JP2001114083A - Brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake control device provided with a fore and aft braking force distributing device capable of improving the stability of a vehicle when braking the vehicle while preventing the generation of rear-first lock without lowering the braking efficiency. SOLUTION: When a driver operates a brake so as to turn a brake switch 11 on, during the predetermined time Tb from the brake switch 11 is turned on, EBD control is unconditionally inhibited by an EBD control determining unit 29, and after the predetermined time Tb is passed, in the case where a quick brake determining unit 28 determines the quick braking, an initial value of the threshold to be used for determining a start of the EBD control is reduced so that the EBD control is easily started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control device for a vehicle, and more particularly to a front-rear braking force distribution device that adjusts a distribution of a braking force of a front wheel and a braking force of a rear wheel.

[0002]

2. Description of the Related Art When a vehicle is braked, the load applied to the front wheels is larger than the load applied to the rear wheels. Therefore, the rear wheels tend to lock more easily during braking than the front wheels. Therefore, conventionally, a proportioning valve (hereinafter, referred to as a P valve) is provided so that the wheel cylinder hydraulic pressure of the rear wheel during braking is lower than the wheel cylinder hydraulic pressure of the front wheel. On the other hand, with the development of electronic control, the function of the P-valve, that is, the distribution of braking force between the front wheels and the rear wheels, has been performed by a front-rear braking force distribution device using electronic control. If the deceleration or a certain speed difference between the front wheel and the rear wheel is detected, the increase in the brake fluid pressure of the rear wheel is limited, and the function of the P valve is substituted.

FIG. 7 is a diagram showing a braking state of a vehicle when a braking force distribution control (hereinafter referred to as EBD control) is performed by a conventional longitudinal braking force distribution device. This shows a case of slow braking in which the pressure rises slowly. As can be seen from FIG. 7, when the brake pedal is operated and the brake switch is turned on during braking, the vehicle body deceleration VCEL increases and the predetermined threshold value T
If it exceeds ha, the EBD control is started, and an increase in the wheel cylinder hydraulic pressure of the rear wheel is limited, thereby avoiding skid of the rear wheel.

[0004]

On the other hand, FIG. 8 is a diagram showing a braking state of a vehicle when EBD control at the time of sudden braking is performed by a conventional longitudinal braking force distribution device. As can be seen from FIG. 8, at the time of rapid braking in which the wheel cylinder fluid pressure rises rapidly during braking, the rear wheel lock has already occurred when the vehicle deceleration VCEL exceeds the threshold value Tha and the EBD control is started. Since the so-called rear-end lock in which the rear wheels lock before the front wheels occurs and the ABS control is started, there is a problem that the vehicle becomes unstable. From this, the value of the threshold value Th is reduced and the EB
It is conceivable to make the timing to start the D control earlier, but in such a case, the EBD can be performed at a low hydraulic pressure during gentle braking.
There is a problem that the control is activated and the braking efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and is intended to identify whether or not sudden braking is performed at the time of braking and determine whether to start EBD control in accordance with the identification result. An object of the present invention is to provide a brake control device having a front-rear braking force distribution device that can improve the stability of a vehicle during braking without reducing braking efficiency by switching a threshold value to be used. And

Although the configuration is different from that of the present invention,
According to Japanese Patent Publication No. 144177, when it is determined that a braking operation exceeding a predetermined braking force has been performed, a braking force distribution control device in which a pressure control mode before control is entered and EBD control is further performed based on a speed difference between front and rear wheels. It has been disclosed. Further, although the configuration and the purpose are different from those of the present invention, Patent Document 2727907
In No., the high μ road sudden braking is determined from the absolute value of the vehicle body deceleration after the start of braking and the amount of time change, and when it is determined that the high μ road sudden braking is performed, the braking force on the front wheels is gradually increased. A brake control device is disclosed.

[0007]

A brake control device according to the present invention is a brake control device for a vehicle having an anti-skid control device for performing ABS control, comprising: a brake operation detecting means for detecting a brake operation for starting braking; A sudden braking determining means for determining whether the braking operation detected by the braking operation detecting means is a sudden braking, and an increase in brake fluid pressure with respect to a rear wheel. Brake fluid pressure limiting means for changing the start timing of the brake fluid pressure increase restriction in response to the brake fluid pressure limiting means. The timing at which the brake fluid pressure increase restriction for the rear wheels is started earlier than when it is determined that

Specifically, the brake operation detecting means includes an elapsed time detecting means for detecting an elapsed time since the brake operation is detected by the brake operation detecting means, and a vehicle body deceleration detecting means for detecting a vehicle deceleration. The determination means is configured to determine whether the elapsed time detected by the elapsed time detection means until the vehicle body deceleration detected by the vehicle body deceleration detection means reaches a predetermined value is a predetermined value Ta.
If it is less than the above, it is determined that the braking is sudden.

When the elapsed time detected by the elapsed time detecting means is within a predetermined value Tb smaller than the predetermined value Ta, the brake fluid pressure limiting means prohibits the increase in the brake fluid pressure for the rear wheels. You may make it.

[0010] More specifically, the brake fluid pressure limiting means determines to start increasing the brake fluid pressure for the rear wheels when the vehicle body deceleration detected by the vehicle body deceleration detecting means exceeds a threshold Th. In addition, the threshold Th is set to be smaller when the sudden braking is determined by the sudden braking determination means than when it is determined that the braking is not sudden.

On the other hand, there is provided a wheel speed detecting means for detecting the wheel speed of each wheel, and a vehicle speed detecting means for detecting the vehicle speed. The brake fluid pressure limiting means includes a vehicle pressure detecting means for detecting the vehicle speed detected by the vehicle speed detecting means. When the difference between the speed and the wheel speed of the rear wheel detected by the wheel speed detecting means exceeds the threshold value β, a determination is made to start the brake fluid pressure increase restriction on the rear wheel, and the sudden braking determining means When it is determined that the braking is sudden, the threshold value β may be set smaller than when it is determined that the braking is not sudden.

[0012] Further, there is provided a wheel speed detecting means for detecting a wheel speed of each wheel, and the brake fluid pressure limiting means comprises:
When the difference between the wheel speed of one of the front wheels detected by the wheel speed detecting means and the wheel speed of the rear wheel corresponding to the front wheel exceeds a threshold value ε, the brake fluid pressure increase for the rear wheel is restricted. May be started, and the threshold ε may be set to be smaller when the sudden braking determination means determines that the braking is abrupt than when it is determined that the braking is not abrupt.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic control system diagram showing an example of a brake control device according to an embodiment of the present invention, and shows a diagonal two-system brake system as an example. In FIG. 1, the right front wheel (FR) and the left rear wheel (R
L) only is shown.

In FIG. 1, a master cylinder 1 and wheel cylinders 2 corresponding to left and right front wheels and left and right rear wheels, respectively.
While the inlet valves 3A to 3D made of ON / OFF type electromagnetic valves are arranged between A to 2D, the outlet valves 4A to 4D made of ON / OFF type electromagnetic valves and the pump 5 are connected to the wheel cylinders 2A to 2D. A recirculation line 6 for recirculating the brake fluid is provided in the master cylinder 1 through the intermediary. A buffer chamber 7 is disposed between the outlet valves 4A to 4D of the reflux line 6 and the pump 5. In addition, A of the code | symbol which shows a wheel cylinder, an inlet valve, and an outlet valve
ＤD respectively indicate left and right front wheels and left and right rear wheels of the vehicle.

The wheel speed sensors S0 to S3 are connected to a signal processing device 8 to be described later.
S3 detects the respective wheel speeds of the corresponding left and right front wheels and right and left rear wheels, and outputs the detected wheel speeds to the signal processing device 8 as wheel speed signals.

FIG. 2 is a schematic block diagram showing an example of the brake control device according to the embodiment of the present invention. In FIG. 2, a brake control device 10 includes a wheel speed sensor S0 to S3 provided for each wheel, a signal processing device 8 of FIG. 1 including a microcomputer and the like, and a brake pedal operation for applying a brake. And a brake switch 11 for detecting whether or not a brake pedal is depressed, for example, and is connected to a hydraulic pressure control device 12 for controlling a wheel cylinder hydraulic pressure of each wheel. The hydraulic pressure control device 12 shows the wheel cylinders 2A to 2D, the inlet valves 3A to 3D, the outlet valves 4A to 4D, the pump 5, and the buffer chamber 7 in FIG.

The signal processing device 8 includes a wheel speed and wheel deceleration calculating unit 21, an estimated vehicle speed calculating unit 22, a wheel state detecting unit 23, and a hydraulic pressure control unit driving unit 24. Further, the signal processing device 8 includes a vehicle deceleration calculating unit 25.
And a brake operation detecting unit 26 that detects an ON / OFF state of the brake switch 11 to determine a brake operation state.
And an elapsed time calculation unit 27 that measures the elapsed time from the start of the braking operation, a rapid braking determination unit 28 that determines whether the braking operation is rapid braking, and an EBD control determination unit 29.

The wheel speed sensors S0 to S3, the wheel speed and wheel deceleration calculating unit 21, the estimated vehicle speed calculating unit 22, the wheel state detecting unit 23, and the hydraulic pressure control unit driving unit 24 are anti-skid control units for performing ABS control. And a brake switch 11, a vehicle body deceleration calculating unit 25, a brake operation detecting unit 26, an elapsed time calculating unit 27, and a sudden braking determining unit 2.
8, EBD control determination unit 29 and hydraulic pressure control device drive unit 24
Form a front / rear braking force distribution device that performs EBD control. Strictly speaking, the wheel speed sensors S0 to S3, the wheel speed and wheel deceleration calculator 21 and the estimated vehicle speed calculator 22
To form the front-rear braking force distribution device.

Each of the wheel speed sensors S0 to S3 is connected to a wheel speed and wheel deceleration calculating unit 21, respectively.
The respective wheel speeds and wheel decelerations are calculated from the signals from the third and third wheels. The wheel speed and wheel deceleration calculating unit 21 is connected to the estimated vehicle speed calculating unit 22, and the estimated vehicle speed calculating unit 2
2 calculates an estimated vehicle body speed VREF from the wheel speeds and the respective wheel speeds calculated by the wheel deceleration calculation unit 21.

Further, a wheel speed and wheel deceleration calculating section 21
The estimated vehicle speed calculating unit 22 includes a wheel state detecting unit 23
The wheel state detection unit 23 calculates the wheel speed based on the wheel speed and the wheel deceleration calculated by the wheel speed and wheel deceleration calculation unit 21 and the estimated vehicle speed VREF calculated by the estimated vehicle speed calculation unit 22. The lock and skid states of are detected. The wheel state detection unit 23 is connected to a hydraulic pressure control device drive unit 24 that drives and controls the hydraulic pressure control device 12 that increases or decreases or maintains the brake hydraulic pressure of each wheel.

On the other hand, the estimated vehicle speed calculation unit 22 is connected to a vehicle deceleration calculation unit 25, and the vehicle deceleration calculation unit 25
Estimated vehicle speed VR calculated by estimated vehicle speed calculator 22
The vehicle body deceleration VCEL is calculated from EF. Further, the brake switch 11 is connected to a brake operation detection unit 26, and the brake operation detection unit 26
It is detected whether or not the brake operation has been performed based on whether or not is turned on.

The elapsed time calculating section 27 connected to the brake operation detecting section 26 has an elapsed time T after the brake operation is performed based on the detection result of the brake operation detecting section 26.
Is calculated. The sudden braking determination unit 28 connected to the vehicle deceleration calculation unit 25 and the elapsed time calculation unit 27 respectively includes the elapsed time T calculated by the elapsed time calculation unit 27 and the vehicle deceleration calculated by the vehicle deceleration calculation unit 25. From the speed VCEL, it is determined whether or not the brake operation is sudden braking.

The EBD control determining unit 29 connected to the estimated vehicle speed calculating unit 22, the vehicle body deceleration calculating unit 25, the elapsed time calculating unit 27, and the sudden braking determining unit 28 is calculated by the estimated vehicle speed calculating unit 22. Based on the estimated vehicle speed VREF, the vehicle deceleration VCEL calculated by the vehicle deceleration calculation unit 25, and the determination result of the sudden braking determination unit 28, the start determination of the EBD control is performed. The EBD control determining unit 29 is further connected to a hydraulic pressure control device driving unit 24, and the hydraulic pressure control device driving unit 24 is configured to perform control based on the command input from the wheel state detecting unit 23 and the determination of the EBD control determining unit 29. To control the hydraulic pressure control device 12 for increasing or decreasing or maintaining the brake hydraulic pressure of each wheel.

The EBD control performed by the front and rear braking force distribution device in such a configuration will be described. Since the ABS control by the anti-skid control device is known, its description is omitted. When the driver operates the brake pedal to perform a brake operation, the brake switch 11 is turned on, and the brake operation detection unit 26
It recognizes that the brake switch 11 has been turned on, and detects that a brake operation has been performed. Elapsed time calculator 27
When the brake operation detection unit 26 detects that the brake operation has been performed, a timer (not shown) is used to determine the elapsed time T since the brake switch 11 is turned on.
Start measurement.

The sudden braking determination unit 28 determines the vehicle body deceleration VCEL
Is longer than a predetermined value α.
If it is less than, it is determined that the braking operation being performed is sudden braking, and otherwise, it is determined that it is not sudden braking.

As shown in FIG. 3, when the brake switch 11 is turned on and the brake operation detection unit 26 detects that the brake operation has been performed, the EBD control determination unit 29 performs a predetermined time Tb (Tb <Tb <). Until Ta), the EBD control is unconditionally prohibited. The elapsed time T is equal to a predetermined value Tb
Exceeds the threshold value Th, the EBD control determination unit 29 sets the initial value of the threshold Th used for determining the start of the EBD control to:
The two predetermined values Th1 and Th2 (Th1 <Th2) are switched and used according to the determination result by the sudden braking determination unit 28. Note that the change of the threshold value Th with respect to the elapsed time after the predetermined value Tb shown in FIG. 3 is an example, and is not limited to this.

That is, when the elapsed time T exceeds the predetermined value Tb and the sudden braking judgment unit 28 detects sudden braking, the EBD control judging unit 29 performs a control on the vehicle body deceleration VCEL for judging the start of the EBD control. The threshold value Th is reduced to the predetermined value Th1, and it is determined that the EBD control is started when the vehicle body deceleration VCEL exceeds the predetermined threshold value Th1 and the estimated vehicle body speed VREF exceeds the predetermined value γ.

On the other hand, when the elapsed time T exceeds the predetermined value Tb and the sudden braking determination unit 28 does not detect the sudden braking,
The EBD control determination unit 29 increases the threshold Th for the vehicle body deceleration VCEL for performing the start determination of the EBD control to Th2, and the vehicle body deceleration VCEL exceeds a predetermined threshold Th2 and the estimated vehicle body speed VREF. Is greater than the predetermined value γ, it is determined to start the EBD control. If the determination to start these EBD controls is not established,
A determination is made to prohibit the EBD control.

When the EBD control determining unit 29 determines to start the EBD control, the EBD control determining unit 29 controls the hydraulic pressure control device driving unit 24 to increase the rate of application of the brake hydraulic pressure of the left and right rear wheels independently or to the left and right. Adjust so that it is smaller than the front wheel brake fluid pressure. The hydraulic pressure control device drive unit 24 controls the drive of the hydraulic pressure control device 12 based on a command from the EBD control determination unit 29.

Next, the flow of the operation of the front and rear braking force distribution device will be described in more detail with reference to FIGS. FIG. 4 is a flowchart showing an operation example of the front and rear braking force distribution device of FIG. 2, and FIG. 4 shows an operation when the brake switch 11 is turned on, that is, when a driver performs a brake operation during braking. ing.

In FIG. 4, first, in step S1
Then, the wheel speed and wheel deceleration calculation unit 21 calculates the wheel speeds SPEED0 to SPEED3 of each wheel. In step S2, the estimated vehicle speed calculation unit 22 calculates the vehicle speed from the calculated wheel speeds SPEED0 to SPEED3. The estimated vehicle speed VREF, which is an estimated value of the speed, is calculated, and the calculated estimated vehicle speed VREF is output to the vehicle body deceleration calculation unit 25 and the EBD control determination unit 29, respectively. Since a method of calculating the estimated vehicle speed from each wheel speed is known, its description is omitted.

Next, in step S3, the vehicle deceleration calculating section 25 calculates the vehicle deceleration VCEL from the estimated vehicle speed VREF calculated by the estimated vehicle speed calculating section 22, and in step S4, the brake operation detecting section 26 detects that the brake switch 11 has been turned on, and accordingly, the elapsed time calculation unit 27 calculates the elapsed time T. Next, in step S5, the sudden braking determination unit 28 detects whether the braking operation performed by the driver is sudden braking based on the vehicle body deceleration VCEL and the elapsed time T.

Here, the sudden braking judgment process by the sudden braking judging section 28 shown in step S5 will be described with reference to the flowchart of FIG. In FIG. 5, unless otherwise specified, all the processing performed in FIG.
8 is performed. In FIG. 5, first, at step S21, it is checked whether or not the vehicle body deceleration VCEL calculated by the vehicle body deceleration calculating section 25 exceeds a predetermined value α (α> 0). (YES), the process proceeds to step S22. If it is determined in step S22 that the value does not exceed the predetermined value α (NO), the process proceeds to step S24, in which it is determined that the braking is not sudden braking in step S24, and the determination result is set to EB.
It outputs to the D control determination part 29, and returns to step S21.

Next, in step S22, it is checked whether or not the elapsed time T is less than a predetermined value Ta, and the predetermined value Ta (Ta
> 0) (YES), in step S23,
It is determined that the braking is sudden, and the determination result is output to the EBD control determination unit 29, and the process returns to step S21.

Next, returning to FIG. 4, in step S6, EB
The D control determination unit 29 checks whether or not the elapsed time T has exceeded the predetermined value Tb, and when the elapsed time T has not exceeded the predetermined value Tb (N
O) proceeds to step S12, and in step S12, E
The BD control determination unit 29 outputs a command to prohibit the EBD control to the hydraulic pressure control device driving unit 24, and the flow ends. If it is determined in step S6 that the value exceeds the predetermined value Tb (YES), the process proceeds to step S7, and the process proceeds to step S7.
Then, the sudden braking determination unit 28 determines whether or not the braking is sudden, and if it is determined that the braking is sudden (YES), the process proceeds to step S8.

The EBD control determination section 29 determines in step S8
The vehicle body deceleration VCEL is set to a predetermined threshold value Th1 (Th
1> 0), and if it exceeds the threshold Th1 (YES), it is determined in step S9 whether the estimated vehicle speed VREF exceeds a predetermined value γ (γ> 0). If it is determined that the value exceeds the predetermined value γ (YES), the process proceeds to step S10. In step S10, the EBD control determination unit 29 determines whether to start the EBD control, and determines in step S1
In step 1, an execution command of the EBD control is output to the hydraulic pressure control device driving unit 24, and the flow ends. Note that the drive output to each valve output from the hydraulic pressure control device drive unit 24 to the hydraulic pressure control device 12 may be a constant rate or a function of the estimated vehicle speed VREF.

If the elapsed time T does not exceed the predetermined value Tb in step S6 (NO), if the vehicle body deceleration VCEL does not exceed the threshold Th1 in step S8 (NO), and if it is estimated in step S9. If the vehicle speed VREF does not exceed the predetermined value γ (NO), the process proceeds to step S12, and in step S12, the EBD control determination unit 29 instructs the hydraulic pressure control device driving unit 24 to prohibit the EBD control. Then, this flow ends.

If it is determined in step S7 that the braking is not sudden braking (NO), in step S13, the EBD control determining unit 29 determines that the vehicle body deceleration VCEL has reached a predetermined threshold Th.
2 (Th2> Th1) is checked, and if it exceeds the threshold Th2 (YES), step S9 is performed.
Then, the process from step S9 to step S11 is performed, and this flow ends. In step S13, the threshold T
If h2 has not been exceeded (NO), the process of step S12 is performed, and this flow ends.

FIG. 6 is a diagram showing a braking state of the vehicle when the EBD control is performed by the front and rear braking force distribution device shown in FIGS. 2 to 5, and FIG. In the case of
FIG. 6B shows a case of slow braking. As can be seen from FIG. 6, the threshold value Th for performing the start determination of the EBD control is smaller at the time of sudden braking than at the time of gentle braking, and the EBD control is started earlier at the time of sudden braking than at the time of gentle braking. I am trying to. For this reason, the rear end of each rear wheel is prevented from being locked at the time of sudden braking as well as at the time of gentle braking, so that the stability of the vehicle is improved.

As described above, when the brake switch is turned on by the driver performing the brake operation in the present embodiment, the EBD control is performed for a predetermined time Tb after the brake switch 11 is turned on. The determination unit 29 unconditionally prohibits the EBD control,
If the predetermined time period is exceeded, the initial value of the threshold value Th used for the determination of the start of the EBD control during the rapid braking is determined by the rapid braking determination unit 28 in the case of the rapid braking, as compared with other braking states such as the gentle braking. And the timing at which the EBD control is started is made earlier.

Thus, without reducing the braking efficiency, it is possible to prevent the occurrence of a so-called rear-end lock in which the rear wheels are locked before the front wheels occur during sudden braking, and the stability of the vehicle during braking is reduced. Can be improved.
Further, it is possible to prevent a malfunction of the EBD control, which is likely to occur when the elapsed time T detected by the elapsed time calculation unit 27 is within the predetermined value Tb, and to prevent unnecessary EBD control from being performed. .

The determination of the sudden braking state is made by determining that the elapsed time T from when the brake operation is performed and the brake switch 11 is turned on until the vehicle deceleration VCEL reaches a predetermined value α is less than a preset time Ta. It depends on whether it is. From this, it is possible to more reliably detect the presence or absence of sudden braking used for the determination of the start of the EBD control, and it is possible to further improve the stability of the vehicle during braking.

In the above-described embodiment, the case where the vehicle body deceleration VCEL is used for the determination of the start of the EBD control is described as an example. However, the occurrence of the slip of the rear wheel is detected to determine the start of the EBD control. You may. In this case, the EBD control determination unit 29 determines the EB based on the wheel speed of each rear wheel calculated by the wheel speed and wheel deceleration calculation unit 21 and the estimated vehicle speed VREF calculated by the estimated vehicle speed calculation unit 22.
A D control start determination is made. That is, the EBD control determination unit 2
9, when the difference between the estimated vehicle speed VREF and the wheel speed of the rear wheel exceeds a threshold value β, a determination is made to start the EBD control, and an initial value of the threshold value β used for determining the start of the EBD control is determined. The two predetermined values β1 and β2 (β1 <β2) are switched and used in accordance with the determination result by the sudden braking determination unit 28.

For example, if the wheel speed of the left rear wheel is SPEED2
And the wheel speed of the right rear wheel is SPEED3. EBD
In step S8 in FIG. 4, the control determination unit 29 determines whether (VREF-SPEED2)> β1 instead of determining whether the vehicle body deceleration VCEL has exceeded a predetermined threshold Th1.
(Β1 is a predetermined value) and / or (VREF-SPEED3)
> V1 is determined, and (VREF-SPE
ED2)> β1 and / or (VREF-SPEED3)>
If β1 (YES), the processing from step S9 is performed, and (VREF-SPEED2)> β1 and / or (V
If (REF-SPEED3)> β1 is not satisfied (NO), the process proceeds to step S12, and the EBD control is prohibited.

Further, instead of determining whether or not the vehicle body deceleration VCEL exceeds a predetermined threshold value Th2 in step S13 of FIG.
It is determined whether or not (EF-SPEED2)> β2 (β2 is a predetermined value of β2> β1) and / or (VREF-SPEED3)> β2, and (VREF-SPEED2)> β2
And / or if (VREF-SPEED3)> β2 (YES), the processing after step S9 is performed, and (VREF-SPEED3)> β2
F-SPEED2)> β2 and / or (VREF-SPE
If ED3)> β2 is not satisfied (NO), the process proceeds to step S12, and the EBD control is prohibited. By doing so, the same effect as in the above embodiment can be obtained.

The EBD is calculated from the difference between the front wheel speed and the rear wheel speed.
Control start determination may be performed. In such a case, the EBD control determination unit 29 performs the EBD control start determination based on the speed difference between the wheel speed of one of the front wheels and the wheel speed of the rear wheel corresponding to the front wheel. That is, EBD
When the speed difference between the wheel speed of one of the front wheels and the wheel speed of the rear wheel corresponding to the front wheel exceeds a threshold value ε, the control determination unit 29 makes a determination to start the EBD control.
The two predetermined values ε1 and ε2 (ε1 <ε2) are switched and used as the initial value of the threshold value ε used to determine the start of the D control according to the determination result by the sudden braking determination unit 28.

For example, the speed of the left front wheel is set to SPEED
0, the wheel speed of the right front wheel is SPEED1, the wheel speed of the left rear wheel is SPEED2, and the wheel speed of the right rear wheel is SPEED3. The EBD control determination unit 29 determines in step S8 of FIG.
Instead of determining whether the vehicle body deceleration VCEL exceeds the predetermined threshold Th1, (SPEED0-S
PEED2)> ε1 (ε1 is a predetermined value) and / or (SPE
It is determined whether or not (ED1-SPEED3)> ε1 and (SPEED0-SPEED2)> ε1 and / or
If (SPEED1-SPEED3)> ε1 (YE
S), the processing after step S9 is performed, and (SPEED0
−SPEED2)> ε1 and / or (SPEED1-SP)
If EED3)> ε1 is not satisfied (NO), step S12
To prohibit the EBD control.

Further, instead of determining whether or not the vehicle body deceleration VCEL exceeds a predetermined threshold Th2 in step S13 of FIG.
EED0-SPEED2)> ε2 (ε2 is a predetermined value of ε2> ε1) and / or (SPEED1-SPEED3)> ε
2 is determined, and (SPEED0-SPEED
ED2)> ε2 and / or (SPEED1-SPEED)
3) If ε2 is satisfied (YES), the processing after step S9 is performed, and if (SPEED0-SPEED2)> ε2 and / or (SPEED1-SPEED3)> ε2 is not satisfied (NO), the flow proceeds to step S12 to inhibit the EBD control. I do. By doing so, the same effect as in the above embodiment can be obtained.

[0049]

As is apparent from the above description, according to the brake control device of the present invention, when the sudden braking determination means determines that the braking is sudden, the braking control is performed in other braking states such as a slow braking. By changing the threshold used for determining whether to start the brake fluid pressure increase restriction on the rear wheels, the timing for starting the brake fluid pressure increase restriction on the rear wheels is earlier than when it is determined that there is. I did it. From this, it is possible to start the EBD control at a substantially constant brake fluid pressure irrespective of the speed at which the brake fluid pressure is increased, and the rear wheels are moved ahead of the front wheels generated during sudden braking without lowering the braking efficiency. It is possible to prevent so-called rear-end lock from occurring, thereby improving the stability of the vehicle during braking.

More specifically, it is determined whether or not the braking that has been performed is sudden braking based on whether or not the elapsed time until the vehicle body deceleration reaches the predetermined value is less than the predetermined value Ta. Thus, it can be accurately determined whether or not the performed braking is sudden braking.

When the elapsed time detected by the elapsed time detecting means is within a predetermined value Tb which is smaller than the predetermined value Ta, the restriction on the increase of the brake fluid pressure for the rear wheels is prohibited. It is possible to prevent a malfunction of the EBD control, which is likely to occur within a predetermined time after the brake operation for starting the braking is performed, and prevent unnecessary EBD control from being performed.

[Brief description of the drawings]

FIG. 1 is a schematic control system diagram showing an example of a brake control device according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram illustrating an example of a brake control device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an elapsed time T and a threshold value Th in the brake control device shown in FIG.

FIG. 4 is a flowchart illustrating an operation example of a front-rear braking force distribution device in the brake control device of FIG. 2;

FIG. 5 is a flowchart illustrating an example of a sudden braking determination process by a sudden braking determination unit 28 of FIG. 2;

FIG. 6 is a diagram illustrating a braking state of the vehicle when EBD control is performed by the front and rear braking force distribution device illustrated in FIGS. 2 to 5;

FIG. 7 is a diagram illustrating a braking state of a vehicle when EBD control is performed during gentle braking by a conventional longitudinal braking force distribution device.

FIG. 8 is a diagram showing a braking state of a vehicle when EBD control is performed during sudden braking by a conventional longitudinal braking force distribution device.

[Explanation of symbols]

 Reference Signs List 8 signal processing device 10 brake control device 12 hydraulic pressure control device 21 wheel speed and wheel deceleration calculation unit 22 estimated vehicle speed calculation unit 24 hydraulic pressure control device drive unit 25 vehicle body deceleration calculation unit 26 brake operation detection unit 27 elapsed time calculation Unit 28 sudden braking determination unit 29 EBD control determination unit

Claims (6)

[Claims] 1. A brake control device for a vehicle having an anti-skid control device for performing ABS control, wherein a brake operation detection means for detecting a brake operation for starting braking, and a brake operation detected by the brake operation detection means. A sudden braking determining means for determining whether or not sudden braking is performed, and a restriction on an increase in brake fluid pressure for the rear wheel, and a start timing of the brake fluid pressure increase restriction is changed according to the determination result of the sudden braking determining means. Brake fluid pressure limiting means, wherein the brake fluid pressure limiting means
A brake control device characterized in that when it is determined that sudden braking is performed, the timing for starting the brake fluid pressure increase restriction on the rear wheels is earlier than when it is determined that sudden braking is not performed. 2. The vehicle according to claim 1, further comprising: an elapsed time detecting means for detecting an elapsed time after the brake operation is detected by the brake operation detecting means; and a vehicle deceleration detecting means for detecting a vehicle deceleration. The means determines that sudden braking is applied if the elapsed time detected by the elapsed time detection means until the vehicle body deceleration detected by the vehicle body deceleration detection means reaches a predetermined value is less than a predetermined value Ta. The brake control device according to claim 1, wherein: 3. The brake fluid pressure limiting means, when the elapsed time detected by the elapsed time detecting means is within a predetermined value Tb smaller than the predetermined value Ta, increases the brake fluid pressure for the rear wheels. 3. The brake control device according to claim 2, wherein the brake control is prohibited. 4. When the vehicle deceleration detected by the vehicle deceleration detecting means exceeds a threshold Th, the brake hydraulic pressure limiting means makes a determination to start a brake hydraulic pressure increase restriction on rear wheels. 4. The threshold value Th is set to be smaller when the sudden braking is determined by the sudden braking determination means than when it is determined that the braking is not sudden braking. The brake control device according to any one of the above. 5. A vehicle speed detecting means for detecting a wheel speed of each wheel, and a vehicle speed detecting means for detecting a vehicle speed, wherein the brake fluid pressure limiting means is detected by the vehicle speed detecting means. When the difference between the vehicle body speed and the wheel speed of the rear wheel detected by the wheel speed detecting means exceeds the threshold value β, a determination is made to start the brake fluid pressure increase restriction on the rear wheel, and the sudden braking determining means The threshold value β is set to be smaller when it is determined that sudden braking is performed than when it is determined that it is not sudden braking.
The brake control device according to any one of claims 1 to 3. 6. A wheel speed detecting means for detecting a wheel speed of each wheel, wherein the brake fluid pressure limiting means comprises:
When the difference between the wheel speed of one of the front wheels detected by the wheel speed detecting means and the wheel speed of the rear wheel corresponding to the front wheel exceeds a threshold value ε, the brake fluid pressure on the rear wheel increases. In addition to performing the determination to start the restriction, when the sudden braking determination unit determines that the braking is sudden, the threshold ε is set to be smaller than when it is determined that the braking is not sudden. The brake control device according to any one of claims 1 to 3.