Patent Publication Number: US-2023143230-A1

Title: Ventilation door device for refrigerator

Description:
This application claims priority to Chinese patent application No. 202010128529.7, filed on Feb. 28, 2020, and Chinese patent application No. 202010128218.0, filed on Feb. 28, 2020. The contents of the above-mentioned Chinese patent applications are incorporated herein as portions of this application. 
     TECHNICAL FIELD 
     The present disclosure relates to a ventilation door device for a refrigerator and a refrigerator having said ventilation door device. 
     BACKGROUND 
     Refrigerator is a common household appliance having main functions including storage and preservation. A refrigerator may have more than one storage compartments to store different kinds of food or other items. Generally, different storage compartments need to be maintained at different temperatures. To this end, a refrigerator is provided with cold air passages leading to each of storage compartments, and the cold air passes through the cold air passages to adjust the temperatures of different storage compartments. Each cold air passage can be provided with a ventilation door device to change the amount of cold air passing through by changing the opening and closing of each cold air passage, thereby realizing dynamic adjustment of the temperature of each storage compartments. However, current ventilation door devices have several problems. 
     First, the existing refrigerator ventilation door solution is unstable, and there is a situation in which the refrigerator issues an order to open or close the ventilation door, but the ventilation door could not be actually opened or closed. This will result in the inability to continuously and dynamically adjust the cold air flowing into each storage compartment as needed, and the food therein could not get appropriate temperature, and the freshness period will be greatly shortened. 
     Second, in the existing ventilation door solutions of refrigerators, most use a multi-stage gear transmission mechanism. When the ventilation door is in the closed position, the teeth of adjacent gears abut against each other. In order to eliminate the tolerances of gears, the pulse number for closing the door of the stepper motor is usually designed greater than the pulse number for opening the door, so that multiple gears will be stalled (in other words, rotor-locked) when the door is closed, and the accuracy of the door closing can be improved. For the traditional multi-stage gear transmission mechanism, the stalling time is too long, and the tooth-breaking phenomenon caused by insufficient gear strength might occur. Moreover, big noise is generated during the stalling process. Traditional solutions are difficult to solve both the problems of noise and tooth-breaking. 
     SUMMARY OF THE INVENTION 
     Regarding to the above-mentioned problems, this disclosure provides a new type of ventilation door device and a refrigerator having said ventilation door device, which solves the above problems due to the following technical features and brings other technical effects. 
     In a first aspect of the present disclosure, a ventilation door device for a refrigerator is provided. The ventilation door device includes: a frame having an end plate provided with an opening portion, and having a blocking plate assembly rotatably mounted to the end plate, the blocking plate assembly is able to rotate between a closed position where the opening portion is completely closed and an open position where the opening portion is completely open; a housing engaging the frame and forming a driving chamber between the housing and the frame; and a driving module at least partially being held in the driving chamber and driving the blocking plate assembly to rotate. 
     In one embodiment, the frame has a housing engagement portion located at the side edge of the end plate and extending substantially perpendicular to the end plate, and the housing is connected to the housing engagement portion of the frame. 
     In one embodiment, the blocking plate assembly includes a blocking plate installed on the end plate and an elastic component disposed on the blocking plate, when the blocking plate assembly is in the closed position, the elastic component abuts the frame and elastically deforms to seal the opening portion. 
     In one embodiment, the end plate of the frame has a sealing portion arranged around the opening portion and protruding from the end plate, and when the blocking plate assembly is in the closed position, the elastic component abuts the sealing portion of the frame. 
     In one embodiment, a reinforcing rib is provided on the side of the blocking plate facing away from the elastic component. 
     In one embodiment, the blocking plate assembly includes a first shaft portion and a second shaft portion provided at both ends of the blocking plate, and the blocking plate assembly is mounted to the frame through the first shaft portion and the second shaft portion, a clamping structure is provided inside the first shaft portion, and the driving module drives the blocking plate assembly to rotate through the clamping structure. 
     In one embodiment, the ventilation door device further includes a heater installed to the end plate and at least partially surrounding the opening portion. 
     In an embodiment, the frame further includes an edge plate extending from an outer edge of the end plate, and the edge plate surrounds the heater. 
     In one embodiment, the shape of the heater at least partially matches the shape of the end plate. 
     In one embodiment, the ventilation door device is configured to generate an electrical signal when the blocking plate assembly is in the closed position or the open position, and when the blocking plate assembly is in a middle position between the closed position and the open position, no electrical signal is generated or another electrical signal is generated. The ventilation door device is configured to activate the heater if the disappearance of said electrical signal or the change from said electrical signal to said another electrical signal is not detected within a predetermined time after receiving the command to rotate the blocking plate assembly. 
     In an embodiment, the ventilation door device further includes a micro switch, and a transmission gear in the driving module includes two contacts extending radially from said transmission gear, wherein the micro switch and the transmission gear are designed as follows: when the blocking plate assembly is in the closed position, one of the two contacts triggers a static contact of the micro switch, so that the micro switch generates the electrical signal; when the blocking plate assembly is in the open position, the other of the two contacts triggers the static contact of the micro switch, so that the micro switch generates the electricity signal; and when the blocking plate assembly is in the middle position between the closed position and the open position, neither of the two contacts triggers the static contact of the micro switch, so that the micro switch does not generate the electrical signal or generates another electrical signal. 
     In one embodiment, the predetermined time is 3 seconds to 8 seconds. 
     In one embodiment, the ventilation door device further has a circuit board, and the circuit board has: a first coupling portion for coupling with the micro switch; a second coupling portion for coupling with the driving module; and a third coupling part for coupling the heater. 
     In one embodiment, the driving module includes: a stepper motor; a teeth missing gear, which is connected to the stepper motor; a sector gear, which meshes with the teeth missing gear; an output shaft, which is connected to the sector gear and is connected to the blocking plate; and the stepper motor can drive the blocking plate to rotate via the teeth missing gear, the sector gear and the output shaft. 
     In one embodiment, the sector gear includes a sector gear teeth portion, a cylindrical portion and a sector gear output portion which are sequentially arranged along an axial direction; and the teeth missing gear includes a shaft portion and a circular gear teeth portion, the circular gear teeth portion includes a circular gear section with gear teeth and an arc section without gear teeth, and the gear teeth on the gear teeth section mesh with the gear teeth on the sector gear teeth portion. The output portion of the sector gear can be in the form of a rotating shaft and is used to connect to a clamping structure in the form of a slot at the first shaft portion of the blocking plate; alternatively, the output portion of the sector gear can also be in the form of a slot and is used to connect to a clamping structure in the form of a protrusion at the first shaft portion. 
     In one embodiment, the frame has a bottom plate portion extending perpendicular to the plane where the opening portion is located, and the bottom plate portion includes: a first cylindrical portion for rotatably supporting the cylindrical portion of the sector gear inside the first cylindrical portion; and a second cylindrical portion for rotatably supporting the shaft portion of the teeth missing gear inside the second cylinder portion. 
     In one embodiment, inside the first cylinder portion, the bottom plate portion has a through hole allowing the sector gear output portion passing through as the output shaft to extend to the blocking plate. 
     In one embodiment, the second cylindrical portion has an arc groove, and the arc groove is recessed away from the end surface of the second cylindrical portion, and the center of the arc groove coincides with the axis of the cylinder part, and the arc groove extends between two limiting surfaces; and the teeth missing gear has an arc-shaped protrusion that protrudes from the side surface of the circular gear teeth portion of the teeth missing gear and is configured to be able to extend into the arc groove, and move along the arc groove with the rotation of the teeth missing gear, any one of the two limiting surfaces is used to abut the arc-shaped protrusion to limit the rotation of the teeth missing gear. 
     In one embodiment, the ventilation door device further includes a micro switch with a static contact; the teeth missing gear further includes a contact portion having two contacts; when the blocking plate is in the open position, one of the two contacts engages the static contact of the micro switch, and the micro switch sends an electrical signal; when the blocking plate is in the closed position, the other of the two contacts engages the static contact of the micro switch, and the micro switch sends the electrical signal; when the blocking plate is in a middle position between the closed position and the open position, the contact portion does not engage the static contact of the micro switch, and the micro switch does not send the electrical signal or sends a different signal from said electrical signal. 
     In one embodiment, the contact portion is arranged on the side of the gear teeth portion of the teeth missing gear away from the shaft portion, and the contact portion has two arms extending radially outwardly, the end of each arm forms a contact, and each contact is located farther from the center of the teeth missing gear than the remaining portions of the contact portion. 
     In one embodiment, the outer periphery of the teeth missing gear has an arc section next to its teeth section; when the blocking plate is in the closed position, the outer surface of the arc section of the teeth missing gear abuts the sector gear, thereby preventing the sector gear from rotating in the direction of opening the blocking plate. 
     In one embodiment, the outer periphery of the sector gear has a concave locking arc next to its teeth section, and the concave locking arc is recessed toward the center of the sector gear; when the blocking plate is in the closed position, a part of the arc section enters the interior of the concave locking arc, preventing the concave locking arc from rotating relative to the arc section, thereby the teeth missing gear prevents the sector gear from rotating in the direction of opening the blocking plate. 
     In one embodiment, when the blocking plate is in the closed position, the distance between any point on the concave locking arc and the center of the teeth missing gear is greater than the radius of the arc section, so as to not block the arc section from rotating relative to the concave locking arc, thereby the teeth missing gear can idly rotate by an idling angle in the direction of closing the ventilation door. 
     In one embodiment, the frame has a second cylindrical portion that rotatably supports the teeth missing gear, and the second cylindrical portion has an arc groove, and the arc groove extends between two limiting surfaces; the teeth missing gear has an arc-shaped protrusion configured to be able to extend the interior of the arc groove and move along the arc groove with the rotation of the teeth missing gear, until it abuts against any one of the two limiting surfaces; and the angle between the two limiting surfaces is a first angle, and the angle across which the teeth missing gear rotates when the blocking plate is driven to rotate from the open position to the closed position is a second angle, and the first angle is equal to the sum of the second angle and the idling angle. 
     In one embodiment, the radius of the arc section of the teeth missing gear is R 1 , the distance from the arc end point of the concave locking arc of the sector gear to the center of the sector gear is L 2 , the distance between centers of the sector gear and the teeth missing gear is L, and wherein R 1 +L 2 −L is the amount of interference L 1 , and L 1  is greater than zero. 
     In one embodiment, the range of the interference amount L 1  is: 0.05 mm≤L 1 ≤1 mm 
     The driving module includes: a stepper motor; a teeth missing gear connected to the stepper motor, and the teeth missing gear includes an arc section without gear teeth; a sector gear meshing with the teeth missing gear; and an output shaft connected to the sector gear and connected to the blocking plate; wherein the stepper motor can drive the blocking plate to rotate via the teeth missing gear, the sector gear and the output shaft; and wherein when the blocking plate is in the closed position, a portion of the arc section of the teeth missing gear is located between two teeth of the sector gear, and the teeth missing gear prevents the sector gear from rotating in the direction of opening the shutter. 
     In one embodiment, the sector gear has a first tooth that enters meshing last when the blocking plate is closed and a second tooth next to the first tooth, the end surface of the first tooth facing the output shaft is farther away from the end surface of the second tooth facing the output shaft; the teeth missing gear further has an arc-shaped groove, the radius of the outer surface of the arc-shaped groove is smaller than the radius of the outer surface of the arc section, the arc-shaped groove is located on the side of the arc section away from the output shaft, the outer surface of the arc section and the outer surface of the arc-shaped groove are connected by an inner end surface; when the blocking plate is in the closed position, the arc-shaped groove accommodates the first tooth inside, and the outer surface of the arc section is partially located between the first tooth and the second tooth and abuts against the second tooth, the second tooth is prevented from rotating relative to the arc section, so that the teeth missing gear prevents the sector gear from rotating in the direction of opening the blocking plate. 
     In one embodiment, when the blocking plate is in the closed position, the distance between any point on the second tooth and the center of the teeth missing gear is greater than the radius of the arc section, so as to not prevent the arc section from rotating relative to the second tooth, so that the teeth missing gear can idly rotate by an idling angle in the direction of closing the ventilation door. 
     In one embodiment, the sector gear further has a third tooth next to the second tooth, the third tooth and the second tooth are connected by a connecting portion at the side adjacent to the output shaft. 
     In one embodiment, the end faces of the third tooth and the second tooth on the side adjacent to the output shaft are closer to the output shaft than the end faces of the other teeth on the sector gear on the side adjacent to the output shaft. 
     In one embodiment, the radius of at least part of the addendum circle of the second tooth of the sector gear is smaller than the radius of the addendum circles of the remaining teeth. 
     In one embodiment, a part of the second tooth away from the output shaft is cut away. 
     In one embodiment, the part of the second tooth outside the inner end surface of the arc section is completely cut off. 
     In one embodiment, both ends of the arc section of the teeth missing gear are immediately connected to the gear teeth section, and the radius of the arc section of the teeth missing gear is larger than that of the addendum circle of the gear teeth section. 
     In one embodiment, the outer peripheral surface of the arc section of the teeth missing gear and the tooth face of the first tooth of the gear teeth section that enters meshing firstly when the door is opened are connected by an arc-shaped guide surface. 
     In a second aspect of the present disclosure, a refrigerator is provided, which includes: one or more storage compartments; one or more cold air passages leading to the one or more storage compartments; and one or more ventilation door devices as mentioned above, wherein the opening portion of each ventilation door device is arranged in the corresponding cold air passage, so that the cold air delivery amount in the corresponding cold air passage is controlled by the opening and closing of the opening portion of the corresponding ventilation door device. 
     Hereinafter, the best embodiments for implementing the present disclosure will be described in more detail with reference to the accompanying drawings, so that the features and advantages of the present disclosure can be easily understood. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In order to explain the technical solutions of the embodiments of the present disclosure more clearly, the accompanying drawings of the embodiments of the present disclosure will be briefly introduced below. The drawings are only used to show some embodiments of the present disclosure, rather than limiting all the embodiments of the present disclosure to them. 
         FIG.  1    shows a perspective view of a ventilation door device according to an exemplary embodiment, in which the blocking plate assembly is in an open position; 
         FIG.  2    shows a perspective view of the ventilation door device according to an exemplary embodiment, wherein the blocking plate assembly is in a closed position; 
         FIG.  3    shows the frame of the ventilation door device, in which the blocking plate assembly of the frame is removed; 
         FIG.  4 A  shows the first embodiment of the blocking plate of the ventilation door device according to the exemplary embodiment from two perspectives; 
         FIG.  4 B  shows the second embodiment of the blocking plate of the ventilation door device according to the exemplary embodiment from two perspectives; 
         FIG.  5    shows a three-dimensional view of the ventilation door device according to an exemplary embodiment, in which the frame and the housing are in a separated state; 
         FIG.  6    shows the drive chamber of the ventilation door device according to an exemplary embodiment; 
         FIG.  7    shows a circuit board of the ventilation door device according to an exemplary embodiment; 
         FIG.  8    shows an explanatory diagram of a driving module and a frame according to an exemplary embodiment; 
         FIG.  9    shows an explanatory diagram of a frame according to an exemplary embodiment; 
         FIGS.  10  and  11 A  show explanatory diagrams of different angles of a sector gear according to an exemplary embodiment; 
         FIG.  11 B  shows an explanatory view of a sector gear according to another exemplary embodiment; 
         FIGS.  12  and  13    show explanatory diagrams of different angles of a teeth missing gear according to an exemplary embodiment; 
         FIG.  14    shows a plan view of a sector gear and a teeth missing gear when the ventilation door is closed according to an exemplary embodiment; 
         FIG.  15    shows an enlarged view of the circular area in  FIG.  14   ; 
         FIGS.  16  and  17    show a perspective view and a side view of the ventilation door device when it is closed; 
         FIGS.  18  and  19    show a perspective view and a side view of the ventilation door device when it is opened; 
         FIG.  20    shows an explanatory view of a sector gear according to another exemplary embodiment; 
         FIG.  21    shows an explanatory view of a teeth missing gear according to another exemplary embodiment; 
         FIGS.  22  and  23    show a plan view and an explanatory view of the sector gear and the teeth missing gear when the ventilation door device is closed according to another exemplary embodiment; 
         FIG.  24    shows an explanatory diagram of a sector gear according to still another exemplary embodiment; and 
         FIG.  25    shows a partial schematic diagram of a sector gear and a teeth missing gear according to still another exemplary embodiment. 
     
    
    
     List of Reference Numbers  10  ventilation door device 
       100  frame 
       101  opening portion 
       102  sealing portion 
       103  end plate 
       104  edge plate 
       105  wiring portion 
       106  bottom plate potion 
       107  housing engagement portion 
       200  housing 
       300  blocking plate assembly 
       301  blocking plate 
       302  elastic component 
       303  flat plate portion 
       305  first shaft 
       306  second shaft 
       307  reinforcing rib 
       400  driving module 
       402  transmission assembly 
       403  stepper motor 
       404  motor output shaft 
       405 ,  405 ′ teeth missing gear 
       406 ,  406  sector gear 
       407  output shaft 
       408  circuit board 
       409  micro switch 
       410  first cylindrical portion 
       411  second cylindrical portion 
       412  first limiting surface 
       413  second limiting surface 
       414  arc groove 
       415  supporting portion 
       416  slot portion 
       417  through hole 
       421  first coupling portion 
       422  second coupling portion 
       423  third coupling portion 
       424  motor limiting portion 
       425  tinned hole 
     H heater 
     X rotation axis 
       431  shaft portion 
       432 ,  432 ′ sector gear teeth portion 
       433  cylindrical portion 
       434 ,  434 ′ sector gear output potion 
       435  flat portion 
       436  gear teeth section 
       437  concave locking arc 
       441  shaft portion 
       442  gear teeth section 
       443 ,  443 ′ contact portion 
       444 ,  444 ′ gear teeth section 
       445 ,  445 ′ arc section 
       446  contact 
       447  shaft hole 
       448 ,  448 ′ arc-shaped protrusion 
       451  first tooth of sector gear 
       452  second tooth of sector gear 
       453  third tooth of the sector gear 
       454  connection portion 
       455  arc shaped groove 
       456  inner surface 
       457  first tooth of teeth missing gear 
       458  arc shaped guiding surface 
     DETAILED DESCRIPTION 
     In order to make the objectives, technical solutions and advantages of the technical solutions of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the specific embodiments of the present disclosure. 
     The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. 
     Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the protection scope of the present disclosure. 
     1. Overall Structure 
     An exemplary embodiment of the ventilation door device  10  of the present disclosure will be described with reference to  FIGS.  1  to  6   .  FIGS.  1  and  2    show three-dimensional views of a ventilation door device  10  according to an exemplary embodiment, in which the blocking plate assembly  300  are in an open position and a closed position, respectively.  FIG.  3    shows a frame  100  of the ventilation door device  10 , in which the blocking door assembly  300  is removed from the frame  100 .  FIGS.  4 A and  4 B  show the blocking plate  301  of the ventilation door device  10  according to an exemplary embodiment from two perspectives.  FIG.  5    shows a perspective view of the ventilation door device  10  according to an exemplary embodiment, in which the frame  100  and the housing  200  are separated.  FIG.  6    illustrates the driving chamber of the ventilation door device  10  according to an exemplary embodiment. 
     The ventilation door device  10  mainly includes a frame  100 , a housing  200  and a driving module. The housing  200  is joined to the frame  100  and a driving chamber is formed between the housing  200  and the frame  100 . The driving module is at least partially held in the driving chamber, as shown in  FIG.  6   . 
     The frame  100  has an end plate  103  provided with an opening portion  101 . The opening portion  101  may be an opening and closing port of a cold air passage that delivers cold air to the storage compartment of the refrigerator to maintain its temperature. In other words, the opening portion  101  is provided in the corresponding cold air passage of the refrigerator, and the cold air delivery amount in the corresponding cold air passage can be adjusted by controlling the opening and closing of the opening portion  101 . 
     The frame  100  also has a blocking plate assembly  300  rotatably mounted to the end plate  103 , and the blocking plate assembly  300  can be rotated between a closed position where it completely closes the opening portion  101  and an open position where it completely opens the opening portion  101 .  FIG.  1    shows a state where the blocking plate assembly  300  is in a fully open position, where the blocking plate assembly  300  is substantially orthogonal to the end plate  103  of the frame  100 , and the rotation axis X of the blocking plate assembly  300  is shown.  FIG.  2    shows a state where the blocking plate assembly  300  is in a closed position. Although the drawings show that the open position may differ from the closed position by an angle of 90 degrees, the solution of the present disclosure is not limited to this, and the open position may differ from the closed position by an angle of more than 90 degrees. 
     The frame  100  also has a housing engagement portion  107  located at the side edge of the end plate  103  and extending substantially perpendicular to the end plate  103 . Specifically, the housing engagement portion  107  may be a structural part extending from the side edge of the frame  100  in a direction perpendicular to the rotation axis of the blocking plate  301  and perpendicular to the end plate  103  of the frame  100 . In this way, the frame  101  may be divided into two portions: the housing engagement portion  107  and the remaining portion including the end plate  103 . For example, referring to  FIG.  5   , these two portions may be arranged in an overall L-shape. For example, the housing engagement portion  107  may have a snap structure, and the housing  200  is connected to the housing engagement portion  107  by snapping. However, the connection between the housing and the frame is not limited to a snap connection, but can also be accomplished by screw fastening or ultrasonic welding. 
       FIG.  3    clearly shows the end plate  103  of the frame  100 . The opening portion  101  is provided in the end plate  103 , and its shape is not limited, and may be, for example, a rectangular opening. For example, the frame  100  has an edge plate  104  extending from the outer peripheral edge of the end plate  103  for protecting the heater H described below. 
       FIGS.  4 A and  4 B  show the blocking plate  301  of the blocking plate assembly  300 . The main function of the blocking plate  301  is to control the amount of air passing through the opening portion  101 . The size and shape of the blocking plate  301  is designed to close the opening portion  101 , for example, it may have a rectangle shape as shown in the drawings, and the size of it is slightly larger than the opening portion  101 . The blocking plate  301  may include a first shaft portion  305  and a second shaft portion  306  provided at both ends thereof, and the blocking plate  301  is mounted to the frame  100  through the first shaft portion  305  and the second shaft portion  306 . Then, the blocking plate  301  is rotatable relative to the frame  100  around the first and second shaft portions  305 ,  306 . A clamping structure is provided inside the first shaft portion  305 , and the driving module can engage the clamping structure, for example, through corresponding features on its output shaft, so as to drive the blocking plate  301  through the clamping structure to rotate. For example, as shown in  FIG.  4 A , a recess is provided inside the first shaft portion  305 , the output shaft of the driving module is provided with a blade that engages in the recess, and the output shaft of the driving module can snap into the recess of the first shaft portion  305  so as to rotate the first shaft portion  305 . Alternatively, a recess may be provided inside the output shaft of the driving module, and a blade may be provided at the end of the first shaft portion, as shown in  FIG.  4 B . For example, on one side of the blocking plate  301  is a flat portion  303  for placing an elastic component  302 , and on the other side, that is, the side facing away from the elastic component  302 , is provided with reinforcing ribs  307 . The arrangement of the reinforcing ribs  307  can reinforce the strength of the blocking plate  301 , prevent the blocking plate assembly  300  from shrinking, and improve the surface appearance. 
     The elastic component  302  may be attached to the flat portion  303  of the blocking plate  301 , and the shape of the elastic component  302  can match the shape of the flat portion  303  of the blocking plate  301 , for example, a sheet-like rectangular shape. The elastic component  302  may be composed of materials such as foamed polyurethane. When the blocking plate assembly  300  is in the closed position, the elastic component  302  abuts the frame  100  and deforms elastically to seal the opening portion  101 . For example, the end plate  103  of the frame  100  has a sealing portion  102  around the opening portion  101  and protruding from the end plate  103 . When the blocking plate assembly  300  is in the closed position, the elastic component  302  abuts against the sealing portion  102  of the frame  100 . The abutment of the elastic component  302  against the sealing portion  102  effectively increases the sealing performance of the blocking plate  301  to the opening portion  101 . 
     According to an exemplary solution, the housing  200  and the frame  100  are connected in a snap-fit manner For example,  FIG.  5    shows that the frame  100  and the housing  200  are in a separated state. 
     The driving module drives the blocking plate assembly  300  to rotate. The driving module may include a motor and a transmission assembly. The motor is, for example, a stepper motor. The transmission assembly transmits the power from the motor to the blocking plate assembly  300  to drive the blocking plate assembly  300  to rotate, thereby controlling the opening and closing degree of the opening portion  101 , and thereby controlling the amount of cold air passing through the cold air passage. The driving module is located within the driving chamber, as shown in  FIG.  6   . 
     2. Heater 
     The ventilation door device  10  may further include a heater H. According to the solution of the present disclosure, the heater H is installed to the end plate  103  of the frame  100  and at least partially surrounds the opening portion  101 . For example, the shape of the heater H may at least partially match the shape of the end plate  103 . For example,  FIG.  1    shows the installation of the heater H in the frame  100 . Since the opening portion  101  shown is rectangular and the end plate  103  is also rectangular, the heater H is a rectangle ring arranged around the opening portion  101 . 
     According to an exemplary solution, the frame  100  further includes an edge plate  104  extending from the outer edge of the end plate  103 , which partially surrounds the heater H. The extension direction of the edge plate  104  is the same as the extension direction of the housing engagement portion  107 , and both extend away from the opening from the side of the opening portion  101  where the blocking plate assembly  300  is installed. For example, referring to the embodiment shown in  FIG.  1   . Thus, the heater H is surrounded by the edge plate  104  at its three edges, and is joined by the housing engagement portion  107  of the frame  100  at the other edge, so that the four edges of the heater H are restricted and protected. Through such structural arrangement of the frame  100 , the heater H can be prevented from being crushed by external parts, and the heater H can be protected. At the same time, easy operation and compact installation of the heater H become possible. 
     Although the figures show that the heater is arranged on the side of the end plate close to the opening direction of the blocking plate assembly, according to another exemplary solution, the heater may be arranged on the back of the end plate, that is, on the side of the end plate away from the opening direction of the blocking plate assembly. For the solution in which the heater is arranged on the back of the end plate, for example, a groove surrounding the opening may be formed on the back of the end plate, and the heater may be arranged in the groove. Through such solution, a compact space arrangement can be realized, and the heater can be also protected. 
     The ventilation door device  10  is configured to generate an electrical signal when the blocking plate assembly  300  is in the closed position or the open position; and not generate an electrical signal or generate another electrical signal when the blocking plate assembly  300  is in a middle position between the closed position and the open position. The ventilation door device  10  is configured to monitor the signals, and if the ventilation door device  10  does not detect the disappearance of said electrical signal or does not detect the transform from said electrical signal to said another electrical signal within a predetermined time period after receiving the command to rotate the blocking plate assembly  300 , the heater H will be activated. For example, the predetermined time period may be 3 to 8 seconds. In an exemplary embodiment, when the blocking plate assembly  300  is in the closed position or the open position, an electrical signal “1” is generated; and when the blocking plate assembly  300  is in a middle position between the closed position and the open position, an electrical signal “0” is generated. The ventilation door device  10  is configured to monitor the signals, and if the ventilation door device  10  does not detect a signal change within a predetermined time after receiving the command to rotate the blocking plate assembly  300 , the heater H is activated. 
     Through this kind of control, when the stepper motor is driven to open the ventilation door, if the electrical signal change can be detected, it indicates that the door is not frozen and can be normally opened; and if the electrical signal change cannot be detected, it indicates the door might be frozen due to frost, then the heater H is activated to melt the frost and return the blocking plate  301  back to normal opening. In this way, it is avoided that the ventilation door freezes in the fully open or fully closed position and could not normally work due to frost or icing. 
     The above heating solution can be specifically realized by using a micro switch  409 . The micro switch  409  can be arranged in the driving chamber, for example, on a circuit board located in the driving chamber. One of the transmission components of the driving module, such as the teeth missing gear described in detail below, may include two contacts  446  protruding in the radial direction. By setting the installation position of the teeth missing gear, when the blocking plate assembly  300  is in the closed position, a contact  446  triggers a static contact of the micro switch  409 , so that the micro switch  409  generates an electrical signal, and when the blocking plate assembly  300  is in the open position, another contact  446  triggers the static contact of the micro switch  409 , so that the micro switch  409  also generates an electrical signal; and when the blocking plate assembly  300  is in a middle position between the closed position and the open position, no contact  446  contacts the static contact of the micro switch  409 , and the micro switch  409  does not generate any electrical signal or generates another electrical signal. 
     The heater H may be electrically connected to the circuit board. More about the circuit board will be introduced below. For example, the frame  100  includes a wiring portion  105 , which is in the form of a groove formed in the frame  100 , and can extend from a position of the housing engagement portion  107  of the frame  100  close to the end plate  103  to a position near the mounting position of the circuit board of the frame  100 . For example,  FIGS.  1 - 3    show the arrangement of the wiring portion  105  in the housing engagement potion  107  of the frame  100 . The wires of the heater H for connecting to the circuit board are arranged along the wiring portion  105 . 
     3. Circuit Board 
     As mentioned above, the ventilation door device  10  may also include a circuit board.  FIG.  7    shows an example implementation of the circuit board. The circuit board can be used to control the motor, the heater H, and the micro switch  409 . 
     According to an exemplary solution, the circuit board has coupling parts for the heater H, the driving module (specifically, the motor of the driving module), and the like. In the embodiment shown in the drawings, the circuit board includes a first coupling portion  421  for coupling the micro switch  409 , a second coupling portion  422  for coupling the driving module, and a third coupling portion  423  for coupling the heater H. In addition, the circuit board has a motor limiting portion  424  for limiting the position of the stepper motor, which is in the form of holes formed in the circuit board. 
     In order to facilitate the installation of the circuit board, the frame  100  is provided with, for example, a slot portion  416  into which the circuit board is inserted. The slot portion  416  may be provided on the side of the housing engagement portion  107  of the frame  100  facing the driving chamber, so that the circuit board is arranged in the driving chamber. As best shown in  FIG.  6   , it shows the layout of the circuit board in the drive chamber. 
     According to an exemplary solution, the circuit board is provided with tin-plated holes penetrating the circuit board, so that when one side of the circuit board fails, the other side can still work to ensure the energizing of the circuit. 
     4. Driving Module 
     The driving module  400  of the ventilation door device  10  is used to drive the blocking plate  301  to rotate between the fully opened state shown in  FIG.  1    and the fully closed state shown in  FIG.  2   . The components of the driving module  400  are accommodated in a driving chamber surrounded by the housing  200  and the frame  100 . 
     In  FIG.  8   , the housing  200  is removed, and the components of the driving module  400  are shown. The driving module  400  includes a transmission assembly  402  and a stepper motor  403 . The transmission assembly  402  includes a teeth missing gear  405  directly connected to the motor output shaft  404  of the stepper motor  403  and a sector gear  406  meshing with the teeth missing gear  405  and directly connected to an output shaft  407 . The output shaft  407  is connected to the blocking plate  301 . By driving the motor rotate positively or reversely, the blocking plate  301  can be driven to rotate positively or reversely to realize the opening or closing action of the ventilation door. 
       FIG.  9    shows the frame  100 . The frame  100  has a bottom plate portion  106  facing the housing  200 , and a structure for mounting and supporting various components of the driving module  400  is provided thereon. The bottom plate portion  106  is an integral part of the housing engagement portion  107  constituting the frame. 
     Referring to  FIG.  9   , the bottom plate portion  106  has a first cylindrical portion  410  for rotatably supporting the sector gear  406 . The first cylindrical portion  410  protrudes from the plane of the bottom plate portion  106  toward the housing  200 . The inner surface of the first cylindrical portion  410  defines a rotation support surface. Inside the first cylinder portion  410 , a through hole  417  is formed through the bottom plate portion  106  for passing the output shaft  407  therethrough. 
     The structure of the sector gear  406  according to an exemplary embodiment is shown in  FIGS.  10  and  11 A . Along the axial direction, the sector gear  406  sequentially includes a shaft portion  431 , a gear teeth portion  432 , a cylindrical portion  433 , and a sector gear output portion  434 . The sector gear output portion  434  may be in the form of a rotating shaft and used as the output shaft  407  of the driving module  400 . The shaft is used for inserting into a clamping structure in the form of a clamping slot disposed at the first shaft portion  305  of the blocking plate  301 , as shown in  FIG.  4 A . In another embodiment, as shown in  FIG.  11 B , the sector gear output portion  434  may be in the form of a clamping slot for receiving and engaging a clamping structure in the form of a rotating shaft disposed at the first shaft portion  305  of the blocking plate  301 , As shown in  FIG.  4 B . The shaft portion  431  may be installed on a corresponding supporting structure (not shown) inside the housing  200 . The gear teeth portion  432  is sector shaped, and has a plurality of gear teeth on its outer peripheral side for meshing with the corresponding plurality of gear teeth of the upstream teeth missing gear  405 . The cylindrical portion  433  can be coaxially inserted into the cavity of the first cylindrical portion  410  so that the outer circumferential surface of the cylindrical portion  433  is rotatably supported on the rotation supporting surface defined by the inner surface of the first cylindrical portion  410 . At the same time, the sector gear output portion  434  in the form of a rotating shaft can pass through the through hole  417  to partially extend to the other side of the bottom plate portion  106 . The sector gear output part  434  has a bonding structure, for example, two flat plans  435  as shown in  FIGS.  11 A and  11 B , for engaging with an engagement hole at the first shaft portion  305  of the blocking plate  301 . 
     Continuing to refer to  FIG.  9   , the bottom plate portion  106  has a second cylindrical portion  411  for rotatably supporting the teeth missing gear  405 . The second cylindrical portion  411  protrudes from the plane of the bottom plate portion  106  toward the housing  200 , and the inner surface of the second cylindrical portion  411  defines a rotation supporting surface. In addition, an arc groove  414  is provided on the outer circumference of the second cylindrical portion  411 , and the arc groove  414  is recessed away from the end surface of the second cylindrical portion  411 . The center of the arc groove  414  coincides with the axis of the second cylindrical portion  411 . The arc groove  414  is used to guide the rotation of the teeth missing gear  405  and limit the angular range of the rotation. The arc groove  414  has two end surfaces, including a first limit surface  412  corresponding to the open position of the ventilation door and a second limit surface  413  corresponding to the closed position of the ventilation door. The arc groove  414  extends between the two limit surfaces  412 ,  413 . 
     The structure of the teeth missing gear  405  according to an exemplary embodiment is shown in  FIGS.  12  and  13   . Along the axial direction, the teeth missing gear  405  includes a shaft portion  441 , a gear teeth portion  442 , and a contact portion  443  in sequence. The shaft portion  441  can be coaxially inserted into the inside of the second cylindrical portion  411  so that the outer peripheral surface of the shaft portion  441  is rotatably supported on the rotation supporting surface of the inner periphery of the second cylindrical portion  411 . The outer periphery of the gear teeth portion  442  is divided into two different sections. The first section has gear teeth and is a gear teeth section  444 , and the second section does not have gear teeth and is an arc section  445 . The multiple gear teeth on the gear teeth section  444  are used to mesh with the corresponding multiple gear teeth on the downstream sector gear  406 . The contact portion  443  has two arms extending away from the axis, and the end of each arm forms a contact  446  for actuating the micro switch  409 . Each contact  446  forms the part on the contact portion  443  being furthest away from the axis. Therefore, during the rotation of the teeth missing gear  405 , only the contact  446  will touch the static contact on the micro switch  409 . In addition, during the rotation of the teeth missing gear  405 , except for the contact  446  touching the static contact on the micro switch  409 , the teeth missing gear  405  will not interfere with any other structures. At a position adjacent to the axis of the contact portion  443 , a shaft hole  447  is formed, and the shaft hole  447  can be firmly connected to the motor output shaft  404 . 
     As shown in  FIG.  13   , an arc-shaped protrusion  448  is provided on the surface of the gear teeth portion  442  facing the shaft portion  441 . When the shaft portion  441  is inserted into the inside of the second cylindrical portion  411 , the arc-shaped protrusion  448  will be inserted into the arc groove  414  of the second cylindrical portion  411 . Thus, while the stepper motor  403  drives the teeth missing gear  405  to rotate, the arc-shaped protrusion  448  will move along the arc groove  414  until the two limit surfaces  412  and  413  of the arc groove  414  abut the arc-shaped protrusion  448 , so as to prevent the tooth missing gear  405  from rotating, thereby playing a position limiting role. 
     Return to refer to  FIG.  9   , the bottom plate portion  106  also has a supporting portion  415  for fixing the mounting structure of the stepper motor  403  by screws, so as to mount the stepper motor  403  to the frame  100 . The bottom plate portion  106  also has a slot portion  416  for clamping and fixing the circuit board  408 . 
     The working mechanism of the driving module  400  of the present disclosure is as follows:
         when opening the ventilation door device, the stepper motor  403  rotates the teeth missing gear  405  counterclockwise (viewed from left to right in  FIG.  8   ), and then drives the blocking plate  301  to rotate clockwise via the sector gear  406 ; when the arc-shaped protrusion  448  of the teeth missing gear  405  abuts the first limiting surface  412 , the blocking plate  301  stops rotating, and reaches the open position at this time, and the opening portion  101  of the frame  100  is opened to allow the cooling air flow to flow therethrough; at this time, the contact  446  of the teeth missing gear  405  touches the static contact on the micro switch  409 , and the micro switch  409  outputs a corresponding electrical signal, indicating that the ventilation door device is fully opened; and   when closing the ventilation door device, the stepper motor  403  rotates the teeth missing gear  405  clockwise, and then drives the blocking plate  301  to rotate counterclockwise via the sector gear  406 ; when the elastic component  302  on the blocking plate  301  abuts against the sealing portion  102  on the frame  100 , the blocking plate  301  stops rotating and reaches the closed position at this time, closing the opening portion  101  of the frame  100 , and blocking the flow of cooling air; at this time, the other contact  446  of the teeth missing gear  405  touches the static contact on the micro switch  409 , and the micro switch  409  outputs the corresponding electrical signal, indicating that the ventilation door device is completely closed.       

     The contacts  446  cooperate with the static contact on the micro switch  409  to provide electrical signal feedback. In an exemplary embodiment, when the blocking plate  301  is fully opened or fully closed, an electrical signal is output (e.g., the output signal “1”); and during the rotation of the blocking plate  301 , no electrical signal is output (e.g., the output signal “0”). When driving the stepper motor to open the ventilation door, if the electrical signal change can be detected, it indicates that the ventilation door is not frozen and is opened normally; and if the electrical signal change cannot be detected, it indicates that the ventilation door may be frozen due to frost. The heating function can then be activated to melt the frost and make the blocking plate  301  return to normal. 
     5. Locking Mechanisms 
     In order to prevent the blocking plate  301  from rotating in the opening direction due to rebound of the elastic component  302 , air flowing, vibration, etc., after reaching the closed position, the driving module  400  may be provided with a locking mechanism. The present disclosure provides the following two different locking structures, namely, an arc-shaped locking structure ( FIGS.  10  to  13   ) and a tooth-shaped locking structure ( FIGS.  14  to  25   ). 
     5.1 Arc-Shaped Locking Structure 
     In the first embodiment, the locking mechanism is composed of a concave locking arc  437  of the sector gear  406  and the arc section  445  of the teeth missing gear  405 . As shown in  FIGS.  10 ,  11 A and  11 B , on the outer periphery of the gear teeth portion  432  of the sector gear  406 , there is a gear teeth section  436  including a plurality of gear teeth, and two concave locking arcs  437  located at both ends of the gear teeth section  436  in the circumferential direction. Each concave locking arc  437  is recessed toward the center of the sector gear  406  and has a circular arc shape. During driving the blocking plate  301  to rotate, the gear teeth section  436  of the sector gear  406  meshes with the gear teeth section  444  of the missing gear  405 . 
     When the blocking plate  301  is in the closed position, as shown in  FIG.  14   , the concave locking arc  437  engages part of the arc section  445  to form a concave-convex arcs locking structure. The curvature of the concave locking arc  437  is set to match the curvature of the arc section  445 . In this configuration, if the teeth missing gear  405  remains fixed, the concave locking arc  437  will not rotate freely relative to the arc section  445 , because part of the arc section  445  extends into the concave locking arc  437 , which will provide a resistance to prevent the concave locking arc  437  from rotating over the arc section  445 . It is precisely due to the locking mechanism of the concave locking arc  437  and the arc section  445  that the sector gear  406  and the blocking plate  301  coupled with it will be stably kept in the closed position and will not be easily displaced. The pushing force toward the blocking plate  301  due to the rebound effect of the elastic component  302  and the airflow, vibration and other factors will not cause the blocking plate  301  to move toward the open position, which improves the airtightness of the closing of the ventilation door, and also reduces the noise problem caused by the shaking of the blocking plate  301 . 
       FIG.  14    and its partial enlargement  FIG.  15    show the structure of the teeth missing gear  405  and the sector gear  406  in the locked state. The radius of the arc section  445  of the teeth missing gear  405  is R 1 , the distance from the arc end points of the concave locking arc  437  of the sector gear  406  to the center of the sector gear  406  is L 2 , and the distance between the centers of the sector gear  406  and the teeth missing gear  405  is L. In order to achieve the above locking effect, L is less than R 1 +L 2 , and the difference between the (R 1 +L 2 ) and L is the interference amount L 1 . The interference amount L 1  can be 0.05 mm≤L 1 ≤1 mm. When interference amount L 1  is greater than 1 mm, there will be interference in the gears due to space design issues; due to factors such as parts manufacturing tolerance, the interference amount L 1  is greater than or equal to 0.05 mm. When the interference amount L 1  is less than 0.05 mm, the locking mechanism does not work. In addition, the size constraints of the shafts need to be considered. The radius of the shaft  441  of the teeth missing gear  405  is r 1 , the radius of the shaft  431  of the sector gear  406  is r 2 , and the radius of the arc section  445  of the teeth missing gear  305  is R 1 , which has the following range: r 1 ≤R 1 ≤L−r 2 . The distance between the arc end points of the concave locking arc  437  of the sector gear  306  and the center of the sector gear  306  is L 2 , which has the following range: r 2 ≤L 2 ≤L−r 1 . 
     In addition to the locking function, this locking structure also has the function of allowing the teeth missing gears to idle and shortening the locked-rotation time of the stepper motor when the door is closed. 
     In this solution, when the blocking plate  301  is closed in place, that is, when the elastic component  302  abuts against the sealing portion  102  of the frame  100  and is elastically deformed, the second limit surface  413  of the circular arc groove  414  of the housing  200  and arc-shaped protrusion  448  of the teeth missing gear  405  has not yet abutted. Then, the arc section  445  of the teeth missing gear  405  has entered the concave locking arc  437  of the sector gear  406 , but it can still continue rotate forward relative to the concave locking arc  437  (at this time, the stepper motor  403  is idling, that is, the blocking plate  301  is not driven to further rotate) until the second limit surface  413  abuts the arc-shaped protrusion  448 , and finally the stepper motor  403  is prevented from rotating. The angle at which the teeth missing gear  405  can continue to rotate is referred as idling angle α. 
       FIG.  16    is a schematic diagram of the sector gear  406  and the teeth missing gear  405  when the blocking plate  301  is completely closed (as shown in  FIG.  17   ).  FIG.  18    is a schematic diagram of the sector gear  406  and the teeth missing gear  405  when the blocking plate  301  is fully opened (as shown in  FIG.  19   ). As shown in the figures, θ is the total angle that the stepper motor  403  drives the teeth missing gear  405  to rotate (that is, the angle from the first limit surface  412  to the second limit surface  413 ), α is the idling angle, and β is the angle across which the teeth missing gear  405  rotates when the ventilation door rotates from the open position to the closed position. These angles have the following relation: θ=α+β. 
     During closing the door, it is necessary to design the stepper motor  403  to stall. The purpose of stalling is to reset the gears of the stepper motor  403  to zero position, so that the ventilation door  301  can return to the same position when the door is closed in the next round. The, the tolerance of the gear rotation is eliminated, so that the ventilation door is closed more accurately, and the opening portion  101  is more reliably closed by the blocking plate  301 . If the pulse number for opening rotation of the stepper motor  403  set by the client is M and the pulse number for closing is N, then N−M=W, W is the pulse number of the stepper motor for minimum stalling, and A is the idling pulse number of the stepper motor. 
     The inventor found that if the overall angle θ that the stepper motor  403  drives the teeth missing gear  406  to rotate is equal to the rotation angle β of the teeth missing gear  406  required for the blocking plate  301  to close in place, after the ventilation door is closed in place, if it needs to complete the pulse number N desired by the motor, the pulse number of the stepper motor  403  that needs to be stalled is W+A. If the stalling time is too long, it will cause the risk of gear breakage. For this reason, in the solution of the present disclosure, the idling angle a is increased by the above-mentioned locking mechanism, so that the arc-shaped protrusion  448  of the teeth missing gear  405  idles for a certain number of pulse steps before reaching the second limit surface  413 . This shortens the blocking time and reduces the risk of tooth breakage. 
     5.2 Tooth-Shaped Locking Structure 
     In the second embodiment, the locking mechanism is composed of the first tooth  451  and the second tooth  452  at the end of the sector gear  406 ′, and the arc section  445 ′ of the teeth missing gear  405 ′. 
     Referring to  FIG.  20   , the structure of the sector gear  406 ′ in the second embodiment is basically the same as the structure of the sector gear  406  in the first embodiment, and only the differences between the two are described below. No concave locking arc is disposed at the two sides of the gear teeth portion  432 ′ of the sector gear  406 ′. On the contrary, the gear teeth portion  432 ′ has a first tooth  451 , a second gear  452 , and a third tooth  453  in sequence on one side (the side is the last to mesh when the ventilation door is closed, and the first to mesh when the ventilation door is opened). The first tooth  451  is located nearest to the end. As shown in  FIG.  20   , the width of the first tooth  451  in the axial direction is shorter relative to the other teeth, so that the end surface of the first tooth  451  facing the sector gear output portion  434 ′ is farther away from the output shaft than the other teeth. In addition, the second tooth  452  and the third tooth  453  are connected by a connecting portion  454  on the side close to the output portion  434 ′ of the sector gear. 
     Referring to  FIG.  21   , the structure of the teeth missing gear  405 ′ in the second embodiment is basically the same as the structure of the teeth missing gear  405  in the first embodiment, and only the difference between the two will be described below. An arc-shaped groove  455  is formed between the arc section  445 ′ and the contact portion  443 ′ of the teeth missing gear  405 ′, which is located between the inner surface  456  of the arc section  445 ′ and the side surface of the contact portion  443 ′. The two ends of the arc-shaped groove  455  each extend to the outer surfaces of the two outermost teeth of the gear teeth section  444 ′. The radial depth of the arc-shaped groove  455  is greater than the radial height of the first tooth  451 , and the axial width of the arc-shaped groove  455  is greater than the axial width of the first tooth  415 . Thus, the first tooth  451  can be received in the arc-shaped groove  455  and slide along the arc-shaped groove  455 . 
     When the blocking plate  301  is in the closed position, as shown in  FIGS.  22  and  23   , part of the outer surface of the arc section  445 ′ of the teeth missing gear  405 ′ enters the space between the first teeth  451  and the second teeth  452  of the sector gear  406 ′. The second tooth  452  abuts the outer surface of the arc section  445 ′. Since the first tooth  451  is offset from the arc section  445 ′ in the axial direction, the first tooth  451  will not block the arc section  445 ′ from entering the space between the first tooth  451  and the second tooth  452 , and the first tooth  451  will be accommodated by the arc-shaped groove  455 . 
     In this configuration, on the one hand, the arc section  445 ′ of the teeth missing gear  405 ′ can continue to rotate over a certain angle relative to the second tooth  452  of the sector gear  406 ′ after the blocking plate  301  reaches the closed position, achieving idling of the teeth missing gear  405 ′ and the stepper motor  403 , until the arc-shaped protrusion  448 ′ on the teeth missing gear  405 ′ abuts the corresponding second limit surface  413 , which helps to shorten the stalling time of the stepper motor. 
     On the other hand, since the outer surface of the arc section  445 ′ abuts against the second tooth  452 , the sector gear  406 ′ can be prevented from rotating in the direction of opening the ventilation door. Then, the ventilation door can be prevented from opening due to the rebound of the elastic element  302  on the blocking plate  301 , the impact of the airflow or the vibration. Then, the tightness of the closed door could be improved. In addition, the tops of the second tooth  452  and the third tooth  453  of the sector gear  406 ′ are connected by the connecting portion  454 . This structure can increase the strength of the gear and increase the contact area of the second tooth  452 , thereby effectively avoiding tooth breakage due to the impact when the arc section  445 ′ of the teeth missing gear  405 ′ abuts against the second tooth  452  of the sector gear  406 ′. 
     The above structure might have noise problem when opening and closing the ventilation door. For example, referring to  FIG.  22   , when opening ventilation door, the stepper motor  403  drives the teeth missing gear  405 ′ to rotate counterclockwise, the first tooth  457  of the teeth missing gear  405 ′ will cross over the second tooth  452  of the sector gear  406 ′, and mesh between the first tooth  451  and the second tooth  452 . At this time, due to factors such as the force acting on the sector gear  406 ′ from the side of the ventilation door and manufacturing tolerances, the rotation center axis of the sector gear  406 ′ may be inclined. In such case, the second tooth  452  of the sector gear  406 ′ is likely to interfere with the inner surface  456  of the arc section  445 ′ and the first tooth  457  of the teeth missing gear  405 ′, thereby causing noise. The situation is similar when closing the ventilation door.
         In order to relieve such noise phenomenon, the structure of the present disclosure can be improved in any of the following ways.   The radius of the addendum circle of part of the second tooth  452  of the sector gear  406 ′ is set smaller than that of the normal tooth, as shown in  FIGS.  22  and  23   . Portion of the second tooth  452  far away from the connecting potion  454  can be removed partially. In this case, when the rotation center axis of the sector gear  406 ′ is inclined, the second tooth  452  of the sector gear  406 ′ does not have a portion protruding toward the inner surface  456  of the arc section  445 ′ of the teeth missing gear  405 ′. Then, there will be no interference and no noise will be generated.   The end surface of the second tooth  452  of the sector gear  406 ′ away from the connecting portion  454  and the inner surface  456  of the arc section  445 ′ of the teeth missing gear  405 ′ are set on the same plane, that is, the portion of the second tooth  452  below the inner surface  456  of the arc section  445 ′ is completely cut off, as shown in  FIG.  24   . In this case, when the rotation center axis of the sector gear  406 ′ is inclined, the second tooth  452  of the sector gear  406 ′ does not have a portion protruding toward the inner surface  456  of the arc section  445 ′ of the teeth missing gear  405 ′. Then, there will be no interference and no noise will be generated.   The radius of the arc section  445 ′ of the teeth missing gear  405 ′ is set greater than the radius of the addendum circle of the gear teeth section  444 ′, as shown in  FIG.  25   , wherein the dashed line is the addendum circle of the gear teeth section  444 ′. In this case, when the rotation center axis of the sector gear  406 ′ is inclined and the arc section  445 ′ abuts the second tooth  452  of the sector gear  406 ′, the addendum position of the second tooth  452  will also be located outside the addendum circle of the teeth missing gear  405 ′. Therefore, when the teeth missing gear  405 ′ and the sector gear  406 ′ start to mesh, the first tooth  457  of the tooth-missing gear  405 ′ and the second tooth  452  of the sector gear  406 ′ will not interfere to generate noise. In addition, in this example, as shown in  FIG.  25   , the outer peripheral surface of the arc section  445 ′ of the teeth missing gear  405 ′ and the tooth surface of the first tooth  457  of the gear teeth section  444 ′ are connected by an arc-shaped guide surface  458 . Therefore, when the second tooth  452  of the sector gear  406 ′ is in contact with the tooth surface of the first tooth  457  of the teeth missing gear  405 ′, the second tooth  452  does not collide with a step, so that the generation of noise can be prevented or suppressed.       

     The ventilation door mechanism provided in the present disclosure can be used in various types of refrigerators. For example, a refrigerator includes one or more storage compartments. The refrigerator has one or more cold air passages leading to the one or more storage compartments, respectively. The opening portions of the ventilation door devices are respectively arranged in the corresponding cold air passages, so that the amount of cold air delivered in the corresponding cold air passages can be controlled by the opening and closing of the opening portions of the corresponding ventilation door devices. 
     Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by those with ordinary skills in the field to which this disclosure belongs. The “first”, “second” and similar words used in the description and claims of this disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as “a”, “an” or “one” do not necessarily indicate quantitative restrictions. “include” or “comprise” and other similar words mean that the element or item appearing before them covers the elements or items listed after them and their equivalents, but does not exclude other elements or items. Similar words such as “connect” or “couple” are not limited to physical or mechanical connections, but may include electrical connections, in both direct or indirect connections. “Upper”, “lower”, “left” and “right” are only used to indicate the relative position relationship. When the absolute position of the described object changes, the relative position relationship may also change accordingly. 
     The exemplary embodiments in the present disclosure are described in detail above. However, those skilled in the art can understand that, without departing from the concept of the present disclosure, there are many variations and modifications to the embodiments, and various technical features and structures in the present disclosure can be combined in various ways without exceeding the protection scope of the present disclosure, which is determined by the appended claims.