Apparatus for detecting a condition of burning in an internal combustion engine

• US 6,104,195 A
• Filed: 04/08/1997
• Issued: 08/15/2000
• Est. Priority Date: 05/10/1995
• Status: Expired due to Term

• Current Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Yamaura, Toshiaki, Yorita, Hiroshi, Yoshinaga, Tohru, Satou, Yasuyuki, Kano, Masao, Kohama, Tokio
• Primary Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US08/832,201
• Time in Patent Office: 1,225 Days
• Field of Search: 123/425, 123/481, 73/35, 73/116, 73/23.31, 73/35.08, 324/399, 324/459, 324/391, 324/392, 324/393, 324/464
• US Class Current: 324/459
• CPC Class Codes: G01N 27/62 by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
• CPC Class Codes: G01N 27/68 using electric discharge to ionise a gas

Abstract

An apparatus for detecting a condition of burning in an internal combustion engine includes a pair of opposed electrodes provided in a combustion chamber of the engine, and an AC voltage applying device for applying an AC voltage between the opposed electrodes. A current detecting device is operative for detecting a current flowing between the opposed electrodes. A current generating means for generating a current-representing signal depending on the detected current, the current generating means having a differentiating circuit for differentiating the AC voltage into the capacitance-current representing signal. In another aspect of this invention, the apparatus further comprises calculating means for calculating ratios between a parameter represented by the burning-ion current representing signal and a parameter represented by a signal depending on the AC voltage applied between the opposed electrodes. A waveform processing device is operative for removing the capacitive current component from the current-representing signal to extract a burning ion current component, and for generating a burning-ion-current representing signal depending on the extracted burning ion current component. The capacitive current component occurs in correspondence with the AC voltage. One aspect of the invention utilizes calculating means for calculating a ratio between a parameter represented by the burning-ion-current representing signal and a parameter represented by a signal depending on the AC voltage applied between opposed electrodes. The burning ion current component corresponds to a burning ion current which flows between the opposed electrodes. A burning condition detecting device is operative for detecting a condition of burning in the combustion chamber of the engine on the basis of the burning-ion-current representing signal generated by the waveform processing device. The waveform processing device includes an integration processing device for integrating the current-representing signal to generate the burning-ion-current representing signal.

Claims

1. An apparatus for detecting a burning condition, comprising:

a pair of opposed electrodes provided in a combustion chamber of an internal combustion engine;

an AC voltage source that applies an AC voltage between the pair of opposed electrodes, the AC voltage being used for detection of an ion current;

a current detector that detects a current flowing between the opposed electrodes, and outputs a current representing signal containing an AC current component associated with the AC voltage and a burning ion current component; and

an ion current component detector that detects the ion current component by eliminating the AC current component from the current detected by the current detector.

2. The apparatus of claim 1, wherein the ion current component detector comprises a detected current controller that outputs the current-representing signal at a given phase with respect to the AC voltage.

3. The apparatus of claim 2, wherein the detected current controlling means comprises a voltage trigger generating circuit for generating a trigger at a given phase with respect to the AC voltage, and a sample-and-hold circuit for latching the current-representing signal when the trigger is generated, the sample-and-hold circuit outputting a burning-ion-current representing signal.

4. The apparatus of claim 1, wherein the ion current component detector comprises a phase difference detector that detects a phase difference between the AC voltage and the current-representing signal, and for outputting a burning-ion-current representing signal in response to the detected phase difference.

5. The apparatus of claim 4, wherein the phase difference detecting means comprises a first phase trigger generating circuit for generating a first trigger at a given phase with respect to the AC voltage, a second phase trigger generating circuit for generating a second trigger when the current-representing signal reaches a given level, and a time measuring circuit for measuring a time from a moment of occurrence of the first trigger to a moment of occurrence of the second trigger, the measured time being the detected phase difference.

6. The apparatus of claim 1, wherein the ion current component detector comprises an AC current generator that generates an AC current representing signal having a given phase with respect to the AC voltage, and a subtracting circuit that generates the ion current component generating signal corresponding to a difference between the AC current representing signal and the current detected by the current detector.

7. The apparatus of claim 6, further comprising calculating means for calculating a ratio between a parameter represented by the burning-ion-current representing signal and a parameter represented by a signal depending on the AC voltage applied between the opposed electrodes.

8. The apparatus of claim 1, wherein the ion current component detector comprises a differentiating circuit for differentiating the AC voltage into the AC current representing signal.

9. The apparatus of claim 8, further comprising calculating means for calculating a ratio between a parameter represented by the burning-ion-current representing signal and a parameter represented by a signal depending on the AC voltage applied between the opposed electrodes.

10. An apparatus according to claim 1, wherein the ion current component detector comprises a low pass filter which passes a lower frequency signal in the current detected by the current detector than the AC voltage frequency.

11. The apparatus of claim 1, wherein said voltage applying means comprises a signal generator, a switching transistor, and a transformer.

12. An apparatus according to claim 1, said ion current component detector comprising an integrator that integrates the current flowing in the opposite electrodes to eliminate the AC current component associated with the AC voltage from the current detected by the current detector to detect the ion current component.

13. An apparatus according to claim 12, wherein the integrator includes an integrator which integrates the current-representing signal during a predetermined interval, and the apparatus further comprises a detector that detects a misfire in the combustion chamber when a value of a result of the integrating by the integrator is below a predetermined reference value.

14. An apparatus according to claim 12, further comprising a peak value detector that detects a peak value of the current-representing signal, and a detector that detects a misfire in the combustion chamber when the peak value detected by the peak value detector is below a predetermined reference value.

15. An apparatus according to claim 12, further comprising:

a knock component filter that filters a knock-related component from the current-representing signal, the knock-related component having a predetermined frequency corresponding to a knocking;

a maximum amplitude detector that detects a maximum value of an amplitude of the knock-related component filtered by the knock component filter; and

a combustion chamber knocking state detector that detects a knocking state when the maximum value detected by the maximum amplitude detector is equal to or greater than a predetermined reference value.

16. An apparatus according to claim 15, wherein the knock component filter comprises a high pass filter.

17. An apparatus according to claim 12, further comprising:

a knock component filter that filters a knock-related component from the current-representing signal, the knock-related component having a predetermined frequency corresponding to a knocking;

a half-wave rectifier for half wave-rectifying the knock-related component filtered by the knock component filter during a predetermined interval;

an integrator for integrating an output signal of the half-wave rectifier; and

a combustion chamber knocking state detector that detects a knocking state when a value of a result of the integrating by the integrator is equal to or greater than a predetermined reference value.

18. An apparatus according to claim 17, wherein the knock component filter comprises a high pass filter.

19. An apparatus for detecting a condition for burning, comprising:

a pair of opposed electrodes provided in a combustion chamber of an internal combustion engine;

an AC voltage source that supplies an AC voltage between the pair of opposed electrodes, the AC voltage source being used for detection of an ion current;

a current detector that detects a current flowing between the pair of opposed electrodes, and outputs a current representing signal depending on the detected current, said current-representing signal containing an AC current component associated with the AC voltage and a burning ion current component; and

a sampling element that samples the current representing signal when the AC current component is at a null during the detection of the current to effectively eliminate the AC current component from the current representing signal and thereby extract the burning ion current from the current representing signal, the AC current component occurring in correspondence with the AC voltage, the burning ion current component corresponding to a burning ion current which flows between the opposed electrodes.

20. An apparatus for detecting a burning condition in an internal combustion engine, comprising:

a pair of opposed electrodes provided in a combustion chamber;

an oscillator capable of producing a rectangular wave signal;

a transistor receiving the rectangular wave signal, said transistor having an emitter-collector path which is periodically made conductive and non-conductive in response to the rectangular wave signal;

a transformer having a primary winding connected to an output of the transistor, the transistor and transformer producing an AC voltage across the opposed electrodes, said AC voltage occurring in response to the smoothing effects on the rectangular wave signal of stray capacitances;

a current detecting circuit capable of detecting a current flowing between said pair of opposed electrodes, said detected current comprising an AC current component and a burning ion current component; and

a circuit capable of eliminating the AC current component from said detected current.

21. The apparatus of claim 20, wherein said eliminating circuit comprises a detected current controlling circuit which samples the detected current at a given phase with respect to the phase of the AC voltage.

22. An apparatus according to claim 20, wherein said detected current controlling circuit samples the detected current at the descending edge of the rectangular signal, said apparatus further comprising:

a sample-and-hold circuit for latching the detected current when said detected current controlling circuit samples the detected current to effectively eliminate the AC current component from the detected current.