JPH06144176A - Braking force distribution control device - Google Patents

Abstract

PURPOSE:To properly judge the start of the braking force distribution control with a braking force distribution control device. CONSTITUTION:Wheel speeds of a front wheel FR and a rear wheel RR are detected by wheel speed detecting means S1, S3, and the wheel speeds of the wheel FR and the wheel RR are compared by a comparing means M1 based on the detected outputs. A hydraulic control valve FV is driven by a driving means M2 in response to the compared result, and the braking force of the wheel RR is adjusted to the preset relation with the braking force of the wheel FR. The braking force distribution control is prohibited during the normal braking action, and the start of the braking force distribution control is allowed when the difference between the wheel speeds of the wheel FR and the wheel RR exceeds a preset value. The so-called dead zone area is formed by a start judging means M3, and the braking force of the wheel RR is adjusted to the preset relation with the braking force of the wheel FR when the speed difference exceeds it.

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 for adjusting a braking force of a wheel behind a vehicle to a predetermined relationship with a braking force of a wheel in front of a vehicle during vehicle braking.

[0002]

2. Description of the Related Art Generally, when a braking operation is performed on a running vehicle, the axial load in the front and rear of the vehicle is different due to the load movement,
The braking force applied to the wheels in front of the vehicle and the braking force applied to the wheels behind the vehicle, which are necessary for the four wheels to be locked simultaneously, are not in a directly proportional relationship, but are in a relationship as indicated by a chain line in FIG. This relationship is called ideal braking force distribution, and this distribution varies depending on the presence / absence of the loading load. When the loading load is present, the ideal braking force distribution indicated by the chain double-dashed line is obtained.

In this regard, if the braking force applied to the rear wheels exceeds the braking force applied to the front wheels, the directional stability of the vehicle is impaired. Therefore, in order to make the braking force distribution as close as possible to the ideal braking force distribution while keeping it lower than this. A proportioning valve is provided between the wheel cylinder and the master cylinder. According to this, the distribution line has a break point as shown by the broken line in FIG. 12, but considering the load difference between the inner and outer wheels when turning, the braking force on the rear wheel is considerably larger than the braking force on the front wheel. It needs to be kept low. Further, when the load is large, the distribution of ideal braking force is greatly deviated. For this reason, a load sensing proportioning valve that can change the position of the folding point according to the load to form different distribution lines is also used.

Further, in Japanese Patent Publication No. 51-40816, the rotational speeds of the front and rear wheels are compared with each other, and the breaking point of the proportioning valve is made variable by a pneumatically operated actuator, specifically, the rotational speed of the rear wheel. Is higher than that of the front wheels, the above-mentioned break point is set high, and when the rotational speed of the rear wheels is lower than that of the front wheels, the above-mentioned break point is disclosed.

[0005]

SUMMARY OF THE INVENTION In the above conventional configuration,
It is not enough to approximate the braking force distribution of the front and rear wheels of the vehicle to the ideal braking force distribution, and the braking force distribution to the rear wheels is reduced and a large brake pedal depression force is required to obtain a predetermined vehicle deceleration, Further, there is a possibility that the load on the braking device for the front wheels will become large, or the distribution of the braking force to the rear wheels will become large, and the rear wheels will tend to lock.

Therefore, the applicant of the present invention filed Japanese Patent Application No. 4-770.
In the application of No. 60, a braking hydraulic pressure control device for an automobile is proposed which drives an actuator in accordance with a difference between a wheel speed in front of the vehicle and a wheel speed in the rear of the vehicle to control a braking force applied to a wheel behind the vehicle. However, when the braking force is distributed based on the wheel speed difference in this way, if the control start determination is also made based on the wheel speed difference as it is, the rough road such as a gravel road or the like with uneven road surface When the braking operation is performed while the vehicle is traveling, the wheel speed difference between the front wheels and the rear wheels may become large depending on the road surface state, and the braking force distribution control may be immediately performed, resulting in unnecessary control.

Therefore, an object of the present invention is to make it possible to appropriately determine the start of the braking force distribution control in a braking force distribution control device for adjusting the braking force of the wheels behind the vehicle.

[0008]

In order to achieve the above object, the braking force distribution control device of the present invention is mounted on a wheel FR in front of a vehicle to apply the braking force as shown in the outline of the configuration of FIG. The front wheel wheel cylinder 51 to be applied and the rear wheel wheel cylinder 53 which is attached to the wheel RR at the rear of the vehicle to apply a braking force, and the front and rear wheel wheel cylinders which pressurize the brake fluid in accordance with the operation of the brake pedal 3. 51, 53
A hydraulic pressure generator PG for applying a brake hydraulic pressure to each of
The hydraulic pressure generator PG and at least the rear wheel cylinder 5
A hydraulic pressure control valve F which is interposed between the hydraulic pressure control valve 3 and the hydraulic pressure control valve F to control the brake hydraulic pressure
V, wheel speed detection means S1 and S3 for detecting the wheel speeds of the wheels FR and RR in the front and rear of the vehicle, and the wheel FR in front of the vehicle and the rear of the vehicle based on the detection outputs of the wheel speed detection means S1 and S3. Comparing means M1 for comparing the wheel speeds of the wheels RR and the hydraulic control valve FV according to the comparison result of the comparing means M1 so that the braking force of the wheels RR on the rear side of the vehicle is compared with the braking force of the wheels FR on the front side of the vehicle. The drive means M2 that performs the braking force distribution control that adjusts to a predetermined relationship, and the braking force distribution control by the driving means M2 during normal braking operation are prohibited, and the wheel speed of the front wheel FR of the vehicle and the rear wheel RR of the vehicle are reduced. A start determination means M3 is provided that allows the start of the braking force distribution control by the drive means M2 when the speed difference between the wheel speeds exceeds a set value.

In the braking force distribution control device, the start determination means M3 sets a set value according to the road surface state determination means M4 for determining the traveling road surface state of the vehicle and the traveling road surface state determined by the road surface state determination means M4. The start condition setting means M5 for setting different values may be provided.

[0010]

In the braking force distribution control device having the above construction, when the brake pedal 3 is operated, the brake fluid pressure is supplied from the fluid pressure generator PG to the front and rear wheel wheel cylinders 51 and 53, respectively. Braking force is applied to the wheels FR and PR. In this case, the hydraulic pressure control valve FV is interposed between the hydraulic pressure generator PG and the rear wheel wheel cylinder 53, and the brake hydraulic pressure applied to the wheel cylinder 53 is controlled by the hydraulic pressure control valve FV. Controlled.

On the other hand, the wheel speeds of the wheel FR and the wheel RR are detected by the wheel speed detecting means S1 and S3, and the wheel speeds of the wheel FR and the wheel RR are compared by the comparing means M1 on the basis of these detection outputs. Is required. Then, the hydraulic pressure control valve FV is driven by the drive means M2 according to the comparison result of the comparison means M1, for example, the wheel speed difference, and the braking force of the vehicle rear wheel RR is changed to the vehicle front wheel F.
The braking force of R is adjusted to have a predetermined relationship, that is, to approximate the ideal braking force distribution.

Whether or not to start the braking force distribution control by the drive means M2 is judged by the start judgment means M3. That is, during the normal braking operation, the braking force distribution control is prohibited, and when the speed difference between the wheel speeds of the wheels FR and RR exceeds the set value, the start of the braking force distribution control is permitted, and the driving means M2. The hydraulic pressure control valve FV is drive-controlled by. That is, a so-called dead zone region is formed, and when the dead zone region is exceeded, the braking force of the wheel RR is adjusted to a predetermined relationship with the braking force of the wheel FR. In this case, it is desirable that the set value serving as the start condition is set in accordance with the traveling road surface state of the vehicle. For example, when the traveling road surface is determined to be a rough road by the road surface state determination means M4,
The start condition setting means M5 sets a value different from the set value for a normal road surface condition, for example, a large value, and the dead zone area becomes large. Therefore, the period in which the hydraulic pressure control valve FV is in the inoperative state becomes long, and unnecessary braking force distribution control is avoided.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a braking force distribution control device according to an embodiment of the present invention, which includes a tandem type master cylinder 2 and a hydraulic booster 5, which are driven in response to an operation of a brake pedal 3. An auxiliary hydraulic pressure source 20 is connected to the hydraulic booster 5 and these are connected to the low pressure reservoir 4. On the other hand, wheel cylinders 51 to 54 are mounted on the wheels FR, FL, RR, RL, and are respectively connected to the hydraulic pressure passages that connect one of the pressure chambers 2a of the master cylinder 2 and the wheel cylinders 51, 52 in front of the vehicle. Solenoid valve 6
1, 62 are interposed. Further, the solenoid valves 61 and 62 are connected to the hydraulic booster 5 via the normally open solenoid valves 31 and 33, and are also connected to the normally closed solenoid valves 32 and 34. Is connected to the low pressure reservoir 4.

A pressure valve 2b of the master cylinder 2 is connected to a positioning valve 6 and a solenoid valve 63.
Solenoid valves 63 and 37, which are normally open, are provided in the hydraulic paths connecting the solenoid valve 63 and the wheel cylinders 53 and 54, respectively, on the rear side of the vehicle, and normally closed solenoid valves are provided between them and the low-pressure reservoir 4. 36 and 38 are interposed. These solenoid valves 3
The hydraulic pressure control valve according to the present invention is constituted by 5 to 38.

The wheel FR indicates the wheel on the front right side as viewed from the driver's seat, the wheel FL indicates the wheel on the front left side, the wheel RR indicates the wheel on the rear right side, and the wheel RL indicates the wheel on the rear left side. In the present embodiment, so-called Y pipes are formed for the wheels RR and RL on the rear side of the vehicle, but so-called X pipes may be used. Further, in this embodiment, the wheel R on the rear side of the vehicle is used.
Although R and RL are so-called rear wheel drive of the drive wheels, they may be front wheel drive.

The auxiliary hydraulic pressure source 20 has a pump 21, an accumulator 22 and a relief valve 23. The pump 21 is driven by an electric motor 24, and boosts and outputs the brake fluid in the low-pressure reservoir 4, and the output brake fluid pressure is supplied to the accumulator 22 via the check valve 25, and the pressure is stored. The relief valve 23 is used for the accumulator 2
It is released when the output brake fluid pressure of 2 becomes equal to or higher than a predetermined pressure, and the brake fluid is circulated to the low pressure reservoir 4 to reduce the pressure. Furthermore, on the output side of the accumulator 22,
A pressure sensor 46 that linearly outputs the pressure and a low-voltage switch 47 that is turned on when the pressure falls below a predetermined pressure are provided. Thus, the so-called power hydraulic pressure is discharged from the auxiliary hydraulic pressure source 20 and supplied to the hydraulic pressure booster 5.

The hydraulic booster 5 regulates the output hydraulic pressure of the auxiliary hydraulic pressure source 20 by means of a spool valve (not shown) which responds to the brake pedal 3, and uses this as a boosting source to boost drive the master cylinder 2. For example, JP-A-64-4
7664, JP-A-64-47665, JP-A-64-
Since it is disclosed in Japanese Patent Publication No. 74156, etc., detailed description will be omitted. The hydraulic booster 5 of the present embodiment has a control hydraulic pressure (that is, the wheel cylinder 2) that is higher than the output brake hydraulic pressure of the wheel cylinder 2 by a predetermined ratio (for example, 20%).
(120% of the output brake hydraulic pressure) of the solenoid valve 31, 33 and the solenoid valve 63,
Piping is provided so that the control hydraulic pressure can be supplied to the wheel cylinders 51 to 54 via 35 and 37. Further, there is provided a control hydraulic pressure switch 48 which is turned on when the control hydraulic pressure of the hydraulic booster 5 becomes equal to or higher than a predetermined pressure. still,
As the dynamic hydraulic pressure control device according to the present invention, the regulator described in the above publication may be used instead of the hydraulic pressure booster 5 of the present embodiment, and the dynamic pressure control device may be configured separately from the master cylinder 2. .

As described above, the solenoid valve 63 is arranged between the solenoid valves 35 to 38, which are hydraulic pressure control valves according to the present invention, and the master cylinder 2, and the solenoid valve 63 and the master cylinder 2 are connected to each other. A positioning valve 6 is interposed between them. Then, the solenoid valves 32, 34 and the solenoid valves 36, 38
Is connected to the low pressure reservoir 4, and the low pressure reservoir 4 is connected to these solenoid valves 32, 34, 36, 38.
Brake fluid that is recirculated through the discharge side hydraulic pressure passage is stored therein, and the brake fluid that is supplied to the master cylinder 2 and the like is stored.

The solenoid valves 61 to 63 are 3-port 2-position solenoid directional control valves, which are in the first position shown in FIG. 2 when the solenoid coil is not energized, and allow the wheel cylinders 51 to 54 to communicate with the master cylinder 2. Then, the communication with the hydraulic booster 5 is cut off, and when the solenoid coil is energized, it is in the second position and is switched to the left side in FIG. Solenoid valves 31 to 38
Is a 2-port 2-position electromagnetic switching valve, each of which is in the first position shown in FIG. 2 when the solenoid coil is not energized,
The wheel cylinders 51, 52 communicate with the hydraulic booster 5 via the solenoid valves 61, 62 when they are in the second position, and the wheel cylinders 53, 54 connect them when the solenoid valve 63 is in the second position. Through the hydraulic booster 5. When the solenoid coils of the solenoid valves 31 to 38 are energized, they are in the second position and the wheel cylinders 51,
The communication of 52 with the hydraulic booster 5 via the solenoid valves 61 and 62 is blocked, the communication with the low pressure reservoir 4 via the solenoid valves 61 and 62, and the solenoid valve 63 of the wheel cylinders 53 and 54. Communication with the hydraulic booster 5 is cut off, and communication with the low pressure reservoir 4 is established. The check valve in FIG. 2 allows the return from the wheel cylinders 51 to 54 side to the hydraulic booster 5 side and shuts off the flow in the opposite direction.

By controlling the energization and de-energization of the solenoid coils of the solenoid valves 61 to 63, the communication between the wheel cylinders 51 to 54, the master cylinder 2 and the hydraulic booster 5 is switched. Further, the brake fluid pressure in the wheel cylinders 51 to 54 can be increased, reduced, or maintained by controlling the energization and de-energization of the solenoid coils of the solenoid valves 31 to 38. That is, when the solenoid coils of the solenoid valves 31 to 38 are not energized, the control hydraulic pressure is supplied from the hydraulic booster 5 to the wheel cylinders 51 to 54 to increase the pressure, and when energized, the control hydraulic pressure is communicated with the low pressure reservoir 4 side to reduce the pressure. In addition, solenoid valves 31, 3
When the solenoid coils 3, 35 and 37 are energized and the solenoid coils of the remaining solenoid valves are de-energized, the brake fluid pressure in the wheel cylinders 51 to 54 is maintained. Therefore, so-called pulse pressure increase (step pressure increase) or pulse pressure decrease can be performed by adjusting the time interval of energization / de-energization, and control can be performed so as to gradually increase or decrease the pressure.

The solenoid valves 31 to 38 and the solenoid valve 61
Reference numerals 63 to 63 are connected to the electronic control unit 10 to control the energization and de-energization of each solenoid coil. The electric motor 24 is also connected to the electronic control unit 10 and driven and controlled by the electronic control unit 10. Further, wheel speed sensors 41 to 44 are arranged on the wheels FR, FL, RR, RL, and these are connected to the electronic control unit 10, and the rotation speed of each wheel, that is, the wheel speed signal is transmitted to the electronic control unit 10. Is configured to be input to. Further, a brake switch 45 which is turned on when the brake pedal 3 is depressed, and the above-mentioned pressure sensor 46, low pressure switch 47 and control hydraulic pressure switch 48 are connected to the electronic control unit 10.

The electronic control unit 10 is, as shown in FIG.
CPU14 and ROM1 connected to each other via a bus
5, a microcomputer 16 including a RAM 16, a timer 17, an input interface circuit 12 and an output interface circuit 13. The wheel speed sensors 41 to 44, the brake switch 45, and the pressure sensor 4
6, output signals of the low pressure switch 47 and the control hydraulic pressure switch 48 are configured to be input to the CPU 14 from the input interface circuit 12 via the amplifier circuits 18a to 18h, respectively. Also, the output interface circuit 1
3, the control signal is output to the electric motor 24 via the drive circuit 19a, and the control signals are output to the solenoid valves 31 to 38 and the solenoid valves 61 to 63 via the drive circuits 19b to 19l. Has been done. In the microcomputer 11, the ROM 15 is shown in FIGS.
The CPU 14 stores a program corresponding to each of the flowcharts shown in FIG. 1, and the CPU 14 executes the program while an ignition switch (not shown) is closed, and the RAM 16
Temporarily stores the variable data necessary for executing the program.

In the present embodiment constructed as described above, the electronic control unit 10 carries out a series of processes for controlling the braking force distribution, and the solenoid valve 63 and the solenoid valves 35 to 38.
Is controlled. That is, the microcomputer 11
At, when the ignition switch (not shown) is closed, execution of the program corresponding to the flowcharts of FIGS. 4 to 9 starts.

First, in FIG. 4 showing the main routine,
In step 100, the microcomputer 11 is initialized and various calculated values are cleared. Next step 10
1, the wheel speeds VwFF, VwFR, Vw of the four wheels based on the output signals from the wheel speed sensors 41 to 44.
RR and VwRL are calculated. Further, in step 102, the wheel speeds of each wheel are differentiated by differentiating the wheel speeds DV.
wFF, DVwFR, DVwRR, DVwRL are calculated.
An acceleration sensor may be provided and the detection signal thereof may be used. Further, in step 103, the estimated vehicle body speed Vso and the acceleration DVso which is a differential value thereof are calculated based on the wheel speed. The estimated vehicle body speed Vso is set as a vehicle body speed, for example, on the assumption that the wheel speed during braking is decelerated at a predetermined deceleration, and even one of the four wheels exceeds this value. Sometimes, the value when the vehicle is decelerated again with a predetermined deceleration is set as the vehicle body speed, which is the same as the reference speed used for the conventional anti-skid control.

Subsequently, the routine proceeds to step 200, and under certain conditions, for example, when the brake pedal 3 is operated and the brake switch 45 is turned on, the solenoid valve 63 is turned on (energized).
And the wheel cylinders 53,
The communication with the master cylinder 2 is cut off at 54, and the communication with the hydraulic booster 5. Then, the routine proceeds to step 500, where it is judged whether or not the anti-skid control start condition is satisfied. When the start condition is satisfied and it is judged that the anti-skid control mode is satisfied, at step 600 the solenoid valves 61, 62 are set to the second
At the same time as switching to the position, the solenoid valves 31 to 38 are drive-controlled to shift to anti-skid control. When it is determined in step 500 that the anti-skid control mode is not in effect, the routine proceeds to step 700, where it is determined whether or not the braking force distribution control mode is in effect.
Go to 0. Whether or not the braking force distribution control mode is set is determined based on various conditions of the vehicle in the braking state. For example, the anti-skid control system is normal, the braking force distribution control system is normal, the wheels RR, RL behind the vehicle are not in the anti-skid control, and the solenoid valve 63
When all the conditions such as the ON state are satisfied, it is determined that the braking force distribution control is possible, the process proceeds to step 800, the braking force distribution control is performed, and the process returns to step 101 after completion.

In step 300, it is determined whether a predetermined braking operation has been performed. Specifically, after the brake pedal 3 is operated, the wheels FR (F
L) wheel speed VwFR (VwFF) is estimated vehicle speed Vso
When the wheel acceleration DVw of the differential value of the wheel speed is below a predetermined acceleration (including deceleration) G1, it is determined that “output before control is possible”, and the process proceeds to step 400 to perform pre-control pulse pressure increase control. Start, otherwise return to step 101. This pre-control pulse pressure increase control is adopted in the conventional anti-skid control device, and before the braking operation is performed and the anti-skid control is performed, the solenoid valve 31,
It is controlled so that 33, 35, and 37 are intermittently connected to hold and increase the brake fluid pressure repeatedly, which is also called pre-control hold control. When the pre-control pulse pressure increasing control is completed, the process returns to step 101.

In addition, a fail-safe function is added to the above control, and when some abnormality occurs in the braking force distribution control system, the solenoid valve 63 is turned off and returned to the first position shown in FIG. At the same time, the solenoid valves 35 and 37 are also set to the open position, and the wheel cylinders 53 and 54 are in communication with the master cylinder 2 via the proportioning valve 6. Thus, the braking force based on the conventional braking force distribution is applied to the wheels RR and RL.

The braking force distribution control of the above step 800 consists of the routine shown in FIG. 5. First, in step 801, various constants for setting the starting condition of the braking force distribution control are set. This will be described later with reference to FIG. Then, in step 802, the wheels FR, F
L, RR, RL wheel speeds VwFR, VwFL, VwRR, V
Each of the reference speeds V is calculated by a predetermined calculation process based on wRL.
wsFR, VwsFL, VwsRR, VwsRL are calculated. This arithmetic processing will be described later with reference to FIG. Furthermore,
In step 803, the reference speed difference between the front and rear wheels (VwsRR-V
wsFR) and (VwsRL-VwsFL) are DVwsRR and
Calculated as DVwsRL. And step 80
4, 805, the braking force distribution control of the wheels RR, RL is performed.

FIG. 6 shows a subroutine of the braking force distribution control for the wheels RR in step 804 of FIG. 5, and the braking force distribution control for the wheels RL in step 805 is similarly processed. First, in step 820, it is determined whether or not the control is being performed, and if the control flag indicating that the braking force distribution control is being performed is not set (“0”), the process proceeds to steps 821 to 826 and is set. If yes (“1”), the process proceeds to steps 827 to 829.

In step 821, it is determined whether or not the braking force distribution control can be started for the wheels RR. As the start condition, for example, the reference speed VwsRR has a predetermined relationship with the reference speed VwsFR of the wheel FR in front of the vehicle, and the reference acceleration DVso has a predetermined value (for example, -0.25).
G. However, G is equal to or lower than the gravitational acceleration, the brake switch 45 is in the ON state, and the estimated vehicle body speed Vso is equal to or higher than a predetermined speed (for example, 15 km / h). The details of this start condition will be described later with reference to FIG. When it is determined that the control can be started when all of these conditions are satisfied, the control-in-progress flag is set ("1") in step 822, and then the process proceeds to step 823. If the control start condition is not satisfied, the process in FIG. Return to routine.

At step 823, the slip ratio SpRR and the like are calculated based on the reference speed VwsRR and the like,
The control reference values TsRR and DfRR are calculated. The control reference value DfRR is calculated as a change in the reference speed difference DVwsRR, that is, a difference between the previous value and the current value (DVwsRR _{(n )} -DVwsRR _(n-1) ). The slip rate SpRR is the slip rate ((Vws) of the reference speed VwsRR of the wheel RR on the rear right side of the vehicle with respect to the reference speed VwsFR of the wheel FR on the front right side of the vehicle.
RR-VwsFR) / VwsFR), and the integrated value I
SpRR is calculated, and these functions f (SpRR, DfRR,
The control reference value TsRR is calculated as ISpRR).

Specifically, in step 824, the control map shown in FIG. 10 is constructed based on the control reference values TsRR and DfRR, and the control mode is determined according to this control map. In the figure, the vertical axis represents the slip ratio Sp
The control reference value TsRR is obtained by adding RR and the integrated value ISpRR, and the horizontal axis is the control reference value DfRR, and X1
It is divided into two regions P and D by a line segment connecting the intersection of (G) and Y1 (%) and the intersection of X2 (G) and Y2 (%) and a line parallel to the X axis. The region P is the pulse pressure increasing control mode, and the region D is the pulse pressure reducing mode. In both regions, the period Tb of the control pulse signal and the ON time are set. The period Tb is calculated as (Tb = Kb−Kc · L), where L is the length of a perpendicular line from an arbitrary point on the control map to a line segment connecting X1, Y1 and X2, Y2. (However, Kb and Kc are constants). Then, based on the control pulse signal, the pulse pressure reducing control or the pulse pressure increasing control is performed in step 825 or 826, respectively.

On the other hand, if it is determined in step 820 that the control-in-progress flag is set ("1"), then it is determined in step 827 whether the control end condition is satisfied. The termination condition is that the brake switch 45 is turned off and the reference acceleration DVso is a predetermined value (-
0.25G), etc., and if any of these conditions is satisfied, it is determined that the control can be ended, the in-control flag is reset (“0”), and normal pressure increasing control is performed in step 829. If the control end condition is not satisfied, the routine proceeds to step 823, and the braking force distribution control is continued.

FIG. 7 shows an example of the constant setting process shown in FIG. 5, and the control start reference is set to be changed according to the running road surface condition. That is, first, at step 811, the traveling road surface condition is determined. When it is estimated that the road surface on which the vehicle is traveling is uneven and it is determined that the vehicle is traveling on a rough road, the bias speed Vwz described below is set to the first set value Vwz1 in step 812, and if the vehicle is not traveling on a rough road. In step 813, the bias speed Vwz is set to the second set value Vwz2 (Vwz2 <Vwz1).
The rough road determination at step 811 is similar to the road surface condition determination performed at the time of the conventional anti-skid control. For example, as described in Japanese Patent Application Laid-Open No. 3-284443, the wheel acceleration is determined within a predetermined time. The condition of the traveling road surface is determined according to the number of times the reference value is exceeded. Then, in step 812, the bias speed Vwz and the slip ratio bias speed VwsFR · Spz are added to obtain a predetermined speed K.
3 (= Vwz + VwsFR · Spz) is calculated.

FIG. 8 shows an example of determination of the start condition of the braking force distribution control in step 821 of FIG. 6, and it is determined in step 831 whether or not the brake switch 45 is in the ON state. If it is off, the start condition is not satisfied and the routine proceeds to the next routine. In step 832, the estimated vehicle body speed Vso is compared with the predetermined speed K1 (for example, 15 km / h), and if it is more than this, the process proceeds to step 832, and if not, the start condition is not satisfied. Subsequently, in step 833, the acceleration DVs
It is determined whether or not o is equal to or less than the predetermined acceleration K2 (for example, -0.25G), and if so, the process proceeds to step 834, and if it exceeds this, the start condition is not satisfied. Further, in step 834, the reference speed VwsRR of the wheel RR is compared with a predetermined reference value (VwsFR-K3), and if it is less than this, the in-control flag is set as the start condition is satisfied ("
1 "), otherwise the starting condition is not satisfied. K3 in the reference value (VwsFR-K3) is the predetermined speed K3 obtained in step 812 of FIG. 7 described above.

FIG. 9 shows the calculation processing of the reference speed in step 802 of FIG. In the figure, an example of the wheel RR on the rear right side of the vehicle is shown, but the remaining wheels are similarly processed. From step 101, the wheel speed VwRR of the wheel speed RR is supplied in a predetermined calculation cycle and sequentially stored in the memory. First, at step 841, the current value (n times) VwRR _(n) is set to A. Next, in step 842, a predetermined value α _UP · t is added to the previous value VwRR _(n-1) to make it B. Then step 8
At 43, the predetermined value α _DN · t is subtracted from the previous value to obtain C.

Then, in step 843, the median values of A, B and C are calculated, and this is set as the reference value VwsRR. It should be noted that α _UP is a value that sets an acceleration with respect to the wheel speed VwRR, that is, a limit for the rate of increase of the wheel speed VwRR, for example, 2
G (where G is gravitational acceleration) is set. t is a calculation cycle, and is set to, for example, 10 mS. α _DN is the wheel speed VwRR
Is a value that sets the limit of the deceleration of the wheel speed VwRR, that is, the acceleration of the differential value DVw in the present embodiment.
A value (DVwRR +) obtained by adding a predetermined ratio value (α ₁ ) to RR
α ₁ ), and α ₁ is, for example, a value of 25% of DVwRR. In a vehicle equipped with an acceleration sensor, α _DN is calculated as (G ₀ + α ₀ ) (where G ₀ is a detection value of the acceleration sensor and α ₀ is a tilt correction value).

FIG. 11 shows the control situation of the wheel RR on the rear right side of the vehicle with respect to the wheel FR on the front right side of the vehicle in the above embodiment. For example, the brake pedal 3 is operated at the point a and the reference speed VwsRR of the wheel RR is changed. The decrease starts, and the reference speed VwsRR is the reference value (VwsFR-K3) of the chain double-dashed line.
The braking force distribution control for the wheels RR starts at a point b that is lower than the point b, and the hydraulic pressure limiting operation for the wheel cylinders 53 starts. Further, when the reference speed VwsRR exceeds the reference value of the upper dashed line, the pulse pressure increasing operation for the wheel cylinder 53 starts. That is, the region between the upper and lower dashed lines in the figure is a dead zone region, and stable control operation is ensured without being affected by disturbance. In the figure, the control ends at point c, and the brake pedal operation is released at point d. Thus, as indicated by the solid line in FIG. 12, the braking force control that follows the ideal braking force distribution curve is performed regardless of the presence or absence of the load.

[0039]

Since the present invention is configured as described above, it has the following effects. That is, the braking force distribution control device of the present invention is provided with the start determination means, whereby the braking force distribution control by the driving means is performed when the speed difference between the wheel speeds in the front of the vehicle and the rear of the vehicle exceeds the set value. Since the start is allowed and the dead zone region is formed, useless braking force distribution control can be avoided.

In particular, in the case of a vehicle equipped with the start determination means for setting the set value to a different value by the start condition setting means in accordance with the traveling road surface state judged by the road surface state judgment means, On the other hand, an appropriate dead zone region can be formed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a braking force distribution control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a braking force distribution control device of the present invention.

FIG. 3 is a block diagram showing a configuration of the electronic control device of FIG.

FIG. 4 is a flowchart showing a process for braking force control in one embodiment of the present invention.

FIG. 5 is a flowchart showing a process for braking force distribution control in one embodiment of the present invention.

FIG. 6 is a flowchart showing a process of a subroutine of a braking force distribution control of a vehicle rear right wheel in an embodiment of the present invention.

FIG. 7 is a flowchart showing a process of a subroutine of a braking force distribution control of a vehicle rear right wheel in the embodiment of the present invention.

FIG. 8 is a flowchart showing a processing of a subroutine of a braking force distribution control of a vehicle rear right wheel in the embodiment of the present invention.

FIG. 9 is a flowchart showing a process of a subroutine of a braking force distribution control of a vehicle rear right wheel in the embodiment of the present invention.

FIG. 10 is a graph showing a control map used for braking force distribution control of wheels on the rear right side of the vehicle in one embodiment of the present invention.

FIG. 11 is a graph showing a control situation of wheels on the rear right side of the vehicle in one embodiment of the present invention.

FIG. 12 is a graph showing the control situation of the braking force distribution in the present invention and the prior art.

[Explanation of symbols]

 2 master cylinder 3 brake pedal 4 low pressure reservoir 5 hydraulic booster 6 proportioning valve 10 electronic control unit 20 auxiliary hydraulic pressure source 21 pump 22 accumulator 24 electric motor 31-38 solenoid valve (hydraulic pressure control valve) 41-44 wheel speed sensor 51-54 Wheel cylinder 61-63 Solenoid valve FR, FL, RR, RL Wheel

Claims (2)

[Claims] 1. A wheel cylinder for a front wheel mounted on a wheel in front of a vehicle to apply a braking force, a wheel cylinder for a rear wheel mounted on a wheel on a rear side of a vehicle to apply a braking force, and a brake fluid in response to an operation of a brake pedal. And a hydraulic pressure generator for applying a brake hydraulic pressure to each of the front and rear wheel cylinders, and interposed between the hydraulic pressure generator and at least each of the rear wheel cylinders. A hydraulic control valve for controlling the brake hydraulic pressure, a wheel speed detecting means for detecting the wheel speed of each of the vehicle front wheel and the vehicle rear wheel, and the vehicle front wheel based on the detection output of the wheel speed detecting means. And a comparison means for comparing the wheel speeds of the wheels behind the vehicle, and the hydraulic pressure control valve is driven according to the comparison result of the comparison means to change the braking force of the wheels behind the vehicle to the braking force of the wheels ahead of the vehicle. To On the other hand, drive means for performing braking force distribution control that adjusts to a predetermined relationship, and braking force distribution control by the driving means during normal braking operation are prohibited, and wheel speeds of the wheels in front of the vehicle and wheels behind the vehicle are A braking force distribution control device, comprising: a start determination unit that allows the driving unit to start the braking force distribution control when the speed difference between the wheel speeds exceeds a set value. 2. The start determination means sets the set value to a different value according to the road surface state determination means for determining the traveling road surface state of the vehicle and the traveling road surface state determined by the road surface state determination means. The braking force distribution control device according to claim 1, further comprising condition setting means.