JP2864976B2 - Internal combustion engine combustion state 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 the combustion of an internal combustion engine suitable for use in a lean-burn internal combustion engine that performs a lean-burn operation at a leaner air-fuel ratio than a stoichiometric air-fuel ratio under required operating conditions. The present invention relates to a state control device.

[0002]

2. Description of the Related Art In recent years, a lean-burn internal combustion engine (so-called lean burn engine) has been provided which performs a lean-burn operation at a leaner air-fuel ratio (lean) than a stoichiometric air-fuel ratio (stoichio) under required operating conditions. I have. In such a lean burn engine, during lean burn operation (lean burn operation), the air-fuel ratio is set as large as possible (that is, the air-fuel mixture is made as lean as possible). It is set near the limit (lean limit) at which the air can perform stable combustion.

[0003] By performing such lean burn operation, fuel efficiency can be greatly improved.

[0004]

By the way, in order to perform lean burn operation, a control device controls a combustion state. In this control, it is necessary to estimate an engine torque from an angular acceleration of a crankshaft. Published in papers. However, these estimates are
It is performed every moment using the changing instantaneous value,
Considering the probability and statistical properties of the engine torque Pi, it has not been considered to perform stable and reliable control at predetermined intervals.

[0005] Further, as shown in FIG. 15, combustion fluctuations in the engine vary among the cylinders, and the variations occur due to variations in the air-fuel ratio due to deviations in injectors, intake pipe shapes, valve timing, and the like. For this reason, in the lean burn operation, the combustion state is controlled so as to correspond to the air-fuel ratio of the cylinder having the largest combustion fluctuation.

However, such means has a problem that the cylinder is not operated at the limit air-fuel ratio in a cylinder having a relatively small variation in combustion. Further, in the lean burn control, when performing control based on the magnitude of the combustion fluctuation, if the fluctuation becomes larger than a predetermined value, it is determined that the combustion state is degraded and the fuel injection is shifted to the rich side. The amount and the like are controlled.

As such control means, when the combustion fluctuation is estimated from the rotation fluctuation of the engine, it is conceivable that a large fluctuation of the rotation occurs even on a rough road.
In such a case, there is a possibility that excessive correction control is performed on the rich side. The present invention has been made in view of such a problem, and during lean burn operation, in consideration of the probability and statistical properties of combustion fluctuation, it is possible to perform reliable combustion control, and when traveling on rough roads. It is another object of the present invention to provide an engine combustion state control device capable of performing accurate control.

[0008]

SUMMARY OF THE INVENTION Therefore, an engine combustion state control apparatus according to the present invention provides an internal combustion engine which can be operated at an air-fuel ratio leaner than a stoichiometric air-fuel ratio. Fluctuation detecting means for detecting a fluctuation value of the angular acceleration; normalized fluctuation value detecting means for normalizing the fluctuation value detected by the fluctuation detecting means according to the operating state of the internal combustion engine to obtain a normalized fluctuation value; Combustion state control means for performing air-fuel ratio lean control based on the normalized variation value; bad road determination means for comparing the normalized variation value with a predetermined rough road determination threshold to determine rough road travel; It is characterized by comprising lean control limiting means for limiting the air-fuel ratio lean control in the combustion state control means based on the determination result by the bad road determining means.

[0009]

In the engine combustion state control apparatus of the present invention described above, in order to operate the engine at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the fluctuation value of the angular acceleration of the rotating shaft driven by the engine is detected by the fluctuation detecting means. The detected fluctuation value is normalized by the normalized fluctuation value detecting means according to the operating state of the engine to obtain a normalized fluctuation value, and the combustion state control means determines the lean air-fuel ratio based on the normalized fluctuation value. Control is performed. Then, when the rough road determination unit determines the rough road traveling by comparing the normalized variation value with a predetermined rough road determination threshold, the air-fuel ratio leaning control in the combustion state control unit is limited by the leaning control limiting unit. Is done.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control system of an engine according to an embodiment of the present invention; FIG. FIG. 3 is a hardware block diagram showing a control system of an engine system having the apparatus, FIGS. 4 and 5 are flowcharts for explaining the operation of the apparatus, FIG. 6 is a waveform diagram for explaining the operation of the apparatus, FIG.
8 is a correction characteristic map for explaining the operation of the present apparatus, and FIG.
Is a schematic graph for explaining the operation of the present apparatus, FIG. 9 is a schematic graph for explaining the operation of the present apparatus, FIG. 10 is a normalized characteristic map for explaining the operation of the present apparatus, and FIG. 1
1 is a schematic perspective view showing a rotation fluctuation detecting unit in the present apparatus, FIGS. 12 and 13 are schematic graphs showing control target characteristics of the present apparatus, and FIG. 14 is a threshold value for judging a bad road and deterioration of combustion. It is a figure for explaining a size relation.

[0011] Now, an engine for a vehicle equipped with this device has a stoichiometric air-fuel ratio (stoichio) under required operating conditions.
Although it is configured as a lean burn engine that performs a lean burn operation (lean burn operation) at a leaner air-fuel ratio (lean), this engine system is as shown in FIG. That is, in FIG. 2, an engine (internal combustion engine) 1 has an intake passage 3 and an exhaust passage 4 that communicate with a combustion chamber 2 of the engine, and communication between the intake passage 3 and the combustion chamber 2 is controlled by an intake valve 5. In addition, the exhaust passage 4 and the combustion chamber 2 are controlled to communicate with each other by an exhaust valve 6.

The intake passage 3 is provided with an air cleaner 7, a throttle valve 8, and an electromagnetic fuel injection valve (injector) 9 in this order from the upstream side, and the exhaust passage 4 is provided in the exhaust passage 4 in order from the upstream side. , A three-way catalyst 10 and a muffler (muffler) not shown. In addition, the injector 9 is provided for each cylinder of the engine 1. Further, a surge tank 3a is provided in the intake passage 3.

The three-way catalyst 10 purifies CO, HC and NOx in a stoichiometric operation state, and is a known one. Further, the throttle valve 8 is connected to an accelerator pedal (not shown) via a wire cable, and the opening is adjusted according to the amount of depression of the accelerator pedal.

A first bypass passage 11A for bypassing the throttle valve 8 is provided in the intake passage 3. The first bypass passage 11A has a stepper motor valve (hereinafter, referred to as an STM valve) functioning as an ISC valve. 12 are interposed. The first bypass passage 11A includes:
A wax type fast idle air valve 13 whose opening is adjusted according to the temperature of the engine cooling water is also provided, and is provided alongside the STM valve 12.

Here, the STM valve 12 has a valve body 12a which can abut on a valve seat formed in the first bypass passage 11A.
And a stepper motor (I) for adjusting the valve body position.
SC actuator) 12b, and a spring 12c that urges the valve body against the valve seat (in a direction that closes the first bypass passage 11A). The position of the valve body 12a with respect to the valve seat is adjusted stepwise (adjustment by the number of steps) by the stepper motor 12b, so that the opening degree of the valve seat 12 and the valve body 12a, that is, the STM valve
The degree of opening is adjusted.

Accordingly, the electronic control unit (ECU) 2 as a controller, which will be described later, determines the degree of opening of the STM valve 12.
5, the intake air can be supplied to the engine 1 through the first bypass passage 11A irrespective of the operation of the accelerator pedal by the driver, and the throttle bypass intake air amount is adjusted by changing the opening degree. You can do it.

The ISC actuator includes:
Instead of the stepper motor 12b, a DC motor may be used. Further, a second bypass passage 11B that bypasses the throttle valve 8 is provided in the intake passage 3, and an air bypass valve 14 is interposed in the second bypass passage 11B.

Here, the air bypass valve 14 is connected to the second
It is composed of a valve element 14a that can abut on a valve seat formed in the bypass passage 11B and a diaphragm actuator 14b for adjusting the position of the valve element. The diaphragm chamber of the diaphragm actuator 14b has: A pilot passage 141 communicating with the intake passage downstream of the throttle valve is provided.
An electromagnetic valve 142 for controlling an air bypass valve is interposed in 41.

Accordingly, by controlling the opening of the solenoid valve 142 for controlling the air bypass valve by the ECU 25, which will be described later, also in this case, regardless of the operation of the accelerator pedal by the driver, the opening through the second bypass passage 11B is performed. The intake air can be supplied to the engine 1 and the throttle bypass intake air amount can be adjusted by changing the opening degree. The air bypass valve control solenoid valve 142 is opened during the lean burn operation.
Other than that, the basic operation is to close.

An exhaust gas recirculation passage (EGR passage) for returning exhaust gas to the intake system is provided between the exhaust passage 4 and the intake passage 3.
The EGR passage 80 is provided with an EG
An R valve 81 is interposed. Here, the EGR valve 81
Is composed of a valve body 81a that can contact a valve seat formed in the EGR passage 80, and a diaphragm actuator 81b for adjusting the position of the valve body. The diaphragm actuator 81b is provided in the diaphragm chamber of the diaphragm actuator 81b. Is provided with a pilot passage 82 communicating with the intake passage downstream of the throttle valve.
In addition, an ERG valve control electromagnetic valve 83 is interposed.

Therefore, by controlling the opening degree of the EGR valve control solenoid valve 83 by the ECU 25 described later, the E
Exhaust gas can be returned to the intake system through the GR passage 80. In FIG. 2, reference numeral 15 denotes a fuel pressure regulator, which operates by receiving a negative pressure in the intake passage 3 and regulates the amount of fuel returning from a fuel pump (not shown) to the fuel tank. Thus, the pressure of the fuel injected from the injector 9 is adjusted.

Various sensors are provided to control the engine system. First, as shown in FIG. 2, the intake air passing through the air cleaner 7 is
An air flow sensor (intake amount sensor) 17 for detecting an intake air amount from Karman vortex information and an intake air temperature sensor 1 as intake air humidity parameter detecting means
8. An atmospheric pressure sensor 19 is provided.

The intake air temperature sensor 18 detects the temperature of the intake air of the engine 1. In addition, the intake passage 3
The throttle valve 8 is provided with an idle switch 21 in addition to a potentiometer type throttle position sensor 20 for detecting the opening of the throttle valve 8.

Further, a linear oxygen concentration sensor (hereinafter simply referred to as “linear O _2” ) for linearly detecting the oxygen concentration (O ₂ concentration) in the exhaust gas on the air-fuel ratio lean side is provided on the exhaust passage 4 side.
₂ ), a water temperature sensor 23 for detecting a temperature of cooling water for the engine 1 and a crank angle sensor 24 for detecting a crank angle shown in FIG. 3 (this crank angle sensor). 24 also functions as a rotation speed sensor for detecting the engine rotation speed Ne), a vehicle speed sensor 30, and the like.

The detection signals from these sensors and switches are input to the ECU 25 as shown in FIG. Here, the hardware configuration of the ECU 25 is as shown in FIG.
Is configured as a computer having a CPU (arithmetic unit) 26 as a main part thereof. The CPU 26 includes an intake air temperature sensor 18, an atmospheric pressure sensor 19, a throttle position sensor 20, a linear O ₂ sensor 22, a water temperature sensor 23. Are detected by the input interface 28
And an analog / digital converter 29.

The CPU 26 includes an air flow sensor 17, an idle switch 21, a crank angle sensor 24,
A detection signal from the vehicle speed sensor 30 or the like is directly input via the input interface 35. Further, the CPU 26 stores, via a bus line, a ROM that stores various data in addition to program data and fixed value data.
(Storage means) 36 or RAM which is updated and sequentially rewritten
Data is exchanged with the T.37.

As a result of the calculation by the CPU 26, EC
From U25, signals for controlling the operating state of the engine 1, such as a fuel injection control signal, an ignition timing control signal,
Various control signals such as an ISC control signal, a bypass air control signal, and an EGR control signal are output. Here, the fuel injection control (air-fuel ratio control) signal is
Through an injection driver 39 to an injector solenoid 9a for driving the injector 9 (more precisely, a transistor for the injector solenoid 9a).
6 through an ignition driver 40 to a power transistor 41, and a spark is sequentially generated in each ignition plug 16 by a distributor 43 from the power transistor 41 via an ignition coil 42.

The ISC control signal is output from the CPU 26 to the stepper motor 12b via the ISC driver 44, and the bypass air control signal is output from the CPU 26 via the bypass air driver 45 to the electromagnetic valve for controlling the air bypass valve. 142 is output to a solenoid 142a. Further, the EGR control signal is transmitted to the CPU 2
6 to the solenoid 83a of the ERG valve control electromagnetic valve 83 via the EGR driver 46.

Now, paying attention to the fuel injection control (air-fuel ratio control), for this fuel injection control (injector drive time control), the ECU 25, as shown in FIG. Fluctuation value detecting means 10
2. Combustion deterioration determination value calculation means 104, combustion state control means 105, combustion fluctuation adjustment element 106, angular acceleration detection means 1
07, a smoothing unit 108, a threshold updating unit 110, a misfire determination reference value 111, a rough road determining unit 113, and a lean control limiting unit 114.

Here, the combustion fluctuation adjusting element 106 adjusts the fuel injection pulse width Tinj to a desired state by a control signal from the combustion state control means 105, and performs a lean burn operation of an air-fuel ratio to be realized. , Injector 9
Functions as the combustion fluctuation adjusting element 106. In addition,
The fuel injection pulse width Tinj is represented by the following equation.

Tinj (j) = TB · KAC (j) · K
KAFL + Td or Tinj (j) = TB KAC (j) K + Td In this equation, TB is the basic drive time of the injector 9, and the information of the intake air amount A from the air flow sensor 17 and the crank angle sensor (engine speed) Sensor) 24, information on the intake air amount A / N per one revolution of the engine is obtained from the information on the engine speed N from the sensor 24, and the basic drive time TB is determined based on this information.

KAFL is a leaning correction coefficient, which is determined from the characteristics stored in the map in accordance with the operating state of the engine, so that the air-fuel ratio can be made lean or stoichiometric according to the operating state. Have been. KAC (j) is a correction coefficient for performing combustion state control corresponding to combustion fluctuation, as described later.

Further, a correction coefficient K corresponding to the engine cooling water temperature, the intake air temperature, the atmospheric pressure and the like is set, and the dead time (invalid time) Td is corrected in accordance with the battery voltage. . Further, the lean burn operation is configured to be performed when it is determined by the lean operation condition determination means that a predetermined condition is satisfied.

Thus, the ECU 25 has a function of air-fuel ratio control means for controlling the air-fuel ratio so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio under required operating conditions. By the way, the combustion state control device of the present embodiment includes an angular acceleration detecting means 107 for detecting an angular acceleration of a rotating shaft (crankshaft) driven by the engine. The angular acceleration detecting means 107 is configured as follows. Have been.

That is, as shown in FIG. 11, the angular acceleration detecting means 107 includes a crank angle sensor 24, a cylinder discriminating sensor 230, and an ECU 25 as a controller as main elements.
A rotating member 221 that rotates integrally with the crankshaft 201 of the engine is provided. The first, second and third vanes 221 projecting in the radial direction are provided on the periphery of the rotating member 221.
A, 221B, and 221C are formed, and a detection unit 222 provided so as to face the vanes 221A, 221B, and 221C from both sides passes the vanes 221A, 221B, and 221C as the rotating member 221 rotates. Is detected optically or electromagnetically, and a corresponding pulse output is performed.

The vanes 221A, 221B, 22
1C each have a circumferential length corresponding to a crankshaft rotation angle of a fixed angle, and are arranged at predetermined intervals in the circumferential direction. That is, the opposing edges of the adjacent vanes are disposed at an angle interval of 120 degrees from each other.

The cylinder discrimination sensor 230 is fixed to a camshaft (not shown),
During one revolution of the camshaft and one revolution of the camshaft, a pulse output is generated each time the camshaft takes a specific rotational position corresponding to one cylinder. The device of this embodiment mounted on a six-cylinder engine in which the ignition operation is performed in the order of the cylinder number is, for example, the third vane 2
The edge (front end 221C ′ or rear end) of 21C is the detection unit 2
22, the first cylinder shaft rotation angle region corresponding to one of the first cylinder and the fourth cylinder (preferably, mainly the expansion stroke in the one cylinder) of the first cylinder group When the crankshaft enters and the edge of the first vane 221A passes the detection unit 222,
The crankshaft is separated from the first rotation angle range.

Similarly, when passing through the edge of the first vane 221A, the first vane 221A enters the second crankshaft rotation angle region corresponding to one of the second and fifth cylinders constituting the second cylinder group. When passing through the edge of the second vane 221B, the second vane 221B is separated from the area. Further, at the time of passing the edge of the second vane 221B, it enters the third crankshaft rotation angle region corresponding to one of the third and sixth cylinders constituting the third cylinder group, and then the third vane 221C. Is separated from the same area when passing through the edge.

The discrimination between the first cylinder and the fourth cylinder, the discrimination between the second cylinder and the fifth cylinder, and the discrimination between the third cylinder and the sixth cylinder are performed based on the output of the cylinder discrimination sensor 230. It is configured as follows. With such a configuration,
The detection of the angular acceleration is performed as follows. That is, during the operation of the engine, the ECU 25 sequentially receives the pulse output from the crank angle sensor 24 and the detection signal of the cylinder discrimination sensor 230, and repeats the calculation periodically.

The ECU 25 includes a crank angle sensor 2
Then, it is determined which of the pulse outputs from the cylinders 4 is sequentially input after the pulse output from the cylinder determination sensor 230 is input. Thereby, the input pulse output from the crank angle sensor 24 is identified as to which cylinder it corresponds to, and preferably,
The cylinder that is currently mainly performing the expansion stroke (output stroke: BTDC 75 °) is identified as the identification cylinder.

Then, in response to the pulse input from the crank angle sensor 24, the ECU 25 determines the identification cylinder group m
When it is determined that the vehicle enters the crankshaft rotation angle region corresponding to (m is 1, 2, or 3), a timer for period measurement (not shown) is started. Then, the crank angle sensor 22
When the next pulse output is input from 0, the ECU 25 determines the departure from the crankshaft rotation angle region corresponding to the identified cylinder group m, stops the timing operation of the period measurement timer, and reads the time measurement result.

The time measurement result is a time interval TN (n) from the time of entry into the crankshaft rotation angle region corresponding to the identified cylinder group m to the time of departure from the region, ie, two time intervals corresponding to the identified cylinder group m. The period TN (n) is determined by a predetermined crank angle. here,
The subscript n in the cycle TN (n) indicates that the cycle corresponds to the n-th (current) ignition operation in the identification cylinder.

In the case of a six-cylinder engine, the cycle TN (n) is a cycle between the 120 ° crank angles of the identified cylinder group (the time interval between the operating states BTDC of 75 ° between adjacent cylinders), and more generally, N cylinders. (720 /
N) degree crank period. Note that the pulse output indicating the departure from the crankshaft rotation angle region corresponding to the current identification cylinder also indicates a rush into the crankshaft rotation angle region corresponding to the next identification cylinder.

Accordingly, in response to the pulse output, the cylinder identification step for the next identified cylinder is executed, and the cycle measurement timer is restarted to start the cycle measurement for the next identified cylinder. . With such an operation, the ECU 25 sets the 120-degree crank period TN
(N) is detected. A series of states from the # 1 cylinder to the # 6 cylinder is illustrated in FIG. 6, and the 120-degree inter-crank period is from TN (n−5) to TN (n). It is represented by Using these detected values, the angular acceleration ACC (n) of the crankshaft in the cycle is calculated by the following equation.

ACC (n) = 1 / TN (n) · ｛KL (m) / TN (n) −
KL (m-1) / TN (n-1) KL where KL (m) is the segment correction value, which is related to the current discriminating cylinder, In order to perform the correction for removing the cycle measurement error, the ECU 25 calculates the segment correction value KL (m) by the following equation.

KL (m) = {KL (m−3) * (1-XMFDKFG) + KR (n) * (XMFDKFD)} where XMFDKFG indicates a segment correction value gain. M in KL (m) is set for each corresponding cylinder group, m = 1 for cylinder groups # 1 and # 4, m = 2 for cylinder groups # 2 and # 5, and cylinder group # 6, m = 3 corresponds to # 3 and # 6, respectively.
KL (1) to KL (3) are repeated as shown in FIG.

Since m-1 in KL (m-1) means the one immediately before the corresponding m, KL (m) = KL
When (1), KL (m-1) = KL (3), KL (m) = KL (2) When KL (m-
When 1) = KL (1) and KL (m) = KL (3), KL (m-1) = KL (2) is shown. Further, KL (m-3) in the above equation indicates the KL (m) of the previous cycle in the same cylinder group, and # 4
KL (m-3) at the time of cylinder calculation is
KL (1) is used, and KL (m-3) at the time of calculation of # 1 cylinder
Uses KL (1) in the previous # 4 cylinder. KL (m-3) at the time of calculation for # 5 cylinder is KL for the previous # 2 cylinder.
(2) is used, and KL (m-3) in the previous # 5 cylinder is used as KL (m-3) in the calculation of the # 2 cylinder. KL (m-3) in the calculation of # 6 cylinder is KL (3) in the previous # 3 cylinder
Is used, and KL (m-3) in the calculation of the # 3 cylinder uses KL (3) in the previous # 6 cylinder.

On the other hand, KR (n) in the above equation is obtained by the following equation. KR (n) = 3 ・ TN (n) / TN (n) + TN (n-1) + TN (n-2) は This is the measurement time from the previous measurement time TN (n-2) two times to the current measurement time
This is a measurement value corresponding to the average measurement time up to TN (n). When calculating the segment correction value KL (m), the primary filter processing with the segment correction value gain XMFDKFG applies the above equation to KR (n). It is performed using.

The engine combustion state control apparatus of this embodiment includes a fluctuation detecting means 101 for detecting a fluctuation value of the angular acceleration by using a detection signal of the angular acceleration detecting means 107. The calculation of the fluctuation detecting means 101 is performed by calculating a difference between a smoothed value obtained by smoothing the detected angular velocity by the smoothing means 108 and the angular acceleration output from the angular acceleration detecting means 107. Have been.

That is, in the fluctuation detecting means 101, the acceleration fluctuation value ΔACC (n) is calculated by the following equation. ΔACC (n) = ACC (n) -ACCAV (n) Here, ACCAV (n) is a smoothed value obtained by smoothing the detected angular velocity by the smoothing means 108, and performs a primary filter process by the following equation. Is calculated by

ACVAC (n) = α · ACCAV (n−
1) + (1−α) · ACC (n) Here, α is an update gain in the primary filter processing, and a value of about 0.95 is adopted. Further, the variation value ΔACC (n) output from the variation detecting means 101 is normalized according to the operating state of the engine, and the normalized variation value IAC
A normalized fluctuation value detecting means 102 for obtaining (n) is provided.

That is, the calculation of the normalized variation value IAC (n) in the normalized variation value detection means 102 is performed by the following equation. IAC (n) = ΔACC (n) · Kte (Ev, Ne) where Kte (Ev, Ne) is an output correction coefficient,
It is set according to the characteristics shown in FIG.

In the characteristic shown in FIG. 10, the volume efficiency Ev is plotted on the horizontal axis, and the output correction coefficient Kte (E
v, Ne) is plotted on the vertical axis, and the characteristic of the upper right line is adopted as the engine speed Ne increases. Therefore, the characteristic of FIG. 10 is stored as a map, and the engine speed Ne and the volumetric efficiency E calculated from the detection signal of the crank angle sensor 24 and the like are stored.
v, the output correction coefficient Kte (Ev, Ne) is calculated by the ECU.
It is set at 25 and is configured to perform normalization by correction corresponding to the engine output.

Then, the normalized fluctuation value IAC (n) is compared with a predetermined threshold value IACTH to determine a combustion deterioration determination value VAC.
A combustion deterioration judgment value calculation means 104 for obtaining (j) is provided, and the combustion deterioration judgment value VAC (j) is configured to accumulate and obtain the deterioration amount in which the normalized fluctuation value IAC (n) falls below the threshold value IACTH. Have been. That is, the combustion deterioration determination value VAC (j) is calculated by the following equation.

VAC (j) = Σ ｛IAC (J) <IACTH｝ * ｛IACTH −
IAC (J)｝ where ｛IAC (J) <IACTH ｛in the above equation is IAC (J) <
This function takes "1" when IACTH is satisfied and "0" when it is not satisfied.
When (n) is below a predetermined threshold value IACTH, the amount below this threshold value is accumulated as a deterioration amount.

Therefore, the combustion deterioration judgment value VAC (j)
Is obtained by accumulating the deterioration amount using the difference between the threshold value IACTH and the normalized variation value IAC (j) as a weight, and reducing the influence of the numerical values near the threshold value so that the deterioration state can be accurately reflected. Is configured. Then, combustion deterioration determination value calculation means 1
04, the predetermined threshold value IACTH
Thus, the information is updated in accordance with the operating state of the engine.

The above-mentioned subscript j indicates a cylinder number. Further, the combustion deterioration determination value VAC (j) may be obtained by accumulating the number of times the normalized fluctuation value IAC (n) falls below the threshold value IACTH using a simpler program (that is, VAC (j) = Σ ｛). IAC (j) <IACTH II). The calculation result from the combustion deterioration determination value calculation means 104 as described above is configured to be used by the combustion state control means 105.

That is, the combustion state control means 105 refers to the combustion deterioration judgment value VAC (j) calculated by the combustion deterioration judgment value calculation means 104, and performs the engine combustion for a predetermined reference value from the reference value setting means 112. It is configured to control the fluctuation adjusting element 106. That is, the combustion state control means 105 is configured to perform the air-fuel ratio lean control based on the normalized fluctuation value.

The upper limit reference value (VACTH1) 112U from the upper limit reference value setting means 112U is used as a reference value for controlling the combustion fluctuation adjusting element 106 by the combustion state control means 105.
And the lower reference value (VACTH) from the lower reference value setting means 112L.
2) is provided. Then, the combustion fluctuation adjusting element 10
The control by 6 is performed so that the combustion deterioration determination value VAC (j) falls between the upper limit reference value (VACTH1) and the lower limit reference value (VACTH2).

That is, as described above, the control by the combustion fluctuation adjusting element 106 is configured to be performed by correcting the basic injection pulse width at the time of fuel injection, and the injection pulse width Tinj (j) is expressed by the following equation. It is configured to be calculated. Tinj (j) = TB × KAC (j) × K × KAFL + Td or Tinj (j) = TB × KAC (j) × K + Td And the correction coefficient KAC (j) in the above equation is as follows: It is being adjusted.

First, when the combustion deterioration determination value VAC (j) exceeds the upper limit reference value VACTH1, it is determined that the combustion fluctuation value has deteriorated beyond a predetermined value, and the fuel injection amount is increased. Is performed by calculating a correction coefficient KAC (j) according to the following equation. KAC (j) = KAC (j) + KAR · ｛VAC (j)-VACTH1｝ This calculates the correction value of the upper right characteristic on the rich side among the correction characteristics shown in FIG. 7, and KAR indicates the slope of the characteristic. It is a coefficient shown. KAC (j) on the right side indicates the correction coefficient calculated in the previous calculation cycle (n-1) for the cylinder number j, and is updated by the above equation.

In FIG. 7, the horizontal axis indicates the combustion deterioration determination value VAC.
The correction characteristic is shown by taking the correction coefficient KAC on the vertical axis. On the other hand, if the combustion deterioration determination value VAC (j) is lower than the lower limit reference value VACTH2, it is determined that there is a margin for further leaning, and the leaning correction for reducing the fuel injection amount is performed next. Correction coefficient KAC by formula
This is performed by calculating (j).

KAC (j) = KAC (j) −KAL ｛{VAC (j) −VACTH2} This is to calculate the correction value of the lean lower-left characteristic shown in FIG. 7, where KAL indicates the characteristic slope. It is a coefficient. Further, the combustion deterioration determination value VAC (j) is set to the lower limit reference value VACTH2.
As described above, when the value is equal to or less than the upper limit reference value VACTH1, it is determined that the operating state is appropriate, and the correction coefficient KAC (j) is not changed in order to keep the fuel injection amount at the previous state.

This corresponds to a flat characteristic between the lower left characteristic on the lean side and the upper right characteristic on the rich side shown in FIG.
This constitutes a dead zone for correction. Here, the lower limit reference value VACTH2 and the upper limit reference value VACTH1 are the combustion variation target value VA.
With reference to C0, the lower reference value VACTH2 is set to a value of (VAC0-ΔVAC), and the upper reference value VACTH1 is set to a value of (VAC0 + ΔVAC).

The combustion fluctuation target value VAC0 is calculated as COV (Coefficie
This is a value corresponding to the target value of nt of variance (approximately 10%), and the rotation fluctuation is limited for a finite period (128 cycles) by not performing fuel correction in the range of ΔVAC on both sides of the combustion fluctuation target value VAC0. In this case, a limit cycle due to an error caused by performing an evaluation using a value less than or equal to a threshold value is prevented.

The above-described correction coefficient KAC (j) is configured to be clipped at the upper and lower limits.
0.9 <KAC (j) <1.1 is set so as to fall within the range, and by performing the correction gradually without performing the rapid correction, the occurrence of a shock or the like is prevented and the stable control is performed. It is configured to be. Further, the combustion deterioration determination value VAC (j) is a set number of times of combustion, for example, 1
It is configured to be updated every 28 cycles. By performing control by grasping the combustion state for a relatively long period, stable and reliable control that reflects statistical characteristics is performed. Have been.

Then, rough road traveling is determined based on the fact that the normalized fluctuation value IAC (n) exceeds a predetermined rough road determination upper limit threshold (bad road determination threshold) IACTHU from the rough road determination threshold setting means 115 toward the acceleration side. And a lean control limiting means (lean control limiting means) for limiting the lean control (air-fuel ratio lean control) in the combustion state control means 105 based on the determination result of the rough road determining means 113. 114 are provided.

The rough road determination means 113 also accumulates the amount by which the normalized variation value IAC (n) falls below a predetermined rough road determination lower limit threshold (bad road determination threshold) IACTHL on the deceleration side, and makes a rough road determination. It is configured so that it can be performed more accurately. The magnitude relationship between the rough road determination upper threshold value IACTHU, the rough road determination lower threshold value IACTHL, and the combustion determination threshold value IACTH is, as shown in FIG. 14, as IACTHU>IACTH> IACTH.
L.

The rough road determination means 113 is configured to perform a predetermined calculation using the following threshold values and reference values as comparison targets to make a required determination. First, the normalized variation value IAC (n) is equal to the rough road determination upper threshold IA.
Each time CTHU exceeds the acceleration side, the excess amount is accumulated,
It is configured to calculate a rough road determination upper value VACU (j) as an accumulation result.

Each time the normalized variation value IAC (n) exceeds the rough road determination lower limit threshold value IACTHL toward the deceleration side, the excess amount is accumulated, and the rough road determination lower value VAC as a cumulative result is obtained.
It is configured to calculate L (j). Then, the rough road determination upper value VACU (j) becomes the upper rough road reference value VACU.
L, and a rough road determination index MM obtained by counting the number of times that the condition that the rough road determination lower value VACL (j) exceeds the lower rough road reference value VACLL is provided. MM is the rough road index determination value m2
Is determined to be when traveling on a bad road.

When it is determined that the vehicle is traveling on a rough road,
When calculating the injection pulse width Tinj (j) in the fuel injection control, the lean control restricting means 114 calculates a value that is not corrected by the lean correction coefficient KAFL, and the lean control is restricted. That is, when the lean control restricting means 114 does not operate, the injection pulse width Tinj (j) is calculated by the following equation.

Tinj (j) = TB × KAC (j) × K × KAFL + Td On the other hand, when the lean control restricting means 114 is determined to be running on a rough road, the injection pulse width Tinj (j) is calculated by the following equation.
Is calculated. Tinj (j) = TB × KAC (j) × K + Td Therefore, lean control is limited for the amount of correction by the leaning correction coefficient KAFL.

Since the combustion state control device for the engine according to one embodiment of the present invention is configured as described above, the operations shown in the flowcharts of FIGS. 4 and 5 are sequentially performed during the lean burn operation. First, in step S1, the angular acceleration ACC is
(N) is detected.

Here, the calculation used for the detection is based on the following equation. ACC (n) = 1 / TN (n) · ｛KL (m) / TN (n) -KL (m-1) / TN (n
-1) KL Note that KL (m) is a segment correction value, and performs correction to eliminate cycle measurement errors due to variations in vane angle intervals in the manufacture and installation of the vane in relation to the current identified cylinder. Therefore, the segment correction value KL is calculated by the following equation.
(M) is calculated.

KL (m) = {KL (m−3) * (1-XMFDKFG) + KR (n) * (XMFDKFD)} where XMFDKFG indicates a segment correction value gain. On the other hand, KR (n) in the above equation is obtained by the following equation. KR (n) = 3 ・ TN (n) / TN (n) + TN (n-1) + TN (n-2) は This is the measurement time from the previous measurement time TN (n-2) two times to the current measurement time
This is a measurement value corresponding to the average measurement time up to TN (n). In calculating the segment correction value KL (m), the primary filter processing using the segment correction value gain XMFDKFG is performed using the above-described equation.

Then, in step S2, the average acceleration ACCAV (n) is calculated. Where ACCAV
(N) is a smoothed value obtained by smoothing the detected angular velocity ACC (n) by the smoothing means 108, and is calculated by performing a primary filter process by the following equation. ACVAC (n) = α · ACCAV (n−1) + (1−
α) · ACC (n) Here, α is an update gain in the primary filter processing, and a value of about 0.95 is adopted.

Next, in step S3, the fluctuation detecting means 101 detects an acceleration fluctuation value ΔACC (n). That is, the angular velocity ACC (n) detected by the angular acceleration detecting means 107 and the average acceleration ACVAC (n) as a smoothed value smoothed by the smoothing means 108
And the difference between the acceleration variation value ΔACC
(N) is calculated by the following equation.

ΔACC (n) = ACC (n) −ACCAV (n) In step S 4, the normalized fluctuation value detecting means 1
As a result, a normalized fluctuation value IAC (n) obtained by normalizing the fluctuation value ΔACC (n) output from the fluctuation detecting means 101 according to the operating state of the engine is calculated by the following equation. IAC (n) = ΔACC (n) · Kte (Ev, Ne) where Kte (Ev, Ne) is an output correction coefficient,
It is set by the characteristics shown in FIG.

In the characteristic shown in FIG. 10, the volume efficiency Ev is plotted on the horizontal axis, and the output correction coefficient Kte (E
v, Ne) are plotted on the vertical axis, and the characteristic of the upper right line is adopted as the engine speed Ne increases. That is, in the characteristic of FIG. 10 stored as a map, the ECU 25 sets the output correction coefficient Kte (Ev, Ne) from the engine speed Ne and the volumetric efficiency Ev calculated from the detection signal of the crank angle sensor 220 and the like. , Normalization is performed by correction corresponding to the engine output.

Here, control characteristics in the case where the above-described normalization corresponding to the engine output is performed will be described. That is, the angular acceleration ω ′ is expressed by the following equation. ω '= 1 / Ie · ( Te-Tl) ···· Here, Te: engine torque Tl: Load torque Ie: Meanwhile moment of _{inertia, ω' = ω 0 '+} Δω' ········· Here, ω ₀ ′: average angular acceleration, ω ₀ ′ + Δω ′ = 1 / Ie · (Te−Tl) = 1 / Ie · (Te ₀ −T1) + ΔTe / Ie Therefore, Δω ′ = ΔTe / Ie ·········· By the way, the angular acceleration AC in step S1 described above.
In the detection method of C (n), the engine torque information is stored relatively well when there is no load disturbance. Then, as shown in the equation, the variation Δω ′ from the average angular acceleration ω ₀ ′
By using the [acceleration fluctuation value ΔACC (n)] and performing control as a normalized output [normalized fluctuation value IAC (n)] in consideration of the inertia moment Ie, the combustion characteristics are considered in consideration of the statistical properties of the combustion fluctuation. Control is performed in which the fluctuation is reliably reflected.

When the operation of step S4 is performed, then, in steps S41 to S44, the rough road determination value VAC
U and VACL are calculated. That is, in step S41, it is determined whether or not the normalized variation value IAC (n) exceeds the rough road determination upper limit threshold value IACTHU. If so, a "YES" route is taken, and the rough road determination is performed by the following equation. An upper value VACU (j) is calculated.

VACU (j) = VACU (j) + IAC
(N) -IACTHU Also, in step S43, the normalized variation value IAC
It is determined whether (n) is below the rough road determination lower limit threshold value IACTHL.
Take the "S" route and use the following formula to determine the rough road lower value VACL.
(J) is calculated.

VACL (j) = VACL (j) + IAC
(N) -IACTHL That is, the rough road determination upper value V that is obtained by accumulating an amount of the normalized variation value IAC (n) exceeding the rough road determination upper threshold IACTHU
ACU (j) and a rough road determination lower value VACL (j) obtained by accumulating an amount of the normalized variation value IAC (n) below the rough road determination lower value VACL (j) are calculated.

When these calculations are performed, the normalized fluctuation value IAC (n) does not change due to the deterioration of the combustion state, but the rotation fluctuation caused by the slipping of the wheels and the like. Combustion deterioration determination value V in steps S7 to S10 by determination value calculation means 104
The process proceeds to step S11 without performing the operation of calculating AC (j).

On the other hand, the normalized variation value IAC (n) is determined by the rough road determination upper threshold IACTHU and the rough road determination lower threshold IACTH.
If the value is a value between L and "NO" in steps S41 and S43,
Operations from 7 to step S10 are performed. That is, the change in the normalized fluctuation value IAC (n) is not caused by a slip or the like due to a bad road, but is caused by a change in the combustion state.
Operation 04 is performed, and the normalized fluctuation value IAC (n) is compared with a predetermined threshold value IACTH, and a combustion deterioration determination value VAC (j) is calculated by the following equation.

VAC (j) = {IAC (J) <IACTH}
* ｛IACTH-IAC (J)｝ First, in step S7, normalized fluctuation value IAC
The difference ΔIAC (n) between (n) and the predetermined threshold value IACTH is calculated, and then, in step S8, the difference ΔIAC
It is determined whether (n) is negative. This decision
This function corresponds to the function {IAC (J) <IACTH} in the above equation, and takes the value "1" when IAC (J) <IACTH holds, and takes the value "0" when it does not hold.

That is, when IAC (J) <IACTH holds, ΔIAC (n) is positive, and therefore, the combustion deterioration determination value VA in step S10 through the “NO” route.
The accumulation of C (j) is performed, and the above-mentioned function assumes a state of “1”. On the other hand, when IAC (J) <IACTH is not satisfied, ΔIAC (n) is negative, so that ΔIAC (n) = 0 is executed in step S9 through the “YES” route. As a result, in step S10, the accumulation of the combustion deterioration determination value VAC (j) is not performed.
The above function takes a state of “0”.

As a result, the normalized variation value IAC (n) as shown by points A to D in FIG.
When the value is below the value, the amount below the value is accumulated as the deterioration amount. Therefore, the combustion deterioration determination value VA
C (j) is obtained by accumulating the deterioration amount using the difference between the threshold value IACTH and the normalized fluctuation value IAC (j) as a weight. It is accurately reflected on the judgment value VAC (j).

The predetermined threshold value IACTH in the combustion deterioration determination value calculating means 104 is configured to be updated by the threshold value updating means 110 in accordance with the operating state of the engine, and the operating state closer to the lean limit is set. Can be realized. The above-mentioned subscript j indicates a cylinder number, and the combustion deterioration determination value VAC is set for each cylinder j.
(J) is accumulated.

Next, step S11 is executed, and it is determined whether or not N indicating the number of times of sampling exceeds 128. That is, it is determined whether or not the integration section shown in FIG. 8 has elapsed, and if not, the “NO” route is taken, step S13 is executed, and the number N is set to “1”.
If the rough road flag is not set and another lean condition is satisfied (step S131,
In step S132), step S2 is performed without performing the fuel correction.
0 is executed. As a result, the correction regarding the correction coefficient KAC (j) at the injection pulse width Tinj is not performed within the integrated section of 128 cycles, and the combustion deterioration determination value VAC (j) is exclusively accumulated.

Therefore, the deterioration judgment value VAC (j) is
The number of combustions is updated every set cycle, for example, every 128 cycles. By performing control by grasping the combustion state for a relatively long period, a stable and reliable operation reflecting the statistical characteristics is performed. Control is performed. Then, when the integration section has elapsed, “YE” in step S11 is performed.
Through the "S" route, the operations in and after step S12 are executed.

First, in step S12, the number N is reset to "1". Next, in step S121,
It is determined whether the rough road determination upper value VACU (j) exceeds a predetermined upper rough road reference value VACUL. If it exceeds, the non-bad road determination index M is reset to “0” in step S124 through the “YES” route.

On the other hand, the rough road determination upper value VACU (j) is
If it does not exceed the upper rough road reference value VACUL,
Through the “NO” route, the determination in step S122 is further performed. In step S122, it is determined whether or not the rough road determination lower value VACL (j) exceeds a predetermined lower rough road reference value VACLL. If it exceeds, the non-bad road determination index M is reset to “0” in step S124 through the “YES” route.

Then, after step S124, it is determined that the vehicle is running on a rough road, and in step S125,
The rough road determination index MM is incremented. If the rough road determination lower value VACL (j) does not exceed the lower rough road reference value VACLL, step S123 is executed through the “NO” route, and “1” is added to the non-rough road determination index M. Thus, the non-bad road determination index M increases.

That is, when the rough road determination upper value VACU (j) exceeds the upper rough road reference value VACUL on the acceleration side, the state shown at the point K in FIG. When VACL (j) is greater than the lower rough road reference value VACLL, the state shown by the point G in FIG. 12 indicates that the engine rotation fluctuation appears on both the acceleration side and the deceleration side.

On the other hand, the angular acceleration fluctuation at the point AK in FIG. 13 appears only on the deceleration side. Comparing and interpreting this phenomenon, the state in FIG. 13 is a change to the deceleration side due to the deterioration of combustion, and the state in FIG. 12 is not caused by the deterioration of combustion, but is a change in angular acceleration caused by a wheel slip or the like on a rough road. Is considered.

Therefore, the situation leading to step S125 corresponding to the situation shown in FIG. 12 is interpreted as running on a rough road, and the rough road determination index MM is added.
Then, in step S130, the rough road determination index MM is compared with a predetermined rough road index determination value m2, and when the rough road determination index MM exceeds the rough road determination index m2, the added rough road determination index MM is added. Since the index MM indicates that the vehicle is to be determined to be traveling on a rough road, step S131 is performed.
Is executed, and the rough road flag is set. Thereafter, the rough road determination index MM is reset to “0” (Step S)
132).

On the other hand, if the non-rough road index determination value M exceeds the non-rough road index determination value m1, a YES route is taken in step S126, step S127 is executed, and the rough road flag is reset. Thereafter, the rough road determination index MM and the non-rough road determination index M are each reset to "0" (steps S128 and S129). That is, the rough road determination upper value VACU calculated by sampling 128 times.
(J) exceeds the upper rough road reference value VACUL, or the lower rough road determination value VACL (j) becomes the lower rough road reference value VACLL.
Is exceeded, it is determined that the vehicle is traveling on a bad road,
The rough road determination index MM is set, and the rough road flag is set. On the other hand, in other cases, it is determined that the vehicle is not running on a rough road, and the rough road flag is reset.

The rough road flag set or reset as described above is referred to in step S133 or S131, and if it is set, step S135 is executed through the "YES" route. Step S
At 135, the operation of the lean control restricting means 114 is performed.
j (j) is calculated by the following equation, and fuel injection control based on the calculated value is performed through the ECU 25.

Tinj (j) = TB × KAC (j) × K + Td Here, the above equation is compared with the fuel injection pulse width Tinj (j) in step S20 described later, and the leaning coefficient K
AFL is omitted. Therefore, according to the above equation, the lean control is restricted without performing the lean correction using the lean coefficient KAFL in the fuel injection control.

By the way, if the rough road flag is not set, "N" is determined in step S133 or S131.
By taking the "O" route, the operation of step S134 or S132 is performed. That is, step S134 or S1
At 32, it is determined whether another lean condition is satisfied.
The determination is made based on the detection signals of the various sensors, and if not satisfied, the lean control in step S135 described above is restricted.

If it is determined in step S134 that the lean condition is satisfied, it is not a time of traveling on a rough road, but a state in which lean control is to be performed. Meanwhile, the operation by the lean control is performed. If the result of step S132 is YES, step S20
Is performed.

That is, if the YES route of step S134 is taken, in step S14 and step S15, comparison with a predetermined reference value is performed with reference to the combustion deterioration determination value VAC (j). That is, a comparison is made between the combustion deterioration determination value VAC (j) and the upper limit reference value (VACTH1) 112U. If the combustion deterioration determination value VAC (j) in FIG. 9 exceeds the upper limit reference value VACTH1, in other words, When the deterioration amount of the combustion fluctuation exceeds the upper limit reference value VACTH1, which is the limit, in step S15, the correction coefficient KAC (j) is calculated by the following equation.

KAC (j) = KAC (j) + KAR ｛{VAC (j) −VACTH1} This is a calculation of the correction value of the rich upper right characteristic shown in FIG. Assuming that the deterioration has occurred, the correction of the enrichment for increasing the fuel injection amount is performed by calculating the correction coefficient KAC (j). Here, KAR is a coefficient indicating the slope of the characteristic, and KAC (j) on the right-hand side is the number of the cylinder j for the previous calculation cycle (n
-1) indicates the correction coefficient calculated in the above, and is updated by the above equation.

If the combustion deterioration determination value VAC (j) is lower than the lower limit reference value VACTH2, the process proceeds to step S16.
In the case of taking the "YES" route in the case where there is a margin for further leaning, the leaning correction for decreasing the fuel injection amount is performed by the correction coefficient KAC by the following equation.
This is performed by calculating (j). KAC (j) = KAC (j)-KAL · ｛VAC (j)-VACTH2｝ This calculates the correction value of the lean lower left characteristic shown in Fig. 7, where KAL is a coefficient indicating the characteristic slope. .

Further, the combustion deterioration judgment value VAC (j) is
If it is equal to or more than the lower limit reference value VACTH2 and equal to or less than the upper limit reference value VACTH1, both of the steps S14 and S16 take the "NO" route, determine that the operating state is appropriate, and maintain the fuel injection amount in the previous state. Correction factor
Do not change KAC (j). This corresponds to a flat characteristic between the lean-side lower left characteristic and the rich-side upper right characteristic shown in FIG. 7, and constitutes a dead zone for correction.

Here, the lower limit reference value VACTH2 and the upper limit reference value VA
CTH1 is the lower limit reference value centered on the combustion fluctuation target value VAC0
VACTH2 to the value of (VAC0-ΔVAC), and the upper reference value VACTH1 to (VAC
0 + ΔVAC). Combustion fluctuation target value VAC0
Is the target value of COV (Coefficient of variance) (10%
The degree of rotation fluctuation is evaluated in a finite period (128 cycles) by not performing fuel correction in the range of ΔVAC on both sides of the target combustion fluctuation value VAC0, A limit cycle due to an error caused by the calculation is prevented.

Then, step S18 is executed, and the combustion deterioration judgment value VAC (j) is reset to "0". Next, in step S20, the basic injection pulse width at the time of fuel injection is corrected by the correction coefficient KAC (j) determined as described above. That is, the injection pulse width Tinj (j) is calculated by the following equation.

Tinj (j) = TB × KAC (j) × K × KAFL + Td By the correction of the basic injection pulse width, the combustion state control means 105 controls the combustion fluctuation adjusting element 106, and the engine operates in a desired manner. Lean operating conditions. By the way, the above-mentioned steps S12 to S18
Is performed when N = 1, which is the first time of the 128 cycles.
The operation of 135 is also performed when N = 1.

That is, step S20 is different from step S20.
At 131 it is determined that the bad road flag is not set,
In step S132, when it is determined that another lean condition is satisfied, the process is executed, and the operation under the lean control is performed. On the other hand, when it is determined in step S131 that the rough road flag is set, or in step S13
If it is determined in step 2 that other lean conditions are not satisfied, step S135 is executed, and the fuel injection control is performed by the lean control limiting unit 114 so that the correction by the leaning coefficient KAFL is not performed. .

Although various operations are performed as described above, the present embodiment has the following effects and advantages. (1) Estimation of combustion fluctuation in consideration of the stochastic characteristics of engine torque and air-fuel ratio control using this estimation can be performed. (2) The combustion state control of the engine in consideration of the statistical properties of combustion fluctuations can be performed in real time and by an on-board computer. (3) The cylinder pipe difference of the combustion fluctuation limit caused by the variation of the air-fuel ratio due to the deviation of the injector, the shape of the intake pipe, and the valve timing can be reliably corrected, and all the cylinders can be set to the combustion limit. Become. (4) According to the preceding paragraph, the emission of NOx can be minimized. (5) Detection and control of rotation fluctuation for each cylinder can be performed by one crank angle sensor, and more reliable lean burn control can be performed at low cost. (6) It is not necessary to add a sensor for rough road countermeasures, and lean operation in which adverse effects due to rough roads are prevented can be achieved without increasing costs. (7) The stoichiometric mode is used on rough roads that are difficult to detect.
Deterioration of exhaust gas and drivability can be avoided.

[0112]

As described above in detail, according to the engine combustion state control apparatus of the present invention, in an internal combustion engine which can be operated at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, the rotation driven by the internal combustion engine is performed. Fluctuation detecting means for detecting a fluctuation value of the angular acceleration of the shaft; normalized fluctuation value detecting means for normalizing the fluctuation value detected by the fluctuation detecting means according to the operating state of the internal combustion engine to obtain a normalized fluctuation value; Combustion state control means for performing air-fuel ratio lean control based on the normalized variation value, and rough road determination means for comparing the normalized variation value with a predetermined rough road determination threshold value to determine rough road travel And a leaning control limiting means for limiting the air-fuel ratio leaning control in the combustion state control means based on the determination result by the bad road determining means, and the following effects or advantages are provided. can get. (1) The control of the combustion state corresponding to the statistical characteristics of the operation state of the engine can be performed, and the lean limit operation can be performed in a wider operation range. (2) The deteriorated combustion state can be quantitatively and reliably grasped, and more reliable combustion state control can be performed. (3) It is not necessary to add a sensor for countermeasures against bad roads, and lean operation can be performed without increasing costs and preventing adverse effects due to bad roads.

[Brief description of the drawings]

FIG. 1 is a control block diagram of an engine combustion state control device as one embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an engine system having a combustion state control device as one embodiment of the present invention.

FIG. 3 is a hardware block diagram showing a control system of an engine system having a combustion state control device as one embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 6 is a waveform diagram for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 7 is a correction characteristic map for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 8 is a schematic graph for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 9 is a schematic graph for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 10 is a normalized characteristic map for explaining the operation of the engine combustion state control device as one embodiment of the present invention.

FIG. 11 is a schematic perspective view showing a rotation fluctuation detecting unit in the engine combustion state control device as one embodiment of the present invention.

FIG. 12 is a schematic graph showing characteristics of a control target in the combustion state control device for the engine as one embodiment of the present invention.

FIG. 13 is a schematic graph showing control target characteristics in the combustion state control device for the engine as one embodiment of the present invention.

FIG. 14 is a diagram for explaining a magnitude relationship between threshold values for determining a bad road and deterioration of combustion combustion.

FIG. 15 is a graph showing combustion fluctuation characteristics in a lean burn engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine (internal combustion engine) 2 Combustion chamber 3 Intake passage 3a Surge tank 4 Exhaust passage 5 Intake valve 6 Exhaust valve 7 Air cleaner 8 Throttle valve 9 Electromagnetic fuel injection valve (injector) 9a Injector solenoid 10 Three-way catalyst 11A First bypass passage 11B Second bypass passage 12 Stepper motor valve (STM valve) 12a Valve body 12b Stepper motor (ISC actuator) 12c Spring 13 First idle air valve 14 Air bypass valve 14a Valve body 14b Diaphragm actuator 15 Fuel pressure regulator 16 Spark plug 17 an air flow sensor (intake air amount sensor) 18 intake air humidity parameter intake air temperature sensor 19 as a detecting means the atmospheric pressure sensor 20 throttle position sensor 21 the idle switch 22 linear O ₂ sensor 2 Water temperature sensor 24 Crank angle sensor (engine speed sensor) 25 ECU as air-fuel ratio control means 26 CPU (arithmetic unit) 28 Input interface 29 Analog / digital converter 30 Vehicle speed sensor 35 Input interface 36 ROM (storage means) 37 RAM 39 Injection Driver 40 Ignition driver 41 Power transistor 42 Ignition coil 43 Distributor 44 ISC driver 45 Bypass air driver 46 EGR driver 80 Exhaust recirculation passage (EGR passage) 81 EGR valve 81a Valve body 81b Diaphragm actuator 82 Pilot passage 83 ERG valve control Solenoid valve 83a Solenoid 101 Fluctuation detection means 102 Normalized fluctuation value detection means 103 Accumulation means 104 Combustion deterioration judgment value calculation means 105 Combustion State control means 106 combustion fluctuation adjustment element 107 angular acceleration detection means 108 smoothing means 109 number of combustions 110 threshold updating means 111 misfire determination reference value 112 reference value setting means 112U upper reference value setting means 112L lower reference value setting means 113 bad road determination Means 114 Lean control restricting means 115 Bad road determination threshold 141 Pilot passage 142 Solenoid valve for air bypass valve control 142a Solenoid 221 Processor 221A First vane 221B Second vane 221C Third vane 222 Detecting unit

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Claims (1)

(57) [Claims] 1. An internal combustion engine capable of operating at an air-fuel ratio leaner than a stoichiometric air-fuel ratio, a fluctuation detecting means for detecting a fluctuation value of an angular acceleration of a rotating shaft driven by the internal combustion engine, and the fluctuation detecting means Normalized fluctuation value detecting means for normalizing the detected fluctuation value in accordance with the operating state of the internal combustion engine to obtain a normalized fluctuation value; and combustion state control for performing air-fuel ratio lean control based on the normalized fluctuation value. Means, a bad road determination means for comparing the normalized variation value and a predetermined rough road determination threshold value to determine rough road traveling, and based on the determination result by the bad road determination means, Characterized in that it is provided with lean control limiting means for limiting the air-fuel ratio lean control.
A combustion state control device for an internal combustion engine.