JP2000238630A - Braking force controller for four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a rear wheel fluid pressure control valve means for controlling brake fluid pressure of wheel brakes for right and left rear wheels from being brought erroneously into a front and rear braking force distribution controlling condition resulting from a condition where all the four wheels are brought into wheel spin conditions. SOLUTION: When a control prohibition determining means 26 determines that a wheel speed detected by anyone of four wheel-speed detecting means 20FL-20RR exceeds an estimated vehicle-body speed calculated by a vehicle-body speed calculating means 21 by a fixed value or more, the control prohibition determining means 26 outputs a prohibition signal for prohibiting the control of rear wheel fluid pressure control valve means VRL, VRR by a braking force distribution control means 25, irrespective of the determination by a control start determining means 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rear wheel side deceleration calculated when a vehicle deceleration calculated based on an estimated vehicle speed is equal to or greater than a set vehicle deceleration and a rear wheel deceleration is equal to or greater than the set rear wheel deceleration. The present invention relates to a brake force control device for a four-wheel drive vehicle, which controls the distribution of front and rear brake forces by making the brake force of the front wheel side weaker than the brake force of the front wheels.

[0002]

2. Description of the Related Art Conventionally, a method of performing front and rear braking force distribution control in a four-wheel vehicle is already known, for example, from Japanese Patent Application Laid-Open No. 6-144176.

[0003]

In a four-wheel drive vehicle, all four wheels may cause wheel spin. In such a four-wheel wheel spin state, the driver performs an operation of returning the accelerator. If a shift down operation is performed, the wheel speeds of all four wheels decrease. Accordingly, at least one of the control start conditions is that the vehicle deceleration calculated from the estimated vehicle speed is equal to or higher than the set vehicle deceleration and the rear wheel deceleration is equal to or higher than the set rear wheel deceleration. In the four-wheel drive vehicle that performs the control, the driver incorrectly determines that the control start condition is satisfied by the accelerator return operation or the shift-down operation in the four-wheel wheel spin state, and the vehicle is in the non-brake operation state. Also, the rear wheel hydraulic pressure control valve means for controlling the brake hydraulic pressures of the left and right rear wheel brakes may be erroneously controlled to perform the front and rear brake force distribution control.

However, in the state where the front and rear brake force distribution control is performed, the rear wheel hydraulic pressure control valve means cuts off between the brake hydraulic pressure generating means and the left and right rear wheel brakes. When the driver performs the brake operation after the down operation, the braking force on the rear wheel side may be reduced.

[0005] The present invention has been made in view of such circumstances, and controls the brake fluid pressure of the left and right rear wheel brakes due to the fact that all four wheels are in a wheel spin state. It is an object of the present invention to provide a brake force control device for a four-wheel drive vehicle that prevents a rear wheel hydraulic pressure control valve unit from being erroneously brought into a front-rear brake force distribution control state.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 is provided with a wheel brake mounted on a left and right front wheel and a left and right rear wheel in a directly connected state, respectively, and a brake operation. Brake fluid pressure generating means for generating a brake fluid pressure in accordance with the above, and between the left and right rear wheel brakes, the left and right rear wheel brakes of the respective wheel brakes and the brake fluid pressure generating means can be disconnected. Rear wheel hydraulic pressure control valve means for controlling the brake hydraulic pressure of the wheel brakes for the wheels, wheel speed detecting means for individually detecting the wheel speeds of the four wheels, and a wheel speed change rate within a predetermined limit when the rate of change of the wheel speeds is within a predetermined limit. The estimated vehicle speed is made to follow the wheel speed, but when the rate of change exceeds a predetermined limit, the estimated vehicle speed is calculated based on the wheel speed obtained by each of the wheel speed detecting means so as to reduce the sensitivity of the following. car Speed calculating means, vehicle body deceleration calculating means for calculating vehicle deceleration from the estimated vehicle speed calculated by the vehicle speed calculating means, and at least one of left and right rear wheel wheel speed detecting means based on a detected value. Rear wheel deceleration calculating means for calculating rear wheel deceleration; and a rear wheel calculated by the rear wheel deceleration calculating means, wherein the vehicle deceleration obtained by the vehicle deceleration calculating means is equal to or greater than a set vehicle deceleration. It is determined whether the deceleration is equal to or greater than the set rear wheel deceleration as at least one control start condition, whether the control start condition is satisfied, and a control start signal when it is determined that the control start condition is satisfied. Control start determining means for outputting the brake fluid pressure of the left and right rear wheel brakes in response to the control start signal being output from the control start determining means, and the left and right rear wheel brakes and A braking force distribution control means for controlling the rear wheel hydraulic pressure control valve means so as to reduce or maintain the pressure in a state where the rake hydraulic pressure generation means is shut off. Whether the control prohibition condition is satisfied as a control prohibition condition that the wheel speed detected by any one of the wheel speed detection means exceeds the estimated vehicle speed calculated by the vehicle speed calculation means by a certain value or more. When it is determined that the control prohibition condition is satisfied, the control of the rear wheel hydraulic pressure control valve means by the brake force distribution control means is prohibited regardless of the determination by the control start determination means. And a control prohibition judging means for outputting a prohibition signal.

According to such a configuration, in a state where the wheels are generating wheel spin, the driver performs an operation of returning the accelerator or performing a downshift operation, so that the wheel speeds of all the four wheels decrease. However, the rear wheel hydraulic pressure control valve means for controlling the brake hydraulic pressure of the left and right rear wheel brakes is not erroneously controlled to perform the front and rear brake force distribution control. That is, in a state where four wheels are directly driven, if one wheel generates a wheel spin, all four wheels generate a wheel spin. Therefore, it is determined whether any one of the four wheels generates a wheel spin. Is detected, it can be determined that all four wheels are generating wheel spin. If the wheel speed of any one wheel exceeds the estimated vehicle speed by a certain value or more, all four wheels are wheel It can be determined that spin is occurring.
Therefore, in the state where the four wheels are generating wheel spin,
By prohibiting the control of the rear wheel hydraulic pressure control valve means by the braking force distribution control means, the control of the front and rear brake force distribution control is started by the accelerator return operation or the shift down operation by the driver in the wheel spin state of the four wheels. Even if it is erroneously determined that the conditions are satisfied, the rear wheel hydraulic pressure control valve means does not erroneously shut off between the left and right rear wheel wheel brakes and the brake hydraulic pressure generating means. When the driver performs the brake operation after the downshift operation, the braking force on the rear wheel side does not decrease.

[0008] The invention according to claim 2 provides the above-mentioned claim 1.
In addition to the configuration of the invention described above, the control prohibition determining unit includes:
The prohibition signal is continuously output for a certain period of time after the control prohibition condition is not satisfied. According to such a configuration, the rear wheel hydraulic pressure control is immediately performed when the control prohibition condition is not satisfied. The wheel brakes and the brake fluid for the left and right rear wheels are prevented until the valve means is erroneously controlled to perform the front and rear brake force distribution control, and the wheel spin state of the four wheels is reliably eliminated. It is possible to avoid shutting off between the pressure generating means and prevent a reduction in the rear wheel braking force during the brake operation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the accompanying drawings.

1 to 5 show an embodiment of the present invention. FIG. 1 is a diagram showing a drive system of a four-wheeled vehicle, and FIG. 2 is a diagram showing a brake hydraulic system of a four-wheeled vehicle. 3 is a block diagram showing a configuration of a braking force distribution control system in a four-wheel drive state, FIG.
FIG. 5 is a flowchart showing the procedure of the judgment by the control start judging means, and FIG. 5 is a timing chart of the judgment processing by the control prohibition judging means.

Referring first to FIG. 1, a pair of left and right front wheels is provided.
W_FL, W_FRAnd a pair of left and right rear wheels W_RL, W_RRIs shown
Are suspended at the front and rear of the vehicle, respectively.
Left and right front wheels W_FL, W_FRAnd left and right rear wheels W_RL, W_RRIs
It is connected to the power unit P via the drive system A. this
The drive system A includes both front wheels W_FL, W_FRAnd power unit P
Front differential D connecting between_FAnd both rear wheels W_RL, W_RRTo
Rear differential D to connect_RAnd the power unit P and
Rear differential D_RAnd a propulsion shaft 1 connecting the
In the middle of the propulsion shaft 1, the left and right front wheels W_FL, W_FRAnd left,
Right rear wheel W_RL, W_RRShut off between both front wheels W_FL, W_FROnly
Two-wheel drive state with drive wheels and left and right front wheels W _FL, W_FRYou
And left and right rear wheels W_RL, W_RRFour-wheel drive with direct drive
And a differential limiting device 2 that can switch between the
Actuator for operating the differential limiter 2
The eta 3 is controlled by the drive state switching control unit 4.
You.

In FIG. 2, each of the four wheels has a wheel brake B.
_FL , B _FR , B _RL , and B _RR are mounted, respectively, and the wheel brakes B _{FL to} B _RR and brake fluid pressure generating means for generating a brake fluid pressure corresponding to the depression force applied to the brake pedal BP by the driver. A brake fluid pressure control device 5 is provided between the tandem type master cylinder M and the tandem type master cylinder M.

[0013] The master cylinder M includes first and second output ports 6 _1, equipped with a 6 _2, the first output port 6 _1, the wheel brake for wheel brake B _FL and the right rear wheel for the left front wheel the first hydraulic pressure output channel ₇₁ is connected corresponding to B _RR, the second output port 6 _2, second corresponding to the wheel brake B _RL of wheel brake B _FR and the left rear wheel for the right front wheel
The output hydraulic pressure passage 7 ₂ are connected.

The brake fluid pressure control device 5 includes a normally-open solenoid valve 8 _FL , corresponding to each of the wheel brakes B _{FL to} B _RR individually.
Check valves 9 _FL , 9 _FR , 9 _RL , 9 connected in parallel with 8 _FR , 8 _RL , 8 _RR and the normally-open solenoid valves 8 _FL- 8 _RR , respectively.
_RR , normally closed solenoid valves 10 _FL , 10 _FR , 10 _RL , 10 _RR individually corresponding to the respective wheel brakes B _FL -B _RR;
And first and second reservoirs 11 ₁ and 11 ₂ respectively corresponding to the first and second output hydraulic pressure paths 7 ₁ and 7 ₂ , and suction valves 12 ₁ and 12 to the first and second reservoirs 11 ₁ and 11 _2.
First and second pumps are connected ₂ through respective 1
3 ₁ , 13 ₂ , one common electric motor 14 for driving both pumps 13 ₁ , 13 ₂ , and first and second pumps 13
_1, 13 ₂ to the discharge valve 15 _1, 15 ₂ of the first and second dampers 16 are connected through respective _1, and 16 _2, the first and second output hydraulic pressure line 7 _1, 7 ₂ and the first And the second
The first interposed between the dampers 16 ₁ and 16 ₂ respectively
Includes and a second orifice 17 _1, 17 _2, and an electronic control unit 18 which controls the normally open electromagnetic valve 8 _FL to 8 _RR, the operation of the normally closed solenoid valves 10 _FL to 10 _RR and the electric motor 14 .

The normally open solenoid valve 8 _FL is connected to the first output hydraulic pressure passage 7 ₁
And provided between the wheel brake B _FL for the left front wheel, the normally open electromagnetic valve 8 _RR is provided between the wheel brake B _RR for the first hydraulic pressure output channel ₇₁ and the right rear wheel, the normally open electromagnetic Valve 8 _FR
The second output hydraulic pressure line 7 ₂ and the wheel brake B _FR for the right front wheel
The normally open solenoid valve 8 _RL is provided between the second output hydraulic pressure path 7
₂ and a wheel brake _BRL for the rear left wheel.

Each of the check valves 9 _{FL to} 9 _RR allows the flow of the brake fluid from the corresponding wheel brakes B _{1 to} B ₄ to the master cylinder M.
_FL- 8 Connected to _RR in parallel.

Normally closed solenoid valve 10_FLIs the wheel block for the left front wheel.
Rake B_FLAnd the first reservoir 11 ₁Provided between
Closed solenoid valve 10_RRIs the wheel brake B for the right rear wheel_RRAnd
And the first reservoir 11₁Normally closed solenoid valve 10
_FRIs the wheel brake B for the right front wheel_FRAnd the second reservoir
11_TwoNormally closed solenoid valve 6_RLIs for the rear left wheel
Wheel brake B_RLAnd the second reservoir 11_TwoSet between
It is.

By the way, the normally-open solenoid valve 8 _FL and the normally-closed solenoid valve 10 _FL corresponding to the wheel brake B _FL for the front left wheel cooperate to constitute a hydraulic pressure control valve means V _FL for the front left wheel. The normally open solenoid valve 8 _RR and the normally closed solenoid valve 10 _RR corresponding to the wheel brake B _RR for the right rear wheel cooperate to constitute a right rear wheel hydraulic pressure control valve means V _RR , for the right front wheel. The normally open solenoid valve 8 _FR and the normally closed solenoid valve 10 _FR corresponding to the wheel brake B _FR cooperate to constitute the right front wheel hydraulic pressure control valve means V _FR, and the wheel brake B for the left rear wheel. _The normally open solenoid valve 8 _RL and the normally closed solenoid valve 10 _RL corresponding to _RL cooperate with each other to control the left rear wheel hydraulic pressure control valve means V _RL.
Is configured.

According to such a brake fluid pressure control device 5, blocks the wheel brakes B _FL .about.B _RR and pressure increasing state providing communication to the master cylinder M, the wheel brakes B _FL .about.B _RR from the master cylinder M And reservoirs 11 ₁ and 1
12 The decompression state to be passed to ₂ and each wheel brake B _FL -B
_The anti-lock brake control can be executed by switching between a hydraulic pressure holding state in which _RR is shut off from the master cylinder M and the reservoirs 11 ₁ and 11 _2, and in a state where the brake hydraulic pressure is output from the master cylinder M, left,
By setting the left and right rear wheel hydraulic control valve means V _RL , V _RR to a reduced pressure state or a hydraulic pressure holding state while keeping the right front wheel hydraulic pressure control valve means V _FL , V _FR in a pressure-increasing state. It is possible to execute the front and rear brake force distribution control in which the braking force of the right rear wheel brakes B _RL and B _RR is made _{weaker than} the braking force of the left and right front wheel brakes B _FL and B _FR. it can.

The electronic control unit 18 is configured to have a function as shown in FIG. 3 for performing braking force distribution control in a four-wheel drive state. Calculating means 21; vehicle deceleration calculating means 22 for calculating a vehicle deceleration from the estimated vehicle speed;
The rear wheel deceleration calculating means 23 for calculating the rear wheel deceleration, the control start determining means 24 for determining the start of the front and rear brake force distribution control, and the control start determining means 24 Braking force distribution control means 25 for controlling the left and right rear wheel hydraulic pressure control valve means V _RL and V _RR accordingly;
Regardless of the judgment by the control start judgment means 24, the left and right rear wheel hydraulic pressure control valve means V by the brake force distribution control means 25
_RL, and a control prohibition determination unit 26 for outputting a prohibition signal for prohibiting the control of the V _RR.

The vehicle speed calculating means 21 includes wheel speed detecting means 20 _FL , 2 for individually detecting the wheel speeds of the four wheels.
The estimated vehicle speed is calculated based on the detected values of 0 _FR , 20 _RL , and 20 _{RR. When} the change rate of the wheel speed is within a predetermined limit, the estimated vehicle speed follows the wheel speed. When the limit is exceeded, the estimated vehicle speed is calculated so that the following sensitivity is reduced. When the rate of change of the wheel speed exceeds the predetermined limit, the vehicle speed calculating means 21
Defines the estimated vehicle speed assuming that the vehicle speed changes at the assumed maximum deceleration and maximum acceleration.

The vehicle deceleration calculating means 22 calculates the vehicle deceleration by differentiating the estimated vehicle speed calculated by the vehicle speed calculating means 21, and the rear wheel deceleration calculating means 23
The rear wheel deceleration is calculated based on at least one of the left and right rear wheel speed detectors 20 _RL and 20 _RR . In this embodiment, the rear wheel deceleration calculator 23 is used.
Calculates the rear wheel deceleration by differentiating the high select value of the detection values of the two wheel speed detecting means 20 _RL and 20 _RR .

The control start judging means 24 comprises a wheel speed obtained by each wheel speed detecting means 20 _{FL to} 20 _RR , a vehicle deceleration obtained by the vehicle deceleration calculating means 22, and a rear wheel deceleration calculating means 23. Based on the rear wheel deceleration obtained in
It is determined whether or not to start the front and rear brake force distribution control according to the procedure shown in FIG. 4. In step S1, the vehicle deceleration obtained by the vehicle deceleration calculating means 22 is equal to or greater than the set vehicle deceleration. When it is determined whether the vehicle body deceleration is equal to or higher than the set vehicle body deceleration, in step S2, it is determined whether the front wheel speed is higher than the rear wheel speed by a predetermined value or more. When it is confirmed that the wheel speed is equal to or greater than the set value, the process proceeds to step S3 to output a control start signal.

If it is determined in step S2 that front wheel speed-rear wheel speed <set value, the process proceeds to step S4, where the rear wheel deceleration obtained by the rear wheel deceleration calculating means 23 is equal to or greater than the set rear wheel deceleration. Check if there is, rear wheel deceleration ≧
If it is the set rear wheel deceleration, the process proceeds from step S4 to step S3 to output a control start signal.

That is, the control start judging means 24 judges that the vehicle deceleration obtained by the vehicle deceleration calculating means 21 is equal to or higher than the set vehicle deceleration, and that the front wheel speed is higher than the rear wheel speed by the set value or more. Either the vehicle deceleration obtained by the speed calculating means 21 is equal to or greater than the set vehicle deceleration and the rear wheel deceleration calculated by the rear wheel deceleration calculating means 23 is equal to or greater than the set rear wheel deceleration. Then, the control start signal is output assuming that the front and rear brake force distribution control should be started.

The control start signal from the control start judging means 24 is inputted to the braking force distribution control means 25. The braking force distribution control means 25 does not receive the prohibition signal from the control prohibition judging means 26. As long as the control start signal is input, the brake fluid pressures of the left and right rear wheel brakes B _RL and B _RR are changed to the left and right rear wheel brakes B _RL and B _RR and the brake fluid pressure generating means. The rear-wheel hydraulic pressure control valve means V _RL , V _RR is controlled so as to reduce or maintain the pressure in a state where M is shut off.

The control prohibition judging means 26 obtains the wheel speed obtained by any one of the wheel speed detecting means 20 _{FL to} 20 _RR (20 _{RR in} this embodiment) by the vehicle speed calculating means 21. As a control prohibition condition for prohibiting the braking force distribution control before and after that the estimated vehicle speed exceeds a predetermined value or more, it is determined whether or not the control prohibition condition is satisfied, and FIG. As shown by, when the rear wheel speed obtained by the wheel speed detecting means 20 _RR is changing, the rear wheel speed exceeds the estimated vehicle speed calculated by the vehicle speed calculating means 21 by a certain value or more. from the time t _1,
As shown in FIG. 5C, the output of the inhibition signal is started.
The control prohibition determination unit 26, when the control prohibition condition exceeds the estimated vehicle speed is rear wheel speed above a certain value is canceled, FIG. 5 from the time t ₂ when the control inhibition condition is eliminated
Starts measuring time by the timer as shown by (b), at time t ₃ when counting the predetermined time by the timer is completed, FIG. 5
The output of the inhibition signal is stopped as shown in FIG.

A prohibition signal from the control prohibition judging means 26
Is input to the braking force distribution control means 25, and the braking force
The distribution control means 25 receives the prohibition from the control prohibition determination means 26.
At the time of signal input, the control start determination means 24
Hydraulic control valve means for rear wheel V _RL, V_RRExecute the control of
No.

Next, the operation of this embodiment will be described. The control start determining means 24 determines that the vehicle deceleration is equal to or greater than the set vehicle deceleration and the rear wheel deceleration is equal to or greater than the set rear wheel deceleration. As one of the conditions, the start of the front and rear brake force distribution control is determined. Therefore, when wheel spin occurs in all four wheels in the four-wheel drive state, the wheel speed of all four wheels decreases due to the driver returning the accelerator or performing a downshift operation. The control start determining means 24 may erroneously determine that the control start condition is satisfied despite the non-brake operation state, and in response to such erroneous control start determination, Left and right rear wheel hydraulic control valve means V _RL ,
If the F _RR is erroneously controlled to perform the front and rear brake force distribution control, the master cylinder M and the wheel brakes B _RL and B _RR for the left and right rear wheels are shut off. When the driver performs the brake operation after the downshift operation, there is a possibility that the braking force on the rear wheel side is reduced.

However, the control prohibition judging means 26 calculates the wheel speed detected by any one of the four wheel speed detecting means 20 _{FL to} 20 _RR as a fixed value of the estimated vehicle speed calculated by the vehicle speed calculating means 21. It is determined whether or not the control prohibition condition is satisfied as a control prohibition condition when it exceeds the above. When it is determined that the control prohibition condition is satisfied, the braking force is determined regardless of the determination by the control start determination means 24. Left and right rear wheel hydraulic pressure control valve means V by distribution control means 25
A prohibition signal for prohibiting the control of _RL and _VRR is output. Therefore, even if the driver performs an operation of returning the accelerator or performing a downshift operation in a state where the four wheels are generating wheel spin, even if the wheel speeds of all four wheels are reduced, the left and right rear wheel The rear wheel hydraulic pressure control valve means V _RL , V _RR for controlling the brake hydraulic pressure of the wheel brakes B _RL , B _RR of the first embodiment is not erroneously controlled to a state in which the front and rear brake force distribution control is performed.

That is, in a state where four wheels are directly driven, if one wheel generates wheel spin, all four wheels generate wheel spin. Therefore, any one of the four wheels generates wheel spin. If it is detected whether all four wheels are generating wheel spin, it is possible to determine that the wheel speed of any one wheel exceeds the estimated vehicle speed by a certain value or more. It can be determined that all the wheels are spinning. Therefore, in a state in which the four wheels are generating wheel spin, the control of the left and right rear wheel hydraulic pressure control valve means V _RL , V _RR by the brake force distribution control means 25 is prohibited, so that the four wheel is in a wheel spin state. Even if the driver mistakenly determines that the control start condition of the front and rear brake force distribution control has been satisfied by the accelerator return operation or shift down operation by the driver in
The rear wheel hydraulic pressure control valve means V _RL , V _RR does not inadvertently shut off the connection between the left and right rear wheel brakes B _RL , B _RR and the master cylinder M, and after the accelerator return operation or the shift down operation. When the driver performs the braking operation, the braking force on the rear wheels does not decrease.

Further, the control prohibition judging means 26 continues to output the prohibition signal for a certain period of time after the control prohibition condition is not satisfied. The control valve means V _RL , V _RR are prevented from being erroneously controlled to perform the front and rear brake force distribution control, and are used for the left and right rear wheels until the wheel spin state of the four wheels is reliably eliminated. Of the wheel brakes B _RL , B _RR and the master cylinder M can be avoided, and a reduction in the rear wheel braking force during the brake operation can be prevented.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible to do.

For example, in the above embodiment, the case where the master cylinder is used as the brake hydraulic pressure generating means has been described. However, the hydraulic pressure is output using an actuator such as an electric motor which operates according to the brake operation amount. This may be used as the brake fluid pressure generating means. Further, in the above embodiment, the case where the present invention is applied to a vehicle in which the two-wheel drive state and the four-wheel drive state can be switched has been described. However, the present invention can also be applied to a four-wheel drive vehicle.

[0035]

As described above, according to the first aspect of the present invention, the driver performs an operation of returning the accelerator or performing a downshift operation while the four wheels are generating wheel spin. Even if the wheel speeds of all the wheels decrease, the rear wheel hydraulic pressure control valve means that controls the brake hydraulic pressure of the left and right rear wheel brakes incorrectly controls the front and rear brake force distribution control. When the driver performs the brake operation after the accelerator return operation or the downshift operation, the braking force on the rear wheel side does not decrease.

According to the second aspect of the present invention, it is possible to avoid shutting off between the wheel brakes for the left and right rear wheels and the brake fluid pressure generating means until the wheel spin state of the four wheels is reliably eliminated. However, it is possible to prevent a decrease in the rear wheel braking force during the brake operation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a drive system of a four-wheel vehicle.

FIG. 2 is a diagram showing a brake hydraulic system of a four-wheeled vehicle.

FIG. 3 is a block diagram showing a configuration of a braking force distribution control system in a four-wheel drive state.

FIG. 4 is a flowchart illustrating a determination procedure in a control start determination unit.

FIG. 5 is a timing chart of a judgment process by a control prohibition judgment unit.

[Explanation of symbols]

20 _FL , 20 _FR , 20 _RL , 20 _RR ... wheel speed detecting means 21 ... body speed calculating means 22 ... body deceleration calculating means 23 ... rear wheel deceleration calculating means 24 ... control Start judging means 25 ・ ・ ・ Brake force distribution control means 26 ・ ・ ・ Control prohibition judging means B _FL・ ・ ・ Wheel brake for left front wheel B _FR・ ・ ・ Wheel brake for right front wheel B _RL・ ・ ・ Left rear wheel Wheel brake B _RR・ ・ ・ Wheel brake for right rear wheel M ・ ・ ・ Master cylinder as brake fluid pressure generating means V _RL , V _RR・ ・ ・ Rear wheel hydraulic pressure control valve means W _FL・ ・ ・Left front wheel W _FR・ ・ ・ Right front wheel W _RL・ ・ ・ Left rear wheel W _RR・ ・ ・ Right rear wheel

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D045 CC01 EE21 FF42 GG05 GG27 GG28 3D046 BB28 BB31 HH23 HH26 HH36 HH39 JJ00 JJ04 JJ06 JJ07

Claims (2)

[Claims] 1. The left and right front wheels (W_FL,
W_FR) And left and right rear wheels (W_RL, W_RR)
Wheel brake (B_FL, B_FR, B_RL, B_RR)
Brake fluid that generates brake fluid pressure in response to rake operation
Pressure generating means (M) and the wheel brakes (B_FL~
B_RR), The left and right rear wheel brakes (B _RL,
B_RR) And the brake fluid pressure generating means (M) is shut off.
To the left and right rear wheel brakes (B
_RL, B_RR) Brake fluid pressure control valve for rear wheel
Means (V_RL, V_RR) And the wheel speeds of the four wheels
Wheel speed detecting means (20)_FL, 20_FR, 2
0_RL, 20_RR), And the rate of change of the wheel speed is within the predetermined limit
The estimated vehicle speed is made to follow the wheel speed.
Beyond the predetermined limit, the sensitivity of the following is reduced.
The wheel speed detecting means (20_FL~ 20_RR)
Vehicle speed to calculate the estimated vehicle speed based on the wheel speed
Calculation means (21) and the vehicle speed calculation means (21)
Vehicle deceleration to calculate vehicle deceleration from the issued estimated vehicle speed
Speed calculating means (22), wheel speed detection for left and right rear wheels
Means (20_RL, 20_RR) Based on at least one of the detected values
Rear wheel deceleration calculating means (2)
3) and the vehicle obtained by the vehicle body deceleration calculating means (21)
The body deceleration is equal to or greater than the set vehicle deceleration and the rear wheel
The rear wheel deceleration calculated by the deceleration calculation means (23) is set.
Start at least one control that the rear wheel deceleration is greater than or equal to
Judge whether the control start condition is satisfied as a condition
And that the control start condition is satisfied.
Control start determining means (2) for outputting a control start signal when the
4) and a control start signal from the control start determining means (24).
Is output according to the left and right rear wheel brakes
(B_RL, B_RR) Brake fluid pressure for left and right rear wheels
Rake (B_RL, B_RR) And brake fluid pressure generating means
(M) Before depressurizing or holding with the interval cut off
The rear wheel hydraulic control valve means (V _RL, V_RRShake to control)
Brake for a four-wheel drive vehicle having a power distribution control means (25).
In the rake force control device, the four wheel speed detecting hands
Step (20_FL~ 20_RR) Wheel detected by any one of
Estimation of the speed calculated by the vehicle speed calculation means (21)
Control prohibition condition that the vehicle speed exceeds a certain value or more
To determine whether the control prohibition condition is satisfied
And that the control prohibition condition is satisfied.
Irrespective of the judgment by the control start judgment means (24)
The rear wheel by the braking force distribution control means (25)
Hydraulic pressure control valve means (V_RL, V_RR) Prohibition of control
Including a control prohibition judging means (26) for outputting a signal.
A braking force control device for four-wheel drive vehicles. 2. The four-wheel drive according to claim 1, wherein the control prohibition judging means (26) continuously outputs the prohibition signal for a certain period of time after the control prohibition condition is not satisfied. Car brake force control device.