JPS61282663A - Hollow cam shaft - Google Patents

Abstract

PURPOSE:To improve the fixation strength between a hollow cam shaft and a hollow journal piece or a hollow cam piece by forming the minute uneven parts on the surface of the hollow hole of each piece and forming a hollow cam shaft through buldge molding. CONSTITUTION:Minute uneven parts are formed onto the surfaces of the hollow holes 2a and 3a of a hollow journal piece 2 and a hollow cam piece 3 which are used for a hollow cam shaft 1. When buldge molding is carried out by inserting these pieces into a hollow shaft 4, the minute uneven parts on the surface of the holes bite into the surface of the hollow shaft 4, and a high fixation strength can be obtained. Therefore, the stress concentration on the journal piece in buldge molding is not generated, and sufficiently also a small- sized journal piece can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a hollow camshaft used as a valve train component of an automobile engine.

(Prior Art) Conventionally, camshafts used in valve train parts of automobile engines have been integrally formed by casting,
There are types in which the shaft is fixed to a hollow journal piece and a hollow cam piece that are made separately, and there are also types in which the shaft is hollow to reduce weight and improve valve operating performance. In the case of manufacturing a hollow camshaft in which such a shaft is made hollow, it is also considered to use bulge forming.

FIG. 6 is a diagram showing an example of a conventional hollow camshaft manufactured by bulge forming.
After fitting, the hollow shaft 104 is expanded by bulge forming which applies pressure inside the hollow shaft 104, and the hollow journal piece 102 and the hollow cam piece 103 are fixed to the hollow shaft 104 (for example, , Japanese Patent Application No. 59-113896).

(Problems to be Solved by the Invention) However, in such a conventional bulge-formed hollow camshaft 101, the hollow journaler, piece 1
02 uses a recess 102b formed in a part of the hollow hole 102a, as shown in FIG. 7, and the hollow cam piece 103 uses a recess 103b formed in a part of the hollow hole 103a, as shown in FIG. In particular, when the outer diameter of the hollow journal piece 102 is made small as shown by the imaginary line in the figure, the minimum wall thickness t of the hollow journal piece 102 is reduced. becomes small, and stress concentration tends to occur in this portion, so there is a problem that the hollow journal piece 102 is unsuitable for an oil bath type camshaft in which the outside diameter is small.

The present invention has been made by focusing on such conventional problems, and provides a hollow camshaft in which a hollow journal piece having a hollow hole, a hollow cam piece, and a hollow shaft are fitted and fixed by bulge forming. An object of the present invention is to provide a hollow camshaft in which even when the outer diameter of the hollow journal piece and/or the hollow cam piece is made small, the adhesion strength between each of these pieces and the hollow shaft can be made high. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a hollow camshaft in which a hollow journal piece having a hollow hole and a hollow cam piece and a hollow shaft are fitted and fixed by bulge forming. The structure is characterized in that fine irregularities are formed on the surface of the hollow hole of at least one of the journal piece and the hollow cam piece, and after bulge forming, the outer surface of the hollow shaft is dug into the irregularities.

In the hollow camshaft according to the present invention, when the hollow journal piece having a hollow hole is of a small diameter, as shown in FIG. 2b is used.

Further, even when the hollow journal piece 2 is not small in diameter, it is possible to use one in which fine irregularities 2b are formed on the surface of the hollow hole 2a.

When the unevenness 2b is formed, for example, by cutting, the degree of finishing can be appropriately adjusted.

- If the outer diameter of the hollow cam piece having a hollow hole is not small, the hole surface of the hollow hole 3a provided in the hollow cam piece 3 may be smoothed as shown in Fig. 3. However, if necessary, fine irregularities may be formed on the hole surface of the hollow hole 3a, and rough concave portions 3c may be formed.
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Further, as the hollow shaft, for example, carbon steel for machine structures (SC) or carbon steel tubes for machine structures (STKM) are used, and if necessary, it is made of low alloy steel for machine structures to which alloying elements are added. Electric resistance welded steel pipes and seamless steel pipes made from these steels are used. If necessary, a material in which the bulging portion resulting from bulge forming is annealed so that the bulging portion is easier to bulge than other portions may also be used.

The bulge forming mold used when fitting and fixing the hollow journal piece 2 and hollow cam piece 3 to the hollow shaft is, for example, a mold that is divided into upper and lower parts. A hollow shaft disposed in a hollow shaft in which a pressurized fluid (for example, water) can be supplied under pressure is used.

After bulge forming, internal stress is often generated on the surfaces of hollow journal piece 2 and hollow cam piece 3 due to the bulge forming, so post-treatment such as heating may be performed to relieve this internal stress. good.

(Embodiment) FIG. 1 shows a hollow camshaft according to an embodiment of the present invention. The hollow camshaft 1 shown in FIG. Unevenness 2b
Hollow journal piece 2 with a relatively small outer diameter
．． And as shown in FIG. 3, a hollow cam piece 3 having a recess 3C formed in a part of the hollow hole 3a is fitted with a hollow shaft 4, which is not shown separately, and fixed by bulge forming.

In this embodiment, the hollow journal piece 2 is made of machine structural alloy steel (JIS 30M440), and is designed to be used as an oil bath type camshaft, as shown in FIG. It has a relatively small outer diameter, and the hollow holes 2 are arranged concentrically.
A is formed on the surface of the hollow hole 2a, and fine irregularities 2b are formed on the surface of the hollow hole 2a. Further, the hollow cam piece 3 is made of an iron-based sintered material (for example, Fe-20%C by weight).
r-1% by weight Ni-0,5% by weight P-2,5f! L amount%
As shown in Fig. 3, a hollow hole 3a is formed almost concentrically with the cam base, and a part of the hollow hole 3a has a radius of curvature smaller than that of the cam base. A fourth portion 3C consisting of an arcuate curved surface with a radius of curvature is formed on the cam nose side.

Furthermore, the hollow shaft 4 is a JIS carbon steel pipe for mechanical structures.
It consists of STKM 13-A electric resistance welded tube.

FIG. 4 is a diagram showing the bulge mold used in this example. This bulge mold 11 is made by combining two molding molds 12.13, and each molding mold 12.13 has a are journal piece fitting portions 12a, 13a and cam piece fitting portion 12b for fitting the hollow journal piece 2 and hollow cam piece 3, respectively.
.

12b, 13b, 13b are formed, and shaft fitting parts 12c, 13 for fitting the hollow shaft 4 are formed.
c is formed. Reference numerals 14 and 15 designate emboluses that close each end of the shaft fitting portions 12c and 13c, and one of the emboluses 15 is attached to a pressure fluid inlet pipe 16.

Next, when fixing the hollow journal piece 2 and the hollow cam piece 3 to the hollow shaft 4 using the bulge forming y1111 shown in FIG.
2.13 is kept in a divided state, and the hollow journal pieces 2 and 3 shown in FIG. The hollow cam pieces 3, 3 shown in the figure are fitted, and then each hollow journal piece 2 and each hollow hole 2a of the hollow cam pieces 3, 3 are fitted.
and 3a,! Inside a, JIS S steel pipes for mechanical structures are specified.
After the hollow shaft 4 made of TKM 13A is inserted into the shaft fitting part 13c, the other split mold 12 for molding is placed on each journal piece fitting part 1.
2a and cam piece fitting portions 12b, 12b respectively.
At the same time, the shaft fitting portion 12c is fitted to the hollow shaft 4. In this state, the recess 3C formed in the hollow hole 3a of the hollow cam piece 3 and the hollow shaft 4
A relatively large bulging space of the hollow shaft 4 is formed between the hollow shaft 4 and a small bulging space of the hollow shaft 4 between each hollow hole 2a, 3a and the hollow shaft 4. ing.

Next, the embolization 14,
15, the split molds 12 and 13 for molding are fixed. In this state, a fluid, for example water, is force-fed into the hollow shaft 4 through the pressure fluid feed pipe 16, and the hollow journal piece is sealed. The hollow shaft 4 is inserted into a space formed between the hollow hole 2a of the hollow cam piece 3 and the hollow shaft 4, and a space formed between the hollow hole 3a and the recess 3C of the hollow cam piece 3 and the hollow shaft 4. By expanding and deforming each hollow shaft 4, the outer surface of the hollow shaft 4 is brought into close contact with the hollow hole 2a of the hollow journal piece 2, and is bitten into the fine irregularities 2b formed in the hollow hole 2a. It is brought into close contact with the hole 3a and the recess 3C or bulged into the recess 3C.

Next, the hollow camshaft 1 as shown in FIG. 1 is obtained by dividing the molding molds 12 and 13.

Therefore, in this example, several types of hollow journal pieces 2 were used in which the hole surface of the hollow hole 2a of the hollow journal piece 2 was formed with unevenness 2b having different surface roughness as shown in the following table. The material of this hollow journal piece 2 is JIS S0M440 as mentioned above.
However, the heat treatment is quenching at 85%.
The material used was heated to 0° C., then oil-cooled, and then tempered under the conditions of heating to 500° C. and then water-cooled to have a hardness of about HB300.

Furthermore, the surface roughness was adjusted by varying the degree of finishing when forming the hollow holes 2a by lathe processing. Then, the adhesion strength (shear load) in the thrust direction between the hollow journal piece 2 and the hollow shaft 4 in each of these hollow camshafts 1 is measured by placing the hollow journal piece 2 on the pedestal 10 as shown in FIG. It was measured by applying a load P to the hollow shaft 4. The results are also shown in the following table.

For comparison, as shown in FIG.
A hollow camshaft (101) was manufactured by the same process as above using a hollow journal piece 102 having the same outer diameter (indicated by a phantom line) in which a recess 102b was formed in a portion of 02a.

As shown in the above table, in the comparative example N096, stress concentration occurred at the concave portion 102b of the hollow journal piece 102 during bulge forming.
2 destroyed it. In contrast, Example Nos. 1 to 5
Now, even when the hollow journal piece 2 is made to have a small diameter so that it can be applied to an oil path type camshaft because no recess is formed in the hollow journal piece 2,
No fracture occurred during bulge forming. It was also observed that the shear load differed depending on the surface roughness of the unevenness 2b of the hollow journal piece 2.

If the surface roughness of the unevenness 2b is too small, a large shearing load cannot be obtained, so it was confirmed that it is more desirable to set the shearing load to a surface roughness of 800 kgf or more, that is, 10 gm or more. On the other hand, even if the surface roughness is made too large, there will not be much effect in terms of increasing shear load, and the strength of the hollow journal piece 2 will decrease, so it is recommended to make the surface roughness less than loOBm. was confirmed to be more desirable.

[Effect of the invention] As explained above, according to the present invention.

In a hollow journal piece having a hollow hole and a hollow camshaft in which the hollow cam piece and the hollow shaft are fitted and fixed by bulge forming, fine particles are formed on the hole surface of the hollow hole of at least one of the hollow journal piece and the hollow cam piece. After forming unevenness and bulge forming,
Since the outer surface of the hollow shaft is cut into the unevenness, it is possible to significantly increase the adhesion strength between the hollow journal piece and the hollow cam piece and the hollow shaft, and the outer diameter of the hollow journal piece can be reduced. Even when the camshaft is made smaller, there is no risk of stress concentration and breakage during bulge forming, unlike when a conventional deep recess is formed, and the bulge-processed hollow camshaft can also be used in oil bath type valve train systems where the journal piece has a small diameter. This brings about a very good effect in that it becomes possible to apply .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a slope of a hollow camshaft according to an embodiment of the present invention, FIGS. 2 and 3 are front views of a hollow journal piece and a hollow cam piece used in the hollow camshaft of FIG. 1, and FIG. The figure is an explanatory cross-sectional view of the bulge forming device used to manufacture the hollow camshaft shown in Fig. 1 by bulge forming, and Fig. 5 shows the procedure for measuring the adhesion strength between the hollow journal piece of the hollow camshaft and the hollow shaft. FIG. 6 is an explanatory cross-sectional view of a conventional hollow camshaft, and FIGS. 7 and 8 are front views of a hollow journal piece and a hollow cam piece used in the hollow camshaft of FIG. 1, respectively. DESCRIPTION OF SYMBOLS 1...Hollow camshaft, 2...Hollow journal heath, 2a...Hollow hole, 2b...Irregularities, 3...Hollow cam piece, 3a...Hollow hole. Patent applicant: Nissan Motor Co., Ltd. Applicant: Steel Tube Processing Co., Ltd. Patent attorney Yutaka Oshio Figure 1 Figure 2 Figure 3 a Figure 5 Figure 7 Figure 8

Claims (1)

[Claims] (1) In a hollow journal piece having a hollow hole and a hollow camshaft in which the hollow cam piece and the hollow shaft are fitted and fixed by bulge forming, the hole surface of at least one of the hollow journal piece and the hollow cam piece. What is claimed is: 1. A hollow camshaft, characterized in that fine irregularities are formed on the hollow camshaft, and the outer surface of the hollow shaft is bitten into the irregularities.