PISTON PUMP

Abstract

The invention relates to a piston pump having a pump housing including a plurality of pump components determining the function of the piston pump, such as a pump piston which is guided in sections, a piston return spring, and a suction and pressure valve. The piston pump also has an annular chamber which delimits the pump piston on the suction side and is designed as a compensating chamber for the liquid, a delivery chamber which delimits the pump piston on the pressure side, and an elastic sealing ring for sealing the pump piston in the direction of a pump drive chamber. To prevent leakage in the direction of the pump drive chamber, the elastic sealing ring is provided with a groove into which is inserted a spring element which presses the sealing ring against the pump piston.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application of PCT/EP2012/062398, filed Jun. 27, 2012, which claims priority to German Application Nos. 10 2011 080 248.7, filed Aug. 2, 2011 and 10 2012 203 931.7, filed Mar. 14, 2012, the contents of such applications being incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a piston pump, in particular for delivering pressure medium in hydraulic brake systems with traction control.

BACKGROUND OF THE INVENTION

DE 10 2010 028 539 A1 discloses a piston pump of this type, having a pump housing which has a plurality of pump components which define the function of the piston pump, such as a pump piston, a piston restoring spring and a suction and pressure valve, and having an annular space which limits the pump piston on the suction side and is configured as a replenishment space for the fluid, and a delivery space which limits the pump piston on the pressure side. In order to seal the pump piston on the low pressure side, an elastic sealing ring with axial prestress is arranged between a bush and a stepped bore, with the result that an axial movement of the sealing ring, which axial movement is initiated by the sliding movement of the pump piston, can be ruled out reliably, in order to prevent increased wear of the sealing ring. Furthermore, a supporting ring is situated between the bush and the sealing ring and a guide band for the pump piston is situated at the end of the pump housing, a further supporting ring being arranged in front of said guide band, with the result that the sealing ring is flanked on both sides by supporting rings. As a result, the bush which is loaded by a spring, the two supporting rings and the guide band are situated in the region of the sealing ring, which results in considerable outlay on parts which, moreover, increases the overall length of the pump.

SUMMARY OF THE INVENTION

An aspect of the present invention provides an improved piston pump in such a way that few components which are as compact as possible are required, and at the same time improved sealing is ensured along the circumferential face of the pump piston.

According to an aspect of the invention, this is achieved for a piston pump of the specified type by an elastic sealing ring provided with a groove, in which a spring element which presses the sealing ring onto the pump piston is inserted.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages of the invention are apparent in the following text from the description of two exemplary embodiments using drawings, in which:

FIG. 1 shows a longitudinal section, arranged on a pump piston, of the essential guide and sealing elements, comprising a guide band which is pressed to the stop into the pump housing and a sealing ring which is fixed in front of said guide band in the pump housing, and, separated by an annular gap, is limited by a supporting ring which is fixed in the pump housing, and

FIG. 2 shows, in a deviation from FIG. 1, a longitudinal section of a sealing ring which is pressed directly to the stop into the pump housing with a guide band which is arranged in front of said sealing ring and is separated from the sealing ring by an annular gap.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows details of an illustration of a piston pump in a longitudinal section, which piston pump is preferably used for conveying pressure medium in hydraulic brake systems with traction control. The pump housing 7 of the piston pump is depicted partially and has a plurality of pump components which define the function of the piston pump, such as an end of a piston pump 6 which is guided in sections in an annular guide band 8, and, diametrically with respect to the guide band 8, an annular space that is configured as a replenishment space 12 for the fluid, and an elastic sealing ring 1 which bears against the circumferential face of the pump piston 6 for the leak-free sealing of the piston end in the direction of a piston drive space 13 which, by way of example, accommodates an eccentric with an eccentric bearing as drive for the pump piston. The pump piston 6 and the replenishment space 12 are likewise shown only in each case in the region which is relevant to the invention, with the result that the details which can be seen from FIG. 1 are restricted to what is necessary.

That region of the piston pump which is not shown to the left of the pump piston 6 comprises substantially a delivery space, a piston restoring spring and a suction and pressure valve with the associated suction and pressure connectors.

In order that leak-free sealing, which remains as constant as possible, of the pump piston 6 is produced in the direction of the piston drive space 13 during pump running, the invention provides that the elastic sealing ring 1 is provided with an axially directed, annularly circumferential groove 3 (what is known as an annular groove) which therefore accommodates a spring element 2 in a manner in which it is inserted laterally, which spring element 2 presses the sealing lip of the sealing ring 1 onto the pump piston 6. In order to generate a constant pressing force of the sealing ring 1 onto the circumferential face of the pump piston 6, the spring element 2 is configured as a spreading element which generates a radial force.

In order for it to be possible to test the functional reliability of the piston pump in dry form, that is to say without the use of hydraulic fluid, the elastic sealing ring 1 is manufactured from a material with dry running characteristics which are sufficiently satisfactory for test purposes, for which purpose polytetrafluoroethylene (PTFE) is particularly suitable.

According to FIG. 1, the sealing ring 1 is fixed directly between the guide band 8 and a supporting ring 4 which is pressed into the stepped bore 10 of the pump housing 7, an annular gap 5 advantageously being provided between the supporting ring 4 and the sealing ring 1 for unimpeded lubrication of the pump piston 6 and therefore also for lubrication of the sealing lip of the sealing ring 1 with the pressure medium which is sucked in by the pump piston 6 via the replenishment space 12. A hydraulic connection is provided for piston lubrication via an axial gap 9 which is arranged between the supporting ring 4 and the pump piston 6 and extends as far as the annular gap 5, with the result that, during operation of the piston pump, a lubricant connection from the replenishment space 12 as far as the sealing ring 1 is produced in a simple, reliable way by the axial gap 9 and the annular gap 5. Here, the brake fluid which is usually used in hydraulic brake systems and is delivered by the piston pump serves as a lubricant.

An alternative proposed solution of the problem which was mentioned at the outset can be gathered from FIG. 2, according to which the sealing ring 1 is then fixed directly between a bore step 11 in the pump housing 7, which bore step 11 adjoins the piston drive space 13, and the guide band 8 which is pressed into the stepped bore 10 of the pump housing 7 and faces the replenishment space 12. Analogously to FIG. 1, in FIG. 2 an annular gap 5 is also arranged between the annular guide band 8 and the sealing ring 1 for lubricating the pump piston 6 in the region of the sealing ring 1, and an axial gap is arranged between the guide band 8 and the stepped bore 10, which axial gap 9 extends to the annular gap 5, as a result of which a pressure medium connection is produced in a reliable way between the replenishment space 12 which is filled with hydraulic fluid during operation of the piston pump and the pump piston 6 which is enclosed by the sealing ring 1. In the simplest embodiment, the axial gap 9 is made as a longitudinal notch on the circumference of the annular guide band 8.

Analogously to FIG. 1, in the exemplary embodiment according to FIG. 2, the groove 3 is also configured as an annular groove which in each case opens laterally into the sealing ring 1, runs around over the side face of the sealing ring 3, and the groove opening of which faces the annular gap 5 which is advantageously exposed to the operating medium, as a rule to the brake fluid to be delivered.

In summary, the result is particularly simple, functionally reliable piston guidance and piston sealing on the low pressure side of the pump piston 6, which low pressure side faces the piston drive space 13, which piston guidance and piston sealing, as a result of the described configuration and arrangement of the sealing ring 1, of the guide band 8 and of the supporting ring 4, have the following advantages:

• • longer leak-free pump running times,
  • improved sealing action of the sealing ring 1 in all temperature ranges,
  • a drastic reduction in components,
  • simpler and less expensive component assembly,
  • smaller axial tolerance of the installation space of the sealing element 1 on account of the reduced number of components (important for the reduction of the pump wear and the improvement of the degree of efficiency of the pump),
  • dispensing with the additional greasing/oil wetting of the sealing element 1 for the purpose of dry running pump testing.

LIST OF DESIGNATIONS

• 1 Sealing ring
• 2 Spring element
• 3 Groove
• 4 Supporting ring
• 5 Annular gap
• 6 Pump piston
• 7 Pump housing
• 8 Guide band
• 9 Axial gap
• 10 Stepped bore
• 11 Bore step
• 12 Replenishment space
• 13 Pump drive space

Claims

1. A piston pump, for delivering pressure medium in hydraulic brake systems with traction control, having a pump housing which a plurality of pump components which define the function of the piston pump, including a pump piston which is guided in sections in a guide band and is pressed into the pump housing and an annular space which limits the pump piston on the suction side and is configured as a replenishment space for the fluid, and having a delivery space which limits the pump piston on the pressure side, and having an elastic sealing ring which is arranged between the annular guide band and a stepped bore in the pump housing for sealing the pump piston in a leak-free manner in the direction of a piston drive space which is formed in the pump housing, wherein the elastic sealing ring is provided with a groove, in which a spring element which presses the sealing ring onto the pump piston is inserted.

2. The piston pump as claimed in claim 1, wherein the elastic sealing ring is manufactured from a material with unrestricted dry running characteristics.

3. The piston pump as claimed in claim 1, wherein the sealing ring is fixed in the pump housing directly between the guide band and a supporting ring which is pressed into the stepped bore, an annular gap being provided between the supporting ring and the sealing ring.

4. The piston pump as claimed in claim 3, wherein an axial gap is arranged between the supporting ring and the pump piston, which axial gap extends to the annular gap, as a result of which a pressure medium connection is produced between the replenishment space and the sealing ring.

5. The piston pump as claimed in claim 1, wherein the sealing ring is fixed directly between a bore step in the pump housing and the guide band in the pump housing, the guide band is pressed into the stepped bore, an annular gap being provided between the guide band and the sealing ring.

6. The piston pump as claimed in claim 5 wherein an axial gap is arranged between the guide band and the stepped bore, the axial gap extending to the annular gap, as a result of which a pressure medium connection is produced between the replenishment space and the sealing ring.

7. The piston pump as claimed in claim 1, wherein, in order to generate a constant pressing force of the sealing ring onto the circumferential face of the pump piston, the spring element is configured as a spreading element which generates a radial force.

8. The piston pump as claimed in claim 1, wherein the groove is configured as an annular groove which opens laterally into the sealing ring, runs around over the side face of the sealing ring, and the groove opening of which faces the annular gap.

9. The piston pump as claimed in claim 2, wherein the material with unrestricted dry running characteristics is polytetrafluoroethylene (PTFE).