Discharge ignition apparatus for internal combustion engine

A discharge circuit for use in a discharge ignition apparatus of the type operative to produce an electrical spark at a spark ignition device, said apparatus comprising:

• (a) a storage capacitor having a first side electrically connected to said relative ground potential;
• (b) a charge coil having a plurality of turns, said charge coil having a first side connected to said relative ground potential;
• (c) a rectifier diode having an anode electrically connected to a second side of said charge coil and a cathode electrically connected to a second side of said storage capacitor;
• (d) a transformer including a primary coil and a secondary coil having a respective plurality of turns defined by a predetermined step-up ratio, said secondary coil electrically connected during operation to the spark ignition device to produce the electrical spark, a first side of the primary coil electrically connected to said relative ground potential;
• (e) an electronic switch electrically connected between said second side of said storage capacitor and said second side of said primary coil, said electronic switch being rendered conductive by a triggering signal applied to a gate electrode thereof;
• (f) a return path diode having an anode electrically connected to a cathode of said electronic switch and a cathode electrically connected to an anode of said electronic switch;
• and
• (g) triggering circuitry electrically connected to said electronic switch for supplying said triggering signal to said gate electrode at a predetermined time.

A discharge ignition apparatus for use in an internal combustion engine to produce an electrical spark at a spark ignition device having a characteristic spark ionization potential and a lower characteristic spark sustaining potential, said apparatus comprising:

• a movable magnet assembly;
• a magnetically permeable core mounted such that said magnet assembly will periodically pass proximate thereto;
• a discharge circuit including:
• (a) a storage capacitor;
• (b) a charge coil situated about said magnetically permeable core such that a charging voltage is induced thereon due to passage of said magnet assembly, said charging voltage producing an accumulation of charge on said storage capacitor;
• (c) a transformer having a primary coil and a secondary coil situated about said magnetically permeable core and having a predetermined step-up ratio, said secondary coil electrically connected during operation to the spark ignition device to produce the ignition spark;
• (d) an electronic switch electrically connected between said energy storage element and said primary coil, said electronic switch being nonconductive as said charge is accumulated on said storage capacitor and being rendered conductive by a triggering signal;
• (e) triggering circuitry electrically connected to said electronic switch for supplying said triggering signal thereto at a predetermined time;
• and
• (f) said discharge circuit being configured such that no greater than a negligible current will flow through said charge coil at the predetermined time and a period immediately thereafter during which a voltage no less than the spark sustaining potential is being induced across said charge coil.

A gasoline engine powered device, such as a chain saw, string trimmer and the like, said device comprising:

• a gasoline engine having a drive shaft;
• a flywheel operatively connected to said drive shaft for rotation during operation of said gasoline engine, said flywheel including a magnet assembly having at least two pole faces located at a periphery of said flywheel;
• a spark ignition device mounted during operation to said gasoline engine;
• a discharge ignition apparatus including a magnetically permeable core mounted adjacent the circular path and having at least two leg portions each including a respective end face, said leg portions being situated so that said pole faces pass proximate to said end faces during revolution of said magnet assembly;
• a discharge circuit including:
• (a) an energy storage element;
• (b) a charge coil situated about said magnetically permeable core such that a first half cycle charge coil voltage and a second half cycle charge coil voltage are induced thereon during revolution of said magnet assembly;
• (c) said discharge circuit being configured to supply electrical energy to said energy storage element during the first half-cycle charge coil voltage and further configured so that no greater than a negligible current flows through said charge coil during the second half-cycle charge coil voltage;
• (d) a transformer having a primary coil and a secondary coil situated about said magnetically permeable core, said secondary coil electrically connected during operation to the spark ignition device to produce the ignition spark;
• (e) an electronic switch electrically connected between said energy storage element and said primary coil, said electronic switch being nonconductive during the first half-cycle charge coil voltage to allow electrical energy to accumulate at said energy storage element and being rendered conductive by a triggering signal at a predetermined time during the second half cycle charge coil voltage;
• and
• (f) triggering circuitry electrically connected to said electronic switch for supplying said triggering signal thereto at the predetermined time.