Patent Publication Number: US-2010128457-A1

Title: Fan unit mounting structure

Description:
TECHNICAL FIELD 
     The present invention relates to a fan unit mounting structure used for mounting a fan unit to a fan unit mounting part provided in a casing of an electronic device. 
     BACKGROUND ART 
     In an electronic device such as a liquid crystal display device or a plasma display device, there is mounted a fan unit having a fan for ventilating a casing in order to inhibit the temperature therein from being risen due to heat generated by a heat generating component that is disposed in the casing. 
     One of conventional structures used for mounting fan units of this type is disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. Hei. 8-172287). 
     As shown in  FIG. 14A , a fan unit  100  according to Patent Document 1 includes a fan  101  that is provided with a plurality of rotary blades, a fan housing  102  that accommodates the fan  101  so as to be rotatable therein, and a band clevis  103  that has a substantially U-letter shape in cross section and surrounds to retain the fan housing  102 . 
     As shown in  FIG. 14B , the band clevis  103  is provided at two ends thereof with screwing holes  103   a  and  103   a  respectively so as to correspond to screw holes  104   a  and  104   a  that are formed in a fan unit mounting part  104  disposed in a casing of an electronic device. The fan unit  100  is mounted to the fan unit mounting part  104  with use of screws  105  that are fitted in the screw holes  104   a  and  104   a  in the fan unit mounting part  104  through the screwing holes  103   a  and  103   a , respectively. 
     However, in such a case as described above of mounting the fan unit  100  with use of the screws  105 , vibration of the fan unit  100  caused by the driven (rotating) fan  101  is transmitted to the fan unit mounting part  104  by way of the screws  105 , thereby resulting in a problem of noise generation. 
     In order to solve this problem, there are provided in the fan unit  100  according to Patent Document 1 elastic plates  106  (see  FIG. 14A ) at three locations between the fan housing  102  and the band clevis  103 , and there is also provided an elastic plate  107  (see  FIG. 14B ) between the fan housing  102  and the fan unit mounting part  104 . These elastic plates  106  and  107  inhibit vibration of the fan unit  100  from being transmitted to the fan unit mounting part  104 . 
     As in Patent Document 2 (Japanese Unexamined Patent Publication No. 2001-313483) other than Patent Document 1, there is disclosed another fan unit mounting structure suppressive of such transmission of vibration. 
     According to the fan unit mounting structure disclosed in Patent Document 2, in order to mount a fan unit, a fan housing has four corners each of which is fitted with an elastic body having a concave part therein, and the fan unit is inserted to a receiving part of a casing of an electronic device. In this configuration, the fan unit is made in contact with the casing (the fan unit mounting part) with the four elastic bodies each interposed therebetween. Therefore, the transmission of vibration is suppressed by the respective elastic bodies. 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     Nevertheless, each of the fan unit mounting structures described above involves a large number of components as there are required a screw and an elastic body at each of the locations (generally four) to be fixed. More specifically, the mounting structure according to Patent Document 1 requires at least a band clevis, four elastic bodies, and two screws, while the mounting structure according to Patent Document 2 requires at least four elastic bodies and a receiving part. Therefore, there are necessarily increased the number of assembling steps. 
     Moreover, the elastic bodies adopted in Patent Documents 1 and 2 are each required to have a smaller size relative to the fan unit as well as to be set to have a low degree of hardness (to be soft) (such as the hardness less than 40 degrees) in order to have a vibration-proofing property. Such elastic bodies are deformable even with a slight external force applied thereto, and thus the mounting operation involving such an elastic body requires increased difficulty as well as quite a lot of working hours. In addition, such an elastic body may be easily damaged or displaced, thereby highly possibly resulting in a poor quality. 
     In order to solve the above problems, it is therefore an object of the present invention to provide a fan unit mounting structure that realizes suppression of noise by inhibiting transmission to a fan unit mounting part of vibration caused by a driven fan, as well as facilitates an operation of mounting the fan unit. 
     Means for Solving the Problems 
     In order to achieve the above object, the present invention provides the following configurations. 
     According to a first aspect of the present invention, there is provided a fan unit mounting structure used for mounting a fan unit to a fan unit mounting part in a casing of an electronic device, the structure comprising: 
     a plurality of fan unit mounting projections each extended substantially in parallel with a rotary shaft of a fan included in the fan unit and provided integrally to the fan unit mounting part; and 
     a belt-shaped elastic body hung onto each of the fan unit mounting projections, 
     the belt-shaped elastic body being made in contact with a plurality of locations on an outer peripheral part of the fan unit, and the fan unit being retained, while being spaced apart from the fan unit mounting part in a direction along the rotary shaft of the fan, due to a clipping force of the belt-shaped elastic body. 
     According to a second aspect of the present invention, there is provided the fan unit mounting structure as defined in the first aspect, wherein the fan unit mounting projections are provided to a fan unit mounting frame that is integrally fixed to the fan unit mounting part. 
     According to a third aspect of the present invention, there is provided the fan unit mounting structure as defined in the second aspect, wherein a plurality of contact portions between the belt-shaped elastic body and the outer peripheral part of the fan unit are located so as to be distant respectively from a plurality of contact portions between the belt-shaped elastic body and the respective fan unit mounting projections. 
     According to a fourth aspect of the present invention, there is provided the fan unit mounting structure as defined in the third aspect, wherein 
     the fan unit includes a plurality of flange parts on the outer peripheral part thereof, 
     the belt-shaped elastic body has a plurality of holes at positions respectively corresponding to the flange parts, and 
     the belt-shaped elastic body is hung onto each of the fan unit mounting projections, the flange parts of the fan unit are inserted respectively to the holes in the belt-shaped elastic body, and the fan unit is retained, while being spaced apart from the fan unit mounting part in the direction along the rotary shaft of the fan, due to the clipping force of the belt-shaped elastic body. 
     According to a fifth aspect of the present invention, there is provided the fan unit mounting structure described in the third aspect, in which the belt-shaped elastic body has a degree of hardness (in accordance with JIS K6301A) ranging from 40 to 50 degrees. 
     According to a six aspect of the present invention, there is provided the fan unit mounting structure as defined in the third aspect, wherein the belt-shaped elastic body is made of one of a silicon rubber and a chloroprene rubber. 
     According to a seventh aspect of the present invention, there is provided the fan unit mounting structure as defined in the third aspect, wherein 
     two ends of the belt-shaped elastic body are fixedly coupled with each other so as to form a ring-shaped elastic body, and 
     the ring-shaped elastic body is hung onto each of the fan unit mounting projections, the ring-shaped elastic body is made in contact with a plurality of locations on the outer peripheral part of the fan unit, and the fan unit is retained, while being spaced apart from the fan unit mounting part in the direction along the rotary shaft of the fan, due to the clipping force of the ring-shaped elastic body. 
     According to an eighth aspect of the present invention, there is provided the fan unit mounting structure as defined in the seventh aspect, wherein the ring-shaped elastic body is provided to extend from a portion for retaining the fan unit toward a discharge opening provided in the casing so as to form a discharge wind tunnel part. 
     According to a ninth aspect of the present invention, there is provided the fan unit mounting structure as defined in the seventh aspect, wherein the ring-shaped elastic body is provided to extend from a portion for retaining the fan unit toward a heat generating component disposed in the casing so as to form a suction wind tunnel part. 
     According to a tenth aspect of the present invention, there is provided the fan unit mounting structure as defined in the eighth aspect, wherein the ring-shaped elastic body has a portion for forming the wind tunnel part, a thickness of the portion being smaller than that of a portion for retaining the fan unit. 
     According to an 11th aspect of the present invention, there is provided the fan unit mounting structure as defined in the seventh aspect, wherein 
     the fan unit has a blast opening partially on the outer peripheral part, and 
     the ring-shaped elastic body is disposed to inclusively surround the fan unit and a heat generating component so that an airflow is guided from the blast opening toward the heat generating component disposed in the casing. 
     EFFECTS OF THE INVENTION 
     According to the first aspect of the present invention, the belt-shaped elastic body is hung onto the plurality of fan unit mounting projections that are provided integrally to the fan unit mounting part (such as the casing or the device body disposed in the casing). Further, according to the first aspect of the present invention, the belt-shaped elastic body is made in contact with the plurality of locations on the outer peripheral part of the fan unit, so that the fan unit is retained, while being spaced apart from the fan unit mounting part in the direction along the rotary shaft of the fan, due to the clipping force of the belt-shaped elastic body. 
     In other words, the fan unit is clipped by the belt-shaped elastic body so as to be retained while being floated from the fan unit mounting part in the direction along the rotary shaft of the fan. Accordingly, even in a case where vibration is generated by the driven fan, such vibration is absorbed by the belt-shaped elastic body, thereby suppressing transmission of the vibration to the fan unit mounting part. 
     More specifically, vibration caused in a direction perpendicular to the rotary shaft of the fan is absorbed by the belt-shaped elastic body that is bent in the perpendicular direction while clipping the fan unit. It is therefore possible to suppress transmission of the vibration in the direction perpendicular to the rotary shaft of the fan to the fan unit mounting projections provided integrally to the fan unit mounting part. 
     On the other hand, vibration caused in a direction along the rotary shaft of the fan is absorbed by the belt-shaped elastic body that is bent in the direction along the rotary shaft while clipping the fan unit. It is therefore possible to suppress transmission of the vibration in the direction along the rotary shaft of the fan to the fan unit mounting projections provided integrally to the fan unit mounting part. In this case, the fan unit is retained while being floated from the fan unit mounting part in the direction along the rotary shaft of the fan. Therefore, it is possible to inhibit contact between the fan unit and the fan unit mounting part even in a case where the fan unit is shifted in the direction along the rotary shaft of the fan due to the bent belt-shaped elastic body. As a result, it is possible to suppress transmission to the fan unit mounting part of the vibration caused by the driven fan so as to achieve suppression of noise. 
     In comparison to any of the elastic bodies adopted in Patent Documents 1 and 2, the belt-shaped elastic body is a component obviously larger in size, thereby being hard to be deformed by a slight external force and being easily handled. Therefore facilitated is the mounting operation involving the elastic body, and the fan unit mounting operation can be easily performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1A  is a plan view showing a state of a fan unit mounting frame and a belt-shaped elastic body respectively attached to a fan unit according to a first embodiment of the present invention; 
         FIG. 1B  is a side view showing the state of the fan unit mounting frame and the belt-shaped elastic body respectively attached to the fan unit according to the first embodiment of the present invention; 
         FIG. 2A  is a plan view of the fan unit according to the first embodiment of the present invention; 
         FIG. 2B  is a side view of the fan unit according to the first embodiment of the present invention; 
         FIG. 3A  is a plan view of the fan unit mounting frame according to the first embodiment of the present invention; 
         FIG. 3B  is a side view of the fan unit mounting frame according to the first embodiment of the present invention; 
         FIG. 4  is a plan view of the belt-shaped elastic body according to the first embodiment of the present invention; 
         FIG. 5  is a graph indicating a relation between degrees of hardness of the belt-shaped elastic body and values of noise caused by a driven fan; 
         FIG. 6  is a side view showing a fan unit mounting structure according to a second embodiment of the present invention; 
         FIG. 7  is a side cross sectional view showing a fan unit mounting structure according to a third embodiment of the present invention; 
         FIG. 8  is a partially-enlarged cross sectional view of a belt-shaped elastic body according to the third embodiment of the present invention; 
         FIG. 9  is a side cross sectional view showing a fan unit mounting structure according to a fourth embodiment of the present invention; 
         FIG. 10  is a perspective view of a belt-shaped elastic body according to a modified example; 
         FIG. 11A  is a plan view showing a fan unit mounting structure according to a fifth embodiment of the present invention; 
         FIG. 11B  is a side view showing the fan unit mounting structure according to the fifth embodiment of the present invention; 
         FIG. 12  is a plan view showing a fan unit mounting structure according to a sixth embodiment of the present invention; 
         FIG. 13A  is a plan view showing a fan unit mounting structure according to a seventh embodiment of the present invention; 
         FIG. 13B  is a plan view showing another fan unit mounting structure according to the seventh embodiment of the present invention; 
         FIG. 14A  is an exploded perspective view of a conventional fan unit; and 
         FIG. 14B  is a perspective view of the conventional fan unit having been assembled. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. 
     Described below with reference to the drawings are some of the most preferred embodiments of the present invention. 
     First Embodiment 
     With reference to  FIGS. 1A ,  1 B,  2 A,  2 B,  3 A,  3 B, and  4 , there is described a fan unit mounting structure according to a first embodiment of the present invention.  FIG. 1A  is a plan view showing a state of a fan unit mounting frame and a belt-shaped elastic body respectively attached to a fan unit according to the first embodiment of the present invention, and  FIG. 1B  is a side view thereof.  FIG. 2A  is a plan view of the fan unit according to the first embodiment of the present invention, and  FIG. 2B  is a side view thereof.  FIG. 3A  is a plan view of the fan unit mounting frame according to the first embodiment of the present invention, and  FIG. 3B  is a side view thereof.  FIG. 4  is a plan view of the belt-shaped elastic body according to the first embodiment of the present invention. 
     A fan unit  1  according to the first embodiment of the present invention is mounted to a fan unit mounting part in a casing of an electronic device. This fan unit is mounted particularly to an electronic device requiring suppression of drive noise (exemplified by a video device such as a liquid crystal display device, a plasma display device, a projection television device, or a personal computer). 
     According to the first embodiment of the present invention, the fan unit  1  is mounted to the fan unit mounting part with use of a fan unit mounting frame  2  and a belt-shaped elastic body  3 . The fan unit mounting part is disposed on an inner surface of the casing of the electronic device or the electronic device body that includes a heat generating device and is located inside the casing, and this fan unit mounting part is used for mounting the fan unit  1 . 
     In  FIG. 2A , the fan unit  1  includes a fan  11  provided with a plurality of ( FIG. 2A  exemplifies a case with four) rotary blades, and a fan housing  12  that accommodates the fan  11  so as to be rotatable therein. 
     The fan  11  may function as a cooling fan for ventilating to cool the inside of the casing of the electronic device. There is mounted to the fan  11   a  drive motor (not shown), so that the fan  11  is driven by the drive motor so as to rotate about a rotary shaft  11   a . The rotary shaft  11   a  of the fan  11  is coupled to the fan housing  12  by a coupling member (not shown). 
     The fan housing  12  is formed in substantially a cylindrical shape, and has an outer peripheral part  12   a  that is provided on a lower portion (the right portion in  FIG. 2B ) thereof with a plurality of ( FIG. 2A  exemplifies a case with four) flange parts  12   b . As shown in  FIG. 2A , the flange parts  12   b  each project radially from the outer peripheral part  12   a  so as to be distant from the rotary shaft  11   a  of the fan  11 . The fan unit  1  has a substantially square outline due to the respective flange parts  12   b  when seen from a plane (that is,  FIG. 2A ) perpendicular to the rotary shaft  11   a  of the fan  11 . 
     In  FIGS. 3A and 3B , the fan unit mounting frame  2  has a frame body  21  in a rectangular-ring flat plate shape, a hanging hook part  22 , a screwing/hanging hook part  23 , and two screwing hook parts  24  and  25 , that each project from one of sides on an outer peripheral part of the frame body  21  in a direction intersecting with (such as perpendicular to) a plane formed by the frame body  21  and each are bent outward at a distal end thereof. 
     The hanging hook part  22  and the screwing/hanging hook part  23  are disposed to face each other, while the two screwing hook parts  24  and  25  are disposed to face each other. The screwing/hanging hook part  23  has a vertically extended portion provided with a screw hole (not shown). The screwing/hanging hook part  23  and the two screwing hook parts  24 ,  25  have outwardly bent distal ends, which are provided with screwing holes  23   a ,  24   a , and  25   a , respectively. These screwing holes  23   a ,  24   a , and  25   a  are provided correspondingly to three screw holes (not shown) that are formed in the fan unit mounting part, respectively. Alternatively, the fan unit mounting part may be provided with three screw holes correspondingly to the screwing holes  23   a ,  24   a , and  25   a . The fan unit mounting frame  2  is integrally fixed to the fan unit mounting part with use of screws that are inserted to the screw holes through the screwing holes  23   a ,  24   a , and  25   a , respectively. 
     In the present first embodiment, the hanging hook part  22  and the screwing/hanging hook part  23  each exemplify a fan unit mounting projection. 
     In  FIG. 4 , the belt-shaped elastic body  3  is a member made of an elastic body such as rubber into a belt shape. The belt-shaped elastic body  3  is provided with four slit holes  31  that exemplify a plurality of holes formed at constant intervals correspondingly to the positions and the sizes of the four flange parts  12   b  on the fan housing  12 , and screwing holes  32   a  and  32   b  provided respectively in the vicinity of two ends thereof. 
     Described next with reference to  FIGS. 1A and 1B  is an exemplified process of mounting the fan unit  1  to the fan unit mounting frame  2 . 
     Firstly, the screw hole (not shown) formed in the vertically extended portion of the screwing/hanging hook part  23  is aligned with the screwing hole  32   a  formed in the first end of the belt-shaped elastic body  3 . 
     While this aligned state being maintained, the flange parts  12   b  of the fan unit  1  are gradually inserted to the slit holes  31  in the belt-shaped elastic body  3  respectively such that the outer peripheral part of the fan unit  1  is surrounded by the belt-shaped elastic body  3 . As shown in FIGS.  1 A and  1 B, during this process, the center portion of the belt-shaped elastic body  3  is hung onto the hanging hook part  22 . 
     Upon completion of insertion of the flange parts  12   b  respectively to the slit holes  31 , the screwing hole  32   b  formed in the second end of the belt-shaped elastic body  3  is placed on the screw hole (not shown) and the screwing hole  32   a  already aligned with each other, and these three holes are aligned with one another. Thereafter, there is mounted a screw (not shown) so as to pass through these three holes. 
     In this way, the fan unit  1  is retained, while being spaced apart from the plane formed by the frame body  21  as shown in  FIG. 1B , due to the clipping force of the belt-shaped elastic body  3 . In a state where the frame body  21  is attached to the fan unit mounting part, the plane formed by the frame body  21  substantially corresponds to the fan unit mounting part. In other words, in the state where the frame body  21  is attached to the fan unit mounting part, the fan unit  1  is retained while being floated from the fan unit mounting part in the direction along the rotary shaft  11   a  of the fan  11  due to provision of the belt-shaped elastic body  3 . 
     The fan unit  1  may be mounted to the fan unit mounting part after only the fan unit mounting frame  2  is attached to the fan unit mounting part, or after the fan unit  1  is mounted to the fan unit mounting frame  2  with use of the belt-shaped elastic body  3 . 
     As described above, in a case where the driven fan  11  causes vibration in the direction perpendicular to the rotary shaft  11   a  of the fan  11  in the fan unit  1  retained by the belt-shaped elastic body  3 , the belt-shaped elastic body  3  is bent in this perpendicular direction while clipping the fan unit  1  so as to absorb the vibration. Accordingly suppressed is transmission of the vibration to the fan unit mounting frame  2  that is integrally fixed to the fan unit mounting part, which results in suppression of noise. 
     Further, as described above, in a case where the driven fan  11  causes vibration in the direction along the rotary shaft of the fan  11  in the fan unit  1  retained by the belt-shaped elastic body  3 , the belt-shaped elastic body  3  is bent in the direction along the rotary shaft while clipping the fan unit  1  so as to absorb the vibration in the direction along the rotary shaft of the fan  11 . Therefore, it is possible to suppress transmission of the vibration to the fan unit mounting frame  2  that is integrally fixed to the fan unit mounting part. In this case, the fan unit  1  is retained while being floated from the fan unit mounting part in the direction along the rotary shaft of the fan  11 . Accordingly, even in a case where the fan unit  1  is displaced in the direction along the rotary shaft due to the belt-shaped elastic body  3  that is bent in the direction along the rotary shaft of the fan  11 , it is possible to inhibit contact between the fan unit  1  and the fan unit mounting part. As a result, the vibration caused by the driven fan  11  is inhibited from being transmitted to the fan unit mounting part so as to achieve suppression of noise. 
     Preferably, a plurality of contact portions between the belt-shaped elastic body  3  and the outer peripheral part  12   a  of the fan unit  1  (fit portions between the slit holes  31  and the flange parts  12   b ) are located so as to be distant respectively from contact portions between the belt-shaped elastic body  3  and the plurality of fan unit mounting projections (the hanging hook part  22  and the screwing/hanging hook part  23 ). More preferably, these contact portions are located so as to be evenly dispersed. In this configuration, the belt-shaped elastic body  3  is allowed to apply the elastic force (the clipping force) evenly to the fan unit  1  so as to maintain a constant space between the fan unit  1  and the fan unit mounting part. 
     In the first embodiment of the present invention, the fan unit  1  is made in contact only with the belt-shaped elastic body  3 , so that the level of noise is dependent on the degree of hardness of the belt-shaped elastic body  3 . A low degree of hardness set to the belt-shaped elastic body  3  increases the vibration absorption effect while reducing the force of retaining (clipping) the fan unit  1 . To the contrary, a high degree of hardness set to the belt-shaped elastic body  3  increases the force of retaining (clipping) the fan unit  1  while reducing the vibration absorption effect. In the expression the other way around, the noise suppression effect can be further increased by balancing the size and weight as well as the vibration property with the impact resistance retention property in the fan unit  1  to appropriately select the degree of hardness of the belt-shaped elastic body  3 . 
     The above conditions are described below with reference to  FIG. 5 .  FIG. 5  is a graph indicating a relation between degrees of hardness of the belt-shaped elastic body  3  and values of noise caused by the driven fan  11 . The data on the degrees of hardness indicated in  FIG. 5  is based on JIS K6301A. The conditions for measuring noise caused by the driven fan  11  are set as follows: 
     Fan: Fan Motor manufactured by NIDEC CORPORATION, Model Number D08A-12BL01B, 80 mm square with 25 mm thick 
     Fan Drive Voltage: 12 V 
     Measurement Position: a location distant by 1 m from the fan mounted in a casing (with no obstacle therebetween) 
     As shown in  FIG. 5 , the noise value is equal to 39.1 dB (decibel) with the belt-shaped elastic body  3  having the hardness of 40 degrees, while the noise value is equal to 39.6 dB (decibel) with the belt-shaped elastic body  3  having the hardness of 55 degrees, and the noise value is equal to 39.7 dB (decibel) with the belt-shaped elastic body  3  having the hardness of 65 degrees. To the contrary, the noise value was constantly equal to 40.5 dB when measured under similar conditions in a conventional fan unit mounting structure  100 A for fixing a fan unit to a fan unit mounting part with use of a screw. 
     Found from the above results is that the fan unit mounting structure according to the present embodiment has the noise values smaller than that of the conventional fan unit mounting structure  100 A in any of the cases where the belt-shaped elastic body  3  is set to have a hardness of a degree within the measurement range (35 to 70 degrees). 
     On the other hand, in some of cases where the belt-shaped elastic body  3  has a hardness of less than 40 degrees (corresponding to the area indicated by arrow A in  FIG. 5 ), the belt-shaped elastic body  3  did not exert a force enough to retain (clip) the fan unit  1  and was incapable of retaining the fan unit  1 . Further, in cases where the belt-shaped elastic body  3  has a hardness of more than 50 degrees (corresponding to the area indicated by arrow C in  FIG. 5 ), the sensible noise was slightly large. 
     According to the above results, the belt-shaped elastic body  3  will be preferably set to have a hardness of 40 degrees or more, and will be more preferably set to have a hardness ranging from 40 to 50 degrees (corresponding to the area indicated by arrow B in  FIG. 5 ). 
     Although not shown in the drawings, also in a case of using, in place of the fan described above, a cooling fan generally adopted in a commercial electrical device of 40 to 120 mm with the rotational speed of several hundreds to several thousands RPM, as well as using a belt-shaped elastic body  3  of 2 to 3 mm thick and 10 mm wide, it has been similarly confirmed that the belt-shaped elastic body  3  is preferably set to have a hardness of 40 degrees or more and is more preferably set to have a hardness ranging from 40 to 50 degrees. 
     As described above, in the structure used for mounting the fan unit  1  according to the first embodiment of the present invention, the fan unit  1  is retained, while being spaced apart from the casing in the direction along the rotary shaft of the fan  11 , due to the clipping force of the belt-shaped elastic body. Accordingly, vibration caused by the driven fan is inhibited from being transmitted to the fan unit mounting part, resulting in suppression of noise. 
     The belt-shaped elastic body  3  is a component obviously larger in size in comparison to any of the elastic bodies adopted in Patent Documents 1 and 2, and therefore is hard to be deformed by a slight external force and is easily handled. In a case where the belt-shaped elastic body  3  is set to have a hardness of 40 degrees or more in order to provide a force of retaining the fan unit  1 , the belt-shaped elastic body  3  is made harder to be deformed and is more easily handled. Accordingly facilitated is the mounting operation involving the belt-shaped elastic body  3 , and the fan unit mounting operation can be easily performed. 
     Since the temperature rises (such as 50° C.) in a casing of an electronic device, the material for the belt-shaped elastic body  3  is preferably selected from substances such as a silicon rubber and a chloroprene rubber, which each have during the live thereof stable vibration absorption and strength properties with no deterioration even under a high temperature. It is confirmed by the accelerated environmental testing that the belt-shaped elastic body  3  made of one these substances has properties hardly deteriorated under a possible environment and for a possible duration of use (average ambient temperature 50° C., maximum temperature 80° C., and extension percentage 10%, for 24000 hours). 
     Second Embodiment 
     It is noted that the present invention is not limited to the embodiment described above but may be embodied in accordance with other various aspects. Shown in  FIG. 6  is a fan unit mounting structure according to a second embodiment of the present invention.  FIG. 6  is a side view showing the fan unit mounting structure according to the second embodiment of the present invention. 
     In the first embodiment described above, the fan unit mounting projections were exemplified respectively by the hanging hook part  22  and the screwing/hanging hook part  23  of the fan unit mounting frame  2 . In the fan unit mounting structure according to the present second embodiment, in place of the above parts, there are provided a plurality of fan unit mounting projections  41  directly to a device body  4  that is disposed in a casing of an electronic device. As the details other than the above are similar to those of the first embodiment, description thereof will not be repeatedly provided. 
     In the fan unit mounting structure according to the present second embodiment, there are required no mount components such as a fan unit mounting frame  2  and a screw used for attaching the frame, thereby achieving further reduction in the number of components as well as cost reduction. In addition, further facilitated is the operation of mounting the fan unit  1 . 
     Third Embodiment 
     Described with reference to  FIG. 7  is a fan unit mounting structure according to a third embodiment of the present invention.  FIG. 7  is a side cross sectional view showing the fan unit mounting structure according to the third embodiment of the present invention. 
     A fan unit  1  and a casing  5 , which configures an outline of an electronic device, are generally disposed with a predetermined space (such as several mm or more) provided therebetween in order to avoid transmission of vibration due to a driven fan  11  to the casing  5  and to result in noise. This space may not allow an airflow discharged from the fan unit  1  to be guided to discharge openings  51  (generally having an aperture ratio ranging from 30 to 60%) formed in the casing  5 , thereby resulting in reduction in airflow and thus deterioration in cooling efficiency. 
     In order to improve these issues, in the fan unit mounting structure according to the third embodiment of the present invention as shown in  FIG. 7 , provided in place of the belt-shaped elastic body  3  (see  FIG. 6 ) is a belt-shaped elastic body  3 A that is formed to extend from the portion for retaining the fan unit  1  toward the discharge openings  51  (so as to be made in contact with the peripheral portion of the discharge openings  51 , as an example). In other words, the third embodiment of the present invention adopts the belt-shaped elastic body  3 A that is obtained by extending the portion close to the discharge openings  51  in the belt-shaped elastic body  3  toward the discharge openings  51 . The belt-shaped elastic body  3 A has two ends fixedly coupled with each other so as to form a ring shape, with a discharge wind tunnel part formed therein. This wind tunnel part guides the airflow discharged from the fan unit  1  to the discharge openings  51 . As the details other than the above are similar to those of the second embodiment, description thereof will not be repeatedly provided. 
     In the fan unit mounting structure according to the third embodiment of the present invention, the belt-shaped elastic body  3 A configures the discharge wind tunnel part so that the airflow discharged from the fan unit  1  is guided to the discharge openings  51 , thereby suppressing deterioration in cooling efficiency. 
     In a case where the discharge wind tunnel part is made of a resin or a metal, vibration of the fan unit  1  may be transmitted by way of the portion for forming the wind tunnel part to generate noise. 
     To the contrary, in the fan unit mounting structure according to the third embodiment of the present invention, the wind tunnel part is configured by the belt-shaped elastic body  3 A so as to absorb vibration of the fan unit  1  and to suppress generation of noise. Furthermore, retention of the fan unit  1  and provision of the wind tunnel part can be both achieved by the single belt-shaped elastic body  3 A, resulting in significant reduction in the number of components in comparison to a conventional case. Therefore remarkably reduced is the number of assembling steps so as to facilitate the operation of mounting the fan unit  1 . 
     As shown in  FIG. 8 , in order to suppress as much as possible transmission of vibration of the fan unit  1  to the casing  5 , a wind tunnel part forming portion  35  for forming a wind tunnel part  34  is preferably set to have a thickness L 2  smaller than a thickness L 1  of a retentive portion  33  in the fan unit  1 . More preferably, the thickness of the wind tunnel part forming portion  35  is half or less of the thickness of the retentive portion  33  (in a case where the thickness of the retentive portion  33  is equal to 3.0 mm, the wind tunnel part forming portion  35  is set to have the thickness of 1.5 mm or less). 
     The thickness of the retentive portion  33  can be easily differentiated from the thickness of the wind tunnel part forming portion  35  by manufacturing these portions by rubber extrusion molding or the like. 
     Although  FIG. 8  shows that there is provided a step at a boundary between the retentive portion  33  and the wind tunnel part forming portion  35 , the present invention is not limited to this case. Alternatively, the retentive portion  33  and the wind tunnel part forming portion  35  may be connected with each other so as to form a boundary in a gradually inclined straight line, that is, in a tapered shape. 
     Fourth Embodiment 
     Described with reference to  FIG. 9  is a fan unit mounting structure according to a fourth embodiment of the present invention.  FIG. 9  is a side cross sectional view showing the fan unit mounting structure according to the fourth embodiment of the present invention. 
     In the fan unit mounting structure according to the fourth embodiment of the present invention as shown in  FIG. 9 , in place of the plurality of fan unit mounting projections  41  (see  FIG. 7 ) provided to the device body  4 , there are provided to a casing  5 A a plurality of fan unit mounting projections  52 A. In other words, the fan unit mounting part is provided on the casing  5 A. In this case, the fan unit  1  may be made distant from a heat generating component  42  that is disposed to the device body  4 , resulting in deterioration in cooling efficiency. 
     In order to prevent such a issue, in the fan unit mounting structure according to the fourth embodiment of the present invention as shown in  FIG. 9 , in place of the belt-shaped elastic body  3 A (see  FIG. 7 ), there is further provided a belt-shaped elastic body  3 B that is formed to extend from the portion for retaining the fan unit  1  toward the heat generating component  42  disposed to the device body  4  (so as to cover the periphery of the heat generating component  42 , as an example). The belt-shaped elastic body  3 B has two ends fixedly coupled with each other so as to form a ring shape, with a suction wind tunnel part configured therein. This wind tunnel part guides air wormed by the heat generating component  42  to the fan unit  1 . As the details other than the above are similar to those of the third embodiment, description thereof will not be repeatedly provided. 
     In the fan unit mounting structure according to the fourth embodiment of the present invention, the belt-shaped elastic body  3 B configures the suction wind tunnel part so that air warmed by the heat generating component  42  is guided to the fan unit  1 , thereby suppressing deterioration in cooling efficiency. 
     Further, in the fan unit mounting structure according to the fourth embodiment of the present invention, the wind tunnel part is configured by the belt-shaped elastic body  3 B so as to absorb vibration of the fan unit  1  and to suppress generation of noise. Furthermore, retention of the fan unit  1  and provision of the wind tunnel part can be both achieved by the single belt-shaped elastic body  3 B, resulting in significant reduction in the number of components in comparison to a conventional case. Therefore remarkably reduced is the number of assembling steps so as to facilitate the operation of mounting the fan unit  1 . 
     In each of the embodiments described above, the ring-shaped elastic body is formed by fixedly coupling the two ends of the belt-shaped elastic body. However, the present invention is not limited to this case. Alternatively, as shown in  FIG. 10 , there may be configured a ring-shaped elastic body  3 C that is originally formed in a ring shape (a rubber band shape). 
     The ring-shaped elastic body  3 C may be attached as follows. 
     Firstly, the ring-shaped elastic body  3 C is elongated to have a larger diameter by an external force. 
     Thereafter, the fan unit  1  is disposed inside the elongated ring-shaped elastic body  3 C, and the plurality of flange parts  12   b  of the fan unit  1  are fitted in the slit holes  31 , respectively. The ring-shaped elastic body  3 C is thus attached to the outer peripheral part  12   a  of the fan unit  1 . 
     Then, portions of the ring-shaped elastic body  3 C located respectively between the adjacent slit holes  31  are clipped so as to be elongated, which are hung onto the fan unit mounting projections. As a result, the fan unit  1  can be retained by the ring-shaped elastic body  3 C while being spaced apart from the fan unit mounting part. 
     In the case where the fan unit  1  is retained by the ring-shaped elastic body  3 C, there is required none of the screwing holes  32   a  and  32   b  and screws to be fitted thereinto. 
     The ring-shaped elastic body  3 C may be manufactured as follows. 
     There is firstly formed a cylindrical elastic body by rubber extrusion molding. The cylindrical elastic body is then double-layered by folding so as to bring the inner surface thereof into contact with each other. The double-layered elastic body is pressed to have slit holes  31  formed at constant intervals. Subsequently, this cylindrical elastic body is cut into an arbitrary width to obtain the ring-shaped elastic body  3 C. 
     In this way, the ring-shaped elastic body  3 C can be easily manufactured at a low cost. 
     Fifth Embodiment 
     Described with reference to  FIGS. 11A and 11B  is a fan unit mounting structure according to a fifth embodiment of the present invention.  FIG. 11A  is a plan view showing the fan unit mounting structure according to the fifth embodiment of the present invention, and  FIG. 11B  is a side view thereof. 
     In the fan unit mounting structure according to the fifth embodiment of the present invention, a plurality of (three as an example) fan units  1  are disposed respectively between a plurality of (four as an example) fan unit mounting projections  41 , and there is provided a belt-shaped elastic body  3 D so as to inclusively surround these parts. As shown in  FIG. 11B , the belt-shaped elastic body  3 D is provided with a plurality (twice or more of the number of fan units  1 ) of slit holes  31 . At least two diagonal flange parts  12   b  of each of the fan units  1  are inserted to the corresponding slit holes  31 , and the belt-shaped elastic body  3 D is hung onto the respective fan unit mounting projections  41  (or screwed thereto), so that the respective fan units  1  are retained by the belt-shaped elastic body  3 D. More specifically, due to the clipping force of the belt-shaped elastic body  3 D, the respective fan units  1  are retained while being spaced apart from the fan unit mounting part (located on the device body  4  in this case). As the details other than the above are similar to those of the second embodiment, description thereof will not be repeatedly provided. 
     In the fan unit mounting structure according to the fifth embodiment of the present invention, the plurality of fan units  1  are retained by the single belt-shaped elastic body  3 D. Accordingly achieved are further reduction in the number of components as well as reduction in the number of assembling steps, which results in further facilitation in the operation of mounting the fan units  1 . 
     Sixth Embodiment 
     Described with reference to  FIG. 12  is a fan unit mounting structure according to a sixth embodiment of the present invention.  FIG. 12  is a plan view showing the fan unit mounting structure according to the sixth embodiment of the present invention. 
     In the fan unit mounting structure according to the sixth embodiment of the present invention as shown in  FIG. 12 , there are provided, in place of the belt-shaped elastic body  3 D, two belt-shaped elastic bodies  3 E and  3 E that each have a length half or less of that of the belt-shaped elastic body  3 D (see  FIG. 11A ). The belt-shaped elastic bodies  3 E and  3 E are each hung between a pair of separate fan unit mounting projections  41 A. The belt-shaped elastic body  3 E is fixed to the corresponding fan unit mounting projections  41 A with use of bolts or the like. There are aligned a plurality of (three as an example) fan units  1  between the belt-shaped elastic bodies  3 E and  3 E that face each other. At least two diagonal flange parts  12   b  of each of the fan units  1  are inserted to a plurality of corresponding slit holes (not shown) formed in each of the belt-shaped elastic bodies  3 E and  3 E, so that the respective fan units  1  are retained by the belt-shaped elastic bodies  3 E and  3 E. More specifically, the respective fan units  1  are retained, while being spaced apart from the fan unit mounting part, due to the clipping forces of the respective belt-shaped elastic bodies  3 E and  3 E. As the details other than the above are similar to those of the fifth embodiment, description thereof will not be repeatedly provided. 
     In the fan unit mounting structure according to the sixth embodiment of the present invention, the plurality of fan units  1  are retained by the two belt-shaped elastic bodies  3 E and  3 E. More specifically, unlike the respective embodiments described above, each of the belt-shaped elastic bodies is configured to retain the fan units  1  with the two ends thereof not being fixedly coupled with each other. Even in such a configuration, the fan units  1  can be retained while being spaced apart from the fan unit mounting part. 
     Although the fan units  1  are retained by the two belt-shaped elastic bodies  3 E and  3 E in the above configuration, the present invention is not limited thereto. Alternatively, the fan units  1  may be retained by more than two belt-shaped elastic bodies. 
     Seventh Embodiment 
     Described with reference to  FIGS. 13A and 13B  is a fan unit mounting structure according to a seventh embodiment of the present invention.  FIGS. 13A and 13B  are plan views each showing the fan unit mounting structure according to the seventh embodiment of the present invention. 
     Shown in each of  FIGS. 13A and 13B  is not a structure used for mounting the fan unit  1  of the axial flow type for blowing air in the direction along the rotary shaft  11   a  as described above, but a structure used for mounting a fan unit  1 A of the sirocco type for suctioning air in the direction along the rotary shaft (in the direction perpendicular to the plane shown in  FIG. 13A ) and discharging an airflow from a blast opening  13 A. 
     The fan unit  1 A has an outer peripheral part  12   a  that is provided with a plurality of (three as an example) flange parts  12   b  similarly to the fan unit  1 . The blast opening  13 A is formed partially on the outer peripheral part  12   a  of the fan unit  1 A. 
     The heat generating component  42  (see  FIG. 9 ) disposed to the device body  4  may be located at a position slightly different from each other or may generate heat of which quantity is different from one another among the separate devices. Specifically, there is a case where the heat generating component  42  is located at a position  42 A (see  FIG. 13A ), and there is another case where the heat generating component  42  is located at a position  42 B (see  FIG. 13B ). In each of these cases, the heat generating component  42  may not be appropriately supplied with an airflow discharged from the blast opening  13 A of the fan unit  1 A, which will result in deterioration in cooling efficiency. 
     In order to inhibit such a issue, according to the seventh embodiment of the present invention, in the case where the heat generating component  42  (see  FIG. 9 ) is located at the position  42 A, as shown in  FIG. 13A , a belt-shaped elastic body  3 F is hung onto the plurality of fan unit mounting projections  41 , and the respective flange parts  12   b  are fitted in a plurality of slit holes (not shown) that are provided in the belt-shaped elastic body  3 F. The fan unit  1 A is thus retained such that the blast opening  13 A is directed to the position  42 A. In this case, because the belt-shaped elastic body  3 F is disposed so as to inclusively surround the fan unit  1 A and the heat generating component  42 , the belt-shaped elastic body  3 F is allowed to guide an airflow from the blast opening  13 A appropriately to the heat generating component  42 , thereby resulting in increase in cooling efficiency. 
     On the other hand, in the case where the heat generating component  42  (see  FIG. 9 ) is located at the position  42 B, as shown in  FIG. 13B , the belt-shaped elastic body  3 F is hung onto the plurality of fan unit mounting projections  41 , and the respective flange parts  12   b  are fitted in the plurality of slit holes (not shown) that are provided in the belt-shaped elastic body  3 F. The fan unit  1 A is thus retained such that the blast opening  13 A is directed to the position  42 B. In this case, because the belt-shaped elastic body  3 F is disposed so as to inclusively surround the fan unit  1 A and the heat generating component  42 , the belt-shaped elastic body  3 F is allowed to guide an airflow from the blast opening  13 A appropriately to the heat generating component  42 , thereby resulting in increase in cooling efficiency. 
     Therefore, in the fan unit mounting structure according to the seventh embodiment of the present invention, even in the case where the position of the heat generating component  42  or the quantity of heat generated by the heat generating component  42  is slightly different from one another among the separate devices, an airflow from the blast opening  13 A can be appropriately guided to the heat generating component  42  by correspondingly selecting the positions to be hung onto the plurality of fan unit mounting projections  41 . Moreover, it is possible to suppress deterioration in cooling efficiency only by selecting the positions to hang the belt-shaped elastic body  3 F, which results in reduction in cost therefor. 
     In each of the embodiments described above, the belt-shaped elastic body is provided with slit holes  31  to which the flange parts  12   b  are respectively inserted, so that the belt-shaped elastic body retains the fan unit while being in contact with each other. However, the present invention is not limited to such a case. Alternatively, the fan unit may be retained only by the elastic force of the belt-shaped elastic body. Further alternatively, the belt-shaped elastic body and the fan unit may be fixed to each other with use of a screw. In such a case, the number of screwed locations is preferably reduced as much as possible (one location as an example), so that the belt-shaped elastic body is capable of absorbing vibration caused by the driven fan  1 . Moreover, the fan unit mounting projections  22 ,  23 ,  41 , and  52 A are preferably provided to extend substantially in parallel with the outer peripheral part  12   a  of the fan unit  1  ( 1 A) or with the rotary shaft  11   a  of the fan  11 , so as to be made in contact with the outer peripheral part  12   a  of the fan unit  1  or  1 A in a large area. 
     The respective effects can be exerted by appropriate combination of arbitrary embodiments in the various embodiments described above. 
     Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom. 
     The entire disclosure of Japanese Patent Application No. 2007-106840 filed on Apr. 16, 2007, including specification, claims, drawings, and summary are incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     A fan unit mounting structure according to the present invention inhibits transmission of vibration caused by a driven fan to a fan unit mounting part so as to achieve suppression of noise, as well as facilitates the operation of mounting the fan unit. The present invention is therefore useful in an electronic device requiring less drive noise, particularly in a video device such as a liquid crystal display device or a plasma display device.