Inductor devices – With outer casing or housing – Potted type
Reexamination Certificate
2000-03-24
2001-09-25
Donovan, Lincoln (Department: 2832)
Inductor devices
With outer casing or housing
Potted type
C336S107000
Reexamination Certificate
active
06294973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition coil for an internal combustion engine, that is attached to an automobile engine, for example, for applying to an ignition plug provided at the bottom of a plug hole of the engine high voltage for causing the ignition plug to generate spark discharge.
2. Description of the Prior Art
JP-P-A HEI 9-246070, for example, discloses an ignition coil comprising a slender cylindrical main body inserted into a plug hole of an engine and having an open magnetic circuit core at its center, a primary coil and a secondary coil outside the core, an armoring core on its outer periphery and a high-voltage terminal at its tip; and an ignition plug provided at the bottom of the plug hole and having a top terminal that is directly connected to the high-voltage terminal to apply high voltage to the top terminal. In this prior art ignition coil, since the slender cylindrical main body is substantially entirely accommodated in the plug hole, the space required outside of the engine for installing the ignition coil is extremely small.
However, since an engine is generally made of aluminum alloy so as to minimize its weight and the open magnetic circuit core is disposed parallel to the axis of the plug hole, when an electric current is applied to the primary coil and the magnetic flux generated by the electric current flows through the core, an eddy current is generated in the aluminum portion surrounding the plug hole. This eddy current generates a magnetic flux that cancels the magnetic flux generated by the electric current to degrade the efficiency of the ignition coil.
There has recently been increasing demand for a high-output ignition coil for an internal combustion engine, that is applicable to a lean-burn engine or an alternative fuel engine. However, since the prior art ignition coil does not have good efficiency as described above, it does not meet this demand. In addition, since the plug hole for accommodating the ignition coil is inevitably restricted in size from the standpoint of the engine structure, it is difficult to secure sufficient insulation distance within the slender cylindrical main body of the ignition coil accommodated in such a size-restricted plug hole. Furthermore, since the temperature inside the plug hole is high owing to the heat from the engine, the ignition coil accommodated in the plug hole is exposed to a high temperature. Therefore, both the insulation distance and the high temperature should be taken into account in designing the ignition coil.
To eliminate these disadvantages, JP-UM Registration No. 3052284 proposes a molded ignition coil having a closed magnetic circuit as shown in
FIG. 3
, that comprises a high-voltage terminal
6
installed outside an engine, an ignition plug
40
attached to the bottom of a plug hole
31
of the engine, and a high-voltage relay joint
42
for electrically connecting the high-voltage terminal
6
and the ignition plug
40
. In this prior art ignition coil, two E-shaped layer-built cores
3
a
and
3
b
constituting the closed magnetic circuit have their respective central legs
3
′ inserted into the interior of a bottomed insulation casing
4
, one from a bottom side and the other from an open top side, so that the central legs
3
′ abut against each other and are joined together by means of an adhesive agent or welding or by other such means within the interior of the casing
4
and support therearound a cylindrical primary coil
1
and a cylindrical secondary coil
2
concentrically disposed. Opposite side legs
3
″ of the core
3
a
abut against and are joined to those
3
″ of the core
3
b
, respectively, in the same manner as the central legs
3
′, but outside the casing
4
.
Further, the hole in the bottom
4
′ of the insulation casing
4
, from which the central leg
3
′ of the core
3
a
, for example, is inserted, is stopped up by a bobbin for the primary coil
1
; and the central leg
3
′ of the core
3
a
is thrust from the bottom side into the inner circumference of the primary coil bobbin. On the other hand, the central leg
3
′ of the core
3
b
is thrust from the open top side into the inner circumference of the primary coil bobbin and abuts against and is joined to the central leg
3
′ of the core
3
a
by means of an adhesive agent or the like means.
The prior art ignition coil is installed on the engine, and high voltage is applied from the ignition coil to the ignition plug
40
provided at the bottom of the plug hole
31
. A rocker cover
33
provided with a cylindrical extension hole
32
communicating with the the upper opening of the plug hole
31
is laid over and fixed to the engine. The bottom
4
′ of the insulation casing
4
of the ignition coil is directed laterally so that the pair of E-shaped cores
3
a
and
3
b
with their respective legs joined together are orthogonal to the axis of the plug hole
31
and extension hole
32
. In this state, the base portion
3
of one of the E-shaped cores
3
a
and
3
b
thrust out of the bottom
4
′ of the insulation casing
4
and the base portion
3
of the other of the E-shaped cores
3
a
and
3
b
thrust out of the open side of the casing
4
are attached by means of bolts etc. to a flange
35
protruding outwardly from a dish-shaped portion
34
integrally formed on the top of the cylindrical extension hole
32
of the rocker cover
33
. A high-voltage cylindrical portion
7
integrally extending from the lateral side of the insulation casing
4
for supporting the high-voltage terminal
6
therein is directed downward and thrust into the interior of the extension hole
32
via the interior of the dish-shaped portion
34
of the rock cover
33
.
An upper socket
43
of the high-voltage relay joint
42
covers the high-voltage cylindrical portion
7
and stops up the upper opening of extension hole
32
, whereas a lower socket
44
of the high-voltage relay joint
42
covers the upper half of the ignition plug
40
provided at the bottom of the plug hole
31
. A conductive member, such as a coil spring
45
, retained within the high-voltage relay joint
42
in a piercing state electrically connects the high-voltage terminal
6
of the ignition coil and the top terminal
41
of the ignition plug.
One of the base portions
3
of the pair of opposed E-shaped cores
3
a
and
3
b
of the ignition plug protrudes outwardly from the bottom side of the insulation casing
4
, and the other thereof protrudes outwardly from the open side of the insulation casing
4
, that is stopped up by a solid layer
5
of insulating resin. When the insulation casing
4
is laid lateral to make the cores
3
a
and
3
b
orthogonal to the axis of the plug hole
31
, the distance between the base portions
3
of the cores
3
a
and
3
b
becomes long. Since the base portions
3
are mounted on the flange
35
of the dish-shaped portion
34
, the size of the dish-shaped cover
34
of the rocker cover
33
fixed outside the engine becomes correspondingly large. This requires a large space outside the engine for the installation of the dish-shaped cover
34
.
One object of the present invention is to provide a small-sized ignition coil that does not require a large space outside an engine for the installation thereof and can suppress output decrease caused by occurrence of an undesirable magnetic flux.
SUMMARY OF THE INVENTION
To attain the above object, the present invention provides an ignition coil for an internal combustion engine, that comprises a core-coil assembly comprising an endless outer ring core, a straight core intersecting an interior of the outer ring core to form a closed magnetic circuit in cooperation with the outer ring core, and a primary coil and a secondary coil concentrically fitted within the outer ring core and supported by the straight core piercing through the primary coil; and an insulation casing having a bottom at which a high-voltage terminal connected electrically to an ignition p
Horil Hidesato
Kimura Hiroshi
Takada Rei
Donovan Lincoln
Hanshin Electric Co., Ltd.
Nguyen Tuyen T.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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