WO1998010431A9

WO1998010431A9 - High power spark plug wire

Info

Publication number: WO1998010431A9
Application number: PCT/US1997/015599
Authority: WO
Filing date: 1997-09-05
Publication date: 1998-07-30

Abstract

A wire capable of carrying high voltage and high current which minimizes electromagnetic interference (EMI) is described comprising an inner conductor having a first layer of insulating material provided thereon, a second layer of insulating material surrounding the first insulating layer, a magnetic flux carrying material disposed between the first and second insulating layers, an outer conductor wound spirally around the second insulating layer, and an outer layer of insulating material surrounding the outer conductor and the second insulating layer. When used in spark ignition engines, the present invention allows remote location of an energy source from a spark plug. Additionally, the present invention provides efficient and low cost delivery of a spark and an arc from an ignition coil having two energy sources.

Description

HIGH POWER SPARK PLUG WIRE

Background of the Invention

This invention relates to high-power wire and more specifically relates to spark plug wire for delivering high current and high voltage with a minimal amount of radio noise or electromagnetic interference (EMI).

Traditionally, high current and voltage wires were made of a solid copper center conductor surrounded by a high voltage insulating material. The insulating material was usually a rubber or plastic based compound. More recently, silicone has become an insulating material of choice because of its tolerance of high temperatures and its flexibility. In spark ignition engines, the need for EMI shielding of spark plug wires first arose with the introduction of radios into automobiles. Today, vehicle manufacturers are required by law to suppress the EMI generated by spark plug wires. To suppress EMI, the traditional spark plug wire was modified and the solid copper conductor was replaced by a resistive carbon conductor. For many automobile applications, EMI is sufficiently suppressed by the increased resistivity of the carbon conductor. Typically, the resistive carbon conductor used in spark plug wire is a polyamide fiber bundle with a carbon paint mixture dispersed therein. For an example of such a resistive carbon conductor, see U.S. Patent No. 4,366,464 to Miyamoto et al.

In the area of high performance spark plug wire, such as that used in race cars, it is desirable to have a high current capacitive discharge ignition. To meet these high current requirements, most spark plug ignition designs utilized solid core copper spark plug wire up until about ten years ago. With the increasing sophistication of race cars and the accompanying expansion of race car electronic systems, EMI suppression in spark plug wires became an important concern. As a result, what is known as inductive suppression spark plug wire became the standard ignition wire for racing applications. In inductive suppression spark plug wire, a steel conductor of a relatively low resistance is wound spirally around the resistive carbon conductor which forms the center core of the wire. The steel conductor provides a relatively low resistance capable of delivering high current. The inductance of the spirally wound steel conductor suppresses the rapid rate of current increase in the wire as the spark jumps the spark plug gap. Thus, EMI in the wire is suppressed.

In even more recent high performance spark plug wire technology, a ferrite material layer is added proximate to the center of the spark plug wire. The ferrite material further increases the inductance of the wire without increasing its resistance.

In the prior art Dual Energy Ignition System, disclosed in U.S. Patent No. 5,197,448 to Porreca et al., the use of two energy sources in an ignition system is described. A first energy source provides a spark at the spark plug, while a second energy source provides a high current arc across the spark plug. This system requires efficient delivery of high current and high voltage. Additionally, much of the EMI in this ignition system is generated by the high voltage portion of the circuit which rises to tens of thousands of volts very quickly. When the voltage induces a spark across the spark plug gap, an electrical path is formed across the gap and the tens of thousands of volts drops instantly to about 500 volts. With the instantaneous drop to 500 volts, the current increases significantly. This rate of current increase requires substantial EMI suppression. Just after the spark, the high current arc is provided to the spark plug from the second energy source. For the system to operate effectively, the high current path should have a very low resistance.

A difficulty in the prior art is that neither the resistive carbon conductor nor the spiraling steel conductor efficiently conduct energy from an energy source to the spark plug. Additionally, the high voltage and high current requirements found in recent ignition system developments, such as the Dual Energy System discussed above, necessitate greater and more effective EMI shielding. Furthermore, the inefficiencies of the prevailing spark plug wire designs require that the spark plug energy source be located very close to the spark plug itself. This requirement reduces the flexibility of energy source type and location within the engine compartment of an automobile.

Summary of the Invention

A general object of this invention is to deliver a very high current through a very low resistance conductor while minimizing EMI transmission.

Another general object of this invention is to deliver a very high voltage while minimizing EMI transmission.

Yet another object of this invention is to efficiently and economically deliver high current and high voltage to a spark plug from a remote energy source.

Still another object of this invention is to improve the implementation of the Dual Energy Ignition System and to allow this ignition system to be located further from a spark plug thereby increasing the adaptability of the Dual Energy Ignition System to various engine configurations.

The present invention comprises a wire capable of carrying high voltage and high current while minimizing electromagnetic interference. The wire includes an inner conductor having a first layer of insulating material provided thereon, a second layer of insulating material surrounding the first insulating layer, a magnetic flux carrying material disposed between the first and second insulating layers, an outer conductor wound spirally around the second insulating layer, and an outer layer of insulating material surrounding the outer conductor and the second insulating layer. When used in spark ignition engines, the present invention allows remote location of a high current energy source from a spark plug. Additionally, the present invention provides efficient delivery of the high energy to a spark plug at a relatively low cost.

Brief Description of the Drawings

Fig. 1 is a perspective view, with portions cut away, of a wire according to the present invention.

Fig. 2 is a circuit diagram of a prior art Dual Energy Ignition System showing an application of present invention.

Detailed Description of the Preferred Embodiment As depicted in Fig. 1, a wire is shown generally by reference numeral 10. Wire 10 includes an inner core 12 around which an outer conductor 14 is spirally wound. The outer conductor 14 is preferably a steel alloy, but other conductive metals are suitable. In the preferred embodiment, the outer conductor is 38 Awg steel. The inductance created in the spirally wound outer conductor 14 provides EMI suppression for the wire 10. Additionally, the resistance (which also provides EMI suppression) of the outer conductor 14 can be varied by using different lengths of wire or different wire gauges.

The outer conductor 14 is surrounded by an outer insulating layer 16. The outer insulating layer 16 is preferably a silicone based material because of its ability to withstand high temperatures and its flexible nature. In the preferred embodiment, the outer insulating layer 16 is 9 millimeters thick. The inner core consists of an inner conductor 18, a first insulating layer 20, a second insulating layer 22, and a ferrite material 24. The first insulating layer 20 surrounds the inner conductor 18 providing electrical insulation and isolation of the inner conductor 18. The second insulating layer 22 surrounds the first insulating layer 20. The ferrite material 24 is disposed between the first insulating layer 20 and the second insulating layer 22.

The inner conductor 18 has a very low resistance and is preferably a solid metallic conductor such as copper or a copper alloy. In the preferred embodiment the inner conductor is 22 Awg copper wire. The inner conductor 18 made of copper is capable of carrying very high currents and provides the high current path to a spark plug (not shown).

The inner and outer insulating layers 20, 22 electrically isolate the ferrite material 24 from the inner conductor 18 and outer conductor 14, respectively. The inner and outer insulating layers 20, 22 can be any suitable insulating material such as a composition of polyethylene and a non-crystalline olefin polymer.

The ferrite material 24 is a magnetic flux carrying material and preferably a ferrite filled plastic. The ferrite material 24 increases the inductance of the wire 10 without increasing its resistance. The inductive effect of the ferrite material 24, along with the inductance of the spirally wound outer conductor 14, provides EMI suppression of the high voltage breakdown within the wire 10.

The inner conductor 18 and the outer conductor 14 are preferably electrically connected at the spark plug end (not shown) of the wire 10.

This reduces the need for voltage isolation because there will be little voltage differential between the two conductors 18, 14.

As depicted in Fig. 2, a wire 10 is shown in use with the prior art

Dual Energy Ignition System, which is disclosed in U.S. Patent 5,197,448 to Porreca et al. and incorporated in full herein by reference. In the Dual

Energy Ignition System 40, a first energy source (and spark creation device)

50, including a voltage amplifying transformer 52, has the sole purpose of creating a spark in a spark gap 54. A second energy source 56 has the sole purpose of creating a high current arc in the spark gap 54. Importantly, the second energy source 56 has a discharge path to the spark gap 54 which is uncoupled from the primary side of the transformer 52. This can be achieved via a saturatable core transformer or a high-voltage diode (not shown). The efficiency of such a system is improved over pre-existing systems because arc energy is not transferred through an inefficient transformer and the second energy source is not charged with energy from the first energy source 50. It is important that the energy released from the secondary energy source is coupled to the spark gap 54 via a low impedance path.

Again referring to Fig. 2, the wire 10 of the present invention connects the first energy source (and spark creation device) 50 and the energy source 56 to the spark gap 54. The inner conductor 18 (Fig. 1) of wire 10 serves to provide a very low resistance path for the high current arc delivered from the energy source 56 to the spark gap 54. The outer conductor 14 (Fig. 1) serves to provide a high voltage to the spark gap 54 from the spark creation device 50. The spirally wound outer conductor 14 (Fig. 1) along with the ferrite material 24 (Fig. 1) provide EMI suppression for the wire 10. The EMI suppression and efficient energy transmission properties of wire 10 allow a more remote siting of the spark gap 54 relative to the first energy source (and spark creation device) 50 and the second energy source 56 of the Dual Energy Ignition System 40.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention. What is claimed is:

Claims

1. A wire comprising an inner core, an outer conductor being spirally wound around the inner core, and an outer layer of insulating material surrounding the outer conductor, the inner core including an inner conductor being electrically isolated from the outer conductor, wherein the inner core further comprises a magnetic flux carrying material.

2. The wire of claim 1 wherein the inner core further comprises a first insulating layer disposed between the inner conductor and the magnetic flux carrying material.

3. The wire of claim 2 wherein the inner core further comprises a second layer of insulation disposed between the magnetic flux carrying material and the outer conductor.

4. A spark plug wire comprising : an inner core, an outer conductor wound spirally around the inner core, and an outer layer of insulating material surrounding the outer conductor, the inner core including an inner conductor and a magnetic flux carrying material, the inner conductor being electrically isolated from the outer conductor, the spark plug wire for use in an ignition system including an energy source and a fuel igniting mechanism, whereby the wire conducts energy from the energy source to the fuel igniting mechanism.

5. The wire of claim 4 wherein the fuel igniting mechanism includes a spark plug having a spark plug gap, the wire being disposed between the spark plug and the energy source whereby the wire provides energy to the spark plug gap.

6. A spark plug wire comprising : an inner conductor, a magnetic flux carrying material substantially surrounding the inner conductor, an outer conductor wound spirally around the magnetic flux carrying material, and an outer layer of insulating material surrounding the outer conductor, the spark plug wire for use in an ignition system including a first and second energy source and a spark plug, whereby the wire delivers voltage from the first energy source and current from the second energy source to the spark plug.

7. The wire of claim 3, 5 or 6 wherein the inner conductor and the spirally wound outer conductor are electrically connected in at least one location.

8. The wire of claim 7 wherein the magnetic flux carrying material is a ferrite filled plastic.

9. The wire of claim 8 wherein the inner conductor is copper or an alloy thereof.

10. The wire of claim 9 wherein the spirally wound outer conductor is steel or an alloy thereof.

11. The wire of claim 10 wherein the outer layer of insulating material is a silicone.