JPS63240459A - Two-system antilock type pressure fluid brake device - Google Patents

Abstract

PURPOSE:To enable a normal side brake device to hold its fluid pressure to a proper value, by setting a target wheel speed, which is set in accordance with an estimated car body speed, so that a difference between the target wheel speed and the estimated car body speed increases larger when a defect is detected in one system of the two-system brake devices. CONSTITUTION:The captioned device, which detects in a wheel speed detecting means E a rotary speed of wheels A, B in each group of plural wheels divided into two groups estimating a car body speed in accordance with the detection output being based on the maximum of the wheel speeds in a target speed setting means F, sets a target wheel speed lower than this estimated speed. And the device, when the speed of each wheel decreases lower than the target wheel speed, controls a brake fluid pressure by a fluid pressure control unit G so that the wheel speed increases to almost the target wheel speed. Here the device is constituted setting the target wheel speed so that its difference from the estimated car body speed increases larger than normal by a defect-time control means I when a defect in one of the two systems is detected by a defect detecting means H.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an anti-lock type hydraulic brake system for a vehicle, and particularly to anti-lock control when one system of a two-system hydraulic brake system fails. It's about improvement.

BACKGROUND OF THE INVENTION As a brake system for conventional vehicles, an l-system hydraulic brake system is widely used. A plurality of wheels of the vehicle are provided in two groups, and brake fluid pressure is transmitted through one system of fluid passages to the brake cylinders provided corresponding to each of the wheels in one group, and the brake fluid pressure is transmitted to each of the wheels in another group. The system is configured such that brake fluid pressure is transmitted to the correspondingly provided brake cylinders through a system of fluid passages independent of the above-mentioned one system.

In this type of hydraulic brake system, if the brake fluid pressure transmitted to the brake cylinder during braking is excessive in relation to the friction coefficient of the road surface, wheel slip becomes excessive and the braking distance increases. , or to avoid deterioration of vehicle running stability, an anti-lock control device that automatically controls brake fluid pressure is disclosed in Japanese Patent Laid-Open No. 58-2.
This is already known from Publication No. 6661 and the like.

This anti-lock control device is configured to include a wheel speed detection means, a target speed setting means, and a hydraulic pressure control device. The wheel speed detection means is capable of detecting the rotational speed of at least one wheel belonging to each of the two groups,
The target speed setting means is configured to estimate the vehicle speed based on the highest wheel speed detected by the wheel speed detection means, and to set the target wheel speed lower than the estimated vehicle speed. For example, normally the highest detected wheel speed is directly estimated as the vehicle speed, and if the absolute value of the deceleration of the highest wheel speed exceeds a set value, the wheel with the highest speed will also be locked. As a result, the vehicle speed is calculated by fixing the deceleration to a set value. The target wheel speed is set by subtracting a constant value representing a predetermined amount of slip from the estimated vehicle speed obtained in this way, or the target wheel speed is set so that the slip ratio becomes a predetermined value.

If the actual wheel speed becomes lower than this target wheel speed, the hydraulic pressure control device controls the hydraulic pressure of the brake cylinder so that the actual wheel speed becomes approximately the target wheel speed, and each wheel is in a locked state. This will prevent you from falling into this situation.

Problems to be Solved by the Invention However, in the conventional two-system anti-lock hydraulic brake system, when one system fails, that is, when one of the two fluid passages is damaged, the system cannot be connected to that system. There is a problem in that when brake fluid pressure is no longer transmitted to the brake cylinders that are connected to the brake system, the brake fluid pressure of the brakes connected to the normal system is controlled to be low, resulting in an extended braking distance of the vehicle.

The target speed setting means estimates the vehicle speed based on the highest wheel speed detected by the wheel speed detection means as described above, but if both systems are normal, the speed is Braking force is applied to the highest wheel, and that wheel also experiences some degree of slip.

Therefore, the vehicle speed estimated based on the wheel speed will be lower than the actual vehicle speed, and the target wheel speed is set taking this fact into consideration.

That is, the target wheel speed is set so that the difference between the estimated vehicle speed and the target wheel speed becomes smaller as the estimated vehicle speed becomes lower than the actual vehicle speed.

However, when one system fails, the brakes of that system do not operate, so that almost no slip occurs in the wheels corresponding to that brake during braking. Naturally, the rotational speed of that wheel is the highest, and the vehicle speed is estimated from that, so the estimated vehicle speed has almost no difference from the actual vehicle speed. Nevertheless, in conventional devices, the target wheel speed was set so that the difference from this vehicle body speed was the same as when both systems were normal, so the target wheel speed was higher than the appropriate value. This resulted in the problem that the brake fluid pressure was kept low to reduce slippage more than necessary, resulting in a longer braking distance.

Means for Solving the Problems The present invention has been made to solve this problem, and as shown in FIG. a brake device;
In a two-system antique type hydraulic brake system including a wheel speed detection means, a target speed setting means, and a hydraulic pressure control device, a failure detection means detects a failure of one of the two systems; A failure control means is provided for causing the target speed determining means to set the target wheel speed so that the difference between the estimated vehicle speed and the estimated vehicle speed becomes larger than usual when a system failure occurs.

In the two-system anti-lock hydraulic brake system configured as described above, when the failure detection means detects failure of one system, the failure control means sets the target speed setting means to set the target wheel. Since the speed is set so that the difference from the estimated vehicle speed is larger than when both systems are normal, the hydraulic pressure in the brake cylinder is not suppressed to an unnecessarily low level.

Effects of the Invention Therefore, according to the present invention, the hydraulic pressure of the brake cylinder on the normal side is controlled to an appropriate value even when the l system fails,
The slip amount or slip ratio of the wheel corresponding to the brake cylinder is maintained at an appropriate value, and the braking distance when one system fails can be shortened compared to the conventional system.

Moreover, for this purpose, it is only necessary to add a failure detection means and a failure control means, and since these can be constructed at low cost, it is possible to obtain the above effects while suppressing an increase in device cost.

Embodiment Hereinafter, an embodiment in which the present invention is applied to a two-system anti-lock type hydraulic brake system for a front engine/rear drive type four-wheel vehicle will be described with reference to the drawings.

In FIG. 2, 10 is a mask cylinder, which is provided with two independent pressurizing chambers. This mask cylinder 10 generates brake fluid pressure at a height proportional to the operating force of the brake pedal 12. The brake fluid pressure generated in one pressurizing chamber is transmitted to the main fluid passage 16 via the provisioning valve/bypass valve 14. The main fluid passage 16 is divided into two parts in the middle, and each part is connected to a front wheel cylinder 20 via an electromagnetic hydraulic pressure control valve 18.

The brake fluid pressure generated in the other pressurizing chamber is transmitted to the main fluid passage 22 via the proboscising valve/bypass valve t4. The main liquid passage 22 is also provided with an electromagnetic hydraulic pressure control valve 24, and after passing through this control valve 24, the main liquid passage 22
is divided into two branches and connected to two roller wheel cylinders 26.

The two front wheel cylinders 20 are brake cylinders that suppress the rotation of the left and right front wheels, respectively.
The rear wheel cylinders 26 are brake cylinders for the left and right rear wheels, respectively. This brake system is a so-called two-system type, front and rear.

The provisioning/bypass valve 14 proportionally reduces the brake fluid pressure in the rear system including the main fluid passage 22 when the front system including the main fluid passage 16 is normal, and when the front system fails, it reduces the brake fluid pressure in the rear system including the main fluid passage 22. It has a function of directly transmitting the brake fluid pressure from the cylinder 10 to the rear wheel cylinder 26.

As shown in FIG. 2, the electromagnetic hydraulic pressure control valve 18 is always in an increased pressure state that communicates the wheel cylinder 20 and the mask cylinder 10, but when the solenoid 30 is energized with a relatively large current, the front When switching to a reduced pressure state in which the wheel cylinder 20 is disconnected from the mask cylinder 10 and communicated with the reservoir 32, and when the solenoid 30 is energized with a relatively small current, the front wheel cylinder 20 is disconnected from the mask cylinder 10 and the reservoir 32. It also switches to a holding pressure state in which the pressure is cut off. The electromagnetic hydraulic pressure control valve 24 also operates in accordance with the switching of the excitation state of the solenoid 34, between an increased pressure state in which the rear wheel cylinder 26 is communicated with the mask cylinder cylinder 10, a reduced pressure state in which the rear wheel cylinder 26 is communicated with the reservoir 36, and a maintained state in which the rear wheel cylinder 26 is not communicated with the reservoir 36. It switches to a pressure state.

The brake fluid in the reservoir 32 is pumped up by a pump 38 and returned to the main fluid passage 16 via a pump passage 40. A damper 42 for reducing discharge pulsation of the pump 38 is connected to the pump passage 40, and a check valve 44 is provided for preventing brake fluid from flowing back from the main liquid passage 16 side to the damper 42. . The rear system also uses pump 46. Pump passage 48. A damper 50 and a check valve 52 are provided.

The front system also includes each front wheel cylinder 20
A recirculation passage 54 is provided that allows the brake fluid to flow back to the mask cylinder cylinder 10 by bypassing the electromagnetic hydraulic pressure control valve 18, and each recirculation passage 54 is provided with a check valve 56 that prevents the brake fluid from flowing back. It is provided. The front system is further provided with a bypass passage 62 equipped with a normally open electromagnetic on-off valve 58 and a check valve 60, so that when brake fluid is supplied from the mask cylinder 10 to the front wheel cylinder 20, the brake fluid is The liquid is supplied at a sufficient flow rate through both the electromagnetic hydraulic pressure control valve 18 and the electromagnetic on-off valve 58. The rear system also includes a recirculation passage 66 equipped with a check valve 64, but does not include a bypass passage.

The above-mentioned electromagnetic hydraulic pressure control valve 18.24 and electromagnetic on-off valves 5 and 8
is controlled by an anti-lock control device 70 shown in FIG. The main body of this device 70 is the CPU 72. ROM74
．． It is a computer equipped with RAM 76 and a bus 78 that connects them.

An input unit 80 is connected to the bus 78, and the input unit 80 includes a rear wheel speed sensor 84 that detects the average rotational speed of the left and right rear wheels from the rotational speed of the propeller shaft, and a speed sensor that detects the rotational speed of the left and right front wheels, respectively. 88 and 90 are connected to a brake switch 92 that detects depression of the brake pedal 12. An output section 94 is further connected to the bus 78, and the electromagnetic hydraulic pressure control valve 18.24 and the electromagnetic on-off valve 58 are connected to this output section 94.

A timer 98 is provided in the CPtJ72. The function of this timer 98 will be explained later. The program memory 100 of the ROM 74 stores control programs including various control routines, including a failure control routine shown in the flowchart of FIG. 4 and a hydraulic pressure control routine (not shown).

Further, the ROM 74 is provided with a normal speed difference memory 102, a failure speed difference memory 104, and a set time memory 105. The normal speed difference memory 102 stores the speed difference that is subtracted from the estimated vehicle speed in order to calculate the target wheel speed when both systems are normal, and the failure speed difference memory stores one system. A speed difference that should be subtracted from the estimated vehicle speed in the event of failure is stored. The latter is considered to be a larger value than the former. The function of the set time memory 106 will be explained later.

A failure flag 108 and a first time flag 110 are provided in the RAM 76. The functions of these flags will also be explained later.

In the two-system anti-lock hydraulic brake system configured as described above, while the depression of the brake pedal 12 is detected by the brake switch 92, the CPU
72 executes the control program stored in the program memory 100 of the ROM 74 for a certain period of time, for example, 20m5e.
Execute every c.

The following is performed by executing a hydraulic pressure control routine, etc., which are not shown. The rotational speed of each wheel is determined based on the signals from the rear wheel speed sensor 84 and the left and right front wheel speed sensors 88, 90, and the vehicle speed is estimated based on the highest of these wheel speeds. The target wheel speed is set by subtracting the speed difference stored in the normal speed difference memory 102 or the failure speed difference memory 104 from the estimated vehicle speed. When each wheel speed becomes smaller than the target wheel speed, the electromagnetic hydraulic pressure control valve 1
8.24 and the electromagnetic on-off valve 58 are controlled, and the hydraulic pressure of the wheel cylinder 20.26 is controlled so that the actual wheel speed becomes approximately equal to the target wheel speed.

In this embodiment, the computer controls the rear wheel speed sensor 8.
4 and the left and right front wheel speed sensors 88, 90 constitute wheel speed detection means, and also constitute target speed setting means. The computer also constitutes a hydraulic control device in cooperation with the electromagnetic hydraulic pressure control valves 18, 24, electromagnetic on-off valves 58, etc.

The selection between the normal speed difference memory 102 and the failure speed difference memory 104 during execution of the hydraulic pressure control routine is performed by executing the failure control routine shown in the flowchart of FIG.

This failure control routine is executed at regular intervals along with other routines. First, step SL (hereinafter simply 81
Expressed as (The same applies to other steps), it is determined whether the above-mentioned hydraulic pressure control is being performed in either of the two systems. If hydraulic pressure control is not being performed in any system, all steps below are bypassed, program execution returns to the main routine, and execution of one failure control routine is completed. .

On the other hand, if hydraulic pressure control is being performed in any of the systems, the determination result of Sl becomes YES, and it is determined in S2 whether or not hydraulic pressure control is being performed in other systems as well. Normally, the two systems of hydraulic pressure control are not started at the same time, so the determination result for S2 is usually No.
Therefore, in S3 and S4, it is determined whether the failure flag 108 and the first time flag 110 are in the ON state, respectively. Since these flags are set to OFF in the initial settings that are executed at the same time as the computer is turned on, the determination results for both S3 and S4 are NO.
Then, S5 and So are executed. The timer 98 is reset in S5, and the first flag 11 is set in So.
0 is turned on.

Next, in S7, it is determined whether the time measured by the timer 98 has reached the set time t0 seconds set in the set time memory 106, but initially the result of this determination is naturally N.
0, bypassing S8 and completing the execution of one failure control routine.

Thereafter, 5t-37 is repeatedly executed, but at this time, since the first flag 110 is ON in So, the determination result in S4 is YES, S5 and So are bypassed, and the timer 98 continues timing. do.

Normally, the hydraulic pressure control of other systems is started before the time measured by the timer 98 reaches the set value t0, so the determination result in S2 is YES, and the initial flag 110 and failure flag 108 are turned OFF in S9 and S10. It is said that While this failure flag 108 is OFF, the normal speed difference memory 10 is used to set the aforementioned target wheel speed.
The speed difference stored in 2 is used to maintain the slip ratio at an appropriate value. That is, as shown in Fig. 5, the magnitude of the braking force that can be generated by the wheels changes depending on the slip ratio, and is maximum near the slip ratio S. Therefore, the brake fluid pressure must be adjusted so that the slip ratio becomes approximately S3. It is controlled.

On the other hand, when one system fails, the brake does not operate in the system on the failed side, so the slip ratio does not become excessive and hydraulic pressure control is not started. Therefore, in this embodiment, after hydraulic pressure control is started in one system, if hydraulic pressure control is not started in the other system within the set time t0, it is assumed that the other system has failed. is estimated, and the speed difference memory 104 at the time of failure is selected. In other words, the judgment result of Sl is YE.
If the determination result in S2 continues for t0 or more while the determination result is NO, the determination result in S7 becomes YES, and the failure flag is turned ON in S8. If the failure flag is turned ON, the failure time speed difference memory 1 is used to set the target wheel speed during execution of a hydraulic pressure control routine (not shown).
04 is selected, and a larger speed difference than when both systems are normal is subtracted from the estimated vehicle speed, and the target wheel speed is set.

This will be explained in more detail. In FIG. 5, when both systems are normal, the slip rate S is also true for the wheels at the highest wheel speed, which is the basis for the estimated vehicle speed.

Since it is normal for a certain amount of slip to occur, the normal speed difference memory 102 stores a speed difference corresponding to the slip rate difference ΔS. If both systems are normal, if the target wheel speed is set using this speed difference, the slip ratio will be controlled to around S and the maximum braking force will be obtained, but if one system fails Sometimes, the brake corresponding to the wheel with the highest wheel speed, which is the basis of the estimated vehicle speed, does not operate, so the slip rate of that wheel becomes So. Therefore, if the same speed difference is used when one system fails as when the two systems are normal, the actual slip ratio will be controlled to around S2, and a braking force that is only ΔF smaller than the maximum value will be obtained. There will be no.

Therefore, the speed difference memory 104 at the time of failure stores a speed difference of a size corresponding to the slip rate difference ΔS', and 1
In the event of a system failure, this speed difference is subtracted from the estimated vehicle speed (
As a result, the target wheel speed is set, and even when one system is normal, the brake fluid pressure of the normal system is controlled so that the slip of that wheel is around S.

Note that even after the failure flag is once turned ON in 88 of FIG. 4, if the determination result in S2 becomes YES,
That is, if hydraulic pressure control is started in both of the two systems, the initial flag 110 and failure flag 108 are turned OFF in S9 and SIO, so the normal speed difference memory 102 is selected again when setting the target wheel speed. It will be done. Even though one system has not failed, for some reason the start of hydraulic pressure control in one system is delayed by more than the set time t0 with respect to the other system, so the failure flag is set to O.
Even if it is determined to be N, if the hydraulic pressure control of that system is started, the failure flag is returned to the OFF state in the SIO.

As is clear from the above explanation, in this embodiment, the part of the computer that executes steps 31 to S7 constitutes a failure detection means, and the part that executes S8 constitutes a failure control means. .

When the failure detection means is configured by software in this way, only a small number of programs are required, so the purpose can be achieved at low cost.
It is also possible to configure the failure detection means by hardware, such as by providing a hydraulic pressure sensor in each of the systems, or by providing a sensor that detects a difference in hydraulic pressure across both systems.

In addition, in the above embodiment, only one target wheel speed is set, but for example, the target wheel speed may be set by setting two speeds: the speed at which pressure reduction should start and the speed at which pressure increase should start. It is also possible to set the speed.

Furthermore, in the above embodiment, the present invention is applied to a two-system anti-lock hydraulic brake system for a four-wheel vehicle, but other systems such as a so-called X-piping dual-system hydraulic brake system may also be used. It is also possible to apply the present invention to a type of two-system hydraulic brake device, and it is also possible to apply the present invention to a two-wheeled vehicle. In the latter case, the front and rear wheels each constitute one group.

In addition, although not illustrated individually, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, such as adding changes to the hydraulic control device and the control program.

[Brief explanation of the drawing]

FIG. 1 is a diagram conceptually showing the configuration of the present invention. FIG. 2 is a circuit diagram of a hydraulic brake device according to an embodiment of the present invention, and FIG. 3 is a block diagram showing a control device thereof. FIG. 4 is a flow chart showing only portions of the program stored in the program memory of FIG. 3 that are particularly closely related to the present invention. FIG. 5 is a graph for explaining why control according to the present invention is desirable. 10: Mask cylinder 16: Main liquid passage 18 Two electromagnetic hydraulic pressure control valves 20: Front wheel cylinder 22: Main liquid passage 24: Electromagnetic hydraulic pressure control valve 26: Rear wheel cylinder 38.46: Pump 70: Anti-lock control device

Claims (1)

[Scope of Claims] A plurality of wheels of a vehicle are divided into two groups, and brake fluid pressure is transmitted to the brake cylinders provided corresponding to each of the wheels in one group through one system of fluid passages, and the brake fluid pressure is transmitted to the brake cylinders provided corresponding to each of the wheels in one group. A two-system hydraulic brake device in which brake fluid pressure is transmitted to brake cylinders provided corresponding to each of the wheels of the group through a fluid passage of another system independent from the system; and a brake system that belongs to each of the two groups. wheel speed detection means for detecting the rotational speed of at least one of the wheels; estimating the vehicle body speed based on the highest wheel speed detected by the wheel speed detection means; and estimating the vehicle body speed from the estimated vehicle body speed. target speed setting means for setting a low target wheel speed; and fluid control in brake cylinders corresponding to each wheel so that when the wheel speed of each wheel becomes lower than the target wheel speed, the wheel speed becomes approximately the target wheel speed. A hydraulic brake device including a hydraulic pressure control device for controlling pressure, a failure detection means for detecting a failure of one of the two systems, and a failure detection means for detecting a failure of one of the two systems, and a failure detection means for determining the target speed in the target speed determining means when one system fails. A two-system anti-lock type hydraulic brake system, characterized in that a failure control means is provided for setting the wheel speed so that the difference between the wheel speed and the estimated vehicle body speed is larger than normal.