Patent Publication Number: US-2019191949-A1

Title: Blowing device and vacuum cleaner

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2017-244948 filed on Dec. 21, 2017. The entire contents of this application are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a blowing device and a vacuum cleaner provided with the same. 
     2. Description of the Related Art 
     Hitherto, a blowing device that includes a plurality of stator blades is known. The blowing device is mounted in a vacuum cleaner or the like. For example, in a known electric blower, air that has been suctioned through an intake port with a rotation of an impeller passes through the impeller, a diffuser, and an inside of a bracket while cooling a stator, a rotor, and the like and is ultimately discharged to a portion external to the electric blower. 
     However, in known electric blowers, air directly enters a bracket inner portion through the diffuser to cool the stator and the rotor. Accordingly, the air blowing efficiency of the electric blower is decreased. 
     SUMMARY OF THE INVENTION 
     A blowing device according to an exemplary embodiment of the present disclosure includes a motor including a rotor rotatable about a central axis extending in an up-down direction, an impeller that is fixed to the rotor and that is rotatable together with the rotor, a motor housing disposed on a radial direction outer side with respect to the motor, a blower case disposed on the radial direction outer side with respect to the motor housing, and a plurality of stator blades arranged in a circumferential direction and between the motor housing and the blower case. The plurality of stator blades include at least a single first stator blade provided with a stator blade recess portion recessed in a surface of the stator blade. A communication hole that connects an internal portion and an external portion of the motor housing to each other is provided in the motor housing. The communication hole is provided between a forward rotation direction end portion and a backward rotation direction end portion in the first stator blade and is in communication with the stator blade recess portion. The first stator blade includes a front wall portion disposed in the forward rotation direction end portion, and a rear wall portion disposed in the backward rotation direction end portion. An axial direction of each of the front wall portion and the rear wall portion is a longitudinal direction. The communication hole is provided in the circumferential direction and between the front wall portion and the rear wall portion. The first stator blade further includes a connection wall portion that connects a lower end portion of the front wall portion and a lower end portion of the rear wall portion to each other. An upper surface of the connection wall portion extends towards an axial direction lower side as the upper surface extends towards a radial direction inner side. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external view of a blowing device. 
         FIG. 2  is a longitudinal section illustrating a configuration example of the blowing device. 
         FIG. 3A  is an enlarged view illustrating an example of a first stator blade. 
         FIG. 3B  is a cross-sectional view of a vicinity of the first stator blade viewed in a circumferential direction. 
         FIG. 3C  is a cross-sectional view of a vicinity of the first stator blade viewed from an axial direction upper side. 
         FIG. 4  is an enlarged view illustrating a first stator blade according to a first modification. 
         FIG. 5  is an enlarged view illustrating a first stator blade according to a second modification. 
         FIG. 6  is an enlarged view illustrating a first stator blade according to a third modification. 
         FIG. 7  is an example of a vacuum cleaner in which the blowing device is mounted. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the drawings. Note that in the present specification, a rotation axis of a motor  110  of a blowing device  100  is referred to as a “central axis CA”, and a direction parallel to the central axis CA is referred to as an “axial direction”. A direction oriented in the axial direction from a substrate  6  described later towards an impeller  120  described later is referred to as an “axial direction upper side” that is a first side in the axial direction, and a direction oriented in the axial direction from the impeller  120  towards the substrate  6  is referred to as an “axial direction lower side” that is a second side in the axial direction. In each of the components, an end portion on the axial direction upper side is referred to as an “upper end portion”, and an end position on the axial direction upper side is referred to as an “upper end”. In each of the components, an end portion on the axial direction lower side is referred to as a “lower end portion”, and an end position on the axial direction lower side is referred to as a “lower end”. Furthermore, among the surfaces of the components, a surface oriented towards the axial direction upper side is referred to as an “upper surface”, and a surface oriented towards the axial direction lower side is referred to as an “undersurface”. 
     A direction orthogonal to the central axis CA is referred to as a “radial direction”. A direction in the radial direction oriented towards the central axis CA is referred to as a “radial direction inner side” and a direction in the radial direction distancing away from the central axis CA is referred to as a “radial direction outer side”. In each of the components, an end portion on the radial direction inner side is referred to as a “radial direction inner end portion”, and an end position on the radial direction inner side is referred to as a “radial direction inner end”. In each of the components, an end portion on the radial direction outer side is referred to as a “radial direction outer end portion”, and an end position on the radial direction outer side is referred to as a “radial direction outer end”. Furthermore, in the lateral surface of each component, a lateral surface oriented towards the radial direction inner side is referred to as a “radial direction inner lateral surface”, and a lateral surface oriented towards the radial direction outer side is referred to as a “radial direction outer lateral surface”. 
     A rotation direction of a rotor  1  about the central axis CA may be referred to as a “circumferential direction”. Furthermore, a direction in which the rotor  1  moves forward in the circumferential direction is referred to as a “forward rotation direction FRD”, and a direction in which the rotor  1  moves backwards in the circumferential direction is referred to as a “backward rotation direction BRD”. In other words, the “backward rotation direction BRD” is a direction opposite to the “forward rotation direction FRD”. In each of the components, an end portion in the forward rotation direction FRD is referred to as a “forward rotation direction end portion” and an end position in the forward rotation direction FRD is referred to as a “rotation direction front end”. Furthermore, in each of the components, an end portion in the backward rotation direction BRD is referred to as a “backward rotation direction end portion”, and an end position in the backward rotation direction BRD is referred to as a “rotation direction back end”. 
     Note that the names of the directions, the end portions, and the surfaces described above do not illustrate the actual positional relationships and directions when installed in a piece of equipment. 
     The blowing device  100  according to an exemplary embodiment of the present disclosure will be described first.  FIG. 1  is an external view of the blowing device  100 .  FIG. 2  is a longitudinal section illustrating a configuration example of the blowing device  100 . Note that in order to facilitate understanding of the configuration, a blower case  32  described later is depicted in a transparent manner in  FIG. 1 .  FIG. 2  illustrates a cross section structure in which the blowing device  100  is imaginarily cut along a plane including the central axis CA. 
     The blowing device  100  includes the motor  110 , the impeller  120 , and a casing  3 . The impeller  120  is a vanes wheel including a plurality of vanes  121  capable of rotating about the central axis CA. The impeller  120  is provided at an upper portion of the motor  110 . The impeller  120  is capable of rotating about the central axis that extends in an up-down direction. The casing  3  houses at least a portion of the motor  110  and at least a portion of the impeller  120 . 
     The motor  110  is of an inner rotor type and drives and rotates the impeller  120 . The motor  110  includes the rotor  1 , a stator  2 , a bracket  4 , and the substrate  6 . 
     The rotor  1  is rotatable about the central axis CA extending in the up-down direction. In other words, the motor  110  includes the rotor  1  rotatable about the central axis CA that extends in the up-down direction. The rotor  1  includes a shaft  10 , a magnet  11 , and a holding member  12 . The shaft  10  is a rotating shaft that extends upwards and downwards in the axial direction. The impeller  120  is attached to the upper portion of the shaft  10 . In other words, the impeller  120  is fixed to the rotor  1  and is rotatable together with the rotor  1 . Furthermore, the vanes  121  are rotatable in the rotation direction of the rotor  1 . The magnet  11  has a tubular shape extending in the axial direction and is fixed to a radial direction outer lateral surface of the shaft  10 . The holding member  12  is fixed to a radial direction outer lateral surface of the magnet  11 . The holding member  12  is disposed on the radial direction inner side with respect to the stator  2  and opposes the stator  2  in the radial direction. 
     The motor  110  further includes the stator  2  disposed on a radial direction outer side of the rotor  1 . The stator  2  is rotated by driving the rotor  1 . The stator  2  includes a stator core  21 , an insulator  22 , and a plurality of coil portions  23 . In other words, the stator  2  includes the stator core  21  provided with the coil portions  23 . The stator core  21  is formed of laminated steel plates that are electromagnetic steel plates laminated in the axial direction, for example, and is fixed to the casing  3 . More specifically, the stator core  21  includes a core back  21 C and teeth  21 T. The core back  21 C has an annular shape surrounding the central axis CA. Not that an “annular shape” herein includes, in addition to a case in which the entire circumstance is continuously connected, a case in which a portion of the circumstance is discontinuous. Furthermore, “the core back  21 C having an annular shape” includes a case in which there are a plurality of core backs  21 C and in which the plurality of core backs  21 C are arranged in the circumferential direction. In the present embodiment, a portion of a radial direction outer end portion of the core back  21 C is fixed to a radial direction inner lateral surface of a cylindrical portion  312 . The cylindrical portion  312  is a portion of a motor housing  31  (described later) in the casing  3 . The teeth  21 T each extend in the radial direction from the core back  21 C towards the holding member  12 . The insulator  22  is, for example, an insulating member formed using a resin material and covers at least a portion of the stator core  21 , in particular, covers the teeth  21 T. The coil portions  23  are winding members formed of conducting wires wound around the teeth  21 T of the stator core  21  with the insulator  22  in between. In other words, the stator core  21  and the coil portions  23  are electrically insulated from each other with the insulator  22 . Furthermore, the plurality of coil portions  23  are arranged in the circumferential direction around the shaft  10 . 
     The bracket  4  includes a lower bearing holder  41  and a lid portion  42 . The lower bearing holder  41  rotatably supports the shaft  10  with a lower bearing  41   a  interposed therebetween. Furthermore, the lower bearing holder  41  has a tubular shape extending in the axial direction. The lower bearing  41   a  is disposed on a radial direction inner lateral surface of the lower bearing holder  41 . The shaft  10  is inserted through both the lower bearing  41   a  and the lower bearing holder  41 . Although not limited to any bearing in particular, a ball bearing, a sleeve bearing, or the like can be used as the lower bearing  41   a . The lid portion  42  extends towards the radial direction outer side from a lower end portion of the lower bearing holder  41  and covers an opening at a lower end portion of the casing  3 . 
     In the present embodiment, the substrate  6  is disposed below the bracket  4  in the axial direction and is fixed to the lid portion  42 . The substrate  6  is a plate-shaped circuit substrate and is formed of a resin material such as an epoxy resin. The substrate  6  is electrically connected to the coil portions  23 . The substrate  6  is electrically connected to a device and the like external to the motor  110  through a connection line (not shown) that is drawn out to the outside of the motor  110 . Furthermore, an electronic component  61  is mounted on the substrate  6 . The electronic component  61  includes a power supply circuit and a control circuit of the motor  110 . 
     The casing  3  includes the motor housing  31 , the blower case  32 , and a plurality of stator blades  33 . In other words, the blowing device  100  includes the motor housing  31 , the blower case  32 , and the plurality of stator blades  33 . The motor housing  31 , the blower case  32 , and the stator blades  33  constitute the same member in the present embodiment, in other words, the motor housing  31 , the blower case  32 , and the stator blades  33  are an integral structure. However, not limited to the above example, at least one of the above may be a separate member, in other words, the above do not have to be an integral structure. 
     The motor housing  31  houses at least a portion of the motor  110 . In the present embodiment, the motor housing  31  houses the rotor  1  and the stator  2 . The motor housing  31  has a tubular shape with a lid. The motor housing  31  includes an upper bearing holder  311  and the cylindrical portion  312 . 
     The upper bearing holder  311  rotatably supports the shaft  10  with an upper bearing  311   a  interposed therebetween. Furthermore, the upper bearing holder  311  extends in the radial direction. The upper bearing holder  311  is, at the center, provided with a through hole  311   b  that penetrates thereof in the axial direction. The upper bearing  311   a  is disposed on an inner lateral surface of the through hole  311   b . The shaft  10  is inserted through both the upper bearing  311   a  and the through hole  311   b . Although not limited to any bearing in particular, a ball bearing, a sleeve bearing, or the like can be used as the upper bearing  311   a.    
     The cylindrical portion  312  extends downwards in the axial direction from a radial direction outer end portion of the upper bearing holder  311 . The cylindrical portion  312  is disposed on the radial direction outer side with respect to the motor  110 . In other words, the motor housing  31  is disposed on the radial direction outer side with respect to the motor  110 . Communication holes  3   a  are provided in the motor housing  31 . In more detail, the communication holes  3   a  are provided in the cylindrical portion  312 . The communication holes  3   a  penetrate the cylindrical portion  312  of the motor housing  31  in the radial direction. In other words, the communication holes  3   a  connects an internal portion and an outer portion of the motor housing  31  to each other. By providing the communication holes  3   a  in the motor housing  31 , the portion internal to the motor  110  can be cooled with the airflow flowing from the portion external to the portion internal to the motor housing  31  through the communication holes  3   a . The arrangement of the communication holes  3   a  is not limited to any arrangement in particular. In the present embodiment, the communication holes  3   a  are provided in a plural number and at equal distances in the circumferential direction. With the above configuration, since the communication holes  3   a  are disposed at equal distances in the circumferential direction, the motor  110  can be cooled evenly in the circumferential direction. 
     The blower case  32  houses the impeller  120 . The blower case  32  is disposed on a radial direction outer side of the motor housing  31 . An intake port  32   a  is provided at an upper end portion of the blower case  32 . The blower case  32  forms a gap with the motor housing  31 . The gap is a distribution passage of the airflow generated by the rotation of the impeller  120 . A ventilation port  32   b  is provided at a lower end portion of the blower case  32  and between a radial direction outer lateral surface of the motor housing  31 . The air drawn in through the intake port  32   a  with the rotation of the impeller  120  flows downwards in the axial direction through a portion between the motor housing  31  and the blower case  32  and is sent out to a portion outside the casing  3  through the ventilation port  32   b . Note that a portion of the airflow flowing between the motor housing  31  and the blower case  32  flows into the motor housing  31  through the communication holes  3   a  and is used to cool the stator  2  and the like. The configuration of the above will be described later. 
     The stator blades  33  are disposed between the motor housing  31  and the blower case  32  and are arranged in a plural number in the circumferential direction. The stator blades  33  are connection portions that connect the motor housing  31  and the blower case  32  to each other in the radial direction. Radial direction inner end portions of the stator blades  33  are connected to the radial direction outer lateral surface of the motor housing  31 . Radial direction outer end portions of the stator blades  33  are connected to a radial direction inner lateral surface of the blower case  32 . 
     Furthermore, the stator blades  33  each extend in the axial direction. As upper end portions of the stator blades  33  extend towards the axial direction upper side, the upper end portions curve towards the backward rotation direction BRD. Accordingly, the airflow generated by the rotation of the impeller  120  easily flows between adjacent stator blades  33  in the circumferential direction. 
     The plurality of stator blades  33  include at least a single first stator blade  7  in which a stator blade recess portion  7   a  that is a recess in a surface of the stator blade  7  is provided. Hereinafter, among the plurality of stator blades  33 , the stator blade  7  in which the stator blade recess portion  7   a  is provided is referred to as the “first stator blade  7 ” and the stator blades  331  other than the first stator blade  7  are referred to as “second stator blades  331 ”. Note that a configuration of the first stator blade  7  will be described later. 
     The stator blade recess portion  7   a  is formed between the forward rotation direction end portion and the backward rotation direction end portion of the first stator blade  7  in the upper portion of the first stator blade  7 . Furthermore, when viewed in the radial direction, the communication hole  3   a  is formed between the forward rotation direction end portion and the backward rotation direction end portion of the first stator blade  7 . When viewed in the radial direction, the communication hole  3   a  overlaps a portion of the stator blade recess portion  7   a  and is in communication with the stator blade recess portion  7   a . In other words, the communication hole  3   a  is provided between the forward rotation direction end portion and the backward rotation direction end portion in the first stator blade  7  and is in communication with the stator blade recess portion  7   a . With the above configuration, the airflow that is generated by the rotation of the impeller  120  and that flows into the stator blade recess portion  7   a  passes through the communication hole  3   a  and flows into the gap between the motor  110  and the motor housing  31  in a smooth manner. Accordingly, the motor  110  can be cooled without decreasing the air blowing efficiency. 
     The stator blade recess portion  7   a  is not formed in each of the second stator blades  331 . In the upper portion of each second stator blade  331 , a forward rotation direction lateral surface and a backward rotation direction lateral surface curve in the backward rotation direction BRD as the upper portion extends towards the axial direction upper side. Furthermore, the forward rotation direction lateral surface is a curved surface protruding towards the axial direction upper side and in the forward rotation direction FRD. The backward rotation direction lateral surface is a curved surface recessed towards the axial direction upper side and in the forward rotation direction FRD. 
     A configuration of the first stator blade  7  will be described next.  FIG. 3A  is an enlarged view illustrating an example of the first stator blade  7 .  FIG. 3B  is a cross-sectional view of a vicinity of the first stator blade  7  viewed in the circumferential direction.  FIG. 3C  is a cross-sectional view of a vicinity of the first stator blade  7  viewed from the axial direction upper side. Note that  FIG. 3A  corresponds to a portion surrounded by a dot and dash line in  FIG. 1 . Furthermore, in  FIG. 3A , in order to facilitate the understanding of the configuration, illustration of the blower case  32  is omitted.  FIG. 3B  illustrates a cross section structure taken along a dot and dash line A-A in  FIG. 3A .  FIG. 3C  illustrates a cross section structure taken along a dot and dash line B-B in  FIG. 3A . 
     The first stator blade  7  includes a front wall portion  71  and the rear wall portion  72 . The front wall portion  71  is disposed in the forward rotation direction end portion of the first stator blade  7 . The rear wall portion  72  is disposed in the backward rotation direction end portion of the first stator blade  7 . The axial direction of each of the front wall portion  71  and the rear wall portion  72  is at least the longitudinal direction. 
     Furthermore, the stator blade recess portion  7   a  is provided between the rotation direction front wall portion  71  and the rotation direction rear wall portion  72  of the first stator blade  7  in the upper portion of the first stator blade  7 . As illustrated in  FIG. 3A , in the present embodiment, the stator blade recess portion  7   a  is recessed in the upper portion of the first stator blade  7  from the forward rotation direction end portion towards the axial direction lower side. Furthermore, when viewed in the radial direction, the communication hole  3   a  is provided between the front wall portion  71  and the rear wall portion  72  in the circumferential direction. With the above configuration, a portion of the airflow flowing between the first stator blade  7  and the stator blade  33  that is adjacent thereto in the forward rotation direction FRD flows into a portion between the front wall portion  71  and the rear wall portion  72 . Accordingly, the portion of the airflow can flow into the motor housing  31  in a smooth manner through the communication hole  3   a.    
     Note that as the bore of the communication hole  3   a  becomes larger, the airflow flowing in through the stator blade recess portion  7   a  flows more easily into the motor housing  31 . Accordingly, a circumferential direction width W 1  of the first stator blade  7  is, among the plurality of stator blades  33 , desirably, larger than the circumferential direction widths W 2  of the second stator blades  331  other than the first stator blade  7 . With the above configuration, the width of the communication hole  3   a  in the circumferential direction can be enlarged. Accordingly, the cooling effect of the motor  110  is improved. 
     In the upper portion of the first stator blade  7 , a forward rotation direction lateral surface  71   a  of the front wall portion  71  is a curved surface that extends downwards in the axial direction as the lateral surface  71   a  extends in the forward rotation direction FRD. The forward rotation direction lateral surface  71   a  protrudes in the forward rotation direction FRD and towards the axial direction upper side. With such a configuration, the airflow flowing between the first stator blade  7  and the stator blade  33  adjacent to the first stator blade  7  in the rotation direction can be guided smoothly towards the axial direction lower side and in the forward rotation direction FRD. Accordingly, the air blowing efficiency of the blowing device  100  can be improved. 
     In the upper portion of the first stator blade  7 , a backward rotation direction lateral surface  71   b  of the front wall portion  71  desirably extends in the axial direction as in the present embodiment. However, the backward rotation direction lateral surface  71   b  of the front wall portion  71  may be a curved surface that extends towards the circumferential direction as the lateral surface  71   b  extends towards the axial direction upper side. In a case in which the backward rotation direction lateral surface  71   b  of the front wall portion  71  extends in the axial direction, when the first stator blade  7  that is molded using a metal mold is released from the metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Accordingly, the first stator blade  7  can be molded without using a complex-shaped metal mold. 
     In the upper portion of the first stator blade  7 , a backward rotation direction lateral surface  72   a  of the rear wall portion  72  is a curved surface that extends downwards in the axial direction as the lateral surface  72   a  extends in the forward rotation direction FRD. The backward rotation direction lateral surface  72   a  is recessed in the forward rotation direction FRD and towards the axial direction upper side. With such a configuration, the airflow flowing between the first stator blade  7  and the stator blade  33  adjacent to the first stator blade  7  in the backward rotation direction BRD can be guided smoothly in the forward rotation direction FRD and towards the axial direction lower side. Accordingly, the air blowing efficiency of the blowing device  100  can be improved. 
     Furthermore, an upper end of the rear wall portion  72  is positioned on the forward rotation direction FRD side with respect to the stator blade  33  adjacent to the first stator blade  7  in the backward rotation direction BRD. With such a configuration, when the first stator blade  7  that is molded using a metal mold is released from the metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Accordingly, the first stator blade  7  can be molded without using a complex-shaped metal mold. 
     The first stator blade  7  further includes a connection wall portion  73 . In the present embodiment, the connection wall portion  73  is a lower portion of the first stator blade  7 . In more detail, the connection wall portion  73  connects a lower end portion of the front wall portion  71  and a lower end portion of the rear wall portion  72  to each other. In other words, the front wall portion  71  protrudes and extends towards the axial direction upper side from the forward rotation direction end portion at the upper end of the connection wall portion  73 . The rear wall portion  72  protrudes and extends towards the axial direction upper side from the backward rotation direction end portion at the upper end of the connection wall portion  73 . In the upper end portion of the first stator blade  7 , as the rear wall portion  72  extends towards the axial direction upper side, the rear wall portion  72  extends towards the backward rotation direction BRD. With such a configuration, the entire airflow that flows into a portion between the front wall portion  71  and the rear wall portion  72  can be distributed through the communication hole  3   a.    
     In the present embodiment, an upper surface  73   a  of the connection wall portion  73  extends towards the axial direction lower side as the upper surface  73   a  extends towards the radial direction inner side. Furthermore, the upper surface  73   a  of the connection wall portion  73  is also a bottom surface of the stator blade recess portion  7   a . Accordingly, in other words, the bottom surface of the stator blade recess portion  7   a  has a shape that extends towards the axial direction lower side as the bottom surface extends towards the radial direction inner side. Note that the upper surface  73   a  may be an inclined surface having a planer shape, or may be a curved surface that protrudes towards the axial direction upper side and the radial direction inner side. Alternatively, the upper surface  73   a  may be a curved surface recessed towards the axial direction lower side and the radial direction outer side. With such a configuration, the airflow flowing into the portion between the front wall portion  71  and the rear wall portion  72  can be distributed along the upper surface  73   a  of the connection wall portion  73  and to the communication hole  3   a  in a smooth manner. 
     Note that by inclining or curving the inner lateral surface of the communication hole  3   a , the airflow can be made the flow in a smoother manner. Accordingly, as illustrated in  FIG. 3C , circumferential direction lateral surfaces of the communication hole  3   a , desirably, extend in the forward rotation direction FRD as the circumferential direction lateral surfaces extend towards the radial direction inner side, for example. Note that in the present embodiment, an inner lateral surface  30   a  of the communication hole  3   a  in the forward rotation direction and an inner lateral surface  30   b  of the communication hole  3   a  in the backward rotation direction are both shaped so as to extend in the forward rotation direction FRD as the inner lateral surfaces extend towards the radial direction inner side. The inner lateral surface  30   a  of the communication hole  3   a  in the forward rotation direction is one of the circumferential direction lateral surfaces of the communication hole  3   a , and an edge portion of inner lateral surface  30   a  of the communication hole  3   a  in the forward rotation direction is the backward rotation direction lateral surface of the motor housing  31 . The inner lateral surface  30   b  of the communication hole  3   a  in the backward rotation direction is the other circumferential direction lateral surface of the communication hole  3   a , and an edge portion of the inner lateral surface  30   b  of the communication hole  3   a  in the backward rotation direction is the forward rotation direction lateral surface of the motor housing  31 . However, not limited to the example of the present embodiment, it is only sufficient that at least either one of the inner lateral surface  30   a  of the communication hole  3   a  in the forward rotation direction and the inner lateral surface  30   b  of the communication hole  3   a  in the backward rotation direction has the shape described above. With such a configuration, the airflow that flows into the portion between the front wall portion  71  and the rear wall portion  72  can be distributed through the communication hole  3   a  in a smooth manner. Accordingly, a decrease in the air blowing efficiency of the motor  110  caused by a portion of the airflow, which is flowing between the first stator blade  7  and another stator blade  33 , flowing between the front wall portion  71  and the rear wall portion  72  can be suppressed. 
     Furthermore, while the inner lateral surfaces  30   a  and  30   b  may each be a curved surface protruding towards the radial direction inner side and in the backward rotation direction or a planer-shaped inclined surface, as illustrated in  FIG. 3C , desirably, the inner lateral surfaces  30   a  and  30   b  are each a curved surface protruding towards the radial direction outer side and in the forward rotation direction. With the above configuration, the airflow can flow further smoothly through the communication hole  3   a.    
     Furthermore, as illustrated in  FIG. 3B , desirably, the inner surfaces of the communication hole  3   a  in the axial direction extend towards the axial direction lower side as the inner surface extends towards the radial direction inner side, for example. Note that in the present embodiment, an inner surface  30   c  of the communication hole  3   a  on the axial direction upper side and an inner surface  30   d  of the communication hole  3   a  on the axial direction lower side are both shaped so as to extend towards the axial direction lower side as the inner surfaces extend towards the radial direction inner side. The inner surface  30   c  of the communication hole  3   a  on the axial direction upper side is one of the inner surfaces of the communication hole  3   a  in the axial direction, and an edge portion of the inner surface  30   c  of the communication hole  3   a  on the axial direction upper side is an upper surface of the motor housing  31 . The inner surface  30   d  of the communication hole  3   a  on the axial direction lower side is the other inner surface of the communication hole  3   a  in the axial direction, and an edge portion of the inner surface  30   d  of the communication hole  3   a  on the axial direction lower side is a lower surface of the motor housing  31 . However, not limited to the example of the present embodiment, it is only sufficient that at least either one of the lower surface of the motor housing  31  at the upper edge portion of the communication hole  3   a  in the axial direction and the upper surface of the motor housing  31  at the lower edge portion of the communication hole  3   a  in the axial direction extends towards the axial direction lower side as the lower surface or the upper surface extends towards the radial direction inner side. Note that the inner surface  30   c  is the lower surface of the motor housing  31  at the axial direction upper edge portion of the communication hole  3   a , and the inner surface  30   d  is the upper surface of the motor housing  31  at the axial direction lower edge portion of the communication hole  3   a . The inner surfaces  30   c  and  30   d  may each be a planer-shaped inclined surface or may be a curved surface that protrudes or that is recessed in the axial direction and in the radial direction. With such a configuration, the airflow that flows into the communication hole  3   a  from between the front wall portion  71  and the rear wall portion  72  can be distributed into the motor housing  31  in a smooth manner. Accordingly, a decrease in the air blowing efficiency of the motor  110  caused by a portion of the airflow, which is flowing in the stator blade recess portion  7   a , flowing between the front wall portion  71  and the rear wall portion  72  can be suppressed. 
     First to third modifications of the embodiment will be described next. 
     A configuration different from that of the embodiment described above will be described in the first modification. Furthermore, components similar to those of the embodiment may be denoted with the same reference numerals and description thereof may be omitted. 
       FIG. 4  is an enlarged view illustrating the first stator blade  7  according to the first modification. Note that  FIG. 4  corresponds to a portion surrounded by the dot and dash line in  FIG. 1 . Furthermore, in  FIG. 4 , in order to facilitate the understanding of the configuration, illustration of the blower case  32  is omitted. 
     As illustrated in  FIG. 4 , in the upper portion of the first stator blade  7  in the first modification, an upper end of the front wall portion  71  is on the axial direction upper side with respect to the upper end of the rear wall portion  72 . Accordingly, the stator blade recess portion  7   a  is recessed towards the axial direction lower side from a backward rotation direction end portion of the first stator blade  7  and along the shape of the upper portion of the first stator blade  7 . 
     Furthermore, in the upper portion of the first stator blade  7 , the backward rotation direction lateral surface  71   b  of the front wall portion  71  is a curved surface that extends downwards in the axial direction as the lateral surface  71   b  extends in the forward rotation direction FRD. The backward rotation direction lateral surface  71   b  is recessed in the forward rotation direction FRD and towards the axial direction upper side. 
     Even with such a configuration, a portion of the airflow flowing between the first stator blade  7  and the stator blade  33  adjacent to the first stator blade  7  in the backward rotation direction BRD can be distributed in a smooth manner between the front wall portion  71  and the rear wall portion  72 . 
     A configuration different from that of the first modification described above will be described in the second modification. Furthermore, components similar to those of the embodiment and the first modification described above may be denoted with the same reference numerals and description thereof may be omitted. Note that the configuration of the second modification described below can also be applied to the embodiment described above. 
       FIG. 5  is an enlarged view illustrating the first stator blade  7  according to the second modification. Note that  FIG. 5  corresponds to a portion surrounded by the dot and dash line in  FIG. 1 . Furthermore, in  FIG. 5 , in order to facilitate the understanding of the configuration, illustration of the blower case  32  is omitted. 
     As illustrated in  FIG. 5 , in the second modification, the front wall portion  71  is a member that is different from the rear wall portion  72  and the connection wall portion  73 . The rear wall portion  72  is a portion of a member that includes the connection wall portion  73 . In other words, the lower end portion of the front wall portion  71  is in contact with an upper end portion of the connection wall portion  73  at the forward rotation direction end portion of the first stator blade  7 . The rear wall portion  72  protrudes towards the axial direction upper side from the backward rotation direction end portion at the upper end of the connection wall portion  73 , and as the rear wall portion  72  extends towards the axial direction upper side, the rear wall portion  72  extends towards the backward rotation direction BRD. Note that not limited to the example illustrated in  FIG. 5 , the front wall portion  71  may be a portion of a member that includes the connection wall portion  73 , and the rear wall portion  72  may be a member that is different from the front wall portion  71  and the connection wall portion  73 . 
     The front wall portion  71  is a portion of a member that includes either one of the motor housing  31  and the blower case  32 . In other words, a first end portion of the front wall portion  71  in the radial direction is connected to either one of the motor housing  31  and the blower case  32 . A second end portion of the front wall portion  71  in the radial direction is in contact with the other one of the motor housing  31  and the blower case  32 . In other words, the front wall portion  71  protrudes in the radial direction from a radial direction lateral surface of either one of the motor housing  31  and the blower case  32  at a portion between the motor housing  31  and the blower case  32 . A front end of the front wall portion  71  in the radial direction is in contact with a radial direction lateral surface of the other one of the motor housing  31  and the blower case  32 . 
     Furthermore, the rear wall portion  72  is a portion of a member that includes the other one of the motor housing  31  and the blower case  32 . In other words, a first end portion of the rear wall portion  72  in the radial direction is in contact with either one of the motor housing  31  and the blower case  32 . A second end portion of the rear wall portion  72  in the radial direction is connected to the other one of the motor housing  31  and the blower case  32 . In other words, the rear wall portion  72  protrudes in the radial direction from a radial direction lateral surface of the other one of the motor housing  31  and the blower case  32  at a portion between the motor housing  31  and the blower case  32 . A front end of the rear wall portion  72  in the radial direction is in contact with a radial direction lateral surface of either one of the motor housing  31  and the blower case  32 . 
     Note that in the third modification, the connection wall portion  73  is, similar to the rear wall portion  72 , a portion of a member that includes the other one of the motor housing  31  and the blower case  32 . However, in a case in which the connection wall portion  73  is a portion of a member that includes the front wall portion  71 , similar to the front wall portion  71 , the connection wall portion  73  is a portion of a member that includes either one of the motor housing  31  and the blower case  32 . 
     With such a configuration, when separating the front wall portion  71  molded together with either one of the motor housing  31  and the blower case  32  from a metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Furthermore, when separating the rear wall portion  72  molded together with the other one of the motor housing  31  and the blower case  32  from a metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Accordingly, as illustrated in  FIG. 5 , even when the first stator blade  7  has a complex shape in which the front wall portion  71  and the rear wall portion  72  overlap each other in the axial direction, for example, the first stator blade  7  can be molded without using a complex-shaped metal mold. 
     A configuration different from that of the second modification described above will be described in the third modification. Furthermore, components similar to those of the embodiment and the second modification described above may be denoted with the same reference numerals and description thereof may be omitted. Note that the configuration of the third modification described below can also be used in the embodiment described above. 
       FIG. 6  is an enlarged view illustrating the first stator blade  7  according to the third modification. Note that  FIG. 6  corresponds to a portion surrounded by the dot and dash line in  FIG. 1 . Furthermore, in  FIG. 6 , in order to facilitate the understanding of the configuration, illustration of the blower case  32  is omitted. 
     As illustrated in  FIG. 6 , in the third modification, the motor housing  31  includes an upper motor housing  31   a  and a lower motor housing  31   b . The lower motor housing  31   b  is attached below the upper motor housing  31   a  in the axial direction. Note that the upper motor housing  31   a  may be a member different from the blower case  32  or may be a portion of a member that includes the blower case  32 . Meanwhile, the lower motor housing  31   b  is a member different from the blower case  32 . Alternatively, in a case in which the blower case  32  is formed of a plurality of members that can be assembled together, the upper motor housing  31   a  may be a portion of a member that includes the blower case  32  and the lower motor housing  31   b  may be a portion of a member that includes another member of the blower case  32 . 
     In  FIG. 6 , while the front wall portion  71  is a portion of a member that includes the upper motor housing  31   a , the front wall portion  71  is a member different from the lower motor housing  31   b . However, not limited to the example in  FIG. 6 , the front wall portion  71  may be a member different from the upper motor housing  31   a , and may be a portion of a member that includes the lower motor housing  31   b . In other words, it is only sufficient that the front wall portion  71  is a portion of a member that includes either one of the upper motor housing  31   a  and the lower motor housing  31   b.    
     In  FIG. 6 , the rear wall portion  72  is a member different from the upper motor housing  31   a ; however, the rear wall portion  72  is a portion of a member that includes the lower motor housing  31   b . However, not limited to the example in  FIG. 6 , the rear wall portion  72  may be a portion of a member that includes the upper motor housing  31   a  and may be a member that is different from the lower motor housing  31   b . In other words, it is only sufficient that the rear wall portion  72  is a portion of a member that includes the other one of the upper motor housing  31   a  and the lower motor housing  31   b.    
     Note that in the third modification, the connection wall portion  73  is, similar to the rear wall portion  72 , a portion of a member that includes the lower motor housing  31   b . However, in a case in which the connection wall portion  73  is a portion of a member that includes the front wall portion  71 , similar to the front wall portion  71 , the connection wall portion  73  is a portion of a member that includes the upper motor housing  31   a.    
     With such a configuration, when separating the front wall portion  71  molded together with either one of the upper motor housing  31   a  and the lower motor housing  31   b  from a metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Furthermore, when separating the connection wall portion  73  molded together with the other one of the upper motor housing  31   a  and the lower motor housing  31   b  from a metal mold, the metal mold can be taken out upwards or downwards, that is, the metal mold can be taken out in the axial direction. Accordingly, as illustrated in  FIG. 6 , even when the first stator blade  7  has a complex shape in which the front wall portion  71  and the rear wall portion  72  overlap each other in the axial direction, for example, the first stator blade  7  can be molded together with the upper motor housing  31   a  and the lower motor housing  31   b  without using a complex-shaped metal mold. 
     An example in which the blowing device  100  described above is mounted in a vacuum cleaner  200  will be described next.  FIG. 7  is a perspective view illustrating a configuration of the vacuum cleaner  200  in which the blowing device  100  is mounted. The vacuum cleaner  200  includes the blowing device  100 . In more detail, the vacuum cleaner  200  includes the blowing device  100 , a nozzle  210 , and a main body  220 . The blowing device  100  is mounted in the main body  220 . A suction brush (not shown) is attached to an intake portion  211  of the nozzle  210 . The main body  220  includes a dust chamber  221  connected to the nozzle  210 , a housing chamber  222  in which the blowing device  100  is housed, and an exhaust space  223  connected to a plurality of exhaust ports (not shown). An opening portion of the blowing device  100  is connected to the dust chamber  221  with a dust collection filter (not shown) interposed therebetween. In other words, a flow passage of the air suctioned by the blowing device  100  is connected from the intake portion  211 , through the nozzle  210  and the dust chamber  221 , and to the opening portion of the blowing device  100  in the above order. The housing chamber  222  is connected to the exhaust space  223 . The airflow sent out with the blowing device  100  is discharged to the outside of the main body  220  through the exhaust space  223  and through the exhaust ports. With the above, the vacuum cleaner  200  including the blowing device  100  capable of effectively suppressing the air blowing efficiency from decreasing can be attained. 
     Note that the blowing device  100  in  FIG. 7  is mounted in a stick-type vacuum cleaner  200 ; however, not limited to the example of the present embodiment described above, the blowing device  100  may be mounted in a vacuum cleaner of another type. For example, the vacuum cleaner  200  may be, for example, a vacuum cleaner of a canister type or of a handy type. 
     The present disclosure is suitable for an apparatus that suctions or sends out gas and that is required to have a high static pressure. The present disclosure can be used in blowing devices other than a vacuum cleaner (see  FIG. 7 ) such as an electric fan or a ventilation fan and, further, can be used in electrical appliances for other purposes such as a drying device. 
     Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.