Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-06-19
2000-07-04
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031132, 3031162, 30312212, 30312213, 303140, B60T 848
Patent
active
060828307
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic brake system including a pedal-operated master cylinder connected to a supply reservoir, a wheel brake which is connected to the master cylinder by way of a brake line, a pump driven by an electric motor and connected to the brake line, and to a method of pressure control implemented in a brake system of this type.
A brake system of this type is disclosed in German patent application No. 41 28 386. The prior art brake system is used for brake slip control and traction slip control. During brake slip control operations, the brake system operates according to the return principle. For traction slip control operations, the pump of the brake system is of the self-priming type and adapted to take in pressure fluid from the supply reservoir by way of a second suction line and the master cylinder. A separating valve in the brake line is an electromagnetically operated valve which is normally open and functions as a pressure limiting valve in its energized condition. When the supply pressure of the pump exceeds a predetermined value, as compared to the master cylinder pressure, pressure fluid discharges through the separating valve to the master cylinder.
When a brake system of this type is also intended to be used for brake management operations, to the effect of not only eliminating brake slip and traction slip but also for ensuring general driving stability control, e.g. during cornering without braking, it is desirable that the supply pressure of the pump is not fixed to a constant differential value between the pressure line and the master cylinder, but is variable in conformity with requirements.
SUMMARY OF THE INVENTION
This objective is achieved by an electronically controlled adjustment of the supply.
Such adjustment operations can be performed by control of the motor current of the electric motor, by an adjustable differential pressure of the separating valve in its operating position, or by limiting the pressure fluid supply to the suction side of the pump.
For example, the master cylinder pressure and the instantaneous, actual supply pressure of the pump may be taken into account as measured variables for the evaluation.
Appropriately, the master cylinder pressure is sensed by pressure sensors which are arranged in the brake line between the master cylinder and the separating valve. The supply pressure of the pump can be determined, for example, by measuring the motor current and comparing it with memorized motor characteristic curves. The resultant volume flow may be converted to the present supply pressure of the pump by way of a pressure volume pattern which is memorized in the electronic control unit. The switching time of the outlet valve and the size of the low-pressure accumulator are taken into account in these considerations.
The idea of the present invention will be explained in detail hereinbelow, making reference to the description of three Figures in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 shows a brake system of the present invention.
FIG. 2 and FIG. 3 each show a segment of the brake system of the present invention, which can be inserted in FIG. 1 instead of the segment shown in dotted lines.
DETAILED DESCRIPTION OF THE DRAWINGS
In the brake system of FIG. 1, two identically designed brake circuits I and II (of which only brake circuit II is shown) originate from a master cylinder 1. The master cylinder 1 is connected to a supply reservoir 2 and operated by brake pedal 3, with the result that braking pressure is built up in brake circuits I and II. A brake line 4 originates from the master cylinder 1 and extends through a separating valve 5. Brake branch lines 6 and 7 extend from the brake line 4 to one of wheel brakes 8 and 9, respectively. Inlet valves 10, 11 are inserted in the brake branch lines 6 and 7, respectively. Return branch lines 12 and 13 extend from the wheel brakes 8 and 9 to a return line 16 to which a low-pressure accumulator 17 is connected. Outlet valves 1
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Dinkel Dieter
Reinartz Hans-Dieter
Volz Peter
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