Internal-combustion engines – High tension ignition system – Specific coil location
Reexamination Certificate
1999-07-27
2001-04-17
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
High tension ignition system
Specific coil location
C123S1690PA, C336S096000, C029S602100
Reexamination Certificate
active
06216679
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ignition coil for an internal combustion engine, and more particularly, to an ignition coil for an internal combustion engine where the ignition coil is encased by a silicone rubber injection molding that serves to form the high-voltage boot to the spark plug.
BACKGROUND OF THE INVENTION
An ignition coil for an internal combustion engine that is installed directly on an engine and that is directly coupled with spark plugs is well known. Various configurations of such ignition coils for internal combustion engines have been proposed to achieve compactness and reduced weight. The ignition coil of the prior art is filled up around a coil portion, as fitted in a housing, with a thermoset resin (molding resin) such as an epoxy resin to prevent the high voltage generated by the coil portion from leaking out of the housing and causing a dielectric breakdown in the coil by the high voltage. Considering the adhesion between the inner wall of the housing and the molding resin, therefore, it is known to make the housing of a thermoplastic polyester resin such as polybutylene terephthalate (PBT) or polyethylene terephthalate (PET).
A device employing insulation material of insulating oil, epoxy resin, or the like to ensure insulation against high voltage is known, and the use of silicone rubber to encapsulate the coil is known.
However, demand for high output and high efficiency is increasing because the cylinder-head portions of engines are increasing in complexity because of adoption of more valves and improvements in combustion-chamber configuration. Space constraints for installation of the ignition coil is an increasing problem and concern. In the case of a DOHC engine in particular, increasingly narrower valve parting angles are being attempted, and the state is such that installation of a thick ignition coil is extremely difficult, and suitable dimensions which are housable within for example a plug hole are necessary.
Moreover, because the ignition coil is placed in the high-temperature environment immediately proximately to the engine body according to the foregoing prior art, there is a problem in which the insulating material is susceptible to temperature degradation. In particular, when the interior of the case is filled completely with insulating resin or oil, there is a problem whereby high-voltage durability declines due to oxidation and degradation of these materials.
SUMMARY OF THE INVENTION
To solve problems of the prior art such as the foregoing, it is an object of the present invention to provide an improved ignition coil for an internal combustion engine.
More particularly, it is an object of the present invention to provide an ignition coil for an internal combustion engine which is housed within a plug hole of an engine and mounted directly on the engine, and which maintains insulation performance against high voltage even with respect to engine heat and vibration.
An ignition coil according to the present invention uses an injection molded silicone rubber as the material for a housing of an ignition coil while at the same time forming the boot to the spark plug. In this way, durability can be improved as compared to the prior art structures.
More specifically, the invention utilizes liquid silicone as the encapsulant of a pencil coil forming the high voltage boot and the sealing feature at the low voltage end in the same molding operation. A case may be added for support and dielectric integrity, or the liquid silicone rubber may also form the case.
The progressive wound secondary may be required to be either pre-impregnated, trickle coated, or protected by tape because, while the pressures from liquid silicone rubber molding are significantly lower than typical thermal plastic molding, it still has the potential to damage the wires.
The wound primary with assembled connector is assembled to the wound secondary spool and then into the case. This assembly is then overmolded with liquid silicone rubber to form the boot to the plug and the sealing feature to the steel outer housing.
With this invention, oil can be eliminated as the encapsulant for the integrated plug/pencil coil. Liquid silicone rubbers have been formulated to withstand temperatures of greater than 300° C., which are 100° C. greater than silicone oil of gel. The cost of the liquid silicone rubber molding process described herein is significantly less than a conventional potting process.
Other objects and features of the invention will appear in the course of the description thereof, which follows.
REFERENCES:
patent: 4514712 (1985-04-01), McDougal
patent: 4960099 (1990-10-01), Shimada et al.
patent: 5685282 (1997-11-01), Murata et al.
patent: 5706792 (1998-01-01), Boyer et al.
patent: 5720264 (1998-02-01), Oosuka et al.
patent: 5949319 (1999-09-01), Nuebel et al.
patent: 6114933 (2000-09-01), Widiger et al.
Boyer James Alva
Huntzinger Dwayne Allen
Skinner Albert Anthony
Castro Arnold
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Dolinar Andrew M.
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