JPH10220334A - Engine combustion analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To analyze combustion states with high accuracy on the basis of an ion current value detected through an ignition plug. SOLUTION: In this analyzer, during a period when high voltage for ignition is discharged to an ignition plug, the power MOSFET 15 of a signal processing circuit 4 is switched OFF, and high ion current detecting voltage which is devided by resistances 8, 10, 11 is applied from an electric power supply source 7 to the ignition plug through the secondary winding side of an ignition coil 2, and also after lapse of the discharge time, the power MOSFET 15 is switched ON, low ion current detecting voltage which is devided by the resistances 8, 10, 11, 13 is applied to the ignition plug. A large amount of ion generated by combustion is moved to both electrodes of the ignition plug by high ion current detecting voltage during a spark discharge period so as to maintain electric discharge, thereby an ion current detected amount is increased. Then, ion current is detected with high sensitivity by low ion current detecting voltage after lapse of the spark discharge time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion analysis device for an engine, which detects an in-cylinder pressure during combustion and a knocking intensity by detecting an ionic current flowing through a spark plug.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for measuring the combustion state of an engine mounted on a vehicle such as an automobile by measuring an ion current flowing through a spark plug during combustion and evaluating the measured value based on the measured value. . For example, JP-A-7-158500
In the publication, after applying a high voltage for ignition to a spark plug, a constant voltage for ion current detection is applied, and a current generated by mediating ions generated by a combustion reaction to both electrodes of the spark plug. There is disclosed a technique of measuring (ion current), analyzing a change in the waveform of the ion current with time, and detecting an air-fuel ratio correlated with the ion concentration, a misfire, or the like.

[0003]

By the way, if the ion current detection voltage applied to the ignition plug is set low,
Although the detection sensitivity increases, the ion current detection amount relatively decreases. In the above prior art, since a constant voltage for ion current detection is applied after the elapse of the spark discharge period, if the detection sensitivity is increased, the ion current cannot be detected, and both the detection amount and the sensitivity are satisfied. Can not do.

In the prior art, the combustion state in the cylinder is analyzed from the relationship between the maximum value or the minimum value of the output waveform of the ion current and the time until the maximum value or the minimum value appears. However, the output waveform of the ionic current includes disturbance factors such as mechanical vibration, and analyzing the combustion state from the output waveform including factors other than the ionic current has a problem of lowering the analysis accuracy. .

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a combustion analysis apparatus for an engine that can easily and accurately detect the combustion state in a cylinder from an ion current.

[0006]

According to a first aspect of the present invention, there is provided a combustion analysis apparatus for an engine, in which a voltage for detecting an ion current is applied to a spark plug, and ions generated by a combustion reaction cause the ignition to occur. An ion current detection circuit for detecting an ion current flowing when the electrode moves to both electrodes of the plug, wherein the ion current detection voltage applied to the ignition plug is applied to the ion current detection circuit during a spark discharge period during a high spark discharge period. It is characterized in that a voltage conversion circuit that is set low during periods other than the discharge period is provided.

A second engine combustion analysis device according to the present invention is the first engine combustion analysis device, wherein the ion current detection circuit includes an ion current value output from the ion current detection circuit that is lower than a specific frequency. A signal processing circuit having a built-in primary processing circuit that passes only components is connected.

A third engine combustion analysis device according to the present invention is the first engine combustion analysis device, wherein the ion current detection circuit is provided with an ion current value output from the ion current detection circuit at a specific frequency or less. A signal processing circuit having a built-in primary processing circuit for passing only the component and a secondary processing circuit for passing only a component having a specific frequency or more of the ion current value output from the ion current detection circuit is connected. And

According to a fourth aspect of the present invention, there is provided a combustion analysis apparatus for an engine, wherein the maximum combustion pressure is detected based on the maximum value of the ion current value processed by the signal processing circuit. Features.

A fifth engine combustion analyzing apparatus according to the present invention, in the second engine combustion analyzing apparatus, detects a maximum combustion pressure based on a maximum value of an ion current value processed by the signal processing circuit. It is characterized by detecting a crank position showing a maximum value.

A sixth engine combustion analysis device according to the present invention, in the second engine combustion analysis device, measures the ion current value processed by the signal processing circuit at least in a specific period sandwiching the compression top dead center. Detecting the maximum value of the ion current value in the specific period, detecting the crank position at that time, detecting the maximum combustion pressure based on the maximum value, and detecting the maximum combustion pressure from the crank position indicating the maximum value. Is detected.

A seventh engine combustion analysis device according to the present invention, in the second engine combustion analysis device, indicates a crank position and a maximum combustion pressure which indicate a maximum value of the ion current value processed by the signal processing circuit. The relationship with the crank position is mapped in advance, and the crank position indicating the maximum combustion pressure is set based on the map.

According to an eighth aspect of the present invention, in the third engine combustion analyzer, the knocking intensity is set based on the integrated value of the change amount of the ion current value processed by the signal processing circuit. It is characterized by the following.

According to a ninth engine combustion analyzer according to the present invention, in the third engine combustion analyzer, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center. The amount of change in the ion current value during the specific period is integrated, and the knocking intensity is set based on the integrated value.

A tenth engine combustion analyzing apparatus according to the present invention, in the third engine combustion analyzing apparatus, measures the ion current value processed by the signal processing circuit at least in a specific period sandwiching the compression top dead center. The relationship between the integrated value of the change amount of the ion current value in the specific period and the knocking intensity is mapped in advance, and the knocking intensity is set based on the map.

An eleventh engine combustion analysis apparatus according to the present invention, in the third engine combustion analysis apparatus, measures the ion current value processed by the signal processing circuit at least in a specific period sandwiching the compression top dead center. In addition, it is characterized in that it is determined whether or not a vibration having a specific envelope shape exists in the ion current waveform in the specific period based on the ion current value, and the knocking intensity is set based on the envelope shape.

According to a twelfth engine combustion analyzer according to the present invention, in the third engine combustion analyzer, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center. The relationship between the type of envelope-shaped vibration present in the measured ion current waveform and the knocking intensity is mapped in advance, and the knocking intensity is set based on the map.

In the first engine combustion analyzing apparatus, the voltage for ion current detection applied from the ion current detection circuit to the spark plug is set to a high value by the voltage conversion circuit, and the spark discharge period is set high. By sustaining the discharge, the amount of ion current detection is increased, and by setting it low during periods other than the spark discharge period, the ion current detection sensitivity after the elapse of the spark discharge period is increased.

In the second engine combustion analyzing apparatus, the first engine
In a combustion analysis device for an engine, a signal processing circuit is connected to the ion current detection circuit, and a primary processing circuit built in the signal processing circuit performs signal processing on an ion current value output from the ion current detection circuit. To remove components above a specific frequency.

In the third engine combustion analyzer, the first engine
A signal processing circuit is connected to the ion current detection circuit, and a primary processing circuit and a secondary processing circuit incorporated in the signal processing circuit output ions from the ion current detection circuit. The current value is subjected to signal processing to remove components above a specific frequency and components below a specific frequency.

In the fourth engine combustion analyzer, the second engine
The maximum combustion pressure is detected based on the maximum value of the ion current value processed by the primary processing circuit built in the signal processing circuit.

In the fifth engine combustion analyzer, the second engine
In the combustion analysis apparatus for an engine described above, the maximum combustion pressure is detected based on the maximum value of the ion current value processed by the primary processing circuit built in the signal processing circuit, and the crank position at that time is detected.

In the sixth engine combustion analysis device, the second engine
In the combustion analysis device for an engine, the ion current value processed by the primary processing circuit incorporated in the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, and the local maximum value in the specific period is detected. At the same time, the crank position at that time is detected, the maximum combustion pressure is detected based on the maximum value, and the crank position indicating the maximum combustion pressure is detected from the crank position indicating the maximum value.

In the seventh engine combustion analyzer, the second engine
In the combustion analysis device for an engine, the relationship between the crank position indicating the maximum value of the ion current value processed by the primary processing circuit built in the signal processing circuit and the crank position indicating the maximum combustion pressure is mapped in advance, Based on the crank position when the map shows the maximum value of the ion current value, the above-mentioned map is referred to and a crank position indicating the corresponding maximum combustion pressure is set.

In the eighth engine combustion analysis device, the third engine
In the combustion analysis device for an engine described above, the amounts of change in the ionic current values processed by the primary processing circuit and the secondary processing circuit incorporated in the signal processing circuit are integrated, and the knocking intensity is set based on the integrated value.

In the ninth engine combustion analyzer, the third engine
In the combustion analysis device for an engine, the ion current value processed by the primary processing circuit and the secondary processing circuit incorporated in the signal processing circuit is measured at least in a specific period around the compression top dead center, and the measured ion current value The change amount is integrated, and the knocking intensity is set based on the integrated value.

According to a tenth engine combustion analyzer, in the third engine combustion analyzer, the ion current value processed by the primary processing circuit and the secondary processing circuit incorporated in the signal processing circuit is at least compression-dead-dead. The relationship between the value obtained by integrating the measured change amount of the ion current value and the measured knocking intensity is measured in a specific period across the point, and the map is referred to based on the integrated value of the change amount of the ion current value. To set the knocking strength.

According to an eleventh engine combustion analyzer, in the third engine combustion analyzer, the ion current value processed by the primary processing circuit and the secondary processing circuit incorporated in the signal processing circuit is at least compression top dead. It is measured in a specific period sandwiching a point, and it is determined whether or not an envelope-shaped knocking vibration appears on the ion current waveform based on the measured ion current value, and a knocking intensity is set based on the envelope shape.

In a twelfth engine combustion analyzer, in the third engine combustion analyzer, the ion current value processed by the primary processing circuit and the secondary processing circuit incorporated in the signal processing circuit is at least compression-dead-dead. The relationship between the knocking intensity and the type of the knocking vibration of the envelope shape that appears on the ion current waveform based on the measured ion current value is measured in a specific period sandwiching the point, and the map is formed based on the envelope shape type. And set the knocking intensity.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 9 show a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a spark plug disposed in each cylinder of a multi-cylinder engine (four-cylinder engine in the present embodiment), and reference numeral 2 denotes a secondary winding connected to each spark plug 1. The ignition coil 3 is a power transistor which is connected to the primary winding side of the ignition coil 2 to cut off the primary current, and is turned ON by a dwell signal output from a control unit 23 which will be described later. It is turned off. Further, an ion current detection circuit 4 is connected to the secondary winding of each of the ignition coils 2, and a signal processing circuit 5 is connected to the ion current detection circuit 4.

FIG. 2 shows a circuit diagram of the ion current detection circuit 4. Reference numeral 6 denotes a diode whose cathode is connected to the secondary winding of each ignition coil 2 and whose anode is grounded. Reference numeral 7 denotes a power supply source such as a DC-DC converter that supplies an ion current detection voltage. The secondary winding of each of the ignition coils 2 is connected via a resistor 8 and a diode 9 connected to the anode of the resistor 8. Connected to the line side.

Further, in order to detect the ionic current, resistors 10 and 11 having a high resistance connected in series are connected between the resistor 8 and the diode 9 and divided into resistors.
The non-inverting input terminal of the amplifier 12 is connected between the voltage dividers 11. The amplifier 12 constitutes a buffer circuit having an output terminal connected in a negative feedback manner. A Zener diode 14 having an anode grounded is connected to the non-inverting input terminal of the amplifier 12.
Are connected on the cathode side. Therefore, amplifier 1
The output voltage 2 indicates the detected value of the ion current.

A power MOSFET which is an example of voltage switching means for switching a voltage value applied to the ignition plug 1 through a resistor 13 between the resistor 8 and the diode 9
(Metal Oxide Semiconductor Field Effect Transisto
r) The drain side of 15 is connected, and this power MOSF
The source side of ET15 is grounded. The output terminal of the amplifier 12 is connected to the gate side of the power MOSFET 15 via a gate resistor 16.
The other end of the resistor 17 whose one end is grounded is divided and connected.
The resistors 13, 16, 17 and the power MOSF
A voltage conversion circuit is configured by ET15.

FIG. 3 shows a circuit block diagram of the combustion analyzer. Reference numeral 21 denotes the amplifier 13 of the ion current detection circuit 4.
Low-pass filter as a primary processing circuit for processing the ion current output from
1, a high-pass filter as a secondary processing circuit for further processing the ion current processed by the control unit 1;
1, high-pass filter 22, and crank angle sensor 2
4. Based on the output signal of the cam angle sensor 25, a maximum combustion pressure, a crank position indicating the maximum combustion pressure, a knocking intensity, and the like are calculated. The crank angle sensor 2
4 outputs a crank pulse at every set crank angle in synchronization with the engine speed, and the cam angle sensor 25 outputs a cylinder discrimination pulse.

Next, the operation of the present embodiment will be described. When a dwell signal is output to the power transistor 3 of the ignition target cylinder, the power transistor 3 is turned on, and a primary current is supplied to the primary winding of the ignition coil 2. Next, the power transistor 3 is turned off by the ignition signal.
Then, the primary current is interrupted, a high voltage is induced on the secondary winding side of the ignition coil 2, a discharge current flows from the diode 6 to both electrodes of the ignition plug 1, and the air-fuel mixture filled in the cylinder To ignite.

Therefore, the voltage between the resistor 8 and the diode 9 during the discharge period of the ignition plug 1 becomes a minimum value as shown by the elapsed time t0 to t1 in FIG. 8, and the voltage at the output terminal of the amplifier 12 becomes 1V. It is as follows. Thereby, the power M
The bias voltage applied to the gate of the OSFET 15 decreases, and the power MOSFET 15 is maintained in the OFF state.

On the other hand, during the discharge period, the power MOSFET 1
5 is kept in the OFF state, the ignition plug 1 is supplied with a high-voltage ion current detection voltage (3 in this embodiment) divided by the resistors 8, 10, and 11.
00V) is supplied, and the discharge is continued even after the discharge period by the high voltage for detecting the ion current. As a result, a large amount of ions generated by the combustion reaction move to both electrodes.

When the discharge period ends, the ion current flows while attenuating in a pattern as shown after the elapsed time t1 in FIG. That is, when the air-fuel mixture filled in the cylinder is ignited by the spark discharge of the spark plug 1 and burns, ions are generated by ionization, and the ions move to the two electrodes of the spark plug 1, and the ions are moved. Then, an ionic current flows from the power supply source 7 through the resistor 8 and the diode 9.

On the other hand, at the end of the discharge period, the voltage at the output terminal of the amplifier 12 rises,
The bias voltage applied to the gate of the power MOSFET 15 increases, and the power MOSFET 15 is turned on. As a result, a low ion current detection voltage divided by the resistors 8, 10, 11, and 13 is applied to the ignition plug 1, and the ion current is detected by the low voltage ion current detection voltage. Is detected.

When the ion current is detected, a large amount of ions are moved to both electrodes of the ignition plug by the high voltage for detecting the ion current applied during the spark discharge period. Is maintained, and as a result, generation of the ion current is continued. In addition, since the ion current detection voltage is switched to a low voltage at the time of ion current detection, the ion current can be detected with high sensitivity.

When an ionic current flows between the electrodes of the ignition plug 1, a voltage is generated across the resistor 8, and this voltage is input to an amplifier 12 that connects a non-inverting input terminal between the resistors 10 and 11 by voltage division. You. Then, an ion current waveform is output from the output terminal of the amplifier 12, the ion current waveform is subjected to signal processing by the low-pass filter 21 of the signal processing circuit 5, and disturbance factors such as mechanical vibrations included in the ion current waveform are reduced. Removed.

FIG. 8 shows a voltage change between the resistor 8 and the diode 9, that is, an ion current waveform. As shown in the figure, in the ion current detection region, the maximum value of the ion current (minimum value of the detection voltage) corresponds to the spark discharge period (elapsed time t0 to t1).
It is detected twice immediately after the elapsed time (elapsed time t2) and after the elapse of the top dead center (elapsed time t4). First maximum value (voltage value V1)
Is considered to be when the outer ring of the flame immediately after ignition reaches the outer electrode of the spark plug 1, and the second maximum value (voltage value V
2) The crank position when the flame grows and the outer ring makes contact with the piston surface and the inner wall surface of the cylinder head with the largest area, and this second maximum value (voltage value V2) is detected Has a very strong correlation with the crank position indicating the maximum value of the combustion pressure.

The ion current processed by the low-pass filter 21 is output to the control unit 23 and also to the high-pass filter 22. Then, the ion current waveform is subjected to signal processing by the high-pass filter 22 to remove a pressure oscillation wave component generated by normal combustion.

Thereafter, the vibration wave of the ion current processed by the high-pass filter 22 is output to the control unit 23. FIG. 9 shows an oscillating wave of the ion current processed by the high-pass filter. For example, when knocking occurs in the combustion stroke, a strong vibration wave is detected as shown in a range surrounded by a dashed line. It is considered that this is because the ion concentration in the vicinity of the electrode of the ignition plug 1 fluctuated due to the pressure vibration based on knocking, and the ion current was disturbed.

Next, a routine for setting the maximum combustion pressure and knocking intensity detected by the control unit 23 for each cylinder will be described with reference to the flowcharts of FIGS.

FIG. 4 shows a maximum combustion pressure detection setting routine. This routine starts when the elapsed time t reaches the set time t3 before the compression top dead center, and ends when the elapsed time t reaches the set time t5 after the compression top dead center (see FIG. 8).

First, in step S1, the low-pass filter 2
The current ion current value i (t) processed in step 1 is read, and the ion current value i (t) is compared with the local maximum value imax in step S2. If i (t)> imax, the flow advances to step S3. Proceed,
If i (t) ≦ imax, the process jumps to step S4. Note that the initial value of the maximum value imax is 0, and since i (t)> imax in the first processing after the execution of the routine,
Proceed to step S3.

In step S3, the maximum value imax is updated with the ion current value i (t) read this time, and the crank position corresponding to the current elapsed time t indicates the maximum ion current. Update θimax (θ
imax ← t).

Next, in step S4, it is determined whether or not the elapsed time t has reached the set time t5 after the compression top dead center. If not, the process proceeds to step S5, where the current elapsed time t is the calculation cycle. At is added (t ← t + Δt), and the process stands by until the operation cycle is reached. When the operation cycle is reached, the process returns to step S1. Therefore, the logic of steps S1 to S3 is repeated for each calculation cycle Δt until the set time t5 elapses, and the maximum value imax of the ion current and the crank position θimax when it is detected are obtained.

When the elapsed time t reaches the set time t5 after the compression top dead center, the steps S4 to S6
The maximum combustion pressure Pmax is calculated by multiplying the detected maximum value imax by the coefficient K (Pmax ← imax · K), and the crank position θimax and the engine speed Ne indicating the maximum ion current detected in step S7. Based on this, the crank position θpmax indicating the maximum combustion pressure is set by referring to the map with interpolation calculation (θpmax ← f (θimax, Ne)), and the routine exits.

The engine speed Ne is calculated based on the interval time between crank pulses indicating the set crank angle output from the crank angle sensor 24 or the count number within the set time of the crank pulse.

FIG. 6 shows an example of the map referred to in step S7. In each region of the figure, the crank position at the maximum combustion pressure obtained from experiments and the like is stored using the crank position θimax at which the ion current is maximized and the engine speed Ne as parameters. In the drawing, a negative value indicates a crank angle before the compression top dead center and a positive value indicates a crank angle after the compression top dead center based on the compression top dead center.

It should be noted that the crank position θimax when the maximum value imax of the ion current is detected may be approximately regarded as the crank position θpmax at the maximum combustion pressure (θimax ≒
θpmax). In this case, the calculation in step S7 is omitted.

FIG. 5 shows a knocking strength setting routine. This routine starts when the elapsed time t reaches the set time t3 before the compression top dead center, and ends when the elapsed time t reaches the set time t5 after the compression top dead center (see FIG. 9).

First, in step S11, the current ion current value i (t) processed by the high-pass filter 22 is read, and in step S12, the differential value which is the amount of change in the ion current value i (t) per operation cycle is read. Is calculated (d (t) ← | i (t) −i (t−Δt) |), and in step S13,
The absolute value d (t) is added to the previous integrated value S to calculate the current integrated value S (S ← S + d (t)).

Note that the initial values of the ion current value i and the integrated value S are 0, and therefore, in the first processing after the execution of the routine, d (t) ← | i (t) | S ← d (t) Becomes

Next, in step S14, it is determined whether or not the elapsed time t has reached the set time t5 after the compression top dead center. If not, the process proceeds to step S15, where the current elapsed time t is the operation cycle. At is added (t ← t + Δt), and the process stands by until the operation cycle is reached. When the operation cycle is reached, the process returns to step S1. Therefore, until the set time t5 elapses,
The processing of steps S11 to S13 is repeated for each calculation cycle Δt.

When the elapsed time t reaches the set time t5 after the compression top dead center, the process proceeds from step S14 to step S14.
Then, based on the integrated value S of the absolute value of the differential value of the ion current in the specific period t3 to t5, the knocking strength KN
Calculate KLEBEL and exit the routine.

KNKLEBEL ← (SK1 + K2) / K3 Here, K1, K2 and K3 are coefficients.

The knocking intensity KNKLEBEL is determined for each operation region by experiment or the like using the integrated value S and the engine speed Ne as parameters, and is mapped to the integrated value S and the engine speed Ne in step S16. The knocking strength KNKLEBEL may be set by referring to the above map with interpolation calculation, and an example of a map referred to in this case is shown in FIG. In this map, the knocking strength KNKLEBELF is represented by a numeral, and a larger value indicates a higher strength.

Based on the analysis of the ion current value as described above, for example, MBT (optimum ignition advance for obtaining the maximum torque)
In the control, the maximum combustion pressure Pmax and the crank position θpmax at this time are read, and the ignition timing is advanced or retarded based on both data, thereby improving the engine output and the fuel efficiency. Exhaust emissions can be reduced.

In knock control, the knocking strength KNKLEBEL is read, and the knocking strength KNKLEBEL is read.
It is possible to effectively protect the engine from knocking by determining the presence or absence of knocking based on the above, and correcting the ignition timing of the corresponding cylinder by retard correction when knocking occurs.

As described above, in the present embodiment, the combustion state of the engine can be detected without using a cylinder pressure sensor or the like, so that the configuration is simplified and the manufacturing cost can be reduced accordingly. .

FIG. 10 shows a second embodiment of the present invention.
When knocking occurs in the combustion stroke, the oscillation waveform of the ion current value i output from the high-pass filter 22 has an envelope shape as shown in a range surrounded by a dashed line in FIG. In the present embodiment, the envelope shape of the vibration waveform is recognized based on the ion current value i output from the high-pass filter 22, and the knocking intensity is set based on the envelope.

The recognition of the envelope shape is based on the absolute amount d of the ion current value i in a very short time (Δt) which is the operation cycle.
This is performed using the characteristic that the amplitude of the vibration waveform increases while (t) increases, and decreases while it decreases.

More specifically, this is executed by a knocking intensity setting routine shown in FIG. This routine starts when the set time t3 before the compression top dead center is reached, and ends when the set time t5 after the compression top dead center is reached (see FIG. 9).

First, in step S11, the ion current value i
(t) is read, and in step S12, the ion current value i (t) is read.
The absolute value of the differential value d (t)
In step S13, the absolute value d (t) is added to the previous integrated value S to calculate the current integrated value S.

Then, in step S21, the difference between the absolute value d (t) of the current differential value and the previous absolute value d (t-Δt) is obtained, and the difference is a negative value (d (t) -d If (t−Δt) <0), that is, if the current absolute amount d (t) is decreasing, the process proceeds to step S22, and the difference is a positive value (d (t) −d (t)
−Δt)> 0), that is, if the absolute amount d (t) is increasing, the process proceeds to step S23, while if there is no change (d
((t) −d (t−Δt) = 0), the process proceeds to step S14.

At step S22, the current absolute amount d
(t) is added to the decrease total Sd up to the previous time (Sd ← Sd +
d (t)), and proceeds to step S14. Step S23
When the process proceeds to, the current absolute amount d (t) is added to the increase sum Si up to the previous time (Si ← Si + d (t)), and the process proceeds to step S14.

In step S14, it is determined whether or not the elapsed time t has reached the set time t5 after the compression top dead center. If not, the process proceeds to step S15, where the current elapsed time t is the calculation cycle. At is added (t ← t + Δt), and the process waits until the operation cycle is reached. When the operation cycle is reached, the process returns to step S11.

When the elapsed time t reaches the set time t5 after the compression top dead center, the process proceeds from step S14 to step S14.
Proceeding to 24, the difference (Si-Sd) between the increase total Si and the decrease total Sd is compared with the knock determination upper limit K4 and the knock determination lower limit K5. Next, the difference (Si−Sd)
Is within the range between the knock determination upper limit K4 and the knock determination lower limit K5 (K4 ≦ Si−Sd ≦ K5), it is determined that the vibration wave is caused by knocking, the process proceeds to step S16, and the value is calculated in step S13. The knocking intensity KNKLEBEL is calculated from the following equation based on the integrated value S, which is the size (area) of the envelope during the specific period t3 to t5, and the routine exits.

KNKLEBEL ← (S · K1 + K2) / K3 where K1, K2 and K3 are coefficients.

On the other hand, in step S24, Si-Sd <
If K4 or K5 <Si−Sd, it is determined that the vibration waveform is not generated by knocking, and the routine jumps to step S25, where the knocking intensity KNKLEBE is determined.
Clear L (KNKLEBEL ← 0) and exit the routine.

In the present embodiment, the envelope of the vibration pattern is determined based on the difference (Si-Sd) between the total sum of increase and decrease of the differential value of the ion current in the predetermined period t3 to t5 with the compression top dead center therebetween. Recognize that the shape is the area of the envelope (S)
Is used to determine the occurrence of knocking and the knocking strength KNKLEBEL. Therefore, the knocking strength can be set with high accuracy without being affected by disturbance or the like.

The knocking intensity KNKLEBEL calculated in step S16 can be set by referring to a map. For example, as shown in FIG. 11, a first map (FIG. 11A) storing a value indicating the type of the envelope-shaped pattern using the difference (Si−Sd) and the integrated value S as parameters is used. A second map storing the knocking intensity KNKLEBEL using the envelope shape type and the engine rotation speed Ne as parameters by referring to the envelope shape with interpolation calculation and specifying the envelope shape is referred to by interpolation calculation. The knocking strength KNKLEBEL is set by referring to the table.

Next, FIG. 12 shows a third embodiment of the present invention. In the present embodiment, the ion current detection circuit 4 is provided with an ignition plug 1 of a secondary winding of an ignition coil 2 provided for each cylinder.
The other side is connected via a high voltage diode 26, and the other configuration is the same as that of the first embodiment.

[0078]

According to the first aspect of the present invention, the voltage for detecting the ion current applied from the ion current detection circuit to the spark plug is set high during the spark discharge period and low during the periods other than the spark discharge period. The discharge can be continued after the spark discharge period by the high ion current detection voltage applied during the discharge period, the amount of ions detected increases accordingly, and a low ion current detection voltage is applied after the spark discharge period By doing so, the detection sensitivity of the ion current is increased.

According to the second aspect of the present invention, in the first aspect of the invention, the ion current value detected by the ion current detection circuit is processed and specified by a primary processing circuit built in the signal processing circuit. Since components higher than the frequency are removed, disturbance factors included in the ion current waveform are removed, and the detection accuracy of the ion current value is improved.

According to a third aspect of the present invention, in the first aspect of the present invention, the ionic current value detected by the ionic current detection circuit is converted into a primary processing circuit and a secondary processing circuit incorporated in a signal processing circuit. To remove the component above the specific frequency and the component below the specific frequency.
The secondary processing circuit removes disturbance factors contained in the ion current waveform, and the secondary processing circuit removes vibration wave components due to normal combustion from the ion current waveform, thereby simplifying the pressure vibration wave generated by knocking. In addition, detection can be performed with high accuracy.

According to the fourth aspect of the present invention, the maximum combustion pressure is detected based on the maximum value of the ion current value processed by the signal processing circuit in the second aspect of the invention, so that the mechanical vibration The maximum combustion pressure can be detected simply and with high accuracy from the ion current value from which disturbance factors due to the above factors have been removed.

According to a fifth aspect of the present invention, in the second aspect of the invention, the maximum combustion pressure is detected based on the maximum value of the ion current value processed by the signal processing circuit, and the crank position at that time is detected. The maximum combustion pressure can be detected easily and with high accuracy from the ion current value from which disturbance factors such as mechanical vibrations have been removed, and this maximum combustion pressure and the crank indicating the maximum value are detected. By performing correction in ignition timing control or the like based on the position, stable combustion can be obtained, fuel efficiency and output can be improved, and exhaust emissions can be reduced.

According to a sixth aspect of the present invention, in the second aspect of the invention, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center. In addition to detecting the maximum value from the value, the crank position at that time is detected, the maximum combustion pressure is detected from the maximum value, and the crank position indicating the maximum combustion pressure is detected from the crank position indicating the maximum value. Therefore, the influence of other disturbance factors is lessened by the limited detection period of the ion current value, the maximum combustion pressure can be detected with high accuracy, and the maximum combustion pressure amount and the crank position indicating the maximum combustion pressure are determined. By performing correction in ignition timing control or the like based on the above, combustion is further optimized.

According to a seventh aspect of the present invention, in the second aspect, the relationship between the crank position indicating the maximum value of the ion current value processed by the signal processing circuit and the crank position indicating the maximum combustion pressure is determined. By mapping in advance, the crank position indicating the maximum combustion pressure can be easily estimated based on the map.

According to an eighth aspect of the present invention, in the third aspect of the invention, the amount of change in the ion current value processed by the signal processing circuit is integrated, and the knocking intensity is set based on the integrated value. Accordingly, the knocking strength can be set without being affected by disturbance such as mechanical vibration, and the presence or absence of knocking can be determined with high accuracy based on the knocking strength.

According to the ninth aspect of the present invention, in the third aspect of the invention, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center. Since the amount of change in the value is integrated and the knocking intensity is set based on this integrated value, knocking is performed by excluding other disturbance factors from the integrated value, since the detection section of the ion current value is limited. Therefore, the amount of change depending only on the disturbance of the ion current value due to the influence of the pressure vibration generated is integrated, and therefore, the knocking strength can be set with high accuracy based on the integrated value.

According to the tenth aspect, the third aspect is provided.
In the invention described, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, and the relationship between the value obtained by integrating the amount of change in the measured ion current value and the knocking intensity is mapped in advance. Thus, the knocking intensity can be easily estimated based on the map, and the calculation load on the control unit can be reduced correspondingly.

According to the eleventh aspect, according to the third aspect,
In the invention described in the above, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, and the knocking vibration having an envelope shape appears on the ion current waveform based on the measured ion current value. Is determined and the knocking strength is set based on the envelope shape, so that the presence or absence of knocking and the knocking strength can be grasped more accurately.

According to the twelfth aspect, the third aspect is provided.
In the invention described in the above, the ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, and the knocking vibration having an envelope shape appears on the ion current waveform based on the measured ion current value. By mapping the relationship between the type and the knocking intensity in advance, the knocking intensity can be accurately and easily estimated based on the map.

[Brief description of the drawings]

FIG. 1 is a block diagram of a combustion analyzer connected to an ignition system according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the same ion current detection circuit.

FIG. 3 is a circuit block diagram of the combustion analyzer.

FIG. 4 is a flowchart showing a routine for setting a maximum combustion pressure and a maximum combustion pressure crank position.

FIG. 5 is a flowchart showing a knocking strength setting routine.

FIG. 6 is a conceptual diagram of a map that stores a maximum combustion pressure crank position.

FIG. 7 is a conceptual diagram of a map for setting the knocking intensity.

FIG. 8 is a waveform diagram of the ion current processed by the low-pass filter.

FIG. 9 is a waveform diagram of the ion current processed by the high-pass filter.

FIG. 10 is a flowchart showing a knocking intensity setting routine according to a second embodiment of the present invention;

FIG. 11 is a conceptual diagram of a map for storing an envelope shape type and a map for storing knocking strength.

FIG. 12 is a main part configuration diagram of a combustion analysis device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Spark plug 4 ... Ion current detection circuit 5 ... Signal processing circuit 13, 15, 16, 17 ... Voltage conversion circuit 21 ... Primary processing circuit (low-pass filter) 22 ... Secondary processing circuit (high-pass filter) d (t) … Change amount (absolute amount of differential value) i… Ion current value imax… Maximum value KNKLEBEL… Knocking strength t3 to t5… Specific period Pmax… Maximum combustion pressure S… Integrated value θimax… Crank position indicating the maximum value θpmax… Maximum combustion Crank position indicating pressure

Claims (12)

[Claims] 1. An engine having an ion current detection circuit for applying an ion current detection voltage to a spark plug and detecting an ion current flowing when ions generated by a combustion reaction move to both electrodes of the ignition plug. An engine according to the combustion analyzer, further comprising a voltage conversion circuit that sets the ion current detection voltage applied to the spark plug to the ion current detection circuit during the spark discharge period and low during the period other than the spark discharge period. Combustion analyzer. 2. A signal processing circuit having a built-in primary processing circuit for passing only a component having a specific frequency or less of an ion current value output from the ion current detecting circuit is connected to the ion current detecting circuit. The combustion analysis device for an engine according to claim 1, wherein 3. A primary processing circuit for allowing the ion current detection circuit to pass only a component of an ion current value output from the ion current detection circuit which is lower than a specific frequency, and an ion output from the ion current detection circuit. 2. The combustion analysis device for an engine according to claim 1, wherein a signal processing circuit having a built-in secondary processing circuit for passing only a component of a current value equal to or higher than a specific frequency is connected. 4. The combustion analysis apparatus for an engine according to claim 2, wherein a maximum combustion pressure is detected based on a maximum value of an ion current value processed by said signal processing circuit. 5. The engine combustion according to claim 2, wherein the maximum combustion pressure is detected based on the maximum value of the ion current value processed by the signal processing circuit, and the crank position at that time is detected. Analysis device. 6. An ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, and a maximum value of the ion current value in the specific period is detected. 3. The combustion analysis of an engine according to claim 2, wherein a position is detected, a maximum combustion pressure is detected based on the maximum value, and a crank position indicating a maximum combustion pressure is detected from a crank position indicating a maximum value. apparatus. 7. A relationship between a crank position indicating a maximum value of an ion current value processed by the signal processing circuit and a crank position indicating a maximum combustion pressure is mapped in advance, and the crank position indicating a maximum combustion pressure is determined based on the map. 3. The combustion analysis device for an engine according to claim 2, wherein: 8. The combustion analysis device for an engine according to claim 3, wherein the knocking intensity is set based on the integrated value of the change amount of the ion current value processed by the signal processing circuit. 9. An ion current value processed by the signal processing circuit is measured at least in a specific period sandwiching the compression top dead center, a change amount of the ion current value in the specific period is integrated, and knocking is performed based on the integrated value. The engine combustion analysis device according to claim 3, wherein the intensity is set. 10. An ion current value processed by the signal processing circuit is measured at least in a specific period around a compression top dead center,
4. The combustion analysis device for an engine according to claim 3, wherein the relationship between the value obtained by integrating the change amount of the ion current value in the specific period and the knocking intensity is mapped in advance, and the knocking intensity is set based on the map. 11. A method for measuring an ion current value processed by the signal processing circuit at least in a specific period around a compression top dead center;
4. The engine according to claim 3, wherein it is determined whether or not a vibration having a specific envelope shape exists in the ion current waveform in the specific period based on the ion current value, and a knocking intensity is set based on the envelope shape. Combustion analyzer. 12. An ion current value processed by said signal processing circuit is measured at least in a specific period around a compression top dead center,
4. The engine combustion analysis according to claim 3, wherein the relationship between the type of envelope-shaped vibration existing in the measured ion current waveform and the knocking intensity is mapped in advance, and the knocking intensity is set based on the map. apparatus.