JP2007032447A - Combustion condition determining device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine a combustion condition in accordance with an ion current in an exhaust stroke. <P>SOLUTION: A system determines the combustion condition in accordance with the ion current detected via an ignition plug in the exhaust stroke. An ion detection starting timing in the exhaust stroke is set to be at a bottom dead center or later (ATDC 180°CA or later), and the ion current is detected in a period when a difference between the detection level of the ion current during stable combustion and that during instable combustion is greater to determine the combustion condition. Furthermore, considering that a period from an exhaust stroke starting timing (a valve opening timing T1 for an exhaust valve) to sufficient lowering of the detection level of the ion current is changed depending on engine operating conditions including an engine speed and a load, the ion detection starting timing in the exhaust stroke is set to be variable depending on the engine operating conditions including a load factor and the engine speed Ne. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a combustion state determination device for an internal combustion engine that determines the combustion state by detecting ions in the combustion gas during the exhaust stroke of the internal combustion engine (engine).

In recent years, focusing on the point that ions are generated when an air-fuel mixture burns in a cylinder of an internal combustion engine, this ion current is detected through a spark plug or the like, and the combustion state is determined based on the detected value of the ion current. A technique for determining and reflecting this in engine control has been put into practical use. In general, many ion currents are detected during the combustion stroke in which the air-fuel mixture burns in the cylinder. However, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 11-324881), ions are detected during the exhaust stroke for the following reasons. Some of them detect the current to determine the combustion state. For example, as the air-fuel ratio is diluted or the EGR amount is increased, the flame propagation speed at the time of combustion of the air-fuel mixture becomes slower and the combustion period becomes longer, and further, when the unstable combustion region is entered beyond the stable combustion limit, Due to the poor flame propagation speed, a phenomenon occurs in which the unburned gas burns after the exhaust stroke. Since the ionic current is generated by the combustion of the air-fuel mixture, in the unstable combustion region, the ionic current is generated by the afterburning even in the exhaust stroke. Patent Document 1 focuses on such characteristics and detects an ionic current during the exhaust stroke to determine whether or not the combustion state is stable combustion.
Japanese Patent Laid-Open No. 11-324881 (first page to second page, etc.)

  According to recent research results of the present inventor, as shown in FIG. 2, for a while from the opening timing T1 of the exhaust valve (at the start of the exhaust stroke), the detection level of the ionic current is considerably high even during stable combustion. It turned out to be high. This is because the in-cylinder pressure suddenly decreases due to the opening of the exhaust valve, causing a rapid gas flow in the cylinder, and the gas flow including ions also increases rapidly around the spark plug electrode. It is thought that the ions collected at the electrodes of the current increase rapidly. Therefore, as shown in FIG. 3, for a while from the exhaust valve opening timing T1 (at the start of the exhaust stroke), the detection level of the ionic current at the time of stable combustion is increased to a level close to the detection level at the time of unstable combustion. Therefore, if the detection of ion current is started from the exhaust valve opening timing T1 (at the start of the exhaust stroke), the stable combustion state may be erroneously determined as unstable combustion, and the combustion state The problem that the judgment accuracy of was bad was found.

  The present invention has been made in view of such circumstances, and therefore, an object of the present invention is to provide a combustion state determination device for an internal combustion engine that can accurately determine the combustion state based on the ionic current during the exhaust stroke. It is in.

  In order to achieve the above object, an invention according to claim 1 is directed to an ion current detection means for detecting ions in combustion gas in an exhaust stroke of an internal combustion engine, and a combustion state based on a detection value of the ion current detection means. In the combustion state determination device for an internal combustion engine having the combustion state determination means for determining, the ion detection start time setting means sets the ion detection start time of the exhaust stroke after the bottom dead center of the piston of the internal combustion engine. Is.

  In general, as shown in FIGS. 2 and 3, when the combustion stroke is finished and the exhaust stroke is started (exhaust valve opening timing T1), the piston of the engine is being lowered (for example, ATDC 120 ° C. A to 140 ° C.). Since A) is set, since the in-cylinder pressure rapidly decreases until the piston moves down to the bottom dead center (ATDC 180 ° C. A) after the exhaust stroke starts, a sudden gas flow occurs in the cylinder and the ions Although the current detection level is considerably high, the amount of residual gas in the cylinder decreases when the piston rises beyond the bottom dead center, so that the ion current detection level decreases during stable combustion. On the other hand, at the time of unstable combustion, since the unburned gas is burned after the bottom dead center, the detection level of the ionic current becomes high. Therefore, if the ion detection start timing of the exhaust stroke is set after the bottom dead center as in the present invention, the difference in the detection level of the ion current between the stable combustion and the unstable combustion becomes large, so Since the stable combustion can be clearly distinguished, the combustion state can be accurately determined.

  By the way, in an internal combustion engine equipped with a variable exhaust valve mechanism that varies the opening / closing timing of the exhaust valve, the exhaust valve opening timing T1 (exhaust stroke start timing) varies depending on the operating conditions and the like. The length of the period from the timing T1 until the detection level of the ionic current sufficiently decreases even if the valve opening timing T1 of the exhaust valve changes.

  Considering this point, when the present invention is applied to an internal combustion engine equipped with a variable exhaust valve mechanism, the ion detection start timing of the exhaust stroke is set to a predetermined crank from the opening timing T1 of the exhaust valve as in claim 2. An angle or a predetermined time may be set later. Here, the predetermined crank angle or the predetermined time is set by measuring or calculating the crank angle or time from the opening timing T1 of the exhaust valve until the detection level of the ionic current falls below the predetermined level by experiment or simulation. It ’s fine. In this way, the ion detection start timing of the exhaust stroke can be advanced or retarded in response to the opening timing T1 of the exhaust valve being advanced or retarded according to the operating conditions, It is possible to make the ion detection start timing of the exhaust stroke correspond to the change in the exhaust valve opening timing T1.

  Further, the period from the opening timing T1 of the exhaust valve until the detection level of the ionic current is sufficiently lowered varies depending on the operating conditions such as the rotational speed, load, air-fuel ratio, etc. In consideration of this point, the ion detection start timing of the exhaust stroke may be variably set according to the operating condition of the internal combustion engine as in claim 3. In this way, the ion detection start timing of the exhaust stroke can be set to an optimal timing according to operating conditions such as the rotational speed, load, and air-fuel ratio of the internal combustion engine.

  In the inventions according to claims 1 to 3 described above, the ion detection start timing of the exhaust stroke is delayed with respect to the valve opening timing T1 (exhaust stroke start timing) of the exhaust valve. In the case where the detection of the ion current is started simultaneously with the timing T1, the means for evaluating the detection value of the ion current detection means with a weight as in claim 4 and the weight from the opening timing of the exhaust valve. It is preferable to have a configuration including means for increasing the time or the elapsed crank angle according to the time or the elapsed crank angle. In this way, in consideration of the fact that the difference in the detected ion current between the stable combustion and the unstable combustion is small during the period from the exhaust valve opening timing T1 to the vicinity of the bottom dead center, During this period, the ion current detection value is evaluated with a small weight, and then the ion current detection value is increased when the difference between the ion current detection value during stable combustion and during unstable combustion increases. Therefore, it is possible to accurately determine the combustion state even if the detection of the ionic current is started at the same time as the exhaust valve opening timing T1 (exhaust stroke start timing). Can do.

  Hereinafter, three Examples 1 to 3 embodying the best mode for carrying out the present invention will be described.

  A first embodiment of the present invention will be described with reference to FIGS. First, the circuit configuration of the ignition control system will be described with reference to FIG. One end of the primary coil 22 of the ignition coil 21 is connected to the battery 23, and the other end of the primary coil 22 is connected to the collector of the power transistor 25 built in the igniter 24. One end of the secondary coil 26 is connected to a spark plug 27, and the other end of the secondary coil 26 is connected to the ground via two Zener diodes 28 and 29.

  The two Zener diodes 28 and 29 are connected in series in opposite directions, a capacitor 30 is connected in parallel to one Zener diode 28, and an ion current detection resistor 31 is connected in parallel to the other Zener diode 29. A potential Vin between the capacitor 30 and the ionic current detection resistor 31 is input to the inverting input terminal (−) of the inverting amplifier circuit 33 via the resistor 32 and is inverted and amplified. The output voltage V of the inverting amplifier circuit 33 is ionized. The current detection signal is input to the engine control circuit 34. The ion current detection circuit 35 (ion current detection means) is composed of Zener diodes 28 and 29, a capacitor 30, an ion current detection resistor 31, an inverting amplification circuit 33, and the like.

  During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition command signal transmitted from the engine control circuit 34 to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary coil 22. After that, when the power transistor 25 is turned off, the primary current of the primary coil 22 is cut off and a high voltage is electromagnetically induced in the secondary coil 26. This high voltage causes spark discharge between the electrodes 36 and 37 of the spark plug 27. This spark discharge current flows from the ground electrode 37 of the spark plug 27 to the center electrode 36, is charged to the capacitor 30 via the secondary coil 26, and flows to the ground side via the Zener diodes 28 and 29. After the capacitor 30 is charged, the ion current detection circuit 35 is driven using the charging voltage of the capacitor 30 regulated by the Zener voltage of the Zener diode 28 as a power source, and the ion current is detected as described later.

  On the other hand, the ion current flows in the opposite direction to the spark discharge current. In other words, after ignition is finished, a voltage is applied between the electrodes 36 and 37 of the spark plug 27 by the charging voltage of the capacitor 30, so that ions generated when the air-fuel mixture burns in the cylinder are connected between the electrodes 36 and 37. Although an ionic current flows, the ionic current flows from the center electrode 36 to the ground electrode 37, and further flows from the ground side through the ion current detection resistor 31 to the capacitor 30. At this time, the input potential Vin of the inverting amplifier circuit 33 changes according to the change of the ionic current flowing through the ionic current detection resistor 31, and the voltage V corresponding to the ionic current is output to the engine control circuit 34 from the output terminal of the inverting amplifier circuit 33. The ionic current is detected.

  The engine control circuit 34 includes a noise mask, a peak hold circuit, an A / D converter, a CPU, a ROM, a RAM, and the like. By executing various engine control routines stored in the ROM, the fuel injection control is performed. Ignition timing control is executed. Furthermore, the engine control circuit 34 determines the combustion state based on the ion current detected during the exhaust stroke by executing a combustion state determination routine of FIG. 4 described later.

  In general, as shown in FIGS. 2 and 3, when the combustion stroke is finished and the exhaust stroke is started (exhaust valve opening timing T1), the piston of the engine is being lowered (for example, ATDC 120 ° C. A to 140 ° C.). Since A) is set, since the in-cylinder pressure rapidly decreases until the piston moves down to the bottom dead center (ATDC 180 ° C. A) after the exhaust stroke starts, a sudden gas flow occurs in the cylinder and the ions Although the current detection level is considerably high, the amount of residual gas in the cylinder decreases when the piston rises beyond the bottom dead center, so that the ion current detection level decreases during stable combustion. On the other hand, at the time of unstable combustion, since the unburned gas is burned after the bottom dead center, the detection level of the ionic current becomes high.

  In consideration of this characteristic, in the first embodiment, the ion detection start timing of the exhaust stroke is set after the bottom dead center (ATDC 180 ° C. and after), and the ion current is detected during stable combustion and unstable combustion. The combustion state is determined by detecting the ionic current during the period in which the level difference becomes large. The ion detection start timing of the exhaust stroke may be set to a predetermined constant crank angle after the bottom dead center (after ATDC 180 ° C. A) to simplify the calculation process, but the exhaust stroke start This period is taken into consideration that the period from the timing (exhaust valve opening timing T1) until the detection level of the ionic current sufficiently decreases depends on the engine operating conditions such as engine speed Ne and load. In Example 1, the ion detection start timing calculation map of FIG. 5 is used to variably set the ion detection start timing of the exhaust stroke according to the engine operating conditions such as the load factor and the engine rotational speed Ne.

  The determination of the combustion state of the first embodiment described above is executed by the engine control circuit 34 as follows according to the combustion state determination routine of FIG. The combustion state determination routine of FIG. 4 is started at a predetermined period (for example, 100 μs period) during engine operation, and functions as a combustion state determination unit in the claims.

  When this routine is started, first, in step 101, the engine operating conditions such as the load factor and the engine speed Ne are read, and in the next step 102, the ion detection start timing θ1 and the ion detection for determining the ion detection section of the exhaust stroke are performed. End time θ2 is calculated.

  In the first embodiment, the period from the exhaust stroke start timing (exhaust valve opening timing T1) until the ion current detection level sufficiently decreases varies according to engine operating conditions such as the engine speed Ne and load. With reference to the ion detection start timing calculation map using the load factor and the engine rotation speed Ne as parameters, the ion detection start timing θ1 corresponding to the current load factor and the engine rotation speed Ne is taken into consideration. Is calculated. The ion detection start time calculation map in FIG. 5 sets the ion detection start time θ1 after the bottom dead center (ATDC 180 ° C. and after), and retards the ion detection start time θ1 as the engine speed Ne increases. Further, in the middle / high rotation region, the ion detection start timing θ1 is set to be gradually retarded as the load factor increases. This function corresponds to the ion detection start time setting means in the claims.

  The ion detection end timing θ2 is obtained by adding a predetermined crank angle to the ion detection start timing θ1 calculated from the ion detection start timing calculation map of FIG. Alternatively, the ion detection end timing θ2 may be set to a predetermined constant crank angle (for example, ATDC 360 ° C. A).

  Thereafter, the process proceeds to step 103, where it is determined whether or not the current time is the ion detection end time θ2, and if it is not the ion detection end time θ2, the process proceeds to step 104, where the current time is the ion detection interval (θ1 to θ2) of the exhaust stroke. If it is not within the ion detection interval, this routine is terminated without doing anything.

  On the other hand, if it is within the ion detection interval, the process proceeds to step 105 to read the ion current peak value Ip of the current sample period (every 100 μs), and in the next step 106, the ion current peak value Ip of the current sample period is Compared with the ion current peak value Iph (i-1) in the ion detection interval from the ion detection start time θ1 to the previous sample cycle, the larger one is the ion current peak value Iph in the ion detection interval up to the current sample cycle ( i) Update and store as and end this routine.

  Thereafter, when the ion detection end timing θ2 is reached, “Yes” is determined in Step 103 and the process proceeds to Step 107, where the ion current peak value Iph (Iph () in the ion detection section detected by the processing in Steps 105 to 106 is performed. Based on i), the combustion state determination parameter is calculated by the following equation.

Combustion state determination parameter = [standard deviation of ion current peak value Iph (i)] × [average value]
Needless to say, the calculation method of the combustion state determination parameter is not limited to the above formula, and may be changed as appropriate.

  Thereafter, the process proceeds to step 108 where the ion current peak value Iph (i) in the current ion detection section is compared with the combustion state determination parameter, and if the ion current peak value Iph (i) is equal to or less than the combustion state determination parameter, The stable combustion state is determined and the routine proceeds to step 109 where the stable combustion flag is turned on. If the ion current peak value Iph (i) is larger than the combustion state determination parameter, it is determined that the combustion state is unstable, and step 110 is performed. Then, the stable combustion flag is turned off. After that, the routine proceeds to step 111 where initialization processing is performed to reset the stored value of the ion current peak value Iph (i) [Iph (i) = 0], and this routine is terminated.

  In the first embodiment described above, the ion detection start timing θ1 in the exhaust stroke is set after the bottom dead center, so that the ion current peak value Iph ( The difference in i) becomes large, so that stable combustion and unstable combustion can be clearly distinguished, and the combustion state can be accurately determined.

  Moreover, in the first embodiment, the period from the exhaust stroke start timing (exhaust valve opening timing T1) until the ion current detection level sufficiently decreases depends on the engine operating conditions such as engine speed Ne and load. The ion detection start timing θ1 is variably set according to the current load factor and the engine rotational speed Ne using the ion detection start timing calculation map of FIG. The ion detection start timing θ1 can be set to the optimal time according to the load factor and the engine speed Ne, and the combustion state can be accurately determined in all regions from the low rotation / low load range to the high rotation / high load range. can do.

  In the ion detection start timing calculation map of FIG. 5, both the load factor and the engine speed Ne are used as the engine operating condition parameter, but only one of the load factor and the engine speed Ne is used as a parameter. The ion detection start timing θ1 may be calculated, and of course, an engine operating condition parameter (for example, an air-fuel ratio) other than the above may be used.

Further, in the ion detection start time calculation map of FIG. 5, the ion detection start time θ1 is set by the crank angle, but it may be set by converting it to time.
In addition, according to the present invention, the calculation process may be simplified by setting the ion detection start timing θ1 of the exhaust stroke to a predetermined crank angle set in advance after bottom dead center regardless of the engine operating conditions. Even in this case, the determination accuracy of the combustion state can be improved as compared with the conventional technique in which the detection of the ion current is started simultaneously with the start of the exhaust stroke.

  When the present invention is applied to an engine equipped with a variable exhaust valve mechanism that varies the opening / closing timing of the exhaust valve, the ion detection start timing θ1 of the exhaust stroke is set to a predetermined crank angle or a predetermined delay time from the opening timing T1 of the exhaust valve. It is only necessary to delay the setting by Δθd. A second embodiment of the present invention that embodies this will be described below.

  In the second embodiment, only the calculation process (step 102) of the ion detection section of the exhaust stroke is different in the combustion state determination routine of FIG. 4, and the other processes are the same as in the first embodiment.

In the second embodiment, in the calculation process of the ion detection interval of the exhaust stroke (step 102), the current exhaust valve opening timing T1 is read, and a predetermined delay time Δθd is added to the current exhaust valve opening timing T1. Thus, the ion detection start timing θ1 is obtained.
θ1 = T1 + Δθd

  Here, the delay time Δθd may be set by measuring or calculating the crank angle or time from the opening timing T1 of the exhaust valve until the detection level of the ionic current falls below a predetermined level by experiment or simulation.

  In this case, the delay time Δθd may be set to a predetermined time regardless of the engine operating condition to simplify the calculation process. However, using the delay time calculation map of FIG. The delay time Δθd may be changed according to the engine operating conditions such as the engine speed Ne.

FIG. 6 is a diagram showing an example of a map for calculating the delay time Δθd using the engine speed Ne as a parameter. The delay time Δθd may be calculated in consideration of engine operating conditions other than the engine speed Ne. In the delay time calculation map of FIG. 6, the delay time Δθd is set in terms of time (ms), but may be set in terms of the crank angle.
Also in the second embodiment, the ion detection end timing θ2 may be set by the same method as in the first embodiment.

  In the second embodiment described above, in an engine with a variable exhaust valve mechanism, the exhaust stroke ion detection is performed in response to the opening timing T1 of the exhaust valve being advanced or retarded according to the engine operating conditions or the like. The start timing θ1 can be advanced or retarded, and the ion detection start timing θ1 of the exhaust stroke can correspond to the change in the exhaust valve opening timing T1. Thereby, even in an engine with a variable exhaust valve mechanism, the combustion state can be accurately determined from the ion current in the exhaust stroke.

  In the first and second embodiments, the ion detection start timing θ1 of the exhaust stroke is delayed from the exhaust valve opening timing T1 (exhaust stroke start timing), but at the same time as the exhaust valve opening timing T1. In the case of starting the detection of the ion current, there are provided means for weighting and evaluating the ion current detection value, and means for increasing the weight according to the elapsed time or the elapsed crank angle from the opening timing of the exhaust valve. It is good to have a configuration. In this way, during the period from the opening timing T1 of the exhaust valve to the vicinity of the bottom dead center, the difference in the ion current peak value Iph (i) in the ion detection interval between stable combustion and unstable combustion is In consideration of the decrease, the ion current peak value Iph (i) is evaluated with a small weight during this period, and thereafter, the ion current peak value Iph (i) is evaluated during stable combustion and unstable combustion. At the time when the difference becomes large, it is possible to perform control such that the ionic current peak value Iph (i) is evaluated by increasing the weight to determine the combustion state.

  A third embodiment of the present invention that embodies this will be described below. In the third embodiment, the combustion state determination routine of FIG. 7 is executed at a predetermined cycle (for example, 100 μs cycle) during engine operation. When this routine is started, first, in step 201, the engine operating conditions such as the load factor and the engine speed Ne are read, and in the next step 202, the ion detection start timing θ1 and the ion detection for determining the ion detection interval of the exhaust stroke are performed. End time θ2 is calculated. In the first embodiment, the ion detection start timing θ1 is set to the exhaust valve opening timing T1 (exhaust stroke start timing), and the ion detection end timing θ2 is obtained by adding a predetermined crank angle to the ion detection start timing θ1. . Alternatively, the ion detection end timing θ2 may be set to a predetermined crank angle (for example, ATDC 360 ° C. A).

  Thereafter, the process proceeds to step 203, and the smoothing coefficient N corresponding to the engine operating conditions such as the current engine speed Ne is calculated with reference to the smoothing coefficient calculation map of FIG. This annealing coefficient N is used to smooth the ion current peak value Ip of the sample period (every 100 μs) in step 208 described later.

  After calculating the annealing coefficient N, the process proceeds to step 204 to determine whether or not the current time is the ion detection end time θ2, and if not the ion detection end time θ2, the process proceeds to step 205 and the current time is the ion detection of the exhaust stroke. It is determined whether or not it is within the section (θ1 to θ2). If it is not within the ion detection section, this routine is terminated without doing anything.

On the other hand, if it is within the ion detection interval, the process proceeds to step 206, where the ion current peak value Ip (i) of the current sample period (100 μs) is read. It is determined whether or not the number of samples of the value Ip (i) is less than a predetermined number (for example, the smoothing coefficient N). Using the smoothing coefficient N, the ion current peak value Ip (i) is annealed by the following equation.
Ip (i) = Ip (i-1) * (N-1) / N + Ip (i) / N

Here, Ip (i-1) is the previous ion current peak value.
As described above, during the period from the ion detection start time θ1 until the number of samples of the ion current peak value Ip (i) reaches a predetermined number, the ion current peak value Ip (i) is smoothed, The value Ip (i) is evaluated with a reduced weight.

  After that, when the number of samples of the ion current peak value Ip (i) reaches a predetermined number from the ion detection start timing θ1, “No” is determined in Step 207, the process proceeds to Step 209, and is read in Step 206 above. The ion current peak value Ip (i) of the current sample period (every 100 μs) is used as it is. Thus, after the number of samples of the ion current peak value Ip (i) reaches a predetermined number from the ion detection start timing θ1, the ion current peak value Ip (i) is evaluated with a greater weight.

  As described above, in step 208 or 209, the ion current peak value Ip (i) of the current sample period is weighted and evaluated, and then the process proceeds to step 210, where the ion current peak value Ip ( i) is compared with the ion current peak value Iph (i-1) in the ion detection interval from the ion detection start time θ1 to the previous sample cycle, and the larger one is the ion current in the ion detection interval until the current sample cycle. The peak value Iph (i) is updated and stored, and this routine is terminated.

  Thereafter, when the ion detection end timing θ2 is reached, “Yes” is determined in Step 204, the process proceeds to Step 211, and the ion current peak value Iph (Iph () in the ion detection section detected by the processing in Steps 206 to 210 is performed. Based on i), the combustion state determination parameter is calculated by the same method as in the first embodiment.

  Thereafter, the process proceeds to step 212, where the ion current peak value Iph (i) in the current ion detection section is compared with the combustion state determination parameter, and if the ion current peak value Iph (i) is equal to or less than the combustion state determination parameter, The stable combustion state is determined and the process proceeds to step 213, where the stable combustion flag is turned on. If the ion current peak value Iph (i) is larger than the combustion state determination parameter, it is determined that the state is an unstable combustion state, and step 214 Then, the stable combustion flag is turned off. Thereafter, the process proceeds to step 215, initialization is performed, the stored values of the ion current peak values Iph (i), Iph (i-1), Ip (i), Ip (i-1) are reset, and this routine is terminated. To do.

  In the third embodiment described above, the period from the ion detection start time θ1 to the time when the number of samples of the ion current peak value Ip (i) reaches a predetermined number of times during the stable combustion and during the unstable combustion. Considering that the difference in ion current peak value Iph (i) is small, during this period, the ion current peak value Iph (i) is evaluated with a small weight. After that, stable combustion and unstable combustion are performed. Considering that the difference in ion current peak value Iph (i) increases with time, the ion current peak value Iph (i) is evaluated with a greater weight to determine the combustion state. Even if the detection of the ionic current is started simultaneously with the valve opening timing T1 (exhaust stroke start timing), the combustion state can be accurately determined.

  In the third embodiment, the timing for changing the weight for the ion current peak value Iph (i) is determined based on the number of samples of the ion current peak value Ip (i) in the sample period (every 100 μs). The ion detection start time θ1 calculated in the first and second embodiments may be set as the weight change time, and the weight may be changed before and after the weight change time.

  In the third embodiment, the annealing process is used as a method for evaluating the ion current peak value Iph (i) with a reduced weight. For example, the ion current peak value Iph (i) is given a predetermined weighting factor K. By multiplying (0 <K <1), the ion current peak value Iph (i) may be evaluated with a reduced weight.

  In the third embodiment, the weight for the ionic current peak value Iph (i) is switched to two levels. However, the weight is set to three levels according to the elapsed time or the elapsed crank angle from the opening timing T1 of the exhaust valve. You may make it switch more or more continuously.

It is a circuit diagram which shows the structure of the ignition control system and ion current detection circuit in Example 1 of this invention. It is a time chart which shows an example of an ion current detection waveform. It is a time chart explaining the difference of the ion current detection level at the time of stable combustion and the time of unstable combustion. 3 is a flowchart showing a flow of processing of a combustion state determination routine of Embodiment 1. It is a figure explaining an example of the ion detection start time calculation map of Example 1. FIG. It is a figure explaining an example of the delay time calculation map of Example 2. FIG. 10 is a flowchart showing a flow of processing of a combustion state determination routine of Example 3. FIG. 10 is a diagram illustrating an example of an annealing coefficient calculation map according to the third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Ignition coil, 22 ... Primary coil, 23 ... Battery, 24 ... Igniter, 25 ... Power transistor, 26 ... Secondary coil, 27 ... Spark plug, 31 ... Ion current detection resistor, 33 ... Inversion amplification circuit, 34 ... Engine Control circuit (combustion state determination means, ion detection start time setting means), 35 ... ion current detection circuit (ion current detection means), 36 ... center electrode, 37 ... ground electrode

Claims (4)

Combustion state determination device for an internal combustion engine comprising ion current detection means for detecting ions in combustion gas in the exhaust stroke of the internal combustion engine, and combustion state determination means for determining the combustion state based on the detection value of the ion current detection means In
A combustion state determination device for an internal combustion engine, comprising: ion detection start timing setting means for setting an ion detection start timing of the exhaust stroke by the ion current detection means after a bottom dead center of a piston of the internal combustion engine. Ion current detection means that detects ions in the combustion gas during the exhaust stroke of an internal combustion engine equipped with a variable exhaust valve mechanism that varies the opening and closing timing of the exhaust valve, and determines the combustion state based on the detection value of the ion current detection means In a combustion state determination device for an internal combustion engine provided with combustion state determination means for
An internal combustion engine comprising ion detection start timing setting means for setting an ion detection start timing of the exhaust stroke by the ion current detection means by delaying a predetermined crank angle or a predetermined time from a valve opening timing of the exhaust valve. Combustion state determination device.   The combustion state determination apparatus for an internal combustion engine according to claim 1 or 2, wherein the ion detection start timing setting means variably sets the ion detection start timing of the exhaust stroke according to an operating condition of the internal combustion engine. Combustion state determination device for an internal combustion engine comprising ion current detection means for detecting ions in combustion gas in the exhaust stroke of the internal combustion engine, and combustion state determination means for determining the combustion state based on the detection value of the ion current detection means In
The combustion state determination means includes means for weighting and evaluating the detection value of the ion current detection means, and means for increasing the weight according to an elapsed time or an elapsed crank angle from the opening timing of the exhaust valve; A combustion state determination apparatus for an internal combustion engine, comprising:

Images