Rotary mechanism, transmission, power transmission pin for transmission, and method for manufacturing power transmission pin

Abstract

The invention provides a rotating mechanism, a transmission, a power transmission pin for the transmission, and a manufacturing method thereof. A power transmission pin (9) according to the present embodiment is provided with: a shaft section (61); and a male thread section (62) which is provided coaxially with the shaft section (61) at the axial end of the shaft section (61) and which fixes the shaft section (61) to the speed reduction mechanism (30). The hardness of at least the surface of the shaft section (61) is higher than the hardness of the male thread section (62).

Description

Technical Field

[0001] The present invention relates to a rotating mechanism, a transmission, a power transmission pin for the transmission and a manufacturing method thereof. Background Art

[0002] As a rotating mechanism, for example, a transmission is known that receives rotation from an electric motor or the like to an input portion, decelerates or speeds up the rotation, and outputs the rotation from an output portion. Also, as a transmission, for example, an eccentric oscillating type speed reducer with high rotation position accuracy and load resistance is known.

[0003] Such a reducer, for example, includes: a housing (frame) having an internal gear formed on the inner circumferential surface; a swing gear (external gear) meshing with the internal gear and swinging and rotating; a crankshaft (input rotating body) having an eccentric portion that supports the swing gear so that it can rotate freely and transmits the rotational force to the swing gear; a power transmission pin (carrying pin) to which the rotational force of the swing gear is transmitted; and a gear rack (output rotating body) connected to the power transmission pin.

[0004] The swing gear is formed with a pin insertion hole for inserting the power transmission pin. The gear frame is formed with a pin insertion hole for inserting or pressing the power transmission pin. By inserting the power transmission pin into these pin insertion holes, the rotation of the swing gear is transmitted to the gear frame via the power transmission pin.

[0005] The pin insertion hole of the swing gear is formed to a size that allows the swing gear to swing relative to the power transmission pin. A cylindrical bushing is inserted into the pin insertion hole of the swing gear. The power transmission pin is inserted into the bushing.

[0006] For example, an external thread portion formed at the top of the power transmission pin and a nut fastened to the external thread portion are used to restrict the movement of the power transmission pin in the direction of falling off relative to the gear frame. The external thread portion formed on the power transmission pin passes through the pin insertion hole of the gear frame and protrudes axially outward. The movement of the power transmission pin in the direction of falling off relative to the gear frame is restricted by fastening a nut to the protruding external thread portion (for example, refer to patent document 1).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2017-82993 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] As in the above-mentioned prior art, the power transmission pin has the function of transmitting the rotational force of the swing gear to the gear frame. Therefore, a large load is applied to the power transmission pin. Therefore, the power transmission pin is required to have improved strength and toughness. In addition, the power transmission pin also has the function of sliding relative to the bushing, so it is also required to have improved wear resistance. Therefore, in addition to requiring improved strength and toughness, the power transmission pin is also required to have improved wear resistance.

[0012] In this regard, there is room for improvement in conventional power transmission pins.

[0013] The present invention provides a transmission power transmission pin, a rotating mechanism, a transmission and a method for manufacturing the transmission power transmission pin, which can improve strength, toughness and wear resistance.

[0014] Solutions for solving problems

[0015] A transmission power transmission pin of one embodiment of the present invention is a transmission power transmission pin for power transmission of a transmission having a speed change mechanism for changing the speed of input rotation and outputting the rotation, and comprises: a shaft portion; and an external thread portion, which is provided at an axial end of the shaft portion and is coaxial with the shaft portion, and is used to fix the shaft portion to the speed change mechanism. The hardness of at least the surface of the shaft portion is higher than that of the external thread portion.

[0016] For example, if one wants to simply improve the wear resistance, strength and toughness of the power transmission pin for a transmission, then one can think of increasing the hardness of the entire power transmission pin for a transmission. However, if this is done, there is a possibility that the external threaded portion of the power transmission pin for a transmission will be damaged. Therefore, the hardness of at least the surface of the shaft portion of the power transmission pin for a transmission is higher than the hardness of the external threaded portion. Thus, it is possible to make it difficult for the external threaded portion to be damaged, and the shaft portion that bears the most load can also obtain the desired strength. Therefore, the strength, toughness and wear resistance of the power transmission pin for a transmission can be improved.

[0017] In the above structure, the surface of the shaft portion may be nitrided to form a nitride layer.

[0018] A rotating mechanism according to another aspect of the present invention comprises: a rotating body having an insertion hole formed therein; a cylindrical bushing provided in the insertion hole; and a power transmission pin inserted into the bushing. The power transmission pin comprises: a shaft portion; and an external thread portion provided at an axial end of the shaft portion to be coaxial with the shaft portion and to integrate the rotating body and the power transmission pin. The hardness of at least the surface of the shaft portion is higher than that of the external thread portion and higher than that of the bushing.

[0019] By configuring in this way, the wear resistance of the shaft portion with respect to the bushing can be reliably improved, so that a rotating mechanism having excellent strength, toughness, and wear resistance can be provided.

[0020] In the above structure, the surface of the shaft portion may be nitrided to form a nitride layer.

[0021] A transmission according to another aspect of the present invention comprises: a rotating input portion; a speed change mechanism that changes the speed of the rotation of the input portion; and an output portion to which the rotation of the input portion is transmitted via the speed change mechanism. The speed change mechanism comprises: a gear formed with a pin insertion hole; a power transmission pin inserted into the pin insertion hole; and a cylindrical bushing inserted into the pin insertion hole and engaged with the power transmission pin. The power transmission pin comprises: a shaft portion; and an external thread portion, which is provided at an axial end of the shaft portion to be coaxial with the shaft portion and is used to integrate the gear and the power transmission pin. The hardness of at least the surface of the shaft portion is higher than that of the external thread portion and higher than that of the bushing.

[0022] By configuring in this way, the wear resistance of the shaft portion with respect to the bush can be reliably improved, so that a transmission having excellent strength, toughness and wear resistance can be provided.

[0023] In the above structure, the surface of the shaft portion may be nitrided to form a nitride layer.

[0024] Another form of a method for manufacturing a power transmission pin for a transmission according to the present invention is a method for manufacturing a power transmission pin for a transmission for power transmission of a transmission having a speed change mechanism for changing the speed of input rotation and outputting it, and comprises: a surface hardening process for hardening the surface of a rod-shaped base material; a surface cutting process for cutting a part of the hardened surface of the end portion in the axial direction of the base material after the surface hardening process; and a thread forming process for forming an external threaded portion on the part of the base material cut by the surface cutting process.

[0025] By adopting such a method, for the shaft portion and the external thread portion formed of the same base material, a power transmission pin for a transmission in which at least the surface hardness of the shaft portion is higher than the hardness of the external thread portion can be easily manufactured.

[0026] In the above method, the step of further performing a quenching and tempering treatment on the base material may be included before the surface hardening step.

[0027] Another form of a method for manufacturing a power transmission pin for a transmission of the present invention is a method for manufacturing a power transmission pin for a transmission used for power transmission of a transmission having a speed change mechanism that changes the speed of input rotation and outputs it, and the method comprises: a thread forming process for forming an external thread portion locally at the axial end of a rod-shaped base material; and a surface hardening process for hardening the surface of the base material except for the external thread portion after the thread forming process.

[0028] By adopting such a method, for the shaft portion and the external thread portion formed of the same base material, a power transmission pin for a transmission in which at least the surface hardness of the shaft portion is higher than the hardness of the external thread portion can be easily manufactured.

[0029] In the above method, in the surface hardening step, the surface of the base material may be nitrided to form a nitrided layer.

[0030] Effects of the Invention

[0031] According to the above-mentioned power transmission pin for transmission, rotating mechanism, transmission, and method for manufacturing the power transmission pin for transmission, the strength, toughness, and wear resistance of the power transmission pin can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a cross-sectional view of the speed reducer in the embodiment of the present invention.

[0033] Figure 2 1 is a process diagram showing a method for manufacturing a power transmission pin in an embodiment of the present invention, wherein (a) to (d) show the respective steps.

[0034] Description of Reference Numerals

[0035] 1. Speed ​​reducer (transmission, rotating mechanism); 2. Housing; 7. Gear rack (rotating body); 9. Power transmission pin (power transmission pin for transmission); 11. First swing gear (rotating body, gear); 12. Second swing gear (rotating body, gear); 25a. First pin insertion hole (pin insertion hole); 25b. Second pin insertion hole (pin insertion hole); 30. Speed ​​reduction mechanism (speed change mechanism); 61. Shaft portion; 62. External threaded portion; 67a. First bushing (bushing); 67b. Second bushing (bushing); N. Nitride layer. DETAILED DESCRIPTION

[0036] Next, embodiments of the present invention will be described based on the drawings.

[0037] <Reduction gear>

[0038] Figure 1 It is a cross-sectional view of the speed reducer 1 .

[0039] The speed reducer 1 is a so-called eccentric oscillating speed reducer and includes a cylindrical housing 2 and a gear carrier 7 rotatably supported by the housing 2 via two bearings 15a and 15b (a first bearing 15a and a second bearing 15b).

[0040] Hereinafter, the axial direction of the housing 2 is simply defined as the axial direction. The circumferential direction of the housing 2 is simply defined as the circumferential direction. The radial direction of the housing 2 is simply defined as the radial direction.

[0041] <Housing>

[0042] The housing 2 is formed of, for example, an iron-based material such as cast iron. In addition, the housing 2 may be formed of, for example, an aluminum alloy, a magnesium alloy, a carbon fiber reinforced plastic (CFRP), a resin containing boron nitride to improve thermal conductivity, or the like. An outer flange portion 4 extending radially outward is integrally formed on the outer peripheral surface 2a of the housing 2. The cross section of the outer flange portion 4 along the axial direction is formed into a quadrilateral shape.

[0043] A plurality of bolt holes 4a penetrating in the axial direction are formed at equal intervals in the circumferential direction on the outer flange portion 4. An unillustrated device for mounting the reducer 1 is stacked on the outer flange portion 4. Furthermore, unillustrated bolts are inserted into the bolt holes 4a of the outer flange portion 4 and the bolts are fastened to the device, thereby fixing the reducer 1 to the device.

[0044] Bearing housings 3a and 3b (first bearing housing 3a and second bearing housing 3b) are formed on both axial sides of the inner circumferential surface 2b of the housing 2. Each bearing housing 3a and 3b is formed to have a larger inner diameter than the inner circumferential surface 2b of the housing 2 by means of a step.

[0045] A first bearing 15a is fitted in the first bearing housing 3a. A second bearing 15b is fitted in the second bearing housing 3b. Each of the bearings 15a and 15b is, for example, a ball bearing.

[0046] A seal housing 5 is formed at a portion of the inner peripheral surface 2b of the housing 2 that is located axially outward from the second bearing housing 3b. The seal housing 5 is formed in such a way that the inner diameter is larger than the inner diameter of the second bearing housing 3b by means of a step. A seal 40 is fitted into the seal housing 5. The seal 40 seals between the housing 2 and the gear frame 7.

[0047] A plurality of internal tooth pins 6 are provided on the portion of the inner peripheral surface 2b of the housing 2 between the two bearing housings 3a, 3b. The internal tooth pins 6 are formed into a cylindrical shape extending in the axial direction. However, this is not limited to this, and the internal tooth pins 6 may also be hollow members. The internal tooth pins 6 are arranged at equal intervals in the circumferential direction. The internal tooth pins 6 function as a part of the speed reduction mechanism 30. That is, the internal tooth pins 6 function as internal teeth that mesh with the swing gears 11, 12 discussed later.

[0048] <Reduction Mechanism>

[0049] The speed reduction mechanism 30 comprises: a gear frame 7; a power transmission pin 9, which is arranged on the gear frame 7; a crankshaft 8, which is supported on the gear frame 7 in a rotatable manner by means of two bearings 15c, 15d (the third bearing 15c and the fourth bearing 15d); and two swing gears 11, 12 (the first swing gear 11 and the second swing gear 12), which are supported on the crankshaft 8 in a rotatable manner.

[0050] The rotation axis of the gear carrier 7 coincides with the rotation axis of the crankshaft 8 . These rotation axes coincide with the central axis of the housing 2 .

[0051] The gear carrier 7 is composed of a disc-shaped first flange 13 and a second flange 14 disposed on both sides in the axial direction. The first flange 13 and the second flange 14 are formed of an iron-based material such as cast iron.

[0052] Of the two flanges 13 and 14 , the second flange 14 is disposed on the sealed case 5 side of the housing 2 .

[0053] A first opening 13a that axially penetrates the first flange 13 is formed in the majority of the radial center of the first flange 13. A first reduced diameter portion 13b is formed in a portion of the outer peripheral surface of the first flange 13 located on the second flange 14 side. The first reduced diameter portion 13b is formed in a manner that the outer diameter is smaller than the outer diameter of the first flange 13 by means of a step. A first bearing 15a is fitted in the first reduced diameter portion 13b.

[0054] A first diameter-enlarged portion 13c is formed on the inner peripheral surface of the first opening 13a at a portion on the second flange 14 side. The first diameter-enlarged portion 13c is formed so that the inner diameter is larger than the inner diameter of the first opening 13a by means of a step. A third bearing 15c is fitted into the first diameter-enlarged portion 13c. The third bearing 15c is, for example, a ball bearing.

[0055] A plurality of first bolt insertion holes 51 are formed in the first flange 13. The plurality of first bolt insertion holes 51 are arranged at equal intervals in the circumferential direction. The first bolt insertion hole 51 is composed of a shaft insertion portion 51a formed on the second flange 14 side and a threaded insertion portion 51b formed on the side opposite to the second flange 14.

[0056] The shaft insertion portion 51a and the screw insertion portion 51b are formed coaxially. The shaft insertion portion 51a and the screw insertion portion 51b are connected. The screw insertion portion 51b is formed so that the inner diameter thereof is smaller than the inner diameter of the shaft insertion portion 51a by the step portion 51c.

[0057] Part of the outer peripheral surface of the second flange 14 faces the seal housing 5 of the housing 2 in the radial direction. A seal 40 is fitted in the facing portion. Thus, the housing 2 and the second flange 14 constituting the gear carrier 7 are sealed.

[0058] A second opening 14a that axially penetrates the second flange 14 is formed in the majority of the radial center of the second flange 14. A second reduced diameter portion 14b is formed in a portion of the outer peripheral surface of the second flange 14 located on the first flange 13 side. The second reduced diameter portion 14b is formed in a manner that the outer diameter is smaller than the outer diameter of the second flange 14 by means of a step. A second bearing 15b is fitted in the second reduced diameter portion 14b.

[0059] A second diameter-enlarged portion 14c is formed on the inner peripheral surface of the second opening 14a at a portion on the first flange 13 side. The second diameter-enlarged portion 14c is formed so that the inner diameter is larger than the inner diameter of the second opening 14a by means of a step. A fourth bearing 15d is fitted into the second diameter-enlarged portion 14c. The fourth bearing 15d is, for example, a ball bearing.

[0060] A plurality of second bolt insertion holes 52 are formed in the second flange 14. The plurality of second bolt insertion holes 52 are arranged at equal intervals in the circumferential direction and are arranged coaxially with the first bolt insertion hole 51. The inner diameter of the second bolt insertion hole 52 is the same as the inner diameter of the shaft insertion portion 51a of the first bolt insertion hole 51. A countersink portion 52a is formed on the side of the second bolt insertion hole 52 opposite to the first flange 13. The countersink portion 52a is formed in such a manner that the inner diameter is larger than the inner diameter of the second bolt insertion hole 52 by means of a step portion 52b.

[0061] A power transmission pin 9 is inserted into each of the bolt insertion holes 51 and 52 of each flange 13 and 14. The power transmission pin 9 is formed of, for example, aluminum-chromium-molybdenum steel. The power transmission pin 9 includes: a cylindrical shaft portion 61; an external thread portion 62 integrally formed at one axial end of the shaft portion 61; and a head portion 63 integrally formed at the other axial end of the shaft portion 61. The shaft portion 61, the external thread portion 62, and the head portion 63 are arranged coaxially.

[0062] The outer diameter of the shaft portion 61 is the same as or slightly smaller than the inner diameter of the shaft insertion portion 51 a of the first bolt insertion hole 51 and the inner diameter of the second bolt insertion hole 52 .

[0063] The external thread portion 62 is formed so that the outer diameter thereof is smaller than the outer diameter of the shaft portion 61 by means of a thread step portion 62a. An incomplete thread portion 62b is formed at the root of the external thread portion 62 on the shaft portion 61 side.

[0064] The head portion 63 is formed so that the outer diameter thereof is larger than the outer diameter of the shaft portion 61 by the head step portion 63a. The outer diameter of the head portion 63 is slightly smaller than the outer diameter of the counterbore portion 52a of the second flange 14.

[0065] Based on such a structure, the power transmission pin 9 inserts the external thread portion 62 from the second flange 14 side toward the first flange 13 side in the order of the second bolt insertion hole 52 and the first bolt insertion hole 51. At this time, the head portion 63 of the power transmission pin 9 is inserted into the countersunk portion 52a of the second bolt insertion hole 52. The power transmission pin 9 is positioned axially relative to the second flange 14 by the head step portion 63a of the power transmission pin 9 abutting against the step portion 52b of the second bolt insertion hole 52.

[0066] On the other hand, the external thread portion 62 of the power transmission pin 9 passes through the first bolt insertion hole 51 and protrudes axially outward. The incomplete thread portion 62b in the external thread portion 62 is inserted into the threaded insertion portion 51b of the first bolt insertion hole 51. The end of the shaft portion 61 on the side of the external thread portion 62 is inserted into the shaft insertion portion 51a of the first bolt insertion hole 51. The power transmission pin 9 is axially positioned relative to the first flange 13 by the threaded step portion 62a of the power transmission pin 9 abutting against the step portion 51c of the first bolt insertion hole 51.

[0067] A flat washer 64 is inserted into the external threaded portion 62 that passes through the first bolt insertion hole 51 and protrudes to the outside in the axial direction. The nut 65 is tightened from the flat washer 64. Thus, the power transmission pin 9 is fixed relative to the gear frame 7 (the first flange 13 and the second flange 14). The details of the manufacturing method for the power transmission pin 9 are described below.

[0068] When the power transmission pin 9 is fixed, two bushings 67a and 67b (first bushing 67a and second bushing 67b) are fitted in the portion of the shaft portion 61 between the first flange 13 and the second flange 14. The bushings 67a and 67b are made of high carbon chromium bearing steel such as SUJ2.

[0069] The crankshaft 8 is inserted into the first opening 13a and the second opening 14a and is rotatably supported by the flanges 13 and 14 via the third bearing 15c and the fourth bearing 15d. The crankshaft 8 is formed of, for example, an aluminum alloy, similarly to the power transmission pin 9. In addition, as the crankshaft 8, stainless steel or various iron-based metals can be used, similarly to the power transmission pin 9.

[0070] The crankshaft 8 is formed in a hollow shape. A keyway 66 is formed on the inner circumferential surface of the crankshaft 8. The keyway 66 is used, for example, to connect the motor shaft of an electric motor provided in a device not shown and the crankshaft 8. The first eccentric portion 21a and the second eccentric portion 21b are formed in the axial direction in a portion of the crankshaft 8 located between the third bearing 15c and the fourth bearing 15d.

[0071] The first eccentric portion 21a is arranged on the first flange 13 side. The second eccentric portion 21b is arranged on the second flange 14 side. Each eccentric portion 21a, 21b is eccentric with respect to the rotation axis of the crankshaft 8 (gear carrier 7). The phase angles of each eccentric portion 21a, 21b are deviated from each other. For example, the phase angles of each eccentric portion 21a, 21b are deviated from each other by 180°.

[0072] The eccentric portions 21a and 21b are provided with bearings 15e and 15f (fifth bearing 15e and sixth bearing 15f), respectively. These bearings 15e and 15f are, for example, needle roller bearings.

[0073] The swing gears 11 and 12 (first swing gear 11 and second swing gear 12) are rotatably supported by the eccentric portions 21a and 21b via bearings 15e and 15f, respectively.

[0074] The two swing gears 11 and 12 are formed of an iron-based material such as chrome-molybdenum steel.

[0075] Crankshaft insertion holes 24a and 24b (first crankshaft insertion hole 24a and second crankshaft insertion hole 24b) penetrating in the thickness direction are formed at the radial centers of the two swing gears 11 and 12. Bearings 15e and 15f are fitted in the crankshaft insertion holes 24a and 24b, respectively.

[0076] External teeth 23a, 23b meshing with the internal tooth pins 6 of the housing 2 are formed on the outer circumferences of the two swing gears 11, 12. The number of teeth of each external tooth 23a, 23b is less than the number of internal tooth pins 6, for example, one.

[0077] Pin insertion holes 25a and 25b (first pin insertion hole 25a and second pin insertion hole 25b) are formed at positions corresponding to the power transmission pin 9 of the two swing gears 11 and 12. The shaft portion 61 of the power transmission pin 9 is inserted into each of the pin insertion holes 25a and 25b. The first bushing 67a that fits with the shaft portion 61 is inserted into the first pin insertion hole 25a. The second bushing 67b that fits with the shaft portion 61 is inserted into the second pin insertion hole 25b.

[0078] Based on such a structure, each swing gear 11, 12 swings and rotates by utilizing each eccentric portion 21a, 21b of the crankshaft 8. The inner diameter of each pin insertion hole 25a, 25b of each swing gear 11, 12 is large enough to allow the swing rotation of each swing gear 11, 12 in a state where the shaft portion 61 of the power transmission pin 9 and each bushing 67a, 67b are inserted.

[0079] <Operation of the speed reducer>

[0080] Next, the operation of the speed reducer 1 will be described.

[0081] When the crankshaft 8 is rotated by an electric motor (not shown), the swing gears 11 and 12 rotatably supported by the eccentric portions 21a and 21b swing and rotate. Then, a part of the external teeth 23a and 23b of the swing gears 11 and 12 meshes with the internal teeth pins 6 of the housing 2.

[0082] At this time, the number of teeth of each external tooth 23a, 23b is less than the number of internal tooth pins 6, for example, by one, and therefore, each swing gear 11, 12 rotates in such a manner that the meshing portion of each external tooth 23a, 23b is sequentially deviated from the internal tooth pin 6 (housing 2) in the circumferential direction. This rotation is decelerated relative to the rotation of the crankshaft 8.

[0083] A power transmission pin 9 is inserted into the pin insertion holes 25a and 25b of each swing gear 11 and 12. Therefore, due to the rotation of each swing gear 11 and 12, the rotational force of the swing gear 11 and 12 in the rotation direction is transmitted to each power transmission pin 9 via the bushings 67a and 67b. Each power transmission pin 9 is fixed to the gear frame 7 (the first flange 13 and the second flange 14). Therefore, the rotational force of the swing gear 11 and 12 is transmitted to the gear frame 7.

[0084] The gear frame 7 is supported by the housing 2 in a rotatable manner by means of the first bearing 15a and the second bearing 15b. Therefore, the gear frame 7 rotates relative to the housing 2. That is, the rotation input to the crankshaft 8 is decelerated and output from the gear frame 7. In this way, the power transmission pin 9 transmits the rotation of each swing gear 11, 12 after the rotation of the crankshaft 8 is decelerated to the gear frame 7, and therefore a large load is applied. Therefore, the power transmission pin 9 is manufactured by the following method.

[0085] <Method for manufacturing power transmission pin>

[0086] Figure 2 1 is a process diagram showing a method for manufacturing the power transmission pin 9, wherein (a) to (d) show the respective processes. Figure 2 (a) to (c) of FIG. 9 show side views of the base material 70 of the power transmission pin 9. Figure 2 (b) Figure 2 (c) shows a partial cross-section of the base material 70.

[0087] like Figure 2 As shown in (a), first, the base material 70 of the power transmission pin 9 is subjected to quenching and tempering treatment (step ST101; semi-processing). The base material 70 referred to here means that the portion corresponding to the external thread portion 62 of the power transmission pin 9 has not been processed and has the same diameter as the shaft portion 61. The head 63 of the power transmission pin 9 is formed. The base material 70 at this moment has not been heat treated.

[0088] In the quenching and tempering treatment, the quenching temperature and the treatment time are, for example, 860° C. and about 1 hour. Tempering is performed at a low temperature. Specifically, the tempering temperature and the treatment time are, for example, 160° C. and about 2 hours. By implementing the above-mentioned quenching and tempering treatment, the toughness (flexibility) of the base material 70 can be improved. The hardness of the base material 70 at this moment is, for example, Rockwell hardness [HRC] 37 to 45.

[0089] Then, if Figure 2 As shown in (b), the surface of the base material 70 is hardened (step ST102; surface hardening process). Specifically, the surface of the base material 70 is subjected to nitriding treatment to form a nitride layer N. The temperature and treatment time of the nitriding treatment are, for example, 520°C and about 35 hours. The nitride layer N is formed to have a thickness of, for example, about 0.2 mm. The hardness of the nitride layer N is, for example, a Vickers hardness [HV] of 1000 to 750. That is, at the moment when the surface hardening process is completed, the hardness of the surface of the base material 70, that is, the nitride layer N, is different from the hardness of the interior (core) that is closer to the nitride layer N. The above-mentioned hardness of the nitride layer N is higher than the hardness of each bushing 67a, 67b.

[0090] Then, if Figure 2 As shown in (c), the nitride layer N of a local portion of the external thread portion 62 is cut and the nitride layer N of the local portion is removed (step ST103; surface cutting process). In the following description, the local portion from which the nitride layer N is removed is referred to as a surface cutting portion 71. The surface of the surface cutting portion 71 has the nitride layer N removed, and therefore, the hardness of the surface of the surface cutting portion 71 is, for example, Rockwell hardness [HRC] 37 to 45.

[0091] The cutting amount when forming the surface cutting portion 71 is about 0.5 mm, for example. Since the nitride layer N is about 0.2 mm, for example, the nitride layer N can be easily removed in the surface cutting step.

[0092] Among them, for example, when the cutting amount is set to a degree that the nitride layer N is not completely removed in the surface cutting process, that is, when the cutting amount is set to about 0.1 mm, only the nitride layer N is cut. In this case, only the layer with a high hardness is cut, so it is difficult to cut extra. The cutting amount in the surface cutting process is deliberately set to a thickness that slightly cuts the material inside the nitride layer N together with the nitride layer N, so that the surface cutting process can be facilitated.

[0093] Then, if Figure 2 As shown in (d) of FIG. 1 , the external thread portion 62 is formed on the surface cut portion 71 (step ST104; thread forming step). In addition, the shaft portion 61 is finely ground. Thus, the production of the power transmission pin 9 is completed.

[0094] Thus, the external thread portion 62 is formed on the surface cutting portion 71. On the other hand, a nitride layer N is formed on the surface of the shaft portion 61. Therefore, the hardness of the surface of the shaft portion 61 is higher than that of the external thread portion 62. In addition, the hardness of the surface of the shaft portion 61 is higher than that of each bushing 67a, 67b.

[0095] Thus, the hardness of the surface of the shaft portion 61 of the power transmission pin 9 is higher than the hardness of the external thread portion 62. Therefore, the strength, toughness, and wear resistance of the power transmission pin 9 can be improved.

[0096] For example, if the wear resistance, strength, and toughness of the power transmission pin 9 are to be simply improved, it is conceivable to increase the hardness of the entire power transmission pin 9. However, in this case, the external thread portion 62 of the power transmission pin 9 may be damaged.

[0097] In contrast, in this embodiment, as in the above-mentioned power transmission pin 9, the hardness of the surface of the shaft portion 61 is made higher than the hardness of the external thread portion 62. As a result, it is possible to prevent the external thread portion 62 from being easily damaged, and the shaft portion 61 that bears the most load can also obtain the desired strength. The external thread portion 62 is also subjected to quenching and tempering treatment, thereby improving toughness. Therefore, the strength, toughness and wear resistance of the power transmission pin 9 can be improved.

[0098] In order to improve the hardness of the surface of the shaft portion 61 , the surface of the shaft portion 61 is subjected to nitriding treatment to form a nitride layer N. Therefore, the hardness of the surface of the shaft portion 61 can be reliably improved.

[0099] The hardness of the surface of the shaft portion 61 is higher than that of the bushings 67a and 67b. Therefore, the wear resistance of the shaft portion 61 with respect to the bushings 67a and 67b can be reliably improved. Therefore, the speed reducer 1 having excellent strength, toughness and wear resistance can be provided.

[0100] The method for manufacturing the power transmission pin 9 includes: a surface hardening process for hardening the surface of the base material 70; a surface cutting process performed after the surface hardening process; and a thread forming process for forming the external thread portion 62 on the surface cutting portion 71 formed by the surface cutting process. Therefore, for the shaft portion 61 and the external thread portion 62 formed from the same base material 70, the hardness of the surface of the shaft portion 61 can be easily made higher than the hardness of the external thread portion 62.

[0101] For example, after the power transmission pin 9 is shaped, the external thread portion 62 of the power transmission pin 9 may be subjected to nitriding treatment while being subjected to nitriding prevention treatment, but this operation is troublesome. Compared with such a method, the power transmission pin 9 can be efficiently manufactured by the above-mentioned manufacturing method.

[0102] Furthermore, the base material 70 is subjected to quenching and tempering treatment before the surface hardening process. Therefore, the desired strength and toughness of the external thread portion 62 can be obtained. By subjecting the base material 70 to quenching and tempering treatment, the time of the subsequent surface hardening process can be shortened. The reason is that the surface hardening process also becomes a high-temperature tempering process. Therefore, by previously performing a low-temperature tempering treatment performed by the quenching and tempering treatment, the time of the surface hardening process can be shortened.

[0103] In the above-mentioned manufacturing method, the following case is described: in order to make the hardness of the surface of the shaft portion 61 higher than the hardness of the external thread portion 62, the base material 70 is subjected to the surface hardening process, the surface cutting process, and the thread forming process in the order of the surface hardening process, the surface cutting process, and the thread forming process. However, this is not limited to this, and in the power transmission pin 9 as a finished product, the hardness of the surface of the shaft portion 61 is higher than the hardness of the external thread portion 62.

[0104] For example, in order to harden the surface of the shaft portion 61, DLC (Diamond Like Carbon) coating may be applied to the surface of the shaft portion 61 instead of nitriding. In this case, in the manufacturing method of the power transmission pin 9, first, an external thread portion 62 is formed on the base material 70 (thread forming process). Thereafter, the surface of the base material 70 other than the external thread portion 62 (the surface of the shaft portion 61) is hardened (surface hardening process). In the case of implementing DLC ​​coating as a method for hardening the surface of the shaft portion 61, the DLC coating is performed after the external thread portion 62 is masked. Even in the case of such a method, the same effect as that of the above-mentioned embodiment is achieved.

[0105] In the above-mentioned embodiment, the case where the power transmission pin 9 is formed of, for example, aluminum-chromium-molybdenum steel is described. However, it is sufficient to make the hardness of the surface of the shaft portion 61 higher than the hardness of the external thread portion 62. The power transmission pin 9 is not limited to aluminum-chromium-molybdenum steel. For example, steel materials such as chromium-molybdenum steel can also be used for the power transmission pin 9. In this case, by performing high-frequency quenching on the surface of the shaft portion 61, the hardness of the surface of the shaft portion 61 can be made higher than the hardness of the external thread portion 62. The manufacturing method in this case is the same as the case of performing the above-mentioned DLC coating.

[0106] In the above-mentioned embodiment, the case where the power transmission pin 9 makes the hardness of the surface of the shaft portion 61 higher than the hardness of the external thread portion 62 is described. That is, in the shaft portion 61, the hardness of the nitride layer N is different from the hardness of the inner part (core part) inside the nitride layer N. However, this is not limited to this, and the hardness of at least the surface of the shaft portion 61 is higher than the hardness of the external thread portion 62. The inner part of the shaft portion 61 may also have the same hardness as the surface hardness.

[0107] In addition, the present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment within a scope that does not depart from the gist of the present invention.

[0108] For example, in the above-mentioned embodiment, the speed reducer 1 having the speed reduction mechanism 30 that reduces the speed of the rotation of the crankshaft 8 and outputs the speed is described. However, this is not limited to this, and the power transmission pin 9 mentioned above may be used in a speed increaser to replace the speed reduction mechanism 30. Furthermore, the power transmission pin 9 mentioned above may be used in a rotating mechanism provided with a rotating body that replaces the speed reduction mechanism 30 (gear frame 7, swing gears 11, 12). A pin insertion hole (pin insertion holes 25a, 25b) for inserting the power transmission pin 9 may be formed in the rotating body of the rotating mechanism.

[0109] In the embodiments disclosed in this specification, a component composed of multiple objects may be integrated into one, or a component composed of one object may be divided into multiple objects. Regardless of whether the components are integrated or not, they may be configured in a manner that can achieve the purpose of the invention.

Claims

1. A power transmission pin for a transmission, which is used for power transmission of a transmission having a speed change mechanism for changing the speed of input rotation and outputting the rotation, wherein: The power transmission pin for the transmission has: A shaft; and an external threaded portion, which is provided at an axial end of the shaft portion and is coaxial with the shaft portion, and is used to fix the shaft portion to the speed change mechanism, The hardness of at least the surface of the shaft portion is higher than the hardness of the external thread portion.

2. The power transmission pin for a transmission according to claim 1, wherein: A nitriding layer is formed by performing nitriding treatment on the surface of the shaft portion.

3. A rotating mechanism, wherein: The rotating mechanism has: a rotating body formed with an insertion hole; a cylindrical bushing provided to the insertion hole; and The power transmission pin, which is inserted into the bushing, The power transmission pin has: A shaft; and an external threaded portion, which is provided coaxially with the shaft portion at an axial end portion of the shaft portion and is used to integrate the rotating body and the power transmission pin, The hardness of at least the surface of the shaft portion is higher than the hardness of the external thread portion and higher than the hardness of the bush.

4. The rotating mechanism according to claim 3, wherein: A nitriding layer is formed by performing nitriding treatment on the surface of the shaft portion.

5. A transmission, wherein: The transmission has: A rotating input portion; a speed change mechanism that changes the speed of rotation of the input portion; and an output portion, to which the rotation of the input portion is transmitted via the speed change mechanism, The speed change mechanism comprises: a gear formed with a pin insertion hole; a power transmission pin inserted into the pin insertion hole; and a cylindrical bushing which is inserted into the pin insertion hole and is engaged with the power transmission pin, The power transmission pin has: A shaft; and an external threaded portion, which is provided coaxially with the shaft portion at an axial end portion of the shaft portion and is used to integrate the gear and the power transmission pin, The hardness of at least the surface of the shaft portion is higher than the hardness of the external thread portion and higher than the hardness of the bush.

6. The transmission according to claim 5, wherein: A nitriding layer is formed by performing nitriding treatment on the surface of the shaft portion.

7. A method for manufacturing a power transmission pin for a transmission, the power transmission pin for a transmission being used for power transmission of a transmission having a speed change mechanism for changing the speed of input rotation and outputting the rotation, wherein: The manufacturing method of the power transmission pin for a transmission comprises: A surface hardening step of hardening the surface of a rod-shaped base material; a surface cutting step of cutting a portion of the hardened surface at an end portion in the axial direction of the base material after the surface hardening step; and A thread forming step of forming a male thread portion on the portion of the base material cut in the surface cutting step.

8. The method for manufacturing a power transmission pin for a transmission according to claim 7, wherein: The method for manufacturing a power transmission pin for a transmission further includes a step of performing a quenching and tempering treatment on the base material before the surface hardening step.

9. A method for manufacturing a power transmission pin for a transmission, the power transmission pin for a transmission being used for power transmission of a transmission having a speed change mechanism for changing the speed of input rotation and outputting the rotation, wherein: The manufacturing method of the power transmission pin for a transmission comprises: a thread forming step of forming a male thread portion at a portion of an axial end portion of a rod-shaped base material; and a surface hardening step of hardening a surface of the base material except for the male thread portion after the thread forming step.

10. The method for manufacturing a power transmission pin for a transmission according to any one of claims 7 to 9, wherein: In the surface hardening step, the surface of the base material is subjected to nitriding treatment to form a nitrided layer.

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