Patent Publication Number: US-2023147319-A1

Title: Mass spectrometer

Description:
TECHNICAL FIELD 
     The present invention relates to a mass spectrometer. 
     BACKGROUND ART 
     In a mass spectrometer, a sample is analyzed in a vacuum chamber in a vacuum state. The vacuum chamber can be opened and closed by a door, and the vacuum chamber is opened as the door is opened at the time of maintenance or the like (see, for example, Patent Document 1 below). 
       FIGS.  4 A to  4 C  are schematic cross-sectional views illustrating a configuration example of an opening and closing mechanism of a conventional door  102 .  FIG.  4 A  illustrates a state where the door  102  is open.  FIG.  4 B  illustrates a state where the door  102  is being rotated from the open state to a closed state.  FIG.  4 C  illustrates a state where the door  102  is closed. In this opening and closing mechanism, an opening  111  formed in a housing  101  can be opened and closed by the door  102 . The door  102  is rotatably supported by a hinge portion  103  extending in a vertical direction. 
     The door  102  includes a closing portion  121  and a holding portion  122  that holds the closing portion  121 . The hinge portion  103  rotatably supports one end portion of the holding portion  122 . The closing portion  121  is fixed to the holding portion  122  with a screw  123  at each of an end portion on the hinge portion  103  side and an end portion on the side opposite to the hinge portion  103  side. In this manner, an entire surface of the closing portion  121  is fixed in a state of being always in close contact with the holding portion  122 . 
     The closing portion  121  includes an O-ring  124  on a surface on the opposite side to the holding portion  122  side. When the door  102  is rotated from the open state illustrated in  FIG.  4 A  to the closed state, as illustrated in  FIG.  4 B , first, the O-ring  124  comes into contact with a peripheral edge portion of the opening  111  on the hinge portion  103  side. In this state, due to repulsive force of the O-ring  124 , the O-ring  124  is separated from a peripheral edge portion of the opening  111  on the side opposite to the hinge portion  103  side. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent Laid-Open No. 2003-346703 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In a case where a vacuum chamber  110  formed in the housing  101  is to be brought into a vacuum state in the state of  FIG.  4 B , air enters the vacuum chamber  110  through a gap  104  formed between the O-ring  124  and the peripheral edge portion of the opening  111 , and thus it is difficult to bring the vacuum chamber  110  into a vacuum state. For this reason, it is necessary to apply external force to the door  102  against repulsive force of the O-ring  124  to obtain the state as illustrated in  FIG.  4 C , and then vacuum the vacuum chamber  110 . As a means for applying the external force to the door  102 , for example, a screw (not illustrated) or the like is used. 
     The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mass spectrometer capable of closing an opening communicating with a vacuum chamber with simpler work. 
     Means for Solving the Problems 
     A first aspect of the present invention is a mass spectrometer including a housing, a door, and a hinge portion. The housing has a vacuum chamber brought into a vacuum state at the time of analysis formed inside, and an opening communicating with the vacuum chamber. The door opens and closes the opening. The hinge portion is configured to rotatably support the door between an open state and a closed state. The door includes a closing portion that closes the opening in a closed state, and a holding portion that holds the closing portion and is connected to the hinge portion. The closing portion is connected to the holding portion on the side opposite to the hinge portion side, and is configured to be separable from the holding portion on the hinge portion side. In a case where the door is rotated from an open state to a closed state, the closing portion is configured to come into contact with a peripheral edge portion of the opening on the side opposite to the hinge portion side before the closing portion comes into contact with a peripheral edge portion of the opening on the hinge portion side. 
     Effects of the Invention 
     According to the first aspect of the present invention, it is possible to bring a closing portion into contact with a peripheral edge portion of an opening on the side opposite to a hinge portion side by rotating a door from an open state to a closed state. Thereafter, it is possible to bring the closing portion into close contact with a peripheral edge portion of the opening on the hinge portion side only by separating the closing portion from a holding portion and bringing the closing portion close to the opening on the hinge portion side. Therefore, it is possible to close the opening communicating with a vacuum chamber by simpler work. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram illustrating a configuration example of a mass spectrometer. 
         FIG.  2    is a schematic side view for explaining a configuration around a door, illustrating a state in which the door is opened. 
         FIG.  3 A  is a schematic cross-sectional view for explaining opening and closing operation of the door, and illustrates a state before a seal member comes into contact with a peripheral edge portion of an opening. 
         FIG.  3 B  is a schematic cross-sectional view for explaining the opening and closing operation of the door, and illustrates a state in which the opposite side to the hinge portion side of the seal member is in contact with the peripheral edge portion of the opening. 
         FIG.  3 C  is a schematic cross-sectional view for explaining the opening and closing operation of the door, and illustrates a state in which the opposite side to the hinge portion side of the seal member is compressed against the peripheral edge portion of the opening. 
         FIG.  3 D  is a schematic cross-sectional view for explaining the opening and closing operation of the door, and illustrates a state in which the entire seal member is compressed against the peripheral edge portion of the opening. 
         FIG.  4 A  is a schematic cross-sectional view illustrating a configuration example of a conventional door opening and closing mechanism, and illustrates a state where the door is in an open state. 
         FIG.  4 B  is a schematic cross-sectional view illustrating a configuration example of the conventional door opening and closing mechanism, and illustrates a state where the door is being rotated from the open state to a closed state. 
         FIG.  4 C  is a schematic cross-sectional view illustrating a configuration example of the conventional door opening and closing mechanism, and illustrates a state where the door is in the closed state. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     1. Overall Configuration of Mass Spectrometer 
       FIG.  1    is a schematic diagram illustrating a configuration example of a mass spectrometer  1 . The mass spectrometer  1  illustrated in  FIG.  1    is a gas chromatograph mass spectrometer that performs mass spectrometry on a component in a sample separated by gas chromatography. The mass spectrometer  1  includes a gas chromatograph unit  2  and a mass spectrometry unit  3 . 
     The gas chromatograph unit  2  includes a column (not illustrated). During analysis, carrier gas is introduced into the column together with a sample, and each component in the sample is separated in a process where the sample passes through the column. Each component in the sample separated in the column is sequentially supplied to the mass spectrometry unit  3 . The carrier gas is, for example, inert gas such as nitrogen gas or helium gas, but is not limited to the inert gas, and may be another type of gas such as hydrogen gas. 
     The mass spectrometry unit  3  includes a hollow housing  300 . An ionization chamber  31 , a first vacuum chamber  32 , and a second vacuum chamber  33  are formed inside the housing  300 . The mass spectrometry unit  3  includes a vacuum pump (not illustrated). At the time of analysis, the ionization chamber  31 , the first vacuum chamber  32 , and the second vacuum chamber  33  can be brought into a vacuum state as the vacuum pump is driven. The ionization chamber  31 , the first vacuum chamber  32 , and the second vacuum chamber  33  are vacuum chambers  30  communicating with each other, and are configured such that degree of vacuum increases in a stepwise manner in this order. 
     The carrier gas is supplied from the gas chromatograph unit  2  to the ionization chamber  31  together with each sample component. Each sample component is ionized in the ionization chamber  31 . Examples of a method of ionization include, but are not limited to, electron ionization (EI), positive chemical ionization (PCI), negative chemical ionization (NCI), and the like. 
     The first vacuum chamber  32  communicates with the ionization chamber  31  via an opening  321 . Ions generated in the ionization chamber  31  are introduced into the first vacuum chamber  32  through the opening  321 . The ions introduced into the first vacuum chamber  32  are converged by an ion guide  322  and flow into the second vacuum chamber  33 . 
     The second vacuum chamber  33  is provided with, for example, a quadrupole filter  331  and a detector  332 . The Ions flowing from the first vacuum chamber  32  into the second vacuum chamber  33  are separated according to a mass-to-charge ratio by the quadrupole filter  331 , and only the ions having a specific mass-to-charge ratio pass through the quadrupole filter  331 . The ions passing through the quadrupole filter  331  are incident on the detector  332 . In the detector  332 , current corresponding to the number of ions that reach the detector  332  is output as a detection signal. 
     The mass spectrometry unit  3  is provided with a door  4  for opening and closing the vacuum chamber  30 . In this example, the door  4  is attached in an openable and closable manner to a part of a wall surface  301  that partitions the ionization chamber  31  in the housing  300 . However, for example, the door  4  may be provided on a wall surface that partitions the vacuum chamber  30  other than the ionization chamber  31 , such as the first vacuum chamber  32  or the second vacuum chamber  33 . 
     Hereinafter, the door  4  side of the housing  300  is referred to as the front side, and the side opposite to the door  4  side is referred to as the rear side. The wall surface  301  to which the door  4  is attached is inclined with respect to a vertical direction. Specifically, since a lower portion of the wall surface  301  is positioned further to the front side than an upper portion, the wall surface  301  is inclined to face the upper side than the vertical direction. An inclination angle of the wall surface  301  with respect to the vertical direction can be optionally set within a range of, for example, more than 0° and 90° or less. In this manner, in a state where the door  4  is closed, weight of the door  4  acts on the wall surface  301  of the housing  300 . 
     2. Configuration Around Door 
       FIG.  2    is a schematic side view for explaining a configuration around the door  4 , illustrating a state in which the door  4  is opened. As illustrated in  FIG.  2   , the door  4  is attached in an openable and closable manner to the housing  300  in which the vacuum chamber  30  is formed. Specifically, the door  4  and the housing  300  are connected via one or a plurality of hinge portions  5 . The door  4  is openable and closable by rotating about the hinge portion  5 . In this example, the door  4  is rotatably supported by the hinge portion  5  about an axis L inclined with respect to the vertical direction. The axis L is inclined in a direction that the upper side of the axis L approaches the housing  300  side (rear side). 
     An opening  302  for a worker to insert a hand or a tool at the time of maintenance or the like in the housing  300  is formed in the wall surface  301  of the housing  300 . The opening  302  is formed in a square shape having a horizontal width and a vertical width of about 10 to 20 cm respectively, for example, but is not limited to such a shape. 
     The opening  302  communicates with the vacuum chamber  30  and is opened and closed by the door  4 . The door  4  is rotatably supported by the hinge portion  5  between an open state in which the opening  302  is opened (a state illustrated in  FIG.  2   ) and a closed state in which the opening  302  is closed by the door  4 . An end portion of the door  4  on the side opposite to the hinge portion  5  side is separated from the opening  302  in the open state and approaches the opening  302  in the closed state. 
     The door  4  includes a closing portion  41  and a holding portion  42 . The closing portion  41  is a plate-like member having a planar shape larger than the opening  302 , and closes the opening  302  in the closed state. The closing portion  41  can be formed of a material containing, for example, aluminum with a thickness of about 10 to 20 mm, but is not limited to such a configuration. 
     The closing portion  41  is provided with a seal member  43  on a surface (inner surface  411 ) on the vacuum chamber  30  side in the closed state. The seal member  43  is composed of an annular O-ring larger than the opening  302  of the housing  300 . When the door  4  is in the closed state, the seal member  43  comes into contact with a peripheral edge portion of the opening  302  in the housing  300 . 
     In this example, the closing portion  41  is formed in a rectangular shape. The seal member  43  is formed in a rectangular annular shape, and an outer periphery of the seal member  43  is smaller than an outer periphery of the closing portion  41 . The opening  302  of the housing  300  is formed in a rectangular shape smaller than an inner periphery of the seal member  43 . However, the opening  302  is not limited to a rectangular shape, and may have another shape such as a circular shape. Further, an optional shape can be employed for the closing portion  41  and the seal member  43  according to the shape of the opening  302 . 
     The holding portion  42  holds the closing portion  41 . Specifically, the holding portion  42  is attached in a state of abutting on a surface (outer surface) of the closing portion  41  on the side opposite to the seal member  43  side. The holding portion  42  is formed of, for example, a plate-like member thinner than the closing portion  41 . The holding portion  42  can be formed of, for example, a material containing stainless steel or the like with a thickness of about  1  to  2  mm, but is not limited to such a configuration. The holding portion  42  has an overhanging portion  421  formed so as to overhang further to the outer side than the closing portion  41 . The hinge portion  5  is connected to the overhanging portion  421  of the holding portion  42 . 
     When the door  4  is rotated from the open state to the closed state, the closing portion  41  is positioned with respect to the opening  302  by a positioning mechanism  6 . The positioning mechanism  6  includes, for example, a protruding portion  61  and a recessed portion  62 . The protruding portion  61  is formed on a peripheral edge portion of the opening  302  in the housing  300 . The recessed portion  62  is formed in a region on the outer side than the seal member  43  on the inner surface  411  of the closing portion  41 . 
     More specifically, the protruding portion  61  is formed in an end portion of a peripheral edge portion of the opening  302  on the side opposite to the hinge portion  5  side. The recessed portion  62  is formed in an end portion of the inner surface  411  of the closing portion  41  on the side opposite to the hinge portion  5  side. An inner diameter of the recessed portion  62  is slightly larger than an outer diameter of the protruding portion  61 . When the door  4  is rotated from the open state to the closed state, the protruding portion  61  is inserted into the recessed portion  62 , so that the closing portion  41  is positioned on the side opposite to the hinge portion  5  side, and the closing portion  41  is always in the closed state at a fixed position with respect to the opening  302 . 
     The hinge portion  5  is attached to the housing  300  via a spacer  7 . The spacer  7  is a plate-like member for adjusting a distance between the housing  300  and the hinge portion  5 . By appropriately setting a thickness of the spacer  7 , the seal member  43  can be brought into contact with a peripheral edge portion of the opening  302  on the side opposite to the hinge portion  5  side before the seal member  43  comes into contact with a peripheral edge portion of the opening  302  on the hinge portion  5  side when the door  4  is rotated from the open state to the closed state. 
     3. Opening and Closing Operation of Door 
       FIGS.  3 A to  3 D  are schematic cross-sectional views for explaining opening and closing operation of the door  4 .  FIG.  3 A  illustrates a state before the seal member  43  comes into contact with a peripheral edge portion of the opening  302 .  FIG.  3 B  illustrates a state in which the side of the seal member  43  opposite to the hinge portion  5  side is in contact with a peripheral edge portion of the opening  302 .  FIG.  3 C  illustrates a state in which the side of the seal member  43  opposite to the hinge portion  5  side is compressed against the peripheral edge portion of the opening  302 .  FIG.  3 D  illustrates a state in which the entire seal member  43  is compressed against the peripheral edge portion of the opening  302 . 
     As illustrated in  FIG.  3 A , when the door  4  is closed until the inner surface  411  of the closing portion  41  is parallel to the peripheral edge portion of the opening  302 , the seal member  43  is not yet in contact with the peripheral edge portion of the opening  302 . This is because a position of the hinge portion  5  with respect to the housing  300  is adjusted by the spacer  7  described above. However, it is also possible to adjust a position of the hinge portion  5  with respect to the housing  300  without using the spacer  7 . 
     In the state of  FIG.  3 A , the closing portion  41  is positioned with respect to the opening  302  by the above-described positioning mechanism  6 . When the door  4  is further rotated from this state to the closed state, as illustrated in  FIG.  3 B , an end portion (second end portion  432 ) on the side opposite to the hinge portion  5  side comes into contact with the peripheral edge portion of the opening  302  before an end portion (first end portion  431 ) on the hinge portion  5  side of the seal member  43  comes into contact therewith. In this state, the first end portion  431  of the seal member  43  is not in contact with the peripheral edge portion of the opening  302 . However, when the door  4  is slightly rotated further to the closed state and the second end portion  432  of the seal member  43  is compressed, the first end portion  431  of the seal member  43  is also in contact with the peripheral edge portion of the opening  302  as illustrated in  FIG.  3 C . 
     In the state of  FIG.  3 C , the entire circumference of the seal member  43  is in contact with the peripheral edge portion of the opening  302 . Therefore, if a vacuum pump is driven in this state, the vacuum chamber  30  can be evacuated. At this time, when the closing portion  41  is in a state of being completely fixed to the holding portion  42 , the inner surface  411  of the closing portion  41  is not parallel to the peripheral edge portion of the opening  302 , and only the second end portion  432  side of the seal member  43  is in a state of being compressed while the first end portion  431  of the seal member  43  is not sufficiently compressed. 
     In order to prevent such a non-uniform compressed state of the seal member  43 , in the present embodiment, the closing portion  41  is connected to the holding portion  42  on the side opposite to the hinge portion  5  side, and is configured to be separable from the holding portion  42  on the hinge portion  5  side. Specifically, the closing portion  41  is fixed to the holding portion  42  only at an end portion on the side opposite to the hinge portion  5  side. 
     In this example, a connector  44  such as a screw connects the closing portion  41  and the holding portion  42  to each other on the side opposite to the hinge portion  5  side, but the closing portion  41  and the holding portion  42  are not connected to each other on the hinge portion  5  side. Therefore, when force is applied in a direction in which an end portion of the closing portion  41  on the hinge portion  5  side approaches the housing  300 , the closing portion  41  rotates toward the housing  300  side about the connector  44 , and a gap S is formed between an outer surface  412  of the closing portion  41  and the holding portion  42  as illustrated in  FIG.  3 D . At this time, the holding portion  42  is bent in the vicinity of the connector  44  along with the rotation of the closing portion  41 . The gap S is, for example, about  1  to  2  mm, but is not limited to this size. 
     Note that “the side opposite to the hinge portion  5  side ” means the side opposite to the hinge portion  5  side as viewed from the closing portion  41 , and is, for example, a region including a portion that first comes into contact with the peripheral edge portion of the opening  302  when the closing portion  41  rotates about the hinge portion  5  in a case where the closing portion  41  is configured not to be separated from the holding portion  42 . On the other hand, the “hinge portion  5  side” means the hinge portion  5  side as viewed from the closing portion  41 , and is, for example, a region closer to the hinge portion  5  than a region on the side opposite to the hinge portion  5  side, and is a region including a portion that comes into contact with the peripheral edge portion of the opening  302  when the closing portion  41  is separated from the holding portion  42 . For example, with respect to the center of the closing portion  41  in a lateral direction (left-right direction in  FIGS.  3 A to  3 D ), the left side may be the “hinge portion  5  side” and the right side may be the “side opposite to the hinge portion  5  side”. 
     In the present embodiment, since the axis L of the hinge portion  5  is inclined as illustrated in  FIG.  2   , the closing portion  41  rotates about the connector  44  toward the housing  300  side due to weight of the closing portion  41  from the state of  FIG.  3 C . As a result, as illustrated in  FIG.  3 D , the entire seal member  43  (the first end portion  431  and the second end portion  432 ) is compressed to be in close contact with the peripheral edge portion of the opening  302 , and the inner surface  411  of the closing portion  41  becomes parallel to the peripheral edge portion of the opening  302 . 
     4. Variation 
     The positioning mechanism  6  is not limited to the configuration including the protruding portion  61  provided on the housing  300  and the recessed portion  62  provided on the closing portion  41 . For example, the configuration may be such that the protruding portion  61  is provided on the closing portion  41  and the recessed portion  62  is provided on the housing  300 . Alternatively, the protruding portion  61  or the recessed portion  62  may be provided on a portion (for example, the holding portion  42 ) other than the closing portion  41  on the door  4 . Furthermore, the configuration may be such that the door  4  is positioned using another member such as a magnet without limitation to the protruding portion  61  and the recessed portion  62 . 
     The configuration of the seal member  43  is not limited to one in which the seal member  43  is provided on the closing portion  41  of the door  4 , and may be one in which the seal member  43  is provided on the peripheral edge portion of the opening  302 . In this case, when the door  4  is rotated from the open state to the closed state, the closing portion  41  may be configured to come into contact with the seal member  43  on the side opposite to the hinge portion  5  side before the closing portion  41  comes into contact with the seal member  43  provided on a peripheral edge portion of the opening  302  on the hinge portion  5  side. 
     The configuration of the door  4  is not limited to the configuration in which the door  4  is rotatable about the axis L inclined in a front-rear direction with respect to the vertical direction. For example, the door  4  may be configured to be rotatable about an axis extending in a horizontal direction at an upper end portion or a lower end portion of the door  4 . 
     The configuration of the closing portion  41  is not limited to the configuration in which the closing portion  41  can be separated from the holding portion  42  as the holding portion  42  is elastically deformed. For example, even when the closing portion  41  is configured to be connected to the holding portion  42  via another hinge portion (not illustrated) on the side opposite to the hinge portion  5  side, the closing portion  41  can be separated from the holding portion  42  on the hinge portion  5  side. 
     The configuration of the closing portion  41  is not limited to the configuration in which the closing portion  41  is rotatable toward the housing  300  side by its own weight with respect to the holding portion  42 . For example, the configuration may be such that an end portion of the closing portion  41  on the hinge portion  5  side can be separated from the holding portion  42  by using the force other than gravity, such as magnetic force generated by using a magnet, and the end portion can be brought closer to the housing  300 . Alternatively, an end portion of the closing portion  41  on the hinge portion  5  side may be separated from the holding portion  42  by the user applying force in a direction in which the end portion approaches the housing  300 . 
     5. Aspect 
     It is to be understood by those skilled in the art that a plurality of exemplary embodiments described above are specific examples of an aspect described below. 
     (Clause 1) A mass spectrometer according to one aspect includes: 
     a housing in which a vacuum chamber brought into a vacuum state at the time of analysis is formed, the housing having an opening communicating with the vacuum chamber; 
     a door for opening and closing the opening; and 
     a hinge portion configured to rotatably support the door between an open state and a closed state, wherein 
     the door includes a closing portion that closes the opening in a closed state, and a holding portion that holds the closing portion and is connected to the hinge portion, 
     the closing portion is connected to the holding portion on the side opposite to the hinge portion side, and is configured to be separable from the holding portion on the hinge portion side, and 
     in a case where the door is rotated from an open state to a closed state, the closing portion is configured to come into contact with a peripheral edge portion of the opening on the side opposite to the hinge portion side before the closing portion comes into contact with the peripheral edge portion of the opening on the hinge portion side. 
     According to the mass spectrometer described in Clause 1, the closing portion can be brought into contact with a peripheral edge portion of the opening on the side opposite to the hinge portion side by rotating the door from the open state to the closed state. Thereafter, it is possible to bring the closing portion into close contact with a peripheral edge portion of the opening on the hinge portion side only by separating the closing portion from a holding portion and bringing the closing portion close to the opening on the hinge portion side. Therefore, it is possible to close the opening communicating with a vacuum chamber by simpler work. 
     (Clause 2) In the mass spectrometer according to Clause 1, in a case where the door is rotated from an open state to a closed state, the closing portion may be configured to come into close contact with the peripheral edge portion of the opening on the hinge portion side by own weight of the closing portion after the closing portion comes into contact with a peripheral edge portion of the opening on the side opposite to the hinge portion side. 
     According to the mass spectrometer described in Clause 2, due to own weight of the closing portion, the closing portion can be separated from the holding portion on the hinge portion side and brought close to the opening, and the closing portion can be automatically brought into close contact with the peripheral edge portion of the opening on the hinge portion side. Therefore, it is possible to close the opening communicating with the vacuum chamber by simpler work without providing an additional configuration. 
     (Clause 3) In the mass spectrometer according to Clause 2, the hinge portion may be configured to rotatably support the door about an axis inclined in a direction in which the upper side of the axis approaches the housing side. 
     According to the mass spectrometer described in Clause 3, the closing portion can be smoothly separated from the holding portion by its own weight and brought close to the opening about the axis, and the closing portion can be automatically brought into close contact with the peripheral edge portion of the opening on the hinge portion side. 
     (Clause 4) In the mass spectrometer according to any one of Clauses 1 to 3, in a case where the door is rotated from an open state to a closed state, the closing portion may be configured to come into close contact with the peripheral edge portion of the opening on the hinge portion side as the holding portion bends after the closing portion comes into contact with the peripheral edge portion of the opening on the side opposite to the hinge portion side. 
     According to the mass spectrometer described in Clause 4, it is possible to realize a configuration in which the closing portion can be separated from the holding portion on the hinge portion side by using elastic deformation of the holding portion. 
     (Clause 5) In the mass spectrometer according to any one of Clauses 1 to 4, 
     the closing portion may include a seal member that comes into contact with a peripheral edge portion of the opening in a closed state, and 
     in a case where the door is rotated from an open state to a closed state, the seal member may be configured to come into contact with the peripheral edge portion of the opening on the side opposite to the hinge portion side before the seal member comes into contact with the peripheral edge portion of the opening on the hinge portion side. 
     According to the mass spectrometer described in Clause 5, the seal member can be brought into contact with the peripheral edge portion of the opening on the side opposite to the hinge portion side by rotating the door from the open state to the closed state. Thereafter, it is possible to bring the seal member into close contact with the peripheral edge portion of the opening on the hinge portion side only by separating the closing portion from the holding portion and bringing the closing portion close to the opening on the hinge portion side. Therefore, it is possible to close the opening communicating with the vacuum chamber by the seal member by simpler work. 
     (Clause 6) The mass spectrometer according to any one of Clauses 1 to 5 may further include a positioning mechanism that positions the closing portion on the side opposite to the hinge portion side when the door is rotated from an open state to a closed state. 
     According to the mass spectrometer described in Clause 6, when the door is rotated from the open state to the closed state, the closing portion is always in the closed state at a fixed position with respect to the opening, so that the vacuum chamber can be reliably sealed to be in the vacuum state. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
           1  mass spectrometer 
           4  door 
           5  hinge portion 
           6  positioning mechanism 
           30  vacuum chamber 
           41  closing portion 
           42  holding portion 
           43  seal member 
           300  housing 
           302  opening 
         L axis