JPH0214954A - Brake pressure controlling apparatus - Google Patents

Abstract

PURPOSE:To prevent a sudden lock of a rear wheel by communicating a master cylinder to a wheel cylinder when brake pressure generated by the master cylinder is lower than the brake pressure by the wheel cylinder. CONSTITUTION:ECU 20 judges a rear wheel's lock tendency by a signal from a wheel speed sensor 12 to output a control signal to an electromagnetic valve 13 and an indicator 16. During running, a driver makes braking action and the ECU 20 judges that a rear wheel comes to show lock tendency, the ECU 20 switches the electromagnetic valve 13 to keep pressure of rear wheel cylinders 4, 5. After that, when braking action is finished or a brake is loosened, pressure difference between the pressure of the master cylinder 1 and pressure of wheel cylinders 4, 5 becomes small and output of a differential pressure switch 15 becomes off, the master cylinder 1 and the wheel cylinders 4, 5 are communicated together to prevent any sudden lock of a rear wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake pressure control device for controlling the pressure of rear wheel brakes.

[Conventional technology]

When braking a vehicle, the center of gravity of the vehicle moves forward, so the rear wheels are more likely to lock than the front wheels. Therefore, it is desirable to suppress the braking force of the rear wheels compared to the braking force of the front wheels. Therefore, conventionally, a provisioning valve (P valve) or the like has been used to change the ratio of brake pressure between the front and rear wheels.

[Problem to be solved by the invention]

However, P pulp only changes the ratio of brake pressure between the front and rear wheels when the master cylinder reaches a predetermined value, and cannot perform control according to the tendency of the wheels to lock. For this reason, the rear wheels may suddenly lock up, for example, when the brakes are applied suddenly or when braking on a low μ road.

The present invention has been made in view of the above points, and it is possible to prevent the rear wheels from suddenly locking up by maintaining or gradually increasing the brake pressure at the rear wheels depending on the tendency of the rear wheels to lock up. The purpose of this invention is to provide a brake pressure control device.

[Means to solve the problem]

In order to achieve the above object, the brake pressure control device according to the present invention includes a rear wheel speed sensor that detects the speed of the rear wheels, and a rear wheel speed sensor that detects the speed of the rear wheels, as shown in FIG. 10(a). A locking tendency determining means for determining a locking tendency of the rear wheel based on wheel speed; and a locking tendency determining means provided between a master cylinder and a wheel cylinder of the rear wheel, and configured to communicate/cut off communication between the master cylinder and the wheel cylinder. a first command means for commanding the switching means to cut off communication between the master cylinder and the wheel cylinder when the lock tendency determining means determines that the rear wheel is in a lock tendency; , a comparison means for comparing the brake pressure generated by the master cylinder and the brake pressure of the wheel cylinder; and after the communication between the master cylinder and the wheel cylinder is cut off by the switching means, the comparison means compares the brake pressure generated by the master cylinder with the brake pressure of the wheel cylinder. second command means for commanding the switching means to communicate between the master cylinder and the wheel cylinder when it is detected that the brake pressure generated by the cylinder has become smaller than the brake pressure of the wheel cylinder; The structure shall be prepared.

Further, as shown in FIG. 10(b), the locking tendency of the rear wheels is determined based on a rear wheel speed sensor that detects the speed of the rear wheels and the rear wheel speed detected by the rear wheel speed sensor. a locking tendency determining means; a switching means provided between a master cylinder and a wheel cylinder of the rear wheel and configured to switch between communication and disconnection between the master cylinder and the wheel cylinder by receiving an electric signal; command means for outputting a pulse-like electric signal to the switching means to repeatedly communicate and disconnect the master cylinder and the wheel cylinder when the determination means determines that the rear wheel is in a locking tendency; The configuration includes the following.

[Effect]

According to the above configuration, when the lock tendency determining means determines that the rear wheels tend to lock during braking, the switching means cuts off communication between the master cylinder and the wheel cylinder. As a result, the brake pressure in the wheel cylinder is maintained at the pressure at the time when the rear wheel shows a tendency to lock. Therefore, the rear wheels do not suddenly lock up, and the rear wheel speed changes gradually. Therefore, the behavior of the vehicle changes gradually, improving safety.

Furthermore, when the rear wheels tend to lock, when a pulsed electric signal is given to the switching means by the command means, the switching means repeatedly communicates and disconnects the master cylinder and the wheel cylinder. As a result, the pressure increase gradient of the brake pressure of the rear wheel cylinder becomes gentler than the pressure increase gradient of the brake pressure generated by the master cylinder.

Thereby, the same effect as described above can be achieved, and the braking distance can be shortened.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described based on the drawings.

In Fig. 1, 1 is a tandem master cylinder, which includes a front wheel cylinder 2.3 and a rear wheel cylinder 4.
．． 5 through independent hydraulic piping. Reference numeral 6 denotes a provisioning valve (P valve) which, when the pressure PMC of the master cylinder 1 reaches a predetermined value, reduces the rate of subsequent pressure increase in the rear wheel cylinders 4 and 5. A wheel speed sensor 12 detects the rotation speed of the rear wheel drive shaft. 13 is a 2-bot, 2-position solenoid valve, and when the power is not energized, the master cylinder 1 is in the A position.
and the wheel cylinders 4 and 5, and the communication is cut off at position B when energized. 15 is a pressure difference switch, and a solenoid valve 13
When a pressure difference occurs between the input and output boats of P valve 6, the pressure P of master cylinder 1 on the downstream side of P valve 6, 4. It turns ON when a pressure difference of more than a predetermined value (for example, 2 atmospheres) occurs between the pressure PWC of the wheel cylinders 4 and 5 and the pressure PWC of the wheel cylinders 4 and 5. Reference numeral 16 denotes a control indicator, which informs the driver that this device is in operation when the rear wheels tend to lock.

20 is an electronic control device (
The ECU) determines whether the rear wheels tend to lock based on the signal from the wheel speed sensor 12 and outputs a control signal to the solenoid valve 13 and indicator 16. Furthermore, the end of the control is determined based on the signal from the pressure difference switch 15.

The operation of the above configuration will be explained.

In FIG. 2, when the driver performs a brake operation while the vehicle is running, it is determined that the rear wheels tend to lock from the wheel speed (8) and wheel acceleration (2) calculated by the ECU 20 (time T). , FIG. 2(C).

As shown in (e), the ECU 20 switches the solenoid valve 13 to the B position to increase the pressure P in the rear wheel cylinders 4 and 5.

Hold C. At the same time, as shown in FIG. 2(f), the ECU 20 turns on the control indicator 16 (O
N) to notify the driver of the tendency of the rear wheels to lock.

After that, the pressure PMC in the master cylinder 1 decreases, and the pressure P in the wheel cylinders 4 and 5 decreases when the driver finishes the braking operation or when the driver releases the brakes when the control indicator 16 lights up. When the difference between , and the pressure difference becomes smaller (time T,), Fig. 2(d)
As shown in , the output of the pressure difference switch 15 is turned OFF. At this time, as shown in FIGS. 2(C), 2(e), and 2), the ECU 20 switches the solenoid valve 13 to the A position to communicate the master cylinder 1 with the wheel cylinders 4 and 5, and displays the control indicator. 16 is turned off to end the control.

Note that if this device is not present, the pressure P, 4c shown by the dotted line in Fig. 2 (C) will be supplied to the wheel cylinders 4, 5 via the P valve 6, so the wheels will not move suddenly or violently. to lock. Wheel speed at that time■. and wheel acceleration ■
. are shown by dotted lines in Figures 2(a) and (b).

As is clear from FIGS. 2(a) and 2(b), it is possible to moderate the changes in the wheel speed (8) and wheel acceleration (2) by this device.

FIG. 3 is a flowchart showing a control processing procedure performed by the ECU 20, and will be described in detail below along this flowchart.

When the ignition switch is turned on, step lO
Check the operation of each part of the device and turn off necessary flags.
Initialization operations such as setting F are performed.

In step 20, the wheel speed v1 of the rear wheel is taken in from the wheel speed sensor 12, and the wheel speed ■ taken in step 20 is taken in. Based on this, in step 30, the rear wheel acceleration v,4 is calculated.

In step 40, it is determined whether or not the control flag indicating that the control is currently in progress is ON, that is, whether the solenoid valve 13 is switched to the B position and the rear wheel cylinder 4 is turned on.
．． It is determined whether or not the pressure of 5 is maintained. When the judgment result in step 40 is negative (N), the process proceeds to step 50, and it is judged whether or not control should be started. In other words, in step 50, the wheel acceleration Vw calculated in step 30 is It is determined whether or not the deceleration is smaller than the maximum deceleration KG (for example, -0, 8C,) that allows stable stopping. If the determination result in step 50 is affirmative (Y), it can be presumed that the rear wheels tend to lock, so the process proceeds to step 90.

In step 90, the under-control indicator 16, which informs the driver that the device is in operation, is turned ON; in step 100, the solenoid valve 13 is switched to position B; in step 110, the under-control flag is turned ON; Return to 20.

On the other hand, if the judgment result in step 50 is negative (N), the process proceeds to step 60, and the control indicator 16 is set to 0F.
FL, in step 70, the solenoid valve 13 is switched to the A position, in step 80, the under control flag is turned off, and the process returns to step 20.

Also, in step 110, the control flag is turned on,
When step 20 → step 30 → step 40 is executed, the judgment result at step 40 becomes affirmative (Y),
Proceed to step 120.

In step 120, the output of the pressure difference switch 15 is turned ON.
It is determined whether or not the control should be terminated depending on whether or not it is. That is, when the pressure difference switch 15 is ON,
Pressure PMC of master cylinder 1 and wheel cylinder 4.
Since there is a pressure difference between the pressure PIC and the pressure PIC of 5, it is determined that the restriction 4vJ continues and the process proceeds to step 90. Moreover, when the output of the pressure difference switch 15 is OFF, the pressure PMC of the master cylinder 1 and the pressure Pw of the wheel cylinders 4 and 5 are
. Since the difference is smaller than the pressure difference KP, it is determined that the control has ended, and the process proceeds from step 60 to step 70 to step 80 to end the control.

Here, step 50 corresponds to lock tendency determining means, solenoid valve 13 corresponds to switching means, step 100 corresponds to first command means, and step 70 corresponds to second command means. In the first embodiment, the end of the control was determined by the pressure difference switch 15, but the master cylinder l and the wheel cylinders 4 and 5
The same pressure as in the first embodiment may be performed by detecting the pressure with a pressure sensor.

Further, in the first embodiment, the control indicator 16 informs the driver that the rear wheels tend to lock, but the driver may be alerted by a sound or the like, or this may be omitted.

Next, a second embodiment of the present invention will be described based on FIGS. 4 and 5.

In the first embodiment, when it is determined that the rear wheels tend to lock, communication between the master cylinder 1 and the wheel cylinders 4 and 5 is cut off, and the pressure in the wheel cylinders 4 and 5 is simply maintained. . In the second embodiment, as shown in FIGS. 4(a) and 4(b), when the rear wheels exhibit a tendency to lock (time TI
), as shown in FIG. 4(e), the electromagnetic valve 13 is repeatedly energized and de-energized in a pulsed manner. This results in
As shown in Figure 4 (C), rear wheel brake pressure P%1
The upward slope of c becomes gentler, which makes it possible to prevent the rear wheels from suddenly locking up and to shorten the braking distance. In addition, what is occupied by the dotted line in FIG. 4(C) is the brake pressure PMC of the master cylinder l.

FIG. 5 is a flowchart showing the processing procedure performed by the ECU 20 of the second embodiment. Steps that perform the same processing as those of the first embodiment are numbered the same, so the explanation here will be omitted. However, in the second embodiment, the under control indicator 16
is omitted.

In step 10a, an initialization operation is performed in the same manner as in the first embodiment, but in addition, O is substituted into the variable CT.

If the determination result in step 120 is that the control has ended, the process proceeds to step 200 and 0 is substituted into the variable CT. Thereafter, the process proceeds from step 70 to step 80 to end the control.

On the other hand, if the determination result at step 120 is to continue the control, the process proceeds to step 210, where the variable CT is increased by one. The variable CT incremented by 1 in step 210 is
In step 220, it is compared with a first reference value KT, .

When the variable CT is less than or equal to the first reference value KTO,
Proceeding to step 250, the solenoid valve 13 is switched to position B and the pressure in the wheel cylinder 4.5 is maintained. Thereafter, when the variable CT increases and becomes larger than the first reference value KT, the process proceeds from step 220 to step 230. In step 230, the variable CT is set to the second reference value KTC,
c(≧KT, ,), and the variable CT is compared to the second reference value K
If Tc,c or less, the process proceeds to step 260.

In step 260, the solenoid valve 13 is switched to the A position, and the pressure in the wheel cylinder 4.degree. 5 is increased. Thereafter, when the variable CT increases and becomes larger than the second reference value KTcyc, the process proceeds to step 240, where the variable CT is set to φ. Then, the process proceeds to step 250, and the solenoid valve 13 is switched to the B position again.

By the above control, the solenoid valve 13 is switched as shown in FIG. 4(e), and the pressure P of the wheel cylinder 4.5 is maintained.

C increases at a constant rate as shown in FIG. 4(C).

In the second embodiment, a pressure difference switch is used to determine whether to end the control, but a brake switch may be used to end the control when the brake switch is turned off.

However, in this case, a check valve that only allows flow from the wheel cylinder 4.5 to the master cylinder 1 is provided at the location where the pressure difference switch 15 is installed. This check valve checks the pressure P w of the wheel cylinder 4.5.
This is to prevent pressure c from becoming larger than the pressure PMC of the master cylinder 1. Here, step 210
260 corresponds to the command means.

Next, a third embodiment of the present invention will be described based on FIGS. 6 and 7.

In the second embodiment, when the rear wheels show a tendency to lock, the solenoid valve 1
3 at predetermined intervals to increase the pressure pwc in the wheel cylinders 4 and 5 at a constant rate. In the third embodiment, as shown in FIGS. 6(a) and (b), time T,
When the rear wheel shows a locking tendency in Fig. 6(C),
As shown in (d), the pressure pwc in the wheel cylinder 4.5 is increased very slowly at the beginning, and then the pressure increase gradient is gradually increased. At this time, by setting in advance the time and number of times the solenoid valve 13 is switched to the A position during control, the pressure difference switch and brake switch can be omitted. Note that in the third embodiment as well, the under-control indicator 16 is omitted as in the second embodiment.

FIG. 7 is a flowchart showing the processing procedure executed by the ECU 20 of the third embodiment, and the following description will be made using this flowchart. However, the steps that perform the same processing as in the first embodiment are numbered the same as in the first embodiment, and the description thereof will be omitted here.

If it is determined in step 40 that the control flag is turned on, the process proceeds to step 300, in which an optimal output pattern is selected based on the previous control result from a map consisting of a plurality of pre-stored output pattern patterns. select.

In step 310, it is determined whether or not all the selected outgoing cover turns have been executed, and if all the outgoing cover turns have been executed, the process proceeds from step 70 to step 80.
End control.

If all the output turns have not yet been executed, the process advances from step 310 to step 320, and the solenoid valve 1
3 to the B position is determined. If it is determined in step 320 that it is time to switch the solenoid valve 13 to the B position, step 33
0 and set the solenoid valve 13 to the B position. On the other hand, if the determination result in step 320 is negative (N), the process proceeds to step 340 and the solenoid valve 13 is set at the A position.

An example of the above control is shown in FIG. 6(d), whereby the pressures pwc in the wheel cylinders 4 and 5 increase quadratically.

Next, a fourth embodiment of the present invention will be described based on FIGS. 8 and 9.

In the fourth embodiment, as shown in FIGS. 8(a) and (b),
When the rear wheels show a small tendency to lock or the vehicle body shows a relatively large deceleration at time T1, as shown in FIGS. The solenoid valve 13 is switched according to a preset output pattern so that the output pattern is smooth and gentle (referred to as slow pulse output).
, When the locking tendency becomes large as shown in (b) (time Tt), FIG. 8(C).

As shown in (d), at that point, the solenoid valve 13 is switched to the B position to maintain the pressure PWC in the wheel cylinders 4 and 5. Here, KG, KG8 shown in FIG. 8(b) are:
For example, KG--0, 70, KG3=-10. Further, the wheel speed V becomes smaller than the extremely low speed KV (for example, 5 kai/h) as shown in FIG. 8(a) (at time T,
) and the pressure Pw of the wheel cylinders 4 and 5, as shown in FIGS. 8(C) and (B). The solenoid valve 13 is switched according to a preset output pattern so that the pressure increase gradient becomes larger than the slow pulse output (referred to as sudden pulse output).
, the control is ended (time T4), and if the locking tendency remains small even after outputting the slow pulse, the sudden pulse is output continuously and the control is ended. If the tendency to lock increases during this sudden pulse output, at that point the solenoid valve 1
3 to position B and pressure P of wheel cylinder 4.5.
hold wc. Moreover, if the tendency to lock becomes small again while the pressure PWC of the wheel cylinders 4 and 5 is maintained, a slow pulse output is executed. Then, the process is repeated in the same manner. Note that the configuration of the fourth embodiment is similar to that of the third embodiment.

Here, in the fourth embodiment, a slow pulse output and a sudden pulse output are generated by changing the period while keeping the pulse width constant; however, by keeping the period constant and changing the pulse width, You can create one.

FIG. 9 is a flowchart showing an example of the processing performed by the ECU 20 of the fourth embodiment, and the steps that perform the same processing as those of the first to third embodiments are given the same numbers, and the explanation here will be omitted.

In step 15, this routine is executed at a predetermined interval KTms (
For example, in order to execute this step every 5 m5), the current execution of step 20 is prohibited until KTIIIs have passed since this step was executed last time.

In step 50a, it is determined whether or not to start the control, and the reference deceleration KG is, for example, -0, 7.
This is to determine whether sudden braking has been performed at G.

In step 410, which is executed when it is determined in step 40 that the control flag is ON, the wheel speed v1
and a reference speed KV (for example, 5 km/h). Here, the wheel speed V. When is smaller than the reference speed KV, the process proceeds to step 420, and when it is larger, the process proceeds to step 440.

In step 420, it is determined whether the sudden pulse output that is executed when the wheel speed V- reaches an extremely low speed has ended. If the sudden pulse output has been completed, the control proceeds from step 70 to step 80 to end the control, and if it has not been completed, the output pattern for the sudden pulse output stored in advance is called up in step 430.

In step 440, wheel acceleration vw and deceleration KGZ(
For example, a comparison is made with -1,0G). That is, here, it is determined that the tendency of the rear wheels to lock is increasing by comparison with the relatively large deceleration. If it is determined in step 440 that there is a strong locking tendency, the process proceeds to step 470 and the solenoid valve 13 is switched to the B position.

Further, if it is determined in step 440 that the tendency to lock is not large, the process proceeds to step 450.

In step 450, it is determined whether or not the slow pulse output has ended. If it has ended, the process proceeds to step 420, and if it has not ended, the process proceeds to step 460.

In step 460, the output pattern of the slow pulse output stored in advance is called, and the process proceeds to step 320.

In addition, in the first to fourth embodiments, the rotation speed of the drive shaft was detected as the rear wheel speed, but a wheel speed sensor was installed on each rear wheel, and the average value or low select value was used as the rear wheel speed. It's good as well.

In addition, in the first to fourth embodiments, the rear wheel acceleration ■. It was determined that there was a tendency to lock when sudden braking was performed, but the rear wheel speed
. The vehicle speed may be estimated from , and the slip rate may be calculated from these two speeds, and the start/end of the control may be determined based on this slip rate, or these may be used together for determination.

[Effects of the Invention] As described above, in the present invention, the brake pressure of the rear wheels is maintained according to the tendency of the rear wheels to lock, so that the rear wheels do not lock suddenly and the rear wheel speed is maintained. changes slowly. Therefore, the behavior of the vehicle changes gradually, improving safety.

Further, by gradually increasing the brake pressure of the rear wheels in accordance with the tendency of the rear wheels to lock, it is possible to shorten the braking distance while improving safety.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, FIG. 2(a),
(b), (c), (d), (e), (f) are time charts explaining the operation of the first embodiment, FIG. 3 is a flowchart explaining the operation of the first embodiment, and FIG. 4 (
a), (b), (C). (d), (e) are time charts explaining the operation of the second embodiment of the present invention, FIG. 5 is a flowchart explaining the operation of the second embodiment, and FIGS. 6 (a), (b), ( C)
, (d) is a time chart explaining the operation of the third embodiment of the present invention, FIG. 7 is a flowchart explaining the operation of the third embodiment, and FIGS. 8 (a), (b), (c), (
a) is a time chart explaining the operation of the fourth embodiment of the present invention, FIG. 9 is a flowchart explaining the operation of the fourth embodiment, and FIGS. 1O (a) and (b) show an outline of the present invention. FIG. 1... Master cylinder, 2, 3, 4.5... Wheel cylinder, 12... Wheel speed sensor, 13... Electric i[BuF. 5...Pressure difference switch. 20...Electronic control unit (ECU)

Claims (2)

[Claims] (1) Based on the rear wheel speed sensor that detects the rear wheel speed and the rear wheel speed detected by the rear wheel speed sensor,
a locking tendency determining means for determining a locking tendency of the rear wheel; a switching means provided between a master cylinder and a wheel cylinder of the rear wheel for switching communication/blocking between the master cylinder and the wheel cylinder; a first command means for commanding the switching means to cut off communication between the master cylinder and the wheel cylinder when the rear wheel is determined to have a lock tendency by the lock tendency determination means; a comparison means for comparing the brake pressure generated by the master cylinder with the brake pressure of the wheel cylinder; and a comparison means for comparing the brake pressure generated by the master cylinder by the comparison means after communication between the master cylinder and the wheel cylinder is cut off by the switching means. The brake is characterized by comprising second command means that commands the switching means to communicate between the master cylinder and the wheel cylinder when it is detected that the brake pressure has become smaller than the brake pressure of the wheel cylinder. Pressure control device. (2) Based on a rear wheel speed sensor that detects the speed of the rear wheels and the rear wheel speed detected by the rear wheel speed sensor,
a locking tendency determining means for determining a locking tendency of the rear wheel; and a locking tendency determining means provided between a master cylinder and a wheel cylinder of the rear wheel, and receiving an electric signal to communicate/cut off communication between the master cylinder and the wheel cylinder. and a switching means for switching between the master cylinder and the wheel cylinder by outputting a pulsed electric signal to the switching means when the locking tendency determining means determines that the rear wheel is in a locking tendency. - A brake pressure control device characterized by comprising a command means for repeatedly executing the cutoff.