JP3257473B2 - Method of manufacturing cathode for discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a cathode for a discharge lamp.

[0002]

2. Description of the Related Art Tungsten containing thorium oxide is used for a cathode of a discharge lamp because a discharge starting voltage is reduced. However, since thorium oxide has a high operating temperature, it causes evaporation of tungsten, causing a problem that the tip of the electrode is worn and deformed, and a problem that the evaporated tungsten adheres to the inner surface of the arc tube.

There is also a cathode in which barium-based emitters are contained in tansutene instead of thorium oxide. Since the barium-based emitter has a low operating temperature, that is, can perform a discharge operation at a low temperature, the above-mentioned problem of evaporation of tungsten is rarely caused.
On the other hand, if the barium-based emitter is exposed too much to the outer surface, that is, the light emitting space, the emitter itself may evaporate. Therefore, in a cathode using a barium-based emitter, the area of the barium-based emitter exposed to the light-emitting space can be reduced, and the barium-based emitter can be accumulated inside the cathode, leading to the arc discharge portion at the tip of the cathode. Required.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a cathode using a barium-based emitter, which reduces the exposed area of the tip of the barium-based emitter and supplies the emitter to the tip during discharge operation. To a novel method of manufacturing a cathode that can be used.

[0005]

A method for manufacturing a cathode for a discharge lamp according to the present invention is characterized in that the cathode is manufactured by the following steps. That is, (1). A step of drilling one end of the base metal. (2). A step of inserting a cylindrical first molded product including the emitter into the hole. (3). A step of inserting a cylindrical second molded product mainly containing tungsten onto the first molded product, and inserting a cylindrical third molded product including an emitter into a hole of the second molded product. (4). A step of sintering after pressurizing in this state, and further performing swage processing in a high-temperature heating state. (5). A step of cutting into a desired shape.

Further, when the inner diameter of the hole provided at one end of the base metal is d0, the outer diameter of the first molded product is D1, and the outer diameter of the second molded product is D2, d0> D.
1 = D2> d0- (0.1). Furthermore, when the inner diameter of the second molded product is d2 and the outer diameter of the third molded product is D3, d2>D3>
d2- (0.1). Further, when the depth of the hole of the base metal is L0 and the inner diameter of the hole is d0, 10 × d0 ≧ L0 ≧ 1 / (2 × d0). Further, the pressure during molding of the first to third molded products before being inserted into the hole of the base metal is 1 to ² Ton / cm ² , and the pressure is applied after inserting these molded products into the hole of the base metal. The pressure when pressing is 3 ~
It is characterized by being 10 Ton / cm ² . further,
The sintering is performed at 1500 to 1700 ° C.

[0007]

FIG. 1 shows a cathode manufactured by the manufacturing method of the present invention. The base metal 11 is made of a refractory metal such as tungsten or molybdenum, and has a conical tip (on the side facing the anode). Inside the conical portion is an emitter-containing portion 1 containing a barium-based emitter.
2, and a small-diameter emitter supply path 13 is subsequently led from the emitter-containing portion 12 to the light emitting space. A metal foil weld 14 is formed at the rear end of the base metal 11.

FIG. 2 shows a discharge lamp using the above cathode. In the arc tube 21, a cathode 22 and an anode 23 are arranged to face each other. The cathode 22 and the anode 23 are connected to the metal foil at the rear ends and are hermetically sealed. The arc tube 21 is filled with mercury as a light emitting substance and argon as a lighting gas.
The lamp is, for example, a high-pressure mercury lamp rated at 25 V and 250 W, or a high-pressure xenon lamp or a high-pressure mercury lamp rated at 25 V and 1000 W.

Next, a method for manufacturing a cathode according to the present invention will be described. First, a base metal is manufactured. Tungsten, which is a high melting point metal, for example, has an outer diameter D0 of φ5 mm and a length of 30
Cut to mm. Next, a hole having an inner diameter d0 and a length L0 is provided at one end of the cut base metal. For example, d
0 is 1.5 mm and L0 is 6 mm. Further, processing for welding a metal foil such as molybdenum is performed on the other end of the base metal. FIG. 3 shows the base metal in this state. Then, it is stored until the next step.

[0010] First, the first molded product and the third molded product are manufactured.
You. Barium emitter powder and tungsten powder
Weigh only the amount determined and mix. Barium emitter and
Is specifically Ba_1.8Sr_0.2Ca_1.0WO6_1.0Etc
is there. The mixed powder is press-molded to form
One molded article and third molded article are made. Press pressure at this time
Is, for example, 1 Ton to 2 Ton / cm^TwoIt is. this
The first molded product at this time has an outer diameter D1 and a length L1, and the third molded product
The product has an outer diameter D3 and a length L3. For example, D1
Is 1.4, L1 is 3.5, D3 is 0.4, L3 is 2.5
(All units are mm). No. made in this way
FIGS. 4A and 4B show the first molded product and the third molded product. So
And store until the next step.

Next, a second molded product is manufactured. First, predetermined, large, medium, and small amounts of tungsten powder particles are weighed and uniformly mixed. As an example of the size, large particles are 10 μ7 g, medium particles are 4 μ2 g, and small particles are 1 μl.
g. The reason for mixing large, medium, and small in this way is that the high temperature portion at the tip does not deform during long-term operation. The mixed tungsten powder is pressed to form a second molded product. The pressing pressure at this time is 1 Ton to 2 Ton /
cm ² . The reason is that if the pressure is lower than 1 Ton, the molded product cannot be handled. On the other hand, if it is higher than 2 Ton, it will not be tightened even if it is pressed into a hole in the base metal and will not weld well in the hole. The second molded product at this time has an outer diameter D2, an inner diameter d2, and a length L2. As an example, D2 is 1.4, d2 is 0.5, and L2 is 2.5 (all units are mm). FIG. 5 shows the second molded product thus produced. Then, it is stored until the next step.

Next, the first to third molded products are inserted into the holes of the base metal. As shown in FIG. 6, first to third holes are formed in the holes of the base metal.
A molded article is inserted. The first molded article (indicated by 1 in the figure) is inserted into the hole of the base metal 11 and then provided in the second molded article (indicated by 2 in the figure). A third molded product (indicated by 3 in the figure) is inserted into the hole, and this combination is inserted into the hole of the base metal. The insertion method may be such that after inserting the third molded article into the hole of the second molded article, this combination may be inserted into the base metal. However, the present invention is not limited to this method. After the insertion, the third molded product may be inserted.

Next, as shown in FIG. 7, each molded product inserted into the hole of the base metal 11 is pressed using a punch 70. Press pressure at this time is 3Ton-10T
on / cm ² . The reason for this is that, in the case of 3 Ton or less, the density does not increase sufficiently and the tip of the electrode wears during lighting. If the pressure is 10 Ton or more, the punch does not have mechanical strength and the base metal 11 may crack.

Next, a sintering process is performed in this state. The sintering temperature is preferably from 1500C to 1700C. This is because if the temperature is lower than 1500 ° C., sintering is insufficient and deformation occurs during lighting, and if the temperature is higher than 1700 ° C., the emitter evaporates. Next, the temperature is slightly lowered, and pressure is applied by, for example, a punch as shown in FIG. As a result, each sintered product has a higher density.

Next, cutting is performed to obtain a desired electrode shape. Here, the desired electrode shape means that the tip of the base metal has a conical shape. FIG. 8 shows the tip portion of the cathode thus completed. The emitter containing portion 12 is made of a first molded product, and the supply path 13 is made of a third molded product. The tungsten 13A around the supply path 13 is made of a second molded product. It is preferable that the leading end of the supply path 13 has a shape in which only the leading end surface is exposed. That is,
The point is to provide a flat portion at the tip corresponding to the supply path (outer diameter of the third molded product). The electrode thus completed is stored in a dry place until the lamp is manufactured.

Next, the effect of the cathode according to the manufacturing method of the present invention will be described. (1) A discharge lamp having a cathode according to the manufacturing method of the present invention, that is, a discharge lamp having a supply path containing a barium-based emitter and an emitter-containing part at the rear end (hereinafter, referred to as
(2) a cathode having a conventional structure, that is, a cathode including a barium-based emitter but having a large number of areas exposed to a light-emitting space on the outer surface of the tip,
(Hereinafter referred to as "conventional lamp 1"), and (3) a discharge lamp (hereinafter referred to as a "conventional lamp 1") having a cathode made of thorium oxide, not including a barium-based emitter.
This is referred to as “conventional lamp 2”. The lamps are the same except for the structure of the cathode, all of which have a rated current of 10 A and a rated power of 250 W
Lights up.

First, comparing the operating temperatures of the cathodes, the lamp of the present invention and the conventional lamp 1 have a temperature of about 1500 ° C., whereas the conventional lamp 2 has a temperature of about 2200 ° C. This is because lamps using barium-based emitters have a lower operating temperature than thorium oxide, so they do not cause problems such as evaporation of tungsten, wear and deformation of the electrode tip, and adhesion of the evaporated tungsten to the inner surface of the arc tube. Is shown.

Next, comparing the light output relatively, when the light output of the conventional lamp 2 is 100, the lamp of the present invention is 95 and the light output of the conventional lamp 1 is 85. This is because the conventional lamp 2 has a small cathode tip diameter so that the arc luminescent spot also becomes small. On the other hand, the lamp of the present invention has a small arc emission point at the tip of the cathode and therefore has a small arc luminescent spot, and thus has a high light output. On the other hand, in the conventional lamp 1, the arc emission portion at the tip of the cathode is large, so that the arc luminescent spot is widened, and the light output is reduced accordingly.

Next, when the degree of wear of the cathode is compared, the lamp of the present invention is 0.05 mm after 2000 hours of operation, whereas the conventional lamp 1 is 0.3 mm in the same time and the conventional lamp 2 is 1000 hours. The lighting was 0.6 mm.
The reason why the lamp of the present invention wears much less than the conventional lamp 2 is because the operating temperature of the cathode is low as described above.
Also, the lamp of the present invention is considered to have less wear than the conventional lamp 1 because the cathode tip is surrounded by tungsten having good thermal conductivity, so that heat can be satisfactorily released to the rear.

Next, comparing the life of the discharge lamp (light output is 50% of the initial value), the lamp of the present invention is 8000 hours, the conventional lamp 1 is 4000 hours, and the conventional lamp 2 is 10 hours.
00 hours.

Next, another embodiment of the present invention will be described. As shown in FIG. 9, the first molded product has a larger diameter than the inner diameter of the hole of the base metal.
This first molded product has a cylindrical shape with a much smaller outer diameter, and is inserted into the hole of the cylindrical fourth molded product 4 containing tungsten as a main component. Inserted inside. Accordingly, the outer diameter D4 of the fourth molded product is substantially equal to the inner diameter d0 of the hole of the base metal 11, and specifically, “d0>D4> d0−
(0.1 mm) ". In addition, the inner diameter d4 of the fourth molded product has a value substantially equal to the outer diameter D1 of the first molded product, and specifically, “d4>D1> d4- (0.
1 mm) ". With such a structure, the volume of the emitter-containing portion is reduced. However, if the emitter-containing portion is small enough, a stepped hole is provided in the base metal according to the size of the first molded product. It has the advantage that it is no longer necessary.

[Brief description of the drawings]

FIG. 1 shows a cathode manufactured by the manufacturing method of the present invention.

FIG. 2 shows a discharge lamp using a cathode manufactured by the manufacturing method of the present invention.

FIG. 3 shows a base metal.

FIG. 4 shows a first molded product and a third molded product.

FIG. 5 shows a second molded article.

FIG. 6 shows a state where first to third molded products are inserted into holes of a base metal.

FIG. 7 shows a state of pressing.

FIG. 8 shows the structure of the tip of the cathode.

FIG. 9 shows another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st molded article 2 2nd molded article 3 3rd molded article 4 4th molded article 11 Base metal 12 Emitter containing part 13 Supply path 21 Arc tube 22 Cathode 23 Anode

────────────────────────────────────────────────── ─── Continuation of the front page Examiner Naohide Murata (56) References JP-A-7-65715 (JP, A) JP-A-9-129179 (JP, A) JP-A-2-226648 (JP, A) ( 58) Fields surveyed (Int. Cl. ⁷ , DB name) H01J 9/04

Claims (9)

(57) [Claims] 1. It is manufactured by the following steps.
Manufacturing method of cathode for discharge lamp. (1). A step of drilling one end of the base metal. (2). A step of inserting a cylindrical first molded product containing a barium-based emitter into the hole. (3). A step of inserting a cylindrical second molded article mainly containing tungsten on the first molded article, and inserting a cylindrical third molded article containing a barium-based emitter into a hole of the second molded article; . (4). A step of sintering after pressurizing in this state, and further performing swage processing in a high-temperature heating state. (5). A step of cutting into a desired shape. 2. When the inner diameter of a hole provided at one end of the base metal is d0, the outer diameter of the first molded article is D1, and the outer diameter of the second molded article is D2, d0> D1. = D2> d0- (0.1 mm). The method of manufacturing a cathode for a discharge lamp according to claim 1, wherein 3. When d2 is the inner diameter of the second molded product and D3 is the outer diameter of the third molded product, d2>D3> d2- (0.1 mm). 2. The method for producing a cathode for a discharge lamp according to item 1. 4. The method according to claim 1, wherein when the depth of the hole in the base metal is L0 and the inner diameter of the hole is d0, 10 × d0 ≧ L0 ≧ 1 / (2 × d0). The method for producing a cathode for a discharge lamp described above. 5. A pressure during molding before inserting the first to third molded products into the holes of the base metal is 1 to 2 Ton /
^{2. The} discharge lamp cathode according to claim 1, wherein the pressure at the time of pressurizing after inserting these molded products into the holes of the base metal is 3 to 10 Ton / cm < ² >. Method. 6. The sintering in the above (4) is performed at 1500 to 17
The method for producing a cathode for a discharge lamp according to claim 1, wherein the method is performed at 00 ° C. 7. In the step (2), the cylindrical first molded product containing the barium-based emitter is inserted into a hole of a cylindrical fourth molded product containing tungsten as a main component.
2. The method for producing a cathode for a discharge lamp according to claim 1, wherein said combination is inserted into a hole of a base metal. 8. When d4 is the outside diameter of the fourth molded product and d0 is the inside diameter of the hole of the base metal 11, d0>D4> d0- (0.1 mm). 4. The method for producing a cathode for a discharge lamp described in 1. above. 9. The method according to claim 7, wherein d4>D1> d4- (0.1 mm), where d4 is the inner diameter of the fourth molded product and D1 is the outer diameter of the first molded product. The method for producing a cathode for a discharge lamp described above.