Abstract:
In an electric blower, exhaust air discharged radially from a centrifugal fan is redirected to a motor drive section by a diffuser and a fan cover. The air passes from a ventilation opening on a motor frame and through a bracket to cool the motor drive section. A portion of the air from the centrifugal fan is bled off through exhaust openings without passing over the motor, whereby this portion remains cooler and cleaner than the air that passes over the motor. Air flows up a wand and then passes over the motor to cool the motor. This air passes through filters before being discharged. The portion of air that is bled off passes along a parallel path in the wand to agitate dirt, and to maintain the wand relatively cool. In one embodiment, some of the bled-off portion is discharged directly without passing along the wand.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electric blower and an electric cleaning device using the same. More specifically, the present invention relates to an improvement in electric blowers that is suitable for use in electric cleaning devices that circulate exhaust air from the electric blower to the suction tool via a hose and a pipe. 
     In order to cool their heat-generating motor drive section, standard electric blowers used in electric cleaning devices and the like have taken all the exhaust air discharged radially from a centrifugal fan and redirected it in the direction of the motor shaft by guiding the air along a diffuser and the inner perimeter surface of a fan cover. The air passes through a diffuser return path and flows from an air passage formed on a motor frame through a bracket to cool the motor drive section. The air is then discharged outside through a bracket discharge opening. 
     In standard cleaning devices that are moved along floors, all the exhaust air from an electric blower mounted in the main cleaning device unit is discharged outside through a discharge opening in the back surface of the main unit or the like. 
     The debris sucked in with air through a floor suction tool or the like is passed through a pipe and a hose and collected in the main cleaning device unit. The debris enters a paper bag or the like and the air eliminated of debris is used to cool the motor drive section of the electric blower after which it is discharged outside through the exhaust opening. This can result in the discharged air blowing up dust that is present on the floor or carpet so that the dust is scattered all around the room. 
     Conventional technologies, e.g., Japanese examined utility model publication number 39-36553 and Japanese examined patent publication number 7-44911, have been developed in order to reduce the exhaust air blown out, improve debris collection, and the like. These technologies provide an electric cleaning device in which a hose, a pipe, and a suction tool connected to the main cleaning device unit are formed with an air intake path as well as a discharge path to allow the exhaust air to circulate. 
     However, in the conventional electric blower described above, the heat-generating motor drive section is cooled by taking all the exhaust air discharged radially by the centrifugal fan and redirecting it with the fan cover and the diffuser so that the air is passed through the bracket in which the motor drive section is mounted. This results in increased ventilation resistance, thus reducing suction properties. 
     Also, when the conventional electric blower described above is used in exhaust circulating cleaning devices described above, the cooling of the motor drive section results in a higher temperature for the exhaust air being circulated, leading to further increases in temperature. This increases the temperature of the main cleaning device unit, the hose, the pipe, and the motor itself. This can result in unpleasantness when using the cleaning device and may also invite deformation of the main cleaning device unit, as well as degradation or destruction of the motor or the like. Also, the contact between the carbon brush and the commutator of the motor generates carbon particles that enter the exhaust air cooling the motor drive section. When this air is circulated, carbon particles will adhere to the exhaust air path and can lead to the carbon particles being blown out from the suction tool and soiling the surface being cleaned. These factors acted as obstacles in the practical use of exhaust circulating cleaning devices. 
     In response to these problems, a separate fan can be attached to the motor shaft on the side opposite from the centrifugal fan (the rear side) in order to cool the motor drive section. Also, the paths of the exhaust air on the suction side and the exhaust air used for cooling are completely separated and a “wet and dry” motor is used to allow air containing moisture to be sucked in. However, with this arrangement, the cooling fan is attached separately, leading to a larger electric blower (and electric cleaning device). This results in a more complex structure, a significant reduction in ease of production, and increased costs. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention is to provide a blower for an electric cleaning device which overcome the problems described. 
     It is a further object of the invention to provide an electric blower having a simple structure that can improve suction properties. 
     Another object of the present invention is to prevent increases in temperature of circulating exhaust air in exhaust-circulation electric cleaning devices. 
     In order to achieve the objects described above, the present invention provides an electric blower wherein a diffuser is interposed between a centrifugal fan and a motor frame. A bracket in which a motor drive section is mounted is disposed downstream from the motor frame. The centrifugal fan and the diffuser are covered by a fan cover. Exhaust air discharged radially from the centrifugal fan is redirected to the motor drive section by the diffuser and the fan cover. The exhaust air passes from a ventilation opening of the motor frame through the bracket to cool the motor drive section. An exhaust opening is formed at a section of the fan cover. A portion of exhaust air discharged from the centrifugal fan is discharged from the exhaust opening of the fan cover. 
     The present invention can also have the exhaust opening formed at an outer perimeter section of the fan cover. 
     Furthermore, the present invention can also have a cooling fan disposed to cool the motor drive section. 
     Also, the present invention provides an electric cleaning device wherein an exhaust flow path and a suction flow path are formed in a hose, pipe, and suction tool connected to a main cleaning device unit in which is mounted an electric blower. The exhaust flow path circulates exhaust air from the electric blower. The electric blower described above is used so that exhaust air discharged from the exhaust opening of the fan cover is circulated to the exhaust flow path. 
     The present invention also provides an electric cleaning device wherein an exhaust flow path and a suction flow path are formed in a hose, pipe, and suction tool connected to a main cleaning device unit in which is mounted an electric blower. The exhaust flow path circulates exhaust air from the electric blower. The electric blower described above is used so that exhaust air discharged 
     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a drawing of the overall structure of an embodiment of an electric blower according to the present invention and an exhaust-circulating cleaning device using the same. An intermediate section of the hose is omitted to facilitate the drawing. 
     FIG. 2 is a cross-section detail drawing of the main cleaning device unit from FIG.  1 . 
     FIG. 3 is a half cross-section drawing showing the structure of the electric blower according to the above embodiment. 
     FIG. 4 is a front-view drawing of the electric blower with the front section of the fan cover cut away. 
     FIG.  5 ( a ) is a front-view of a vaned diffuser, having volute ribs, showing the side toward the centrifugal fan. 
     FIG.  5 ( b ) is a side-view of the vaned diffuser of FIG.  5 ( a ). 
     FIG.  5 ( c ) is a rear-view of the vaned diffuser of FIG.  5 ( a ) showing the side toward the motor frame. 
     FIG. 6 is a detail drawing of the main elements from FIG. 3 with air flows indicated by arrows. 
     FIG. 7 is a detail drawing of the main elements from FIG. 4 with air flows indicated by arrows. 
     FIG. 8 is a detail cross-section drawing of a main clearing device unit according to another embodiment. 
     FIG. 9 is a drawing showing the structure inside the main cleaning device unit as seen from above. 
     FIG. 10 is a partially cut-away cross-section drawing showing the structure of the electric blower according to the above embodiment. 
     FIG.  11 ( a ) shows a vertical cross-section drawing of a connecting pipe. 
     FIG.  11 ( b ) is a cross-section drawing along the A—A line from FIG.  11 ( a ). 
     FIG.  11 ( c ) is a side-view drawing of the connecting pipe of FIG.  11 ( a ). 
     FIG.  11 ( d ) is an end-surface drawing seen from one end of FIG.  11 ( c ). 
     FIG.  11 ( e ) is an end-surface drawing seen from the other end of FIG.  11 ( c ). 
     FIG.  11 ( f ) is a cross-section drawing along the B—B line from FIG.  11 ( c ). 
     FIG.  12 ( a ) is a cross- section detail drawing of a connecting pipe of FIG.  11 ( a ) with one section omitted. 
     FIG.  12 ( b ) is a cross-section detail drawing of FIG.  11 ( b ) with one section omitted. 
     FIG.  13 ( a ) is a vertical cross-section drawing showing the structure of the connecting pipe. 
     FIG.  13 ( b ) is an exploded view of FIG.  13 ( a ). 
     FIG.  14 ( a ) shows formations of the exhaust openings in the outer perimeter section of the fan cover with roughly uniform intervals. 
     FIG.  14 ( b ) shows formations of the fan cover with non-uniform intervals. 
     FIG.  14 ( c ) shows formations on only on one side of the perimeter of the fan cover outer perimeter section. 
     FIG.  15 ( a ) is a front-view drawing of the centrifugal fan of a vane-less diffuser without volute ribs. 
     FIG.  15 ( b ) is a side-view drawing if FIG.  15 ( a ). 
     FIG.  15 ( c ) is a rear-view drawing of the motor frame side. 
     FIG. 16 is a perspective drawing of the vane-less diffuser without volute ribs. 
     FIG. 17 is a half cross-section drawing showing the main elements of the electric blower that uses the vane-less diffuser described above. 
     FIG.  18 ( a ) shows rectangular exhaust openings on the outer perimeter of the fan cover. 
     FIG.  18 ( b ) shows openings in the fan cover in which the edge of the opening opposite from the direction of rotation of the centrifugal fan is formed in alignment with and to match the rib sloped toward the direction of rotation of the centrifugal fan. 
     FIG.  18 ( c ) shows openings in which the edge of the opening toward the direction of rotation of the centrifugal fan is sloped relative to the motor shaft. 
     FIG.  18 ( d ) is a combination of FIG.  18 ( b ) and FIG.  18 ( c ). 
     FIG. 19 is a drawing showing the positioning of the outer perimeter surface of the diffuser and the exhaust openings when the exhaust opening shape shown in FIG.  18 ( d ) is used. 
     FIG. 20 is a schematic cross-section drawing showing the position of a fan cover positioning/fixing section formed projecting inward on the outer perimeter section of the fan cover and the positioning/fixing state according to one embodiment. 
     FIG. 21 is a schematic cross-section drawing showing the position of a fan cover positioning/fixing section and the positioning/fixing state according to another embodiment. 
     FIG. 22 is a schematic cross-section drawing showing the position of a fan cover positioning/fixing section and the positioning/fixing state according to another embodiment. 
     FIG.  23 ( a ) is a schematic cross-section drawing of fan cover positioning/fixing sections as seen from the front of the fan cover. 
     FIG.  23 ( b ) is a schematic plan drawing of the fan cover positioning/fixing sections of FIG.  23 ( a ). 
     FIG.  23 ( c ) is a schematic cross-section drawing of FIG.  23 ( a ) as seen from the side. 
     FIG.  24 ( a ) is a schematic cross-section drawing of another embodiment of a fan cover positioning/fixing section as seen from the front of the fan cover. 
     FIG.  24 ( b ) is a schematic plan drawing of  24 ( a ). 
     FIG.  24 ( c ) is a schematic cross-section drawing of  24 ( a ) as seen from the side. 
     FIG.  25 ( a ) is a schematic cross-section drawing of another embodiment of a fan cover positioning/fixing section as seen from the front of the fan cover. 
     FIG.  25 ( b ) is a schematic plan drawing of FIG.  25 ( a ). 
     FIG.  25 ( c ) is a schematic cross-section drawing of FIG.  25 ( a ) as seen from the side. 
     FIG.  26 ( a ) is a schematic cross-section drawing of another embodiment of a fan cover positioning/fixing section as seen from the front of the fan cover. 
     FIG.  26 ( b ) is a schematic plan drawing of FIG.  26 ( a ). 
     FIG.  26 ( c ) is a schematic cross-section drawing of FIG.  26 ( a ) as seen from the side. 
     FIG.  27 ( a ) is a schematic cross-section drawing of another embodiment of a fan cover positioning/fixing section as seen from the front of the fan cover. 
     FIG.  27 ( b ) is a schematic plan drawing of FIG.  27 ( a ). 
     FIG.  27 ( c ) is a schematic cross-section drawing of FIG.  27 ( a ) as seen from the side. 
     FIG.  28 ( a ) is a front-view drawing of a fan cover on which a roughly V-shaped piece is bent up as a positioning/fixing section. 
     FIG.  28 ( b ) is a side-view drawing of the section of FIG.  28 ( a ). 
     FIG.  29 ( a ) is a front-view drawing of a fan cover on which a roughly V-shaped piece is bent up and combined with an exhaust opening. 
     FIG.  29 ( b ) is a side-view drawing of the fan cover of FIG.  29 (A). 
     FIG.  30 ( a ) is a front- view drawing of a fan cover on which an exhaust opening is formed integrally with a piece that is bent up to form a positioning/fixing piece. 
     FIG.  30 ( b ) is a side-view drawing of the piece of FIG.  30 ( a ). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG.  1  and FIG. 2, an electric blower and an exhaust-circulation electric cleaning device, shown generally at  100 , includes a main cleaning device unit  1 , a hose  2 , a connecting pipe  3 , a floor suction tool  4 , and the like. 
     Inside the main cleaning device  1  are disposed: a motor chamber  6  holding an electric blower  5  used for suction; and a dust collection chamber  9  using a paper pack  7  and a fine dust filter  8 . 
     An exhaust opening  11  located on the side toward the back surface of the main cleaning device unit  1 . Exhaust air cools a motor drive section, described later, of the electric blower  5 . The exhaust air is discharged from a bracket exhaust opening and finally discharged outside through an exhaust opening  11  via an exhaust filter  10 . 
     A section of the main cleaning device unit  1 , the hose  2 , the connecting pipe  3 , and the floor suction tool  4  are formed with counterflowing flow paths having a two-layer structure divided into a suction flow path A and an exhaust flow path B. 
     A portion of the exhaust flow path B, within main cleaning device unit  1 , which circulates the exhaust air discharged from the exhaust opening of the fan cover outer perimeter, described later, of the electric blower  5 , is located below the dust collection chamber  9  and the electric motor chamber  6 . This exhaust flow path B communicates with the exhaust flow path B of a hose joint  20  mounted on a hose insertion opening  12  of the main cleaning device unit  1 . The circulating exhaust flow path B toward the bottom of the main cleaning device unit  1  is separated by a partition wall  13  from the exhaust flow path to the exhaust opening  11  toward the back surface of the main cleaning device unit  1 . 
     In the hose joint  20 , connecting pipes  20   a ,  20   b  form a two-layered concentric structure. The end of the inner connecting pipe  20   a , which forms the suction flow path A, projects beyond the end of outer connecting pipe  20   b . One end of inner connecting pipe  20   a  is inserted into an attachment section  7   a  of the paper pack  7 . The exhaust flow path B, formed by the outer connecting pipe  20   b , communicates with the exhaust flow path B in the main unit  1 . 
     The two layers at one end of a two-layered hose  2  is connected to the ends of the connecting pipes  20   a ,  20   b . The hose  2  is formed from an inner flexible hose  2   a  known as a conduit hose such as those used to discharge water from washing machines and an outer flexible hose  2   b . The outer flexible hose  2   b  is a standard flexible hose used in electric cleaning devices known as single-layer two-line hoses. Outer flexible hose  2   b  contains within it a coil  21  that is conductive (to allow it to be used as a signal line or the like) that has shape retention. 
     The inner conduit hose  2   a  is mounted and adhered to the projecting end of the inner connecting pipe  20   a . The outer single-layer two-line hose  2   b  is twisted onto helical ribs  22  formed on the outer surface of the outer connecting pipe  20   b.    
     The other end of the hose  2  is mounted and fixed in the manner described above to a grip  24 , used to permit manual operator control, via inner and outer connecting pipes  24   a ,  24   b , respectively. The inner flexible hose  2   a  is mounted and adhered to the projecting end of the inner connecting pipe  24   a . The outer single-layer two-line hose  2   b  is mounted and fixed to the outer connecting pipe  24   b  by being twisted onto concentric or helical ribs  25  on the outer surface of the outer connecting pipe  24   b . A cylindrical protective cover  26  covers the attachment section of the hose  2 . 
     Connecting pipes  3 ,  3  each include: an inner cylinder  3   a  forming the suction flow path A having a roughly circular cross section; and an outer cylinder  3   b  forming the exhaust flow path B between itself and the inner cylinder  3   a . The outer cylinder  3   b  covers the inner cylinder  3   a . The upper portion of the outer cylinder  3   b  is formed integrally with the inner cylinder  3   a.    
     Referring to FIG. 3, the electric blower  5  includes a motor section  5   a  and a blower section  5   b . A motor drive section  53 , in the motor section  5   a , includes a rotor  51  and a stator  52 . The rotor  51  and the stator  52  are enclosed between a motor frame  54  and a bracket  55 . A shaft  56  of the rotor  51  is rotatably supported on bearings  57 ,  57  disposed on the motor frame  54  and the bracket  55 . The bracket  55  includes an exhaust opening  55   a  through which exhaust air used to cool the motor drive section  53  is discharged. A brush supporter  58  is attached to the bracket  55 . A carbon brush  60  is pushed downward in the brush supporter  58  by a coil spring  59  so that the inner end of the carbon brush  60  is pressed into contact with the commutator  61  of the motor shaft  56 . 
     The blower section  5   b  includes: a centrifugal fan  63  fixed via a nut  62  to the motor shaft  56  projecting from the motor frame  54 . A diffuser  64  is fixed to the motor frame  54  interposed between the centrifugal fan  63  and the motor frame  54 . The above elements of the blower section  5   b  are covered by a metallic fan cover  65 . 
     The centrifugal fan  63  includes: a spiral blade  66  (see FIG. 4) and a front shroud  67  and a rear shroud  68  disposed on either side of the spiral blade  66 . The front shroud  67  is formed with a suction opening  69  at a central portion thereof to suction air. The front shroud  67  is formed so that distance between it and the rear shroud  68  gets smaller toward the outer perimeter. At the outer perimeter section a discharge opening  70  is formed so that the air sucked in through the suction opening  69  toward the center is discharged radially from the discharge opening  70  toward the outer perimeter. 
     Referring now to FIGS.  4  and  5 ( a ), the diffuser  64  is a vaned diffuser having multiple volute ribs  71  are on the side facing the centrifugal fan at its outer perimeter. The volute ribs  71  are inclined in the direction of rotation of the centrifugal fan  63  (counterclockwise in the figure). 
     Referring to FIG.  5 ( c ), on the side of the motor frame, the exhaust air discharged from the centrifugal fan  63  and redirected via the volute ribs  71  and the fan cover  65  is guided to a ventilation opening (not shown in the figure) formed on the motor frame  54  by spiral-shaped guide ribs  72 . 
     The fan cover  65  is formed so that it can be mounted to the outer perimeter section of the motor frame  54  where it covers the front surface and the outer perimeter surface of the centrifugal fan  63  and the diffuser  64 . A suction opening  73  (FIG. 3) corresponding to the suction opening  69  of the centrifugal fan  63 , is formed on the front surface of the fan cover  65 . To position the fan cover  65  when it is mounted, the fan cover  65  is pushed in until the ends of the volute ribs  71  formed on the diffuser  64  touch the ceiling of the fan cover  65 . This allows the fan cover  65  to be easily positioned. 
     The suction opening  73  of the fan cover  65  is formed with a cylindrical section  74 , the end of which extends to the inside of the suction opening  69  of the centrifugal fan  63 . A ring-shaped sealing member  75  formed from PTFE (polytetrafluoroethylene) resin or the like is mounted and fixed around the cylindrical section  74 . The sliding contact of the end of the suction opening  69  of the centrifugal fan  63  prevents bypass air flow in which the air discharged from the discharge opening  70  of the centrifugal fan  63  is sucked into the suction opening  69  from the front side of the front surface of the centrifugal fan  63 . 
     A plurality of rectangular exhaust openings  65   a  is formed at roughly identical intervals in the outer perimeter section of the centrifugal fan  63  downstream from the position of the centrifugal fan, i.e., toward the motor frame  54  of the diffuser  64 . The exhaust openings  65   a  discharge a portion of the exhaust air discharged from the centrifugal fan  65 . 
     Referring again to FIG. 2, when the electric blower  5  described above is attached to the motor chamber  6  of the main cleaning device unit  1 , the edge of the outer perimeter on the front of the fan cover  65  is sealed and supported by a motor cushion  14  formed from a soft material such as rubber. The exhaust openings  65   a  at the outer perimeter section of the fan cover are not covered up by the motor cushion  14 . Thus, bypass air flow, in which the air discharged from the exhaust opening circulates to the front of the fan cover  65 , is avoided. Thus, the motor cushion  14  can be identical to the motor cushions used conventionally. 
     Referring to FIG.  6  and FIG. 7, detail drawings of the main elements from FIG.  3  and FIG. 4, include the direction of the flow of air indicated by arrows. 
     When the centrifugal fan  63  is rotated, the air sucked in from the suction opening  69  at the center of its front surface is discharged radially from the discharge opening  70  at the outer perimeter section. The air passes through the volute ribs  71 ,  71  of the diffuser  64  until it comes up against the inner surface of the outer perimeter section of the fan cover  65 , where it is redirected in the direction of the guide ribs  72  of the diffuser  64 . 
     The exhaust openings  65   a  are formed, as described above, at the outer perimeter section of the fan cover  65  corresponding to the guide ribs  72  of the diffuser  64 . This allows a portion of the exhaust air to be discharged from the exhaust openings  65   a  outside the fan cover  65 . 
     As with the conventional technology, the remaining exhaust air is guided along the guide ribs  72  of the diffuser  64  to the ventilation opening of the motor frame  54 . The air passes into the bracket  55  from the ventilation opening where it cools the motor drive section  53 . Finally, the air is discharged out from the bracket exhaust opening  55   .    
     By forming the exhaust openings  65   a  at the outer perimeter section of the fan cover  65 , as described above, a portion of the exhaust air discharged from the centrifugal fan  63  is discharged outside from the exhaust openings  65   a  of the fan cover outer perimeter section without undergoing a major redirection. This reduces the overall ventilation resistance, thus increasing the suction air volume and improving the properties of the electric blower  5 . 
     A prototype was tested by the inventors. It was found that with 600 W input, the suction power for the conventional technology that does not include exhaust openings was 254 W. In contrast, the prototype formed with exhaust openings  65   a  showed an improvement to 270 W. This improvement demonstrates the advantages of the structure described above. 
     When an exhaust-circulating cleaning device equipped with the electric blower  5  as described above (FIG.  1 ), the suction of the electric blower  5  causes air mixed in with debris sucked in from the floor suction tool  4  to flow through the suction flow path A of the connecting pipe  3  and the suction flow path A of the hose  2 . This air is collected in the main cleaning device unit  1 . In the main unit  1 , the debris is removed by the paper pack  7 . The air is cleaned further by passing through the fine dust filter  8 . The air is then sucked into the electric blower  5 . 
     As described above, a portion of the exhaust air from the electric blower  5  is discharged from the exhaust openings  65   a  at the outer perimeter section of the fan cover. This air is then circulated back to the exhaust flow path B formed toward the bottom of the main cleaning device unit  1 . This air passes through the exhaust flow path B of the hose  2  and the exhaust flow path B of the connecting pipe  3  and is circulated to the floor suction tool  4 . The debris blown up by this exhaust air and newly suctioned outside air is circulated back into the suction flow path A of the connecting pipe  3 . 
     A portion of the exhaust air from the electric blower  5  is directly circulated from the exhaust opening  65   a  formed on the outer perimeter section of the fan cover  65  to the exhaust flow path B formed toward the bottom of the main cleaning device unit  1 . Thus, this air does not pass through the head-generating motor drive section  53 , and the exhaust air is circulated in a cool state. As a result, the surface temperature of the hose  2  and the pipe  3  remain at a safe temperature, thereby preventing the user from experiencing discomfort. Also, problems relating to heat resistance and lifespan of the resin elements such as the hose  2  or the pipe  3 , deformation of the main cleaning device unit  1 , and deterioration or destruction of the electric blower  5  can be eliminated. 
     The exhaust air passing through the bracket  55  is used as in the conventional technology to cool the motor drive section  53 . The exhaust air discharged from the fan cover exhaust openings  65   a  is circulated back to the floor suction tool  4  via the exhaust flow path B formed toward the bottom of the main cleaning device unit I and the exhaust flow path B of the hose  2  and the pipe  3 . The air is blown on the floor surface to blow up debris, which is then sucked in. This improves the effectiveness of debris collection. Since this circulated exhaust air does not pass through the bracket  55 , it does not contain carbon particles generated by the contact between the carbon brush  60  and the commutator  61 , thus preventing the exhaust flow paths B, the floor surface, and the like from being soiled by carbon particles. 
     An electric blower  5  that is optimal for exhaust-circulating cleaning devices can be implemented simply by modifying the fan cover from a conventional electric blower. Thus, compared to the use of conventional “wet and dry” motors, the structure can be smaller, lighter, less expensive, and easier to produce. 
     Also, since the exhaust air for circulation and for cooling are not completely separated, the ratio between these can be easily changed simply by adjusting the total area of the exhaust openings  65   a  of the fan cover  65 . This allows debris collection efficiency and easy adjustment of exhaust air temperature. Simply by changing the exhaust opening shape of the fan cover  65 , the blower and the electric cleaning device can be made to easily accommodate various demands. 
     The exhaust openings  65   a  at the outer perimeter section of the fan cover  65  are formed downstream from the position of the centrifugal fan. This prevents the exhaust air discharged from the centrifugal fan  63  from being directly discharged out from the fan cover  65 . The path formed by the diffuser  64  and the inner perimeter surface of the fan cover  65  converts dynamic pressure to static pressure. This air is then divided into exhaust air discharged out from the fan cover  65  and exhaust air used to cool the motor drive section  53 . Thus adequate air flow for cooling the motor drive section is provided, while the conversion of dynamic pressure to static pressure increases the degree of vacuum. This increases the suction efficiency. Also, with the rotation of the centrifugal fan  63 , noise is generated when the blades  66  of the centrifugal fan  63  pass by the volute ribs  71  of the diffuser  64 . However, this noise can be restricted so that it does not directly go outside since the exhaust openings  65   a  at the outer perimeter section of the fan cover  65  are formed downstream from the position of the centrifugal fan and also because the exhaust openings  65   a  are not aligned with the noise source. 
     Referring to FIG.  8  through FIG. 10, there is shown another embodiment of the present invention. Elements that are identical or similar to those from the embodiment described above will be assigned identical numerals and their descriptions will be omitted. 
     A cover body  76  covers the outer perimeter surface of the fan cover  65 . A communicating opening  76   a  at the bottom of the cover body  76  provides communication between the cover body  76  and the exhaust flow path B. These elements form a bypass flow path  77  that circulates exhaust air from the electric blower  5  to the exhaust flow path B without going through the motor  5 . 
     A cooling fan  78 , attached toward the rear end of the rotation shaft  53   a  of the motor  53 , is covered by a housing  79 , which includes a suction opening  79   a  that faces the exhaust opening  11  of the main cleaning device unit  1 . The bracket  55  of the motor  53  is formed with an air blower opening  55   a  that blows outside air brought in by the cooling fan  78  on the coils (heat-generating bodies) of the rotor  51  and the stator  52  that form the motor  53 . After cooling the coils of the rotor  51  and the stator  52 , the exhaust air is discharged from the bracket  55  and the discharge opening  79   b  formed on the housing  79  into the motor chamber  6 . The exhaust air is then discharged outside the exhaust opening  11  of the main cleaning device unit  1  via the opening  6   a  formed at the bottom of the motor chamber  6 . 
     An exhaust opening  80  is formed at the rear end of the exhaust flow path B formed toward the bottom of the main cleaning device unit  1 . A portion of the exhaust air circulated from the bypass flow path  77  to the exhaust flow path B is discharged from the discharge opening  80  to the exhaust opening  11  of the main cleaning device unit  1 . Thus, a portion of the exhaust air from the electric blower is discharged out from the exhaust opening  11  of the main cleaning device unit  1 . An equivalent flow of air is sucked in from the outside into the floor suction tool  4 . This improves the debris suction properties of the exhaust-circulating electric cleaning device. The proportion of exhaust air circulated to the exhaust flow path B to the floor suction tool  4  and the exhaust air discharged outside form the exhaust opening  11  of the main cleaning device  1  can be set to an optimum proportion by adjusting the area of the opening in the exhaust opening  80  or the like. 
     When using the electric cleaning device according to this embodiment, the exhaust air from the electric blower  5  is directly circulated from the fan cover  65  to the exhaust flow path B formed toward the bottom of the main cleaning device unit  1  via the bypass flow path  77 . Thus, the air does not pass through the motor coils, which are heat-generating bodies, and can be circulated at a low temperature through the exhaust flow path B formed in the hose  2 , the pipe  3 , and the like. This allows the surface temperature of the hose  2  and the pipe  3  to be no more than about 45 deg C, thus preventing the user from feeling discomfort and preventing heat-resistance or lifespan problems in the resin parts such as the hose  2  and the pipe  3 . Also, the motor  53  is cooled by a separate cooling fan  78 . This prevents the motor  53  from overheating and malfunctioning. 
     As described above, the exhaust-circulating electric cleaning device according to this embodiment can prevent temperature increases in the circulating exhaust air. Also, the reduced temperature permits the hose  2 , through which are formed the suction flow path A and the exhaust flow path B, to be made lighter and easier to assemble. Furthermore, the connecting pipe  3  can be made lighter and slimmer. Thus, the advantages provided by exhaust circulation can be implemented in a practical manner. 
     By circulating a portion of the exhaust air, the exhaust air blown outside is reduced and weakened. This efficiently restricts the blowing up of dust in the room during cleaning. 
     Also, the air speed of the exhaust air blown out from the exhaust opening  11  is reduced. This improves the effectiveness of the filtering performed by the exhaust filter  10  and allows the exhaust air to be cleaner. This is in line with the current trend toward increased concern for cleanliness. 
     Referring to FIGS.  11 ( a ) through FIG.  13 ( b ), another embodiment of the connecting pipe  3  provides an improvement in the connecting pipe  3  to increase the heat dissipation effect and to prevent temperature increases in the circulated exhaust air. 
     Due to the necessities of the connecting structure, the ends of the connecting pipe  3  use two-layered pipes  31 ,  32  formed from resin as in the embodiments described above. However, a two-layered pipe  33  formed from aluminum having high heat dissipation properties is used between the ends  31 - 32 . 
     In these two-layered pipes  31 - 33 , inner cylindrical sections  31   a - 33   a  form suction flow paths A having roughly circular cross-sections. Outer cylindrical sections  31   b - 33   b  are formed integrally with the upper sections of the inner cylindrical sections  31   a - 33   a  and cover the inner cylindrical sections  31   a - 33   a , forming exhaust flow paths B. 
     The exhaust air flowing through the exhaust flow paths B is clean air from which dust has been removed by the paper pack  7  and the fine dust filter  8  of the main cleaning device unit  1 . Thus, there is no need to form the flow paths with a roughly circular cross-section to prevent clogging as with the inner cylindrical sections  31   a - 33   a . Thus, in this embodiment the exhaust flow paths B is formed with a roughly crescent-shaped cross-section and the outer cylindrical sections  31   b - 33   b  are formed with roughly circular cross-sections. 
     The aluminum two-layered pipe  33  having the structure described above can be easily formed integrally using extrusion molding. 
     The outer surface of the aluminum outer cylindrical section  33   b  is covered by resin covers  34   a - 34   c  in order to prevent direct contact from hands of the user. The cover  34   b , which covers the lower half having a large exhaust flow area, is formed with a plurality of slits  34   d  in order to dissipate heat outside. 
     As with the conventional technology, a cover  34   e  is mounted above the connecting pipes  3  to cover cables and the connecting clamp  35 . 
     Connecting pipe  3  described above, can be two or more connecting pipe  3  connected end to end as is conventional. On the side toward the suction opening  36  connecting to the floor suction tool  4 , the partition wall (inner cylindrical section  32 ) separating the suction flow path A and the exhaust flow path B is offset toward the inside of the pipe by a predetermined distance. 
     At the other end of the connecting pipe  3 , the outer cylindrical section  31   b  is formed with a slightly smaller diameter corresponding to the suction opening of the grip  24  and the suction opening  36  of the connecting pipe  3 . This allows the outer cylindrical section  31   b  to be fitted into the inner perimeter of the suction opening side. A projection  37  is formed on the upper section of the outer cylindrical section  31   b  to engage a clamp on the suction opening side. 
     By using aluminum for the section of the connecting pipe  3  through which exhaust air passes, heat dissipation properties are improved and temperature increases in the circulating exhaust air are restricted. 
     Also, since the upper section of the connecting pipe  3  described above is formed integrally, the use of aluminum makes the structure lighter and more slim. Furthermore, since the inner and outer layers are both formed with roughly circular cross-sections, the structure is easy to use while still being strong. Thus, the connecting pipe  3  according to this embodiment is no less comfortable compared to the conventional structure for suction only, while roughly the same shape and ease of use is provided. 
     Referring to FIG.  14 ( a ), in the embodiments described above the exhaust openings  65   a  are formed at roughly equal intervals on the outer perimeter section of the fan cover  65 . Referring to FIG.  14 ( b ), however, it would also be possible to form the exhaust openings  65   a  with non- uniform intervals. Referring to FIG. 14 ( c ), it would also be possible to form the exhaust openings  65   a  on only one side of the perimeter of the outer perimeter section of the fan cover  65 . 
     Referring to FIG.  14 ( b ), by forming the exhaust openings  65   a  at non-uniform intervals, the discharge openings  70  formed at equal intervals at the outer perimeter section of the centrifugal fan  63  are not simultaneously aligned with each of the exhaust openings  65   a  of the fan cover  65 . Thus, the noise emitted from the fan cover exhaust openings  65   a  is dispersed without going completely out from the fan cover  65 . This allows the noise to be reduced. 
     Referring to FIG.  14 ( c ), by forming the exhaust openings  65   a  on one side of the perimeter of the outer perimeter section of the fan cover  65 , the exhaust space of the outer perimeter section of the fan cover  65  can be concentrated at one section. The creation of a section that does not require exhaust space allows space to be conserved while the concentration of the exhaust openings  65   a  improves the exhaust efficiency. Also, by having the exhaust openings  65   a  disposed at positions away from the outer fringe of the electric cleaning device or the like, the emitted noise can be reduced. 
     The embodiments described above use a vaned diffuser  64  having volute ribs  71  due to the ease of fixing and positioning the fan cover  65 . Referring to FIGS.  15 ( a )- 16 , however, it is also possible to use a vane-less diffuser  84  that does not have volute ribs. The absence of volute ribs results in reduction of ventilation resistance, improved air flow, and reduced noise, thus making this structure useful for exhaust-circulating cleaning devices. 
     In place of volute ribs, this diffuser  84  is formed with a plurality of sloped ribs  85  disposed at the outer perimeter section of the diffuser  84 . These sloped ribs  85  are sloped from the centrifugal fan  63  to the motor frame  54  along the direction of rotation of the centrifugal fan  63 . Sloped paths  86  are formed between these sloped ribs  85 . 
     Referring to FIG.  17  and FIG.  18 ( a ), the exhaust openings  65   a  at the outer perimeter section of the fan cover  65  can be formed with rectangular shapes as in the embodiments described above. Referring to FIG.  18 ( b )- 18 ( d ), however, it would also be possible to use alternative shapes for the exhaust openings  65   b - 65   d  to provide the advantages described below. 
     Referring to FIG.  18 ( b ), an exhaust opening edge  65   e  opposite from the rotation direction of the centrifugal fan is formed so that it is aligned with the sloped rib shape  85   e  (see FIG. 16) in the rotation direction of the centrifugal fan  63 . Thus, as the exhaust air is discharged outside from the fan cover exhaust openings  65   b  via the diffuser sloped paths  86 , the dynamic pressure is converted to static pressure, thus providing similar advantages as those of the embodiments described above. Also, since exhaust openings  65   b  are formed at areas that are not covered up by the sloped ribs  85  of the diffuser  84 , the reduction in strength of the fan cover  65  resulting from the formation of the exhaust openings  65   b  can be kept to a minimum. 
     Referring to FIG.  18 ( c ), an exhaust opening edge  65   f  toward the rotation direction of the centrifugal fan  63  is sloped relative to the motor axis direction. Thus, when the exhaust air is discharged, it is not separated into portions inside and outside the fan cover  65  at once at the opening edge  65   f  toward the centrifugal fan rotation direction, which is where the most noise is generated. Instead, the incline provides an offset so that noise can be reduced. 
     Referring to FIG.  18 ( d ), in which the above shapes are combined, the exhaust opening  65   d  can be positioned relative to the outer perimeter surface of the diffuser  84  as indicated by the dotted lines in FIG.  19 . Thus, reductions in the strength of the fan cover  65  can be avoided while noise is reduced. 
     As described above, the electric motor  5  used in electric cleaning devices and the like can be formed with vaned diffusers  64  having volute ribs  71  or vane-less diffusers  84 . Referring to FIG. 3, if the vaned diffuser  64  is used, the volute ribs  71  abut the ceiling of the fan cover  65  thus allowing the fan cover  65  to be accurately positioned and fixed in the axial direction. 
     With the vane-less diffuser  84 , however, the absence of volute ribs prevents accurate positioning of the fan cover  65  in the axial direction. Thus, to allow accurate positioning, a skirt-shaped shelf needs to be formed at the outer perimeter edge of the motor frame  54  to allow fixing. Alternatively, an offset can be formed at the outer perimeter section of the fan cover  65  to abut the outer perimeter edge of the motor frame  54  to allow fixing. 
     With the former method, however, providing an adequate shelf for the fixing of the motor frame  54  and the fan cover  65  results in a larger motor frame  54 , leading to increased weight and costs. Also, the shelf of the motor frame  54  determines the maximum outer diameter, and the ends have to be processed in order to protect lead wires. This reduces ease of production and increases costs. 
     With the latter method, the maximum outer diameter of the electric blower  5  does not change but the offset reduces the air flow area within the fan cover  65 , thus decreasing performance. 
     With either method, modifying dies from their current shapes requires major changes. This creates problems such as die modification costs and inability to reuse dies since there is no compatibility with current products. More specifically, two dies would be necessary. 
     As described above, in electric blowers that seek to provide high performance, a ring-shaped sealing member  75  formed from PTFE or the like is disposed between the suction opening  69  of the centrifugal fan  63  and the suction opening  73  of the fan cover  65 , thus allowing the rim of the suction opening  69  of the centrifugal fan  63  to slide against the ring-shaped sealing member  75 . However, variations and deformations in the various parts can change the position of the centrifugal fan, resulting in too much or not enough contact with the ring-shaped sealing member  75 . Each time this happens, the die must be modified to adjust the axial height of the suction opening  73  of the fan cover  65 . This requires die modification costs and reduces the lifespan of a die, while also preventing the use of the die during modification. 
     Referring to FIG.  20  through FIG. 22, there is shown a schematic cross-section drawing of a structure that eliminates the problems described above. The figures show the positioning and the fixing effect provided by an inwardly projecting fan cover positioning/fixing section (here, a roughly V-shaped piece  65   j  formed by cutting and bending and shown in FIGS.  24 ( a )-( c ) described later) formed at the outer perimeter section of the fan cover  65 . The reason the shape of the diffuser  84  appears different is that the cross-section position of the vane-less diffuser  86  shown in FIG.  15  and FIG. 16 is different. 
     Referring to FIG. 20, the positioning/fixing section (the roughly V-shaped piece  65   j ) is formed at the outer perimeter section projecting inward and abutting the fan cover mounting edge  54   a  of the motor frame  54  in order to fix the fan cover mounting position at a predetermined position. With this structure, the fan cover can be fixed along the direction of the axis of the fan cover  65  for the vane-less diffuser  84  not having volute ribs without changing the outer dimensions of the electric blower  5  at all. Also, this structure can be formed at the same time that the exhaust openings  65   a   65   d  are formed on the fan cover  65 , thus allowing the number of steps required to be minimized. 
     Referring to FIG. 21, the positioning/fixing section (the roughly V-shaped piece  65   j ) for fixing the fan cover mounting position at a predetermined position is formed at the outer perimeter section of the fan cover  65  projecting inward and abuts the outer perimeter edge of the diffuser  84  toward the centrifugal fan. In addition to the advantages described above, this structure holds the outer perimeter edge of the diffuser  84  to reliably fix the diffuser  84 , thus vibrating contact with the motor frame  54  and the fan cover  65  can be prevented and vibration and noise from the electric blower  5  can be reduced. 
     In FIG. 21, the piece  65   j  abuts the outer perimeter edge of the diffuser  84  toward the centrifugal fan. 
     Referring to FIG. 22, it would also be possible to have the piece  65   j  abut an intermediate position of the sloped rib  85  at the outer perimeter edge of the diffuser  84 . 
     Referring to FIG.  23 ( a ) through FIG.  27 ( c ), there are shown various examples of structures for the fan cover positioning/fixing section described above. In each figure, ( a ) is a schematic cross- section drawing as seen from the front of the fan cover  65 , ( b ) is a schematic plan drawing, and ( c ) is a schematic cross-section drawing as seen from the side. 
     Referring to FIGS.  23 ( a )-( c ), the positioning/fixing section shown is the most simple. An inwardly projecting projection  65   h  is formed using a punch or the like. This requires only slight modification to the fan cover  65  and can be performed through post-processing or the like. Since the projection  65   h  can be formed through post-processing, the same dies used in the conventional technology can be used. Also, the position of the projection  65   h  can be easily modified by adjusting automated devices. Thus it is possible to easily adjust the sliding contact between the edge of the suction opening  69  of the centrifugal fan  63  and the ring-shaped sealing member  75  made from PTFE or the like and attached to the edge of the suction opening  73  of the fan cover  65 . As a result, if variations or deformations in parts cause the fan position to change, leading to too much or not enough contact with the ring-shaped sealing member  75 , adjustments can be made immediately. 
     Referring to FIGS.  24 ( a )-( c ), grooves  65   i ,  65   i  are formed parallel to the perimeter of the outer perimeter section of the fan cover  65 . The roughly V-shaped piece  65   j  is projected inward (same as in FIG.  20  through FIG. 22 described above). In addition to the advantages described above, in this structure the abutment of the V-shaped piece  65   j  occurs over a uniform line, thus preventing variations in the fixing position of the fan cover  65  that occur with the projection  65   h  described above due to the depth of the projection and the manner of abutment. 
     Referring to FIGS.  28 ( a )-( b ), there is shown an example of the fan cover  65  formed with a plurality of the roughly V-shaped piece  65   j  spaced about its perimeter. 
     Referring to FIGS.  29 ( a )-( b ), there is shown an example where a structure is formed in combination with the exhaust openings  65   a . In this example the presence of the exhaust openings  65   a  allows the pieces  65   j  to be somewhat larger without affecting performance or noise. 
     Referring to FIGS.  25 ( a )-( c ), roughly U-shaped indentations  65   k  are formed along the direction of the motor shaft at the outer perimeter section of the fan cover  65 . Pieces  65   m  are bent roughly perpendicularly inward. In addition to the advantages described above, this structure provides a uniform surface abutment at the pieces  65   m , thus allowing the fan cover  65  to be reliably fixed. 
     Referring to FIGS.  26 ( a )-( c ), ends  65   n  of the pieces  65   m  are bent roughly perpendicular toward the motor frame  54  based on the thickness of the fan cover mounting edge  54   a  of the motor frame  54 . As a result, the fan cover  65  is fixed so that the fan cover mounting end  54   a  of the motor frame  54  is sandwiched in from both sides, thus allowing, the fan cover  65  to be reliably fixed. 
     Referring to FIGS.  27 ( a )-( b ), pieces  65   p  are formed by bending inward the edge extending along the perimeter of the exhaust opening  65   a , at the outer perimeter section of the fan cover  65 , at roughly a right angle. This structure can be formed by simply leaving behind a section of the material that is cut away to open the exhaust opening  65   a  and bending it. This reduces the modifications required for the die and minimizes cost increases. Also, the fan cover  65  is reinforced and the structure also substitutes for the processing of the edge. 
     Referring to FIG. 30, there is shown an example of the fan cover  65  where the exhaust opening  65   a  and the positioning/fixing piece  65   p  are formed integrally. 
     In the description of the above embodiments, the fixing/positioning section is formed on the fan cover  65  where the vane-less diffuser  84  with no volute ribs is used. Referring to FIG. 5, the positioning/fixing sections can also be formed with the vaned diffuser  64  having the volute ribs  71 . If for some reason the volute ribs  71  are deformed or destroyed, the positioning/fixing section will serve as a stopper to prevent the fan cover  65  from moving along the axial direction, where it would come into contact with the centrifugal fan  63  and be damaged. 
     In the embodiments described above, the exhaust openings  65   a  are formed at the outer perimeter section of the fan cover  65 . However, it would also be possible to form the exhaust openings  65   a  at other positions such as at the front of the fan cover  65  or at the rear of the fan cover  65 . When an electric blower in which the exhaust openings  65   a  are formed at the outer perimeter section of the fan cover  65  is mounted on the main cleaning device unit, an exhaust flow path must be formed at the outer perimeter section of the fan cover  65  and the radial dimension of the main cleaning device unit  1  must be increased. However, with these structures the exhaust flow path is formed at the front or the rear of the fan cover  65  so that there is no need to increase the radial dimension of the main cleaning device unit  1 . This allows the main cleaning device unit  1  to be made more compact. 
     Also, in the embodiments described above the exhaust opening  11  is formed on the main cleaning device unit  1 . However, it would also be possible to form the exhaust opening at the exhaust flow path B. For example, an air permeable material can be used to form the outer hose  2   b  and this permeable section of the outer hose  2   b  can serve as the exhaust opening. 
     The invention described above provides an electric blower in which the exhaust air discharged radially from the centrifugal fan is redirected toward the motor drive section by the diffuser and the fan cover. The air passes through the ventilation opening of the motor frame and through the bracket to cool the motor drive section. Exhaust openings are formed at a section of the fan cover and a portion of the exhaust air from the centrifugal fan is discharged from the exhaust openings of the fan cover. This reduces the overall ventilation resistance and increases the suction volume, thus improving the performance of the electric blower. 
     Also, by forming the exhaust openings at the outer perimeter section of the fan cover, the amount of ventilation resistance can be reduced and the suction volume can be increased, thus improving the performance of the electric blower. 
     Also, by having a cooling fan disposed to cool the motor drive section, problems such as malfunction of the motor due to overheating are eliminated and the temperature of the circulating exhaust air is prevented from increasing. Thus, discomfort to the user if the hose or the pipe is touched is prevented. 
     Also, the electric blower described above can be used in exhaust-circulating cleaning devices, where an exhaust path for circulating exhaust air from the electric blower is formed along with a suction path in the hose, pipe, and the suction tool connected to the main cleaning device unit. The exhaust air from the exhaust opening at the outer perimeter section of the fan cover is circulated in the exhaust flow path. This prevents the temperature of the circulating exhaust air from increasing and prevents soiling due to carbon particles while providing a compact, low-cost structure without the use of a “wet and dry” motor. Thus, the implementation of the exhaust-circulating cleaning device is made easier. 
     When the electric blower described above is used in exhaust-circulating cleaning devices, where an exhaust path for circulating exhaust air from the electric blower is formed along with a suction path in the hose, pipe, and the suction tool connected to the main cleaning device unit, the exhaust air from the exhaust openings of the fan cover can be circulated through the exhaust flow path while a portion of the exhaust air circulating in the exhaust flow path is discharged outside through an exhaust hole. This prevents the temperature of the circulating exhaust air from increasing while avoiding problems such as malfunctions of the motor due to overheating. As a result, problems such as user discomfort due to touching the hose or pipe as well as limited heat resistance and lifespan of resin elements such as the hose and the pipe can be avoided. Thus, the implementation of the exhaust-circulating cleaning device is made easier. 
     Furthermore, exhaust openings can be formed on the main cleaning device unit to discharge air used for cooling the motor to the outside. This prevents the temperature in the main cleaning device unit and eliminates the need for heat resistance in the elements used in the main cleaning device unit. 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.