Electromagnetic relay having a reduced height

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to electromagnetic relays and, more particularly, to an electromagnetic relay suitable for an electric component incorporated into electric equipment for automobile.

Electromagnetic relays are incorporated into various equipments. Since a space into which an electromagnetic relay is accommodated has been reduced in connection with miniaturization of electric equipment, there is a demand for reducing heights of electromagnetic relays.

A maximum electric current of an electromagnetic relay used in electric equipment for automobile is required to be as high as 30 amperes. Such a high maximum electric current causes a large amount of heat generated in the electromagnetic relay, and it is necessary to achieve an efficient radiation of heat from the electromagnetic relay.

2. Description of the Related Art

FIG. 1

is a perspective view of a conventional electromagnetic relay

10

of electric equipment for automobile in a state where a cover is removed.

FIG. 2

is a side view of the electromagnetic relay

10

shown in FIG.

1

. In

FIG. 1

, directions X

1

and X

2

correspond to a direction of width of the electromagnetic relay

10

; directions Y

1

and Y

2

correspond to a longitudinal direction; and directions Z

1

and Z

2

correspond to a direction of height.

The electromagnetic relay

10

comprises, as shown in

FIG. 3

, a subassembly

11

, a base unit

30

and a terminal member

40

having a make fixed contact. The subassembly

11

is attached on the base unit

30

, and the terminal member

40

is inserted from the X

2

side.

The subassembly

11

comprises, as shown in

FIG. 4

, a plastic bobbin

12

on which a coil

13

is wound. An iron core

14

, a yoke

16

, a movable leaf spring/armature assembly

17

are incorporated into the bobbin

12

. The coil

13

, the iron core

14

and the yoke

16

together constitute an electromagnet.

The bobbin

12

has a square frame part

12

a

on the Y

2

side and a square frame part

12

b

on the Y

1

side. A hook part

12

c

is formed on a bottom part of the square frame part

12

a

. A cylindrical projection

12

d

is formed on a bottom part of the square frame part

12

b

. A coil terminals

25

and

26

are insert-molded with the square frame part

12

b.

The iron core

14

having an iron base plate

15

is incorporated into the bobbin

12

from the Y

1

side. The L-shaped yoke

16

is incorporated into the bobbin

12

from the Y

2

side, and an end of the iron core

14

is secured to the yoke by caulking. Additionally, the movable leaf spring/armature assembly

17

is attached to the bobbin

12

on the Y

1

side.

The movable leaf spring/armature assembly

17

comprises a generally L-shaped movable leaf spring

20

, a square armature

21

and a movable contact member

22

. The movable leaf spring

20

comprises a main part

20

a,

a spring arm part

30

b

extending from the main part

20

a

in the Y

2

direction and a common terminal

20

c

extending from the main part

20

a

in the Z

2

direction. The armature

21

is fixed to a root of the spring arm part

20

b

. The movable contact member

22

is fixed on an end of the spring arm part

20

b

. The main part

20

a

is fixed to iron base plate

15

by caulking.

The base unit

30

has a structure in which a break fixed contact member

32

is insert-molded with a plastic base

31

. A break terminal part

32

a

extends from the base

31

in the Z

2

direction. A break fixed contact

33

is exposed on the break fixed contact member

32

. The base

31

is provided with apertures

34

and

35

for attaching the subassembly

11

. The base

31

is also provided with an aperture

36

and a notch

37

for attaching the terminal member

40

having the make fixed contact.

The terminal

40

wit the make fixed terminal has a generally L-shape, and comprises a make terminal part

40

a,

a concave part

40

b

and a make fixed contact member

41

.

The subassembly

11

is attached to the base unit

30

by the cylindrical projection

12

d

being fit in the aperture

35

and the hook part

12

c

being fit in the aperture

34

. The terminal

40

is attached to the attached to the base unit

30

, after the subassembly

11

and base unit

30

are assembled together, by being inserted from the X

2

side in a state in which the concave part

40

b

is fit in the aperture

36

and a root of the make terminal

40

a

is fit in the notch

37

.

The yoke

16

is located under the coil

13

, and the armature

21

is located under the yoke

16

. Additionally, the movable contact member

22

contacts the break fixed contact member

32

. The make fixed contact member

41

is located above the movable contact member

22

. In the normal state, the common terminal part

20

c

and the break terminal part

32

a

are in a “closed” state, and the common terminal part

20

c

and the make terminal part

40

a

are in an “open” state.

The electromagnetic relay

10

has a height h

1

as shown in

FIG. 1

, and is mounted to a printed board in a state in which the terminals and terminal parts are inserted into through holes formed in the printed board.

When a current is supplied to the coil

13

, the electromagnet is exited, and the armature

21

is magnetically attracted by the yoke

16

. Accordingly, the spring arm part

20

b

is formed upward, which causes the movable contact member

22

being brought into contact with the make fixed contact member

41

. Thereby, the state of the common terminal part

20

c

and the break terminal part

32

a

is changed to an “open” state, and the state of the common terminal part

20

c

and the make terminal part

40

a

is changed to a “closed” state.

The conventional electromagnetic relay

10

shown in

FIG. 1

has a problem in that it is difficult to reduce the height for the following reasons.

(1) The base unit

30

has a relatively large thickness t

1

as shown in

FIG. 1

so as to maintain a strength of engagement of the hook part

12

c,

which fixes the subassembly

11

to the base unit

30

.

(2) The terminal member

40

is attached to the base

31

by the concave part

40

b

is fit in the aperture

36

and the root of the make terminal part

40

a

is fit in the notch

37

. This structure for attaching the terminal member

40

cannot provide a high positioning accuracy of the terminal member

40

. Additionally, since the member to which the terminal member

40

is attached is different from the member to which the yoke

16

is attached, a distance a between the make fixed contact member

41

and the yoke

16

tends to fluctuate when the electromagnetic relay

10

is assembled. Thus, the distance a between the make fixed contact member

41

and the yoke

16

is set larger than an actually necessary distance so as to maintain a sufficient withstand voltage, thereby increasing the height of the electromagnetic relay

10

.

(3) Since the accuracy of attaching the terminal member

40

is not so high, a distance b between the make fixed contact member

41

and the break fixed contact member

32

is set larger than an actually required distance as shown in

FIG. 2

so as to maintain a sufficient withstand voltage. This prevents a reduction in the height of the electromagnetic relay

10

.

In the conventional electromagnetic relay

10

shown in

FIG. 1

, the coil

13

is excited so as to close the contact between the common terminal part

20

c

and the make terminal part

40

a

. When an electric current of

30

amperes flows through the contact, a large amount of heat is generated. The generated heat is transferred to and spread into the printed bard through the common terminal part

20

c

and the make terminal part

40

a,

and the heat is dispersed into the printed board, and is radiated to the atmosphere. However, a heat transmission path of the heat generated in the electromagnetic relay is small, and the resistance of the heat transmission path is high. Thus, the conventional electromagnetic relay

10

has a low heat radiation.

Additionally, in the electromagnetic relay

10

, each of the terminal parts

20

c,

32

a

and

40

a

and the terminals

25

and

26

has a small width and directions of extension are not the same. Accordingly, it is impossible to spot-weld the terminal parts

20

c,

32

a

and

40

a

and terminals

25

and

26

to other terminals. Thus, it is difficult to use a spot-welding to mount the electromagnetic relay

10

to a relay box of an automobile.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an electromagnetic relay in which the above-mentioned problems are eliminated.

A more specific object of the present invention is to provide an electromagnetic relay having a reduced height while maintaining a good voltage withstand.

In order to achieve the above-mentioned objects, there is provided according to the present invention an electromagnetic relay comprising: a base unit including a metal plate member and a base mold made of a plastic, the metal plate member having a break fixed contact point and a break terminal and being insertion-molded with the base mold; a subassembly fixed to an upper side of the base unit and including an electromagnet assembly and a movable leaf spring/armature assembly attached to the electromagnetic assembly, the electromagnet assembly including a bobbin, a coil, an iron core and a yoke, the movable leaf spring/armature assembly including a movable leaf spring having a movable contact point and an armature fixed to the movable leaf spring; and a make terminal member fixed to the base unit and having a make fixed contact point and a make terminal, wherein the base mold of the base unit has a yoke attaching part to which the yoke of the electromagnetic assembly is attached and a make terminal member attaching part to which the make terminal member is attached, and the sub assembly is mounted to the base unit by the yoke of the electromagnet assembly being attached to the yoke attaching part of the base mold, and the make terminal member is mounted to the base unit by being attached to the make terminal attaching part of the base mold.

According to the present invention, the subassembly is mounted to the base unit by attaching the yoke of the electromagnet assembly to the base mold of the base unit. Accordingly, it becomes possible to adopt a slide fit mechanism to mount the subassembly to the base unit. The slide fit mechanism for mounting the subassembly does not increase a height of the electromagnetic relay.

Additionally, since the make terminal member is fittingly attached to the make terminal member attaching part, the position of the make terminal member can be attached to the base unit with high accuracy. Therefore, it becomes unnecessary to consider the variation in the position of the make terminal member, and the height of the electromagnetic relay is reduced accordingly.

Moreover, a part of space between the yoke and the make terminal member and a part of a space between the metal plate member and the make terminal member are occupied by a part of the base mold, which gives a better insulation than a case in which the above-mentioned spaces are empty. Further, the number of factors of the variation in assembly decreases, and it becomes possible to reduce a distance between adjacent parts, which gives a low-height electromagnetic relay.

In the electromagnetic relay according to the present invention, the metal plate member may have a base plate part having the same horizontal projection size as that of the electromagnetic relay; the base mold may extend along a periphery of the base plate part and has long side base mold parts opposite to each other; each of the yoke attaching part and the make terminal member attaching part may be formed on each of the long side base mold parts; and both sides of each of the yoke and the make terminal member may be secured to the respective long side base mold parts.

According to the above-mentioned invention, the base mold is mechanically strengthened by the base plate part. Additionally, both sides of the yoke and the make terminal member are attached to the long side base mold parts. Accordingly, the yoke and the make terminal member can be attached to the base unit with high accuracy, and the mechanical strength of the attaching part is high.

Additionally, the metal plate member may have a base plate part having the same horizontal projection size as that of the electromagnetic relay; and the base mold may extend along a periphery of the base plate part and has an armature offset preventing projection, which faces a lower surface of the armature.

Accordingly, when the armature tends to greatly deform downward due to a shock applied to the electromagnetic relay, the armature offset preventing projection contacts the armature, which prevents a permanent deformation of a the movable leaf spring part to which the armature is fixed.

Additionally, in the electromagnetic relay according to the present invention, a number of each of common terminals, the brake terminals and the make terminals, which are electrically connected to the movable leaf spring, may be plural.

Preferably, the brake terminals and the make terminals, which are electrically connected to the movable leaf spring, is two; and one of the two terminals is located on one side of the electromagnetic relay and the other is located on the other side of the electromagnetic relay.

Additionally, in the electromagnetic relay according to the present invention, an end of each of the terminals may be bent outward.

Accordingly, the electromagnetic relay can be mounted to a printed circuit board by an SMT mounting method. Since a plurality of terminals are collectively provided in a small area, a thermal stress due to a difference in the thermal expansion coefficient between the electromagnetic relay and the printed circuit board can be reduced. Thus, a number of heat cycles until a soldered portion of the terminal breaks is increased, which improves the reliability of the electromagnetic relay with respect to a thermal stress.

Additionally, in the electromagnetic relay according to the present invention, each of the terminals may include a leg part and a foot part, the foot part being formed by bending each terminal to as to extend horizontally; and a width of the foot part is larger than a width of the leg part.

Since a soldering area of each terminal is increased due an increase in the width of the foot part, the terminal can be soldered to a pad of the printed circuit board with a good bonding force, and a good resistance of thermal stress can be achieved.

Further, in the electromagnetic relay according to the present invention, each of the terminals may include a leg part and a foot part, the foot part being formed by bending each terminal to as to extend horizontally; and a thickness of the leg part may be smaller than a thickness of the foot part.

Since the leg part is easily bent, a thermal stress can be relaxed, which improves the reliability with respect to a thermal stress.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of a conventional electromagnetic relay of electric equipment for automobile in a state where a cover is removed;

FIG. 2

is a side view of the electromagnetic relay shown in

FIG. 1

;

FIG. 3

is an exploded perspective view of the electromagnetic relay shown in

FIG. 1

;

FIG. 4

is a perspective view of a subassembly shown in

FIG. 3

;

FIG. 5

is a perspective view of the electromagnetic relay from which a cover is removed;

FIG. 6A

is a side view of an interior of the electromagnetic relay viewed from Y

2

side;

FIG. 6B

is a side view of the interior of the electromagnetic relay viewed from X

1

side;

FIG. 6C

is a side view of the interior of the electromagnetic relay viewed from Y

1

side;

FIG. 7A

is a bottom view of the interior of the electromagnetic relay viewed from Z

1

side;

FIG. 7B

is a top plan view of the electromagnetic relay viewed from Z

2

side;

FIG. 7C

is a circuit diagram of the electromagnetic relay;

FIG. 8

is an exploded perspective view of the interior of the electromagnetic relay shown in

FIG. 5

;

FIG. 9

is a perspective view of the interior of the electromagnetic relay from which a base mold is removed;

FIG. 10

is an exploded perspective view of a subassembly;

FIG. 11

is an exploded perspective view of an electromagnet assembly;

FIG. 12

is an exploded perspective view of a movable leaf spring armature assembly;

FIG. 13

is a perspective view of a base unit;

FIGS. 14A and 14B

are perspective views for explaining a manufacturing process of the base unit shown in

FIG. 13.

;

FIG. 15

is a side view of the electromagnetic relay being mounted onto a printed circuit board;

FIG. 16A

is a side view of the electromagnetic relay being mounted to a relay box;

FIG. 16B

is a perspective view of an interior of the relay box;

FIG. 17

is a side view of an electromagnetic relay according to a second embodiment of the present invention;

FIG. 18A

is a side view of an electromagnetic relay according a third embodiment of the present invention; and

FIG. 18B

is a perspective view of an interior of the electromagnetic relay shown in FIG.

18

A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given of an electromagnetic relay

50

according to a first embodiment of the present invention.

FIG. 5

is a perspective view of the electromagnetic relay

50

for automobile equipment in a state in which a cover

51

is removed.

FIG. 6A

is a side view of an interior of the electromagnetic relay

50

viewed from Y

2

side.

FIG. 6B

is a side view of the interior of the electromagnetic relay

50

viewed from X

1

side.

FIG. 6C

is a side view of the interior of the electromagnetic relay

50

viewed from Y

1

side. It should be noted that, a cross-sectional part shown in

FIG. 6A

is taken along a line I—I in

FIG. 6B

, and a cross-sectional part shown in

FIG. 6B

is taken along a line II—II in FIG.

6

A.

FIG. 7A

is a bottom view of the interior of the electromagnetic relay

50

viewed from Z

1

side.

FIG. 7B

is a top plan view of the electromagnetic relay

50

viewed from Z

2

side. In each of the above-mentioned figures, directions X

1

and X

2

correspond to a direction of width of the electromagnetic relay

50

; directions Y

1

and Y

2

correspond to a longitudinal direction; and directions Z

1

and Z

2

correspond to a direction of height.

FIG. 8

is an exploded perspective view of the interior of the electromagnetic relay

50

. The electromagnetic relay

50

comprises, as shown in

FIG. 8

, a subassembly

52

, a base unit

80

and a terminal member

120

with a make fixed contact point. In the electromagnetic relay

50

, the base unit

80

serves as a reference part.

The subassembly

52

is attached to the base unit

80

on Z

1

side, and the terminal member

120

with the make fixed contact point is attached to the base unit

80

on Y

2

side. A make terminal tip part

130

as a foot part, a break terminal tip part

131

, a common terminal tip part

132

and a coil terminal tip part

133

are arranged on X

1

side of the electromagnetic relay

50

from Y

2

side in the direction Y

1

. Similarly, a makeup terminal tip part

135

as a foot part, a break terminal tip part

136

, a common terminal tip part

137

and a coil terminal tip part

138

are arranged on X

2

side from Y

2

side in the direction Y

1

.

Each of the make terminal tip parts

130

and

135

, the break terminal tip parts

131

and

136

, the common terminal tip parts

132

and

137

and the coil terminal tip parts

133

and

138

is bent outward so as to extend horizontally. Therefore, the electromagnetic relay

50

is surface-mountable to a printed circuit board.

FIG. 9

is a perspective view of the interior of the electromagnetic relay

50

from which a base mold

100

is removed.

Next, an assembly constituting the electromagnetic relay

50

is explained. First, a description will be given of the subassembly

52

.

The subassembly

52

comprises an electromagnet assembly

53

and a movable leaf spring armature assembly

70

, as shown in FIG.

10

. The movable leaf spring armature assembly

70

is attached to the electromagnet assembly

53

on Y

1

side. As shown in

FIG. 11

, the electromagnet assembly

53

is formed by incorporating an iron core

57

and a yoke

58

into a bobbin

56

made from a liquid crystal polymer having a coil

55

formed by a wound electric wire

54

.

The bobbin

56

comprises a flange part

56

a

of a reverse U-shape on Y

2

side, a flange part

56

b

of a reverse U-shape on Y

1

side and a channel part

56

c

having a U-shaped cross section and connecting the flange part

56

a

and the flange part

56

b

to each other. The coil terminals

59

-

1

and

59

-

2

are insertion-molded in the flange part

56

b

. Opposite ends of the electric wire

54

are wound around bend parts

59

-

1

a

and

59

-

2

a

of upper bent portions of the coil terminals

59

-

1

and

59

-

2

, respectively.

The iron core

57

with an iron board

60

is incorporated into the bobbin

56

from Y

1

side in the longitudinal direction of the bobbin

56

. The iron core

57

passes through the inside of the channel part

56

c,

and an end of the iron core

57

projects from the flange part

56

a

. The iron board

60

is accommodated in a concave part of the flange part

56

b

. The L-shaped yoke

58

is incorporated into the bobbin

56

from Y

2

side in the longitudinal direction of the bobbin

56

. A perpendicular part

58

a

of the yoke

58

is accommodated in a concave part of the flange part

56

a

. An opening

58

c

fits on an end of the iron core, and the yoke

58

is fixed by caulking. A horizontal part

58

b

of the yoke

58

horizontally extends under the coil

55

. Two pairs of convex parts

58

d,

58

e,

58

f

and

58

g

are formed on both X

1

side and X

2

sides of the horizontal part

58

b

of the yoke

58

, respectively.

The movable leaf spring armature assembly

70

comprises, as shown in

FIG. 12

, a movable leaf spring

71

having a substantially L-shape, an armature

72

having a substantially square board shape and a movable contact point

73

. The movable leaf spring

71

comprises a main part

71

a

and a spring arm part

71

b

extending in the Y

2

direction from the main part

71

a.

The main part

71

a

has a U-shape when viewed from Z

1

side, and has a central part

71

c

and arm parts

71

d

and

71

e

on both sides of the central part

71

c.

The spring arm

71

b

and the main part

71

a

are connected to each other by two connection arm parts

71

f

and

71

g

. A slit

74

exists between two connection arm parts

71

f

and

71

g.

The spring arm part

71

b

is fixed to the armature

72

by caulking. Therefore, the armature

72

is fixed to the upper surface of the portion by the side of the root of spring arm part

71

b,

and bridges over a space part

74

. When the armature

72

is magnetically attracted in the direction Z

1

, an upper edge part

72

a

of the armature

72

is brought into contact with parts

75

and

76

, which serve as fulcrum of rotation of the spring arm part

71

b.

A movable contact point member

73

is fixed to the tip portion of the spring arm part

71

b

by caulking. The main part

71

a

of the movable leaf spring armature assembly

70

is located on Y

1

side of the electromagnet assembly

53

, and the arm part

71

b

and the armature are located under the horizontal part

58

b

of the yoke

58

. Main part

71

a

is fit on the flange part

56

b

so as to enclose the flange part

56

b,

and the central part

71

c

is fixed to a concave part of the iron board

60

by the caulking.

A description will now be given of the base unit

80

.

The base unit

80

shown in

FIG. 8

is an insertion-molded part. The base unit

80

comprises a metal plate press member

81

, which is formed by pressing a metal plate, and a base mold

100

made of a liquid crystal polymer. The base mold

100

covers the metal plate press member

81

.

FIG. 13

is a perspective view of the base unit

80

. The base unit

80

is formed by pressing a belt-like metal plate material. First, as shown in

FIG. 14A

, the metal plate press member

81

A connected to a belt part

82

is placed in a molding die. Then, as shown in

FIG. 14B

, the metal plate press member

81

A is insertion-molded, and, thereafter, bending is performed along a chain line

83

a.

The bending is also performed on the opposite side. Then, the belt part

83

is cut out along a chain line

83

d,

and also a connecting part

90

connecting a break terminal

85

(

86

) and a common terminal

87

(

88

) is cut out along chain lines

83

b

and

83

c.

The metal plate press member

81

has a base plate part

84

, the brake terminals

85

and

86

and the common terminals

87

and

88

. The base plate part

84

has a rectangular shape, and has substantially the same size as a plan view size of the electromagnetic relay

50

. A break fixed contact point member

89

is fixed to the base plate part in the vicinity of the end of Y

2

side by caulking. An elongated slit

84

a

is formed in the base plate part

84

between the break fixed contact point member

89

and an end of Y

1

side along the direction Y

1

-Y

2

. The periphery of the base plate part

84

includes long sides

84

b

1

and

84

b

2

along the direction Y

1

-Y

2

and a short side

84

b

3

along the direction X

1

-X

2

.

The break terminals

85

and

86

extend from positions on the long sides

84

b

1

and

84

b

2

near the break fixed contact point member

89

in the directions X

1

and X

2

, respectively, and then extend to the direction Z

2

. The break terminals

85

and

86

have connecting parts

85

a

and

86

a

having a reverse U-shape, which connect to the base plate part

84

. The connecting parts

85

a

and

86

a

project from an upper surface of the base plate part

84

.

The common terminals

87

and

88

are connected to the break terminals

85

and

86

by the connecting parts

90

, respectively. The common terminals

87

and

88

are located on Y

1

side with respect to the break terminals

85

and

86

, and are located adjacent to the break terminals

85

and

86

, respectively. The common terminals

87

and

88

extend in the direction Z

1

-Z

2

. The common terminals

87

and

88

have connecting parts

87

a

and

88

a

at the upper end thereof, respectively, which are connected to the movable leaf spring armature assembly

70

at the upper end. Parts

87

b

and

88

b

are formed under the connecting parts

87

a

and

88

a,

respectively.

The base mold

100

made from a liquid crystal polymer has a U-shape hen viewed from above. The base mold

100

covers both the lower surface

84

c

and the upper surface

84

d

of the base plate part

84

, and fills the slit

84

a.

The base mold

100

has portions extending along the periphery of base plate part

84

. That is, the base mold

100

has long side base mold parts

101

and

102

extending along the long sides

84

b

1

and

84

b

2

of the base plate part

84

, respectively, and also has a short side base mold part

103

extending along the short side

84

b

3

of the base plate part

84

. The base mold

100

is reinforced by the base plate part

84

. The long side base mold parts

101

and

102

are reinforced by the connecting parts

85

a

and

86

a

having a reverse U-shape. Insulation resistance of the liquid crystal polymer is 10

16

Ω/cm, which is higher than the insulation resistance 10

13

Ω/cm of air.

The long side base mold part

101

encloses the connecting part

85

a

of the break terminal

85

and the part

87

b

of the common terminal

87

. After the connecting part

90

is removed and the common terminal

87

is separated from the break terminal

85

, the common terminal

87

is maintained at the original position by the long side base mold part

101

. The long side base mold part

102

encloses the connecting part

86

a

of the break terminal

86

and the part

88

b

of the common terminal

88

. After the connecting part is removed and the common terminal

88

is separated from the break terminal

86

, the common terminal

88

is maintained at the original position by the long side base mold part

102

.

The break fixed contact point member

89

is located between the long side base mold parts

101

and

102

. As shown in

FIG. 14B

, the long side base mold parts

101

and

102

have yoke attachment parts

104

and

105

for attaching the yoke

58

of the electromagnet assembly

53

and make fixed contact point terminal member attaching parts

106

and

107

for attaching a make fixed contact point terminal member

120

.

The yoke attaching parts

104

and

105

have the same rail structure, which extends in the direction Y

1

-Y

2

. The yoke attaching parts

104

and

105

comprises X-Y surfaces

108

and

109

and pressing parts

110

and

111

having a reverse U-shape, which project from the surfaces

108

and

109

, respectively. Notch parts

110

a

and

111

a

are formed in the pressing parts

110

and

111

, respectively, in response to the convex parts

58

d,

58

e,

58

f

and

58

g

of the yoke

58

.

The make fixed contact point terminal member attaching parts

106

and

107

contain slits

112

and

113

formed in the long side base mold parts

101

and

102

, respectively. The slits

112

and

113

have a reverse L-shape when viewed from Y

2

side. The slits

112

and

113

comprise horizontal slit parts

112

a

and

113

a

located in the same X-Y plane and vertical slit parts

112

b

and

113

b,

respectively. First spacer parts

115

and

116

are located between surfaces

108

and

109

and the slits

112

and

113

, respectively. The first spacer parts

115

and

116

extend toward the center from both X

1

and X

2

sides, and have a thickness t

10

. Second spacer parts

117

and

118

are located between the slits

112

and

113

and the base plate part

84

, respectively. The second spacer parts

117

and

118

extend toward the center from both X

1

and X

2

sides, and have a thickness t

20

.

The short side base mold part

103

has an armature offset preventing part

119

, which prevents the armature

72

from being offset.

Next, a description will be given of the make fixed contact point terminal member

120

. As shown in

FIG. 8

, the make fixed contact point terminal member

120

comprises a square plate part

121

, make terminals

122

and

123

extending in the direction Z

2

from X

1

and X

2

sides on Y

2

side of the plate part

121

and a make fixed contact point member

124

fixed to the plate part

121

by caulking.

A description will now be given of the assembling operation of the subassembly

52

to the base unit

80

.

As shown in

FIG. 8

, a subassembly

52

is located above the base unit

80

. The subassembly

52

is first moved in the direction Z

2

in a state in which the convex parts

58

d,

58

e,

58

f

and

58

g

of the yoke

58

are aligned with corresponding notch parts

110

a

and

111

a

. Then, the subassembly

52

is attached to the base unit

80

by sliding the subassembly

52

in the direction Y

2

to the end position where the convex part

56

g

enters a concave part

110

b

and abuts against a bottom surface of the concave part

110

b

. The convex parts

58

d,

58

e,

58

f

and

58

g

pass through the notch parts

110

a

and

111

a,

and are fit and engage with the pressing parts

110

and

111

. Therefore, as shown in

FIGS. 6A and 6B

, the horizontal part

58

b

of the yoke

58

is supported on the surfaces

108

and

109

while being bridged between the long side base parts

101

and

102

. The opposite sides of the horizontal part

58

b

of the yoke

58

in the direction X

1

-X

2

are mounted to the yoke attaching parts

104

and

105

, respectively. The subassembly

52

is assembled in a state in which the yoke

58

and the flange part

56

b

are attached to the base unit

80

.

The spring arm part

71

b

is located on the side of the upper surface of the base plate

84

. In addition, the position of the subassembly

52

with respect to the base unit

80

in the direction Y

1

-Y

2

is accurately fixed by the convex part

110

b

abutting against the bottom surface of the concave part

110

b

. Moreover, the position of the subassembly

52

with respect to the base unit

80

in the direction X

1

-X

2

is accurately fixed by the pressing parts

110

and

111

. Therefore, as shown in

FIGS. 6A and 6B

, the movable contact point member

73

abuts against the break fixed contact point member

89

in a state in which the center thereof aligns with the center of the break fixed contact point member

89

. It should be noted that the both sides of the yoke

58

in the direction X

1

-X

2

are fixed, and, thus, the yoke

58

is firmly attached to the base unit

80

with good positioning accuracy.

A description will now be given of an assembling operation of the make fixed contact terminal member

120

to the base unit

80

.

As shown in

FIG. 8

, the make fixed contact point terminal member

120

is located on Y

2

side with respect to the base unit

80

. The make fixed contact point terminal member

120

is assembled to the attaching parts

106

and

107

by being moved in the direction Y

1

with respect to the base unit

80

and being inserted into the slits

112

and

113

to the end position.

The square plate part

121

is inserted into horizontal slit parts

112

a

and

113

a,

and is bridging between the long side base parts

101

and

102

. The make terminals

122

and

123

are inserted into vertical slit parts

112

b

and

113

b,

respectively. Accordingly, the position of the make fixed contact point terminal member

120

in the direction X

1

-X

2

is fixed, and also the positions of the make terminals

122

and

123

are fixed.

The make fixed contact point member

124

is located above the movable contact point member

73

. Here, the side on which the make fixed contact point terminal member

120

is assembled to the base unit

80

is Y

2

side. Accordingly, it is possible to assemble the terminal member

120

to the base unit

80

in a state in which the terminal member

120

bridges between the long side base parts

101

and

102

, that is, the opposite sides of the terminal member

20

in the direction X

1

-X

2

are fixed.

Since Y

2

side of the base unit

80

is open, the terminal member

120

is assembled to the base unit

80

on Y

2

side. That is, the portion of the subassembly

52

attached to the base unit

80

is the yoke

53

of the electromagnet assembly

53

.

A description will now be given, with reference to

FIGS. 6A and 6B

, of positional relationships in the direction Z

1

-Z

2

.

(1) A positional relationship between the horizontal part

58

b

of the yoke

58

of the subassembly

52

and the square plate part

121

of the make fixed contact point terminal member

120

:

The positional relationship between the horizontal part

58

b

and the plate part

121

is determined by the first spacer parts

115

and

116

. The horizontal part

58

b

and the plate part

121

are separated from each other by a distance a

10

, which is equal to the thickness t

10

of the first spacer parts

115

and

116

.

(2) A positional relationship between the square plate part

121

of the make fixed contact point terminal member

120

and the base plate part

84

having the break fixed contact point member

89

:

The positional relationship between the plate part

121

and the base plate part

84

is determined by the second spacer parts

117

and

118

. The plate part

121

and the base plate part

84

are separated from each other by a distance b

20

, which is equal to the thickness t

20

of the second spacer parts

117

and

118

.

As mentioned above, the position of the horizontal part

58

b

of the yoke

58

of the subassembly

52

in the direction Z

1

-Z

2

, the position of the square plate part

121

of the make fixed contact point terminal member

120

in the direction Z

1

-Z

2

and the position of the base plate part

84

having the break fixed contact point member

89

are accurately determined by the base mold

100

made of a liquid crystal polymer. Therefore, the variation in the size of attachment is very much smaller than that of a conventional one.

In consideration of the variation in the size of attachment, the above-mentioned distance a

10

and b

20

are determined with a margin. In the present embodiment, since the variation in the size of attachment is much smaller than that of the conventional electromagnetic relay, the above-mentioned distances a

10

and b

20

are smaller than the corresponding distances a and b of the conventional electromagnetic relay

10

shown in

FIG. 1

by about 1 mm, respectively.

Therefore, as shown in

FIG. 5

, the height of the electromagnetic relay

50

is h

10

, which is smaller than the height h

1

of the conventional electromagnetic relay

10

of

FIG. 1

by about 2 mm. Moreover, the movable contact point member

73

abuts against the break fixed contact point member

89

. The common terminal tip parts

132

and

137

and the break terminal tip parts

131

and

136

are in the state of “closed”, and the common terminal tip parts

132

and

137

and the make terminal tip parts

130

and

135

are in the state of “open”.

The electromagnetic relay

50

having the above-mentioned structure is surface-mounted to a printed circuit board

140

, as shown in

FIG. 15

, by soldering the make terminal tip parts

130

and

135

, the break terminal tip parts

131

and

136

, the common terminal tip parts

132

and

137

and the coil terminal tip parts

133

and

138

to pads

141

on the printed circuit board

140

. Then, the printed circuit board

140

is attached to an automobile.

When a current is supplied to the coil

55

, the coil

55

is excited and the yoke

58

is magnetically attracted by the armature

72

. Accordingly, the spring arm part

71

b

rotates upward about the fulcrums

75

and

76

, which results in the movable contact points member

73

separated from the break fixed contact point member

89

and contacting the make fixed contact point member

124

. Therefore, the common terminal tip parts

132

and

137

and the break terminal tip parts

131

and

136

are changed to the state of “open”, and the common terminal tip parts

132

and

137

and the make terminal tip parts

130

and

135

are changed to the state of “closed” When the current flowing in the coil

55

is cut off, the electromagnetic relay

50

returns to the original normal state.

A description will now be given of a heat radiation of the electromagnetic relay

50

in use.

When the coil

55

is excited and the movable contact point member contacts the make fixed contact point member

124

and the common terminal tip parts

132

and

137

and the makeup terminal tip parts

130

and

135

are changed to the state of “closed”, and if an electric current of

30

A flows in the coil

55

, a large amount of heat is generated especially between the common terminal tip parts

132

and

137

and the makeup terminal tip parts

130

and

135

, which are brought into contact with each other. The generated heat is transmitted to the printed circuit board

140

via two routes, first and second transmission routed, as shown in FIG.

9

.

The first transmission route

151

extends in the direction X

1

from the make fixed contact point member

124

, and includes the movable contact point member

73

→the make fixed contact point member

124

→the plate part

121

→the make terminal

122

→the make terminal tip part

130

→the printed circuit board

140

. The second transmission route

152

extends in the direction X, which is opposite to the direction X

1

, from the make fixed contact member

124

, and includes the movable contact point member

73

→the make fixed contact point member

124

→the plate part

121

→the make terminal

123

→the make terminal tip part

135

→the printed circuit board

140

.

Thus, as shown in

FIG. 9

, the heat generated inside the electromagnetic relay

50

transmits the two transmission routes

151

and

152

, which are extending in opposite directions, to reach the printed circuit board, and is efficiently radiated from the printed circuit bard

140

.

It should be noted that the number of make terminals can be three or four. In such a case, the number of the transmission routes for heat radiation is three or four, and the heat generated inside the electromagnetic relay can be radiated more efficiently.

Also the number of the break terminals and common terminals can be three or four. Here, the width w

1

of the make terminal tip parts

130

and

135

in the direction Y

1

-Y

2

is larger than the width w

2

of the make terminals

122

and

123

. Therefore, a contact surface area between the make terminal tip parts

130

and

135

and the printed circuit board

140

is large, and, thus, the heat resistance between the make terminal tip parts

130

and

135

and the printed circuit board

140

is small. Therefore, transfer of heat from the make terminal tip parts

130

and

135

to the printed circuit board

140

is performed smoothly. This also allows the efficient transfer of heat generated inside the electromagnetic relay

50

to the printed circuit board

140

.

It should be noted that, depending on an electric circuit incorporated into the electromagnetic relay

50

, there is a case in which a current flows in the electromagnetic relay

50

in a state where the movable contact point member

73

is brought into contact with the break fixed contact point member

89

. In such a case, heat generated in a portion in which the movable contact point member

73

contacts the break fixed contact point member

89

is transmitted to the printed circuit board

140

via two routes, which are transfer routes

153

and

154

, and the transmitted heat is efficiently radiated from the printed circuit board

140

. The transfer route

153

includes the movable contact point member

73

→the break fixed contact point member

89

→the base plate part

84

→the break terminal

85

→the break terminal tip part

131

→printed circuit board

140

. The transfer route

154

includes the movable contact point member

73

→the break fixed contact point member

8943

the base plate part

84

→the break terminal

86

→the break terminal tip part

136

the printed circuit board

140

.

A description will now be given of a heat stress exerted on the electromagnetic relay

50

, which is surface-mounted on the printed circuit board

140

.

A heat stress is generated due to a difference in a thermal expansion coefficient between the electromagnetic relay

50

and the printed circuit board

140

. The generated heat stress is exerted on soldered portions between the terminal tip parts and pads

141

formed on the printed circuit board

140

. When the heat stress is large, a problem may occur that the soldered portions between terminal tip parts and the pads

141

on the printed circuit board

140

break within a comparatively short time after the beginning of use.

The common terminals

87

and

88

, the break terminals

85

and

86

and the make terminals

122

and

123

form pairs, respectively, and the pair of terminals are connected in parallel electrically. Therefore, if an electric current flowing through one terminal, which comprises a pair of contact points, is 30 A, a current which flows through one of the contact points is 15 A. Accordingly, a cross-sectional area of each terminal can be one half of a cross-sectional area of each terminal of a case in which the number of the common terminals, the break terminals and the make terminals is one, respectively. Therefore, each of the common terminals

87

and

88

, the break terminals

85

and

86

and the make terminal

122

and

123

can be formed with a smaller bending strength (stiffness) than that of the conventional one. Thus, each terminal can bend easily, and the heat stress exerted on the soldered portions can be relaxed easily.

Moreover, as shown in

FIG. 7A

, the make terminal tip parts

130

and

135

, the break terminal tip parts

131

and

136

, the common terminal tip parts

132

and

137

and the coil terminal tip parts

133

and

138

align along the respective sides extending in the longitudinal direction of the electromagnetic relay

50

. Additionally, each terminal projects from the electromagnetic relay

50

in the direction X

1

or X

2

, and is accommodated inside a rectangle

160

indicated by double dashed dotted lines in FIG.

7

A. Therefore, a distance L

1

between the make terminal tip part

130

and the coil terminal tip part

138

, which distance L

1

is the largest distance from among distances between the terminal tip parts, is smaller than that of the conventional one. Thus, the difference in an amount of thermal deformation between the electromagnetic relay

50

and the printed circuit board

140

is smaller than the conventional electromagnetic relay, the thermal deformation of the electromagnetic relay

50

being generated between the make terminal tip part

130

and the coil terminal tip part

138

Accordingly, the heat stress which acts on the soldered portion between each terminal tip part and the corresponding pad

141

on the printed circuit board

140

is smaller than that of the conventional electromagnetic relay. Therefore, the reliability of surface mounting of the electromagnetic relay

50

onto the printed circuit board

140

is improved. In addition, since a width w

1

of each terminal tip part (foot part) in the direction Y

1

-Y

2

is larger than a width w

2

of the terminal (leg), a soldering area of each terminal tip with the pad is large. This composition also improves the reliability of surface mounting of the electromagnetic relay

50

onto the printed circuit board

140

.

The electromagnetic relay

50

can also be incorporated into a relay box

170

of an automobile, as shown in

FIGS. 16A and 16B

. As shown in

FIG. 16B

, the relay box

170

comprises a box-like housing

171

made of a plastic, a plurality of terminal members

172

insertion-molded in the housing

171

and a plurality of the electromagnetic relays

50

provided inside the housing

171

. A connector

175

attached to ends of cables

176

is connected to terminal parts

172

a

formed at ends of the terminal members. Terminal pars

172

b

at opposite ends of the terminal members

172

extend horizontally. The terminal parts

172

b

are arranged correspondingly to the arrangement of the terminal tip parts of each electromagnetic relay

50

.

As shown in

FIG. 16A

, the terminal tip parts

130

and

135

of the electromagnetic relay

50

are spot-welded to the terminal parts

172

b

in a state where the terminal tip parts

130

and

135

are placed on the corresponding terminal parts

172

b

and sandwiched by the electrodes

180

and

181

. It should be noted that the spot welding can be carried out since each of the terminal tip parts

130

and

135

has a large width. The terminal parts

172

b

of the other ends of the terminal members

172

extend horizontally, and there is no need to bend the terminal members

172

downward.

A description will now be given, with reference to

FIGS. 6B and 6C

, of an action of the armature offset preventing projection

119

.

When the electromagnetic relay

50

falls from a high position, a strong shock may act on the electromagnetic relay

50

. The spring arm

71

b

of the electromagnetic relay

50

may deforms due to the shock, and, thereby, the position of the armature

72

may shift. In such a case, the position of fulcrums

75

and

76

is shifted, which results in an undesired problem in that a condition of contract between the movable contact point member

73

and the break contact point member

89

or the make contact point member

124

is changed.

In the present embodiment, the armature offset preventing projection

119

is provided under the armature

72

within the slit

74

between the connecting parts

71

f

and

71

g

. When a strong shock is exerted on the electromagnetic relay

50

and the armature tends to greatly deform in the direction Z

2

, the armature offset preventing projection

119

contacts the armature

72

. Accordingly, the spring arm

71

b

is prevented from being bent at a root thereof, which prevents the position of the armature

72

from shifting. Therefore, the electromagnetic relay

50

has a high shock resistance.

A description will now be given, with reference to

FIG. 17

, of a second embodiment of the present invention.

FIG. 17

is a side view of an electromagnetic relay

50

A for automobile electric devise according to the second embodiment of the present invention. The electromagnetic relay

50

A has basically the same structure as that of the above-mentioned electromagnetic relay

50

except for the following points.

In the present embodiment, a thickness t

30

of each terminal (leg part)

200

of the electromagnetic relay

50

A is smaller than a thickness t

31

of each terminal tip part (foot part)

201

. According to this composition, a bending strength (stiffness) of the terminal

200

is small, and, therefore, the terminal

200

can further relax the thermal stress.

A description will now be given, with reference to

FIGS. 18A and 18B

, of a third embodiment of the present invention.

FIG. 18A

is a side view of an electromagnetic relay

50

B for automobile electric devices according to the third embodiment of the present invention.

FIG. 18B

is a perspective view of an interior of the electromagnetic relay

50

B shown in FIG.

18

A. The electromagnetic relay

50

B has basically the same structure as that of the above-mentioned electromagnetic relay

50

except for the following points.

In the present embodiment, each of terminal tip parts

130

B and

135

B of the electromagnetic relay

50

B extends vertically. The electromagnetic relay

50

B is mounted to a relay box

170

B by spot welding the vertically extending terminal tip parts

130

B and

135

B to terminal parts

172

B

b

of terminal members

172

B. The connector

175

attached to ends of the cables

176

is connected to terminal parts

172

B

a

formed at ends of the terminal members

172

B. In this embodiment, the terminal part

172

B

b

of each of the terminal members

172

B is bent downward.

The present invention is not limited to specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.

The present application is based on Japanese priority application No. 2001-133057 filed on Apr. 27, 2001, the entire contents of which are hereby incorporated by reference.

Electromagnetic relay having a reduced height

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (1)