Electromechanical Brake

Abstract

The present invention relates to an electromechanical brake (4) with an electromechanical actuation device (8), which comprises an electric motor (16) cooperating with a transmission (24) and a ramp mechanism (44), the ramp mechanism (44) being adapted to generate a braking force (F B The electric motor (16) converts rotary drive motion into translational motion to exert a force on the electric motor (16). The electric motor (16) and the transmission (24) are coaxially disposed with one another and are at least partially surrounded by a ramp mechanism (44).

Description

[Technical Field]

[0001] The present invention relates to an electromechanical brake and to a vehicle braking system comprising at least one such electromechanical brake.

[0002] Service brakes are typically used to press a brake piston together with brake pads against a brake disc via brake fluid to brake the vehicle. Parking brakes, on the other hand, are designed as electromechanical brakes. With the trend toward electrification of vehicle assemblies, service brakes should also be designed as electromechanical brakes, thereby eliminating the need for brake fluid and the associated complex valve and piping structures. Such electromechanical brakes should also significantly reduce maintenance efforts. [Background technology]

[0003] Patent Document 1 discloses an electromechanical friction brake in which an electric motor drives one of two cam discs via a transmission. Rolling elements are arranged between the cam discs and roll on a wedge-shaped cam along the cam disc, thereby generating a closing motion. The cam disc has recesses in which the rolling elements can be stably locked to form a parking brake. A threaded spindle provides wear readjustment between the cam disc and the brake pads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE 102007055637 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem underlying the present invention is to provide a smaller and more compact electromechanical brake. [Means for solving the problem]

[0006] The above problem is solved by an electromechanical brake having the features of claim 1. Preferred embodiments can be read from the dependent claims.

[0007] The present invention provides an electromechanical brake with an electromechanical actuator having an electric motor cooperating with a transmission and a ramp mechanism. The present invention includes a ramp mechanism for converting the rotary drive motion of the electric motor into translational motion to apply a braking force. Various ramp mechanisms are already known. A ball ramp mechanism is known, which includes two coaxially arranged discs between which, for static stability, typically three balls are distributed circumferentially. One of the two discs is rotatably driven. The discs have circumferentially extending ramps on or within their facing end faces, which rise circumferentially and allow the balls to roll along the ramp. The ramps are typically groove-like recesses that decrease in diameter circumferentially.

[0008] Rotation of one disc causes the balls to roll up the ramp, pushing the discs away from each other and creating a translational motion. Rotation in the opposite direction moves the two discs toward each other. Instead of balls, other rolling elements, such as cylindrical or tapered rollers, can be used. These can be rotatably supported on one disc, leaving only the other disc with a ramp on which rollers or other rolling elements roll. Ramp mechanisms without rolling elements are also conceivable, which have one or more circumferentially extending ramps that press against a mating element as they rotate, creating a translational motion similar to the known ball ramp mechanism.

[0009] Ramp mechanisms have the advantage of low friction, at least when they have rolling elements. Another advantage of ramp mechanisms is that the rise of the ramp can vary over its length. The initial high gradient quickly overcomes the air gap, i.e., the gap between the friction brake pads and the braking element when the friction brake is released. The reduced gradient increases the brake pad pressure, resulting in a larger power transmission ratio, and thus greater power can be achieved with limited drive torque.

[0010] According to the present invention, the electric motor and the transmission are arranged coaxially with one another and are at least partially surrounded by the ramp mechanism. Therefore, the electric motor and the transmission are not arranged next to each other in the radial direction, and the required radial space can be reduced by this arrangement. Also according to the present invention, the electric motor and the ramp mechanism together with the transmission are not arranged one behind the other in the axial direction, but the ramp mechanism surrounds the electric motor and the transmission. This arrangement of the components significantly reduces the required axial space. Therefore, a much more compact electromechanical brake can be provided.

[0011] In a preferred embodiment of the present invention, the ramp mechanism includes a cup-shaped drive element connected to the transmission and a cam ring. Therefore, the ramp mechanism has a cam ring instead of a cam disc, which allows the ramp mechanism to surround at least a portion of the axial length of the electric motor and transmission. The electric motor and transmission are therefore arranged radially centered around the cam ring. The drive element is connected to the output of the transmission and is driven via it. The cup-shaped form of the drive element provides a housing area in which the electric motor and transmission are housed. Correspondingly, the cup-shaped drive element also surrounds the electric motor and transmission, thereby achieving a compact design. The cup-shaped drive element is preferably made of plastic, which reduces the weight and cost of such an electromechanical brake.

[0012] In another preferred embodiment of the present invention, a bearing assembly having at least one radial bearing cooperating with the cam ring is disposed between the cam ring and the housing base, and braking force can be supported by the housing base via the bearing assembly. In this case, the bearing assembly has a plurality of the same or different bearings. The radial bearing is preferably supported by the edge of the cup-shaped drive member. The radial bearing supports the braking force on the housing base via the bearing assembly. Therefore, the braking force is transmitted to the housing base with low friction.

[0013] Preferably, the cam ring is arranged on the brake piston, with which it forms a wear adjustment. Particularly preferably, an external thread is arranged on the cam ring and an internal thread is arranged on the brake piston, so that the cam ring can be screwed onto the brake piston. This arrangement allows the axial length of the brake piston and the cam ring to be changed. Therefore, brake pad wear can be compensated for by increasing the axial length. This makes it possible to easily form the wear adjustment. Furthermore, wear adjustment via the cam ring and the brake piston eliminates the need for additional components, thereby reducing the required space and component costs. Furthermore, arranging the cam ring on the brake piston has the advantage of requiring less space compared to an axial arrangement of components, thereby enabling the electromechanical brake to be more compact.

[0014] In an advantageous development, the cam ring has stops at the ends of the cams formed thereon, which, when struck, can cause the cam ring to rotate on the brake piston for wear adjustment. In this case, the stops are gradient changes in the cam that cannot be overcome by the rolling elements or radial bearings. These stops allow the cam ring to rotate as the electric motor continues to rotate. This makes it possible to easily perform wear adjustment during operation.

[0015] In an alternative embodiment, the drive element and the cam ring have engagement means which engage with each other at a position between the cam ring and the drive element, thereby enabling rotation of the cam ring on the brake piston for wear adjustment, which is also possible via such engagement means.

[0016] Advantageously, the cam ring has a recess formed on the cam after the lift, by which the brake can be fixed in the parking position. This recess in the cam creates a stable position for the rolling elements or radial bearings, so that this position can be braked even when the vehicle is parked, thereby easily implementing the parking brake.

[0017] In another advantageous embodiment, the cam ring has internal teeth that engage with a gear formed together with the freewheel, thereby allowing the cam ring to rotate in only one direction for wear readjustment. One direction of rotation of the gear is blocked by the freewheel. This allows only rotation of the gear for wear readjustment. This embodiment prevents the cam ring from unintentionally displacing in the direction opposite to the wear direction during normal braking. This reduces the requirement for sufficient thread-to-thread friction for wear readjustment, thereby improving the reliability of wear readjustment.

[0018] According to a suitable embodiment, the gear is arranged eccentrically with respect to a cylindrical part attached to the brake piston, which can be rotated to disengage the gear and thereby return the cam ring. By arranging the gear eccentrically with respect to the axis of rotation of the part, the distance between the cam ring and the gear can be changed by rotating the part. This makes it easy to return the cam ring during maintenance without having to remove the part.

[0019] According to another suitable embodiment, a compression spring is disposed between the brake pads of the brake, and the brake pads can be separated from the brake disc via the compression spring. In this case, the compression spring constantly applies force to both brake pads. After the braking process, the brake pads are quickly pulled away from the brake disc, thereby minimizing pad rubbing on the brake disc. This reduces brake pad wear and fine dust load. Furthermore, a predetermined gap is adjusted via the compression spring after braking. The compression spring also ensures that all components in the force flow are preloaded with a predetermined force, thereby eliminating play between the components.

[0020] Preferably, the transmission is at least one single-stage planetary gear. Planetary gears have the advantage that high torques can be transmitted in a compact manner, which allows the electromechanical brake to be made smaller. Furthermore, planetary gears allow the electric motor to be made smaller, which also saves construction space. Advantageously, the planetary gear is a two-stage planetary gear.

[0021] Furthermore, a vehicle braking system is presented that includes at least one such electromechanical brake, with which substantially the aforementioned advantages are achieved. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of an electromechanical brake according to a first exemplary embodiment of the present invention; [Figure 2] FIG. 10 is a perspective view of an exemplary embodiment of a cam ring. [Figure 3] FIG. 2 is a cross-sectional view of a drive disk. [Figure 4] FIG. 10 is a diagram of the cam of the cam ring. [Figure 5] FIG. 4 is a cross-sectional view of an electromechanical brake according to a second exemplary embodiment of the present invention. [Figure 6]FIG. 10 is a cross-sectional view of an electromechanical brake according to a third exemplary embodiment of the present invention. [Figure 7] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0024] In Figure 1, a cross-sectional view of an electromechanical brake 4 according to a first exemplary embodiment of the invention is shown. The electromechanical brake 4 comprises an actuation device 8, through which a braking force F B The actuation device 8 can apply a force to the brake pads 12 of the electromechanical brake. In that case, the actuation device 8 comprises an electric motor 16 configured as an electronically commutated motor. The electric motor 16 drives a drive shaft 20 which is connected to a transmission 24. In the illustrated exemplary embodiment, the transmission 24 is configured as a two-stage planetary gear arrangement arranged coaxially with the electric motor 16. In order to be able to detect the position of the rotor of the electric motor 16, a rotor position sensor 28 is arranged on the drive shaft 20 on the side opposite the transmission 24.

[0025] The planetary gear 24 is connected on the output side to a cup-shaped drive element 32. The cup-shaped drive element 24 is configured in such a way that it partially surrounds the planetary gear 24 and the electric motor 16 from the outside. Additionally, the cup-shaped drive element 32 defines a ring disc 36 that is arranged coaxially with the drive shaft 20. Together with a cam ring 40, the ring disc 36 forms a ramp mechanism 44 via which the rotary drive movement of the ring disc 36 can be converted into a translational movement of a brake piston 48 that is connected to the cam ring 40.

[0026] FIG. 2 shows a perspective view of an exemplary embodiment of the cam ring 40. It can be seen in this view that the cam ring 40 has three identical cams 52 arranged along the end face 56 of the cam ring 40, where the cams 52 have different axial ridges on the cam ring 40. The cam ring 40 cooperates with three cam radial bearings 60, shown in FIGS. 1 and 3, which roll on the cams 52 of the cam ring 40. The cam radial bearings 60 are held in the ring disc 36 via ring disc axles 64, as shown in FIG. 3. The ring disc 36 forms three notches 68 in which the radially extending ring disc axles 64 are respectively located.

[0027] In addition to the cam radial bearing 60, two support radial bearings 72 are arranged on the ring disc shaft 64, one on each side of the cam radial bearing 60. As shown in FIG. 1, the support radial bearings 72 have a larger outer diameter D S The support radial bearing 72 thereby abuts against a support ring disc 76 arranged in the housing base 80 of the electromechanical brake 4. The outer diameter D of the cam radial bearing 60 K The outer diameter D of the supported radial bearing 72 S Because it is smaller, this radial bearing 60 does not abut against the support ring disc 76. Because the radial thickness of the cam ring 40 is small, the support radial bearings 76 do not abut against the cam ring 40 and are free to move on either side of the cam ring 40.

[0028] The cam ring 40 is housed in a brake piston 48 that acts on the brake pads 12. The brake piston 48 and the cam ring 40 each have a thread 88, via which the cam ring 40 is screwed onto the brake piston 48. The thread 88 allows adjustment of the wear of the brake pads 12. The cam ring 40 can thus be unscrewed from the brake piston 48 to readjust the wear of the brake pads 12. The thread 88 is formed in such a way that rotation generated by normal operating movement is prevented. Compression springs 92 are arranged between the brake pads 12, and the brake pads 12 are pressed apart by these compression springs after the braking process. This prevents the brake pads 12 from rubbing against a brake disc (not shown), thereby reducing pad wear.

[0029] FIG. 4 shows a diagram of the cam 52 of the cam ring 40. The cam radial bearing 60 rotates on this cam 52. After the first incline 96, a recess 100 is formed, in which the cam radial bearing 60 can rest securely. This recess 100 provides the parking brake function. Additionally, the cam 52 forms two stops 104 against which the cam radial bearing 60 can rest. Further rotation beyond these stops 104 can generate a rotation of the cam ring 40 on the brake piston 48. This allows for easy adjustment of wear. This also allows for complete reversal of wear after replacing the brake pads 12.

[0030] In Figure 5, a cross-sectional view of an electromechanical brake 4 according to a second exemplary embodiment of the invention is shown. This exemplary embodiment differs from the electromechanical brake 4 from Figure 1 in that the brake piston 48 is configured as a stepped brake piston 48. Thus, a further step 108 is provided in the area of ​​the electric motor 16 and the transmission 24. This allows the electromechanical brake 4 to be configured even more compactly. The stepped shape of the brake piston 48 makes it possible to arrange the frontmost part of the brake piston 48 in the area of ​​the rim.

[0031] 5 further differs from the first exemplary embodiment in that the support radial bearing 72 is not provided. In this exemplary embodiment, only the cam radial bearing 60 is provided. Instead of the support radial bearing 72, a support axial bearing 112 is arranged between the cam radial bearing 60 and the housing base 80. By means of the support axial bearing 112, it is possible that forces can be transmitted to the housing base 80.

[0032] 6 shows a cross-sectional view of an electromechanical brake 4 according to a third exemplary embodiment of the present invention. This exemplary embodiment differs from the exemplary embodiment from FIG. 1 in that a detent 116 is arranged for the cam ring 40. Via this detent 116, rotation of the cam ring 40 is permitted in only one direction, thereby preventing the cam ring 40 from rotating unintentionally during normal use. The cam ring 40 has internal teeth 124 on its inner circumferential surface 120 for the detent 116.

[0033] The detent 116 includes a cylindrical pin 128. The pin 128 is divided into two regions 128a, 128b, with the first region 128a located on the brake piston 48. The first region 128a is followed by the second region 128b, which extends to the region of the internal teeth 124 of the cam ring 40. A gear 132 is attached to the second region 128b of the pin 128 and engages with the internal teeth 124. A freewheel 136 is provided between the pin 128 and the gear 132, allowing the gear 132 to rotate in only one direction.

[0034] 7 shows an enlarged view of the pin 128 and the gear 132. In this view, it can be seen that the second region 128b, and therefore the rotation axis 138 of the gear 132, is arranged eccentrically with respect to the rotation axis 139 of the first region 128a. Thus, rotation of the first region 128a allows the gear 132 to disengage from the internal teeth 124. This allows the cam ring 40 to be screwed back onto the brake piston 48 when replacing the brake pads 12, thereby reducing wear to zero again.

[0035] To prevent unintentional rotation of the first region 128a during use, a slot 140 is formed at one axial end of the first region 128a. This slot 140 cooperates with a protrusion 144 on the brake pad, which engages in this slot 140 and prevents rotation. Furthermore, this slot-and-protrusion connection allows for a Poka-Yoka ("Poka-Yoka") secure assembly. If the pin 128 rotates, assembly of the brake pad 12 is not possible, so assembly of the brake pad 12 is only possible with the pin 128 correctly aligned. [Explanation of symbols]

[0036] 4. Brakes 8 Actuating device 12 Brake pads 16 Electric motor 20 Drive shaft 24 Transmission, planetary gear 28 Rotor position sensor 32 Driving Elements 36 Ring Disc 40 Cam Ring 44 Ramp mechanism 48 Brake piston 52 Cam 56 End face 60 Cam Radial Bearings 64 Ring disc shaft 68 Notch 72 Support and Radial Bearings 76 Support Ring Disc 80 Housing Base 88 threads 92 Compression spring 96 increase 100 depressions 104 Stopper 108 steps 112 Radial bearing 116 Stopper 120 Inner surface 124 Inner teeth 128 pins 128a, 129b area 132 Gears 136 Freewheel 138 Gear rotation axis 139 Rotation axis of the first region 140 slots 144 Projection piece F B braking force D S Outer diameter

Claims

1. An electromechanical brake (4) comprising an electromechanical actuator (8) having an electric motor (16) cooperating with a transmission (24) and a ramp mechanism (44), the ramp mechanism (44) being adapted to generate a braking force (F Ｂ 1. An electromechanical brake for converting a rotary drive motion of said electric motor (16) into a translational motion to exert a Electromechanical brake, characterized in that the electric motor (16) and the transmission (24) are arranged coaxially with each other and are at least partially surrounded by the ramp mechanism (44).

2. 2. The electromechanical brake (4) according to claim 1, characterized in that the ramp mechanism (44) comprises a cup-shaped drive element (32) connected to the transmission (24) and a cam ring (40).

3. A bearing assembly (60, 72, 112) having at least one radial bearing (60) cooperating with the cam ring (40) is disposed between the cam ring (40) and the housing base (80), and a braking force (F Ｂ 3. The electromechanical brake (4) according to claim 1 or 2, characterized in that a bearing (41) can be supported by the housing base (80).

4. 4. An electromechanical brake (4) according to any one of claims 1 to 3, characterized in that the cam ring (40) is arranged on a brake piston (48), the cam ring and the brake piston together forming a wear adjustment.

5. 5. An electromechanical brake (4) according to claim 4, characterized in that the cam ring (40) has stops (104) at the ends of the cams (52) formed on the cam ring, and when hitting these stops (104), rotation of the cam ring (40) can be performed on the brake piston (48) for wear adjustment.

6. 6. An electromechanical brake (4) according to any one of claims 1 to 5, characterized in that the cam ring (40) has a recess (100) after the rise (96) in the cam (52) formed on the cam ring, thereby making it possible to fix the brake in a park position.

7. 7. An electromechanical brake (4) according to any one of claims 1 to 6, characterized in that the cam ring (40) has internal teeth (124) which engage with a gear (132) formed with a freewheel (136), whereby the cam ring (40) can rotate in only one direction for the wear readjustment.

8. 8. An electromechanical brake (4) according to claim 7, characterized in that the gear (132) is arranged eccentrically with respect to a cylindrical part (128) attached to the brake piston (48), the cylindrical part being capable of rotating to disengage the gear (132) and thereby return the cam ring (40).

9. 9. The electromechanical brake (4) according to claim 1, wherein a compression spring (92) is arranged between the brake pads (12) of the brake (4), and the brake pads (12) can be separated from the brake disc via the compression spring.

10. 10. An electromechanical brake (4) according to any one of claims 1 to 9, characterized in that the transmission (24) is at least one single-stage planetary gear.

11. A vehicle braking system comprising at least one electromechanical brake (4) according to any one of claims 1 to 10.

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