Inductor devices – With outer casing or housing – Potted type
Reexamination Certificate
2000-03-03
2001-05-15
Sellner, M. L. (Department: 2832)
Inductor devices
With outer casing or housing
Potted type
C336S225000, C336S222000, C336S182000, C336S198000
Reexamination Certificate
active
06232863
ABSTRACT:
TECHNICAL FIELD
This invention relates to ignition coils for spark ignition engines, and more particularly to an ignition coil having a spool that has generally sawtooth shaped grooves to reduce wire slippage of the winding.
BACKGROUND OF THE INVENTION
It is well known in the art of ignition systems for automotive vehicles to have an ignition coil that produces a magnetic energy upon discharge to create a high voltage spark for initiating combustion in an engine cylinder. Typically, the ignition coil includes primary and secondary windings each wound around a spool and disposed about a magnetic core.
The windings may be progressively wound around the spool. With this winding method, wires are wound in layers at an angle to reduce the number of turns between adjacent wires and thus keep the voltage potential low between two adjacent wires. A problem associated with this type of winding method is wire slippage between wire layers wound around the coil bobbin, which creates a large voltage potential between adjacent wires, resulting in wires shorting together. When wires are wound at an angle, the wires at the surface of the spool can slip and slide axially along the spool due to the tension and force that is in the wires above the surface of the spool. After slippage occurs wires will be wound on top of the slipped wire as the winding continues, resulting in a high wire to wire voltage when the coil is operated. There is a need to decrease wire slippage which is critical to maintain a high quality progressive winding.
SUMMARY OF THE INVENTION
The present invention provides an ignition coil that includes a magnetic core having opposite first and second ends. A primary winding is wound about the magnetic core between the first and second ends. A secondary winding is wound about a spool and is disposed about the primary winding and magnetic core. The second winding is inductively coupled to the primary winding. Alternatively, the primary winding may be wound around a spool and disposed about the secondary winding and the magnetic core. An outer case is disposed about the magnetic core and primary and secondary windings.
The spool includes a winding section between opposite first and second ends. There is a conical winding surface at one end of the spool that tapers from a larger diameter at the one end to a smaller diameter. A grooved surface extends axially toward another end of the spool and is connected with the smaller diameter. The grooved surface has longitudinally spaced continuous circular grooves. The grooves have unequally angled sides. The sides toward the one end are sloped at a greater angle relative to a radial direction than are the sides toward the other end. The secondary winding is wound around the winding section such that it forms a plurality of layers of turns of wire wound one over the other at a desired angle with one turn of the wire disposed within each groove.
The present invention provides a grooved surface on the secondary spool to prevent the layers of wire wound around the spool from slipping down in the axial direction. The grooves are designed to accommodate only one turn of wire. Thus, the maximum distance that a wire on the surface of the spool will slip is the distance from the crest to the trough of the groove. By having one side have a greater angle, a positive stop is created, preventing the wire from slipping away from the conical end of the spool where winding of the coil is initiated. By designing the coil with specific grooves, the voltage potential between adjacent wires may be more controlled and result in fewer secondary wire to wire shorts. Further, the grooved surface increases the surface area of the spool and improves the adhesion of the spool to an epoxy used to encapsulate the windings.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
REFERENCES:
patent: 5929736 (1999-07-01), Sakamaki et al.
patent: 0750324A2 (1996-12-01), None
Knight Paul G.
Moga Viorel N.
Paul Mark Albert
Skinner Albert Anthony
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Nguyen Minh
Sellner M. L.
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