Internal-combustion engines – High tension ignition system – Having a specific ignition coil
Reexamination Certificate
2003-01-14
2003-09-23
Solis, Erick (Department: 3747)
Internal-combustion engines
High tension ignition system
Having a specific ignition coil
C336S096000
Reexamination Certificate
active
06622712
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition coil for a vehicle and, particularly, a stick-type resin-insulated ignition coil to be mounted in each plug hole of a vehicle engine.
2. Description of the Related Art
JP-A-2000-182859 discloses a stick-type ignition coil that includes a coil housing and a tower housing. The coil housing accommodates a center core, a primary coil and a secondary coil, and the tower housing accommodates a high-tension terminal. Insulation epoxy resin is filled in the coil housing and the tower housing to insulate the accommodated members from each other.
As shown in
FIG. 8
, a high tension terminal
101
of a known ignition coil
100
is a bullet-like metal member. The tower housing
104
is a cylindrical member made of resin. The high tension terminal
101
is disposed in the tower housing
104
to be coaxial therewith. The high tension terminal
101
has an upper flange
102
and a middle barrel
103
. There is a comparatively small circumferential gap
105
between the inside surface of the tower housing
104
and the outer periphery of the upper flange
102
. The high tension terminal
101
is held by a cylindrical guide
79
to be coaxial with the tower housing
104
, so that a projection
75
can be inserted into the lower end of a spool easily when assembled. There is a comparatively large circumferential gap
106
between the outer periphery of the middle barrel
103
and the inside surface of the tower housing
104
. Although the circumferential gap
105
around the high tension terminal
101
is comparatively small, liquid state epoxy resin is poured through the circumferential gap
105
into the space formed between the middle barrel and the tower housing
104
. Thereafter, the epoxy resin is solidified in the smaller circumferential gap
105
and the larger circumferential gap
106
.
Because the high tension terminal
101
is made of metal while the tower housing
104
is made of resin, the coefficient of thermal expansion of the high tension terminal
101
is much different from that of the tower housing
104
. The temperature of the ignition coil
100
increases when it is operated and decreases after it is stopped. Therefore, the high tension terminal
101
and the tower housing
104
are heated and cooled cyclically. Accordingly, the epoxy resin disposed in the circumferential gaps
105
,
106
is subjected to thermal stress.
As shown in
FIG. 8
, the high tension terminal
101
has the middle barrel
103
that has a smaller outside diameter than the upper flange in order to elongate the mean distance between the high tension terminal
101
and the inside surface of a plug hole (indicated by
91
in
FIG. 7
) formed in an engine. This structure reduces stray capacitance between the high tension terminal and the plug hole to increase the high tension voltage. However, voids
107
may be formed in the epoxy resin disposed in the gap
106
when liquid state epoxy resin is poured into the large gap
106
through the small gap
105
. If there are voids
107
in the epoxy resin disposed between the high tension terminal
101
and the tower housing
104
, insulation performance of the ignition coil lowers, and the ignition coil may not supply sufficient high tension voltage to a spark plug.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a reliable ignition coil in which voids are not formed in the insulation resin disposed between the tower housing and the high tension terminal.
According to a feature of the invention, an ignition coil includes a center core with primary and secondary coils wound around, a cylindrical coil housing, a cylindrical tower housing having an upper flange and a middle barrel disposed under the coil housing, a high tension terminal connected to the secondary coil and solid insulation resinous members that are solidified after being filled in the coil housing and the tower housing. In the above ignition coil, at least the tower housing or the upper flange has a void-purging passage for purging air from the insulation resinous members when filled in the coil housing and the tower housing.
When liquid state insulation resin is poured from the upper end of the coil housing into- the inside of the coil housing and the tower housing, air can be purged from the circumferential gap and the void-purging passage.
Preferably the void-purging passage is vertically formed in the upper flange. The void-purging passage may be a groove disposed on the inside surface of the tower housing. The high tension terminal may be molded in the tower housing so as to eliminate a chance to form voids around the high tension terminal.
REFERENCES:
patent: 6561173 (2003-05-01), Betz et al.
patent: 6571784 (2003-06-01), Shimada et al.
patent: 2000-182859 (2000-06-01), None
Nakashima Hidetoshi
Osuka Kazutoyo
Denso Corporation
Nixon & Vanderhye P.C.
Solis Erick
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