Shaft member

Abstract

To provide a shaft member capable of suppressing the risk of crack generation.SOLUTION: A shaft member 100 includes a female spline 20, and a male spline 10 press-fitted in the female spline 20. The male spline 10 includes a first external tooth 11 and a second external tooth 12. The female spline 20 includes a first internal tooth 21 and a second internal tooth 22. The shaft member 100 includes: a large diameter press-fitting region 30 where a tooth tip surface 11c of the first external tooth 11 and a tooth bottom surface 21e of the first internal tooth 21 are mutually plastic-deformed; and a tooth surface press-fitting region 40 where a tooth surface 12d of the second external tooth 12 and a tooth surface 22a of the second internal tooth 22 are mutually plastic-deformed. Carburization hardening processing is performed on the tooth surfaces 22a, 22d of the second internal tooth 22, and carburization hardening processing is not performed on a tooth bottom surface 22e of the second internal tooth 22.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a shaft member.

Background Art

[0002] The fitting structure of the shaft member disclosed in Patent Document 1 includes a ring in which a plurality of internal teeth are formed on the inner circumference of a hole, and a spline shaft that is disposed inside the hole and has a plurality of external teeth that mesh with the plurality of internal teeth. The spline shaft is press-fitted into the ring. The fitting structure of the shaft member includes a first press-fitting portion and a second press-fitting portion. In the first press-fitting portion, the tooth tip surface of any one of the plurality of external teeth and the tooth bottom surface of the internal teeth are in contact with each other and plastically deformed. In the second press-fitting portion, the tooth surface of the external teeth other than the external teeth where the first press-fitting portion is formed and the tooth surface of the internal teeth are in contact with each other and plastically deformed. Further, Patent Document 1 also discloses a male spline press-fitted into a female spline after heat treatment such as quenching.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors of the present application have discovered the following problems. In such a fitting structure of a shaft member, after heat treatment of the spline shaft, it may be press-fitted into a ring. Further, when a plurality of first press-fitting portions are arranged at intervals in the circumferential direction of the ring, the plurality of first press-fitting portions apply stress radially outward from the tooth bottom surface of the internal teeth of the ring. As a result, stress is generated in the circumferential direction at the tooth bottom of the internal teeth of the ring. In addition, the second press-fitting portion applies two stresses in the normal directions of the two tooth surfaces from the two tooth surfaces of the internal teeth of the ring. As a result, stress is generated in the circumferential direction at the tooth bottom of the internal teeth of the ring. Due to the first press-fitting portion and the second press-fitting portion, stress concentrates at the tooth bottom of the internal teeth of the ring, that is, at the same part. As a result, there was a risk of cracking.

[0005] The present disclosure has been made in view of the above-described problems, and provides a shaft member capable of suppressing the risk of cracking.

Means for Solving the Problems

[0006] The shaft member according to the present disclosure is a shaft member including a female spline and a male spline press-fitted into the female spline, wherein the male spline includes first and second external teeth, the female spline includes first and second internal teeth, the shaft member includes a large-diameter press-fitting region in which the tooth tip surface of the first external tooth and the tooth bottom surface of the first internal tooth are plastically deformed with each other, and a tooth surface press-fitting region in which the tooth surface of the second external tooth and the tooth surface of the second internal tooth are plastically deformed with each other, the tooth surface of the second internal tooth is case-hardened and quenched, and the tooth bottom surface of the second internal tooth is not case-hardened and quenched.

Effects of the Invention

[0007] According to the present disclosure, the risk of cracking can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are simplified as appropriate.

[0010] <Embodiment 1> Embodiment 1 will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic diagram showing a shaft member according to Embodiment 1. FIG. 2 is a schematic diagram showing the main part of the shaft member shown in FIG. 1. FIG. 3 is a schematic diagram showing another main part of the shaft member shown in FIG. 1. FIG. 4 is a graph showing the stress with respect to the strain of each part.

[0011] Of course, the right-handed XYZ coordinates shown in FIG. 1 and other drawings are for convenience in explaining the positional relationship of the components. Usually, the positive Z-axis direction is vertically upward, the XY plane is a horizontal plane, and is common among the drawings.

[0012] As shown in FIG. 1, the shaft member 100 includes a male spline 10 and a female spline 20. The axis Z0 of the shaft member 100 according to the present embodiment extends in the positive Z-axis direction.

[0013] The male spline 10 includes a first external tooth 11, a second external tooth 12, and a shaft body 13. The shaft body 13 is a substantially cylindrical body extending along the axis Z0. The first external tooth 11 and the second external tooth 12 protrude radially outward from the outer peripheral surface of the shaft body 13. The first external tooth 11 and the second external tooth 12 are alternately arranged at a predetermined interval on the outer peripheral surface of the shaft body 13. For example, a set of a plurality of first external teeth 11 and a set of a plurality of second external teeth 12 may be alternately arranged at a predetermined interval on the circumferential surface of the shaft body 13. In an example of the male spline 10 shown in FIG. 1, a set of two first external teeth 11 and a set of three second external teeth 12 are alternately arranged at a predetermined interval on the circumferential surface of the shaft body 13. An example of the male spline 10 shown in FIG. 1 includes six sets each of a set of two first external teeth 11 and a set of three second external teeth 12.

[0014] As shown in FIG. 2, the first external tooth 11 includes a tooth bottom surface 11a, a tooth surface 11b, a tooth tip surface 11c, a tooth surface 11d, and a tooth bottom surface 11e. The tooth bottom surface 11a, the tooth surface 11b, the tooth tip surface 11c, the tooth surface 11d, and the tooth bottom surface 11e are connected in this order. The tooth bottom surfaces 11a and 11e extend in a substantially circumferential direction extending around the axis Z0 shown in FIG. 1. The tooth surface 11b extends radially outward from the tooth bottom surface 11a and connects to the tooth tip surface 11c. The tooth surface 11b may extend in a linear shape or an involute shape. The tooth tip surface 11c protrudes from the tooth bottom surfaces 11a and 11e. The tooth surface 11d extends radially outward from the tooth bottom surface 11e and connects to the tooth tip surface 11c.

[0015] As shown in FIG. 3, the second external tooth 12 includes a tooth bottom surface 12a, a tooth surface 12b, a tooth tip surface 12c, a tooth surface 12d, and a tooth bottom surface 12e. The tooth bottom surface 12a, the tooth surface 12b, the tooth tip surface 12c, the tooth surface 12d, and the tooth bottom surface 12e are connected in this order. The tooth bottom surfaces 12a and 12e extend in a substantially circumferential direction extending around the axis Z0 shown in FIG. 1. The tooth surface 12b extends radially outward from the tooth bottom surface 12a and connects to the tooth tip surface 12c. The tooth surface 12b may extend in a linear shape or an involute shape. The tooth tip surface 12c protrudes from the tooth bottom surfaces 12a and 12e. The tooth surface 12d extends radially outward from the tooth bottom surface 12e and connects to the tooth tip surface 12c.

[0016] The female spline 20 includes a first internal tooth 21, a second internal tooth 22, and a cylindrical body 23. The cylindrical body 23 extends along the axis Z0. The cross-sectional shape of the cylindrical body 23 is substantially an annular shape. The first internal tooth 21 and the second internal tooth 22 protrude from the inner peripheral surface of the cylindrical body 23 radially inward of the cylindrical body 23.

[0017] The first internal tooth 21 and the second internal tooth 22 are arranged on the inner peripheral surface of the cylindrical body 23 so as to mesh with the first external tooth 11 and the second external tooth 12 when the male spline 10 is press-fitted into the female spline 20. Specifically, the first internal tooth 21 and the second internal tooth 22 are alternately arranged on the inner peripheral surface of the cylindrical body 23 with a predetermined interval therebetween. For example, a set of a plurality of first internal teeth 21 and a set of a plurality of second internal teeth 22 may be alternately arranged on the inner peripheral surface of the cylindrical body 23 with a predetermined interval therebetween. In an example of the male spline 10 shown in FIG. 1, a set of two first internal teeth 21 and a set of three second internal teeth 22 are alternately arranged on the inner peripheral surface of the cylindrical body 23 with a predetermined interval therebetween. An example of the female spline 20 shown in FIG. 1 includes six sets each of a set of two first internal teeth 21 and a set of three second internal teeth 22.

[0018] As shown in FIG. 2, the first internal tooth 21 includes a tooth tip surface 21c, a tooth surface 21d, and a tooth bottom surface 21e. The tooth tip surface 21c, the tooth surface 21d, and the tooth bottom surface 21e are connected in this order. The tooth bottom surface 21e extends in a substantially circumferential direction centered on the axis Z0 shown in FIG. 1. The tooth tip surface 21c protrudes from the tooth bottom surface 21e. The tooth surface 21d extends radially inward from the tooth bottom surface 21e and connects to the tooth tip surface 21c. The tooth surface 21d may extend in a linear shape or an involute shape.

[0019] As shown in Fig. 3, the second internal teeth 22 include a tooth tip surface 22c, a tooth surface 22d, a tooth bottom surface 22e, a tooth surface 22a, and a tooth tip surface 22b. The tooth tip surface 22c, the tooth surface 22d, the tooth bottom surface 22e, the tooth surface 22a, and the tooth tip surface 22b are connected in this order. The tooth bottom surface 22e extends in a substantially circumferential direction centered on the axis Z0 shown in Fig. 1. The tooth surface 22d extends radially outward from the tooth bottom surface 22e and connects to the tooth tip surface 22c. The tooth surface 22d may extend linearly or in an involute shape. The tooth tip surfaces 22c and 22b protrude from the tooth bottom surface 22e. The tooth surface 22a extends radially outward from the tooth bottom surface 22e and connects to the tooth tip surface 22b. The tooth surface 22a may extend linearly or in an involute shape.

[0020] The tooth surfaces 22a and 22d are subjected to carburizing and quenching treatment. The tooth bottom surface 22e is not subjected to carburizing and quenching treatment. Specifically, only the tooth surfaces 22a and 22d may be irradiated with a laser to perform carburizing and quenching treatment on the tooth surfaces 22a and 22d. Alternatively, after the second internal teeth 22 are subjected to carburizing and quenching treatment, only the tooth bottom surface 22e may be tempered. Alternatively, the second internal teeth 22 may be subjected to carburizing and quenching treatment while covering the tooth bottom surface 22e. Alternatively, the tooth surfaces 22a and 22d may be subjected to carburizing and quenching treatment before the male spline 10 is press-fitted into the female spline 20.

[0021] The tooth surfaces 22a and 22d are superior in wear resistance compared to the tooth bottom surface 22e. The tooth bottom surface 22e is superior in ductility compared to the tooth surfaces 22a and 22d. The stress curve σ a for the strain of the tooth surfaces 22a and 22d and the stress curve σ e for the strain of the tooth bottom surface 22e are shown in Fig. 4. As shown in Fig. 4, the tooth surfaces 22a and 22d have a stress value σ e1 at a strain ε1, and the tooth bottom surface 22e has a stress value σ a1 at the strain ε1. The stress value σ a1 is lower compared to the stress value σ e1 .

[0022] The male spline 10 is press-fitted into the female spline 20. The shaft member 100 has a large-diameter press-fitting region 30 and a tooth surface press-fitting region 40. The shaft member 100 has a plurality of large-diameter press-fitting regions 30 and tooth surface press-fitting regions 40. Further, the large-diameter press-fitting regions 30 and the tooth surface press-fitting regions 40 may be alternately arranged on the boundary between the male spline 10 and the female spline 20 shown in FIG. 1.

[0023] As shown in FIG. 2, in the large-diameter press-fitting region 30, the tooth tip surface 11c of the first external tooth 11 and the tooth bottom surface 21e of the first internal tooth 21 are plastically deformed with each other. Specifically, when the male spline 10 is press-fitted into the female spline 20, the tooth tip surface 11c of the first external tooth 11 and the tooth bottom surface 21e of the first internal tooth 21 come into contact with each other, and the plastic deformation occurs. A stress σ1 is applied from the tooth tip surface 11c of the first external tooth 11 to the tooth bottom surface 21e of the first internal tooth 21.

[0024] As shown in FIG. 3, in the tooth surface press-fitting region 40, the tooth surface 12b of the second external tooth 12 and the tooth surface 22d of the second internal tooth 22 are plastically deformed with each other. Specifically, when the male spline 10 is press-fitted into the female spline 20, the tooth surface 12b and the tooth surface 22d come into contact with each other, and the plastic deformation occurs. A stress σ2 is applied from the tooth surface 12b to the tooth surface 22d.

[0025] As shown in FIG. 3, in the tooth surface press-fitting region 40, the tooth surface 12d of the second external tooth 12 and the tooth surface 22a of the second internal tooth 22 are plastically deformed with each other. Specifically, when the male spline 10 is press-fitted into the female spline 20, the tooth surface 12d and the tooth surface 22a come into contact with each other, and the plastic deformation occurs. A stress σ3 is applied from the tooth surface 12d to the tooth surface 22a.

[0026] As described above, in the tooth surface press-fitting region 40, stresses σ2 and σ3 are respectively applied from the tooth surfaces 12b and 12d of the second external teeth 12 to the tooth surfaces 22a and 22d of the second internal teeth 22. Also, as described above, as shown in FIG. 2, a stress σ1 is applied from the tooth tip surface 11c of the first external teeth 11 to the tooth bottom surface 21e of the first internal teeth 21. Since the shaft member 100 has a plurality of large-diameter press-fitting regions 30, as shown in FIG. 1, the plurality of stresses σ1 are generated in the circumferential direction of the cylindrical body 23. By the generation of the plurality of stresses σ1 and the above-described stresses σ2 and σ3, a stress σ4 is generated in the circumferential direction at or near the tooth bottom surface 22e. Due to the large-diameter press-fitting region 30 and the tooth surface press-fitting region 40, the stress σ4 is concentrated at or near the tooth bottom surface 22e, that is, at the same part. As described above, the tooth surfaces 22a and 22d are subjected to carburizing and quenching treatment. The tooth bottom surface 22e is not subjected to carburizing and quenching treatment. Thus, when the strain values of the tooth bottom surface 22e, the tooth surfaces 22a and 22d are the same strain ε1, the stress generated in the tooth bottom surface 22e is lower than the stress generated in the tooth surfaces 22a and 22d. Therefore, the stress can be reduced to suppress cracking.

[0027] Incidentally, by reducing the press-fitting allowance between the male spline 10 and the female spline 20, the stress σ4 can be reduced. Along with this, the tolerances of the pitch diameter between balls and the overhaul diameter of the tooth profile may be reduced, and there is a possibility that the processing cost and defective products increase. Since the above-described shaft member 100 does not need to reduce the press-fitting allowance between the male spline 10 and the female spline 20, there is no possibility that such processing costs and defective products increase.

[0028] Note that the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist. Also, the present invention may be implemented by appropriately combining the above-described embodiments and examples thereof.

Explanation of Signs

[0029] 100 Shaft member 10 Male spline 11 First external teeth 11a, 11e Tooth bottom surface 11b, 11d Tooth surface 11c Tooth tip surface 12 Second external teeth 12a, 12e Tooth bottom surface 12b, 12d Tooth surface 12c Tooth tip surface 13 Shaft body 20 Female spline 21 First internal teeth 21c Tooth tip surface 21d Tooth surface 21e Tooth bottom surface 22 Second internal teeth 22a, 22d Tooth surface 22b, 22c Tooth tip surface 22e Tooth bottom surface 23 Cylindrical body

Claims

1. A shaft member comprising a female spline and a male spline press-fitted into the female spline, wherein the male spline has first and second external teeth, the female spline has first and second internal teeth, the shaft member includes a large-diameter press-fitting region in which the tip surface of the first external tooth and the bottom surface of the first internal tooth are plastically deformed with each other, and a tooth surface press-fitting region in which the tooth surface of the second external tooth and the tooth surface of the second internal tooth are plastically deformed with each other, the tooth surface of the second internal tooth is case-hardened, the bottom surface of the second internal tooth is not case-hardened, Shaft member.

2. the bottom surface of the second internal tooth has higher ductility than the tooth surface of the second internal tooth, The shaft member according to claim 1.

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