JP3018254B2 - Hollow valve for internal combustion engine and method of manufacturing the same - Google Patents

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 in particular, a sintered body as a cooling medium is sealed in a hollow hole provided from an umbrella to a stem. And a method for manufacturing the same.

[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] Since the hollow valve is inferior in strength and rigidity to the ordinary solid valve, the exhaust valve in which the temperature of the umbrella portion becomes high,
It is necessary to reduce the heat load on the umbrella to increase the high-temperature strength.
In such a hollow valve with improved cooling, metal sodium as a cooling medium is sealed in a hollow hole drilled from the umbrella to the stem to increase the efficiency of heat transfer from the umbrella to the stem. In order to reduce the load (e.g., Japanese Patent Application Laid-Open No. 60-145410, Japanese Utility Model Application Laid-Open No. 63-151911) or a metal rod-shaped cooling medium having excellent heat conductivity in a hollow hole (e.g., See Japanese Utility Model Laid-Open No. 56-142204).

[0006]

In the above-mentioned hollow valve in which metallic sodium is sealed, metallic sodium easily reacts with water, oxygen, or the like, and this reaction causes sodium oxide or sodium oxide to form inside the hollow hole. When sodium hydroxide, sodium hydride, etc. are generated, the internal pressure of the hollow hole is increased,
Or reduce heat transfer efficiency. 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.

In addition, since sodium metal 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.

Further, after being assembled to the engine, the time of scrap processing and disposal, by any chance stem folding <br/> loss is very dangerous metallic sodium flows out. On the other hand, as in the latter case, in the case where a metal rod-shaped cooling medium having a large thermal conductivity is sealed in the hollow hole, since the cooling medium is made of a solid material, the weight of the valve body cannot be expected much. .

In general, a material having a large thermal conductivity has a large coefficient of thermal expansion.
When the cooling medium is heated by the operating temperature of the valve, the thermal expansion in the radial direction cannot be absorbed, so that stress is applied to the umbrella and the stem from inside.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to fill a hollow medium with a cooling medium in place of a metal sodium or a metal rod-shaped cooling medium, thereby manufacturing the same. It is an object of the present invention to provide a hollow valve for an internal combustion engine and a method for manufacturing the same, which is easy, has high safety, can be reduced in weight, and can absorb thermal expansion.

[0011]

The above object is achieved by sealing a sintered body made of a powder material having a higher thermal conductivity than the material of the stem into at least a hollow hole formed in the stem. can do. Further, the manufacturing method includes a method in which a stem is provided at least in a hollow hole formed in the stem.
By inserting a powder material having a higher thermal conductivity than that of the material from the opening communicating with the hollow hole, pressing it into a green compact, and then heating the stem and the green compact. The method is characterized in that the green compact is sintered, and then the opening is closed.

[0012]

[Function] The heat of the umbrella is derived from the material of the stem sealed in the hollow hole .
Since heat is radiated is transmitted immediately to the stem side a sintered body made of a powder material of high material having remote thermal conductivity as a medium, it is not necessary to enclose the cooling medium of the metal sodium or metal rod-shaped into the hollow bore Therefore, there is no problem in terms of safety and weight reduction (claim 1).

Further, the process of the powder material to be sintered,
Since all the processes are performed using the hollow hole of the valve itself, the manufacturing process is simplified (claim 2).

[0014]

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 and has an umbrella section (2) whose diameter increases downward and a stem ( 3) and a terminal member (4) made of a titanium alloy or the like and forming a part of the stem (3), which is joined to the upper end thereof.

On the central axis extending from the umbrella portion (2) to a position just before the annular concave groove (5) for locking the cotter (not shown) of the terminal member (4), the umbrella portion (2) side is a wrapper. Hollow hole (6)
Are drilled.

Reference numeral (7) denotes a closing plate for closing the opening (2a) of the umbrella (2), which is fixed by means such as friction welding or welding. In the hollow (6), a sintered body (8) as a cooling medium is provided.
However, leaving a space (6a) almost 1/3 of the height of the hollow hole (6),
That is, when the hollow valve (1) is assembled to an engine, a part of the sintered body (8) is positioned in the stem (3) at a portion that comes into sliding contact with the valve guide (9) and sealed. Have been.

The material of the sintered body (8) has a melting point higher than the operating temperature of the valve during the firing operation of the engine, has a relatively low specific gravity, and is excellent in heat conductivity which is easily heated and cooled. , For example, Cu, Al, Mg,
Fine metal powder such as Zn, Ti, or Al-Cu-Mg-Mn, Al-Cu
-Ni-Mg system, Mg-Al-Zn-Mn system, Mg-Zn-Zr system, Al-Si
-Alloy powders such as Fe-based alloys are preferred.

When the sintered body (8) is a substance which is easily oxidized, it is preferable that the inside of the space (6a) is evacuated or an inert gas such as nitrogen gas is filled.

Next, the procedure for manufacturing the hollow valve (1) of the first embodiment will be described. First, as shown in FIG. 2, a required amount of metal powder or alloy powder made of the above-mentioned material is put into the hollow hole (6) of the first intermediate product (1 ′) before the terminal member (4) is joined. After that, a push rod (10) attached to a press (not shown)
Is inserted from above the hollow hole (6) and pressed into the compact (8 ').
To form

Then, as shown in FIG. 3, a terminal member (4) having a hollow hole formed at the lower end is connected to a gap (6a) if necessary.
With the inert gas sealed therein, a second intermediate product (1 ") is formed by joining to the end face of the stem (3).

Finally, as shown in FIG. 4, the secondary intermediate product (1 ") shown in FIG. 3 is placed in a sintering furnace (11) or a coiled sheath heater (12). And the like are closely inserted from the umbrella part (2) to the stem (3), etc.
When the surface of the metal particles constituting (8 ′) is heated to a temperature at which the surfaces of the metal particles can be melted and bonded to each other, the green compact (8 ′) becomes a sintered body (8).
Thus, a hollow valve (1) as shown in FIG. 1 is obtained.

As described above, when the process up to turning the metal powder into the sintered body (8) is performed using the hollow hole (6) of the hollow valve (1) itself, the preform is formed in another process. The following advantages are obtained as compared with the case where the sintered body (8) is sealed in the hollow hole (6).

That is, according to the above-mentioned procedure, there is no need for a dedicated press die for turning the metal powder into a compact (8 ').
The green compact (8 ') is removed from the pressing die, and the sintered body (8) is hollowed out.
(6) The process of encapsulation can be omitted, and the sintered body
It is not necessary to consider the dimensional accuracy of (8) and the hollow hole (6)
It has a number of advantages, such as being able to respond immediately to changes in the shape.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, a hollow valve (1) has a stem (3) extending from an umbrella (2) to a joint of a terminal member (4). ), A straight hollow hole (13) is formed on the central axis, and the entire hollow hole (13) is filled with the same sintered body (8) as in the first embodiment.

In the hollow valve (1) of the second embodiment,
It can be manufactured in the same manner as in the first embodiment described above.

The hollow valve according to the first and second embodiments described above.
In (1), when the umbrella portion (2) is heated to a high temperature by a combustion gas or the like, the heat is generated using the sintered body (8) sealed in the hollow holes (6) and (13) as a medium. , Is quickly transmitted to the stem (3) side, and is passed through the valve guide (9) to the cylinder head.
Since the heat is radiated to (not shown) or the like, the heat load on the umbrella (2) is significantly reduced.

Moreover, a low specific gravity material is used for the sintered body (8),
In addition, since the terminal member (4) is made of a titanium alloy, the weight increase of the valve body is small. Further, since the sintered body (8) has a porous structure formed by bonding countless metal particles, even if the sintered body (8) is heated by the operating temperature of the valve and thermally expanded, the metal Since it is absorbed by the gap between the stem and the umbrella (2), no stress acts on the stem (3) or the umbrella (2) from inside.

The present invention is not limited to the above embodiments, but can take various forms. For example, in the hollow valve of the first embodiment, the sintered body (8) may be filled in the entire hollow hole (6). In this case, after joining the terminal member (4) first, metal powder is put into the umbrella portion (2) from the opening (2a) side to form a green compact, and then the opening (2a) is closed by the closing member (7). Shut off,
Finally, the green compact may be sintered by a sintering furnace or the like.

In the hollow valve of the second embodiment, the hollow hole (13)
Of the sintered body (8) with respect to
It may be up to about 2/3, and the rest may be voids. This makes it possible to further reduce the weight of the hollow valve (1).

In the hollow valves of the first and second embodiments, the terminal member
Although (4) is a titanium alloy, it may be a normal heat-resistant steel of the same material as that of the umbrella (2). Nickel plating or the like may be applied to the inner surfaces of the hollow holes (6) and (13) to increase the heat conduction efficiency.

For example, in the case of a hollow valve used as an exhaust valve, if a material having a melting point near the operating temperature of the valve is selected as the material of the metal powder, it is assembled into the engine in a compact state, It is also possible to use a sintered body.

The shapes of the hollow holes (6) and (13) are, of course, not limited to the above embodiment.

[0033]

According to the present invention, the following effects can be obtained. (a) Compared to a hollow valve in which metallic sodium is sealed, it is easier to manufacture, and is advantageous in terms of safety and cost. (b) Since it is lighter than a hollow valve in which a cooling medium in the form of a metal rod is sealed and can absorb thermal expansion, it is possible to prevent stress from being applied to the stem. (c) A powder material having a higher thermal conductivity than the material of the stem is used as a green compact, and the entire process up to sintering is completed at the same time as sintering, using the hollow holes of the hollow valve to be manufactured. Since a product is obtained, the manufacturing process can be simplified and productivity can be increased. (d) Since the heat of the head portion is effectively transmitted to the stem side via the sintered body, the heat load on the head portion is reduced, and a hollow valve having excellent durability and reliability can be provided.

[Brief description of the drawings]

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

FIG. 2 is an explanatory view showing a manufacturing procedure of the hollow valve according to the first embodiment, in which metal powder is put into a hollow hole, compacted into a green compact.

FIG. 3 is an explanatory view of a state where the terminal members are similarly joined.

FIG. 4 is an explanatory view showing a procedure for sintering a green compact.

FIG. 5 is a central longitudinal sectional front view showing a second embodiment of the present invention.

[Explanation of symbols]

 (1) Hollow valve (1 ') Primary intermediate (1 ") Secondary intermediate (2) Head (2a) Opening (3) Stem (4) Terminal member (5) Annular groove (6) ) Hollow hole (6a) Gap (7) Closure plate (8) Sintered body (8 ') Green compact (9) Valve guide (10) Push rod (11) Sintering furnace (12) Seed heater (13) Hollow Hole

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 3/14 F01L 3/02

Claims (2)

(57) [Claims] 1. A hollow valve for an internal combustion engine, wherein a sintered body made of a powder material having a higher thermal conductivity than the material of the stem is sealed in at least a hollow hole formed in the stem. . 2. A powder material having a higher thermal conductivity than a material of the stem is inserted into at least a hollow hole formed in the stem from an opening communicating with the hollow hole, and is compacted. A method for manufacturing a hollow valve for an internal combustion engine, comprising: sintering a green compact by heating a stem and a green compact after forming a green compact; and then closing the opening.