JPH0760401A - Core for cam shaft and method for casting hollow cam shaft - Google Patents

Abstract

PURPOSE:To cast a hollow cam shaft which has high torsional rigidity and is difficult to be bent the shaft hole. CONSTITUTION:Many short length metal pipes 3 are concentrically fitted to the outside of the shaft core part 2a of a core 1 for cam shaft. The core 1 for cam shaft is formed of a solid sand core mold and the short length metal pipe 3 is formed from a steel pipe. The short length metal pipes 3 are held with the shaft core part 2a, journal core parts 2b and cam core parts 2c, and concentrically arranged with the shaft part of the hollow cam shaft by restraining the bending of the short length metal pipe 3 developed at the time of casting cast iron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cast iron hollow camshaft for an internal combustion engine, and more specifically, a core for casting a hollow portion of a cast iron hollow camshaft and a core for the hollow core. The present invention relates to a method for casting a used hollow camshaft.

[0002]

2. Description of the Related Art Conventionally, as a method of providing a hollow portion in a cast iron camshaft, a method of forming a casting hole by using a sand core (for example, Japanese Patent Laid-Open No. 59-229258) or a pipe casting Method (for example, JP-A-57
-81950).

[0003]

In the method of drilling a casting hole using a sand core, the torsional rigidity of the cast hollow camshaft is insufficient, so that the camshaft is twisted when the camshaft rotates. There is a problem. Also,
The method of using cast pipe stuffing can increase the torsional rigidity of the hollow camshaft, but since the metal pipe is long and thin, the metal pipe tends to bend when casting cast iron, and the hollow camshaft with a bent axial hole is cast. There is a problem. Therefore, the present invention has been made in order to solve the above problems, and provides a method for manufacturing a hollow camshaft having high torsional rigidity and being hard to bend the shaft hole.

[0004]

A camshaft core of the present invention comprises a core body having a shaft core portion, a journal core portion and a cam core portion, and a plurality of short metal pipes. The plurality of short metal pipes are externally fitted to the shaft core portion, and the method for casting a hollow camshaft according to the present invention further comprises placing the camshaft core in a mold, A large number of short metal pipes are cast around the shaft portion of the camshaft, and a hollow portion is bored in the camshaft.

[0005]

Operation: A large number of short metal pipes are externally fitted to the shaft core portion, the short metal pipes are arranged concentrically with the shaft core portion, and the bending of the short metal pipe occurs when casting cast iron. And the short metal pipe is arranged concentrically with the shaft portion of the hollow camshaft.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is shown in FIGS. 1 to 3, FIG. 1 is a core for a camshaft according to the present invention, and FIGS. 2 to 3 are hollow cast iron camshafts cast by the method of the present invention. Are shown respectively.

The camshaft core 1 is composed of a solid core 2 made of a sand core and a short metal pipe 3 made of steel. The core body 2 has a shaft core 2a and a journal core. 2b and a cam core portion 2c, a large number of short metal pipes 3 are externally fitted to the shaft core portion 2a, and a large number of short metal pipes 3 are arranged concentrically with the shaft core portion 2a. Shaft core 2a and journal core 2
b and the cam core portion 2c are formed so as to hold the short metal pipe 3 and suppress the bending of the short metal pipe 3 that occurs during casting of cast iron.

Next, a method for casting the hollow camshaft will be described. The camshaft core 1 shown in FIG. 1 is placed in a mold (not shown), cast iron is cast, the cast camshaft (not shown) is taken out, and the core body 2 is removed. When the outer surface of the camshaft (not shown) is processed, the cast iron hollow camshaft 4 as shown in FIGS.
Is obtained.

A hollow portion 5 penetrating the inside of the hollow cam shaft 4 is bored, and a hollow journal portion 4b and a cam portion 4c are vertically provided at a predetermined interval on the outer peripheral surface of the hollow shaft portion 4a. A large number of short metal pipes 3 are cast around the inner peripheral surface of the shaft portion 4a, and the short metal pipes 3 are arranged concentrically with the shaft portion 4a. The torsional rigidity of the hollow camshaft can be increased by casting a large number of short metal pipes 3 around the shaft portion 4a. The hollow portion 5 is formed of a long hole 5a along the axial center of the shaft portion 4a and an annular or substantially annular recess 5b provided in the journal portion 4b and the cam portion 4c. It is intended to reduce the weight.

In the first embodiment, the short metal pipe 3 having no flanges at both ends was used, but the same operation as that of the first embodiment can be achieved by using the short metal pipe 3 having flanges at both ends.

A second embodiment of the camshaft core is shown in FIG. 4, in which the camshaft core 11 is made by inserting a steel rod 6 into the shaft core 2a. The camshaft core 1 is formed in the same manner as the camshaft core 1 of the first embodiment except that it is reinforced, and has the same effect as the camshaft of the first embodiment. Further, the camshaft core 11 of the second embodiment.
When a hollow camshaft is cast by using, a hollow camshaft similar to that obtained in the first embodiment can be obtained.

It is recognized that the cast iron hollow cam shaft formed by casting a large number of short metal pipes has a bending strength improved by about 30% as compared with a cast iron hollow cam shaft of the same shape in which the metal pipe is not cast. Was given.

[0013]

According to the present invention, a core body having a shaft core portion, a journal core portion, and a cam core portion, and a plurality of short metal pipes are provided, and the plurality of short metal pipes are provided. A plurality of short metal pipes are cast around the shaft portion of the camshaft by using a core for a camshaft externally fitted to the shaft core portion, and the shaft portion, the journal portion and the cam portion are formed hollow As a result, a cast iron hollow camshaft that is free from misalignment of the short metal pipe and excellent in rigidity and light weight can be obtained. Also, in order to prevent the short metal pipe from protruding from both ends of the shaft part, the short metal pipe is cast around the shaft part and the hollow part is bored in the cam shaft with the core body, so that the cast hollow cam Shaft finishing work can be reduced and production efficiency is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a camshaft core according to a first embodiment of the present invention.

FIG. 2 is a front view of a hollow camshaft cast by the method of the present invention.

3 is a cross-sectional view of FIG.

FIG. 4 is a sectional view of a camshaft core according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Core for Camshaft 2 Core Main Body 2a Shaft Core 2b Journal Core 2c Cam Core 3 Short Metal Pipe 4 Hollow Camshaft 4a Shaft 5 Hollow 6 Bar 11 Core for Camshaft

Claims (3)

[Claims] 1. A core main body having a shaft core portion, a journal core portion, and a cam core portion, and a plurality of short metal pipes, wherein the plurality of short metal pipes are connected to the shaft core portion. A core for a camshaft, which is fitted to the outside. 2. A core main body having a shaft core portion, a journal core portion, and a cam core portion, a large number of short metal pipes, and a bar member. A core for a camshaft, characterized in that the rod is externally fitted to the shaft core part and the rod is fitted into the shaft core part. 3. A method for casting a hollow camshaft using a camshaft core, wherein the camshaft core according to claim 1 or 2 is arranged in a mold, and a large number of camshaft shaft parts are provided. A method for casting a hollow camshaft, characterized in that a hollow portion is bored in the camshaft while the individual short metal pipes are cast.