JPH10110647A - Combustion control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve combustion in each cylinder and reduce an NOx discharging ratio without deteriorating fuel consumption ratio. SOLUTION: A mean temperature of gas inside cylinders are calculated in every specified crank angle based on a signal from an inner-cylinder pressure sensor 16 arranged on each cylinder (22). A maximum value of the inner-cylinder gas mean temperature is sensed (23). The maximum value is compared to an permission value which is set through map reference with engine conditions as parameters (26). When the maximum value exceeds the permission value, an ignition timing is retarded (27, 28). The combustion highest temperature in that cylinder is reduced for decreasing an NOx discharging ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for improving the combustion state and reducing the fuel consumption rate without reducing nitrogen oxides (NO
The present invention relates to an engine combustion control device for reducing x).

[0002]

2. Description of the Related Art Conventionally, various technologies for improving fuel efficiency by improving combustion speed or thermal efficiency of an engine mounted on an automobile or the like have been proposed.

As a technique for improving the combustion speed, for example, Japanese Patent Application Laid-Open No. 61-250354 or Japanese Patent Application Laid-Open
As disclosed in Japanese Patent No. 59573, a swirl flow (horizontal swirling flow orthogonal to the cylinder axis) and a tumble flow (vertical swirling along the cylinder axis) There is known a technique of increasing the combustion speed by strengthening the flow rate. In this prior art, the shape of the intake port is formed so that a swirl flow or a tumble flow is easily generated, and a valve for controlling the generation of a swirl flow or a tumble flow is interposed in the intake port. Swirl flow,
Alternatively, a tumble flow is generated to improve the mixture formation and promote the turbulence of the mixture.

As a technique for improving thermal efficiency, an engine incorporating a variable compression ratio mechanism for varying a compression ratio in a cylinder, or a variable valve timing mechanism for varying intake timing or exhaust timing in accordance with an operation range is used. Embedded engines are known. According to this prior art, the actual compression ratio is varied according to the operating range,
The theoretical thermal efficiency can be improved, and knocking can be effectively avoided.

[0005] Further, as another technique for improving the thermal efficiency, the air-fuel ratio is made lean according to the operating range or the amount of exhaust gas recirculation (EGR) is increased to reduce the pumping loss, thereby reducing the specific heat ratio. There are known techniques for improving thermal efficiency as a result.

[0006]

Each of the above-mentioned prior arts is effective in improving the fuel consumption rate, but the maximum pressure and the maximum temperature of the in-cylinder gas increase due to rapid combustion. And, as a result, nitrogen oxides (NO
The emission rate of x) increases.

[0007] As a countermeasure, in various engine controls such as fuel injection control and ignition timing control, each control value is set at a level at which the NOx emission rate is not increased. Environmental changes,
Alternatively, there is a case where NOx is discharged at a level higher than the assumed NOx discharge level due to a change over time of each sensor or actuator.

In general, it is known that the generation of NOx increases rapidly when the temperature of the combustion gas exceeds a certain temperature (for example, 2000 K). Therefore, various techniques have been proposed for suppressing the increase in the temperature of the combustion gas to reduce the NOx emission rate.

For example, Japanese Patent Application Laid-Open No. 1-80749 discloses that in a region where the combustion temperature is high, the air-fuel ratio is set to the rich side, the fuel injection amount is increased, and the combustion temperature is lowered by the latent heat of vaporization of the fuel. Thus, a technique for reducing the NOx emission rate has been disclosed.

[0010] However, if the air-fuel ratio is made rich in order to reduce the NOx emission rate, the fuel consumption rate is correspondingly deteriorated and the economic efficiency is impaired.

Japanese Patent Application Laid-Open No. 3-149332 discloses that
The air-fuel ratio is variably set in accordance with the intensity of the combustion light to suppress an increase in the combustion speed when the combustion chamber is at a high temperature.
A technique for reducing the emission rate is disclosed.

However, in this prior art, the correlation between the combustion light and the in-cylinder gas temperature is not clearly shown, which is not only technically problematic, but also provides a window for detecting the combustion light on the wall surface of the combustion chamber. The window must be formed, and there is a problem in durability, and the window is easily stained by the combustion gas, which is poor in practicality.

The present invention has been made in view of the above circumstances, and has as its object to provide an engine combustion control device that can reduce the NOx emission rate without deteriorating the fuel consumption rate.

[0014]

In order to achieve the above object, a first engine combustion control apparatus according to the present invention comprises at least an in-cylinder pressure detected by an in-cylinder pressure detecting means, a crank angle detected by a crank angle detecting means, and a suction angle. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the intake air amount and the fuel injection amount detected by the air amount detecting means; Maximum value detection means for detecting a maximum value of the in-cylinder gas average temperature; maximum value comparison means for comparing the maximum value with a first allowable value set based on an engine operating state; Ignition timing correction value setting means for setting a retardation correction value for retarding the ignition timing of the cylinder when the ignition timing is equal to or more than a first allowable value;
An ignition timing setting means for correcting an ignition timing with at least the ignition timing correction value to set a final ignition timing.

The second engine combustion control apparatus according to the present invention is characterized in that at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detecting means; maximum value comparing means for comparing the maximum value with a first allowable value set based on the engine operating state; and empty value of the cylinder when the maximum value is equal to or greater than the first allowable value. Air-fuel ratio correction value setting means for setting an air-fuel ratio correction value for making the fuel ratio lean, and fuel injection amount setting means for correcting the fuel injection amount at least with the air-fuel ratio correction value to set a final fuel injection amount. Be prepared The features.

A third engine combustion control apparatus according to the present invention is characterized in that at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detecting means; maximum value comparing means for comparing the maximum value with a first allowable value set based on the engine operating state; and empty value of the cylinder when the maximum value is equal to or greater than the first allowable value. Air-fuel ratio correction value setting means for setting an air-fuel ratio correction value for making the fuel ratio lean, and fuel injection amount setting means for correcting a fuel injection amount at least with the air-fuel ratio correction value to set a final fuel injection amount, Above cylinder Combustion variation rate calculating means for calculating the indicated mean effective pressure based on the signal from the detection means and calculating the variation rate of the indicated mean effective pressure; and the combustion variation rate when the combustion is performed by the combustion injection amount corrected by the air-fuel ratio correction value. A combustion fluctuation rate comparison means for comparing the combustion fluctuation rate with a second allowable value set based on the engine operating state; and retarding the ignition timing of the cylinder when the combustion fluctuation rate is equal to or higher than the second allowable value. Ignition timing correction value setting means for setting a retardation correction value to be corrected; and ignition timing setting means for correcting an ignition timing with at least the retardation correction value to set a final ignition timing. .

According to a fourth aspect of the present invention, there is provided a combustion control apparatus for an engine, comprising at least an in-cylinder pressure detected by an in-cylinder pressure detecting means, a crank angle detected by a crank angle detecting means, and an intake air amount detected by an intake air amount detecting means. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detection means, maximum value comparison means for comparing the maximum value with a first allowable value set based on the engine operating state, and exhaust gas recirculation when the maximum value is equal to or greater than the first allowable value Exhaust gas recirculation amount correction value setting means for setting an exhaust gas recirculation amount correction value for increasing the amount; and correcting the final exhaust gas recirculation amount by correcting the exhaust gas recirculation amount with at least the exhaust gas recirculation amount correction value. Circulation amount Characterized in that it comprises an exhaust gas recirculation amount setting means for constant.

According to a fifth aspect of the present invention, there is provided a combustion control apparatus for an engine, comprising at least an in-cylinder pressure detected by an in-cylinder pressure detecting means, a crank angle detected by a crank angle detecting means, an intake air amount detected by an intake air amount detecting means, and a fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detection means, maximum value comparison means for comparing the maximum value with a first allowable value set based on the engine operating state, and exhaust gas recirculation when the maximum value is equal to or greater than the first allowable value Exhaust gas recirculation amount correction value setting means for setting an exhaust gas recirculation amount correction value for increasing the amount; and correcting the final exhaust gas recirculation amount by correcting the exhaust gas recirculation amount with at least the exhaust gas recirculation amount correction value. Circulation amount An exhaust gas recirculation amount setting means for calculating the indicated average effective pressure based on a signal from the in-cylinder pressure detecting means, and a combustion fluctuation rate calculating means for calculating a fluctuation rate of the indicated average effective pressure; A combustion fluctuation rate comparison that compares the combustion fluctuation rate when the exhaust gas recirculation amount corrected by the circulation amount correction value is supplied into the cylinder and is burned with a second allowable value set based on an engine operating state. Means, ignition timing correction value setting means for setting a retardation correction value for retarding the ignition timing of the cylinder when the combustion fluctuation rate is equal to or greater than the second allowable value, and ignition at least with the retardation correction value Ignition timing setting means for correcting the timing and setting the final ignition timing.

A sixth engine combustion control apparatus according to the present invention is characterized in that at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detection means; maximum value comparison means for comparing the maximum value with a first allowable value set based on the engine operating state; and gas in the cylinder when the maximum value is equal to or greater than the first allowable value. Valve correction amount setting means for setting a valve correction amount for correcting the opening of the gas flow generating valve for generating the flow in a direction in which the vortex is weakened, and correcting the opening of the gas flow generating valve with at least the valve correction amount Characterized in that it comprises a opening setting means for setting the opening degree of the final the gas flow generator valve Te.

According to a seventh aspect of the present invention, there is provided a combustion control apparatus for an engine, wherein at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detecting means, maximum value comparing means for comparing the maximum value with a first allowable value set based on the engine operating state, and provided in each cylinder when the maximum value is equal to or greater than the first allowable value. Compression ratio correction value setting means for setting a compression ratio correction value for correcting the compression ratio variable means in the direction of decreasing the compression ratio; and correcting the operation amount of the compression ratio variable means with at least the compression ratio correction value to obtain a final value. Target Characterized in that it comprises an operation amount setting means for setting the operation amount of Chijimihi varying means.

According to an eighth aspect of the present invention, there is provided an engine combustion control apparatus comprising at least an in-cylinder pressure detected by an in-cylinder pressure detecting means, a crank angle detected by a crank angle detecting means, an intake air amount detected by an intake air amount detecting means, and a fuel. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature from an intake valve closing time to an exhaust valve opening time based on the injection amount; and detecting a maximum value of the in-cylinder gas average temperature in one cycle. Maximum value detecting means; maximum value comparing means for comparing the maximum value with a first allowable value; and opening / closing timing of an intake valve or an exhaust valve when the maximum value is equal to or greater than the first allowable value. Valve timing correction amount setting means for setting a valve timing correction amount for correcting the operation amount of the valve timing variable means for reducing the effective compression ratio; Characterized in that at timing correction amount and a valve timing setting means for setting a final valve timing to correct the operation amount of the variable valve timing means.

In the first engine combustion control device, at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, the fuel injection amount, and the like. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state, and when the maximum value is equal to or greater than the first allowable value, the ignition timing of the next combustion of the cylinder is delayed. A retard correction value to be corrected in the angular direction is set, and the ignition timing set based on the engine operating state is corrected with the retard correction value.

In the combustion control device for the second engine, at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state. When the maximum value is equal to or greater than the first allowable value, the air-fuel ratio of the cylinder at the next combustion is leaned. An air-fuel ratio correction value to be changed is set, and the fuel injection amount set based on the engine operating state is lean-corrected with the air-fuel ratio correction value.

In the third engine combustion control device, at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, the fuel injection amount, and the like. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state. When the maximum value is equal to or greater than the first allowable value, the air-fuel ratio of the cylinder at the next combustion is leaned. An air-fuel ratio correction value to be changed is set, and the fuel injection amount set based on the engine operating state is lean-corrected with the air-fuel ratio correction value. On the other hand, the indicated mean effective pressure is calculated based on the signal from the in-cylinder pressure detecting means, and the fluctuation rate of the indicated mean effective pressure is calculated.
Then, the combustion variation rate when the fuel is burned by the fuel injection amount corrected by the air-fuel ratio correction value for leaning the air-fuel ratio is compared with a second allowable value set based on the engine operating state. When the fluctuation rate is equal to or greater than the second allowable value, a retard correction value for retarding the next ignition timing of the cylinder is set, and the ignition timing is set based on the engine operating state using the retard correction value. Is retarded.

The fourth engine combustion control apparatus includes at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state, and when the maximum value is equal to or greater than the first allowable value, the amount of exhaust gas recirculated during the next combustion of the cylinder. The exhaust gas recirculation correction value is set to increase the exhaust gas recirculation amount, and the exhaust gas recirculation amount set based on the engine operating state is corrected by the exhaust gas recirculation correction value.

The fifth engine combustion control apparatus comprises at least an in-cylinder pressure detected by the in-cylinder pressure detecting means, a crank angle detected by the crank angle detecting means, an intake air amount detected by the intake air amount detecting means, and a fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state, and when the maximum value is equal to or greater than the first allowable value, the amount of exhaust gas recirculated during the next combustion of the cylinder. The exhaust gas recirculation correction value is set to increase the exhaust gas recirculation amount, and the exhaust gas recirculation amount set based on the engine operating state is corrected by the exhaust gas recirculation correction value. On the other hand, the indicated average effective pressure is calculated based on the signal from the in-cylinder pressure detecting means, and the fluctuation rate is calculated from the indicated average effective pressure. Then, the combustion fluctuation rate when the increased amount of exhaust gas recirculated is supplied into the cylinder and burned is compared with a second allowable value set based on the engine operating state. Is greater than or equal to the second allowable value, a retard correction value for retarding the next ignition timing of the cylinder is set, and the ignition timing set based on the engine operating state is retarded by the retard correction value. Correct the angle.

The sixth engine combustion control apparatus comprises at least an in-cylinder pressure detected by the in-cylinder pressure detecting means, a crank angle detected by the crank angle detecting means, an intake air amount detected by the intake air amount detecting means, and a fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on an engine operating state, and when the maximum value is equal to or greater than the first allowable value, a gas flow generating valve for generating a gas flow in the cylinder. A valve correction amount for correcting the opening degree of the gas flow in the direction in which the vortex due to the gas flow is weakened is set, and the opening degree of the gas flow generation valve is corrected with the valve correction amount to weaken the vortex generated in the cylinder.

The seventh engine combustion control apparatus includes at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the in-cylinder gas average temperature in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state, and when the maximum value is equal to or greater than the first allowable value, the compression ratio variable means provided for the cylinder is operated. Is set in such a manner that the compression ratio is corrected in the direction in which the compression ratio is reduced, and the operation amount of the compression ratio variable means is corrected with the compression ratio correction value to lower the compression ratio of the cylinder.

The eighth engine combustion control apparatus comprises at least an in-cylinder pressure detected by the in-cylinder pressure detecting means, a crank angle detected by the crank angle detecting means, an intake air amount detected by the intake air amount detecting means, and a fuel injection amount. The average value of the in-cylinder gas temperature of each cylinder is sequentially calculated from the closing of the intake valve to the opening of the exhaust valve based on the above, and the maximum value of the average gas temperature in the cylinder in one cycle of each cylinder is detected. Thereafter, the maximum value is compared with a first allowable value set based on the engine operating state, and when the maximum value is equal to or greater than the first allowable value, the opening / closing timing of the intake valve or the exhaust valve of the cylinder is determined. A valve timing correction amount for correcting the operation amount of the variable valve timing means to be variable in a direction to lower the effective compression ratio is set, and the operation amount of the valve timing variable means is corrected by the valve timing correction amount to perform combustion. Let it slow down.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 5 show a first embodiment of the present invention.
An embodiment will be described.

FIG. 2 shows an overall schematic view of the engine. Reference numeral 1 in FIG. 1 denotes an engine having a plurality of cylinders. An intake pipe 4 is communicated via an air chamber 3 to an aggregate of intake manifolds 2 communicating with intake ports 1a of the cylinders. An air cleaner 5 is interposed in the air intake. The exhaust port 1 of each cylinder of the engine 1
b, a muffler 8 is communicated through a discharge pipe 7 to a collection portion of an exhaust manifold 6 which communicates with a catalyst 9.
Is interposed. A spark plug 10 faces the combustion chamber of each cylinder, and an injector 11 faces the upstream of the intake port 1a of the intake manifold 2 communicating with each cylinder. An ignition coil 10a is connected to the ignition plug 10, and an igniter 12 is connected to the ignition coil 10a.

On the other hand, an intake air amount sensor 13 is located immediately downstream of the air cleaner 5 in the intake pipe 4, and a throttle opening sensor 15 is connected to a throttle valve 14 provided in the middle of the intake pipe 7. ing. Further, an in-cylinder pressure sensor 16 is provided for each cylinder, and O
Two sensors 17 are facing. Further, a crank angle sensor 19 is provided opposite to a crank rotor 18 which rotates synchronously with the crankshaft. The crank rotor 18 has a projection for detecting the crank angle at every predetermined crank angle.

Each of the above sensors is connected to an input terminal of an electronic control unit (ECU) 20 mounted on the vehicle.
The electronic control unit 20 is composed of a computer such as a well-known microcomputer, and the input terminals of the electronic control unit 20 are connected to the sensors 13, 15, 16, 17, 19 and the like.
Each actuator such as the injector 11 and the igniter 12 is connected to an output terminal.

The electronic control unit 20 sets a fuel injection amount, an ignition timing, and the like for each cylinder based on signals output from the sensors 13, 15, 16, 17, 19, and the like. A drive signal corresponding to the fuel injection pulse width is output at a predetermined timing, and an igniter 12 connected to the ignition coil 10a of each ignition plug 10
, An ignition signal is output at a predetermined timing.

As shown in the functional block diagram of FIG. 1, the electronic control unit 20 calculates the engine speed Ne based on the input interval time of the output signal from the crank angle sensor 19 as a function of controlling the ignition timing. The in-cylinder pressure P detected by the in-cylinder pressure sensor 16
A predetermined crank angle based on the output signal (crank pulse) of the crank angle sensor 19, the intake air amount detected by the intake air amount sensor 13, and a fuel injection amount (pulse width) Ti set in a fuel injection control system (not shown). Cylinder average gas temperature calculating means 22 for sequentially calculating the cylinder average gas temperature T for each cylinder, and maximum value detecting means 23 for detecting the maximum value Tmax of the cylinder average gas temperature T in one cycle for each cylinder. Based on the engine load (for example, the basic fuel injection pulse width Tp set in the fuel injection control), the allowable value Tlim of the maximum value Tmax is stored in a map stored in the allowable value storage means 24 provided in the ROM or the like. An allowable value setting means 25 to be set with reference to; a maximum value comparing means 26 for determining whether the maximum value Tmax is equal to or greater than the allowable value Tlim;
The ignition timing correction value setting means 27 for setting the retardation correction value RTD based on the comparison result of the maximum value comparison means 26, the intake air amount Q detected by the intake air amount sensor 13, and the basic fuel injection set in the fuel injection control. The basic ignition advance SPK set based on the pulse width Tp is changed to the retard correction value RT.
An ignition timing setting means 28 is provided for setting the ignition timing ADV by correcting with various correction items such as D.

More specifically, the ignition timing control is performed as shown in FIG.
It is executed according to the flowchart shown in FIG. The in-cylinder gas average temperature calculation routine shown in FIG. 3 is executed for each cylinder at a constant crank angle cycle. First, in step S1, the in-cylinder pressure P detected by the in-cylinder pressure sensor 16 and the output signal of the crank angle sensor 19 ( The average in-cylinder gas temperature T for each predetermined crank angle is determined based on the crank pulse), the intake air amount detected by the intake air amount sensor 13, and the fuel injection amount (pulse width) Ti set in a fuel injection control system (not shown). It is calculated based on the formula. T ← PV / {R · (Gs + Gi)} where V is the cylinder volume, R is the gas constant, Gs is the weight of the newly-inhaled air-fuel mixture, and Gi is the weight of the residual gas.

Next, in step S2, it is determined whether one cycle of the cylinder has been completed based on, for example, a signal from the crank angle sensor 19. If one cycle has not yet been completed, the routine directly exits the routine. When the cycle ends, the process proceeds to step S3. In the present embodiment,
As shown in FIG. 5, one cycle is defined as a period from the start of the intake stroke to the end of the exhaust stroke based on the signal from the crank angle sensor 19.

In step S3, the maximum value Tmax of the in-cylinder gas average temperature T during one cycle is detected. In step S4, the current engine operating state, for example, the engine speed Ne and the basic fuel injection pulse are determined. With reference to the map stored in the ROM based on the width Tp, NOx
An allowable value Tlim, which is the upper limit of the in-cylinder gas average temperature T at which the discharge rate exceeds the allowable value, is set. In step S5, the maximum value Tmax is compared with the allowable value Tlim, and Tmax ≧
If Tlim (see FIG. 5), the process proceeds to step S7, where the retard correction value RTD # i (#i: cylinder number) of the cylinder is set with a predetermined retard amount θRTD (RTD # i ← θRTD), and the routine is performed. Through. On the other hand, if Tmax <Tlim, the process proceeds to step S6, where the retard correction value RTD # i of the cylinder is cleared (RT
D # i ← 0), exits the routine.

The retard correction value RTD is read in an ignition timing setting routine shown in FIG. This ignition timing setting routine is executed for each specific crank angle of the cylinder to be ignited,
First, in step S11, the current engine speed Ne and the basic fuel injection pulse width T calculated in the fuel injection control are set.
The basic ignition timing ADVBASE is set with reference to the map stored in the ROM based on the value p, and the retard correction value RTD # i of the cylinder is read in step S12, and the process proceeds to step S13.
The acceleration / deceleration correction value SPKACC set based on the opening change amount of the throttle opening sensor 15 is read in step S1.
4, the basic ignition timing ADVBASE is added to the retard correction value R
By adding the TD # i and the acceleration / deceleration correction value SPKACC, the final ignition timing ADV for the cylinder is calculated (ADV ←
ADVBASE + RDT # i + SPKACC), step S15
Then, the ignition timing is set in the ignition timer, and the routine exits.

When the specified crank angle before the ignition of the cylinder has been reached, the timer of the ignition timer is started, and when the ignition timing has been reached, an ignition signal is output to the igniter 12 to ignite the ignition plug 10 of the cylinder. Let it.

As a result, the maximum combustion temperature of the cylinder can be suppressed, and the NOx emission rate can be reduced without deteriorating the fuel consumption rate.

FIGS. 6 to 9 show a second embodiment of the present invention. In the above-described first embodiment, the maximum combustion temperature is suppressed by retarding the ignition timing to reduce the NOx emission rate. However, in the present embodiment, the fuel injection amount is reduced. The correction slows down the combustion speed and suppresses the maximum combustion temperature.

As shown in the functional block diagram of FIG. 6, the electronic control unit 20 employed in the present embodiment has an ignition timing,
The engine speed calculating means 21 calculates the engine speed Ne based on the input interval time of the output signal from the crank angle sensor 19, the function of controlling the fuel injection amount, the cylinder pressure P detected by the cylinder pressure sensor 16, The output signal (crank pulse) of the crank angle sensor 19, the intake air amount detected by the intake air amount sensor 13, the fuel injection amount (pulse width) Ti set in a fuel injection control system (not shown)
Means 22 for calculating the in-cylinder gas average temperature T for each cylinder based on the predetermined crank angle, and the maximum value Tmax of the in-cylinder gas average temperature T in one cycle.
Value detecting means 23 for detecting the maximum value T for each cylinder.
The allowable value Tlim of max is set to the engine load (for example, the basic fuel injection pulse width Tp set in the fuel injection control).
Based on a map stored in a permissible value storage means 24a provided in a ROM or the like, a maximum value comparing means 26 for determining whether or not the maximum value Tmax is equal to or greater than the permissible value Tlim. As a result of the comparison by the maximum value comparing means 26, the maximum value Tmax exceeds the allowable value Tlim, and the combustion fluctuation rate P
When it is determined that the irac is within the allowable value Pilim, the air-fuel ratio correction value setting means 31 for setting the air-fuel ratio correction value KA / F to make the air-fuel ratio lean, and the current air-fuel ratio is set based on the output voltage of the O2 sensor 17 Air-fuel ratio feedback correction coefficient setting means 32 for setting an air-fuel ratio feedback correction coefficient λ for converging to an air-fuel ratio, and correcting acceleration / deceleration of basic fuel injection pulse width Tp set based on engine speed Ne and intake air amount Q. Correction coefficient COE for cooling water temperature correction
F, an air-fuel ratio feedback correction coefficient λ, a fuel injection pulse width setting means 33 that calculates a fuel injection pulse width Ti by correcting the air-fuel ratio correction value KA / F, etc., and a drive signal corresponding to the fuel injection pulse width Ti. Injector drive circuit 34 for outputting to injector 11 and in-cylinder pressure sensor 1
A combustion fluctuation rate calculating means 35 for calculating, for each cylinder, a combustion fluctuation rate Pirac, which is a fluctuation rate per cycle of the indicated mean effective pressure Pi calculated based on the in-cylinder pressure P detected at 6 and the signal of the crank angle sensor 19; Permissible value P of combustion fluctuation rate Pirac
ilim is calculated based on the engine load (for example, the basic fuel injection pulse width Tp set in the fuel injection control).
An allowable value setting means 36 for setting by referring to a map stored in an allowable value storage means 24b provided in the OM or the like; a combustion fluctuation rate comparing means 37 for determining whether the combustion fluctuation rate Pirac is equal to or higher than the allowable value Pilim; This combustion variation rate comparing means 37
As a result of the comparison, when the combustion fluctuation rate Pirac exceeds the allowable value Pilim and the maximum value comparing means 26 determines that the maximum value Tmax exceeds the allowable value Tlim, the ignition timing is retarded to correct the ignition timing. The ignition timing correction value setting means 27 for setting the correction value RTD, the basic ignition advance SPK set based on the intake air amount Q detected by the intake air amount sensor 13 and the basic fuel injection pulse width Tp set in the fuel injection control. And an ignition timing setting means 28 that corrects the ignition timing ADV by various correction items such as the retardation correction value RTD.

More specifically, the fuel injection control and the ignition timing control according to the present embodiment are executed according to the flowcharts shown in FIGS.

The in-cylinder gas average temperature determination routine shown in FIG. 7 is executed for each cylinder at a constant crank angle cycle, and steps S1 to S5 are executed through the same routine as that of the above-described first embodiment. In this step S5, the maximum value Tmax of the in-cylinder gas average temperature T searched in step S3,
A comparison is made with the allowable value Tlim set in step S4, and Tmax
If ≧ Tlim, the routine proceeds to step S20, where the air-fuel ratio flag FA / F is set, and the routine exits. Also, Tmax <Tli
If m, the process proceeds to step S21, where the air-fuel ratio flag FA / F is cleared, and the routine exits.

Then, when the air-fuel ratio flag FA / F is set in step S20, the fuel injection amount is corrected so as to make the air-fuel ratio lean in a fuel injection amount setting routine described later. As a result, the indicated mean effective pressure P during one cycle
Since i changes, the following combustion variation rate determination routine is executed.

The combustion variation rate determination routine shown in FIG.
It is executed for each cycle. First, the indicated average effective pressure Pi in one cycle is calculated based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 16 in step S31 and the signal of the crank angle sensor 19, and in step S32, The combustion fluctuation rate Pirac is calculated from the ratio between the calculated indicated mean effective pressure Pi and the previously calculated PiOLD (Pirac ← Pi / PiOLD).

In step S33, the permissible value of the combustion fluctuation rate Pirac is determined by referring to a map stored in the ROM based on the current engine operating state, for example, the engine speed Ne and the basic fuel injection pulse width Tp. Pilmi is set, and in step S34, the combustion fluctuation rate Pirac is compared with an allowable value Pilmi.

If Pirac <Pilmi, the routine proceeds to step S35, where the ignition timing retard correction value RTD for the cylinder is determined.
Clear #i (#i: cylinder number) and exit the routine. On the other hand, when Pirac ≧ Pilmi, the process proceeds to step S36,
The air-fuel ratio flag FA / F is cleared, and in step S37, the ignition timing retard correction value RDT # i of the cylinder is set to the predetermined retard amount θRT.
Set with D and exit the routine.

The ignition timing retard correction value RTD # i is
It is read when the same routine as the ignition timing setting routine shown in FIG. 4 of the first embodiment is executed.

The fuel injection amount setting routine shown in FIG. 9 is executed at every predetermined crank angle in the fuel injection target cylinder. First, in step S41, the basic fuel injection is performed based on the intake air amount Q and the engine speed Ne. The pulse width Tp is calculated (Tp ← K · Q / NeK: injector characteristic correction coefficient). In step S42, various increase correction coefficients COEF such as acceleration / deceleration correction set based on a change in throttle opening and water temperature correction set based on cooling water temperature are set. In step S43, based on the output voltage of the O2 sensor 17, The air-fuel ratio feedback correction coefficient λ for converging to the target air-fuel ratio set by the proportional integral control or the like is read, and the value of the air-fuel ratio flag FA / F is referred to in step S44.

When FA / F = 0, step S4
5, the air-fuel ratio correction coefficient KA / F is set to 1, and step S
Go to 47. If FA / F = 1, step S45
Then, the air-fuel ratio correction coefficient KA / F is changed to the lean correction value LEAN.
(However, LEAN <1) is set and the process proceeds to step S47.

In step S47, a voltage correction coefficient Ts for complementing the invalid injection pulse width of the injector 11 is set on the basis of the battery voltage. In step S48, the basic fuel injection pulse width Tp is changed by various increase correction coefficients COEF and air-fuel ratio. Feedback correction coefficient λ, air-fuel ratio correction coefficient KA / F
And the voltage correction coefficient Ts is added to set the final fuel injection pulse width Ti for the injector 11 of the fuel injection target cylinder (Ti ← Tp · COEF ·
λ · KA / F + Ts).

Then, in step S49, the fuel injection pulse width Ti is set in the injection timer, and the routine exits. Thereafter, when a predetermined crank angle is reached, the injection timer is started, and a predetermined amount of fuel is injected from the injector 11 of the fuel injection target cylinder.

As described above, in the present embodiment, when the maximum combustion temperature Tmax is too high (Tmax ≧ Tlim), the fuel injection amount is lean-corrected to lower the combustion temperature, so that N
Since the Ox emission rate is reduced, the fuel efficiency is slightly improved by the amount of the lean correction. If the combustion fluctuation rate Pirac does not fall within the permissible value Pilim, the lean correction for the fuel injection amount is stopped and the ignition timing ADV is retarded, so that the combustion state of each cylinder during one cycle. Is always maintained in an optimum state, and the air-fuel ratio does not become overlean, and misfire can be effectively avoided.

FIGS. 10 to 14 show a third embodiment of the present invention. In the present embodiment, in an engine equipped with an EGR (exhaust gas recirculation) device, if the maximum combustion temperature is too high, the EGR (exhaust gas recirculation) rate (amount) is increased, the combustion temperature is reduced, and the NOx emission rate is reduced. To reduce

As shown in FIG. 10, the exhaust pipe 7 of the engine 1 and the portion immediately upstream of the collecting portion of the intake manifold 2 are connected to the EGR passage 4.
The EGR valve 4 is connected to the EGR passage 41 through the EGR valve 4.
The electronic control unit 20 sets an opening control amount of the EGR valve 42.

As shown in the block diagram of FIG. 11, the electronic control unit 20 employed in the present embodiment has an engine speed calculating means 21, an in-cylinder gas averaging means, as functions for controlling the ignition timing and the EGR rate. Temperature calculating means 22, maximum value detecting means 23, allowable value setting means 25, combustion variation rate calculating means 35, allowable value storing means 24b, allowable value setting means 3
6. The combustion fluctuation rate comparing means 37 which determines whether the combustion fluctuation rate Pirac is equal to or more than the permissible value Pilim. As a result of the comparison by the combustion fluctuation rate comparing means 37, the combustion fluctuation rate Pirac is
ilim and the maximum value Tma
If it is determined that x exceeds the allowable value Tlim, the EGR rate correction value setting means 43 sets the EGR rate correction value KR that increases the EGR rate, the throttle opening THv detected by the throttle opening sensor 15 and the engine speed. EGR rate setting means 44 for correcting the target EGR rate EGRO set with reference to the map and the like based on the number Ne by the EGR rate correction value KR or the like to set the EGR rate ηEGR, and the EGR rate setting means 44
An EGR valve drive circuit 4 that outputs a drive signal such as a duty ratio corresponding to the EGR rate ηEGR set to the EGR valve 42 to the EGR valve 42
5.

More specifically, the ignition timing control and the EGR control in the present embodiment are executed according to the flowcharts shown in FIGS.

The in-cylinder gas average temperature determination routine shown in FIG. 12 is executed for each cylinder at a constant crank angle cycle, and steps S1 to S5 are executed through the same routine as that of the first embodiment. In step S5, the maximum value Tmax of the in-cylinder gas average temperature T searched in step S3.
And the allowable value Tlim set in step S4.
If Tmax ≧ Tlim, the process proceeds to step S51, in which the EGR increase flag FEGR is set, and the routine exits. Also, Tm
If ax <Tlim, the routine proceeds to step S52, where the EGR flag FEGR is cleared and the routine exits.

When the EGR increase flag FEGR is set in step S51, the EGR amount is increased and corrected in an EGR rate setting routine described later. As a result, the indicated mean effective pressure Pi in one cycle changes, so that the following combustion variation rate determination routine is executed.

The combustion variation rate determination routine shown in FIG.
This is almost the same as the flowchart shown in FIG. 8 of the second embodiment described above, and instead of step S36 in FIG. 8,
A routine for clearing the EGR flag FEGR in step S57 is executed, and the process proceeds to step S37. The EGR flag FEGR is read in an EGR setting routine shown in FIG.

This EGR rate setting routine is executed every predetermined cycle (time cycle or crank angle cycle). First, in step S61, a map is referred to or calculated based on the throttle opening THv and the engine speed Ne. The target EGR rate ηEGRO is set by the following.

Then, in step S62, the value of the EGR flag FEGR is referred to, and when FEGR = 0, step S6 is executed.
Then, the process proceeds to step S3, where the EGR rate correction value KR is set to 0, and step S
Proceed to 65. If FEGR = 1, the process proceeds to step S64, and the EGR rate correction value KR is set to a predetermined increase value Rs.
And the process proceeds to step S65.

In step S65, the target EGR rate E
The EGR rate correction value KR is added to GRO to obtain an EGR rate ηEG.
R is set (ηEGR ← EGRO + KR), and the routine exits. When a signal having a predetermined duty ratio corresponding to the EGR rate ηEGR is output to the EGR valve drive circuit 45 at a predetermined timing, the EGR drive circuit 45 drives the actuator of the EGR valve 42 in accordance with the duty ratio. A signal is output, and the opening of the EGR valve 42 is controlled via the actuator. As a result, the combustion temperature is reduced by an amount corresponding to the increase in the EGR rate, and the emission amount of NOx is reduced.

On the other hand, if the combustion fluctuation rate Pirac does not fall within the allowable value Pilim due to the increase in the EGR rate (Pirac ≧ Pilim), the correction of the increase in the EGR rate is stopped, and the ignition timing control is performed. Since the combustion is controlled by retarding the ignition timing of the cylinder (step S5
7, S37), and good control performance can be obtained without setting an excessive EGR rate ηEGR.

FIGS. 15 to 18 show a fourth embodiment of the present invention. In the present embodiment, in the engine 1 in which the gas flow generation valve 46 is interposed immediately upstream of the intake port 1a communicating with each cylinder, for the cylinder whose combustion maximum temperature is too high, the above-mentioned cylinder provided in the cylinder is used. The swirl flow or the tumble flow is weakened by adjusting the opening of the gas flow generation valve 46, the gas flow generated in the cylinder is suppressed, and the combustion speed is reduced to reduce the NOx emission rate.

As shown in FIG. 15, the gas flow generating valve 4 is located immediately upstream of the intake port 1a communicating with each cylinder of the engine 1.
A gas flow (swirl flow or tumble flow) of intake air supplied to each cylinder is reinforced by variably setting the degree of opening of the gas flow generation valve 46.
Or they can be weakened. The gas flow generation valve 46 is connected to the control actuator 46a, and the rotation angle of the control actuator 46a is variably set by a drive signal from the electronic control unit 20.

As shown in FIG. 16, the electronic control unit 2
In the same manner as in the first embodiment, the engine speed calculating means 21, the in-cylinder gas average temperature calculating means 22, and the function for controlling the opening degree of the gas flow generation valve 46 for each cylinder are set to 0. In addition to the functions of the value detecting means 23, the allowable value storing means 24, the allowable value setting means 25, and the maximum value comparing means 26, as a result of the comparison by the maximum value comparing means 26, the maximum value Tmax exceeds the allowable value Tlim. Is determined, the valve correction amount setting means 47 for setting the valve correction amount θk for correcting the opening of the gas flow generation valve 46 to the side where the gas flow of the cylinder is suppressed, the engine speed Ne and the intake air amount Q The target opening amount C set by referring to a map using the engine operating state detected based on the
The valve opening setting means 48 for correcting OVO with various correction terms such as the valve correction amount θk and setting the final valve opening COV, which corresponds to the valve opening COV set by the valve opening setting means 48 The drive signal is sent to the gas flow generation valve 4
And a valve drive circuit 49 that outputs the control actuator 46a to rotate the control actuator 6a.

More specifically, the gas flow control according to the present embodiment is executed according to the flowcharts shown in FIGS.

The in-cylinder gas average temperature determination routine shown in FIG. 17 is executed for each cylinder at a constant crank angle cycle, and steps S1 to S5 are executed through the same routine as that of the first embodiment. In step S5, the maximum value Tmax of the in-cylinder gas average temperature T searched in step S3.
And the allowable value Tlim set in step S4.
If Tmax <Tlim, the flow proceeds to step S71 since the combustion temperature of the cylinder is appropriate, the valve correction amount θk is cleared, and the routine exits. On the other hand, when Tmax ≧ Tlim, the process proceeds to step S72 because the maximum combustion temperature Tmax of the cylinder is too high, and the valve correction amount θk is set to the set opening θ
Set at v (opening acting in the direction to weaken the gas flow) and exit the routine. This valve correction amount θk is calculated as shown in FIG.
Is read in the valve opening degree setting routine shown in FIG.

This valve opening setting routine is executed for each cylinder at predetermined intervals, and in step S81, the engine operating state detected based on the engine speed Ne, the intake air amount Q, and the like is used as a parameter to refer to a map or to calculate. The target opening COVO of the gas flow generating valve 46 for generating the optimum gas flow is set, and the valve correction amount θk of the cylinder set in the above-described in-cylinder gas average temperature determination routine is read in step S82, and in step S83, The above target opening CO
VO is corrected by the various correction items such as the valve correction amount θk and the final valve opening COV is set, and the routine exits. During the intake stroke of the cylinder, an opening signal corresponding to the valve opening COV is output to the control actuator 46a via the valve driving circuit 49, and the gas flow generation valve 46 connected to the control actuator 46a is opened for a predetermined time. Open the valve.

The opening of the gas flow generating valve 46 of the cylinder whose combustion maximum temperature Tmax is too high is controlled in the direction of weakening the gas flow, so that the gas flow of the intake air supplied to the cylinder is reduced by the amount corresponding to the weakened gas flow. The combustion temperature of the cylinder is lowered and N
Ox emission rate is reduced.

FIGS. 19 to 22 show a fifth embodiment of the present invention. As shown in FIG. 19, each cylinder of the engine 1 employed in the present embodiment faces a variable compression ratio actuator 52 such as a rotary solenoid having a variable compression ratio piston 51 fixed to the end. In the present embodiment, the NOx emission rate is reduced by lowering the compression ratio of a cylinder whose combustion maximum temperature Tmax is too high to lower the combustion temperature of the cylinder.

As shown in FIG. 20, the electronic control unit 20 has a function of controlling the operation amount of the variable compression ratio actuator 52 for each cylinder, as in the first embodiment. In addition to the functions of the in-cylinder gas average temperature calculating means 22, the maximum value detecting means 23, the allowable value storing means 24, the allowable value setting means 25, and the maximum value comparing means 26, the result of the comparison by the maximum value comparing means 26 When it is determined that the maximum value Tmax exceeds the allowable value Tlim, the compression ratio correction coefficient setting means 53 for setting the compression ratio correction coefficient Ki for operating the compression ratio variable piston 51 in the direction of reducing the compression ratio, and the engine. The target operation amount ε set by referring to a map or by calculation using the engine operation state detected based on the rotation speed Ne and the intake air amount Q as a parameter.
O is corrected by the compression ratio correction coefficient Ki to set the operation amount ε of the variable compression ratio actuator 52, a voltage or pulse corresponding to the operation amount ε set by the operation amount setting unit 54. Is output to the variable compression ratio actuator 52.

More specifically, the compression ratio variable control according to the present embodiment is executed according to the flowcharts shown in FIGS.

The in-cylinder gas average temperature determination routine shown in FIG. 21 is executed for each cylinder at a constant crank angle cycle, and steps S1 to S5 are executed through the same routine as that of the first embodiment. In step S5, the maximum value Tmax of the in-cylinder gas average temperature T searched in step S3.
And the allowable value Tlim set in step S4.
If Tmax <Tlim, the process proceeds to step S86 because the combustion temperature of the cylinder is appropriate, and the compression ratio correction coefficient Ki is set to 1
To exit the routine. On the other hand, when Tmax ≧ Tlim, the process proceeds to step S87 because the maximum combustion temperature Tmax of the cylinder is too high, and the compression ratio correction coefficient Ki is set to the set value α.
(However, α <1) is set and the routine exits.

The compression ratio correction coefficient Ki is read in the operation amount setting routine shown in FIG. This operation amount setting routine is executed at predetermined intervals.
At 91, the target operation amount εO for the variable compression ratio actuator 52 that sets the optimum compression ratio by referring to a map or by calculation using the engine operation state detected based on the engine speed Ne, the intake air amount Q, etc. as a parameter, In step S92, the compression ratio correction coefficient Ki of the cylinder is read.

In step S93, the target operation amount εO is corrected by the compression ratio correction coefficient Ki to set the final operation amount ε for the variable compression ratio actuator 52 (ε ← εO · Ki), and the routine is executed. Through.

Then, a current value corresponding to the operation amount ε,
Alternatively, the voltage value is output to the variable compression ratio actuator 52 of the cylinder via the actuator drive circuit 55, and the compression ratio of the cylinder is variably set.

As a result, by lowering the compression ratio ε of the cylinder whose combustion maximum temperature Tmax is too high, the combustion temperature of the cylinder is reduced and the NOx emission rate of the cylinder is reduced.

FIGS. 23 to 26 show a sixth embodiment of the present invention. As shown in FIG. 23, in the engine 1 employed in the present embodiment, a variable intake timing cam is provided on a camshaft 1c.
A hydraulic or electromagnetic type variable valve timing actuator 56 which is an example of a valve timing variable means is provided continuously.
By individually advancing or retarding the variable intake timing cam to greatly advance or delay the closing timing of the intake valve, the effective compression ratio is varied, and the cylinder having the highest combustion maximum temperature is too high. Lower the combustion temperature of

As shown in FIG. 24, the electronic control unit 20 has a function of controlling the operation amount of the variable valve timing actuator 56 for each cylinder, as in the first embodiment. In addition to the functions of the in-cylinder gas average temperature calculating means 22, the maximum value detecting means 23, the allowable value storing means 24, the allowable value setting means 25, and the maximum value comparing means 26, the result of the comparison by the maximum value comparing means 26 When it is determined that the maximum value Tmax exceeds the allowable value Tlim,
Valve timing correction coefficient setting means 57 for setting a valve timing correction coefficient Kv for operating the variable intake timing cam in the direction of greatly advancing or retarding the variable intake timing cam via the variable valve timing actuator 56, the engine speed Ne and the intake air amount The operation amount ρ of the variable valve timing actuator 56 is set by referring to a map using the engine operation state detected based on the Q or the like as a parameter, or correcting the target operation amount ρO set by calculation with the valve timing correction coefficient Kv. The valve timing setting means 58, the valve timing setting means 5
And an actuator drive circuit 59 for outputting the operation amount ρ set at 8 to a variable valve timing actuator 56 of a hydraulic type or an electromagnetic type.

More specifically, the valve timing control according to the present embodiment is executed according to the flowcharts shown in FIGS.

The in-cylinder gas average temperature determination routine shown in FIG. 25 is executed for each cylinder at a constant crank angle cycle, and steps S1 to S5 are executed through the same routine as that of the first embodiment. In step S5, the maximum value Tmax of the in-cylinder gas average temperature T searched in step S3.
And the allowable value Tlim set in step S4.
If Tmax <Tlim, the combustion state of the cylinder is good, and the process proceeds to step S91, where the valve timing correction coefficient Kv is set to 1 and the routine exits. On the other hand, Tmax ≧ Tl
If im, the maximum combustion temperature Tmax of the cylinder is too high, and the process proceeds to step S92, where the valve timing correction coefficient Kv is set at the set value β (where β ≠ 1), and the routine exits.

The valve timing correction coefficient Kv is read in a valve timing setting routine shown in FIG. This valve timing setting routine is executed at predetermined intervals. First, in step S101, an optimal intake air is obtained by referring to a map or calculating a parameter using the engine operating state detected based on the engine speed Ne, the intake air amount Q, and the like. A target operation amount ρ serving as a valve timing is set, and a valve timing correction coefficient Kv of the cylinder is read in step S102.

In step S103, the target operation amount ρO is corrected by the valve timing correction coefficient Kv to set a final operation amount ρ for the variable valve timing actuator 56 (ρ ← ρO · Kv). Exit.

Then, a current value corresponding to the operation amount ρ,
Alternatively, the voltage value is output to the variable valve timing actuator 56 via the actuator drive circuit 59, and the valve timing of the intake cam of the cylinder with respect to the intake valve is variably set.

As a result, in a cylinder whose combustion temperature is too high,
The closing timing of the intake valve is greatly advanced or retarded by the valve timing correction coefficient Kv. Therefore, the effective compression ratio of the cylinder is reduced, the maximum combustion temperature is reduced, and the NOx emission rate is reduced. In this case, the valve timing of the exhaust valve may be variably controlled in combination with the intake valve timing.

[0090]

As described above, according to the first aspect of the present invention, the cylinder average gas temperature during one cycle is calculated, the maximum value of the cylinder average gas temperature is detected, and When the value exceeds the allowable value, the ignition timing of the cylinder is retarded and the maximum combustion temperature is suppressed, so that the NOx emission rate can be reduced without deteriorating the fuel consumption rate.

According to the second aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and when this maximum value exceeds the allowable value, Since the fuel injection amount to the cylinder is corrected to the side where the air-fuel ratio becomes lean, the NOx emission rate can be reduced by slowing down the combustion in the cylinder having the highest combustion temperature.

According to the third aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and the maximum value exceeds the first allowable value. In this case, the fuel injection amount for the cylinder is corrected to the side where the air-fuel ratio becomes lean, and the indicated average effective pressure P of the cylinder thereafter is corrected.
When the rate of change of i does not fall within the second allowable value, the ignition timing is corrected for retardation. In addition to the above effects, the combustion state of each cylinder is monitored based on the indicated mean effective pressure. The NOx emission rate can be reduced without difficulty.

According to the fourth aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and when the maximum value exceeds the allowable value, Since the amount of exhaust gas recirculation is increased, the combustion is slowed down by increasing the amount of exhaust gas recirculation, and the NOx emission rate is reduced by suppressing the combustion temperature of a cylinder whose combustion maximum temperature is too high. Can be.

According to the fifth aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and the maximum value exceeds the first allowable value. When the detected change rate of the indicated mean effective pressure Pi does not fall within the second allowable value, the ignition timing of the cylinder is corrected so as to be retarded. Therefore, in addition to the above effects, the NOx emission rate can be reduced without difficulty while monitoring the combustion state of each cylinder after increasing the exhaust gas recirculation amount using the indicated average effective pressure.

According to the sixth aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and when the maximum value exceeds the allowable value, The degree of opening of the gas flow generating valve that generates gas flow in each cylinder is adjusted to weaken the generation of gas flow, so that the combustion temperature of the cylinder becomes appropriate and the NOx emission rate is reduced. Instead, the fuel consumption rate is improved by improving combustion.

According to the seventh aspect of the present invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and when the maximum value exceeds the allowable value, Since the compression ratio is reduced by the compression ratio variable means provided in the cylinder, the combustion temperature of the cylinder is optimized and the NOx emission rate can be reduced.

According to the eighth aspect of the invention, the average gas temperature in the cylinder during one cycle is calculated, the maximum value of the average gas temperature in the cylinder is detected, and when the maximum value exceeds the allowable value, Since the operation amount of the variable valve timing actuator that changes the opening / closing timing of the intake valve or the exhaust valve of the cylinder is corrected in a direction to lower the effective compression ratio, the combustion of the cylinder whose combustion maximum temperature is too high is improved, Not only the NOx emission rate is reduced, but also the fuel consumption rate is improved by improving the combustion.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an electronic control device according to a first embodiment of the present invention.

FIG. 2 is an overall schematic view of the engine.

FIG. 3 is a flowchart showing an in-cylinder gas average temperature calculation routine;

FIG. 4 is a flowchart showing an ignition timing setting routine;

FIG. 5 is a timing chart showing the relationship between the in-cylinder pressure and the in-cylinder gas average temperature.

FIG. 6 is a functional block diagram of an electronic control unit according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing an in-cylinder gas average temperature calculation routine;

FIG. 8 is a flowchart showing a combustion fluctuation rate determination routine.

FIG. 9 is a flowchart showing a fuel injection pulse width setting routine.

FIG. 10 is an overall schematic diagram of an engine according to a third embodiment of the present invention.

FIG. 11 is a functional block diagram of the electronic control unit.

FIG. 12 is a flowchart showing an in-cylinder gas average temperature calculation routine;

FIG. 13 is a flowchart showing a combustion fluctuation rate determination routine.

FIG. 14 is a flowchart showing an EGR rate setting routine.

FIG. 15 is an overall schematic diagram of an engine according to a fourth embodiment of the present invention.

FIG. 16 is a functional block diagram of the electronic control device.

FIG. 17 is a flowchart showing an in-cylinder gas average temperature calculation routine;

FIG. 18 is a flowchart showing a valve opening setting routine of the same.

FIG. 19 is an overall schematic diagram of an engine according to a fifth embodiment of the present invention.

FIG. 20 is a functional block diagram of the electronic control device.

FIG. 21 is a flowchart showing an in-cylinder gas average temperature calculation routine;

FIG. 22 is a flowchart showing an operation amount setting routine.

FIG. 23 is an overall schematic diagram of an engine according to a sixth embodiment of the present invention.

FIG. 24 is a functional block diagram of the electronic control device.

FIG. 25 shows the same cylinder average gas temperature calculation routine.

FIG. 26 is a flowchart showing a valve timing setting routine of the same.

[Explanation of symbols]

16: In-cylinder pressure detecting means (in-cylinder pressure sensor) 22: in-cylinder gas average temperature calculating means 23 ... maximum value detecting means 26 ... maximum value comparing means 27 ... ignition timing correction value setting means 28 ... ignition timing setting means 31 ... air-fuel ratio Correction value setting means 33 ... Fuel injection amount setting means (fuel injection pulse width setting means) 35 ... Combustion fluctuation rate calculating means 43 ... Exhaust gas recirculation amount correction value setting means (EGR rate correction value setting means) 44 ... Circulation amount setting means (EGR rate setting means) 46 ... Gas flow generation valve 47 ... Valve correction amount setting means 48 ... Valve opening degree setting means 51 ... Compression ratio variable means (compression ratio variable piston) 53 ... Compression ratio correction value setting means (Compression ratio correction coefficient setting means) 54 ... operation amount setting means 56 ... variable valve timing means (variable valve timing actuator) 58 ... valve timing setting means A DV: ignition timing EGR: exhaust gas recirculation amount (EGR rate) KA / F: air-fuel ratio correction value Ki: compression ratio correction value (compression ratio correction coefficient) KR: exhaust gas recirculation amount correction value (EGR rate correction value) P: In-cylinder pressure Tmax: Maximum value Tlim: First allowable value Pirac: Combustion variation rate Prac: In-cylinder gas average temperature RTD # i: Ignition timing retard correction value Ti: Fuel injection amount (fuel injection pulse width) θK: Valve correction amount ρ ... Operation amount (of compression ratio variable means)

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁶ identifications FI F02D 43/00 301 F02D 43/00 301B 301H 301N 45/00 360 45/00 360A 368 368Z F02M 25/07 550 F02M 25/07 550R F02P 5/15 F02P 5/15 B

Claims (8)

[Claims] An intake valve is closed to an exhaust valve based on at least an in-cylinder pressure detected by an in-cylinder pressure detector, a crank angle detected by a crank angle detector, an intake air amount detected by an intake air amount detector, and a fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing the maximum value with the first allowable value; and ignition timing correction value setting means for setting a retard correction value for retarding the ignition timing of the cylinder when the maximum value is equal to or greater than the first allowable value. An ignition timing setting means for correcting the ignition timing with at least the ignition timing correction value to set a final ignition timing. 2. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing an air-fuel ratio correction value for leaning the air-fuel ratio of the cylinder when the maximum value is equal to or greater than the first allowable value; and A fuel injection amount setting means for correcting a fuel injection amount with at least the air-fuel ratio correction value to set a final fuel injection amount. 3. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing an air-fuel ratio correction value for leaning the air-fuel ratio of the cylinder when the maximum value is equal to or greater than the first allowable value; and A fuel injection amount setting means for correcting a fuel injection amount with at least the air-fuel ratio correction value to set a final fuel injection amount; calculating an indicated average effective pressure based on a signal from the in-cylinder pressure detecting means; Combustion fluctuation rate calculating means for calculating a fluctuation rate of the effective pressure; and a second allowable value set based on the combustion fluctuation rate and the engine operating state when the fuel is burned by the combustion injection amount corrected by the air-fuel ratio correction value. A combustion variation rate comparison unit that compares the combustion variation rate with the ignition timing correction value setting unit that sets a retardation correction value that retards the ignition timing of the cylinder when the combustion variation rate is equal to or greater than the second allowable value. At least the above retard Combustion control system for an engine characterized in that it comprises an ignition timing setting means for the ignition timing by a positive value a correction to set the final ignition timing. 4. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing the maximum value with the first allowable value, and setting the exhaust gas recirculation amount correction value to increase the exhaust gas recirculation amount when the maximum value is equal to or greater than the first allowable value. Value setting means, and exhaust gas recirculation amount setting means for correcting the exhaust gas recirculation amount with at least the exhaust gas recirculation amount correction value and setting a final exhaust gas recirculation amount. Engine combustion control device. 5. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing the maximum value with the first allowable value, and setting the exhaust gas recirculation amount correction value to increase the exhaust gas recirculation amount when the maximum value is equal to or greater than the first allowable value. Value setting means, at least an exhaust gas recirculation amount correction means for correcting the exhaust gas recirculation amount with the exhaust gas recirculation amount correction value to set a final exhaust gas recirculation amount, and from the in-cylinder pressure detecting means Combustion variation rate calculating means for calculating the indicated mean effective pressure based on the signal and calculating the change rate of the indicated mean effective pressure; and supplying the exhaust gas recirculation amount corrected by the exhaust gas recirculation amount correction value to the cylinder. Combustion variation rate comparison means for comparing the combustion variation rate when the combustion is performed with a second allowable value set based on the engine operating state; and when the combustion variation rate is equal to or greater than the second allowable value. Delay correction of ignition timing of the relevant cylinder An ignition timing correction value setting means for setting a retardation correction value, and an ignition timing setting means for correcting the ignition timing with at least the retardation correction value to set a final ignition timing. Combustion control device. 6. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
Maximum value comparing means for comparing the maximum value with the allowable value of the gas flow generating valve for generating a gas flow in the cylinder when the maximum value is equal to or greater than the first allowable value. Valve correction amount setting means for setting a valve correction amount to be corrected, and an opening for setting the final opening of the gas flow generation valve by correcting the opening of the gas flow generation valve with at least the valve correction amount An engine combustion control device comprising: a setting unit. 7. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; First set based on operating state
And a compression ratio correction value that corrects the compression ratio variable means provided for each cylinder in a direction to decrease the compression ratio when the maximum value is equal to or greater than the first allowable value. A compression ratio correction value setting unit for setting, and an operation amount setting unit for correcting an operation amount of the compression ratio variable unit with at least the compression ratio correction value to set a final operation amount of the compression ratio variable unit. A combustion control device for an engine, comprising: 8. An intake valve closing to an exhaust valve based on at least the in-cylinder pressure detected by the in-cylinder pressure detecting means, the crank angle detected by the crank angle detecting means, the intake air amount detected by the intake air amount detecting means, and the fuel injection amount. An in-cylinder gas average temperature calculating means for sequentially calculating an in-cylinder gas average temperature until opening; a maximum value detecting means for detecting a maximum value of the in-cylinder gas average temperature in one cycle; A maximum value comparing means for comparing with an allowable value of 1 and an operation amount of a variable valve timing means for enabling opening and closing timing of an intake valve or an exhaust valve to be variable when the maximum value is equal to or more than the first allowable value. Valve timing correction amount setting means for setting a valve timing correction amount for correcting the ratio in a direction to decrease the ratio; A combustion control device for an engine, comprising: valve timing setting means for correcting the operation amount of a stage to set final valve timing.