Patent Publication Number: US-8994482-B2

Title: Electromagnetic contactor

Description:
TECHNICAL FIELD 
     The present invention relates to an electromagnetic contactor wherein a contact mechanism including fixed contacts and a movable contact is housed in an arc extinguishing chamber. 
     BACKGROUND ART 
     As an electromagnetic contactor wherein a contact mechanism is housed in an arc extinguishing chamber, there is provided a sealed contact device having a sealed receptacle formed in a box-form with one surface opened from a heat resistant material such as a ceramic (for example, refer to Patent Document 1). The sealed contact device described in PTL 1 is such that fixed terminals are hermetically joined by brazing in through holes formed in two places in the bottom portion of the sealed receptacle. A movable contact provided with movable contact points contacting with and separating from the fixed contact points formed on the fixed terminals is disposed in the sealed receptacle. The sealed contact device has a configuration wherein an opened end portion of the sealed receptacle is connected to a first joint member formed in a rectangular form from a magnetic metal material, to which a bottomed cylindrical portion is hermetically joined, via a cylindrical second joint member formed from a metal material. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent No. 3,107,288 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the heretofore known example described in Patent Document 1 is such that the sealed receptacle is formed in a box-form with one surface opened from a heat resistant material, such as a ceramic, to which the fixed terminals are brazed. It is necessary to perform a metalizing process on a surface of the bottom portion of the sealed receptacle in order to braze the fixed terminals but, as the receptacle is formed in a box-form, there is an unsolved problem in that it is necessary to screen print one sealed receptacle after another, resulting in a low productivity. Also, as a brazing jig used when assembling also corresponds to the three-dimensional structure of the sealed receptacle, there is also an unsolved problem in that a fabricating jig is of a complex form. Furthermore, there is an unsolved problem in that it is also difficult to control the flatness and warpage of the bottomed portion to which the fixed terminals of the sealed receptacle is brazed. 
     Therefore, the invention, focusing on the unsolved problems of the heretofore known example, has an object of providing an electromagnetic contactor such that it is possible to improve productivity, and simplify a brazing jig, and furthermore, to control the flatness and warpage of a plate portion supporting fixed contacts. 
     Solution to Problem 
     In order to achieve the heretofore described object, an electromagnetic contactor according to one aspect of the invention is characterized by including an arc extinguishing chamber housing a contact mechanism having a pair of fixed contacts and a movable contact that contacts with the pair of fixed contacts. 
     The arc extinguishing chamber has a plate-shaped fixed contact support insulating substrate including through holes to fix at least the pair of fixed contacts and formed with metal foils on an outer peripheral edge of one surface by a metalizing process. The pair of fixed contacts and a metal cylindrical body are brazed and joined to the metal foils of the fixed contact support insulating substrate. An insulating cylindrical body is disposed on the inner peripheral surface of the metal cylindrical body. 
     According to this configuration, as the arc extinguishing chamber is configured of the plate-like fixed contact support insulating substrate to which the fixed contacts are brazed, the metal cylindrical body brazed to the outer peripheral edge of one surface of the fixed contact support insulating substrate, and the insulating cylindrical body disposed on the inner side of the metal cylindrical body, it is possible, when performing a metalizing process for brazing the fixed contact support insulating substrate, to carry out a screen printing process in a condition in which a plurality of fixed contact support insulating substrates is vertically and horizontally arranged in close contact on a flat surface, and thus possible to improve productivity. Also, as the fixed contact support insulating substrate is plate-like, it is possible to simplify the assembly and brazing jigs, and thus possible to adopt an inexpensive configuration. Furthermore, it is also possible to easily carry out the control and management of flatness and warpage. Furthermore, it is possible to simultaneously carry out processes of brazing the fixed contacts and metal cylindrical body to the fixed contact support insulating substrate. 
     Also, an electromagnetic contactor according to another aspect of the invention is characterized in that the fixed contact support insulating substrate is formed of a ceramic insulating substrate. 
     According to this configuration, as the fixed contact support insulating substrate is configured of a ceramic insulating substrate, mass production is possible, thus enabling a reduction in fabrication cost. 
     Also, an electromagnetic contactor according to another aspect of the invention is characterized in that the insulating cylindrical body is configured by combining ceramic plates. 
     According to this configuration, as the insulating cylindrical body is configured of ceramic plates, the fabrication is easy. 
     Advantageous Effects of Invention 
     According to the invention, as the fixed contact support insulating substrate is formed plate-like, when performing a metalizing process for brazing, it is possible to carry out a screen printing in a condition in which a plurality of fixed contact support insulating substrates is vertically and horizontally arranged in close contact on a flat plate, and thus productivity dramatically improve. Also, as the fixed contact support insulating substrate is plate-like, it is possible to simplify jigs for fabrication and brazing. Furthermore, it is possible to easily carry out the control and management of the flatness and warpage of the fixed contact support insulating substrate. It is possible to simultaneously carry out brazings of the fixed contacts and metal cylindrical body to the fixed contact support insulating substrate, and thus possible to reduce fabrication cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view showing a first embodiment of an electromagnetic contactor according to the invention. 
         FIG. 2  an exploded perspective view showing an arc extinguishing chamber of  FIG. 1 . 
         FIGS. 3(   a )- 3 ( c ) are diagrams showing an insulating cover of a contact mechanism, wherein  FIG. 3(   a ) is a perspective view,  FIG. 3(   b ) is a plan view before mounting, and  FIG. 3(   c ) is a plan view after mounting. 
         FIG. 4  is a perspective view showing an insulating cover mounting method. 
         FIG. 5  is a sectional view along line A-A in  FIG. 1 . 
         FIG. 6  is an illustration accompanying a description of arc extinguishing by an arc extinguishing permanent magnet according to the invention. 
         FIG. 7  is an illustration accompanying a description of arc extinguishing when the arc extinguishing permanent magnet is disposed on the outer side of an insulating case. 
         FIG. 8  is a perspective view showing another example of an insulating cylindrical body configuring the arc extinguishing chamber. 
         FIGS. 9(   a )- 9 ( b ) are diagrams showing another example of the contact mechanism, wherein  FIG. 9(   a ) is a sectional view, and  FIG. 9(   b ) is a perspective view. 
         FIGS. 10(   a )- 10 ( b ) are diagrams showing another example of a movable contact of the contact mechanism, wherein  FIG. 10(   a ) is a sectional view, and  FIG. 10(   b ) is a perspective view. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereafter, a description will be given, based on the drawings, of an embodiment of the invention. 
       FIG. 1  is a sectional view showing one example of an electromagnetic switch according to the invention, while  FIG. 2  is an exploded perspective view of an arc extinguishing chamber. In  FIGS. 1 and 2 , numeral  10  is an electromagnetic contactor, and the electromagnetic contactor  10  is configured of a contact device  100  in which a contact mechanism is disposed, and an electromagnet unit  200  that drives the contact device  100 . 
     The contact device  100  has an arc extinguishing chamber  102  in which a contact mechanism  101  is housed, as is clear from  FIGS. 1 and 2 . The arc extinguishing chamber  102 , as shown in  FIG. 2 , includes a metal rectangular cylindrical body  104  having a metal flange portion  103  protruding outward from a lower end portion, and a fixed contact support insulating substrate  105  having a plate-like ceramic insulating substrate that closes off the upper end of the metal rectangular cylindrical body  104 . 
     The metal rectangular cylindrical body  104  is such that the flange portion  103  thereof is sealingly joined and fixed to an upper magnetic yoke  210  of the electromagnet unit  200 , to be described hereafter. 
     Also, through holes  106  and  107  in which a pair of fixed contacts  111  and  112  to be described hereafter is inserted, are formed maintaining a predetermined interval in a central portion of the fixed contact support insulating substrate  105 . A metalizing process is performed around the through holes  106  and  107  on the upper surface side of the fixed contact support insulating substrate  105 , and in a position on the lower surface side that contacts with the metal rectangular cylindrical body  104 . To carry out the metalizing process, in a condition in which a plurality of fixed contact support insulating substrates  105  is arranged vertically and horizontally on a flat surface, metal foils  106   a  and  107   a  (for example, a copper foil) are formed around the through holes  106  and  107  and metal foils  104   a  is formed at a position that contacts with the metal rectangular cylindrical body  104 . 
     The contact mechanism  101 , as shown in  FIG. 1 , includes the pair of fixed contacts  111  and  112  inserted into and fixed in the through holes  106  and  107  of the fixed contact support insulating substrate  105  of the arc extinguishing chamber  102 . Each of the fixed contacts  111  and  112  includes a support conductor portion  114 , having a flange portion protruding outward on an upper end thereof, inserted into the through holes  106  and  107  of the fixed contact support insulating substrate  105 , and a C-shaped portion  115  having the inner side opened, linked to the support conductor portion  114  and disposed on the lower surface side of the fixed contact support insulating substrate  105 . 
     The C-shaped portion  115  is formed in a C-shape of an upper plate portion  116  extending to the outer side along the lower surface of the fixed contact support insulating substrate  105 , an intermediate plate portion  117  extending downward from the outer side end portion of the upper plate portion  116 , and a lower plate portion  118  extending from the lower end side of the intermediate plate portion  117 , parallel with the upper plate portion  116 , toward the inner side, that is, in a direction facing the fixed contacts  111  and  112 , wherein the upper plate portion  116  is added to an L-shape formed by the intermediate plate portion  117  and lower plate portion  118 . 
     Herein, the support conductor portion  114  and C-shaped portion  115  are fixed by, for example, brazing in a condition in which a pin  114   a  formed protruding from the lower surface of the support conductor portion  114  is inserted into a through hole  120  formed in the upper plate portion  116  of the C-shaped portion  115 . The fixing of the support conductor portion  114  and C-shaped portion  115 , not being limited to brazing, may be such that the pin  114   a  is fitted into the through hole  120 , or an external thread is formed on the pin  114   a  and an internal thread formed in the through hole  120 , and the two are screwed together. 
     Further, an insulating cover  121 , made of a synthetic resin material, that regulates arc generation is mounted on the C-shaped portion  115  of each of the fixed contacts  111  and  112 . The insulating cover  121  covers the inner peripheral surfaces of the upper plate portion  116  and intermediate plate portion  117  of the C-shaped portion  115 , as shown in  FIGS. 3(   a ) and  3 ( b ). 
     The insulating cover  121  includes an L-shaped plate portion  122  that follows the inner peripheral surfaces of the upper plate portion  116  and intermediate plate portion  117 , side plate portions  123  and  124 , each extending upward and outward from front and rear end portions of the L-shaped plate portion  122 , that cover side surfaces of the upper plate portion  116  and intermediate plate portion  117  of the C-shaped portion  115 , and fitting portions  125 , each formed on the inward side from the upper end of each of the side plate portions  123  and  124 , that fit onto a small diameter portion  114   b  formed on the support conductor portion  114  of each of the fixed contacts  111  and  112 . 
     Consequently, the insulating cover  121  is placed in a condition in which the fitting portions  125  are facing the small diameter portion  114   b  of the support conductor portion  114  of each of the fixed contacts  111  and  112 , as shown in  FIGS. 3(   a ) and  3 ( b ), after which, as shown in  FIG. 3(   c ), the fitting portions  125  are fitted onto the small diameter portion  114   b  of the support conductor portion  114  by pushing the insulating cover  121 . 
     Actually, with the arc extinguishing chamber  102  after the fixed contacts  111  and  112  have been attached in a condition wherein the fixed contact support insulating substrate  105  is on the lower side, the insulating cover  121  is inserted from an upper aperture portion between the fixed contacts  111  and  112  in a vertically reversed condition of that in  FIGS. 3(   a ) to  3 ( c ), as shown in  FIG. 4(   a ). 
     Next, in a condition in which the fitting portions  125  are in contact with the fixed contact support insulating substrate  105 , as shown in  FIG. 4(   b ), the fitting portions  125  are fitted onto and fixed to the small diameter portion  114   b  of the support conductor portion  114  of each of the fixed contacts  111  and  112  by pushing the insulating cover  121  to the outer side, as shown in  FIG. 4(   c ). 
     By mounting the insulating cover  121  on the C-shaped portion  115  of each of the fixed contacts  111  and  112  in this way, only the upper surface side of the lower plate portion  118  of the inner peripheral surface of the C-shaped portion  115  is exposed, thus forming a contact portion  118   a.    
     Further, the movable contact  130  is disposed in such a way that both end portions are disposed in the C-shaped portions  115  of the fixed contacts  111  and  112 . The movable contact  130  is supported by a connecting shaft  131  fixed in a movable plunger  215  of the electromagnet unit  200 , to be described hereafter. The movable contact  130  is such that, as shown in  FIGS. 1 and 5 , a central portion in the vicinity of the connecting shaft  131  protrudes downward, whereby a depressed portion  132  is formed, and a through hole  133  in which the connecting shaft  131  is inserted is formed in the depressed portion  132 . 
     A flange portion  131   a  protruding outward is formed on the upper end of the connecting shaft  131 . The connecting shaft  131  is inserted from the lower end side thereof into a contact spring  134 , then inserted into the through hole  133  of the movable contact  130 , bringing the upper end of the contact spring  134  into contact with the flange portion  131   a , and the movable contact  130  is positioned using, for example, a C-ring  135  so as to obtain a predetermined urging force from the contact spring  134 . 
     The movable contact  130 , in a released condition, takes on a condition wherein contact portions  130   a  at either end and the contact portions  118   a  of the lower plate portions  118  of the C-shaped portions  115  of the fixed contacts  111  and  112  are separated from each other and maintaining a predetermined interval. Also, the movable contact  130  is set so that, in a closed position, the contact portions at either end contact with the contact portions  118   a  of the lower plate portions  118  of the C-shaped portions  115  of the fixed contacts  111  and  112  at a predetermined contact pressure due to the contact spring  134 . 
     Furthermore, an insulating cylindrical body  140  formed in a bottomed rectangular cylindrical form by a rectangular cylindrical portion  140   a  and a bottom plate portion  140   b  formed on the lower surface side of the rectangular cylindrical portion  140   a  is disposed on the inner peripheral surface of the metal rectangular cylindrical body  104  of the arc extinguishing chamber  102 , as shown in  FIGS. 9(   a )- 9 ( b ). The insulating cylindrical body  140 , made of, for example, a synthetic resin, is such that the rectangular cylindrical portion  140   a  and bottom plate portion  140   b  are integrally formed. Further, magnet housing cylindrical bodies  141  and  142  acting as magnet housing portions are formed integrally in positions on the insulating cylindrical body  140  facing the side surfaces of the movable contact  130 . Arc extinguishing permanent magnets  143  and  144  are inserted into and fixed in the magnet housing cylindrical bodies  141  and  142  respectively. 
     The arc extinguishing permanent magnets  143  and  144  are magnetized in a thickness direction so that mutually opposing faces thereof are homopolar, for example, N-poles. Also, the arc extinguishing permanent magnets  143  and  144  are set so that both end portions in a left-right direction are slightly inward of positions in which the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions of the movable contact  130  are opposed, as shown in  FIG. 5 . Further, arc extinguishing spaces  145  and  146  are formed on the outer sides in a left-right direction of the magnet housing cylindrical bodies  141  and  142  respectively, that is, in a longitudinal direction of the movable contact. 
     Also, movable contact guide members  148  and  149 , which regulate the turning of the movable contact  130 , are formed protruding, sliding against side edges of the magnet housing cylindrical bodies  141  and  142  toward either end of the movable contact  130 . 
     Consequently, the insulating cylindrical body  140  includes the function of positioning the arc extinguishing permanent magnets  143  and  144  with the magnet housing cylindrical bodies  141  and  142 , the function of protecting the arc extinguishing permanent magnets  143  and  144  from an arc, and an insulating function that blocks the effect of the arc on the metal rectangular cylindrical body  104  improving the rigidity of the external portion. 
     Further, by disposing the arc extinguishing permanent magnets  143  and  144  on the inner peripheral surface side of the insulating cylindrical body  140 , it is possible to bring the arc extinguishing permanent magnets  143  and  144  near to the movable contact  130 . Because of this, as shown in  FIG. 6(   a ), magnetic flux φ emanating from the N-pole sides of the two arc extinguishing permanent magnets  143  and  144  crosses portions in which the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130  are opposed in a left-right direction, from the inner side to the outer side, with a large flux density. 
     Consequently, assuming that the fixed contact  111  is connected to a current supply source and the fixed contact  112  is connected to a load side, the current direction in the closed condition is such that the current flows from the fixed contact  111  through the movable contact  130  to the fixed contact  112 , as shown in  FIG. 6(   b ). Then, when changing from the closed condition to the released condition by causing the movable contact  130  to move away upward from the fixed contacts  111  and  112 , an arc is generated between the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130 . 
     The arc is extended to the arc extinguishing space  145  side on the arc extinguishing permanent magnet  143  side by the magnetic flux φ from the arc extinguishing permanent magnets  143  and  144 , as shown in  FIG. 6(   c ). At this time, as the arc extinguishing spaces  145  and  146  are formed as widely as the thickness of the arc extinguishing permanent magnets  143  and  144 , it is possible to obtain a long arc length, and thus possible to reliably extinguish the arc. 
     Incidentally, when the arc extinguishing permanent magnets  143  and  144  are disposed on the outer side of the insulating cylindrical body  140 , as shown in  FIGS. 7(   a ) to  7 ( c ), there is an increase in the distance to the positions in which the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130  are facing each other, and when the same permanent magnets as in this embodiment are applied, the density of the magnetic flux crossing the arc decreases. 
     Because of this, the Lorentz force acting on an arc generated when shifting from the closed condition to the released condition decreases, and it is no longer possible to sufficiently extend the arc. In order to improve the arc extinguishing performance, it is necessary to increase the magnetization of the arc extinguishing permanent magnets  143  and  144 . Moreover, in order to shorten the distance between the arc extinguishing permanent magnets  143  and  144  and the contact portions of the fixed contacts  111  and  112  and movable contact  130 , it is necessary to reduce the depth in a front-back direction of the insulating cylindrical body  140 , and there is a problem in that it is not possible to secure sufficient arc extinguishing space to extinguish the arc. 
     However, according to the heretofore described embodiment, the arc extinguishing permanent magnets  143  and  144  are disposed on the inner side of the insulating cylindrical body  140 , meaning that the problems occurring when the arc extinguishing permanent magnets  143  and  144  are disposed on the outer side of the insulating cylindrical body  140  can all be solved. 
     The electromagnet unit  200 , as shown in  FIG. 1 , has a magnetic yoke  201  of a flattened U-shape when seen from the side, and a cylindrical auxiliary yoke  203  is fixed to a central portion of a bottom plate portion  202  of the magnetic yoke  201 . A spool  204  is disposed on the outer side of the cylindrical auxiliary yoke  203 . 
     The spool  204  is configured of a central circular cylindrical portion  205  in which the cylindrical auxiliary yoke  203  is inserted, a lower flange portion  206  protruding outward in a radial direction from a lower end portion of the central circular cylindrical portion  205 , and an upper flange portion  207  protruding outward in a radial direction from slightly below the upper end of the central circular cylindrical portion  205 . Further, an exciting coil  208  is mounted wound in a housing space configured of the central circular cylindrical portion  205 , lower flange portion  206 , and upper flange portion  207 . 
     Further, an upper magnetic yoke  210  is fixed between upper ends forming an opened end of the magnetic yoke  201 . A through hole  210   a  facing the central circular cylindrical portion  205  of the spool  204  is formed in a central portion of the upper magnetic yoke  210 . 
     Further, the movable plunger  215 , in which a return spring  214  is disposed between a bottom portion and the bottom plate portion  202  of the magnetic yoke  201 , is disposed in the central circular cylindrical portion  205  of the spool  204  so as to be slidable up and down. A peripheral flange portion  216  protruding outward in a radial direction is formed on an upper end portion of the movable plunger  215  protruding upward from the upper magnetic yoke  210 . 
     Also, a permanent magnet  220  formed in a ring-form by having, for example, a quadrate external form and a circular central aperture  221  is fixed to the upper surface of the upper magnetic yoke  210  so as to enclose the peripheral flange portion  216  of the movable plunger  215 . The permanent magnet  220  is magnetized in an up-down direction, that is, a thickness direction, so that, for example, the upper end side is an N-pole while the lower end side is an S-pole. Taking the form of the central aperture  221  of the permanent magnet  220  to be a form tailored to the form of the peripheral flange portion  216 , the form of the outer peripheral surface can be any form, such as a circle or a quadrate. 
     Further, an auxiliary yoke  225  of the same external form as the permanent magnet  220 , and having a through hole  224  with an inner diameter smaller than the outer diameter of the peripheral flange portion  216  of the movable plunger  215 , is fixed to the upper end surface of the permanent magnet  220 . The peripheral flange portion  216  of the movable plunger  215  contacts with the lower surface of the auxiliary yoke  225 . 
     Also, the connecting shaft  131  that supports the movable contact  130  is screwed to the upper end surface of the movable plunger  215 . 
     Further, the movable plunger  215  is covered with a cap  230  formed in a bottomed cylindrical form made of a non-magnetic body, and a flange portion  231  formed extending outward in a radial direction on an opened end of the cap  230  is sealingly joined to the lower surface of the upper magnetic yoke  210 . By doing so, a hermetic receptacle, wherein the arc extinguishing chamber  102  and cap  230  are in communication via the through hole  210   a  of the upper magnetic yoke  210 , is formed. Further, a gas such as hydrogen gas, nitrogen gas, a mixed gas of hydrogen and nitrogen, air, or SF 6  is encapsulated inside the hermetic receptacle formed by the arc extinguishing chamber  102  and cap  230 . 
     Next, a description will be given of an operation of the heretofore described embodiment. 
     For now, it is assumed that the fixed contact  111  is connected to, for example, a power supply source that supplies a large current, while the fixed contact  112  is connected to a load. 
     In this condition, it is assumed that the exciting coil  208  in the electromagnet unit  200  is in a non-excited state, and there exists a released condition wherein no exciting force causing the movable plunger  215  to descend is being generated in the electromagnet unit  200 . In this released condition, the movable plunger  215  is urged in an upward direction away from the upper magnetic yoke  210  by the return spring  214 . Simultaneously with this, an attracting force caused by the permanent magnet  220  acts on the auxiliary yoke  225 , and the peripheral flange portion  216  of the movable plunger  215  is attracted. Because of this, the upper surface of the peripheral flange portion  216  of the movable plunger  215  contacts with the lower surface of the auxiliary yoke  225 . 
     Because of this, the contact portions  130   a  of the contact mechanism  101  movable contact  130  connected to the movable plunger  215  via the connecting shaft  131  are separated by a predetermined distance upward from the contact portions  118   a  of the fixed contacts  111  and  112 . Because of this, the current path between the fixed contacts  111  and  112  is in an interrupted condition, and the contact mechanism  101  is in a condition wherein the contacts are opened. 
     In this way, as the urging force of the return spring  214  and the attracting force of the ring-form permanent magnet  220  both act on the movable plunger  215  in the released condition, there is no unplanned downward movement of the movable plunger  215  due to external vibration, shock, or the like, and it is thus possible to reliably prevent malfunction. 
     On the exciting coil  208  of the electromagnet unit  200  being excited in the released condition, an exciting force is generated in the electromagnet unit  200 , and the movable plunger  215  is pressed downward against the urging force of the return spring  214  and the attracting force of the ring-form permanent magnet  220 . 
     The descent of the movable plunger  215  is stopped by the lower surface of the peripheral flange portion  216  contacting with the upper surface of the upper magnetic yoke  210 . 
     By the movable plunger  215  descending in this way, the movable contact  130  connected to the movable plunger  215  via the connecting shaft  131  also descends, and the contact portions  130   a  of the movable contact  130  come into contact with the contact portions  118   a  of the fixed contacts  111  and  112  with the contact pressure of the contact spring  134 . 
     Because of this, there exists a closed contact condition wherein the large current of the external power supply source is supplied via the fixed contact  111 , movable contact  130 , and fixed contact  112  to the load. 
     At this time, an electromagnetic repulsion force is generated between the fixed contacts  111  and  112  and the movable contact  130  in a direction such as to cause the contacts of the movable contact  130  to open. 
     However, as the fixed contacts  111  and  112  are such that each C-shaped portion  115  is formed of the upper plate portion  116 , intermediate plate portion  117 , and lower plate portion  118 , as shown in  FIG. 1 , the current in the upper plate portion  116  and lower plate portion  118  and the current in the opposing movable contact  130  flow in opposite directions. Because of this, from the relationship between a magnetic field formed by the lower plate portions  118  of the fixed contacts  111  and  112  and the current flowing through the movable contact  130 , it is possible, in accordance with Fleming&#39;s left-hand rule, to generate a Lorentz force that presses the movable contact  130  against the contact portions  118   a  of the fixed contacts  111  and  112 . 
     Because of this Lorentz force, it is possible to oppose the electromagnetic repulsion force generated in the contact opening direction between the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130 , and thus possible to reliably prevent the contact portions  130   a  of the movable contact  130  from opening. Because of this, it is possible to reduce the pressing force of the contact spring  134  supporting the movable contact  130 , as a result of which it is also possible to reduce thrust generated in the exciting coil  208 , and it is thus possible to reduce the size of the overall configuration of the electromagnetic contactor. 
     When interrupting the supply of current to the load in the closed contact condition of the contact mechanism  101 , the exciting of the exciting coil  208  of the electromagnet unit  200  is stopped. 
     By so doing, the exciting force causing the movable plunger  215  to move downward in the electromagnet unit  200  stops, as a result of which the movable plunger  215  is raised by the urging force of the return spring  214 , and the attracting force of the ring-form permanent magnet  220  increases as the peripheral flange portion  216  nears the auxiliary yoke  225 . 
     By the movable plunger  215  rising, the movable contact  130  connected via the connecting shaft  131  rises. As a result of this, the movable contact  130  is in contact with the fixed contacts  111  and  112  for as long as contact pressure is applied by the contact spring  134 . Subsequently, there starts an opened contact condition, wherein the movable contact  130  moves upward away from the fixed contacts  111  and  112  at the point at which the contact pressure of the contact spring  134  stops. 
     On the opened contact condition starting, an arc is generated between the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130 , and the condition in which current is conducted is continued due to the arc. At this time, as the insulating cover  121  is mounted for covering the upper plate portion  116  and intermediate plate portion  117  of the C-shaped portion  115  of each of the fixed contacts  111  and  112 , it is possible to cause the arc to be generated only between the contact portions  118   a  of the fixed contacts  111  and  112  and the contact portions  130   a  of the movable contact  130 . Because of this, it is possible to reliably prevent the arc from moving on the C-shaped portions  115  of the fixed contacts  111  and  112 , thereby stabilizing the arc generation condition, and thus possible to improve arc extinguishing performance. Moreover, as both side surfaces of each of the fixed contacts  111  and  112  are also covered with the insulating cover  121 , it is also possible to reliably prevent the leading end of the arc from short-circuiting. 
     Further, as it is possible for the insulating cover  121  to be mounted on each of the fixed contacts  111  and  112  simply by fitting the fitting portions  125  onto the small diameter portion  114   b  of each of the fixed contacts  111  and  112 , it is possible to easily carry out the mounting on each of the fixed contacts  111  and  112 . 
     At this time, as the opposing magnetic pole faces of the arc extinguishing permanent magnets  143  and  144  are N-poles, and the outer sides thereof are S-poles, magnetic flux emanating from the N-poles, seen in plan view as shown in  FIG. 6(   a ), crosses an arc generation portion of a portion in which the contact portion  118   a  of the arc extinguishing permanent magnets  143  and  144  fixed contact  111  and the contact portion  130   a  of the movable contact  130  are opposed, from the inner side to the outer side in the longitudinal direction of the movable contact  130 , and reaches the S-pole, whereby a magnetic field is formed. In the same way, the magnetic flux crosses an arc generation portion of the contact portion  118   a  of the fixed contact  112  and the contact portion  130   a  of the movable contact  130 , from the inner side to the outer side in the longitudinal direction of the movable contact  130 , and reaches the S-pole, whereby a magnetic field is formed. 
     Consequently, the magnetic fluxes of the arc extinguishing magnets  143  and  144  both cross between the contact portion  118   a  of the fixed contact  111  and the contact portion  130   a  of the movable contact  130  and between the contact portion  118   a  of the fixed contact  112  and the contact portion  130   a  of the movable contact  130 , in mutually opposite directions in the longitudinal direction of the movable contact  130 . 
     Because of this, a current I flows from the fixed contact  111  side to the movable contact  130  side between the contact portion  118   a  of the fixed contact  111  and the contact portion  130   a  of the movable contact  130 , and the orientation of the magnetic flux φ is in a direction from the inner side toward the outer side, as shown in  FIG. 6(   b ). Because of this, in accordance with Fleming&#39;s left-hand rule, a large Lorentz force F acts toward the arc extinguishing space  145 , perpendicular to the longitudinal direction of the movable contact  130  and perpendicular to the switching direction of the contact portion  118   a  of the fixed contact  111  and the movable contact  130 , as shown in  FIG. 6(   c ). 
     Due to the Lorentz force F, an arc generated between the contact portion  118   a  of the fixed contact  111  and the contact portion  130   a  of the movable contact  130  is greatly extended so as to pass from the side surface of the contact portion  118   a  of the fixed contact  111  through the inside of the arc extinguishing space  145 , reaching the upper surface side of the movable contact  130 , and is extinguished. 
     Also, at the lower side and upper side of the arc extinguishing space  145 , magnetic flux inclines to the lower side and upper side with respect to the orientation of the magnetic flux between the contact portion  118   a  of the fixed contact  111  and the contact portion  130   a  of the movable contact  130 . Because of this, the arc extended to the arc extinguishing space  145  is further extended by the inclined magnetic flux in the direction of the corner of the arc extinguishing space  145 , it is possible to increase the arc length, and it is thus possible to obtain good interruption performance. 
     Meanwhile, the current flows from the movable contact  130  side to the fixed contact  112  side between the contact portion  118   a  of the fixed contact  112  and the movable contact  130 , and the orientation of the magnetic flux φ is in a rightward direction from the inner side toward the outer side, as shown in  FIG. 6(   b ). Because of this, in accordance with Fleming&#39;s left-hand rule, a large Lorentz force F acts toward the arc extinguishing space  145 , perpendicular to the longitudinal direction of the movable contact  130  and perpendicular to the switching direction of the contact portion  118   a  of the fixed contact  112  and the movable contact  130 . 
     Due to the Lorentz force F, an arc generated between the contact portion  118   a  of the fixed contact  112  and the movable contact  130  is greatly extended so as to pass from the upper surface side of the movable contact  130  through the inside of the arc extinguishing space  145 , reaching the side surface side of the fixed contact  112 , and is extinguished. 
     Also, at the lower side and upper side of the arc extinguishing space  145 , as heretofore described, magnetic flux inclines to the lower side and upper side with respect to the orientation of the magnetic flux between the contact portion  118   a  of the fixed contact  112  and the contact portion  130   a  of the movable contact  130 . Because of this, the arc extended to the arc extinguishing space  145  is further extended by the inclined magnetic flux in the direction of the corner of the arc extinguishing space  145 , it is possible to increase the arc length, and thus possible to obtain good interruption performance. 
     Meanwhile, in the closed condition of the electromagnetic contactor  10 , when adopting a released condition in a condition wherein a regenerative current flows from the load side to the direct current power source side, the direction of current in  FIG. 6(   b ) is reversed, meaning that the Lorentz force F acts on the arc extinguishing space  146  side, and excepting that the arc is extended to the arc extinguishing space  146  side, the same arc extinguishing function is fulfilled. 
     At this time, as the arc extinguishing permanent magnets  143  and  144  are disposed in the magnet housing cylindrical bodies  141  and  142  formed in the insulating cylindrical body  140 , the arc does not directly contact with the arc extinguishing permanent magnets  143  and  144 . Because of this, it is possible to stably maintain the magnetic characteristics of the arc extinguishing permanent magnets  143  and  144 , and thus possible to stabilize interruption performance. 
     Also, as it is possible to cover and insulate the inner peripheral surface of the metal arc extinguishing chamber  102  with the insulating cylindrical body  140 , there is no short circuiting of the arc when the current is interrupted, and it is thus possible to reliably carry out current interruption. 
     Furthermore, as it is possible to carry out the insulating function, the function of positioning the arc extinguishing permanent magnets  143  and  144 , the function of protecting the arc extinguishing permanent magnets  143  and  144  from the arc, and an insulating function that prevents the arc reaching the external metal rectangular cylindrical body  104 , with the one insulating cylindrical body  140 , it is possible to reduce manufacturing cost. 
     Also, as it is possible to increase the distance between the side edges of the movable contact  130  and the inner peripheral surface of the insulating cylindrical body  140  by an amount equivalent to the thickness of the arc extinguishing permanent magnets  143  and  144 , it is possible to provide the sufficiently large arc extinguishing spaces  145  and  146 , and thus possible to reliably carry out the extinguishing of the arc. 
     Furthermore, as the movable contact guide members  148  and  149  that slide against the side edges of the movable contact are formed protruding in positions on the permanent magnet housing cylindrical bodies  141  and  142  housing the arc extinguishing permanent magnets  143  and  144  opposing the movable contact  130 , it is possible to reliably prevent the turning of the movable contact  130 . 
     In the heretofore described embodiment, a description has been given of a case wherein the insulating cylindrical body  140  is configured by integrally forming the bottom plate portion  140   b  and rectangular cylindrical portion  140   a  but, this not being limiting, the insulating cylindrical body  140  may be formed by disposing an assembly of four side plate portions  256  to  259  configuring side walls on front and back and left and right end portions of a bottom plate portion  253  on which a magnet housing portion  252  of a base member  251  is formed, and connecting the side plate portions  256  to  259 , as shown in  FIG. 8 . In this case, as the side wall portion is divided into the four side plate portions  256  to  259 , manufacturing is easy compared with the case in which the whole is formed integrally. Furthermore, a rectangular cylindrical body wherein the four side plate portions  256  to  259  are integrated may also be formed. 
     Also, in the heretofore described embodiment, a description has been given of a case wherein the opposing magnetic pole faces of the arc extinguishing permanent magnets  143  and  144  are N-poles but, the invention is not being limited to this. Even when the opposing magnetic pole faces of the arc extinguishing permanent magnets  143  and  144  are S-poles, it is possible to obtain the same advantage as in the heretofore described embodiment, with the exception that the direction in which the magnetic flux crosses the arc and the direction of the Lorentz force are opposite. 
     In the heretofore described embodiment, a description has been given of a case wherein the C-shaped portion  115  is formed in each of the fixed contacts  111  and  112  but, the invention is not being limited to this. An L-shaped portion  160 , of a form such that the upper plate portion  116  of the C-shaped portion  115  is omitted, may be connected to the support conductor portion  114 , as shown in  FIGS. 9(   a ) and  9 ( b ). 
     In this case too, in the closed contact condition wherein the movable contact  130  contacts with the fixed contacts  111  and  112 , it is possible to cause magnetic flux generated by the current flowing through a vertical plate portion of the L-shaped portion  160  to act on portions in which the fixed contacts  111  and  112  and the movable contact  130  are in contact. Because of this, it is possible to increase the magnetic flux density in the portions in which the fixed contacts  111  and  112  and the movable contact  130  are in contact, generating a Lorentz force that opposes the electromagnetic repulsion force. 
     Also, in the heretofore described embodiment, description has been given of a case wherein the movable contact  130  has the depressed portion  132  in the central portion thereof but, the invention is not being limited to this, the depressed portion  132  may be omitted, forming a flat plate, as shown in  FIGS. 10(   a ) and  10 ( b ). 
     Also, in the heretofore described embodiment, a description has been given of a case wherein the connecting shaft  131  is screwed to the movable plunger  215 , but the movable plunger  215  and connecting shaft  131  may also be formed integrally. 
     Also, a description has been given of a case wherein the connection of the connecting shaft  131  and movable contact  130  is such that the flange portion  131   a  is formed on the leading end portion of the connecting shaft  131 , and the lower end of the movable contact  130  is fixed with a C-ring after the connecting shaft  131  is inserted into the contact spring  134  and movable contact  130 , but the invention is not limited to this. That is, a positioning large diameter portion may be formed protruding in a radial direction in the C-ring position of the connecting shaft  131 , the contact spring  134  disposed after the movable contact  130  contacts with the large diameter portion, and the upper end of the contact spring  134  fixed with the C-ring. 
     Also, in the heretofore described embodiment, a description has been given of a case wherein a hermetic receptacle is configured of the arc extinguishing chamber  102  and cap  230 , and gas is encapsulated inside the hermetic receptacle but, the invention is not limited to this, the gas encapsulation may be omitted when the interrupted current is small. 
     INDUSTRIAL APPLICABILITY 
     According to the invention, it is possible to provide an electromagnetic contactor such that it is possible to improve productivity, and simplify a brazing jig, and furthermore, it is possible to control the flatness and warpage of a plate portion supporting fixed contacts.