Reducer

Abstract

To provide a speed reducer capable of being miniaturized.SOLUTION: A speed reducer includes: an annular external tooth gear having a plurality of outer teeth and provided with a plurality of through holes arranged in a circumferential direction; an input shaft penetrating through a space surrounded by an inner peripheral face of the external tooth gear; a bearing disposed between the external tooth gear and the input shaft; an annular internal tooth gear having a plurality of inner teeth engaged with the outer teeth and surrounding an outer peripheral face of the external tooth gear; a plurality of inner peripheral pins penetrating through the plurality of through holes in an axial direction; and an inner peripheral pin holder for holding both ends of the inner peripheral pin. 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; and a pillar portion connecting the first holder portion and the second holder portion and penetrating through the through holes. The speed reducer further includes a fixing member fixing end faces of the pillar portions to the first holder portion and the second holder portion and inserted to the inside of the pillar portions from the end faces.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, a speed reducer has 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 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 inner peripheral pin includes a shaft, an outer ring rotatably disposed with respect to the shaft, and a roller that rolls between the shaft and the outer ring. Both ends of the shaft are fixed to the hub and the output shaft pin holder by fixing bolts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, in the speed reducer described in Patent Document 1, both ends of the shaft of the inner peripheral pin are fixed to the hub and the output shaft pin holder by fixing bolts. Therefore, it is necessary to form holes for inserting the fixing bolts at the end portions of the shaft of the inner peripheral pin. In this case, since it is difficult to make the shaft of the inner peripheral pin thin, it is difficult to reduce the radial size of the speed reducer. Therefore, there is room for improvement in the conventional speed reducer in terms of miniaturization.

[0006] An object of the present disclosure is to provide a speed reducer that can be miniaturized.

Means for Solving the Problems

[0007] The speed reducer according to the present disclosure includes an annular external gear having a plurality of external teeth arranged along the circumferential direction on the outer peripheral surface and a plurality of through holes penetrating in the axial direction formed side by side in the circumferential direction, an input shaft penetrating through the space surrounded by the inner peripheral surface of the external gear and extending in the axial direction, a 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, an annular internal gear having a plurality of internal teeth arranged along the circumferential direction on the inner peripheral surface and meshing with the external teeth and surrounding the outer peripheral surface of the external gear, a plurality of inner peripheral pins penetrating through the plurality of through holes in the axial direction, and an inner peripheral pin holder holding both ends of the inner peripheral pins and forming a space through which the input shaft penetrates. The inner peripheral pin holder includes a first holder portion having an annular holding portion for holding the first end portion of the inner peripheral pin, a second holder portion having an annular holding portion for holding the second end portion opposite to the first end portion of the inner peripheral pin, and 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 through hole. The speed reducer further includes a fixing member for fixing the end surface of the column portion to the first holder portion or the second holder portion, and a fixing member inserted into the column portion from the end surface.

Advantages of the Invention

[0008] According to the present disclosure, a speed reducer that can be miniaturized can be provided.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 10

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Figure 16

Embodiments for Carrying Out the Invention

[0010] [Overview of the Embodiment] The speed reducer according to the present disclosure includes an annular external gear having a plurality of external teeth arranged along the circumferential direction on the outer peripheral surface, and a plurality of through holes penetrating in the axial direction formed side by side in the circumferential direction; an input shaft penetrating the space surrounded by the inner peripheral surface of the external gear and extending in the axial direction; a 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; an annular internal gear having a plurality of internal teeth arranged along the circumferential direction on the inner peripheral surface and meshing with the external teeth, and surrounding the outer peripheral surface of the external gear; a plurality of inner peripheral pins penetrating the plurality of through holes in the axial direction; and an inner peripheral pin holder holding both ends of the inner peripheral pins and forming a space through which the input shaft penetrates. The inner peripheral pin holder includes a first holder portion having an annular holding portion holding the first end portion of the inner peripheral pin, a second holder portion having an annular holding portion holding the second end portion of the inner peripheral pin opposite to the first end portion, and a column portion connecting the first holder portion and the second holder portion and disposed at intervals in the circumferential direction and penetrating the through hole. The speed reducer further includes a fixing member fixing the end surface of the column portion to the first holder portion or the second holder portion, and a fixing member inserted into the column portion from the end surface thereof.

[0011] In the speed reducer, the end surface is fixed to the first holder portion or the second holder portion by a fixing member inserted into the column portion from the end surface of the column portion. Therefore, unlike conventional speed reducers, it is not necessary to insert the fixing member into the axis of the inner peripheral pin. Thus, according to the speed reducer, the inner peripheral pin can be made thinner compared to conventional speed reducers, and the radial size can be reduced to achieve compactification.

[0012] In the speed reducer, the cross-sectional shape perpendicular to the longitudinal direction of the column portion may be an arc shape extending in the circumferential direction. The plurality of through holes formed in the external gear may be elongated holes extending in the circumferential direction. According to this configuration, since the area of the end surface of the column portion can be increased, the restriction on the position of the insertion hole of the fixing member is reduced. As a result, the degree of freedom in the design of the speed reducer is improved.

[0013] In the above-described speed reducer, the plurality of inner peripheral pins may be arranged so as to sandwich the column portion in the circumferential direction. The inner peripheral pins may be rolling bearings or sliding bearings. According to this configuration, it is possible to suppress the both side portions in the circumferential direction of the column portion from directly contacting the inner surface of the through hole of the external gear, and thus it is possible to reduce the friction between the both side portions and the inner surface of the through hole. And since the inner peripheral pins, which are rolling bearings or sliding bearings, rotate by contacting the inner surface of the through hole, it is possible to suppress an increase in the rotational torque of the input shaft.

[0014] The above-described speed reducer may further include a lubricating member that is disposed inside the through hole formed in the external gear and contacts the inner peripheral pins. According to this configuration, since the inner peripheral pins can be lubricated, it is possible to reduce the friction between the outer peripheral surface of the inner peripheral pins and the inner surface of the through hole of the external gear. Thereby, the loss due to the friction can be reduced, and an increase in the rotational torque of the input shaft can be suppressed.

[0015] In the above-described speed reducer, the lubricating member may include a base portion extending in the radial direction, a first convex portion protruding from a first end portion of the base portion, a second convex portion protruding from a second end portion of the base portion opposite to the first end portion, and a third convex portion protruding from between the first end portion and the second end portion of the base portion, in a cross section cut by a plane perpendicular to the axial direction. The lubricating member may be swingable so as to achieve a first contact state in which the first convex portion and the third convex portion contact the inner peripheral pins and the second convex portion is separated from the inner peripheral pins, and a second contact state in which the second convex portion and the third convex portion contact the inner peripheral pins and the first convex portion is separated from the inner peripheral pins. According to this configuration, the lubricating member can be brought into contact with the inner peripheral pins at the first to third convex portions. Therefore, compared with the case where the lubricating member is in full surface contact with the inner peripheral pins, it is possible to suppress torque cross and temperature rise.

[0016] In the above-described speed reducer, a groove for accommodating the lubricating member may be formed in the column portion. The outer shape of the groove in a cross section perpendicular to the longitudinal direction may correspond to the lubricating member. According to this configuration, the lubricating member can swing smoothly in the groove of the column portion.

[0017] [Specific Example of Embodiment] 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 their descriptions will not be repeated.

[0018] (Embodiment 1) First, the configuration of the cycloid speed reducer 1 according to Embodiment 1 (hereinafter, also simply referred to as "speed reducer 1") will be described. The speed reducer 1 is used, for example, in the joint portion of a robot or the 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 input shaft 10 side. FIG. 3 is a rear view of the speed reducer 1 as viewed from the output shaft 53 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 13 and a second eccentric bearing 14 (bearings), a plurality of outer peripheral pins 31 and an outer peripheral pin holder 30 (internal gear), an inner peripheral pin holder 40, and a main bearing 50. Hereinafter, these components will be described in detail. In this embodiment, lubricants such as grease are pre-encapsulated in the bearings.

[0019] The input shaft 10 has a hollow cylindrical shape and extends in the axial direction D1. 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 an end portion on the opposite side of the output shaft 53 and protrudes outside the axial direction D1 from the end face 40A of the inner peripheral pin holder 40. A driving motor (not shown) is attached to the second end portion 10B, and the input shaft 10 rotates around the axis by driving the motor. Note that the input shaft is not limited to a hollow shape, and a solid shape may be adopted.

[0020] The input shaft 10 includes a first shaft portion 17 including a first end portion 10A, a second shaft portion 18 including a second end portion 10B, and a third shaft portion 19 connecting the first shaft portion 17 and the second shaft portion 18. The outer diameter of the third shaft portion 19 is larger than the outer diameter of the first shaft portion 17, and the outer diameter of the second shaft portion 18 is larger than the outer diameter of the third shaft portion 19. That is, the outer diameter of the input shaft 10 gradually increases from the first end portion 10A toward the second end portion 10B. On the other hand, the inner diameters of the first to third shaft portions 17 to 19 are the same respectively.

[0021] As shown in FIG. 4, the third shaft portion 19 is inserted into the inner rings of the first support bearing 12, the first eccentric bearing 13, and the second eccentric bearing 14 respectively. The first shaft portion 17 is inserted into the inner ring of the second support bearing 15. Both ends of the input shaft 10 are supported by the first support bearing 12 and the second support bearing 15. The first eccentric bearing 13 is disposed between the first external gear 20 and the input shaft 10 (the third shaft portion 19), and holds the input shaft 10 rotatable relative to the first external gear 20 in the circumferential direction. The second eccentric bearing 14 is disposed between the second external gear 21 and the input shaft 10 (the third shaft portion 19), and holds the input shaft 10 rotatable relative to the second external gear 21 in the circumferential direction. A key groove 19A into which a key 11 is inserted is formed on the outer peripheral surface of the third shaft portion 19 so as to extend in the axial direction D1. By means of the key 11, the inner rings of the first eccentric bearing 13 and the second eccentric bearing 14 are fixed to the input shaft 10.

[0022] As shown in FIG. 4, the first support bearing 12, the first eccentric bearing 13, and the second eccentric bearing 14 are arranged in this order from the second end portion 10B toward the first end portion 10A, and their inner rings are sandwiched in the axial direction D1 by a stepped end surface between the second shaft portion 18 and the third shaft portion 19 and a pressing member 23. The pressing member 23 is attached to the outer peripheral surface of the input shaft 10 (the third shaft portion 19) by fixing screws 24. A plurality (three in this embodiment) of pressing members 23 are provided at intervals in the circumferential direction of the input shaft 10.

[0023] An annular concave groove in which the retaining ring 16 is arranged is formed on the outer peripheral surface of the first shaft portion 17. As shown in FIG. 4, the inner ring of the second support bearing 15 is axially sandwiched in the D1 direction by the stepped end surface between the first shaft portion 17 and the third shaft portion 19 and the retaining ring 16.

[0024] FIG. 6 is a perspective view showing the configuration of the input shaft 10 inserted into each bearing. FIG. 7 is a perspective view showing the configuration of the pressing member 23. As shown in FIG. 6, the retaining ring 16 is a circular ring-shaped (C-shaped) member in which a notch 16A is formed in a part of the circumferential direction. As shown in FIG. 7, the pressing member 23 is open in a U shape so that a fixing screw can be inserted. The upper surface 23A of the pressing member 23 is an inclined surface (a surface inclined with respect to a surface perpendicular to the thickness direction of the pressing member 23), and the lower surface 23B is a curved surface along the outer peripheral surface of the input shaft 10.

[0025] The first support bearing 12, the first eccentric bearing 13, and the second eccentric bearing 14 are, for example, cylindrical roller bearings. The first eccentric bearing 13 and the second eccentric bearing 14 are fixed to the input shaft 10 in a state where the eccentric phases are shifted from each other by 180°. Each of the first eccentric bearing 13 and the second eccentric bearing 14 includes an eccentric inner ring, cylindrical rollers (rolling elements), a cylindrical outer ring, and a cage. As the cage, a lightweight resin one can be adopted, but it is not limited thereto. For example, a metal cage may be adopted in the first eccentric bearing 13 and the second eccentric bearing 14.

[0026] As shown in FIG. 4, each inner ring of the first eccentric bearing 13 and the second eccentric bearing 14 includes a pair of flange portions that regulate the movement of the cylindrical rollers in the axial direction D1. Further, the inner ring is fixed to the outer peripheral surface of the input shaft 10 by a key 11, thereby preventing rotation with respect to the input shaft 10. In the present embodiment, the first support bearing 12 is not provided with a seal, but it is not limited thereto, and a seal may be provided. The second support bearing 15 is, for example, a deep groove ball bearing with a seal, but it is not limited thereto, and one without a seal may be adopted.

[0027] 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 with respect to the outer ring of the first eccentric bearing 13. The second external gear 21 is fitted from the outside in the radial direction D2 with respect to the outer ring of the second eccentric bearing 14.

[0028] FIG. 8 is a plan view of the first external gear 20. As shown in FIG. 8, the first external gear 20 is an annular member having a plurality of external teeth 27 arranged along the circumferential direction on the outer peripheral surface, and a plurality of long holes 26 (through holes) penetrating in the axial direction are formed side by side in the circumferential direction. A central hole 25 (space) surrounded by the inner peripheral surface 20A is formed in the first external gear 20, and the input shaft 10 (FIG. 4) penetrates through the central hole 25.

[0029] The plurality (eight in the present embodiment) of long holes 26 are formed so as to extend in the circumferential direction and surround the periphery of the central hole 25. The central hole 25 is a circular hole. Note that the outer ring of the first eccentric bearing 13 (FIG. 4) may be omitted, and the inner peripheral surface 20A may function as the raceway surface of a cylindrical roller.

[0030] The external teeth 27 in the present embodiment have the shape of an epitrochoid parallel curve, but are not limited thereto. Also, the number of the external teeth 27 is not particularly limited, and can be appropriately selected to achieve a desired reduction ratio.

[0031] 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. For example, in addition to aluminum, resin materials such as carbon fiber reinforced plastics (CFRP) 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.

[0032] The outer peripheral pins 31 (Fig. 4) have a cylindrical shape extending in the axial direction D1 and constitute internal teeth that mesh with the external teeth 27 (Fig. 8). The outer peripheral pins 31 are held on the inner peripheral surface of the outer peripheral pin holder 30 and are arranged along the circumferential direction on the inner peripheral surface. The number of the outer peripheral pins 31 is not particularly limited, but in the present embodiment, it is one more than the number of the external teeth 27.

[0033] Fig. 9 is a perspective view showing the configuration of the outer peripheral pin holder 30. The outer peripheral pin holder 30 is an annular member that surrounds the outer peripheral surfaces of the first external tooth gear 20 and the second external tooth gear 21 (Fig. 4). A plurality of through holes 30A penetrating from the outer peripheral surface to the inner peripheral surface are formed over the entire circumferential direction in the outer peripheral pin holder 30. The through holes 30A are formed for weight reduction of the outer peripheral pin holder 30, and the inner diameter becomes smaller toward the inner side in the radial direction. Note that the shape and number of the through holes 30A are not particularly limited. Also, the through holes 30A are not an essential configuration in the speed reducer of the present disclosure and may be omitted.

[0034] As shown in Fig. 9, a first pin holding ring 32A and a second pin holding ring 33A spaced apart from the first pin holding ring 32A in the axial direction D1 are provided on the inner peripheral surface of the outer peripheral pin holder 30, respectively. Each of the first pin holding ring 32A and the second pin holding ring 33A has a plurality of arc-shaped grooves arranged in the circumferential direction and each extending in the axial direction D1, and is provided annularly along the inner peripheral surface of the outer peripheral pin holder 30. The outer peripheral pin 31 (Fig. 4) has its first end fitted into the groove of the first pin holding ring 32A and its second end on the side opposite to the first end in the axial direction D1 fitted into the groove of the second pin holding ring 33A. Thereby, the plurality of outer peripheral pins 31 and the outer peripheral pin holder 30 have a plurality of internal teeth arranged along the circumferential direction on the inner peripheral surface and meshing with the external teeth 27 (Fig. 8), and constitute an annular internal tooth gear that surrounds the outer peripheral surfaces of the first external tooth gear 20 and the second external tooth gear 21. Note that in the present embodiment, the outer peripheral pins 31 are arranged every other one with respect to the grooves of the first pin holding ring 32A and the second pin holding ring 33A, but it is not limited thereto.

[0035] As shown in FIG. 4, an input shaft 10, a first external gear 20, a second external gear 21, and an inner peripheral pin holder 40 are respectively accommodated inside the outer peripheral pin holder 30 in the radial direction D2. The speed reducer 1 includes a first pin restricting member 33 and a second pin restricting member 34 that restrict the movement of the outer peripheral pin 31 in the axial direction D1. The first pin restricting member 33 is a ring-shaped member and faces the first end surface (the right end surface in FIG. 4) of the outer peripheral pin 31 in the axial direction D1. The second pin restricting member 34 is a ring-shaped member similar to the first pin restricting member 33 and faces the second end surface (the left end surface in FIG. 4) of the outer peripheral pin 31 in the axial direction D1.

[0036] The speed reducer 1 includes a dust-proof exterior plate 35 fixed by bolts B2 to the first end surface (the end surface opposite to the main bearing 50, the right end surface in FIG. 4) of the outer peripheral pin holder 30. As shown in FIG. 4, the exterior plate 35 extends radially inward in the radial direction D2 beyond the inner peripheral surface of the outer peripheral pin holder 30 so as to close the gap in the radial direction D2 between the outer peripheral pin holder 30 and the inner peripheral pin holder 40. In the speed reducer of the present disclosure, the first pin restricting member 33, the second pin restricting member 34, and the exterior plate 35 are not essential components and may be omitted.

[0037] The speed reducer 1 includes an outer peripheral pin lubricating member 32. The outer peripheral pin lubricating member 32 is, for example, a ring-shaped member in which a lubricant is impregnated in a porous sintered resin member. The outer peripheral pin lubricating member 32 is disposed on the inner peripheral surface of the outer peripheral pin holder 30 (FIG. 4). More specifically, the outer peripheral pin lubricating member 32 is disposed at a portion between the first pin holding ring 32A and the second pin holding ring 33A on the inner peripheral surface of the outer peripheral pin holder 30 (FIG. 9).

[0038] The outer peripheral pin 31 rotates around its axis due to contact with the first external gear 20 and the second external gear 21. Also, the outer peripheral pin 31 contacts the outer peripheral pin lubricating member 32. Therefore, as the outer peripheral pin 31 rotates around its axis, the outer peripheral pin lubricating member 32 also rotates around its axis (around the rotation axis of the speed reducer 1). Since the outer peripheral pin lubricating member 32 can supply lubricant to the outer peripheral pin 31, the friction between the outer peripheral pin 31 and the first external gear 20 and the second external gear 21 can be reduced. Thereby, the loss due to friction can be reduced, and the increase in the rotational torque of the input shaft 10 can be suppressed. Note that the outer peripheral pin lubricating member 32 is not an essential component in the speed reducer of the present disclosure and may be omitted.

[0039] The speed reducer 1 includes a plurality (16 in the present embodiment) of inner peripheral pins 60 that axially penetrate a plurality of long holes 26 formed in the first external gear 20 and the second external gear 21 (FIG. 5). FIG. 10 is a perspective view showing the configuration of the inner peripheral pin 60 in the present embodiment, and the rolling elements 63 are shown by dashed lines. As shown in FIG. 10, the inner peripheral pin 60 is a rolling bearing including a cylindrical shaft 61, a pair of annular outer rings 62, and a plurality of rolling elements 63 (needle rollers). Note that the inner peripheral pin is not limited to a rolling bearing as in the present embodiment, and may be a sliding bearing, for example.

[0040] As shown in FIG. 10, the shaft 61 has chamfered corners at both ends and is inserted into each of the pair of outer rings 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.

[0041] The inner peripheral pin holder 40 (Fig. 4) holds both ends of the inner peripheral pin 60. A space through which the input shaft 10 passes is formed in the inner peripheral pin holder 40. 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. Thrust washers 22 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 22 is made of a thermoplastic resin such as PEEK, for example. 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 is not an essential component in the speed reducer of the present disclosure and may be omitted.

[0042] Fig. 11 is a perspective view showing a cage structure in which both ends of the inner peripheral pin 60 in the axial direction D1 are held by the inner peripheral pin holder 40. In Fig. 11, the input shaft 10, the first external gear 20, and the second external gear 21 are omitted. As shown in Fig. 11, the first holder portion 41 has an annular holding portion that holds the first end portion of the inner peripheral pin 60.

[0043] Fig. 12 is an enlarged view of the region XII in Fig. 11. As shown in Fig. 12, a plurality of holes 45 into which the first end portion of the shaft 61 is press-fitted are formed at intervals in the circumferential direction in the first holder portion 41. The holes 45 penetrate the first holder portion 41 in the thickness direction. Further, in order to prevent the shaft 61 from coming off, only the press-fitted portion of the shaft 61 is reamed in the holes 45.

[0044] 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. As shown in Fig. 11, the second holder portion 42 is an annular portion having substantially the same diameter as the first holder portion 41 and is spaced apart from the first holder portion 41 in the axial direction D1. Similar to the first holder portion 41, a plurality of holes into which the second end portion of the inner peripheral pin 60 is press-fitted are formed at intervals in the circumferential direction in the second holder portion 42.

[0045] The column part 43 connects the first holder part 41 and the second holder part 42 and is arranged at intervals in the circumferential direction (Fig. 11). The column part 43 penetrates through the long holes 26 formed in the first external gear 20 and the second external gear 21 together with the inner circumferential pins 60 (Fig. 5). Note that the number of column parts 43 is not particularly limited, but it is preferably half the number of inner circumferential pins 60 and 4 or more.

[0046] Fig. 13 shows a state in which the first holder part 41 is removed from the inner circumferential pin holder 40. As shown in Fig. 13, the column part 43 has an arc shape in which the cross-sectional shape perpendicular to the longitudinal direction (axial direction D1) extends in the circumferential direction. In the present embodiment, the second holder part 42 and the column part 43 are integrally formed. The column part 43 includes an end face 46 on the side opposite to the second holder part 42. The end face 46 is fixed to the first holder part 41 (Fig. 12). Note that the present invention is not limited to the case where the second holder part 42 and the column part 43 are integrally formed, and the first holder part 41, the second holder part 42, and the column part 43 may be constituted by separate members, respectively.

[0047] The speed reducer 1 fixes the end face 46 of the column part 43 to the first holder part 41 and includes a plurality of bolts B1 (fixing members) inserted from the end face 46 into the inside of the column part 43 (Figs. 11 and 12). As shown in Fig. 4, bolt holes 41A (through holes) into which the bolts B1 are inserted are formed in the first holder part 41. On the other hand, female screw holes 43A that mesh with male threads formed on the outer peripheral surface of the shaft part of the bolt B1 are formed in the column part 43. The female screw holes 43A are bottomed holes that open to the first holder part 41 side and are formed corresponding to the bolt holes 41A.

[0048] As shown in Fig. 5, the column part 43 is inserted into the long holes 26 together with a pair of inner circumferential pins 60. More specifically, a plurality (two) of inner circumferential pins 60 are arranged so as to sandwich the column part 43 from both sides in the circumferential direction. Also, the inner circumferential pins 60 are in contact with the inner surface of the long holes 26.

[0049] The speed reducer 1 is provided with an inner peripheral pin lubricating member 70 for lubricating the inner peripheral pin 60 (FIG. 5). The inner peripheral pin lubricating member 70 is disposed inside the long hole 26 and contacts the outer peripheral surface of the inner peripheral pin 60 (the outer peripheral surface of the outer ring 62). More specifically, as shown in FIG. 5, grooves extending in the axial direction and having an arc-shaped cross-sectional shape perpendicular to the axial direction are formed on both side portions in the circumferential direction of the column portion 43, and the inner peripheral pin lubricating member 70 is accommodated in the grooves. The outer shape of the groove in a cross-section perpendicular to the longitudinal direction (the cross-section of FIG. 5) corresponds to the inner peripheral pin lubricating member 70. The inner peripheral pin lubricating member 70 is, for example, a porous sintered resin member impregnated with a lubricant, but is not limited thereto.

[0050] FIG. 14 is a perspective view showing the configuration of the inner peripheral pin lubricating member 70. Referring to FIGS. 5 and 14, the inner peripheral pin lubricating member 70 includes a base portion 75 extending in the radial direction D2, a first convex portion 72, a second convex portion 73, and a third convex portion 71 in a cross-section (the cross-section of FIG. 5) cut by a plane perpendicular to the axial direction D1. The first convex portion 72 protrudes from the first end portion of the base portion 75. The second convex portion 73 protrudes from the second end portion of the base portion 75 on the side opposite to the first end portion in the radial direction D2. The third convex portion 71 protrudes from between the first end portion and the second end portion of the base portion 75.

[0051] The above-described first to third convex portions have a shape protruding toward the outer peripheral surface of the inner peripheral pin 60, and the tips thereof are curved surfaces. That is, the inner peripheral pin lubricating member 70 is arranged such that the tips of the first to third convex portions face the outer peripheral surface side of the inner peripheral pin 60. Further, the back surface 74 (FIG. 14) of the inner peripheral pin lubricating member 70 on the side opposite to the first to third convex portions is a curved surface that is arcuately recessed in a direction away from the column portion 43 (FIG. 5). For this reason, when the drive of the speed reducer 1 stops, a gap is formed between the side portion in the circumferential direction of the column portion 43 and the inner peripheral pin lubricating member 70.

[0052] The inner circumferential pin lubricating member 70 is capable of swinging in the grooves formed on both sides in the circumferential direction of the column portion 43 so as to achieve a first contact state in which the first convex portion 72 and the third convex portion 71 contact the outer peripheral surface of the inner circumferential pin 60 while the second convex portion 73 is separated from the outer peripheral surface of the inner circumferential pin 60, and a second contact state in which the second convex portion 73 and the third convex portion 71 contact the outer peripheral surface of the inner circumferential pin 60 while the first convex portion 72 is separated from the outer peripheral surface of the inner circumferential pin 60. More specifically, as the inner circumferential pin lubricating member 70 swings along the arc-shaped curved surfaces formed on both sides in the circumferential direction of the column portion 43, the first convex portion 72 and the second convex portion 73 alternately contact the outer peripheral surface of the inner circumferential pin 60. The inner circumferential pin lubricating member 70 assumes the first contact state when the input shaft 10 rotates clockwise in FIG. 5. At this time, the outer ring 62 (FIG. 10) of the inner circumferential pin 60 rotates counterclockwise in FIG. 5. On the other hand, the inner circumferential pin lubricating member 70 assumes the second contact state when the input shaft 10 rotates counterclockwise in FIG. 5. At this time, the outer ring 62 of the inner circumferential pin 60 rotates clockwise in FIG. 5.

[0053] When the inner circumferential pin lubricating member 70 comes into full contact with the outer ring 62 that becomes the outer peripheral surface of the inner circumferential pin 60, the inner circumferential pin lubricating member 70 adheres to the outer ring 62, and as a result, torque cross and temperature rise may occur. In contrast, by adopting a configuration in which the first to third convex portions contact the outer ring 62 of the inner circumferential pin 60, the occurrence of the above-mentioned problems can be prevented. Note that the inner circumferential pin lubricating member 70 is not an essential component in the speed reducer of the present disclosure and may be omitted.

[0054] The main bearing 50 (FIG. 4) is, for example, a cross roller bearing. As shown in FIG. 4, the main bearing 50 includes an outer ring 51, an inner ring 53, a plurality of rolling elements 52 annularly disposed between the raceway surface (inner circumferential surface) of the outer ring 51 and the raceway surface (outer circumferential surface) of the inner ring 53, and a seal 54.

[0055] The outer ring 51 is fixed to the second end face (the end face opposite to the first end face, the left end face in Fig. 4) of the outer peripheral pin holder 30 by bolts B2. The outer ring 51 and the outer peripheral pin holder 30 together constitute a fixed shaft. An insertion hole for the rolling elements 52 is formed in the outer ring 51, and a lid 51A (Fig. 1) for closing the insertion hole is provided. The lid 51A is retained by a pin. Note that the lid may be a side lid, and it is not limited to the case where it is provided on the outer ring 51. Also, the lid is not limited to the case where it is retained by a pin extending in the axial direction D1, and a pin extending in the circumferential direction or a bolt may be employed.

[0056] The inner ring 53 is fixed to the surface of the second holder portion 42 opposite to the column portion 43 by bolts B3 (Fig. 11), and is fitted onto the outer ring of the second support bearing 15 from the outside in the radial direction D2. The inner ring 53 and the inner peripheral pin holder 40 together constitute an output shaft and are attached to a mating member (not shown).

[0057] The rolling elements 52 are cylindrical rollers, and the rotation axes of the cylindrical rollers adjacent in the circumferential direction are orthogonal to each other. The outer ring 51 and the inner ring 53 are made of a metal material such as JIS high-carbon chromium bearing steel, but are not limited thereto. Also, the main bearing 50 may further include a cage or a separator.

[0058] Next, the operation of the speed reducer 1 according to Embodiment 1 will be described.

[0059] 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 every time the input shaft 10 makes one revolution, the external teeth 27 (Fig. 8) of the first external gear 20 and the second external gear 21 come into contact with the adjacent outer peripheral pins 31 in the circumferential direction in order. As a result, the first external gear 20 and the second external gear 21 revolve at high speed and rotate at low speed inside the outer peripheral pin holder 30 in the radial direction D2.

[0060] As a result, it is pushed in the circumferential direction via the outer ring 62 of the inner circumferential pin 60 that is inscribed in each elongated hole 26 of the first external gear 20 and the second external gear 21, and the inner circumferential pin holder 40 rotates at a low speed as the first external gear 20 and the second external gear 21 rotate. As a result, the inner ring 53 attached to the inner circumferential pin holder 40 (second holder portion 42) rotates at a lower speed than the input shaft 10. At this time, the direction in which the input shaft 10 rotates and the direction in which the inner ring 53 rotates are opposite to each other.

[0061] Next, the operation and effect of the speed reducer 1 according to the first embodiment will be described.

[0062] In the speed reducer 1, the end face 46 of the column portion 43 is fixed to the first holder portion 41 by a bolt B1 inserted into the column portion 43 from the end face 46 of the column portion 43. For this reason, in the speed reducer 1, there is no need to insert the bolt B1 into the shaft 61 of the inner circumferential pin 60. Therefore, according to the speed reducer 1, unlike the case of inserting the bolt B1 into the shaft 61, the inner circumferential pin 60 can be formed thinner. Therefore, the radial size of the speed reducer 1 can be reduced, and it can be made more compact.

[0063] (Second Embodiment) Next, the configuration of the cycloid speed reducer 2 (hereinafter simply referred to as "speed reducer 2") according to the second embodiment will be described with reference to FIGS. 15 and 16. The speed reducer 2 according to the second embodiment basically has the same configuration as the speed reducer 1 according to the first embodiment and exhibits the same effects, but mainly differs in the number of external gears and the like. Hereinafter, only the differences from the speed reducer 1 according to the first embodiment will be described.

[0064] FIG. 15 is a perspective view showing the external structure of the speed reducer 2 according to Embodiment 2. FIG. 16 is a cross-sectional view taken along the line XVI-XVI in FIG. 15. As shown in FIG. 16, in addition to the first external gear 20 and the second external gear 21, the speed reducer 2 further includes a third external gear 82 and a fourth external gear 83. A third eccentric bearing 80 is disposed between the inner peripheral surface of the third external gear 82 and the outer peripheral surface of the input shaft 10 (the third shaft portion 19). Also, a fourth eccentric bearing 81 is disposed between the inner peripheral surface of the fourth external gear 83 and the outer peripheral surface of the input shaft 10 (the third shaft portion 19). Both the third external gear 82 and the fourth external gear 83 are cycloid gears similar to the first external gear 20. The third eccentric bearing 80 and the fourth eccentric bearing 81 are, for example, cylindrical roller bearings. As shown in FIG. 16, the second eccentric bearing 14, the first eccentric bearing 13, the third eccentric bearing 80, the fourth eccentric bearing 81, and the first support bearing 12 are arranged in this order from the first end portion 10A toward the second end portion 10B.

[0065] In Embodiment 2, compared with Embodiment 1, the input shaft 10 and the inner peripheral pin 60 are longer in the axial direction D1, and the outer peripheral pin holder 30 and the inner peripheral pin holder 40 are also formed thicker in the axial direction D1. Also, as the number of external gears increases, the outer peripheral pin 31 is formed longer in the axial direction D1, and two outer peripheral pin lubricating members 32 are arranged side by side in the axial direction D1. According to the speed reducer 2 according to Embodiment 2, by increasing the number of cycloid gears, effects such as improvement of the allowable load torque, reduction of vibration, and reduction of backlash can be obtained. Note that in FIG. 15, although no through hole is formed in the outer peripheral pin holder 30, the present invention is not limited to this, and a through hole may be formed in the same manner as in Embodiment 1.

[0066] (Other Embodiments) Here, other embodiments will be described.

[0067] In the above Embodiment 1, the long hole 26 was described as an example of the through hole, but the present invention is not limited to this. For example, the through hole may be a circular hole.

[0068] The first holder portion 41 and the column portion 43 may be integrally formed, and the end face 46 of the column portion 43 may be fixed to the second holder portion 42 by a bolt B1.

[0069] The inner circumferential pin 60 is not limited to the case where it is arranged so as to sandwich the column portion 43 from both sides in the circumferential direction, and only one inner circumferential pin 60 may be arranged in the long hole 26.

[0070] 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

[0071] 1,2 speed reducer, 10 input shaft, 10A first end portion, 10B second end portion, 11 key, 12 first support bearing, 13 first eccentric bearing, 14 second eccentric bearing, 15 second support bearing, 16 retaining ring, 16A notch portion, 17 first shaft portion, 18 second shaft portion, 19 third shaft portion, 19A key groove, 20 first external gear, 20A inner circumferential surface, 21 second external gear, 22 thrust washer, 23 pressing member, 23A upper surface, 23B lower surface, 24 fixing screw, 25 central hole, 26 long hole, 27 external teeth, 30 outer circumferential pin holder, 30A through hole, 31 outer circumferential pin, 32 outer circumferential pin lubricating member, 32A first pin retaining ring, 33 first pin regulating member, 33A second pin retaining ring, 34 second pin regulating member, 35 exterior plate, 40 inner circumferential pin holder, 40A end face, 41 first holder portion, 41A bolt hole, 42 second holder portion, 43 column portion, 43A female screw hole, 45 hole, 46 end face, 50 main bearing, 51 outer ring, 52 rolling element, 53 inner ring, 54 seal, 60 inner circumferential pin, 61 shaft, 62 outer ring, 63 rolling element, 64 thrust washer, 70 inner circumferential pin lubricating member, 71 third convex portion, 72 first convex portion, 73 second convex portion, 74 back surface, 75 base portion, 80 third eccentric bearing, 81 fourth eccentric bearing, 82 third external gear, 83 fourth external gear, B1,B2,B3 bolt, D2 radial direction

Claims

1. An annular external gear having a plurality of external teeth arranged along the circumferential direction on the outer circumferential surface, and a plurality of through holes penetrating in the axial direction are formed side by side in the circumferential direction; An input shaft that penetrates the space surrounded by the inner circumferential surface of the external gear and extends in the axial direction; A 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; An annular internal gear having a plurality of internal teeth arranged along the circumferential direction on the inner circumferential surface and meshing with the external teeth, and surrounding the outer circumferential surface of the external gear; A plurality of inner circumferential pins penetrating the plurality of through holes in the axial direction; An inner circumferential pin holder that holds both ends of the inner circumferential pin and forms a space through which the input shaft penetrates; The inner circumferential pin holder includes: A first holder portion having an annular holding portion for holding the first end portion of the inner circumferential pin; A second holder portion having an annular holding portion for holding the second end portion of the inner circumferential pin opposite to the first end portion; 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 through hole; A fixing member that fixes an end surface of the column portion to the first holder portion or the second holder portion, and further includes the fixing member inserted into the inside of 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 plurality of through holes are elongated holes extending in the circumferential direction; A speed reducer, wherein one of the column portions and a pair of the inner circumferential pins sandwiching one of the column portions in the circumferential direction are inserted into each of the plurality of through holes.

2. The speed reducer according to claim 1, wherein the plurality of through holes are elongated holes extending in an arc shape in the circumferential direction.

3. The speed reducer according to claim 1 or claim 2, wherein the inner circumferential pin is a rolling bearing or a sliding bearing.

4. Further comprising a lubricating member disposed inside the through hole and contacting the inner circumferential pin; A groove for accommodating the lubricating member is formed in the column portion; The speed reducer according to any one of claims 1 to 3, wherein an outer shape of a cross section perpendicular to the longitudinal direction of the groove corresponds to the lubricating member.

5. The lubricating member, in a cross section cut by a plane perpendicular to the axial direction, includes: A base portion extending in the radial direction; A first convex portion protruding from a first end portion of the base portion; A second convex portion protruding from a second end portion of the base portion opposite to the first end portion; including a third convex portion protruding from between the first end portion and the second end portion of the base portion; The speed reducer according to claim 4, wherein the lubricating member is swingable so as to achieve a first contact state in which the first convex portion and the third convex portion contact the inner peripheral pin and the second convex portion is separated from the inner peripheral pin, and a second contact state in which the second convex portion and the third convex portion contact the inner peripheral pin and the first convex portion is separated from the inner peripheral pin.

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