Abstract:
Provided is an air-conditioning blower motor unit that includes: a brushless motor which has an output shaft to be coupled with an air-conditioning blower fan constituting an air conditioner; a circuit board configured to allow the brushless motor to be driven by a supply of electric power; a casing configured to house the brushless motor and the circuit board; and a base frame configured to support the circuit board and the output shaft. The circuit board on the base frame is disposed at a position eccentric with respect to the output shaft inside the casing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Priority is claimed on Japanese Patent Application No. 2016-038410, filed on Feb. 29, 2016, the content of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a blower motor unit of an air conditioner mounted in a vehicle such as an automobile. 
         [0004]    Description of Related Art 
         [0005]    A centrifugal fan unit with a built-in electronic control circuit section (a circuit board) for a motor, the electronic control circuit section being disposed at a position eccentric with respect to an output shaft of the motor, is disclosed, for example, in Japanese Unexamined Patent Application, First Publication No. 2008-215330 (hereinafter, Patent Literature 1). According to the centrifugal fan unit related to Patent Literature 1, since the electronic control circuit section is disposed at a place which was recognized as an unused space of the centrifugal fan unit, an axial size of the centrifugal fan unit can be minimized, and the centrifugal fan unit can be made thinner. 
       SUMMARY OF THE INVENTION 
       [0006]    In the control circuit section (the circuit board) in Patent Literature 1, since a given electronic parts mounting region of the board itself is to be small, a distance between the electronic parts is short and amount of heat generation is easily increased. Furthermore, since the control circuit section (the circuit board) in Patent Literature 1 is fixed to a casing, an area in which the control circuit section (the circuit board) can be installed is restricted depending on an internal shape of the casing. Therefore, the control circuit section (the circuit board) cannot be disposed at an optimal position for cooling, and hence a cooling efficiency of the circuit board is poor. 
         [0007]    An aspect according to the present invention has been made in view of the above problems, and is directed to providing a thin air-conditioning blower motor unit in which cooling efficiency of a circuit board is improved. 
         [0008]    To accomplish the above object, the present invention employs the following aspects. 
         [0009]    (1) An aspect according to the present invention provides an air-conditioning blower motor unit that includes: a brushless motor which has an output shaft to be coupled with an air-conditioning blower fan constituting an air conditioner; a circuit board configured to allow the brushless motor to be driven by a supply of electric power; a casing configured to house the brushless motor and the circuit board; and a base frame configured to support the circuit board and the output shaft. The circuit board on the base frame is disposed at a position eccentric with respect to the output shaft inside the casing. 
         [0010]    (2) In the aspect (1), the circuit board may be supported by the base frame inside the casing so as to be spaced from the casing. 
         [0011]    (3) In the aspect (1) or (2), the casing may have an air introduction opening for an introducing air introduced inside the casing, the introducing air being divided from an air, which is sent by the blower fan to the air conditioner, through the air introduction opening. 
         [0012]    (4) In the aspect (3), the casing may have a central opening around the output shaft, the central opening being intended to discharge the introducing air from the casing. The circuit board may be supported by the base frame within streamlines of the introducing air flowing in from the air introduction opening to the central opening. 
         [0013]    (5) In the aspect (4), the base frame may include a plurality of base frame openings through which the introducing air passes within the streamlines of the introducing air flowing in from the air introduction opening to the central opening. 
         [0014]    (6) In the aspect (5), the circuit board may include a cut-out portion through which the introducing air passes to the base frame openings. 
         [0015]    (7) In the aspect (5) or (6), the casing may include a wall section that guides a flow of the air, which flows in from the air introduction opening, to the central opening. 
         [0016]    (8) In any one of the aspects (5) to (7), the brushless motor may include gas flow channels through which the introducing air passes. 
         [0017]    (9) In any one of the aspects (1) to (8), the air-conditioning blower motor unit may further include a heat sink member which is partially exposed outside the casing and is adjacent to the circuit board to allow thermal conduction. 
         [0018]    According to the aspects of the present invention, the base frame supporting the circuit board is provided. That is, the circuit board is not directly mounted on the casing. Thereby, the circuit board can be installed at an arbitrary position regardless of a shape of the casing, and be disposed at an optimum position which adapted to cooling the circuit board. Therefore, it is possible to improve cooling efficiency of the circuit board. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a side view illustrating a blower provided with a blower motor unit according to an embodiment of the present invention. 
           [0020]      FIG. 2  is a perspective view illustrating the blower motor unit according to the embodiment of the present invention. 
           [0021]      FIG. 3  is a cross-sectional view illustrating a flow of air of the blower motor unit according to the embodiment of the present invention. 
           [0022]      FIG. 4A  is a bottom view in which a lower casing section of the blower motor unit according to the present embodiment is omitted. 
           [0023]      FIG. 4B  is a top view in which an upper casing section of the blower motor unit according to the present embodiment is omitted. 
           [0024]      FIG. 5  is an exploded perspective view including a part of a blower motor and a base frame in the embodiment of the present invention. 
           [0025]      FIG. 6  is a perspective view including the lower casing section indicating a flow of air inside the blower motor unit according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Hereinafter, an embodiment of a blower motor unit  1  (an air-conditioning blower motor unit) according to the present invention will be described with reference to the drawings. 
         [0027]    A blower A is disposed in a duct constituting an air conditioner for a vehicle. This blower A is provided with a blower motor unit  1 , a blower fan B, and a fan case C housing the blower fan B. The blower fan B is a centrifugal fan having a plurality of blades on an outer circumferential portion thereof. This blower fan B is turned by the blower motor unit  1 , and thereby suctions an air from an air inlet C 1  formed in the fan case C to send the air via an air outlet (not shown). The blower motor unit  1  is attached to the fan case C via a bracket D. Although not illustrated, an evaporator cooling the air and an air-conditioning device such as a heater core heating the air are set up downstream in an air-sending direction of the air sent from the blower fan B. 
         [0028]    In the following description, a side at which the blower fan B is coupled with the blower motor unit  1  is referred to as an upper side. 
         [0029]    The blower motor unit  1  is an air-conditioning blower motor unit provided for the blower A and, as illustrated in  FIGS. 2 and 3 , is provided with a casing  2 , a base frame  3 , a motor  4 , a circuit board  5 , a heat sink member  6 , and elastic members  7 . The casing  2  has a casing section  20  and a gas guide section  21 , the casing section  20  housing the base frame  3 , the motor  4 , the circuit board  5 , the heat sink member  6 , and the elastic members  7 . The casing section  20  and the gas guide section  21  are integrally formed by combining an upper casing section  2 A and a lower casing section  2 B, as divided into two parts as upper and lower parts, these parts are abutted at a circumferential surface section  20   b . The upper casing section  2 A is an upper member including a top section  20   a  and an introduction opening  21   a  that will be described below, and the lower casing section  2 B is a lower member including a bottom section  20   c  that will be described below. 
         [0030]    The casing section  20  is a container-like part that has the top section  20   a , the circumferential surface section  20   b  and the bottom section  20   c , and is formed in an approximately cylindrical flat shape. This casing section  20  has a central opening  20   d  that is opened to the top section  20   a , a heat sink member exposure opening  20   e , protrusion sections  20   f  provided for the top section  20   a , and a guide wall section  20   g  provided for the bottom section  20   c  (see  FIGS. 4A and 4B ). 
         [0031]    The central opening  20   d  is an opening that is formed in the central portion of the top section  20   a  and spatially connects an inside of the casing  2  in which the motor  4  is housed and an inside of the fan case C in which the blower fan B is housed. That is, the central opening  20   d  is in a state in which the motor  4  is exposed to the fan case C side. The heat sink member exposure opening  20   e  is an opening that freely fits an upper end  60  of the heat sink member  6  in a swingable way wherein the upper end  60  of the heat sink member  6  is formed at a position corresponding to the heat sink member  6  disposed nearly midway between an output shaft  42  of the motor  4  and the introduction opening  21   a . This heat sink member exposure opening  20   e  is provided to expose the upper end  60  of the heat sink member  6  to the fan case C side by causing the upper end  60  of the heat sink member  6  to protrude outside of the casing  2 . 
         [0032]    The protrusion sections  20   f  are cylindrical parts that are formed by protruding downward (inside the casing  2 ) from the top section  20   a  of the upper casing section  2 A at a plurality of places (three places). As illustrated in  FIGS. 4A and 4B , the guide wall section  20   g  is a standing wall section that rises from the bottom section  20   c  of the lower casing section  2 B and becomes a tapered shape to form a tapered surface at a position opposite to the gas guide section  21 . This guide wall section  20   g  guides a flow of an introducing air, which flows in from the introduction opening  21   a  to pass through a side below the output shaft  42  along the lower casing section  2 B as will be described below, to the central opening  20   d.    
         [0033]    As illustrated in  FIG. 1 , the gas guide section  21  is an air conducting passage that is related to the introduction opening  21   a , and communicates with the inside of the casing  2  downstream in an air-sending direction of the fan case C via the introduction opening  21   a , wherein the introduction opening  21   a  is pointing the upward direction of the casing  2 . 
         [0034]    The base frame  3  is a holding member that has a plurality of fitting openings  30  into which the elastic members  7  are fitted, a motor holder  31  holding the motor  4  via a connecting member  43  (to be described below), and a heat sink member fixture  32  supporting the heat sink member  6 . Moreover, the base frame  3  further includes a circuit board fixture  35  fixing the circuit board  5 . This base frame  3  fits the plurality of elastic members  7  into the protrusion sections  20   f , and thereby is elastically supported by the upper casing section  2 A. 
         [0035]    A predetermined space is provided between the heat sink member exposure opening  20   e  of the casing  2  and an outer periphery of the upper end  60  of the heat sink member  6 . A frame-shaped elastic member  7   a , which can maintain water tightness (drip-proof) of the upper casing section  2 A even if a width of the predetermined space varies under the influence of vibration during operation of the motor  4 , is interposed in this space. In this way, the plurality of these elastic members  7  and  7   a  are interposed inside the casing  2 , and thereby the base frame  3  is elastically supported (floated) in the casing  2 . The elastic members  7  are fixed to the upper casing section  2 A by fastening members such as screws, and do not drop from the protrusion sections  20   f.    
         [0036]    As illustrated in  FIGS. 4A and 4B  along with  FIG. 5 , the motor  4  and the heat sink member  6  are mounted on a surface (hereinafter referred to as a front surface) of the base frame  3  which is located at the upper casing section  2 A side, and the circuit board  5  is mounted on a surface (hereinafter referred to as a rear surface) of the base frame  3  which is located at the lower casing section  2 B side. The motor holder  31  is a part that is recessed in a circular shape along a shape of the motor  4  mounted on the front surface of the base frame  3 . An output shaft opening  31   a  into which the output shaft  42  is passed, base frame openings  33  ( 33   a  and  33   b ), and a lower ball bearing holder  34  are formed in the center of the part recessed in the circular shape of the motor holder  31 . 
         [0037]    The base frame openings  33  have a board-side opening  33   a  that is formed at a position corresponding to a cut-out portion  50  of the circuit board  5  (to be described below), and motor-side openings  33   b  that are a plurality of fan-shaped openings arranged to correspond in an approximately semicircular range to slot positions of teeth  40   f  of the motor  4  (to be described below). The board-side opening  33   a  and the motor-side openings  33   b  are provided to pass the air flows of the introducing air between the lower casing section  2 B and the base frame  3  from the introduction opening  21   a  toward the central opening  20   d  of the upper casing section  2 A. 
         [0038]    The lower ball bearing holder  34  is a rear surface of the motor holder  31  and is a cylindrical bearing boss formed around the output shaft opening  31   a.    
         [0039]    As illustrated in  FIG. 3 , the connecting member  43  has a lower ball bearing  43   c  held on the aforementioned lower ball bearing holder  34  to be slidable in a direction of the output shaft  42 , an upper ball bearing  43   b , and a sleeve member  43   a . The sleeve member  43   a  is an annular member that is provided between the stator core  40   a  and the upper ball bearing  43   b  and fixes the upper ball bearing  43   b  to a stator core  40   a . The output shaft  42  is inserted into a central opening of this sleeve member  43   a  without contact, and the sleeve member  43   a  is fixed to an upper surface side of the lower ball bearing holder  34  of the base frame  3 . 
         [0040]    The output shaft  42  is press-fitted into an inner race portion of the upper ball bearing  43   b , and the sleeve member  43   a  is press-fitted onto an outer race portion of the upper ball bearing  43   b . Thereby, the upper ball bearing  43   b  rotatably supports the output shaft  42  inside the sleeve member  43   a . The output shaft  42  is press-fitted into an inner race portion of the lower ball bearing  43   c , and an outer race portion of the lower ball bearing  43   c  is slidably-fitted into the lower ball bearing holder  34  of the base frame  3  in the axial direction of the output shaft  42 . Thereby, the lower ball bearing  43   c  rotatably supports the output shaft  42 . To bias the upper ball bearing  43   b  and the lower ball bearing  43   c  to thereby apply a predetermined pressure to each ball bearing, a wave washer  43   d  is interposed between the outer race of the lower ball bearing  43   c  and the lower ball bearing holder  34 . 
         [0041]    The motor  4  is a 3-phase AC brushless motor that is pivotably supported via the connecting member  43  by the base frame  3 . This motor  4  is provided with a stator  40 , a rotor  41 , and the output shaft  42 .  FIG. 5  is an exploded perspective view including a part of the motor  4  and the base frame  3 . The stator  40  of the motor  4  is provided with the stator core  40   a , an upper insulator  40   b , a lower insulator  40   c , and windings  40   d . Further, the stator core  40   a  is provided with a yoke  40   e  and the teeth  40   f . The yoke  40   e  is a cylindrical portion in central part of the stator core  40   a , and the sleeve member  43   a  is press-fitted inside the yoke  40   e . Thereby, the stator  40  is fixed to the base frame  3 . A plurality of yoke openings  40   g  are formed in this yoke section  40   e . The teeth  40   f  are a plurality of field parts that are formed to radially protrude from an outer circumference of the yoke  40   e  in a direction perpendicular to the output shaft  42  and are intended to generate a rotating magnetic field in a circumferential direction centered on the output shaft  42 . In the present embodiment, the teeth  40   f  give a constitution of 15 slots by way of example. 
         [0042]    The upper insulator  40   b  and the lower insulator  40   c  are insulating members that are provided to cover a surface of the stator core  40   a  and are formed by a resin material. As the stator core  40   a  is sandwiched between the upper insulator  40   b  and the lower insulator  40   c  in a vertical axial direction, the windings  40   d  and the stator core  40   a  are insulated. The windings  40   d  are wound around the teeth  40   f  more than once in a state while the stator core  40   a  is insulated by the upper insulator  40   b  and the lower insulator  40   c . Each of the windings  40   d  of three-phase is a metal thin wire (a copper wire) whose surface is covered with an insulating coating layer such as enamel. The upper insulator  40   b  has upper insulator openings  40   h  formed at positions at which they are related to the flow of the introducing air for the yoke openings  40   g  of the yoke  40   e . Similarly, the lower insulator  40   c  also has lower insulator openings  40   k  formed at positions at which they are related to the flow of the introducing air for the yoke openings  40   g . Therefore, as the yoke openings  40   g , the upper insulator openings  40   h , and the lower insulator openings  40   k  are superposably disposed, gas flow channels  4 A are formed inside the motor  4  as illustrated in  FIG. 3 . 
         [0043]    As illustrated in  FIG. 5 , L-shaped winding catches  40   m  projected from circumferential walls of the lower insulator openings  40   k  toward a lower side of the motor  4  are formed at a position corresponding to the board-side opening  33   a  of the base frame  3  at the lower insulator openings  40   k  of the lower insulator  40   c . The windings  40   d  are tied on the winding catches  40   m , and are inserted into the board-side opening  33   a  to run along an axis of the output shaft  42 , thereby being drawn out to the lower side of the motor  4 . 
         [0044]    The rotor  41  is a rotary member (an outer rotor) which is outside the stator  40 , is fitted onto and connected to the output shaft  42  at an upper side of the stator  40 , and is rotatably provided around the stator  40 . This rotor  41  is provided with a frame  41   a  at which a circular top section  41   c  and a circumferential surface section  41   d  are formed, and a plurality of magnets  41   b  that are disposed on an inner surface of the circumferential surface section  41   d  to face the stator  40 . 
         [0045]    This frame  41   a  has an output shaft fixture  41   e  to which the output shaft  42  is fixed after being inserted into the center of the top section  41   c . Moreover, the frame  41   a  has a plurality of rotor openings  41   f  formed around the output shaft fixture  41   e . The magnets  41   b  are provided inside the circumferential surface section  41   d  of the frame  41   a  in a plurality of rows to form a plurality of magnetic poles that are facing each other with a predetermined gap therebetween in an outer circumferential direction of the stator core  40   a . In the present embodiment, the magnets  41   b  give a constitution of 14 pieces (14 poles) by way of example. The circular top section  41   c  of the rotor  41  is exposed from the central opening  20   d  of the upper casing section  2 A. 
         [0046]    As illustrated in  FIGS. 4A and 4B , the circuit board  5  has an approximately semi-circular shape and is screwed to the circuit board fixture  35  of the base frame  3  by a plurality of screw members. As illustrated in  FIG. 3 , the circuit board  5  is supported by the base frame  3 , and thereby is spaced from the casing  2  inside the casing  2 . When viewed in the axial direction of the output shaft  42  of the motor  4 , this circuit board  5  is disposed between the introduction opening  21   a  of the casing  2  and the output shaft  42  of the motor  4 . That is, the circuit board  5  is housed inside the casing  2 , and is supported by the base frame  3  to be disposed at a position eccentric with respect to the output shaft  42 . The circuit board  5  is supported by the base frame  3  to be separated (deviated, displaced) from the output shaft  42  in a radial direction of the output shaft  42 . Thereby, the circuit board  5  is disposed within streamlines of air flowing from the introduction opening  21   a  to the central opening  20   d.    
         [0047]    This circuit board  5  has the cut-out portion  50  formed at a position corresponding to the board-side opening  33   a  of the base frame  3  in the vicinity of the output shaft  42 . Further, the circuit board  5  is provided with a connecting terminal  51  adjacent to the cut-out portion  50 . This connecting terminal  51  has a connecting concave that is to catch an end of the windings  40   d  of the motor  4 . The connecting concave has an open side that is forming approximate U shape when a state of the end of the windings  40   d  is unconnected to the connecting concave. The ends of the windings  40   d  of the motor  4  which are drawn out to the lower side of the motor  4  via the board-side opening  33   a  are caught by the connecting concave, and are clamped by the connecting concave. Thereby the motor  4  and the circuit board  5  are electrically connected. 
         [0048]    A drive circuit that is provided with a switching element for supplying a PWM controlled drive current to the motor and a control circuit that is connected to the switching element and supplies a control signal to the switching element are disposed on this circuit board  5 . The magnets  41   b  of the rotor  41  are attracted by rotating magnetic fields of the stator core  40   a  and the windings  40   d  which are generated on the basis of an instruction from this circuit board  5 , and thereby the rotor  41  is rotated. The control circuit is a sensorless control system that does not require a rotation detection sensor. Thereby, the circuit board  5  need not be provided with a rotation angle detector for detecting a state of a rotation angle of the output shaft  42  in the vicinity of the output shaft  42 . Therefore, the cut-out portion  50  can be easily formed in the vicinity of the output shaft  42 . 
         [0049]    An upper thermal conductive surface (a thermal pad) that is adjacently installed to allow thermal conduction with a lower end side of the heat sink member  6  exposed to the rear surface side of the base frame  3  is formed at the circuit board  5 . A lower thermal conductive surface (a thermal land) on which electronic parts having a large amount of heat generation such as the switching element of the drive circuit are mounted is formed on the opposite surface of the upper thermal conductive surface, and the upper thermal conductive surface and the lower thermal conductive surface are connected by thermal conducting means (not shown) such as a thermal through-hole. Thereby, the heat sink member  6  can efficiently discharge heat of the circuit board  5  outside of the blower motor unit  1 . Thermal conductive grease or a sheet-like thermal conducting member may be fixedly sandwiched between the lower end side of the heat sink member  6  and the upper thermal conductive surface. In this case, the heat of the circuit board  5  can be more efficiently discharged to the outside of the blower motor unit  1 . 
         [0050]    Subsequently, an operation of the blower motor unit  1  according to the present embodiment will be described with reference to  FIGS. 3 and 6 . 
         [0051]    In the blower A provided with this blower motor unit  1 , when a rotating magnetic field is generated at the stator  40  on the basis of an instruction from the circuit board  5 , the rotor  41 , the output shaft  42 , and the blower fan B are rotated as one body. When the blower fan B is rotated in this way, the blower fan B suctions air from the air inlet C 1  side of the fan case C, and sends it via the air outlet. Here, as illustrated in  FIG. 3 , part of the sent air having a positive pressure due to the blower fan B flows into the blower motor unit  1  from the introduction opening  21   a  communicating downstream in an air-sending direction of the air of the fan case C. In this way, the air introduced into the casing  2  from the introduction opening  21   a  passes through the gas guide section  21 , and branches off in multiple directions. Here, part of the air flows into the upper side of the base frame  3 , namely the air gap between the base frame  3  and the upper casing section  2 A. 
         [0052]    As illustrated in  FIG. 6 , the air flowing into the upper side of the base frame  3  comes into contact with the heat sink member  6 , and flows along the heat sink member  6  in a direction of the circumferential surface section  20   b  of the casing  2 , thereby cooling the upper side of the circuit board  5  and the heat sink member  6 . Further, the air cooling the heat sink member  6  to flow out in the direction of the circumferential surface section  20   b  proceeds to an inner upper side of the casing  2  along the outer periphery of the rotor  41 , passes through the central opening  20   d , and is discharged to the fan case C side. 
         [0053]    The remaining air flows into the lower side of the base frame  3  and the circuit board  5 , namely the air gap between the circuit board  5  and the lower casing section  2 B, and that is, the air gap between the base frame  3  and the lower casing section  2 B. A part of the air flowing into the air gap between the circuit board  5  and the lower casing section  2 B passes the cut-out portion  50  of the circuit board  5  in front of the output shaft  42  (at the left side of the output shaft  42  in  FIG. 3 ), and then proceeds to the board-side opening  33   a  of the base frame  3 . The rest of the air flowing into the air gap between the circuit board  5  and the lower casing section  2 B reaches the back of the output shaft  42  (the right side of the output shaft  42  in  FIG. 3 ) while cooling the lower side of the circuit board  5 , and then proceeds to the motor-side openings  33   b  of the base frame  3 . 
         [0054]    The air proceeding to the cut-out portion  50  of the circuit board  5  and the motor-side openings  33   b  of the base frame  3  in this way passes through the gas flow channels  4 A and the slot of between the teeth  40   f  of the stator core  40   a  to cool the entire of the stator  40 . Then, the air cooling the stator  40  is discharged from the rotor openings  41   f  of the rotor  41  to the fan case C side. At this point, the introducing air, which flows into the air gap between the circuit board  5  and the lower casing section  2 B to pass through the lower side of the output shaft  42  along the lower casing section  2 B, is guided by the guide section  20   g  into the axial direction of the output shaft  42 . Thereby, the introducing air is introduced from the air gap to the motor-side openings  33   b , and does not stay in the lower casing section  2 B. Further, the air discharged to the fan case C side flows along the outer surface of the upper casing section  2 A toward the introduction opening  21   a , and is fed back to outflow air sent out in a centrifugal direction by the blower fan B. 
         [0055]    The air flowing along the outer surface of the upper casing section  2 A toward the introduction opening  21   a  comes into contact with the upper end  60  of the heat sink member  6 . Therefore, since the heat sink member  6  is cooled by both of the flow of the air inside the casing  2  and the flow of the air outside the casing  2 , heat of heat sink parts of the circuit board  5  is efficiently discharged to the outside. 
         [0056]    According to this blower motor unit  1  of the present embodiment, the base frame  3  supporting the circuit board  5  is provided. Thereby, the circuit board  5  can be disposed within the streamlines of the introducing air, and be efficiently cooled. 
         [0057]    Further, according to the blower motor unit  1  of the present embodiment, the base frame  3  supports the circuit board  5  such that the circuit board  5  is spaced from the casing  2 . Thereby, the air gap through which the air can circulate is formed between the circuit board  5  and the casing  2 , and the circuit board  5  can be cooled from both sides thereof. Therefore, the circuit board  5  can be efficiently cooled thereby. 
         [0058]    According to the blower motor unit  1  of the present embodiment, the casing  2  has the introduction opening  21   a  in the gas guide section  21 . Thereby, the flow of the air caused by the blower fan B can efficiently flow into the casing  2 . Therefore, the circuit board  5  can be efficiently cooled thereby. 
         [0059]    According to the blower motor unit  1  of the present embodiment, the central opening  20   d  is provided, and the circuit board  5  is disposed within the streamlines of the air flowing from the introduction opening  21   a  to the central opening  20   d . Thereby, the circuit board  5  is efficiently cooled by the flow of the air. 
         [0060]    According to the blower motor unit  1  of the present embodiment, the base frame  3  is provided with the board-side opening  33   a  and the motor-side openings  33   b  within the streamlines of the air flowing from the introduction opening  21   a  to the central opening  20   d . Thereby, the air can flow from the introduction opening  21   a  to the central opening  20   d  without barring the flow of the air due to the base frame  3 . Therefore, the entire blower motor unit  1  can be efficiently cooled. 
         [0061]    According to the blower motor unit  1  of the present embodiment, the circuit board  5  is provided with the cut-out portion  50  corresponding to the board-side opening  33   a  within the streamlines of the introducing air flowing from the introduction opening  21   a  to the central opening  20   d . Thereby, the introducing air can flow from the introduction opening  21   a  to the central opening  20   d  without barring the streamlines due to the circuit board  5 . Therefore, the entire blower motor unit  1  can be efficiently cooled. 
         [0062]    According to the blower motor unit  1  of the present embodiment, the stator core  40   a , the upper insulator  40   b , and the lower insulator  40   c  have the yoke openings  40   g , the upper insulator openings  40   h , the lower insulator openings  40   k , respectively. Thereby, the gas flow channels  4 A are formed. Moreover, the rotor openings  41   f  are also formed in the rotor  41 . Thereby, the air inside the casing  2  passes through the gas flow channels  4 A and is discharged from the central opening  20   d  to the outside. Therefore, the air inside the casing  2  can be efficiently discharged to the outside, and the entire blower motor unit  1  can be efficiently cooled. 
         [0063]    According to the blower motor unit  1  of the present embodiment, the casing  2  is provided with the guide wall section  20   g . Thereby, the introducing air passing through the lower side of the output shaft  42  along the lower casing section  2 B is guided to the motor-side openings  33   b  of the base frame  3  by the guide wall section  20   g , and does not stay in the casing  2 . Therefore, the entire blower motor unit  1  can be efficiently cooled. 
         [0064]    According to the blower motor unit  1  of the present embodiment, the heat sink member  6  is provided that has the upper end  60 , which is partially exposed outside the casing  2  and is adjacent to the circuit board  5 . Since this heat sink member  6  is cooled by both of the flow of the introducing air inside the casing  2  and the flow of the air outside the casing  2 , heat of heat sink parts of the circuit board  5  is efficiently discharged to the outside. Therefore, the circuit board  5  can also be efficiently cooled thereby. 
         [0065]    Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and includes various changes in design without departing from the scope of the present invention. For example, the following modifications can be conceived. 
         [0066]    (1) In the above embodiment, the base frame  3  is supported via the elastic members  7  by the top section  20   a  of the casing  2 , but the present invention is not limited thereto. The base frame  3  may be directly fixed to the top section  20   a  and/or the bottom section  20   c  of the casing  2 . 
         [0067]    (2) In the above embodiment, the electronic parts such as the switching element having a large amount of heat generation are mounted on the lower thermal conductive surface (the thermal land) of the circuit board  5 , and the lower end side of the heat sink member  6  exposed to the rear surface side of the base frame  3  and the upper thermal conductive surface (the thermal pad) of the circuit board  5  are adjacently installed to allow thermal conduction, but the present invention is not limited thereto. The electronic parts such as the switching element may be mounted at the upper side of the circuit board  5 , and the lower end side of the heat sink member  6  may be adjacently installed above the electronic parts. 
         [0068]    (3) In the above embodiment, the guide wall section  20   g  of the casing  2  is formed on the tapered surface becoming the tapered shape at the position opposite to the gas guide section  21 , but the present invention is not limited thereto. The guide wall section  20   g  may be formed to follow a planar shape of the base frame  3  in a curved shape at the position opposite to the gas guide section  21 . According to this guide wall section  20   g , the introducing air passing through the lower side of the output shaft  42  along the lower casing section  2 B is guided by the wall section  20   g  of the curved shape into the axial direction of the output shaft  42 . Thereby, the air is introduced from the air gap to the motor-side openings  33   b , and does not stay in the lower casing section  2 B.