MASTER PISTON FOR A HYDRAULIC VEHICLE BRAKE

Abstract

A master piston for a hydraulic vehicle brake is arranged in a master cylinder of the hydraulic vehicle brake and is movable in a reciprocal manner along a master piston longitudinal axis. The master piston has at least one piston element and a seal which is injection molded onto the piston element. The master piston has at least one guide portion for guiding the master piston in the master cylinder. The guide portion is elastically deformable at least in some portions in a radial direction to the master piston longitudinal axis. The guide portion is formed at least partially from a different material from the piston element. The piston element, the seal and the guide portion are produced together by a multi-component injection molding method. A method for producing the master piston is disclosed.

Claims

1. A master piston for a hydraulic vehicle brake configured to be arranged in a master cylinder of the hydraulic vehicle brake to be movable in a reciprocal manner along a master piston longitudinal axis, the master piston comprising: a piston element with at least one seal; wherein the seal is injection molded onto the piston element; wherein the master piston has at least one guide portion configured for guiding the master piston in the master cylinder; wherein the at least one guide portion is elastically deformable at least in some portions in a radial direction to the master piston longitudinal axis; wherein the at least one guide portion is formed at least partially from a different material from the piston element; and wherein the piston element, the at least one seal and the at least one guide portion are produced together by a multi-component injection molding method.

2. The master piston as claimed in claim 1, wherein the piston element has at least one circumferential groove which is open radially outwards and the seal bears on three sides against the groove.

3. The master piston as claimed in claim 1, wherein the guide portion has at least one recess which extends in an axial direction from one side of the guide portion to the other side of the guide portion, wherein fluid is configured to be conducted through the recess from an axial side of the guide portion to the other side of the guide portion.

4. The master piston as claimed in claim 1, wherein the guide portion has projections which extend away outwardly in a radial direction and which are spaced apart from one another in the circumferential direction of the master piston, wherein the projections are configured to be elastically deformed in the radial direction of the master piston.

5. The master piston as claimed in claim 1, wherein the guide portion is configured where it radially encompasses the seal in some portions in the axial direction.

6. The master piston as claimed in claim 1, wherein at least one spring is integrated in the seal, wherein this spring is configured where a sealing lip or sealing edge of the seal is subjected to a spring force radially outwardly in the radial direction.

7. The master piston as claimed in claim 1, wherein the at least one further seal is injection molded onto the piston element.

8. The master piston as claimed in claim 1, wherein the master piston has at least one further guide portion which is arranged spaced apart from the first guide portion in the axial direction.

9. The master piston as claimed in claim 1, wherein the respective guide portion or at least one of the guide portions has two segments, wherein one respective segment is arranged on one respective axial side of a seal or the seal.

10. The master piston as claimed in claim 1, wherein at least the first and/or each further guide portion has at least one scraper edge and/or scraper lip which extends radially away from the respective guide portion.

11. A hydraulic vehicle brake having the master piston as claimed in claim 1.

12. The hydraulic vehicle brake as claimed in claim 11, wherein the hydraulic vehicle brake is configured for a vehicle with handlebars.

13. The hydraulic vehicle brake as claimed in claim 12, wherein the vehicle with handlebars is a bicycle.

14. A method for producing the master piston as claimed in claim 1 in the multi-component injection molding method, comprising the following method steps, which can be carried out in any sequence or at the same time: injection molding of the piston element; injection molding of the at least one guide portion onto the piston element; and injection molding of the at least one seal onto the piston element.

15. The method as claimed in claim 14, wherein prior to injection molding of the at least one seal, an insert part is inserted into a cavity of an injection mold of the at least one seal.

16. The method as claimed in claim 15, wherein the insert part is a spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention is explained in more detail hereinafter with reference to exemplary embodiments shown in the drawing. In the drawing:

[0039] FIG. 1 shows a master piston in a sectional view (FIG. 1a) and in a partial sectional view (FIG. 1b);

[0040] FIG. 2 shows a further master piston in a perspective sectional view;

[0041] FIG. 3 shows a master piston in a partial sectional view (FIG. 3a) and in a partial perspective sectional view (FIG. 3b);

[0042] FIG. 4 shows a master piston in a partial sectional view;

[0043] FIG. 5 shows a master piston in a perspective detailed view;

[0044] FIG. 6 shows a master piston in a perspective detailed view;

[0045] FIG. 7 shows the master piston according to FIG. 1a in a detailed view;

[0046] FIG. 8 shows a master piston in a partial sectional view; and

[0047] FIG. 9 shows a block diagram of the method according to the invention for producing the master piston.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0048] FIG. 1a shows a master piston 1 for a hydraulic vehicle brake 2. The vehicle brake 2 is indicated in FIG. 1a by a dashed line. The master piston 1 comprises a piston element 4 and two seals 6, 8. The seals 6, 8 are arranged spaced apart from one another in an axial direction relative to the longitudinal axis of the master piston 1. The seal 6 is a primary seal and the seal 8 is a secondary seal. Moreover, the master piston 1 has two guide portions 10, 12 for guiding the master piston 1 in a master cylinder of the vehicle brake 2.

[0049] The piston element 4 is configured rotationally symmetrically and has two circumferential grooves 14, 16 for the seals 6, 8. The grooves 14, 16 are arranged spaced apart from one another. The grooves 14, 16 in this case are cut off at right-angles, wherein other groove shapes are also possible, however. The grooves 14, 16 can differ from one another or can be the same in terms of size and shape. The seals 6, 8 are injection molded onto the piston element. The seals 6, 8 in each case bear on three sides against the respective groove 14, 16. In other words, the seals 6, 8 in each case bear with their respective internal circumferential sides 18, 20 and in each case with their respective lateral circumferential sides 22, 24 against the respective grooves 14, 16.

[0050] The guide portion 10 is arranged on a low-pressure side N of the seal 6 and supports the seal in the direction of the low-pressure side N. In other words, the seal 6 bears against the guide portion 10 on a lateral circumferential side 22 on the low-pressure side N.

[0051] The guide portion 12 has two segments 26, 28 which are arranged on one respective axial side of the seal 8. The segments 26, 28 support the seal 8 in each case on the lateral circumferential sides 24 in the axial direction.

[0052] In FIG. 1b it is shown that the seal 6 has a foot portion 30 on the internal circumferential side. The foot portion 30 extends in the axial direction and encompasses the piston element 4 in a radial direction. Moreover, the seal 6 has a connecting portion 32 which extends from the foot portion 30 on an axial side of the foot portion 30, in this exemplary embodiment on the low-pressure side N, outwardly in the radial direction and a seal edge portion 34 which extends away from the foot portion 30 axially in the direction of a high-pressure side H and radially outwardly, so that a sealing edge of the seal 6 sealingly bears against a master cylinder which is not shown in FIG. 1b.

[0053] The seal 8, see FIG. 1a, is configured symmetrically in the axial direction and has in its axial center a bulge 36 which extends outwardly in the radial direction, so that an apical sealing edge of the seal 8 bears sealingly against the master cylinder.

[0054] FIG. 2a shows a master piston 1, the guide portion 42 thereof differing from the guide portion 10 of FIG. 1. The guide portion 42 in this case encompasses the seal 6 in some portions in a radial direction and also in an axial direction. In other words, the guide portion 42 has a bottom portion 44 which protrudes radially outwardly, and an encompassing portion 46 which protrudes in the axial direction in the direction of the high-pressure side H and encompasses the seal in some portions in the radial direction. In other words, the guide portion 42 forms an approximately C-shaped recess which is open in the axial direction and in the direction of the high-pressure side H and in which the seal 6 is inserted. FIG. 2b shows the master piston 1 from a different perspective.

[0055] FIG. 3a shows a further master piston 1, which differs substantially from the master piston 1 of FIG. 1 in that a spring 50 is integrated in the seal 6 or in the material thereof. The spring 50 protrudes from the guide portion 10 in the direction of the high-pressure side H and radially outwardly. The spring 50 can be produced in one piece with the piston element 4, for example, by an injection molding method. However, it is also possible that the spring 50 is over-molded with the seal. The sealing edge portion 34 of the seal 6 is subjected to a spring force by the spring 50, so that the sealing edge is pushed radially outwardly in order to bear sealingly against the master cylinder.

[0056] According to FIG. 3b the spring 50 can be configured from a plurality of spring elements 52 which are arranged spaced apart from one another in the circumferential direction.

[0057] FIG. 4 shows a master piston 1 with a guide portion 56 which is formed from a different material from the piston element 4. In other words, the master piston 1 is configured by a multi-component injection molding method, wherein the guide portion 56 forms one component.

[0058] A master piston 1 which has a guide portion 60 with rib-shaped projections 62 which extend in the axial direction of the master piston 1 is shown in FIG. 5. The projections 62 protrude outwardly in a radial direction and are arranged spaced apart uniformly from one another in the circumferential direction. The projections 62 serve for guiding the master piston 1. As fluid can flow between the projections 62, it is ensured that the guide portion 60 is sufficiently lubricated during the operation of the master piston 1. The seal 6 can be lubricated thereby on both sides in the axial direction.

[0059] A master piston 1 which has a guide portion 66 with Y-shaped recesses 68 which are arranged spaced apart uniformly from one another in the circumferential direction is shown in FIG. 6. A first portion of one respective recess 68 can extend parallel to the axial direction from the low-pressure side N to the high-pressure side H. In each case two portions of one respective recess 68, which are spaced apart from one another over the circumference and which approach one another from the high-pressure side H to the low-pressure side N, extend from the high-pressure side so that the three portions form the respective Y-shaped recess 68.

[0060] In FIG. 7 the master piston 1 according to FIG. 1 is shown enlarged in some portions, wherein the seal 8 and the guide portion 12 are shown in detail.

[0061] FIG. 8 shows a master piston 1 with a secondary seal 72 and a second guide portion 74. The seal 72 has a foot portion 76 which extends in the axial direction and which contains an internal circumferential surface of the seal 72. A connecting portion 78 extends in the radial direction away from this foot portion on a low-pressure side N1 of the seal 72. A sealing edge portion 80 extends away from the connecting portion 78 in the axial direction in the direction of the high-pressure side H1 of the seal 72, and in the radial direction, wherein the sealing edge portion 80 has a sealing edge which sealingly bears against the master cylinder, which is not shown.

[0062] The guide portion 74 encompasses the seal 72 in the axial direction so that the connecting portion 78 in the radial direction is encompassed partially by the guide portion 74, viewed from radially outwardly. On the low-pressure side N1 the guide portion 74 has a scraper lip 82. This scraper lip can be injection molded or configured in one piece with the guide portion 74. This can prevent the ingress of dirt.

[0063] FIG. 9 shows a block diagram of a method 100 for producing a master piston 1, for example according to FIG. 1. In an optional first step 82, an insert part, for example the spring 50 of FIG. 3a, is inserted into a cavity for injection molding, i.e., into an injection mold. Subsequently, in a further optional step 84, a piston element 4 is produced by injection molding. If the piston element is to have one or more guide portions, they can be generated in step 84. It is also possible that the piston element 4 is configured as a turned part from aluminum or another metal or plastics material and accordingly inserted into the injection mold. Subsequently in step 86, a seal 6, 8, 72 is injection molded onto the piston element 4 (arranged in the injection mold). Additionally, in a further optional step 88, one or more further seals 6, 8, 72 can be injection molded onto the piston element 4. Additionally, in a further optional step 90, a guide portion 10, 12, 42, 56, 60, 66, 74 can be produced, in particular, on the remaining piston element 4. The steps 86, 88, 90 can be carried out in any sequence or at the same time.