Patent Publication Number: US-11047121-B2

Title: Toilet space deodorizing device and sanitary washing device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-154841, filed on Aug. 21, 2018 and Japanese Patent Application No. 2018-154842, filed on Aug. 21, 2018; the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present invention relates to a toilet space deodorizing device and a sanitary washing device. 
     BACKGROUND 
     Various toilet space deodorizing devices that deodorize a toilet space are known. It is known that the offensive-odor components included in the air of the toilet space include highly water-soluble components; and a toilet space deodorizing device has been proposed in which the offensive-odor components included in the air are dissolved in water by causing the air to contact the water. 
     For example, there is a device that includes a water spraying device that is provided in a warm-water washing toilet seat and sprays water into suctioned air (e.g., Japanese Patent Application Publication No. 2017-223030). The water spraying device includes a water storage part storing water and a vibrator disposed at the bottom part of the water storage part; or the water spraying device is a nozzle spraying water in a mist-like form. 
     Another device of this type of deodorizing device introduces suctioned air into stored water stored inside a deodorizing chamber (e.g., Japanese Utility Model Application Publication No. Hei 4-117074). 
     SUMMARY 
     In an embodiment such as that of Japanese Patent Application Publication No. 2017-223030, a vibrator or a nozzle is necessary; and the deodorizing device may become large and complex due to the vibrator itself, the nozzle itself, the mechanism for operating the vibrator or the nozzle, etc. In an embodiment in which the air is introduced to water such as Japanese Utility Model Application Publication No. Hei 4-117074, the deodorizing device may become large because a large suction device normally is necessary to provide a relatively strong suction force. The larger size and the higher complexity described above can be avoided by not including such a configuration having the larger size or the higher complexity, but the deodorizing performance may degrade. 
     A toilet space deodorizing device according to an aspect of the invention includes an intake port part forming an intake port; an exhaust port part forming an exhaust port; a fan device intaking air through the intake port; a water collecting part provided inside a deodorizing air channel, the deodorizing air channel linking the intake port and the exhaust port and allowing the air to flow, the water collecting part being configured to collect water inside the deodorizing air channel; a water supply part supplying water to the water collecting part; a drainage part forming a drainage port draining water from the water collecting part; a negative pressure generation device forming a negative pressure in the water collecting part; and a controller controlling a driving of the negative pressure generation device. The controller drives the negative pressure generation device to generate a negative pressure. And the water supplied from the water supply part is collected in the water collecting part due to air flowing into the water collecting part and pressing on the water supplied from the water supply part by the negative pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exterior perspective view of a toilet device according to one embodiment; 
         FIG. 2  is a plan view of a toilet space deodorizing device according to one embodiment; 
         FIG. 3  is a perspective view of a water deodorizing unit of the toilet space deodorizing device according to one embodiment; 
         FIG. 4  is a perspective view of a state in which a cover is removed from the water deodorizing unit of  FIG. 3 ; 
         FIG. 5  is a cross-sectional perspective view of the water deodorizing unit of the toilet space deodorizing device according to one embodiment; 
         FIG. 6  is a cross-sectional view of a water collection operation in the toilet space deodorizing device according to one embodiment; and 
         FIG. 7  is a cross-sectional view of a drainage operation of the toilet space deodorizing device according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     One of the embodiments of the invention will now be described with reference to the accompanying drawings. For easier understanding of the description, the same components in the drawings are marked with the same reference numerals when possible; and duplicate descriptions are omitted. 
       FIG. 1  is an exterior perspective view of a toilet device  1  according to one embodiment. 
     As shown in  FIG. 1 , the toilet device  1  that is mounted in a toilet space includes a sit-down flush toilet (hereinbelow, called simply the toilet)  100 , and a sanitary washing device  200  mounted on the toilet  100 . The toilet  100  includes a bowl part  101  open upward in which water stores. By a user operating an operation part (not illustrated), the bowl part  101  is washed by washing water and drains the washing water through a drainage pipe (not illustrated). The sanitary washing device  200  includes a private part washing functional part that washes a private part such as the bottom or the like of the user sitting on the toilet  100  with a toilet seat (not illustrated) interposed, etc. The sanitary washing device  200  also includes a toilet space deodorizing device (hereinbelow, called simply the deodorizing device)  10 . 
       FIG. 2  is a plan view of the deodorizing device  10  according to the embodiment, and illustrates a state in which a cover  201  of the sanitary washing device  200  of  FIG. 1  is removed. The nozzle and the like that are included in the private part washing functional part are not illustrated in  FIG. 2 . 
     As shown in  FIG. 2 , the deodorizing device  10  includes a water deodorizing unit  20  and a controller  30 . 
       FIG. 3  is a perspective view of the water deodorizing unit  20 . 
       FIG. 4  is a perspective view of a state in which a cover  22  is removed from the water deodorizing unit  20  of  FIG. 3 . 
       FIG. 5  is a cross-sectional perspective view of the water deodorizing unit  20 . 
     As shown in  FIG. 3  to  FIG. 5 , the water deodorizing unit  20  includes a case  21  and the cover  22 . A water deodorizing part  40 , a fan device  60 , and an oxidation catalyst  70  are provided in the space between the case  21  and the cover  22 . 
     Air is caused to flow through the space between the case  21  and the cover  22  by driving the fan device  60 . An intake port part is provided at one end part of an air channel (a deodorizing air channel)  80  through which the air flows; and an exhaust port part is provided at the other end part of the deodorizing air channel  80 . The intake port part forms an intake port  23 ; and the exhaust port part forms an exhaust port  24 . The deodorizing air channel  80  links the intake port  23  and the exhaust port  24 . The region of the deodorizing air channel  80  other than the intake port  23  and the exhaust port  24  is covered with the case  21  and the cover  22 . The fan device  60  is a sirocco fan; for example, an axial fan or a cross-flow fan may be used. 
     The intake port  23  is positioned furthest upstream in the deodorizing air channel  80 ; and the exhaust port  24  is positioned furthest downstream in the deodorizing air channel  80 . The fan device  60  is disposed downstream of the water deodorizing part  40  in the deodorizing air channel  80 . The oxidation catalyst  70  is disposed downstream of the fan device  60  in the deodorizing air channel  80 . The water deodorizing part  40 , the fan device  60 , and the oxidation catalyst  70  are arranged in order from the intake port  23  side between the intake port  23  and the exhaust port  24 . 
     The water deodorizing part  40  includes a water collecting part  50 . The water collecting part  50  includes a first space  51  and a second space  52 . The first space  51  and the second space  52  communicate with each other; and the second space  52  is positioned further toward the intake port  23  than is the first space  51 . The second space  52  is provided between the intake port  23  and the first space  51 . 
     The intake port  23  is open toward the bowl part  101  in the state in which the water deodorizing unit  20  is mounted on the toilet  100  shown in  FIG. 2 . 
     Air is intaken through the intake port  23  into the first space  51  via the second space  52  by driving the fan device  60 . The height of the downstream end of the second space  52  in the deodorizing air channel  80  is lower than the height of the upstream end of the first space  51  in the deodorizing air channel  80 . Here, “height” refers to the height along the vertical direction between the inner surface of the case  21  and the inner surface of the cover  22 . The second space  52  functions as a restricting part having a reduced air channel cross-sectional area compared to the first space  51 . The first space  51  is an enlarged part having an enlarged air channel cross-sectional area compared to the second space  52 . 
     As shown in  FIG. 4 , a water supply part  45  is provided in a part of the case  21  forming the sidewall of the water collecting part  50 . For example, the water supply part  45  is provided at a position of the water collecting part  50  proximal to the downstream-most end of the deodorizing air channel  80 . For example, water is supplied from a water supply source (a service water line) to the water supply part  45  and inflows toward the water collecting part  50  from a water supply port (not illustrated) formed in the water supply part  45 ; and the water collecting part  50  can collect the water. In the invention, the position where the water supply part  45  is provided is not limited to a position of the water collecting part  50  proximal to the downstream-most end of the deodorizing air channel  80 ; and it is sufficient for the water supply to the water collecting part  50  to be possible from the position. 
     The water that collected in the water collecting part  50  is drained through a drainage part. The drainage part forms a drainage port  25 ; in the embodiment, the intake port  23  also is used as the drainage port  25 ; the drainage port  25  is open toward the bowl part  101 ; and the water that is collected in the water collecting part  50  is drained into the bowl part  101  through the drainage port  25 . The bottom surface of the water collecting part  50  forms a downward incline toward the drainage port  25 . 
     A water-receiving barrier  41  is provided in the water collecting part  50  at the most end of the fan device  60  side. The water-receiving barrier  41  protrudes from the bottom surface of the water collecting part  50  into the deodorizing air channel  80  of the first space  51 . In the deodorizing air channel  80 , the upper end of the water-receiving barrier  41  is positioned upstream of the lower end of the water-receiving barrier  41 . The upper end of the water-receiving barrier  41  is positioned higher than the upper surface of the second space  52 ; and the distance (the height) between the upper end of the water-receiving barrier  41  and the bottom surface of the water collecting part  50  is higher than the height of the second space  52 . A space is formed between the cover  22  and the upper end of the water-receiving barrier  41  and permits the flow of air from the first space  51  toward the fan device  60 . 
     An operation of the deodorizing device  10  according to the embodiment will now be described. 
       FIG. 6  is a cross-sectional view of the water collection operation in the deodorizing device  10 . 
       FIG. 7  is a cross-sectional view of the drainage operation of the deodorizing device  10 . 
     When seat contact of the user on the toilet  100  is detected, the fan device  60  is driven by a control of the controller  30 ; and water is supplied from the water supply part  45  to the water collecting part  50  by a control of the controller  30 . For example, the driving of the fan device  60  and the water supply from the water supply part  45  are started simultaneously. Or, there may be a time lag between the water supply timing and the timing of driving the fan device  60 . The controller  30  controls the start and the stop of the driving of the fan device  60  and the start and the stop of the supply of the water from the water supply part  45 . The seat contact of the user on the toilet  100  is detected by a sensor provided in the toilet space (e.g. in the toilet seat and/or the toilet  100 ). It is sufficient for the sensor to be able to detect the presence or absence of the user. For example, the sensor may detect the user&#39;s departure, the user&#39;s approach. The sensor is an infrared sensor; for example, a microwave sensor or a pressure sensor may be used. The driving of the fan device  60  and the water supply from the water supply part  45  may be started by the operation of the operation unit (e.g. a remote controller or a touch panel) by the user. The fan device  60  that is driven by the controller  30  intakes air through the intake port  23  into the deodorizing air channel  80 . In  FIG. 6 , the flow of the air inside the deodorizing air channel  80  is illustrated by black thick arrows. The air that is intaken through the intake port  23  flows through the second space  52  and the first space  51  of the water collecting part  50  and is suctioned into the fan device  60 ; and the air that is discharged from the fan device  60  passes through the oxidation catalyst  70  and is exhausted from the exhaust port  24 . 
     Air that is at atmospheric pressure is suctioned through the intake port  23  into the deodorizing air channel  80 . In other words, the fan device  60  functions as a negative pressure generation device generating a negative pressure in the deodorizing air channel  80 . The bottom surface of the water collecting part  50  forms a downward incline toward the drainage port  25  (also used as the intake port  23 ); therefore, the water that is supplied to the water collecting part  50  by the controller  30  can flow along the bottom surface of the water collecting part  50  toward the drainage port  25 . A structure that might dam the flow of the water is not provided at the bottom surface of the water collecting part  50 . Therefore, the water that is supplied to the water collecting part  50  by the controller  30  can be drained as-is through the drainage port  25 . 
     However, in the state in which the fan device  60  is driven, the water that is supplied from the water supply part  45  can be collected in the water collecting part  50  because the negative pressure generated in the water collecting part  50  pushes, onto the water, air flowing in the reverse direction of the drainage direction of the water. 
     After a prescribed period of time, the supply of the water from the water supply part  45  is stopped by the controller  30 . For example, the magnitude of the negative pressure generated in the water collecting part  50  can be controlled by the rotational speed control of the fan device  60 . According to the magnitude of the negative pressure, the total amount of the water supplied from the water supply part  45  may be held in the water collecting part  50 , or some of the water supplied from the water supply part  45  may be drained through the drainage port  25  and a remaining prescribed amount of the water may be held in the water collecting part  50 . It is desirable for the total amount of the water supplied from the water supply part  45  to be held in the water collecting part  50 ; and because this configuration can hold more water in the water collecting part  50 , the deodorizing performance can be ensured further. On the other hand, because the amount of the water held in the water collecting part  50  can be controlled according to the magnitude of the negative pressure, for example, by setting the water supplied from the water supply part  45  to be not less than the amount to be collected, the water amount to be collected can be held in the water collecting part  50  more reliably while draining some of the supplied water through the drainage port  25  even when the amount of the water supplied from the water supply part  45  fluctuates. 
     The air that includes offensive-odor components and is intaken through the intake port  23  flows along the surface of water W collected in the water collecting part  50 ; and the surface of the water W collected in the water collecting part  50  forms a part of the deodorizing air channel  80 . Then, the highly water-soluble offensive-odor components such as ammonia, trimethylamine, etc., that cause a urine odor are deodorized by being dissolved in the water W collected in the water collecting part  50 . 
     The offensive-odor components such as hydrogen sulfide, methylmercaptan, etc., that cause a feces odor, are not dissolved in the water W, and are in the air flowing further downstream through the deodorizing air channel  80  are deodorized by the oxidation catalyst  70 . The oxidation catalyst  70  oxidizes and decomposes hydrogen sulfide and methylmercaptan. 
     Thus, according to the embodiment, ammonia and trimethylamine which are highly water-soluble can be deodorized by the water deodorizing part  40 ; and hydrogen sulfide and methylmercaptan which do not dissolve as easily in water as do ammonia and trimethylamine can be deodorized by the oxidation catalyst  70 . The deodorized air is exhausted from the exhaust port  24 . 
     Also, fine debris such as dust, paper bits, etc., suctioned through the intake port  23  with the air can be trapped by the water W collected in the water collecting part  50 ; and the performance decrease of the oxidation catalyst  70  due to the fine debris flowing into the oxidation catalyst  70  can be suppressed. The fine debris that undesirably reaches the fan device  60  also can be suppressed because the fan device  60  is disposed downstream of the water collecting part  50  in the deodorizing air channel. Normally, a mesh filter for trapping fine debris is provided at the intake port of the deodorizing device; however, in the embodiment, the fine debris can be trapped by the water collecting part  50 ; and a mesh filter may not be provided. Therefore, in the embodiment, the trouble of performing maintenance of the mesh filter can be eliminated. 
     By using a simple configuration in which one fan device  60  is used and the water deodorizing part  40  and the oxidation catalyst  70  are disposed inside one deodorizing air channel  80 , both offensive-odor components having high water solubility and offensive-odor components having lower water solubility but higher oxidative decomposition capability can be deodorized effectively. Both the deodorizing performance and the avoidance of a larger size and a higher complexity can be realized. 
     The water collecting part  50  includes the second space  52  that functions as a restricting part, is lower than the first space  51 , and has a small air channel cross-sectional area. The air that is intaken through the intake port  23  is accelerated by the second space  52 . Thereby, the surface of the water W of the water collecting part  50  forming a part of the deodorizing air channel  80  undulates easily (waves form easily); and the contact surface area between the air and the water surface can be increased. The increase of the contact surface area between the air and the water surface increases the dissolution efficiency in water of the offensive-odor components having high water solubility in air. Therefore, for example, the degradation of the deodorizing performance can be avoided while avoiding the larger size and the higher complexity of a configuration that uses a water spraying device to spray water or guides water to stored water. 
     When the air is accelerated by the second space  52  (the restricting part), the pressure of the air pushing the water W increases; and the effect of holding the water W in the water collecting part  50  also increases. 
     An aromatic often is placed in the toilet space. Generally, the oxidation catalyst may generate an offensive odor when the alcohol component (e.g., ethanol or methanol) included in the aromatic or the like adheres. Although the alcohol component can be dissolved in the water in the water deodorizing part  40 , water in which the alcohol component has dissolved may splash downstream; and the water in which the alcohol component has dissolved may contact the oxidation catalyst  70 . Particularly when the water deodorizing unit  20  is provided in the sanitary washing device  200 , downsizing is desirable; therefore, the distance between the water deodorizing part  40  and the oxidation catalyst  70  is likely to be short. 
     In the embodiment, the water-receiving barrier  41  is provided as a splash suppression device suppressing the splashing toward the oxidation catalyst  70  of the water W collected in the water collecting part  50 . According to such an embodiment, the water in which the alcohol component has dissolved can avoid contacting the oxidation catalyst  70  because the adhesion to the oxidation catalyst  70  of the alcohol component dissolved in the water W of the water collecting part  50  is avoided effectively; and the water-receiving barrier  41  suppresses the splashing toward the oxidation catalyst  70  of the water in which the alcohol component has dissolved. 
     According to the embodiment, alcohol dissolution is possible merely by storing the water W in the water collecting part  50 ; therefore, the configuration is simple compared to, for example, mist spraying from a nozzle, etc. The water-receiving barrier  41  also has a simple configuration; therefore, according to the embodiment, the offensive odor generation by the oxidation catalyst  70  caused by alcohol components can be avoided while avoiding a larger size and a higher complexity. 
     The first space  51  of the water collecting part  50  is higher than the second space  52  and has a larger volume, and is provided as an enlarged part having an enlarged air channel cross-sectional area. Such a first space  51  also can function as the splash suppression device recited above. In other words, by enlarging the air channel cross-sectional area at the first space  51 , the air velocity of the air can be reduced; and the splashing of the water W downstream can be suppressed thereby. The splashing of the water toward the fan device  60  also can be suppressed; and the malfunction and the performance decrease of the fan device  60  can be avoided. 
     An example is shown in  FIG. 6  in which the water W collects in a region extending from the water-receiving barrier  41  through the first space  51  to the second space  52 . It is sufficient for the water W to collect in at least a partial region of the first space  51 ; and it is unnecessary for the water W to collect in the second space  52 . If the water W collects in the second space  52  as well, the contact surface area between the air and the water surface can be increased, which increases the dissolution efficiency in water of the offensive-odor components having high water solubility in air. 
     The water W that is pushed by the air is dammed by the water-receiving barrier  41  and impeded from receding downstream in the deodorizing air channel  80 . In this state, a water surface Wa that has a wall-like shape forms easily and opposes the air inflowing through the intake port  23  and flowing along the upper surface of the second space  52 . The wall-like shape water surface Wa forms a boundary around which the water surface upstream of the water surface Wa in the deodorizing air channel  80  is formed at a position lower than the water surface downstream in the deodorizing air channel  80 . A level difference forms between the water surface upstream of the water surface Wa and the water surface downstream of the water surface Wa. Because the air contacts the wall-like shape water surface Wa in addition to the upper surface of the water W, the dissolution efficiency in water of the highly water-soluble offensive-odor components can be increased; and the fine debris is trapped by the water W even more easily. 
     Because the water-receiving barrier  41  extends higher than the upper surface of the second space  52  at the intake port  23  side, the height inside the first space  51  of the water W dammed by the water-receiving barrier  41  easily becomes higher than the height inside the second space  52  of the water W dammed by the water-receiving barrier  41 . This easily forms the level difference of the water surface at the vicinity of the boundary between the first space  51  and the second space  52 ; and the wall-like shape water surface Wa forms easily. 
     The user rises from the toilet  100 ; and the controller  30  stops the driving of the fan device  60  based on the user rising from the toilet  100 . When the fan device  60  is stopped, the water collecting part  50  returns to atmospheric pressure; and the force that holds the water W in the collected state is released. Then, because the bottom surface of the water collecting part  50  has the downward incline toward the drainage port  25 , the water W that collected in the water collecting part  50  is drained into the bowl part  101  of the toilet  100  (shown in  FIGS. 1 and 2 ) through the drainage port  25  as shown in  FIG. 7 . The sensor that is provided in the toilet space detects the user rising from the toilet  100 . The driving of the fan device  60  may be stopped by the operation of the operation unit (e.g. a remote controller or a touch panel) by the user. The driving of the fan device  60  may be automatically stopped after a predetermined period of the starting of the driving of the fan device  60  by the operation of the operation unit. 
     If a movable member, e.g., a solenoid valve is used as the drainage mechanism, the water may not be drained due to a valve-opening failure caused by sticking of the solenoid valve; but in the embodiment, water drainage is possible merely by stopping the formation of the negative pressure by the fan device  60  without providing such a drainage mechanism. A simple configuration can drain the water from the water collecting part  50  and reduce the water remaining in the water collecting part  50 ; and the formation of the biofilm caused by the remaining water can be suppressed. The fine debris that is trapped by the water W collected in the water collecting part  50 , etc., also is drained with the water W. 
     The collection and the drainage of the water can be realized by using, as the device forming the negative pressure, the fan device that is originally necessary in the deodorizing device to intake and exhaust the air as a minimum electrical component; it is unnecessary to provide separately a pump or the like for forming the negative pressure; and a lower cost and downsizing are possible. 
     Because the water collecting part  50  bottom surface has a downward incline, the water is drained easily from the water collecting part  50 ; the water that remains in the water collecting part  50  can be reduced further; and the effect of suppressing the formation of the biofilm can be increased. 
     According to the embodiment described above, by the formation of the negative pressure accompanying the flow of the air, the water W collects in the water collecting part  50 ; the surface of the water W forms a part of the deodorizing air channel  80 ; and the air that includes offensive-odor components flows along the surface of the water W. Such a configuration can cause a higher amount of air to contact the water surface compared to, for example, a configuration in which the water does not collect due to the formation of a negative pressure but the air is caused to contact the surface of water prestored in a tank; and the dissolution efficiency of the offensive-odor components in water can be increased. Accordingly, the embodiment realizes both the deodorizing performance and the avoidance of a larger size and a higher complexity. 
     For example, the oxidation catalyst  70  has a cartridge form, is attachable and detachable, and is replaceable in the sanitary washing device  200 . As shown in  FIG. 2 , the user can replace the oxidation catalyst  70  easily because the oxidation catalyst  70  is disposed at the outer edge part side of a casing  202  of the sanitary washing device  200 . 
     For example, the oxidation catalyst  70  has a honeycomb structure and has the effect of suppressing the operation sound of the fan device  60 . The arrangement relationship between the oxidation catalyst  70  and the fan device  60  described above reduces the noise when deodorizing compared to a configuration in which the fan device  60  is disposed further toward the outer edge part of the casing  202  than is the oxidation catalyst  70 . 
     Although an example is described in the embodiments described above in which the deodorizing device  10  is provided in the sanitary washing device  200 , it is sufficient for the deodorizing device according to the invention to be provided in a toilet space including at least one of a flush toilet or a urinal; for example, the deodorizing device  10  may be provided in a urinal. 
     Although an example is described in the embodiments described above in which a fan device is employed as the negative pressure generation device, the invention is not limited to forming the negative pressure by the air suction of the fan device; and it is sufficient for the negative pressure generation device to be able to form a negative pressure in the water collecting part. For example, a pump may be employed as the negative pressure generation device; and a negative pressure may be formed by the air suction of the pump. 
     Although an example is described in the embodiments described above in which the intake port also is used as the drainage port, the invention is not limited to a configuration in which the intake port  23  also is used as the drainage port  25 ; and the intake port  23  and the drainage port  25  may be provided as separate components. 
     Although an example is described in the embodiments described above in which the drainage port is open toward the bowl part, the drainage port  25  may not be open toward the bowl part  101  in the invention. For example, a configuration may be used in which the water of the water collecting part  50  is drained through a drainage port opening inside the water collected in the bowl part  101 ; or a configuration may be used in which the water of the water collecting part  50  is drained through a drainage port into a drainage pipe in which the drainage water of the toilet device  1  flows. 
     Among toilet space deodorizing devices, downsizing of a deodorizing device provided in the sanitary washing device  200  is particularly desirable; and a higher complexity and a larger size of the deodorizing device can be suppressed more for the configuration in which the drainage port  25  is open toward the bowl part  101  than for a configuration in which the water is drained inside the water collected in the bowl part  101  or a configuration in which the water is drained into a drainage pipe. 
     By setting the distance (the length in the vertical direction) between the upper surface and the lower surface of the second space  52  to be less than the distance (the length in the vertical direction) between the upper surface and the lower surface of the first space  51 , the air channel cross-sectional area of the second space  52  can be less than the air channel cross-sectional area of the first space  51 ; and the second space  52  can function as the restricting part described above. 
     In the example shown in  FIG. 6 , the length in the vertical direction of the second space  52  is set to be less than the length in the vertical direction of the first space  51  by providing a level difference between the upper surface of the second space  52  and the upper surface of the first space  51 . 
     Or, the length in the vertical direction of the second space  52  can be set to be less than the length in the vertical direction of the first space  51  by providing a level difference between the lower surface of the second space  52  and the lower surface of the first space  51 . 
     Or, the air channel cross-sectional area of the second space  52  can be set to be less than the air channel cross-sectional area of the first space  51  by setting the inter-side surface distance (the length in the horizontal direction) of the second space  52  to be smaller than the inter-side surface distance (the length in the horizontal direction) of the first space  51 . 
     Hereinabove, the embodiments of the invention are described with reference to specific examples. However, the invention is not limited to such specific examples; and various modifications based on the technical spirit of the invention are possible.