Inductor devices – Combined – With connector
Reexamination Certificate
1999-01-25
2001-09-25
Donovan, Lincoln (Department: 2832)
Inductor devices
Combined
With connector
C336S096000, C336S185000, C336S212000, C336S234000
Reexamination Certificate
active
06294974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an ignition coil for an internal combustion engine for use in a vehicle or the like, and to a method of manufacturing the ignition coil for an internal combustion engine.
2. Description of Related Art
It is known to provide an independent ignition type-ignition coil for each cylinder of an internal combustion engine. One ignition coil of this kind is shown in
FIGS. 20 and 21
and is of the so-called upward-set type in which a casing
116
is installed on an opening of a plug hole Ha formed in a cylinder head H of an internal combustion engine.
The casing
116
accommodates a coil
114
of a concentric type including a primary coil section
111
with an enamel wire wound on the periphery of a magnetic core
110
and a secondary coil section
112
with an enamel wire wound on the periphery of the primary coil section
111
, with the magnetic core
110
being kept horizontal. A high secondary voltage generated in the secondary coil section
112
of the coil
114
is applied to an ignition plug P positioned at the bottom of the plug hole Ha through a connection member
118
accommodated inside the plug hole Ha.
In recent years, there has been a growing demand for reduction of the height of the part of the ignition coil projecting from the cylinder head H. This is because when the height of this projecting part is large, as shown in
FIGS. 20 and 21
, it may interfere with suction and exhaust component parts accommodated inside the engine room.
To overcome this problem, as shown in
FIG. 22
, a so-called in-hole type ignition coil has been proposed. This has a concentric-type coil
103
including a primary coil section
101
with an enamel wire wound on the periphery of a rod-shaped magnetic core
100
and a secondary coil section
102
with an enamel wire wound on the periphery of the primary coil section
101
(or the secondary coil section
102
is formed on the periphery of the magnetic core
100
, and the primary coil section
101
is formed on the periphery of the secondary coil section
102
). A plug hole Ha accommodates the coil
103
. A high secondary voltage generated in the secondary coil section
102
is applied to an ignition plug P positioned at the bottom of the plug hole Ha through a connection member
108
accommodated inside the plug hole Ha.
In this type of ignition coil, because the coil
103
is accommodated inside the plug hole Ha, it is possible to reduce the height of a part
112
projecting from the plug hole Ha.
However, generally, the inner diameter of the plug hole Ha is as small as 23-24 mm. Thus, in the ignition coil shown in
FIG. 22
, there are restrictions on the thickness of the enamel wire forming the primary coil section
101
and the secondary coil section
102
, the number of turns of the enamel wire, and the layout of the magnetic core
100
. Thus, it is impossible for the ignition coil to generate a sufficiently great secondary energy.
In particular, in recent years, the direct fuel injection type of internal combustion engine has been rapidly widely adopted. In this type of engine, the ignition coil is required to generate large secondary energy in order to ignite a gas mixture in the cylinder. The ignition coil shown in
FIG. 22
is incapable of satisfying such a demand to a sufficient extent. Another problem is that, because the coil
103
is accommodated in the narrow and closed plug hole Ha, the ignition coil is inferior in heat-radiating performance.
In order to overcome the problem the present inventors have devised, but not made public, an ignition coil, such as is shown in
FIG. 23
, including a coil
124
having a primary coil section
121
and a secondary coil section
122
formed on the periphery of the primary coil section
121
. The coil
124
is of concentric type and laterally flat. The coil
124
is installed on a plug hole Ha (e.g., see FIGS.
20
and
22
), with the lateral (flat) direction being horizontal. However, it has been revealed that in order to secure a secondary energy having the required magnitude, it is necessary to considerably increase the number of turns of an enamel wire forming the primary and secondary coil sections
121
and
122
. When the number of turns of the enamel wire is increased, the ignition coil becomes large radially. Consequently, the ignition coils interfere with each other when assembled adjacent to each other on the engine head.
In a known kind of ignition coil for an internal combustion engine, an enamel wire of circular cross-section is used as a coil winding to be wound on a primary coil winding seat and a secondary coil winding seat.
FIGS. 31 and 32
show conventional methods of winding such an enamel wire of circular cross-section on the primary and secondary coil winding seats.
FIG. 31
shows a cross-section of a coil in which a coil winding
410
such as an enamel wire having a diameter of 0.5 mm is wound 80 times between a pair of flange portions
402
of a primary coil winding seat
404
. In this method, the wire of the coil winding
410
is wound between the two flange portions
402
. The wire is wound such that, as viewed in cross-section, the winding displays columns of four circles (each circle being a cross-section of the wire), each circle of a column being at the same level as a respective circle of an adjacent column.
FIG. 32
shows a cross-section of a coil in which a coil winding
410
such as an enamel wire having a diameter of 0.5 mm is wound 81 times between a pair of the flange portions
402
of the primary coil winding seat
404
. In this method, the coil winding
410
is wound so that in cross-section the winding displays alternating columns of three and four circles, each circle of a column being displaced in the direction between the flanges
402
from a respective circle in a neighbouring column by a distance equal to the radius of the coil winding
410
.
In the above-described conventional ignition coils for an internal combustion engine, the coil winding
410
is circular in cross-section. Thus, even though the coil winding
410
is packed tightly between both flange portions
402
, gaps are formed between the adjacent rounds of the coil winding
410
. Consequently, the size of the ignition coil for an internal combustion engine is increased according to the size of the gaps.
Also, each gap is filled with air. The heat conductivity of air is lower than that of the coil winding
410
of enamel wire. Thus, heat generated at the primary coil during the use of the ignition coil is not radiated efficiently and promptly.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide an ignition coil which can have a small height, can be small enough to avoid or minimize interference with adjacent ignition coils in an engine, and can provide a sufficiently large secondary energy.
A second object of the present invention is to provide an ignition coil for an internal combustion engine which is compact and superior in heat-radiating performance.
In order to at least partially address the first object, in a first aspect the present invention provides an ignition coil for an internal combustion engine which includes a coil member, the coil member including a substantially disk-shaped primary coil section having a primary coil winding wound thereon and a substantially disk-shaped secondary coil section having a secondary coil winding wound thereon. The primary coil section and the secondary coil section face each other, and a core region of each coil section is aligned with a core region of the other coil section. The coil member has a thickness parallel to the thickness direction of the primary and secondary coil sections of 10-25 mm (that is, it is “flat”).
At least one pair of radial core sections each formed of a plurality of core portions having an overlapping portion at a center thereof are combined with each other in a radial formation and installed on upper and lower sides of the coil member, such that the coil member is sandwiched between the at leas
Donovan Lincoln
Nguyen Tuyen
Oliff & Berridge PLC.
Sumitomo Wiring Systems Ltd.
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