Patent Publication Number: US-2021170859-A1

Title: Traveling air introducing mechanism

Description:
TECHNICAL FIELD 
     The present disclosure relates to a traveling air introducing mechanism of vehicles and the like. 
     BACKGROUND ART 
     Conventionally, vehicles such as automobiles are provided with a traveling air introducing mechanism in a front portion thereof to change a state of traveling air introduction. 
     A traveling air introducing mechanism is disclosed in Japanese Patent Laid-Open No. 2015-93666 and includes a frame, plate-shaped flaps that are rotatably provided inside the frame, and a drive part that rotates between a position where the flaps are open and a position where the flaps are closed. Additionally, a cover covering a pivot shaft portion of each flap is provided to prevent a foreign material from being caught by the pivot shaft portion (i.e., prevent a foreign material from being caught in a gap between the pivot shaft and a shaft receiving hole of the frame). The cover is integrally formed with the frame. 
     SUMMARY 
     In the traveling air introducing mechanism disclosed in Japanese Patent Laid-Open No. 2015-93666, the cover covering the pivot shaft portion of the flap is integrally formed with the frame, which makes it difficult to ensure a large effective opening area of the frame. Consequently, it is difficult to achieve both preventing a foreign material from being caught and ensuring an effective opening area of the frame. 
     The present disclosure has been made in view of the above circumstances and aims to provide a traveling air introducing mechanism that can prevent a foreign material from being caught by a pivot shaft portion of a flap while ensuring a large effective opening area of a frame. 
     To solve the above problem, a traveling air introducing mechanism of the present disclosure includes a frame having an opening through which traveling air is introduced; and a flap having a plate shape and provided inside the frame so as to be rotatable between a position where the flap closes the opening and a position where the flap opens the opening. The flap includes a body having a plate shape, a pivot shaft portion formed on at least one end of the body, and a plate portion disposed at the pivot shaft portion so as to intersect a direction in which the pivot shaft portion extends. The frame has an inner surface with an insertion hole into which the pivot shaft portion is rotatably inserted, and the plate portion is positioned between the inner surface of the frame and the body, and is sized to cover the insertion hole from the body side. 
     In this configuration, the flap includes the plate portion disposed at the pivot shaft portion so as to intersect the direction in which the pivot shaft portion extends. Meanwhile, the frame is formed with the insertion hole into which the pivot shaft portion is rotatably inserted. When the flap is attached inside the frame, the plate portion is situated between the inner surface of the frame and the body, which is space that has not conventionally been used (i.e., dead space). This means that the plate portion does not affect an effective opening area of the frame, making it possible to ensure a large effective opening area. Additionally, as the plate portion is sized to cover the insertion hole of the frame, the plate portion can close the entire insertion hole. Hence, this configuration not only ensures a large effective opening area of the frame but also prevents a foreign material from being caught by the pivot shaft portion of the flap. 
     In certain embodiments of the above-described traveling air introducing mechanism, the plate portion includes a protrusion on a face of the plate portion facing the frame. In this configuration, the presence of the protrusion between the plate portion and the frame prevents surface contact between the plate portion and the frame, making it possible to reduce friction resistance of the plate portion during rotation. This helps reduce motive power required to open and close the flap. 
     In certain embodiments of the above traveling air introducing mechanism, the body is shaped to extend radially outward from the pivot shaft portion, the protrusion is a rib extending radially outwardly away from the pivot shaft portion and in the same direction as the body, and the rib is dimensioned such that a length of the rib in a plate width direction of the body is longer than a length of the rib in a thickness direction of the body. In this configuration, when the flap is closed, the rib closes a gap between the plate portion and the frame, preventing a foreign material from being caught. Meanwhile, when the flap is open, the rib falls together with the body of the flap to an open position, making it possible to ensure a larger opening area that is increased by the amount by which the rib is open. 
     In certain embodiments of the above traveling air introducing mechanism, a plurality of the flaps is provided inside the frame, the above traveling air introducing mechanism further includes a drive part disposed within a wall portion constituting the frame, the drive part being configured to rotate and drive the pivot shaft portion of a predetermined flap out of the plurality of the flaps; and a transmission mechanism configured to transmit rotary driving force from the predetermined flap to others of the plurality of the flaps than the predetermined flap and cause the others of the plurality of the flaps to rotate in conjunction with the predetermined flap, and the plate portion is provided only to the pivot shaft portion of the predetermined flap. 
     In this configuration, the plate portion is provided only to the pivot shaft portion of the predetermined flap, which is rotated and driven by the drive part. This helps surely reduce situations where entry of a foreign material into the insertion hole inhibits operation of the drive part. On the other hand, the other flaps, to which the drive part is not provided, are not provided with the plate portion, and this helps ensure a large effective opening area of the frame even in the configuration having the multiple flaps. 
     In certain embodiments, the above traveling air introducing mechanism further includes a drive part configured to rotate and drive the pivot shaft portion of the flap, the drive part having a function of learning positioning of a predetermined open position and a predetermined closed position for the body as initial settings in a state where the pivot shaft portion is coupled to the drive part, the pivot shaft portion is provided on a periphery of the pivot shaft portion with a protrusion for use in learning positioning of the body, and the insertion hole is sized to be able to accommodate the protrusion. 
     In this configuration, the plate portion can close the entire insertion hole even when the insertion hole is sized to be able to accommodate the protrusion provided on the periphery of the pivot shaft portion for use in learning positioning of the body, and this allows the plate portion to prevent a foreign material from entering the insertion hole with such a large diameter. 
     The traveling air introducing mechanism of the present disclosure can prevent a foreign material from being caught by the pivot shaft portion of the flap while ensuring a large effective opening area of the frame. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a configuration of major parts in a front portion of a vehicle having a traveling air introducing mechanism according to an embodiment of the present disclosure. 
         FIG. 2  illustrates the traveling air introducing mechanism in  FIG. 1  as viewed from a front face side. 
         FIG. 3  illustrates the traveling air introducing mechanism in  FIG. 1  as viewed from a right front side. 
         FIG. 4  illustrates the traveling air introducing mechanism in  FIG. 1  as viewed from a right rear side. 
         FIG. 5  is an enlarged view of a link mechanism when the traveling air introducing mechanism in  FIG. 1  is viewed from a left rear side. 
         FIG. 6  is an enlarged perspective view of major parts of a predetermined drive-side flap out of multiple flaps in  FIG. 5  and that is directly driven by a drive part. 
         FIG. 7  is an enlarged perspective view of a center pillar portion of a frame in  FIG. 5  and its surroundings. 
         FIG. 8  is an explanatory sectional view of an internal structure of the center pillar portion of the frame in  FIG. 5 . 
         FIG. 9A  shows the state where the predetermined flap in  FIG. 5  is closed and a rib is closed, as viewed from the front face side, and  FIG. 9B  shows the state where the predetermined flap in  FIG. 5  is closed and the rib is closed, as viewed in a direction in which a pivot shaft portion extends. 
         FIG. 10  shows the state where the rib of the predetermined flap in  FIG. 5  is open, as viewed from the front face side. 
     
    
    
     DETAILED DESCRIPTION 
     Below, a detailed description will be given of an embodiment of the present disclosure with reference to the drawings. 
       FIG. 1  illustrates a structure in which a traveling air introducing mechanism  1  according to an embodiment of the present disclosure is installed in a front portion of a vehicle such as an automobile. In this configuration of the front portion of the vehicle, the traveling air introducing mechanism  1  is coupled to a front portion of a radiator  2  by bolt fastening or the like. The radiator  2  is fixed, by welding or the like, to front ends of side frames  3  and lower frames  4  extending in a front-rear direction of the vehicle. 
     As shown in  FIGS. 1 to 5 , the traveling air introducing mechanism  1  of the present embodiment includes; a frame  5  that has multiple openings  5   a  through which traveling air is introduced; multiple plate-shaped flaps  6  that are provided inside the frame  5  so as to be rotatable between a position where the flaps  6  close the opening  5   a  and a position where the flaps  6  open the opening  5   a;  a drive part  7  as a mechanism to open and close these multiple plate-shaped flaps  6 ; and a link mechanism  8  as a transmission mechanism.  FIG. 4  illustrates support bodies  9  that support the flaps  6  at the open position. Here, the phrase “close the opening  5   a  by the multiple plate-shaped flaps  6 ” as used in the present disclosure means changing the opening so as to reduce an opening area of the opening  5   a  and does not necessarily require fully closing the opening  5   a.  Also, the phrase “open the opening  5   a  by the multiple plate-shaped flaps  6 ” as used in the present disclosure means changing the opening so as to increase an opening area of the opening  5   a  and does not necessarily require fully opening the opening  5   a.    
     The drive part  7  includes an electric motor of any of various kinds, such as a brushless motor. The drive part  7  is accommodated inside a center pillar portion  5   b  (described later) of the frame  5 . Also, the drive part  7  has a function of learning positioning of a predetermined open position and a predetermined closed position for a body  6   a  of a predetermined flap out of the multiple flaps  6 , i.e., a drive-side flap  61  (see  FIG. 3 ), as initial settings in the state where a pivot shaft portion  12  of the drive-side flap  61  is coupled to the drive part  7 . 
     The traveling air introducing mechanism  1  is capable of taking in a large amount of air through the openings  5   a  of the frame  5  by opening the flaps  6  (pivoting the flaps  6  toward the horizontal direction) when operating conditions of an engine of the automobile require a large amount of air. Meanwhile, the traveling air introducing mechanism  1  is capable of reducing resistance of the traveling air by closing the flaps  6  (pivoting the flaps  6  until they become vertical) and thus closing the openings  5   a  when a large amount of air is not required. 
     As shown in  FIGS. 2 and 3 , to form the multiple openings  5   a,  the frame  5  includes a center pillar portion  5   b  extending in an up-down direction, a pair of side pillar portions  5   c  disposed spaced apart from the center pillar portion  5   b  on left and right sides thereof, and multiple beams extending in the horizontal direction to connect ends of the center pillar portion  5   b  and the side pillar portions  5   c.  Each of the multiple plate-shaped flaps  6  can open and close the corresponding opening  5   a  of the frame  5  as the flap  6  pivots around a shaft extending in the horizontal direction (the pivot shaft portion  12  and a support shaft  6   c  described later) while being supported at its ends by the center pillar portion  5   b  and the corresponding side pillar portion  5   c.    
     The frame  5  is formed on its inner surface (side face of the center pillar portion  5   b  in the present embodiment) with an insertion hole  15  and multiple support holes  17  arranged in the up-down direction as holes into which shaft portions (the pivot shaft portion  12  and a support shaft  6   c  described later) of the respective flaps  6  are rotatably inserted, as shown in  FIG. 7 . The insertion hole  15  in the center pillar portion  5   b  is disposed so as to communicate with an engagement recess  7   a  of the above-described drive part  7 . 
     The insertion hole  15  is sized to be able to accommodate positioning protrusions  13  (described later; see  FIGS. 6 and 8 ) of the drive-side flap  61 . 
     The insertion hole  15  is provided therein with a pair of positioning protrusions  16  for regulating a rotary position of the positioning protrusions  13 . The positioning protrusions  16  are capable of positioning the drive-side flap  61  by contacting the positioning protrusions  13  when the drive-side flap  61  is at the open position or the closed position. 
     The side pillar portions  5   c  horizontally spaced apart from the center pillar portion  5   b  of the frame  5  are also formed with support holes for supporting the shaft portions of the respective flaps  6 , though not shown in the figures. 
     As shown in  FIG. 5 , the multiple plate-shaped flaps  6  have in common that they each include a body  6   a  having a plate shape and a link coupling portion  6   b  coupled with a link pin  22  (described later). Of the multiple plate-shaped flaps  6 , the drive-side flap  61  connected to the drive part  7  opens and closes by directly receiving rotary driving force from the drive part  7 . The other flaps  6  open and close in conjunction with the drive-side flap  61  via a link mechanism  8  (described later). 
     As shown in  FIG. 6 , the drive-side flap  61  includes a pivot shaft portion  12  formed at least on one end of the body  6   a  (an end closer to the drive part  7  in the present embodiment) and a plate portion  11 . The body  6   a  extends radially outward from the pivot shaft portion  12  and also in the axial direction of the pivot shaft portion  12 . 
     The pivot shaft portion  12  includes multiple projections on its periphery and is capable of engaging with the engagement recess  7   a  of the drive part  7  through the insertion hole  15  of the center pillar portion  5   b  of the frame  5  shown in  FIGS. 7 and 8 . The pivot shaft portion  12  is rotatable by receiving rotary driving force from the drive part  7  in the state where the pivot shaft portion  12  is engaged with the engagement recess  7   a.    
     The pivot shaft portion  12  is provided only to the drive-side flap  61 , as shown in  FIGS. 6 and 8 . The other flaps  6  are each provided with a support shaft  6   c  instead of the pivot shaft portion  12 , as shown in  FIGS. 5 and 8 . The support shaft  6   c  is inserted into the corresponding support hole  17  in the center pillar portion  5   b  of the frame  5  and is rotatably supported by the inner face of the support hole  17 . 
     The plate portion  11  is a disk-like portion and disposed at the pivot shaft portion  12  so as to intersect (perpendicularly intersect in the present embodiment) the direction in which the pivot shaft portion  12  extends. It should be noted that the plate portion  11  does not necessarily perpendicularly intersect the direction in which the pivot shaft portion  12  extends, and may intersect the pivot shaft portion  12  at any angle that does not impede the rotation of the plate portion  11 . 
     The plate portion  11  is integrally formed with the body  6   a  such that the plate portion  11  is situated continuously with the body  6   a  in the direction in which the pivot shaft portion  12  extends. Thus, the presence of the plate portion  11  eliminates the need for widening a gap between the body  6   a  and the frame  5 . 
     As shown in  FIG. 8 , a diameter D 2  of the plate portion  11  is set larger than an inner diameter D 1  of the insertion hole  15  in the center pillar portion  5   b  of the frame  5 . In other words, the plate portion  11  has a size that allows the plate portion  11  to cover the insertion hole  15  from the body  6   a  side. When the flap  6  is attached inside the frame  5 , the plate portion  11  is positioned between the inner surface of the frame  5  and the body  6   a  and disposed at a position to close the insertion hole  15 . Here, to achieve the “size that allows the plate portion  11  to cover the insertion hole  15  from the body  6   a  side” as referred to in the present disclosure, the plate portion  11  may have a larger area than that of the insertion hole  15  when the plate portion  11  is viewed along the axial direction of the pivot shaft portion  12 . 
     In the present disclosure, the plate portion  11  includes ribs  14  as protrusions on its face facing the center pillar portion  5   b  of the frame  5 , as shown in  FIGS. 6, 9A -B, and  10 , to reduce a load during rotation that would come from contact between the plate portion  11  and the side face of the center pillar portion  5   b  of the frame  5  as the plate portion  11  rotates along with opening and closing of the flap  6 . 
     Each rib  14  extends radially outwardly away from the pivot shaft portion  12  and in the same direction as the body  6   a.  In the present embodiment, the pair of ribs  14  extend from respective sides of the pivot shaft portion  12  in opposite directions radially outwardly away from each other. 
     As shown in  FIG. 10 , the rib  14  is dimensioned such that its length in a plate width direction of the body  6   a  is longer than its length in a thickness direction of the body  6   a.    
     Provided on respective side edges of the pivot shaft portion  12  shown in  FIG. 6  is a pair of positioning protrusions  13  that is used for learning positioning of the body  6   a  of the drive-side flap  61 . Inside the insertion hole  15  (see  FIG. 7 ) of the frame  5 , the pair of positioning protrusions  13  moves in a circumferential direction of the pivot shaft portion  12  as the drive-side flap  61  pivots between an open position and a closed position. The drive-side flap  61  is rotatable within a restricted range between a predetermined open position (0 degree relative to the horizontal plane) and a predetermined closed position (90 degrees) as the positioning protrusions  13  of the drive-side flap  61  abut on the respective positioning protrusions  16  (see  FIG. 7 ) protruding inside the insertion hole  15 . Thus, by manual rotation of the drive-side flap  61  from 0 to 90 degrees with the pivot shaft portion  12  of the flap  6  engaged with the engagement recess  7   a  (see  FIG. 7 ) of the drive part  7 , the drive part  7  can learn positioning of the drive-side flap  61  relative to the drive part  7  (i.e., initial settings for the closed position and the open position of the drive-side flap  61 ). 
     As shown in  FIGS. 4, 5, and 8 , the link mechanism  8  is configured to link-couple the multiple flaps  6  other than the drive-side flap  61  to the drive-side flap  61 . This allows the link mechanism  8  to function as a transmission mechanism that transmits rotary driving force from the drive-side flap  61  to the other multiple flaps  6  than the drive-side flap  61  and causes these other flaps  6  to rotate in conjunction with the drive-side flap  61 . Specifically, the link mechanism  8  is composed of a link plate  21  extending in the up-down direction along the center pillar portion  5   b  of the frame  5 , multiple link pins  22  protruding from respective sides of the link plate  21 , and link coupling portions  6   b  of the respective flaps  6 . 
     The link plate  21  is disposed on a rear face side of the center pillar portion  5   b  of the frame  5  (downstream side in a flow direction of the traveling air). The link plate  21  is disposed such that it can move in the up-down direction along the center pillar portion  5   b.  The link pins  22  of the number equal to the number of the flaps  6  are provided on respective side edges of the link plate  21  so as to protrude to the left and right. 
     The link coupling portion  6   b  of each flap  6  is a plate-shaped portion extending in a direction perpendicular to the pivot shaft portion  12 . The link coupling portion  6   b  is formed at its distal end with a link hole  6   b   1  (see  FIG. 6 ). Insertion of the link pins  22  into the respective link holes  6   b   1  results in the state where the bodies  6   a  of the flaps  6  other than the drive-side flap  61  are link-coupled to the body  6   a  of the drive-side flap  61  via the link coupling portions  6   b,  the link pins  22 , the link plate  21 , and the link coupling portion  6   b  of the drive-side flap  61 . Hence, opening and closing of the body  6   a  of the drive-side flap  61  enables the bodies  6   a  of the other multiple flaps  6  to also open and close in conjunction therewith via the link mechanism  8 . 
     As described above, the traveling air introducing mechanism  1  of the present embodiment includes the frame  5  having the openings  5   a  through which traveling air is introduced and the multiple plate-shaped flaps  6  provided inside the frame  5  so as to be rotatable between the position where the flaps  6  close the opening  5   a  and the position where the flaps  6  open the opening  5   a.  The predetermined drive-side flap  61  out of the multiple flaps  6  includes the body  6   a  having a plate shape, the pivot shaft portion  12  formed at least one end of the body  6   a,  and the plate portion  11  disposed at the pivot shaft portion  12  so as to intersect (perpendicularly intersect in the present embodiment) the direction in which the pivot shaft portion  12  extends. The frame  5  is formed on its inner surface with the insertion hole  15  into which the pivot shaft portion  12  is rotatably inserted. The plate portion  11  is positioned between the inner surface of the frame  5  and the body  6   a  and sized to cover the insertion hole  15  from the body  6   a  side. 
     In this configuration, the drive-side flap  61  includes the plate portion  11  disposed at the pivot shaft portion  12  so as to intersect the direction in which the pivot shaft portion  12  extends. Meanwhile, the frame  5  is formed with the insertion hole  15  into which the pivot shaft portion  12  is rotatably inserted. When the drive-side flap  61  is attached inside the frame  5 , the plate portion  11  is situated between the inner surface of the frame  5  and the body  6   a,  which is space that has not conventionally been used (i.e., dead space). This means that the plate portion  11  does not affect an effective opening area of the frame  5 , making it possible to ensure a large effective opening area. Additionally, as the plate portion  11  is sized to cover the insertion hole  15  of the frame  5 , the plate portion  11  can close the entire insertion hole  15 . Hence, this configuration not only ensures a large effective opening area of the frame  5  but also prevents a foreign material from being caught by the pivot shaft portion  12  of the drive-side flap  61  (i.e., prevents a foreign material from being caught in a gap between the pivot shaft portion  12  and the insertion hole  15  (or the engagement recess  7   a  of the drive part  7 )). 
     In the traveling air introducing mechanism  1  of the present embodiment, the plate portion  11  includes the ribs  14  as protrusions on its face facing the frame  5 . In this configuration, the presence of the ribs  14  between the plate portion  11  and the frame  5  prevents surface contact between the plate portion  11  and the frame  5 , making it possible to reduce friction resistance of the plate portion  11  during rotation. This helps reduce motive power required to open and close the drive-side flap  61 . 
     In the traveling air introducing mechanism  1  of the present embodiment, the body  6   a  is shaped to extend radially outward from the pivot shaft portion  12 . The ribs  14  extending radially outwardly away from the pivot shaft portion  12  and in the same direction as the body  6   a  are used as protrusions. The rib  14  is dimensioned such that its length in the plate width direction of the body  6   a  is longer than its length in the thickness direction of the body  6   a.    
     In this configuration, when the drive-side flap  61  is closed as shown in  FIGS. 9A-B , the body  6   a  and the ribs  14  are positioned so as to extend in the vertical direction, closing the opening  5   a.  At this time, the ribs  14  close a gap A (see  FIG. 10 ) between the plate portion  11  and the frame  5 , preventing a foreign material from being caught. Meanwhile, when the drive-side flap  61  is open as shown in  FIG. 10 , the ribs  14  falls to a horizontal position together with the body  6   a  of the drive-side flap  61  and come to the open position, making it possible to ensure a larger opening area that is increased by the amount equal to the gap A (see  FIG. 10 ) opened by the ribs  14 . 
     Additionally, in the present embodiment, the length of the rib  14  in the thickness direction of the body  6   a  (i.e., the length of the rib  14  in the up-down direction in  FIG. 10 ) is smaller than the thickness of the body  6   a  (i.e., the length of the body  10  in the up-down direction in  FIG. 10 ). This helps ensure a still larger opening area in the gap A created by opening of the flap  6 , as shown in  FIG. 10 . 
     The traveling air introducing mechanism  1  of the present embodiment further includes the drive part  7  and the link mechanism  8  in the configuration in which the multiple flaps  6  are provided inside the frame  5 . The drive part  7  is configured to rotate the pivot shaft portion  12  of the drive-side flap  61  out of the multiple flaps  6  and is disposed inside the wall portion (the center pillar portion  5   b ) constituting the frame  5 . The link mechanism  8  as a transmission mechanism is configured to transmit rotary driving force of the drive-side flap  61  to the other multiple flaps  6  than the drive-side flap  61  and cause these other flaps  6  to rotate in conjunction with the drive-side flap  61 . The plate portion  11  is provided only to the pivot shaft portion  12  of the drive-side flap  61 . 
     In this configuration, the plate portion  11  is provided only to the pivot shaft portion  12  of the drive-side flap  61 , which is rotated and driven by the drive part  7 . This helps surely reduce situations where entry of a foreign material into the insertion hole  15  inhibits operation of the drive part  7 . On the other hand, the other flaps  6 , to which the drive part  7  is not provided, are not provided with the plate portion  11 , and this helps ensure a large effective opening area of the frame  5  even in the configuration having the multiple flaps  6 . 
     While the present embodiment depicts the link mechanism as an example of the transmission mechanism to transmit rotary driving force of the drive-side flap  61  to the other flaps  6 , the present disclosure is not limited to this. Besides the link mechanism, the transmission mechanism may be one composed of gears or wires. 
     In the traveling air introducing mechanism  1  of the present embodiment, the drive part  7  has a function of learning positioning of a predetermined open position and a predetermined closed position for the body  6   a  as initial settings in the state where the pivot shaft portion  12  of the drive-side flap  61  is coupled to the drive part  7 . The pivot shaft portion  12  is provided on its periphery with the positioning protrusions  13  for use in learning positioning of the body  6   a.  The insertion hole  15  is sized to be able to accommodate the positioning protrusions  13 . 
     In this configuration, the plate portion  11  can close the entire insertion hole  15  even when the insertion hole  15  is sized to be able to accommodate the positioning protrusions  13  provided on the periphery of the pivot shaft portion  12  for use in learning positioning of the body  6   a,  and this allows the plate portion  11  to prevent a foreign material from entering the insertion hole  15  with such a large diameter. 
     While the above embodiment depicts the rib  14  extending in the direction away from the pivot shaft portion  12  as an example of the protrusion provided to the plate portion  11 , the present disclosure is not limited to this. The protrusion provided to the plate portion  11  is only required to be formed at a position where the protrusion can contact the inner surface of the frame  5 . 
     Hence, as a modification of the present disclosure, the protrusion may be a rib  14  in the form of a dot-like protrusion disposed slightly outside of an outer periphery of the insertion hole  15  or may be a round rib  14  extending in the circumferential direction of the pivot shaft portion  12  at slightly outside of the outer periphery of the insertion hole  15 , besides the above rib  14  extending in the direction away from the pivot shaft portion  12 . In such cases too, the presence of the protrusion between the plate portion  11  and the frame  5  prevents surface contact between the plate portion  11  and the frame  5 , making it possible to reduce friction resistance of the plate portion  11  during rotation and thus reduce motive power required to open and close the drive-side flap  61 . 
     While the above embodiment depicts a configuration having multiple flaps, the present disclosure is not limited to this. The present disclosure is applicable to a configuration having a single flap.