WORM GEAR DRIVE WITH ADJUSTABLE BACKLASH

Abstract

A worm gear drive mechanism (1) having a housing (8), a rotatably mounted worm gear (4) and a worm shaft (2) rotatably mounted at at least one bearing point (7), wherein the bearing point (7) has a displacement element (10) for displacing the axial spacing (17) between the gear axis of rotation (6) of the worm gear (4) and the shaft axis of rotation (5) of the worm shaft (2).

Claims

1. A worm gear drive mechanism (1) comprising a worm gear (4) and a worm shaft (2), an axial spacing (17) between a gear axis of rotation (6) of the worm gear (4) and a shaft axis of rotation (5) of the worm shaft (2) is displaceable by an adjustable mounting of the worm shaft (2) allowing movement of the worm shaft (2) in a radial direction relative to the worm gear (4).

2. The worm gear drive mechanism (1) as claimed in claim 1, wherein the worm shaft (2) is rotatably mounted at two bearing points (7).

3. The worm gear drive mechanism (1) as claimed in claim 14, further comprising a housing (8) with cylindrical openings (9), into which the threaded rings (10) are screwed.

4. The worm gear drive mechanism (1) as claimed in claim 3, further comprising an axial bearing (23) and a radial bearing (16) at each said bearing point (7) for rotational mounting of the worm shaft (2).

5. The worm gear drive mechanism (1) as claimed in claim 4, further comprising at least one shim (28) arranged at least at one of the bearing points (7) between the threaded ring (10) and the axial bearing (23).

6. The worm gear drive mechanism (1) as claimed in claim 4, wherein the axial and radial bearings (16, 23) are formed as needle bearings.

7. The worm gear drive mechanism (1) as claimed in claim 3, wherein at least one marking is arranged on each of the threaded rings (10) in a fixed position in relation to the eccentricity.

8. A method for adjusting a circumferential backlash in a worm gear drive mechanism (1), wherein, starting from a basic setting, the following method steps are carried out repeatedly until a desired circumferential backlash is reached: a) inspecting the circumferential backlash between a worm shaft (2) and a worm gear (4), b) adapting the circumferential backlash by varying an axial spacing (17) between a gear axis of rotation (6) of the worm gear (4) and a shaft axis of rotation (5) of the worm shaft (2).

9. The method as claimed in claim 8, further comprising, in step b) for varying the axial spacing (17), displacing at least one eccentric bore (15) in a threaded ring in which the worm shaft (2) is mounted.

10. The method as claimed in claim 8, further comprising, in step b) for varying the axial spacing (17), displacing two eccentric bores (15) in threaded rings, in which the worm shaft (2) is mounted that are located on both sides of the worm (3).

11. The method as claimed in claim 10, wherein, in step b), the threaded rings on both sides of the worm (3) of the worm shaft (2) are displaced synchronously.

12. The method as claimed in claim 8, further comprising, in step b), at least one of enlarging the circumferential backlash by toothing of the worm shaft (2) being moved out of toothing of the worm gear (4) or reducing the circumferential backlash is by the toothing of the worm shaft (2) being moved into the toothing of the worm gear.

13. The worm gear drive mechanism (1) as claimed in claim 2, wherein the bearing points are on both sides of a worm (3) of the worm shaft (2), and a rotatable adjuster is located at each of the bearing points (7).

14. The worm gear drive mechanism (1) as claimed in claim 13, wherein each of the rotatable adjusters comprises a threaded ring (10) having an eccentric bore (15), in which the worm shaft (2) is rotatably mounted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention is explained in more detail below by using a preferred exemplary embodiment and with reference to the appended drawings, in which:

[0033] FIG. 1 shows a sectional view of a worm gear mechanism according to the invention, and

[0034] FIG. 2 shows a detailed view of FIG. 1 of a bearing point.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In FIG. 1, a sectional view of a worm gear drive mechanism designated overall by 1 is shown. The worm gear drive mechanism 1 has a mechanism housing 8, in which there are arranged a worm shaft 2 having a worm 3 and a worm gear 4 in engagement with the worm 3. The worm shaft 2 has a shaft axis of rotation 5, which is perpendicular to the gear axis of rotation 6 of the worm gear 4. In the image, the gear axis of rotation 6 is perpendicular to the paper plane, for which reason the gear axis of rotation 6 is indicated by the intersection of the two axes of symmetry of the worm gear 4.

[0036] The worm 3 is arranged on the worm shaft 2, as a result of which it also engages with the worm gear 4.

[0037] Arranged at each of the two ends of the worm shaft 2 is a bearing point 7, at which the worm shaft 2 is rotatably mounted.

[0038] The two bearing points 7 are in principle identically designed, for which reason the following description of one bearing point 7 applies in principle to both bearing points 7.

[0039] FIG. 2 shows a bearing point 7 in detail. At each bearing point 7, the housing 8 has a cylindrical housing opening 9 with an internal thread 26. A threaded ring 10 having an external thread 27 is screwed into said internal thread 26. In this example, the external thread 27 is arranged on the outer axial end 11 of the threaded ring 10 and covers about one third of the axial length of the threaded ring 10. In the axial section of the threaded ring 10 without an external thread 27 there is arranged a radial groove 12 on the threaded ring 10 (FIG. 1), into which an O-ring 13 or another seal is inserted in order to seal the housing 8.

[0040] The threaded ring 10 has a bore 15 offset radially by the eccentricity E in relation to the opening axis 14 of the housing opening 9. Arranged in this bore 15 is a radial bearing 16, in which the worm shaft 2 is rotatably mounted. In the example, the radial bearing 16 is a needle roller cage, by which a low overall height is achieved. However, it is also possible for any other desired rolling-contact or sliding bearing to be used.

[0041] The eccentricity E is defined as the spacing between the bore axis 14 of the housing opening 9 and the bore axis 24 of the bore 15, which coincides with the shaft axis of rotation 5. The eccentricity is preferably chosen such that a rotation of the threaded ring through 180° in order to adjust the radial backlash of 1.5 mrad is possible.

[0042] The circumferential backlash between worm 3 and worm gear 4 is adjustable by changing the axial spacing 17. The circumferential backlash between worm 3 and worm gear 4 can thus be varied, according to the invention, by changing the axial spacing 17 between the gear axis of rotation 6 of the worm gear 4 and the shaft axis of rotation 5 of the worm shaft 2.

[0043] In the embodiment shown, said axial spacing 17 can be changed by the threaded ring 10 being rotated. The eccentric bore 15 in which the worm shaft 2 is mounted then effects a change in the axial spacing 17.

[0044] In the bore 15, at the inner axial end 18, the threaded ring 10 has a radially inwardly projecting rim 19, on which the radial bearing 16 is arranged axially but does not touch the shaft 2.

[0045] The worm shaft 2 has a radial step 20, which is located opposite the inner end face 21 of the threaded ring 10 and serves as a contact face 22 for the contact of the axial bearing washer. An axial bearing 23 is arranged between this contact face 22 and the end face 21. In the example, this axial bearing 23 is also formed as a needle bearing, in order to permit the most compact structure possible. The axial bearing 23 here comprises two thrust washers and a needle roller cage. Of course, the axial bearing can also be any desired rolling-contact or sliding bearing.

[0046] The two axial bearings 23 are braced against the contact faces 22 by the threaded rings 10. The two threaded rings 10 must be aligned exactly relative to each other such that the respective bore axes 24 are in alignment.

[0047] As shown in FIG. 2, at one or both bearing points 7 between the contact face 22 and the axial bearing 23 and/or between the axial bearing 23 and the end face 21 of the threaded ring 10, a shim 28 can be inserted in order to adapt the axial bracing of the worm shaft. If necessary, multiple shims 28 can also be used. In order to assist the accurate alignment of the two threaded rings 10, a marking in relation to the eccentricity can be arranged on each of the threaded rings 10.

[0048] At both bearing points 7, the openings 9 are covered by covers 25 or suitable seals, by which the penetration of dirt and/or water and/or the emergence of lubricants is prevented.

[0049] The invention provides a worm gear drive mechanism 1 having a housing 8, a rotatably mounted worm gear 4 and a worm shaft 2 rotatably mounted at at least one bearing point 7, wherein the bearing point 7 has a displacement element for displacing the axial spacing 17 between the gear axis of rotation 5 of the worm gear 4 and the shaft axis of rotation 5 of the worm shaft 2.

[0050] In a worm gear drive mechanism 1 according to the invention, in order to adjust the circumferential backlash between worm 3 and worm gear 4, the following method can be carried out. The worm gear mechanism 1 is firstly completely assembled. Care must be taken that the two threaded rings 10 are aligned exactly such that their bore axes 24 are identical.

[0051] Following the assembly, the circumferential backlash between worm 3 and worm gear 4 is determined. Several methods, which will not be discussed in more detail here, are known for this purpose.

[0052] If the current circumferential backlash does not correspond to the desired target circumferential backlash, then the two threaded rings 10 are rotated synchronously. As a result of the eccentric position of the worm shaft 2 within the bore 15 in the threaded ring 10, the axial spacing 17 between shaft axis of rotation 5 and gear axis of rotation 6 changes as a result. Depending on the direction of rotation, the axial spacing 17 between the worm 3 in the worm gear 4 becomes larger or smaller as a result. With a larger axial spacing, the circumferential backlash is larger, and with a small axial spacing the circumferential backlash is smaller.

[0053] Following the adjustment, the circumferential backlash is measured again and possibly re-adjusted. This method is repeated until the desired circumferential backlash is reached.

[0054] A worm gear drive mechanism 1 having a housing 8, a rotatably mounted worm gear 4 and a worm shaft 2 rotatably mounted at at least one bearing point 7, wherein the bearing point 7 has a displacement element 10 for displacing the axial spacing 17 between the gear axis of rotation 6 of the worm gear 4 and the shaft axis of rotation 5 of the worm shaft 2.

LIST OF DESIGNATIONS

[0055] 1 Worm gear drive mechanism [0056] 2 Worm shaft [0057] 3 Worm [0058] 4 Worm gear [0059] 5 Shaft axis of rotation [0060] 6 Gear axis of rotation [0061] 7 Bearing point [0062] 8 Bearing housing [0063] 9 Housing opening [0064] 10 Threaded ring [0065] 11 Outer axial end of the threaded ring [0066] 12 Groove [0067] 13 O ring [0068] 14 Bore axis [0069] 15 Eccentric bore [0070] 16 Radial bearing [0071] 17 Axial spacing [0072] 18 Inner axial end of the threaded ring [0073] 19 Rim [0074] 20 Radial projection [0075] 21 End face [0076] 22 Contact face [0077] 23 Axial bearing [0078] 24 Bore axis [0079] 25 Covers [0080] 26 Internal thread [0081] 27 External thread [0082] 28 Shim [0083] E Eccentricity