WO2009059842A1

WO2009059842A1 - Piston pump

Info

Publication number: WO2009059842A1
Application number: PCT/EP2008/062664
Authority: WO
Inventors: Wolfgang Schuller; Michael Schuessler
Original assignee: Robert Bosch Gmbh
Priority date: 2007-11-06
Filing date: 2008-09-23
Publication date: 2009-05-14
Also published as: EP2207959A1; DE102007052755A1

Abstract

The invention relates to a piston pump (1) for a hydraulic vehicle brake system, having a pump piston (4), which can be driven to carry out an axial back-and-forth stroke movement, and having a valve (21) that is configured as a return valve, having a valve-closing body (25) to which a spring force is applied by a closing spring (24) in the direction of a valve seat (29). The valve-closing body (25) has a concave section (26) interacting with the valve seat (29) and a shaft section (27) facing away from the valve seat (29).

Description

description

title

piston pump

State of the art

The invention relates to a piston pump for a vehicle brake system according to the preamble of claim 1.

Such piston pumps are used in motor vehicles with hydraulic vehicle brake systems and often referred to as return pumps. With slip control, they serve to selectively lower or increase the brake pressure in the wheel brake cylinders in order to be able to regulate the brake pressure in the wheel brake cylinders.

DE 197 32 770 Al shows a generic piston pump, wherein the outlet valve is designed as a check valve. The outlet valve comprises a spherical valve-closing body which is spring-loaded by means of a closing spring embodied as a helical spring in the direction of a valve seat. Efforts are being made to optimize the piston pump, which is used in particular as an ABS / ESP pump element, with regard to its noise emission.

DISCLOSURE OF THE INVENTION Technical Problem

The invention has for its object to provide a noise-optimized piston pump for a hydraulic vehicle brake system. Technical solution

This object is achieved with a piston pump having the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures also fall within the scope of the invention.

The invention is based on the idea of minimizing the noise emission of the piston pump by virtue of the fact that the valve closing body of at least one valve of the piston pump has a shaft section and a calotte section which sealingly engages the valve seat of the valve in a closed position of the valve. Under a Kalottenabschnitt a ball segment section is understood, which has a curved (dome-shaped) surface portion. This preferably cooperates with a valve seat formed in particular as an internal cone seat in such a way that an annular sealing surface or sealing line is obtained when the valve-closing body is in contact with the valve seat. A piston pump with a valve closing body designed in this way has a multiplicity of advantages over known piston pumps, in particular with regard to their noise development. Thus, the vibration behavior of the valve closing body due to the provision of the particular serving as a guide shaft portion over known spherical valve closing bodies can be significantly reduced. In addition, depending on the axial extent, the shaft section can serve as a stroke limitation, so that the adjustment path of the valve closing body is the same for each opening movement. Due to the spherical segment-shaped (dome-shaped) training of cooperating with the valve seat (front) portion of the valve closing body, the overall construction of the piston pump does not need to be changed, but the optimized in terms of noise valve closing body is used with previously used, inner cone-shaped valve seats. Due to the inventive design of the valve closing body with a Kalottenabschnitt and an adjoining shank portion also, especially in a one-piece design of the valve closing body made of plastic, the wear behavior can be optimized at the valve seat, whereby an improved tightness of the valve over the life of the piston pump is obtained. A trained according to the concept of the invention piston pump can be used both as a pressure and as a suction pump.

In a development of the invention, it is advantageously provided that the valve with optimized valve closing body is the outlet valve of the piston pump. When the outlet valve is open, that is, when the valve closing body is lifted off the valve seat, brake fluid flows in the axial direction past the calotte section, preferably to a radial groove embossed in a closure cover, through which the brake fluid can flow out of the piston pump.

Of particular advantage is an embodiment of the piston pump in which the valve closing body is made of steel, or made of plastic as usual, whereby the mass of the valve closing body can be reduced by about a factor of 10 compared to a steel ball. As a result, the opening pulse of, in particular, as an outlet Valve trained valve reduced, which in turn prevents overshooting of the valve closing body. Overall, this can further reduce the noise of the piston pump. Also, as explained at the beginning, the wear behavior on the valve seat improves. In addition, a cost-effective and only slightly tolerant production of the valve closing body by injection molding or steel forming part is possible.

Particularly advantageous is the formation of the valve closing body made of plastic in one embodiment of the piston pump, in which the shaft portion serves as a guide portion for the valve closing body. Of particular advantage is an embodiment of the piston pump, wherein the shaft portion is contoured cylindrical. The cylindrical design of the shaft portion allows the integration of the valve closing body in a blind hole with a circular cross section, in particular in a closure cap of the piston pump in a simple manner.

In a further development of the invention is advantageously provided that a plurality of, preferably evenly distributed over the circumference, guide ribs are provided on the shaft portion, with which the shaft portion and thus the entire valve closing body is guided in a blind hole or a receiving hole in the radial direction. Preferably, the guide ribs extend in the axial direction, preferably over at least almost the entire axial extension of the, in particular between adjacent guide ribs cylindrical, shaft portion. The provision of a valve closing body with a Kalottenabschnitt has compared to a spherical valve closing body further has the advantage that the opening cross-section compared to a purely spherical valve closing body can be made enlarged. This can be achieved in particular by virtue of the fact that twice the radius of curvature of the calotte section, ie twice the radius of curvature of the curved surface of the front section of the valve-closing body, is greater than the diameter of the shaft section. Particularly preferred is an embodiment in which, in the case of providing guide ribs on the shaft portion, the double radius of curvature of the calotte portion is even greater than the (outer) diameter of the shaft portion of the valve closing body formed by the guide ribs.

Of particular advantage is an embodiment of the piston pump, wherein the shaft portion is guided in a blind hole in a closure lid of the piston pump, wherein the closure lid preferably axially adjacent to a pump piston receiving portions of bushing for the pump piston. In this case, the valve seat, with which the valve closing body or its calotte section sealingly cooperates, is preferably formed on the bushing, in particular on the end face thereof.

The space can be further optimized in a piston pump with a valve closing body, which has a Kalottenabschnitt and a shaft portion, ie exploited, in particular reduced, that the cooperating with the valve closing body closing spring in sections within the shaft portion, in particular radially within an outer guide surface, is received.

For this purpose, a front-side annular groove extending in the axial direction is preferably provided for receiving the closing spring, wherein the annular groove is preferably arranged at a radial distance from the lateral surface or from the guide ribs of the shaft section. Particularly preferably, a stroke stop for axially limiting the stroke movement of the valve closing body is formed by a core section of the valve closing body enclosed by the closing spring. Additionally or alternatively, the stroke stop can be formed by an end face of a peripheral wall section.

For reasons of material savings and with regard to an optimized flow behavior of the brake fluid lifted off the valve seat valve closing body is an embodiment of advantage in which the Kalottenabschnitt or the curved surface portion is formed as a ring portion, the Kalottenabschnitt frontally of a flattened, in particular circular surface portion is limited.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show in:

1 shows a detail of a piston pump with an optimized outlet valve, 2a is a perspective view of an optimized valve closing body obliquely from the front,

FIG. 2b shows a longitudinal sectional view of the valve closing body according to FIG. 2a, FIG.

3a shows a perspective view of a valve closing body with four equally distributed over the circumference guide ribs and

3b: a longitudinal sectional view of the valve closing body of FIG. 3a.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1, a piston pump 1 is shown. This is arranged in a hydraulic block 2, in which, apart from the piston pump 1, further components, not shown, of a hydraulic vehicle brake system having a slip control, such as solenoid valves, check valves and hydraulic accumulators, are housed and hydraulically interconnected. The hydraulic block 2 forms a pump housing of the piston pump 1. In this hydraulic block 2, a multi-stepped pump bore 3 is arranged.

The piston pump 1 has a pump piston 4, one of which, a displacement chamber 5 opposite end with a ring seal 6 (low pressure seal) against a Eccentric 7 is sealed. In the eccentric 7 an eccentric 8 is rotatably driven about a perpendicular to the longitudinal extent of the pump piston 4 extending axis of rotation rotatably, the pump piston 4 facing away from the displacer 5 end face 9 rests on the circumference of the eccentric 8, which drives the pump piston in the axial direction.

Another, the displacer 5 facing the end of the pump piston 4 is received in a bushing 10 (pump cylinder), which sits in the pump bore 3 by means of a press fit. The interference fit provides a seal between the inlet and outlet sides, i. Axially on the pump piston 4 includes in the direction of the displacement chamber 5, a plastic sealing element 38 which rests radially outwardly on the inner circumference of the bushing 10, and which seals the displacement chamber 5 in the direction of a pump inlet of the piston pump 1 ,

For the pump inlet, an axial passage 11 which continues in the pump piston 4 is provided in the plastic sealing element 38 and is crossed near its base by transverse bores 12. The axial channel, which is designed as a blind hole in the pump piston 4, and the transverse bores 12 communicate with an inflow bore 13 in the hydraulic block 2.

At the displacement chamber side end of the pump piston 3, a check valve is provided as the inlet valve 14. The inlet valve 14 has a valve plate 15 (alternatively eg valve ball) which cooperates with a conical inlet valve seat 16, which at an orifice of the axial channel 11 is attached to the plastic sealing element 38. A helical compression spring as inlet valve closing spring 17 presses the valve ball 15 against the inlet valve seat 16. The valve ball 15 and the inlet valve closing spring 17 are received in an inlet valve housing 18, which is formed as a cup-shaped injection molded part made of plastic with flow openings, not shown. The inlet valve housing 18 has an annular step 19 on which a return spring 20 for the pump piston 4, which is arranged within the displacement chamber 5, engages. In the axial direction, the inlet valve housing 18 is supported on the plastic sealing element 38, which is thereby subjected to force against the pump piston 4.

In addition to the inlet valve 14, the piston pump 1 has a valve 21 designed as an outlet valve. This is how the inlet valve 16 is formed as a check valve.

Within a closure cap 22 of the piston pump 1, a blind hole 23 (outlet valve chamber) is arranged centrally. In this a closing spring 24 (helical compression spring) of the valve 21 is arranged. The closing spring 24 is supported at one end at the bottom of the blind hole 23 and at the other end against a valve closing body 25 of the valve 21. The designed as an injection molded plastic valve closing body 25 has a right in the plane of the drawing, the Verdrängerraum 5 facing Kalottenabschnitt 26 and an adjoining in the axial direction, in the direction of the bottom of the blind hole 23 extending shank portion 27. By means of the outer circumference of the shaft portion 27, the valve closing body 25 is guided on the circumference of the blind hole 23. The trained as a circumferential ring, part spherical surface 28 (dome) of the Kalottenabschnittes 26 cooperates with an inner cone-shaped valve seat 29 which is formed on the left in the drawing plane end face of the bush 10.

If the pump piston 4 is moved by the eccentric 8 in the axial direction in the drawing plane to the left in the displacement chamber 5, the valve closing body 25 is hineinverstellt against the spring force of the closing spring 24 in the plane to the left in the blind hole 23. As a result, hydraulic fluid (brake fluid) located in the displacement chamber 5 can flow axially between the dome section 26 and the valve seat 29 into the blind hole 23 and from there via a radial groove 30 impressed into the closure cover 22 to an outflow channel 31.

The lifting movement of the valve closing body 25 is limited by a stroke stop 32 (stroke limitation), which is formed by the located in the left half of the drawing end side of the shank portion 27, more precisely from the end face of a central portion 33 of the valve closing body 25. Due to the provision of the shaft portion 27, which is guided with its outer circumference on the inner circumference of the blind hole 23, vibrations of the valve closing body 25 are minimized during its adjustment movement. In addition, the opening pulse is minimized due to the integral formation of the valve closing body 25 made of plastic.

As can be seen from Fig. 1, the double radius R of the curved surface 28 is greater than the diameter D of the cylindrical shaft portion (2R> D), whereby a large opening cross-section of the valve 21 is realized. This results in a rapid outflow of Hydraulic fluid from the displacement chamber 5 and as a result a rapid pressure change in the brake cylinder (not shown).

As can also be seen from FIG. 1, the closing spring 24 extends in the axial direction into an end-side annular groove 34 in the valve closing body 25. The annular groove 34 encloses the central portion 33, the free end face forms the stroke stop. As can be seen from Fig. 1, the axial extent of the annular groove is about 2/3 of the axial extent of the shaft portion 27th

In Fig. 2a and 2b, a possible embodiment of the valve closing body 25 is shown. Evident is the (pre-) Kalottenabschnitt 26 with its partially curved surface 28. The curved surface 28 extends annularly around the Kalottenabschnitt 26, the end face 35 is formed flattened. In this case, the circular end face 35 extends perpendicularly to the longitudinal extent of the valve closing body 25. The cylindrical shaft section 27 adjoins the dome section 26 in the axial direction. The diameter D (see Fig. 2b) of the shaft portion 27 corresponds to the diameter of the blind hole 23 minus a minimum guide clearance. As can be seen from FIG. 2 b, the radius of curvature R of the curved surface 28 of the calotte section 26 is greater than half the diameter of the shaft section 27.

From Fig. 2b is further seen that the annular groove 34 divides the shaft portion in the radial direction in the

Central portion 33 and a peripheral wall portion 36th Die

Ring groove 34 serves, as can be seen from FIG. sectional recording of the trained as a helical compression spring closing spring 24 of the valve 21st

In Fig. 3b, an alternative embodiment of a valve closing body 25 made of plastic (alternatively Stahlumformteil) is shown. In the embodiment according to FIGS. 3 a and 3 b, the cylindrical shaft portion 27 is provided with four equally circumferentially spaced guide ribs 37, which extend almost over the entire longitudinal extent of the shaft portion 27 and which serve to guide the valve closing body 25 on the inner periphery of the blind hole. By providing the guide ribs 37, the outflow behavior (larger outflow cross-section) of the hydraulic fluid can be improved.

As can further be seen from FIGS. 3 a and 3 b, the radius of curvature R of the calotte section 6 is more than twice as large as half the diameter D of the shaft section, the diameter D of the shaft section being formed by the guide ribs 37 in the embodiment shown. is limited. Otherwise, the embodiment of the valve closing body 25 according to FIGS. 3a and 3b corresponds to the exemplary embodiment shown in FIGS. 2a and 2b.

Claims

claims

A piston pump for a hydraulic vehicle brake system, comprising a pump piston (4) which is drivable for an axial reciprocating stroke movement and having a valve (21) designed as a check valve, comprising one of a closing spring (24) in the direction of one Valve seat (29) spring-loaded valve closing body (25),

characterized,

the valve-closure member (25) has a calotte portion (26) cooperating with the valve seat (29) and a shaft portion (27) facing away from the valve seat (29).

2. Piston pump according to claim 1, characterized in that the valve (21) is designed as an outlet valve.

3. Piston pump according to one of claims 1 or 2, characterized in that the valve closing body (25) made of plastic, in particular as an injection molded part, or as a steel forming part is formed.

4. Piston pump according to one of the preceding claims, characterized in that the shank portion (27), at least approximately, is cylindrical in shape.

5. Piston pump according to one of the preceding claims, characterized in that the shank portion (27) has a plurality, preferably uniformly distributed over the circumference, guide ribs (37).

6. Piston pump according to one of the preceding claims, characterized in that the double radius of curvature (R) of the Kalottenabschnitts (26) is greater than the diameter (D) of the shank portion (27).

7. Piston pump according to one of the preceding claims, characterized in that the shank portion (27) in a blind hole (23) in a closure cover (22) of the piston pump (1) is guided, adjacent to a pump piston (4), receiving in sections Bushing (10) is arranged.

8. Piston pump according to one of the preceding claims, characterized in that the closing spring (24) is partially received within the shank portion (27).

9. Piston pump according to one of the preceding claims, characterized in that in the shaft portion (27) extending in the axial direction of an annular groove (34) for partially receiving the closing spring (24) is provided.

10. Piston pump according to one of the preceding claims, characterized in that the Kalottenabschnitt (26) has a flattened, in particular flat, end face (35).