JP2007198401A - Spline interconnecting structure, power transmission shaft and outer ring stem of constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spline interconnecting structure capable of relaxing stress on a spline root part when a spline part of a power transmission shaft is fit with a spline part of an inner ring of a constant velocity universal joint wherein a spline can be manufactured relatively easily. <P>SOLUTION: In the spline interconnecting structure, the spline 14 is formed in a member outer circumference face. After forming the spline 14, thermal treatment is conducted so that hardening depth of a part 14b except for the spline root part 14a of the spline 14 becomes deeper than the hardening depth of the spline root part 14a. Thus, increase ratio of spline diameter of the part 14b except for the spline root part 14a is larger than that of spline diameter of the spline root part 14a before and after hardening. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spline connection structure, and is particularly applicable to a power transmission shaft and an outer ring stem of a constant velocity universal joint.

  As shown in FIG. 1, the automobile drive shaft 10 or the like has constant velocity universal joints 12 and 13 connected to both ends of a power transmission shaft 11. The power transmission shaft 11 and the constant velocity universal joints 12 and 13 are, for example, splines 14 and 15 provided on the outer peripheral surface of the end portion of the power transmission shaft 11, and the inner circumferences of the inner rings 16 and 17 of the constant velocity universal joints 12 and 13. The splines 18 and 19 provided on the surface are fitted and connected. In the illustrated drive shaft 10 for an automobile, splines 22 and 23 are formed on the outer peripheral surfaces of the end portions of the outer ring stems 20 and 21 of the constant velocity universal joints 12 and 13 and connected to other members. Yes.

  Examples of spline forming methods include rolling and pressing. Rolling is a processing method in which a pair of racks are used and a spline is formed by rolling a shaft material between the racks. The press working is a working method in which a spline is formed by press-fitting a shaft end portion in an axial direction into a die provided with a spline forming portion on an inner peripheral surface. Usually, in order to obtain high torsional strength, the spline of the power transmission shaft is subjected to induction hardening after molding.

  In such a power transmission shaft, when torque is transmitted between the power transmission shaft and the inner ring of the constant velocity universal joint, stress concentrates on the spline root portion of the power transmission shaft serving as a fulcrum of torsion. For this reason, the torsional strength of the spline root portion of the power transmission shaft and the inner ring spline portion fitted to the portion tends to be insufficient.

  In addition, it is required to reduce the backlash of the drive system in order to improve the riding comfort of the automobile. In order to reduce this backlash, it is formed by adding a twist angle to the spline of the power transmission shaft to transmit power. The spline of the shaft may be fitted to the inner ring of the constant velocity universal joint. In this case, depending on the direction of torque, stress tends to concentrate on the spline root of the power transmission shaft. For this reason, the strength of the spline root portion of the power transmission shaft and the spline portion of the constant velocity universal joint fitted to the portion are likely to be insufficient.

Several methods have been proposed for the spline of the power transmission shaft as a method for solving the shortage of strength of the spline of the constant velocity universal joint that is fitted to the spline root portion of the power transmission shaft as described above. For example, in Utility Model No. 2551702, in order to reduce the stress applied to the spline root of the power transmission shaft, the tooth thickness of the spline of the power transmission shaft is gradually reduced from the shaft end toward the spline root. Has been proposed. In addition, Japanese Utility Model Publication No. 6-33220 proposes a structure in which the direction of the torsion angle is separately set with respect to the splines at both ends of the shaft in a pair of left and right drive shafts used in an automobile. Further, JP 2001-287122 A, JP 2001-323920 A, and JP 2001-343023 A each propose a shape in which the tooth thickness of the spline of the power transmission shaft is axially crowned. Yes.
Utility Model No. 2551702 No. 6-33220 JP 2001-287122 A JP 2001-323920 A JP 2001-343023 A

  To reduce stress concentration on the spline root of the power transmission shaft, the shape of the power transmission shaft spline that gradually decreases from the shaft end toward the spline root, or the spline of the power transmission shaft The shape in which the crowning is added to the tooth thickness in the axial direction makes it extremely difficult to evenly mold all the teeth into the above-mentioned shape, which requires a very expensive processing tooth tool, which causes an increase in cost.

  Further, the method of setting the direction of the twist angle separately for the splines on both sides of the power transmission shaft increases the types of products because the shapes of the splines are different on both sides. Moreover, since it is necessary to process the spline of both sides separately, productivity becomes worse. Furthermore, since it is difficult to visually discriminate the difference in torsion angle, the number of man-hours for management increases. Further, there is a risk that the power transmission shaft and the inner ring of the constant velocity universal joint are assembled by mistake in a combination in which the stress of the spline root portion of the power transmission shaft increases.

  Further, when the spline is formed by press working, the spline diameter tends to increase on the spline root side of the power transmission shaft as compared with the other portions. When the power transmission shaft and the inner ring of the constant velocity universal joint are fitted in this state, the stress due to the fitting force tends to concentrate on the spline root portion of the power transmission shaft, and it fits with the spline root portion and its part of the power transmission shaft. The strength of the inner ring spline part is likely to be insufficient.

  The spline connection structure according to the present invention is a spline connection structure in which a spline formed on one member outer peripheral surface and a spline formed on the other member inner peripheral surface are fitted to connect both members, When forming the spline on the outer peripheral surface of the member, after forming the spline, heat treatment is performed so that the quenching depth of the part excluding the spline root of the spline is deeper than the quenching depth of the spline root, before and after quenching. The feature is that the increase rate of the spline diameter of the portion excluding the spline root portion is made larger than the increase rate of the spline diameter of the spline root portion.

  According to this spline connection structure, when the spline portion of the power transmission shaft is fitted to the spline portion of the inner ring of the constant velocity universal joint, the stress applied to the spline root portion can be relieved. Also, the production of splines is relatively easy.

  Hereinafter, a spline connection structure according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the spline connecting structure 30 according to this embodiment includes splines 14 and 15 formed on the outer peripheral surface of one member 11 and splines 18 formed on the inner peripheral surface of the other members 16 and 17. 19 is connected to connect both members (11, 16) and (11, 17). As shown in FIG. 3, when splines 14 and 15 are formed on the outer peripheral surface of one member 11, after splines 14 and 15 are formed, portions excluding spline root portions 14 a and 15 a of splines 14 and 15. Heat treatment is performed so that the quenching depth of 14b and 15b is deeper than the quenching depth of the spline root portions 14a and 15a, and the spline diameter of the portions 14b and 15b excluding the spline root portions 14a and 15a is increased before and after quenching. The rate is made larger than the increase rate of the spline diameter of the spline root portions 14a and 15a.

  In the embodiment shown in FIG. 1, the spline connection structure 30 is applied to the connection structure of the power transmission shaft 11 and the stems 20 and 21 of the constant velocity universal joints 12 and 13. The spline connection structure 30 similar to the above is also applied to a spline connection structure between the splines 22 and 23 formed on the outer peripheral surface of the member and a member (for example, a hub or a side gear (not shown)) fitted thereto.

  As shown in FIG. 2, the power transmission shaft 11 has a spline 14 formed at the end. After forming the spline 14, the spline 14 is subjected to heat treatment so that the quenching depth of the portion excluding the spline root portion 14a of the spline 14 becomes deeper than the quenching depth of the spline root portion 14a. The increase rate of the spline diameter of the portion 14b excluding the spline root portion 14a is set larger than the increase rate of the spline diameter of the spline root portion 14a. In addition, although illustration is abbreviate | omitted, the same heat processing is performed also in the spline 15 of the edge part on the opposite side.

  In this embodiment, the splines 14 and 15 are formed by rolling. At this time, the spline diameter may be formed so as to be substantially uniform in the axial direction. In the heat treatment, as shown in FIG. 3, the quenching depth of the spline 14 excluding the spline root portion 14a is made deeper than the quenching depth of the spline root portion 14a. In addition, in the cross-sectional part in FIG. 3, the area | region B which changed the hatching of the outer diameter side has shown notionally the site | part which the quenching process has reached. Then, due to the property that the thermal expansion increases as the quenching depth increases, the portions 14b and 15b excluding the spline root portions 14a and 15a of the splines 14 and 15 before and after quenching are formed as shown in FIG. It becomes relatively thicker than 14a and 15a. In this embodiment, as shown in FIG. 4, the splines 14 and 15 are formed so that the spline diameters are substantially the same in the entire axial direction of the splines, and thereafter, the spline root portions 14 a of the splines 14 and 15 are obtained by quenching. , 15a, the spline diameters of the portions 14b, 15b are made thicker than the spline root portions 14a, 15a.

  Further, when the splines 14 and 15 are formed by press working, the spline diameter tends to increase from the shaft end surface side toward the spline root portions 14a and 15a as shown in FIG. In this case, as shown in FIG. 3, in the heat treatment, the quenching depth of the portions 14b and 15b excluding the spline root portions 14a and 15a of the splines 14 and 15 is deeper than the quenching depth of the spline root portions 14a and 15a. As a result, as shown in FIG. 5, the rate of increase of the spline diameter of the portions 14b and 15b excluding the spline root portions 14a and 15a is made larger than the rate of increase of the spline diameter of the spline root portions 14a and 15a. Thereby, the tendency for the spline diameter to increase from the shaft end faces 14c, 15c side toward the spline root portions 14a, 15a side is alleviated.

  For example, as shown in FIG. 6, the quenching may be performed by passing the power transmission shaft 11 through the high-frequency heating device 31 and energizing the high-frequency heating device 31. It is good to adjust by the time to make it stagnate and the output of the high frequency heating device 31. The quenching method is not limited to the above. In this manner, in the quenching operation, the spline diameters of the portions 14b and 15b excluding the spline root portions 14a and 15a and the spline root portions 14a and 15a are adjusted. Is easy.

  According to this power transmission shaft 11, as shown in FIGS. 1, 4 and 5, the rate of increase in the spline diameter of the portions 14b and 15b excluding the spline root portions 14a and 15a is increased by the heat treatment. 15a is larger than the increase rate of the spline diameter. For this reason, when the splines 14 and 15 of the power transmission shaft 11 are fitted to the spline portions 18 and 19 of the inner rings 16 and 17 of the constant velocity universal joints 12 and 13, the portion 14b excluding the spline root portions 14a and 15a. 15b is pressed into the inner rings 16 and 17 of the constant velocity universal joints 12 and 13 in a state of being compressed more than the spline root portions 14a and 15a, so that it is applied to the spline root portions 14a and 15a as shown in FIG. Stress is relieved. As a result, it is possible to eliminate insufficient strength that occurs at the spline root portion of the power transmission shaft and the inner ring spline portion that is fitted to the portion.

  The power transmission shaft according to the embodiment of the present invention has been described above, but the power transmission shaft according to the present invention is not limited to the above.

  The power transmission shaft is not limited to a solid shaft, and may be a hollow shaft as shown in FIG. Further, the quenching depth of the portion 14b excluding the spline root portion 14a is made deeper than the quenching depth of the spline root portion 14a, and the increase rate of the spline diameter of the portion 14b excluding the spline root portion 14a is determined by the spline root portion. What is necessary is just to make larger than the increase rate of the spline diameter of 14a. Accordingly, the increase rate of the spline diameter of the portion 14b excluding the spline root portion 14a does not necessarily need to be larger than the increase rate of the spline diameter of the spline root portion 14a in the entire area of the portion 14b excluding the spline root portion 14a.

  For this reason, it is not necessary for the quenching operation to bake the entire region of the portion 14b excluding the spline root portion 14a deeper than the spline root portion 14a. For example, in the case where the groove 14d is formed on the shaft end surface 14c side, if the quenching on the shaft end surface side is excessively deepened, there is a possibility that a defect such as a crack in the groove 14d occurs. For this reason, as shown in FIG.8 and FIG.9, about such a part, hardening may be made shallow or hardening may not be given.

  The present invention can be widely applied to spline connection structures, and can be applied not only to splines of power transmission shafts but also to spline connections of various members, such as splines formed on outer ring stems.

The fragmentary sectional view which shows the drive shaft for motor vehicles. The figure which shows the power transmission shaft which concerns on one Embodiment of this invention. The figure which shows the spline of the power transmission shaft which concerns on one Embodiment of this invention. The figure which shows the influence of the heat processing of the power transmission shaft which concerns on one Embodiment of this invention. The figure which shows the influence of the heat processing of the power transmission shaft which concerns on other embodiment of this invention. The figure which shows an example of a hardening process. The figure which shows the influence of the heat processing of the power transmission shaft which concerns on other embodiment of this invention. The figure which shows the spline of the power transmission shaft which concerns on other embodiment of this invention. The figure which shows the spline of the power transmission shaft which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor vehicle drive shaft 11 Power transmission shaft 12, 13 Constant velocity universal joints 14, 15 Spline 14a, 15a Spline root part 14b, 15b Part 16 except spline root part of spline Inner ring 18, 19 Spline 20, 19 Outer ring Stem 22, 23 Spline 30 Spline connection structure

Claims (4)

A spline connection structure that connects a spline formed on one member outer peripheral surface and a spline formed on the other member inner peripheral surface to connect both members,
When forming the spline on the outer peripheral surface of the one member, after forming the spline, heat treatment is performed so that the quenching depth of the portion excluding the spline root of the spline is deeper than the quenching depth of the spline root. The spline connecting structure characterized in that the increase rate of the spline diameter of the portion excluding the spline root portion before and after quenching is larger than the increase rate of the spline diameter of the spline root portion.   A power transmission shaft with splines at the ends, and after forming the spline, heat treatment is performed so that the quenching depth of the spline excluding the spline root becomes deeper than the quenching depth of the spline root. A power transmission shaft in which the increase rate of the spline diameter of the portion excluding the spline root portion is larger than the increase rate of the spline diameter of the spline root portion before and after quenching.   The outer ring stem of a constant velocity universal joint with splines formed at the end, and after forming the spline, the quenching depth of the portion excluding the spline root of the spline becomes deeper than the quenching depth of the spline root The outer ring stem of the constant velocity universal joint in which the increase rate of the spline diameter of the portion excluding the spline root portion is larger than the increase rate of the spline diameter of the spline root portion before and after quenching.   The spline connection structure according to claim 1, which is applied to a hollow shaft.