Gearing having an elastic gear

Abstract

A gearing (1), in particular a strain wave gearing, including an elastic gear (2) having a flange (16), which flange is fastened to a housing component (7) of the gearing (1). A connecting assembly (8) for retaining the flange (16) on the housing component (7) includes a plurality of fastening points (14), wherein, outside of the fastening points (14), the connecting assembly (8) has axial play between the flange (16) and the housing component (7), with respect to the center axis (M) of the gear (2).

Claims

1. Gearing comprising: an elastic gear having a flange extending radially outwardly and a toothed section extending in a first axial direction from the flange, the toothed section defining external teeth, a housing component on which the flange of the gear is fastened, a connecting assembly that holds the flange on the housing component and includes a plurality of fastening points, the connecting assembly including: a plurality of intermediate components formed as washers that are arranged on a first axial side of the flange in the first axial direction and contacting both the flange and the housing component, the plurality of intermediate components only being provided at the plurality of fastening points, and an adapter contacting a second axial side of the flange, the plurality of intermediate components define a space that provides axial play between the flange and the housing component with respect to a center axis of the gear.

2. The gearing according to claim 1, wherein the flange has a same wall thickness as the cylindrical section outside of said external teeth.

3. The gearing according to claim 1, wherein the space which defines the axial play is provided radially between the fastening points and in circumferential sections between the fastening points.

4. The gearing according to claim 3, wherein the circumferential sections in which the space which defines the axial play is provided between the flange and the housing component extend in total for at least 85% of a circumference of the flange.

5. The gearing according to claim 1, wherein no more than five of the fastening points are provided.

6. The gearing according to claim 1, wherein the adapter is formed as a single, ring-shaped component that includes a base ring having thicker reinforcement regions in areas of the plurality of fastening points.

7. The gearing according to claim 1, wherein the plurality of intermediate components are arranged radially outward relative to the external teeth of the gear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, an embodiment of the invention will be explained in more detail with reference to a drawing. Shown herein, partially as schematics, are:

(2) FIG. 1 an end-side plan view of an elastic gear of gearing, namely strain wave gearing, and

(3) FIGS. 2, 3 different sections through the strain wave gearing having the gear according to FIG. 1.

DETAILED DESCRIPTION

(4) FIGS. 1 to 3 show an embodiment of gearing marked as a whole with the reference symbol 1, which is constructed as strain wave gearing and has an elastic gear 2. The gearing 1 is part of an electric camshaft adjuster of an internal combustion engine as gearing with a high degree of speed reduction. With respect to the principle function of the gearing 1, refer to the cited prior art.

(5) The gearing 1 has a housing component 3 that is driven directly or indirectly by a not-shown traction mechanism, that is, a belt or a chain, by the crankshaft of the internal combustion engine, i.e., a gasoline or diesel engine. The rotational movement of the housing component 3 is transferred without play, with reference to the circumferential direction, to the elastic gear 2 with the help of bolts 4 that are fastened in the drive wheel 3. Recesses 5 of the gear 2 through which a bolt 4 is inserted have a circular shape. Bolt heads of the bolts 4 are designated with 6. In total, the gearing 1 has five bolts 4 for fastening the gear 2 to the housing component 3.

(6) The connecting assembly marked as a whole with the reference symbol 8 between the gear 2 and the housing component 3 of the gearing 1 is constructed such that play designated with S.sub.1 and S.sub.2 in the axial direction exists with respect to the center axis designated with M in the gear 2. In this way, deformation of the elastic gear 2 can be absorbed.

(7) The deformation of the elastic gear 2 is produced by a strain wave generator that is designated with 9 and has an outer ring designated with 12 and an elliptical inner ring 10. The outer ring 12 adapts in each operating state to the elliptical shape of the inner ring 10. The elastic gear 2 directly surrounds, in turn, the outer ring 12 under adaptation to its non-circular shape. As rolling bodies, balls 11 roll between the bearing rings 10, 12, i.e., the inner ring 10 and the outer ring 12, of the wave generator 9. The outer ring 12 assuming an elliptical shape presses the elastic gear 2 at two diametrically opposite points against an internal toothed driven wheel 13. This is connected, in turn, locked in rotation to a camshaft of the internal combustion engine.

(8) The elastic gear 2 has a cylindrical, toothed section 15 and an adjoining section 16 extending outward in the radial direction, i.e., a flange, wherein the recesses 5 are located in the flange 16. The teeth designated with 7, namely external teeth, of the gear 2 are located on the cylindrical section 15. The inner ring 10 of the wave generator 9 is set in rotation by a not-shown electrical drive device. The wave driving the inner ring 10 is a regulating shaft; the gearing 1 as a whole is a three-shaft gearing.

(9) The cross section according to FIG. 2 is set through one of the bolts 4 while the cross section according to FIG. 3 shows an open circumferential section 17 of the flange 16. This circumferential section 17 extends over an angle range of more than 45° designated with S.sub.3.

(10) In total, the gearing 1 has five open circumferential sections 17 corresponding to the number of bolts 4. Between every two circumferential sections 17 there is a fastening point designated with 14 and shown in FIG. 2. The flange 16 contacts the housing component 3 only at the fastening points 14, wherein the flange 16 is held on the housing component 3 by the bolt 4 with the intermediate arrangement of an intermediate piece 18 and an adapter 19. The adapter 19 is a single, ring-shaped part that is reinforced in the area of every fastening point 14. In contrast, the intermediate pieces 18 that are found between the flange 16 and the housing component 3 are individual washers through each of which a bolt 4 is inserted. The axial play S.sub.1 on the side facing the housing component 3 and the axial play S.sub.2 on the side facing away from the housing component 3 correspond to the thickness of the intermediate pieces 18 and the thicker section of the adapter 19 at the fastening points 14, respectively.

(11) The connecting assembly 8 that is realized with the help of the fastening points 14 and the open circumferential sections 17 is provided to absorb deformation of the gear 2, without permitting play between the gear 2 and the housing component 3 in the circumferential direction of the specified parts. Due to the flexible—with reference to the axial direction—connection of the gear 2 to the housing component 3, the gear 2 does not require any significant elasticity that is generated, for example, by sections with reduced material thickness and that goes beyond the measure required for the functioning of the wave generator 9. The fastening points 14 realized by threaded connections can be alternatively constructed as welded connections.

LIST OF REFERENCE SYMBOLS

(12) 1 Gearing 2 Gear 3 Housing component 4 Bolt 5 Recess 6 Bolt head 7 Teeth 8 Connecting assembly 9 Wave generator 10 Inner ring 11 Ball 12 Outer ring 13 Driven wheel 14 Fastening point 15 Cylindrical, toothed section 16 Flange 17 Open circumferential section 18 Intermediate piece 19 Adapter M Center axis S.sub.1, S.sub.2 Play in the axial direction S.sub.3 Angle range of the open circumferential range