JP2006045605A - Method for manufacturing hollow-state power transmitting shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a hollow-state power transmitting shaft with which even when there are differences in thickness and in hardening rate in the axial direction, stable quality can be secured. <P>SOLUTION: A high frequency induction hardening is conducted from the outer peripheral surface 1g side by externally arranging a moving type induction heating coil 5 at the outer peripheral surface 1g side of a hollow-state shaft blank 1' and moving this coil in the axial direction while making the high frequency current of a prescribed frequency flow to the induction heating coil 5. At this time, to the small diameter part 1b of a comparatively thick thickness, the frequency of the high frequency current made to flow to the induction heating coil 5 is made relatively low, and to the large diameter part 1a of a comparatively thin thickness, the frequency of the high frequency current made to flow to the induction heating coil 5 is made relatively high. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a hollow power transmission shaft connected to a joint such as a constant velocity universal joint. The hollow power transmission shaft manufactured by the manufacturing method of the present invention can be applied to, for example, a drive shaft (drive shaft) and a propeller shaft (propulsion shaft) that constitute a power transmission system of an automobile.

  For example, in a power transmission system of an automobile, a power transmission shaft that transmits power from a speed reducer (differential) to drive wheels may be called a drive shaft (drive shaft). In particular, a drive shaft used in an FF vehicle requires a large operating angle and constant velocity during front wheel steering, and also requires a function of absorbing axial displacement in relation to the suspension system. Is connected to the reducer side through a sliding type constant velocity universal joint such as a double offset type constant velocity universal joint or a tripod type constant velocity universal joint, and the other end is connected to a barfield type constant velocity universal joint (Zepper joint). In many cases, a mechanism that is connected to the drive wheel side via a fixed-side constant velocity universal joint is employed.

  As a drive shaft as described above, a solid shaft is often used in the past and now, but the weight of the car is improved, the function is improved by increasing the rigidity of the drive shaft, and the tuning of the bending primary natural frequency is optimized. Recently, there has been an increasing demand for a drive shaft to be a hollow shaft from the viewpoint of improving the quietness of the interior of the vehicle.

  As a hollow power transmission shaft applied to a drive shaft or the like, for example, those described in Patent Documents 1 to 3 below are known.

  In Patent Document 1, the inner peripheral surface of the hollow shaft is heat-cured over almost the entire region in the axial direction. This thermosetting treatment is performed on the entire depth region from the outer peripheral surface to the inner peripheral surface, for example, by induction hardening and tempering from the outer peripheral surface side of the hollow shaft (see paragraph number 0012 of the same document). ).

  In Patent Document 2, for example, thermosetting treatment is performed on the entire depth region from the outer peripheral surface to the inner peripheral surface over almost the entire axial direction of the hollow shaft by induction hardening and tempering (paragraph of the same document). No. 0012).

In Patent Document 3, in order to make the static strength and torsional fatigue strength of the hollow shaft higher than that of the solid shaft, the hollow shaft is induction-hardened at a quenching rate of 0.7 to 0.9.
JP 2002-349538 A JP 2002-356742 A JP 2003-90325 A

  In general, this kind of hollow power transmission shaft is formed with a large diameter portion and a relatively thin wall in the axial direction in order to achieve high rigidity and light weight, and a small diameter portion on both sides in the axial direction ensures strength. Therefore, it is formed relatively thick. Thus, since this type of hollow power transmission shaft has a thickness difference in the axial direction, it is difficult to set quenching conditions, and stable quality may not be ensured by heat treatment. That is, when the quenching conditions are set in accordance with the relatively thin large-diameter portion, the hardened layer depth may be insufficient at the relatively thick small-diameter portion, and the required strength may not be obtained. On the other hand, when quenching conditions are set in accordance with a relatively thick and small-diameter portion, the relatively thin-walled and large-diameter portion is overheated, and the quenched structure may become coarse and cause a decrease in strength. .

  Further, in this type of hollow power transmission shaft, in order to increase the strength balance and the like, for example, the quenching rate (ratio between the depth of the hardened layer and the thickness) may be changed between the large diameter portion and the small diameter portion, The conventional manufacturing method may have the same disadvantages as described above.

  The subject of this invention is providing the manufacturing method of the hollow-shaped power transmission shaft which can ensure the stable quality, even when there is a difference in thickness or a quenching rate in the axial direction.

  In order to solve the above-described problems, the present invention provides a method for manufacturing a hollow power transmission shaft in which an axially intermediate portion is formed in a large diameter portion, and both axial side portions are formed in small diameter portions with respect to the large diameter portion. The pipe material is plastically processed to form a hollow shaft material having a large diameter portion and a small diameter portion, and a high frequency current is generated in a predetermined region and other regions with respect to the hollow shaft material. A configuration for performing induction hardening by changing the frequency is provided.

  In general, induction hardening is a heat treatment method in which the vicinity of the surface of a steel material is heated using electromagnetic induction by high frequency current, and induction current (eddy current) generated by electromagnetic induction is a high frequency that leads to an induction heating coil. It is known that the higher the current frequency is, the more concentrated the current flows near the steel surface, and the more the current tends to decrease toward the center. That is, the skin effect in which the induced current concentrates near the surface of the steel material increases as the frequency of the high-frequency current increases, and conversely decreases as the frequency of the high-frequency current decreases. Therefore, the quality of heat treatment at each part can be improved by performing induction hardening by changing the frequency of the high-frequency current in a predetermined area and other areas according to the difference in the axial thickness of the hollow shaft material and the difference in quenching rate. And stable quality can be ensured as a whole.

  As described above, this type of hollow power transmission shaft usually has a relatively large wall portion in the axial direction and a relatively thick wall portion in the axial direction. Yes. Therefore, the frequency of the high frequency current when induction hardening the large diameter portion of the hollow shaft material is relatively increased, and the frequency of the high frequency current when induction hardening the small diameter portion of the hollow shaft material is relatively reduced. Thereby, the heat treatment quality in the large diameter portion and the small diameter portion can be improved, and stable quality can be ensured as a whole.

  In addition, as the induction hardening method, there are a stationary method and a moving method, and any of these methods can be employed in the present invention. When the stationary method is adopted, a plurality of induction heating coils may be arranged according to the frequency type of the high frequency current. When the moving method is adopted, the frequency of the high-frequency current leading to the induction heating coil is changed.

  As the plastic processing, swaging processing, press processing, or the like is employed. The former swaging process includes rotary swaging and link type swaging, both of which can be employed. For example, in the rotary swaging, a pair or a plurality of pairs of dies and a backer incorporated in a main shaft in the machine perform a rotational motion, and a vertical stroke of a fixed stroke is performed by a peripheral roller and a protrusion on the backer, and then inserted. This is a processing method in which a pipe material is blown and drawn. The press working is a working method in which a pipe material is pushed into a die in the axial direction to perform drawing.

  The material of the pipe material is, for example, carbon steel for mechanical structures such as STKM and STMA, alloy steel to which alloy elements are added for improving workability and hardenability based on these, or SCr , SCM, SNCM, etc. can be used.

  According to the present invention, it is possible to provide a method for manufacturing a hollow power transmission shaft that can ensure stable quality even when there is a difference in thickness or quenching rate in the axial direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a hollow power transmission shaft 1, a sliding type constant velocity universal joint 2 connected to one end of the power transmission shaft 1, and a fixed type constant speed connected to the other end of the power transmission shaft 1. The power transmission mechanism of the motor vehicle provided with the universal joint 3 is shown. In the power transmission mechanism of this embodiment, the sliding type constant velocity universal joint 2 is connected to a reduction gear (differential), and the fixed type constant velocity universal joint 3 is connected to the drive wheel side. One end of the power transmission shaft 1 is splined to a tripod member 2a of the sliding type constant velocity universal joint 2, and a boot 2c is provided on the outer periphery of the outer ring 2b of the sliding type constant velocity universal joint 2 and the outer periphery of the power transmission shaft 1. Are fixed respectively. The other end of the power transmission shaft 1 is splined to the inner ring 3 a of the fixed type constant velocity universal joint 3, and a boot 3 c is provided on the outer circumference of the outer ring 3 b of the fixed type constant velocity universal joint 3 and the outer circumference of the power transmission shaft 1. Are fixed respectively. In the drawing, a tripod type constant velocity universal joint is illustrated as the sliding type constant velocity universal joint 2, and a barfield type constant velocity universal joint is illustrated as the fixed type constant velocity universal joint 3. Some types of constant velocity universal joints may be used.

  FIG. 2 shows a power transmission shaft (drive shaft) 1. The power transmission shaft 1 is hollow over the entire region in the axial direction, and has a large-diameter portion 1a at an axial intermediate portion and small-diameter portions 1b at both axial sides of the large-diameter portion 1a. The large-diameter portion 1a and the small-diameter portion 1b are continuous via a tapered portion 1c that is gradually reduced in diameter toward the shaft end side. The small-diameter portion 1b includes an end-side connection portion 1d used for connection with the constant velocity universal joints (2, 3), and an axial intermediate portion-side boot fixing portion 1e to which the boots (2c, 3c) are fixed. And have. A retaining ring groove for attaching a spline 1d1 splined to the constant velocity universal joints (2, 3) and a retaining ring for axially retaining the constant velocity universal joints (2, 3) to the coupling portion 1d. 1d2 is formed. The boot fixing portion 1e is formed with a fitting groove 1e1 for fitting the inner circumference of the small diameter end portion of the boot (2c, 3c).

  The large diameter portion 1a is formed to be relatively thin, and the small diameter portion 1b is formed to be relatively thick. The ratio of the thickness of the large diameter portion 1a to the thickness of the small diameter portion 1b (large diameter portion 1a / small diameter portion 1b) is, for example, 0.7 or less.

  Further, as shown in the drawing with hatching, the power transmission shaft 1 has a hardened layer S formed by quenching over substantially the entire region in the axial direction. In the entire axial direction, the hardened layer S is formed in a region having a predetermined depth h from the outer peripheral surface 1g, and the region from the hardened layer S to the inner peripheral surface 1i is an uncured layer S0 that has not been hardened by the quenching process. Yes. The quenching rate α defined by the ratio (h / t) between the depth h and the wall thickness t of the hardened layer S having a Rockwell hardness HRC40 (Hv391) or higher is, for example, 0. 6 or less and 0.6 or more for the small diameter portion 1b.

  The power transmission shaft 1 having the above-described configuration is formed by, for example, drawing a pipe material to form a hollow shaft material having a large diameter portion at an axial intermediate portion and small diameter portions at both axial side portions. Manufactured by subjecting the material to required machining (spline rolling, etc.) and then quenching.

  FIG. 3 shows the hollow pipe material 1 ′ before quenching. First, a pipe material such as a machine structural carbon steel pipe (STKM) is subjected to a swaging process to form a large diameter portion 1a at an intermediate portion in the axial direction and a small diameter portion 1b at both axial portions. Then, the spline 1d1 is formed by rolling or the like at the end of the small diameter portion 1b to form the connecting portion 1d, and the retaining ring groove 1d2 is formed in the connecting portion 1d by rolling or cutting. Further, the boot fixing groove 1e1 is formed by rolling or cutting at a portion that becomes the boot fixing portion 1e.

  Thereafter, as shown in FIG. 3, for example, a movable induction heating coil 5 is sheathed on the outer peripheral surface 1 g side of the hollow shaft material 1 ′, and a high-frequency current having a predetermined frequency is passed through the induction heating coil 5. It is moved in the axial direction, and induction hardening is performed from the outer peripheral surface 1g side. At that time, the frequency of the high-frequency current leading to the induction heating coil 5 is relatively lowered for the relatively thick small-diameter portion 1b, and the induction heating coil 5 for the relatively thin-walled large diameter portion 1a. The frequency of the high-frequency current leading to is relatively increased. Thereby, even if there is a thickness difference between the large diameter portion 1a and the small diameter portion 1b, and even when a difference in the quenching rate α is provided, the heat treatment quality in each part is enhanced, and the stable quality as a whole is achieved. Can be secured.

  FIG. 4 shows a hollow power transmission shaft 11 according to another embodiment. The power transmission shaft 11 according to this embodiment is different from the power transmission shaft 1 described above in that the quenching rate α is set to 1.0 for the large diameter portion 1a, that is, over the entire thickness t of the large diameter portion 1a. Thus, the cured layer S is formed. Since other matters are the same as those in the above-described embodiment, a duplicate description is omitted.

  FIG. 5 shows a hollow power transmission shaft 21 according to another embodiment. The power transmission shaft 21 according to this embodiment is different from the power transmission shaft 1 described above in that the quenching rate α is 1.0 over the entire axial direction, that is, over the entire thickness t in the entire axial direction. Thus, the cured layer S is formed. Since other matters are the same as those in the above-described embodiment, a duplicate description is omitted.

  FIG. 6 shows a hollow power transmission shaft 31 according to another embodiment. The power transmission shaft 31 according to this embodiment is different from the above-described power transmission shaft 1 in that the hardening rate α is 1.0 for the small diameter portion 1b, that is, it is cured over the entire thickness t of the small diameter portion 1b. The layer S is formed. Since other matters are the same as those in the above-described embodiment, a duplicate description is omitted.

It is a figure which shows the power transmission mechanism of a motor vehicle. It is sectional drawing which shows the power transmission shaft which concerns on embodiment. It is sectional drawing which shows a hollow shaft raw material. It is sectional drawing which shows the power transmission shaft which concerns on other embodiment. It is sectional drawing which shows the power transmission shaft which concerns on other embodiment. It is sectional drawing which shows the power transmission shaft which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power transmission shaft 11 Power transmission shaft 21 Power transmission shaft 31 Power transmission shaft 1 'Hollow pipe material 1a Large diameter part 1b Small diameter part

Claims (2)

A method of manufacturing a hollow power transmission shaft in which an axially intermediate portion is formed in a large diameter portion, and both axial sides are formed in small diameter portions from the large diameter portion, respectively.
Plastic processing is performed on the pipe material to form a hollow shaft material having the large diameter portion and the small diameter portion,
A method for manufacturing a hollow power transmission shaft, comprising subjecting the hollow shaft material to induction hardening by changing a frequency of a high-frequency current in a predetermined region and other regions.   The frequency of the high frequency current when induction hardening the large diameter portion of the hollow shaft material is relatively high, and the frequency of the high frequency current when induction hardening the small diameter portion of the hollow shaft material is relatively low. The method for manufacturing a hollow power transmission shaft according to claim 1.

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