Electromechanical drum brake

Abstract

To provide an electromechanical drum brake which has an improved braking effect and requires less cost.SOLUTION: An electromechanical drum brake according to the present invention includes: a drum, in which brake shoes are disposed; and an adjusting device (42), which is disposed between the brake shoes and driven by a drive unit, through which the brake shoes can be spread apart for braking. The adjusting device includes a rack (66) driven by the drive unit, is floatingly mounted between the brake shoes and is in engagement with a coupling gear (74) that acts on a first brake shoe via a thrust rod (82) connected to the coupling gear. An actuating rack (94) which acts on a second brake shoe is in engagement with the coupling gear on a side of the coupling gear opposite to the rack, and the coupling gear can move freely on the rack between the brake shoes so that force differences that occur between the brake shoes can be compensated by rotation of the coupling gear.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electromechanical drum brake for automobiles. Furthermore, the present invention relates to an automobile having such an electromechanical drum brake.

Background Art

[0002] In today's automobiles, drum brakes having various actuation modes are known. In passenger cars, drum brakes are generally actuated hydraulically. In this case, hydraulic pressure is generated within a double piston, whereby this double piston is expanded, whereby force acts on each brake shoe of the drum brake. By means of a configuration having pistons that are movably connected on both sides via a fluid, it is ensured that the forces acting on the two brake shoes are always of the same magnitude. For future passenger cars, hydraulic actuation can be replaced by electromechanical actuation. With mechanical actuation, a greater variety of variations can be obtained.

[0003] In the truck field, drum brakes are generally pneumatically controlled. In this case, pneumatic pistons are arranged outside the brake, whereby the original actuation is mechanically performed. In such a structure, the actuation is carried out by an S-cam and a wedge member. In such a structure, generally, the brake shoes perform an actuation of the same stroke without force correction. In mechanical actuation, generally, it is necessary to ensure actuation with force correction by incurring significantly high mechanical costs. This is because it is generally necessary to guarantee low-friction movement of individual parts of the actuator device by means of additional mechanical components and it cannot be achieved via pressure correction within a hydraulic fluid as in hydraulic braking.

[0004] According to Patent Document 1, an electromechanical drum brake device is disclosed that includes a drum in which two brake shoes are disposed inside. At one end of the brake shoes, these brake shoes are rotatably connected to each other. An S-shaped cam is disposed between the second ends of these brake shoes, and by rotating this cam, these brake shoes are expanded apart from each other, whereby these brake shoes engage with the drum and a braking action is obtained. The shaft of the cam is driven via an electric motor. In this case, the electric motor may be directly connected to a planetary gear transmission, a worm gear transmission, or the shaft.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem underlying the present invention is to provide an electromechanical drum brake having an improved braking action and requiring relatively little structural cost.

Means for Solving the Problems

[0007] This problem is solved by an electromechanical drum brake having the subject matter according to claim 1. Preferred embodiments can be read from the dependent claims.

[0008] The present invention provides an electromechanical drum brake for an automobile. The electromechanical drum brake has a drum inside which a plurality of brake shoes are arranged, and an adjusting device arranged between these brake shoes and driven by a drive unit, through which the brake shoes can be expanded for braking. The adjusting device has a rack that is floatingly supported between the brake shoes and driven by a drive unit, and this rack meshes with a connecting gear, and the connecting gear acts on a first brake shoe via a thrust rod connected to this connecting gear. An actuating rack that acts on a second brake shoe is adapted to mesh with the connecting gear on the side of the connecting gear facing the rack, and the connecting gear can move freely between the brake shoes on the rack, whereby the difference in the forces generated between the brake shoes can be corrected by the rotation of the connecting gear.

[0009] The adjusting device is a device that can apply a force to the brake shoes, thereby pressing these brake shoes against the drum. The adjusting device is arranged in a suitable form at the upper end of the brake shoes. Preferably, the drive unit has an electric motor. The floating support is interpreted as meaning that the rack is not firmly fixed to the drum but is movable relative to the drum, for example via bearings. In this case, the rack is movable along its longitudinal direction and thus moves between the brake shoes. The connecting gear is also freely movable between the brake shoes.

[0010] The connecting gear is correspondingly moved between the brake shoes, thereby obtaining a force balance between the brake shoes. As a result, it is possible to correct the tolerance and eccentricity within the drum brake. As a result, the brake shoes can be optimally applied to the drum, so that the brake shoes can exhibit their self-increasing characteristics. As a result, the braking effect of the drum brake is improved. By correcting the force applied to the brake shoes, the supporting force existing in the adjusting device is significantly reduced. As a result, the mechanical strength is significantly reduced, and a support that can be implemented more easily becomes possible. As a result, the structural cost for such a drum brake can be reduced.

[0011] By means of the connecting gear, not only is there a means to press the brake shoes against each other, but also a tensile force can be applied to the brake shoes by correspondingly controlling the rack. Therefore, the brake shoes can be released from the drum after the braking process. As a result, dragging of the brake shoes after the braking process can be avoided. Also, it is possible to release the stuck brake shoes that may occur after a relatively long stop phase in the drum brake.

[0012] In a preferred configuration of the present invention, the connecting gear is configured as a multiple gear, and the rack and the actuating rack mesh with different ring gears of the multiple gear respectively, thereby forming a transmission device. As a result, the ring gear can be designed according to the desired requirements. As a result, the variability for driving the actuating rack and driving the connecting gear is increased.

[0013] In another preferred configuration of the present invention, the actuating rack is configured in a fork shape within the region of the connecting gear, and each part of the actuating rack configured in a fork shape meshes with a ring gear having the same number of teeth. The fork-shaped configuration of the actuating rack is interpreted as the actuating rack being divided along its longitudinal direction, and these two parts of the actuating rack being spaced apart from each other. In this case, the fork-shaped actuating rack meshes symmetrically with the connecting gear. Accordingly, it is possible to avoid torque being applied to the connecting gear during the braking process. Further, through the fork-shaped meshing of the actuating rack and the connecting gear, additional support of the connecting gear may be omitted. Thereby, the structural configuration of the electromechanical drum brake configured in this way is simplified.

[0014] In a preferred form, the thrust rod has a joint, and this joint enables the movement of the thrust rod that is orthogonal to the rotational axis of the connecting gear and orthogonal to the extending direction of the thrust rod. Accordingly, the thrust rod is not fixedly arranged on the connecting gear. Since the brake shoe moves within the drum during the braking process, this mobility is ensured through such a joint. Thereby, the brake shoe can occupy an optimal position within the drum to improve the braking effect.

[0015] In a preferred development, the drive unit is driven in a torque-controlled manner. By the drive unit controlling torque instead of stroke, it can be ensured that a predefined braking force is continuously applied to the brake shoe. Similarly, the wear of the brake lining arranged on the brake shoe is corrected thereby.

[0016] In a preferred form, the rack is driven via a drive pinion having a smaller diameter than the connecting gear. Also, by using a smaller drive pinion, a smaller electric motor having a smaller weight can be used. Thereby, the total weight and size of the electromechanical brake can also be reduced.

[0017] In a further preferred configuration, the actuating rack is configured to apply a force to the second brake shoe at the height of the axis of the connecting gear. Due to the corresponding configuration of the actuating rack, the force of the thrust rod and the force of the actuating rack are located at the same height. This avoids torque being applied to the connecting gear. Such torque would cause an uneven distribution of forces in the brake shoe. The corresponding configuration improves the force balance between the brake shoes.

[0018] The invention further provides a motor vehicle having an electromechanical drum brake according to the invention. Such a motor vehicle has the advantages and functions described above.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0020] Embodiments of the invention are shown in the drawings and are described in detail in the following description.

[0021] FIG. 1 shows an electromechanical drum brake 10 according to an embodiment of the invention. The electromechanical drum brake 10 has a drive unit 14, which is arranged on the rear wall 18 of the drum 22. The drive unit 14 has an electric motor 26, which drives a transmission unit 30. The transmission unit 30 is driven on the input side by a worm 34 protruding from the electric motor 26. The transmission unit 30 is composed of a plurality of spur gears 38. The transmission unit 30 drives the adjusting device 42 of the drum 22 on the output side.

[0022] Figure 2 shows a view of the drum 22 according to an embodiment of the present invention. The adjusting device 42 shown in FIG. 1 has already been arranged inside the drum 22. Further, brake shoes 46 are arranged inside the drum 22, and these brake shoes 46 cooperate with the drum 22 for braking. In this case, the adjusting device 42 is provided at the upper end portion 50 of the brake shoe 46. For braking, the adjusting device 42 acts on the brake shoe 46, whereby these brake shoes 46 are expanded and pressed against the drum 22. A support element 58 is arranged at the lower end portion 54 of the brake shoe 46, and two brake shoes 46 are connected via this support element 58. Further, a spring 62 is arranged between the brake shoes 46, and via this spring 62, the brake shoes 46 can be released from the drum 22 after the braking process.

[0023] Figure 3 shows a view of the adjusting device 42 according to an embodiment of the present invention. The adjusting device 42 has a rack 66 supported in a floating state, and this rack 66 meshes with a drive pinion 70. In this case, the drive pinion 70 is driven via a drive unit 14. Due to the rotation of the drive pinion 70, the rack 66 is movable between the brake shoes 46. The adjusting device 42 further has a connecting gear 74 that meshes with the rack 66. A thrust rod 82 is arranged on the shaft 78 of the connecting gear 74, and this thrust rod 82 acts on the first brake shoe 46a of the drum brake 10.

[0024] In the embodiment shown here, the connecting gear 74 is configured as a multi-gear. In this case, the first ring gear 86 that meshes with the rack 66 has a diameter d1 that is larger than the diameter d2 of the second ring gear 90. Due to the different diameters, a transmission is formed. In the embodiment shown here, the diameter d of the drive pinion 70 R is smaller than the diameter d1 of the first ring gear 86. Thereby, the size of the electric motor 26 and the associated weight can be reduced.

[0025] The adjusting device 42 further has an actuating rack 94, which meshes with a second ring gear 90 on the side of the connecting gear 74 facing the rack 66. The actuating rack 94 has a bent section 98, and a section 102 acting on the second brake shoe 46b applies a force F A to the second brake shoe 46b at the height of the shaft 78. Thereby, torque is prevented from being applied to the second ring gear 90. In this case, the force F A of the actuating rack 94 D is located at the same height as the force F A of the thrust rod 82. Accordingly, the correction of the force F D , F

[0026] FIG. 4 shows a perspective view of the adjusting device 42 shown in FIG. 3. Here, it can be seen that the actuating rack 94 is configured in a fork shape within the region of the connecting gear 74. In this case, the actuating rack 94 meshes with the second ring gear 90 on both sides of the first ring gear 86. Correspondingly, the second ring gear 90 is arranged on both sides of the first ring gear 86. Thereby, torque is prevented from being applied to the connecting gear 74. In the embodiment shown here, the thrust rod 82 has a joint 106, and through this joint 106, movement orthogonal to the shaft 78 of the connecting gear 74 and movement orthogonal to the extending direction of the thrust rod 82 are possible. Through this joint 106, the movement of the brake shoe 46 can be corrected.

Explanation of Reference Signs

[0027] 10 Drum brake 14 Drive unit 18 Rear wall 22 Drum 26 Electric motor 30 Transmission unit 34 Worm 38 Spur gear 42 Adjusting device 46 Brake shoe 46a First brake shoe 46b Second brake shoe 50 Upper end 54 Lower end 58 Support element 62 Spring 66 Rack 70 Driving pinion 74 Connecting gear 82 Thrust rod 86 First ring gear 90 Second ring gear 94 Actuating rack 98 Bending section 106 Joint F A Force of the actuating rack 94 F D Force of the thrust rod 82 d1 Diameter of the first ring gear d R Diameter of the driving pinion 70

Claims

1. 1. An electromechanical drum brake (10) for a motor vehicle, comprising a drum (22) having a number of brake shoes (46) arranged therein, and an adjusting device (42) arranged between the brake shoes (46) and driven by a drive unit (14), the adjusting device (42) enabling the brake shoes (46) to be spread apart for braking, 1. An electromechanical drum brake for a motor vehicle, comprising: a rack (66) supported in a floating manner between the brake shoes (46) and driven by the drive unit (14), the rack (66) meshing with a connecting gear (74) which acts on a first brake shoe (46a) via a thrust rod (82) connected to the connecting gear (74), wherein an operating rack (94) acting on a second brake shoe (46b) meshes with the connecting gear (74) on a side of the connecting gear (74) facing the rack (66), the connecting gear (74) being freely movable between the brake shoes (46) on the rack (66), whereby a force difference occurring between the brake shoes (46) can be compensated for by rotation of the connecting gear (74).

2. 2. The electromechanical drum brake (10) of claim 1, wherein the connecting gear (74) is configured as a multiple gear, and the rack (66) and the operating rack (94) mesh with different ring gears (86, 90) of the multiple gear, thereby forming a transmission.

3. 3. The electromechanical drum brake (10) according to claim 2, characterized in that the actuating rack (94) is configured in a fork-like manner in the region of the connecting gear (74), each portion of the fork-like actuating rack (94) meshing with a ring gear (90) having the same number of teeth.

4. 4. The electromechanical drum brake (10) of claim 1, wherein the thrust rod (82) has a joint (106) that allows movement of the thrust rod (82) perpendicular to the axis (78) of the connecting gear (74) and perpendicular to the extension direction of the thrust rod (82).

5. 5. The electromechanical drum brake (10) according to claim 1, wherein the drive unit (14) is driven in a torque-controlled manner.

6. 6. The electromechanical drum brake (10) according to claim 1, wherein the rack (66) is driven via a drive pinion (70) having a smaller diameter than the connecting gear (74).

7. The actuation rack (94) exerts a force (F Ａ 7. The electromechanical drum brake (10) according to claim 1, further comprising a brake shoe (46b) configured to apply a force of 0.1 V to the second brake shoe (46b).

8. 8. A motor vehicle comprising an electromechanical drum brake (10) according to any one of claims 1 to 7.

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