Electromechanical drum brake

Abstract

To provide an electromechanical drum brake (10) for automobile.SOLUTION: An electromechanical drum brake (10) includes a drum (18) in which a plurality of brake shoes (70) are provided, and an adjusting device (42) which is located between the plurality of brake shoes (70) and is driven by a drive unit (14), and can expand the brake shoe (70) via the adjusting device (42) for the purpose of braking. An end (72) of each brake shoe (70) facing the adjusting device (42) is supported by support means (46) cooperating with the adjusting device (42) so as to be movable with respect to the support means (46). In this case, an expanding force (FS) of the adjusting device (42) can be transmitted to the brake shoe (70) via the support means (46).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to electromechanical drum brakes for automobiles. [Background technology]

[0002] Drum brakes with different operating modes are known for today's vehicles. In passenger cars, drum brakes are typically hydraulically operated. In this case, hydraulic pressure is generated in a double piston, which spreads out and thus exerts a force on the brake shoes of the drum brake. Since the piston is guided axially, it is relatively unproblematic for the force to be introduced slightly eccentrically with respect to the piston face. Therefore, the brake shoes are often only roughly positioned by support bearings and return springs, and can find their own position inside the drum depending on the tolerances and the wear state.

[0003] In the case of tracks, the actuation by pivoting an S-shaped cam is a common form of actuation. In this case, a cam fixedly supported on a back plate is pneumatically actuated to pivot a certain angle, which spreads the shoes. In this type of actuation, the required torque and the direction of the contact force depend on the position of the roller that transmits the force directly to the shoes. To reduce the required torque, the lever arm that applies the contact force to the cam is made as small as possible, so that small position changes of the shoes and the rollers linked to them strongly affect the actuation torque. Therefore, this type of brake is usually implemented with several brake shoes supported at one pivot point, which ensures a uniform kinematics of the cam / roller mechanism regardless of wear and tolerances.

[0004] The patent US 2005 / 0133993 discloses a drum brake arrangement with a drum in which two brake shoes are arranged. The brake shoes are pivotably connected to one another at one end. S-shaped cams are arranged at the second ends of the brake shoes, which spread apart as a result of the rotation of the brake shoes, so that the brake shoes engage the drum and a braking action is obtained. The shaft of the cams is driven by an electric motor, which may be connected to the shaft via a planetary or worm gear or directly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 10001186B2 Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE DISCLOSURE The basic object of the invention is to provide an electromechanical drum brake for motor vehicles which is capable of compensating for the out-of-roundness and eccentricity of the drum brake and which has low mechanical complexity. [Means for solving the problem]

[0007] This problem is solved by an electromechanical drum brake for a motor vehicle, which has the subject matter of patent claim 1. Advantageous embodiments can be read from the dependent claims.

[0008] The present invention provides an electromechanical drum brake for a motor vehicle, which comprises a drum in which a number of brake shoes are arranged, and an adjusting device arranged between the brake shoes and driven by a drive unit, via which the brake shoes can be spread for braking. An end of each brake shoe facing the adjusting device is supported by a support means cooperating with the adjusting device and movable relative to the support means, in which the spreading force of the adjusting device can be transmitted to the brake shoes via the support means.

[0009] The adjusting device is a device capable of applying a force to the brake shoe so that the brake shoe rests against the drum. The adjusting device is preferably arranged at the upper end of the brake shoe. Advantageously, the drive unit has an electric motor. According to the invention, the spreading force is not applied directly from the adjusting device to the brake shoe, but to the support means. It is therefore only necessary that the support means rests rigidly against the adjusting device. Correspondingly, the brake shoe does not rest rigidly against the adjusting device. The brake shoe is supported only at the support means. The support means and the brake shoe are therefore not rigidly connected to each other, so that the brake shoe can move relative to the support means and take up an optimal position in the drum during the braking process. This makes it possible to compensate for the roundness and eccentricity of the drum brake. In addition, this results in uniform wear of the brake shoe. Thus, complex mechanical structures for compensating for the roundness and eccentricity can be omitted.

[0010] In a preferred embodiment of the invention, a support bearing is arranged on the end of the brake shoe facing away from the adjusting device, on which the brake shoe is movably supported. Such a support bearing is usually already provided in drum brakes. The brake shoe is also movable relative to this support bearing. Correspondingly, the brake shoe is not fixed in the drum, so that it can move during the braking process and thus compensate for eccentricity.

[0011] In a further advantageous embodiment of the invention, the support means is formed as a semi-ring-shaped spreading clamp. By forming the support means as a semi-ring-shaped spreading clamp, the amount of material required for the support means can be reduced, which reduces the additional weight required by the support means.

[0012] Preferably, a support bearing is arranged on the end of the brake shoe facing away from the adjusting device, on which the spreading clamp is rotatably supported. Such a support bearing is usually already provided in the drum brake. As a result, no additional parts are required to rotatably support the spreading clamp. This allows the weight of the drum brake to be reduced.

[0013] In a further advantageous embodiment, the brake shoes are fitted with at least one holding element which cooperates with the respective spreading clamp and by means of which the brake shoes can be held in the normal direction of the drum. In this case, the holding element is not rigidly fixed to the spreading clamp. The brake shoes together with the holding element can thus move relative to the spreading clamp. In this case, the holding element prevents the brake shoes from moving in the normal direction in the drum.

[0014] The holding element is preferably designed as a holding clamp, which can then be designed as a simple sheet metal component, so that the manufacturing costs and weight of the holding element are kept low.

[0015] According to an expedient embodiment, the spreading clamps have roller carriers at their ends facing the cams, on which rollers are arranged that are in contact with the cams. The rollers roll on the surfaces of the cams. The use of roller carriers on which the rollers are fixed therefore reduces the rotational resistance of the adjusting device. This allows the adjusting device to spread the brake shoes with less torque. Correspondingly, the electric motors for driving the adjusting device can be made more compact and therefore lighter.

[0016] In an advantageous embodiment, the adjusting device is configured as an S-shaped cam. The use of such a cam has the advantage that the widening can be achieved by a simple rotation of the cam. As a result, the gearing of the drive unit can be implemented as purely rotary. This cam makes it possible to dispense with complex and expensive components for the rotational and translational movements.

[0017] In a further advantageous embodiment, the adjustment path of the cam is designed such that it also includes the wear of the brake shoe. This type of design of the cam makes it possible to avoid a separate device for wear management. This reduces the complexity of the electromechanical drum brake. Similarly, the weight of the unsprung wheel can be reduced. Overall, this makes it possible to manufacture such an electromechanical drum brake more economically. In addition, the air gap of the brake can be arbitrarily adjusted depending on the driving state in order to achieve sufficient response dynamics of the brake with minimal losses due to excess drag in any situation.

[0018] According to a further expedient embodiment, the drive unit has a transmission unit that is formed without a locking mechanism. Therefore, the transmission unit does not have a self-locking mechanism. After braking, the brake linings can be automatically released again by the force generated in the drum via the spreading clamp. This allows the brake to be released in a current-free state, for example in a fault state. This allows such electromechanical drum brakes to be used as service brakes in passenger cars.

[0019] Preferably, the drive unit has a transmission unit which includes at least a worm gear stage and a spur gear stage, which have a high gear ratio and which on the other hand require a small construction space, so that a drive unit with such a worm gear stage and a spur gear stage can be used in the area of ​​the rim.

[0020] Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of an electromechanical drum brake according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the internal arrangement within the drum according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view of the electromechanical drum brake of FIG. 2 in the region of a cam. [Figure 4] FIG. 2 is a diagram of a support bearing according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 1 shows an overview of an electromechanical drum brake 10 according to an embodiment of the invention. The electromechanical drum brake 10 comprises a drive unit 14 and a drum 18. The drive unit 14 comprises an electric motor 22 which drives a transmission unit 26. The transmission unit 26 comprises a worm 30 which is driven by the electric motor 22, and which drives a number of spur gears 34 of the transmission unit 26. The drive unit 14 is mounted on a rear wall 38 of the drum 18. An adjustment device 42 arranged in the drum 18 is driven via the spur gear 34.

[0023] 2 shows a plan view of the internal arrangement in the drum 18 according to an embodiment of the invention. In this illustration, the drum 18 has been omitted for clarity. The figure also shows the adjustment device 42, which in this embodiment is formed as an S-shaped cam. The cam 42 cooperates with two support means 46, which in this embodiment are formed as spreader clamps. In this embodiment, the spreader clamps 46 are formed in the shape of a half ring. At the spreader clamp ends 50 facing towards the cams 42, a roller carrier 54 is respectively arranged, on which a roller 58 is fitted which cooperates with the cam 42. In this case, the roller 58 rolls on a surface 62 of the cam 42 and thus follows the contour of the cam 42.

[0024] At the end of the spreading clamp 46 facing away from the cam 42, the spreading clamp is rotatably supported on a support bearing 66. As a result of the rotation of the cam 42, the spreading clamp 46 performs a rotational movement around the support bearing 66 in the region of the cam 42. Correspondingly, the spreading clamp 46 is spread by the rotation of the cam 42. As a result of the spreading movement, the spreading clamp 46 exerts a spreading force F S The force F is applied to the brake shoe 70 disposed in the drum 18. S The force is applied to an end 72 of a brake shoe 70, which is directed towards the adjusting device 42. This end 72 of the brake shoe is movably supported in the spreading clamp 46. Correspondingly, the brake shoe 70 is brought into abutment against the drum 18 for braking.

[0025] Between the center M of the drum 18 and the spreading clamp 46, a holding element 74 is arranged for each brake shoe 70, via which the brake shoes 70 are supported in the normal direction N of the drum 18. T (See Figure 1) This allows the brake shoe to move in the normal direction N T In the embodiment shown, the retaining element 74 is configured as a retaining clamp. The retaining element 74 rests only against the spreading clamp 46. This ensures that the brake shoe 70 can move relative to the spreading clamp 46.

[0026] 3 shows a cross section of the electromechanical drum brake 10 of FIG. 2 in the region of the cam 42. It can be seen in this figure how the cam 42 acts on the spreading clamp 46 via the roller 58. At the spreading clamp end 50 facing the adjusting device 42, the spreading clamp 46 forms an upper stop 78 for the brake shoes 70. The brake shoes 70 are supported only by the respective upper stop 78 and are therefore supported movably in the region of the upper stop 78. Via this upper stop 78 and thus via the spreading clamp 46, a spreading force F S can also be given.

[0027] 4 shows a support bearing 66 according to an embodiment of the invention, which at its end 80 facing away from the adjusting device 42 forms a lower stop 82 for the brake shoe 70. The brake shoe 70 is also only supported at the lower stop 82, so that it is movable relative to the lower stop 82. Correspondingly, the brake shoe 70 only rests against the lower and upper stops 78, 82, so that the brake shoe 70 is not fixed in the drum 18 but can move. This makes it possible to compensate for the out-of-roundness and eccentricity of the drum brake 10. Compensation possibilities in the area of ​​the cam 42 can therefore be omitted. [Explanation of symbols]

[0028] 10 Drum brake 14 Drive unit 18 Drums 26 Transmission unit 42 Cam (adjustment device) 46 Expansion clamp (support means) 50 Spread clamp end 54 Roller carrier 58 Lola 66 Support bearing 70 Brake shoe 72 The end of the brake shoe that faces the adjustment device 74 Retaining clamp (retaining element) 80 The end of the brake shoe opposite the adjustment device F S Expansion force N T Normal direction of the drum

Claims

1. An electromechanical drum brake (10) for an automobile includes a drum (18) having a plurality of brake shoes (70) disposed therein, and an adjustment device (42) arranged between the plurality of brake shoes (70) and driven by a drive unit (14), the brake shoes (70) being capable of being spread apart for braking via the adjustment device (42), The end (72) of each brake shoe (70) facing the adjusting device (42) is supported by a support means (46) cooperating with the adjusting device (42) so as to be movable relative to the support means (46), and the spreading force (F) of the adjusting device (42) is transmitted through the support means (46). Ｓ ) to the brake shoe (70).

2. 2. The electromechanical drum brake (10) according to claim 1, characterized in that a support bearing (66) is arranged at an end (80) of the brake shoe (70) opposite the adjusting device (42), and the brake shoe (70) is movably supported by the support bearing (66).

3. 3. An electromechanical drum brake (10) according to claim 1 or 2, characterized in that the support means (46) is formed as a half-ring-shaped spreading clamp (46).

4. 4. The electromechanical drum brake (10) according to claim 3, characterized in that a support bearing (66) is arranged at an end (80) of the brake shoe (70) opposite the adjusting device (42), and the expansion clamp (46) is rotatably supported by the support bearing (66).

5. At least one holding element (74) is attached to the brake shoe (70) which cooperates with each of the spreading clamps (46) and through which the brake shoe (70) is held in a normal direction (N Ｔ 5. The electromechanical drum brake (10) according to claim 3 or 4, characterized in that it can be held on a bearing.

6. 6. The electromechanical drum brake (10) according to claim 5, characterized in that the retaining element (74) is formed as a retaining clamp.

7. 7. The electromechanical drum brake (10) according to claim 3, characterized in that the spreading clamps (46) have, at their spreading clamp ends (50) facing towards the cam (42), respectively, roller carriers (54), on which roller carriers (54) are arranged rollers (58) which are in contact with the cam (42).

8. 8. An electromechanical drum brake (10) according to claim 1, characterized in that the adjusting device (42) is designed as an S-cam.

9. 9. The electromechanical drum brake (10) according to claim 8, characterized in that the adjustment path of the cam (42) is designed such that it also takes into account the wear of the brake shoe (70).

10. 10. The electromechanical drum brake (10) according to claim 1, characterized in that the drive unit (14) has a transmission unit (26) which is formed without a locking mechanism.

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