Electromechanical brake cylinder for actuating a wheel brake, wheel brake with the electromechanical brake cylinder and method for releasing a wheel brake

Abstract

An electromechanical brake cylinder (2) for actuating a wheel brake (1), in particular a wheel brake (1) of a rail vehicle, comprises: an electric motor (3) with a rotor (5), a spindle nut (7), a torque transmission device provided between the rotor (5) and the spindle nut (7), and a threaded spindle (8). The spindle nut (7) and the spindle (8) are configured to convert a rotary movement of the spindle nut (7) into an axial movement of the spindle (8), wherein the axial movement of the spindle (8) can be converted into a movement of a brake pad (17) of the wheel brake (1) relative to a braking element of the wheel brake (1), and wherein the torque transmission device is configured to transmit a torque less than or equal to a maximum predetermined torque value between the rotor (5) and the spindle nut (7).

Description

[0001] The invention relates to an electromechanical brake cylinder for actuating a wheel brake, a wheel brake with the electromechanical brake cylinder and a method for releasing a wheel brake, in particular for rail vehicles.

[0002] An electromechanical brake cylinder operates using an electric motor that converts electrical energy into mechanical energy—specifically, motion, which can be used to transmit force. When the electromechanical brake cylinder is activated, the electric motor generates a rotational movement of its rotor. This rotational movement is transferred to a spindle nut fixed within a hollow shaft of the brake cylinder, resulting in a feed motion of a spindle located in the hollow shaft and the spindle nut. This feed motion is then transmitted via a braking mechanism to a brake pad holder, pressing brake pads against a rotating brake disc and thereby generating a braking force.

[0003] To release the brake, the motor of the electromechanical brake cylinder generates a counter-rotating motion, causing the spindle to move in the opposite direction to the feed motion. An end position of the spindle in this opposite direction, in which the brake is released, is typically detected by an end-position sensor and transmitted to a brake control device, which then switches off the electric motor.

[0004] Publication WO 2018 / 036 676 A1 discloses such a braking device which includes the features according to the preamble of claim 1.

[0005] In the event of a malfunction of this detection system, there is a risk that the spindle will collide with the hollow shaft at full speed, potentially causing permanent damage to the spindle nut, the spindle itself, or other components of the electromechanical brake cylinder. However, the components used in the electromechanical brake cylinder to convert the rotor's rotational motion into the spindle's feed motion are expensive, so premature replacement must be avoided.

[0006] The object underlying the invention is therefore to eliminate the above disadvantage and to provide an electromechanical brake cylinder and a wheel brake, as well as a method that prevents damage to components of the electromechanical brake cylinder, even in the event of a sensor malfunction.

[0007] The problem is solved by an electromechanical brake cylinder according to claim 1, a wheel brake according to claim 8, and a method according to claim 10. Advantageous further developments of the invention are contained in the dependent claims.

[0008] According to one aspect of the invention, an electromechanical brake cylinder for actuating a wheel brake, in particular a wheel brake of a rail vehicle, comprises: an electric motor with a rotor, a spindle nut, a torque transmission device provided between the rotor and the spindle nut and configured to transmit a torque between the rotor (5) and the spindle nut (7), and a spindle having a thread, wherein the spindle nut and the spindle are configured to convert a rotary movement of the spindle nut into an axial movement of the spindle relative to the spindle nut, wherein the axial movement of the spindle can be converted into a movement of a brake lining of the wheel brake relative to a braking element of the wheel brake, and wherein the torque transmission device is configured tothat it transmits a torque less than or equal to a maximum predetermined torque value between the rotor and the spindle nut.

[0009] The wheel brake acts either on an element of a wheel that needs to be braked or on an element of an axle that needs to be braked by means of the wheels of the axle.

[0010] By incorporating a torque transmission device that allows for pre-setting the maximum transmittable torque, this maximum torque can be adjusted to prevent permanent damage to the spindle nut, spindle, or other components of the electromechanical brake cylinder when the brake is released. This avoids the need for premature replacement of these components. The maximum transmittable torque is set to generate the required braking force while preventing damage.

[0011] According to the invention, the torque transmission device has a first friction surface on the spindle nut and a second friction surface connected to the rotor, and the first friction surface and the second friction surface are designed to generate a maximum frictional force corresponding to the maximum predetermined torque value.

[0012] According to an advantageous embodiment of the electromechanical brake cylinder, the electromechanical brake cylinder has a hollow shaft rotatable about a rotational axis of the spindle as a component of the torque transmission device, which is rigidly connected to the rotor. The hollow shaft rotatably receives the spindle nut relative to the hollow shaft, the hollow shaft having the second friction surface.

[0013] In a further advantageous embodiment of the electromechanical brake cylinder, the electromechanical brake cylinder has a housing, and the housing is designed to rotatably mount the hollow shaft in the housing.

[0014] Advantageously, the torque transmission device has a preloading device designed to apply a predetermined normal force to the first friction surface and second friction surface.

[0015] In a further advantageous embodiment of the electromechanical brake cylinder, a direction of movement of the spindle for approaching the brake pad to the element to be braked is defined as the first direction of movement, and the preloading device is designed to apply the predetermined normal force in a direction opposite to the first direction of movement to the first and second friction surfaces.

[0016] According to a further advantageous embodiment of the electromechanical brake cylinder, the preload device has a disc spring and a locking element, and the disc spring is designed to be supported on the hollow shaft via the locking element and to apply the predetermined normal force to the first and second friction surfaces via the spindle nut.

[0017] In a further advantageous embodiment of the electromechanical brake cylinder, the hollow shaft has a stop designed to halt the axial movement of the spindle in a second direction of movement opposite to the first direction of movement when it runs up against the stop, wherein the electromechanical brake cylinder is designed such that, after running up against the stop, the rotary movement of the spindle nut is converted into the axial movement of the spindle relative to the spindle nut, and the spindle nut moves in the direction of the first direction of movement in order to reduce a normal force applied to the first and second friction surfaces.

[0018] On the one hand, it is possible to adjust the transmissible torque for initiating the braking by moving the spindle in the first direction of movement to the required torque value, while on the other hand, the transmissible torque decreases when releasing the brake by moving the spindle in the second direction of movement as it runs up against the stop, in order to prevent damage to the components.

[0019] According to a further aspect of the invention, a wheel brake with an electromechanical brake cylinder according to the invention comprises a brake pad, an element to be braked, and a brake mechanism designed to convert the axial movement of the spindle into the movement of the brake pad relative to the element to be braked.

[0020] In an advantageous embodiment of the wheel brake, a direction of movement of the spindle for removing the brake pad from the element to be braked is defined as a second direction of movement, and the wheel brake has a sensor which is designed to detect whether the spindle is in an end position in the second direction of movement.

[0021] In accordance with a further aspect of the invention, a method for releasing a wheel brake by means of an electromechanical brake cylinder according to the invention when the spindle runs up against a stop in a hollow shaft of the electromechanical brake cylinder, so that an axial movement of the spindle is stopped, the torque transmission device reduces a torque transmitted from the spindle nut to the spindle to a maximum predetermined torque value.

[0022] According to an advantageous embodiment of the method, wherein a first axial direction of movement of the spindle is defined such that a brake pad approaches an element to be braked and a second axial direction of movement is defined opposite to the first axial direction of movement, after the spindle has reached the stop in the second axial direction of movement, during a continued conversion of the rotary motion of the spindle nut into the axial motion of the spindle relative to the spindle nut, the spindle nut moves in the direction of the first direction of movement in order to reduce a normal force applied axially to the spindle on a first and second friction surface in order to reduce the maximum predetermined torque value.

[0023] The invention is explained below with reference to exemplary embodiments and the accompanying drawings.

[0024] In particular, it shows Fig. 1 a partially cutaway top view of a section of a wheel brake with an electromechanical brake cylinder according to the invention; and Fig. 2 A partially broken-up top view of the wheel brake.

[0025] Fig. Figure 1 shows a partially cutaway top view of a section of a wheel brake 1 with an electromechanical brake cylinder 2 according to the invention. The wheel brake 1 serves to act either on a braked element of a wheel or an axle by means of whose wheels the axle is braked. The wheel brake 1 is a component of a rail vehicle (not shown), but can alternatively also be used, for example, in a road vehicle such as a commercial vehicle.

[0026] The electromechanical brake cylinder 2 comprises an electric motor 3 with a stator 4 and a rotor 5. Furthermore, the electromechanical brake cylinder 2 has a hollow shaft 6 which is rigidly connected to the rotor 5. In addition, the electromechanical brake cylinder 2 has a spindle nut 7 and a spindle 8 which are positively connected by means of balls (not shown), wherein the spindle nut 7 and the spindle 8 are designed to convert a rotary movement of the spindle nut 7 into an axial movement of the spindle 8 relative to the spindle nut 7. The hollow shaft 6 is rotatably mounted about an axis of rotation of the spindle 8 in a housing 14 of the electromechanical brake cylinder 2 by means of a bearing arrangement 23 and rotatably receives the spindle nut 7 relative to the hollow shaft 6.

[0027] Finally, the electromechanical brake cylinder 2 has a torque transmission device between the rotor 5 and the spindle nut 7, which is designed to transmit a torque less than or equal to a maximum predetermined torque value between the rotor 5 and the spindle nut 7.

[0028] The torque transmission device has a first friction surface 9 on the hollow shaft 6 and a second friction surface 10 on the spindle nut 7. Furthermore, the torque transmission device has a preload device 11.

[0029] The preloading device 11 is designed to apply a predetermined normal force axially to the spindle 8 on the first friction surface 9 and the second friction surface 10. For this purpose, the preloading device 11 comprises disc springs 12 and a retaining ring as a locking element 13. The disc springs 12 are supported on the hollow shaft 6 via the retaining element 13 and apply a normal force to the first friction surface 9 and the second friction surface 10 via the spindle nut 7.

[0030] The first friction surface 9 and the second friction surface 10 each have surface properties, such as structure and roughness, which, in conjunction with the normal force, can transmit a suitable torque.

[0031] In an alternative embodiment, the spindle nut 7 is not connected to the rotor 5 via the hollow shaft 6, but the hollow shaft is omitted and the spindle nut 7 is connected directly to the rotor 5 via a different type of torque transmission device. Furthermore, in alternative embodiments, the torque transmission device does not have the first friction surface on the spindle nut or the second friction surface 10 connected to the rotor 5, but instead, the torque transmission device includes, for example, ball plungers that engage in recesses and whose transmissible force is adjustable. In addition, alternative embodiments do not have disc springs 12 and a locking element 13 for the preload element, but instead, for example, a different number of and / or different types of springs, such as coil springs, and / or the locking element 13 is designed, for example, as a radial pin.In another alternative embodiment, no pre-tensioning device is provided, but the normal force is achieved via coordinated dimensions of the components involved.

[0032] Fig. Figure 2 shows a partially broken-up top view of wheel brake 1.

[0033] In addition to the electromechanical brake cylinder 2, the wheel brake 1 has a brake mechanism with a caliper lever 15 and a further lever 16. A brake pad 17 is provided on each of the caliper lever 15 and the further lever 16.

[0034] Furthermore, the brake mechanism includes an eccentric shaft lever 18, which is bolted to an eccentric shaft 19 on one side and connected to the spindle 8 on the other. The axial movement of the spindle 8 rotates the eccentric shaft lever 18 together with the eccentric shaft 19 about its axis. The rotation of the eccentric shaft 19 causes the caliper lever 15, which is mounted on an eccentric shaft journal, to move towards the brake disc 20. By shifting the caliper lever 15 towards the further lever 16, the brake pad 17 provided on the caliper lever 15 comes into contact with a brake disc 20, as an element to be braked, whereby an entire wheel brake linkage, which has the caliper lever 15, a wear adjuster (not shown) and the further lever 16, is twisted so that the brake pad 17 provided on the further lever 16 also comes into contact with the brake disc 20.With further movement of the spindle 8 in the same direction, a clamping force is generated in the wheel brake linkage and applied to the brake disc 20. The braking mechanism thus converts the axial movement of the spindle 8 into the movement of the brake pad 17 relative to the brake disc 20.

[0035] A first direction of movement BR1 of the spindle 8 is defined such that the brake pad 17 approaches the brake disc 20, i.e. the element to be braked, and a second direction of movement BR2 of the spindle 8 is defined such that the brake pad 17 moves away from the brake disc 20.

[0036] The in Fig. The preloading device 11 shown is designed to apply the predetermined normal force in a direction opposite to the first direction of movement BR1 of the spindle 8 to the first and second friction surfaces 9, 10.

[0037] The in Fig. The hollow shaft 6 shown in Figure 1 has a stop 21 designed to halt the axial movement of the spindle 8 in the second direction of movement BR2 when it encounters the stop 21. If the spindle nut 7 continues to rotate after the spindle 8 has encountered the stop 21, i.e., if the rotational movement of the spindle nut 7 continues to be converted into the axial movement of the spindle 8 relative to the spindle nut 7, the spindle nut 7 is moved minimally in the direction of the first direction of movement BR1 without the second friction surface 10 lifting off the first friction surface 9. This reduces the normal force applied to the first and second friction surfaces 9 and 10, and thus the transmissible torque.This makes it possible to reduce the torque that can be transmitted by the torque transmission device when rotating the spindle nut 7, causing the spindle 8 to move relative to the spindle nut 7 in the second direction of movement BR2, compared to the torque that can be transmitted when rotating the spindle nut 7, causing the spindle 8 to move relative to the spindle nut 7 in the first direction of movement BR1. Thus, a greater torque can be transmitted for braking, ensuring the required braking force, than for releasing the brake, preventing permanent damage to the components of the electromechanical brake cylinder 2.

[0038] The wheel brake 1 further comprises a sensor 22, which is designed to detect whether the spindle 8 is in an end position in the second direction of movement BR2. This end position can either be the position of the spindle 8 in which the spindle 8 has just reached the stop 21, or alternatively a position shortly before the spindle 8 reaches the stop 21.

[0039] During operation, the braking effect of the wheel brake 1 is generated by moving the spindle 8 in the first direction of movement BR1. For this purpose, the electric motor 3 is controlled such that a rotation of the rotor 5 relative to the stator 4, via the hollow shaft 6 or the torque transmission device, causes a rotation of the spindle nut 7, resulting in the axial movement of the spindle 8 in the first direction of movement BR1.

[0040] By transmitting the movement of the spindle 8 in the first direction of movement BR1 to the eccentric shaft lever 18, the clamping lever 15 is pivoted by the eccentric shaft 19 so that the brake pad 17 provided on the clamping lever 15 rests against the brake disc 20 and, with a further movement of the spindle 8 in the first direction of movement BR1, the entire wheel brake linkage, which includes the clamping lever 15, the wear adjuster (not shown) and the further lever 16, is pivoted so that the brake pad 17 provided on the further lever 16 also rests against the brake disc 20 and subsequently the brake disc 20 is subjected to the clamping force.

[0041] To release the wheel brake 1, the spindle 8 is moved in the second direction of movement BR2 by means of the electric motor 3 via the rotor 5, the hollow shaft 6 or the torque transmission device and the spindle nut 7. This moves the brake pads 17 away from the brake disc 20 and the wheel brake 1 is released. As soon as the spindle 8 is in its end position, i.e. in the Fig. When the spindle 8 is in the right-hand position shown in Figure 1, in which it has just reached the stop 21, or in a position just before the spindle 8 reaches the stop 21, the sensor 22 detects this position of the spindle 8 and sends a signal to a brake control device to stop the electric motor 3.

[0042] In the event of a malfunction, for example if the sensor 22 is defective or the transmission of the signal from the sensor 22 is disrupted, the electric motor 3 is not stopped when the spindle 8 has reached its end position and the spindle 8 runs hard against the stop 21 in the hollow shaft 6 in the second axial movement direction BR2 of the spindle 8, whereby the axial movement of the spindle 8 is then stopped.

[0043] In this case, namely when the spindle 8 runs up against the stop 21, the torque transmission device limits the torque transmitted from the spindle nut 7 to the spindle 8 to the maximum predetermined torque value.

[0044] The torque to be transmitted by the torque transmission device is determined in such a way that the torque of the electric motor can be safely transmitted in normal operation to achieve the required braking effect, but in the event of a malfunction, damage to the components of the electromagnetic brake cylinder is prevented.

[0045] If the in Fig.In the torque transmission device shown in Figure 1, after the spindle 8 has reached the stop 21 in the second axial direction BR2, the spindle nut 7 moves minimally in the direction of the first direction BR1 during the continued conversion of the rotational movement of the spindle nut 7 relative to the spindle nut 7 into the axial movement of the spindle 8, without the second friction surface 10 lifting off the first friction surface 9. In alternative embodiments, the second friction surface 10 can also lift off the first friction surface 9. This reduces the normal force applied axially to the spindle 8 on the first and second friction surfaces 9 and 10. As a result, the transmitted torque is also reduced, thus preventing permanent damage to the spindle nut 7, the spindle 8, or other components of the electromechanical brake cylinder 2 in the event of a malfunction.This feature allows the torque to be transmitted during normal operation to be set to a higher torque value in order to safely generate the required braking force, since the torque is automatically reduced in the event of a malfunction when the spindle 8 hits the stop 21.

[0046] In alternative embodiments, in which the normal force is not applied axially to the spindle 8, the prevention of permanent damage is achieved by ensuring that the transmitted torque is less than or equal to the maximum predetermined torque value, which also prevents permanent damage, since the torque transmission device essentially slips when the maximum predetermined torque value is reached and does not transmit a higher torque. REFERENCE MARK LIST 1 wheel brake 2 electromagnetic brake cylinders 3 Electric motor 4 Stator 5 Rotor 6 Hollow shaft 7 Spindle nut 8 spindles 9 first friction surface 10 second friction surface 11 Pre-tensioning device 12 Belleville washers 13 Safety element 14 cases 15 pliers levers 16 more levers 17 brake pads 18 eccentric shaft levers 19 Eccentric shaft 20 brake discs 21 attacks 22 Sensor 23 Storage facility BR1 first direction of movement of the spindle BR2 second direction of spindle movement

Claims

[1] Electromechanical brake cylinder (2) for actuating a wheel brake (1), wherein the electromechanical brake cylinder (2) comprises: an electric motor (3) with a rotor (5), a spindle nut (7), a torque transmission device provided between the rotor (5) and the spindle nut (7) and designed to transmit a torque between the rotor (5) and the spindle nut (7), and a spindle (8) having a thread, wherein the spindle nut (7) and the spindle (8) are configured to convert a rotary movement of the spindle nut (7) into an axial movement of the spindle (8) relative to the spindle nut (7), wherein the axial movement of the spindle (8) can be converted into a movement of a brake pad (17) of the wheel brake (1) relative to a braked element of the wheel brake (1), and where the torque transmission device is designed to transmit a torque less than or equal to a maximum predetermined torque value between the rotor (5) and the spindle nut (7), characterized by , that the torque transmission device has a first friction surface (9) on the spindle nut (7) and a second friction surface (10) connected to the rotor (5), and the first friction surface (9) and the second friction surface (10) are designed to generate a maximum frictional force corresponding to the maximum predetermined torque value. [2] Electromechanical brake cylinder (2) according to claim 1, wherein the electromechanical brake cylinder (2) has a hollow shaft (6) rotatable about an axis of rotation of the spindle (8) as a component of the torque transmission device, which is rigidly connected to the rotor (5), and the hollow shaft (6) rotatably receives the spindle nut (7) to the hollow shaft (8), wherein the hollow shaft (8) has the second friction surface (10). [3] Electromechanical brake cylinder (2) according to claim 2, wherein the electromechanical brake cylinder (2) has a housing (14) and the housing (14) is designed to rotatably mount the hollow shaft (6) in the housing (14). [4] Electromechanical brake cylinder (2) according to claim 2 or 3, wherein the torque transmission device has a preloading device (11) configured to apply a predetermined normal force to the first friction surface (9) and second friction surface (10). [5] Electromechanical brake cylinder (2) according to claim 4, wherein a direction of movement of the spindle (8) to bring the brake pad (20) closer to the element to be braked is defined as the first direction of movement (BR1), and the pre-tensioning device (11) is designed to apply the predetermined normal force in a direction opposite to the first direction of movement (BR1) to the first and second friction surfaces (9, 10). [6] Electromechanical brake cylinder (2) according to claim 4 or 5, wherein the preloading device (11) comprises a disc spring (12) and a locking element (13), and the disc spring (12) is designed to be supported on the hollow shaft (6) via the locking element (13) and to apply the predetermined normal force to the first and second friction surfaces (9, 10) via the spindle nut (7). [7] Electromechanical brake cylinder (2) according to claim 5 or 6, wherein the hollow shaft (6) has a stop (21) which is designed to stop the axial movement of the spindle (8) in a second direction of movement (BR2) opposite to the first direction of movement (BR1) when it runs into the stop (21), wherein the electromechanical brake cylinder (2) is designed such that, in the event of a continued conversion of the rotary motion of the spindle nut (7) into the axial motion of the spindle (8) relative to the spindle nut (7) after the initial impact, the spindle nut (7) moves in the direction of the first direction of movement (BR 1) in order to reduce a normal force applied to the first and second friction surfaces (9, 10). [8] Wheel brake (1) with an electromechanical brake cylinder (2) according to one of the preceding claims, wherein the wheel brake (1) comprises: a brake pad (17), an element to be braked, and a braking mechanism designed to convert the axial movement of the spindle (8) into the movement of the brake pad (17) relative to the element to be braked. [9] Wheel brake (1) according to claim 8, wherein a direction of movement of the spindle (8) for removing the brake pad (17) from the element to be braked is defined as a second direction of movement (BR2), and the wheel brake (1) has a sensor (22) designed to detect whether the spindle (8) is in an end position in the second direction of movement (BR2). [10] Method for releasing a wheel brake (1) by means of an electromechanical brake cylinder (2) according to one of claims 1 to 7, wherein when the spindle (8) runs onto a stop (21) in a hollow shaft (6) of the electromechanical brake cylinder (2) so that an axial movement of the spindle (8) is stopped, the torque transmission device limits a torque transmitted from the spindle nut (7) to the spindle (8) to a maximum predetermined torque value. [11] Method according to claim 10, wherein a first axial direction of movement (BR1) of the spindle (8) is defined such that a brake pad (17) approaches an element to be braked and a second axial direction of movement (BR2) is defined opposite to the first axial direction of movement (BR1), and After the spindle (8) has come to rest against the stop (21) in the second axial direction of movement (BR2), the spindle nut (7) continues to be converted into the axial movement of the spindle (8) relative to the spindle nut (7), in order to reduce a normal force applied axially to the spindle (8) on a first and second friction surface (9, 10) in order to reduce the maximum predeterminable torque value.

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