Power transmission pin for transmission, rotary mechanism, transmission, method for manufacturing power transmission pin for transmission

Abstract

To provide a power transmission pin for a transmission that can improve strength, toughness and wear resistance, and to provide a rotary mechanism, a transmission and a method for manufacturing a power transmission pin for a transmission.SOLUTION: A power transmission pin 9 includes: a shaft part 61; and a male screw part 62 installed coaxially with the shaft part 61 in an end of the shaft part 61 in an axial direction to fix the shaft part 61 to a speed reduction mechanism 30. The hardness of at least surface of the shaft part 61 is higher than the hardness of the male screw part 62.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power transmission pin for a transmission, a rotation mechanism, a transmission, and a method for manufacturing a power transmission pin for a transmission. [Background technology]

[0002] Among the rotating mechanisms, there is a transmission in which rotation is input to an input section from, for example, an electric motor, and the rotation is accelerated or decelerated before being output from an output section. Among the transmissions, there is, for example, an eccentric oscillating type reducer that has high rotational position accuracy and high load resistance. This type of reducer includes, for example, a case (frame) with an internal gear formed on its inner circumferential surface, an oscillating gear (external gear) that meshes with the internal gear and oscillates and rotates, a crankshaft (input rotor) that has an eccentric part that rotatably supports the oscillating gear and transmits a rotational force to the oscillating gear, a power transmission pin (carrier pin) to which the rotational force of the oscillating gear is transmitted, and a carrier (output rotor) connected to the power transmission pin.

[0003] The oscillating gear has pin insertion holes formed therein, into which the power transmission pins are inserted. The carrier has pin insertion holes formed therein, into which the power transmission pins are inserted or press-fitted. By inserting the power transmission pins into these pin insertion holes, the rotation of the oscillating gear is transmitted to the carrier via the power transmission pins. The pin insertion hole of the oscillating gear is formed to a size that allows the oscillating motion of the oscillating gear relative to the power transmission pin. A cylindrical bush is inserted into the pin insertion hole of the oscillating gear. The power transmission pin is inserted into this bush.

[0004] The movement of the power transmission pin in the removal direction relative to the carrier is restricted, for example, by forming a male thread on the tip of the power transmission pin and using a nut fastened to the male thread. That is, the male thread of the power transmission pin protrudes outward in the axial direction through a pin insertion hole in the carrier. The movement of the power transmission pin in the removal direction relative to the carrier is restricted by fastening a nut to the protruding male thread (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-82993 A Summary of the Invention [Problem to be solved by the invention]

[0006] As in the above-mentioned conventional technology, the power transmission pins are subjected to a large load because they have the role of transmitting the rotational force of the oscillating gear to the carrier. Therefore, the power transmission pins are required to have improved strength and toughness. In addition, the power transmission pins slide against the bushes, so they are also required to have improved wear resistance. Therefore, the power transmission pins are required to have improved strength, toughness, and wear resistance. In this regard, there was room for improvement in conventional power transmission pins.

[0007] The present invention provides a power transmission pin for a transmission, which can have improved strength, toughness, and wear resistance, a rotating mechanism, a transmission, and a method for manufacturing a power transmission pin for a transmission. [Means for solving the problem]

[0008] A power transmission pin for a transmission according to one embodiment of the present invention is a power transmission pin for a transmission used for transmitting power in a transmission having a speed change mechanism that changes the speed of an input rotation and outputs it, and comprises a shaft portion and a male thread portion provided coaxially with the shaft portion at an axial end portion of the shaft portion for fixing the shaft portion to the speed change mechanism, and the hardness of at least the surface of the shaft portion is greater than the hardness of the male thread portion.

[0009] For example, in order to simply improve the wear resistance, strength, and toughness of a power transmission pin for a transmission, it is conceivable to increase the hardness of the entire power transmission pin for a transmission. However, doing so may cause the male thread portion of the power transmission pin for a transmission to break. Therefore, the hardness of at least the surface of the shaft portion of the power transmission pin for a transmission is made higher than the hardness of the male thread portion. This makes it possible to make the male thread portion less likely to break, and also to ensure that the shaft portion, which receives the most load, has the desired strength. Therefore, the strength, toughness, and wear resistance of the power transmission pin for a transmission can be improved.

[0010] In the above configuration, a nitride layer may be formed on the surface of the shaft portion by performing a nitriding treatment.

[0011] A rotation 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, wherein the power transmission pin comprises a shaft portion and a male thread portion provided coaxially with the shaft portion at an axial end of the shaft portion for integrating the rotating body and the power transmission pin, and the hardness of at least the surface of the shaft portion is higher than the hardness of the male thread portion and higher than the hardness of the bushing.

[0012] With this configuration, it is possible to reliably improve the wear resistance of the shaft portion against the bushing, thereby providing a rotating mechanism with excellent strength, toughness, and wear resistance.

[0013] In the above configuration, a nitride layer may be formed on the surface of the shaft portion by performing a nitriding treatment.

[0014] A transmission according to another aspect of the present invention comprises a rotating input section, a speed change mechanism that changes the rotation of the input section, and an output section to which the rotation of the input section is transmitted via the speed change mechanism, wherein the speed change mechanism comprises a gear having a pin insertion hole formed therein, a power transmission pin that is inserted into the pin insertion hole, and a cylindrical bush that is inserted into the pin insertion hole and fitted with the power transmission pin, wherein the power transmission pin comprises a shaft section and a male thread section that is provided coaxially with the shaft section at an axial end section of the shaft section and for integrating the gear and the power transmission pin, and the hardness of at least the surface of the shaft section is higher than the hardness of the male thread section and higher than the hardness of the bush.

[0015] With this configuration, it is possible to reliably improve the wear resistance of the shaft portion against the bushing, thereby providing a transmission with excellent strength, toughness, and wear resistance.

[0016] In the above configuration, a nitride layer may be formed on the surface of the shaft portion by performing a nitriding treatment.

[0017] A manufacturing method for a power transmission pin for a transmission according to another aspect of the present invention is a manufacturing method for a power transmission pin for a transmission used for transmitting power in a transmission having a transmission mechanism that changes the speed of an input rotation and outputs it, and includes a surface hardening process for hardening the surface of a rod-shaped base material, a surface cutting process for cutting the hardened surface of a portion of an end portion in the axial direction of the base material after the surface hardening process, and a thread forming process for forming a male thread portion in the portion of the base material cut by the surface cutting process.

[0018] By using this method, it is possible to easily manufacture a power transmission pin for a transmission in which the hardness of at least the surface of the shaft is greater than the hardness of the male thread portion, for a shaft portion and male thread portion formed from the same base material.

[0019] In the above method, the base material may be subjected to a quenching and tempering treatment prior to the surface hardening step.

[0020] A method for manufacturing a power transmission pin for a transmission according to another aspect of the present invention is a method for manufacturing a power transmission pin for a transmission used for transmitting power in a transmission having a transmission mechanism that changes the speed of an input rotation and outputs it, and includes a thread forming process for forming a male thread portion on a part of an end portion in the axial direction of a rod-shaped base material, and a surface hardening process for hardening the surface of the base material excluding the male thread portion after the thread forming process.

[0021] By using this method, it is possible to easily manufacture a power transmission pin for a transmission in which the hardness of at least the surface of the shaft is greater than the hardness of the male thread portion, for a shaft portion and male thread portion formed from the same base material.

[0022] In the above method, the surface hardening step may include performing a nitriding treatment on the surface of the base material to form a nitride layer. Effect of the Invention

[0023] The above-mentioned power transmission pin for a transmission, the rotation mechanism, the transmission, and the method for manufacturing a power transmission pin for a transmission can improve the strength, toughness, and wear resistance of the power transmission pin. [Brief description of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view of a reducer according to an embodiment of the present invention. [Diagram 2] 5A to 5D are process diagrams illustrating a method for producing a power transmission pin according to an embodiment of the present invention, with (a) to (d) illustrating each process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Next, an embodiment of the present invention will be described with reference to the drawings.

[0026] <Reducer> FIG. 1 is a cross-sectional view of a reducer 1. The reducer 1 is a so-called eccentric oscillating type reducer. The reducer 1 includes a cylindrical case 2 and a carrier 7 rotatably supported by the case 2 via two bearings 15a, 15b (first bearing 15a, second bearing 15b). Hereinafter, the axial direction of the case 2 will be simply referred to as the axial direction. The circumferential direction of the case 2 will be simply referred to as the circumferential direction. The radial direction of the case 2 will be simply referred to as the radial direction.

[0027] <Case> The case 2 is formed of an iron-based material such as cast iron. Alternatively, the case 2 may be formed of an aluminum alloy, a magnesium alloy, a carbon fiber reinforced plastic (CFRP), a resin containing boron nitride to increase thermal conductivity, or the like. An outer flange portion 4 that protrudes radially outward is integrally formed on the outer circumferential surface 2a of the case 2. The outer flange portion 4 has a cross section along the axial direction that is formed into a square shape. A plurality of bolt holes 4a penetrating in the axial direction are formed at equal intervals in the circumferential direction in the outer flange portion 4. A device (not shown) for mounting the reducer 1 is placed on the outer flange portion 4. Then, bolts (not shown) are inserted into the bolt holes 4a in the outer flange portion 4 and the bolts are fastened to the device, thereby fixing the reducer 1 to the device.

[0028] Bearing housings 3a, 3b (first bearing housing 3a, second bearing housing 3b) are formed on both axial sides of the inner peripheral surface 2b of the case 2. Each of the bearing housings 3a, 3b is formed so that its inner diameter is larger than the inner diameter of the inner peripheral surface 2b of the case 2 via a step. A first bearing 15a is fitted into the first bearing housing 3a. A second bearing 15b is fitted into the second bearing housing 3b. Each of the bearings 15a, 15b is, for example, a ball bearing.

[0029] A seal housing 5 is formed on the inner circumferential surface 2b of the case 2, axially outward of the second bearing housing 3b. The seal housing 5 is formed so that its inner diameter is larger than the inner diameter of the second bearing housing 3b via a step. A seal 40 is fitted into the seal housing 5. The seal 40 provides a seal between the case 2 and the carrier 7.

[0030] A plurality of internal tooth pins 6 are provided on the inner circumferential surface 2b of the case 2 between the two bearing housings 3a, 3b. The internal tooth pins 6 are formed in a cylindrical shape extending in the axial direction. However, this is not limited thereto, and the internal tooth pins 6 may 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 reduction mechanism 30. In other words, the internal tooth pins 6 function as internal teeth that mesh with oscillating gears 11, 12 described later.

[0031] <Deceleration mechanism> The reduction gear mechanism 30 includes a carrier 7, a power transmission pin 9 provided on the carrier 7, a crankshaft 8 rotatably supported by the carrier 7 via two bearings 15c, 15d (third bearing 15c, fourth bearing 15d), and two oscillating gears 11, 12 (first oscillating gear 11, second oscillating gear 12) rotatably supported by the crankshaft 8. The rotation axis of the carrier 7 and the rotation axis of the crankshaft 8 coincide with each other. These rotation axes coincide with the central axis of the case 2.

[0032] The carrier 7 is composed of a disk-shaped first flange 13 and a second flange 14 arranged on both sides in the axial direction. The first flange 13 and the second flange 14 are made of an iron-based material such as cast iron.

[0033] Of the two flanges 13 and 14, the second flange 14 is disposed on the seal housing 5 side of the case 2. A first opening 13a is formed in the radial center of the first flange 13, penetrating the first flange 13 in the axial direction. A first reduced diameter portion 13b is formed on the outer circumferential surface of the first flange 13 on the second flange 14 side. The first reduced diameter portion 13b is formed so that its outer diameter is smaller than the outer diameter of the first flange 13 via a step. A first bearing 15a is fitted into the first reduced diameter portion 13b.

[0034] A first enlarged diameter portion 13c is formed on the inner peripheral surface of the first opening 13a on the second flange 14 side. The first enlarged diameter portion 13c is formed so that the inner diameter is larger than the inner diameter of the first opening 13a via a step. A third bearing 15c is fitted into the first enlarged diameter portion 13c. The third bearing 15c is, for example, a ball bearing.

[0035] 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. Each first bolt insertion hole 51 is composed of a shaft insertion portion 51a formed on the second flange 14 side and a screw insertion portion 51b formed on the opposite side to the second flange 14. 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 in communication with each other. 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 via a step portion 51c.

[0036] A part of the outer peripheral surface of the second flange 14 faces the seal housing 5 of the case 2 in the radial direction. A seal 40 is fitted into this facing portion. This provides a seal between the case 2 and the second flange 14 of the carrier 7. A second opening 14a is formed in the radial center of the second flange 14, penetrating the second flange 14 in the axial direction. A second reduced diameter portion 14b is formed on the outer circumferential surface of the second flange 14 on the first flange 13 side. The second reduced diameter portion 14b is formed so that its outer diameter is smaller than the outer diameter of the second flange 14 via a step. A second bearing 15b is fitted into the second reduced diameter portion 14b.

[0037] A second enlarged diameter portion 14c is formed on the inner peripheral surface of the second opening 14a on the first flange 13 side. The second enlarged diameter portion 14c is formed so that the inner diameter is larger than the inner diameter of the second opening 14a via a step. A fourth bearing 15d is fitted into the second enlarged diameter portion 14c. The fourth bearing 15d is, for example, a ball bearing.

[0038] 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 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 countersunk portion 52a is formed on the opposite side of the second bolt insertion hole 52 from the first flange 13. The countersunk portion 52a is formed so that the inner diameter is larger than the inner diameter of the second bolt insertion hole 52 via a step portion 52b.

[0039] A power transmission pin 9 is inserted into each of the bolt insertion holes 51, 52 of each flange 13, 14. The power transmission pin 9 is made of, for example, aluminum chrome molybdenum steel. The power transmission pin 9 includes a cylindrical shaft portion 61, a male thread portion 62 integrally formed with one axial end of the shaft portion 61, and a head portion 63 integrally formed with the other axial end of the shaft portion 61. The shaft portion 61, the male thread portion 62, and the head portion 63 are arranged coaxially.

[0040] The outer diameter of the shaft portion 61 is equal to 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 . The male thread portion 62 is formed so that the outer diameter thereof becomes smaller via a thread step portion 62a than the outer diameter of the shaft portion 61. An incomplete thread portion 62b is formed at the base of the male thread portion 62 on the shaft portion 61 side. The head 63 is formed so that its outer diameter is larger via a head step 63a than the outer diameter of the shaft portion 61. The outer diameter of the head 63 is slightly smaller than the outer diameter of the countersunk portion 52a of the second flange 14.

[0041] With this configuration, the power transmission pin 9 is inserted from the second flange 14 side into the second bolt insertion hole 52 and the first bolt insertion hole 51 in that order, with the male thread portion 62 facing the first flange 13 side. At this time, the head 63 of the power transmission pin 9 is inserted into the countersunk portion 52a of the second bolt insertion hole 52. The head stepped portion 63a of the power transmission pin 9 abuts against the stepped portion 52b of the second bolt insertion hole 52, thereby positioning the power transmission pin 9 in the axial direction with respect to the second flange 14.

[0042] On the other hand, the male thread portion 62 of the power transmission pin 9 protrudes axially outward through the first bolt insertion hole 51. The incomplete thread portion 62b of the male thread portion 62 is inserted into the screw insertion portion 51b of the first bolt insertion hole 51. The end of the shaft portion 61 on the male thread portion 62 side is inserted into the shaft insertion portion 51a of the first bolt insertion hole 51. The screw step portion 62a of the power transmission pin 9 abuts against the step portion 51c of the first bolt insertion hole 51, thereby positioning the power transmission pin 9 in the axial direction with respect to the first flange 13.

[0043] A flat washer 64 is inserted into the male thread portion 62 that protrudes axially outward through the first bolt insertion hole 51. A nut 65 is tightened from above the flat washer 64. This fixes the power transmission pin 9 to the carrier 7 (first flange 13, second flange 14). The manufacturing method of the power transmission pin 9 will be described in detail later. With the power transmission pin 9 fixed, two bushes 67a, 67b (a first bush 67a and a second bush 67b) are fitted between the first flange 13 and the second flange 14 of the shaft portion 61. The bushes 67a, 67b are made of high carbon chromium bearing steel, such as SUJ2.

[0044] The crankshaft 8, inserted into the first opening 13a and the second opening 14a, is rotatably supported by the flanges 13, 14 via the third bearing 15c and the fourth bearing 15d. The crankshaft 8 is made of, for example, an aluminum alloy, similar to the power transmission pins 9. Alternatively, the crankshaft 8 may be made of, for example, stainless steel or various iron-based metals, similar to the power transmission pins 9.

[0045] The crankshaft 8 is formed to be hollow. A key groove 66 is formed on the inner peripheral surface of the crankshaft 8. The key groove 66 is used to connect the crankshaft 8 to a motor shaft of an electric motor provided in a device (not shown), for example. A first eccentric portion 21a and a second eccentric portion 21b are formed side by side in the axial direction on the crankshaft 8 between the third bearing 15c and the fourth bearing 15d.

[0046] The first eccentric portion 21a is disposed on the first flange 13 side. The second eccentric portion 21b is disposed on the second flange 14 side. The eccentric portions 21a, 21b are eccentric from the rotation axis of the crankshaft 8 (carrier 7). The eccentric portions 21a, 21b are shifted in phase angle from each other. For example, the eccentric portions 21a, 21b are shifted in phase angle from each other by 180°.

[0047] The eccentric parts 21a and 21b are provided with bearings 15e and 15f (a fifth bearing 15e and a sixth bearing 15f), respectively. These bearings 15e and 15f are, for example, needle bearings. The eccentric parts 21a and 21b rotatably support the oscillating gears 11 and 12 (the first oscillating gear 11 and the second oscillating gear 12) via bearings 15e and 15f, respectively. That is, the oscillating gears 11 and 12 are disposed between the first flange 13 and the second flange 14.

[0048] The two oscillating gears 11 and 12 are formed from an iron-based material such as chrome-molybdenum steel.

[0049] Crankshaft insertion holes 24a, 24b (first crankshaft insertion hole 24a, second crankshaft insertion hole 24b) penetrating in the thickness direction are formed in the radial centers of the two oscillating gears 11, 12. Bearings 15e, 15f are fitted into the crankshaft insertion holes 24a, 24b, respectively. External teeth 23a, 23b that mesh with the internal pin 6 of the case 2 are formed on the outer periphery of the two oscillating gears 11, 12. The number of teeth of each of the external teeth 23a, 23b is less than the number of the internal pin 6 by, for example, one.

[0050] Pin insertion holes 25a, 25b (first pin insertion hole 25a, second pin insertion hole 25b) are formed in the two oscillating gears 11, 12 at positions corresponding to the power transmission pin 9. A shaft portion 61 of the power transmission pin 9 is inserted into each of the pin insertion holes 25a, 25b. A first bushing 67a fitted to the shaft portion 61 is inserted into the first pin insertion hole 25a of the pin insertion holes 25a, 25b. A second bushing 67b fitted to the shaft portion 61 is inserted into the second pin insertion hole 25b of the pin insertion holes 25a, 25b.

[0051] With this configuration, the oscillating gears 11, 12 are oscillatingly rotated by the eccentric portions 21a, 21b of the crankshaft 8. The inner diameters of the pin insertion holes 25a, 25b of the oscillating gears 11, 12 are large enough to allow the oscillating rotation of the oscillating gears 11, 12 with the shaft portion 61 of the power transmission pin 9 and the bushes 67a, 67b inserted therein.

[0052] <Reduction gear operation> Next, the operation of the reducer 1 will be described. For example, when the crankshaft 8 is rotated by an electric motor (not shown), the oscillating gears 11 and 12 rotatably supported by the eccentric portions 21a and 21b are oscillated and rotated. Then, the internal tooth pin 6 of the case 2 meshes with a part of the external teeth 23a and 23b of the oscillating gears 11 and 12. At this time, since the number of teeth of each of the external teeth 23a, 23b is, for example, one less than the number of the internal tooth pins 6, each of the oscillating gears 11, 12 rotates on its axis such that the meshing points of each of the external teeth 23a, 23b with respect to the internal tooth pins 6 (case 2) are shifted sequentially in the circumferential direction. This rotation is decelerated with respect to the rotation of the crankshaft 8.

[0053] A power transmission pin 9 is inserted into the pin insertion holes 25a, 25b of each oscillating gear 11, 12. Therefore, as each oscillating gear 11, 12 rotates, the rotational force of the oscillating gears 11, 12 in the rotation direction is transmitted to each power transmission pin 9 via the bushes 67a, 67b, respectively. Each power transmission pin 9 is fixed to the carrier 7 (first flange 13, second flange 14). Therefore, the rotational force of the oscillating gears 11, 12 is transmitted to the carrier 7.

[0054] The carrier 7 is rotatably supported by the case 2 via a first bearing 15a and a second bearing 15b. Therefore, the carrier 7 rotates relative to the case 2. That is, the rotation input to the crankshaft 8 is decelerated and output from the carrier 7. In this way, the power transmission pin 9 transmits the rotation of each of the oscillating gears 11, 12, which is the decelerated rotation of the crankshaft 8, to the carrier 7, and therefore is subjected to a large load. Therefore, the power transmission pin 9 is manufactured by the following method.

[0055] <Manufacturing method of power transmission pins> Fig. 2 is a process diagram showing a method for manufacturing a power transmission pin 9, with (a) to (d) showing each process. Also, Fig. 2(a) to (c) show side views of a base material 70 of the power transmission pin 9. Of these, Fig. 2(b) and Fig. 2(c) show a part of the base material 70 cut away. As shown in Fig. 2(a), first, a base material 70 of the power transmission pin 9 is subjected to quenching and tempering treatment (step ST101; semi-machining). The base material 70 here refers to a portion of the power transmission pin 9 that corresponds to the male thread portion 62 that has not been machined and has the same diameter as the shaft portion 61. The head portion 63 of the power transmission pin 9 has been formed. The base material 70 at this point has not been subjected to heat treatment.

[0056] In the quenching and tempering process, the quenching temperature and processing time are, for example, 860°C and about 1 hour. Tempering is performed at a low temperature. Specifically, the tempering temperature and processing time are, for example, 160°C and about 2 hours. By carrying out the above quenching and tempering process, the toughness (tenacity) of the base material 70 can be improved. The hardness of the base material 70 at this point is, for example, about Rockwell hardness [HRC] 37 to 45.

[0057] Next, as shown in FIG. 2(b), the surface of the base material 70 is hardened (step ST102; surface hardening step). Specifically, the surface of the base material 70 is subjected to a 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 a thickness of, for example, about 0.2 mm. The hardness of the nitride layer N is, for example, about 1000 to 750 Vickers hardness [HV]. That is, at the time when the surface hardening step is completed, the hardness of the surface of the base material 70, that is, the nitride layer N, differs from the hardness of the inside (core) of the nitride layer N. The hardness of the nitride layer N is higher than the hardness of each of the bushes 67a and 67b.

[0058] 2(c), the nitride layer N is cut from a portion of the surface that will become the male thread portion 62, and the nitride layer N is removed from this portion (step ST103; surface cutting step). In the following description, the portion from which the nitride layer N has been removed is referred to as a surface cut portion 71. Since the nitride layer N has been removed from the surface of the surface cut portion 71, the surface hardness of the surface cut portion 71 is, for example, about 37 to 45 in Rockwell hardness [HRC]. The cutting allowance when forming the surface cut portion 71 is, for example, about 0.5 mm. Since the nitride layer N is, for example, about 0.2 mm, the nitride layer N can be easily removed in the surface cutting process.

[0059] Here, for example, if the cutting allowance is set to a thickness that does not completely remove the nitride layer N in the surface cutting process, that is, if the cutting allowance is set to about 0.1 mm, for example, only the nitride layer N will be cut. In such a case, only the layer with high hardness will be cut, making cutting even more difficult. By deliberately setting the cutting allowance in the surface cutting process to a thickness that cuts the nitride layer N as well as a little of the material inside the nitride layer N, the surface cutting process can be made easier.

[0060] 2(d), the male screw portion 62 is formed in the surface cut portion 71 (step ST104; thread forming step). In addition, the shaft portion 61 is subjected to finish polishing. This completes the manufacture of the power transmission pin 9. In this manner, the male thread portion 62 is formed on the surface cut portion 71. Meanwhile, 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 the hardness of the male thread portion 62. Also, the hardness of the surface of the shaft portion 61 is higher than the hardness of each of the bushes 67a, 67b.

[0061] Thus, in the above-described power transmission pin 9, the surface hardness of the shaft portion 61 is greater than the hardness of the male thread portion 62. Therefore, the strength, toughness, and wear resistance of the power transmission pin 9 can be improved. That is, for example, in order to simply improve the wear resistance, strength, and toughness of the power transmission pin 9, it is conceivable to increase the hardness of the entire power transmission pin 9. However, doing so would cause the male thread portion 62 of the power transmission pin 9 to be damaged. Therefore, as in the power transmission pin 9 described above, the hardness of the surface of the shaft portion 61 is made higher than the hardness of the male thread portion 62. This makes it possible to make the male thread portion 62 less likely to be damaged, and also to allow the shaft portion 61, which receives the most load, to have the desired strength. The male thread portion 62 is also quenched and tempered, so that its toughness is improved. This makes it possible to improve the strength, toughness, and wear resistance of the power transmission pin 9.

[0062] In order to increase the hardness of the surface of the shaft portion 61, a nitride layer N is formed by nitriding the surface of the shaft portion 61. This ensures that the hardness of the surface of the shaft portion 61 is high. The hardness of the surface of the shaft portion 61 is higher than the hardness of each of the bushes 67a, 67b. This reliably improves the wear resistance of the shaft portion 61 against each of the bushes 67a, 67b. This makes it possible to provide a reducer 1 with excellent strength, toughness, and wear resistance.

[0063] The method for manufacturing the power transmission pin 9 includes a surface hardening step of hardening the surface of a base material 70, a surface cutting step performed after the surface hardening step, and a thread forming step of forming a male thread portion 62 in a surface cut portion 71 formed by the surface cutting step. Therefore, for the shaft portion 61 and the male thread portion 62 formed from the same base material 70, the surface hardness of the shaft portion 61 can be easily made higher than the hardness of the male thread portion 62. For example, after completing the shape of the power transmission pin 9, it is possible to perform anti-nitriding treatment on the male thread portion 62 of the power transmission pin 9 while performing nitriding treatment, but this work is troublesome. Compared to such a method, the above-mentioned manufacturing method makes it possible to manufacture the power transmission pin 9 efficiently.

[0064] Furthermore, the base material 70 is quenched and tempered before the surface hardening process. This makes it possible to obtain the desired strength and toughness of the male thread portion 62. By quenching and tempering the base material 70, the time required for the subsequent surface hardening process can be shortened. This is because the surface hardening process is also a high-temperature tempering process. Therefore, by performing a low-temperature tempering process in advance using the quenching and tempering process, the time required for the surface hardening process can be shortened.

[0065] In the above-described manufacturing method, a case has been described in which the base material 70 is subjected to a surface hardening step, a surface cutting step, and a thread forming step in this order in order to make the surface hardness of the shaft portion 61 higher than the hardness of the male thread portion 62. However, the present invention is not limited to this, and it is sufficient that the surface hardness of the shaft portion 61 is higher than the hardness of the male thread portion 62 in the finished power transmission pin 9.

[0066] For example, instead of nitriding, it is also possible to apply a DLC (Diamond Like Carbon) coating to the surface of the shaft portion 61 in order to harden the surface of the shaft portion 61. In this case, the method of manufacturing the power transmission pin 9 is to first form the male thread portion 62 in the base material 70 (thread forming process). Thereafter, the surface of the base material 70 excluding the male thread portion 62 (the surface of the shaft portion 61) is hardened (surface hardening process). When applying a DLC coating as a method of hardening the surface of the shaft portion 61, this is done after masking the male thread portion 62. Even with such a method, the same effects as those of the above-mentioned embodiment can be achieved.

[0067] In the above embodiment, the power transmission pin 9 is formed of, for example, aluminum chromium molybdenum steel. However, it is only necessary that the hardness of the surface of the shaft portion 61 is made higher than the hardness of the male screw portion 62. The power transmission pin 9 is not limited to aluminum chromium molybdenum steel. For example, the power transmission pin 9 may be made of a steel material such as chromium molybdenum steel. In this case, the hardness of the surface of the shaft portion 61 can be made higher than the hardness of the male screw portion 62 by subjecting the surface of the shaft portion 61 to induction hardening. The manufacturing method in this case is the same as that in the case of applying the DLC coating described above.

[0068] In the above embodiment, the power transmission pin 9 has been described as having a surface hardness of the shaft portion 61 that is higher than the hardness of the male thread portion 62. That is, in the shaft portion 61, the hardness of the nitride layer N differs from the hardness of the interior (core portion) of the nitride layer N. However, this is not limited to the above, and it is sufficient that the hardness of at least the surface of the shaft portion 61 is higher than the hardness of the male thread portion 62. The interior of the shaft portion 61 may have the same hardness as the surface.

[0069] Furthermore, the present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.

[0070] For example, in the above embodiment, the reducer 1 is described that includes the speed reduction mechanism 30 that reduces the speed of rotation of the crankshaft 8 and outputs the reduced speed. However, the present invention is not limited to this, and the power transmission pin 9 may be used in a speed increaser instead of the speed reduction mechanism 30. Furthermore, the power transmission pin 9 may be used in a rotation mechanism provided with a rotating body that replaces the speed reduction mechanism 30 (the carrier 7 or the oscillating gears 11 and 12). It is only necessary that the rotating body of the rotation mechanism is formed with a pin insertion hole (pin insertion holes 25a and 25b) into which the power transmission pin 9 is inserted.

[0071] Among the embodiments disclosed in this specification, those that are composed of multiple objects may be integrated, and conversely, those that are composed of one object may be divided into multiple objects. Regardless of whether they are integrated or not, it is sufficient that they are configured to achieve the object of the invention. [Explanation of symbols]

[0072] 1...Reduction gear (transmission, rotation mechanism) 2. Case 7...Carrier (rotating body) 9...Power transmission pin (power transmission pin for transmission) 11...First oscillating gear (rotating body, gear) 12...Second oscillating gear (rotating body, gear) 25a…First pin insertion hole (pin insertion hole) 25b…Second pin insertion hole (pin insertion hole) 30...Reduction mechanism (transmission mechanism) 61...Shaft 62…Male thread 67a…1st Bush (Bush) 67b…Second Bush (Bush) N: Nitrided layer

Claims

1. A power transmission pin for a transmission used for transmitting power in a transmission having a speed change mechanism that changes the speed of an input rotation and outputs the changed speed, A shaft portion, a male screw portion provided coaxially with the shaft portion at an axial end portion of the shaft portion for fixing the shaft portion to the speed change mechanism; Equipped with The hardness of at least the surface of the shaft portion is higher than the hardness of the male thread portion. Power transmission pin for transmission.

2. A nitride layer is formed on the surface of the shaft portion by performing nitriding treatment.

2. The power transmission pin for a transmission according to claim 1.

3. A rotor having an insertion hole; A cylindrical bush provided in the insertion hole; A power transmission pin inserted into the bush; Equipped with The power transmission pin is A shaft portion, a male screw portion provided coaxially with the shaft portion at an axial end of the shaft portion for integrating the rotor and the power transmission pin; Equipped with The hardness of at least the surface of the shaft portion is higher than the hardness of the male thread portion and higher than the hardness of the bushing. Rotation mechanism.

4. A nitride layer is formed on the surface of the shaft portion by performing nitriding treatment. The rotation mechanism according to claim 3.

5. A rotating input unit; a speed change mechanism that changes the speed of rotation of the input portion; an output section to which the rotation of the input section is transmitted via the speed change mechanism; Equipped with The speed change mechanism includes: A gear having a pin insertion hole; A power transmission pin to be inserted into the pin insertion hole; a cylindrical bushing that is inserted into the pin insertion hole and fitted onto the power transmission pin; Equipped with The power transmission pin is A shaft portion, a male screw portion provided coaxially with the shaft portion at an axial end portion of the shaft portion for integrating the gear and the power transmission pin; Equipped with The hardness of at least the surface of the shaft portion is higher than the hardness of the male thread portion and higher than the hardness of the bushing. Transmission.

6. A nitride layer is formed on the surface of the shaft portion by performing nitriding treatment.

6. The transmission according to claim 5.

7. A method for manufacturing a power transmission pin for a transmission used for power transmission in a transmission having a speed change mechanism that changes the speed of an input rotation and outputs the changed speed, comprising the steps of: a surface hardening process for hardening the surface of the rod-shaped base material; a surface cutting step of cutting the hardened surface of a portion of an end portion in an axial direction of the base material after the surface hardening step; a thread forming step of forming a male thread portion in the part of the base material cut by the surface cutting step; having A method for manufacturing a power transmission pin for a transmission.

8. The base material is subjected to a quenching and tempering treatment before the surface hardening process. A method for producing the power transmission pin for a transmission according to claim 7.

9. A method for manufacturing a power transmission pin for a transmission used for power transmission in a transmission having a speed change mechanism that changes the speed of an input rotation and outputs the changed speed, comprising the steps of: a thread forming step of forming a male thread portion on a part of an end portion in an axial direction of the rod-shaped base material; a surface hardening process for hardening a surface of the base material excluding the male thread portion after the thread forming process; having A method for manufacturing a power transmission pin for a transmission.

10. In the surface hardening step, a nitriding treatment is performed on the surface of the base material to form a nitride layer. A method for manufacturing the power transmission pin for a transmission according to any one of claims 7 to 9.

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