Brake Actuating Device

Abstract

A brake actuating device of a vehicle brake system has a pump housing which has a housing opening surrounded by a wall. The housing opening includes a housing axis along which a piston is to be accommodated in the housing opening in an axially displaceable manner. The housing opening further has a guide region in which a guide element to be arranged between the wall and the piston is to be accommodated. The brake actuating device further has a projection projecting from the wall into the housing opening. The projection is provided axially next to the guide region in the housing opening. The guide element is placed axially on the projection.

Claims

1. A brake actuating device of a vehicle brake system, comprising: a piston; a pump housing having a wall that defines a housing opening, wherein the housing opening defines a housing axis along which the piston is configured to be accommodated in an axially displaceable manner, and wherein the housing opening further defines a guide region; a guide element arranged in the guide region between the wall and the piston; and a projection projecting from the wall into the housing opening, wherein the projection is located axially next to the guide region in the housing opening, and wherein the guide element is placed axially on the projection.

2. The brake actuating device according to claim 1, wherein the projection is formed integrally with the pump housing.

3. The brake actuating device according to claim 1, further comprising a sealing element, wherein: the housing opening further defines a sealing region in which the sealing element is arranged, the sealing region is arranged on a side of the projection opposite the guide region, and the sealing element is located between the wall and the piston.

4. The brake actuating device according to claim 1, wherein the guide element possesses a radial outer surface which is designed with a transition fit so as to be positioned axially in the direction of the projection.

5. The brake actuating device according to claim 1, wherein the guide element possesses a radial inner surface which is designed with a bevel that is positioned axially in the direction of the projection.

6. The brake actuating device according to claim 1, wherein the guide element possesses a radial outer surface which is designed with a step that is directed radially inward and is positioned axially remote from the projection.

7. The brake actuating device according to claim 6, wherein at least one segment is provided, by way of which the step of the guide element and the pump housing are press-fit when the guide element is accommodated in the guide region.

8. The brake actuating device according to claim 7, wherein the at least one segment is punctiform.

9. The brake actuating device according to claim 1, wherein at least one cavity is provided radially next to the guide region outside the housing opening in the pump housing.

10. A use of a brake actuating device according to claim 1 in a master brake cylinder of the vehicle brake system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Exemplary embodiments of the solution according to the disclosure are explained in more detail below with reference to the attached schematic drawings. In the drawings:

[0026] FIG. 1 shows a section of a hydraulic diagram with a master brake cylinder on which the disclosure is based,

[0027] FIG. 2 shows a longitudinal section of a part of the master brake cylinder according to FIG. 1,

[0028] FIG. 3 shows the detail III in FIG. 2,

[0029] FIG. 4 shows a part of a longitudinal section of a first exemplary embodiment of a brake actuating device according to the disclosure without a piston,

[0030] FIG. 5 shows the detail V according to FIG. 4,

[0031] FIG. 6 shows the view VI according to FIG. 4 with a piston,

[0032] FIG. 7 shows the section VII-VII according to FIG. 6,

[0033] FIG. 8 shows the view according to FIG. 6 of a second exemplary embodiment of a brake actuating device according to the disclosure, and

[0034] FIG. 9 shows the section IX-IX according to FIG. 8.

DETAILED DESCRIPTION

[0035] FIGS. 1 to 3 show a highly schematic master brake cylinder 10 and an associated brake actuating device 11 of a hydraulic vehicle brake system (not shown in further detail), as used in brake systems with slip control systems such as ABS and ESP. In the present case, the master brake cylinder 10 is integrated in a cuboid hydraulic block 12 made of aluminum, which is only partially shown in the figures. A so-called one-box system and therefore a so-called integrated power brake (IPB) is present which is to be assembled directly on a bulkhead (not shown) of a vehicle.

[0036] The master brake cylinder 10 is arranged in a master brake cylinder borehole as a housing opening 16 provided parallel to a transverse side 14 of the hydraulic block 12. The housing opening 16 and the hydraulic block 12 provide a pump housing 18, in which the housing opening 16 forms an interior 20 which is surrounded by a wall 22 and has a housing axis 24.

[0037] The housing axis 24 corresponds to a piston axis associated with a piston 26. In this case, the piston 26 is connected in an articulated manner outside the pump housing or housing 18 to a piston rod 28 which is coupled to a brake pedal 30 which can be actuated by a user of the vehicle. When the brake pedal 30 is actuated, the piston 26 is mechanically moved along the housing axis 24 in the housing opening 16 by means of the piston rod 28. The piston 26 is a so-called rod piston or primary piston which is braced by a compression spring 29 against a second piston 32 arranged axially downstream from the piston 26. In addition, the second piston 32 is axially displaceable and braced by a second compression spring 34 against a housing side 36 opposite the piston 26 at the end face. The piston 32 is also called a pressure piston or secondary piston. A piston pump 33 is therefore formed with two brake cylinders, arranged axially one behind the other, of a master brake cylinder 10 designed as a tandem master brake cylinder.

[0038] Given this design, a dual-circuit brake system (not shown) is to be actuated. For this purpose, a first pressure chamber 38 is located between the two pistons 26 and 32 and the housing 18, into which pressure chamber a hydraulic fluid or fluid from a storage container (not shown) is sucked through a line 40. The fluid is then to be pumped through a further line 42 into a first brake circuit. A second pressure chamber 44 provided between the piston 32 and the housing side 36 is equipped with corresponding lines 40 and 42, with which a second brake circuit is to be supplied with fluid. When the brake pedal 30 is actuated, the piston 26 is pushed into the housing opening 16 and thereby generates a hydraulic pressure in the first pressure chamber 38. The pressure shifts the piston 32 in the direction of the housing side 36, whereby hydraulic pressure is generated in the second pressure chamber 44.

[0039] Both pistons 26 and 32 are sealed in the interior 20 by radially surrounding sealing rings 46. For this purpose, each sealing ring 46 is arranged in an associated annular groove 48 in the wall 22. Furthermore, an additional sealing element 50 designed as a sealing ring is provided radially around the piston 26 in the direction of the piston rod 28. The sealing element 50 is accommodated in an annular space 52 which is created by means of an annular step 54 of the wall 22 that extends radially outward. The sealing ring 46 closest to the step 54 is referred to as the first insulation seal, and the sealing element 50 itself is referred to as the second insulation seal.

[0040] Furthermore, a guide element 56 is provided in the brake actuating device 11 axially outside the sealing element 50, which guide element radially surrounds the piston 26 as a guide ring. The guide element 56 serves to absorb axial and transverse forces arising during operation. The transverse forces occur primarily when the brake pedal 30 is actuated, since the piston rod 28, at its end remote from the piston 26, is moved by the brake pedal 30 on a circular path. The axial forces are primarily caused by hydraulic pressure.

[0041] In this case, the guide element 56 in the brake actuating device 11 is axially arranged with its contact surface 58 directly on the sealing element 50. In addition, the guide element 56 is axially placed radially on the outside with a small region of the contact surface 58 on a further step 60 of the housing opening 16. In this case, the wall 22 of the interior 20 is displaced further radially outwards with the further step 60 compared to the step 54. Furthermore, a circumferential, radially outwardly projecting edge 62 is provided on the guide element 56, which edge is fastened to the housing 18 by means of press-fitting. The press-fit 64 is a plastic deformation of material of the housing 18 around a mouth 66 surrounding the housing opening 16, which mouth overlaps the edge 62. The guide element 56 is therefore held axially on or in the housing 18.

[0042] FIGS. 4 to 7 show an exemplary embodiment of a brake actuating device 68 which is shown in part without the piston 26 for better clarity. In contrast to the brake actuating device 11, a projection 72 is provided in the interior 20, on which projection a guide element 70 is axially placed. For this purpose, the guide element 70 is accommodated in a guide region 73 which extends in the housing opening 16 from the projection 72 in the direction of the mouth 66. In contrast to the step 60, the projection 72 projects radially inward from the wall 22 into the housing opening 16. Furthermore, the projection 72 in the form of an annular bar is designed as a flat component which extends transversely at a right angle to the housing axis 24 into the interior 20 and is designed integrally with the housing 18.

[0043] In this case, the projection 72 has an outer side 74 which faces away from the interior 20 in the axial direction, and on which the guide element 70 is axially placed by its contact surface 76. Both the contact surface 76 and the outer side 74 are designed as a flat ring and are also largely flat. Furthermore, the contact surface 76 extends completely over its contact side 78 of the guide element 70 facing the projection 72. A substantially larger contact area of the guide element 70 on the projection 72 is therefore created in comparison with the small section of the contact surface 58 of the guide element 56 at the step 60. In this way, axially acting forces are absorbed more extensively by the guide element 70 and correspondingly transmitted more extensively to the block-shaped housing 18.

[0044] Opposite the outer side 74 and facing into the interior 20, the projection 72 has an annular and largely flat interior or side 80 which is opposite the guide element 70. A sealing region 82 of the housing opening 16, in which the sealing element 50 designed as a sealing ring and lip seal is arranged, is provided axially between the side 80 and the step 54. Thus, forces on the side 80 acting axially from the inside to the outside are transmitted via the sealing element 50 to the projection 72 and from there to the housing 18.

[0045] In addition, the guide element 70 has a radial outer surface 84 on its circumference, which surface is formed with a transition fit 86 in the direction of its contact surface 76 and therefore in the direction of the outer side 74 of the projection 72. The transition fit 86, starting from a lateral surface 88 of the guide element 70, is designed with a first bevel 90 facing radially inward in the direction of the projection 72. Following the first bevel 90, a lateral surface 92 with a smaller diameter in comparison with the lateral surface 88 is provided, and a radially inward facing second bevel 94 is connected thereto. Furthermore, radially to the inside, the guide element 70 comprises a radial inner surface 96 which is designed to taper in the direction of the projection 72 with a bevel 98. Starting from an inner lateral surface 100, the bevel 98 is formed with a radially outwardly directed bevel 102.

[0046] For assembling the guide element 70 on the housing 18, the guide element 70 is introduced and pressed into the housing opening 16 at the mouth 66 in a first assembly step. In so doing, the transition fit 86 facilitates targeted introduction with corresponding play. In a further pressing-in operation, the guide element 70 is pressed into the interior 20 until the guide element 70 rests against the projection 72 on its outer side 74. An excess force that occurs is absorbed by the projection 72 of the housing 18. In addition, deformations produced by the pressing-in process are absorbed by the bevel 98.

[0047] Furthermore, the radial outer surface 84 of the guide element 70 is designed with a radially inward directed step 104 remote from the projection 72. With the step 104, an offset shoulder 106 is provided on the guide element 70 opposite the contact surface 76, which shoulder extends, in the present case, radially circumferentially over the entire circumference of the guide element 70.

[0048] For further assembly of the guide element 70, the shoulder 106 or step 104 is press-fit in a second assembly step with a plurality of punctiform segments 108 of the housing 18. In the exemplary embodiment, four segments 108 are provided which are arranged uniformly distributed on the mouth 66 of the housing opening 16, which mouth has a circular cross section (FIG. 6). For this purpose, a pressing force is exerted by a press-fitting tool 110 segmentally on the material of the housing 18 at the mouth 66, in such a way that the material is deformed on the individual segment 108 over the shoulder 106 (FIG. 7). The shoulder 106 is therefore segmentally overlapped by the deformed material of the housing 18. The guide element 70 is held on the housing 18 in the housing opening 16 by means of such segmental press-fitting.

[0049] During assembly, axial assembly forces 112, which are directed from the outside in the direction of the projection 72, occur while pressing-in and press-fitting (FIG. 7). These assembly forces 112 are absorbed by the projection 72 and transmitted to the housing 18. In addition, frictional forces occur during actuation of the brake pedal 30 and a forward movement of the piston rod 28 and the piston 26 caused thereby. Like the assembly forces 112, the frictional forces also act axially on the projection 72 from the outside and are transmitted from the projection 72 to the housing 18. Reduced forces therefore act from the outside to the inside on the guide element 70 and the sealing element 50.

[0050] Axial forces 114 which act from the inside to the outside or from the interior 20 in the direction of the projection 72 result from friction during a backward stroke of the piston 26 caused by releasing the brake pedal 30. In addition, these forces 114 also include functional forces generated by hydraulic pressure. The forces 114 act on the sealing element 50 placed on the projection 72, and are transmitted via the sealing element 50 to the projection 72 and from there to the housing 18. The outwardly acting forces 114 on the guide element 70 and on the segments 108 are therefore also reduced by means of the projection 72.

[0051] It has been shown that such a force transmission by the projection 72 on the entire housing 18 and the resulting reduced force in an axial direction is particularly easy on components and therefore also saves material. The sealing element 50 is therefore held by means of the projection 72 and is protected, and therefore reliably seals the passenger compartment as an additional seal. The sealing element 50 is therefore part of an expanded sealing concept for the IBP as a second insulation seal. In this case, the sealing element 50 offers a reliable additional safety seal which prevents the hydraulic fluid from contaminating an interior of a passenger compartment if it leaks through a first insulation seal that may be damaged.

[0052] In addition, the described segmental press-fitting and therefore only partial press-fitting of the housing 18 with the guide element 70 is sufficient to hold the guide element 70 in the housing opening 16 in a stable manner. Furthermore, it is sufficient for the guide element 70 to have a reduced press-in zone 116 and a reduced diameter 117 in comparison to the guide element 56. This creates a particularly space-saving and cost-effective brake actuating device 68 with reduced operating weight at the same time.

[0053] FIGS. 8 and 9 show the brake actuating device 68 in an exemplary embodiment in which three ball locks 118 arranged eccentrically to the housing axis 24 are provided peripherally to the housing opening 16 or interface. Each ball lock 118 includes a ball 120, which is in each case press-fit axially at the level of the guide region 73 and radially in the vicinity of the guide region 73 in a channel 122 arranged in the housing 18. Such ball press-fits or ball locks 118 lead to deformations in the guide region 73 of the housing opening 16.

[0054] For receiving each such deformation, an eccentrically arranged cavity 124 is provided radially outside the housing opening 16, axially at the level of the guide region 73 and in the region of the individual ball lock 118. The individual cavity 124 is therefore arranged radially adjacent to the guide region 73 peripheral to the associated channel 122 of the ball lock 118.

[0055] Each cavity 124 is therefore located in the pressing region of the guide element 70 and the associated ball lock 118. Due to the cavity 124, the deformation of the housing 18 by the associated ball lock 118 has no influence on a fit of the guide element 70 in the housing opening 16. Finally, the deformation accommodated by the cavity 124 does not overlap the centric diameter of the guide element 70. Defects in a guide between the piston 26 and the guide element 70 are therefore avoided.

[0056] In order to produce each cavity 124, a milling operation is carried out after interface machining a metal block used as a housing 18. The milling operation removes additional material axially at the level of the guide region 73 eccentric to the housing opening 16 and therefore forms the individual cavity 124. The cavity 124 is therefore designed as a recess.