Abstract: The present invention related generally to a method for determining spark plug malfunction and more particularly to a method for determining spark plug malfunction in an internal combustion engine in which at least two spark plugs are disposed in each cylinder. In a dual plug configuration, a spark plug malfunction is detected by disabling one of the spark plugs during a test period in a particular cylinder. A misfire provides an indication of malfunction of the other spark plug.

Abstract: A method of detecting spark plug fouling in an internal combustion engine is provided. The method comprises calculating an integration value of discharge current flowing between electrodes of a spark plug during a period of a spark discharge and judging if the calculated discharge current integration value is smaller than an integration value criterion. The integration value criterion is set at such a value that can discriminate between normal discharge and interior jumping (i.e., jumping due to short circuit caused by fouling). When the calculated discharge current integration value is smaller than the integration value criterion, it is judged that the spark plug has been fouled. By this, it becomes possible to detect a spark plug fouling before the electrodes of the spark plug are short-circuited and disabled to generate spark discharge, i.e., before the spark plug is fouled to such an extent as to cause a misfire. An ignition system for detecting spark plug fouling is also provided.

Abstract: An improved system for measuring spark plug suppressor resistance under simulating operating conditions includes a controller, a high voltage power supply, a mounting fixture, and a non-contact IR temperature detector. The controller commands the high voltage power supply to source a preselected level of current through the spark plug having a magnitude consistent with actual spark currents. The current sourcing establishes a self-heating arrangement, and the heightened spark plug temperatures and associated resistance simulate actual engine operating conditions. The controller outputs a display of measured resistance values as a function of time, and overlays a trace of the corresponding temperature values.

Abstract: In an ignition coil assembly of an ion sensing ignition system having an ignition coil output, a buffered ion-sense current source circuit is provided and includes a current sensing circuit, the current sensing circuit being disposed so as to be communicated with the ignition coil output and an active current source circuit, the active current source circuit being disposed so as to be communicated with the current sensing circuit and a current measuring device.

Abstract: A method and an arrangement for detecting combustion misfires in internal combustion engines are presented where a measured ionic current signal is subjected to a floating short-time integration and a feature is formed which corresponds to the maximum value of the floating short-time integrator within the entire measuring window. The window length of the short-time integrator is shorter than the total measuring window and is floatingly displaced over the measuring window.

Abstract: The invention is a strategy to detect spark plug misfires in a multiple spark plug per cylinder internal combustion engine (ICE). The present invention monitors spark plug misfires for each plug within each cylinder and initiates diagnostic fault code setting and failure mode actions such as modifying spark timing and the air/fuel ratio for the cylinder with the misfiring plug to optimize emissions and performance. The strategy modifies spark timing (such as spark retard) of a spark plug not under test but within the same cylinder of the tested spark plug and tests the tested spark plug for misfire (such as changes in crankshaft velocity or acceleration). The amount of spark retard invoked can be a calibrated value such as 30 or 50 degrees off Maximum Brake Torque (MBT) timing. The invention provides improvement over the prior art in that the strategy does not require the complete disabling of a spark plug within the same cylinder as the tested spark plug.

Abstract: A method of measuring the particle content, in particular the soot particle content, in the exhaust gases of an internal combustion engine using a sensor arranged in contact with the exhaust gases. The sensor detects in at least one combustion chamber of the internal combustion engine an electrical quantity, the size of which is dependent on the particle content in the exhaust gases. The level of a measurement signal output from the sensor, the signal is dependent on the detected quantity, is determined and compared with a desired value level of a signal which corresponds to a desired particle content in the exhaust gases.

Abstract: An apparatus for diagnosing and controlling an ignition system of an Internal combustion engine includes an ignition coil controllable by an ignition control circuit, a spark voltage sensor electrically connected to the high tension side of the ignition coil secondary and an ion voltage sensor electrically connected to the low tension side of the ignition coil secondary. A computed processes the ion voltage signal to determine a combustion quality value and a roughness value. If the combustion quality value is outside a predefined range or if the roughness value exceeds a roughness threshold, the computer is operable to adjust the engine fueling, spark timing and/or spark energy.

Abstract: An ignition coil with an isolated internal lead in proximity to the secondary side can be used in a capacitive discharge ignition system with a microprocessor-based signal-processing module to monitor system performance. The diagnostic lead is fed into a diagnostic signal interface circuit that provides a logic edge to the microprocessor when the spark plug fires. By measuring the time from the firing signal provided by the microprocessor to the logic edge provided by the diagnostic signal interface circuit, the precise energy necessary to fire the plug can be determined. An ignition system that includes an ignition coil with a diagnostic lead can extend spark plug life by automatically adjusting spark energy to minimize wear on the spark plug.

Abstract: A combustion state detecting apparatus for an internal combustion engine which can ensure adequate thermal insulation between a transformer and a bias circuit and which can be manufactured in a miniaturized structure.

Abstract: A failure of a detecting circuit such as an ion current detecting circuit for detecting a combustion condition of an engine can be diagnosed at a stage for detecting a combustion condition by a combustion condition detecting apparatus equipped with a malfunction diagnosing apparatus. The engine combustion condition detecting apparatus equipped with the malfunction diagnosing apparatus is arranged by a sensing circuit for sensing an ion current flowing through a combustion chamber, a misfire judging means for judging misfire occurred in the engine in response to the detection signal derived from the sensing circuit, and a malfunction judging means for judging malfunction of the sensing circuit.

Abstract: A knock control apparatus for suppressing knock event in an internal combustion engine by correcting a control quantity such as ignition timing for the engine while evading erroneous knock decision and erroneous knock control when a spark plug of the engine is in a sooting state.

Abstract: The present invention is an assembly line testing apparatus and method for automatically determining whether a size of a gap, within at least one component of an article of manufacture, is within an acceptable range, during assembly of the article of manufacture. The present invention uses a microcontroller to control the operation of the assembly line testing apparatus of the present invention such that the size of the gap may be checked in a flexible and reliable manner by repeating the cycle of checking for the size of the gap. The present invention may be used to particular advantage for checking that the size of a spark plug gap within a vehicle engine is within an acceptable range during assembly of the vehicle engine.

Abstract: Method and apparatus for inspecting a spark plug as installed in an engine, for an abnormal size of a discharge gap and cracking of porcelain, based on a shape parameter value Sn (=Vn/Tn) calculated from a voltage parameter value Vn which is an average of primary voltage V1 during a period of substantially inductive discharge, and a time parameter value Tn indicative of the period of the substantially inductive discharge. The inspection for the abnormal discharge gap size is effected with the engine held at rest, while the inspection for the porcelain cracking is effected with the engine controlled by a motor so as to increase air pressure within the cylinder bore, contrary to conventional system wherein the inspection is effected during operation of the engine by combustion of an air-fuel mixture.

Abstract: An ion current detection apparatus which can detect ion current with a high degree of accuracy regardless of the presence of voltage damped oscillation and which does not cause contamination of a spark plug. A spark discharge current Isp generated upon spark discharge of a spark plug 10 flows through a charge diode 28, a capacitor 24, and a diode 22, which form a closed loop together with the spark plug 10 and a secondary winding L2 of an ignition coil 12 that constitutes an ignition apparatus. As a result, a Zener diode 26 connected in parallel to these components generates a Zener voltage Vz and thereby charges the capacitor 24. When a preset wait time has elapsed after the ignition timing for starting spark discharge, the discharge switch 30 short-circuits the opposite ends of the charge diode 28 to discharge the capacitor 24, so that a high voltage having a polarity opposite that in the case of spark discharge is applied to the spark plug.

Abstract: An ion current detection device is disclosed that is designed to hold an ion current output voltage within a prescribed limit to ensure proper operation of a processing device connected to the output side thereof, while, at the same time, shortening the decay time of the LC resonance associated with an ignition coil. An ion current flows from one end of a capacitor and back to the other end thereof passing through an ignition coil secondary winding, a spark plug, an ion current detecting resistor, and a load resistor. A voltage equal to -(ion current value).times.detecting resistor value appears at a node between the ion current detecting resistor and the load resistor. This voltage is inverted by an inverting circuit and supplied as an ion current output to the processing circuit.

Abstract: The invention is directed to a method of detecting combustion misfires of an internal combustion engine wherein an ion current is generated during the operation of the engine. The ion current signal is detected over a pregiven time interval starting with the discharge of a spark plug. The ion current signal is integrated over time with a weighting function to obtain a weighted integrated signal and the weighting function is adapted to previously detected ion current signals. The maximum of the weighted integrated signal is compared to a threshold value (s.sub.-- io) dependent upon engine rpm (nmot) and load (rl). A fault signal is outputted when the threshold value (s.sub.-- io) is not exceeded. The invention is also directed to an arrangement for detecting the combustion misfires.

Abstract: An apparatus for diagnosing and controlling an ignition system of an internal combustion engine includes an ignition coil controllable by an ignition control circuit, a spark voltage sensor electrically connected to the high tension side of the ignition coil secondary and an ion voltage sensor electrically connected to the low tension side of the ignition coil secondary. A computer processes the spark voltage signal by comparing the signal to a number of predefined spark voltage waveforms in memory. If the spark voltage signal matches any of the spark voltage waveforms in memory that correspond to a predefined ignition system failure mode, a corresponding error code is stored in memory. The computer is further operable to process a voltage peak of the spark voltage, wherein the voltage peak corresponds to the breakdown voltage in the spark gap of a spark plug connected to the secondary coil.

Abstract: A combustion state detecting apparatus for an internal combustion engine is capable of ensuring a satisfactory ion current detection sensitivity and reliability by preventing discharge of bias voltage to an ignition coil to thereby protect the bias voltage against lowering.

Abstract: A circuit arrangement measures an ion current generated in the combustion chamber of an internal combustion engine during an iron current flow phase following an ignition phase. A voltage drop across a feedback resistor (R.sub.1) connected in parallel to an inverting amplifier is measured since the voltage drop is proportional to the ion current resistance. The amplifier is connected with its inverting input to a low voltage end of a secondary winding of an ignition transformer or coil. The high voltage end of the secondary winding is connected through a spark gap of a spark plug to ground, whereby the spark plug functions as an ion current sensor during the ion current flow phase. Negative voltage peaks flowing during an ignition phase and the ignition current flowing during the ignition phase are diverted through respective first and second circuit branches. The first branch has a first semiconductor diode (D.sub.

Abstract: A combustion state detecting apparatus for an internal-combustion engine does not incur deteriorated ignition characteristics because the ionic current detecting circuit thereof is not affected by ignition current. The combustion state detecting apparatus is equipped with an ionic current detecting circuit (10A) which includes a biasing device (C) connected to the low voltage end of a secondary winding (2b) of an ignition coil (2) and which detects ionic current (i) flowing from the biasing device via a spark plug (4); rectifying device (5) which is inserted between the biasing device and the secondary winding so that the ionic current flows in the forward direction; a voltage clamping device (6) inserted between the secondary winding and the ground; and an ECU (20) which detects the combustion state according to the ionic current.

Abstract: A method of carrying out ionic current measurement in an internal combustion engine, using a lean fuel mixture which requires an increased burning duration, comprises the steps of (a) generating an ignition spark, (b) detecting initiation of combustion of the lean fuel mixture by the ignition spark, (c) cutting off the ignition spark within 20 microseconds after the initiation of combustion and (d) thereafter performing the ionic current measurement. The combustion start can be detected by measuring the change in the burning potential and/or the burning current, detected at the low-tension side of the secondary coil of the ignition system, using leak capacitances of the ignition coil, or by using a separate winding of the ignition coil. The ignition spark is cut off by a controllable ignition magneto.

Abstract: A combustion monitoring apparatus for an internal combustion engine is provided which includes a voltage supply circuit, a combustion monitoring circuit, and a control circuit. The voltage supply circuit applies the voltage to plug electrodes of a spark plug mounted in a combustion chamber of the engine. The combustion ion monitoring circuit monitors a variation in amount of combustion ions existing between the plug electrodes to determine a combustion condition of the engine based on the current flowing through the plug electrodes produced by application of the voltage to the electrodes. The control circuit controls an operation of the voltage supply circuit so that the voltage is applied across the plug electrodes prior to a discharge duration of a spark plug mounted in the combustion chamber of the engine for monitoring preignition.

Abstract: An ion current detection device of an internal combustion engine includes a detection voltage generation device which applies a voltage to an ignition plug to generate an ion current in a cylinder of the engine. A current to voltage conversion circuit detects and converts the generated ion current to a voltage signal. A bandpass filter extracts an ac component within a specified frequency range from the voltage signal produced by the current to voltage conversion circuit. An ion current threshold detection portion produces an ion current detection signal when the detected ion current exceeds a predetermined threshold current. A filter characteristic control circuit controls the characteristic of the bandpass filter to suppress the sensitivity of the filter for a predetermined period of time right after the ion current detection signal is detected and, after the predetermined period of time, increase the sensitivity of the filter for detection of the ac signal with the specific frequency.

Abstract: A failure of a detecting circuit such as an ion current detecting circuit for detecting a combustion condition of an engine can be diagnosed at a stage for detecting a combustion condition by a combustion condition detecting apparatus equipped with a malfunction diagnosing apparatus. The engine combustion condition detecting apparatus equipped with the malfunction diagnosing apparatus is arranged by a sensing circuit for sensing an ion current flowing through a combustion chamber, a misfire judging means for judging misfire occurred in the engine in response to the detection signal derived from the sensing circuit, and a malfunction judging means for judging malfunction of the sensing circuit.

Abstract: An engine analyzing device for an internal combustion engine including a spark generator and means for testing the voltage of the sparks generated for a diagnosis of engine performance, the testing of the sparks generated relating to analysis of the spark voltage wave form from the breakdown voltage, the collapsing field voltage and the duration of the spark pulse or some combination of these.

Abstract: A combustion monitoring apparatus for an internal combustion engine is provided which is designed to distinguish abnormal combustion conditions from a normal combustion conditions using a combustion ion current included in a current flowing through plug electrodes of a spark plug, resulting from motion of ions between the plug electrodes which are produced by combustion. For example, if a maximum value of the combustion ion current during one combustion cycle is smaller than a given value, it is determined that a misfire has occurred. If an attenuation time from generation of the current flowing through the plug electrodes until a variation in the current is decreased to a given value is shorter than a given time period, it is determined that a flame has been blown out before combustion is completed.

Abstract: An ion current in the combustion chamber of an internal combustion engine is measured by using the spark plug as an ion current sensor. The ignition circuit arrangement has an ignition coil or transformer with a primary winding forming a primary circuit and a secondary winding forming a secondary circuit in which the spark plug is connected. A measuring voltage is applied to the secondary circuit by circuit components forming a measuring circuit for measuring the ion current. The measuring circuit provides a measuring voltage at a value that is lower than the battery voltage of the ignition system or corresponds to the battery voltage at most. A rectifying element is connected to the secondary circuit which feeds the secondary or ignition current into the battery circuit of the ignition system while an ion current caused to flow by the measuring voltage applied to the secondary circuit is measured between sparking times when no ignition current is flowing.

Abstract: A measuring circuit for sensing ionization within a combustion chamber of an engine is arranged in the grounded end of the secondary winding (5) of an ignition coil (2), and includes a voltage source for measurements having a substantially constant potential. The voltage source for measurements used is a capacitor 13 which is charged by the spark current SC, and subsequently after the ignition spark goes out will apply a bias voltage over the spark plug gap 3 with a reversed polarity in relation to the spark voltage. The ionisation within the combustion chamber is detected with a measuring resistance 14 arranged in series with the capacitor 13. A rectifying element 11 is connected in parallel with the measuring resistance, which will secure that the spark current is developed in the spark plug gap 4 and that the measurement current passes through the measuring resistance 14. The rectifying element is grounded with a separated ground strap which does not pass the ground plane of the measuring resistance.

Abstract: A method of detecting defective ignition or fuel injection system of an internal combustion engine with several cylinders and at least two spark plugs or two fuel injection devices per cylinder with separate control circuits, at least a second control circuit for the ignition or fuel injection systems is disabled so that all the spark plugs or injection devices of the at least second ignition or injection systems become inoperative, the engine running smoothness is then measured, the first system which was not disabled is identified as including the defective spark plug or injection device if the engine running smoothness was found to be affected, then the ignition or injection systems for any other spark plugs or injection devices are disabled cylinder-by-cylinder and the engine running smoothness is monitored to identify the cylinder which includes the defective spark plug or injection device.

Abstract: An apparatus for detecting a condition of burning in an internal combustion engine includes a spark plug and an ignition coil. The ignition coil has a primary winding and a secondary winding. The secondary winding is connected to the spark plug. An ion current sensing resistor is connected to a low voltage side of the secondary winding of the ignition coil for sensing an ion current. A diode is connected in parallel with the primary winding of the ignition coil. A switching element is connected in series with the primary winding of the ignition coil. The switching element is movable into and out of an on state. A suitable device is operative for resisting a current flowing through the diode when the switching element is in the on state.

Abstract: An combustion state detecting apparatus for an internal-combustion engine is equipped with: an ignition coil (4) for applying a high voltage (V2) for igniting to the spark plugs (8a through 8d) of the cylinders of an internal-combustion engine; an ionic current detecting circuit for applying a bias voltage (VBi) to at least one spark plug to detect ionic currents (ia, ib) flowing via the spark plug which has just been subjected to ignition control; comparator circuits (14a, 14b) which compare detected ionic current signals (Eia, Eib) with threshold values (TH1, TH2) and turn them into ionic current pulses (Gia, Gib); and an ECU (2A) which drives the ignition coil according to a crank angle signal (SGT) and determines the combustion state of the internal-combustion engine. The ECU changes the threshold values for each ignition control and judges the combustion state according to the respective threshold values and the state in which the ionic current pulses are generated.

Abstract: A discriminator circuit for detecting an event spark plug in a distributorless ignition system. The voltage waveform during event and waste cycles of the ignition system is conditioned and applied to a pair of comparators which compare the voltage waveform with different voltage reference levels. Both comparators switch states to a logical high level upon the firing of the event spark plug. The first comparator switches back to a low logical state after the end of the burn time in the event cycle. The second comparator remains in a high logic state following the burn time in the event cycle due to the negative voltage remaining on the spark cable, but switches back to a low logical state after the firing of the event spark plug in the waste cycle when the voltage on the spark plug cable goes positive. A delay element connected to the output of the first comparator holds the output of the first comparator at the high logical for a predetermined time period that is longer than the burn time in the event cycle.

Abstract: An ignition system for internal combustion engines, which have means for detecting the secondary voltage transformed to the primary side of an ignition coil, the signal detected by these means being fed to an evaluation device. The evaluation device determines the damping of the voltage signal after the end of sparking, this damping representing a measure for the magnitude of the shunt resistance on the secondary side.

Abstract: The quality of a fuel-air mixture shall be evaluated by a process and a device during a phase of combustion, especially in a spark ignition engine, in order to make possible a low-emission, fuel-saving and knock-free operation. An electrical testing pulse P is sent for this purpose to the spark plug during the phase of combustion V following the ignition pulse Z. The effect of the actual fuel-air mixture of the combustion chamber on the testing pulse is detected and evaluated as an electrical variable.

Abstract: An alternating current ignition system which can be used in one of two ways for ion current measurement. On the one hand, an oscillating circuit at the primary end of the ignition coil can be driven such that, after ignition has taken place, an alternating current signal is generated at the primary end; the amplitude of the alternating current signal must be sufficiently low so as not to cause any sparks at the secondary end, but lead to an alternating voltage signal which is modulated in relation to the ionisation degree of the ignition spark gap and thus represents an ion current measurement signal. On the other hand, however, if an auto transformer is used as an ignition coil, the intermediate circuit voltage applying at the primary end will be modulated in the medium-high voltage range of, e.g, 180 V in relation to the degree of ionisation, so that this supply voltage is used as a measurement signal.

Abstract: An ion current detection apparatus for detecting an ion current caused by combustion in a cylinder of an internal combustion engine comprises an ion current detection circuit for detecting the ion current, a gain adjustment circuit for controlling to keep the magnitude of low frequency components of the detected ion current at a constant value, an amplifier for amplifying high frequency components of the detected ion current and outputting a high frequency component detection signal, a magnitude detection circuit for detecting the magnitude of the detected ion current to output an ion current detection signal when the detected magnitude is larger than a predetermined value, and a comparator for comparing the high frequency component detection signal with the ion current detection signal delayed by a delay circuit to output a knocking detection signal.

Abstract: Provided is a high power ignition system for internal combustion engines with a detection circuit for sensing and measuring ionization in a spark plug gap. The detection circuit utilizes a dual-purpose second energy source to apply the voltage necessary to generate a high current arc and then an ionization current. A signal processor analyzes an ionization signal created by the detection circuit to derive useful ignition system data such as engine misfire, combustion duration, engine knocking, approximate air/fuel ratio, indications of spark plug fouling, and preignition.

Abstract: A misfire detecting device for an ignition system, comprises high voltage applying means for applying a pulsed high voltage to each spark plug of an engine after completion of firing of the spark plug, voltage restricting means for restricting a peak of the pulsed high voltage to a highest possible value that does not cause firing of the spark plug, voltage detecting means for detecting a plug voltage across a center electrode-to-outer electrode of the spark plug after reducing the same, and misfire detecting means for detecting a misfire at each cylinder on the basis of a decay characteristic of a detection voltage which is caused by application of the pulsed high voltage.

Abstract: A preignition detecting method which prevents preignition (PI) from being misjudged as having occurred when an ignition plug is fouling. It is determined whether or not the ignition plug fouls in accordance with a voltage, developed across a detecting resistor which is fetched into a microcomputer 18 at a relatively early timing after an ignition command signal is outputted from an ignition device. Further it is determined whether or not preignition occurs in accordance with another voltage fetched at a relatively late timing after the ignition command signal is outputted. When it is determined that the ignition plug is fouling, it is inhibited to fetch the another voltage at a relatively late timing to prevent a misjudgment that preignition occurs due to a leakage current from being caused though preignition does not actually occur.

Abstract: A misfire detecting device for a multi-cylinder internal combustion engine is provided. The misfire detecting device comprises high voltage pulse producing means for producing, after spark discharge of a spark plug, a high voltage pulse which is not so high as to cause the spark plug to discharge, voltage applying means for applying the high voltage pulse to a conductive path connecting between the secondary winding of the ignition coil to the spark plug, by way of a reverse current preventing diode and a leakage preventing diode for preventing intrusion of the high voltage for ignition, voltage dividing means for dividing a voltage at the junction between the reverse current preventing diode and the leakage preventing diode to obtain a divided voltage thereat, and misfire detecting means for detecting a misfire on the basis of a decay characteristic of the divided voltage obtained after application of the high voltage pulse.

Abstract: An apparatus for testing an internal combustion engine is disclosed. The apparatus comprises a probe for electrical connection to at least one spark plug wire of the engine being tested. A peak hold circuit operates to store a representation of a peak firing voltage of the rectified secondary ignition signal and attenuates the stored representation at a predetermined rate over time to enable measurement of peak firing voltage. The testing apparatus is connected to a voltmeter to display a value of the peak firing voltage. Alternatively, the testing apparatus includes a display for displaying the value of the peak firing voltage. Preferably, the testing apparatus is housed in a housing of a size to be held in a user's hand, with a power supply contained therein.

Abstract: A method of detecting a misfire of a gasoline internal combustion engine is provided. By this method, a high voltage pulse which is not so high as to cause spark discharge, is applied to a secondary winding side of an ignition coil by way of a diode during the time after completion of spark discharge and before generation of a high voltage for next ignition, a misfire at each cylinder is detected on the basis of a decay characteristic of a voltage at a cathode side of the diode, and a charge accumulated at the secondary winding side of the ignition coil is forcedly discharged before a next high voltage pulse is supplied to the secondary winding side. A device for carrying out the above method is also provided.

Abstract: A device for diagnosing the state of health of an ignition system is provided, where the system includes at least one spark producing channel comprising an exciter, output circuit and igniter plug. The device provides a diagnosis of the state of health for both the exciter and igniter plug by monitoring the high energy pulses at the output of the exciter. By monitoring the ignition system at an intermediate point in the system such as the output of the exciter, the sensor and electronics of the device may be completely contained within the electronic environment of the exciter, thereby avoiding any need for attaching sensors at the output of the system adjacent to the igniter plug in order to diagnose the plug's state of health. As an alternative to the device being built into the ignition system, it can be incorporated into automatic test equipment that produces high energy pulses for delivery to an igniter plug to be tested.

Abstract: An internal combustion engine misfire sensing circuit comprises an ion current sensing circuit for sensing an ion current in the combustion chamber of an internal combustion engine, a current/voltage conversion circuit for converting the sensed ion current into a voltage and a waveform shaping circuit for shaping the waveform of an output of the current/voltage conversion circuit. The waveform shaping circuit includes a second comparator for comparing a voltage of a third capacitor with first and second reference voltages for outputting a misfire sensing signal and a capacitor charging/discharging circuit for charging the third capacitor in response to the rising up of an output of the current/voltage conversion circuit and discharging the third capacitor based on the input of the misfire sensing signal. With this arrangement a misfire can be sensed even in an internal combustion engine having multiple cylinders, the number of parts can be reduced as well as the area of circuits can be reduced.

Abstract: An engine monitor includes, in a self-contained preferably sealed unit, a spark sensor, inductively and capacitively coupled through the case to a spark pick up wire, a timer, and a running time detector, responsive to inputs from the spark pick up to provide total running time, job time, and service time metering. Preferably, storage means are included for storing maximum RPM and spark mode data, that is, data indicating the number of firings per RPM for the particular engine, as well as a preset service interval and one or more auxiliary timers.

Abstract: An apparatus and method for measuring a breakdown voltage between two electrodes separated by a dielectric. The output of a sensor perceiving the voltage across the two electrodes is transferred to a peak-hold circuit. A spark through the dielectric and across the two electrodes is detected, Restrikes between the electrodes are clamped by precluding further transfers of sensor output to the peak-hold circuit for a predetermined period of time subsequent to the detected occurrence of the spark.

Abstract: A misfire detecting device for an internal combustion engine is provided.

Abstract: A method of detecting a misfire of an ignition system for an internal combustion engine is provided. By the method, after completion of spark discharge of a spark plug, a high tension pulse which is not so high as to cause spark discharge is applied to each spark plug by way of a reverse current preventing diode and a secondary winding of an ignition coil or by way of a reverse current preventing diode and a leakage preventing diode for preventing ingress of an ignition high voltage. Misfire at each cylinder is detected on the basis of a voltage attenuation characteristic at a passing side terminal of the reverse current preventing diode. A device for carrying out the above method is also provided.

Abstract: A misfire detecting device for an ignition system, comprises high voltage applying device for applying a pulsed high voltage to each spark plug of an engine after completion of firing of the spark plug, voltage restricting device for restricting a peak of the pulsed high voltage to a highest possible value that does not cause firing of the spark plug, voltage detecting component for detecting a plug voltage across a center electrode-to-outer electrode of the spark plug after reducing the same, and misfire detecting device for detecting a misfire at each cylinder on the basis of a decay characteristic of a detection voltage which is caused by application of the pulsed high voltage.