JPS6229607Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a camshaft.

In recent years, internal combustion engines have been required to be lighter in weight from the viewpoint of energy conservation, and at the same time, higher speeds and higher outputs have been required. Accordingly, there is a current demand for a camshaft that is lightweight, has excellent strength and wear resistance, and is also excellent in productivity.

Traditionally, forged camshafts were used for relatively low-load applications, but as the performance of internal combustion engines improves, quenched or chilled cast camshafts, which have excellent wear resistance, are now commonly used. .

However, cast iron camshafts are generally heavy and not particularly strong.
Furthermore, when casting a large camshaft, bending and casting defects are likely to occur, and in addition, special techniques are required to control the chilled layer and quenching, which is often technically difficult to manufacture.

On the other hand, in order to improve strength and weight reduction, a camshaft is known in which the cam lobe is made of a sintered alloy and the stem is made of a steel pipe, that is, each member is made of different materials.

However, these camshafts have various problems because each member is directly assembled to the stem. First, it is necessary to provide the stem with grooves and pins for positioning each member in the axial and rotational directions with respect to the stem, which not only requires a complicated process but also reduces the strength of the stem. Next, the stem and each member are bonded together by brazing or sintering while assembled to the stem, so if there is a defect in bonding at even one point, the entire camshaft becomes unusable. Furthermore, the sintered alloy has poor weldability even when attempting to join it to a steel stem by normal welding. Furthermore, when brazing, there is no suitable brazing agent for joining the steel journal and gear, the sintered metal cam lobe, and the steel stem, and there are concerns about joining by brazing. On the other hand, if only the cam lobe remains unsintered and is assembled to the stem along with the journal and gear, and this assembled body is sintered and bonded in a sintering furnace, bond strength will be obtained, but production efficiency will be poor as well. The stem may be bent or distorted due to sintering heating.

In order to solve the above problems, this invention reduces weight by fixing a collar to the outer circumference of the stem, fixing a sintered metal cam lobe to the outer circumference of the collar, and forming a journal at one location on the collar. It is an object of the present invention to provide a camshaft in which the strength and productivity of the stem portion are improved.

Hereinafter, embodiments embodying the present invention will be described based on the drawings.

FIG. 1 shows an embodiment of the camshaft of the present invention, in which a stem 1 made of steel pipe is provided with:
Fix collar 2 and gear 5. A sintered metal cam lobe 3 is fixed to the outer peripheral side of the collar 2, and one end of the collar 2 is expanded to form a journal 4. This journal 4 may be formed by one collar 2, or may be formed by having two collars 2, 2 with their enlarged ends facing each other, as shown in the center of FIG. Also, a cap 8 is attached to one end of the stem 1, and a belt wheel 9 is attached to the other end.
A bushing 7 for mounting is coupled to support the journal 4. As a means for fixing the collar 2 and the gear 5 to the stem 1, either press fitting or hardening is possible.

FIG. 2 shows another embodiment of the camshaft of the present invention. In the figure, the same components as those in FIG. 1 are given the same reference numerals. The same applies to the embodiments described below. In this embodiment, a collar 2 is integrally provided for each cam lobe. Thereby, rotational positioning of the cam lobe 3 can be made unnecessary. Further, the journal 4 can also be formed in the center of the collar 2.

FIG. 3 shows yet another embodiment of the camshaft of the present invention. In this embodiment, the journal 4 formed on the collar 2 is supported in the radial direction by the plate 42 to increase the strength of the journal 4.

Figure 4 shows a state in which the collar 2 and the cam lobe 3 are joined by special welding.The cam lobe 3 is arranged near the end of the collar 2, and a high energy beam 10 (electron beam, laser beam, etc.) is applied to the joint. etc.) and welded by irradiation. Since the present invention is equipped with the collar 2, it is possible to perform special welding with a high-energy beam, which is impossible with complex-shaped objects such as camshafts. Of course, the collar 2 and the cam lobe 3 can also be joined together by brazing. Furthermore, by assembling and sintering the cam lobe 3 with the collar 2 in the form of a powder compact or a primary sintered body, it is also possible to combine the two by utilizing the shrinkage and diffusion of the cam lobe 3.

In this invention, the color obtained in this way,
Heat treatments such as strain relief, hardening, and tempering can be performed using only the collar, and the risk of bending, quench cracking, etc. that tends to occur in long camshafts with a large number of cylinders due to heat treatment can be eliminated.

FIG. 5 shows yet another embodiment of the camshaft of the present invention. In this example,
The collar 2 is provided with a recess 20 for positioning, and the gear 5 is provided with a projection 40 that fits into the recess 20 for positioning. This positioning recess 20 is fitted with the protrusion 40 of the gear 5 to assemble the collar 2 and gear 5, and then the stem 1 is press-fitted into the collar 2 and gear 5 to form a camshaft. Although the camshaft has sufficient strength even when the stem 1 is press-fitted, it may be fixed by shrink-fitting. Further, the strength can be further increased by welding or brazing the collar 2 and the gear 5 to the stem 1 after press-fitting or hardening.

As mentioned above, in the present invention, the journal is formed at one place on the collar, so there is no need to provide a separate journal, and in contrast to the conventional journal, which was formed of a steel cylinder and had a large weight and rotational inertia. Since the journal of the present invention is hollow, it is extremely lightweight and the rotational inertia can be reduced.

In addition, since there are no restrictions on the means of connecting the cam lobe and the collar, not only can the strength of this bond be strengthened, but the contact area between the collar and stem is large, so they are extremely strongly bonded, and they form a double structure. Therefore, the rigidity against torsional bending of the camshaft is increased. Furthermore, since the cam lobe only requires positioning for each collar, there is no need to drill grooves or holes in the stem or collar for positioning, so the mechanical strength of the stem or collar can be increased.

Furthermore, since the cam lobe only requires positioning for each collar, rotational positioning is easy, and no special indexing device is required, so productivity can be improved. In addition, since the cam lobe is connected to the outer circumferential side of the collar, both can be assembled in advance, and since the collar is independent, the stem to which the cam lobe is fixed can be heat-treated using only the collar, increasing productivity. It has various advantages such as being able to improve both strength and strength.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal side view showing one embodiment of the camshaft of the present invention, FIG. 2 is a longitudinal side view showing another embodiment of the camshaft of the present invention, and FIG.
The figure is a part of a vertical side view showing still another embodiment of the camshaft of the present invention, FIG. 4 is a diagram showing a state in which the collar and cam lobe are combined, and FIG. 5 is a diagram showing still another embodiment of the camshaft of the present invention. It is an exploded side view showing an example of this. In the diagram, 1... Stem, 2... Collar, 3... Cam lob, 4... Journal, 5... Gear, 20...
... hollow, 40 ... protrusion, 42 ... plate.

Claims (1)

[Scope of utility model registration request] In a camshaft in which a sintered metal cam lobe is assembled to a stem, a collar 2 is attached to the outer circumferential side of the stem 1.
, a cam lobe 3 is fixed to the outer peripheral side of the collar 2, and a journal 4 is formed by expanding a part of the collar at one location of the collar 2.