Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-04-10
2002-10-01
Mai, Anh (Department: 2832)
Metal working
Method of mechanical manufacture
Electrical device making
C336S096000, C336S090000
Reexamination Certificate
active
06457229
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an ignition coil device for an internal combustion engine, and more particularly, to an ignition coil device for an internal combustion engine which is to be mounted in a plug hole of an engine body to apply high voltages directly to a spark plug.
FIG. 4
shows a conventional ignition coil device for an internal combustion engine. In
FIG. 4
, reference numeral
21
denotes a cylindrical case made of an insulating resin, and a flat plate portion is integrally formed at the top of the case
21
. Reference numeral
22
denotes a primary coil wound on a cylindrical bobbin
22
A, the primary coil
22
being disposed in the case
21
. Reference numeral
23
denotes a secondary coil wound on a cylindrical bobbin
23
A, the secondary coil
23
being disposed inside the bobbin
22
A for the primary coil
22
. Reference numeral
24
denotes an iron core made of a magnetic material, the iron core
24
being inserted into the bobbin
23
A for the secondary coil
23
. Reference numeral
25
denotes magnets provided at upper and lower ends of the iron core
24
, the magnets
25
being used for producing a bias magnetic field. Reference numeral
26
denotes a high-voltage output terminal attached to the lower end of the bobbin
23
A for the secondary coil
23
, and
27
denotes a coiled spring which is connected to the high-voltage output terminal
26
by screwing a screw
28
into a hole of the high-voltage output terminal
26
.
The high-voltage output terminal
26
is connected to the secondary coil
23
. Reference material
29
denotes a cylindrical shielding case with a slit, and
30
denotes a cylindrical insulating shell made of rubber. While being kept hot, an epoxy resin based insulating resin
31
vacuum-injected into the case
21
housing the secondary coil
23
, the primary coil
22
, the iron core
24
and the magnets
25
so that the insulating resin
31
is filled in between the iron core
24
and the secondary coil
23
, between the secondary coil
23
and the primary coil
22
and between the primary coil
22
and the case
21
to thereby enhance the insulating performance. Reference number
32
denotes an ignitor unit in which a power transistor, a switching element and so on are housed. The ignitor unit
32
is mounted at its lower portion on the flat plate portion of the case
21
. The ignitor unit
32
is integrally formed with a connector portion and a mounting portion. By making use of holes in the mounting portion, the ignitor unit
32
is screwed to a cylinder head attached to the outer surface of an engine block.
When the ignition coil device shown in
FIG. 4
is inserted into a plug hole of an engine body, a connecting portion of a spark plug is caused to come into an opening formed in the lower portion of the insulating cylindrical shell
30
made of rubber until the spring
27
is brought into contact with the connecting portion of the spark plug. in this condition, the ignitor unit
32
is screwed to the cylinder head by making use of the holes in the mounting portion of the ignitor unit
32
.
In the state that the ignition coil device is inserted into the plug hole of the engine body as described above, the electric power and an on-off signal are supplied to a drive circuit and the switching element such as the power transistor housed in the ignitor unit
32
through the connector portion formed integrally with the ignitor unit
32
mounted on the case
21
, so as to turn on/off the power transistor to thereby supply high ignition voltages to the spark plug.
Namely, when the switching element provided in the ignitor unit
32
of the above-described ignition coil device is turned off, the electric current flowing through the power transistor to the primary coil
22
is cut off and then high voltages are produced in the secondary coil
23
so as to be applied to the spark plug through the high-voltage output terminal
26
, the screw
28
and the spring
27
.
However, in the above-described conventional ignition coil device, since it is impossible for the compact type device that is to be mounted in the plug hole to increase the thickness of the layer of the insulating resin
31
, and since the difference in thermal expansion between the bobbins
22
A,
23
A and the insulating resin
31
attributed to the temperature cycle causes separation to occur at the boundary surface, it is difficult to secure the withstand voltages of the primary coil and the secondary coil.
SUMMARY OF THE INVENTION
The present invention enables the above-described problems of the prior art, to be solved and an object or the invention is to provide an ignition coil device for an internal combustion engine which is capable of securing the withstand voltage and preventing the separation from occurring at the boundary surface of an insulating resin attributed to the temperature cycle.
In order to achieve the above object, there is provided according to the present invention an ignition coil device for an internal combustion engine which comprises a primary coil wound to have larger diameter, a secondary coil wound on a bobbin having smaller diameter and disposed inside the primary coil, an iron core disposed inside the bobbin having smaller diameter, and a cylindrical case disposed around the primary coil, the primary coil being made bobbinless so as to secure the withstand voltages of the primary coil and the secondary coil.
According to the invention, there is provided a device which comprises the primary coil wound to have larger diameter, the secondary coil wound on the bobbin having smaller diameter and disposed inside the primary coil, the iron core disposed inside the bobbin having smaller diameter and the cylindrical case disposed around the primary coil, and the primary coil is made bobbinless so as to secure the withstand voltages of the primary coil and the secondary coil.
Also, according to additional aspects of the invention, the inside of the case is sealed up with an insulating casting material made of the same elastic resin as the inside of the bobbin having smaller diameter, and therefore it is possible to prevent the insulation deterioration attributed to the temperature cycle and improve the insulation resistance between the coils and the like.
Further, according to still further aspects of the invention, gaps between the primary coil and the cylindrical case, between the primary coil and the secondary coil and between the iron core and the bobbin having smaller diameter are sealed up with a single kind of insulating resin, and therefore it is possible to prevent the insulation deterioration attributed to the temperature cycle and improve the insulation resistance between the coils and the like.
REFERENCES:
patent: 3043994 (1962-07-01), Anderson et al.
patent: 4019167 (1977-04-01), Barker
patent: 4199743 (1980-04-01), Martincic
patent: 5778863 (1998-07-01), Oosuka et al.
patent: 5870012 (1999-02-01), Sakamaki et al.
patent: 5986532 (1999-11-01), Kikuta et al.
Aoki Harumi
Kanazawa Akira
Murata Noriyuki
Nakatsuka Akira
Saito Toshiharu
Mai Anh
Matsushita Electric - Industrial Co., Ltd.
Stevens Davis Miller & Mosher LLP
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