Pumps – Expansible chamber type – Valved piston
Patent
1999-07-28
2000-11-14
Freay, Charles G.
Pumps
Expansible chamber type
Valved piston
417514, 417495, 417415, 417569, F04B 3910, F04B 700, F04B 704, F04B 1700
Patent
active
061461156
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention relates to a piston pump which is intended in particular for use as a pump for a hydraulic vehicle brake system.
One such piston pump is known for instance from German Patent Disclosure DE 41 07979 A1. The known piston pump has a piston which is received axially displaceably in a pump housing and can be driven to execute a reciprocating stroke motion in the axial direction by means of an eccentric element that can be driven to rotate by an electric motor.
ADVANTAGES OF THE INVENTION
The piston pump of the invention has, in addition to the piston, a body that just like the piston is received axially displaceably in the pump housing. The body is furthermore axially displaceable relative to the piston counter to the force of a spring element which is supported on the piston. The piston can not only move together with the body axially in the pump housing, but can also move axially in the pump housing and relative to the body when the body is in repose in the pump housing. It is also possible for the piston and the body to move at different speeds and for different distances in the pump housing. The body increases a cross-sectional area of the piston. If the body in a stroke motion moves with the piston, the pumping volume per piston stroke of the piston pump of the invention increases in accordance with the cross-sectional area of the body. When the body is in repose in the pump housing, the pumping volume per piston stroke is correspondingly less. The body moves together with the piston whenever a force which a fluid pumped by the piston pump exerts on the body by reason of its pressure is no greater than the force of the spring element which is braced on the piston and presses axially against the body. Conversely, if the pressure of the pumped fluid is so high that the force exerted on the body by the fluid exceeds the force of the spring element, braced on the piston, at maximum force of the spring element, then the body does not move in the pump housing. If the pressure of the pumped fluid is between these two pressures, then the body moves by a shorter axial distance than the piston, and a fluid quantity is pumped that is greater than the pumped fluid quantity when only the piston moves and is less than the fluid quantity when the body moves together with the piston.
The piston pump of the invention has the advantage that at low pumping pressure, it pumps an increased fluid volume per piston stroke. Since a drive motor of the piston pump is designed for high pressure, the drive motor is not overloaded by the increased pumping quantity at low pressure. If the piston pump is pumping at high pressure, its pumping volume per piston stroke is reduced. As a result, the force required to drive the piston is reduced at the same time. The piston pump of the invention thus has the advantage of a pumping volume that is dependent on the pumping pressure. When the piston pump of the invention is used in a hydraulic vehicle brake system, this has the advantage of improved pressure buildup dynamics: For instance, if in order to initiate braking, pressure first has to be built up in wheel brake cylinders, then the piston pump of the invention, without changing its drive, pumps an increased volumetric flow and thus assures a rapid pressure buildup. When a high final pressure is reached, or for instance in slip control if after a limited pressure reduction in a wheel brake cylinder the pressure has to be increased again, then the pumping volume of the piston pump of the invention is reduced, so that with a predetermined axial force on the piston, the pump pressure is increased.
In a preferred feature of the invention, the body is embodied as an annular body which is axially displaceable in the manner of a sliding sleeve on the piston and is also axially displaceable in the pump housing. Because the body is embodied as an annular body, the invention can be realized in a simple way.
In particular, in one feature of the invention, a sealing and/or guide ring that is necessary anyway is employed as
REFERENCES:
patent: 5123819 (1992-06-01), Schuller et al.
patent: 5232273 (1993-08-01), Eckstein et al.
patent: 5320498 (1994-06-01), Fuchida
patent: 5588817 (1996-12-01), Zirps et al.
patent: 5688113 (1997-11-01), Bareiss et al.
patent: 5746111 (1998-05-01), Mueller et al.
Freay Charles G.
Gray Michael K.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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-2059406