Actuator for oscillating torque transmission

Abstract

Actuator 1 for oscillating torque transmission along a torque path 30 with an actuator housing 2, an output shaft 3 mounted in the actuator housing 2 and a first pivotable element 4 arranged coaxially to the output shaft 3, wherein the torque path 30 is defined by the transmission path of a tensile torque transmitted from the first pivotable element 4 to the output shaft 3, and wherein, in the opposite direction to this torque path 30, a torque transmission from the output shaft 3 to the first pivotable element 4 is at least reduced, wherein a passive overload clutch 10 is further provided within the torque path 30, the overload clutch 10 is closed by a preload force F1, so that during actuator operation torque is transmitted via the overload clutch 10 along the torque path 30, and the preload force F1 is designed such that, in the event of a torque transmission that is greater than a limit torque,the overload clutch 10 is opened, so that only a smaller or no torque is transmitted via the overload clutch 10 in the direction of the torque path 30 or in the opposite direction.

Description

The invention relates to an actuator for oscillating torque transmission along a torque path, comprising an actuator housing, an output shaft mounted in the actuator housing, and a first pivotable element arranged coaxially to the output shaft, wherein the torque path is defined by the transmission path of a tensile torque transmitted from the first pivotable element to the output shaft, and wherein, in the opposite direction to this torque path, a torque transmission from the output shaft to the first pivotable element is at least reduced. The invention further relates to a windshield wiper drive with such an actuator. Such actuators are known for the oscillating drive of a windshield wiper, with a braking agent for frictionally holding a component of the actuator, especially when the wiper arm is in the parked position. Windscreen wiper devices are known and described in DE 103 12 982 A1, whose wiper drive comprises a so-called reversing electric motor whose direction of rotation is reversible, so that the wiper arm performs an oscillating back-and-forth movement during operation. A problem with the known windscreen wiper devices with a reversing electric motor is that the elimination of a crank mechanism also eliminates the self-locking effect provided by the crank mechanism. This means that torques acting on the output shaft, for example, from the airflow over the wiper arm and wiper blade or from snow accumulation on the wiper arm and blade, are transmitted to the electric motor, since the worm gear typically used has insufficient self-locking.Since the electric motor is not powered when at rest (i.e., when the wiper arm is in the parked position) and therefore free to rotate, there is a risk that the wiper arm and wiper blade will be moved into the wiped area by the wind. The same effect can occur in a car wash due to the force exerted on the wiper arm by the rotating brushes. Furthermore, there is also a risk that the wiper arm could be moved in a direction that drives the wiper mechanism by snow load or similar forces. To solve this problem, DE 103 12 982 A1 proposes providing energy storage devices that absorb energy when the output shaft rotates in one direction and release it in the other. A disadvantage of the known windshield wiper device is that the inclusion of an energy storage device negates the advantage of low self-locking, namely the ability to use motors with lower power consumption, since the motor must adjust the wiper arm against the counterforce generated by the energy storage devices. From DE 10 2007 030 796 A1, a known solution involves providing a brake fluid in the area of ​​a component of the windshield wiper drive to hold the component, and thus the windshield wiper drive, in the parked position by means of frictional engagement. An actuator is provided for actuating the brake fluid. This means that additional components to be actuated are required. Other relevant devices are known, for example, from DE 698 12 520 T2, JP 2009 - 165 284 A and JP 2010 - 148 300 A. The object of the present invention is to at least reduce the disadvantages of the prior art described above. The object of the invention is solved by an actuator of the generic type with the characterizing features of claim 1. A passive overload clutch is integrated within the torque path and is closed by a preload force. During actuator operation, torque is transmitted along the torque path via the overload clutch. The preload force is designed such that if the torque transmission exceeds a certain limit, the overload clutch opens, resulting in reduced or no torque being transmitted along the torque path or in the opposite direction. While this accepts torque transmission in the opposite direction to the torque path, it effectively and simply prevents the thrust torque from exceeding a predefined limit, as the overload clutch opens when this limit is reached. Depending on the specific overload clutch used, either no torque or only a minimal amount of torque is then transmitted.Since the actuator's gearbox is designed for a certain amount of thrust torque anyway, even this incomplete suppression of thrust torque can be tolerated. In particular, it can be stipulated that the limiting torque is at least above the possible torque in the pulling direction, i.e., during actuator operation, so that the actuator can always operate. The limiting torque can be determined such that a maximum expected torque is transmitted during actuator operation, and the overload clutch is only opened when this maximum expected torque is exceeded in the direction of the torque path. This maximum expected torque then corresponds exactly to the limiting torque. Furthermore, it is provided that a power storage device is supported on one side by the output shaft or by a component non-rotatably connected to the output shaft, and on the other side by an output element or an input element of the overload clutch, so that the power storage device exerts the preload force F1 on the overload clutch to close the overload clutch. The overload clutch has an input element and an output element, whereby, during actuator operation, the torque is first transmitted along the torque path to the input element and then to the output element, and from there to the output shaft.Since relative movement between the input and output elements of this type of overload clutch is to be avoided when the clutch is closed, as long as the torque remains below the limit torque, it is sufficient to preload the input and output elements against the preload force using the energy storage device. The preload force can act on both the input and output elements. The energy storage device can be supported accordingly on the input and / or output element on one side and on the output shaft on the other. This support can be direct or indirect. According to the invention, the overload coupling is further designed as a ball coupling. In one embodiment, the input element is a gear which, for example, receives torque from a transmission element via external teeth during actuator operation. The output element is an internally toothed coupling ring. The coupling ring can be connected to the output shaft directly or indirectly via the internal teeth to transmit torque. The gear and / or the coupling ring can be axially movable relative to the output shaft. Preferably, the gear is mounted axially fixed to the output shaft but rotatably on it. To implement the overload coupling, balls are held in ball pockets between the gear and the coupling ring. These ball pockets are formed on the respective inner surfaces of the gear and coupling ring. Preferably, these are the axial inner surfaces.While the balls are held in their pockets during torque transmission below the limit torque, the gear and coupling can rotate relative to each other above the limit torque. In this case, the balls are moved out of their pockets and push the gear and coupling ring axially away from each other in the opposite direction to the preload force. The relative rotation of the coupling ring and gear initially occurs up to the angle at which the balls are moved into, or enter, an adjacent ball pocket in the circumferential direction. The balls can remain in one ball pocket on one side of the gear and coupling ring while the other ball pocket rotates relative to the ball. Even after the balls enter the next ball pocket, the transmitted torque may still be sufficient to allow further rotation.A slight rotation occurs when the balls repeatedly enter the ball pockets in a circumferential direction until the torque is sufficiently low for the balls to remain in the pockets. The resulting clunking noise is tolerated, as it is a protective mechanism of the actuator that is only rarely activated. As described above, it is possible to effectively prevent torque exceeding a limit torque from entering the actuator. For this purpose, the internal area of ​​the actuator, i.e., in particular the electric motor and a gearbox, is decoupled from the output shaft. However, this does not prevent the movement of the output shaft by a force acting upon it. The same applies to forces acting externally on elements connected to the output shaft, such as wiper arms or blades. These external forces can lead to uncontrolled movements of the output shaft and its connected elements, which can, for example, cause damage to the paintwork or other areas of a vehicle. Therefore, a further development envisages that the output element, or...The coupling ring has at least one projection, while the actuator housing has at least one, preferably two, stops cooperating with the projection. These stops are designed such that, when the output element pivots beyond a limit angle, at least one projection abuts the stop, preventing further pivoting of the output element and thus of the output shaft beyond this limit angle. For example, the output element may have two spaced-apart projections that abut different side surfaces of a single stop, thereby limiting the movement of the output shaft in both pivoting directions. Conversely, two stops or two stop surfaces may be provided, between which the projection can move circumferentially.This also effectively prevents the output shaft from pivoting beyond a limit angle. In a further development, the actuator housing can be constructed in multiple parts, particularly with a housing cover, the housing cover including a passage for the output shaft. A receptacle is formed in the area of ​​the passage, designed to receive the projection of the output element or the coupling ring. This receptacle is formed by two stops and limited in the circumferential direction, so that the projection can pivot freely within the receptacle. However, the stops prevent the output shaft from pivoting beyond a certain angle over the output element or the coupling ring, as the projection abuts the stops accordingly. Furthermore, the object of the invention is solved by a windscreen wiper drive with an actuator according to the above description, which is designed to drive a windscreen wiper arm, preferably a rear windscreen wiper. An embodiment of the invention, to which it is not limited and from which further features of the invention may arise, is shown in the following figures. They show: Fig. 1: sectional view of an actuator for oscillating torque transmission, Fig. 2: an oblique view of the gear according to Fig. 1, Fig. 3: a top view of the coupling ring from Fig. 1, and Fig. 4: an oblique view of the actuator cover according to Fig. 1. Fig. 1 shows an actuator 1 for oscillating torque transmission along a torque path 30. The direction of the torque path 30, indicated by arrows, specifies the path of torque transmission during actuator operation, i.e., during the pulling operation of the actuator 1. During the pulling operation of the actuator 1, an oscillating torque, i.e., one that regularly changes its direction of rotation, is generated by corresponding changes in the direction of rotation of an electric motor 17. The torque is transmitted by a pinion 22 from a rotor shaft 23 of the electric motor 17 to a first pivotable element 4, here a gear 13. Starting from gear 13, the torque during traction is transmitted along the torque path 30 via balls 14 to a coupling ring 7. Gear 13 represents an input element 11 and coupling ring 7 an output element of a ball coupling 5. The ball coupling 5 functions as an overload coupling 10. The coupling ring 7 has internal teeth 19 that mesh with external teeth 20 of an output shaft 3. By reversing the direction of rotation due to the electric motor 17, an oscillating motion of the output shaft 3 is generated. The output shaft 3 is a wiper shaft of a windshield wiper drive. To operate, in particular, a rear window wiper, the output shaft 3 is connected to a wiper arm (not shown) which has a wiper blade for wiping a windshield. The output shaft 3 oscillates, i.e., it is regularly pivoted about a rotational axis 24 that is parallel to the rotational axis 25 of the rotor shaft 23. For the supply of spray water, the output shaft 3 has a spray water channel 26 that runs coaxially to the rotational axis 24. The ball coupling 5 has a gear 13 as its input element 11, which meshes with the teeth of the pinion 22 via an external toothing 27. The gear 13 is arranged coaxially around the output shaft 3 and supported on it by a bearing 16. The bearing races of the bearing 16 are integrally formed from a bearing surface of the gear 13 and the output shaft 3. Therefore, there is no direct torque transmission from the gear 13 to the output shaft 3. In the case of actuator operation, torque transmission along the torque path 30 occurs via the balls 14 axially between the gear 13 and the coupling ring 7. The gear 13 is driven by the electric motor 17 via the pinion 22 and rotates on the bearing 16 about the output shaft 3, i.e., about the axis of rotation 24. As shown in Fig. 2, the gear 13 has ball pockets 15 on its axial inner surface 28. The ball pockets 15 are all radially equidistant from the axis of rotation 24 and serve to partially receive the balls 14. As long as the balls 14 are received in the ball pockets 15 of the gear 13, torque is transmitted from the gear 13 to the balls 14. As shown in Fig. 3, the coupling ring 7 also has ball pockets 15' on its axial inner surface 29. The distance of the ball pockets 15' to the axis of rotation 24 corresponds to the distance of the ball pockets 15 to the axis of rotation 24. The inner surfaces 28 and 29 of the gear 13 and coupling ring 7 are axially opposite each other and accommodate the balls 14 between them. When the balls 14 are each received in the ball pockets 15, 15', the torque is transmitted from the gear 13 to the balls 14 and then to the coupling ring 7. Through the internal teeth 19 of the coupling ring 7, the torque is finally transmitted to the output shaft 3, thereby actuating the windshield wiper. The torque transmission from the electric motor 17 is independent of the direction of rotation of the electric motor 17 or the gear 13, thereby generating a corresponding pendulum movement of the windshield wiper. As shown in Fig. 1, the internal teeth 19 of the clutch ring 7 mesh with external teeth 20 of the output shaft 3 and are axially displaceable within it. A force storage element 9, designed here as a helical compression spring 21, presses the clutch ring 7 against the gear 13 with a preload force F1, thereby clamping the balls 14 in the respective ball pockets 15, 15' between the gear 13 and the clutch ring 7, thus transmitting torque. For this purpose, the helical compression spring 21 is supported on one side by a support plate 50 on the output shaft 3 and on the other side directly on the clutch ring 7. The support plate 50 is axially secured by a retaining ring 51 in a circumferential groove (not shown) in the output shaft 3.The preload force F1 is designed such that, at the expected maximum torque during actuator operation, the balls 14 are securely clamped axially in their respective ball pockets 15, 15', ensuring that the maximum expected torque is reliably transmitted. Therefore, no torque is expected in the direction of the torque path that could actuate the overload clutch 10, thus preventing any further torque transmission. In the parked position of the windshield wiper, or actuator 1, a thrust torque can be introduced into the output shaft 3 in the opposite direction to the torque path 30, for example, due to a snow load or wind. This thrust torque is not opposed by any tensile torque generated by the electric motor 17, so it is initially transmitted unimpeded from the clutch ring 7 to the gear 13 and then on to the pinion 22. However, if the thrust torque exceeds a limit torque that corresponds at least to the maximum expected tensile torque, the energy storage device 9, or the helical compression spring 21, is designed such that, by converting the thrust torque into an axial force via the balls 14, the thrust torque is sufficient to overcome the preload force F1 when the limit torque is exceeded.As a result, the coupling ring 7 shifts axially away from the gear 13 to such an extent that the balls 14 are moved out of the ball pockets 15, 15' at least far enough for the gear 13 and coupling ring 7 to rotate relative to each other. When the limit torque is exceeded, the output shaft 3, and thus the coupling ring 7, rotates freely relative to the gear 13 until the balls 14 can engage in the next ball pockets 15, 15' in the circumferential direction. If the thrust torque then falls below the limit torque again, the coupling ring 7 and the gear 13 are once more coupled to each other via the balls 14. On the other hand, the coupling ring 7 continues to rotate freely. A possible "knocking noise" is accepted as a necessary consequence. For better guidance of the balls 14 in the circumferential direction, a corresponding guide groove can be provided in the circumferential direction between the ball pockets 15, 15'.In this way, overloading of the electric motor 17 or other gear elements of the actuator 1 by excessive thrust torque can be avoided. To prevent the wiper arm from pivoting beyond a certain angle in the parked position, even under snow load or other influences such as wind, stops 32 are provided in a housing cover 41 of the actuator housing 2, as shown in Fig. 4. For this purpose, the actuator housing 2 is designed in multiple parts, specifically a base body 44, a bottom 45, and a housing cover 41. A stator overmolding 46 is provided axially between the bottom 45 and the base body 44. This overmolding accommodates the rotor 48 of the electric motor 17 with the rotor shaft 23 in a first receptacle 47 and the rotor shaft 3 in a second receptacle 49, which is arranged axially parallel to the first. The rotor shaft 3 is supported in the second receptacle 49 by a first bearing 52 and in the housing cover 41 by a second bearing 53.As shown in Fig. 4, the housing cover 41 includes a passage 42 for the output shaft 3. Circumferentially equidistant from the axis of rotation 24 of the output shaft 3, the housing cover 41 has a receptacle 43, which is circumferentially limited or formed by two stops 32. The receptacle 43 corresponds to a projection 31 of the coupling ring 7, as shown in Fig. 3. The coupling ring 7 is axially movably mounted on an external toothing 20 of the output shaft 3, as described, and is received in the housing cover 41 in the receptacle 43 such that, at least in the actuated case of the overload clutch 10, i.e., when a thrust torque exceeds the limit torque, side surfaces 40 of the projection 31 abut against stop surfaces 33 of one of the stops 32 when a limit angle is exceeded. In the circumferential direction within the receptacle 43, the projection 31 is freely pivotable and thus also the clutch ring 7 and output shaft 3.A pivoting beyond a limit angle can be reliably prevented by the stops 32 in the housing cover 41. In combination with the overload coupling 10 or ball coupling 5 and the stops 32 in the housing cover 41 of the actuator housing 2, both overloading of the actuator gearbox or actuator drive and pivoting of a wiper arm beyond a limit angle can be safely and easily avoided. Reference symbol list 1 Actuator 2 Actuator housing 3 Output shaft 4 First pivoting element 5 Ball coupling 7 Coupling ring 9 Energy storage 10 Overload coupling 11 Input element 12 Output element 13 Gear 14 Balls 15, 15' Ball pockets 16 Bearing 17 Electric motor 19 Internal gearing 20 External gearing 21 Helical compression spring 22 Pinion 23 Rotor shaft 24 Axis of rotation 25 Axis of rotation 26 Splash water channel 27 External gearing 28 Axial inner side 29 Axial inner side 30 Torque path 31 Projection 32 Stop 33 Stop surface 40 Side surface 41 Housing cover 42 Feedthrough 43 Mount 44 Base body 45 Bottom 46 Stator overmolding 47 First mount 48 Rotor 49 Second mount 50 Support plate 51 Retaining ring F1 Preload force

Claims

Actuator (1) for oscillating torque transmission along a torque path (30) comprising an actuator housing (2), an output shaft (3) mounted in the actuator housing (2), and a first pivotable element (4) arranged coaxially to the output shaft (3), wherein the torque path (30) is defined by the transmission path of a tensile torque transmitted from the first pivotable element (4) to the output shaft (3), and wherein, in the opposite direction to this torque path (30), a torque transmission from the output shaft (3) to the first pivotable element (4) is at least reduced, wherein a passive overload clutch (10) is further provided within the torque path (30), the overload clutch (10) is closed by a preload force F1, so that during actuator operation, torque is transmitted via the overload clutch (10) along the torque path (30), the preload force F1 is designed such that during torque transmission,which is greater than a limit torque, the overload clutch (10) is opened so that only a smaller or no torque is transmitted via the overload clutch (10) in the direction of the torque path (30) or in the opposite direction, a power storage device (9) is supported on one side on the output shaft (3) or on a component non-rotatably connected to the output shaft (3) and on the other side on an output element (12) and / or an input element (11) of the overload clutch (10) so that it exerts the preload force F1 on the overload clutch (10) to close the overload clutch (10), characterized in that the overload clutch (10) is designed as a ball clutch (5), wherein a gear (13) is the input element (11), and an internally toothed clutch ring (7) is the output element (12) of the ball clutch (5), balls (14) are arranged between the gear (13) and the clutch ring (7),which, during torque transmission below the limit torque, are received in ball pockets (15, 15') on the respective inner side of the gear (13) and coupling ring (7), and wherein, when the limit torque is exceeded, the gear (13) and the coupling ring (7) are rotated circumferentially relative to each other, the balls (14) are moved out of at least one of the ball pockets (15, 15'), so that the gear (13) and / or the coupling ring (7) are displaced axially against the preload force F1, until the balls (14) are moved into a circumferentially adjacent ball pocket (15, 15') by means of the preload force F1. Actuator (1) according to claim 1, characterized in that the output element (12) has at least one projection (31), the actuator housing (2) has at least one, preferably two stops (32) cooperating with the projection (31), wherein the stops (32) are designed such that when the output element (12) is pivoted beyond a limit angle, at least one projection (31) abuts the stop (32) and further pivoting of the output element (12) and thus of the output shaft (3) beyond this limit angle is prevented. Actuator (1) according to claim 2, characterized in that the coupling ring (7) has a radially outwardly extending projection (31), the actuator housing (2) has two stops (32) corresponding to the projection (31), the stops (32) have circumferentially extending stop surfaces (33) so that when the coupling ring (7) is pivoted beyond a limit angle, a side surface (40) of the projection (31) abuts a stop surface (33). Actuator (1) according to one of claims 2 or 3, characterized in that the actuator housing (2) has a housing cover (41), the housing cover (41) comprises a passage (42) for the output shaft (3), the housing cover (41) has in the area of ​​the passage (42) a receptacle (43) formed circumferentially around the output shaft (3) for receiving the projection (31), which is limited by two stops (32) formed directly from the housing cover (41). Windscreen wiper drive with an actuator (1) according to one of claims 1 to 4 for oscillating drive of a windscreen wiper arm, preferably a rear windscreen wiper.

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