Piston pump

Details Piston pump Piston pump

2000-05-15

2001-07-31

Thorpe, Timothy S. (Department: 3746)

Pumps

Expansible chamber type

Biasing means effects induction stroke of abutment driven,...

C417S549000, C092S171100

Reexamination Certificate

active

06267569

ABSTRACT:

PRIOR ART
The invention relates to a piston pump for a vehicle brake system according to the preamble to the main claim.
Piston pumps of this kind are known, for example, as return feed pumps for antilock and/or traction controlled hydraulic vehicle brake systems. For example, reference is made to the piston pump disclosed by DE 41 07 979 A1. The known piston pump has a pump housing with a pump bore which encloses a piston so that it can move axially. The piston can be driven into an axially reciprocating stroke motion in the pump bore by means of a cam drive. The piston can be guided directly in the pump bore of the pump housing or, as in the known piston pump, can be guided in a bushing inserted into the pump bore. Furthermore, it is known to provide a filter for filtering fluid that is supplied by the piston pump.
ADVANTAGES OF THE INVENTION
The piston pump according to the invention, which has the features of the main claim, has a filter with a rough counter surface that rests against a surface that is smooth, for example, or is likewise rough. As a result of the rough surface resting against the counter surface, channels are formed that are small in cross section, through which the fluid to be supplied is conveyed and thereby filtered. The roughness of the surface is selected so that the channels formed have a cross section that corresponds to the size of through openings of filters for piston pumps of this kind. The invention has the advantage that the filter can be easily and inexpensively produced.
Advantageous embodiments and improvements of the invention disclosed in the main claim are the subject of the dependent claims.
For example, the rough surface can have nubs or a fluting, it can be manufactured as a knurling or so that it resembles a knurling (claim
2
), wherein with a fluting or the like, attention must be paid that the fluting is not embodied extending lateral to the through flow direction of the fluid to be supplied so that the fluid is permitted to flow through.
In one embodiment of the invention, the filter is disposed in the pump bore and the rough surface is formed so that it is complementary to the wall of the pump bore, wherein the wall of the pump bore constitutes the counter surface against which the rough surface rests (claim
3
). Complementary means that the rough surface and the wall of the pump bore have the same curvature. This embodiment of the invention has the advantage that the filter is accommodated in a space-saving manner in the pump bore and that the piston pump can be embodied as short in structure.
In an improvement according to claim
4
, the piston pump has a bushing whose outer circumference surface is rough at least on a part of the total surface area, and rests against the wall of the pump bore that constitutes the counter surface. This embodiment has the advantage that no separate parts are necessary; in particular, the production and installation of a filter are no longer necessary.
Conversely, it is also possible to embody the wall of the pump bore as rough, at least on a part of the total surface area, wherein the bushing resting against the wall of the pump bore constitutes the counter surface (claim
7
). The outer circumference surface of the bushing can be smooth or likewise rough in this embodiment of the invention.
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, TCS, ESP, or EHB are used for such brake systems, depending on the type of brake system involved. In the brake system, the pump serves for example to return brake fluid from one or a number of wheel brake cylinders to a master cylinder (ABS) and/or to supply brake fluid from a storage tank into one or a number of wheel brake cylinders (TCS, ESP, or EHB). The pump is required, for example, in a brake system with wheel slip control (ABS or TCS) and/or a brake system serving as a steering aid (ESP) and/or an electrohydraulic brake system (EHB). With wheel slip control (ABS or TCS), for example a locking of the wheels of the vehicle during a braking maneuver 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 (TCS). In a brake system that serves as a steering aid (ESP), 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 example in order 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 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: 3773441 (1973-11-01), Scherta
patent: 5335984 (1994-08-01), Alaze et al.
patent: 6082244 (2000-07-01), Siegel et al.
patent: 6109896 (2000-08-01), Schuller et al.
patent: 6161466 (2000-12-01), Schuller et al.
patent: 6171083 (2001-01-01), Schuller

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