Heat radiating structure for use in image projecting apparatus

Disclosed herein is a heat radiating structure for radiating the heat generated by a lamp in an image projecting apparatus for projecting an image onto a screen to display the image thereon, including a heat sink for radiating heat generated by the lamp, the heat sink including heat transfer means for transferring the heat from the lamp, the heat transfer means being held in close contact with the lamp, heat storage means for storing the heat transferred from the lamp through the heat transfer means, and a plurality of fins serving as heat radiating means for radiating the heat stored by the heat storage means, wherein the heat transfer means, the heat storage means, and the heat radiating means are of a separable structure.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2005-236046 filed in the Japanese Patent Office on Aug. 16, 2005, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat radiating structure for efficiently radiating the heat generated by a lamp as a light source to cool the lamp in an image projecting apparatus for projecting an image onto a screen to display the image thereon.

2. Description of the Related Art

Image projecting apparatus have a lamp as a light source which is a largest heat source. For cooling the lamp, the image projecting apparatus need to have an efficient heat radiating structure. One heat radiating structure includes a heat sink of metal mounted on the surface of the lamp. Heat is transferred and radiated from the lamp to the heat sink to cool the lamp.

The heat radiating structures in the past where a heat sink is mounted on a lamp are disclosed in Japanese patent No. 2720253 and Japanese patent laid-open No. 2005-31549, for example.

SUMMARY OF THE INVENTION

According to the heat radiating structures in the past, the heat sink is of a unitary structure from its portion mounted on the lamp as the heat source to heat radiating fins. Therefore, it is difficult for the heat radiating structures in the past to be held in close contact with and to provide a sufficient heat radiating capability for all of a plurality of types of lamps having different shapes and output specifications. If the heat radiating structures in the past are to be used with different types of lamps, then it is necessary to redesign the heat radiating structures in their entirety. Furthermore, since the heat sink of the heat radiating structures in the past is of a unitary structure, its shape is limited by casting and machining restrictions, and the heat sink needs to be made of the same material throughout, resulting in a high total cost.

It is desirable for the present invention to provide a heat radiating structure which can be used with a plurality of types of lamps having different shapes and output specifications, and which is of a low total cost.

In order to meet the above demand, there is provided in accordance with the present invention a heat radiating structure for radiating the heat generated by a lamp in an image projecting apparatus for projecting an image onto a screen to display the image thereon, including a heat sink for radiating heat generated by the lamp, the heat sink including heat transfer means for transferring the heat from the lamp, the heat transfer means being held in close contact with the lamp, heat storage means for storing the heat transferred from the lamp through the heat transfer means, and a plurality of fins serving as heat radiating means for radiating the heat stored by the heat storage means, wherein the heat transfer means, the heat storage means, and the heat radiating means are of a separable structure.

According to the present invention, the heat transfer means is shaped complementarily to the lamp, and is replaceable depending on the lamp used. Therefore, the heat sink can easily be used with a plurality of different types of lamps having different shapes. Heat radiating means having different heat radiating areas and different materials may be used depending on the temperature to which the lamp is heated. Consequently, the heat radiating structure can easily be used with a plurality of different types of lamps having different output specifications. According to the present invention, furthermore, the heat transfer means, the heat storage means, and the heat radiating means are of a separable structure, components thereof may be available in various shapes and materials, and the heat radiating structure may be of a low total cost while maintaining a high heat radiating capability.

The above and other features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows in perspective an image projecting apparatus1, or in other words, a video projector, to which the principles of the present invention are applicable. As shown inFIG. 1, the image projecting apparatus1has a housing2incorporating therein a lamp as a light source, an optical system for modulating light emitted from the lamp, and a cooling section for cooling the lamp and the optical system. The image projecting apparatus1projects image light which has been modulated by the optical system from a front projecting lens3onto a front screen, not shown, to display the image thereon.

The housing2includes a separate top cover4shaped to cover an upper surface of the housing2substantially in its entirety. The top cover4is slidable along the fore-and-aft axis of the housing2to selectively open and close the housing2.

FIG. 2shows in plan the image projecting apparatus1with the housing2being closed by the top cover4.FIG. 3shows in plan the image projecting apparatus1with the housing2being partly open by the top cover4which has slid forwards. As shown inFIG. 3, when the housing2being partly open by the top cover4which has slid forwards, a lamp unit storage13storing a lamp unit14having a lamp16as a light source is exposed from an upper rear area of the housing2.

An opening and closing section for selectively opening and closing the top cover4will be described below. The opening and closing section includes a rolling mechanism5mounted on the reverse side of the top cover4and two guide rails6mounted on an upper surface of the housing2in alignment with the rolling mechanism5and serving as a guide section for guiding the rolling mechanism5.

The rolling mechanism5includes four rollers, i.e., two rollers in front left and right positions on the reverse side of the top cover2and two rollers in rear left and right positions on the reverse side of the top cover2. The guide rails6extend in fore-and-aft directions respectively in left and right areas of the upper surface of the housing2. When the rollers roll on and along the guide rails6, the top cover4slides fore and aft with respect to the housing2to selectively open and close the housing2.

The image projecting apparatus1also has a light lock mechanism for locking the top cover4under a light retaining force in the position where the top cover4is open and also the position where the top cover4is closed. The light lock mechanism includes two engaging teeth8mounted on the reverse side of the top cover4and two pairs of front and rear engaging hooks9a,9bmounted on the upper surface of the housing2in alignment with the engaging teeth8. When the top cover4is open (seeFIG. 3), the engaging teeth8engage the respective front engaging hooks9a, lightly locking the top cover4in the open position. When the top cover4is closed (seeFIG. 2), the engaging teeth8engage the respective rear engaging hooks9b, lightly locking the top cover4in the closed position. To release the top cover4from either one of the lightly locked positions, the user may push the top cover4with a slightly strong force to cause the top cover4to slide, forcing the engaging teeth8to disengage from the engaging hooks9a,9bwhile the engaging hooks9a,9bare flexing.

The image projecting apparatus1also has a lock mechanism for completely locking the top cover4when the top cover4is closed. The lock mechanism includes a lock hole10defined in the reverse side of the top cover4and a lock pin11projecting from the upper surface of the housing2in alignment with the lock hole10. When the top cover4is completely closed, the lock pin11is inserted into the lock hole10, locking the top cover4against sliding movement with respect to the housing2. For unlocking the top cover4, the user presses an unlock button (not shown) on the bottom of the housing2to pull the lock pin11out of the lock hole10.

When the unlocked top cover4is slid forwards, the lamp unit14that is removably stored in the lamp unit storage13in the housing2is exposed, as shown inFIG. 3. The lamp unit14is fastened to the housing2by screws15. For replacing the lamp16which is dead, the screws15are removed by a tool such as a screwdriver or the like, and the lamp unit14is taken out upwards from the lamp unit storage13. Therefore, the lamp unit14can easily be replaced with a new lamp unit. After the lamp unit14is replaced, the top cover4is slid backwards to the closed position. After the top cover4is completely closed, the top cover4is locked by the lock mechanism.

Since the lamp unit14is replaced by opening and closing the top cover4with respect to the housing2, the appearance of the image projecting apparatus1remains undamaged. The lamp unit14can smoothly be replaced without the need for a hard labor to turn the image projecting apparatus1upside down for lamp replacement.

The lamp16used in the image projecting apparatus1will be described below. The lamp16includes a xenon lamp having a lamp bulb filled with a xenon gas under a high pressure ranging from 20 to 200 atmospheric pressures. The lamp16emits light due to an electric discharge caused when a voltage is applied across the high-pressure xenon gas.

The lamp16is shown in perspective inFIG. 4. The lamp16has a casing constructed of a front case17A and a rear case17B that are joined to each other. The casing is filled with the high-pressure xenon gas. Each of the front case17A and the rear case17B is made of metal, with an insulation interposed between the front case17A and the rear case17B. The front case17A and the rear case17B serve as respective electrodes. Specifically, the front case17A serves as a negative electrode in its entirety, and the rear case17B as a positive electrode in its entirety. When a drive voltage is applied between the front case17A and the rear case17B, an electric discharge is produced in the high-pressure xenon gas, emitting light that is radiated from an exit port18of sapphire glass on the front end of the front case17A.

The lamp16is an electric heating element whose temperature rises as it emits light. The lamp unit14includes a heat radiating structure in the form of a heat sink of metal for efficiently radiating the heat of the lamp16.

Details of the heat radiating structure are shown inFIGS. 5 through 10.FIG. 5shows the heat radiating structure in perspective as viewed obliquely from front.FIG. 6shows the heat radiating structure in front elevation.FIG. 7shows the heat radiating structure in rear elevation.FIG. 8shows the heat radiating structure in plan.FIG. 9shows the heat radiating structure in side elevation.FIG. 10shows the heat radiating structure in side elevation partly in vertical cross section. The heat sink includes a front heat sink20and a rear heat sink30which separately fitted over the front case17A and the rear case17B, respectively, of the lamp16.

The front heat sink20and the rear heat sink30have respective attachments21,31serving as a heat transfer section held in close contact with the lamp16, respective base blocks22,32serving as a heat storage section for storing the heat that is transferred from the lamp16through the attachments21,31, and respective sets of fins23,33serving as a heat radiating section for radiating the heat that has been stored by the base clocks22,32. These components of the front heat sink20and the rear heat sink30are separably combined with each other.

As shown inFIGS. 6,7, and10, the base blocks22,32are divided by respective central grooves22b,32binto respective left and right divided segments which are connected by connectors22a,32aat upper ends of the base blocks22,32. The divided left and right segments have recesses22c,32cdefined therein across the central grooves22b,32b. The lamp16is fitted in the recesses22c,32cby respective attachments21,31, and clamp springs24,34are mounted on the lower ends of the divided left and right segments, causing the divided left and right segments to tighten the lamp16.

The attachments21,31that are interposed between the lamp16and the base blocks22,32are partly cylindrical in shape, and have inner circumferential surfaces shaped complementarily to the outer shapes of the front and rear cases17A,17B of the lamp16and outer circumferential surfaces shaped complementarily to the recesses22c,32cin the base blocks22,32. Therefore, the lamp16and the base blocks22,32are sufficiently held in close contact with each other. The attachments21,31can easily be replaced with other attachments depending on the lamp16that is used.

The fins23,33serving as a heat radiating section include a number of heat radiating fins. The fins23,33are oriented in directions perpendicular to the optical axis of the lamp16and disposed symmetrically with respect to the base blocks22,32. The fins23,33are detachably fastened to the base blocks22,32by screws25,35.

The attachments21,31, the base blocks22,32, and the fins23,33of the heat sinks20,30are made of a metal such as aluminum, copper, or the like which has high thermal conductivity. The heat transferred from the lamp16through the attachments21,31is stored in the base blocks22,32, and the stored heat is radiated from the fins23,33. Therefore, the lamp16is efficiently cooled. Furthermore, a cooling fan incorporated as a cooling section in the image projecting apparatus1applies cooling air to the heat sinks20,30, more efficiently radiating the heat from the lamp16and preventing the temperature from unduly rising in the image projecting apparatus1.

The attachments21,31may be made of a material different from the base blocks22,32and the fins23,33, e.g., copper of high thermal conductivity, and the base blocks22,32may be made of inexpensive aluminum. With this arrangement, the heat radiating structure may be lower in cost and highly effective in radiating heat.

A heat transfer accelerating section such as silicone grease, a heat transfer sheet, or the like may be interposed between the lamp16and the attachments21,31for better heat transfer from the lamp16to the base blocks22,32for more efficient heat radiation. The heat transfer accelerating section may be interposed between the attachments21,31and the base blocks22,32for efficient heat radiation.

As shown inFIG. 8, the fins23,33have surfaces knurled to produce grooves40, providing small surface irregularities for the fins23,33to have a greater area for contact with air for better heat radiation.

The heat sinks20,30may be used with a plurality of types of lamps having different shapes by replacing the attachments21,31depending on the lamp16to be used. Specifically, if the heat sinks20,30are to be used with a lamp16having a different shape, then the existing attachments21,31are replaced with other attachments shaped to match the lamp16. Therefore, the heat sinks20,30can be held in close contact with the lamp16for a desired cooling capability without the need for changing the heat radiating structure in its entirety.

Since the fins23,33are removably mounted on the base blocks22,32, fins23,33having a different heat radiating area and made of a different material may be used depending on the temperature to which the lamp16is heated, thereby allowing the heat sinks20,30to be used with a plurality of types of lamps having different output specifications. Specifically, if the heat sinks20,30are to be used with a lamp16having a greater output capability, i.e., generating a greater amount of heat, then the existing fins23,33are replaced with fins23,33having a greater heat radiating area or made of a material having a greater heat radiating capability. Therefore, the heat sinks20,30can maintain a high cooling capability while at the same time keeping the heat radiating structure unchanged in its entirety.

With the heat radiating structure according to the present embodiment, since the fins23,33extend horizontally, the vertical dimension, i.e., the thickness, of the lamp unit14incorporating the fins23,33is relatively small. Even if the heat sinks20,30are used with a lamp16having a different shape or output specifications, the vertical dimension of the lamp unit14remains unchanged though the attachments21,31and the fins23,33may be changed. Therefore, the heat radiating structure can be used with a plurality of types of lamps without the need for major design changes such as changes in the appearance.

Because the attachments21,31, the base blocks22,32, and the fins23,33are of a separable structure, casting and machining restrictions on those components are much smaller than if the components are of a unitary structure. As the components may thus be available in various shapes and materials, the heat radiating structure may be of a low total cost while maintaining a high heat radiating capability.

FIG. 11shows a heat radiating structure according to another embodiment of the present invention. The heat radiating structure shown inFIG. 11includes fins23,33having a modified shape. InFIG. 11, the fins23,33are inclined at an angle to the base blocks so as to be oriented in the direction in which cooling air W from a cooling fan is applied obliquely to the heat sinks20,30. Accordingly, the cooling air W from the cooling fan flows smoothly between the fins23,33for effectively and efficiently cooling the lamp16.

As shown inFIGS. 5 and 8, electrode terminals27,37serving as a voltage applying section for applying a voltage to the lamp16are mounted on the base blocks22,32, respectively. A power supply circuit, not shown, has output terminals connected respectively to the electrode terminals27,37. The voltage supplied from the power supply circuit is applied from the electrode terminals27,37through the base blocks22,32and the attachments21,31to the front and rear cases17A,17B which serve as the electrodes of the lamp16, thereby energizing the lamp16. The electrode terminals27,37are sufficiently insulated from each other by an air layer that is present between the heat sinks20,30.