JPH0874871A - Mechanical element having shaft pressed into fitting member - Google Patents

Abstract

PURPOSE: To provide a flat knurling in which the force required for press-in can be reduced while keeping the connecting strength between a fitting member and a shaft. CONSTITUTION: A mechanical element is formed by forming a flat knurling 2 on the fitting area outer circumferential surface of a shaft 1, pressing the flat knurling of the shaft into a fitting member having a shaft hole inner circumferential surface having a diameter smaller than the outer diameter of the knurling, and integrally assembling them. The flat knurling 2 having a form in which the area of a top end part 3 protruded outward from the shaft outer circumferential surface in the section is 0.6-1.0 times of the area of a root part 4 situated inward from the shaft outer circumferential surface is rolled on the fitting area outer circumferential surface of the shaft 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a mechanical element in which a shaft is press-fitted into a fitting member manufactured by casting, forging, sintering or the like as a separate body and integrally assembled,
More specifically, it relates to the shape of an axially extending ridge formed by rolling the outer peripheral surface of the fitting region of the shaft in order to press-fit the shaft into the fitting member.

[0002]

2. Description of the Related Art The axially extending ridge rolled on the outer peripheral surface of the fitting area of a shaft is a flat knurl, but the conventional flat knurl has a width of the tip in a cross section as shown in FIG. Was very small and had a substantially triangular saw-tooth shape.

[0003]

As shown in FIG. 1, a flat knurl 2 formed on the outer peripheral surface of a fitting region of a shaft 1.
The ridge diameter (outer diameter) of the ridge, that is, the outer diameter D1 is larger than the outer diameter D0 of the shaft by the tooth height h, and the root diameter of the ridge, that is, the root portion D2, is the tooth height h than the outer diameter D0 of the shaft.
Only small. Further, the inner diameter D3 of the inner peripheral surface of the shaft hole 11 of the fitting member shown by the chain line is slightly larger than the outer diameter D0 of the shaft.

As described above, in the conventional flat knurling, the inner diameter D3 of the inner peripheral surface of the fitting member shaft hole is equal to the outer diameter D1 of the shaft protrusion.
Is relatively small in comparison with the above, that is, the radial thickness of the interference band which is plastically and / or elastically deformed by press fitting is relatively large. As a result, the force required for press-fitting is increased, and there is a problem that the time required for the press-fitting process is long. However, if the inner diameter D3 of the inner peripheral surface of the shaft hole is increased to reduce the radial thickness of the interference, the area of the interference is reduced, and the joint strength between the fitting member and the shaft is reduced. occured.

Further, since it has a substantially triangular saw-tooth shape, a thin burr (hair burr) is formed on a part of the flat knurled surface, and the hair burr remains at the fitting end due to press fitting and falls off during use. Then, there was a problem of causing dust wear. The present invention has been made to solve these problems, and an object of the present invention is to reduce the radial thickness of the tightening margin and press-fit it while maintaining the joint strength between the fitting member and the shaft. It is intended to provide a flat knurl that can reduce the required force and that can prevent the occurrence of burr and reduce dust wear.

[0006]

In order to achieve the above-mentioned object, the means adopted by the present invention is a flat knurl or a diagonal knurl formed by rolling the outer peripheral surface of the fitting region of the shaft in a cross section. The area ratio of the tip portion outside the shaft outer peripheral surface to the root portion inside the shaft outer peripheral surface is set to 0.6 to 1.0. In this flat knurl, it is desirable that the tip and the root of the flat knurl have a straight line in the cross section, and the intersection of the straight lines is rounded. Further, it is also possible to form all the contours of the tip portion and the root portion with curved lines.

[0007]

As shown in FIG. 1, in the conventional flat knurl with a substantially triangular cross section, when the inner diameter D3 of the inner peripheral surface of the shaft hole of the fitting member is made substantially equal to the outer diameter D0 of the shaft (D3 = D0), the maximum joining is achieved. Strength is obtained. The plastic deformation and / or elastic deformation cross-section, that is, the cross-sectional area of the interference is the cross-sectional area of the tip 3 outside the shaft outer peripheral surface of the flat knurl, and is 0.25 hp when the knurl pitch is p. .

As shown in FIG. 2, the flat knurls 2 formed on the shaft 1 have the same pitch p and height h as in FIG. 1, and in the cross section, the widths of the tip 3 and the root 4 are the same.
That is, assuming that the area ratio of the tip portion 3 outside the shaft outer peripheral surface to the root portion 4 inside the shaft outer surface is 1.0 and the cross-sectional area of the interference is 0.25 hp which is the same as in FIG. And the inner diameter D3 of the fitting member shaft hole 11 is D3 = D0 +
It becomes 0.5h. That is, the inner diameter D of the fitting member shaft hole in FIG.
Compared with 3 = (D0), the radial thickness of the interference band is halved.

As described above, when the bonding strength is the same,
The inner diameter of the inner peripheral surface of the fitting member shaft hole of the present invention is considerably larger than the conventional one, and the radial thickness of the tightening margin is reduced accordingly, so the force required for press fitting is reduced, and the working time of the press fitting process is reduced. Is shortened. The cross section of the flat knurls or the slanted knurls is not a sawtooth shape having a substantially triangular shape but a rectangular diameter with rounded corners, a trapezoid or a circle (waveform by a curve), and it is possible to prevent the generation of fine burr.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A mechanical element of the present invention will be described based on an embodiment shown in the drawings. As shown in FIG. 3, the fitting region of the shaft 1 is knurled to form a flat knurl 2. Here, the outer diameter of the shaft 1 is D0, the outer diameter of the flat knurls 2 is D1, and the root diameter is D2. As shown by the arrow, the shaft hole 11 of the cam piece 10 is press-fitted into the flat knurl 2 of the shaft 1. The inner diameter D3 of the shaft hole 11 is larger than the outer diameter D0 of the shaft 1, but smaller than the outer diameter D1 of the flat knurls 2.

The pitch p, the outer diameter D1, the root diameter D2, and the tooth height h of the flat knurl 2 in FIG. 2 are all the same as those in FIG. 1, and D1 = D0 + h, D2 = D0-h. . In the cross section, the corners of the tip 3 and the root 4 of the knurl have roundness, but the width a of the tip and the width b of the root are the same except for the roundness, and a = b = 0.5p. . That is, the area ratio of the tip 3 to the root 4 is 1.0.

When the inner peripheral surface of the cam piece shaft hole 11 shown by the chain line is between the shaft outer diameter D0 and the knurl outer diameter D1, the inner diameter D3 is D3 = D0 + 0.5h. In this case, since the cross-sectional area of the interference due to the fitting of the cam piece and the shaft is 0.25 hp, which is the same as that in FIG. 1, the joint strength is the same as that in FIG. Regarding the radial thickness of the interference, the thickness in FIG. 1 is 0.5 h,
In the case of FIG. 2, it is 0.25 h, so it is halved. Therefore, the camshaft of FIG. 2 has the same joint strength as the camshaft of FIG. 1, but the force required for press fitting is reduced.

As shown in FIG. 4, when a conical guide surface 14 is formed at the press-fitting start end of the shaft hole 11 of the cam piece 10 which is press-fitted in the direction of the arrow in order to facilitate press-fitting of the shaft 1, a fitting surface is formed. The fitting area is reduced by the decrease in the axial length of. The guide surface becomes larger as the inner diameter of the cam piece shaft hole inner peripheral surface becomes smaller due to the decrease in the axial length. The guide surface 14 in the drawing has an inclination of 45 degrees, the solid line shows the shaft hole inner diameter D3 in FIG. 2, and the chain line shows the shaft hole inner diameter D3 '(= D3-0.
25h). The decrease in axial length is e1 in Fig. 1
2 is e2, and e2 is 0.2 more than e1.
The axial length reduction is small by 5 h, that is, a quarter of the knurl height. Therefore, the one in FIG. 2 has a smaller fitting area than that in FIG. 1, so that the decrease in the joint strength due to the formation of the guide surface is less.

As shown in FIG. 5, the area ratio of the tip portion 3 outside the flat knurled shaft outer peripheral surface to the root portion 4 inside the shaft outer peripheral surface is limited to 0.6. When the area ratio becomes 0.6 or less, the cam piece shaft hole 1 shown by the chain line
Since the inner diameter D3 of the inner peripheral surface of 1 approaches the outer diameter D0 of the shaft 1, the force required for press-fitting increases. As shown in FIG.
In the cross section, the contours of the tip portion 3 of the flat knurl 2 outside the shaft outer peripheral surface and the root portion 4 inside the shaft outer peripheral surface may be formed by continuous curves. Also in this case, in order to reduce the radial thickness of the interference, the area ratio of the tip portion 3 to the root portion 4 is set in the range of 0.6 to 1.0, and the inner diameter D3 of the cam piece shaft hole 11 is set outside the shaft 1. Make it much larger than the diameter D0.

The fitting member may be a cam piece with an inner piece, and the cam piece may be made of sintered alloy, forged or cast. The fitting member is not limited to the cam piece, and the gear shaft and the rotor shaft can be assembled by press-fitting the shaft such as the gear and the rotor. In the embodiment, the flat knurl is rolled. However, the knurl is not limited to the flat knurl, and the slanted knurl whose ridge extends in a screw shape may be rolled.

[0016]

As described above, in the mechanical element of the present invention, the flat knurl is formed on the outer peripheral surface of the fitting region of the shaft, and at least a part of the inner peripheral surface of the shaft hole of the fitting member has a diameter smaller than the outer diameter of the knurl. It is formed with a small diameter, and the flat knurl of the shaft is press-fitted into the shaft hole of the fitting member to be integrally assembled, but unlike the conventional flat knurl whose cross section is close to a triangle, the cross section is outside the outer surface of the shaft. The area ratio of the tip of one side to the root of the inner side of the outer peripheral surface of the shaft is 0.6 to
Since the flat knurls or the diagonal knurls are 1.0, the inner diameter of the inner peripheral surface of the shaft hole of the fitting member is relatively large, and the radial thickness of the interference during press fitting is reduced accordingly.
As a result, it is possible to reduce the force required for press-fitting and to prevent the generation of fine hair burr, so that it is possible to eliminate dust abrasion of the cam.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a conventional flat knurl,

FIG. 2 is an enlarged cross-sectional view of a flat knurl according to an embodiment of the present invention,

FIG. 3 is a side sectional view showing the assembly of a camshaft according to an embodiment of the present invention,

FIG. 4 is an enlarged side sectional view showing a guide surface of a cam piece of another embodiment,

FIG. 5 is a view corresponding to FIG. 2 of another embodiment,

FIG. 6 is a view corresponding to FIG. 2 of still another embodiment,

[Explanation of symbols]

1: Shaft, 2: Knurl, 3: Tip part, 4: Root part, 10: Cam piece, 11: Shaft hole, D0: Shaft outer diameter, D1: Knurled outer diameter, D3, D3 ': Cam piece shaft hole inner diameter

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[Procedure amendment]

[Submission date] September 21, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

Claims (3)

[Claims] 1. A knurling (2) which is formed by rolling the outer peripheral surface of a fitting region of a shaft (1) to extend a ridge in an axial direction.
To form an inner peripheral surface having a diameter (D3) smaller than the outer diameter (D1) of the knurl in the shaft hole of the fitting member (10) and press-fitting the knurl into the shaft hole to integrally assemble The knurl is a mechanical element, and the area of the tip portion (3) outside the shaft outer peripheral surface is 0.6 to 1.0 times the area of the root portion (4) inside the shaft outer peripheral surface in the transverse section. A mechanical element comprising a shaft and a fitting member press-fitted into the shaft. 2. The knurling (2) is characterized in that, in a cross section, the contours on both sides of the tip portion (3) and the root portion (4) are straight lines, and the intersections of the straight lines are rounded. A mechanical element obtained by press-fitting the shaft according to 1 into a fitting member. 3. The shaft according to claim 2, wherein the knurling (2) has a curved cross-section of the tip (3) and the root (4) in cross section. Machine element.