Patent Grant
8207673
The present invention relates to a high-pressure discharge lamp, and in particular, relates to a configuration of a sealing portion of an arc tube. The present invention further relates to a lamp unit using the high-pressure discharge lamp and a projection-type image display device using the lamp unit.
As a light source for projection-type image display devices such as a liquid crystal projector, a light source of nearly a point light source and having high brightness and high color rendering property, for example, a high-pressure mercury lamp, has been used widely.
In the sealing portions 103 and 104, parts of the rear end sides of the electrode bars 105a and 106a are embedded. Although the electrode bars 105a and 106a are embedded therein, this does not mean that, in the portions of the electrode bars 105a and 106a located in the sealing portions 103 and 104, the entire outer peripheral surfaces thereof are perfectly in close contact with the quartz glass. That is, when a certain region of the outer peripheral surface of the electrode bars 105a and 106a is seen, unavoidably, a part of the outer peripheral surface is not in close contact with the quartz glass, while the remaining part is in close contact with the quartz glass. Thus, a minute gap is formed that allows the ingress of, for example, gas filled in the light-emitting portion 102. Especially in a region A where the electrode bar 105a (106a) and the metal-foil 107 (108) overlap one another, a gap X slightly larger than the above-described gap is formed as shown in an enlarged partial view of
To cope with this, in general, the metal-foils 107 and 108 thinned to a thickness of 20 μm are used in the sealing portions 103 and 104, whereby the occurrence of the above-described gap during the sealing process can be suppressed, and the airtightness in the sealing portions 103 and 104 are secured. Further, the use of the thinned metal-foils 107 and 108 can relieve the stress caused by the difference in thermal expansion coefficient between the metal-foils 107, 108 and the quartz glass that is a constituent material of the sealing portions 103, 104. Thus, the occurrence of microcracks in that region can be suppressed.
However, regarding the electrode bars 105a and 106a, unlike the metal-foils 107 and 108, the stress caused by the difference in thermal expansion coefficient from the quartz glass during the sealing process cannot be relieved, and this sometimes causes microcracks in that region. Although only microcracks occur in this situation, in a high-pressure discharge lamp aimed at improving brightness by increasing the amount of filled mercury (e.g. 0.15 mg/mm3 or more) to increase a vapor pressure at the time of lighting, the following problem arises: starting from a few microcracks, microcracks gradually grow due to the stress applied by a high vapor pressure at the time of lighting, which has sometimes resulted in the fracture in the sealing portions 103 and 104 (for example, see Patent Document 1).
Especially in the regions where the gaps X are formed, i.e., the overlapped regions of the electrode bars 105a, 106a and the metal-foils 107, 108, cracks larger (e.g. twice or triple as large) than microcracks occurring in the other regions where the electrode bars 105a and 106a are embedded have occurred even before the lighting for unknown reasons.
In view of this, for suppressing this kind of fracture in the sealing portions 103 and 104, various techniques have been known conventionally. For example, in the case of an arc tube 201 shown in
Furthermore, for suppressing the occurrence and growth of the microcracks caused by the gap X shown in the enlarged cross-sectional view of the region A in
Recently, a higher brightness and higher color rendering property have been demanded with respect to high-pressure discharge lamps mounted in the projection-type image display devices. In response to these demands, there has been a growing trend to increase the amount of filled mercury for the purpose of increasing a mercury vapor pressure in the arc tube.
In view of the above, the inventors of the present invention examined the high-pressure discharge lamp with a rated power of 300 W by setting the amount of filled mercury to 0.35 mg/mm3, and targeting the rated lifetime up to 2000-hour. At that time, because of the concern for the fracture in the sealing portion, all of the above conventional techniques were applied for preventing its occurrence. However, in every trial lot of the lamps with the above conventional techniques applied thereto, 20% to 50% of the sealing portions were fractured by the time the targeted rated lifetime of 2000-hour was reached.
The present invention has been achieved in view of the above situation, and an object is to provide a high-pressure discharge lamp capable of further suppressing the fracture in the sealing portion.
A high-pressure discharge lamp according to the present invention has an arc tube made of quartz glass including a light-emitting portion that fills mercury inside thereof and has a pair of electrodes arranged so as to face each other, and a sealing portion connected to the light-emitting portion, wherein the pair of electrodes respectively have an electrode bar, one end of the electrode bar is located in an internal space of the light-emitting portion, the other end of the electrode bar is embedded in the sealing portion and bonded to a conductive metal-foil sealed in the sealing portion, and in at least a part of a portion of the electrode bar embedded in the sealing portion, an entire outer peripheral surface thereof is covered tightly with a metal-foil sleeve.
Further, a high-pressure discharge lamp according to the present invention having another configuration includes an arc tube made of quartz glass including a light-emitting portion that fills mercury inside thereof and has a pair of electrodes arranged so as to face each other, and a sealing portion connected to the light-emitting portion, wherein the pair of electrodes respectively have an electrode bar, one end of the electrode bar is located in an internal space of the light-emitting portion, the other end of the electrode bar is embedded in the sealing portion and bonded to a conductive metal-foil sealed in the sealing portion, a narrow foil piece part having a width narrower than that of the other portion is formed at an end of the conductive metal-foil, in at least a part of a portion of the electrode bar embedded in the sealing portion, a part of an outer peripheral surface thereof in a circumferential direction is covered tightly with the narrow foil piece part, and in the narrow foil piece part and the electrode bar, an entire outer peripheral surface of a region corresponding to the narrow foil piece part is covered with a metal-foil sleeve.
Here, the phrase “a pair of electrodes arranged so as to face each other” includes not only the case in which the respective axes of the electrodes in the longitudinal direction are aligned perfectly, but also the case in which these axes are displaced due to the variation in assembly or the like.
The phrase “a portion of the electrode bar embedded in the sealing portion” refers to a portion of the electrode bar from a point where the electrode bar starts contacting the quartz glass, which is a constituent material of the sealing portion, to the end of the electrode bar on the side connected to the metal-foil.
The phrase “tightly covered” refers to a state in which the metal-foil sleeve substantially covers the electrode bar so as not to create any gap therebetween. This means that, for example, in the case where the electrode bar is inserted into the metal-foil sleeve, the diameter of the electrode bar is equal to the internal diameter of the metal-foil sleeve. However, in view of the variation in processing, for example, the internal diameter of the metal-foil sleeve practically is set slightly larger than the diameter of the electrode bar. Therefore, the phrase “tightly covered” also refers to this case, although gaps are formed partially.
Further, the wording “covered” includes the case in which the electrode bar is covered by being inserted into the metal-foil preformed in a sleeve shape, the case in which the electrode bar is covered by being wrapped with a metal-foil sheet, and the like. It should be noted that, as described later, this “metal-foil sleeve” is composed of a different member functioning as a buffering member having mechanical elasticity. Therefore, the feature of the above is essentially different from an electrode bar obtained by processing itself, such as an electrode bar plated with a desired material and an electrode bar with the surface thereof modified, and they are not included herein.
According to the present invention, it is possible sufficiently to relieve the stress applied to the sealing portion caused by the difference in thermal expansion coefficient between the electrode bars and the quartz glass. As a result of this, the occurrence of microcracks in the sealing portion can be suppressed surely, and the fracture in the sealing portion can be suppressed effectively.
Based on the configuration described above, the high-pressure discharge lamp of the present invention can assume the following characteristics.
That is, a region of the electrode bar covered with the metal-foil sleeve can include at least a portion of the electrode bar that overlaps with the conductive metal-foil.
Further, it is possible to employ a configuration in which a metal-foil piece portion is provided at the end of the conductive metal-foil, and the metal-foil piece portion is wrapped around the electrode bar to form the metal-foil sleeve.
Still further, it is possible to employ a configuration in which the metal-foil piece portion is fixed to the electrode bar at least one spot by welding, and the spot at which the metal-foil piece portion is fixed by the welding is covered with another portion of the metal-foil piece portion.
Still further, it is possible to employ a configuration in which, when the electrode bar is made of tungsten, the metal-foil sleeve is composed of any one of molybdenum, niobium, rhenium, tungsten and tantalum, or composed of an alloy containing any one of molybdenum, niobium, rhenium, tungsten and tantalum as a main component.
Still further, a lamp unit according to the present invention includes the high-pressure discharge lamp having any one of the configurations described above, and a reflection mirror that has a concave reflecting surface, wherein the high-pressure discharge lamp is attached to the reflection mirror in such a manner that light emitted by the high-pressure discharge lamp is reflected by the reflecting surface.
Still further, a projection-type image display device according to the present invention includes the lamp unit having any one of the configurations described above, an optical unit that forms an optical image by modulating illumination light from the lamp unit, and a projection device that enlarges and projects the optical image.
Hereinafter, embodiments of the present invention will be described specifically with reference to the drawings.
A vessel of an arc tube 1 is made of quartz glass. The arc tube 1 includes a substantially spheroidal light-emitting portion 2 in the central portion thereof, and substantially columnar sealing portions 3 and 4 that are connected respectively with both sides of the light-emitting portion 2 and extend outward. Inside the light-emitting portion 2, a pair of electrodes 5 and 6 made of tungsten (W) are disposed opposite to each other. In the sealing portions 3 and 4, embedded portions of electrode bars 5a and 6a (circular in lateral cross-section) constituting a part of the electrodes 5 and 6 are sealed by a so-called drawing sealing process. As described later, the embedded portions utilize a configuration that characterizes the present embodiment.
Additionally in the sealing portions 3 and 4, conductive metal-foils 7 and 8 made of molybdenum (Mo), to which the rear ends of the electrode bars 5a and 6a are bonded respectively by welding, are sealed airtightly. At the other ends of the conductive metal-foils 7 and 8 opposite to the ends bonded to the electrode bars 5a and 6a, external lead wires 9 and 10 made of molybdenum (Mo) are bonded, respectively, and drawn out of the arc tube 1.
Inside the arc tube 1, predetermined amounts of mercury (Hg) 11 as a light-emitting material, argon (Ar) 12 as starting-assistant rare gas, and further bromine (Br) 13 as a halogen are filled. The specific configuration of the arc tube 1 will be described in detail.
The light-emitting portion 2 has a substantially spheroidal shape, and the dimensions thereof are set to, for example, an internal diameter φ ai of the central portion: 5.0 mm; an outer diameter φ ao: 12.0 mm; a shaft length inside the tube Lao: 8.0 mm; and an internal capacity Vai: 0.1 cc. The sealing portions 3 and 4 have a substantially columnar shape, and the dimensions thereof are set to an outer diameter φ so: 5.8 mm; a total length Ls: 30 mm. In this case, a total length Lo of the arc tube 1 becomes 68 mm. Further, the distance between the electrodes 5 and 6, that is, an interelectrode distance Ld is set to 1.2 mm. Furthermore, the amount of filled mercury 11 is set to 35 mg (0.35 mg/mm3) in total weight, the amount of filled argon 12 is set to 30 kPa (at room temperature), and bromine 13 is set to 0.5×10−3 μmol in total weight.
As shown in
As shown in
The dimensions of the electrode 5 are set to, for example, a total length Le: 7.5 mm; and an embedded portion length Las of the electrode bar 5a in the sealing portion 3 (see
Next, a configuration of the embedded portion of the electrode 5 will be described specifically (the same applies to the electrode 6). As shown in
Next, members to be sealed in the sealing portion 3 of the arc tube 1 and the assembling process in the present embodiment will be described with reference to
First, as shown in
Next, as shown in
It should be noted that, in one example, the dimensions of the conductive metal-foil 7 were set to: a total length Lm shown in
In
As described above, according to the configuration of the high-pressure mercury lamp of Embodiment 1, the metal-foil sleeves 7a and 8a are interposed between the quartz glass in the sealing portions 3 and 4 and the electrode bars 5a and 6a. Thus, the metal-foil sleeves 7a and 8a function as buffering members having mechanical elasticity, whereby the stress applied to the sealing portions 3 and 4 caused by the difference in thermal expansion coefficient with respect to the electrode bars 5a and 6a can be relieved (absorbed) greatly. Therefore, in the sealing process, the occurrence of microcracks in the regions of the sealing portions 3 and 4 itself can be suppressed effectively. Furthermore, even if stress is caused due to the increased amount of the filled mercury and the raised vapor pressure inside the arc tube 1 at the time of lighting, this stress also can be relieved by the metal-foil sleeves 7a and 8a. Moreover, even if the microcracks occur, the growth can be suppressed, whereby the fracture in the sealing portions 3 and 4 surely can be suppressed.
As described above, in the portions of the electrode bars 5a and 6a positioned in the region of the gap X (see
Further, preferably, the metal-foil sleeves 7a and 8a are composed of any one of molybdenum, niobium (Nb), rhenium (Re), tungsten (W) and tantalum (Ta), or composed of an alloy containing any one of them as a main component. Thus, the metal-foil sleeves 7a and 8a can attain sufficient heat resistance.
Furthermore, preferably, the thicknesses of the metal-foil sleeves 7a and 8a are set to 40μ or less as the maximum value. The minimum value thereof preferably is 10 μm or more for practical purposes.
Next, an experiment performed to confirm the functional effects of the high-pressure mercury lamp according to the present embodiment will be described below.
With respect to the arc tube 1 (20 units) of the high-pressure mercury lamp according to the above-described Embodiment 1, the lifetime test was conducted using a configuration of a lamp unit 23 of the later-described Embodiment 7 shown in
For comparison, two kinds of comparative arc tubes 101 and 201 provided with conventional sealing portions, respectively shown in
Specifically, the comparative arc tube 101 (
Further, configurations of the lamps and the lamp units equipped with the comparative arc tubes 101 and 201 were set completely in the same way as in a lamp 20 and a lamp unit 23 of Embodiment 7.
Table 1 shows the number of lamps in which sealing portions are fractured by the time when each accumulated lighting time up to the rated lifetime of 2000-hour is reached, regarding the arc tube 1 of the present embodiment and the comparative arc tubes 101, 201.
As is clear from Table 1, as to the comparative arc tube 101, the fracture in the sealing portion was started at the accumulated lighting time of 1-hour, and 14 lamps out of 20 lamps were fractured at the time of 2000-hour. Further, as to the comparative arc tube 201, the fracture in the sealing portion was started at the accumulated lighting time of 100-hour, and 10 lamps out of 20 lamps were fractured at the time of 2000-hour.
On the other hand, as to the arc tube of Embodiment 1, even at the rated lifetime of 2000-hour, no fractures occurred in the sealing portions 3 and 4. Moreover, the sealing portions 3 and 4 of the arc tube 1 were inspected visually, and no microcracks were found in the embedded portions of the electrode bars 5a and 6a.
As a result of this experiment, it was confirmed that the metal-foil sleeves 7a and 8a tightly covering the electrode bars 5a and 6a were able to greatly relieve the stress caused by the difference in thermal expansion coefficient applied to the sealing portions 3 and 4. Therefore, the metal-foil sleeves 7a and 8a were proved to have functioned effectively as buffering members having high mechanical elasticity.
An arc tube according to Embodiment 2 of the present invention will be described with reference to
Next, as shown in
It should be noted that, in one example, the dimensions of the conductive metal-foil 14 were set to: the total length Lm: 18 mm, the width Wm: 1.8 mm, and the thickness tm: 20 μm, respectively. The length Lma of the rectangular the metal-foil piece portion 14b was set to 2.7 mm. The dimensions of the metal-foil sleeve 14a were set to: the length Lma: 2.7 mm, and the cylindrical internal diameter φ si: 0.51 mm, respectively. The length Lae of the rear-end welding portion 5ae of the electrode bar 5a bonded to the front-end welding portion 14t of the conductive metal-foil 14 was set to 0.6 mm. This rear-end welding portion 5ae is neither wrapped nor covered with the metal-foil sleeve 14a. Moreover, an external lead wire 9 is bonded to a rear-end welding portion 14e of the conductive metal-foil 14 by resistance welding or the like.
Next,
With respect to such an arc tube (20 units) in the high-pressure mercury lamp according to Embodiment 2, the lifetime test was conducted using a completed lamp unit, and the fracture conditions of the sealing portions 3 and 4 of the arc tube were observed. At this time, the conditions of the lifetime test were set similarly to those of the lifetime test of the arc tube 1 according to the above-described Embodiment 1. As a result of this experiment, as also shown in Table 1, no fractures occurred in the sealing portions 3 and 4 of the arc tube of Embodiment 2 even at the rated lifetime of 2000-hour, and no microcracks were found by the visual inspection, in the same way as in the arc tube 1 of Embodiment 1.
As described above, according to the configuration of Embodiment 2, the metal-foil sleeve 14a functions as a buffering member having mechanical elasticity when being interposed between the electrode bar 5a and the quartz glass in the sealing portion 3 (hereinafter, the same applies to the sealing portion 4), in the same way as in the configuration of the high-pressure mercury lamp according to Embodiment 1. Because of this, the stress applied to the sealing portion 3 caused by the difference in thermal expansion coefficient with respect to the electrode bar 5a can be relieved (absorbed) greatly. Therefore, in the sealing process, the occurrence of microcracks in the region of the sealing portion 3 itself can be suppressed effectively. Moreover, even if stress is caused due to the increased amount of the filled mercury and the raised vapor pressure inside the arc tube 1 at the time of lighting, this stress also can be relieved by the metal-foil sleeve 14a. Therefore, even if the microcracks occur, the growth can be suppressed, whereby the fracture in the sealing portion 3 can be suppressed surely.
An arc tube according to Embodiment 3 of the present invention will be described with reference to
First, as shown in
Next, as shown in
Furthermore, as shown in
As described above, when the welding spots We of the metal-foil piece portion 14b are covered with another portion of the metal-foil piece portion 14b, the effect of suppressing the occurrence of microcracks in the sealing portion by the metal-foil sleeve 14a can be improved. The reason for this is as follows: since the metal-foil sleeve 14a is fixed to the electrode bar 5a at the welding spots We, this limits the function of the metal-foil sleeve 14a as a buffering member. Therefore, if the welding spots We are exposed and come into contact with the sealing glass, the effect of relieving the stress caused by the difference in thermal expansion coefficient by the buffering function of the metal-foil sleeve 14a is reduced in that region. On the contrary, if the welding spots We are covered with different portions of the metal-foil piece portion 14b, such a disadvantageous situation can be avoided.
An arc tube according to Embodiment 4 of the present invention will be described with reference to
First, as shown in
Next, as shown in
Next, as shown in
Further, as shown in
As described above, similarly to Embodiment 3, the effect of suppressing the occurrence of microcracks in the sealing portion by the metal-foil sleeve 14a can be improved.
An arc tube according to Embodiment 5 of the present invention will be described with reference to
First, as shown in
Next, as shown in
Next, as shown in
Further, as shown in
As described above, when the welding spot We of the metal-foil piece portion 14f is covered with another portion of the metal-foil piece portion 14f, the effect of suppressing the occurrence of microcracks in the sealing portion by the metal-foil sleeve 14i can be improved in the same way as in Embodiment 3.
An arc tube according to Embodiment 6 of the present invention will be described with reference to
A process of manufacturing the sealing portion having the above-described configuration will be described below. However, as to the external Mo lead wire 9, illustrations and descriptions shall be omitted. First, as shown in
Next, as shown in
Next, as shown in
As described in the present embodiment, when the outer peripheral surfaces of the electrode bar 5a and the narrow foil piece part 15b are covered with the metal-foil sleeve 16a, the occurrence of microcracks in the sealing portion can be suppressed. That is, the cover using the metal-foil sleeve 16a allows itself to function as a buffering member, whereby, in that region, the stress caused by the difference in thermal expansion coefficient can be relieved.
The high-pressure discharge lamp 20 is configured in such a manner that a cylindrical metal-cap 22 with a power source-connecting terminal 21 is attached to one sealing portion 3 of the above-described arc tube 1. Here, an external Mo lead wire 9 extended from one sealing portion 3 of the above-described arc tube 1 is connected (not shown) to the power source-connecting terminal 21. The lamp unit 23 has a configuration in which the metal-cap 22 of the high-pressure discharge lamp 20 is attached to and held by a reflection mirror 24. Further, a lead wire 25, which is connected to an external Mo lead wire 10 extended from the other sealing portion 4 in the high-pressure discharge lamp 20, is drawn outside via a through-hole 26 provided in the reflection mirror 24.
As the reflection mirror 24, for example, a spheroidal mirror, a rotational parabolic mirror, or a concave surface (spherical surface) mirror can be used. The mirror surface, for example, is configured in such a manner that a reflecting film made of a multilayer interference film is evaporated on a concave surface portion that is formed on the spheroid of a hard glass base.
A projection-type image display device according to Embodiment 8 of the present invention will be described with reference to
The front projector 30 is composed of a lamp unit 23 as a light source, an optical unit 32, a control unit 33, a projection lens 34, a cooling fan unit 35, a power source unit 36 and the like, which are stored in the housing 31.
The optical unit 32 has an image formation unit that modulates incident light so as to form an image, and an illumination unit for irradiating the image formation unit (neither of them is illustrated) with illumination light from the lamp unit 23. The illumination unit has a color wheel or the like (not shown) composed of color filters of three colors, thereby decomposing the illumination light into the three primary colors so as to irradiate the image formation unit with them.
The control unit 33 drives and controls the image formation unit and the like. The projection lens 34 enlarges and projects an optical image that is formed by modulation by the image formation unit. The power source unit 36 converts electric power that is supplied from a commercial power supply into electric power that is suitable for the control unit 33 and the lamp unit 23, and supplies the electric power to the control unit 33 and the lamp unit 23, respectively.
Moreover, the lamp unit 23 also can be used as a light source of a rear projector 40 that is an example of the projection-type image display device shown in
The high-pressure discharge lamp according to the present invention surely can suppress the occurrence of microcracks in the sealing portion and effectively suppress the fracture in the sealing portion, and therefore, is useful as a high-pressure mercury lamp used as a light source for a projection-type image display device. Further, in addition to the use as the high-pressure mercury lamp, the high-pressure discharge lamp according to the present invention directly can be applied to, for example, a high-pressure discharge lamp such as a metal halide lamp, and therefore, is useful as a metal halide lamp for an automobile headlight and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-186093 | Jul 2007 | JP | national |
| 2008-050578 | Feb 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/001876 | 7/14/2008 | WO | 00 | 1/13/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/011117 | 1/22/2009 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4550269 | Dixon | Oct 1985 | A |
| 5200669 | Dixon et al. | Apr 1993 | A |
| 6426592 | Nishida et al. | Jul 2002 | B2 |
| 6600266 | Nakagawa | Jul 2003 | B1 |
| 6624576 | Mittler | Sep 2003 | B1 |
| 7514871 | Scholl et al. | Apr 2009 | B2 |
| 7671536 | Takagaki et al. | Mar 2010 | B2 |
| 7759871 | Chowdhury et al. | Jul 2010 | B2 |
| 20010005117 | Nishida et al. | Jun 2001 | A1 |
| 20030052603 | Takahashi et al. | Mar 2003 | A1 |
| 20030076040 | Kumada et al. | Apr 2003 | A1 |
| 20030168981 | Kanzaki | Sep 2003 | A1 |
| 20040183442 | Kanzaki | Sep 2004 | A1 |
| 20100013369 | Kitahara et al. | Jan 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 1442878 | Sep 2003 | CN |
| 0 479 087 | Apr 1992 | EP |
| 1 049 134 | Nov 2000 | EP |
| 1-151149 | Jun 1989 | JP |
| 6-251749 | Sep 1994 | JP |
| 11-176385 | Jul 1999 | JP |
| 2001-189149 | Jul 2001 | JP |
| 2001-250504 | Sep 2001 | JP |
| 2003-123696 | Apr 2003 | JP |
| 2003-257373 | Sep 2003 | JP |
| 2004-006424 | Jan 2004 | JP |
| 3518533 | Feb 2004 | JP |
| 3570414 | Jul 2004 | JP |
| 2004-265753 | Sep 2004 | JP |
| 2004-296178 | Oct 2004 | JP |
| 2005-100874 | Apr 2005 | JP |
| 2008-71718 | Mar 2008 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20100188855 A1 | Jul 2010 | US |
