Brake system with elastic protective device and method for mounting the protective device

Abstract

The invention relates to a braking device (1) for a motor vehicle braking system, comprising at least one braking device housing (2) and at least one elastic protective device (3) fixed to the braking device housing (2) designed as a barrier against dirt, in particular against dust, the protective device (3) having at least one axially compressible bellows section (5) with a plurality of outer folds (7) and inner folds (8) arranged axially alternately and connected by side surfaces (6). According to the invention, in order to improve the mounting of the universal protective device, in particular to perform automatic mounting, the protective device (3) has at least one integrated support means (9) for defining and reducing the axial degree of compression of the bellows area (5). The invention also relates to a method for mounting the protective device (3) on the braking device housing (2).

Description

[Technical Field]

[0001] The present invention relates to a brake unit for a hydraulic motor vehicle brake system according to the preamble of the claims. [Background technology]

[0002] Most motor vehicle brake units are actuated by an actuating member, specifically a piston rod, which is inserted into the brake unit and connected to a piston therein. This type of joint must be carefully isolated from the environment to prevent dirt, moisture or dust from accumulating therein or entering the brake unit and impairing its operation. Since an actuating member such as a piston rod is not only moved in a translational manner during operation, but is also easily rotated at the same time, sliding seals are not suitable for sealing such joints. In addition, such sealing elements place particularly high demands on the surface quality of the actuating member.

[0003] In practice, therefore, it has become common to use hose-like, axially compressible elastic protective devices fastened at one end to the brake unit housing and at the other end to the actuating member, and in order to ensure that such protective devices are sufficiently flexible, it is known to provide them with bellows.

[0004] For information on general-purpose brake units, see, for example, International Publication No. 2018 / 054619A1.

[0005] However, the installation of such thin-walled elastic protective devices poses challenges due to their flexibility. When axially directed forces are applied during installation of the protective device, its deformation behavior is highly influenced by even the smallest deviations of the initial configuration (angle, dimensional accuracy, friction coefficient, etc.) and is therefore difficult to predict. Such behavior runs counter to the desired automation function, which therefore has to be performed manually to ensure proper assembly. However, manual operations or manual work steps are time-consuming and require additional control measures to avoid variability in results, resulting in relatively high assembly costs. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem is therefore to propose a solution which improves the assembly of universal protective devices and in particular allows for an assembly which can be automated.

[0007] This object is achieved according to the invention by a brake unit having the combination of features set forth in claim 1. The dependent claims specify further advantageous embodiments and developments of the invention. [Means for solving the problem]

[0008] The present invention provides that at least one support means is integrated into the protective device, thereby selectively reducing the axial compression of the bellows region and limiting the bellows region to a defined dimension. The protective device is thus fixed to a defined degree of compression, and the protective device is able to transmit assembly forces from one axial end to the other through the support means. The deformation behavior of the protective device becomes predictable.

[0009] Further measures described below additionally optimize the design of the joint to the brake unit housing and implement an automatic locking function.

[0010] This allows for fully automatic mounting of the protection device and then uniform, reproducible execution of the assembly steps in the production series of brake units with increased cycle frequency. Control means can thus be reduced without loss of safety and manufacturing costs can be reduced.

[0011] Further features and advantages of the present invention will become apparent from the following description of one exemplary embodiment according to the present invention. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a general-purpose brake unit equipped with a known disadvantageous protection device; [Figure 2] 1 shows an embodiment in axial cross section in an inactivated state fitted with an improved protection device. [Figure 3] 3 shows a cross section through the outer fold of the protection device according to FIG. 2; [Figure 4] The figures show enlarged views of the folds of the bellows portion in a relaxed state (a) and in an axially compressed state (b). [Figure 5] 1 shows the protective device being installed with an assembly tool. [Figure 6] 1 shows an enlarged view of the joint between the protection device and the brake unit housing in axial section; [Figure 7] 1 shows a three-dimensional view of the reinforcing ribs of the fastening part of the protection device. DETAILED DESCRIPTION OF THE INVENTION

[0013] Figure 1 The generic known brake unit 1 shown as an example has a brake unit housing 2 with a piston 24 arranged therein, which can be actuated in actuation direction B by an actuating member 4 for which the actuating member 4 can be actuated, for example, by a brake pedal (coupled thereto, not shown here) or an actuator. A coil spring 17 is clamped between the brake unit housing 2 and the actuating member 4, which acts as a return spring and resets the actuating member 4 together with the piston 24 to their original, unactuated starting position in relaxation direction L after the braking operation is completed.

[0014] A thin-walled protection device 3 fastened to the brake unit housing 2 is made from an elastic material, encases part of the actuating member 4 together with a coil spring 17 and acts as a barrier against dirt particles in the vicinity of the brake unit 1. This prevents, for example, dirt and dust from getting into the joint between the actuating member 4 and the brake unit 1 or directly into the brake unit 1 and impairing its function.

[0015] The protection device 3 must be axially compressible when the actuating member 4 is actuated, and for this purpose has a bellows portion 5 .

[0016] The known protective device 3 shown here is snapped at both ends into substantially rectangularly configured radial grooves 21, 21', each with a correspondingly shaped end profile, and is thereby fixed axially in a positive locking manner. To prevent the protective device 3 from slipping off the actuating member 4 during actuation of the brake unit 1, it additionally comprises a reinforcing ring 22 inserted radially outward. Installation of such a protective device 3 on the brake unit 1 can only be done manually.

[0017] Figure 2 FIG. 2 shows an embodiment of the inventively improved protection device 3 in axial section in the assembled state.

[0018] The protection device 3 is made in a substantially thin-walled manner from a resilient material, preferably an elastomer, such as EPDM.

[0019] The bellows portion 5 has a plurality of outer folds 7, which are in each case arranged alternately in the axial direction, and inner folds 8, which are formed as round folds. It is not important here whether the rounding radius is constant or variable. The outer folds 7 and inner folds 8 are connected by side faces 6, which are substantially straight in cross section.

[0020] Solid axial protrusions 10 or thickenings are formed on the inside of the side surfaces 6. All axial protrusions together form support means 9, which in particular shorten the stroke or axial degree of compression of the bellows portion 5 to a desired dimension.

[0021] The mode of action of the support means 9 is explained in more detail below, and in particular in FIG.

[0022] Within the context of the present invention, the support means 9 can also be formed on the outside of the bellows 5, rather than on the inside as shown. The outside, however, is more susceptible to the accumulation of dirt, which may tend to impair the correct functioning of the support means 9.

[0023] At its end facing the brake unit housing 2, a fastening portion 11 is formed on the protective device 3, via which the protective device 3 is fixed to a corresponding fastening stub 12 of the brake unit housing 2, which forms an axial undercut 13.

[0024] The mode of action of fastener 11 is explained in more detail below, and in particular in FIG.

[0025] At the opposite end of the protection device 3 relative to the brake unit housing 2, a separate support disc 18 is attached. The support disc 18 is made from a stable material, for example steel sheet or fiber-reinforced plastic, and serves firstly as a spring cup or mount for the internal return spring 12. In this case, the support disc 18 is supported in the relaxation direction L on a stop 23 on the actuating member 4. For a permanent, stable connection, the support disc 18 is preferably at least partially overmolded in a positive-locking manner with the elastic material of the protection device 3 or embedded therein.

[0026] Figure 3 Figure 3 shows the bellows part 5 according to Figure 2 in cross section through the outer fold 7. The support means 9 are designed here in the form of several block-shaped axial protrusions 10, 10', 10'', ... formed on the inside of the side surface 6 so as to be spaced apart from one another in a segmented manner in the circumferential direction.

[0027] In further embodiments not shown here, the support means 9 may instead be configured in small segmental fashion with a number of short block-like axial projections, or may have only a few axial projections in the circumferential direction with a bead-like extending design, or a single axial projection 10 may be shaped as a circumferential bead.

[0028] Figure 4 FIG. 4 shows in cross section the bellows 5 in the area of ​​a single fold in the unactuated starting position according to FIG. 2 (view a) and in the compressed position according to FIG. 5 (view b).

[0029] The axial protrusions 10, 10' are formed opposite each other on the adjacent side surfaces 6, 6', which are oriented toward each other. When the bellows portion 5 is compressed, an input force is applied to one end of the protection device 3. Here, the folds 7 bend until the axial protrusions 10, 10' collide. This prevents further axial compression of the bellows portion 5, and the input force is transmitted to the other end through the wall of the protection device 3. The wall in the area of ​​the folds is thin and remains flexible during the process.

[0030] Compared to simply increasing the wall thickness of the protection device 3 in general, the structure described in the present invention has several advantages. First, the bellows portion 5 generates low resistance during normal operation. Second, the durability of the protection device 3 is improved, since if the wall thickness in the area of ​​the folds 7 and 8 were increased, the material would be subjected to much greater stress in stretching and crushing during bending, which could lead to long-term crack formation and functional failure.

[0031] Figure 5 FIG. 5 shows the process of automatically assembling the protection device 3 onto the brake unit housing 2 using a separate assembly tool 19 .

[0032] For this purpose, the coil spring 17 is pressed into the protection device 3, which is positioned with its fastening part 11 on the fastening stub of the brake unit housing 2, so that the coil spring 17 is likewise positioned on the side seat of the brake unit housing. An assembly tool 19 is applied to the opposite end of the protection device 3. For this purpose, the tip of the tool, which is conically shaped in a manner optimized from the standpoint of self-centering of the assembly tool 19, is inserted into the central opening of the support disk 18, which is engaged through actuation by the actuating member 4.

[0033] The assembly tool 19 is then pressed linearly in the direction of the brake unit housing 2 with an assembly force F. The assembly force F is first introduced into the coil springs 17 via the support disks 18, so that they are compressed together with the bellows portion 5. After the distance has been defined, the support means 9 is actuated by the individual axial projections 10, 10' abutting against each other, thereby preventing further axial compression of the bellows portion 5. The assembly force F is then introduced into the wall of the protection device 3 and the support means 9 and transmitted to the fastening part 11, which is thereby pressed onto the fastening stub 12 and latches onto it.

[0034] For simplicity of explanation, the dissipation of the assembly force F that actually results from compression of the coil spring 17 and the bellows 5, as well as friction and other effects, is not shown here, but it goes without saying that it would have to be taken into account in practice when designing the assembly device.

[0035] The assembly tool 19 is then moved to its starting position or removed. It must now be ensured that the coil spring 17 does not detach the protection device 3 from the fastening stub 12 when it is relaxed. Indeed, in one defined embodiment, if the holding force on the fastening stub 12 alone is not sufficient for this purpose, the lateral edges of the support disk of the protection device 3 can be held at a defined reduced distance from the brake unit housing 2, optionally by means of suitable means, for example external stops. The holding must be maintained until the actuating member 4 is mounted and fixed in the brake unit 1.

[0036] In another embodiment (not shown), the support means 9 can be dimensioned, for example by a defined design of the height of the axial projection, in particular so that a separate assembly tool 19 can be dispensed with and the protection device 3 can be mounted directly by the actuating member 4. An assembly force F is introduced here from the actuating member 4 into the support disc 18, for example during its first actuation.

[0037] Within the present invention, the protection device 3 can be provided as a pre-assembled composite together with the support disk 18, the coil spring 17 and the actuating member 4, which is then finally assembled in a fully automatic manner in a single assembly step in the direction of the brake unit housing 2 by a simple linear pressing movement. At the same time, the actuating member 4 is latched into the piston and the protection device 3 is latched onto the fastening stub 12. For this purpose, the coil spring 17 and the actuating member 4 must be fixed to the support disk 18. This can be achieved by using common fixing means, such as latch connections, spring rings, snap rings and the like.

[0038] Figure 6 Figure 6 shows an enlarged view of the special design of the fastening portion 11 of the protection device 3, which facilitates self-centering and self-latching engagement on the fastening stub 12 of the brake unit housing 2 during assembly, thus simplifying the automatic function of the assembly operation.

[0039] The axial locking is carried out by means of an undercut 13. To form the undercut 13, a radial protrusion 15 formed on the fastening part 11 is introduced into a circumferential radial recess 14 formed on the fastening stub 12. Within the scope of the present invention, the radial protrusion 15 can be designed as a kind of circumferential collar and in the form of several latching teeth circumferentially spaced apart from one another. An inverted design of the undercut 13 with a radial protrusion on the fastening stub 12 and a radial recess on the fastening part 11 is also permitted within the scope of the present invention.

[0040] The fastening portion 11 is radially elastic and formed with a smaller diameter than the fastening stub 12, so that under the action of the axially directed assembly force F, it is radially enlarged from the fastening stub 12 and pressed axially, while at the same time being radially tightened until the radial projections 15 latch into the radial recesses 14. Here, the assembled radial tightening force supports the adhesion of the protection device 3 to the fastening stub 12 both axially and circumferentially, thus also acting as a kind of anti-rotation safety device.

[0041] To improve self-centering of the protection device 3 during assembly and to improve sliding, the fastening stub 12 is tapered at its radially outer edge and forms a mounting cone 20 thereon.

[0042] The fastening part 11 is of a funnel-shaped design in the direction of the brake unit housing 2 for the same purpose, thus creating a run-up slope.

[0043] Preferably, the axial length of the fastener 11 should be designed to be greater than the maximum winding distance of the coil spring 17. This ensures that the protection device 3 can slide reliably on the coil spring 17 during assembly and will not get pinched between the individual windings.

[0044] Figure 7 7 shows in three-dimensional view the area of ​​the fastening part 11 of the preferred embodiment according to the above. A number of reinforcing ribs 16, arranged circumferentially spaced from one another, are formed on the radial periphery of the fastening part 11.

[0045] These increase the axial stiffness of the fastening portion 11 while maintaining a low radial stiffness that makes it easy to install, and ensure that the fastening portion 11 does not compress axially when pressed onto the fastening stubs 12, thereby preventing the protection device 3 from being properly fixed to the brake unit housing 2.

[0046] When lubricating oil is used to improve the sliding characteristics in the contact area between the fastening part 11 and the fastening stub 12, it is also considered within the scope of the present invention to omit the reinforcing ribs 16. The present invention may also include the following aspects: 1. A brake unit (1) for a motor vehicle brake system, comprising at least one brake unit housing (2) and at least one elastic protective device (3) fastened to the brake unit housing (2) and arranged as a barrier against dirt, in particular against dust, the protective device (3) having at least one axially compressible bellows region (5) with a plurality of outer folds (7) and inner folds (8) connected by side surfaces (6) and arranged alternately in the axial direction, characterized in that the protective device (3) has at least one integrated support means (9) for defining and reducing the axial compression dimension of the bellows region (5). 2. A brake unit (1) as described in 1. above, characterized in that the support means (9) includes at least one axial protrusion (10) arranged on, and in particular integrally formed with, the side surface (6). 3. The brake unit (1) described in 2. above, characterized in that the support means (9) includes at least two axial protrusions (10, 10') positioned opposite each other and arranged towards each other on each of the adjacent side surfaces (6, 6'). 4. A brake unit (1) as described in 2. or 3. above, characterized in that a plurality of axial protrusions (10, 10') positioned circumferentially spaced from each other are arranged on the side surface (6). 5. A brake unit (1) as described in 2. or 3. above, characterized in that the axial projection (10) is formed as a bead running around the circumferential direction. 6. The brake unit (1) according to at least one of the above items 1 to 5, characterized in that the support means (9) is disposed inside the bellows portion (5). 7. A brake unit (1) described in at least one of 1. to 6. above, characterized in that the protective device (3) has a fastening portion (11) at its end facing the brake unit housing (2) that forms an axial undercut (13) and is configured to be positioned on a corresponding fastening stub (12) of the brake unit housing (2). 8. A brake unit (1) as described in item 7 above, characterized in that the undercut (13) is formed by at least one radial protrusion (15) engaging in a circumferential radial recess (14). 9. A brake unit (1) as described in 7. or 8. above, characterized in that the fastening portion (11) is configured to widen in a funnel-shaped manner in the direction of the brake unit housing (2) to form an ascending slope. 10. A brake unit (1) described in at least one of 7. to 9. above, characterized in that the fastening portion (11) has a plurality of reinforcing ribs (16) arranged circumferentially spaced from each other on its radial outer periphery. 11. A brake unit (1) described in at least one of items 7 to 10 above, characterized in that an axially oriented coil spring (17) is arranged radially within the protection device (3), and the axial length of the fastening portion (11) is greater than the maximum winding distance of the coil spring (17). 12. A brake unit (1) described in at least one of 1. to 11. above, characterized in that a separate support disc (18) is arranged at the end of the protection device (3) opposite the brake unit housing (2), an operating member (4) for operating the brake unit (1) is supported on the support disc (18) in the axial direction toward the brake unit housing (2), and a coil spring (17) is clamped between the brake unit housing (2) and the support disc (18). 13. A brake unit (1) described in at least one of 1. to 12. above, characterized in that the outer fold (7) and / or the inner fold (8) are formed as rounded folds having a constant or variable radius. 14. A method for mounting a protection device (3) on a brake unit housing (2) of a brake unit (1) according to at least one of 1. to 13. above, comprising: In a first step, the protection device (3) is attached to a corresponding joint of the brake unit housing (2); a method characterized in that in a second step the protection device (3) is finally assembled by means of a defined axially directed assembly force applied to the end of the protection device (3) opposite the brake unit housing (2) and by this end being moved a defined length in the direction of the brake unit housing (2). 15. The method according to claim 14, characterized in that the assembly force from the actuating member (4) of the brake unit (1) is introduced into the protection device (3). 16. The method according to claim 14, characterized in that the assembly force from a separate assembly tool (19) is introduced into the protection device (3). 17. A method according to claim 16 for use with at least a brake unit (1) according to claim 12, characterized in that the assembly force from the assembly tool (19) is introduced into the support disc (18). 18. The method according to claim 17, characterized in that the assembly tool 19 engages in an opening in the support disc 18, which is configured to pass through together with the actuating member 4 during actuation of the brake unit 1. [Explanation of symbols]

[0047] 1 Brake unit 2 Brake unit housing 3 Protective device 4. Actuating member 5 Bellows 6 Side 7 Outward Fold 8 Inner Fold 9 Support means 10 Axial protrusion 11 Fastening part 12 Fastening stub 13 Undercut 14 Depression 15 Radial projection 16 Reinforcing rib 17 Coil spring 18 Support Disc 19 Assembly Tools 20 Mounting cone 21 Groove 22 Reinforcement ring 23 Stop part B Actuation direction F Assembly force L relaxation direction

Claims

1. 1. A brake unit (1) for a motor vehicle brake system, comprising: at least one brake unit housing (2); and at least one elastic protective device (3) fastened to the brake unit housing (2) and arranged as a barrier against dirt, in particular against dust, the protective device (3) having at least one axially compressible bellows portion (5) with a plurality of outer folds (7) and inner folds (8) connected by side surfaces (6) and arranged alternately in the axial direction, characterized in that the protective device (3) has at least one integrated support means (9) comprising at least one axial protrusion (10) arranged on the side surface (6) for defining and reducing the axial compression dimension of the bellows portion (5).

2. 2. A brake unit (1) according to claim 1, characterized in that the support means (9) comprise at least two axial projections (10, 10') positioned opposite each other and arranged towards each other on each of the adjacent side surfaces (6, 6').

3. 3. A brake unit (1) according to claim 1 or 2, characterized in that a plurality of axial projections (10, 10') positioned circumferentially spaced from one another are arranged on said side surface (6).

4. 3. Brake unit (1) according to claim 1 or 2, characterized in that the axial projection (10) is formed as a bead running around the circumference.

5. 3. Brake unit (1) according to claim 1 or 2, characterized in that the support means (9) are arranged inside the bellows portion (5).

6. 3. A brake unit (1) according to claim 1 or 2, characterized in that the protection device (3) has, at its end facing the brake unit housing (2), a fastening portion (11) that forms an axial undercut (13) and is configured to be placed on a corresponding fastening stub (12) of the brake unit housing (2).

7. 7. Brake unit (1) according to claim 6, characterized in that said undercut (13) is formed by at least one radial protrusion (15) engaging in a circumferential radial recess (14).

8. 7. Brake unit (1) according to claim 6, characterized in that the fastening portion (11) is configured to widen in a funnel-shaped manner in the direction of the brake unit housing (2) in order to form a run-up slope.

9. 7. A brake unit (1) according to claim 6, characterized in that the fastening portion (11) has on its radial outer periphery a plurality of reinforcing ribs (16) arranged circumferentially spaced from one another.

10. 7. The brake unit (1) according to claim 6, characterized in that an axially oriented coil spring (17) is arranged radially within the protection device (3), and the axial length of the fastening portion (11) is greater than the maximum winding distance of the coil spring (17).

11. 3. A brake unit (1) according to claim 1 or 2, characterized in that a separate support disc (18) is arranged at the end of the protection device (3) opposite the brake unit housing (2), on which an actuating member (4) for actuating the brake unit (1) is supported axially in the direction of the brake unit housing (2), and a coil spring (17) is clamped between the brake unit housing (2) and the support disc (18).

12. 3. Brake unit (1) according to claim 1 or 2, characterized in that the outer fold (7) and / or the inner fold (8) are formed as rounded folds with a constant or variable radius.

13. A method for mounting a protection device (3) on a brake unit housing (2) of a brake unit (1) according to claim 1 or 2, comprising the steps of: In a first step, the protection device (3) is attached to a corresponding joint of the brake unit housing (2), a method characterized in that in a second step, the protection device (3) is finally assembled by means of a defined axially directed assembly force applied to the end of the protection device (3) opposite the brake unit housing (2) and by this end being moved a defined length in the direction of the brake unit housing (2).

14. 14. A method according to claim 13, characterized in that the assembly force from an actuating member (4) of the brake unit (1) is introduced into the protection device (3).

15. 14. A method according to claim 13, characterized in that the assembly force from a separate assembly tool (19) is introduced into the protection device (3).

16. 16. A method according to claim 15 for use with a brake unit (1) according to claim 11, characterized in that the assembly force from the assembly tool (19) is introduced into the support disc (18).

17. A method as described in claim 16, characterized in that the assembly tool (19) engages with an opening in the support disc (18) configured for an actuating member (4) to pass through during operation of the brake unit (1).

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