Electricity: measuring and testing – Internal-combustion engine ignition system or device – Ignition timing
Reexamination Certificate
1999-05-27
2001-08-28
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Internal-combustion engine ignition system or device
Ignition timing
C324S388000, C324S390000, C324S393000
Reexamination Certificate
active
06281682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to ignition systems for internal combustion engines and more particularly to an ignition secondary circuit sensor for detecting both of ignition current flowing through a spark plug of an ignition system at the time of spark discharge of the spark plug and ion current flowing through the spark plug at the time of combustion of fuel in a cylinder of the engine. The present invention further relates to a device for detecting an ignition timing and a combustion timing of an internal combustion engine by the use of the above described ignition secondary circuit sensor. The present invention further relates to an apparatus for detecting pre-ignition of an internal combustion engine on the basis of an ignition timing and a combustion timing detected by the above described ignition timing-and-combustion timing detecting device.
2. Description of the Related Art
The above described ignition secondary circuit sensor is known as for example disclosed in Japanese patent provisional publication No. 4-308362. The sensor has a detection path connected to a detecting circuit. The detection path is capacitively coupled with a high voltage path of an ignition system so that the sensor can detect ignition current flowing through the high voltage path in addition to ion current. Due to this, after spark discharge of a spark plug, reverse current which flows through the high voltage path in the reverse direction to the ignition current is caused to flow into the detecting circuit by way of a capacitive coupling portion, thus causing a problem that the detecting circuit erroneously judges the reverse current as ion current.
Namely, at the time of spark discharge of the spark plug, ignition current flows through the high voltage path in one direction, i.e., from the spark plug to an ignition circuit side. Thereafter, by an energy stored in a secondary winding of an ignition coil, reverse current is caused to flow through the high voltage path in the reverse direction to the ignition current. Then, currents in one and the other directions flow through the high voltage path alternately until the energy stored in the secondary winding of the ignition coil is discharged completely. The detecting circuit erroneously judges the current flowing through the high voltage path in the reverse direction to the ignition current as ion current.
Another problem is that erroneous detection of an ignition timing and ion current results from noise or the like since the noise caused on the ignition secondary circuit side of the ignition system is inputted to the detecting circuit by way of the capacitive coupling portion.
SUMMARY OF THE ONE INVENTION
Accordingly, the present invention is intended to overcome the above-mentioned problems encountered with the known ignition secondary circuit sensor.
An object of the present invention is to provide a novel and improved ignition secondary circuit sensor of the type which is operative to detect by itself both of ignition current at the time of spark discharge of a spark plug and ion current at the time of combustion of fuel, which can detect the ignition current and the ion current accurately without being affected by noise caused in an ignition secondary circuit and reverse current flowing through the ignition secondary circuit after spark discharge of the spark plug.
Another object of the present invention is to provide a device for detecting an ignition timing and combustion timing of an internal combustion engine by the use of the ignition secondary circuit sensor of the foregoing character, which can detect the ignition timing and combustion timing accurately.
A further object of the present invention is to provide an apparatus for detecting pre-ignition of an internal combustion engine by the use of the ignition timing-and-combustion timing detecting device of the foregoing character, which can detect the pre-ignition accurately.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a sensor for detecting ignition current flowing through a spark plug of an internal combustion engine at the time of spark discharge of the spark plug and ion current flowing through the spark plug at the time of combustion of fuel in a cylinder of the engine. The engine has an ignition system including a high voltage path connecting between an ignition coil and the spark plug. The sensor comprises an ignition path connected in series to the high voltage path and having at least two reverse current preventing diodes for permitting current to flow through the high voltage path only in one direction, and a detection path having at least one current detecting diode connected at an electrode to that same polarity electrode of one of the reverse current preventing diodes closer to the spark plug (e.g., an anode of the current detecting diode is connected to an anode of the reverse current preventing diode or a cathode of the current detecting diode is connected to a cathode of the reverse current preventing diode), for detecting the ignition current and the ion current by way of the current detecting diode, wherein a path portion of the detection path on the side of the current detecting diode opposite to the ignition path and a path portion of the ignition path connecting between the reverse current preventing diodes are capacitively coupled.
According to another aspect of the present invention, there is provided a device for detecting an ignition timing at which ignition current flows through a spark plug of an ignition system of an internal combustion engine and a combustion timing at which ion current flows through the spark plug. The device comprises a sensor for detecting ignition current and ion current flowing through the spark plug, which is structured substantially the same as that described as above. The device further comprises a capacitor connected at one of opposite ends thereof to an end of the path portion of the detection path which is located on the side of the coupling portion opposite to the current detecting diode, a charging circuit for supplying the capacitor by way of the detection path with an electric charge for causing ion current to flow through the spark plug, a pair of detecting circuit diodes connected at an anode and a cathode to the other of the ends of the capacitor, respectively, and an ignition current detecting circuit and an ion current detecting circuit connected to electrodes of the detecting circuit diodes other than the above-mentioned anode and cathode thereof for detecting the ignition current and the ion current, respectively.
According to a further aspect of the present invention, there is provided an apparatus for detecting pre-ignition of an internal combustion engine. The apparatus comprises a device for detecting an ignition timing and a combustion timing described as above. The apparatus further comprises a judgment circuit responsive to a signal from the ignition current detecting circuit and a signal from the ion current detecting circuit, for judging, in timed relation to an ignition timing at which the ignition current is detected by the ignition current detecting circuit, whether the ion current is detected by the ion current detecting circuit before the ignition timing. The judgment circuit outputs a signal indicating occurrence of pre-ignition in the engine at the time it judges that the ion current is detected before the ignition timing.
REFERENCES:
patent: 4547734 (1985-10-01), Spaude
patent: 5237278 (1993-08-01), Bumen
patent: 5493227 (1996-02-01), Shimasaki et al.
patent: 4-308362 (1992-10-01), None
Kameda Hiroyuki
Matsubara Yoshihiro
Brown Glenn W.
NGK Spark Plug Co. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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