JPH02296567A - Control circuit against pressure drop - Google Patents

Abstract

PURPOSE: To evade an excessive wheel slip by controlling the switching of the wheel valves leading to the rear wheel brakes so as to delay by a prescribed time at an initial control stage, when a first wheel showing a lock tendency is a front wheel. CONSTITUTION: The brake pressure liquid in a master cylinder 11 installed in parallel to a servo device 12 is transmitted to front wheel side wheel brakes 20, 21 and rear wheel side wheel brakes 22, 23 through valves 2, 3, 4 interposed in brake circuits I, II. Meantime, the information of the rotation state of respective wheels is detected by wheel sensors 6-9. Respective valves 2-4 as well as a modulator pressure operation valve 5 are controlled by a control device 10 based on those outputs. In other words, in an anti-lock control state, respective valves 2-4 are controlled so as to be switched to a close position. Meantime, when a first wheel showing a lock tendency is the front wheel, the switching of the valve 4 of the rear brake side is controlled so as to be delayed by a prescribed time at an initial control stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used in conjunction with an anti-lock brake system to control wheel brakes through a multi-way switching valve that is initially placed in an open position and can be switched to a closed position. a master cylinder connected to the master cylinder and a brake pressure regulator connected to the master cylinder, which is controlled by a multiplex process and switches the multi-way control valve leading to the wheel brakes to the closed position when anti-lock control is initiated. , relates to a circuit arrangement for controlling a pressure drop capable of reducing the pressure of a master cylinder.

PRIOR ART AND ITS PROBLEMS In conventional systems of the type mentioned above, the pressure regulator is formed as an assembly operated by auxiliary hydraulic pressure or by negative pressure. This pressure regulating device increases the braking force, creates a force in the opposite direction to the pedal depression force, and reduces the pressure in the working chamber of the master cylinder during control (German Patent Publication DE-A
O331l7 629. DE-O33641105;
Patent application P 38 22 260.4). This type of brake system operates by a multiplex process and therefore requires relatively few brake pressure control valves. A multi-way control valve is arranged in each pressure fluid line leading from the master cylinder to one or two wheel brakes, which multi-way control valve is initially arranged in an open position and can be switched to a closed position. . antiro・
When the brake control starts, all valves connected to the wheel brakes are first switched. The brake pressure in the master cylinder is then reduced and only the wheel valve leading to the unstable wheel is opened again. As a result, the braking pressure of the wheel brake for that wheel decreases, while the braking pressure of the remaining wheel brakes remains constant. The braking pressures of the other wheel brakes are subsequently adjusted in a similar manner. That is, it is lowered, remains constant, or even increased.

While the large mouth valve is closed at this initial stage of anti-lock control, the auxiliary force in the opposite direction to the pedal depression force increases, possibly binding or separating the pedal (see patent application P.
38 22 260.4), the pressure in the master cylinder may rise further or increase excessively, at least under unfavorable conditions. This is problematic in that it delays the pressure drop in the wheels tending to lock, which is necessary at this stage, and this delay affects the control and control functions.

Therefore, it is an object of the present invention to solve the above problems while avoiding complications and inconveniences.

[Means, Actions and Effects for Solving the Problems] To achieve the above object, the present invention provides a multi-directional brake system which is used with an anti-lock brake system and which is initially placed in an open position and can be switched to a closed position. It comprises a master cylinder connected to the wheel brake via a switching valve and a braking pressure regulator connected to this master cylinder, which is controlled by a multiplex process and has a multidirectional connection to the wheel brake when anti-lock control is initiated. A circuit device for controlling the pressure drop capable of reducing the pressure in the master cylinder by switching the control valve to the closed position of the wheel valve leading to the rear brake when the locking tendency is not reduced and the first wheel is the front wheel. A circuit arrangement is provided in which the switching can be delayed by a predetermined time in an initial control phase.

The invention is based on the principle that in most cases, especially in critical or limit conditions, the first wheel to become unstable is the front wheel. In such a situation, a further increase in the pressure on the rear wheels for a short period of time does not significantly affect the stable running of the wheels, and on the contrary, it is even advantageous for the braking operation. However, preventing the pressure from increasing too much and reducing the unstable front wheel brake pressure particularly quickly will provide better control. This is because excessive wheel slip due to extremely slow reduction in braking pressure can be avoided.

According to an advantageous embodiment of the circuit arrangement according to the invention, the delay time for switching the wheel valves at the rear wheels is between 4 and 2.
0 ms, preferably between 5 and 10 ms. This time is closely related to the respective brake system, in particular the brake pressure generator and its ineffective time. The numerical value can be set to an optimal value based on experience.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Embodiment] FIG. 1 shows a brake system in which the circuit device of the present invention is used. This brake system includes a brake pressure generator 1, wheel valves 2, 3.4, and a pressure regulating control valve (med
controller control valve) 5, wheel sensors 6.7, 8.9, and electronic control device 10
This electronic control device 10 constitutes a part of the circuit device of the present invention.

The brake pressure generator 1 includes a master cylinder 11 and a servo device 12. The servo device 12 is connected to the master cylinder 11, acts as a braking force booster, and also generates an auxiliary force H in the opposite direction to the pedal depression force F.

Braking force is applied to the brake cassienator 1 and the servo device 12 via the pedal 13, respectively.

In the embodiment of the invention described below, the servo system 12 is substantially similar to a conventional vacuum pressure brake power booster.

The interior of the servo device 12 is divided by the piston 14 into two chambers 15 and 16. In the rest position of the brake system shown, vacuum pressure is applied to the compartment via the connection "Vac and the modulator pressure control valve 5 of the working chamber. The valve 17, shown schematically, is open in the rest position of the brake. , supplies vacuum pressure to the chamber 15 on the pedal side.
1 schematically shows the connection between the brake system and the intake system of an Otto engine, which serves as an auxiliary energy source for increasing and regulating the braking force.

The braking force increased by the servo device 12 is transferred in the usual way to the working piston 18.1 of the tandem master cylinder 11.
9, the valves 2 and 3 are switched to the open position from the working chamber of the master cylinder 11 through the brake circuits I and .
．． Wheel brakes 20, 21, 22.23 through 4
can be conveyed to.

Information on the rotation status of each wheel of the vehicle is provided by the wheel sensor 6.7.
．． 7.9 detected by the control device 1 in the form of an electrical signal
Sent to 0. Control device 10 generates control signals for wheel valves 2, 3.4 and control valve 5 accordingly.

The method of operation of the above type of brake system is shown below.

Unless a locking tendency occurs, all valves are held in their switched positions as shown in FIG. The servo device 12 acts as a braking force booster. When a tendency to lock is detected in one wheel, for example the left front wheel VL, anti-lock control is initiated. Initially, all wheel valves 2.3.4 are closed and atmospheric pressure is supplied to the working chamber 16 by switching the pressure regulating control valve 5. Therefore, an auxiliary force H that reacts against the pedal depression force F is formed. If the brake pressure generator 1 is equipped with a device for locking or separating the pedal 13 from the piston 14, the pedal 13 is deactivated or separated at the same time as the anti-lock control is initiated. This type of device is not shown because it is known and easy to understand.

When the pressure in the master cylinder 11 decreases or falls below a pressure level lower than the pressure at the start of braking pressure control, the wheel valve 2 leading to the unstable wheel (in this case the left front wheel VL) returns to the open position. , and the braking pressure of the wheel brake 20 decreases. remaining brakes 21, 22
．． The braking pressure at 23 remains constant due to the wheel valves 3,4.

Thereafter, the braking pressure on the remaining wheels is similarly reduced or even increased.

FIG. 2 shows the master cylinder 1 in the control phase described above.
1 shows the change in braking pressure poz. At time t0 the braking process begins. 1 wheel at time t1, that is, the left front wheel VL
becomes unstable and anti-lock control is started. At time t1, the pressure regulating control valve 5 is switched to increase the pressure in the chamber 16. The wheel valve 2 leading to the left front wheel VL, which has become unstable, remains switched to the open position (or is switched immediately back to the original open position at the start of control). The wheel valve 3 leading to the right front wheel VR is switched again to the closed position. However, according to the invention, the multi-way control valve 4 leading to the rear wheels is activated at the time t2, for example from 4 to 20
It is switched to the closed position within milliseconds, preferably after 5 to 10 milliseconds. Therefore, the pressure P at time t1 acts on the right front wheel brake 21, while the slightly higher braking pressure P2 (or part of it, if a brake pressure reducing device is provided) acts on the rear wheel brake 21. 22, 23
It acts on As shown in FIG. 2, after the anti-lock control starts at time t1, the braking pressure of the wheel brake 20 of the wheel VL that has become unstable is quickly reduced.

The wheel valve 4 connected to the rear wheels HL, HR has a delay Δt.
When switched without wt, -t, the pressure change P'H2 of the master cylinder 11 becomes as shown by the dotted line in FIG. This also acts on the wheel brakes 20.

The dashed line pressure curve shows the braking pressure when the braking pressure is increased without being shut off. At time t, all valves 2,
3.4 at the same time is equivalent to abruptly stopping all pressure fluid supply from the brake pressure generator. For example, due to the inertial mass, the increase in braking pressure will then change, albeit slightly, resulting in an increase or excessive pressure. Instead of rapidly reducing the pressure at time t1 as a countermeasure against wheel locking, all wheel brakes are isolated, resulting in the control cycle starting with increased pressure. In a critical state control phase where the success or failure of achieving anti-lock depends on the rate of pressure drop, an excessive pressure increase as described above is highly undesirable. The reduction in the braking pressure of the wheel brake 20 needs to start at time t3 at the earliest.

Therefore, when carrying out the present invention, anti-lock control can be greatly improved with extremely simple changes or modifications to the control circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing basic components of a brake system according to an embodiment of the present invention, and FIG. 2 is a graph diagram showing changes in braking pressure in the initial stage of anti-lock control. DESCRIPTION OF SYMBOLS 1... Braking pressure generator, 2, 3.4... Wheel valve, 5... Pressure regulation control valve, 6, 7, 8.9... Wheel sensor, 11... Master cylinder, 12...・・・
Braking pressure modulator, 13... pedal, 20, 21,
22.23...Wheel brake applicant's patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) A master cylinder used with an anti-lock brake system and connected to a wheel brake via a multi-way switching valve that is initially placed in an open position and can be switched to a closed position, and a brake that is connected to this master cylinder. a pressure regulating device, controlled by a multiplex process, which switches a multi-way control valve leading to the wheel brakes to a closed position when anti-lock control is initiated;
A circuit device for controlling a pressure drop capable of reducing the pressure in a master cylinder, said circuit device controlling the switching of a wheel valve leading to the rear brakes for a predetermined period of time ( A circuit device characterized in that it can be delayed by Δt). (2) The array circuit according to claim 1, wherein the predetermined time (Δt) is 4 to 20 milliseconds, preferably 5 to 10 milliseconds.