Gearbox

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 the strain wave gearing supported in the rolling bearing form a gear box. Gear boxes of this type are used in a wide variety of technical fields. In particular, gear boxes of this type are increasingly used in robotics and also in prosthetics technology.

[0003] The wave gearing consists of three components, or constituent 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 thin-walled, bush-shaped gear component with external teeth. The wave generator deforms the toothed region 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, thereby moving the tooth engagement area in the circumferential direction. The flexspline of the gearing typically has two fewer teeth than the circular spline, so the flexspline rotates relative to the circular spline by an angle equal to one tooth pitch during half a rotation of the wave generator, and by an angle equal to 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. The circular spline can be fixably mounted within a rotary bearing ring.

[0005] To achieve the rotary motion, the externally toothed gear components or flexsplines in the strain wave gearing and the hollow gears or circular splines are connected to 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 component and the rolling bearing ring each have at least one receiving portion through which rolling elements can be introduced into the rolling bearing between the rolling bearing surface of the hollow gear or transmission component and the rolling bearing surface of the rolling bearing ring at 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 having an inner rolling bearing ring and an outer rolling bearing ring, in which a rolling bearing having a receiving portion for a rolling element 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 at least one receiving portion a guide ring for the rolling element is arranged between the receiving opening of the rolling bearing and the rolling element. [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 to secure the rolling elements axially (prevent them from falling out), which increases the number of components, manufacturing costs, wear and susceptibility to failure.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the above-mentioned gear arrangement so that the drawbacks of the prior art are overcome. [Means for solving the problem]

[0011] According to the invention, this object is achieved in that the circular spline or hollow gear has a securing element (blocking element) which prevents the axial movement of the rolling elements. That is, according to one aspect of the present invention, A gearbox comprising: a strain wave gearing device having a central longitudinal axis supported in the rolling bearing, the strain wave gearing device comprising a rolling bearing having an outer rolling bearing ring and an inner rolling bearing ring disposed within the outer rolling bearing ring, with loading grooves for rolling elements formed between the outer rolling bearing ring and the inner rolling bearing ring; the strain wave gearing device having a central longitudinal axis supported in the rolling bearing, the strain wave gearing device comprising a wave generator, an elastic flexspline with external toothing, and a circular spline with internal toothing, the flexspline being insertable onto the wave generator and elastically deformable by the wave generator so that the external toothing of the flexspline can engage with the internal toothing of the circular spline in opposing regions of the major axes of an ellipse; the circular spline has a securing element that prevents axial movement of the rolling elements; A gearbox is provided, characterized in that: More specifically, in the above aspect, A gearbox comprising: a strain wave gearing device having a central longitudinal axis supported in the rolling bearing, the strain wave gearing device comprising a rolling bearing having an outer rolling bearing ring and an inner rolling bearing ring disposed within the outer rolling bearing ring, with loading grooves for rolling elements formed between the outer rolling bearing ring and the inner rolling bearing ring; the strain wave gearing device having a central longitudinal axis supported in the rolling bearing, the strain wave gearing device comprising a wave generator, an elastic flexspline with external toothing, and a circular spline with internal toothing, the flexspline being insertable onto the wave generator and deformable into an elliptical shape by the wave generator so that the external toothing of the flexspline can engage with the internal toothing of the circular spline in opposing regions of the ellipse major axis; the circular spline has a securing element that prevents the rolling element from moving in the axial direction and from falling off, and the securing element is configured as one piece with the circular spline; It is characterized by: It should be noted that the reference numerals used in the claims of this application are intended solely to facilitate understanding of the present invention and are not intended to limit the present invention to the illustrated forms.

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

[0013] The present invention can have the following configurations. (Form 1) A gearbox comprising: a rolling bearing having an outer rolling bearing ring and an inner rolling bearing ring disposed within the outer rolling bearing ring, with loading grooves for rolling elements formed between the outer rolling bearing ring and the inner rolling bearing ring; a strain wave gearing having a central longitudinal axis supported within the rolling bearing, the strain wave generator, an elastic flexspline with external toothing, and a circular spline with internal toothing, the flexspline being insertable onto the wave generator and elastically deformable by a drive component so that the external toothing of the flexspline can engage with the internal toothing of the circular spline in opposing regions of the major axis of the ellipse; The circular spline has a securing element that prevents axial movement of the rolling elements. (Form 2) The securing element is preferably configured in particular rotationally symmetrically around the entire circumference of the circular spline. (Form 3) Preferably, the securing elements only subtend a predetermined finite angle on the periphery. (Form 4) The securing element preferably has a running surface portion for contacting the rolling element, the running surface being perpendicular to the central longitudinal axis of the strain wave gear device. (Form 5) The securing element preferably has a size lying between 4% and 10%, in particular 7%, of the radius of the rolling element in a direction perpendicular to the central longitudinal axis of the strain wave gearing. (Form 6) Preferably, the securing element limits axial movement of the rolling element to less than 10% of the radius of the rolling element. (Form 7) The securing element is preferably configured as an axial collar. (Form 8) The securing element is preferably configured as a flat axial projection whose cross section is defined by two circular arcs. (Form 9) The gears of the circular spline are preferably made from steel or cast material. (Form 10) The strain wave gear device is preferably configured as a spur gear device.

[0014] The invention is based on the idea that the falling off of rolling elements from a rolling bearing must be prevented at all costs. Replacing a rolling bearing is extremely complicated, especially in installation situations where access is difficult. Furthermore, malfunctioning or blocking of the bearing during operation can lead to dangerous situations. The use of a separate component as a guide ring for axially restricting the rolling elements increases the assembly time of the rolling bearing.

[0015] It was then recognized that the falling out of the rolling elements can be prevented without the use of 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, thereby eliminating the need for additional components. In other words, the retaining element is configured integrally with the circular spline or the hollow gear, which means that both parts are integral or made from one material.

[0016] The securing element thereby functions, so to speak, as a securing nose, so that 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 gearbox, i.e. both rolling bearing rings and the component groups, i.e. the wave generator, the flexspline or externally toothed gearbox component and the circular spline or hollow gear, are arranged coaxially relative to the central longitudinal axis of the wave gear or gearbox.

[0018] In a preferred embodiment, the retaining elements are configured in a rotationally symmetrical manner 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, thereby simplifying the assembly of the gearbox, and at the same time allowing for centering, so that the rotationally symmetrical retaining elements perform a dual function.

[0019] In an alternative preferred embodiment, the retaining elements are configured so that they only take up a predetermined finite angle on the periphery. This configuration is based on the idea that the rolling elements only need to be secured in the area of ​​the loading groove. The size of the angle depends on the size of the rolling elements, i.e., should be selected so that they do not fall out or become trapped. The angle is preferably within the range of 5° to 15°. This allows for weight savings in the manufacture of the gear.

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

[0021] The securing element preferably has 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 element, 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 box.

[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 near the inner circular arc. The axis of the projection can extend parallel to the central longitudinal axis of the gear unit or can be inclined relative to the axis of the loading opening. An 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 made of steel or cast material.

[0026] In a first preferred embodiment, the strain wave gear device is configured as a spur gear device (flat gear device). In a second preferred embodiment, the strain wave gear device is configured as a pan gear device (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 gearbox is provided. Assembly of the gearbox is simplified, since no separate components are required for the axial movement restriction of the rolling elements. Furthermore, the securing elements are fixed via screwing or bolting the circular spline.

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

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

[0030] In all figures, the same parts are given the same reference numerals.

[0031] FIG. 1 shows a longitudinal cross-sectional view of an assembled embodiment of a rotary bearing 50 according to the present invention, in which a strain wave gear 40 is supported therein, and the rotary bearing 50 and strain wave gear 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 raceway (see FIG. 2), an inner rolling bearing ring 1b arranged coaxially with the outer rolling bearing ring 1a and with a rolling bearing surface 7 or raceway (see FIG. 2), and a plurality of rolling elements. The raceways of both rolling bearing rings 1a and 1b are interrupted at predetermined circumferential locations by loading openings 18 through which rolling elements 16 are loaded into the rolling bearing 50. In a preferred embodiment, the raceways are configured as in a four-point bearing (four-point contact bearing). In the illustrated example, the rolling elements 16 are configured as balls, which allow low-friction relative rotation of the rolling bearing rings 1a and 1b while simultaneously preventing tilting and displacement of the components of the strain wave gearing 40. The radial shaft seal ring 30 shown in FIG. 1 is a radially acting seal that prevents lubricant from leaking out of the rolling bearing 50. Furthermore, the seal prevents foreign matter from entering the rotary 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 selected 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 a cross section resembling an ellipse on its radially outer side. The wave generator bearing 12 is mounted on this mantle surface (outer peripheral surface) with an elliptical cross section. The wave generator bearing 12 is configured to withstand deformation to the elliptical cross section.

[0035] The multiple components of the strain wave gearing 40 are arranged coaxially. 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 tooth portion 3 to engage with the internal tooth 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 region of the major axis of the ellipse. When the wave generator 10 rotates, the elliptical deformation moves along the periphery of the flexspline 4, causing relative rotational motion between the flexspline 4 and the circular spline 6, thereby achieving a high reduction ratio with just 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 of one tooth pitch angle 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 around 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 axially, i.e., in the direction of the central longitudinal axis 15, into the loading groove 18. The axial collar 22 has a contact running surface 17 for the rolling elements 16 that is 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 around the entire 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 gearbox 70.

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

[0042] Figure 5 shows a perspective view of a circular spline 6 for a strain wave gearing 40 in a preferred embodiment. The circular spline 6 according to Figure 5 is shown in a side view in Figure 6, and its longitudinal cross section is shown in Figure 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 of 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 slightly larger angle α. In this embodiment, the angle α is, for example, 10°. The axially projecting collar 22 has a contact running surface 17 for the rolling elements 16 that is perpendicular to the central longitudinal axis 15 of the strain wave gear 40.

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

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

[0046] 1 to 10, the securing element 20 is made in one piece with the circular spline 6. The circular spline 6 is preferably made 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 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 device 50 swivel bearing 70 Gear Box α angle

Claims

1. A gearbox comprising: A wave gear device (40) having a central longitudinal axis (15) and a rolling bearing (50) including an outer rolling bearing ring (1 a) and an inner rolling bearing ring (1 b) disposed in the outer rolling bearing ring (1 a), with a loading groove (18) for a rolling element (16) formed between the outer rolling bearing ring (1 a) and the inner rolling bearing ring (1 b), is supported in the rolling bearing (50). a flexible flexspline (4) with external toothing (3) and a circular spline (6) with internal toothing (5), the flexspline (4) being insertable onto the wave generator (10) and deformable by the wave generator (10) into an elliptical shape such that the external toothing (3) of the flexspline (4) can engage with the internal toothing (5) of the circular spline (6) in an opposing region of the major axis of the ellipse; The circular spline (6) has a securing element (20) that prevents the axial movement of the rolling elements (16) and prevents the rolling elements (16) from falling off, and the securing element (20) is configured as a single member with the circular spline (6). A gearbox characterized by:

2. the securing element (20) is configured rotationally symmetrically around the entire circumference of the circular spline (6) or around the entire circumference of the circular spline (6); 2. The gearbox according to claim 1, wherein:

3. the securing element (20) only takes a predetermined finite angle (α) on the periphery side; 2. The gearbox of claim 1, wherein:

4. the securing element (20) has a contact running surface (17) for the rolling element (16) perpendicular to the central longitudinal axis (15) of the strain wave gear device (40); 2. The gearbox of claim 1, wherein:

5. the securing element (20) has a size lying between 4% and 10%, or 7% of the radius of the rolling element (16) in a direction perpendicular to the central longitudinal axis (15) of the strain wave gearing (40); 2. The gearbox according to claim 1, wherein:

6. the securing element (20) restricts the axial movement of the rolling element (16) to less than 10% of the radius of the rolling element (16); 2. The gearbox according to claim 1, wherein:

7. the securing element (20) is configured as an axial collar (22); 2. The gearbox according to claim 1, wherein:

8. the securing element (20) is configured as a flat axial projection (24) whose cross section is formed by two circular arcs; 2. The gearbox according to claim 1, wherein:

9. The circular spline (6) is made of steel material or cast material; 2. The gearbox according to claim 1, wherein:

10. The strain wave gear device (40) is configured as a spur gear device; 2. The gearbox according to claim 1, wherein:

Images