Patent Publication Number: US-2023133986-A1

Title: Brake Actuating Device

Description:
This application claims priority under 35 U.S.C. § 119 to patent application no. DE 10 2021 212 295.7, filed on Nov. 2, 2021 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
     The disclosure relates to a brake actuating device, in particular of a vehicle brake system, having a pump housing which has a housing opening surrounded by a wall, wherein the housing opening comprises a housing axis along which a piston is to be accommodated in the housing opening in an axially displaceable manner, and comprises a guide region in which a guide element to be arranged between the wall and the piston is to be accommodated. The disclosure further relates to the use of such a brake actuating device in a vehicle brake system. 
     BACKGROUND 
     Generic vehicle brake systems are used to decelerate the driving speed of vehicles such as cars and trucks. For this purpose, hydraulic brake systems are usually used, with which functions of an anti-lock braking system (ABS) and/or an electronic stability program (ESP) are also realized. A controlled brake pressure is provided in associated brake circuits by means of a hydraulic assembly and a hydraulic fluid. To generate the brake pressure, a pedal-actuatable master brake cylinder is provided to which usually two brake circuits are connected, each comprising a brake line through which hydraulic fluid can flow. If a brake pedal is actuated by a driver, a mechanical force exerted therewith is converted into a hydraulic force by increasing a pressure on the hydraulic fluid. This force then acts as a braking force on associated wheel brakes. 
     Known master brake cylinders or pressure-generating cylinders generally have a brake actuating device, which is usually designed in a block shape or as a block. A housing opening with a housing axis, in which housing opening a cylinder and a piston are arranged, is formed by means of a bore hole in the block. The piston is axially displaceable in the cylinder or the housing opening by the brake pedal, and is sealed from the outside by at least one sealing ring in the housing opening. In addition, the piston is guided during its translational movement along the housing axis by a guide element arranged radially around the piston. In this case, the guide element is used, in particular, to support against transverse forces which occur predominantly while actuating the brake pedal during operation. Such a brake actuating device is known from DE 10 2015 207 634 A1. 
     SUMMARY 
     The disclosure relates to a brake actuating device or a braking request specification device, in particular of a vehicle brake system, comprising a pump housing which has a housing opening surrounded by a wall, wherein the housing opening comprises a housing axis along which a piston is to be accommodated in the housing opening in an axially displaceable manner, and comprises a guide region in which a guide element to be arranged between the wall and the piston is to be accommodated. In this case, a projection projecting from the wall into the housing opening is provided axially next to the guide region in the housing opening, on which projection the guide element is to be axially placed. 
     The projection therefore projects from the wall and extends into the housing opening or an interior of the pump housing or housing created by the wall. In addition, the projection is arranged in particular directly next to the guide region. If the guide element accommodated in the guide region is axially placed on the projection, axial forces acting on the guide element during assembly and operation are absorbed by the projection. Thus absorbed, the forces are transmitted from the projection to the housing. In comparison to the guide element, the housing is substantially larger and comprises more material, so that the axial forces acting on the guide element are absorbed by the housing in a manner distributed over a wide region. Such a force distribution acts in a particularly stabilizing and gentle manner on involved components. The axial forces that occur are, in particular, axially acting assembly forces, frictional forces acting when the piston is moving into the housing opening, and functional forces acting as a result of hydraulic pressure. According to the disclosure, a brake actuating device is therefore created by means of which forces arising during the assembly and operation of the piston pump can be absorbed in a particularly well distributed manner by the housing itself. In addition, the piston which is guided by the guide element placed on the projection receives additional stability. It is therefore sufficient to design the guide element with a reduced diameter and a reduced length in comparison to a conventional guide element. A particularly lightweight brake actuating device is created. 
     In addition, the projection or protrusion according to the disclosure creates a housing opening which in particular has a substantially similar cross section in the axial direction before and behind the projection. Only in the region of the projection is the cross section and therefore the interior of the housing reduced. A relatively large interior space is thereby created, in particular axially within the projection, which provides space for further pump elements. Preferably, a sealing element can be positioned therein. 
     The projection is preferably designed as a bar. Such a bar extends radially into the housing opening and is designed to be relatively flat in the axial direction. It has been found that, despite its small axial extension, such a bar has a surprisingly good stabilizing effect on arising contact forces. 
     In addition, the projection and in particular the bar has, on its side or outer side facing toward the guide element, a substantially flat surface for applying the guide element. There, the guide element can be or is applied in a particularly stable and effective force-transmitting manner. The guide element, by means of its contact side facing toward the projection, can be or is applied to the projection preferably over the entire contact side in a particularly effective force-transmitting manner. 
     More preferably, the projection is designed to extend transversely to the housing axis, particularly preferably approximately at a right angle to the housing axis. A particularly uniform force distribution is therefore achieved together with, at the same time, an advantageous spatial design for further components. 
     Furthermore, the housing is preferably designed in a block shape, whereby arising forces are absorbed in a particularly effective force-distributing manner. Particularly preferably, the housing in particular of the master brake cylinder is integrated in a hydraulic block. This creates a very compact and space-saving brake system. 
     According to the disclosure, the projection is advantageously designed integrally with the housing. The projection is therefore arranged in a particularly stable manner on the housing, and force transmitted by means of the projection to the housing is particularly high. 
     In addition, according to the disclosure, the housing opening advantageously comprises a sealing region in which a sealing element to be arranged between the wall and the piston is to be accommodated. In this case, the sealing region is arranged on a side of the projection opposite the guide region so that the projection is located axially between the guide region and the sealing region. When the sealing element is accommodated in the sealing region, the sealing element is therefore arranged radially between the wall and the piston and axially on a side or sealing side of the projection facing away from the guide element. The sealing side of the projection is a side which faces the interior of the housing and has an inner surface on which the sealing element is axially placed. The projection is therefore positioned axially between the sealing element and the guide element, and correspondingly directly absorbs acting axial forces and transmits them to the housing. For this purpose, the sealing element is preferably designed with a sealing ring which completely surrounds the piston radially. A particularly good sealing effect is therefore achieved. 
     The brake actuating device according to the disclosure is preferably part of a master brake cylinder. This results in axial forces acting on the sealing element from the interior in the direction of the projection, in particular during a return stroke of the piston caused by releasing the brake pedal. These forces are absorbed by the projection and transmitted to the housing. By means of such a force absorption, the sealing element is conserved and stabilized during operation. A particularly reliable and durable sealing effect of the brake actuating device in the master brake cylinder is therefore achieved. Axial forces directed from the outside in the direction of the interior occur while assembling the brake actuating device and during operation by a forward movement of the piston, in particular when the brake pedal is actuated. Correspondingly acting assembly forces, functional forces and frictional forces are also absorbed by the projection. 
     The guide element is preferably designed with a guide ring. The guide ring is to be arranged radially around the piston, and therefore completely surrounds the piston over its circumference on its lateral surface in an assembled state. The piston is therefore particularly compact, stable and uniformly guided. 
     In addition, according to the disclosure, the guide element advantageously has a radial outer surface which is designed with a transition fit to be positioned axially in the direction of the projection. The transition fit is in particular a radial press fit which aligns the guide element coaxially with the housing opening. This facilitates targeted assembly when the guide element is pressed in the direction of the projection. In addition, the transition fit creates a certain play between the guide element and the wall of the housing. Accordingly, the transition fit is preferably designed with a reduction in the diameter of the guide element in the direction of the projection, particularly preferably as a radially inward facing bevel or gradation. 
     Furthermore, according to the disclosure, the guide element advantageously has a radial inner surface which is designed with a bevel to be positioned axially in the direction of the projection. The guide element is therefore designed to taper radially inward in the direction of the projection. Thus, deformations which are generated during a pressing-in process of the guide element into the interior are accommodated in the guide element. A guide region of the guide element facing the piston is then not deformed in an undesired braking manner after pressing in, but rather is protected by means of the bevel. 
     According to the disclosure, the guide element furthermore advantageously has a radial outer surface which is designed with a step which is directed radially inward and is to be positioned axially remote from the projection. With such a step, a shoulder on the guide element is created axially opposite the contact side of the guide element, which shoulder is positioned opposite the projection in the brake actuating device. Further components on the guide element can preferably be arranged or placed in a space-saving manner on the shoulder. Particularly preferably, the guide element is held compactly on the housing by press-fitting the housing on the shoulder. 
     For this purpose, at least one segment is advantageously provided according to the disclosure, with which segment the step of the guide element and the housing are press-fit when the guide element is accommodated in the guide region of the housing opening. In particular for this purpose, the individual segment comprises a material which is placed in a form-fitting manner, by means of press-fitting, over the shoulder of the guide element produced by the step, and an associated interface of the housing. The associated interface is located at a mouth of the housing opening into which the piston and the guide element are introduced. Such a segmental press-fit in combination with the projection according to the disclosure is sufficient to counteract an arising hydraulic pressure in the interior of the housing. By means of the projection, the hydraulic pressure is absorbed via the projection and therefore directly in the housing. The press-fitting of the guide element is therefore not stressed. 
     The individual segment is preferably designed with a material introduced from the outside. The press-fitting is therefore flexible with regard to required material properties. Particularly preferably, the individual segment is formed on the interface of the housing by the material of the housing itself. For this purpose, the housing is correspondingly deformed during press-fitting on the individual segment, which yields simple and material-saving assembly. More preferably, at least two segments are provided with which stable partial press-fitting is achieved. Particularly preferably, four segments are provided, which are arranged in particular at the same distance from one another. Material-saving and nevertheless sufficiently stable segment press-fitting is therefore achieved by means of a partial form-fit. 
     According to the disclosure, the at least one segment is advantageously designed to be punctiform. A particularly space-saving connection of the guide element to the housing is therefore produced. 
     Furthermore, according to the disclosure, at least one cavity is preferably provided radially next to the guide region outside the housing opening in the pump housing. The individual cavity is preferably arranged at a distance from the housing opening. Given a block-shaped housing and a borehole forming the housing opening, the individual cavity is in particular a recess which is arranged radially to the housing opening and extends axially parallel to the housing axis. If the guide element is accommodated in the guide region, the at least one cavity is arranged radially around the guide element. The guide element is therefore surrounded radially in portions by at least one cavity. For this purpose, the individual cavity is preferably arranged eccentrically and particularly preferably centrically with respect to the housing axis. The individual cavity therefore serves as a buffer for the guide element, by means of which buffer forces acting in particular radially from the outside are absorbed, and the guide element is therefore protected. 
     According to the disclosure, the individual cavity is advantageously provided in the region of an associated ball lock which is arranged in the housing peripherally to the guide region of the housing opening. Preferably, at least two ball locks are provided which are arranged eccentrically peripherally to the guide region of the housing opening. In this case, the individual ball lock with its associated ball leads to deformations in the guide region, which are accommodated and compensated for by the at least one cavity in the housing. The deformations therefore do not overlap the centric diameter of the guide element so that negative effects of the deformations on the guide region are avoided. 
     In addition, the disclosure relates to a use of such a brake actuating device on or in a master brake cylinder of a vehicle brake system, wherein in particular the master brake cylinder is integrated in a hydraulic block of a hydraulic assembly. In this way, a particularly lightweight, space-saving and cost-effective vehicle brake system is provided, as can also be seen from the aforementioned advantages of the brake actuating device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG.  1    shows a section of a hydraulic diagram with a master brake cylinder on which the disclosure is based, 
         FIG.  2    shows a longitudinal section of a part of the master brake cylinder according to  FIG.  1   , 
         FIG.  3    shows the detail III in  FIG.  2   , 
         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, 
         FIG.  5    shows the detail V according to  FIG.  4   , 
         FIG.  6    shows the view VI according to  FIG.  4    with a piston, 
         FIG.  7    shows the section VII-VII according to  FIG.  6   , 
         FIG.  8    shows the view according to  FIG.  6    of a second exemplary embodiment of a brake actuating device according to the disclosure, and 
         FIG.  9    shows the section IX-IX according to  FIG.  8   . 
     
    
    
     DETAILED DESCRIPTION 
       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. 
     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 . 
     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. 
     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 . 
     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. 
     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. 
     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 . 
       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 . 
     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 . 
     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 . 
     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 . 
     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 . 
     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 . 
     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. 
     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 . 
     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 . 
     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. 
     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. 
       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 . 
     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 . 
     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. 
     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.