JPH0241961A - Anti-lock brake control device with failure detecting means - Google Patents

Abstract

PURPOSE:To detect failure caused by a mechanical factor by detecting a differential pressure between each brake flow control valve and each wheel cylinder of right and left front wheels, outputting a pressurization command and detecting that the differential pressure more than a designated value continues during the period of a designated time. CONSTITUTION:The brake hydraulic pressure generated in a master cylinder 2 by operation of a brake pedal 1 is passed through flow control valves 3 through two systems of pipelines PB, PB' and supplied to the respective wheel cylinders FL, FR, RL, RR of front and rear wheels to form a designated antilock brake control device. Differential pressure between each flow control valve 3 and each wheel cylinder FL, RR of right and left front wheels by a differential pressure switch 7. A brake pressurization command is output, and it is detected that differential pressure more than a designated value continues during the period of a designated time to generate a warning of abnormality. Thus, it is possible to detect a mechanical failure such as stick of an electromagnetic solenoid of the flow control valve.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to failures in anti-lock brake systems for automobiles, particularly those in which the supply pressure to the wheel cylinders cannot be increased normally due to mechanical factors. The present invention relates to an anti-lock brake control device having failure mode detection means.

(Prior art) As a device for braking an automobile, the braking pressure caused by pressing the brake pedal is transmitted to the wheels through a hydraulic piping system to apply the brakes. Excessive braking pressure locks the rotation of the wheels and causes tire slippage. Anti-lock brake control devices are already known that, when this occurs, relieve the opening dynamic pressure for a short period of time to avoid locking, and then apply braking pressure again to repeat braking.

Such a conventional anti-lock brake control device is a two-channel system in which the front two wheels are independently controlled, and the rear two wheels are controlled to a predetermined hydraulic pressure by the control pressure applied to the front two wheels.
Various systems have been proposed, including a 3-channel system that controls the front two wheels independently and the rear two wheels using a common independent control pressure, and a 4-channel system that controls all four wheels independently. . Regardless of the method, the control device that makes up each channel calculates wheel speed, estimated vehicle speed, wheel deceleration, slip amount, etc. based on the speed signal from the wheel speed sensor that detects the rotational state of the wheel. An electronic control circuit that outputs a command signal for pressurization, holding, or depressurization (or only pressurization or depressurization) based on the calculation results, and an electronic control circuit installed in the middle of the braking pressure piping system route that connects the master cylinder and the wheel output. The hydraulic pressure control unit outputs the braking pressure from the master cylinder as pressures controlled respectively for pressurization, holding, and depressurization according to command signals from the electronic control circuit.

There are various types of hydraulic control unit t-, such as a combination of two solenoid valves, a flow control valve and a solenoid valve, a cut-off valve and an expansion valve, or a solenoid valve, and generally used to supply control pressure. Each braking pressure system is equipped with a hydraulic pump, accumulator, reserve tank, etc.

Depress the brake pedal, anti-lock i91 '<N
When U is started, the wheel speed, estimated vehicle speed, wheel deceleration, slip amount, etc. are calculated based on the speed signal from the wheel speed sensor, and as a result, the electronic control circuit determines that the wheels are heading toward lock. Then, a pressure reduction command is output, followed by a hold command to check the status of lock recovery, and when the lock is recovered, a pressure increase command is output again, and brake braking is performed by making the most effective use of tire friction force.

In such a conventional anti-lock brake system, if the hydraulic pressure control unit for adjusting the hydraulic pressure fails, the failure can be detected by electrically checking the operation of the solenoid driving the solenoid valve or During a pressure reduction operation, which is one of the long control operations, a method is generally used in which a method is used to electrically check whether the wheels are still unlocked even if the pressure reduction operation is performed for a predetermined time or longer.

[Problem to be Solved by the Invention] However, in the former case of the failure detection method for the hydraulic control unit described above, only an electrical failure is detected, and for example, the solenoid of a solenoid valve is stuck. Failures due to mechanical factors such as these cannot be detected.

In the latter case, based on the wheel behavior measured by the wheel speed sensor, it is estimated that normal anti-lock control operation cycle is not being performed, and a failure due to mechanical factors is detected and an alarm is issued. be able to. However, the only failure mode that can be alerted is when the pressure is not reduced even though it should be in the mode, and it is not possible to warn about the serious failure mode where the pressure is not pressurized even though it is in the mode where it should be pressurized. . This is because the pressure to be applied in the pressurization mode varies to various values due to changes in the friction coefficient of the road surface, making it impossible to identify the failure mode.

This invention was made in view of the current state of the art regarding failure detection methods for the hydraulic pressure adjustment mechanism in the conventional anti-lock brake control device, and its purpose is to detect when the solenoid of the solenoid valve in the hydraulic pressure control unit is stuck. An object of the present invention is to provide an anti-lock brake control device having a failure detection means that can reliably detect failures caused by mechanical factors such as.

[Means to solve the problem]

Therefore, in this invention, as a means for solving the above problem, at least one brake pressure piping system is provided for at least two or more mutually independent braking pressure piping systems that adjust the braking pressure generated in the master cylinder when the brake pedal is depressed and send it to the wheel cylinder. Wheel speed, wheel deceleration, estimated vehicle speed, slip amount, etc. are calculated and determined based on signals from one or more hydraulic control units and a wheel speed sensor that detects the rotational state of each wheel.As a result, wheel lock tendency is calculated. Or an electronic control circuit that outputs a deceleration or pressurization command to the hydraulic pressure control unit when a recovery tendency from lock is detected, and a piping section between the hydraulic pressure control unit of each braking pressure system and the wheel cylinder that corresponds to each other in each system. and a differential pressure switch that detects a differential pressure of more than a predetermined value between positions, the electronic control circuit outputs a pressurization command to the hydraulic pressure control unit of the part where the differential pressure is to be detected, and the differential pressure switch. When it is detected that a pressure difference greater than a predetermined value continues for a predetermined period of time, an abnormality alarm is output to detect a failure of the hydraulic pressure control unit.

[Function] The anti-lock brake braking device according to the present invention configured as described above can normally perform anti-lock control in the same way as conventional devices, unless there is a failure in the hydraulic pressure control unit in the braking pressure piping system. Normal brake braking is possible during control.

The differential pressure input signal from the differential pressure switch is sent to the electronic control circuit, and the electronic control circuit determines that the command signals from the electronic control circuit to the fluid pressure control unit are both pressurization commands and that the differential pressure signal continues for a predetermined period of time or more. If detected in the circuit, this means that a mechanical failure has occurred in any part of the hydraulic control unit, such as a flow control valve, a solenoid valve, or two solenoid valves. Mechanical factors include things that cannot be immediately detected as electrical signals, such as a stuck spool, a clogged orifice, or a stuck solenoid.

Therefore, in such a case, a warning signal is output, for example, anti-lock control is stopped and safe braking is performed.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic system diagram of a first embodiment of an anti-lock brake control device having a failure detection means according to the present invention.

1 is a brake pedal, 2 is a master cylinder, and the two systems of braking pressure P* and Pg generated here are supplied to the left and right front wheel cylinders 4 via a flow rate control valve 3, and are branched midway. The braking pressure pipes are used as X pipes and are also supplied to the two diagonally opposite rear wheels via their respective flow control valves 3.

The flow rate control valve 3 includes a spool 32 and a spring 33 that presses the spool 32 inside the valve body 31, and the spool 32 is provided with an orifice 34, and further has a solenoid valve 5 integrated therein as shown. When the solenoid valve 5 is opened during anti-lock control, the spool 32 is pushed down and the main flow path is cut off.
The discharge path communicates with the electromagnetic valve 5 and the hydraulic pressure from the wheel cylinder 4 is returned to the pressurization source 6. 35 is the rear ply room, 36
is a decompression chamber, and 37 is a sleeve. P, ,P,,P,
are the first port, second port, and third port of the spool 32; Pt, Po+, and R0a are the inlet port, the second outlet port, and the second outlet port; Ro, R+, and R2 are the annular grooves;
There are two branching paths. Further, the pressurization source 6 includes a pump 61, a motor 62, and a reserve tank 63.

The hydraulic pressure control device shown in FIG.
A differential pressure switch 8 for detecting the differential pressure between 1P and 1P' is provided. Differential pressure switch? , 8 may be of a displacement type as shown in FIG. 3 or of various other types.

Reference numeral 10 denotes an electronic control circuit (ECU) that outputs a pressure reduction or pressure increase command to the hydraulic pressure control device, and a schematic block diagram thereof is shown in FIG. Signals from the wheel-side sensors S, -S, which detect the rotational state of the wheels, are converted into pulse signals by the A/D converter 11, then subjected to pulse processing by the pulse processing circuit 12, and then sent to the microcomputer 13. . The microcomputer 13 calculates the wheel speed, wheel deceleration, estimated vehicle speed, slip amount, etc. from the above signals, and when it detects a tendency of the wheels to lock or a tendency to recover from locking, it drives a pressure reduction or pressure increase command. Circuits 143-14. It is sent to the solenoid valves 51-54 via.

14.14. are the driving circuits for the warning lamp WL and the relay circuit 16, respectively. In addition, differential pressure spin chia,
8 is input to the microcomputer 13 via an interface 141.14. Generally, an electronic control circuit has a self-diagnosis function to detect whether the electrical operation in the circuit is normal or not, and when a failure occurs, the failure location, type of failure, etc. are stored in the failure code memory 15.

The above-mentioned anti-lock brake control device normally operates in the same manner as before, whether during anti-lock control or non-anti-lock control. That is, during non-antilock control, the braking pressure P, (PI') is applied to the inlet P8 of the flow control valve 3, the first boat PI, the rear braai chamber 35, the second boat P2, and the branch path R.
5, the main flow path passing through the annular groove Re and the first outlet port Pol is sent to the wheel cylinder 4.

During anti-lock control, when the solenoid valve 5 is opened, the spool 32 is
descends and the main flow path is blocked, and the exit boat POI,
Annular groove Ro, branch path Rz, third bow) P, decompression chamber 36
, the solenoid valve 5, and the discharge path passing through the second outlet boat P02 are communicated with the low pressure side of the pressurization 1fi6, so that the hydraulic pressure in the wheel cylinder 4 is reduced.

When the solenoid valve 5 is closed, the fluid pressure difference between the rear ply chamber 35 and the decompression chamber 36 is reduced by the orifice 34, and the spool 32 is pushed back by the spring 33 and rises, and the braking pressure P is again increased. .

During such anti-lock control, when the differential pressure switch 7 detects the hydraulic pressure difference between the meteor control valve 3 of the left and right front wheels and the wheel cylinder 4 at corresponding positions in each left and right system, the differential pressure switch 7 If the hydraulic pressure difference is above a predetermined value, it is detected regardless of the cause of the hydraulic pressure difference. The cause of the difference in fluid pressure is that if a pressure increase command is given to one front wheel and a pressure reduction command is given to the other front wheel, the pressure increase command is given to both front wheels, but the friction coefficients of the left and right road surfaces are different, so This occurs when the maximum control pressures during pressurization are different, or when one of the flow control valves or solenoid valves malfunctions and normal control pressure cannot be applied.

When the above-mentioned hydraulic pressure difference occurs, there is no problem because the first and second cases are normal operations of normal anti-lock control. However, since the third case is due to a mechanical failure of the hydraulic control unit, it is necessary to detect this state separately from the first two. Therefore, in this embodiment, the signal of the differential pressure switch 7 is input to the electronic control circuit 10,
The following simple subprograms are provided for the program for performing normal anti-lock control provided in the microcomputer 13.

As shown in Fig. 5, anti-lock control is started and the main program performs normal anti-lock control calculations and outputs pressure reduction and pressurization commands based on these calculations, and each cycle of execution of the program. An interrupt is generated at an appropriate timing, and the three judgments shown in the figure are made. First, the presence or absence of a differential pressure signal input to the differential pressure switch 7 is checked, and if there is an input, then the flow control valves 3 for the left and right front wheels are activated. It is checked whether the command signals to .3 and 3 are pressurization commands, and whether the input of the differential pressure signal continues for a predetermined period of time or longer.

Here, the predetermined time can be, for example, a time sufficient to restore the pressure in the wheel cylinder, which has been reduced to the maximum by the flow control valve, to the maximum braking pressure generated by the maximum pedal effort.

When neither of the command signals to the flow control valve 3.3 is a pressurization command, or even if both are pressurization commands, if the input of the differential pressure signal does not continue for a predetermined period of time or more, each state is normal anti-lock control operation. This is the hydraulic pressure difference caused by the Therefore, in this case, the flow control valves 3, 3, etc. are immediately assumed to be normal and normal anti-lock control is continued.

If the above two conditions are met and the differential pressure signal of the differential pressure switch continues for a predetermined time or more, the solenoid valve 5 of the flow control valve 3.3
．． 5, the determination signal causes the drive circuit 14. The warning lamp WL is turned on via the warning lamp WL to give a warning. At the same time, the contents of this fault diagnosis are stored in the fault code memo 1J15 as a code.

In this example, a four-channel system is illustrated in which all four wheels are independently controlled by four flow control valves 3, but for the sake of simplicity, the differential pressure for the rear wheel flow control valve 3. Switches are not shown. Further, in the case of a 3-channel system or a 2-channel system, a differential pressure switch may be provided depending on each case.

Another differential pressure switch 8 is provided in FIG. This differential pressure switch 8 is activated when the differential pressure between the braking pressures P and P' exceeds a predetermined value. When the master cylinder 2 is normal, the braking pressures Ps and Ps' are generally approximately the same pressure, and no pressure difference occurs. Therefore, the differential pressure switch 8 detects a mechanical failure in the master cylinder 2 or a defect in any one of the braking pressure systems.

However, when the differential pressure switch 8 is inoperative and the differential pressure switch 7 is activated, there is a possibility that the above-mentioned failure has occurred on the hydraulic pressure control unit side, and both the differential pressure switches 7 and 8 are activated. In this case, it can generally be considered that the master cylinder 2 is malfunctioning.

Therefore, when a differential pressure is detected by the differential pressure switch 8, the differential pressure switch 7 does not detect a failure or issue an alarm.

FIG. 2 shows an embodiment in which an anti-lock brake control device is configured by two solenoid valves 5.5'. The first embodiment is basically the same as the first embodiment.

〔effect〕

As explained in detail above, in the present invention, the hydraulic pressure control circuit has a pressure difference greater than or equal to the destination at the piping site between the hydraulic control unit of each braking pressure system and the wheel cylinder. is detected by a differential pressure switch, and electronically detects that the differential pressure signal is during a time when pressurization commands are being output to the hydraulic control units of both systems, and that the signal continues for a predetermined time or longer. By detecting it in the control circuit, we can determine whether the failure is due to mechanical factors in the hydraulic control unit, and if a failure is detected, an alarm will be output, which is why the above-mentioned failures, which are difficult to judge, occur. This can be detected immediately and the brakes can be applied in a safer direction.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of an embodiment of an anti-lock brake control device according to the present invention, and FIG. 2 is a schematic diagram of another embodiment.
FIG. 3 is a schematic configuration diagram of the differential pressure switch, FIG. 4 is a block diagram of the electronic control circuit, and FIG. 5 is a flowchart of the subprogram. 1...Brake pedal, 2...Master cylinder, 3...Flow control valve, 4...Wheel cylinder, 5...Solenoid valve , 6...
・Pressure source, 7.8...Differential pressure switch, 10...Electronic control circuit, 13...Microcomputer, 15...
・・Fault code memory, WL・・・・Warning lamp. Patent applicant Sumitomo Electric Industries Co., Ltd. Agent Fumi Kamata

Claims (3)

[Claims] (1) At least one or more hydraulic pressure control units provided for each of at least two or more mutually independent braking pressure piping systems that adjust the braking pressure generated in the master cylinder when the brake pedal is depressed and send it to the wheel cylinders. Then, the wheel speed, wheel deceleration, estimated vehicle speed, slip amount, etc. are calculated and determined based on the signals from the wheel speed sensor that detects the rotational state of each wheel.As a result, the tendency of the wheels to lock or to recover from locking is detected. Then, an electronic control circuit outputs a deceleration or pressurization command to the hydraulic pressure control unit, and a pressure difference greater than a predetermined value between the corresponding positions of each braking pressure system at the piping site between the hydraulic pressure control unit and the wheel cylinder of each braking pressure system. The electronic control circuit outputs a pressurization command to the hydraulic pressure control unit of the part where the differential pressure is to be detected, and the differential pressure switch detects a differential pressure above a predetermined value. 1. An anti-lock brake control device having a failure detection means configured to detect a failure of a hydraulic control unit by outputting an abnormality alarm when detecting that the hydraulic pressure control unit continues for a predetermined time or more. (2) The signals outputted by the electronic control circuit to the hydraulic pressure control unit are both pressurization signals, and the differential pressure detected by the differential pressure switch is equal to or higher than a predetermined pressure, and the wheel cylinder is the one whose pressure has been reduced to the maximum by the hydraulic pressure control unit. 2. The brake pedal having a failure detection means according to claim 1, wherein the brake pedal outputs an alarm when it detects that the pressure has been maintained for a sufficient time to restore the pressure to the maximum control pressure generated by the maximum pedal force. Lock brake control device. (3) In addition to the differential pressure switch, the electronic control circuit includes a second differential pressure switch that detects a differential pressure between corresponding braking pressure piping systems at a piping site between the hydraulic control unit and the master cylinder. If the second differential pressure switch detects a differential pressure above a predetermined value, the detection of the differential pressure by the first differential pressure switch and its alarm are cut off, and the second differential pressure switch detects a differential pressure above a predetermined value. The anti-lock brake control having failure detection means according to claim 1, wherein the first differential pressure switch detects the differential pressure and issues an alarm only when the differential pressure is not detected. Device.