Internal-combustion engines – High tension ignition system – Having a specific ignition coil
Reexamination Certificate
1998-07-06
2001-04-10
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
High tension ignition system
Having a specific ignition coil
C336S107000
Reexamination Certificate
active
06213109
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an ignition coil for use in an internal combustion engine which is connected directly to an ignition plug and is accommodated in a plug hole of the internal combustion engine and further relates an internal combustion engine having such an ignition coil.
2. Prior Art
In a conventional ignition coil, as shown in Japanese patent laid-open publication No. Hei 3-149805, as a potting type resin which fixe and insulates the components such as a primary coil and a secondary coil etc. A thermoplastic resin comprised of an epoxy resin is used and further as a filling-up agent a crystalline silica is mainly employed.
In the conventional type ignition coil, since the ignition coil is accommodated in a plug hole having a diameter of 20-30 mm degree, a size in a radial direction of the coil is small and a distance between the primary coil and an outer side magnetic core is short. As a result, there is a case in which an insulation between the secondary coil having a high potential, the primary coil having a substantial ground potential and the outer side magnetic core can not be obtained. In particular, since a coil interior portion temperature is more than 150° C., there is an insulation endurance performance problem caused in a comparatively short time.
A technique to cope with the above problem a technique has known, namely such a technique is one (namely an inside secondary coil method), in which the primary coil having the substantial ground potential is arranged at an outer side magnetic core side and the secondary coil having the high potential is arranged at a center magnetic core side.
In this conventional technique, the center magnetic core presents a floating potential and a potential difference causes between the secondary coil having the high potential and the center magnetic core but since the potential difference is about half that of an outer side secondary coil system of an ignition coil in which a secondary coil is arranged at an outer side magnetic core, accordingly it has a merit that an insulation performance is superior.
However, as to the above stated inside secondary coil system ignition coil, in an operation endurance test in a heat cycle oven in which a drive mode of an actual vehicle is supposed, a breakdown between a secondary winding and an outer side magnetic core causes according to a heat shock, therefore there is a problem (a disturbance in a rotation of the engine) in the internal combustion engine. As a result of the study of this cause, it has become clear that since a thermal stress is concentrated at a vicinity of a crossover wire portion of a winding finish portion of the secondary coil, minute voids are generated in an insulation resin which is filled up at a neighborhood of the above stated winding crossover wire portion vicinity and an electric treeing generates at this portion according to the voids as a trigger and this electric treeing develops, as a result it is understood an insulation or dielectric breakdown in the ignition coil occurs.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ignition coil for use in an internal combustion engine wherein the ignition coil has a superior endurance performance against a heat cycle oven.
Another object of the present invention is to provide an ignition coil for use in an internal combustion engine wherein an electric tree hardly occurs and/or the electric tree hardly develops.
The above stated objects can be attained by a provision of a shielding member for restraining a development of an electric treeing even minute voids generate in an insulation resin, or at a portion for restraining the development of the electric treeing by a constitution of an insulation material in which the electric treeing hardly develop.
According to the present invention, since a high electric field portion in which the electric treeing generates easily is constituted by an insulation material in which sulfur (S) is put in an aromatic main chain and since an electric treeing shielding member comprised of the above stated material is arranged between a secondary coil and an outer side magnetic core, as a result a lowering in insulation performance due to the minute voids generation can be avoided and thus the heat cycle oven endurance performance can be improved.
Further the present invention can be attained by an ignition coil in which as a thermoplastic resin an epoxy resin in which melting silica powders are filled as a filling-up agent is potted.
The concrete constructions are as following.
(1) The thermoplastic potting type resin contains a filling-up agent in the resin, and at least part of the filling-up agent is formed by a melting silica, and the melting silica of 20 wt %-85 wt % is blended in a total filling-up agent amount.
In the above stated (1) item, in the ignition coil, said filling-up agent includes a mixture material comprised of said melting silica and a crystalline silica.
In the above stated (1) item, in the ignition coil, said secondary coil is arranged at a side of said center magnetic core, and said primary coil is arranged between said secondary coil and said outer side magnetic core.
In the above stated (1) item, in the ignition coil, said meting silica in said resin has a spherical shape.
(2) An internal combustion engine having an ignition coil comprises an ignition plug for igniting the engine, an ignition coil accommodated in a plug hole which is provided on an engine block to install said ignition plug and connected directly to said ignition plug, an igniter for controlling said ignition coil, and a potting type resin for fixing a primary coil, a secondary coil and a center magnetic core etc., said potting type resin containing a filling-up agent including a melting silica, and said melting silica in said resin containing 20 wt %-85 wt % in a total filling-up agent amount.
With the above stated construction, as the resin for fixing and insulating the components such as the primary coil and the secondary coil etc. of the ignition coil, by potting the thermoplastic resin in which the melting silica powders are filled up, since the occurrence and the development of the electric treeing under the high temperature is restrained, as a result an inconvenience in the insulation performance of the ignition coil can be reduced and the anti-endurance performance of the ignition coil can be heightened.
The particle diameter of the melting silica in the present invention is not limited in particularly but it is preferable to use the particle diameter having a range of 1-300 &mgr;m and preferably 5-44 &mgr;m. Further, it is preferable to use the spherical shape melting silica and the suitable effects can be expected. Further, as the melting silica and the crystalline silica of the present invention, fluorine system and silicone system coupling agent processing article can be used.
REFERENCES:
patent: 4893105 (1990-06-01), Maeda et al.
patent: 5101803 (1992-04-01), Nakamura et al.
patent: 5714922 (1998-02-01), Suzuki et al.
patent: 5720264 (1998-02-01), Oosuka et al.
patent: 0 647 002 (1995-04-01), None
patent: 0 703 588 (1996-03-01), None
patent: 3-149805 (1991-06-01), None
Kobayashi Kazutoshi
Satoo Takanori
Takeuchi Ryozo
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Gimie Mahmoud M.
Hitachi , Ltd.
Yuen Henry C.
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