JP2005297771A - Braking force control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hardly feel early operation feeling that ABS operation is early by ABS operation at one brake system when anti-skid control is performed relative to first and second brake systems having the different feed forms of liquid pressure. <P>SOLUTION: When ABS is operated only at a front wheel (determination of step S31 and S32 is "Yes"), difference of target pressure and actual pressure of rear wheel wheel cylinders 3RL, 3RR is a predetermined value or more (determination of step S33 is "Yes") and a reservoir allowance amount is predetermined amount or more (processing of step S35 is "Yes"), driving of an ABS pump 11 is stopped (step S36). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle braking force control device that performs anti-skid control on first and second brake systems having different hydraulic supply modes.

Conventionally, for example, the hydraulic pressure from the master cylinder is supplied to the wheel cylinder of the front wheel in conjunction with the driver's brake operation, while the hydraulic pressure according to the driver's brake operation is supplied from a hydraulic pressure source different from the master cylinder. Some have been supplied to the wheel cylinder of the rear wheel to control the braking force (see Patent Document 1).
Japanese Patent No. 2653224

When the first brake system that mechanically generates the braking force and the second brake system that performs the braking force control as in the conventional example described above are compared, the response characteristic when the braking force is increased is 1 brake system is better. For this reason, when anti-skid control that detects the tendency of the wheels to lock during braking and controls the hydraulic pressure (hereinafter referred to as ABS operation) is performed on both brake systems, the anti-skid control is more effective than the second brake system. The brake system operates ABS earlier. Therefore, although the ABS operation of the second brake system is actually delayed, the increase in the braking force of the entire vehicle is insufficient by the response delay of the second brake system, so that the entire vehicle is controlled. The driver may feel that the ABS operation is fast due to the ABS operation of the first brake system with respect to the power, which may give a sense of discomfort. In anti-skid control, the hydraulic pressure extracted from the wheel cylinder is temporarily stored in a reservoir during decompression, and this hydraulic pressure is generally returned to the master cylinder by a pump. The hydraulic pressure is transferred to the master cylinder by the pump. The driver recognizes the ABS operation from the pedal kickback and the drive sound / vibration of the pump when returning.
Therefore, the present invention has been made paying attention to the above points, and when anti-skid control is performed on the first and second brake systems having different hydraulic supply modes, It is an object of the present invention to provide a braking force control device for a vehicle that can make it difficult to feel an early operation feeling that the ABS operation is fast due to the ABS operation.

  In order to solve the above-described problem, a vehicle braking force control device according to the present invention performs anti-skid control on the first and second brake systems having different hydraulic supply modes. If only one of the first and second brake systems detects a wheel locking tendency, the hydraulic pressure reduced by one brake system is moved to the hydraulic pressure supply side until the wheel locking tendency is detected by the other brake system. The returning pump is stopped.

  According to the vehicle braking force control device of the present invention, when a wheel locking tendency is detected by only one of the first and second brake systems, one of the other braking systems is detected until the wheel locking tendency is detected. By stopping the pump that returns the hydraulic pressure depressurized by the brake system to the hydraulic pressure supply side, it is possible to suppress the generation of pump drive noise and vibration, and the ABS operation is fast due to the ABS operation in one brake system. It is possible to make it difficult to feel the early feeling of operation. In addition, if the pump returns the hydraulic pressure of one brake system that has detected a locking tendency to the master cylinder that generates hydraulic pressure in conjunction with the driver's brake operation, the pedal kickback when the pump is driven Therefore, it is possible to reliably make it difficult to feel an early feeling of operation.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. The tandem master cylinder 2 that is interlocked with the operation of the brake pedal 1 supplies the hydraulic pressure corresponding to the pedaling force of the driver to the wheel cylinder 3FL for the left front wheel and the wheel cylinder 3FR for the right front wheel. Between the brake pedal 1 and the master cylinder 2, for example, a vacuum servo type brake booster 4 that boosts the pedal depression force by using the negative pressure of the engine is interposed. In addition, an ABS actuator 6 is interposed between the master cylinder 2 and the front wheel cylinders 3FL and 3FR. The ABS actuator 6 is driven and controlled by the controller 5 and can reduce, hold and increase the hydraulic pressure of the wheel cylinders 3FL and 3FR. Yes. On the other hand, the BBW actuator 7 capable of generating an arbitrary hydraulic pressure is driven and controlled by the controller 5 and supplies the hydraulic pressure corresponding to the driver's brake operation to the wheel cylinders 3RL and 3RR of the rear wheels. That is, the front wheel side is constituted by a hydraulic brake that generates a braking force by using hydraulic pressure as a transmission medium from the mechanical operation of the brake pedal 1 by the driver, and the one rear wheel side corresponds to the driver's brake operation. It is composed of brake-by-wire that performs braking force control.

The wheel cylinders 3FL to 3RR are incorporated in a disc brake that presses a disc rotor with a brake pad to generate a braking force and a drum brake that generates a braking force by pressing a brake shoe against the inner peripheral surface of the brake drum. .
As shown in FIG. 2, the ABS actuator 6 supplies the hydraulic pressure from the master cylinder 2 to the front wheel cylinders 3FL and 3FR and the hydraulic pressures of the normally open type pressure increase valves 8L and 8R and the front wheel cylinders 3FL and 3FR. The normally closed pressure reducing valves 9L and 9R for reducing pressure, the reservoirs 10L and 10R for temporarily storing the hydraulic pressure extracted from the front wheel cylinders 3FL and 3FR, and the hydraulic pressure stored in the reservoirs 10L and 10R for the master cylinder 2 And an ABS pump 11 to be returned. That is, when the pressure increasing valves 8L and 8R are opened and the pressure reducing valves 9L and 9R are closed, the hydraulic pressure of the front wheel cylinders 3FL and 3FR can be increased according to the driver's brake operation. Further, when both the pressure increasing valves 8L and 8R and the pressure reducing valves 9L and 9R are closed, the hydraulic pressure of the front wheel cylinders 3FL and 3FR can be maintained. Further, when the pressure increasing valves 8L and 8R are closed and the pressure reducing valves 9L and 9R are opened, the hydraulic pressure of the front wheel cylinders 3FL and 3FR can be reduced. 11 is returned to the master cylinder 2 side. Therefore, the controller 5 increases, holds, and reduces the hydraulic pressure of the front wheel cylinders 3FL and 3FR by driving and controlling the pressure increasing valves 8L and 8R, the pressure reducing valves 9L and 9R, and the ABS pump 11.

  For example, the BBW actuator 7 sucks brake fluid from the reservoir tank 2a of the master cylinder 2 and discharges it to the rear wheel cylinders 3RL and 3RR, and supplies the brake fluid from the reservoir tank 2a to the BBW pump 12. An open type suction valve 13 and a pressure reducing valve 14 for reducing the hydraulic pressure of the rear wheel cylinders 3RL and 3RR are configured. That is, when the suction valve 13 is opened, the pressure reducing valve 14 is closed, and the BBW pump 12 is driven, the hydraulic pressure of the rear wheel cylinders 3RL and 3RR can be increased. Further, when both the suction valve 13 and the pressure reducing valve 14 are closed, the hydraulic pressure of the rear wheel cylinders 3RL and 3RR can be maintained. Further, when the suction valve 13 is closed and the pressure reducing valve 14 is opened, the hydraulic pressure of the rear wheel cylinders 3RL and 3RR can be reduced. Therefore, the controller 5 increases, holds, and reduces the hydraulic pressures of the rear wheel cylinders 3RL and 3RR by driving and controlling the suction valve 13, the pressure reducing valve 14, and the BBW pump 12.

  The controller 5 detects the master cylinder pressure Pm detected by the pressure sensor 15, the front wheel wheel cylinder pressure Pf detected by the pressure sensor 16, the rear wheel wheel cylinder pressure Pr detected by the pressure sensor 17, and the wheel rotation sensor 18. Each wheel speed Vwi (i = FL, FR, RL, RR) is input, and the BBW control process of FIG. 3 for the rear wheels, the ABS control process of FIG. 4 for the front and rear wheels, and the pump drive stop of FIG. 5 for the front wheels Process.

First, the BBW control process executed by the controller 5 will be described based on the flowchart of FIG.
The BBW control process is executed as a timer interruption process every predetermined time (for example, 10 msec). First, in step S1, a front wheel braking force Ff is calculated from the master cylinder pressure Pm as shown in the following equation (1). Here, k1 is a coefficient.
Ff = k1 × Pm (1)
In the subsequent step S2, the vehicle braking force Ftotal is calculated according to the master cylinder pressure Pm as shown in the following equation (2).
Ftotal = f (Pm) (2)
In the subsequent step S3, as shown in the following equation (3), the front wheel braking force Ff is subtracted from the vehicle braking force Ftotal to calculate the rear wheel target braking force Fr.
Fr = Ftotal−Ff (3)
In the subsequent step S4, the rear wheel target braking force Fr is output to the BBW actuator 7 as a braking force command value, and then the routine returns to a predetermined main program.

Next, the ABS control process executed by the controller 5 will be described based on the flowchart of FIG.
The ABS control process is executed as a timer interrupt process for every predetermined time (for example, 10 msec). First, in step S11, the vehicle body speed V is estimated based on any of the select high, select second, average value, etc. of each wheel speed Vwi. Then, the slip ratio Si of each wheel is calculated according to the following equation (4).
Si = (V−Vwi) / V (4)
In subsequent step S12, it is determined whether or not each slip ratio Si is equal to or greater than a predetermined value Sa. When this determination result is Si <Sa, it is determined that there is no tendency to lock, and the process proceeds to step S13, where the ABS is deactivated and then returns to a predetermined main program.

On the other hand, when the determination result is Si ≧ Sa, it is determined that the wheel tends to be locked, and the process proceeds to step S14, where the difference between the actual slip ratio Si and the target slip ratio S ^* (for example, about 10%) is obtained. Accordingly, target values of the respective wheel cylinder pressures are calculated, and the ABS actuator 6 and the BBW actuator 7 are driven and controlled based on the target values, so that the ABS is brought into an operating state and then returns to a predetermined main program.

Next, the pump drive stop process executed by the controller 5 will be described based on the flowchart of FIG.
The pump drive stop process is executed as a timer interrupt process every predetermined time (for example, 10 msec). First, in step S31, it is determined whether or not the ABS is operating on the front wheels. If the ABS is not operating on the front wheels, the process returns to the predetermined main program. If the ABS is operating, the process proceeds to step S32.

In step S32, it is determined whether or not the rear wheel ABS is inactive. If the rear wheel ABS is operating, the process returns to the predetermined main program, and if the ABS is not operating, the process proceeds to step S33.
In step S33, whether or not the difference between the target pressure of the rear wheel wheel cylinder corresponding to the target braking force Fr and the actual pressure of the rear wheel wheel cylinder is greater than or equal to a predetermined value, that is, actual pressure−target pressure ≧ predetermined value (for example, 1 bar). If this difference is less than the predetermined value, the process returns to the predetermined main program, and if it is equal to or greater than the predetermined value, it is determined that the response characteristic when increasing the braking force of the rear wheel is delayed with respect to the front wheel, and the process proceeds to step S34. .

In step S34, a reservoir margin amount calculation process of FIG. 6 to be described later is executed to calculate the margin amounts of the reservoirs 10L and 10R that can store the hydraulic pressure extracted from the front wheel cylinders 3FL and 3FR.
In the subsequent step S35, it is determined whether or not the reservoir margin amount is greater than or equal to a predetermined value (for example, 50% to 80% or more). When the reservoir margin is less than the predetermined amount, the process returns to the predetermined main program, and when it is equal to or larger than the predetermined amount, the process proceeds to step S36.
In step S36, the ABS pump 11 is controlled to be in a drive stop state and then returned to a predetermined main program.

Next, the reservoir margin amount calculation process executed in step S34 will be described based on the flowchart of FIG.
First, in step S41, an inflow amount ΔVin from the front wheel cylinders 3FL and 3FR per unit time is calculated according to the front wheel cylinder pressure Pf with reference to the control map of FIG. This control map is set so that the inflow amount ΔVin increases at an increasing rate that gradually increases when the front wheel cylinder pressure Pf increases.

In subsequent step S42, the discharge amount ΔVout of the ABS pump 11 per unit time is calculated according to the pump rotation speed with reference to the control map of FIG. This control map is set so that the discharge amount ΔVout increases at a constant increase rate when the pump speed increases.
In the subsequent step S43, as shown in the following equation (5), an increase ΔVres in the liquid amount stored in the reservoirs 10L and 10R is calculated.
ΔVres = ΔVin−ΔVout (5)

In subsequent step S44, the current reservoir fluid amount Vres is calculated as shown in the following equation (6). Here, Vres _(n-1) is the amount of reservoir fluid before one sampling.
Vres = Vres _(n-1) + ΔVres (6)
In the subsequent step S45, as shown in the following equation (7), the reservoir margin amount Vt is calculated, and then the reservoir margin amount calculation process ends. Here, Vfull is the capacity of the reservoirs 10L and 10R.
Vt = Vfull-Vres (7)

  As described above, the brake pedal 1, the master cylinder 2, and the front wheel wheel cylinders 3FL and 3FR correspond to "one brake system", and the BBW control process of FIG. 3, the BBW actuator 7, and the rear wheel wheel cylinder 3RL.・ 3RR corresponds to “the other brake system”. Also, the ABS control process in FIG. 4 corresponds to “anti-skid control means”, and the pump drive stop process in FIG. 5 corresponds to “pump drive stop means”.

Next, the operation and effects of the one embodiment will be described.
Assuming that the driver suddenly performs a brake operation, the hydraulic pressure from the master cylinder 2 is supplied to the front wheel cylinders 3FL and 3FR in conjunction with the brake operation, and from the BBW actuator 7 corresponding to the brake operation. Is supplied to the wheel cylinders 3RL and 3RR of the rear wheels.

  At this time, on the rear wheel side where the braking force control is performed, the calculation of the target braking force Fr by the controller 5 and the drive control of the BBW actuator 7 corresponding to the target braking force Fr are performed. The response characteristic is delayed with respect to the front wheel side that mechanically generates a braking force. For this reason, when anti-skid control is performed on the brake systems of the front and rear wheels, the ABS operation of the front wheels is faster than the rear wheels. Therefore, although the ABS operation of the rear wheel is actually delayed, the increase in the braking force of the entire vehicle is insufficient by the response delay of the brake system of the rear wheel. This may cause the driver to feel that the ABS operation is fast due to the ABS operation of the front wheels, which may give a sense of discomfort. In this anti-skid control, the hydraulic pressure extracted from the front wheel cylinders 3FL and 3FR is temporarily stored in the reservoirs 10L and 10R during decompression, and this hydraulic pressure is returned to the master cylinder 2 by the ABS pump 11. Therefore, the driver recognizes the ABS operation from the pedal kickback when the hydraulic pressure is returned to the master cylinder 2 by the ABS pump 11 and the driving sound / vibration of the ABS pump 11.

  Therefore, the ABS operates only on the front wheels (both determinations in steps S31 and S32 are “Yes”), and the difference between the target pressure and the actual pressure in the rear wheel cylinders 3RL and 3RR is greater than or equal to a predetermined value (determination in step S33). If the reservoir margin amount is equal to or greater than the predetermined value ("Yes" in step S35), the driving of the ABS pump 11 is stopped (step S36). Thereby, since generation | occurrence | production of the drive sound and vibration of the ABS pump 11 can be suppressed, it can be made hard to feel the feeling of early operation that ABS operation is early by ABS operation of a front wheel.

  At this time, even if the driving of the ABS pump 11 is stopped, since the driving of the pressure increasing valves 8L and 8R and the pressure reducing valves 9L and 9R is continued, the pressure increasing valves 8L and 8R are closed to prevent an increase in the tendency to lock the front wheels. The anti-skid control effect can be secured. Further, since the hydraulic pressure extracted from the front wheel cylinders 3FL and 3FR cannot be returned to the master cylinder 2 by stopping the driving of the ABS pump 11, the ABS is operated on the rear wheels (determination in step S32 is “ The pressure of the front wheel cylinders 3FL and 3FR cannot be increased until "No", but the ABS of the rear wheel is activated within a very short time, so that the driver does not feel uncomfortable.

Further, since the ABS pump 11 is configured to return the hydraulic pressure of the front wheel cylinders 3FL and 3FR to the master cylinder 2 that generates hydraulic pressure in conjunction with the driver's brake operation, the pedal when the pump is driven Kickback can be eliminated, and it is possible to reliably make it difficult to feel an early feeling of operation.
Further, when the difference between the target pressure and the actual pressure of the rear wheel cylinders 3RL and 3RR is less than a predetermined value (determination in step S33 is “No”), the operation delay of the rear wheel ABS causes the braking force to increase. Judging that the response delay is not the cause, the pump drive by the anti-skid control is permitted. As a result, when the ABS operates properly, such as when the operation of the rear wheel ABS is delayed because the road surface friction coefficient on the front wheel side is lower than that on the rear wheel side, the ABS operation is made to be recognized by the driver. You can call attention.

  Further, when the reservoir margin is less than the predetermined amount (the process of step S35 is “No”), it is determined that sufficient pressure cannot be reduced even if the pressure reducing valves 9L and 9R are opened, and the pump driving by the anti-skid control is permitted. To do. As a result, the hydraulic pressure stored in the reservoirs 10L and 10R can be returned to the master cylinder 2 to increase the reservoir margin, so that a large pressure reduction is required when shifting from a road surface with a high friction coefficient to a road surface with a low friction coefficient. A sufficient decompression allowance can be ensured for when it is done.

  In the above embodiment, in step S33, when the difference between the target pressure and the actual pressure of the rear wheel cylinders 3RL and 3RR is greater than or equal to a predetermined value, the response when the braking force of the rear wheel is increased. Although it is determined that the characteristics are delayed with respect to the front wheels, the present invention is not limited to this. It is considered that the response delay when the braking force is increased becomes more conspicuous as the driver's brake operation becomes steeper. Therefore, the process of step S33 of FIG. 5 is changed to the process of step S53 for determining whether or not the brake operation is abrupt based on the speed and acceleration of the brake operation, as shown in FIG. When it is determined that the braking operation is sudden, it is determined that the response characteristic when the braking force of the rear wheel is increased is delayed with respect to the front wheel, and the driving of the ABS pump 11 is stopped. Good.

  Further, in the above-described embodiment, the process of just stopping the driving of the ABS pump 11 is performed in the process of step S36, but the present invention is not limited to this. As described above, when the reservoir margin is less than the predetermined amount, it is determined that sufficient pressure reduction cannot be performed even if the pressure reducing valves 9L and 9R are opened, and pump driving by anti-skid control must be allowed. Therefore, in order to prevent the reservoir margin from becoming less than the predetermined value, the processing of step S36 in FIG. 5 is stopped, as shown in FIG. 10, the driving of the ABS pump 11 is stopped and the pressure reducing valves 9L and 9R are closed. Thus, the pressure reduction control amount may be changed to step S56 so as to limit the pressure reduction of the rear wheel cylinders 3RL and 3RR. As a result, the frequency of allowing the pump to be driven can be reduced, making it difficult to feel an early feeling of operation. In addition, the holding control may be performed for the amount in which the pressure reduction control amount is limited in step S56.

  In the above embodiment, the BBW actuator 7 supplies an arbitrary hydraulic pressure to the rear wheel cylinders 3RL and 3RR to perform the braking force control. However, the present invention is not limited to this. For example, the electric actuator And an electric brake that clamps the disk rotor with a brake pad (or presses a brake shoe against the inner peripheral surface of the brake drum). In short, since it is only necessary to be able to control the braking force of the rear wheels by brake-by-wire, any brake may be used as long as it has an electronically controllable energy source.

  Further, in the above-described embodiment, the front and rear wheels include a brake system that mechanically generates a braking force in conjunction with a driver's brake operation, and a brake system that performs a braking force control according to the driver's brake operation. Although the front and rear division method for dividing is adopted, the present invention is not limited to this, and an X division method for dividing the left front wheel and the right rear wheel and the right front wheel and the left rear wheel may be adopted. Of course, the divided brake systems can be interchanged. Further, the ABS actuator 6 and the BBW actuator 7 may be integrated.

Moreover, as long as response delay occurs in a plurality of brake systems, the embodiment is not limited, and a hybrid brake system of a mechanical brake and a by-wire brake is not necessarily required.
In the above embodiment, the front wheel braking force Ff and the vehicle braking force Ftotal are calculated according to the master cylinder pressure Pm. However, the present invention is not limited to this, and is detected from the operation amount of the brake pedal 1. May be. Further, the rear wheel target braking force Fr is calculated by subtracting the front wheel braking force Ff from the vehicle braking force Ftotal. However, the present invention is not limited to this, and may be calculated according to the driver's brake operation. It may be calculated from the cylinder pressure Pm or the operation amount (stroke or pedaling force) of the brake pedal 1.

It is a schematic structure figure showing an embodiment of the present invention. It is a hydraulic circuit of an ABS actuator and a BBW actuator. It is a flowchart which shows a BBW control process. It is a flowchart which shows an ABS control process. It is a flowchart which shows a pump drive stop process. It is a flowchart which shows a reservoir margin amount calculation process. It is a control map used for calculation of inflow amount (DELTA) Vin. It is a control map used for calculation of discharge amount (DELTA) Vout. It is a flowchart which shows another example of a pump drive stop process. It is a flowchart which shows another example of a pump drive stop process.

Explanation of symbols

1 Brake Pedal 2 Master Cylinder 2a Reservoir Tank 3FL / 3FR Front Wheel Cylinder 3RL / 3RR Rear Wheel Wheel Cylinder 4 Brake Booster 5 Controller 6 ABS Actuator 7 BBW Actuator 8L / 8R Booster Valve 9L / 9R Pressure Reducer Valve 10L / 10R Reservoir 11 ABS Pump 12 BBW pump 13 Suction valve 14 Pressure reducing valve 15, 16, 17 Pressure sensor 18 Wheel rotation sensor

Claims (7)

The first and second brake systems having different hydraulic supply modes, and anti-skid control for controlling the hydraulic pressure by detecting the tendency of the wheels to lock during braking are applied to the first and second brake systems. An anti-skid control means for performing a braking force control device for a vehicle,
When the anti-skid control means has a pump that detects the tendency of the wheel to be locked only in one of the first and second brake systems and returns the hydraulic pressure reduced by the one brake system to the hydraulic pressure supply side, A vehicular braking force control device comprising pump drive stopping means for stopping driving of the pump by the anti-skid control means until a wheel locking tendency is detected in the other brake system.   The vehicle according to claim 1, wherein the pump is configured to return the hydraulic pressure of the one brake system to a master cylinder side that generates hydraulic pressure in conjunction with a driver's brake operation. Braking force control device.   The pump driving stop means stops the driving of the pump by the anti-skid control means when a response characteristic when the braking force is increased in the other brake system is delayed with respect to the one brake system. The braking force control apparatus for vehicles according to claim 1 or 2 characterized by things.   The pump drive stopping means determines that the response characteristic when the braking force is increased in the other brake system is delayed with respect to the one brake system when a sudden braking operation of the driver is detected. The vehicular braking force control apparatus according to claim 3. The anti-skid control means includes a reservoir for storing a hydraulic pressure when the one brake system is decompressed,
5. The pump drive stop means stops drive of the pump by the anti-skid control means when the capacity of the reservoir is greater than or equal to a predetermined amount. 6. Vehicle braking force control apparatus.   The anti-skid control means limits pressure reduction of the one brake system while the pump drive is stopped by the pump drive stop means. The braking force control apparatus for vehicles as described.   The vehicular braking force control apparatus according to claim 6, wherein the anti-skid control means limits the pressure reduction of the one brake system by holding and controlling the hydraulic pressure of the one brake system.

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