JPH06200711A - Hollow camshaft for internal combustion engine and manufacture thereof - Google Patents

Abstract

(57) [Summary] [Structure] Core sand (6) was cast into a hollow (22) with both ends open, and a blind plug (24,43,51,61,71) was attached to the open end (22a). At the same time, the camshaft drive means (3) is attached to the open end (22b) of the other side to close it. [Effect] Even if the core sand remains in the hollow camshaft, there is no risk of the core sand falling outside during engine operation, and the lubricating oil of the engine may enter the hollow camshaft. There is none. In addition, the hollow cam shaft with open ends can support the core sand at both ends during casting, and the core center of the core sand is not eccentric to the shaft center of the cam shaft. Unlike the hollow cam shaft, the hole for core sand support does not need to be formed at a position other than the axially open end of the cam shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow camshaft for an internal combustion engine, which is cast in a hollow shape with both ends open by core sand, and a method for manufacturing the hollow camshaft.

[0002]

2. Description of the Related Art As a method for reducing the weight of a camshaft which constitutes one of valve operating system parts of an engine, it is common to make it hollow, and in some cases, the hollow is used as a passage for lubricating oil. There are also things to do. Conventionally, a valve rocker shaft in which a blind lid is provided on both ends of a pipe material and an internal space is used as a lubricating oil passage is disclosed in, for example, Japanese Utility Model Laid-Open No. 50-58109.
It is known from the publication. In the case of such a valve rocker shaft, since it has a cylindrical shape, it suffices to cut out the pipe member, and its manufacture is simple. However, in the case of the cam shaft, casting is general, and hollowing is required. Casting using core sand has the highest productivity and can be manufactured at low cost.

As a hollow cam shaft of this type, an open-ended type and an open-ended type can be considered. FIG. 8 shows a hollow camshaft 1 of which both ends are open, one opening end 2a of the hollow 2 is open, and a screw is formed on the inner peripheral surface of the other opening end 2b to drive the camshaft. A timing belt pulley 3 for use is screwed and fixed by a bolt 4 via a seal member 5. The seal member 5 is for preventing oil that has entered the hollow 2 from the opening end 2a from leaking to the timing belt pulley 3 side.

Further, FIG. 9 shows a hollow cam shaft 11 of which one end is open, and one end 12a of the hollow 12 is opened,
The other end 12b is closed, and the timing belt pulley 3 is inserted in the screw hole 11b formed at the axial center of the closed end surface 11a.
Are screwed and fixed by bolts 4.

[0005]

In the case of the hollow shaft 11 of which one end is open type, it is necessary to cast a member for supporting the core sand at an appropriate position in order to prevent the core sand from being eccentric at the time of casting. However, there is a drawback that this remains in the product as a hole 12d for supporting core sand. In addition, both the open-ended type and the open-ended type hollow camshafts 1 and 11 have hollows 2c and 12c outwardly in accordance with the shapes of the cam portions 1c and 11c in order to more effectively reduce the weight. It is bulged to form a modified hollow camshaft.

However, particularly in the above-mentioned deformed hollow camshafts 1 and 11, each cam portion 1 after casting is used.
It is extremely difficult to completely remove the core sand 6 in the hollows 2c and 12c corresponding to c and 11c, and the core sand 6 remains in these hollows 2c and 12c.
Therefore, in the case of the hollow camshaft 1, the remaining core sand 6 during operation of the engine is the open end 2a of the hollow 2
Therefore, in the case of the hollow camshaft 11, the hollow core 6 falls outside through the open end 12a of the hollow 12 or the hole 12d for supporting the core sand 6, and the core sand 6 that has fallen is a rotating part such as a crankshaft of an engine or a cam. If it adheres to the cam surfaces of the portions 1c and 11c, there is a problem that it becomes a major cause of abnormal wear or seizure of the rotating portion and the sliding portion.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a lightweight hollow camshaft which prevents the residual core sand after casting from falling outside the camshaft.

[0008]

In order to achieve the above object, in the present invention, a core sand is cast into a hollow with both ends open, and a blind plug is applied to one open end and the other end is closed. A hollow camshaft for an internal combustion engine is provided, wherein a camshaft driving means is attached to the open end and is closed.

The present invention comprises a shaft portion having the hollow portion and a cam portion formed on the outer circumference of the shaft portion, and the hollow portion is formed by bulging outward in the cam portion. It is suitable for a hollow camshaft provided with a portion. The hollow camshaft according to the present invention comprises the steps of casting a hollow camshaft whose both ends are open using core sand whose both ends are supported, and a step of applying a blind plug to one open end of the camshaft, And a cam shaft driving means is attached to the other open end of the cam shaft.

Preferably, the step of mounting the camshaft driving means on the other side opening end of the camshaft comprises the step of engraving a screw on the other side opening end, and the camshaft driving means being screwed onto the screw. And a step of fixing with a bolt.

[0011]

After the casting of the camshaft, the core sand is extracted, and after the core sand in the hollow is completely removed, a blind plug is attached to one open end of the hollow. A camshaft drive means is attached to the other open end of the hollow, whereby both ends of the hollow camshaft are closed, and core sand remaining in the hollow camshaft is prevented from being discharged to the outside of the camshaft. To do.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same elements as those of the camshafts of the respective modes described in FIGS. 8 and 9 are designated by the same reference numerals. In FIG. 1, the camshaft 21 includes a shaft portion in which a hollow 22 having a substantially circular cross-section whose both ends are open is formed by using core sand, and an appropriate outer circumference of the shaft portion (four locations in the case of the embodiment). ) Is formed in the hollow 22. In order to more effectively reduce the weight, the hollow 22 is a hollow (expanded in the radial direction) in accordance with the shape of each cam portion 21c. The protruding portion) 22c is formed to form a modified hollow camshaft.

After casting the hollow camshaft 21, the core sand 6 forming the hollow 22 is removed. And hollow 2
After removing the core sand 6 from 2, the metal hard ball 24 is press-fitted into the one open end 22a of the hollow 22 of the camshaft 21, that is, the open end 22a opened in the rocker cover 23, and is closed. The hard ball 24 functions as a blind plug. Further, a screw is formed on the inner peripheral surface of the other side opening end 22b, and a timing belt pulley 3 as a cam shaft driving means is screwed and fixed by a bolt 4.

Next, the process up to the press-fitting of the hard balls 24 and the attachment of the timing belt pulley 3 will be described with reference to FIGS. FIG. 2 shows a state in which the core sand 6 is still clogged after the hollow camshaft 21 is cast. From this state, for example, as shown in FIG. Most of the sand core 6 is pulled out. Then, when the removal of the core sand 6 inside the hollow 22 is completed, as shown in FIG. 1, the hard ball 24 is pressed into the one open end 22a of the hollow 22 and the other open end 22b.
A screw is engraved on the inner peripheral surface of, and the timing belt pulley 3 is screwed by a bolt 4.

As a result, one open end 22a of the hollow 22 is closed by the hard ball 24, and the other open end 22b is closed by mounting and fixing the timing belt pulley 3, and the core sand 6 in the hollow 22 is closed. It is sealed in the hollow 22. Therefore, even if some of the core sand 6 remains in the hollow camshaft 21, no inconvenience occurs. 4 to 7 show another embodiment of the blind plug used in the hollow camshaft 21 according to the present invention, and FIG. 4 shows the hollow camshaft 2
A bolt 43 is screwed into the one open end 22a of the hollow 22 of 1 through a packing 41 for sealing and a washer 42,
This is a blind plug together with the packing 41, and in FIG. 5, the resin member 51 is press-fitted into one open end 22a of the hollow 22 to form a blind plug. In addition, FIG. 6 shows a blind plug obtained by inserting a plug 61 formed of a metal member into one opening end 22a of the hollow 22 and then fixing the plug 61 to the opening end 22a over the entire circumference by welding. In FIG. 7, a cylindrical cap 71 having a bottom is press-fitted into one open end 22a of the hollow 22 to form a blind plug.

[0016]

As is apparent from the above description, according to the hollow camshaft of the internal combustion engine and the method of manufacturing the same of the present invention, the camshaft is cast into a hollow with both ends open by core sand, and one side Since a blind plug is applied to the open end and a camshaft drive means is attached to the other open end so as to be closed, one hollow open end of the hollow camshaft is closed with a blind plug. Since the other side open end is closed by the camshaft drive means and both ends are closed, even if the core sand remains in the hollow camshaft, the core sand may fall outside during engine operation. Moreover, there is no possibility that the lubricating oil of the engine will enter the hollow camshaft.

Further, since the hollow cam shaft of which both ends are open can be used, the core sand can be supported at both ends during casting, and the axis of the core sand is eccentric with respect to the axis of the cam shaft. In addition, it is not necessary to form a hole for core sand support at a position other than the axially open end of the camshaft, like a hollow camshaft with one end open, so the strength of the camshaft can be improved. It has excellent effects such as

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a hollow camshaft according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which core sand remains stuck in a hollow camshaft.

FIG. 3 is a vertical cross-sectional view showing a state where core sand is extracted.

FIG. 4 is a vertical sectional view showing another embodiment of the blind plug used in the hollow camshaft according to the present invention.

FIG. 5 is a vertical sectional view showing another embodiment of the blind plug used in the hollow camshaft according to the present invention.

FIG. 6 is a vertical sectional view showing still another embodiment of the blind plug used in the hollow camshaft according to the present invention.

FIG. 7 is a vertical sectional view showing still another embodiment of the blind plug used in the hollow camshaft according to the present invention.

FIG. 8 is a vertical cross-sectional view showing one embodiment of a hollow cam shaft for an internal combustion engine.

FIG. 9 is a vertical cross-sectional view showing another mode of the hollow camshaft for an internal combustion engine.

[Explanation of symbols]

 3 Timing Belt Pulley 6 Core Sand 21 Hollow Cam Shaft 21c Cam Part 22 Hollow 22a Opening End 22b Opening End 22c Hollow Swelling Part 24 Hard Ball 41 Packing 43 Bolt 51 Resin Member 61 Plug 71 Cap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Daisuke Mibayashi, No. 1 Uzumasa Town, Ukyo-ku, Kyoto City, Kyoto Prefecture Mitsubishi Motors Corporation, Kyoto Works (72) Inventor Takashi Dogahara, Tatsumi Hata Town, Ukyo-ku, Kyoto Prefecture No. 1 Mitsubishi Motors Corporation Kyoto Works (72) Inventor Masahiko Matsuda No. 1 Uzumasa-cho, Ukyo-ku, Kyoto City Kyoto Prefecture Mitsubishi Motors Co., Ltd. Kyoto Works

Claims (4)

[Claims] 1. A core sand is cast into a hollow with both ends open, a blind plug is provided at one open end, and a camshaft drive means is attached to the other open end to close the open end. The hollow camshaft of an internal combustion engine. 2. A shaft portion having the hollow formed therein, and a cam portion formed on the outer periphery of the shaft portion, wherein the hollow has a bulging portion formed by bulging outward in the cam portion. The hollow camshaft of an internal combustion engine according to claim 1, wherein the hollow camshaft is provided. 3. A step of casting a hollow camshaft whose both ends are open using core sand whose both ends are supported, a step of applying a blind plug to one open end of the camshaft, and the other steps of the camshaft. And a step of mounting a camshaft drive means on the side opening end. A method of manufacturing a hollow camshaft of an internal combustion engine, comprising: 4. A step of mounting a camshaft driving means on the other side opening end of the camshaft, a step of engraving a screw on the other side opening end, and a step of screwing the camshaft driving means on the screw. The method for manufacturing a hollow camshaft of an internal combustion engine according to claim 3, further comprising a step of fixing the hollow camshaft with a bolt.