JPH07239009A - Cam shaft and its manufacture - Google Patents

Abstract

PURPOSE:To facilitate the fitting of multiple cams to a cam shaft in which a shaft main body is separated from the cams. CONSTITUTION:A shaft main body 2 is inserted into a forming mold beforehand, and a cam 3 is injection-molded on the outer periphery of the shaft main body 2 out of plastics. Multiple cams 3 are connected integrally to each other. Thus a highly accurate cam shaft 1 can be mass-produced easily at reduced cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft used in a power transmission system and a method for manufacturing the camshaft.

[0002]

2. Description of the Related Art A camshaft used for a power transmission system or the like is provided with a cam for controlling the movement of a cam follower on the outer periphery of a shaft body which is rotatably supported. As a conventional camshaft, for example, JP-A-4-8915
As described in Japanese Patent Publication No. 6, a shaft body and a cam that are entirely cast with cast iron, a steel shaft body that is welded with a cam made of a sintered alloy, or the like. As described in JP-A-2-213402, there is one in which a cam is fixed to the outer circumference of the shaft body by mechanical press fitting.

However, in the case of integrally casting the entire shaft body and the cam, there are restrictions on the selection of the respective materials, and precision is difficult to obtain because of casting.
Further, if a separate cam is incorporated into the shaft body by welding or press fitting, the number of manufacturing steps and the cost are increased. This becomes more remarkable as the number of cams incorporated in one shaft body increases. For example, in the case of press-fitting, the knurling for press-fitting is rolled on the outer circumference of the shaft main body, and then this shaft main body is press-fitted into the cam, but this has to be repeated many times, and the number of steps is very large. Become.

Japanese Patent Laid-Open No. 4-36417 discloses casting a shaft main body and a cam on the outer periphery of a core material. However, in this case, the same problem as in the case of casting the whole is also encountered. is there.

[0005]

As described above, in the conventional method for manufacturing a camshaft in which the entire shaft body and cam are cast, there are restrictions on the selection of the respective materials of the shaft body and the cam, and the accuracy is improved. There was a problem that it was difficult to put out. Further, in the conventional camshaft manufacturing method in which a separate cam is incorporated into the shaft body by welding or press fitting, there is a problem that the number of manufacturing steps and the cost are increased.

The present invention is intended to solve such a problem, and the shaft main body and the cam are formed as separate bodies, so that the degree of freedom in selecting the materials of the shaft main body and the cam can be increased and the high precision camshaft can be obtained. A first object of the present invention is to enable easy manufacturing at low cost. A second purpose is to increase the strength of a plurality of cams, and a third purpose is to increase the coupling strength between the shaft body and the cams.

[0007]

According to a first aspect of the present invention, there is provided a method for manufacturing a camshaft, wherein a shaft main body is previously inserted into a molding die in order to achieve the first object.
A cam is injection-molded on the outer periphery of the shaft main body by using plastic to enclose it.

According to a second aspect of the present invention, in order to achieve the second object as well, in the camshaft manufactured by the method for manufacturing a camshaft according to the first aspect, a plurality of cams are integrally connected. Is.

According to a third aspect of the present invention, in order to achieve the third object as well, in the camshaft manufactured by the method for manufacturing a camshaft according to the first aspect, the cam forming portion on the outer periphery of the shaft body is formed. It has a non-cylindrical surface.

[0010]

In the method of manufacturing a camshaft according to the first aspect of the present invention, since the cam is injection-molded with the shaft body as an insert, the material of the shaft body is
Appropriate materials that can withstand heat and chemical reactions during molding can be used. As the material of the cam, an appropriate material that can be injection-molded can be adopted. And even if there are many cams, these cams can be molded at once. The accuracy of the cam depends on molding conditions including the dimensional accuracy of the molding die.

According to the second aspect of the present invention, since the plurality of cams are integrally connected, the strength is increased, and in the molding die, the gate is provided for the plurality of integrally connected cams. Can be shared.

In the cam shaft of the third aspect of the present invention, the cam body is formed on the outer periphery of the shaft body having a non-cylindrical surface, so that the coupling strength between the shaft body and the cam is high.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the camshaft 1. The present camshaft has a plurality of cams 3 incorporated on the outer periphery of the shaft body 2. The cams 3 are eccentric with respect to the shaft body 2 and are fixed with a predetermined directionality. The plurality of cams 3 are integrally connected in the axial direction. In addition, in the present embodiment, the outer peripheral surface of the shaft body 2 is a cylindrical surface.
May be hollow pipe-shaped or solid.

The material of the shaft body 2 is steel,
Examples include stainless steel, damping alloy, copper, aluminum or plastic. The material of the cam 3 is plastic. As this plastic, various thermoplastic resins and thermosetting resins are used. As the thermoplastic resin, polyamide, polycarbonate, polyethylene terephthalate, polyacetal, polyether sulfone, polyimide or the like is used. As the thermosetting resin, epoxy resin, ADC resin or the like is used. Besides, polymer alloy or carbon fiber reinforced plastic (CFRP) may be used. When the shaft body 2 is made of plastic, it may be made of the same material as the cam 3, but may be made of a different material.

During manufacture, the cam 3 is cast around the outer periphery of the shaft body 2 by injection molding. FIG. 2 shows an example of the molding die 11. In the figure, 12 is a fixed type, 13 is a movable type, and these fixed type 12 and movable type 13
Are to move in the vertical direction in the figure to be opened and closed to form a cavity 14 in the shape of the cam 3 between them when the mold is closed. Since multiple cams 3 are connected together, the cavity
14 is one in a row. A gate 15 is formed on the fixed mold 12 so as to face the cavity 14. Further, the outer peripheral surface of each cam 3 is formed by the nests 16 and 17 which are embedded and fixed in the fixed die 12 and the movable die 13 respectively corresponding to the respective cams 3. Such a structure of the inserts 16 and 17 requires that the positions of the split surfaces of the fixed die 12 and the movable die 13 be changed in each cam 3 due to the difference in directionality, and that the outer circumference of the cam 3 to be formed in particular be changed. It was adopted to improve the accuracy of the surface.

At the time of injection molding, the mold is first closed. At the time of this mold closing, the shaft body 2 is previously inserted between the fixed mold 12 and the movable mold 13. In this state, a fluid plastic material is filled from the gate 15 into the cavity 14. Then, after the plastic with which the cavity 14 is filled is solidified, the mold is opened and the cam shaft 1 in which the cam 3 is cast around the shaft body 2 is taken out.

According to the configuration of the above-described embodiment, the shaft main body 2 and the cam 3 are separated, so that the degree of freedom in selecting the material of the shaft main body 2 and the cam 3 is increased.
Of course, different materials can be used. As the material of the shaft body 2, an appropriate material that can withstand heat or chemical reaction during molding can be adopted. As the material of the cam 3, any material that can be injection-molded can be adopted. For example, if the shaft main body 2 and the cam 3 are made of a material that is melted and integrated as the cam 3 is molded, the coupling strength between the shaft main body 2 and the cam 3 can be increased. Also,
If the material of the shaft body 2 is a damping alloy, excellent damping and soundproofing effects can be obtained. Furthermore, the shaft body 2 also
It can be made of a material with excellent corrosion resistance. Further, since the cam 3 is made of plastic, the weight can be reduced.

Further, a large number of cams 3 can be molded at one time with respect to one shaft main body 2. Therefore, the camshaft 1 can be manufactured at a low cost with a small number of steps. Furthermore, since the plurality of cams 3 are integrally connected, the gate 15 can be shared by the plurality of cams 3 in the molding die 11.
Therefore, the structure of the molding die 11 can be simplified. Further, the fact that a plurality of cams 3 are integrally connected increases the strength of these plastic cams 3.

Further, since the accuracy of the cam 3 depends on the molding conditions including the dimensional accuracy of the molding die 11, if this is first set appropriately, then the highly accurate camshaft 1 can be easily manufactured thereafter. Can be mass-produced. Further, the fact that the molding method is injection molding is also advantageous in improving accuracy. The improved accuracy also improves the weight balance of the camshaft 1 as a whole.

Further, as the injection molding, in addition to usual thermoplastic resin injection molding, injection compression molding or transfer molding in the case of a thermosetting resin can be adopted.

FIG. 3 shows another example of the molding die 11. The molding die 11 includes a fixed die 11 and a movable die 12 that are closed.
To form a runner 21 between and this runner
The side gate 22 at the tip of 21 is opened to a position corresponding to the end faces of the cams 3 at both ends of the cavity 14. If the gate 15 is opened at a position corresponding to the outer peripheral surface of the cam 3, a gate mark remains on the outer peripheral surface of the cam 3 that requires high accuracy, and then machining is required, but as described above,
If the gate 22 is provided at a position corresponding to the end surface of the cam 3, the processing of the trace of the gate becomes easy.

FIG. 4 shows still another example of the molding die 11. The molding die 11 has an extending portion 26 at a position further axially outside the cams 3 at both ends in the cavity 14.
The pinpoint gate provided on the fixed mold 12 side
27 is opened. The extending portion 26 forms a convex portion of the camshaft 1 that is not the cam 3. That is,
Since this convex portion is not the cam 3, there is no problem in accuracy or the like, and the processing of the gate mark becomes easy.

FIG. 5 shows a second embodiment of the camshaft 1 according to the present invention. In this camshaft 1, the plurality of cams 3 themselves are located discretely, but these cams 3 are integrally connected by a cylindrical connecting portion 31 that covers the outer periphery of the shaft body 2. That is, this connecting portion 31 is injection molded integrally with the cam 3. The connecting portion 31 improves the strength of the plurality of cams 3 and allows the molding die 11 to share the gate 15 with the plurality of cams 3.

FIG. 6 shows a third embodiment of the camshaft 1 according to the present invention. In this camshaft 1, a plurality of cams 3 are located separately from each other. In this case, in the molding die 11, the cavities 14 are separated from each other for each cam 3, so that it is necessary to provide the gate 36 for each of the cavities 14.

FIG. 7 shows a fourth embodiment of the camshaft 1 according to the present invention. The camshaft 1 is formed by rolling a flat knurl 41 along the axial direction of the cam body 3 at least at the cam 3 forming portion before the cam 3 is formed. This flat knurled 41
Even if the shaft body 2 and the cam 3 are made of a material that cannot be integrated due to melting, the cam 3 can be surely prevented from rotating with respect to the shaft body 2 by digging into the molded cam 3. The coupling strength between the cam 2 and the cam 3, especially the strength against torsion is increased.

The shape for the detent is the fourth
The shape is not limited to the flat knurl 41 as in the embodiment, and may be an appropriate shape such as a hexagonal prism surface as in the fifth embodiment shown in FIG. 8, another prismatic surface, or a cylindrical surface having an elliptical cross section.

FIG. 9 shows a camshaft 1 according to a sixth embodiment of the present invention. In this camshaft 1, a circumferential convex portion 42 is formed on at least the cam 3 forming portion on the outer periphery of the shaft body 2 before the cam 3 is molded.
Further, FIG. 9 shows a sixth embodiment of the camshaft 1 of the present invention. In this camshaft 1, a circumferential knurl 43 is formed at least on the outer periphery of the shaft body 2 where the cam 3 is formed before the cam 3 is formed. The projections 42 and the twill knurls 43 also increase the coupling strength between the shaft body 2 and the cam 3. In particular, the convex portion 42 in the circumferential direction is effective in preventing axial displacement,
The twill knurl 43 is effective both as a rotation stopper and an axial shift stopper.

In the fourth to seventh embodiments, the bearings such as both ends of the shaft body 2 need to have a perfect circular cross section.

[0029]

According to the first aspect of the present invention, the shaft main body is inserted into the molding die in advance, and the cam is injection-molded around the outer periphery of the shaft main body with plastic, so that the shaft main body is cast. Also, the degree of freedom in selecting the material of the cam is great, and even if there are many cams for one shaft body, it is possible to easily mass-produce a high-precision cam shaft at low cost.

According to the invention of claim 2, since a plurality of cams are integrally connected, the strength of these cams made of plastic is improved, and in the molding die, the plurality of cams are integrally connected to each other. Gate can be shared, and the structure of the molding die can be simplified.

According to the third aspect of the present invention, since the cam forming portion on the outer periphery of the shaft body is a non-cylindrical surface, the coupling strength between the shaft body and the cam can be increased.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing an example of a molding die for forming the same cam.

FIG. 3 is a plan view of a divided surface showing another example of the same metal mold for forming the cam.

FIG. 4 is a cross-sectional view showing still another example of the metal mold for forming the cam.

FIG. 5 is a sectional view showing a second embodiment of the camshaft of the present invention.

FIG. 6 is a sectional view showing a third embodiment of the camshaft of the present invention.

7A and 7B show a fourth embodiment of a camshaft according to the present invention, where FIG. 7A is a sectional view and FIG. 7B is a side view of a shaft body.

FIG. 8 is a sectional view showing a fifth embodiment of the camshaft of the present invention.

FIG. 9 is a side view of a shaft body showing a sixth embodiment of the camshaft of the present invention.

FIG. 10 is a side view of a shaft body showing a seventh embodiment of the camshaft of the present invention.

[Explanation of symbols]

 1 Camshaft 2 Shaft body 3 Cam 11 Mold for molding

Claims (3)

[Claims] 1. A method of manufacturing a cam shaft, wherein a shaft main body is inserted into a molding die in advance, and a cam is injection-molded from the outer periphery of the shaft main body with a plastic to be cast. 2. A camshaft manufactured by the method for manufacturing a camshaft according to claim 1, wherein a plurality of cams are integrally connected. 3. A camshaft manufactured by the method for manufacturing a camshaft according to claim 1, wherein the cam forming portion on the outer periphery of the shaft body is a non-cylindrical surface.