FORM 2
THE PATENT ACT 197 0 {39 of 1970)
The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13)
1. TLE OF INVENTION
METHOD FOR PRODUCING METALLIC-SODIUM-FILLED ENGINE VALVE
2. APPLICANT(S)
a) Name : MITSUBISHI HEAVY INDUSTRIES, LTD.
b) Nationality : JAPANESE Company
c) Address : 16-5, KONAN 2-CHOME,
MINATO-KU, TOKYO 1088215, JAPAN
AND
a) Name : YOSHIMURA COMPANY
b) Nationality : JAPANESE Company
c) Address : 2685-173, AZA MINAMIHARA,
OAZA NAKASHIDAMI, MORIYAMA-KU, NAGOYA-SHI, AICHI 4630002, JAPAN
3 . PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

Technical Field
The present invention relates to a method for producing an engine valve filled inside with metallic sodium.
Background Art
In an engine valve of an automobile or the like, in order to respond to an increase in performance, a reduction in fuel consumption of an engine, and the like, the weight is reduced and the heat transmission is increased by filling an inside of the engine valve with metallic sodium.
Such an engine valve has a stem portion which has a hollow portion formed in an inner portion and which has an opening formed at an upper end. To this stem portion, for example, (1) solid metallic sodium is extruded into a bar shape, cut into a predetermined length, and then inserted into the hollow portion from the opening; or (2) solid metallic sodium is heated to melt (about 120°C to 300°C) into a liquid state and then put into the hollow portion by injecting a predetermined amount of metallic sodium into the hollow portion from the opening. Thereafter, the opening is sealed and the engine valve is thus produced (for example, see Patent Literatures 1 to 3 and the like listed below).
Citation List Patent Literatures
Patent Literature 1: Japanese Patent Application Publication No. Hei 03-018605 Patent Literature 2: Japanese Patent Application Publication No. Hei 04-232318 Patent Literature 3: Japanese Patent Application Publication No. Hei 04-272413

Summary of Invention Technical Problem
However, a conventional method for producing a metallic-sodium-filled engine valve as described above has the following problems.
(1) Solid metallic sodium is difficult to extrude and the workability of shaping the solid metallic sodium is thereby poor.
(2) When liquid metallic sodium adheres to an inner wall of the elongated hollow portion (a diameter of about 2 to 4 mm) during the injection of liquid metallic sodium into the hollow portion, metallic sodium immediately cools and becomes solid thereby closing the hollow portion. Thus, the liquid metallic sodium needs to be injected while the stem portion is heated (98°C or higher) and the workability of injection is thereby poor.
The present invention is made in view of the problems describe above, and an object thereof is to provide a method for producing a metallic-sodium-filled engine valve by which metallic sodium can be easily put into the inside of an engine valve.
Solution to Problem
In a method for producing an engine valve filled inside with metallic sodium, according to a first aspect of the invention for solving the aforementioned problems, the engine valve is produced by: putting metallic sodium into a hollow portion from an opening of a stem portion having the hollow portion in an inner portion and having the opening at an upper end; and thereafter sealing the opening, the method characterized by comprising: cooling and solidifying metallic sodium heated and melted to a liquid state into a bar-shaped piece; and thereafter inserting the bar-shaped piece of metallic sodium into the hollow portion from the opening of the stem portion.

The method for producing a metallic-sodium-filled engine valve according to a second aspect of the invention is characterized in that, in the first aspect of the invention, the metallic sodium heated and melted to a liquid state is discharged linearly into a hydrocarbon-based liquid and is cooled to be solidified into the bar-shaped piece.
The method for producing a metallic-sodium-filled engine valve according to a third aspect of the invention is characterized in that in the first aspect of the invention, the metallic sodium heated and melted to a liquid state is injected into a bar-shaped space in an inside of a metal mold having the space in the inside and is then cooled to be solidified into the bar-shaped piece.
The method for producing a metallic-sodium-filled engine valve according to a fourth aspect of the invention is characterized in that, in the third aspect of the invention, the bar-shaped space of the metal mold is formed such that at least an end portion on one side is formed in a tapered shape or an elongated ellipse shape.
Advantageous Effects of Invention
In the method for producing a metallic-sodium-filled engine valve of the present invention, the metallic sodium heated and melted to a liquid state is cooled to be solidified into a bar-shaped piece and the bar-shaped piece of metallic sodium is thereafter inserted into the hollow portion from the opening of the stem portion. Thus, the bar-shaped piece of metallic sodium can be easily shaped without performing extrusion and a predetermined amount of metallic sodium can be easily put into the hollow portion without heating the stem portion of the engine valve.
Brief Description of Drawings
Fig. 1 is a view for explaining a first embodiment of a method for producing a metallic-sodium-filled engine valve of the present invention.

Fig. 2 is an explanatory view subsequent to Fig. 1.
Fig. 3 is a view for explaining a second embodiment of a method for producing a metallic-sodium-filled engine valve of the present invention.
Fig. 4 is an explanatory view subsequent to Fig. 3.
Description of Embodiments
Embodiments of a method for producing a metallic-sodium-filled engine valve of the present invention are described below based on the drawings. However, the present invention is not limited to the embodiments described below based on the drawings.

In the aforementioned first embodiment, the piece of metallic sodium Na may be obtained as follows. The metallic sodium Na discharged linearly (in a bar shape) is caused to continuously fall into the hydrocarbon-based liquid 120 and then cooled to be solidified in such a way that an elongated bar material of metallic sodium Na is obtained. Thereafter, the bar material is cut in a required length and the cut piece is put into the hollow portion H of the engine valve V. Alternatively, the piece of metallic sodium Na may be obtained as follows. The metallic sodium Na is caused to intermittently fall into the hydrocarbon-based liquid 120 and then cooled to be solidified in such a way that bar materials of the required length are obtained. Thereafter, each of the bar materials can be inserted into the hollow portion H of the engine valve V without being cut.
In the aforementioned second embodiment, descriptions are given of the case where the bar shaped piece of metallic sodium Na whose end portions respectively on both sides are tapered is shaped with the metal mold 220. However, as other embodiments, a bar-shaped piece of metallic sodium Na whose end portion on one side alone is tapered or a bar-shaped piece of metallic sodium Na having an elongated ellipse shape may be shaped with a metal mold, for example. Even in such cases, operational effects similar to the case of the aforementioned second embodiment can be obtained.

Moreover, in the aforementioned second embodiment, descriptions are given of the case where the bar-shaped piece of metallic sodium Na is obtained one by one by using the metal mold 220 having the single space 220a. However, as another embodiment, it is also possible to obtain multiple bar-shaped pieces of metallic sodium Na simultaneously by using, for example, a metal mold having multiple spaces.
Industrial Applicability
In the method for producing a metallic-sodium-filled engine valve of the present invention, the bar-shaped piece of metallic sodium can be easily shaped without performing extrusion and the predetermined amount of metallic sodium can be easily put into the hollow portion without heating the stem portion of the engine valve. Thus, the method can be used very effectively in the industrial field.

Reference Signs List
111 cylinder 111a discharge port
112 piston
113 piston rod
114 heater

120 hydrocarbon-based liquid
121 container
220 metal mold
220a space
221 lower mold
222 upper mold
222a communication port
Na metallic sodium
V engine valve
A umbrella portion
S stem portion
H hollow portion
M opening

WE CLAIM:
1. A method for producing an engine valve filled inside with metallic sodium,
the engine valve produced by: putting metallic sodium into a hollow portion
from an opening of a stem portion having the hollow portion in an inner
portion and having the opening at an upper end; and thereafter sealing the
opening, the method characterized by comprising:
cooling and solidifying metallic sodium heated and melted to a liquid state into a bar-shaped piece; and
thereafter inserting the bar-shaped piece of metallic sodium into the hollow portion from the opening of the stem portion.
2. The method for producing a metallic-sodium-filled engine valve according to claim 1, characterized in that the metallic sodium heated and melted to a liquid state is discharged linearly into a hydrocarbon-based liquid and is cooled to be solidified into the bar-shaped piece.
3. The method for producing a metallic-sodium-filled engine valve according to claim 1, characterized in that the metallic sodium heated and melted to a liquid state is injected into a bar-shaped space in an inside of a metal mold having the space in the inside and is then cooled to be solidified into the bar-shaped piece.
4. The method for producing a metallic-sodium-filled engine valve according to claim 3, characterized in that the bar-shaped space of the metal mold is formed such that at least an end portion on one side is formed in a tapered shape or an elongated ellipse shape.