Electromagnetic relay

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an electromagnetic relay and, more particularly, to a small electromagnetic relay capable of cutting-off a high voltage.

2. Description of the Related Art

Recently, the motorization of car-mounted parts (for example, sideview mirrors and seats) has been promoted. Electromagnetic relays are frequently used for controlling supply of electric power to electric motors or solenoids, which act as electrically-driven actuators. Needless to say, compactness is required of car-mounted electromagnetic relays.

Further, if electric power is supplied thereto at a low voltage in a conventional manner even when the number of the electrically-driven parts is increased, the diameter of a wire harness for transfer of electric power becomes large. This results in increase in weight and cost of the wire harness. It has, thus, been proposed that a battery having a terminal voltage of 40 to 60 volts (V) should be used instead of the presently-used battery having a terminal voltage of 12 to 16 V.

Therefore, to control the supply of electric power to the electrically-driven actuator, currently, an electromagnetic relay capable of cutting-off a low voltage is used. Conversely, in future, the use of an electromagnetic relay capable of cutting-off a high voltage will be needed.

However, when high voltage is cut-off by the electromagnetic relay for cutting off low voltage, an arcing time at the cut-off becomes long, so that welding or sticking between the contacts of the electromagnetic relay easily occurs. Consequently, the service life of the contacts thereof becomes short.

There has been publicly known a method of broadening the space between the contacts of the electromagnetic relay so as to extend the service life of the contacts thereof. However, when the space therebetween is broadened, there is the necessity for increasing the size not only the contacts thereof but also of an electromagnetic coil so as to increase a magnetic force for operating the contacts thereof. Thus, the size of the entire eleptromagnetic relay inevitably becomes big.

The present invention is accomplished to solve the aforementioned problems. Accordingly, an object of the present invention is to provide an electromagnetic relay that has contacts, whose service life can be long, and can be miniaturized even when used for cutting-off a high voltage.

SUMMARY OF THE INVENTION

To achieve the foregoing object, according to the first aspect of the present invention, there is provided an electromagnetic relay that comprises an iron core, a coil wound around the iron core, an armature attracted by the iron core when electric power is supplied to the coil, a first common contact driven by the armature, a first make contact contacted with the common contact when the armature is attracted by the iron core, and an arc suppressing means for suppressing an occurrence of arc between the common contact and the make contact when the common contact is separated from the make contact by stopping supply of electric power to the coil.

Thus, according to this, aspect, an occurrence of arc between the common contact and the make contact is suppressed when the common contact is separated from the make contact. Consequently, the abrasion of the contacts is reduced. Further, the service life of the electromagnetic relay becomes long. Additionally, the space between the contacts is decreased, so that miniaturization of the electromagnetic relay is achieved.

According to the second aspect of the present invention, the arc suppressing means comprises at least one second common contact driven by the armature, at least one second make contact contacted with each of the at least one second common contacts when the armature is attracted to the iron core, and a series connecting means not only for serially connecting at least one second keying circuit each other, each of which consists of a second common contact and a second make contact, but also for serially connecting the serial connection of the at least one second keying circuit to the first keying circuit consisting of the first common contact and the first make contact.

Thus, according to this aspect, an occurrence of arc at the time of circuit interruption is suppressed by serially connecting two or more keying circuits, each of which comprises one common contact and one make contact.

According to the third aspect of the present invention, the arc suppressing means is arc extinguishing means for extinguishing an arc generated between the common contact and the make contact by using a magnetic field which is caused by electric current generated when the supply of electric power to the coil is stopped.

Thus, according to thIs aspect, arc generated between the contacts is extinguished by the magnetic field which is caused by the back electromotive force generated when the circuit is opened, and an electric current flowing in the arc.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the drawings in which:

FIG. 1

is a circuit diagram illustrating an electric circuit of an electromagnetic relay according to the first embodiment of the present invention;

FIG. 2

is a perspective diagram illustrating the electromagnetic relay of

FIG. 1

;

FIG. 3

is a circuit diagram illustrating an electric circuit of an electromagnetic relay according to the second embodiment of the present invention;

FIG. 4

is a perspective diagram illustrating the electromagnetic relay of

FIG. 3

;

FIG. 5

is a circuit diagram illustrating an electric circuit of an electromagnetic relay according to the third embodiment of the present invention;

FIG. 6

is a perspective diagram illustrating the electromagnetic relay of

FIG. 5

;

FIGS. 7A and 7B

are graphs illustrating effects of the first to third embodiments of the present invention;

FIG. 8

is a graph illustrating effects of the present invention;

FIG. 9

is a diagram illustrating the principle of a magnetic arc extinguishing electromagnetic relay;

FIG. 10

is a diagram schematically illustrating the constitution of an electromagnetic relay according to the fourth embodiment of the present invention;

FIG. 11

is a diagram illustrating a situation in which a magnetic flux is generated when a switching device is turned off;

FIGS. 12A

to

12

D are graphs illustrating the transient characteristics of a make contact, magnetic fluxes generated in a closed magnetic circuit and an extension yoke, and the exciting current;

FIG. 13

is a diagram schematically illustrating the constitution of an electromagnetic relay according to the fifth embodiment of the present invention;

FIG. 14

is a diagram illustrating a situation in which a magnetic flux is generated; and

FIGS. 15A

to

15

E are graphs illustrating the transient characteristics of a make contact, a magnetic flux generated in a closed magnetic circuit, electric current flowing through an auxiliary coil, a magnetic flux generated in an extension yoke, and the existing current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1

is a circuit diagram illustrating the electric circuit of an electromagnetic relay according to the first embodiment of the present invention.

FIG. 2

is a perspective diagram illustrating the electromagnetic relay of

FIG. 1. A

load

11

, such as an electric motor or a solenoid, is connected to a battery

12

functioning as a power source through an electromagnetic relay

1

, which has two series-connected contacts.

The electromagnetic relay

1

has two common contacts (

1

C and

2

C), two make contacts (

1

M and

2

M), and two break contacts (

1

B and

2

B). The two common contacts

1

C and

2

C are connected each other in the electromagnetic relay and have no terminal connected to external circuits.

Further, the first make contact

1

M is connected to one of terminals of the load

11

. The second make contact

2

M is connected to a positive pole of the battery

12

. Moreover, the other terminal of the load

11

is directly connected to the negative pole of the battery

12

.

Therefore, when the coil of the electromagnetic relay is energised, the make contacts

1

M and

2

M contact with the two common contacts

1

C and

2

C, respectively. Thus, the load

11

receives electric power from the battery

12

and then starts acting. Conversely, when the coil of the electromagnetic relay is deenergised, the make contacts

1

M and

2

M are separated from the two common contacts

1

C and

2

C, respectively. Thus, the load

11

stops acting.

At that time, the separation of the first make contact

1

M from the first common contact

1

C and that of the second make contact

2

M from the second common contact

2

C are simultaneously performed. Power cut-off is performed by using the two series-connected contacts. As compared with the case that the power cut-off is performed by using one contact, the duration of arc generated when the contacts are separated is shortened. Consequently, the service life of the contacts is lengthened.

Incidentally, in the case that the load

11

is an inductive load such as an electric motor or a solenoid, it is preferable to short-circuit the load

11

to prevent it acting when electric power is not supplied thereto and for consuming a back electromotive force in a D.C. load.

Thus, in the first embodiment, the first break contact

1

B is connected to one of the terminals of the load, while the second break contact

2

B is connected to the other terminal of the load.

In the case of the electromagnetic relay

1

of the first embodiment which acts as described above, the first arm of a U-shaped yoke

103

penetrates a substrate

101

and extends upward. A coil

102

is wound around the arm. The second arm of the U-shaped yoke

103

extends upward along a side surface of the substrate

101

.

A movable spring

105

is attached to an upper part of the second arm of the U-shaped yoke

103

. The moving spring

105

is bent at a right angle in a direction of the former arm of the yoke

103

, and extends horizontally beyond the first arm.

An armature

107

is attached to the movable spring

105

by a caulking member

106

. Incidentally, the armature

107

is sized so that an end of the armature

107

contacts with the second arm of the yoke

103

and that the armature

107

covers the first arm of the U-shaped yoke

103

. That is, the armature

107

closes an opening portion of the U-shaped yoke

103

and constitutes a closed magnetic circuit when the coil

102

is energised.

Two common contacts

1

C and

2

C are formed in a portion of the moving spring

105

, which extends beyond the first arm of the U-shaped yoke

103

. The movable spring

105

is made of an electrically conductive material, so that the two common contacts

1

C and

2

C are electrically connected to each other.

Two separate break contacts

1

B and

2

B are placed above the common contacts. Further, two separate make contacts

1

M and

2

M are placed under the common contacts.

Each of the two break contacts

1

B and

2

B is placed on the lower surfaces of two break contact support members

108

and

109

that are formed as a reversed-L shape and erected perpendicularly on the substrate

101

. These break contact support members

108

and

109

are electrically conductive. The support members

108

and

109

connect, correspondingly, the two break contacts

1

B and

2

B with two break terminals

110

and

111

, which project downwardly from the substrate

101

.

The two make terminals

1

M and

2

M are placed on the upper surfaces of the two make contact support members

112

and

113

that are formed as a reversed-L shape and are erected perpendicularly on the substrate

101

. These make contact support members

112

and

113

are electrically conductive. The make contact support members

112

and

113

connect, correspondingly, the two make contacts

1

M and

2

M to the two make terminals

114

and

115

, which project downwardly from the substrate

101

.

FIG. 3

is a circuit diagram illustrating the electric circuit of an electromagnetic relay according to the second embodiment of the present invention.

FIG. 4

is a perspective diagram illustrating the electromagnetic relay of

FIG. 3. A

load

11

is connected to a battery

12

functioning as a power source through an electromagnetic relay

1

, which has two series-connected contacts.

The electromagnetic relay

1

has two common contacts (

1

C and

2

C), two make contacts (

1

M and

2

M), and two break contacts (

1

B and

2

B). The two make contacts

1

M and

2

M are internally connected to each other in the electromagnetic relay and have no terminal connected to external circuits. The first common contact

1

C is connected to one of terminals of the load

11

. The second make contact

2

C is connected to a negative pole of the battery

12

. Moreover, the first break contact

1

B, the other terminal of the load

11

, and a positive pole of the battery

12

are connected in common.

Therefore, when the coil of the electromagnetic relay is energised, the make contacts

1

M and

2

M contact with the two contacts

1

C and

2

C, respectively. Thus, the load

11

receives electric power from the battery

12

and then starts acting. Conversely, when the coil of the electromagnetic relay is deenergised, the make contacts

1

M and

2

M are separated from the two common contacts

1

C and

2

C, respectively. Thus, the load

11

stops acting.

Incidentally, in this embodiment, the load

11

is preferably short-circuited as in the first embodiment. Thus, in the second embodiment, the first break terminal

1

B is connected to the latter terminal of the load

11

.

In the case of the electromagnetic relay

1

of the second embodiment acting as described above, the first arm of a U-shaped yoke

103

penetrates a substrate

101

and extends upward. A coil

102

is wound around it. The second arm of the U-shaped yoke

103

extends upward along the side surface of the substrate

101

.

Two moving springs

401

and

402

are electrically insulated from the yoke

103

and one end of each is attached to an upper part of the second arm of the U-shaped yoke

103

. The other ends of the moving springs

401

and

402

are bent at a right angle in a direction of the first arm of the yoke

103

, and extend horizontally beyond the first arm. Incidentally, one end of each of the moving springs

401

and

402

extends downward beyond the bottom of the U-shaped yoke

103

, and are respectively connected to a first common terminal (not shown) and a second common terminal

404

.

An armature

107

is attached to the moving springs

401

and

402

through an insulating member

403

by caulking members

106

. Incidentally, the armature

107

is sized so that one edge of the armature

107

contacts with the second arm of the U-shaped yoke

103

and that the armature

107

covers the first arm of the U-shaped yoke

103

. That is, the armature

107

closes an opening portion of the U-shaped yoke

103

and constitutes a closed magnetic circuit when the coil

102

is energised.

Two common contacts

1

C and

2

C are formed at an extending portion of the first arm of the U-shaped yoke

103

.

Two separate break contacts

1

B and

2

B are placed above the common contacts. Further, two separate make contacts

1

M and

2

M formed on an electrically conductive substrate are placed under the common contacts.

The two break contacts

1

B and

2

B are placed on the lower surface of two break contact support members

108

and

109

that are formed as a reversed-L shape and erected perpendicularly on the substrate

101

. These break contact support members

108

and

109

are electrically conductive. The support members

108

and

109

connect the two break contacts

1

B and

2

B to the two break terminals

110

and

111

, which project downward from the substrate

101

.

The make substrate

405

is electrically insulated from the two break contact support members

108

and

109

, which are formed as a reversed-L shape, and is fixed by a suitable method, for example, by being screwed.

FIG. 5

is a circuit diagram illustrating the electric circuit of an electromagnetic relay according to the third embodiment of the present invention.

FIG. 6

is a perspective diagram illustrating the electromagnetic relay of

FIG. 4. A

load

11

is connected to a battery

12

functioning as a power source through an electromagnetic relay

1

, which has two series-connected contacts.

The electromagnetic relay

1

has two common contacts (

1

C and

2

C), two make contacts (

1

M and

2

M), and two break contacts (

1

B and

2

B). The first make contact

1

M and the second make contact

2

M are connected to each other in the electromagnetic relay and have no terminal connected to external circuits. The first common contact

1

c

is connected to one terminal of the load

11

. The second make contact

2

C is connected to a positive pole of the battery

12

. Moreover, the other terminal of the load

11

and a negative pole of the battery

12

are directly connected to each other.

Therefore, when the coil of the electromagnetic relay is energised, the make contacts

1

M and

2

M contact with the two contacts

1

C and

2

C, respectively. Thus, the load

11

receives electric power from the battery

12

and then starts acting. Conversely, when the coil of the electromagnetic relay is deenergised, the make contacts

1

M and

2

M are separated from the two common contacts

1

C and

2

C, respectively. Thus, the load

11

stops acting.

Incidentally, if the load

11

is an electric motor, the load

11

is preferably short circuited as in the first embodiment. Thus, in the third embodiment, the first break terminal

1

B is connected to one of terminals of the load

11

.

In the case of the electromagnetic relay

1

of the third embodiment acting as described above, the first arm of a U-shaped yoke

103

penetrates a substrate

101

and extends upward. A coil

102

is wound around the first arm. The second arm of the U-shaped yoke

103

extends upward along a side surface of the substrate

101

.

Two moving springs

401

and

402

are attached to an upper surface of the second arm of the U-shaped yoke

103

. The moving springs

401

and

402

are bent at a right angle in a direction of the first arm of the yoke

103

, and extend horizontally beyond the first arm. Incidentally, the first moving spring

401

is connected through an insulating member

601

to the second arm of the yoke and the second moving spring

402

is connected directly to it.

An insulating member

602

is placed on a horizontal part of the two moving springs

401

and

402

and just above the second arm of the yoke so that the two moving springs

401

and

402

do not contact with each other. Further, an armature

107

is attached to a central portion of the insulating member

602

by a caulking member

106

. Incidentally, the armature

107

is sized so that an end edge of the armature

107

contacts with the second arm of the U-shaped yoke

103

and that the armature

107

covers the first arm of the U-shaped yoke

103

. That is, the armature

107

closes an opening of the U-shaped yoke

103

and constitutes a closed magnetic circuit when the coil

102

is energised.

Two common contacts

1

C and

2

C are formed in an extending portion of the first arm of the U-shaped yoke

103

.

Two break contacts

1

B and

2

B are placed above the common contacts. That is, the two break contacts

1

B and

2

B are electrically connected by an electrically conductive break contact substrate

603

. Further, two separate make contacts

1

M and

2

M are placed under the common contacts.

The break contact substrate

603

is attached to a break contact support member

604

, which is erected perpendicularly on the substrate

101

and formed like a reversed-L shape. The electrically conductive member provided inside the break contact support member

604

connects the break contact substrate

603

to a break terminal (not shown) protruding downward from the substrate

101

.

The two make contacts,

1

M and

2

M are placed on the upper surfaces of the two make contact support members

112

and

113

(not shown) that are formed as a reversed-L shape and erected perpendicularly on the substrate

101

. These make contact support members

112

are electrically conductive. The support members

112

and

113

connect the two make contacts

1

M and

2

M with the two break terminals

114

, which project downward from the substrate

101

. Incidentally, the first make contact

1

M is directly provided on the U-shaped yoke

103

, so that the first make contact

1

M is electrically connected to the second common terminal

2

C.

FIGS. 7A and 7B

are graphs illustrating effects of the first to third embodiments of the present invention.

FIG. 7A

illustrates a transient characteristic of the voltage across the load when the circuit is cut-off by one cut-off element comprised of a make contact and a common contact. FIG.

7

B. illustrates a transient characteristic of the voltage across the load when the circuit is cut-off by two series connected cut-off elements, each of which is comprised of a make contact and a common contact. In each of these two graphs, the ordinate represents the voltage across the load, while the abscissa represents time.

As shown in these graphs, the time required to completely separate the make contact from the common contact in

FIG. 7A

is 65.8 μsec., while in

FIG. 7B

36.5 μsec. Thus, the arcing time of the relay according the present invention is, reduced by half.

FIG. 8

is a graph illustrating the effects of the present invention. This graph shows the relation between the cutoff voltage (V) and the arcing time (μsec.) when the circuit is cut-off bygone cut-off element and two cut-off elements. In this graph, the ordinate represents the arcing time, while the abscissa represents the cutoff voltage.

As shown in this graph, when the cutoff voltage is increased, the arcing time when applying two series connected cut-off elements is a half of that when applying one cut-off elements.

Namely, in the case of the first to third embodiments, the arcing time thereof can be reduced by a half of that when applying a single cut-off element. The service life of the contacts can be lengthened.

As described above, the first to third embodiments shorten the arcing time and lengthen the service time of contact by applying a plurality of series connected cut-off elements. However, the service life of the contacts can be lengthened by adopting a magnetic arc extinguishing method in which a magnet is placed in the vicinity of the contact and the arc is extinguished by a magnetic force.

FIG. 9

is a diagram illustrating the principle of an electromagnetic relay with a magnetic arc extinguishing mechanism in which a primary coil

92

is wound around the first arm of a U-shaped yoke

91

.

A blade spring

93

is attached to an upper part of the second arm of the yoke

91

. The blade spring

93

is bent nearly at a right angle and has a part that extends beyond the first arm of the yoke

91

. An armature

94

is attached to this part of the blade spring

93

having an end that is in contact with the first arm of the yoke

91

. Incidentally, the armature

94

is sized to cover the first arm of the yoke

91

. The armature

94

functions to short circuit an opening portion of the U-shaped yoke

91

and to constitute a closed magnetic circuit when the primary coil

92

is energised.

A common contact C is formed at the tip of the extended part of the blade spring

93

. A break contact B and a make contact M are respectively placed above and under the common contact C. Further, a magnet

95

is disposed in the proximity of the common contact C and the make contact M so that a magnetic field is generated in a gap between the common contact C and the make contact M.

That is, when the primary coil

92

is energised, the common contact C contacts with the make contact M. Conversely, when the primary coil

92

is deenergised, the make contact M is separated from the common contact C. However, when circuit is cut-off by separating the common contact C from the make contact M, an arc is generated between the common contact C and the make contact M. A force based on the Fleming's left-hand rule acts in a direction perpendicular to an electric current flowing in the arc and a magnetic field in the gap between the common contact C ad the make contact M. As a result, the arc is pushed out from the gap between the contacts. Thus, abrasion of the contacts due to the arc is suppressed.

The electromagnetic relay with a magnetic arc extinguishing mechanism can use a permanent magnet as the magnet

95

. However, in view of the facts that the permanent magnet is costly and that a magnetic field is applied only when the circuit is cut-off, the electromagnetic relay of the present invention generates a magnetic field, for extinguishing arc, by using the back electromotive force, caused when the primary coil

92

is deenergised.

FIG. 10

is a diagram schematically illustrating the constitution of an electromagnetic relay according to the fourth embodiment of the present invention. Incidentally, same reference numerals designate same constituent elements of FIG.

9

.

In the fourth embodiment, an extension yoke

41

, which extends to a direction of a make contact M at the upper part of one of the,arms of the U-shaped yoke

91

, and an extinguishing coil

42

wound around this extension yoke

41

are added to the constituent elements of

FIG. 9

which shows the principle of the electromagnetic relay.

A primary coil

92

is connected in series to an exciting power supply

43

and a switching device

44

. Further, the extinguishing coil

42

is connected in parallel to the primary coil

72

through a reverse-current blocking diode

45

for preventing an energising current from flowing through the extinguishing coil

42

when primary coil

92

is energised by turning on the switching device

44

.

Namely, in the embodiment shown in

FIG. 10

, the primary coil

92

and the extinguishing coil

42

have a common beginning end

921

of the winding. A reverse-current blocking diode

45

is connected between the terminating end

922

of the primary coil

92

and the terminating end

422

of the extinguishing coil

42

so that the cathode of the diode

45

is connected to the terminating end

922

of the extinguishing coil and its anode is connected to the terminating end

922

of the primary coil. Further, the beginning end

921

of the primary coil

92

is connected to the positive pole of the energising power source

43

. The terminating end

922

of the primary coil

92

is connected to the negative pole of the energising power source

43

through the switching device

44

.

FIG. 11

is a diagram illustrating a situation in which a magnetic flux is generated when the switching device

44

is turned off.

FIGS. 12A

to

12

D are graphs respectively illustrating the state of the make contact, a magnetic flux φ

1

generated in a closed magnetic circuit, a magnetic flux φ

2

generated in the extension yoke, and the exciting current.

When the switching device

44

is turned on in this embodiment, the energising current I

E

flows through the primary coil

92

. This energising current is, however, blocked by the reverse-current blocking diode

45

, and thus does not flow into the extinguishing coil

42

. Therefore, when the primary coil

92

is energised, the magnetic flux φ

1

is generated in the closed magnetic circuit formed by covering an opening portion of the U-shaped yoke

91

with the armature

94

. Conversely, the magnetic flux is not generated in the extension yoke

41

.

When the switching device

44

is turned off, the magnetic flux φ

1

generated in the closed magnetic circuit composed of the U-shaped yoke

91

and the armature

94

is extinguished. At that time, a back electromotive force is generated in the closed magnetic circuit, so that electric current I

R

flows in the primary coil

92

in a direction opposite to the direction of the electric current I

E

generated when the primary coil is energised. This opposite current flows through the reverse current blocking diode

45

, and also flows in the extinguishing coil

42

. Thus, a magnetic flux φ

2

is generated in the extension yoke

41

and the gap between the common contact C and the make contact M, so that a magnetic field is generated. Then, a force F

1

caused by the interaction between this magnetic field and the electric current flowing in the arc generated between the common contact C and the make contact M is applied to the arc. Consequently, the arc is extinguished.

FIG. 13

is a diagram schematically illustrating the constitution of an electromagnetic relay according to the fifth embodiment of the present invention. Incidentally, same reference numerals designate same constituent elements of

FIGS. 9 and 10

.

In the fifth embodiment, an extension yoke

41

, which extends in a direction of the make contact M at an upper part of one of the arms of the U-shaped yoke

91

, an extinguishing coil

42

wound around this extension yoke

41

, and an auxiliary coil

51

wound around the first arms of the U-shaped yoke

91

are added to the constituent elements of

FIG. 9

illustrating the principle of the electromagnetic relay. The reverse current blocking diode

45

is unnecessary.

The beginning end

921

of the winding of the primary coil

92

, and the terminating ends of the auxiliary coil

51

and the extinguishing coil

42

are connected in common. Moreover, the terminating end of the auxiliary coil

51

and that of the extinguishing coil

42

are connected in common.

Further, an energising circuit consisting of the energising power source

43

and the switching device

44

, which are connected in series, is connected between the beginning end

921

and the terminating end

922

of the primary coil

92

.

FIG. 14

is a diagram illustrating a situation in which a magnetic flux is generated when the switching device

44

is turned off.

FIGS. 15A

to

15

E are graphs respectively illustrating the state of the make contact, a magnetic flux φ

1

generated in a closed magnetic circuit, an electric current flowing through the auxiliary coil, a magnetic flux φ

2

generated in the extension yoke

41

, and the energising current.

When the switching device

44

is turned on, the magnetic flux φ

1

is generated in the U-shaped yoke

91

, and the make contact contacts with the common contact. When the magnetic flux φ

1

is generated, the electric current I

E

is caused in the auxiliary coil

51

, and the magnetic flux φ

2

is generated in the extension yoke

41

. This, however, has no special effects.

When the switching device

44

is turned off, the magnetic flux φ

1

generated in the U-shaped yoke

91

is extinguished. However, a back electromotive force generated at that time causes electric current I

R

to flow in the auxiliary coil

51

and the arc extinguishing coil

42

. Thus, a magnetic flux φ

2

is generated in the extension yoke

41

and the gap between the common contact C and the make contact M, so that a magnetic field is generated. Then, a force caused due to the interaction between this magnetic field and the electric current flowing in the arc generated between the common contact C and the make contact M is applied to the arc. Consequently, the arc is extinguished.

Although the preferred embodiments of the present invention have been described above, it should be understood that the present invention is not limited thereto and that other modifications will be apparent to those skilled in the art without departing from the sprint of the invention.

The scope of the present invention, therefore, should be determined solely by the appended claims.

Number	Name	Date	Kind
4004260	Happach	Jan 1977	A
4185259	Fovarque	Jan 1980	A
4402033	Mayer	Aug 1983	A
4404443	Coynel et al.	Sep 1983	A
5536980	Kawate et al.	Jul 1996	A

Number	Date	Country
6-260070	Apr 1991	JP
3-156822	Jul 1991	JP
8-195153	Jul 1996	JP

Electromagnetic relay

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CPC

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