JP2005166513A - Xenon lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a xenon lamp capable of reducing an arc lift caused by disturbance of gas convection, capable of extending the time required until a flicker phenomenon occurs, that is, capable of extending a flicker life. <P>SOLUTION: The xenon lamp has an anode and a cathode, which face each other and are placed and separated by a predetermined gap, and a sealed xenon gas inside a light emitting tube, where electrode axes of the anode and the cathode are set on a same line; the electrode axes are the center axes in the length direction, and a surface of the anode, which faces the cathode, is inclined to a surface orthogonal to the electrode axes by 5° to 10°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a short arc type discharge lamp used for a projection or projector light source, and more particularly to a DC lighting type xenon short arc type discharge lamp.

  A so-called short arc type discharge lamp in which an anode and a cathode are arranged to face each other is used as a light source lamp mounted on a projection device for projection or a projector device. In such a discharge lamp, a so-called flicker phenomenon in which the arc shake increases as the lamp lighting time elapses. When the flicker phenomenon occurs, the image projected on the screen flickers and feels uncomfortable visually. Therefore, in the above application, the lamp is replaced when the flicker is confirmed. This is called the lamp flicker life.

It is known that the flicker phenomenon occurs due to electrode wear and gas convection disturbance in the arc tube. Conventionally, various techniques have been proposed for improving electrodes and improving gas convection for the purpose of suppressing the flicker phenomenon in lamps used in the above applications.
The present inventors pay attention to the gas convection inside the arc tube, and the gas is moved backward along the anode body portion of the short arc lamp that is generally used in the above field and in which the tube axis of the lamp is lit in a horizontal posture. Patent Document 1 has been filed for a xenon lamp that can flow smoothly and maintain a stable arc state for a long time, thereby improving the flicker life.
Japanese Patent Application No. 2003-93865

  The present inventors have further studied the gas convection of the short arc lamp in which the tube axis of the lamp is lit in a horizontal posture, and obtained new knowledge.

FIG. 6 is an enlarged view of a main part of the state of gas convection in the arc tube that is lit in a horizontal posture in a xenon lamp according to the prior art.
In FIG. 6A, the broken line between the anode 81 and the cathode 82 shows the outline of the arc shape. In addition, the arrows in the figure indicate the state of gas convection inside the arc tube 83.

  When the lamp is turned on, the sealed gas is accelerated in the direction from the cathode 82 to the anode 81 due to the pressure difference between the front surface of the cathode spot and the vicinity of the anode, and travels approximately parallel to the tube axis L between the electrodes. The gas accelerated by the arc flows toward the rear of the anode 81 along the substantially cylindrical anode 81. At the same time, the gas heated by the arc moves upward of the arc tube 83, and the arc is slightly lifted with respect to the tube axis L.

When the arc is lifted with respect to the tube axis L, a part of the gas below the arc collides with the flat surface 2 a at the tip of the anode 81 and the flow to the rear of the anode 81 is prevented. The gas whose flow is prevented flows downward in the figure along the plane 2a.
In FIG. 6B, when the lamp lighting time elapses, the distance between the two electrodes becomes longer due to wear of the tip of the cathode 82, and the amount of arc lifting (the amount of upward movement) increases. Therefore, the amount of gas that hits the flat surface 2 a at the tip of the anode 81 also increases, and the gas flowing backward along the anode 81 decreases accordingly.

The gas that has collided with the plane 2a once flows downward along the plane 2a in the figure, but since it is heated by the arc, it immediately starts to rise immediately below the arc to further lift the arc. As described above, when the arc is lifted, turbulence in the convection is generated in the vicinity of the arc, and arc shake occurs.
As the arc is lifted, the amount of gas hitting the plane 2a increases, so that the turbulence in the gas convection near the arc becomes more severe and the arc runout also increases.

Further, as the lamp lighting time increases, the amount of emitter material that reduces arc swing decreases, so that the arc shake increases.
As described above, the flicker phenomenon occurs at an early stage due to the interaction between the rising of the arc, the turbulence of the gas convection in the vicinity of the arc, and the wear of the cathode and the depletion of the emitter material.

  Therefore, the present invention provides a xenon lamp that can reduce the lift of the arc due to disturbance of gas convection and can increase the time until the flicker phenomenon occurs, that is, can extend the flicker life. There is to do.

  In order to solve the above-mentioned problems, a xenon lamp according to the present invention is a xenon lamp in which an anode and a cathode are arranged to face each other at a predetermined interval inside a luminous tube, and the xenon gas is sealed. Each of the ends has a flat surface or a curved surface, and has a diameter-expanded portion formed so as to gradually increase in diameter behind the anode tip, and a diameter that is gradually reduced behind the diameter-increased portion. A diameter-reduced portion formed longer than the length of the diameter-enlarged portion in the electrode axial direction, and the vicinity of the boundary between the diameter-enlarged portion and the diameter-reduced portion is smoothly formed. The electrode axis which is the central axis in the longitudinal direction is provided on the same straight line, and the surface of the anode facing the cathode is inclined within a range of 5 ° to 10 ° with respect to a plane perpendicular to the electrode axis. To do.

  According to the xenon lamp of the present invention, since the surface of the anode facing the cathode is inclined within a range of 5 ° to 10 ° with respect to the plane orthogonal to the electrode axis, the gas accelerated by the arc is the anode. When hitting the tip, the gas under the arc flows toward the back of the anode along the inclined anode tip surface. Therefore, turbulence of the convection in the vicinity of the arc is less likely to occur, the lifting of the arc is mitigated, and the stable state of the arc can be maintained for a long time. As a result, the time until the flicker phenomenon occurs can be lengthened and the flicker life can be extended.

FIG. 1 is a partial cutaway view of the entire short arc type xenon lamp according to the present invention cut in the tube axis direction, and FIG. 2 is an explanatory side view showing the anode in FIG. Further, the lamp in the figure is a xenon lamp with a rated current consumption of 160 A, and the lamp tube axis is lit in a horizontal posture.
In the xenon lamp 1, xenon gas is enclosed in an arc tube 10 made of quartz glass at 1 × 10 ⁶ Pa (converted at 25 ° C.), and an anode 2 and a cathode 3 are disposed in an arc tube portion 11 having a substantially elliptical spherical shape. Are opposed to each other with a distance of about 8 mm between the electrodes.

The electrode rods 4 and 4 ′ connected to each of the anode 2 and the cathode 3 are both made of tungsten rods, and are inserted into the side tube portions 12 and 12 ′ that are connected to both sides of the arc tube portion 11. They are welded at the welded glass portions 12a and 12a ′ and the stepped glass portions provided in order to approximate the thermal expansion coefficients of the electrode rods 4 and 4 ′. In the figure, reference numerals 13 and 13 'denote electrode bar holding members which are fixed inside the side tube portions 12 and 12' by inserting the electrode bars 4 and 4 'into holes provided in the center.
As shown in the drawing, the longitudinal center axes (hereinafter referred to as electrode axes) of the cathode 3 and the anode 2 are on the same straight line and coincide with the tube axis L.

  In FIG. 2, the anode 2 has a substantially columnar shape centered on the electrode axis as a whole, and is made of tungsten as a material. In this embodiment, only the main body portion (columnar portion) of the electrode on the anode side is referred to as “anode”, and the electrode rod is excluded.

  A flat surface 2 a is formed at the tip of the anode 2, and the flat surface 2 a is inclined at a predetermined inclination angle θ with respect to a plane P orthogonal to the electrode axis (tube axis L). As described above, the lamp is lit in a horizontal posture. At this time, the lamp is attached to the apparatus so that the slope of the plane 2a faces downward.

Further, the anode 2 is formed with an enlarged diameter portion 21 having a shape in which the outer diameter gradually increases toward the rear, that is, gradually taper toward the tip, following the flat surface 2a at the tip. The electrode rod 4 described above is fixed to the rear end 2b of the anode 2 by being fitted into a hole drilled in the center, and is integrated.
The surface of the enlarged-diameter portion 21 is formed of a rotating curved surface that is rounded outwardly as obtained by rotating an arc as an electrode axis, as shown in FIG. Part 2A. Then, following the maximum outer diameter portion 2A, a reduced diameter portion 22 having a shape in which the outer diameter is gradually reduced toward the rear, that is, is gradually tapered toward the rear end 2b.

  The surface of the reduced diameter portion 22 is also formed of a rotating curved surface that is rounded outward as obtained by rotating an arc as an electrode axis.

FIG. 3 is a diagram for explaining a state in which the xenon lamp is lit while holding the tube axis in a horizontal posture. The same components as those described in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.
In the figure, a broken line between the tip of the cathode 3 and the tip of the anode 2 indicates an arc. When the lamp is turned on, the gas in the vicinity of the cathode 3 is accelerated in the direction of the arc, that is, from the cathode 3 to the anode 2 as in the case of the background art described above, and travels approximately parallel to the tube axis L between the electrodes. Further, since the gas is heated by the arc, the gas moves toward the upper side of the arc tube 83 and the arc is slightly lifted with respect to the tube axis L.

  As the arc is lifted, the gas under the arc collides with the flat surface 2 a at the tip of the anode 81. However, as described above, the plane 2a is inclined downward at an inclination angle θ with respect to the plane orthogonal to the electrode axis (tube axis L), so that the gas can be prevented from flowing behind the anode. Then, it reaches the enlarged diameter portion 21 along the slope of the flat surface 2a, and then flows along the curved surface of the side surface of the anode 2 through the maximum outer diameter portion 2A and the reduced diameter portion 22 to the rear end 2b. Therefore, in the background art, the turbulence of gas convection near the arc, that is, the gas flow in the downward direction in the figure, which is caused by the anode front end surface hindering the flow of the gas to the rear of the anode, is less likely to occur.

Even if the time between the lamps elapses and the distance between the two electrodes becomes longer and the amount of gas hitting the flat surface 2a increases, the gas flow along the inclination of the flat surface 2a is maintained in the same manner as described above. In addition, it is difficult to generate a gas flow that lifts the arc from the downward direction immediately below the arc, and the gas convection in the vicinity of the arc is not disturbed. Therefore, arc deflection is less likely to occur and the flicker life is improved.
In the above embodiment, the tip surface of the anode 2 is shown as a plane, but as shown in FIG. 4, it is formed with a gentle curved surface 2a ′ within the range of θ = 10 ° with respect to the plane P in FIG. May be.

[Flicker life test]
In the xenon lamp shown in FIG. 1, lamps having different inclination angles of the flat surface 2a at the tip of the anode 2 were manufactured, and the range of the optimum inclination angle was obtained by measuring the flicker life. In addition, comparison was made with the flicker life of a conventional electrode-shaped lamp.
There are five types of xenon lamps manufactured, and the basic configuration other than the anode configuration is the same. 1 × 10 6 Pa (25 ° C.) xenon gas is sealed in the arc tube, and the rated power consumption is 6 kW.

The structure of the anode of the above five types of xenon lamps is shown below.
(1) An anode having the conventional shape shown in FIG. 6, a tapered portion having an axial length of 14 mm on the tip side of a substantially cylindrical tungsten rod having a diameter of 25 mm and a length of 45 mm, and a taper of 6 mm on the rear end side. Formed with an electrode rod on the rear end face. The anode plane is not tilted (tilt angle 0 °).
(2) An anode having the shape shown in FIG. 1, the tip surface diameter of the anode being 7 mm, the maximum outer diameter diameter being 25 mm, the total length being 40 mm, the expanded diameter being 14 mm, and the reduced diameter being the length. The boundary between the enlarged diameter portion and the reduced diameter portion is formed smoothly and continuously, and the plane of the tip of the anode is not inclined (inclination angle 0 °).
(3) In the anode configuration of (2) above, the tip surface has an inclination angle of 5 °.
(4) In the anode configuration of (2) above, the tip surface has an inclination angle of 10 °.
(5) In the anode configuration of (2) above, the tip surface has an inclination angle of 15 °.

The above five lamps were lit at a current value of 160 A, and the lighting time and lamp voltage fluctuation until the flicker life was reached were measured. The lamp was turned on in a horizontal posture and the slope of the flat surface 2a at the tip of the anode faced downward.
Here, the flicker life was defined as the time when the touch of the lamp voltage during lighting reached 1.2V. The reason is that arc flicker, which is a flicker phenomenon, can be measured as lamp voltage fluctuation. In the case of a lamp of this rating, if the lamp voltage fluctuation is 1.2 V or more, no light from the projection device is emitted. This is because flickering can be felt by visual observation when projected onto a screen without being projected.
FIG. 5 shows the experimental results. The horizontal axis represents the lamp lighting time (time), and the vertical axis represents the lamp voltage fluctuation (V).

  In the case of the conventional product (1), the fluctuation of the lamp voltage immediately after the lamp is lit is about 0.7V. ).

In contrast, (2) (3) (4) (5), in which the anode is configured with a smooth curved surface as shown in FIG. 1, improved gas convection when the lamp was turned on, and extended the flicker life to 900 hours or more. However, when the inclination angle of the flat surface of the anode tip increased from 0 ° to 5 ° and 10 °, the flicker life increased from about 950 hours to about 1050 hours to about 1100 hours. In addition, the lamp voltage fluctuation in the initial stage of lamp lighting was smaller at 5 ° (3) and 10 ° (4) than at (2) where the tilt angle was 0 °, and the arc stable state was improved. Is shown.
However, when the inclination angle becomes 15 ° (5), the fluctuation of the lamp voltage starts to increase at an earlier stage than the inclination angles of 5 ° (3) and 10 ° (4), and the flicker life is as short as about 1000 hours. became.

From the above results, it was found that by tilting the tip surface, the stable state of the arc can be improved and the flicker life can be extended.
It has also been found that when the inclination angle of the tip surface is 15 ° or more, the stable state of the arc is deteriorated again and the flicker life is shortened. The reason is considered to be that when the inclination angle is increased, the tip of the anode becomes sharper, the arc is concentrated on the tip, the anode melts, and the flicker phenomenon is likely to occur. Therefore, it is considered that a range of 5 ° to 10 ° is suitable as the inclination angle of the tip surface of the anode.

It is a cutaway view in the tube axis direction showing a xenon lamp according to the present invention. It is a side view which expands and shows the anode in FIG. It is a figure explaining the state which turned on the xenon lamp which concerns on this invention. It is a side view explaining another embodiment of an anode. It is a figure which shows the result of a flicker life test. It is a figure which expands the principal part and shows the state of the convection of the xenon lamp which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Xenon lamp 10 Light emission tube 11 Light emission tube part 12, 12 'Side tube part 12a, 12a' Welding part 13, 13 'Electrode rod holding member 2 Anode 2a Front end plane 2b Rear end 2A Maximum outer diameter part 21 Large diameter part 22 Reduced diameter part 3 Cathode 4, 4 'Electrode rod

Claims (1)

A xenon lamp in which an anode and a cathode are opposed to each other at a predetermined interval inside the arc tube, and a xenon gas is sealed therein,
The anode has a flat surface or a curved surface at the front end and the rear end,
A diameter-expanded portion formed so as to gradually increase the diameter in the rear from the tip of the anode;
The diameter is gradually reduced at the rear of the enlarged diameter portion, and the reduced diameter portion is formed such that the length in the electrode axis direction is longer than the length in the electrode axis direction of the enlarged diameter portion.
The electrode axis which is the central axis in the longitudinal direction of the anode and the cathode is provided on the same straight line,
The xenon lamp, wherein a surface of the anode facing the cathode is inclined in a range of 5 ° to 10 ° with respect to a plane orthogonal to the electrode axis.
A xenon lamp characterized in that the vicinity of the boundary between the enlarged diameter portion and the reduced diameter portion is smoothly formed.

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