JP4314994B2 - Vehicle braking force control device - Google Patents

Description

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

  A conventional vehicle braking force control device is described in, for example, Patent Document 1 below. In this device, when braking the vehicle, ABS (anti-skid brake system) control for controlling the brake pressure of each brake device to be reduced, held or increased so that the slip rate of each wheel converges to the target slip rate; 2. Description of the Related Art In a braking control device having a control unit that performs EBD (Electronically Controlled Braking Force Distribution System) control that restricts an increase in brake pressure on the left and right rear wheels of a vehicle, the braking force of the rear wheels is conventionally controlled by EBD control and ABS control. The braking distance is shortened by cooperating so as to increase.

  In the conventional vehicle braking force control device, when the increase in the brake pressure of the left and right rear wheels is restricted by EBD control, and when the rear wheel ABS control is executed, the rear wheel is corrected by correcting the EBD control. The degree of regulation of increase in brake pressure is relaxed.

Further, in the conventional vehicle braking force control device, the ABS control is performed when it is detected that the parking brake device is in a braking state or the vehicle is traveling on a low μ road surface during the execution of the EBD control. Since the driving situation is easy to break, the value of the set deceleration in the EBD control is increased to relax the degree of restriction of the increase in braking force by the EBD control in advance.
JP 11-192930 A

  However, in the conventional vehicle braking force control device, there is a case where the braking force cannot be improved when the EBD control for preventing the rear wheel from being locked and the operation of the parking brake overlap. For example, when a parking brake is activated while the vehicle is running, a wheel slip occurs, so that EBD control may be executed and sufficient braking force may not be obtained.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a vehicle braking force control device capable of improving the braking force.

In order to solve the above-described problem, the vehicle braking force control device according to the present invention is configured to determine that the EBD control start permission condition for preventing an increase in the braking force of the rear wheels and the fact that the brake pedal has been depressed. Brake pedal detection means for detecting, operation detection means for detecting the operation of a parking brake connected to the braking device of each wheel via a hydraulic path, and control means for performing or prohibiting the EBD control, (A) The determination means permits the start of the EBD control, the brake pedal detection means detects that the brake pedal is not depressed, and the operation detection means parks the vehicle while traveling. When the brake operation is detected, the EBD control is prohibited, and (B) the start of the EBD control is permitted by the determination means, and the brake That the brake pedal is depressed it is detected by the pedal detection unit, and, when the parking brake actuation is detected during the vehicle running by the operation detecting means, and performs the EBD control.

  In EBD control, it is possible to prevent the rear wheels from being locked by suppressing an increase in braking force by adjusting the brake fluid pressure. According to the vehicle braking force control device of the present invention, the start of the EBD control is permitted by the determination means, and when the parking brake operation is detected by the operation detection means when performing the EBD control, the EBD control is prohibited. By doing so, the braking force can be increased.

  Further, the determining means is characterized in that the EBD start permission condition is satisfied when the ratio of the slip ratio of the rear wheel to the slip ratio of the front wheel becomes larger than a predetermined value. That is, when the slip ratio of the rear wheel becomes relatively large, this can be set as a condition for starting the EBD control.

  According to the vehicle braking force control apparatus of the present invention, the braking force can be improved.

  Hereinafter, a vehicle braking force control apparatus according to an embodiment will be described. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted.

FIG. 1A is a block diagram of a vehicle provided with a vehicle braking force control apparatus according to the embodiment, and FIG. 1B is a hydraulic control valve mechanism A (= A shown in FIG. 1A. _(FL , _AFR , _ARL , _ARR ).

This vehicle includes two front wheels W _FL and W _FR attached to the vehicle body, and two rear wheels W _RL and W _RR . Foil cylinders H (= H _FL , H _FR , H _RL , H _RR ) are respectively attached to the wheels W _FL , W _FR , W _RL , W _RR (braking devices). Each wheel cylinder H _FL , H _FR , H _RL , H _RR drives the brake shoes BS _FL , BS _FR , BS _RL , BS _RR . The wheel cylinders H _FL , H _FR , H _RL , H _RR are connected to the master cylinder M through a hydraulic path. A brake pedal BP is linked to the piston of the master cylinder M.

When the brake pedal BP is depressed, the hydraulic pressure in the master cylinder M increases, and in principle, the master cylinder pressure is transmitted to the wheel cylinders H _FL , H _FR , H _RL , H _RR via the hydraulic path. This hydraulic path is composed of X-shaped piping, and there is a hydraulic path OP1 of one system corresponding to the wheel cylinders _HFR , _HRL of the right front wheel and the left rear wheel, and the wheel of the left front wheel and the right rear wheel Corresponding to the cylinders H _FL and H _RR , there is a hydraulic path OP2 of another system, and these hydraulic paths OP1 and OP2 intersect with the X type.

A first root valve _VROOT1 is provided on the upstream side of the master cylinder M and one hydraulic path (hydraulic path including the right front wheel and left rear wheel wheel cylinders HFR, HRL) OP1. (Wheel cylinders _H FL of the left front wheel and right rear _wheel, a hydraulic passage including _{H RR)} master cylinder M and the other hydraulic pressure passage on the upstream side of the OP2 is the second root valve _{V Root2} is provided. A route for transmitting the master cylinder pressure to the wheel cylinder without passing through the root valve is also set separately.

  Brake fluid (oil) from the end valves VAL1, VAL2 and the reservoir tank RS for increasing, holding, and reducing pressure during ABS (anti-lock braking system) control is provided at the end of the hydraulic path OP1 of each wheel. Is provided with a suction valve VAL3 for controlling supply in the hydraulic path to the end valve.

  The hydraulic control valve mechanism A is driven by a hydraulic path 201 that connects the master cylinder M and the wheel cylinder H, a hydraulic path 203 that pumps brake fluid to the end valve VAL1 for holding hydraulic pressure, a motor 50, and the motor 50. The hydraulic pressure pump 51, the hydraulic pressure path 203 connecting the hydraulic pressure pump 51 and the hydraulic pressure path 201, the check valve 253 interposed in the hydraulic pressure path, the hydraulic pressure path 202 for guiding the wheel cylinder pressure to the reservoir 40 via the hydraulic pressure path 201. , A pressure reducing terminal valve VAL2 provided in the hydraulic path 202, a hydraulic path 204 connecting the reservoir 40 and the hydraulic pump 51, and check valves 251 and 252 provided in the hydraulic path 204 are provided.

  The master cylinder M is provided with a reservoir tank RS for containing the brake fluid. From the reservoir tank RS, a hydraulic pump pumps the brake fluid by driving the motor 50, and the hydraulic path 203, The hydraulic pressure P is supplied into 201 (OP1, OP2). Further, when the decompression-side end valve VAL2 is open, the wheel cylinder pressure of each wheel is reduced, and the hydraulic pressure R is returned to the reservoir tank RS.

Here, the root valves V _ROOT (V _ROOT1 , V _ROOT2 ) are linear valves that can control the valve closing pressure by an electric signal supplied from the outside, but the present invention is not limited to the linear valves. This electric signal is a current supplied from the electronic control unit ECU, and the higher the current value, the higher the valve closing pressure of the linear valve. The pressure applied to each end valve from the upstream side is a pressure obtained by adding the valve closing pressure of the linear valve to the master cylinder pressure. That is, if the amount of current supplied to the linear valve is increased, the pressure on the end side increases.

The electronic control unit ECU receives signals from the yaw rate sensor S1, the steering wheel steering angle sensor S2, the acceleration sensor S3, and the wheel speed sensor S4, and based on the received detection values, the root valves _VROOT1 , _VROOT2 and the end valves Controls opening and closing of VAL1, VAL2, and VAL3.

  Here, a stop switch STP is provided at the front position in the stroke of the brake pedal BP, and a master cylinder pressure sensor PMC is provided in the hydraulic path. The stop switch STP generates an output at the front position or more (turns on).

During vehicle behavior control, the root valves (switching valves) V _ROOT1 and V _ROOT2 are _normally closed, and the vehicle behavior is controlled by the wheel cylinder end valves (pressure regulating valves) VAL1, VAL2, and VAL3 (pressure increase, Decompression, hold).

  When the pressure is increased, the end valve VAL1 is opened and the pressure reducing valve VAL2 is closed, and the brake fluid is supplied to the wheel cylinder H from the reservoir tank RS through the hydraulic passages 205 and 203. The unit time of the end valve VAL1 as the pressure increasing valve The hydraulic pressure release time (connection time) with respect to the pressure becomes the duty ratio of pressure increase.

  Note that the terminal valve VAL2 is opened during pressure reduction. The hydraulic pressure release time (connection time) with respect to the unit time of the end valve VAL2 as the pressure reducing valve becomes the pressure reducing duty ratio.

  At the time of holding, the end valve VAL1 as a holding valve is closed.

At the time of ABS control, with the root valve V _ROOT opened, the motor 50 is driven to the extent that the brake fluid is replenished into the hydraulic path 201, and the pressure increasing mode is executed. In this case, the master cylinder pressure is transmitted to the wheel cylinder H in accordance with the depression amount of the brake pedal BP, and a braking force is generated in the braking device, which is applied to the wheels. On the other hand, when the locked state of the wheel is detected from the output value of the wheel speed sensor S4, the decompression mode is executed.

At the time of EBD control, the root valve V _ROOT is opened. Under the initial conditions, the left and right rear wheel end valves VAL1 are opened, the pressure reducing end valve VAL2 is closed, and a flag FEBD = 0 indicating that the EBD control is not being executed is set.

  Here, the EBD control start permission condition determination is performed. When the EBD control start permission condition (C) is satisfied, the EBD control is executed.

  In the EBD control, the current value is subtracted from the previous value of the vehicle body speed output from the wheel speed sensor S4, the vehicle body deceleration is obtained, and this vehicle body deceleration is compared with a predetermined deceleration set value B. When the actual vehicle deceleration is equal to or less than the deceleration set value B, the value of the flag FEBD is determined. If FEBD = 0, it is determined that the vehicle deceleration is still below the set deceleration, and the control is repeated.

  On the other hand, until the actual deceleration reaches the target deceleration set value B, FEBD = 0 and the pressure-reducing end valve VAL1 is closed while the pressure-reducing end valve VAL2 is closed. When the actual deceleration reaches the target deceleration set value B by repeatedly switching between the open state and the closed state at a time interval of, and repeating the control to make the wheel cylinder pressure increase gradually. In this case, both the end valve VAL1 and the end valve VAL2 of the left and right rear wheels are closed, and the wheel cylinder pressure is maintained, thereby preventing an increase in the braking force of the rear wheel, and the value of the flag FEBD is set to FEBD. = 1 and repeat control.

Further, the vehicle described above includes a parking brake PKB. The parking brake PKB is connected to the braking device of each wheel (wheel cylinder of each wheel, brake shoe BS (including BS _FL , BS _FR , BS _RL , BS _RR )) via a hydraulic path, and the parking brake PKB When operated, the operation detection switch (detection means) SW is turned on, while the braking device for each wheel is driven to apply a braking force to all the wheels.

  Hereinafter, various controls by the electronic control unit ECU will be described.

  FIG. 2 is a flowchart for explaining the control of the electronic control unit ECU.

  First, it is determined whether or not the parking brake PKB is activated during vehicle travel (S11). Whether or not the vehicle is traveling can be detected by the fact that the output of the wheel speed sensor S4 is equal to or greater than a predetermined value, and whether or not the parking brake PKB has been operated is determined by the operation detection switch SW. Can be detected from the output. If the parking brake PKB is not activated, the control is repeated.

  When the parking brake PKB is operated, it is determined whether or not the EBD control start permission condition (C) is satisfied (S12). Here, even when the EBD control start permission condition (C) is satisfied, since the parking brake PKB is operating as described above, the execution of the EBD control is prohibited in this case (S13). If the EBD control start permission condition (C) is not satisfied, the control is repeated.

  In the determination of the EBD control start permission condition (C), it is assumed that the start permission condition is satisfied when the ratio of the slip ratio of the rear wheel to the slip ratio of the front wheel becomes larger than a predetermined value. For example, such a condition (C) can be satisfied when the parking brake PKB is operated during traveling. Further, as the EBD control start permission condition (C), the start condition can be satisfied when the deceleration of the vehicle body or the deceleration of the right rear wheel exceeds a predetermined value. It should be noted that another condition can be set as the EBD control start permission condition (C) according to the vehicle control specification. Further, as conventionally known, cooperative control of EBD control and ABS control can be performed.

  Next, the relationship between establishment and execution of the EBD control start permission condition (C) will be described.

  FIG. 3 is a table showing the relationship of execution of the EBD control start permission condition (C), the brake pedal, the parking brake, and the EBD control.

  When the EBD control start permission condition is satisfied, the brake pedal is depressed (ON), and the parking brake PKB is not operated (OFF), the EBD control is executed (ON).

  When the EBD control start permission condition is not satisfied, the brake pedal is not depressed (OFF), and the parking brake PKB is not operated (OFF), the EBD control is naturally not executed (OFF).

  When the EBD control start permission condition is satisfied, the brake pedal is not depressed (OFF), and the parking brake PKB is operated (ON), the EBD control is not executed (OFF).

  When the EBD control start permission condition is satisfied, the brake pedal is depressed (ON), and the parking brake PKB is operated (ON), the EBD control is executed in consideration of the intention of operating the brake pedal (ON). I will do it.

  As described above, the above-described vehicle braking force control device includes a determination unit (ECU) that determines an EBD control start permission condition, an operation detection unit (SW) that detects the operation of the parking brake PKB, and a determination unit. The control means (ECU) for prohibiting the EBD control when the start of the EBD control is permitted and the parking brake operation is detected by the operation detecting means. However, when the brake pedal is operated simultaneously with the parking brake, EBD control is executed.

  The present invention can be used in a vehicle braking force control device.

It is a block diagram (a) of a vehicle provided with the vehicle braking force control device concerning an embodiment, and a detailed view (b) of a hydraulic control valve mechanism. It is a flowchart for demonstrating control of electronic control unit ECU. It is a table | surface shown about the execution relationship of EBD control start permission conditions (C), a brake pedal, a parking brake, and EBD control.

Explanation of symbols

40 ... reservoir, 50 ... motor, 51 ... hydraulic pump, 201 ... hydraulic path, 202 ... hydraulic path, 203 ... hydraulic path, 204 ... hydraulic path, 205 ..Hydraulic path, 251 ... Check valve, 253 ... Check valve, A ... Hydraulic control valve mechanism, BP ... Brake pedal, BS ... Brake shoe, ECU ... Electronic control Unit, H ... wheel cylinder, M ... master cylinder, OP1, OP2 ... hydraulic path, PKB ... parking brake, PMC ... master cylinder pressure sensor, RS ... reservoir tank, S1, ..Yaw rate sensor, S2 ... steering angle sensor, S3 ... acceleration sensor, S4 ... wheel speed sensor, STP ... stop switch, SW ... actuation detection switch, VAL1 ... Intensifying terminal valve, VAL2 · · · depressurization terminal _{valve, V ROOT} · · · root _{valves, W FL,} W _FR ··· _{wheel, W RL,} W _RR ··· rear wheel.

Claims (2)

In the vehicle braking force control device,
Determination means for determining an EBD control start permission condition for preventing an increase in braking force of the rear wheel;
Brake pedal detection means for detecting that the brake pedal has been depressed;
An operation detecting means for detecting an operation of a parking brake connected to a braking device for each wheel via a hydraulic path ;
Control means for performing or prohibiting the EBD control;
With
The control means includes
(A) The start of EBD control is permitted by the determination means,
The brake pedal detecting means detects that the brake pedal is not depressed, and
When parking brake operation is detected while the vehicle is running by the operation detection means,
Prohibiting the EBD control,
(B) The determination means permits the start of EBD control,
The brake pedal detection means detects that the brake pedal has been depressed, and
When parking brake operation is detected while the vehicle is running by the operation detection means,
Performing the EBD control;
A vehicle braking force control device.   2. The vehicle braking force control according to claim 1, wherein the determination unit establishes the start permission condition when a ratio of a rear wheel slip ratio to a front wheel slip ratio is larger than a predetermined value. apparatus.

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