Flexure mesh gearing

Abstract

The object of the present invention is to suppress the increase in cost and the occurrence of pitching. The flexure meshing gear device (1) of the present invention comprises: an oscillator (10A); an external gear (30) that is flexed and deformed by the oscillator (10A); and a first internal gear (31G) and a second internal gear (32G) that mesh with the external gear (30). The number of teeth of the first internal gear (31G) is different from the number of teeth of the external gear (30), and the number of teeth of the second internal gear (32G) is the same as the number of teeth of the external gear (30). The first meshing portion (51) where the first internal gear (31G) meshes with the external gear (30) has a higher pitching resistance characteristic than the second meshing portion (52) where the second internal gear (32G) meshes with the external gear (30).

Description

[0001] This application claims priority based on Japanese Patent Application No. 2020-001141 filed on January 8, 2020. The entire contents of the Japanese Patent Application are incorporated herein by reference. Technical Field

[0002] The invention relates to a flexure meshing gear device. Background Art

[0003] In the past, there is known a so-called cylindrical flexural meshing gear device in which a flexurally deformed external gear meshes with a first internal gear and a second internal gear arranged side by side (for example, refer to Patent Document 1). The vibrator shaft is embedded in the external gear via a vibrator bearing, and the external gear is flexurally deformed by the rotation of the vibrator shaft on the inside. The number of teeth of the first internal gear is different from the number of teeth of the external gear, and the first internal gear is fixed to the device. On the other hand, the number of teeth of the second internal gear is the same as the number of teeth of the external gear, and the decelerated rotation is output from the second internal gear.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-112214

[0005] In the above-mentioned conventional flexure meshing gear device, pitching may occur in each gear. In this case, it is sufficient to improve the anti-pitch property of each gear, but this will lead to an increase in cost. Summary of the invention

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the occurrence of pitching while suppressing an increase in cost.

[0007] The flexure meshing gear device according to the present invention comprises: a vibrating body; an external gear that is flexed and deformed by the vibrating body; and a first internal gear and a second internal gear that mesh with the external gear.

[0008] The number of teeth of the first internal gear is different from the number of teeth of the external gear, and the number of teeth of the second internal gear is the same as the number of teeth of the external gear, wherein:

[0009] A first meshing portion where the first internal gear meshes with the external gear has a higher anti-pitch characteristic than a second meshing portion where the second internal gear meshes with the external gear.

[0010] According to the present invention, it is possible to suppress the occurrence of pitching while suppressing an increase in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view showing a flexure meshing gear device according to the present embodiment.

[0012] Figure 2It is a diagram showing the analysis results of the distribution of the tooth surface pressure and the film thickness ratio of the first internal gear and the second internal gear.

[0013] Figure 3 It is an enlarged cross-sectional view of the first meshing portion and the second meshing portion in a modification of the present embodiment.

[0014] Figure 4 It is an enlarged cross-sectional view of the first meshing portion and the second meshing portion in another modified example of the present embodiment.

[0015] Figure 5 It is an enlarged cross-sectional view of the first meshing portion and the second meshing portion in still another modified example of the present embodiment.

[0016] Figure 6 It is an enlarged cross-sectional view of the first meshing portion and the second meshing portion in still another modified example of the present embodiment.

[0017] In the figure: 1-flexural meshing gear device, 10-vibrator shaft, 10A-vibrator, 30-external gear, 30A-first external gear part, 30B-second external gear part, 31-first internal gear component, 31G-first internal gear, 32-second internal gear component, 32G-second internal gear, 51-first meshing part, 52-second meshing part, 60-V-ring, 61-lip, 302-groove, O1-rotating shaft. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] [Overall structure of the flexure meshing gear device]

[0020] Figure 1 It is a cross-sectional view showing a flexure meshing gear device 1 according to the present invention.

[0021] like Figure 1 As shown, the flexure meshing gear device 1 is a cylindrical flexure meshing gear device including a vibrator shaft 10 , an external gear 30 , a first internal gear 31G, a second internal gear 32G, a vibrator bearing 12 , a housing 33 , a first cover 34 , and a second cover 35 .

[0022] The vibrator shaft 10 is a hollow cylindrical shaft that rotates around the rotation axis O1, and includes a vibrator 10A whose cross-section perpendicular to the rotation axis O1 is non-circular (e.g., elliptical) in shape, and shaft portions 10B and 10C provided on both sides of the vibrator 10A in the axial direction. The ellipse is not limited to an ellipse in the strict geometric sense, and also includes a substantially ellipse. The shaft portions 10B and 10C are shafts whose cross-section perpendicular to the rotation axis O1 is circular in shape.

[0023] In the following description, the direction along the rotation axis O1 is referred to as the "axial direction", the direction perpendicular to the rotation axis O1 is referred to as the "radial direction", and the rotation direction centered on the rotation axis O1 is referred to as the "circumferential direction". Furthermore, the side in the axial direction that is connected to an external driven component and outputs the decelerated motion to the driven component (the left side in the figure) is referred to as the "output side", and the side opposite to the output side (the right side in the figure) is referred to as the "opposite output side".

[0024] The external gear 30 is a flexible cylindrical member centered on the rotation axis O1 , and has teeth provided on its outer circumference.

[0025] The first internal gear 31G and the second internal gear 32G rotate around the vibrator shaft 10 with the rotation axis O1 as the center. The first internal gear 31G is formed by providing internal teeth at corresponding positions of the inner circumference of the first internal gear member 31. The second internal gear 32G is formed by providing internal teeth at corresponding positions of the inner circumference of the second internal gear member 32.

[0026] The first internal gear 31G and the second internal gear 32G are arranged side by side in the axial direction and mesh with the external gear 30. The first internal gear 31G meshes with the tooth portion of the external gear 30 that is closer to the output side than the center in the axial direction, and these meshing portions constitute the first meshing portion 51. On the other hand, the second internal gear 32G meshes with the tooth portion of the external gear 30 that is closer to the output side than the center in the axial direction, and these meshing portions constitute the second meshing portion 52.

[0027] Furthermore, the number of teeth of the first internal gear 31G is different from the number of teeth of the external gear 30 , and the number of teeth of the second internal gear 32G is the same as the number of teeth of the external gear 30 .

[0028] The vibrator bearing 12 is, for example, a roller bearing, and is disposed between the vibrator 10A and the external gear 30 . The vibrator 10A and the external gear 30 are relatively rotatable via the vibrator bearing 12 .

[0029] The vibrator bearing 12 includes an outer ring 12 a that is fitted inside the external gear 30 , a plurality of rolling elements (rollers) 12 b , and a cage 12 c that holds the plurality of rolling elements 12 b .

[0030] The plurality of rolling elements 12b include: a first group of rolling elements 12b, which are arranged radially inwardly of the first internal gear 31G and arranged circumferentially; and a second group of rolling elements 12b, which are arranged radially inwardly of the second internal gear 32G and arranged circumferentially. These rolling elements 12b roll on the outer peripheral surface of the vibrator 10A and the inner peripheral surface of the outer ring 12a as rolling surfaces. With respect to the outer ring 12a, two outer rings of the same shape are arranged in the axial direction corresponding to the arrangement of the plurality of rolling elements 12b. In addition, the vibrator bearing 12 may also have an inner ring that is separate from the vibrator 10A.

[0031] Spacer rings 41 and 42 are provided as restriction members on both sides of the vibrator bearing 12 and the external gear 30 in the axial direction so as to abut against these and restrict their axial movement.

[0032] The housing 33 is connected to the first internal gear member 31 and covers the outer diameter side of the second internal gear 32G. The housing 33 has an outer ring portion of a main bearing 38 (for example, a cross roller bearing) formed on its inner circumference, and the housing 33 supports the second internal gear member 32 to be rotatable via the main bearing 38. When the flexure meshing gear device 1 is connected to an external target device, the housing 33 and the first internal gear member 31 are fastened and connected to the target device (a fixed member different from the driven member).

[0033] The first cover 34 is connected to the first internal gear member 31, and covers the meshing portion between the external gear 30 and the first internal gear 31G from the axially opposite output side. A first bearing 36 (e.g., a ball bearing) is disposed between the first cover 34 and the shaft portion 10B of the vibrator shaft 10, and the first cover 34 supports the vibrator shaft 10 rotatably via the first bearing 36.

[0034] The second cover 35 is connected to the second internal gear member 32, and the second cover 35 covers the meshing portion between the external gear 30 and the second internal gear 32G from the output side in the axial direction. The second cover 35 and the second internal gear member 32 are connected to the target device (driven member) that outputs the decelerated motion. A second bearing 37 (for example, a ball bearing) is arranged between the second cover 35 and the shaft portion 10C of the vibrator shaft 10, and the second cover 35 supports the vibrator shaft 10 rotatably via the second bearing 37.

[0035] Furthermore, the crimping mesh gear device 1 includes oil seals 43 , 44 , 45 and O-rings 46 , 47 , 48 for sealing.

[0036] The oil seal 43 is disposed between the shaft portion 10B of the vibrator shaft 10 at the end portion on the opposite side of the output in the axial direction and the first cover 34, and suppresses the lubricant from flowing out to the opposite side of the output. The oil seal 44 is disposed between the shaft portion 10C of the vibrator shaft 10 at the end portion on the output side in the axial direction and the second cover 35, and suppresses the lubricant from flowing out to the output side. The oil seal 45 is disposed between the housing 33 and the second internal gear member 32, and suppresses the lubricant from flowing out from this portion.

[0037] An O-ring 46 is provided between the first internal gear member 31 and the first cover 34 , an O-ring 47 is provided between the first internal gear member 31 and the housing 33 , and an O-ring 48 is provided between the second internal gear member 32 and the second cover 35 to prevent the lubricant from flowing out therebetween.

[0038] That is, a lubricant (for example, grease) is sealed in the sealed space S inside the flexure meshing gear device 1 which is sealed by the oil seals 43 to 45 and the O-rings 46 to 48 .

[0039] [Anti-pitch characteristics of the meshing part]

[0040] Next, the anti-pitch characteristics of the first meshing portion 51 and the second meshing portion 52 will be described.

[0041] Figure 2 The graph shows the results of analyzing the distribution of the tooth surface pressure and the film thickness ratio of the first internal gear 31G and the second internal gear 32G under a predetermined load. Figure 3 is an enlarged cross-sectional view of the first meshing portion 51 and the second meshing portion 52 in a modified example of the present embodiment. Figures 4 to 6 It is an enlarged cross-sectional view of the first meshing portion 51 and the second meshing portion 52 in another modified example of the present embodiment.

[0042] In addition, among the first meshing portion 51 and the second meshing portion 52, the first meshing portion 51 on the side connected to the fixed member of the counterpart device is referred to as the "fixed side", and the second meshing portion 52 on the side connected to the driven member is referred to as the "output side".

[0043] In a conventional flexure meshing gear device in which the first meshing portion 51 and the second meshing portion 52 have the same pitch characteristics, the pitch is generated differently in the first meshing portion 51 and the second meshing portion 52, and the first meshing portion 51 on the fixed side is more susceptible to pitch than the second meshing portion 52 on the output side.

[0044] After analysis, the inventors of the present invention believe that the difference in the occurrence of the pitching is caused by the relationship between the tooth surface pressure and the film thickness ratio. The film thickness ratio is an index indicating the ratio of the oil film thickness to the surface roughness of the tooth surface.

[0045] That is, Figure 2 As shown, if the distribution of the tooth surface pressure and the film thickness ratio in the first internal gear 31G on the fixed side and the second internal gear 32G on the output side are compared, the value of the tooth surface pressure in the second internal gear 32G on the output side is larger, but the film thickness in this part is larger. In contrast, in the first internal gear 31G on the fixed side, the film thickness in the part with high tooth surface pressure is smaller. It can be considered that the difference in the distribution of the tooth surface pressure and the film thickness ratio between the fixed side and the output side is caused by whether there is a difference in the number of teeth between the internal teeth and the external teeth (there is a difference in the number of teeth on the fixed side, but there is no difference in the number of teeth on the output side). As a result, it can be considered that the first internal gear 31G on the fixed side (the first meshing portion 51) is more prone to pitching than the second internal gear 32G (the second meshing portion 52) on the output side.

[0046] Therefore, the present embodiment is configured so that the first meshing portion 51 on the fixed side has a higher anti-pitch characteristic than the anti-pitch characteristic of the second meshing portion 52 on the output side.

[0047] Specifically, the first internal gear 31G of the first meshing portion 51 has a higher anti-pitch characteristic than the anti-pitch characteristic of the second internal gear 32G of the second meshing portion 52 .

[0048] As such a structure, for example, it is sufficient to set the surface roughness of the tooth surface of the first internal gear 31G and the surface roughness of the tooth surface of the second internal gear 32G to be different and to make the surface roughness of the tooth surface of the first internal gear 31G smaller than the surface roughness of the tooth surface of the second internal gear 32G. This can be achieved by simply changing the finishing or finishing accuracy of the first internal gear 31G and the second internal gear 32G. For example, it is sufficient to distinguish whether finishing such as shot peening is performed or to set the processing time to be different. Specifically, shot peening is performed on the first internal gear 31G and shot peening is not performed on the second internal gear 32G, or the finishing processing time of the first internal gear 31G is set to be longer than the finishing processing time of the second internal gear 32G. As a result, the pitch of the first internal gear 31G can be suppressed, and the finishing cost of the second internal gear 32G can be suppressed.

[0049] Alternatively, the gear precisions of the first internal gear 31G and the second internal gear 32G may be set to be different so that the first internal gear 31G can be processed more accurately (i.e., meshed well) than the second internal gear 32G. The types of gear precisions that are set to be different are not particularly limited, and for example, a single pitch error may be listed. This can be achieved by, for example, changing the processing machinery or changing the settings of the processing machinery (focusing on speed or precision) or changing the life management of the gear cutting tool (the new tool has higher processing precision) in the first internal gear 31G and the second internal gear 32G. In this way, the pitch of the first internal gear 31G can be suppressed, and the processing cost of the second internal gear 32G can be suppressed.

[0050] In addition, in the present embodiment, the teeth meshing with the first internal gear 31G and the teeth meshing with the second internal gear 32G of the external gear 30 are formed integrally as the same gear. Therefore, the teeth meshing with the first internal gear 31G and the teeth meshing with the second internal gear 32G of the external gear 30 have the same anti-pitch characteristics such as surface roughness and gear accuracy of the tooth surface.

[0051] However, the anti-pitch characteristic of the external gear 30 may be changed so that the first meshing portion 51 has a higher anti-pitch characteristic than the anti-pitch characteristic of the second meshing portion 52. That is, for example, Figure 3As shown, it is sufficient to form a groove 301 throughout the entire circumference on the outer peripheral surface of the center in the axial direction of the external gear 30 and to form the tooth portion (the first external gear portion 30A) on the opposite side of the output than the groove 301 and the tooth portion (the second external gear portion 30B) on the output side than the groove 301 to have different anti-pitch characteristics. In other words, it is sufficient to form the first external gear portion 30A meshing with the first internal gear 31G to have a higher anti-pitch characteristic than the second external gear portion 30B meshing with the second internal gear 32G, similarly to the first internal gear 31G and the second internal gear 32G. Specifically, it is sufficient to make at least one of the surface roughness of the tooth surface and the gear accuracy different between the first external gear portion 30A and the second external gear portion 30B.

[0052] In this case, the anti-pitch characteristics of the first internal gear 31G and the second internal gear 32G may be set higher in the first meshing portion 51 or the same as described above.

[0053] Furthermore, the lubricant applied to the first meshing portion 51 and the lubricant applied to the second meshing portion 52 may be different. Specifically, the lubricant applied to the first meshing portion 51 may be a lubricant having a higher base oil viscosity than the lubricant applied to the second meshing portion 52 or a lubricant to which an extreme pressure additive having a higher anti-pitch property is added. Alternatively, the extreme pressure additive may be added only to the lubricant applied to the first meshing portion 51.

[0054] In this case, if Figure 4 As shown, it is preferred to arrange a V-ring (end face seal) 60 for suppressing the flow of lubricant between the first meshing portion 51 and the second meshing portion 52. Specifically, a groove 302 is formed on the outer peripheral surface of the center in the axial direction of the external gear 30 over the entire circumference, and the tooth portion (first external gear portion 30A) on the opposite side of the output than the groove 302 is meshed with the first internal gear 31G, and the tooth portion (second external gear portion 30B) on the output side is meshed with the second internal gear 32G. Then, a V-ring 60 is arranged in the groove 302. The V-ring 60 is arranged so that its inner peripheral portion is in close contact with the bottom of the groove 302 over the entire circumference, and its lip portion 61 is in contact with the end face (side face on the opposite side of the output) of the second internal gear member 32. As a result, the flow of lubricant between the first meshing portion 51 and the second meshing portion 52 can be suppressed, and different lubricants can be used in the first meshing portion 51 and the second meshing portion 52.

[0055] In addition, the V-ring 60 can be used as long as it can prevent the lubricant from flowing between the first meshing portion 51 and the second meshing portion 52, and the side sealed by the lip portion 61 is not particularly limited. Figure 5 As shown, the lip 61 may also contact the end surface of the first internal gear member 31, as shown in FIG. Figure 6As shown, the lip portion 61 may contact both the end surface of the first internal gear member 31 and the end surface of the second internal gear member 32 .

[0056] Furthermore, the structure of using different lubricants can be used in combination with the above-mentioned structure of making the anti-pitch characteristics of the first internal gear 31G and the anti-pitch characteristics of the second internal gear 32G different and the structure of making the anti-pitch characteristics different in the external gear 30 (the first external gear part 30A and the second external gear part 30B).

[0057] [Deceleration action of flexure meshing gear device]

[0058] Next, the speed reduction operation of the crimping mesh type gear device 1 will be described.

[0059] If the vibrator shaft 10 is driven to rotate by a driving source such as a motor, the movement of the vibrator 10A is transmitted to the external gear 30. At this time, the shape of the external gear 30 is limited to conform to the outer peripheral surface of the vibrator 10A, so that when viewed from the axial direction, the external gear 30 is bent into an elliptical shape having a major axis portion and a minor axis portion. Moreover, the external gear 30 meshes with the fixed first internal gear 31G through the major axis portion. Therefore, the external gear 30 does not rotate at the same speed as the vibrator 10A, and the vibrator 10A rotates relatively on the inner side of the external gear 30. Moreover, along with this relative rotation, the external gear 30 is bent and deformed in such a way that its major axis position and minor axis position move in the circumferential direction. The period of this deformation is proportional to the rotation period of the vibrator shaft 10.

[0060] When the external gear 30 is flexed and deformed, its long axis position moves, and therefore, the meshing position between the external gear 30 and the first internal gear 31G changes in the rotation direction. Here, for example, if the number of teeth of the external gear 30 is set to 100 and the number of teeth of the first internal gear 31G is set to 102, the meshing teeth of the external gear 30 and the first internal gear 31G will be offset every time the meshing position rotates one circle, so that the external gear 30 rotates (rotates). When the number of teeth is set to the above number of teeth, the rotational motion of the oscillator shaft 10 is decelerated at a reduction ratio of 100:2 and transmitted to the external gear 30.

[0061] On the other hand, since the external gear 30 is also meshed with the second internal gear 32G, the meshing position of the external gear 30 and the second internal gear 32G also changes in the rotation direction by the rotation of the vibrator shaft 10. Here, if the number of teeth of the second internal gear 32G is set to be the same as the number of teeth of the external gear 30, the external gear 30 and the second internal gear 32G will not rotate relative to each other, and the rotational motion of the external gear 30 is transmitted to the second internal gear 32G at a reduction ratio of 1:1. As a result, the rotational motion of the vibrator shaft 10 is transmitted to the second internal gear component 32 and the second cover body 35 after being reduced at a reduction ratio of 100:2, and then the rotational motion is output to the driven component.

[0062] Here, in the flexure meshing gear device 1, the first meshing portion 51 on the fixed side has a higher anti-pitch characteristic than the anti-pitch characteristic of the second meshing portion 52 on the output side. Therefore, although the first meshing portion 51 is more susceptible to pitching than the second meshing portion 52, the pitching in the first meshing portion 51 can be well suppressed.

[0063] [Technical Effects of the Present Embodiment]

[0064] As described above, according to the present embodiment, the first meshing portion 51 where the first internal gear 31G meshes with the external gear 30 with different numbers of teeth has a higher anti-pitch characteristic than the second meshing portion 52 where the second internal gear 32G meshes with the external gear 30 with the same number of teeth.

[0065] Thus, in the first meshing portion 51, which is more prone to pitching than the second meshing portion 52, the occurrence of pitching can be well suppressed. Therefore, the probability of occurrence of pitching in the first meshing portion 51 and the second meshing portion 52, which have different numbers of teeth, can be equalized. Moreover, with respect to the anti-pitch characteristic, unnecessary design can be avoided. That is, there is no need to make the second meshing portion 52, which has a relatively low probability of occurrence of pitching, oversize, and processing can be omitted, or processing time can be shortened, or cheap lubricants can be used, etc., which can suppress the increase in costs.

[0066] [other]

[0067] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment.

[0068] For example, in the above-mentioned embodiment, the first meshing portion 51 on the fixed side is more prone to pitching than the second meshing portion 52 on the output side. However, as described above, the probability of pitching is related to the number of teeth. That is, meshing portions meshing with different numbers of teeth are more prone to pitching than meshing portions meshing with the same number of teeth. Therefore, in a case where the meshing portions on the output side are meshed with different numbers of teeth and the meshing portions on the fixed side are meshed with the same number of teeth (or a smaller difference in the number of teeth), it can be considered that the meshing portions on the output side are more prone to pitching. Therefore, in this case, it is necessary to set the pitching resistance characteristics of the meshing portion on the output side to be higher than the pitching resistance characteristics of the fixed side.

[0069] Furthermore, the details shown in the above-described embodiment can be appropriately modified within the scope not departing from the spirit of the invention.

Claims

1. A flexure meshing gear device comprising: an oscillator; an external gear that is flexed and deformed by the oscillator; and a first internal gear and a second internal gear that mesh with the external gear. The number of teeth of the first internal gear is different from the number of teeth of the external gear, and the number of teeth of the second internal gear is the same as the number of teeth of the external gear, wherein: By making the lubricant applied to the first meshing portion where the first internal gear meshes with the external gear different from the lubricant applied to the second meshing portion where the second internal gear meshes with the external gear, the first meshing portion has a higher anti-pitch property than the anti-pitch property of the second meshing portion. A suppressing member for suppressing the flow of the lubricant is provided between the first meshing portion and the second meshing portion.

2. The flexure meshing gear device according to claim 1, wherein: The first internal gear has a higher anti-pitch characteristic than the anti-pitch characteristic of the second internal gear. The surface roughness of the tooth surface of the first internal gear is different from the surface roughness of the tooth surface of the second internal gear.

3. The flexure meshing gear device according to claim 1, wherein: The lubricant applied to the first meshing portion contains an extreme pressure additive having a higher anti-pitch property than the lubricant applied to the second meshing portion, or the extreme pressure additive is added only to the lubricant applied to the first meshing portion.

4. The flexure meshing gear device according to claim 2 or 3, wherein: The gear accuracy of the first internal gear is different from the gear accuracy of the second internal gear.

5. The flexure meshing gear device according to claim 2 or 3, wherein: The external gear includes: a first external gear portion meshing with the first internal gear; and a second external gear portion meshing with the second internal gear. The anti-pitch property of the first external gear portion is the same as the anti-pitch property of the second external gear portion.

6. The flexure meshing gear device according to any one of claims 1 to 3, wherein: The external gear includes: a first external gear portion meshing with the first internal gear; and a second external gear portion meshing with the second internal gear. The first external gear portion has a higher anti-pitch characteristic than the anti-pitch characteristic of the second external gear portion.

7. The flexure meshing gear device according to claim 1, wherein: The suppression member has a lip portion that contacts an end surface of at least one of the first internal gear and the second internal gear.

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