Especially for actuators used in automobiles

Abstract

An actuator (11) which can be used, for example, for an electromechanical parking brake, wherein the housing (12) of the actuator is equipped with a transmission (16), and a worm body (17) is supported axially and radially by means of a support bracket (21), the legs (23) on both sides of which axially hook the worm body (17) and radially clamp its shaft (18). As a jamming protection to prevent the worm body (17) and the worm wheel (20) from getting stuck, the support bracket (21) can be slightly displaced in the housing (12). For this purpose, due to the restoring force exerted by the compressed spring element (30), the support bracket (21) is axially displaced together with the worm body (17), and the worm wheel 20 rotates.

Description

Field of the Invention

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

[0002] Such actuators equipped with low-voltage variable-speed motors are widely used, for example, in motor vehicles for comfort drives, such as to move seat belts, windows or sliding sunroofs, to adjust seats, and especially to engage and disengage parking brakes. Such actuators operating on the vehicle electrical system can be controlled manually via a switch or directly by the output of a vehicle electronic data processing.

[0003] Such actuators usually have a small-sized, high-speed electromechanically or electronically rectified DC motor, which is followed by a multi-stage significantly decelerating spur gear transmission in order to not only reduce the noise generated mainly due to high-speed components, but also especially to provide sufficient torque on the output shaft for the corresponding working applications.

[0004] In the general DE 10 2015 226 770 A1, the motor does not drive a spur gear transmission, but rather a worm gear transmission, the worm body of which is fixed in a form-fitting manner to the protruding end of the motor shaft by means of a coaxial blind hole. The worm body engages with a worm wheel inside the actuator housing, and the worm wheel drives the output shaft of the actuator. Here, the torque transmission from the worm body to the worm wheel is structurally problematic because this torque transmission causes a dangerous axial load on the worm body and thus on the motor shaft during operation. When using inexpensive mass-produced motors, it is actually not possible to absorb the axial load on the motor cover. The support for absorbing the axial load at the end of the worm body remote from the motor requires a large installation space in the actuator housing, and moreover, it is necessary to ensure that the worm wheel is radially supported in the actuator housing. Summary of the Invention

[0005] Recognizing this situation, the technical problem underlying the invention is to provide a long-lasting support for the worm body that can be easily manufactured and assembled and that also supports, as far as possible, additional functions during the operation of the worm gear transmission.

[0006] According to the invention, this object is achieved by the combination of the main features given in the independent claims. Accordingly, a U-shaped stretched support bracket is provided, which has bent side legs, the yoke of the support bracket being eccentrically offset and extending along the worm body, and the support bracket axially engaging the worm body in the corresponding regions of its two end sides by means of its side legs that are transverse to the yoke, i.e., radially and centripetally directed relative to the worm axis. In this regard, the support bracket is fixedly assembled with the housing, thereby axially supporting the shaft equipped with the worm body in two opposite axial directions.

[0007] Within the scope of the present invention, the support bracket, preferably composed of a hard elastic material such as spring steel, does not necessarily have to be bent integrally in a U-shape. It can also consist of two L-shaped bent corner parts, which are held relative to each other parallel to the worm axis and offset from each other.

[0008] Preferably, at least one support bracket side leg is provided with a transverse and open slot that extends longitudinally beyond half the width of the side leg. The slot can be centered onto the shaft before the adjacent end sides of the worm body, and the shaft is thereby radially supported in the support bracket over more than half of its circumference with steel against steel. This reduces the easily worn radial support of the steel shaft between the plastic half-shells fixed to the housing, thereby extending the reliable function of the steel body rotating in the plastic.

[0009] The worm body is mounted on or before the motor shaft without material connection, and the motor shaft thereby also becomes the worm shaft; in principle, any other coupling method can also be considered, such as pressing the axial hole in the worm body onto the knurled axial region of the motor shaft protruding from the motor housing: up to directly pressing the worm thread into the outer surface of the extended protruding motor shaft.

[0010] The worm shaft does not have to be axially aligned with the end side of the worm body remote from the motor; the worm shaft can also axially extend beyond this end side, for example, to abut in a defined small area against an axial bearing in the form of a support bracket side leg with a spherical crown-shaped rounded end. Contrary to the directly axial support of the side leg abutting axially against the end side there considered previously, this is equivalent to indirectly axially supporting the worm body here.

[0011] If the sufficiently long, radially oriented side legs extend meanderingly along the worm axis due to multiple foldings, this increases a certain elasticity when axially supporting the worm body. But mainly it reduces the burden of receiving the shaft in the slots, because the multiple receptions offset axially relative to each other reduce the surface pressure at the corresponding radial receptions.

[0012] For installation in an actuator housing, a support bracket is fixed, for example, force - fittingly or form - fittingly, to an integral or multi - component fixing body, or between the fixing body and the housing - section joint. In principle, the support bracket is thus rigidly held on the housing. Preferably, however, the fixing body and thus the support bracket are allowed to move slightly axially relative to the housing; that is, the fixing body is axially elastically abutted against elastic components such as elastic cushioned bodies, which elastic components are in turn rigidly supported in the housing. Thereby, it can be ensured that when reaching the linear end stop of the support bracket, the meshing between the worm body and the worm wheel will not jam against each other (the so - called vise - effect), because the worm body axially presses against the teeth of the worm wheel - with the end torque being introduced into the worm wheel - and is immediately slightly guided back by the elastic components by means of axially supporting the worm body by means of the support bracket.

[0013] This prevention of jamming is supported not only by the aforementioned elastic components and by the elastic legs of the support bracket, but also by the axially - caused production - related clearance of the motor shaft equipped with the rotor. The motor receiving part in the actuator housing allows a slight axial clearance of the motor itself, thereby further enhancing this jamming protection.

[0014] Furthermore, anti - jamming can be provided for the worm wheel, for example, by causing a rod to swing concentrically against one of two elastic components fixed to the housing relative to the worm wheel and then being turned back to the unloaded position to the minimum extent by these elastic components. Description of the Drawings

[0015] Additional improvements and alternatives thereof can be obtained from other claims and, considering their advantages, also from the following description of the preferred implementation examples of the solution of the present invention. In the drawings directed to the main functions:

[0016] Figure 1 An actuator provided with a support bracket according to the present invention is shown almost dimension - precisely in an axial - longitudinal sectional view;

[0017] Figure 2 showing a part of Figure 1 with an improved support bracket. Detailed Description of the Invention

[0018] The exemplary actuator 11 has a separate housing 12, which has a motor receiving part 13 and a transmission receiving part 14 for assembling a high - speed motor 15 and a speed - reducing worm - gear transmission 16 as the first speed - reduction stage. Its worm body 17 is constructed on or in any case torsion - resistant fixed to a shaft 18 that projects coaxially from the motor 15. The shaft 18 is radially supported in the motor cover 19 and was previously supported in a plastic half - shell (not shown).

[0019] As a first transmission stage for increasing the torque due to a reduction in rotational speed, the motor-driven worm body 17 engages into the external tooth section of the worm wheel 20. The worm wheel is designed as a pan-shaped hollow wheel with a surrounding internal tooth section (not shown in the figure), and the planet wheels of the surrounding transmission as a second transmission stage engage with this internal tooth section. Thereby, the planet cross, on which the output shaft is concentrically and torsionally mounted, is rotated.

[0020] The axial load occurring during the torque transmission from the worm body 17 to the worm wheel 20 on the shaft 18 depending on the direction of rotation is absorbed in principle by the support bracket 21 fixed to the housing and made of a hard elastic material such as spring steel. The support bracket 21 is designed in a U-shaped manner for this purpose, but with a relatively long U-shaped yoke 22 that is offset centrifugally along the worm body 17 parallel to the shaft 18. The two ends of the yoke 22 are each bent vertically to form side legs 23, and these side legs thus face radially towards the shaft 18 after the support bracket 21 is centrically slipped onto the shaft 18. The support bracket 21 is fixed to a fixing body 24, for example, made by plastic injection molding, and this fixing body itself is arranged in the region of the transmission receiving part 14 in the actuator housing 12.

[0021] Not shown is that the yoke 22 of the axial support bracket 21 can also be separated. Then, two L-shaped parts that complement each other to form the support bracket are held on the fixing body 24 with an axial offset relative to each other.

[0022] In any case, in order to centrically slip the support bracket 21 onto the shaft 18 as described, the side legs 23 have a slot 25 on the motor side, which extends transversely to the longitudinal direction of the side legs 23 and is open. The side legs 23 radially clamp the shaft 18 with this opening, and at the same time, the side legs axially barb the end side 26 of the worm body 17 facing the motor 15. Thereby, a certain radial support for the shaft 18 is generated in the horseshoe-shaped profile of the slot 25; wherein the shaft 18 is supported in the housing 12 at other places (not shown) between two radial half-shells made of plastic. In particular, an axially non-skewed support for the worm body 17 is generated because the side legs 23 not only extend centrically to the shaft 18 but also extend straight beyond the shaft across the entire diameter of the end side 26 of the worm body 17.

[0023] On the axially opposite side, the side legs 23 can also be designed on the side facing away from the motor for centrically slipping onto the shaft 18 through such a slot 25 or horseshoe-shaped hole 25 and barbing the worm body 17 at the end side. However, in order to reduce the frictional losses of this axial support, it can be beneficial that, as shown on the side facing away from the motor, the shaft 18 that extends concentrically from the worm body 17 is axially supported not through the worm body 17 but at the free end 28 of this worm body. In order to make the side legs 23 rest as point-like as possible near their end 27 here, the shaft end 28 is preferably rounded approximately into a spherical cap 29.

[0024] The integral or multi-component support bracket 21 is fixed to the fixed body 24, which is preferably not rigidly fixed to the housing 12, but rather is slightly displaceable in one or the other axial direction according to the current rotation direction of the shaft 18 equipped with a worm and thus bearing against the worm wheel 20. Thereby, when moving to the end position, the elastic member 30 arranged there is compressed. The spring member is, for example, a soft elastic cushion, or a similar soft component protruding axially parallel to the fixed body 24, and these soft components are arranged between the axially adjacent regions of the fixed body 24 and the housing 12. Due to the effect of the elastic return movement, not only is the assembly error compensated, but especially when the worm wheel 20 approaches the terminal stop, a jamming protection is also generated to prevent the worm thread from jamming on the worm wheel 20.

[0025] For this purpose, the worm body 17 can be displaced relative to the shaft 18, and the worm body is anti-torsionally mounted on this shaft. Alternatively, when the worm body 17 is rigidly on the shaft 18, the worm body moves axially together with the shaft 18.

[0026] If the axial clearance of the rotor in the electric motor 15 is not sufficient for the elastically induced return stroke of the shaft 18 due to structural reasons to avoid moving to the jamming position, then the electric motor 15 itself can also be arranged in its receiving part 13 in a minimally but sufficiently axially displaceable manner.

[0027] In the drawings, it is considered beneficial to inhibit the worm from jamming on the terminal stop not only in terms of the linear movement of the worm body 17 but also in terms of the rotational movement of the worm wheel 20. For this purpose, the oscillating rod 31 rotatable concentrically with the worm wheel 20 is tightly embedded between two other elastic members 30 according to the rotation direction of the worm wheel 20, so that the worm wheel 20 rotates slightly back when unloaded. For this purpose, a friction fit can be formed between the oscillating rod 31 and the worm wheel 31. However, from the perspective of transmission efficiency, it is beneficial that the oscillation of the rod 31 is derived from the movement component of the fixed body 24; this is considered in the schematic diagram in the following way: the fixed body 24 and the oscillating rod 31 are hooked to the worm wheel 20.

[0028] As described above with reference to Figure 1 Detailed description, the side legs 23 of the support bracket 21 are used to support the worm body 17 on the axially opposite sides, and thus support the shaft 18 anti-torsionally connected to the worm body. However, in addition, there is also a radial support effect transversely to the direction of the narrow holes 25 in the corresponding side legs 23. This radial support can be strengthened by repeating along the shaft 18 in such a way that the support bracket 21 is provided with a plurality of such side legs 23 axially staggered from each other at least at one end, and these side legs result in a corresponding plurality of axially staggered radial support portions. As shown by Figure 2It can be seen that for this purpose, the long side legs 23 can be folded multiple times to form a meandering trend and have axially aligned narrow holes 25. In this way, the dangerous surface pressure between the edge of the narrow hole 25 and the shaft 18 abutting against this edge is avoided, in that the total load is distributed to a plurality of such radially supporting positions that are relatively closely adjacent to each other.

[0029] At the end 28 of the shaft facing away from the electric motor - where the axial support of the worm body 17 is effected indirectly via the shaft 18 - the last folded side leg 23 is not provided with an opening, so that here the shaft 18 abuts axially with its end - side spherical cap 29.

[0030] All these axial and radial supporting positions are assembled in one go, in that the support bracket 21 fixed to the fixing body 24 - which axially clamps the worm body 17 - is slipped centripetally onto the shaft 18 by means of the narrow holes 25.

[0031] In an actuator 11 which can be used, for example, for an electromechanical parking brake, the housing 12 of the actuator is equipped with an electric motor 15 and a worm gear transmission 16 along the shaft 18. Thus, according to the invention, the worm body 17 is supported by means of a support bracket 21 which is fixed to a fixing body 24 which can be displaced slightly axially. The relatively long U - shaped yoke 22 of the support bracket 21 extends axially parallel to the worm body 17, and the side legs 23 on both sides of the support bracket 21 axially hook onto the worm body 17 directly or indirectly at the end sides. Here, the side legs 23 clamp the shaft 18 by means of the centripetally directed narrow holes 25. As a jamming protection against jamming between the worm body 17 and the worm wheel 20 when reaching the end stop of the worm wheel 20, the fixing body 24 which abuts against the elastic member 30 is axially displaceable slightly in the housing 12 in order to relieve the worm engagement under the torque - transmission load. For this purpose, based on the restoring force exerted by the spring member 30 which has just been compressed respectively, the fixing body 24 together with the axial support bracket 21 and the worm body 17 is displaced slightly axially against the load relative to the shaft 18 - or together with the shaft 18 or the electric motor 15. Advantageously, the worm wheel 20 also rotates slightly elastically back from its end - stop position.

[0032] List of reference numerals

[0033] 11 Actuator (with 15 and 16)

[0034] 12 Housing of (11)

[0035] 13 Motor - receiving part in (12) for 15

[0036] 14 Transmission - receiving part in (12) for 16

[0037] 15 Electric motor of (11)

[0038] 16 Transmission behind (15)

[0039] 17 worm body (on 18)

[0040] 18 shaft (of 15 and 17)

[0041] 19 motor cover

[0042] 20 worm gear (of 16)

[0043] 21 support bracket (for 17)

[0044] 22 yoke (of 21)

[0045] 23 side legs (of 21; on both sides of 22)

[0046] 24 fixing body (in 12; for 21, 31)

[0047] 25 narrow hole (in 23)

[0048] 26 end side (of 17)

[0049] 27 end (of 23)

[0050] 28 end (of 18)

[0051] 29 spherical crown (before 28)

[0052] 30 elastic member (between 24 and 12 and between 31 and 12)

[0053] 31 swing rod (between 30 - 30)

Claims

1. An actuator (11) with a housing (12) equipped with a motor (15) and a transmission (16) driven by the motor along an axis (18), the transmission having a worm body (17) coaxial with the motor (15) and engaging with a worm wheel (20), the worm body also being supported away from the motor, characterized in that: A support bracket (21) is held in the housing (12), a U-shaped yoke (22) of the support bracket extending along the worm body (17), and side legs (23) on both sides of the support bracket that are centripetal relative to the shaft (18) directly or indirectly hook the worm body (17) axially at the end side, and the side legs support the worm body on two axially opposite sides; The worm body has a first end face and a second end face opposite to the first end face, and the side leg not only extends centrifugally to the axis, but also extends beyond the axis and straightly passes over the first end face and the second end face of the worm body; The leg (23) facing away from the motor bears against the spherical end (28) of the shaft (18) at the axial end.

2. The actuator according to claim 1, characterized in that At least one of the two legs (23) bears axially against the worm body (17) at the end and radially surrounds the shaft (18) with a slot (25) which is open transversely to the longitudinal direction of the leg (23).

3. The actuator according to claim 1, characterized in that At least one of the legs (23) extends in a folded, meandering manner along its length.

4. The actuator according to claim 1, characterized in that The support bracket (21) is axially displaceable together with the shaft (18).

5. The actuator according to claim 1, characterized in that The supporting bracket (21) is fixed on a fixing body (24) arranged in the housing (12).

6. The actuator according to claim 5, characterized in that An elastic component (30) is provided between the fixing body (24) and the housing (12).

7. The actuator according to claim 1, characterized in that: The worm body (17) is arranged on the shaft (18) in a rotationally fixed manner and is axially displaceable along the shaft (18) together with the support bracket (21).

8. The actuator according to claim 1, characterized in that The shaft (18) is axially displaceable together with the worm body (17) rigidly fixed thereto and the support bracket (21).

9. The actuator according to claim 1, characterized in that: The motor (15) is axially displaceable.

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