WO2006078673A1

WO2006078673A1 - Health indicating ignition system

Info

Publication number: WO2006078673A1
Application number: PCT/US2006/001655
Authority: WO
Original assignee: SEIPELT CHRISTOPHER
Current assignee: SEIPELT CHRISTOPHER
Priority date: 2005-01-19
Filing date: 2006-01-19
Publication date: 2006-07-27
Anticipated expiration: 2007-07-19

Abstract

A health indicating ignition system (HIIS) verifies that an ignition system is achieving an established level of performance at the igniter's spark-gap (17), derived from sensing the system's rate-of-current change as detected with a sensing coil (68, 69, 70) located at the output of any component, and potentially several components. The system isolates faults in the system to the component that has failed, reducing troubleshooting, test equipment and personnel use, and avoiding the attachment of a test device which could mask, disguise, temporarily correct, or alter the characteristics of the fault.

Description

ATTORNEY DOCKET NO: SEIC/02WO

HEALTH INDICATING IGNITION SYSTEM

Cross Reference To Related Applications

This application claims the benefit of US Provisional Application Serial No.

60/645,281 filed January 19, 2005, which is hereby incorporated by reference

herein in its entirety.

Field of the Invention

This invention relates broadly to electrical ignition systems, specifically to

diagnosing ignition system health and the isolation of any fault in the system to the

component level.

Background of the Invention

Most electrical ignition systems furnish essentially the functions blocked-out

per Figs. IA, IB, and 1C. The functions are as follows: first, a means of electrical

energy conditioning and/or storage, such as an exciter or ignition transformer 10;

second, some means to route the stored and/or conditioned energy to the sparking

means, such as a lead, conductor, conduit, or wire 14; and third, the sparking

means 16 or device, such as an igniter, spark plug, or spark-gap 17. These

functions produce the electrical energy needed at the igniter spark-gap 17 to raise

the temperature of the combustible atmosphere at the gap 17 to its ignition

temperature to initiate and/or sustain combustion. The spark-gap energy is

produced by the current flowing through the circuit. The functions may be

implemented in close proximity and therefore be packaged as one unit, or the igniter 16 may be located in a high temperature location some considerable distance away

from the exciter 10 which is in a cooler location, which necessitates the use of a

long lead. In the later case, the functions are typically implemented as three

separate replaceable components. In other configurations where the igniter 16 is

only a short distance from the exciter 10, the lead and igniter 16 are typically

combined into one replaceable component. Such configurations are common for

aircraft, tank, and missile, turbine engines; and automotive and other reciprocating

piston engines; and stoves, furnaces, and other combustion ignition systems.

For an understanding of how the ignition system functions are implemented,

Figs 2A, 2B, and 2C show a simplified functional schematic of one representative

type of ignition system which provides the functions described per Figs IA, IB, and

1C. Figs 2A, 2B, and 2C depict the functions provided by a representative

capacitive-discharge (CD) type of ignition system. High- voltage-high energy CD

type ignition systems provide highly effective ignition for turbine and reciprocating

piston engines and produce igniter spark energies ranging from 0.25 to 5 joules or

more. US Patent Numbers 5,508,618 and 5,572,135 issued to Qwens on April

16, 1996 and November, 5, 1996 respectively, provide detailed descriptions of

how CD type exciters operate.

As a functional summary of the CD type system per Fig 2, as later

converted into a health indicating system, the CD type exciter 20, converts its

electrical input power into the stored energy needed to produce the energy required at the igniter spark-gap 17. The CD type exciter stores energy as a voltage in

capacitor C 21. The energy stored is equal to ¹A CV² . The exciter typically uses a

remote control input 12 (Fig. IA) for turning it OiVor OFF, or it is automatically

activated and deactivated when input power is applied and removed. The closure

of internal switch Sl 23, commonly a spark-gap or electronic device, initiates the

igniter spark. The closure of Sl applies the capacitor voltage Vc 22 to the exciter's

output circuit, which is generally boosted to the high voltage needed to ionize the

igniter's spark-gap 17 and cause it to conduct. Once the gap conducts, the energy

stored by capacitor C is distributed to the igniter spark-gap and the rest of the

ignition system circuit and C discharges rapidly. Each discharge produces the

circuit current designated here as id(t) 25, which flows through the circuit to

produce a spark intended to meet or exceed minimum energy requirements. The

current produced by a CD type system can be unipolar or bipolar as shown per

representative current characteristic waveforms, Fig 3 and Fig 4. The peak current

typically occurs within several microseconds and may range from 100 to 2500

amps or more. The lead 14, provides the electrical link to route the exciter's stored

energy to the igniter's spark-gap 17. Lead lengths from 2 to 10 feet are common

but can be considerably longer. The energy developed at the igniter's spark-gap

17 is equal to the integral of the voltage v_g 27 developed across the gap terminals

17a & 17b, multiplied by the current id(t) 25, averaged over the time the current

flows, expressed mathematically by equation 1, as follows: Equation 1: gap energy =

The spark-gap energy is often an engine system parameter specified to assure

detonation of the combustible atmosphere, and proper engine starting and running

conditions. Equation 1 is valid for all types of ignition systems.

For ignition systems other than capacitive discharge types, such as those

used for furnaces, continuous current is often applied to the spark-gap. Most

automotive ignition systems use methods of interrupting the ignition coil current to

excite the spark plug gap and produce a bipolar oscillatory current pulse.

Figs. 5 A and 5B show a cross-sectional view of one representative type of

high- voltage-high-energy lead 14 and igniter 16, these type parts being commonly

used throughout the aerospace and defense industry, and which are controlled by

SAE ARP 670 (SAE ARP 670, Rev B, Society of Automotive Engineers,

Aerospace Recommended Practice, 1995). For this example, the lead 14

terminates into a high- voltage electrical connector plug 37 comprised of a steel nut

31, a spring-loaded sealing washer 32, a discus-type electrical

contact 33, and a ceramic insulator 34. A high voltage cable 35 is contained within

an outer conduit 36 which provides protective sheathing and electromagnetic

shielding. Many other non-health indicating lead and igniter types exist, such as automotive and marine ignition wires and spark plugs, for the

numerous varieties of ignition systems, all which can be converted to health

indicating components by the approach, techniques, and apparatus presented

herein.

For this representative example, the igniter 16 consists of a metal shell 19,

an internal ceramic insulator 42, a center electrode with a discus-type contact 43, a

spark-gap 17, and an SAE ARP 670 style input receptacle 45. This example

igniter mounts to the combustion chamber by threads and its tip protrudes into the

combustor. The tip is often exposed to temperatures of 1600⁰F or higher. The

center electrode 43 is the anode and the shell 41 is the cathode. At the tip, the

space between the electrodes is the spark-gap 17. A similar threaded mounting

configuration is used with the common automotive and marine type spark plug.

Fig. 6 shows a cross-sectional view of a representative SAE ARP 670

type lead and igniter connected as common to aerospace and defense applications.

The spring-loaded plug applies pressure to the sealing washer 32 and discus-type

contact 33.

US Patent Number 5,508,618 Fig 1, presents one possible approach to

producing a health-indicating signal in an ignition system. This patent utilizes a wire

to sense current pulses to produce a sparking event indicator, for the representative

CD type ignition system. The current pulse detector disposes a wire in close

proximity to any current carrying element in the circuit so that a sense current is induced in the wire across a coreless gap, the sense current then being converted

into an output that indicates the occurrence of a spark discharge.

While the wire current-pulse detector per patent 5,508,618 can provide an

indication of a current pulse in a CD type ignition system which produces large

current pulses, the wire current-pulse detector may not provide a sense-current

signal large enough or with sufficient integrity to be detected reliably, especially for

small current pulses, or in the typical electromagnetically noisy environment

produced by ignition systems. Detection of small current pulses most often

necessitates the use of detector circuits requiring high amplification, which are prone

to instability. Furthermore, the detector circuit presented per patent 5,508,618

provides no common-mode noise rejection and may provide false indications of

ignition currents and igniter sparking events.

False indications can result from the rapid high- voltage changes produced in

the circuit by a properly operating ignition system, as needed to ionize the spark-

gap. Such rapid high- voltage changes are used to provide indications of ignition

sparking events as presented per patents 6,396,278 issued to Makhija on May 28,

2002 and 6,359,439 issued to Crecelius on March 19, 2002. The rapid voltage

changes inject charges into the sense device equal to C*dv/dt where C is the

capacitance between the sense device and the conductor of the ignition current (or

element in proximity to the sense device), and dv/dt is the ionizing (or any other)

rapid voltage change. While the rapid high- voltage changes typically ionize the spark-gap, cause it to conduct, and produce a spark this is not always the case, and

therefore false indications of sparking would be provided. A spark-gap may fail to

ionize due to many causes, such as: high pressure, oil contamination and electrode

wear. Such false indications of ignition currents and sparking are also possible-in

the wire current pulse detector shown at 31 in US Patent 5,508,618. Here, any

sense current resulting from the wire-detector is essentially produced only due to

capacitive coupling, since any loop formed by the spiraled wire is not in a plane

aligned with the current and not oriented so as to enclose the magnetic flux lines

produced by and orthogonal to the current.

U.S. Patent Nos. 6,850,070 issued to McQueeney on Feb. 1, 2005 and

5,491,416 issued to Klinstra on Feb. 13, 1996, provide approaches for sparking

event detectors using inductive pickup coils. Here, ferrous material is used to

concentrate the lines of flux produced from the ignition current through the loops of

wire formed by the windings around an iron-based toroid-shaped core. A first

disadvantage of this approach is that the inductive pick-up does not sense the

ignition current directly at the outputs of any link in the system or at the spark plug's

gap. Consequently, an arc-over in the lead, or an arc occurring anywhere in or

outside the spark plug or in the electrical connection or path up to it, may

erroneously be identified as an igniter sparking event, even though a spark did not

occur at the igniter's gap. Furthermore, since the magnetic flux which is used to

detect the ignition current is not detected solely at the end of any link in the system, there is no way to discern in which link a fault has occurred. A second

disadvantage of the use of the inductive pickup devices referenced, is the weight

added by their iron-based toroid core. Other ways to implement an ignition system

current detector which eliminate the weight of the iron, are preferred in aerospace

applications, which demand the lightest weight systems possible. Another

disadvantage of the use of the iron-based material is the degradation of its magnetic

properties at temperatures higher than its Curie temperature. A final disadvantage

of using the inductive pickup devices, referenced is that the devices are not intended

to be designed into the components nor intended to be permanent fixtures for

continuous monitoring of the ignition system heath or for component fault isolation.

Another disadvantage of the prior- art sparking event detection methods

previously referenced is the absence of any features which indicates the failed-open

condition of the means which senses, detects, and indicates the ignition current. For

an open-circuit failure, a signal will not be provided even when there is proper

ignition current, and the system and/or a component will appear failed, even though

a failure has not occurred.

A final disadvantage of the prior-art sparking event detection methods

previously referenced is the absence of any features providing electromagnetic

common-mode noise rejection, to prevent false indications of sparking events.

Considerable electromagnetic noise is produced by ignition systems. In view of the above, it is clear that improvement can be made to the prior

art approaches so as to provide an ignition system which more accurately indicates

the performance and health of ignition systems, and which may be designed into and

reside within the system for continuously indicating its health and the failure of any of

its components.

Accordingly, several objects and advantages of the invention presented

herein are:

a) to provide a simple way to indicate, detect, and monitor the health of an ignition

system and its components,

b) to provide an economical way to indicate, detect, and monitor the health of an

ignition system and its components,

c) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which is designed into and resides in the system

d) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which is implemented with the smallest weight possible.

e) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which indicates which component in the system has failed.

f) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which indicates performance and health for low-level ignition

currents. g) to provide a way to indicate, detect and monitor the health of an ignition system

and its components that is unlikely to produce false and erroneous indications of

ignition current and sparking of the igniter gap due to rapid voltage changes and/or

electromagnetic noise.

h) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which discerns that its own sensing, detection, and indicating

means have failed in an open-circuit manner so that false indications of system or

component failures are not provided,

i) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which is non-invasive, and makes no electrical contact with the

high- voltage circuits or ground, so as to maintain the integrity and reliability of the

monitored system.

j) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which, by being built into the system, eliminates the need for

supplemental testing devices, to validate that the system meets performance

requirements and its components are healthy.

k) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which indicates that the current supplied to the spark-gap meets

requirements so as to indicate that the igniter spark-gap energy produced meets

requirements. 1) to provide a way to indicate, detect, and monitor the health of an ignition system

and its components which provides a means to indicate the repetition rate of the

sparking cycle.

Further objects and advantages will become apparent from a consideration

of the ensuing description and drawings of the health indicating ignition system and

its implementation, which provides a ways to indicate, detect, and monitor the

system performance and health and component health, for diagnostic purposes, and

which inflicts no impact on the system or component integrity and reliability.

Summary of the Invention

In accordance with the present invention a method, and technique and

apparatus to realize and implement a health indicating ignition system (HIIS) is

presented herein. In the preferred embodiment, the system comprises a current

sense coil (CSC) designed into and residing at the output of any ignition system

component, that senses the rate-of-change of the ignition system current, and

provides a signal which is proportional to that rate-of-change of current. The rate-

of-change signal may be used to indicate whether ignition current and igniter spark-

gap energy requirements are achieved. In addition, the system comprises an

electric circuit apparatus used to detect the rate-of-current change signal which is

capable of discerning that the CSC or the input circuit to has failed in an open

circuit manner. In specific embodiments, multiple coils are utilized in conjunction with each

of several replaceable components, so as to identify in the case of a failure, which

component has failed, as well as to indicate proper system operation.

A combustion engine may be difficult or fail to start or run poorly even

though its ignition system is healthy and functioning properly, due to many causes,

such as too lean or rich a fuel-air mixture, improper fuel atomization, or fouled fuel

injection. The health indication provided by the methods and techniques and

apparatus presented herein can be used in conjunction with any other ignition

system health indication, such as combustor pressure, temperature, ultraviolet, or

ionic sensing to supplement knowledge of engine ignition, startup and running

conditions.

Knowing ignition system health supplements the knowledge of the overall

control system health and diagnostic capabilities, enhances service and mission

capability and reliability, and expedites troubleshooting and maintenance.

The methods, techniques, and apparatus presented herein provide a simple,

low cost, low weight way to acquire system and component health knowledge, with

minimal impact or invasion to the integrity or reliability of the base system or

components. Furthermore, the system may be incorporated and designed into and

reside in the system components, and provide a way to continuously monitor

ignition system health and provide fault isolation to the component level. The above and other objects and advantages of the present invention shall

be made apparent from the accompanying drawings and the description thereof.

Brief Description of the Drawing

The accompanying drawings, which are incorporated in and constitute a

part of this specification, illustrate embodiments of the invention and, together with a

general description of the invention given above, and the detailed description of the

embodiments given below, serve to explain the principles of the invention.

Figs. IA, IB and 1C present the functions essentially furnished by most

electrical ignition systems.

Figs. 2 A, 2B and 2C shows a simplified internal functional schematic of a

CD ignition system.

Figs. 3 and 4 show typical discharge current waveforms for unipolar and

bipolar CD type ignition systems.

Figs. 5 A and 5B show an SAE ARP 670 type of representative electrical

plug and receptacle used for high- voltage-high-energy ignition systems.

Figs. 6 A and 6B show the normal connection of the representative SAE

ARP 670 type electrical plug and receptacle.

Figs. 7A. 7B and 7C provide a block diagram and a simplified internal

functional schematic, of one representative way to implement a health indicating

ignition system.

Fig. 8A shows a current sensing coil; Fig. 8B shows one particular embodiment of a current sense coil (CSC) in

accordance with the principles of the present invention.

Fig. 9 shows the preferred setup of the current sense coil so as to most

effectively detect the rate-of-change of the ignition current.

Fig. 10 shows the increasing levels of sense voltage ed(t) produced as a

result of the increasing rate-of-change of the ignition current due to increased energy

levels stored in capacitor C.

Figs. 1 IA and 1 IB shows one embodiment of how the representative SAE

ARP 670 type lead and igniter components are converted into health indicating

components.

Figs. 12A, 12B, and 12C shows one embodiment of how the

representative health indicating SAE ARP 670 type lead pins are implemented.

Figs. 13A, 13B and 13C shows one embodiment of how the representative

health indicating SAE ARP 670 type igniter sockets are implemented.

Fig. 14 shows one embodiment of how the representative health indicating

SAE ARP 670 type lead and igniter interconnect.

Fig. 15 shows one representative health indicating signal detection means

which indicates the open-circuit condition of it inputs.

Fig. 16 shows the ignition system heath diagnosis discernable by using

CSCl, CSC2, and CSC3, in the H.I. exciter,. H.I. lead, and H.I. igniter,

respectively. Fig. 17 shows the ignition system heath diagnosis discernable by using

CSC3 in the H.I. igniter only.

Fig. 18 shows the ignition system heath diagnosis discernable by using

CSCl and CSC3, in the H.I. exciter, and combined H.I. lead/igniter, respectively.

Fig. 19 shows the ignition system heath diagnosis discernable by using

CSCl₅ CSC2, and CSC3, in the H.I. exciter,. H.I. lead, and H.I. igniter,

respectively, and using ignition information from one other source.

Fig. 20 shows the ignition system heath diagnosis discernable by using

CSCl and CSC3, in the H.I. exciter, and combined H.I. lead/igniter, respectively,

and using one additional source of ignition system information.

Detailed Description of Specific Embodiments

Figs. 7 A, 7B and 7C show a simplified internal functional schematic

providing one implementation of the methods, techniques and apparatus as

disclosed herein, to realize a health indicating ignition system for the representative

CD type system as shown in Fig 2. It is the rate-of-change of the ignition system

current id(t) 25 which is sensed in each component to provide an indication of

ignition system performance and system and component health. System

performance and health is indicated by a voltage signal proportional to the rate-of-

change of the current, which is produced by the current sense coil (CSC). Each

health indicating (H.I.) component, H.I. exciter 60, H.I. lead 65, and H.I. igniter 71,

is equipped with a CSC; shown as CSC 68, CSC2 69, and CSC3 70, respectively. In the preferred embodiment, any CSC is located as close to the

output of each component as possible, so as to encircle the last length of its

conductor. Each CSC produces a voltage signal: edl(t) 64, ed2(t) 66 and ed3(t)

67, respectively, at its terminals, proportional to the rate-of-change of the ignition

system current. The system current is sourced by the exciter capacitor C.

Continuous rate-of-change information is available by continuously monitoring the

voltage signals. A specific rate-of-change is indicated by a specific ed(t) voltage.

Achieving a specific voltage provides verification that a specific ignition system

performance criterion is being met. If peak rate-of-change information is desired,

peak detection techniques are used to capture the ed(t) signal. In the preferred

embodiment, meeting or exceeding a pre-determined ed(t) level, also indicates that

ignition system current has passed through the output of each component and a

sparking has occurred at the igniter's spark-gap . The presence of the signal ed(t)

indicates that no open, short circuit, or arc-over condition exists in the circuit of

each component prior to the CSC. The ed3(t) signal 67, provides component and

system health indication, since ed3(t) indicates current is flowing as close to the

igniter's spark-gap 26 as possible, and since the igniter's spark-gap is output of the

ignition system. For this implementation, the ed(t) voltage signals from the CSCs

are routed to a diagnostic connector 72 for processing by a host system. For this

example, the host system processes the signals to derive system performance and

system and component health. For ignition system types other than capacitive discharge, such as those

used for furnaces, which apply continuous current to the spark-gap, the CSC may

still be used to indicate ignition system performance and health. For these types of

ignition systems a valid indication can be achieved, if either the rate-of-change of the

current can produce, or the number of loops of wire on the coil can be increased to

provide, a signal voltage ed(t) large enough to be reliably detected and processed.

The use of a CSC is feasible for ignition systems which apply high-frequency

current to the spark-gap. In addition, the use of a CSC is feasible for ignition

systems which provide pulsating bipolar oscillatory type current to the spark-gap,

such as those commonly used in automotive applications which-interrupt the ignition

coil current to excite the spark plug's gap.

In the basic realization as shown per Fig. 8A, a current sense coil (CSC)

consists of only one loop of wire which crosses itself at some point 77 along the

wire to form an enclosed area 78. At the cross point 77, the wire cannot make an

electrical connection to itself. Fig. 8B shows another representative realization of a

current sense coil CSC 75 consisting of multiple loops of wire. In this embodiment,

a spiraling continuous channel is formed around some suitable insulating material

(typically ceramic) to make a coil-form structure for the placement of wire or some

conductor. Wire suitable for the environment is wrapped in the channel to form one

or many non-contacting loops or turns. The structure must be capable of

withstanding the environmental extremes (temperature, vibration, shock, stress, strain, etc.) to which it is exposed. No iron-based material is needed in the coil-

form. The primary purpose of the form is to provide a means to prevent uninsulated

loops from shorting to each other at the cross point 77 and/or to the housing of the

component in which the coil resides. A coil form is not always needed. Insulated

wire can be used to prevent loops from shorting.

The CSC produces the signal voltage ed(t) 76, at the end of any loop(s)

terminals 76a and 76b, by magnetic induction, derived from the changing lines of

magnetic flux produced by the ignition system current. Each CSC is insulated from

and makes no electrical contact with any point in the system or ground, and

therefore does not provide an opportunity for arc-over due to dielectric

breakdown. Therefore the CSC does not affect, disturb or alter the integrity or

reliability of the base system.

Fig. 9 shows that the preferred embodiment orients any loop of a CSC in a

plane aligned axially with the ignition current conductor, so as to enclose the

maximum number magnetic flux lines possible. Therefore any wire loop is optimally

oriented at a 90 degree angle with respect to the lines of magnetic flux F which

circle the conductor (in planes aligned with the Z-axis). Exact 90 degree angle

orientation is not required however, and any coils can be skewed, as shown per Fig

8B, and still produce a signal voltage ed(t) which adequately indicates the rate-of-

change of the current and sparking occurrences at the igniter's spark-gap. For any health indication ignition system using the means disclosed herein,

e..g, a CD type system, the ignition system current id(t) produces a signal voltage

ed(t) at the terminals of each CSC in accordance with Faraday's Law

(Electromagnetics, Second Edition, John D. Krauss , Keith R. Carver, McGraw

Hill Inc. 1973, page 307) as follows: ed(t) = N*d Φ / d t, where N is the number of

turns, Φ is the magnetic flux, and t is the time. The magnetic flux [ Φ ] intensity is

proportional to the circuit current [id(t)]. The change-in-flux [d Φ] is proportional

to the change in the current [d (id(t)]. Since the number of turns N is constant for

any CSC realization, ed(t) is proportional to the number of loops (N) multiplied by

the-rate-of-current change, which is expressed mathematically as follows: ed(t) a

(N) * [d (id(t) / d t]. -

The ignition current sensing method presented herein, improves upon US

Patent No. 5,508,618, Fig. 1, which uses a wire to sense an ignition current and

produce a sense current signal, by the ability to provide a larger, more robust signal

and which is easily increased by supplementing the number of loops on the coil form

structure as shown in Fig. 8B, and which for slow rate-of-change or low level

currents is reliably produced and detectable.

The present disclosure foremost presents the use of ignition system current

rate-of-change sensing and the use of the CSC, to indicate that ignition system

current and igniter spark-gap energy requirements are met. To get a precise measurement of the energy produced at the igniter's spark-

gap, precision voltage and current measuring equipment must be used and the

product of these parameters processed per equation 1. This measurement often

necessitates using a calibrated current indicating transformer device with sufficient

bandwidth and adequate coercive force capability so as not to be magnetically

saturated, in order to process equation 1. Such precise energy determining

instrumentation devices become impractical as a health indicating technique, as the

current measuring device requires a massive ferromagnetic core. For any finalized

health indicating ignition system as realized by the techniques presented herein, a

precise energy measurement is not needed to get an indication that the ignition

system meets igniter spark-gap energy requirements. Precision measurements are

only needed at the initial calibration of any realization and application of a current

sense coil, as disclosed in the following text.

The technique of using current rate-of-change sensing to indicate that igniter

spark-gap energy requirements are met can be understood by considering that for

any set of ignition system needs, such as; lead length, gap energy, gap spacing, and

a type of exciter design, a particular system design approach will be selected and

become fixed. Once the approach is fixed, the next step is to determined how

much energy must be stored in capacitor C 21, in order to produce the amount of

energy required at the igniter spark-gap. Precision measurements are needed

initially to determine the energy produced at the igniter spark-gap. For the fixed approach selected, different rate-of-current changes will occur

for different amounts of energy stored in C 21 (Fig. 7A), upon discharge, as shown

in Fig 10 for three different stored energy levels. Once the amount of energy that

must be stored in C as needed to produce the energy required at the igniter spark-

gap has been determined, an associated rate-of-current change and respective ed(t)

voltage will have been established for any CSC realization. Then, when the CSC is

used to indicate performance, if the established sense voltage ed(t) is produced, this

indicates that the igniter's spark-gap energy requirement has been met. In

summary, achieving the estabilshed ed(t) set-point, verifies that a spark-gap energy

requirement has been met if the ed(t) signal is from the CSC located at the igniter's

spark-gap.

For any specific CSC design, the voltage signal ed(t) indicating the current

rate-of-change requires calibration. Since ed(t) is proportional to [N] * [d (id(t) /

d t], ed(t) is equal to [K] * [N] * [d (id(t) / d t], where K is a calibration constant

determined for any particular CSC design. For each design, the value of K and the

calibration of ed(t), as a signal representing the rate-of-change of the current, is

determined by precision current and voltage measuring instruments.. The stability of

K and ed(t) is mapped for the environment to which the CSC design is exposed to

determine the total variation of the signal ed(t) for each CSC design and application.

After the stability of K and calibration of ed(t) is determined, the signal ed(t) is

ready to be used to provide a calibrated performance indication. Figs 1 IA and 1 IB show a cross-sectional view of a representative health

indicating (H.I.) lead 65 and H.I. igniter 71, realized by adding health indicating

means disclosed herein to the baseline SAE ARP 670 style plug 37 and receptacle

45. hi the preferred embodiments socket contacts are added to the lead and pin

contacts are added to the igniter, however, the socket and pin contacts may be

placed in the igniter and lead components, respectively. The H.I. lead 65 adds

socket contacts 81, 82, 83, and 84, to the plug 37. The Figs 12B and 12C view of

the H.I. lead 65, shows a right-angle perspective of Fig 12A and the socket

contacts. Two of many possible forms of the contacts are either straight bores per

Fig 12B or arced bores per Fig 12C.

The H.I. igniter 71 adds pin contacts 91, 92, 93, and 94 to the igniter

recepticle 45, and current sense coils CSC2 95 and CSC3 96 to the igniter 71.

The Figs 13A and 13B views of the H.I. igniter 71 Figl3C, shows a right-angle

perspective of the pin contacts. Two of many possible forms of the contacts are

either straight pins per Fig 13B or arced pins per Figl3A. The H.I igniter 71 as

implemented herein is only one of many possible realizations of adding a current

sense coil to an ignition device utilizing a spark-gap. Any common automotive or

marine type spark plug can easily be converted into a performance and health

indicating device by the preferred embodiment means of adding a current-sense coil

as close to the gap as possible. Fig 14 shows the representative H.I. lead 65 and H.I. igniter 71 connected

per the representative health indicating configuration. The socket contacts 81, 82,

83, 84 in the H.I. lead 65, engage the pin contacts 71, 92, 93, and 94 in the H.I.

igniter and connect and route the ed2(t) 66 and ed3(t) 67 signals from CSC2 95

and CSC3 96 in the igniter to the lead and to the diagnostic connector 72, per Fig

7A. CSC2 95 is added to the igniter to indicate the ignition current id(t) at the

output of the lead, and CSC3 96 is added to the igniter tip to indicate the ignition

current id(t) at the spark-gap 26, where achieving igniter spark-gap energy

requirements is necessary.

The representative health indicating exciter 60 (detailed cross-section

artwork not provided) is realized similarly to the H.I. igniter 71, by adding CSCl

to the exciter's output connector the same way CSC2 is added to the H.I. igniter's

input electrical connector receptacle 45. The representative H.I. exciter uses an

output connector similar to the igniter's input connector receptacle 45.

Fig 15 presents an electrical circuit apparatusllO which reliably processes

and conditions the performance and health indication signal voltage ed(t). The

detection circuit 110 preferably resides in the host system, where the environment is

generally less severe than that of the ignition system components. Any CSC signal

voltage ed(t) 76, as represented by the waveform shown, is applied the detection

circuit 110. Signal 112 is typical of the signal produced at the output of the circuit

apparatus for the ed(t) 76 input signal. The circuit apparatus configures operational amplifier OAl and resistors R_e, R_f, R_g, R_h to form a differential amplifier sub-circuit

114, with input terminals 114a and 114b. The circuit apparatus 110 uses resistors

R_a, R_b, R_c and R_dto establish a continuous fixed voltage of -2 volt across terminals

114a and 114b. The absolute value of any resistor element R in the circuit is not

critical. The circuit provides proper operation with R having a nominal value of

10,000 ohms.

The detection circuit 110 provides self-diagnostics to indicate the presence

of an open-circuit condition ahead of its input terminals 115a and 115b, which

includes the open circuit condition of a CSC or any circuit path from the CSC to

the input terminals. For any such open circuit condition, the output 112 will change

from a +2V continuous level to a +V_S continuous level, where +Vs is typically 15

volts.

The differential amplifier circuit apparatus 114 provides the low differential

gain of 10 to the input signal ed(t) and is therefore very stable. The preferred

embodiment provides a high degree of common-mode noise rej ection, by using

resistors Rg, Re, Rh and Rf which are matched in value as closely as possible.

Matching within 0.1% yields a circuit 114 common-mode noise rejection ratio of

5000 If necessary, higher common-mode noise rejection can be achieved by using

high grade instrumentation-type amplifiers, and better resistor matching to achieve

better common-mode gain matching. Additional electrical noise rejection can be

achieved through the use of input signal bandwidth limiting capacitors C_a, C_d, C_g, and C_h, if needed. The value of these capacitors is not critical and are easily

determined by those skilled in the art of designing such circuit as needed to properly

process the bandwidth of the signal ed(t). If additional, common-mode noise

rejection is needed, electromagnetic filters can be added to the input terminals.

The detector circuit output signal 112 is to be applied to a continuous or

peak monitoring circuit provided by the host diagnostic system 73, to in order to

derive maximum ignition system performance and system and component health

information.

Fig 16 presents the heath diagnosis discernable from a health indicating

ignition system which uses CSC voltage signals edl(t), ed2(t), and ed3(t). By

sensing these signals on a signal / no-signal basis, three logical bits of information

provide the 8 health indications shown. As shown, indication of proper and failed

ignition system and component operation and component level fault isolation is

provided.

The simplest health indicating system using rate-of-current change sensing is

realized if only knowledge of ignition system performance and health is desired. Fig

17 shows the health diagnosis discernable for the simplest system which provides

only CSC3 located at the igniter tip.

The next simplest health indicating system using rate-of-current change

sensing is realized if only knowledge of ignition system performance and health and

exciter and igniter fault isolation is desired, as shown in Fig. 18. Fig. 18 shows the health diagnosis discernable for a system which has two CSCs, one located at the

exciter output and the other located at the igniter tip. This approach is preferred

where the igniter is only a short distance from the exciter, where lead faults are

unlikely to occur, or for ignition systems where a short lead and igniter are

combined as one component.

Frequently, additional ignition system performance information from other

combustion sensors such as pressure, temperature, speed, or flame are available

which can be used in conjunction with the ed(t) signals from the CSCs to provide

more thorough ignition performance and system and component health information.

Fig 19 presents the ignition system performance and heath diagnosis discernable

from the voltage signals edl(t), ed2(t), and ed3(t), produced from current sense

coils CSCl, 2 and 3, and one other sensor signal such as combustor pressure level,

designated as CP. By sensing these four signals on a signal / no-signal basis, four

logical bits of information provide the 16 health indications shown. By adding this

one other indicator of ignition performance, complete ignition system performance

system health and component fault isolation is provided.

For those ignition systems which combine the igniter and lead into one

component, exciter and igniter fault isolation and system heath indication can be

expanded by adding the CP signal as described above, as shown per Fig 20. By

adding this one other indicator of ignition performance, complete ignition system

health and component fault isolation is provided. Accordingly, the reader will see that the methods, techniques, and

apparatus a provided herein provide a way to implement an indication of ignition

system performance and health which verifies that spark-gap energy requirements

have been met and provides system health and fault detection and isolation to the

component level. In addition, the methods, techniques, and apparatus provided

herein provide a way to implement the health indicating ignition system providing

these benefits simply and with minimum costs and weight, in a non-invasive manner,

not disturbing to or altering the integrity of reliability of the non-heath indicating

system.

While the above descriptions contains many specificities, these should not

be construed as limitations of the scope of the invention, but as exemplifications of

the presently preferred embodiments of the methods, techniques and apparatus to

implement a health indicating ignition system. Many other ramifications and

variations are possible within the teachings presented herein.

Thus the scope of the invention should be determined by the appended

claims and the legal equivalents and not by the examples given.

What is claimed is:

Claims

1. A health indicating ignition detector, comprising a current sense coil

adjacent to an ignition system component carrying a current, the current sense coil

producing a rate-of-current-change indication reflecting an ignition system current,

the health indicating ignition detector evaluating the rate-of-current-change

indication to verify the system delivers a specified energy for ignition to a location

where sparking is intended to occur.

2. The health indicating ignition detector of claim 1 , wherein said rate-of-

current-change indication is a voltage induced in said coil, between a first and a

second terminal of said coil.

3. The health indicating ignition detector of claim 1, wherein said detector

further detects continuity from said first to second terminal through said coil.

4. The health indicating ignition detector of claim 2, wherein said detector

includes common mode noise reduction to reduce electrical noise present upon said

first and second terminals.

5. The health indicating ignition detector of claim 1 , wherein said ignition

system comprises a plurality of replaceable components, and further comprising a current sense coil in each of said replaceable components in the systems to indicate

the ability of each component to deliver energy for sparking.

6. The ignition detector of claim 1, wherein said detector senses current

passing through the system to an igniter spark gap where sparking is intended to

occur.

7. The ignition detector of claim 5, wherein said detector verifies that each said

replaceable component is able to deliver energy for sparking.

8. The ignition detector of claim 5, wherein said detector isolates a fault to one

of said replaceable components.

9. The ignition detector of claim 5, wherein said detector detects health in all

replaceable components in the system, whereby said detector may be used

determine if any component in the system should be replaced.

10. The ignition detector of claim 1, wherein the health indicating detector

makes no direct electrical contact with the system.

11. The ignition detector of claim 1 , wherein the health indicating detector

detects current flow with said coil without the use of magnetic materials subject to

temperature varying magnetic properties.

12. The ignition detector of claim 1, wherein said detector has a differential-

mode gain no greater than 40 dB responsive to said coil.

13. The ignition detector of claim 1 wherein said detector is further responsive

to a second signal indicative of ignition system performance.

14. The ignition detector of claim 1 wherein said coil and detector are

integrated into said ignition system whereby extra test equipment is not required for

detection of ignition system health.

15. The ignition detector of claim 1 wherein said detector indicates and verifies

one or more of ignition system performance and operability.

16. A method of detecting the health of an ignition system, comprising:

providing a current sense coil adjacent to an ignition system component

carrying a current, detecting with the current sense coil a rate-fo-current-change indication

reflecting an ignition system current, and

evaluating the rate-of-current-change indication to verify the system delivers

a specified energy for ignition to a location where sparking is intended to occur.

17. The method of claim 16, further comprising detecting continuity from a first

to a second terminal through said coil.

18. The method of claim 16, wherein said ignition system comprises a plurality

of replaceable components, and further comprising providing a current sense coil in

each of said replaceable components in the system, and detecting from said signals

from said coils the ability of each component to deliver energy for sparking.

19. The method of claim 18 further comprising isolating a fault to one of said

replaceable components in the system based upon signals from said coils.

20. The method of claim 16 further comprising integrating said coil into said

ignition system, whereby extra test equipment is not required for detection of

ignition system health.