JPH08270409A - How to assemble a prefabricated camshaft - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an assembling camshaft capable of maintaining a high joining torque for a long time and an assembling method. [Structure] A ridge portion 3 is formed on a shaft 1, a joint hole 5 is opened in a cam piece 4 which is gazed to the ridge portion, and a high hardness portion 8 is formed at least around the joint hole 5 to form a ridge portion. The hardness is made higher than that of the portion 3, and when the joining hole 5 is pushed into the ridge portion 3, the peak portion 3a of the ridge portion 3 is deformed and fitted into the joining hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling an assembling camshaft.

[0002]

2. Description of the Related Art In recent years, from the standpoint of protecting the global environment, further reduction of CO ₂ emission from automobiles has been demanded,
As part of such measures, there is an increasing need for vehicle weight reduction. Further, there is a tendency to increase the surface pressure of the cam piece in order to strengthen exhaust gas and increase engine output. Further, in the case of trucks, the revision of the Road Traffic Law has strengthened crackdowns on overloading, making weight reduction of vehicles an important issue.

Therefore, in recent years, the camshaft is made of an optimal material for each component, and the shaft is also made of a prefabricated camshaft using a hollow pipe for weight reduction. Various means such as press fitting and shrink fitting have been proposed as means for assembling the cam piece to the shaft, but mass production by the galling fitting method described with reference to FIG. 6 has begun.

The process of assembling this assembling camshaft will be described with reference to FIG. In FIG. 6, knurling is performed at a predetermined position of the hollow shaft 1 by the cutting tool 2, and a predetermined number of ridges 3 parallel to the axial direction are formed on the surface of the shaft 1 (in FIG. 6). The ridge portion 3 is formed so as to protrude from the shaft surface s as shown by and has high strength. In addition, reference numeral 2a shown in is a knurl, and 2b is a holder.

A cam piece 4 assembled on the shaft 1
The joining hole 5 is formed in (). The diameter of this joint hole 5 is
It is larger than the shaft 1 and smaller than the protrusion 3. Then, the cam piece 4 is pushed to a predetermined position of the protruding portion 3 portion by gazing, and the mountain portion 3a of the protruding portion 3 is bited into the joint hole 5 (the drawing on the right side). As described above, the assembling camshaft 6 by the gall-fitting method is configured to increase the strength of the ridge portion 3 and to allow the mountain portion to bite into the cam piece 4 side to be joined, and this portion serves as a key. And the joining torque in the rotation direction can be made extremely high.

[0006]

By the way, in an engine for a truck or the like which is required to have high output, long-distance running, and long life, it is required to increase the joining torque between the cam piece and the shaft. Therefore, when the gall-fitting method is applied to the assembly type camshaft of the truck engine, as shown in the enlarged view at the right end of FIG. The pressing force F acting on the apex due to pressure is locally extremely high because the peaks 3a may be sharp.

Therefore, during a long period of time, plastic deformation occurs on the inner peripheral side of the cam piece 4, the actual tightening margin is gradually reduced, the joining force is deteriorated, and as a result, the life of the engine is shortened. Therefore, it was not possible to use a prefabricated camshaft by gall fitting on the truck. The present invention has been made in view of the above problems, and adopts a gall-fitting method that can obtain a high joining force, prevents deterioration of the joining torque, and extends the life of an assembled camshaft. It is intended to provide an assembly method.

[0008]

In order to achieve the above object, the structure of the method for assembling the assembling camshaft according to the present invention has a structure in which the shaft circumferential direction of the portion for fixing the cam piece of the shaft is parallel to the axial direction of the shaft. A plurality of ridges to be formed, and a joining hole for joining to the ridges is opened in the cam piece, and the diameter of the joining hole is formed to be smaller than the diameter of the top of the ridge, at least around the joining hole. The cam piece has a hardness higher than that of the ridge, and when the ridge is pushed into the joint hole, the ridge interferes with the joint hole so that the protrusion is fitted into the joint hole while being deformed. It was done.

There is no particular limitation on the means for forming the ridge, but it is usually formed by knurling. The shaft is not particularly limited, but a hollow shaft is used when it is lightweight. However, it is also possible to use a solid shaft. The shaft material is usually carbon steel.

The means for increasing the hardness of at least the peripheral portion of the joint hole is not particularly limited. As a preferable means, the cam piece is made of carbon steel, and the periphery of the joint hole is induction hardened, or the entire cam piece is quenched. It is also possible to employ a method such as sinter-bonding to the above and integrating them.

[0011]

The hardness of at least the peripheral portion of the joint hole is made higher than the hardness of the ridge portion, and when the ridge portion is pushed into the joint hole, the means for pushing while deforming the ridge portion is While the mountain portion is deformed into a trapezoidal shape, the joint hole is also deformed, and gall fitting is adopted, and the protrusion of the ridge portion into the cam piece as in the conventional method is prevented. In addition, the above-mentioned deformation can minimize the part to be shaved, and can obtain a large press-fitting margin that cannot be generated by shrink fitting.

Therefore, the high stress generated by the deformation is more widely dispersed, the contact pressure acting on the joint is reduced, and a very high joint torque is obtained as a whole. Stress reduction can be prevented. As mentioned above, the protrusion of the ridges bites into the cam piece, but the effect as a so-called key is lost, but since a stable high joining torque is obtained as a whole, it can be applied to the camshaft of a truck engine used under severe conditions. It can be applicable.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The ridge portion 3 of the hollow shaft 1 of Example 1 shown in FIG. 1A was formed by knurling. Further, carbon steel was used to form a joint hole 5 on the cam piece 4 for galling. The same members as those used in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

Then, the high-frequency coil 7 for quenching is arranged in the joining hole 5 of Example 1, and the peripheral portion of the joining hole 5 (hatched portion B in FIG. 1) is quenched, and the height of this portion is increased. The hardness portion 8 was formed. Next, the ridge 3 of the shaft 1
The joining hole 5 of the cam piece 4 was pushed in to form the assembled cam shaft 6 shown in FIG. By the way, since the high hardness portion 8 is formed around the joint hole 5 as described above, the deformation that occurs during the gall-fitting is that the peak portion 3a of the softer ridge portion 3 is deformed into a trapezoidal shape. Actually, the joint hole 5 side is also deformed, and deformation is also generated around the joint hole 5 of the cam piece 4, but the mountain portion 3a side is deformed much more.

Therefore, as shown in the partially enlarged view of FIG. 3 (in the circle on the right side), the protrusion 3 hardly bites into the cam piece 4, so that the protrusion 3 and the joint surface 5 are not separated from each other. A very large press-fitting margin due to deformation can be secured, and a large joining torque can be generated. Moreover, local concentration of stress is prevented, and the pressing force f that acts per unit area is much smaller than that of the conventional example shown in FIG. 6 (f
<< F), the joining torque was 850 Nm or more, and the decrease could be prevented for a long period of time. Therefore, it can be used as a camshaft of a truck engine used under more severe conditions.

FIG. 4 shows a modified example in which the quenching of Example 1 shown in FIG. 1B is performed by another means. That is, the high frequency coil 7 is used so that the entire cam piece 4 can be induction hardened.
Is provided to satisfy both the high surface pressure of the cam face and the high hardness of the peripheral portion of the joint surface 5.
And, so that the inner peripheral surface of the joint hole 5 can be quenched,
The quenching time and temperature were adjusted.

In the cam piece 4 of the third embodiment shown in FIG. 5, the main body 4a is made of a sintered material, and the ring member 4b made of a hard material such as S50C is sintered on the inner peripheral side of the main body 4a. In doing so, they were integrated by sintering bonding. Others were the same as in Example 1 to obtain an assembly type cam shaft (not shown). Similar to the assembled camshaft 6 of the first embodiment, this one can maintain a high joining torque for a long period of time.

[0018]

As described above, according to the method of assembling the assembling camshaft of the present invention, the hardness of at least the periphery of the joint hole formed in the cam piece is made higher than the hardness of the ridge formed on the shaft, and the cam piece is formed. When is pushed into the shaft, the ridges of the ridges are deformed into trapezoidal shapes and gazed into the joint holes, so the ridges and the joint surface can be joined without biting into each other, and local It is possible to obtain a high joining force without excessive stress concentration, and to maintain a high joining torque for a long period of time.

Therefore, even when the assembled camshaft of the present invention is applied to a camshaft of a truck engine used under severe conditions such as long-term operation for a long period of time, deterioration of the joining torque is prevented. , Can provide a highly reliable engine.

[Brief description of drawings]

FIG. 1A is a sectional view of a main part of a shaft used in a prefabricated camshaft according to a first embodiment of the present invention, and B is a front view showing a state of quenching a cam piece used in the first embodiment. .

FIG. 2 is a side view of the essential parts of the assembly type cam shaft of the first embodiment formed by the shaft shown in FIG. 1A and the cam piece shown in FIG. 1B.

3 is a sectional view taken along the line III-III of FIG.

FIG. 4 is a front view of a cam piece for explaining how quenching is performed in Example 2;

FIG. 5 is a front view of a cam piece according to a third embodiment.

FIG. 6 is an assembly process diagram of a conventional assembly type camshaft, which is a side view showing how knurling is performed;
The left side of the figure is a side view showing the ridge portion formed by knurling, the right side of the figure is a left EE line cross-sectional view,
FIG. 4A is a side view showing how the cam piece is assembled to a knurled shaft, FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft 2 Cutting tool 3 Ridge portion 3a Mountain portion 4 Cam piece 5 Joining hole 6 Assembly type cam shaft 7 High frequency coil 8 High hardness portion s Shaft surface

Claims (4)

[Claims] 1. A plurality of ridges parallel to the axial direction of the shaft are formed in the shaft circumferential direction of a portion of the shaft where the cam piece is fixed, and a joint hole for joining the ridge is formed in the cam piece. The diameter of the joint hole is formed smaller than the diameter of the top of the ridge, and at least the hardness of the cam piece around the joint hole is formed higher than the hardness of the ridge, and the ridge is pushed into the joint hole. At this time, the assembling method of the assembling camshaft is such that the protrusions are fitted into the joining hole while deforming the crests that interfere with the joining hole. 2. The method for assembling the assembly type camshaft according to claim 1, wherein the protrusion is formed by knurling. 3. The method of assembling a camshaft according to claim 1, wherein the cam piece is made of carbon steel, and the means for increasing the hardness of the peripheral portion of the joint hole is performed by induction hardening. 4. A cam piece having a shape having an opening having a diameter larger than the diameter of the joining hole is formed at a portion where the joining hole is formed by a sintered material, and a cylindrical member having a high hardness is fitted into the opening. 2. The method for assembling a prefabricated camshaft according to claim 1, wherein the joint hole is formed by a tubular member.