JP5281940B2 - Door opening mechanism - Google Patents

Description

  The present invention relates to a door opening mechanism for assisting opening of a door.

  In recent years, differential pressure is frequently generated indoors and outdoors due to factors such as high airtightness in condominiums and houses. In this way, when differential pressure is generated inside and outside the door, when opening the entrance door etc., wind pressure acts on the door body, and door opening and closing trouble such as heavy door may occur, It is a problem.

  Conventionally, as a measure for reducing such door opening / closing obstacles, for example, an opening for differential pressure adjustment is formed in the main body of the entrance door, the door is rotatably installed in the opening, and the indoor and outdoor air is A mechanism (see Patent Document 1) that circulates indoor and outdoor air by connecting an outdoor air supply opening that opens to the outside of the room and an indoor air supply opening that opens to the indoor side (see Patent Document 2) )was there. In addition, a ventilation system has been proposed in which a differential pressure damper is installed in a dwelling unit and a pressure difference between indoors and outdoors is eliminated by a fan or the like (see Patent Document 3). According to the above configuration, by reducing the differential pressure inside and outside the room, the pressure applied to the door can be reduced, the opening of the door can be assisted, and the door opening / closing failure can be reduced.

JP-A-10-131642 JP 2000-28171 A JP 2000-65406 A

  However, the conventional configuration described above has the following problems. Forming a differential pressure adjusting opening as in Patent Document 1 in the entrance door is difficult to put into practical use from the viewpoint of fire prevention. In addition, in the configuration of Patent Document 2, a space for installing a pass duct for connecting the outdoor air supply port and the indoor air supply port is required. Depending on the shape of the corridor outside the entrance door, the pass duct may be installed due to the fit. In some cases, it was not possible.

  Moreover, in the structure of patent document 2 and patent document 3, in order to adjust the pressure inside and outside, an air supply port and a differential pressure damper must be separately provided, resulting in a complicated structure and an increase in construction cost. was there.

  Accordingly, the present invention has been devised to solve the above-described problem, and provides a door opening mechanism that can assist opening and closing of the door with a simple configuration without forming an opening in the door. This is the issue.

In order to solve the above problems, the present invention provides a door opening mechanism for assisting in opening a door provided at a position where a differential pressure is generated inside and outside, and is provided on a frame side provided on a door frame surrounding a door body. A magnetic body, and a door main body side magnetic body disposed at a position facing the frame side magnetic body provided on the door main body, wherein the frame side magnetic body is provided on the low pressure side and the door main body side magnetic body is provided. The body is provided on the high pressure side, and both the frame side magnetic body and the door main body side magnetic body are constituted by electromagnets, and the electromagnet is magnetized according to the operation of the door opening handle of the door main body, A magnetizing means for generating a repulsive force between the frame side magnetic body and the door main body side magnetic body is further provided, and the repulsive force biases the door main body in the opening direction that becomes the high pressure side. This is a door opening mechanism.

In the present invention, the door opening handle refers to a portion that is gripped and rotated or pushed or pulled by a hand when a door such as a door knob, a lever handle, or a push door handle is opened. According to the door opening mechanism having such a structure, the door body is urged in the opening direction by the repulsive force generated between the frame side magnetic body and the door body side magnetic body, so that opening and closing of the door is assisted. The door can be opened smoothly with a small force. Furthermore, since the electromagnet is magnetized in response to the operation of the door opening handle, no repulsive force is generated when the latch bolt is locked to the door frame, so that excessive stress is not applied to the door body or door frame. . Moreover, according to this structure, it is not necessary to form the opening part for differential pressure | voltage adjustment in a door, and there is no problem on fire prevention. Furthermore, the frame-side magnetic body is provided inside the door frame, and the door body-side magnetic body is provided inside the door body, so that it does not require a separate installation space for each device, and has a simple configuration. Therefore, an increase in construction costs can be suppressed. Furthermore, the repulsive force generated between the frame side magnetic body and the door body side magnetic body urges the door body in the opening direction against the pressure applied to the door body by the differential pressure, thus assisting in opening and closing the door. The door can be opened to a predetermined angle with a small force. When the door is opened, the differential pressure inside and outside the door is eliminated, and thereafter, the door body can be opened smoothly with normal force.

  Furthermore, the present invention is characterized in that the door body is configured to open by the repulsive force.

  According to the door opening mechanism having such a configuration, the door main body resists the pressure applied to the door main body due to the generated differential pressure by the repulsive force generated between the frame side magnetic body and the door main body side magnetic body. Since it opens automatically, the pressure difference inside and outside the door is eliminated at that time. After that, the door body can be opened smoothly with normal force.

  The present invention further includes a door check spanned between the door body and the door frame, and the door check moves the door body at a differential pressure canceling position where the door body can eliminate the differential pressure. It is configured to be temporarily stopped.

  Here, the differential pressure release position means that the door body is opened at a predetermined angle, and air can flow between the door frame and the door body, allowing air to flow in and out of the door. This is a position where the door body is not closed back to the door frame side. According to the door opening mechanism having such a configuration, the door body opens too much due to the repulsive force generated between the frame side magnetic body and the door body side magnetic body, or the air that flows between the door frame and the door body. Therefore, the person who opens and closes the door can be prevented from being pushed or pulled by the door body while holding the door opening handle. Furthermore, since the differential pressure has been eliminated once stopped, the door can be opened smoothly.

  Furthermore, the present invention is characterized in that the magnetizing means is configured to release the magnetization of the electromagnet when the door body opens to the differential pressure elimination position.

  According to the door opening mechanism having such a configuration, since the magnetization of the electromagnet is released after the differential pressure inside and outside the door is eliminated, the door body is not closed back to the door frame side. Further, the door body does not open too much due to the repulsive force generated between the frame side magnetic body and the door body side magnetic body.

  According to the present invention, it is possible to provide an excellent effect that opening and closing of a door can be assisted with a simple configuration without forming an opening in the door.

It is the perspective view which showed the door opening mechanism which concerns on embodiment of this invention. It is sectional drawing which showed the door opening mechanism which concerns on embodiment of this invention. It is the sectional view on the AA line of FIG. It is sectional drawing which showed an example of a differential pressure | voltage sensor, Comprising: (a) is a figure which showed the case where a differential pressure is small or is not, (b) is the figure which showed the case where a differential pressure is large.

  The form for implementing the door opening mechanism which concerns on this invention is demonstrated in detail, referring an accompanying drawing.

  As shown in FIG. 1, the door opening mechanism 1 assists the opening of the door against the pressure applied to the door body 10 (hereinafter sometimes referred to as “wind pressure”) by the differential pressure generated inside and outside the door. For example, the door 2 is formed. The opening door 2 includes a door body 10, a door frame 30 that surrounds the door body 10, and a hinge 3 that rotatably attaches the door body 10 to the door frame 30. The opening door 2 is provided at a position where a differential pressure is generated inside and outside, and is arranged so that the door body 10 opens toward the high pressure side.

  The door body 10 is provided with a door knob 12 as a door opening handle. The door knob 12 is attached to a key case 14 to which a cylinder 13 and a thumb turn (not shown) are integrally attached. When the door knob 12 is rotated (actuated), the latch bolt 15 appears and disappears from the side surface of the door body 10. It is like that. The key case 14 has a thin box shape and is accommodated in the door body 10. When the key is inserted into the cylinder 13 and turned, or the thumb turn is turned, the dead bolt 16 appears and disappears from the side surface of the door body 10. The door opening handle is not limited to the door knob 12 and may be a lever handle or a push door handle.

  The door frame 30 includes a three-way frame 32 that surrounds the side surface and the upper surface of the door body 10 and a lower frame 33 that surrounds the lower surface of the door body 10. The three-way frame 32 includes an upper frame portion 32a and side frame portions 32b and 32b. As shown in FIGS. 2 and 3, the upper frame portion 32 a and the side frame portions 32 b and 32 b both have substantially the same L-shaped cross-section and cover the outer peripheral edge of the door body 10 in a closed state. The peripheral part 34 and the latching | locking part 35 bent from the outer peripheral part 34 to the center side of the door main body 10 are comprised. The locking part 35 contacts the peripheral edge of the surface of the door body 10 and locks the door body 10 in a closed state. In the present embodiment, as shown in FIG. 1, in order to obtain airtightness inside and outside the opening door 2, the lower frame 33 also includes an outer peripheral edge portion 34 and a locking portion 35, and has an L-shaped cross section. It is configured.

  As shown in FIGS. 1 to 3, the door opening mechanism 1 includes a frame-side magnetic body 31 provided inside a door frame 30 that surrounds the door body 10, and a door-body side magnetic provided inside the door body 10. And a body 11. The door main body side magnetic body 11 and the frame side magnetic body 31 are arranged at positions facing each other. At least one of the frame-side magnetic body 31 and the door main body-side magnetic body 11 (both in the present embodiment) is composed of an electromagnet. Further, the door opening mechanism 1 magnetizes the electromagnet in accordance with the rotation of the door knob 12 of the door body 10 (operation of the door opening handle), and between the frame side magnetic body 31 and the door body side magnetic body 11. Magnetizing means 50 for generating a repulsive force is provided, and the door body 10 is configured to be opened by the repulsive force described above.

  The door main body side magnetic body 11 is composed of an electromagnet, and is electrically connected to the magnetizing means 50. The door main body side magnetic body 11 is magnetized by energizing the coil by the magnetizing means 50. The door main body side magnetic body 11 is accommodated in the door main body 10. Specifically, as shown in FIG. 2, the door main body side magnetic body 11 is accommodated inside the upper end edge of the door main body 10, and abuts on the locking portion 35 of the upper frame portion 32 a of the three-way frame 32. One magnetic pole (for example, N pole) is arranged to face the surface.

  The frame side magnetic body 31 is also composed of an electromagnet and is electrically connected to the magnetizing means 50. The frame-side magnetic body 31 is magnetized when the coil is energized by the magnetizing means 50. The frame side magnetic body 31 is accommodated in the door frame 30. Specifically, as shown in FIG. 2, the frame-side magnetic body 31 is housed inside the locking portion 35 of the upper frame portion 32 a of the three-sided frame 32, and on one side facing the door body 10. The magnetic poles (for example, N poles) are arranged to face each other.

  Thus, the door main body side magnetic body 11 and the frame side magnetic body 31 are arranged so that the same magnetic poles face each other, and when both are energized by the magnetizing means 50, they repel each other. The door main body side magnetic body 11 is disposed on the high pressure side, and the frame side magnetic body 31 is disposed on the low pressure side. When a repulsive force is generated, the door main body 10 is biased to the high pressure side. The magnetic force generated in the door main body side magnetic body 11 and the frame side magnetic body 31 generates a strength that generates a repulsive force that the door main body 10 can open against the wind pressure, that is, a stress larger than the door opening force. Make the magnetic force to be. The magnetic force generated in the door main body side magnetic body 11 and the frame side magnetic body 31 can be adjusted by the value of the current flowing in the magnetizing means 50.

  The magnetizing means 50 energizes the coil of the electromagnet according to the rotation of the door knob 12 of the door body 10 (operation of the door opening handle). The magnetizing means 50 is set to start energization when the door knob 12 rotates and the latch bolt 15 is submerged in the door body 10, and to stop energization after a predetermined time has elapsed from the start of energization. The stoppage of energization is not limited to setting the time from the start of energization. For example, the energization may be stopped when the door knob 12 is returned to the original position. Further, the energization may be stopped when the door body 10 is opened to a predetermined angle.

  Specifically, the magnetizing means 50 includes a power source connected to the distribution board, a converter connected to the power source, and a switch mechanism connected to the converter. The converter converts alternating current into direct current. The switch mechanism includes, for example, a rotation sensor (not shown) that detects the rotation of the rotation axis of the door knob 12, and the rotation axis of the door knob 12 rotates until the latch bolt 15 is immersed in the door body 10. When the rotation sensor detects that it has moved, a signal for sending an electric current is sent to the converter. Further, the switch mechanism is configured to send a signal for stopping the current to the converter so as to stop the energization after a predetermined time (for example, several seconds) has elapsed since the start of energization. The time from the start of energization to the stop of energization is set to a time required for the door body 10 to open to the differential pressure elimination position. When the door body 10 opens to the differential pressure elimination position, the magnetization of the electromagnet is eliminated. It is like that. That is, in this embodiment, the switch mechanism is operated by a rotation sensor and stopped by a timer. Further, the switch mechanism is configured not to energize the coil when the dead bolt 16 protrudes from the door body 10 and is locked.

  The converter and the electromagnet are connected by an electric wire 51 made of copper wire. The electric wire 51 that connects the converter and the frame-side magnetic body 31 passes through the hinge 3 from the door body 10 and extends into the door frame 30. In addition, although not shown in figure, the electric wire which connects an electricity distribution panel and a power supply passes through the inside of the hinge 3 from the inside of the wall, and extends into the door body 10.

  In the present embodiment, the power source is connected to the distribution board through which an alternating current flows. However, the present invention is not limited to this. For example, a battery may be used as a power source. In this case, the converter need not be provided, and the switch function is connected to the battery. In this way, differential pressure can be eliminated even during a power failure, and door opening / closing obstacles can be eliminated.

  The door opening mechanism 1 according to the present embodiment further includes a door check 55 that assists in opening and closing the door body 10. The door check 55 is also referred to as a door closer, and automatically closes the opened door and adjusts the closing speed. The door check 55 is provided between the upper surface of the door body 10 and the upper frame portion 32a of the three-way frame 32. The door check 55 is configured to temporarily stop the door main body 10 at a differential pressure canceling position where the door main body 10 can cancel the differential pressure inside and outside the door. As shown in FIG. 1, the differential pressure release position means that the door body 10 is opened at a predetermined angle with respect to the door frame 30 and passes between the door frame 30 and the door body 10 (open space). It is a position where the pressure difference can be eliminated by circulating air inside and outside the door body 10 and the door body 10 is not closed back to the door frame 30 side by the air circulation. The door body 10 once stopped at the differential pressure release position is opened by the person who opens the door subsequently performing an opening operation (pushing operation or pulling operation).

  Next, the operation and effect of the door opening mechanism 1 will be described while explaining the operation of each part when the door including the door opening mechanism 1 having the above-described structure is opened.

  First, a person who opens the door stands in front of the door body 10 and holds the door knob 12 to rotate it to a predetermined angle. Then, the latch bolt 15 is immersed in the door body 10 and the door body 10 can be opened. Here, the rotation sensor detects the rotation of the rotation shaft of the door knob 12, and a signal for sending current from the switch mechanism to the converter is sent. Then, a current is passed from the magnetizing means 50 to energize the electromagnet coils of the door main body side magnetic body 11 and the frame side magnetic body 31.

  Thereby, both the door main body side magnetic body 11 and the frame side magnetic body 31 are magnetized, and a repulsive force is generated between the door main body side magnetic body 11 and the frame side magnetic body 31. And by this repulsive force, the door main body 10 is urged | biased in the direction (opening direction) spaced apart from the door frame 30, and opens against the wind pressure by differential pressure | voltage.

  The door body 10 opens to the differential pressure release position and is temporarily stopped by the door check 55. In this state, air flows between the door frame 30 and the door body 10 inside and outside the door, so that the differential pressure is eliminated. Thereafter, the person who opens the door subsequently performs an opening operation (pushing operation or pulling operation) to open the door body 10. Thus, since the door main body 10 is temporarily stopped by the door check 55, the person who opens the door is not pushed or pulled by the door main body 10 while holding the door knob 12, and has a stable posture. The door can be opened.

  Here, if there is a differential pressure of 47.6 Pa or more inside and outside the door, a general door requires a door opening force of 90 N or more, which makes the door very heavy and difficult to open. In the present embodiment, the door main body 10 is automatically opened to the differential pressure release position by the repulsive force due to the magnetic force as described above, so that the differential pressure inside and outside the door is eliminated, and thereafter the door with a small force of 50 N or less. The main body 10 can be opened.

  Thereafter, the energization is stopped by a switch mechanism of the magnetizing means 50 after a predetermined time (for example, several seconds) has elapsed since the energization started. At this time, the door main body 10 is opened to the differential pressure elimination position, and in this state, the magnetization of the electromagnet is eliminated, and the repulsive force between the door main body side magnetic body 11 and the frame side magnetic body 31 is eliminated. Therefore, the door main body 10 is not subjected to stress due to magnetic force, and the differential pressure is also eliminated. Therefore, the door main body 10 is opened in the same state as a normal door after being temporarily stopped at the differential pressure elimination position. be able to. That is, since the repulsive force due to the magnetic force is not applied, the door body 10 does not open too much, and the person who opens the door is not pushed or pulled by the door body 10 while holding the door knob 12. In addition, since the energization is stopped after the door body 10 is opened to the differential pressure elimination position, the electromagnet is demagnetized after the differential pressure inside and outside the door is eliminated, and the door body 10 and the door frame are released. Since there is no air flow between the corners of the door 30, the door body 10 is not closed back to the door frame 30 side.

  As described above, in the door opening mechanism 1 according to the present embodiment, the door body due to the differential pressure generated inside and outside the door due to the repulsive force generated between the frame side magnetic body 31 and the door body side magnetic body 31. Since the door body 10 is opened against the pressure applied to the door 10, the pressure difference inside and outside the door is eliminated at that time, and thereafter, the door body can be opened smoothly with a normal force. Therefore, the door opening / closing obstacle can be eliminated.

  Furthermore, since the electromagnet is magnetized according to the rotation of the door knob 12 (operation of the door opening handle), no repulsive force is generated when the latch bolt 15 is locked to the door frame 30. Therefore, excessive stress is not applied to the door body 10 and the door frame 30.

  Further, according to the door opening mechanism 1, since the differential pressure is eliminated by opening the door body 10, it is not necessary to form an opening for adjusting the differential pressure in the door as in the prior art, and the fire prevention There is no problem. Further, since the frame-side magnetic body 31 is provided inside the door frame 30 and the door main body-side magnetic body 11 is provided inside the door main body 10, it does not require a separate installation space for each device, and is simple. Since it is a simple structure, an increase in construction costs can be suppressed.

  Next, another embodiment of the door opening mechanism according to the present invention will be described.

  In the embodiment, the door main body 10 is opened to a predetermined angle only by the repulsive force generated between the door-side magnetic body 11 and the frame-side magnetic body 31, but the present invention is not limited to this. In this embodiment, the door body is not opened only by the repulsive force, but the repulsive force is made smaller than the door opening force. That is, the repulsive force becomes an assisting force for opening the door, and the door body is opened together with the force of the person opening the door. According to such a configuration, it is necessary for a person to open the door body for the first time, but the door can be smoothly opened with a small force of 50 N or less. In the present embodiment, the same operation as in the above embodiment is performed except that the person who opens the door performs the initial opening of the door body. Moreover, the same effect as the said embodiment can be acquired.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, a design change is possible suitably. For example, in the above-described embodiment, the door opening mechanism 1 is applied to a door provided at a position where a differential pressure is generated inside and outside the door main body 10. However, the present invention is not limited to this, and the weight is simply heavy. Of course, the present invention may be applied to a door that requires a large door opening force. Even in such a case, the opening of the door can be assisted, and the door can be opened with a small door opening force.

  In the above-described embodiment, the switch mechanism of the magnetizing unit 50 has a function of sending a signal to stop the current after a predetermined time has elapsed from the start of energization to the converter, so that the door body 10 is opened to the differential pressure release position. Although the magnetization of the electromagnet is eliminated, the present invention is not limited to this. Specifically, the door check 55 is provided with an opening angle sensor that detects that the door body 10 has been opened to the differential pressure release position, and this opening angle sensor indicates that the door body 10 has been opened to the differential pressure release position. What is necessary is just to comprise so that the signal which stops an electric current may be sent to the converter of the magnetization means 50, if it detects. Even if it does in this way, since the magnetization of the electromagnet is canceled after the differential pressure is eliminated, the door body 10 can be prevented from closing and returning.

  Further, a differential pressure sensor for measuring the differential pressure inside and outside the door is provided, and this differential pressure sensor is connected to the magnetizing means 50 via a control device (not shown), and the door is set according to the value of the differential pressure. You may make it determine the electric current value sent through the coil of the electromagnet of the main body side magnetic body 11 and the frame side magnetic body 31. FIG. In this way, even when the differential pressure inside and outside the door fluctuates, an appropriate repulsive force can always be generated between the door main body side magnetic body 11 and the frame side magnetic body 31.

  For example, a differential pressure sensor as shown in FIG. 4 may be used. As shown in FIG. 4A, the differential pressure sensor 60 is provided on the side frame portion 32 b located on the hand side of the three-way frame 32 of the door frame 30. A recessed portion 36 is formed in the engaging portion 35 that receives the pressure of the door body 10 of the side frame portion 32 b, and the elastic packing 61 is accommodated in the recessed portion 36. The elastic packing 61 is formed in a size protruding from the surface of the locking portion 35. Inside the elastic packing 61, a rod-shaped member 62 provided along the pressing direction by the pressure of the door body 10 (the orthogonal direction of the door body 10), a metal plate 63 fixed to the tip of the rod-shaped member 62, A strain detecting means 64 for detecting the strain of the metal plate 63 is provided. The metal plate 63 is formed in a thin flat plate shape. The metal plate 63 is disposed orthogonally to the rod-shaped member 62, both ends in the horizontal direction are fixed to the inner wall surface of the recess 36, and the central portion thereof is configured to be elastically deformable. The strain detection means 64 includes a strain gauge and a strain sensing unit. The strain gauge is affixed to the surface of the metal plate 63 opposite to the rod-shaped member 62. The strain detection means 64 is electrically connected to a control device (not shown). The control device calculates the differential pressure inside and outside the door from the detected value of the strain gauge 64, and the value of the current passed through the electromagnet coils of the door main body side magnetic body 11 and the frame side magnetic body 31 according to the differential pressure value. To decide. The shape of the metal plate 63 is not limited to a flat plate shape, and may be another shape such as a loop shape or a curved plate shape as long as elastic deformation is possible.

  As shown in FIG. 4B, the differential pressure sensor 60 compresses the elastic packing 61 when the door body 10 side becomes high pressure and the door body 10 is pressed against the locking portion 35 side. The rod-shaped member 62 pushes the metal plate 63 and the metal plate 63 is distorted. The strain gauge of the strain detection means 64 transmits this strain to the strain sensing unit, and this strain sensing unit passes a current proportional to the strain to a control device (not shown). In the control device, the pressure difference inside and outside the door is calculated from the received current value, and the current value flowing through the electromagnet coils of the door main body side magnetic body 11 and the frame side magnetic body 31 is determined according to the value of the differential pressure. . As a result, an appropriate repulsive force is obtained between the door main body side magnetic body 11 and the frame side magnetic body 31 with the minimum necessary power, and the door main body 10 is opened by a predetermined angle to eliminate the differential pressure. Then, the door can be opened with a small door opening force (90 N or less).

  In the above-described embodiment, the door main body side magnetic body 11 is accommodated inside the upper end edge of the door main body 10, and the frame side magnetic body 31 is accommodated inside the locking portion 35 of the upper frame portion 32 a of the three-side frame 32. However, the accommodation position is not limited to this, and the door main body 10 and the door frame 30 may be provided anywhere as long as they face each other. The accommodation position of the door main body side magnetic body 11 and the frame side magnetic body 31 may be set as appropriate according to the magnetic force of the electromagnet used and the size and weight of the door main body 10. Note that the closer the storage position of the door main body side magnetic body 11 and the frame side magnetic body 31 is to the hinge 3 (the suspension base side), the larger the magnetic force is required, but the door main body side magnetic body 11 and the frame side magnetic body 31 are. The separation distance of can be short.

DESCRIPTION OF SYMBOLS 1 Door opening mechanism 10 Door main body 11 Door main body side magnetic body 12 Door knob (handle for door opening)
30 Door frame 31 Frame side magnetic body 50 Magnetizing means 55 Door check

Claims (4)

A door opening mechanism for assisting in opening a door provided at a position where differential pressure is generated inside and outside ,
A frame-side magnetic body provided on a door frame surrounding the door body;
A door main body side magnetic body disposed in a position provided on the door main body and facing the frame side magnetic body,
The frame side magnetic body is provided on the low pressure side.
The door main body side magnetic body is provided on the high pressure side,
Both said frame-side magnetic body and the door body-side magnetic bodies are constituted by an electromagnet,
Magnetizing the electromagnet according to the operation of the door opening handle of the door body to further generate a repulsive force between the frame side magnetic body and the door body side magnetic body,
The door opening mechanism is configured to urge the door body in the opening direction on the high pressure side by the repulsive force. The door opening mechanism according to claim 1, wherein the door body is configured to open by the repulsive force. Further comprising a door check spanned between the door body and the door frame,
The door opening mechanism according to claim 2, wherein the door check is configured to temporarily stop the door main body at a differential pressure canceling position where the door main body can cancel the differential pressure. The door opening mechanism according to claim 3, wherein the magnetizing unit is configured to release the magnetization of the electromagnet when the door body is opened to the differential pressure release position.

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