Piston pump in a brake system of a vehicle

Details Piston pump in a brake system of a vehicle Piston pump in a brake system of a vehicle

1999-05-28

2001-05-01

Thorpe, Timothy S. (Department: 3746)

Pumps

Combined

C092S078000, C417S549000, C417S554000

Reexamination Certificate

active

06224352

ABSTRACT:

PRIOR ART
The invention relates to a piston pump in a brake system of a vehicle.
Such a piston pump is known from German Patent Disclosure DE 40 27 794 A1. The known piston pump has a rodlike piston, which is received axially displaceably in a bush that is inserted into a pump housing. One end of the piston protrudes from the bush. On this end of the piston, the piston is driven to execute an axially reciprocating stroke motion by means of an eccentric element that can be driven to rotate by an electric motor and that acts upon the piston on its face end that protrudes from the bush. In the bush, the piston is axially displaceably guided by a plastic guide ring inserted into the bush. On its end protruding out of the bush, the piston is axially displaceably guided in the pump housing by a further plastic guide ring that is inserted into the pump housing.
ADVANTAGES OF THE INVENTION
The piston pump of the invention has the advantage first that fluid pumped by the piston pump is filtered. The filter element is preferably disposed in the inflow region of the piston pump and thus prevents dirt particles from getting into the piston pump.
The filter element is mounted on the bush in the extension of the bush and has a guide element outside the bush that displaceably guides the piston axially to the bush. This has the advantage that a separate guide element can be dispensed with, thus saving the expense of producing a separate guide element, and the effort of assembly of a separate guide element is omitted. The invention also makes it possible to shorten the structural length of the piston pump by leaving out a separate guide element and/or enlarging the filter area by making the filter element longer. As a result, the filtration can be made more effective, and in particular the aspiration performance of the piston pump of the invention in pumping a viscous fluid, such as cold brake fluid, can be improved. The invention also makes it possible, by omitting a separate filter element, to use a sealing ring with a larger diameter for sealing off the piston in the pump housing on the end of the piston protruding from the bush, without increasing the structural length of the piston pump. A sealing ring with a larger qt reduces leakage from the piston pump toward the eccentric element that drives the piston, since the sealing ring has a larger wearing volume.
The piston pump of the invention is intended in particular as a pump in a brake system of a vehicle and is used to control the pressure in wheel brake cylinders. Depending on the type of brake system, the abbreviations ABS, ASR, FDR and EHB are used for such brake systems. In the brake system, the pump serves for instance to return brake fluid from a wheel brake cylinder or a plurality of wheel brake cylinders to a master cylinder (ABS) and/or to pump brake fluid out of a supply container into a wheel brake cylinder or a plurality of wheel brake cylinders (ASR or FDR or EHB). For instance, the pump is needed in a brake system with wheel slip control (ABS or ASR) and/or a brake system serving as a steering aid (FDR) and/or an electrohydraulic brake system (EHB). With wheel slip control (ABS or ASR), locking of the vehicle wheels during a braking event involving strong pressure on the brake pedal (ABS), and/or spinning of the driven wheels of the vehicle in the event of strong pressure on the gas pedal (ASR), can for instance be prevented. In a brake system serving as a steering aid (FDR), a brake pressure is built up in one or more wheel brake cylinders independently of an actuation of the brake pedal or gas pedal, for instance to prevent the vehicle from breaking out of the track intended by the driver. The pump can also be used in an electrohydraulic brake system (EHB), in which the pump pumps the brake fluid into the wheel brake cylinder or wheel brake cylinders if an electric brake pedal sensor detects an actuation of the brake pedal, or in which the pump is used to fill a reservoir of the brake system.


REFERENCES:
patent: 4958553 (1990-09-01), Ueno
patent: 6082244 (2000-07-01), Siegel et al.

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