JPH07269405A - Bad road judging method in vehicle equipped with lean burn internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance judging accuracy in the case where an internal combustion engine is operated in the vicinity of a lean burn limit by detecting rotation variation caused in operation with a lean air-fuel ratio for each cylinder, by judging or estimating that a vehicle is traveling on a bad road when a rotation variation state indicating combustion degradation is detected in a plurality of cylinders. CONSTITUTION:A difference between a smoothened value obtained by smoothening angular velocity and angular acceleration is found by a rotation variation detecting means 101, wherein a detection signal of an angular acceleration detecting means 107 is inputted during vehicle operation, so as to compute an acceleration variation value. A variation data indicating combustion degradation of each cylinder is detected during operation in the vicinity of a lean burn limit air-fuel ratio of an engine. An air-fuel ratio change data obtained by accumulating degradation quantity of the variation data being lower than a threshold value is detected by an air-fuel ratio change data detecting means 104. In the case where a rotation variation state indicating combustion degradation is detected a vehicle is judged traveling on a bad road and shifted into a control state of bad road complying mode B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lean-burn internal combustion engine (engine) suitable for a lean-burn internal combustion engine (engine) that performs lean-burn operation at a leaner side air-fuel ratio than the stoichiometric air-fuel ratio under required operating conditions. The present invention relates to a rough road determination method in a vehicle equipped with an engine.

[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. There is. 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 becomes lean as much as possible) in order to reduce the NOx emission amount. The value of the fuel ratio is set near a limit (lean limit) at which the air-fuel mixture can perform stable combustion.

By performing such lean burn operation, NOx emission can be suppressed and fuel consumption can be greatly improved.

[0004]

By the way, in order to perform the lean burn operation, a control device controls the combustion state. Then, as a method of this control, the engine torque is estimated from the angular acceleration of the crankshaft, this estimation is performed for each moment using a changing instantaneous value, and in consideration of the probability and statistical properties of the engine torque,
It is considered that stable and reliable control is performed every predetermined period.

Further, as shown in FIG. 14, combustion fluctuations in the engine vary among cylinders, and this variation occurs due to variations in the air-fuel ratio due to deviations in injector, intake pipe shape, valve timing and the like. Therefore, in the lean burn operation, the combustion state is controlled so as to correspond to the air-fuel ratio of the cylinder with the largest combustion fluctuation.

When a vehicle equipped with such control means travels on a bad road, the engine speed fluctuation is affected by the bad road, and it is difficult to identify whether or not the rotation fluctuation is due to deterioration of combustion. Could be. That is, when the rotation fluctuation increases due to traveling on a rough road, the control system may be overcorrected to the rich side (rich side), and the NOx emission amount may increase.

On the contrary, when the rotation fluctuation becomes small due to traveling on a rough road, the control system is corrected to the lean side (lean side), which may lead to a decrease in drivability. The present invention has been devised in view of such problems, and even when the vehicle travels on a bad road during lean burn operation, the engine rotation fluctuation is caused by either bad road running or combustion deterioration. It is possible to identify and judge whether it is
An object of the present invention is to provide a rough road determination method in a vehicle equipped with a lean burn internal combustion engine.

[0008]

Therefore, a rough road determination method for a vehicle equipped with the lean burn internal combustion engine of the present invention is as follows:
Rotational fluctuation that occurs when operating at a leaner air-fuel ratio than the stoichiometric air-fuel ratio in a multi-cylinder internal combustion engine is detected for each cylinder,
When the internal combustion engine is operated in the vicinity of the lean combustion limit based on the detection result, a rotational fluctuation state indicating combustion deterioration in a plurality of cylinders is detected during operation in the vicinity of the lean combustion limit air-fuel ratio of the internal combustion engine. Based on the above, it is determined or estimated that the vehicle equipped with the internal combustion engine is traveling on a rough road.

According to another aspect of the present invention, there is provided a method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine, wherein angular acceleration of a rotary shaft driven by a multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder. Fluctuation data that correlates to rotation fluctuations associated with combustion deterioration during operation at a leaner side air-fuel ratio than the theoretical air-fuel ratio of the internal combustion engine is calculated for each cylinder based on the above detection results, and the internal combustion engine is calculated based on the calculated results. In the case of operating near the lean burn limit, the vehicle equipped with the internal combustion engine has a bad behavior based on the fact that the fluctuation data shows deterioration of combustion in a plurality of cylinders during operation near the lean burn limit air-fuel ratio of the internal combustion engine. It is characterized by determining or estimating that the vehicle is traveling on a road.

Further, in the method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to a third aspect, in the method according to the second aspect, the rotation fluctuation is a value on a combustion worse side than a combustion state determination threshold value. Is generated in the set period over a plurality of ignition periods, the fluctuation data is calculated as a rotation fluctuation state indicating deterioration of combustion.

According to a method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 4, the method according to claim 3 is such that the fluctuation data indicates that the combustion has deteriorated, and the combustion state is determined based on the combustion state determination threshold value. The vehicle is characterized in that it is determined or estimated that the vehicle is traveling on a rough road, with the minimum condition that the average value of the variation data on the worsening side is on the combustion worsening side than the second combustion state determination threshold.

Further, a method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to a fifth aspect is the method according to the second aspect, wherein a plurality of running conditions are provided during operation of the internal combustion engine in the vicinity of the lean burn limit air-fuel ratio. It is estimated that the vehicle equipped with the internal combustion engine is traveling on a bad road based on the fact that the fluctuation data indicates combustion deterioration in the cylinder, and then the internal combustion engine is operated at an inspection air-fuel ratio on the rich side of the air-fuel ratio near the lean limit. Then, it is characterized in that it is determined that the vehicle is traveling on a rough road based on the rotation fluctuation detected during the driving.

Further, the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 6 is the method according to claim 5, wherein the fluctuation data is calculated under the operation at the inspection air-fuel ratio, It is characterized in that the rotation fluctuation during operation is detected based on the fluctuation data.
The method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 7 is the method according to claim 6, wherein the fluctuation data in a plurality of cylinders represents a rotation fluctuation under the operation at the inspection air-fuel ratio. It is sometimes characterized in that the vehicle is judged to be traveling on a rough road.

A method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 8 is the method according to any one of claims 5 to 7, wherein the vehicle is running on a bad road. When the engine is operated, the internal combustion engine is operated at a lean air-fuel ratio for a bad road that is leaner than the inspection air-fuel ratio, and it is determined that traveling on a bad road has ended when the convergence state of the rotational fluctuation during the operation is detected. Is characterized by.

Further, a method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to claim 9 is the method according to claim 8, wherein the variation data is calculated under the operation at the lean air-fuel ratio for bad road. However, the convergence state of the rotation fluctuation during the operation is detected based on the fluctuation data. Further, a method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to claim 10 is the method according to claim 9, wherein the fluctuation data in the plurality of cylinders does not detect deterioration of combustion. The feature is that the convergence state of fluctuation is detected.

According to another aspect of the present invention, there is provided a method for determining a rough road in a vehicle equipped with a lean burn internal combustion engine, the angular acceleration of a rotary shaft driven by a multi-cylinder internal combustion engine being detected for each specific stroke of each cylinder. Based on the detection result, the fluctuation data correlated with the rotation fluctuation accompanying the combustion deterioration caused by the operation at the lean side air-fuel ratio from the theoretical air-fuel ratio of the internal combustion engine is calculated for each cylinder, and based on the fluctuation data for each cylinder. To determine whether the combustion is good or not for each cylinder, and to slightly change the air-fuel ratio of the internal combustion engine operating near the lean-burn limit air-fuel ratio to the lean side when the combustion is good and to the rich side when the combustion is poor. Of the air-fuel ratio change data for each cylinder and operating the internal combustion engine in the vicinity of the lean combustion limit based on the detection result. While the fluctuation data indicating the deterioration of combustion in the cylinder is detected, the air-fuel ratio change data in at least one cylinder continues during operation in the vicinity of the lean combustion limit air-fuel ratio of the internal combustion engine to the rich side of the air-fuel ratio. It is characterized in that it is determined or estimated that the vehicle equipped with the internal combustion engine is traveling on a rough road on the condition that the change is prompted.

[0017]

According to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to the above-mentioned claim 1, in a multi-cylinder internal combustion engine, the rotational fluctuation that occurs when operating at an air fuel ratio leaner than the stoichiometric air fuel ratio is generated for each cylinder. In the operation of the internal combustion engine in the vicinity of the lean combustion limit based on the detection result, the vehicle mounted with the internal combustion engine is based on the fact that the rotational fluctuation state of the combustion deterioration in the plurality of cylinders is detected during the operation. Is determined or estimated to be traveling on a rough road.

According to the method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to a second aspect of the invention, the angular acceleration of the rotary shaft driven by the multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder, and the theoretical Fluctuation data correlating to rotation fluctuations associated with combustion deterioration during operation at a leaner air-fuel ratio than the air-fuel ratio is calculated for each cylinder based on the detection result, and the lean-burn limit of the internal combustion engine based on the calculation result is calculated. In operation in the vicinity, it was determined that the vehicle equipped with the internal combustion engine was running on a rough road based on the fact that fluctuation data showed combustion deterioration in multiple cylinders while operating in the vicinity of the lean combustion limit air-fuel ratio of the internal combustion engine. Or estimation is performed.

Further, in the bad road determination method for a vehicle equipped with the lean burn internal combustion engine according to the third aspect, in addition to the operation of the method according to the second aspect, the rotation fluctuation is a value on the combustion worse side of the combustion state determination threshold value. When the above occurs for a set number of times or more within a set period over a plurality of ignition periods, the variation data is calculated as a rotation variation state indicating deterioration of combustion.

According to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to the fourth aspect, in addition to the function of the method according to the third aspect, the fluctuation data indicates that the combustion has deteriorated and the combustion state determination threshold value is exceeded. It is determined or estimated that the vehicle is traveling on a rough road with the minimum condition that the average value of the fluctuation data on the worsening combustion side is on the worsening combustion side than the second combustion state determination threshold value.

Further, in the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to the fifth aspect, in addition to the operation of the method according to the second aspect, during the operation of the internal combustion engine in the vicinity of the lean burn limit air-fuel ratio, , It is estimated that the vehicle equipped with the internal combustion engine is running on a bad road based on the fluctuation data showing combustion deterioration in multiple cylinders, and then the internal combustion engine is operated at the test air-fuel ratio on the rich side of the air-fuel ratio near the lean limit. Then, it is determined that the vehicle is traveling on a rough road based on the rotation fluctuation detected during the driving.

Further, in the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to the sixth aspect, in addition to the operation of the method according to the fifth aspect, fluctuation data is calculated under the operation at the inspection air-fuel ratio, Rotational fluctuations during the operation are detected based on the fluctuation data. In addition, in the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 7, in addition to the operation of the method according to claim 6, the fluctuation data in a plurality of cylinders causes a rotation fluctuation during operation at an inspection air-fuel ratio. When represented, it is determined that the vehicle is traveling on a rough road.

The method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 8 is the method according to claims 5 to 7.
In addition to the action of the method described in any one of the above, when it is determined that the vehicle is traveling on a bad road, the internal combustion engine is operated at a lean air-fuel ratio for a bad road on the lean side of the inspection air-fuel ratio, and during the operation. When the convergence state of the rotation fluctuation is detected, it is determined that the rough road traveling has ended.

Further, according to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to the ninth aspect, in addition to the operation of the method according to the eighth aspect, the variation data is obtained under the operation at the lean air-fuel ratio for the bad road. The calculated convergence state of the rotation fluctuation during the operation is detected based on the fluctuation data. Furthermore, in the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 10, in addition to the operation of the method according to claim 9, the fluctuation data in a plurality of cylinders does not detect combustion deterioration, The convergence state of fluctuation is detected.

According to the method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to an eleventh aspect, the angular acceleration of the rotating shaft driven by the multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder. Fluctuation data is calculated for each cylinder that correlates with the rotation fluctuation that accompanies the deterioration of combustion that occurs when the air-fuel ratio is leaner than the theoretical air-fuel ratio of the internal combustion engine based on the detection results. Whether or not the combustion is good is determined for each, and the air-fuel ratio of the internal combustion engine operating near the lean burn limit air-fuel ratio is changed slightly to lean when combustion is good and to rich when combustion deteriorates. The air-fuel ratio change data is detected for each cylinder, and the internal combustion engine is operated near the lean combustion limit based on the detection result. Then, fluctuation data indicating combustion deterioration in a plurality of cylinders is detected during operation of the internal combustion engine near the lean burn limit air-fuel ratio, and at least one cylinder is operated during operation of the internal combustion engine near the lean burn limit air-fuel ratio. It is determined or estimated that the vehicle equipped with the internal combustion engine is running on a rough road, with the minimum condition that the air-fuel ratio change data in step S1 is to promptly change the air-fuel ratio to the rich side. .

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rough road determination method for a vehicle equipped with a lean burn internal combustion engine as an embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a control block diagram of an apparatus for carrying out the present method. 2 is an overall configuration diagram of an engine system having this device, FIG. 3 is a hardware block diagram showing a control system of an engine system having this device, FIGS. 4 to 7 are flowcharts for explaining the operation of this device, and FIG. Is a waveform diagram for explaining the operation of the apparatus, FIG. 9 is a correction characteristic map for explaining the operation of the apparatus, FIG. 10 is a schematic graph for explaining the operation of the apparatus, and FIG. 11 is a book. FIG. 12 is a schematic graph for explaining the operation of the apparatus, FIG. 12 is a normalized characteristic map for explaining the operation of the apparatus, and FIG. 13 is a schematic perspective view showing a rotation fluctuation detection unit in the apparatus.

An engine for an automobile equipped with the present device has a theoretical air-fuel ratio (Stoichio) under required operating conditions.
It is configured as a lean burn engine that performs lean burn operation (lean burn operation) at a leaner air-fuel ratio (lean) than this, and 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 communicating with a combustion chamber 2 thereof, and the intake passage 3 and the combustion chamber 2 are controlled to communicate with each other 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.

Further, 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 in the exhaust passage 4 from the upstream side. A three-way catalyst 10 and a muffler (silencer) not shown are provided. The injector 9 is provided for each cylinder of the engine 1. Further, the intake passage 3 is provided with a surge tank 3a.

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

A first bypass passage 11A for bypassing the throttle valve 8 is provided in the intake passage 3, and a stepper motor valve (hereinafter referred to as an STM valve) which functions as an ISC valve is provided in the first bypass passage 11A. 12 are installed. In addition, in the first bypass passage 11A,
A wax-type fast idle air valve 13 whose opening is adjusted according to the engine cooling water temperature is also provided, and is attached to the STM valve 12.

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

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

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

Here, the air bypass valve 14 has a second
It is composed of a valve body 14a capable of contacting a valve seat portion formed in the bypass passage 11B, and a diaphragm type actuator 14b for adjusting the position of the valve body, and a diaphragm chamber of the diaphragm type actuator 14b is provided with: A pilot passage 141 communicating with the intake passage on the downstream side of the throttle valve is provided.
An air bypass valve control solenoid valve 142 is provided at 41.

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

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
The R valve 81 is interposed. Here, this EGR valve 81
Is composed of a valve body 81a capable of contacting a valve seat portion formed in the EGR passage 80, and a diaphragm type actuator 81b for adjusting the position of the valve body, and is provided in a diaphragm chamber of the diaphragm type actuator 81b. Is provided with a pilot passage 82 communicating with the intake passage downstream of the throttle valve.
An ERG valve control solenoid valve 83 is interposed in the.

Therefore, by controlling the opening degree of the EGR valve control solenoid valve 83 by the ECU 25, which will be described later, E
The 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 returned from a fuel pump (not shown) to the fuel tank. Thus, the pressure of 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 that has passed through the air cleaner 7 is introduced into the intake passage 3
An air flow sensor (intake air amount sensor) 17 that detects the intake air amount from the Karman vortex information and an intake air temperature sensor 1 that detects the temperature of the intake air to the engine 1 are provided in the inside.
8. An atmospheric pressure sensor 19 for detecting atmospheric pressure is provided.

Further, the throttle valve 8 in the intake passage 3
In addition to the potentiometer-type throttle position sensor 20 that detects the opening of the throttle valve 8, an idle switch 21 is provided in the portion where is arranged. Further, on the exhaust passage 4 side, an oxygen concentration sensor (hereinafter, simply referred to as “O ₂ sensor”) 22 for detecting the oxygen concentration (O ₂ concentration) in the exhaust gas is provided, and other sensors are used as the engine 1 Water temperature sensor 23 for detecting the temperature of the cooling water for cooling, and crank angle sensor 24 for detecting the 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). The vehicle speed sensor 30 and the like.

Detection signals from these sensors and switches are input to the ECU 25 as shown in FIG. Further, a shift detecting means 231 is provided so that a detection signal is inputted to the ECU 25. The shift detecting means 231 is configured to obtain a detection signal by detecting that the shift stage has been changed by ELC communication from the shift control computer.

Here, the hardware configuration of the ECU 25 is as shown in FIG. 3, and the ECU 25 is configured as a computer having a CPU (arithmetic unit) 26 as its main part, and the CPU 26 includes Detection signals from the intake air temperature sensor 18, the atmospheric pressure sensor 19, the throttle position sensor 20, the O ₂ sensor 22, the water temperature sensor 23, etc. are input through the input interface 28 and the analog / digital converter 29. There is.

The CPU 26 has an air flow sensor 17, an idle switch 21, a crank angle sensor 24,
Detection signals from the vehicle speed sensor 30, the cylinder discrimination sensor 230, the shift detecting means 231 and the like are directly input through the input interface 35. Furthermore, CP
The U 26 exchanges data with a ROM (storage unit) 36 that stores various data in addition to program data and fixed value data and a RAM 37 that is updated and sequentially rewritten via a bus line. There is.

Further, as a result of the calculation by the CPU 26, EC
From U25, a signal 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 sent to the CPU 26.
Is output to the injector solenoid 9a for driving the injector 9 (accurately, the transistor for the injector solenoid 9a) via the injection driver 39, and the ignition timing control signal is output from the CPU 2
6 is output to a power transistor 41 via an ignition driver 40, and a spark is sequentially generated from the power transistor 41 to an ignition plug 42 by a distributor 43 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 air bypass valve controlling solenoid valve. It is adapted to be output to the solenoid 142a of 142. Further, the EGR control signal is sent to the CPU2.
6 through the EGR driver 46 to the solenoid 83a of the ERG valve control solenoid valve 83.

Now, focusing on the fuel injection control (air-fuel ratio control), the ECU 25 controls the rotation fluctuation detecting means 101, as shown in FIG. 1, for the fuel injection control (injector drive time control). Data calculation means 10
2. Air-fuel ratio change data detection means 104, angular acceleration detection means 107, bad road running determination means 202, inspection air-fuel ratio operating means 203, lean road lean air-fuel ratio operating means 204, bad road running end determination means 205, rotational fluctuation. Convergence state detection means 206
It has the function of.

Further, the ECU 25 performs the rotation fluctuation state determination logic A which operates according to the flowchart of FIG. 5, the rough road response mode logic B which operates according to the flowchart of FIG. 6, and the rotation which operates according to the flowchart of FIG. It has a variation control mode logic C. Further, the ECU 25 has functions of a combustion state control means, a combustion fluctuation adjusting element, a smoothing means, a threshold updating means, and a misfire determination reference value, which are not shown.

Here, the combustion fluctuation adjusting element uses the control signal from the combustion state control means to inject the fuel injection pulse width Tinj.
Is performed to perform a lean burn operation of an air-fuel ratio to be realized, and the injector 9 functions as a combustion fluctuation adjusting element. The fuel injection pulse width Tin
j is represented by the following equation. Tinj (j) = TB · KAC (j) · K · KAFL +
Td in this formula is the basic drive time of the injector 9, and is based on the intake air amount A information from the air flow sensor 17 and the engine speed N information from the crank angle sensor (engine speed sensor) 24 per engine revolution. The intake air amount A / N information is calculated, and the basic drive time TB is determined based on this information.

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

Further, the correction coefficient K is set according to the engine cooling water temperature, the intake air temperature, the atmospheric pressure, etc., and the driving time is corrected according to the battery voltage by the dead time (ineffective time) Td. There is. Further, the lean burn operation is configured to be performed when the lean operation condition determining means determines that a predetermined condition is satisfied.

As a result, 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 the required operating conditions. By the way, the present combustion state control device has an angular acceleration detecting means 107 for detecting the angular acceleration of a rotating shaft (crank shaft) driven by the engine, and the angular acceleration detecting means 107 is configured as follows. .

That is, as shown in FIG. 13, the angular acceleration detecting means 107 includes a crank angle sensor 24, a cylinder discrimination sensor 230, and an ECU 25 as a controller as main elements.
It has a rotating member 221 that rotates integrally with the crankshaft 201 of the engine. The first, second and third vanes 221 protruding in the radial direction are provided on the periphery of the rotating member 221.
A, 221B, 221C are formed, and a detection unit 222 equipped so as to face the vanes 221A, 221B, 221C from both sides passes through the vanes 221A, 221B, 221C as the rotating member 221 rotates. Is detected optically or electromagnetically, and a corresponding pulse output is performed.

Then, the vanes 221A, 221B, 22
Each of 1C has a circumferential length corresponding to a crankshaft rotation angle of a constant angle, and is spaced apart at a predetermined angular interval in the circumferential direction. That is, the opposite edges of the adjacent vanes are arranged at an angular interval of 120 degrees from each other.

By the way, the cylinder discrimination sensor 230 is fixed to a cam shaft (not shown), and is connected to the crank shaft 20.
While 1 rotates twice and the camshaft rotates once, a pulse output is generated every time the camshaft takes a specific rotational position corresponding to one cylinder. The device of this embodiment mounted on a 6-cylinder engine in which the ignition operation is performed in the order of the cylinder numbers is, for example, the third vane 2
The edge of 21C (front end 221C 'or rear end) is the detection unit 2
When passing 22, the first crankshaft rotation angle region corresponding to either one of the first cylinder and the fourth cylinder (preferably, mainly the expansion stroke in the one cylinder) of the first cylinder group is passed. When the crankshaft rushes in and the edge of the first vane 221A passes the detection portion 222,
The crankshaft is adapted to be disengaged from the first rotation angle range.

Similarly, when passing through the edge of the first vane 221A, it rushes into the second crankshaft rotation angle region corresponding to either one of the second and fifth cylinders forming the second cylinder group, and then, When passing through the edge of the second vane 221B, the second vane 221B is detached from the same area. Further, when passing through the edge of the second vane 221B, it rushes into the third crankshaft rotation angle region corresponding to one of the third and sixth cylinders forming the third cylinder group, and then the third vane 221C. At the time of passing the edge of the, the departure from the same area is performed.

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 cylinder discrimination sensor 230. Is configured. With this configuration,
The detection of angular acceleration is performed as follows. That is, during engine operation, 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 periodically repeats the calculation.

Further, the ECU 25 uses the crank angle sensor 2
It is determined whether the pulse output from No. 4 is the one that is sequentially input after the pulse output from the cylinder determination sensor 230 is input. This makes it possible to identify which cylinder the input pulse output from the crank angle sensor 24 corresponds to, and preferably,
A cylinder that is currently executing the expansion stroke (output stroke: BTDC75 °) is identified as an identification cylinder.

Then, the ECU 25 responds to the pulse input from the crank angle sensor 24 in accordance with the identified cylinder group m.
When the entry into the crankshaft rotation angle region corresponding to (m is 1, 2 or 3) is determined, a cycle measuring timer (not shown) is started. Next, 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 time counting operation of the cycle measuring timer, and reads the time counting result.

This time measurement result is the 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 that region, that is, two time intervals corresponding to the identified cylinder group. A cycle TN (n) determined by a predetermined crank angle is shown. here,
The subscript n in the cycle TN (n) indicates that the cycle corresponds to the n-th (current) ignition operation in the identified cylinder.

Further, the cycle TN (n) is the cycle between 120-degree crank angles of the discriminating cylinder group in the 6-cylinder engine (time interval between operating states BTDC75 ° in adjacent cylinders), and more generally, N cylinders. In the engine (720 /
N) degree crank angle cycle. The pulse output indicating the departure from the crankshaft rotation angle region corresponding to the presently identified cylinder also represents the entry into the crankshaft rotation angle region corresponding to the next identified cylinder.

Therefore, in accordance with this pulse output, the cylinder identification step for the next identified cylinder is executed, and the period measuring timer is restarted to start the period measurement for the next identified cylinder. . By such an operation, the ECU 25 causes the 120 degree crank cycle TN
Although (n) is detected, a series of states from the # 1 cylinder to the # 6 cylinder is shown in FIG. 8, and the 120-degree crank cycle is from TN (n-5) to TN (n). It is represented by. By using these detected values, the angular acceleration ACC (n) of the crankshaft in the period is calculated by the following equation.

ACC (n) = 1 / TN (n)-{KL (m) / TN (n)-
KL (m-1) / TN (n-1)} where KL (m) is a segment correction value, which is related to the identified cylinder this time, due to variations in vane angular intervals during vane manufacturing and mounting. The ECU 25 calculates the segment correction value KL (m) by the following equation in order to perform the correction for removing the cycle measurement error.

KL (m) = {KL (m-3) * (1-XMFDKFG) + KR (n) * (XMFDKFD)} where XMFDKFG represents the segment correction value gain. Further, m in KL (m) is set for each corresponding cylinder group, and m = 1 for cylinder groups # 1 and # 4, m = 2 for cylinder groups # 2 and # 5, cylinder group # In FIG. 8, m = 3 corresponds to 3 and # 6, respectively.
KL (1) to KL (3) are repeated as shown in.

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) KL (m-
1) = KL (1), KL (m) = KL (3), KL (m-1) = KL (2). Further, KL (m-3) in the above equation indicates KL (m) of the previous cycle in the same cylinder group, and # 4
KL (m-3) at the time of calculation of cylinder is in the previous # 1 cylinder
KL (1) is used, and KL (m-3) when calculating # 1 cylinder
Uses KL (1) in the previous # 4 cylinder. KL (m-3) when calculating # 5 cylinder is KL in previous # 2 cylinder
(2) is used, and KL (m-3) at the time of calculation for the # 2 cylinder is KL (2) for the previous # 5 cylinder. KL (m-3) when calculating # 6 cylinder is KL (3) in the previous # 3 cylinder
Is used, and the KL (m-3) in the calculation of the # 3 cylinder is the KL (3) of 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)} This is the measured time from the previous measured time TN (n-2) to the current measured time.
It is a measurement value corresponding to the average measurement time up to TN (n). When calculating the segment correction value KL (m), the first-order filter processing by the segment correction value gain XMFDKFG is applied to KR (n) using the above equation. Performed using.

By the way, in order to realize the rough road determination method in the vehicle equipped with the lean burn internal combustion engine of the present embodiment, the engine combustion state control device includes the angular acceleration detecting means 107.
The rotation fluctuation detecting means 101 for detecting the fluctuation value of the angular acceleration by using the detection signal of 1. The calculation of the rotation fluctuation detecting means 101 is performed by obtaining the difference between the smoothed value obtained by smoothing the detected angular velocity by the smoothing means and the angular acceleration output from the angular acceleration detecting means 107. Has been done.

That is, in the rotation 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, and by performing the primary filter processing by the following equation. It is calculated.

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

That is, the calculation of the normalized fluctuation value IAC (n) in the fluctuation data calculating 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 by the characteristics shown in FIG.

In the characteristic of FIG. 12, the horizontal axis represents the volumetric efficiency Ev, and the output correction coefficient Kte (E
(v, Ne) is shown on the vertical axis, and the characteristic of the upper right line is adopted as the engine speed Ne increases. Therefore, the characteristics of FIG. 12 are stored as a map, and the engine speed Ne and the volumetric efficiency E calculated from the detection signals of the crank angle sensor 24 and the like are stored.
From v, the output correction coefficient Kte (Ev, Ne) is calculated by the ECU
25, and normalization by correction corresponding to the engine output is performed.

Then, the variation data IAC (n) is compared with a predetermined threshold value IACTH to compare the air-fuel ratio change data VAC.
The air-fuel ratio change data detection means 104 for determining (j) is provided, and the air-fuel ratio change data VAC (j) is configured to accumulate and obtain the deterioration amount in which the fluctuation data IAC (n) is below the threshold value IACTH. There is. That is, the air-fuel ratio change data 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 is a function that takes "1" when IACTH is established and takes "0" when IACTH is not established.
When (n) is below a predetermined threshold value IACTH, the amount of decrease is accumulated as a deterioration amount.

Therefore, the air-fuel ratio change data VAC
(J) is obtained by accumulating the deterioration amount with the difference between the threshold value IACTH and the fluctuation data IAC (j) as the weight, and the influence of the numerical value near the threshold value can be reduced to accurately reflect the deterioration state. Is configured. Then, the predetermined threshold value IACTH in the air-fuel ratio change data detecting means 104 is configured to be updated by the threshold value updating means in accordance with the operating state of the engine.

The subscript j indicates the cylinder number. As the air-fuel ratio change data VAC (j), the number of times the variation data IAC (n) falls below the threshold value IACTH may be accumulated by using a simpler program (that is, VAC (j) = Σ {IAC ( j) <IACTH}). The calculation result from the air-fuel ratio change data detection means 104 as described above is configured to be used by the combustion state control means.

That is, the combustion state control means has a rotation fluctuation control mode logic C described later, and is calculated by referring to the air-fuel ratio change data VAC (j) calculated by the air-fuel ratio change data detection means 104. Correction coefficient KAC
(J) is configured to control the combustion fluctuation adjusting element of the engine. An allowable fluctuation value VAC0 is provided as a reference value for controlling the combustion fluctuation adjusting element by the combustion state control means, and the air-fuel ratio change data VAC is provided.
The control corresponding to the difference between (j) and the fluctuation allowable value VAC0 is
It is configured to be performed in the flowchart of FIG.

The control by the combustion fluctuation adjusting element is
It is configured so that the air-fuel ratio change data VAC (j) is stored within the fluctuation allowable value VAC0. That is, the control by the combustion fluctuation adjusting element is configured to be performed by correcting the basic injection pulse width at the time of fuel injection as described above, and the injection pulse width Tinj (j) is
It is configured to be calculated by the following formula.

Tinj (j) = TB × KAC (j) × K × KAFL + Td Then, the correction coefficient KAC (j) in the above equation is adjusted as follows. First, the fluctuation data IAC
If (n) is less than the threshold value IACTH three times or more, it is considered that the combustion fluctuation value has deteriorated more than a predetermined value, and the correction of the enrichment for increasing the fuel injection amount is performed by the correction coefficient KAC according to the following equation. This is done by calculating (j).

KAC (j) = KAC (j) + ZFCPAL ・ {VAC
(j) -VAC0} This is for calculating the correction value of the rich side upper right characteristic of the correction characteristics shown in FIG. 9, and ZFCPAL is a coefficient indicating the inclination of the characteristic. Then, KAC (j) on the right side represents the correction coefficient calculated in the previous calculation cycle (n-1) for the number j cylinder, and is updated by the above equation.

In FIG. 9, the horizontal axis represents the air-fuel ratio change data VA.
The correction characteristic is shown by taking C and taking the correction coefficient KAC on the vertical axis. On the other hand, the fluctuation data IAC (n) is the threshold value IAC.
If less than TH is less than once in 128 cycles, it is considered that there is a margin for further leaning, and the leaning correction for reducing the fuel injection amount is a correction coefficient according to the following equation. The calculation is performed by calculating KAC (j).

KAC (j) = KAC (j)-ZFCPAL * {VAC
(j) -VAC0} This is for calculating the correction value of the lean side lower left characteristic shown in FIG. 9, and ZFCPAL is a coefficient indicating the inclination of the characteristic. Further, when the variation data IAC (n) is below the threshold value IACTH once or twice in 128 cycles, it is determined that the operating state is appropriate, and the fuel injection amount is maintained in the previous state. The coefficient KAC (j) is not changed.

This corresponds to the flat characteristic between the lean side lower left characteristic and the rich side upper right characteristic shown in FIG.
It forms a dead zone for correction. By the way, the fluctuation allowable value VAC0 is a value corresponding to the target value (about 10%) of COV (Coefficient of variance).
By not compensating the fuel in the range of ΔVAC on both sides of, the rotation fluctuation can be evaluated in a finite period (128 cycles), and the limit cycle due to the error caused by the calculation below the threshold value can be prevented. It is supposed to do.

The above-mentioned correction coefficient KAC (j) is configured to be clipped by the upper and lower limit values.
It is set so that it falls within the range of 0.85 <KAC (j) <1.1, and the shock is prevented from occurring and stable control is performed by performing the correction gradually without performing the rapid correction. It is configured to Further, the air-fuel ratio change data VAC (j) is updated every set number of combustions, for example, 128 (or 256) cycles, and the control is performed by grasping the combustion state for a relatively long period. Is performed, stable and reliable control that reflects statistical characteristics is performed.

In this manner, control is performed to slightly change the air-fuel ratio of the internal combustion engine operating near the lean burn limit air-fuel ratio to lean side when combustion is good and to rich side when combustion is bad. It is supposed to be. By the way, in the present embodiment, a vehicle equipped with an internal combustion engine runs on a rough road based on the fact that a rotational fluctuation state indicating combustion deterioration is detected in a plurality of cylinders during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio. It is configured to determine or estimate that it is in the middle and to shift to the rough road response mode.

Further, in the case where the rotation fluctuation becomes a value on the combustion worse side than the combustion state judgment threshold value for the number of times set or more within the set period over a plurality of ignition periods, the fluctuation data indicates the rotation fluctuation state indicating the combustion deterioration. It is configured to be calculated. That is, in the 128 cycles, the variation data IAC (n) is the threshold value IACT three times or more.
On the condition that three or more cylinders that are equal to or less than H are detected, the mode is changed to the rough road response mode.

The minimum condition is that the variation data indicates combustion deterioration and the average value of the variation data on the combustion deterioration side of the combustion state determination threshold value is on the combustion deterioration side of the second combustion state determination threshold value. Is determined or estimated to be traveling on a rough road, and the mode is changed to the rough road handling mode. That is, the variation data IAC (n) is on the combustion worse side of the threshold value IACTH.
On the condition that the average value of (n) is on the worse side of combustion than the set value as the second combustion state determination threshold, the mode is changed to the rough road response mode.

Further, it is a minimum condition that the air-fuel ratio change data in at least one cylinder continuously promotes the change to the rich side of the air-fuel ratio during the operation of the internal combustion engine in the vicinity of the lean burn limit air-fuel ratio. It is configured to determine or estimate that the vehicle equipped with the internal combustion engine is traveling on a rough road and to shift to the rough road response mode. That is, in the fluctuation data calculation means 102 of the rotation fluctuation detection means 101, fluctuation data IAC indicating combustion deterioration in a plurality of cylinders during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio.
(N) is detected, and at the air-fuel ratio change data detection means 104, the air-fuel ratio change data VAC (j) in at least one cylinder continues to prompt the change of the air-fuel ratio to the rich side. As a minimum condition, it is determined or estimated that the vehicle equipped with the internal combustion engine is traveling on a rough road, and the rotation fluctuation state determination logic A causes the rotation fluctuation control mode logic C to change from the control state to the rough road response mode B.
It is configured to shift to the control state.

Specifically, the above-mentioned air-fuel ratio change data VA
On the condition that there is a cylinder in which the state in which C (j) exceeds a predetermined set value is generated three times in a row, the mode is switched to the rough road response mode. Furthermore, it is estimated that the vehicle equipped with the internal combustion engine is running on a bad road based on the fact that the fluctuation data indicates deterioration of combustion in multiple cylinders, and then the internal combustion engine is tested at an air-fuel ratio on the rich side of the air-fuel ratio near the lean limit. It is configured to drive and determine that the vehicle is traveling on a rough road based on the rotation fluctuation detected during the driving.

That is, when the mode is changed to the rough road handling mode as described above, in the rough road handling mode, the test air-fuel ratio operation means 203 performs the test air-fuel ratio operation at a predetermined test air-fuel ratio. It is configured. The inspection air-fuel ratio is set on the rich side of the air-fuel ratio near the lean limit, and in order to distinguish whether the rotation fluctuation is due to deterioration of combustion or due to running on a bad road, the lean operation is stopped for the time being and rich. It is driven by the side.

In the test air-fuel ratio operation, the stoichiometric feedback state is maintained for 128 × 2 cycles, and E
The operation is performed by an open loop ignition timing without GR (ignition timing corresponding to without EGR), and is performed in a state where interference due to other elements can be eliminated.
Then, the variation data is calculated under the operation at the inspection air-fuel ratio, and the rotation variation during the operation is detected based on the variation data.

Further, when the fluctuation data in the plurality of cylinders represent the rotation fluctuation under the operation at the inspection air-fuel ratio, it is determined that the vehicle is traveling on a bad road. That is, also during the operation by the inspection air-fuel ratio operating means 203, the fluctuation data detecting means 101 calculates the fluctuation data IAC (n) by the fluctuation data calculating means 102, and the rough road running judging means 202 calculates the fluctuation data IA.
It is determined whether or not C (n) satisfies a predetermined condition and whether or not the vehicle is traveling on a rough road.

Here, the judgment by the rough road running judging means 202 is "the fluctuation data IAC (n) below the threshold value IACTH is generated 3 times or more in 3 cylinders in 256 cycles.
If the condition is met, the rotation fluctuation does not improve despite the operation on the rich side.Therefore, the rotation fluctuation is not caused by lean combustion, It has come to be determined that it is caused by road traveling.

When it is determined that the vehicle is traveling on a rough road, the internal combustion engine is operated at a lean air-fuel ratio for a bad road on the lean side of the test air-fuel ratio, and the convergence state of the rotational fluctuation during the running is detected. When it is performed, it is configured to determine that the rough road traveling has ended. That is, the rough road traveling determination means 20
When it is determined by 2 that the vehicle is running on a bad road, the lean air-fuel ratio operation means for bad road 204 operates at a lean air-fuel ratio for a bad road that is leaner than the test air-fuel ratio. Has become.

Therefore, even if the lean limit operation is not reached, the desired lean side operation is performed to improve fuel efficiency and NOx.
Are being reduced. This is based on the recognition that when traveling on a rough road, it is not a state in which the combustion state should be improved but a lean operating state. Then, such a lean operation is performed for 128 cycles, and the correction coefficient KAC relating to the fuel injection control at this time is the value immediately before the transition to the rough road mode.

Further, every time the above-mentioned 128 cycles of the lean air-fuel ratio operation for bad roads are completed, the rotation fluctuation convergence state detection means 206 determines whether the rotation fluctuations have converged. Inside threshold IA
The condition of whether or not there are three or more cylinders that do not generate the fluctuation data IAC (n) equal to or lower than CTH is determined. If the condition is satisfied, the rough road traveling end determination unit 205
It is determined that the rough road has ended and the rotation fluctuation has been eliminated.

When the end of the bad road is not detected, the operation by the lean air-fuel ratio operation means for bad road 204 is continued for 128 × 20 cycles. Also, after 128 × 20 cycles have passed,
The operation by the inspection air-fuel ratio operation means 203 is performed again,
It is configured to confirm that the vehicle is traveling on a rough road.

The reference value for misfire determination is set,
The misfire is determined based on the variation data IAC (n) exceeding the misfire determination reference value on the worsening combustion side, and the misfire information is stored in the misfire information address (j) of the current cylinder so that the misfire control is performed. It is configured. Since the control system for realizing the rough road determination method in the vehicle equipped with the lean burn internal combustion engine as one embodiment of the present invention is configured as described above, the control system shown in FIG.
The operations shown in the flowchart of FIG. 7 are sequentially performed.

First, in step S1 shown in FIG.
The angular acceleration detecting means 107 detects the angular acceleration ACC (n). Here, the calculation used for detection is according to the following equation. ACC (n) = 1 / TN (n) ・ {KL (m) / TN (n) -KL (m-1) / TN (n
-1)) Note that KL (m) is a segment correction value, and is related to the identified cylinder this time, and is corrected to eliminate cycle measurement errors due to variations in vane angle intervals during vane manufacturing and mounting. Therefore, the segment correction value KL
(M) is calculated.

KL (m) = {KL (m-3) * (1-XMFDKFG) + KR (n) * (XM
FDKFD)} However, XMFDKFG shows the segment correction value gain. On the other hand, KR (n) in the above equation is calculated by the following equation. KR (n) = 3 ・ TN (n) / {TN (n) + TN (n-1) + TN (n-2)} This is the measured time from the previous measured time TN (n-2) to the current measured time.
This is a measurement value corresponding to the average measurement time up to TN (n), and when the segment correction value KL (m) is calculated, the first-order filter processing by the segment correction value gain XMFDKFG is performed using the above-mentioned formula.

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 a smoothing means, and is calculated by performing a primary filter process according to the following equation. ACCAV (n) = α.ACCAV (n-1) + (1-
α) · ACC (n) Here, α is an update gain in the primary filter processing, and takes a value of about 0.95.

Next, in step S3, the rotation fluctuation detecting means 101 detects the acceleration fluctuation value ΔACC (n). That is, the acceleration fluctuation value ΔACC (n) is obtained by obtaining the difference between the angular velocity ACC (n) detected by the angular acceleration detection means 107 and the average acceleration ACCAV (n) as a smoothed value smoothed by the smoothing means.
Is calculated by the following formula.

ΔACC (n) = ACC (n) −ACCAV (n) In step S4, the fluctuation data calculation means 10
2, the fluctuation data IAC (n) obtained by normalizing the fluctuation value ΔACC (n) output from the rotation 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 according to the characteristics shown in FIG.

In the characteristic of FIG. 12, the horizontal axis represents the volumetric efficiency Ev, and the output correction coefficient Kte (E
(v, Ne) is shown 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. 12 stored as a map, the output correction coefficient Kte (Ev, Ne) is set in the ECU 25 from the engine speed Ne and the volumetric efficiency Ev calculated from the detection signals of the crank angle sensor 220 and the like. , Normalization by correction corresponding to the engine output is performed.

Now, the control characteristics in the case where the normalization corresponding to the engine output as described above is performed will be described. That is, the angular acceleration ω'is represented by the following equation. ω ′ = 1 / Ie · (Te−Tl) ... Here, Te: engine torque Tl: load torque Ie: moment of inertia while ω ′ = ω ₀ ′ + Δω ′ .... - here, omega ₀ ': the average angular acceleration, the _{equation, ω 0' + Δω '=} 1 / Ie · (Te-Tl) = 1 / Ie · (Te 0 -Tl) + ΔTe / Ie Thus, [Delta] [omega' = .DELTA.Te / Ie ..... By the way, the angular acceleration AC in step S1 described above.
With the C (n) detection method, 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 ′
Normalized output [variation data I using [acceleration variation value ΔACC (n)] and considering the inertia moment Ie
By performing the control as AC (n)], the control that reliably reflects the combustion fluctuation is performed in consideration of the statistical property of the combustion fluctuation.

When the operation of step S4 is performed, then in step S5, misfire determination is performed. That is, it is determined whether or not the fluctuation data IAC (n) exceeds the misfire determination reference value set by the misfire determination reference value setting means, and if it exceeds, it is determined that a misfire has occurred. To be done.

If this determination is made,
Step S6 is executed, misfire information is stored in the misfire information address (j) of the current cylinder, and misfire control is performed. On the other hand, if the misfire is not judged,
Alternatively, after the misfire is determined and step S6 is executed, the operation of the air-fuel ratio change data detection means 104 in steps S7 to S10 is executed to compare the fluctuation data IAC (n) with the predetermined threshold value IACTH. Then, the air-fuel ratio change data VAC (j) is calculated by the following equation.

VAC (j) = Σ {IAC (J) <IACTH}
* {IACTH-IAC (J)} First, in step S7, fluctuation data IAC (n)
And a predetermined threshold value IACTH are calculated, the difference ΔIAC (n) is calculated, and then, in step S8, the difference ΔIAC (n) is calculated.
Is determined to be negative. This judgment corresponds to the function {IAC (J) <IACTH} in the above equation,
When IAC (J) <IACTH is satisfied, “1” is taken, and when not, it is taken as “0”.

That is, since ΔIAC (n) is positive when IAC (J) <IACTH, the air-fuel ratio change data V in step S10 is passed through the “NO” route.
AC (j) is accumulated, and the above function is in a state of taking "1". On the other hand, when IAC (J) <IACTH is not established, ΔIAC (n) is negative, so ΔIAC (n) = 0 is executed in step S9 through the “YES” route. As a result, in step S10, the accumulation of the air-fuel ratio change data VAC (j) is not performed, and the above function takes a state of "0".

As a result, when the variation data IAC (n) is below the predetermined threshold value IACTH, as shown by points a to d in FIG. 10, this lower amount is accumulated as the deterioration amount. Therefore, the air-fuel ratio change data VA
C (j) is obtained by accumulating the deterioration amount with the difference between the threshold value IACTH and the fluctuation data IAC (j) as the weight, and the influence of the numerical value near the threshold value is reduced so that the deterioration state is the air-fuel ratio change data. Accurately reflected in VAC (j).

Then, the air-fuel ratio change data detection means 104
The predetermined threshold value IACTH in (1) is configured to be updated by the threshold value updating means in accordance with the operating state of the engine, so that an operating state closer to the lean limit can be realized. The subscript j indicates the cylinder number, and the air-fuel ratio change data VAC (j) for each cylinder j.
Is accumulated.

In this way, the variation data IAC (n)
And the air-fuel ratio change data VAC (j) are calculated for each calculation cycle. On the other hand, the rotation fluctuation state determination logic A
Is performed according to the flowchart of FIG. First, in step A1, it is determined whether the lean combustion feedback operation is being performed. If the lean combustion feedback operation is being performed, steps A2 and thereafter are executed.

When the lean-burn feedback operation is not being performed, the return operation is performed and the next operation cycle is awaited. In step A2, the shift detection means 23
Based on the detection signal of No. 1, it is judged whether or not the gear is being changed or within 3 seconds after the gear change, and if the conditions are satisfied, the process returns to the judgment of Step A1 through the “YES” route without executing Step A3 and thereafter.

This is for continuing the current operating state without changing the operation mode during the shift or for 3 seconds after the shift. During such a period, the rotation fluctuation occurs due to the shift, combustion deterioration or This is because it is difficult to detect the rotation fluctuation due to traveling on a rough road. By the way, in step A3 to step A5, the condition for shifting to the rough road countermeasure mode is determined.

First, in step A3, the fluctuation data IAC (n) calculated by the fluctuation data calculation means 102 in the rotation fluctuation detection means 101 is used to calculate fluctuation data IAC equal to or less than the threshold value IACTH in 128 cycles.
It is determined whether or not there are three or more cylinders that have generated (n) three or more times. As a result, the fluctuation data IAC (n)
Judgment is made when the occurrence state of the rotation fluctuation is equal to or more than a predetermined value, as viewed from the individual values of

Then, in step A4, fluctuation data IA equal to or less than the threshold value IACTH in 128 cycles
It is determined whether the average value of C (n) is greater than or equal to the set value. As a result, the judgment is made as to the case where the occurrence state of the rotation fluctuation is more than the predetermined value on average, as seen from the individual values of the fluctuation data IAC (n).

Then, in step A5, the air-fuel ratio change data detecting means 10 in the rotation fluctuation detecting means 101.
Using the air-fuel ratio change data VAC (j) calculated in step 4, the air-fuel ratio change data VAC in 128 cycles
It is determined whether (j) exceeds a predetermined determination value. Thereby, the threshold value IAC of the fluctuation data IAC (n)
A determination is made as to the case where the occurrence state of the rotation fluctuation as seen from the accumulated value of the amount exceeding TH is more than a predetermined amount in total.

When all the three conditions in the above steps A3 to A5 are satisfied, "YES"
Through the route, a transition is made to the rough road countermeasure mode in which the rough road countermeasure mode logic B is activated. If at least one of the three conditions is not satisfied, it is not the rotation fluctuation state when the vehicle is traveling on a rough road, so the possibility of traveling on a rough road is not estimated, and the normal route is performed through the “NO” route. Fluctuation control mode logic C which is the control system of
The rotation fluctuation control mode for activating is selected.

By the way, the rough road response mode logic B operates according to the flowchart of FIG. 6, and first, in step B1, the inspection air-fuel ratio operation means 203 performs the inspection air-fuel ratio operation. The inspection air-fuel ratio is set on the rich side of the air-fuel ratio near the lean limit, and in order to distinguish whether the rotation fluctuation is due to deterioration of combustion or due to running on a bad road, the lean operation is stopped for the time being and rich. Driving on the side is performed.

Then, the test air-fuel ratio operation is performed for 128 × 2 cycles in the stoichiometric feedback state and with an open loop ignition timing without EGR (ignition timing corresponding to without EGR), and other elements. Is performed in a state in which interference due to can be eliminated. Further, also during operation by the inspection air-fuel ratio operating means 203, the fluctuation data detecting means 101 calculates the fluctuation data IAC (n) by the fluctuation data calculating means 102, and the rough road running judging means 202 calculates the fluctuation data IAC ( It is determined whether or not n) satisfies a predetermined condition to determine whether or not the vehicle is traveling on a rough road.

That is, in step B2, "25
Fluctuation data IAC below threshold IACTH during 6 cycles
It is determined whether or not (n) has three or more cylinders that occur three times or more. " When the conditions are satisfied, the occurrence of rotation fluctuation is not improved despite the operation on the rich side, so the occurrence of rotation fluctuation is not due to lean combustion but due to running on a rough road. It is determined that step B3 and subsequent steps are executed through the “YES” route.

In step B3 and subsequent steps, when it is determined that the vehicle is traveling on a rough road, the internal combustion engine is operated at a lean air-fuel ratio for bad roads, which is leaner than the inspection air-fuel ratio, and convergence of rotation fluctuations during the operation. When the condition is detected, it is determined that the rough road traveling has ended. First, in step B3, lean operation is performed for 128 cycles. That is, when the rough road running determination unit 202 determines that the vehicle is in a bad road running state, the bad road lean air-fuel ratio operation unit 204 sets the lean road lean air-fuel ratio on the lean side of the inspection air-fuel ratio. Is being operated.

As a result, the desired lean side operation is performed even before the lean limit operation is reached, which improves fuel efficiency and NOx.
Can be reduced. Here, when the vehicle is traveling on a rough road, the combustion state should not be improved, so that no problem occurs even if the lean operation is performed. Note that such lean operation is performed by adopting the value immediately before the transition to the rough road mode as the correction coefficient KAC related to the fuel injection control.

Next, step B4 is executed, and every time the above-mentioned 128 cycles of the rough road lean air-fuel ratio operation is completed, the rotation fluctuation convergence state detecting means 206 determines whether the rotation fluctuation converges. That is, fluctuation data IAC (n) equal to or less than the threshold value IACTH during the 128 cycles.
The condition is determined whether there are three or more cylinders that do not generate.

When the condition is satisfied, the bad road traveling end judging means 205 judges that the bad road is ended and the rotation fluctuation is eliminated. When the end of the rough road is not detected, the rough road is being continued, so step B5 is executed through the “NO” route, and thereafter, step 128 is executed through the “NO” route for 128 × 20 cycles. B3 is executed and the lean air-fuel ratio operation means 2 for bad roads is executed.
The operation according to 04 is continued.

Further, after 128 × 20 cycles have passed, step B1 is executed through the “YES” route from step B5, the operation by the inspection air-fuel ratio operation means 203 is performed again, and it is confirmed that the vehicle is traveling on a rough road. Done.
By the way, when the mode for executing the rotation fluctuation control mode logic C is selected in the rotation fluctuation state determination logic A of FIG. 5, the operation according to the flowchart of FIG. 7 is performed.

First, in step C1, the fluctuation data IAC (n) is equal to the threshold value IACT in 128 cycles.
It is determined whether or not the state of being H or less is generated three times or more. If it is, it is assumed that the combustion fluctuation value has deteriorated more than a predetermined value, and step C2 is executed through the “YES” route, and the enrichment correction for increasing the fuel injection amount is corrected by the following equation. The calculation is performed by calculating the coefficient KAC (j).

KAC (j) = KAC (j) + ZFCPAL • {VAC
(j) -VAC0} This is for calculating the correction value of the rich side upper right characteristic of the correction characteristics shown in FIG. 9, and ZFCPAL is a coefficient indicating the inclination of the characteristic. Then, KAC (j) on the right side represents the correction coefficient calculated in the previous calculation cycle (n-1) for the number j cylinder, and is updated by the above equation.

On the other hand, the variation data IAC (n) is set to the threshold value IA.
If the number of times of CTH or less is less than once in 128 cycles, the “NO” route is taken in step C1 and step C3. In this case, assuming that the step C5 is executed and there is a margin for further leaning, the leaning correction for reducing the fuel injection amount is calculated by the correction coefficient KAC (j) by the following equation. It is supposed to be done.

KAC (j) = KAC (j)-ZFCPAL * {VAC
(j) -VAC0} This is for calculating the correction value of the lean side lower left characteristic shown in FIG. 9, and ZFCPAL is a coefficient indicating the inclination of the characteristic. Furthermore, when the variation data IAC (n) is set to be equal to or less than the threshold value IACTH once or twice in 128 cycles,
The correction coefficient KAC (j) is not changed in order to keep the fuel injection amount in the previous state, assuming that the operating state is appropriate (see step C4).

This corresponds to the flat characteristic between the lean side lower left characteristic and the rich side upper right characteristic shown in FIG.
It forms a dead zone for correction. By the way, the fluctuation allowable value VAC0 is a value corresponding to the target value (about 10%) of COV (Coefficient of variance).
By not compensating the fuel in the range of ΔVAC on both sides of the rotation speed, the rotation fluctuation can be evaluated in a finite period (128 cycles) and the limit cycle due to the error due to the calculation below the threshold value is prevented. To be done.

Then, the above-mentioned correction coefficient KAC (j) is clipped by the upper and lower limit values in step C6. That is, the correction coefficient KAC (j) is 0.85 <KAC (j) <1.
The value is set to fall within the range of 1, and the shock is prevented from occurring by performing the correction gradually without performing the rapid correction, and stable control is performed.

In this way, control is performed to slightly change the air-fuel ratio of the internal combustion engine operating near the lean burn limit air-fuel ratio to lean side when combustion is good and to rich side when combustion deteriorates. It is supposed to be. Although the operation is performed as described above, the present embodiment has the following effects and advantages.

(1) It becomes possible to reliably correct the cylinder pipe difference at the combustion fluctuation limit due to the variation in the air-fuel ratio due to the injector, intake pipe shape, and valve timing deviation.
It becomes possible to set the combustion limit for each of the cylinders. (2) According to the above item, NOx emission can be minimized. (3) The rotation fluctuation of each cylinder can be detected and controlled by one crank angle sensor, and more reliable lean burn control can be performed at low cost.

(4) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (5) The lean operation can be performed even when traveling on a rough road, so that fuel consumption can be reduced and NOx emission amount can be reduced.

[0133]

As described in detail above, according to the method for determining a bad road in the vehicle equipped with the lean burn internal combustion engine of the present invention according to claim 1, in the multi-cylinder internal combustion engine, the air leaner than the stoichiometric air-fuel ratio is used. Rotational fluctuations that occur when operating at a fuel ratio are detected for each cylinder, and based on the detection results, the internal combustion engine is operated near the lean burn limit, while the internal combustion engine is running near the lean burn limit air-fuel ratio. Based on the fact that a rotational fluctuation state indicating deterioration of combustion is detected in a plurality of cylinders, a simple configuration of determining or presuming that the vehicle equipped with the internal combustion engine is traveling on a bad road has the following effects or There are advantages.

(1) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (2) The lean operation can be performed even when traveling on a rough road, so that the fuel consumption can be reduced and the NOx emission amount can be reduced. According to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 2, the angular acceleration of the rotating shaft driven by the multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder, and the internal combustion engine is operated. Fluctuation data that correlates to rotation fluctuations associated with combustion deterioration during operation at a leaner air-fuel ratio than the theoretical air-fuel ratio of the engine is calculated for each cylinder based on the above detection results, and the internal combustion engine is diluted based on the calculated results. In the case of operating in the vicinity of the combustion limit, the vehicle equipped with the internal combustion engine has a bad road based on the fact that the fluctuation data shows combustion deterioration in a plurality of cylinders during operation in the vicinity of the lean combustion limit air-fuel ratio of the internal combustion engine. The simple configuration of determining or estimating that the vehicle is running has the following effects and advantages.

(3) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (4) The lean operation can be performed even when traveling on a rough road, fuel consumption can be reduced, and NOx emission amount can be reduced. further,
According to the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 3, the method according to claim 2
When the rotation fluctuation becomes a value on the combustion worse side than the combustion state determination threshold value occurs a set number of times or more within a set period over a plurality of ignition periods, the fluctuation data is calculated as a rotation fluctuation state indicating combustion deterioration. The simple configuration of the above has the following effects and advantages.

(5) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (6) It becomes possible to perform lean operation even when traveling on a rough road, so that fuel consumption can be reduced and NOx emission amount can be reduced. And
According to the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 4, the method according to claim 3
As a minimum condition, the variation data indicates combustion deterioration and the average value of the variation data on the combustion deterioration side of the combustion state determination threshold value is on the combustion deterioration side of the second combustion state determination threshold value. The simple configuration of determining or estimating that the vehicle is traveling on a rough road has the following effects or advantages.

(7) The shift to the rough road countermeasure mode can be performed accurately. (8) It is not necessary to add a sensor for countermeasures against rough roads, and lean operation is possible without increasing costs. (9) The lean operation can be performed even when traveling on a rough road, fuel consumption can be reduced, and NOx emission amount can be reduced.

According to the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 5,
According to the method described above, during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio, the vehicle equipped with the internal combustion engine is traveling on a rough road based on the fact that the fluctuation data shows combustion deterioration in a plurality of cylinders. Estimating, and then operating the internal combustion engine at an inspection air-fuel ratio on the rich side of the air-fuel ratio near the lean limit, and determining that the vehicle is traveling on a rough road based on the rotation fluctuation detected during the operation. With such a configuration, there are the following effects and advantages.

(10) It becomes possible to reliably determine the traveling on the rough road, and it is possible to reliably discriminate the rotational fluctuation due to the deterioration of combustion and the rotational fluctuation due to the traveling on the rough road. (11) It is not necessary to add a sensor for measures against rough roads, and lean operation can be performed without increasing costs. (12) The lean operation can be performed even when traveling on a rough road, so that fuel consumption can be reduced and NOx emission amount can be reduced.

Further, according to the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to the sixth aspect, the variation data is calculated under the operation at the inspection air-fuel ratio according to the method according to the fifth aspect. The simple configuration in which the rotation fluctuation during the operation is detected based on the fluctuation data has the following effects and advantages. (13) It becomes possible to reliably perform traveling on a rough road, and it is possible to reliably discriminate between rotation fluctuations due to deterioration of combustion and rotation fluctuations due to rough road travel.

(14) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (15) The lean operation can be performed even when traveling on a rough road, the fuel consumption can be reduced, and the NOx emission amount can be reduced.

According to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 7, the variation data for a plurality of cylinders under the operation at the inspection air-fuel ratio according to the method according to claim 6. Has a simple configuration in which it is determined that the vehicle is traveling on a bad road when represents rotation fluctuation, and has the following effects and advantages. (16) It becomes possible to reliably perform traveling on a rough road, and it is possible to reliably discriminate between rotational fluctuations due to deterioration of combustion and rotational fluctuations due to traveling on a rough road.

(17) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation can be performed without increasing the cost. (18) The lean operation can be performed even when traveling on a rough road, so that the fuel consumption can be reduced and the NOx emission amount can be reduced.

According to the rough road determination method for a vehicle equipped with the lean burn internal combustion engine according to claim 8,
In any one of the methods 1 to 7, when it is determined that the vehicle is traveling on a rough road, the internal combustion engine is operated at a lean air-fuel ratio for a rough road that is leaner than the inspection air-fuel ratio, and the vehicle is running. The simple configuration in which it is determined that the traveling on the rough road has ended when the convergence state of the rotation fluctuation in is detected has the following effects or advantages.

(19) It becomes possible to reliably make a judgment on running on a rough road, and it is possible to reliably distinguish between a fluctuation in rotation due to deterioration of combustion and a fluctuation in rotation due to running on a rough road. (20) It is not necessary to add a sensor for measures against rough roads, and lean operation can be performed without increasing costs. (21) Lean operation is performed even when driving on rough roads,
Fuel consumption can be reduced and NOx emissions can be reduced.

Further, according to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to the ninth aspect, the variation data under the lean air-fuel ratio for the bad road according to the method according to the eighth aspect. With a simple configuration in which the convergence state of the rotation fluctuation during the operation is detected based on the fluctuation data, and the following effects or advantages are obtained.

(22) It becomes possible to reliably make a judgment on running on a rough road, and it is possible to reliably distinguish between a fluctuation in rotation due to deterioration of combustion and a fluctuation in rotation due to running on a rough road. (23) It is not necessary to add a sensor for countermeasures against rough roads, and lean operation can be performed without increasing costs. (24) Lean operation is performed even when driving on rough roads.
Fuel consumption can be reduced and NOx emissions can be reduced.

According to the method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine according to claim 10, the variation data in the plurality of cylinders does not detect deterioration of combustion in the method according to claim 9. Based on this, a simple configuration in which the converged state of the rotation fluctuation is detected has the following effects and advantages. (25) It becomes possible to reliably perform traveling on a rough road, and it is possible to reliably discriminate between rotational fluctuations due to deterioration of combustion and rotational fluctuations due to traveling on a rough road.

(26) It is not necessary to add a sensor as a countermeasure against rough roads, and lean operation is possible without increasing costs. (27) Lean operation is performed even when driving on rough roads.
Fuel consumption can be reduced and NOx emissions can be reduced. According to the method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine according to claim 11, the angular acceleration of the rotary shaft driven by the multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder, and the detection is performed. Based on the results, the fluctuation data correlated with the rotation fluctuation due to the combustion deterioration caused by the operation at the leaner air-fuel ratio than the theoretical air-fuel ratio of the internal combustion engine is calculated for each cylinder, and the cylinder is calculated based on the fluctuation data for each cylinder. For each combustion, a judgment is made as to whether or not the combustion is good, and the air-fuel ratio of the internal combustion engine operating near the lean-burn limit air-fuel ratio is slightly changed to lean side when combustion is good and to rich side when combustion is bad. Air-fuel ratio change data is detected for each cylinder, and based on the detection result, the internal combustion engine is operated near the lean combustion limit, and a plurality of cylinders are operated during operation near the lean combustion limit air-fuel ratio of the internal combustion engine. While the fluctuation data indicating deterioration of combustion is detected, the air-fuel ratio change data in at least one cylinder is continuously changed to the rich side of the air-fuel ratio during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio. A simple configuration in which it is determined or estimated that the vehicle equipped with the internal combustion engine is traveling on a bad road on the condition that the change is urged as a minimum condition has the following effects or advantages.

(28) It becomes possible to reliably make a judgment on running on a rough road, and it is possible to reliably distinguish between a fluctuation in rotation due to deterioration of combustion and a fluctuation in rotation due to running on a rough road. (29) It is not necessary to add a sensor as a countermeasure for rough roads, and lean operation is possible without increasing costs. (30) Lean operation is performed even when driving on rough roads.
Fuel consumption can be reduced and NOx emissions can be reduced.

(31) It is possible to reliably correct the cylinder pipe difference of the combustion fluctuation limit due to the variation of the air-fuel ratio due to the injector, intake pipe shape, and valve timing deviation, and set each of the cylinders to the combustion limit. become able to. (32) According to the above item, NOx emission can be minimized. (33) The rotation fluctuation detection and control for each cylinder is set to 1
This allows the crank angle sensor to be used, which enables more reliable lean burn control at low cost.

[Brief description of drawings]

FIG. 1 is a control block diagram of a combustion state control device for carrying out a rough road determination method as one embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an engine system having a combustion state control device for carrying out a rough road determination method 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 for carrying out a rough road determination method as one embodiment of the present invention.

FIG. 4 is a flow chart for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 5 is a flow chart for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 6 is a flow chart for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 7 is a flow chart for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 8 is a waveform diagram for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 9 is a correction characteristic map for explaining the operation of the combustion state control device for implementing the rough road determination method as one embodiment of the present invention.

FIG. 10 is a schematic graph for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 11 is a schematic graph for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 12 is a normalized characteristic map for explaining the operation of the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 13 is a schematic perspective view showing a rotation fluctuation detection unit in the combustion state control device for carrying out the rough road determination method as one embodiment of the present invention.

FIG. 14 is a graph showing combustion fluctuation characteristics in a lean burn engine.

[Explanation 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 2nd 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 type actuator 15 Fuel pressure regulator 16 Spark plug 17 an air flow sensor (intake air amount sensor) 18 intake air temperature sensor 19 atmospheric pressure sensor 20 throttle position sensor 21 the idle switch 22 O ₂ sensor 23 water temperature sensor 24 crank angle sensor (engine Number of revolutions 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 gas 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 Rotation fluctuation detection Means 102 Fluctuation data calculation means 104 Air-fuel ratio change data detection means 107 Angular acceleration detection means 141 Pilot passage 142 Air bypass valve Control solenoid valve 142a Solenoid 202 Rough road running determination means 203 Inspection air-fuel ratio operating means 204 Rough air lean air-fuel ratio operating means 205 Rough road running end determining means 206 Rotation fluctuation converged state detecting means 221 Rotating member 221A First vane 221B 1st No. 2 vane 221C No. 3 vane 222 Detection unit 230 Cylinder discrimination sensor 231 Shift detection means

Claims (11)

[Claims] 1. A multi-cylinder internal combustion engine detects rotational fluctuations occurring for each cylinder when operating at an air-fuel ratio leaner than the stoichiometric air-fuel ratio, and operates the internal combustion engine near the lean burn limit based on the detection result. In the engine, a vehicle equipped with the internal combustion engine is traveling on a rough road based on the fact that a rotational fluctuation state indicating combustion deterioration is detected in a plurality of cylinders during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio. A method for determining a bad road in a vehicle equipped with a lean-burn internal combustion engine, characterized by determining or estimating that there is. 2. The angular acceleration of a rotary shaft driven by a multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder, and the combustion deteriorates when the internal combustion engine operates at a leaner air-fuel ratio than the theoretical air-fuel ratio. The fluctuation data correlated with the rotational fluctuation is calculated for each cylinder based on the above detection result, and the internal combustion engine is operated near the lean combustion limit based on the calculation result. A lean burn internal combustion engine, characterized in that it is determined or estimated that the vehicle equipped with the internal combustion engine is traveling on a rough road based on the fact that the fluctuation data indicates deterioration of combustion in a plurality of cylinders during operation in Road judgment method for vehicles equipped with. 3. When the rotation fluctuation becomes a value on the combustion deterioration side with respect to the combustion state determination threshold value more than a set number of times within a set period over a plurality of ignition periods, the fluctuation data indicates the rotation fluctuation state indicating the combustion deterioration. Is configured to be calculated.
A method for determining a bad road in a vehicle equipped with the lean burn internal combustion engine. 4. The minimum condition is that the fluctuation data indicates combustion deterioration and an average value of the fluctuation data that is on the combustion deterioration side of the combustion state determination threshold value is on the combustion deterioration side of the second combustion state determination threshold value. 4. A method for determining a bad road in a vehicle equipped with a lean-burn internal combustion engine according to claim 3, wherein the method determines or estimates that the vehicle is traveling on a bad road. 5. When a vehicle equipped with the internal combustion engine is traveling on a rough road based on the fact that the fluctuation data indicates combustion deterioration in a plurality of cylinders during operation of the internal combustion engine in the vicinity of the lean combustion limit air-fuel ratio. Estimate and then operate the internal combustion engine at an inspection air-fuel ratio that is on the rich side of the air-fuel ratio near the lean limit, and determine that the vehicle is traveling on a bad road based on the rotation fluctuation detected during the operation. A rough road determination method in a vehicle equipped with the lean burn internal combustion engine according to claim 2. 6. The lean burn internal combustion engine according to claim 5, wherein the fluctuation data is calculated under the operation at the inspection air-fuel ratio, and the rotation fluctuation during the operation is detected based on the fluctuation data. A method for determining a bad road in a vehicle equipped with an engine. 7. The vehicle according to claim 6, wherein the vehicle is judged to be traveling on a rough road when the fluctuation data of a plurality of cylinders represent a rotation fluctuation under the operation at the inspection air-fuel ratio. A method for determining a bad road in a vehicle equipped with a lean burn internal combustion engine. 8. When it is determined that the vehicle is traveling on a rough road, the internal combustion engine is operated at a lean air-fuel ratio for a bad road that is leaner than an inspection air-fuel ratio, and a rotational fluctuation convergence state during the operation is converged. The method for determining a bad road in a vehicle equipped with the lean-burn internal combustion engine according to any one of claims 5 to 7, characterized in that it is determined that the rough road traveling has ended when is detected. 9. The variation data is calculated under the operation with the lean air-fuel ratio for bad roads, and the convergence state of the rotation variation during the operation is detected based on the variation data. Item 9. A rough road determination method in a vehicle equipped with the lean burn internal combustion engine according to item 8. 10. The lean burn internal combustion engine according to claim 9, wherein the convergence state of the rotational fluctuation is detected based on the fact that the fluctuation data in the plurality of cylinders does not detect combustion deterioration. Method for rough road in a damaged vehicle. 11. An angular acceleration of a rotary shaft driven by a multi-cylinder internal combustion engine is detected for each specific stroke of each cylinder, and operation is performed at a leaner air-fuel ratio than the theoretical air-fuel ratio of the internal combustion engine based on the detection result. The fluctuation data that correlates with the rotation fluctuation that accompanies the deterioration of combustion that occurs is calculated for each cylinder, and the quality of combustion is judged for each cylinder based on the fluctuation data for each cylinder. The air-fuel ratio change data for slightly changing the air-fuel ratio of the internal combustion engine to the lean side when the combustion is good and to the rich side when the combustion is bad is detected for each cylinder, and the internal combustion engine is based on the detection result. When the engine is operated in the vicinity of the lean combustion limit, the fluctuation data indicating combustion deterioration in a plurality of cylinders is detected during operation in the vicinity of the lean combustion limit air-fuel ratio of the internal combustion engine, and the internal combustion engine The internal combustion engine is installed with the minimum condition that the air-fuel ratio change data in at least one cylinder continuously promotes the change to the rich side of the air-fuel ratio during operation near the lean-burn limit air-fuel ratio of Road determination method for a vehicle equipped with a lean-burn internal combustion engine, characterized by determining or estimating that the vehicle is traveling on a rough road.