Electromagnetic relay having a reduced height

Details Electromagnetic relay having a reduced height Electromagnetic relay having a reduced height

2001-12-03

2002-09-10

Barrera, Ramon M. (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Electromagnetically actuated switches

Polarity-responsive

C335S083000

Reexamination Certificate

active

06448877

ABSTRACT:

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,

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