JP2914825B2 - Gasoline engine combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus for stably operating a gasoline engine for controlling the air-fuel ratio to a lean limit or a stoichiometric air-fuel ratio.

[0002]

2. Description of the Related Art In an automobile engine, there is an increasing demand for purifying exhaust gas and improving fuel efficiency. For this purpose, an ignition combustion state is detected for each cylinder of the engine, and the engine is near an air-fuel ratio lean limit. It is desirable to operate under operating conditions.
For this reason, a full-range air-fuel ratio sensor that combines the pump element and the oxygen sensor to detect the air-fuel ratio of the intake air-fuel mixture in the entire air-fuel ratio region based on the remaining oxygen amount and the flammable amount in the exhaust gas is used. Combustion control for burning is performed. Further, when the engine approaches the lean burn limit of stable combustion, fluctuations (variations) in the crank angular velocity (synonymous with the engine speed) and the peak value of the combustion pressure increase, and when the fluctuations exceed a certain value, the engine becomes smooth. It is known that difficult driving becomes difficult.

[0003]

However, in the combustion control using the full-range air-fuel ratio sensor, the ignition can be normally performed even in the leanest cylinder in consideration of the variation in the air-fuel ratio between the cylinders. In addition, since the air-fuel ratio must be controlled, there is a disadvantage that exhaust gas purification and fuel efficiency cannot be sufficiently improved. SUMMARY OF THE INVENTION It is an object of the present invention to provide a gasoline engine in which, in addition to air-fuel ratio feedback control using a full-range air-fuel ratio sensor based on detection of components in exhaust gas, the current density of ionic current flowing through a spark plug is limited to a lean air-fuel ratio limit operation. It is an object of the present invention to provide a combustion control device that detects an ion current density and operates a gasoline engine in a state close to the limit of stable operation for each cylinder based on the finding that the state varies greatly as the state approaches.

[0004]

According to a first aspect of the present invention, there is provided a combustion control apparatus for a gasoline engine according to the present invention, which is mounted on an exhaust passage of the engine and has a full range of an air-fuel ratio based on a residual oxygen amount and a flammable amount in the exhaust gas. A full-range air-fuel ratio sensor that detects the air-fuel ratio of the intake air-fuel mixture, backflow prevention means provided between the ignition coil of the secondary circuit of the ignition circuit and the spark plug, at a predetermined time after spark discharge at the spark plug. For a predetermined period of time, the primary circuit of the ignition coil is energized to generate an electromotive force in the secondary circuit to charge the floating capacitance of the spark plug to the ion current detection voltage generating means, and the secondary voltage between the electrodes of the spark plug is divided. A combustion state detection device comprising a voltage divider for compressing, a secondary voltage attenuation characteristic detection circuit connected to the voltage divider, and a determination circuit for determining the degree of change in the secondary voltage attenuation characteristic detected during the set period; Mind A fuel injection device provided in each, so that the provisional lean air-fuel ratio set in advance depending on the operating conditions,
While controlling the fuel injection amount from all the fuel injection devices while performing feedback control by the all-region air-fuel ratio sensor, the stable operation limit for each cylinder is detected by the combustion state detection device, and from each fuel injection device. A control circuit for adjusting the fuel injection amount to a lean air-fuel ratio that is close to the stable operation limit, and rewriting and controlling the provisional lean air-fuel ratio to a target lean air-fuel ratio determined by the limit lean air-fuel ratio of each cylinder. Consists of

According to a second aspect of the invention, there is provided a combustion control apparatus for a gasoline engine, wherein a control circuit performs feedback control by the full-range air-fuel ratio sensor so as to attain a target lean air-fuel ratio set in advance according to operating conditions. The total amount of fuel injection from all the fuel injection devices is controlled, and the operation state of each cylinder is detected by the combustion state detection device, and the amount of fuel injection from each fuel injection device is approximately equal to the operation state of each cylinder. Control.

According to a third aspect of the present invention, there is provided a combustion control apparatus for a gasoline engine, wherein the air-fuel ratio sensor detects the air-fuel ratio of the intake air-fuel mixture in the entire range of the air-fuel ratio from the residual oxygen amount and the flammable amount in the exhaust gas. An oxygen sensor that detects whether the area air-fuel ratio sensor is greater than or equal to the stoichiometric air-fuel ratio, and the control circuit performs feedback control by the air-fuel ratio sensor so that the intake air-fuel mixture becomes the stoichiometric air-fuel ratio. Controlling the total amount of fuel injection from all the fuel injection devices,
The operating state of each cylinder is detected by the combustion state detecting device, and the amount of fuel injected from each fuel injection device is controlled so that the operating state of each cylinder is substantially the same.

According to a fourth aspect of the present invention, a crank angular velocity sensor for detecting a change in the crank angular velocity of the engine (synonymous with the rotational speed of the engine) is provided in place of the full area air-fuel ratio sensor, and the control circuit detects the change in the crank angular velocity sensor. So that the range of the variation of the crank angular velocity becomes equal to or less than a certain value.
While performing feedback control of the air-fuel ratio of the intake air-fuel mixture to a provisional lean air-fuel ratio set in advance according to the operating conditions, the amount of fuel injection from all the fuel injection devices is controlled, and the stable operation limit for each cylinder is burned. Detected by the state detection device,
The fuel injection amount from each fuel injector is adjusted lean to the limit lean air-fuel ratio close to the stable operation limit, and the provisional lean air-fuel ratio is rewritten to the target lean air-fuel ratio determined by the limit lean air-fuel ratio of each cylinder. Control.

According to a fifth aspect of the present invention, a combustion pressure sensor in the cylinder of the engine is provided in place of the full range air-fuel ratio sensor, and the control circuit determines that the range of the variation in the combustion pressure detected by the combustion pressure sensor is equal to or less than a predetermined value. In such a manner, while controlling the air-fuel ratio of the intake air-fuel mixture to a provisional lean air-fuel ratio set in advance according to operating conditions, the amount of fuel injection from all the fuel injection devices is controlled, and stable operation of each cylinder is performed. The limit is detected by the combustion state detection device, the fuel injection amount from each fuel injection device is adjusted to be lean to the limit lean air-fuel ratio close to the stable operation limit, and the provisional lean air-fuel ratio is determined by the limit lean air-fuel ratio of each cylinder. The target lean air-fuel ratio is rewritten and controlled.

[0009]

According to the first aspect of the present invention, the gasoline engine is feedback-controlled to the provisional lean air-fuel ratio which is set to the lean side with a margin according to the operating conditions by using the full-range air-fuel ratio sensor. At the same time, a variation in the air-fuel ratio of each cylinder is detected by a combustion state detection device, and control is performed so that lean combustion is performed for each cylinder to the limit of normal ignition. According to the second aspect of the present invention, the gasoline engine is feedback-controlled to the target lean air-fuel ratio set in accordance with the operating conditions using the full-range air-fuel ratio sensor, and the variation in the operating state of each cylinder is reduced by the combustion state. The detection is performed by the detection device, and only the variation between the cylinders is adjusted. According to the third aspect of the present invention, the gasoline engine is feedback-controlled to the stoichiometric air-fuel ratio by using the full-range air-fuel ratio sensor or the oxygen sensor that detects whether the air-fuel ratio λ is 1 or more, and operates each cylinder. The variation in the state is detected by the combustion state detecting device, and only the variation between the cylinders is adjusted.

[0010] In the invention according to claim 4, the provisional lean air-fuel ratio of the gasoline engine is set to a lean side with a margin according to the operating conditions by taking advantage of the fact that the variation in the crank angular speed increases as the lean burn occurs. In addition to the feedback control, the variation in the air-fuel ratio of each cylinder is detected by a combustion state detection device, and control is performed so that lean combustion is performed for each cylinder to the limit of normal ignition. According to the fifth aspect of the invention, the gasoline engine is provided with a provisional lean air-fuel ratio set on the lean side with a margin according to the operating conditions by utilizing the fact that the variation in the combustion pressure of the cylinders increases as the leaner the combustion. Along with the feedback control, a variation in the air-fuel ratio of each cylinder is detected by a combustion state detection device, and control is performed so that lean combustion is performed for each cylinder to the limit of normal ignition.
Thereby, in the steady operation and the warm-up operation, the exhaust gas purification and the improvement of the fuel efficiency can be achieved at the same time.

[0011]

FIG. 1 is a schematic diagram showing the configuration of a gasoline engine 100. An exhaust gas passage 200 is provided with an air-fuel ratio sensor 201 for all regions, and an intake passage 300 is provided with a fuel injection device 3 for each cylinder.
01 is attached. 400 indicates an ignition device,
The apparatus includes an ignition coil 1, a distributor (distributor) 2, and a spark plug 3, and a combustion state detection device 500 is provided. The whole-range air-fuel ratio sensor 201 has a known configuration, and combines a pump element and an oxygen sensor to detect the air-fuel ratio of the intake air-fuel mixture in the whole range of the air-fuel ratio from the remaining oxygen amount and combustible amount in the exhaust gas. . The primary circuit 11 of the ignition coil 1 is connected to the vehicle power supply V and the primary current interrupting means 4, and the secondary circuit 12 is connected to the spark plug 3 via the power distributor 2. A backflow prevention diode 22 is inserted between the secondary coil L of the ignition coil 1 and the rotor gap 21 of the power distributor 2.

The combustion state detecting device 500 includes a backflow prevention diode 22 provided between the ignition coil 1 of the secondary circuit 12 of the ignition circuit and the rotor gap 21, an ion current detection voltage generating means described later, and a rotor gap 21. A voltage divider 5 is provided in the secondary circuit 12 between the spark plug 3 and the spark discharge gap of the spark plug 3 and divides a secondary voltage between the electrodes of the spark plug 3. In this embodiment, the primary current interrupting means 4 also serves as an ion current detection voltage generating means,
At a predetermined time after the spark discharge from the spark plug 3, the primary circuit 11 of the ignition coil 1 is energized for a predetermined time and the secondary circuit 1
2 generates an electromotive force to charge the floating capacitance of the spark plug 3. Further, a secondary voltage attenuation characteristic detection circuit 6 is connected to the voltage divider 5, and the attenuation characteristic detection circuit 6
A control circuit 7 such as a microcomputer including a determination unit for determining the degree of variation (variation) of the attenuation characteristic of the secondary voltage detected during the set period is connected.

The primary current interrupting means (ion current detection voltage generating means) 4 comprises a switch element 41 and a signal generator 42, detects the crank angle and the throttle opening of the engine, and determines the spark discharge timing based on the load and rotation speed of the engine. The primary current is interrupted so that the ignition advance angle is adapted to The voltage divider 5 has a high impedance element 51 arranged close to the secondary circuit 12 of the ignition coil 1 and a low impedance element 52 connected between the high impedance element 51 and the ground.

In this embodiment, the voltage divider 5 is composed of a conductor provided as the high impedance element 51 so as to generate a capacitance of about 1 pF (picofarad) between the high voltage lead of the secondary circuit 12 and the high voltage lead. Is used, a capacitor having a capacitance of 3000 pF is used as the low impedance element 52, and the secondary voltage generated in the secondary circuit 12 is set to 1
/ Partial pressure to about 3000. In this case, the capacitor (5
When a 2 Mohm resistor (not shown) forming a discharge circuit is connected in parallel to 2), the time constant of the voltage divider 5 becomes 6 ms (millisecond), and a relatively long decay time of 3 ms described later can be reliably determined. it can. As a result, a high voltage waveform of up to about 30,000 volts is reduced to a level of 10 volts, and is input to the secondary voltage attenuation characteristic detecting circuit 6.

The secondary voltage attenuation characteristic detecting circuit 6 includes a peak hold circuit 61 to which the voltage divided by the voltage divider 5 is input, a voltage divider circuit 62 of the output of the peak hold circuit 61, and a voltage divider of the voltage divider circuit 62. The comparator 63 compares the (reference voltage) with the output of the voltage divider 5 and generates a pulse output. The comparator 63 detects the duration of a voltage of a certain level or more in the divided secondary voltage waveform.

The control circuit 7 provides a provisional lean mixture in which the mixture ratio (air-fuel ratio) of air and fuel supplied to the engine 100 is set based on data stored in a storage device previously calculated or measured according to operating conditions. The fuel injection amount from all the fuel injection devices 301 is controlled while performing feedback control by the full-range air-fuel ratio sensor 201 so that the air-fuel ratio is obtained, and the stable operation limit for each cylinder is determined by the combustion state detection device 500. Detected and each fuel injection device 3
The fuel injection amount from 01 is adjusted so as to be lean to the limit lean air-fuel ratio close to the stable operation limit of the cylinder, and the provisional lean air-fuel ratio is set to the target lean air-fuel ratio determined by the limit lean air-fuel ratio of each cylinder. Rewrite to control.

The operation will be described with reference to FIG. Control circuit 7
Is a provisional air-fuel ratio leaner than the stoichiometric air-fuel ratio set on the safe side (rich side) in consideration of the air-fuel ratio variation between cylinders,
For example, the fuel injection device 30 is set to have an air-fuel ratio of 20: 1.
The fuel supply amount from the engine 1 is adjusted, and the combustion of the engine 100 is controlled. This air-fuel ratio is detected by the full-range air-fuel ratio sensor 201 and is subjected to feedback control so that there is no difference from the target value.

The operation of the combustion state detecting device 500 for adjusting the air-fuel ratio of each cylinder to the limit lean air-fuel ratio close to the limit at which normal ignition and combustion are possible for each cylinder is performed as follows. A pulse signal for interrupting the primary current shown by the signal generator 42 is output, and a primary current such as shown in FIG. The pulse wave a having a large width h is an ignition pulse for generating a spark discharge in the spark plug 3, and 0.5 to
The small pulse wave b delayed by the delay time i of about 1.5 ms is a detection pulse for charging the floating capacitance of the spark plug 3 and using it as an ion current detection power supply.

The interruption of the primary current causes the secondary circuit 12
A secondary voltage shown in FIG. The spark discharge starts due to the high voltage p generated at the end of the pulse wave a, followed by a gentle voltage waveform q due to the induction discharge. Next, corresponding to the pulse wave b,
The secondary circuit 12 has a back electromotive force waveform r followed by a waveform s
Appears. The re-boost level of the secondary voltage can be set to a desired level by the delay time i and the width of the pulse wave b. In the present invention, the level of the waveform s is set to 4 to 6 so that the dielectric breakdown of the rotor gap 21 is possible and the discharge is impossible in the spark discharge gap of the spark plug 3.
Set to kilovolts.

The backflow prevention diode 22 is configured so that the charge of 3 to 5 kV stored in the capacitance of the spark plug 3 jumps over the rotor gap 21 and ignites the ignition coil 1.
Back to the side to prevent it from dropping to 2-3 kilovolts. Thereby, the rotor gap 21 of the distributor 2
Between the spark plug 3 and the spark discharge gap of the spark plug 3, mainly the capacitance (typically 10 to 20 pF) of the spark plug 3
A charge of ~ 5 kV is charged.

This charge voltage is discharged as an ionic current and attenuated. As shown in FIG. 2, when the air-fuel ratio is close to the stoichiometric air-fuel ratio of about 15: 1, the discharge current is represented by a waveform s _2. Small variation in waveform width. In contrast,
Air-fuel ratio is the ignition limit 23: as waveforms s ₁ As the 1, variations in the width of the discharge current waveform becomes very large. The degree of this variation is detected by the attenuation characteristic detection circuit 6 as follows. From the output waveform of the voltage divider 5, the peak value of the charging voltage is held by a peak hold circuit 61 and divided by a voltage dividing circuit 62 to, for example, 1/3 of the level. And the comparator 63 compares the output waveform.

As shown in FIG. 2, the output pulse of the comparator 63 detects the time of the secondary voltage equal to or higher than the reference voltage v and outputs pulse waves t _{1 to} t ₄ to the control circuit 7. The pulse waves t ₂ and t ₄ indicate variations in the decay time of the charge. That is, the variation of the pulse wave t ₂ near the limit of the stable operation is large. The control circuit 7 controls, for example, ten consecutive pulse waves t ₂ of the pulse wave t ₂ for each cylinder.
The variation amount from the reference value of ₂ is integrated, and when the integrated amount is equal to or more than a certain value, it is determined that the limit of stable operation is near. The fuel supply by the fuel injection device 301 is adjusted based on this discrimination information, and the stable operation near the lean limit of the air-fuel ratio is executed for each cylinder. The control circuit 7 has a provisional lean air-fuel ratio of 20: 1.
Is rewritten to a target lean air-fuel ratio (for example, 22: 1) determined by the sum of the limit lean air-fuel ratios of the cylinders, and the total fuel injection amount from the fuel injection device 301 is controlled.

The combustion control according to the second aspect is performed as follows. The control circuit 7 sets the target lean air-fuel ratio to the set mixture ratio (air-fuel ratio) of air and fuel to be supplied to the engine 100 based on data stored in a storage device previously calculated or measured according to the operating conditions. In such a manner, the total amount of fuel injection from all the fuel injection devices 301 is controlled while performing feedback control by the full area air-fuel ratio sensor 201.

[0024] Along with this, detects a variation in air-fuel ratio for each cylinder in the combustion state detecting device 500, it integrates the variation amount from the reference value of the pulse wave t ₂ of each cylinder, variations among the cylinders Each fuel injection device 30
The fuel injection amount from 1 is controlled. Thereby, the variation in the air-fuel ratio of each cylinder is reduced, and the cylinders can be operated under substantially the same conditions.

That is, the control circuit 7 controls all the fuel injection devices so that the target lean air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio preset in consideration of the air-fuel ratio variation among the cylinders, for example, the air-fuel ratio of 22: 1. The combustion control of the engine 100 is performed by adjusting the total amount of fuel supply from the engine 301. This target air-fuel ratio is detected by the full-range air-fuel ratio sensor 201 and is subjected to feedback control so as not to cause a difference from the target value. At the same time, the combustion state detection device 500 detects and adjusts only the variation between cylinders without changing the total fuel supply amount.

In the above embodiment, the case where the gasoline engine is operated at the limit of the lean air-fuel ratio has been described. However, the air-fuel ratio control during the warm-up operation at the time of the cold start is the same as the above. It is possible to control the air-fuel ratio close to the limit. In this case, since the warm-up combustion control is performed, the apparent air-fuel ratio is controlled to a rich side such as 13: 1. In this warm-up air-fuel ratio control, purification of exhaust gas and improvement of fuel efficiency can be achieved.

The theoretical combustion control according to the third aspect will be described with reference to FIG. The control circuit 7 of the present invention uses the full-range air-fuel ratio sensor 201 or an oxygen sensor that utilizes the fact that the oxygen concentration in the exhaust gas increases on the leaner side than the stoichiometric air-fuel ratio and the sensor output voltage sharply decreases. Feedback control is performed by controlling the total amount of fuel injection from all the fuel injection devices 301 so that the mixture ratio of air and fuel (air-fuel ratio) becomes the stoichiometric air-fuel ratio. For this reason, the variation in the damping characteristics of each cylinder is small. For example, as shown in FIG. Since the variation amount is significantly smaller than that of the combustion control of the second aspect, it is necessary to sufficiently increase the detection accuracy for the variation in the damping characteristics of each cylinder.

At the same time as the feedback control, the variation in the air-fuel ratio of each cylinder is detected by the combustion state detecting device 500. In this case, by integrating the variation amount from the amount of variation and the pulse wave t ₆ from the pulse wave t _5, to control the fuel injection amount from the fuel injector 301 such that the variation between these cylinders is reduced. Thereby, the conditions for each cylinder can be brought close to the details under the same condition closer to the stoichiometric air-fuel ratio. The combustion state detection device 500 includes:
With the total fuel supply unchanged, only the variation between cylinders
The degree of variation (pulse waves t ₅ , t ₆ ) of the decay characteristic of the electric charge charged to the floating capacitance of the spark plug of each cylinder is detected and adjusted.

This combustion control is a method of returning a part of the exhaust gas to the intake system again and adding it to the air-fuel mixture.
R) can also be used effectively. If the EGR rate varies from cylinder to cylinder, EGR is performed to ensure engine operation stability.
The rate could not be increased to the limit. In order to increase the EGR rate to near the limit, the variation of each cylinder is detected, and the EGR amount for each cylinder is controlled, whereby effective EGR can be performed.

In the start-up warm-up operation, the supplied fuel must be increased to compensate for the shortage of the vaporization rate by increasing the amount of fuel supplied in order to lower the vaporization rate of gasoline at low temperatures. That is, it is necessary to increase the apparent air-fuel ratio at the time of starting as the temperature becomes lower, so that the actual air-fuel mixture becomes in the flammable range. Further, even when the engine is started, it is necessary to reduce the air-fuel ratio in accordance with the warm-up state. For this reason, according to the combustion control device of the present invention, the air-fuel ratio that varies for each cylinder can be adjusted to the optimum air-fuel ratio in accordance with the temperature and the warm state of the engine.

In the present invention, a current is caused to flow through the primary circuit 11 at a predetermined timing, and the ion current detection voltage generating means may be provided separately from the primary current interrupting means 4. In the distributor-less igniter (DLI), a backflow prevention diode normally mounted to prevent the occurrence of spark discharge other than the ignition timing performs its function.

The polarity of the ignition coil 1 can be either positive or negative, and the polarity of the secondary voltage shown in FIG. 2 can be negative, but positive can improve the detection accuracy at the time of measurement. Further, the generation timing of the detection pulse is based on the crank angle of the engine, for example, ATD.
When the angle is set to C10 °, the accuracy with respect to changes in operating conditions such as the rotation speed of the engine can be improved.

The combustion state detecting device 500 according to claim 4
Will be described with reference to FIG. 4 and FIG. In the present invention,
1. Instead of the full-range air-fuel ratio sensor 201 in FIG.
And a crank angular speed sensor 8 for detecting the crank angular speed of the engine as shown in FIG. The crank angular speed of the engine is shown in FIG.
As shown in the figure, the smaller the air-fuel ratio of the intake air-fuel mixture becomes, the larger the variation becomes. If the air-fuel ratio A / F exceeds 22, the engine cannot be operated stably. The control circuit 7 controls the lean air-fuel ratio (for example, A) to allow the crank angular speed sensor 8 to change the crank angular speed within a certain range and perform stable operation of the engine.
/ F = 20), taking into account the variation in air-fuel ratio between cylinders,
Set as the provisional lean air-fuel ratio with a margin. Next,
The stable operation limit of each cylinder is detected by the combustion state detection device 500, and the fuel injection amount from each fuel injection device 301 is adjusted to be lean to the limit lean air-fuel ratio close to the stable operation limit. Rewriting and controlling the target lean air-fuel ratio determined by the limit lean air-fuel ratio of each cylinder is the same as in the above embodiment.

A combustion state detecting device 500 according to claim 5.
Will be described with reference to FIGS. 6 and 7. FIG. In the present invention,
Instead of the crank angular velocity sensor 8, a combustion pressure sensor 9 for detecting the combustion pressure in the cylinder is provided as shown in FIG. As shown in FIG. 7, the combustion pressure in the cylinder varies greatly as the air-fuel ratio of the intake air-fuel mixture becomes leaner.
When / F exceeds 22, stable operation of the engine cannot be achieved.
The control circuit 7 determines a lean air-fuel ratio (for example, A / F = 20) at which the fluctuation of the crank angular velocity is within a certain range by the combustion pressure sensor 9 and the engine can be operated stably, in consideration of the variation of the air-fuel ratio between cylinders. , With a margin, set as the provisional lean air-fuel ratio. Next, the stable operation limit of each cylinder is detected by the combustion state detection device 500, and the fuel injection device 301
It is necessary to adjust the fuel injection amount from the target lean air-fuel ratio to a limit lean air-fuel ratio close to the stable operation limit, and rewrite and control the provisional lean air-fuel ratio to a target lean air-fuel ratio determined by the limit lean air-fuel ratio of each cylinder. , Are the same as in the above embodiment. The combustion pressure sensor 9 is incorporated in a spark plug,
A known sensor of the pressure sensor plug type independent of the spark plug can be used.

[Brief description of the drawings]

FIG. 1 is an ignition circuit diagram of a gasoline engine equipped with a combustion state detecting device of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the combustion state detecting device.

FIG. 3 is a waveform diagram for explaining the operation of the combustion state detecting device.

FIG. 4 is an ignition circuit diagram showing a combustion state detection device according to a fourth embodiment.

FIG. 5 is a waveform chart showing crank angle fluctuation.

FIG. 6 is an ignition circuit diagram showing a combustion state detecting device according to claim 5;

FIG. 7 is a waveform diagram showing a change in combustion pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Distributor 3 Spark plug 4 Primary current intermittent means (ion current detection voltage generating means) 5 Voltage divider 6 Damping characteristic detection circuit 7 Control circuit 8 Crank angle sensor 9 Combustion pressure sensor 12 Secondary circuit 22 Backflow prevention diode (Backflow prevention means) 100 Gasoline engine 200 Exhaust path 300 Intake path 400 Ignition device 500 Combustion state detection device 201 Full-range air-fuel ratio sensor 301 Fuel injection device

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuo Ito 14-18, Takatsuji-cho, Mizuho-ku, Nagoya Japan Special Ceramics Co., Ltd. (56) References JP-A-60-187724 (JP, A) JP-A Sho 59-46352 (JP, A) JP-B-60-50973 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-41/40 F02D 45/00 362 F02P 17 / 00

Claims (5)

(57) [Claims] An ignition circuit for detecting an air-fuel ratio of an intake air-fuel mixture in an entire air-fuel ratio region based on a residual oxygen amount and a flammable amount in exhaust gas; Backflow prevention means provided between the ignition coil of the next circuit and the spark plug, for a predetermined time at a predetermined time after spark discharge in the spark plug,
Ion current detection voltage generating means for energizing the primary circuit of the ignition coil and generating an electromotive force in the secondary circuit to charge the floating capacitance of the spark plug, a voltage divider for dividing the secondary voltage between the electrodes of the spark plug A combustion state detection device comprising: a secondary voltage attenuation characteristic detection circuit connected to the voltage divider; and a determination circuit for determining the degree of variation of the secondary voltage attenuation characteristic detected during the set period. The fuel injection device provided, while controlling the fuel injection amount from all the fuel injection devices while performing feedback control by the full-range air-fuel ratio sensor so that the provisional lean air-fuel ratio is set in advance according to the operating conditions. The stable operation limit of each cylinder is detected by the combustion state detection device, and the fuel injection amount from each fuel injection device is adjusted lean to a limit lean air-fuel ratio close to the stable operation limit, Serial combustion control device for a gasoline engine comprising a provisional lean air-fuel ratio and a control circuit for controlling rewriting the target lean air-fuel ratio which is determined by limiting lean air-fuel ratio of each cylinder. 2. The control circuit according to claim 1, wherein the control circuit performs feedback control by the full-range air-fuel ratio sensor so as to attain a target lean air-fuel ratio set in advance according to an operating condition. Combustion of a gasoline engine that controls the total amount of fuel injection, detects the operating state of each cylinder with a combustion state detector, and controls the amount of fuel injected from each fuel injector so that the operating state of each cylinder is comparable Control device. 3. The air-fuel ratio sensor according to claim 1, wherein the air-fuel ratio sensor detects the air-fuel ratio of the intake air-fuel mixture in the entire air-fuel ratio region from the remaining oxygen amount and the flammable amount in the exhaust gas. Or an oxygen sensor that detects whether or not the stoichiometric air-fuel ratio is greater than or equal to. In addition to controlling the total amount of fuel injection, the operating state of each cylinder is detected by a combustion state detector, and the amount of fuel injected from each fuel injector is controlled so that the operating state of each cylinder is substantially the same. Combustion control device. 4. A crank angular velocity sensor according to claim 1, further comprising: a crank angular velocity sensor for detecting a change in crank angular velocity of the engine, instead of the full area air-fuel ratio sensor; While controlling the air-fuel ratio of the intake air-fuel mixture to a provisional lean air-fuel ratio set in advance according to the operating conditions while controlling the fuel injection amount from all the fuel injection devices, The stable operation limit of each cylinder is detected by the combustion state detection device, and the fuel injection amount from each fuel injection device is adjusted lean to the limit lean air-fuel ratio close to the stable operation limit, and the provisional lean air-fuel ratio of each cylinder is adjusted. A combustion control device for a gasoline engine that rewrites and controls a target lean air-fuel ratio determined by a limit lean air-fuel ratio. 5. A combustion pressure sensor according to claim 1, further comprising a combustion pressure sensor in the cylinder of the engine instead of the full range air-fuel ratio sensor, wherein the control circuit has a range of variation of the combustion pressure detected by the combustion pressure sensor which is equal to or less than a predetermined value. While controlling the air-fuel ratio of the intake air-fuel mixture to the provisional lean air-fuel ratio set in advance according to the operating conditions, the amount of fuel injection from all the fuel injection devices is controlled, and the stability of each cylinder is controlled. The operating limit is detected by the combustion state detecting device, and the fuel injection amount from each fuel injection device is adjusted to be lean to the limit lean air-fuel ratio close to the stable operating limit, and the provisional lean air-fuel ratio is set to the limit lean air-fuel ratio of each cylinder. A combustion control device for a gasoline engine that controls by rewriting to a target lean air-fuel ratio determined by the following equation.