JPH1140106A - Electric discharge tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric discharge tube, in which a fused metal is utilized for jointing an electrode and a metal foil so as to increase strength at this jointed part. SOLUTION: When a metal foil 7 and an electrode 10 are jointed via a fused metal 17, the fused metal 17 is sandwiched between an abutment part 13 provided at on end of a main body 7a of the metal foil 7 and a jointing part 10a of the electrode 10, and an electric welding jig is utilized to fuse and connect the abutment part 13 and the jointing part 10a of the electrode 10. At this time, even if the fused metal 17 is not interposed between the abutment part 13 and a backing part 12, the fused metal 17 is fused at the backing part 12 through a penetrating part 16 formed at the abutment part. As a result, the fused metal 17 fused form the penetrating part 16 is employed as a medium to surely connect the abutment part 13 and the backing part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube such as a metal halide lamp and a xenon lamp.

[0002]

2. Description of the Related Art Conventionally, there is Japanese Utility Model Publication No. Sho 62-53563 as a technique in such a field. In the discharge tube described in this publication, a sealing body (bulb) made of quartz glass is used.
Has sealing portions on both sides thereof, and a molybdenum foil (metal foil) is sealed in each sealing portion. Electrodes are bonded to the ends of the molybdenum foils, respectively, and the electrodes are opposed to each other so as to form both poles in a spherical light-emitting portion filled with xenon gas. The ends of the molybdenum foil are folded back and overlapped, and the overlapped portion is used as a spot welding portion of the electrode, thereby avoiding breakage of the molybdenum foil which occurs at the time of spot welding.

[0003]

However, since the conventional discharge tube is configured as described above, there are the following problems.

[0004] That is, if spot welding is used when the molybdenum foil and the electrode are directly joined, it is unavoidable that the molybdenum foil is more likely to break. Furthermore, since the molybdenum foil and the electrode can be joined only at a point by spot welding, even if the molybdenum foil is folded back, the mechanical and electrical strength at the joint cannot be increased, and when the discharge tube is assembled. There is a possibility that the welding portion may come off during handling, and the electrode may fall off the molybdenum foil. Also, increasing the number of spots by spot welding increases the risk of breaking the molybdenum foil. JP-A-8-255593 discloses an example in which an electrode and a molybdenum foil are joined via a metal foil.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In particular, the present invention is intended to increase the strength at the joint while utilizing a fusion metal for joining the electrode and the metal foil. An object is to provide a discharge tube.

[0006]

According to a first aspect of the present invention, a thin metal foil is provided in each of the sealing portions provided at both ends of the light emitting portion, and one side of the metal foil is provided on one side of the metal foil. Is, the discharge electrode protruding to the light emitting part is joined via a fusion metal,
On the other side of the metal foil, an external conductor exposed from the end of the sealing portion is joined via a fusion metal, and the electrode and the external conductor are electrically connected via the main body of the metal foil. In the discharge tube, a contact portion having a surface joined to the joining portion of the electrode and a backing portion facing the back surface of the contact portion are provided at one end of the main body of the metal foil. At the time of joining, a through portion for bringing the fusion metal and the backing portion into contact with each other is provided.

In this discharge tube, when the metal foil and the electrode are joined through the fusion metal, the fusion is performed between the contact portion provided at one end of the main body of the metal foil and the joint portion of the electrode. The metal is sandwiched, and the contact portion and the joint portion of the electrode are fusion-bonded using an electric welding jig. At this time, the fused metal that has melted into the penetrating portion formed in the contact portion comes into contact with the backing portion without interposing the fusion metal between the contact portion and the backing portion. As a result, the fused metal that has melted into the through portion serves as a medium, so that the contact portion and the backing portion are reliably connected. That is, even if the fusion metal is not separately interposed between the backing portion and the backing portion, the backing portion and the backing portion are extremely hardly separated from each other. Then, by integrating the contact portion and the backing portion via the fusion metal, expansion and contraction of the metal foil due to thermal expansion of the electrode and the like can be reliably absorbed. In addition, when the contact portion and the backing portion are integrated via the fusion metal, the metal foil is fatigued by thermal shock due to repeated lighting, and even if one of the contact portion and the backing portion is broken, the other is conductive. Since the state is maintained, a trouble such as disconnection is properly avoided. In addition, the direct current type discharge tube generates a large amount of heat at the anode side electrode, and is likely to cause thermal shock.

In this case, the other end of the main body of the metal foil is
A contact portion having a surface to be joined to the joint portion of the external conductor, and a backing portion facing the back surface of the contact portion are provided, and the contact portion has a through portion that contacts the fused metal and the backing portion at the time of joining. Is preferably provided. When such a configuration is adopted, the metal foil and the external conductor can be reliably fusion-connected to each other via the fusion metal, and the abutting portion and the backing portion are fused to the through portion. It can be easily connected with the arrival metal.

Preferably, the backing portion extends from an end of the main body of the metal foil, and the abutment portion is disposed so as to face the surface of the backing portion and extends from the tip of the backing portion.
In the case of adopting such a configuration, the contact portion and the backing portion can be formed in a continuous state from the main body of the metal foil, and the metal work can be performed simply by bending the end of one metal foil. An abutment and a backing can be created on the foil. And this structure is particularly significant in automating the manufacture of the discharge tube.

[0010] The backing portion and the backing portion are connected by an auxiliary backing portion composed of a plurality of folded pieces, and each turned back piece of the auxiliary backing portion has an auxiliary penetration portion aligned with the penetrating portion of the backing portion. Is preferably provided. When such a configuration is employed, the backing portion can be superposed many times, which contributes to the formation of a firm backing portion that is strong against mechanical and electric shocks.

Preferably, the contact portion extends from an end of the main body of the metal foil, and the backing portion is disposed so as to face the back surface of the contact portion and extends from the tip of the contact portion. When such a configuration is employed, the length of the backing portion can be adjusted. For example, if the backing portion is lengthened, the range of mechanical and electrical reinforcement of the metal foil is extended in the length direction, so that a large and heavy electrode can be accommodated.

It is preferable that an auxiliary contact portion sandwiching the joint portion between the electrodes is provided in cooperation with the contact portion. By using the auxiliary contact part, when sealing the metal foil inside the glass sealing part, the flow of the glass softened by the heating of the burner etc. is made uniform by the auxiliary contact part, and the displacement of the electrode during sealing is ensured. Can be blocked.

It is preferable that an auxiliary contact portion sandwiching the joint portion of the external conductor be further provided in cooperation with the contact portion. When the auxiliary contact portion is adopted, when the metal foil is sealed in the glass sealing portion, the flow of the glass softened by heating of the burner or the like is made uniform by the auxiliary contact portion, and the displacement of the external conductor during sealing is reduced. It can be reliably prevented.

Further, it is preferable that the contact portion and the auxiliary contact portion are formed as sandwiching portions by bending. By employing such a sandwiching portion, an electrode or an external conductor may be simply inserted between the contact portion and the auxiliary contact portion when the discharge tube is assembled. This configuration is particularly significant in automating the manufacture of a discharge tube.

Preferably, the penetrating portion is a hole or a notch. When such a configuration is adopted, when the through portion is a hole, the through portion can be formed by drilling or punching, and when the through portion is notched, the through portion is formed by cutting. can do.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a discharge tube according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a front view showing a xenon lamp as a first embodiment of a discharge tube according to the present invention. DC compatible xenon lamp 1 shown in FIG.
Is provided with a bulb 2 made of quartz glass. The bulb 2 has a hollow light emitting portion 3 having a substantially elliptical sphere at the center thereof, and a xenon gas is sealed in the light emitting portion 3. Further, the bulb 2 has a pair of sealing portions 4 and 5 extending from both sides of the light emitting portion 3, and in each of the sealing portions 4 and 5, a thin metal foil made of molybdenum and having a thickness of about 30 μm (for example, Molybdenum foils 6 and 7 are sealed, and one end of the metal foil 6 is electrically connected to a discharge electrode (anode) 8 having a tip end protruding into the light emitting section 3. A lead wire 9 as an external conductor exposed from the end of the sealing portion 4 is electrically connected to the other end. Similarly, a discharge electrode (cathode) 10 is electrically connected to one end of the metal foil 7, and a lead wire 11 is electrically connected to the other end.

Here, at both end portions of the metal foil 7 shown in FIG. 2, welding portions A and B created by bending the metal foil 7 are provided. Of the lead wire 11 is connected to the welded portion B by resistance electric welding.

In forming the metal foil 7 having the welds A and B, as shown in FIG. 3, an elongated flat metal foil 7 having a thickness of about 30 μm is prepared. Welds A and B are formed by folding the end twice. That is, the end of the metal foil 7 is bent once in a V shape along the inner bending line L1, and the end of the metal foil 7 is bent in a V shape along the outer bending line L2. By folding back, a weld A is created. Similarly, two bending lines L3 and L4 are also provided on the other end side of the metal foil 7, and the welded portion B is bent along the respective bending lines L3 and L4 in a V-shape.
To produce

As a result of such bending, the weld A
As shown in FIG. 4, a backing portion 12 extending continuously and integrally with the end of the main body portion 7 a of the metal foil 7, and a backing portion 12 Abutment portion 13 extending continuously from the tip of
3 and an auxiliary contact portion 14 extending continuously from the distal end of the contact portion 13. In other words, the backing portion 12 is formed between the end of the main body portion 7a and the bending line L1, the contact portion 13 is formed between the bending line L1 and the bending line L2, and the bending line L2 is formed. And metal foil 7
An auxiliary contact portion 14 is formed between the support portion 14 and the front end of the auxiliary contact portion.

As described above, the backing portion 12, the contact portion 13, and the auxiliary contact portion 14 can be continuously formed on the metal foil 7 by a simple operation of bending only one end of the single metal foil 7. . V between the contact portion 13 and the auxiliary contact portion 14
A letter-shaped sandwiching portion 15 is formed.
, The joint 10a of the electrode 10 can be inserted. This structure is particularly significant in automating the manufacture of the discharge tube 1. That is, the contact portion 1 is formed by a simple operation of merely inserting the joint portion 10a of the electrode 10 into the sandwiching portion 15.
The position of the three members, the auxiliary contact portion 14, and the joint portion 10a can be reliably aligned. When the metal foil 7 is sealed in the sealing portion 5 made of glass, the flow of the glass softened by the heating of the burner or the like is made uniform by the auxiliary contact portion 14, and the displacement of the electrode 10 at the time of sealing is ensured. Can be blocked.

Further, in a process before applying such a bending process to the metal foil 7, a circular through hole 16 as a through portion is formed between the bending lines L1 and L2 by punching. I have. This through hole 16 is arranged in the contact portion 13,
It is formed at a position where the lining portion 12 is viewed. Through hole 16
Is a fused metal 17 (for example, Mt. made of Pt foil) melted when the contact portion 13 and the joint portion 10a of the electrode 10 are subjected to resistance electric welding.
o foil sandwiched) has such a size that it melts out from the contact portion 13 toward the backing portion 12.

Similarly, as shown in FIGS. 2 and 3, the welded portion B also includes a backing portion 22, a contact portion 23, and an auxiliary contact portion 24. That is, the backing portion 22 is formed between the end of the main body 7a and the bending line L3, the contact portion 23 is formed between the bending line L3 and the bending line L4, and the bending line L4 and the metal An auxiliary contact portion 24 is formed between the tip of the foil 7. Then, a V-shaped sandwiching portion 25 is formed by the contact portion 23 and the auxiliary contact portion 24, and the joining portion 11 a of the lead wire 11 is inserted into the sandwiching portion 25.

Further, in a process before applying such a bending process to the metal foil 7, a circular through hole 26 as a through portion is formed between the bending lines L3 and L4 by punching. I have. This through hole 26 is arranged in the contact portion 23,
It is formed at a position where the lining portion 22 is viewed. Through hole 26
The fusion metal 27 (for example, a Mo foil sandwiched with a Pt foil) melted when the contact portion 23 and the joint portion 11a of the lead wire 11 are resistance-electrically welded to the backing portion 22 from the contact portion 23 side. It has a size enough to melt toward.

Next, the procedure for assembling the xenon lamp 1 will be briefly described.

As shown in FIGS. 2 and 4, at the welded portion A, a fusion metal 17 is attached from the front surface 10aA to the back surface 10aB of the joint 10a of the electrode 10, and in this state,
The joining portion 10a is inserted into the V-shaped sandwiching portion 15.
At this time, it is necessary to make the through hole 16 and the fusion metal 17 face each other. Thereafter, while crushing the welded portion A from above and below, the contact portion 13 and the auxiliary contact portion 14 of the sandwiching portion 15 are pressed against the fusion metal 17, and the contact portion 13 and the backing portion 1 are pressed.
Hit 2 When resistance electric welding is performed on the welded portion A in this state, Pt (platinum) of the fusion metal 17 is instantaneously melted, and the abutment portion 13 and the auxiliary abutment portion 14 are joined via the fusion metal 17 to the joining portion 10a. (See FIG. 5). At this time, the melted Pt of the fusion metal 17 melts into the through-hole 16 and the fusion metal 17 comes into contact with the backing portion 12 to join the contact portion 13 and the backing portion 12 by pressing (see FIG. 6). When the molten metal 17 flows, it is not always necessary to press the contact portion 13 and the backing portion 12 against each other.

Although not shown, the joining portion 11a of the lead wire 11 and the sandwiching portion 25 are welded via the fusion metal 27 in the same procedure at the welding portion B. At this time, the melted Pt of the fusion metal 27 melts out into the through-hole 26 and the fusion metal 27 comes into contact with the backing portion 22 to join the contact portion 23 and the backing portion 22 by pressing (see FIG. 6). Note that when the molten metal 27 flows, it is not always necessary to press the contact portion 23 and the backing portion 22 against each other.

According to such a welding procedure, the cathode electrode 10 and the lead wire 11 are welded to both ends of the metal foil 7, and the cathode unit 30 is formed. As shown in FIG. 1, welding portions A and B having the same configuration as described above are provided at both ends of the metal foil 6, and the anode 8 is provided with a resistance electrode 8 at the welding portion A. The lead wire 9 is resistance-welded to the welded portion B to form the anode unit 31.

Next, as shown in FIG. 7, the cathode side unit 3 is inserted through the opening 5a of the sealing portion 5 formed in a cylindrical shape.
The tip of the cathode-side electrode 10 is made to face the inside of the light emitting unit 3 while inserting the zero electrode 10. Similarly, the anode-side unit 31
The tip of the anode-side electrode 8 is made to face the inside of the light emitting section 3 while inserting the electrode 8 through an opening (not shown) of the sealing section 4 formed in a cylindrical shape. In this state, the cathode side electrode 1
0 and the tip of the anode 8 are aligned.
Thereafter, the burner is heated from the ends of the sealing portions 5 and 4 while bleeding air from the exhaust pipe 32, and the glass is softened and crushed from the ends of the sealing portions 5 and 4 using a predetermined jig. Then, when the sealing operation of the sealing portions 5 and 4 reaches the light emitting portion 3, the exhaust from the exhaust pipe 32 is stopped, and xenon gas or the like is introduced into the light emitting portion 3 using the exhaust pipe 32. Then, the exhaust pipe 32 is sealed.

[Second Embodiment] As shown in FIGS. 8 and 9, a welded portion A1 of a metal foil 7A has a backing portion extending continuously and integrally with an end of a main body portion 7a of the metal foil 7A. 34
And a plurality of (two in this case) contact portions 35 which are arranged to face the surface of the backing portion 34 and are joined to the joining portion 10a of the electrode 10 and between the backing portion 34 and the contact portion 35.
And an auxiliary backing portion 36 connected by the folded pieces 36a and 36b of the above-mentioned, and an auxiliary backing portion 37 disposed opposite to the surface of the backing portion 35 and continuously extending from the tip of the backing portion 35. In other words, the backing portion 34 is formed between the end of the main body 7a and the bending line L5, and the bending line L5
A first folded piece 36a is formed between the fold line L6 and the fold line L6, a second fold piece 36b is formed between the fold line L6 and the fold line L7, and the fold line L7 and the fold line are formed. L8
Is formed between the bending line L8 and the tip of the metal foil 7A, and a V-shaped sandwiching portion 39 is formed between the contact portion 35 and the auxiliary contact portion 37. Is formed.

As described above, the welded portion A1 is formed by the simple operation of bending only one end of one metal foil 7A.
It can be produced in a continuous state from the main body 7a of A. Further, in a pre-process in which such a bending process is performed on the metal foil 7A, a circular through hole 38 as a through portion is formed in the contact portion 35 by punching. The through hole 38 is formed at a position where the second folded piece 36b of the auxiliary backing portion 36 is viewed. And the auxiliary backing part 36
Each of the folded pieces 36a, 36b is provided with auxiliary through holes 40a, 40b aligned with the through holes 38 of the abutment 35.

Therefore, while the welded portion A1 is crushed from above and below, the contact portion 35 of the sandwiching portion 39 and the auxiliary contact portion 37 are pressed against the fusion metal 17, and the auxiliary backing portion 36 is pressed against the contact portion 35, and the auxiliary backing portion 36 is pressed. The backing portion 34 is abutted against the portion 36, and the through hole 38 and the auxiliary through holes 40a, 40b are aligned in a line. When resistance welding is performed on the welded portion A1 in this state, Pt (platinum) of the fusion metal 17 is instantaneously melted, and the joint 10a and the sandwiching portion 39 are welded. At this time, the molten Pt passes through the through hole 38 and the auxiliary through hole 40.
a, 40b to reach the surface of the backing portion 34,
The sandwiching portion 39, the auxiliary backing portion 36, and the backing portion 34 are joined via the fusion metal 17 (see FIG. 9). In addition,
The other end side of the metal foil 7A to which the lead wire 11 is joined has the same configuration as the above-described welded portion A1, and the description and drawings are omitted.

[Third Embodiment] As shown in FIG.
The welded portion A2 of the metal foil 7B is provided with a backing portion 41 extending integrally and integrally with the end of the main body portion 7a of the metal foil 7B, and disposed opposite to the surface of the backing portion 41 to form the electrode 10A.
Abutment portion 42 to be joined to joining portion 10a of
An auxiliary contact portion 43 that is arranged to face the surface of the contact portion and is joined to the joining portion 10a;
And a V-shaped buffer section 44 for connecting between the ends. The buffer section 44 includes a first buffer piece 44a extending continuously from the abutment section 42 along the backing section 41, and a second buffer piece 44b extending continuously from the auxiliary abutment section 43. . In addition, the contact portion 42 includes
A circular through hole 45 as a through portion is formed by punching, and a first buffer piece 44 extending from the contact portion 42 is formed.
Also, a circular through-hole 46 as a penetrating portion is formed in a of FIG. Further, the through holes 45 and 46 are formed at positions where the backing portion 41 is viewed.

In such a metal foil 7B, when resistance welding is performed on the welding portion A2 and the joining portion 10a, the molten Pt of the fusion metal 17 passes through the through holes 45 and 46, and the backing portion 4 is formed.
1 and the contact portion 42 and the buffer portion 44 are joined to the backing portion 41 via the fusion metal 17. By providing such a buffer section 44, the expansion and contraction of the metal foil 7B caused when the sealing section 5 thermally expands can be reliably absorbed by the buffer section 44. In order to ensure the welding between the first buffer piece 44a and the second buffer piece 44b, the fusion metal 17 is arranged between the first buffer piece 44a and the second buffer piece 44b. Alternatively, the fusion pieces 17 may be plated on the buffer pieces 44a and 44b.

[Fourth Embodiment] As shown in FIG.
The welded portion A3 of the metal foil 7C is provided with a backing portion 47 that extends continuously integrally with the end of the main body portion 7a of the metal foil 7C, and is disposed opposite to the surface of the backing portion 47 so as to face the electrode 10A.
Abutment portion 48 to be joined to joining portion 10a of
And a circular through hole 49 as a penetrating portion formed in the hole. Such a welded portion A3 is not provided with an auxiliary contact portion and has a simple shape. The lead wire 11
Has the same configuration as the above-described welded portion A3 on the other end side of the metal foil 7C to be joined, and the description and drawings are omitted.

[Fifth Embodiment] As shown in FIG.
The welded portion A4 of the metal foil 7D extends continuously from the end of the main body portion 7a of the metal foil 7D, and is arranged opposite to the back surface of the abutment portion 50 to be joined to the joint portion 10a of the electrode 10. The backing portion 51 extends continuously from the distal end portion of the contact portion 50, and an auxiliary contact portion 52 that is separately disposed to face the contact portion 50 and is joined to the joining portion 10a. Furthermore, the metal foil 7D has a circular through hole 53 as a through portion formed in the contact portion 50. Such a backing portion 51 can be made as long as necessary toward the main body portion 7a.
The area where the metal foil 7D overlaps with the backing portion 51 is enlarged, and the mechanical and electrical reinforcement range of the metal foil 7D is enlarged, so that the electrode 10 can be large and heavy.

The present invention is not limited to the above-described various embodiments. For example, as shown in FIG. 13, the above-described penetrating portions 16, 26, 38, 40a, 40b, 4
5, 46, 49, and 53 are not limited to circular through-holes, but may have cutout shapes, and the number thereof is not limited to one. Further, the welded portion of the metal foil may be plated with a fusion metal in advance, or the joint portion between the electrode and the lead wire may be plated with the fusion metal in advance. Further, in the welded portions A and B, a pair of abutting portions are arranged so as to sandwich the joint portion, a backing portion is provided at a position facing the back surface of each abutting portion, and a penetrating portion is formed in each abutting portion. You may.

[0038]

The discharge tube according to the present invention is constructed as described above, and has the following effects. That is,
At one end of the main body of the metal foil, a contact portion having a surface to be joined to the joint portion of the electrode and a backing portion facing the back surface of the contact portion are provided. By providing a penetrating part that makes the metal and the backing part contact,
The strength at the joint can be increased while utilizing the fusion metal for joining the electrode and the metal foil.

[Brief description of the drawings]

FIG. 1 is a front view showing one embodiment of a discharge tube according to the present invention.

FIG. 2 is a perspective view showing a first modified example of a metal foil.

FIG. 3 is a perspective view showing a state before a welded portion of a metal foil is bent.

FIG. 4 is an enlarged sectional view of a main part showing a state before resistance electric welding of a metal foil and an electrode.

FIG. 5 is an enlarged sectional view of a main part showing a state after resistance metal welding of a metal foil and an electrode.

FIG. 6 is an enlarged sectional view of a main part showing a state in which a fused metal after melting has entered a through hole.

FIG. 7 is a cross-sectional view showing a state where an anode-side unit and a cathode-side unit are inserted into a sealing portion in a discharge tube assembling step.

FIG. 8 is a sectional view showing a second modification of the metal foil.

9 is an enlarged sectional view of a main part showing a state after the metal foil and the electrode of FIG. 8 have been subjected to resistance electric welding.

FIG. 10 is a sectional view showing a third modification of the metal foil.

FIG. 11 is a sectional view showing a fourth modification of the metal foil.

FIG. 12 is a sectional view showing a fifth modification of the metal foil.

FIG. 13 is a perspective view showing a notched through portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge tube, 3 ... Light emitting part, 4, 5 ... Sealing part, 6, 7, 7
A, 7B, 7C, 7D: metal foil, 7a: main body, 8, 1
0 ... electrode, 9,11 ... lead wire (external conductor), 10a ...
Joints of electrodes, 11a ... Joints of external conductors, 12, 2
2, 34, 41, 47, 51 ... lining part, 13, 23,
35, 42, 48, 50 ... abutment part, 14, 24, 37,
43, 52: auxiliary contact portion, 15, 25: sandwiching portion, 1
6, 26, 38, 45, 46, 49, 53 ... through-holes (penetrations), 17 ... fusion metal, 36a, 36b ... folded pieces, 36 ... auxiliary backing parts, 40a, 40b ... auxiliary penetration parts.

Claims (9)

[Claims] 1. A thin metal foil is provided in each sealing portion provided at both ends of a light emitting portion, and one side of the metal foil is provided with:
A discharge electrode protruding from the light emitting portion is joined via a fusion metal, and an external conductor exposed from an end of the sealing portion is joined to the other side of the metal foil via the fusion metal. A discharge tube in which the electrode and the external conductor are electrically connected to each other through a main body of the metal foil; and at one end of the main body of the metal foil, A contact portion having a surface to be joined and a backing portion facing the back surface of the contact portion are provided, and the contact portion is provided with a penetrating portion for bringing the fused metal into contact with the backing portion at the time of joining. Discharge tube characterized by being performed. 2. The other end of the main body of the metal foil,
A contact portion having a surface joined to the joint portion of the external conductor, and a backing portion facing the back surface of the contact portion are provided, and the joining portion has, at the time of joining, the fused metal and the backing portion. The discharge tube according to claim 1, further comprising a through portion for contacting the discharge tube. 3. The backing portion extends from an end of the main body portion of the metal foil, and the abutment portion is disposed to face a surface of the backing portion and extends from a tip end of the backing portion. The discharge tube according to claim 1 or 2, wherein 4. The backing portion and the backing portion are connected by an auxiliary backing portion composed of a plurality of folded pieces, and each of the turned back pieces of the auxiliary backing portion has the through portion of the backing portion. The discharge tube according to claim 3, further comprising an auxiliary through-hole that is aligned with the discharge tube. 5. The contact portion extends from an end of the main body portion of the metal foil, and the backing portion is disposed to face a back surface of the contact portion and extends from a tip end of the contact portion. The discharge tube according to claim 1 or 2, wherein 6. The discharge tube according to claim 1, further comprising an auxiliary contact portion for sandwiching the joint portion of the electrode in cooperation with the contact portion. 7. The discharge tube according to claim 2, further comprising an auxiliary contact portion for sandwiching the joint portion of the outer conductor in cooperation with the contact portion. 8. The discharge tube according to claim 6, wherein the contact portion and the auxiliary contact portion are formed as a sandwiched portion by bending. 9. The discharge tube according to claim 1, wherein the through portion is a hole or a notch.