JP2002308082A - Brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost, and to miniaturize a device by miniaturizing a pump by reducing a required workload of the pump by preventing an overshoot of braking fluid pressure of rear wheels even at sudden braking time, and precisely performing braking restraining control for the rear wheels. SOLUTION: This brake control device has a hydraulic control valve b capable of reducing and increasing fluid pressure of a wheel cylinder a, a wheel speed detecting means c for detecting a wheel speed, and a braking control means d for performing rear wheel braking restraining control for prohibiting a pressure increase in the rear wheels when the rear wheels become a prescribed slip state on the basis of the detected wheel speed. The braking control means d is formed as a means for performing emergency rear wheel braking restraining control for prohibiting the pressure increase in the rear wheels for a prescribed time when car body deceleration is larger tan a present sudden deceleration determining value, and when wheel deceleration of a control object wheel of the rear wheels is larger than a preset deceleration present value even if the rear wheels do not become the prescribed slip state.

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 which controls the operation of a proportioning valve, which is conventionally provided to prevent the rear wheel from locking before the front wheel, by controlling a hydraulic pressure control valve. .

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 10-12944
As described in Japanese Patent Laid-Open No. 2 (1993), a target slip vehicle speed (this value is a vehicle speed greater than a pressure reduction threshold) is obtained from a pseudo vehicle speed formed by the wheel speeds of the front wheels, and the wheel speed of the rear wheels is determined by the target wheel speed. When the speed falls below the slip vehicle speed,
2. Description of the Related Art There is known a technique in which a pressure increase is prohibited and a brake fluid pressure is held to suppress rear wheel slip and prevent anti-skid control from being executed early. In this specification,
This control is called rear wheel braking suppression control.

FIG. 15 is a time chart showing an operation example of the above-mentioned prior art. As shown in FIG.
When braking is performed in which I changes as shown in the figure, a target slip vehicle speed λB slightly lower than the pseudo vehicle speed VI is set. In the figure, VWS is an optimum slip ratio value at which a braking force is most efficiently obtained on a dry road, and when the wheel speed VW falls below this value, pressure reduction is started by anti-skid control. is there.

In this prior art, as shown by a dotted line in FIG.
When it becomes lower than B, the increase in the brake fluid pressure (W / C pressure) is prohibited and held, and the reduction to the optimum slip ratio value VWS, that is, the execution of the anti-skid control is suppressed.

[0005]

However, the above-described prior art has the following problems to be solved. In other words, when the brake pedal is depressed slowly during braking, and when the brake pedal is suddenly depressed, the load fluctuation state of the rear wheels is different. In FIG. 15, the dotted line indicates the case where the driver steps down slowly, and the solid line indicates the case where the driver steps down suddenly. Rises without delay with respect to the rise of. In this case, the execution of the anti-skid control as described above is suppressed.

On the other hand, in the case of a sudden step indicated by a solid line in the figure, while the longitudinal acceleration rises sharply,
The rising timing of the load fluctuation of the rear wheel is delayed. For this reason, in the early stage of braking, since a sufficient load is left on the rear wheels, the braking fluid pressure rises significantly more than when the pedal is stepped on slowly (the amount indicated as overshoot in the figure). Further, after the brake fluid pressure is significantly increased in this manner, the load on the rear wheel fluctuates greatly, so that the rear wheel slips rapidly and anti-skid control is executed.

As described above, in the prior art, since the rear wheel braking suppression control is performed based only on the target slip vehicle speed, there is a possibility that sufficient braking of the rear wheel may not be sufficiently suppressed during sudden braking. Further, when the braking is not sufficiently suppressed as described above, when the anti-skid control is executed, the amount of the brake fluid discharged from the wheel cylinder toward the reservoir increases, and the brake fluid of the reservoir is supplied to the brake circuit. The amount of work of the pump returned to the pump increases, and a pump having a large capacity is required. In this case, there is a problem that the cost is increased and the size of the apparatus is increased.

The present invention has been made in view of the above-mentioned problems, and the braking suppression pressure of the rear wheels can be accurately executed by preventing the overshoot of the braking fluid pressure of the rear wheels even at the time of sudden braking. As a result, it is another object of the present invention to reduce the required work amount of the pump and reduce the size of the pump, thereby reducing the cost and the size of the device.

[0009]

In order to achieve the above object, the present invention provides a hydraulic pressure control valve b capable of reducing and increasing the hydraulic pressure of a wheel cylinder a, as shown in FIG. Wheel speed detecting means c for detecting wheel speed;
Braking control means d for performing rear wheel braking suppression control for inhibiting pressure increase of the rear wheel when the rear wheel enters a predetermined slip state based on the detected wheel speed. Even if the rear wheel is not in the predetermined slip state, the control means d determines that the vehicle deceleration is larger than the preset sudden deceleration determination value and the wheel deceleration of the rear wheel to be controlled is An emergency rear wheel braking suppression control that prohibits the rear wheel pressure increase for a predetermined time when the set value is larger than the set deceleration set value is executed.

[0010] The invention described in claim 2 is the same as the claim 1.
Wherein the sudden deceleration determination value is a value by which it can be determined that the vehicle has sufficiently started deceleration. According to a third aspect of the present invention, in the brake control device according to the second aspect, the sudden deceleration determination value is a value within a range of -0.2 g to -0.7 g.

The invention described in claim 4 is the first invention.
4. The brake control device according to any one of the first to third aspects, wherein the deceleration set value is a value corresponding to a vehicle deceleration on a dry road. The invention according to claim 5 is the brake control device according to claim 4, wherein the deceleration set value is:
The value is in the range of -0.85 g to -1.2 g.

[0012]

When the vehicle is suddenly braked, the deceleration of the vehicle rapidly rises, but the load fluctuation of the rear wheels is delayed. In this case, the slip amount of the rear wheels does not increase, and the rear wheels are not increased. Decrease in the wheel speed is equivalent to the vehicle speed. Therefore, in such a case, the vehicle deceleration suddenly rises and becomes larger than the sudden deceleration judgment value set by the sudden deceleration, and the wheel deceleration also shows an increase corresponding to the vehicle deceleration at the time of sudden braking. Greater than the value.
Therefore, the braking control means executes the emergency rear wheel braking suppression control, and prohibits the rear wheel pressure increase for a predetermined time. Therefore,
Since the rear wheel braking is suppressed earlier than before and the increase in the brake fluid pressure of the rear wheel is suppressed, when the load fluctuation occurs in the rear wheel and the wheel load becomes lighter, the locking tendency becomes stronger. Can be suppressed. In addition, by executing the emergency rear wheel braking suppression control early in this way, even if the anti-skid control is performed thereafter, the amount of brake fluid discharged from the wheel cylinder is reduced, and the necessary operation amount of the pump is reduced. , The size of the pump can be reduced, thereby reducing the cost and the size of the device.

According to the second aspect of the present invention, the sudden deceleration determination value is a value that can be used to determine that the vehicle has started to sufficiently decelerate. It is possible to accurately determine the braking state in which the load change is delayed. It should be noted that the sudden deceleration judgment value is determined according to claim 3.
As described in above, by setting the value in the range of -0.2 g to -0.7 g, optimization can be achieved. This value determines an optimum value according to vehicle specifications.

According to the present invention, the deceleration set value is set to a value corresponding to the vehicle deceleration on a dry road, so that even if the rear wheels are not in a slip state, the vehicle is decelerated. Can be reliably determined that the braking corresponding to the sudden braking is performed. The deceleration set value can be optimized by setting the deceleration set value to a value within a range of -0.85 g to -1.2 g.
This value determines an optimum value according to vehicle specifications.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The brake control device according to this embodiment corresponds to the invention described in all claims,
Further, anti-skid control for preventing the wheels from locking during braking is also executed. First, the configuration of the brake device will be described. In FIG. 2, M / C indicates a master cylinder, and this master cylinder M / C
Are connected to four wheel cylinders W / C via two brake circuits 1, 1.

Each of the brake circuits 1 is branched into two wheel cylinders W / C at a branch point 1d, respectively, and further downstream of the branch point 1d (wheel cylinder W / C).
Side) are provided with pressure-intensifying valves 5 and 5. These booster valves 5
Is a normally open 2-port 2-position ON / OFF solenoid valve which is opened by a spring force when not in operation and closed when activated (when energized). Each of the pressure-intensifying valves 5 is provided in parallel with a bypass 1h for returning the brake fluid smoothly from the wheel cylinder W / C when the braking operation is completed. / C side) is provided with a one-way valve 1g that allows only return from the upstream (master cylinder M / C side).

A drain circuit 10 for connecting the brake circuit 1 and the reservoir 7 is connected downstream of each pressure increasing valve 5. The drain circuit 10 is provided with a pressure reducing valve 6. Each of the pressure reducing valves 6 is a normally closed 2-port 2-position ON / OFF solenoid valve that closes when not operating and opens when operating.

The drain circuit 10 is connected to a position upstream of the branch point 1d in each brake circuit 1 via a return circuit 11. Further, a pump 4 for returning the brake fluid stored in the reservoir 7 to the brake circuit 1 is provided in the middle of the return circuit 11. Therefore, the recirculation circuit 11 includes the suction circuit 11a and the discharge circuit 11b.

The pump 4 sucks the brake fluid from the suction circuit 11a by the reciprocating stroke of a pair of plungers 41 arranged opposite to each other by the cam 4c rotated by the motor M, and brakes it to the discharge circuit 11b. It is configured to discharge a liquid, provided with a suction valve 4a and a discharge valve 4b for preventing backflow, a filter member 42 is provided on the suction side, and a pulsation absorbing damper 4d is provided on the discharge side. I have.

Therefore, in this brake device, when a wheel tends to lock during braking, the pressure-intensifying valve 5 in the circuit connected to the wheel cylinder W / C of the wheel having the tendency to lock is closed. The pressure reducing valve 6 is opened to release the brake fluid from the wheel cylinder W / C to the reservoir 7 to reduce the brake fluid pressure, and the pressure increasing valve 5 is returned to the open state and the pressure reducing valve 6 is closed. And the pressure increasing control for supplying the master cylinder pressure to the wheel cylinders W / C is repeated as appropriate, or if necessary, a holding control for closing both the pressure increasing valve 5 and the pressure reducing valve 6 is added, and Anti-skid control that performs braking while preventing locking, and increases the wheel cylinder pressure (braking fluid pressure) of the rear wheels to prevent the rear wheels from locking before the front wheels during braking. It is those capable of performing the wheel braking suppression control after win, pressure increase valve 5 and the pressure reducing valve 6 corresponds to the hydraulic pressure control valve of the claims.

The anti-skid control and the rear wheel braking suppression control are executed by the control unit 12 shown in FIG. That is, the control unit 12
On the input side, a wheel speed sensor 13 for detecting each wheel speed of the front and rear left and right wheels is connected, and on the output side, a pair of pressure increasing valves 5 and pressure reducing valves 6 provided for the respective wheels, and a motor. M is connected.

Next, the anti-skid control and the rear wheel braking suppression control executed by the control unit 12 will be described. FIG. 4 shows the overall flow of the anti-skid control. This anti-skid control is performed at a period of 10 msec.
The sensor frequency is obtained from the number and cycle of the sensor pulses of each wheel speed sensor 13 generated for each c, and the wheel speed Vw and the wheel acceleration △ Vw are calculated. In the following description or drawings, FR, FR, etc. are followed by FR,
The symbols FL, RR, and RL indicate the wheel speed or wheel acceleration of the wheel.
xx, the symbols FR, FL, RR, RL
, That is, any one of the wheels. In step 102, a pseudo vehicle body speed VI is calculated based on the wheel speed Vw. This pseudo vehicle speed V
Details of the calculation of I will be described later. In step 103, the vehicle body deceleration VI is determined based on the rate of change of the pseudo vehicle speed VI.
Calculate K. The method of obtaining the vehicle body deceleration VIK will be described later. In step 104, the target wheel speed VWM is calculated. The details will be described later.
In step 105, a PI control calculation process for obtaining the target hydraulic pressure PB is performed. Details of this PI control will be described later.

In step 106, it is determined whether or not the wheel speed VW is less than the optimum slip ratio value VWS, which is a threshold value for determining the start of pressure reduction control, and whether a pressure increase flag ZFLAG, which will be described later, indicates = 1. And YES, that is, VW <
When VWS and ZFLAG = 1, the process proceeds to step 107, and when NO, the process proceeds to step 108. Here, in step 107, the anti-skid timer AS = A indicating that the ABS control is being executed, and the holding timer THOJI = 0 indicating that the holding is being performed, indicating that the pressure reduction control is being performed. Decompression flag GFLAG =
After setting to 1, the routine proceeds to step 109, where pressure reduction control is executed. In this pressure reduction control, a pressure reduction amount is controlled by outputting a duty signal to the pressure reduction valve 6 and controlling the valve opening amount.

Next, if NO is determined in step 106, the process proceeds to step 108, and it is determined whether any one of the following three conditions is satisfied. The routine proceeds to step 107, where the pressure reduction control is executed.
Proceeding to 8, a pressure increase / hold determination is made. Step 1
The three conditions in 08 are: 1) the feedforward depressurization amount FFG is larger than the depressurization timer DECT, 2)
The value of the holding timer THOJI exceeds 30 msec and the value of PB- (DECT-FFG) exceeds 8 msec. 3) The value of the holding timer THOJI exceeds 60 msec and the value of PB- (DECT-FFG) exceeds 3 msec. Is. Note that PB is the current target hydraulic pressure, and DECT is a pressure reduction timer that is an integrated value of the pressure reduction processing time. That is, the process proceeds to the pressure reduction control in the following manner. 1) When the pressure reduction counter DECT has not reached the feedforward pressure reduction amount FFG, 2) After performing the feedforward pressure reduction (this will be described later), 30 msec is held. 3) If the target hydraulic pressure PB exceeds 3 msec while holding the pressure for 60 msec in the same manner. Here, the target hydraulic pressure PB is converted into a valve opening time of the pressure reducing valve 6 by multiplying a coefficient K described later.

Next, in step 110, it is determined whether or not any of the following three conditions is satisfied. If it is determined that any of the following three conditions is satisfied, then the holding in step 113 is performed. Proceeding to control, if none of the three is satisfied, proceed to pressure increase control in step 111. In addition,
As will be described later, in the pressure increase control in step 111, braking suppression control for the rear wheels is executed. Here, the three conditions are 1) FFZ ≦ INCT and PB + (INC
T-FFZ) <-3 msec, 2) THOJI <
In the case of 60 msec, 3) GFLAG = 1 and VWD>
In the case of 0 g, Note that FFZ is a feedforward pressure increase amount described later, and INCT is a pressure increase timer that is an integrated value of the pressure increase control time. In the case of pressure increase, both the pressure increase timer INCT and the feedforward pressure increase amount FFZ are given as negative values. That is, the control proceeds to the pressure increase control when the pressure increase timer INCT has not reached the feedforward pressure increase amount FFZ or when the pressure is maintained at 60%.
This is the case where the wheel acceleration VWD exceeds 0 g after the execution of msec or during the execution of the pressure reduction control.

After executing the pressure increase control in step 111, in step 112, the pressure increase flag ZFLAG =
Set to 1 and hold timer THOJI = 0. After executing the holding control in step 113,
In step 114, the holding timer THOJI is incremented (addition of 1).
It is determined whether or not 0 msec has elapsed. If 10 msec has elapsed, the process proceeds to step 116, and step 115 is repeated until 10 msec has elapsed.

Next, in step 116, step 11
As in the case of 5, it is determined whether or not 10 msec has elapsed. That is, after executing the pressure reduction control of step 109 or the pressure increase control of step 111, step 116 is executed.
If 10 msec has not elapsed, the process proceeds to step 117 to determine whether 1 msec has elapsed. If 1 msec has elapsed, the process proceeds to step 118 to determine whether GFLAG = 1. And GFLA
If G = 1 (during pressure reduction control), the process returns to step 109,
If GFLAG ≠ 1 (pressure increase control is in progress), step 111
Proceed to. In other words, in the case of pressure reduction control or pressure increase control,
Step 109 or step 11 every 1 msec
1 is executed, and after 10 msec elapses, the process proceeds to step 119, where the anti-skid timer AS is set to:
The larger of the value obtained by subtracting 1 and 0 is selected, and the process returns to step 101.

Next, details of the calculation of the pseudo vehicle speed in step 102 will be described with reference to the flowchart of FIG.
First, in step 201, the highest wheel speed among the four wheel speeds VW is set as the control wheel speed VFS.
Next, in step 202, it is determined whether or not the anti-skid timer AS = 0, that is, whether or not the pressure reduction control has been executed. When AS = 0, that is, before pressure reduction, the process proceeds to step 203, where AS ≠ 0 That is, after the pressure reduction, the process proceeds to step 204. In step 203 proceeding to the case before the pressure reduction, the control wheel speed VFS is set to the larger one of the wheel speeds VWRR and VWRL of the rear wheels which are the driven wheels, and the low μ flag indicating the low μ road determination is set. LoμF is set to 0
Reset to.

In step 204, it is determined whether or not the pseudo vehicle speed VI is equal to or higher than the control wheel speed VFS.
That is, if VI ≧ VFS, the routine proceeds to step 205, where the pseudo vehicle body speed VI is obtained based on the vehicle body deceleration VIK based on the calculation formula of VI = VI− (VIK) × k, and N
In the case of O, that is, if VI <VFS, a process of obtaining the pseudo vehicle speed VI without performing the process based on the vehicle body deceleration VIK is performed by the processes after step 206. In step 206, the constant x used for the calculation is set to 2 km / h, and in the following step 207, it is determined whether the anti-skid timer AS = 0, that is, whether or not the pressure reduction has been executed, and AS = 0
In the case of, the routine proceeds to step 208, where the constant x is 0.1 km.
/ H or the like, and in a succeeding step 209, the pseudo vehicle speed VI is obtained by calculating VI = VI-x. That is, preferably, the wheel speed V
When W returns to the pseudo vehicle speed VI, or thereafter, exceeds a spin-up point which is a point deviating from the pseudo vehicle speed VI or in the vicinity of the spin-up point, the pseudo vehicle speed VI is determined based on the vehicle deceleration VIK. After that, the wheel speed VW returns to the actual vehicle speed due to the pressure reduction, so that the control wheel speed VFS becomes the pseudo vehicle speed V.
When I exceeds I, until the spin-up point is obtained,
The calculation based on the fixed value is performed without being based on the vehicle body deceleration VIK. Step 208 is a control wheel speed VF.
It functions as a limiter when S takes a value extremely larger than the pseudo vehicle speed VI.

Next, the vehicle body deceleration calculation processing in step 103 of FIG. 4 will be described with reference to the flowchart of FIG. First, in step 401, it is determined whether or not the anti-skid timer AS has switched from the state of = 0 to the state of $ 0, that is, whether or not the anti-skid control has been started, and when the anti-skid control has been started (AS = 0 → AS ≠
In step 0), the process proceeds to step 402, where the pseudo vehicle speed VI at that time is set as the calculation reference value V0, and the calculation reference timer T0 is reset to 0. On the other hand, the anti-skid control is not started (AS = 0). ), Go to step 403 as it is.

In the following step 403, the calculation reference timer T0 is incremented (addition of 1). Next, at step 404, the pseudo vehicle body speed VI is changed to the control wheel speed VFS.
It is determined whether or not the state has changed from the state of less than the above to the state of the above. That is, the wheel speed VW increases due to the pressure reduction and returns to the actual vehicle speed. This is determined by detecting a spin-up point at which the pseudo vehicle speed VI changes from upward to downward. It is determined whether a spin-up point has occurred. When the spin-up point occurs, the process proceeds to step 405, where the pseudo vehicle speed VI at this time, the calculation reference value V0 at the start of the anti-skid control, and the calculation started to measure from the start of the anti-skid control VI- (V0- based on the reference timer T0)
VI) / T0 is used to determine the vehicle body deceleration VIK.

Next, at step 406, it is determined whether or not the anti-skid timer AS is 0. If AS = 0, the routine proceeds to step 407, where VIK is set to 1.3 g. That is, in the first cycle of the anti-skid control, the wheel speed VW is lower than the actual vehicle speed, and the spin-up point has not occurred.
5 cannot calculate the vehicle deceleration VIK. Therefore, until a spin-up point is generated and the actual vehicle deceleration can be calculated, a fixed value corresponding to high μ road braking is used. In the last step 408, the latest pseudo vehicle deceleration VID100 at 100 msec used for the rear wheel braking suppression control is calculated as follows: VID100 = VI
-Calculated by 100 ms before VI x KVI. Note that VI
100 ms before, the pseudo vehicle speed before 100 ms, K
VI is a constant.

Next, details of the target wheel speed calculation processing in step 104 of FIG. 4 will be described with reference to the flowchart of FIG. First, in step 501, the constant xx is set to 8 km / h. Next, in step 502, it is determined whether the vehicle body deceleration VIK is less than 0.4 g or the low μ flag LoμF is set to 1. If YES, that is, if the road surface is estimated to be low μ, , And proceeds to step 503 to change the constant xx to 4 km / h.
If the road is estimated, the process proceeds to step 504 without changing the constant xx.

In step 504, the optimum slip ratio value V
WS is calculated by VWS = 0.95 × VI-xx. The optimum slip ratio value VWS indicates a wheel speed that is a slip ratio at which a braking force can be efficiently obtained with respect to the current pseudo vehicle body speed VI. Next step 505
Now, the decompression flag GF indicating that decompression control is being performed
LAG = 1 and wheel acceleration VWD is 0.8 g
It is determined whether or not the wheel speed VW is greater than the optimum slip ratio value VWS. If YES, the process proceeds to step 506, where the target wheel speed VWM is set to the wheel speed VWS.
On the other hand, in the case of NO, the routine proceeds to step 507, where the target wheel speed VWM is obtained by a first-order lag low-pass filter by the calculation of VWM = VWM 10 m before + (VWS 10 m before-VWM 10 m before) × k. That is, in the present embodiment, when the wheel acceleration VWD returns to the actual vehicle speed at an acceleration greater than the predetermined value 0.8 g after the execution of the pressure reduction control, the target wheel speed VWM is set to the wheel speed VW. From the time when the wheel speed VW approaches the actual vehicle speed and reaches the vicinity of the spin-up point, the target wheel speed VWM is converged with a first-order lag toward the optimum slip rate value VWS. For the change of the target wheel speed VWM, see the time chart of FIG.

Next, the PI at step 105 in FIG.
The details of the control calculation process will be described with reference to the flowchart of FIG. In this flowchart, step 6
The flow of 11 to 618 is a part for determining the execution of the rapid pressure reduction prohibition control described in the claims. In step 611,
The control start time is determined based on the fact that the anti-skid timer AS has switched from the state of 0 to the state of $ 0. At the time of the control start, the routine proceeds to step 612, where the calculation reference value V
0 is the pseudo vehicle speed VI at that time. Step 61
In step 613 following 1 or 612, it is determined whether or not the wheel is locked based on whether or not the wheel speed VW is 0 km / h. When VW = 0 km / h, that is, when the wheel is locked, the process proceeds to step 614, and the calculation is performed. It is determined whether or not the reference value V0 is equal to or higher than the high-speed braking determination value of 60 km / h. If V0 ≧ 60 km / h, the process proceeds to step 615, where the rapid depressurization prohibition speed VLK is reduced to the first rapid decompression prohibition speed #VL.
K1 is set. On the other hand, if V0 <60 km / h, the routine proceeds to step 616, where the rapid pressure reduction inhibition speed VLK is set to the second rapid pressure reduction inhibition speed # VLK2. In the present embodiment, the first rapid pressure reduction inhibition speed # VLK1 is 20 km / h
And the second rapid decompression inhibition speed # VLK2 is 10 km /
h. In step 617 following step 6115 or 616, it is determined whether or not the pseudo vehicle speed VI is equal to or higher than the rapid depressurization prohibition speed VLK. If VI ≧ VLK, rapid depressurization is permitted. 61
In step 8, a process for setting PB = 10000 is performed.

At step 601, the target wheel speed VWM
ΔVW between the wheel speed and the wheel speed VW is determined. In the following step 602, a deviation pressure value PP is calculated by multiplying the deviation ΔVW by the pressure proportional gain KP to convert the deviation ΔVW into a braking fluid pressure. Further, in step 603, the integrated pressure value IP is calculated from IP = 10 m before IP + KI × ΔVW. Note that the value of 10 m before IP is a value one control cycle before the integrated pressure value IP.

Subsequent steps 604 and 605
Then, it is determined whether or not the state of the wheel acceleration VWD> 0 has changed to the state of VWD ≦ 0, and whether or not the state where the wheel speed VW is greater than the optimum slip rate value VWS has changed to the state of VW ≦ VWS. If it is determined that there is any change, the process proceeds to step 606 to set the integrated pressure value IP = 0, and then in step 607, the target hydraulic pressure PB
Is obtained by PB = PP + IP. The target hydraulic pressure PB increases when the value is negative, and decreases when the value is positive.

Next, the details of the solenoid pressure reduction control in step 110 of FIG. 4 will be described with reference to the flowchart of FIG. In step 701, the pressure increasing timer INC
T is reset to zero, and the feedback pressure increase amount FFZ is reset to zero. In step 702, the decompression time GAW is obtained by GAW = PB- (DECT-FFG). Therefore, when PB = 10000 is set in step 618, the decompression time G
AW is a value corresponding to rapid pressure reduction. In step 703,
Whether the pressure increase flag ZFLAG is set to 1
That is, it is determined whether or not it is the first time of the pressure reduction control.
If G = 1 and the first time of decompression, the process proceeds to step 704. If ZFLAG ≠ 1, the process proceeds to step 705 without performing the process of step 704. In step 704, the feedback pressure reduction amount FFG is calculated as FFG = VWD ×
It is determined by α / VIK and ZFLAG is reset to zero. Here, the initial pressure reduction amount is obtained based on the wheel acceleration VWD, and is referred to as a feedforward pressure reduction amount in this specification.

In the next step 705, it is determined whether or not one of the following two conditions is satisfied. If any of the following two conditions is satisfied, the flow advances to step 707 to perform a holding output, and both are satisfied. If not, the process proceeds to step 706 to output a reduced pressure, and increments (adds 1 to) the reduced pressure timer DECT. Step 705
The two conditions in 1) are: 1) the pressure reduction time GAW is 0 or less, and the pressure reduction timer DECT is equal to or more than the feedforward pressure reduction amount FFG. 2) The wheel acceleration VWD is 0.8 g.
Larger than the two. That is, during the pressure reduction control, the pressure reduction output is performed for the first time until the pressure reduction timer DECT exceeds the feedforward pressure reduction amount FFG. Also, if the wheel acceleration VWD becomes larger than 0.8 g and is returning to the vehicle speed during or after that, the pressure reduction output is stopped and the holding output is performed.
After the first output of the feedforward depressurization amount FFG is executed, only the difference from the previous output is output at the target hydraulic pressure PB. The details will be described later.

Next, the details of the solenoid pressure increasing control in step 111 of FIG. 4 will be described with reference to the flowchart of FIG. In step 801, a pressure reduction counter DECT that measures the time during which the pressure reduction control is being executed is reset to 0, and the feedback pressure reduction amount FFG is reset to 0. In step 802, the pressure increase time (corresponding to the ON pulse width in the claims) ZAW is set to ZAW.
W = | PB + (INDT-FFZ) | In step 803, it is determined whether or not the pressure reduction flag GFLAG is set to 1, that is, whether or not the pressure increase control is performed for the first time. If GFLAG = 1 and the pressure increase is performed for the first time, the process proceeds to step 804, and the process proceeds to step 804. In the case of $ 1, the process proceeds to step 805 without performing the process of step 804. In step 804, the feedforward pressure increase amount F
FZ is determined by FFZ = VWD × β / VIK and GFLAG = 0 is reset. Here, the initial pressure increase amount is obtained based on the wheel acceleration VWD, and is referred to as a feedforward pressure increase amount in this specification.

In the next step 805, the pressure increase time ZAW
Is greater than or equal to 0 and the pressure increase timer INCT is greater than or equal to the feedforward pressure increase amount FFZ, and YES
In the case of, the process proceeds to step 807 to perform the holding output,
In the case of O, the routine proceeds to step 806, where the pressure increase output is performed, and the pressure increase timer INCT is incremented (addition of 1). That is, during the pressure increase control, the pressure increase output is performed for the first time until the pressure increase timer INCT exceeds the feedforward pressure increase amount FFZ. Thereafter, when the pressure increase time ZAW becomes positive, an output is made. In the last step 808, the rear wheel braking suppression control is executed.

Next, the rear wheel braking suppression control will be described with reference to the flowchart of FIG. First step 901
Then, it is determined whether or not the control target is the rear wheel. If the control target is the rear wheel, the process proceeds to step 902. If the control target is not the rear wheel, the rear wheel braking suppression control is not executed. Next, step 90
In step 2, it is determined whether or not the anti-skid control is not being executed, based on whether or not the anti-skid timer AS = 0. If AS = 0 and the anti-skid control is not being executed, the process proceeds to step 903. When AS ≠ 0 and the anti-skid control is being performed, the rear wheel braking suppression control is not executed. Next, in step 903, it is determined whether or not the wheel speed VW has decreased to less than the target slip vehicle speed λB. If VW <λB, step 909 is performed to execute the rear wheel braking suppression control.
In step 909, a holding output for closing the pressure increasing valve 5 and the pressure reducing valve 6 is performed.

On the other hand, at step 903, VW ≧ λB
In the case of, the rear wheel braking suppression control was not executed conventionally, but in the present embodiment, step 904 is further performed.
, The pseudo vehicle deceleration VID100 and the wheel deceleration VWD60 (the wheel speed VW in the latest 60 msec)
The emergency rear wheel braking suppression determination is performed based on the differential value of In this step 904, it is determined whether VID100 <-0.4g (sudden deceleration determination value) and VWD <-1.0g (deceleration set value), and if both conditions are satisfied, the emergency rear wheel The process proceeds to step 905 to execute the braking suppression control. The following steps 905 and 906 limit the time for executing the emergency rear wheel braking suppression control in this case to 300 msec, which is a predetermined time.
Then, it is determined whether or not a holding counter EHOJI that counts the execution time of the emergency rear wheel braking suppression control executed based on the determination of step 904 is less than 300 msec.
I is incremented (added by 1).

If the emergency rear wheel braking suppression determination condition is not satisfied in step 904, the holding counter EHOJI is reset to 0 in step 907, and the flow advances to step 908 to perform pressure increase output.
The execution time of the emergency rear wheel braking suppression control based on the judgment of 4 is 3
When the time exceeds 00 msec, the balloon rear wheel braking suppression control is hunted, and the routine proceeds from step 905 to step 908 to perform pressure increase output.

FIG. 12 is a block diagram showing a portion of the control unit 12 for executing the anti-skid control. In the figure, a target wheel speed creating unit 12a is a part that performs the processing of step 104, and includes a pseudo vehicle body speed VI, a vehicle body deceleration VIK, and a wheel speed V
The target wheel speed VWM is created by inputting W and the wheel acceleration VWD, and is constituted by a primary low-pass filter. The target wheel speed VWM formed here is input to the wheel speed deviation calculation unit 12b to obtain the deviation ΔVW.
1 corresponds to the part that executes the process. Target hydraulic pressure calculator 1
In 2c, the deviation pressure value PP and the integral pressure value IP are obtained based on the deviation ΔVW, and based on these, the target hydraulic pressure PB
Is calculated, and the part that performs this processing is the part that performs the processing of steps 602 to 607. The target hydraulic pressure PB is converted into a pulse by the pulse converter 12d and output from the pulse output controller 12e. The pulse conversion unit 12d and the pulse output control unit 12e correspond to the part that executes the processing of steps 106 to 119 in FIG. 4, and includes the pressure reduction time GAW and the pressure increase time obtained based on the target hydraulic pressure PB. A duty signal having an ON pulse width corresponding to ZAW is output.

Next, the operation of the basic anti-skid control of the embodiment will be described with reference to the time chart of FIG. As shown in this time chart, as the pseudo vehicle speed VI decreases due to braking, the target wheel speed VWM is formed so as to converge from a value equal to the wheel speed VW toward the optimum slip rate value VWS. . Here, the value in which the target wheel speed VWM is equal to the wheel speed VW is a value near the time when the wheel speed VW changes from upward to downward, and corresponds to the wheel speed (に お け る body speed) near the spin-up point. I do.

As shown in the figure, if the wheel speed VW falls below the optimum slip rate value VWS in a state where the anti-skid control has not been started (at time t1), step 106 →
The flow becomes 107 → 109, and the pressure reduction control is started.
In the first time of this pressure reduction control, steps 701 → 70
Based on the flow of 2 → 703 → 704, the feedforward depressurization amount FFG is determined based on the wheel acceleration VWD and the vehicle body deceleration VIK, and further, step 705 →
Based on the flow in 706, a reduced pressure output is made. This pressure reduction output is performed until the pressure reduction counter DECT reaches the feedforward pressure reduction amount FFG. In this time chart, at time t2, the pressure-reducing counter DECT reaches the feedforward pressure-reducing amount FFG, and at that time, the flow proceeds from step 106 → 108 → 110 → 113, and the holding control is performed. Here, as shown in the figure, even after time t2, the target wheel speed VWM and the wheel speed VW
When the deviation ΔVW from
The target hydraulic pressure PB formed by integrating the deviation ΔVW in the I control arithmetic processing also increases. And this target hydraulic pressure PB
In the above, the value obtained by subtracting the feedforward depressurization amount FFG exceeds 8 msec at the time of holding 30 msec from the time t2, or 30 to 60 m
If the pressure exceeds 8 msec during the sec, a reduced pressure output is generated. If the pressure exceeds 3 msec at the end of the holding of 60 msec from the time t2, or if the pressure exceeds 3 msec thereafter, the reduced pressure output is generated. This reduced pressure output is determined in step 702 by the target hydraulic pressure PB
Is performed only for the decompression time GAW obtained based on. This is the reduced pressure output that is output between t3 and t4 in the figure, and is a gentle reduced pressure output. That is, the decompression output after the second time (slow decompression output) is performed after 30 msec has elapsed even in the shortest time since the first output. In this case, the value of the decompression time GAW is larger than 8 msec. It is executed when it becomes. In addition, 60msec
Before elapse, the pressure reduction output is made when the pressure reduction time GAW exceeds 8 msec. When the decompression time GAW is relatively small, a decompression output is made at a point in time after 60 msec has elapsed and at a point in time when the decompression time GAW exceeds 3 msec.

Next, rear wheel braking suppression control and emergency rear wheel braking suppression control which are features of the present embodiment are shown in FIG.
It will be described based on. FIG. 14 is a time chart showing an example when sudden braking is performed. In the figure, a solid line indicates the present embodiment, and a dotted line indicates a conventional technique. When the rapid braking is executed, basically, the pseudo vehicle deceleration VID100 formed by the front wheel speed VW at the time of braking rapidly increases (as a value, increases to the minus side). Here, the sudden deceleration judgment value as the judgment threshold value is set to -0.4 g. However, the case where the pseudo vehicle deceleration VID100 is equal to or less than this value means that the rising of the load fluctuation of the rear wheels during braking. This shows a braking state delayed with respect to a change in longitudinal acceleration. Also, at the time of sudden braking, the wheel deceleration VWD60 of the rear wheel is also reduced as shown in the figure. VW is initially a value close to the pseudo vehicle speed VI. Here, the deceleration set value as the judgment threshold is set to -1.0 g, which corresponds to the vehicle deceleration when sudden braking is applied on a dry road. The wheel deceleration VWD60 close to the deceleration is -1.
If it is less than 0 g, it can be determined that sufficiently rapid deceleration has been achieved.

Therefore, in the present embodiment, VID100 <−0.4 g and VWD60 <−1.
In the case of 0 g, steps 903 → 904 → 905 → 9
From 06 to 909, the emergency rear wheel braking suppression control is executed at time t1 in the time chart, and the hold output is generated for a predetermined time (300 msec). As a result, the overshoot of the wheel cylinder pressure (W / C pressure) is suppressed as compared with the case of the related art shown by the dotted line as shown in the figure, and the rapid decrease in the wheel speed VWR of the rear wheel is suppressed. Thereafter, when the anti-skid control is executed (at time t2), the pressure reduction amount is suppressed to a small value.

As described above, in this embodiment,
It cannot be determined based only on the target slip vehicle speed λB,
It is possible to determine a situation in which the wheel cylinder pressure of the rear wheel is excessive, prevent an overshoot in which the wheel cylinder pressure of the rear wheel is excessive, and improve the accuracy of the rear wheel braking suppression control. Furthermore, when the anti-skid control is subsequently performed, the amount of brake fluid discharged from the wheel cylinder is reduced, and the pump 4
By reducing the required operation amount of the pump 4, the pump 4 can be downsized, whereby the cost can be reduced and the apparatus can be downsized.

Further, in the present embodiment, the vehicle body deceleration VID is obtained from the pseudo vehicle body speed VI formed by the output from the wheel speed sensor 13, so that the longitudinal acceleration sensor can be omitted. In this respect, the cost of the apparatus can be reduced.

Although the embodiment has been described with reference to the drawings, the present invention is not limited to this embodiment. For example, the sudden deceleration determination value and the deceleration set value are determined appropriately as appropriate based on the specifications of each vehicle, and are not limited to the values shown in the embodiment.
Further, a longitudinal acceleration sensor may be used as a means for detecting the vehicle body deceleration.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing a brake control device of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a part of the brake device according to the embodiment.

FIG. 3 is a block diagram illustrating a control unit according to the embodiment.

FIG. 4 is a flowchart showing a flow of anti-skid control in the embodiment.

FIG. 5 is a flowchart showing a flow of calculating a pseudo vehicle body speed in the embodiment.

FIG. 6 is a flowchart showing a flow of a vehicle body deceleration calculation in the embodiment.

FIG. 7 is a flowchart showing a flow of target wheel speed calculation in the embodiment.

FIG. 8 is a flowchart showing a flow of a PI control calculation process in the embodiment.

FIG. 9 is a flowchart showing a flow of pressure reduction control in the embodiment.

FIG. 10 is a flowchart showing a flow of pressure increase control in the embodiment.

FIG. 11 is a flowchart showing a flow of rear wheel braking suppression control in the embodiment.

FIG. 12 is a block diagram illustrating a main part of the brake control device according to the embodiment;

FIG. 13 is a time chart showing an operation example of the anti-skid control of the embodiment.

FIG. 14 is a time chart illustrating an operation example of the rear wheel braking suppression control according to the embodiment;

FIG. 15 is a time chart for explaining the operation of the conventional technique.

[Explanation of symbols]

 Reference Signs List 1 brake circuit 1d branch point 1g one-way valve 1h bypass path 2 port 4 pump 4a suction valve 4b discharge valve 4c cam 4d damper 41 plunger 42 filter member 5 pressure increasing valve 6 pressure reducing valve 7 reservoir 10 drain circuit 11 reflux circuit 11a suction circuit 11b discharge Circuit 12 Control unit 12a Target wheel speed generator 12b Wheel speed deviation calculator 12c Target hydraulic pressure calculator 12d Pulse converter 12e Pulse output controller 13 Wheel speed sensor

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuyuki Otsu 1370 Onna, Atsugi-shi, Kanagawa F-term in Unisia Gex Co., Ltd.

Claims (5)

[Claims] 1. A hydraulic pressure control valve capable of reducing and increasing the hydraulic pressure of a wheel cylinder, a wheel speed detecting means for detecting a wheel speed, and determining whether a rear wheel is in a predetermined slip state based on the detected wheel speed. Brake control means for performing rear wheel braking suppression control for prohibiting pressure increase of the rear wheels when the rear wheel is in a state where the rear wheels are not in the predetermined slip state. Also, when the vehicle deceleration is greater than the preset sudden deceleration determination value and the wheel deceleration of the rear wheel to be controlled is greater than the preset deceleration setting value, the rear wheel pressure increase is determined. A brake control device that executes emergency rear wheel braking suppression control that prohibits time. 2. The brake control device according to claim 1, wherein the sudden deceleration determination value is a value that can determine that the vehicle has started deceleration sufficiently. 3. The sudden deceleration determination value is from -0.2 g to -0.2 g.
3. A value within a range of 0.7 g.
The brake control device according to item 1. 4. The brake control device according to claim 1, wherein the deceleration setting value is a value corresponding to a vehicle deceleration on a dry road. 5. The deceleration setting value is from -0.85 g to -0.85 g.
5. A value within a range of 1.2 g.
The brake control device according to item 1.