Electromechanical actuator for a motor vehicle and method for actuating such an actuator

Abstract

Electromechanical actuator (1) for a motor vehicle, comprising a drive unit (2) with a drive shaft (3) and a driven gear (4) operatively connected to the drive shaft (3), wherein the drive unit (2) is rotatably mounted on an actuator housing (6) by means of bearing means (5) with limited rotational elasticity, wherein a locking device (7) is arranged between the drive unit (2) and the driven gear (4), which, in an unactuated state of the drive unit (2), blocks a rotational movement of the driven gear (4), wherein, in an actuated state of the drive unit (2), the locking device (7) releases a rotational movement of the driven gear (4) of the drive unit (2), wherein the locking device (7) has a spring-loaded locking pin (8), the sliding section (9) of which is provided for bearing against a switching contour (13a) of the drive unit (2).and whose detent section (11) is provided for engagement in a detent contour (12) of the output gear (4).

Description

[0001] The invention relates to an electromechanical actuator for a motor vehicle, comprising a drive unit with a drive shaft and an output gear operatively connected to the drive shaft. Furthermore, the invention relates to a method for actuating such an actuator.

[0002] DE 10 2013 211 230 A1 discloses a device for steering a rear axle of a motor vehicle having at least one rear axle and at least one front axle. The device comprises an actuator with which a steering movement can be performed between a point fixed to the vehicle and at least one articulation point of a steering linkage to which the actuator is connected. To generate a translational displacement movement, the actuator has a shaft element rotatably mounted relative to a housing element. Furthermore, means are provided for at least temporarily preventing a rotational movement between the shaft element and the housing element.These means comprise at least two pins arranged in the housing element or in the shaft element, wherein the pins are designed to engage in corresponding recesses in the shaft element or in the housing element in order to establish a positive connection between the housing element and the shaft element.

[0003] From DE 10 2012 025 096 A1, a drive unit is known which comprises: an electric motor (1) for generating a rotary movement of a drive shaft and a planetary gear mechanism with at least three wheels, wherein a first wheel of the planetary gear mechanism transmits power directly or indirectly to an output shaft via the drive shaft of the electric motor and a second wheel of the planetary gear mechanism transmits power directly or indirectly. In order to create a drive unit which, even in the event of a power failure, still has sufficient mechanical energy to bridge a predetermined time, the invention proposes an energy storage device for storing potential energy, which transfers the energy to a third wheel of the planetary gear mechanism.

[0004] DE 3520502 A1 discloses a drive device for a valve spindle with an electric motor and a downstream gear. The motor and gear are arranged offset from the axis of the valve spindle so that the spindle can be moved through the drive device unhindered by the motor and gear and can be adjusted to any stroke. A hand crank is provided for emergency operation of the gear. The handle is made of a transparent material and also serves as a visual indicator for the position of the spindle. The spindle is operated by means of a nut driven by the gear via a toothed belt. The toothed belt is loaded by a tension pulley, and this pulley is provided with a detent which, when the gear is stationary, engages in a notch on the circumference of the nut, thereby blocking it from rotating to prevent further rotation and, in particular, reverse rotation of the nut and thus the spindle.

[0005] The object of the present invention is to further develop an electromechanical actuator for a motor vehicle, with the particular aim of reducing the actuator's energy consumption. According to the invention, this object is achieved by the actuator according to claim 1. Appropriate further developments can be found in the dependent claims.

[0006] An electromechanical actuator according to the invention for a motor vehicle comprises a drive unit with a drive shaft and an output gear operatively connected to the drive shaft. The drive unit is mounted on an actuator housing in a rotationally elastic manner by bearing means for limited rotation. A blocking device is arranged between the drive unit and the output gear, which, when the drive unit is not actuated, blocks a rotational movement of the output gear. When the drive unit is actuated, the blocking device releases a rotational movement of the output gear of the drive unit. In other words, the blocking device is unlocked by actuating the drive unit.

[0007] The drive unit is preferably designed as an electric motor, wherein the drive unit is provided to set the drive shaft in a rotational movement, wherein furthermore the drive unit is operable independently of the direction of rotation. The drive unit is spatially delimited, for example, by a motor housing and mounted on the actuator housing by the bearing means, wherein in this case the means are formed or arranged on the motor housing. The rotationally elastic mounting of the drive unit is to be understood that the motor housing is arranged on the actuator housing in such a way that movement of the motor housing in an axial direction and in a transverse direction is prevented, but rotation about a rotational axis is possible to a limited extent.

[0008] The bearing means comprise elastic elements, for example spring elements, which are pre-tensioned when the drive unit rotates in the actuated state of the drive unit and are released again in the non-actuated state of the drive unit in order to return the drive unit to its starting position. In other words, in the non-actuated state, the drive unit is not in operation and is switched off or de-energized, whereby the elastic elements of the bearing means are not loaded. Furthermore, the blocking device is deactivated or inactive when the drive unit is not actuated. In contrast, in the actuated state, the drive unit is in operation and is switched on or supplied with electrical energy. Furthermore, the blocking device is activated when the drive unit is actuated.

[0009] The rotation of the drive shaft causes the drive unit to rotate, resulting in a reaction torque of the drive unit. This reaction torque is used to actuate or activate the locking device by rotating the drive unit, thus enabling rotation of the output gear during actuator operation. If the drive shaft is not rotating, the drive unit is returned to its original position, leaving the locking device unactuated or inactive.

[0010] The blocking device comprises a spring-loaded blocking pin which, in the unactuated state of the drive unit, is provided to come into contact with a sliding portion on an outer circumferential surface of the drive unit and with a locking portion in a locking contour of the output gear in order to block the rotational movement of the output gear, wherein the drive unit, in the actuated state, is provided to rotate counter to the bearing means as a result of the reaction torque, wherein the sliding portion of the blocking pin slides along a switching contour of the outer circumferential surface in order to release the rotational movement of the output gear.

[0011] In other words, when the drive unit is in the non-actuated state, the blocking pin comes into contact with both the drive unit, in particular its housing element, and the output gear, in particular its outer circumferential surface. Preferably, there is a positive connection between the blocking pin and the output gear, which blocks the rotational movement of the output gear when not in operation. In other words, unwanted rotation of the output gear is prevented when the drive unit is in the non-actuated state or when the drive unit is not in operation. When the drive unit is actuated, the blocking pin only comes into contact with the drive unit, whereby the positive connection between the blocking device and the output gear is released.

[0012] Preferably, each bearing means comprises two spring elements, which are accommodated in a respective recess on the drive unit and between which a housing-fixed bearing pin is arranged and guided. The bearing pin is attached to the actuator housing and projects into the respective recess. The bearing pin preferably has a cylindrical shape to ensure low-friction guidance of the drive unit relative to the bearing pin and to prevent unintentional tilting. The recess is designed such that rotation of the drive unit about the rotation axis is possible during operation. In particular, the recess can be elongated, oval, or rectangular.

[0013] During actuator operation, depending on the direction of rotation of the drive unit, only one of the two spring elements is compressed and thus preloaded between the inner wall of the recess and the bearing pin, i.e., the two contact surfaces of the respective spring element. When the actuator is switched off, i.e., while the drive unit is not operating, the spring element relaxes again, so that the drive unit is returned to its original position and both spring elements are de-tensioned when not in operation.

[0014] The invention includes the technical teaching that the blocking device comprises a preload spring for axially preloading the blocking pin, wherein the preload spring is axially supported relative to a support section fixed to the housing. As the drive unit rotates, the sliding section of the blocking pin of the blocking device, which is spring-loaded by the preload spring, slides over the outer surface of the drive unit or the motor housing, specifically along the switching contour. The blocking pin is constantly pressed axially against the outer surface by the preload spring, so that the sliding section rests against the drive unit at all times. This spring force of the preload spring is supported against the support section, which is, for example, firmly connected to the actuator housing.

[0015] The switching contour is preferably designed such that the distance between the output gear and the outer surface of the drive unit increases when the drive unit rotates, so that the positive connection between the blocking pin and the output gear is released by the blocking pin being constantly pressed against the switching contour and thus being guided radially out of the detent contour of the output gear as it slides over the switching contour of the outer surface. The advantage here is that no additional actuator is required to actuate the blocking pin. The blocking pin is actuated exclusively by the relaxation of the preload spring, which results from the blocking pin sliding over the switching contour on the outer surface of the drive unit. In other words, a rotational movement of the drive unit is converted into a longitudinal movement of the blocking pin radially to the drive unit.Another advantage is that the position of the output gear is maintained by the positive connection when the drive unit is not in operation, as the locking device prevents rotation of the output gear. The actuator is thus designed to be particularly energy-efficient, as the actuator is only switched on or actuated to position the output gear.

[0016] The locking contour is preferably designed to correspond to the outer contour of the locking section on the locking pin to ensure a secure, positive connection between the locking device and the output gear and prevent unwanted rotation of the output gear. Furthermore, the locking contour ensures a uniform load transfer to the locking device.

[0017] Preferably, the switching contour is at least partially ramp-shaped. The switching contour can, for example, have an incline or decline in the form of a linear function or in the form of a curve.

[0018] Furthermore, a further switching contour is preferably formed on the outer circumferential surface of the drive unit, wherein the sliding portion of the blocking pin slides off the further switching contour when the drive unit rotates in the opposite direction. The two switching contours are, in particular, formed mirror-inverted to each other on the outer circumferential surface of the drive unit, wherein an apex portion is preferably formed between the two switching contours, against which the sliding portion of the blocking pin rests during non-operation.

[0019] When the drive unit is actuated, the drive unit rotates clockwise or counterclockwise depending on the direction of rotation of the drive shaft, with the sliding section consequently sliding along either the first switching contour or the second switching contour. This enables the positive connection between the locking device and the output gear to be released, regardless of the direction of rotation of the drive unit.

[0020] Preferably, two recesses are provided, each with a bearing pin and two spring elements, wherein the two recesses are arranged opposite one another on the drive unit relative to a rotational axis of the drive unit and parallel to one another. As a result, the rotation of the drive unit is guided evenly and continuously by the symmetrically arranged recesses. Alternatively, three or more recesses with associated spring elements and bearing pins can be provided, wherein in this case the recesses are arranged evenly spaced from one another on the drive unit or on the motor housing. The higher the number of recesses or spring elements, the greater the overall rigidity of the bearing means.

[0021] According to a preferred embodiment, the drive shaft of the drive unit is operatively connected to the output gear via a belt. The actuator is therefore designed as a belt drive, with the drive shaft being designed as a pinion and the output gear as a belt pulley. The term "operatively connected" means that two elements, in this case the drive shaft and the output gear, can be directly connected to one another, or that further elements, for example one or more shafts or gears, are located between the two elements. Alternatively, the actuator can also be designed as a gear transmission, with the drive shaft in this case being connected in a rotationally fixed manner to a first gear and the output gear being a second gear or being connected to a second gear that meshes with the first gear.

[0022] Preferably, a plurality of locking contours are formed on the outer circumferential surface of the output gear for at least partially receiving the locking portion of the blocking pin. The locking contours can be distributed around the circumference or arranged in a defined circumferential section of the outer circumferential surface of the output gear, whereby the spacing of the locking contours can be chosen to be equal or unequal. Preferably, the locking contours are arranged evenly distributed on an outer circumferential surface of the output gear.

[0023] The electromechanical actuator according to the invention can be used in particular for rear-wheel steering of one or more rear axles of a motor vehicle.

[0024] According to a method according to the invention for actuating an electromechanical actuator for a motor vehicle, a rotational movement of an output gear, which is operatively connected to a drive shaft of a drive unit, is blocked in an unactuated state of the drive unit by a blocking device arranged between the drive unit and the output gear, wherein the rotational movement of the output gear is released in an actuated state of the drive unit by a reaction torque of the drive unit.

[0025] Further measures improving the invention are described in more detail below together with the description of a preferred embodiment of the invention with reference to the figures, wherein identical or similar elements are provided with the same reference numerals. Fig. 1 a schematic view of an electromechanical actuator according to the invention according to a preferred embodiment, and Fig. 2 a detailed view of a blocking device of the actuator according to the invention according to Fig. 1.

[0026] According to Fig. 1, an electromechanical actuator 1 for a motor vehicle (not shown here) comprises a drive unit 2, in the present case designed as an electric motor, with a drive shaft 3 and an output gear 4. The actuator 1 is in the present case designed as a belt drive, wherein the drive shaft 3 is a pinion and the output gear 4 is in the present case a belt gear, and wherein the drive shaft 3 is operatively connected to the output gear 4 via a belt 18.

[0027] Here, a motor housing 23 of the drive unit 2 is shown, wherein the motor housing 23 is elastically mounted on an actuator housing 6 by two bearing means 5 for limited rotation. Each of these two means 5 comprises two spring elements 14a, 14b with a bearing pin 16a or 16b arranged therebetween, wherein the two spring elements 14a, 14b and the respective bearing pin 16a or 16b are received in a respective recess 15a, 15b on the drive unit 2. The two recesses 15a, 15b are designed in the shape of an elongated hole and are arranged opposite and parallel to one another with respect to a rotation axis 17 of the drive unit 2. In other words, the motor housing 23 of the drive unit 2 is rotatable to a limited extent about the rotation axis 17, wherein the motor housing 23 is guided by the bearing pins 16a, 16b during rotation.

[0028] A stationary blocking device 7 is arranged between the motor housing 23 and the output gear 4, on which a spring-loaded blocking pin 8 is arranged for axial displacement. The blocking device 7 is intended to create a positive connection with the output gear 4 in an unactuated state or when the drive unit 2 is not in operation. In an actuated state or when the drive unit 2 is in operation, the blocking pin 8 slides, depending on the direction of rotation of the drive shaft 3, either over a first or second switching contour 13a, 13b formed on an outer surface 10 of the motor housing 23 in order to release the positive connection between the blocking device 7 and the output gear 4.

[0029] By releasing this connection, rotation of the driven gear 4 is released. The exact functioning of the blocking device 7 is explained below in Fig. 2 described in more detail.

[0030] After Fig. 2, the blocking pin 8 of the blocking device 7 has a sliding section 9 that rests against the outer surface 10 of the motor housing 23. In this case, the blocking device 7 is shown when the actuator 1 is not in operation. The blocking pin 8 is axially preloaded by a biasing spring 19, so that the sliding section 9 is constantly pressed against the outer surface 10 of the motor housing 23. The spring force of the biasing spring 19 is supported against a support section 20 connected to the actuator housing 6.

[0031] Furthermore, the blocking pin 8 has a locking portion 11, which, when the actuator 1 is not in operation, is received in a locking contour 12 of the output gear 4 and creates a positive connection between the blocking device 7 and the output gear 4. Thus, this positive connection blocks or prevents unwanted rotation of the output gear 4 when the actuator 1 is not in operation. Furthermore, a set angular position of the output gear 4 is maintained by the positive connection.

[0032] During operation of the actuator 1, the drive unit 2 is supplied with electrical energy to set the drive shaft 3 in a rotational movement. Due to a reaction torque acting on the motor housing 23, the motor housing 23 is rotated clockwise or counterclockwise depending on the direction of rotation of the drive shaft 3. This rotation is achieved by the Fig. 1 described means 5.

[0033] When the motor housing 23 is rotated counterclockwise, the first spring element 14a in the first recess 15a and the first spring element 14a in the second recess 15b are axially compressed and preloaded. The sliding portion 9 of the locking pin 8 slides over the first ramp-shaped switching contour 13a on the outer surface 10 of the motor housing 23. In this case, the first switching contour 13a has a curved profile or a concave shape, so that when the motor housing 23 is rotated counterclockwise and while the sliding portion 9 is guided along the first switching contour 13a, the distance between the outer surface 10 and the output gear 4 and the support portion 20 increases.

[0034] The preload spring 19 causes the axial displacement of the blocking pin 8, with the sliding section 9 constantly resting against and guided by the first switching contour 13a. The spring-loaded blocking pin 8 thereby moves out of the locking contour 12, and the positive connection between the blocking device 7 and the driven gear 4 is released. By releasing the positive connection between the blocking device 7 and the driven gear 4, rotation of the driven gear 4, which is driven by the drive shaft 3 and the belt 18, is released.

[0035] When the motor housing 23 is rotated clockwise, the second spring element 14b in the first recess 15a and the second spring element 14b in the second recess 15b are compressed and preloaded. The sliding portion 9 of the blocking pin 8 slides over the second ramp-shaped switching contour 13b on the outer surface 10 of the motor housing 23. The second switching contour 13b is mirror-inverted to the first switching contour 13a, with an apex portion 21 formed between the two switching contours 13a, 13b to form a support surface for the sliding portion 9 when the actuator 1 is not in operation. The process for releasing the positive connection between the blocking device 7 and the output gear 4 is analogous to the previously described counterclockwise rotation of the motor housing 23.By releasing the positive connection between the blocking device 7 and the output gear 4, rotation of the output gear 4 in an opposite direction of rotation is released.

[0036] In this case, a plurality of locking contours 12 are formed on the outer circumferential surface 10 of the output gear 4 for at least partially receiving the locking section 11 of the blocking pin 8. The locking contours 12 are evenly distributed on an outer circumferential surface 22 of the output gear 4 and are designed to correspond to the locking section 11 of the blocking pin 8. In this case, the locking contours 12 are triangular in cross-section, with the locking section 11 having an arrow shape complementary to the locking contours 12. Alternatively, it is conceivable for the locking contours 12 to be spaced at different distances from one another.

[0037] Furthermore, alternatively, only a single locking contour 12 can be provided on the outer peripheral surface 22 of the output gear 4. List of reference symbols 1 actuator 2 drive unit 3 drive shaft 4 Output gear 5 Storage means 6 Actuator housing 7 Blocking device 8 locking pin 9 sliding section 10 Outer surface 11 Rest section 12 locking contour 13a, 13b Switching contour 14a, 14b spring element 15a, 15b recess 16a, 16b Positioning pin 17 Rotation axis 18 belts 19 Preload spring 20 support section 21 apex section 22 Outer peripheral surface 23 Engine housing

Claims

[1] An electromechanical actuator (1) for a motor vehicle, comprising a drive unit (2) with a drive shaft (3) and an output gear (4) operatively connected to the drive shaft (3), wherein the drive unit (2) is mounted on an actuator housing (6) in a rotationally elastic manner by means of bearing means (5), wherein a blocking device (7) is arranged between the drive unit (2) and the output gear (4), which, in an unactuated state of the drive unit (2), blocks a rotational movement of the output gear (4), wherein the blocking device (7) releases a rotational movement of the output gear (4) of the drive unit (2) in an actuated state of the drive unit (2), wherein the blocking device (7) has a spring-loaded blocking pin (8), the sliding portion (9) of which is provided for engagement with a switching contour (13a) of the drive unit (2),and whose locking section (11) is provided for engagement in a locking contour (12) of the output gear (4). [2] Actuator (1) according to claim 1, characterized by in that the blocking device (7) comprises a spring-loaded blocking pin (8) which, in the unactuated state of the drive unit (2), is provided to come into contact with the sliding section (9) on an outer circumferential surface (10) of the drive unit (2) and with the locking section (11) in the locking contour (12) of the output gear (4) in order to block the rotational movement of the output gear (4), wherein the drive unit (2) in the actuated state is provided to rotate counter to the bearing means (5), wherein the sliding section (9) of the blocking pin (8) slides along the switching contour (13a) of the outer circumferential surface (10) in order to release the rotational movement of the output gear (4). [3] Actuator (1) according to one of claims 1 or 2, characterized bythat each bearing means (5) comprises two spring elements (14a, 14b) which are received in a recess (15a) on the drive unit (2) and between which a housing-fixed bearing pin (16a) is arranged and guided. [4] Actuator (1) according to claim 3, characterized by that two recesses (15a, 15b) with a respective bearing pin (16a, 16b) and two spring elements (14a, 14b) are provided, wherein the two recesses (15a, 15b) are formed opposite one another and parallel to one another on the drive unit (2) with respect to a rotation axis (17) of the drive unit (2). [5] Actuator (1) according to one of the preceding claims, characterized by that the drive shaft (3) of the drive unit (2) is operatively connected to the output gear (4) via a belt (18). [6] Actuator (1) according to one of claims 2 to 5, characterized bythat the blocking device (7) comprises a preload spring (19) for axially preloading the blocking pin (8), wherein the preload spring (19) is axially supported relative to a support section (20) fixed to the housing. [7] Actuator (1) according to one of claims 2 to 6, characterized by that the switching contour (13a) is at least partially ramp-shaped. [8] Actuator (1) according to one of claims 2 to 7, characterized by that a plurality of locking contours (12) are formed on the outer circumferential surface (10) of the output gear (4) for at least partially receiving the locking section (11) of the blocking pin (8). [9] Actuator (1) according to one of claims 2 to 8, characterized by that a further switching contour (13b) is formed on the outer circumferential surface (10) of the drive unit (2), wherein the sliding section (9) of the blocking pin (8) slides off the further switching contour (13b) when the drive unit (2) rotates in the opposite direction. [10] Method for actuating an electromechanical actuator (1) for a motor vehicle, wherein a rotational movement of an output gear (4), which is operatively connected to a drive shaft (3) of a drive unit (2), is blocked in an unactuated state of the drive unit (2) by a blocking device (7) arranged between the drive unit (2) and the output gear (4), the blocking pin (8) of which is received in a detent contour (12) of the output gear (4) when the actuator (1) is not in operation and establishes a positive connection with the output gear (4), wherein the rotational movement of the output gear (4) is released in an actuated state of the drive unit (2) by a reaction torque of the drive unit (2) with release of the positive connection.

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