Title of Invention

A BOBBIN FOR THE SECONDARY WINDING OF THE IGNITION COIL OF THE IGNITION SYSTEM OF A PETROL ENGINE

Abstract

The present invention discloses a bobbin for the secondary winding of the ignition coil of an ignition system an internal combustion engine comprising a tubular core made of electrical grade kraft paper, a plurality of segments also made of electrical grade kraft paper fixed to the core and a coil wound on the core between the plurality of segments. The segments are fixed perpendicularly along the axis of the core. The electrical grade kraft paper is soaked in an electrically insulating material to provide better insulation.

Full Text

This invention relates to a bobbin for the secondary winding of the ignition coil of the ignition system of a petrol engine. Ignition coils are used in internal combustion petrol engines for producing high voltage required for igniting the air-fuel mixture in the engine cylinders through spark plugs. The bobbin for the secondary winding of the ignition coil of the ignition system of a petrol engine, according to this invention, comprises a plurality of segments made of kraft paper (electrical grade paper) soaked in an electrically insulating medium; the segments being fixed to the bobbin, and the coil being located between the segments. This invention will now be described in further detail by reference to the accompanying drawings which illustrate, by way of example, and not by way of limitation, one of possible embodiments of the bobbin proposed herein, Fig. 1 illustrating a separate view of a segment Fig. 2 illustrating a separate view of a paper bobbin Fig. 3 illustrating a separate view of the bobbin assembly. Generally, an ignition coil has a primary winding which receives the input from an external source and a secondary winding which steps up the source voltage, usually of the order of few hundred volts to several kilo volts. Typically the primary consists of 50 ~ 300 turns and secondary 3000 ~ 30,000 turns of insulated conductor depending on the specific requirement. A magnetic circuit core links the primary and secondary. Since the secondary winding has a large number of turns and produces high voltage usually of the order of 10 ~ 60 kilo volts, the winding needs to be adequately insulated so that a winding at a lower potential does not come into contact with a winding at a potential much higher than the insulation between the two. The required insulation is generally provided in two steps. In the first step, the windings are segregated or isolated from one another and in the second step, the windings are impregnated under vacuum process to increase the insulation to withstand the high voltage seen by the winding during operation. One of the well known types of windings used in industry is where the secondary winding is built segment by segment on a plastic former. Here, the segments are separated by the flanges of the plastic bobbin. Thus the windings are segregated by segments and the insulation is increased by entrapment of insulating material, generally, epoxy or varnish, during the vacuum process used conventionally. One of the major failure modes associated with the known bobbin winding is caused by poor adhesion of the insulating material with the plastic material of the bobbin. If the adhesion is poor, which can happen due to vacuum process variations or by long usage, voltage breakdown occurs through the interface between bobbin and winding. This invention addresses the elimination of this major failure mode that is failure of the ignition coil caused by the poor adhesion of the insulating material with the plastic bobbin. In the invention proposed herein, the segments S of the bobbin B are made of kraft paper (electrical grade). The bobbin B is also made of kraft paper. The segments are soaked in the insulating material during vacuum process to provide through and through insulation thereby eliminating the factor of poor adhesion of bobbin with insulating material. The bobbin B is made in two halves H, H which are brought together in alignment to make the whole bobbin. The advantages of the segmented paper bobbin is given below: a) Voltage breakdown caused by poor adhesive of insulating material with the bobbin is eliminated, thereby enhancing the life of the coil significantly. b) The number of segments can be determined depending on the specific coil requirement. c) In the case of the known plastic bobbin, since a dedicated mould is required, it is difficult to make moulds for each application and therefore for a range of number of turns, a common bobbin is used. This puts constraints on optimizing the size of the coil. d) In the new segmented paper bobbin proposed herein, the number of segments can be arranged based on the requirement of specific number of turns in the secondary winding. Hence the size of the bobbin can be made to suit specific requirements thereby achieving size optimization. The terms and expressions herein are of description and not of limitation inasmuch as various embodiments of this invention are possible without departing from the scope and ambit of this invention.

Documents:

746-CHE-2006 ABSTRACT.pdf

746-CHE-2006 CORRESPONDENCE OTHERS.pdf

746-CHE-2006 CORRESPONDENCE PO.pdf

746-CHE-2006 DESCRIPTION (COMPLETE).pdf

746-CHE-2006 DESCRIPTION (PROVISIONAL).pdf

746-CHE-2006 DRAWINGS.pdf

746-CHE-2006 FORM-1.pdf

746-CHE-2006 FORM-13.pdf

746-CHE-2006 FORM-18.pdf

746-CHE-2006 FORM-3.pdf

746-CHE-2006 FORM-5.pdf

746-CHE-2006 POWER OF ATTORNEY.pdf

746-CHE-2006 AMANDED CLAIMS 30-04-2010.pdf

746-CHE-2006 FORM-13 27-08-2009.pdf

746-CHE-2006 OTHER PATENT DOCUMENT 27-08-2009.pdf

746-che-2006-claims.pdf

746-che-2006-correspondence-others.pdf

746-che-2006-description-complete.pdf

746-che-2006-drawings.pdf

746-che-2006-form 1.pdf

746-che-2006-form 26.pdf