Gear Box

Abstract

To provide a gear box that does not require additional components for securing a rolling element in the axial direction. [Solution] A gear box (70) includes a rolling bearing (50) having an outer rolling bearing ring (1a) and an inner rolling bearing ring (1b) disposed in the outer rolling bearing ring (1a), and a mounting groove (18) for a rolling element (16) is formed between the outer rolling bearing ring (1a) and the inner rolling bearing ring (1b). A wave gear (40) having a central longitudinal axis (15) supported in the rolling bearing (50) includes a wave generator (10) and an external toothed wheel (11). The flexspline (4) has an elastic flexspline (4) with an external toothing (3) and a circular spline (6) with an internal toothing (5), the flexspline (4) can be inserted onto a wave generator (10) and can be elastically deformed by the wave generator (10) such that the external toothing (3) of the flexspline (4) can engage with the internal toothing (5) of the circular spline (6) in the opposing region of the major axis of the ellipse, the circular spline (6) having a retaining element (20) which prevents axial movement of the rolling elements (16).

Description

[Technical field]

[0001] The present invention relates to a gearbox according to the preamble of claim 1. [Background technology]

[0002] The rolling bearing and a strain wave gearing supported in the rolling bearing form a gear box, which is used in a wide variety of technical fields, particularly in robotics and increasingly in prosthetics technology.

[0003] The wave gearing consists of three components or groups arranged coaxially with one another: a wave generator having an elliptical cross section, a circular spline which is a rigid hollow gear with internal teeth, and a flexspline which is a gearing component in the form of a thin-walled bush with external teeth. The wave generator deforms the toothed area of ​​the flexspline via ball bearings, so that the external teeth of the flexspline are in engagement with the internal teeth of the circular spline on both sides of the major axis of the ellipse.

[0004] As the wave generator rotates, the major axis of the ellipse moves, which causes the tooth engagement area to move in the circumferential direction. The flexspline of the gearing usually has two fewer teeth than the circular spline, so that the flexspline rotates relative to the circular spline by an angle of one tooth pitch during half a rotation of the wave generator, and by an angle of two tooth pitches during one full rotation. If the circular spline is fixed in position, the flexspline rotates in the opposite direction to the wave generator as a driven element. In this case, the circular spline can be arranged in a fixable manner within a rotating bearing ring.

[0005] To achieve the rotary motion, the externally toothed gear components or flexsplines in the strain wave gear and the hollow gears or circular splines are connected with the respective rings of the rotary bearing.

[0006] From DE 10 2015 104 308 A1 it is known to configure a rolling bearing in such a way that the hollow gear or transmission part and the rolling bearing ring each have at least one receiving portion through which rolling bodies can be introduced into the rolling bearing between the rolling bearing surface of the hollow gear or transmission part and the rolling bearing surface of the rolling bearing ring in the position where the two receiving portions coincide with one another.

[0007] The following Patent Document 2 (DE 10 2020 109 646 A1) discloses a rolling bearing with an inner rolling bearing ring and an outer rolling bearing ring, in which a rolling bearing with a receiving portion for the rolling elements is arranged between the rolling bearing surface of the inner rolling bearing ring and the rolling bearing surface of the outer rolling bearing ring, and in which in at least one receiving portion a guide ring for the rolling elements is arranged between the receiving opening of the rolling bearing and the rolling elements. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Application Publication No. 102015104308 [Patent Document 2] German Patent Application Publication No. 102020109646 Summary of the Invention [Problem to be solved by the invention]

[0009] A disadvantage of known solutions is that additional components must be used for axial retention of the rolling elements, thereby increasing the number of components, manufacturing costs, wear and susceptibility to failure.

[0010] SUMMARY OF THE PRESENT DISCLOSURE The object of the present invention is therefore to improve the above-mentioned gear arrangement in such a way that the disadvantages of the prior art are overcome. [Means for solving the problem]

[0011] This object is achieved according to the invention in that the circular spline or hollow gear has a retaining element (stopping element) which prevents the axial movement of the rolling elements.

[0012] Advantageous configurations of the invention are the subject of the subclaims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a mode for carrying out the invention will be described.

[0014] The invention proceeds from the idea that the falling out of the rolling elements from the rolling bearing must be avoided. The replacement of rolling bearings is very complicated, especially in mounting situations with difficult access. Furthermore, malfunction of the bearing during operation or blocking of the bearing can lead to dangerous situations. The use of a separate component as a guide ring for axially limiting the rolling elements increases the assembly effort of the rolling bearing.

[0015] It was then realized that the falling out of the rolling elements can be prevented without additional components by incorporating a retaining element into an existing component adjacent to the loading groove for the rolling elements. Since the circular spline can be arranged adjacent to the loading groove, the retaining element can be integrated with the circular spline, so that no further components are required. The retaining element is thus integrated with the circular spline or with the hollow gear, which means that both parts are integral or manufactured from one material.

[0016] The securing element thereby functions, so to speak, as a securing nose, whereby the circular spline or hollow gear fulfills a double function by preventing the rolling elements from falling out in addition to its gearing function.

[0017] The components of the gear box, i.e. both rolling bearing rings and the component groups, i.e. the wave generator, the flexspline or externally toothed gear component and the circular spline or hollow gear, are arranged coaxially relative to the central longitudinal axis of the wave gear or gear box.

[0018] In a preferred embodiment, the retaining elements are configured in particular rotationally symmetrically around the entire circumference of the hollow gear, which has the advantage that the rolling elements are secured or held in all rotational positions of the hollow gear, which simplifies the assembly of the gearbox, and at the same time allows for centering, so that the rotationally symmetric retaining elements perform a double function.

[0019] In an alternative preferred embodiment, the retaining element is designed such that it only takes up a predefined finite angle on the periphery. This is based on the idea that the retention of the rolling elements only has to take place in the area of ​​the loading groove. The size of the angle depends on the size of the rolling elements, i.e. it should be selected such that they are prevented from falling out or being pinched. The angle is preferably in the range of 5° and 15°. In this way weight can be saved in the manufacture of the gear.

[0020] The securing element preferably has a bearing surface for the rolling body perpendicular to the central longitudinal axis of the wave gear. The bearing surface is preferably designed as a flat surface. Alternatively, the bearing surface can be designed convexly or concavely.

[0021] The securing elements preferably have a size in the radial direction (perpendicular to the central longitudinal axis of the strain wave gear) that lies between 4% and 10% of the radius of the rolling elements, in particular 7%.

[0022] Preferably, the securing element limits axial movement of the rolling element to less than 10% of the radius of the rolling element.

[0023] In a preferred embodiment, the retaining element is configured as an axial collar, which preferably projects axially into the loading groove, i.e. in a direction parallel to the central longitudinal axis of the gearbox or gearbox.

[0024] In a further preferred embodiment, the securing element is configured as an axial projection whose cross section is formed by two circular arcs. The inner circular arc has a larger radius and its center is located on the component axis. The center of the outer circular arc, which has a smaller radius, is located on or close to the inner circular arc. The axis of the projection can run parallel to the central longitudinal axis of the gear unit or can be inclined corresponding to the axis of the loading opening. The advantage of this embodiment is the significantly increased resistance of the securing element to deformation under extreme loads.

[0025] Preferably, the hollow gear or circular spline is manufactured from a steel material or from a cast material.

[0026] In a first preferred embodiment, the strain wave gear device is configured as a spur gear device. In a second preferred embodiment, the strain wave gear device is configured as a pot gear device.

[0027] The advantages of the present invention are, inter alia, that by integrating the securing elements for the rolling elements with the circular spline, a particularly reliable and robust construction of the gear box is provided. The assembly of the gear box is simplified, since no separate components are required for the axial movement limitation of the rolling elements. In addition, the securing elements are fixed via screwing or bolting the circular spline.

[0028] Further objects, advantages, features and applicability of the present invention become apparent from the following description of an embodiment based on the drawings, in which all features described in this specification and / or illustrated in the drawings, by themselves or in any meaningful combination thereof, constitute the subject of the present invention, regardless of their association in the claims or claim dependencies. [Brief description of the drawings]

[0029] [Figure 1] FIG. 2 shows a front view in longitudinal section of a rolling bearing in which a pan gear is supported in a preferred embodiment; [Diagram 2] FIG. 2 is a diagram showing an enlarged view of a portion from FIG. [Diagram 3] FIG. 2 shows a front view of a longitudinal section of a rolling bearing with a spur gear arrangement. [Figure 4] FIG. 4 is a diagram showing an enlarged view of a portion from FIG. [Diagram 5] FIG. 1 is a perspective view of a circular spline according to a preferred embodiment. [Figure 6] FIG. 6 shows the circular spline of FIG. 5 as a side view from the left side. [Figure 7] FIG. 7 is a diagram showing a vertical cross section of FIG. [Figure 8] FIG. 13 is a perspective view of a circular spline according to another preferred embodiment. [Figure 9]FIG. 9 shows the circular spline of FIG. 8 as a side view from the left side. [Figure 10] FIG. 10 is a diagram showing a vertical cross section of FIG. EXAMPLES

[0030] In all figures, the same parts are provided with the same reference numbers.

[0031] FIG. 1 shows a longitudinal sectional view of an assembled embodiment of a rotary bearing 50 according to the present invention, in which a strain wave gear device 40 is supported therein, and the rotary bearing 50 and the strain wave gear device 40 together form a gear box 70.

[0032] The rolling bearing 50 comprises an outer rolling bearing ring 1a with a rolling bearing surface 9 or race (see FIG. 2), an inner rolling bearing ring 1b arranged coaxially with the outer rolling bearing ring 1a with a rolling bearing surface 7 or race, and a number of rolling elements. The races of both rolling bearing rings 1a, 1b are interrupted at certain points on their circumference by a loading opening 18 through which the rolling elements 16 are loaded into the rolling bearing 50. In a preferred embodiment, the races are configured as in a four-point bearing (four-point contact bearing). The rolling elements 16 are configured as balls in the illustrated example, allowing a low-friction relative rotation of the rolling bearing rings 1a, 1b and at the same time preventing tilting and displacement of the components of the strain wave gear 40. The radial shaft seal ring 30 illustrated in FIG. 1 is a radially acting seal that prevents the leakage of lubricant from the rolling bearing 50. Additionally, the seal prevents the ingress of foreign matter into the rolling bearing 50 .

[0033] The strain wave gear device 40 is configured as a pan gear device (pot gear device) and has an elliptical wave generator 10, a flexspline 4 with an external tooth portion 3, and a circular spline 6 with an internal tooth portion 5.

[0034] The wave generator 10, in the embodiment chosen here, is composed of a central hub, the so-called plug 28, and a ball bearing, the so-called wave generator bearing 12. The plug 28 has, on its radially outer side, a cross section similar to an ellipse. On this mantle surface (outer peripheral surface) with an elliptical cross section, the wave generator bearing 12 is mounted. The wave generator bearing 12 is designed to withstand deformation to an elliptical cross section.

[0035] The multiple components of the strain wave gear device 40 are coaxially arranged. The flexspline 4 is similarly deformed into an elliptical shape by the wave generator 10. The flexspline 4 deformed into an elliptical shape uses its external teeth portion 3 to engage with the internal teeth portion 5 of the circular spline 6 in an opposing region of the major axis of the ellipse.

[0036] The flexspline 4, with its external toothing 3, is in engagement with the internal toothing 5 of the circular spline 6 only in the area of ​​the major axis of the ellipse. Due to the rotation of the wave generator 10, the deformation of the ellipse moves along the circumference of the flexspline 4, causing a relative rotational motion between the flexspline 4 and the circular spline 6, whereby a high reduction ratio can be achieved with only one gear stage.

[0037] The flexspline 4, in the embodiment chosen here, has two fewer teeth than the circular spline 6, which results in a relative rotation between the flexspline 4 and the circular spline 6 through an angle of one tooth pitch during half a rotation of the wave generator 10, and two tooth pitches during a full rotation.

[0038] The components of the rolling bearing 50 and strain wave gearing 40, i.e., the inner rolling bearing ring 1b, the outer rolling bearing ring 1a, the wave generator 10, the flexspline 4, and the circular spline 6, are arranged coaxially about a common central longitudinal axis 15. The flexspline 4 is connected to the inner rolling bearing ring 1b. The circular spline 6 is connected to the outer rolling bearing ring 1a.

[0039] The gearbox 70, and thus the rolling bearing 50, are optimized for high reliability and durability (lifespan). To prevent the rolling elements 16 from falling out of the loading groove 18, the circular spline 6 has or is configured integrally with a retaining element 20, which in the preferred embodiment is configured as an axial collar 22 (see FIG. 2). This means that the retaining element 20 extends in the loading groove 18 in the axial direction, i.e. in the direction of the central longitudinal axis 15. The axial collar 22 has abutment running surface 17 for the rolling elements 16, perpendicular to the central longitudinal axis 15 of the strain wave gear 40. In addition, the axial collar 22 has a constant thickness in the radial direction, i.e. in the direction perpendicular to the central longitudinal axis 15. The axial collar 22 extends entirely around the circumference of the circular spline 6, ie over 360°.

[0040] Since the securing element 20 is configured integrally with the circular spline 6 or is integrated with the circular spline 6, a separate guide ring as an additional component can be omitted, thereby simplifying the assembly of the gear box 70.

[0041] 3 and 4 show a rolling bearing 50 with a strain wave gear 40 in another preferred embodiment. Here, the strain wave gear 40 is configured as a spur gear (flat gear). In this strain wave gear 40, the circular spline 6 also has a retaining element 20, which is configured as a collar portion 22 and has a contact running surface portion 17 for the rolling elements 16, which is oriented perpendicular to the central longitudinal axis 15 of the strain wave gear 40.

[0042] In Fig. 5, a circular spline 6 for a strain wave gear drive 40 in a preferred embodiment is shown in a perspective view. The circular spline 6 according to Fig. 5 is shown in a side view in Fig. 6 and its longitudinal section is shown in Fig. 7.

[0043] The circular spline 6 has a securing element 20 configured as a collar 22. In contrast to the collar 22 of the embodiment shown in FIGS. 1 and 2, the collar 22 does not extend entirely in the circumferential direction at the circular spline 6. The collar 22 advantageously extends at an angle α (see FIG. 6) that is the same as the loading opening for the rolling elements 16 or a somewhat larger angle α. In the present embodiment, the angle α is, for example, 10°. The axially projecting collar 22 has a bearing running surface 17 for the rolling elements 16 that is perpendicular to the central longitudinal axis 15 of the strain wave gear 40.

[0044] In Fig. 8, a circular spline 6 for a strain wave gear drive 40 in another preferred embodiment is shown in a perspective view. The circular spline 6 according to Fig. 8 is shown in a side view in Fig. 9 and its longitudinal section is shown in Fig. 10.

[0045] The circular spline 6 has a retaining element 20 which in this embodiment is configured as an axial projection 24. In contrast to the collar 22 of the embodiment shown in Figs. 1-4, the axial projection 24 does not extend entirely around the circumference of the circular spline 6. In another preferred embodiment, the retaining element 20 is configured as an axial projection 24 whose cross section is formed by two circular arcs. The inner circular arc has a larger radius and its centre lies on the component axis. The centre of the outer circular arc, which has a smaller radius, lies on or close to the inner circular arc, i.e. this projection 24 has a larger abutment running surface 17 for the rolling elements 16. The axial projection 24 (see Fig. 9) is slightly smaller than the loading opening for the rolling elements 16. The axial projection 24 has abutment running surface 17 for the rolling elements 16 which is perpendicular to the central longitudinal axis 15 of the strain wave gear 40 in the embodiment shown. The advantage of this embodiment is the increased resistance to the outgoing ball.

[0046] 1 to 10, the securing element 20 is respectively manufactured in one piece with the circular spline 6. The circular spline 6 is preferably manufactured from a cast material or a steel material. [Explanation of symbols]

[0047] 1a Outer swivel bearing ring 1b Inner rotating bearing ring 3 External teeth 4 Flexspline 5 Internal teeth 6 Circular spline 7 Rolling bearing surface on the inner rolling bearing ring 8 Rolling elements 9 Rolling bearing surface on the outer rolling bearing ring 10. Wave Generator 12 Wave generator bearing 15 Central longitudinal axis 16 Rolling elements 17 Contact running surface 18 Loading groove 20. Securing Elements 22 Axial collar 24 Protrusion 28 Plug 30 Radial shaft seal ring 40 Strain Wave Gear 50 swivel bearing 70 Gear Box α angle

Claims

1. A gearbox (70), a strain wave gear (40) having a central longitudinal axis (15) supported in the rolling bearing (50), the strain wave gear (40) comprising a rolling bearing (50) with an outer rolling bearing ring (1 a) and an inner rolling bearing ring (1 b) arranged in the outer rolling bearing ring (1 a), between which a mounting groove (18) for rolling elements (16) is formed, the strain wave gear (40) comprising a wave generator (10), an elastic flexspline (4) with an external toothing (3) and a circular spline (6) with an internal toothing (5), the flexspline (4) being insertable onto the wave generator (10) and elastically deformable by a drive component (2) such that the external toothing (3) of the flexspline (4) can engage with the internal toothing (5) of the circular spline (6) in the opposing region of the major axis of an ellipse, the circular spline (6) having a retaining element (20) for preventing axial movement of the rolling elements (16); A gear box (70) characterized by:

2. the securing element (20) is configured in particular rotationally symmetrically around the entire circumference of the circular spline (6); The gearbox (70) of claim 1, characterized in that:

3. the securing element (20) only takes a predetermined finite angle (α) on the peripheral side; The gearbox (70) of claim 1, characterized in that:

4. the securing element (20) has a contact running surface portion (17) for the rolling element (16) perpendicular to the central longitudinal axis (15) of the strain wave gear device (40); A gearbox (70) according to any one of claims 1 to 3, characterized in that

5. the securing element (20) has a size, in a direction perpendicular to the central longitudinal axis (15) of the strain wave gear (40), lying between 4% and 10% of the radius of the rolling elements (16), in particular 7%; A gearbox (70) according to any one of claims 1 to 4, characterized in that

6. the securing element (20) restricts the axial movement of the rolling body (16) to less than 10% of the radius of the rolling body (16); A gearbox (70) according to any one of claims 1 to 5, characterized in that

7. the securing element (20) being configured as an axial collar (22); A gearbox (70) according to any one of claims 1 to 6, characterized in that

8. said securing element (20) being configured as a flat axial projection (24) whose cross section is defined by two circular arcs; A gearbox (70) according to any one of claims 1 to 6, characterized in that

9. the gear (6) of the circular spline is manufactured from steel material or cast material; A gearbox (70) according to any one of claims 1 to 8, characterized in that

10. The wave gear device (40) is configured as a spur gear device; A gearbox (70) according to any one of claims 1 to 9, characterized in that

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