Switch valve and accumulator on pump discharge line for pressure

Details Switch valve and accumulator on pump discharge line for pressure Switch valve and accumulator on pump discharge line for pressure

1994-07-25

1996-01-16

Ballato, Josie A.

Fluid-pressure and analogous brake systems

Speed-controlled

Having a valve system responsive to a wheel lock signal

3031132, B60T 848

Patent

active

054841941

DESCRIPTION:

BRIEF SUMMARY
The invention is related to brake pressure control apparatus, and in particular for traction slip control of the driven wheels.
An apparatus of this kind is generally known from the German patent application published without examination, No. 3,831,426.
A hydraulic brake unit with anti-lock control system working by the recirculating principle is illustrated. In order to be able to utilize this unit also for the traction slip control, it is proposed to provide both a separating valve in the brake piping with the aid of which the master cylinder allows to be cut off from the brake circuit and a lockable connection between the suction side of the pump and the reservoir.
The rotational behavior of the driven wheels is monitored by means of sensors. If it becomes evident that a driven wheel is about to race, then the unit switches into the traction slip control mode. For this purpose the master cylinder is cut off from the brake circuit and the connecting line is opened. The pump aspirates hydraulic pressure agent from the reservoir and conveys it into the wheel brake. The brake pressure that has been built up generates a brake torque which counteracts the driving torque whereby a deceleration of the :racing wheel is achieved.
In traction slip systems the wheel brake pressure must be adjusted by modulating valves (inlet valve, discharge valve) in such a manner that the driving forces can be transmitted in an optimum way.
However, in the earlier referred to brake unit the following problem exists. In some cases, the driver may attempt to operate the brake at the same time the traction slip controller is engaged in traction slip control action. In that case hydraulic pressure agent is displaced out of the master cylinder toward the wheel brake through a non-return valve which is connected in parallel with the separating valve. When the brake pedal is actuated and the accelerator pedal is released the driving torque will be reduced so that there will no longer be any need for a traction slip control.
It can, moreover, be imagined that during the braking operation a brake slip control action is required since the braked wheel may threaten to lock. According to the recirculating principle the pump delivers the hydraulic pressure agent let off from the wheel brake back into the master cylinder. In the brake circuit there is, however, not only pressure agent from the master cylinder but also pressure agent which has been conveyed before by the pump into the brake circuit from the reservoir during the traction slip control action. This quantity of hydraulic pressure agent, too, will now be delivered back into the master cylinder, so that the piston will be urged back into its normal position. In that event a connection to the reservoir will be opened up, so that the hydraulic pressure agent is allowed to flow off into the reservoir through the connection. In a master cylinder which is furnished with a sleeve/breathing-hole-bore-type valve the aforesaid procedure will cause the sleeve to be damaged because the latter will be slid at high pressure across the breathing hole bore.
It is, therefore, proposed according to the teachings of the present invention through a switch valve to connect a transitional accumulator to the discharge side of the pump. The switch will be in the closed condition during a traction slip control action.
This valve may be actuated electromagnetically or hydraulically, in which case the master cylinder pressure may be utilized as the control pressure.
It can, furthermore, be imagined that constructionally the switch valve is combined with the valve in the connecting line.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the hydraulic connecting diagram of the brake apparatus of the present invention.
FIG. 2 shows a section of the hydraulic connecting diagram in FIG. 1 with a hydraulic actuation of the switch valve.
FIG. 3 shows a variant of FIG. 2.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, reference is made to FIG. 1, illustrating at first those elements which are of i

REFERENCES:
patent: 5013097 (1991-05-01), Gutzeit et al.
patent: 5288142 (1994-02-01), Burgdorf
patent: 5335981 (1994-08-01), Volz et al.

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