Electromechanical drum brakes and automobiles equipped with such drum brakes

Abstract

The present invention relates to an electromechanical drum brake (10) for automobiles. [Solution] This drum brake (10) has two brake shoes (18) and an actuator (26) positioned between these brake shoes (18), and pressure can be applied to the brake shoes (18) via the actuator (26), thereby causing the brake shoes (18) to be pressed against the drum (14) for braking. In this case, at least one means (42, 72, 86) is provided that is in conjunction with the actuator (26) and each of the brake shoes (18), thereby allowing the actuator (26) to move in a load-reducing direction (64) to apply a tensile force to the brake shoes (18).

Description

Technical Field

[0001] The present invention relates to an electromechanical drum brake for an automobile. The present invention additionally relates to an automobile having such a drum brake.

Background Art

[0002] In a drum brake, a semi-circular brake shoe is pressed against a cylindrical drum via an electromechanical actuator. Thereby, a braking force is applied to the drum. Drum brakes are often also used as parking brakes, in which the brake shoe remains in contact with the drum to continuously brake the automobile. Since drum brakes do not require brake fluid, the braking force does not decrease due to leakage during stopping.

[0003] As devices in automobiles are becoming increasingly electrified, drum brakes are becoming more attractive again. This is because it is possible to dispense with brake fluid and the costly valve structure and pipeline structure associated therewith. Similarly, maintenance costs can be significantly reduced by such electromechanical brakes.

[0004] Patent Document 1 discloses an electromechanically operable parking brake for an automobile, configured as a drum brake. In this case, the drum brake has two crescent-shaped brake shoes, which are located within a drum. An expanding element is positioned between the upper ends of the two brake shoes, and through this expanding element, the two brake shoes are pressed apart to brake by contacting the drum. The expanding element has a spindle drive unit, which is driven by an electric motor via a reduction gear transmission. A floating support device is positioned between the lower ends of the two brake shoes. Additionally, a tension coil spring is positioned between the brake shoes, and through this tension coil spring, the brake shoes are pulled back to their initial position after braking. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102008045693 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide an electromechanical drum brake for automobiles that has improved release capability of the brake shoe from the drum. [Means for solving the problem]

[0007] This problem is solved by an electromechanical drum brake for an automobile having the subject matter of claim 1. Preferred embodiments are described in the dependent claims.

[0008] The present invention provides an electromechanical drum brake for an automobile. This electromechanical drum brake has two brake shoes and an actuator positioned between these brake shoes, through which pressure can be applied to the brake shoes, thereby causing the brake shoes to press against the drum for braking. At least one means is provided that is in conjunction with the actuator and each brake shoe, thereby allowing a tensile force to be applied to the brake shoes by moving the actuator in a load-reducing direction.

[0009] The brake shoe is preferably positioned facing the drum. In this case, the motion in the load-reducing direction is the motion that reduces the braking force in the direction toward the drum. Generally, the motion of the actuator in the load-reducing direction creates a gap between the brake shoe and the drum. This means is preferably a structural embodiment that can be formed via another component, through which the tensile force of the actuator can be transmitted to the brake shoe. However, due to the large surface area of ​​the brake shoe, it may freeze to the drum or adhere to the drum due to corrosion. Despite the motion of the actuator in the load-reducing direction, according to the prior art, the brake shoe may not be released from the drum. At startup, a driving torque is applied to the brake lining, which may produce a perceptible release shock, causing the vehicle to move forward or backward.

[0010] The tensile force applied by the actuator according to the present invention ensures that the brake shoe is reliably released from the drum even when the actuator is moving in the load-reducing direction. In this case, the tensile force is sufficient to release even brake shoes that are frozen or seized due to corrosion. This avoids the release shock when the vehicle is started.

[0011] In a preferred configuration, the brake shoe is movable relative to the actuator in a direction of brake shoe motion perpendicular to the load reduction direction. In this case, the direction of brake shoe motion is preferably also perpendicular to the axial direction of the drum. Because the brake shoe is movable relative to the actuator, the actuator is not rigidly coupled to the brake shoe. Therefore, the brake shoe is free to move up and down. This has the advantage that the brake shoe can be pressed into an ideal position within the drum. This ensures uniform surface pressure along the entire friction surface, even if the ideal position changes during operation due to thermal expansion or wear. This allows the brake shoe to follow a drum that wobbles in an elliptical or eccentric manner.

[0012] According to a preferred embodiment of the present invention, there is play between the means and the actuator, or between the means and each brake shoe, and this play can be reduced in the load-reducing direction via the movement of the actuator. In this case, the play is interpreted in a structural form, and through this structural form, the means applies a tensile force to the brake shoe only after the stroke of the actuator in the load-reducing direction, defined by the play. This prevents the application of a tensile force at the start of the actuator's movement in the load-reducing direction. This further allows the brake shoe to be pulled back via the return spring. However, if the force of the return spring is insufficient, the means applies a tensile force, which ensures that the brake shoe is reliably released from the drum. Therefore, this function is not affected by the means during normal operation of the drum brake.

[0013] In another preferred embodiment of the present invention, the actuator has a mushroom-head shaped end that interlocks with a groove in the brake shoe. This groove is preferably configured in a T-shape. In this case, since the groove interlocks with the mushroom-head shaped end, the mushroom-head shaped end pulls the brake shoe back through the groove during movement in the load-reducing direction. Thus, only minor modifications are required to solve the problems of the present invention compared to the prior art. As a result, drum brakes configured in this way can be manufactured economically.

[0014] In a preferred configuration, the means is configured as a U-shaped clamp, where a first leg is connected to the brake shoe and a second leg is connected to the actuator. In this case, the U-shaped clamp connects the actuator and the brake shoe, allowing tensile force to be transmitted to the brake shoe. Such a clamp has the advantage of connecting the brake shoe and the actuator by simple means. This makes such a drum brake economically feasible to manufacture. Similarly, it can be appropriately added to existing drum brakes.

[0015] According to a preferred embodiment, the actuator has a piston that can slide in the axial direction. In this case, the actuator may be configured, for example, as a spindle drive. Since various such systems already exist, there is no need to change the basic principle of the drum brake.

[0016] In a preferred configuration, the actuator is configured as an S-shaped cam. The S-shaped cam, also known as an S-cam, is another configuration of a drum brake already known. Since the present invention can also be used for such drum brakes, such drum brakes only require minor modifications. Therefore, the present invention is economically applicable to such drum brakes as well.

[0017] In another preferred embodiment, the actuator is configured as a wedge-shaped member. The wedge shape of the actuator causes the brake shoe to move toward the drum. This type of drum brake is often used for LkW (truck) brakes. The applicability of the present invention for such brakes provides a wide range of applications.

[0018] In a preferred embodiment, the means is configured as a cable, which can be tensioned by the rotation of an S-shaped cam in the load-reducing direction. Preferably, the cable is made of steel so that sufficient tensile force can be applied. In this case, the cable is particularly advantageously wound around the shaft of the actuator so that the cable can be tensioned by the rotation of the cam in the load-reducing direction. Preferably, the cable is unloaded during normal operation of the drum brake, thereby creating slack. The cable is then tensioned only after the brake shoe remains fixed to the drum. Thus, the cable creates a configuration with less mechanical complexity. Such a configuration allows for the addition of an S-shaped cam to an existing drum brake in a simple manner.

[0019] According to another preferred embodiment, the cable is elastic. In other words, since the cable has a spring constant, a tensile force accompanied by motion in the load-reducing direction can only be increased continuously. Therefore, it can be carefully released from the drum.

[0020] The present invention further provides an automobile having such an electromechanical drum brake. Such an automobile has the aforementioned advantages. [Brief explanation of the drawing]

[0021] [Figure 1] This diagram shows a drum brake using conventional technology. [Figure 2] This is a partial view of a drum brake according to the first embodiment of the present invention. [Figure 3] Partial view of a drum brake according to the second embodiment of the present invention. [Figure 4] Partial view of a drum brake according to the third embodiment of the present invention. [Figure 5] Partial view of a drum brake according to the fourth embodiment of the present invention. [Figure 6] Partial view of a drum brake according to the fifth embodiment of the present invention.

Mode for Carrying Out the Invention

[0022] Multiple embodiments of the present invention are shown in the drawings and will be described in detail below.

[0023] In FIG. 1, a drawing of a drum brake 10 according to the prior art is shown. The drum brake 10 has a drum 14, and two semi-circular brake shoes 18 facing each other are arranged within this drum 14. An actuator 26 is arranged between these brake shoes 18 at the first end 22 of this brake shoe 18, and the brake shoe 18 can be applied to the drum 14 via this actuator 26. The actuator 26 is driven via an electric motor not shown here. A support element 34 is arranged between these brake shoes 18 at the second end 30 of the brake shoe 18, and the two brake shoes 18 are connected via this support element 34.

[0024] The drum brake 10 additionally has two return springs 38, and these return springs 38 are each connected to the two brake shoes 18. Since the return spring 38 is configured as a tension coil spring, the brake shoe 18 is pulled back to the inoperative position after the brake operation. In this inoperative position, the brake shoe 18 is kept at a distance from the drum 14.

[0025] Figure 2 shows a partial view of a drum brake 10 according to a first embodiment of the present invention. Only one side of the drum brake 10 is shown in this figure. In this case, the same reference numerals are used for the same parts as in Figure 1. In this embodiment, an additional U-shaped clamp 42 is provided. The U-shaped clamp 42 has first and second legs 46, 50, which are connected to each other via a web 54. The first leg 46 engages with a groove 62 in the brake shoe, which is formed in a direction perpendicular to the direction of motion 58 of the actuator 26 or in the axial direction of the drum brake 10. The end 66 of the second leg 50 is connected to the end of the actuator 26, so that the clamp 42 is movable together with the actuator 26.

[0026] The groove 62 of the brake shoe 18 has play S in the direction of motion 58 of the actuator 26. This ensures that the first leg 46 of the clamp 42 is positioned within the groove 62 so as not to contact the brake shoe 18 during normal operation of the drum brake 10. Since the actuator 26 is not rigidly connected to the brake shoe 18 together with the clamp 42, the brake shoe 18 can move in the brake shoe motion direction 63 in a direction perpendicular to the load reduction direction 64 of the brake shoe 18. This allows the brake shoe 18 to be precisely pressed into the ideal position within the drum 14.

[0027] If, after the actuator 26 moves in the load-reducing direction 64, the brake shoe 18 is not released from the drum 14 despite the presence of the return spring 38, the clamp 42 actively pulls the brake shoe from the drum 14 after overcoming the play S in the groove 62. This ensures that the brake shoe 18 is released from the drum 14. This avoids the release shock at startup.

[0028] Figure 3 shows a partial view of a drum brake 10 according to a second embodiment of the present invention. Here again, only one side of the drum brake 10 is shown for simplification. In this embodiment, the brake shoe 18 has a T-shaped groove 70 that extends axially relative to the drum brake 10. In this case, the T-shaped groove 70 is open toward the actuator 26. The end 72 of the actuator piston 74 is formed in a mushroom head shape and engages within the T-shaped groove. The mushroom head component 72 of the actuator piston 74 is positioned within the T-shaped groove 70, maintaining play S in the direction of motion 58 of the actuator 26. The upper surface of the mushroom-shaped component 72 presses against the brake shoe 18 to press the brake shoe 18 against the drum 14. If the brake shoe 18 is not automatically released from the drum 14 by the return spring 38 when the actuator piston 74 retracts, the mushroom head component 72 pulls the brake shoe 18 back together after overcoming the play S within the T-shaped groove 70. This ensures that the brake shoe 18 is released from the drum 14.

[0029] Figure 4 shows a partial view of a drum brake 10 according to a third embodiment of the present invention. In this embodiment, the actuator 26 is configured as an S-shaped cam or S-cam. By rotating the cam 26 counterclockwise, a force is applied to the brake shoe 18 based on the shape of the cam 26, thereby pressing the brake shoe 18 against the drum 14. In the opposite direction of rotation, the load on the brake shoe 18 is reduced and it is normally pulled to a non-operating position by a return spring 38. In this embodiment, an additional U-shaped clamp 42 is provided, which is in conjunction with the actuator 26 and the brake shoe 18.

[0030] Additionally, the cam 26 has an elongated hole 78 on each side that extends along the direction of extension of the cam 26. The end 66 of the second leg 50 of the clamp 42 is fixed within the elongated hole 78 so that this end 66 is movable along the elongated hole 78. The end of the first leg 46 is rotatably connected to the brake shoe 18. In this case, the elongated hole 78 provides play S so that the clamp 42 moves along the elongated hole 78 during normal operation and does not apply force to the brake shoe 18. When the actuator 26 moves in the load-reducing direction 64, if the brake shoe 18 should not be automatically released by the return spring 38, the brake shoe 18 is pulled back by the clamp 42 after overcoming the play S within the elongated hole 78.

[0031] Figure 5 shows a partial view of a drum brake 10 according to a fourth embodiment of the present invention. In this embodiment, the actuator 26 is configured as a wedge-shaped member, which presses the brake shoes 18 away from each other based on its wedge shape. In this embodiment as well, a U-shaped clamp 42 is provided that is in conjunction with the brake shoes 18 and the actuator 26. A wedge-shaped notch 82 is formed within the wedge-shaped member 26. In this case, the end 66 of the second leg 50 is movably fixed within the wedge-shaped notch 82. The end of the first leg 46 is rotatably connected to the brake shoes 18. When the actuator 26 moves in the load-reducing direction, if the brake shoes 18 are not released from the drum 14, a tensile force is applied to the brake shoes 18 via the clamp 42 after overcoming the play S provided by the wedge-shaped notch 82, thereby releasing the brake shoes 18 from the drum 14.

[0032] Figure 6 shows a partial view of a drum brake 10 according to a fifth embodiment of the present invention. In this case, Figure 6 is divided into two partial drawings. Partial drawing a) shows the brake position of the S-shaped actuator 26, at which point force is applied to the brake shoe 18. In contrast, partial drawing b) shows the position of the actuator 26 where the load on the brake shoe 18 is reduced. In this embodiment, a cable 86 that is interlocked with the actuator 26 and the brake shoe 18 is positioned between the actuator 26 and the brake shoe 18. For example, a steel cable is used as the cable 26. In this case, the cable 26 is fixed to the shaft 90 of the actuator 26. At the position shown in partial drawing a), the cable 86 is not under load and is slightly slack. This creates play S. When the shaft 90 of the actuator 26 rotates, the cable 86 is wrapped around the shaft 90, thereby tightening the cable 86. If the brake shoe 18 is not automatically released from the drum 14 by the return spring 38 after the actuator 26 has rotated in the load-reducing direction, the cable 86 is further tensioned, thereby applying a tensile force to the brake shoe 18. This releases the brake shoe 18 from the drum 14. [Explanation of Symbols]

[0033] 10 Drum brakes 14 Drums 18 Brake shoes 22 First end 26 Actuators, cams, and wedge-shaped members 30 Second end 38 Return Spring 42. Means, U-shaped clamp 46 First leg 50 Second leg 54 Web 58 Direction of motion of actuator 62 Groove 63 Brake shoe motion direction 64 Load reduction direction 66 End 70 T-shaped grooves 72 Means, mushroom head shaped end, component 74 Actuator piston, piston 78 long hole 82 Wedge-shaped notch 86 means, cable S Play

Claims

1. An electromechanical drum brake (10) for an automobile, comprising two brake shoes (18) and an actuator (26) positioned between the brake shoes (18), wherein pressure can be applied to the brake shoes (18) via the actuator (26), thereby causing the brake shoes (18) to be pressed against a drum (14) for braking, An electromechanical drum brake (10) for an automobile is provided, characterized in that at least one means (42, 72, 86) is provided that is interlocked with the actuator (26) and each of the brake shoes (18), thereby allowing the actuator (26) to move in a load-reducing direction (64) and apply a tensile force to the brake shoes (18).

2. The electromechanical drum brake (10) according to claim 1, characterized in that the brake shoe (18) is movable relative to the actuator (26) in a brake shoe motion direction (63) oriented perpendicular to the load reduction direction (64).

3. The electromechanical drum brake (10) according to claim 1 or 2, characterized in that there is play (S) between the means (42, 72, 86) and the actuator (26), or between the means (42, 72, 86) and each of the brake shoes (18), and the play (S) can be reduced in the load reduction direction (64) via the movement of the actuator (26).

4. The electromechanical drum brake (10) according to any one of claims 1 to 3, characterized in that the actuator (26) has a mushroom-head shaped end (72) that is interlocked with the groove (70) of the brake shoe (18).

5. The electromechanical drum brake (10) according to any one of claims 1 to 3, characterized in that the means is configured as a U-shaped clamp (42), the first leg (46) of the clamp (42) is linked to the brake shoe (18), and the second leg (50) is linked to the actuator (26).

6. The electromechanical drum brake (10) according to any one of claims 1 to 3 or claim 5, characterized in that the actuator (26) has a piston (74) that can slide in the axial direction.

7. The electromechanical drum brake (10) according to any one of claims 1 to 3 or claim 5, characterized in that the actuator (26) is configured as an S-shaped cam.

8. The electromechanical drum brake (10) according to any one of claims 1 to 3 or claim 5, characterized in that the actuator (26) is configured as a wedge-shaped member.

9. The electromechanical drum brake (10) according to any one of claims 1 to 3, characterized in that the means is configured as a cable (86), and the cable (86) can be tensioned by an S-shaped cam (26) rotating in the load reduction direction (64).

10. The electromechanical drum brake (10) according to claim 9, characterized in that the cable (86) is elastic.

11. An automobile having an electromechanical drum brake (10) according to any one of claims 1 to 10.

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