Patent Application
20090195158
This application claims priority from Japanese Patent Application Serial Nos. 2008-023665 filed Feb. 4, 2008, the content of which is incorporated herein by reference in its entirety.
The present invention relates to a short arc type high pressure discharge lamp. The present invention especially relates to an extra-high pressure discharge lamp, in which 0.15 mg/mm3 or more of mercury is enclosed in an arc tube thereof and the mercury vapor pressure at time of lighting becomes 110 or more of atmospheric pressure, and which is used as a light source for a projector apparatus, such as a DLP (digital light processor) apparatus using a liquid crystal display apparatus or a DMD (digital mirror device) etc.
A projection type projector apparatus requires uniform image illumination with sufficient color rendering properties to a rectangle screen. Therefore, a lamp in which 0.15 mg/mm3 or more of mercury is enclosed so as to obtain high mercury vapor pressure, is used as a light source.
Such a lamp includes a pair of electrodes which are arranged so as to face each other at an interval of 2 mm or less in the arc tube made of quartz glass. In this arc tube, 0.15 mg/mm3 or more of mercury and halogen in a range of 1×10−6 to 1×10−2 μmol/mm3 is enclosed. Although the main purpose of enclosing the halogen is to prevent devitrification of the arc tube, this causes the so-called halogen cycles. Moreover, the so-called melted electrode, which is made by winding a coil around an axis rod and melting the coil, is used therefor.
On the other hand, in recent years, an output of a discharge lamp used for such a purpose is progressively increased, and electric power (current) applied to the lamp is also increased. Since the increase of applied current makes the temperature of the electrode high, more measures against the temperature rise is required in order to use it as a lamp. On the other hand, miniaturization is increasingly required in an apparatus such as a projector apparatus having a lamp, so that miniaturization of the lamp which is a light source thereof is strongly called for. That is, such a discharge lamp must be miniaturized, while the demands of a high output thereof and the measures against high temperature of the electrode are fulfilled. Here,.as the measure against high temperature, the volume of an electrode may be increased so as to increase the heat capacity thereof. However, if the size of the electrode becomes large, the discharge lamp must be made from an unprocessed glass pipe having a large inner diameter, so that the outer diameter of the sealing portions of the discharge lamp also becomes large, and the increase in the size is contradictory to the demand of the miniaturization.
Moreover, a technology is known in which a “pleat” like heat release portion formed by cutting raw material thereof, is used, instead the melted electrode described above. Since no coil is winded around the main body of the electrode, the size thereof can be made small as a whole. However since the “pleat” portion and the electrode axis portion are formed so as to be integrally connected to each other so that heat is released through the electrode axis portion, the temperature of the “pleat” like heat release portion does not rise so much. That is, even if glow discharge occurs in the “pleat” like heat release portion, since the temperature rise of the “pleat” like heat release portion may not progress after that, there is a problem that it cannot shift to arc discharge. Such an electrode structure is disclosed in Japanese Laid Open Patent No. 2007-265624.
It is an object of the present invention is to offer a short arc type high-pressure discharge lamp having an electrode structure which is high-temperature-tolerant and high-input tolerant, while it has a good lighting property.
One of the aspects of the present invention is a short arc type high pressure discharge lamp, in which 0.20 mg/mm3 or more of mercury and halogen are enclosed in a light emission portion, comprising a pair of electrodes, each of which has-a block portion at a tip thereof, wherein a pseudo coil area made up of two or more ring-like portions is formed in part of the block portion, and an unprocessed area whose diameter is approximately the same as that of the pseudo coil area is formed in a back side of the pseudo coil area.
In the short arc type high pressure discharge lamp 80% or more of an outer surface of the ring-like portions is physically separated from the block portion.
The ring-like portions may be physically separated from the block portion.
The pseudo coil area may be formed by irradiating laser light on the block portion.
Another aspect of the present invention is a method of producing a short arc type high pressure discharge lamp, wherein 0.20 mg/mm3 or more of mercury and halogen are enclosed in a light emission portion, and a pair of electrodes facing each other at an interval of 2.0 mm, each of which has a block portion at a tip thereof, is arranged in the light emission portion. The method comprises the following steps of irradiating laser light on an outer surface of the block portion so as to form grooves having a minute gap, relatively moving the block portion in a circumferential direction with respect to the laser light so as to form a ring-like portion in the circumferential direction, and moving the block portion in an axis direction of the block portion thereby forming another ring-like portion in the axis direction of the block portion.
In the above mentioned structure according to the present invention, first of all, the ring-like member functions similarly to a coil, so as to have a good lighting property. That is, since the ring-like member is provided so as to be physically separated from the electrode as another component, or since the ring-like member is connected only to a far end portion of the electrode block portion, a high temperature state can be maintained without decreasing the temperature even after glow discharge occurs. Secondly, while the ring-like member is provided at a front area of the electrode block portion, i.e. in the side of the electrodes facing each other, since the cylinder section has an outer diameter which is approximately equal to the outer diameter of the ring of the ring-like member in a back area of the electrode block portion, it is possible to make the electrode structure having large heat capacity, without using a large unprocessed pipe from which a lamp is made.
Other features and advantages of the present short arc type high-pressure discharge lamp will be apparent from the ensuing description, taken in conjunction with the accompanying drawings, in which:
A description of embodiments of the present short arc type high-pressure discharge lamp will now be given below, referring to drawings. While the claims are not limited to such embodiments, an appreciation of various aspects of the present short arc type high-pressure discharge lamp are best gained through a discussion of various examples thereof.
Mercury, rare gas, and halogen gas are enclosed in the light emission section 11. The mercury whose amount is 0.15 mg/mm3 or more is enclosed the light emission section 11 to obtain radiation light having the required visible light wavelength of, for example, 360-780 nm. Although depending on temperature conditions of the light emission section 11, with the enclosed amount of the mercury, the vapor pressure thereof becomes extremely high at time of lighting, that is, 150 or more atmospheric pressure. Moreover, by enclosing more mercury, it is possible to make a discharge lamp whose mercury vapor pressure is higher at time of lighting, such as 200 or more atmospheric pressure or 300 or more atmospheric pressure. The higher the mercury vapor pressure becomes, the more a light source for a projector apparatus is suitably realized. Argon gas as the rare gas whose amount is, for example, 13 kPa is enclosed in the light emission section 11, so as to improve the lighting starting nature. The halogen, such as iodine, bromine, chlorine, etc. is enclosed in form of a compound with mercury or other metals. The amount of enclosed halogen is chosen in a range of 10−6 to 10−2 μmol/mm3. Although the function thereof is for long-life which is attributed to the halogen cycle, in case the discharge lamp is very small as in the present invention and the inner pressure thereof is extremely high, such halogen is mainly used to prevent devitrification of the electric discharge container.
An example of specification of the discharge lamp will be given below. For example, the maximum outer diameter of the light emission section is 9.5 mm, a distance between the electrodes is 1.5 mm, and the arc tube internal volume is 75 mm3, rated voltage is 80 V, and rated power is 150 W, and lighting is carried out with alternating current. Moreover, since this type of discharge lamp is built in the projector apparatus to be miniaturized, and high light intensity is required while the overall dimension of the apparatus is extremely miniaturized, thermal influence in the arc tube portion becomes very severe. The lamp tube wall load value is set to 0.8-2.0 W/mm2, and specifically to 1.5 W/mm2. When the discharge lamp in which the mercury vapor pressure and the lamp tube wall load value are high is installed in an apparatus for presentation such as a projector apparatus or an overhead projector, it is possible to obtain radiation light with good color rendering properties.
The taper portion 210 is formed in a front side of the body portion 200, and has an approximately circular truncated cone shape as a whole, and the outer diameter of the taper portion 210 in the base side thereof is equal to that of the body portion 200. The projection portion 220 is formed in the front side of the taper portion 210 and is a small projection having a circular truncated cone shape or a cylindrical shape. In an alternating current lighting lamp, at the projection portion 220, an arc is formed, so that the temperature thereof becomes highest. In addition, although the projection portion 220 may be formed together with the block portion 20 when performing cutting work to form the block portion 20, it may be automatically formed with progress of lighting time, in a lamp in which halogen is enclosed.
The block portion 20 is made of tungsten whose purity is, for example, 4N or higher. This is because if impurities are contained therein, they adhere to the arc tube so as to exert a bad influence thereon. The dimension of the respective parts is shown for convenience of explanation in the figures. An example of specification thereof is described below. The outer diameter of the body portion 200 of the block portion 20 is φ 1.0-3.0 mm, for example, 1.5 mm, and the length thereof in the axial direction is 2.0-5.0 mm, for example, 3.6 mm. The outer diameter at a tip of the taper portion 210 is φ 0.2-1.0 mm, for example, 0.5 mm, and the length thereof in the axial direction is 0.5-3.0 mm, for example, 0.7 mm. The length in the axial direction of the projection portion 220 is 0.1-0.9 mm, for example, 0.2 mm. Moreover, the outer diameter of the axis portion 21 is φ 0.3-1.0 mm, for example, 0.4 mm, and the length thereof in the axial direction is 0.5-3.0 mm, for example, 1.5 mm. The length of the axis portion 21 is 1.6 mm and is inserted in the block portion 20.
The ring-like portion area 40 (ring-like portions 40a, 40b, 40c) is formed by processing part of the body portion 200. Specifically, a groove portion 41 (comprising minute grooves 41a1, 41a2, 41b1, 41b2, 41c1, 41c2) is formed by irradiating laser light onto the cylindrical body portion 200. The grooves 41a1, 41b1, and 41c2 are formed by irradiating the laser light, aslant from the front side of the body portion 200 (the side of the projection portion 220). Moreover, the groove 41a2, 41b2, and 41c2 are formed by irradiating the laser light, aslant from the back side of the body portion 200 (the side of the axis portion 21). Therefore, these three ring-like portions (40a, 40b, 40c) are formed in the ring-like portion area 40 in the axial directions of the block portion 20 in this embodiment. Specifically, the ring-like portion 40a formed by the groove 41a1 and the groove 41a2, the ring-like portion 40b formed by the groove 41b1 and the groove 41b2, and the ring-like portion 40c formed by the groove 41c1 and the groove 41c2, are sequentially formed from the side of the projection portion 220.
Thus, the grooves are formed aslant from the outer surface of the electrode to the inner portion thereof, by irradiating the laser light aslant from both the front and back directions to one part. As a result, the shape of each ring-like portion in the ring-like portion area 40, is approximately a triangle in a cross sectional view of the electrode taken along the axis of the electrode. Moreover, in this embodiment, since the laser light is irradiated while rotating the body portion 200 about the axis portion, the grooves are formed throughout the circumference of the body portion 200 in a circumferential direction.
The ring-like portion 40a is formed of the groove area 41a2 formed throughout the circumferential direction and the groove 41a1 formed throughout the circumferential direction. Although it is integrally connected with the body portion 200 in an area 42, most of the outer surface of the ring-like portion 40a is physically separated from the body portion 200 (block portion 20). In such a structure, the ring-like portions are formed like a coil.
The pseudo coil area 50 is an outer surface area of the body portion 200, and the ring-like portion area 40 (where the ring-like portions 40a, 40b, 40c are formed). Moreover, the unprocessed area 60 is an outer surface of the body portion 200 and an area other than the ring-like portion area 40 (the ring-like portions 40a, 40b, 40c are formed), that is, an unprocessed area formed in the back side of the pseudo coil area 50. In addition, the unprocessed area formed in the front side of the pseudo coil area 50 is referred to as the front unprocessed area 61.
After a glow discharge occurs in the ring-like portion area according to the present invention, the temperature of the ring-like portions hardly falls. This is because since most of the outer surfaces of the ring-like portions are physically separated from the body portion (block portion) like separate components, even after the glow discharge occurs in the ring-like portion area, the high temperature state can be maintained in the ring-like portion area, without temperature fall.
Moreover, in the electrode structure according to the present invention, since the electrode block portion is provided in an area in a relatively front side of the ring-like portion, i.e., in a side of the other electrode which the electrode faces, and the unprocessed area 60 having an outer diameter 60od which is almost equal to an outer diameter 50od of rings of the ring-like portions is formed in an area in the back side of the electrode block portion, it is possible to offer an electrode with a large heat capacity without making a lamp large in size.
An example of specification (dimension) of the ring-like portion area 40 is given below. A length 40L in the axial direction in the triangle portion a cross sectional view is 0.1-0.4 mm, for example, 0.3 mm, a length (height) 40D in a depth direction of the triangle portion in the cross-sectional view is 0.1-0.4 mm, for example, 0.3 mm, and a length 42L of the area 42 which is integrally connected to the body portion 200 is 0.02-0.3 mm, for example, 0.05 mm. An angle 410 formed by the groove 41 and the body portion 200 as shown in
The number the ring-like portions 40 formed in the body portion is one to twenty (1-20), for example, three (3). The length of the pseudo coil area 50 in the axial direction of the body portion 200 is 1.0-3.0 mm, for example, 1.5 mm, and the length of the unprocessed area 60 in the axial direction of the body portion 200 is 5.0 mm or less, for example, 0.7 mm.
In the electrode shown in
Next, a method for forming the groove 41 in the block portion 20 will be described below. The electrode 2 (the block portion 20 and the axis portion 21) is attached to an electrode processing machine. While the electrode 2 is rotated at, for example, 500 rpm, laser light is irradiated for 30 seconds, thereby repeatedly irradiating the laser light on the same part about 250 times. The laser is a YVO4 solid laser and is irradiated at an average output of 8 W.
First of all, since the present invention has the above-mentioned structure, the ring-like portion functions as a coil functions, thereby obtaining good lighting property. That is, since the ring-like portion is physically separated from an electrode so as to exist as a separate component from the electrode, or since it is connected to the block portion only at a far inner portion of an electrode block portion, it is possible to keep the temperature thereof high without decreasing the temperature even after glow discharge is generated. Secondly, while providing the ring-like portion at the front side of an electrode block portion, i.e., a side of the other electrode which the electrode faces, and it is has a cylinder section whose outer diameter is almost equal to the outer diameter of the ring of the ring-like portion in the back side of the electrode block portion, it is possible to form the electrode structure where heat capacity is large, without using a large unprocessed pipe to make a lamp.
The preceding description has been presented only to illustrate and describe exemplary embodiments of the present short arc type high-pressure discharge lamp according to the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-023665 | Feb 2008 | JP | national |
