JP2013257968A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp in which an emitter material can be supplied to the cathode tip with high supply efficiency.SOLUTION: The discharge lamp includes a cathode constituted of a columnar cathode body composed of pure tungsten and having a tip forming the cathode tip, and a rod-like emitter supply member inserted into the cathode body. In the cathode body, an emitter supply member insertion recess opening to the rear end of the cathode body and having a tapered bottom face reducing the diameter in the depth direction, and a through hole elongating from the bottom face of the emitter supply member insertion recess toward the cathode tip are formed. The emitter supply member has a tip where an apical surface, having a surface area larger than the projection area from axially forward, is formed.

Description

  The present invention relates to a discharge lamp, and more particularly, to a discharge lamp including a cathode having a structure in which a rod-shaped emitter supply member is inserted into a cathode body.

2. Description of the Related Art Conventionally, in a short arc type discharge lamp having a high load with an input power of 500 W or more, for example, an emitter material for facilitating electron emission from the cathode has been used (for example, Patent Documents 1 to 3). (See Patent Document 3).
As shown in FIG. 6, a cathode body 54 made of a refractory metal such as tungsten and a rod-like emitter supply member 58 containing an emitter supply material are used as a certain type of cathode in which the emitter material is used. The cathode main body 54 includes an emitter supply member insertion recess 55 that opens to the rear end surface 54A of the cathode main body 54, and a bottom surface 55A of the emitter supply member insertion recess 55 (left end in FIG. 6). There is a configuration in which one end portion of the emitter supply member 58 is inserted into the emitter supply member insertion recess 55 of the cathode main body 54.
In the illustrated example, the emitter supply member 58 also functions as a lead rod for supporting the cathode, and an emitter supply material is contained in one end portion inserted into the cathode body 54.

In the cathode having such a configuration, the emitter supply member insertion recess 55 of the cathode body 54 has a tapered bottom surface 55A whose diameter is reduced in the depth direction (left direction in the figure). Since the front end surface 58A of the emitter supply member 58 is flat, the front end surface 58A of the emitter supply member 58 is in contact with the bottom surface 55A of the emitter supply member insertion recess 55 in the emitter supply member insertion recess 55. It is located so that it may oppose through a space | gap. An emitter material supply surface is formed by the tip surface 58A of the emitter supply member 58 exposed in the emitter supply member insertion recess 55.
That is, when the discharge lamp is turned on, the emitter material (alkaline earth metal or rare earth element) extracted from the emitter supply material contained in the emitter supply member 58 is advanced at the cathode by the action of grain boundary diffusion. The light is guided to the surface 58A, and supplied from the front end surface 58A to the cathode front end (tip of the cathode main body) by an action such as surface diffusion and gas phase diffusion.

  Thus, in the discharge lamp, it is necessary to increase the supply efficiency of the emitter material to the cathode tip from the viewpoint of further lighting stabilization.

Japanese Patent Application Laid-Open No. 11-96965 Japanese Utility Model Publication No. 63-9762 JP-A-11-154488

  In the present invention, based on the above situation, the inventors have conducted research focusing on the fact that it is effective to increase the supply surface of the emitter material in order to increase the supply efficiency of the emitter material to the cathode tip. The object of the present invention is to provide a discharge lamp capable of supplying an emitter material with high supply efficiency to the cathode tip.

The discharge lamp of the present invention is a discharge comprising a cathode composed of a columnar cathode body made of pure tungsten and forming a cathode tip by the tip, and a rod-shaped emitter supply member inserted into the cathode body. In the ramp,
Inside the cathode body, there is an emitter supply member insertion recess having a tapered bottom surface that opens at the rear end of the cathode body and has a diameter that decreases in the depth direction, and the emitter supply member insertion recess. A through-hole extending from the bottom surface to the cathode tip is formed,
The emitter supply member has a tip portion on which a tip surface having a surface area larger than a projected area from the front in the axial direction is formed.

  In the discharge lamp of the present invention, the tip of the emitter supply member has a conical shape having a convex conical tip surface, and the tip angle of the tip of the emitter supply member is in the emitter supply member insertion recess. It is preferably larger than the solid angle of the tapered bottom surface.

  In the discharge lamp of the present invention, the cathode main body has a tapered tip portion whose outer diameter decreases toward the cathode tip, and the tip portion of the emitter supply member is located in the tip portion. It is preferable.

  In the discharge lamp of the present invention, by utilizing the fact that the recess for inserting the emitter supply member has a tapered bottom surface, the tip surface of the emitter supply member is exposed inside the cathode body. The tip surface forms a supply surface for supplying the emitter material to the tip of the cathode by the action of surface diffusion and vapor phase diffusion. And, since the amount of emitter material supplied per unit time to the cathode tip due to the action of surface diffusion and gas phase diffusion, in particular, the action of gas phase diffusion increases as the emitter material supply surface increases, By increasing the emitter material supply surface using a tip surface having a surface area larger than the projected area from the front in the axial direction, the amount of emitter material supplied per unit time to the cathode tip can be increased. The emitter material can be supplied to the cathode tip with high supply efficiency.

  In the discharge lamp of the present invention, the tip of the emitter supply member has a conical shape having a convex conical tip surface, and the tip angle of the tip portion is a tapered bottom surface in the recess for inserting the emitter supply member. The emitter supply member has an emitter supply member inserted into the emitter supply member insertion recess so that the entire front end surface of the emitter supply member is opposed to the bottom surface of the emitter supply member insertion recess through a gap. It will be in a state directly facing the space communicating with. In addition, the supply path from the emitter material supply surface, which is the tip surface of the emitter supply member, to the cathode tip due to the action of surface diffusion and vapor phase diffusion hinders the movement of the emitter material. It has a structure without barriers. Therefore, since the supply amount of the emitter material per unit time to the cathode tip can be further increased, the emitter material can be supplied to the cathode tip with extremely high supply efficiency.

It is sectional drawing for description which shows an example of a structure of the discharge lamp of this invention. It is sectional drawing for description which shows the structure of the cathode in the discharge lamp of FIG. It is explanatory drawing which shows the principal part of the cathode of FIG. It is sectional drawing for description which shows the principal part of the other structure of the cathode in the discharge lamp of this invention. It is sectional drawing for description which shows the principal part of the further another structure of the cathode in the discharge lamp of this invention. It is sectional drawing for description which shows the structure of the conventional cathode.

  The present invention will be described in detail below.

FIG. 1 is an explanatory sectional view showing an example of the configuration of the discharge lamp of the present invention, and FIG. 2 is an explanatory sectional view showing the configuration of the cathode in the discharge lamp of FIG.
The discharge lamp 10 is made of, for example, quartz glass, and includes an arc tube 11 having a light emitting portion 12 having an elliptical spherical shape and tubular sealing portions 13 provided at both ends of the light emitting portion 12. In the light emitting portion 12 of the arc tube 11, a cathode 30 and an anode 20 are disposed so as to face each other while being separated from each other. The anode 20 is supported by a lead rod 17 made of tungsten, for example, and the cathode 30 is supported by an emitter supply member 40 described later. Each of the lead rod 17 and the emitter supply member 40 extends along the tube axis direction from the inside of the light emitting portion 12, passes through the sealing portion 13 in an airtight manner, and outwards from the outer end portion of the sealing portion 13. It is arranged to protrude. Further, the lead rod 17 and the emitter supply member 40 are held through the holding cylinder 16 made of, for example, quartz glass, which is fixedly disposed in the sealing portion 13, and is disposed outside the sealing portion 13. It is sealed to the sealing portion 13 by a stepped portion 13a formed at the end. In addition, an appropriate luminescent material or the like is enclosed in the light emitting portion 12 of the arc tube 11.

  The anode 20 is composed of an anode body 21 made of tungsten, for example. The anode body 21 has a flat tip at the tip that forms the anode tip, and a truncated cone-shaped tip 22A whose outer diameter decreases toward the tip, and the tip 22A that is continuous with the tip. The cylindrical rear end portion 22B is formed.

  The cathode 30 includes a cathode main body 31 made of pure tungsten. Inside the cathode main body 31, a tip side portion (a left end side portion in FIG. 2) of the rod-like emitter supply member 40 is connected to the emitter supply member 40. The central axis is inserted so as to coincide with the central axis of the cathode body 31.

The cathode body 31 has a cylindrical shape, and as shown in FIG. 2, the tip P forming the cathode tip is a flat surface, and the outer diameter decreases toward the tip P. Is formed of a truncated cone-shaped tip end portion 32A and a columnar rear end portion 32B formed integrally and continuously with the tip end portion 32A.
In the cathode body 31, the central axis of the cathode 30 is configured by the central axis of the cathode body 31.

  Inside the cathode body 31, there is an emitter supply member insertion recess having a tapered bottom surface 36 that opens to the rear end surface 31A of the cathode body 31 and decreases in diameter in the depth direction (left direction in FIG. 2). And a through hole 38 extending from the bottom surface 36 of the emitter supply member insertion recess 34 toward the cathode tip (tip P) is formed along the central axis of the cathode body 31, that is, the central axis of the cathode 30. Has been.

In the cathode main body 31, the emitter supply member insertion recess 34 has a cylindrical space suitable for the tip side portion of the emitter supply member 40, the internal space of which is defined by the peripheral surface 35, and the cylindrical space. And a frustoconical space defined by a tapered bottom surface 36. These communicating columnar space and frustoconical space are formed along the central axis of the cathode body.
Here, the peripheral surface 35 of the emitter supply member insertion recess 34 has a small-diameter peripheral surface portion 35A having an internal diameter suitable for the small-diameter portion 43A of the emitter supply member 40 and an internal diameter suitable for the large-diameter portion 43B of the emitter supply member 40. A large diameter peripheral surface portion 35B having a tapered shape, and a tapered shape formed between the small diameter peripheral surface portion 35A and the large diameter peripheral surface portion 35B and having a diameter that decreases from the large diameter peripheral surface portion 35B toward the small diameter peripheral surface portion 35A. The taper peripheral surface portion 35C.

In addition, as shown in FIG. 2, the emitter supply member insertion recess 34 preferably has a depth greater than the axial length of the rear end portion 32 </ b> B of the cathode body 31.
By making the depth of the recess 34 for inserting the emitter supply member larger than the axial length of the rear end portion 32B of the cathode main body 31, the tip end portion 41 of the emitter supply member 40 is moved into the tip end portion 32A of the cathode main body 31. Accordingly, the axial length of the through hole 38 communicating with the emitter supply member insertion recess 34 can be reduced, and the distance from the tip surface 41A of the emitter supply member 40 to the cathode tip can be reduced. . That is, the tip 41 of the emitter supply member 40 can be positioned in the vicinity of the tip of the cathode.

  In the cathode body 31, the through hole 38 has an inner diameter smaller than the inner diameter of the emitter supply member insertion recess 34, and communicates with the emitter supply member insertion recess 34 by one end thereof (the right end in FIG. 2). An opening 38B for supplying the emitter material to the cathode tip (tip P) is formed by the other end (left end in FIG. 2). .

The through hole 38 has a length smaller than the axial length of the tip 32A of the cathode body 31 so that the tip 41 of the emitter supply member 40 can be positioned in the vicinity of the tip of the cathode. Preferably there is.
Specifically, the length of the through hole 38 is preferably smaller than the maximum outer diameter (maximum length in the radial direction) of the tip portion 41 of the emitter supply member 40.

The cathode body 31 having such a configuration is prepared, for example, by a cathode body forming member, and the outer diameter suitable for the emitter supply member insertion recess 34 and the through hole 38 to be formed with respect to the cathode body forming member. It is possible to manufacture the emitter supply member by forming the recess 34 for inserting the emitter supply member and the through hole 38.
Here, the tapered shape of the bottom surface 36 and the tapered peripheral surface portion 35C in the emitter supply member insertion recess 34 is such that the tip shape of the drill is a cone in the process of forming the emitter supply member insertion recess 34 using a drill. It is formed using the shape.

As the emitter supply member 40, various materials can be used as long as they can supply an emitter material (alkaline earth metal or rare earth element) that acts as an emitter. It is preferable to have a region where the feed material is supported.
The emitter supply member 40 has a region in which an emitter supply material is supported on a porous body made of tungsten, so that the emitter supply member 40 is a common member with a lead bar for supporting the cathode 30. be able to.
In the example of this figure, the emitter supply member 40 is formed by integrally forming an emitter supply material-containing porous body in which an emitter supply material is supported on a porous body made of tungsten and a lead rod made of tungsten. And having an emitter supply function region mainly functioning as an emitter supply member and a lead function region mainly functioning as a lead bar.

As shown in FIG. 2, the emitter supply member 40 has a conical tip 41 having a diameter that decreases toward the tip (the left end in FIG. 2), and a columnar shape that is continuously formed integrally with the tip 41. It has a cylindrical bar shape constituted by the body portion 43. The body portion 43 is continuous with the tip portion 41, and has a small diameter portion 43A having the same outer diameter as the maximum outer diameter of the tip portion 41 and the small diameter portion 43A, and has a larger diameter than the small diameter portion 43A. It is comprised by the large diameter part 43B which has an outer diameter.
In this emitter supply member 40, the emitter supply member insertion recess 34 is constituted by the tip 41 and the small diameter portion 43A of the body portion 43 and the small diameter portion 43A side portion (the left end side portion in FIG. 2) of the large diameter portion 43B. A distal end portion inserted into the distal end portion is configured, and an emitter supply material is contained in the distal end portion 41 and the small diameter portion 43A in the distal end side portion, thereby forming an emitter supply functional region. Further, a lead functional region is formed by the rear end side portion (the right end portion in FIG. 2) of the large diameter portion 43B at the front end side portion of the emitter supply member 40, and the rear end side portion is the rear end surface of the cathode body 31. It is in a state of protruding outward from the opening formed in 31A.
In the example of this figure, the tip end portion 41 of the emitter supply member 40 is a frustoconical space defined by the bottom surface 36 of the emitter supply member insertion recess 34 in the emitter supply member insertion recess 34. It is supposed to be positioned.

In the emitter supply member 40, a convex conical tip surface 41A is formed by the tip portion 41, and the tip surface 41A has a surface area larger than the projected area from the front in the axial direction (left side in FIG. 2). It is said that.
Here, the surface area of the convex conical tip surface 41 </ b> A indicates the side area of the cone related to the tip 41.

As shown in FIG. 3, the tip 41 of the emitter supply member 40 has a tip angle θ1 larger than the solid angle θ2 of the tapered bottom surface 36 of the emitter supply member insertion recess 34. Is preferred.
By making the tip angle θ1 at the tip portion 41 larger than the solid angle θ2 at the bottom surface 36 of the emitter supply member insertion recess 34, the tip surface of the emitter supply member 40 as shown in FIGS. 41A is opposed to the bottom surface 36 of the emitter supply member insertion recess 34 via a gap (hereinafter also referred to as “a cavity in the recess”), and the entire front end surface 41A of the emitter supply member 40 is placed on the emitter supply member. It can be in the state exposed in the recess 34 for insertion. In addition, the emitter material supply path is formed by communicating the cavity in the recess with the through-hole 38, and the emitter material supply path has a structure without a barrier that hinders the movement of the emitter material. The entire surface of the tip surface 41A of the emitter supply member 40 is in a state of directly facing the tip of the cathode through the emitter material supply path.

  When the tip angle θ1 of the tip 41 of the emitter supply member 40 is smaller than the solid angle θ2 of the bottom surface 36 of the emitter supply member insertion recess 34, the tip angle θ1 is larger than the solid angle θ2. Thus, although the surface area of the tip surface 41A can be increased, a part of the tip portion 41 is very close to the bottom surface 36, or the continuous opening 38A formed on the bottom surface 36 is blocked by the tip portion 41. (A state in which a part of the tip 41 is in contact with the bottom surface 36 and the tip of the tip 41 is positioned in the through hole 38). Therefore, the portion where the tip 41 is extremely close to the bottom surface 36 or the portion where the tip 41 is in contact with the bottom 36 (hereinafter collectively referred to as “barrier portion”) is outside the barrier portion on the tip surface 41A. Since the movement of the emitter material from the region (radially outward region) to the cathode tip is hindered, the supply amount of the emitter material per unit time to the cathode tip may not be sufficiently increased. There is.

  As the emitter supply material, it is preferable to use at least one compound selected from rare earth compounds and barium compounds.

Examples of the rare earth compounds include oxides or borides of rare earth elements made of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), or gadolinium (Gd).
Specific examples of rare earth element oxides (rare earth oxides) include, for example, lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), neodymium oxide (Nd ₂ O ₃ ). , Samarium oxide (Sm ₂ O ₃ ), and gadolinium oxide (Gd ₂ O ₃ ).
Specific examples of rare earth element borides (rare earth borides) include, for example, lanthanum boride (LaB ₆ ), cerium boride (CeB ₆ ), praseodymium boride (PrB ₆ ), neodymium boride (NdB ₆ ). , Samarium boride (SmB ₆ ), gadolinium boride (GdB ₆ ), and the like.

Examples of the barium compound include barium - calcium - aluminate (Ba-Ca-Al-O ), barium tungstate (Ba ₃ WO ₆₎ and barium - strontium - calcium - tungstate (Ba-Sr-Ca-W -O) and the like.

The emitter supply member 40 includes lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), neodymium oxide (Nd ₂ O ₃ ), and samarium oxide (Sm ₂ ) as emitter supply materials. O _3), gadolinium oxide (Gd ₂ O _3), barium - calcium - aluminate (Ba-Ca-Al-O ), barium tungstate (Ba ₃ WO ₆₎ and barium - strontium - calcium - tungstate (Ba- It is preferable to contain at least one compound selected from Sr—Ca—W—O).

The emitter supply member 40 having a region in which an emitter supply material is supported on a porous body made of tungsten can be manufactured as follows, for example, in the process of manufacturing the cathode 30.
First, a ratio of 1/10 to 3/10 by mass ratio (emitter supply material / tungsten) of powdered emitter supply material and powdered tungsten having an average particle diameter of 3 to 5 μm, preferably 2/10 After adding about 2% by mass of stearic acid to this mixture, the surface of particles (powder) constituting the mixture is coated with stearic acid by heating at a temperature of 100 to 200 ° C. A film is formed.
Then, a press body is formed by press-pressing the mixture of particles on which the coating film has been formed, and the obtained press body is temporarily fired at a temperature of 1000 to 1200 ° C. in a hydrogen atmosphere. By performing, a provisionally fired body is obtained.
Next, after the obtained temporary fired body is placed in the emitter supply member insertion recess 34 of the cathode body 31, a lead bar made of tungsten is inserted into the emitter supply member insertion recess 34 and fixed. Then, the temporary fired body disposed in the emitter supply member insertion recess 34 is subjected to main firing at a temperature of 1400 to 1600 ° C. in a vacuum or in a reducing atmosphere, whereby a porous body made of tungsten. Thus, an emitter material-containing member 40 having a structure in which the sintered body is fixed to the tip end portion of the lead bar and integrated is obtained.

As a specific example of the dimensions of the cathode 30 having such a configuration, an example of the dimensions of the cathode used in the high-pressure mercury lamp having an input power of 7 kW is 60 mm in total length (electrode length). The length of the tip 32A in the axial direction is 15 mm, the length of the rear end 32B in the cathode body 31 in the axial direction is 45 mm, the outer diameter of the rear end 32B is 15 mm, and the outer diameter of the flat surface of the tip P. 1.3 mm, the length of the through-hole 38 in the cathode body 31 is 3 mm, the inner diameter of the through-hole 38 is 0.2 mm, and the small-diameter peripheral surface portion 35A of the emitter supply member insertion recess 34 is formed. The inner diameter is 3 mm, and the solid angle θ2 of the bottom surface 36 of the emitter supply member insertion recess 34 is 110 °. Further, the tip angle θ1 of the emitter supply member 40 is 160 °, the outer diameter of the small diameter portion 43A of the trunk portion 43 of the emitter supply member 40 is 2.9 mm, and the insertion length of the emitter supply member 40 in the emitter supply member insertion recess 34 is The length (the axial length of the peripheral surface 35 of the emitter supply member insertion recess 34) is 56 mm.
The dimensions of the cathode used in the short arc xenon lamp with an input power of 2 kW are as follows: the overall length (electrode length) of the cathode body 31 is 15 mm, the axial length of the tip 32A of the cathode body 31 is 8 mm, The axial length of the rear end portion 32B in the main body 31 is 7 mm, the outer diameter of the rear end portion 32B is 6 mm, the outer diameter of the flat surface of the front end P is 0.6 mm, and the through hole 38 in the cathode main body 31 is The length is 4 mm, the inner diameter of the through hole 38 is 0.2 mm, the inner diameter of the small-diameter peripheral surface portion 35A of the emitter supply member insertion recess 34 is 1.0 mm, and the bottom surface 36 of the emitter supply member insertion recess 34 The solid angle θ2 is 110 °. Further, the tip angle θ1 of the emitter supply member 40 is 180 °, the outer diameter of the small diameter portion 43A of the trunk portion 43 of the emitter supply member 40 is 1.0 mm, and the insertion length of the emitter supply member 40 in the emitter supply member insertion recess 34 The length (the axial length of the peripheral surface 35 of the emitter supply member insertion recess 34) is 11 mm.

  In such a discharge lamp 10, when discharge is started, the temperature of the emitter supply member 40 rises at the cathode 30 due to the temperature rise of the cathode body 31, and the emitter supply material contained in the emitter supply member 40. As a result of reduction, metal atoms (alkaline earth metal or rare earth element), which is an emitter material acting as an emitter, are extracted. This emitter material acts as an emitter by radiating and diffusing to the cathode tip of the cathode 30, that is, the tip P of the cathode body 31 and its peripheral part.

Thus, in the discharge lamp 10, the tip surface 41 </ b> A of the emitter supply member 40 is formed inside the cathode body 31 by utilizing the fact that the emitter supply member insertion recess 34 has the tapered bottom surface 36. Since it is in an exposed state, a supply surface for supplying an emitter material to the cathode tip is formed by the action of surface diffusion and gas phase diffusion by this tip surface 41A. That is, when the discharge lamp is turned on, the emitter substance extracted from the emitter supply material contained in the emitter supply member 40 is guided to the tip surface 41A by the action of grain boundary diffusion, and surface diffusion and gas phase diffusion are performed from the tip surface 41A. As a result, the cathode tip (tip P) is supplied.
In addition, since the supply amount of the emitter material per unit time to the cathode tip due to the action of surface diffusion and gas phase diffusion, particularly the action of gas phase diffusion, increases as the emitter material supply surface increases, the tip of the convex cone shape By using the emitter supply member 40 having the tip portion 41 with the surface 41A formed, the emitter material supply surface is increased as compared with the case where a rod-like emitter supply member having a flat tip surface is used, and thus the cathode. Since the supply amount of the emitter material per unit time to the tip can be increased, the emitter material can be supplied with high supply efficiency to the cathode tip.

  Further, in the discharge lamp 10, since the tip angle θ1 of the tip portion 41 of the emitter supply member 40 is larger than the solid angle θ2 of the bottom surface 36 of the emitter supply member insertion recess 34, the emitter supply member insertion recess. 34, the entire front end surface 41 </ b> A of the emitter supply member 40 directly faces the cathode front end via the emitter material supply path including the cavity in the recess and the through hole 38. In addition, the emitter material supply path has a structure without a barrier that hinders the movement of the emitter material due to surface diffusion and vapor phase diffusion from the emitter material supply surface (tip surface 41A). . Accordingly, since the supply amount of the emitter material per unit time to the cathode tip is extremely large, a very high supply efficiency of the emitter material is obtained.

  Furthermore, since the discharge lamp 10 has the tip 41 of the emitter supply member 40 positioned in the vicinity of the tip of the cathode, the emitter material per unit time with respect to the cathode tip by increasing the supply surface of the emitter material. The increase rate of the supply amount of the emitter material becomes large, and thus the effect of improving the supply efficiency of the emitter material to the cathode tip is remarkably obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
For example, the emitter supply member only needs to have a tip having a tip surface with a surface area larger than the projected area from the front in the axial direction, and the shape of the tip surface is as shown in FIGS. It is not limited to a convex cone shape.
Specifically, the shape of the tip surface of the emitter substance-containing member may be a concave cone shape as shown in FIG. 4 or an uneven shape as shown in FIG.
4 and 5 are different from each other in the shape of the tip surfaces 48 and 49 of the emitter supply member, and the tip 47A of the cathode body 46 is conical. It has the same configuration as the cathode 30 constituting the lamp 10.

  Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.

(Experimental example 1)
First, a discharge lamp (hereinafter, also referred to as “experimental discharge lamp (1)”) having a cathode having the following dimensions was manufactured based on FIGS.
In this experimental discharge lamp (1), the tip surface (41A) of the emitter supply member (40) is opposed to the bottom surface (36) of the emitter supply member insertion recess (34) through a gap (gap in the recess). The front end surface (41A) is in a state where the entire surface directly faces the front end of the cathode via the emitter supply member insertion recess (34) and the through hole (38). The area of the tip surface (41A) that directly faces the cathode tip through the emitter supply member insertion recess (34) and the through hole (38), ie, the entire surface of the tip surface (41A) was 1.46 mm ^2. It was.

-Total length of the cathode body (31) (electrode length): 15 mm
-Axial length of the tip (32A) of the cathode body (31): 7 mm
-Axial length of the rear end (32B) of the cathode body (31): 8 mm
-Outer diameter of the rear end (32B) of the cathode body (31): 6 mm
-The outer diameter of the flat surface of the tip (P): 0.6 mm
-Length of the through hole (38) in the cathode body (31): 3 mm
-Inner diameter of through hole (38) in cathode body (31): 0.2 mm
Inner diameter of the small diameter peripheral surface portion (35A) in the emitter supply member insertion recess (34): 1.3 mm
Solid angle θ2 of the bottom surface (36) of the emitter supply member insertion recess (34): 110 °
The tip angle (θ1) of the emitter supply member (40): 130 °
-Outer diameter of the small diameter portion (43A) in the body (43) of the emitter supply member (40): 1.3 mm
-Insertion length of the emitter supply member (40) into the emitter supply member insertion recess (34): 5 mm

Next, in the discharge lamp (1), the emitter supply member (40) constituting the cathode (30) has a tip angle (θ1) of 90 °, and the insertion length of the emitter supply member (40) is set to the tip. A discharge lamp (hereinafter, also referred to as “experimental discharge lamp (2)”) having the same configuration as that of the discharge lamp (1) except that the communication opening (38A) is extended by the portion (41). Was made.
In this experimental discharge lamp (2), the continuous opening (38A) formed in the bottom surface 36 of the emitter supply member insertion recess (34) is blocked by the tip (41) of the emitter supply member (40). Only the portion of the tip surface (41A) positioned in the through hole (38) directly faces the cathode tip through the through hole (38). And the area of the part which directly faces the cathode front-end | tip in a front end surface (41A) through a through-hole (38) was 1.46 mm < ² >.

Each of the produced experimental discharge lamp (1) and the experimental discharge lamp (2) directly faces the space communicating with the cathode tip on the tip surface (41A) of the emitter supply member (40) under the same temperature condition. When the supply amount per unit time of the emitter material (hereinafter also simply referred to as “emitter material supply amount”) due to the effect of vapor phase diffusion from the portion to the cathode tip is confirmed, the emitter material of the experimental discharge lamp (1) is confirmed. The supply amount was larger than the emitter material supply amount of the experimental discharge lamp (2). Further, the relative value of the emitter material supply amount of the experimental discharge lamp (2) with respect to the emitter material supply amount of the experimental discharge lamp (1) (experiment when the emitter material supply amount of the experimental discharge lamp (1) is 1) The emitter substance supply amount of the discharge lamp (2) for use was 0.09.
From the above experimental results, the tip of the emitter supply member has a conical shape having a convex conical tip surface, and the tip angle of the tip is determined from the solid angle of the tapered bottom surface of the emitter supply member insertion recess. In addition, it is possible to increase the area of the portion directly facing the space communicating with the cathode tip on the tip surface of the emitter supply member, and the space communicating with the cathode tip on the tip surface of the emitter supply member. It has been clarified that the emitter material can be supplied with higher supply efficiency to the cathode tip by increasing the area of the portion facing directly.

DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Light emission tube 12 Light emission part 13 Sealing part 13a Step part 16 Holding cylinder 17 Lead rod 20 Anode 21 Anode main body 22A Front end part 22B Rear end part 30 Cathode 31 Cathode main body 31A Rear end face 32A Front end part 32B Rear End 34 Emitter supply member insertion recess 35 Peripheral surface 35A Small diameter peripheral surface portion 35B Large diameter peripheral surface portion 35C Tapered peripheral surface portion 36 Bottom surface 38 Through holes 38A, 38B Opening 40 Emitter supply member 41 Front end portion 41A Front end surface 43 Body Portion 43A small diameter portion 43B large diameter portion 46 cathode body 47A tip portion 48 tip surface 49 tip surface 54 cathode body 54A rear end surface 55 emitter supply member insertion recess 55A bottom surface 56 through hole 58 emitter supply member 58A tip surface

Claims (3)

In a discharge lamp comprising a cathode composed of a columnar cathode body made of pure tungsten and forming a cathode tip by its tip, and a rod-shaped emitter supply member inserted into the cathode body,
Inside the cathode body, there is an emitter supply member insertion recess having a tapered bottom surface that opens at the rear end of the cathode body and has a diameter that decreases in the depth direction, and the emitter supply member insertion recess. A through-hole extending from the bottom surface to the cathode tip is formed,
The emitter supply member has a tip portion on which a tip surface having a surface area larger than a projected area from the front in the axial direction is formed.   The tip of the emitter supply member has a conical shape having a convex conical tip surface, and the tip angle of the tip of the emitter supply member is greater than the solid angle of the tapered bottom surface of the recess for inserting the emitter supply member. The discharge lamp according to claim 1, wherein   2. The cathode main body has a tapered tip portion whose outer diameter decreases toward the tip of the cathode, and the tip portion of the emitter supply member is located in the tip portion. Or the discharge lamp of Claim 2.