Abstract:
A lamp unit and an intake fan are connected together by a duct, and a partition plate is formed within the duct so as to extend between the two ends of the duct, thus dividing the interior of the duct into a plurality of blocks, and thereby venting between the two ends of the duct. Furthermore, the partition plate intersects the direct optical path of emitted ultraviolet light passing from the lamp along within the duct towards the intake fan. This ultraviolet light does not arrive directly at the intake fan, since the partition plate cuts off the ultraviolet light emitted from the lamp directly towards the fan, so that it is possible to prevent the intake fan from being bathed in this ultraviolet light.

Description:
CROSS REFERENCE  
       [0001]     This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2006-101796 filed in Japan on Apr. 3, 2006, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a projector having a construction in which ultraviolet radiation, which is irradiated from a lamp unit in the direction of a cooling fan, is intercepted.  
         [0003]     Projectors are per se known in the prior art which irradiate light from a lamp upon an image display device such as a digital micro mirror device (DMD) or a liquid crystal display device, thus projecting an image displayed on this image display device upon a screen.  
         [0004]     With this type of projector, an ultra high voltage mercury lamp is used as a light source, and it attains an extremely high temperature due to generation of heat. Furthermore, in order for the lamp to emit light at high efficiency, it is necessary to keep the temperature of the lamp constant. Thus, as described in Japanese Laid-Open Patent Publication 2005-173019, a projector has been proposed of a structure in which the interior of the lamp unit is vented by the fan, in order to cool the lamp and to keep its temperature constant.  
         [0005]     Along with revision of the UL standard, in the case of plastic resin components for a projector which are directly bathed in UV light from the lamp which is used for a light source, it is necessary for all of them to conform a standard of ultraviolet radiation resistance.  
         [0006]     However, no fan for air cooling a lamp unit has actually been produced in practice, in which a resin which conforms to the standard of ultraviolet radiation resistance described above is used for both the chassis and the blades.  
         [0007]     Because of this, if a fan made from resin is to be used as the fan for cooling the lamp unit, it has been necessary to provide a construction in which the fan is not directly bathed in the light from the lamp unit.  
         [0008]     Furthermore it is known by experience that, with a projector, if the target of the air flow which the intake fan blows for cooling the lamp is made to be the central portion of the lamp bulb, then the lamp emits light at high efficiency. However since, if a path is provided which directs an air flow at this target in a straight line, then the UV light from the lamp directly impinges upon the case of the intake fan which is made from resin, accordingly it becomes impossible to conform to the ultraviolet radiation resistance standard which is prescribed by the UL standard.  
         [0009]     Due to this, if the UL standard is to be complied with, then it is necessary to implement some countermeasure for making the path for the air flow between the intake fan and the lamp in a shape which is not a straight line, or the like. However, if this is done, then the efficiency at which air is blown for air cooling also becomes bad, since the space occupied between the light source lamp and the intake fan becomes larger.  
         [0010]     The object of the present invention is to provide a projector with a lamp unit cooling fan which has a structure which can air cool the lamp unit with good efficiency, without being bathed in ultraviolet radiation emitted from the lamp unit.  
       SUMMARY OF THE INVENTION  
       [0011]     A projector according to the present invention comprises a lamp unit containing a lamp which emits light for projecting an image upon a screen; a fan which air cools the interior of said lamp unit; a duct, connected between said fan and said lamp unit, which feeds air blown by said fan towards said lamp unit; and a partition plate within said duct, formed in a shape extending along the flow of air fed in towards said lamp unit.  
         [0012]     The partition plate is arranged in a position which intersects the direct optical path of light from said lamp entering into said duct.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a perspective view, schematically showing the internal structure of a projector;  
         [0014]      FIG. 2  is a planar cutaway view showing the general structure of a lamp unit of this projector, and of the surroundings thereof;  
         [0015]      FIG. 3  is a perspective view showing the positional relationship of this lamp unit and of a duct and an intake fan;  
         [0016]      FIG. 4A  is an enlarged view of the lamp unit, duct, and intake fan; and  
         [0017]      FIG. 4B  is an enlarged view of the duct and intake fan on their own. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]      FIG. 1  is a perspective view, schematically showing the internal structure of a projector. This projector  1  comprises a lamp unit  10 , an image projection unit  30 , a power supply board  40 , a control board  50 , a main fan  60 , and another main fan  70 . Each of these is fitted to a chassis  80 .  
         [0019]     The lamp unit  10  emits light for image projection. Moreover, the lamp unit  10  is stored within a lamp unit storage unit  20 , and can be removed from the projector  1  through the bottom surface of its main portion.  
         [0020]     The image projection unit  30  comprises an image display device such as a DMD or the like and a color wheel, neither of which is shown in the figures. Using light from the light unit  10 , this unit  30  projects an image formed by the image display device through a projection lens  31 .  
         [0021]     The power supply boards  40  and  41  supply electrical power to the lamp unit  10  and so on. And the control board  50  controls the operation of the color wheel and the image display device and so on, provided to the unit  30 .  
         [0022]     The main fans  60  and  70  are propeller fans, and are fitted in respective air intake apertures  81  and  82  which are formed in one side of the chassis  80 . These main fans  60  and  70  suck in external air through the intake apertures  81  and  82 , and exhaust this air through exhaust apertures  83  and  84  which are formed in the opposite side of the chassis  80 . The interior of the projector  1  is air cooled in this manner.  
         [0023]     Furthermore, this projector  1  comprises an intake fan  91  for air cooling the lamp unit  10 . This intake fan  91  sucks in air which has been blown into the interior of the projector main body by the main fans  60  and  70 , and thereby cools a lamp which is provided within the lamp unit  10 . Air which is discharged from an exhaust aperture  93  of the lamp unit t  10  strikes against a partition plate  94 , and is then discharged to the interior of the projector main body by the main fans  60  and  70 .  
         [0024]      FIG. 2  is a planar cutaway view showing the general structure of the lamp unit  10 , and of the surroundings thereof. And  FIG. 3  is a perspective view showing the positional relationship of this lamp unit  10  and of a duct and the intake fan  91 .  
         [0025]     As shown in  FIG. 2 , this lamp unit  10  comprises a lamp  11  which comprises a lamp bulb  12  and a reflector  13 , a front cover  14 , a rear cover  15 , a cable not shown in the figures which supplies electrical power to the lamp bulb  12 , and the like.  
         [0026]     As mentioned above, the lamp unit  10  houses the lamp unit storage unit  20 . The front cover  14  and the rear cover  15  of the lamp unit  10  are sealed to it, so that no air leaks from their joining portions. This front cover  14  and rear cover  15  are made from aluminum.  
         [0027]     The front cover  14  is formed with a projection aperture  141  through which light from the lamp bulb  12  is projected, and with an intake aperture  142  for entry of air for cooling the lamp  11 . This front cover  14  is fitted to a front surface of the lamp  11 .  
         [0028]     The rear cover  15  has an exhaust aperture  151  for discharge of air which has cooled the lamp  11 . Furthermore, the exhaust aperture  151  is connected with an exhaust aperture  18  which is formed in a wall  17  of the lamp unit storage unit  20 . This rear cover  15  is fitted to a rear surface of the lamp  11 .  
         [0029]     Moreover, as shown in  FIGS. 2 and 3 , the intake fan  91  and a duct  92  are attached to the lamp unit  10 . This intake fan  91  is a sirocco fan (a sirocco type multi-bladed fan), and an exhaust aperture  912  thereof functions to join it to an intake aperture  921  of the duct  92 . Furthermore, an exhaust aperture  922  of the duct  92  joins it to the intake aperture  142  of the front cover  14  of the lamp unit  10 . Even further, the duct  92  and the intake aperture  142  of the front cover  14  are arranged in a configuration which is directed so as to blow air towards and against the lamp bulb  12 .  
         [0030]     With the present invention, since the structure is as described above, the intake fan  91  blows air which it has sucked in from its intake aperture  911  directly against the lamp bulb  12  of the lamp  11  from the front, and thus is able to cool the lamp bulb  12 . In other words, the lamp  11  is cooled by a flow of air as shown by the black arrow signs  101 ˜ 112  in  FIG. 2 . First, air which has been sucked in by the intake fan  91  through its intake aperture  911  passes along the duct  92 , and is blown against the lamp bulb  12  in the lamp unit  10  from the intake aperture  142  of the front cover  14  (as shown by the black arrow signs  101 ˜ 104 ). This air which is blown against the lamp bulb  12  cools the lamp bulb  12 . Then the air which has been thus blown against the lamp bulb  12  passes along the vicinity of the inner surface of the reflector  13 , proceeds between the rear cover  15  and the reflector  13 , and then is exhausted from the exhaust aperture  151  (as shown by the black arrow signs  105 ˜ 112 ).  
         [0031]     Next, the characteristic structure of the present invention will be explained. As shown in  FIG. 2 , the ultraviolet light (UV light)  121 U in the lamp light which is emitted from the light emission point  121  of the lamp bulb  12  passes through within the lamp bulb  12  and arrives at the intake fan  91 , which is not desirable. Due to this, the intake fan  91  becomes unable to satisfy the UL regulations, since it is bathed in this ultraviolet light (UV light) included in the lamp light.  
         [0032]     Thus, with the present invention, the duct  92  which connects between the intake fan  91  and the lamp unit  10  is formed from a plastic resin which satisfies the ultraviolet radiation resistance standard prescribed by the UL regulations. Furthermore, with the present invention, a partition plate  923  is provided within the duct  92 , along the flow of the feed in air (the air flow) from the intake fan  91  to the lamp unit  10 . In  FIG. 2 , as an example, the partition plate  923  is provided from the intake aperture  921  of the duct  92  all the way across to its exhaust aperture  922 , thus dividing it into two sub-apertures  922 A and  922 B. Furthermore, this partition plate  923  is arranged in a position so as to intersect the optical path of the lamp light  121 U which is emitted from the light emission point  121  of the lamp bulb  121  and is incident upon the exhaust aperture  921  of the duct  92 . By providing the partition plate  923  in this manner, it is possible to intercept the ultraviolet light included in the lamp light emitted from the light emission point of the lamp bulb  12  directly towards the intake fan  91 , without any hindrance being opposed to the flow of air within the duct  92 .  
         [0033]     Since the ultraviolet light which is emitted from the lamp bulb  12  in the direction of the intake fan  91  does not impinge directly upon this fan  91 , accordingly it is possible to employ even a fan which is not made from a plastic resin which satisfies the ultraviolet radiation resistance standard prescribed by the UL regulations, without any problem occurring.  
         [0034]     Moreover since, as described above, by providing the partition plate  923  within the interior of the duct  92  and endowing it with a function of acting as a plate which provides shielding from light, it is possible to utilize a duct of a straight tubular form which does not require any bending process for its manufacture, accordingly it is possible to feed in blown air to the lamp unit  10  at high efficiency.  
         [0035]     Furthermore, it would also be acceptable to perform a process upon the inner surface of the duct  92  and upon the partition plate  923  in order to enhance their absorption of ultraviolet light. In other words, it would be possible to form the duct  92  and/or the partition plate  923  from a resin which functions to absorb ultraviolet radiation, or to coat the inner surface of the duct  92  and/or the partition plate  923  with a material which is endowed with an ultraviolet radiation absorption function, or to apply a paint which is endowed with an ultraviolet radiation absorption function upon the inner surface of the duct  92  and/or the inner surface of the partition plate  923 . By doing this, even if the ultraviolet light which is emitted by the lamp  11  is incident upon the inside of the duct  92 , nevertheless this ultraviolet light is absorbed by the inner surface of the duct  92  and by the partition plate  923 . Accordingly, it is possible to prevent this ultraviolet light from being reflected so as to shine upon the intake fan  91 .  
         [0036]     Yet further, it would also be acceptable to perform a process upon the inner surface of the duct  92  and upon the partition plate  923  in order to prevent reflection therefrom. Since, by doing this, the ultraviolet light which is incident upon the inside of the duct  92  is not reflected within the duct, accordingly this ultraviolet light can be prevented from impinging upon the intake fan  91 .  
         [0037]      FIG. 4A  is an enlarged view of the lamp unit, duct, and intake fan. Moreover,  FIG. 4B  is an enlarged view of the duct and intake fan on their own. In this projector  1 , at the light emission point  121  of the lamp bulb  12  and at the tip end portion  122  of the lamp bulb  12 , the amounts of heat generation and the temperatures at which they are to be kept constant are different. Due to this, it is necessary to vary the amount of air blown against the lamp bulb  12  according to its position. Accordingly, with the present invention, the amounts of air which is blown into the intake aperture  142  of the cover  14  from the exhaust apertures  922 A and  922 B of the duct  92  are adjusted by varying the position at which the partition plate  923  is provided within the duct  92 , and by changing the orientation of the partition plate. For example, as shown in  FIG. 4A , in the shape of the duct  92  in the vicinity of one of the exhaust apertures  922 A, the direction of the tip end portion of the partition plate  923  may be processed so as to blow air from this exhaust aperture  922 A towards the light emission point  121  of the lamp bulb  12 . Or, in the shape of the duct  92  in the vicinity of the other exhaust aperture  922 B, the configuration of the partition plate  923  may be arranged so that air is blown from this exhaust aperture  922 B towards the tip end portion of the lamp bulb  12 .  
         [0038]     Moreover, as shown in  FIG. 4B , the position at which the partition plate is fitted may be adjusted, so that so that the width within the duct  92  at which it is partitioned by the partition plate  923  is varied. For example, the configuration of the partition plate  923  may be arranged so that the amount of air which is blown out from the exhaust aperture  922 A becomes greater than the amount of air which is blown out from the exhaust aperture  922 B. By doing this, it is possible to blow more air against the light emission point  121  of the lamp bulb  12 .  
         [0039]     Since it is possible, in this manner, to blow air in a suitable amount according to the position of the lamp bulb  12 , accordingly it is possible to keep the light emission point of the lamp bulb  12  at an appropriate temperature, so that it is possible to emit light with good efficiency.  
         [0040]     It should be understood that while, in the above explanation, the case was explained in which a single partition plate  923  was provided within the duct  92 , so that the duct was partitioned into two air paths, the present invention should not be limited to this particular structure; it would also be possible, for example, to provide a plurality of these partition plates, so as to divide the interior of the duct  92  into more than two paths. By doing this, it would become possible to adjust the orientation of the air flow which is blown out from the duct more finely, so that it would become possible to adjust the temperature of the lamp bulb  12  more finely.  
         [0041]     Finally, in the above described explanation of an embodiment of the present invention, all of the features are shown by way of example, and should not be considered as being limitative of the present invention. The scope of the present invention is not to be defined by any of the features of the embodiment described above, but only by the scope of the appended Claims. Moreover, equivalents to elements in the Claims, and variations within their legitimate and proper scope, are also to be considered as being included within the range of the present invention.