JP3189058B2 - Mechanical element obtained by press-fitting a shaft into a fitting member and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical element in which a shaft is press-fitted into a shaft hole of a separately manufactured fitting member to assemble the fitting member and the shaft, and a method of manufacturing the same. To be more specific, shaft holes such as a camshaft for an internal combustion engine and a compressor crankshaft having a relatively large rotational torque are eccentric with respect to the center of the fitting member, and shaft holes such as a rotor shaft for a gear shaft pump. Relates to a mechanical element located at the center of the fitting member.

[0002]

2. Description of the Related Art A mechanical element such as a camshaft, which is formed by integrally fitting a separately manufactured fitting member and a shaft by press fitting, is well known. Japanese Patent Application Laid-Open No. 63-297707 discloses a method of manufacturing a mechanical element such as a camshaft by fitting involving cutting when press-fitting a fitting member into a shaft in order to increase the load torque of this kind of mechanical element. ing.

In the disclosed camshaft, a protruding portion extending in the circumferential or helical direction is formed on the peripheral surface of the shaft by compression processing such as rolling, and the camshaft extends in the axial direction on the inner peripheral wall of the shaft hole of the cam piece. The cam piece is fitted into the shaft such that a protrusion is formed on the shaft and a groove is formed in the protruding portion, and the cam piece and the shaft are integrally assembled.

[0004]

In the above camshaft, a protruding portion provided on the inner peripheral surface of the cam piece and extending in the axial direction must be sharply finished.
In addition, since the cross section has a mountain shape, there is a problem that the finishing process is troublesome and the cost is high. The present invention has been made to solve this problem, and an object of the present invention is to provide a method in which an inner peripheral surface of a shaft hole of a fitting member elastically and plastically deforms a raised portion formed on a peripheral surface of a shaft. It is an object of the present invention to provide a mechanical element that is assembled by being fitted to a shaft, and that does not require labor for finishing the inner peripheral surface of the shaft hole of the fitting member.

[0005]

In order to achieve the above object, a means adopted by the present invention is to provide a shaft in which a continuous or discontinuous extending ridge is formed on a peripheral surface of a fitting area of a fitting member. The shaft protrusion is press-fitted into the shaft hole of the fitting member having a smaller inner diameter than the outer diameter of the shaft protrusion, and the shaft protrusion is partially elastically and plastically deformed by a portion where the inner diameter of the fitting member is smaller than the protrusion outer diameter. In the mechanical element in which the fitting member is fitted to the shaft, the ridge is extended in the axial direction.
And a portion smaller than the raised portion of the shaft hole of the fitting member is formed as a chord in the cross section.

[0006]

When the fitting member is fitted to the shaft and pressed into the fitting region of the fitting member in the axial direction, a portion having an inner diameter larger than the outer diameter of the raised portion on the inner periphery of the fitting member shaft hole is loosely fitted. The portion except for both ends of the chord surface has a smaller inner diameter than the protruding portion, and thus corresponds to the protruding portion. Therefore, the central portion of the chordal surface elastically and plastically deforms the raised portion, and both sides of the chordal surface fit into the fitting region while elastically and plastically deforming the raised portion. In this way, the mating member is firmly fitted to the shaft to assemble an integral mechanical element. Since the connection between the fitting member and the shaft is a kind of square joint, it has high anti-idling properties.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments shown in the drawings. The camshaft used in the valve mechanism of the internal combustion engine shown in FIGS. 1 and 2 is a mechanical element having the cam piece 20 as a fitting member. A plurality of parallel annular ridges 12 are formed on the peripheral surface of the fitting area A of the shaft 10 by rolling such as knurling. A cam piece 20 is fitted on the shaft 10 in the axial direction, and a chordal surface portion forming an inner peripheral surface of the shaft hole 25 of the cam piece 20 on the raised portion 12.
By fitting the 22, the shaft 10 and the cam piece 20 are assembled into an integral camshaft.

The annular raised portion 12 formed on the peripheral surface of the shaft 10 by compression processing such as rolling can extend continuously in the circumferential direction as shown in FIG.
It may extend continuously in the spiral direction or may extend intermittently in the circumferential or spiral direction as shown in FIG. As shown in FIGS. 2 and 3, the outer diameter D1 of the raised portion 12 is larger than the outer diameter D of the shaft 10 excluding the fitting area A, and the outer diameter of the valley adjacent to the raised portion 12 is larger than the outer diameter D of the shaft. Is also small. Note that the raised portion discontinuously extending in the circumferential or spiral direction has a knurled shape, and the knurled shape is desirable from the viewpoint of assembly efficiency. Note that the raised portion is not limited to plastic working such as rolling, but may be formed by cutting.

As shown in FIG. 2, the inner peripheral surface of the cam piece 20 comprises an arc surface 21 and a chord surface 22 which are alternately connected.
Is larger than the outer diameter D1 of the shaft ridge 12. The distance of the chord surface 22 to the axis is larger than the radius of the valley in the fitting region, but smaller than the radius of the raised portion 12. When the inner diameter D2 is the same as or smaller than the outer diameter D1, the fitting becomes stronger, but from the viewpoint of assembly efficiency, the inner diameter D2 is preferably larger than the outer diameter D1. In the embodiment, the arc surface 21 and the chord surface 22 have the same number of four each, but the length of the arc and the chord may be changed, and the number of them may be more or less than four. For example, one arc surface and one chord surface may be used. Further, when the shaft hole 25 is formed only of the chordal surface, the inner periphery becomes polygonal, but it is firmly fitted and has higher anti-idling properties. Since the chord surface 22 is flat, the cost required for finishing is significantly reduced as compared with the chevron projection.

As shown in FIG. 5, the cam piece 20 is pushed axially from one side into a fitting area A of the shaft 10 as shown by an arrow B. At this time, the chord surface 22 on the inner circumference of the cam piece fits into the fitting area A while elastically deforming the raised portion 12 at both ends and elastically and plastically deforming the inner portion. As shown in FIG. 6, the cam piece 20 is connected to the cam fitting area A of the shaft 10.
When the edge of the chord surface 22 on the front side when pushed in the direction of arrow B is cut obliquely to form a slope 23, the elasticity and plastic deformation of the raised portion 12 due to the chord surface 22 become smooth only by the wedge action. Instead, the cam piece can be positioned in the axial direction by making the slope 23 abut on the raised portion at the end of the fitting area.

The mechanical element shown in FIG. 7 is a crankshaft of a compressor, and a thick disk-shaped crank 20 is a fitting member. The shaft hole 25 of the crank 20 is located eccentrically with respect to the center of the crank 20. As in the previous embodiment, a raised portion 12 is formed on the peripheral surface of the fitting region of the shaft 10 by compression processing such as rolling, and an inner diameter D2 larger than the outer diameter D1 of the raised portion 12 is formed in the shaft hole 25 of the crank 20. And a chord surface 22 whose distance to the arc 21 and the axis is smaller than the radius of the raised portion 12 is provided. The cross section including the axis of the crankshaft is the same as FIG.

FIG. 8 shows a gear shaft assembly, in which a thick gear 20 is a fitting member. The shaft hole 25 of the gear 20 is located at the center of the gear 20. As in the previous embodiment, the raised portion 12 is formed by compression on the peripheral surface of the fitting area of the shaft, and the shaft hole 25 of the gear 20 has an arc surface 21 having an inner diameter D2 larger than the outer diameter D1 of the raised portion 12 and the shaft. A chord surface 22 having a distance to the center smaller than the radius of the raised portion 12 is provided.

FIG. 9 is a graph summarizing test results of an insertion load and a joining strength when a fitting member having a regular hexagonal shaft hole is fitted to three types of raised portions formed on the peripheral surface of the shaft. The shaft is a steel material equivalent to SAE1050, and the three kinds of raised portions are flat knurls extending continuously in the axial direction, twill knurls extending discontinuously in the spiral direction,
An annular knurl that is continuous in the circumferential direction. The fitting member is a cam piece made of a material of Fe-8% Cr alloy, the shaft hole is a regular hexagon, and the axial width is 11 mm. The fitting margin between the fitting member and the shaft is a maximum of 0.8 mm. This graph shows that the joint strength or load torque of the flat knurl ridge extending in the axial direction is relatively small, and the twill knurl extending in the helical direction and the annular knurl ridge extending in the circumferential direction have sufficient joint strength or load torque. It shows that it is big.

FIG. 10 is a graph showing the test results of the joining strength when the raised portion of the twill knurl is fitted into various regular polygonal shaft holes having the same diameter circumcircle of the fitting member. The shaft is steel material equivalent to SAE1050, and the fitting member is Fe-
This is an 8% Cr alloy cam piece. The axial width of the fitting member is 11 mm, the axial hole is a regular hexagon, a regular octagon, a regular decagon,
It is a regular dodecagon. This graph shows that the octagonal or decagonal shaft hole has a larger joint strength, that is, the load torque, than the hexagonal or dodecagonal regular polygonal shaft hole.

[0015]

As described above, the mechanical element of the present invention includes a fitting member in which a raised portion formed on a shaft has an inner diameter smaller than the outer diameter of the raised portion provided on the inner peripheral surface of the shaft hole. Although the fitting member is integrally fitted to the shaft by press-fitting, the shaft hole portion having an inner diameter smaller than the outer diameter of the protruding portion is a chordal surface, so that the conventional cross-sectionally mountain-shaped extending in the axial direction. Finishing of the inner peripheral surface of the shaft hole is easier and less expensive than the protruding portion. Therefore, the method of the present invention is more suitable for mass production than the conventional method.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a camshaft according to the present invention;

FIG. 2 is a sectional view taken along the line II-II in FIG. 1;

FIG. 3 is a view showing a fitting region of a shaft according to another embodiment;

FIG. 4 is a cross-sectional view of another embodiment of a shaft;

FIG. 5 is a view showing a state where the cam piece is fitted to the shaft;

FIG. 6 is a view corresponding to FIG. 5 of another embodiment,

FIG. 7 is a cross-sectional view of the crankshaft of the present invention;

FIG. 8 is a cross-sectional view of the gear shaft assembly of the present invention;

FIG. 9 is a graph showing the relationship between the shape of the raised portion of the peripheral surface of the shaft, the bonding strength, and the insertion load;

FIG. 10 is a graph showing the relationship between the number of angles of a regular polygonal shaft hole of the fitting member and the joining strength;

[Explanation of symbols]

10: shaft (shaft), 12: raised part, 20: fitting member (cam piece, crank, gear), 21: arc surface, 22: chord surface, 23: inclined surface, 25: shaft hole

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-56-97627 (JP, A) JP-A-63-297707 (JP, A) JP-A-3-121315 (JP, A) 106469 (JP, U) Japanese Utility Model 1-80825 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16D 1/06 F01L 1/04 F16H 53/02

Claims (5)

(57) [Claims] 1. A shaft having a continuous or discontinuous protruding portion formed on a peripheral surface thereof, and a shaft having a smaller inner diameter than an outer diameter of the protruding portion provided on an inner periphery of a shaft hole of a fitting member. a machine elements assembled together by press-fit in a direction, it said raised
The portion is formed in a shape extending in the axial direction, and at least one or more chord surfaces whose distance to the axis is smaller than the outer radius of the raised portion are provided in advance on the inner peripheral surface of the fitting member shaft hole. A mechanical element obtained by press-fitting a shaft into a fitting member, wherein the raised portion is elastically and plastically deformed. 2. The mechanical element according to claim 1, wherein the shaft hole is located at an eccentric position with respect to the center of the fitting member. 3. The mechanical element according to claim 2, wherein the fitting member is a cam piece, and the mechanical element is a camshaft. 4. The mechanical element according to claim 1, wherein the shaft hole is located concentrically with respect to the center of the fitting member. 5. A machine comprising: a protruding portion forming step of forming a protruding portion extending continuously or discontinuously on a peripheral surface of a shaft; and a fitting step of axially press-fitting the shaft into a shaft hole of a fitting member. In the method of manufacturing an element, the ridge is extended in an axial direction.
An elongated shape , at least one or more chord surfaces whose distance to the axis is smaller than the outer radius of the raised portion are previously formed on the inner peripheral surface of the shaft hole of the fitting member, and the raised portion is formed by the chord surface. A method for manufacturing a mechanical element comprising press-fitting a shaft into a fitting member, characterized by elastically and plastically deforming the shaft.