WO2024231013A1

WO2024231013A1 - Roller harmonic drive transmission having a flex spline and a circular spline

Info

Publication number: WO2024231013A1
Application number: PCT/EP2024/059735
Authority: WO
Inventors: Frank Zens
Original assignee: Harmonic Drive Se
Priority date: 2023-05-11
Filing date: 2024-04-10
Publication date: 2024-11-14

Abstract

The invention relates to a roller harmonic drive transmission (8) comprising: a wave generator (6) having a rolling bearing (7); a flex spline (4) having outer teeth (9); and a circular spline (1); wherein in the circular spline (1), in particular at least in parts, cylindrical pockets (2) are formed which face the outer teeth (9) of the flex spline (4) and in which rollers (3) are disposed, wherein the ratio of the difference between the major axis (A) of the wave generator (6) and the inside diameter (I) of the flex spline (4) to twice the ratio of the pitch circle diameter (T) of the rollers to the number of rollers is less than 0.8.

Description

Designation: Roller shaft gear with one flexspline and one circular spline

Description

The invention relates to a roller shaft drive according to the preamble of claim 1.

For wave gears, 30 is currently the smallest commercially available reduction ratio. Wave gears with small reduction ratios (<=50) have limited performance data and are subject to more wear.

Based on the disadvantages described above, the object of the invention is to provide a wave gear for small reduction ratios and with improved performance data compared to wave gears of the prior art.

This object is achieved according to the invention with a roller shaft gear according to claim 1.

According to the invention, a roller shaft gear is provided comprising a wave generator with a rolling bearing, a flexspline (FS) with external teeth and a circular spline (CS), wherein cylindrical pockets facing the external teeth of the flexspline are formed in the circular spline, in particular at least partially, in which rollers are arranged/guided, and wherein the ratio of the difference between the major axis of the wave generator and the inner diameter of the flexspline and twice the ratio of the pitch circle diameter of the rollers and the number of rollers is less than 0.8. Expressed as a formula, this means (A - I) / (2 * (T/n)) < 0.8 where A is the major axis of the wave generator (WG), I is the inner diameter of the flexspline (FS), T is the pitch diameter of the rollers, and n is the number of rollers. The symbol denotes multiplication, the symbol "/" denotes division.

It is therefore expressed as a mathematical formula

or

The large axis A of the wave generator is the largest diametrically measured distance on the wave generator on the outer diameter of the outer ring of the wave generator bearing. The inner diameter I is the inner diameter of the tubular area of the flex spline, measured in the area of contact with the outer ring of the wave generator bearing. The pitch circle diameter of the rollers refers to the diameter of the circle on which the centers of the rollers lie, related to the front section. The ratio of the pitch circle diameter of the rollers to the number of rollers is equivalent to the module of a gear. Advantageous embodiments of the invention are the subject of the subclaims and the description.

The invention is based on the consideration that roller shaft gears with low reduction ratios and improved performance data are required in a variety of applications. As has now been recognized, these requirements can be met by implementing the CS (Circular Spline) gearing using rollers or needles or needle rollers. The use of rollers allows the deformation of the Flexspline necessary for the gear to function to be reduced. This reduces the functional stresses on the Flexspline and allows it to transmit higher external loads. This can be achieved by making the ratio (A - I) / (2 * (T/n)) less than 0.8. This also increases the service life of the roller shaft gear.

With roller shaft gears designed in this way, smaller reduction ratios (e.g. 25) can be achieved, which are less susceptible to wear and are also suitable for continuous operation. The rollers are also referred to as pins or needles.

Advantageously, the radius of the rollers is larger than the ratio of the pitch circle diameter of the rollers to the number of rollers.

Advantageously, the height of the teeth of the flexspline is smaller than the radius of the rollers.

Advantageously, the wave generator has a rolling bearing which is designed as a thin-ring bearing and/or the wave generator has an elliptical disk.

The design of the Circular Spline/CS is essential for the invention. The rollers are guided in a solid part in cylindrical pockets. Each cylindrical pocket extends over more or less or exactly 180° of the circumference of the roller. In particular, the toothing of the CS is made up of rollers (pins). For the present design, it is advantageous to choose the radius of the rollers larger than the ratio of the pitch circle diameter of the rollers and the number of rollers.

The structural design of the roller holder is guided by a carrier wheel over more or less than half the circumference. The roller radius is advantageously larger than the ratio of PCD rollers to number of rollers. The height of the respective FS tooth is advantageously smaller than the radius of the roller. For the present design, it is advantageous to choose the height of the teeth of the Flexspline smaller than the radius of the rollers.

Also described is a roller shaft gear, comprising a wave generator with a rolling bearing, a flexspline with an internal toothing and a circular spline, wherein cylindrical pockets facing the internal toothing of the flexspline are formed in the circular spline, in particular at least partially, and rollers are arranged in said pockets, wherein the ratio of the difference between the major axis of the wave generator and the inner diameter of the flexspline and twice the ratio of the pitch circle diameter of the rollers and the number of rollers is less than 0.8. In this variant, the wave generator is arranged inside the flexspline as seen in the radial direction and the circular spline is arranged outside the flexspline.

The pockets are preferably at least partially cylindrical. This preferably means that they have a cross-section that essentially corresponds to a circular arc segment and that this cross-section is constant over the axial length of the respective pocket so that it can accommodate a roll.

The respective pocket can also be curved, which means in particular that it is seen along the cross section Deviations from a circular arc segment. For example, the local radius of the contour of the cross-section can increase/widen or decrease/narrow in certain areas. The rollers can be cylindrical or pin-shaped in particular. The rollers can also have profiles, as is usual in rolling bearings to avoid edge wear. These can be, for example, crowned or logarithmic profiles.

In a preferred embodiment, the roller shaft gear is designed in a pot design. The flexspline is pot-shaped with a wall that surrounds a base. The flexspline preferably has a flange on the inside for connection to a connecting element. The flange can be designed for a welded connection to a connecting element.

In another preferred embodiment, the roller shaft gear is designed in a silk hat design. For this purpose, the flexspline preferably has a flange on the outside for connection to a connecting element.

Preferably, the respective cylindrical pocket extends over an angle between 170° and 190° of the circumference of the respective roll. This angle can in particular also be 180°.

The advantages of the invention are in particular that the inventive design of the roller shaft gear makes it possible to provide a gear for high loads and with a long service life. The described shaft gear is particularly applicable in wheel drives for AGVs, in robotics (Delta robots, Scara robots), wheel drives in general, drives for measuring machines as well as packaging machines and systems for the production of food (drive tasks with high dynamics). By using the rollers, a more load-bearing surface (high hardness and smoother surface) can be realized. They can rotate in the pocket, which reduces the wear energy. This allows a gear with smaller deformations in the flexspline to be realized, which reduces the load on the flexspline due to the gear principle. The effect is particularly true for small reduction ratios.

Further aims, advantages, features and possible applications of the present invention emerge from the following description of an embodiment with reference to the drawing. All described and/or illustrated features form the subject matter of the present invention on their own or in any meaningful combination, also independently of their summary in the claims or their reference back to them.

The following are shown schematically:

Figure 1 shows a roller shaft gear in a preferred embodiment in a cross section;

Figure 2 shows a detail from Figure 4;

Figure 3 shows a tooth engagement of the wave gear according to Figure 1;

Figure 4 shows a partial cross-section of the wave gear according to Figure 1;

Figure 5 shows the wave generator of the roller wave gear according to Figure 1 with the major axis marked;

Figure 6 shows the circular spline of the roller shaft gear according to Figure 1 with the pitch circle diameter marked; Figure 7 shows a detailed section of a roller in a pocket of the circular spline in a preferred embodiment;

Figure 8 shows a detailed section of a roller in a pocket of the circular spline in another preferred embodiment;

Figure 9 shows a detailed section of a roller in a pocket of the circular spline in another preferred embodiment;

Figure 10 shows a detailed section of a roller in a pocket of the circular spline in another preferred embodiment;

Figure 11 shows a cross-section of a flexspline with the inner diameter indicated;

Figure 12 shows a roller shaft gear in a preferred embodiment, and

Figure 13 shows a roller shaft gear in a further preferred embodiment, and

Figure 14 shows a roller shaft gear in a further preferred embodiment.

In the following figures of the drawing, identical or equivalent components are provided with reference numerals based on an embodiment in order to improve readability.

A roller shaft gear 8 shown in Figures 1 - 4 has a wave generator 6 with a rolling bearing 7 designed as a thin-ring bearing and an elliptical disk on which a flexspline 4 with external teeth 9 is arranged. The roller shaft gear 8 also has a circular Spline 1. Rollers 3 serving as internal gearing are guided in a solid part or circular spline 1 in cylindrical pockets 2. The pockets 2 are in particular at least partially designed as cylinders. The respective cylindrical pocket 2 extends over more or less or exactly 180° of the circumference of the roller 3, preferably between 170° and 190°.

The roller wave gear 8 is designed to reduce the functional internal loads of the flexspline 4 and the wear in the tooth contact in order to enable the transmission of higher external loads and a longer service life. For this purpose, the ratio of the difference between the large axis of the wave generator 6 and the inner diameter of the flexspline 4 and twice the ratio of the pitch circle diameter of the rollers and the number of rollers is less than 0.8.

In the advantageous embodiment shown, the radius R of the rollers 3 is larger than the ratio of the pitch circle diameter T of the rollers 3 and the number of rollers n.

In the advantageous embodiment shown, the height h of the teeth of the flexspline 4 is to be selected smaller than the radius R of the rollers 3.

Figure 5 shows the wave generator 7 of the roller wave gear according to Figure 1 with the major axis A marked. Figure 6 shows the circular spline with the rollers 3 and the pitch circle diameter T. Figure 11 shows the flex spline 4 with the inner diameter I marked.

Figure 7 shows a section of the circular spline 1 with a pocket 2 and a roller 3 arranged therein in a preferred embodiment. Viewed in the radial direction, the pocket 2 has an indentation 10. Viewed in the lateral direction, the pocket has a spread-out area, the local radius of the pocket cross-section is tangentially enlarged by a straight section. The pocket 2 surrounds the roller 3 at an angle of < 180°. The recess can also hold lubricant. By avoiding an undercut at the pocket outlet, the pocket is easier to manufacture.

Figure 8 shows a detail of the circular spline 1 with a pocket 2 and a roller 3 arranged therein in a preferred embodiment. In this embodiment, the pocket 2 encloses the roller 3 at an angle that is greater than 180°, in particular 190°.

Figure 9 shows a detail of the circular spline 1 with a pocket 2 and a roller 3 arranged therein in a preferred embodiment. In this embodiment, the pocket 2 encloses the roller 3 at an angle that is smaller than 180°, in particular 170°.

Figure 10 shows a section of the circular spline 1 with a pocket 2 and a roller 3 arranged therein in a preferred embodiment. In this embodiment, the pocket 2 encloses the roller 3 at an angle of approximately 180°.

Figure 11 shows a cross-section of a Flexspline 4 with the inner diameter I marked.

Figure 12 shows a roller shaft gear 8 in a pot design. In this preferred variant, the flexspline 4 has an internal flange 12 for connection to a connecting element, such as a bearing ring.

Figure 13 shows a roller shaft gear 8 in silk hat design. In this variant, the Flexspline 4 has an external flange for connection to a connecting element, such as a bearing ring. Figure 14 shows a roller shaft gear 8 in a pot design. In this preferred variant, the flexspline 4 has an internal flange 12 for connection to a connecting element, such as a bearing ring. The flange is designed in such a way that the connection can be made by welding.

list of reference symbols

1 Circular Spline

2 bags

3 rolls

4 Flexspline

5 Flexspline tooth

6 Wave Generator

7 rolling bearings

8 roller shaft gears

9 external gearing

10 indentation

1 1 area

12 flange

A large axis of the Wave Generator

I Inner diameter of the flexspline

T Pitch circle diameter of the rollers

Claims

patent claims

1. Roller shaft gear (8), comprising a wave generator (6) with a rolling bearing (7), a flexspline (4) with external teeth (9) and a circular spline (1), characterized in that cylindrical pockets (2) facing the external teeth (9) of the flexspline (4) are formed in the circular spline (1), in particular at least partially, and in which rollers (3) are arranged, wherein the ratio of the difference between the major axis (A) of the wave generator (6) and the inner diameter (I) of the flexspline (4) and twice the ratio of the pitch circle diameter (T) of the rollers and the number of rollers is less than 0.8.

2. Roller shaft drive (8) according to claim 1, characterized in that the radius (R) of the rollers (3) is larger than the ratio of the pitch circle diameter (T) of the rollers (3) and the number of rollers (3).

3. Roller shaft drive (8) according to claim 1 or 2, characterized in that the height (h) of the teeth (5) of the flexspline (4) is smaller than the radius (R) of the rollers (3).

4. Roller wave transmission (8) according to one of the preceding claims, characterized in that the wave generator (6) is a rolling bearing (7) which is designed as a thin-ring bearing and/or has an elliptical disk.

5. Roller shaft gear (8) according to one of claims 1 to 4, which in

pot construction.

6. Roller shaft gear (8) according to claim 5, wherein the flexspline (4) has a flange (12) on the inside for connection to a connecting element.

7. Roller shaft gear (8) according to claim 6, wherein the flange (12) for

welded connection with a connecting element.

8. Roller shaft gear (8) according to one of claims 1 to 4, which is in silk-

Hat construction.

9. Roller shaft drive (8) according to claim 8, wherein the flexspline (4) has a flange (12) on the outside for connection to a connecting element.

10. Roller shaft drive (8) according to one of the preceding claims, wherein the respective cylindrical pocket (2) extends over an angle between 170° and 190° of the circumference of the respective roller (3).