JP4957362B2 - CVT shaft and manufacturing method thereof - Google Patents

Description

  The present invention relates to a belt drive type continuously variable transmission used as a transmission of an automobile or the like (the belt drive type includes a rubber belt type, a metal belt type, a chain belt type, etc. Hereinafter, a belt type continuously variable transmission and It is related with the shaft for CVT used for.

  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 a conventional problem. The shaft and sheave made of different members are integrated and fixed, 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 CVT shaft used in a belt-type continuously variable transmission (hereinafter referred to as CVT),
The CVT shaft is formed by connecting 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 via a plastic coupling portion and a press-fit portion. Become
The sheave portion has an insertion hole into which the shaft portion is inserted, and the insertion hole has a coupling inner surface portion for forming the plastic coupling portion and a press-fit inner surface portion for forming the press-fit portion. Continuing in the direction and provided so that the press-fit inner surface portion is located on the side closer to the sheave surface,
The inner peripheral surface of the inner surface portion has a plurality of tooth portions protruding inward and having tooth traces in the axial direction,
The inner peripheral surface of the press-fitted inner surface portion is a flat surface and has an inner diameter smaller than the diameter of the inscribed circle of the tooth portion,
In addition, the sheave portion is subjected to a curing treatment for curing at least the surface of the tooth portion before being coupled to the shaft portion,
The shaft portion has a coupling outer surface portion for forming the plastic coupling portion and a press-fitting outer surface portion for forming the press-fitting portion in an axial direction.
The coupling outer surface portion has an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The press-fit outer surface portion has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion and an outer diameter larger than the inner diameter of the press-fit inner surface portion so as to allow press-fitting,
The tooth portion of the sheave portion has a surface hardness of Hv 600 or more, and is greater than the surface hardness of the coupling outer surface portion of the shaft portion by Hv 300 or more,
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. As shown in FIG. 1, a first holding part is provided that smoothly connects the inclined surfaces facing each other.
The tooth portion is bitten into the joint outer surface portion to form the plastic joint portion in which a part of the joint outer surface portion is plastically flowed, and the press-fit portion is formed by press-fitting the press-fit outer surface portion into the press-fit inner surface portion. Accordingly, the CVT shaft is characterized in that the shaft portion and the sheave portion are integrally coupled to each other (claim 1).
A second invention is a CVT shaft used in a belt-type continuously variable transmission (hereinafter referred to as CVT),
The CVT shaft is formed by connecting 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 via a plastic coupling portion and a press-fit portion. Become
The sheave portion has an insertion hole into which the shaft portion is inserted, and the insertion hole has a coupling inner surface portion for forming the plastic coupling portion and a press-fit inner surface portion for forming the press-fit portion. Continuing in the direction and provided so that the press-fit inner surface portion is located on the side closer to the sheave surface,
The inner peripheral surface of the inner surface portion has a plurality of tooth portions protruding inward and having tooth traces in the axial direction,
The inner peripheral surface of the press-fitted inner surface portion is a flat surface and has an inner diameter smaller than the diameter of the inscribed circle of the tooth portion,
In addition, the sheave portion is subjected to a curing treatment for curing at least the surface of the tooth portion before being coupled to the shaft portion,
The shaft portion has a coupling outer surface portion for forming the plastic coupling portion and a press-fitting outer surface portion for forming the press-fitting portion in an axial direction.
The coupling outer surface portion has an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The press-fit outer surface portion has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion and an outer diameter larger than the inner diameter of the press-fit inner surface portion so as to allow press-fitting,
The tooth portion of the sheave portion has a surface hardness of Hv 600 or more, and is greater than the surface hardness of the coupling outer surface portion of the shaft portion by Hv 300 or more,
Further, the tooth portion of the sheave portion has an arc having a smaller diameter than a reference circle in which a tooth groove formed between the tooth portions is a circumscribed circle of the tooth groove in a cross section orthogonal to the axial direction, and the reference The tooth gap inscribed in the circle is configured to form a petal shape regularly arranged in the circumferential direction,
The tooth portion is bitten into the joint outer surface portion to form the plastic joint portion in which a part of the joint outer surface portion is plastically flowed, and the press-fit portion is formed by press-fitting the press-fit outer surface portion into the press-fit inner surface portion. Accordingly, the CVT shaft is characterized in that the shaft portion and the sheave portion are integrally coupled (claim 2).

The CVT shaft according to the first and second aspects of the present invention includes 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. In addition to forming a plastically joined portion that is (plastically deformed), a press-fit portion is formed by press-fitting the press-fit outer surface portion of the shaft portion into the press-fit inner surface portion of the sheave portion. Therefore, the bonding strength between the two is very high.

In particular, since the joint outer surface portion and the tooth portion are firmly fixed on the contact surface in a state in which compressive residual stress is exerted by plastic deformation, minute displacements repeatedly occur on the contact surface even during use. This can be suppressed and there is no need to worry about fretting.
The press-fit portion is provided on the side closer to the sheave surface than the plastic coupling portion. Here, the sheave surface is a portion where the highest tensile stress is generated in the circumferential direction of the sheave surface due to a load caused by winding of the belt when used as a CVT shaft, and the press-fit outer surface portion, the press-fit inner surface portion, The contact surface (interface of the press-fit portion) is flat, and has a shape in which cracks are unlikely to occur compared to the plastic joint portion. Therefore, by providing the press-fitting inner surface portion so as to be positioned on the side closer to the sheave surface, stress concentration can be avoided and the strength against the sheave surface pressure can be improved. As a result, despite the fact that the construction method that is difficult to secure the durability of the two-part joint is adopted, the necessary drive transmission force is sufficiently secured by the plastic joint part, and even with a large load caused by belt wrapping. It has a great effect that it is possible to ensure the durability that can be sufficiently endured.

In addition, since the coupling force between the shaft portion and the sheave portion can be sufficiently ensured, the shaft length is shorter than that of a CVT shaft manufactured only by press fitting as described in Non-Patent Document 1. Necessary torsional strength can be ensured. Thereby, improvement of productivity and reduction of cost can be aimed at.
Further, by combining plastic bonding with high bonding force and press-fitting that provides sufficient strength against sheave surface pressure, the contact area of the coupling portion between the shaft portion and the sheave portion can be reduced, and sufficient It can have high surface pressure resistance and torsional strength. As a result, the CVT shaft can be reduced in size and weight.

  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, compared with the case where both are provided as an integrated product, the dimensional accuracy and productivity of the CVT shaft can be improved and the cost can be reduced.

  That is, by providing separate members, the shape of each member of the shaft portion and the sheave portion is simpler than that of an integrated product, and is small and light. 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, and cost reduction can be expected.

  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 part can be improved, and the plastic coupling of the said coupling | bonding outer surface part and the said tooth 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.
In the present invention, the necessary torsional strength is mainly secured by plastic bonding. Therefore, when sufficient torsional strength can be ensured, the press-fitting allowance of the press-fitting portion is set to 0, and the diameter of the press-fitting outer surface portion of the shaft portion is set to the sheave. It is also possible to make it smaller than the diameter of the press-fitting inner surface part of the part. However, even in that case, in order to ensure the accuracy of the combined product, it is desirable that the difference in diameter between the two is within 0.05 mm.

3rd invention is the manufacturing method of the shaft for CVT used for CVT,
It is made of steel for machine structural use, and has an inner peripheral surface having axial teeth on the inner peripheral surface and a plurality of tooth portions projecting inward, and an inner peripheral surface formed of a flat surface and A sheave part preparation step of preparing a disk-shaped sheave part having an insertion hole formed in the center of a press-fitting inner surface part having an inner diameter smaller than the diameter of the inscribed circle;
A sheave portion curing process for curing at least the surface of the tooth portion;
It is made of steel for machine structural use, has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion, an outer diameter smaller than the diameter of the inscribed circle of the tooth portion, and is capable of being press-fit. A shaft portion preparation step of preparing a rod-shaped shaft portion having a press-fit outer surface portion having an outer diameter larger than the inner diameter of the press-fit inner surface portion in the axial direction;
A plastic coupling process for inserting the shaft portion into the insertion hole of the sheave portion and forming a plastic coupling portion in which the tooth portion is bitten into the coupling outer surface portion and a part of the coupling outer surface portion is plastically flowed. , and a press-fitting process of forming a press-fit portion press-fitted to the press-fit outer surface to the press-fit the inner surface portion, possess a binding step of combining integrally the shaft portion and the sheave portion,
In the sheave portion preparing step, the pressure receiving surface having an angle α with the axial plane including the axis of the shaft portion and an inclined surface having an angle β with the axial plane β (β> α) And forming a first fastening tooth in which the pressure receiving surface is positioned in the first direction in the circumferential direction and a second fastening tooth in which the pressure receiving surface is positioned in the second direction on the opposite side.
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. So as to be located outside and provide a first holding part that smoothly connects the inclined surfaces facing each other,
In the said sheave part hardening process process, the surface hardness of the said tooth | gear part of the said sheave part shall be Hv600 or more, and Hv300 or more is made larger than the surface hardness of the said coupling outer surface part of the said shaft part, The manufacture of the shaft for CVT characterized by the above-mentioned. It is in the method (claim 9 ).
4th invention is the manufacturing method of the shaft for CVT used for CVT,
It is made of steel for machine structural use, and has an inner peripheral surface having axial teeth on the inner peripheral surface and a plurality of tooth portions projecting inward, and an inner peripheral surface formed of a flat surface and A sheave part preparation step of preparing a disk-shaped sheave part having an insertion hole formed in the center of a press-fitting inner surface part having an inner diameter smaller than the diameter of the inscribed circle;
A sheave portion curing process for curing at least the surface of the tooth portion;
It is made of steel for machine structural use, has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion, an outer diameter smaller than the diameter of the inscribed circle of the tooth portion, and is capable of being press-fit. A shaft portion preparation step of preparing a rod-shaped shaft portion having a press-fit outer surface portion having an outer diameter larger than the inner diameter of the press-fit inner surface portion in the axial direction;
A plastic coupling process for inserting the shaft portion into the insertion hole of the sheave portion and forming a plastic coupling portion in which the tooth portion is bitten into the coupling outer surface portion and a part of the coupling outer surface portion is plastically flowed. A press-fitting process for forming a press-fitting part in which the press-fitting outer surface part is press-fitted into the press-fitting inner surface part, and a coupling step for integrally joining the shaft part and the sheave part,
In the sheave portion preparation step, the tooth portion of the sheave portion is an arc having a smaller diameter than a reference circle in which a tooth groove formed between the tooth portions is a circumscribed circle of the tooth groove in a cross section orthogonal to the axial direction. And the tooth gap inscribed in the reference circle is regularly arranged in the circumferential direction to form a petal shape,
In the said sheave part hardening process process, the surface hardness of the said tooth | gear part of the said sheave part shall be Hv600 or more, and Hv300 or more is made larger than the surface hardness of the said coupling outer surface part of the said shaft part, The manufacture of the shaft for CVT characterized by the above-mentioned. In the method (claim 10).

In the method of manufacturing the CVT shaft according to the third and fourth inventions, in the coupling step, the shaft portion is inserted into the insertion hole of the sheave portion by a plastic coupling process, and the tooth portion is formed on the coupling outer surface portion. And forming a press-fitting part in which the press-fitting outer surface part is press-fitted into the press-fitting inner surface part by press-fitting treatment to form a plastic joint part in which a part of the joint outer surface part is plastically flowed (plastic deformation). And the sheave portion are integrally coupled. Thus, according to the manufacturing method of the present invention, as described above, the coupling force between the shaft portion and the sheave portion is very high, and downsizing can be realized, such as surface pressure resistance strength and torsion strength. A CVT shaft having high strength, durability, and performance can be obtained with excellent dimensional accuracy and productivity at low cost.

The manufacturing method of the said 3rd and 4th invention has a sheave part preparation process, a sheave part hardening process process, a shaft part preparation process, and a coupling | bonding process as mentioned above.
In the sheave part preparation step, the sheave part is prepared by performing hot forging, cold forging, cutting, or the like on the machine structural steel.

  In addition, in the above-mentioned sheave part hardening treatment process, the surface and its peripheral part such as carburizing, carbonitriding, and induction hardening are concentrated and hardened, and the entire part is completely quenched and tempered. A tempering treatment or the like for curing at the same time is applied to cure at least the surface of the tooth part. Therefore, it is necessary to select a material suitable for the surface hardening treatment to be performed inevitably. In particular, when carburizing or carbonitriding is performed, case hardening steel such as Cr steel or Cr—Mo steel is suitable.

  Moreover, also in the said shaft part preparatory process, the said shaft part is prepared by performing hot forging, cold forging, cutting, etc. with respect to steel for machine structure similarly to the first sheave part preparatory process. The shaft part may also be induction-hardened in parts that require high strength, but it does not require higher strength than the sheave part, so the material is cheaper carbon than Cr steel and Cr-Mo steel. Steel (SC) can be used. In addition, you may perform an annealing and a normalizing process as needed.

Next, in the first to fourth inventions, as shown in FIG. 4 described later, the inner diameter of the press-fitting inner surface portion is d ₁ , the diameter of the sheave portion is d ₂ , and the center diameter d ₃ = (d ₁ + d in case of a ₂₎ / 2, the position is pressed inner surface which intersects the said vertical line and said insertion hole inner surface when minus the line perpendicular to the center axis of the central diameter d ₃ position on the surface of the sheave portion (Claims 3 and 11 ).
In this case, the effects of the torsional strength by the plastic joint and the surface pressure resistance by the press-fit portion can be obtained particularly well.

  When the press-fitting part is narrow and the position where the perpendicular and the inner surface of the insertion hole intersect is a plastic joint part, cracks are more likely to occur than the plastic joint part, which is more likely to crack than the press-fitting part. Therefore, the surface pressure resistance against the load caused by actual belt winding may be insufficient.

Further, the tooth portion of the sheave portion has a surface hardness of Hv600 or more .
In this case, due to the excellent strength characteristics of the tooth part, the plastic joint part formed by causing the tooth part to bite into the joint outer surface part and plastically flowing a part of the joint outer surface part is more stable. It becomes a coupling part, and the stability of the positional accuracy when two parts are coupled can be increased.

Further, 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 .
That is, when the difference in hardness is small, the plastic flow on the surface of the outer surface of the joint at the time of plastic joining does not proceed smoothly, and the dimensional accuracy after joining decreases. 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 performed by the process (Claims 4 and 12 ).
Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 (each element symbol means mass%)

  Of course, the induction outer surface portion is not subjected to induction heat treatment, but the surface hardness of the shaft portion can be increased by applying induction hardening treatment to a portion requiring high strength at a portion other than the attachment outer surface portion. . 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 (Claims 5 and 13 ).
In this case, compressive residual stress is generated in the teeth of the sheave by performing shot peening. Therefore, the tensile stress generated in the bottom surface of the tooth part can be reduced during the plastic connection between the outer surface part and the tooth part and during subsequent use, and the sheave part after the plastic connection is delayed. Can be suppressed.

In the second and fourth inventions, the tooth portion of the sheave portion is a reference circle in which a tooth groove formed between the tooth portions is a circumscribed circle of the tooth groove in a cross section orthogonal to the axial direction. Further, the above-described tooth groove inscribed in the reference circle is regularly arranged in the circumferential direction to form a petal shape (see FIGS. 5 and 6 to be described later).
Since the tooth part which comprises a petal shape can be formed by cold forging, cost reduction can be aimed at.
In addition, since the tooth gap portion is formed in a smooth curved shape, not only can a sufficient torsional strength be obtained, but also the tensile stress of the tooth root after plastic bonding can be relieved, and the sheave portion is ruptured. Thus, delayed destruction, misplacement, and the like can be suppressed, and the dimensional accuracy of the CVT shaft can be improved. In addition, the said tooth | gear part becomes high intensity | strength with respect to torsion torque, so that it is fine.

In the first and third invention, in order to ensure a particularly high torsional strength in the plastic coupling part, the shape of the teeth of the sheave portion, formed as follows.
Specifically, the tooth portion has an acute angle due to 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 (β> α) with the axial plane. And the first fastening tooth in which the pressure receiving surface is positioned in the first direction in the circumferential direction and the second fastening tooth in which the pressure receiving surface is positioned in the second direction opposite to the first fastening tooth. 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, and the first fastening The portion where the inclined surface of the tooth and the inclined surface of the second fastening tooth face each other is outward so as not to come inward from the circumscribed circle of the valley formed by the pressure-receiving surface and the inclined surface. A first holding portion is provided that smoothly connects the inclined surfaces facing each other .

In this case, the tooth portion of the sheave portion is bitten into the coupling outer surface portion of the shaft portion, and a part of the coupling outer surface portion is plastically flowed (plastically deformed) into the trough portion of the tooth portion, resulting in extremely high coupling force and high torsion. It is possible to form a plastic joint that can ensure strength.
Further, when the tooth portion and the joint outer surface portion are plastically coupled, the largest tensile stress is applied to a portion where the inclined surface of the first fastening tooth and the inclined surface of the second fastening tooth face each other. appear. 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.

  Further, in order to further effectively reduce the tensile stress generated in the first holding portion during the plastic bonding between the tooth portion and the bonding outer surface portion, the first holding portion is formed by a plastic flowed bonding outer surface. It is preferable that a gap is provided between the two portions.

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 part does not become an obstacle when plastically coupled, even if the dimensional accuracy of the outer diameter of the coupled outer surface part and the inner diameter of the tooth part varies, the plasticity of the coupled outer surface part The flow can be performed smoothly. After the plastic coupling, by adjusting the dimensions of the second retaining portion so that the coupling outer surface portion contacts the second retaining portion, the axial position of the shaft portion and the sheave portion can be adjusted. Misalignment 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, in order to reduce the tensile stress which generate | occur | produces in each trough part.

In the first to fourth inventions, a recess having an inner diameter larger than the inner diameter of the tooth portion may be formed between the coupling inner surface portion and the press-fitting inner surface portion of the sheave portion. Preferred (Claims 6 and 14 ).
In this case, at the time of the plastic coupling between the coupling outer surface portion and the tooth portion, a part of the coupling outer surface portion can plastically flow into the recess, and the shaft portion and the sheave portion of the CVT shaft are Position accuracy can be improved.

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. It is preferable that they are formed (claims 7 and 15 ).
In this case, the shaft portion and the sheave portion can be positioned in the axial direction, and the positional accuracy of the shaft portion and the sheave portion 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. It is preferable that it contacts (Claims 8 and 16 ).
In this case, the shaft portion and the sheave portion are sufficiently fixed.

Further, the plastic bonding process and the press-fitting process may be started simultaneously, the press-fitting process may be started after the plastic bonding process is started, or the plastic bonding process is started after the press-fitting process is started. and may be, but in particular, in the third and fourth manufacturing method of the CVT shaft of the invention, the coupling step is preferably started plastic binding process after the start of the press-process (claim 17) .
In this case, the CVT shaft can be manufactured with little variation in dimensional accuracy because it can be plastically coupled with the positional relationship between the shaft portion and the sheave portion being accurately fixed.

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 includes a rod-shaped shaft portion 2 made of mechanical structural steel, and a disk-shaped sheave portion 3 made of mechanical structural steel to be extrapolated to the shaft portion 2. It is connected via the plastic connecting portion 4 and the press-fit portion 5.

  The sheave portion 3 has an insertion hole 31 into which the shaft portion 2 is inserted. The insertion hole 31 forms a coupling inner surface portion 32 for forming the plastic coupling portion 4 and the press-fit portion 5. The press-fit inner surface portion 33 is connected to the axial direction, and is provided so that the press-fit inner surface portion 33 is located on the side closer to the sheave surface 30. And has a plurality of tooth portions 34 projecting inwardly, and the inner peripheral surface of the press-fit inner surface portion 33 is a flat surface and is smaller than the diameter of the inscribed circle of the tooth portion 34. Further, the sheave portion 3 is subjected to a hardening process for hardening at least the surface of the tooth portion 34 before being coupled to the shaft portion 2.

  The shaft portion 2 has a coupling outer surface portion 21 for forming the plastic coupling portion 4 and a press-fit outer surface portion 22 for forming the press-fit portion 5 in an axial direction, and the coupling outer surface. The portion 21 has an outer diameter larger than the diameter of the inscribed circle of the tooth portion 34, and the press-fit outer surface portion 22 has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion 34. It has an outer diameter larger than the inner diameter of the press-fitting inner surface portion 33 so that press-fitting is possible.

Then, the toothed portion 34 of the sheave portion 3 is bitten into the coupling outer surface portion 21 of the shaft portion 2 to form the plastic coupling portion 4 in which a part of the coupling outer surface portion 21 is plastically flowed, and the press-fitting inner surface The shaft portion 2 and the sheave portion 3 are integrally coupled by forming the press-fit portion 5 in which the press-fit outer surface portion 22 is press-fitted into the portion 33.
This will be described in detail below.

  As shown in FIGS. 4 and 5, the sheave portion 3 has the insertion hole 31 into which the shaft portion 2 is inserted as described above, and the joint inner surface portion 32 of the insertion hole 31 has tooth traces in the axial direction. And a plurality of teeth 34 projecting inwardly. On the side opposite to the sheave surface 30 of the tooth portion 34, as shown in FIG. 6, it has a large-diameter tip portion 35 that can accommodate the coupling outer surface portion 21 on the inner peripheral side, and gradually reduces the diameter toward the rear end side. The positioning inclined portion 36 is provided. Further, a tip end contact surface 37 capable of contacting an outer flange portion 23 of the shaft portion described later is provided on the axial end surface of the tooth portion 34. The inclination angle γ of the tip contact surface 37 with respect to the rear end surface 9, which is a surface orthogonal to the axial direction of the sheave portion 3, is 150 °, and the angle ω formed by the inclined portion 36 and the tip contact surface 37 is 140 °. did.

As shown in FIG. 4, when the inner diameter of the press-fitting inner surface portion 33 is d ₁ , the diameter of the sheave portion 3 is d ₂ , and the center diameter d ₃ = (d ₁ + d ₂ ) / 2, the sheave portion 3 When a perpendicular perpendicular to the central axis O is drawn from the position of the center diameter d _{3 on the} surface, a position 311 where the perpendicular intersects the inner surface of the insertion hole is the press-fitting inner surface portion 33.
In this example, the inner diameter of the press-fit inner surface portion 33 is d ₁ is 48 mm, the diameter of the sheave portion 3 is d ₂ is 156 mm, the central diameter d ₃ is 102 mm, and the sheave surface inclination θ is 11 °. The axial length of the press-fit portion 33 was 8.5 mm.

  As shown in FIG. 5, the tooth portion 34 of the sheave portion 3 has a petal shape formed by regularly arranging arcs 92 having a smaller diameter than the reference circle 91 so as to be inscribed in the reference circle 91. Yes. A concave portion 38 having an inner diameter larger than the inner diameter of the tooth portion 34 is formed at the interface between the coupling inner surface portion 32 and the press-fit inner surface portion 33 of the sheave portion 3.

  As shown in FIGS. 2 and 3, the shaft portion 2 has a cylindrical shape, has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion 34, and the press-fit inner surface portion so that press-fit is possible. The press-fit outer surface portion 22 having an outer diameter larger than the inner diameter of 33, the coupling outer surface portion 21 having an outer diameter larger than the diameter of the inscribed circle of the tooth portion 34 of the sheave portion 3, and the outer diameter larger than the coupling outer surface portion 21. And an outer casing 23. Moreover, the said coupling | bonding outer surface part 21 of the said shaft part 2 has the contact surface 24 inclined in the outer peripheral corner | angular part.

  Further, as shown in FIGS. 7 to 9, the shaft portion 2 and the sheave portion 3 have the plasticity in which the tooth portion 34 is bitten into the joint outer surface portion 21 and a part of the joint outer surface portion 21 is plastically flowed. The shaft portion 2 and the sheave portion 3 are integrally coupled by forming the joint portion 4 and forming the press-fit portion 5 in which the press-fit outer surface portion 22 is press-fitted into the press-fit inner surface portion 33. .

  The plastic coupling portion 4 accommodates the coupling outer surface portion 21 in the large-diameter tip portion 35 of the tooth portion 34 and contacts the contact surface 24 and the positioning inclined portion 36, and then the tooth portion 34. Is formed by biting into the joint outer surface portion 21. Further, in the state where the plastic coupling portion is formed, the outer flange portion 23 and the tip contact surface 37 are in contact with each other.

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 34 in the sheave part 3 is subjected to carburizing treatment (quenching, tempering) as a surface hardening treatment, and the surface hardness is 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.

Next, a method for manufacturing the CVT shaft 1 will be described with reference to the drawings.
As shown in FIGS. 1 to 9, the manufacturing method of the CVT shaft 1 of this example is made of steel for machine structural use, and has a plurality of tooth portions 34 having teeth on the inner peripheral surface in the axial direction and projecting inward. And an insertion hole 31 formed by connecting an inner surface 32 having a flat inner surface and a press-fitting inner surface 33 having an inner diameter smaller than the diameter of the inscribed circle of the tooth portion 34 in the axial direction. A sheave portion preparing step for preparing a disk-shaped sheave portion 3 at the center, a sheave portion hardening treatment step for hardening at least the surface of the tooth portion 34, a steel for machine structural use, and an inscribed circle of the tooth portion 34 And an outer diameter larger than the inner diameter of the press-fitting inner surface portion 33 so as to allow press-fitting and an outer diameter smaller than the diameter of the inscribed circle of the tooth portion 34. A rod-shaped sheath having a press-fit outer surface portion 22 connected in the axial direction. The shaft portion preparing step for preparing the shaft portion 2, the shaft portion 2 is inserted into the insertion hole 31 of the sheave portion 3, and the toothed portion 34 is bitten into the coupling outer surface portion 21, thereby the coupling outer surface portion 21. A plastic bonding process for forming a plastic coupling part 4 in which a part of the press-fitting part is plastically flowed, and a press-fitting process for forming a press-fitting part 5 in which the press-fitting outer surface part 22 is press-fitted into the press-fitting inner surface part 33. 2 and the sheave part 3 are integrally joined.
This will be described in detail below.

<Sheave part preparation process>
SCM20 (chromium molybdenum steel) used as a material for the sheave portion 3 is cut into a predetermined length. Thereafter, hot forging, heat treatment (normalizing), cold working (plastic working), and machining are performed, and a plurality of tooth portions 34 that have teeth on the inner peripheral surface in the axial direction and protrude inward are formed. The insertion hole 31 is formed by connecting the connecting inner surface portion 32 and the press-fitting inner surface portion 33 having an inner diameter smaller than the diameter of the inscribed circle of the tooth portion 34 in the axial direction. A disk-shaped sheave portion 3 (FIGS. 4 and 5) is prepared.
In addition, the shape of the tooth | gear part 34 is exhibiting the petal shape (refer FIG. 5).

<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 34 of the sheave portion 3 is set to Hv 600 or more. In this example, the surface hardness of the tooth portion 34 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 a carbonitriding process, 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 34 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 outer surface of the coupling outer surface portion 21 is larger than the diameter of the inscribed circle of the tooth portion 34 in the sheave portion 3, and the tooth A rod-shaped shaft portion 2 having an outer diameter smaller than the diameter of the inscribed circle of the portion 34 and having a press-fit outer surface portion 22 having an outer diameter larger than the inner diameter of the press-fit inner surface portion 33 so as to allow press-fitting (FIGS. 2 and Prepare 3).
Note that the heat treatment (normalizing) in this step can be omitted if not necessary. In this example, the surface hardness of the joint outer surface portion of the shaft portion is Hv230.

<Bonding process>
Next, the shaft portion 2 is inserted into the insertion hole 31 of the sheave portion 3, and the shaft portion 2 and the sheave portion 3 are integrally coupled by performing a plastic coupling process and a press-fitting process. This will be described in detail below.
(Plastic bonding process)
First, as shown in FIG. 7, the sheave portion 3 is set in the receiving die 6 and the shaft portion 2 is pushed into the insertion hole 31 of the sheave portion 3 in the plastic bonding process. As shown in FIG. 8, the coupling outer surface portion 21 of the shaft portion 2 is accommodated in the large-diameter tip portion 35 of the tooth portion 34 of the sheave portion 3, and the positioning inclination of the contact surface 24 of the shaft portion 2 and the sheave portion 3. The part 36 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. 9, while the tooth portion 34 of the sheave portion 3 is biting into the coupling outer surface portion 21 of the shaft portion 2, that is, the coupling outer surface portion 21 is a tooth between the tooth portions 34 shown in FIGS. 5 and 6. While causing the groove 39 to plastically flow, the shaft portion 2 is pushed into the insertion hole 31 of the sheave portion 3 until the outer flange portion 23 of the shaft portion 2 and the tip contact surface 37 of the sheave portion 3 abut. As a result, the plastic coupling portion 4 in which a part of the coupling outer surface portion 21 is plastically flowed into the tooth groove 39 of the tooth portion 34 is formed and coupled.

(Press-fit process)
In the press-fitting process, as described above, the sheave portion 3 is set on the receiving die 6 and the shaft portion 2 is pushed into the insertion hole 31 of the sheave portion 3.
Thereafter, the press-fit outer surface portion 22 having an outer diameter larger than the inner diameter of the press-fit inner surface portion 33 is press-fitted into the press-fit inner surface portion 33 so as to be press-fit. As a result, the press-fit portion 5 is formed and joined.

<Shaft surface treatment process>
Next, in this example, after the plastic bonding step, induction hardening is performed on a portion other than the outer surface portion of the shaft portion where 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 and the sheave part 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 are a plastic coupling portion in which a tooth portion 34 of the sheave portion 3 is bitten into the coupling outer surface portion 21 of the shaft portion 2 and a part of the coupling outer surface portion 21 is plastically flowed. 4, and a press-fitting portion 5 in which the press-fitting outer surface portion 22 of the shaft portion 2 is press-fitted into the press-fitting inner surface portion 33 of the sheave portion 3. Therefore, the binding force between the two becomes high.

In particular, since the plastic coupling portion 4 is firmly fixed on the contact surface in a state where compressive residual stress is exerted due to plastic deformation, it is possible to suppress repeated occurrence of minute displacement on the contact surface even during use. There is no need to worry about fretting.
Further, since the press-fitting portion 5 has a flat contact surface, cracks are unlikely to occur at the interface between the press-fitting inner surface portion 33 and the press-fitting outer surface portion 22, and the press-fitting portion having a shape that is difficult to crack is used in the present invention. It is provided on the sheave surface side where the highest tensile stress is generated by winding the belt. As a result, the strength against the sheave surface pressure 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 ensured, the necessary torsional strength can be ensured with a short shaft length as compared with the CVT shaft manufactured only by press-fitting. Thereby, productivity can be improved and cost can be reduced.
Further, by using a combination of plastic bonding having a high bonding force and press-fitting that provides sufficient strength against the sheave surface pressure, even if the contact area of the coupling portion between the shaft portion 2 and the sheave portion 3 is reduced, sufficient resistance is achieved. The surface pressure strength and torsional strength can be ensured, the CVT shaft 1 can be reduced in size and weight, and excellent durability can be obtained.

  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 positional accuracy and productivity of the shaft portion 2 and the sheave portion 3 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. As a result, the CVT shaft 1 in which the shaft portion 2 and the sheave portion 3 are coupled has high positional 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 tooth portion 34 of the sheave portion 3 has a petal shape. Since the petal-shaped tooth portion 34 can be formed by forging, it leads to cost reduction. Further, the petal-shaped tooth portion 34 is formed with a smooth curved shape of the tooth gap portion 39, so that not only a sufficient torsional strength can be obtained, but also the tensile stress of the tooth root after plastic bonding is relieved. It is possible to suppress rupture, delayed fracture, misplacement, and the like of the sheave portion 3 and improve durability.
Further, the sheave portion 3 is subjected to a hardening process on the surface of the tooth portion 34. Thereby, the surface hardness of the tooth | gear part 34 can be improved and the plastic coupling of the coupling | bonding outer surface part 21 and the tooth | gear part 34 can be performed accurately.

  Moreover, in this example, the tooth part 34 of the sheave part 3 is Hv300 or more larger than the surface hardness of the coupling outer surface part 21 of the shaft part 2. Therefore, due to the hardness difference between the tooth portion 34 and the coupling outer surface portion 21, the plastically deformed coupling outer surface portion 21 is likely to plastically flow into the valley portion of the tooth portion 34, thereby making the plastic coupling portion more stable and accurate. Obtainable.

  Moreover, in the manufacturing method of this example, after the sheave portion processing step, a shot peening processing step for performing shot peening processing on the tooth portion 34 of the sheave portion 3 is performed. Thereby, compressive residual stress is generated in the tooth portion 34 of the sheave portion 3. Therefore, when the shaft portion 2 and the sheave portion 3 are plastically joined in the plastic joining process, the tensile stress generated in the tooth portion 34 can be reduced, and the delayed fracture of the sheave portion 3 after the plastic joining can be suppressed. it can.

  As described above, according to this example, the shaft portion 2 and the sheave portion 3 made of different members are integrated, and the position accuracy and durability of the shaft portion 2 and the sheave portion 3 are excellent, and further, productivity is achieved. The shaft for CVT which can aim at improvement and cost reduction can be provided.

(Example 2)
In this example, the surface pressure resistance strength, torsional 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 combined was prepared.
Further, as a comparative product, a sample C1 in which the shaft portion and the sheave portion were joined only by press fitting, and a sample C2 in which the shaft portion and the sheave portion were joined only by plastic joining were prepared.

  In the sample E1, the diameter of the coupling outer surface portion 21 of the shaft portion 2 is 54 mm, the diameter of the press-fit outer surface portion 22 is 48.05 mm, and the inner hole diameter is 15 mm. Further, the sheave portion 3 has an axial height of 40 mm (the press-fitting inner surface portion is 8.5 mm high and the coupling inner surface portion is 15 mm high), the outer diameter is 102 m, and the sheave surface 30 has an inclination of 11 °. is there. Moreover, the protrusion height of the tooth part 34 of the coupling inner surface part 32 is 1 mm, the number of tooth parts is 40 teeth (first fastening teeth 41: 20 teeth, second fastening teeth 42: 20 teeth), and the inscribed circle of the tooth parts. The diameter of the press-fit inner surface portion 33 is 48 mm.

  Further, in the sample C1, a coupling portion is formed by press-fitting by providing a press-fitting allowance (70 μm) on both sides in the radial direction so that the axial length of the coupling portion is the same as that of the sample E1. The diameter of the press-fitting outer surface portion of the shaft portion, the diameter of the inner hole, the height in the axial direction of the sheave portion 3 (height of the press-fit inner surface portion), the outer diameter, the inclination angle of the sheave surface, and the diameter of the press-fitted inner surface portion are The same size was used. 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.

  In addition, the sample C2 has a coupling portion formed by plastic coupling so that the axial length of the coupling portion is the same as that of the sample E1. The diameter of the coupling outer surface part of the shaft part, the inner hole diameter, the height of the sheave part in the axial direction (height of the coupling inner surface part), the outer diameter, the inclination angle of the sheave surface, the protruding height of the tooth part of the coupling inner part, The number of teeth and the diameter of the inscribed circle of the teeth were set to the same size as the sample E1. 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.

<Surface pressure strength>
A method for evaluating the surface pressure resistance will be described with reference to FIGS.
As shown in FIG. 10, for the CVT shaft 1, the CVT shaft 1 is held by using a fixed lower jig 71 and an upper jig 72 movable up and down so that the surface of the sheave portion 3 is on the lower side. did. In the lower jig 71, two spheres 73 having a diameter of 35 mm are arranged at a position of 120 ° (angle α) around the axis of the CVT shaft 1 (see FIG. 11). Then, pressure was applied to the surface of the sheave portion 3 of the CVT shaft 1 by causing the upper jig 72 to stroke downward (direction B). Then, the maximum load force measured until the crack occurred at point D shown in FIG. 11 (angle β = 60 ° (portion receiving the maximum tensile stress)) was defined as the surface pressure resistance. The results are shown in FIG.

  In FIG. 12, the right vertical axis represents surface pressure resistance [N], the left vertical axis represents torsional strength [Nm] described later, and the horizontal axis describes how samples were bonded. . In the figure, reference numeral E1 indicates the result of the sample E1, reference numeral C1 indicates the result of the sample C1, reference numeral C2 indicates the result of the sample C2, reference sign S indicates the resistance to surface pressure, and reference sign T indicates the torsion strength.

  As is known from FIG. 12, the sample E1 and the sample C1 in which the joint part on the surface side of the sheave part is a flat joint part by press-fitting are samples in which the joint part on the surface side of the sheave part is a joint part by plastic joining. Compared with C2, cracking hardly occurred and excellent surface pressure strength was exhibited.

<Torsion strength>
The torsional strength is measured by applying a torsional torque to the shaft portion while the sheave portion is fixed so as not to rotate.
The torsional strength is measured by measuring the maximum torsional torque measured until the plastic joint loses torsional torque and begins plastic deformation or the frictional force of the press-fit part loses and slips It was. The results are also shown in FIG.

As can be seen from FIG. 12, the sample E1 and the sample C2 having the plastic joint portion showed excellent torsional strength as compared with the sample C1 having the joint portion including only the press-fit portion.
As described above, it was confirmed that by combining the press-fit portion and the plastic joint portion, it was possible to manufacture a CVT shaft excellent in balance with respect to both torsion strength and surface pressure strength.

In addition, this is a case where the dimension of a coupling | bond part is made the same. Therefore, in the case of press-fitting, it is possible to obtain the same torsional strength by increasing the axial length of the press-fitting part so as to obtain the same torsional strength, but in that case, the weight increases. Another problem will arise.
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 a problem-free strength as long as it is the torsional strength described above.

<Dimensional accuracy>
The dimensional accuracy was evaluated by measuring the shake of the sheave part. 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. The sample was measured after bonding and before finishing.
Here, for comparison, SCM20 was used as a material, an integrated product having a shaft portion and a sheave portion was formed by hot forging, and a carburized treatment was separately prepared.

As a result, the distortion due to quenching tends to increase in the integrated product, and the deflection was 0.1 mm, whereas the deflection of the sample E1, the sample C1, and the sample C2 was 0.05 mm. showed that. That is, the CVT shaft made of a separate member with respect to the integrated product can reduce the quenching distortion, so that high accuracy can be achieved and the machining allowance can be reduced.
For comparison, the difference between the surface hardness of the tooth portion of the sheave portion and the surface hardness of the coupling outer surface portion of the shaft portion is small (Hv200 (the tooth portion of the sheave portion is Hv600, the coupling outer surface portion of the shaft portion). When Hv400)) was evaluated, the deflection was as large as 0.30 mm. Therefore, it can be seen that if the difference in hardness between the two is not Hv300 or more, the material flow at the time of joining does not proceed smoothly, and it becomes difficult to manufacture a highly accurate CVT shaft.

  Thereby, according to this invention, the shaft and sheave which consist of another member are integrated and fixed, and it is excellent in dimensional accuracy and durability, and also can improve productivity and cost reduction. It can be seen that a shaft and a method for manufacturing the shaft can be provided.

(Example 3)
In this example, the CVT shaft 102 is manufactured by changing the petal shape of the tooth portion of the sheave portion of the first embodiment to a shape described later. Others were performed in the same manner as in Example 1.
As shown in FIGS. 13 to 15, in the sheave portion 302 of this example, each tooth portion 34 provided on the coupling inner surface portion 32 has a pressure receiving surface 81 whose angle formed with the axial plane 200 including the axis of the shaft portion 2 is α. And an inclined surface 82 having an angle of β (β> α) with respect to the axial plane. In this example, α = 0 ° and is not shown.

  Further, the tooth portion 34 includes a first fastening tooth 341 in which the pressure receiving surface 81 is positioned in the first direction G1 (clockwise direction) in the circumferential direction, and a second direction G2 (counterclockwise direction) on the opposite side. And a second fastening tooth 342 having the pressure receiving surface 82 positioned in the direction). Further, in the tooth portion 34, the first regions 83 in which the first fastening teeth 341 are arranged and the second regions 84 in which the second fastening teeth 342 are arranged are alternately arranged in the circumferential direction of the insertion hole 31.

  Further, as shown in FIG. 14, an inclined surface facing portion 85 where the inclined surface 82 of the first fastening tooth 341 and the inclined surface 82 of the second fastening tooth 342 face each other is formed by the pressure receiving surface 81 and the inclined surface 82. There is provided a first holding portion 851 that is located outwardly so as not to come out of the circumscribed circle 860 of the valley portion 86 and that smoothly connects the inclined surfaces 82 facing each other. In addition, the trough part 86 is formed in the smooth curve shape.

  On the other hand, as shown in FIG. 15, the pressure receiving surface facing portion 87 where the pressure receiving surface 81 of the first fastening tooth 341 and the pressure receiving surface 81 of the second fastening tooth 342 face each other is inside the inscribed circle 340 of the tooth portion 34. The second holding portion 871 is provided so as to be located outside and smoothly connect the pressure-receiving surfaces 81 facing each other.

The manufacturing method of the CVT shaft 102 of this example was performed in the same manner as in Example 1 except that the sheave part preparation step of the manufacturing method of Example 1 was changed.
In the sheave part preparation step, first, a material similar to that in Example 1 is cut into a predetermined length. Thereafter, hot forging, heat treatment (normalizing), and cutting are performed, and an inner surface 32 having a plurality of tooth portions 34 that have inwardly protruding teeth and an inward protrusion on the inner peripheral surface, A disk-shaped sheave portion 302 having an insertion hole 31 in the center formed by connecting a press-fitting inner surface portion having an inner diameter smaller than the diameter of the inscribed circle of the tooth portion 34 in the axial direction and having a flat peripheral surface. prepare.
In addition, the shape of the tooth | gear part 34 is as having mentioned above (refer FIGS. 13-15).

The joining process is performed in the same manner as in Example 1. However, as shown in FIGS. 13 to 15, the plastic joint part of the obtained CVT shaft is composed of the shaft part 2 and the sheave part 3, and a part of the joint outer surface part. A plastic coupling portion 402 is formed by plastic flow (plastic deformation) in a valley portion 86 formed by the pressure receiving surface 81 and the inclined surface 82 of the tooth portion 34.
In addition, the first holding portion 851 is disposed in a state where a gap 852 is provided between the first outer surface portion 211 and the joined outer surface portion 211 that has undergone plastic flow (plastic deformation).
Moreover, the 2nd holding | maintenance part 871 is arrange | positioned in the state contact | abutted to the joint outer surface part 211 which flowed plastically.
14 and 15, the outer peripheral surface 210 of the coupling outer surface portion 21 before coupling (before plastic deformation) is shown.

Next, the effect of the CVT shaft 102 of this example will be described.
Since the shaft for CVT 102 of this example processes the tooth portion by cutting in the sheave portion preparation step, the manufacturing cost is higher than the processing by the cold forging of the first embodiment. However, in the plastic coupling portion 402, the tooth portion 34 of the sheave portion 302 bites into the coupling outer surface portion of the shaft portion 2, and a part of the coupling outer surface portion is plastically flowed (plastically deformed) into the valley portion 86 of the tooth portion 34, In particular, it is possible to form the plastic coupling portion 402 that can ensure a high torsional strength. Therefore, the coupling force between the shaft portion 2 and the sheave portion 302 becomes extremely high.

In addition, the sloped surface facing portion 85 where the sloped surface 82 of the first fastening tooth 341 and the sloped surface 82 of the second fastening tooth 342 face each other is circumscribed by the valley 86 formed by the pressure receiving surface 81 and the sloped surface 82. A first holding portion 851 is provided which is located outward so as not to come out of the circle 860 and smoothly connects the facing inclined surfaces 82.
By providing the first holding portion 851 having a smooth shape on the inclined surface facing portion 85 where stress is concentrated when the shaft portion 2 and the sheave portion 302 are plastically coupled, the generated tensile stress can be reduced. Thereby, rupture, delayed fracture, misplacement and the like of the sheave portion 302 after plastic bonding can be suppressed, and the dimensional accuracy of the CVT shaft 102 can be improved.
In addition, the CVT shaft 102 of this example can obtain the same effects as those of the first embodiment.

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. Sectional drawing which shows the shaft part in Example 1. FIG. Sectional drawing which shows the sheave part in Example 1. FIG. The figure seen from the A direction of FIG. The enlarged view which looked at the H section of Drawing 4 from the A direction. 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 of the positioning of the plastic coupling process 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. Explanatory drawing which shows the measuring method of pressure | voltage resistant surface strength in Example 2. FIG. CC sectional view taken on the line of FIG. The figure which shows the evaluation result in Example 2. FIG. Explanatory drawing which shows the plastic coupling part in Example 3. FIG. The enlarged view of the E section of FIG. The enlarged view of the F section of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft for CVT 2 Shaft part 3 Sheave part 4 Plastic coupling part 5 Press-fit part

Claims (17)

A CVT shaft used in a belt type continuously variable transmission (hereinafter referred to as CVT),
The CVT shaft is formed by connecting 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 via a plastic coupling portion and a press-fit portion. Become
The sheave portion has an insertion hole into which the shaft portion is inserted, and the insertion hole has a coupling inner surface portion for forming the plastic coupling portion and a press-fit inner surface portion for forming the press-fit portion. Continuing in the direction and provided so that the press-fit inner surface portion is located on the side closer to the sheave surface,
The inner peripheral surface of the inner surface portion has a plurality of tooth portions protruding inward and having tooth traces in the axial direction,
The inner peripheral surface of the press-fitted inner surface portion is a flat surface and has an inner diameter smaller than the diameter of the inscribed circle of the tooth portion,
In addition, the sheave portion is subjected to a curing treatment for curing at least the surface of the tooth portion before being coupled to the shaft portion,
The shaft portion has a coupling outer surface portion for forming the plastic coupling portion and a press-fitting outer surface portion for forming the press-fitting portion in an axial direction.
The coupling outer surface portion has an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The press-fit outer surface portion has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion and an outer diameter larger than the inner diameter of the press-fit inner surface portion so as to allow press-fitting,
The tooth portion of the sheave portion has a surface hardness of Hv 600 or more, and is greater than the surface hardness of the coupling outer surface portion of the shaft portion by Hv 300 or more,
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. As shown in FIG. 1, a first holding part is provided that smoothly connects the inclined surfaces facing each other.
The tooth portion is bitten into the joint outer surface portion to form the plastic joint portion in which a part of the joint outer surface portion is plastically flowed, and the press-fit portion is formed by press-fitting the press-fit outer surface portion into the press-fit inner surface portion. By doing so, the shaft portion and the sheave portion are integrally coupled to each other. A CVT shaft used in a belt type continuously variable transmission (hereinafter referred to as CVT),
The CVT shaft is formed by connecting 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 via a plastic coupling portion and a press-fit portion. Become
The sheave portion has an insertion hole into which the shaft portion is inserted, and the insertion hole has a coupling inner surface portion for forming the plastic coupling portion and a press-fit inner surface portion for forming the press-fit portion. Continuing in the direction and provided so that the press-fit inner surface portion is located on the side closer to the sheave surface,
The inner peripheral surface of the inner surface portion has a plurality of tooth portions protruding inward and having tooth traces in the axial direction,
The inner peripheral surface of the press-fitted inner surface portion is a flat surface and has an inner diameter smaller than the diameter of the inscribed circle of the tooth portion,
In addition, the sheave portion is subjected to a curing treatment for curing at least the surface of the tooth portion before being coupled to the shaft portion,
The shaft portion has a coupling outer surface portion for forming the plastic coupling portion and a press-fitting outer surface portion for forming the press-fitting portion in an axial direction.
The coupling outer surface portion has an outer diameter larger than the diameter of the inscribed circle of the tooth portion,
The press-fit outer surface portion has an outer diameter smaller than the diameter of the inscribed circle of the tooth portion and an outer diameter larger than the inner diameter of the press-fit inner surface portion so as to allow press-fitting,
The tooth portion of the sheave portion has a surface hardness of Hv 600 or more, and is greater than the surface hardness of the coupling outer surface portion of the shaft portion by Hv 300 or more,
Further, the tooth portion of the sheave portion has an arc having a smaller diameter than a reference circle in which a tooth groove formed between the tooth portions is a circumscribed circle of the tooth groove in a cross section orthogonal to the axial direction, and the reference The tooth gap inscribed in the circle is configured to form a petal shape regularly arranged in the circumferential direction,
The tooth portion is bitten into the joint outer surface portion to form the plastic joint portion in which a part of the joint outer surface portion is plastically flowed, and the press-fit portion is formed by press-fitting the press-fit outer surface portion into the press-fit inner surface portion. By doing so, the shaft portion and the sheave portion are integrally coupled to each other. In claim 1 or 2 , when the inner diameter of the press-fitted inner surface is d ₁ , the diameter of the sheave is d ₂ , and the center diameter is d ₃ = (d ₁ + d ₂ ) / 2, the surface of the sheave is A shaft for CVT, wherein when a perpendicular perpendicular to the central axis is drawn from the position of the center diameter d _{3, a} position where the perpendicular intersects the inner surface of the insertion hole is a press-fitting inner surface 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%) The shaft for CVT according to any one of claims 1 to 4 , wherein the tooth portion of the sheave portion is subjected to shot peening after the curing treatment. In any 1 item | term of Claims 1-5, the recessed part which has an internal diameter larger than the internal diameter of the said tooth | gear part is formed between the said joint inner surface part and the said press-fit inner surface part of the said sheave part. Characteristic CVT shaft. In any one of Claims 1-6 , the said coupling | bonding outer surface part of the said shaft part has a 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 to 7, wherein the shaft portion has an outer collar portion having a larger outer diameter than the coupling outer surface,
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,
It is made of steel for machine structural use, and has an inner peripheral surface having axial teeth on the inner peripheral surface and a plurality of tooth portions projecting inward, and an inner peripheral surface formed of a flat surface and A sheave part preparation step of preparing a disk-shaped sheave part having an insertion hole formed in the center of a press-fitting inner surface part having an inner diameter smaller than the diameter of the inscribed circle;
A sheave portion curing process for curing at least the surface of the tooth portion;
It is made of steel for machine structural use, has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion, an outer diameter smaller than the diameter of the inscribed circle of the tooth portion, and is capable of being press-fit. A shaft portion preparation step of preparing a rod-shaped shaft portion having a press-fit outer surface portion having an outer diameter larger than the inner diameter of the press-fit inner surface portion in the axial direction;
A plastic coupling process for inserting the shaft portion into the insertion hole of the sheave portion and forming a plastic coupling portion in which the tooth portion is bitten into the coupling outer surface portion and a part of the coupling outer surface portion is plastically flowed. , and a press-fitting process of forming a press-fit portion press-fitted to the press-fit outer surface to the press-fit the inner surface portion, possess a binding step of combining integrally the shaft portion and the sheave portion,
In the sheave portion preparing step, the pressure receiving surface having an angle α with the axial plane including the axis of the shaft portion and an inclined surface having an angle β with the axial plane β (β> α) And forming a first fastening tooth in which the pressure receiving surface is positioned in the first direction in the circumferential direction and a second fastening tooth in which the pressure receiving surface is positioned in the second direction on the opposite side.
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. So as to be located outside and provide a first holding part that smoothly connects the inclined surfaces facing each other,
In the said sheave part hardening process process, the surface hardness of the said tooth | gear part of the said sheave part shall be Hv600 or more, and Hv300 or more is made larger than the surface hardness of the said coupling outer surface part of the said shaft part, The manufacture of the shaft for CVT characterized by the above-mentioned. Method. In the manufacturing method of the shaft for CVT used for CVT,
It is made of steel for machine structural use, and has an inner peripheral surface having axial teeth on the inner peripheral surface and a plurality of tooth portions projecting inward, and an inner peripheral surface formed of a flat surface and A sheave part preparation step of preparing a disk-shaped sheave part having an insertion hole formed in the center of a press-fitting inner surface part having an inner diameter smaller than the diameter of the inscribed circle;
A sheave portion curing process for curing at least the surface of the tooth portion;
It is made of steel for machine structural use, has a coupling outer surface portion having an outer diameter larger than the diameter of the inscribed circle of the tooth portion, an outer diameter smaller than the diameter of the inscribed circle of the tooth portion, and is capable of being press-fit. A shaft portion preparation step of preparing a rod-shaped shaft portion having a press-fit outer surface portion having an outer diameter larger than the inner diameter of the press-fit inner surface portion in the axial direction;
A plastic coupling process for inserting the shaft portion into the insertion hole of the sheave portion and forming a plastic coupling portion in which the tooth portion is bitten into the coupling outer surface portion and a part of the coupling outer surface portion is plastically flowed. A press-fitting process for forming a press-fitting part in which the press-fitting outer surface part is press-fitted into the press-fitting inner surface part, and a coupling step for integrally joining the shaft part and the sheave part,
In the sheave part preparing step, the tooth part of the sheave part is a cross section orthogonal to the axial direction, and the inner wall surface of the tooth gap formed between the tooth parts becomes an arc having a smaller diameter than a predetermined reference circle, The tooth gap is inscribed in the reference circle and is regularly arranged in the circumferential direction to form a petal shape,
In the sheave portion preparation step, the tooth portion of the sheave portion is an arc having a smaller diameter than a reference circle in which a tooth groove formed between the tooth portions is a circumscribed circle of the tooth groove in a cross section orthogonal to the axial direction. And the tooth gap inscribed in the reference circle is regularly arranged in the circumferential direction to form a petal shape,
In the said sheave part hardening process process, the surface hardness of the said tooth | gear part of the said sheave part shall be Hv600 or more, and Hv300 or more is made larger than the surface hardness of the said coupling outer surface part of the said shaft part, The manufacture of the shaft for CVT characterized by the above-mentioned. Method. 11. The sheave portion preparation step according to claim 9, wherein the inner surface portion of the press-fit inner surface portion is d ₁ and the center diameter is d ₃ = (d ₁ + d ₂ ) / 2. A method for producing a CVT shaft, wherein when a perpendicular perpendicular to the central axis is drawn from the position of the diameter d _{3, a} position where the perpendicular intersects the inner surface of the insertion hole is a press-fitted inner surface. In any one of claims 9-11, the shaft portion, the carbon equivalent Ceq represented by the following formula is from 0.4 or more materials, before or after the plastic coupling process, other than the binding outer surface 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 CVT according to any one of claims 9 to 12 , further comprising a shot peening treatment step of performing shot peening treatment on the tooth portion of the sheave portion after the sheave portion curing treatment step. Manufacturing method. In any one of claims 9-13, in the sheave portion preparation step, between the coupling inner surface portion and the press-fit the inner surface of the sheave portion, the recess having an inner diameter larger than the inner diameter of the teeth A method of manufacturing a shaft for CVT, characterized by comprising: In any one of claims 9-14, in the shaft portion preparation step, the coupling outer surface of the shaft portion is provided with a contact surface inclined in the outer peripheral corner portion,
In the sheave 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 9-15, in the shaft portion preparation step, onto the shaft portion is provided with an outer collar portion having a larger outer diameter than the coupling outer surface,
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 process, the outer flange portion and the tip contact surface are brought into contact with each other. The method of manufacturing a shaft for CVT according to any one of claims 9 to 16 , wherein the joining step starts plastic joining after starting the press-fitting.

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