Roller-type harmonic drive with flexible and rigid wheels

Abstract

A roller-type harmonic drive device (8) includes a wave generator (6) with rolling bearings (7), a flexible wheel (4) with an external gear system (9), and a rigid wheel (1), wherein a cavity (2) that is at least partially cylindrical and faces the external gear system (9) of the flexible wheel (4) is constructed in the rigid wheel (1), and rollers (3) are provided in such cavity, wherein the ratio of "the difference between the major axis (A) of the wave generator (6) and the inner diameter (I) of the flexible wheel (4)" to "twice the ratio of the pitch circle diameter (T) of the roller to the number of rollers" is less than 0.8.

Description

Technical Field

[0001] The present invention relates to a roller-type harmonic transmission device as described in the preamble of claim 1. Prior Art

[0002] As far as harmonic drive devices are concerned, the smallest reduction ratio on the market is currently 30. Harmonic drive devices with a small reduction ratio (<=50) have limited performance data and are subject to severe wear. Summary of the Invention

[0003] In view of the above-mentioned shortcomings, the object of the present invention is to provide a harmonic transmission device with a smaller reduction ratio and improved performance data compared with the harmonic transmission device of the prior art.

[0004] The solution of the present invention for achieving the above-mentioned object is a roller-type harmonic transmission device as claimed in claim 1.

[0005] According to the present invention, a roller-type harmonic drive device includes a wave generator having a rolling bearing, a flexspline (FS) having an external gear system, and a rigid spline (CS), wherein a cylindrical cavity (particularly, at least partially) is constructed in the rigid spline, facing the external gear system of the flexspline, and guide rollers are arranged in the cavity. Moreover, the ratio of "the difference between the major axis of the wave generator and the inner diameter of the flexspline" to "twice the ratio of the pitch diameter of the rollers to the number of rollers" is less than 0.8.

[0006] That is, the formula is (A - I) / (2 * (T / n)) < 0.8 Where A represents the major axis of the wave generator (WG), I represents the inner diameter of the flexspline (FS), T represents the pitch diameter of the roller, and n represents the number of rollers. The * symbol indicates multiplication, and the / symbol indicates division.

[0007] That is, the mathematical expression is or The major axis A of the wave generator is the maximum distance measured radially on the wave generator at the outer diameter of the wave generator bearing's outer race. The inner diameter I is the inner diameter of the tubular area of ​​the flexspline measured in contact with the outer race of the wave generator bearing. The roller pitch diameter is the diameter of a circle based on the end face tooth profile, on which the roller's center point lies. The ratio of the roller pitch diameter to the number of rollers is an equivalent to the gear module.

[0008] For the advantageous technical solutions of the present invention, please refer to the appendix and the specification.

[0009] The invention is based on the idea that a roller-type harmonic drive with a smaller reduction ratio and improved performance data is needed in a large number of applications.

[0010] As is currently known, these requirements can be met by implementing a CS (rigid-spindle) tooth system using rollers, needles, or needle rollers. The use of rollers can reduce the deformation of the flexspline required to achieve the transmission's function. This reduces the functional stress on the flexspline and increases the external load it can transmit. This can be achieved by using a ratio of (A - I) / (2 * (T / n)) less than 0.8. This also extends the life of the roller-type harmonic drive.

[0011] The roller-type harmonic drive device constructed in this way can achieve a smaller transmission ratio (for example, 25), its wear resistance is reduced and it is also suitable for continuous operation. The roller can also be called a pin or a needle.

[0012] Preferably, the radius of the roller is greater than the ratio of the pitch diameter of the roller to the number of rollers.

[0013] Preferably, the height of the teeth of the flexible wheel is smaller than the radius of the rollers.

[0014] Preferably, the wave generator has a rolling bearing which is designed as a thin-ring bearing and / or the wave generator has an elliptical disk.

[0015] The design of the rigid wheel / CS is crucial to the present invention. The rollers are guided in cylindrical grooves within the solid core. The respective cylindrical grooves extend over, under, or exactly 180° of the roller's circumference. The CS toothing is primarily composed of rollers (pins).

[0016] Preferably, for this embodiment, the radius of the selected roller is greater than the ratio of the pitch radius of the roller to the number of rollers.

[0017] The roller housing is preferably designed to be guided by the carrier wheel over a range exceeding or less than half a circumference. The roller radius is preferably greater than the ratio of the roller PCD to the number of rollers. The height of the corresponding FS teeth is preferably less than the roller radius. For this embodiment, the flexspline tooth height is preferably selected to be less than the roller diameter.

[0018] A roller-type harmonic drive is also described, comprising a wave generator with a rolling bearing, a flexspline with an internal gear system, and a rigid wheel. The rigid wheel has cylindrical cavities (particularly, at least partially) formed facing the internal gear system of the flexspline, and rollers are disposed in the cavities. The ratio of "the difference between the major axis of the wave generator and the inner diameter of the flexspline" to "twice the ratio of the pitch diameter of the rollers to the number of rollers" is less than 0.8. In this variant, the wave generator is disposed radially inside the flexspline, and the rigid wheel system is disposed outside the flexspline.

[0019] The cavities are preferably at least partially cylindrical, which preferably means that the cross section of the cavity substantially corresponds to a circular arc segment and that the cross section is constant over the axial length of the respective cavity, so that the cavity can accommodate the roller.

[0020] The corresponding grooves can also be designed as curved, meaning that, viewed in cross-section, the grooves differ from circular arc segments. For example, the local radius of the cross-sectional profile can increase / widen or decrease / narrow in specific areas. The rollers can be cylindrical or pin-shaped. As is common in rolling bearing applications, the rollers can also have a profile to prevent edge wear. This profile can be, for example, spherical or logarithmic.

[0021] In a preferred embodiment, the roller-type harmonic drive is constructed in a pot-shaped structure. The flexspline is pot-shaped, having a wall portion surrounding the bottom. To this end, the flexspline preferably has a flange on its inner side for connecting to a connecting element. The flange can be welded to the connecting element.

[0022] In another preferred embodiment, the roller type harmonic transmission device is constructed in a top hat-shaped structure. To this end, the flexible wheel preferably has a flange on the outside for connecting with a connecting element.

[0023] Preferably, the corresponding cylindrical cavity extends within an angle range of between 170° and 190° of the circumference of the corresponding roller. This angle can also be 180°.

[0024] A particular advantage of the present invention is that, through the inventive design of a roller harmonic drive, a roller harmonic drive capable of handling high loads and having a long service life can be provided. The described harmonic drive is particularly suitable for use in wheel drives for automated guided vehicles (AGVs), robots (Delta robots, Scara robots), general wheel drives, drives for measuring and packaging machines, and equipment for food production (for highly dynamic drive tasks).

[0025] The use of rollers creates a surface with a higher load-bearing capacity (higher hardness and smoother surface). The rollers rotate within the grooves, reducing wear energy. This allows for a transmission with reduced deformation in the flexspline, thereby reducing the load on the flexspline due to the transmission mechanism. This effect is particularly noticeable at smaller transmission ratios.

[0026] For further objects, advantages, features, and uses of the present invention, please refer to the following description of the embodiments in conjunction with the accompanying drawings. All individual features or combinations of features described in the description or shown in the accompanying drawings, regardless of how they are summarized or referenced retroactively in the patent claims, constitute the invention. Simple diagram description

[0027] in: Figure 1 is a schematic cross-sectional view of a roller-type harmonic drive device according to a preferred embodiment; Figure 2 is a partial schematic diagram of Figure 4; Figure 3 is a schematic diagram of the teeth meshing of the harmonic drive device shown in Figure 1; Figure 4 is a schematic partial cross-sectional view of the harmonic drive device shown in Figure 1; Figure 5 is a schematic diagram of the wave generator of the roller-type harmonic drive device shown in Figure 1, wherein the major axis is depicted; Figure 6 is a schematic diagram of the rigid wheel of the roller-type harmonic drive device shown in Figure 1, wherein the pitch circle diameter is shown; Figure 7 is a schematic detail view of the roller located in the cavity groove of the wheel according to a preferred embodiment; Figure 8 is a schematic detail view of the roller located in the cavity groove of the wheel according to another preferred embodiment; Figure 9 is a schematic detail view of the roller located in the cavity groove of the wheel according to another preferred embodiment; Figure 10 is a schematic detail view of the roller located in the cavity groove of the wheel according to another preferred embodiment; Figure 11 is a schematic cross-sectional view of the flexible wheel, showing the inner diameter; FIG12 is a schematic diagram of a roller-type harmonic transmission device according to a preferred embodiment, and FIG13 is a schematic diagram of a roller-type harmonic transmission device according to another preferred embodiment, and FIG14 is a schematic diagram of a roller-type harmonic transmission device according to another preferred embodiment. Implementation Method

[0028] In the drawings shown below in conjunction with the embodiments, the same or equivalent components are marked with element symbols to facilitate understanding.

[0029] The roller-type harmonic drive 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. A flexspline 4 with an external toothing 9 is mounted on the wave generator. The roller-type harmonic drive 8 also has a rigid wheel 1. Within the solid portion or rigid wheel 1, rollers 3, which serve as the internal toothing, are guided in cylindrical grooves 2. The grooves 2 are, in particular, at least partially cylindrical. The respective cylindrical grooves 2 extend over, less than, or exactly 180° of the circumference of the rollers 3, preferably between 170° and 190°.

[0030] The roller-type harmonic drive 8 is designed to reduce the functional internal load of the flexspline 4 and reduce wear during tooth contact, thereby transmitting higher external loads and extending its service life. To this end, the ratio of the difference between the major axis of the wave generator 6 and the inner diameter of the flexspline 4 to twice the ratio of the pitch diameter of the rollers to the number of rollers is less than 0.8.

[0031] In the advantageous embodiment shown, the radius R of the roller 3 is greater than the ratio of the pitch diameter T of the roller 3 to the number n of rollers.

[0032] In the advantageous embodiment shown, the height h of the teeth of the flexspline 4 is selected to be smaller than the radius R of the roller 3 .

[0033] Figure 5 shows the wave generator 7 of the roller-type harmonic drive according to Figure 1 , wherein the major axis A is indicated. Figure 6 shows a rigid wheel with rollers 3 and a pitch diameter T. Figure 11 shows a flexible wheel 4 , wherein the inner diameter I is indicated.

[0034] Figure 7 shows a fragment of a circular ring 1 having a groove 2 and a roller 3 disposed therein, according to a preferred embodiment. Radially, the groove 2 has a recess 10. Laterally, the groove has a protruding area, and the local radius of the groove cross section is tangentially enlarged by a straight line segment. The groove 2 surrounds the roller 3 at an angle of less than 180°. This recess allows for additional lubricant storage. By avoiding undercuts on the groove outlet, groove manufacturing is simplified.

[0035] Figure 8 partially shows a circular ring 1 having a cavity 2 and a roller 3 arranged in the cavity according to a preferred embodiment. In this embodiment, the cavity 2 surrounds the roller 3 at an angle greater than 180°, in particular 190°.

[0036] Figure 9 partially shows a circular ring 1 having a cavity 2 and a roller 3 arranged in the cavity according to a preferred embodiment. In this embodiment, the cavity 2 surrounds the roller 3 at an angle of less than 180°, in particular 170°.

[0037] Figure 10 partially shows a circular ring 1 having a cavity 2 and a roller 3 disposed in the cavity according to a preferred embodiment. In this embodiment, the cavity 2 surrounds the roller 3 at an angle of about 180 degrees.

[0038] FIG11 is a cross-sectional view of the flexspline 4, wherein the inner diameter I is shown.

[0039] Figure 12 shows a roller type harmonic drive device 8 with a pot-shaped structure. In this preferred variant, the flexible wheel 4 has an inner flange 12, which is used to connect with a connecting element (such as a bearing ring).

[0040] Figure 13 shows a roller-type harmonic drive device 8 with a top-hat structure. In this variant, the flexible wheel 4 has an outer flange, which is used to connect with a connecting element (such as a bearing ring).

[0041] FIG14 shows a roller-type harmonic drive 8 with a pot-shaped structure. In this preferred embodiment, the flexspline 4 has an inner flange 12 for connection to a connecting element (e.g., a bearing ring). This flange is designed to enable connection via welding.

[0042] 1: Steel wheel 2: Cavity 3: Roller 4: Flexspline 5: Flexspline teeth 6: Wave Generator 7: Rolling bearings 8: Roller type harmonic drive device 9: External dentition 10: Notch 11: Region 12: Flange A: Long axis of the wave generator I: Inner diameter of the flexspline T: Roller pitch diameter

Claims

1. A roller-type harmonic drive device (8), comprising a wave generator (6) having rolling bearings (7), a flexible wheel (4) having an external gear system (9), and a rigid wheel (1), characterized in that the rigid wheel (1) has a cavity (2) facing the external gear system (9) of the flexible wheel (4), which is particularly at least partially cylindrical, and rollers (3) are provided in the cavity, wherein, The ratio of "the difference between the major axis (A) of the wave generator (6) and the inner diameter (I) of the flexible wheel (4)" to "twice the ratio of the pitch circle diameter (T) of the rollers to the number of rollers" is less than 0.

8.

2. The roller-type harmonic drive device (8) of claim 1, characterized in that the radius (R) of the rollers (3) is greater than the ratio of the pitch circle diameter (T) of the rollers (3) to the number of rollers (3).

3. The roller-type harmonic drive device (8) of claim 1 or 2 is characterized in that the height (h) of the tooth portion (5) of the flexible wheel (4) is less than the radius (R) of the rollers (3).

4. The roller-type harmonic drive device (8) of claim 1 or 2, characterized in that the wave generator (6) has a rolling bearing (7) and / or an elliptical disc, the rolling bearing being constructed as a thin ring bearing.

5. The roller harmonic drive device (8) of claim 1 or 2, wherein the roller harmonic drive device is constructed with a pot-shaped structure.

6. The roller-type harmonic drive device (8) as claimed in claim 5, wherein, The flexible wheel (4) has a flange (12) on its inner side for connecting with a connecting element.

7. The roller-type harmonic drive device (8) as claimed in claim 6, wherein, The flange (12) is constructed to be welded to the connecting element.

8. The roller harmonic drive device (8) of claim 1 or 2, wherein the roller harmonic drive device is constructed with a top hat-shaped structure.

9. The roller-type harmonic drive device (8) as claimed in claim 8, wherein, The flexible wheel (4) has a flange (12) on its outer side for connecting with a connecting element.

10. The roller-type harmonic drive device (8) as requested in item 1 or 2, wherein, The corresponding cylindrical cavity (2) extends within an angle range of 170° to 190° on the circumference of the corresponding roller (3).

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