JPH11117718A - Hollow valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate manufacture and improve safety by using a green compact excepting metallic sodium as a cooling medium. SOLUTION: A hollow hole 5 whose diameter of umbrella part side 2 is enlarge in a circular cone shape is drilled from a front surface 2a side of the umbrella part 2, on a center axis extending over from the umbrella part 2 short of an annular recessed groove 4 for locking a cotter formed on an upper end part of a stem 3. A green compact 6 excepting metallic sodium as a cooling medium is filled into the hollow hole 5 leaving a clearance 5a having a height of nearly 1/3 compared with the height of the green compact 6. As a material of the green compact 6, a material having a fusing point which is not fused under an operating temperature of a valve element, having a comparatively low specific gravity, and having a good heat conductivity which is heated or cooled easily, is used. For example, fine metallic powder such as copper, aluminum, zinc, titanium, or a complex formed by mixing those metallic powder with each other is used as the material of the green compact 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow valve used as an intake / exhaust valve for an internal combustion engine, and more particularly, to encloses a compact as a cooling medium in a hollow hole provided from an umbrella to a stem. The present invention relates to a hollow valve.

[0002]

2. Description of the Related Art Recent automobile engines tend to have higher rotation speed and higher output by mounting a supercharger or adopting a multi-valve mechanism.

The most hindrance in increasing the allowable rotation speed of the engine is the increase in the inertial mass due to the weight of the valve train. When the total weight of the components of the valve train increases, the inertia increases. In addition, as the rotation speed increases, the follow-up performance of the valve body with respect to the cam decreases, and the valve body generates a dance and the like, which causes a decrease in output.

Since the hollow valve is very advantageous in reducing the weight of the valve body and reducing the inertial mass of the valve train,
It is used in racing car engines that are constantly used at high speeds and in high-power engines for some passenger cars.

[0005] In this kind of hollow valve, metallic sodium as a cooling medium is sealed in a hollow hole opened from the head to the stem to increase the efficiency of heat transfer from the head to the stem and reduce the heat load. Some are designed to reduce (Japanese Patent Application Laid-Open
145410, Japanese Utility Model Application Laid-Open No. 63-151911).

[0006]

In a hollow valve in which metallic sodium is sealed as described above, metallic sodium is
It easily reacts with water, oxygen, etc., and when sodium oxide, sodium hydroxide, sodium hydride, etc. are generated inside the hollow by this reaction, the internal pressure of the hollow is increased or the heat transfer efficiency is reduced. I do. Therefore, it is necessary to remove the moisture and the like remaining in the hollow hole and to perform the operation of injecting the metallic sodium into the hollow hole in an inert gas atmosphere.

[0007] In addition, since metallic sodium has a strong alkalinity in addition to the above properties, it is necessary to pay sufficient attention to safety when injecting it.
Its production requires many complicated steps and requires strict safety management.

[0008] Further, in the event of scrap processing or disposal after being assembled to the engine, it is extremely dangerous if the stem is cut off and metallic sodium flows out.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a simple and safe manufacturing method by enclosing a cooling medium instead of metallic sodium in a hollow hole. It is to provide a high hollow valve.

[0010]

According to the present invention, the above-mentioned problem is solved as follows.

(1) A hollow valve for an internal combustion engine in which a compact excluding metallic sodium is sealed as a cooling medium in at least a hollow hole formed in the stem.

(2) In the above item (1), a gap is provided between the upper end of the hollow hole and the upper end of the green compact.

(3) In the above item (2), the gap is evacuated.

(4) In the above item (2), the space is filled with an inert gas.

(5) In any one of the above items (1) to (4), the green compact is made of any of copper, aluminum, magnesium and zinc, or a mixture thereof.

[0016]

The manufacturing process is simplified by using a non-hazardous substance other than metallic sodium as the cooling medium to be sealed in the hollow hole and sealing it in the form of a compact.
Even if the valve is cut off and the green compact flows out, there is no harm to the human body or the like.

The heat of the umbrella is quickly transmitted to the stem using the green compact as a medium and radiated, so that the heat load on the umbrella can be reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a hollow valve (1) according to a first embodiment of the present invention, which is formed of heat-resistant steel, from an umbrella portion (2) expanding downward, to an upper end of a stem (3). A hollow hole (5) in which the umbrella part (2) side is enlarged in a trumpet shape on a central axis extending to a position just before an annular concave groove (4) for locking a cotter (not shown) formed in the part. Are formed from the front (2a) side of the umbrella (2).

In the hollow hole (5), a green compact (6) excluding metallic sodium as a cooling medium is placed at approximately the same height as the hollow hole (5).
Leaving about 1/3 void (5a), that is, this hollow valve
When (1) is assembled to the engine, the green compact (6) is sealed so that a part of the green compact (6) is located in the stem (3) at the portion that comes into sliding contact with the valve guide (7).

The material of the green compact (6) has a melting point that does not melt even at the operating temperature of the valve body during the firing operation of the engine, has a relatively low specific gravity, and is easily heated and easily cooled. Materials with excellent conductivity, for example,
A fine metal powder such as copper, aluminum, magnesium, zinc, and titanium, or a composite obtained by selecting and mixing these metal powders is preferable.

In this embodiment, the above-described metal powder is
(5) is pressed and solidified to form a green compact (6) in advance, which is formed in an opening formed in the lower surface (2a) of the umbrella (2).
After being inserted into the hollow hole (5) from (2b), the opening (2b) is closed with a closing plate (8).

When the green compact (6) is an oxidizing substance, the space (5a) is preferably evacuated or filled with an inert gas such as nitrogen gas.

Also, due to vibrations or the like during valve operation, the compact
If (6) is likely to be crushed, a suitable heat-resistant binder may be used during the molding of the green compact (6).

Next, a second embodiment of the present invention will be described with reference to FIG.

In the hollow valve (11) shown in this embodiment, the stem
(12) is replaced with a hollow shaft part slightly shorter than in the first embodiment.
(13) and a terminal member (14) fixed to the upper end thereof.

The lower portion of the hollow hole (13a) in the hollow shaft portion (13) reaches the inside of the umbrella portion (15) following the lower end of the stem (12), and the hollow hole (13a) has The same green compact (16) as in the first embodiment is filled.

The terminal member (14) is provided with an annular groove (14a) at an important point, is fixed to the upper end of the hollow shaft (13) by friction welding or the like, and closes the hollow hole (13a).

As the green compact (16), the metal powder is previously filled with hollow holes (13).
After being pressed into the same shape as in a), it may be inserted into the hollow hole (13a), or may be compacted after filling the hollow hole (13a) with metal powder.

The green compact according to the present invention is essentially different from, for example, a metal powder simply densely packed. The compact in the present invention refers to a compact that does not break due to vibration or the like at the time of normal valve operation, but a metal powder that is simply densely packed is essentially a fine powder. The two have different modes of heat conduction during valve operation.

That is, in the present invention, the green compact is
Although heat conduction is performed in a predetermined shape as a whole, in the case of fine powder, heat conduction is performed by flowing the fine powder.

(17) is a valve guide. In the hollow valves (1) and (11) of the respective embodiments described above,
(2) When (15) is heated to a high temperature by a combustion gas or the like, the heat is transferred to the green compact (6) (16) sealed in each hollow hole (5) (13a).
Is quickly transmitted to the stem (3) (12) side using
Heat is radiated to the cylinder head and the like through the valve guides (7) and (17).

As a result, the heat load on the heads (2) and (15) is significantly reduced. Further, since the green compacts (6) and (16) are formed by the particle bonding of innumerable metal powders and have very small gaps between the particles, the green compact (6) (16) Even if 16) is thermally expanded, no stress acts on the stem (3) or (12) from inside.

In the first embodiment, the green compact (6) is
(5) The whole may be filled, and in the second embodiment, the amount of the compact (16) filled in the hollow hole (13a) is adjusted by the portion of the stem (12) which is in sliding contact with the valve guide (17). About 1 /
It may be up to about 2 and the remainder may be voids.

It goes without saying that the shape of the hollow holes (5) and (13a) may be arbitrarily determined.

[0036]

According to the present invention, the following effects can be obtained. (a) Since the cooling medium to be filled in the hollow hole is a green compact excluding sodium metal, the manufacturing process is simplified and the manufacturing cost is reduced as compared with the conventional hollow valve containing sodium metal. Not only is there no danger, but a highly safe hollow valve can be provided.

(B) Since the heat of the umbrella is effectively transmitted to the stem via the green compact, there is no possibility that the cooling of the umbrella is impaired.

(C) As in the second aspect of the present invention, when a gap is left in the hollow hole, the difference in thermal expansion in the axial direction can be absorbed, and the weight can be reduced.

(D) If the gap is evacuated or an inert gas is filled as in the third or fourth aspect of the present invention, even if the green compact is an oxidizing substance, its oxidation is prevented. be able to.

(E) A conventional hollow valve in which metallic sodium is sealed by forming the compact into any one of copper, aluminum, magnesium and zinc or a mixture thereof, as in the invention of claim 5. As compared with the above, it is possible to provide a hollow valve which is safer and has no danger, and can effectively radiate the heat of the umbrella portion by using a compact made of these substances as a medium.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a first embodiment of a hollow valve according to the present invention.

FIG. 2 is a vertical sectional front view showing the second embodiment.

[Explanation of symbols]

 (1) Hollow valve (2) Head (2a) Lower surface (2b) Opening (3) Stem (4) Annular groove (5) Hollow hole (5a) Void (6) Compact (7) Valve guide ( 8) Blocking plate (11) Hollow valve (12) Stem (13) Hollow shaft (13a) Hollow hole (14) Terminal member (15) Head (16) Compact (17) Valve guide

Claims (5)

[Claims] 1. A hollow valve for an internal combustion engine, wherein a green compact excluding metallic sodium is sealed as a cooling medium at least in a hollow hole formed in a stem. 2. Between the upper end of the hollow hole and the upper end of the green compact,
2. The hollow valve for an internal combustion engine according to claim 1, wherein an air gap exists. 3. The hollow valve for an internal combustion engine according to claim 2, wherein the space is a vacuum. 4. The hollow valve for an internal combustion engine according to claim 2, wherein an inert gas is sealed in the gap. 5. The hollow valve for an internal combustion engine according to claim 1, wherein the green compact is made of any one of copper, aluminum, magnesium, and zinc, or a mixture thereof.