JPH0435245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a hollow tube material as a camshaft for an internal combustion engine, and utilizes hydraulic bulge processing etc. to form a separate cam part and, if necessary, a journal part and a shaft end. This invention relates to an assembled camshaft in which members etc. are fixed.

BACKGROUND ART In this type of bulge-assembled camshaft, a hollow shaft with a polygonal cross section that fits the cam piece through hole is inserted into a cam piece in which a through hole having a polygonal cross section is formed, and then the hollow shaft is inserted into the hollow shaft. The method of press-fitting a mandrel and mechanically expanding the diameter of the hollow shaft to firmly connect the outer surface of the hollow shaft and the cam piece is known as
7130 etc.

Problems to be Solved by the Invention As described above, the method of mechanically expanding and connecting the tubes using a mandrel is effective in preventing the cam piece from loosening in the circumferential direction, but it has the disadvantage that it tends to loosen in the axial direction.

That is, this is because it is difficult to obtain a sufficient bulge in the hollow shaft at the end in the axial direction of the cam piece. Furthermore, the flexural rigidity of the completed assembled camshaft is low, and this problem must be overcome by increasing the thickness of the hollow shaft.

It is also known that hydraulic bulge forming is used to join a hollow shaft with a circular cross section and a hollow shaft with a polygonal cross section through hole, but this method requires a great deal of pressure to expand the diameter of the hollow shaft, which may cause the cam piece to crack. There was a drawback that this easily occurred.

Means for solving the problem: A hollow shaft with a polygonal cross section that approximately fits the cam piece through hole is inserted into a cam piece in which a through hole with a polygonal cross section is formed, and then a hydraulic bulge is formed on the hollow shaft. is applied to form a bulge portion between the adjacent cam pieces, at least a portion of which has a substantially polygonal cross section.

Function: A bulge having a substantially polygonal cross section is formed between adjacent cam pieces, and the bulge is formed by low hydraulic pressure.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 and FIG. 2, which is a cross-sectional view thereof, show an embodiment of the assembled camshaft 10.
0 is a hollow shaft with a polygonal cross section made of steel pipe or the like. Reference numeral 12 denotes a cam piece, which has a desired cam profile formed in advance by casting, forging, or sintering, and has a polygonal shape into which the hollow shaft 20 before diameter expansion can be inserted, and into which the hollow shaft 20 fits. a through hole 14 exhibiting a cross section;
Chamfered portions 16, 16 are provided on the cross section of the cam piece by cutting both edges of the through hole 14, respectively.

The chamfered portion 16 is rounded because it is formed to prevent pipe cracking caused by a sudden change in cross section of the hollow shaft 20 at the edge of the cam piece through hole due to the enlarged diameter of the hollow shaft 20. It is not limited to the circular arc shape, but may be formed into a truncated conical shape or the like so that the diameter increases toward the side surface of the cam piece.

Reference numeral 11 denotes a journal piece, which, like the cam piece, has a desired cylindrical outer peripheral surface formed in advance by casting, forging, or sintering, and into which a hollow shaft 20 before diameter expansion can be inserted. A through hole 13 exhibiting a polygonal cross section that fits, and a chamfered portion 1 in which both edges of the through hole are cut out on the side surface of the journal piece.
5 and 15 are provided.

These cam pieces 12 and journal pieces 11 are subjected to surface treatment such as carburizing treatment, if necessary.

To connect the hollow shaft 20 of the assembled camshaft 10 to the cam piece 12 and journal piece 11, first insert the hollow shaft 20 with a polygonal cross section into the cam piece 11 and journal piece 11 as shown in FIG. .

Then, this is set in a split bulge mold (not shown) having a mold surface in a predetermined camshaft shape, and the mold is closed.

Then, with the mold closed, an emulsion or the like is injected into the hollow shaft, and the emulsion is compressed and pressurized.

Then, the hollow shaft 20 expands outward and plastically deforms so as to come into close contact with the inner peripheral surfaces of the through holes of the cam piece 12 and the journal piece 11, and facing chamfered portions 15, 16 (16, 16, 16), common gentle annular bulges 22 and 23 are formed.

At the same time, an annular bulge is also formed on the side surface of the journal piece 11 on the end side.

Swelling parts 22 and 23 formed between adjacent pieces
The closer to the chamfered portions 15, 16, the more perfectly polygonal the cross section, and the farther away from the chamfered portions 15, 16, as the outer circumferential diameter increases, the more nearly circular the cross section becomes.

In this way, the bulges 22, 2 bulge out between each piece.
3 has a much larger diameter than the polygonal cross-section hollow shaft portion located inside the polygonal through-holes 13 and 14 of the bridge. Improves bending properties.

As a result, each cam piece 12, each journal piece 11
is firmly fixed to the hollow shaft 20 so as to be sandwiched between the bulges 21, 22, and 23.

After taking it out from the bulge mold, the cam surface and journal part are ground and finished if necessary.
The desired assembled camshaft 10 is completed by machining oil holes and the like.

In the above embodiment, the through holes of the cam piece and the journal piece and the hollow shaft have hexagonal cross sections, but they may have other polygonal cross sections such as a square cross section.

Effects As described above, according to the present invention, a bulge having a substantially polygonal cross section is formed between adjacent cam pieces, so the bending rigidity of the assembled camshaft is increased and the weight of the camshaft can be further reduced. At the same time, since the bulge is formed with low hydraulic pressure, cracking of the cam piece can be avoided.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a partially sectional plan view of an assembled camshaft. FIG. 2 is a sectional view taken along - in FIG. 1. FIG. 3 is an explanatory elevational view of the main parts of the assembly camshaft manufacturing process shown in FIG. 1. Explanation of symbols, 10...Assembled camshaft. 11
...Journal piece. 12...Cam piece. 14... Cam piece through hole. 16... Chamfered portion. 20...Hollow shaft. 21, 22, 23... bulge.

Claims (1)

[Claims] 1. A hollow shaft 20 having a polygonal cross section that substantially fits the cam piece through hole 14 is inserted into the cam piece 12 in which a through hole 14 having a polygonal cross section is formed, and then the hollow shaft 20 has a polygonal cross section.
A method of manufacturing an assembled camshaft, characterized in that a hydraulic bulging process is applied to the camshaft 0, and a bulge 23 having at least a portion of a substantially polygonal cross section is formed between the adjacent cam pieces 12.