Harmonic reducer

Abstract

A harmonic reducer according to the present invention comprises: a wave generator; a flex spline that changes to an elliptical shape on the basis of the rotational movement of the wave generator and has an odd number of gear teeth arranged on the outside along the circumferential direction; and a circular spline that engages with the flex spline according to the change in shape thereof and has an odd number of gear teeth arranged on the inside along the circumferential direction. The flex spline and the circular spline are output at the speed reduction ratio of the following <Mathematical expression>.

Description

Harmonic reducer

[0001] The present invention relates to a harmonic reducer, and more particularly, to a harmonic reducer capable of outputting a reduction ratio by partial engagement of a flex spline and a circular spline based on the rotational motion of a wave generator.

[0002] Reducers are generally categorized into planetary reducers, harmonic reducers, and cycloidal reducers. Harmonic reducers offer the advantages of compactness and lightweight design, yet achieving high reduction ratios. They also offer high transmission torque and low backlash, enabling precise reduction ratios. Harmonic reducers, with their aforementioned advantages, are used in a variety of industrial fields, including industrial robots.

[0003] This conventional harmonic reducer (100) includes a wave generator (110), a flex spline (130), and a circular spline (150), as shown in FIGS. 1 and 2.

[0004] The flex spline (130) includes a flex spline body (132) whose shape changes into an oval based on the rotational motion of the wave generator (110) and external gear teeth (134) arranged along the outer circumference of the flex spline (130). In addition, the circular spline (150) includes a circular spline body (152) surrounding the flex spline (130) and internal gear teeth (154) formed along the inner circumference of the circular spline body (152) and meshed with the external gear teeth (134) based on the rotational motion of the wave generator (110).

[0005] The external gear teeth (134) of the flex spline (130) and the internal gear teeth (154) of the circular spline (150) each have an even number. For example, when the external gear teeth (134) are 200 and the internal gear teeth (154) are 202 and the circular spline (150) is used as the output shaft, the reduction ratio becomes 1:101. At this time, as shown in FIGS. 1 and 2, the major axes of the ellipses meshing with the internal gear teeth (154) and the external gear teeth (134) each having an even number of numbers have lengths of L1 and L2 based on the mutually symmetrical points.

[0006] As shown in detail in Fig. 1, the length (L1) of the major axis based on the internal gear tooth (154) is the radius (R) corresponding to the distance from the center to the peak of the internal gear tooth (154). 1) is calculated as the sum of. On the other hand, as illustrated in FIG. 2, the length (L2) of the major axis based on the internal gear tooth (154) is calculated as the sum of the radii (R2) corresponding to the distance from the center to the valley of the internal gear tooth (154). That is, the conventional harmonic reducer (100) illustrated in FIGS. 1 and 2 faces each other at the symmetrical point of the peak and peak of the same gear tooth or the valley and valley of the gear tooth based on the center.

[0007] Meanwhile, the conventional harmonic reducer (100) may have the lengths of the radii (R1) and (R2) as shown in FIGS. 1 and 2 based on the rotational motion of the wave generator (110), and accordingly may have the lengths (L1) of the major axis of the ellipse and (L2) of the major axis of the ellipse corresponding to the sum of the lengths of the radii (R1) and (R2), respectively. In addition, in the conventional harmonic reducer (100), if the tooth shapes of the internal gear teeth (154) and the external gear teeth (134) are the same, a gap corresponding to the backlash occurs between the internal gear teeth (154) and the external gear teeth (134), and this gap is proportional to the respective elliptical major axis lengths (L1, L2). The gap between the above-described flex spline (130) and the circular spline (150) may be referred to as an error or tolerance. In theory, the gap is the tolerance corresponding to the error that deviates from the ideal tooth shape with 0 angular transmission error, or the dimensional error that occurs in the actual spline machining process even if designed with the ideal tooth shape.

[0008] However, since the conventional harmonic reducer (100) has the length of the major axis of the ellipse (L1, L2) according to the period of the tooth width, an increase or decrease in the gap occurs according to the change in the length of the major axis, which amplifies the angular transmission error. That is, as illustrated in FIG. 3, the conventional harmonic reducer (100) having a reduction ratio of 1:101 has an angular transmission error in which the short-period error (P1) generated based on the gap per contact between the internal gear teeth (154) and the external gear teeth (134) is 277.62 arc seconds in test data, and the long-period error (P2) corresponding to the average value of the short-period errors (P1) according to one rotation of the output shaft is 102 arc seconds.

[0009] As described above, the increase or decrease in backlash corresponding to the increase or decrease in the gap of the conventional harmonic reducer (100) increases the wear between the internal gear teeth (154) and the external gear teeth (134), which increases the problem of increased maintenance costs. In addition, the conventional harmonic reducer (100) also has the problem of an increase in angular transmission error due to an increase or decrease in the gap (or error / tolerance), which reduces the precision of the reduction ratio.

[0010] The purpose of the present invention is to provide a harmonic reducer capable of maintaining a constant gap (or error / tolerance) by improving the meshing structure of a flex spline and a circular spline.

[0011] In addition, another object of the present invention is to provide a harmonic reducer capable of reducing angular transmission error between gear teeth of a flex spline and gear teeth of a circular spline by improving the meshing structure of a flex spline and a circular spline.

[0012] The solution to the above problem is achieved by a harmonic reducer comprising a wave generator according to the present invention, a flex spline having an odd number of gear teeth arranged circumferentially on the outside and having an oval shape changed based on the rotational motion of the wave generator, and a circular spline having an odd number of gear teeth arranged circumferentially on the inside and meshing according to the shape change of the flex spline, wherein the flex spline and the circular spline are output with a reduction ratio of the following <formula>.

[0013] Formula (N, M are natural numbers)

[0014] Here, the reduction ratio according to the above <formula> can be determined by dividing the value calculated by (the number of gear teeth of the circular spline - the number of gear teeth of the flex spline) when the circular spline is used as the output shaft by the value calculated by the number of gear teeth of the circular spline.

[0015] Meanwhile, the reduction ratio according to the above <formula> can be determined by dividing the value calculated by (the number of gear teeth of the circular spline - the number of gear teeth of the flex spline) when the flex spline is used as the output shaft by the value calculated by the number of gear teeth of the flex spline.

[0016] The above <formula> (N, M are natural numbers) It is desirable that the value of M is 1.

[0017] The major axis of the ellipse formed when the gear teeth of the above flex spline and the gear teeth of the above circular spline mesh with each other can be formed at either the peak and valley of the mutually opposed gear teeth of the above flex spline or the peak and valley of the mutually opposed gear teeth of the above circular spline.

[0018] When the above wave generator rotates, it is preferable that the length between the contact points where the flex spline and the circular spline face each other in the extension of the major axis of the ellipse formed by the engagement of the flex spline and the circular spline is constant.

[0019] When the gear teeth of the above flex spline and the gear teeth of the above circular spline are engaged, it is preferable that the gap between the gear teeth of the above flex spline and the gear teeth of the above circular spline be constant in proportion to the length between the contact points where the flex spline and the above circular spline face each other in an extension of the major axis of a constant ellipse.

[0020] Specific details of other embodiments are included in the detailed description and drawings.

[0021] The harmonic reducer according to the present invention can reduce angular transmission error by arranging the gear teeth of the flex spline and the gear teeth of the circular spline in an odd number to maintain a constant gap (or error / tolerance) when the gear teeth of the flex spline and the gear teeth of the circular spline mesh, thereby minimizing vibration and noise and outputting a high-precision reduction ratio.

[0022] Figure 1 is a first operational front view of a conventional harmonic reducer.

[0023] Figure 2 is a second operational front view of a conventional harmonic reducer.

[0024] Figure 3 is an operational graph of the output angle-angle transmission error of a conventional harmonic reducer.

[0025] Figure 4 is a front view of a harmonic reducer according to an embodiment of the present invention;

[0026] Figure 5 is a first operational front view of a harmonic reducer according to an embodiment of the present invention;

[0027] Figure 6 is a second operational front view of a harmonic reducer according to an embodiment of the present invention;

[0028] FIG. 7 is an operational graph of the output angle-angle transmission error of a harmonic reducer according to an embodiment of the present invention.

[0029] Hereinafter, a harmonic reducer according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0030] Before explaining, it is to be noted that the harmonic reducer according to an embodiment of the present invention is described with different drawing reference numerals even though it has the same component name in order to distinguish it from the harmonic reducer illustrated in FIGS. 1 to 3.

[0031] FIG. 4 is a front view of a harmonic reducer according to an embodiment of the present invention, FIG. 5 is a first operation front view of a harmonic reducer according to an embodiment of the present invention, and FIG. 6 is a second operation front view of a harmonic reducer according to an embodiment of the present invention.

[0032] As shown in FIGS. 4 to 6, a harmonic reducer (1) according to an embodiment of the present invention includes a wave generator (10), a flex spline (30), and a circular spline.

[0033] The wave generator (10) rotates so that the flex spline (30) and the circular spline (50) mesh with each other. The wave generator (10) basically includes an elliptical cam and a bearing, which are not shown in the present invention. The rotational motion of the wave generator (10) provides a rotational motion according to a reduction ratio by using one of the flex spline (30) and the circular spline (50) as an output shaft through the meshing of the flex spline (30) and the circular spline (50).

[0034] The flex spline (30) is shaped into an ellipse based on the rotational motion of the wave generator (10). The flex spline (30) includes a flex spline body (32) and an external gear tooth (34).

[0035] The flex spline body (32) changes shape into an ellipse based on the rotational movement of the wave generator (10).

[0036] The external gear teeth (34) are arranged along the outer circumferential direction of the flex spline body (32). The external gear teeth (34) are arranged in an odd number along the outer circumferential direction of the flex spline body (32). In one embodiment of the present invention, 203 external gear teeth (34) are arranged, but this is not limited to this and may be arranged in a different odd number depending on a change in the reduction ratio in the design.

[0037] The circular spline (50) is meshed with the flex spline (30) based on a shape change of the flex spline (30), i.e., a shape change of the flex spline (30) into an elliptical shape. In fact, the entire area of ​​the circular spline (50) and the flex spline (30) is not meshed, but the circular spline (50) and the flex spline (30) are partially meshed in a symmetrical area forming the major axis of the elliptical shape. The circular spline (50) includes a circular spline body (52) and internal gear teeth (54).

[0038] The circular spline body (52) is made of a material having relatively higher rigidity than the flex spline body (32) and has a diameter that is relatively larger than the flex spline body (32) to accommodate the flex spline body (32).

[0039] The internal gear teeth (54) are arranged in an odd number along the inner circumferential direction of the circular spline body (52). The internal gear teeth (54) are arranged in an odd number along the outer circumferential direction of the circular spline body (52). In one embodiment of the present invention, 205 internal gear teeth (54) are arranged, but this is not limited thereto and may be arranged in a different odd number depending on changes in the reduction ratio in the design.

[0040] The flex spline (30) and circular spline (50), each having an odd number of external gear teeth (34) and internal gear teeth (54), are output with a reduction ratio satisfying the following <formula>.

[0041] Formula (N, M are natural numbers)

[0042] That is, the reduction ratio is set by the above <formula> as 1:natural number. It is set including the decimal point like a natural number. For example, when N is 100 and M is 1, the reduction ratio becomes 1:100.5.

[0043] The reduction ratio according to the above <formula> is determined by dividing the value calculated by (number of gear teeth of circular spline (50) - number of gear teeth of flex spline (30)) by the number of gear teeth of circular spline (50) when the circular spline (50) is used as the output shaft.

[0044] As an embodiment of the present invention, when a circular spline (50) is used as an output shaft and the number of internal gear teeth (54) is 205 and the number of external gear teeth (34) is 203, a reduction ratio of (205-203) / 205 = 1 / 102.5, i.e., a reduction ratio of 1:102.5 can be obtained.

[0045] On the other hand, the reduction ratio according to the above-mentioned <formula> is determined by the value calculated by dividing the value calculated by (the number of gear teeth of the circular spline (50) - the number of gear teeth of the flex spline (30)) by the number of gear teeth of the flex spline (30) when the flex spline (30) is used as the output shaft.

[0046] As an embodiment of the present invention, when the flex spline (30) is used as an output shaft and the number of internal gear teeth (54) is 205 and the number of external gear teeth (34) is 203, a reduction ratio of (205-203) / 203 = 1 / 101.5, i.e., a reduction ratio of 1:101.5 can be obtained.

[0047] The major axis of the ellipse formed when the gear teeth of the flex spline (30) and the gear teeth of the circular spline (50) mesh is formed at either the peak and valley of the mutually opposed gear teeth of the flex spline (30) or the peak and valley of the mutually opposed gear teeth of the circular spline (50).

[0048] In detail, the major axis of the ellipse formed when the gear teeth of the flex spline (30) and the gear teeth of the circular spline (50) mesh with each other is based on the distance from the peak of the internal gear tooth (54) of the symmetrical flex spline (30) to the valley of the internal gear tooth (54). Alternatively, as an embodiment of the present invention, the symmetrical point of the major axis of the ellipse formed when the gear teeth of the flex spline (30) and the gear teeth of the circular spline (50) mesh with each other has a radius (R3) corresponding to the distance from the center to the peak of the external gear tooth (34) and a radius (R4) corresponding to the distance from the center to the valley of the external gear tooth (34), as shown in FIGS. 5 and 6, respectively.

[0049] The above-described radii (R3, R4) have a relatively long length compared to the radius (R0) of the harmonic reducer (1) forming a circular shape before the rotational motion of the wave generator (10) illustrated in Fig. 4. Of course, the major axis length (L) of the ellipse illustrated in Figs. 5 and 6 corresponds to the sum of the radii (R3) and (R4), and therefore has a relatively longer length than the length (L0) of the diameter corresponding to the sum of the two radii (R0) illustrated in Fig. 4.

[0050] The flex spline (30) and the circular spline (50), each having an odd number of internal gear teeth (54) and external gear teeth (34), maintain a constant length (L) of the major axis of the ellipse formed by the engagement of the flex spline (30) and the circular spline (50) during the rotational movement of the wave generator (10), which corresponds to the sum of the lengths of the radii (R3) and (R4).

[0051] In detail, when the wave generator (10) rotates, the length between the contact points where the flex spline (30) and the circular spline (50) face each other in the extension of the major axis of the ellipse formed by the engagement of the flex spline (30) and the circular spline (50) is constant. In more detail, when the external gear tooth (34) of the flex spline (30) and the internal gear tooth (54) of the circular spline (50) are engaged, the gap between the external gear tooth (34) of the flex spline (30) and the internal gear tooth (54) of the circular spline (50) is constant in proportion to the length between the contact points where the flex spline (30) and the circular spline (50) face each other in the extension of the major axis of the ellipse that is maintained constant.

[0052] On the other hand, the conventional harmonic reducer (100) having an even number of external gear teeth (134) and internal gear teeth (154) as shown in FIGS. 1 and 2 has two radii (R1) according to the rotational motion of the wave generator (110). It has a length of the major axis (L1) according to the sum of the lengths of the radii (R2) and a length of the major axis (L2) according to the sum of the lengths of the two radii (R2). Here, since the length of the radius (R1) is relatively shorter than the length of the radius (R2), each of the lengths of the major axis of the ellipse (L1, L2) increases and decreases, which causes the problems mentioned in the prior art. However, as described above, the harmonic reducer (1) according to the present invention has an odd number of external gear teeth (34) and internal gear teeth (54), so that the length (L) of the major axis is constant, thereby resolving the problems of the conventional harmonic reducer (100) having an even number of external gear teeth (134) and internal gear teeth (154).

[0053] Finally, Fig. 7 is an operational graph of the output angle-angle transmission error of a harmonic reducer according to an embodiment of the present invention.

[0054] The harmonic reducer (1) according to the present invention has a constant gap between the gear teeth of the flex spline (30) and the gear teeth of the circular spline (50) in proportion to the length of a constant major axis when the gear teeth of the flex spline (30) and the gear teeth of the circular spline (50) mesh with each other. Specifically, since the external gear teeth (34) and the internal gear teeth (54) are each arranged in an odd number, the major axis length (L) of the ellipse formed during the rotational movement of the wave generator (10) is maintained constant, thereby making the gap constant.

[0055] As illustrated in FIG. 7, the harmonic reducer (1) according to the present invention can maintain a constant gap between the flex spline (30) and the circular spline (50), and thus, as an example, the short-period error (P3) becomes 98.25 arc seconds and the long-period error (P4) becomes 82 arc seconds. That is, compared to the conventional harmonic reducer (100) having an even number of external gear teeth (134) and internal gear teeth (154) illustrated in FIG. 3, the harmonic reducer (1) according to the present invention shows test data showing that the angular transmission error is reduced to about 34% with a difference of about 184 arc seconds based on the short-period error (P3) and that the angular transmission error is reduced to about 80% with a difference of about 20 arc seconds based on the long-period error (P4).

[0056] The harmonic reducer (1) according to the present invention, each having an odd number of external gear teeth (34) and internal gear teeth (54), can significantly reduce angular transmission error compared to the conventional harmonic reducer (100) having an even number of external gear teeth (134) and internal gear teeth (154).

[0057] Accordingly, by arranging the gear teeth of the flex spline and the gear teeth of the circular spline in an odd number, a constant gap (or error / tolerance) is maintained when the gear teeth of the flex spline and the gear teeth of the circular spline mesh, thereby reducing the angular transmission error, and thus outputting with a high-precision reduction ratio while minimizing vibration and noise.

[0058] Although the embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

Claims

1. Wave generator; A flex spline having an odd number of gear teeth arranged along the circumference on the outside and having an elliptical shape based on the rotational motion of the wave generator; It includes a circular spline having an odd number of gear teeth arranged along the circumference on the inside, which meshes according to the shape change of the above flex spline, A harmonic reducer characterized in that the above flex spline and the above circular spline are output with a reduction ratio of the following <formula>. <수식> (N, M are natural numbers) 2. In paragraph 1, The reduction ratio according to the above <formula> is when the above circular spline is used as the output shaft. A harmonic reducer characterized in that the value is determined by dividing the value calculated by (the number of gear teeth of the circular spline - the number of gear teeth of the flex spline) by the number of gear teeth of the circular spline.

3. In paragraph 1, The reduction ratio according to the above <formula> is when the above flex spline is used as the output shaft. A harmonic reducer characterized in that the value is determined by dividing the value calculated by (the number of gear teeth of the circular spline - the number of gear teeth of the flex spline) by the number of gear teeth of the flex spline.

4. In paragraph 1, The above <formula> A harmonic reducer characterized in that the value of M in (N, M are natural numbers) is 1.

5. In paragraph 1, The major axis of the ellipse formed when the gear teeth of the above flex spline and the gear teeth of the above circular spline mesh with each other is A harmonic reducer characterized in that it is formed between the peaks and valleys of the mutually opposed gear teeth of the above flex spline and between the peaks and valleys of the mutually opposed gear teeth of the above circular spline.

6. In paragraph 5, A harmonic reducer characterized in that, when the wave generator rotates, the length between the contact points where the flex spline and the circular spline face each other in the extension of the major axis of the ellipse formed by the engagement of the flex spline and the circular spline is constant.

7. In paragraph 6, A harmonic reducer characterized in that when the gear teeth of the flex spline and the gear teeth of the circular spline are engaged, the gap between the gear teeth of the flex spline and the gear teeth of the circular spline is constant in proportion to the length between the contact points where the flex spline and the circular spline face each other in an extension of the major axis of the ellipse that is maintained constant.

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