JPH04269312A - Hollow valve for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain a hollow valve of which manufacture is easy, safety is high, light weight orientation is attained, and thermal expansion can be absorbed, by enclosing a cooling medium instead of metallic sodium or a metallic cylindrical cooling medium in the hollow. CONSTITUTION:By fitting a cylindrical body 6 made of material of high thermal conductivity and low specific gravity and having a slit 6a in the axial direction on one part of the circumference in a hollow 5 drilled on the center axis of a stem 3 from a valve head part 2, heat of the valve head part 2 can be effectively transmitted to the stem 3 side through the cylindrical body 6, while minimizing increase of weight of the whole hollow valve 1. Further, because the thermal expansion of the cylindrical body 6 is absorbed with the slit 6a, stress is not applied on the stem 3 from the inside.

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 a hollow valve with improved heat transfer efficiency from a cap portion to a stem.

0002

BACKGROUND OF THE INVENTION Recent automobile engines tend to have higher rotation speeds and higher outputs, such as by being equipped with a supercharger or using a multi-valve mechanism.

The biggest obstacle to increasing the permissible engine speed is the increase in inertial mass due to the weight of the valve train, and as the total weight of the valve train components increases, the inertia increases. Furthermore, as the rotation speed increases, the ability of the valve body to follow the cam deteriorates, causing the valve body to dance or the like, resulting in a decrease in output.

[0004] Hollow valves are very advantageous in terms of reducing the weight of the valve body and the inertial mass of the valve train.
It is used in racing car engines that are constantly running at high speeds, as well as high-output engines in some passenger cars.

[0005] Hollow valves are inferior in strength and rigidity compared to ordinary solid valves, so in particular, exhaust valves where the temperature of the umbrella part is high,
It is necessary to reduce the heat load on the umbrella part and increase its high temperature strength. In hollow valves with improved cooling performance, metal sodium is filled as a cooling medium in the hollow hole drilled from the cap to the stem to increase the efficiency of heat transfer from the cap to the stem. Those designed to reduce the load (for example, Japanese Patent Application Laid-Open No. 60-145410, Japanese Utility Model Application No. 63-15191)
(Refer to Publication No. 1) and those in which a metal rod-shaped cooling medium with excellent thermal conductivity is sealed in a hollow hole (for example, Utility Model Publication No. 56-142)
(Refer to Publication No. 204 and Japanese Utility Model Application Publication No. 171605/1983)
and so on.

[0006]

[Problems to be Solved by the Invention] In a hollow valve that is filled with metallic sodium as described above, metallic sodium easily reacts with water, oxygen, etc., and this reaction causes sodium oxide and other substances to form inside the hollow hole. When sodium hydroxide, sodium hydride, etc. are generated, the internal pressure of the hollow hole increases,
or reduce heat transfer efficiency. Therefore, it is necessary to remove moisture etc. remaining in the hollow hole and to inject metallic sodium into the hollow hole in an inert gas atmosphere.

[0007] In addition to the above-mentioned properties, metallic sodium has strong alkalinity, so when injecting it, it is necessary to pay sufficient attention to safety.
Its manufacture requires many troublesome processes and requires strict safety control.

[0008]Furthermore, it would be extremely dangerous if the stem were to break and metallic sodium would flow out during scrap processing or disposal after being assembled into an engine. On the other hand, in the latter case where a metal rod-shaped cooling medium with high thermal conductivity is sealed in a hollow hole, the cooling medium is a solid material or a shape close to it, so the valve body is lightweight. We cannot expect much change.

Furthermore, since materials with high thermal conductivity generally have high coefficients of thermal expansion, if the cooling medium is made of a solid material, when the cooling medium is heated by the operating temperature of the valve, its thermal expansion in the radial direction will be reduced. Since it cannot be absorbed, stress is applied to the umbrella and stem from the inside.

The present invention has been made to solve the above-mentioned problems, and its purpose is to improve manufacturing efficiency by filling a hollow hole with a cooling medium in place of metallic sodium or metal rod-shaped cooling medium. To provide a hollow valve for an internal combustion engine which is easy to operate, highly safe, lightweight, and capable of absorbing thermal expansion.

[0011]

[Means for Solving the Problems] The above object is to have at least a hollow hole bored in the stem, which is made of a low specific gravity material with high thermal conductivity, and has a slit oriented in the axial direction in a part of the circumference. This can be achieved by fitting cylindrical bodies.

0012

[Operation] The heat of the umbrella portion is effectively transmitted to the stem side and radiated through the cylindrical body having a slit fitted in the hollow hole. Furthermore, since the slit absorbs thermal expansion of the cylindrical body, it is possible to prevent stress from being applied to the stem from the inside.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. 1 and 2 show a hollow valve (1) of a first embodiment of the present invention molded from heat-resistant steel, from the umbrella part (2) whose diameter expands downward, to the upper end of the stem (3). A straight hollow hole (5) of the required diameter is located on the central axis extending to the front of the annular groove (4) for locking the cotter (not shown) formed in the umbrella face (2). It is perforated from the front (umbrella front) (2a) side.

As shown in FIG. 2, inside the hollow hole (5),
A slit (6a) of the required width facing in the axial direction on a part of the circumference
A thin-walled pipe-like cylindrical body (6) with a hollow hole (5)
In other words, when this hollow valve (1) is assembled into an engine, a gap (5a) of approximately 1/3 of the height of the hollow valve is left in the stem (3) at the part that slides into contact with the valve guide (7). , and are fitted so that a part of the cylindrical body (6) is located therein.

[0015] (8) is a closing member that closes the front opening of the umbrella portion (2) after the cylindrical body (6) is fitted. The material for the cylindrical body (6) is a substance that has a melting point higher than the operating temperature during firing operation of the engine, has a relatively low specific gravity, has excellent thermal conductivity, and has some elasticity, such as Cu, Al, Mg, Zn, T
Pure metal materials such as i, or Al-Cu-Mg-Mn system, A
l-Cu-Ni-Mg system, Mg-Al-Zn-Mn system,
Mg-Zn-Zr based and Al-Si-Fe based alloy materials are preferred.

In this embodiment, the above-mentioned material is appropriately selected and formed into a cylindrical body (6) whose outer diameter is slightly larger than the inner diameter of the hollow hole (5), and a part of the circumference is formed into a cylindrical body (6). After cutting the slit (6a), the cylindrical body (6) is inserted into the hollow hole (5) to a predetermined position while being elastically deformed in the direction of diameter reduction, and the cylindrical body (6) is inserted into the hollow hole (5). It is held in the hollow hole (5) by the elastic force that tries to restore its shape in the diametrically expanding direction.

FIG. 3 shows a hollow valve (1) of a second embodiment of the present invention.
), and in this example, from the umbrella part (2) to the stem (3
) A hollow hole (9) that expands in a trumpet shape on the side of the umbrella (2) is bored on the central axis that reaches the shaft end of the hole (9).
Inside, there is a slit (similar to the first embodiment) on a part of the circumference.
10a) and a thin-walled cylindrical body (10) whose lower part has a trumpet-like shape with approximately the same curvature as the hollow hole (9),
After fitting the hollow hole (9) leaving a gap (9a) of approximately 1/3 of the height, the opening on the umbrella part (2) side is closed with the closing plate (11).
).

Hollow valves of the first and second embodiments explained above (
In 1), when the umbrella part (2) side is heated by high-temperature combustion gas, the heat is transferred to each hollow hole (5) (9).
) is quickly transmitted to the stem (3) side using the cylindrical bodies (6) and (10) fitted in the valve guide (7) as a medium.
Since the heat is effectively radiated to the cylinder head (not shown) etc. through the cylinder head, the heat load on the umbrella part (2) can be significantly reduced. In particular, the hollow valve (1) of the second embodiment has an umbrella portion (2
) side is made into a trumpet shape to increase the surface area, and the cylindrical body (10
), it is suitable for use in exhaust valves with large heat loads.

Even if each cylindrical body (6) (10) is heated and expands thermally in the radial direction, it is absorbed by the gap between each slit (6a) (10a), so that the stem (3) and umbrella part (
2) No stress is applied from inside.

Moreover, during thermal expansion, each cylindrical body (6
) (10) has good adhesion to the hollow holes (5) and (9), improving heat transfer efficiency. In addition, each cylindrical body (6)
Since (10) is made thin and made of a low specific gravity material, the increase in weight of the valve is small.

Slits (6a) in the cylinders (6) and (10)
(10a) is formed, so the cylindrical body (6) (10)
By reducing the diameter of the hollow holes (5) and (9), the insertion work into the hollow holes (5) and (9) becomes extremely easy, and productivity can be increased.

In the first and second embodiments described above, the cylindrical bodies (6) and (10) may be fitted into the hollow holes (5) and (9) entirely or up to the vicinity of the upper end of the valve guide (7). Of course, the material of the valve may be, for example, titanium, titanium alloy, aluminum alloy, etc. instead of heat-resistant steel.

The inner peripheral surfaces of the hollow holes (5) and (9) and the cylindrical body (
6) One or both of the outer circumferential surfaces of (10) may be plated or sprayed with a material having excellent thermal conductivity, and in this way, the cylindrical bodies (6) and (10),
Heat exchange between the umbrella portion (2) and the stem (3) is quickly performed, and the heat load on the umbrella portion (2) can be further reduced.

[0024]

[Effects of the Invention] According to the present invention, the following effects can be achieved. (a) Since a pre-formed pipe-shaped cylindrical body simply needs to be fitted into a hollow hole, it is much easier to manufacture than the conventional hollow valve filled with metallic sodium, and it is safer and cheaper. advantageous in terms of (b) Since the slit formed in a part of the cylindrical body absorbs thermal expansion, there is no fear that stress will be applied to the stem from the inside, and there will be no problem in terms of weight reduction. (c) Since the heat of the umbrella part is effectively transferred to the stem side through the cylindrical body, the heat load on the umbrella part is reduced, and a hollow valve with excellent durability and reliability can be provided.

[Brief explanation of the drawing]

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

FIG. 2 is a cross-sectional plan view taken along line AA in FIG. 1;

FIG. 3 is a central longitudinal sectional front view showing a second embodiment of the present invention.

[Explanation of symbols]

(1) Hollow valve
(2) Umbrella (3) Stem
(4) Annular groove (5) Hollow hole
(5a)
Gap (6) Cylindrical body
(6a) Slit (7) Valve guide
(8) Closing member (9) Hollow hole (9
a) Gap (10) Cylindrical body
(10a) Slit (11) Closure plate

Claims (2)

[Claims] Claim 1: A cylindrical body made of a low specific gravity material with high thermal conductivity and having a slit oriented in the axial direction on a part of the circumference is fitted into at least a hollow hole bored in the stem. Characteristic hollow valve for internal combustion engines. 2. The diameter of the hollow hole is gradually expanded in a trumpet shape toward the umbrella portion, and a portion of the cylindrical body located inside the umbrella portion is formed in a trumpet shape complementary to the expanded diameter portion. The hollow valve for an internal combustion engine according to claim 1.