METHOD FOR MANUFACTURING A REDUCTION GEAR, REDUCTION GEAR AND ROTATING DEVICE

Description

[0001] The present invention relates to a method of manufacturing a speed reducer, a speed reducer, and a rotating device.

[0002] DE 10 2019 203 058 A1 discloses a gear unit that includes a first gear that is connected to a drive source, a second gear that engages with the first gear, a third gear that engages with the first gear, and a fourth gear that engages with the second gear and the third gear. CN 103 394 884 A describes an integrated machining method of a planet carrier of a robot RV reducer. The method comprises the steps as follows: forging a first casing and a second casing, and performing hot extrusion on the first casing and the second casing respectively; performing thermal refining; performing tempering; performing finish machining on end surfaces respectively; connecting the first casing with the second casing to be clamped to a clamp, and performing finish machining on inner holes formed in the first casing and the second casing with a center of gyration serving as a locating basis; performing finish machining on outer surface with the locating basis; directly machining inner rings of rolling bearings on the first casing and the second casing; accurately grinding an outer track on each inner ring simultaneously; and performing finish machining bearing positions of three tapered roller bearings on the first casing and the second casing with the location reference, and directly machining outer rings of the tapered roller bearings. CN 106 499 777 A discloses a casing, an output flange, a swing gear, a crankshaft for rocking and rotating the swing gear, a crankshaft bearing arranged between the crankshaft and the output flange, and an oil seal disposed between the casing and the output flange. The output flange includes a flange main body on which a crankshaft bearing is disposed and a mating member. And the auxiliary body is connected in a fitted state in a fitted manner, and the auxiliary body restricts the movement of the crankshaft bearing in the axial direction, and the auxiliary body supports the flange body and the auxiliary body. The fitting portion and the oil seal are overlapped when viewed from the radial direction. EP 0 551 918 A2 describes that the eccentric body shaft bearing holes, the eccentric body bearing holes and the carrier pin holding holes are set to satisfy the following relationship. Namely, when the first and second supporting blocks and the externally toothed gears are appropriately rearranged in the axial positions thereof, the diameters of the eccentric body shaft bearing holes and the diameters of the eccentric body bearing holes become smaller toward one direction. Also, while keeping the above rearrangement, the diameters of the carrier pin holding holes become smaller in the same direction. The outside diameter of the first and second supporting blocks is set to be smaller than the root diameter of the external teeth of each externally toothed gear. Further, the teeth number of each externally toothed gear is set to be the integral magnification of the number thereof, and the teeth number difference between the internal gear and the externally toothed gear is set to be the integral magnification of the number of the externally toothed gears. Industrial robots and machine tools typically include a motor unit provided at a connection portion (joint) between a pair of arms, which are rotatably coupled to each other, to drive the arms. The motor unit includes a motor and a speed reducer coupled with the motor. A motor torque generated by rotation of the motor is reduced by the reducer and then outputted to the arm (see, for example, JP 2021 - 095 964 A).

[0003] To keep high precision in terms of runout of an output rotating shaft end in the speed reducer for the industrial robots described above, it was necessary to fabricate parts constituting the industrial robots with a high dimension accuracy and assemble the parts with a high assembling accuracy. This resulted in a high price of finished products, and there was room for improvement in this respect.

[0004] It is an object of the present invention to provide a speed reducer and a method of manufacturing a speed reducer with which a high-precision speed reducer can be manufactured with simple adjustment work in the manufacturing process and which can reduce the manufacturing costs. According to the present invention said object is solved by a speed reducer having the features of the independent claim 1 and a method for manufacturing that speed reducer according to claim 8. Preferred embodiments are laid down in the dependent claims.

[0005] According to one aspect of the invention, provided is a speed reducer. The speed reducer includes: an outer tube; a shaft portion rotatably provided inside the outer tube, the shaft portion being fixedly coupled to an output shaft and having a shaft end surface; an input shaft coupled to a drive source; a pair of bearings rotatably supporting the outer tube relative to the shaft portion, the pair of bearings including a first bearing provided near the shaft end surface and a second bearing different from the first bearing; a speed reducing portion connected with the input shaft and rotatably supporting the shaft portion; and an attachment member having a flange, the flange having a flange mounting surface fastened to the outer tube by a bolt, the flange extending perpendicular to a rotational axis of the shaft portion and being attachable to the drive source. The shaft portion has a first receiving surface. The outer tube has a second receiving surface. The first bearing has a first inner ring and a first outer ring. The first receiving surface contacts the first inner ring in a direction of the rotational axis. The second receiving surface contacts the first outer ring in the rotational axis direction. A first parallelism is defined between the first receiving surface (4a) and the shaft end surface (4b), and wherein a second parallelism is defined between the second receiving surface (2b) and the flange mounting surface (61a), and the first and second parallelisms are defining a first and second manufacturing accuracy value for manufacturing the speed reducer (10), wherein the first machining accuracy becomes is higher than the second machining accuracy.

[0006] In this configuration, only the first machining accuracy based on the first parallelism between the first receiving surface of the shaft portion and the shaft end surface of the shaft portion can be adjusted at the final step of the manufacturing process of the speed reducer. By adjusting the first machining accuracy, it is possible to produce the speed reducer that can minimize the runout of the shaft portion, i.e., the runout of the output shaft. Thus, according to the aspect, the speed reducer with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0007] In the above speed reducer, the first parallelism of the first machining accuracy becomes 10 µm or less, regardless of a rotation phase between the shaft portion and the outer tube.

[0008] In the above speed reducer, the axial runout of the pair of bearings may be equal to or less than 90 µm.

[0009] In the above speed reducer, the outer tube may have a flange mounted surface. The flange mounting surface may be coupled to the flange mounted surface. A third parallelism between the flange mounting surface and the flange mounted surface is 20 µm or less.

[0010] In the above speed reducer, the second bearing may have a second inner ring and a second outer ring. The outer tube may have a third receiving surface and a flange mounted surface. The third receiving surface may contact the second outer ring in the rotational axis direction. The flange mounting surface may be coupled to the flange mounted surface. A parallelism between each of the second receiving surface, the third receiving surface, and the flange mounted surface may be 30 µm or less.

[0011] In the above speed reducer the second parallelism of the second machining accuracy may be 170 µm or less.

[0012] In the above speed reducer, an axial runout of the pair of bearings may be equal to or less than 90 µm. The shaft portion has a first receiving surface. The outer tube has a second receiving surface. The first bearing has a first inner ring and a first outer ring. The first receiving surface contacts the first inner ring in a direction of the rotational axis. The second receiving surface contacts the first outer ring in the rotational axis direction. A first machining accuracy is obtained based on a first parallelism between the first receiving surface and the shaft end surface. A second machining accuracy is obtained based on a second parallelism between the second receiving surface and the flange mounting surface. The outer tube has a third receiving surface and a flange mounted surface. The flange mounting surface is coupled to the flange mounted surface. The second bearing has a second inner ring and a second outer ring. The third receiving surface contacts the second outer ring in the rotational axis direction. The first parallelism of the first machining accuracy is 10 µm or less, regardless of a rotation phase between the shaft portion and the outer tube. Further, machining is performed such that a third parallelism between the flange mounting surface and the flange mounted surface is 20 µm or less. Further, a parallelism between each of the second receiving surface, the third receiving surface, and the flange mounted surface is 30 µm or less.

[0013] In this configuration, only the first machining accuracy based on the first parallelism between the first receiving surface of the shaft portion and the shaft end surface of the shaft portion can be adjusted at the final step of the manufacturing process of the speed reducer. By adjusting the first machining accuracy, it is possible to produce the speed reducer that can minimize the runout of the shaft portion, i.e., the runout of the output shaft. Thus, according to the aspect, the speed reducer with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0014] A manufacturing method for the above mentioned speed reducer according the invention includes: providing an above defined speed reducer, obtaining a first machining accuracy based on a first parallelism between the first receiving surface and the shaft end surface, obtaining a second machining accuracy based on a second parallelism between the second receiving surface and the flange mounting surface, and adjusting the first machining accuracy to be higher than the second machining accuracy.

[0015] In this configuration, only the first machining accuracy based on the first parallelism between the first receiving surface of the shaft portion and the shaft end surface of the shaft portion can be adjusted at the final step of the manufacturing process of the speed reducer. By adjusting the first machining accuracy, it is possible to produce the speed reducer that can minimize the runout of the shaft portion, i.e., the runout of the output shaft. Thus, according to the aspect, the speed reducer with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0016] According to still yet another aspect of the invention provides a rotating device that includes a device body, a rotated body with a working head, an electric motor provided on the device body, where the electric motor is configured to produce a driving force to rotate the rotated body, and a speed reducer for reducing speed of rotation of the electric motor. The speed reducer includes: an outer tube; a shaft portion rotatably provided inside the outer tube, the shaft portion being fixedly coupled to an output shaft and having a shaft end surface; an input shaft coupled to a drive source; a pair of bearings rotatably supporting the outer tube relative to the shaft portion, the pair of bearings including a first bearing provided near the shaft end surface and a second bearing different from the first bearing; a speed reducing portion connected with the input shaft and rotatably supporting the shaft portion; and an attachment member having a flange, the flange having a flange mounting surface fastened to the outer tube by a bolt, the flange extending perpendicular to a rotational axis of the shaft portion and being attachable to the drive source. The shaft portion has a first receiving surface. The outer tube has a second receiving surface. The first bearing has a first inner ring and a first outer ring. The first receiving surface contacts the first inner ring in a direction of the rotational axis. The second receiving surface contacts the first outer ring in the rotational axis direction. A first machining accuracy is obtained based on a first parallelism between the first receiving surface and the shaft end surface. A second machining accuracy is obtained based on a second parallelism between the second receiving surface and the flange mounting surface. The first machining accuracy is higher than the second machining accuracy.

[0017] In this configuration, only the first machining accuracy based on the first parallelism between the first receiving surface of the shaft portion and the shaft end surface of the shaft portion can be adjusted at the final step of the manufacturing process of the speed reducer. By adjusting the first machining accuracy, it is possible to produce the speed reducer that can minimize the runout of the shaft portion, i.e., the runout of the output shaft. This speed reducer can be provided in the rotating device. According to this aspect, the speed reducer with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0018] With the manufacturing method of a speed reducer, the speed reducer, and the rotating device above, it is possible to manufacture a speed reducer with high accuracy by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. Fig. 1 is a side view of an industrial robot including a speed reducer relating to an embodiment. Fig. 2 is a schematic side view of the speed reducer related to the embodiment. Fig. 3 is an enlarged view of a part of the speed reducer of Fig. 2, illustrating a manufacturing method of the speed reducer. Fig. 4 illustrates a relationship between a correction margin between I and B and an amplitude between A and B.

[0019] The embodiments of the present invention will be hereinafter described with reference to the drawings. In the following embodiments and modifications, like elements will be denoted by the same reference signs and redundant descriptions will be partly omitted.

[0020] Fig. 1 is a side view of an industrial robot 100 including a speed reducer 10 used for a motor with the speed reducer in a drive unit. The industrial robot 100 (rotating device) relating to the embodiment is an industrial robot used, for example, for feeding, shipping, transporting, and assembling parts of precision equipment and the like. The industrial robot 100 has a base 110 (device body), a first arm 120 (rotated body), a second arm 130 (rotated body), a work head 140, and an end-effector 150.

[0021] The first arm 120, which is rotatable around an axis 01, is coupled with the base 110. The first arm 130, which is rotatable around an axis parallel to the axis 01, is coupled with the second arm 120. The work head 140 is provided at the front end of the second arm 130 and coupled with the end-effector 150. The base 110 has therein an electric motor 31 such as a servomotor, and the speed reducer 10 for reducing the speed of rotations of the electric motor 31. The first arm 120 is rotatable when acted upon by a driving force form the electric motor 31. As shown in Fig. 2, an input shaft 3 (described below) of the speed reducer 10 is coupled with a rotational shaft (motor shaft 20) of the electric motor 31. An output shaft 40 of the speed reducer 10 is coupled with the first arm 120. When the driving force from the motor 31 is transmitted to the first arm 120 through the speed reducer 10, the first arm 120 rotates within a horizontal plane around the axis 01.

[0022] As shown in Fig. 1, the speed reducer 10 is provided in the industrial robot 100 at a connecting portion (joint portion) of the fist arm 120 rotatably coupled thereto. The speed reducer 10 reduces a motor torque inputted thereto from the electric motor 31 serving as a power source with a predetermined reduction ratio and outputs the reduced torque to the output shaft 40. In other words, the speed reducer 10 is configured to change the number of rotations at a predetermined ratio and transmit a resulting driving force between the drive source and a mechanical part such as the arm.

[0023] In the description of the embodiment, the direction extending along the axis 01 of the electric motor 31 of the speed reducer 10 is simply referred to as an axial direction (rotational axis direction). The direction intersecting the axis 01 when viewed in the axial direction is hereunder referred to as a radial direction. The direction extending around the axis 01 is referred to as a circumferential direction. The inwardly facing side of an object is hereunder referred to an axially inner side. The side opposite to the axially inner side is hereunder referred to as an axially outer side. Furthermore, the side of the speed reducer 10 connected to the drive source is referred to as input side X1. The side of the speed reducer 10 connected to a mechanical part such as the arm described above receiving the output from the speed reducer 10 is referred to as output side X2.

[0024] Fig. 2 is a sectional view of the speed reducer 10 relating to the embodiment (cut along a plane including the axis 01 shown in Fig. 1).

[0025] As shown in Fig. 2, in the speed reducer 10 relating to the present embodiment, an input shaft 3 including the input gear 30 is rotated to rotate a crankshaft 13. The speed reducer 10 is configured to oscillate and rotate oscillating gears 14 and 15 in conjunction with eccentric portions 13A and 13B of the crankshaft 13 by the rotation of the crankshaft 13. The speed reducer is configured to reduce the input rotation through the oscillatory rotations of the oscillating gears 14 and 15 and output the decelerated rotation.

[0026] The speed reducer 10 includes an outer tube 2, a shaft portion 4, the input shaft 3, a pair of bearings 5 (first bearing 5A and second bearing 5B), a speed reducing portion 10A, and an attachment member 6. The outer tube 2 has a second receiving surface 2b and a third receiving surface 2c, which will be described below. The shaft portion 4 is rotatable inside the outer tube 2 and is fixedly provided on the output shaft 40. The shaft portion 4 has a shaft end surface 4b. The output shaft 40 is the portion connected to the first arm 120 of the industrial robot 100 of Fig. 1. The shaft portion 4 has a first receiving surface 4a, which will be described below. The input shaft 3 is also situated in the electric motor 31 (drive source, shown by the dotted line shown in Fig. 2). The axial runout of the pair of bearings 5 is equal to or less than 90 µm. The pair of bearings 5 rotatably support the outer tube 2 relative to the shaft portion 4. The first bearing 5A, which is one of the pair of bearings 5, is situated near the shaft end surface 4b in the axial direction. The second bearing 5B, which is the other of the pair of bearings 5, is situated closer to the first bearing 5A than the shaft end surface 4b in the axial direction. In other words, the second bearing 5B is a different bearing from the first bearing 5A. The speed reducing portion 10A is connected to the input shaft 3. The speed reducing portion 10A rotatably supports the shaft portion 4. The attachment member 6 has a flange 61. The flange 61 has a flange mounting surface 61a. The flange 61 can be attached to the electric motor 31. The flange 61 extends perpendicular to the axis of rotation of the shaft portion 4. The flange mounting surface 61a of the flange 61 is coupled to the outer tube 2 with first fixing bolts 62 (bolts).

[0027] The outer tube 2 forms the outer surface of the speed reducer 10. The external cylinder 2 has a cylindrical shape. Multiple pin grooves are formed in an inner peripheral surface 2a of the outer tube 2. The pin grooves each extend in the axial direction of the external cylinder 2. Each of the pin grooves 2b has a semicircular sectional shape when cut along a plane orthogonal to the axial direction. The pin grooves 2b are arranged at regular intervals in the circumferential direction along the inner peripheral surface 2a of the outer tube 2. The outer tube 2 forms a cylindrical internal space in which the crankshafts 13 and the first and second oscillating gears 14 and 15 are housed, when combined with the shaft portion 4.

[0028] The outer tube 2 has a plurality of internal tooth pins 21. Each of the internal tooth pins 21 is a substantially cylindrical member extending in the axial direction and placed in the corresponding pin groove. Specifically, the plurality of the internal tooth pins 21 are fitted into the corresponding pin grooves. In other words, the plurality of the internal tooth pins 21 are fitted into the pin grooves in a one-to-one correspondence. Each of the internal tooth pins 21 is oriented to extend in the axial direction of the outer tube 2. In this manner, the plurality of internal tooth pins 21 are arranged at regular intervals along the circumference of the outer tube 2. The internal tooth pins 21 mesh with external teeth of the first oscillating gear 14 and external teeth of the second oscillating gear 15.

[0029] The outer tube 2 has an input-side end surface. The input-side end surface of the outer tube 2 corresponds to a flange mounted surface. In the following description, the input-side end surface of the outer tube 2 is referred to as the flange-mounted surface 2d. The flange mounting surface 61a is attached to the flange mounted surface 2d. A plurality of female screw holes 22 are formed in the flange-mounted surface 2d. The first fixing bolts 62 for fixing the flange 61 of the attachment member 6 are fitted in the female screw holes 22, respectively. The screw axis of each of the plurality of female screw holes 22 extends parallel to the axis 01. The flange mounted surface 2d of the outer tube 2 resides in a plane perpendicular to the axis 01. With the flange 61 fixed to the outer tube 2, the flange mounted surface 2d is in surface contact with the flange mounting surface 61a of the flange 61.

[0030] The input shaft 3 serves as an input portion for receiving a driving force from the electric motor 31 (see Fig. 1). The shaft center of the input shaft 3 is different from the shaft center (axis 01) of the outer tube 2 and the shaft portion 4. The input shaft 3 is rotatable about the shaft center C. The input gear 30 is provided on the input shaft 3 on the outer circumferential surface of the front end thereof.

[0031] The shaft portion 4 is housed within the outer tube 2 while they are coaxially arranged. The shaft portion 4 is rotatable relative to the outer tube 2 about the same axis. More specifically, the shaft portion 4 is placed on the radially inner side of the external cylinder 2. In this state, the shaft portion 4 is supported by the pair of bearings 5A and 5B, which are spaced away from each other in the axial direction. With this configuration, the shaft portion 4 is rotatable relative to the outer tube 2.

[0032] The shaft portion 4 has a shaft body 41, a plurality of (e.g., three) shafts 42, and an end plate 43 disposed on the input side X1 of the shafts 42.

[0033] The shaft body 41 is disposed inside the outer tube 2. The shaft body 41 is located near one end of the outer tube 2 in the axial direction. A circular central opening 41a is formed in the radially center of the shaft body 41. Around the central opening 41a, a plurality (e.g., two) of mounting holes are formed at equal intervals in the circumferential direction. The crankshaft 13 is disposed in each of the plurality of mounting holes. In the end surface of the shaft body 41 on the input side X1, a bolt hole 41b is formed into which a second fixing bolt 44 described below is engaged.

[0034] The end plate 43 is axially spaced apart from the shaft body 41. The end plate 43 is disposed inside the outer tube 2. The end plate 43 is disposed near the other end of the outer tube 2 in the axial direction. A through hole 43a is formed in the radial center of the end plate 43. Around the through hole 43a, a plurality (e.g., two) of crankshaft mounting holes are provided. The plurality of crankshaft mounting holes are provided at positions corresponding to the plurality of mounting holes in the shaft body 41. A closed space is formed in the outer tube 2. This closed space is surrounded by the inner surfaces of both the end plate 43 and the shaft body 41 facing each other and the inner circumferential surface 2a of the outer tube 2. The shaft body 41 has an output-side end surface. The output-side end surface of the shaft body 41 corresponds to the shaft end surface. In the following description, the output-side end surface of the shaft body 41 is referred to as the shaft end surface 4b. The shaft end surface 4b is formed in a plane perpendicular to the axis 01.

[0035] The three shafts 42 are formed integrally with the shaft body 41. The three shafts 42 extend linearly from one main surface (inner surface) of the shaft body 41 toward the end plate 43. The three shafts 42 are arranged at equal intervals in the circumferential direction. Each of the three shafts 42 is fastened to the shaft body 41 by the second fixing bolt 44. In this way, the shaft body 41, shafts 42, and end plate portion 43 are integrated to form a single unit.

[0036] The speed reducing portion 10A has the plurality (e.g., two) of crankshafts 13 rotatably supported by the shaft portion 4, the first oscillating gear 14, and the second oscillating gear 15 as described above. The first and second oscillating gears 14 and 15 surround the crankshafts 13.

[0037] The pair of bearings 5 includes the first bearing 5A disposed on the output side X2 and the second bearing 5B disposed on the input side X1. Each of the first bearing 5A and the second bearing 5B has an inner ring 51 and an outer ring 52. The inner ring of the first bearing 5A corresponds to a first inner ring. The outer ring of the first bearing 5A corresponds to a first outer ring. The inner ring of the second bearing 5B corresponds to a second inner ring. The outer ring of the second bearing 5B corresponds to a second outer ring. The inner ring 51 of the first bearing 5A is held by the shaft body 41 of the shaft portion 4. In the axial direction, the first receiving surface 4a of the shaft portion 4 contacts an output-side end surface 51a of the inner ring 51 of the first bearing 5A. In the axial direction, the second receiving surface 2b of the outer tube 2 contacts an input-side end surface 52a of the outer ring 52 of the first bearing 5A. In the axial direction, the third receiving surface 2c of the outer tube 2 contacts an output-side end surface 52b of the outer ring 52 of the second bearing 5B.

[0038] The attachment member 6 is fixed to the flange mounted surface 2d on the input side X1 of the outer tube 2 with the first fixing bolt 62 such that it covers the speed reducer 10A from the input side X1. The attachment member 6 has a disk portion 63, a cylindrical portion 64, and a flange 61. The cylindrical portion 64 extends from the outer periphery of the disk portion 63 toward the output side X2. The flange 61 extends radially outward from a part of the circumference of the cylindrical portion 64. The disk portion 63, the cylindrical portion 64, and the flange 61 form the attachment member 6 that has a top-closed cylindrical shape. The disk portion 63 has an opening 63a formed in the center of the disk portion 63. The disk 63 has a plurality of retaining holes 63b formed around the opening 63a. The plurality of retaining holes 63b are provided for retaining the input gear 30.

[0039] The flange 61 is provided on the entire circumference of the cylindrical portion 64. The flange 61 has a plurality of through holes 61b. The plurality of through holes 61b are formed at predetermined intervals in the circumferential direction of the flange 61. The first fixing bolt 62 is inserted into each of the plurality of through holes 61b from the input side X1. The plurality of through holes 61b are arranged at the positions corresponding to the positions of the plurality of female screw holes 22 formed in the flange mounted surface 2d of the outer tube 2.

[0040] A manufacturing method of the above speed reducer 10 will now be described in detail with reference to Fig. 3. Fig. 3 is an enlarged view of the speed reducer 10 of Fig. 2 including its essential portions. Fig. 3 is for illustrating the method of manufacturing the speed reducer 10. The manufacturing method of the speed reducer 10 described here relates to the accuracy of each of the components constituting the speed reducer 10. Here, "accuracy" means the assembly accuracy in assembling the plurality of components and the machining accuracy obtained by machining each of the plurality of components. In the manufacturing method of the speed reducer 10 according to the embodiment, five manufacturing methods (first to fifth manufacturing methods) are implemented. In the following embodiment, the first manufacturing method hereunder described is the essential manufacturing method, and the second to fifth manufacturing methods can be employed in combination with the first manufacturing method as appropriate.[First Manufacturing Method]

[0041] As shown in Fig. 3, the first receiving surface 4a (first accuracy-required surface indicated by "I") of the shaft portion 4 contacts the inner ring 51 of the first bearing 5A in the axial direction. A first machining accuracy is calculated based on a first parallelism between the first receiving surface 4a of the shaft portion 4 and the shaft end surface 4b (second accuracy-required surface indicated by "B") of the shaft portion 4. In other words, the first parallelism is obtained by machining the first receiving surface 4a and the shaft end surface 4b, and the first machining accuracy is obtained based on the first parallelism. As shown in Fig. 3, the second receiving surface 2b (fourth accuracy-required surface indicated by "G") of the outer tube 2 contacts the outer ring 52 of the first bearing 5A in the axial direction. A second machining accuracy is calculated based on a second parallelism between the second receiving surface 2b of the outer tube 2 and the flange mounting surface 61a (third accuracy-requiring surface indicated by "A") of the flange 61 of the attachment member 6. In other words, the second parallelism is obtained by machining the second receiving surface 2b and the flange mounting surface 61a, and the second machining accuracy is obtained based on the second parallelism. In the first manufacturing method, machining is performed such that the first machining accuracy becomes higher than the second machining accuracy.[Second Manufacturing Method]

[0042] In the second manufacturing method, machining is performed such that the first parallelism of the first machining accuracy (i.e., the parallelism between the first accuracy-required surface I and the second accuracy-required surface B) described above is 10 µm or less, regardless of the rotation phase between the shaft portion 4 and the outer tube 2.

[0043] Fig. 4 shows the relationship between a correction margin (µm), which is the parallelism between the first accuracy-required surface I and the second accuracy-required surface B, and the amplitude (µm) between the third accuracy-required surface A and the second accuracy-required surface B. As shown in Fig. 4, it can be seen that the amplitude between A and B (runout of the shaft portion 4) can be adjusted only by adjusting the correction margin between the surfaces I and B. The line P in Fig. 4 indicates the reference value (10 µm) of the amplitude between the surfaces A and B. For example, if the parallelism between the surfaces I and B exceeds the standard value, it can be corrected and adjusted by finding, from the graph of Fig. 4, a correction margin that realizes a parallelism between the surfaces I and B of less than the standard value (10 µm).[Third Manufacturing Method]

[0044] In the third manufacturing method, machining is performed such that a third parallelism between the flange mounting surface 61a of the attachment member 6 (third accuracy-required surface A) and the flange mounted surface 2d (fifth accuracy-required surface indicated by "E") of the outer tube 2 becomes 20 µm or less.[Fourth Manufacturing Method]

[0045] In the fourth manufacturing method, the second receiving surface 2b (fourth accuracy-required surface indicated by "G") of the outer tube 2, the third receiving surface 2c (sixth accuracy-required surface indicated by "F") of the outer tube 2, and the flange-mounted surface 2d (fifth accuracy-required surface E) of the outer tube 2 are each machined to have a parallelism of 30 µm or less.[Fifth Manufacturing Method]

[0046] In the fifth manufacturing method, machining is performed such that the second parallelism of the second machining accuracy (i.e., parallelism between the third accuracy-required surface A and the fourth accuracy-required surface G) described above becomes 170 µm or less.

[0047] Here, when a bolt(s) is used to secure the shaft to the end plate 43 from the output side X2 (shaft end surface 4b side) of the shaft body 41, the bolt is subjected to a load generated by a squeeze margin when the pair of bearings 5A and 5B are assembled. To address this in this embodiment, the second fixing bolt 44 that secures the shaft portion 4 and the bearings 5 does not apply a fastening force to the output side X2 (shaft end surface 4b side) of the shaft portion 4. The second fixing bolt 44 is inserted from the input side X1 of the end plate 43 of the shaft portion 4 into the bolt hole 41b formed in the shaft body 41. The second fixing bolt 44 is not screwed into the shaft end surface 4b, which is the second accuracy-required surface B. This prevents the influence of the load generated by the squeeze margin described above.

[0048] The above embodiment has described the method of manufacturing the speed reducer 10. The speed reducer includes: the outer tube 2; the shaft portion 4 rotatably provided inside the outer tube 2, the shaft portion 4 being fixedly coupled to an output shaft and having a shaft end surface 4b; the input shaft 3 coupled to the electric motor 31; the pair of bearings 5 rotatably supporting the outer tube 2 relative to the shaft portion 4, the pair of bearings 5 including a first bearing 5A provided near the shaft end surface 4b and a second bearing 5B provided closer to the first bearing 5A rather than the shaft end surface 4b; the speed reducing portion 10A connected with the input shaft 3 and rotatably supporting the shaft portion 4; and the attachment member 6 having a flange 61, the flange 61 having a flange mounting surface 61a fastened to the outer tube 2 by the first fixing bolt 62, the flange 61 extending perpendicular to the rotational axis of the shaft portion 4 and being attachable to the electric motor 31. The shaft portion 4 has the first receiving surface 4a. The outer tube 2 has the second receiving surface 2b. The first bearing 5A has the first inner ring 51 and the first outer ring 52. The first receiving surface 4a contacts the first inner ring 51 in the axis direction. The second receiving surface 2b contacts the first outer ring 52 in the axis direction. The first machining accuracy is obtained based on the first parallelism between the first receiving surface 4a and the shaft end surface 4b. The second machining accuracy is obtained based on the second parallelism between the second receiving surface 2b and the flange mounting surface 61a. In the manufacturing method, machining is performed such that the first machining accuracy becomes higher than the second machining accuracy. In the method of manufacturing the speed reducer 10 related to the embodiment, only the first machining accuracy based on the first parallelism between the first receiving surface 4a (first accuracy-required surface I) of the shaft portion 4 and the shaft end surface 4b (second accuracy-required surface B) of the shaft portion 4 can be adjusted at the final step of the manufacturing method. By adjusting the first machining accuracy, it is possible to produce the speed reducer 10 that can minimize the runout of the shaft portion 4, i.e., the runout of the output shaft. As described above, in the embodiment, the method can manufacture the speed reducer 10 with high accuracy by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0049] In addition, in the embodiment, machining is performed such that the first parallelism of the first machining accuracy becomes 10 µm or less, regardless of a rotation phase between the shaft portion 4 and the outer tube 2. Accordingly, the runout of the shaft portion 4 can be more reliably minimized, and the speed reducer 10 can be manufactured with high precision and at low cost.

[0050] In the manufacturing method of the speed reducer 10, the axial runout of the bearing 5 is less than 90 µm. Thus, the runout of the shaft portion 4 can be more reliably minimized, and the speed reducer 10 can be manufactured with high precision and at low cost.

[0051] Furthermore, in the embodiment, the outer tube 2 has the flange-mounted surface 2d. The flange mounted surface 2a is coupled to the flange mounting surface 61a of the attachment member 6. Machining is performed such that the third parallelism between the flange mounting surface 61a of the attachment member 6 and the flange mounted surface 2d of the outer tube 2 becomes 20 µm or less. Accordingly, the runout of the shaft portion 4 can be more reliably minimized, and the speed reducer 10 can be manufactured with high precision and at low cost.

[0052] The second bearing 5B has the second inner ring 51 and the second outer ring 52. The outer tube 2 has the third receiving surface 2c and the flange mounted surface 2d. The third receiving surface 2c contacts the second outer ring 52 in the axis direction. The flange mounting surface 61a is coupled to the flange mounted surface 2d. Machining is performed such that the parallelism between each of the second receiving surface 2b, the third receiving surface 2c of the outer tube 2, and the flange mounted surface 2d of the outer tube 2 becomes 30 µm or less. Accordingly, the runout of the shaft portion 4 can be more reliably minimized, and the speed reducer 10 can be manufactured with high precision and at low cost.

[0053] Moreover, in the embodiment, machining is performed such that the second parallelism of the second machining accuracy becomes 170 µm or less. Accordingly, the runout of the shaft portion 4 can be more reliably minimized, and the speed reducer 10 can be manufactured with high precision and at low cost.

[0054] The speed reducer 10 related to the embodiment includes: the outer tube 2; the shaft portion 4 rotatably provided inside the outer tube 2, the shaft portion 4 being fixedly coupled to an output shaft and having a shaft end surface 4b; the input shaft 3 coupled to the electric motor 31; the pair of bearings 5 rotatably supporting the outer tube 2 relative to the shaft portion 4, the pair of bearings 5 including a first bearing 5A provided near the shaft end surface 4b and a second bearing 5B provided closer to the first bearing 5A rather than the shaft end surface 4b; the speed reducing portion 10A connected with the input shaft 3 and rotatably supporting the shaft portion 4; and the attachment member 6 having a flange 61. The flange 61 has a flange mounting surface 61a fastened to the outer tube 2 by the first fixing bolt 62. The flange 61 extends perpendicular to the rotational axis of the shaft portion 4. The flange 61 is attachable to the electric motor 31. The shaft portion 4 has the first receiving surface 4a. The outer tube 2 has the second receiving surface 2b. The first bearing 5A has the first inner ring 51 and the first outer ring 52. The first receiving surface 4a contacts the first inner ring 51 in the axis direction. The second receiving surface 2b contacts the first outer ring 52 in the axis direction. The first machining accuracy is obtained based on the first parallelism between the first receiving surface 4a and the shaft end surface 4b. The second machining accuracy is obtained based on the second parallelism between the second receiving surface 2b and the flange mounting surface 61a. The speed reducer is configured such that the first machining accuracy is higher than the second machining accuracy. In the speed reducer 10 related to the embodiment, only the first machining accuracy based on the first parallelism between the first receiving surface 4a (first accuracy-required surface I) of the shaft portion 4 and the shaft end surface 4b (second accuracy-required surface B) of the shaft portion 4 can be adjusted at the final step of the manufacturing method. By adjusting the first machining accuracy, it is possible to produce the speed reducer 10 that can minimize the runout of the shaft portion 4, i.e., the runout of the output shaft. As described above, in the embodiment, the speed reducer 10 with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0055] The industrial robot 100 related to embodiment includes the base 110, the first arm 120 with the working head 140, the electric motor provided in the base 110 for providing a driving force to rotate the first arm 120, and the speed reducer 10 for reducing the speed of the rotation of the electric motor 31. The speed reducer 10 includes: the outer tube 2; the shaft portion 4 rotatably provided inside the outer tube 2, the shaft portion 4 being fixedly coupled to an output shaft and having a shaft end surface 4b; the input shaft 3 coupled to the electric motor 31; the pair of bearings 5 rotatably supporting the outer tube 2 relative to the shaft portion 4, the pair of bearings 5 including a first bearing 5A provided near the shaft end surface 4b and a second bearing 5B provided closer to the first bearing 5A rather than the shaft end surface 4b; the speed reducing portion 10A connected with the input shaft 3 and rotatably supporting the shaft portion 4; and the attachment member 6 having a flange 61, the flange 61 having a flange mounting surface 61a fastened to the outer tube 2 by the first fixing bolt 62, the flange 61 extending perpendicular to the rotational axis of the shaft portion 4 and being attachable to the electric motor 31. The shaft portion 4 has the first receiving surface 4a. The outer tube 2 has the second receiving surface 2b. The first bearing 5A has the first inner ring 51 and the first outer ring 52. The first receiving surface 4a contacts the first inner ring 51 in the axis direction. The second receiving surface 2b contacts the first outer ring 52 in the axis direction. The first machining accuracy is obtained based on the first parallelism between the first receiving surface 4a and the shaft end surface 4b. The second machining accuracy is obtained based on the second parallelism between the second receiving surface 2b and the flange mounting surface 61a. The speed reducer is configured such that the first machining accuracy is higher than the second machining accuracy.

[0056] In the industrial robot 100 related to the embodiment, only the first machining accuracy based on the first parallelism between the first receiving surface 4a (first accuracy-required surface I) of the shaft portion 4 and the shaft end surface 4b (second accuracy-required surface B) of the shaft portion 4 can be adjusted at the final step of the manufacturing method. By adjusting the first machining accuracy, it is possible to produce the speed reducer 10 that can minimize the runout of the shaft portion 4, i.e., the runout of the output shaft. This speed reducer 10 can be used for the industrial robot 100. As described above, in the embodiment, the speed reducer 10 with high accuracy can be manufactured by the simple adjustment work in the manufacturing process. Therefore, the manufacturing cost can be reduced. In other words, it is possible to manufacture precision reducers (RVs) for which runout adjustment is unnecessary or can be minimized.

[0057] In the foregoing embodiments, the speed reducer 10 is applied to the industrial robot 100, but the present invention is not limited to such. As an alternative example, the speed reducer of the present invention can be applied to construction machines and automobiles.

Claims

1. A speed reducer (10), comprising: an outer tube (2); a shaft portion (4) rotatably provided inside the outer tube (2), the shaft portion (4) being fixedly coupled to an output shaft (40) and having a shaft end surface (4b); an input shaft (3) coupled to a drive source (31); a pair of bearings (5) rotatably supporting the outer tube (2) relative to the shaft portion (4), the pair of bearings (5) including a first bearing (5A) provided near the shaft end surface (4b) and a second bearing (5B) different from the first bearing (5A); a speed reducing portion (10A) connected with the input shaft (3) and rotatably supporting the shaft portion (4); and an attachment member (6) having a flange (61), the flange (61) having a flange mounting surface (61a) fastened to the outer tube (2) by a bolt (62), the flange (61) extending perpendicular to a rotational axis of the shaft portion (4) and being attachable to the drive source (31), wherein the shaft portion (4) has a first receiving surface (4a), wherein the outer tube (2) has a second receiving surface (2b), wherein the first bearing (5A) has a first inner ring (51) and a first outer ring (52), wherein the first receiving surface (4a) contacts the first inner ring (51) in a direction of the rotational axis, wherein the second receiving surface (2b) contacts the first outer ring (52) in the rotational axis direction, characterized in that a first parallelism is defined between the first receiving surface (4a) and the shaft end surface (4b), wherein a second parallelism is defined between the second receiving surface (2b) and the flange mounting surface (61a), and the first and second parallelisms are defining a first and second manufacturing accuracy for manufacturing the speed reducer (10), wherein the first machining accuracy is higher than the second machining accuracy.

2. The speed reducer (10) of claim 1, wherein the first parallelism of the first machining accuracy is 10 µm or less, regardless of a rotation phase between the shaft portion (4) and the outer tube (2).

3. The speed reducer (10) of claim 1 or claim 2, wherein an axial runout of the pair of bearings (5) is equal to or less than 90 µm.

4. The speed reducer (10)of claim 1 or claim 2, wherein the outer tube (2) has a flange mounted surface (2d), wherein the flange mounting surface (61a) is attached to the flange mounted surface (2d), and a third parallelism between the flange mounting surface (61a) and the flange mounted surface (2d) is 20 µm or less.

5. The speed reducer (10)of claim 1 or claim 2, wherein the second bearing (5B) has a second inner ring (51) and a second outer ring (52), wherein the outer tube (2) has a third receiving surface (2c) and a flange mounted surface (2d), wherein the third receiving surface (2c) contacts the second outer ring (52) in the rotational axis direction, and wherein the flange mounting surface (61a) is attached to the flange mounted surface (2d), wherein a parallelism between each of the second receiving surface (2b), the third receiving surface (2c), and the flange mounted surface (2d) is 30 µm or less.

6. The speed reducer (10)of claim 1 or claim 2, wherein the second parallelism of the second machining accuracy is170 µm or less.

7. The speed reducer (10)of claim 1, wherein an axial runout of the pair of bearings (5) is equal to or less than 90 µm, wherein the outer tube (2) has a third receiving surface (2c) and a flange mounted surface (2d), wherein the flange mounting surface (61a) is attached to the flange mounted surface (2d), wherein the second bearing (5B) has a second inner ring (51) and a second outer ring (52), wherein the third receiving surface (2c) contacts the second outer ring (52) in the rotational axis direction, and wherein the first parallelism of the first machining accuracy is10 µm or less, regardless of a rotation phase between the shaft portion (4) and the outer tube (2); a third parallelism between the flange mounting surface (61a) and the flange mounted surface (2d) is 20 µm or less; a parallelism between each of the second receiving surface (2b), the third receiving surface (2c), and the flange mounted surface (2d) is 30 µm or less; and the second parallelism of the second machining accuracy is 170 µm or less.

8. A method for manufacturing a speed reducer (10), comprising steps of : providing step of a speed reducer according to claims 1-7, obtaining step of a first machining accuracy based on a first parallelism between the first receiving surface and the shaft end surface, and a second machining accuracy based on a second parallelism between the second receiving surface and the flange mounting surface; and adjusting step of the first machining accuracy to be higher than the second machining accuracy.

9. A rotating device (100) comprising: a device body (110); a rotated body (120) with a working head; an electric motor (31) provided on the device body (110), the motor being configured to produce a driving force to rotate the rotated body (120); and the speed reducer (10) according to claim 1 - 7 for reducing speed of rotation of the electric motor.