JPS6229608Y2 - - 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 perspective of energy conservation, while increasing speed and
Higher output is required. Accordingly, there is a current demand for camshafts that are lightweight, have excellent strength and wear resistance, and are also excellent in productivity.

Conventionally, forged camshafts have been used in relatively low-load applications, but as the performance of internal combustion engines improves, quenched or chilled cast iron camshafts, which have excellent wear resistance, are now being used.

However, cast iron camshafts are generally heavy and not particularly strong.
Furthermore, when casting large camshafts,
Bends and casting defects are likely to occur, and in addition, chilled layers,
Manufacturing is often technically difficult, such as requiring special techniques to control quenching.

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, the present invention fixes separate collars to the inner circumferential sides of each of the sintered metal cam lobes, journals, and gears, and brings the axial ends of the collars into contact with each other. The purpose of this invention is to improve the strength of the stem portion and provide a camshaft with high productivity by fixing the stem to the circumferential side. 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 cam lobe 3, a journal 4, a gear 5 each have separate collars 2, 2, .
is fixed. The axial ends of the collars 2, 2, . Further, a cap 8 is coupled to one end of the stem 1, and a bush 7 for mounting a belt pulley 9 to the other end. The collars 2, 2, . . . and the stem 1 are sufficiently fixed by press-fitting or shrink-fitting, but conventional welding may also be used.

Further, in this embodiment, one cam lobe 3 is fixed to each collar, but only adjacent cam lobes 3 may be fixed to the same collar 2. This eliminates the need for positioning the cam lobes 3, thereby reducing the number of production steps.

FIG. 2 shows a state in which the collar 2 and the cam lobe 3 are joined by special welding.

As shown in the above embodiments, in the present invention, the sintered metal cam lobe is not fixed to the stem, but is fixed to the collar in advance, and the collar is fixed to the stem, so that various coupling methods are possible.

First, the cam lobe 3 is assembled with the collar 2 in the form of a powder compact or a primary sintered body, and is sintered to shrink the cam lobe 3 and promote diffusion to be fixed to the collar 2. In this method, only the collar 2 and the cam lobe 3 are passed through the sintering furnace, so that not only high production efficiency but also sufficient bonding strength can be obtained. This means that even when brazing the cam lobe 3 and the collar 2, brazing can be performed under conditions suitable for brazing sintered alloys, resulting in improved production efficiency and bonding. On the other hand, since the present invention is equipped with the collar 2, as shown in Fig. 3, the collar 2 and the cam lobe are irradiated with a high energy beam 10 (electron beam, laser, etc.), which is impossible for a complex shaped object such as a camshaft. 3 can also be specially welded.

Figure 3 shows the steps for joining color 2, 2 comrades.
This shows one embodiment of the collar, in which a protrusion 2 is provided at the end of each collar to connect the collars 2 and 2 together.
0 and a recess 40 are provided, and the protrusion 20 of one collar 2 is fitted into the recess 40 of the other collar 2 to facilitate positioning.

As mentioned above, the present invention makes it easy to position in the axial direction because the collars are brought into contact in order, and since the cam lobes, journals, and gears are each fixed to separate collars, the fixing method can be selected according to each. , productivity can be improved.

In addition, the collar and stem have a large contact area, so they are extremely firmly connected, and since the cam lobe only requires positioning for each collar, positioning grooves such as keyways and splines, and rotation stopper grooves are required on the stem and collar. There is no need to provide a collar and stem, and the strength of the collar and stem itself can be increased. Furthermore, since the present invention has no restrictions on the means for connecting the cam lobe and the collar, it is possible to select various means for connecting the cam lobe and the collar, and since the present invention provides the collar, the cam lobe can be It is only necessary to heat-treat the collar to which the camshaft is fixed, and it has various advantages such as eliminating the bending and quenching cracks that conventionally tend to occur in long camshafts due to heat treatment.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional side view showing one embodiment of the camshaft of the present invention, Fig. 2 is a diagram showing a state in which a collar and a cam lobe are combined, and Fig. 3 is a diagram showing an embodiment of a collar to which a cam lobe is fixed. It is a front view. In the diagram, 1... Stem, 2... Collar, 3... Cam lob, 4... Journal, 5... Gear, 20...
... protrusion, 40 ... recess.

Claims (1)

[Scope of utility model registration request] In a camshaft in which a cam lobe made of a sintered metal is assembled to a shaft, a separate collar 2 is fixed to the inner circumferential side of each of the cam lobe 3, journal 4, and gear 5, and the axial ends of the collars 2 are attached to the respective inner peripheral sides. A camshaft in which the stem 1 is completely enclosed by each collar, and the entire outer peripheral surface of the stem 1 is fixed to the collar.