Resin gears and gear devices

Abstract

To improve the strength of a resin gear and a resin gear of a gear unit.SOLUTION: A first internal gear 22g and a second internal gear 23g are formed by using a molding material in which reinforcing fibers f are mixed with base resins r, and the reinforcing fibers are arranged along tooth surfaces on meshing surfaces 221b, 231b of each tooth, and a fiber direction is random. Alternatively, the reinforcing fibers are arranged along the tooth surfaces on the meshing surfaces 221b, 231b of each tooth, and the fiber direction is random in a deep part d that overlaps with the tooth surfaces when viewed from a circumferential direction. The reinforcing fibers along the meshing surfaces 221b, 231b contribute to improving the strength of the meshing surfaces 221b, 231b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a resin gear and a gear device. [Background technology]

[0002] In recent years, due to demands for weight reduction, it has been proposed to use gears made of resin in gear devices. In such resin gears, reinforcing fibers are blended into the base resin to increase strength, and the fiber direction of the reinforcing fibers is uniformly aligned along the tooth surface at the meshing surface of each tooth, while the fiber direction is random at the tooth bottom (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-218994 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the resin gear of Patent Document 1 has room for improvement in strength.

[0005] An object of the present invention is to improve the strength of a resin gear and a resin gear of a gear device. [Means for solving the problem]

[0006] The present invention provides A resin gear molded using a molding material in which reinforcing fibers are blended with a base resin, The reinforcing fibers are arranged along the tooth surface at the meshing surface of each tooth; and The reinforcing fibers located on the tooth surface are oriented in a random direction within the tooth surface, with the fiber direction of the reinforcing fibers being aligned along the tooth surface. Resin gears were used.

[0007] The present invention also provides A resin gear molded using a molding material in which reinforcing fibers are blended with a base resin, The meshing surface of each tooth includes reinforcing fibers arranged along the tooth surface, and the fiber direction of the reinforcing fibers arranged along the tooth surface is About three-dimensional directions It's random the law of nature, When viewed from the circumferential direction, at a central position between a deep portion overlapping with the tooth surface of the meshing surface and the tooth surface of the meshing surface, the proportion of reinforcing fibers along the tooth surface of the meshing surface is smaller than that of the tooth surface of the meshing surface. Resin gears were used.

[0008] The present invention also provides A gear device having an internal gear and an external gear, one of the internal gear and the external gear is formed by the resin gear, The other of the internal gear and the external gear is made of metal. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the strength of a resin gear and a resin gear of a gear device. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an axial cross-sectional view showing a flexible mesh gear device according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a view of one tooth of an internal gear of a flexible mesh gear device as viewed from the axial direction. [Figure 3] 3 is a diagram showing the direction of reinforcing fibers in the base resin in a plane along line UU which is the tooth surface of the meshing surface in FIG. 2. FIG. [Figure 4] 3 is a cross-sectional view of a surface along line VV inside the tooth surface in FIG. 2. [Figure 5] 3 is a cross-sectional view taken along the line WW passing through the deep part in FIG. 2. [Figure 6] FIG. 2 is a view of one tooth of an internal gear of a flexible mesh gear device as viewed from the axial direction. [Figure 7] 7 is a diagram showing the direction of reinforcing fibers in the base resin in a plane along line LL, which is the tooth tip surface in FIG. 6. FIG. [Figure 8] FIG. 7 is a cross-sectional view of a surface along line MM inside the tooth tip surface in FIG. 6. [Figure 9] FIG. 7 is a cross-sectional view taken along line NN, which is located further inward than the tooth tip surface in FIG. 6. [Figure 10] 3 is a diagram showing the direction of reinforcing fibers in a base resin in a rectangular region S in an axial end face shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Outline of the embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view showing a flexure mesh gear device as a gear device according to an embodiment. In the following, the direction along the rotation axis O1 in the figure is defined as the "axial direction," the direction perpendicular to the rotation axis O1 as the "radial direction," and the rotation direction around the rotation axis O1 as the "circumferential direction."

[0012] As shown in FIG. 1, the flexible mesh gear device 1 is a cylindrical flexible mesh gear device in which an external gear 12 (second gear) is flexibly deformed to transmit rotational motion around a rotation axis O1. Specifically, the flexible mesh gear device 1 includes a vibrator shaft 10, an external gear 12 that is flexibly deformed by the vibrator shaft 10, a first internal gear 22g and a second internal gear 23g that mesh with the external gear 12, and a vibrator bearing 15. Furthermore, the flexible mesh gear device 1 includes a first casing 22, an internal gear member 23, a second casing 24, a first cover 26, a second cover 27, input bearings 31 and 32, and a main bearing 33.

[0013] The vibrator shaft 10 is hollow and includes a vibrator 10A having an elliptical cross section perpendicular to the rotation axis O1, and shaft portions 10B and 10C located on either side of the vibrator 10A in the axial direction, each having a circular cross section perpendicular to the rotation axis O1. Note that the elliptical shape is not limited to a strict geometric ellipse, but also includes an approximate ellipse. The vibrator shaft 10 rotates around the rotation axis O1, and the center of the cross section of the vibrator 10A perpendicular to the rotation axis O1 coincides with the rotation axis O1. This vibrator shaft 10 is an input shaft that is connected to a drive source (not shown), such as a motor, to input driving force.

[0014] The external gear 12 is a cylindrical flexible metal member having teeth on its outer periphery.

[0015] The first internal gear 22g and the second internal gear 23g rotate around the vibration exciter shaft 10 with the rotation axis O1 as the center. The first internal gear 22g and the second internal gear 23g are arranged side by side in the axial direction and mesh with the external gear 12. Specifically, one of the first internal gear 22g and the second internal gear 23g meshes with teeth on one side of the axial center of the external gear 12, and the other meshes with teeth on the other side of the axial center of the external gear 12. The first internal gear 22g is configured by having internal teeth provided at a corresponding location on the inner periphery of the first casing 22. The second internal gear 23g is configured by having internal teeth provided at a corresponding location on the inner periphery of the internal gear member 23.

[0016] The vibrator bearing 15 is disposed between the vibrator 10A and the external gear 12. The vibrator bearing 15 has a plurality of rolling elements (rollers) 15A and a cage 15C that holds the plurality of rolling elements 15A. The plurality of rolling elements 15A roll on the outer circumferential surface of the vibrator 10A and the inner circumferential surface of the external gear 12 as rolling surfaces. The vibrator bearing 15 may have an inner ring separate from the vibrator 10A and an outer ring separate from the external gear 12.

[0017] Spacer rings 36 and 37 are provided on both axial sides of the external gear 12 and the retainer 15C of the vibrator bearing 15, as restricting members that come into contact with them and restrict their axial movement.

[0018] The first casing 22 and the second casing 24 are connected to each other by bolts 57, which are connecting members, and cover the radial outside of the first internal gear 22g, the second internal gear 23g, and the external gear 12. Of these, the first casing 22 has internal teeth on part of its inner periphery, as described above, and is configured integrally with the first internal gear 22g.

[0019] The first casing 22 and the second casing 24 are provided with bolt connection holes 22h, 24h that extend continuously in the axial direction at their ends on the anti-load side (right side in FIG. 1 ). When the flexible mesh gear device 1 is connected to an external member 55 (e.g., a base-end arm member of a robot) outside the device, the first casing 22 and the second casing 24 are fastened together to the external member 55 by bolts 53, which serve as connecting members, via the bolt connection holes 22h, 24h. These bolt connection holes 22h, 24h are provided at multiple locations in the circumferential direction. The first casing 22 and the second casing 24 also have bolt holes 22j, 24j that are separate from the bolt connection holes 22h, 24h, and are connected (temporarily fastened) to each other by the aforementioned bolts 57 that are inserted and screwed into the bolt holes 22j, 24j.

[0020] At least a portion of the internal gear member 23 is disposed radially inside the second casing 24 and radially outside the vibrator shaft 10. As described above, the internal gear member 23 has internal teeth on a portion of its inner periphery, and is configured integrally with the second internal gear 23g.

[0021] The first cover 26 and the first casing 22 have bolt holes 26k, 22k on the anti-load side, and are connected to each other by bolts 51 inserted and screwed into the bolt holes 26k, 22k. The first cover 26 covers the outer periphery of one end of the vibrator shaft 10 .

[0022] The second cover 27 is connected to the internal gear member 23 and covers the outer periphery at the other end of the vibrator shaft 10. The second cover 27 and the internal gear member 23 are provided with bolt connection holes 27h, 23h that extend continuously in the axial direction at their load-side (left side in FIG. 1) ends. When the flexible mesh gear device 1 is connected to a driven member 56 outside the device (for example, a distal arm member of a robot), the second cover 27 and the internal gear member 23 are fastened together to the driven member 56 by bolts 54, which serve as connecting members, via the bolt connection holes 27h, 23h. These bolt connection holes 27h, 23h are provided at multiple locations in the circumferential direction. In addition, the second cover 27 and the internal gear member 23 have bolt holes 27j, 23j separate from the bolt connection holes 27h, 23h, and are connected (temporarily fastened) to each other by bolts 52 inserted and screwed into these bolt holes 27j, 23j.

[0023] The input bearing 31 is, for example, a ball bearing having an inner ring 31a, an outer ring 31b, and rolling elements 31c, and is arranged between the shaft portion 10B of the vibrator shaft 10 and the first cover 26. The first cover 26 rotatably supports the vibrator shaft 10 via the input bearing 31. Note that the input bearing 31 is not limited to a ball bearing, and various types of bearings can be used, such as a roller bearing. Furthermore, without having dedicated inner and outer rings, the inner ring may be configured integrally with the vibrator shaft 10, or the outer ring may be configured integrally with the first cover 26. The input bearing 32 is, for example, a ball bearing having an inner ring 32a, an outer ring 32b, and rolling elements 32c, and is arranged between the shaft portion 10C of the vibrator shaft 10 and the second cover 27. The second cover 27 rotatably supports the vibrator shaft 10 via the input bearing 32. Note that the input bearing 32 is not limited to a ball bearing, and various types of bearings can be used, such as a roller bearing. Furthermore, without having dedicated inner and outer rings, the inner ring may be configured integrally with the vibrator shaft 10, or the outer ring may be configured integrally with the second cover 27. Furthermore, although both the input bearings 31 and 32 are bearings with seals and lubricant sealed inside, they do not necessarily have to be sealed.

[0024] The main bearing 33 is, for example, a ball bearing having an inner ring 33a, an outer ring 33b, and rolling elements 33c, and is disposed between the internal gear member 23 and the second casing 24. The second casing 24 rotatably supports the internal gear member 23 via the main bearing 33. The main bearing 33 is not limited to a ball bearing, and various bearings can be used. For example, it may be a cross roller bearing, or it may be configured with multiple bearings (angular contact ball bearings, tapered bearings, etc.) spaced apart in the axial direction between the internal gear member 23 and the second casing 24. The main bearing 33 may not have a dedicated inner ring or outer ring, but the inner ring may be configured integrally with the internal gear member 23, or the outer ring may be configured integrally with the second casing 24. The main bearing 33 is not particularly limited, and may be a sealed bearing with a lubricant sealed inside.

[0025] Seal sections 41 to 43, which are shaft seal sections for ensuring sealing performance for the input bearings 31, 32 and the main bearing 33, are provided axially outside the lubricant-filled space S in which the mechanical sections of the flexible mesh gear device 1 are housed.

[0026] The seal portion 41 of the input bearing 31 extends radially inward from the first cover 26 to near the outer circumferential surface of the vibrator shaft 10 (shaft portion 10B), and consists of a wall surface that covers the axial outside of the input bearing 31, forming a narrow gap between it and the outer periphery of the shaft portion 10B, which inhibits the movement of lubricant. The seal portion 42 of the input bearing 32 extends radially inward from the second cover 27 to near the outer circumferential surface of the vibrator shaft 10 (shaft portion 10C), and consists of a wall surface that covers the axial outside of the input bearing 32, forming a narrow gap between it and the outer periphery of the shaft portion 10C, which inhibits the movement of lubricant. The seal portion 43 of the main bearing 33 extends radially inward from the second casing 24 to near the outer circumferential surface of the second cover 27, and is made of a wall surface that covers the axially outer side of the main bearing 33, forming a small gap between it and the outer periphery of the second cover 27 to inhibit the movement of lubricant. In addition, the inside of the seal portion 43 (the side facing the main bearing 33) has a protrusion that protrudes radially outward from the second cover 27. The seal portion 43 and the protrusion form a labyrinth structure.

[0027] [Operation description] In the flexible mesh gear device 1 configured as described above, when the vibrator shaft 10 is driven to rotate by a drive source such as a motor, the movement of the vibrator 10A is transmitted to the external gear 12. At this time, because the external gear 12 is meshed with the fixed first internal gear 22g at the longitudinal axis position of the vibrator 10A, it does not rotate at the same speed as the vibrator 10A, and the longitudinal axis position of the vibrator 10A moves due to flexible deformation. For example, if the number of teeth of the external gear 12 is 100 and the number of teeth of the first internal gear 22g is 102, each time the meshing position makes one revolution, the external gear 12 rotates (spins) by an amount equal to the difference in the number of teeth with the first internal gear 22g. With the above number of teeth, the rotational motion of the vibration exciter shaft 10 is transmitted to the external gear 12 after being decelerated at a reduction ratio of 100:2. On the other hand, since the external gear 12 is also meshed with the second internal gear 23g, if, for example, the number of teeth of the second internal gear 23g is the same as the number of teeth of the external gear 12, the external gear 12 and the second internal gear 23g rotate at the same speed, and this rotational motion is output to the driven member 56.

[0028] [Materials of each component] In this embodiment, the materials of the respective members are configured as follows. The vibrator shaft 10, external gear 12, and spacer rings 36, 37 are made of metal materials such as steel. Although not particularly limited, more specifically, the vibrator shaft 10 is made of steel materials such as chromium-molybdenum steel. The external gear 12 is made of steel materials such as nickel-chromium-molybdenum steel. The spacer rings 36, 37 are made of steel materials such as high-carbon chromium bearing steel.

[0029] The input bearings 31, 32 and the main bearing 33 have inner and outer rings and rolling elements made of metal, for example, high carbon chromium bearing steel. In addition, the vibrator bearing 15 has rolling elements 15A and a cage 15C made of metal, for example, high carbon chromium bearing steel. Each of the bolts 51 to 54, 57 is made of metal, for example, rolled steel for general structure, carbon steel wire for cold heading, carbon steel for machine structure, or the like.

[0030] On the other hand, the first casing 22, the internal gear member 23, the second casing 24, the first cover 26, and the second cover 27 are made of resin.

[0031] In this embodiment, a resin containing reinforcing fibers in its base material is used for the second casing 24, the first cover 26, and the second cover 27. However, a resin that does not contain reinforcing fibers may also be used. The base resin is, for example, an engineering plastic (general-purpose engineering plastic) that has a heat resistance of about 50 to 60°C. Specific examples include polyamide (PA), polycarbonate (PC), polyacetal (POM), modified polyphenylene ether (m-PPE), and polybutylene terephthalate (PBT). Heat resistance here refers to the temperature at which the gear's performance can be maintained, rather than the temperature at which the gear can statically maintain its shape. Examples of reinforcing fibers include glass fiber, aramid fiber, polyethylene fiber, Zylon fiber, boron fiber, etc. General-purpose engineering plastics containing these fibers (for example, polyacetal containing glass fiber) have a thermal conductivity of less than 0.3 W / m°C.

[0032] In this embodiment, the resin used for the first casing 22 and the internal gear member 23 contains reinforcing fibers in the base material of the resin. The base resin is preferably a resin with heat resistance of 70°C or higher, for example, a super engineering plastic (special engineering plastic) with heat resistance of 100°C or higher. Specific examples include polyether ether ketone (PEEK), polyamide imide (PAI), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), aromatic polyamide (PPA), liquid crystal polymer (LCP), polysulfone (PSU), polyether sulfone (PES), polyether imide (PEI), polyarylate (PAR), thermoplastic polyimide (TPI), etc. Furthermore, as the reinforcing fibers, fibers with higher thermal conductivity than the aforementioned reinforcing fibers are used, such as carbon fibers. The thermal conductivity of the high thermal conductive resin member is preferably 0.5 W / m°C or higher, and in the case of a resin in which carbon fibers are incorporated into a super engineering plastic (e.g., polyether ether ketone), the thermal conductivity is 0.95 W / m°C.

[0033] In consideration of heat dissipation, the resin and reinforcing fibers used for the first casing 22 and the internal gear member 23 are selected to have higher thermal conductivity and heat resistance than the second casing 24, the first cover 26, and the second cover 27. However, the resin and reinforcing fibers used for the first casing 22 and the internal gear member 23 may be the same as those exemplified for the second casing 24, the first cover 26, and the second cover 27.

[0034] [Fiber direction in gears] As described above, the first casing 22 and the internal gear member 23 are made of resin and reinforcing fibers (hereinafter referred to as reinforcing fibers), and the first internal gear 22g and the second internal gear 23g formed on the inner periphery thereof are also made of resin and reinforcing fibers. Both the first internal gear 22g and the second internal gear 23g are resin gears. The first internal gear 22g and the second internal gear 23g have an unprecedented feature in terms of the longitudinal direction (fiber direction) of the reinforcing fibers in the resin (referred to as base resin) that forms them.

[0035] The first internal gear 22g and the second internal gear 23g each have internal teeth made up of multiple teeth 221, 231 formed at equal intervals along the inner circumference. FIG. 2 is a view of one tooth 221, 231 as viewed from the axial direction. Note that although there are slight differences in dimensions and various parts between the tooth 221 of the first internal gear 22g and the tooth 231 of the second internal gear 23g, they are essentially identical in structure, and therefore are commonly illustrated in FIG. 2 and in FIGS. 3 to 10, which illustrate the internal structure described below. In these figures, the reference numeral for the tooth 231 of the second internal gear 23g is written in parentheses.

[0036] The teeth 221, 231 of the first internal gear 22g and the second internal gear 23g each have tooth crest surfaces 221a, 231a that are generally circumferentially aligned at their radially innermost positions. Furthermore, the teeth 221, 231 each have meshing surfaces 221b, 231b adjacent to both circumferential sides of the tooth crest surfaces 221a, 231a. Furthermore, the teeth 221, 231 each have tooth bottom surfaces 221c, 231c between the teeth 221, 231 on the circumferential outer side of the meshing surfaces 221b, 231b (in the direction away from the tooth crest surfaces 221a, 231a in the circumferential direction). Although the tooth tip surfaces 221a, 231a, the meshing surfaces 221b, 231b, and the tooth bottom surfaces 221c, 231c are shown as flat surfaces in FIG. 2, they are not limited to this and may be formed as curved surfaces.

[0037] Figure 3 is a diagram showing the direction of the reinforcing fibers f in the base resin r on the tooth surface (or the interior as close to the tooth surface) along line UU of the meshing surfaces 221b, 231b in Figure 2, Figure 4 is a cross-sectional view on a surface (a surface parallel to the tooth surface) along line VV inside the tooth surface (inside the base resin r) in Figure 2, and Figure 5 is a cross-sectional view on a surface (a surface parallel to the tooth surface) along line WW passing through the deep portion d in Figure 2.

[0038] The deep portion d indicates a deep portion that overlaps with the meshing surfaces 221b, 231b when viewed from the circumferential direction. In other words, when the circumferential surface that passes through the position of the midpoint h / 2 of the total tooth height h in the radial direction of the teeth 221, 231 is defined as p, the deep portion d indicates a position that is midway in the circumferential direction from the position where the circumferential surface p passes through the meshing surfaces 221b, 231b on both sides of the circumferential direction of the teeth 221, 231. Furthermore, the surface along the line VV in FIG. 4 has a depth corresponding to the center position between the meshing surfaces 221b, 231b and the deep portion d.

[0039] 2 to 4, the reinforcing fibers f drawn as lines indicate that their fiber direction is aligned with the meshing surfaces 221b, 231b, and the more inclined they are with respect to the meshing surfaces 221b, 231b, the shorter their lengths become. Also, the reinforcing fibers f drawn as dots indicate that their fiber direction is significantly inclined with respect to the meshing surfaces 221b, 231b. Here, "the reinforcing fibers f are along a certain surface" means that the reinforcing fibers f appear linearly on a certain surface or in a cross section parallel to a certain surface. A certain surface may be a meshing surface, a tooth tip surface, an axial end surface, etc. Additionally, "the reinforcing fibers f appear linearly" means that the reinforcing fibers f have a longitudinal and a transverse direction, and the longitudinal dimension is at least three times larger than the transverse dimension.

[0040] 3, the majority of the reinforcing fibers f are shown as lines on or near the meshing surfaces 221b, 231b of the teeth 221, 231, and it can be seen that the fiber direction of these reinforcing fibers f is aligned with the meshing surfaces 221b, 231b. For example, in this embodiment, the area ratio of the reinforcing fibers f along the tooth surfaces is 10% or more, preferably 30% or more (the same applies to the tooth tip surfaces 221a, 231a and axial end surfaces, which will be described later). Note that the fiber direction (longitudinal direction) of these reinforcing fibers f is aligned with the meshing surfaces 221b, 231b, but each fiber is oriented in a different random direction within the surfaces.

[0041] Here, "random" means that the reinforcing fibers f are not oriented in a uniform direction, or even that the reinforcing fibers f are oriented in roughly random directions. For example, if the variation in the angle (angle of 90 degrees or less) between a certain direction (e.g., the tooth trace direction) and the fiber direction (longitudinal direction) of each reinforcing fiber f (the difference in angle between the reinforcing fiber with the maximum angle and the reinforcing fiber with the minimum angle) is 45 degrees or more, it can be said to be "random." In the above-mentioned interlocking surfaces 221b, 231b, it is assumed that the fibers are aligned along the interlocking surfaces 221b, 231b, and the state is shown in which each fiber faces in a different direction within the surface. However, when no particular assumption is mentioned, the term "random" means that each reinforcing fiber f does not follow a single surface, but faces in roughly different directions.

[0042] 3, there are reinforcing fibers f (reinforcing fibers f that do not align with the meshing surfaces 221b, 231b) shown as dots, but these are regions that are radially outward (inside the base resin r) of the tooth bottom surfaces 221c, 231c and are separated from the meshing surfaces 221b, 231b, in other words, regions that do not overlap with the meshing surfaces 221b, 231b when viewed from the circumferential direction. Thus, in this embodiment, on the tooth surfaces along line UU, the boundary between the region where the reinforcing fibers f align with the tooth surfaces and the region where the reinforcing fibers f do not align with the tooth surfaces is clearly visible.

[0043] On the other hand, at the center position between the meshing surfaces 221b, 231b of the teeth 221, 231 and the deep portion d, as shown in Figure 4, the reinforcing fibers f shown as dots and the reinforcing fibers f shown as lines are mixed, and the reinforcing fibers f along the meshing surfaces 221b, 231b are fewer than those along the meshing surfaces 221b, 231b. Furthermore, in the deep portion d away from the meshing surfaces 221b, 231b of the teeth 221, 231, as shown in FIG. 5, the dotted reinforcing fibers f are predominant, while the linear reinforcing fibers f are fewer and shorter. In other words, in the deep portion d away from the meshing surfaces 221b, 231b of the teeth 221, 231, the number of reinforcing fibers f along the meshing surfaces 221b, 231b is even fewer than at the central position, and the fiber directions are random, pointing in all three-dimensional directions. Furthermore, at the central position and the deep portion d, the boundary between the region where the reinforcing fibers f run along the tooth surfaces and the region where the reinforcing fibers f do not run along the tooth surfaces is not clearly visible. As described above, in this embodiment, the number of reinforcing fibers f along the meshing surfaces 221b, 231b decreases as one moves from the meshing surfaces 221b, 231b toward the deep portion d.

[0044] Next, the fiber direction of the reinforcing fibers f on the tooth tip surfaces 221a, 231a of the teeth 221, 231 will be described. Fig. 6 is a view of the teeth 221, 231 as viewed from the axial direction. Fig. 7 is a view showing the direction of the reinforcing fibers f in the base resin r in a plane along line LL, which is the tooth tip surfaces 221a, 231a (or the interior as close as possible to the tooth tip surfaces 221a, 231a) in Fig. 6. Fig. 8 is a cross-sectional view in a plane along line MM (a plane parallel to the tooth tip surfaces 221a, 231a) inside (in the base resin r) the tooth tip surfaces 221a, 231a in Fig. 6. Fig. 9 is a cross-sectional view in a plane along line NN (a plane parallel to the tooth tip surfaces 221a, 231a) further inside (in the base resin r) the tooth tip surfaces 221a, 231a in Fig. 6. The depth of the line MM relative to the tooth tip surfaces 221a, 231a in Fig. 8 corresponds to the depth of the line VV relative to the meshing surfaces 221b, 231b in Fig. 4 (the center position between the lines LL and NN). The depth of the line NN relative to the tooth tip surfaces 221a, 231a in Fig. 9 corresponds to the depth of the line WW relative to the meshing surfaces 221b, 231b in Fig. 5 (the center position in the tooth height direction).

[0045] 7, a large number of reinforcing fibers f are shown as lines on or near the tooth tip surfaces 221a, 231a of the teeth 221, 231, and it can be seen that these reinforcing fibers f extend along the tooth tip surfaces 221a, 231a. Note that, on the tooth tip surfaces 221a, 231a, the fiber directions (longitudinal directions) of the reinforcing fibers f are also oriented in different random directions within the tooth tip surfaces 221a, 231a, as in the case of the meshing surfaces 221b, 231b.

[0046] On the other hand, slightly inside the tooth tip surfaces 221a, 231a of the teeth 221, 231 (at the position of the MM line), as shown in Fig. 8, the reinforcing fibers f shown as dots and the reinforcing fibers f shown as lines are mixed, and it can be seen that the number of reinforcing fibers f that do not run along the tooth tip surfaces 221a, 231a is increasing. In other words, the number of reinforcing fibers f running along the tooth tip surfaces 221a, 231a is fewer than that on the tooth tip surfaces 221a, 231a. Furthermore, at positions farther from the tooth crest surfaces 221a, 231a of the teeth 221, 231 (the position of the line NN), as shown in Fig. 9, the reinforcing fibers f shown as dots are more prevalent, and the reinforcing fibers f shown as lines are fewer and shorter. In other words, at positions farther from the tooth crest surfaces 221a, 231a of the teeth 221, 231, the reinforcing fibers f do not align with the tooth crest surfaces 221a, 231a, but are randomly oriented in all directions. At the position of the line NN, the number of reinforcing fibers f aligned with the tooth crest surfaces 221a, 231a is fewer than at the position of the line MM.

[0047] In Figures 8 and 9, the proportion of reinforcing fibers f, shown as dots, is higher near the axial end faces (upper and lower ends in Figures 8 and 9) of the first internal gear 22g and the second internal gear 23g. This is because the reinforcing fibers f are aligned along the axial end faces near the axial end faces of the first internal gear 22g and the second internal gear 23g.

[0048] Next, we will explain the fiber direction of the reinforcing fibers f on the axial end faces of the teeth 221, 231. Fig. 10 is a diagram showing the direction of the reinforcing fibers f in the base resin r in the rectangular region S on the axial end face (or the interior as close as possible to the axial end face) shown in Fig. 2. 10, a large number of reinforcing fibers f are shown as lines on or near the axial end faces of the teeth 221, 231, and it can be seen that these reinforcing fibers f are aligned along the axial end faces. Note that even on the axial end faces, the reinforcing fibers f are aligned along the axial end faces, but each fiber faces in a different direction within the face, forming a random arrangement.

[0049] [Gear molding] The first internal gear 22g and the second internal gear 23g can be molded using an injection molding device that includes a hopper that supplies the resin material of the base resin r and the reinforcing fibers f (pellets in which the base resin r and the reinforcing fibers f are integrated may be supplied, or they may be supplied separately), a heater that plasticizes the supplied resin material by heating, a screw that kneads the plasticized resin material and the reinforcing fibers f, a cylinder that injects the kneaded resin material and the reinforcing fibers f, a pair of molds in which cavities corresponding to the outer shape of the first internal gear 22g or the second internal gear 23g are formed, and a mold holding mechanism that maintains pressure on the pair of molds. In the molding device, the resin material of the base resin r supplied from the hopper into the cylinder is heated together with the reinforcing fibers f by the heater, and the plasticized resin material and the reinforcing fibers f are kneaded by the screw. Then, the kneaded resin material and reinforcing fibers f are injected from the cylinder into the cavity of a pair of molds, which are kept pressurized by a mold holding mechanism, and after waiting for the resin material to cool, the pair of molds are released, and the first internal gear 22g or the second internal gear 23g is removed from the cavity, completing the molding process. The molding conditions in the injection molding may be adjusted as appropriate to form the first internal gear 22g or the second internal gear 23g having teeth 221 or 231 in which the fiber direction of the reinforcing fibers f is more preferable.

[0050] Furthermore, the injection molding of the first internal gear 22g or the second internal gear 23g may be carried out in two stages. For example, the first internal gear 22g or the second internal gear 23g may be molded in a mold having a cavity designed so that the outer dimensions of the teeth 221 or 231 are slightly smaller than those of the teeth 221 or 231, and then a second injection molding step may be performed using a mold having a cavity designed so that the outer dimensions of the teeth 221 or 231 are appropriate, in which plasticized resin material and reinforcing fibers f are filled into gaps that occur on the meshing surfaces 221b, 231b, the tooth tip surfaces 221a, 231a, the axial end surfaces, etc. in the cavity, thereby molding the reinforcing fibers f so that the fiber direction is more aligned with each surface. Alternatively, after a spraying process of reinforcing fibers f is performed on positions corresponding to the meshing surfaces 221b, 231b, tooth tip surfaces 221a, 231a, and axial end faces of the first internal gear 22g or the second internal gear 23g molded in the first stage, a second stage of injection molding may be performed in which plasticized resin material is filled into gaps generated at positions corresponding to the axial end faces, etc.

[0051] [Technical effect of this embodiment] In the above-mentioned flexible meshing gear device 1, the first internal gear 22g and the second internal gear 23g are made of a molding material in which reinforcing fibers f are blended with a base resin r matrix, and the meshing surfaces 221b, 231b of each tooth 221, 231 contain reinforcing fibers f arranged along the tooth surface, and the fiber direction of the reinforcing fibers arranged along the tooth surface is random. When such a fiber structure is present, it is possible to improve the bending strength, fatigue strength, and durability against shear force of the meshing surfaces 221b, 231b of each tooth 221, 231 of the first internal gear 22g and the second internal gear 23g, and to strengthen the meshing surfaces 221b, 231b in multiple directions along the meshing surfaces 221b, 231b.

[0052] In contrast, if the fiber directions of the reinforcing fibers f along the mating surfaces 221b, 231b were all aligned in a fixed direction, the mating surfaces 221b, 231b would be reinforced only in that fixed direction, and would not be reinforced in any other direction. Furthermore, if the reinforcement direction were biased in this way, the difference in strength between the mating surfaces 221b, 231b and the tooth root surfaces 221c, 231c in a fixed direction would be excessively large, which could result in breakage of the teeth 221, 231 along the tooth root circle. On the other hand, if the reinforcing fibers f are aligned along the meshing surfaces 221b, 231b of each tooth 221, 231 and the fiber direction is random, the difference in strength in a certain direction between the meshing surfaces 221b, 231b and the tooth bottom surfaces 221c, 231c can be reduced, making it possible to prevent breakage of the teeth 221, 231.

[0053] In addition, in deep portions d where the teeth 221, 231 of the first internal gear 22g and the second internal gear 23g overlap with the meshing surfaces 221b, 231b when viewed from the circumferential direction, the fiber direction of the reinforcing fibers f is random and does not follow the meshing surfaces 221b, 231b. In this case, the surface strength of the meshing surfaces 221b, 231b of each tooth 221, 231 can be increased, and the difference in strength between the inside of the meshing surfaces 221b, 231b and the tooth bottom surfaces 221c, 231c can be reduced, making it possible to more effectively prevent breakage of the teeth 221, 231.

[0054] Also, at the center position between the meshing surfaces 221b, 231b of the teeth 221, 231 and the deep portion d as shown in FIG. 4 described above, the proportion of reinforcing fibers f along the tooth surfaces of the meshing surfaces 221b, 231b is smaller than that of the tooth surfaces of the meshing surfaces 221b, 231b. As a result, the proportion of reinforcing fibers f along the tooth surfaces of the meshing surfaces 221b, 231b gradually decreases in the range from the meshing surfaces 221b, 231b to the deep portion d, thereby reducing the difference in strength between the meshing surfaces 221b, 231b and their inner sides, and effectively suppressing the occurrence of peeling, breakage, and cracks on the inner sides of the meshing surfaces 221b, 231b.

[0055] Furthermore, in the deep portion d of the meshing surfaces 221b, 231b of the teeth 221, 231 shown in FIG. 5, the proportion of the reinforcing fibers f along the meshing surfaces 221b, 231b is even smaller than in the central position. As a result, the proportion of reinforcing fibers f along the tooth surfaces of the meshing surfaces 221b, 231b gradually decreases in the range from the meshing surfaces 221b, 231b through the central position to the deep part d, which further reduces the difference in strength between the meshing surfaces 221b, 231b and their inner sides, making it possible to more effectively suppress the occurrence of peeling, breakage, and cracks on the inner sides of the meshing surfaces 221b, 231b.

[0056] The first internal gear 22g and the second internal gear 23g include reinforcing fibers f arranged on the tooth tip surfaces 221a and 231a of the respective teeth 221 and 231 along the tooth tip surfaces 221a and 231a. This improves the bending strength, fatigue strength, and durability against shear force on the tooth crest surfaces 221a, 231a, and also makes it possible to strengthen the tooth crest surfaces 221a, 231a in all directions. Therefore, in addition to the effect of improving the strength of the meshing surfaces 221b, 231b, it is possible to strengthen each tooth 221, 231 as a whole.

[0057] Furthermore, the first internal gear 22g and the second internal gear 23g include reinforcing fibers f arranged along the axial end faces of the respective teeth 221, 231. This improves the bending strength, fatigue strength, and durability against shear force on the surface of the axial end face, and also makes it possible to strengthen the end face in multiple directions along the axial end face. Furthermore, in combination with the effect of improving the strength of the meshing surfaces 221b and 231b and the effect of improving the strength of the tooth tips 221a and 231a, it is possible to further strengthen each tooth 221, 231 as a whole.

[0058] Furthermore, in the flexible meshing gear device 1, the first internal gear 22g and the second internal gear 23g are resin gears having a unique structure with respect to the reinforcing fibers f, and the external gear 12 is a gear made of metal, so while the device is made lighter, it is possible to improve the durability of the entire device by strengthening the first internal gear 22g and the second internal gear 23g.

[0059] [others] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, in each tooth 221, 231 of the first internal gear 22g and the second internal gear 23g described above, the fiber direction is random in the deep portion d of the meshing surfaces 221b, 231b, not along the meshing surfaces 221b, 231b, thereby improving the effect of suppressing fractures and cracks along the root circle. In this way, when the fiber direction of the reinforcing fibers f is random in the deep portion d, the reinforcing fibers f on the meshing surfaces 221b, 231b may be arranged along the tooth surface and may be oriented in a uniform direction. In this case, even if the difference in strength in a certain direction between the meshing surfaces 221b, 231b and the tooth bottom surfaces 221c, 231c becomes large, the difference in strength between the inside of the meshing surfaces 221b, 231b and the inside of the tooth bottom surfaces 221c, 231c is sufficiently reduced, making it possible to sufficiently suppress the occurrence of fractures or cracks along the tooth bottom circle.

[0060] Furthermore, in the above embodiment, a characteristic configuration is applied to each tooth 221, 231 of the first internal gear 22g and the second internal gear 23g of the flexible meshing gear device 1 with respect to the fiber direction of the reinforcing fibers f in the base resin r, but a characteristic configuration with respect to the fiber direction of the reinforcing fibers f may also be applied to an external gear, and the above characteristic configuration with respect to the fiber direction of the reinforcing fibers may be applied to each tooth of a resin gear used in any type of gear mechanism, not limited to the flexible meshing gear device 1. In addition, in the case of various gear mechanisms in which an internal gear and an external gear mesh, one of the internal gear and the external gear may be a metal gear, and the other may be a resin gear to which the above-mentioned characteristic configuration is applied in the fiber direction of the reinforcing fibers.

[0061] In addition, the details shown in the above embodiment can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0062] 1 Gearing 12 External gear 23 Internal gear member 221,231 teeth 221a, 231a Tooth tip 221b, 231b mating surface 221c, 231c tooth bottom surface O1 Rotational Axis d deep part f Reinforced fiber h / 2 midpoint r Base resin

Claims

1. A resin gear molded using a molding material in which reinforcing fibers are blended with a base resin, A resin gear including reinforcing fibers arranged along the tooth surface at the meshing surface of each tooth, and the reinforcing fibers located on the tooth surface have fiber directions that are along the tooth surface and are oriented in random directions within the tooth surface.

2. The tooth tip surface of each tooth includes reinforcing fibers arranged along the tooth tip surface. The resin gear according to claim 1.

3. The axial end surface of each tooth includes reinforcing fibers arranged along the axial end surface. The resin gear according to claim 1 or 2.

4. A gear device having an internal gear and an external gear, one of the internal gear and the external gear is formed by the resin gear according to any one of claims 1 to 3, A gear device in which the other of the internal gear and the external gear is made of metal.

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