GB2476157A

GB2476157A - Piston pump for a hydraulic vehicle brake system

Info

Publication number: GB2476157A
Application number: GB1020661A
Authority: GB
Inventors: Oliver Gaertner; Wolfgang Schuller; Michael Schuessler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-12-10
Filing date: 2010-12-06
Publication date: 2011-06-15
Also published as: DE102009054520A1; GB201020661D0; FR2953890A1; CN102094808A

Abstract

A piston pump (recirculating pump) 1 for a hydraulic vehicle brake system comprises a cylinder 3 which is open at both ends, eg it is a simple tube without steps or undercuts. The end of the cylinder 3 remote from the pump actuating eccentric 4 is provided with a separate disk-like outlet valve seat part 13 which may be made by deep drawing from sheet metal. The seat part 13 may have an apertured dome 15 that receives, with only slight radial play, a spring-loaded valve ball 19. A radial flange 23 of the seat part 13 rests against one end of the cylinder tube 3. A number of flow grooves 24 may be provided in the face of the seat part 13 remote from the cylinder 3.

Description

Description Title

Piston pump The invention relates to a piston pump for a hydraulic vehicle brake system having the features of the preamble of claim 1. The piston pump is provided in particular for a slip-regulated, hydraulic vehicle brake system, where such pumps are also referred to as recirculating pumps, or in an electrohydraulic, i.e. external-energy vehicle brake system.

Background art

Such piston pumps are known. They generally comprise a cylinder, in which a piston is accommodated in an axially displaceable manner. The piston usually projects from one end of the cylinder and lies with an end face projecting from the cylinder against the circumference of a rotatable eccentric. The eccentric of known piston pumps is a cylinder that may be set in rotation about an eccentric axis of rotation, wherein the axis of rotation of the eccentric cuts a (central longitudinal) axis of the cylinder at right angles. By rotation of the eccentric the piston is set in a reciprocating motion in the cylinder that brings about the delivery of fluid in a manner known from piston pumps. In a vehicle brake system the fluid delivered by the piston pump is brake fluid.

An end -remote from the eccentric -of the cylinders of known piston pumps for hydraulic vehicle brake systems has a base, which is an integral part of the cylinder and has a hole as a passage of a pump valve of the piston pump. The pump valve is an inlet-or outlet valve, which controls a throughflow direction of the piston pump and is commonly a non-return valve. The one, eccentric-remote end of the cylinder of known piston pumps is closed, except for the valve passage, by the cylinder base that is an integral part of the cylinder. An example of such a piston pump is disclosed in DE-OS 10 2006 035 055 Al.

Disclosure of the invention

In the piston pump according to the invention having the features of claim 1, the cylinder itself is open at both ends, i.e. does not have a cylinder base formed integrally therewith or the like. The cylinder may therefore in the simplest case be a tube, preferably without undercuts, steps or the like. The tube may be cut to length from rod material, the invention enabling a cost-effective cylinder that may, apart from the cutting-to-length from rod material, be manufactured without cutting.

One end of the cylinder of the piston pump according to the invention is, with the exception of a valve passage, closed by means of a valve seat part that is manufactured separately from the cylinder and disposed during assembly of the piston pump on one end of the cylinder. The valve seat part may for example be manufactured easily in the form of a perforated disk by punching. Equally cost-effective is manufacture of the valve seat part in the form of a shaped part, for example a deep-drawn part, in particular from sheet metal.

Advantageous refinements and developments of the invention indicated in claim 1 are the subject matter of the sub-claims.

Brief description of the drawings

There now follows a detailed description of the invention with reference an embodiment that is represented in the drawings. The drawings show: Figure 1 an axial section of a piston pump according to the invention; and Figure 2 a valve seat part of the piston pump according to the invention of Figure 1 in perspective half-sectional representation.

Embodiment of the invention The piston pump 1 according to the invention that is represented in the drawings comprises a cylindrical piston 2, which is guided in an axially displaceable manner in a cylinder 3. The piston 2 projects at one end from the cylinder 3 and rests with its end face against a circumference of a rotatable, cylindrical eccentric 4. By rotation of the eccentric 4 the piston 2 is set in axial reciprocating motion in the cylinder 3.

On an end of the piston 2 remote from the eccentric a tubular piston part 5 is mounted, which in its peripheral wall has holes 6 to let in brake fluid. The piston part 5 may be conceived as a component part of a multi-part piston 2, 5. On its end remote from the piston 2 and situated in the cylinder 3, the piston part 5 has a conical valve seat 7 of an inlet valve 8 of the piston pump 1. The inlet valve 8 is a spring-loaded non-return valve having a valve ball 9, which is pressed towards the valve seat 7 by a valve closing spring 10. The valve closing spring 10 is supported in a valve cage 11, which is mounted on an end of the piston part 5 remote from the piston 2. The valve ball 9 is also accommodated in the valve cage 11. The valve cage 11 is made of plastics material and has a circumferential sealing lip 12 that seals the piston 2, 5 in the cylinder 3.

The cylinder 3 is introduced into a pump bore 32 in a pump housing 33. The pump housing 33 may be a dedicated housing for the piston pump 1. In the illustrated embodiment of the invention, the pump housing 33 is formed by a hydraulic block of the vehicle brake system (otherwise not represented), in which the pump bore 32 is provided.

Besides the piston pump 1, further hydraulic components such as solenoid valves, non-return valves, hydraulic accumulators are installed in the hydraulic block and hydraulically connected to one another by bores in the hydraulic block. Such hydraulic blocks are known from slip-regulated hydraulic vehicle brake systems and are not to be described in detail here. The pump bore 32 opens out at one end into an eccentric space 34, in which the eccentric 4 is accommodated. The other end of the pump bore 32 is closed by the cylinder head 26, which is inserted into a mouth of the pump bore 32 and fastened by means of a circumferential caulked joint (not represented) The cylinder 3 is a simple tube without steps, undercuts or the like. On an end of the cylinder 3 remote from the eccentric 4 a valve seat part 13 of an outlet valve 14 of the piston pump 1 is disposed. The valve seat part 13, which is separately represented in Figure 2 in a perspective half-section, is a shaped part, in the illustrated embodiment of the invention being a profiled perforated disk manufactured by deep drawing from sheet metal. In its centre the valve seat part 13 has a dome 15 with a central hole that forms a valve passage 16. The dome is elevated in the direction of the piston 2, the valve passage 16 being adjoined by a conical portion 17 and an approximately cylindrical portion that forms a guide 18 for a shut-off body 19 of the outlet valve 14. In the illustrated embodiment of the invention the shut-off body 19 is a valve ball, which is pressed towards the valve passage 16 by a helical compression spring as valve closing spring 20. The outlet valve 14 of the piston pump 1, like the inlet valve 8, is a spring-loaded non-return valve.

The cylindrical and/or tubular portion of the dome 15 of the valve seat part 13 that forms the guide 18 for the valve ball forming the shut-off body 19 may be comparatively close-tolerance. By this is meant that an inside diameter of the tubular guide 18 is only slightly larger than a diameter of the valve ball forming the shut-off body 19 of the outlet valve 14. consequently the valve ball, when it is lifted off a valve seat in the open state of the outlet valve 14, is capable of only slight radial movement, this improving a closing performance of the outlet valve 14.

The tubular guide 18 of the valve seat part 13 is adjoined by an annular-disk-shaped portion 21, which at its outer circumference verges via an annular step 22 into a radial flange 23. The radial flange 23 rests sealingly against an annular end face of the cylinder 3. At a side of the annular-disk-shaped portion 21 remote from the cylinder 3 a number of flow-off grooves 24 extend radially outwards from the dome 15. The flow-off grooves 24 are semicylindrical grooves, which are formed by deep drawing and are open at both ends, i.e. both in the direction of the dome 15 and in the direction of the annular step 22.

The valve seat part 13 is pressed into a cylindrical countersunk portion 25 of a cylinder head 26, which forms a valve housing of the outlet valve 14. The cylinder head 26 has an axial blind hole 27, in which the valve ball forming the shut-off body 19 and the valve closing spring 20 of the outlet valve 14 are accommodated.

The annular step 22 of the valve seat part 13 encloses an annular collecting channel 28 at the bottom of the countersunk portion 25 of the cylinder head 26, into which collecting channel 28 the flow-off grooves 24 open. By means of openings 29 in a wall 30 surrounding the countersunk portion 25 the collecting channel 28 communicates with a pump outlet 31. Brake fluid, which during a reciprocating motion of the piston 2 is displaced from the cylinder 3 through the outlet valve 14, flows through the valve passage 16 into the dome 15 and, from there, on through the flow-off grooves 24 into the collecting channel 28 and, from there, through the openings 29 into the pump outlet 31. 3D

The cylinder head 26 is mounted by its countersunk portion onto the end of the cylinder 3. The valve seat part 13, which is pressed into the countersunk portion 25 of the cylinder head 26, holds the parts of the outlet valve 14, namely the valve ball forming the shut-off body 19 and the valve closing spring 20, in the cylinder head 26. In this way, an easy-to-handle preassembly unit of the outlet valve 14 disposed in the cylinder head 26 is formed. The cylinder head 26, as already mentioned, forms a valve housing of the outlet valve 14. The pump inlet valve 8 and the pump outlet valve 14 form pump valves that control a throughflow direction of the brake fluid through the piston pump 1.

Disposed in the cylinder 3 is a helical compression spring as piston spring 35, which is supported against the valve seat part 13 of the outlet valve 14 and presses against an annular edge 36 of the valve cage 11. The piston spring 35 holds the valve cage 11 against the piston part 5 and, where necessary, also the piston part 5 against the piston 2. The piston spring 35 keeps the piston 2 in contact with the circumference of the eccentric 4.

In an extension of its eccentric-side end of the cylinder 3 a tubular filter 37 is disposed in the pump bore 32 and surrounds the piston 2 at the level of the piston part 5.

The filter 37 comprises a filter screen 38, a tubular filter cloth or some other filter material, which is embedded in a filter frame 39. The filter frame 39 is made of plastics material that is extruded round the filter screen 33.