JP2007309369A - Shaft for cvt, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft for a CVT and its manufacturing method which provide an excellent dimensional precision and durability, and can increase the productivity and reduce the costs by combining the shaft and a sheave made from another members. <P>SOLUTION: The shaft 1 for the CVT has a shaft portion 2 and a sheave 3 externally fitted in the shaft portion 2. The sheave portion 3 has an inserting hole 31 to be inserted for the shaft portion 2, and has a plurality of teeth 4 projecting inward in the inner peripheral surface 311 of the inserting hole 31. At least teeth 4 are face-hardened to harden the surface before the engagement with the shaft portion 2. The shaft portion 2 has a combined outer surface 21 the diameter of which is greater than the diameter of an inscribed circle of the teeth 4. The teeth 4 is made to bite into the combined outer surface 21, and part of the combined outer surface 21 is plastically flowed to form a plastic connector 6, so that the shaft portion 2 and the sheave portion 3 are integrally combined. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a CVT shaft used in a belt type continuously variable transmission (CVT) used as a transmission of an automobile or the like.

  Generally, a belt type continuously variable transmission (CVT) used for a transmission such as an automobile has a pair of shafts (a primary shaft and a secondary shaft). Each shaft has a fixed sheave fixed to the shaft and a movable sheave slidably mounted on the shaft. These fixed sheave and movable sheave constitute a pulley (primary pulley, secondary pulley) having a variable groove width. Further, a belt made of metal or the like is wound between the pair of pulleys, and the gears can be shifted by changing the groove width between the fixed sheave and the movable sheave.

  Of the above CVTs, most shafts and fixed sheaves (hereinafter simply referred to as sheaves as appropriate) are manufactured as integral parts because of problems with current strength. Of these, a belt made of metal or the like as described above is wound around the surface of the sheave, and it is used in a state in which a large load is applied between the belt and the belt during running. Securing is essential. Therefore, the required wear resistance is usually ensured by increasing the surface hardness by performing a process such as carburizing or carbonitriding.

  Moreover, although it is limited to a part, a shaft and a fixed sheave may be manufactured separately, and may be manufactured integrally afterward. For example, as described in the embodiment of Patent Document 1, the shaft and the fixed pulley are coupled by spline fitting, or as described in Non-Patent Document 1, they are coupled by press-fitting. An example of using it as an integral part has been reported.

However, the above-mentioned CVT has the following problems.
In the case of ordinary CVT, there is no problem in strength even if the carburizing or carbonitriding is not performed, and a sufficient strength can often be secured by partially quenching with high frequency or the like. Therefore, in such a case, the material used for the sheave is required to have excellent carburization because the wear resistance must be ensured, but the material used for the shaft is Not required.

However, in the case of being manufactured integrally, as a matter of course in manufacturing, the material must be fixed to one type and it is impossible to select a suitable material for each of the shaft and the sheave. Therefore, as a result, the material is selected with an emphasis on carburization. As a result, a more expensive material must be selected, resulting in a problem that the material cost increases.
In addition, in the case of integration, it is necessary to process the entire integrated component as a matter of course in the case of processing such as carburization. Therefore, not only the carburizing distortion increases due to the large parts, but also the number of parts that can be processed at one time is greatly reduced even in the same size carburizing furnace, and the productivity is lowered. There is a problem that more energy is required.

In addition, when manufactured by spline fitting or press-fitting, the contact surface between the shaft and sheave is not firmly fixed, so it is in use no matter how high the accuracy is. In other words, it is not possible to completely prevent a minute shift on the contact surfaces of each other, and there is a possibility of causing fretting fatigue due to long-term use.
Furthermore, since spline fitting requires machining with extremely high accuracy before fitting, there is a problem that the manufacturing cost increases. In the case of press-fitting, although depending on the press-fitting allowance, there is a problem that sufficient strength cannot be obtained unless the contact surface between the shaft and the sheave is considerably enlarged, and the parts become larger and heavier. .

JP 2002-106658 A ATZ / MTZ “Der new Audi A4”, November 2000, pp. 137-140

  The present invention has been made in view of such conventional problems, and is formed by integrating a shaft and a sheave made of different members, and is excellent in dimensional accuracy and durability, and further improved in productivity and cost. It is an object of the present invention to provide a CVT shaft that can be reduced and a method for manufacturing the same.

A first invention is a shaft for CVT used for CVT,
The CVT shaft has a rod-shaped shaft portion made of mechanical structural steel, and a disk-shaped sheave portion made of mechanical structural steel extrapolated to the shaft portion,
The sheave portion has an insertion hole into which the shaft portion is inserted, and the inner peripheral surface of the insertion hole has a plurality of tooth portions that have tooth traces in the axial direction and protrude inward. And before the engagement with the shaft part, at least the surface of the tooth part is cured,
The shaft portion has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The shaft portion and the sheave portion are integrally coupled by forming a plastic coupling portion in which a part of the coupling outer surface portion is plastically flowed by biting the tooth portion into the coupling outer surface portion. (Claim 1).

The shaft for CVT of the present invention is composed of a shaft (primary shaft, secondary shaft) and a sheave (fixed sheave) fixed to the shaft.
That is, the CVT shaft has the shaft portion and the sheave portion extrapolated to the shaft portion. The shaft portion and the sheave portion cause the tooth portion of the sheave portion to bite into the coupling outer surface portion of the shaft portion, and a part of the coupling outer surface portion is plastically flowed into the tooth gap between the tooth portions. (Plastic deformation) plastic coupling portions are formed and are integrally coupled by so-called plastic coupling. For this reason, the coupling force between the two becomes higher than that when coupled by press fitting or spline fitting. In particular, since both of the above are firmly fixed on the contact surface in a state where compressive residual stress is applied due to plastic deformation, it is possible to suppress the occurrence of repetitive minute displacement on the contact surface even during use. There is no need to worry about. As a result, the strength of the CVT shaft can be increased and the durability can be improved.

In addition, since the coupling force between the shaft portion and the sheave portion can be sufficiently ensured, it is not necessary to form a boss portion or the like for supplementing the strength of the CVT shaft. Thereby, improvement of productivity and reduction of cost can be aimed at.
Moreover, the contact area of the coupling | bond part of the said shaft part and the said sheave part can be made small by using plastic coupling with high coupling force. Thereby, size reduction of the said shaft for CVT is realizable.

  In the CVT shaft of the present invention, as described above, the shaft portion and the sheave portion are provided as separate members, and these are integrally coupled. Therefore, the dimensional accuracy and productivity of the CVT shaft can be improved as compared with the case where both are provided as an integrated product. That is, by providing separate members, the shape of each member of the shaft portion and the sheave portion is simpler and smaller than the integrated product. Therefore, each member can be processed and molded with high accuracy and can be produced efficiently. In particular, when carrying out a hardening process such as carburizing on the sheave part, it is possible to process a larger number of parts in one process even in the same heat treatment furnace due to simplification and miniaturization of the members, so that the processing time is reduced. It can be shortened. Accordingly, the CVT shaft in which the shaft portion and the sheave portion are coupled has high dimensional accuracy and productivity.

  Furthermore, by providing the shaft portion and the sheave portion as separate members, it is possible to produce materials using materials that are suitable for cost, productivity, required performance, and the like. Thereby, it is possible to easily reduce the cost and secure the performance of the CVT shaft.

Further, the plastic bonding in the present invention is a method in which a material having a low hardness is plastically deformed and a material having a high hardness is bonded. Therefore, in the present invention, it is premised that at least the hardness (surface hardness) of the tooth portion of the sheave portion is larger than that of the outer surface portion of the shaft portion. For this reason, the sheave part is subjected to a hardening process at least on the surface of the tooth part. Thereby, the surface hardness of the said tooth | gear part can be improved and the plastic coupling of the said shaft part and the said sheave part can be performed accurately.
In addition, by applying a hardening process that hardens at least the surface of the sheave part other than the tooth part at the same time, it improves the wear resistance of the sheave part that comes into contact with a belt made of metal or the like and is heavily worn. Can be made.

  As described above, according to the present invention, a shaft and a sheave made of different members are integrated to form a CVT that is excellent in dimensional accuracy and durability, and that can further improve productivity and reduce costs. Shafts can be provided.

2nd invention is the manufacturing method of the shaft for CVT used for CVT,
A sheave part preparing step for preparing a disk-shaped sheave part made of machine structural steel and having an insertion hole in the center;
A tooth part forming step of providing a plurality of tooth parts protruding inward on the inner peripheral surface of the insertion hole in the axial direction;
A sheave portion curing process for curing at least the surface of the tooth portion;
A shaft part preparation step of preparing a rod-shaped shaft part having a coupling outer surface part having an outer diameter larger than the diameter of the inscribed circle of the tooth part, made of mechanical structural steel;
The shaft portion is inserted into the insertion hole of the sheave portion, and the tooth portion is bitten into the coupling outer surface portion to form a plastic coupling portion in which a part of the coupling outer surface portion is plastically flowed. A method for producing a shaft for CVT, comprising a plastic coupling step of integrally coupling the shaft portion and the sheave portion (claim 12).

  In the method for manufacturing a CVT shaft according to the present invention, in the plastic coupling step, the tooth portion of the sheave portion bites into the coupling outer surface portion of the shaft portion, and a part of the coupling outer surface portion is interposed between the tooth portions. A plastic coupling portion that is plastically flowed (plastically deformed) is formed in the tooth groove, and the shaft portion and the sheave portion are integrally coupled by so-called plastic coupling. Therefore, as described above, the coupling force between the two becomes higher than the case of coupling by press-fitting, spline fitting, or the like. Thereby, the intensity | strength of the shaft for CVT obtained can be raised, and durability can be improved.

In addition, since the coupling force between the shaft portion and the sheave portion can be sufficiently secured, it is not necessary to form a boss portion or the like for supplementing the strength of the obtained CVT shaft. Thereby, improvement of productivity and reduction of cost can be aimed at.
Moreover, the contact area of the coupling | bond part of the said shaft part and the said sheave part can be made small by using plastic coupling with high coupling force. Thereby, size reduction of the said shaft for CVT is realizable.

  Moreover, in the manufacturing method of this invention, in the said sheave part preparatory process and the said shaft part preparatory process, the said shaft part and the said sheave part are each produced separately, and these are integrally couple | bonded in the said plastic joining process. . Therefore, the dimensional accuracy and productivity of the obtained CVT shaft can be improved as compared with the case where both are produced as an integrated product. That is, by producing separately, the shape of each member of the said shaft part and the said sheave part becomes simple compared with an integrated product, and becomes small. Therefore, each member can be processed and molded with high accuracy and can be produced efficiently. In particular, when performing the above-described sheave curing process, it is possible to process a larger number of parts in a single process even in the same heat treatment furnace by simplifying and downsizing the members, thereby reducing the processing time. Can do. As a result, dimensional accuracy and productivity can be improved.

  Furthermore, by separately producing the shaft portion and the sheave portion, materials suitable for cost, productivity, required performance, and the like can be selectively used for both. Thereby, it is possible to easily reduce the cost and secure the performance in the manufacture of the CVT shaft.

Further, in the sheave portion curing process, at least the surface of the tooth portion in the sheave portion is cured. Thereby, the surface hardness of the said tooth | gear part can be improved, and the plastic coupling of the said shaft part and the said sheave part in the said plastic coupling process can be performed accurately.
Further, in the sheave part curing treatment step, at least the surface of the sheave part other than the tooth part is simultaneously cured so that the sheave part comes into contact with a belt such as metal and wear resistance of the sheave part is severely worn. Can be improved.

  As described above, according to the manufacturing method of the present invention, the shaft and the sheave made of different members are integrated to be excellent in dimensional accuracy and durability, and further, productivity is improved and cost is reduced. It is possible to obtain a CVT shaft that can be used.

  In the first and second inventions, as the curing process of the sheave part, a so-called surface curing process in which the surface and its peripheral part such as carburizing, carbonitriding, and induction hardening are concentrated and the entire part is used. It is possible to apply a tempering treatment that simultaneously cures the inside by tempering.

Moreover, in the said 1st invention, it is preferable that the surface hardness of the said tooth | gear part of the said sheave part is Hv600 or more (Claim 2).
In this case, due to the excellent strength characteristics of the tooth portion, the plastic joint portion between the shaft portion and the sheave portion becomes a more stable joint portion, and the stability of dimensional accuracy can be increased.

Moreover, it is preferable that the said tooth | gear part of the said sheave part is Hv300 or more larger than the surface hardness of the said coupling | bonding outer surface part of the said shaft part.
That is, when the hardness difference is small, the plastic flow on the surface of the shaft portion at the time of plastic joining does not proceed smoothly, and the dimensional accuracy after joining is lowered. Therefore, by setting the hardness difference to be Hv300 or more, due to the hardness difference between the tooth part and the joint outer surface part, the plastically deformed joint outer surface part is likely to plastically flow between the tooth parts, and is more stable. Thus, it is possible to obtain the above-described plastic coupling portion with high accuracy.

Further, the shaft portion is made of a material having a carbon equivalent Ceq of 0.4 or more represented by the following formula, and before or after the coupling with the sheave portion, at least a part other than the coupling outer surface portion is induction-hardened. It is preferable that the surface hardening process is given by the process (Claim 4).
Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 (each element symbol means mass%)
In this case, the surface hardness of the shaft portion can be sufficiently ensured by performing the induction hardening process. In addition, when the carbon equivalent Ceq of the shaft portion is less than 0.4, problems such as insufficient hardness after induction hardening, insufficient strength, and reduced wear resistance of the sliding portion may occur.

Moreover, it is preferable that the said tooth | gear part of the said sheave part has performed the shot peening process after performing the said hardening process.
In this case, compressive residual stress is generated in the teeth of the sheave by performing shot peening. Therefore, when the shaft portion and the sheave portion are plastically coupled, the tensile stress generated in the tooth portion can be reduced, and delayed fracture of the sheave portion after the plastic coupling can be suppressed.

Further, the tooth portion of the sheave portion includes a pressure receiving surface having an angle α with an axial plane including the axis of the shaft portion, and an inclined surface having an angle β with the axial plane β (β> α). A first fastening tooth having an acute angle shape and having the pressure receiving surface positioned in the first direction in the circumferential direction and a second fastening tooth having the pressure receiving surface positioned in the second direction opposite to the first fastening tooth. Configure one,
The first region in which the first fastening teeth are arranged and the second region in which the second fastening teeth are arranged are alternately arranged in the circumferential direction of the insertion hole,
The portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other does not come inward from the circumscribed circle of the valley formed by the pressure receiving surface and the inclined surface. The CVT shaft is characterized in that a first holding portion is provided which smoothly connects the inclined surfaces facing each other and located on the outer side (Claim 6).

  When the shaft portion and the sheave portion are plastically coupled, the largest tensile stress is generated at a portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other. Therefore, the part is located outside so as not to come out of the circumscribed circle of the trough formed by the pressure receiving surface and the inclined surface, and the inclined surface facing each other is smoothly connected. A first holding part is provided. In other words, the tensile stress generated can be reduced by providing the first holding portion having a smooth shape at a portion where the stress is concentrated. Thereby, rupture, delayed fracture, misplacement, and the like of the sheave portion after plastic bonding can be suppressed, and the dimensional accuracy of the CVT shaft can be improved.

In addition, it is preferable that the first holding portion is disposed with a gap between the first outer portion and the coupling outer surface portion.
In this case, when the shaft portion and the sheave portion are plastically coupled, the tensile stress generated in the first holding portion can be further effectively reduced.

Further, the portion where the pressure receiving surface of the first fastening tooth and the pressure receiving surface of the second fastening tooth face each other is located outward so as not to come inward from the outer diameter of the coupling outer surface portion, It is preferable that a second holding portion that smoothly connects the pressure-receiving surfaces facing each other is provided.
In this case, since the second holding portion does not become an obstacle when the plastic coupling is performed, even if the dimensional accuracy of the outer diameter of the shaft portion and the inner diameter of the sheave portion varies, the plastic flow of the shaft portion is prevented. It can be done smoothly. In addition, after the plastic coupling, the shaft portion and the above-mentioned shaft portion are adjusted by adjusting the dimension of the second collar portion so that the outer diameter of the shaft portion is in contact with the second collar portion, that is, the coupling outer surface portion. Deviation of the axial position with the sheave portion can be suppressed, and the dimensional accuracy of the CVT shaft can be improved.

Moreover, it is preferable that the said trough part is formed in the smooth curve shape (Claim 9).
In this case, the tensile stress which generate | occur | produces in each said trough part can be reduced.

Further, the coupling outer surface portion of the shaft portion has a contact surface inclined at an outer peripheral corner portion,
The tooth portion has a large-diameter tip portion that can accommodate the combined outer surface portion on the inner peripheral side, and a positioning inclined portion that gradually decreases in diameter on the rear end side,
The plastic coupling portion accommodates the coupling outer surface portion in the large-diameter tip portion of the tooth portion and causes the tooth portion to bite into the coupling outer surface portion after contacting the contact surface and the positioning inclined portion. (Claim 10).
In this case, the shaft portion and the sheave portion can be positioned in the axial direction, and the dimensional accuracy of the CVT shaft can be improved.

Further, the shaft portion has an outer flange portion having an outer diameter larger than that of the coupling outer surface portion,
An axial end surface of the tooth portion has a tip contact surface that can contact the outer flange portion. When the plastic coupling portion is formed, the outer flange portion and the tip contact surface are in contact with each other. Preferably, they are in contact with each other (claim 11).
In this case, the shaft portion and the sheave portion are sufficiently fixed.

In the second aspect of the invention, in the sheave portion surface treatment step, the surface hardness of the tooth portion of the sheave portion is preferably set to Hv 600 or more (claim 13).
In this case, in the plastic joining step, the plastic joint part between the shaft part and the sheave part can be more stably formed by the excellent strength characteristics of the tooth part, and the dimensional accuracy is stable. Can also be high.

Further, in the sheave portion surface treatment step, it is preferable that the surface hardness of the tooth portion of the sheave portion is larger than the surface hardness of the coupling outer surface portion of the shaft portion by Hv300 or more (claim 14).
In this case, in the plastic joining step, the joined outer surface portion that has undergone plastic deformation easily plastically flows into the tooth portion due to the hardness difference between the tooth portion and the joined outer surface portion. It is possible to form the above-described plastic joint.

Further, the shaft portion is made of a material having a carbon equivalent Ceq represented by the above formula of 0.4 or more, and at least a part other than the outer surface portion is subjected to induction hardening before or after the plastic bonding step. It is preferable to further include a shaft portion surface hardening treatment step for performing a surface hardening treatment.
In this case, the surface hardness of the shaft portion can be sufficiently secured by performing induction hardening in the shaft portion surface hardening treatment step. In addition, when the carbon equivalent Ceq of the shaft portion is less than 0.4, problems such as insufficient hardness after induction hardening, insufficient strength, and reduced wear resistance of the sliding portion may occur.

Moreover, it is preferable to further have a shot peening treatment step of performing shot peening treatment on the tooth portion of the sheave portion after the sheave portion treatment step.
In this case, by performing shot peening processing in the shot peening processing step, compressive residual stress is generated in the tooth portions of the sheave portion. Therefore, when the shaft portion and the sheave portion are plastically coupled in the plastic coupling step, the tensile stress generated in the tooth portion can be reduced. Thereby, the delayed fracture of the sheave part after plastic bonding can be suppressed.

Further, in the tooth portion forming step, an acute angle shape is formed by a pressure receiving surface having an angle α with respect to an axial plane including the axis of the shaft portion and an inclined surface having an angle β (β> α) with the axial plane. And a second fastening tooth in which the pressure-receiving surface is positioned in the second direction opposite to the first fastening tooth in which the pressure-receiving surface is positioned in the first direction in the circumferential direction. And
The first region in which the first fastening teeth are arranged and the second region in which the second fastening teeth are arranged are alternately arranged in the circumferential direction of the insertion hole,
The portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other does not come inward from the circumscribed circle of the valley formed by the pressure receiving surface and the inclined surface. Thus, it is preferable to provide a first holding portion that is located outward and smoothly connects the inclined surfaces facing each other (claim 17).

  At the time of plastic coupling between the shaft portion and the sheave portion in the plastic coupling step, the portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other has the largest tensile force. Stress is generated. Therefore, in the tooth part forming step, the slope is located outside and faces the circumscribed circle of the valley formed by the pressure-receiving surface and the inclined surface. The said 1st reserve part which connected the surface smoothly is provided. In other words, the tensile stress generated can be reduced by providing the first holding portion having a smooth shape at a portion where the stress is concentrated. As a result, bursting, delayed fracture, misplacement, and the like of the sheave portion after plastic bonding can be suppressed, and the resulting CVT shaft has high dimensional accuracy.

In the plastic bonding step, it is preferable that the first holding portion is disposed with a gap between the first outer surface portion and the outer surface portion of the bonding.
In this case, it is possible to further effectively reduce the tensile stress generated in the first holding portion when the shaft portion and the sheave portion are plastically joined in the plastic joining step.

Further, the portion where the pressure receiving surface of the first fastening tooth and the pressure receiving surface of the second fastening tooth face each other is located outward so as not to come out of the inscribed circle of the tooth portion, It is preferable to provide a second holding part that smoothly connects the pressure-receiving surfaces facing each other (claim 19).
In this case, since the second holding portion does not become an obstacle when the plastic bonding is performed in the plastic bonding step, the shaft can be used even if the dimensional accuracy of the outer diameter of the shaft portion and the inner diameter of the sheave portion varies. The plastic flow of the part can be performed smoothly. In addition, after the plastic coupling, the shaft portion and the above-mentioned shaft portion are adjusted by adjusting the dimension of the second collar portion so that the outer diameter of the shaft portion is in contact with the second collar portion, that is, the coupling outer surface portion. A shift in the axial position with the sheave portion can be suppressed. Thereby, the obtained CVT shaft has high dimensional accuracy.

In the tooth portion forming step, the valley portion is preferably formed in a smooth curved shape (claim 20).
In this case, the tensile stress generated in each valley can be reduced in the plastic bonding step.

Further, in the shaft portion preparation step, the coupling outer surface portion of the shaft portion is provided with a contact surface inclined at an outer peripheral corner portion,
In the tooth portion forming step, the tooth portion is provided with a large-diameter leading end portion that can accommodate the coupling outer surface portion on the inner peripheral side, and a positioning inclined portion that gradually decreases in diameter on the rear end side,
In the plastic coupling step, the coupling outer surface portion is accommodated in the large-diameter tip portion of the tooth portion, and after the contact surface and the positioning inclined portion are brought into contact with each other, the tooth portion is bitten into the coupling outer surface portion. It is preferable to form the plastic joint portion (claim 21).
In this case, in the plastic joining step, it is possible to suppress the deviation of the axial position between the shaft portion and the sheave portion. Thereby, the obtained CVT shaft has high dimensional accuracy.

Further, in the shaft portion preparation step, an outer flange portion having an outer diameter larger than the combined outer surface portion is provided on the shaft portion,
In the tooth portion forming step, a tip contact surface capable of contacting the outer flange portion is provided on the axial end surface of the tooth portion,
In the plastic bonding step, it is preferable that the outer flange portion and the tip contact surface are brought into contact with each other (claim 22).
In this case, the shaft portion and the sheave portion can be sufficiently fixed in the plastic joining step.

Example 1
The shaft for CVT concerning the Example of this invention and its manufacturing method are demonstrated using figures.
As shown in FIG. 1, the CVT shaft 1 of this example is used for a belt type continuously variable transmission (CVT) used for a transmission of an automobile or the like, and is fixed to the shaft (shaft portion 2) and the shaft. Sheave (sheave part 3).

As shown in FIGS. 1 to 9, the CVT shaft 1 has a rod-shaped shaft portion 2 made of mechanical structural steel and a disk-shaped sheave portion 3 made of mechanical structural steel extrapolated to the shaft portion 2. The sheave portion 3 has an insertion hole 31 into which the shaft portion 2 is inserted. A plurality of tooth portions that protrude inward and have tooth traces in the axial direction on the inner peripheral surface 311 of the insertion hole 31. 4, and before the engagement with the shaft portion 2, at least the surface of the tooth portion 4 is hardened, and the shaft portion 2 has an inscribed circle 400 of the tooth portion 4. The coupling outer surface portion 21 has an outer diameter larger than the diameter.
Then, the shaft portion 2 and the sheave portion 3 are integrally coupled by forming the plastic coupling portion 6 in which a portion of the coupling outer surface portion 21 is plastically flowed by biting the tooth portion 4 into the coupling outer surface portion 21. ing.
This will be described in detail below.

  As shown in FIGS. 3 and 6, the sheave portion 3 has the insertion hole 31 into which the shaft portion 2 is inserted as described above, and tooth traces are axially provided on the inner peripheral surface 311 of the insertion hole 31. And a plurality of teeth 4 projecting inwardly. The tooth portion 4 has a large-diameter distal end portion 33 that can accommodate the coupling outer surface portion 21 on the inner peripheral side, and a positioning inclined portion 32 that gradually decreases in diameter toward the rear end side. Further, a tip end contact surface 34 that can contact an outer flange portion 22 of the shaft portion 2 to be described later is provided on an end surface in the axial direction of the tooth portion 4.

Further, as shown in FIGS. 7 to 9, each tooth portion 4 provided on the inner peripheral surface 311 of the sheave portion 3 has a pressure receiving surface 431 whose angle formed with the axial plane 200 including the axis of the shaft portion 2 is α, An acute angle is formed by the inclined surface 432 having an angle of β (β> α) with the axial plane. In this example, α = 0 ° and is not shown.
Further, the tooth portion 4 includes a first fastening tooth 41 in which the pressure receiving surface 431 is positioned in the first direction D1 (clockwise direction) in the circumferential direction, and a second direction D2 (counterclockwise direction) on the opposite side. And the second fastening tooth 42 having the pressure receiving surface 432 positioned in the direction). Further, in the tooth portion 4, the first region 51 in which the first fastening teeth 41 are arranged and the second region 52 in which the second fastening teeth 42 are arranged are alternately arranged in the circumferential direction of the insertion hole 311.

  Further, as shown in FIG. 8, an inclined surface facing portion 46 where the inclined surface 432 of the first fastening tooth 41 and the inclined surface 432 of the second fastening tooth 42 face each other is formed by a pressure receiving surface 431 and an inclined surface 432. There is provided a first retaining portion 441 that is located outward so as not to come out of the circumscribed circle 430 of the valley portion 433 and smoothly connects the inclined surfaces 432 facing each other. The first holding part 441 is arranged in a state where a gap 45 is provided between the first holding part 441 and the coupling outer surface part 21. The valley 433 is formed in a smooth curved shape.

  On the other hand, as shown in FIG. 9, the pressure receiving surface facing portion 47 where the pressure receiving surface 431 of the first fastening tooth 41 and the pressure receiving surface 431 of the second fastening tooth 42 face each other is inside the inscribed circle 400 of the tooth portion 4. The second holding portion 442 is provided so as to be located outside and smoothly connect the pressure-receiving surfaces 431 facing each other. The second holding portion 442 is disposed in contact with the outer surface portion 21 that has undergone plastic flow (plastic deformation).

  Further, as shown in FIGS. 2 and 6, the shaft portion 2 has a cylindrical shape and is coupled with a coupling outer surface portion 21 having an outer diameter larger than the diameter of the inscribed circle 400 of the tooth portion 4 of the sheave portion 3. The outer flange portion 22 has an outer diameter larger than that of the outer surface portion 21. Moreover, the coupling | bonding outer surface part 21 has the contact surface 211 which inclined in the outer peripheral corner | angular part.

Further, as shown in FIGS. 6 to 9, the shaft portion 2 and the sheave portion 3 include a plastic coupling portion 6 in which a part of the coupling outer surface portion 21 is plastically flowed (plastically deformed) to the valley portion 433 between the tooth portions 31. And are integrally coupled by the plastic coupling portion 6. That is, the shaft portion 2 and the sheave portion 3 are coupled by so-called plastic coupling.
In FIGS. 8 and 9, the outer peripheral surface 210 of the joint outer surface portion 21 before joining (before plastic deformation) is shown.

Further, as the material for the shaft portion 2 and the sheave portion 3, steel for machine structure is used.
As a material of the shaft portion 2, a carbon equivalent Ceq (Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4, each element symbol means each mass%. The same shall apply hereinafter) having S45C of 0.4 or more. Carbon steel) was used.
As a material for the sheave portion 3, SCM20 (chromium molybdenum steel) was used. The tooth part 4 in the sheave part 3 has a surface hardness of Hv750 (hardening depth of 0.5 mm according to JIS G0557).

Moreover, the joint outer surface part 21 of the shaft part 2 is subjected to heat treatment (normalizing), and the surface hardness is Hv250. Further, in the portion other than the coupling outer surface portion 21 of the shaft portion 2, a portion requiring a higher surface hardness is subjected to an induction hardening treatment as a surface hardening treatment.
The tooth portion 4 of the sheave portion 3 is subjected to carburizing treatment (quenching, tempering) as a surface hardening treatment, and the surface hardness is Hv750.

Next, a method for manufacturing the CVT shaft 1 will be described with reference to the drawings.
As shown in FIGS. 4 to 6, the method for manufacturing the CVT shaft 1 of this example is made of steel for machine structural use, and a sheave portion preparing step of preparing a disk-shaped sheave portion 3 having an insertion hole 31 in the center, A tooth portion forming step of providing a plurality of tooth portions 4 which have tooth traces in the axial direction and protrude inward on the inner peripheral surface 311 of the insertion hole 31, and a sheave portion hardening treatment step of hardening the surface of the tooth portion 4; A shaft part preparation step of preparing a rod-shaped shaft part 2 made of mechanical structural steel and having a coupling outer surface part 21 having an outer diameter larger than the diameter of the inscribed circle 400 of the tooth part 4, and the shaft part 2 as a sheave part 3 and the shaft portion 2 and the sheave portion by forming a plastic coupling portion 210 in which a portion of the coupling outer surface portion 21 is plastically flowed by causing the tooth portion 4 to bite into the coupling outer surface portion 21. A plastic bonding process for integrally bonding To.
This will be described in detail below.

<Sheave preparation process>
SCM20 (chromium molybdenum steel) used as a material for the sheave portion 3 is cut into a predetermined length. Then, it shape | molds by hot forging, heat processing (normalizing) is performed, and the disk-shaped sheave part 3 (FIG. 3) which has the insertion hole 31 in the center is prepared.

<Tooth part formation process>
Next, cold forging or cutting is performed on the inner peripheral surface 311 of the insertion hole 31 of the sheave portion 3 to form a plurality of tooth portions 4 having tooth traces in the axial direction and protruding inward. In addition, the shape of the tooth part 4 is as having mentioned above (refer FIGS. 7-9).

<Sheave part curing process>
Next, carburizing treatment (quenching and tempering) as surface hardening treatment is performed on the sheave portion 3 to cure the surface of the sheave portion 3. At this time, the surface hardness of the tooth portion 4 of the sheave portion 3 is set to Hv 600 or more. In this example, the surface hardness of the tooth portion 4 is Hv750.
In addition, as a hardening process of the sheave part 3 in this process, it can replace with a carburizing process and can also perform an induction hardening process, a tempering process, etc.

<Shot peening process>
Next, in this example, a shot peening process is performed on the tooth part 4 of the sheave part 3 after the sheave part curing process.

<Shaft section preparation process>
Next, S45C (carbon steel) having a carbon equivalent Ceq of 0.4 or more used as a material for the shaft portion 2 is cut into a predetermined length. Thereafter, heat treatment (normalizing) and cold working (plastic working, cutting work) are performed, and the rod-like shape having the coupling outer surface portion 21 having an outer diameter larger than the diameter of the inscribed circle 400 of the tooth portion 4 in the sheave portion 3. The shaft portion 2 (FIG. 2) is prepared.
Note that the heat treatment (normalizing) in this step can be omitted if not necessary.

<Plastic bonding process>
Next, the shaft portion 2 is inserted into the insertion hole of the sheave portion 3, and the shaft portion 2 and the sheave portion 3 are integrally coupled by plastic coupling. This will be described in detail below.
First, as shown in FIG. 4, the sheave portion 3 is set on the receiving die 8, and the shaft portion 2 is pushed into the insertion hole 311 of the sheave portion 3. Then, as shown in FIG. 5, the coupling outer surface portion 21 of the shaft portion 2 is accommodated in the large-diameter tip portion 33 of the tooth portion 4 of the sheave portion 3, and the positioning inclination of the contact surface 211 of the shaft portion 2 and the sheave portion 3. The part 32 is brought into contact. Thereby, the shaft part 2 and the sheave part 3 are positioned in the axial direction.

  Thereafter, as shown in FIG. 6, while the tooth portion 4 of the sheave portion 3 is bitten into the coupling outer surface portion 21 of the shaft portion 2, that is, while the coupling outer surface portion 21 is plastically flowed to the valley portion 433 between the tooth portions 4, The shaft portion 2 is pushed into the insertion hole 31 of the sheave portion 3 until the outer flange portion 22 of the portion 2 and the tip contact surface 34 of the sheave portion 3 abut. As a result, a plastic coupling portion 6 is formed in which a part of the coupling outer surface portion 21 is plastically flowed to the valley portion 433 of the tooth portion 4, and the shaft portion 2 and the sheave portion 3 are integrally coupled by plastic coupling. .

<Shaft surface treatment process>
Next, in this example, after the plastic bonding step, induction hardening is performed on a portion other than the bonding outer surface portion 21 of the shaft portion 2 where more surface hardness is required.
In addition, you may perform this shaft part surface hardening process process before a plastic joining process.

<Finishing>
Finally, a finishing process (cutting process) for adjusting the dimensions of the shaft part 2 and the sheave part 3 is performed.
Thus, the CVT shaft 1 (FIG. 1) is obtained.

Next, the effect of the CVT shaft 1 of this example will be described.
The CVT shaft 1 of this example includes a shaft portion 2 and a sheave portion 3 that is extrapolated to the shaft portion 2. The shaft portion 2 and the sheave portion 3 cause the tooth portion 4 of the sheave portion 3 to bite into the joint outer surface portion 21 of the shaft portion 2, and a part of the joint outer surface portion 21 is plastically flowed to the valley portion 433 of the tooth portion 4. The (plastic deformation) plastic coupling portion 6 is formed and integrally coupled by so-called plastic coupling. For this reason, the coupling force between the two becomes higher than that when coupled by press fitting or spline fitting. In particular, since both of the above are firmly fixed on the contact surface in a state where compressive residual stress is applied due to plastic deformation, it is possible to suppress the occurrence of repetitive minute displacement on the contact surface even during use. There is no need to worry about. As a result, the strength of the CVT shaft 1 can be increased and the durability can be improved.

In addition, since the coupling force between the shaft portion 2 and the sheave portion 3 can be sufficiently secured, it is not necessary to form a boss portion or the like for supplementing the strength of the CVT shaft 1. Thereby, productivity can be improved and cost can be reduced.
Moreover, the contact area of the coupling | bond part of the shaft part 2 and the sheave part 3 can be made small by using plastic coupling with high coupling force. Thereby, size reduction of the shaft 1 for CVT is realizable.

  Moreover, the shaft 1 for CVT is provided with a shaft portion 2 and a sheave portion 3 as separate members, and these are integrally coupled. Therefore, the dimensional accuracy and productivity of the CVT shaft 1 can be improved as compared with the case where both are provided as an integrated product. That is, by providing separate members, the shape of each member of the shaft portion 2 and the sheave portion 3 is simpler and smaller than the integrated product. Therefore, each member can be processed and molded with high accuracy and can be produced efficiently. In particular, when the curing process is performed on the sheave part 3 and the shaft part 2, the processing time can be shortened by simplifying and downsizing the members. Thereby, the shaft 1 for CVT which combined the shaft part 2 and the sheave part 3 becomes a thing with high dimensional accuracy and productivity.

  Furthermore, by providing the shaft portion 2 and the sheave portion 3 as separate members and producing them, it is possible to selectively use materials suitable for the cost, productivity, required performance, and the like. Thereby, the cost reduction, performance ensuring, etc. in the CVT shaft 1 can be easily performed.

  Further, the sheave portion 3 is subjected to a hardening process on the surface of the tooth portion 4. Thereby, the surface hardness of the tooth | gear part 4 can be improved and the plastic coupling of the shaft part 2 and the sheave part 3 can be performed accurately.

  Further, in this example, the tooth portion 4 of the sheave portion 3 is Hv300 or more larger than the surface hardness of the coupling outer surface portion 21 of the shaft portion 2. Therefore, due to the hardness difference between the tooth portion 4 and the coupling outer surface portion 21, the plastically deformed coupling outer surface portion 21 easily plastically flows into the valley portion 433 of the tooth portion 4, making the plastic coupling portion more stable and accurate. 6 can be obtained.

In addition, the inclined surface facing portion 46 where the inclined surface 432 of the first fastening tooth 41 and the inclined surface 432 of the second fastening tooth 42 face each other is circumscribed by a trough 433 formed by the pressure receiving surface 431 and the inclined surface 432. A first holding portion 441 is provided so as not to come out from the inside of the circle 430 and is smoothly connected to the inclined surfaces 432 facing each other.
By providing the first holding portion 441 having a smooth shape on the inclined surface facing portion 46 where stress is concentrated when the shaft portion 2 and the sheave portion 3 are plastically coupled, the generated tensile stress can be reduced. Thereby, rupture, delayed fracture, misplacement and the like of the sheave portion 3 after plastic bonding can be suppressed, and the dimensional accuracy of the CVT shaft 1 can be improved.

  Moreover, in the manufacturing method of this example, after the sheave portion processing step, a shot peening processing step of performing shot peening processing on the teeth 4 of the sheave portion 3 is performed. Thereby, compressive residual stress is generated in the tooth portion 4 of the sheave portion 3. Therefore, when the shaft portion 2 and the sheave portion 3 are plastically coupled in the plastic coupling step, the tensile stress generated in the tooth portion 4 can be reduced, and the delayed fracture of the sheave portion 3 after the plastic coupling can be suppressed. it can.

  As described above, according to this example, the shaft and the sheave made of different members are integrated to form a CVT that is excellent in dimensional accuracy and durability, and that can further improve productivity and reduce costs. Shafts can be provided.

(Example 2)
In this example, the strength and dimensional accuracy of the CVT shaft are evaluated.
As a product of the present invention, a CVT shaft (sample E1) of Example 1 in which a shaft portion and a sheave portion made of different members were plastically coupled was prepared.
Further, as a comparative product, a sample C1 in which the shaft portion and the sheave portion were press-fitted and a sample C2 in which the shaft portion and the sheave portion were provided as an integrated product were prepared.

In the sample E1, the diameter of the coupling outer surface portion 21 of the shaft portion 2 is 45 mm, and the inner hole diameter is 17 mm. Further, the sheave portion 3 has an axial height of 18 mm and an outer diameter of 175 mm. The protruding height of the tooth portion 4 is 1 mm, and the number of tooth portions is 40 teeth (first fastening teeth 41:20 teeth, second fastening teeth 42:20 teeth).
In addition, conditions, such as a raw material of each member, heat processing, hardness, are shown in Table 1.

Further, in the sample C1, a press-fitting allowance (80 μm) is provided on both sides in the radial direction at a joint portion between the shaft portion and the sheave portion. In addition, conditions, such as a raw material of each member and hardness, are the same as that of the sample E1. Further, as the heat treatment, carburizing treatment is performed on the shaft portion and the sheave portion.
Sample C2 is obtained by using SCM20 as a material, molding an integrated product having a shaft portion and a sheave portion by hot forging, and performing a carburizing process.

  As evaluation of strength, static torsional strength of sample E and sample C1 was measured. In the measurement of the static torsional strength, a torsional torque is applied to the shaft portion while the sheave portion is fixed so as not to rotate. And in the sample E1, the yield torque of the shaft part at the time of the plastic deformation of the outer surface coupling part of the shaft part was measured. Further, in sample C1, the slip torque between the shaft portion and the sheave portion at the time when slip occurred between the shaft portion and the sheave portion and no increase in torque was recognized was measured.

As a result, the static torsional strength of sample C1 was 3 kNm, while the static torsional strength of sample E1 was 13 kNm. That is, it can be seen that the sample E1 which is a plastic bond has a higher bonding force between the shaft portion and the sheave portion than the sample C1 which is the press-fit bond.
In addition, this is a case where the dimension of a joint part is made the same. Therefore, in the case of press-fitting, it is necessary to increase the axial length of the press-fitting part so that the torsional strength is equivalent, and in that case, the weight increases. Further, in the case of the conventional integrated product, naturally the torsional strength is higher than that of the CVT shaft of the present invention, but the weakest part is not the position evaluated in this test, but a small diameter part that transmits torque. Therefore, it can be said that the product of the present invention has no problem as long as the static torsional strength described above.

Next, as evaluation of the dimensional accuracy, the shake of the sheave portions of the sample E1 and the sample C2 was measured. The sheave portion was measured by measuring the axial displacement at the outer peripheral end of the sheave portion when the shaft portion was rotated once. Sample E1 was measured after bonding and before finishing. Moreover, about the sample C2, the thing of the state before a finishing process similarly after a carburizing process was measured.
As a result, the shake of the sheave part of the sample C2 was 0.1 mm, whereas the shake of the sheave part of the sample E1 was 0.05 mm. That is, it can be seen that the sample E1 which is a separate member and plastically coupled to the sample C2 which is an integral product has a high dimensional accuracy for each member as well as the overall dimensional accuracy.

Furthermore, in this example, a sample was prepared in which the hardness difference between the coupling outer surface portion of the shaft portion and the tooth portion of the sheave portion was variously measured, and the sheave portion run-out was measured. Here, samples E1 and E2 having a hardness difference Hv300 or more and a sample C3 having a hardness difference Hv300 or less were prepared and measured. In addition, the conditions of the raw material of each sample, heat processing, hardness, and hardness difference are as Table 1.
As a result, as can be seen from Table 1, for the sample C3 having a surface hardness of the tooth portion of Hv600 or less and a hardness difference of Hv300 or less, the shake of the sheave portion increased. Therefore, it can be seen that the hardness difference between the tooth portion and the coupling outer surface portion is preferably Hv300 or more in order to ensure sufficient dimensional accuracy.

FIG. 3 is an explanatory view showing a CVT shaft in the first embodiment. FIG. 3 is an explanatory diagram showing a shaft portion in the first embodiment. FIG. 3 is an explanatory diagram illustrating a sheave portion in the first embodiment. Explanatory drawing which shows the state before the coupling | bonding of the shaft part and sheave part in Example 1. FIG. Explanatory drawing which shows the state in the middle of the coupling | bonding of the shaft part and sheave part in Example 1. FIG. Explanatory drawing which shows the state after the coupling | bonding of the shaft part and sheave part in Example 1. FIG. FIG. 2 is a cross-sectional view taken along the line S-S in FIG. 1. The enlarged view of the A section of FIG. The enlarged view of the B section of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft for CVT 2 Shaft part 21 Coupling outer surface part 3 Sheave part 31 Insertion hole 311 Inner peripheral surface 4 Tooth part 6 Plastic coupling part

Claims (22)

A CVT shaft used in a belt type continuously variable transmission (hereinafter referred to as CVT),
The CVT shaft has a rod-shaped shaft portion made of mechanical structural steel, and a disk-shaped sheave portion made of mechanical structural steel extrapolated to the shaft portion,
The sheave portion has an insertion hole into which the shaft portion is inserted, and the inner peripheral surface of the insertion hole has a plurality of tooth portions that have tooth traces in the axial direction and protrude inward. And before the engagement with the shaft part, at least the surface of the tooth part is cured,
The shaft portion has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The shaft portion and the sheave portion are integrally coupled by forming a plastic coupling portion in which a part of the coupling outer surface portion is plastically flowed by biting the tooth portion into the coupling outer surface portion. The shaft for CVT characterized by this.   2. The CVT shaft according to claim 1, wherein the tooth portion of the sheave portion has a surface hardness of Hv600 or more.   3. The CVT shaft according to claim 1, wherein the tooth portion of the sheave portion is Hv300 or more larger than the surface hardness of the coupling outer surface portion of the shaft portion. The shaft portion according to any one of claims 1 to 3, wherein the shaft portion is made of a material having a carbon equivalent Ceq of 0.4 or more represented by the following formula, and before or after being combined with the sheave portion. A shaft for CVT, wherein a surface hardening treatment is applied to at least a part other than by an induction hardening treatment.
Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 (each element symbol means mass%)   5. The CVT shaft according to claim 1, wherein the tooth portion of the sheave portion is subjected to a shot peening treatment after the curing treatment. 6. The tooth portion of the sheave portion according to claim 1, wherein the tooth portion of the sheave portion has a pressure receiving surface whose angle formed with an axial plane including the axis of the shaft portion is α, and an angle formed with the axial plane is β ( [beta]> [alpha]) and an inclined surface, and the pressure receiving surface is positioned in the first direction in the circumferential direction, and the pressure receiving force in the second direction opposite to the first fastening tooth. Configure one of the second fastening teeth with the surface positioned,
The first region in which the first fastening teeth are arranged and the second region in which the second fastening teeth are arranged are alternately arranged in the circumferential direction of the insertion hole,
The portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other does not come inward from the circumscribed circle of the valley formed by the pressure receiving surface and the inclined surface. The CVT shaft is characterized in that a first holding portion is provided which smoothly connects the inclined surfaces facing each other and located outward.   7. The CVT shaft according to claim 6, wherein the first holding portion is disposed with a gap between the first outer portion and the coupling outer surface portion.   In Claim 6 or 7, in the site | part which the said pressure receiving surface of the said 1st fastening tooth and the said pressure receiving surface of the said 2nd fastening tooth face, it is outside so that it may not come out inside the inscribed circle of the said tooth part. The CVT shaft is characterized in that a second holding portion is provided which is located on the opposite side and smoothly connects the pressure-receiving surfaces facing each other.   The shaft for CVT according to any one of claims 6 to 8, wherein the valley portion is formed in a smooth curved shape. In any one of Claims 1-9, the said coupling | bonding outer surface part of the said shaft part has the contact surface inclined in the outer peripheral corner | angular part,
The tooth portion has a large-diameter tip portion that can accommodate the combined outer surface portion on the inner peripheral side, and a positioning inclined portion that gradually decreases in diameter on the rear end side,
The plastic coupling portion accommodates the coupling outer surface portion in the large-diameter tip portion of the tooth portion and causes the tooth portion to bite into the coupling outer surface portion after contacting the contact surface and the positioning inclined portion. A shaft for CVT characterized by being formed. In any one of Claims 1-10, the said shaft part has an outer collar part whose outer diameter is larger than the said coupling | bonding outer surface part,
An axial end surface of the tooth portion has a tip contact surface that can contact the outer flange portion. When the plastic coupling portion is formed, the outer flange portion and the tip contact surface are in contact with each other. A shaft for CVT, which is in contact with each other. In the manufacturing method of the shaft for CVT used for CVT,
A sheave part preparing step for preparing a disk-shaped sheave part made of machine structural steel and having an insertion hole in the center;
A tooth part forming step of providing a plurality of tooth parts protruding inward on the inner peripheral surface of the insertion hole in the axial direction;
A sheave portion curing process for curing at least the surface of the tooth portion;
A shaft part preparation step of preparing a rod-shaped shaft part having a coupling outer surface part having an outer diameter larger than the diameter of the inscribed circle of the tooth part, made of mechanical structural steel;
The shaft portion is inserted into the insertion hole of the sheave portion, and the tooth portion is bitten into the coupling outer surface portion to form a plastic coupling portion in which a part of the coupling outer surface portion is plastically flowed. A method for producing a shaft for CVT, comprising a plastic coupling step of integrally coupling the shaft portion and the sheave portion.   13. The method for manufacturing a shaft for CVT according to claim 12, wherein in the sheave portion curing treatment step, the surface hardness of the tooth portion of the sheave portion is set to Hv 600 or more.   14. The CVT according to claim 12 or 13, wherein, in the sheave portion curing treatment step, the surface hardness of the tooth portion of the sheave portion is set to be greater than the surface hardness of the joint outer surface portion of the shaft portion by Hv300 or more. Manufacturing method for an automobile. The shaft portion according to any one of claims 12 to 14, wherein the shaft portion is made of a material having a carbon equivalent Ceq of 0.4 or more represented by the following formula, and before or after the plastic bonding step. A method for producing a shaft for CVT, characterized by further comprising a shaft portion surface hardening treatment step in which at least a portion is subjected to a surface hardening treatment by induction hardening.
Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 (each element symbol means mass%)   The shaft for a CVT according to any one of claims 12 to 15, further comprising a shot peening treatment step of performing shot peening treatment on the tooth portion of the sheave portion after the sheave portion treatment step. Production method. In any one of Claims 12-16, in the said tooth | gear part formation process, the angle which the angle made with the axis plane containing the axis line of the said shaft part is (alpha) and the angle with the said axis plane is (beta) ((beta)>). α) and an inclined surface, and the pressure receiving surface is positioned in the first direction in the circumferential direction and the pressure receiving surface in the second direction opposite to the first fastening tooth. Forming a second fastening tooth in which
The first region in which the first fastening teeth are arranged and the second region in which the second fastening teeth are arranged are alternately arranged in the circumferential direction of the insertion hole,
The portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other does not come inward from the circumscribed circle of the valley formed by the pressure receiving surface and the inclined surface. A method for manufacturing a CVT shaft, comprising: a first holding portion that smoothly connects the inclined surfaces that face each other and face each other.   18. The method for manufacturing a CVT shaft according to claim 17, wherein in the plastic coupling step, the first holding portion is disposed with a gap between the first outer portion and the coupling outer surface portion.   In Claim 17 or 18, in the part which the said pressure receiving surface of the said 1st fastening tooth and the said pressure receiving surface of the said 2nd fastening tooth face, it is outside so that it may not come out inside the inscribed circle of the said tooth part. A method for producing a CVT shaft, comprising: a second holding portion that is located on the opposite side and smoothly connects the pressure-receiving surfaces facing each other.   The method for manufacturing a CVT shaft according to any one of claims 17 to 19, wherein, in the tooth portion forming step, the valley portion is formed in a smooth curved shape. In any one of Claims 12-20, in the above-mentioned shaft part preparation process, the above-mentioned joint outer surface part of the above-mentioned shaft part provides the contact surface which inclined to the perimeter corner,
In the tooth portion forming step, the tooth portion is provided with a large-diameter leading end portion that can accommodate the coupling outer surface portion on the inner peripheral side, and a positioning inclined portion that gradually decreases in diameter on the rear end side,
In the plastic coupling step, the coupling outer surface portion is accommodated in the large-diameter tip portion of the tooth portion, and after the contact surface and the positioning inclined portion are brought into contact with each other, the tooth portion is bitten into the coupling outer surface portion. And forming the plastic joint. A method for producing a CVT shaft, wherein: In any one of Claims 12-21, in the said shaft part preparation process, the outer flange part whose outer diameter is larger than the said coupling | bonding outer surface part is provided in the said shaft part,
In the tooth portion forming step, a tip contact surface capable of contacting the outer flange portion is provided on the axial end surface of the tooth portion,
The method for manufacturing a CVT shaft, wherein the outer flange portion and the tip contact surface are brought into contact with each other in the plastic coupling step.

Images