speed reducer

Abstract

To provide a speed reducer which can secure stable operation while achieving improvement of productivity.SOLUTION: A speed reducer includes: an input unit having first bearings each having an input shaft and an eccentric first inner ring which rotates with the input shaft; cycloidal gears; multiple inner peripheral pins; an inner peripheral pin holder which holds both axial ends of the inner peripheral pins and encloses an outer peripheral surface of the input unit; a second bearing disposed at the outer diameter side of the cycloidal gear and having a second inner ring serving as an output shaft, a second outer ring disposed at the outer diameter side of the second inner ring, and rolling elements disposed between the second inner ring and the second outer ring; and multiple outer peripheral pins which are held on an inner diameter surface of the second inner ring and engage with external teeth of the cycloidal gear. The first inner ring is provided separately from the input shaft. The input unit includes a movement restriction part which restricts movement of the first inner ring in a circumferential direction relative to the input shaft.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The present disclosure relates to a speed reducer.

Background Art

[0002] Conventionally, speed reducers have been used in drive control units for wheels in mobile devices, robots, machine tools, and the like. This type of technology is described in, for example, Patent Document 1.

[0003] The speed reducer described in Patent Document 1 includes an input shaft having a pair of eccentric portions, a pair of cycloid gears that contact the pair of eccentric portions, a hub that constitutes an output shaft, an output shaft pin holder, a plurality of outer peripheral pins, an outer peripheral pin holder that holds the outer peripheral pins, and an inner peripheral pin supported by the hub. The hub is supported by the outer peripheral pin holder via a cross roller bearing. The cross roller bearing includes an outer ring fixed to the outer peripheral pin holder, an inner ring fixed to the hub, and a plurality of rollers disposed between the outer ring and the inner ring.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In speed reducers, improvement in productivity is required. Also, ensuring stable operation is required. From the viewpoints of improving productivity and ensuring stable operation, the technology disclosed in Patent Document 1 described above is insufficient.

[0006] Therefore, one of the objectives is to provide a speed reducer that can improve productivity while ensuring stable operation.

Means for Solving the Problems

[0007] A gearbox according to this disclosure includes an input unit including an input shaft and a first bearing having an eccentric first inner ring that rotates with the input shaft; a cycloidal gear disposed on the outer diameter side of the first bearing and having a plurality of external teeth arranged circumferentially on its outer circumference, and having a first through hole through which the input unit passes and a plurality of second through holes arranged circumferentially spaced apart on the outer diameter side of the first through hole; a plurality of inner pins that pass through the second through holes in the axial direction; an inner pin holder that holds both axial ends of the plurality of inner pins and surrounds the outer circumference of the input unit; a second bearing disposed on the outer diameter side of the cycloidal gear and including a second inner ring which is an output shaft, a second outer ring disposed on the outer diameter side of the second inner ring, and rolling elements disposed between the second inner ring and the second outer ring; and a plurality of outer pins held on the inner diameter surface of the second inner ring and meshing with the external teeth of the cycloidal gear. The first inner ring is provided separately from the input shaft. The input unit includes a movement restricting section that restricts the circumferential movement of the first inner ring relative to the input shaft. [Effects of the Invention]

[0008] The above-described gearbox makes it possible to improve productivity while ensuring stable operation. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic perspective view showing a speed reducer in Embodiment 1 of the present disclosure. [Figure 2] Figure 2 is a schematic front view of the gearbox shown in Figure 1. [Figure 3] Figure 3 is a schematic side view of the gearbox shown in Figure 1. [Figure 4] Figure 4 is a schematic rear view of the gearbox shown in Figure 1. [Figure 5] Figure 5 is a schematic cross-sectional view obtained when the section is cut along the line segment VV in Figure 2. [Figure 6] Figure 6 is a magnified view of a portion of the cross-section of the gearbox shown in Figure 5. [Figure 7] Figure 7 is a magnified view of a portion of the cross-section of the gearbox shown in Figure 5. [Figure 8] FIG. 8 is a schematic cross-sectional view when cut along the line segment VIII-VIII in FIG. 5. [Figure 9] FIG. 9 is a schematic cross-sectional view when cut along the line segment IX-IX in FIG. 5. [Figure 10] FIG. 10 is a schematic perspective view showing a part of an input unit included in a speed reducer. [Figure 11] FIG. 11 is an exploded perspective view showing a part of the input unit shown in FIG. 10 in an exploded manner. [Figure 12] FIG. 12 is a schematic perspective view in which the illustration of a part of the input unit shown in FIG. 10 is omitted by a dashed line. [Figure 13] FIG. 13 is a schematic perspective view showing a part of a first bearing included in the input unit. [Figure 14] FIG. 14 is a schematic cross-sectional view showing a part of the input unit shown in FIG. 10. [Figure 15] FIG. 15 is a schematic cross-sectional view showing a part of the input unit shown in FIG. 10. [Figure 16] FIG. 16 is a schematic perspective view in which a part of an inner peripheral pin is shown by a dashed line. [Figure 17] FIG. 17 is a schematic perspective view of an inner peripheral pin holder showing a state in which the inner peripheral pin is held by combining a first holder part and a second holder part. [Figure 18] FIG. 18 is a schematic perspective view of the first holder part. [Figure 19] FIG. 19 is a schematic perspective view of the second holder part. [Figure 20] FIG. 20 is a view of a cycloid gear seen from the axial direction. [Figure 21] FIG. 21 is a schematic perspective view of a second outer ring. [Figure 22] FIG. 22 is a schematic cross-sectional view showing a part of the speed reducer shown in FIG. 5 in an enlarged manner. [Figure 23] FIG. 23 is a schematic cross-sectional view showing a part of the second outer ring in an enlarged manner. [Figure 24] FIGS. 24 and 25 are schematic perspective views of a second inner ring. [Figure 25]Figs. 24 and 25 are schematic perspective views of the second inner ring. [Figure 26] Fig. 26 is a schematic cross-sectional view showing an enlarged part of the speed reducer including the second inner ring. [Figure 27] Fig. 27 is a schematic cross-sectional view showing an enlarged part of the second inner ring and one outer peripheral pin. [Figure 28] Fig. 28 is a schematic view further enlarging a part of the second inner ring and one outer peripheral pin shown in Fig. 27. [Figure 29] Fig. 29 is a schematic view showing an example of a cylindrical grinding machine used when grinding the second inner ring.

Embodiments for Carrying out the Invention

[0010] [Summary of the Embodiment] The speed reducer of the present disclosure includes an input unit including an input shaft and a first bearing having an eccentric first inner ring that rotates with the input shaft, a cycloid gear disposed on the outer diameter side of the first bearing, having a plurality of external teeth arranged along the circumferential direction on the outer circumferential surface, provided with a first through hole through which the input unit passes, and a plurality of second through holes arranged at intervals in the circumferential direction on the outer diameter side of the first through hole, a plurality of inner circumferential pins axially penetrating the second through holes, an inner circumferential pin holder holding both axial ends of the plurality of inner circumferential pins and surrounding the outer circumferential surface of the input unit, a second bearing disposed on the outer diameter side of the cycloid gear, including a second inner ring that is an output shaft, a second outer ring disposed on the outer diameter side of the second inner ring, and rolling elements disposed between the second inner ring and the second outer ring, and a plurality of outer circumferential pins held on the inner diameter surface of the second inner ring and meshing with the external teeth of the cycloid gear. The first inner ring is provided separately from the input shaft. The input unit includes a movement restricting portion that restricts the circumferential movement of the first inner ring with respect to the input shaft.

[0011] With this configuration, the input unit's components, such as the input shaft and the first inner ring, can be constructed using different materials. This allows for the selection of materials suitable for the required function of each component, enabling the assembly of the input unit. In this case, since it includes a movement restricting section that restricts the circumferential movement of the first inner ring relative to the input shaft, the circumferential positioning of the first inner ring can be reliably ensured, and the first inner ring can be reliably rotated together with the input shaft. Therefore, stable operation of the reduction gear can be ensured. Furthermore, because each component is made of separate parts, it becomes easier to improve the precision of grinding, for example, an eccentric first inner ring, thereby improving productivity. Moreover, because the first inner ring is a separate part, it becomes easier to change the eccentricity of the first inner ring and select for different precision, which was difficult with an integrated input unit. In other words, a first inner ring manufactured according to the required specifications can be selected and combined with a separately manufactured input shaft to produce an input unit that meets the requirements. Of course, since the input shaft is also a separate part, it becomes easier to perform additional machining on the input shaft or to incorporate design changes according to the application. Specifically, the input shaft, one of the components constituting the input unit, can be made of a light metal such as aluminum or resin, taking into consideration high-speed rotation, weight reduction, and torque resistance. The first inner ring can be made of bearing steel from the perspective of improving durability. As a result, such a gearbox can ensure stable operation while improving productivity.

[0012] In the above-described reduction gear, the movement restricting unit may restrict the axial movement of the first inner ring relative to the input shaft. By doing so, the positioning of the first inner ring in the axial direction can be reliably ensured, and more stable operation of the reduction gear can be secured.

[0013] In the above-described reduction gear, the movement restricting section may include a first key groove recessed from the outer circumferential surface of the input shaft, a second key groove recessed from the inner circumferential surface of the first inner ring, and a key member that fits into both the first and second key grooves. By fitting the key member into the first and second key grooves in this way, the circumferential positioning of the first inner ring can be reliably achieved.

[0014] In the above-described reduction gear, the first keyway may be provided so as to extend axially in a portion of the circumferential surface of the input shaft. The second keyway may be provided at a position opposite to the first keyway. The key member may be a rod-shaped member extending axially. By doing so, the circumferential positioning of the first inner ring can be achieved more reliably with a relatively simple structure.

[0015] In the above-described speed reducer, a flange portion projecting toward the outer diameter may be provided at least one axial end of the first inner ring. By doing so, for example, when the needle rollers contained in a needle cage, which is composed of needle rollers and a cage that holds the needle rollers, roll on the outer circumferential surface of the first inner ring as the raceway surface, the axial movement of the cage contained in the needle cage can be restricted by the flange portion. Therefore, more stable operation of the speed reducer can be ensured.

[0016] In the above-described speed reducer, the input unit is provided separately from the input shaft and the first inner ring, and may further include a disc-shaped guide ring positioned on at least one side in the axial direction of the first inner ring, projecting outward from the raceway surface of the first inner ring. In this way, the axial movement of the retainer included in the needle cage described above can also be restricted by the guide ring. Therefore, even more stable operation of the speed reducer can be ensured. Similarly, the guide ring included in the input unit can be selected regardless of the material of the other components, and can be made of a resin such as fiber-containing PEEK, or a light metal such as aluminum.

[0017] In the above-described reduction gear, the first bearings may be provided in pairs aligned in the axial direction. The pair of first inner rings included in each pair of first bearings may be arranged with a 180-degree phase difference in the circumferential direction. By doing so, the influence of the eccentric first inner rings during rotation of the input shaft can be reduced, thereby ensuring more stable rotation of the input shaft.

[0018] In the above-described reduction gear, the first inner ring may be fixed to the input shaft by an interference fit. By doing so, the axial movement of the first inner ring relative to the input shaft can also be restricted.

[0019] [Specific examples of embodiments] Next, an example of a specific embodiment of the speed reducer of this disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and their descriptions will not be repeated.

[0020] (Embodiment 1) First, Embodiment 1, which is an embodiment of the present disclosure, will be described. Figure 1 is a schematic perspective view showing the speed reducer in Embodiment 1 of the present disclosure. Figure 2 is a schematic front view of the speed reducer shown in Figure 1. Figure 3 is a schematic side view of the speed reducer shown in Figure 1. Figure 4 is a schematic rear view of the speed reducer shown in Figure 1. Figure 5 is a schematic cross-sectional view when cut along the cross section indicated by line segment VV in Figure 2. Figures 6 and 7 are enlarged views of a part of the cross section of the speed reducer shown in Figure 5. Figure 6 is a cross-sectional view when cut at a circumferential position that does not include the cover portion, which will be described later. Figure 7 is a cross-sectional view when cut at a circumferential position that includes the cover portion, which will be described later. Figure 8 is a schematic cross-sectional view when cut along the cross section indicated by line segment VIII-VIII in Figure 5. Figure 9 is a schematic cross-sectional view when cut along the cross section indicated by line segment IX-IX in Figure 5. Note that arrow D1 in Figure 5 etc. indicates the axial direction, and arrow D2 indicates the radial direction. Also, the dashed line R1 indicates the rotational center axis of the speed reducer 10a.

[0021] Referring to Figures 1 to 9, the gearbox 10a in Embodiment 1 of this disclosure reduces the rotational speed of the high-speed rotating input shaft 11a and outputs it from the output shaft, which will be described later. In this embodiment, the reduction ratio is 1 / 36. That is, for example, when the rotational speed of the input shaft is 3000 rpm (revolutions per minute), the rotational speed of the output shaft will be approximately 83.3 rpm. The reduction ratio can, of course, be arbitrarily determined according to requirements, depending on the number of teeth of the cycloidal gear, the number of outer pins, the degree of eccentricity of the first inner ring, etc., which will be described later.

[0022] The gearbox 10a includes an input unit 12a having an input shaft 11a and first bearings 31a and 31b, each having an eccentric first inner ring 32a and 32b that rotate with the input shaft 11a; cycloidal gears 13a and 13b; a plurality of inner pins 14a; an inner pin holder 15a; a second bearing 16a including a second inner ring 81a and a second outer ring 81b; and a plurality of outer pins 17a. The first bearings 31a and 31b and the cycloidal gears 13a and 13b are each arranged in pairs in the axial direction. The following describes each component.

[0023] The input shaft 11a has a hollow cylindrical shape. Specifically, the input shaft 11a is provided with a shaft through hole 23a that extends axially from a first shaft end 21a, which is one end in the axial direction, to a second shaft end 21b, which is the other end in the axial direction. A shaft internal circumferential keyway 24a is provided on the inner circumferential surface 25a of the input shaft 11a that constitutes the shaft through hole 23a. The shaft internal circumferential keyway 24a is provided by recessing a part of the circumferential direction of the inner circumferential surface 25a toward the outer diameter. By utilizing such a shaft internal circumferential keyway 24a, when the motor's rotating shaft (not shown) is connected to the input shaft 11a, it is possible to suppress the input shaft 11a from sliding in the rotational direction relative to the rotating shaft. The outer circumferential surface 25b of the input shaft 11a is configured to extend straight in the axial direction. The inner circumferential surface 25a of the input shaft 11a is configured to extend straight in the axial direction, except for the area in which the shaft internal circumferential keyway 24a is provided. Since such an input shaft 11a has a relatively simple configuration, costs can be reduced. If necessary, the input shaft 11a may be a solid cylindrical shape.

[0024] The material of the input shaft 11a can be, for example, metal. In this embodiment, aluminum is used as the material of the input shaft 11a. However, the material of the input shaft 11a can be any material that can withstand the torque of the motor, such as resin.

[0025] Two bearings, a first input shaft bearing 29a and a second input shaft bearing 29b, are mounted on the input shaft 11a to support it. The first input shaft bearing 29a is mounted on the first shaft end 21a side, and the second input shaft bearing 29b is mounted on the second shaft end 21b side. The first input shaft bearing 29a and the second input shaft bearing 29b are spaced apart in the axial direction. The inner rings of both the first input shaft bearing 29a and the second input shaft bearing 29b are fixed to the input shaft 11a. The outer rings of both the first input shaft bearing 29a and the second input shaft bearing 29b are fixed to an inner circumferential pin holder 15a, which will be described later. The first input shaft bearing 29a and the second input shaft bearing 29b are, for example, deep groove ball bearings. The input shaft 11a is rotatably supported by the first input shaft bearing 29a and the second input shaft bearing 29b. The first input shaft bearing 29a is in axial contact with the stepped portion 78a of the first holder portion 71a included in the inner circumferential pin holder 15a, which will be described later, and its axial movement is restricted. Similarly, the second input shaft bearing 29b is in axial contact with the stepped portion 78b of the second holder portion 71b included in the inner circumferential pin holder 15a, which will be described later, and its axial movement is restricted.

[0026] Next, the detailed configuration of the input unit 12a will be described. Figure 10 is a schematic perspective view showing a part of the input unit 12a included in the reduction gear 10a. Figure 11 is an exploded perspective view showing a part of the input unit 12a shown in Figure 10 in an exploded view. Figure 12 is a schematic perspective view showing a part of the input unit 12a shown in Figure 10 with dashed lines indicating its absence. Figure 13 is a schematic perspective view showing a part of the first bearing 31a included in the input unit 12a. Figure 14 is a schematic cross-sectional view showing a part of the input unit 12a shown in Figure 10. Figure 14 is a cross-sectional view when cut through a plane containing the rotational axis of the first bearing 31a. Figure 15 is a schematic cross-sectional view showing a part of the input unit 12a shown in Figure 10. Figure 15 is a cross-sectional view including the first bearing 31a when cut through a plane perpendicular to the axial direction.

[0027] Referring to Figures 10 to 15, as described above, the input unit 12a includes an input shaft 11a, a first bearing 31a, and a first bearing 31b. The first bearing 31a includes an eccentric first inner ring 32a that rotates with the input shaft 11a, a first outer ring 33a positioned on the outer diameter side of the first inner ring 32a, and a needle cage 36a. The needle cage 36a consists of a plurality of needle rollers 34a as rolling elements positioned radially between the first inner ring 32a and the first outer ring 33a, and a cage 35a that holds the plurality of needle rollers 34a. The needle rollers 34a included in the needle cage 36a, which is composed of the needle rollers 34a and the cage 35a that holds the needle rollers 34a, roll on the outer circumferential surface of the first inner ring 32a as the raceway surface. The first bearing 31b includes an eccentric first inner ring 32b that rotates with the input shaft 11a, a first outer ring 33b positioned on the outer diameter side of the first inner ring 32b, and a needle cage 36b. The needle cage 36b consists of a plurality of needle rollers 34b as rolling elements positioned radially between the first inner ring 32b and the first outer ring 33b, and a cage 35b that holds the plurality of needle rollers 34b. The needle rollers 34b included in the needle cage 36b, which is composed of the needle rollers 34b and the cage 35b that holds the needle rollers 34b, roll on the outer circumferential surface of the first inner ring 32b as the raceway surface. The first inner rings 32a and 32b are fixed to the input shaft 11a by interference fit. The first bearings 31a and 31b are positioned axially between the first input shaft bearing 29a and the second input shaft bearing 29b, respectively. The first input shaft bearing 29a and the first bearing 31a are arranged adjacent to each other in the axial direction, and the second input shaft bearing 29b and the first bearing 31b are arranged adjacent to each other in the axial direction.

[0028] In the gearbox 10a of this disclosure, the first inner ring 32a included in the first bearing 31a and the first inner ring 32b included in the first bearing 31b are each provided separately from the input shaft 11a. The input unit 12a includes movement restricting parts 40a and 40b that restrict the movement of the first inner rings 32a and 32b relative to the input shaft 11a. The movement restricting parts 40a and 40b included in the input unit 12a include first keyways 41a and 41b, second keyways 42a and 42b, and key members 43a and 43b. The first keyways 41a and 41b are each provided so as to be recessed from the outer circumferential surface 25b of the input shaft 11a. In this embodiment, the first keyways 41a and 41b are each provided so as to extend axially in a part of the circumferential direction of the outer circumferential surface 25b of the input shaft 11a. The first keyways 41a and 41b are provided at different positions in the axial and circumferential directions, respectively. Specifically, in the axial direction, the first keyway 41a is formed between the position where the guide ring 49a is positioned and the first shaft end 21a, and the first keyway 41b is formed between the position where the guide ring 49a is positioned and the second shaft end 21b. In the circumferential direction, the first keyway 41a is provided at a position rotated 180 degrees from the first keyway 41b. Furthermore, the first keyways 41a and 41b are provided at positions rotated 90 degrees in the circumferential direction from the position where the inner circumferential surface keyway 24a is provided.

[0029] The second keyways 42a and 42b are provided so as to be recessed from the inner circumferential surfaces of the first inner rings 32a and 32b. In this embodiment, the second keyways 42a and 42b are provided so as to penetrate the first inner rings 32a and 32b in a groove-like manner in the axial direction in a part of the circumferential direction. The second keyways 42a and 42b are provided in the region of the first inner rings 32a and 32b in the circumferential direction where the eccentricity is greatest. The second keyways 42a and 42b are provided at positions corresponding to the first keyways 41a and 41b when the first inner rings 32a and 32b are attached to the input shaft 11a and arranged so that the inner circumferential surfaces of the first inner rings 32a and 32b face the outer circumferential surface of the input shaft 11a.

[0030] The key members 43a and 43b are each rod-shaped with a rectangular cross-section. The key members 43a and 43b are shaped to fit into the space formed by the first key grooves 41a and 41b and the second key grooves 42a and 42b when the second key grooves 42a and 42b are positioned opposite the first key grooves 41a and 41b, respectively. In other words, the key members 43a and 43b are shaped to fit into the first key grooves 41a and 41b and the second key grooves 42a and 42b, respectively. The corners at both ends of the key members 43a and 43b are rounded.

[0031] The axial ends of the first inner rings 32a and 32b are provided with flanges 37a and 37b that extend outward. The input unit 12a is disc-shaped and is positioned on one axial side of the first inner rings 32a and 32b, and includes a guide ring 49a that protrudes outward from the raceway surface of the first inner ring 32a. The guide ring 49a is positioned on the other axial side of each of the first inner rings 32a and 32b. That is, the first bearing 31a and the first bearing 31b are positioned axially with the guide ring 49a in between. The flange 37a is positioned on one axial end of the raceway surface of the first inner ring 32a, and the guide ring 49a is positioned on the other axial end of the raceway surface of the first inner ring 32a. A ring-shaped collar 48a is positioned on one axial side of the first inner ring 32a to adjust the axial gap when the first inner ring 32a is installed. A flange 37b is positioned at one axial end of the raceway surface of the first inner ring 32b, and a guide ring 49a is positioned at the other axial end of the raceway surface of the first inner ring 32b. A ring-shaped collar 48b is positioned on one axial side of the first inner ring 32b to adjust the axial gap when the first inner ring 32b is installed. In this embodiment, the guide ring 49a is made of metal and may be heat-treated and ground. Specifically, the guide ring 49a is made of duralumin and may be anodized or otherwise treated.

[0032] Next, the assembly of the input unit 12a will be briefly explained. First, the input shaft 11a is prepared. Then, the guide ring 49a is inserted from one side in the axial direction, and the key members 43a and 43b are fitted into the first key grooves 41a and 41b, respectively. The guide ring 49a is sandwiched between the axial ends of the two opposing key members 43a and 43b and fixed in the axial direction. In this way, the guide ring 49a is positioned in the axial direction. Then, the first inner ring 32a, with the needle cage 36a attached to its outer diameter side, is inserted from one side in the axial direction, from the side where the flange portion 37a is not located. At this time, it is fitted so that the circumferential position of the second key groove 42a is the position of the key member 43a. Then, the first inner ring 32a is pushed in the axial direction until the end face of the first inner ring 32a on the side where the flange portion 37a is not located contacts the guide ring 49a. In this way, the first inner ring 32a is fitted onto the input shaft 11a. The retainer 35a of the needle cage 36a is sandwiched between the guide ring 49a and the flange 37a of the first inner ring 32a, and is restricted in the axial direction. The first inner ring 32b, with the needle cage 36b attached to its outer diameter side, is inserted from the other axial side, from the side where the flange 37b is not located. The first inner ring 32b is then pushed in the axial direction until the end face of the first inner ring 32b on the side where the flange 37b is not located contacts the guide ring 49a. At this time, as with the first inner ring 32a, it is fitted so that the circumferential position of the second keyway 42b is at the position of the key member 43b. The retainer 35b of the needle cage 36b is sandwiched between the guide ring 49a and the flange 37b of the first inner ring 32b, and is restricted in the axial direction. In this manner, the first inner rings 32a and 32b are fitted onto the input shaft 11a. The fit between the first inner rings 32a and 32b and the input shaft 11a is an interference fit. Specifically, for example, the first inner rings 32a and 32b are press-fitted onto the input shaft 11a, and are also assembled by shrink-fitting. After that, the collars 48a and 48b are inserted from the axial direction. In this way, the input unit 12a is assembled.

[0033] Next, the configuration of the inner circumferential pin 14a will be described. Figure 16 is a schematic perspective view showing a part of the inner circumferential pin 14a with dashed lines. Referring to Figure 16 as well, the inner circumferential pin 14a includes a hollow cylindrical shaft portion 61a, two annular inner circumferential pin outer rings 62a and 62b, each having an inner diameter larger than the outer diameter of the shaft portion 61a, a plurality of rollers 63a as rolling elements positioned between the outer circumferential surface of the shaft portion 61a and the inner circumferential surfaces of the inner circumferential pin outer rings 62a and 62b, and a plurality of thrust washers 64a, 64b, 64c, and 64d arranged in the thrust direction. In other words, the inner circumferential pin 14a is composed of a rolling bearing with a plurality of rollers 63a as rolling elements. The inner circumferential pin outer rings 62a and 62b are arranged in the axial direction with the thrust washers 64b and 64c in between. The thrust washers 64a, 64b, 64c, and 64d are each made of a thermoplastic resin such as PEEK (Polyetheretherketone), but are not limited to this. The inner circumferential pin 14a does not include a so-called cage and is of the full-complement type. The inner circumferential pin 14a may be made of a sliding bearing. The inner circumferential pin 14a functions as a so-called planetary shaft. In this embodiment, a total of eight inner circumferential pins 14a are provided.

[0034] Next, the configuration of the inner circumference pin holder 15a will be described. The inner circumference pin holder 15a includes a first holder portion 71a and a second holder portion 71b. The inner circumference pin holder 15a supports both ends of the inner circumference pin 14a, specifically the shaft portion 61a included in the inner circumference pin 14a. When the shaft portion 61a of the inner circumference pin 14a is a planetary axis, the inner circumference pin holder 15a functions as a planetary axis support portion that supports the planetary axis. Figure 17 is a schematic perspective view of the inner circumference pin holder 15a showing the state in which the inner circumference pin 14a is held by combining the first holder portion 71a and the second holder portion 71b. Figure 18 is a schematic perspective view of the first holder portion 71a. Figure 19 is a schematic perspective view of the second holder portion 71b. In Figure 17, thrust washers 65a, 65b, 65c, and 65d are also shown.

[0035] Referring together to Figures 17, 18, and 19, the first holder portion 71a includes a disc-shaped plate portion 72a with a through hole extending through the thickness direction at its radial center, and a plurality of support columns 73a protruding in the thickness direction from one surface of the plate portion 72a in the thickness direction. The plate portion 72a and the plurality of support columns 73a are integrally molded. In this embodiment, four support columns 73a are provided at 90-degree intervals. The plate portion 72a has a plurality of press-fit holes 74a spaced apart in the circumferential direction, into which one end of the shaft portion 61a of the inner circumference pin 14a can be press-fitted. The press-fit holes 74a penetrate the plate portion 72a in the thickness direction, and a total of eight are provided, corresponding to the number of inner circumference pins 14a. In addition, an annular groove 75a recessed toward the inner diameter side is provided on the outer circumferential surface of the plate portion 72a from the viewpoint of weight reduction.

[0036] The support column 73a is the part that connects the plate-shaped part 72a of the first holder part 71a to the second holder part 71b. A total of four support columns 73a are provided. When assembled into the reduction gear 10a, each support column 73a is positioned within the second through holes 52a, 52b of the cycloidal gears 13a, 13b, which will be described later. Both circumferential sides of the support column 73a are recessed in an arc shape in the circumferential direction when viewed in the axial direction, so as to conform to the outer shape of the inner pin outer rings 62a, 62b included in the inner pin 14a. Both radial sides of the support column 73a are arc-shaped when viewed in the axial direction. Each support column 73a is provided with a screw hole 76a recessed in the thickness direction of the plate-shaped part 72a, which is used when attaching the first holder part 71a to the second holder part 71b. In this embodiment, four screw holes 76a are provided at 90-degree intervals in the circumferential direction. Furthermore, from the viewpoint of weight reduction, in the thickness direction of the plate-like portion 72a, on the surface opposite to the surface from which the support column 73a protrudes, an annular groove 77a is provided on the outer diameter side of the through hole provided in the radial center, recessed in the thickness direction.

[0037] The second holder portion 71b is disc-shaped with a through hole that penetrates in the thickness direction located in the center in the radial direction. The second holder portion 71b includes a first portion 72b located on the radial center side and a second portion 73b located on the outer diameter side of the first portion 72b and thinner than the first portion 72b. The first portion 72b has multiple press-fit holes 74b spaced apart in the circumferential direction, into which the other end of the shaft portion 61a of the inner circumference pin 14a can be press-fitted. The press-fit holes 74b penetrate in the thickness direction of the second holder portion 71b and there are a total of eight of them, corresponding to the number of inner circumference pins 14a. The outer circumferential surface of the first portion 72b is provided with an annular groove 75b that is recessed inward from the viewpoint of weight reduction. The first portion 72b has multiple through holes 76b spaced apart in the circumferential direction, which penetrate in the thickness direction of the first portion 72b and are used when attaching the first holder portion 71a to the second holder portion 71b. In this embodiment, four through holes 76b are provided at 90-degree intervals, corresponding to the number and arrangement of screw holes 76a. In addition, the second portion 73b of the second holder portion 71b is provided with notches 79b along the outer circumference to reduce the thickness at circumferential intervals. Furthermore, through holes are provided in the area where the notches 79b are provided, penetrating in the axial direction. These notches 79b and through holes are provided at positions corresponding to the bolt holes 89b of the second outer ring 81b, which will be described later, and the second outer ring 81b is fixed to the second holder portion 71b via bolts 27a.

[0038] A brief explanation of one example of how to assemble the inner circumference pin holder 15a is as follows. First, one end of the shaft portion 61a of the eight inner circumference pins 14a is press-fitted into the eight press-fit holes 74a of the first holder portion 71a. The other end of the shaft portion 61a of the inner circumference pins 14a is press-fitted into the eight press-fit holes 74b of the second holder portion 71b. Then, using the four prepared bolts 26a, the body of each bolt 26a is passed through the four through holes 76b and fastened using the four screw holes 76a to assemble the inner circumference pin holder 15a. The support column 73a, which is positioned between the two inner circumference pins 14a and the two inner circumference pins 14a in the circumferential direction, is positioned in the second through holes 52a of the cycloidal gears 13a and 13b, which will be described later.

[0039] Next, the configuration of the cycloidal gear 13b will be described. Figure 20 is a view of the cycloidal gear 13b from the axial direction. Referring to Figure 20, the cycloidal gear 13b is positioned on the outer diameter side of the first bearing 31a. The cycloidal gear 13b has a plurality of external teeth 50b arranged along the circumferential direction on its outer surface. In this embodiment, the external teeth 50b have the shape of an epitrochoidal parallel curve. In this embodiment, the number of external teeth 50b is 35. The cycloidal gear 13b is provided with a first through-hole 51b, which is a circular hole through which the input unit 12a passes, and a plurality of second through-holes 52b, which are arranged at circumferential intervals on the outer diameter side of the first through-hole 51b. From the viewpoint of reducing the weight of the reducer 10a, the cycloidal gear 13b is further provided with a plurality of third through-holes 53b, which are circular holes, positioned between each of the plurality of second through-holes 52b, which are arranged at circumferential intervals on the outer diameter side of the first through-hole 51b. Each of the multiple third through holes 53b is provided between adjacent second through holes 52b in the circumferential direction. In this embodiment, there are four of each of the multiple second through holes 52b and the multiple third through holes 53b. The first outer ring 33b of the first bearing 31b is fitted into the first through hole 51b of the cycloidal gear 13b. The second through hole 52b is an elongated hole extending along the circumferential direction, and the radially positioned wall surface has an arc-shaped portion. There is a circumferential gap between the second through hole 52b and the two inner circumferential pins 14a located within the second through hole 52b. There is also a gap between the cycloidal gear 13b and the outer circumferential pin 17a, which will be described later.

[0040] Like the cycloidal gear 13b, the cycloidal gear 13a has a plurality of external teeth 50a arranged circumferentially on its outer surface. Furthermore, like the cycloidal gear 13b, the cycloidal gear 13a is provided with a first through hole 51a, a plurality of second through holes 52a, and a plurality of third through holes 53a. Since the configuration of the cycloidal gear 13a is the same as that of the cycloidal gear 13b, a detailed explanation is omitted.

[0041] Next, the configuration of the outer peripheral pin 17a will be briefly described. The outer peripheral pin 17a is a solid cylindrical shape. Both ends of the outer peripheral pin 17a in the axial direction are chamfered. The outer peripheral pin 17a is positioned in the reduction gear 10a such that its axial direction is indicated by arrow D1. In this embodiment, there are 36 outer peripheral pins 17a. That is, there is one more pin than the number of teeth of the external teeth 50a and 50b of the cycloidal gears 13a and 13b described above. In order to restrict the axial movement of the outer peripheral pin 17a, an annular outer peripheral pin guide plate 66a and a retaining ring 67a are provided on one end of the outer peripheral pin 17a in the axial direction. The retaining ring 67a has a shape in which a part of the annular member is cut out, and can be positioned on the inner diameter side of the second inner ring 81a in a reduced diameter state on the inner diameter side. After positioning, the retaining ring 67a returns to its original shape due to elastic deformation.

[0042] Next, the configuration of the second bearing 16a, which is the main bearing, will be described. In this embodiment, the second bearing 16a, which is the main bearing of the reducer 10a, includes a second inner ring 81a having raceway surfaces 82a, 82b, a second outer ring 81b having raceway surfaces 83a, 83b, and a plurality of cylindrical rollers 84a, 84b. In the reducer 10a of Embodiment 1 of this disclosure, the second inner ring 81a of the second bearing 16a is the output shaft that reduces the rotation of the input shaft 11a and outputs the result.

[0043] The second bearing 16a is a cross-roller bearing. That is, the cylindrical rollers 84a and 84b included in the main bearing are arranged alternately orthogonally in the space provided radially between the second inner ring 81a and the second outer ring 81b. In other words, the rolling axes of two adjacent cylindrical rollers 84a and 84b in the circumferential direction are orthogonal to each other. In this embodiment, the second bearing 16a is a double-row cross-roller bearing. Specifically, the row in which the cylindrical rollers 84a are arranged and the row in which the cylindrical rollers 84b are arranged are arranged adjacent to each other in the axial direction. The second bearing 16a employs a full-roller type. That is, the second bearing 16a does not include a cage that holds the multiple cylindrical rollers 84a and 84b.

[0044] Next, the specific configurations of the second inner ring 81a and the second outer ring 81b, which are components of the second bearing 16a, will be described. First, the configuration of the second outer ring 81b will be described. Figure 21 is a schematic perspective view of the second outer ring 81b. Figure 22 is a schematic cross-sectional view showing an enlarged portion of the reduction gear 10a shown in Figure 5. Figure 23 is a schematic cross-sectional view showing an enlarged portion of the second outer ring 81b. Referring together to Figures 21, 22, and 23, the second outer ring 81b is annular in shape, and has two rows of raceway surfaces 83a and 83b on its inner circumferential surface on which cylindrical rollers 84a and 84b roll. The raceway surfaces 83a and 83b are arranged adjacent to each other in the axial direction. The raceway surfaces 83a and 83b are provided as a pair, side by side in the axial direction, and each is provided so as to be recessed toward the outer diameter in a V-shaped cross-section. The pair of raceway surfaces 83a and 83b are inclined at 45 degrees with respect to the axial direction. Between the axial directions of the raceway surfaces 83a and 83b, an annular oil groove 85a is provided, recessed toward the outer diameter in a V-shaped cross-section. Similarly, an annular oil groove 85b is provided on the outer circumferential surface of the second outer ring 81b, recessed toward the inner diameter in a V-shaped cross-section. In the axial direction, the positions of the oil grooves 85a and 85b are the same. Furthermore, an oil hole 86a is provided, extending radially through to connect the oil grooves 85a and 85b. In the axial direction, an annular groove 87a recessed toward the outer diameter is provided at the opening of the second outer ring 81b on the side opposite to the bolt hole 89b (described later). This annular groove 87a can be used to attach a seal to enhance sealing performance. In this embodiment, no seal is used and is not shown.

[0045] The second outer ring 81b is provided with insertion holes 44a and 44b that penetrate from the outer circumferential surface to the area where the cylindrical rollers 84a and 84b are arranged, and into which the cylindrical rollers 84a and 84b are inserted. Multiple cylindrical rollers 84a and 84b are sequentially inserted through the insertion holes 44a and 44b. After all the cylindrical rollers 84a and 84b have been inserted, spacers 45a are inserted to adjust the circumferential gap between the cylindrical rollers 84a and 84b. After all the components have been inserted, the insertion holes 44a and 44b are closed by covers 46a and 46b. The covers 46a and 46b are fixed by cover fixing pins 47b that penetrate the covers 46a and 46b and a part of the second outer ring 81b in the axial direction. Furthermore, from the viewpoint of weight reduction, the second outer ring 81b is provided with multiple elongated holes 55a that are oriented longitudinally in the circumferential direction and penetrate radially, at equal intervals in the circumferential direction. Furthermore, the second outer ring 81b is provided with a plurality of bolt holes 89b spaced apart in the circumferential direction. Using these bolt holes 89b, the second outer ring 81b can be attached to the inner circumferential pin holder 15a, specifically the second holder portion 71b, via bolts 27a. In other words, the second outer ring 81b also serves as a fixed part and, like the inner circumferential pin holder 15a, is a component that does not rotate or revolve.

[0046] Next, the configuration of the second inner ring 81a will be described. Figures 24 and 25 are schematic perspective views of the second inner ring 81a. Figures 24 and 25 show the second inner ring 81a viewed from different directions. Figure 26 is a schematic cross-sectional view showing an enlarged portion of the reducer 10a including the second inner ring 81a. In Figure 26, some components are omitted from the illustration. Figure 27 is a schematic cross-sectional view showing an enlarged portion of the second inner ring 81a and one outer peripheral pin 17a. Figure 28 is a schematic diagram showing a further enlargement of the portion of the second inner ring 81a and one outer peripheral pin 17a shown in Figure 27. For ease of understanding, the outer peripheral pin 17a is also shown in Figures 24 to 28.

[0047] Referring to Figures 24, 25, 26, 27, and 28, the second inner ring 81a is an annular member, and its outer circumferential surface is provided with raceway surfaces 82a, 82a on which cylindrical rollers 84a, 84b roll. From the viewpoint of weight reduction, the second inner ring 81a has multiple elongated holes 54a that are oriented longitudinally in the circumferential direction and penetrate radially, spaced equally apart in the circumferential direction. In addition, the second inner ring 81a has multiple oil holes 58a that are oriented longitudinally in the circumferential direction and penetrate radially, spaced equally apart in the circumferential direction.

[0048] The raceway surfaces 82a and 82b are arranged adjacent to each other in the axial direction. A pair of raceway surfaces 82a and 82b are provided side by side in the axial direction, and each is provided so as to be recessed inward in a V-shaped cross section. The pair of raceway surfaces 82a and 82b are inclined at 45 degrees with respect to the axial direction. The raceway surfaces 82a and 82b are configured to accommodate the cylindrical rollers 84a and 84b in the space formed radially between them and the raceway surfaces 83a and 83b of the opposing second outer ring 81b. The cylindrical rollers 84a and 84b are arranged between the raceway surfaces 82a, 82b, 83a, and 83b in the form of a cross-roller bearing, that is, alternately arranged so that the rolling axes of the cylindrical rollers 84a and 84b are perpendicular to each other.

[0049] Here, the inner circumferential surface of the second inner ring 81a is provided with a plurality of outer circumferential pin housing grooves 90a that are recessed toward the outer diameter when viewed in the axial direction, arranged along the circumferential direction, and accommodating the outer circumferential pins 17a. The wall surface 91a constituting the outer circumferential pin housing grooves 90a includes a curved surface that constitutes part of an arc surface when viewed in the axial direction. The wall surface 91a constituting the outer circumferential pin housing grooves 90a is composed of so-called R surfaces when viewed in the axial direction. The inner circumferential surface of the second inner ring 81a is also provided with groove portions 90b that are simply recessed toward the outer diameter when viewed in the axial direction. The outer circumferential pin housing grooves 90a and groove portions 90b are arranged alternately along the circumferential direction. That is, the outer circumferential pins 17a are arranged alternately in the circumferential direction in the groove-shaped recessed portion on the inner diameter side of the second inner ring 81a.

[0050] The circumferential wall surface 91a constituting the outer pin housing groove 90a is provided with claw portions 92a and 92b that restrict the movement of the outer pin 17a from the outer pin housing groove 90a toward the inner diameter side. In this embodiment, the second bearing 16a is a double-row, specifically a cross roller bearing with two rows of rollers arranged in the axial direction. The inner circumferential surface of the second inner ring 81a has axial central portions 95a and 95b that protrude toward the inner diameter side more than the axial ends 93a, 93b, 94a, and 94b of each of the double-row cylindrical rollers 84a and 84b (see Figure 22 in particular). By adopting this configuration in which the axial central portions 95a and 95b protrude toward the inner diameter side, the wall thickness of the portion constituting the raceway surface 82a and 82b of the second inner ring 81a can be made the same as that of other portions, such as the axial ends 93a, 93b, 94a, and 94b. Therefore, a decrease in rigidity in the portion where the claw portions 92a and 92b are provided can be suppressed. The claw portions 92a and 92b are provided in the axial central portions 95a and 95b, respectively. In addition, an oil reservoir 97a for accumulating lubricating oil is formed between the axial central portions 95a and 95b.

[0051] Furthermore, when viewed in the axial direction, the pitch circle diameter (PCD) of the outer peripheral pin 17a is larger than the diameter of the virtual circle formed by connecting the positions where the claw portion 92a is provided in the circumferential direction. Specifically, if the pitch circle diameter corresponding to the virtual circle connecting the rotation centers of the outer peripheral pin 17a when viewed in the axial direction is diameter P1, and the diameter of the virtual circle formed by connecting the positions where the claw portion 92a is provided is diameter P2, then diameter P1 is larger than diameter P2. Also, the inner diameter surface of the claw portion 92a is formed as a curved surface with a single radius of curvature from the center of the virtual circle formed by connecting the positions where the claw portion 92a is provided in the circumferential direction. In this case, the radius of curvature R is represented by diameter P2 / 2.

[0052] Furthermore, the circumferential wall surface 91b that does not constitute the outer pin housing groove 90a is provided with a relief portion 96b that is recessed toward the outer diameter to reduce the wall thickness. The relief portion 96b is provided so that the external teeth 50a and 50b of the cycloidal gears 13a and 13b do not interfere with each other. The wall surface constituting the relief portion 96b is arc-shaped when viewed in the axial direction.

[0053] Next, an example of how to assemble the reduction gear 10a described above will be explained. First, prepare the input shaft 11a and the first bearings 31a and 31b as described above, and assemble the input unit 12a. At this time, press-fit the first outer rings 33a and 33b into the first through holes 51a and 51b of the cycloidal gears 13a and 13b, respectively, and assemble the input unit 12a with the cycloidal gears 13a and 13b attached. Then, place the inner circumferential pin 14a in the second through holes 52a and 52b of the cycloidal gears 13a and 13b, and attach the inner circumferential pin holder 15a from the axial direction. Also, house the outer circumferential pin 17a in the outer circumferential pin housing groove 90a provided on the inner circumferential surface of the second inner ring 81a. At this time, the outer pin 17a is fitted into the outer pin housing groove 90a from the back side of the second inner ring 81a (the side where the outer pin guide plate 66a and retaining ring 67a will be placed later). Next, the outer pin guide plate 66a and retaining ring 67a are attached to the second inner ring 81a. Then, the second outer ring 81b is attached to the outer diameter side of the second inner ring 81a. Next, multiple cylindrical rollers 84a and 84b are inserted alternately from the insertion holes 44a and 44b so that their rolling axes are perpendicular to each other, and after all the cylindrical rollers 84a and 84b have been inserted, the spacer 45a is inserted. Then, the cover portions 46a and 46b are fitted into the insertion holes 44a and 44b, and the cover fixing pin 47b is attached to secure the cover portions 46a and 46b. Subsequently, an input unit 12a, which has cycloidal gears 13a and 13b, an inner circumferential pin 14a, and an inner circumferential pin holder 15a attached, is mounted on the inner diameter side of the second inner ring 81a that houses the outer circumferential pin 17a. At this time, even if the second inner ring 81a is tilted with the front side (opposite the rear side in the axial direction) facing upward, the wall surface constituting the outer circumferential pin housing groove 90a is provided with claws 92a, so that the outer circumferential pin 17a in the outer circumferential pin housing groove 90a does not fall out from the rear side. In this way, the cycloidal gears 13a and 13b and the input unit 12a are mounted on the inner diameter side of the second inner ring 81a, and the reduction gear 10a is assembled.

[0054] Next, the operation of the gearbox 10a in Embodiment 1 of the present disclosure described above will be explained. When the input shaft 11a rotates at high speed, the eccentric first inner rings 32a and 32b of the first bearings 31a and 31b rotate accordingly. Here, for the cycloidal gears 13a and 13b, in which the first outer rings 33a and 33b of the first bearings 31a and 31b are press-fitted into the first through holes 51a and 51b, an inner circumference pin 14a is positioned in the second through holes 52a and 52b. Since the shaft portion 61a of the inner circumference pin 14a is press-fitted into the inner circumference pin holder 15a, which is a fixed portion, the inner circumference pin 14a itself does not rotate. Therefore, the cycloidal gears 13a and 13b do not revolve, but rotate while being eccentric by one pitch when the input shaft 11a rotates once. As the cycloidal gears 13a and 13b rotate by one pitch, the outer peripheral pin 17a, which meshes with the outer teeth 50a and 50b of the cycloidal gears 13a and 13b, revolves while rotating within the outer peripheral pin housing groove 90a provided on the inner surface of the second inner ring 81a. As the outer peripheral pin 17a, housed in the outer peripheral pin housing groove 90a, revolves, the wall surface provided on the inner side of the second inner ring 81a that constitutes the outer peripheral pin housing groove 90a is pushed in the direction of rotation (direction of rotation), causing the second inner ring 81a to rotate at a low speed, that is, by one pitch. In this way, the rotational speed input from the input shaft 11a is reduced and output from the second inner ring 81a. In this case, the direction of rotation of the input shaft 11a and the direction of rotation of the second inner ring 81a are the same. In this embodiment, the number of outer pins 17a is 36, and the number of external teeth 50a and 50b of the cycloidal gears 13a and 13b is 35. Therefore, the rotational speed of the second inner ring 81a, which is the output shaft, is 1 / 36 of the rotational speed of the input shaft 11a. In other words, in this embodiment, one pitch corresponds to 1 / 36 of the circumference.

[0055] According to the reduction gear 10a of this disclosure, the inner circumferential surface of the second inner ring 81a is provided with a plurality of outer circumferential pin housing grooves 90a that are recessed toward the outer diameter side when viewed in the axial direction, arranged along the circumferential direction, and accommodating the outer circumferential pin 17a. The circumferential wall surface 91a constituting the outer circumferential pin housing groove 90a is provided with claw portions 92a and 92b that restrict the movement of the outer circumferential pin 17a toward the inner diameter side from the outer circumferential pin housing groove 90a. With this configuration, even when the gap between the cycloidal gears 13a and 13b and the outer circumferential pin 17a becomes large when the cycloidal gears 13a and 13b rotate during the operation of the reduction gear 10a, the claw portions 92a and 92b can restrict the tilting of the outer circumferential pin 17a toward the inner diameter side. This stabilizes the position of the outer circumferential pin 17a within the outer circumferential pin housing groove 90a and reduces rattle of the outer circumferential pin 17a. Therefore, even when the gap between the cycloidal gears 13a, 13b and the outer pin 17a becomes larger, the catching between the cycloidal gears 13a, 13b and the outer pin 17a is suppressed, making the rotation of the outer pin 17a housed in the outer pin housing groove 90a and the rotation of the cycloidal gears 13a, 13b smoother. As a result, the generation of rotational noise during the operation of the reducer 10a is suppressed, improving quietness. In this case, the rotational smoothness of the rotating part relative to the fixed part of the reducer 10a can also be improved.

[0056] Furthermore, for the second inner ring 81a provided with such claw portions 92a and 92b, the outer peripheral pin 17a can be pre-positioned and held in the outer peripheral pin housing groove 90a. In this case, even if the second inner ring 81a is tilted with the front side facing upward while the outer peripheral pin 17a is housed in the outer peripheral pin housing groove 90a, it is possible to prevent the outer peripheral pin 17a from falling out from the rear side. Therefore, the second inner ring 81a can be assembled by tilting it with the outer peripheral pin 17a pre-positioned in the outer peripheral pin housing groove 90a, thereby improving the workability when assembling the reduction gear 10a.

[0057] In this embodiment, the circumferential wall surface 91b that does not constitute the outer pin housing groove 90a is provided with a relief portion 96b that is recessed toward the outer diameter to reduce the wall thickness. Therefore, the risk of interference between the outer teeth 50a, 50b of the cycloidal gears 13a, 13b and the inner circumferential surface of the second inner ring 81a when the cycloidal gears 13a, 13b rotate can be reduced. Consequently, the cycloidal gears 13a, 13b can be rotated more smoothly, and quietness can be improved.

[0058] In this embodiment, when viewed in the axial direction, the pitch circle diameter of the outer peripheral pin 17a is larger than the diameter of the virtual circle formed by connecting the positions where the claw portions 92a and 92b are provided in the circumferential direction. Therefore, the movement of the outer peripheral pin 17a on the inner diameter side by the claw portions 92a and 92b can be restricted more reliably.

[0059] In this embodiment, the inner circumferential surface of the second inner ring 81a protrudes inward more at the axial center portion 95a, 95b than at the axial ends 93a, 93b, 94a, 94b. Claw portions 92a, 92b are provided at the axial center portion 95a, 95b. Therefore, the contact area between the claw portions 92a, 92b and the outer circumferential pin 17a can be reduced, ensuring smooth rotation of the outer circumferential pin 17a. Furthermore, since the outer circumferential pin 17a is guided by the claw portions 92a, 92b at the axial center portion 95a, 95b, the risk of the outer circumferential pin 17a tilting in the axial direction can be reduced, ensuring more stable rotation.

[0060] In this embodiment, the inner circumferential surfaces 98a and 98b of the claw portions 92a and 92b are formed in a curved shape with a single radius of curvature from the center of a virtual circle formed by connecting the positions where the claw portions 92a and 92b are provided in the circumferential direction. Therefore, when the cycloidal gears 13a and 13b rotate, the external teeth 50a and 50b of the cycloidal gears 13a and 13b can easily overcome the positions where the claw portions 92a and 92b are provided. Consequently, the cycloidal gears 13a and 13b can rotate more smoothly, improving quietness.

[0061] In this embodiment, the second bearing 16a includes a double-row cross roller bearing in which cylindrical rollers 84a and 84b are arranged in double rows in the axial direction. Therefore, while achieving a compact configuration, the second bearing 16a can appropriately receive loads applied from various directions. Consequently, it is easier to miniaturize the reducer 10a. In addition, it becomes easier to arrange the rotational axis of the cross roller bearing and the rotational axis of the components constituting the reduction mechanism on the same plane, thereby suppressing twisting of the input shaft 11a and the output shaft, the second inner ring 81a, due to load torque.

[0062] In this embodiment, the inner circumferential surface of the second inner ring 81a has axial central portions 95a and 95b that protrude inward relative to the axial ends 93a, 93b, 94a, and 94b of each of the double rows of cylindrical rollers 84a and 84b. Claw portions 92a and 92b are provided on the axial central portions 95a and 95b. Therefore, the claw portions 92a and 92b provided on the axial central portions 95a and 95b corresponding to the cylindrical rollers 84a and 84b of each row can be brought into contact with the outer peripheral pin 17a. As a result, the outer peripheral pin 17a can be guided by multiple claw portions 92a and 92b in the axial direction, further reducing the risk of the outer peripheral pin 17a tilting in the axial direction. Therefore, even more stable rotation can be ensured.

[0063] Here, the input shaft 11a and the first bearings 31a and 31b included in the input unit 12a, specifically the eccentric first inner rings 32a and 32b included in the input shaft 11a and the first bearings 31a and 31b respectively, need to rotate together with the input shaft 11a, so it is conceivable that they be formed integrally with the input shaft 11a. In this case, for example, the input shaft 11a and the first inner rings 32a and 32b could be manufactured by machining or other means from a metal rod-shaped member of the same material. However, with such a configuration, it is not possible to differentiate the functions required for each component, specifically the input shaft 11a and the first inner rings 32a and 32b. Such a configuration is undesirable.

[0064] In the reduction gear 10a of this disclosure, the first inner rings 32a and 32b are provided separately from the input shaft 11a. The input unit 12a includes movement restricting parts 40a and 40b that restrict the circumferential movement of the first inner rings 32a and 32b relative to the input shaft 11a. With this configuration, the input unit 12a can be constructed by changing the material of each component, such as the input shaft 11a and the first inner rings 32a and 32b. This allows for the selection of a material suitable for the required function of each component and the assembly of the input unit 12a. In this case, because it includes movement restricting parts 40a that restrict the circumferential movement of the first inner rings 32a and 32b relative to the input shaft 11a, the positioning of the first inner rings 32a and 32b in the circumferential direction can be reliably ensured, and the first inner rings 32a and 32b can be reliably rotated together with the input shaft 11a. Therefore, stable operation of the reduction gear 10a can be ensured. Furthermore, because each component is made of a separate part, it becomes easier to improve the precision of grinding the eccentric first inner rings 32a and 32b, for example, thereby improving productivity. In addition, because the first inner rings 32a and 32b are separate parts, it is easy to change the eccentricity of the first inner rings 32a and 32b and select them for precision, which was difficult with an integrated input unit 12a. In other words, the first inner rings 32a and 32b manufactured according to the required specifications can be selected and combined with a separately manufactured input shaft 11a to manufacture an input unit 12a that meets the requirements. Of course, since the input shaft 11a is also a separate part, it becomes easier to perform additional machining on the input shaft 11a or to reflect design changes according to the application. Specifically, for the input shaft 11a, which is one of the components that make up the input unit 12a, light metals such as aluminum or resin can be used, taking into consideration high-speed rotation, weight reduction, and torque resistance, while bearing steel can be used for the first inner rings 32a and 32b from the perspective of improving durability. Based on the above, such a gearbox 10a can ensure stable operation while improving productivity.

[0065] In this embodiment, the movement restricting units 40a and 40b restrict the axial movement of the first inner rings 32a and 32b relative to the input shaft 11a. Therefore, the positioning of the first inner rings 32a and 32b in the axial direction can be reliably ensured, and more stable operation of the reduction gear 10a can be secured.

[0066] In this embodiment, the movement restricting sections 40a and 40b include first key grooves 41a and 41b recessed from the outer circumferential surface of the input shaft 11a, second key grooves 42a and 42b recessed from the inner circumferential surfaces of the first inner rings 32a and 32b, and key members 43a and 43b that fit into both the first key grooves 41a and 41b and the second key grooves 42a and 42b. Therefore, by fitting the key members 43a and 43b into the first key grooves 41a and 41b and the second key grooves 42a and 42b, the circumferential positioning of the first inner rings 32a and 32b can be reliably achieved.

[0067] In this embodiment, the first keyways 41a and 41b are provided so as to extend axially in a portion of the circumferential direction of the outer surface of the input shaft 11a. The second keyways 42a and 42b are provided at positions opposite to the first keyways 41a and 41b. The key members 43a and 43b are rod-shaped and extend axially. Therefore, the circumferential positioning of the first inner rings 32a and 32b can be achieved more reliably with a relatively simple structure.

[0068] In this embodiment, flanges 37a and 37b are provided at least one axial end of the first inner rings 32a and 32b, projecting outwards toward the outer diameter. Therefore, the axial movement of the retainers 35a and 35b included in the needle cages 36a and 36b can be restricted using the flanges 37a and 37b. Consequently, more stable operation of the reducer 10a can be ensured.

[0069] In this embodiment, the input unit 12a is provided separately from the input shaft 11a and the first inner rings 32a and 32b, and includes a disc-shaped guide ring 49a that is positioned on at least one side in the axial direction of the first inner rings 32a and 32b and protrudes outward from the raceway surface of the first inner rings 32a and 32b. Therefore, the axial movement of the retainers 35a and 35b included in the needle cages 36a and 36b can also be restricted by the guide ring 49a. Thus, even more stable operation of the reducer 10a can be ensured. Similarly, the guide ring 49a included in the input unit 12a can be selected regardless of the material of the other components, and can be made of a resin such as fiber-containing PEEK or a light metal such as aluminum.

[0070] In this embodiment, the first bearings 31a and 31b are provided as a pair, aligned in the axial direction. The pair of first inner rings 32a and 32b included in the pair of first bearings 31a and 31b are arranged with a 180-degree phase difference in the circumferential direction. Therefore, the influence of the eccentric first inner rings 32a and 32b during the rotation of the input shaft 11a can be reduced, ensuring more stable rotation of the input shaft 11a.

[0071] In this embodiment, the first inner rings 32a and 32b are fixed to the input shaft 11a by interference fit. Therefore, the axial movement of the first inner rings 32a and 32b relative to the input shaft 11a can also be restricted.

[0072] Next, a brief explanation will be given of an example of a manufacturing method for the second inner ring 81a, one of the components constituting the reduction gear 10a described above. First, an annular metal member is prepared and machined to approximate the outer diameter shape of the second inner ring 81a. Then, the raceway surfaces 82a and 82b, which require smoothness, are ground. Figure 29 is a schematic diagram showing an example of a cylindrical grinding machine used when grinding the second inner ring 81a. Referring to Figure 29, the cylindrical grinding machine 101a includes a grinding wheel section 102a and a rotary dresser 103a. The cylindrical grinding wheel section 102a, which grinds the mating member, includes projections 104a and 104b that protrude outward, corresponding to the raceway surfaces 82a and 82b of the second inner ring 81a. The spacing between the projections 104a and 104b is equivalent to the spacing between the raceway surfaces 82a and 82b. The rotary dresser 103a, which has a cylindrical portion, is provided with recesses 105a and 105b that are recessed on the inner diameter side corresponding to the inner circumferential surface of the second inner ring 81a.

[0073] Using such a cylindrical grinding machine 101a, the raceway surfaces 82a and 82b of the second inner ring 81a are ground. Specifically, the second inner ring 81a is attached to the outer diameter side of the rotary dresser 103a (not shown in the figure). Then, with the projections 104a and 104b pressed against the raceway surfaces 82a and 82b from the outer diameter side of the second inner ring 81a, the grinding wheel 102a attached to the spindle 106a is rotated to grind the raceway surfaces 82a and 82b.

[0074] By doing so, even if the spindle 106a expands due to thermal expansion during grinding, the risk of the gap between the raceway surfaces 82a and 82b shifting can be greatly reduced. In other words, if the raceway surfaces 82a and 82b are ground one by one, the gap between the raceway surfaces 82a and 82b will shift due to thermal expansion of the spindle 106a during grinding and processing errors of the cylindrical grinding machine 101a, resulting in a deterioration of dimensional accuracy. However, by adopting the above manufacturing method, the deviation in the gap and depth of the raceway surfaces 82a and 82b can be greatly reduced. Therefore, the second inner ring 81a can be manufactured with high accuracy. In addition, since the raceway surfaces 82a and 82b can be ground at once, the lead time can be shortened compared to grinding the raceway surfaces 82a and 82b one by one. Furthermore, by using a similar configuration for the raceway surfaces 83a and 83b of the second outer ring 81b and grinding them at once, dimensional accuracy can be improved and the lead time can be shortened.

[0075] (Other embodiments) In the above embodiment, a pair of cycloidal gears are arranged in the axial direction, but the reduction gear is not limited to this configuration, and may include a single cycloidal gear.

[0076] Furthermore, in the above embodiment, the covers for the double-row cross roller bearings were provided at the same position in the circumferential direction. However, the invention is not limited to this, and the covers may be provided at staggered positions in the circumferential direction.

[0077] In the above embodiment, a double-row cross roller bearing was used, but the design is not limited to this, and a double-row angular contact bearing may also be used. Furthermore, at least one of the first and second bearings may be replaced with another type of bearing, such as a combination of a radial bearing and an axial bearing. A sliding bearing may also be used.

[0078] In the above embodiment, the gap between the cylindrical rollers of the cross roller bearing is adjusted using spacers, but the cross roller bearing is not limited to this, and may also include a cage that holds the cylindrical rollers, or a separator that is placed between the cylindrical rollers.

[0079] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the present invention is defined by the claims and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of symbols]

[0080] 10a Reducer, 11a Input shaft, 12a Input unit, 13a,13b Cycloidal gear, 14a Inner pin, 15a Inner pin holder, 16a Second bearing, 17a Outer pin, 21a First shaft end, 21b Second shaft end, 23a Through hole, 24a Inner shaft keyway, 25a,98a Inner surface, 25b Outer surface, 26a,27a Bolt, 29a Bearing for first input shaft, 29b Bearing for second input shaft, 31a,31b First bearing, 32a,32b First inner ring, 33a,33b First outer ring, 34a,34b Needle roller, 35a,35b Cage, 36a,36b Needle cage, 37a,37b Flange, 40a,40b Movement restricting section, 41a, 41b First keyway, 42a, 42b Second keyway, 43a, 43b Key member, 44a, 44b Insertion hole, 45a Spacer, 46a, 46b Cover section, 47b Cover fixing pin, 48a, 48b Collar, 49a Guide ring, 50a, 50b External teeth, 51a, 51b First through hole, 52a, 52b Second through hole, 53a, 53b Third through hole, 54a, 55a Slotted hole, 58a, 86a Oil hole, 61a Shaft section, 62a, 62b Inner circumference pin outer ring, 63a Roller, 64a, 64b, 64c, 64d, 65a, 65b, 65c, 65d Thrust washer, 66a Outer circumference pin guide plate, 67a Retaining ring, 71a First holder section, 71b Second holder section, 72a Plate-shaped section, 72b First part, 73a Support column, 73b Second part, 74a, 74b Press-fit hole, 75a, 75b, 77a Recessed groove, 76a Screw hole, 76b Through hole, 78a, 78b Step section, 79b Notch, 81a Second inner ring, 81b Second outer ring, 82a, 82b, 83a, 83b Raceway surface, 84a, 84b Cylindrical roller, 85a, 85b Oil groove, 87a Annular groove, 89b Bolt hole, 90a Outer circumference pin housing groove, 90b Groove section, 91a, 91b Wall surface, 92a, 92b Claw section, 93a, 93b, 94a, 94b End section, 95a, 95b Central section, 96b Relief section, 97a oil reservoir, 101a cylindrical grinding machine, 102a grinding wheel section, 103a rotary dresser, 104a, 104b projections, 105a, 105b recesses, 106a spindle.

Claims

1. An input unit including an input shaft and a first bearing having an eccentric first inner ring that rotates together with the input shaft, A cycloidal gear is provided, which is located on the outer diameter side of the first bearing, has a plurality of external teeth arranged along the circumferential direction on its outer circumference, and has a first through-hole through which the input unit passes, and a plurality of second through-holes arranged at circumferential intervals on the outer diameter side of the first through-hole, Multiple inner circumferential pins that penetrate the second through hole in the axial direction, An inner circumferential pin holder that holds both axial ends of the plurality of inner circumferential pins and surrounds the outer circumferential surface of the input unit, The cycloidal gear is positioned on the outer diameter side and includes a second inner ring which is the output shaft, a second outer ring positioned on the outer diameter side of the second inner ring, and a second bearing which includes rolling elements positioned between the second inner ring and the second outer ring. The second inner ring comprises a plurality of outer peripheral pins held on the inner diameter surface and meshing with the outer teeth of the cycloidal gear, The first inner ring is provided separately from the input shaft. Multiple first bearings are provided in the axial direction, The aforementioned input unit is It includes a movement restricting unit that restricts the circumferential movement of the first inner ring relative to the input shaft, The aforementioned movement restricting portion is provided for each of the multiple first inner rings included in the first bearing, The aforementioned movement control unit is, A first key groove is provided so as to be recessed from the outer surface of the input shaft, A second keyway is provided so as to be recessed from the inner circumferential surface of the first inner ring, The system includes a key member that fits into both the first keyway and the second keyway, The first keyway, the second keyway, and the key member are provided in multiple quantities for each of the multiple first bearings. Each of the first keyways is provided so as to extend axially in a portion of the circumferential direction of the outer surface of the input shaft, Each of the second keyways is provided in a position opposite to the first keyway, Each of the aforementioned key members is rod-shaped and extends in the axial direction. Each of the second keyways is provided so as to penetrate through in a groove shape in the axial direction. The input unit is provided separately from the input shaft and the first inner ring, and further includes a guide ring that is disc-shaped, positioned on at least one side in the axial direction of the first inner ring, and protruding outward from the raceway surface of the first inner ring. The guide ring is fixed in the axial direction by being sandwiched between the axial ends of the two opposing key members. The outer surface of the input shaft is configured to extend straight in the axial direction, thereby providing a reduction gear.

2. The reduction gear according to claim 1, wherein the movement restricting unit restricts the axial movement of the first inner ring with respect to the input shaft.

3. The gearbox according to claim 1 or claim 2, wherein at least one end of the first inner ring in the axial direction is provided with a flange that protrudes toward the outer diameter.

4. The first bearing is provided in a pair, arranged in the axial direction. The gearbox according to claim 1 or claim 2, wherein the pair of first inner rings included in each of the pair of first bearings are arranged with a 180-degree phase difference in the circumferential direction.

5. The gearbox according to claim 1 or claim 2, wherein the first inner ring is fixed to the input shaft by an interference fit.

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