JP2000145606A - Time course detecting method for ignition plug in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain an appropriate duration regardless of the extent of time course and to facilitate the detection of an ion current by measuring the discharge time in spark discharge and detecting the time course of an ignition plug. SOLUTION: A bias power supply 24 for measuring an ion current is connected to a spark plug 18 via a high-pressure diode 23. While controlling the fuel injection, an electronic controller 6 measures the ion current flowing in each ignition so as to detect the combustion state of an engine 100 and control the combustion state based on the detection results. The combustion state, for example, is so controlled that the occurrence of knock is detected based on the knock signal superimposed on the ion current and in a case of occurring the knock, the ignition time is delayed so as to absorb knocking. A program measuring the duration of the spark discharge generated in impressing high voltage to the spark plug 18 of the engine 100 and detecting the time course of the spark plug 18 based on the measured duration is incorporated in the electronic controller 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a temporal change of a spark plug of an internal combustion engine, which determines a temporal change of a spark plug mainly from a state of spark discharge in an automobile engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, an ignition plug is used to detect an ionic current flowing in combustion gas at the time of combustion, and to use a signal level of the detected ionic current to detect occurrence of knock, It is known to detect a misfire state. As a method of detecting the occurrence of knock by using the ion current, for example, as described in Japanese Patent Application Laid-Open No. 58-7536, the occurrence of knock is determined from the amplitude and width of the ion signal corresponding to the detected ion current. Is known (determined). In this example,
In order to prevent spark noise from being superimposed on the ion signal, detection of the ion signal is performed after a predetermined time delay from ignition. Even in the case of such a method of detecting the occurrence of knock due to the ion current, a signal of a predetermined frequency band (knock frequency component) of the ion current is peak-held as in a general knock sensor. There is known an apparatus that performs signal processing on the basis of the signal.

[0003]

As described above, when the combustion state of the internal combustion engine is controlled by utilizing the ionic current, the electrode of the spark plug is provided with an electrode for detecting the ionic current. Become. In general, the electrodes of a spark plug have a narrow gap between the electrodes when the electrodes are new, and the gap increases due to wear due to aging.
Usually, when the gap is small, the required voltage required for spark discharge is small, and when the gap is wide, the required voltage is large.

As described above, when the required voltage changes with the aging of the spark plug, the discharge time for spark discharge differs. This relates to the fact that the same energy is required for spark discharge regardless of the operating condition of the engine. That is, when the gap between the electrodes of the ignition plug is narrow, the initial energy required for spark discharge can be small and the discharge time is long, but when the gap is wide, a large initial energy is required and the discharge time is short. . On the other hand, since the ion current is measured after the spark discharge is completed, if the discharge time changes, the measurement of the ion current becomes irregular and cannot be accurately measured. Therefore, if the ion current cannot be measured normally,
For example, the combustion state of the internal combustion engine such as knock detection may not be controlled.

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, the method for detecting the change with time of the spark plug of the internal combustion engine according to the present invention measures the discharge time by focusing on the fact that the discharge time at the time of spark discharge changes due to the change with time, and determines the change with time based on the measurement result. Is configured to be detected.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to the present application measures the duration of spark discharge generated when a high voltage is applied to a spark plug of an internal combustion engine, and detects a change with time of the spark plug based on the measured duration. A method for detecting a change over time of a spark plug of an internal combustion engine, characterized in that: With such a configuration, when the ignition plug starts to change over time, the duration becomes short. By measuring this duration, the degree of the change over time can be detected. By controlling the energizing time of the high voltage applied to the ignition plug according to the degree of this change over time, it is possible to achieve an appropriate duration regardless of the degree of change over time, making it easy to detect the ion current. become.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. The engine 100 schematically shown in FIG. 1 is of a three-cylinder type for an automobile, and has a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown) in an intake system 1 thereof.
The surge dunk 3 is provided on the downstream side. In the vicinity of one end communicating with the surge tank 3, a fuel injection valve 5 is further provided. The fuel injection valve 5 is controlled by the electronic control unit 6 so as to be independently injected for each cylinder. ing. A spark plug 18 that generates sparks and serves as an electrode for ion current is attached to a cylinder head 31 that forms the combustion chamber 30. Further, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of a three-dimensional catalyst 22 disposed in a pipe leading to a muffler (not shown). I have.

The electronic control unit 6 includes a central processing unit 7
, A storage device 8, an input interface 9, an output interface 11, and an A / D converter 10. The input interface 9 has an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 3 and a cylinder output from a cam position sensor 14 for detecting the rotation state of the engine 100. Vehicle speed sensor 1 for detecting discrimination signal G1, crank angle reference position signal G2, engine speed signal b, and vehicle speed
5, an IDL signal d output from an idle switch 16 for detecting the open / close state of the throttle valve 2, and a water temperature signal e output from a water temperature sensor 17 for detecting the engine coolant temperature. , The current signal h output from the O ₂ sensor 21 and the like are input. On the other hand, the output interface 11 outputs a fuel injection signal f to the fuel injection valve 5 and an ignition pulse g to the spark plug 18.

[0010] The ignition pulse g is generated by an ignition coil IGC of an ignition system schematically shown in FIG. That is, when the switching transistor TR connected to the primary side of the ignition coil IGC is turned on, the ignition pulse g applies the output voltage (+12 V) of the battery (not shown) to the primary side of the ignition coil IGC, and turns the switching transistor TR on. When turned off, it is an ultra-high voltage generated on the secondary side of the ignition coil TR due to self-induced back electromotive force generated on the primary side. The voltage value of the ignition pulse g is controlled by the length of time for energizing the primary side of the ignition coil IGC by the switching operation of the switching transistor TR.

The spark plug 18 is connected via a high voltage diode 23 to a bias power supply 24 for measuring an ion current. Various methods known in the art can be used for the bias power supply 24, the circuit 25 for measuring the ion current, and the measuring method itself. In this embodiment, the ion current can be detected for each cylinder, and therefore, control of the combustion state such as detection of knock can be performed for each cylinder.

The electronic control unit 6 includes an intake pressure signal a output from the intake pressure sensor 13 and a cam position sensor 14.
The basic injection time is corrected by various correction coefficients determined according to the operating state of the engine 100 to determine the fuel injection valve opening time, that is, the injector final energization time T, with the rotation speed signal b output from the main information as main information. A program for controlling the fuel injection valve 5 based on the determined energizing time and injecting fuel corresponding to the engine load into the intake system 1 is built in.

In addition, while controlling the fuel injection of the engine 100 as described above, the ionic current flowing at each ignition is measured, the combustion state of the engine 100 is detected, and the combustion state is controlled based on the detection result. The electronic control unit 6 is programmed. The control of the combustion state detects, for example, the occurrence of knock based on a knock signal superimposed on the ion current, and in the case where knock has occurred, retards the ignition timing to eliminate the occurrence of knock. Or detecting the occurrence of misfire from the current value of the ion current.

Further, a program for measuring the duration of spark discharge generated when a high voltage is applied to the spark plug 18 of the engine 100 and detecting a temporal change of the spark plug 18 based on the measured duration is provided by an electronic control unit. 6
Built in. FIG. 3 shows an outline of the program for detecting the change with time of the spark plug.

In step S1, the discharge time, which is the duration of the spark discharge, is measured. As shown in FIG. 4, the discharge time is measured by detecting a change in the collector voltage of the switching transistor TR (voltage change at point P shown in FIG. 2).
Normally, when the transistor TR is turned on and off, the collector voltage instantaneously shows a voltage value several times the output voltage of the battery due to self-induced back electromotive force. Then, at the start of the discharge, the collector voltage becomes about three times the output voltage of the battery, and this voltage is maintained while the spark discharge continues. Therefore, specifically, the counter measures the discharge time from the time when the collector voltage becomes equal to or more than the threshold value for measuring the discharge time to the time when the collector voltage becomes equal to or less than the threshold value, and measures the discharge time. I do.

In step S2, the energizing time to the ignition coil IGC is multiplied by a deterioration coefficient indicating a temporal change of the spark plug 18 set based on the discharging time, with the energizing time set according to the operating state of the engine. To calculate. As shown in FIG. 5, the deterioration coefficient is set to be smaller as the discharge time becomes longer. Therefore, for example, when the spark plug 18 is new and the degree of change with time is small, the measured discharge time becomes long, so that the deterioration coefficient becomes small and the calculated energization time becomes short. On the other hand, if the degree of change with time of the spark plug 18 is large, the gap between the electrodes is widened, so that the discharge time becomes long. Therefore, the deterioration coefficient increases, and the calculated energization time increases.

According to such a configuration, since the energizing time is adjusted according to the degree of change with time of the spark plug 18, the initial energy at the time of spark discharge can be controlled. Therefore, when the spark flag 18 is new and the degree of change with time is small, the deterioration coefficient is reduced and the energization time is shortened, so that the discharge time in spark discharge is shortened. Can be prevented from being shortened. As a result, the discharge time does not overlap with the period during which the ion current is measured, and the ion current can be accurately measured. Also,
If the spark plug 18 has been used for a long time and the degree of change with time is large, the deterioration time is increased and the energization time is lengthened, so that the discharge time is appropriate and the ion current must be measured accurately. Can be.

As described above, by accurately measuring the ion current, the operating state of the engine 100 can be accurately grasped, and appropriate control of the combustion state can be performed in the occurrence of knocking, misfire detection, and the like. . In addition, since the energization time is changed in the state of the aging of the spark plug 18 as described above, the period for measuring the ion current may be changed according to the energization time that has been changed. Also,
Since the degree of change with time of the spark plug 18 is detected by measuring the discharge time, it is possible to display the time of replacement of the spark plug 18.

The present invention is not limited to the embodiment described above. In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0020]

As described above, according to the present invention, when the spark plug starts to change with time, the duration is shortened. Therefore, by measuring this duration, it is possible to detect the degree of change with time. it can. By controlling the energizing time of the high voltage applied to the ignition plug according to the degree of the aging, an appropriate duration can be achieved regardless of the degree of the aging, and the ion current can be easily and accurately adjusted. Can be detected. Therefore, combustion control such as knock detection and misfire detection can be appropriately performed based on the ion current.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a schematic configuration of an ignition system of the embodiment.

FIG. 3 is a flowchart showing a schematic control procedure of the embodiment.

FIG. 4 is an operation explanatory view of the embodiment.

FIG. 5 is a graph showing a relationship between a deterioration coefficient and a discharge time in the example.

[Explanation of symbols]

 Reference Signs List 6 ... Electronic control device 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 10 ... A / D converter 11 ... Output interface 18 ... Spark plug 30 ... Combustion chamber

Claims (1)

[Claims] An internal combustion engine characterized by measuring a duration of a spark discharge generated when a high voltage is applied to a spark plug of the internal combustion engine, and detecting a temporal change of the ignition plug based on the measured duration. Method for detecting change with time of spark plug.