Vacuum brake booster

Abstract

Vacuum brake booster (26) for a vehicle brake system of a motor vehicle, comprising a first housing shell (28) and a second housing shell (16), wherein the housing shells (16, 28) form the housing (12) of the vacuum brake booster (26) and together delimit a working chamber (20) and a vacuum chamber (22) separated by a movable wall (18), wherein the first housing shell (28) delimits the vacuum chamber (22) of the vacuum brake booster (26) and has a base (30) which has a central opening (34) via which the vacuum brake booster (26) can be coupled to a master brake cylinder unit (17), and a circumferentially closed collar (32) which extends from the edge (58) of the base (30) in the axial direction away from the base (30) and thereby laterally delimits the vacuum chamber (22), wherein the base (30) has a circumferentially closed, has a trough (38) extending in the direction of the vacuum chamber (22),characterized in that the trough (38) is formed in the radially outer third of the base (30).

Description

[0001] The invention relates to a vacuum brake booster for a vehicle brake system of a motor vehicle.

[0002] Vacuum brake boosters are installed upstream of the master cylinder unit and amplify the force applied to a brake pedal. The amplified force is then transmitted to the master cylinder unit.

[0003] Vacuum brake boosters known from the prior art typically comprise a housing within which a movable wall is arranged. The movable wall divides the housing into a working chamber and a vacuum chamber. Such vacuum brake boosters are known, for example, from the publications DE 10 2015 001 944 A1, WO 95 / 12 511 A1, and EP 2 855 222 B1.

[0004] There are requirements for the minimum stroke of the master brake cylinder of the master brake cylinder unit and accordingly the movable wall within the housing of the vacuum brake booster must also be able to move over a certain distance.

[0005] However, the space for the vehicle braking system within the motor vehicle, for example within the engine compartment, is limited.

[0006] It is therefore the object of the invention to provide a vacuum brake booster which is more compact in the adjustment direction of the movable wall.

[0007] The object is achieved according to the invention by a vacuum brake booster for a vehicle brake system of a motor vehicle. The vacuum brake booster has a first and a second housing shell which form the housing of the vacuum brake booster and delimit the working chamber and vacuum chamber separated by a movable wall. The first housing shell delimits the vacuum chamber and has a base and a circumferentially closed collar. The base has a central opening via which the vacuum brake booster can be coupled to a master brake cylinder unit, and the collar extends from the edge of the base in the axial direction away from the base, laterally delimiting the vacuum chamber. The base has a circumferentially closed recess extending towards the vacuum chamber.

[0008] The invention is based on the fundamental idea that the annular recess forms an outer wall region in the first housing shell that is offset axially inward, i.e., toward the vacuum chamber. Due to the recess, the first housing shell is shorter in the axial direction than known first housing shells and is therefore also more compact. With the same axial adjustment range of the movable wall, the vacuum brake booster according to the invention can therefore be shorter in the axial direction. This makes it possible to use a vacuum brake booster for the first time in some motor vehicles.

[0009] In other words, the housing of the vacuum brake booster according to the invention is shorter in the adjustment direction of the movable wall than comparable housings known from the prior art, ie housings in which the movable wall can be moved over the same adjustment path.

[0010] If the vacuum brake booster according to the invention has the same axial extent as a vacuum brake booster in the prior art, the movable wall of the vacuum brake booster according to the invention can be moved over a larger adjustment range.

[0011] Unless otherwise stated, previous and subsequent geometric directions such as “circumferential”, “radial” and “axial” refer to the central opening of the base and the central axis of the vacuum brake booster and thus to the adjustment direction of the movable wall.

[0012] One aspect of the invention provides that the recess is designed symmetrically to the opening. This ensures that the forces acting on the housing shell are evenly distributed. The trough can be formed in the radially outer third of the base.

[0013] To enable a flat connection to the master brake cylinder unit and thus prevent tilting, a flange area can be provided on the outside of the base. The flange area connects directly to the central opening.

[0014] The flange area can be flat and / or oval in the front view of the vacuum brake booster.

[0015] For example, the flange area is elliptical.

[0016] A further aspect of the invention provides that the flange region has an axially projecting portion. This offset portion allows the first housing shell, and thus the vacuum brake booster, to be easily adapted to the available space in the engine compartment of the motor vehicle in the direction of the central axis.

[0017] In this case, the axially projecting portion preferably adjoins the central opening directly.

[0018] In one embodiment of the invention, at least one fastening opening is formed in the flange area, through which the housing can be flange-mounted to a master brake cylinder unit. The flange ensures the precise positioning of the housing on the master brake cylinder unit.

[0019] For example, the oval shape of the flange region has a greater extent in a direction perpendicular to an axis formed by the connection of the central axis to the at least one fastening opening (fastening axis) than in the direction of the fastening axis. Along the fastening axis, the first housing shell is additionally stabilized by its attachment to the master cylinder unit. Due to the oval shape, a relatively steep angle can be realized in the recess in the direction perpendicular to the fastening axis, which increases the buckling stability of the first housing shell in the direction perpendicular to the fastening axis.

[0020] The housing can be penetrated by at least one fastening bolt. Its axial end protrudes from the fastening opening in the first housing shell, and the other axial end protrudes from an opening in the second housing shell. The fastening bolt has two axially offset widened portions against which the housing shells rest on the inside. The spacing of the widened portions defines the volume of the vacuum chamber. This reduces the number of required components, as the fastening bolt simultaneously ensures the connection to the master brake cylinder unit and a certain distance between the housing shells.

[0021] In other words, the expansions determine the distance between the housing shells when assembled, and thus the volume of the vacuum chamber. The recess can initially be tapered from its radially inner end, allowing it to transition smoothly and without kinks into the adjoining conical section, which extends to the central flange.

[0022] In one embodiment of the invention, the conical region has an angle of at least 10° and at most 20°, in particular at least 13° and at most 15°, relative to a plane perpendicular to a central axis of the central opening. This angular range has proven particularly suitable for ensuring a compact design of the vacuum brake booster and high stability of the housing shell.

[0023] In particular, the conical region has the angle of at least 13° and at most 15° in a region perpendicular to the fastening axis.

[0024] A vacuum connection can be formed in the conical region. Since the first housing shell defines the vacuum chamber, the vacuum connection can be very easily configured in the area of ​​the recess or near the recess. A further aspect of the invention provides that the edge is designed as an axially projecting, closed-circumferential bead, the radially inner portion of which forms the outer boundary of the recess. The bead ensures a stable connection of the recess to the collar.

[0025] The bead forms a circumferential groove when viewed from the vacuum chamber. The movable wall can be tapered outward in its radially outer region and axially inclined toward the first housing shell, and can have an edge section that can move into the groove at maximum axial displacement of the wall. This increases the range over which the movable wall can move.

[0026] In order to allow the movable wall to have the greatest possible adjustment range within the housing, the wall can be bent at the edge section towards the first housing shell and strike a channel wall at maximum axial displacement.

[0027] The first and / or second housing shell can be a sheet metal part. Sheet metal parts are inexpensive to manufacture, lightweight, and the required geometry can be easily formed with sheet metal parts.

[0028] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings, to which reference is made below. In the drawings: - Fig. 1 is a longitudinal sectional view of a vacuum brake booster known from the prior art, - Fig. 2 a vacuum brake booster according to the invention in a perspective view, - Fig. 3 in a perspective view a first housing shell of the vacuum brake booster of the Fig. 2, - Fig. 4 a longitudinal sectional view of the vacuum brake booster according to the invention of Fig. 2, - Fig. 5 a comparison of the vacuum brake booster according to the invention of the Fig. 2 with a housing shell known from the prior art in a longitudinal section, and - Fig. 6 a perspective view of a first housing shell of a vacuum brake booster according to the invention in a further embodiment.

[0029] In Fig. 1 shows a sectioned part of a vacuum brake booster 10 of a vehicle brake system of a motor vehicle, known from the prior art.

[0030] The vacuum brake booster 10 has a housing 12 formed by a first housing shell 14 and a second housing shell 16. A master brake cylinder unit 17 of the vehicle brake system is flanged to the first housing shell 14.

[0031] Arranged within the housing 12 is a movable wall 18, which, with an adjacent diaphragm 19, separates the chamber formed by the housing shells 14, 16 into a working chamber 20 and a vacuum chamber 22. The diaphragm 19 is clamped between the first and second housing shells 14, 16 and acts as a seal between the working chamber 20 and the vacuum chamber 22. The movable wall 18 lies flat against the diaphragm 19.

[0032] In this respect, the first housing shell 14 and the movable wall 18 including the diaphragm 19 delimit the vacuum chamber 22, and the second housing shell 16 and the movable wall 18 including the diaphragm 19 delimit the working chamber 20 of the vacuum brake booster 10.

[0033] The movable wall 18 has an edge section 23 which is bent towards the first housing shell 14. In the area of ​​the edge section 23, the movable wall 18 extends conically outwards and towards the first housing shell 14. Accordingly, the edge section extends in the view of the Fig. 1 obliquely, i.e. radially outwards and in the direction of the first housing shell 14.

[0034] The radially outermost end of the edge portion 23 is bent circumferentially inwardly in order to obtain a rounding and to stabilize the edge portion 23.

[0035] The movable wall 18 is connected to a control valve unit 24 of the vacuum brake booster 10 and is movable by means of the control valve unit 24 between a first position (in Fig. 1) and a second, axially displaced position. In Fig. 1, the second position is indicated by the dashed edge section 23.

[0036] The distance between the two positions is the maximum adjustment range v of the movable wall 18.

[0037] In the first position, the vacuum chamber 22 is fluidly connected to the working chamber 20. Accordingly, in the first position of the wall, the same pressure prevails in the working chamber 20 and the vacuum chamber 22.

[0038] When a brake pedal (not shown) is actuated, the movable wall 18 is urged toward the second position, and the working chamber 20 is filled with ambient air. Accordingly, in the second position, a pressure difference exists between the working chamber 20 and the vacuum chamber 22, via which the force applied to the brake pedal is amplified by the vacuum brake booster. The amplified force is transmitted through the movable wall 18 to the master brake cylinder unit 17. Based on the Fig. 2 to 5, a vacuum brake booster 26 according to the invention is explained below. The components known from the vacuum brake booster 10 known from the prior art are provided with the same reference numerals.

[0039] The difference to the known vacuum brake booster 10 lies in the first housing shell 28.

[0040] The first housing shell 28 is a sheet metal part and has a base 30 and a closed, circumferential collar 32 extending away from the base 30, resulting in a pot shape.

[0041] Furthermore, the second housing shell 16 can also be designed as a sheet metal part.

[0042] The collar 32 extends from an edge 58 of the base 30 and thus laterally delimits the vacuum chamber 22. The collar 32 is bent radially outward at the end of the collar 32 remote from the base 30.

[0043] The base 30 has a central opening 34 which defines a central axis 36 of the first housing shell 28, and a recess 38 which is formed, for example, symmetrically to the central axis 36, i.e. to the opening 34.

[0044] The vacuum brake booster 26 can be coupled to the master brake cylinder unit 17 via the central opening 34 and a flange area 40 is connected to the outside of the central opening 34.

[0045] The vacuum brake booster 26 can be flanged to the master brake cylinder unit 17 via the flange area 40 and the flange area 40 has an axially offset, flat partial area 41.

[0046] In other words, the portion 41 projects axially in the direction of adjustment of the movable wall 18 from the first to the second position. In the flange area 40, more precisely in the partial area 41, fastening openings 42 are provided in the base 30 ( Fig. 3) which are arranged symmetrically, here diametrically to the central axis 36, and via which the vacuum brake booster 26 can be flanged to the master brake cylinder unit 17.

[0047] As in the Fig. 2 and Fig. As shown in Figure 3, the outer contour of the flange region 40 has an oval shape. The flange region 40 is therefore oval in the frontal view of the outer side of the base 30.

[0048] The flange region 40 has a greater extent in and against a direction 45 which is perpendicular to a fastening axis 43 defined by the connection of the fastening openings 42 than in the direction of the fastening axis 43.

[0049] The vacuum brake booster 26 has fastening bolts 44 adapted to the fastening opening 42 ( Fig. 2) which penetrate the housing 12.

[0050] One axial end of each fastening bolt 44 protrudes from the corresponding fastening opening 42 in the base 30 and the other axial end of the fastening bolt 44 protrudes from a corresponding opening 46 in the second housing shell 16 ( Fig. 5).

[0051] On each fastening bolt 44, two radial widenings 48 are formed, which are arranged axially offset from one another with respect to the central axis of the fastening bolt 44.

[0052] In other words, the widenings 48 have a certain axial distance d from each other.

[0053] In the assembled state, the housing shells 16, 28 rest on the inside against the corresponding widenings 48 of the fastening bolts 44, so that a spacer is formed.

[0054] In the design of the Fig. 2 to 5, the second housing shell 16 lies directly against the corresponding widening 48 of the fastening bolt 44 and the first housing shell 28 lies against the corresponding widening 48 via an intermediate element 50.

[0055] For example, the intermediate element 50 is a spring washer.

[0056] The distance d between the widened portions 48 determines the distance between the housing shells 16, 28. Thus, the distance d between the widened portions defines the volume of the housing 12 and thus the volume of the vacuum chamber 22.

[0057] As in Fig. As shown in Figure 4, a conical region 54 radially adjoins the flange region 40 and extends outwardly toward the vacuum chamber 22, i.e., toward the second housing shell 16. The region 54 extends into the recess 38 and forms a radially inner wall section of the recess 38 in a radially outer transition region 56.

[0058] The trough 38 is arranged in the radially outer third of the base 30. In the figure, the outer third of the base 30 is represented by the arrow 52.

[0059] The trough 38 is delimited by the radially inner conical region 54 and a radially outer transition region 56 in which the trough 38 merges into the edge 58 of the base 30.

[0060] In the conical region 54 and in the transition region 56, the trough 38 has an angle α with respect to a plane perpendicular to the central axis 36.

[0061] The angle α is at least 10° and at most 20°. In the design of the Fig. 4 the angle is 14°.

[0062] Within the conical area 54, a vacuum connection 60 is also formed in the base 30 ( Fig. 2), via which the vacuum chamber 22 can be connected to a vacuum source (not shown). For example, the vacuum source is a vacuum pump or the engine of the motor vehicle.

[0063] The edge 58 is formed as a circumferentially closed, arcuate bead 62, seen in section, which projects axially outwards, i.e. away from the second housing shell 16.

[0064] The radially inner section of the bead 62 forms the radially outer boundary of the trough 38.

[0065] The transition between the bead 62 and the transition region 56 forms a hollow base which is arched in section and which defines the deepest section of the hollow 38.

[0066] The bead 62 forms a circumferential groove 64 within the vacuum chamber 22, into which the edge section 23 of the movable wall 18 can move.

[0067] More precisely, the bent edge section 23 of the movable wall 18 strikes at maximum axial displacement of the wall 18 (dashed position of the edge section 23 in Fig. 4) on the inside to a channel wall 66 of the channel 64.

[0068] Fig. 5 shows a comparison of the vacuum brake booster 26 with the first housing shell 14 of the vacuum brake booster 10 known from the prior art with the same adjustment path v of the movable wall 18. The first housing shell 14 known from the prior art is shown by dashed lines.

[0069] It can be seen that the vacuum brake booster 26 is shorter in the axial direction than the vacuum brake booster 10 known from the prior art due to the design of the first housing shell 28.

[0070] In other words, the vacuum brake booster 26 is shorter in the axial direction by a length difference l.

[0071] Accordingly, the vacuum brake booster 26 can be designed more compactly in the axial direction than in the prior art or it allows a larger adjustment range with the same overall length as in the prior art.

[0072] Fig. 6 shows a further embodiment of the first housing shell 28 of the vacuum brake booster 26, which essentially corresponds to the embodiment of the Fig. 2 to 5, so only the differences will be discussed below.

[0073] The difference from the first embodiment is that the flange region 40 does not have an axially offset portion 41. Instead, the flange region 40 is flat over its entire area.

[0074] In addition, the recess 38 is no longer symmetrical to the central axis 36, but has two curvatures 68 in which, for example, the vacuum connection 60 is formed or a pressure sensor can be coupled.

Claims

[1] Vacuum brake booster (26) for a vehicle brake system of a motor vehicle, with a first housing shell (28) and a second housing shell (16), wherein the housing shells (16, 28) form the housing (12) of the vacuum brake booster (26) and together delimit a working chamber (20) and vacuum chamber (22) separated by a movable wall (18), wherein the first housing shell (28) delimits the vacuum chamber (22) of the vacuum brake booster (26) and has a base (30) which has a central opening (34) via which the vacuum brake booster (26) can be coupled to a master brake cylinder unit (17), and has a circumferentially closed collar (32) which extends from the edge (58) of the base (30) in the axial direction away from the base (30) and thereby laterally delimits the vacuum chamber (22), wherein the base (30) has a circumferentially closed trough (38) extending in the direction of the vacuum chamber (22),characterized by that the recess (38) is formed in the radially outer third of the base (30). [2] Vacuum brake booster (26) according to claim 1, characterized by that the recess (38) is formed symmetrically to the opening (34). [3] Vacuum brake booster (26) according to one of the preceding claims, characterized by that a flange region (40) is provided on the outside of the base (30), wherein the flange region (40) directly adjoins the central opening (34), wherein the flange region (40) has an oval shape in a frontal view of the base (30). [4] Vacuum brake booster (26) according to claim 3, characterized by that the flange area (40) has an axially projecting portion (41). [5] Vacuum brake booster (26) according to claim 3 or 4, characterized bythat at least one fastening opening (42) is formed in the flange region (40), via which the housing (12) can be fastened to the master brake cylinder unit (17). [6] Vacuum brake booster (26) according to claim 5, characterized by that the housing (12) is penetrated by at least one fastening bolt (44), one axial end protruding from the fastening opening (42) of the first housing shell (28) and the other axial end protruding from an opening (34) of the second housing shell (16), the fastening bolt (44) having two axially offset widened portions (48) against which the housing shells (16, 28) bear on the inside, and the distance between the widened portions defining the volume of the vacuum chamber (22). [7] Vacuum brake booster (26) according to one of the preceding claims, characterized by that the trough (38) initially runs conically from its radially inner end. [8] Vacuum brake booster (26) according to claim 7, characterized by that the conical region (54) has an angle (α) of at least 10° and at most 20° with respect to a plane which is perpendicular to a central axis (36) of the central opening (34). [9] Vacuum brake booster (26) according to one of the preceding claims, characterized by that the edge (58) is designed as an axially projecting, closed circumferential bead (62), the radially inner section of which forms the outer boundary of the trough (38) on the edge side. [10] Vacuum brake booster (26) according to claim 9, characterized bythat the bead (62) forms a circumferential groove (64) on the side of the vacuum chamber (22) and that the movable wall (18) in its radially outer region extends conically obliquely outwards and axially in the direction of the first housing shell (28) and has an edge section (23) which is movable into the groove (64) at maximum axial displacement of the wall (18). [11] Vacuum brake booster (26) according to claim 10, characterized by that the wall (18) is bent at the edge section (23) in the direction of the first housing shell (28) and that the wall (18) strikes a channel wall (66) of the channel (64) at maximum axial displacement.

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