# Patent

## Title
Lamp unit and projector employing same

## Abstract

A lamp unit includes a reflector with a lamp mounted therein, a reflector holder holding the reflector, and an ejector member fixed to the reflector holder, for ejecting air to cool the lamp, the ejector member including an insertion member with a tubular stud inserted therein for supplying compressed air, a fluid passage forming member having a fluid passage for being supplied with air from the stud, and a hole defined in a distal end of the ejector member.

## Background
TECHNICAL FIELD
The present invention relates to a lamp unit including a cooling mechanism.
BACKGROUND ART
Generally, projectors include a cooling device for cooling an installed lamp. A fan is widely used as the cooling device.
JP-A No. 2003-215706 discloses a lamp unit including a reflector with a lamp located at its focal point and a holder for holding the open end of the reflector. The open end of the reflector is covered with a transparent plate for preventing fragments from being scattered around in the event that the lamp blows up.
The holder has an inlet port for introducing air into the reflector and an outlet port for discharging air from the reflector. When cooling air from a fan disposed outside of the reflector is introduced from the inlet port into the reflector and air in the reflector is discharged from the outlet port, an air flow (cooling air flow) is developed in the reflector, and impinges upon the lamp to cool the lamp.
DISCLOSURE OF THE INVENTION
However, it is difficult to obtain a sufficient cooling capability only when the air flow (cooling air flow) produced by introducing the cooling air from the fan into the reflector impinges upon the lamp.
High-pressure mercury lamps that are widely used with projectors have a heated region that should desirably be cooled locally. It is difficult to perform such local cooling with a fan.
It is an exemplary feature of the present invention to provide a lamp unit which will solve the above and other exemplary problems and which is capable of applying cooling air at a sufficient speed highly accurately to a desired region of a lamp.
To achieve the above and other exemplary features, a lamp unit according to an exemplary aspect of the present invention includes a reflector with a lamp mounted therein, by which light from the lamp is reflected, a reflector holder that holds the reflector, and an ejector member fixed to the reflector holder, which ejects air to cool the lamp. The ejector member includes an insertion member to which a tubular air supply member that supplies compressed air to the ejector member is inserted, a fluid passage forming member that includes a fluid passage to which air is supplied from a distal end of the air supply member inserted in the insertion member, and at least one hole (e.g., a small hole having a predetermined small diameter) defined in a distal end of the ejector member and that extends through a fluid passage wall defining the fluid passage. The fluid passage forming member includes a fluid passage cross-sectional area which is smaller at the distal end of the ejector member than at the insertion member.
According to the present invention as described above, compressed air from a pressurized is supplied through the air supply member to the ejector member which discharges the cooling air through the small hole defined in the distal end thereof. The cooling air discharged from the small hole is applied to the lamp unit to cool the lamp locally.
In the present invention, furthermore, the reflector with the lamp mounted therein is held by the reflector holder, and the ejector member is fixed to the reflector holder. Thus, both the lamp and the ejector member are positioned with respect to the reflector holder. Since the same member is used as a reference for positioning the lamp and the ejector member, the positional relationship between the lamp and the ejector member is set with high accuracy, and the cooling air discharged from the small hole of the ejector member can be applied highly accurately to a desired area of the lamp.
Conversely if the lamp and the ejector member are positioned with respect to different reference members, then the positioning accuracy with which the reference members position the lamp and the ejector member and the positioning accuracy between the reference members need to be considered, and it is difficult to set the positional relationship between the lamp and the ejector member highly accurately.
According to the present invention, the air supply member is inserted in the ejector member to realize an exchangeable unit (e.g., modular) structure. In such a structure, the size of the cross section of the fluid passage at the insertion member is greater than the outer profile of the air supply member. If the fluid passage cross-sectional area is the same as the fluid passage cross-sectional area at the insertion member throughout the fluid passage forming member, then the compressed air supplied from the air supply member is introduced into the fluid passage as a large space, whereupon the air suffers a pressure loss, resulting in a reduction in the speed of the air discharged from the small hole. The fluid passage cross-sectional area of the fluid passage forming member can be reduced advantageously to minimize a reduction, caused by the pressure loss, in the speed of the air discharged from the small hole. According to the present invention, since the fluid passage cross-sectional area at the distal end of the ejector member is smaller than the fluid passage cross-sectional area at the insertion member, the speed of the air discharged from the small hole is increased.
According to the present invention, as described above, inasmuch as the cooling air is discharged at a sufficient speed from the small hole of the ejector member, and the cooling air is applied highly accurately to a desired area of the lamp (e.g., a high-pressure mercury lamp or the like), the lamp can be maintained at an appropriate temperature. Therefore, the lamp is prevented from becoming clouded and blackened (e.g., due to mercury deposition or anode spot on the inner wall surface of the lamp), and, as a consequence, has a longer service life and has higher reliability than heretofore.
The above and other exemplary aspects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a lamp unit according to an exemplary embodiment of the present invention;
FIG. 2 is an exploded perspective view of a nozzle assembly including an ejector member shown in FIG. 1;
FIG. 3 is a cross-sectional view of an example of the ejector member shown in FIG. 1;
FIG. 4 is a cross-sectional view of another example of the ejector member shown in FIG. 1;
FIG. 5 is a characteristic diagram showing the relationship between the diameter of a small hole and the air speed;
FIG. 6 is a view showing the positional relationship between the ejector member and a lamp (light emission tube);
FIG. 7 is a view showing the positional relationship between the ejector member and the lamp (light emission tube);
FIG. 8 is a perspective view of a major portion of a projector which incorporates the lamp unit shown in FIG. 1; and
FIG. 9 is an exploded perspective view of some of the major portion of the projector shown in FIG. 8.



BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a perspective view of a lamp unit according to an exemplary embodiment of the present invention. As shown in FIG. 1, the lamp unit, which is to be incorporated in a projector, includes reflector 10 including a lamp and reflector holder 20 holding the open end of reflector 10. Reflector 10 has a concave reflecting surface, e.g., a reflecting surface formed as a paraboloid of revolution, with the lamp located at the focal point thereof. Light from the lamp is emitted directly from the opening or reflected by the reflecting surface and then emitted from the opening in a certain direction.
Reflector holder 20 is in the form of a cup covering the open end of reflector 10, and has circular window 21 for passing therethrough the light emitted from the open end of reflector 10. Window 20 is made of a transparent material (e.g., such as glass or resin) having such properties that the material passes therethrough light in a wavelength range used in the device which incorporates the lamp unit.
Reflector holder 20 includes attachment 27 on which ejector member 22 is mounted, positioning members 24 through 26 by which reflector holder 20 is positioned on an engine base, inlet duct 29 for introducing air from a fan, not shown, into the reflector, and outlet port 100 for discharging air from the reflector. Positioning members 24 through 26 are in the form of pins for engaging in receptacles (e.g., holes or the like) in certain locations on an external member. Reflector holder 20 may have four or more positioning members. Reflector holder 20 is positioned by positioning members 24 through 26 and then fastened to the engine base by screws. In addition to the lamp unit, optical components of an illuminating optical system, a projection lens, and an image display device (e.g., a digital micromirror device (DMD)) are mounted on the engine base.
FIG. 2 is an exploded perspective view of a nozzle assembly including ejector member 22. As shown in FIG. 2, ejector member 22 is tubular and has small hole 221 for ejecting air which is defined therein near the distal end thereof. Ejector member 22 has an open end remote from the distal end thereof. Connector 23 has stud 23a inserted into ejector member 22 through the open end thereof.
Connector 23 includes an L-shaped vent pipe and has an end attached to a tube connected to the outlet port of a pressurizing pump, not shown. Tubular stud 23a for supplying ejector member 22 with compressed air is mounted on the other end of connector 23. Stud 23a is inserted through packing 28 into ejector member 22. Packing 28 serves to prevent air from leaking from the junction between packing 23a and ejector member 22, and is made of silicone, for example. Packing 28 may be fixed to the open end of ejector member 22 by an adhesive, and stud 23a may removably be fixed in position by fixed packing 28.
The open end of ejector member 22 has holes 222, 223 through which ejector member 22 is fastened to attachment 27 of reflector holder 20. Attachment 27 has an opening through which ejector member 22 is inserted, and also has pin 271 and screw hole 272 near the opening. Pin 271 is inserted in hole 222 of ejector member 22, and ejector member 22 is positioned to keep hole 223 immediately above screw hole 272. A screw, not shown, is then inserted through hole 223 into screw hole 272, fastening ejector member 22 to attachment 27 of reflector holder 20. With ejector 22 fastened to reflector holder 20, compressed air discharged from small hole 221 impinges upon a desired area of the lamp in reflector 10.
FIG. 3 is a cross-sectional view of an example of ejector member 22. As shown in FIG. 3, ejector member 22 includes tube 22a into which stud 23a is inserted, and tube 22b which has a smaller side diameter than that of tube 22a. Tubes 22a, 22b have respective centers “a” substantially aligned with each other on a sectional plane transverse to the longitudinal direction of these tubes. Small hole 221 is defined in the side wall of tube 22b. The side wall of tube 22b has a thickness which should preferably be about three times the diameter of small hole 221. For example, if the diameter of small hole 221 is 0.3 mm, then the thickness of the side wall of tube 22b is 1.0 mm. Of course, the present invention is not limited to such a ratio, and others may be employed depending upon the designer's constraints and requirements.
As stud 23a is inserted in ejector member 22, the inside diameter of tube 22a is greater than the outer profile of stud 23a. If the inside diameters of tubes 22a, 22b are essentially the same as each other, then the inside diameter of the entire tube assembly is greater than the outer profile of stud 23a. In other words, the cross-sectional area of the fluid passage in ejector member 22 is greater than the cross-sectional area of the fluid passage in stud 23a. In this case, compressed air discharged from stud 23a is introduced into the fluid passage (having a relatively large space) and thereafter ejected out of ejector member 22 through small hole 221. When the compressed air discharged from stud 23a is introduced into the fluid passage having the relatively large space, the air suffers a pressure loss, resulting in a reduction in the speed of the air discharged from small hole 221.
The difference between the cross-sectional area of the fluid passage in ejector member 22 and the cross-sectional area of the fluid passage in stud 23a is reduced to minimize a reduction, caused by the pressure loss, in the speed of the air discharged from small hole 221. Specifically, the cross-sectional area of the fluid passage in ejector member 22 which leads to small hole 221 is reduced stepwise (or continuously) from the side where the stud is inserted, thereby lowering a pressure loss and increasing the speed of the air discharged from small hole 221. With the structure shown in FIG. 3, since the inside diameter of tube 22b is smaller than the inside diameter of tube 22a, the cross-sectional area of the fluid passage in ejector member 22 is reduced correspondingly, thereby increasing the speed of the air discharged from small hole 221.
FIG. 4 is a cross-sectional view of another example of ejector member 22. As shown in FIG. 4, ejector member 22 includes tube 22a into which stud 23a is inserted, and tube 22c which has a smaller side diameter than that of tube 22a. Tubes 22a, 22c have respective centers displaced from each other in a sectional plane transverse to the longitudinal direction of these tubes. Specifically, ejector member 22 has an eccentric structure wherein the center “b” of tube 22c is displaced from the center “a” of tube 22a toward the side where small hole 221 is defined.
In the ejector member shown in FIG. 3, a step (unreferenced) is present in the boundary between tube 22a and tube 22b on the side where small hole 221 is defined, and the outlet port of small hole 221 is spaced from the lamp by the step. The speed of the compressed air discharged from small hole 221 is lower as it is spaced greater from the outlet port. According to the eccentric structure shown in FIG. 4, there is no step in the boundary between tube 22a and tube 22c on the side where small hole 221 is defined. In the absence of the step, outlet port of small hole 221 is positioned more closely to the lamp, so that the speed of the compressed air for cooling the lamp can be higher than with the structure shown in FIG. 3.
The speed of the compressed air discharged from small hole 221 varies depending on the diameter of small hole 221. FIG. 5 shows the relationship between the diameter of the small hole and the air speed. The graph shown in FIG. 5 indicates the results of an experiment in which the relationship between the diameter of the small hole and the air speed was measured when constant compressed air was introduced. The results show that if the diameter of small hole 221 is smaller than 0.2 mm, then the value of the air speed drops sharply (e.g., below about 30 m/s) because of increased resistance to the compressed air as it passes through small hole 221. Further, if the diameter of small hole 221 is in excess of 0.4 mm, then the value of the air speed becomes lower than about 20 m/s. As at least the air speed of about 20 m/s is required for locally cooling the lamp used in the projector, the diameter of small hole 221 should preferably be in the range from about 0.2 mm to about 0.4 mm. More preferably, the diameter of small hole 221 should be in the range from about 0.2 mm to about 0.3 mm. With this diameter range, the air speed is equal to or higher than about 30 m/s.
The positional relationship between ejector member 22 and the lamp (light emission tube) will be described in specific detail below.
FIGS. 6 and 7 are views showing the positional relationship between ejector member 22 and the lamp (light emission tube). FIG. 6 illustrates the lamp unit shown in FIG. 1, with reflector holder 20 omitted from illustration, and FIG. 7 illustrates the lamp unit shown in FIG. 6, showing the small hole and parts near the light emission tube as viewed from above.
As shown in FIGS. 6 and 7, ejector member 22 is disposed at such an angle that the compressed air discharged from small hole 221 impinges upon a desired area of light emission tube 30 disposed in reflector 10, and in such a position that ejector member 22 does not block light fluxes emitted from reflector 10 and passing through window 21 (e.g., light fluxes in an effective range). In FIGS. 6 and 7, the arrow A represents the direction in which the compressed air is discharged from small hole 221.
If the ejector member and the reflector holder have an integral structure, then it is difficult to form precisely the small hole. With the lamp unit according to the present embodiment, since ejector member 22 is separate from reflector holder 20, small hole 221 can be machined with high accuracy. The positioning means (holes 222, 223, pin 271) shown in FIG. 2 allows the ejector member to be mounted highly accurately on the reflector holder. As the highly accurate machining process and the highly accurate positioning process are realized, it is possible to apply the compressed air from small hole 221 exactly to a desired area of the lamp. The stepped structure shown in FIG. 3 and the eccentric structure shown in FIG. 4 are effective to apply the compressed air from small hole 221 at a higher speed to a desired area of the lamp. Consequently, the desired area of the lamp can be maintained at an appropriate temperature, with the results that the lamp is prevented from becoming clouded and blackened (e.g., due to mercury deposition or anode spot on the inner wall surface of the lamp), has a long service life, and has increased reliability.
A projector incorporating the lamp unit according to the present exemplary embodiment will be described in specific detail below.
FIG. 8 is a perspective view of a major portion of a projector which incorporates the lamp unit shown in FIG. 1. FIG. 9 is an exploded perspective view of some of the major portion of the projector shown in FIG. 8.
As shown in FIG. 8, the major portion of the projector includes lamp unit 1, engine base 2, fan 3, and diaphragm-type air blower 4. Lamp unit 1, which is the lamp unit shown in FIG. 1, is accurately positioned on engine base 2 by positioning members 24 through 26 and fastened to engine base 2.
Diaphragm-type air blower 4 includes an existing pressurizing pump and has an outlet port connected to connector 23 through silicone tube 5. Compressed air discharged from diaphragm-type air blower 4 flows successively through silicone tube 5, connector 23, and stud 23a into ejector member 22, from which the compressed air is discharged through small hole 221 toward the lamp. Fan 3 draws air from fan duct 3a. An air stream delivered by fan 3 is introduced through an inlet duct 29 into reflector 10.
On engine base 2, there are mounted an illuminating optical system to which light fluxes (e.g., parallel light fluxes) emitted from window 21 of lamp unit 1 are applied, and a spatial modulator device for being irradiated with the light fluxes from the illuminating optical system. The spatial modulator device comprises, for example, a liquid crystal panel or DMD (Digital Micromirror Device), for example. Image light that is generated by the spatial modulator device is projected onto an external screen by a projection optical system, not shown.
The projector is cooled by both diaphragm-type air blower 4 and fan 3. Specifically, diaphragm-type air blower 4 can locally cool a heated region of the lamp, and fan 3 can cool the lamp in its entirety. The local cooling provided by diaphragm-type air blower 4 allows performing accurate temperature management of various parts of the lamp, which has not been achieved by the cooling provided by the fan alone, for increasing the service life of the lamp.
In the lamp unit according to the present invention, the compressed air from the pressurizing pump is supplied through the stud, which serves as an air supply member, to the ejector member which discharges the cooling air through the small hole defined in the distal end thereof. The cooling air discharged from the small hole is applied to the lamp unit to cool the lamp locally.
In the lamp unit according to the present invention, furthermore, the reflector with the lamp mounted therein is held by the reflector holder, and the ejector member is fixed to the reflector holder. Thus, both the lamp and the ejector member are positioned with respect to the reflector holder. Since the same member is used as a reference for positioning the lamp and the ejector member, the positional relationship between the lamp and the ejector member is set with high accuracy, and the cooling air discharged from the small hole of the ejector member can be applied highly accurately to a desired area of the lamp.
In the lamp unit according to the present invention, as shown in FIGS. 3 and 4, the cross-sectional area of the fluid passage which leads to the small hole is reduced stepwise or continuously toward the distal end of the ejector member. Consequently, a reduction, caused by a pressure loss, in the speed of the air discharged from the small hole is minimized.
According to the present invention, as described above, inasmuch as the cooling air is discharged at a sufficient speed from the small hole of the ejector member, and the cooling air is applied highly accurately to a desired area of the lamp (e.g., high-pressure mercury lamp or the like), the lamp can be maintained at an appropriate temperature. Therefore, the lamp is prevented from becoming clouded and blackened (e.g., due to mercury deposition or anode spot on the inner wall surface of the lamp), and, as a consequence, has a longer service life and has higher reliability than heretofore.
The lamp unit which has been described above is an example of the present invention, and can be changed in structure without departing from the scope of the invention. For example, ejector member 22 may have any structure insofar as the cross-sectional area of the fluid passage of ejector member 22 can be reduced. For example, ejector member 22 may have a tapered structure in which the cross-sectional area of the ejector member is gradually smaller from the side wherein stud 23a is inserted.
The small hole 221 defined in the distal end of ejector member 22 is not limited to a single small hole. Instead, a plurality of small holes 221 may be defined in the distal end of ejector member 22 for simultaneously cooling a plurality of areas of the lamp with cooling air from the small holes.
Small hole 221 may be defined in the surface of the distal end of ejector member 22 (specifically, the wall at the end of the fluid passage in tube 22b).
A plurality of ejector members 22 may be provided on reflector holder 20 for simultaneously cooling a plurality of areas of the lamp with cooling air from the ejector members.
The lamp unit according to the present invention is applicable to projectors in general. The lamp unit according to the present invention is also applicable to display devices for use with personal computers, e.g., liquid crystal display devices, in addition to projectors.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-275086 filed in Japan Patent Office on Oct. 6, 2006, the contents of which are hereby incorporated by reference.
While exemplary embodiments of the present invention have been described using specific terms, such description is for illustrates purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

## Claims

1. A lamp unit, comprising:
a reflector with a lamp mounted therein, by which light from said lamp is reflected;
a reflector holder that holds said reflector; and
an ejector member fixed to said reflector holder, which ejects air into said reflector and cools said lamp,
said ejector member including:
an insertion member to which a tubular air supply member that supplies compressed air to said ejector member is inserted;
a fluid passage forming member that includes a fluid passage to which air is supplied from a distal end of said air supply member inserted in said insertion member; and
at least one hole defined in a distal end of said ejector member and that extends through a fluid passage wall defining said fluid passage,

wherein said fluid passage forming member that includes a fluid passage cross-sectional area which is smaller at the distal end of said ejector member than at said insertion member.

2. A lamp unit according to claim 1, wherein said fluid passage cross-sectional area of the fluid passage forming member is smaller stepwise from said insertion member toward the distal end of said ejector member.

3. A lamp unit according to claim 1, wherein said fluid passage cross-sectional area of the fluid passage forming member is smaller continuously from said insertion member toward the distal end of said ejector member.

4. A lamp unit according to claim 1, wherein said fluid passage forming member comprises:
a first fluid passage forming member; and
a second fluid passage forming member that includes a fluid passage cross-sectional area smaller than said first fluid passage forming member, said hole being defined in said second fluid passage forming member,
said second fluid passage forming member including a cross-sectional center displaced toward a side where said hole is defined from a cross-sectional center of said first fluid passage forming member.

5. A lamp unit according to claim 1, wherein said ejector member is removably fixed to said reflector holder.

6. A projector, comprising:
a lamp unit according to claim 1;
a spatial modulator that spatially modulates light from said lamp unit to generate image light; and
a projection optical system that projects the image light generated by said spatial modulator.

7. A lamp unit, comprising:
reflecting means for reflecting light from a lamp which is mounted in said reflecting means;
reflector holding means for holding said reflector; and
ejecting means for ejecting air to cool said lamp, said ejecting means being fixed to said reflector holder,
wherein said ejecting means includes:
an insertion member to which tubular air supplying means for supplying compressed air to said ejector member is inserted;
a fluid passage forming member that includes a fluid passage to which air is supplied from a distal end of said tubular air supplying means inserted in said insertion member; and
at least one hole defined in a distal end of said ejecting means and that extends though a fluid passage wall defining said fluid passage,

wherein said fluid passage forming member that includes a fluid passage cross-sectional area which is smaller at the distal end of said ejecting means than at said insertion member.