阅读说明：本技术 减速器和驱动装置 (Speed reducer and driving device ) 是由 井上信二 于 2021-05-06 设计创作，主要内容包括：本申请涉及减速器和驱动装置。本发明的减速器具有：减速单元,其将输入侧的旋转减速并向输出侧传递；输入齿轮,其以能够与所述减速单元的输入侧的轴一体地旋转的方式设置于所述减速单元的输入侧的轴；驱动齿轮,其受到驱动源的动力而旋转；以及环形带,其与所述驱动齿轮以及所述输入齿轮啮合而将所述驱动齿轮的旋转向所述输入齿轮传递。(The present application relates to a speed reducer and a drive device. The speed reducer of the invention comprises: a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; an input gear provided on the input-side shaft of the reduction unit so as to be rotatable integrally with the input-side shaft of the reduction unit; a drive gear that rotates by power of a drive source; and an endless belt that meshes with the drive gear and the input gear and transmits rotation of the drive gear to the input gear.)

1. A speed reducer, wherein,

the speed reducer is provided with:

a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side;

an input gear provided on the input-side shaft of the reduction unit so as to be rotatable integrally with the input-side shaft of the reduction unit;

a drive gear that rotates by power of a drive source; and

an endless belt that meshes with the drive gear and the input gear to transmit rotation of the drive gear to the input gear.

2. A speed reducer, wherein,

the speed reducer is provided with:

a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; and

a driving force transmission portion that transmits power of a driving source to an input side of the reduction unit,

the speed reduction unit includes:

a housing having internal teeth on an inner peripheral side;

a carrier module assembled to be rotatable with respect to the housing;

a plurality of crankshafts rotatably supported at positions on concentric circles of the carrier module; and

a wobble gear having a smaller number of teeth than the internal teeth and having external teeth on an outer periphery thereof that mesh with the internal teeth, the wobble gear being rotated in a manner to oscillate integrally with eccentric portions of the plurality of crankshafts,

the driving force transmission portion includes:

a drive gear that rotates by power of a drive source;

an input gear provided to each of the crankshafts so as to be rotatable integrally with the crankshaft; and

an endless belt that meshes with the drive gear and the plurality of input gears to transmit rotation of the drive gear to the plurality of input gears,

the crankshaft is rotated by the power of the drive source via the drive gear and the endless belt.

3. A speed reducer, wherein,

the speed reducer is provided with:

a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; and

a driving force transmission portion that transmits power of a driving source to an input side of the reduction unit,

the speed reduction unit includes:

a housing having internal teeth on an inner peripheral side;

a carrier module assembled to be rotatable with respect to the housing;

three crankshafts rotatably supported at positions on concentric circles of the carrier module; and

a wobble gear having a smaller number of teeth than the internal teeth and having external teeth on an outer periphery thereof that mesh with the internal teeth, the wobble gear being rotated in a manner to oscillate integrally with eccentric portions of the three crankshafts,

the driving force transmission portion includes:

a drive gear that rotates by power of a drive source;

an input gear provided to each of the crankshafts so as to be rotatable integrally with the crankshaft; and

an endless belt that meshes with the drive gear and the three input gears to transmit rotation of the drive gear to the three input gears,

the annular belt is erected on the peripheral surfaces of the three input gears in a roughly regular triangle shape.

4. A decelerator according to claim 2 or 3 wherein,

the endless belt has:

a 1 st meshing tooth that is disposed on an inner peripheral side and meshes with the plurality of input gears; and

and a 2 nd meshing tooth that is disposed on an outer peripheral side and meshes with the drive gear.

5. A decelerator according to claim 4 wherein,

the drive gear is configured to mesh with the 2 nd meshing tooth at positions equidistant from each other with respect to the adjacent two input gears.

6. A decelerator according to claim 1 wherein,

the endless belt has:

a core material extending in a rotation direction; and

an elastic member covering the core material.

7. A drive device, wherein,

the driving device comprises:

a speed reducer; and

a drive source that transmits a drive force to the reduction gear,

the speed reducer has:

a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side;

an input gear provided on the input-side shaft of the reduction unit so as to be rotatable integrally with the input-side shaft of the reduction unit;

a drive gear that rotates by power of a drive source; and

an endless belt that meshes with the drive gear and the input gear to transmit rotation of the drive gear to the input gear.

Technical Field

The present invention relates to a reduction gear and a drive device using the same.

Background

A reduction gear is used for an industrial robot, a machine tool, or the like to reduce the rotation of a drive source such as a motor (see, for example, patent document 1).

The reduction gear described in patent document 1 has internal teeth formed on the inner periphery of a housing, and a reduction mechanism portion that is engaged with the internal teeth to reduce the input rotation is housed inside the housing. A crankshaft (input-side shaft) is provided on the input side of the speed reduction mechanism, and the crankshaft is rotated by the power of the drive source. The input gear is attached to the crankshaft so as to be rotatable integrally with the crankshaft. The input gear can be interlocked with the drive gear on the drive source side via an intermediate gear (spur gear). In this reduction gear, when the rotation of the drive gear is transmitted to the input gear via the intermediate gear, the crankshaft eccentrically rotates, and the reduction mechanism section operates. Thereby, the rotation of the driving source decelerated by the deceleration mechanism is transmitted to the driven side.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-

Disclosure of Invention

Problems to be solved by the invention

Since the conventional reduction gear is configured such that the rotation of the drive gear rotating at a high speed is transmitted to the input gear via the intermediate gear, there is a concern that abnormal noise due to meshing of the tooth surfaces may occur in the drive force transmission portion from the drive gear to the input gear. In particular, when there is tolerance accumulation of various components and there is a slight deformation of the components due to long-term use, a gap is likely to be generated in the meshing portion of the gears. The gap thus generated is coupled with the high-speed rotation of the drive gear, and is likely to cause abnormal noise in the drive force transmission portion.

The invention provides a speed reducer and a driving device capable of restraining abnormal noise generated at a driving force transmission part.

Means for solving the problems

A speed reducer according to an aspect of the present invention includes: a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; an input gear provided on the input-side shaft of the reduction unit so as to be rotatable integrally with the input-side shaft of the reduction unit; a drive gear that rotates by power of a drive source; and an endless belt that meshes with the drive gear and the input gear and transmits rotation of the drive gear to the input gear.

A reduction gear according to another aspect of the present invention includes: a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; and a driving force transmission unit that transmits power of a driving source to an input side of the reduction unit, the reduction unit including: a housing having internal teeth on an inner peripheral side; a carrier module assembled to be rotatable with respect to the housing; a plurality of crankshafts rotatably supported at positions on concentric circles of the carrier module; a wobble gear having a smaller number of teeth than the internal teeth, having external teeth on an outer periphery thereof that mesh with the internal teeth, and rotating in a wobbling manner integrally with eccentric portions of the plurality of crankshafts, the drive force transmission portion including: a drive gear that rotates by power of a drive source; an input gear provided to each of the crankshafts so as to be rotatable integrally with the crankshaft; and an endless belt that meshes with the drive gear and the input gears to transmit rotation of the drive gear to the input gears, wherein the crankshaft is rotated by power of the drive source via the drive gear and the endless belt.

A reduction gear according to still another aspect of the present invention includes: a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; and a driving force transmission unit that transmits power of a driving source to an input side of the reduction unit, the reduction unit including: a housing having internal teeth on an inner peripheral side; a carrier module assembled to be rotatable with respect to the housing; three crankshafts rotatably supported at positions on concentric circles of the carrier module; and a wobble gear having a smaller number of teeth than the internal teeth, having external teeth on an outer periphery thereof, the external teeth meshing with the internal teeth, and rotating in a wobble manner integrally with eccentric portions of the three crankshafts, the driving force transmission portion including: a drive gear that rotates by power of a drive source; an input gear provided to each of the crankshafts so as to be rotatable integrally with the crankshaft; and an endless belt that is engaged with the drive gear and the three input gears and transmits rotation of the drive gear to the three input gears, wherein the endless belt is provided around outer peripheral surfaces of the three input gears in a substantially regular triangle shape.

The endless belt may also be of the following construction, having: a 1 st meshing tooth that is disposed on an inner peripheral side and meshes with the plurality of input gears; and a 2 nd meshing tooth that is disposed on an outer peripheral side and meshes with the drive gear.

The drive gear may also be configured to mesh with the 2 nd meshing tooth at positions equidistant from each other with respect to the adjacent two input gears.

Preferably, the endless belt has: a core material extending in a rotation direction; and an elastic member covering the core material.

The driving device according to an aspect of the present invention includes: a speed reducer; and a drive source that transmits a drive force to the reduction gear, the reduction gear including: a deceleration unit that decelerates rotation on an input side and transmits the decelerated rotation to an output side; an input gear provided on the input-side shaft of the reduction unit so as to be rotatable integrally with the input-side shaft of the reduction unit; a drive gear that rotates by power of a drive source; and an endless belt that meshes with the drive gear and the input gear and transmits rotation of the drive gear to the input gear.

ADVANTAGEOUS EFFECTS OF INVENTION

The speed reducer has the following structure: the drive gear and the input gear that are rotated by power of the drive source mesh with the endless belt, and rotation of the drive gear is transmitted to the input gear via the endless belt. Therefore, the backlash between the drive gear and the input gear is absorbed by the endless belt. Therefore, when the above-described speed reducer is used, the generation of abnormal noise in the driving force transmission portion can be suppressed.

Drawings

Fig. 1 is a perspective view of a driving device according to an embodiment.

Fig. 2 is a front view of the speed reducer of the embodiment as viewed from the input side.

Fig. 3 is a partial sectional view showing a speed reducer according to an embodiment.

Fig. 4 is a perspective view showing the endless belt of the embodiment, and is also a partial sectional view showing the endless belt.

Description of the reference numerals

1. A drive device; 2. a motor (driving source); 10. a speed reducer; 15A, 1 st gear rack module (gear rack module); 15B, 2 nd carrier module (carrier module); 17. an outer cylinder (housing); 18. a crankshaft; 19A, 1 st oscillating gear (oscillating gear); 19B, 2 nd oscillating gear (oscillating gear); 19Aa, 19Ba, external teeth; 20. internal gear pins (internal teeth); 31. a crankshaft gear; 33. a drive gear; 40. an endless belt; 41. 1 st meshing tooth; 42. a 2 nd meshing tooth; 43. a core material; 44. an elastic member; 50. a deceleration unit; 51. a driving force transmitting portion.

Detailed Description

Next, embodiments of the present invention will be described based on the drawings.

Fig. 1 is a perspective view of a drive device 1 used for welding, component assembly, and the like.

The drive device 1 includes: a base assembly 11 disposed on a ground surface F; a speed reducer 10 fixedly provided on an upper surface of one end side in a longitudinal direction of the base unit 11; a motor 2 which is a driving source for outputting power to the reduction gear 10; a holding device 12 that is fixedly provided on an upper surface of the other end side in the longitudinal direction of the base member 11; and a rotating unit 13 whose both ends in the longitudinal direction are supported by the reduction gear 10 and the holding device 12.

The motor 2 is mounted integrally with the input side of the reducer 10. The speed reducer 10 decelerates the rotation of the motor 2 and transmits the rotation to one end side in the longitudinal direction of the rotating unit 13. The holding device 12 rotatably supports the other end side in the longitudinal direction of the rotating unit 13. The power from the motor 2 is transmitted through the reduction gear 10, whereby the rotation member 13 rotates about the shaft center o1 substantially in the horizontal direction.

In the present embodiment, the rotary unit 13 has a plurality of workpiece support surfaces 13a around the axial center o 1. A workpiece w to be worked is mounted on each workpiece support surface 13 a. The workpiece w attached to the workpiece support surface 13a is moved toward the working position by the rotation of the rotary unit 13 by the motor 2. A working device 3 such as a welding robot is provided at the working position.

Fig. 2 is a front view of the reduction gear 10 as viewed from the input side, and fig. 3 is a partial cross section of the reduction gear 10 and a side view of the reduction gear 10. The partial cross-section of fig. 3 corresponds to the cross-section along the line II-II of fig. 2.

The speed reducer 10 includes: a fixing unit 14 (not shown in fig. 2 and 3) fixedly provided on one end side in the longitudinal direction of the base unit 11 (see fig. 1); a reduction unit 50 coupled to the fixing unit 14; and a driving force transmission portion 51 disposed between the reduction unit 50 and the fixed unit 14. A motor 2 as a driving source is mounted on the fixed unit 14. The reduction unit 50 reduces the rotation of the input side and transmits the rotation to the output side.

The reduction unit 50 has: a 1 st and a 2 nd carrier modules 15A, 15B secured to the stationary assembly 14; an outer cylinder 17 (housing) rotatably supported on the outer peripheral sides of the 1 st carrier module 15A and the 2 nd carrier module 15B; three crankshafts 18 rotatably supported by the 1 st and 2 nd carrier modules 15A and 15B; and a 1 st oscillating gear 19A and a 2 nd oscillating gear 19B that oscillate integrally with the two eccentric portions 18a, 18B of each crankshaft 18. The speed reducer 10 is provided on the base unit 11 such that a rotation center axis c1 of the output portion is aligned with an axial center o1 (see fig. 1) of the drive device 1.

The 1 st carrier module 15A is formed in a perforated disc shape. The 1 st gear frame module 15A is fixed to a base flange, not shown, of the fixing unit 14 by bolt fastening or the like. The 2 nd carrier module 15B is fixed to the end surface of the 1 st carrier module 15A on the side opposite to the base flange by bolt fastening or the like. The 2 nd carrier module 15B includes: a disc-shaped substrate portion 15Ba having an opening; and a plurality of support portions, not shown, extending from an end surface of the base plate portion 15Ba in a direction toward the 1 st carrier module 15A. The end surfaces of the strut portions of the 2 nd carrier module 15B are butted against the end surface of the 1 st carrier module 15A, and each strut portion is fixed to the 1 st carrier module 15A. An axial gap is secured between the base plate portion 15Ba of the 2 nd carrier module 15B and the 1 st carrier module 15A. The 1 st oscillating gear 19A and the 2 nd oscillating gear 19B are disposed in the gap.

The 1 st and 2 nd swing gears 19A and 19B are formed with a relief hole, not shown, through which each column portion of the 2 nd carrier module 15B passes. The relief hole is formed with an inner diameter sufficiently large enough for the column portion not to interfere with the swing rotation (eccentric rotation) of the 1 st swing gear 19A and the 2 nd swing gear 19B.

The outer cylinder 17 is disposed across the outer peripheral surface of the 1 st carrier module 15A and the outer peripheral surface of the substrate portion 15Ba of the 2 nd carrier module 15B. Both end portions of the outer cylinder 17 in the axial direction are rotatably supported by the base plate portions 15Ba of the 1 st carrier module 15A and the 2 nd carrier module 15B via bearings 16. Further, a plurality of pin grooves 35 extending parallel to the rotation center axis c1 are formed in the inner peripheral surface of the central region (region facing the outer peripheral surfaces of the 1 st and 2 nd oscillating gears 19A, 19B) in the axial direction of the outer tube 17. The substantially cylindrical internal gear pin 20 is rotatably housed in each pin groove 35. The plurality of internal gear pins 20 held in the pin grooves 35 of the outer cylinder 17 face the outer peripheral surfaces of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B, respectively.

The 1 st and 2 nd oscillating gears 19A and 19B are formed to have an outer diameter slightly smaller than the inner diameter of the outer cylinder 17. External teeth 19Aa and 19Ba are formed on the outer peripheral surfaces of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B, respectively, and the external teeth 19Aa and 19Ba are in contact with a plurality of internal-tooth pins 20 held on the inner peripheral side of the outer cylinder 17 in a meshed state with the plurality of internal-tooth pins 20. The number of teeth of the external teeth 19Aa and 19Ba formed on the outer peripheral surfaces of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B is set to be slightly smaller (for example, one smaller) than the number of the internal pins 20.

The three crankshafts 18 are disposed on the same circumference around the rotation center axis c1 of the 1 st carrier module 15A and the 2 nd carrier module 15B. Each crankshaft 18 is rotatably supported by the 1 st carrier module 15A and the 2 nd carrier module 15B via a bearing 22. The eccentric portions 18a and 18B of the crankshafts 18 penetrate the 1 st and 2 nd oscillating gears 19A and 19B, respectively. The eccentric portions 18a and 18B are rotatably engaged with support holes 21 formed in the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B via eccentric portion bearings 23. The two eccentric portions 18a and 18b of each crankshaft 18 are eccentric so as to be out of phase by 180 ° around the axis of the crankshaft 18. Further, each crankshaft 18 penetrates the 1 st carrier module 15A to the outside in the axial direction. The crank gear 31 is attached to an end of each crankshaft 18 protruding outward in the axial direction from the 1 st carrier block 15A so as to be rotatable integrally with the crank gear 31 (input gear).

When the three crankshafts 18 are rotated in one direction by an external force, the eccentric portions 18a and 18B of the crankshafts 18 are rotated in the same direction with a predetermined radius, and the 1 st rocking gear 19A and the 2 nd rocking gear 19B are rotated in the same direction with the same radius. At this time, the external teeth 19Aa and 19Ba of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B are in meshing contact with the plurality of internal-tooth pins 20 held on the inner periphery of the outer cylinder 17.

In the present embodiment, the internal teeth pins 20 held in the pin grooves 35 constitute internal teeth of the outer cylinder 17.

In the reduction gear 10 of the present embodiment, the number of internal teeth pins 20 (internal teeth) on the outer cylinder 17 side is set to be slightly larger (for example, one) than the number of teeth of the external teeth 19Aa and 19Ba of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B, respectively. Therefore, while the 1 st and 2 nd oscillating gears 19A and 19B oscillate and rotate one rotation, the outer cylinder 17 is pushed and rotated by a predetermined pitch in the same direction as the oscillating and rotating direction. As a result, the rotation of the crankshaft 18 is greatly decelerated and output as the rotation of the outer cylinder 17. In the present embodiment, since the eccentric portions 18a and 18B of the crankshafts 18 are eccentric so as to be offset by 180 ° about the axial center, the oscillation phases of the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B are offset by 180 °.

An output plate 26 having a perforated disc shape is attached to an end portion of the outer cylinder 17 in the axial direction on the side opposite to the base flange (fixing member 14). The output plate 26 covers the end of the 2 nd carrier module 15B in a non-contact state. The rotary unit 13 for holding a workpiece as a driven portion can be attached to the axially outer end surface of the output plate 26 by fastening with a bolt or the like (see fig. 1).

The driving force transmission portion 51 of the reduction gear 10 includes: a drive gear 33 coupled to a rotating shaft of the motor 2; a crank gear 31 (input gear) attached to each end of the three crankshafts 18 so as to be rotatable integrally with each end of the crankshafts 18; and an endless belt 40 that meshes with the drive gear 33 and the three crank gears 31 to transmit the rotation of the drive gear 33 to the respective crank gears 31. The three crank gears 31 are formed in the same size and the same shape. The outer diameter of the crank gear 31 is set larger than the outer diameter of the drive gear 33. The number of teeth of the crank gear 31 is set to be larger than that of the drive gear 33. Therefore, the rotation of the motor 2 input to the drive gear 33 is reduced by a predetermined speed reducer and transmitted to each crank gear 31.

In the present embodiment, the drive gear 33 and the crank gear 31 are spur gears.

Fig. 4 is a perspective view showing a part of the endless belt 40 in cross section.

As shown in fig. 2 and 4, the endless belt 40 of the present embodiment is formed of an endless belt-like member having a constant width without twisting. On the inner peripheral side of the endless belt 40, 1 st teeth 41 that mesh with the three crank gears 31 are formed, and on the outer peripheral side of the endless belt 40, 2 nd teeth 42 that mesh with the drive gear 33 are formed. The 1 st engaging tooth 41 and the 2 nd engaging tooth 42 are each formed such that a tooth trace extends in a direction orthogonal to the revolving direction (moving direction) of the endless belt 40.

As shown in fig. 4, the endless belt 40 of the present embodiment includes: a core material 43 extending in the revolving direction of the endless belt 40; and an elastic member 44 of rubber, soft resin, or the like, which covers the outside of the core member 43. The elastic member 44 forms actual functional portions of the 1 st tooth 41 and the 2 nd tooth 42, and the core 43 is embedded inside the elastic member 44 to reinforce the strength of the endless belt 40 in the revolving direction. The core member 43 may be formed of, for example, a bundle of metal wires or resin wires. In this case, the bundled metal wires and resin wires are preferably arranged in parallel in the width direction of the endless belt 40. In the endless belt 40 of the present embodiment, the outer sides (inner circumferential side and outer circumferential side) of the elastic members 44 are covered with the skin material 45, and the skin material 45 is made of a cloth material or the like having high frictional strength.

As shown in fig. 2, the three crank gears 31 are configured as: the straight lines L1, L2, L3 connecting the gear centers cg have a regular triangle shape as viewed in the axial direction. The endless belt 40 is mounted on the outer peripheral surfaces of the three crank gears 31 in a substantially triangular shape. The drive gear 33 is disposed at the following positions: the drive gear 33 meshes with the 2 nd meshing teeth 42 of the endless belt 40 on the center side (the side of the rotation center axis c 1) of the reduction gear 10 with respect to the linear orbit a of the endless belt 40 when the endless belt 40 is mounted on the two crank gears 31 at the shortest distance. In addition, the drive gear 33 is configured to mesh with the 2 nd meshing tooth 42 of the endless belt 40 at a position equidistant from the adjacent two crank gears 31.

When the motor 2 serving as a drive source is driven in the drive device 1 using the reducer 10, the drive gear 33 rotates together with the rotation shaft of the motor 2, and the rotation of the drive gear 33 is transmitted to the three crank gears 31 as rotation in phase via the endless belt 40. Thereby, the three crank gears 31 rotate with the same phase, and the 1 st and 2 nd oscillating gears 19A and 19B are caused to oscillate and rotate. At this time, the 1 st and 2 nd oscillating gears 19A and 19B mesh with the internal gear pins 20 on the outer tube 17 side, and transmit the decelerated rotation to the outer tube 17. The rotation of the outer cylinder 17 is output to the driven part (the rotating unit 13) via the output plate 26.

As described above, the speed reducer 10 of the present embodiment has the following structure: the drive gear 33 and the crank gear 31 (input gear) of the drive force transmission portion 51 mesh with the endless belt 40, and the rotation of the drive gear 33 is transmitted to the crank gear 31 via the endless belt 40. Therefore, the meshing gap between the drive gear 33 and the crank gear 31 is absorbed by the endless belt 40 having a flexibly changeable shape. Therefore, when the reduction gear 10 of the present embodiment is used, the generation of abnormal noise in the driving force transmission portion 51 can be suppressed.

Further, the drive gear 33 of the driving force transmission portion 51 of the reduction gear 10 of the present embodiment and the plurality of crank gears 31 (input gears) are engaged with the endless belt 40, and the rotation of the drive gear 33 is transmitted to the plurality of crank gears 31 in parallel via the endless belt 40. Therefore, the speed reducer 10 of the present embodiment has a simple structure that does not require a plurality of intermediate gears, but can transmit the input rotation to the plurality of crankshafts 18 that rotate the 1 st oscillating gear 19A and the 2 nd oscillating gear 19B of the speed reduction unit 50 in an oscillating manner in synchronization with each other.

Further, the speed reducer 10 of the present embodiment has three crankshafts 18 as input shafts, but the number of crankshafts 18 may be two or more, and is not limited to three but arbitrary.

The three crank gears 31 of the speed reducer 10 of the present embodiment are arranged: the straight lines L1, L2, and L3 connecting the gear center cg of the crank gear 31 (input gear) are regular triangular in shape. The endless belt 40 is mounted on the outer peripheral surfaces of the three crank gears 31 in a substantially regular triangular shape. Therefore, the space in the radial direction occupied by the three crank gears 31 and the endless belt 40 can be easily made smaller than the inner circumferential dimension of the outer cylinder 17. Therefore, when the reduction gear 10 of the present embodiment is used, the entire device can be further downsized.

In the reduction gear 10 of the present embodiment, the 1 st tooth 41 that meshes with the crank gear 31 is provided on the inner peripheral side of the endless belt 40, and the 2 nd tooth 42 that meshes with the drive gear 33 is provided on the outer peripheral side of the endless belt 40. Therefore, a load that presses the annular belt 40 radially outward acts on the annular belt 40 from the crank gear 31, and a load that presses the annular belt 40 radially inward acts on the annular belt 40 from the drive gear 33. Therefore, in the case of using the speed reducer 10 of the present embodiment, the variation in the pressing load acting in the outer direction and the inner direction of the endless belt 40 is reduced, and therefore the durability of the endless belt 40 can be further improved.

The drive gear 33 of the driving force transmission portion 51 of the reduction gear 10 according to the present embodiment is disposed so as to mesh with the 2 nd meshing tooth 42 of the endless belt 40 at a position equidistant from the two adjacent crank gears 31. Therefore, when the endless belt 40 is bent between the two adjacent crank gears 31 and meshes with the drive gear 33, the inclination angle of the endless belt 40 on the side of one crank gear 31 (1 st crank gear) and the inclination angle of the endless belt 40 on the side of the other crank gear 31 (2 nd crank gear) are substantially equal. Therefore, when the reduction gear 10 of the present embodiment is used, the meshing state between the drive gear 33 and the endless belt 40 can be stabilized.

The endless belt 40 of the driving force transmission portion 51 of the reduction gear 10 of the present embodiment has a structure including a core 43 extending in the revolving direction and an elastic member 44 covering the core 43. Therefore, when the reduction gear 10 of the present embodiment is used, the core material 43 can maintain the strength of the endless belt 40, and the elastic member 44 can be bent to eliminate the gap between the meshing portions of the gears and the endless belt 40.

Further, when the outside of the elastic member 44 is covered with the skin material 45 having high frictional strength as in the present embodiment, the abrasion resistance of the endless belt 40 can be improved.

In the embodiment described above, only the drive gear 33 is in contact with the outer peripheral side of the endless belt 40, but a tension adjusting roller for adjusting the tension of the endless belt 40 may be in contact with the outer peripheral side of the endless belt 40. In this case, the tension of the endless belt 40 is appropriately adjusted by the tension adjusting roller, whereby the meshing state between the endless belt 40 and each gear can be stabilized.

The present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the scope of the invention.

For example, in the above-described embodiment, the reduction unit 50 is constituted by a swing-type reduction mechanism including: an outer cylinder 17, a 1 st swing gear 19A and a 2 nd swing gear 19B, a crankshaft 18, a 1 st carrier module 15A and a 2 nd carrier module 15B, and the like. On the other hand, the speed reducer unit may be constituted by a planetary gear type speed reducing mechanism.