JP2013180629A - Brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake control device capable of effectively utilizing the braking force of rear wheels while suppressing the lock of the rear wheels.SOLUTION: An ABS (antilock brake system) actuator 9 is controlled in EBD (electronic brake force distribution) control to cause a rise in wheel cylinder hydraulic pressure of brakes 3RL, 3RR of rear wheels 2RL, 2RR with the lapse of time during a transient state until a load applied to the rear wheels 2RL, 2RR becomes steady. Braking force applied to the rear wheels 2RL, 2RR is thereby kept relatively small at the beginning of the transient state of the load applied to the rear wheels 2RL, 2RR, and braking force applied to the rear wheels 2RL, 2RR rises toward the steady state from the transient state of rear load application. As a result, braking force applied to the rear wheels 2RL, 2RR can be effectively utilized while suppressing the lock of the rear wheels 2RL, 2RR.

Description

  The present invention relates to a vehicle brake control device.

  In a vehicle such as an automobile, if the wheels are locked by a brake, the posture of the vehicle body becomes unstable, and it becomes difficult to control the direction of the vehicle by a steering operation.

  Therefore, recent vehicles are provided with an ABS actuator having a built-in valve or the like for controlling the hydraulic pressure of the wheel cylinder of each wheel brake (wheel cylinder hydraulic pressure). In order to prevent the rear wheels from being locked, EBD (Electronic Brake force Distribution) control by the ABS actuator and in order to prevent each wheel from being locked, ABS (Antilock Brake System) control by the ABS actuator are performed.

  For example, when the brake is operated, the load moves forward of the vehicle, the load applied to the front wheels (front load) increases, and the load applied to the rear wheels (rear load) decreases. Therefore, the braking force (rear braking force) applied to the rear wheel tends to exceed the rear load, and when the rear braking force exceeds the rear load, the rear wheel is locked. Therefore, before the rear braking force exceeds the rear load, EBD control for preventing the rear wheels from being locked is performed, and the distribution of the braking force to the front wheels and the rear wheels is changed, so that the wheel cylinder of the rear wheel brake is changed. Increase in hydraulic pressure is suppressed.

Japanese Patent No. 4244454

  FIG. 4 is a graph showing temporal changes in the rear load and the rear braking force during a brake operation.

  At the time of a sudden braking operation in which the brake pedal is strongly depressed instantaneously, as shown by a solid line in FIG. 4, the rear braking force increases sharply, and the rear load is changed from the initial load A to the minimum load B by forward load movement. Steeply decreases. Thereafter, the rear load passes through a transient state that repeatedly increases and decreases with the vibration of the vehicle body by the spring system, and becomes a steady state that is substantially unchanged at a stable load C that is smaller than the initial load A and larger than the minimum load B.

  After the rear load reaches a steady state, the rear wheels do not lock even if the rear braking force is increased to the vicinity of the stable load C. However, the EBD control is started before the rear braking force exceeds the minimum load B in order to prevent the rear wheel from being locked at the initial stage of the sudden braking operation, that is, when the rear load is in a transient state. Therefore, in conventional vehicles, it cannot be said that the rear braking force is effectively utilized during a sudden braking operation.

  An object of the present invention is to provide a brake control device that can effectively use the braking force of the rear wheel while suppressing the locking of the rear wheel.

  In order to achieve the above object, a brake control device according to the present invention includes a master cylinder, a brake that is provided on each wheel of the front wheel and the rear wheel, and applies a braking force to the wheel by hydraulic pressure of the wheel cylinder, The present invention is applied to a vehicle including an ABS actuator that distributes the hydraulic pressure of the master cylinder to each wheel cylinder. When the braking force of the brake is applied to the wheel and the load applied to the rear wheel is in a transient state where the brake control device repeatedly increases and decreases, the brake control device is configured to reduce the fluid in the wheel cylinder of the brake provided on the rear wheel. EBD control means for controlling the ABS actuator so that the pressure increases with time.

  A brake is provided on each of the front wheel and the rear wheel. The hydraulic pressure in the master cylinder is distributed to the wheel cylinders of each brake by the ABS actuator. A braking force is applied from the brake to the wheel by the hydraulic pressure of the wheel cylinder of the brake.

  When the braking force of the brake is applied to the wheel and the load (rear load) applied to the rear wheel is in a transient state where the increase and decrease repeats, the brake provided on the rear wheel over time is controlled by the ABS actuator. The hydraulic pressure of the wheel cylinder is increased. Thereby, at the initial stage of the transient state, the braking force (rear braking force) of the rear wheels is suppressed to be relatively small, and the rear braking force increases as the rear-weighted transient state approaches the steady state. As a result, the rear braking force can be effectively utilized while the rear wheel lock can be suppressed.

  In addition, since the rear braking force can be used effectively, the load on the brakes of the front wheels can be reduced throughout the traveling of the vehicle. As a result, the temperature rise of the front wheel brake can be suppressed, so that the occurrence of a fade phenomenon of the front wheel brake can be suppressed. In addition, the service life of the front wheel brake can be extended.

  The brake control device may include a hydraulic pressure detection unit that detects the hydraulic pressure of the master cylinder. In this case, the EBD control means may control the ABS actuator based on the hydraulic pressure detected by the hydraulic pressure detection means.

  According to the present invention, it is possible to effectively utilize the braking force of the rear wheel while suppressing the locking of the rear wheel. As a result, the braking distance of the vehicle can be shortened.

FIG. 1 is a diagram schematically showing a configuration of a brake control device according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of processing executed during EBD control. FIG. 3 is a graph showing changes over time in the load applied to the rear wheel and the braking force applied to the rear wheel during a brake operation. FIG. 4 is a graph showing temporal changes in the rear load and the rear braking force during a brake operation in a conventional vehicle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing a configuration of a brake control device according to an embodiment of the present invention.

  The brake control device 1 is applied to a vehicle including four wheels, that is, left and right front wheels 2FL and 2FR and left and right rear wheels 2RL and 2RR.

  The wheels 2FL, 2FR, 2RL, 2RR are provided with brakes 3FL, 3FR, 3RL, 3RR, respectively. The brakes 3FL, 3FR, 3RL, and 3RR include wheel cylinders 4FL, 4FR, 4RL, and 4RR, respectively. Each wheel 2FL, 2FR, 2RL, 2RR is provided with a wheel speed sensor 5FL, 5FR, 5RL, 5RR for detecting the rotational speed.

  A brake pedal 6 that is operated by a driver's foot is provided in the vehicle interior of the vehicle. The brake pedal 6 is connected to a brake booster 8 provided integrally with the master cylinder 7.

  When the brake pedal 6 is depressed, the pedaling force input to the brake pedal 6 is transmitted to the brake booster 8. The pedaling force transmitted to the brake booster 8 is amplified (boosted) by the action of the brake booster 8 and input from the brake booster 8 to the master cylinder 7. In the master cylinder 7, a hydraulic pressure (master cylinder hydraulic pressure) Pm corresponding to the force (amplified pedaling force) input from the brake booster 8 is generated.

  The master cylinder hydraulic pressure Pm is transmitted to the ABS actuator 9. The ABS actuator 9 incorporates a valve for controlling the hydraulic pressure of each wheel cylinder 4FL, 4FR, 4RL, 4RR, a pump for returning the brake fluid to the master cylinder 7, and the like. The hydraulic pressure transmitted from the master cylinder 7 to the ABS actuator 9 is distributed and transmitted to the wheel cylinders 4FL, 4FR, 4RL, 4RR. A braking force is applied from the brakes 3FL, 3FR, 3RL, 3RR to the wheels 2FL, 2FR, 2RL, 2RR by the hydraulic pressures of the wheel cylinders 4FL, 4FR, 4RL, 4RR (wheel cylinder hydraulic pressure).

  In order to control the ABS actuator 9, an ABS-ECU 11 including a CPU and a memory is provided.

  Wheel speed sensors 5FL, 5FR, 5RL, and 5RR are connected to the ABS-ECU 11, and detection signals of the wheel speed sensors 5FL, 5FR, 5RL, and 5RR are input. The ABS-ECU 11 is connected to a master cylinder hydraulic pressure sensor 12 for detecting the master cylinder hydraulic pressure Pm, and a detection signal from the master cylinder hydraulic pressure sensor 12 is inputted.

The ABS-ECU 11 controls the ABS actuator 9 based on the detection signals of the wheel speed sensors 5FL, 5FR, 5RL, 5RR and the detection signal of the master cylinder hydraulic pressure sensor 12, thereby performing ABS (Antilock Brake System) control and EBD. (Electronic
Brake force distribution) control is realized.

When the vehicle is braked (when the brakes 3FL, 3FR, 3RL, 3RR are actuated), load movement occurs ahead of the vehicle, and the load applied to the front wheels 2FL, 2FR (hereinafter referred to as “front load”).
) And the load applied to the rear wheels 2RL and 2RR (hereinafter referred to as “rear load”) Pr decreases. Therefore, the rear wheels 2RL and 2RR are easier to lock than the front wheels 2FL and 2FR.

  If the condition that the rear wheels 2RL and 2RR are locked is established during braking of the vehicle, the EBD control is performed. In the EBD control, the ABS actuator 9 is controlled by the ABS-ECU 11, and the wheel cylinder hydraulic pressures of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR, which are light loads, become the wheel cylinder fluids of the brakes 3FL and 3FR of the front wheels 2FL and 2FR. The distribution of the hydraulic pressure to each wheel cylinder 4FL, 4FR, 4RL, 4RR is changed so as to be kept lower than the pressure. This prevents the rear wheels 2RL and 2RR from being locked.

  Then, during the EBD control, when a condition that any one of the wheels 2FL, 2FR, 2RL, and 2RR is locked is established, the EBD control is terminated and the ABS control is performed. In the ABS control, the ABS actuator 9 is controlled by the ABS-ECU 11 so that the wheel slip ratios of the wheels 2FL, 2FR, 2RL, and 2RR are equal to or less than a threshold value. The distribution of hydraulic pressure is changed. Thereby, the lock | rock of wheel 2FL, 2FR, 2RL, 2RR can be prevented.

  The wheel slip ratio is calculated by the ABS-ECU 11 based on detection signals from the wheel speed sensors 5FL, 5FR, 5RL, and 5RR. That is, based on detection signals from the wheel speed sensors 5FL, 5FR, 5RL, and 5RR, first, the wheel speeds of the wheels 2FL, 2FR, 2RL, and 2RR are calculated. Further, the vehicle body speed of the vehicle is estimated by calculation based on the average value of the wheel speeds. Then, for each of the wheels 2FL, 2FR, 2RL, and 2RR, a value obtained by subtracting the wheel speed from the vehicle body speed is divided on the vehicle body side, so that a wheel slip ratio (= (vehicle body speed−wheel speed) / vehicle body speed). ) Is calculated.

  FIG. 2 is a flowchart showing the flow of processing executed during EBD control.

  When the EBD control is started, the ABS-ECU 11 executes the process shown in FIG.

  First, the master cylinder hydraulic pressure Pm is acquired based on the detection signal of the master cylinder hydraulic pressure sensor 12 (step S1).

  Next, the change speed (hydraulic pressure change speed) dPm / dt of the master cylinder hydraulic pressure is obtained by differential calculation of the master cylinder hydraulic pressure (step S2).

  Thereafter, the rear load Pr that changes transiently by the operation of the brakes 3FL, 3FR, 3RL, 3RR is calculated (step S3). The rear load Pr is obtained by multiplying a function f (Pm, dPm / dt) having parameters of the master cylinder hydraulic pressure Pm and the hydraulic pressure change rate dPm / dt by sin ωt and a damping amount g (t) with time. Decrease rate r (t) over time from the value obtained by subtracting or multiplying sin ωt by the function f (Pm, dPm / dt) having the master cylinder hydraulic pressure Pm and the hydraulic pressure change rate dPm / dt as parameters. By multiplying, it can be calculated as an approximate value. That is, the rear load Pr that changes transiently by the operation of the brakes 3FL, 3FR, 3RL, and 3RR can be calculated as an approximate value according to either the following formula (1) or formula (2).

    Pr = f (Pm, dPm / dt) · sin ωt−g (t) (1)

    Pr = f (Pm, dPm / dt) · sin ωt · r (t) (2)

  Thereafter, it is determined whether or not the minimum value of the rear load Pr accompanying the change with time is detected (step S4). Steps S1 to S3 are repeated until the minimum value of the rear load Pr is detected, and the rear load Pr is repeatedly calculated.

  When the minimum value of the rear load Pr is detected (YES in step S4), the wheel cylinder hydraulic pressures of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR are increased by a predetermined pressure (step S5).

  Subsequently, it is determined whether or not the EBD control is finished (step S6). If the EBD control is not finished, the processes of steps S1 to S5 are executed again.

  When the foot is released from the brake pedal 6 or the ABS control start condition is satisfied, the EBD control ends. When the EBD control is finished (YES in step S6), the process shown in FIG. 2 is finished.

  FIG. 3 is a graph showing changes over time in the load applied to the rear wheel and the braking force applied to the rear wheel during a brake operation.

  During braking, the braking force (hereinafter referred to as “rear braking force”) applied to the rear wheels 2RL and 2RR increases, and the rear load Pr changes from the initial load A to the minimum load B due to forward load movement in the vehicle. Decrease to. After that, the rear load Pr becomes a steady state that does not substantially change with the stable load C through a transient state that repeatedly increases and decreases with the vibration of the vehicle body by a spring system such as a suspension spring.

  When the brake is operated, EBD control is started before the rear braking force exceeds the minimum load B in order to prevent the rear wheels 2RL and 2RR from being locked. Thereafter, when the rear load Pr takes a minimum value, in response to this, the wheel cylinder hydraulic pressure of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR is increased by a predetermined pressure, thereby increasing the rear braking force by one step. . Thereafter, when the rear load Pr takes a minimum value, the brake cylinder 3RL of the rear wheels 2RL and 2RR and the wheel cylinder hydraulic pressure of the 3RR are increased by a predetermined pressure in response to this, thereby increasing the rear braking force by one step. To do.

  Thus, in the EBD control, the ABS actuator 9 is controlled so that the wheel cylinder hydraulic pressure of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR increases with time until the rear load Pr becomes a steady state. Is done. Thereby, at the initial stage of the transient state of the rear load Pr, the rear braking force is relatively small, and the rear braking force increases as the rear load transient state approaches the steady state. As a result, the rear braking force can be effectively utilized while the locking of the rear wheels 2RL and 2RR can be suppressed.

  In addition, since the rear braking force can be used effectively, the load on the brakes 3FL and 3FR of the front wheels 2FL and 2FR can be reduced throughout the traveling of the vehicle. As a result, the temperature rise of the brakes 3FL and 3FR can be suppressed, so that the fade phenomenon of the brakes 3FL and 3FR can be suppressed. Further, the service life of the brakes 3FL and 3FR of the front wheels 2FL and 2FR can be extended.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  In the above-described embodiment, when the rear load Pr is approximately calculated and the minimum value of the rear load Pr is detected, the wheel cylinder hydraulic pressure of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR is increased by a predetermined pressure. Was taken up.

  However, not limited to this method, the operating states of the brakes 3FL, 3FR, 3RL, 3RR are divided into two or more states, and the transient state of the rear load Pr is investigated for each of these states. Based on this, A map that defines the relationship between the time in EBD control and the wheel cylinder hydraulic pressures of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR may be created. A map for each state is stored in the memory. In the EBD control, a map corresponding to the operating state of the brakes 3FL, 3FR, 3RL, 3RR is referred to, and the brakes of the rear wheels 2RL, 2RR corresponding to the passage of time are referred to. The ABS actuator 9 may be controlled so that wheel cylinder hydraulic pressures of 3RL and 3RR can be obtained.

  For example, the operating states of the brakes 3FL, 3FR, 3RL, 3RR may be divided into a first brake state, a second brake state, a third brake state, and a fourth brake state. If the master cylinder hydraulic pressure is less than the first hydraulic pressure threshold and the hydraulic pressure change speed is less than the first speed threshold when the brake pedal 6 is operated, the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the first. It is determined that the vehicle is in a brake state. The master cylinder hydraulic pressure is less than a second hydraulic pressure threshold greater than the first hydraulic pressure threshold, and the hydraulic pressure change speed is less than a second speed threshold greater than the first speed threshold, and the master cylinder hydraulic pressure is the first hydraulic pressure. If it is less than the threshold and the hydraulic pressure change speed is not less than the first speed threshold, it is determined that the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the second brake state. The master cylinder hydraulic pressure is less than a third hydraulic pressure threshold greater than the second hydraulic pressure threshold, and the hydraulic pressure change speed is less than a third speed threshold greater than the second speed threshold, and the master cylinder hydraulic pressure is less than the second hydraulic pressure. If it is less than the threshold and the hydraulic pressure change speed is not less than the second speed threshold, it is determined that the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the third brake state. The master cylinder hydraulic pressure must be greater than or equal to the third hydraulic pressure threshold or the hydraulic pressure change speed must be greater than or equal to the third speed threshold, the master cylinder hydraulic pressure must be less than the third hydraulic pressure threshold, and the hydraulic pressure change speed must be less than the third speed threshold. For example, it is determined that the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the fourth brake state.

  Then, when the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the first brake state, the first map is referred to and according to the gradual change of the rear load Pr compared to the second brake state, When the wheel cylinder hydraulic pressure of the brakes 3RL, 3RR of the rear wheels 2RL, 2RR is increased and the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the second brake state, the second map is referred to and the third brake In comparison with the state, the wheel cylinder hydraulic pressure of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR is increased in response to a gradual change in the rear load Pr, and the operating state of the brakes 3FL, 3FR, 3RL and 3RR is the third. When the vehicle is in the brake state, the third map is referred to and responds to a gradual change in the rear load Pr as compared with the fourth brake state. When the wheel cylinder hydraulic pressure of the brakes 3RL, 3RR of the rear wheels 2RL, 2RR is increased and the operating state of the brakes 3FL, 3FR, 3RL, 3RR is the fourth brake state, the fourth map is referred to, and the rear load The wheel cylinder hydraulic pressure of the brakes 3RL and 3RR of the rear wheels 2RL and 2RR may be increased in accordance with the change of Pr.

  Further, although the rear load Pr is approximately calculated, for example, the vehicle is provided with a vehicle height sensor that detects the vertical displacement of the vehicle body, and the rear load Pr is calculated based on the detection signal of the vehicle height sensor. It may be estimated.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1 Brake Control Device 2FL Front Wheel 2FR Front Wheel 2RL Rear Wheel 2RR Rear Wheel 3FL Brake 3FR Brake 3RL Brake 3RR Brake 4FL Wheel Cylinder 4FR Wheel Cylinder 4RL Wheel Cylinder 4RR Wheel Cylinder 7 Master Cylinder 9 ABS Actuator 11 ABS Control Unit 11B
12 Master cylinder hydraulic pressure sensor (hydraulic pressure detection means)

Claims (2)

A master cylinder, a brake provided on each wheel of the front wheel and the rear wheel, and applying a braking force to the wheel by the hydraulic pressure of the wheel cylinder; and an ABS actuator for distributing the hydraulic pressure of the master cylinder to the wheel cylinders A brake control device applied to a vehicle comprising:
When the braking force of the brake is applied to the wheel and the load applied to the rear wheel is in a transient state where the increase and decrease repeats, the hydraulic pressure of the wheel cylinder of the brake provided on the rear wheel increases with time. The brake control device includes an EBD control means for controlling the ABS actuator so as to rise. A fluid pressure detecting means for detecting fluid pressure of the master cylinder;
The brake control device according to claim 1, wherein the EBD control unit controls the ABS actuator based on a hydraulic pressure detected by the hydraulic pressure detection unit.

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