CN111113479A

CN111113479A - Industrial robot

Info

Publication number: CN111113479A
Application number: CN201910981764.6A
Authority: CN
Inventors: 矢泽隆之; 藤原真志
Original assignee: Nidec Sankyo Corp
Current assignee: Nidec Sankyo Corp
Priority date: 2018-10-31
Filing date: 2019-10-16
Publication date: 2020-05-08
Also published as: JP7195111B2; KR20200049509A; KR102260521B1; JP2020069575A

Abstract

The present invention provides an industrial robot, which is provided with a belt wheel connected with the input side of a speed reducer arranged on a joint part and a rolling bearing arranged on the inner circumference side of the belt wheel, wherein, even if the belt wheel is formed by aluminum alloy, the rolling bearing can be prevented from being damaged by heat generated by the speed reducer. The industrial robot is provided with a speed reducer (22) arranged at a joint (16), a pulley (32) made of aluminum alloy connected to the input side of the speed reducer (22), a rolling bearing (36) having a steel outer ring and arranged on the inner peripheral side of the pulley (32), and a sleeve (45) fixed to the pulley (32) and arranged between the outer ring of the rolling bearing (36) and the pulley (32) in the radial direction of the pulley (32). The sleeve (45) is made of a material having a thermal expansion coefficient closer to that of steel than that of an aluminum alloy or steel, and the inner peripheral surface of the sleeve (45) is in contact with the outer peripheral surface of the outer ring of the rolling bearing (36) at a predetermined contact pressure.

Description

Industrial robot

Technical Field

The present invention relates to an industrial robot including a joint.

Background

Conventionally, an industrial robot that transports a glass substrate in a vacuum is known (for example, see patent document 1). The industrial robot described in patent document 1 includes a hand on which a glass substrate is placed, an arm to which the hand is rotatably connected at a distal end side, and a main body portion to which a proximal end side of the arm is rotatably connected. The arm is composed of a first arm portion whose base end side is rotatably connected to the main body portion and a second arm portion whose base end side is rotatably connected to a leading end side of the first arm portion. A hand is rotatably connected to the tip end side of the second arm portion.

In the industrial robot described in patent document 1, the hand and the arm are arranged in a vacuum. The first arm portion and the second arm portion are formed in a hollow shape. The pressure inside the first arm and the second arm is atmospheric pressure. A first motor for rotating the second arm with respect to the first arm and a second motor for rotating the hand with respect to the second arm are disposed inside the first arm. A speed reducer for reducing the rotation of the first motor and transmitting the rotation to the second arm is disposed in a joint portion that is a connection portion between the first arm and the second arm. The speed reducer is a hollow speed reducer, and a hollow rotating shaft is disposed on the inner peripheral side of the speed reducer.

In the industrial robot described in patent document 1, a pulley is fixed to an input shaft of a reduction gear. The power of the first motor is transmitted to the pulley via the belt. A rolling bearing is disposed on the inner peripheral side of the pulley. The inner ring of the rolling bearing is fixed on the hollow rotating shaft. The inner peripheral surface of the pulley is in contact with the outer peripheral surface of the outer ring of the rolling bearing at a predetermined contact pressure, and the pulley and the outer ring rotate together by a frictional force between the outer peripheral surface of the outer ring of the rolling bearing and the inner peripheral surface of the pulley. A pulley is fixed to a lower end portion of the hollow rotating shaft, and power of the second motor is transmitted to the pulley via a belt.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-144527

Disclosure of Invention

Technical problem to be solved by the invention

In the industrial robot described in patent document 1, a reducer disposed in a joint portion generates heat. In order to effectively dissipate the heat generated by the reduction gear, it is desirable that the pulley fixed to the input shaft of the reduction gear (i.e., the pulley in contact with the input shaft of the reduction gear) be formed of a material having a high thermal conductivity and a high heat dissipation property. In the industrial robot described in patent document 1, a lightweight pulley is preferable in order to reduce the moment of inertia of the joint. Therefore, the present inventors are studying to form a pulley fixed to an input shaft of a speed reducer with an aluminum alloy.

However, according to the research of the present inventors, it has been found that in the industrial robot described in patent document 1, when the pulley fixed to the input shaft of the reduction gear is formed of an aluminum alloy, the outer ring of the rolling bearing is generally formed of steel, and the thermal expansion coefficient of the pulley is much larger than that of the outer ring, so that when the pulley and the outer ring are thermally expanded by the influence of heat generated by the reduction gear, the contact pressure between the outer circumferential surface of the outer ring and the inner circumferential surface of the pulley is reduced, and there is a possibility that slip occurs between the outer ring and the pulley. In addition, as a result of the research by the present inventors, when a slip is generated between the outer ring and the pulley, frictional heat is generated between the outer ring and the pulley in addition to heat generated from the reducer, and thus the rolling bearing may be damaged due to the influence of heat.

Accordingly, an object of the present invention is to provide an industrial robot including a pulley connected to an input side of a speed reducer disposed in a joint portion and a rolling bearing disposed on an inner peripheral side of the pulley, wherein damage to the rolling bearing due to heat generated by the speed reducer can be suppressed even if the pulley is formed of an aluminum alloy.

Technical scheme for solving technical problem

In order to solve the above-described problems, the present invention provides an industrial robot including a joint unit, comprising: a speed reducer disposed at the joint; a pulley made of an aluminum alloy, the pulley being connected to an input side of the speed reducer; a rolling bearing having a steel outer ring and disposed on an inner circumferential side of the pulley; and a cylindrical sleeve fixed to the pulley and disposed between the outer ring of the rolling bearing and the pulley in a radial direction of the pulley, the sleeve being made of a material having a thermal expansion coefficient closer to that of steel than that of aluminum alloy or steel, and an inner peripheral surface of the sleeve being in contact with an outer peripheral surface of the outer ring at a predetermined contact pressure.

In the industrial robot according to the present invention, the inner circumferential surface of the sleeve fixed to the pulley made of aluminum alloy and disposed between the outer ring of the rolling bearing and the pulley in the radial direction of the pulley is in contact with the outer circumferential surface of the outer ring of the rolling bearing at a predetermined contact pressure. In the present invention, the sleeve is made of a material having a thermal expansion coefficient closer to that of steel than the aluminum alloy or steel. Therefore, in the present invention, even if the pulley is formed of an aluminum alloy, it is possible to suppress a decrease in contact pressure between the outer circumferential surface of the outer ring and the inner circumferential surface of the sleeve when the outer ring and the sleeve of the rolling bearing are thermally expanded by the influence of heat generated by the speed reducer.

Therefore, in the present invention, even if the pulley is formed of an aluminum alloy, slip between the outer ring and the sleeve when the outer ring and the sleeve of the rolling bearing are thermally expanded by the influence of heat generated by the speed reducer can be suppressed, and generation of frictional heat between the outer ring and the sleeve can be suppressed. As a result, in the present invention, even if the pulley is formed of an aluminum alloy, damage to the rolling bearing due to heat generated by the speed reducer can be suppressed.

In the present invention, it is desirable that the sleeve is formed of steel. When constituted in this manner, the hardness of the sleeve can be made the same as that of the outer ring of the rolling bearing, or the hardness of the sleeve can be made close to that of the outer ring of the rolling bearing. Therefore, even if a slip occurs between the outer ring and the sleeve when the outer ring and the sleeve of the rolling bearing are thermally expanded by the influence of heat generated by the speed reducer, wear of the outer ring and the sleeve can be suppressed.

In the present invention, it is preferable that the pulley is fixed to the input shaft of the reduction gear and is in contact with the input shaft. With this configuration, even if the sleeve is disposed between the outer ring of the rolling bearing and the pulley in the radial direction of the pulley, the heat generated by the speed reducer can be efficiently dissipated using the pulley made of the aluminum alloy that is in contact with the input shaft of the speed reducer.

In the present invention, it is preferable that the sleeve includes a cylindrical portion and an annular ring portion connected to one end of the cylindrical portion and connected to an inner peripheral side of the cylindrical portion, the pulley has a fixed portion fixed to the input shaft, an inner peripheral surface of the cylindrical portion is in contact with an outer peripheral surface of the outer ring at a predetermined contact pressure, and the pulley and the sleeve are fixed to the input shaft by screws inserted through the ring portion and the fixed portion in a state where the fixed portion is sandwiched between one end surface of the input shaft and the ring portion in the axial direction of the input shaft.

When so configured, the pulley can be fixed to the input shaft of the reducer using a common screw, and the sleeve can be fixed to the pulley. Therefore, the structure of the joint portion can be simplified as compared with a case where a screw for providing the pulley on the input shaft and a screw for fixing the sleeve on the pulley are separately provided. In addition, in the case of the above configuration, since the cylindrical portion having the inner peripheral surface in contact with the outer peripheral surface of the outer ring at the predetermined contact pressure has a simple cylindrical shape, the sleeve can be easily manufactured even if the dimensional tolerance of the inner peripheral surface of the cylindrical portion is reduced. Therefore, the inner circumferential surface of the cylindrical portion can be formed with high accuracy while reducing the manufacturing cost of the sleeve, and as a result, variation in contact pressure between the inner circumferential surface of the cylindrical portion and the outer circumferential surface of the outer ring can be suppressed.

In the present invention, an industrial robot includes, for example: a hand that loads a transport object; an arm rotatably connected to a hand at a leading end side; and a main body portion rotatably connecting a proximal end side of the arm, the arm including: a first arm portion whose base end side is rotatably connected to the main body portion; and a second arm having a base end side rotatably connected to a tip end side of the first arm and a hand rotatably connected to a tip end side of the second arm, wherein a speed reducer, a pulley, a rolling bearing, and a sleeve are arranged at a joint portion serving as a connection portion between the first arm and the second arm.

Effects of the invention

As described above, in the present invention, in the industrial robot including the pulley connected to the input side of the speed reducer disposed in the joint portion and the rolling bearing disposed on the inner peripheral side of the pulley, even if the pulley is formed of an aluminum alloy, damage of the rolling bearing due to heat generated by the speed reducer can be suppressed.

Drawings

Fig. 1 is a diagram showing an industrial robot according to an embodiment of the present invention, in which (a) is a plan view and (B) is a side view.

Fig. 2 is a sectional view for explaining the internal structure of the joint section shown in fig. 1 from the side.

Fig. 3 is an enlarged view of a portion E of fig. 2.

Description of the reference numerals

1 robot (Industrial robot)

2 substrate (glass substrate, object to be conveyed)

3 hand

4 arm

5 body part

13 first arm part

14 second arm part

16 joint part

22 speed reducer

23 input shaft

32 belt wheel

32b to be fixed

36 Bearings (Rolling bearing)

36b outer ring

45 sleeve

45a cylindrical part

45b ring part

47 screw

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Overall Structure of Industrial robot)

Fig. 1 is a diagram showing an industrial robot 1 according to an embodiment of the present invention, in which (a) is a plan view and (B) is a side view. Fig. 2 is a sectional view for explaining the internal structure of the joint unit 16 shown in fig. 1 from the side.

An industrial robot 1 (hereinafter referred to as "robot 1") according to the present embodiment is a horizontal articulated robot for conveying a glass substrate 2 (hereinafter referred to as "substrate 2") for an organic EL (organic electroluminescence) display as a conveyance target. The robot 1 is incorporated into a manufacturing system of an organic EL display for use. The robot 1 includes a hand 3 on which the substrate 2 is mounted, an arm 4 having the hand 3 rotatably connected to a distal end side thereof, and a main body 5 rotatably connecting a proximal end side of the arm 4.

The robot 1 further includes a housing 7 that houses the main body 5. A lifting mechanism (not shown) for lifting the main body 5 is housed in the housing 7. A flange 8 formed in a disc shape is fixed to an upper end of the housing 7. The flange 8 is formed with a through hole in which the upper end portion of the main body 5 is disposed. In fig. 1(a), illustration of the case 7 and the flange 8 is omitted.

The hand 3 and the arm 4 are disposed above the main body 5. The hand 3 and the arm 4 are disposed above the flange 8. The upper portion of the robot 1 with respect to the lower end surface of the flange 8 is disposed inside a vacuum chamber constituting a manufacturing system of an organic EL display. That is, the portion of the robot 1 above the lower end surface of the flange 8 is disposed in the vacuum region VR, and the hand 3 and the arm 4 are disposed in the vacuum. On the other hand, a portion of the robot 1 below the lower end surface of the flange 8 is disposed in the atmosphere area AR (in the atmosphere). The robot 1 transports the substrate 2 in vacuum.

The hand 3 includes a base 10 connected to the arm 4 and four linear fork portions 11 on which the substrate 2 is mounted. The arm 4 is constituted by two arm portions, a first arm portion 13 and a second arm portion 14. The first arm portion 13 and the second arm portion 14 are formed in a hollow shape. The base end side of the first arm portion 13 is rotatably connected to the main body portion 5. The base end side of the second arm portion 14 is rotatably connected to the tip end side of the first arm portion 13. The hand 3 (specifically, the base 10) is rotatably connected to the distal end side of the second arm portion 14. The second arm portion 14 is disposed above the first arm portion 13. The hand 3 is disposed above the second arm portion 14.

The joint portion between the arm 4 and the main body 5 (i.e., the joint portion between the first arm portion 13 and the main body 5) serves as a joint portion 15. The joint portion 16 is a joint portion between the first arm portion 13 and the second arm portion 14. The joint portion between the arm 4 and the hand 3 (i.e., the joint portion between the second arm portion 14 and the hand 3) serves as a joint portion 17. That is, the robot 1 includes a plurality of joint units 15 to 17. Specifically, the robot 1 includes three joint portions 15 to 17.

A turning mechanism (not shown) for turning the first arm portion 13 with respect to the main body portion 5 is housed in the housing 7. The turning mechanism includes a motor, a speed reducer for reducing the rotation of the motor and transmitting the rotation to the first arm portion 13, and the like. A magnetic fluid seal (not shown) for preventing air from flowing into the vacuum region VR is disposed in the joint portion 15. A bellows (not shown) for preventing air from flowing into the vacuum region VR is disposed in the joint portion 15. The bellows is disposed on the outer peripheral side of the magnetic fluid seal, and expands or contracts when the main body 5 is lifted or lowered.

As described above, the first arm portion 13 and the second arm portion 14 are formed in a hollow shape. The pressure inside the first arm portion 13 and the second arm portion 14 formed in the hollow shape is atmospheric pressure. A first motor 21 for rotating the second arm portion 14 with respect to the first arm portion 13 and a second motor (not shown) for rotating the hand 3 with respect to the second arm portion 14 are disposed inside the first arm portion 13. A speed reducer 22 for reducing the speed of rotation of the first motor 21 and transmitting the rotation to the second arm portion 14 is disposed in the joint portion 16.

The reducer 22 is a hollow reducer having a through hole formed at the center in the radial direction of the reducer 22. Specifically, the speed reducer 22 is a hollow wave gear device. The speed reducer 22 includes an input shaft 23 and an output shaft 24 formed in a hollow shape. The input shaft 23 is disposed so that the axial direction of the input shaft 23 coincides with the vertical direction. That is, the vertical direction is the axial direction of the input shaft 23. The output shaft 24 is disposed so that the axial direction of the output shaft 24 coincides with the vertical direction. The output shaft 24 is disposed above the input shaft 23.

The reducer 22 includes a bearing 25 that rotatably supports the output shaft 24, and a magnetic fluid seal 26 disposed on the outer peripheral side of the output shaft 24. The speed reducer 22 includes a rigid internally-toothed gear 28, a flexible externally-toothed gear 29, a wave bearing 30 attached to the outer peripheral side of the input shaft 23, and a housing 31 that holds the bearing 25 and the magnetic fluid seal 26.

The upper end of the housing 31 is fixed to the upper surface side of the front end of the first arm 13. The bearing 25 is a cross roller bearing. The outer race of the bearing 25 is fixed to the upper end portion of the housing 31. The inner race of the bearing 25 is fixed to the output shaft 24. The upper end surface of the output shaft 24 is fixed to the lower surface of the base end portion of the second arm portion 14. The magnetic fluid seal 26 is located on the upper side of the bearing 25 and has a function of preventing air from flowing into the vacuum region VR. The magnet and the pole piece of the magnetic fluid seal 26 are fixed to the inner peripheral surface of the upper end portion of the case 31. A magnetic fluid is held between the inner peripheral surface of the pole piece and the outer peripheral surface of the output shaft 24.

The input shaft 23 is rotatably supported at a lower end portion of the housing 31 via a bearing. The input shaft 23 is formed with an elliptical portion whose outer peripheral surface has an elliptical shape when viewed in the vertical direction. The rigid internally-toothed gear 28 is fixed to a lower end portion of the housing 31. Internal teeth are formed on the inner peripheral surface of the rigid internally-toothed gear 28. The upper end portion of the flexible externally toothed gear 29 is fixed to the lower end of the output shaft 24. Outer teeth that mesh with the inner teeth of the rigid internally toothed gear 28 are formed on the outer peripheral surface of the lower end portion of the flexible externally toothed gear 29. The flexible externally toothed gear 29 is relatively rotatable with respect to the input shaft 23.

The wave bearing 30 is a ball bearing having a flexible inner ring and an outer ring. The wave bearing 30 is disposed along the outer peripheral surface of the elliptical portion of the input shaft 23 and is curved into an elliptical shape. The lower end portion of the flexible externally toothed gear 29, on which external teeth are formed, is disposed on the outer peripheral side of the wave bearing 30 so as to surround the wave bearing 30, and this portion is elliptically curved. The external teeth of the flexible externally toothed gear 29 mesh with the internal teeth of the rigid internally toothed gear 28 at two points in the longitudinal direction of the lower end side portion of the flexible externally toothed gear 29 that is bent into an ellipsoidal shape. Further, when the power of the first electric motor 21 is transmitted to the reduction gear 22, heat is generated mainly in the meshing portion of the rigid internally-toothed gear 28 and the flexible externally-toothed gear 29 in the reduction gear 22.

A pulley 32 is connected to an input side of the reduction gear 22. Specifically, the pulley 32 is fixed to the input shaft 23 of the reduction gear 22. A pulley 32 is fixed to the lower end of the input shaft 23. The pulley 32 is rotatably supported at a lower end portion of the housing 31 via a bearing, and is rotatable with respect to the housing 31 together with the input shaft 23. A through hole penetrating in the vertical direction is formed in the center of the pulley 32. The power of the first motor 21 is transmitted to the pulley 32 via the belt 33. The belt 33 is a toothed belt.

A hollow rotary shaft 34 is disposed on the inner peripheral side of the reduction gear 22. Specifically, a hollow rotary shaft 34 is disposed on the inner peripheral side of the input shaft 23, the output shaft 24, and the pulley 32. The hollow rotary shaft 34 is formed in a cylindrical shape elongated in the vertical direction. A bearing 35 is disposed between the outer peripheral surface of the hollow rotary shaft 34 and the inner peripheral surface of the output shaft 24. Further, a bearing 36 is disposed between the outer peripheral surface of the hollow rotary shaft 34 and the inner peripheral surface of the pulley 32.

A pulley 37 is fixed to a lower end of the hollow rotary shaft 34. A through hole penetrating in the vertical direction is formed in the center of the pulley 37. The pulley 37 is disposed below the pulley 32. The power of the second motor is transmitted to the pulley 37 via the belt 38. The belt 38 is a toothed belt. A pulley 39 is fixed to an upper end of the hollow rotary shaft 34. A through hole penetrating in the vertical direction is formed in the center of the pulley 39. The pulley 39 is disposed inside the base end side of the second arm portion 14.

A speed reducer (not shown) for reducing the speed of rotation of the second motor and transmitting the rotation to the hand 3 is disposed in the joint 17. The reducer is a hollow wave gear device as is the reducer 22. A pulley (not shown) is fixed to the input shaft of the speed reducer, and a belt 40 is stretched over the pulley and the pulley 39. The belt 40 is a toothed belt. The output shaft of the speed reducer is fixed to the hand 3, and the housing is fixed to the distal end of the second arm 14.

(Structure of Joint portion)

Fig. 3 is an enlarged view of a portion E of fig. 2.

As described above, the speed reducer 22 is disposed in the joint portion 16. Further, the joint 16 is provided with a pulley 32 and a bearing 36. As described above, the bearing 36 is disposed between the outer peripheral surface of the hollow rotary shaft 34 and the inner peripheral surface of the pulley 32. That is, the bearing 36 is disposed on the inner circumferential side of the pulley 32. Further, a tubular sleeve 45 disposed between the bearing 36 and the pulley 32 in the radial direction of the pulley 32 is disposed in the joint portion 16.

The bearing 36 is a rolling bearing. Specifically, the bearing 36 is a ball bearing (ball bearing) and includes an inner ring 36a made of steel, an outer ring 36b made of steel, and a plurality of balls 36c made of steel arranged between the inner ring 36a and the outer ring 36 b. The inner race 36a is fixed to the hollow rotary shaft 34. In the present embodiment, the inner ring 36a is fixed to the hollow rotary shaft 34 by a screw 46 inserted through the pulley 37 in a state of being sandwiched between the hollow rotary shaft 34 and the pulley 37 in the vertical direction.

Specifically, a contact surface against which the upper end surface of the inner ring 36a contacts is formed at the lower end portion of the hollow rotating shaft 34, and the contact surface is an annular flat surface orthogonal to the vertical direction. Further, a through hole through which the screw 46 is inserted is formed in the pulley 37 so as to penetrate the pulley 37 in the vertical direction, and a screw hole into which an upper end portion of the screw 46 is screwed is formed in a lower end surface of the hollow rotating shaft 34. The inner ring 36a is fixed to the hollow rotary shaft 34 by a screw 46 inserted through a through hole of the pulley 37 and screwed into a screw hole of the hollow rotary shaft 34 in a state of being sandwiched between an abutment surface of the hollow rotary shaft 34 and an upper surface of the pulley 37. In addition, the pulley 37 is fixed to the hollow rotary shaft 34 by a screw 46.

The pulley 32 is formed of an aluminum alloy. As described above, the pulley 32 has a through hole formed at its center in the vertical direction. The pulley 32 includes an annular belt engaging portion 32a to which the belt 33 is engaged and an annular fixed portion 32b fixed to the input shaft 23. The pulley 32 of the present embodiment is composed of a belt engaging portion 32a and a fixed portion 32 b. The belt engaging portion 32a constitutes a lower portion of the pulley 32, and the fixed portion 32b constitutes an upper portion of the pulley 32.

The belt engaging portion 32a has an outer diameter larger than that of the fixed portion 32 b. The belt engaging portion 32a has an inner diameter larger than that of the fixed portion 32 b. A step surface 32c is formed at the boundary between the inner peripheral surface of the belt engaging portion 32a and the inner peripheral surface of the fixed portion 32 b. The step surface 32c is a plane perpendicular to the up-down direction. The stepped surface 32c is an annular flat surface centered on the axial center of the pulley 32. A plurality of teeth are formed on the outer peripheral surface of the belt engaging portion 32 a. A through hole through which a screw 47 is inserted is formed in an inner portion of the fixed portion 32b of the pulley 32 in the radial direction, and the screw 47 is used to fix the pulley 32 to the input shaft 23. The through hole penetrates the fixed portion 32b in the vertical direction.

The sleeve 45 is formed of steel. The sleeve 45 includes a cylindrical portion 45a and an annular ring portion 45b connected to one end of the cylindrical portion 45 a. The sleeve 45 of the present embodiment is composed of a cylindrical portion 45a and an annular portion 45 b. The cylindrical portion 45a is arranged such that the axial direction of the cylindrical portion 45a coincides with the vertical direction. The annular portion 45b is continuous with the upper end of the cylindrical portion 45 a. The annular portion 45b is connected to the inner peripheral side of the cylindrical portion 45 a. The cylindrical portion 45a and the annular portion 45b are coaxially arranged.

The outer diameter of the cylindrical portion 45a is substantially equal to the inner diameter of the belt engagement portion 32 a. The inner diameter of the annular portion 45b is substantially equal to the inner diameter of the fixed portion 32 b. The outer peripheral surface of the cylindrical portion 45a contacts the inner peripheral surface of the belt engaging portion 32 a. The upper surface of the annular portion 45b contacts the step surface 32 c. The annular portion 45b is formed with a through hole through which the screw 47 is inserted. The through hole penetrates the annular portion 45b in the vertical direction.

The sleeve 45 is fixed to the pulley 32 and to the input shaft 23. As described above, the pulley 32 is fixed to the lower end of the input shaft 23. Specifically, the pulley 32 and the sleeve 45 are fixed to the input shaft 23 by screws 47 inserted through holes of the annular portion 45b and through holes of the fixed portion 32b in a state where the fixed portion 32b is sandwiched between the lower end surface of the input shaft 23 and the annular portion 45b in the vertical direction. A screw hole into which the upper end of the screw 47 is screwed is formed on the lower end surface of the input shaft 23.

The upper end surface of the fixed portion 32b contacts the lower end surface of the input shaft 23. That is, the pulley 32 is in contact with the input shaft 23. The sleeve 45 is disposed between the outer race 36b of the bearing 36 and the pulley 32 in the radial direction of the pulley 32. The inner peripheral surface of the sleeve 45 contacts the outer peripheral surface of the outer ring 36b of the bearing 36 at a predetermined contact pressure. Specifically, the cylindrical portion 45a of the sleeve 45 is disposed between the outer ring 36b of the bearing 36 and the belt engaging portion 32a of the pulley 32 in the radial direction of the pulley 32, and the inner circumferential surface of the cylindrical portion 45a contacts the outer circumferential surface of the outer ring 36b at a predetermined contact pressure. In the present embodiment, the outer ring 36b is fitted into the sleeve 45 by transition fitting.

(main effect of the present embodiment)

As described above, in the present embodiment, the sleeve 45, the inner peripheral surface of which is in contact with the outer peripheral surface of the outer ring 36b of the steel bearing 36 at a predetermined contact pressure, is formed of steel. Therefore, in the present embodiment, even if the pulley 32 is formed of an aluminum alloy, it is possible to suppress a decrease in the contact pressure between the outer circumferential surface of the outer ring 36b and the inner circumferential surface of the sleeve 45 when the outer ring 36b and the sleeve 45 are thermally expanded due to the influence of heat generated by the reduction gear 22.

Therefore, in the present embodiment, even if the pulley 32 is formed of an aluminum alloy, slip between the outer ring 36b and the sleeve 45 when the outer ring 36b and the sleeve 45 are thermally expanded due to the influence of heat generated by the reduction gear 22 can be suppressed, and generation of frictional heat between the outer ring 36b and the sleeve 45 can be suppressed. As a result, in the present embodiment, even if the pulley 32 is formed of an aluminum alloy, damage to the bearing 36 due to heat generated by the reduction gear 22 can be suppressed.

In the present embodiment, since the sleeve 45 is made of steel, the hardness of the sleeve 45 can be made the same as that of the outer ring 36b, or the hardness of the sleeve 45 can be made close to that of the outer ring 36 b. Therefore, in the present embodiment, even if a slip occurs between the outer ring 36b and the sleeve 45 when the outer ring 36b and the sleeve 45 are thermally expanded by the influence of heat generated by the reduction gear 22, it is possible to suppress wear of the outer ring 36b and the sleeve 45.

In the present embodiment, the cylindrical portion 45a, the inner peripheral surface of which is in contact with the outer peripheral surface of the outer ring 36b at a predetermined contact pressure, has a simple cylindrical shape. Therefore, in the present embodiment, even if the dimensional tolerance of the inner peripheral surface of the cylindrical portion 45a is reduced, the sleeve 45 can be easily manufactured. Therefore, in the present embodiment, the inner circumferential surface of the cylindrical portion 45a can be formed accurately while reducing the manufacturing cost of the sleeve 45, and as a result, variation in the contact pressure between the inner circumferential surface of the cylindrical portion 45a and the outer circumferential surface of the outer ring 36b can be suppressed.

In the present embodiment, the pulley 32 is in contact with the input shaft 23 of the reduction gear 22. Therefore, in the present embodiment, even if the sleeve 45 is disposed between the outer race 36b and the pulley 32 in the radial direction of the pulley 32, the heat generated by the reduction gear 22 can be efficiently dissipated using the pulley 32 made of an aluminum alloy in contact with the input shaft 23.

In the present embodiment, the pulley 32 and the sleeve 45 are fixed to the input shaft 23 by screws 47 inserted through the through holes of the annular portion 45b and the through holes of the fixed portion 32b in a state where the fixed portion 32b is sandwiched between the lower end surface of the input shaft 23 and the annular portion 45b in the vertical direction. That is, in the present embodiment, the pulley 32 is fixed to the input shaft 23 by the common screw 47, and the pulley 32 is fixed to the sleeve 45. Therefore, in the present embodiment, the structure of the joint portion 16 can be simplified as compared with a case where a screw for fixing the pulley 32 to the input shaft 23 and a screw for fixing the pulley 45 to the pulley 32 are separately provided.

(other embodiments)

The above-described embodiment is an example of the best mode of the present invention, but is not limited thereto, and various modifications can be made without changing the gist of the present invention.

In the above embodiment, the sleeve 45 may be formed of a material other than steel. Specifically, the sleeve 45 may be formed of a material having a thermal expansion coefficient closer to that of steel than that of aluminum alloy. For example, the sleeve 45 may be formed of a copper alloy such as brass (copper-zinc alloy). Even in this case, since the reduction in the contact pressure between the outer circumferential surface of the outer ring 36b and the inner circumferential surface of the sleeve 45 when the outer ring 36b and the sleeve 45 are thermally expanded due to the influence of the heat generated by the reduction gear 22 can be suppressed, even if the pulley 32 is formed of an aluminum alloy, the damage of the bearing 36 due to the heat generated by the reduction gear 22 can be suppressed. In this case, the sleeve 45 is preferably formed of a material having a hardness closer to that of steel than the aluminum alloy.

In the above-described embodiment, the screw for fixing the pulley 32 to the input shaft 23 and the screw for fixing the pulley 45 to the pulley 32 may be provided separately. In the above-described embodiment, the pulley 32 may not be in contact with the input shaft 23 of the reduction gear 22. In this case, the sleeve 45 is in contact with the input shaft 23. In the above embodiment, the bearing 36 may be a roller bearing.

In the above-described embodiment, the inner ring 36a may be insert-fixed to the lower end portion of the hollow rotary shaft 34 by interference fit, or may be fixed to the lower end portion of the hollow rotary shaft 34 by another fixing unit. In the above-described embodiment, as in the joint 16, the following may be used: a pulley made of an aluminum alloy is fixed to an input shaft of a reduction gear disposed at the joint 17, a bearing 36 is disposed on an inner peripheral side of the pulley, and a sleeve 45 is disposed between the bearing 36 and the pulley in a radial direction of the pulley.

In the above-described embodiment, the hand 3 and the arm 4 may be disposed in the atmosphere. That is, the robot 1 may transport the substrate 2 in the atmosphere. In the above embodiment, the inside of the first arm portion 13 and the second arm portion 14 may be vacuum. In the above-described embodiment, the transmission mechanism for transmitting power from the motor to the arm 4 may be configured such that the second arm portion 14 is rotated with respect to the first arm portion 13 and the hand 3 is rotated with respect to the second arm portion 14 by one motor.

In the above embodiment, the arm 4 may be formed of three or more arm portions. In the above-described embodiment, the arm 4 may be configured by one first arm portion 13 and two second arm portions 14 connected to the one first arm portion 13 so as to be rotatable. In the above-described embodiment, the robot 1 may include two arms 4 whose base end sides are rotatably connected to the main body 5 and two hands 3 rotatably connected to the tip ends of the two arms 4. That is, the robot 1 may include four or more joint portions. The number of joints provided in the robot 1 may be one.

In the above-described embodiment, the object to be conveyed by the robot 1 is the substrate 2 for the organic EL display, but the object to be conveyed by the robot 1 may be a glass substrate for a liquid crystal display, a semiconductor wafer, or the like. In the above-described embodiment, the robot 1 is a horizontal articulated robot for conveying a conveying object, but the robot 1 may be a vertical articulated robot used for other applications such as a welding robot.

In the above embodiment, the pulley 32 may be formed of a material other than an aluminum alloy. In this case, the pulley 32 is formed of a metal or resin having a higher thermal expansion coefficient than that of steel, such as brass, for example.

Claims

1. An industrial robot comprising a joint unit, characterized by comprising:

a speed reducer disposed at the joint;

a pulley made of an aluminum alloy, the pulley being connected to an input side of the speed reducer;

a rolling bearing having a steel outer ring and disposed on an inner peripheral side of the pulley; and

a cylindrical sleeve fixed to the pulley and disposed between the outer ring of the rolling bearing and the pulley in a radial direction of the pulley,

the sleeve is formed of a material or steel having a coefficient of thermal expansion closer to that of steel than the aluminum alloy,

the inner peripheral surface of the sleeve is in contact with the outer peripheral surface of the outer ring at a predetermined contact pressure.

2. The industrial robot of claim 1,

the sleeve is formed of steel.

3. The industrial robot according to claim 1 or 2,

the belt wheel is fixed on the input shaft of the speed reducer and is in contact with the input shaft.

4. The industrial robot of claim 3,

the sleeve includes a cylindrical portion and an annular ring portion connected to one end of the cylindrical portion and connected to an inner circumferential side of the cylindrical portion,

the pulley has a fixed portion fixed to the input shaft,

an inner peripheral surface of the cylindrical portion is in contact with an outer peripheral surface of the outer ring at a predetermined contact pressure,

the pulley and the sleeve are fixed to the input shaft by screws inserted through the annular portion and the fixed portion in a state where the fixed portion is sandwiched between one end surface of the input shaft and the annular portion in an axial direction of the input shaft.

5. The industrial robot according to any one of claims 1 to 4, comprising:

a hand that loads a transport object;

an arm rotatably connected to the hand at a leading end side; and

a body portion rotatably connected to a base end side of the arm,

the arm is provided with: a first arm portion whose base end side is rotatably connected to the main body portion; a second arm whose base end side is rotatably connected to the leading end side of the first arm and to which the hand is rotatably connected on the leading end side of the second arm,

the speed reducer, the pulley, the rolling bearing, and the sleeve are disposed in the joint portion that is a connection portion between the first arm portion and the second arm portion.