ELECTROMAGNETIC RELAY

FIELD

The present invention relates to an electromagnetic relay.

BACKGROUND

An electromagnetic relay has been conventionally known that opens and closes an electrical circuit. For example, Japanese Unexamined Patent Application Publication No. 2012-142195 discloses an electromagnetic relay that includes a fixed terminal, a fixed contact on the fixed terminal, a movable contact piece, and a movable contact on the movable contact piece. The movable contact is configured to contact the fixed contact, and when the movable contact separates from or contacts the fixed contact, an electric circuit is opened or closed, respectively. The electromagnetic relay further includes a permanent magnet for extending an arc that occurs when the movable contact separates from the fixed contact.

SUMMARY

In the electromagnetic relay of Japanese Unexamined Patent Application Publication No. 2012-142195, when an arc occurs, the arc is likely to adhere to the ends of the fixed and movable contacts or the boundary between the contacts and terminal, which may hinder the transfer of the arc.

An object of the present invention is to quickly transfer an arc in an electromagnetic relay.

An electromagnetic relay according to one aspect of the present invention includes a fixed terminal, a movable contact piece, a first contact, a second contact, a movable mechanism, and a magnet unit. The first contact is disposed on one of the fixed terminal or the movable contact piece. The second contact is configured to contact the first contact and disposed on another of the fixed terminal or the movable contact piece. The movable mechanism is configured to move the movable contact piece between a closed position where the first contact is in contact with the second contact and an open position where the first contact is separated from the second contact. The magnet unit generates a magnetic field to apply a Lorentz force to an arc that occurs between the first contact and the second contact. The magnet unit applies the Lorentz force in a first direction to the arc when the current flowing through the arc is directed from the second contact toward the first contact. One of the first contact or the second contact protrudes in the first direction with respect to the other of the first contact or the second contact. A center position of the first contact and a center position of the second contact are shifted from each other in the first direction in a state in which the first contact is in contact with the second contact.

In the electromagnetic relay, for example, when the first contact protrudes in the first direction with respect to the second contact, one end of the first contact lies beyond one end of the second contact in the first direction. Thus, the end of an arc on the first-contact side is offset in the first direction from the end of an arc on the second-contact side. Accordingly, the direction of the Lorentz force acting on the arc changes, facilitating the end of the arc on the second-contact side to transfer to the terminal where the second contact is positioned (one of the fixed terminal and the movable contact piece). That is, the direction of the Lorentz force acting on the arc changes, and thereby it is possible to cause the end of the arc on the second-contact side to quickly transfer to the terminal where the second contact is disposed. As a result, the arc can be quickly transferred in the first direction.

The first contact may protrude in the first direction with respect to the second contact. In this case, when the current flowing through the arc is directed from the second contact toward the first contact, the Lorentz force acts in the direction in which the end of the arc on the second contact is transferred to the terminal: the end of the arc on the second contact that provides an anode-side contact is transferred more easily than that on the first contact that provides a cathode-side contact. As a result, one of the ends of the arc can be transferred to the terminal more effectively, enhancing the quick transfer of the arc.

The second contact may protrude in the second direction opposite to the first direction more than the first contact. The magnet unit may apply the Lorentz force in second direction to the arc when the current flowing through the arc is directed from the first contact toward the second contact. In this case, it is possible to cause the end of the arc to be quickly transferred to the terminal where one of the first and second contacts is disposed to provide an anode-side contact, regardless of the direction of the current flow.

In a state in which the first contact is separated from the second contact, the center position of the first contact and the center position of the second contact may be shifted each other in the first direction. In this case, also, the arc can be quickly transferred in the first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an electromagnetic relay.

FIG. 2 is a schematic cross-sectional view of the electromagnetic relay.

FIG. 3 is a schematic diagram of the inside of a contact case, viewed from above.

FIG. 4 is a schematic cross-sectional view of and around a movable contact when the movable contact is in an open position, taken along the line L-L in FIG. 3.

FIG. 5 is a schematic cross-sectional view of and around the movable contact when the movable contact is in a closed position, taken along the line L-L in FIG. 3.

FIG. 6 is a schematic view of the inside of a contact case according to another embodiment, viewed from above.

FIG. 7 is a schematic cross-sectional view of and around a movable contact when the movable contact is in an open position, taken along the line L1-L1 in FIG. 6.

FIG. 8 is a schematic view of the inside of a contact case according to another embodiment, viewed from above.

FIG. 9 is a schematic view of the inside of a contact case according to another embodiment, viewed from above.

FIG. 10 is a schematic diagram of the inside of a contact case according to another embodiment, viewed from above.

DETAILED DESCRIPTION

Hereinafter, an electromagnetic relay of an embodiment according to an aspect of the presentation will be described with reference to the drawings. When referring to the drawings, the upper side in FIG. 1 is referred to as “up”, the lower side as “down”, the left side as “left”, and the right side as “right” for the brevity of description. Also, the direction orthogonal to the plane of FIG. 1 is defined as the front-rear direction. However, these directions are defined for the convenience of description and are not intended to limit the directions of arrangements of an electromagnetic relay 100.

FIGS. 1 and 2 are each a schematic cross-sectional view of the electromagnetic relay 100. The electromagnetic relay 100 includes a contact case 2, a contact device 3, a drive device 4, and a magnet unit 5.

The contact case 2 has a substantially rectangular box shape and is comprised of insulating material. In the present embodiment, the contact case 2 is comprised of resin. The contact case 2 accommodates the contact device 3.

FIG. 3 is a schematic diagram of the inside of the contact case 2, viewed from above. The contact case 2 includes first to fourth inner surfaces 2a to 2d. The first to fourth inner surfaces 2a to 2d are the inner surfaces of the contact case 2, respectively, on the front, rear, left, and right sides. The first inner surface 2a and the second inner surface 2b are disposed facing each other in the front-rear direction. The first inner surface 2a and the second inner surface 2b extend in the up-down direction and the left-right direction. The third inner surface 2c and the fourth inner surface 2d are disposed to face each other in the left-right direction. The third inner surface 2c and the fourth inner surface 2d extend in the up-down direction and the front-rear direction.

The contact device 3 includes fixed terminals 6 and 7, fixed contacts 8a and 8b, a movable contact piece 9, movable contacts 10a and 10b, and a movable mechanism 11. The fixed terminals 6 and 7, the fixed contacts 8a and 8b, the movable contact piece 9, and the movable contacts 10a and 10b are comprised of conductive material. The fixed contact 8a and the movable contact 10b in the present embodiment are examples of the first contact, and the fixed contact 8b and movable contact 10a in the present embodiment are examples of the second contact.

The fixed terminals 6 and 7 are plate-shaped terminals and extend in the left-right direction. The fixed terminals 6 and 7 are disposed to be separated from each other in the left-right direction. The fixed terminal 6 includes an external connection 6a projecting leftward from the contact case 2. The fixed terminal 7 includes an external connection 7a projecting rightward from the contact case 2.

The fixed contacts 8a and 8b are disposed inside the contact case 2. The fixed contacts 8a and 8b are substantially rectangular when viewed in the up-down direction. The fixed contacts 8a and 8b may have chamfered ends. The fixed contact 8a is disposed on the fixed terminal 6. The fixed contact 8a protrudes, toward the movable contact piece 9, from the surface of the fixed terminal 6 facing the movable contact piece 9. Here, the fixed contact 8a protrudes downward from the fixed terminal 6. The fixed contact 8b is disposed on the fixed terminal 7. The fixed contact 8b protrudes, toward the movable contact piece 9, from the surface of the fixed terminal 7 facing the movable contact piece 9.

The movable contact piece 9 is a plate-like member elongated in one direction and extends in the left-right direction within the contact case 2. In the present embodiment, the longitudinal direction of the movable contact piece 9 corresponds to the left-right direction. Also, the lateral direction of the movable contact piece 9 corresponds to the front-rear direction. The movable contact piece 9 moves integrally with the movable contacts 10a and 10b. The movable contact piece 9 is disposed to be separated from the first inner surface 2a and the second inner surface 2b in the front-rear direction. Between the movable contact piece 9 and the first inner surface 2a and between the movable contact piece 9 and the second inner surface 2b, extension spaces 12a and 12b are defined for extending an arc, respectively.

The movable contacts 10a and 10b are disposed on the movable contact piece 9. The movable contacts 10a and 10b are substantially rectangular when viewed in the up-down direction. The movable contacts 10a and 10b may have chamfered ends. The movable contacts 10a and 10b are movable between a closed position (the position shown in FIG. 1) to be in contact with the fixed contacts 8a and 8b and an open position (the position shown in FIG. 2) to be separated from the fixed contacts 8a and 8b. The movable contacts 10a and 10b are movable in a contact direction Z1 to contact the fixed contacts 8a and 8b and in a separation direction Z2 to be separated from them. In the present embodiment, the contact direction Z1 and the separation direction Z2 correspond to the up-down direction.

The movable contact 10a is at a position facing the fixed contact 8a and protrudes from the movable contact piece 9 toward the fixed contact 8a. The movable contact 10b is at a position facing the fixed contact 8b and protrudes from the movable contact piece 9 toward the fixed contact 8b.

The movable mechanism 11 moves the movable contact piece 9 between the closed position shown in FIG. 1 and the open position shown in FIG. 2. The movable mechanism 11 moves the movable contacts 10a and 10b via the movable contact piece 9. The movable mechanism 11 includes a drive shaft 21, a first holding member 22, a second holding member 23, and a contact spring 24. The drive shaft 21 is coupled to the movable contact piece 9. The drive shaft 21 extends in the up-down direction and passes through the movable contact piece 9 in the up-down direction. The drive shaft 21 is set to be movable in the contact direction Z1 and the separation direction Z2.

The first holding member 22 is fixed to the drive shaft 21 above the movable contact piece 9. The second holding member 23 is fixed to the drive shaft 21 below the movable contact piece 9. The contact spring 24 is disposed between the movable contact piece 9 and the second holding member 23. The contact spring 24 urges the movable contact piece 9 in the contact direction Z1 via the second holding member 23.

The drive device 4 moves the movable mechanism 11 by electromagnetic force in the contact direction Z1 and the separation direction Z2. In the present embodiment, the drive device 4 moves the movable contact piece 9 in the contact direction Z1 and the separation direction Z2 via the drive shaft 21. The drive device 4 includes a coil 31, a movable iron core 32, a fixed iron core 33, a yoke 34, and a return spring 35.

Upon application of a voltage to the coil 31 for excitation, the coil 31 generates an electromagnetic force to move the movable iron core 32 in the contact direction Z1. The movable iron core 32 is coupled to the drive shaft 21 so as to be movable together. The fixed iron core 33 is at a position facing the movable iron core 32. The yoke 34 is set to surround the coil 31. The return spring 35 is disposed between the movable iron core 32 and the fixed iron core 33. The return spring 35 urges the movable iron core 32 in the separation direction Z2.

The magnet unit 5 generates a magnetic field to apply Lorentz forces F1 and F2 to the arcs that are generated between the fixed contact 8a and the movable contact 10a and between the fixed contact 8b and the movable contact 10b. The magnet unit 5 is disposed such that the Lorentz force F1 acts, in the first direction D1, on an arc occurring between the fixed contact 8a and the movable contact 10a when the current flowing through the arc is directed from the movable contact 10a to the fixed contact 8a (from the rear to the front of the paper surface of FIG. 3). That is, the first direction D1 is the direction in which the arc that occurs between the fixed contact 8a and the movable contact 10a is extended. However, in the present embodiment, the direction of the Lorentz force F1 acting on the arc changes as the arc is transferred. As such, more precisely, the first direction D1 means the direction of the Lorentz force F1 acting on the arc at the point of time when the arc occurs between the fixed contact 8a and the movable contact 10a. The first direction D1 in the present embodiment is forward. The first direction D1 is parallel to the lateral direction of the movable contact piece 9 and is the direction from the movable contact piece 9 toward the first inner surface 2a.

The magnet unit 5 includes a first magnet 5a and a second magnet 5b. The first magnet 5a and the second magnet 5b are permanent magnets. The first magnet 5a and the second magnet 5b are substantially rectangular and extend in the front-rear direction and the up-down direction. The first magnet 5a is disposed on the outer periphery of the contact case 2 below the fixed terminal 6. The second magnet 5b is disposed on the outer periphery of the contact case 2 below the fixed terminal 7. The first magnet 5a is positioned to face the second magnet 5b in the left-right direction. The first magnet 5a and the second magnet 5b are disposed such that their opposite poles face each other in the longitudinal direction of the movable contact piece 9. The first magnet 5a is placed with its N pole facing the contact case 2. The second magnet 5b is placed with its S pole facing the contact case 2.

The first magnet 5a and the second magnet 5b disposed as described above produce magnetic flux in the direction from the first magnet 5a toward the second magnet 5b. That is, around the fixed contacts 8a and 8b and the movable contacts 10a and 10b, the magnetic flux flows in a direction substantially parallel to the longitudinal direction of the movable contact piece 9. Thus, for example, when a current flows from the movable contact 10a toward the fixed contact 8a, the Lorentz force F1 acts on the arc occurring between the fixed contact 8a and the movable contact 10a, and the arc is transferred to the arc extension space 12a. In contrast, on the arc occurring between the fixed contact 8b and the movable contact 10b, the Lorentz force F2 acts in the second direction D2 opposite to the first direction D1. That is, the arc that occurs between the fixed contact 8b and the movable contact 10b is subjected to the Lorentz force F2 acting in the direction toward the second inner surface 2b, and the arc is transferred to the arc extension space 12b. In the present embodiment, unless otherwise specified, the direction in which a current flow is assumed to be the direction from the movable contact 10a toward the fixed contact 8a. As such, on the movable contact 10b side, a current flows in the direction from the fixed contact 8b toward the movable contact 10b.

Next, the operations of the electromagnetic relay 100 will be described. While the drive device 4 is not excited, the movable contacts 10a and 10b are in the open position as shown in FIG. 1. As shown in FIG. 2, when the drive device 4 is excited, the movable contacts 10a and 10b move from the open position to the closed position. Specifically, when a voltage is applied to the coil 31, the movable iron core 32 moves in the contact direction Z1 against the elastic force of the return spring 35. As the movable iron core 32 moves in the contact direction Z1,the drive shaft 21 and the movable contact piece 9 move in the contact direction Z1, moving the movable contacts 10a and 10b to the closed positions to come into contact with the fixed contacts 8a and 8b. When the application of voltage to the coil 31 is stopped, the movable iron core 32 moves in the separation direction Z2 together with the movable contact piece 9 according to the elastic force of the return spring 35, moving the movable contacts 10a and 10b to the open position.

Next, the fixed contact 8a and the movable contact 10a will be described in detail. FIG. 4 is a schematic cross-sectional view of and around the movable contact 10a when the movable contact 10a is in the open position, taken along the line L-L in FIG. 3. FIG. 4 schematically shows how the arc occurring between the fixed contact 8a and the movable contact 10a is extended. FIG. 5 is a schematic cross-sectional view of and around the movable contact 10a when the movable contact 10a is in the closed position, taken along the line L-L in FIG. 3.

The fixed contact 8a protrudes in the first direction D1 (here, forward) more than the movable contact 10a. The movable contact 10a is shorter than the fixed contact 8a in the first direction D1. The fixed contact 8a is out of alignment with the movable contact 10a in the first direction D1. That is, the fixed contact 8a is out of alignment with the movable contact 10a in the direction in which an arc is extended (the same direction as that of the Lorentz force F1).

As shown in FIGS. 4 and 5, in the state where the fixed contact 8a is in contact with the movable contact 10a and in the state where the fixed contact 8a is separated from the movable contact 10a, the center position C1 of the fixed contact 8a is out of alignment with the center position C2 of the movable contact 10a in the first direction D1. The center position C1 of the fixed contact 8a is located at the center of the fixed contact 8a in the front-rear direction. The center position C2 of the movable contact 10a is located at the center of the movable contact 10a in the front-rear direction. As shown in FIG. 3, when viewed from the moving direction of the movable contact 10a, the center position C1 of the fixed contact 8a and the center position C2 of the movable contact 10a are offset from each other in the first direction D1. That is, the center position C1 of the fixed contact 8a does not overlap the center position C2 of the movable contact 10a in the up-down direction. In the present embodiment, the center position C1 of the fixed contact 8a is out of alignment with the center position C2 of the movable contact 10a in the first direction D1.

As shown in FIG. 4, when the Lorentz force F1 acts on the arc that occurs between the fixed contact 8a and the movable contact 10a, the first end A1 of the arc on the fixed contact 8a side and the second end A2 of the arc on the movable contact 10a side are transferred in the direction toward the inner surface 2a. At this point of time, since the fixed contact 8a is out of alignment with the movable contact 10a in the first direction D1 in which the arc is extended, the first end A1 of the arc is transferred toward the first inner surface 2a more than the second end A2 of the arc. Accordingly, the first end A1 of the arc gets offset from the second end A2 of the arc in the up-down direction, and thereby the Lorentz force F1 acting on the arc is directed forward and toward the separation direction Z2. That is, the Lorentz force F1 acts in the direction which facilitates the transfer of the second end A2 of the arc from the movable contact 10a to the movable contact piece 9, allowing the second end A2 of the arc to be quickly transferred to the movable contact piece 9. As such, the arc can be quickly transferred in the first direction D1.

Here, an arc that occurs between the fixed contact 8a and the movable contact 10a is likely to adhere to the ends of the fixed contact 8a and the ends of the movable contact 10a. Also, the arc on a cathode-side contact tends to be movable more than that on an anode-side contact. The anode-side contact and the cathode-side contact are determined by the direction of a current flow. Specifically, regarding the fixed contact 8a and the movable contact 10a, the contact upstream in the direction of the current flow is defined as an anode-side contact, and the contact downstream is defined as a cathode-side contact. Thus, when a current flows from the movable contact 10a toward the fixed contact 8a, the movable contact 10a provides an anode-side contact, and the fixed contact 8a provides a cathode-side contact. In the present embodiment, the Lorentz force F1 acts in the direction in which the second end A2 of the arc is transferred to the movable contact piece 9: the second end A2 of the arc on the movable contact 10a side can be transferred more easily than the first end A1 of the arc on the fixed contact 8a side. As a result, the end of the arc can be transferred to the movable contact piece 9 more effectively, enhancing the quick transfer of the arc.

Note that, in the case of the movable contact 10b, as shown in FIG. 3, the movable contact 10b that provides a cathode-side contact is preferably out of alignment, in the second direction D2, with the fixed contact 8b that provides an anode-side contact. With the configuration, the same effect as that of the movable contact 10a can be obtained.

One embodiment of the electromagnetic relay according to one aspect of the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. For example, the shapes or arrangements of the contact case 2, the contact device 3, and the drive device 4 may be changed. In the above embodiment, the present invention has been described by exemplifying a plunger-type electromagnetic relay, but the present invention may be applied to, for example, a hinge-type electromagnetic relay. In the case of a hinge-type electromagnetic relay, the structures corresponding to the fixed terminal 7, the fixed contact 8b, and the movable contact 10b may be omitted. In addition, the present invention may be applied to an electromagnetic relay in which the movable contact piece 9 moves to be pulled toward the fixed terminals 6 and 7.

In the above embodiment, the fixed contact 8a protrudes in the first direction D1 more than the movable contact 10a, but the movable contact 10a may protrude in the first direction D1 more than the fixed contact 8a. That is, the fixed contact 8a may have the shape of the movable contact 10a in the above embodiment, and the movable contact 10a may have the shape of the fixed contact 8a in the above embodiment. In this case, the movable contact 10a is an example of the first contact, the fixed contact 8a is an example of the second contact, and then the first end A1 of the arc can be quickly transferred to the fixed terminal 6 by the Lorentz force F1.

FIG. 6 is a schematic view of the inside of a contact case 2 according to another embodiment, viewed from above. FIG. 7 is a schematic cross-sectional view of and around the movable contact 10a when the movable contact 10a is in the open position, taken along the line L1-L1 in FIG. 6. As shown in FIGS. 6 and 7, the movable contact 10a may protrude in the second direction D2 more than the fixed contact 8a. Note that, as in the above embodiment, the fixed contact 8a protrudes in the first direction D1 more than the movable contact 10a. The magnet unit 5 is disposed such that, when the current flowing through the arc is directed from the fixed contact 8a to the movable contact 10a (from the front to the rear of the paper surface of FIG. 6), the Lorentz force F2 acts in the second direction D2 onto the arc that occurs between the fixed contact 8a and the movable contact 10a. The configuration of the magnet unit 5 is the same as that of the above embodiment. In this case, when the current flowing through the arc is directed from the fixed contact 8a toward the movable contact 10a, the Lorentz force F2 acts in the direction in which the first end A1 of the arc on the fixed contact 8a providing an anode side contact is transferred to the fixed terminal 6. That is, even when the direction of the current flow changes, the end of the arc can be quickly transferred to the fixed terminal 6 or the movable contact piece 9 which has the fixed contact 8a or the movable contact 10a, wherein the fixed contact 8a or the movable contact 10a provides an anode side contact.

As for the movable contact 10b side, preferably the fixed contact 8b is out of alignment with the movable contact 10b in the first direction D1. With the configuration, the same effect as that on the movable contact 10a side can be obtained on the movable contact 10b side.

The configuration of the magnet unit 5 is not limited to the above embodiment. For example, as shown in FIG. 8, the first magnet 5a and the second magnet 5b may be disposed such that their north poles face each other in the longitudinal direction of the movable contact piece 9. That is, the magnet unit 5 may be configured such that magnetic flux flows around the fixed contact 8a and the movable contact 10a in the direction from the first magnet 5a toward the second magnet 5b and also magnetic flux flows around the fixed contact 8b and the movable contact 10b in the direction from the second magnet 5b toward the first magnet 5a. The fixed contact 8a and the movable contact 10a have the same configurations as those shown in FIG. 6. The fixed contact 8b and the movable contact 10b have the same configuration as the fixed contact 8a and the movable contact 10b. In this case, even when the current direction changes, the anode-side contact is invariably shorter, both on the movable contact 10a side and the movable contact 10b side, than the cathode-side contact in the direction of arc extension. As a result, the end of the arc can be quickly transferred.

As shown in FIG. 9, the first magnet 5a and the second magnet 5b may be disposed such that their south poles face each other in the longitudinal direction of the movable contact piece 9. That is, the magnet unit 5 may be configured such that magnetic flux flows around the fixed contact 8a and the movable contact 10a in the direction from the second magnet 5b toward the first magnet 5a and also magnetic flux flows around the fixed contact 8b and the movable contact 10b in the direction from the first magnet 5a toward the second magnet 5b. The fixed contacts 8a and 8b and the movable contacts 10a and 10b have the same configurations as those of the fixed contact 8b and the movable contact 10b shown in FIG. 6.

As shown in FIG. 10, the magnet unit 5 may be configured such that magnetic flux flows in a direction substantially parallel to the lateral direction of the movable contact piece 9. For example, the first magnet 5a and the second magnet 5b may be disposed to face each other in the lateral direction of the movable contact piece 9. Further, in the case where the relay has a polar structure, or in the case where the magnetic flux flows in the direction from the second inner surface 2b toward the first inner surface 2a, as shown in FIG. 10, the fixed contacts 8a, 8b and the movable contacts 10a, 10b may be disposed to be out of alignment in the direction of arc extension (here, in the left-right direction). In this case, the directions in which the Lorentz forces F1 and F2 act are parallel to the longitudinal direction of the movable contact piece 9. When a current flows from the movable contact 10a toward the fixed contact 8a, the Lorentz force F1 acts, in the direction toward the third inner surface 2c, onto the arc that occurs between the fixed contact 8a and the movable contact 10a. In contrast, when a current flows in the direction from the fixed contact 8a toward the movable contact 10a, the Lorentz force F2 acts, in the direction toward the fourth inner surface 2d, onto the arc that occurs between the fixed contact 8b and the movable contact 10b. In this case, also, the anode-side contact is invariably shorter than the cathode-side contact in the direction of arc extension, and thereby the end of the arc can be quickly transferred.

REFERENCE NUMERALS

5 Magnet unit

6 Fixed terminal

7 Movable contact piece

8
a Fixed contact

10
a Movable contact

11 Movable mechanism

100 Electromagnetic relay

D1 First direction

D2 Second direction

ELECTROMAGNETIC RELAY

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