Patent Publication Number: US-2011063582-A1

Title: Cooling pump unit and projection display apparatus including the same

Description:
TECHNICAL FIELD 
     The present invention relates to a cooling pump unit of a projection display apparatus represented by a liquid crystal projector. 
     BACKGROUND ART 
     For a cooling apparatus of the projection display apparatus, a cooling pump such as a diaphragm pump is used. Generally, the pump has a usable life period. Thus, a cooling apparatus (cooling pump unit) of an exchangeable unit structure is used. 
     The cooling pump vibrates during its operation. The vibration of the cooling pump is transmitted to the casing of the projection display apparatus to generate noise. 
     Japanese Utility Model Application Laid-Open No. 05-13402 describes a pump fixing structure where measures have been taken against pump vibration. The pump fixing structure includes a pressure pump, a cushion material to cover the outer circumferential surface of the pressure pump, a receiving body having a surface on which a half surface of the outer circumference of the pressure pump covered with the cushion material abuts, and a cover body which is joined to the receiving body and by which the pressure pump is pressed against the surface of the receiving body. Absorbing vibration of the pressure pump suppresses generation of noise. 
     The vibration of the pump is transmitted to the casing not only from the outer circumferential surface of the pump but also through a communicating tube attached to the discharge opening of the pump. In the pump fixing structure, while the vibration transmitted to the casing from the outer circumferential surface of the pump is absorbed, the vibration transmitted to the casing through the communicating tube cannot be absorbed. Consequently, the vibration transmitted to the casing through the communicating tube generates noise. 
     Thus, a pump unit has been presented, which can absorb not only the vibration transmitted to the casing from the outer circumferential surface of the pump but also the vibration transmitted to the casing through the communicating tube (see JP2008-96459A). 
       FIG. 8  is a sectional view showing the pump unit described in JP2008-96459A. This pump unit includes main pump body  501  that includes discharge opening  511  and suction opening  512 , communicating tube  503  which is made of an elastomer and one end of which is fitted to discharge opening  511 , and pump fixing portion  502  for fixing a part of communicating tube  503 . Main pump body  501  is fixed to cover  504  only by pump fixing portion  502 . 
     Disk-shaped gasket portion  503   a  is disposed in the other end of communicating tube  503 . When cover  504  is attached to the casing, the other end of communicating tube  503  is pressed against an area of the casing side that includes a ventilating hole. Communicating tube  350  accordingly communicates with the ventilating hole. In this state, gasket portion  503   a  serves to prevent leakage of compressed air supplied through communicating tube  503 . 
     Cushions  513   a  and  513   b , which serves as buffer members, are arranged in portions of the outer circumferential surface of main pump body  501  that come into contact with other members. 
     The vibration of main pump body  501  is transmitted to the casing through the portion for fixing main pump body  501  and a portion contacted by main pump body  501 . According to the configuration shown in  FIG. 8 , a part of communicating tube  503  attached to discharge opening  511  is fixed by pump fixing portion  502 , while main pump body  501  itself is not fixed to cover  4 . Thus, when main pump body  501  is not in contact with any other members, the vibration of main pump body  501  is transmitted to the casing only through communicating tube  503  attached to discharge opening  511 . Communicating tube  503  is made of the elastomer, and hence most of the vibration transmitted through communicating tube  503  to the casing is absorbed by communicating tube  503 . 
     In the state where the circumferential surface of main pump body  501  is in contact with cover  4  or the casing, vibrations of main pump body  501  are transmitted through the contact area to the casing, thereby generating noise. According to the configuration shown in  FIG. 8 , cushions  513   a  and  513   b  are arranged in the areas of the outer circumferential surface of main pump body  501  that come into contact with cover  4  and the casing. Most of the vibration transmitted from the outer circumferential surface of main pump body  501  to the casing side is accordingly absorbed by cushions  513   a  and  513   b.    
     DISCLOSURE OF THE INVENTION 
     However, the pump unit described in JP2008-96459A has the following problems. 
     Generally, a motor is used as the power source of a pump. The motor generates heat, which increases the temperature of the air flow fed by pressure from the pump. In the diaphragm pump, the bearing of the diaphragm generates heat by friction, which increases the temperature of the air flow fed by pressure from the pump. When the temperature of the air flow fed by pressure from the pump increases, communicating tube  503  is heated by the air flow, and the temperature of communicating tube  503  increases. Communicating tube  503  is made of an elastomer such as rubber, and hence the temperature increase is accompanied by an increase in communicating tube length A shown in  FIG. 8 . As a result, force is applied on main pump body  501  to press main pump body  501  in a direction (first direction) opposed to communicating tube  503  side. 
     Cushions  513   a  and  513   b  are made of foam materials excellent in buffer performance and sound insulation. Friction coefficients of the surfaces thereof are accordingly high. Thus, in the contacted state of cushions  513   a  and  513   b  with cover  504  or the casing, when the force of the first direction is applied on main pump body  501 , frictional forces on the contacted portions may be greater than the force of the first direction. In this case, the force of the first direction is received by cushions  513   a  and  513   b  that are in contact with the outer circumferential surface of main pump body  501 , which results in the crushing of cushions  513   a  and  513   b  by main pump body  501 . When cushions  513   a  and  513   b  are crushed, a crushing margin for absorbing the vibration of the pump is reduced by a corresponding amount. This results in a problem in which noise is generated because of insufficient absorption of the vibration of the pump by cushions  513   a  and  513   b.    
     When the frictional forces are smaller than the force of the first direction, main pump body  501  moves in the first direction. The movement of main pump body  501  causes wear of cushions  513   a  and  513   b  on the contacted portions. When the pump stops, the temperature of communicating tube  503  drops due to natural cooling, which is accompanied by a reduction in communicating tube length A. In this case, force is applied in a second direction reverse to the first direction to move main pump body  501  in the second direction. This movement of main pump body  501  also causes wear of cushions  513   a  and  513   b  on the contacted portions. Thus, when the pump is driven or stopped, main pump body  501  moves in the first or second direction, causing wear of cushions  513   a  and  513   b . With further wear of cushions  513   a  and  513   b , the buffer performance of the cushions is reduced. This results in a problem in which noise is generated because of insufficient absorption of the vibration of the pump by cushions  513   a  and  513   b.    
     Vibration during transport causes movement of main pump body  501 , which results in the wear of cushions  513   a  and  513   b . This wear increases noise. 
     It is an object of the present invention to provide a pump unit capable of solving the abovementioned problems and suppressing generation of noise caused by crushing or wear of cushions, and a projection display apparatus. 
     In order to achieve the object, a pump unit according to the present invention includes a cooling pump for discharging compressed air, and a cover for housing the cooling pump. The pump unit includes: 
     a communicating tube made of an elastomer, and having one end fitted to a discharge opening of the cooling pump, and a portion other than the fitting portion set as a fixing portion with the cover; 
     buffer members arranged on an outer circumferential surface of the cooling pump; and 
     lubricating members arranged on surfaces of the buffer members. 
     In this case, the lubricating members include smooth surfaces, and friction coefficients of the smooth surfaces are smaller than those of the buffer members. 
     Another pump unit according to the present invention includes a cooling pump for discharging compressed air, and a cover for housing the cooling pump. The pump unit includes: 
     a communicating tube made of an elastomer, and having one end fitted to a discharge opening of the cooling pump, and a portion other than the fitting portion set as a fixing portion with the cover; 
     lubricating members arranged on an inner surface of the cover; and 
     lubricating members arranged on surfaces of the buffer members. 
     In this case, the lubricating members include smooth surfaces, and friction coefficients of the smooth surfaces are smaller than those of the buffer members. 
     A projection display apparatus according to the present invention includes a light source, and an optical system that projects image light obtained by spatially modulating light from the light source. The projection display apparatus includes: 
     a casing for housing the light source and the optical system; and 
     a pump unit attached to the casing. 
     In this case, the pump unit includes: 
     a cooling pump for discharging compressed air; 
     a communicating tube made of an elastomer, and having one end fitted to a discharge opening of the cooling pump, and a portion other than the fitting portion set as a fixing portion with the cover; 
     buffer members arranged on an outer circumferential surface of the cooling pump; and 
     lubricating members arranged on surfaces of the buffer. members. 
     The lubricating members include smooth surfaces, and friction coefficients of the smooth surfaces are smaller than those of the buffer members. 
     At least the light source is cooled by the compressed air introduced into the casing through the communicating tube. 
     Another projection display apparatus according to the present invention includes a light source, and an optical system that projects image light obtained by spatially modulating light from the light source. The projection display apparatus includes: 
     a casing for housing the light source and the optical system; and 
     a pump unit attached to the casing. 
     In this case, the pump unit includes: 
     a cooling pump for discharging compressed air; 
     a communicating tube made of an elastomer, and having one end fitted to a discharge opening of the cooling pump, and a portion other than the fitting portion set as a fixing portion with the cover; 
     lubricating members arranged on an inner surface of the cover; and 
     lubricating members arranged on surfaces of the buffer members. 
     The lubricating members include smooth surfaces, and friction coefficients of the smooth surfaces are smaller than those of the buffer members. 
     A least the light source is cooled by the compressed air introduced into the casing through the communicating tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [ FIG. 1 ]A perspective view showing a pump unit according to an embodiment of the present invention. 
       [ FIG. 2 ] An exploded perspective view of the pump unit shown in  FIG. 1 . 
       [ FIGS. 3A and 3B ] Explanatory diagrams of a state where a main pump body shown in  FIG. 1  is fixed by a pump fixing portion:  FIG. 3A  is a top view, and  FIG. 3B  is a sectional view taken along the line A-A shown in  FIG. 3A . 
       [ FIG. 4 ] A schematic view showing an example of a cushion structure provided in the main pump body shown in  FIG. 1 . 
       [ FIG. 5 ] A perspective view showing a configuration of a projector on which the pump unit shown in  FIG. 1  is mounted. 
       [ FIG. 6 ] A perspective view showing a configuration of a member for forming a main-body cooling ventilating hole shown in  FIG. 5 . 
       [ FIG. 7 ] A sectional view showing a loaded state of the pump unit shown in  FIG. 1  on a casing. 
       [ FIG. 8 ] A sectional view of a pump unit described in JP2008-96459A. 
     
    
    
     EXPLANATIONS OF REFERENCE NUMERALS 
     
         
         
           
               1  Main pump body 
               2  Pump fixing portion 
               3  Communicating tube 
               3   a  Gasket portion 
               4  Cover 
               4   a  Projection 
               6  Electric contact 
               13   a ,  13   b  Cushion 
               15   a ,  15   b  Film 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, referring to the drawings, an embodiment of the present invention is described. 
       FIG. 1  is a perspective view showing a configuration of a pump unit according to the embodiment of the present invention, and  FIG. 2  is an exploded perspective view of the pump unit shown in  FIG. 1 . 
     Referring to  FIG. 1  and  FIG. 2 , the pump unit is a detachable unit attached to a casing of an electronic device that includes a heat source such as a light source. A main portion thereof includes main pump body  1 , pump fixing portion  2 , communicating tube  3 , and cover  4 . Main pump body  1  is a pressure pump such as a diaphragm pump. 
     A portion of main pump body  1  likely to come into contact with other members is covered with a cushion member serving as a buffer member. The cushion member is made of an elastomer such as spongy rubber or a synthetic resin (foam material) capable of absorbing vibration or shocks. In  FIG. 1 , an outer circumferential surface of main pump body  1  is covered with cushions  13   a  and  13   b.    
     Films  15   a  and  15   b  serving as lubricating members are formed on surfaces of cushions  13   a  and  13   b . Surfaces of films  15   a  and  15   b  are smooth, and friction coefficients thereof are smaller than those of the surfaces of cushions  13   a  and  13   b . Films  15   a  and  15   b  and cushions  13   a  and  13   b  are fixed together by, for example, adhesives. For films  15   a  and  15   b , polyethylene terephthalate (PET) sheets, polycarbonate (PC) sheets, or kapton sheets can be used. When cushions are formed on curved surfaces, the thicknesses of films  15   a  and  15   b  are advisably set to 0.05 millimeters to 0.5 millimeters. According to the embodiment, for films  15   a  and  15   b , PET sheets having thicknesses of 0.15 millimeters are used. 
     Main pump body  1  gets air from suction opening  12 , compresses the air, and discharges the compressed air from discharge opening  11 . Cylindrical filter  14  is attached to suction opening  12  to prevent incursion of dust into the pump. 
     Communicating tube  3  is made of an elastomer such as rubber or a synthetic resin, and has its one end fitted to discharge opening  11 . Disk-shaped gasket portion  3   a  is disposed in the other end of communicating tube  3 . In a state where the other end of communicating tube  3  is pressed against an area of a casing side that has a ventilating hole that enables communication between communicating tube  3  and the ventilating hole, gasket portion  3   a  serves to prevent leakage of the compressed air supplied through communicating tube  3 . 
     Cover  4  includes projection  4   a  inserted into a hole formed in a predetermined place of a unit attaching portion of the casing, receiving portion  4   b  engaged with the projection located in the predetermined place of the unit attaching portion, a plurality of outside aid inlets  4   c , and hole  4   d  for screwing cover  4  to the casing. Engaging the projection of the casing side with receiving portion  4   b  in the inserted state of projection  4   a  into the hole of the casing side enables accurate attaching positioning of the pump unit to the casing. In the positioned state, hole  4   d  is located directly above a screw hole formed in a predetermined place of the casing. Through hole  4   d , a screw is inserted into the screw hole of the casing side to fix cover  4  to the casing. 
     Cover  4  includes, in its inner wall, pump fixing portion  2  for fixing main pump body  1 , and electric contact support portion  5 . Electric contact support portion  5  is for attaching electric contact  6 . Projection  5   a  and hole  5   b  for inserting rivet  7  are formed in an attaching surface of electric contact  6 . Electric contact  6  includes the construction in which a plurality of contacts is arranged on a substrate to interconnect pump man body  1  and a pump driving portion (not shown). On the substrate, hole  6   a  into which projection  5   a  is fitted, and hole  6   b  into which rivet  7  is inserted are formed. In the fitted state of hole  6   a  of electric contact  6  around projection  5   a  of electric contact support portion  5 , rivet  7  is inserted into holes  6   b  and  5   b  to fix electric contact  6  to electric contact support portion  5 . 
     Pump fixing portion  2  includes pressing member  21  and receiving member  22 . Receiving member  22  is formed into a U shape in section, and includes wall portion  221  of a front side (side where the ventilating hole of the casing is located during unit loading), wall portion  222  of a rear side (side where main pump body  1  is located), and columnar screwing portion  223  disposed between these wall portions to screw pressing member  21 . Front receiving portion  221   a  and rear receiving portion  222   a  are respectively formed on upper ends of wall portions  221  and  222 . Front receiving portion  221   a  and rear receiving portion  222   a  are formed by notching parts of the wall portions in concave shapes. 
     Pressing member  21  includes wall portion  211  of a front side having its lower end abutted on the upper end of wall portion  221  and wall portion  212  of a rear side having its lower end abutted on the upper end of wall portion  222 . Columnar guide portion  213  is disposed between wall portions  211  and  212  to guide insertion of the screw into screwing portion  223 . Front receiving portion  211   a  and rear receiving portion (not shown) are respectively formed in the lower ends of wall portions  211  and  212 . Front receiving portion  211   a  and rear receiving portion are formed by notching parts of the wall portions in concave shapes. 
     In the screwed state of pressing member  21  to receiving member  22 , wall portion  211  of pressing member  21  and wall portion  221  of receiving member  22  constitute a uniform surface. On a part of the surface, front receiving portion  211   a  of wall portion  211  and front receiving portion  221   a  of wall portion  221  constitute an opening. Since the diameter of the opening is smaller than the outer diameter of communicating tube  3 , a part of communicating tube  3  can be fixed by the opening. Similarly, in the screwed state, wall portion  212  of pressing member  21  and wall portion  222  of receiving member  22  constitute a uniform surface. On a part of the surface, the rear receiving portion of wall portion  212  and rear receiving portion  222   a  of wall portion  222  constitute an opening. The space generated by this opening is large enough to insert discharge opening  11  and suction opening  12  of main pump body  1 . Discharge opening  11  and suction opening  12  of main pump body  1  do not come into contact with the rear receiving portion of wall portion  212  and rear receiving portion  222   a  of wall portion  222 . 
       FIGS. 3A and 3B  are explanatory diagrams of a state where main pump body  1  is fixed by pump fixing portion  2 :  FIG. 3A  is a top view, and  FIG. 3B  is a sectional view taken along the line A-A shown in  FIG. 3A . 
     As shown in  FIG. 3A , pressing member  21  is screwed to receiving member  22  by screws  8 . As shown in  FIG. 3B , one end of communicating tube  3  is fitted to discharge opening  11  of main pump body  1 . A part of a portion (portion that includes gasket portion  3   a ) of communicating tube  3 , excluding the portion fitted to discharge opening  11 , is fixed by front receiving portion  211   a  of wall portion  211  and front receiving portion  221   a  of wall portion  221 . Gasket portion  3   a  is disposed on the uniform surface constituted by wall portions  211  and  221 . During unit loading, gasket portion  3   a  prevents leakage of compressed air supplied through communicating tube  3 . Discharge opening  11  and suction opening  12  of pump man body  1  are arranged in the opening constituted by rear receiving portion  212   a  of wall portion  212  and rear receiving portion  222   a  of wall portion  222 . 
     Vibrations from main pump body  1  are transmitted to the casing through a portion of fixing main pump body  1  and a portion contacted by main pump body  1 . According to the fixed state shown in  FIGS. 3A and 3B , a part of communicating tube  3  attached to discharge opening  11  is fixed by pump fixing portion  2 . This means that main pump body  1  is not actively fixed. In other words, no unit is provided to fix main pump body  1  itself to cover  4 . Thus, unless main pump body  1  is in contact with the other members, the vibrations from main pump body  1  are transmitted to the casing only through communicating tube  3  attached to discharge opening  11 . However, since communicating tube  3  is made of the elastomer, most of the vibrations transmitted from main pump body  1  to communicating tube  3  are absorbed by communicating tube  3 . This prevents problems such as generation of noise due to transmission of vibrations from main pump body  1  through pump fixing portion  2  to the casing. 
     The pump is fixed only by communicating tube  3 , and hence main pump body  1  may come into contact with cover  4  or the casing. Cushions  13   a  and  13   b  area arranged on portions of the outer circumferential surface of main pump body  1  likely to come into contact with cover  4  or the casing. Most of the vibrations transmitted from the outer circumferential surface of main pump body  1  to cover  4  or the casing are accordingly absorbed by cushions  13   a  and  13   b.    
     When a power source (motor) of main pump body  1  or the bearing of the diaphragm generates heat, and the heat raises the temperature of the air flow fed by pressure from discharge opening  11 , the temperature of communicating tube  3  increases. The temperature increase is accompanied by an increase in the length of communicating tube  3  due to thermal expansion. Consequently, a force is applied on main pump body  1  to press main pump body  1  in a direction (first direction) opposed to communicating tube  3  side. Films  15   a  and  15   b  serving as lubricating members are formed on the surfaces of cushions  13   a  and  13   b . Sufficiently reducing friction coefficients of the smooth surfaces of films  15   a  and  15   b  enables setting of frictional forces on contact surfaces between the smooth surfaces and the other members (the cover and the casing) smaller than that (force of a first direction) applied on the cooling pump by thermal expansion of communicating tube  3 . When the frictional forces on the contact surfaces are smaller than that of the first direction generated by the thermal expansion of communicating tube  3 , cooling pump  1  moves in the first direction. Crushing of films  15   a  and  15   b  by the force of the first direction can accordingly be suppressed. Thus, the vibration of the pump can be sufficiently absorbed by films  15   a  and  15   b  to reduce noise. 
     The surfaces of cushions  13   a  and  13   b  are protected by films  15   a  and  15   b  serving as the lubricating members. This prevents wear of cushions  13   a  and  13   b  when main pump body  1  moves following driving or stopping of the pump, or when main pump body  1  moves due to vibration during transport. Thus, buffer performance and sound insulation of cushions  13   a  and  13   b  can be maintained for a long period of time. 
     The places where the cushions are installed are not limited to the outer circumferential surface of main pump body  1 . In addition to the outer circumferential surface of main pump body  1 , the cushions can be arranged in other contact areas that come into contact with main pump body  1 . For example, a rear portion of main pump body  1  (the portion opposed to the side that includes discharge opening  11 ) comes into contact with electric contact support portion  5 , or suction opening  12  comes into contact with rear receiving portion  212   a  of wall portion  212 . The surface of main pump body  1  that includes discharge opening  11  and suction opening  12  comes into contact with the surface constituted by wall portion  212  of pressing member  21  and wall portion  222  of receiving member  22 . In such a case, a cushion is advisably installed in each contact area. Also advisably, a lubricating member such as a film is installed in a surface of the cushion disposed in each contact area to suppress wear of the cushion. 
       FIG. 4  shows an example of a cushion structure provided in main pump body  1 . Referring to  FIG. 4 , the outer circumferential surface of main pump body  1  is covered with cushions  13   a  and  13   b , suction opening  12  is covered with cushion  13   c , and the surface of main pump body  1  that includes discharge opening  11  and suction opening  12  is covered with cushion  13   d . Cushion  13   d  is almost equal in size to the surface that includes discharge opening  11  and suction opening  12 , and includes holes to insert discharge opening  11  and suction opening  12 . Films  15   a  and  15   b  serving as lubricating members are arranged on surfaces of cushions  13   a  to  13   d.    
     According to the cushion structure shown in  FIG. 4 , when the outer circumferential surface of main pump body  1  comes into contact with the inner wall of cover  4  (including electric contact support portion  5 ) or the members of the casing side, vibrations from main pump body  1  or shocks to pump man body  1  are absorbed by cushions  13   a  and  13   b . When suction opening  12  comes into contact with rear receiving portion  212   a  of wall portion  212 , vibrations from main pump body  1  or shocks to main pump body  1  are absorbed by cushion  13   c . When the surface that includes discharge opening  11  and suction opening  12  comes into contact with the surface constituted by wall portion  212  of pressing member  21  and wall portion  222  of receiving member  22 , vibrations from main pump body  1  or shocks to main pump body  1  are absorbed by cushion  13   d.    
     The surfaces of cushions  13   a  to  13   d  are protected by films  15   a  to  15   d  serving as the lubricating members. This prevents wear of cushions  13   a  to  13   d  when main pump body  1  moves following driving or stopping of the pump or when main pump body  1  moves due to vibrations during transport. Thus, buffer performance and sound insulation of cushions  13   a  to  13   d  can be maintained for a long period of time. 
     In the configuration shown in  FIGS. 1 to 4 , cushions  13   a  and  13   b  are arranged to cover the entire outer circumferential surface of main pump body  1  in a circumferential direction. However, the arrangement is not limited to this. Cushions  13   a  and  13   b  can be formed only in places of the outer circumferential surface that come into contact with the other members. Limiting a forming range of cushions enables cost reduction. Advisably, however, a range of contact areas (range where cushions are arranged) is determined based on a moving range of main pump body  1  due to thermal expansion of communicating tube  3  or vibration during the transport. 
     When the cushions are partially provided, cushion sticking positions must be accurately obtained. On the other hand, when the cushions are arranged over the entire circumference, cushion sticking positions do not need to be obtained accurately, and hence the cushions can be easily struck to main pump body  1 . Cushions  13   c  and  13   d  can also be formed only in places that come into contact with the other members. 
     Films  15   a  and  15   b  are formed on the entire surfaces of cushions  13   a  to  13   d . However, the arrangement is no limited to this. Films  15   a  and  15   b  can be formed only in some parts (places that come into contact with the other members) of the surfaces of cushions  13   a  to  13   d . In this case, similarly, a range of contact areas (range where films are stuck) is advisably determined based on the moving range of main pump body  1  due to thermal expansion of communicating tube  3  or vibration during transport. Limiting a film forming range enables cost reduction. 
     When the films are partially provided, film sticking positions on the cushion surfaces must be accurately obtained. On the other hand, when the films are arranged on the entire cushion surfaces, film sticking positions do not need to be accurately obtained, and hence the films and the cushions can be easily stuck together. 
     Next, a structure of attaching the pump unit according to the embodiment to a casing of an electronic device will be described. 
       FIG. 5  is a perspective view showing a configuration of a projector on which the pump unit according to the embodiment is mounted. Referring to  FIG. 5 , projector  200  includes casing  200   a  for housing a light source, a liquid crystal display panel, and an illumination optical system that irradiates the liquid crystal panel with light from the light source, and detachable pump unit  100  loaded on casing  200   a . Pump unit  100  is the aforementioned pump unit according to the embodiment. 
     A portion of casing  200   a  to fix pump unit  100  includes member  201  for forming a main-body cooling ventilating hole, to which gasket portion  3   a  of communicating tube  3  is pressed, projection  202  engaged with receiving portion  4   b  of cover  4 , and hole  203  to insert projection  4   a  of cover  4 . 
     As shown in  FIG. 5 , member  201  for forming the main-body cooling ventilating hole includes planar receiving portion  2012  having ventilating hole  2011  formed in its center, communicating tube  2013  for connecting ventilating hole  2011  to a tube (communicating tube for guiding compressed air discharged from main pump body  1  to the heat source) in casing  200   a , and protrusion  2014  formed on receiving portion  2012  to surround ventilating hole  2011 . Member  201  for forming the main-body cooling ventilating hole is attached to a wall portion of the side into which projection  4   a  of cover  4  is inserted. Protrusion  2014  is provided to keep airtightness. 
       FIG. 7  shows a sectional structure in a state where pump unit  100  is loaded on casing  200   a . As shown in  FIG. 7 , pump unit  100  is positioned with respect to casing  200   a  by inserting projection  4   a  of pump unit  100  into hole  203  of casing  200   a  and by engaging receiving portion  4   b  of pump unit  100  with projection  202  of casing  200   a . In the positioned state, hole  4   d  is located directly above a screw hole formed in projection  202  of casing  200   a . Pump unit  100  is fixed to casing  200   a  by inserting screw  204  through hole  4   d  into the screw hole of casing  200   a.    
     In the fixed state of pump unit  100  to casing  200   a , gasket portion  3   a  of communicating tube  3  is pressed, by the surface constituted by front wall portions  211  and  221 , against receiving portion  2012  of member  201  for forming the main-body cooling ventilating hole by an appropriate force. This results in a state in which the discharge opening of the end of communicating tube  3  and ventilating hole  2011  of receiving portion  2012  are in communication with each other. Thus, high static-pressure air discharged from discharge opening  11  of main pump body  1  can be supplied from ventilating hole  2011  into the tube in casing  200   a . The heat source such as a light source is located ahead of the tube, and a desired place of the heat source can be cooled by the compressed air from main pump body  1 . 
     The force of pressing gasket portion  3   a  that is applied to receiving portion  2012  is uniform on the entire surface. To obtain the force of pressing gasket portion  3   a  applied against protrusion  2014  of receiving portion  2012 , in the fixed state of pump unit  100  to casing  200   a , an interval D between the surface (pressing surface) constituted by front wall portions  211  and  221  and receiving portion  2012  (ventilating hole forming surface) of member  201  for forming the main-body cooling ventilating hole is set smaller than the total of thickness T 1  of gasket portion  3   a  and thickness T 2  of protrusion  2014 . Depending on a size of the interval D with respect to thickness (T 1 +T 2 ), a force of pressing gasket portion  3   a  against receiving portion  2012  is determined. Since the ([T 1 +T 2 ]−D) value is larger, the force of pressing gasket portion  3   a  against protrusion  2014  is greater. As a result, the effect of preventing air leakage is higher. 
     In the fixed state of pump unit  100  to casing  200   a , the pressing surface and the ventilating hole forming the surface are placed almost parallel to each other. This enables pressing of gasket portion  3   a  against entire protrusion  2014  by a uniform force. 
     Guide portion  213  and screwing portion  223  are arranged on a rear portion of wall portions  211  and  221  (side opposed to the side where gasket portion  3   a  is disposed), thereby increasing rigidity of the surface constituted by wall portions  211  and  221 . Thus, gasket portion  3   a  can be pressed against protrusion  2014  of receiving portion  2012 . 
     Protrusion  2014  is advisably positioned oppositely to the highly rigid portion of the surface constituted by wall portions  211  and  221 . Specifically, protrusion  2014  is advisably disposed in a position facing the portion where guide portion  213  and screwing portion  223  are arranged. Thus, when gasket portion  3   a  is pressed against protrusion  2014  by the surface constituted by wall portions  211  and  221 , gasket portion  3   a  can be crushed by the highly rigid portion of the surface. When the surface is low in rigidity, it is difficult to press gasket portion  3   a  against protrusion  2014  by a uniform force, and air leakage may occur. 
     The pump unit described above is an example of the present invention. The configuration can be appropriately changed without departing from the gist of the present invention. For example, the buffer members (cushions) are arranged in the portions of the main pump body likely to come into contact with the other members. In place of these portions, the buffer members can be located in portions of the cover or the casing side that come into contact with the main pump body side. The buffer members can be arranged on both the main pump body side and the member side of the cover or the casing. In any case, the lubricating members (films) rare arranged on the surfaces of the buffer members. This can prevent problems such as crushing of the cushions or wear of the cushions due to thermal expansion of the communicating tube. 
     The pump unit employs the exchangeable unit structure. However, the pump unit can be a fixed unit integrally attached to the casing. 
     The pump unit of the present invention can be applied to a general computer, a general information processing apparatus represented by a personal computer, and a general display apparatus represented by a liquid crystal display apparatus or a plasma display.