inner ring of the wave generator

Abstract

A wave generator (1) has a rolling bearing (2) comprising a rigid inner ring (3) having a non-circular outer profile and a compliant outer ring (4). The inner ring (3) has raceways (7) arranged outside the median plane (25) of the plate.

Description

Technical Field

[0001] This invention relates to an inner ring for a wave generator suitable for wave propagation, according to the preamble of claim 1. The invention also relates to a method for manufacturing such an inner ring. Background Technology

[0002] Such wave generators are known, for example, in DE 10 2014 202 060 A1. This wave generator is a gear in the actuator of an electrically powered camshaft adjuster. Other electrically powered camshaft adjusters with wave generators are disclosed, for example, in documents DE 10 2004 009 128 A1, DE 10 2008 053 ​​914 A1, DE 10 2009 037 403 A1, DE 102010 031 218 A1, and DE 10 2013 220 220 A1. An inner ring for large bearing applications is found in EP 3343 051 A1.

[0003] In wave drives, the task of the wave generator is to deform a flexible, toothed gear element. For this purpose, the wave generator has a rolling bearing with a non-circular, typically elliptical, bearing ring. In mass production, it is advantageous to manufacture the inner ring of the wave generator from sheet metal. However, it has been found that the bearing life is insufficient in certain situations. Summary of the Invention

[0004] The objective of this invention is to provide an inner ring for a wave generator used in wave transmission that enables a high bearing life.

[0005] This task is achieved by an inner ring having the features of claim 1. This inner ring is used in a wave generator for wave transmission, which, in a basic configuration known per se, includes a rolling bearing, and therefore has raceways on its outer periphery for the rolling elements of the rolling bearing. The inner ring itself is rigid and has a non-circular, particularly elliptical, outer profile. The corresponding outer ring of the rolling bearing is designed as a compliant bearing ring.

[0006] The inner ring is made of sheet metal. For this purpose, a semi-finished product can be cut to length, or a circular piece can be punched from it, preferably already having a non-circular outer contour. The sheet metal used as the raw material has a substantially constant thickness and a central plane is centrally located between the two outer surfaces.

[0007] The raceways of the inner ring, made of sheet metal, are arranged outside the midplane of the sheet metal. This can be achieved by shaping the inner ring to obtain an asymmetrical, particularly L-shaped, longitudinal section. If a plane perpendicular to the axis of rotation of the inner ring is drawn through it, an asymmetrical, particularly L-shaped, longitudinal section region is given on each side. The first, outer arm of the L-shaped longitudinal section forms a non-circular circumferential surface of the inner ring, on which the rolling elements roll in the case of a rolling bearing. This circumferential surface may have a flange, which does not necessarily have to be formed completely around the entire ring. For example, it may be interrupted by a single groove, which can serve as the engagement portion of the connecting parts. From the said L-arm, the second, inner L-arm extends radially inward along the bearing. In the longitudinal section, the inner arm forms an annular disc.

[0008] The lifespan of the inner ring is improved by arranging the raceway outside the midplane of the sheet metal. Due to casting and subsequent rolling processes, the sheet metal may contain non-metallic inclusions due to segregation. For the inner ring of a sheet metal with raceways symmetrically imprinted within its annular disk plane, these raceways are located on the midplane of the sheet metal, precisely where the non-metallic inclusions are located. This invention is based on the understanding that if the raceway does not coincide with the midplane of the sheet metal, the lifespan of the inner ring of the sheet metal can be improved because this results in fewer, ideally none, non-metallic inclusions located in or immediately below the raceway.

[0009] It has been shown that an L-shaped longitudinal section for the inner ring of the wave generator is sufficient compared to a symmetrical shape (e.g., a T-shape). By deep drawing the flange, the original plate midplane no longer extends strictly radially, but is offset axially toward the flange due to the deep drawing. This leaves sufficient space radially to obtain a sufficiently robust area of ​​the plate. Non-metallic inclusions are thus removed from the raceway area. The plate "core," which is the central fiber orientation, is therefore deflected axially and, in a preferred embodiment, is no longer exposed at the radially pointing outer contour.

[0010] The L-shaped profile also has the advantage of maintaining almost the same moment of inertia and stiffness compared to the T-shaped profile. The moment of inertia can be further reduced by adding additional axial grooves in the annular region besides the central opening. The axial grooves can also provide additional functionality. For example, bolts that are part of an Oldham coupling can engage in the first axial groove. A second axial groove can further ensure lubricant exchange.

[0011] It has been found that certain ratios between the plate thickness of the ring disc and the plate thickness of the deep-drawn flange are particularly advantageous. When this ratio is between 0.7 and 0.8, sufficient surface material is obtained, so even a slight deflection of the plate's midplane is enough to achieve a sufficient distance between the surface and the plate. This results in sufficient plate surface material in the side surface areas. When this ratio is between 0.6 and 0.7, the degree of deformation is significantly greater. However, through subsequent upsetting, a particularly advantageous displacement of the plate's "core" can also be achieved in this case, thus ensuring a sufficiently large minimum distance between it and the raceway.

[0012] According to the present invention, the following steps are proposed to manufacture the inner ring of a wave generator: Provide semi-finished boards with a flat center plane. Stamping non-circular discs, By cold forming a flange in a disc, the center plane of the sheet metal is offset radially in the flange area. Upsetting of the disc.

[0013] Depending on the inner ring size, the non-circular disc can initially be pre-drilled to facilitate tool clamping. Chamfering can be performed before forming (preferably deep drawing). After the forming step, the originally flat disc has a three-dimensional shape comprising an annular disc and a portion extending from the plane of the annular disc, such as a flange. The disc can also be selectively upset and may undergo final drilling. Additional axial grooves can be introduced into the annular disc simultaneously, before, or after the forming process. Post-processing steps such as deburring or chamfering can then be performed.

[0014] Preferably, the inner ring with an L-shaped profile is manufactured by cold forming. Due to the L-shaped longitudinal sections on both sides of the axis of rotation, the inner ring as a whole has a shallow cup shape with an open bottom. With this shape, the inner ring is comparable to an inner ring with a T-shaped profile in terms of its moment of inertia, as well as its radial and torsional stiffness. Conversely, an inner ring arranged in an L-shape along its longitudinal section has significantly better strength characteristics than a flat ring or flat disc.

[0015] Rolling bearing components manufactured by forming methods are known in principle, for example, from DE 101 32 470 A1 and DE 102005 003 987 A1.

[0016] According to one possible improvement, the rolling bearing is coupled to a compensating coupling (especially the Oldham coupling). The Oldham coupling, suitable for wave generators, is known in principle, for example, in DE 10 2007 049 072 A1.

[0017] To couple the compensating coupling to the inner ring of the wave generator, for example, two bolts are suitable, which are respectively fixed in the radially inward-pointing L-arms of the inner ring.

[0018] With various advantageous improvements, the compensating coupling achieves coupling with the inner ring of the wave generator without the need for a separate connecting element such as bolts. For example, the Oldham disc of the compensating coupling, made of plastic or metal, is guided radially in a restricted movable manner on two guide lugs formed on the inner ring. Another guidance of the Oldham disc on the inner ring can be achieved through guide grooves formed directly from the inner ring and engaging with the opposing profiles on the sides of the Oldham disc.

[0019] In both cases, torque can be transmitted to the Oldham disk, for example, via a dual-wing drive element coupled to, and particularly rigidly connected to, a drive shaft, and is movable in a restricted manner relative to the Oldham disk along the drive shaft and the radial direction of the compensating coupling. This drive shaft is preferably electrically driven, particularly the same as the motor shaft of an electric motor.

[0020] According to a simplified structure, a biplane drive element fixed to a drive shaft directly mates with the inner ring of a wave generator. As long as there is no radial compliance of the drive shaft and the drive element is rigidly connected to it, the limited functionality of the compensating coupling can be provided by guiding the drive element in a slippery manner on the inner ring. The full functionality of the compensating coupling can be achieved by using a radially deflectable drive shaft. For example, such a drive shaft may comprise a single helical spring, or two concentric helical springs wound in opposite directions. As an alternative to the biplane drive element, a single-finger coupling can also be used, as is known in principle, for example, in document DE 10 2004 041 769 A1.

[0021] The wave generator is suitable for use in a wave drive, for example, in an electrically operated camshaft adjuster. Similarly, the wave generator is also suitable for the actuating gear of a device for changing the compression ratio of a reciprocating piston engine. In the latter case, an eccentric shaft can be adjusted by means of the actuating gear, which interacts with other components of the crank mechanism of the reciprocating piston engine via a connecting rod. Attached Figure Description

[0022] The three embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0023] Figure 1. A cross-sectional view of a first embodiment of a wave generator with an inner ring. Figures 2 and 3 Figure 1 The inner ring of the wave generator shown. Figure 4. An end view of a second embodiment of a wave generator with an inner ring. Figure 5 Figure 4 The cross-sectional view of the wave generator shown is similar to... Figure 1 , Figures 6 and 7 Figure 4 The inner ring of the wave generator shown is similar to Figure 2 and Figure 3 The view, Figure 8. A third embodiment of a wave generator with an inner ring, similar to... Figure 4 The view, Figure 9 Figure 8 The wave generator shown is similar to Figure 1 The view, Figures 10 and 11 Figure 8 The inner ring of the wave generator shown is similar to Figure 2 and Figure 3 The view, Figure 12. Another inner ring for a wave generator. Detailed Implementation

[0024] Unless otherwise stated, the following description relates to all embodiments. Corresponding or substantially identical components are labeled with the same reference numerals in all figures.

[0025] The wave generator, generally designated 1, includes a rolling bearing 2, with its inner ring marked 3 and its outer ring marked 4. Wave generator 1 is part of a wave drive (not shown further), the function of which can be found in the prior art cited at the beginning. This wave drive is used in an electrically powered camshaft adjuster.

[0026] Between the inner ring 3 and the outer ring 4, which serve as bearing rings, the rolling elements 5 are steel balls and guided in the cage 6. The inner ring 3 has an L-shaped profile LP in longitudinal section, where the raceways 7 for the rolling elements are formed by the outer L-arm 8. The inner L-arm 9, pointing in the direction of the rotation axis R, is connected to the outer L-arm 8. Generally, the outer L-arm 8 forms a cylindrical wall, where the portion protruding from the plane of the inner L-arm 9 forms a flange 24, which is continuously formed circumferentially in this example. The inner L-arm 9 forms the bottom of a shallow, integral cup-shaped structure connected to the outer L-arm 8, which is also called the ring disc 23 and has an opening in the middle. The entire inner ring 3 is manufactured from metal (i.e., steel, such as 100Cr6) through a forming process. The outer circumferential surface of the inner ring 3 (on which the raceways 7 are provided) has a non-circular elliptical shape. Corresponding to this shape, the outer ring 4 (which, unlike the inner ring 3, is designed to be compliant) is also forced to be non-circular. A flexible gear element 10 is adjacent to but not fixedly connected to the outer ring 4, and conforms to the shape of the outer ring. This flexible external meshing gear element 10 is also called a flexring and partially meshes into the internal teeth of a rigid gear element (not shown). In addition to the flexring ring 10, flanged sleeves or compliant cup-shaped gear elements can also be used as flexible gear elements.

[0027] Figure 3 schematically illustrates the original plate midplane 25 used to manufacture the inner ring 3. Because the inner ring 3 acquires an asymmetrical shape through deep drawing and upsetting processes, the plate midplane 25, representing the "core" of the plate with the most non-metallic inclusions, is radially deflected within the region of the outer L-arm 8 for this reason only. The length and thickness of the flange 24 are designed such that the plate midplane 25 no longer intersects with the raceway 7, and in this example, with the remaining radial walls.

[0028] The inner ring 3 is coupled to a compensating coupling 11, which is designed as an Oldham coupling in the structural forms shown in Figures 1 and 4.

[0029] The compensating coupling 11, designed as an Oldham coupling, includes an Oldham disc 12, which, in the embodiments shown in Figures 1 to 3, is coupled to an inner ring 3 by two bolts 13. The bolts 13 are fixed in the inner ring 3 and also guided in elongated holes 14 in the Oldham disc 12, thereby allowing the Oldham disc 12 to move in a restricted manner relative to the inner ring 3 in a defined radial direction. Through holes 15 in the inner ring 3 are used to secure the bolts 13. (Figures 1 to 3 are not directly related to the coupling description and can be omitted.) Figure 3In this embodiment, the Oldham disc 12 abuts against the outer L-arm 8 of the inner ring 3 on one side and against the head 16 of the bolt 13 on the other side, thus being held on the inner ring 3 without loss, and thus also held on the entire rolling bearing 2.

[0030] In the embodiments shown in Figures 4 through 7, there are no bolts or other separate fasteners for holding the Oldham disc 12 on the inner ring 3. Instead, two guide lugs 17 are formed on the inner ring 3, extending axially from the outer L-arm 8. The guide lugs 17 engage with grooves 18 in the Oldham disc 12, thus performing a function equivalent to that of the bolts 13 in the wave generator shown in Figure 1. Furthermore, two grooves 19 in the Oldham disc 12, rotated 90° relative to the grooves 18, are also visible in Figure 4 and are used to engage with drive elements not shown here.

[0031] This is a dual-wing drive element 20, which is also provided in the embodiments of Figures 8 to 11. However, in the embodiments of Figures 8 to 11, the drive element 20 differs from the structure of Figures 1 and 4; instead of being via the Oldham disc 12, it directly engages with the inner ring 3. The drive element 20 of the wave generator 1 shown in Figure 8 is preferably fixed to a flexible drive shaft, thus providing the full functionality of the compensating coupling 11 without a separate compensating disc. The two blades 22 of the drive element 20 engage in the guide grooves 21 of the inner ring 3. Similar to the embodiment of Figure 4, the guide grooves 21 do not provide any axial guidance function, which is advantageous in terms of assembly.

[0032] Figure 12 shows another inner ring 3, which has an annular disk 23. A first axial groove 26 and a second axial groove 27 are provided in the annular disk 23. In this example, they are formed as circles, and the first axial groove 26 and the second axial groove 27 are different in diameter.

[0033] Explanation of reference numerals in the attached figures 1 Wave Generator 2. Rolling bearings, rolling bearings 3 Inner Circle 4 Outer ring 5. Rolling element 6. Cage 7. Rolling track 8 Outer L-arm 9 Inner L-arm 10 Flexible gear components 11. Compensating Coupling 12 Oldham Plates 13 bolts 14 long holes 15 Through Holes 16 Head 17 Guide Lug 18 Grooves 19 Grooves 20 Driving Components 21 Guide groove 22 winglets 23. Ring Disc 24 Flange 25. Middle plane of the board 26 First Axial Groove 27 Second Axial Groove LP L-shaped profile R Rotation axis d S thickness of the ring disk d B Flange thickness

Claims

1. An inner ring (3) of a wave generator (1), wherein the inner ring (3) is made of a plate having a plate midplane (25), having a non-circular outer contour and raceways (7) for rolling elements (5), characterized in that, The raceway (7) is arranged outside the middle plane (25) of the plate.

2. The inner ring (3) according to claim 1, characterized in that, The inner ring (3) is formed by an annular disc (23) with a flange (24), and the two together form an L-shaped longitudinal section.

3. The inner ring (3) according to claim 2, characterized in that, The ratio of the forming plate thickness (dB) of the flange (24) to the plate thickness (dS) of the ring disc (23) is between 0.7 and 0.

8.

4. The inner ring (3) according to claim 2, characterized in that, The ratio of the forming plate thickness (dB) of the flange (24) to the plate thickness (dS) of the ring disc (23) is between 0.5 and 0.

6.

5. The inner ring (3) according to any one of the preceding claims, characterized in that, The annular disk has first and second axial grooves (26, 27).

6. A wave generator (1) having a rolling bearing (2) comprising a compliant outer ring (4) and an inner ring (3) according to any of the preceding claims.

7. The wave generator (1) according to claim 6, wherein the inner ring conforms to claim 5, characterized in that, The wave generator (1) has a compensating coupling (11) connected to the rolling bearing (2), the compensating coupling (11) having two bolts (13) connected to a first axial groove (26) of the inner ring (3), and the second axial groove (27) forming a lubricant channel.

8. The wave generator (1) according to claim 6 or 7, characterized in that, The rolling bearing (2) is a ball bearing.

9. A method for manufacturing an inner ring (3) of a wave generator (1), comprising the following steps: • Provide a semi-finished board product with a central plane (25) on the board. • Stamping non-circular blanks • The blank is cold-formed to form a flange (24), such that the mid-plane (25) of the sheet metal in the region of the flange (24) is offset radially. • Upsetting the blank.

10. The method according to claim 9, characterized in that, The cold forming of the flange (24) is achieved by deep drawing.

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