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 that is transmitted from the first pivotable element 4 to the output shaft 3, and wherein, in the opposite direction to this torque path 30, torque transmission from the output shaft 3 to the first pivotable element 4 is avoided or at least reduced, wherein a braking device 5 is provided parallel to the torque path, the braking device 5 is effective between the output shaft 3 and the actuator housing 2 or a component non-rotatably connected to the actuator housing 2, and the braking device 5 is closed when the actuator 1 is inactive.so that a torque transmission from the output shaft 3 to the first rotating element 4 in the opposite direction to the torque path 30 is avoided or at least reduced, and furthermore the braking device 5 is opened by the torque transmitted from the first pivotable element 4 to the output shaft 3 when the actuator 1 is active, i.e. in the pulling operation of the actuator 1 regardless of the direction of rotation of the first pivotable element 4.

Description

[0001] 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, torque transmission from the output shaft to the first pivotable element is avoided or at least reduced. The invention further relates to a windshield wiper drive with such an actuator.

[0002] 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.

[0003] 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 due to driving conditions 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.

[0004] 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.

[0005] 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.

[0006] The object of the present invention is to at least reduce the disadvantages of the prior art described above.

[0007] The object of the invention is solved by an actuator of the generic type with the characterizing features of claim 1.

[0008] A braking device is provided parallel to the torque path. The torque path is defined by the transmitted tensile torque within the actuator such that it runs in one direction, from a drive to the actuator's output shaft, and is transmitted from one component to the next along this path. "Parallel to the torque path" means, with respect to the braking device, that no torque is transmitted via the braking device itself.

[0009] The braking device is effectively installed between the output shaft and the actuator housing. It can interact with a component that is rotationally fixed to the output shaft or the actuator housing.

[0010] The braking device is closed when the actuator is inactive, thus preventing or at least reducing torque transmission from the output shaft to the first rotating element in the opposite direction to the torque path. This is a normally closed (NC) brake.

[0011] The braking device is opened by the torque transmitted from the first pivoting element to the output shaft when the actuator is active, i.e., during traction operation, regardless of the direction of rotation of the first pivoting element. Therefore, no additional energy is required to actuate the braking device. The necessary energy is derived directly from the transmitted traction torque. This eliminates the need for separate mechanisms to actuate the braking device.

[0012] By further stipulating that the braking device be designed as a multi-plate brake with inner plates non-rotatably connected to the output shaft and outer plates non-rotatably connected to the actuator housing, a simple, scalable, and space-saving braking device can be provided within the actuator. The inner and / or outer plates are axially displaceable for opening and closing the multi-plate clutch, while preferably transmitting torque or providing braking support via a toothed connection. Scalability can be achieved through the friction material used, the diameter of the plates, and / or the number of inner and outer plates.

[0013] The axial direction here and in the following refers to the axis of rotation of the output shaft.

[0014] In a further development, it may be provided that a power storage device is supported on the one hand on the actuator housing or on the output shaft or on a component non-rotatably connected to one of these components and on the other hand on an inner or outer lamella or a pressure plate of the multi-disc brake, so that it exerts a preload force F to close the multi-disc brake.

[0015] The energy storage device for closing the multi-disc brake can be, for example, one from the group, a compression spring, a coil compression spring or a disc spring.

[0016] As described, the multi-disc brake can be designed with a pressure plate that is subjected to a preload force by the energy storage device, causing the inner and outer discs to be pressed together to generate friction. The pressure plate can be fixed against rotation by means of an internal toothing on an external toothing of the output shaft, so that it rotates with the output shaft. On the axially opposite side of the energy storage device, a support disc can be similarly fixed against rotation to the output shaft, so that the preload force of the energy storage device is generated by its axial clamping between the support disc and the pressure plate. The preload force that must be overcome to release the brake or multi-disc brake can then be determined by the distance between the pressure plate and the support disc, i.e., the deflection of the energy storage device, and by the choice of the energy storage device itself.For example, a preferred spring constant can be set. In particular, by selecting a helical compression spring or a compression spring, a radially very low-profile closing mechanism for the brake system / multi-disc brake can be achieved. Supporting the actuator exclusively on components that are rotationally fixed to the output shaft ensures that the energy storage device rotates with the output shaft. This eliminates rubbing or friction points. While the support disc can alternatively be rotationally fixed to the actuator housing instead of the output shaft, this necessitates accepting friction points either between the support disc and the energy storage device (if the energy storage device rotates with the output shaft) or between the pressure plate and the energy storage device (if it is rotationally fixed to the actuator housing).

[0017] Furthermore, a ramp unit can be provided between the first pivotable element and the output shaft. This ramp unit can advantageously serve to actuate the braking device, or multi-disc brake. The ramp unit comprises a ramp input element and a release element that interacts with the ramp input element, wherein rolling elements, preferably balls, are inserted between the ramp input element and the release element, which interact with ramps on the respective inner sides of the ramp input element and the release element.

[0018] The ramp entry element and the release mechanism can then be axially spaced apart from each other in the direction of the axis of rotation and each extend substantially radially to this axis. They each form axial inner surfaces facing each other. The ramps for interacting with the rolling elements can be provided on these inner surfaces, i.e., these axial inner surfaces. The rolling elements can generally be bodies that generate sliding or rolling friction between themselves and the ramps. Rolling friction, as with balls, is initially preferred due to its efficiency.

[0019] The ramps are designed such that, during traction operation of the actuator, the rolling elements in at least one of the ramps are displaced relative to the rolling elements, or at least one of the ramps rotates circumferentially relative to the rolling elements, resulting in an axial displacement of the release mechanism. This, in turn, interacts with the multi-plate brake and / or the energy storage device in such a way that the multi-plate brake is opened against the preload force of the energy storage device. A corresponding actuating plunger can be provided for this purpose. Preferably, this actuating plunger can comprise pushrods that extend axially in the interspaces of an external toothing of the output shaft. These pushrods can be positioned axially between the release mechanism and the energy storage device. They can act axially on the pressure plate, which is arranged axially between the outer or inner plates of the multi-plate clutch and the energy storage device, or, more preferably, a helical compression spring.In the unactuated state, this pressure plate is located axially between the energy storage device and the multi-plate clutch, so that the latter is compressed by the force of the energy storage device, which leads to an increase in the frictional force between the inner and outer plates, so that ideally no shear forces can be directed into the actuator against the direction of the torque path.

[0020] In a preferred embodiment, this actuating plunger is cylindrical with a circumferential rim that connects individual pushrods in the tooth spaces. The cylindrical rim itself can then have an inner diameter that lies radially outside the teeth of the output shaft's external splines, so that a corresponding contact force from the release mechanism is sufficient to displace the actuating plunger radially outside the output shaft's external splines. This saves axial installation space.

[0021] In a further development, radial protrusions can be provided in the area of ​​the teeth of the external gearing, limiting further axial displacement of the actuating plunger and thus of the release mechanism. These protrusions directly serve as stops for the release mechanism. This also limits the axial distance between the release mechanism and the ramp entry element, preventing the balls from exiting the ramps on the inside of both the ramp entry element and the release mechanism. The balls always remain in defined positions within the ramps.

[0022] The external teeth of the output shaft serve to provide a rotationally fixed mounting for the inner plates of the multi-plate brake, so that these inner plates are axially displaceable but rotationally fixed to the output shaft for pressing together with the outer plates.

[0023] To minimize the number of components and simplify the assembly of the actuator, the ramp input element can be fixed to the first pivotable element or even be the first pivotable element itself. Preferably, the first pivotable element is a gear mounted on the output shaft via a bearing. This gear can mesh directly with a pinion on the rotor shaft of an electric motor or be connected to it via further gears. The electric motor can drive the gear in two pivoting directions. In principle, a rotary motion could be transmitted by the gear.

[0024] It is preferably designed that the output shaft oscillates during the actuator's traction operation, i.e., constantly changes its direction of rotation without completing a full revolution. This corresponds, for example, to the movement of a windshield wiper arm. In the application of such an oscillating actuator, it is advantageous if the electric motor already transmits this oscillating traction torque, i.e., torque, to the gear.

[0025] The release mechanism, which together with the first pivotable element or gear forms the ramp unit, further features internal teeth for rotationally fixed engagement with external teeth on the output shaft. This allows a tensile torque to be transmitted from the gear, via the balls, into the release mechanism and, via the internal teeth, into the external teeth of the output shaft, i.e., into the output shaft itself, after the release mechanism has been axially displaced to open the multi-disc brake. The external teeth on the output shaft are preferably the same external teeth used for the rotationally fixed but axially displaceable engagement of the internal discs of the multi-disc brake. A second, different external tooth design would be possible but would entail increased manufacturing costs. The external teeth can extend axially along the output shaft in such a way that the engagement of the internal teeth of the gear with the external teeth is permanent.This prevents the release bearing from twisting before the multi-disc brake is actuated. However, it is also possible that the internal teeth only engage with the external teeth during the axial displacement of the release bearing.

[0026] The invention further provides a windshield wiper drive with an actuator just described for the oscillating drive of a windshield wiper arm, preferably a rear windshield wiper.

[0027] An embodiment of the invention, to which it is not limited and from which further features of the invention may emerge, is shown in the following figures. The figures show: Fig. 1: Cross-sectional view of an actuator for oscillating torque transmission, Fig. 2: an oblique view of a ramp unit and a braking device in an actuator according to Fig. 1, Fig. 3: an oblique view of a gear as a ramp entrance element, and Fig. 4: An oblique view of a release lever as part of a ramp unit.

[0028] Fig. Figure 1 shows an actuator 1 for oscillating torque transmission along a torque path 30. The direction of the torque path, indicated by arrows, specifies the path of torque transmission during the traction operation of the actuator 1. During the traction 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.

[0029] Starting from gear 13, the torque is transmitted along the torque path 30 via balls 14 to a release bearing 12 of a ramp unit 10. The release bearing 12 has internal teeth 19 that mesh with external teeth 20 of an output shaft 3. A oscillating motion of the output shaft 3 is thus generated by the alternating torque applied to the electric motor 17. 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 oscillating motion of the output shaft 3 can be limited by stops in the torque path 30 or by limiting the rotational movement of the rotor, or the rotor shaft 23 of the electric motor 17, for example, by software control.

[0030] 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.

[0031] The ramp unit 10 in the torque path 30 is composed of multiple parts consisting of at least one ramp entry element 11, balls 14 and a release bearing 12.

[0032] In Fig. Figure 2 shows a top view of a section of the actuator 1, which shows the ramp unit 10 and a braking device 5. The gear 13 serves as the torque input, or ramp input element 11, and 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 by a bearing 16, as shown in Figure 2. Fig. 1 is recognizably supported on this. The bearing shells of bearing 16 are integrally formed here from a bearing surface of the gear 13 and the output shaft 3. A direct torque transmission from the gear 13 to the output shaft 3 therefore does not occur.

[0033] In Fig. Figure 3 shows a view of the gear 13, depicting the axial inner surface 28 of the gear 13 with the ramps 15 incorporated therein. The ramp 15 is characterized by a profile in which the axial depth of the ramp 15 is at its maximum in a circumferentially central region 31. In both circumferential directions, both the axial depth and the radial width 33 decrease towards an outer region 32 of the ramp.

[0034] In Fig. Figure 4 shows the release bearing 12 as the output of the ramp unit 10. The axial inner surface 29 of the release bearing 12 with ramps 15' is also shown here. Analogous to the gear 13, the axial depth of the ramp 15' decreases from a central area 31' to the outer areas 32' of the ramp 15', as does the radial width 33'.

[0035] The release bearing 12 further features radially internal internal teeth 19 for a rotationally fixed connection with the external teeth 20 of the output shaft 3. The internal teeth 19 have alternating teeth 34 and tooth gaps 35.

[0036] The axial inner surfaces 28, 29 of gear 13 and release bearing 12 are arranged axially opposite each other and spaced apart. As in Fig. As can be seen, balls 14 are arranged in the ramps 15, 15' between the two axial inner surfaces 28, 29 of gear 13 and release bearing 12. For this purpose, gear 13 and release bearing 12 are aligned circumferentially with respect to each other such that the ramps 15, 15' lie axially on top of each other circumferentially, so that the balls 14 are always axially received in both ramps 15, 15' of both gear 13 and release bearing 12.

[0037] The functionality of ramp unit 10 will now be explained using the following examples: Fig. 2 explained in more detail. The ramp unit 10, together with the braking device 5, serves to transmit torque along the torque path 30 during traction operation, while preventing the input of thrust torque from the output shaft 3 into the actuator 1 when the actuator 1 is inactive. This means that when the windshield wiper is paused, no torque from the wiper lever can enter the actuator 1.

[0038] In the Fig. In the case shown in Figure 2, the actuator 1 is inactive; no tensile torque is transmitted. In this case, all balls 14 of the ramp unit 10 are located in the central areas 31, 31' of the ramps 15, 15' of both the gear 13 and the release bearing 12. The axial distance between the release bearing 12 and the gear 13 is then minimal. In the case shown here, the gear 13 is axially fixed in the actuator housing 2, so that the axial distance between the gear 13 and the release bearing 12 is determined solely by the axial position of the release bearing 12 on the output shaft 3.

[0039] The braking device 5, designed here as a multi-disc brake 6, is arranged between the output shaft 3 and the actuator housing 2.

[0040] The multi-plate brake 6 has axially alternating inner plates 7 and outer plates 8. The inner plates 7 are rotationally fixed to the external teeth 19 of the output shaft 3 via an internal toothing 36. The outer plates 8 are rotationally fixed to an internal toothing 38 of the actuator housing 2 via an external toothing 37. An axially displaceable pressure plate 39 is also provided on the output shaft 3 for axially pressing the inner plates 7 and outer plates 8 together. This pressure plate 39 also has internal teeth 38 for engagement with the external teeth 19 of the output shaft 3. By means of a force storage device 9, which here is designed as a spiral compression spring 21, a preload force F is exerted on the pressure plate 39 in the axial direction, so that the inner lamellae 7 and outer lamellae 8 are pressed together to form a frictional connection.Since the outer lamellae 8 are rotationally fixed to the actuator housing 2, the output shaft 3 is rotatably supported on the actuator housing 2, preventing torque transmission as long as the applied torque remains below a limit value determined by the preload force F and the total frictional area between the inner and outer lamellae 7, 8. Potential torques in the form of shear torques are transmitted to the output shaft 3 via a windshield wiper arm (not shown) by wind, particularly wind from driving, or by a snow load. The limit value is therefore set such that, as a rule, no movement of the output shaft 3 relative to the actuator housing 2 can occur under the expected shear torques. A safety tolerance can also be incorporated accordingly.

[0041] To pre-tension the helical compression spring 21, it is axially spaced from the pressure plate 39 and supported on a support plate 40, which is at least axially fixed to the output shaft 3. A retaining ring 41 is provided for this purpose, which is received in a circumferential groove 42 in the external teeth 19 of the output shaft 3. The support plate 40 therefore has, identically to the pressure plate 39, an internal toothing 38 for engagement with the external teeth 19 of the output shaft 3. The support plate 40 is thus constructed identically to the pressure plate 39, which simplifies production by using identical parts. The support plate 40 is located axially between the helical compression spring 21 and the retaining ring 41, so that the helical compression spring 21 is axially supported by it.

[0042] In the Fig.In the state shown in Figure 2, the lamellar brake 6 is in the closed state, while the axial distance between gear 13 and release bearing 12 is minimal.

[0043] When actuator 1 is activated, a tensile torque is transmitted along the torque path 30 to the gear 13. The direction of the tensile torque is irrelevant. Since the gear 13 is decoupled from the output shaft 3 via the bearing 16, it begins to rotate or pivot. The release bearing 12 is rotationally fixed to the output shaft 3 and thus also fixed to the actuator housing 2 via the multi-disc brake 6. This results in a relative rotation of the gear 13 with respect to the release bearing 12. The balls 14 move in the ramps 15, 15' of the release bearing 12 and gear 13 from their respective central areas 31, 31' to opposite outer areas 32, 32'. Due to the decreasing axial depth and the decreasing radial width 33, 33' of the ramps 15, 15', an axial force F1 is exerted on the balls 14 and above on the release bearing 12, which is directed opposite to the preload force F.Since the release bearing 12 is arranged to be axially movable within the external teeth 19, an axial displacement of the release bearing 12 occurs when the axial force F1 is greater than the preload force F. The release bearing 12 then exerts axial pressure on push rods 43 arranged in tooth gaps 44 of the external teeth 19, causing the push rods to be axially displaced within the tooth gaps 44. Preferably, the push rods 43 have a smaller radial extension than the teeth 46 of the external teeth 19 of the output shaft 3, so that the internal teeth 36 of the internal plates 7 can still engage with the external teeth 19 radially outside the push rods 43. It is also possible that push rods 43 are only present in individual tooth gaps 44 and that these have a correspondingly deeper radial depth, so that the circumferential location of the push rods 43 has no effect on the installation position of the inner lamellae 7.

[0044] The push rods 43 can be connected to each other via a circumferential force band (not shown), so that the release lever 12 exerts pressure on the entire force band and not on individual push rods 43. In particular, push rods 43 do not need to be present in all tooth gaps 44, as also shown here. The push rods 43 are axially coupled to the pressure plate 39, so that they displace it against the preload force F due to the effect of the axial force F1. By overcoming the preload force F, the frictional engagement between the inner plates 7 and the outer plates 8 is released, and the multi-plate brake 6 is opened. As a result, the output shaft 3, and thus also the release lever 12, is no longer fixed against the actuator housing 2, and the tensile torque can be transmitted via the balls 14 from the gear 13 to the release lever 12 and thus to the output shaft 3. The direction of rotation of the tensile torque is periodically reversed to create the oscillating movement of the output shaft 3.This periodic movement of the gear 13 is followed by corresponding periodic movements of the balls 14 in the ramps 15, 15' with corresponding axial adjustments of the release bearing 12. The sliding surfaces of the release bearing 12 on the output shaft are to be designed for service life.

[0045] To prevent the balls 14 from exiting the ramps 15, 15', stops 45 are provided on the teeth 46 of the external gearing 19. At maximum axial displacement, the release lever 12 strikes these stops, effectively limiting the axial distance between the gear 13 and the release lever 12, ensuring that the balls 14 always remain at least partially in the ramps 15, 15'.

[0046] When actuator 1 is deactivated, no torque acts on gear 13, which is now rotated by an axial movement of the release bearing 12 via the balls 14, as it is axially fixed. During this rotation, the balls 14 return to the central area 31, 31' of the ramps 15, 15', resulting in a minimal axial distance between gear 13 and release bearing 12. For this purpose, the pressure plate 39 is moved axially towards the release bearing 12 by the helical compression spring 21. This axial movement is transmitted to the release bearing 12 via the push rods 43. At the end of the movement, the frictional engagement between the inner and outer plates 7, 8 is re-established, the multi-plate brake 6 is closed, and both the output shaft 3 and the release bearing 12 are supported against rotation on the actuator housing 2.

[0047] In this way, it can be repeatedly ensured that only a tensile torque is transmitted from the electric motor 17 of the actuator 1 to the output shaft 3, regardless of direction. In the case of torques acting against the torque path 30, originating from the output shaft 3 towards the gear 13 (i.e., thrust torques), the thrust torque is supported by the closed multi-disc brake 6 from the output shaft 3 to the actuator housing 2. Reference symbol list 1 actuator 2 actuator housings 3 Output shaft 4 first swiveling element 5. Braking system 6-disc brake 7 inner slat 8 Outer slat 9 energy storage units 10 ramp units 11 Ramp entrance element 12 deployment vehicles 13 gear 14 balls 15, 15' Ramp 16 warehouses 17 Electric motor 18 Direction of swivel 19 Internal teeth 20 External teeth 21 helical compression spring 22 sprockets 23 Rotor shaft 24 Rotation axis 25 Rotation axis 26 Splash water channel 27 External teeth 28 axial inner side 29 axial inner side 30 Torque path 31, 31' middle range 32, 32' outer area 33, 33' radial width 34 teeth 35 gaps in teeth 36 Internal teeth 37 External teeth 38 Internal teeth 39 Pressure plate 40 support plate 41 Retaining ring 42 Nut 43 Push rod 44 tooth gap 45 stop 46 teeth F Preload force F1 Axial force QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 103 12 982 A1 [0003, 0004] DE 10 2007 030 796 A1

[0005]

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