Patent Publication Number: US-2020303145-A1

Title: Relay

Description:
RELAY 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2019-051034, filed Mar. 19, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a relay. 
     BACKGROUND 
     Relays (electromagnetic relays) comprise an electromagnet, an armature, a movable terminal including a movable contact, and a fixed terminal including a fixed contact. In such relays, the armature is moved by the excitation of the electromagnet, whereby the armature is pressed against the movable terminal, and contact between the movable contact and the fixed contact come is established. 
     JP 5085754 B discloses a relay with an opening/closing part including one movable contact piece having a pair of movable contact and two fixed contact piece each having one fixed contact. This relay has an arc-extinguishing member including a permanent magnet for extinguishing an arc generated at the opening/closing part and a connecting member made from magnetic material for magnetically connecting the permanent magnet. 
     JP 5202072 B discloses a relay with two opening/closing parts respectively having a movable terminal with one movable contact and a fixed terminal with one fixed contact, wherein the opening/closing parts constitute separate circuits. A permanent magnet is provided to each opening/closing part, and each permanent magnet extinguishes an arc generated at the corresponding opening/closing part. 
     SUMMARY 
     In a relay having a contact structure including a plurality of movable contacts and a plurality of fixed contacts, a structure for arc-extinguishing may be complicated, the relay may increase in size, and a degree of difficulty in assembling the relay may be increased. 
     One aspect of the present invention is a relay comprising: a first terminal having a pair of first contacts; a second terminal having a pair of second contacts which are opposed to the pair of first contacts so as to contact and separate from the respective first contacts; and a first magnet positioned on a side opposed to the pair of first contacts of the first terminal and between the pair of first contacts so that the first magnet does not contact the first terminal, wherein the first magnet is magnetized in a direction along which the pair of first contacts and the pair of second contacts are opposed. 
     According to the relay of the one aspect, by virtue of the location of the first magnet and the magnetizing direction, the arcs, generated at two sets of contacts constituted by the first and second contacts, can be elongated in a direction different from the alignment direction of the first (or second) contacts and can be extinguished. As a result, the distance between the first (or second) contacts in the alignment direction can be increased, and the arcs generated at the two sets of contacts can be extinguished. Moreover, the arc can be extinguished by a simple structure, and the relay can be easily assembled. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a relay according to an embodiment; 
         FIG. 2  is a top view of an inner structure of the relay; 
         FIGS. 3A and 3B  are views explaining a motion of an armature; 
         FIG. 4  is a view of a positional relationship of components of the relay; 
         FIG. 5  is a view of a location of a first magnet viewed in a direction V of  FIG. 4 ; 
         FIG. 6  is a side view of the first magnet; 
         FIG. 7  is a view of locations of the first magnet and a yoke according to a modification; 
         FIG. 8  is a view of locations of the first magnet and a second magnet according to a modification; 
         FIG. 9  is an exploded perspective view of an attachment member and the other components of the modification; 
         FIGS. 10A and 10B  are views explaining a fixing method of the attachment member of  FIG. 9 ; 
         FIG. 11  is an exploded perspective view of a yoke and the other components of the modification; 
         FIG. 12  is a view of a positional relationship of components of the modification; and 
         FIG. 13A and 13B  are views explaining a fixing method of the first magnet of the modification. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will be described below with reference to the attached drawings.  FIG. 1  is an exploded perspective view of a relay  2 . The relay  2  comprises a housing  4  in which various components are incorporated, and a cover  6  attached to the housing  4 . The housing  4  and the cover  6  may, for example, be formed from resin.  FIG. 2  is a top view of the relay  2  while the cover  6  is removed. 
     The components incorporated in the housing  4  include an electromagnet  8 , an actuator  10 , a pair of plate-like armatures  12 ,  14 , a permanent magnet  16 , a card  18 , a first terminal  20 , a conductive base  21 , and a second terminal  22 . The electromagnet  8  includes a coil assembly  24 , an iron core  26 , and a yoke  28 . 
     The coil assembly  24  includes four coil terminals  30   a,    30   b,    30   c,    30   d,  a coil  32  having two wirings, and a bobbin  34  on which the coil  32  is wound. The coil terminals  30   a,    30   c  are connected to one of the wirings of the coil  32 , and coil terminals  30   b,    30   d  are connected to the other wiring. The bobbin  34  may, for example, be formed from resin. 
     A shaft  26   a  of the iron core  26  is inserted into a cavity  34   a  of the bobbin  34  and a hole  28   a  of the yoke  28 , so that the shaft is positioned at the center of the coil  32 . 
     By inserting a shaft  10   a  of the actuator  10  into a hole  4   a  of the hosing  4 , the actuator  10  is attached to the housing  4  rotatably about the shaft  10   a.  The actuator  10  may, for example, be formed from resin. 
     The armatures  12 ,  14  and the card  18  are attached to the actuator  10 . The armatures  12 ,  14  may be formed from magnetic material such as iron. 
     The permanent magnet  16  is positioned between the armatures  12 ,  14 , and the permanent magnet  16  and the armatures  12 ,  14  form a magnetic path. 
     The first terminal  20  has a pair of contact members  42 ,  44  attached to a front end  62 . The contact member  42  has a first contact  50 , and an attachment part  54  attached to the front end  62 . The contact member  44  has a first contact  52 , and an attachment part  56  attached to the front end  62 . 
     The first terminal  20  has a first extended part  103  extending from the front end  62 , and a proximal end  63  positioned at the opposite side of the front end  62  with respect to the first extended part  103 . In this embodiment, the front end  62 , the first extended part  103  and the proximal end  63  are configured by a plate having conductivity and springiness. 
     Holes  64 ,  66  are formed on the front end  62 . By inserting the attachment parts  54 ,  56  into the holes  64 ,  66 , respectively, and then swaging the attachment parts, the first contacts  50 ,  52  are fixed to the front end  62 . The first contacts  50 ,  52  are electrically connected via a plate having conductivity. 
     The first terminal  20  is connected to the base  21  by connecting members  46 ,  48 . The base  21  has a front end  72  exposed to the outside of the relay  2 , an extended part  107  extending from the front end  72 , and a proximal end  74  positioned at the opposite side of the front end  72  with respect to the first extended part  107 . 
     Holes  68 ,  70  are formed on the proximal end  63 , and holes  76 ,  78  are formed on the proximal end  74 . While the hole  68  is superimposed on the hole  76  and the hole  70  is superimposed on the hole  78 , by inserting the attachment parts  58  into the holes  68 ,  76  and inserting the attachment parts  60  into the holes  70 ,  78 , and then swaging the attachment parts, the first terminal  20  is fixed to the base  21 . 
     The base  21  supports the first terminal  20  including the plate having springiness, and constitutes a movable terminal  23 . The first terminal  20  and the base  21  may, for example, be formed from a metal plate. 
     The second terminal  22  has a pair of contact members  82 ,  84  attached to a front end  94 . The contact member  82  has a second contact  86 , and an attachment part  90  attached to the front end  94 . The contact member  84  has a second contact  88 , and an attachment part  92  attached to the front end  94 . 
     The second terminal  22  has a second extended part  105  extending from the front end  94 , and a proximal end  96  positioned at the opposite side of the front end  94  with respect to the second extended part  105 . The front end  94 , the second extended part  105  and the proximal end  96  are configured by a plate having conductivity. 
     Holes  98 ,  100  are formed on the front end  94 . By inserting the attachment parts  90 ,  92  into the holes  98 ,  100 , respectively, and then swaging the attachment parts, the second contacts  86 ,  88  are fixed to the front end  94 . The second contacts  86 ,  88  are electrically connected via a plate having conductivity. 
     The second contact  86  and the first contact  50  are opposed to each other so that they can contact and separate from each other, and the second contact  88  and the first contact  52  are opposed to each other so that they can contact and separate from each other. The first contacts  50 ,  52  are electrically connected to each other, and the second contacts  86 ,  88  are electrically connected to each other. Therefore, the contact structure of this embodiment is a twin contact structure in which an opening/closing motion is performed by the electrically connected first contacts  50 ,  52  and the electrically connected second contacts  86 ,  88 . A set of the second contact  86  and the first contact  50  and a set of the second contact  88  and the first contact  52  are electrically connected to each other in parallel, when the closing motion of the relay  2  is performed. 
     With reference to  FIGS. 2, 3   a  and  3   b , the opening/closing motion of the relay  2  is explained.  FIGS. 3 a  and 3 b    show a positional relationship between the armatures  12 ,  14  attached to the actuator  10 , the permanent magnet  16 , the iron core  26 , and the yoke  28 . In this embodiment, the first terminal is the movable terminal, and the second terminal  22  is the fixed terminal. 
       FIG. 3A  shows the positional relationship between the first contacts  50 ,  52  and the second contacts  86 ,  88  when the contacts are separated from each other, and  FIG. 3B  shows the positional relationship between the first contacts  50 ,  52  and the second contacts  86 ,  88  when the contacts contact each other. 
     In  FIG. 3A , the armatures  12 ,  14  are adsorbed to the iron core  26  and the yoke  28 , respectively. In  FIG. 3B , the armature  14  is separated from the yoke  28 , and the armature  12  is adsorbed to the yoke  28 . When the electromagnet  8  is not excited, one of the positional relationships of  FIGS. 3 a  and 3 b    is maintained, due to a magnetic force of the permanent magnet  16 . Hereinafter, the arrangement of  FIGS. 3 a    is explained as a state before the electromagnet  8  is excited. 
     In the relay  2 , a voltage is applied between the coil terminals  30   a,    30   c  so as to excite the electromagnet  8  and generate a magnetic force in a direction A of  FIG. 3B  larger than the magnetic force of the permanent magnet  16 . Due to this, the armatures  12 ,  14  and the permanent magnet  16  are shifted from the positions of  FIG. 3A  to the positions of  FIG. 3B . According to the shift, the actuator  10  is rotated in a direction of an arrow  101  of  FIG. 2 , the card  18  interlocking with the actuator  10  presses and moves the first terminal  20  in the vertical direction of  FIG. 2 , and the first contacts  50 ,  52  come into contact with the second contacts  86 ,  88 , respectively. 
     On the other hand, a voltage is applied between the coil terminals  30   b,    30   d  so as to excite the electromagnet  8  and generate a magnetic force in a direction B of  FIG. 3B  larger than the magnetic force of the permanent magnet  16 . Due to this, the armatures  12 ,  14  and the permanent magnet  16  are shifted from the positions of  FIG. 3B  to the positions of  FIG. 3A . According to the shift, the actuator  10  is rotated in the opposite direction of the arrow  101 , the pressing force of the card  18  against the first terminal  20  is released, and the first contacts  50 ,  52  are separated from the second contacts  86 ,  88 , respectively. 
     Due to the above configuration, the relay  2  opens/closes the first contacts  50 ,  52  and the second contacts  86 ,  88 . This embodiment is merely an example, and thus an arbitrary configuration may be used for the opening/closing motion. The opening/closing motion may be performed by inverting each direction of the applied voltage between the coil terminals  30   a,    30   c  and between the coil terminals  30   b,    30   d.  Further, the first terminal  20  may be the fixed terminal, and the second terminal  22  may be the movable terminal. 
     With reference to  FIGS. 4 to 6 , a first magnet  102  is explained.  FIGS. 4, 5 and 6  show the positional relationship between the first terminal  20 , the base  21 , the second terminal  22  and the first magnet  102 . The first magnet  102  of  FIG. 4  is formed as a rectangular parallelepiped. The first magnet  102  may, for example, be formed from ferrite, samarium-cobalt, or neodymium, etc. 
     When the difference in the electrical potentials is generated between the first terminal  20  and the second terminal  22  during the opening/closing motion, an arc may be generated between the first contact  50  and the second contact  86  and/or between the first contact  52  and the second contact  88 . The first magnet  102  is provided to the relay  2  in order to extinguish the arc. 
     The first magnet  102  is positioned on a side opposed to the first contacts  50 ,  52  of the first terminal  20  and on a position corresponding to between the pair of first contacts  50 ,  52  so that the first magnet  102  does not contact the first terminal  20 . The illustrated first magnet  102  is positioned on a surface  21   a  of the base  21  and equidistant from the first contacts  50 ,  52 . 
     The first magnet  102  is magnetized in a direction along which the first contacts  50 ,  52  and the second contacts  86 ,  88  are opposed. As exemplified in  FIG. 5 , the first magnet  102  is magnetized so that a surface  102   a  near the first contacts  50 ,  52  has a polarity of N-pole and a surface  102   b  far from the first contacts  50 ,  52  has a polarity of S-pole, whereby magnetic fluxes  104 ,  106  are generated. 
     Hereinafter, a principle for extinguishing an arc by the first magnet  102  is explained, by using an example wherein the current flows from the first terminal  20  to the second terminal  22  via the first contacts  50 ,  52  and the second contacts  86 ,  88 , in a direction of an arrow  108  of  FIG. 5 . 
     Between the first contact  52  and the second contact  88 , the flux  104  acts in the left direction in  FIG. 5 . Therefore, based on Fleming&#39;s left-hand rule, a Lorentz force acts from a back side to a front side of  FIG. 5 , between the first contact  52  and the second contact  88 . As a result, the arc is elongated in a direction C in  FIG. 6 , and then is extinguished. 
     Between the first contact  50  and the second contact  86 , the flux  106  acts in the right direction in  FIG. 5 . Therefore, based on Fleming&#39;s left-hand rule, a Lorentz force acts from the front side to the back side of  FIG. 5 , between the first contact  50  and the second contact  86 . As a result, the arc is elongated in a direction D in  FIG. 6 , and then is extinguished. 
     When the current flows in the opposite direction of the arrow  108  in  FIG. 5 , based on Fleming&#39;s left-hand rule, the directions of the Lorentz force due to the fluxes  104 ,  106  are opposite to the directions as described above. Therefore, the arc generated between the first contact  52  and the second contact  88  is elongated in the direction D, the arc generated between the first contact  50  and the second contact  86  is elongated in the direction C, and then the arcs are extinguished. 
     Due to the above configuration, the arcs generated between the first contact  52  and the second contact  88  and between the first contact  50  and the second contact  86  can be extinguished, without locating the first magnet  102  in the juxtaposing direction of the first contacts  50 ,  52  or the second contacts  86 ,  88 . Further, the arc is not elongated in the juxtaposing direction of the first contacts  50 ,  52  or the second contacts  86 ,  88 . As a result, in the relay  2 , the dimension in the juxtaposing direction of the first contacts  50 ,  52  or the second contacts  86 ,  88  can be reduced, while ensuring the arc-extinguishing property. Moreover, since the arc can be extinguished by a simple structure, the assembling of the relay is facilitated. 
     In addition, the first magnet  102  may be magnetized so that the surface  102   a  is the S-pole and the surface  102   b  is the N-pole. 
     As shown in  FIGS. 4 and 6 , the first extended part  103  and the second extended part  105  extend in opposite directions to each other. By locating the conductive first extended part  103  or the conductive second extended part  105  in the direction C or D along which the arc is elongated, the arc is elongated so as to be moved on the first extended part  103  and the second extended part  105  without staying at the first contacts  50 ,  52  or the second contacts  86 ,  88 , whereby the arc can be assuredly extinguished. 
     A width  110  of the first magnet  102  along the extending direction of the first extended part  103  and the second extended part  105  is larger than dimensions of the first magnet in the other directions. For example, the width  110  is longer than a width  112  in the juxtaposing direction of the first contacts  50 ,  52  or the second contacts  86 ,  88 . By extending the first magnet  102  in the elongating direction of the arc, a high-density flux is generated in a space to which the arc is elongated, whereby the arc can be assuredly extinguished. 
     As shown in  FIG. 5 , the width  112  of the first magnet  102  corresponds to a dimension received in a space  114  between the attachment parts  54 ,  56 . For example, the width  112  is shorter than a width  116  of the space  114 . The first terminal  20  is moved in the vertical direction in  FIG. 5 , corresponding to the opening/closing motion of the relay  2 . Therefore, in view of a movable range of the first terminal  20 , it is necessary to locate the first magnet  102  so that it does not contact the first terminal  20 . 
     By setting the width  112  of the first magnet  102  to the dimension as described above, even when the first terminal  20  is displaced downward in  FIG. 5 , the first magnet  102  can be positioned close to the first terminal  20  without contacting the attachment parts  54 ,  56 . As a result, the first magnet  102  is positioned so that the flux densities between the first contact  52  and the second contact  88  and between the first contact  50  and the second contact  86  are increased, whereby the arc can be assuredly extinguished. 
       FIG. 7  shows a modification including a yoke  118 . In  FIG. 7 , the positional relationship, the shapes and the sizes of the first terminal  20 , the second terminal  22  and the first magnet  102 , and the polarity of the first magnet  102 , are the same as  FIG. 5 . The yoke  118  has a bottom  120  and walls  122 ,  123  which are bent from the bottom  120  and extend toward the first terminal  20 . The yoke  118  may be formed from magnetic material such as iron. 
     The first magnet  102  is adhered to the surface  120   a  of the yoke  118  by an adhesive such as epoxy resin, so as to form a magnetic path. A magnetic flux  124  passes through the wall  122  and the bottom  120 , and a magnetic flux  126  passes through the wall  123  and the bottom  120 , whereby the fluxes  124  and  126  can be concentrated between the first contact  52  and the second contact  88  and between the first contact  50  and the second contact  86 , respectively, without being dispersed. Therefore, by using the yoke  118 , the flux densities between the first contact  50  and the second contact  86  and between the first contact  52  and the second contact  88  can be further increased, and the arc-extinguishing property can be further improved. 
       FIG. 8  shows a modification including a second magnet  128 . In  FIG. 8 , the positional relationship, the shapes and the sizes of the first terminal  20 , the second terminal  22  and the first magnet  102 , and the polarity of the first magnet  102 , are the same as  FIG. 5 . For example, the second magnet  128  has the same shape and size as the first magnet  102 . The second magnet  128  may, for example, be formed from ferrite, samarium-cobalt, or neodymium, etc. 
     The second magnet  128  is positioned on a side opposed to the second contacts  86 ,  88  of the second terminal  22  and on a position corresponding to between the pair of second contacts  86 ,  88  so that the second magnet  128  contacts the second terminal  22 . The second magnet  128  of  FIG. 8  is positioned on a surface  22   a  of the second terminal  22 , between the attachment parts  90 ,  92 , and equidistant from the second contacts  86 ,  88 . 
     The second magnet  128  is magnetized in a direction along which the first contacts  50 ,  52  and the second contacts  86 ,  88  are opposed, so that the second magnet has a reverse polarity to the polarity of the first magnet  102 . The second magnet  128  of  FIG. 8  is magnetized so that a surface  128   a  near the second contacts  86 ,  88  has a polarity of N-pole and a surface  128   b  far from the second contacts  86 ,  88  has a polarity of S-pole, whereby magnetic fluxes  130 ,  132  are generated. 
     Hereinafter, a principle for extinguishing an arc by the first magnet  102  and the second magnet  128  is explained, by using an example wherein the current flows from the first terminal  20  to the second terminal  22  via the first contacts  50 ,  52  and the second contacts  86 ,  88 , in a direction of the arrow  108  of  FIG. 8 . Note that the explanation of the first magnet  102  is omitted, since the first magnet  102  acts on the arc similarly to the above. 
     In the above magnetizing direction, the directions of the fluxes  130  and  104  are the same between the first contact  52  and the second contact  88 . Therefore, based on Fleming&#39;s left-hand rule, a Lorentz force acts from a back side to a front side of  FIG. 8 , between the first contact  52  and the second contact  88 . As a result, the arc is subject to a resultant force of the Lorentz force due to the flux  104  and the Lorentz force due to the flux  130 . 
     Further, the directions of the fluxes  132  and  106  are the same between the first contact  50  and the second contact  86 . Therefore, based on the Fleming&#39;s left-hand rule, a Lorentz force acts from the front side to the back side of  FIG. 8 , between the first contact  50  and the second contact  86 . As a result, the arc is subject to a resultant force of the Lorentz force due to the flux  106  and the Lorentz force due to the flux  132 . 
     Accordingly, by arranging the second magnet  128  as well as the first magnet  102 , the larger force can be applied to the arcs generated between the first contact  50  and the second contact  86  and between the first contact  52  and the second contact  88 , whereby the arc-extinguishing property can be further improved. 
     Note that the first magnet  102  and the second magnet  128  may be magnetized so that each magnet has a reverse polarity to the polarity as shown in  FIG. 8 . The second magnet  128  may be arranged so as not to contact the second terminal  22 . Moreover, the relay  2  may not have the first magnet  102  and may be configured to extinguish the arc by arranging the second magnet  128 . 
       FIG. 9  is an exploded perspective view showing the positional relationship between the components of a modification including an attachment member  134 . In  FIG. 9 , the positional relationship between the first terminal  20 , the base  21 , the second terminal  22  and the first magnet  102  may be the same as in  FIGS. 4 to 6 . 
     The attachment member  134  is a member for attaching the first magnet  102  to the base  21 , and may be formed, for example, from resin. For example, the attachment member  134  is formed as a box, and the first magnet  102  is contained in a containing part  136  which opens downward in  FIG. 9 . 
     The attachment member  134  has an extended plate  138  extending from an outer surface  134   a  toward the outside of the containing part  136 , and an extended plate  140  extending from an outer surface  134   b  opposed to the outer surface  134   a  toward the outside of the containing part  136 . Columnar protrusions  142 ,  144  extending downward in  FIG. 9  are formed on the extended plates  138 ,  140 , respectively. A pair of holes  146 ,  148  are formed on the base  21 . By inserting the protrusion  142 ,  144  into the holes  146 ,  148 , respectively, and then swaging the protrusions, the attachment member  134  is fixed to the base  21 . 
       FIGS. 10 a  and 10 b    are views explaining a fixing method of the attachment member  134  of  FIG. 9 .  FIG. 10A  shows a state before the attachment  134  is fixed, and  FIG. 10B  shows a state after the attachment  134  is fixed. 
     As shown in  FIG. 10A , while the protrusions  142 ,  144  are inserted into the holes  146 ,  148 , respectively, a front end  142   a  of the protrusion  142  and a front end  144   a  of the protrusion  144  protrude at a surface  21   b  of the base  21 . As shown in  FIG. 10B , by plastically deforming (e.g., by heating) the protruded front ends  142   a  and  144   a,  the attachment member  134  is fixed to the base  21 . Note that this embodiment is merely an example, and an arbitrary shape and an arbitrary fixing method can be applied to the attachment member  134 . 
       FIG. 11  is an exploded perspective view showing a positional relationship between components of a modification including a yoke  150 . In  FIG. 11 , the positional relationship between the components except for the yoke  150  may be the same as  FIG. 9 . The yoke  150  may be formed from magnetic material such as iron, and may have the same shape and the size of the yoke  118  of  FIG. 7 . The yoke  150  is positioned between the attachment member  134  and the base  21 , is attached to the first magnet  102 , and forms a magnetic path. 
     As shown in  FIG. 11 , the yoke  150  has through holes  152 ,  154 , through which the protrusions  142 ,  144  are inserted, respectively. The protrusion  142  passes through the hole  152 , is inserted into the hole  146 , and then is swaged. The protrusion  144  passes through the hole  154 , is inserted into the hole  148 , and then is swaged. By swaging the protrusions  142 ,  144 , the attachment member  134  fixes the yoke  150  to the base  21 . 
     With reference to  FIGS. 12 to 13   b , another modification is explained.  FIG. 12  shows a positional relationship between components of the modification.  FIGS. 13 a  and 13 b    are partial enlarged views of  FIG. 12 .  FIG. 13A  shows a state before the first magnet  102  is fixed, and  FIG. 13B  shows a state after the first magnet  102  is fixed. 
     The housing  4  has a wall  156  for holding the first magnet  102 . The wall  156  forms a space  158  cooperatively with the base  21 . The first magnet  102  is positioned in the space  158 , and is held by and fixed to the wall  156 . 
     The wall  156  has a gap  160  at a position between the first contacts  50 ,  52 . The surface  102   a  of the first magnet  102  is partially exposed from the gap  160  and is opposed to the first terminal  20 . By providing the gap  160  in the wall  156 , the first magnet  102  can be positioned close to the first terminal  20 , without taking the thickness of the wall  156  into consideration. As a result, high-density fluxes are generated between the first contact  50  and the second contact  86  and between the first contact  52  and the second contact  88 , and the arc-extinguishing property can be obtained. Further, since the fixing structure is formed integrally with the housing  4 , the first magnet  102  can be fixed without increasing the number of components. 
     The wall  156  may have an arbitrary shape and may be configured so that it holds the first magnet  102  and is attached to the base  21  by the attachment member  134 . 
     The embodiments described above can be appropriately combined. Furthermore, in the drawings described above, identical or corresponding portions are assigned the same reference signs. Note that the embodiments described above are merely exemplary and do not limit the invention.