Inductor devices – With outer casing or housing – Potted type
Reexamination Certificate
1998-12-10
2001-06-26
Gellner, Michael L. (Department: 2832)
Inductor devices
With outer casing or housing
Potted type
C336S096000, C336S090000, C336S092000, C123S634000, C123S635000
Reexamination Certificate
active
06252482
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application Nos. Hei 9-213073 filed on Aug. 7, 1997, Hei 9-356425 filed on Dec. 25, 1997, and Hei 9-357144 filed on Dec. 25, 1997.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ignition coil for installation inside an engine plug-hole.
2. Related Art
A conventional stick-type ignition coil includes primary and secondary coils rolled around two spools having respective different diameters and a bar-like center core. The primary and secondary coils and the center core are concentrically installed inside a cylindrical coil casing. A high-voltage terminal connectable to an ignition plug is attached to the lower end of the coil casing by adhesive. Filler such as epoxy-based thermosetting resin fills the upper otherwise open end of the coil casing. In this conventional ignition coil, as shown in
FIGS. 9A and 9B
, a high-voltage terminal
1
is formed at one coil and by bending copper wire into a U-shape, for reducing manufacturing cost. This high voltage terminal
1
is vertically press-inserted into a terminal support
2
integrally formed at the lower end of the secondary spool
5
. Further, a pin-shaped central high-voltage terminal
3
protruding upwardly from a high-voltage tower portion (not illustrated) is upwardly inserted into and connected to the U-shaped high-voltage terminal
1
. Here, the terminal support
2
has a circularly-shaped terminal insertion hole
4
into which the high-voltage terminal
3
is upwardly inserted.
However, as shown in
FIG. 9B
, when the high-voltage terminal
3
is pinched by the U-shaped high-voltage terminal
1
, both sides of the high-voltage terminal
3
are expanded to a certain degree to attain sufficient contacting pressure therebetween. In this condition, the resilient forces of both sides of the high-voltage terminal
1
push the high-voltage terminal
3
toward the opening side of the U-shaped high-voltage terminal
1
as denoted by arrow A. When the high-voltage terminal
3
is inserted into the high-voltage terminal
1
, the coil casing is not yet filled and the lower end of the secondary spool
5
(terminal support
2
) is not fixed. Thus, the lower end of the secondary spool
5
slides toward the opposite side of arrow A to an eccentric position due to the reaction force acting on high-voltage terminal
3
opposite arrow A. Therefore, the desired concentricity between each component inside the coil casing is reduced and the electrical insulating distance therebetween varies, thereby reducing the degree of insulation between components.
In this case, as the maximum offset of the secondary coil
5
is defined by clearance B between the terminal insertion hole
4
and the high-voltage terminal
3
, the offset of spool
5
can be reduced by making clearance B small. However, when clearance B is made small, it becomes more difficult to insert high-voltage terminal
3
into hole
4
, and the assembling process becomes less desirable. That is, in the above-described conventional high-voltage terminal connection structure, it is difficult to simultaneously attain both high accuracy distances between assembled parts (insulating performance) and efficient, relatively easy assembly processes.
JP-A-8-213259 discloses another conventional stick type ignition coil. This ignition coil includes, as shown in
FIG. 10
, a bar-like center core
102
, a secondary coil
104
rolled around a secondary spool
103
disposed at the outer side of center core
102
, a primary coil
106
rolled around a primary spool
105
disposed at the outer side of secondary coil
104
, and an outer core
107
disposed at the outer side of primary coil
106
. A thermosetting resin fills the gaps between these components to attain electrical insulation and mechanical strength inside housing
101
.
In general, an ignition coil needs to be installed in a restricted space like an engine plug-hole in which the coil portion outer diameter is less than 24 mm. Thus, permanent magnets
109
,
110
need to be disposed at both ends of center core
102
for generating required ignition coil voltage. Here, the excitation poles of permanent magnets
109
,
110
are opposite to the polarity of center core
102
.
A rare-earth magnet such as neodymium is used for permanent magnets
109
,
110
, so as to generate sufficiently high magnetic force in the restricted small space. The need for permanent magnets
109
,
110
increases manufacturing cost for the ignition coil.
SUMMARY OF THE INVENTION
The present invention provides an ignition coil with improved assembling accuracy and process for connecting together a coil-side high-voltage terminal and a tower-side high-voltage terminal.
The invention also provides required ignition coil performance without a permanent magnet.
In one exemplary embodiment, a convex portion is formed at the inner peripheral surface of a terminal insertion hole to improve assembling accuracy of a tower-side high-voltage terminal with respect to the terminal insertion hole. That is, the lower portion of a secondary spool (terminal support portion) is very accurately set in place with respect to the tower side high-voltage terminal. In this way, the convex portion can adjust the center of the secondary spool lower end, thereby improving concentricity and insulating performance between components inside a coil casing.
As the convex portion improves concentricity, the inner diameter of the terminal insertion hole does not need to be made so small. Even when the tower-side high-voltage terminal contacts the convex portion while the tower-side high-voltage terminal is inserted into the terminal insertion hole, because the contacting area is small, the resistant force is not so large. Therefore, the tower-side high-voltage terminal can be easily inserted into the terminal insertion hole. In general, the terminal support portion and the convex portion are made of insulating resin (as is the spool). Thus, when the tower-side high voltage terminal contacts the convex portion, the convex portion easily moves relative to the outer shape of the tower-side high-voltage terminal. As a result, the resisting force is made small, and assembling performance is improved.
If the diameter x mm of a center core and the thickness y mm of an outer core satisfy certain specified relationships, the size of an ignition coil having no permanent magnet need not be substantially increased with respect to a coil having permanent magnets.
REFERENCES:
patent: 59-155720 U (1984-10-01), None
patent: 5-21240 (1993-01-01), None
patent: 8-213259 (1996-08-01), None
patent: 9-275026 (1997-10-01), None
U.S. Patent Application SN 08/567708, filed Dec. 05, 1999.
Aoyama Masahiko
Chiba Tomonari
Okazaki Keiichi
Oonishi Hiromitsu
Oosuka Kazutoyo
Denso Corporation
Gellner Michael L.
Nguyen Minh
Nixon & Vanderhye P.C.
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