Reciprocating pump

Details Reciprocating pump Reciprocating pump

1999-07-21

2001-12-11

Look, Edward K. (Department: 3745)

Expansible chamber devices

Piston

Nonmetallic portion

C092S255000, C092SDIG001

Reexamination Certificate

active

06327964

ABSTRACT:

PRIOR ART
The invention is based on a piston pump, for hydraulic vehicle brake systems.
A piston pump of this kind is described in the German Patent Application DE 197 12 147.0. The piston pump in said application has a pump housing in which essentially cylindrical pistons are contained so that they can slide in the axial direction and can be driven into a reciprocating stroke motion in the axial direction, for example by means of a cam that can be driven to rotate. For its axial guidance in the pump housing, the piston has a guide ring slid onto it, which reciprocates together with the piston in the pump housing. In order to secure the guide ring on the piston in the axial direction, a support ring is attached to the piston and the guide ring rests against one end face of this support ring. In the piston pump described, the guide ring and the support ring are disposed on the piston so that the support ring supports the guide ring in the axial direction in opposition to a pressure produced by the piston in a displacement chamber of the piston pump during a feed stroke of the piston pump.
ADVANTAGES OF THE INVENTION
In the piston pump according to the invention, the guide ring and the support ring are connected to each other in a detachable or non-detachable manner. Firstly, this has the advantage of a reduced assembly cost since only one ring has to be slid onto the piston and has the advantage of a reduced assembly error frequency since the support ring and the guide ring cannot be mounted on the piston in reverse order nor can one of the two rings be forgotten. Another advantage is that a structural length of the piston and therefore also of the pump housing can be shortened by an axial thickness of the guide ring, wherein the shortening of the pump housing in particular could be significant in the future when used in slip-controlled hydraulic vehicle brake systems. Moreover there is the advantage that between the support ring and the pump housing, there is no pinch gap into which the guide ring could intrude.
In an embodiment of the invention provision is made to press the support ring with frictional, non-positive fit onto the piston in order to fix the support ring axially on the piston.
In an embodiment of the invention the support ring is supported axially in at least one direction against a support face embodied on the piston. The support face can, for example, be embodied circumferentially as a flank of a groove that is let into the piston and in which the support ring engages with positive fit. The support face can also be embodied circumferentially as a transition from a smaller diameter section of the piston to a larger diameter section, against which the support ring is axially supported with a positive fit in one direction. As other possibilities, the support face can be embodied at one or a number of points of the circumference of the piston in the form of radially protruding projections or recesses in the piston circumference in which the support ring engages with a positive fit.
The piston pump according to the invention is particularly provided as a pump in a brake system of a vehicle and is used when controlling the pressure in wheel brake cylinders. The abbreviations ABS, ASR, FDR, or EHB are used for such brake systems, depending on the type of brake system. 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 supply brake fluid out of a storage tank into a wheel brake cylinder or a plurality of wheel brake cylinders (ASR, FDR, or EHB). The pump is required, for example, 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), for example, a locking of the wheels of the vehicle during a braking event can be prevented when there is strong pressure on the brake pedal (ABS) and/or a spinning of the driven wheels of the vehicle can be prevented when there is strong pressure on the gas pedal (ASR). In a brake system that serves 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 supplies the brake fluid into the wheel brake cylinder or cylinders if an electrical 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: 6109896 (2000-08-01), Schuller et al.
patent: 19712147-A1 (1998-03-01), None
patent: 1603849 (1981-12-01), None
patent: 0519533-A1 (1992-12-01), None

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