Motors: expansible chamber type – With motive fluid valve – Valved piston
Patent
1999-06-14
2000-12-19
Ryznic, John E.
Motors: expansible chamber type
With motive fluid valve
Valved piston
92256, 417470, 417549, B70K 1100
Patent
active
061614661
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention relates to a piston pump for a vehicle brake system.
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). 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), the pump is needed. With the wheel slip control (ABS or ASR), locking of the wheels of the vehicle 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 desired 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.
Many such piston pumps are known. As examples, the piston pumps known from German Patent Disclosures DE 41 07 979 A1 and DE 44 07 978 A1 can be named. These known piston pumps have a rodlike piston, which is axially displaceably guided in a bush. For driving the piston to a reciprocating stroke motion, an eccentric element that can be driven to rotate by an electric motor is used, which acts on the piston on a face end protruding from the bush. The bush is inserted into a cylinder bore of a pump housing.
For assembly of the known piston pumps, their pistons are introduced into the bush and are retained in the bush by installing a loss-prevention means. As the loss-prevention means, in the first of these references a rivet is inserted into a radial bore of the bush; the rivet protrudes inward and into an encompassing groove in the piston, which is wider by at least one piston stroke than a diameter of the rivet, and in this way secures the piston in the bush. In the second of these references, a sleeve is press-fitted into one end of the bush. This piston of this piston pump narrows at an annular shoulder at which the sleeve, press-fitted into the bush, holds the piston in the bush. After that, the bush is screwed or press-fitted into the cylinder bore of the pump housing and caulked. The assembly of the piston pump is made simpler by the loss-prevention means of the piston in the bush, especially in the piston pumps that have a piston restoring spring which presses the piston out of the bush.
ADVANTAGES OF THE INVENTION
The piston pump of the invention has the advantage that the loss-prevention means, upon introduction of the piston into the bush, snaps automatically into the piston or the bush and engages the undercut on its own; as a result, although the piston is pressed more deeply into the bush, still it cannot be pulled any farther out of the bush once the undercut strikes the loss-prevention means. This facilitates the captive introduction of the piston into the bush, compared with the known piston pumps. With the aid of the easily mounted loss-prevention means, a preassembled unit that includes the bush and the piston is obtained. The preassembled unit is sturdy and easily manipulated, and all its parts are held together in captive fashion. It can be inserted easily, for instance by press-fitting, into a cylinder bore of
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Fluck Tobias
Schuller Wolfgang
Weh Andreas
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Ryznic John E.
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