Abstract:
A heating and ventilation fan for a bathroom comprises an ventilation fan frame, a scroll casing provided with fan blades and a motor, an air passage-switching plate, and a heater; characterized in that: an air leakage-preventing structure is provided between an air outlet of the scroll casing and the air passage. The advantage of the present invention is that a desired air amount can be ensured and a noise can be reduced while guaranteeing a gap required for smooth rotation of the air passage-switching plate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a heating and ventilation fan for a bathroom, and in particular, to an air leakage-preventing structure for a heating and ventilation fan for a bathroom. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    As shown in  FIG. 1 , a heating and ventilation fan  100  for a bathroom in the prior art comprises a frame  110  having an opening  101  open toward the bathroom and an opening  102  connected with a joint, an ventilation fan profile constituted by a hood  110   a  for covering the opening  101  at the lower side of the frame  110 , fan blades  120 , a motor  130 , a heater  140  and an air passage-switching plate  150 . When the heating and ventilation fan  100  is operated, the air is drawn from an air inlet  160  of the hood  110   a  of the heating and ventilation fan  100  toward the air passage-switching plate  150 . The air passages are switched by rotation of the air passage-switching plate  150 , so that one of a heating function, an air-exchanging function, and a drying function of the heating and ventilation fan  100  is selected. 
         [0003]    Since selection of the above functions should be performed by rotation of the air passage-switching plate  150 , a certain gap  180  between the air passage-switching plate  150  and the air passage wall  170  should be ensured, and thus the air passage-switching plate  150  can be smoothly rotated. In this way, when the heating and ventilation fan  100  is operated, a small amount of the air is blown into the gap  180 , causing lost of air volume and generation of noise. However, if the gap  180  between the air passage-switching plate  150  and the surrounding air passage wall  170  is too small, the small gap will cause noise when the air is blow into the gap or the air passage-switching plate  150  can not be smoothly rotated during operation of the heating and ventilation fan. 
       SUMMARY 
       [0004]    Accordingly, it is desired to provide a heating and ventilation fan for a bathroom which is capable of reducing noise. 
         [0005]    In order to achieve the above object, the heating and ventilation fan for a bathroom according to the present invention is an ventilation fan for a bathroom, comprising an ventilation fan frame, a scroll casing provided with fan blades and a motor, an air passage-switching plate provided downstream of an air outlet of the scroll casing and configured to switch air passages directed in at least two directions, and a heater. An air leakage-preventing structure is provided at the air outlet of the scroll casing to direct the air to an inside of the air passage-switching plate. 
         [0006]    The air leakage-preventing structure comprises a protrusion piece configured to protrude from the air outlet of the scroll casing to the inside of the air passage-switching plate, and the air passage-switching plate has a rotation piece configured to overlap with the outer side of the protrusion piece. 
         [0007]    An air passage wall forming an air passage extends from the air outlet of the scroll casing, and the protrusion piece and the air passage wall forming the air passage form a gap for receiving the rotation piece of the air passage-switching plate downstream of the air outlet of the scroll casing 
         [0008]    The protrusion piece is provided at the periphery of the whole air outlet of the scroll casing. 
         [0009]    The protrusion piece is protruded from a position higher than the position at which a rotation shaft, passing across the air outlet of the scroll casing, of the air passage-switching plate is located. 
         [0010]    The protrusion piece is protruded from a position lower than the position at which a rotation shaft, passing across the air outlet of the scroll casing, of the air passage-switching plate is located. 
         [0011]    The air leakage-preventing structure comprises protruding structures provided on the air passage-switching plate and on the air passage wall forming the air passage and operable to be engaged with each other. 
         [0012]    The protruding structures comprise protrusions provided on the left and right sides of the air passage-switching plate and of the air passage wall, respectively, and the protrusions on the air passage-switching plate and the protrusions on the air passage wall can be engaged with each other. 
         [0013]    The protrusions of the air passage-switching plate comprise a first air passage-switching plate protrusion and a second air passage-switching plate protrusion provided on side plates of the air passage-switching plate adjoining the air passage wall, respectively, and the protrusions of the air passage wall comprise a first air passage wall protrusion provided at the middle of the air passage wall. 
         [0014]    The protrusions of the air passage-switching plate comprise a third air passage-switching plate protrusion and a fourth air passage-switching plate protrusion provided on a front end portion and a rear end portion of the air passage-switching plate adjoining the air passage wall, respectively, and the protrusions of the air passage wall comprise a second air passage wall protrusion provided at the middle of the air passage wall on the air outlet side. 
         [0015]    A third air passage wall protrusion is provided on a top surface side of the air passage wall, and the lowest point of the third air passage-switching plate protrusion is higher than the lowest point of the third air passage wall protrusion. 
         [0016]    The advantage of the present invention is that a desired air volume can be ensured and a noise can be reduced while guaranteeing a gap required for smooth rotation of the air passage-switching plate. 
         [0017]    Further, the present invention comprises the following structures: 
         [0018]    a control unit for controlling the motor, the heater, and the air passage-switching plate and a sensor for detecting the position of the air passage-switching plate and sending a signal to the control unit are provided. 
         [0019]    The sensor comprises a first body-side sensing element provided on the side face of the air passage wall of the scroll casing and a first air passage switching plate-side sensed element provided outside of a rotation piece of the air passage-switching plate and provided at a position corresponding to the position of the first body-side sensing element. 
         [0020]    The first body-side sensing element is provided to correspond to movable limit points of the first air passage switching plate-side sensed elements moved along with the air passage-switching plate. 
         [0021]    The sensor comprises a second body-side sensing element provided on the top portion of the air passage wall of the scroll casing and a second air passage switching plate-side sensed element provided outside of a rotation piece of the air passage-switching plate and located at a position corresponding to the position of the second body-side sensing element. 
         [0022]    The sensor comprises a third body-side sensing element provided on the bottom portion of the air passage wall of the scroll casing and a third air passage switching plate-side sensed element provided outside of a rotation piece of the air passage-switching plate and located at a position corresponding to the position of the third body-side sensing element. 
         [0023]    The first, second, and third body-side sensing elements are magnetic sensors, and the first, second, and third air passage switching plate-side sensed elements are magnets. 
         [0024]    The magnetic sensors are electromagnets. 
         [0025]    With the above structure, a necessary space required for smooth rotation of the air passage-switching plate and a desired air volume can be ensured and a noise can be reduced. Furthermore, since the position of the air passage-switching plate can be detected by the sensor, in a case where the position of the air passage-switching plate offsets from the normal position due to external factors during the heating operation or the air-exchanging operation, the control unit can be used to correct the position of the air passage-switching plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a schematic view of the prior art; 
           [0027]      FIGS. 2A ,  2 B,  2 C, and  2 D are schematic views of a first embodiment; 
           [0028]      FIGS. 3A and 3B  are schematic views of a second embodiment; 
           [0029]      FIGS. 4A and 4B  are schematic views of a third embodiment; 
           [0030]      FIGS. 5A ,  5 B,  5 C, and  5 D are schematic views of a fourth embodiment; 
           [0031]      FIGS. 6A ,  6 B,  6 C, and  6 D are schematic views of a fifth embodiment; 
           [0032]      FIGS. 7A and 7B  are schematic views of a first embodying example of a sixth embodiment; 
           [0033]      FIG. 8  is a schematic view of a second embodying example of the sixth embodiment; and 
           [0034]      FIG. 9  is a schematic view of a third embodying example of the sixth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    With reference to  FIGS. 2A ,  2 B,  2 C, and  2 D, schematic views of a first embodiment of the present invention are shown. As shown in  FIG. 2A , a heating and ventilation fan  100  for a bathroom comprises an ventilation fan frame  110 , an ventilation fan appearance formed by a hood  110   a  for covering an opening  101  positioned at the lower side of the ventilation fan frame  110 , a scroll casing  131  provided with fan blades  120  and a motor  130 , an air passage-switching plate  150 , a heater  140 , and so on. A side wall of the ventilation fan frame  110  is provided with an air outlet  111 . The hood  110   a  has an air inlet  160  and an indoor air outlet  112 . The scroll casing  131  has an air outlet  132  in a square-tube shape defined by a top wall, side walls, and a bottom wall. The body of the heating and ventilation fan  100  has an air passage from the air outlet  132  to the air outlet  111  provided in the side wall of the ventilation fan frame  100  and an air passage from the air outlet  132  to the indoor air outlet  112  provided at the hood and through which air is blown toward the indoor. 
         [0036]    As shown in  FIGS. 2B and 2D , the air passage-switching plate  150  comprises a rotation shaft  151  passing across the air outlet  132  of the scroll casing. Around the rotation shaft  151 , a main plate  152  configured to switch the air passages and a rotation piece  155  configured to drive the main plate  152  to continuously rotate toward the rotation shaft and having side plates  154  are provided. The air passage-switching plate  150  is provided downstream of the air outlet  132  of the scroll casing  131 . The air outlet  132  is switched to two directions, that is, to the above-mentioned two air passages according to the position of the main plate  152 . At the air outlet  132  of the scroll casing  131 , an air leakage-preventing structure for guiding the air to an inside of the air passage-switching plate  150  is provided. 
         [0037]    The air leakage-preventing structure shown in  FIG. 2B  is a protrusion piece  200  configured to protrude from the periphery of the whole air outlet  132  of the scroll casing  131  to an inside of the air passage-switching plate  150 . The rotation piece  155  of the air passage-switching plate  150  and the outer side of the protrusion piece  200  overlap with each other. 
         [0038]    An air passage wall  170  for forming the air passages extends from the air outlet  132  of the scroll casing  131  to the indoor air outlet  112 , through which the air is blown toward the indoor, and the air outlet  111  of the ventilation fan. There is a certain gap  190  downstream of the air outlet  132  of the scroll casing  131  between the protrusion piece  200  and the air passage wall  170 . The gap  190  receives the rotation piece  155  of the air passage-switching plate  150 . 
         [0039]    The protrusion piece  200  protrudes from the periphery of the whole air outlet  132  toward an inside of the air passage to form a “□” shape. The “□” shape is divided by the rotation shaft  151  of the air passage-switching plate  150  as a boundary into an upper portion and a lower portion, of which the portion close to the top surface  134  of the scroll casing  131  is the upper portion  210  of the protrusion piece  200 , and the portion close to the bottom surface  135  of the scroll casing  131  is the lower portion  220  of the protrusion piece  200 . 
         [0040]    The heating and ventilation fan  100  for a bathroom realizes selection among a heating function, an air-exchanging function and a drying function of the heating and ventilation fan  100  by controlling a rotation position of the air passage-switching plate  150 . 
         [0041]    With reference to  FIG. 2A  again, a sectional view of the heating and ventilation fan  100  for a bathroom in a heating mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131 . The side plates  154  on the two sides of the air passage-switching plate  150  and a front end portion  1521  of the main plate  152  are inserted into the gap  190  between the upper portion  210  of the protrusion piece  200  and the air passage wall  170  from a downstream side of the air outlet  132 . That is to say, the upper portion  210  of the protrusion piece  200  and the air passage wall  170  form a structure for receiving the side plates  154  on the two sides of the air passage-switching plate  150  and the front end portion  1521  of the main plate  152 . When the heating and ventilation fan  100  operates, the air is sucked from the air inlet  160  of the heating and ventilation fan, passes through the fan blades  120 , and are blown out from the air outlet  132  of the scroll casing  131  toward the heater  140 . With such a structure, the air can be prevented from directly flowing out from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0042]    That is to say, the protrusion piece  200  is provided downstream of the scroll casing  131 , and the outer side of the protrusion piece  200  and the air passage-switching plate  150  overlap with each other to form a receiving structure, so that the air blown out of the scroll casing  131  will not leak to outside of the air passage-switching plate  150  but will be guided into the air passage-switching plate  150 . Finally, the air can flow to one of the two air passages from the air outlet  132  to the indoor air outlet  112  through which air is blown toward the indoor. 
         [0043]    With reference to  FIG. 2C , a sectional view of the heating and ventilation fan  100  for a bathroom in an air-exchanging mode is shown. By control of the step motor, the air passage-switching plate  150  is rotated to the bottom surface  135  side of the scroll casing  131 . The side plates  154  on the two sides of the air passage-switching plate  150  and a rear end portion  1522  are inserted into the gap  190  between the lower portion  220  of the protrusion piece  200  in a “□” shape and the air passage wall  170  from the downstream side of the air outlet  132 . That is to say, the lower portion  220  of the protrusion piece  200  and the air passage wall  170  form a structure for receiving the side walls  154  on the two sides of the air passage-switching plate  150  and the rear end portion  1522  of the main plate  152 . When the heating and ventilation fan  100  operates, the air is sucked from the air inlet  160  of the heating and ventilation fan, passes through the fan blades  120 , and are blown out from the air outlet  132  of the scroll casing  131  toward the air outlet  111 . With such a structure, the air can be prevented from directly flowing out from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0044]    That is to say, the protrusion piece  200  is provided downstream of the scroll casing  131 , and the outer side of the protrusion piece  200  and the lower portion  220  of the air passage-switching plate  150  overlap with each other to form a receiving structure, so that the air blown out of the scroll casing  131  will not leak to outside of the air passage-switching plate  150  but will be guided into the air passage-switching plate  150 . Finally, the air can flows to one of the two air passages from the air outlet  132  to the air outlet  111  of the ventilation fan. 
         [0045]    As described above, when the air passage-switching plate  150  is rotated, there is a gap between the air passage wall  170  and the portions, contacting with the air passage wall  170 , of the air passage-switching plate  15 . By providing an air leakage-preventing structure, i.e., the protrusion piece  200  in a “□” shape, between the air outlet  132  of the scroll casing  131  and the air passages to cover the gap between the air passage-switching plate  150  and the air passage wall  170  from an upstream side of the air flow, the air can be prevented from being blown into the gap between the air passage-switching plate  150  and the air passage wall  170 , so that generation of noise and undesired rotation of the air passage-switching plate  150  can be prevented and the desired air volume can be ensured. In this way, performance of products and utilization efficiency of energy can be improved. 
         [0046]      FIGS. 3A and 3B  show sectional views of a second embodiment of the present invention. Downstream of the air outlet  132  of the scroll casing  131 , the air passage wall  170  extends, and a protrusion piece  300  protruded from the air outlet  132  of the scroll casing  131  toward a downstream side and the inner side of the air passage wall  170  form a certain gap  290 . 
         [0047]    The protrusion piece  300  is provided at an upper location than the rotation shaft  151  of the air passage-switching plate  150  for the air outlet  132  of the scroll casing  131 , i.e., forming an inverse “U” shape. 
         [0048]    At a certain rotation position, the air passage-switching plate  150  is received by the gap  290  formed between the outer side of the protrusion piece  300  and the air passage wall  170 . 
         [0049]    With reference to  FIG. 3A  again, a sectional view of the heating and ventilation fan  100  for a bathroom in a heating mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131 . The side plates  154  on the two sides of the air passage-switching plate  150  and a front end portion  1521  of the main plate  152  are inserted from a downstream side in a direction of the air flow into the gap  290  between the protrusion piece  300  in an inverse “U” shape and the air passage wall  170 . The protrusion piece  300  and the air passage wall  170  form a structure for receiving the side plates  154  on the two sides of the air passage-switching plate  150  and the front end portion  1521  of the main plate  152 . When the heating and ventilation fan  100  operates, the air is sucked from the air inlet  160  of the heating and ventilation fan  100 , passes through the fan blades  120 , and is blown out from the air outlet  132  of the scroll casing  131  toward the heater  140 . With such a structure, the air can be prevented from directly flowing out from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0050]    That is to say, the protrusion piece  300  protrudes toward the downstream side of the scroll casing  131 , and the outer side of the protrusion piece  300  and the air passage-switching plate  150  overlap with each other to form a receiving structure, so that the air blown out of the scroll casing  131  will not leak out and will be guided into the air passage-switching plate  150 . Finally, the air can flow to one of the two air passages from the air outlet  132  to the indoor air outlet  112  through which air is blown toward the indoor. In this way, performance of products and utilization efficiency of energy can be improved. 
         [0051]      FIGS. 4A and 4B  show sectional views of a third embodiment of the present invention. Downstream of the air outlet  132  of the scroll casing  131 , the air passage wall  170  extends, and a protrusion piece  400  protruded from the air outlet  132  of the scroll casing  131  toward a downstream side and the inner side of the air passage wall  170  form a certain gap  390 . 
         [0052]    The protrusion piece  400  is provided at a lower location than the rotation shaft  151  of the air passage-switching plate  150  for the air outlet  132  of the scroll casing  131 , i.e., forming a “U” shape. 
         [0053]    At a certain rotation position, the air passage-switching plate  150  is received by the gap  390  formed between the outer side of the protrusion piece  400  and the air passage wall  170 . 
         [0054]    With reference to  FIG. 4A  again, a sectional view of the heating and ventilation fan  100  for a bathroom in an air-exchanging mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the bottom surface  135  side of the scroll casing  131 . The side plates  154  on the two sides of the air passage-switching plate  150  and a rear end portion  1522  are inserted from a downstream side in a direction of the air flow into the gap  390  between the protrusion piece  400  in a “U” shape and the air passage wall  170 . The protrusion piece  400  and the air passage wall  170  form a structure for receiving the side plates  154  on the two sides of the air passage-switching plate  150  and the rear end portion  1522 . When the heating and ventilation fan  100  operates, the air is sucked from the air inlet  160  of the heating and ventilation fan  100 , passes through the fan blades  120 , and is blown out from the air outlet  132  of the scroll casing  131  toward the air outlet  111 . With such a structure, the air can be prevented from directly flowing out from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0055]    That is to say, the protrusion piece  400  is provided to protrude toward the downstream side of the scroll casing  131 , and the outer side of the protrusion piece  400  and the air passage-switching plate  150  overlap with each other to form a receiving structure, so that the air blown out of the scroll casing  131  will not leak out and will be guided into the air passage-switching plate  150 . Finally, the air can flow to one of the two air passages from the air outlet  132  to the air outlet  111  of the ventilation fan. In this way, performance of products and utilization efficiency of energy can be improved. 
         [0056]      FIGS. 5A ,  5 B,  5 C, and  5 D show sectional views of a fourth embodiment of the present invention. As shown in  FIGS. 5A and 5B , the side plates  154  of the air passage-switching plate  150  are provided with a pair of a first air passage-switching plate protrusion  161  and a second air passage-switching plate protrusion  162  on the left side surface  1541  and the right side surface  1542  of the side plates  154  facing the air passage wall  170 , respectively. That is to say, the first air passage-switching plate protrusion  161  and the second air passage-switching plate protrusion  162  look like flanges on end surfaces of the side plates  154  of the air passage-switching plate  150  and radially extend from the rotation shaft  151 . 
         [0057]    The air passage wall  170  is provided with first air passage wall protrusions  171  at the middle positions on the left side and the right side  176  thereof, respectively. That is to say, the first air passage wall protrusions  171  are provided along a line from the rotation shaft  151  of the air passage-switching plate  150  to the lower end of the air outlet  111 . Furthermore, the first air passage wall protrusions  171  are located between the first air passage-switching plate protrusion  161  and the second air passage-switching plate protrusion  162 . 
         [0058]    When the heating and ventilation fan  100  is operated in the air-exchanging mode or in the heating mode, the position of the air passage-switching plate  150  is set to separate the air passage from the air outlet  132  to the air outlet  111  of the ventilation fan provided on the side wall of the ventilation fan frame  110  from the air passage from the air outlet  132  to the indoor air outlet  112  provided at the hood and through which air is blown toward the indoor, by means of protruding structures formed by superposing the first air passage-switching plate protrusion  161  of the air passage-switching plate  150  and the first air passage wall protrusion  171  of the air passage wall  170  on each other and engaging the first air passage-switching plate protrusion  161  with the first air passage wall protrusion  171 , or formed by superposing the second air passage-switching plate protrusion  162  and the first air passage wall protrusion  171  on each other and engaging the second air passage-switching plate protrusion  162  with the first air passage wall protrusion  171 , so that the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0059]    The detailed description is provided as follows. 
         [0060]    With reference to  FIG. 5C , a sectional view of the heating and ventilation fan  100  for a bathroom in a heating mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131 . At this point, the second air passage-switching plate protrusions  162  provided on the left side surface (not shown) and the right side surface  1542  of the air passage-switching plate  150  engage with the first air passage wall protrusions  171  provided on the left side (not shown) and the right side  176  of the air passage wall  170 , respectively, to form a tight engagement state, so that the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0061]    With reference to  FIG. 5D , a sectional view of the heating and ventilation fan  100  for a bathroom in an air-exchanging mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the bottom surface  135  side of the scroll casing  131 . At this point, the first air passage-switching plate protrusions  161  provided on the left side surface (not shown) and the right side surface  1542  of the air passage-switching plate  150  engage with the first air passage wall protrusions  171  provided on the left side and the right side  176  of the air passage wall  170 , respectively, to form a tight engagement state, so that the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0062]      FIGS. 6A ,  6 B,  6 C, and  6 D show sectional views of a fifth embodiment of the present invention. As shown in  FIGS. 6A and 6B , the front end portion  1521  and the rear end portion  1522  of the air passage-switching plate  150  are provided on the outer sides thereof with a third air passage-switching plate protrusion  164  and a fourth air passage-switching plate protrusion  165 , respectively, and the third air passage-switching plate protrusion  164  and the fourth air passage-switching plate protrusion  165  face the air passage wall  170 . A second air passage wall protrusion  186  is provided on the lower end, on the air outlet  111  side, of the middle portion of the air passage wall  170 . Furthermore, the second air passage wall protrusion  186  is located between the third air passage-switching plate protrusion  164  and the fourth air passage-switching plate protrusion  165 . 
         [0063]    When the heating and ventilation fan is operated in the air-exchanging mode or in the heating mode, the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170  by superposing the third air passage-switching plate protrusion  164  of the air passage-switching plate  150  and the second air passage wall protrusion  186  of the air passage wall  170  on each other and engaging the third air passage-switching plate protrusion  164  with the second air passage wall protrusion  186 , or by superposing the fourth air passage-switching plate protrusion  165  and the second air passage wall protrusion  186  on each other and engaging the fourth air passage-switching plate protrusion  165  with the second air passage wall protrusion  186 . 
         [0064]    The detailed description is provided as follows. 
         [0065]    With reference to  FIG. 6C , a sectional view of the heating and ventilation fan  100  for a bathroom in a heating mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131 . At this point, the fourth air passage-switching plate protrusion  165  provided on the rear end portion  1522  of the air passage-switching plate  150  engages with the second air passage wall protrusion  186  of the air passage wall  170  to form a tight engagement state, so that the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0066]    With reference to  FIG. 6D , a sectional view of the heating and ventilation fan  100  for a bathroom in an air-exchanging mode is shown. By control of a step motor, the air passage-switching plate  150  is rotated to the bottom surface  135  side of the scroll casing  131 . At this point, the third air passage-switching plate protrusion  164  provided on the front end portion  1521  of the air passage-switching plate  150  engages with the second air passage wall protrusion  186  of the air passage wall  170  to form a tight engagement state, so that the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 . 
         [0067]    With reference to  FIG. 6C  again, in this embodiment, the air passage wall  170  is provided on the top surface  172  side thereof with a “V”-shaped third air passage wall protrusion  177  protruding downwards, and the lowest point  1640  of the third air passage-switching plate protrusion  164  on the front end portion  1521  of the air passage-switching plate  150  is higher than the lowest point  1770  of the “V”-shaped third air passage wall protrusion  177 . The third air passage wall protrusion  177  has a front side  1772  on the air outlet  132  side and a rear side  1771  downstream of the air outlet  132 , and has a vertex on the lower side thereof. Moreover, the cross section of the third air passage wall protrusion  177  is in a right triangle shape, with the front side  1772  forming hypotenuse and the rear side  1771  forming a side. 
         [0068]    When the heating and ventilation fan  100  is operated in a heating mode, the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131  by control of a step motor. At this point, the third air passage-switching plate protrusion  164  on the front end portion  1521  of the air passage-switching plate  150  engages with the rear side  1771  of the third air passage wall protrusion  177 , and the fourth air passage-switching plate protrusion  165  on the rear end portion  1522  of the air passage-switching plate  150  engages with the second air passage wall protrusion  186  of the air passage wall  170 , so that a tight engagement state is formed. Moreover, as described above, the front side  1772  of the “V”-shaped third air passage wall protrusion  177  forms hypotenuse of the right triangle, that is, the front side  1772  also serves as a guiding plate to direct the air blown out from the air outlet side to the inside of the air passage-switching plate  150 . Therefore, with the “V”-shaped third air passage wall protrusion  177 , not only the air can be prevented from directly flowing toward outside of the air passage-switching plate  150  from the gap between the air passage-switching plate  150  and the air passage wall  170 , but also the resistance to the air flow can be reduced and a performance can be enhanced. In this way, product performance and utilization efficiency of energy can be improved. 
         [0069]    The sixth embodiment of the present invention is based on the above second embodiment. On the basis of the above second embodiment provided with the protrusion piece  300  as the air leakage-preventing structure, the sixth embodiment of the present invention further comprises a control unit for controlling the motor  130 , the heater  140 , and the air passage-switching plate  150 , and a sensor for detecting the position of the air passage-switching plate  150  and sending signals to the above control unit. 
         [0070]    During the heating operation or the air-exchanging operation, the sensor detects the position of the air passage-switching plate  150  and sends the position signals to the control unit. In a case where the position of the air passage-switching plate  150  offsets from the normal position, the control unit controls the step motor according to the position signals to rotate the air passage-switching plate to the normal position. 
         [0071]    Since the position of the air passage-switching plate  150  can be detected, the control unit can correct the position of the air passage-switching plate  150  if the position of the air passage-switching plate  150  offsets from the normal position due to external factors during the heating operation or the air-exchanging operation. 
         [0072]    Therefore, with the air leakage-preventing structure of the present invention, not only the air can be certainly directed into the air passage-switching plate  150 , but also the air leakage caused by offset of the position of the air passage-switching plate  150  can be prevented. 
         [0073]    Further, the sensor comprises a first body-side sensing element provided on the side face of the air passage wall  170  of the scroll casing  131  and a first air passage switching plate-side sensed element provided outside of the side plate  154  of the rotation piece  155  of the air passage-switching plate  150  and provided at a position corresponding to the position of the first body-side sensing element. 
         [0074]      FIGS. 7A and 7B  are schematic views showing the sixth embodiment in a first embodying form. As shown in  FIG. 7A , the first body-side sensing elements  0011 ,  0012  provided on the side face of the air passage wall  170  of the scroll casing  131  are provided to correspond to movable limit points of the first air passage switching plate-side sensed elements  551  moved along with the air passage-switching plate  150 . 
         [0075]    As shown in  FIG. 7A , the side plate  154  of the air passage-switching plate  150  is provided with the first air passage switching plate-side sensed element  551 . In this embodying form, the first air passage switching plate-side sensed element  551  looks like a flange on an upper portion of an end surface of the side plate  154  of the air passage-switching plate  150  and is disposed along a direction radially extending from the rotation shaft  151  (at the same positions as the first air passage-switching plate protrusions in  FIG. 5A ). 
         [0076]    As shown in  FIG. 7A , the first body-side sensing elements  0011 ,  0012  are disposed along a direction radially extending from the rotation shaft  151  and are provided at two positions on the side face or side faces of the left side or right side  176  of the air passage wall  170 . 
         [0077]    The first body-side sensing elements  0011 ,  0012  provided at the two positions on the side face of the air passage wall  170  are provided to correspond to movable limit points of the first air passage switching plate-side sensed element  551  moved along with the air passage-switching plate  150 . 
         [0078]    That is to say, the position of the first body-side sensing element  0011  on one side of the air passage wall  170  corresponds to the position of the first air passage switching plate-side sensed element  551  on the air passage-switching plate side in the heating mode. In other words, when the air passage-switching plate  150  is rotated to the top surface  134  side of the scroll casing  131 , the first air passage switching plate-side sensed element  551  provided on the upper portion of the end surface of the side plate  154  of the air passage-switching plate  150  is rotated along with the air passage-switching plate  150 , and the first body-side sensing element  0011  and the first air passage switching plate-side sensed element  551  in a state of reaching the upper limit point are disposed along a direction radially extending from the rotation shaft  151  and opposite to each other. 
         [0079]    Further, as shown in  FIG. 7B , the position of the first body-side sensing element  0012  on the other side of the air passage wall  170  corresponds to the position of the first air passage switching plate-side sensed element  551  on the air passage-switching plate side in the air-exchanging mode. In other words, when the air passage-switching plate  150  is rotated to the bottom surface  135  side of the scroll casing  131 , the first air passage switching plate-side sensed element  551  provided on the upper portion of the end surface of the side plate  154  of the air passage-switching plate  150  is rotated along with the air passage-switching plate  150 , and the first body-side sensing element  0012  and the first air passage switching plate-side sensed element  551  in a state of reaching the lower limit point are disposed along a direction radially extending from the rotation shaft  151  and opposite to each other. 
         [0080]    As described above, since the first body-side sensing elements  0011 ,  0012  provided at two positions on the side face of the air passage wall  170  are provided to correspond to the upper and lower movable limit points of the air passage switching plate-side sensed element  551 , in the heating mode, when, along with rotation of the side plate  154  of the air passage-switching plate  150 , the first air passage switching plate-side sensed element  551  moves up to the upper movable limit point, the normal position of the air passage-switching plate  150  operated in the heating mode is detected by means of the first body-side sensing element  0011  disposed on one side and corresponding to the upper limit point, 
         [0081]    In the air-exchanging mode, when, along with rotation of the side plate  154  of the air passage-switching plate  150 , the first air passage switching plate-side sensed element  551  moves up to the lower movable limit point, the normal position of the air passage-switching plate  150  operated in the air-exchanging mode is detected by means of the first body-side sensing element  0012  disposed on the other side and corresponding to the lower limit point. 
         [0082]    The control unit sends a signal to the step motor according to this position signal and controls rotation of the air passage-switching plate  150 . 
         [0083]    Further, the first air passage switching plate-side sensed element  551  is disposed along a direction radially extending from the rotation shaft  151  and is provided on separated locations, like a flange on the upper portion of the end surfaces of the side plates  154 . If the first body-side sensing elements  0011 ,  0012  provided at two positions on the side face of the air passage wall  170  are disposed along a direction radially extending from the rotation shaft  15  and are provided on the separated locations, since the first body-side sensing element  0011  and the second body-side sensing element  0012  are distant from each other and will not interfere with each other when detecting the first air passage switching plate-side sensed element  551 , the first air passage switching plate-side sensed element  551  can be stably detected by the first body-side sensing elements  0011 ,  0012 . 
         [0084]    By use of the non-contact axially-sensing operation performed by the first body-side sensing elements  0011 ,  0012  provided at the two positions on the side face of the air passage wall  170  and the first air passage switching plate-side sensed element  551  provided on the side plate  154  of the air passage-switching plate  150 , the position of the air passage-switching plate  150  can be detected. 
         [0085]    Since the normal position of the air passage-switching plate  150  during the drying operation and the air-exchanging operation can be accurately detected, if the position of the air passage-switching plate  150  offsets from the normal position due to the outer factors during the heating operation or the air-exchanging operation, the control unit can correct the position of the air passage-switching plate  150 . 
         [0086]    Therefore, with the air leakage-preventing structure of the present invention, not only the air can be certainly directed into the air passage-switching plate  150 , but also the air leakage caused by offset of the position of the air passage-switching plate  150  can be prevented. 
         [0087]      FIG. 8  is a schematic view showing the sixth embodiment in a second embodying form. As shown in  FIG. 8 , the sensor also may comprise a second body-side sensing element  0021  provided on the top portion of the air passage wall  170  of the scroll casing  131  and a second air passage switching plate-side sensed element  552  provided outside of the front end portion  1521  of the rotation piece  155  of the air passage-switching plate  150  and located at a position corresponding to the position of the second body-side sensing element  0021 . 
         [0088]    By use of the non-contact radially-sensing operation performed by the second body-side sensing element  0021  provided on the inside of the top portion of the air passage wall  170  and the second air passage switching plate-side sensed element  552  provided on the front end portion  1521  of the air passage-switching plate  150 , the normal position of the air passage-switching plate during the heating operation can be detected. 
         [0089]    That is to say, the position of the air passage-switching plate  150  in the heating mode is such arranged that when the air passage-switching plate  150  is rotated to the top  134  side of the scroll casing  131 , the second body-side sensing element  0021  and the second air passage switching plate-side sensed element  552  provided on the front end portion  1521  of the air passage-switching plate  150  are disposed along two opposite directions. 
         [0090]    The second body-side sensing element  0021  and the second air passage switching plate-side sensed element  552  may be provided at any position on the inside surface of the top portion of the air passage wall  170  and at any position on the outside surface of the front end portion  1521  of the air passage-switching plate  150 , respectively. The two elements are disposed along two opposite directions when being in the heating mode. 
         [0091]    The control unit sends a signal to the step motor according to the position signal from the second body-side sensing element  0021  and the second air passage switching plate-side sensed element  552  and controls rotation of the air passage-switching plate. 
         [0092]    In a case where the position of the air passage-switching plate  150  offsets from the normal position due to the outer factors during the heating operation, the control unit can correct the position of the air passage-switching plate  150 . 
         [0093]    Therefore, with the air leakage-preventing structure of the present invention, not only the air can be certainly directed into the air passage-switching plate  150 , but also the air leakage caused by offset of the position of the air passage-switching plate  150  can be effectively prevented. 
         [0094]      FIG. 9  is a schematic view showing the sixth embodiment in a third embodying form. As shown in  FIG. 9 , the sensor may comprise a third body-side sensing element  0031  provided on the bottom portion of the air passage wall  170  of the scroll casing  131  and a third air passage switching plate-side sensed element  553  provided outside of the rotation piece  155  of the air passage-switching plate  150  and located at a position corresponding to the position of the third body-side sensing element  0031 . 
         [0095]    By use of the non-contact radially-sensing operation performed by the third body-side sensing element  0031  provided on the inside of the bottom portion of the air passage wall  170  and the third air passage switching plate-side sensed element  553  provided on the rear end portion  1522  of the air passage-switching plate  150 , the normal position of the air passage-switching plate during the air-exchanging operation can be detected. 
         [0096]    That is to say, the position of the air passage-switching plate  150  in the air-exchanging mode is such arranged that when the air passage-switching plate  150  is rotated to the bottom  135  side of the scroll casing  131 , the third body-side sensing element  0031  and the third air passage switching plate-side sensed element  553  provided on the rear end portion  1522  of the air passage-switching plate  150  are disposed along two opposite directions. 
         [0097]    The third body-side sensing element  0031  and the third air passage switching plate-side sensed element  553  may be provided at any position on the inside surface of the bottom portion of the air passage wall  170  and at any position on the outside surface of the rear end portion  1522  of the air passage-switching plate  150 , respectively. The two elements are disposed along two opposite directions when being in the air-exchanging mode. 
         [0098]    The control unit sends a signal to the step motor according to the position signal from the third body-side sensing element  0031  and the third air passage switching plate-side sensed element  553  and controls rotation of the air passage-switching plate. 
         [0099]    The normal position of the air passage-switching plate  150  during the air-exchanging operation can be accurately detected. 
         [0100]    In a case where the position of the air passage-switching plate  150  offsets from the normal position due to the outer factors during the air-exchanging operation, the control unit can correct the position of the air passage-switching plate  150 . 
         [0101]    Therefore, with the air leakage-preventing structure of the present invention, not only the air can be certainly directed into the air passage-switching plate  150 , but also the air leakage caused by offset of the position of the air passage-switching plate  150  can be effectively prevented. 
         [0102]    Further, the first, second, and third body-side sensing elements may be magnetic sensors, and the first, second, and third air passage switching plate-side sensed elements may be magnets. 
         [0103]    The first body-side sensing element, the second body-side sensing element, and the third body-side sensing element are hole elements in the magnetic sensors. Moreover, the first, second, and third air passage switching plate-side sensed elements are magnets. 
         [0104]    With rotation of the air passage-switching plate  150 , when the first, second, and third air passage switching plate-side sensed elements enter into the detection range of the first, second, and third body-side sensing element, the magnetic sensor can detect a magnetic field generated by the magnet. 
         [0105]    The first, second, and third body-side sensing elements may be magnetic sensors using hole elements. If magnets are used as the first, second, and third air passage switching plate-side sensed elements, the first, second, and third air passage switching plate-side sensed elements are non-contacting compared with a mechanical switch and may facilitate miniaturization of the sensor. 
         [0106]    Further, the above described magnetic sensor (the first, second, and third body-side sensing elements) may be an electromagnet. 
         [0107]    That is, the first, second, and third body-side sensing elements may be electromagnets. 
         [0108]    With rotation of the air passage-switching plate  150 , when the first, second, and third air passage switching plate-side sensed elements enter into the detection range of the first, second, and third body-side sensing elements, the magnetic field of the magnet will change, and the coil of the electromagnet will generate a voltage. 
         [0109]    During the air-exchanging operation or the heating operation, when the control unit controls the step motor to rotate the air passage-switching plate, the first, second, and third body-side sensing elements first detect that the magnets (the first, second, and third air passage switching plate-side sensed elements) enter into the detection range of the electromagnet. Then, the magnetic sensors on the body side for the electromagnet (the first, second, and third body-side sensing elements) are switched on and the air passage-switching plate  150  is rotated to the vicinity of the normal position during the air-exchanging operation or the heating operation. The magnetic sensors on the body side (the first body-side sensing element, the second body-side sensing element) will attract the magnets on the air passage-switching plate  150  side (the first air passage switching plate-side sensed element and the second air passage switching plate-side sensed element). 
         [0110]    The air passage-switching plate  150  can be ensured to be retained in the normal position during the heating operation and the air-exchanging operation. If the position of the air passage-switching plate  150  offsets from the normal position, the position of the air passage-switching plate  150  can be adjusted to the normal position and then be locked. 
         [0111]    Further, the air leakage-preventing structure according to the sixth embodiment is a structure having the protrusion piece  300  of the second embodiment, or an embodying form of any one of the first embodiment, the second embodiment, and the fifth embodiment in combination of the air leakage-preventing structure. With the control unit and the sensor according to the sixth embodiment and the air leakage-preventing structure according to the embodiments, not only the air can be certainly directed into the air passage-switching plate  150 , but also the air leakage caused by position offset of the air passage-switching plate  150  toward the air-exchanging position side due to the self weight thereof during the heating operation can be effectively prevented and the air leakage caused by position offset of the air passage-switching plate  150  due to the air pressure during the air-exchanging operation can be effectively prevented.