Patent Publication Number: US-9903386-B2

Title: Air conditioning apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2014-101149, filed May 15, 2014. The entire disclosure of Japanese Patent Application. No. 2014-101149 is hereby incorporated herein by reference. 
     FIELD OF INVENTION 
     The present invention relates to an air conditioning apparatus, particularly to an air conditioning apparatus that a rearward bladed centrifugal fan is mounted in a fan compartment having a fan entrance bored in opposition to a blow-out port such that a rotary shall of the centrifugal fan is oriented to an opening direction of the fan entrance and an opening direction of the blow-out port. 
     BACKGROUND INFORMATION 
     As described in Japan Laid-open Patent Application Publication No. H06-281194, an air conditioning apparatus has been produced so far that a rearward bladed centrifugal fan is mounted in a ventilation unit (a fan compartment) having a fan entrance bored in opposition to a blow-out port such that a rotary shaft of the centrifugal fan is oriented to an opening direction of the fan entrance and an opening direction of the blow-out port. 
     SUMMARY 
     In the positional arrangement of the centrifugal fan in the fan compartment as described above, immediately after blown out by the bladed wheel of the centrifugal inn, air has a strong flow component directed in a radial direction. Hence, the radial flow component increases ventilation resistance in the fan compartment, and this serves as a factor of hindering enhancement in ventilation performance. 
     It is an object of the present invention to enhance the ventilation performance of a rearward bladed centrifugal fan in an air conditioning apparatus that the rearward bladed centrifugal fan is mounted in a fan compartment having a fan entrance bored in opposition to a blow-out port such that a rotary shaft of the rearward bladed centrifugal fan is oriented to an opening direction of the fan entrance and an opening direction of the blow-out port. 
     An air conditioning apparatus according to a first aspect includes a casing, a partition member, a heat exchanger and a centrifugal fan. The casing has an intake port and a blow-out port. The partition member divides an interior of the casing into a heat exchanger compartment located on an intake port side and a fan compartment located on a blow-out port side, and has a fan entrance that is bored in opposition to the blow-out port and makes the heat exchanger compartment and the fan compartment communicate with each other, The heat exchanger is mounted in the heat exchanger compartment. The centrifugal fan includes a bladed wheel having a plurality of rearward blades and is configured to suck air existing in the heat exchanger compartment into the fan compartment through the fan entrance, with the bladed wheel being mounted in the fan compartment such that a rotary shaft of the bladed wheel is oriented to an opening direction of the fan entrance and an opening direction of the blow-out port. Additionally, the bladed wheel further includes a hub that connects blow-out port side ends of the plural rearward blades and is configured to be rotated about the rotary shaft. Furthermore, the hub has an outer diameter smaller than an outer diameter of the rearward blades. 
     As described above, a type of bladed wheel, having the construction that the outer diameter of the hub is set to be smaller than that of the rearward blades, is herein employed as the bladed wheel of the centrifugal fun that is mounted in the fan compartment such that the rotary shaft thereof is oriented to the opening direction of the fan entrance and the opening direction of the blow-out port. With the construction, immediately after blown out by the bladed wheel of the centrifugal fan, air can be herein strengthened in its flow component directed in the axial direction, and simultaneously, can be weakened in its flow component directed in the radial direction. Thus, the tendency of oblique flow can be strengthened. 
     Consequently, the ventilation resistance in the fan compartment can be herein reduced, and the ventilation performance of the centrifugal fan can be enhanced. 
     An air conditioning apparatus according to a second aspect relates to the air conditioning apparatus according to the first aspect, and wherein the outer diameter of the rearward blades is greater than or equal to 0.75 times a hydraulic diameter of lateral parts of the casing that enclose an outer peripheral side of the bladed wheel. Additionally; the outer diameter of the hub is 0.91 to 0.96 times the outer diameter of the rearward blades. 
     The extent to which the ventilation resistance in the fan compartment is increased by the air that has just been blown out from the bladed wheel of the centrifugal fan is affected by the distance between the rearward blades and the lateral parts of the casing. Put differently, the ventilation resistance tends to increase with decrease in distance between the rearward blades and the lateral parts of the casing. On the other hand, the extent of oblique flow is affected by the outer diameter of the hub. Put differently, the tendency of oblique flow can be strengthened with decrease in outer diameter of the hub. It should be noted that when the outer diameter of the hub is extremely small, the ventilation function of the rearward blades itself is inevitably impaired. Due to the characteristics as described above, in employing a type of bladed wheel having the construction that the outer diameter of the hub is set to be smaller than that of the rearward blades, it is preferable to achieve the tendency of oblique flow without impairing the ventilation function of the rearward blades under the condition that the distance between the rearward blades and the lateral parts of the casing is short. 
     In view of the above, in employing a type of bladed wheel having the construction that the outer diameter of the hub is set to be smaller than that of the rearward blades, the outer diameter of the hub is herein set, as described above, to be 0.91 to 0.96 times the outer diameter of the rearward blades under the condition that the outer diameter of the rearward blades is greater than or equal to 0.75 times the hydraulic diameter of the lateral parts of the casing that enclose the outer peripheral side of the bladed wheel. 
     Consequently, in employing a type of bladed wheel that the outer diameter of the hub is set to be smaller than that of the rearward blades, the ventilation performance of the centrifugal fan can be herein effectively enhanced in view of the characteristics as described above. 
     An air conditioning apparatus according to a third aspect relates to the air conditioning apparatus according to the first or second aspect, and wherein a length Obtained by subtracting the outer diameter of the hub from the outer diameter of the rearward blades is less than or equal to 0.4 times a chord length, which is a length obtained by subtracting an inner diameter of the rearward blades from the outer diameter of the rearward blades. 
     In employing a type of bladed wheel that the outer diameter of the hub is set to be smaller than that of the rearward blades, the length obtained by subtracting the outer diameter of the huh from that of the rearward blades is herein set, as described above, to be less than or equal to 0.4 times the chord length. 
     Consequently, in employing a type of bladed wheel that the outer diameter of the hub is set to be smaller than that of the rearward blades, the rearward blades can be herein reliably supported by the hub, and the structural strength of the bladed wheel can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1  is an external perspective view of an air conditioning apparatus according to a preferred embodiment of the present invention (in a vertical mount configuration); 
         FIG. 2  is a front lateral view of the air conditioning apparatus from which a first lateral part is detached (in the vertical mount configuration); 
         FIG. 3  is a rear lateral view of the air conditioning apparatus from which a second lateral part is detached (in the vertical mount configuration); 
         FIG. 4  is a right lateral view of the air conditioning apparatus from which a third lateral part is detached (in the vertical mount configuration); 
         FIG. 5  is a left lateral view of the air conditioning apparatus from which a fourth lateral part is detached (in the vertical mount configuration); 
         FIG. 6  is an external perspective view of a bladed wheel of a centrifugal fan; 
         FIG. 7  is a schematic cross-sectional view of the centrifugal fan; 
         FIG. 8  is an external perspective view of the air conditioning apparatus (in a horizontal mount configuration); 
         FIG. 9  is a right lateral view of the air conditioning apparatus from which the first lateral part is detached (in the horizontal mount configuration); 
         FIG. 10  is a cross-sectional view of  FIG. 2  taken along line I-I; 
         FIG. 11  is an external perspective view of the bladed wheel seen from a hub side; 
         FIG. 12  is a chart representing a relation between the ratio of the outer diameter of the hub to the outer diameter of rearward blades and ventilation efficiency (where the ratio of the outer diameter of the rearward blades to the hydraulic diameter of a casing is 0.798); 
         FIG. 13  is a chart representing a relation between the ratio of the outer diameter of the hub to the outer diameter of the rearward blades and ventilation efficiency (where the ratio of the outer diameter of the rearward blades to the hydraulic diameter of the casing is 0.779); 
         FIG. 14  is a chart representing a relation between the ratio of the outer diameter of the hub to the outer diameter of the rearward blades and ventilation efficiency (where the ratio of the outer diameter of the rearward blades to the hydraulic diameter of the casing is 0.755); and 
         FIG. 15  is a chart representing a relation between the ratio of the outer diameter of the hub to the outer diameter of the rearward blades and ventilation efficiency (where the ratio of the outer diameter of the rearward blades to the hydraulic diameter of the casing is 0.733). 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An air conditioning apparatus according to a preferred embodiment of the present invention will be hereinafter explained on the basis of the attached drawings. It should be noted that a specific construction of the air conditioning apparatus according to the present invention is not limited to the following preferred embodiment and the modifications thereof, and can be changed without departing from the scope of the present invention. 
     (1) Basic Construction of Air Conditioning Apparatus 
     First, a basic construction of an air conditioning apparatus I will be explained with  FIGS. 1 to 9 . Here,  FIG. 1  is an external perspective view of the air conditioning apparatus  1  according to the preferred embodiment of the present invention (in a vertical mount configuration).  FIG. 2  is a front lateral view of the air conditioning apparatus  1  from which a first lateral part  23  is detached (in the vertical mount configuration).  FIG. 3  is a rear lateral view of the air conditioning apparatus  1  from which a second lateral part  24  is detached (in the vertical mount configuration).  FIG. 4  is a right lateral view of the air conditioning apparatus  1  from which a third lateral part  25  is detached (in the vertical mount configuration).  FIG. 5  is a left lateral view of the air conditioning apparatus  1  from which a fourth lateral part  26  is detached (in the vertical mount configuration).  FIG. 6  is an external perspective view of a bladed wheel of a centrifugal fan.  FIG. 7  is a schematic cross-sectional view of the centrifugal fan  5 .  FIG. 8  is an external perspective view of the air conditioning apparatus  1  (in a horizontal mount configuration).  FIG. 9  is a right lateral view of the air conditioning apparatus  1  from which the first lateral part  23  is detached (in the horizontal mount configuration). 
     The air conditioning apparatus  1  is an apparatus installed in a building in order to perform a cooling operation and a heating operation for the indoor space of the building. The air conditioning apparatus  1  includes a casing  2 , a partition member  3 , a heat exchanger  4  and a centrifugal fan  5 . The casing  2  has an intake port  11  and a blow-out port  12 . The partition member  3  divides the interior of the casing  2  into a heat exchanger compartment S 1  located on the intake port  11  side and a fan compartment S 2  located on the blow-out port  12  side, and has a fan entrance  13  making the heat exchanger compartment S 1  and the fan compartment S 2  communicate with each other. The heat exchanger  4  is mounted in the heat exchanger compartment Si. The centrifugal fan  5  includes a bladed wheel  51  having a plurality of rearward blades  53  and is configured to suck air existing in the heat exchanger compartment S 1  into the fan compartment S 2  through the fan entrance  13 , with the bladed wheel  51  being mounted in the fan compartment S 2  such that a rotary shaft  52  (its axis will be referred to as a rotary axis A) is oriented to an opening direction B of the fan entrance  13 . 
     Moreover, the fan entrance  13  is herein opposed to the blow-out port  12 , and the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  is oriented to the opening direction B of the fan entrance  13  and an opening direction C of the blow-out port  12 . Furthermore, the intake port  11  is herein opposed to the fan entrance  13 , and the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  is oriented to the opening direction B of the fan entrance  13 , the opening direction C of the blow-out port  12  and an opening direction D of the intake port  11 . 
     Moreover, the air conditioning apparatus  1  is herein capable of taking two configurations, i.e., the vertical mount configuration and the horizontal mount configuration. in the vertical mount configuration, the casing  2  is disposed such that the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  is oriented to a vertical direction Z (see  FIGS. 1 to 5 ). In the horizontal mount configuration, the casing  2  is disposed such that the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  is oriented to a horizontal direction X (see  FIGS. 8 and 9 ). 
     As described above, the casing  2  has the intake port  11  and the blow-out port  12 . The casing  2  is mainly composed of an upstream lateral part  21 , a downstream lateral part  22 , the first lateral part  23 , the second lateral part  24 , the third lateral part  25  and the fourth lateral part  26 . These lateral parts  21  to  26  form the elongated cuboid casing  2 . The upstream lateral part  21  is a member configured to form the bottom lateral surface of the casing  2  in the vertical mount configuration and form the rear lateral surface of the casing  2  in the horizontal mount configuration. The downstream lateral part  22  is a member configured to form the top lateral surface of the casing  2  in the vertical mount configuration and form the front lateral surface of the casing  2  in the horizontal mount configuration. The upstream lateral part  21  and the downstream lateral part  22  are disposed away from each other in the lengthwise direction of the casing  2  (i.e., a direction along the rotary axis A and the opening directions B, C and D). The upstream lateral part  21  has the intake port  11 . The intake port  11  is an opening bored in the middle of the upstream lateral part  21  and is made in the form of a rectangular aperture. The downstream lateral part  22  has the blow-out port  12 . The blow-out port  12  is an opening bored in the downstream lateral part  22  so as to be displaced from the middle of the downstream lateral part  22 , and is made in the form of a rectangular aperture. The blow-out port  12  is herein located in a position close to the second lateral part  24  within the downstream lateral part  22 . The first lateral part  23  is a member configured to form the front lateral surface of the casing  2  in the vertical mount configuration and form the right lateral surface of the casing  2  in the horizontal mount configuration. The second lateral part  24  is a member configured to form the rear lateral surface of the casing  2  in the vertical mount configuration and form the left lateral surface of the casing  2  in the horizontal mount configuration. The first lateral part  23  and the second lateral part  24  are disposed away from each other in a direction orthogonal to the lengthwise direction of the casing  2  (i.e., the horizontal direction X orthogonal to the rotary axis A and the opening directions B, C and D in the vertical mount configuration; a right-and-left direction Y orthogonal to the rotary axis A and the opening directions B, C and D in the horizontal mount configuration). The third lateral part  25  is a member configured to from the right lateral surface of the casing  2  in the vertical mount configuration and form the top lateral surface of the casing  2  in the horizontal mount configuration. The fourth lateral part  26  is a member configured to form the left lateral surface of the casing  2  in the vertical mount configuration and form the bottom lateral surface of the casing  2  in the horizontal mount configuration. The third lateral part  25  and the fourth lateral part  26  are disposed away from each other in a direction orthogonal to the lengthwise direction of the casing  2  (i.e., the right-and-left direction Y orthogonal to the rotary axis A and the opening directions B and C in the vertical mount configuration; the vertical direction Z orthogonal to the rotary axis A and the opening directions B, C and D in the horizontal mount configuration). 
     Moreover, a plurality of ridges  21   a  are herein formed on the upstream lateral part  21  so as to enclose the circumferential edges of the intake port  11 , whereas a plurality of ridges  22   a  are formed on the downstream lateral part  22  so as to enclose the circumferential edges of the blow-out port  12 . Furthermore, an intake duct  18  is connected to the intake port  11  through the ridges  21   a , whereas a blow-out duct  19  is connected to the blow-out port  12  through the ridges  22   a . With the construction, the air conditioning apparatus  1  is herein configured to be of a duct connection type for sucking and blowing air from and to an air-conditioned room indirectly through the ducts  18  and  19 . It Should be herein noted that the intake port  111  and the blow-out port  12  are made in forms of rectangular apertures, and likewise, the ducts  18  and  19  are made in forms of rectangular tubes. However, the ports  11  and  12  and the ducts  18  and  19  are not limited to be made in the aforementioned forms, and may employ a variety of forms. Furthermore, the air conditioning apparatus  1  is not limited to be of the duct connection type, and may be of a variety of types such as a type for sucking and blowing air from and to an air-conditioned room directly through the intake port  11  and the blow-out port  12 . 
     As described above, the partition member  3  divides the interior of the casing  2  into the heat exchanger compartment S 1  located on the intake port  11  side and the fan compartment S 2  located on the blow-out port  12  side, and has the fan entrance  13  that makes the heat exchanger compartment S 1  and the fan compartment S 2  communicate with each other, The partition member  3  is mainly composed of a partition body  31  made in the form of a rectangular plate. The partition body  31  is disposed in parallel to a direction orthogonal to the lengthwise direction of the casing  2  (i.e., a direction orthogonal to the rotary axis A and the opening directions B, C and D). The fan entrance  13  is bored in the partition body  31  and is herein made in the form of a circular aperture. The partition body  31  has a partition circumferential part  32  made in the form of a rectangular frame. The partition circumferential part  32  extends from the circumferential edges of the partition body  31  toward the fan compartment S 2  along the inner surfaces of the lateral parts  23  to  26  of the casing  2 . 
     As described above, the heat exchanger  4  is mounted in the heat exchanger compartment S 1 . In a cooling operation, the heat exchanger  4  is configured to cool air flowing through the heat exchanger compartment S 1  by a refrigerant. Contrarily in a heating operation, the heat exchanger  4  is also capable of heating air flowing through the heat exchanger compartment S 1  by the refrigerant. A fin tube heat exchanger, composed of multiple fins and a heat transfer tube, is herein employed as the heat exchanger  4 . Furthermore, the refrigerant is configured to be supplied to the heat exchanger  4  from an outdoor unit installed outside the building or so forth. The heat exchanger  4  is composed of a part  41  located closely to the third lateral part  25  of the casing  2  and a part  42  located closely to the fourth lateral part  26  of the casing  2 . Moreover, the part  41  of the heat exchanger  4 , located closely to the third lateral part  25 , is disposed in a tilt position so as to get closer to the third lateral part  25  from a side near to the fan entrance  13  to a side near to the intake port  11 . The part  42  of the heat exchanger  4 , located closely to the fourth lateral part  26 , is disposed in a tilt position so as to get closer to the fourth lateral part  26  from the side near to the fan entrance  13  to the side near to the intake port  11 . With the construction, the heat exchanger  4  has a V shape so as to get closer to the third lateral part  25  and the fourth lateral part  26  of the casing  2  from the side near to the fan entrance  13  to the side near to the intake port  11 . It should be noted that the heat exchanger  4  is not limited to have the V shape, and may employ a variety of shapes. 
     Moreover, drain pans  43  and  44  are mounted in the heat exchanger compartment S 1  in order to receive water produced by dew condensation in the heat exchanger  4 . The first drain pan  43  is configured to be used when the casing  2  is disposed such that the rotary shaft  52  (the rotary axis A) of the bladed wheel S 1  is oriented to the horizontal direction X (in the horizontal mount configuration). The second drain pan  44  is configured to be used when the casing  2  is disposed such that the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  is oriented to the vertical direction Z (in the vertical mount configuration). The first drain pan  43  is disposed in a position close to the fourth lateral part  26 , which is one of the lateral parts  23  to  26  of the casing  2  that are disposed along the opening direction B of the fan entrance  13 . With the construction, the first drain pan  43  is configured to be disposed over the fourth lateral part  26  forming the bottom lateral surface of the casing  2  and receive the bottom side of the heat exchanger  4  in the horizontal mount configuration. The second drain pan  44  is disposed in a position close to the upstream lateral part  21 , which is one of the lateral parts  21  and  22  of the casing  2  that are disposed along the direction orthogonal to the opening direction B of the fan entrance  13 . With the construction, the second drain pan  44  is configured to be disposed over the upstream lateral part  21  forming the bottom lateral surface of the casing  2  and receive the bottom side of the heat exchanger  4  in the vertical mount configuration. Furthermore, the first and second drain pans  43  and  44  are herein compatible with the vertical mount configuration and the horizontal mount configuration, but the first drain pan  43  to be used in the horizontal mount configuration exists in the heat exchanger compartment S 1  even in the vertical mount configuration, whereas the second drain pan  44  to be used in the vertical mount configuration exists in the heat exchanger compartment S 1  even in the horizontal mount configuration. 
     As described above, the centrifugal fan  5  includes the bladed wheel  51  having the plural rearward blades  53  and is configured to suck air existing in the heat exchanger compartment S 1  into the fan compartment S 2  through the fan entrance  13 , with the bladed wheel  51  being mounted in the fan compartment S 2  such that the rotary shaft  52  (the rotary axis A) is oriented to the opening direction B of the fan entrance  13 . Furthermore, a fan motor  59  is mounted in the fan compartment S 2  in order to drive and rotate the bladed wheel  51 . Here in the fan compartment  2 , the bladed wheel  51  is disposed proximally to the fan entrance  13  and the fan motor  59  is disposed on the downwind side of the bladed wheel  51  along the rotary shaft  52  (the rotary axis A) of the bladed wheel  51 . Moreover, a bell mouth  33  is mounted to the fan entrance  13 . A space, located on the downwind side of the bladed wheel  51  in the fan compartment S 2 , is herein defined as a fan downwind space S 21 . Thus, the fan motor  59  is disposed in the fan downwind space S 21 . 
     The bladed wheel  51  is composed of a hub  54 , a shroud  55  and the plural rearward blades  53  disposed between the hub  54  and the shroud  55 . The hub  54  connects the blow-out port  12  side ends of the plural rearward blades  53 , and is configured to be rotated about the rotary shaft  52  (the rotary axis A), The hub  54  is a disc-shaped member and has a hub protrusion  54   a  protruding from its middle toward the shroud  55 . The hub protrusion  54   a  is coupled to the fan motor  59 . The rotary shaft  52  of the fan motor  59  is herein fixed to a shaft hole  54   b  formed in the middle of the hub protrusion  54   a . The shroud  55  is disposed on the fan entrance  13  side of the hub  54  so as to be opposed to the hub  54 , connects the fan entrance  13  side ends of the plural rearward blades  53 , and is configured to be rotated about the rotary shaft  52 . (the rotary axis A). The shroud  55  is an annular member and has a fan opening  55   a  that is bored in the thrill of a circular aperture and is centered at the rotary shaft  52  (the rotary axis A). The shroud  55  has a curved shape that its outer diameter increases toward a side near to the hub  54 . The plural rearward blades  53  are disposed between the huh  54  and the shroud  55  so as to be aligned at predetermined intervals along the circumferential direction of the rotary shaft  52  (the rotary axis A). Each rearward blade  53  tilts oppositely to a rotary direction R of the bladed wheel  51  (herein a clockwise direction in a view seen from the blow-out port  12  side) with respect to the radial direction of the hill)  54 . 
     The bell mouth  33  is mounted to the fan entrance  13  of the partition member  3  so as to be opposed to the fan opening  55   a  of the bladed wheel  51  and directs air, flowing thereto from the heat exchanger compartment S 1 , to the fan opening  55   a  of the bladed wheel  51 . The bell mouth  33  is an annular member centered at the rotary shaft  52  (the rotary axis A). The bell mouth  33  has a curved shape that its outer diameter decreases toward a side near to the shroud  55 . 
     The fan motor  59  is disposed concentrically to the rotary shaft  52  (the rotary axis A) of the bladed wheel  51  in the fan downwind space S 21 . The fan motor  59  has a columnar shape centered at the rotary shaft  52  (the rotary axis A). The fan motor  59  is herein fixed to the partition member  3  through a motor support base  34 . Specifically, the motor support base  34  is composed of support frames  35  and  36  forming a roughly squared U shape. The support frames  35  and  36  respectively extend toward the vicinity of the outer peripheral surface of the fan motor  59  from parts of the partition circumferential part  32  of the partition member  3 , i.e., a part located closely to the third lateral part  25  of the casing  2  and a part located closely to the fourth lateral part  26  of the casing  2 . Moreover, the fan motor  59  is fixed at its end plate parts  59   a  to the support frames  35  and  36  through a bracket  37 . The end plate parts  59   a  extend from the outer peripheral surface of the fan motor  59  toward the third lateral part  25  and the fourth lateral part  26 . Thus, the centrifugal fan  5 , including the bladed wheel  51  and the fan motor  59 , is designed to be fixed to the partition member  3  through the motor support base  34 . With the construction, the entirely of the centrifugal fan  5  is configured to be detachable by detaching the partition member  3  from the casing  2  in performing a maintenance work or so forth. 
     Moreover, the fan downwind space S 21  of the fan compartment S 2  has a blow-out port opposed space S 22  as a region opposed to the blow-out port  12 . The blow-out port  12  is herein disposed in the position close to the second lateral part  24  within the downstream lateral part  22 . Thus, when the casing  2  is seen from the blow-out port  12 . side, the blow-out port opposed space S 22  is formed by a space enclosed by parts located along the circumferential edges of the opening of the blow-out port  12 , i.e., the second lateral part  24 , a part of the third lateral part  25  that is located closely to the second lateral part  24 , and a part of the fourth lateral part  26  that is located closely to the second lateral part  24 . Furthermore, a blow-out port non-opposed surface part  27  is mounted in a position on the downwind side of the bladed wheel  51  so as to be opposed to the fan entrance  13 , and accordingly, a blow-out port non-opposed space S 23  is formed as a space excluding the blow-out port opposed space S 22  within the fan downwind space S 21  so as not to be opposed to the blow-out port  12  but to be opposed to the blow-out port non-opposed surface part  27 , Moreover, a blow-out port circumferential surface part  28  is herein provided so as to extend from the blow-out port  112  side end of the blow-out port non-opposed surface part  27  toward the blow-out port  12  along the opening direction B of the Fin entrance  13  and the opening direction C of the blow-out port  12 . With the construction, an electric component compartment S 3  is herein formed by the blow-out port non-opposed surface part  27 , the blow-out port circumferential surface part  28 , the first lateral part  23 , the third lateral part  25 , the fourth lateral part  26 , and a part of the downstream lateral part  22  that is located closely to the first lateral part  23  and in which the blow-out port  12  is not formed. The electric component compartment S 3  accommodates electric components  14  to be used for controlling devices that make up the air conditioning apparatus  1 . Furthermore, a blow-out pathway region S 24 , having the same opening size as the blow-out port  12 , is formed by a region located closely to the blow-out port  12  within the blow-out port opposed space S 22 , i.e., a space enclosed by the blow-out port circumferential surface part  28 , the second lateral part  24 , a part of the third lateral part  25  that is located closely to the second lateral part  24 , and a part of the fourth lateral part  26  that is located closely to the second lateral part  24 . 
     Moreover, an electric heater  6  is herein mounted in the fan downwind space S 21  of the fan compartment  52  in order to heat air blown out to the fan downwind space S 21  by the bladed wheel  51  of the centrifugal fan  5 . The electric heater  6  is heating means for heating air flowing through the fan compartment S 2  in a heating operation. A heating element assembly with coiled electric heating wires is herein employed as the electric heater  6  (heating means). The electric heater  6  (the heating means) is disposed in the blow-out port opposed space S 22 , i.e., a region opposed to the blow-out port  12  within the fan downwind space S 21 . More specifically, the electric heater  6  (the heating means) disposed in the blow-out pathway region S 24  close to the blow-out port  12  within the blow-out port opposed space S 22 . It should be noted that the electric heater  6  (the heating means) is not limited to the heating element assembly with the coiled electric heating wires, and alternatively, may employ a variety of types of heater. 
     (2) Basic Action of Air Conditioning Apparatus 
     Next, a basic action of the air conditioning apparatus  1  will be explained with  FIGS. 1 to 9 . 
     In the air conditioning apparatus  1  having the aforementioned construction, the bladed wheel  51  of the centrifugal fan  5  is configured to be rotated by driving of the fan motor  59 . This produces the flow of air passing through the interior of the casing  2  sequentially in the order of the intake port  11 , the heat exchanger compartment S 1 , the fan entrance  13 , the fan compartment S 2  and the blow-out port  12 . 
     Now in the cooling operation, air fed to the interior of the casing  2  through the intake port Ill flows into the heat exchanger compartment SI, and is cooled by the refrigerant flowing through the heat exchanger  4 . Then, the air cooled by the heat exchanger  4  flows into the fan compartment  52  through the tan entrance  13  and is sucked into the bladed wheel  51  of the centrifugal fan  5 . The air sucked into the bladed wheel  51  is blown out to the fan downwind space S 21  located on the downwind side of the bladed wheel  51 . The air blown out to the fan downwind space S 21  is fed to the outside of the casing  2  through the blow-out port  12 . 
     On the other hand, in the heating operation, air fed to the interior of the casing  2  through the intake port  11  flows into the heat exchanger compartment S 1 , and is heated by the refrigerant flowing through the heat exchanger  4 . The air heated by the heat exchanger  4  flows into the fan compartment S 2  through the fan entrance  13 , and is sucked into the bladed wheel  51  of the centrifugal fan  5 . The air sucked into the bladed wheel  51  is blown out to the fan downwind space S 21  located on the downwind side of the bladed wheel  51 . The air blown out to the fan downwind space S 21  is further heated by the electric heater  6  (the heating means), and is then fed to the outside of the casing  2  through the blow-out ports  12 . 
     (3) Construction for Enhancing Ventilation Performance of Centrifugal Fan 
     In the air conditioning apparatus  1  having the aforementioned construction, the centrifugal fan  5  having the rearward blades  53  is mounted in the fan compartment S 2  having the fan entrance  13  bored in opposition to the blow-out port  12  such that the rotary shaft  52  (the rotary axis A) is oriented to the opening direction B of the fan entrance  13  and the opening direction C of the blow-out port  12 . 
     In the positional arrangement of the centrifugal fan  5  in the fan compartment S 2  as described above, immediately after blown out by the bladed wheel  51  of the centrifugal fan  5 , air has a strong flow component directed in the radial direction. Hence, the radial flow component increases ventilation resistance in the fan compartment S 2 , and this serves as a cause of hindering enhancement in ventilation performance. 
     Therefore, it is demanded for the air conditioning apparatus  1  to enhance the ventilation performance of the centrifugal fan  5  in consideration of the tendency, as described above, that air has a strong flow component directed in the radial direction immediately after blown out by the bladed wheel  51 . 
     In view of the above, the bladed wheel  51  is herein contrived in shape. Specifically, as shown in  FIGS. 7, 10 and 11 , the bladed wheel  51  to be employed has a construction that an outer diameter φx of the hub  54  is set to be smaller than an outer diameter φ 2  of the rearward blades  53  (the diameter of the outermost peripheral ends of the plural rearward blades  53 ).  FIG. 10  is herein a cross-sectional view of  FIG. 2  taken along line  14 , whereas  FIG. 11  is an external perspective view of the bladed wheel  51  seen from the hub  54  side. 
     Thus, a type of bladed wheel, having the construction that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53 , is herein employed as the bladed wheel  51  of the centrifugal fan  5  that is mounted in the fan compartment  52  such that the rotary shaft  52  (the rotary axis A) is oriented to the opening direction B of the fan entrance  13  and the opening direction C of the blow-out port  12 . With the construction, immediately after blown out by the bladed wheel  51  of the centrifugal fan  5 , air can be herein strengthened in its flow component directed in the axial direction, and simultaneously; can be weakened in its flow component directed in the radial direction. Thus, the tendency of oblique flow can be strengthened. 
     Consequently, the ventilation resistance in the fan compartment S 2  can be herein reduced, and the ventilation performance of the centrifugal fan  5  can be enhanced. 
     The extent to which the ventilation resistance in the fan compartment S 2  is increased by the air that has just been blown out from the bladed wheel  51  of the centrifugal fan  5  is herein affected by the distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2 . Put differently, the ventilation resistance tends to increase with decrease in distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2 . On the other hand, the extent of oblique flow is affected by the outer diameter φx of the hub  54 . Put differently, the tendency of Oblique flow can be strengthened with decrease in the outer diameter φx of the hub  54 . It should be noted that when the outer diameter φx of the hub  54  is extremely small, the ventilation function of the rearward blades  54  itself is inevitably impaired. Due to the characteristics as described above, in employing the bladed wheel  51  having the construction that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53  (the diameter of the outermost peripheral ends of the plural rearward blades  53 ), it is preferable to achieve the tendency of oblique flow without impairing the ventilation function of the rearward blades  53  under the condition that the distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2  is short. 
     In view of the above, in employing the bladed wheel  51  having the construction that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53  (the diameter of the outermost peripheral ends of the plural rearward blades  53 ), the outer diameter φx of the hub  54  is herein set to be 0.91 to 0.96 times the outer diameter φ 2  of the rearward blades  53  under the condition that the outer diameter φ 2  of the rearward blades  53  is greater than or equal to 0.75 times a hydraulic diameter dh of the lateral parts  23  to  26  of the casing  2  that enclose the outer peripheral side of the bladed wheel  51 . When the casing  2  is seen from a direction along the rotary shaft  52  (the rotary axis A), the lateral parts  23  to  26  of the casing  2  have a quadrilateral cross-section, Hence, the hydraulic diameter dh of the casing  2  can be herein expressed by the following formula using a width W of the lateral part  23 ,  26  and a width H of the lateral part  24 ,  25 . It should be noted that “W×H” indicates the cross-sectional area of the lateral parts  23  to  26  of the casing  2  that enclose the outer peripheral side of the bladed wheel  51 , whereas “2×W+2×H” indicates the circumferential length of the lateral parts  23  to  26  of the casing  2  that enclose the outer peripheral side of the bladed wheel  51 .
 
 dh =4×( W×H )/(2 ×W+ 2× H )
 
     Next,  FIGS. 12 to 15  represent relations between the ratio of the outer diameter φx of the huh  54  to the outer diameter φ 2  of the rearward blades  53  (=φx/φ 2 ) and ventilation efficiency under various conditions regarding the ratio of the outer diameter φ 2  of the rearward blades  53  to the hydraulic diameter dh of the casing  2  (=φ 2 /dh). According to the charts, the ventilation efficiency is maximized when φx/φ 2  falls in a range of 0.91 to 0.96 under the condition that φ 2 /dh is greater than or equal to 0.75, put differently, that the distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2  is short (see  FIGS. 12 to 14 ). As a reason for this, it can be assumed that the tendency of oblique flow can be obtained by setting the outer diameter φx of the hub  54  to be smaller than the outer diameter φ 2  of the rearward blades  53  such that φx/φ 2  falls in a range of 0.91 to 0.96; ventilation resistance is thus inhibited by the tendency of oblique flow; and this results in enhancement in ventilation efficiency. On the other hand, the ventilation efficiency is not maximized when φx/φ 2  falls in a range of 0.91 to 0.96 under the condition that φ 2 /dh is smaller than 0.75, put differently, that the distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2  is long. The ventilation efficiency becomes higher by setting the outer diameter φx of the hub  54  not to be smaller than the outer diameter φ 2  of the rearward blades  53  (φx/φ 2 =1.00) rather than by setting the outer diameter φx of the hub  54  to be smatter than the outer diameter φ 2  of the rearward blades  53 . As a reason for this, it can be assumed that the tendency of oblique flow can be obtained by setting the outer diameter φx of the huh  54  to be smaller than the outer diameter φ 2  of the rearward blades  53  such that φx/φ 2  falls in a range of 0.91 to 0.96; but even if the tendency of oblique flow could be obtained under the condition that φ 2 /dh is smaller than 0.75, put differently, that the distance between the rearward blades  53  and the lateral parts  23  to  26  of the casing  2  is long, the effect of inhibiting ventilation resistance is remarkably small and the adverse effect of impairing the ventilation function of the rearward blades  54 , which is caused by setting the outer diameter φx of the hub  54  to be smaller than the outer diameter φ 2  of the rearward blades  53 , is relatively larger than the effect of inhibiting ventilation resistance. Thus, φ 2 /dh, φx/φ 2  and the ventilation efficiency are closely related to each other. In consideration of the characteristics, it is preferable to appropriately set the sizes (W and H) of the lateral parts  23  to  26  of the casing  2 , and it is more preferable to appropriately set the sizes (φx and φ 2 ) of the hub  54  with respect to the rearward blades  53 . 
     Consequently, in employing the bladed wheel  51  that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53 , the ventilation performance of the centrifugal fan  5  can be herein effectively enhanced in view of the characteristics as described above. 
     Moreover, a length obtained by subtracting the outer diameter φx of the hub  54  from the outer diameter φ 2  of the rearward blades  53  (=φ 2 −φx) is herein less than or equal to 0.4 times a chord length, which is a length obtained by subtracting an inner diameter φ 1  of the rearward blades  53  (the diameter of the innermost peripheral ends of the plural rearward blades  53 ) from the outer diameter φ 2  of the rearward blades  53  (=φ 2 −φ 1 ), 
     Thus, in employing the bladed wheel  51  that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53 , the length (φ 2 −φx) obtained by subtracting the outer diameter φx of the hub  54  from the outer diameter φ 2  of the rearward blades  53  is herein set to be less than or equal to 0.4 times the chord length (φ 2 −φ 1 ). 
     Consequently, in employing the bladed wheel  51  that the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53 , the rearward blades  53  can be herein reliably supported by the huh  54  and the structural strength of the bladed wheel  51  can be enhanced. 
     (4) Modification 
     In the aforementioned bladed wheel  51  of the centrifugal fan  5 , the outer diameter φx of the hub  54  is set to be smaller than the outer diameter φ 2  of the rearward blades  53  in the entire circumferential direction of the hub  54 . However, the setting of the outer diameter φx of the hub  54  is not limited to the above. For example, although not herein shown in the drawings, only parts of the hub  54 , located between circumferentially adjacent ones of the plural rearward blades  53 , may have an outer diameter smaller than the outer diameter φ 2  of the rearward blades  53  when the bladed wheel  51  is seen from the direction along the rotary shaft  52  (the rotary axis A). It should be noted that the effect of strengthening the oblique flow is herein smaller than by setting the outer diameter φx of the hub  54  to be smaller than the outer diameter φ 2  of the rearward blades  53  in the entire circumferential direction of the hub  54 , and thus, the extent of enhancement in ventilation performance herein tends to be somewhat small.