Inductor devices – Winding with terminals – taps – or coil conductor end...
Reexamination Certificate
1997-10-16
2004-06-08
Nguyen, Tuyen T. (Department: 2832)
Inductor devices
Winding with terminals, taps, or coil conductor end...
C336S090000, C336S096000, C336S107000
Reexamination Certificate
active
06747540
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
The present application is based on and claims priority from Japanese Patent Applications Hei 8-275677, filed on Oct. 18, 1996 and Hei 9-104370, filed on Apr. 22, 1997, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition coil for an internal combustion engine, particularly, a stick-like ignition coil installed directly in the plug holes of an internal combustion engine.
2. Description of the Related Art
A high tension terminal of a conventional stick-like ignition coil for an internal combustion engine (hereinafter referred to as the ignition coil) is shown in FIG.
9
.
A secondary coil
600
is wound around a secondary spool which has a flange member
603
and a high tension output terminal
602
for providing a high tension voltage generated by the secondary coil
600
. A core is inserted in the secondary spool, which usually projects from the secondary coil
600
toward the high tension output terminal, and a spacer portion
604
is formed between the secondary coil
600
and the high tension terminal
602
.
If permanent magnets are fixed to an end of the core, the spacer portion
604
becomes longer.
The secondary coil
600
and the high tension output terminal
602
are connected by a lead wire
601
extending from the end of the secondary coil through the spacer portion
604
.
However, the stick-like ignition coil has such a small diameter that the low tension primary coil, the core and a portion of the engine block are close to one another. In addition, a surface of the lead wire
601
facing the low tension portion or components is so small that the electric field strength around the lead wire becomes very high.
If a high tension voltage is generated by the secondary coil
600
, electric breakdown may arise between the lead wire
601
and the low tension portion, thereby causing failure in supplying high tension voltage to the spark plugs (not shown).
In an ignition coil insulated by insulating resin, a “tree” is produced around the lead wire as a result of the electric discharge in the insulating resin and may extend to the low tension components. If the tree bridges the high tension lead wire and the low tension components, the high tension voltage can not be supplied to the spark plugs.
SUMMARY OF THE INVENTION
A main object of the present invention is to provide a highly reliable ignition coil which prevents the electric breakdown between high tension portions or components and low tension portions or components.
According to a feature of the present invention, a conductive member is disposed around the portion connecting the secondary coil and the high tension terminal to provide a wide surface area facing low tension components enough to moderate the electric field strength around the connecting section, thereby preventing electric discharge between the connecting section and the low tension components. As a result, a highly reliable ignition coil is provided.
According to another feature of the present invention, the conductive member comprises a cylindrical coil of a wire extended from the secondary coil toward the high tension terminal. Accordingly, a wide surface area of the connecting member is provided in the winding step of the secondary coil without addition of specific steps.
According to another feature of the present invention, the connecting member comprises a cylindrical conductive member which covers the wire connecting the secondary coil and the high tension terminal.
If the adhesive strength of the insulating resin and the primary spool is not enough and the two members are separated from each other due to thermal expansion and contraction, the growing speed of the “treeing” increases in proportion to the length of the separation.
According to another feature of the present invention, the primary spool is made of a material which is bonded to the epoxy resin at a high adhesive strength so that the separation between the insulating resin and the primary spool can be prevented. As a result, even if the treeing grows from a crack and reaches the primary spool, the treeing must bypass the primary spool, so that the time for the treeing to reach the low tension components increases. In other words, time of the electric breakdown is delayed, thereby increasing the life time of the ignition coil.
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patent: A-2-23269 (1990-01-01), None
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Patent Abstracts of Japan, vol. 096, No. 008, Aug. 30, 1996 & JP 08 107027A (Nippondenso Co Ltd), Apr. 23, 1996.
Itou Shigemi
Kondou Masahiro
Nakase Yosimi
Denso Corporation
Nguyen Tuyen T.
Nixon & Vanderhye
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