Method for filling with metallic sodium

Abstract

Provided is a method for filling a stem-side hollow area of an engine valve with metallic sodium. The method includes injecting melted metallic sodium into a cylinder having a larger diameter than an inner diameter of the hollow area of the engine valve, forming a solidified metallic sodium rod having a substantially uniform structure in the cylinder, inserting the metallic sodium into the hollow area of the engine valve through a nozzle having a small diameter, and sealing the engine valve.

Claims

1. A method for filling a hollow area of a hollow engine valve with metallic sodium, the method comprising: injecting melted metallic sodium into a cylinder having a larger diameter than an inner diameter of the hollow area of the engine valve under a directional solidification condition, at a speed faster than a speed at which a droplet solidifies, and in a form in which no discontinuity occurs; forming a solidified metallic sodium rod having a substantially uniform structure in the cylinder; inserting metallic sodium into the hollow area of the engine valve through a nozzle shaped die while keeping the uniform structure of the metallic sodium rod; cutting the inserted metallic sodium; and sealing the engine valve.

2. The method for filling with metallic sodium according to claim 1, wherein the melted metallic sodium is injected into the cylinder with a boundary of the metallic sodium in the cylinder kept in a semi-solidified condition.

3. The method for filling with metallic sodium according to claim 1, wherein the melted metallic sodium is injected into the cylinder by dripping.

4. The method for filling with metallic sodium according to of claim 1, wherein an inner diameter of the cylinder is within a range of 20 mm to 50 mm, a temperature of the metallic sodium is within a range of 180 C. to 250 C., and an injection speed is within a range of 150 g/min to 300 g/min.

5. A method for purifying metallic sodium including organic solvent and filling a hollow area of a hollow engine valve with purified metallic sodium, the method comprising: placing metallic sodium in a melting tank which is sealed; heating the melting tank under reduced pressure to vaporize and remove the organic solvent coating the metallic sodium; injecting the metallic sodium in a melting state into a cylinder having a larger diameter than an inner diameter of the hollow area of the engine valve under a directional solidification condition, at a speed faster than a speed at which a droplet solidifies, and in a form in which no discontinuity occurs; forming a solidified metallic sodium rod having a substantially uniform structure in the cylinder; inserting metallic sodium into the hollow area of the engine valve through a nozzle shaped die while keeping the uniform structure of the metallic sodium rod; cutting the inserted metallic sodium; and sealing the engine valve.

6. The method for filling with metallic sodium according to claim 2, wherein the melted metallic sodium is injected into the cylinder by dripping.

7. The method for filling with metallic sodium according to claim 2, wherein an inner diameter of the cylinder is within a range of 20 mm to 50 mm, a temperature of the metallic sodium is within a range of 180 C. to 250 C., and an injection speed is within a range of 150 g/min to 300 g/min.

8. The method for filling with metallic sodium according to claim 3, wherein an inner diameter of the cylinder is within a range of 20 mm to 50 mm, a temperature of the metallic sodium is within a range of 180 C. to 250 C., and an injection speed is within a range of 150 g/min to 300 g/min.

9. The method for filling with metallic sodium according to claim 4, wherein the inner diameter of the cylinder is within a range of 20 mm to 40 mm.

10. The method for filling with metallic sodium according to claim 7, wherein the inner diameter of the cylinder is within a range of 20 mm to 40 mm.

11. The method for filling with metallic sodium according to claim 8, wherein the inner diameter of the cylinder is within a range of 20 mm to 40 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an entire constitution diagram illustrating a system for purifying metallic sodium and filling with the metallic sodium by inserting, cutting and enclosing the metallic sodium, according to an embodiment of the present invention;

(2) FIG. 2 is a vertical cross-section view of a modification of a melting tank shown in the entire configuration diagram of FIG. 1;

(3) FIG. 3 is a plan view of a modification of a filling device by inserting, cutting and enclosing the metallic sodium in the entire constitution diagram of FIG. 1; and

(4) FIG. 4 is a vertical cross-section view of a cylinder in the entire constitution diagram of FIG. 1, illustrating an example in which a nozzle shaped die for injection is attached.

DESCRIPTION OF THE EMBODIMENTS

(5) An embodiment of the present invention will now be described with reference to the accompanying drawings but are not limited to.

(6) The embodiment is illustrated as a series of systems for purifying unpurified metallic sodium in addition to for filling with the metallic sodium by inserting, cutting and enclosing the metallic sodium. However, the embodiment can be performed as a system only for filling with metallic sodium. As illustrated in FIG. 1, the system 10 for purifying and filling with metallic sodium mainly includes a melting tank 12, a solvent trap 14, a reservoir tank 16, a cold trap 18 and a filling device 20.

(7) The melting tank 12 is a cylindrical container with a bottom. Connected to the upper side surface of the melting tank 12 is a pressure-reducing suction pipe 22. Connected to the lower side surface of the melting tank 12 are a purified-metallic-sodium discharge pipe 24 and a valve 82. The pressure-reducing suction pipe 22 is connected to the solvent trap 14 filled with an organic solvent 28 such as liquid paraffin. The tip end of the pressure-reducing suction pipe 22 reaches in the organic solvent 28. The solvent trap 14 is configured in such a manner as to keep inside thereof under reducing pressure by a decompression pump (not shown). The purified-metallic-sodium discharge pipe 24 is connected to the reservoir tank 16.

(8) The melting tank 12 is provided with a heater 30 on entire side surface below the pressure-reducing suction pipe 22 and on the bottom surface. The melting tank 12 is sealed by fixing a lid 33 at an upper opening thereof and the lid 33 is connected with an inert-gas supply pipe 32.

(9) The reservoir tank 16 is a closed tank for temporarily reserving purified metallic sodium which is purified in the melting tank 12 and which is supplied to the reservoir tank 16 through the purified-metallic-sodium discharge pipe 24. The reservoir tank 16 is connected with a feed pipe 36 and a return pipe 38 of a purified-sodium circulation line 34, in addition to the purified-metallic-sodium discharge pipe 24. The feed pipe 36 is branched into two at an opposite end to the end connected with a circulation pump 40. One of the two branches configures the other end of the return pipe 38 and is connected to the reservoir tank 16 through a first solenoid valve 42 and the cold trap 18.

(10) The other of the two branches configures a filling device supply pipe 46. The supply pipe 46 is connected to a quantitative supply device 49 through a second solenoid valve 48. In the illustrated example, the lower surface of a top plate 50 of the quantitative supply device 49 is electrically connected with five liquid level detection sensors S.sub.1 to S.sub.5, each having different length. Differences in the lengths in the vertical direction between each pair of adjacent sensors are the same length of d. The quantitative supply device 49 is connected with a supply pipe 53 having a quantitative supply valve 52 at the bottom plate 51. The supply pipe 53 extends to the filling device 20 and is equipped with a sodium dripping nozzle 54 at one end thereof. The filling device 20 is mounted inside thereof with a donut-shaped support 55 to come into contact with the inner circumferential surface of the filling device 20. The filling device 20 is equipped inside thereof with a cylinder 57 having a cylindrical shape with a flange 58. On the lower end of the flange 58, a cap 56 having a disk shape is detachably attached such that the flange 58 is engaged with a center opening of the support 55 located directly under the sodium dripping nozzle 54.

(11) Next, a function of the system for purifying and filling with metallic sodium according to the embodiment, which has the configuration as mentioned above, will be described.

(12) A suitable amount of liquid paraffin is put in the solvent trap 14 in FIG. 1, and the lid 33 of the melting tank 12 is taken off. A bulk body of unpurified metallic sodium that has been immersed and stored in the liquid paraffin is put in the melting tank 12 after wiping off the liquid paraffin with a cloth from the bulk body. Then, the lid 33 is attached again. Thereafter, by supplying an inert gas such as argon or nitrogen, from the inert-gas supply pipe 32, inside of the melting tank 12 is made under inert gas atmosphere so as to be sufficiently blocked from water and oxygen.

(13) Then, by activating the decompression pump (not shown), insides of the solvent trap 14 and the melting tank 12 are made under reduced pressure. Heating the bulk body of the metallic sodium in the melting tank 12 by energizing the heater 30 allows the liquid paraffin coating the bulk body of the metallic sodium to vaporize to be introduced into the solvent trap 14. The liquid paraffin is absorbed into the liquid paraffin 28 in the solvent trap 14, and thus a purification of the metallic sodium is completed.

(14) Even though a commercially available metallic sodium is stored in an organic solvent such as liquid paraffin or the like, it cannot be avoided that the commercially available metallic sodium contacts a small amount of water and oxygen, and it is oxidized at the surface to form sodium oxide. Likewise, a formation of sodium oxide by oxidization of the surface of the metallic sodium in this embodiment cannot be avoided even though a purification operation according to this embodiment is performed under inert gas atmosphere substantially including no water and no oxygen. The sodium oxide is formed as porous oxide so as to have bulk specific gravity less than that of metallic sodium. Accordingly, as illustrated in FIG. 1, the sodium oxide floats on the surface of the melted metallic sodium 60 to form a sodium oxide layer 62 when the metallic sodium in the melting tank is melted completely.

(15) Due to the existence of the sodium oxide layer 62 on the surface of the melted metallic sodium 60, the melted metallic sodium 60 cannot come into contact with the atmosphere in the melting tank 12. Even if the liquid paraffin in the melted metallic sodium 60 tries to vaporize, it cannot escape from the melted metallic sodium 60, so that purification of the metallic sodium cannot proceed. In order to avoid such situation, the sodium oxide layer 62 on the surface of the melted metallic sodium 60 can be scooped manually or mechanically with the lid 33 taken off, or, for example as shown in FIG. 2, at least a part of the sodium oxide layer 62 can be broken by generating a forcible flow with a stir bar.

(16) FIG. 2 is a vertical cross-section view of a modification of the melting tank in the entire constitution diagram of FIG. 1. The same components as FIG. 1 are denoted with the same numeral references and detailed descriptions thereof are omitted. In short, as shown in FIG. 2, a motor 64 is disposed to come into contact with a heater 30 in a lower part of a melting tank 12 and a stir bar 66 is set in the melting tank 12. By energizing a motor 64 during heating under reducing pressure, the stir bar 66 rotates in the melted metallic sodium 60 to generate a spiral flow 68 in the melted metallic sodium 60. The spiral flow 68 breaks at least a part of the sodium oxide layer 62 covering the entire surface of the melted metallic sodium 60, so as to make the melted metallic sodium 60 come into contact with the vaporization atmosphere inside the melting tank 12. Thus, removal of the liquid paraffin by vaporization can be achieved regardless of the presence or absence of the sodium oxide layer 62.

(17) Thus, purified metallic sodium is supplied to the reservoir tank 16 from the melting tank 12 in FIG. 1 through a purified-metallic-sodium discharge pipe 24 by opening a valve 82. The purified metallic sodium is temporarily reserved in the reservoir tank 16. The purified metallic sodium in the reservoir tank 16 is supplied to the circulation line 34 through the feed pipe 36. Under an ordinary state, the first solenoid valve 42 is opened and the second solenoid valve 48 is closed. In this state, the melted metallic sodium supplied to the circulation line 34 is supplied to the cold trap 18 through the first solenoid valve 42. Impurities mainly composed of a metal oxide of sodium and the like are isolated by filtration with the cold trap 18, and the melted metallic sodium is returned to the reservoir tank 16 through the return pipe 38. The purity of the melted metallic sodium in the reservoir tank 16 is further improved by the melted metallic sodium circulating through the circulation line 34 for one or more times.

(18) When it is required to load the cylinder 57 with the purified metallic sodium in the reservoir tank 16, the first solenoid valve 42 is closed and the second solenoid valve 48 is opened. This enables to supply the purified metallic sodium in a melting state from the feed pipe 36 to the quantitative supply device 49 through the filling device supply pipe 46. While the purified metallic sodium is being supplied to the quantitative supply device 49, a liquid level of the purified metallic sodium rises gradually. When the liquid surface of the melted metallic sodium comes into contact with the lower end of the first liquid-level detection sensor S.sub.1 having the shortest vertical length, a detection signal is transmitted to the quantitative supply valve 52 and the second solenoid valve 48, so as to open the quantitative supply valve 52 and close the second solenoid valve 48. Thereby, supply of the melted metallic sodium to the quantitative supply device 49 is stopped, and the melted metallic sodium in the quantitative supply device 49 is supplied to the filling device 20 to be loaded into the cylinder 57 through the sodium dripping nozzle 54, for example, in a droplet form. This operation usually can be performed by self-weight of the melted metallic sodium, but it may be performed by applying a little positive pressure in the quantitative supply device 49 or applying a little negative pressure in the filling device 20.

(19) When the liquid level of the melted metallic sodium in the quantitative supply device 49 lowers to reach to the lower end of the second liquid-level detection sensor S.sub.2, the second liquid-level detection sensor S.sub.2 detects the liquid level, so that the quantitative supply valve 52 is closed to stop supplying the purified metallic sodium. Thereby, the cylinder 57 is loaded with a predetermined amount of the purified metallic sodium, corresponding to the vertical length of d of the quantitative supply device 49. At that time, by properly determining an injection speed, the temperature of the metallic sodium in the sodium injection nozzle 54, and the amount of the purified metallic sodium to be supplied to the cylinder 57 (a diameter of a cylindrical body of the metallic sodium formed in the cylinder) and by performing injection under a directional solidification condition, a directionally solidified molded body of the purified metallic sodium having uniform structure without a gap can be provided.

(20) Then, the cylinder 57 loaded with the predetermined amount of the metallic sodium is detached from the filling device 20 and replaced with a second cylinder ready to be loaded with the metallic sodium next. The melted metallic sodium in the quantitative supply device 49 is supplied to the second cylinder by opening the quantitative supply valve 52 again. When the liquid level of the metallic sodium coming into contact with the lower end of the third liquid-level detection sensor S.sub.3 is detected, the quantitative supply valve 52 is closed again. Thereby, the second cylinder is loaded with the predetermined amount of the melted metallic sodium, corresponding to the vertical length of d of the quantitative supply device 49, in a similar manner to the above previous loading. By repeating such operations by predetermined times, a constant amount of the metallic sodium can be loaded to a predetermined plural number of the cylinders.

(21) In this embodiment, the melting tank is intended for removal of the organic solvent such as liquid paraffin or the like, while the cold trap 18 is mainly intended for removal of metallic sodium oxide or the like. Accordingly, when it is intended to remove only the organic solvent and it is unnecessary to remove the metallic sodium oxide or the like, the cold trap 18 and accompanying equipment are unnecessary.

(22) FIG. 3 is a plan view of a modification of the filling device in the entire constitution diagram. In FIG. 3, the filling device 20a is a large-diameter cylindrical container with a flange 70. The filling device 20a is rotatable in the direction indicated by an arrow in FIG. 3. The filling device 20a has an upper opening 72. A cylinder mounting lid 75 having eight cylinder mounting holes 74 in total at equal intervals is fitted with the upper opening 72. Each of the cylinder mounting holes 74 is engaged with a cylinder having the same configuration as in FIG. 1, so that the cylinder mounting holes 74 are engaged with eight cylinders 57 in total. Positioned above one of the eight cylinders 57 is a sodium injection (dripping) nozzle 54 same as in FIG. 1.

(23) In the state of FIG. 3, a predetermined amount of melted metallic sodium is injected (dripped) into the cylinder 57 from the sodium injection (dripping) nozzle 54. As a result, in the same way as in the case of FIG. 1, the predetermined amount of metallic sodium is loaded into the cylinder 57 under directional solidification condition. Thereby, the quantitative filling of the solidified metallic sodium into the first cylinder 57 is completed.

(24) Then, when the filling device 20a is rotated by one eighth of the circumference in the direction indicated by the arrow, a second cylinder 57 adjacent to the first cylinder 57 is positioned under the nozzle 54. As in the case of the first cylinder 57, the second cylinder 57 is also filled with the melted metallic sodium. By repeating this operation by eight times in total, the all eight cylinders of the filling device 20a can be filled with the metallic sodium.

(25) Subsequently, a cap member 56 is detached from the cylinder 57 of FIG. 1 filled with the metallic sodium, preferably while the inert gas atmosphere is maintained. The metallic sodium molding 69 in the cylinder 57 is maintained in a solidified state. As illustrated in FIG. 4, a tapered extrusion nozzle shaped die 78 is mounted on the cylinder 57 in place of the cap member. Then, a hollow engine valve 76 is put under the tip portion of the nozzle shaped die 78 with the stem-side hollow area 77 opening upward. The nozzle shaped die 78 is designed such that the inner diameter of the stem-side hollow area 77 is larger than the tip portion of the nozzle shaped die 78.

(26) When a piston (not shown) is inserted into the cylinder 57 and pressed downward, the metallic sodium molding 69 having a relatively large diameter enters the nozzle shaped die 78. The metallic sodium molding 69 contracts at the tip portion of the nozzle shaped die 78 to be in the form of a line or a wire thinner than the inner diameter of the stem-side hollow area 77. Then, the metallic sodium is introduced into the stem-side hollow area to be inserted and cut with a cutter (not shown) to be enclosed. Thus, the metallic sodium serves as a metallic sodium coolant 82. During introduction into the stem-side hollow area 77, the metallic sodium is formed to be thinner than the inner diameter of the stem-side hollow area 77. Further, the metallic sodium has a uniform structure. Accordingly, the metallic sodium can smoothly pass through the nozzle shaped die 78 to easily enter the stem-side hollow area 77.

EXAMPLES

(27) Hereinafter, Examples will be described. However, the embodiment of the present invention is not limited to the Examples.

Example 1

(28) A melting tank for purifying metallic sodium was configured by connecting a cylindrical container with a bottom which was 250 mm in diameter and 375 mm in height with one end of a pressure-reducing suction pipe at the upper side surface and with one end of a purified-sodium take off pipe and a valve 82 at the lower side surface. Connected to the other end of the pressure-reducing suction pipe was a solvent trap (paraffin trap) filled with liquid paraffin. Connected to the other end of the purified-sodium take off pipe was a reservoir tank for purified metallic sodium. Further, the melting tank was provided with a heater on the bottom surface and the side surface below the pressure-reducing suction pipe of the melting tank.

(29) Then, unpurified metallic sodium immersed in liquid paraffin was purchased and taken off from a storage container. After that, the unpurified metallic sodium was put into the melting tank from an upper opening thereof, a lid to which an inert-gas supply pipe was connected was fastened on the upper round opening to seal the melting tank. Argon gas was supplied into the melting tank from the inert-gas supply pipe, so that internal air in the melting tank was substituted by argon gas.

(30) By activating a pressure-reducing pump connected to the solvent trap and the heater, the pressure in the melting tank was reduced to about 50 kPa and the temperature of the wall of the melting tank was kept at about 200 C., then this condition was maintained for five minutes.

(31) A cylindrical body made of a stainless steel having an inner diameter of 30 mm and a length of 300 mm was prepared. An open bottom of the cylindrical body was sealed with a disc shaped cap member. The cylindrical body was used as a cylinder. The metallic sodium in the melting tank was supplied to the cylinder by injecting the metallic sodium through a supply pipe for the filling device. At the tip of the supply pipe, a sodium injection nozzle was attached. A heater was disposed around the nozzle so as to heat the outer wall of the nozzle. The supply pipe for the filling device was configured in such a way as to increase and reduce the inner pressure to regulate the injection speed.

(32) The outer wall of the nozzle was heated with the heater to about 200 C. The injection speed of the melted metallic sodium was set about 200 g/min. About 1 minutes later, as the cylinder was filled with the metallic sodium, the injection was stopped. After the cylinder was cooled, the metallic sodium which was solidified was taken out of the cylinder and was cut along the horizontal direction with a knife. The cut section was visually checked. However, the metallic sodium had a uniform structure as a whole, and no gaps were observed at all.

Example 2

(33) The metallic sodium purified in the melting tank as in Example 1 was filled in a cylinder under the same condition as in Example 1 except for the inner diameter of the cylinder being set 40 mm. As the metallic sodium was filled in the cylinder, injection was stopped. After the cylinder was cooled, the metallic sodium which was solidified was taken out from the cylinder, and the metallic sodium was cut along the horizontal direction with a knife. The cut section was visually checked. The metallic sodium was uniform as a whole, and no gaps were observed at all.

Example 3

(34) An experiment was performed under the same condition as in Example 2 except for the inner diameter of the cylinder being set to 50 mm. When the horizontal section of the solidified metallic sodium was visually checked, micro gaps with diameters of about 1 mm were observed in a circular portion of about 10 mm in diameter at the center of the circular cross section.

Comparative Example 1

(35) An experiment was performed under the same condition as in Example 2 except for the inner diameter of the cylinder being set to 60 mm. When the horizontal section of the solidified metallic sodium was visually checked, relatively large gaps with diameters of about several millimeters were observed in a circular portion of about 20 mm in diameter at the center of the circular cross section.

Example 4

(36) Filling a cylinder with metallic sodium was performed under the same condition as in Example 2 except for the injection speed being set to 300 g/min, which is faster than that of Example 2. After that, the horizontal section of the solidified metallic sodium was visually checked, the metallic sodium was uniform as a whole and no gaps were observed at all.

Comparative Example 2

(37) Filling a cylinder with metallic sodium was performed under the same condition as in Example 5 except for the injection speed being set to 350 g/min, which is faster than that of Example 5. After that, the horizontal section of the solidified metallic sodium was visually checked. Shadings are found in the whole section and the uniformity was impaired.

DESCRIPTION OF REFERENCE NUMERALS

(38) 10 System for purifying and filling metallic sodium 12 Melting tank 14 Solvent trap (paraffin trap) 16 Reservoir tank 18 Cold trap 20, 20a Filling device 22 Pressure-reducing suction pipe 24 Purified-metallic-sodium discharge pipe 28 Organic solvent 30 Heater 34 Purified-sodium circulation line 46 Filling device supply pipe 49 Quantitative supply device 54 Sodium dripping nozzle 57 Cylinder 60 Melted metallic sodium 62 Sodium oxide layer 64 Motor 66 Stir bar 69 Metallic sodium molding 76 Engine valve 77 Stem-side hollow area 78 Nozzle shaped die 80 Metallic sodium coolant S.sub.1-S.sub.5 Liquid-level detection sensor