Pumps – Expansible chamber type – Valved piston
Reexamination Certificate
1999-12-28
2001-10-16
Tyler, Cheryl J. (Department: 3746)
Pumps
Expansible chamber type
Valved piston
C417S549000, C417S470000
Reexamination Certificate
active
06302663
ABSTRACT:
PRIOR ART
The invention relates to a piston pump which is provided for use in a slip-controlled or electrohydraulic vehicle brake system.
A multitude of such piston pumps have been disclosed. One such example is DE 40 27 794 A1. The known piston pump has a pump housing into which a bushing is inserted which contains an axially movable piston which can be driven into a reciprocating stroke motion. The piston is a part that is produced in a cutting fashion by means of boring and turning. The manufacture of the piston is therefore complex and cost intensive.
ADVANTAGES OF THE INVENTION
In the piston pump according to the invention, the piston is embodied as tubular and its manufacture takes place for example by means of deep drawing. By means of shaping, for example by means of axially compressing the tubular piston, an outwardly protruding bead is produced on the piston, and this bead constitutes an axial support for a sealing ring or a guide ring of the piston. First, the invention has the advantage that the piston can be produced in a non-cutting fashion by means of shaping and therefore can be produced rapidly, simply, and inexpensively. Moreover, the piston is distinguished by means of a high degree of measurement precision and surface quality so that a finishing is not necessary and the piston can also be inserted without a bushing directly into the cylinder bore of the pump housing and can be guided so that it can move axially. An inner chamber of the tubular piston acts as a damper chamber which eliminates the need for a separate fluid pressure fluctuation damper of the piston pump.
The piston of the piston pump according to the invention can be embodied as a so-called simple piston, i.e. the piston can be guided at two locations axially spaced from each other and which location have the same diameter. The piston is embodied as a stepped piston, i.e. the piston is guided in the vicinity of its bead on a different diameter, for example a larger diameter than in a region oriented in particular toward a drive cam. The stepping of the piston influences the delivery behavior of the piston pump; in particular, a suction can be produced both during a so-called suction stroke and during a so-called feed stroke, which evens out the delivery flow at least on the suction side of the piston pump.
The piston has a valve seat of an inlet or outlet valve of the piston pump and this valve seat is formed by means of shaping. This shaping has the advantage of a simple valve seat manufacture, which takes place in one work cycle with the piston production, has high quality, and has high abrasion resistance due to a material hardening during the shaping process.
In an embodiment of the invention, a striking piece is affixed to the piston, whose end face oriented toward a drive cam constitutes a striking face of the piston, with which the piston rests against the circumference of the drive cam element. The striking piece is abrasion resistant, at least in the vicinity of the striking face, for example by means of hardening or through the use of an abrasion resistant material. The piston is thus simply resistant to the stresses that occur due to friction on the striking face.
Accordingly, instead of the striking piece, the piston is embodied with an end wall, which is of one piece with the piston and is preferably formed onto the piston by means of shaping, with which the end wall rests against the circumference of the drive cam element. The end wall is embodied as abrasion resistant, at least in the region in which the end wall rests against the drive cam element, for example as a result of local hardening. In this manner, a separate striking piece is no longer needed and the manufacture of the end wall takes place in one work cycle with the piston production.
In an embodiment of the invention, the piston pump has a tubular bushing which is inserted into the cylinder bore of the pump housing. In an improvement, a valve seat of an outlet or inlet valve of the piston pump is affixed to the bushing by means of shaping. As a result, the valve seat is produced in a simple manner in one work cycle with the production of the bushing. The valve seat has a high surface quality and, due to material hardening during the shaping, has a high degree of abrasion resistance.
In order to close the cylinder bore on an end remote from the drive cam, the piston pump according to the invention has a closing element that is produced as a deep drawn part. This embodiment of the invention has the advantage that the closing element can be produced rapidly, inexpensively, and without cutting. The valve seat of an outlet or inlet valve of the piston pump is affixed to a valve seat part that is produced by means of shaping, for example deep drawing. This embodiment has the same advantages as the valve seat produced on the bushing by means of shaping; it is particularly provided for piston pumps without bushings.
The piston pump according to the invention is provided as a pump in a brake system of a vehicle and is used in the control of 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. 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 from a storage tank into a wheel brake cylinder or a plurality 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 event when there is strong pressure on the brake pedal (ABS) and/or a spinning of the driven wheels of the vehicle when there is strong pressure on the gas pedal (TCS) can be prevented. 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 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: 1854455 (1932-04-01), Day
patent: 3532030 (1970-10-01), Margetts
patent: 4085634 (1978-04-01), Sattler
patent: 5320498 (1994-06-01), Fuchida
patent: 5395219 (1995-03-01), Hosoya et al.
patent: 5601345 (1997-02-01), Tackett
patent: 5988997 (1999-11-01), Siegel
patent: 6093003 (2000-07-01), Hauser et al.
patent: 6109896 (2000-08-01), Schuller et al.
patent: 6113365 (2000-09-01), Siegel
Mayer Franz
Schiller Christiane
Schuller Wolfgang
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Tyler Cheryl J.
LandOfFree
Piston pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Piston pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piston pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2616240