Patent ID: 7501923

Claim:
An ignition coil for a sparkplug of an engine, the ignition coil comprising: a coil main body including a coil case accommodating a primary coil and a secondary coil; a plug mount portion provided to a high voltage end of the coil main body, the plug mount portion having a cap mount portion being in a substantially cylindrical shape extending from a primary spool of the primary coil or the coil case; a plug cap, which is formed of rubber and connected with the cap mount portion, the plug cap having a fitting hole in which an insulator portion of the sparkplug is to be inserted; and a coil spring inserted in the fitting hole for electrically connecting the sparkplug with a high voltage terminal, which is connected with a high voltage winding end of a winding of the secondary coil, wherein the plug mount portion and the coil main body are adapted to being inserted in a plughole of the engine, the coil spring has a low voltage end being electrically connected with the high voltage winding end of the secondary coil via the high voltage terminal, the coil spring has a high voltage end to be in contact with a terminal portion of a tip end of an insulator portion of the sparkplug, the coil spring has an intermediate portion between the low voltage end and the high voltage end, and the plug cap has a spring support portion defining a part of the fitting hole for restricting the intermediate portion of the coil spring from being radially deformed, wherein the coil spring has a spaced winding portion and a closed winding portion, which are formed by a winding steel wire to form a plurality of loops with respect to the axial direction, the spaced winding portion is formed by winding the steel wire with axial spaces between axially adjacent two of the plurality of loops of the steel wire, the closed winding portion is formed by winding the steel wire with axial spaces, which are less than the axial spaces of the spaced winding portion, between axially adjacent two of the plurality of loops of the steel wire, the closed winding portion is located at an intermediate position of the winding portion, the spring support portion supports the closed winding portion, the closed winding portion has an outer diameter greater than an outer diameter of the spaced winding portion, the plug cap has an inner circumferential periphery defining the fitting hole, the inner circumferential periphery of the plug cap has a small diameter portion radially inwardly protruding from the inner circumferential periphery of the plug cap, and the intermediate portion of the coil spring is hooked to the small diameter portion.