WO2015169844A1

WO2015169844A1 - Reduction gear and steering system

Info

Publication number: WO2015169844A1
Application number: PCT/EP2015/059936
Authority: WO
Inventors: Thomas Riepold; Eugen LASS; Peter Knoll
Original assignee: Thyssenkrupp Presta Ag
Priority date: 2014-05-07
Filing date: 2015-05-06
Publication date: 2015-11-12
Also published as: DE102014009579A1; DE202014003775U1

Abstract

The invention relates to a reduction gear of an electromechanical steering unit comprising an adjusting device (15). Said adjusting device is associated with a compensating element (19) for compensating material and/or construction tolerances of the reduction gear.

Description

Reduction gearbox and steering system

The present invention relates to a reduction gear according to the preamble of independent claim 1 and a steering system with a power assistance according to claim 10.

Electromechanical power steering systems, which introduce the auxiliary power generated by an electric motor to a steering column or to a steering pinion, transmit this auxiliary power by means of a reduction gear to these components. Such reduction gear can be designed as helical gear or worm gear, optionally also with a globoidalen design.

The reduction gears allow only small tolerances, so that a backlash occurring between the components over an entire work area can be kept within a tolerance range. These tolerances are usually compensated by appropriate measures, which also can increase over a lifetime of the transmission, the tolerances and games by wear or settling.

There are various systems known to compensate for the tolerances. When integrated in a motor worm shaft this is displaced by a displacement of the motor in the radial direction relative to the worm wheel, whereby an axial distance and thus the backlash is adjusted. Furthermore, systems are known in which gear and / or worm wheel are mounted elastically, whereby both elements are biased against each other. Here, however, the preload force is to be dimensioned such that under operating loads or impact loads both elements are not separated from each other, so that rattling or knocking noises occur.

The arrangements inherent in the disadvantage that the friction between the components is significantly increased over rigid arrangements by the permanent radial bias of the elements. This is disadvantageous if the model tor, which is coupled to the worm, is driven by the worm wheel, which is the case with a return of the steering.

It is therefore an object of the present invention to further develop the reduction gear mentioned above and to provide a transmission and a steering system which has no excessive friction and thus increased wear.

A reduction gear for achieving the object has the features of independent claim 1. The reduction gear, in particular worm gear or helical gear, has a gear and a worm shaft which engage with each other, wherein the worm shaft is mounted in at least one radial bearing, which is arranged in a gear housing and wherein an adjusting device exerts a radial pressure on the worm shaft, and wherein the adjusting device has an elastic compensating element for compensating material and / or design tolerances of the reduction gear.

In this way, in addition to a force exerted on the worm shaft, in particular a bearing, radial pressure, whereby the worm shaft and the gear are biased, a further compensation can be created. If in the prior art with an adjusting tolerances between the two rotatable components, the gear and the worm shaft can be compensated, the invention goes one step further and additionally compensates by the material or the geometry of the components caused tolerances.

The object is solved with the features of independent claim 1.

The reduction gear, in particular worm gear or helical gear, has a gear (10) which is rotatable about a longitudinal axis (Z), and a worm shaft (11) which is rotatable about a longitudinal axis (Y), which engage with each other, wherein the worm shaft (11) is mounted in at least one radial bearing (12, 14) mounted in a gear housing. is arranged, and wherein an adjusting device (15) exerts a radial pressure on the worm shaft (11), and wherein the adjusting device (15) in the longitudinal direction (X) is slidably disposed and an elastic compensation element (19) for balancing material and / or design tolerances of the reduction gear, wherein the longitudinal direction (X) at an angle in the range of 70 ° to 110 ° to the longitudinal axis (Y) of the worm shaft (11) and tangent to the outer ring of the bearing is aligned and at an angle in the range of -90 ° to + 90 ° to the axis of rotation of the gear (10) is aligned.

In a preferred embodiment, the reduction gear has a drive device, preferably an electric motor, for driving the worm shaft. The worm shaft and or the motor shaft of the electric motor are supported in at least one radial bearing, wherein at several bearings, the radial bearing is arranged on the side facing away from the drive motor side of the worm shaft.

Particularly preferably, this remote from the motor side of the worm shaft radial bearing is arranged movably in the housing. Particularly preferably, the adjusting device acts on this radial bearing.

It is preferred here to align the adjusting device 90 ° +/- the tolerances resulting from the tilting with respect to the longitudinal axis (Y) parallel to the longitudinal axis (Z) of the toothed wheel (10).

For this purpose, according to a preferred embodiment, it may be provided that a compensation enabled by the compensation element substantially corresponds to an amount of a concentricity tolerance and / or a thermal expansion. Although clearance tolerances can be compensated with the adjusting device, installation tolerances and part tolerances are not taken into consideration by which the worm shaft or the gear does not run exactly round. In addition, the components expand or contract, which is why further tolerances can be expected here as well. With the compensation in the adjuster these special tolerances can be met sustainably.

Furthermore, it is provided according to an advantageous embodiment that the Adjusting means comprises an adjusting element, which is arranged in a recess of the housing in the region of the radial bearing, wherein preferably the recess has a holding portion for the adjusting element. With the adjusting element, the transmission can be manipulated directly, wherein in a contact area of adjusting element and worm shaft and the compensation element can be arranged. Thus, the compensation can be easily done without providing intermediate steps.

First and foremost, the compensating element is designed to balance between two expected geometries of one or more components. Therefore, it is advantageous if the compensation element is elastic, so it can return to an original form.

In addition, it may be advantageous in another embodiment of the invention, when the adjusting device is designed to be self-locking, especially the worm shaft permanently urges against the gear. With the self-locking can be ensured that the adjusting device is permanently connected to the transmission, so that at any time a clearance compensation takes place.

Furthermore, it is preferred if the compensating element is integrated in the adjusting element. As a result, a space requirement in the transmission housing can be kept within acceptable limits.

According to another embodiment, the compensating element may be designed as a leaf spring, wherein the leaf spring between the adjusting element and the radial bearing is arranged- The leaf spring, for example, by their elasticity, compensate for the change in length caused by the different thermal expansions of the individual components.

Due to the geometry in the region of the adjusting element, it is advantageous to provide the leaf spring in the abutment region between the adjusting element and the radial bearing, since only a comparatively small spring needs to be used here.

Furthermore, the compensation element may be formed as an elastomeric spring, wherein the elastomeric spring between the adjusting element and the Radi- Allag and / or the housing is arranged. A spring made of a plastic or a combination of elastomer and metallic spring is alternatively effective as well, wherein such a spring is also to be arranged simultaneously between the adjusting element and the radial bearing and the housing. As a result, the spring can be dimensioned smaller. Such a hybrid compensating element advantageously combines the spring characteristics of the metallic and elastomeric springs.

It can also be provided that a misalignment of the worm shaft is compensated by a preferably rigid or elastic coupling in the reduction gear. Together with the compensating element so unwanted, but with einzuberechnchnende tolerances can be compensated in the transmission.

The invention is further achieved with a steering system with a power assistance, comprising at least one reduction gear according to one of claims 1 to 13.

Further advantageous embodiments of the invention are part of the dependent claims.

A preferred embodiment is shown in the drawing. In this show:

Fig. 1 a worm assembly without compensating element,

Fig. 2 a worm assembly with a leaf spring as

Compensation element,

Fig. 3 shows a screw arrangement with an elastomeric

Compensation element,

Fig. 4 shows a screw arrangement with an elastomeric compensation element according to a further exemplary embodiment,

Fig. 5 an adjusting device without compensating element,

Fig. 6 an adjusting device with a leaf spring as compensation element, Fig. 7 an adjusting device with an elastomeric compensating element,

Fig. 8 shows an adjusting device with an elastomeric compensating element according to a further exemplary embodiment,

Fig. 9 an adjusting device with a metallic equivalent,

Fig. 10 an adjusting element with axial spring,

Fig. 11 an adjusting element with axial spring and leaf spring as compensating element,

Fig. 12 an adjusting element with axial spring and elastomeric compensating element,

Fig. 13 an adjusting element with axial spring and elastomeric compensation element, and

Fig. 14 an adjusting element with axial spring and metallic compensation element.

The invention relates to a reduction gear, which is partially shown in the figures. Shown in the figures are a gear (10) and a meshing with this worm shaft (11). The reduction gear can be designed as a helical gear or as a worm gear.

The gear (10) is rotatably mounted about a rotational axis (Z), but stationary and is arranged substantially perpendicular to the worm shaft (11) in a transmission housing, not shown. The two components (10) and (11) are in engagement with each other via their teeth or their threads, wherein the respective other component is moved by a respective rotational movement. The reduction gear is part of an electromechanical steering system with or without mechanical connection between a steering wheel and a steered wheel ("EPS" or "steer-by-wire"), which generates the auxiliary power generated by an electric motor by means of the reduction gear on a steering column Steering pinion initiates. The worm shaft (11) is rotatably supported about a longitudinal axis (Y) in two radial bearings disposed at the respective end portions of the worm shaft (11). One of the radial bearings (12) is arranged radially movable in the housing. It is held in a guide (13), which allows above all a mobility in a radial plane to the gear (10). In other words, the supported worm shaft (11) can be moved in the direction of the teeth of the gear (10).

The radially opposite radial bearing (14) is substantially fixedly disposed in the housing, but allows tilting of the worm shaft (11). This is made possible by a rigid or elastic coupling, which is not shown in the drawing. By the movement of the worm shaft (11) in the radially movable bearing (12) thereby allows the bearing (14) a tension-free movement of the worm shaft (11). The coupling also compensates for angular or misalignment caused by movement of the worm shaft (11) relative to a motor shaft.

Associated with the movable radial bearing (12) is an adjusting device (15) which is designed to bias the meshing engagement between the gear 10 and the worm shaft (11) more or less. For this purpose, the adjusting device (15) has an adjusting element (16), which is displaceably guided in a longitudinal direction (X) and is biased axially by a spring. The adjusting element (16) is wedge-shaped with an oblique underside (17) in a support region of adjusting element (16) and the bearing (12). The oblique underside (17) is directed obliquely, especially in relation to the axial direction of biasing the adjusting device (15), whereby the adjusting device (15) or the adjusting element (16) obliquely to the bearing (12) exerts a force on this. The adjusting device (15) is an automatic device that exerts permanent force on the bearing.

The applied force is a radial force acting on the bearing (12) and depressing the bearing in the guide (12). As a result, the worm shaft (11) is urged against the gear (10). Thus, a backlash-free gearing is guaranteed. The adjusting element (16) is self-locking, whereby the

Worm shaft (11) can not lift off the gear (10). The adjusting device (15) has an adjusting region (18), within which the adjusting element (16) is movable. This area (18) is limited, resulting in an upper maximum, to which the adjusting element (16) can be performed.

In steering-typical load profiles of electromechanical steering systems with frequent zero crossings of the operating loads, the adjusting device (15) is designed such that a readjustment process essentially takes place in a load-free state. Thereby, the biasing force necessary for adjustment can be reduced to an amount which is necessary to overcome a friction of the adjusting element (16) and the friction between the radial bearing (12) and its guide (13), so that a reliable adjustment can be ensured. Furthermore, the radial force can be minimized to the worm shaft bearing or the bias of the teeth in a no-load condition, which significantly reduces the friction.

It is intended to design the adjusting device such that an angular error of the central axis of the worm shaft (11) relative to the central axis of a motor shaft is zero when it is in the middle of its adjustment. Thus, the adjusting element (16) uniformly exert pressure on the bearing (12) without being increased in phases by limiting the pressure.

Assigned to the adjusting device (15) is a compensating element (19) which is provided in the region of the adjusting element (16). According to the embodiments shown in the drawing, the compensating element (19) in the adjusting element (16) is integrated, but can also be arranged according to further embodiments of the adjusting element (16) and the adjusting device (15). The compensating element (19) is used to compensate for concentricity tolerances of the worm shaft (11) and the gear (10) on the one hand and a thermal expansion of the components forming the reduction gear. Other component or design parameters can also be compensated by the compensation element (19). The compensating element (19) is designed as an elastic element or a working spring and is being able to retreat through a pressure caused by the material tolerances and part tolerances while maintaining the reset pressure exerted by the readjusting means (15). A stroke of the compensating element (19) accordingly corresponds essentially to an amount of concentricity tolerance and thermal expansion of the worm shaft (11) and gear (10) and the housing 24. The stroke is also limited to these tolerances, which is why the compensation element exclusively to compensate for the concentricity tolerance and / or the thermal expansion is used.

Together with the adjusting device thus decoupling of gear (10) and worm shaft (11) can be largely avoided, the cyclic fluctuations of torque, which is caused by the runout of worm shaft (11) and gear (10), compared to a rigid adjustment can be reduced. In addition, with the compensating element (19) a friction torque in engagement of gear (10) and worm shaft (11) against an exclusively elastic adjustment, which has a reduced bias, are also reduced.

It is provided that a bias voltage and a characteristic of the compensating element (19) are designed such that a full stroke is ensured in interaction with the spring (25) of the adjusting element (16).

The compensating element (19) can be embodied both as a metallic spring element or as an elastomer element or a combination of both. Other embodiments are also conceivable; and the balancing member (19) is not limited only to these two embodiments. Both embodiments may be either between the radial bearing (12) and the adjusting element (16), the adjusting element (16) and the housing, or both between the radial bearing (12) and the adjusting element (16) and the adjusting element (16) and the housing be arranged.

FIG. 6 shows a region of the radial bearing (12) in which the adjusting element (16) rests on the radial bearing (12) and exerts a pressure on the radial bearing (12) as a result of the prestressing. By means of the oblique Surface (17) presses the adjusting element (16) the radial bearing (12) in the guide (13) downwards, whereby the mounted worm shaft (11) is urged against the gear (10). In the region of the inclined surface (17), the compensating element (19) is arranged in the form of a leaf spring. The leaf spring replaces a part of the inclined surface (17), wherein, as shown in Fig. 6, the leaf spring covers a recessed area (20). This recessed area (20) is arranged in the contact area between adjusting element (16) and the bearing (12), whereby the leaf spring receives a working field, in which the stroke of the compensating element (19) can protrude. The stroke or a travel of the leaf spring are therefore determined by the geometry of the recessed area (20).

In one embodiment, the leaf spring is secured by means of a fuse (21) on the adjusting element (16) and spans the recessed area. The fuse (21) is arranged on the inclined surface (17), laterally to the working field of the leaf spring. The leaf spring is held on an opposite side to the fuse (21) only in contact with the inclined surface (17), whereby the leaf spring can be easily deformed.

According to another embodiment, it is also possible to use other types of fastening. In a particularly advantageous embodiment, the compensation element (19) is positively and / or non-positively connected to at least one contact surface with the adjusting element (16).

According to another embodiment, which in the FIG. 7, the compensating element (19) is an elastomeric element. The elastomeric element is disposed in a likewise recessed area (20), wherein the elastomeric element is in contact with the radial bearing (12). The elastomeric element is resilient, allowing the stroke to compensate. Accordingly, the spring travel and also a spring characteristic of the elastomer element are determined by its geometry and the geometry of the recessed area (20).

A compensation element (19) spanning a substantial part of the adjustment element (16) is shown in FIGS. 8 and 9 shown. In the Fig. 8 is an elastomeric spring element is provided, on the one hand, the inclined surface (17) spanned, wherein the inclined surface (17) has no recessed area (20), and on the other hand, a top (22) of the adjusting element (16). The elastomeric spring element is designed either in one piece or split. It is held in recesses (23), wherein the spring element engages in the recesses (23) with projections. A spring travel and also a spring characteristic of the elastomeric spring element are formed by its geometry and also the geometry of the adjusting element (16).

FIG. 9 likewise shows an external compensating element (19) which is arranged similarly to the elastomeric spring element. But this is a metallic spring element, which also covers the inclined surface (17) and the top (22) of the adjusting element (16). The metallic spring element recesses (23) are also associated, wherein in the recesses (23) holding means are provided which hold the metallic spring element and thereby allow him a working field. As with the elastomeric spring element, the spring travel and also the spring characteristic are formed by its geometry and also the geometry of the adjusting element (16) in the metallic spring element.

To the above described embodiments in the region of the radial bearing (12) and reduction gear can be provided which on both radial bearings (12) and (14) an adjusting device (15) with adjusting element (16) and compensating element (19).

Claims

P a n t a n s p r e c h e

Reduction gear, in particular worm gear or

A helical gear, a gear (10) and a worm shaft (11) which is rotatable about a longitudinal axis (Y) having, which are engaged with each other, wherein the worm shaft (11) is mounted in at least one radial bearing (12, 14), which is arranged in a transmission housing and wherein an adjusting device (15) exerts a radial pressure on the worm shaft (11), characterized in that at least one of the radial bearings (12, 14) is arranged displaceably in the transmission housing perpendicular to the longitudinal axis (Y) and wherein the adjusting device (15) is displaceably arranged in a longitudinal direction (X) and an elastic compensating element (19) for

Compensation of material and / or design tolerances of

Reduction gear has

Reduction gear according to claim 1, characterized in that a compensation element (19) enables compensation in the

Essentially corresponds to an amount of a concentricity tolerance and / or a thermal expansion.

Reduction gear according to one of the preceding claims, characterized in that the adjusting device (15) a

Adjusting element (16) which in a recess of the

Housing is arranged in the region of the radial bearing, wherein

Preferably, the recess has a holding portion for the

Adjusting element (16).

Reduction gear according to one of the preceding claims, characterized in that the compensating element (19) is a metallic spring element or an elastomer element, wherein it is arranged in particular between the adjusting device (15) and the radial bearing (12, 14) and / or the housing.

5. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) is a metallic spring element with an elastomeric element, wherein it is arranged in particular between the adjusting device (15) and the radial bearing (12, 14) and / or the housing ,

6. reduction gear according to one of the preceding claims, characterized in that the adjusting device (15) is designed to be self-locking, in particular the worm shaft (11) permanently against the gear (10) urges.

7. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) in the

Adjusting element (15) is integrated.

8. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) is designed as a leaf spring, wherein the leaf spring between the adjusting element (16) and the radial bearing (12, 14) is arranged.

9. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) as a

Elastomer spring is formed, wherein the elastomeric spring between the adjusting element (16) and the radial bearing (12, 14) and / or the housing is arranged.

10. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) is designed as a hybrid element consisting of a metallic and an elastomeric element, wherein the hybrid element between the adjusting element (16) and the radial bearing (12 , 14) and / or the housing is arranged.

11. reduction gear according to one of the preceding claims, characterized in that the compensating element (19) is aligned tangentially to the outer ring of the bearing.

12. reduction gear according to claim 10, characterized in that the compensating element (19) is aligned tangentially to the outer ring of the bearing, wherein the compensating element (19) at an angle in the range of -90 ° to + 90 ° to the axis of rotation of the gear (10) aligned is.

13. reduction gear according to one of the preceding claims, characterized in that by a preferably rigid or elastic coupling in the reduction gear an alignment error of

Worm shaft (11) is balanced.

14. Steering system with an auxiliary power assistance having at least one reduction gear according to one of the preceding claims.