JP2011007216A - Shaft for constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact shaft for a constant velocity universal joint, which is vibration-absorbing, and improved in strength and durability.SOLUTION: The shaft for the constant velocity universal joint includes a first shaft member 10 in which a recessed groove 11 axially extending is formed in a plurality of positions in the circumferential direction of an inner diameter surface of a cylindrical portion 12, and a second shaft member 20 having a shaft 21 inserted in the cylindrical portion 12 of the first shaft member 10, wherein projections 22, 23 axially extending are formed in a plurality of circumferential positions of the outer diameter surface of the shaft 21, and housed in the recessed groove 11. A low torque transmission 30 having an elastic body 31 inserted between the recessed groove 11 of the first shaft member 10 and the projection 22 of the second shaft member 20 is provided between the cylindrical portion 12 and the shaft 21, and a high torque transmission 40 having a gap formed between the recessed groove 11 of the first shaft member 10 and the projection 23 of the second shaft member 20 is provided in the axial position different from the low torque transmission 30 between the cylindrical portion 12 and the shaft 21 so that the low torque transmission 30 remains in an uncured state.

Description

  The present invention relates to a constant velocity universal joint shaft that is used in a power transmission system of, for example, an automobile, an aircraft, a ship, and various industrial machines and connects two axes of a driving side and a driven side.

  For example, in a power transmission system of an automobile, transmission gear vibrations, particularly differential gear meshing vibrations are generated when the automobile is running due to variations in manufacturing accuracy of transmission gears and differential gears. In this case, this vibration is transmitted to the axle and further transmitted to the vehicle body via the front hub and the front suspension, which may cause a problem that the passenger hears an unpleasant sound. In particular, when the vehicle speed, that is, the rotational speed of the drive axle is close to the natural frequency of the torsional vibration of the drive system, the drive system resonates, and this vibration is transmitted to the vehicle body via the front suspension, etc. It becomes.

  Therefore, conventionally, an automobile drive axle aimed at reducing this kind of vibration has been proposed (for example, see Patent Document 1).

  This drive axle has a spline-shaped first engagement portion provided on one opening side of the inner diameter surface and a connecting member provided with a spline-shaped second engagement portion on the other opening side of the inner diameter surface. And a first shaft member in which the first engaged portion is provided at one end portion of the outer diameter surface, and a second shaft member in which the second engaged portion is provided at one end portion of the outer diameter surface. Yes.

  In the driving axle configured as described above, the first engaged portion of the first shaft member is engaged with the first engaging portion of the connecting member via the elastic body, and the second engaged portion of the connecting member is the second engaging portion. A structure in which the second engaged portion of the biaxial member is engaged via an elastic body is provided. By providing such a structure, vibration transmitted to the drive system is reduced.

No. 5-1442

  By the way, in the drive axle for automobiles disclosed in Patent Document 1 described above, the first engaged portion of the first shaft member engages with the first engaging portion of the connecting member via the elastic body, and the connecting member. By providing the second engaging portion with a structure in which the second engaged portion of the second shaft member is engaged through an elastic body, vibration transmitted to the drive system is reduced.

  However, it is difficult to ensure the strength and durability of the elastic body when a high torque is applied when the vehicle starts. That is, in order to ensure the strength and durability of the elastic body, it is necessary to increase the size diameter of the shaft, which increases the diameter of the shaft, increases the weight, and increases the cost of the product.

  Accordingly, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to provide a compact constant velocity universal joint shaft capable of reducing vibration and improving strength and durability. There is to do.

  As a technical means for achieving the above-mentioned object, the constant velocity universal joint shaft according to the present invention is a first in which concave grooves extending in the axial direction are formed at a plurality of locations in the circumferential direction of the inner diameter surface of the cylindrical portion. The shaft member has a shaft-like portion inserted and arranged in the cylindrical portion of the first shaft member, and protrusions extending in the axial direction are formed and recessed at a plurality of circumferential positions on the outer diameter surface of the shaft-like portion. A low torque transmission portion comprising a second shaft member housed in the groove and having an elastic body interposed between the concave groove of the first shaft member and the protrusion of the second shaft member. And a gap between the groove of the first shaft member and the protrusion of the second shaft member at an axial position different from that of the low torque transmission portion between the tubular portion and the shaft portion. The formed high torque transmission part is provided, and the low torque transmission part is in an uncured state.

  In the constant velocity universal joint shaft according to the present invention, the torque formed by the high torque transmitting portion between the concave groove of the first shaft member and the protrusion of the second shaft member can be maintained (at the time of low torque operation). ) Transmits torque through the elastic body between the groove of the first shaft member and the protrusion of the second shaft member at the low torque transmission portion, and the elastic body is deformed to When the torque action cannot be maintained (during high torque action), the concave groove of the first shaft member and the protrusion of the second shaft member are in direct contact with each other at the high torque transmission portion to transmit torque.

  Thus, since low torque is transmitted through the elastic body during low torque operation, vibration can be reduced, and during high torque operation, the high torque transmission unit can be connected without using the elastic body of the low torque transmission unit. Therefore, it is easy to secure the strength and durability of the elastic body in the low torque transmission portion, and the shaft can be made compact.

  Further, since the low torque transmitting portion is in an uncured state, the groove of the first shaft member and the protrusions of the second shaft member are not deformed by heat due to the curing process. Sometimes it becomes easy to insert an elastic body between the concave groove of the first shaft member and the protrusion of the second shaft member in the low torque transmission portion, and the assembly of the elastic body is improved. Further, the elastic body can be evenly interposed between the concave groove of the first shaft member and the protrusion of the second shaft member. Further, when the elastic body is inserted, a scale is difficult to be generated, and a scale removing step is not necessary.

  In this invention, it is desirable to make the opening edge part of the cylindrical part of a 1st shaft member into the state of an unhardened process. If it does in this way, since an opening end part does not change with the heat by hardening processing, it becomes easy to insert a 2nd axis member to the 1st axis member at the time of an assembly of a shaft, and it is the 2nd to the 1st axis member. Assembling property of the shaft member is improved, and occurrence of burning cracks at the opening end portion of the first shaft member can be prevented in advance.

  In the present invention, it is desirable to perform a curing process on the high torque transmission unit. If it does in this way, the abrasion resistance of the site | part which the ditch | groove of the 1st shaft member in the high torque transmission part and the protrusion of the 2nd shaft member contact directly can be improved.

  In the present invention, it is desirable that the curing ratio at the bottom of the groove in the high torque transmission portion of the first shaft member is larger than the curing ratio at the side wall of the groove. In this way, the torsional fatigue strength of the shaft can be ensured, and the curing process can be completed in a short time. Here, the above-mentioned “curing ratio” means the ratio of the effective curing depth to the thickness at the groove bottom and the groove sidewall.

  For example, it is preferable that the curing ratio at the bottom of the groove in the high torque transmission portion of the first shaft member is 1 and the curing ratio at the side wall of the groove is 0.3 to 0.8. In this way, it becomes much easier to ensure the torsional fatigue strength of the shaft and shorten the curing process time. If the curing ratio at the bottom of the groove is smaller than 1 or the curing ratio at the side wall of the groove is smaller than 0.3, it is difficult to ensure the torsional fatigue strength of the shaft. Moreover, when the hardening ratio in a groove side wall part is larger than 0.8, shortening of hardening processing time will become difficult.

  In the present invention, it is desirable that the carbon content of the first shaft member and the second shaft member is 0.15 to 0.46%. If it does in this way, it will become easy to reduce material cost. When the material carbon content is less than 0.15%, the hardness of the first shaft member and the second shaft member is lowered and wear proceeds remarkably, and when the material carbon content is greater than 0.46%, The inter-workability is remarkably lowered, making it difficult to manufacture the first shaft member and the second shaft member.

  In the present invention, when a structure in which a shaft-like member is friction-welded to the end portion of the cylindrical portion is provided, it is desirable that the end portion of the cylindrical portion, that is, the friction-welded portion is separated from the low torque transmission portion by 30 mm or more. . If it does in this way, it can control that the elastic body of a low torque transmission part receives the bad influence of the heat which arises at the time of friction welding.

  In this invention, it is desirable to provide the taper part which diameter-expands toward the opening end part in the opening end part internal diameter of the cylindrical part of a 1st shaft member. In this way, when the high torque transmission part is disposed on the opening side of the cylindrical part of the first shaft member, the concave groove of the first shaft member and the protrusion of the second shaft member in the high torque transmission part Since the contact portion is located in the aforementioned tapered portion, the stress concentration in the opening of the cylindrical portion of the first shaft member during torque transmission can be reduced.

  In the present invention, it is desirable to provide the concave grooves of the first shaft member and the protrusions of the second shaft member at 3 to 6 locations in the circumferential direction. In this way, torque transmission between the first shaft member and the second shaft member can be efficiently performed, and the concave grooves of the first shaft member and the protrusions of the second shaft member can be easily formed. It becomes.

  In the present invention, it is desirable that the ratio of the outer diameter of the cylindrical portion of the first shaft member to the shaft-shaped portion diameter of the second shaft member is 1.8 to 2.4. This is effective in terms of securing torsional rigidity of the elastic body and vehicle assembly. Note that if the ratio of the outer diameter of the cylindrical portion of the first shaft member to the shaft-shaped portion diameter of the second shaft member is smaller than 1.8, the torsional rigidity of the elastic body becomes low and vibration due to impact torque cannot be reduced. If the ratio is larger than 2.4, it interferes with other parts when assembled in the vehicle.

  In the present invention, it is desirable that the inscribed circle diameter of the high torque transmission portion of the second shaft member is larger than the shaft-shaped portion diameter of the second shaft member. This is effective in terms of strength and durability of the high torque transmission portion.

  In the present invention, the inscribed circle diameter of the low torque transmitting portion of the second shaft member is made smaller than the inscribed circle diameter of the high torque transmitting portion of the second shaft member, and the inscribed circle of the low torque transmitting portion of the second shaft member is It is desirable that the ratio of the outer diameter of the cylindrical portion of the first shaft member to the diameter is 1.8 to 2.8. This is effective in terms of the torsional rigidity of the elastic body and the vehicle assembly property. Note that if the ratio of the outer diameter of the cylindrical portion of the first shaft member to the inscribed circle diameter of the low torque transmission portion of the second shaft member is smaller than 1.8, the torsional rigidity of the elastic body is lowered and vibration due to impact torque is caused. If the ratio cannot be reduced and the ratio is larger than 2.8, it will interfere with other parts when assembled to the vehicle.

  According to the present invention, a low torque transmission portion having an elastic body interposed between the concave groove of the first shaft member and the protrusion of the second shaft member is provided between the tubular portion and the shaft portion, A high torque transmission portion in which a gap is formed between the concave groove of the first shaft member and the protrusion of the second shaft member at an axial position different from the low torque transmission portion between the cylindrical portion and the shaft portion. By providing the low torque, the low torque is transmitted through the elastic body when the low torque is applied, so that vibration can be reduced. Moreover, the vibration can be reduced even with respect to the initial vibration at the time of the torque action and the vibration due to the impact torque. In addition, when high torque is applied, torque is transmitted by the high torque transmission portion without using the elastic body of the low torque transmission portion, so that it is easy to ensure the strength and durability of the elastic body, and the shaft can be made compact. .

  Further, since the low torque transmitting portion is in an uncured state, the groove of the first shaft member and the protrusions of the second shaft member are not deformed by heat due to the curing process. Sometimes it becomes easy to insert an elastic body between the concave groove of the first shaft member and the protrusion of the second shaft member in the low torque transmission part, the assembly of the elastic body is improved, and the productivity of the shaft is improved. Can be planned. Moreover, an elastic body can be evenly interposed between the concave groove of the first shaft member and the protrusion of the second shaft member, and a stable quality shaft can be provided. Furthermore, when an elastic body is inserted, scales are not easily generated, and a scale removal step is not necessary, so that the cost of the product can be reduced.

It is a longitudinal cross-sectional view which shows the shaft for constant velocity universal joints comprised by the 1st shaft member and the 2nd shaft member in embodiment of this invention. (A) is a longitudinal cross-sectional view which shows the 1st shaft member of FIG. 1, (b) is a left view of (a). (A) is the front view which shows the 2nd shaft member of FIG. 1, (b) is a cross-sectional view which follows the AA line of (a), (c) is a cross section which follows the BB line of (a). FIG. It is a longitudinal cross-sectional view which shows the drive shaft which connected the constant velocity universal joint to the both ends of the shaft of FIG. It is a cross-sectional view which follows the CC line of FIG. It is a cross-sectional view which follows the DD line | wire of FIG. It is a cross-sectional view which shows the hardening process state in the high torque transmission part of a 1st shaft member.

  Embodiments of the constant velocity universal joint shaft according to the present invention will be described in detail below. 1 shows a constant velocity universal joint shaft 1 composed of a first shaft member 10 and a second shaft member 20, and FIGS. 2A and 2B show the constant velocity universal joint shaft 1 shown in FIG. The first shaft member 10, FIGS. 3A to 3C are the second shaft member 20 of the constant velocity universal joint shaft 1 shown in FIG. 1, and FIG. 4 is a constant velocity universal joint at both ends of the shaft 1 of FIG. The connected drive shaft is shown.

  1-3, the constant velocity universal joint shaft 1 of the embodiment shown in FIG. 1 has a plurality of circumferentially extending concave grooves 11 on the inner surface of the cylindrical portion 12 (four locations at 90 ° pitch in the figure). The first shaft member 10 is formed on the first shaft member 10, and the shaft portion 21 is inserted into the cylindrical portion 12 of the first shaft member 10. The main part is composed of the second shaft member 20 formed at a plurality of locations in the circumferential direction of the outer diameter surface (four locations at a pitch of 90 ° in the figure) and accommodated in the groove 11 of the first shaft member 10. .

  As shown in FIG. 2A, the shaft-shaped member 13 is joined and integrated to the end portion (right side in the drawing) of the cylindrical portion 12 of the first shaft member 10 by friction welding. A spline 14 is formed on the outer diameter surface of the end portion of the shaft-like member 13 as shown in FIG. 1, and the sliding type constant velocity universal joint 50 is connected so as to be able to transmit torque with a fitting structure by the spline 14. (See FIG. 4). Moreover, the taper part 15 diameter-expanded toward the opening end part 12a is formed in the internal diameter of the opening end part 12a of the cylindrical part 12 of the 1st shaft member 10. As shown in FIG. The concave groove 11 formed in the inner diameter surface of the cylindrical portion 12 of the first shaft member 10 includes a pair of side wall surfaces 16 and a bottom surface 17 that connects both side wall surfaces 16 as shown in FIG. Yes.

  As shown in FIG. 3A, the second shaft member 20 includes a shaft-shaped portion 21 (right side in the drawing) that is inserted into the tubular portion 12 of the first shaft member 10, and a tubular portion of the first shaft member 10. 12 (see FIG. 1), and the outer surface of the former shaft-shaped portion 21 has a circumferentially wide protrusion 23 [FIG. 3 (c). )] And a circumferentially narrow ridge 22 (see FIG. 3B) extending continuously from the ridge 23 toward the shaft end side (see FIG. 3B) at a plurality of locations in the circumferential direction (at 90 ° pitch in the figure). 4 places). A spline 25 is formed on the outer diameter surface of the end portion of the latter shaft-shaped portion 24 as shown in FIGS. 1 and 3A, and the fixed type constant velocity universal joint 60 has a fitting structure by the spline 25. Are coupled so that torque can be transmitted (see FIG. 4).

The shaft portion 21 of the second shaft member 20 is inserted into the tubular portion 12 of the first shaft member 10 described above, and the protrusions 22 and 23 of the shaft portion 21 are accommodated in the concave groove 11 of the tubular portion 12. Thus, the first shaft member 10 and the second shaft member 20 are assembled to form the constant velocity universal joint shaft 1. At this time, the outer diameter d ₁ of the cylindrical portion 12 of the first shaft member 10 (see FIG. 2A) with respect to the outer diameter d ₂ of the shaft-shaped portion 24 of the second shaft member 20 (see FIG. 3A). The ratio d ₁ / d ₂ is 1.8 to 2.4.

Thus, by defining the range of the ratio d ₁ / d ₂ , it is effective in terms of ensuring the torsional rigidity of the elastic body and the ease of assembling the vehicle. In addition, if the ratio d ₁ / d ₂ of the outer diameter d ₁ of the cylindrical portion 12 of the first shaft member 10 to the outer diameter d ₂ of the shaft-shaped portion 24 of the second shaft member 20 is smaller than 1.8, it is elastic. The torsional rigidity of the body becomes low and vibration due to impact torque cannot be reduced. If the ratio d ₁ / d ₂ is larger than 2.4, it interferes with other parts when assembled to the vehicle.

  As shown in FIG. 1, in the constant velocity universal joint shaft 1 in which the first shaft member 10 and the second shaft member 20 are assembled, the concave groove 11 of the tubular portion 12 of the first shaft member 10 and the second shaft member 20. A low torque transmission portion 30 is formed by the narrow protrusion 22 of the shaft-shaped portion 21, and the axial position is different from that of the low torque transmission portion 30, that is, a position adjacent to the low torque transmission portion 30 in the axial direction. The high torque transmission portion 40 is configured by the concave groove 11 of the cylindrical portion 12 of the first shaft member 10 and the wide protrusion 23 of the shaft portion 21 of the second shaft member 20.

In addition, the inscribed circle diameter d ₄ of the high torque transmission portion 40 of the second shaft member 20 (see FIG. 3C) is made larger than the outer diameter d ₂ of the shaft-like portion 24 of the second shaft member 20. By doing in this way, it becomes effective at the point which ensures the intensity | strength and durability of the high torque transmission part 40. FIG.

Further, the ratio d ₁ / d of the outer diameter d ₁ of the cylindrical portion 12 of the first shaft member 10 to the inscribed circle diameter d ₃ of the low torque transmission portion 30 of the second shaft member 20 (see FIG. 3B). ₃ is set to 1.8 to 2.8. This is effective in terms of torsional rigidity of the elastic body and ease of assembly to the vehicle. When the ratio d ₁ / d ₃ of the outer diameter d ₁ of the cylindrical portion 12 of the first shaft member 10 to the inscribed circle diameter d ₃ of the low torque transmission portion 30 of the second shaft member 20 is smaller than 1.8. The torsional rigidity of the elastic body becomes low and vibration due to impact torque cannot be reduced. If the ratio is larger than 2.8, it interferes with other parts when assembled to the vehicle.

In the low torque transmission portion 30, the width of the protrusion 22 of the shaft portion 21 of the second shaft member 20 is larger than the width dimension W of the concave groove 11 of the tubular portion 12 of the first shaft member 10 as shown in FIG. The dimension W ₁ is set small, and an elastic body 31 is interposed between the side wall surface 16 of the concave groove 11 of the first shaft member 10 and the side wall surface 27 of the protrusion 22 of the second shaft member 20. The elastic body 31 only needs to exhibit an elastic function without being deteriorated in the usage environment of the shaft 1. For example, various rubbers such as nitrile rubber, acrylic rubber, natural rubber, or silicone rubber, mixed rubber, and resin Can be used. In this embodiment, the bottom surface 17 of the groove 11 of the first shaft member 10 and the tip surface 26 of the protrusion 22 of the second shaft member 20 are subjected to a bending load on the shaft without the elastic body 31 interposed. Although it is configured to come into contact with it, an elastic body may be interposed because of the cost of removing burrs from the rubber.

In the high torque transmission part 40, the width of the protrusion 23 of the shaft part 21 of the second shaft member 20 is larger than the width dimension W of the groove 11 of the cylindrical part 12 of the first shaft member 10 as shown in FIG. The dimension W ₂ is set to be slightly small, and a slight gap 41 is formed between the side wall surface 16 of the groove 11 and the side wall surface 29 of the ridge 23. In this embodiment, the bottom surface 17 of the concave groove 11 of the first shaft member 10 and the tip surface 28 of the protrusion 23 of the second shaft member 20 form a gap, and when a bending load acts on the shaft, It has a structure that suppresses bending by contact.

  As shown in FIG. 1, in the structure in which the shaft-like member 13 is joined and integrated to the end of the cylindrical portion 12 by friction welding, the friction welding portion m located at the end of the cylindrical portion 12 is transmitted with low torque. 30 mm or more away from the portion 30 (axial dimension L> 30 mm in the figure). Thereby, it can suppress that the elastic body 31 of the low torque transmission part 30 receives the bad influence of the heat which arises at the time of the friction welding of the shaft-shaped member 13. FIG.

  In the constant velocity universal joint shaft 1 configured as described above, the gap 41 formed between the concave groove 11 of the first shaft member 10 and the protrusion 23 of the second shaft member 20 in the high torque transmission unit 40 is maintained. At the time of the torque action that can be performed, that is, at the time of low torque action, the elasticity between the side wall surface 16 of the concave groove 11 of the first shaft member 10 and the side wall surface 27 of the protrusion 22 of the second shaft member 20 is reduced. Torque is transmitted through the body 31. At this time, in the high torque transmission unit 40, a gap 41 is formed between the side wall surface 16 of the concave groove 11 of the first shaft member 10 and the side wall surface 29 of the ridge 23 of the second shaft member 20. Therefore, torque is not transmitted.

  On the other hand, when a high torque is input at the time of starting the automobile, the elastic body 31 interposed between the concave groove 11 of the first shaft member 10 and the protrusion 22 of the second shaft member 20 in the low torque transmission unit 30. Is deformed into a flat shape and the gap 41 of the high torque transmission unit 40 cannot be maintained. As described above, when the elastic body 31 is deformed so that the above-described gap 41 cannot be maintained, that is, when the torque is high, that is, when the high torque is applied, the high torque transmission portion 40 and the side wall surface 16 of the concave groove 11 of the first shaft member 10 Torque is transmitted by direct contact with the side wall surface 29 of the protrusion 23 of the shaft member 20. In this way, high torque is transmitted in a state where the side wall surface 16 of the groove 11 and the side wall surface 29 of the ridge 23 are in pressure contact with each other by the high torque transmission unit 40, and thus the elastic body 31 of the low torque transmission unit 30. It is never transmitted.

  As described above, since the torque is transmitted by the low torque transmission unit 30 via the elastic body 31 during the low torque operation, the elastic body 31 can reduce vibration. Moreover, the vibration can be reduced even with respect to the initial vibration at the time of the torque action and the vibration due to the impact torque. In addition, when high torque is applied, torque is transmitted by the high torque transmission unit 40 without passing through the elastic body 31 of the low torque transmission unit 30, and thus high torque is not transmitted to the elastic body 31, so that the strength and durability of the elastic body 31 are increased. It becomes easy to ensure.

  Since the low torque transmission unit 30 is only loaded with a low torque, the function as the constant velocity universal joint shaft 1 is not impaired even without performing a hardening process by heat treatment such as induction hardening. Therefore, in this embodiment, the concave groove 11 of the first shaft member 10 and the protrusion 22 of the second shaft member 20 in the low torque transmission unit 30 are not subjected to hardening treatment, and the side wall surface 16 and the protrusion 22 of the recess groove 11. Thus, a hardened surface layer is not formed on the side wall surface 27.

  Accordingly, the side wall surface 16 of the concave groove 11 and the side wall surface 27 of the protrusion 22 are not deformed by heat due to the curing process. Therefore, the concave groove of the first shaft member 10 in the low torque transmission unit 30 is assembled when the shaft 1 is assembled. It becomes easy to insert the elastic body 31 between 11 and the protrusion 22 of the 2nd shaft member 20, the assembly property of the elastic body 31 improves, and the improvement of the productivity of the shaft 1 can be aimed at. Further, the elastic body 31 can be evenly interposed between the concave groove 11 of the first shaft member 10 and the protrusion 22 of the second shaft member 20, and the shaft 1 with stable quality can be provided. Further, when the elastic body 31 is inserted, a scale is hardly generated and a scale removing step is not necessary, so that the cost of the product can be reduced.

  Similarly, the opening end portion 12a of the cylindrical portion 12 of the first shaft member 10 does not impair the function as the constant velocity universal joint shaft 1 without performing a hardening process by heat treatment such as induction hardening. The opening end 12a of the cylindrical portion 12 of the first shaft member 10 is not cured, and a surface hardened layer is not formed on the opening end 12a.

  Thereby, since the open end 12a of the cylindrical portion 12 of the first shaft member 10 is not deformed by heat due to the curing process, the second shaft member 20 is inserted into the first shaft member 10 when the shaft 1 is assembled. As a result, the assembly of the second shaft member 20 with respect to the first shaft member 10 is improved, and the occurrence of burning cracks at the open end 12a of the cylindrical portion 12 can be prevented in advance. Improvement can be achieved.

  The low torque transmitting portion 30 and the opening end portion 12a of the cylindrical portion 12 of the first shaft member 10 are not subjected to heat treatment such as induction hardening, whereas the high torque transmitting portion 40 is used when the vehicle is started. Since high torque is applied in such a case, the high torque transmission unit 40 is subjected to a heat treatment such as induction hardening so that the high torque transmission unit 40 is cured. That is, as shown by cross hatching in FIG. 7, the groove bottom 18 and the groove sidewall 19 of the cylindrical portion 12 of the first shaft member 10 in the high torque transmission portion 40 are heat-treated by induction hardening. In addition, although not shown in figure, the protrusion 23 of the shaft-shaped part 21 of the 2nd shaft member 20 in the high torque transmission part 40 is also heat-processed by induction hardening. Thereby, the abrasion resistance of the site | part which the ditch | groove 11 of the 1st shaft member 10 in the high torque transmission part 40 and the protrusion 23 of the 2nd shaft member 20 contact directly can be improved.

  This induction hardening can be easily achieved by heating from the outer diameter side of the cylindrical portion 12 of the first shaft member 10, and forms a hardened surface layer having a hardness of about 350 to 600 HV. In this induction hardening, the curing ratio at the groove bottom 18 in the high torque transmission portion 40 of the first shaft member 10 is made larger than the curing ratio at the groove sidewall 19. Thereby, the torsional fatigue strength of the shaft 1 can be ensured and the curing process can be completed in a short time. Here, the above-mentioned “curing ratio” means the ratio of the effective curing depth to the thickness at the groove bottom 18 and the groove sidewall 19.

  In this embodiment, for example, the curing ratio at the groove bottom 18 in the high torque transmission unit 40 of the first shaft member 10 is 1, and the curing ratio at the groove sidewall 19 is 0.3 to 0.8. And That is, as shown by cross hatching in FIG. 7, the groove bottom 18 is fully cured, and the groove sidewall 19 is cured leaving the innermost diameter portion. This makes it easier to ensure the torsional fatigue strength of the shaft 1 and shorten the curing processing time. If the curing ratio at the groove bottom 18 is smaller than 1 or the curing ratio at the groove sidewall 19 is smaller than 0.3, it is difficult to ensure the torsional fatigue strength of the shaft 1. Moreover, when the hardening ratio in the groove side wall part 19 is larger than 0.8, it becomes difficult to shorten the hardening processing time.

  Here, in order to achieve optimal induction hardening, the carbon content of the first shaft member 10 and the second shaft member 20 is set to 0.15 to 0.46%. Thereby, it becomes easy to reduce material cost. When the material carbon content is less than 0.15%, the hardness of the first shaft member 10 and the second shaft member 20 is reduced, and wear progresses remarkably, and when the material carbon content is greater than 0.46%. As a result, the cold workability is remarkably lowered, making it difficult to manufacture the first shaft member 10 and the second shaft member 20.

  As shown in FIGS. 1 and 2 (a), the inner diameter of the open end 12a of the tubular portion 12 of the first shaft member 10 where the high torque transmitting portion 40 is located is expanded toward the open end 12a. A tapered portion 15 is provided. In the structure in which the high torque transmission portion 40 is disposed on the opening side of the tubular portion 12 of the first shaft member 10 by the taper portion 15, the concave groove 11 of the first shaft member 10 in the high torque transmission portion 40 and the second Since the contact part with the protrusion 23 of the biaxial member 20 is located in the above-mentioned taper part 15, the stress concentration at the time of torque transmission can be relieved.

  In the above-described embodiment, the concave groove 11 of the first shaft member 10 and the protrusions 22 and 23 of the second shaft member 20 are provided at four locations at a 90 ° pitch in the circumferential direction. 16 and the side walls 27 and 29 of the ridges 22 and 23 are evenly torqued to stabilize torque transmission. However, as another embodiment, the concave groove 11 of the first shaft member 10 and the protrusions 22 and 23 of the second shaft member 20 may be provided at three, five, or six locations in the circumferential direction. Thereby, while being able to relieve | moderate the load concerning the torque transmission part between the 1st shaft member 10 and the 2nd shaft member 20, the groove | channel 11 of the 1st shaft member 10 and the protrusion 22 of the 2nd shaft member 20, Formation of 23 becomes easy.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the gist of the present invention. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 10 1st shaft member 11 Groove | groove 12 Tubular part 12a Open end 13 Shaft-shaped member 15 Tapered part 18 Groove bottom part 19 Groove side wall part 20 Second shaft member 21 Shaft-like part 22, 23 Projection 24 Shaft-like part 30 Low torque transmission part 31 Elastic body 40 High torque transmission part 41 Crevice

Claims (12)

  A first shaft member in which concave grooves extending in the axial direction are formed at a plurality of locations in the circumferential direction of the inner diameter surface of the cylindrical portion, and a shaft-shaped portion that is inserted and disposed in the cylindrical portion of the first shaft member; A protrusion extending in the axial direction includes a second shaft member formed at a plurality of locations in the circumferential direction of the outer diameter surface of the shaft-shaped portion and accommodated in the groove, and the groove of the first shaft member and the A low torque transmission part having an elastic body interposed between the protrusions of the second shaft member is provided between the cylindrical part and the shaft-like part, and between the cylindrical part and the shaft-like part, A high torque transmission part having a gap formed between the groove of the first shaft member and the protrusion of the second shaft member is provided at a different axial position from the low torque transmission part, and the low torque transmission part is uncured. A shaft for a constant velocity universal joint, characterized in that   The constant velocity universal joint shaft according to claim 1, wherein the opening end portion of the cylindrical portion of the first shaft member is in an uncured state.   The constant velocity universal joint shaft according to claim 1, wherein the high torque transmission portion is cured.   The constant velocity universal joint shaft according to claim 3, wherein a curing ratio at the bottom of the concave groove in the high torque transmission portion of the first shaft member is larger than a curing ratio at the side wall of the concave groove.   5. The constant velocity according to claim 4, wherein a curing ratio at the bottom of the groove in the high torque transmission portion of the first shaft member is 1 and a curing ratio at the side wall of the groove is 0.3 to 0.8. Universal joint shaft.   The shaft for a constant velocity universal joint according to any one of claims 1 to 5, wherein a material carbon amount of the first shaft member and the second shaft member is 0.15 to 0.46%.   The shaft for a constant velocity universal joint according to any one of claims 1 to 6, wherein a shaft-shaped member is friction-welded to an end portion of a cylindrical portion that is separated from the low torque transmission portion by 30 mm or more.   The shaft for a constant velocity universal joint according to any one of claims 1 to 7, wherein a taper portion whose diameter is increased toward the opening end portion is provided on an inner diameter of the opening end portion of the cylindrical portion of the first shaft member. .   The shaft for constant velocity universal joints as described in any one of Claims 1-8 which provided the groove of the said 1st shaft member and the protrusion of the said 2nd shaft member in the circumferential direction 3-6 places. The ratio d ₁ / d ₂ of the outer diameter d ₁ of the cylindrical portion of the first shaft member to the shaft-shaped portion diameter d ₂ of the _second shaft member is set to 1.8 to 2.4. A shaft for a constant velocity universal joint according to claim 1.   The shaft for constant velocity universal joints as described in any one of Claims 1-10 which made the inscribed circle diameter of the high torque transmission part of said 2nd shaft member larger than the shaft-shaped part diameter of a 2nd shaft member. The ratio d ₁ / d ₃ of the outer diameter d ₁ of the cylindrical portion of the first shaft member to the inscribed circle diameter d ₃ of the low torque transmission portion of the second shaft member is set to 1.8 to 2.8. The shaft for constant velocity universal joints as described in any one of 1-11.

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