Actuator, particularly for use in a motor vehicle

Abstract

Actuator (11) with a housing (12) which is equipped along a shaft (18) with a motor (15) and a gear (16) driven by it, which has a worm body (17) which engages in a worm wheel (20) and is coaxial with the motor (15), and which is also mounted remote from the motor, characterized in that a bearing bracket (21) is held in the housing (12), the U-yoke (22) of which extends along the worm body (17) and the legs (23) of which on both sides, extending centripetally towards the shaft (18), axially engage behind the worm body (17) directly or indirectly at the end face, the leg (23) remote from the motor axially bearing against a spherical end face (28) of the shaft (18).

Description

[0001] The present invention relates to an actuator according to the preamble of the independent claim.

[0002] These types of actuators, equipped with low-voltage geared motors, are used in a variety of applications, for example in motor vehicles for comfort functions such as moving seatbelt buckles, windows, or sunroofs, adjusting seats, and especially for engaging and disengaging parking brakes. Such actuators, powered by the vehicle's electrical system, can be controlled manually via switches or directly from the vehicle's electronic data processing system.

[0003] Such an actuator is typically equipped with a compact, high-speed electromechanical or electronically commutated DC motor with a subsequent, multi-stage, heavily reducing spur gear transmission, not only to reduce the noise generated primarily by high-speed components, but also, in particular, to provide sufficient torque at the output shaft for the respective application.

[0004] From DE 199 42 252 A1, a worm gear is known in which a spring-loaded tension roller runs on a smooth raceway of the worm wheel and presses the worm radially against the worm wheel. This ensures backlash-free operation of the gear teeth and prevents knocking noises during changes in direction of rotation. The tension roller system can be constructed cost-effectively from stamped sheet metal parts and ball bearings.

[0005] US Patent 2015 / 0219271 A1 discloses a worm gear mechanism comprising a first retaining element, a second retaining element, and a worm. The worm is rotatably mounted between the retaining elements. The backlash of the worm is adjustable by axially displacing the second retaining element. The mechanism enables backlash-free coupling with a worm gear.

[0006] From DE 26 19 989 A1, a worm gear transmission is known in which a worm ring mounted on a housing is subjected to an adjustable preload force via pivotally arranged bearings. The first bearing is pivotally designed and axially connected to the housing. The preload is adjusted via a lever system and a spring.

[0007] From CH 113791, a worm gear is known in which the worm and worm wheel are arranged such that the gears are always in contact with each other on both the front and back sides. This results in increased uniformity of the motion transmission. The device is particularly suitable for gear-cutting machines, as it enables more precise indexing and reduces minor indexing errors.

[0008] In the generic application DE 10 2015 226 770 A1, the motor does not drive a spur gear, but rather a worm gear, whose worm body is bonded to the projecting end of the motor shaft via a coaxial blind hole. Inside the actuator housing, the worm body meshes with a worm wheel, which drives the actuator's output shaft. A design challenge lies in the torque transmission from the worm body to the worm wheel, as this can lead to an axial stress on the worm body and, consequently, on the motor shaft, which is critical from an operational perspective. When using inexpensive, mass-produced motors, there is no practical way to absorb this axial stress in a motor shield.A bearing for absorbing the axial load at the motor-remote end of the worm body requires considerable installation space in the actuator housing, in addition to the radial bearing of the worm wheel in the actuator housing that must be ensured here.

[0009] Recognizing such circumstances, the present invention is based on the technical problem of creating a simple, durable bearing for the worm body that is easy to manufacture and assemble and also supports additional functions during the operation of the worm gear.

[0010] This problem is solved according to the invention by the interaction of the essential features specified in the independent claim. According to this claim, an elongated U-shaped bearing bracket with angled legs is provided, the yoke of which extends centrifugally offset along the screw body and whose legs, oriented transversely thereto, i.e., radially centripetally with respect to the screw axis, axially engage the screw body in the respective region of its two end faces. Insofar as the bearing bracket is fixedly mounted to the housing, this results in axial support of the shaft equipped with the screw body in the two opposing axial directions.

[0011] Within the scope of the present invention, the bearing bracket, preferably made of a stiff-elastic material such as spring steel, does not have to be U-shaped in one piece; it can also be grouped from two L-shaped angles to the bearing bracket, which are held parallel to the worm axis and offset from each other.

[0012] Preferably, at least one of the bearing bracket legs is provided with a slotted hole oriented transversely to its longitudinal extent, the length of which extends over approximately half the width of the leg. The slotted hole can be slid centripetally onto the shaft in front of the adjacent end face of the worm body, which is then radially supported in the bearing bracket, steel on steel, over half its circumference. This relieves the wear-prone radial bearing of the steel shaft between housing-mounted plastic half-shells and thus extends the reliable function of the steel body rotating within the plastic.

[0013] The worm body does not need to be materially bonded to or mounted in front of a motor shaft, which thereby simultaneously becomes the worm shaft; any other coupling is fundamentally just as possible, such as pressing an axial bore in the worm body onto a knurled axial area of ​​the motor shaft projecting from the motor housing: up to and including a worm thread stamping directly into the cylindrical surface of an extended, projecting motor shaft.

[0014] The worm shaft does not need to be axially aligned with the surface of the worm body furthest from the motor; it can also extend axially beyond this surface, for example, with a spherically rounded end cap to provide a defined, small-area contact against an axial bearing in the form of a bearing bracket leg. This corresponds to an indirect axial bearing arrangement for the worm body, in contrast to the previously considered direct axial bearing arrangement of the leg bearing axially against the end face.

[0015] If sufficiently long, radially oriented legs meander along the worm axis as a result of multiple folds, this increases a certain degree of elasticity in the axial support of the worm body. Most importantly, however, the shaft receptacles in the slotted holes are relieved of stress because the multiple receptacles, offset axially from one another, reduce the surface pressure at each radial receptacle.

[0016] For mounting in the actuator housing, the bearing bracket is attached, either by force-fit or form-fit, to a one- or multi-part fixing body or between this body and a housing parting line. In principle, the bearing bracket is thus rigidly held to the housing. Preferably, however, a slight axial movement of the fixing body, and thus of the bearing bracket, relative to the housing is permitted; namely, under direction-of-rotation-dependent elastic axial support of the fixing body against spring elements such as spring-elastic cushion-like bodies, which in turn are then rigidly supported in the housing. This ensures that the gear mesh between the worm body and the worm gear does not jam when the linear end stop of the bearing bracket is reached (so-called...).(vise effect), because the axial pressure of the worm body against the teeth of the worm wheel is immediately reduced by the spring elements via the axial support of the worm body by means of the bearing bracket when torque is no longer applied to the worm wheel.

[0017] Such blockage prevention is promoted not only by the aforementioned spring elements and by the spring-elastic arms of the bearing bracket, but also by the axial play inherent in the manufacturing process of the motor shaft fitted with the rotor. This blockage protection can be further enhanced by allowing a small amount of axial play in the motor mounting within the actuator housing.

[0018] Furthermore, a jamming protection for the worm gear can be provided by pivoting a lever concentrically to the worm gear against one of two housing-fixed spring elements and then turning it back minimally to a load-free position.

[0019] Further developments and their alternatives arise from the further claims and, also taking into account their advantages, from the following description of preferred implementation examples of the solution according to the invention. The sketches, abstracted to the functional essentials according to the drawing, show in Fig. 1 an actuator designed according to the invention with a bearing bracket in axial longitudinal section approximately to scale and Fig. 2 an excerpt from Fig. 1 with further developed bearing bracket.

[0020] The actuator 11, sketched as an example, has a split housing 12 with a motor mount 13 and a gearbox mount 14 for fitting a high-speed motor 15 and a reducing worm gear 16 as the first gear stage. The worm body 17 of the worm gear is formed on the shaft 18, which projects coaxially from the motor 15, or at least is fixed to it in a rotationally fixed manner. The shaft 18 is radially supported in the motor shield 19 and, in front of it, in plastic half-shells (not shown).

[0021] As the first gear stage for increasing torque by reducing rotational speed, the motor-driven worm body 17 engages with the external teeth of a worm gear 20. This is designed as a flat, cup-shaped ring gear with circumferential internal teeth (not shown in the drawing), with which the planet gears of an epicyclic gear unit mesh as the second gear stage. This rotates the planet carrier, which is concentrically and rigidly connected to an output shaft.

[0022] The axial load on the shaft 18, which occurs during torque transmission from the worm body 17 to the worm wheel 20 and is dependent on the direction of rotation, is absorbed by a bearing bracket 21 made of a stiff-elastic material such as spring steel. The bearing bracket 21 is, in principle, fixed to the housing. It is U-shaped, but with a relatively long, U-shaped yoke 22 extending centrifugally parallel to the shaft 18 along the worm body 17. At both ends, the yoke 22 is bent at right angles to form legs 23, which are thus oriented radially to the shaft 18, after the bearing bracket 21 is mounted centripetally on the shaft 18. The bearing bracket 21 is attached to a fixing element 24, which is produced, for example, by injection molding and is itself mounted in the actuator housing 12 in the area of ​​the gearbox mounting 14.

[0023] Not shown is that the yoke 22 of the axial bearing bracket 21 can also be divided. In this case, two L-shaped parts, which together form a bearing bracket, are held axially offset from each other on the fixing body 24.

[0024] In any case, the motor-side leg 23 has a slotted hole 25 for the aforementioned centripetal mounting of the bearing bracket 21 onto the shaft 18. This slotted hole extends transversely to the longitudinal extent of the leg 23 and opens. Through this opening, the leg 23 radially overlaps the shaft 18, while axially engaging the end face 26 of the worm body 17 facing the motor 15. This results in a certain degree of radial bearing of the shaft 18 within the horseshoe profile of the slotted hole 25; the shaft 18 is otherwise (not shown) supported between two radial plastic half-shells in the housing 12. In particular, an untilted axial support of the worm body 17 is achieved because the leg 23 not only extends centripetally to the shaft 18, but also diametrically spans the entire diameter of the end face 26 of the worm body 17 beyond it.

[0025] Axially opposite, the motor-remote leg 23 can also be designed, via a slotted or horseshoe-shaped hole 25, to be pushed centripetally onto the shaft 18 by engaging the worm body 17 from the front. However, to reduce friction losses at this axial support, it may be more advantageous, as sketched, to provide the axial support for the shaft 18, which projects concentrically from the worm body 17, not via the worm body 17, but at its free end 28. In order to ensure that the leg 23 in this respect contacts as close as possible to its end face 27, the Welfen end face 28 is advantageously rounded to approximately a spherical cap 29.

[0026] The fixing body 24, to which the one- or multi-part bearing bracket 21 is attached, is preferably not rigidly fixed in the housing 12, but rather slightly displaceable in one or the other axial direction with the worm-equipped shaft 18, which is thereby supported against the worm wheel 20, depending on its current direction of rotation. This causes spring elements 30 arranged there to be compressed when the shaft is moved into an end position. These spring elements are, for example, soft elastic cushions or similar soft components projecting axially parallel from the fixing body 24 and arranged between the fixing body 24 and the axially adjacent area of ​​the housing 12. The spring-elastic return movement effect not only compensates for assembly tolerances, but also, in particular, when the worm wheel 20 approaches an end stop, provides protection against jamming of the worm thread in the worm wheel 20.

[0027] For this purpose, the worm body 17 can be displaced relative to the shaft 18 on which it is mounted in a rotationally fixed manner. Alternatively, if the worm body 17 is rigidly fixed to the shaft 18, it can be axially displaced together with the shaft 18.

[0028] If the axial play of the rotor in the motor 15 is insufficient for the spring-loaded return stroke of the shaft 18 to avoid entering a locked position due to design constraints, the motor 15 itself can also be mounted in its mounting 13 with minimal but sufficient axial displacement.

[0029] The drawing takes into account the fact that it is advantageous to counteract jamming of the worm gear engagement at the end stop not only with respect to the linear movement of the worm body 17, but also with respect to the rotational movement of the worm wheel 20. For this purpose, a pivoting lever 31, which is rotatable concentrically with respect to the worm wheel 20, engages compressively between two further spring elements 30, depending on the direction of rotation of the worm wheel 20, in order to slightly reverse the rotation of the worm wheel 20 when the pressure is released. A frictional connection between the pivoting lever 31 and the worm wheel 31 can be formed for this purpose. However, from the perspective of the gear efficiency, it is more advantageous to derive the pivoting of the lever 31 from a movement component of the fixing element 24; this is taken into account in the schematic diagram of the drawing by the fact that the fixing element 24 and the pivoting lever 31 engage behind the worm wheel 20.

[0030] As above with reference to Fig. As shown in more detail in Figure 1, the legs 23 of the bearing bracket 21 serve to provide axial support on both sides in opposite directions to the worm body 17 and thus to the shaft 18 rigidly connected to it. In addition, there is the effect of radial bearing transverse to the orientation of the slotted hole 25 in the respective leg 23. This radial bearing can be multiplied by repeating it along the shaft 18, by equipping the bearing bracket 21 at least at one end with several such legs 23 axially offset from one another, resulting in a corresponding number of axially offset radial bearings. As shown in Figure 1, this can be achieved by... Fig.As can be seen in Figure 2, the long legs 23 are folded several times into a meandering shape, with axially aligned slotted holes 25. A critical surface pressure between the edge of the slotted hole 25 and the shaft 18 supported against it is avoided by distributing the total load over a plurality of such radially adjacent support points.

[0031] At the motor-remote shaft end 28, where the axial bearing of the worm body 17 is indirectly provided via the shaft 18, the last folding leg 23 is not perforated in order to allow the shaft 18 with its end-face ball cap 29 to rest axially against it.

[0032] All these axial and radial bearing points are mounted in one operation by sliding the bearing bracket 21, which is attached to the fixing body 24, axially overlapping the worm body 17, onto the shaft 18 centripetally with the slotted holes 25.

[0033] In an actuator 11, which can be used, for example, for an electric parking brake, whose housing 12 is equipped along a shaft 18 with a motor 15 and a worm gear 16, the worm body 17 is supported according to the invention by means of a bearing bracket 21, which is fixed to a slightly axially displaceable fixing body 24. The comparatively long U-shaped yoke 22 of the bearing bracket 21 extends axially parallel to the axis along the worm body 17, while its two legs 23 engage the worm body 17 directly or indirectly at its end face, axially behind it. The legs 23 overlap the shaft 18 with centripetally oriented slotted holes 25.As a locking mechanism to prevent jamming between the worm body 17 and the worm gear 20 when the worm gear 20 reaches its end stop, the locking element 24, supported against spring elements 30, is axially displaceable within the housing 12 to relieve the worm engagement under the load of torque transmission. For this purpose, the locking element 24, together with the axial bearing bracket 21 and the worm body 17, is axially displaced slightly relative to the shaft 18, or together with the shaft 18 or the motor 15, against the load engagement, due to the restoring forces exerted by the spring elements 30. Advantageously, the worm gear 20 is also slightly spring-loaded back from its end stop position. Reference symbol list 11 Actuator (with 15 and 16) 12 cases (out of 11) 13 Motor mount (in 12 for 15) 14 Gearbox mounting (in 12 for 16) 15 engine (out of 11) 16 gearboxes (behind 15) 17 snail bodies (out of 18) 18th wave (of 15 and of 17) 19 Engine plate 20 worm gears (out of 16) 21 bearing brackets (for 17) 22 yokes (out of 21) 23 thighs (of 21; 22 on each side) 24 fixatives (in 12; for 21, 31) 25 slotted holes (in 23) 26 Front side (of 17) 27 forehead (out of 23) 28 forehead ends (out of 18) 29 ball cap (before 28) 30 spring elements (between 24 and 12 as well as 31 and 12) 31 swivel levers (between 30-30)

Claims

[1] Actuator (11) with a housing (12) which is fitted along a shaft (18) with a motor (15) and a gearbox (16) driven by it, which has a worm body (17) engaging in a worm wheel (20) and coaxial with the motor (15), which is also mounted remotely from the motor, characterized by , that a bearing bracket (21) is held in the housing (12), the u-yoke (22) of which extends along the worm body (17) and the legs (23) of which extend centripetally towards the shaft (18) directly or indirectly engage axially behind the worm body (17) at the end face, with the leg (23) furthest from the motor bearing axially against a convex end face (28) of the shaft (18). [2] Actuator according to claim 1, characterized by, that at least one of the two legs (23) bears axially against the worm body (17) at its end face and the shaft (18) overlaps radially with a slotted hole (25) that opens transversely to the longitudinal extent of the leg (23). [3] Actuator according to any of the preceding claims, characterized by , that at least one of the legs (23), when folded along its length, runs meanderingly. [4] Actuator according to any of the preceding claims, characterized by , that the bearing bracket (21) can be axially displaced with the shaft (18). [5] Actuator according to any of the preceding claims, characterized by , that the bearing bracket (21) is attached to a fixing body (24) arranged in the housing (12). [6] Actuator according to the preceding claim, characterized by , that spring elements (30) are arranged between the fixing body (24) and the housing (12). [7] Actuator according to any of the preceding claims, characterized by, that the worm body (17) which is arranged rigidly to the rotation on the shaft (18) is axially displaceable along the shaft (18) with the bearing bracket (28). [8] Actuator according to any one of the preceding claims 1 to 7, characterized by , that the shaft (18) with worm body (17) rigidly attached to it, including bearing bracket (28), is axially displaceable. [9] Actuator according to any of the preceding claims, characterized by , that the motor (15) is axially displaceable.

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