Electromechanical brake

Abstract

The invention relates to an electromechanical brake (10) for a motor vehicle. The electromechanical brake (10) comprises a brake caliper (14) which at least partially surrounds a brake disc (18), and a brake caliper housing (22) in which a spindle drive unit (62) driven by an electric motor (26) is arranged. The spindle drive unit (62) comprises a spindle (58) and a spindle nut (70), the spindle nut (70) being secured against rotation with respect to the brake caliper housing (22). The spindle nut (70) is held in a rotationally fixed manner in a brake piston (74) of the brake and, between the brake piston (74) and brake caliper housing (22), an anti-rotation insert (86) is provided in which the brake piston (74) is guided. The anti-rotation insert (86) is secured, via anti-rotation means (106), against rotation with respect to the brake caliper housing (22), and the brake piston (74) interacts with the anti-rotation insert (86) in such a manner that the brake piston (74) is secured against rotation. The brake piston (74) and the anti-rotation insert (86) have the same coefficient of thermal expansion, and the coefficient of thermal expansion of the brake caliper housing (22) differs therefrom.

Description

[0001] Description

[0002] Title:

[0003] Electromechanical brake

[0004] The present invention relates to an electromechanical brake for a motor vehicle. Furthermore, the invention relates to a motor vehicle having such an electromechanical brake.

[0005] State of the art

[0006] Typically, the service brake is a brake in which a brake piston, together with a brake pad, is pressed onto a brake disc via brake fluid to slow the vehicle. With the increasing electrification of motor vehicle components, the service brake is also being designed as an electromechanical brake, eliminating the need for brake fluid and the associated complex valve and line assembly. Such an electromechanical brake could also significantly reduce maintenance requirements.

[0007] EP 1 030 979 B1 discloses an electromechanical braking device for braking a motor vehicle wheel. The braking device comprises a brake caliper in which an electric motor is arranged. The electric motor drives a spindle drive unit, via which brake pads arranged on a brake caliper of the brake caliper can be applied to a brake disc for braking.

[0008] The object underlying the invention is to provide an electromechanical brake that is lighter yet still offers high strength. This object is achieved by an electromechanical brake having the subject matter of patent claim 1. Preferred embodiments can be found in the dependent claims.

[0009] Disclosure of the invention

[0010] The invention specifies an electromechanical brake for a motor vehicle. The electromechanical brake comprises a brake caliper which at least partially surrounds a brake disc, and a brake caliper housing in which a spindle drive unit driven by an electric motor is arranged. The spindle drive unit comprises a spindle and a spindle nut, wherein the spindle nut is secured against rotation relative to the brake caliper housing. The spindle nut is held in a brake piston of the brake in a rotationally fixed manner, and an anti-rotation insert in which the brake piston is guided is arranged between the brake piston and the brake caliper housing. The anti-rotation insert is secured against rotation relative to the brake caliper housing via anti-rotation means, and the brake piston interacts with the anti-rotation insert in such a way that the brake piston is secured against rotation.The brake piston and the anti-rotation insert have the same coefficient of thermal expansion, and the thermal expansion coefficient of the brake caliper housing is different.

[0011] The anti-rotation insert is an insert that prevents the brake piston from rotating relative to the brake caliper housing. Rotation of the anti-rotation insert relative to the brake caliper housing is prevented solely by the anti-rotation means. The thermal expansion coefficient of the anti-rotation insert and the brake piston is the same. This ensures that the brake piston is guided uniformly by the anti-rotation insert during the axial movement of the brake piston across the entire temperature range. In other words, the distance between the anti-rotation insert and the brake piston does not change. The anti-rotation insert is advantageously made of the same material as the brake piston. The brake caliper housing has a different thermal expansion coefficient than the anti-rotation insert and the brake piston.The material of the brake caliper housing can thus be selected independently of the brake piston and the anti-rotation insert, allowing the materials to be optimally selected to suit the loads. Although the distance between a cylinder bore of the brake caliper housing and the anti-rotation insert varies over the temperature range, the anti-rotation means ensure that the anti-rotation insert does not rotate relative to the brake caliper housing. Contrary to the prior art, the brake piston is not guided through the brake caliper housing. Accordingly, the brake caliper housing can be made of a lighter material, while a stronger material can be selected for the brake piston and the anti-rotation insert. This allows such an electromechanical brake to be designed with a lighter weight, reducing the unsprung mass on the wheel and increasing driving comfort for the driver.

[0012] In a preferred embodiment of the invention, a guide ring is arranged on the anti-rotation insert between the brake piston and the anti-rotation insert, over which the brake piston is guided. The guide ring is arranged on the anti-rotation insert and surrounds the brake piston on the outside. Furthermore, the guide ring has an axial extension, so that the brake piston is guided over the area of ​​the axial extension. The guide ring thus achieves improved guidance of an axial movement of the brake piston. Advantageously, the guide ring is made of a different material than the anti-rotation insert.

[0013] In a further preferred embodiment of the invention, the guide ring is made of a plastic material. The plastic material chosen is advantageously one that enables low friction with the brake piston. This minimizes the friction loss between the brake piston and the guide ring. Polyoxymethylene (POM) or thermoset materials are preferably used as the plastic material. A plastic material is lighter and can be used cost-effectively. The guide ring is preferably made of a sintered metal. The sintered metal is preferably impregnated with oil. The sintered metal thus provides a low coefficient of friction with the brake piston. This also minimizes the friction loss between the brake piston and the guide ring.

[0014] In an advantageous development, locating pins are arranged between the brake caliper housing and the anti-rotation insert, by means of which the anti-rotation insert is secured against rotation. Preferably, at least three axially aligned locating pins are arranged between the brake caliper housing and the anti-rotation insert, which are provided at an equal angular distance from one another. However, four locating pins are particularly preferably provided. In contrast to other anti-rotation devices, locating pins have the advantage that they can be used to center the anti-rotation insert within a cylinder bore of the brake caliper housing. This ensures a centric alignment of the anti-rotation insert and thus of the brake piston across the entire temperature range, despite different thermal expansion of the brake caliper housing and the anti-rotation insert.

[0015] Advantageously, the brake piston and the anti-rotation insert are made of a steel material. Steel is highly durable, allowing the brake piston to absorb the forces. This ensures that the brake piston will not fail over its service life.

[0016] In a further advantageous embodiment, the brake caliper housing is made of aluminum. Aluminum has the advantage of being significantly lighter than, for example, steel. This makes it possible to design a lighter electromechanical brake. Furthermore, the aluminum material allows for better dissipation of the high temperatures that occur during braking. Overheating of the electromechanical brake can thus be prevented.

[0017] According to a practical design, the spindle drive unit is designed as a ball screw. A ball screw has the advantage of being designed to withstand the high loads encountered during braking. Furthermore, a ball screw has low friction, so friction losses during rotation of the spindle drive unit can be kept to a minimum. This also makes it possible to use a smaller and therefore lighter electric motor.

[0018] The invention also provides a motor vehicle having such an electromechanical brake. Such a motor vehicle has the advantages and properties described above.

[0019] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. It shows:

[0020] Figure 1 Perspective view of an electromechanical brake according to an embodiment of the invention,

[0021] Figure 2 Longitudinal section of the brake caliper housing according to a

[0022] Embodiment of the invention in an exploded view,

[0023] Figure 3 Further longitudinal section view of the spindle drive unit and the

[0024] Anti-rotation insert according to Figure 2,

[0025] Figure 4 Cross-sectional view of the spindle drive unit and the

[0026] Anti-rotation insert according to Figure 3, and

[0027] Figure 5 shows a perspective view of the anti-rotation insert according to an embodiment of the invention. Figure 1 shows a perspective view of an electromechanical brake 10 according to an embodiment of the invention. The electromechanical brake 10 comprises a brake caliper 14, which engages around a brake disc 18. Brake pads (not shown) are arranged in the brake caliper 14 and can be applied to the brake disc 18 to brake the motor vehicle. Additionally, the electromechanical brake 10 comprises a brake caliper housing 22.

[0028] An electric motor 26 of the electromechanical brake 10 is attached to the brake caliper housing 22. The electromechanical brake 10 is connected to a brake caliper holder 34 in the area of ​​the brake caliper 14 via guide pins 30. A cover 38 is arranged on the brake caliper housing 22, by means of which the housing can be closed. The cover 38 is held by three holding elements 42. In the exemplary embodiment shown here, the holding elements 42 are designed as screws which are screwed into the brake caliper housing 22 and simultaneously have a holding piece 42a resting against the cover 38. The cover 38 has a feedthrough 46 at one point, through which cables (not shown) for the electric motor 26 can be introduced into the brake caliper housing 22.

[0029] Figure 2 shows a longitudinal sectional view of the brake caliper housing 22 according to an embodiment of the invention in an exploded view. The figure shows a worm shaft 50 driven by the electric motor 26, which drives a worm gear 54. The worm gear 54 is fixedly connected to a spindle 58 of a spindle drive unit 62, so that the spindle 58 can be rotated via the worm gear 54. In addition, a bearing 66 is provided, via which the spindle 58 is rotatably mounted with the worm gear 54. A spindle nut 70 of the spindle drive unit 62, designed here as a ball screw drive, is arranged in a rotationally fixed manner in a brake piston 74 of the electromechanical brake 10. At the axial end of the brake piston 74, a brake pad holder 78 with a brake pad 82 is attached, which can be applied to the brake disc 18 via the brake piston 74 for braking.In the radial direction, an anti-rotation insert 86 is arranged between the brake caliper housing 22 and the brake piston 74, by means of which the brake piston 74 and thus also the spindle nut 70 are secured against rotation. To prevent rotation, the brake piston 74 has radial projections 90 that engage in axial recesses 94 of the anti-rotation insert 86. The brake piston 74 is movable in the axial direction in the axial recesses 94. Plastic sliding shoes 98 are arranged on the radial projections 90 of the brake piston 74, by means of which friction with the anti-rotation insert 86 is reduced.

[0030] In the region of one axial end of the anti-rotation insert 86, a guide ring 102 is arranged, over which the brake piston 74 is guided in the anti-rotation insert 86. To reduce friction between the guide ring 102 and the brake piston 74, the guide ring 102 is advantageously made of plastic.

[0031] Figure 3 shows a further longitudinal sectional view of the spindle drive unit 62 and the anti-rotation insert 86. In this longitudinal sectional view, anti-rotation means designed as locating pins 106 are arranged between the brake caliper housing 22 and the anti-rotation insert 86. As shown in Figure 4, these are provided in corresponding housing recesses 110 and recess 114 of the anti-rotation insert. In the embodiment shown in Figure 4, four round locating pins 106 are arranged. The locating pins 106 enable the anti-rotation insert 86, and thus also the brake piston 74, to be centered in the brake caliper housing 22.

[0032] The brake piston 74 and the anti-rotation insert 86 are advantageously made of the same material and therefore have the same coefficient of thermal expansion. In contrast, the brake caliper housing 22 is made of a different material and thus has a different coefficient of thermal expansion. Despite the different thermal expansion coefficients of the brake caliper housing 22 and the anti-rotation insert 86, good centering is still possible via the locating pins 106.

[0033] Figure 5 shows a perspective view of the anti-rotation insert 86 according to one embodiment of the invention. This figure again shows the two axial recesses 94 and the recess 114 for the locating pins 106. The guide ring 102 is also shown in the area of ​​a lower inner end of the anti-rotation insert 86.

Claims

Claims 1 . An electromechanical brake (10) for a motor vehicle, comprising a brake caliper (14) which at least partially surrounds a brake disc (18), and a brake caliper housing (22) in which a spindle drive unit (62) driven by an electric motor (26) is arranged, wherein the spindle drive unit (62) comprises a spindle (58) and a spindle nut (70), wherein the spindle nut (70) is secured against rotation relative to the brake caliper housing (22), characterized in that the spindle nut (70) is held in a brake piston (74) of the brake in a rotationally fixed manner, and an anti-rotation insert (86) is arranged between the brake piston (74) and the brake caliper housing (22), in which anti-rotation insert the brake piston (74) is guided, wherein the anti-rotation insert (86) is secured against rotation relative to the brake caliper housing (22) via anti-rotation means (106), and the brake piston (74) cooperates with the anti-rotation insert (86) in such a way thatthat the brake piston (74) is secured against rotation, wherein the brake piston (74) and the anti-rotation insert (86) have the same thermal expansion coefficient, and the thermal expansion coefficient of the brake calliper housing (22) is different., 2. Electromechanical brake (10) according to claim 1, characterized in that between the brake piston (74) and the anti-rotation insert (86) a guide ring (102) is arranged on the anti-rotation insert (86), over which the brake piston (74) is guided 3. Electromechanical brake (10) according to claim 2, characterized in that the guide ring (102) is formed from a plastic material 4. Electromechanical brake (10) according to claim 2, characterized in that the guide ring (102) is formed from a sintered metal 5. Electromechanical brake (10) according to one of the preceding claims, characterized in that dowel pins (106) are arranged between the brake caliper housing (22) and the anti-rotation insert (86), by means of which the anti-rotation insert (86) is secured against rotation.

6. Electromechanical brake (10) according to one of the preceding claims, characterized in that the brake piston (74) and the anti-rotation insert (86) are formed from a steel material.

7. Electromechanical brake (10) according to one of the preceding claims, characterized in that the brake caliper housing (22) is formed from an aluminum material.

8. Electromechanical brake (10) according to one of the preceding claims, characterized in that the spindle drive unit (62) is designed as a ball screw drive.

9. Motor vehicle comprising an electromechanical brake (10) according to one of the preceding claims.

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