JP2011219010A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking force control device that, in the occurrence of rear lift, quickly cancels out the rear lift and stabilizes vehicle movement.SOLUTION: A brake ECU 6 determines the occurrence of rear lift in a vehicle 100 on the basis of a change in wheel speed Vwr of rear wheels (right rear wheel 73, left rear wheel 74), a change in wheel speed Vcr of rear wheel origin calculated based on the wheel speed of the rear wheels, and pitching moment generated in the vehicle 100. Then, in the occurrence of the rear lift in the vehicle 100, a braking force imparted to the front wheels (right front wheel 71, left front wheel 72) is restricted to reduce deceleration. Further, the brake ECU 6 shifts the change and the phase of the braking force of the left front wheel 72 to change the braking force of the right front wheel 71, thereby generating yaw moment for the vehicle 100.

Description

  The present invention relates to a braking force control device that controls a braking force of a vehicle.

  For vehicles with a short wheelbase and a high center of gravity, such as wagons, one-box vehicles, and light trucks, there is a lift-up (hereinafter referred to as a rear lift) in which one or two of the rear wheels are lifted during sudden braking while driving. May occur. In particular, when a rear lift occurs on a downhill, the driver is greatly discomforted.

For example, a light truck has an extremely short wheelbase in order to improve usability on a narrow farm road.
In recent years, vehicles with high vehicle height, such as wagon cars and one-box cars, are increasing in order to improve the comfort, comfort and storage of the vehicles.
Furthermore, there are many vehicles in which the engine is installed at the front and the rear load is smaller than that at the front.

  In this way, since the number of vehicles with short wheelbases, vehicles with high vehicle height and high center of gravity, and vehicles with light rear loads are increasing, it is important to effectively suppress rear lift during brake operation. It is growing.

  For example, Patent Document 1 discloses a vehicle control technique related to a rear lift. According to the technique of Patent Document 1, when the rear lift occurs, the estimated vehicle body speed can be changed to apply a braking force to the vehicle.

Japanese Patent No. 3533420

  However, with the technique disclosed in Patent Document 1, it is possible to effectively decelerate and stop the vehicle when a rear lift occurs, but it is impossible to quickly eliminate the rear lift and stabilize the operation of the vehicle. There's a problem.

  Accordingly, an object of the present invention is to provide a braking force control apparatus that quickly eliminates a rear lift and stabilizes the operation of the vehicle when the rear lift occurs.

  In order to solve the above-mentioned problems, a first aspect of the present invention includes a lift determination means for determining occurrence of lift-up of a rear wheel of the vehicle during the anti-lock brake control by the anti-lock brake control means. The control means is a braking force control device that limits a braking force applied to a front wheel of the vehicle when the lift determination means determines the occurrence of the lift-up.

According to the invention of claim 1, when the rear wheel lifts up, the anti-lock brake control means can limit the braking force applied to the front wheel of the vehicle. Therefore, when the rear wheel lifts up, the deceleration of the vehicle can be reduced.
Since the rear wheel lift-up occurs when the vehicle deceleration is large, the lift-up can be eliminated by reducing the vehicle deceleration.

  Further, a second aspect of the present invention is the braking force control apparatus according to the first aspect, wherein the lift determining means is configured to increase the lift based on a change in wheel speed of the rear wheel during the antilock brake control. It is characterized by determining the occurrence of.

  According to the invention of claim 2, the lift determination means can determine that lift-up has occurred based on a change in the wheel speed of the rear wheel.

  According to a third aspect of the present invention, there is provided the braking force control device according to the first or second aspect, wherein the lift determination means generates the lift-up based on a vehicle body momentum during the antilock brake control. It is characterized by determining.

  According to the invention of claim 3, the lift determination means can determine that the lift-up has occurred based on the vehicle body momentum.

  According to a fourth aspect of the present invention, there is provided the braking force control device according to any one of the first to third aspects, wherein the lift determining means is preset with a pitching moment generated in the vehicle. The occurrence of the lift-up is determined when a threshold value is exceeded.

  According to the invention of claim 4, the lift determination means can determine that lift-up has occurred based on a pitching moment generated in the vehicle under anti-lock brake control.

  A fifth aspect of the present invention is the braking force control apparatus according to any one of the first to fourth aspects, wherein the load determination for determining a maximum load front wheel to which the largest load is applied among the front wheels. The anti-lock brake control means applies to the maximum load front wheel so that the braking force applied to the maximum load front wheel does not increase beyond a limit value than the braking force applied to the other front wheels. The braking force is limited.

  According to the invention of claim 5, the anti-lock brake control means can limit the braking force applied to the maximum load front wheel to which the load is most applied.

  A sixth aspect of the present invention is the braking force control device according to any one of the first to fifth aspects, wherein the anti-lock is detected when the lift determination means determines the occurrence of the lift-up. The brake control means is characterized in that the braking force applied to the right front wheel of the vehicle is changed by shifting the phase and the phase of the braking force applied to the left front wheel of the vehicle.

  According to the sixth aspect of the present invention, when the rear wheel lifts up, a phase difference can be provided between the change in the braking force applied to the left front wheel of the vehicle and the change in the braking force applied to the right front wheel. Then, the yaw moment can be generated by swinging the vehicle left and right.

  According to the present invention, when a rear lift occurs, it is possible to provide a braking force control device that quickly eliminates the rear lift and stabilizes the operation of the vehicle.

It is a figure which shows the structure of the braking force control apparatus which concerns on this embodiment. It is a flowchart which shows the procedure which brake ECU determines generation | occurrence | production of a rear lift. (A) is a figure which shows an example of the hydraulic pressure pattern of FL oil pressure OP _FL and FR oil pressure OP _FR , (b) is a figure which shows the change of the wheel speed of a left front wheel and a right front wheel. (A) is a figure which shows the limiting value provided in a hydraulic pressure pattern, (b) is a figure which shows the state in which FR oil pressure _OPFR was restrict _| limited by the limiting value, (c) is FR oil pressure restrict | limited by the limiting value It is a figure which shows the change of the wheel speed of the right front wheel according to OP _FR . It is a flowchart which shows the procedure in which brake ECU eliminates a rear lift.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the braking force control device 1 provided in the vehicle 100 includes a brake pedal 2 that is operated by a driver, and a brake booster 3 that boosts a brake operating force when the driver depresses the brake pedal 2. The brake operating force boosted by the brake booster 3 is converted into hydraulic pressure, and the hydraulic oil is supplied to the oil supply unit 5. The hydraulic oil supplied from the master cylinder 4 is supplied to the brake operating portion of the wheel 7. 9 includes an oil feeding unit 5 that feeds oil to 9 and a brake ECU (Electronic Control Unit) 6 that controls the braking force control device 1.

The vehicle 100 includes four wheels 7 (a right front wheel 71, a left front wheel 72, a right rear wheel 73, and a left rear wheel 74), and one brake operation unit 9 is provided for each wheel 7.
Each wheel 7 is provided with a wheel speed sensor 8 for detecting each wheel speed Vw. That is, as shown in FIG. 1, the FR brake operation unit 91 and the FR wheel speed sensor 81 are applied to the right front wheel 71, the FL brake operation unit 92 and the FL wheel speed sensor 82 are applied to the left front wheel 72, and the RR brake operation unit is applied to the right rear wheel 73. 93, the RR wheel speed sensor 83, and the left rear wheel 74 are provided with an RL brake operation unit 94 and an RL wheel speed sensor 84.

The oil feeding unit 5 supplies hydraulic oil to four brake operation units 9 (FR brake operation unit 91, FL brake operation unit 92, RR brake operation unit 93, and RL brake operation unit 94) in response to a command from the brake ECU 6. Is distributed and fed, and the brake operation unit 9 is operated.
Further, the oil feeding unit 5 is provided with a hydraulic pressure sensor 5 a that detects the hydraulic pressure (hereinafter referred to as MC hydraulic pressure) input from the master cylinder 4.

  The vehicle 100 includes a yaw rate sensor SY that detects a yaw rate, an acceleration sensor SG that detects acceleration generated in the front-rear direction and the left-right direction, and the brake ECU 6 includes a wheel speed Vw of each wheel 7 detected by the wheel speed sensor 8. , A yaw rate signal indicating the yaw rate detected by the yaw rate sensor SY, an acceleration signal indicating the longitudinal and lateral acceleration detected by the acceleration sensor SG, and an MC hydraulic pressure signal indicating the MC hydraulic pressure detected by the hydraulic sensor 5a. Is entered.

  The brake ECU 6 calculates the vehicle speed (vehicle speed) Vc of the vehicle 100 based on the wheel speed Vw of the wheel 7. For example, the brake ECU 6 determines the average value of the two wheel speeds Vw that are high among the wheel speeds Vw of the four wheels 7 or the wheel speed Vw that is the fastest on the second surface among the wheel speeds Vw of the four wheels 7. Is a representative value, and the vehicle speed Vc of the vehicle 100 is calculated based on the representative value.

  Further, the brake ECU 6 calculates the slip ratio Sr based on the calculated vehicle speed Vc and the wheel speed Vw of each wheel 7. For example, the brake ECU 6 uses the average value of the wheel speeds of the four wheels 7 as the wheel speed Vw of the vehicle 100, and calculates the slip ratio Sr based on the difference between the vehicle speed Vc and the wheel speed Vw.

Then, the brake ECU 6 gives a command to the oil feeding unit 5 based on the calculated vehicle speed Vc, slip ratio Sr, etc., and the FR brake operation unit 91, the FL brake operation unit 92, the RR brake operation unit 93, and the RL brake operation unit 94. The hydraulic pressure (hereinafter referred to as brake hydraulic pressure) of the hydraulic oil to be fed to the vehicle is suitably adjusted to suitably control the braking force of the four wheels 7.
Thus, the brake ECU 6 can perform ABS control (anti-lock brake system control) of the braking force control device 1 by suitably controlling the braking force of the four wheels 7. The brake ECU 6 serves as an antilock brake control unit that performs ABS control of the braking force control device 1.

In the vehicle 100 including the braking force control device 1 configured as described above, if a rear lift occurs during a brake operation by the driver, the driver feels uncomfortable.
Therefore, the braking force control apparatus 1 according to the present embodiment is configured to detect the rear lift with high accuracy and to quickly eliminate the rear lift when the rear lift occurs.

《Judgment of occurrence of rear lift》
When the vehicle 100 is an FF (Front engine Front drive) vehicle, the brake ECU 6 according to the present embodiment determines the occurrence of a rear lift according to the procedure shown in FIG. 2 (see FIG. 1 as appropriate).
The procedure shown in FIG. 2 is configured such that, for example, the brake ECU 6 executes the brake ECU 6 while the brake force control apparatus 1 is performing ABS control. With this configuration, the brake ECU 6 determines the rear lift of the vehicle 100 during the ABS control.

  First, the brake ECU 6 calculates a gradient acceleration (gradient G) (step S1). The brake ECU 6 calculates the gradient G by a known method based on the longitudinal acceleration of the vehicle 100 detected by the acceleration sensor SG.

  Next, the brake ECU 6 estimates the friction coefficient μr of the road surface (step S2). In step S2, the brake ECU 6 detects the MC hydraulic pressure based on the MC hydraulic pressure signal input from the hydraulic pressure sensor 5a. Further, the vehicle speed (front wheel-derived vehicle speed Vcf) based on the wheel speed Vwf of the front wheels (the right front wheel 71 and the left front wheel 72) is calculated.

For example, since the relationship between the vehicle speed deceleration rate (standard deceleration rate dV _std ) and the MC hydraulic pressure on the road surface with the standard friction coefficient μr is obtained in advance, the brake ECU 6 determines the standard deceleration rate based on the calculated MC hydraulic pressure. dV _std is calculated. Then, the brake ECU 6 calculates (estimates) the road friction coefficient μr based on the standard deceleration rate dV _std and the deceleration rate of the front wheel derived vehicle speed Vcf.

The brake ECU 6 determines whether the friction coefficient μr calculated (estimated) in this way is greater than or equal to a predetermined value (step S3). When the friction coefficient μr is greater than or equal to the predetermined value (step S3 → Yes), the procedure proceeds to step S4. Continue to determine the rear lift. On the other hand, when the friction coefficient μr is smaller than the predetermined value (step S3 → No), the brake ECU 6 determines that the rear lift cannot be accurately detected because the road friction coefficient μr is small and the road surface is slippery. The judgment ends.
Note that the predetermined value that the brake ECU 6 compares with the friction coefficient μr in order to determine the occurrence of the rear lift in step S2 is a value that is appropriately set according to the required rear lift detection accuracy and the like.

  Next, the brake ECU 6 determines whether the longitudinal acceleration (front-rear G) of the vehicle 100 detected by the acceleration sensor SG is equal to or greater than a predetermined value (step S4). For example, the maximum deceleration when the vehicle 100 decelerates is determined as the eigenvalue from the performance of the brake operation unit 9 provided in the vehicle 100 and the tire specifications (not shown). Therefore, the brake ECU 6 uses a value obtained by adding a predetermined margin value to the total value of the gradient G and the maximum deceleration calculated in step S1 as a threshold, and when the front and rear G is equal to or greater than the threshold (step S4 → Yes), the rear lift is It determines with having generate | occur | produced (step S9). Further, when the front and rear G is less than the threshold (step S4 → No), the procedure proceeds to step S5.

Although the longitudinal G generated in the vehicle 100 is an acceleration generated by the deceleration and the gradient G, the longitudinal G is also generated when a pitching moment is generated in the vehicle 100. Therefore, when the acceleration obtained by combining the maximum deceleration and the gradient G is larger than the longitudinal G, the difference indicates the pitching moment. Then, the brake ECU 6 determines that the rear lift has occurred when the pitching moment has exceeded a predetermined threshold (step S9). That is, the brake ECU 6 determines the occurrence of the rear lift when the pitching moment exceeds the predetermined threshold value in step S4.
Therefore, the margin value used for calculating the threshold value that the brake ECU 6 compares with the front and rear G in step S4 is a value corresponding to the pitching moment in a range where the rear lift does not occur, and is a value determined as a design value of the vehicle 100. .

In step S5, the brake ECU 6 calculates the vehicle speed (rear wheel derived vehicle speed Vcr) based on the wheel speeds (rear wheel speed Vwr) of the rear wheels (right rear wheel 73, left rear wheel 74), and the rear wheel derived vehicle speed Vcr. The deceleration rate dVcr is compared with the standard deceleration rate dV _std .
When a rear lift is generated in the FF vehicle, the rear wheels (the right rear wheel 73 and the left rear wheel 74) are idled, so that the deceleration rate of the rear wheels due to the braking force increases. Therefore, the deceleration rate dVcr of the rear wheel derived vehicle speed Vcr is larger than the standard deceleration rate dV _std based on the MC hydraulic pressure. Therefore, if the deceleration rate dVcr of the rear wheel derived vehicle speed Vcr is larger than the standard deceleration rate dV _std (step S5 → Yes), the brake ECU 6 determines that a rear lift has occurred (step S9).
The vehicle speed (rear wheel derived vehicle speed Vcr) is a value indicating the momentum (vehicle momentum) of the vehicle 100, and the brake ECU 6 determines the occurrence of the rear lift based on the vehicle momentum in step S5.

On the other hand, when the deceleration rate dVcr of the vehicle speed Vcr derived from the rear wheels is equal to or less than the standard deceleration rate dV _std (step S5 → No), the brake ECU 6 supplies the brake hydraulic pressure (hereinafter, referred to as “RR brake operation unit 93”, “RL brake operation unit 94”). If the rear wheel hydraulic pressure OPr is not reduced (step S6 → No), it is determined that the rear lift has not occurred (step S8), and if the rear wheel hydraulic pressure OPr is reduced (step S6 → Yes). ), The occurrence of rear lift is determined based on the reduced pressure of the rear wheel hydraulic pressure OPr and the recovery state of the rotational speed of the rear wheels (the right rear wheel 73 and the left rear wheel 74).

  When the rear wheel hydraulic pressure OPr is reduced when the rear wheels (the right rear wheel 73 and the left rear wheel 74) are in contact with the ground, the rear wheel speed Vwr increases due to the inertia of the vehicle 100. Therefore, the brake ECU 6 determines that the rear lift has occurred when the rear wheel speed Vwr does not change when the rear wheel hydraulic pressure OPr is reduced.

That is, the brake ECU 6 determines that a rear lift has occurred when the rear wheel speed Vwr does not change (step S7 → No) (step S9), and when the rear wheel speed Vwr changes (step S7 → Yes). It is determined that no rear lift has occurred (step S8).
In step S7, the brake ECU 6 determines the occurrence of the rear lift based on the change in the rear wheel speed Vwr.

  As described above, the brake ECU 6 according to the present embodiment performs the following operation when the magnitude of the front-rear G generated in the vehicle 100, the magnitude of the deceleration rate dVcr of the rear-wheel-derived vehicle speed Vcr, and the rear-wheel hydraulic pressure OPr are reduced. The occurrence of rear lift (rear wheel lift up) is determined based on the change in the wheel speed Vwr. Therefore, the brake ECU 6 becomes the lift determination means described in the claims.

<Elimination of rear lift>
When the brake ECU 6 (see FIG. 1) according to the present embodiment executes the procedure shown in FIG. 2 and determines that a rear lift has occurred in the vehicle 100 (see FIG. 1), the braking force control device 1 so as to eliminate the rear lift. (See FIG. 1).

  Conventionally, when controlling the braking force control device 1 (ABS control), the brake ECU 6 shown in FIG. 1 estimates a state in which the vehicle speed Vc is decelerated (that is, a change in estimated vehicle speed) from the vehicle speed Vc, the friction coefficient μr of the road surface, and the like. The brake hydraulic pressure supplied to the brake operation unit 9 is controlled so that the vehicle speed of the vehicle 100 decelerates following the change in the estimated vehicle speed. At this time, if the acceleration (deceleration) at which the vehicle speed Vc decelerates is large, a rear lift occurs. Further, when the rear lift is generated and the state where the deceleration is large is maintained, the rear lift is not eliminated.

  Therefore, the brake ECU 6 (see FIG. 1) according to the present embodiment controls the brake operation unit 9 (see FIG. 1) so as to reduce the deceleration of the vehicle 100 (see FIG. 1) when a rear lift occurs. Therefore, when the rear lift occurs, the brake ECU 6 adjusts the brake hydraulic pressure of the hydraulic oil supplied to the FR brake operation unit 91 (see FIG. 1) and the FL brake operation unit 92 (see FIG. 1), and the right front wheel 71 (see FIG. 1). 1) and the braking force of the left front wheel 72 (see FIG. 1) is limited.

For example, assuming that the deceleration of the vehicle speed Vc calculated by the brake ECU 6 (see FIG. 1) under normal ABS control is the standard deceleration a _std , the brake ECU 6 reduces the vehicle 100 (see FIG. 1) when a rear lift occurs. The hydraulic pressure of the hydraulic oil supplied to the FR brake operation unit 91 (see FIG. 1) and the FL brake operation unit 92 (see FIG. 1) is limited so that the speed becomes smaller than the standard deceleration a _std .

In addition, when the rear lift occurs, the brake ECU 6 (see FIG. 1) according to the present embodiment is out of phase with the change in the braking force of the left front wheel 72 (see FIG. 1) to control the right front wheel 71 (see FIG. 1). The FR brake operation unit 91 and the FL brake operation unit 92 (see FIG. 1) are controlled so that the power changes. Specifically, as shown in FIG. 3A, the brake ECU 6 shifts the phase and phase of the change in the brake hydraulic pressure (FL hydraulic pressure OP _FL ) of the hydraulic oil supplied to the FL brake operating unit 92, thereby changing the FR brake operating unit. The brake hydraulic pressure (FR hydraulic pressure OP _FR ) of the hydraulic oil supplied to 91 is changed.

Under normal ABS control, the brake ECU 6 (see FIG. 1) has the FR hydraulic pressure OP _{FR of the} hydraulic oil supplied to the FR brake operation unit 91 (see FIG. 1) based on the estimated vehicle speed and the FL brake operation unit 92 (see FIG. 1). FR and FL hydraulic OP _FL of the hydraulic oil supplied to the reference), the pressure increasing, holding, pressure reduction pattern (hereinafter referred to repeatedly arranged in time series is referred to as a hydraulic pattern) is calculated respectively in accordance with the calculated pressure pattern The hydraulic pressure OP _FR and the FL hydraulic pressure OP _FL are controlled. In the normal ABS control, the brake ECU 6 sets the hydraulic pressure patterns so that the timings of increasing, holding, and depressing the FR hydraulic pressure OP _FR are substantially synchronized with the timings of increasing, holding, and depressurizing the FL hydraulic pressure OP _FL. calculate.
Therefore, in normal ABS control, the pressure increase, retention, and pressure reduction of the FR hydraulic pressure OP _{FR and} the pressure increase, retention, and pressure reduction of the FL hydraulic pressure OP _FL are substantially synchronized.

The brake ECU 6 (see FIG. 1) according to the present embodiment temporally determines the timing of increasing, holding, and depressurizing the FR hydraulic pressure OP _FR and the timing of increasing, holding, and depressurizing the FL hydraulic pressure OP _FL when the rear lift occurs. By shifting, the FR hydraulic pressure OP _FR and the FL hydraulic pressure OP _FL are changed with a suitable phase difference. With this configuration, the brake ECU 6 can change the braking force applied to the right front wheel 71 (see FIG. 1) by shifting the phase from the change of the braking force applied to the left front wheel 72 (see FIG. 1).

  Such a phase difference is preferably set based on, for example, the vehicle speed Vc and the friction coefficient μr. If the map showing the relationship between the vehicle speed Vc, the friction coefficient μr and the phase difference is provided in a storage unit (not shown). Good. The brake ECU 6 can calculate the phase difference by referring to the map based on the vehicle speed (in this case, the vehicle speed Vcf derived from the front wheels) and the friction coefficient μr. Such a map can be easily set by, for example, experimental measurement.

Further, the brake ECU 6 calculates a hydraulic pressure pattern when the rear lift occurs by using a logic that calculates a hydraulic pressure pattern used in normal ABS control (ABS control when the rear lift is not generated). Further, the brake ECU 6 corrects the pressure increasing portion of the hydraulic pattern with a predetermined coefficient. In this way, by correcting the pressure increasing portion of the hydraulic pattern, the deceleration of the vehicle 100 (see FIG. 1) can be suppressed to be smaller than the standard deceleration a _std . In other words, the pressurizing portion of the hydraulic pattern is a portion indicating a pressure increase in FR hydraulic _{OP FR} and FL hydraulic _{OP FL,} by correcting the pressurizing portion can be corrected FR hydraulic _{OP FR} and FL hydraulic _{OP FL.} Therefore, if the pressure increasing portion is corrected to be small, the FR hydraulic pressure OP _FR and the FL hydraulic pressure OP _FL become small, and the braking force applied to the right front wheel 71 and the left front wheel 72 can be limited to a small value. As a result, the deceleration of the vehicle 100 can be reduced.

  Thus, the coefficient for correcting the pressure increasing portion of the hydraulic pattern is preferably a coefficient for correcting the pressure increasing portion to be small, and is a value set based on the vehicle speed Vc and the friction coefficient μr, for example. Therefore, a configuration may be adopted in which a map indicating the relationship between the vehicle speed Vc, the friction coefficient μr, and the coefficient is provided in a storage unit (not shown). The brake ECU 6 can calculate a coefficient for correcting the pressure increasing portion with reference to the map based on the vehicle speed (in this case, the front wheel derived vehicle speed Vcf) and the friction coefficient μr. Such a map can be easily set by, for example, experimental measurement.

Then, the brake ECU 6 corrects the pressure increase portion of the hydraulic pressure pattern by the calculated coefficient, and further shifts the hydraulic pressure pattern of the FR hydraulic pressure OP _{FR and} the hydraulic pressure pattern of the FL hydraulic pressure OP _FL temporally to shift the FR hydraulic pressure OP _FR and the FL hydraulic pressure OP. by controlling the _FL, providing a phase difference to a change in FR hydraulic _{OP FR} and FL hydraulic _{OP FL.}
As described above, the brake ECU 6 uses the logic for calculating the hydraulic pressure pattern in a normal state to calculate the hydraulic pressure pattern when the rear lift occurs, thereby calculating the hydraulic pressure pattern when the rear lift occurs. There is no need to design a new logic, and the design man-hour of the brake ECU 6 can be reduced.

As shown in FIG. 3B, the wheel speed Vw _FR (solid line) of the right front wheel 71 is an FR hydraulic pressure OP _FR that increases, holds, and reduces pressure according to the hydraulic pattern shown by the solid line in FIG. Accordingly, deceleration, speed maintenance, and acceleration are repeated, and the wheel speed Vw _FL (broken line) of the left front wheel 72 is increased, held, and reduced according to the hydraulic pattern shown by the broken line in FIG. _Repeats deceleration, speed maintenance, and acceleration with _FL . Thus, if a phase difference is provided between the change in the FR hydraulic pressure OP _{FR and} the change in the FL hydraulic pressure OP _FL , the braking force of the right front wheel 71 (see FIG. 1) and the braking force of the left front wheel 72 (see FIG. 1) are changed. A phase difference occurs, causing the vehicle 100 (see FIG. 1) to swing in the left-right direction, generating a yaw moment.
Then, the pitching moment that generates the rear lift is converted into the yaw moment, and the pitching moment is reduced. Accordingly, the rear lift generated in the vehicle 100 is eliminated. Thus, the brake ECU 6 (see FIG. 1) according to the present embodiment generates a yaw moment in the vehicle 100 to eliminate the rear lift.

  However, if the difference between the braking force of the right front wheel 71 (see FIG. 1) and the braking force of the left front wheel 72 (see FIG. 1) is too large, a load movement occurs, and a brake lock occurs due to the load movement. . In particular, when the vehicle 100 (see FIG. 1) is turning, the load applied to the left and right front wheels is greatly different, and a large braking force is applied to the wheel 7 (hereinafter referred to as the maximum load front wheel) to which the maximum load is applied. The brake will lock strongly, giving the driver a great sense of discomfort.

Therefore, the brake ECU 6 (see FIG. 1) controls the FR brake operation unit 91 and the FL brake operation unit 92 (see FIG. 1) so as to limit the difference between the braking force of the right front wheel 71 and the braking force of the left front wheel 72. . In particular, the FR brake operation unit 91 and the FL brake operation unit 92 are controlled so that a large braking force is not applied to the maximum load front wheel. For example, the right front wheel 71 is the case of the front wheel maximum load, the brake ECU6 is, FR hydraulic _{OP FR} limits the FR hydraulic _{OP FR} so as not to increase than FL hydraulic _{OP FL} exceeds a predetermined limit value.

Therefore, for example, when the right front wheel 71 (see FIG. 1) is the maximum load front wheel, a limit value on the high pressure side with respect to the FL hydraulic pressure OP _FL is set as indicated by a one-dot chain line in FIG. Such a limit value indicates that when the hydraulic oil of the FL hydraulic pressure OP _FL indicated by a broken line is supplied to the FL brake operation unit 92 (see FIG. 1), the braking force in a range where no brake lock is generated is applied to the right front wheel 71 ( It is determined in the range of the FR hydraulic pressure OP _FR generated in FIG.

Then, the brake ECU 6 (see FIG. 1) determines that the FR hydraulic pressure OP _FR changing with a phase difference from the FL hydraulic pressure OP _FL exceeds the limit value indicated by the one-dot chain line in FIG. As shown, the limit value is set to the FR hydraulic pressure OP _FR . Then, the set hydraulic fluid of the FR hydraulic pressure OP _FR is supplied to the FR brake operation unit 91 (see FIG. 1).
As a result, the wheel speed Vw _FR of the right front wheel 71 changes as indicated by a solid line in FIG. 4C, and the wheel speed Vw _FL of the left front wheel 72 changes as indicated by a broken line. From the state shown in (b) of FIG. 3, a decrease in the wheel speed Vw _FR of the right front wheel 71 is suppressed.

In this way, it is possible to suppress the decrease in the wheel speed Vw _FR of the right front wheel 71 (see FIG. 1) that is the maximum load front wheel, and it is possible to suppress the occurrence of brake lock. Further, a phase difference can be caused in the change in the wheel speed Vw _FR of the right front wheel 71 and the wheel speed Vw _FL of the left front wheel 72, and a yaw moment can be generated in the vehicle 100 (see FIG. 1). Therefore, the rear lift generated in vehicle 100 can be eliminated.
When the left front wheel 72 (see FIG. 1) becomes the maximum load front wheel, the FL hydraulic pressure OP _FL is limited.

  With reference to FIG. 5, the procedure by which the brake ECU 6 controls the brake operating unit 9 when the rear lift is occurring will be described (see FIG. 1 as appropriate). The procedure shown in FIG. 5 is executed by the brake ECU 6 when the brake ECU 6 determines that a rear lift has occurred in the procedure shown in FIG. 2 during the ABS control.

When the brake ECU 6 detects the occurrence of the rear lift, it determines whether or not the vehicle 100 is turning (step S10).
When the difference between the wheel speed Vw of the left wheel (left front wheel 72, left rear wheel 74) and the wheel speed Vw of the right wheel (right front wheel 71, right rear wheel 73) is greater than or equal to a predetermined value in step S10, the brake ECU 6 It is determined that the vehicle is turning toward the slow side of the speed Vw. For example, when the wheel speed Vw of the right wheel (right front wheel 71, right rear wheel 73) is slower than the wheel speed Vw of the left wheel (left front wheel 72, left rear wheel 74), the brake ECU 6 causes the vehicle 100 to turn right. Is determined.

When the vehicle 100 is not turning (step S10 → No), the brake ECU 6 applies a load from the change in the wheel speed (front wheel speed Vwf) of the front wheels (the right front wheel 71 and the left front wheel 72) with respect to the MC hydraulic pressure. The front wheel, that is, the maximum load front wheel is determined (step S11). For example, map data indicating a standard change relationship between the change in MC hydraulic pressure and the front wheel speed Vwf of the front wheels (the right front wheel 71 and the left front wheel 72) on which a load is applied is set in advance and is stored in the brake ECU 6 (not shown). What is necessary is just to set it as the structure memorize | stored in a part. The brake ECU 6 can obtain a standard change in the wheel speed Vw _FR of the right front wheel 71 and the wheel speed Vw _FL of the left front wheel 72 corresponding to the change in the MC hydraulic pressure detected by the hydraulic sensor 5a with reference to the map. . And the front wheel which has the change of the front wheel speed Vwf near the standard change of the wheel speed Vw of the acquired wheel 7 can be determined as the maximum load front wheel.

  Then, the brake ECU 6 calculates the vehicle speed Vc of the vehicle 100 based on the front wheel speed Vwf of the maximum load front wheel (step S13), the calculated vehicle speed Vc, the road friction coefficient μr estimated in step S2 shown in FIG. To estimate the change in estimated vehicle speed. As a method for estimating a change in the estimated vehicle speed, a method widely used in conventional ABS control can be applied. Then, the brake ECU 6 controls the brake operation unit 9 according to the estimated vehicle speed (step S14).

  On the other hand, when the vehicle 100 is turning (step S10 → Yes), the brake ECU 6 sets the front wheel outside the turn as the maximum load front wheel (step S12). Then, the brake ECU 6 calculates the vehicle speed Vc of the vehicle 100 based on the front wheel speed Vwf of the front wheel with the maximum load (step S13), advances the procedure to step S14, and controls the brake operation unit 9.

As described above, the brake ECU 6 supplies the FR hydraulic pressure OP supplied to the FR brake operation unit 91 and the FL brake operation unit 92 (see FIG. 1) so that the vehicle 100 does not decelerate beyond the standard deceleration a _std in step S14. _FR and FL hydraulic pressure OP _FL is controlled.
In this embodiment, the brake ECU 6 is configured to determine the front wheel with the maximum load. Therefore, the brake ECU 6 functions as a load determination unit described in the claims.

For example, when the maximum load front wheel is the right front wheel 71 (see FIG. 1), the brake ECU 6 (see FIG. 1) sets the FR hydraulic pressure OP _FR and the FL hydraulic pressure OP _FL to a suitable position as shown in FIG. The hydraulic oil is supplied to the FR brake operation unit 91 (see FIG. 1) and the FL brake operation unit 92 (see FIG. 1) by changing the phase difference. At this time, the FR oil pressure OP _FR is limited so as not to exceed a preset limit value. Then, the wheel speed Vw _FR of the right front wheel 71 and the wheel speed Vw _FL of the left front wheel 72 are changed with a phase difference to generate a yaw moment in the vehicle 100 (see FIG. 1) to eliminate the rear lift.

As described above, the braking force control apparatus 1 (see FIG. 1) according to the present embodiment is configured such that the magnitude of the deceleration rate dVcr of the rear wheel-derived vehicle speed Vcr and the rear wheel hydraulic pressure during the ABS control by the brake ECU 6 (see FIG. 1). The occurrence of the rear lift can be determined based on the change in the rear wheel speed Vwr when OPr is depressurized and the size of the front and rear G generated in the vehicle 100 (see FIG. 1). When the rear lift occurs, the brake ECU 6 adjusts the FR hydraulic pressure OP _{FR of the} hydraulic oil supplied to the FR brake operation unit 91 and the FL hydraulic pressure OP _FL of the hydraulic oil supplied to the FL brake operation unit 92 to quickly perform the rear lift. This can be eliminated and the operation of the vehicle 100 can be stabilized.
Therefore, there is an excellent effect that the discomfort given to the driver by the rear lift can be preferably eliminated.

Further, when eliminating the rear lift, the brake ECU 6 (see FIG. 1) can use the logic for calculating the hydraulic pressure pattern of the FR hydraulic pressure OP _FR and the FL hydraulic pressure OP _FL by normal ABS control as it is, and eliminate the rear lift. Therefore, it is not necessary to newly provide logic for calculating the hydraulic pressure pattern. Therefore, the brake ECU 6 can be provided with a function of eliminating the rear lift without significantly increasing the design man-hour.

The present invention has been described above with the vehicle 100 (see FIG. 1), which is an FF vehicle, as an embodiment. However, the present invention can also be applied to an FR (Front engine Rear drive) vehicle.
In this case, the process of step S5 shown in FIG. 2 is changed. In the case of an FR vehicle, the right rear wheel 73 and the left rear wheel 74 (see FIG. 1) are driven by an engine (not shown). Therefore, when lift-up occurs, road resistance decreases and wheel speed Vw increases. Therefore, the deceleration rate dVcr of the rear wheel derived vehicle speed Vcr is smaller than the standard deceleration rate dV _std based on the MC hydraulic pressure.

Therefore, when the vehicle 100 (see FIG. 1) is an FR vehicle, the brake ECU 6 (see FIG. 1) determines that a rear lift has occurred when the deceleration rate dVcr is smaller than the standard deceleration rate dV _std in step S5 of FIG. To do. On the other hand, when the deceleration rate dVcr is equal to or greater than the standard deceleration rate dV _std , the brake ECU 6 determines that no rear lift has occurred.
In addition, the procedure shown in FIG. 2 and the procedure shown in FIG. 5 are the same as those of the FF vehicle, and the present invention can be applied to the FR vehicle.

The embodiment of the present invention has been described above, but the present invention can be appropriately modified within the scope of the invention.
For example, in step S10 in FIG. 5, the brake ECU 6 (see FIG. 1) determines turning of the vehicle 100 (see FIG. 1) based on the difference between the wheel speeds Vw of the left wheel and the right wheel. The configuration may be such that turning of the vehicle 100 is determined based on a detection value of a sensor SY (see FIG. 1) or a steering angle sensor (not shown).

  Further, for example, in step S4 of FIG. 2, the brake ECU 6 (see FIG. 1) calculates the pitching moment based on the gradient G, the longitudinal G of the vehicle 100 (see FIG. 1), and the maximum deceleration. The pitching moment may be directly detected by a sensor or the like.

1 Braking force control device 6 Brake ECU (Anti-lock brake control means, lift judgment means, load judgment means)
71 Right front wheel (front wheel)
72 Front left wheel (front wheel)
73 Right rear wheel (rear wheel)
74 Left rear wheel (rear wheel)
91 FR brake operation unit 92 FL brake operation unit 93 RR brake operation unit 94 RL brake operation unit 100 vehicle

Claims (6)

During the anti-lock brake control by the anti-lock brake control means, the lift determination means for determining the occurrence of lift up of the rear wheel of the vehicle,
The antilock brake control means includes:
A braking force control device that restricts a braking force applied to a front wheel of the vehicle when the lift determination means determines the occurrence of the lift-up.   The braking force control device according to claim 1, wherein the lift determination means determines the occurrence of the lift-up based on a change in wheel speed of the rear wheel during the antilock brake control.   The braking force control apparatus according to claim 1 or 2, wherein the lift determination means determines the occurrence of the lift-up based on a vehicle body momentum during the antilock brake control.   The lift determination means determines the occurrence of the lift-up when a pitching moment generated in the vehicle under the anti-lock brake control exceeds a preset threshold value. 4. The braking force control apparatus according to any one of 3 above. Load determining means for determining the maximum load front wheel to which the largest load is applied among the front wheels,
The anti-lock brake control means limits the braking force to be applied to the maximum load front wheel so that the braking force to be applied to the maximum load front wheel does not exceed a limit value more than the braking force to be applied to the other front wheels. The braking force control device according to any one of claims 1 to 4, wherein When the lift determination means determines the occurrence of the lift-up,
6. The anti-lock brake control means changes the braking force applied to the right front wheel of the vehicle by shifting a phase from the change of the braking force applied to the left front wheel of the vehicle. The braking force control apparatus according to any one of the above.

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