JPH10119742A - Braking force distribution controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accomplish both of prevention of a spin and sure acquisition of a braking force by performing control so that a rear wheel braking force is relatively increased during turning traveling on a high μ road as against that during turning traveling on a low μ road. SOLUTION: Braking force distribution control in a step 112 is finished when three decisions in steps 113-115 are normally executed and continued and the predetermined condition is satisfied in each of the decisions. It is determined whether or not a road surface is a low μ road surface, and a road surface μis determined on the basis of an Rr relative slip ratio to a front wheel slip ratio during a braking force distribution control, and its absolute value is high on a low μ road, while its absolute vale is low on a low μroad. A low μ road is determined if the road surface μ is the predetermined vale or less, while a high μ road is determined if the road surface μ is the predetermined value or more. On the low μ road, the step 112 is executed unless conditions in the steps 113 114 are satisfied, and a spin in turning traveling on the low μroad is suppressed. Contrarily, when the high μ road is determined, process is transferred to a step 116, and a braking force for turning traveling on the high μroad is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force distribution control device that adjusts a braking force of a wheel behind a vehicle to a predetermined relationship with a braking force of a wheel in front of the vehicle when the vehicle turns.

[0002]

2. Description of the Related Art Generally, when turning braking is performed on a road having a low coefficient of road friction (hereinafter simply referred to as μ) (hereinafter simply referred to as a low μ road), a phenomenon in which the rear portion of the vehicle protrudes (spin tendency). Can be seen. This phenomenon can improve the stability of the vehicle by making the rear wheel braking force smaller than the front wheel braking force. As a device for improving the stability, there is a brake fluid pressure control valve device described in JP-A-7-215188.

According to Japanese Patent Application Laid-Open No. Hei 7-215188, when the acceleration applied in the left-right direction of the vehicle, that is, the lateral G exceeds a predetermined value, it is determined that the vehicle is turning and the brake hydraulic circuit is bypassed. A brake fluid pressure control valve device is disclosed in which a solenoid valve provided in a passage is closed to make a braking force of a rear wheel smaller than a braking force of a front wheel.

[0004]

However, according to this prior art, when it is determined that the vehicle is turning, the braking force of the rear wheels is made smaller than the braking force of the front wheels regardless of the condition of the road surface. Although spin can be prevented when turning on a low μ road, a sufficient braking force cannot be secured when turning on a high μ road, that is, a high μ road.

[0005]

SUMMARY OF THE INVENTION Accordingly, a front-rear braking force distribution control device according to the present invention is mounted on a vehicle and controls braking force distribution so as to make rear wheel braking force smaller than front wheel braking force during cornering. In the device, the rear wheel braking force is controlled so that the rear wheel braking force is relatively large when the vehicle is traveling on a high μ road and when the vehicle is traveling on a low μ road.

According to the front / rear braking force distribution control device, when turning on a low μ road, the rear wheel braking force becomes sufficiently smaller than the front wheel braking force, so that spin can be prevented, and high μ μ
During road turning, the rear wheel braking force is increased to some extent within a range not exceeding the front wheel braking force, so that the braking force can be secured.

[0007]

FIG. 1 is a block diagram showing an embodiment of a braking force distribution control device according to the present invention.
The depressing force of each wheel cylinder of the four wheels 6-9
And an electronic control unit 60 that controls the opening and closing of a plurality of solenoid valves provided in the hydraulic circuit 70 to adjust the braking force distribution of the front and rear wheels. The hydraulic circuit 70 is configured so as to be compatible with an antilock brake system (ABS) that suppresses wheel slip during braking by increasing or decreasing the brake oil pressure, and thus is an unnecessary element for the braking force distribution control. Is also included.

First, the basic configuration and operation of the hydraulic circuit 70 will be described. The hydraulic path includes a front right wheel system FR for controlling the oil pressure of the front right wheel cylinder 6, a front left wheel system FL for controlling the oil pressure of the front left wheel cylinder 7, a rear right wheel system RR for controlling the oil pressure of the rear right wheel cylinder 8, And a left rear wheel system RL for controlling the hydraulic pressure of the left rear wheel cylinder 9. Each system has one of the holding solenoid valves 12, 13, 14 and 15, and the pressure reducing solenoid valves 16, 17, 18 and 19, respectively.
Are provided as a set, and by the combination of the open / close state of the holding solenoid valve and the pressure reducing solenoid valve, and the on / off of the pumps 54 and 55,
Four modes of a normal mode, a pressure reducing mode, a holding mode, and a pressure increasing mode can be selected for each system. The braking force distribution control device of the present embodiment controls so that all four systems are selected in the normal mode when not operating, and only the left and right rear wheel systems RR and RL are selected in the holding mode when operating.

The operation of each system is the same, so the operation of the right rear wheel system RR will be described as a representative of the four systems. The holding solenoid valve 14 is a normally open valve, and the valve closes when the solenoid is turned on. On the contrary, the pressure reducing solenoid valve 18 is a normally-closed valve, and opens when the solenoid is turned on.

In the normal mode, the holding solenoid valve 1
4 and the pressure reducing solenoid valve 18 are both off, the holding solenoid valve 14 is open, and the pressure reducing solenoid valve 18 is closed. When the brake pedal 1 is depressed in this state, the hydraulic pressure of the master cylinder 3 increases, and the brake fluid is sent to the wheel cylinder 8 via the pipe 11, the pipe 22, the holding solenoid valve 14, and the pipe 26. As a result, the wheel cylinder 8 tightens the rotor to apply braking to the wheel. When the brake pedal 1 is released, the brake fluid of the wheel cylinder 8 returns to the master cylinder 3 via the pipe 26, the holding solenoid valve 14, the pipe 22, and the pipe 11. In the return operation, the holding solenoid valve 14
Two paths, a path passing through the main valve and a path passing through the check valve 44, are formed therein, so that the brake can be released quickly.

In the pressure reducing mode, the holding solenoid valve 1
4 and the pressure reducing solenoid valve 18 are both on, the holding solenoid valve 14 is closed, and the pressure reducing solenoid valve 18 is open. Holding solenoid valve 14
Is closed, even if the brake pedal 1 is depressed and the hydraulic pressure of the master cylinder 3 rises, the brake fluid from the master cylinder 3 is shut off here. On the other hand, the brake fluid of the wheel cylinder 8 flows from the pressure reducing solenoid valve 18 to the reservoir 5, and the hydraulic pressure of the wheel cylinder 8 decreases. The brake fluid accumulated in the reservoir 5 is returned to the master cylinder 3 by the pump 55. This mode is selected when the ABS operates, but is not selected in the braking force distribution control of the present embodiment.

In the holding mode, the holding solenoid valve 1
4 is turned on, the pressure reducing solenoid valve 18 is turned off, and the holding solenoid valve 14 and the pressure reducing solenoid valve 1 are turned off.
8 are both closed. Therefore, the oil pressure of the wheel cylinder 8 is shut off both the path to the master cylinder 3 and the path to the reservoir 5, so that the oil pressure at the time of switching to the holding mode is held. To perform the braking force distribution control in the present embodiment means to set the left and right rear wheel systems RR and RL to this holding mode, and to set the left and right front wheel systems FR and FL to the normal mode.

In the pressure increasing mode, the holding solenoid valve 1
4 and the pressure reducing solenoid valve 18 are both turned off,
The holding solenoid valve 14 opens and the pressure reducing solenoid valve 18 closes. This is the same as the normal mode, but in the pressure increasing mode, the pump 55 is further turned on, and the brake fluid of the reservoir 5 is sent to the master cylinder 3. This mode is selected in the ABS similarly to the pressure reduction mode, but is not selected in the braking force distribution control of the present embodiment.

The hydraulic circuit 70 according to this embodiment includes a proportioning valve (P valve), which is a mechanical valve for distributing the front and rear braking force, and a point for suppressing the rear wheel braking force. Load-sensitive type P that changes according to load
If no mechanical valve such as a valve is provided and the control is performed in the normal mode, the braking force is determined by the basic distribution of the braking device.

Although the illustration of the electronic control unit 60 is omitted,
CPU, ROM, RAM, interconnected via a bus,
A microcomputer including an input / output interface and a timer is provided, and executes a braking force distribution control operation according to a flowchart shown in FIG. In particular,
A wheel speed sensor 63 to 66 that outputs a pulse signal having a frequency corresponding to the wheel speed, a stop switch 67 that maintains an off state when the brake pedal 1 is released, and an on state when the brake pedal 1 is depressed, and the like. A signal is input, processed according to a program stored in the ROM, and on / off control of a solenoid valve of the hydraulic circuit 70 is performed.

Next, the operation of the braking force distribution control device of the present embodiment will be described with reference to the flowchart of FIG. This flowchart shows the process from the start to the end of the front and rear wheel braking force distribution control. Before and after the start of this control, the braking operation in the normal mode is normally performed on all four wheels. This flowchart includes not only front and rear wheel braking force distribution control during turning traveling but also front and rear wheel braking force distribution control during straight running braking.

First, it is determined whether a control permission condition is satisfied (step 101). The control permission condition is a basic condition for performing braking force distribution control during turning and straight running braking.
Abnormalities in basic elements necessary for braking control, such as braking force distribution control and ABS control, such as disconnection of lines 66 to 66, disconnection of each solenoid used in the hydraulic circuit 70, and failure of the motor relay that operates the pumps 54, 55. There is no. It is a major premise that control is not permitted when a basic element for braking control is abnormal.

In addition to the abnormality of the basic element, one of the permission conditions is that the ABS control is not performed. Since both the braking force distribution control and the ABS control control the hydraulic circuit, they can be executed only alternatively, and the priority of the braking force distribution control is set lower than the ABS control.

If these control permission conditions are satisfied, the routine proceeds to step 102, where it is determined whether or not the control start conditions for straight-ahead braking are satisfied. The front-rear braking force distribution control at the time of cornering is executed only when the control start condition at the time of straight-ahead braking in step 102 is not satisfied. Therefore, prior to the description of the longitudinal braking force distribution control during turning traveling, the braking force distribution control during straight-ahead braking will be described.

FIG. 3 is an ideal braking force distribution characteristic diagram in which the abscissa represents the braking force of the front wheels and the ordinate represents the braking force of the rear wheels when the four wheels are simultaneously locked. is there.
The ideal braking force distribution differs between when the vehicle is empty and when it is loaded. In the figure, a characteristic curve A shows an ideal braking force distribution when the vehicle is empty, and a characteristic curve B shows an ideal braking force distribution when the vehicle is standard. The braking force distribution control at the time of straight-ahead braking is to perform braking control so that the actual braking force distribution approaches the ideal braking force distribution. Control is performed so that the braking force of the rear wheel is suppressed when a predetermined condition is satisfied so as not to exceed the braking force of the rear wheel.

The control disclosure condition in step 102 in FIG. 2 is this predetermined condition, and various conditions can be set. In this embodiment, a plurality of auxiliary conditions are satisfied and the following description will be given. The determination is made based on whether any of the first or second main conditions is satisfied.

The first main condition for starting the control is that the estimated vehicle deceleration DV _SOF satisfies a positive predetermined value K1 or more and the longitudinal slip amount difference satisfies a predetermined value S1 or more. That is, the estimated vehicle deceleration ≧ K1 (1) The difference between the front and rear slip amounts ≧ S1 (2) is satisfied.

Here, the longitudinal slip amount difference is the longitudinal slip amount difference = the rear wheel slip amount−the front wheel slip amount (3), which is obtained by subtracting the rear wheel speed from the front wheel speed ( = Front wheel speed-rear wheel speed). The situation that satisfies the first main condition occurs during the deceleration operation.

In this embodiment, the gravitational acceleration is G,
The value of K1 is set to 0.4G. S1 varies depending on the estimated vehicle speed V _SOF . When V _SOF ≧ 50 km / h, S1 = 0.01V _SOF (4) When 50 km / h> V _SOF ≧ 6 km / h, S1 = 0. 5 km / h ... (5)

The front-rear slip amount difference is a difference between the front wheel speed and the rear wheel speed, as described above, and is obtained, for example, every 12 ms based on signals from the wheel speed sensors 63 to 66. Processing is performed such that the difference between the wheel speeds of the front and rear wheels is obtained five times in succession from the wheel speed, and the average value is adopted.

The estimated vehicle speed V _SOF is estimated based on the wheel speed and its temporal change.
It is given by the following equation.

V _{SOF (N)} = MED (V _W0 , V _{SOF (N−1)} −α
_DW * t, V _{SOF (N-1)} + α _UP * t) V _W0 is the maximum wheel speed value of the four wheel speeds, α _DW is the guard value of the vehicle deceleration, for example, 1G α _UP is the vehicle acceleration For example, 2G MED (A, B, C) is the median value of A, B, C t = 12 ms “V _{SOF (N−1)} −α _DW * t” is α from the previous vehicle speed.
This is the current vehicle speed when the vehicle speed is changed by _DW (guard value of vehicle deceleration), and is the lower limit guard of the vehicle speed. “V _{SOF (N−1)} + α _UP * t” is the current vehicle speed when the vehicle speed is changed by α _UP (a guard value of the vehicle acceleration) from the previous vehicle speed, and the upper limit of the vehicle speed Becomes Therefore, V _{SOF (N)} has upper and lower guards with respect to the maximum wheel speed value of the four wheel speeds. The guard may be eliminated, and the maximum wheel speed value of the four wheel speeds may be used as the vehicle speed.

The estimated vehicle deceleration DV _SOF is calculated as a change of the estimated vehicle speed V _SOF , and DV _{SOF (N)} = (V _{SOF (N−1)} −V _{SOF (N)} ) / Δt Δt
= 12 ms. The subscript N indicates the current value, and N-1
Indicates the value at the time of the previous calculation (12 ms before).

The second main condition for starting the control is that the estimated vehicle deceleration DV _SOF is a positive predetermined value K2 larger than the above-mentioned K1.
That is all. That is, the estimated vehicle deceleration ≧ K2 (6) is satisfied. In the present embodiment, K2 is set to 0.6G.
(G is the gravitational acceleration). The second main condition is that when the estimated vehicle body deceleration indicates a large value, the start of the braking force distribution control is permitted regardless of the magnitude of the difference between the front and rear slip amounts. The start timing of the braking force distribution control should be originally determined based on the difference between the front and rear slip amounts during deceleration. However, when different-diameter tires are mounted as wheels, the longitudinal slip amount difference calculated based on the output of the wheel speed sensor may not accurately indicate the actual longitudinal slip amount difference. Therefore, in the determination based on only the first main condition, the braking force distribution control may not be started in spite of the situation where the rear wheel braking force should be suppressed. Even in such a case, when the estimated vehicle body deceleration shows a large value that satisfies Expression (6), the braking force distribution control is started. This makes it possible to perform braking force distribution control relatively close to the ideal braking force distribution even when a difference in front-rear slip amount cannot be accurately detected due to the mounting of tires of different diameters.

The auxiliary conditions for the control start conditions include:
The estimated vehicle speed V _SOF satisfies 10 km / h ≦ V _SOF <250 km / h (7). This is because when the vehicle speed is low, the braking force distribution control is unnecessary, and when the vehicle speed is extremely high, the wheel speed sensor may be abnormal, so the braking force distribution control is prohibited.

When the braking force distribution control start condition at the time of straight-ahead braking in step 102 is satisfied, the flow proceeds to the braking force distribution control processing in step 103, and the hydraulic circuits for the left and right rear wheels are switched from the normal mode to the holding mode. That is, the holding solenoid valves 14 and 15 are switched on while the pressure reducing solenoid valves 18 and 19 are kept off. As a result, the pressure of the wheel cylinders 6 and 7 of the left and right front wheels is increased by the braking operation of the vehicle driver, but the hydraulic pressure of the wheel cylinders 8 and 9 of the left and right rear wheels is maintained, and the ratio of the braking force of the rear wheels to the braking force of the front wheels is maintained. Becomes smaller.

The timing at which the braking force distribution control process 103 should be terminated is monitored in two determination steps 104 and 106 described below. There are two ways of termination. When the termination condition of the determination step 104 is satisfied, the process proceeds to step 105 to immediately terminate the braking force distribution control, and when the termination condition of the determination step 106 is satisfied, the rear wheel cylinder 8 and After the pressure of 9 is gradually increased, the process is terminated.

The termination conditions in the determination step 104 are as follows: (1) when the stop switch 67 is turned off, that is, when the driver releases the brake pedal 1 to stop the braking operation. (3) When the braking force distribution control is continuously executed for a predetermined time, for example, 15 seconds. (4) The estimated vehicle speed V _SOF is a predetermined value, for example, 6 km / h.
(5) When the estimated vehicle deceleration DV _SOF is a predetermined value, for example, 0.3
There are five types when it becomes smaller than G (G is the gravitational acceleration).

When any of these conditions are met,
Proceeding to step 105, immediately turn off the holding solenoid valves 14 and 15 provided in the hydraulic circuit of the rear wheels,
Switch from hold mode to normal mode.

The conditions for termination in the determination step 106 are as follows: when control of the ABS is prohibited, that is, disconnection of the wheel speed sensors 63 to 66, disconnection of each solenoid used in the hydraulic circuit 70, pump 54, 5
There is a case where an abnormality occurs in a basic element necessary for the braking control such as a failure of the motor relay that moves the motor 5, or a case where the ABS control is started for one of the left and right front wheels. In this case, the processing shifts to the end processing 107 and, for example, a table showing the next slowly increasing output pattern is displayed.

[Table 1] By performing on / off switching control of the rear wheel holding solenoid valves 14 and 15 in accordance with
Then, the brake oil pressure of the rear wheels is gradually increased as compared with the case of ending based on the ending conditions, and then both holding solenoid valves are fixed to the off state to terminate the braking force distribution control. After the braking force distribution control ends, the process returns to step 101.

Next, the braking force distribution control during turning will be described. If the control start condition determination regarding the distribution of braking force during straight running in step 102 is not satisfied, the process proceeds to step 110, where the lateral acceleration Gy applied to the left and right direction of the vehicle is a predetermined value of 0.3G (G is the gravitational acceleration). It is determined whether or not this is the case. The lateral acceleration Gy is calculated based on the following equation (8).

Gy = (V _SOF × ΔV) / T (8) where V _SOF is the estimated vehicle speed, and ΔV is the front wheel (follower wheel).
And T is the wheel tread of the vehicle.

If the lateral acceleration Gy is 0.3 G or more, the routine goes to step 111 to determine whether or not the stop switch is on, that is, whether or not the brake operation is being performed. If the stop switch is ON, it is determined that the vehicle is turning, and the braking force distribution control in step 112 is executed. As described above, the determination as to whether or not the vehicle is turning is made based on the value of the lateral acceleration Gy and the state of the stop switch. If both of the conditions are satisfied, the braking force distribution control is executed, and if any one of the conditions is not satisfied. It is determined that the vehicle is not turning so that the braking force distribution control is necessary, and the braking force distribution control is not executed.

The braking force distribution control in step 112 is the same control as the braking force distribution control in step 103 described above, and switches the hydraulic circuits for the left and right rear wheels from the normal mode to the holding mode. That is, the pressure reducing solenoid valves 18, 1
9 while the holding solenoid valve 1 is in the off state.
4 and 15 are switched on. Thereby, the wheel cylinders 6 of the left and right front wheels are operated by the braking operation of the vehicle driver.
And 7 increase the pressure, but the right and left rear wheel cylinders 8
And 9 are maintained, and the ratio of the braking force of the rear wheels to the braking force of the front wheels decreases.

The braking force distribution control in step 112 is continued while constantly executing the three judgments in steps 113 to 115, and is terminated when a predetermined condition is satisfied in each judgment. In step 113, it is determined whether or not the road surface is a low μ road. Μ of the road surface is Rr which is the magnitude of the rear wheel slip ratio with respect to the front wheel slip ratio during braking force distribution control.
The determination is made based on the relative slip ratio. A specific calculation formula of the Rr relative slip ratio is given by the following formula (9).

Rr relative slip ratio = (SLIPR + SLIPL) / 2− (SLIP0R + SLIP0L) / 2 (9) where SLIPR is a difference between right and left front wheel slip ratios, SLI.
PL is the difference between the left and front wheel slip rates, and SLIPOR is the stop switch changed from off to on (ie,
The difference between the right and left front wheel slip rates when the brake is changed from the non-operating state to the operating state, SLIP0L is the left when the stop switch changes from off to on (that is, the brake changes from the non-operating state to the operating state). This is the difference between the front and rear wheel slip rates.

The slip ratio is a ratio of a slip amount to an estimated vehicle speed, and is a one-side longitudinal slip ratio obtained by subtracting a front wheel slip ratio from a rear wheel slip ratio for a left wheel or a right wheel. The difference (SLIP) is expressed by the following equation (10).

[0043]

(Equation 1) Where V _WF is the front wheel speed, V _WR is the rear wheel speed, V
_SOF is the estimated vehicle speed. The one-side front-rear slip ratio difference is averaged for the left and right wheels as shown in the above equation (9), and the left-right average value of the front-rear slip ratio difference when the stop switch changes from off to on is subtracted.

As described above, by subtracting the front-rear slip ratio difference in the predetermined state from the current front-rear slip ratio difference,
An offset component with respect to the true wheel speed value generated in the case of different diameter tires can be canceled. Thereby, the influence of the error due to the different diameter tire can be reduced. However, the offset component can be canceled by the addition / subtraction offset component, and the proportional component cannot be canceled.

The Rr relative slip ratio thus obtained has a negative value in principle, and its absolute value is large on a low μ road and small on a high μ road.

This will be described with reference to FIG. FIG.
Is a coordinate system in which the horizontal axis represents the braking force of the front wheels and the vertical axis represents the braking force of the rear wheels, as in FIG. Curve E is an ideal braking force distribution curve, and broken lines F and G are respectively high μ roads (μ =
1.0) is a front wheel lock line and a rear wheel lock line,
Dashed lines H and I are a front wheel lock line and a rear wheel lock line on a low μ road (μ = 0.3), respectively. Arrow J indicates the braking force during the braking force distribution control in step 112. The front wheel lock lines F and H indicate the braking force distribution at which the front wheel slip ratio is 100% on the high μ road and the low μ road, respectively. The rear wheel lock lines G and I indicate that the rear wheel slip ratio is high. 100% on μ road and low μ road
Is shown.

The braking force distribution control during cornering is immediately executed when it is determined in step 111 that the stop switch has shifted from off to on, and the rear wheel braking force at that time is maintained. It is in the non-braking state. Therefore, the braking force is almost distributed to the front wheels as indicated by the arrow J, and the slip ratio of the rear wheels becomes almost zero. On the other hand, the slip ratio of the front wheels when the braking force is indicated by the arrow J is larger than the front wheel lock line H indicating the slip ratio 100% on the low μ road and the front wheel lock line F indicating the slip ratio 100% on the high μ road. Also shows a much smaller value, which means that the value is large on a low μ road and small on a high μ road.

Accordingly, the Rr relative slip ratio, which is obtained by subtracting the front wheel slip ratio from the rear wheel slip ratio, has a negative value, and its absolute value is large on a low μ road and small on a high μ road. Therefore, if the Rr relative slip ratio is equal to or less than a predetermined value having a negative value, it is determined that the road is a low μ road, and if it is larger than the predetermined value, it is determined that the road is a high μ road.

In this embodiment, the predetermined value is set to -1.5%. If the Rr relative slip ratio is less than -1.5%, it is determined that the road is a low μ road. Judge as μ road.

When it is determined that the road is a low μ road by such processing, the braking force distribution control in step 112 is continuously executed unless the control end conditions in steps 113 and 114 are satisfied. As a result, spin during turning on a low μ road can be suppressed.

Conversely, if it is determined that the road is a high μ road, step 1
The process proceeds to 16 to immediately stop the braking force distribution control. Therefore, it is possible to sufficiently secure the braking force in the turning traveling on the high μ road.

The control termination condition in step 114 is as follows.
Similar to step 104 already described, (1) when the stop switch 67 is turned off, that is, when the driver releases the brake pedal 1 to stop the braking operation. (2) The rear wheel enters the ABS control. Time (3) The braking force distribution control may be continuously executed for a predetermined time, for example, 15 seconds, and (4) The lateral acceleration Gy may be smaller than a predetermined value.

When any of these conditions are met,
Proceeding to step 116, immediately turn off the holding solenoid valves 14 and 15 provided in the hydraulic circuit of the rear wheels,
Switch from hold mode to normal mode.

The termination condition in the determination step 115 is the same as that in the step 106 already described. When the control of the ABS is prohibited, that is, when the wheel speed sensor 63
When an abnormality occurs in a basic element necessary for braking control such as disconnection of the solenoids 66 to 66, disconnection of each solenoid used in the hydraulic circuit 70, failure of a motor relay that operates the pumps 54 and 55, For example, when the ABS control is started for any of them. In this case, end processing 1
In step 17, the brake oil pressure of the rear wheels is gradually increased, and then both the holding solenoid valves are fixed to the off state to terminate the braking force distribution control. The method is the same as step 107 described above.

In the present embodiment, when it is determined in step 113 that the road is a high μ road, the flow proceeds to step 116 to immediately terminate the braking force distribution control, but instead proceeds to step 117. It may be terminated gently.

[0056]

As described above, according to the braking force distribution control device of the present invention, the rear wheel braking force is set to be relatively large when turning on a high μ road compared to when turning on a low μ road. Control to prevent spin during low-μ
It is possible to ensure both braking force during road turning.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation flow of the electronic control device of FIG. 1;

FIG. 3 is a characteristic diagram for explaining distribution of braking force between front and rear wheels during straight running.

FIG. 4 is a characteristic diagram for explaining estimation of a road surface μ during a turning operation.

[Explanation of symbols]

1: brake pedal, 3: master cylinder, 6-9: wheel cylinder, 12-15: holding solenoid valve,
16-19: pressure reducing solenoid valve, 60: electronic control unit, 63-66: wheel speed sensor, 70: hydraulic circuit.

Claims (1)

[Claims] 1. A braking force distribution control device mounted on a vehicle for controlling a rear wheel braking force to be smaller than a front wheel braking force during a turning operation, wherein the road surface friction coefficient is determined when the vehicle is turning on a road having a high road surface friction coefficient. A braking force distribution control device that controls the rear wheel braking force to be relatively large as compared to turning on a low road.