Patent Publication Number: US-11043346-B2

Title: Electromagnetic relay

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2017/045888 filed on Dec. 21, 2017, which designated the United States and claims the benefit of priority from Japanese Patent Application No. 2016-251040 filed on Dec. 26, 2016. The entire disclosures of all of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an electromagnetic relay. 
     BACKGROUND 
     An electromagnetic relay includes a coil that generates a magnetic force when energized, a contact unit that is opened and closed by the magnetic force, and arc-extinguishing magnets placed on a lateral side of the contact unit. 
     SUMMARY 
     According to an aspect of the present disclosure, an electromagnetic relay includes a contact mechanism unit, a base frame, a permanent magnet, an intermediate cover and an outer cover. The contact mechanism unit includes: a fixed element having a fixed contact; and a movable element having a movable contact facing the fixed contact in a central-axis line direction of a coil. The movable element reciprocates in the central-axis line direction in accordance with an energization state of the coil. The base frame includes: a main body that fixes and supports the fixed element; and a bottom plate that is a rectangular plate portion having a plate thickness direction in an extending direction that is orthogonal to the central-axis line direction. The bottom plate fixes and supports the main body, and the main body extends from the bottom plate in the extending direction. The base frame is formed integrally from an insulating material. The permanent magnet has a magnetic pole direction parallel to a width direction that is orthogonal to the central-axis line direction and the extending direction. The permanent magnet is placed in proximity, in the width direction, to the fixed element and the movable element. The intermediate cover includes: a magnet retainer that retains the permanent magnet; and a covering plate that is a rectangular plate portion extending in the width direction from an end of the magnet retainer in the central-axis line direction. The covering plate faces the contact mechanism unit, and the intermediate cover is formed integrally from an insulating material and supported and fixed by the base frame. The outer cover includes: a top plate extending in the central-axis line direction and the width direction and facing the bottom plate across the contact mechanism unit; a first side plate extending in a direction parallel to the extending direction from one end of the top plate in the central-axis line direction and facing the covering plate; a second side plate extending in a direction parallel to the extending direction from another end of the top plate in the central-axis line direction and facing the first side plate across the contact mechanism unit and the coil; and a pair of third side plates connected to the top plate, the first side plate and the second side plate. The outer cover is formed integrally from an insulating material, and the outer cover has an opening of a bathtub shape formed by the top plate, the first side plate, the second side plate and the pair of third side plates. The bottom plate is attached to the opening, and the outer cover covers the contact mechanism unit and the intermediate cover. A first gap formed between the covering plate and the bottom plate in the extending direction and a second gap formed between the covering plate and the top plate in the extending direction are arranged to be substantially symmetric across the covering plate in the extending direction. The first gap and the second gap are provided on the first side plate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view illustrating a schematic configuration of an electromagnetic relay according to an embodiment. 
         FIG. 2  is a sectional view taken along line II-II in  FIG. 1 . 
         FIG. 3  is a sectional view taken along line III-III in  FIG. 2 . 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 1 . 
         FIG. 5  is an exploded perspective view of permanent magnets, a base frame, and an intermediate cover illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     An electromagnetic relay includes a coil that generates a magnetic force when energized, a contact unit that is opened and closed by the magnetic force, and arc-extinguishing magnets placed on a lateral side of the contact unit. The arc-extinguishing magnets are provided for using the Lorentz force to stretch and extinguish an arc that occurs at the contact unit during the transition from an energization state to a shutoff state. Extinguishing spaces for stretching an arc using the Lorentz force based on the magnetic flux of the arc-extinguishing magnets are placed on different outer sides of the arc-extinguishing magnets in a direction orthogonal to an opening/closing direction of the contact unit and a magnetic pole direction of the arc-extinguishing magnet. 
     In this type of electromagnetic relay, the size of the extinguishing space affects the shutoff performance significantly. Maximizing the extinguishing space can thus ensure high shutoff performance. 
     The direction of current flow in this type of electromagnetic relay can vary. In a specific example, a powering current and a regenerative current which flows in the direction opposite to the powering current may flow through an electromagnetic relay. To maintain favorable shutoff performance regardless of the direction of current flow in such cases, the size difference between an extinguishing space for shutting off the powering current and that for shutting off the regenerative current needs to be minimized. 
     An embodiment of the present disclosure is described with reference to the drawings below. Various changes applicable to the embodiment are presented as modifications together after the description of the embodiment. 
     (Configuration) 
     With reference to  FIGS. 1 to 5 , a configuration of an electromagnetic relay  1  according to the present embodiment is described. The electromagnetic relay  1  according to the present embodiment can be suitably used in a drive power supply system installed in an electrically driven vehicle including a hybrid vehicle. That is, the electromagnetic relay  1  is configured so as to be suitably installed in a power supply system that switches current flow between a powering current and a regenerative current, which flows in a direction opposite to that of the powering current. 
     The electromagnetic relay  1  includes a coil  2 , a contact mechanism unit  3 , a permanent magnet  4 , a drive unit  5 , a base frame  6 , an intermediate cover  7 , and an outer cover  8 . The coil  2 , the contact mechanism unit  3 , the permanent magnet  4 , the drive unit  5 , and the intermediate cover  7  are accommodated in an accommodation space S surrounded by the base frame  6  and the outer cover  8 . 
     A direction parallel to an X axis in each of the figures, that is, any direction parallel to a central axis line C of the coil  2 , is referred to as a central-axis line direction. An X-axis negative direction in the figures is referred to as an attraction direction, and an X-axis positive direction is referred to as a return direction. When a direction parallel to the central axis line C is not specified as the attraction direction or the return direction, the term “central-axis line direction” is used hereinafter. The central-axis line direction can be also referred to as a contact opening/closing direction. 
     A Y-axis direction, which is a direction orthogonal to the central-axis line direction, in the figures is referred to as a width direction. A Z-axis direction, which is a direction orthogonal to the central-axis line direction and an extending direction, is referred to as an extending direction. 
     The coil  2  is placed on a one end side of the accommodation space S in the central-axis line direction (i.e., at an end of the accommodation space S toward the attraction direction). The coil  2 , which generates a magnetic force when energized, is electrically connected to a coil terminal plate  21  secured to the base frame  6 . The coil terminal plate  21  extends from the base frame  6  toward the outside of the electromagnetic relay  1  in a direction parallel to the extending direction (i.e., toward a Z-axis negative direction). 
     The contact mechanism unit  3  is placed in a location toward the return direction with respect to the coil  2 . The contact mechanism unit  3  is configured to switch between an energization state and a shutoff state of the powering current or the regenerative current when driven by the drive unit  5  in accordance with an energization state of the coil  2 . The contact mechanism unit  3  includes a first fixed element  31 A, a second fixed element  31 B, a first input/output terminal  32 A, a second input/output terminal  32 B, a first fixed contact  33 A, a second fixed contact  33 B, a movable element  34 , a first movable contact  35 A, a second movable contact  35 B, a fixed yoke  36 , a movable yoke  37 , and a contact pressure spring  38 . 
     The first fixed element  31 A is a metal plate having a tongue-like shape. The first fixed element  31 A has a longitudinal direction thereof in the extending direction and a plate thickness direction thereof in the central axis line direction. The first fixed element  31 A is placed toward a Y-axis positive direction with respect to the central axis line C. The second fixed element  31 B is a metal plate having a tongue-like shape. The second fixed element  31 B has a longitudinal direction thereof in the extending direction and a plate thickness direction thereof in the central axis line direction. The second fixed element  31 B is placed toward a Y-axis negative direction with respect to the central axis line C. That is, the first fixed element  31 A and the second fixed element  31 B are arranged in the width direction. The first fixed element  31 A and the second fixed element  31 B are supported firmly by the base frame  6 , which is made from an insulating material (for example, synthetic resin), such that the first fixed element  31 A and the second fixed element  31 B are electrically isolated from each other in the shutoff state. 
     The first fixed element  31 A is formed integrally and seamlessly with the first input/output terminal  32 A, which is a metal plate having a tongue-like shape. The first input/output terminal  32 A extends from the base frame  6  toward the outside of the electromagnetic relay  1  in a direction parallel to the extending direction (i.e., toward the Z-axis negative direction). The second fixed element  31 B is formed integrally and seamlessly with the second input/output terminal  32 B, which is a metal plate having a tongue-like shape. The second input/output terminal  32 B extends from the base frame  6  toward the outside of the electromagnetic relay  1  in a direction parallel to the extending direction (i.e., toward the Z-axis negative direction). One of the first input/output terminal  32 A and the second input/output terminal  32 B is electrically connectable to a power source side of the power supply system described above, while the other one thereof is electrically connectable to a load in the power supply system (for example, a motor generator that functions as an electric motor and a generator). 
     The first fixed element  31 A includes the first fixed contact  33 A. The first fixed contact  33 A is an electrical contact member made from metal and having a substantially cylindrical shape with an axial center thereof parallel to the central axis line C. The first fixed contact  33 A is secured to the first fixed element  31 A by crimping or the like. The first fixed element  31 A includes one first fixed contact  33 A in the present embodiment. The first fixed contact  33 A is placed such that the axial center thereof passes through a middle line L (see  FIG. 3 ). The middle line L is a straight line orthogonal to the central axis line C and parallel to the width direction. As illustrated in  FIG. 3 , when viewed along the central axis line direction, the middle line L passes through the central axis line C, which looks like a dot in the view set forth. 
     The second fixed element  31 B includes the second fixed contact  33 B. The second fixed contact  33 B is an electrical contact member made from metal and having a substantially cylindrical shape with an axial center thereof parallel to the central axis line C. The second fixed contact  33 B is secured to the second fixed element  31 B by crimping or the like. The first fixed contact  33 A and the second fixed contact  33 B are disposed on the different sides of the central axis line C in the width direction. 
     The second fixed element  31 B includes two second fixed contacts  33 B that are substantially symmetrically placed with respect to the middle line L in the present embodiment. The second fixed contacts  33 B are placed such that a midpoint of a line segment connecting the two second fixed contacts  33 B and the axial center of the first fixed contact  33 A are substantially symmetrically placed with respect to the middle line L. 
     The movable element  34  is placed toward the return direction with respect to the first fixed element  31 A and the second fixed element  31 B so as to reciprocate in the central axis line direction in accordance with the energization state of the coil  2 . Specifically, the movable element  34  is a metal plate member having a longitudinal direction thereof in the width direction and a plate thickness direction thereof in the central axis line direction. The movable element  34  is placed to face the first fixed element  31 A and the second fixed element  31 B in the central axis line direction. 
     The movable element  34  includes the first movable contact  35 A on one end of the movable element  34  in the longitudinal direction. The movable element  34  includes the second movable contact  35 B on the other end thereof in the longitudinal direction. That is, the first movable contact  35 A and the second movable contact  35 B are disposed on the different sides of the central axis line C in the width direction. 
     The first movable contact  35 A is an electrical contact member made from metal and having a substantially cylindrical shape with an axial center thereof parallel to the central axis line C. The first movable contact  35 A is secured to the movable element  34  by crimping or the like. The first movable contact  35 A is placed to face the first fixed contact  33 A in the central axis line direction. That is, the movable element  34  includes one first movable contact  35 A in the present embodiment. When viewed along the central axis line direction, the first movable contact  35 A coincides with the first fixed contact  33 A. 
     The second movable contact  35 B is an electrical contact member made from metal and having a substantially cylindrical shape with an axial center thereof parallel to the central axis line C. The second movable contact  35 B is secured to the movable element  34  by crimping or the like. Second movable contacts  35 B are placed to face the second fixed contacts  33 B in the central axis line direction. That is, the movable element  34  includes two second movable contacts  35 B in the present embodiment. When viewed along the central axis line direction, the second movable contacts  35 B coincide with the second fixed contacts  33 B. 
     The fixed yoke  36  is made from a ferromagnetic material (for example, magnetic metal) and supported firmly to the base frame  6  in a location near the first fixed element  31 A and the second fixed element  31 B. Specifically, the fixed yoke  36  is embedded in the base frame  6  by insert-molding or the like in a location that is closer to the central axis line C than the first fixed element  31 A and the second fixed element  31 B. 
     The movable yoke  37  is made from a ferromagnetic material (for example, magnetic metal) and coupled to the movable element  34 . The movable yoke  37  is placed to face the fixed yoke  36  in the central axis line direction. The fixed yoke  36  and the movable yoke  37  are provided so as to generate a yoke attraction force therebetween in the energization state. In the energization state, the first fixed contact  33 A is in contact with the first movable contact  35 A, and the second fixed contacts  33 B is in contact with the second movable contacts  35 B, thereby causing the powering current or the regenerative current to flow through the movable element  34 . 
     The contact pressure spring  38  is placed between the intermediate cover  7  and the coupled body of the movable element  34  and the movable yoke  37 . The contact pressure spring  38  is a coil spring that urges the movable element  34  toward the attraction direction toward the first fixed element  31 A and the second fixed element  31 B. 
     The permanent magnet  4  is placed in proximity, in the width direction, to a location where the first fixed element  31 A or the second fixed element  31 B faces the movable element  34 . Specifically, the permanent magnet  4  is attached to the intermediate cover  7 , facing the said location across the intermediate cover  7  in the width direction. The phrase “placed in the proximity to” means that the permanent magnet  4  is placed in the proximity to the said location to the extent that the Lorentz force generated along the extending direction due to the magnetic flux of the permanent magnet  4  causes an arc that occurs between the first fixed element  31 A or the second fixed element  31 B and the movable element  34  at the time of the current shutoff to be stretched and extinguished favorably. The permanent magnet  4  is supported firmly to the intermediate cover  7  on an outer surface of the intermediate cover  7 . The permanent magnet  4  is placed such that a magnetic pole direction thereof is parallel to the width direction. 
     The electromagnetic relay  1  according to the present embodiment includes two permanent magnets  4 . One of the two permanent magnets  4  is placed toward the Y-axis positive direction with respect to the central axis line C, facing the first fixed contact  33 A and the first movable contact  35 A in the width direction across the intermediate cover  7 . The other one of the two permanent magnets  4  is placed toward the Y-axis negative direction with respect to the central axis line C, facing the second fixed contacts  33 B and the second movable contacts  35 B in the width direction across the intermediate cover  7 . That is, the permanent magnets  4  are disposed on the different sides of the central axis line C in the width direction. 
     The two permanent magnets  4  are oriented such that the respective S-poles face the central axis line C in the present embodiment. The two permanent magnets  4  have the same shape and are placed in the same position in the central-axis line direction and in the extending direction, coinciding with each other when viewed along the width direction. 
     The drive unit  5  is configured to cause the movable element  34  to reciprocate in the central axis line direction in accordance with the energization state of the coil  2 . Specifically, the drive unit  5  includes a fixed core  51 , a shaft  52 , a movable core  53 , a return spring  54 , and a movable insulator  55 . 
     The fixed core  51  is a substantially cylindrical member formed integrally and seamlessly from a ferromagnetic material (for example, a ferromagnetic metal material) and is accommodated in the coil  2 . The shaft  52  is a cylindrical rod-like member made from metal and is placed such that a longitudinal direction thereof is parallel to the central-axis line direction. The shaft  52  is accommodated in a through hole formed in the fixed core  51  along an axial center of the fixed core  51  and can reciprocate along the central-axis line direction. 
     The movable core  53  is a substantially disk-like member made from a ferromagnetic material (for example, a ferromagnetic metal material) and is fixed to the shaft  52  in an intermediate position of the shaft  52  in the longitudinal direction of the shaft  52 . The movable core  53  faces the fixed core  51  in the central axis line direction. The movable core  53  is thus attracted to the fixed core  51  when the coil  2  is energized. The attraction direction is a direction in which the movable core  53  is attracted to the fixed core  51  when the coil  2  is energized. 
     The return spring  54  is a coil spring placed around the fixed core  51  and the shaft  52  and urges the movable core  53  toward the return direction. The movable insulator  55  is made from an insulating material (for example, synthetic resin). The movable insulator  55  is secured to an end of the shaft  52  located toward the return direction, covering the end. When energization to the coil  2  is shut off and the movable core  53  moves toward the return direction, urged by the return spring  54 , the movable insulator  55  comes in contact with the movable element  34 , moving the movable element  34  toward the return direction. 
     The base frame  6  firmly supports the coil  2 , the contact mechanism unit  3 , the drive unit  5 , and the intermediate cover  7 . The base frame  6  is formed integrally and seamlessly from an insulating material (for example, synthetic resin). The base frame  6  includes a main body  61 , a bottom plate  62 , and a guide  63 . 
     The main body  61  protrudes from the bottom plate  62  in the extending direction (i.e., toward the Z-axis positive direction). The main body  61  supports the fixed yoke  36  internally. The first fixed element  31 A and the second fixed element  31 B are supported firmly on a surface of the main body  61  that faces the movable element  34  in the central-axis line direction. The main body  61  has a through hole, through which the movable insulator  55  can pass, in a location corresponding to the central axis line C. 
     The bottom plate  62  is a plate portion having a plate thickness direction thereof in the extending direction and supports the main body  61  firmly. The main body  61  extends from the bottom plate  62  in the extending direction in a cantilever fashion. The bottom plate  62  has a rectangular shape when viewed along the extending direction. 
     The guide  63  extends from the main body  61  in the return direction. The guide  63  is formed to guide the reciprocating movement of the movable element  34  along the central-axis line direction. 
     The intermediate cover  7  is supported firmly to the main body  61  of the base frame  6  and covers the contact mechanism unit  3  from an upper side in the  FIGS. 1 and 2 . The intermediate cover  7  includes a pair of magnet retainers  71  facing each other in the width direction, and a covering plate  72  placed between the magnet retainers  71 . The intermediate cover  7  is formed integrally and seamlessly from an insulating material (for example, synthetic resin). 
     The magnet retainer  71  has a recess having an opening in the return direction in one specific example illustrated in  FIGS. 1 to 5  (note that the direction of the opening of the recess is presented as a mere example and that the recess can have an opening in another direction). The recess is formed so as to be able to retain the permanent magnet  4  internally. The magnet retainer  71  has a thin-plate wall facing the contact mechanism unit  3 . The wall has an end located toward the return direction that is connected to the covering plate  72 . That is, the permanent magnet  4  is in contact with an outer surface of the thin-plate wall described above. 
     The covering plate  72  is a plate portion having a rectangular shape with a plate thickness direction thereof in the central-axis line direction. The covering plate  72  extends in the width direction from the ends of the magnet retainers  71  located toward the return direction. The covering plate  72  thus faces the contact mechanism unit  3 . The intermediate cover  7  is thus substantially U-shaped when viewed along the extending direction, with the magnet retainers  71  connected to the both ends of the covering plate  72  in the width direction. The intermediate cover  7  has a shape substantially symmetrical with respect to a plane passing through the central axis line C, the normal line of the plane being the middle line L. 
     A spring locking groove  73  is provided in an inner surface of the covering plate  72  that faces the contact mechanism unit  3 . The spring locking groove  73  has a substantially ring-like shape and locks an end of the contact pressure spring  38  located toward the return direction. 
     The outer cover  8  has a bathtub shape having an opening in one face of the cuboid shape and is formed from an insulating material (for example, synthetic resin) integrally and seamlessly. Specifically, the outer cover  8  includes a top plate  80 , a first side plate  81 , a second side plate  82 , and a pair of third side plates  83 . 
     The top plate  80  is a flat-plate portion having a rectangular shape with a plate thickness direction thereof in the extending direction. The top plate  80  extends in the central-axis line direction and in the width direction. The top plate  80  is disposed to face the bottom plate  62  of the base frame  6  across the contact mechanism unit  3 . 
     The first side plate  81  is a flat-plate portion having a rectangular shape with a plate thickness direction thereof in the central-axis line direction. The first side plate  81  is placed near the covering plate  72 , facing the covering plate  72 . That is, the first side plate  81  extends from an end of the top plate  80  that is located toward the return direction, facing the covering plate  72 . The first side plate  81  extends in a direction parallel to the extending direction (i.e., toward the Z-axis negative direction). 
     The second side plate  82  is a flat-plate portion having a rectangular shape with a plate thickness direction thereof in the central-axis line direction. The second side plate  82  is disposed to face the first side plate  81  across the coil  2  and the contact mechanism unit  3 . That is, the second side plate  82  extends from an end of the top plate  80  that is located toward the attraction direction. The second side plate  82  extends in a direction parallel to the extending direction (i.e., toward the Z-axis negative direction). 
     Each of the third side plates  83  is a flat-plate portion having a rectangular shape and has a plate thickness direction thereof in the width direction. One of the third side plates  83  is connected to one end of the top plate  80  located in the width direction, one end of the first side plate  81  located in the width direction, and one end of the second side plate  82  located in the width direction. The other one of the third side plates  83  is connected to the other end of the top plate  80  located in the width direction, the other end of the first side plate  81  located in the width direction, and the other end of the second side plate  82  located in the width direction. 
     The aforementioned bathtub shape, which is formed by the top plate  80 , the first side plate  81 , the second side plate  82 , and the third side plates  83 , has an opening  84  that opens along the extending direction (i.e., toward the Z-axis negative direction). The outer cover  8  and the bottom plate  62  of the base frame  6  cover the coil  2 , the contact mechanism unit  3 , the permanent magnets  4 , the drive unit  5 , and the intermediate cover  7  with the bottom plate  62  attached to the opening  84 . 
     The outer cover  8  and/or the bottom plate  62  of the base frame  6  have/has a vent hole (not shown) through which the accommodation space S communicates with the outside air. The electromagnetic relay  1  according to the present embodiment thus has what one calls an “open-type” configuration, which allows the accommodation space S to communicate with the outside air. 
     A first gap G 1  is formed between the covering plate  72  and the bottom plate  62  in the extending direction. A second gap G 2  is formed between the covering plate  72  and the top plate  80  in the extending direction. The first gap G 1  and the second gap G 2  are spaces constituting portions of the accommodation space S and occupied by gas present in the accommodation space S (i.e., air). The first gap G 1  and the second gap G 2  are positioned toward the Y-axis positive direction with respect to the central axis line C (i.e., on the side of the central axis line C where the first fixed contact  33 A and the first movable contact  35 A are located). The first gap G 1  and the second gap G 2  are arranged in the extending direction substantially symmetrically with respect to the covering plate  72 . The first gap G 1  and the second gap G 2  face the first side plate  81 . 
     A third gap G 3  is formed between the covering plate  72  and the bottom plate  62  in the extending direction. A fourth gap G 4  is formed between the covering plate  72  and the top plate  80  in the extending direction. The third gap G 3  and the fourth gap G 4  are spaces constituting portions of the accommodation space S. The third gap G 3  and the fourth gap G 4  are positioned toward the Y-axis negative direction with respect to the central axis line C (i.e., on the side of the central axis line C where the second fixed contacts  33 B and the second movable contacts  35 B are located). The third gap G 3  and the fourth gap G 4  are arranged in the extending direction substantially symmetrically with respect to the covering plate  72 . The third gap G 3  and the fourth gap G 4  face the first side plate  81 . 
     A first extinguishing space E 1 , a second extinguishing space E 2 , a third extinguishing space E 3 , and a fourth extinguishing space E 4  are also provided in the accommodation space S. The first extinguishing space E 1  and the second extinguishing space E 2  are spaces constituting portions of the accommodation space S. The first extinguishing space E 1  and the second extinguishing space E 2  are positioned toward the Y-axis positive direction with respect to the central axis line C (i.e., on the side of the central axis line C where the first fixed contact  33 A and the first movable contact  35 A are located). The third extinguishing space E 3  and the fourth extinguishing space E 4  are spaces constituting portions of the accommodation space S. The third extinguishing space E 3  and the fourth extinguishing space E 4  are positioned toward the Y-axis negative direction with respect to the central axis line C (i.e., on the side of the central axis line C where the second fixed contacts  33 B and the second movable contacts  35 B are located). 
     The first extinguishing space E 1  is positioned toward the bottom plate  62  with respect to the middle line L (i.e., toward the Z-axis negative direction) for use as an extinguishing space when the regenerative current is shut off. The regenerative current flows from the second input/output terminal  32 B through the second fixed element  31 B, the second fixed contacts  33 B, the second movable contacts  35 B, the movable element  34 , and the first movable contact  35 A, the first fixed contact  33 A, the first fixed element  31 A, to the first input/output terminal  32 A. The first extinguishing space E 1  includes a space between the contact mechanism unit  3  and the bottom plate  62 , the first gap G 1 , and a space between one of the magnet retainers  71  and the bottom plate  62 . 
     The second extinguishing space E 2  is positioned toward the top plate  80  with respect to the middle line L (i.e., toward the Z-axis positive direction) for use as an extinguishing space when the powering current is shut off. The powering current flows from the first input/output terminal  32 A through the first fixed element  31 A, the first fixed contact  33 A, the first movable contact  35 A, the movable element  34 , the second movable contacts  35 B, the second fixed contacts  33 B, and the second fixed element  31 B, to the second input/output terminal  32 B. The second extinguishing space E 2  includes a space between the contact mechanism unit  3  and the top plate  80 , the second gap G 2 , and a space between the one of the magnet retainers  71  and the top plate  80 . 
     The first extinguishing space E 1  and the second extinguishing space E 2  are arranged in the extending direction substantially symmetrically with respect to the covering plate  72  (i.e., substantially symmetrically with respect to the middle line L). The first extinguishing space E 1  and the second extinguishing space E 2  thus have substantially the same volume. 
     The first gap G 1  and the second gap G 2  are thus substantially symmetrical with respect to an imaginary plane including the middle line L and the central axis line C. The space between the contact mechanism unit  3  and the bottom plate  62 , which is included in the first extinguishing space E 1 , and the space between the contact mechanism unit  3  and the top plate  80 , which is included in the second extinguishing space E 2 , are also substantially symmetrical with respect to the aforementioned imaginary plane. The space between the one of the magnet retainers  71  and the bottom plate  62 , which is included in the first extinguishing space E 1 , and the space between the one of the magnet retainers  71  and the top plate  80 , which is included in the second extinguishing space E 2 , are also substantially symmetrical with respect to the aforementioned imaginary plane. 
     The third extinguishing space E 3  is positioned toward the bottom plate  62  with respect to the middle line L (i.e., toward the Z-axis negative direction) for use as an extinguishing space when the regenerative current is shut off. The third extinguishing space E 3  includes a space between the contact mechanism unit  3  and the bottom plate  62 , the third gap G 3 , and a space between the other one of the magnet retainers  71  and the bottom plate  62 . 
     The fourth extinguishing space E 4  is positioned toward the top plate  80  with respect to the middle line L (i.e., toward the Z-axis positive direction) for use as an extinguishing space when the powering current is shut off. The fourth extinguishing space E 4  includes a space between the contact mechanism unit  3  and the top plate  80 , the fourth gap G 4 , and a space between the other one of the magnet retainers  71  and the top plate  80 . 
     The third extinguishing space E 3  and the fourth extinguishing space E 4  are arranged in the extending direction substantially symmetrically with respect to the covering plate  72  (i.e., substantially symmetrically with respect to the middle line L). The third extinguishing space E 3  and the fourth extinguishing space E 4  thus have substantially the same volume. 
     As described above, the first extinguishing space E 1  and the third extinguishing space E 3  are disposed on the different sides of the central axis line C in the width direction in the electromagnetic relay  1  according to the present embodiment. The second extinguishing space E 2  and the fourth extinguishing space E 4  are also disposed on the different sides of the central axis line C in the width direction. 
     The electromagnetic relay  1  according to the present embodiment is configured to allow air to flow from the first gap G 1  to the second gap G 2  via the first extinguishing space E 1 , a space in the intermediate cover  7 , and the second extinguishing space E 2 . The electromagnetic relay  1  according to the present embodiment is configured to allow air to similarly flow from the third gap G 3  to the fourth gap G 4  via the third extinguishing space E 3 , a space in the intermediate cover  7 , and the fourth extinguishing space E 4 . 
     (Effects) 
     When the regenerative current is shut off, the direction of current flow of an arc occurring between the first fixed contact  33 A and the first movable contact  35 A is from the first movable contact  35 A toward the first fixed contact  33 A. The arc is thus subjected to the Lorentz force extending toward the Z-axis negative direction in the first extinguishing space E 1 . 
     When the powering current is shut off, the direction of current flow of an arc occurring between the first fixed contact  33 A and the first movable contact  35 A is from the first fixed contact  33 A toward the first movable contact  35 A. The arc is thus subjected to the Lorentz force extending toward the Z-axis positive direction in the second extinguishing space E 2 . 
     When the regenerative current is shut off, the direction of current flow of an arc occurring between the second fixed contacts  33 B and the second movable contacts  35 B is from the second fixed contacts  33 B to the second movable contacts  35 B. The arc is thus subjected to the Lorentz force extending toward the Z-axis negative direction in the third extinguishing space E 3 . 
     When the powering current is shut off, the direction of current flow of an arc occurring between the second fixed contacts  33 B and the second movable contacts  35 B is from the second movable contacts  35 B toward the second fixed contacts  33 B. The arc is thus subjected to the Lorentz force extending toward the Z-axis positive direction in the fourth extinguishing space E 4 . 
     The first extinguishing space E 1  in the present embodiment includes a space adjacent to the contact mechanism unit  3  (i.e., where the first fixed contact  33 A faces the first movable contact  35 A) in the extending direction as well as the first gap G 1 , which is adjacent to the said space in the central-axis line direction. That is, the first extinguishing space E 1  according to the present embodiment is a space enlarged in the central-axis line direction, extending from the space adjacent to the contact mechanism unit  3  in the extending direction to a location facing the first side plate  81 . The same applies to the third extinguishing space E 3 . The configuration thus enables favorable extinction of an arc in the first extinguishing space E 1  and the third extinguishing space E 3 . Favorable shutoff performance can thus be ensured for shutting off the regenerative current. 
     The second extinguishing space E 2  in the present embodiment includes a space adjacent to the contact mechanism unit  3  in the extending direction as well as the second gap G 2 , which is adjacent to the said space in the central-axis line direction. That is, the second extinguishing space E 2  according to the present embodiment is a space enlarged in the central-axis line direction, extending from the space adjacent to the contact mechanism unit  3  in the extending direction to a location facing the first side plate  81 . The same applies to the fourth extinguishing space E 4 . The configuration thus enables favorable extinction of an arc in the second extinguishing space E 2  and the fourth extinguishing space E 4 . Favorable shutoff performance can thus be ensured for shutting off the powering current. 
     The electromagnetic relay  1  according to the present embodiment has what one calls an “open-type” configuration, which allows the accommodation space S to communicate with the outside air as described above. That is, the accommodation space S of the electromagnetic relay  1  according to the present embodiment is not filled with an arc-extinguishing gas for facilitating extinction of an arc. The electromagnetic relay  1  according to the present embodiment, however, includes the first extinguishing space E 1  to the fourth extinguishing space E 4 , which are extinguishing spaces that enable favorable current shutoff, as described above. The configuration can thus provide favorable current shutoff properties without employing a sealed structure filled with an arc-extinguishing gas. 
     Additionally, the first extinguishing space E 1  for shutting off the regenerative current and the second extinguishing space E 2  for shutting off the powering current are arranged in the extending direction substantially symmetrically with respect to the covering plate  72  and have substantially the same volume in the present embodiment. The third extinguishing space E 3  for shutting off the regenerative current and the fourth extinguishing space E 4  for shutting off the powering current are similarly arranged in the extending direction substantially symmetrically with respect to the covering plate  72  and have substantially the same volume. 
     The configuration can thus curb to the extent possible a significant difference in shutoff performance between when the regenerative current is shut off and when the powering current is shut off. The configuration thus eliminates constraints of polarity in connection to the first input/output terminal  32 A and the second input/output terminal  32 B in the electromagnetic relay  1 . Accordingly, a heightened degree of freedom in design and a wide applicable range can be provided. 
     Additionally, the first extinguishing space E 1  according to the present embodiment includes the space between the contact mechanism unit  3  and the bottom plate  62  as well as the first gap G 1  and the space between the one of the magnet retainers  71  and the bottom plate  62 . The same applies to the second extinguishing space E 2  to the fourth extinguishing space E 4 . Furthermore, the accommodation space S including the first extinguishing space E 1  to the fourth extinguishing space E 4  communicates with the outside air. The configuration can thus release heat produced in the contact mechanism unit  3  to the outside favorably. 
     Furthermore, the configuration according to the present embodiment allows air to flow favorably from the first gap G 1  to the second gap G 2  via the first extinguishing space E 1 , the space in the intermediate cover  7 , and the second extinguishing space E 2 . The configuration according to the present embodiment similarly allows air to favorably flow from the third gap G 3  to the fourth gap G 4  via the third extinguishing space E 3 , the space in the intermediate cover  7 , and the fourth extinguishing space E 4 . 
     The configuration can thus release heat produced in the contact mechanism unit  3  to the outside favorably. When a high-speed compressed air flow is injected from a second extinguishing space E 2  side toward the Z-axis negative direction for removal of dust and the like during the manufacturing process of the electromagnetic relay  1 , the air flow favorably passes through the first gap G 1  toward the X-axis positive direction. When a high-speed compressed air flow is similarly injected from a fourth extinguishing space E 4  side toward the Z-axis negative direction, the air flow favorably passes through the third gap G 3  toward the X-axis positive direction. Even when the direction of the compressed air flow is opposite to those in the examples described above, the result is similar. 
     (Modification) 
     The present disclosure is not limited to the specific examples described in the foregoing embodiment. The embodiment described above can be modified as appropriate. Some representative modifications are described below. Difference from the embodiment described above only is explained in the description of modifications presented below. Constituent elements of the modifications identical with or equivalent to those in the embodiment described above are designated with the identical symbols. For constituent elements of the modifications described below that are designated with symbols identical with those in the embodiment described above, the description provided in the foregoing embodiment can be referenced as appropriate as long as there is no technical contradiction or no specific additional explanation is provided. 
     The present disclosure is not limited to the specific configuration described in the foregoing embodiment. For example, the use of the electromagnetic relay  1  is not limited to a drive power supply system installed in an electrically driven vehicle. That is, the current that flows through the electromagnetic relay  1  is not limited to the powering current and the regenerative current. 
     The electromagnetic relay  1  may have a sealed structure in which an accommodation space S is a sealed space. In such cases, the accommodation space S may be filled with an arc-extinguishing gas. 
     Two first fixed contacts  33 A may be placed symmetrically with respect to the middle line L, similarly to the second fixed contacts  33 B. Alternatively, one second fixed contact  33 B may be placed on the middle line L, similarly to the first fixed contact  33 A. 
     Other arbitrary modifications can be also made to the contact mechanism unit  3 . 
     The orientations of the magnetic poles of the permanent magnets  4  can be changed as appropriate. For example, the two permanent magnets  4  may be oriented such that the respective N-poles face the central axis line C. Alternatively, the two permanent magnets  4  may be oriented such that the respective N-poles face the Y-axis positive direction. That is, the two permanent magnets  4  may be oriented such that the respective like-poles face each other. The configuration of the drive unit  5  is not limited to the specific example in the embodiment described above. 
     As described above, each of the magnet retainers  71  has a recess that can retain the permanent magnet  4  internally, the recess having an opening in the return direction. The direction of the opening is not limited to the return direction and may be, for example, in the attraction direction or the extending direction. 
     While the first gap G 1  and the second gap G 2  are placed substantially symmetrically with respect to the covering plate  72  or the middle line L, the first gap G 1  and the second gap G 2  are not required to be perfectly symmetrical. That is, the first gap G 1  and the second gap G 2  only have to have symmetry in position and shape to the extent that can be substantially described as symmetry; thus, a slight loss of symmetry, a minute difference in volume, and a minute difference in dimension between the first gap G 1  and the second gap G 2  are permissible. The same applies to the symmetries between the first extinguishing space E 1  and the second extinguishing space E 2 , between the third gap G 3  and the fourth gap G 4 , and between the third extinguishing space E 3  and the fourth extinguishing space E 4 . 
     Any of the constituent elements formed seamlessly and integrally in the foregoing description may be formed integrally with a seam using methods such as bonding multiple constituent elements. For example, the main body  61  of the base frame  6  may be bonded to the bottom plate  62 . Similarly, any of the constituent elements joined together with a seam may be formed seamlessly and integrally. 
     The materials of the constituent elements are not particularly limited. For example, the movable insulator  55 , the base frame  6 , the intermediate cover  7 , and the outer cover  8  are typically made from insulating synthetic resin as described above. The constituent elements that are conductive and the constituent elements that are ferromagnetic are typically made from metal. The present disclosure, however, is not limited to such materials. 
     Modifications are also not limited to the examples described above. Multiple modifications can be combined. Furthermore, all or part of the embodiment described above and all or part of the modifications can be combined. 
     While the present disclosure has been described with reference to embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. To the contrary, the present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various elements are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.