JPH07243509A - Cam shaft - Google Patents

Abstract

PURPOSE:To certainly increase the strength of a cam such as the bonding strength with a shaft body by forming metal cams on the periphery of the shaft body by means of insert die-casting, and shaping the cam formed part on the shaft body in square columnar surfaces. CONSTITUTION:A cam shaft 1 is made by forming a plurality of cams 3 on the periphery of a shaft body 2 in such a way as positioned eccentrically with respectivly specified directionalities by means of insert die-casting. The cams 3 are laid in tight attachment with one another in the axial direction. The cam formed part on the shaft body 2 is made in square columnar surfaces, which heightens the bonding strength of the cams 3 with the shaft body 2, and the cams 3 can be precluded from turning relative to the shaft body 2 certainly.

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.

On the other hand, Japanese Unexamined Patent Publication No. 52-73212 discloses that a cam and a cam gear made of an aluminum alloy are cast around the outer circumference of a steel shaft body by die casting. Further, it is described that the cam and the cam gear forming portion on the outer periphery of the shaft main body is formed into an elliptic cylindrical surface or roughened in order to prevent the rotation and the disengagement.

The above-mentioned Japanese Patent Laid-Open Publication No. 52-73212 only discloses that one set of cam and cam gear is mounted on one shaft main body. Even if there are a plurality of cams, if they are die-cast at the same time, the number of manufacturing steps can be reduced.
However, when there are a plurality of cams, if they are separated, the strength of the cams will be weakened due to die casting. Further, as described in JP-A-52-73212, only by forming the cam and cam gear formation portion on the outer periphery of the shaft main body into an elliptic cylindrical surface or roughening the surface, a rotation stopper or a slip-out prevention member can be obtained. The effect is weak.

[0006]

As described above, even when the cams are formed around the outer circumference of the shaft body by die casting, if a plurality of cams are separated from each other,
There is a problem that the strength of the cam becomes weak. In addition, because the cam and the shaft body are connected by die casting, the method disclosed in Japanese Patent Laid-Open No. 52-7
As described in Japanese Patent No. 3212, there is a problem that sufficient bonding strength cannot be obtained only by forming the cam and cam gear forming portions on the outer periphery of the shaft body into an elliptic cylindrical surface or roughening the surface.

The present invention is intended to solve such problems, and in a cam shaft in which a cam is die-cast on the shaft body, the strength of the cam such as the coupling strength with the shaft body is surely increased. Is the first purpose. In addition to that, the second purpose is to enhance vibration damping and soundproofing effects.

[0008]

According to a first aspect of the present invention, in order to achieve the first object, there is provided a cam shaft, which is formed by die-casting a metal cam on the outer periphery of the shaft main body, and which is formed by casting. The cam forming portion on the outer periphery of the shaft body is a prismatic surface.

According to a second aspect of the present invention, in order to achieve the first object, a cam shaft formed by die-casting a metal cam on the outer periphery of the shaft main body to form a cast metal cam is provided on the outer periphery of the shaft main body. A plurality of concave and convex portions are cut and formed in the formation portion of.

According to a third aspect of the present invention, in order to achieve the first object, a plurality of cams are brought into close contact with each other in a cam shaft which is formed by die-casting a metal cam on the outer periphery of the shaft main body and is cast around. Are connected together.

According to a fourth aspect of the present invention, in order to achieve the second object as well, in the camshaft according to any one of the first to third aspects, the material of the shaft body is a damping alloy. .

[0012]

According to the camshaft of the first aspect of the present invention,
The shaft main body is inserted in advance in the molding die, and a metal cam is formed on the outer periphery of the shaft main body by die casting to be cast. Therefore, even if there are many cams, these cams can be molded at once. Further, the cam forming portion on the outer periphery of the shaft body is a prismatic surface, which enhances the coupling strength between the shaft body and the cam, and particularly prevents the cam from rotating with respect to the shaft body.

Further, in the camshaft according to the second aspect of the present invention, the plurality of concave and convex portions cut and formed in the cam forming portion on the outer periphery of the shaft body surely enhances the coupling strength between the shaft body and the cam.

Further, in the camshaft according to the third aspect of the present invention, since the plurality of cams are closely contacted and integrally connected to each other, the strength thereof is increased, and in the molding die, the plurality of cams integrally connected to each other. You can share the gate.

Further, in the camshaft according to the fourth aspect of the present invention, the shaft main body made of the damping alloy provides damping and soundproofing.

[0016]

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 closely connected in the axial direction and are integrally connected. In the present embodiment, the outer peripheral surface of the shaft body 2 is a cylindrical surface, but the shaft body 2 may be hollow pipe-shaped or solid.

The material of the shaft body 2 is steel,
Examples include stainless steel, damping alloys, copper and aluminum. The material of the cam 3 is aluminum, zinc, magnesium or alloys thereof. The shaft body 2 and the cam 3 may be made of the same material,
Different materials can be used.

At the time of manufacture, the cam 3 is formed on the outer periphery of the shaft body 2 by die casting and is wrapped around.
2 and 3 show an example of the molding die 11. In the figure, 12 is a fixed die and 13 is a movable die. The fixed die 12 and the movable die 13 move in the vertical direction in the drawing to open and close, and when the mold is closed, a cavity 14 having a shape of a cam 3 is formed between them. Is formed. Since the plurality of cams 3 are integrally connected, the cavity 14 is one continuous one. And this cavity 14
Facing each other, a gate 15 is formed between the fixed die 12 and the movable die 13 which are closed. Further, the outer peripheral surface of each cam 3 is embedded in and fixed to the fixed die 12 and the movable die 13 in correspondence with each cam 3, respectively.
Is formed by. Due to the difference in directionality, the structure of the inserts 16 and 17 has a fixed die 12 and a movable die 13 for each cam 3.
That the position of the dividing plane with and must be changed, and
In particular, it is adopted to improve the accuracy of the outer peripheral surface of the cam 3 to be molded.

When die casting, the mold is first closed, but when the die is closed, the fixed die 12 and the movable die are closed.
The shaft main body 2 is previously inserted between 13 and 13. In this state, the molten metal is injected into the cavity 14 through the sprue 15 and filled. Then, after the molten metal filled in the cavity 14 is cooled and 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 provided separately, 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 the heat of die casting can be adopted. The cam 3 may be made of any material that can be die-cast. For example, if the shaft main body 2 and the cam 3 are made of a material which is melted and integrated with each other when the cam 3 is molded, the shaft main body 2
And the coupling strength of the cam 3 can be increased. Further, if the material of the shaft body 2 is a damping alloy, excellent damping and soundproofing effects can be obtained. Further, the shaft body 2 can also be made of a material having excellent corrosion resistance. Further, by making the cam 3 of aluminum or the like, it is possible to reduce the weight.

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 sprue 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. Also,
The fact that the plurality of cams 3 are integrally connected enhances the strength of these cams 3 by die casting. That is, cam 3
Even if the strength of the material itself is weak, this can be compensated.

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, it is also advantageous in accuracy improvement that the molding method is die casting instead of casting such as the lost wax method. The improved accuracy also improves the weight balance of the camshaft 1 as a whole.

FIG. 4 shows another example of the molding die 11. The molding die 11 opens the sprue 15 to a position corresponding to the end surface of the cam 3 at the end of the cavity 14. When the sprue 15 is opened at a position corresponding to the outer peripheral surface of the cam 3, a sprue mark remains on the outer peripheral surface of the cam 3 which requires high accuracy, and machining is required thereafter, but as described above,
If the sprue 15 is provided at a position corresponding to the end face of the cam 3, the sprue trace can be easily treated.

FIG. 5 shows still another example of the molding die 11. The molding die 11 has an extending portion 21 at a position further axially outside the cams 3 at both ends in the cavity 14.
Is provided, and the sprue 15 is opened here. Extension part
Reference numeral 21 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 and the like, and the sprue mark is easily processed.

FIG. 6 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, the connecting portion 31 is formed integrally with the cam 3 by die casting. The connecting portion 31
As a result, the strength of the plurality of cams 3 is improved, and the sprue 15 can be shared by the plurality of cams 3 in the molding die 11.

FIG. 7 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, and therefore it is necessary to provide the sprue 15 for each of the cavities 14.

FIG. 8 shows a fourth embodiment of the camshaft 1 according to the present invention. The cam shaft 1 is formed by cutting a flat knurl 41 along the axial direction of the cam main body 2 at least at a portion where the cam 3 is formed by rolling or the like before molding the cam 3. By engaging the flat knurls 41, which are a plurality of uneven portions, into the formed cam 3, the cam 3 can be reliably prevented from rotating with respect to the shaft body 2, and the shaft body 2 made of a different material having different solidification shrinkage rates. Even with the cam 3 and the cam 3, the coupling strength, particularly the strength against torsion can be surely increased.

The shape for the detent is the fourth
Not limited to the flat knurls 41 as in the embodiment, a hexagonal prismatic surface 40 as in the fifth embodiment shown in FIG. 9, another convex prismatic surface, or an uneven prismatic surface such as a star-shaped cross section may be used. Even with such a prismatic surface, the coupling strength between the shaft body 2 and the cam 3 can be reliably increased.

FIG. 10 shows the sixth camshaft 1 of the present invention.
An example is shown. The camshaft 1 is formed by cutting a plurality of circumferentially uneven portions 42 at least in a portion where the cam 3 is formed on the outer periphery of the shaft body 2 before the cam 3 is molded. Further, FIG. 11 shows a sixth embodiment of the camshaft 1 of the present invention. This camshaft 1
In the outer periphery of the shaft body 2, at least the cam 3 is formed with a plurality of concave and convex circumferential knurls 43 in the circumferential direction before the cam 3 is formed.
The unevenness 42 and the twilled knurl 43 surely increase the coupling strength between the shaft body 2 and the cam 3. In particular, the uneven portion 42 in the circumferential direction is effective for preventing axial displacement, and the twill knurl 43 is effective for both rotation prevention and axial displacement prevention.

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

[0031]

According to the invention of claim 1, in a cam shaft in which a cam is die cast on the outer periphery of the shaft body, the cam forming portion on the outer periphery of the shaft body is a prismatic surface. The coupling strength with the cam can be reliably increased.

Further, according to the second aspect of the present invention, since the plurality of concave and convex portions are formed in the cam forming portion on the outer periphery of the shaft main body by cutting, the coupling strength between the shaft main body and the cam can be surely increased.

According to the third aspect of the invention, since the plurality of cams are closely contacted and integrally connected, the strength of these cams by die casting is improved, and the plurality of integrally connected cams are formed in the molding die. The sprue can be shared with the cam, and the structure of the molding die can be simplified.

Further, according to the invention of claim 4, since the material of the shaft main body is the damping alloy, excellent damping and soundproofing effects can be obtained.

[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 vertical cross-sectional view showing an example of the same metal mold for forming the cam.

FIG. 3 is a cross-sectional view of the same molding die.

FIG. 4 is a plan view of a divided surface showing another example of the same metal mold for forming the cam.

FIG. 5 is a plan view of a split surface showing still another example of the metal mold for forming the cam.

FIG. 6 is a sectional view showing a second embodiment of the cam shaft of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the camshaft of the present invention.

8A and 8B show a fourth embodiment of a camshaft of the present invention, FIG. 8A is a sectional view, and FIG. 8B is a side view of a shaft body.

FIG. 9 is a sectional view showing a fifth embodiment of the camshaft of the present invention.

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

FIG. 11 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 main body 3 Cam 40 6 Square prism surface (square prism surface) 41 Flat knurl (uneven portion) 42 Uneven portion 43 Twill knurl (uneven portion)

Claims (4)

[Claims] 1. A camshaft in which a metal cam is formed by die casting on the outer circumference of a shaft body and cast around, and the cam forming portion on the outer circumference of the shaft body is a prismatic surface. Production method. 2. A cam shaft, which is formed by die-casting a metal cam on the outer circumference of the shaft body and casts it, wherein a plurality of concave and convex portions are formed in the cam formation portion on the outer circumference of the shaft body. And camshaft. 3. A camshaft in which a metal cam is formed by die casting on the outer periphery of a shaft body and cast around, and a plurality of cams are closely contacted and integrally connected. 4. The camshaft according to claim 1, wherein the material of the shaft body is a damping alloy.