Note: Descriptions are shown in the official language in which they were submitted.
1~3~1~
TITLE OF THE INVENTION
ELECTROMAGNETIC SWITCH
BACKGROUND OF THE INVENTION
This invention relates to electromagnetic
switches which are used to close and open starting
motor circuits for engines in automotive vehicles, and
like circuits.
An electromagnetic switch of this kind has been
proposed by Japanese Provisional Utility Model
10 Publication (Kokai) No. 61-18556 (hereinafter referred
to as "Publication A"), which comprises a casing
formed of an electrically conductive magnetic material
and adapted to be fixed to a mounting structure such
as a vehicle body, a bobbin wound with a coil, a
plunger fitted in the bobbin for movement therein in
response to energization of the coil to move a movable
contact member into or out of contact with a pair of
fixed contact members, yokes arranged at opposite
axial ends of the bobbin and in contact with the
casing, and an insulating plate member secured to an
axial end of the plunger opposed to the movable
contact member. The fixed contact members are rigidly
fitted through a covering member, and each have a flat
contact portion at its base end disposed for contact
with the movable contact member, and a rod-shaped
portion extending through the covering member and
having an opposite outer end externally threaded for
connection with a connecting member of an external
circuit by means of a nut fitted on the threaded outer
end.
~'
1~93~1~
According to the electromagnetic switch of
Publication A, the aforementioned insulating member is
interposed between the plunger and the movable contact
member for the following reason: the movable and
fixed contact members, which are usually formed of
copper, are worn due to their repeated contacting
actions to produce a considerable amount of fine chips
or particles (particles of copper). These chips or
particles are scattered and accumulated on peripheral
parts, which causes leakage current to flow from the
contact members to the mounting structure (vehicle
body) through the plunger, yokes, and casing,
particularly when the contacts are closed by the
plunger receded into the bobbin due to energization of
the coil. The insulating member serves to prevent the
flow of leakage current.
However, the use of the insulating member does
not only result in an increased number of component
parts as well as in an increased number of man-hour
ror assemblage, but also involves the problem that the
it is necessary to provide a supplemental structure to
obtain sufficient heat radiation of the hot contacts,
especially the movable contact member, if an
insulating member as aforementioned is employed.
Further, according to Publication A, if the
electromagnetic switch is used to turn on and off an
engine starting motor which consumes a large amount of
current, the amount of fine chips or particles of
copper produced is particularly large. The chips or
particles are scattered and adheres to the movable
contact member and the fixed contact members to
degrade the insulation therebetween. To prevent this,
a recess is formed in an upper end face of the plunger
for collecting the chips or particles. However, since
i'~934~11
the chips or particles are not only scattered to the
contact members, but also even to leader ends of the
coil which are exposed to the outside of the coil, so
that after a long term use the chips or particles may
form an additional contact between the opposite leader
ends of the coil.
Further, according to Publication A, the
electromagnetic switch is not always used in a fashion
being uprightly mounted on a mounting structure, but
may be mounted in an inverted fashion, depending upon
the conditions of the mounting space. However, when
the electromagnetic switch is thus invertedly mounted,
the above-mentioned additional contact will be formed,
since the conventional switch has no suitable place on
which the chips or particles are accumulated.
Another disadvantage with Publication A is that
the fixed contact members have a special configuration
having the flat contact portion and the rod-shaped
portion. To obtain the special configuration, for
example, a copper bar is wrought such that one end of
the bar is squashed and stamped into a flat shape, and
the the other end threaded to form an external thread
thereon, which takes much labor and time, resulting in
a high manufacturing cost.
Another electromagnetic switch of this kind has
been proposed by Japanese Provisional Utility Model
Publication (Kokai) No. 61-16840 (hereinafter referred
to as "Publication B"), which comprises a cylindrical
bobbin, a coil wound around the bobbin, a plunger
fitted in the bobbin for movement therein in response
to energization of the coil, a movable contact member
arranged for movement in response to the movement of
the plunger, fixed contact members arranged for
contact with the movable contact members, and a
4 1293~11
cylindrical casing accommodating the above-mentioned
components and also serving as a magnetic path-forming
yoke.
The electromagnetic switch according to
Publication B essentially requires means for
preventing rotation of the cylindrical bobbin relative
to the cylindrical casing. Further, the
electromagnetic switch is so constructed that when the
coil is energized, the plunger downwardly moves into
contact with the bottom surface of the casing whereby
the movable contact member correspondingly moves into
contact with the fixed contact members. Therefore, it
also essentially requires means for preventing leakage
current from flowing from the contacts to the casing
through the plunger. Specifically, an insulating
member as the leakage current-preventing means is
interposed between the plunger and the movable contact
member, or between the plunger and the casing.
Moreover, the electromagnetic switch according
to Publication B structurally has limited resistance
to vibrations. Therefore, in the case of mounting the
switch in the body of an automotive vehicle, the
switch has to be mounted at a location other than one
where large vibrations may occur, thus being limited
in mounting location.
Another electromagnetic switch of this kind has
been proposed by Japanese Provisional Pa~ent
Publication (Kokai) No. 61-91820 (hereinafter referred
to as "Publication C"), which carries a fuse unit
formed of a fuse casing and a blade fuse accommodated
therein, the fuse casing bsing secured on top of a
main casing of the switch by means of engagement of
engaging protuberances formed on opposite lateral side
edges of a covering member covering the main casing,
lZ93~11
with respective engaging holes formed in opposite
lateral side edges of the fuse casing. Further, the
fuse casing in turn carries thereon a coupler for
connecting the electromagnetic switch to connecting
wires leading to load circuits. The coupler has a
cover fitted over the fuse casing and engaged
therewith by means of engagement of downwardly
depending engaging pieces provided at opposite lateral
side surfaces of the cover, with respective
protuberances formed on opposite lateral side surfaces
of the fuse casing.
The main casing has a pair of fixed contact
members, one of which is to be connected to a power
supply such as a car battery, and the other to a
starting motor circuit, and a movable contact member
being movable in response to movement of a plunger
energized by a coil into and out of contact with the
fixed contact members. The fuse casing has a coupling
terminal formed integrally therewith and which couples
the one fixed contact member connected to the power
supply, to one end of the blade fuse, the other end of
which is connected to load circuits which apply
electrical loads on the automotive vehicle. The fuse
casing also has another coupling terminal formed
integrally therewith. The first-mentioned and another
coupling terminals of the fuse casing are joined,
respectively, to the one and the other fixed contact
members of the main casing, by means of nuts
threadedly fitted on externally threaded outer ends of
the fixed contact members, to thus unite the fuse unit
with the main casing of the electromagnetic switch.
According to Publication C, the coupling between
the fuse casing and the cover of the coupler, and the
coupling between the fuse casing and the covering
- 6 - lZ93¢11
member of the main casing are made by means of mere
engagement of protuberances with engaging pieces, and
that of probuberances with engaging pieces,
respectively. Therefore, the assembly of the fuse
unit and the electromagnetic switch is not perfectly
resistant or proof against water. Moreover, since the
two coupling terminals laterally project from the fuse
casing, it is difficult to provide waterproof means
for the assembly.
Further, according to Publication C, since the
fuse casing of the fuse unit is formed integrally with
the two coupling terminals, this integral formation
requires a great number of man-hour to fabricate.
Besides, the provision of the another coupling
terminal on the fuse casing invites an increase in the
manufacturing cost.
SUMMARY OF THE INVENTION
A first object of the invention is to reduce the
number of component parts of the electromagnetic
switch as well as the number of man-hour for
assembling same, and also to enhance the heat
radiation of the contacts.
A second object of the invention is to prevent
consumption of leakage current flowing from the
contacts to the mounting structure and avoid formation
of additional contact when the contacts are in an open
state, due to production of chips or particles of the
contacts-forming material caused by repeated closing
and opening actions of the contacts.
A third object of the invention is to simplify
the structure of the contacts and its peripheral parts
and facilitate the connection with external circuits.
-- 7 --
lZ93~ 11
A fourth object of the invention is to prevent
dislocation of the bobbin relative to the casing of
the electromagnetic switch, and enhance the resistance
to vibrations.
A fifth object of the invention is to facilitate
the coupling of the electromagnetic switch with a fuse
unit, and also facilitate application of perfect
waterproofing to the coupling.
A sixth object of the invention is to enhance
the water resistance of the fuse unit per se.
According to the invention, there is provided an
electromagnetic switch including:
a yoke formed of a magnetic material;
a bobbin received in the yoke;
a coil wound around the bobbin;
a plunger accommodated within the bobbin, the
plunger being movable axially of the bobbin in
response to energization of the coil;
a movable contact member being movable with
movement of the plunger;
at least one fixed contact member with which the
movable contact member is brought into and out of
contact; and
a casing in which are received the yoke, bobbin,
coil, plunger, movable contact member and fixed
contact member.
In a first aspect of the invention, the
electromagnetic switch is characterized in that the
plunger is formed of an electrically conductive
material and the casing is formed of an insulating
material.
In a second aspect of the invention, the casing
comprises a square box-shaped body having a closed end
and another open end, and a covering member fitted in
- 8 -
1~3~il
the another open end of the body; and
the yoke comprises a sheet member having a
generally U-shaped section and having opposite end
portions between which a portion of the covering
member is interposed, the opposite end portions being
formed in part into at least one pair of inwardly
extending lugs, the lugs being force-fitted in the
portion of the covering member.
In a third aspect of the invention, the casing
comprises a body, and a covering member covering the
body, the covering member having a recess formed a
side surface thereof opposed to the contact means: and
the covering member has a partition wall formed
thereon and separating the contact means from the
leader ends of the coil.
In a fourth aspect of the invention, the fixed
contact member is formed of a sheet member bent in a U-
shape, the sheet member having a pair of horizontal
portions extending parallel with and being spaced from
each other, and a vertical portion bridged between the
horizontal portions, one of the horizontal portions
being located at one side of the covering member
remote from the plunger, the other of the horizontal
portions being located at another side of the covering
member close to the plunger, the one of the horizontal
portions having a through hole formed therein, the one
of the horizontal portions being connectible to a
connecting terminal of an external circuit by a bolt
fitted through the through hole and a nut threadedly
fitted on the bolt, the other of the horizontal
portions being disposed to be in and out of contact
with the movable contact member.
In a fifth aspect of the invention, the
electromagnetic switch also has a fuse unit including
~ 9 ~ 12~3~1~
a housing joined to the casing, a fuse mounted in the
housing and connected between the one fixed contact
member and at least one load circuit, and a coupling
terminal connected between the one fixed contact
member and the fuse, wherein:
at least one pair of engaging protuberances is
formed on one of the housing of the fuse unit and the
casing and projecting laterally therefrom, at least
one pair of recesses being formed on the other of the
housing of the fuse unit and the casing, the engaging
protuberances elastically engaging in the recesses;
and
the coupling terminal has a portion thereof
interposed between the fuse unit and the casing, the
one fixed contact member and the coupling terminal
being fastened to the connecting terminal of the power
supply by a bolt.
In a sixth aspect of the invention, the fuse
unit is composed of a fuse holding frame accommodating
the fuse and fitted to the casing, a removable cap
covering the fuse holding frame, a sealing member
interposed between the fuse holding frame and the cap,
and a water-proofing agent filled in a space defined
between the fuse unit and the casing.
The above and other objects, features, and
advantages of the invention will be apparent from the
ensuing detailed description taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is an exploded perspective view of an
electromagnetic switch according a first embodiment of
the invention;
- lo- 1293Bll
Fig. 2 is a top plan view of the electromagnetic
switch of Fig. 1, which is in an assembled state;
Fig. 3 is a longitudinal sectional view taken
along line III - III in Fig. 2;
Fig. 4 is a longitudinal sectional view taken
along line IV - IV in Fig. 3;
Fig. 5 is a longitudinal sectional view taken
along line V - V in Fig. 2;
Fig. 6 is a longitudinal sectional view taken
along line VI - VI in Fig. 2;
Fig. 7 is a side view, partly in section, of the
electromagnetic switch of Fig. 3, which is in an
inverted position;
Fig. 8 Is an exploded perspective view of a
fixed contact member and its peripheral parts for
connection to a power supply;
Fig. 9 is an exploded perspective view of a
fixed contact member for connection to a starting
motor circuit;
Fig. 10 is a top plan view of the fixed contact
members of Figs. 8 and 9;
Fig. 11 is a circuit diagram showing an example
of an electrical cirucit including the electromagnetic
switch of Fig 1 as a component part;
Fig. 12, is a side view, partly in section, of
an electromagnetic switch according to a second
embodiment of the invention;
Fig. 13, is a side view, partly in section,
taken along line XIII - XIII in Fig. 12; and
Fig. 14 is a side view, partly in section, taken
along line XIV - XIV in Fig. 13.
DETAILED DESCRIPTION
lZ93~1i
The invention will be described in detail with
reference to the drawings showing embodiments thereof.
Figs. 1 through 11 show a first embodiment of
the invention.
Referring first to Figs. 1 through 3, an
electromagnetic switch 30 according to the first
embodiment has a square casing 1 with an open upper
side. Fitted in the casing 1 along a bottom and
opposite sides thereof is a yoke 2 having a generally
U-shaped section and accommodating a bobbin 3 with a
pair of rectangular flanges 3A and 3B at its opposite
ends. The bobbin 3 has an central hollow shaft
portion wound with a coil 4. A plunger 6 is slidably
fitted in the central hollow shaft portion and biased
in one axial direction by a return spring 5.
A generally U-shaped movable contact member 7 is
arranged opposite an upper end of the plunger 6 as
viewed in Fig. 3, and kept in urging contact therewith
by a spring 9 seated on a covering member 8 of the
casing 1. The movable contact member 7 is disposed
for contact with a pair of fixed contact members 10
and 11 mounted on the casing through the covering
member 8, one of which is to be connected to a power
supply, and the other to a first load circuit.
Another plate-shaped yoke 12 is interposed between the
upper flange 3A and the covering member 8, through
which the plunger 6 movably extends.
The upper end of the plunger 6 has an end face
formed with an annular recess 6a, while the covering
member 8 has a lower side surface formed with an
annular recess 8a extending along the periphery of the
movable contact member 7. Further, the covering
member 8 has a downwardly pending partition wall 8b
formed integrally therewith and separating the
- 12 - lZ~3~1i
contacts 14 formed by the movable and fixed contact
members 7, 10 and 11 from leader ends 4a and 4b of the
coil 4. The partition wall 8b downwardly extends to
the yoke 2 interposed between the rest of the covering
member 8 and the upper flange 3A of the bobbin 3.
The leader ends 4a, 4b of the coil 4 extend to
the outside, respectively, through notches 3a and 3b
formed in an outer peripheral edge of the upper flange
3A, as shown in Fig. 4. The upper flange 3A is
further formed with fitting holes 3c and 3d at
locations corresponding, respectively, to the notches
3a, 3b. Force fitted, respectively, in these fitting
holes 3c, 3d are base ends of connecting terminals 13a
and 13b to which are soldered the leader ends 4a, 4b
of the coil 4. The yoke 2 is formed with clearance
recesses 2a and 2b at locations corresponding,
respectively, to the notches 3a, 3b, for preventing
the leader ends 4a, 4b of the coil 4 from coming into
contact with the yoke 2.
The connecting terminals 13a, 13b upwardly
extend through the covering member 8 to be connected
to a switch 37, hereinafter referred to, and grounded,
respectively (Fig. 11).
As shown in Figs. 2 and 6, the covering member 3
has an upper side surface formed with terminal-
accommodating recesses 15 and 16 with a partition 3c
intervening therebetween, and in which are loosely
fitted square nuts 17 and 18, respectively, on which
are superimposed ends of the fixed contact members 10
and 11, respectively.
As shown in detail in Fig. 10, both the fixed
contact members 10 and 11 each comprise a sheet member
which has a generally U-shaped section. The fixed
contact members 10 and 11 each have upper and lower
~ 13 - 1~93~ 11
horizontal portions lOa and lOb; lla and llb extending
parallel with each other in a spaced and slightly
offset manner, and a vertical portion lOc; llc bridged
between the horizontal portions lOa and lOb; lla, llb.
The upper horizontal portions 10a and lla have
respective through bores lOd and lld formed
therethrough for inserting bolts therethrough. The
lower horizontal portions lOb and llb have respective
semicircular cut-outs lOe and lle formed therein for
being brought into and out of contact with the
peripheral edge of the movable contact member 1. As
shown in Fig. 6, the lower horizontal portions 10b and
llb are fitted through holes 8B, only one of which is
shown, formed in the covering member 8 at its opposite
sides. The lower horizontal portions 10b and llb
have, as shown in Figs. 8 and 9, respective lower end
faces thereof formed with a suitable number of, e.g.
two in the first embodiment, engaging ribs lOf and llf
downwardly projecting, which are formed by pressing
and the like.
As will be understood from Fig. 8, the upper
horizontal portion lOa of the fixed contact member 10
is clamped to an power supply-connecting terminal 20
and a coupling terminal 28 by a bolt 21, a washer 31,
and a nut 17. The upper horizontal portion lla of the
fixed contact member 11 is clamped to a load-
connecting terminal 22 connected to the starting motor
by a bolt 23 and a nut 18.
On the other hand, a fuse unit 40 is provided on
an upper portion of the casing 1, which has a housing
formed of a fuse mounting section 24 on which a blade
fuse 24 is mounted, and a terminal holding frame 25
disposed adjacent the fuse mounting section 24. The
terminal holding frame 25 has a bottom wall thereof
1293~1~
formed with through holes 30a and 30b through which
extend the connecting terminals 13a and 13b, and also
formed with through holes, not shown, through which
extend bifurcated tips 26a and 26b of an output
terminal 26 which is connected via the blade fuse 21
to a second load circuit.
The output terminal 26 and the coupling terminal
28 are first mounted into the housing of the fuse unit
40 through the bottom wall thereof, and then the power
supply-connecting terminal 20, the fixed contact
member 10, and the coupling terminal 28 are clamped
together by the nut 27, etc. as mentioned before.
Thus, the output terminal 26 and the coupling
terminal 28 are interposed between the electromagnetic
switch 30 and the fuse unit 40. The terminals 26, 28
are each formed in a separate body from the housing of
the fuse unit 40, and formed of a bent electrically
conductive sheet.
As shown in Fig. 8, the coupling terminal 28 and
the output terminal 26 have respective horizontal
intermediate portions 28c, 26d extending along the
lower end wall of the housing of the fuse unit 40, and
respective vertical connecting portions 28b and 26c
extend continuously from ends of the horizontal
portions. The respective connecting portions 28b and
26c are force fitted from the bottom side of the fuse
unit 40 into holes, not shown, formed through a
central partition wall of the fuse mounting section 29
of the fuse unit 40, as indicated by the two-dot chain
lines in Fig. 3 showing the connecting portion 26c
alone. The output terminal 26 has the other end with
the bifurcated connecting portions 26a and 26b
extending vertically and continuously therefrom, which
are also force fitted into the through holes from the
- 15 -
~ ~30;11
bottom side of the fuse unit 40. The connecting
portions 28b and 26c are thus connected to blades 24a
and 24b of the blade fuse 24, together with connectors
2lA, only one of which is shown in Fig. 3. The
coupling terminal 28 further has a vertical portion
28d extending from the other end of the intermediate
horizontal portion 28c along a side wall of the fuse
mounting section 29, and a connecting end portion 28e
extending from the vertical portion 28d and connected
to the fixed contact member 10 and the power supply-
connecting terminal 20.
The lower end portion of the fuse unit 40 and
the upper end portion of the cover member 8 form
joining portions having corresponding shapes, so that
the former is snugly fitted in the latter.
When the fuse unit 40 is mounted onto an
electromagnetic switch 30, a pair of engaging
protuberances 27A and a pair of engaging protuberances
27B (in Fig. 2) formed on opposite sides of the fuse
mounting section 29 are elastically engaged in
recesses lA and lB (in Fig. 1) formed in opposite
inner walls of the square casing 1, as described
later.
After thus mounting the fuse unit 40 onto the
electromagnetic switch 30, an adhesive is filled as a
waterproof agent into a space defined between the
upper portion of the casing 1 and the fuse unit 40.
As shown in detail in Fig. 5, two pairs of lugs
2A and 2B, only one pair of which are shown, are
formed on the U-shaped yoke 2 at opposite upper ends
thereof, and are inserted into two pairs of grooves 8C
and 8D, only one pair of which are shown, formed in
opposite side surfaces of the covering member 8. The
lugs are caulked to firmly join the yoke 2 to the
- 16 -
1~93~11
covering member 8.
The manner of assembly of the electromagnetic
switch according to the invention having the above-
described construction is as follows. First, the
connecting terminals 13a, 13b are force fitted into
the upper flange 3A of the bobbin 3 wound with the
coil 4. The yoke 12 is then mounted onto the upper
flange 3A of the bobbin 3. The plunger 6 is then
fitted into the bobbin 3, together with the return
spring 5. Thus the yoke 2 accommodates the bobbin,
the plunger and the return spring 5 put together as
above.
In the meanwhile, the movable contact member 7
is mounted onto the lower side of the covering member
8, with the spring 9 interposed therebetween. Two
nuts 17, 18 are mounted into the upper side of the
covering member 8, and then the fixed contact members
lO, 11 are engaged into the terminal-accommodating
recesses 15, 16 such that the horizontal portions lOa,
lla are positioned on the nuts 17, 18 and the fixed
contact members lO, 11 are opposed to each other.
The thus assembled covering member 8, contact
members, etc. are mounted onto the assembled yoke 2,
plunger 6 etc. and the lugs 2A, 2B protruding from the
opposite inner side walls of the yoke 2 are caulked to
firmly join the yoke 2 and the covering member 8
together. On this occasion, the leader ends 4a, 4b of
the coil 4 are pulled outward along the notches 3a, 3b
of the flange 3A, and soldered to the base ends of the
connecting terminals 13a, 13b.
Then, the output terminal 26 with the connector
21A is mounted onto the lower side of the fuse unit
40, followed by mounting the blade fuse 24 onto the
fuse-mounting section 29 on the upper side of the fuse
- 17 -
1~93~
unit 40. With the above components in this assembled
state, the engaging protuberances 27A, 27B formed on
opposite sides of the fuse mounting portion 29 are
elastically engaged with the upper end of the casing 1
while at the same time the connecting terminals 13a,
13b and the coupling terminal 28 are inserted into the
terminal holding frame 30.
The yoke 2 and the covering member 8 thus
assembled together is placed into the casing 1. Then,
the power supply-connecting terminal 20 of the battery
is superposed onto the coupling terminal 28 mounted in
the casing 1, followed by fitting the bolt 27 through
the through hole 20a of the power supply-connecting
terminal 10, the through hole 28a of the coupling
terminal 28, and the through hole lOg of the fixed
contact member 10, to fasten them together with the
nut 17 screwed onto the bolt 27. In the meanwhile,
the connecting terminal 22 of the starting motor, is
superposed onto the fixed contact member 11, followed
by fitting the bolt 23 through the through hole 22a of
the connecting terminal 22 and the through hole lla of
the fixed contact member 11, to fasten them together
with the nut 18 screwed onto the bolt 23.
Fig. 11 illustrates an example of a circuit
formed by component parts of the electromagnetic
switch provided with the fuse unit and load circuits
for an automotive vehicle. When a main switch 33
(e.g. a key switch of the vehicle) is closed, electric
power is supplied from the battery 35 to a load 34 or
electrical device of the vehicle as a second load
circuit through the blade fuse 24 and the bifurcated
connecting portion 26b. Then, when a starting switch
37 of the vehicle is closed, the coil 4 is energized
to move the plunger 6 downward as viewed in Fig. 3
- 18 - 1~93~11
against the biasing force of the return spring 5. The
movable contact member 7 is accordingly moved downward
by the biasing force of the spring 9 whereby
connection between the movable contact member 7 and
the two fixed contact members 10 and 11 is
established, which permits electric power to be
supplied from the battery 35 to the starting motor 25.
In the meanwhile, the bifurcated portion 26a is
connected with an AC generator 39 as another second
load circuit through a rectifier 38 to charge the
battery 35 with output current from the AC generator
39.
After the electromagnetic switch 30 is
repeatedly opened and closed over a long time, chips
or particles produced at the contacts 14 are
accumulated in the annular recess 6a formed in the
upper end face of the plunger 6. Further, since the
casing 1 is formed of an insulating material, when the
coil 4 is energized to pull the plunger 6 into the
bobbin 3 to bring the movable contact member 7 into
contact with the fixed contact members 10, 11, no
leakage current caused by the presence of chips or
particles is allowed to flow from the contacts 14 to
the mounting structure (vehicle body) through the
plunger 6 and the yokes 2, 12.
Furthermore, since the chips or particles are
blocked by the partition wall 8b, they are not
scattered as far as the leader ends 4a, 4b of the coil
4. Further, as shown in Fig. 7, when the
electromagnetic switch is invertedly mounted in use,
the chips or particles produced at the contacts 14 are
accumulated in the annular recess 8a of the covering
member 8, and in this case as well, the chips or
particles scattering toward the ends 4a, 4b of the
- 19 -
3Gi~
coil 4 are blocked by the partition wall 8b.
Since the movable contact member 7 is always
kept in contact with the plunger 6 by the spring 9,
heat produced at the contacts 14 is sufficiently
dissipated through the plunger 6.
The fixed contact members 10, 11 may be formed
by bending a metal sheet into a generally U-shaped
section. Therefore, it is quite easy to manufacture
the fixed contact members 10, 11. Further, while
conventional fixed contact members having a connecting
threaded portion and a plate-shaped contact portion
formed of copper formed integrally therewith, have the
disadvantage that the threaded or bolt portion can be
broken when terminals of connecting wires are fastened
to the fixed contact members with nuts. However,
according to the above described embodiment of the
invention, since the connecting terminals 20, 22 are
fastened to the flat upper surfaces of the horizontal
portions lOa, lla of the U-shaped fixed contact
members 10, 11 by the bolts 32, 27 and nuts 17, 18,
the above disadvantage can be overcome.
Further, since the U-shaped fixed contact
members 10, 11 are assembled to the covering member 8
from outside thereof, it is easy to effect the
assemblage. Further, if engaging ribs lOf, llf are
provided on the respective lower end faces of the
lower horizontal portions lOb, llb of the U-shaped
fixed contact members 10, 11, when the upper
horizontal portions lOa, lla of the fixed contact
members 10, 11 are inserted into the holes 8B of the
covering member 8, the engaging ribs lOf,i llf are
pressed against the bottom surfaces of the holes 8B,
whereby the fixed contact members 10, 11 can be stably
held in place within the covering member 8 without
- 20 -
1~93S~
being shaken.
The provisional assembly in which the square
bobbin 3 is held between the covering member 8 and the
yoke 2, and the lugs 2A, 2B of the yoke 2 have been
caulked to firmly join the yoke 2 and the covering
member 8 together is placed into the casing 1 made of
resin. Thus, a rigid assembly is obtained with high
vibration resistance, wherein the rotation of the
bobbin 3 relative to the casing 1 is prevented.
Since the fuse unit 40 is coupled to the casing
with the engaging protuberances 27A, 27B of the fuse
unit 40 elastically engaged with the fitting recesses
lA, lB of the casing 1, it is easy to firmly assemble
the fuse unit into the electromagnetic switch.
Thereafter, a waterproofing agent may be poured into a
space defined between the fuse unit 40 and the upper
end of the casing 1. Thus, waterproofing of the
electromagnetic switch can be easily carried out after
assembly.
Since the output terminal 26 and the coupling
terminal 28 are force fitted into the fuse unit, and
the terminals are enclosed by the bottom of the fuse
unit 40 and the covering member 8 of the
electromagnetic switch 30, waterproofing can further
be enhanced.
Figs. 12 and 14 show an electromagnetic switch
according to a second embodiment of the invention. In
the second embodiment, like reference numerals are
used to designate component parts corresponding to
those of the first embodiment, and description thereof
is therefore omitted.
The leader ends of a coil 4 (only one 4a of
which is shown) are connected to connecting terminals
(only one 13a of which is shown) which upwardly
- 21 -
3~il
project from a covering member 8 with their tips
located below the level of the upper end of a cas.ing
1. The tips of the connecting terminals 13a are
soldered to wires 42a of a connecting cord 42. The
connecting cord 42 is clamped by a cord clamper 43,
part of which is firmly held between a lateral side
wall of the casing 1 and a holding portion 41 formed
integrally with the casing 1.
Mounted on an upper end portion of the
electromagnetic switch 30 is a fuse unit 40A, which
comprises a fuse holding frame 45 having a square
configuration in which a fuse mounting section 44 is
formed on which is dismountably mounted a blade fuse
24, and a cap 46 removably fitted over the fuse
15 holding frame 45. One blade 24a of the blade fuse 24
is connected to a coupling terminal, not shown, via a
connector 21A, while the other blade, not shown, of
the blade fuse 24 is connected to an output terminal
26 via another connector, not shown. The output
terminal 26 is connected to one or more load circuits,
such as electric devices of an automotive vehicle.
As shown in Fig. 13, the fuse mounting frame 45
is fitted in an upper end of the casing 1, and
engaging protuberances 45a are formed at a lower edge
of the fuse holding frame 45. The engaging
protuberances 45a are engaged in engaging recesses la
formed in the casing 1 at portions slightly downward
of the upper end edge thereof. A waterproof agent 4
such as epoxy resin is filled into a space defined
between an outer periphery of the fuse holding frame
45 and the upper end of the casing 1.
Formed in an upper outer suface of the fuse
holding frame 45 is an annular groove 45b in which a
square O-ring 48 is fitted as a sealing member in
3~11
contact with an inner surface of the cap 46. The cap
46 has an inner ceiling surface thereof formed
integrally with a boss 46B on which a spare fuse 49
for the blade fuse 24 is mounted. Integrally formed
at opposite sides of the cover 46 are legs 46A and 46A
extending downwardly from an upper end of the cover 46
and having respective engaging claws at lower free
ends thereof, as best shown in Fig. 14. The engaging
claws of the legs 46A and 46A extend through engaging
holes 45A and 45A formed in flanges integral with the
fuse holding frame 45 at opposite sides thereof.
Since the waterproof agent 47 is filled in the
space between the fuse holding frame 45 of the fuse
unit 40 and the upper end of the casing l of the
electromagnetic switch 30, the open upper end of the
casing l or the lower end portion of the fuse unit 40,
which is liable to intrusion of water from the
outside, is completely sealed. Further, since the cap
46 covers the upper end portion of the fuse unit 40
via the O-ring 48, the fuse unit 40 is also completely
sealed agaist water intrusion through the upper end
thereof.
