Reducer

Abstract

To provide a speed reducer capable of being miniaturized in an axial direction.SOLUTION: A speed reducer includes: an annular external tooth gear having a plurality of external teeth and provided with a first through hole and a plurality of second through holes arranged in a circumferential direction in a manner of surrounding the first through hole; an input shaft penetrating through the first through hole; a first bearing holding the input shaft relatively rotatably in a circumferential direction to the external tooth gear; a plurality of inner peripheral pins penetrating through the second through holes in an axial direction; inner peripheral pin holders holding both ends of the plurality of inner peripheral pins and surrounding an outer peripheral face of the input shaft; a second bearing surrounding an outer peripheral face of the external tooth gear; and internal teeth pins engaged with the external teeth. The second bearing includes: an outer ring fixed to the inner peripheral pin holders; an inner ring disposed at a radial inner side with respect to the outer ring and constituting an output shaft rotating at a speed lower than the input shaft; and rolling elements kept into contact with an inner peripheral face of the outer ring and an outer peripheral face of the inner ring. On the inner ring, a pin holding portion having an annular shape surrounding the outer peripheral face of the external tooth gear and holding the internal teeth pins, is formed along an inner peripheral face.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, speed reducers have been used in a drive control unit for wheels in a mobile device, a robot, a machine tool, or 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 the speed reducer described in Patent Document 1, the outer peripheral pin holder and the inner ring of the cross roller bearing are arranged side by side in the axial direction. Therefore, in the conventional speed reducer, the axial thickness becomes large, and there is room for improvement in terms of downsizing.

[0006] An object of the present disclosure is to provide a speed reducer capable of being downsized in the axial direction.

Means for Solving the Problems

[0007] The speed reducer according to the present disclosure has a plurality of external teeth arranged along the circumferential direction on the outer peripheral surface, an annular external gear tooth with a first through hole penetrating in the axial direction and a plurality of second through holes arranged in the circumferential direction so as to surround the first through hole, an input shaft penetrating the first through hole and rotatable around the rotation axis, a first bearing disposed between the external gear tooth and the input shaft and holding the input shaft rotatable relative to the external gear tooth in the circumferential direction, a plurality of inner peripheral pins penetrating the second through holes in the axial direction, an inner peripheral pin holder holding both ends of the plurality of inner peripheral pins and surrounding the outer peripheral surface of the input shaft, a second bearing surrounding the outer peripheral surface of the external gear tooth, and an internal tooth pin meshing with the external teeth. The second bearing includes an outer ring fixed to the inner peripheral pin holder, an inner ring disposed radially inside the outer ring and constituting an output shaft rotating at a lower speed than the input shaft, and rolling elements contacting the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring. The inner ring has an annular shape surrounding the outer peripheral surface of the external gear tooth, and a pin holding portion for holding the internal tooth pin is formed along the inner peripheral surface.

Advantages of the Invention

[0008] According to the present disclosure, a speed reducer capable of being compact in the axial direction can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

DETAILED DESCRIPTION OF THE INVENTION

[0010] [Overview of the Embodiment] The speed reducer according to the present disclosure has a plurality of external teeth arranged along the circumferential direction on the outer peripheral surface, an annular external gear tooth having a first through hole penetrating in the axial direction and a plurality of second through holes arranged in the circumferential direction so as to surround the first through hole, an input shaft penetrating through the first through hole and rotatable around the rotation axis, a first bearing disposed between the external gear tooth and the input shaft and holding the input shaft rotatable relative to the external gear tooth in the circumferential direction, a plurality of inner peripheral pins penetrating through the second through holes in the axial direction, an inner peripheral pin holder holding both ends of the plurality of inner peripheral pins and surrounding the outer peripheral surface of the input shaft, a second bearing surrounding the outer peripheral surface of the external gear tooth, and an internal tooth pin meshing with the external teeth. The second bearing includes an outer ring fixed to the inner peripheral pin holder, an inner ring disposed radially inward of the outer ring and constituting an output shaft rotating at a lower speed than the input shaft, and rolling elements contacting the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring. The inner ring has an annular shape surrounding the outer peripheral surface of the external gear tooth, and a pin holding portion for holding the internal tooth pin is formed along the inner peripheral surface.

[0011] In the speed reducer, the internal tooth pin is held on the inner peripheral surface of the inner ring constituting the output shaft. That is, the inner ring functions as a holder for the internal tooth pin. Therefore, compared with a conventional speed reducer in which the inner ring and the holder (outer peripheral pin holder) of the internal tooth pin are arranged axially as separate members, the axial thickness can be made smaller. Therefore, according to the speed reducer according to the present disclosure, the speed reducer can be made more compact in the axial direction than the conventional speed reducer.

[0012] In the speed reducer, an oil supply hole penetrating in the radial direction may be formed in the inner ring of the second bearing. According to this configuration, the lubricating oil supplied between the outer ring and the inner ring of the second bearing can be guided to the region radially inside the inner ring through the oil supply hole. Thereby, the internal tooth pin held on the inner peripheral surface of the inner ring can be easily lubricated.

[0013] In the speed reducer described above, a groove may be formed on the outer peripheral surface of the inner ring such that the distance between the raceways widens as it moves away from the bottom in a cross section including the rotation axis. The oil supply hole may be formed at the bottom of the groove. According to this configuration, the lubricating oil supplied between the outer ring and the inner ring of the second bearing easily flows into the oil supply hole along the raceway as the rolling elements roll.

[0014] In the speed reducer described above, the inner peripheral pin holder may include a first holder portion having an annular holding portion that holds the first end portion of the inner peripheral pin, a second holder portion having an annular holding portion that holds the second end portion of the inner peripheral pin opposite to the first end portion, and a column portion that connects the first holder portion and the second holder portion and is arranged at intervals in the circumferential direction and penetrates the second through hole of the external gear. The speed reducer may further include a fixing member that fixes the end face of the column portion to the first holder portion or the second holder portion, and a fixing member that is inserted into the column portion from the end face. According to this configuration, since it is not necessary to insert the fixing member into the inner peripheral pin, the inner peripheral pin can be formed thinner.

[0015] In the speed reducer described above, the cross-sectional shape perpendicular to the longitudinal direction of the column portion may be an arc shape extending in the circumferential direction. The second through hole may be a long hole extending in the circumferential direction. According to this configuration, since the area of the end face of the column portion is further widened, the restrictions on the position where the fixing member is inserted are reduced. Therefore, the degree of freedom in the design of the speed reducer is improved.

[0016] In the speed reducer described above, the plurality of inner peripheral pins may be arranged so as to sandwich the column portion in the circumferential direction. The inner peripheral pin may be a rolling bearing or a sliding bearing. According to this configuration, since the inner peripheral pin, which is a rolling bearing or a sliding bearing, rotates by contact with the inner surface of the second through hole, an increase in the rotational torque of the input shaft during driving of the speed reducer can be suppressed.

[0017] The above-described speed reducer may further include a lubricating member that is disposed inside the second through hole and contacts the inner peripheral pin. According to this configuration, since the inner peripheral pin can be lubricated, the friction between the outer peripheral surface of the inner peripheral pin and the inner surface of the second through hole of the external gear can be reduced. Thereby, the loss due to the friction between the two can be reduced, and an increase in the rotational torque of the input shaft during the driving of the speed reducer can be suppressed.

[0018] In the above-described speed reducer, the lubricating member may have a hole penetrating in the axial direction. According to this configuration, compared with the case where the lubricating member is a solid member, weight reduction can be achieved more effectively.

[0019] [Specific Examples of Embodiments] Next, an embodiment of the speed reducer of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0020] (Embodiment 1) First, the configuration of the cycloid speed reducer 1 (hereinafter, also simply referred to as "speed reducer 1") according to Embodiment 1 will be described. The speed reducer 1 is used, for example, in a joint portion of a robot or a drive control unit of a wheel in a moving device. FIG. 1 is a perspective view showing the external structure of the speed reducer 1. FIG. 2 is a front view of the speed reducer 1 as viewed from the first holder portion 41 side. FIG. 3 is a rear view of the speed reducer 1 as viewed from the output shaft side. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. As shown in FIG. 4, the speed reducer 1 mainly includes an input shaft 10, a first external gear 20 and a second external gear 21 (external gears), a first eccentric bearing 15 (first bearing) and a second eccentric bearing 16 (first bearing), an inner peripheral pin holder 40, a second bearing 50, and an internal gear pin 54. Hereinafter, these components will be described in detail respectively.

[0021] The input shaft 10 has a hollow cylindrical shape and is rotatable about the rotation axis R1. As shown in FIG. 4, the input shaft 10 includes a first end portion 10A and a second end portion 10B on the opposite side of the first end portion 10A in the axial direction D1. The second end portion 10B is the end portion on the side opposite to the output shaft and protrudes outside the end face 40B of the inner peripheral pin holder 40 in the axial direction D1. A drive motor (not shown) is attached to the second end portion 10B, and by driving the motor, the input shaft 10 rotates around the rotation axis R1 at a predetermined rotational speed. Note that the input shaft is not limited to a hollow shape, and a solid shaft may be employed.

[0022] The input shaft 10 includes a first shaft portion 11 including the first end portion 10A and a second shaft portion 12 including the second end portion 10B. As shown in FIG. 4, the outer diameter of the second shaft portion 12 is larger than the outer diameter of the first shaft portion 11. On the other hand, the inner diameters of the first shaft portion 11 and the second shaft portion 12 are substantially the same.

[0023] The second shaft portion 12 is inserted into the inner ring of the first support bearing 14. As shown in FIG. 4, an annular shoulder portion 10C protruding outward in the radial direction D2 is provided at a portion of the outer peripheral surface of the second shaft portion 12 adjacent to the first shaft portion 11. By means of the shoulder portion 10C, the movement of the inner ring of the first support bearing 14 toward the output shaft side (the left side in FIG. 4) is restricted. The first shaft portion 11 is inserted into the inner rings of the first eccentric bearing 15, the second eccentric bearing 16, and the second support bearing 17, respectively. The input shaft 10 is supported at both ends by the first support bearing 14 and the second support bearing 17. The first eccentric bearing 15 is disposed between the first external gear 20 and the input shaft 10 (the first shaft portion 11) and holds the input shaft 10 rotatable relative to the first external gear 20 in the circumferential direction. The second eccentric bearing 16 is disposed between the second external gear 21 and the input shaft 10 (the first shaft portion 11) and holds the input shaft 10 rotatable relative to the second external gear 21 in the circumferential direction. As shown in FIG. 4, a key groove 11A into which the key 13 is inserted is formed on the outer peripheral surface of the first shaft portion 11 so as to extend in the axial direction D1. By means of the key 13, the inner rings of the first eccentric bearing 15 and the second eccentric bearing 16 are fixed to the outer peripheral surface of the input shaft 10 (the first shaft portion 11).

[0024] The first support bearing 14 and the second support bearing 17 are, for example, deep groove ball bearings. In the present embodiment, since the end face in the axial direction D1 of the first support bearing 14 is covered by the inner peripheral pin holder 40, the first support bearing 14 is not provided with a seal, but the presence or absence of the seal is not particularly limited. On the other hand, the second support bearing 17 is provided with a seal, but the seal may be omitted.

[0025] The first eccentric bearing 15 and the second eccentric bearing 16 are, for example, cylindrical roller bearings. The first eccentric bearing 15 and the second eccentric bearing 16 are respectively fixed to the input shaft 10 in a state where the eccentric phases are shifted by 180°. FIG. 6 is a perspective view showing the input shaft 10 inserted into the first support bearing 14, the first eccentric bearing 15, the second eccentric bearing 16, and the second support bearing 17. The first eccentric bearing 15 has a resin cage 15B in addition to an inner ring, an outer ring, and rolling elements 15A (cylindrical rollers) that are eccentric with respect to the center (rotation axis R1) of the input shaft 10. Similarly, the second eccentric bearing 16 has a resin cage 16B in addition to an inner ring, an outer ring, and rolling elements 16A (cylindrical rollers) that are eccentric with respect to the center of the input shaft 10. As shown in FIG. 4, a pair of flange portions for restricting the movement of the rolling elements 15A in the axial direction D1 are provided on the inner ring of the first eccentric bearing 15, and a pair of flange portions for restricting the movement of the rolling elements 16A in the axial direction D1 are provided on the inner ring of the second eccentric bearing 16. Note that the material of the cages 15B and 16B is not particularly limited.

[0026] The first external gear 20 and the second external gear 21 are cycloid gears. The first external gear 20 is fitted from the outside in the radial direction D2 to the outer ring of the first eccentric bearing 15. The second external gear 21 is fitted from the outside in the radial direction D2 to the outer ring of the second eccentric bearing 16.

[0027] FIG. 7 is a perspective view of the first external gear 20. As shown in FIG. 7, the first external gear 20 has a plurality of external teeth 24 arranged along the circumferential direction on the outer peripheral surface, and is an annular member in which a first through hole 22 penetrating in the axial direction D1 and a plurality of second through holes 23 are formed. The first through hole 22 is a circular hole including the center of the first external gear 20, into which the outer ring of the first eccentric bearing 15 (FIG. 4) is fitted and through which the input shaft 10 (FIG. 4) passes. The second through hole 23 is an arc-shaped long hole extending in the circumferential direction, and is formed side by side in the circumferential direction so as to surround the first through hole 22. Further, the first external gear 20 is further formed with a plurality (four in the present embodiment) of third through holes 25 for weight reduction and screw attachment. The third through hole 25 is a circular hole and is sandwiched in the circumferential direction by a pair of second through holes 23. A power cord or the like may be passed through the third through hole 25. The external teeth 24 have a shape of an epitrochoid parallel curve, but are not limited thereto. Also, the number of the external teeth 24 is not particularly limited and can be appropriately selected to achieve a desired reduction ratio.

[0028] The first external gear 20 is made of, for example, heat-treated steel materials such as high-carbon chromium bearing steel (SUJ2) or chromium molybdenum steel (SCM) of JIS (Japanese Industrial Standards), but is not limited thereto. In order to reduce the weight of the first external gear 20, for example, resin materials such as aluminum or carbon fiber reinforced plastic (CFRP; Carbon Fiber Reinforced Plastics) may be adopted as the material of the first external gear 20. Since the second external gear 21 is basically the same as the first external gear 20, a detailed description of the second external gear 21 is omitted. The outer ring of the second eccentric bearing 16 (FIG. 4) is fitted into the first through hole 22 of the second external gear 21 and the input shaft 10 (FIG. 4) passes through it.

[0029] The speed reducer 1 includes a plurality (eight in this embodiment) of inner peripheral pins 60 that penetrate a plurality of second through holes 23 formed in the first external gear 20 and the second external gear 21 in the axial direction D1 (FIG. 5). FIG. 8 is a perspective view showing the configuration of the inner peripheral pin 60 in this embodiment, and the rolling elements 63 are indicated by broken lines. As shown in FIG. 8, the inner peripheral pin 60 is a rolling bearing including a cylindrical shaft 61, a pair of annular outer rings 62 having an inner diameter larger than the outer diameter of the shaft 61, and a plurality of rolling elements 63 (needle rollers). Note that the inner peripheral pin is not limited to a rolling bearing and may be, for example, a sliding bearing.

[0030] As shown in FIG. 8, both ends of the shaft 61 are chamfered and inserted inside the outer ring 62. The rolling elements 63 are annularly arranged between the outer peripheral surface of the shaft 61 and the inner peripheral surface of the outer ring 62. The inner peripheral pin 60 includes a thrust washer 64 disposed between the outer end surfaces of the outer rings 62 and between the outer rings 62. The thrust washer 64 is made of, for example, a thermoplastic resin such as PEEK (Poly Ether Ether Ketone), but is not limited thereto.

[0031] The inner peripheral pin holder 40 (FIG. 4) holds both ends of the plurality of inner peripheral pins 60 and surrounds the outer peripheral surface of the input shaft 10. As shown in FIG. 4, the inner peripheral pin holder 40 includes a first holder portion 41, a second holder portion 42, and a column portion 43. An annular seal 94 is disposed between the inner peripheral surface of the first holder portion 41 and the outer peripheral surface of the input shaft 10 (second shaft portion 12). The seal 94 is made of, for example, rubber and is disposed to prevent dust and leakage of lubricant. The lip of the seal 94 contacts the outer peripheral surface of the input shaft 10 (second shaft portion 12). Thrust washers are disposed between the first external gear 20 and the first holder portion 41, between the first external gear 20 and the second external gear 21, and between the second external gear 21 and the second holder portion 42. This thrust washer is made of, for example, a thermoplastic resin such as PEEK. Thereby, wear due to contact between the external gear and the inner peripheral pin holder 40 and wear due to contact between the external gears can be suppressed, and heat generation can be prevented. Note that this thrust washer and the seal 94 are not essential components in the speed reducer of the present disclosure and may be omitted.

[0032] FIG. 9 is a perspective view showing a structure in which both ends of the inner peripheral pin 60 are held by the inner peripheral pin holder 40. In FIG. 9, the input shaft 10, the first external gear 20, and the second external gear 21 are omitted. The first holder portion 41 and the second holder portion 42 have a flat annular shape and are arranged to face each other in the axial direction D1. The first holder portion 41 has an annular holding portion that holds the first end portion of the inner peripheral pin 60, and the second holder portion 42 has an annular holding portion that holds the second end portion of the inner peripheral pin 60 on the side opposite to the first end portion. More specifically, a plurality of holes into which the end portions of the shaft 61 of the inner peripheral pin 60 are press-fitted are formed at intervals in the circumferential direction in the first holder portion 41 and the second holder portion 42.

[0033] The column portion 43 is a portion that connects the first holder portion 41 and the second holder portion 42. FIG. 10 shows a state in which the first holder portion 41 is removed from the inner peripheral pin holder 40. In the present embodiment, the second holder portion 42 and the column portion 43 are integrally formed. As shown in FIG. 10, a plurality (four) of the column portions 43 are arranged at intervals in the circumferential direction and extend in the axial direction D1. As shown in FIG. 5, the column portion 43 penetrates the second through hole 23 formed in the first external gear 20 and the second external gear 21 together with the inner peripheral pin 60.

[0034] As shown in Fig. 4, the speed reducer 1 includes a plurality of bolts B1 (fixing members) that fix the end face of the column portion 43 (the face opposite to the second holder portion 42) to the first holder portion 41. The bolt B1 is inserted into the inside of the column portion 43 along the axial direction D1 from the end face of the column portion 43. A bolt hole 41A into which the bolt B1 is inserted is formed in the first holder portion 41, and female screw holes 40A that engage with the male threads formed on the outer peripheral surface of the shaft portion of the bolt B1 are formed in the second holder portion 42 and the column portion 43. Both the bolt hole 41A and the female screw hole 40A are through holes and extend in the axial direction D1. As shown in Fig. 4, the first support bearing 14 is disposed between the outer peripheral surface of the input shaft 10 (the second shaft portion 12) and the inner peripheral surface of the first holder portion 41, and the second support bearing 17 is disposed between the outer peripheral surface of the input shaft 10 (the first shaft portion 11) and the inner peripheral surface of the second holder portion 42. The outer diameter of the first holder portion 41 is larger than the outer diameter of the second holder portion 42.

[0035] As shown in Fig. 5, the cross-sectional shape perpendicular to the longitudinal direction of the column portion 43 (the direction toward the front of the paper in Fig. 5) is an arc shape extending in the circumferential direction. A plurality of inner peripheral pins 60 are arranged so as to sandwich the column portion 43 from both sides in the circumferential direction. That is, one column portion 43 and a pair of inner peripheral pins 60 that sandwich the one column portion 43 are inserted into one second through hole 23. In the present embodiment, four column portions 43 are provided and eight inner peripheral pins 60, which are twice that number, are provided, but these numbers are not particularly limited. However, the number of column portions 43 is preferably three or more. As shown in Fig. 5, the inner peripheral pin 60 can come into contact with a point on the inner surface in the circumferential direction of the second through hole 23.

[0036] The speed reducer 1 is disposed inside the second through hole 23 and includes an inner circumferential pin lubricating member 70 that contacts the inner circumferential pin 60. As shown in FIG. 5, grooves that are recessed in a direction away from the inner circumferential pin 60 are formed on both side portions in the circumferential direction of the column portion 43, and the inner circumferential pin lubricating member 70 is disposed in the grooves. The inner circumferential pin lubricating member 70 is, for example, a porous sintered resin member impregnated with a lubricant, and has a solid cylindrical shape extending in the axial direction D1 (the depth direction of the paper surface of FIG. 5). Note that, in the speed reducer of the present disclosure, the inner circumferential pin lubricating member 70 is not an essential component and may be omitted.

[0037] As shown in FIG. 4, the second bearing 50 surrounds the outer peripheral surfaces of the first external gear 20 and the second external gear 21. The second bearing 50 in the present embodiment is a cross roller bearing and includes an outer ring 51, an inner ring 52 disposed radially inward of the outer ring 51 by a radial direction D2, a plurality of rolling elements 53 that contact the inner peripheral surface 51A of the outer ring 51 and the outer peripheral surface 52A of the inner ring 52, and an annular seal 59. The outer ring 51 and the inner ring 52 are made of a metal material capable of heat treatment (quenching, tempering) such as JIS high-carbon chromium bearing steel, but are not limited thereto. Note that the second bearing 50 may further include a cage, a separator, or the like.

[0038] As shown in FIG. 1, the outer ring 51 has substantially the same diameter as the first holder portion 41 and is fixed to the outer peripheral portion of the first holder portion 41 by a plurality (six in the present embodiment) of bolts B2. The outer ring 51 and the inner circumferential pin holder 40 constitute a fixed shaft. As shown in FIG. 5, an insertion hole 51B for the rolling element 53 is formed in the outer ring 51 so as to penetrate the outer ring 51 in the radial direction. The insertion hole 51B is closed by a lid member 30, and the lid member 30 is prevented from coming off the insertion hole 51B by a pin 31. Further, as shown in FIG. 5, a grease nipple 32 is disposed in the outer ring 51, and a lubricant such as grease can be supplied to the inside of the outer ring 51.

[0039] The inner ring 52 constitutes the output shaft of the speed reducer 1 and rotates around the rotation axis R1 at a lower speed than the input shaft 10. A mating member (not shown) is attached to the outer end face 52D (Fig. 4) of the inner ring 52. As shown in Fig. 4, the inner ring 52 is thicker in the axial direction D1 than the outer ring 51 and protrudes outside the outer ring 51 in the axial direction D1. Also, the inner ring 52 has an annular shape surrounding the outer peripheral surfaces of the first external gear 20 and the second external gear 21. An annular seal 90 is disposed between the inner peripheral surface of the inner ring 52 and the outer peripheral surface of the second holder portion 42 of the inner peripheral pin holder 40. This seal 90 has the same shape as the seal 94. The lip of the seal 90 contacts an annular groove 52C formed outside the holding portion of the internal tooth pin 54 in the axial direction D1 on the inner peripheral surface of the inner ring 52.

[0040] Fig. 11 is a perspective view showing a state in which a plurality of rolling elements 53 are arranged on the outer peripheral surface of the inner ring 52 and a plurality of internal tooth pins 54 are arranged on the inner peripheral surface of the inner ring 52. Fig. 12 is a perspective view showing the inner ring 52 with the rolling elements 53 and the internal tooth pins 54 omitted. Fig. 13 is a plan view of the inner ring 52. Fig. 14 is a cross-sectional view taken along the line segment XIV-XIV in Fig. 13.

[0041] As shown in Fig. 11, a plurality of rolling elements 53 (cylindrical rollers) are arranged over the entire circumferential direction on the outer peripheral surface of the inner ring 52. Here, the rolling axes of two adjacent rolling elements 53 in the circumferential direction are orthogonal to each other. A plurality of internal tooth pins 54 are arranged over the entire circumferential direction on the inner peripheral surface of the inner ring 52. The internal tooth pins 54 have a cylindrical shape, and the longitudinal direction thereof coincides with the axial direction of the inner ring 52. The internal tooth pins 54 mesh with the external teeth 24 (Fig. 7) of the first external gear 20 and the second external gear 21. The number of the internal tooth pins 54 is not particularly limited, but at most one more than the number of the external teeth 24 (Fig. 7).

[0042] As shown in FIG. 12, a pin holding portion 58 for holding an internal tooth pin 54 (FIG. 11) is formed along the inner peripheral surface of the inner ring 52. The pin holding portion 58 includes a first annular portion 56 and a second annular portion 57 spaced apart from the first annular portion 56 in the axial direction D1. The first annular portion 56 and the second annular portion 57 are formed by a plurality of grooves being continuous over the entire circumferential direction. The first end portion of the internal tooth pin 54 (FIG. 11) is fitted into the groove of the first annular portion 56, and the second end portion of the internal tooth pin 54 (the end portion on the side opposite to the first end portion in the axial direction D1) is fitted into the groove of the second annular portion 57. As shown in FIG. 13, the grooves of the first annular portion 56 and the second annular portion 57 are arc-shaped grooves when viewed planar from the axial direction D1.

[0043] Referring to FIG. 4, the speed reducer 1 includes an annular pin guide plate 91 and a retaining ring 92. The pin guide plate 91 and the retaining ring 92 are attached to a portion of the inner peripheral surface of the inner ring 52 that is axially outside of the holding portion of the internal tooth pin 54. As shown in FIG. 4, the pin guide plate 91 faces the first end portion (the end portion on the side of the first holder portion 41) of the internal tooth pin 54 in the axial direction D1. The retaining ring 92 is disposed on the side opposite to the internal tooth pin 54 when viewed from the pin guide plate 91 and faces the pin guide plate 91 in the axial direction D1. The pin guide plate 91 is, for example, a metal plate, but is not limited thereto.

[0044] When assembling the speed reducer 1, the internal tooth pin 54 is inserted into the grooves of the first annular portion 56 and the second annular portion 57 in order from the axial direction D1 (FIGS. 11 and 12). Thereafter, the pin guide plate 91 and the retaining ring 92 are attached to the inner peripheral surface of the inner ring 52. Thereby, the movement of the internal tooth pin 54 toward the first holder portion 41 side in the axial direction D1 is restricted. The internal tooth pin 54 rotates around the axis by contact with the external teeth 24 of the first external tooth gear 20 and the second external tooth gear 21.

[0045] An oil supply hole 55 penetrating radially from the outer peripheral surface 52A to the inner peripheral surface 52B is formed in the inner ring 52. As shown in FIG. 14, a plurality (four in the present embodiment) of the oil supply holes 55 are formed at intervals in the circumferential direction. Lubricating oil flows into the inner ring 52 from the outer peripheral surface 52A side to the inner peripheral surface 52B side through the oil supply hole 55.

[0046] As shown in FIG. 4, on the outer peripheral surface 52A of the inner ring 52, in a cross section including the rotation axis R1, a groove is formed in which the distance between the raceways 52AA and 52AB widens as it moves away from the bottom. The oil supply hole 55 is formed at the bottom of the groove. One raceway 52AA has a reduced diameter from the first end 10A to the second end 10B of the input shaft 10 in a cross section including the rotation axis R1 (the cross section of FIG. 4). The other raceway 52AB has a reduced diameter from the second end 10B to the first end 10A. The raceways 52AA and 52AB are surfaces on which the rolling elements 53 roll.

[0047] The oil supply hole 55 opens into the oil groove 93. As shown in FIG. 12, the oil groove 93 is an annular region between the first annular portion 56 and the second annular portion 57. By forming the oil supply hole 55, lubricants such as grease supplied from the outside of the outer ring 51 can reach the inside of the speed reducer 1.

[0048] Next, the operation of the speed reducer 1 according to Embodiment 1 will be described.

[0049] First, when a motor (not shown) is driven, the input shaft 10 rotates at high speed. Along with this, the centers of the first external gear 20 and the second external gear 21 rotate (revolve) around the center of the input shaft 10, and the external teeth 24 (FIG. 7) of the first external gear 20 and the second external gear 21 come into contact with the internal teeth 54. At this time, the first external gear 20 and the second external gear 21 swing inside the inner ring 52, but do not rotate because the inner peripheral pin holder 40 is fixed to the outer ring 51. Also, the outer ring 62 (FIG. 8) of the inner peripheral pin 60 rotates by contact with the inner surface of the second through hole 23 of the first external gear 20 and the second external gear 21.

[0050] On one hand, the internal gear pin 54 is pushed circumferentially by the external teeth 24 of the first external gear 20 and the second external gear 21. As a result, the inner ring 52 that holds the inner circumferential pin 54 rotates around the rotation axis R1 at a lower speed than the input shaft 10 as the output shaft. At this time, the direction in which the inner ring 52 rotates is the same as the direction in which the input shaft 10 rotates. Also, the position of the rotation axis of the inner ring 52 and the position of the rotation axis of the input shaft 10 coincide with each other.

[0051] Next, the operation and effect of the speed reducer 1 according to the first embodiment will be described.

[0052] In the speed reducer 1, the internal gear pin 54 is held on the inner circumferential surface of the inner ring 52 that constitutes the output shaft. That is, the output shaft functions as an internal gear. For this reason, compared with a conventional speed reducer in which the output shaft and the internal gear are arranged in the axial direction, the thickness in the axial direction D1 can be further reduced. Therefore, according to the speed reducer 1 according to the present embodiment, it is possible to achieve a more compact design in the axial direction D1 compared with a conventional speed reducer.

[0053] (Second Embodiment) Next, the speed reducer according to the second embodiment will be described. The speed reducer according to the present embodiment basically has the same configuration as the speed reducer 1 according to the first embodiment described above and exhibits the same effects, but is different from the speed reducer 1 according to the first embodiment in the configuration of the inner circumferential pin lubricating member. Hereinafter, only the differences from the speed reducer 1 according to the first embodiment will be described.

[0054] FIG. 15 is a perspective view showing the configuration of the inner circumferential pin lubricating member 71 in the present embodiment. As shown in FIG. 15, the inner circumferential pin lubricating member 71 has a cylindrical shape and a hole 71A penetrating in the axial direction D1 is formed. The hole 71A is a circular hole when viewed from the axial direction D1, but the hole shape is not limited to this. Thereby, weight reduction can be achieved compared with the case where the inner circumferential pin lubricating member is solid.

[0055] (Other Embodiments) Here, other embodiments will be described.

[0056] In the first eccentric bearing 15 and the second eccentric bearing 16, the outer ring may be omitted. In this case, the rolling elements 15A of the first eccentric bearing 15 contact the inner surface of the first through hole 22 of the first external gear 20, and the rolling elements 16A of the second eccentric bearing 16 contact the inner surface of the first through hole 22 of the second external gear 21.

[0057] The drive motor is not limited to being attached to the second end portion 10B side of the input shaft 10, and may be attached to, for example, the outer end surface of the second holder portion 42.

[0058] In the first external gear 20 and the second external gear 21, the second through hole 23 is not limited to an elongated hole, and may be a circular hole. Also, the third through hole 25 may be omitted.

[0059] The second bearing 50 is not limited to a cross roller bearing, and other types of bearings may be employed. Also, in the second bearing 50, the oil supply hole 55 of the inner ring 52 may be omitted.

[0060] In the above-described Embodiment 1, the case where the second holder portion 42 and the column portion 43 are integrally formed has been described as an example, but the present invention is not limited thereto. The first holder portion 41 and the column portion 43 may be integrally formed. In this case, the end surface of the column portion 43 (the surface of the column portion 43 on the side opposite to the first holder portion 41) is fixed to the second holder portion 42 by a fixing member (for example, a bolt) inserted into the column portion 43 from the end surface.

[0061] The embodiments disclosed this time should be construed as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0062] 1 Reducer, 10 Input shaft, 10A First end, 10B Second end, 10C Shoulder, 11 First shaft portion, 11A Key groove, 12 Second shaft portion, 13 Key, 14 First support bearing, 15 First eccentric bearing (first bearing), 15A Rolling element, 15B Retainer, 16 Second eccentric bearing (first bearing), 16A Rolling element, 16B Retainer, 17 Second support bearing, 20 First external gear, 21 Second external gear, 22 First through hole, 23 Second through hole, 24 External teeth, 25 Third through hole, 30 Cover member, 31 Pin, 32 Grease nipple, 40 Inner peripheral pin holder, 40A Female screw hole, 40B End face, 41 First holder portion, 41A Bolt hole, 42 Second holder portion, 43 Column portion, 50 Second bearing, 51 Outer ring, 51A Inner peripheral surface, 51B Feed hole, 52 Inner ring, 52A Outer peripheral surface, 52AA, 52AB Side wall, 52B Inner peripheral surface, 52C Groove, 52D Outer end face, 53 Rolling element, 54 Internal gear pin, 55 Oil supply hole, 56 First annular portion, 57 Second annular portion, 58 Pin holding portion, 59 Seal, 60 Inner peripheral pin, 61 Shaft, 62 Outer ring, 63 Rolling element, 64 Thrust washer, 70, 71 Inner peripheral pin lubricating member, 71A Hole, 90 Seal, 91 Pin guide plate, 92 Retaining ring, 93 Oil groove, 94 Seal, B1, B2 Bolt, D1 Axial direction, D2 Radial direction, R1 Rotation axis

Claims

1. An annular external gear having a plurality of external teeth arranged along the circumferential direction on the outer peripheral surface, and a first through hole penetrating in the axial direction and a plurality of second through holes arranged in the circumferential direction so as to surround the first through hole; An input shaft penetrating through the first through hole and rotatable around the rotation axis; A first bearing disposed between the external gear and the input shaft, and holding the input shaft rotatable relative to the external gear in the circumferential direction; A plurality of inner peripheral pins penetrating through the second through hole in the axial direction; An inner peripheral pin holder holding both ends of the plurality of inner peripheral pins and surrounding the outer peripheral surface of the input shaft; A second bearing surrounding the outer peripheral surface of the external gear; An internal tooth pin meshing with the external teeth, and comprising: The second bearing includes: An outer ring fixed to the inner peripheral pin holder; An inner ring disposed radially inside the outer ring and constituting an output shaft that rotates at a lower speed than the input shaft; Rolling elements contacting the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring; The inner ring has an annular shape surrounding the outer peripheral surface of the external gear, and a pin holding portion for holding the internal tooth pin is formed along the inner peripheral surface; The inner peripheral pin holder includes: A first holder portion having an annular holding portion for holding a first end portion of the inner peripheral pin; A second holder portion having an annular holding portion for holding a second end portion of the inner peripheral pin opposite to the first end portion; A column portion connecting the first holder portion and the second holder portion and arranged at intervals in the circumferential direction and penetrating through the second through hole; A fixing member for fixing an end surface of the column portion to the first holder portion or the second holder portion, and further comprising the fixing member inserted into the column portion from the end surface; A cross-sectional shape perpendicular to the longitudinal direction of the column portion is an arc shape extending in the circumferential direction; The second through hole is a long hole extending in the circumferential direction; In each of the second through holes, one of the column portions and a pair of the inner peripheral pins sandwiching one of the column portions in the circumferential direction are inserted, a speed reducer.

2. The speed reducer according to claim 1, wherein an oil supply hole penetrating in the radial direction is formed in the inner ring.

3. On the outer peripheral surface of the inner ring, in a cross section including the rotation axis, a groove is formed in which the distance between the raceways widens as it moves away from the bottom; The oil supply hole is formed at the bottom of the groove, the speed reducer according to claim 2.

4. The second through hole is a long hole extending in an arc shape in the circumferential direction, the speed reducer according to any one of claims 1 to 3.

5. The inner peripheral pin is a rolling bearing or a sliding bearing, the speed reducer according to any one of claims 1 to 4.

6. The speed reducer according to any one of claims 1 to 5, further comprising a lubricating member disposed inside the second through hole and contacting the inner peripheral pin.

7. The speed reducer according to claim 6, wherein a hole penetrating in the axial direction is formed in the lubricating member.

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