Patent Application
20100253202
The present invention relates generally to vehicle ignition coils.
Ignition coils are components that use the coupling between a primary winding and a secondary winding to transform relatively low voltages from the battery into high voltages that are supplied to the spark plugs in vehicle gasoline engines. The spark plugs start the internal combustion process that drives the rods and hence, crankshaft and axles. In older systems, a single ignition coil is provided, and a distributor sends the pulses from the coil through respective high voltage spark plug wires to the spark plugs in the cylinders in accordance with a timing that is established by the distributor.
In relatively modem engines, an engine can have several ignition coils, one for each cylinder or for each pair of cylinders, thereby advantageously eliminating the need for distributors and high voltage wires and also providing more precise control of the engine timing. One example of such an ignition coil system is set forth in U.S. Pat. No. 6,556,118, owned by the present assignee and incorporated herein by reference.
To provide a magnetic return path to the primary core around which the primary windings are wound, steel shields have been provided that surround the inside or outside of the case which holds the core. The primary core typically is centrally disposed in a secondary winding spool around which the secondary windings are wound, and the case holds the primary/secondary assembly. Such a shield, which also serves to direct flux to a main air gap that is associated with pole pieces, is described in U.S. Pat. No. 5,015,982, incorporated herein by reference.
As understood herein, were a case holding the spool with core to be made of composite Iron and thereby obviate the need for the above-mentioned steel shield, which tends to crack because of its low coefficient of thermal expansion and which can entail additional cost and complexity attendant thereto, such a case might require an integral primary core and pole to direct the flux to the top of the case wall. Such a design might also require sealing at the bottom relative to the potting orientation.
A spark plug coil assembly includes a primary core bearing primary windings and a secondary winding spool around which secondary windings are wound. The primary core is received in the spool. A case receives the spool with core. The case is made of composite Iron to function as a magnetic return path for the core. The case defines a generally parallelepiped-shaped periphery and is configured to eliminate need for a separate pole piece and a shield such that no magnetic shield is provided on an inside or outside surface of the case.
The case can be electrically grounded. In some embodiments the case is formed with opposed first walls which are orthogonal to a longitudinal axis defined by the core and opposed second walls connecting the first walls. The first walls are thicker than the second walls to promote transfer of flux from the core to the case. Also, if desired the first walls can define a thickness of between about five to seven millimeters, inclusive. Respective mounting brackets may extend from the first walls and may be integral therewith.
In example embodiments the first walls are centrally formed on their inside surfaces with respective slots closely receiving respective ends of the core. Each slot may have a respective curved bottom surface on which the core rests. The entire case can be 40%-70% by volume Iron particles injection molded into a thermoplastic carrier.
In another aspect, a holding member for a secondary spool with primary core disposed centrally therein includes a composite Iron case formed with slots supporting respective ends of the core and configured to function as pole pieces for the core.
In another aspect, a method includes providing a primary core bearing primary windings and a secondary winding spool around which secondary windings are wound. The primary core is received in the spool. The method includes supporting opposite ends of the core using a case made of composite Iron to provide a magnetic flux return path for the core.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:
Referring initially to
Cross-referencing
As shown in
A hollow case 32 that may have a generally parallelepiped-shaped periphery centrally holds the spool 20 with primary core 26. The case 32 may be made in some examples of composite Iron and more particularly may be 40%-70% by volume Iron particles injection molded into a thermoplastic carrier/fiberglass. As understood herein, by making the case 32 of composite Iron, the need for a second pole piece and a shield are eliminated, meaning that no magnetic shield is provided on the inside or outside surface of the case 32. Accordingly, the case 32 itself preferably is electrically grounded.
The example case 32 shown in
As perhaps best shown in
The connector to the primary windings may exit the potting surface or may be configured as a “tongue and groove” connector through a wall of the case 32.
While the particular IGNITION COIL FOR VEHICLE is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.
