit pressure compared based on the derived correction amount and the positional relationship between the compared data at the time of releasing the depression and the negative pressure-assisting limit pressure map. A new negative pressure-assistance limit pressure map is derived from the map. Specifically, a value obtained by adding a deviation (MC1-MCA) to α before correction is set as a new α, so that the negative pressure-assistance limit pressure map is moved upward by the derived correction amount. A negative pressure-assistance limit pressure map (corrected map in FIG. 27) is corrected.

  Note that the determination means exceeds the actual assisting limit of the vacuum booster 22 when the brake operation member 21 is depressed due to a change in the negative pressure in the negative pressure chamber R1 after the depression of the brake operation member (brake pedal) 21 is released. It is determined whether or not. In the present embodiment, the determination means is the data determination unit 26g described above. That is, the data discriminating unit 26g allows the brake pedal 21 to exceed the actual assisting limit of the vacuum booster 22 once the negative pressure in the negative pressure chamber R1 once increases and returns after the release of the brake pedal 21 is released. By determining that the depression of the brake pedal 21 has been released after the depression, the data when the depression of the brake pedal 21 is released is the data that exceeded the actual assisting limit of the vacuum booster 22 when the brake pedal 21 was depressed. It is determined (determined that the actual assist limit of the vacuum booster 22 was exceeded when the brake operation member 21 was depressed). On the other hand, if the negative pressure in the negative pressure chamber decreases after the brake pedal 21 is released, the data discriminating unit 26g does not exceed the actual assisting limit of the vacuum booster 22 and after the brake pedal 21 is depressed. By determining that the depression has been released, it is determined that the data when the depression of the brake pedal 21 is released does not exceed the actual assist limit of the vacuum booster 22 when the brake pedal 21 is depressed ( It is determined that the actual assisting limit of the vacuum booster 22 was not exceeded when the brake operating member 21 was depressed).

  The correcting means corrects the reference value corresponding to the assisting limit pressure, which is the pressure limit of the master cylinder 23 corresponding to the assisting limit of the vacuum booster 22, based on the determination result of the determining means. In the present embodiment, the correction means includes the comparison unit 26h, the correction amount deriving unit 26i, and the map deriving unit 26j described above. In the present embodiment, a negative pressure-assistance limit pressure map is used as the reference value. The drive means drives the hydraulic pumps 44a and 54a when the master cylinder pressure acquired by the master cylinder pressure acquisition means is equal to or higher than a reference value. In the present embodiment, the drive means is the assist control unit 26e described above.

  As is clear from the above description, according to the present embodiment, the storage means (26c) corresponds to an arbitrary negative pressure in the negative pressure chamber R1 and the assist limit of the vacuum booster 22 at the negative pressure. A negative pressure-assistance limit pressure map (FIG. 11) showing the relationship with the assist limit pressure, which is the pressure of the master cylinder 23, is stored. It is determined whether the correction means (26, 26f-26j, the flowchart of FIG. 18) has exceeded the actual assist limit of the vacuum booster 22 when the brake operation member 21 is depressed and the negative pressure / assist limit pressure map. Further, the negative pressure acquired at the time of release of the brake operation member 21 and the data including the master cylinder pressure are compared with each other in the acquired negative pressure, and the negative pressure-assistance limit pressure map is corrected based on the comparison result. The update means (26, 26k) stores the new negative pressure-assistance limit pressure map corrected by the correction means in the storage means. The determination assisting limit pressure calculating means (26d, step 106) determines the assisting limit pressure obtained from the negative pressure acquired by the negative pressure acquiring means (26a, step 104) and the negative pressure-assistance limit pressure map. Calculated as the limit pressure. The assist control means (26e, steps 108-112) is such that the master cylinder pressure acquired by the master cylinder pressure acquisition means (26b, step 102) is greater than or equal to the determination assisting limit pressure calculated by the determination assisting limit pressure calculating means. In some cases, the hydraulic pumps 44a and 54a are driven, and the brake fluid pressure formed by the driving is increased to the master cylinder pressure formed according to the operation of the brake operation member 21, so that the operation is performed according to the operation of the brake operation member. Assistance control for supplying the target brake fluid pressure to the wheel cylinder WC ** is performed.

  The correction means uses an arbitrary negative pressure in the negative pressure chamber R1 as a reference value of the assist limit pressure (a reference value corresponding to the negative pressure-assistance limit master cylinder pressure characteristic), and assist of the vacuum booster 22 at the negative pressure. There is provided a storage means (26c) in which a negative pressure-assistance limit pressure map (FIG. 11) showing the relationship with the assist limit pressure, which is the pressure of the master cylinder 23 corresponding to the limit, is stored, and the correction means is negative pressure− The assist limit pressure map, the data obtained from the release of the brake operation member 21 and the master cylinder pressure, and whether or not the actual assist limit of the vacuum booster 22 when the brake operation member 21 is depressed has been exceeded. The negative pressure-assistance limit pressure map is corrected based on the determination result. Then, the new negative pressure-assistance limit pressure map corrected by the correction unit is stored in the storage unit.

  According to this, the negative pressure-assistance limit pressure map is acquired when the brake operation member 21 is depressed, and it is determined whether or not the actual assist limit of the vacuum booster 22 has been exceeded when the brake operation member 21 is depressed. It is corrected using data consisting of the negative pressure and the master cylinder pressure. Therefore, when only one type of negative pressure-assistant limit pressure map is used and the map is applied to a large number of brake devices, the map initially has an actual negative pressure-assist limit pressure characteristic of the vacuum booster 22 and Even if they are different, the correction according to the present invention can be corrected so that the initial map has an actual negative pressure-assist limit pressure characteristic. In addition, although the negative pressure-assistance limit pressure map initially coincided with the actual negative pressure-assistance limit pressure relationship of the vacuum booster 22, even when the actual negative pressure-assistance limit pressure characteristic changes due to changes over time, With the correction according to the present invention, the initial map can be corrected so as to have an actual negative pressure-assistance limit pressure characteristic. In this way, even if the negative pressure-assistance limit pressure characteristic of the vacuum booster 22 varies or is generated afterwards, the negative pressure-assistance limit pressure map corresponding to the characteristic is corrected appropriately, It is possible to suppress the negative pressure-assistance limit pressure map from deviating from the actual negative pressure-assistance limit pressure relationship. Therefore, the assisting limit pressure for determination for determining the start of the assist control (start of driving of the hydraulic pumps 44a and 54a) can be appropriately derived based on the appropriately corrected negative pressure-assistant limit pressure map, and consequently Assistance control can be started at an appropriate timing. That is, the influence of the characteristic variation of the vacuum booster 22 can be suppressed as much as possible, and the desired braking performance can be sufficiently exerted on the brake device A. Further, the assisting limit pressure for determination can be appropriately derived based on the negative pressure-assisting limit pressure map appropriately corrected without being calculated at the time of deriving.

  Further, the reference value of the negative pressure-assistance limit pressure characteristic (negative pressure-assistance limit pressure map) is obtained by changing the negative pressure when the brake operation member 21 is released to the actual value of the vacuum booster 22 when the brake operation member 21 is depressed. It is determined whether or not the assist limit has been exceeded, and correction is performed using data including the negative pressure and the master cylinder pressure acquired when the brake operation member 21 is released. Therefore, the assisting limit pressure for determination for determining the start of control (start of driving of the hydraulic pumps 44a and 54a) is based on the negative pressure-assisting limit pressure reference value appropriately corrected by the result of the actual negative pressure assisting limit. Thus, the assist control can be started at an appropriate timing. That is, the influence of the characteristic variation of the vacuum booster 22 can be suppressed as much as possible, and the desired braking performance can be sufficiently exerted on the brake device A.

  The correction means determines that the data at the time when the brake operation member 21 is released is over the actual assist limit of the vacuum booster 22 when the brake operation member 21 is depressed, and the negative pressure-assist When located below the limit pressure map, the assist limit pressure corresponding to the negative pressure in the negative pressure chamber R1 when the brake operation member is depressed is derived from the negative pressure-assistance limit pressure map, and the master when the depressing is released A deviation from the cylinder pressure is derived as a correction amount, and correction is performed by moving the negative pressure-assistance limit pressure map downward by the correction amount (steps 414 and 416). As a result, even if the actual negative pressure-assistance limit pressure characteristic is shifted downward from the negative pressure-assistance limit pressure map stored in the storage means or afterwards, the negative pressure-assistance is deviated. The limit pressure map can be corrected appropriately.

  In addition, the correction means is configured so that the brake operation member 21 exceeds the actual assisting limit of the vacuum booster 22 once the negative pressure in the negative pressure chamber R1 once increases and returns to the original level after the release of the brake operation member 21 is released. By determining that the depression has been released after the depression, the data when the depression of the brake operation member 21 is released exceeds the actual assisting limit of the vacuum booster 22 when the brake operation member 21 is depressed. (Steps 410 and 412). Thereby, based on the negative pressure detected conventionally, the data at the time of releasing the depression of the brake operation member 21 exceeded the actual assisting limit of the vacuum booster 22 when the brake operation member 21 was depressed. Can be determined. Therefore, since it is not necessary to provide another detection means, the determination can be performed reliably without causing an increase in cost, a complicated structure, and an increase in size.

  The correction means determines that the data when the brake operation member 21 is released is not exceeding the actual assist limit of the vacuum booster 22 when the brake operation member 21 is depressed, and the negative pressure − When located above the assist limit pressure map, the assist limit pressure corresponding to the negative pressure in the negative pressure chamber R1 when the brake operation member 21 is depressed and derived from the negative pressure-assistance limit pressure map, and when the depressing is released The deviation from the master cylinder pressure is derived as a correction amount, and is corrected by moving the negative pressure-assistance limit pressure map upward by the correction amount (step 422). As a result, even if the actual negative pressure-assistance limit pressure characteristic is shifted upward from the negative pressure-assistance limit pressure map stored in the storage means or afterwards, the negative pressure-assist The limit pressure map can be corrected appropriately.

  In addition, if the negative pressure in the negative pressure chamber R <b> 1 decreases after the brake operation member 21 is released, the correction means does not exceed the actual assist limit of the vacuum booster 22 and after the brake operation member 21 is depressed. By determining that the depression has been released, it is determined that the data when the depression of the brake operation member 21 is released does not exceed the actual assist limit of the vacuum booster 22 when the brake operation member 21 is depressed. (Steps 418 and 420). Thereby, based on the negative pressure detected conventionally, the data at the time of releasing the depression of the brake operation member 21 did not exceed the actual assist limit of the vacuum booster 22 when the brake operation member 21 was depressed. It can be determined that there is. Therefore, since it is not necessary to provide another detection means, the determination can be performed reliably without causing an increase in cost, a complicated structure, and an increase in size.

  Further, when the master cylinder pressure decreases, the correction means determines that the depression of the brake operation member 21 has been released (step 406, flowchart of FIG. 19). Thereby, the depression release determination of the brake operation member 21 can be performed accurately and accurately.

  Further, the correction means determines that the depression of the brake operation member 21 is released when the stroke amount of the brake operation member 21 decreases. Thereby, the depression release determination of the brake operation member 21 can be performed accurately and accurately.

  In the embodiment described above, the correction means stores a plurality of derived correction amounts, derives a correction amount based on the plurality of correction amounts, and negative pressure-assist limit pressure based on the derived correction amount. The map may be corrected. Specifically, the flowchart of FIG. 28 may be implemented instead of the flowchart of FIG. That is, the brake ECU 26 calculates and stores the correction amount in steps 730 and 732 instead of the processing in steps 416 and 418 in FIG. At this time, the brake ECU 26 performs a correction amount calculation process during the processing of steps 416 and 416, and stores the correction amount. Thereafter, when the brake ECU 26 stores a predetermined number of correction amounts, it determines “YES” in step 734, and calculates an average correction amount based on the predetermined number of correction amounts stored in step 736 as the correction amount. Then, the brake ECU 26 corrects the negative pressure-assistance limit pressure map using the correction amount (average correction amount) in step 738, as in step 416 (or 424). As a result, a highly accurate and reliable correction amount can be derived, and as a result, the negative pressure-assistance limit pressure map can be accurately corrected with high reliability.

  In the above-described embodiment, if the data including the negative pressure and the master cylinder pressure acquired when the brake operation member 21 is released is located outside a predetermined range with reference to the negative pressure-assistance limit pressure map, the correcting means The derivation of the correction amount may be prohibited and no correction may be performed. Specifically, the flowchart of FIG. 29 may be implemented instead of the flowchart of FIG. That is, the brake EUC 26 performs the processes of steps 742 to 748 in addition to the processes of steps 702 to 706. In step 742, the brake ECU 26 steps into the equation MCE1 = A × negative pressure− (α−β) (see FIG. 30) indicating the upper limit range of the negative pressure-assistance limit pressure map stored in the first storage unit 26c. The negative pressure 1 acquired at the time of release is substituted, and the master cylinder pressure at the negative pressure 1 (in the negative pressure at the time of release of depression) is derived. In step 744, the brake ECU 26 cancels the depression of the expression MCE2 = A × negative pressure− (α + β) (see FIG. 30) indicating the lower limit range of the negative pressure-assistance limit pressure map stored in the first storage unit 26c. The acquired negative pressure 1 is substituted to derive the master cylinder pressure at the negative pressure 1 (in the negative pressure at the time of releasing the depression). β is a value that defines the predetermined range.

  In step 746, the brake ECU 26 compares the master cylinder pressure MCE1 at the negative pressure 1, which is the negative pressure at the time of releasing the depression, derived at step 742 with the master cylinder pressure MC1 acquired at the time of releasing the depression. In step 748, the brake ECU 26 compares the master cylinder pressure MCE2 at the negative pressure 1, which is the negative pressure at the time of release of the depression derived in step 744, with the master cylinder pressure MC1 acquired at the time of release of the depression. If the master cylinder pressure MC1 acquired when the depression is released is between the master cylinder pressure MCE1 and the master cylinder pressure MCE2, and if the master cylinder pressure MC1 is in the region I, a correction amount is calculated (step 706). If it is not between MCE1 and master cylinder pressure MCE2, the correction amount is not calculated and correction is not performed. Note that the flowchart of FIG. 25 may be changed similarly to the flowchart of FIG.

  As a result, by appropriately selecting and using only the highly reliable data, it is possible to correct the map to be accurate, and as a result, more accurate control can be performed.

  Further, the above-described embodiment further includes negative pressure supply state detection means for detecting normality / abnormality of the negative pressure supply state of the negative pressure source, and the negative pressure supply state detection means is abnormal in the negative pressure supply state. If the fact is detected, the correction means may prohibit the derivation of the correction amount and not perform the correction. Specifically, the brake ECU 26 executes a flowchart shown in FIG. That is, the brake ECU 26 determines in step 750 whether or not the negative pressure supply state of the negative pressure source is normal. For example, when the negative pressure source is the engine 11, it is determined from the information from the engine ECU 17 whether or not it is normal. If the negative pressure supply state of the negative pressure source is normal, the brake ECU 26 determines “YES” in step 750 and permits correction of the negative pressure-assistance limit pressure map (step 752). On the other hand, if the negative pressure supply state of the negative pressure source is abnormal, the brake ECU 26 determines “NO” in step 750 and prohibits correction of the negative pressure-assisting limit pressure map (step 754). As a result, by excluding the low-reliability data in advance, it is possible to correct the map with high accuracy without performing wasteful control for processing the low-reliability data, and thus more accurate control. Can be done.

  In the present embodiment, the negative pressure-assistance limit pressure characteristic is used as a map, and the map value is corrected. For example, the negative pressure-assistance limit pressure characteristic is obtained by an arithmetic expression using negative pressure as a variable. It is also possible to correct the coefficient or deviation and correct the reference value that results in the calculation. In this case, as in the present embodiment, the deviation between the negative pressure at the time of depressing, the assist limit pressure obtained by the calculation formula, and the master cylinder pressure at the time of depressing the depression is added (subtracted) to the deviation of the calculation formula. The correction may be performed by adding or subtracting a predetermined constant for each correction.

DESCRIPTION OF SYMBOLS 11 ... Engine, 12 ... Transmission, 13 ... Differential, 15a ... Throttle valve, 15b ... Motor, 15c ... Throttle opening sensor, 16 ... Accelerator pedal, 16a ... Accelerator opening sensor, 17 ... Engine ECU, 21 ... Brake pedal , 22 ... Vacuum booster, 22f2 ... Negative pressure sensor (negative pressure detecting means), 23 ... Master cylinder, 23a, 23b ... First and second hydraulic pressure chambers, 23c, 23d ... First and second output ports, 24 ... Reservoir tank, 25 ... Brake actuator, 25a1 ... Master cylinder pressure sensor (master cylinder pressure detection means), 26 ... Brake ECU (control device), 26a ... Negative pressure acquisition unit (negative pressure acquisition means), 26b ... Master cylinder pressure acquisition Part (master cylinder pressure acquisition means), 26c... Storage part (storage means), 26d Determination assisting limit pressure calculating unit (determining assisting limit pressure calculating unit), 26e... Assisting control unit (assisting control unit), 26f... Negative pressure when depressing, master cylinder pressure deriving unit, 26g. ... Comparison part, 26i ... Correction amount deriving part, 26j ... Map deriving part, 26k ... Map updating part (updating means), 41, 51 ... Differential pressure control valve, 42a, 43a, 52a, 53a ... Booster valve, 42b, 43b , 52b, 53b ... pressure reducing valve, 44c, 54c ... pressure regulating reservoir, 44a, 54a ... pump (hydraulic pump), A ... hydraulic brake device, Wfl, Wfr, Wrl, Wrr ... wheels, Sfl, Sfr, Srl, Srr ... Wheel speed sensor, WCfl, WCfr, WCrl, WCrr ... Wheel cylinder.

Claims (9)

A master cylinder (23) for forming a brake fluid pressure according to the operation of the brake operation member (21);
A vacuum booster (22) that is supplied with negative pressure and uses the negative pressure to assist the operating force of the brake operating member and output it to the master cylinder;
A wheel cylinder (WC **) that receives a brake fluid pressure supplied from the master cylinder and applies a braking force to each wheel (W **) of the vehicle (M);
Connected to the hydraulic path (25a, 25b) connecting the master cylinder and the wheel cylinder, driven by the output of the electric motor (44b) to form a brake fluid pressure, and supplied to the wheel cylinder independently of the master cylinder Hydraulic pumps (44a, 54a) to
Negative pressure acquisition means (26a, step 104) for acquiring the negative pressure in the negative pressure chamber of the vacuum booster;
Master cylinder pressure acquisition means (26b, step 102) for acquiring the pressure of the master cylinder;
Discriminating means (26) for determining whether or not an actual assisting limit of the vacuum booster has been exceeded when the brake operating member is stepped on, based on a change in negative pressure in the negative pressure chamber after the brake pedal is released. , 26 g)
Correction means (26, 26h-26j) for correcting a reference value corresponding to the assistance limit pressure, which is a pressure limit of the master cylinder corresponding to the assistance limit of the vacuum booster, based on the determination result of the determination means;
Drive means (26e, steps 108-112) for driving the hydraulic pump when the master cylinder pressure acquired by the master cylinder pressure acquisition means is greater than or equal to the reference value;
A brake device comprising: In claim 1,
The correction means uses an arbitrary negative pressure in the negative pressure chamber as a reference value of the assist limit pressure, and an assist limit pressure that is a pressure of the master cylinder corresponding to the assist limit of the vacuum booster at the negative pressure. Storage means (26c) in which a negative pressure-assistance limit pressure map (FIG. 11) showing the relationship is stored;
Exceeding the actual assist limit of the vacuum booster when the brake operation member is depressed, and the negative pressure-assistance limit pressure map, data including the negative pressure and master cylinder pressure acquired when the brake operation member is depressed The negative pressure-assistance limit pressure map is corrected based on the determination result of whether or not (26, 26f-26j, flowchart of FIG. 18), and the new negative pressure-assistance limit pressure map corrected by the correction means is The brake device is updated by update means (26k) stored in the storage means.   The correction means according to claim 2, wherein the data at the time of releasing the depression of the brake operation member is determined to have exceeded an actual assisting limit of the vacuum booster at the time of depression of the brake operation member. The assist limit corresponding to the negative pressure of the negative pressure chamber when the brake operation member is released is derived, which is derived from the negative pressure-assistance limit pressure map when positioned below the negative pressure-assistance limit pressure map. The deviation between the pressure and the master cylinder pressure when the depression is released is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved downward by the correction amount for correction (steps 414 and 416). Brake device characterized by.   4. The vacuum booster according to claim 1, wherein after the stepping release of the brake operation member is released and the negative pressure in the negative pressure chamber once increases and returns to the original value, the correction means Determining that the stepping is released after the brake operation member is stepped on exceeding the actual assisting limit, so that the data when the brake operation member is stepped off is obtained when the brake operation member is stepped on. A brake device characterized in that it is determined that the actual boost limit of the vacuum booster has been exceeded (steps 410 and 412).   5. The correction means according to claim 2, wherein the data when the brake operation member is released exceeds the actual assisting limit of the vacuum booster when the brake operation member is released. 5. The negative pressure-assistance limit pressure map, the negative pressure-assistance limit pressure map derived from the negative pressure-assistance limit pressure map is deducted when the brake operation member is released. A deviation between the assist limit pressure corresponding to the negative pressure of the pressure chamber and the master cylinder pressure at the time of release of the depression is derived as a correction amount, and the negative pressure-assistance limit pressure map is moved upward by the correction amount. (Steps 422 and 424).   The correction means according to any one of claims 1 to 5, wherein when the negative pressure in the negative pressure chamber decreases after the release of the depression of the brake operation member, the correction operation is performed when the depression of the brake operation member is released. The brake device is characterized in that it is determined that the data does not exceed the actual assist limit of the vacuum booster when the brake operation member is depressed (steps 418, 420).   7. The correction unit according to claim 3, wherein the correction unit stores a plurality of the derived correction amounts, derives a correction amount based on the plurality of correction amounts, and based on the derived correction amount. And correcting the negative pressure-assistance limit pressure map (flow chart of FIG. 28).   8. The data of the negative pressure and the master cylinder pressure acquired when the brake operating member is released is located outside a predetermined range based on the negative pressure-assisting limit pressure map according to claim 2. Then, the correction means prohibits derivation of the correction amount and does not perform correction (flow chart of FIG. 29). 9. The negative pressure supply state detection unit according to claim 1, further comprising negative pressure supply state detection means for detecting normality / abnormality of the negative pressure supply state of the negative pressure source, wherein the negative pressure supply state detection unit is a negative pressure. If it is detected that the supply state is abnormal, the correction means prohibits derivation of the correction amount and does not perform correction (flowchart in FIG. 31).

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