Pumps – Expansible chamber type – Valved piston
Reexamination Certificate
1999-10-29
2001-09-04
Walberg, Teresa (Department: 3742)
Pumps
Expansible chamber type
Valved piston
C092S078000
Reexamination Certificate
active
06283733
ABSTRACT:
PRIOR ART
The invention relates to a piston pump for a vehicle brake system.
One such piston pump is known from German Patent Disclosure DE 41 07 979 A1. The known piston pump has a piston which can be driven to a reciprocating stroke motion by an eccentric element which can be driven to rotate. The piston is axially displaceably guided in a bush which is screwed into a cylinder bore of a pump housing. On the bush of the known piston pump is a turned part which is geometrically complicated in form and complex to produce, having a graduated inner bore with an undercut, having undercuts, and having a radially protruding collar on the outside which is threaded for being screwed into the cylinder bore, and having transverse bores as inlet and longitudinal bores for engagement by a screwdriving tool.
ADVANTAGES OF THE INVENTION
The piston pump of the invention claim has a bush made by a deforming operation, preferably cold forming, such as upsetting. The invention has the advantage that the bush can be made quickly and inexpensively in one or more steps.
Another advantage is that inserting the bush into the cylinder bore of the pump housing is simplified.
A press fit brings about sealing between the bush and the cylinder bore, so that such separate sealing means as sealing rings become unnecessary.
According to the invention, the bush of the piston pump of the invention has a bottom that is integral with it, which lends the bush greater stability and increases the resistance of the bush to unintended deformation, particularly on being pressfitted into the pump housing or if a closure part is pressed on it.
The bottom of the bush is preferably provided, with a through hole and a valve seat for an inlet or outlet valve of the piston pump at an orifice of the through hole. The through hole and the valve seat can advantageously be manufactured in this way in a single operation along with the production of the bush by deforming. Another advantage of this feature of the invention is the elimination of a separate valve seat carrier part, and that the piston pump is compact and short in the axial direction.
In a piston pump, a closure part, which closes the cylinder bore in pressure tight fashion on the side of a positive-displacement chamber, is firmly joined to the bush, for instance by press-fitting of the bush into the closure part, and secured in pressure-tight fashion in the pump housing by a caulking. The closure part can be made simply and quickly, like the bush, as a deformed part. Caulking the closure part and the housing allows a radial offset compensation, in order to avoid overdetermination in mounting the bush with the closure part fixed firmly to it in the cylinder bore of the pump housing. A further advantage is the elimination of a sealing ring or the like between the closure part and the bush, because the sealing is effected by the press fit between these two parts.
A flow conduit particularly as a pump outlet is realized by a groove extending from the inside outward, which is made in faces oriented toward one another of the closure part or the bush. This has the advantage that the groove in the closure part or the bush, which is open toward the bush or the closure part, as applicable, which when the closure part is pressed onto the bush is covered by the bush or a bottom of the bush or by the closure part to form a flow conduit, can be manufactured in a single operation together with the production of the closure part or the bush by deforming.
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.
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Fritsch Siegfried
Hellebrandt Michael
Merklein Dieter
Weh Andreas
Zitzelsberger Ralf
Fastovsky Leonid
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Walberg Teresa
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