JP3147858B2 - Brake pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake pressure control device having a simple structure and capable of preventing wheel slippage during braking of a vehicle.

[0002]

2. Description of the Related Art Conventionally, an apparatus having a simple structure without providing a pump for pumping brake fluid stored in a reservoir is disclosed in, for example, JP-A-61-222850 or JP-A-62-125942. Known devices are known. In this conventional device, in order to prevent a slip that occurs at the time of vehicle braking, control is performed to reduce the brake pressure of the wheel cylinder by communicating the wheel cylinder with the reservoir in accordance with the wheel speed.

[0003]

However, in such a conventional brake pressure control device, when the flow of brake fluid into the reservoir exceeds a predetermined amount, further flow into the reservoir is restricted. Therefore, when the same volume of brake fluid as the reservoir flows into the reservoir from the wheel cylinder when the wheel cylinder pressure is reduced, the reservoir may become full and the wheel cylinder pressure may not be reduced thereafter. Even in such a case, the control for reducing the wheel cylinder pressure is performed by connecting the wheel cylinder and the reservoir according to the wheel speed, and the control valve and the control device by the long-term pressure reduction control are not used. There is a problem that significant heat is generated.

In view of the above, it is a first object of the present invention to accurately determine that the amount of brake fluid stored in a reservoir during control of brake pressure is equal to or greater than a predetermined value. It is a second object of the present invention to prevent the meaningless pressure reduction control of the wheel cylinder pressure from being performed when the amount of brake fluid stored in the reservoir becomes equal to or greater than a predetermined value.

[0005]

In order to solve the above-mentioned problems, a brake control device according to the present invention includes a slip tendency determining means for determining a tendency of a wheel to slip, and a method for determining a slip tendency of the wheel. An anti-skid control means comprising: output means for outputting a signal for controlling a brake pressure applied to the wheel cylinder; andadjustment means for adjusting the brake pressure applied to the wheel cylinder based on the signal from the output means. A reservoir for storing brake fluid flowing out of the wheel cylinder when a signal for reducing the brake pressure applied to the wheel cylinder is output by the output unit and the adjusting unit executes the reduction of the brake pressure applied to the wheel cylinder; The slip inclination of the wheel is determined by the slip tendency determining means. It is determined that the amount of brake fluid flowing into the reservoir is equal to or greater than a predetermined value when the wheel is still slipping even after a predetermined time has elapsed after the signal for reducing the brake pressure is output by the output unit. Determining means for determining.

[0006] Also, the slip tendency determining means for determining the slip tendency of the wheel, anti-skid control means for controlling the brake pressure applied to the wheel cylinder of the wheel according to the slip tendency of the wheel, and the anti-skid control means When the brake pressure applied to the wheel cylinder is reduced, when the brake pressure applied to the wheel cylinder is reduced by the reservoir for storing the brake fluid flowing out from the wheel cylinder and the anti-skid control unit, And determining means for determining that the amount of brake fluid flowing into the reservoir is equal to or greater than a predetermined value when the determination that the wheels have a tendency to slip has continued for a predetermined time by the slip tendency determining means. Is also good.

According to the first or second aspect of the present invention, the amount of brake fluid accurately stored in the reservoir in the control system is equal to or more than a predetermined value without adding a mechanical structure. , For example, a state in which the reservoir is full. Further, the brake control device may be simplified by not providing a pump for returning the brake fluid stored in the reservoir to the master cylinder during execution of the anti-skid control means. . As described above, in a device without a pump, there is a high possibility that a state in which the amount of brake fluid in the reservoir becomes full is high, and it is very advantageous to be able to accurately determine that the amount of brake fluid in the reservoir has exceeded a predetermined value. is there.

[0008]

If the determination means determines that the amount of brake fluid flowing into the reservoir is equal to or greater than a predetermined value, the anti-skid control means increases the brake pressure applied to the wheel cylinder gradually. Alternatively, the brake pressure generated in the master cylinder may be applied to the wheel cylinder. In this manner, when the amount of brake fluid in the reservoir is equal to or more than a predetermined value and there is a possibility that the wheel cylinder pressure cannot be further reduced, not only will there be no meaningless pressure reduction control, but also the brake fluid in the reservoir will be reduced. When the amount is more than specified,
It is possible to suppress a sudden change in the wheel cylinder pressure when increasing the wheel cylinder pressure, which is advantageous for suppressing an occupant's discomfort or the like.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a brake pressure control device according to one embodiment of the present invention. Reference numeral 1 denotes a tandem master cylinder, in which brake fluid from the master cylinder 1 generates wheel cylinders 2 and 3 for generating a braking force for braking the front wheels FL and FR and wheels for generating a braking force for braking the rear wheels RL and RR. The cylinders 4 and 5 are respectively connected so as to be supplied by two pipes separated from each other.

In this embodiment, the brake fluid from the master cylinder 1 is supplied to a proportioning pulp 6 (hereinafter, referred to as P pulp 6) and a solenoid valve 7 (hereinafter, referred to as a 3 port 3 position).
Via a three-position valve 7) so as to be supplied to the wheel cylinders 4 and 5 on the rear wheels RL and RR. When the pressure of the master cylinder 1 reaches a predetermined value, the P pulp 6 is moved to the rear wheel cylinders 4 and 5.
Is to reduce the rate of pressure rise. Further, the three-position valve 7 includes the wheel cylinders 4 and 5 and the master cylinder 1
And selectively communicates with the reservoir 8 that can store brake fluid.
In the position A, the master cylinder 1 and the wheel cylinders 4 and 5 communicate with each other, and the master cylinder 1
To the wheel cylinders 4 and 5,
A normal brake operation of increasing the brake pressure in accordance with the depression operation of the brake pedal 13 can be performed.

At the position B, the brake cylinders 4 and 5 are shut off completely to maintain the brake pressure. At the position C, the wheel cylinders 4 and 5 and the reservoir 8 are communicated with each other. 4 and 5, the brake pressure can be reduced.
9 and 10 are check valves. The check valve 9 prevents the brake fluid from flowing directly from the master cylinder 1 to the reservoir 8 when the brake pressure of the master cylinder 1 increases, and stores the brake fluid in the reservoir 8 when the brake pressure decreases. The brake fluid is connected to return to the master cylinder 1 side. The check valve 10 is connected so as to prevent the brake pressure of the wheel cylinders 4 and 5 from increasing more than the brake pressure of the master cylinder 1.

Further, reference numeral 11 denotes a wheel speed sensor, and the rear wheel R
It is attached to the differentials L and RR and detects the rotation speed of the drive shaft. The 12 brake depression switch detects whether the driver is depressing the brake pedal 13 or not. The wheel speed sensor 11, the brake depression switch 12, and the three-position valve 7 are connected to an electronic control circuit 20, respectively. The electronic control circuit 20 includes a well-known CPU 21, a ROM 22 for storing control programs and data in advance, and a readable / writable RAM 23, and an input / output circuit 24 connected to each other via a common path 25. The CPU 21 inputs signals from the wheel speed sensor 11 and the brake depression switch 12 via the input / output circuit 24, and these signals, ROM 22, RAM 23
CPU 21 based on the programs and data in
By controlling the position valve 7, the brake pressure of the wheel cylinders 4, 5 is adjusted. When a failure occurs, the alarm lamp 14 is turned on.

In the electronic control circuit 20, when a power switch (not shown) is turned on, the CPU 21 starts executing arithmetic processing according to a program preset in the ROM 23. Next, a brake pressure control process performed by the electronic control circuit 20 will be described with reference to a flowchart shown in FIG.

The brake pressure control process is performed for a predetermined time T
The processing of step 120 and subsequent steps is repeatedly executed every ms (for example, 5 ms). In step 110, the operation of each part is checked, and initialization operations such as initialization of flags are performed. Next, at step 120, the wheel speed Vw is read from the signal output from the wheel speed sensor 11, and the wheel acceleration Aw is calculated based on the wheel speed Vw. Subsequently, at step 130, the pseudo vehicle speed Vb is calculated by the following equation.

Vb (n) = MED (Vw (n), Vb (n-1) + K
up · T, Vb (n−1) + Kdw · T) where Kup is the acceleration upper limit and Kdw is the deceleration upper limit. The above equation limits the speed difference between the previous and current pseudo vehicle speeds Vb to below the speed due to the acceleration Kup during acceleration and below the speed due to the deceleration Kdw during deceleration.
That is, the speed (V) obtained when the vehicle is accelerated by the acceleration Kup from the current wheel speed Vw (n) and the pseudo vehicle speed Vb (n-1) obtained last time.
b (n-1) + Kup · T) and the pseudo body speed Vb obtained last time.
The speed (Vb (n-
1) + Kdw · T), and the speed of an intermediate value among them is set as the current pseudo speed Vb.

In step 140, it is determined whether or not a control flag indicating that anti-skid control is being performed is on. This control-in-progress flag is set in a process to be described later, and is initially off.
Proceed to. In step 150, it is determined whether the wheel speed Vw is lower than the reference speed Vl set from the pseudo vehicle speed Vb, and whether the wheel acceleration Aw is lower than a predetermined reference deceleration Al. When the result of this determination is affirmative (YES), it can be determined that the wheels have a tendency to slip, and the routine proceeds to step 160.

In step 160, the brake pressure of the wheel cylinders 4, 5 is reduced by switching the three-position valve 7 to the C position in order to control the tendency of the wheels to slip. At the same time, the control-in-progress flag indicating that the anti-skid control is being performed is turned on, and the process returns to step S120.
On the other hand, when the result of the determination at step 150 is negative (NO), the routine proceeds to step 170. In step 170, the control-in-progress flag that was turned on in step 160 is turned off, and at the same time, an increase in the brake pressure of the wheel cylinders 4, 5 is instructed, and the three-position valve 7 is switched to the A position. Return.

After the wheel has a tendency to slip and the process of step 160 is executed, the process returns to step 120,
The following processing is executed. In the processing of step 140, it is determined that the control-in-progress flag is on, and the routine proceeds to step 180. In step 180, the brake release switch 12 determines whether or not the driver has released the brake pedal 13 and ended the braking operation. If the brake depression switch 12 is off, it is determined that the braking operation by the driver has been completed, and the routine proceeds to step 190. In step 190, as in step 170, the control-in-progress flag is turned off, and the three-position valve 7 is switched to the A position, and the process returns to step 120.

On the other hand, if it is determined in step 180 that the brake pedal 13 is still depressed by the driver and the brake depression switch 12 is on, the routine proceeds to step 200. In step 220, it is determined whether the brake fluid flowing into the reservoir 8 has reached a predetermined amount,
For example, in the present embodiment, it is determined whether or not the reservoir 8 is full.
Go to 0. Whether or not the reservoir 8 is full is determined by execution of the processing of step 220 described later, when the tendency of the wheels to slip has passed for a certain period of time or more, even though the brake pressure has been reduced. It may be determined that there is. Alternatively, a switch for detecting the level of the brake fluid in the reservoir 8 may be provided so that the determination can be made.
A flow sensor for detecting the amount of brake fluid flowing into the
It may be determined from the amount of brake fluid that has flowed into the reservoir 8 whether or not the reservoir is full. Not only whether the reservoir 8 is full, but also a predetermined amount of brake fluid that makes it impossible to reduce the brake pressure of the wheel cylinders 4, 5 by communicating the wheel cylinders 4, 5 with the reservoir 8. What is necessary is just to be able to determine that it has flowed into.

Next, in step 210, step 1
As in the case of 50, the wheel speed Vw and the reference speed Vl, and the wheel acceleration Aw and the reference deceleration Al are respectively compared to determine whether or not the wheels have a tendency to slip. At this time,
If it is determined that the wheels have a tendency to slip, step 2
Proceeding to 20, the three-position valve 7 is switched to the C position, the wheel cylinders 4 and 5 communicate with the reservoir 8, the brake fluid of the wheel cylinders 4 and 5 flows into the reservoir 8, and the wheel cylinders 4 and 5 Reduce the brake pressure of
Return to step 120.

On the other hand, if it is determined that the wheels have no tendency to slip, the routine proceeds to step 230. In step 230,
It is determined whether the drop of the wheel acceleration Aw has stopped and it is determined whether or not the slip of the wheel is in a recovery tendency. In step 240, the three-position valve 7 is switched to the B position to maintain the pressure of the wheel cylinders 4, 5, and the process returns to step 120.

If it is determined in step 230 that the wheel slip does not tend to recover, that is, it is determined that the grip force of the wheel has already recovered and the wheel is in a stable state, the process proceeds to step 250. In step 250, the three-position valve 7 is periodically switched between the A position and the B position, and the wheel cylinder 4,
The brake pressure at 5 is gradually increased, and the process returns to step 120.

If it is determined in step 200 that the reservoir 8 is full, that is, it is determined that a predetermined amount of brake fluid is flowing into the reservoir 8, the process proceeds to step 260. In step 260, it is determined whether or not the step-intensified pressure output by the processing in step 270 described later when the reservoir 8 is full has been completed. If it is determined that the step-intensified pressure output has not been terminated, , Step 27
Go to 0. In step 270, the three-position valve 7 is periodically switched between the A position and the B position, and the brake pressure on the wheel cylinders 4, 5 is gradually increased.
Return to 0.

On the other hand, if it is determined that the step pressure increase output has been completed, the routine proceeds to step 280, where the three-position valve 7 is set to the A position.
The position is switched to the position, the master cylinder 1 and the wheel cylinders 4 and 5 are communicated, the wheel cylinders 4 and 5 brake pressure is increased, and the process returns to step 120. Next, the basic control timing by the above-mentioned brake pressure control processing is shown in the time charts of FIGS. 3 (a), (b), (c) and (d).

When the driver starts braking the vehicle, the time Tl
When the wheel speed Vw becomes smaller than the reference speed Vl and the wheel acceleration Aw becomes smaller than the reference deceleration Al (steps 120 to 210), the 3-position valve 7 is switched from the position A to the position C (step 160 or step 160). 2
20), the wheel cylinders 4 and 5 communicate with the reservoir 8, the brake fluid flows into the reservoir 8, and the brake pressure is reduced (in this period a, it is determined that the wheels have a tendency to slip) .

At time T2, when the wheel acceleration Aw starts to recover (step 230), the three-position valve 7 is switched from the C position to the B position (step 240), and the brake pressure of the wheel cylinders 4, 5 is maintained. (In this period b, the wheels are determined to be in a recovery tendency). At time T3, the wheel speed Vw becomes equal to the reference speed Vl.
(Step 230), the three-position valve 7 is switched between the A position and the B position at regular intervals (Step 250), and the brake pressure is gradually increased (in this period C, the wheels are stable). State is determined).

At time T4, when the wheel speed Vw becomes lower than the reference speed Vl again and the wheel acceleration Aw becomes lower than the reference deceleration Al (step 210),
The three-position valve 7 switches to the C position (step 22).
0), the brake pressure of the wheel cylinders 4, 5 is reduced. Then, similarly, every time the process of step 220 is executed, the predetermined brake fluid flows into the reservoir 8 and the pressure is reduced, held, and maintained until it is determined that the reservoir 8 is full.
A control cycle of pressure increase is repeatedly executed.

At time T5, when the wheel speed Vw becomes smaller than the reference speed Vl and the wheel acceleration Aw becomes smaller than the reference deceleration Al again (step 21).
0) The three-position valve 7 is switched to the C position (step 220), and the brake pressure of the wheel cylinders 4, 5 is reduced. At time T6, if a certain time tl has elapsed while the wheels are locked even though the brake pressure has been reduced (step 220), the reservoir 8
Is full (step 200), the three-position valve 7 is switched between the A position and the B position at regular intervals, and a step pressure increase in which the brake pressure is gradually increased is executed. (Steps 260 and 270).

Then, when the step pressure increase is output for a predetermined time t2 and the process is completed (step 260), the three-position valve 7 is switched to the position A (step 280), and the wheel cylinders 4, 5 and the master cylinder 1 are communicated. , The brake pressure is increased. Also, while the reservoir 8 is full,
Regardless of the tendency of the wheels to slip, the process of step 280 is executed, and the pressure increase control in which the wheel cylinders 4, 5 and the master cylinder 1 are communicated is maintained.

In this embodiment, steps 150, 21
Execution of the processing of 0 acts as the slip tendency determination means M1 and the three-position valve 7 and steps 160 to 190, 220 to
Execution of the process at 250 serves as pressure control means M3. Further, the execution of the processing of step 200 functions as the judgment interruption M5, and the execution of the processing of steps 260 to 280 functions as the pressure increase maintaining means M6.

Thus, when the reservoir 8 is full,
Since the brake pressure is gradually increased, and the pressure increase control is performed so that the wheel cylinders 4 and 5 and the master cylinder 1 are communicated with each other, the reservoir 8 becomes full even if the reservoir 8 becomes full. As a result, the wheel cylinder 4,
There is no sudden increase in the brake pressure due to sudden increase in the brake pressure of No. 5. When the reservoir 8 becomes full, the electronic control circuit 20 does not perform the processing of repeatedly performing steps 210 to 250 or the frequent switching operation of the three-position valve 7 by repeatedly performing the processing of steps 210 to 250. . Therefore, since the meaningless processing and operation after the reservoir 8 is full are not performed, heat generation of the three-position valve, the electronic control circuit 20, and the like can be prevented.

As described above, the present invention is not limited to such an embodiment, and can be carried out in various modes without departing from the gist of the present invention. As described in detail above, the brake pressure control device of the present invention determines that the amount of brake fluid flowing into the reservoir has reached a predetermined amount, and after reaching the predetermined amount, gradually increases the pressure and then performs the pressure increase control. So that the brake pressure does not fluctuate rapidly,
After that, the control valve and the control device can be prevented from generating heat without executing meaningless brake pressure control.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a brake pressure control device as one embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a brake pressure control process performed in the electronic control circuit according to the embodiment.

FIG. 3 is a time chart illustrating the operation of the present embodiment.

[Explanation of symbols]

 1 Master Cylinder 2 Wheel Cylinder 3 Wheel Cylinder 4 Wheel Cylinder 5 Wheel Cylinder 7 3 Position Valve 8 Reservoir 11 Wheel Speed Sensor 20 Electronic Control Circuit

Continuation of the front page (56) References JP-A-60-206760 (JP, A) JP-A-61-222850 (JP, A) JP-A-62-12452 (JP, A) JP-A-62-125942 (JP) JP-A-62-175249 (JP, A) JP-A-2-169359 (JP, A) JP-A-3-148359 (JP, A) JP-A-6-32223 (JP, A) 10-250552 (JP, A) JP 6-69789 (JP, B2) Patent 2681945 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/58 B60T 8/46

Claims (4)

(57) [Claims] An output means for outputting a signal for controlling a brake pressure applied to a wheel cylinder of the wheel in accordance with the slip tendency of the wheel; An anti-skid control unit including an adjustment unit that adjusts a brake pressure applied to the wheel cylinder based on the signal; and a signal for reducing the brake pressure applied to the wheel cylinder is output from the output unit. When the brake pressure applied to the wheel cylinder is reduced, a reservoir for storing the brake fluid flowing out of the wheel cylinder is determined by the slip tendency determining means as a tendency of the wheels to slip, and the output means determines the slip tendency of the wheels. The signal to reduce the brake pressure was output And a determination means for determining that the amount of brake fluid flowing into the reservoir is equal to or greater than a predetermined value when the wheels still tend to slip even after a predetermined time has elapsed. 2. An anti-skid control means for determining a slip tendency of a wheel, an anti-skid control means for controlling a brake pressure applied to a wheel cylinder of the wheel in accordance with the slip tendency of the wheel, and When the brake pressure applied to the wheel cylinder is reduced, a reservoir for storing the brake fluid flowing out of the wheel cylinder is provided, and when the brake pressure applied to the wheel cylinder is reduced by the anti-skid control unit, ,
And determining means for determining that the amount of brake fluid flowing into the reservoir is equal to or greater than a predetermined value when the determination that the wheels have a tendency to slip has continued for a predetermined time by the slip tendency determining means. Brake pressure control device. 3. The pump according to claim 1, further comprising a pump that returns the brake fluid stored in the reservoir to a master cylinder during execution of the anti-skid control unit. A brake pressure control device as described. 4. The anti-skid control means, when the brake means determines that the amount of brake fluid flowing into the reservoir is equal to or more than a predetermined value, gradually increases the brake pressure applied to the wheel cylinder. 4. The brake pressure control device according to claim 1, wherein a brake pressure generated in a master cylinder is applied to the wheel cylinder.