Electromechanical drum brake

Abstract

The invention relates to an electromechanical drum brake (10) for a motor vehicle. The electromechanical drum brake (10) comprises: a brake drum (18) in which a plurality of brake shoes (70) are arranged; and an adjusting device (42) arranged between the brake shoes (70) and driven by a drive unit (14), by means of which adjusting device the brake shoes (70) can be expanded for braking. An end (72) of each brake shoe (70) directed towards the adjusting device (42) is supported on a supporting means (46) interacting with the adjusting device (42) in a displaceable manner relative to the supporting means (46), and an expansion force (FS) of the adjusting device (42) can be transmitted to the brake shoe (70) via the supporting means (46).

Description

Technical Field

[0001] The invention relates to an electromechanical drum brake for a motor vehicle. Background Art

[0002] Drum brakes with different types of actuation are known in today's vehicles. In passenger cars, drum brakes are usually hydraulically actuated. Here, hydraulic pressure builds up in a double piston and then spreads out, generating a force on each brake shoe of the drum brake. Since the pistons are guided axially, a slightly eccentric application of force on the piston face is relatively problem-free. The brake shoes are therefore usually positioned only roughly by means of a support seat and a return spring and can determine their position within the brake drum depending on tolerances and wear conditions.

[0003] In trucks, driving by rotating S-shaped cam is a common driving form. Here, the cam firmly supported on the back plate rotates a certain angle by pneumatic drive, thereby expanding the shoe. For this type of drive, the direction of the torque required and the contact force directly depends on the position of the roller that transmits the force to the shoe. Because the lever arm used for the contact force acting on the cam is kept as small as possible to keep the required lower torque, the slight change of the position of the shoe and the roller related to the shoe can have a strong impact on the driving torque. Therefore, this type of brake is usually designed to support the brake shoe on the fulcrum support (Drehpunktlagerung), thereby ensuring that the kinematics of the cam / roller mechanism is consistent, regardless of wear and tolerance.

[0004] Document US10,001,186B2 discloses a drum brake device with a brake drum, in which two brake shoes are arranged. At one end of the brake shoes, they are pivotally connected to each other. An S-shaped cam is arranged between the second ends of the brake shoes, which expands the brake shoes away from each other by rotation, so that the brake shoes engage with the brake drum and achieve a braking effect. The shaft of the cam is driven by an electric motor. Here, the electric motor can be connected to the shaft via a planetary gear transmission or a worm gear transmission, or directly connected to the shaft. Summary of the invention

[0005] The object of the present invention is to provide an electromechanical drum brake for a motor vehicle with which out-of-roundness and eccentricity of the drum brake can be compensated and which has a low mechanical complexity.

[0006] This object is achieved by an electromechanical drum brake for a motor vehicle having the subject matter of patent claim 1. Preferred embodiments are described in the dependent claims.

[0007] The invention provides an electromechanical drum brake for a motor vehicle. The electromechanical drum brake comprises a brake drum in which brake shoes are arranged, and an adjustment device arranged between the brake shoes and driven by a drive unit, by which the brake shoes can be expanded to achieve braking. The end of each brake shoe pointing to the adjustment device is supported on a support device that interacts with the adjustment device in a manner that it can move relative to the support device, wherein the expansion force of the adjustment device can be transmitted to the brake shoe via the support device.

[0008] The adjusting device is a device capable of applying a force to the brake shoe so that the brake shoe rests on the brake drum. The adjusting device is preferably arranged at the upper end of the brake shoe. The drive unit preferably comprises an electric motor. According to the present invention, the expansion force is not applied directly from the adjusting device to the brake shoe, but to the supporting device. Therefore, only the supporting device must rest firmly on the adjusting device. Accordingly, the brake shoe does not rest firmly on the adjusting device. The brake shoe is only supported on the supporting device. Therefore, the supporting device and the brake shoe are not firmly connected to each other, so that the brake shoe can move relative to the supporting device and can occupy the best position in the brake drum during the braking process. Thereby, the out-of-roundness and eccentricity of the drum brake can be compensated. This also leads to more uniform wear of the brake shoe. Thereby, a complex mechanical structure can be omitted to compensate for out-of-roundness and eccentricity.

[0009] In a preferred embodiment of the present invention, a support seat is provided at the end of the brake shoe facing away from the adjustment device, and the brake shoe is movably supported on the support seat. Such a support seat is usually already provided in drum brakes. The brake shoe can also be moved relative to the support seat. Therefore, the brake shoe is not fixed in the brake drum, so that the brake shoe can move during braking and thus compensate for eccentricity.

[0010] In another preferred embodiment of the present invention, the support means is configured as a semi-annular expansion jaw. By configuring the support means as a semi-annular expansion jaw, the material requirement for configuring the support means can be kept low. This can reduce the additional weight required for the support means.

[0011] Preferably, a support seat is provided at the end of the brake shoe facing away from the adjustment device, on which the expansion caliper is rotatably supported. Such a support seat is usually already provided in drum brakes. As a result, no additional components are required for rotatably supporting the expansion caliper. As a result, the weight of the drum brake can be kept low.

[0012] In an advantageous development, at least one retaining element is attached to the brake shoe and interacts with the corresponding expansion pliers, by means of which the brake shoe can be retained in the normal direction of the brake drum. In this case, the retaining element is not fixedly attached to the expansion pliers. The brake shoe together with the retaining element can therefore be moved relative to the expansion pliers. The retaining element prevents the brake shoe from moving in the normal direction in the brake drum.

[0013] The holding element is advantageously designed as a holding clamp. Such a holding clamp can be designed as a simple sheet metal part. This keeps the manufacturing costs and weight of the holding element low.

[0014] According to a suitable embodiment, the expansion pliers each have a roller support at the expansion pliers end pointing toward the cam, on which rollers are arranged that contact the cam. Here, the rollers roll on the surface of the cam. By using a roller support to which the rollers are fixed, the rotational resistance of the adjustment device can be reduced. As a result, the adjustment device can expand the brake shoe with a smaller torque. As a result, the electric motor used to drive the adjustment device can be designed to be smaller and therefore also lighter.

[0015] The adjusting device is advantageously designed as an S-shaped cam. The advantage of using such a cam is that the expansion can be achieved by simply turning the cam. Therefore, the transmission of the drive unit can be designed as a purely rotary drive. The cam can save complex and expensive components for the rotation-translation conversion.

[0016] In another advantageous embodiment, the adjustment path of the cam is designed in such a way that it takes into account the wear of the brake shoe. By designing the cam in this way, a separate device for adjusting the wear can be omitted. The complexity of the electromechanical drum brake can thereby be reduced. At the same time, the weight of the unsprung wheel can be reduced. Overall, such an electromechanical drum brake can thus be produced more economically. In addition, the air gap of the brake can be adjusted as desired depending on the driving situation in order to minimize the losses caused by the residual resistance in each case and to achieve adequate brake response dynamics.

[0017] According to another advantageous embodiment, the drive unit has a transmission unit which is designed without latching. The transmission unit is therefore not self-locking. After braking, the brake pad can be released again automatically by the force generated in the brake drum by the expansion caliper. As a result, the brake can be disconnected in the de-energized state (e.g., in the event of a fault). Such an electromechanical drum brake can therefore also be used as a service brake in a passenger car.

[0018] The drive unit preferably has a transmission unit which comprises at least one worm stage and a spur gear stage. Such a worm stage and a spur gear stage have a high transmission ratio and require little installation space. Thus, a drive unit having such a worm stage and a spur gear stage can be used in the wheel rim region. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.

[0020] in:

[0021] Figure 1 A schematic diagram showing an electromechanical drum brake according to an embodiment of the present invention is shown;

[0022] Figure 2 A top view showing the internal arrangement in a brake drum according to an embodiment of the present invention;

[0023] Figure 3 Shown according to Figure 2 a sectional view in the cam region of an electromechanical drum brake; and

[0024] Figure 4 A support base according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0025] Figure 1 A schematic diagram of an electromechanical drum brake 10 according to an embodiment of the invention is shown. The electromechanical drum brake 10 comprises a drive unit 14 and a brake 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 driven by the electric motor 22, which drives a plurality of spur gears 34 of the transmission unit 26. The drive unit 14 is attached to a rear wall 38 of the brake drum 18. An adjustment device 42 arranged in the brake drum 18 is driven via the spur gears 34.

[0026] Figure 2 A top view of the internal arrangement in a brake drum 18 according to an embodiment of the invention is shown. In this view, the brake drum 18 has been omitted for better visibility. The figure also shows an adjustment device 42, which is designed as an S-shaped cam in this embodiment. Here, the cam 42 interacts with two support means 46, which are designed as expansion pliers in this embodiment. In this embodiment, the expansion pliers 46 are designed in a semi-annular shape. A roller support 54 is arranged at each of the expansion pliers ends 50 pointing toward the cam 42, to which rollers 58 that interact with the cam 42 are attached. Here, the rollers 58 roll on the surface 62 of the cam 42 and thus follow the contour of the cam 42.

[0027] At the end of the expansion pliers 46 facing away from the cam 42, the expansion pliers are rotatably supported on a support seat 66. By rotating the cam 42, the expansion pliers 46 perform a rotational movement around the support seat 66 in the region of the cam 42. Thus, the expansion pliers 46 are expanded by rotating the cam 42. The expansion pliers 46 exert an expansion force F on the brake shoe 70 arranged in the brake drum 18 by the expansion movement. S Here, the expansion force F S The force is applied to the end 72 of the brake shoe 70 directed toward the adjustment device 42. The end 72 of the brake shoe is movably supported on the expansion caliper 46. Therefore, the brake shoe 70 is pressed against the brake drum 18 for braking.

[0028] A retaining element 74 is arranged on each brake shoe 70 between the center point M of the brake drum 18 and the expansion caliper 46 , through which the retaining element 74 is arranged in the normal direction N of the brake drum 18 . T (See Figure 1 ) to hold the brake shoe 70. This prevents the brake shoe from moving in the normal direction N in the brake drum. T In the embodiment shown here, the retaining element 74 is configured as a retaining caliper. Here, the retaining element 74 only abuts against the expansion caliper 46. This ensures the relative mobility of the brake shoe 70 relative to the expansion caliper 46.

[0029] Figure 3 Shows Figure 2 4. A sectional view of an electromechanical drum brake 10 in the region of a cam 42. In this figure, it can be seen how the cam 42 acts on the expansion jaws 46 via the rollers 58. The expansion jaws 46 form an upper stop 78 for the brake shoe 70 at the expansion jaw end 50 pointing toward the adjustment device 42. In this case, the brake shoe 70 is supported only on the corresponding upper stop 78 and is therefore movably supported in the region of the upper stop 78. As a result, the expansion force F S It is also possible to act on the brake shoe 70 via the expansion pliers 46 via the upper stop 78 .

[0030] Figure 4 The support seat 66 according to an exemplary embodiment of the invention is shown. The support seat 66 forms a lower stop 82 for the brake shoe 70 at the end 80 of the brake shoe 70 facing away from the adjustment device 42. The brake shoe 70 is also supported only on the lower stop 82, so that the brake shoe is movable relative to the lower stop 82. Therefore, the brake shoe 70 only rests on the upper stop 78 and the lower stop 82, so that the brake shoe 70 is not fixed in the brake drum 18 and can be moved. In this way, out-of-roundness and eccentricity of the drum brake 10 can be compensated. Therefore, a compensation solution in the area of ​​the cam 42 can be omitted.

Claims

1. An electromechanical drum brake (10) for a motor vehicle, the electromechanical drum brake comprising: a brake drum (18) in which a plurality of brake shoes (70) are arranged; as well as an adjusting device (42) arranged between the brake shoes (70) and driven by a drive unit (14), through which the brake shoes (70) can be expanded to achieve braking, It is characterized in that The end (72) of each brake shoe (70) pointing toward the adjusting device (42) is supported on a support element (46) interacting with the adjusting device (42) in a manner movable relative to the support element (46), wherein the expansion force (F S ) can be transmitted to the brake shoe (70) via the supporting device (46).

2. The electromechanical drum brake (10) according to claim 1, characterized in that A support seat (66) is arranged at the end (80) of the brake shoe (70) facing away from the adjustment device (42), and the brake shoe (70) is movably supported on the support seat.

3. The electromechanical drum brake (10) according to claim 1 or 2, characterized in that The supporting means (46) is designed as a semi-annular expansion jaw (46).

4. The electromechanical drum brake (10) according to claim 3, characterized in that A support seat (66) is arranged at the end (80) of the brake shoe (70) facing away from the adjustment device (42), on which the expansion jaws (46) are rotatably supported.

5. The electromechanical drum brake (10) according to claim 3 or 4, characterized in that At least one retaining element (74) is attached to the brake shoe (70) and interacts with a corresponding expansion caliper (46), and can be used in a normal direction (N) of the brake drum (18) via the retaining element. T ) to hold the brake shoe (70).

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

7. An electromechanical drum brake (10) according to any one of claims 3 to 6, characterized in that The expansion jaws (46) each have a roller support (54) at the expansion jaw ends (50) pointing toward the adjusting device (42), on which rollers (58) are arranged that are in contact with the adjusting device (42).

8. An electromechanical drum brake (10) according to any one of the preceding claims, characterized in that The adjusting device (42) is designed as an S-shaped cam.

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 takes into account the wear of the brake shoe (70).

10. An electromechanical drum brake (10) according to any one of the preceding claims, characterized in that The drive unit (14) has a transmission unit (26) which is designed to be non-locking.

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