JP3333850B2 - Sealing method by pressure welding of metal pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sealing a liquid or a gas having a high volatility (a volatile fluid), for example, as a cooling medium or an insulating medium. The present invention relates to a method for sealing a metal pipe introduced into a closed container by press contact.

[0002]

2. Description of the Related Art A method of using an oxygen-free copper pipe for an electron tube as a metal pipe and performing sealing by cold pressure welding in a high vacuum atmosphere is known as, for example, a method of sealing a valve for a vacuum circuit breaker. In this case, in order to obtain a high vacuum, impurities such as an oxide film on the inner wall surface of the metal pipe have been completely removed in advance, and pressure welding is performed by a diffusion bonding method in a state where the pressure contact surface is activated, so there is no vacuum leakage. Sealing becomes possible. However, in electric equipment such as a boil-cooling rectifier using a volatile fluid such as a compressor motor or a fluorocarbon of an air conditioner as a cooling medium and an insulating medium, a closed container contains the volatile fluid and the contents of the electric equipment. It is necessary to perform sealing work when the joint surface of the metal pipe is contaminated with impurities such as volatile liquid and vapor, and activation of the joint surface including removal of oxide film on the joint surface There is a need for a sealing method capable of simultaneously performing processing and sealing work while applying an internal pressure due to the vapor pressure of a volatile fluid to a closed container without leaking the volatile fluid.

FIG. 4 is a plan view schematically showing a conventional sealing method by welding metal pipes. The metal pipe 1 air-tightly connected to an airtight container (not shown) has completed the operation of introducing a volatile fluid. At this point, a certain length of the end portion is mechanically crushed, and the crushed portion 1B is narrowed by a pair of outflow prevention dies 2 to prevent leakage of the volatile fluid.
The oxide film at the cut end of the crushed portion is removed using a wire brush or the like, and the heating element 3 is attached to the end of the crushed portion and heated to, for example, the melting temperature of silver solder. In this state, the silver solder is poured into the cut end of the metal pipe. The sealed container is sealed by forming the silver brazing weld 4 with the above.

FIG. 5 is a side view schematically illustrating a conventional sealing method for a metal pipe, in which a sealing portion of the metal pipe 1 is rounded at its tip to a pressure receiving table 5A and a constriction jig 5 composed of a chip 5B. A tightening load is applied to the contact surfaces between the inner walls of the metal pipes which have been crushed and constricted, and ultrasonic vibration is applied to the chip 5B using the ultrasonic vibrator 6 while maintaining this state. At this time, when an ultrasonic vibration is applied to the pressurized contact surface of the constricted portion, an oxide film or the like is destroyed and the contact surface is activated, and the metal on the contact surface is melted by frictional heat to form the sealing portion 7. Is done.

[0005]

In the conventional sealing method by welding, there are many series operations including crushing of a metal pipe, treatment for preventing volatile fluid from flowing out, polishing, heating, and silver brazing. Requires different processing machines and jigs, which increases the processing man-hour and processing time,
In addition, there is a problem that the obtained sealing performance tends to differ depending on the skill level of the operator. In addition, in the conventional sealing method using ultrasonic vibration together, the heat loss due to conduction is large and a large amount of ultrasonic energy is required to melt the sealing portion. As the pressure is limited and the size of the ultrasonic oscillator increases,
There is a problem that the range that can be activated by the ultrasonic vibration under the influence of the volatile fluid vapor is narrow, and the sealing performance obtained tends to vary due to the narrow melting region.

SUMMARY OF THE INVENTION It is an object of the present invention to form a highly reliable and small-to-individual sealing portion efficiently by a simplified process using a simple and small processing jig without being affected by a volatile fluid. Is to do.

[0007]

According to the present invention, there is provided a method for sealing a metal pipe connected to an airtight container and introducing a volatile fluid into the airtight container. A sealing portion of the metal pipe is sandwiched by a pair of press-contact dies having a predetermined semi-cylindrical curved surface and arranged along a direction orthogonal to the axial direction of the metal pipe, and the sealing portion is locally formed. When the temperature of the sealing portion reaches a predetermined temperature, a clamping load is applied between the pair of pressing dies to crush the metal pipe, and the sealing portion is almost completely crushed at the center. .

The radius of the semi-cylindrical curved surface of the pressing die is
It is assumed to be in the range of 0.75 to 1.5 times the outer diameter of the metal pipe. Local heating of the sealing portion is performed from one side close to the sealing portion. Local heating of the sealing portion is performed from both sides of the sealing portion.

[0009]

In the present invention, the sealing portion of the metal pipe is sandwiched between a pair of press-contact dies having a semi-cylindrical curved surface having a predetermined diameter at the tip, and the sealing portion is locally heated to form the sealing portion. At the time when the temperature reaches a predetermined temperature, a metal pipe is crushed by applying a tightening load between a pair of dies for press-fitting, and a sealing method by press-fitting is configured to crush the sealing portion substantially at the center thereof, The radius of the semi-cylindrical curved surface of the crimping die is, for example, 0.
By increasing the size of the metal pipe from 75 times to 1.5 times and crushing the sealing portion almost at the center thereof, the tips of the two metal pipes that have been crushed take advantage of the large ductility of metal pipes such as copper and aluminum. The two pressing dies are extended in a wedge shape along the semi-cylindrical curved surface of the two pressing dies, and the oxide film and the like formed on the pressing surface are destroyed in the process of being extended in the wedge shape, so that a wide range is obtained. Press-contact surface is activated, and a pressure-bonded portion is formed by diffusion bonding having a pressure-bonded length several times the wall pressure of the metal pipe. Sealing can be performed at the same time, and the sealing part with a large pressure contact length and excellent stability of sealing performance can be stabilized without being affected by the skill of the operator by a simplified pressure welding process. Can be obtained. In addition, by heating the temperature of the sealing portion to a predetermined temperature, first, the vapor pressure of the volatile fluid at the pressure contact surface is increased, and the pressure contact portion can be dried to eliminate the influence of the volatile fluid, and the metal at the pressure contact portion can be eliminated. The function of increasing the ductility and the degree of activation of the pipe and facilitating the bonding of the pressure contact surfaces based on the diffusion of metal atoms in the pressure contact surfaces is obtained.

On the other hand, if the local heating of the sealing portion is performed from one side close to the sealing portion, the temperature of the pressure contact portion can be reduced to about 2 to 3 minutes when the metal pipe is made of copper. It is possible to heat up to about 300 ° C, after that, increase the oil pressure applied to the pressure welding dies, crush the metal pipe, and crush the sealing part almost at the center, an automated short-time operation The sealing process can be performed, so that the function of simplifying the sealing process can be obtained. In addition, the pressing jig is connected to a pressing die connected to a hydraulic pump with a hose,
Since only the heating element connected to the power supply by a cable is used, the working jig can be lightened so that an operator can handle it manually, and the sealing operation can be performed efficiently.

If the local heating of the sealing portion is performed from both sides of the sealing portion, the heating time can be reduced only by adding a pair of heating elements for holding the metal pipe. At the same time, since there is no temperature gradient in the press-contact portion and the press-contact conditions are symmetric to each other, a wedge-shaped seal portion having substantially equal sealing performance is formed in the two crushed metal pipes. Therefore, when both are connected to a product, wedge-shaped sealing portions having substantially the same sealing performance can be formed at the same time, and one of the sealing portions is used as a sealing performance test sample. By performing a leak test, a water pressure strength test, a microscopic inspection, and the like, a function that enables highly accurate quality control can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a principle explanatory view of a sealing method of a metal pipe by pressure welding according to an embodiment of the present invention. In the figure, a highly ductile copper, aluminum, or the like is used for a metal pipe 1 having an outer diameter D and a wall thickness t, one end of which is air-tightly connected to a closed container of an electric device (not shown), and the other end of which is not shown. The introduction of the volatile fluid into the closed container is performed by being connected to the supply source of the volatile fluid. When the operation of introducing the volatile fluid is completed, the sealing portion 13 of the metal pipe 1 is sandwiched between a pair of press-contact dies 15A and 15B each having a cylindrical curved surface 12R having a radius R at the tip, and the sealing portion 13 is closed. When the temperature is locally increased and the temperature of the sealing portion reaches a predetermined temperature, the metal pipe is crushed by applying oil pressure between the pair of pressing dies 15A and 15B. In this process, the metal pipe 1 becomes a cylindrical curved surface 12.
At the tip position of R (contact line O), the inner wall surface comes into line contact, the volatile fluid in the pipe is cut off by the tangent line O, and the volatile fluid flows through the inner wall surface of the locally heated metal pipe. The vapor pressure increases to a dry state, so that the influence of the volatile fluid at the pressure contact portion can be eliminated. Therefore,
When the oil pressure between the pair of press-contact dies 15A and 15B is further increased, the highly ductile metal pipe 1 is rolled to the left and right around the contact line O, and accordingly, the oxidized metal pipe 1 is less ductile than the base material. The film is broken, and the metal structure of the activated base material is exposed on the press-contact surface. Therefore, when the metal pipe 1 is completely crushed on the tangent line O, a wedge-shaped sealing portion 13 pressed into contact with each end of the cut metal pipes 11A and 11B is formed.

As described above, the sealing method according to the present invention is characterized in that the pressing portion is extended in a wedge shape to simultaneously perform the activation process of the pressing surface due to the destruction of the oxide film and the sealing process by the pressing. Therefore, in order to form a sealed portion with excellent long-term reliability that can maintain the airtightness of the press-contact surface and the internal pressure stably for a long period of time, the length of the wedge-like extension of the press-contact portion, in other words, the press-contact length X must be somewhat large. is necessary. The pressing length X of the wedge-shaped pressing portion is determined by the radius R of the cylindrical curved surface 12R of the pair of pressing dies 15A and 15B and the wall pressure t of the metal pipe 1, and R = (X ² −
The relational expression of t ² ) / 2t holds. Also, copper pipe,
Since the wall pressure t of a metal pipe such as an aluminum pipe is determined in proportion to the outer diameter D of the metal pipe by Japanese Industrial Standards or the like, the radius R of the cylindrical curved surface corresponds to the outer diameter D of the metal pipe. When the press-contact length X is 4 to 5 times the wall pressure t, the radius R of the cylindrical curved surface is about 0.75 to 1.5 times the outer diameter D of the metal pipe. Must be a range.

As an example, the outer diameter D of the metal pipe 1 is 12 m.
m, and a phosphoric acid deoxidized copper pipe having a wall pressure t of 1.2 mm, and a radius R of the cylindrical curved surface 12R of the pressing dies 15A and 15B.
Immediately after completing the operation of introducing the volatile fluid (fluorocarbon) into the closed container, sealing was performed by pressure welding while maintaining the temperature of the pressure contact portion uniformly at 300 ° C. Among the phosphorus-deoxidized copper pipes 11A and 11B which have been crushed and cut by the contact line O by the sealing process, a pipe which is not connected to the closed vessel, for example, 11B is used as a test piece, and a leak test, a hydraulic test, and a sealing section are performed. Was examined under a microscope.
As a result, in the leak test using negative pressure, low leak rate data of 1 × 10 ⁻¹¹ atm-cc / sec or less was obtained for a plurality of test samples. Further, the withstand voltage test of 10 kgf / cm ² in pressure test, high breaking strength of 35 kgf / cm ² was obtained. Further, it was confirmed by microscopic inspection at a magnification of 14 times that a wedge-shaped press-contact portion having a press-contact length X of about 6 mm was formed, and as a result of observing the metal structure of the press-contact portion by microscopic inspection at a magnification of 80 times, It was impossible to discriminate the pressure contact surface, and it was demonstrated that the metal structure was almost completely integrated in the pressure contact surface. Therefore, according to this method, even in a state in which the volatile fluid vapor is filled in the pipe, the influence is eliminated, and the activation treatment and the pressure contact processing of the pressure contact surface are simultaneously performed in one step of crushing the sealing portion with the pressure contact die. As a result, it has been found that the sealing portion 13 having a large pressure contact length and excellent sealing performance stability and pressure resistance strength can be easily obtained by the simplified pressure contact process without depending on the skill of the operator. .

FIG. 2 is a cross-sectional view schematically showing a method of heating the sealing portion in the embodiment of the present invention.
An example is shown in which a heating element 17 is attached to the side 11A connected to the closed container of FIG. 1 and local heating of the sealing portion is performed from one side close to the sealing portion. By doing so, it is possible to heat the press-contact portion to about 300 ° C. in about 2 to 3 minutes by using the electrothermal heating element 17 when the metal pipe is made of copper, for example. The function to simplify the sealing process can be achieved by increasing the oil pressure applied to the pressure welding dies, crushing the metal pipe, and crushing the sealing part at almost the center with an automated and short operation. At the same time, the pressing jig consists of only the pressing die 15 connected to the hydraulic pump by a hose and the heating element 17 connected to a power supply by a cable, so that the processing jig can be handled manually by an operator. The advantage is that the sealing work can be performed efficiently by reducing the weight.

FIG. 3 is a side view schematically showing a different method of heating the sealing portion in the embodiment of the present invention. The heating element 17 is located symmetrically with respect to the center position (contact line O) of the press contact portion.
A and 17B are attached, and the local heating of the sealing portion is performed from both sides of the sealing portion. The heating time is increased only by adding a pair of heating elements for holding the metal pipe. In addition, since the pressure contact portion has no temperature gradient and the pressure contact conditions are symmetric with each other, a wedge-shaped sealing portion 13 having substantially equal sealing performance is formed in the two crushed metal pipes 11A and 11B. Is done. Therefore, when both are connected to the product, wedge-shaped sealing portions with almost equal sealing performance can be formed at the same time, and one sealing portion should be used as a test sample for sealing performance. As a result, an advantage of high quality control can be obtained.

[0017]

As described above, according to the present invention, a metal pipe is sealed with a pair of pressure welding dies having a semi-cylindrical curved surface at the tip, for example, about 0.75 to 1.5 times the outer diameter of the metal pipe. The sealing portion is sandwiched, and the sealing portion is locally heated from one side or both sides. When the temperature of the sealing portion reaches a predetermined temperature, a metal pipe is crushed by applying a tightening load between a pair of pressure welding dies. In addition, a sealing method by pressure contact is configured so that the sealing portion is almost completely crushed at the center. as a result,
By extending the press-contact portion in a wedge shape, it is possible to simultaneously perform the activation process of the press-contact surface due to the destruction of the oxide film and the sealing process by press-contact. As compared with the conventional sealing method which is easy to receive, it is possible to provide a sealing method by pressure welding which has less variation in the number of processing steps and quality and has high processing efficiency.

Further, by crushing the press-contact portion, a sealing portion having a long press-contact length proportional to the radius of the semi-cylindrical curved surface can be formed, and the influence of the volatile fluid can be eliminated by local heating. It is possible to form a highly reliable sealing part with excellent pressure resistance without using expensive deoxidized copper pipes for electron tubes in an internal atmosphere in which a volatile fluid is interposed, and using ultrasonic waves. Since there is no limitation on the pipe diameter that can be applied unlike the conventional sealing method, there is obtained an advantage that a large-sized electric device using a volatile fluid as a cooling medium or an insulating medium can be provided economically and advantageously.

Further, the press-welding processing jig comprises a press-welding die 1.
5 and only the heating element, and the advantage is obtained that the working jig is lightened to the extent that an operator can handle it manually and the sealing operation can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a principle explanatory diagram of a sealing method by pressure welding of a metal pipe according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a method of heating a sealing portion according to an embodiment of the present invention.

FIG. 3 is a side view schematically showing a different method of heating a sealing portion in the embodiment of the present invention.

FIG. 4 is a plan view schematically showing a conventional sealing method by welding metal pipes.

FIG. 5 is a schematic side view showing a different conventional sealing method for metal pipes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal pipe (high ductility) 1B Crushed part 2 Outflow prevention die 3 Heating element 4 Silver brazing weld 5 Stenosis jig 6 Ultrasonic vibrator 7 Sealing part (fusion) 11A Metal pipe 11B Flattened Metal pipe 12R Semi-cylindrical curved surface 13 Wedge-shaped sealing portion 15 Die for press contact 15A Die for press contact (lower) 15B Die for press contact (upper) 17 Heating element (17A, 17B) O Center of press contact ( Contact line) R Radius of semi-cylindrical curved surface D Outer diameter of metal pipe t Thickness of metal pipe X Pressure welding length

Claims (4)

(57) [Claims] 1. A method of sealing a metal pipe connected to an airtight container and introducing a volatile fluid into the airtight container, wherein the metal pipe has a predetermined semi-cylindrical curved surface at its tip and is orthogonal to the axial direction of the metal pipe. When the sealing portion of the metal pipe is sandwiched between a pair of pressing dies arranged opposite to each other along the direction, the sealing portion is locally heated, and the temperature of the sealing portion reaches a predetermined temperature. A method for sealing metal pipes by press-fitting, wherein a clamping load is applied between a pair of pressing dies to crush the metal pipe, and the sealing portion is crushed substantially at the center thereof. 2. The semi-cylindrical curved surface of the pressing die has a radius of:
2. The sealing method according to claim 1, wherein the outer diameter of the metal pipe is 0.75 times to 1.5 times the outer diameter of the metal pipe. 3. The method according to claim 1, wherein the local heating of the sealing portion is performed from one side close to the sealing portion. 4. The sealing method according to claim 1, wherein the local heating of the sealing portion is performed from both sides of the sealing portion.