JP2016044748A - Rotation transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost of a rotation transmission device which controls the engagement and release of a two-way clutch by an electromagnetic clutch.SOLUTION: A cage 16 of a two-way clutch 10 which is controlled in engagement and release by an electromagnetic clutch 50 is formed of a controlling cage 16A and a rotating cage 16B, a pocket is formed between adjacent columns 28, 34 with the controlling cage 16A and the rotating cage 16B as a combination in which the columns 28, 34 are alternately aligned in a peripheral direction, and a pair of rollers 15 which are incorporated in the pocket are shifted to an engagement release position by being pressed by the columns 28, 34 by the relative rotation of the controlling cage 16A and the rotating cage 16B. A cost is reduced by press-molding cage main bodies 22, 30 of the controlling cage 16A and the rotating cage 16B and the columns 28, 34, columns of the controlling cage 16A and the rotating cage 16B are made common in use by forming the columns 28, 34 into symmetric cross section shapes, and the number of part items is reduced.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a rotation transmission device capable of switching between rotation transmission and cutoff.

  2. Description of the Related Art Conventionally, a rotation transmission device that transmits and blocks rotation from a drive shaft to a driven shaft has a two-way clutch, and the engagement and release of the two-way clutch are controlled by an electromagnetic clutch. It has been.

  In the rotation transmission device described in Patent Document 1, a plurality of column portions provided in the control holder and a plurality of column portions provided in the rotation holder are provided between the outer ring and the inner ring incorporated inside the outer ring. Incorporating to be alternately arranged in the circumferential direction, incorporating a pair of opposed rollers in a pocket formed between adjacent pillars, and separating the pair of rollers with an elastic member incorporated between the opposed portions And is put on standby at a position where it engages with a cylindrical surface formed on the inner periphery of the outer ring and a cam surface formed on the outer periphery of the inner ring. The rotation of the inner ring is transmitted to the outer ring by engaging with the cam surface.

  In addition, an electromagnetic clutch is provided on the input shaft connected to the inner ring, and the control cage is moved in the axial direction by energizing the electromagnetic coil of the electromagnetic clutch, and the opposing surfaces of the flange of the control cage and the flange of the rotary cage The control cage and the rotary cage are rotated relative to each other so that the circumferential width of the pocket is reduced by the action of the torque cam provided between them, and the pair of rollers are moved to the disengagement position at the pillar portion of each cage. The rotation transmission from the inner ring to the outer ring is cut off.

  In the above rotation transmission device, when energization of the electromagnetic coil of the electromagnetic clutch is released, the circumferential width of the pocket between the control holder and the rotation holder increases due to the pressing action of the elastic member incorporated between the pair of opposed rollers. Since the pair of opposed rollers are held in a standby state where they contact each other with the cylindrical surface and the cam surface, the roller immediately engages with the cylindrical surface and the cam surface due to the rotation of the inner ring. Is extremely small and has excellent responsiveness.

  By the way, if each of the control holder and the rotary holder is machined, it takes time and effort to manufacture. In order to eliminate such inconvenience, in the rotation transmission device described in Patent Document 2, each of the control cage and the rotation cage is a press-molded product.

JP 2009-293679 A JP 2013-204764 A

  By the way, in the rotation transmission device described in the above-mentioned Patent Document 2, the control retainer and the rotation retainer are joined and integrated with the press-molded column portion to the press-molded retainer body. Since the section is asymmetrical in cross-sectional shape, two kinds of pillar parts, that is, a pillar part for a control cage and a pillar part for a rotary cage are required, and there are points to be improved in order to reduce costs.

  An object of the present invention is to provide a cost for a rotation transmission device having a two-way clutch that transmits and blocks rotation from an input shaft to an output shaft, and that controls engagement and release of the two-way clutch by an electromagnetic clutch. It is intended to reduce this.

  In order to solve the above-described problems, in the present invention, a two-way clutch that transmits and blocks rotation between an input shaft and an output shaft that is arranged coaxially with the input shaft, and the two-way clutch are provided. An electromagnetic clutch for controlling engagement and disengagement, wherein the two-way clutch is between the inner periphery of the outer ring provided at the shaft end of the output shaft and the outer periphery of the inner ring provided at the shaft end of the input shaft. In addition, the pillars provided in the control cage and the rotary cage are assembled so that they are alternately arranged in the circumferential direction, and the inner circumference of the outer ring and the outer circumference of the inner ring are placed in pockets formed between adjacent pillar parts. A pair of engagement elements that can be engaged with each other, and an elastic member that urges the pair of engagement elements in a direction away from each other, and the electromagnetic clutch is coupled to the control retainer. Armature and its armature A rotor that is opposed to the rotor in the axial direction, and an electromagnet disposed opposite to the rotor, and the control cage is moved in the axial direction by energizing the electromagnet, and the movement in the axial direction is controlled and held by the motion conversion mechanism In the rotation transmission device in which the cage and the rotary cage are converted into relative rotational motion in a direction in which the circumferential width of the pocket is reduced to disengage the pair of engagement elements, the control cage is connected to the armature A retainer body made of a press-formed product of an annular plate provided with a portion, and a plurality of pillar parts made of a press-formed product whose ends are joined and integrated with the annular plate, A retainer body made of a press-formed product of an annular plate, and a pillar part made of a press-formed product whose ends are joined and integrated with the annular plate, and the pillars of the control retainer and the rotary retainer Part Is the surface shape was adopted common parts and the configuration of the column part as symmetrical.

  As described above, each of the control retainer and the rotational retainer is a combined assembly of the press-formed column portions as well as the press-formed retainer body, and the cross-sectional shape of the column portions is symmetric. The column portion can be a common component for the control cage and the rotary cage, and the cost can be reduced by reducing the number of components.

  Here, methods such as welding, diffusion bonding, adhesion, and press-fitting can be employed for joining the column portion and the cage body.

  In addition, by heat-treating the cage body in the control cage and the rotary cage before the column portion is joined, the hardness of the cage body is increased without considering the heat treatment deformation of the column portion, thereby improving the durability. Can be planned. As the heat treatment, carburizing, quenching, or nitriding can be employed.

  In the present invention, as described above, the retainer body and the column part of the control retainer and the retainer body and the pillar part of the rotary retainer are each made of a press-molded product. Therefore, the manufacturing is easy and the cost can be reduced, and the column part is a symmetric cross-sectional shape and is used as a common part of the control cage and the rotary cage, thereby reducing the number of parts and reducing the cost. Further reduction can be achieved.

A longitudinal sectional view showing an embodiment of a rotation transmission device according to the present invention Sectional drawing which expands and shows the built-in part of the control holder and rotation holder of FIG. Sectional view along line III-III in FIG. Sectional drawing which shows the disengagement state of the roller shown in FIG. Sectional view along line VV in FIG. Sectional view along line VI-VI in FIG. Sectional view along line VII-VII in FIG. (A) is sectional drawing which followed the VIII-VIII line of FIG. 7, (b) is sectional drawing which shows an operation state. Exploded perspective view of control cage Exploded perspective view of rotating cage

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a rotation transmission device according to the present invention. As shown in the figure, the rotation transmission device includes an input shaft S ₁ , an output shaft S ₂ arranged coaxially with the input shaft S ₁ , a housing 1 covering the shaft ends of both shafts, and the housing 1. engagement of two-way clutch 10 and a two-way clutch 10 that is incorporated into the inner performing an interrupting a transmission of rotation from the input shaft S ₁ to the output shaft S _2, an electromagnetic clutch 50 for controlling the release.

  The housing 1 has a cylindrical shape, a small-diameter bearing cylinder 2 is provided at one end thereof, and a retaining ring 3 for retaining the electromagnetic clutch 50 is attached to the inner periphery of the other end.

As shown in FIGS. 1 and 2, two-way clutch 10, a cylindrical surface 12 provided on the inner periphery of the outer ring 11 provided on the shaft end of the output shaft S _2, provided on the shaft end of the input shaft S ₁ A plurality of cam surfaces 14 are formed in the circumferential direction on the outer periphery of the inner ring 13, and a roller 15 and an elastic member 21 (see FIG. 3) as a pair of engaging members between each of the plurality of cam surfaces 14 and the cylindrical surface 12. And the roller 15 is held by the cage 16, and one of the pair of rollers 15 is engaged with the cylindrical surface 12 and the cam surface 14 by rotating the inner ring 13 in one direction, thereby rotating the inner ring 13 to the outer ring. 11, and the other roller 15 is engaged with the cylindrical surface 12 and the cam surface 14 during rotation in the other direction of the inner ring 13 to transmit the rotation of the inner ring 13 to the outer ring 11.

Here, a small-diameter concave portion 18 is formed on the inner surface side of the closed end portion of the outer ring 11, and the shaft end portion of the input shaft S ₁ is rotatably supported by a bearing 19 incorporated in the concave portion 18.

The inner ring 13 is formed integrally with the input shaft S _1. As shown in FIG. 3, the cam surface 14 formed on the outer periphery of the inner ring 13 is formed of a pair of inclined surfaces 14 a and 14 b that are inclined in opposite directions, and is circumferential between the cylindrical surface 12 of the outer ring 11. The both ends of the inner space 13 form a narrow wedge-shaped space, and a flat surface 20 facing the tangential direction of the inner ring 13 is provided between the pair of inclined surfaces 14 a, 14 b, and the elastic member 21 is supported by the flat surface 20. ing.

  The elastic member 21 is a coil spring. The elastic member 21 is installed between the pair of rollers 15, and the elastic member 21 biases the pair of rollers 15 away from each other to engage the cylindrical surface 12 and the cam surface 14. Is arranged.

  The holder 16 includes a control holder 16A and a rotary holder 16B. As shown in FIGS. 2 and 9, the control retainer 16 </ b> A includes a retainer body 22 and the same number of column portions 28 as the cam surface 14. Here, there are three pillar portions 28. The cage body 22 is a metal plate press-molded product in which the same number of connecting pieces 24 as the cam surface 14 are radially arranged on the outer periphery of the annular plate 23, and the cylindrical portion 25 is provided on the outer periphery of the connecting piece 24. An arc-shaped elongated hole 26 is provided between the outer periphery of the annular plate 23 and the inner periphery of the cylindrical portion 25 between the connecting pieces 24. A fitting hole 27 is formed in each of the plurality of connecting pieces 24.

  The column portion 28 has a sectoral cross section and is bilaterally symmetric. An insertion piece 29 is provided at one end of the column portion 28 and is formed by press molding. The insertion piece 29 of the column portion 28 is fitted into the fitting hole 27 provided in the connecting piece 24 and integrated by bonding to form the control holder 16A. In joining the column part 28, here, a welding method is employed, but diffusion joining may be performed or adhesion may be performed. Or you may press-fit.

  As shown in FIGS. 2 and 10, the rotary cage 16 </ b> B includes a cage body 30 and the same number of pillars 34 as the cam surface 14. In this embodiment, three column portions 34 are provided, but in FIG. 10, only one column portion 31 is illustrated, and the remaining two are omitted. The cage body 30 is formed of a metal plate press-molded product in which the same number of connecting pieces 32 as the cam surface 14 are radially provided on the outer periphery of the annular plate 31, and a fitting hole 33 is provided in each of the connecting pieces 32. ing.

  The column portion 34 is a press-molded product having the same shape and the same size as the column portion 28 in the control holder 16A, and is a common part with the column portion 28 of the control holder 16A, and is provided at one end thereof. The inserted piece 35 is fitted into the fitting hole 33 of the connecting piece 32 and integrated by joining to form the rotary cage 16B. In joining the column part 34, the welding method, the diffusion joining method, the adhering method, and the press-fitting method can be employed similarly to the joining of the column part 28 in the control cage 16A.

As shown in FIGS. 2 and 7, the control holder 16 </ b> A and the rotary holder 16 </ b> B are inserted into the elongated holes 26 of the control holder 16 </ b> A, and the column portions 28 and 34 thereof are inserted. Is a combination that is alternately arranged in the circumferential direction. Then, the distal end portion of the pillar portion 28, 34 is disposed between the outer ring 11 and inner ring 13 in the combination state, the outer peripheral annular plate 31 of the input shaft _{S 1} of the annular plate 23 and the rotary cage 16B of the control retainer 16A Incorporation is positioned between the fitted support ring 36 and the outer ring 11.

  By incorporating the cages 16A and 16B as described above, as shown in FIGS. 3 and 4, a pocket 37 is formed between the column portion 28 of the control cage 16A and the column portion 34 of the rotary cage 16B. 37 is opposed to the cam surface 14 of the inner ring 13 in the radial direction, and a pair of opposed rollers 15 and an elastic member 21 are incorporated in each pocket 37.

As shown in FIG. 2, the annular plate 31 of annular plate 23 and the rotary cage 16B of the control retainer 16A is slidably supported along the slide guide surface 38 formed on the outer periphery of the input shaft S _1, the rotation a thrust bearing 39 is incorporated with the annular plate 31 of the retainer 16B between the input shaft _{S 1} of the support ring 36.

  As shown in FIGS. 2, 7, and 8, a torque cam 40 as a motion conversion mechanism is provided between the annular plate 23 of the control holder 16A and the annular plate 31 of the rotary holder 16B. The torque cam 40 is provided with a pair of opposed cam grooves 41 and 42 that gradually become shallower toward the opposite ends of the annular plate 23 of the control cage 16A and the annular plate 31 of the rotary cage 16B. The ball 43 is incorporated between one end of one cam groove 41 and the other end of the other cam groove 42.

  The cam grooves 41 and 42 are arc-shaped grooves here, but may be V-grooves.

  When the control holder 16A moves in the axial direction in the direction in which the annular plate 23 of the control holder 16A approaches the annular plate 31 of the rotary holder 16B, the torque cam 40 is as shown in FIG. The ball 43 rolls and moves toward the deepest groove depth of the cam grooves 41 and 42, and the control holder 16A and the rotary holder 16B are relatively rotated in the direction in which the circumferential width of the pocket 37 is reduced. ing.

  Here, if the control retainer 16A and the rotation retainer 16B are simple press-molded products, the surface hardness of the cam grooves 41 and 42 is low, and there is a possibility that the balls 43 are deformed and damaged by the biting of the balls 43. Therefore, it is preferable to increase the hardness of the surfaces of the cam grooves 41 and 42 by heat treatment. However, if the control retainer 16A and the rotation retainer 16B are heat treated in an assembled state, there is a possibility that the column portions 28 and 34 may be deformed due to thermal influence. is there.

  In order to prevent the occurrence of such inconvenience, the retainer bodies 22 and 30 in the control retainer 16A and the rotational retainer 16B are heat-treated before joining the column portions 28 and 34, so that the hardness of the cam grooves 41 and 42 is increased. After the heat treatment, the column portions 28 and 34 are joined to the cage main bodies 22 and 30. The heat treatment may be any of carburizing, quenching, or nitriding. In addition, the column parts 28 and 34 are press-molded products and are not subjected to quenching, thereby reducing costs.

  As shown in FIGS. 5 and 6, a cylindrical surface 45 is formed on the other side surface of the inner ring 13. The cylindrical surface 45 has a larger diameter than the slide guide surface 38, and an annular holding plate 46 is fitted to the cylindrical surface 45 and fixed to the inner ring 13. On the outer peripheral surface of the holding plate 46, a plurality of detent pieces 47 are formed which are arranged in the respective pockets 37 between the column portion 28 of the control holder 16A and the column portion 34 of the rotary holder 16B.

  When the control retainer 16A and the rotation retainer 16B rotate relative to each other in the direction of reducing the circumferential width of the pocket 37, the plurality of detent pieces 47 are connected to the column portion 28 of the control retainer 16A and the rotation retainer 16B. The column portion 34 is received at both side edges to hold the pair of opposed rollers 15 in a neutral position.

  On the outer periphery of the holding plate 46, spring pressing arms 48 are provided to project to the outer diameter sides of the plurality of elastic members 21, and the elastic pressing members 48 escape to the outer diameter side between the pair of rollers 15 by the spring pressing arms 48. It is prevented from coming out.

  As shown in FIG. 1, the electromagnetic clutch 50 includes an armature 51 that faces the end face of the cylindrical portion 25 formed in the control retainer 16A in the axial direction, a rotor 52 that faces the armature 51 in the axial direction, and the rotor 52 and an electromagnet 53 facing in the axial direction.

The armature 51 is fitted to the outer periphery of the support ring 36 and is rotatably and slidably supported. The cylindrical portion of the control retainer 16 </ b> A is formed on the inner diameter surface of the connecting cylinder 55 provided on the outer peripheral portion of the armature 51. The control retainer 16A and the armature 51 are connected and integrated. Armature 51 by the Linking is the support of the slidable in two places in the axial direction of the outer periphery of the slide guide face 38 of the cylindrical radially outer surface 54 and the input shaft S ₁ of the support ring 36.

Here, the support ring 36, as shown in FIG. 2, which is axially positioned by a step portion 44 formed on the other axial side of the input shaft S ₁ of the sliding guide surfaces 38.

As shown in FIG. 1, the rotor 52 has an outer cylindrical portion 52a and the inner cylinder portion 52b, the inner cylindrical portion 52b is fitted to the input shaft S _1, incorporated between the support ring 36 It is axially positioned by means of the shim 56, and are prevented from rotating relative to the input shaft S _1.

The electromagnet 53 includes an electromagnetic coil 53a and a core 53b that supports the electromagnetic coil 53a. The core 53b is fitted into the other end opening of the housing 1 and is attached to the other end opening of the housing 1. It is secured by a ring 3. The core 53b is freely rotated relative to the input shaft S ₁ via a bearing 57 fitted to the input shaft S _1.

  The rotation transmission device shown in the embodiment has the above structure, and FIGS. 2 and 3 show a state in which the roller 15 of the two-way clutch 10 is engaged with the cylindrical surface 12 and the cam surface 14. When the electromagnetic coil 53a of the electromagnetic clutch 50 is energized in the engaged state of the two-way clutch 10, an attractive force acts on the armature 51, and the armature 51 moves in the axial direction and is attracted to the rotor 52.

  Here, since the armature 51 is connected and integrated with the control holder 16A, the annular plate 23 of the control holder 16A is connected to the annular plate 31 of the rotary holder 16B as the armature 51 moves in the axial direction. Move in the direction of approach.

  At this time, as shown in FIG. 8 (a), the ball 43 shown in FIG. 8 (b) rolls and moves toward the deepest groove depth of the cam grooves 41, 42, and rotates and holds the control holder 16A. The container 16B relatively rotates in the direction in which the circumferential width of the pocket 37 is reduced, and the pair of opposed rollers 15 shown in FIG. 3 are pushed by the column part 28 of the control holder 16A and the column part 34 of the rotation holder 16B, so Move in the direction of approach.

  Therefore, as shown in FIG. 4, the roller 15 is displaced to the neutral position where the engagement with the cylindrical surface 12 and the cam surface 14 is released, and the two-way clutch 10 is disengaged.

In the disengaged state of the two-way clutch 10, the pillar portion of the input shaft when rotating the inner ring 13 in one direction by inputting the rotational torque into S _1, detent pieces 47 formed in the holding plate 46 is controlled retainer 16A The control holder 16A and the rotary holder 16B are rotated together with the inner ring 13 in order to press one of the pole portion 34 of the rotary holder 16 and the rotary holder 16B. At this time, since the pair of opposed rollers 15 is held in the neutral position where the engagement is released, the rotation of the inner ring 13 is not transmitted to the outer ring 11 and the inner ring 13 rotates freely.

  When the energization of the electromagnetic coil 53a is released in the free rotation state of the inner ring 13, the armature 51 is released from the suction and becomes rotatable. By releasing the suction, the control holder 16A and the rotary holder 16B are relatively rotated by the pressing of the elastic member 21 in the direction in which the circumferential width of the pocket 37 is increased, and each of the pair of opposed rollers 15 is as shown in FIG. In addition, a standby state is established in which the cylindrical surface 12 and the cam surface 14 are engaged, and a unidirectional rotational torque is transmitted between the inner ring 13 and the outer ring 11 via one of the pair of opposed rollers 15.

Here, when the input shaft S ₁ is stopped and the rotation direction of the input shaft S ₁ is switched, the rotation of the inner ring 13 is transmitted to the outer ring 11 via the other roller 15.

  As described above, when the energization of the electromagnetic coil 53a is interrupted, the control holder 16A and the rotary holder 16B rotate relative to each other in the direction in which the circumferential width of the pocket 37 increases, and each of the pair of opposed rollers 15 has the cylindrical surface 12. Further, since the standby state in which the cam surface 14 is immediately engaged is set, the rotation direction play is small, and the rotation of the inner ring 13 can be immediately transmitted to the outer ring 11.

  Further, since the rotational torque is transmitted from the inner ring 13 to the outer ring 11 through the same number of rollers 15 as the cam surface 14, a large rotational torque can be transmitted from the inner ring 13 to the outer ring 11.

  As shown in the embodiment, the retainer body 22 and the column portion 28 of the control retainer 16A and the retainer body 30 and the column portion 34 of the rotation retainer 16B are formed by pressing, and are formed by cutting. Compared to the case, the manufacturing is easier and the cost can be reduced.

  Further, each of the column part 28 in the control holder 16A and the column part 34 in the rotation holder 16B has a symmetrical cross-sectional shape, so that a single column part is shared by the control holder 16A and the rotation holder 16B. The cost can be greatly reduced by reducing the number of parts.

  In the embodiment shown in FIG. 1, the control holder 16 </ b> A and the rotation holder 16 </ b> B are configured such that the column portions 28 and 34 are positioned between the outer ring 11 and the inner ring 13, and the annular plates 23 and 31 that are opposed in the axial direction are the outer ring 11. Therefore, the axial length of the outer ring 11 can be reduced in size and weight.

  In the embodiment shown in FIGS. 1 to 3, as the two-way clutch 10, the control cage 16A is moved in the axial direction by energizing the electromagnet 53, and the control cage 16A and the rotary cage 16B are rotated relative to each other. Although the roller type that engages the roller 15 as the engagement element with the inner periphery of the outer ring 11 and the outer periphery of the inner ring 13 is shown, the two-way clutch is not limited to this, and is a sprag type. It may be a thing.

S ₁ input shaft S ₂ output shaft 11 outer ring 13 inner ring 15 roller (engagement element)
16A Control retainer 16B Rotating retainer 21 Elastic member 22 Retainer body 23 Annular plate 24 Connecting piece 25 Cylindrical portion 28 Column portion 30 Retainer body 31 Annular plate 32 Connecting piece 34 Column portion 37 Pocket 40 Torque cam (motion conversion mechanism)
50 Electromagnetic clutch 51 Armature 52 Rotor

Claims (4)

A two-way clutch that transmits and blocks rotation between the input shaft and an output shaft that is arranged coaxially with the input shaft, and an electromagnetic clutch that controls engagement and release of the two-way clutch;
The two-way clutch is provided in each of the control cage and the rotary cage between the inner circumference of the outer ring provided at the shaft end portion of the output shaft and the outer circumference of the inner ring provided at the shaft end portion of the input shaft. A pair of engaging elements that can be engaged with the inner periphery of the outer ring and the outer periphery of the inner ring in a pocket formed between adjacent column parts, so as to be alternately arranged in the circumferential direction. It is configured to incorporate an elastic member that urges the pair of engagement elements in the direction of separating,
The electromagnetic clutch has an armature connected to the control cage, a rotor facing the armature in the axial direction, and an electromagnet arranged to face the rotor, and the control cage is axially moved by energizing the electromagnet. The movement in the axial direction is converted into a relative rotational motion in a direction in which the circumferential width of the pocket is reduced by the motion conversion mechanism, and the pair of engagement elements are disengaged by the motion conversion mechanism. In the rotation transmission device
The control retainer includes a retainer body made of a press-formed product of an annular plate provided with a connecting portion for the armature, and a plurality of column parts made of a press-formed product whose ends are joined and integrated with the annular plate. Have
The rotary cage has a cage body made of a press-formed product of an annular plate, and a column part made of a press-formed product with an end joined and integrated with the annular plate,
A rotation transmission device characterized in that the cross-sectional shapes of the control retainer and the column of the rotation retainer are symmetrical, and the column is a common component.   The control retainer is provided with a plurality of connecting pieces radially on the outer periphery of the annular plate, a cylindrical portion for connecting to the armature is provided on the outer periphery of the connecting pieces, and a column portion is provided on each of the connecting pieces. The rotation transmission device according to claim 1, wherein the rotation retainer is formed by joining a plurality of connecting pieces radially on an outer periphery of the annular plate, and a pillar is joined to each of the connecting pieces.   The rotation transmission device according to claim 1 or 2, wherein a surface of the control cage and the cage body in the rotation cage is heat-treated in a stage before joining the column portions to harden the surface.   The rotation transmission device according to claim 3, wherein the heat treatment is one of carburizing quenching, submerged quenching, and nitriding treatment.

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