JP2000326028A - Assembled camshaft - Google Patents

Abstract

(57) [Problem] To provide an assembling camshaft for reducing the pushing load of an expanding pipe punch and the like. SOLUTION: A cam lobe 5 is a forged product made of steel, and eight concave stripes 11 are formed at equal intervals by broaching or the like on an inner peripheral surface of a shaft fitting hole 9 thereof. On the other hand, the hollow shaft 3 is a drawn steel pipe, and eight convex ridges 13 corresponding to the concave ridges 11 are formed on the outer peripheral surface thereof in a drawing step. After the cam lobe 5 is loosely fitted at a predetermined position of the hollow shaft 3, a circular section expanding punch is pushed into the hollow shaft 3 by using a hydraulic press machine or the like.
The hollow shaft 3 is plastically deformed outward, and the convex ridge 13 is fitted and pressed against the concave ridge 11, and the cam lobe 5 is firmly fixed to the hollow shaft 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembling camshaft used for an engine, and more particularly to a technique for reducing a pushing load of an expanding pipe punch.

[0002]

2. Description of the Related Art As a valve operating mechanism of an engine, a rocker arm, a swing arm, and the like are interposed between a cam and an intake / exhaust valve. There is also a direct drive type with a cam arranged directly above the camera. For the camshaft on which the cam is formed, an integrated product made by casting or forging has been used, but the mechanical properties (rigidity, hardness, lubricity, etc.) can be set freely between the cam lobe and the shaft. In addition to this, the assembly type camshaft has begun to be used in part because the valve train can be reduced in weight and cost.

An assembling camshaft is composed of a hollow shaft made of a drawn steel pipe or the like, and externally fitted parts such as a cam lobe, a journal, and a nosepiece. Is fixed by a diffusion bonding method, a press-fitting bonding method, or the like. In the mainstream expansion connection method, as described in JP-A-1-125506, an outer fitting part having a plurality of concave streaks formed on an inner peripheral surface of a shaft fitting hole is loosely fitted to a cylindrical hollow shaft. After that, the hollow shaft is expanded by inserting a pipe expanding punch having a projection corresponding to the concave streak into the hollow part, and the external fitting part is fixed. The hollow shaft is generally made of a drawn steel pipe or the like, while a cast, forged, or cut product made of cast steel or steel is used as the external fitting.

[0004]

However, in the above-mentioned assembled camshaft of the expansion connection type, the expansion punch is hollow because the outer peripheral portion of the hollow shaft is inserted into the concave portion on the outer fitting part side by plastic deformation. It is necessary to increase the pushing load (or pulling load) when inserting the shaft. For this reason, large-sized hydraulic presses and the like used for inserting the expanding pipe punch are required, and assembling equipment becomes expensive and large-scale, and at the same time, the manufacturing cost per assembled camshaft increases. Was.
In addition, since the shank of the pipe expanding punch needs to have a large shaft with large buckling (or tensile strength), the diameter of the hollow portion of the hollow shaft cannot be reduced. It was difficult to realize SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an assembling camshaft in which the pushing load of a pipe expanding punch is reduced.

[0005]

In order to solve the above-mentioned problems, according to the present invention, an outer fitting part having a recess formed on an inner peripheral surface of a shaft fitting hole is fitted to a hollow shaft, and then the hollow fitting is formed. An assembling camshaft in which the hollow shaft is fixed to the outer fitting part by expanding a shaft, wherein a convex ridge corresponding to the concave ridge is previously formed on an outer peripheral surface of the hollow shaft. suggest.

In the assembled camshaft according to the present invention, for example, after the externally fitted part is loosely fitted to the hollow shaft at a position where the convex ridge is fitted to the concave ridge, a pipe expanding punch is formed in the hollow shaft using a hydraulic press or the like. Press. Then, the hollow shaft is plastically deformed outward by pushing the expanding pipe punch with a relatively small pushing load, and the convex ridge is fitted and pressed into the concave ridge, and the external fitting part is fixed to the outer periphery of the hollow shaft. .

[0007]

FIG. 1 is a side view showing an embodiment of an assembled camshaft (hereinafter simply referred to as a camshaft) according to the present invention. Camshaft 1 is 4 cycle DO
It drives the intake valve of an HC multi-cylinder engine. A cam lobe 5, a journal 7, etc. are fitted around the hollow shaft 3.
It is manufactured by fixing. In the case of the present embodiment, the cam lobe 5 is a forged product made of steel, and as shown in FIG. 2, the inner peripheral surface of the shaft fitting hole 9 is provided with eight concave stripes 11 by broaching or the like. Are formed at equal intervals. On the other hand, the hollow shaft 3 is a drawn steel pipe, and as shown in FIGS. 3 and 4, eight convex ridges 13 corresponding to the concave ridges 11 are formed on the outer peripheral surface thereof in the drawing step. In FIG. 1, a member indicated by reference numeral 15 is a nosepiece provided for mounting a timing gear (not shown).

In this embodiment, in assembling the camshaft 1, first, as shown in FIG. 5, a cam lobe 5 or the like is loosely fitted at a predetermined position of the hollow shaft 3, and then the exaggerated illustration is shown in FIG. As described above, the pipe expanding punch 21 having a circular cross section is pushed into the hollow portion 17 of the hollow shaft 3 using a hydraulic press or the like. Then, as shown in FIG. 7 (a cross-sectional view taken along the line AA in FIG. 1), the hollow shaft 3 is plastically deformed outward, and the convex ridge 13 is fitted and pressed into the concave ridge 11, and the hollow shaft 3 is brought into contact with the hollow shaft 3. The cam lobe 5 is firmly fixed. At this time, since the ridge 13 is formed on the outer periphery of the hollow shaft 3 in advance, the amount of plastic deformation of the hollow shaft 3 is relatively small.
The indentation load can also be kept low. In this embodiment, the journal 7 and the nosepiece 15 are fixed to the hollow shaft 3 in the same manner as the cam lobe 5.

In the present embodiment, by adopting such a configuration, the hydraulic press and the like for pushing the pipe-expanding punch 21 can be downsized, and the equipment cost can be greatly reduced. Further, a punch having a shank 23 with a thin shaft can be adopted as the pipe expanding punch 21, and the diameter of the hollow shaft 3, that is, the weight of the camshaft 1 can be reduced.

FIGS. 8 and 9 both show a modified example of the hollow shaft 3. FIG. 8 shows a concave shaft 31 on the inner peripheral surface of the hollow portion 17 in a shape corresponding to the convex line 13 on the outer peripheral side. Has,
In FIG. 9, the outer periphery and the hollow portion 17 are similar octagons, and each apex angle on the outer periphery is a ridge 13. In these modified examples, the thickness of the hollow shaft 3 is substantially uniform in the circumferential direction, so that the drawing process is easier than in the above embodiment. still,
In both of these modified examples, the camshaft 1 is assembled in the same manner as in the above-described embodiment by using a pipe expanding punch having a circular cross section.

The description of the specific embodiment has been completed.
Aspects of the present invention are not limited to this embodiment.
For example, in each of the embodiments described above, a punch having a circular cross section is used as the tube expanding punch, but a punch having a protrusion on the outer periphery may be used. Also, the specific configuration of the camshaft, the specific shape of the concave streak, and the specific shape of the convex streak can be appropriately changed without departing from the gist of the present invention.

[0012]

According to the present invention, after the outer fitting part having a recess formed on the inner peripheral surface of the shaft fitting hole is fitted externally to the hollow shaft, the hollow shaft is expanded to expand the hollow shaft. An assembling camshaft in which the external fitting part is fixed, wherein a convex ridge corresponding to the concave ridge is formed in advance on the outer peripheral surface of the hollow shaft, so that a hydraulic press machine or the like for pushing a pipe expansion punch is used. In addition to being able to reduce the size, it is possible to realize a significant reduction in equipment costs,
An expansion pipe punch having a thin shaft shank can be used.
It is also possible to reduce the diameter of the hollow shaft and the weight of the camshaft.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of an assembled camshaft according to the present invention.

FIG. 2 is a side view of a cam lobe.

FIG. 3 is a perspective view of a hollow shaft.

FIG. 4 is a longitudinal sectional view of a hollow shaft.

FIG. 5 is a perspective view showing a state in which a cam lobe is loosely fitted to a hollow shaft.

FIG. 6 is an explanatory view showing a tube expanding process of a hollow shaft.

FIG. 7 is a sectional view taken along the line AA in FIG.

FIG. 8 is a longitudinal sectional view showing a first modification of the hollow shaft.

FIG. 9 is a longitudinal sectional view showing a second modification of the hollow shaft.

[Explanation of symbols]

 1 Camshaft 3 Hollow shaft 5 Cam lobe 9 Shaft insertion hole 11 Concave strip 13 Convex strip 17 Hollow section 21 Expanding punch

Claims (1)

[Claims] 1. An outer fitting part having a recess formed on an inner peripheral surface of a shaft fitting hole is externally fitted to a hollow shaft, and then the hollow shaft is expanded to connect the hollow shaft and the outer fitting part. An assembling camshaft which is fixed, wherein a ridge corresponding to the recess is formed in advance on an outer peripheral surface of the hollow shaft.