Pumps – Expansible chamber type – Valved piston
Reexamination Certificate
2000-01-19
2001-04-17
Walberg, Teresa (Department: 3742)
Pumps
Expansible chamber type
Valved piston
C092S078000, C417S454000
Reexamination Certificate
active
06217300
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a piston pump for a brake system of a vehicle.
The pump assembly of the invention is intended 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 (for anti-lock brake system), TCS (traction control system), ESP (electronic stability program) and EHB (electrohydraulic brake system) are used for such brake systems. In the brake system, the pump serves 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 (TCS or ESP or EHB). 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), the pump is needed. With the wheel slip control (ABS or TCS), locking of the wheels of the vehicle during a braking event involving a 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 (TCS) can for instance be prevented. In a brake system serving 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 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. For instance, the piston pumps known from German Patent Disclosures DE 41 07 979 A1 and DE 44 07 978 A1 are set forth. The known piston pumps have a rod-like piston, which is axially displaceably guided in a bush. For driving the piston to execute a reciprocating stroke motion, an eccentric element is used that can be driven to rotate by an electric motor and that acts upon the piston on a face end protruding from the bush. The bush is inserted into a cylinder bore of a pump housing.
For assembling the known piston pumps, their pistons are introduced into the bush and are retained in the bush by the installation of a retention means. As the retention means, in the first reference cited, a rivet is inserted into a radial bore of the bush. The rivet protrudes on the inside, 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 reference cited, a sleeve is press-fitted into one end of the bush. The piston of this piston pump tapers at an annular shoulder at which the sleeve press-fitted into the bush retains the piston in the bush. After that, the bush is screwed or press-fitted into the cylinder bore of the pump housing and caulked. Because the piston is secured in the bush for retention therein assembling the piston pump is made simpler, especially for piston pumps that have a piston restoring spring that presses the piston out of the bush.
OBJECT AND SUMMARY OF THE INVENTION
The piston pump of the invention has an advantage that the retention means automatically quasi-snaps onto the piston and engages the undercut automatically; as a result, while the piston is pressed farther into the bush, the piston cannot be pulled out from the bush any farther than where the piston is when the undercut meets the retention means. Compared with the known piston pumps, this makes it easier to introduce the piston into the bush in such a way that the piston is retained there. Because the retention means can be attached easily, a preassembled group that includes both the bush and the piston is obtained. The preassembled group is sturdy and easily manipulated; all of its parts are held together in a way secure for retention. The group can easily be inserted into a cylinder bore of the pump housing, for instance by press-fitting.
Another advantage of the piston pump of the invention is that it has a filter disposed in a space- saving way and at the same time the filter has the retention means. The assembly step of attaching the loss-prevention means to the bush is dispensed with and this step is accomplished by attaching the filter. The filter is a component of the preassembled group. By clamping attachment of the filter to the bush, the attachment can be done quickly and easily by slipping the filter onto the bush. For attaching the filter, the bush is not deformed by crimping, and thus there is no risk that metal chips or particles will form that could damage the piston in the bush in a piston pump operation. The clamping connection produces a firm seat of the filter on the bush with close tolerance in a way that can be reproduced in mass production and is always the same; an overly loose or overly firm seat of the filter is avoided.
Another advantage of the piston pump of the invention is that no stepped piston, as for instance in the piston pump known from DE 44 07 979 A1 mentioned above, is needed for the retention means; the piston can be guided at two axially spaced-apart points by the same guide diameter.
The undercut on the piston of the piston pump of the invention need not be embodied extending all the way around. For instance, it can also be formed by one or more recesses in the circumference of the piston, distributed over the circumference.
Advantageous features and refinements of the invention are defined hereinafter.
In a refinement, the filter serves as a guide for the piston in the bush and keeps the piston oriented axially to the bush before the preassembled group is inserted into the pump housing. This advantageously makes building in the parts that have to be built into the pump housing substantially easier.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawing.
REFERENCES:
patent: 5395219 (1995-03-01), Hosoya et al.
patent: 5580226 (1996-12-01), Staib
patent: 5688113 (1997-11-01), Bareiss et al.
patent: 5823639 (1998-10-01), Zinnkann et al.
patent: 6042350 (2000-03-01), Beck
patent: 6082244 (2000-07-01), Siegel et al.
patent: 6093003 (2000-07-01), Hauser et al.
Eckstein Ursula
Schuller Wolfgang
Fastovsky Leonid
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Walberg Teresa
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-2550702