JP4475207B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine with improved startability of the internal combustion engine.

  At the start of the internal combustion engine and before the completion of warm-up after the start, the amount of fuel (wet amount) adhering to the wall surface of the intake port differs due to the difference in the properties (volatility) of the fuel used. The air-fuel ratio (hereinafter referred to as “combustion air-fuel ratio”) may deviate from the target air-fuel ratio, which may cause deterioration in startability and exhaust emission.

  As a countermeasure, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 8-284708), an addition is performed in which a rotational fluctuation is detected for each combustion stroke immediately after the start of the internal combustion engine, and the rotational fluctuation is added a specified number of times. Some have learned the fuel property based on the data, and corrected the fuel injection amount based on the learned value of the fuel property.

Further, as described in Patent Document 2 (Japanese Patent No. 3498392), the time when the rotation speed is equal to or higher than the predetermined rotation speed from the start, the initial maximum rotation speed immediately after the start, or the start after the rotation speed exceeds the predetermined rotation speed. The fuel injection amount is corrected to increase when a non-optimal start of the internal combustion engine is detected based on the rate of change in the rotational speed until the maximum rotational speed is reached immediately after, the minimum rotational speed after the maximum rotational speed, etc. There is.
JP-A-8-284708 (second page etc.) Japanese Patent No. 3498392 (first page, etc.)

  However, in the technique of the above-mentioned Patent Document 1, since the proper fuel correction according to the fuel property cannot be performed during the period until the learning of the fuel property sufficiently proceeds after the internal combustion engine is started, the deviation of the air-fuel ratio due to the fuel property is not achieved. May occur, causing fluctuations in rotational speed.

  Further, in the technique disclosed in Patent Document 2, since the fuel injection amount is increased and corrected after detecting the non-optimal start of the internal combustion engine, the rotational speed fluctuation may occur until the non-optimal start is detected.

  Further, as shown in FIG. 2, when the combustion air-fuel ratio deviates in the lean direction from the target air-fuel ratio due to the fuel properties of the fuel used or the aging of the internal-combustion engine at the time of starting the internal combustion engine, the generated torque is reduced accordingly. It is lower than the torque that should be obtained at the fuel ratio. However, in the above prior art, such torque fluctuations at the time of starting are not taken into consideration at all, so even if the generated torque at the time of starting deviates from an appropriate torque corresponding to the target air-fuel ratio, the amount of torque deviation is completely eliminated. There is a problem that the correction cannot be made and the internal combustion engine cannot be started smoothly with an appropriate rotational speed behavior.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to control the generated torque to an appropriate torque according to the target air-fuel ratio at an early stage when the internal combustion engine is started. An object of the present invention is to provide a control device for an internal combustion engine that can smoothly start the internal combustion engine with an appropriate rotational speed behavior.

In order to achieve the above object, according to the first aspect of the present invention, the rotational speed increase amount is calculated by the rotational speed increase amount calculation means for each combustion of the internal combustion engine during the rotational speed increase period immediately after the start of the internal combustion engine or information correlated therewith. (Hereinafter referred to as “rotational speed increase information”), the calculated rotational speed increase information is integrated by the rotational speed increase amount integration means, and the integrated rotational speed increase information integrated value corresponds to the target air-fuel ratio. Compared with the target rotational speed increase information integrated value , the deviation amount from the appropriate torque according to the target air-fuel ratio (hereinafter referred to as “torque fluctuation amount”) is calculated by the torque fluctuation amount calculation means, and the calculated torque fluctuation amount is calculated. Accordingly, the generated torque of the internal combustion engine is corrected .

When the generated torque increases or decreases during the rotation speed increase period immediately after the start of the internal combustion engine from the appropriate torque corresponding to the target air-fuel ratio, the amount of increase in the rotation speed for each combustion corresponds to the target rotation corresponding to the target air-fuel ratio. Compared with the speed increase information and the target speed increase information because it increases or decreases more than the speed increase (rotation speed increase when the combustion air-fuel ratio is matched with the target air-fuel ratio from the start) if it is possible to leave calculate the amount of torque fluctuation is the amount of deviation of the actual torque with respect to the proper torque corresponding to the target air-fuel ratio.
Further, as in claim 1, the rotational speed increase information calculated for each combustion of the internal combustion engine is integrated during the rotational speed increase period immediately after the start of the internal combustion engine, and the rotational speed increase information integrated value is obtained as the target air-fuel ratio. If the torque fluctuation amount is calculated by comparing with the target rotational speed increase information integrated value corresponding to the above, the rotational speed increase information calculated for each combustion includes the influence of combustion variation among cylinders, etc. However, the use of the rotational speed increase information integrated value can reduce the influence of combustion variation between cylinders and the like, and can further improve the calculation accuracy of the torque fluctuation amount.
As a result, the control for correcting the generated torque so as to coincide with the appropriate torque corresponding to the target air-fuel ratio is started based on the torque fluctuation amount from the time when the torque fluctuation amount is calculated in the rotation speed increase period immediately after the start of starting. As a result, the generated torque can be accurately controlled to an appropriate torque early at the time of starting, the internal combustion engine can be started smoothly with an appropriate rotational speed behavior, and startability can be improved. it can.

Further, as in claim 2 , the rotational speed increase information is compared with the target rotational speed increase information corresponding to the target air-fuel ratio, and the rotational speed increase information integrated value is compared with the target rotational speed increase amount corresponding to the target air-fuel ratio. The torque fluctuation amount of the internal combustion engine may be calculated based on the comparison result with the information integrated value. In this way, the torque fluctuation is obtained using both the comparison result between the rotation speed increase information and the target rotation speed increase information and the comparison result between the rotation speed increase information integrated value and the target rotation speed increase information integrated value. The amount can be calculated with higher accuracy.

Further, when the torque is corrected, the fuel injection amount is preferably corrected based on the torque fluctuation amount as in the third aspect . In this way, the fuel injection amount is corrected so that the generated torque becomes an appropriate torque based on the torque fluctuation amount, and the generated torque can be accurately controlled to the appropriate torque.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. Further, a spark plug 22 is attached to each cylinder of the cylinder head of the engine 11, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  The cylinder block of the engine 11 includes a coolant temperature sensor 26 that detects the coolant temperature, and a crank angle sensor 28 that outputs a crank angle signal (pulse signal) every time the crankshaft 27 of the engine 11 rotates a predetermined crank angle. It is attached. Based on the crank angle signal of the crank angle sensor 28, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

  Incidentally, as shown in FIG. 2, when the combustion air-fuel ratio deviates in the lean direction from the target air-fuel ratio due to the fuel properties of the fuel used at the start of the engine 11 or aging of the engine 11, the generated torque is reduced to the target air. It is lower than the appropriate torque corresponding to the fuel ratio (generated torque when starting with the combustion air-fuel ratio matched with the target air-fuel ratio from the start). In this case, as indicated by a broken line in FIG. 3, the engine speed cannot be sufficiently increased at the time of starting, and the engine 11 may not be started with an appropriate rotational speed behavior.

  Therefore, the ECU 29 executes each program for starting torque correction control shown in FIGS. 4 to 6 described later, thereby increasing the engine rotational speed for each combustion of the engine 11 during the rotational speed increasing period immediately after the engine 11 starts. The engine speed increase amount is integrated and the engine speed increase amount integrated value and the target engine speed increase amount integrated value corresponding to the target air fuel ratio (the combustion air fuel ratio is made the target air fuel ratio from the beginning of the start). After calculating the torque fluctuation amount of the engine 11 (the amount of excess or deficiency of the generated torque with respect to the appropriate torque) based on the deviation from the integrated value of the engine rotation speed increase when starting with matching, based on this torque fluctuation amount Thus, the fuel injection correction amount is calculated so that the generated torque becomes an appropriate torque corresponding to the target air-fuel ratio.

  If the generated torque is increased or decreased from the appropriate torque corresponding to the target air-fuel ratio during the rotation speed increase period immediately after the start of the engine 11, the target engine rotation speed corresponding to the target air-fuel ratio is correspondingly increased. The engine speed increase integrated value and the target engine speed increase integrated value are increased or decreased from the increase amount (the engine speed increase amount when starting with the combustion air-fuel ratio matched with the target air-fuel ratio from the start). If the value is compared, the amount of torque fluctuation (the amount of torque generated that is excessive or insufficient relative to the appropriate torque) can be calculated with high accuracy.

Thus, as shown by a solid line in FIG. 3, from the time when the torque fluctuation amount is calculated during the rotation speed increase period immediately after the start of the engine 11, the torque is generated so that the generated torque becomes an appropriate torque based on the torque fluctuation amount. The correction control can be started, and the generated torque can be accurately controlled to an appropriate torque at an early stage when starting, and the engine 11 can be started smoothly with an appropriate rotational speed behavior.
Hereinafter, processing contents of each program for starting torque correction control shown in FIGS. 4 to 6 executed by the ECU 29 will be described.

[Startup torque correction control]
The start time torque correction control program shown in FIG. 4 is executed at a predetermined cycle when the engine 11 is started. When this routine is started, first, in step 101, the engine state such as the coolant temperature detected by the coolant temperature sensor 26 is read. Thereafter, the process proceeds to step 102, the target air-fuel ratio is calculated based on the engine state (cooling water temperature, etc.), and then the process proceeds to step 103, where the basic fuel injection amount is calculated based on the target air-fuel ratio.

  Thereafter, the routine proceeds to step 104, where a torque fluctuation amount calculation program shown in FIG. 5 to be described later is executed to calculate the rotation speed increase amount for each combustion of the engine 11 during the rotation speed increase period immediately after the start of the engine 11. Based on the deviation between the accumulated value of the rotational speed increase and the integrated value of the target rotational speed increase corresponding to the target air-fuel ratio, the torque fluctuation amount (the excess or deficiency of the generated torque with respect to the appropriate torque) is calculated. calculate.

  Thereafter, the routine proceeds to step 105, where a fuel injection correction amount calculation program shown in FIG. 6 to be described later is executed to set the fuel injection correction amount so that the generated torque becomes an appropriate torque corresponding to the target air-fuel ratio based on the torque fluctuation amount. calculate.

[Calculation of torque fluctuation]
The torque fluctuation amount calculation program shown in FIG. 5 is a subroutine executed in step 104 of the starting torque correction control program shown in FIG. When this program is started, first, in step 201, an engine rotation speed calculation program (not shown) is executed, and each time the engine 11 burns, the combustion TDC ( Crankshaft in a predetermined rotation speed calculation section (rotation speed calculation section set across the combustion TDC or rotation speed calculation section set immediately after the combustion TDC) set near the top dead center of the combustion stroke) 27 angular speed information (for example, the time required for the crankshaft 27 to rotate in the rotational speed calculation section) is calculated, and the engine rotational speed is calculated based on the angular speed information. As a result, an engine rotation speed having high correlation with the combustion state of the engine 11 and the generated torque is calculated.

  Thereafter, the process proceeds to step 202, and the amount of increase in the engine rotation speed is calculated by subtracting the previous value from the current value of the engine rotation speed for each combustion of the engine 11 during the rotation speed increase period immediately after the start of the engine 11. The process in step 202 serves as a rotational speed increase calculation means in the claims.

  Thereafter, the process proceeds to step 203, where the engine rotational speed increase amount for a predetermined period (for example, 8 combustion minutes) from the start of combustion of the engine 11 is integrated to obtain an engine rotational speed increase integrated value. The process of step 203 serves as a rotational speed increase amount integration means in the claims.

  Thereafter, the routine proceeds to step 204, where a map of the target engine speed increase amount integrated value is searched, and the target engine speed increase amount integrated value corresponding to the target air fuel ratio (the combustion air fuel ratio matches the target air fuel ratio from the start). The integrated value of the amount of increase in engine speed when the engine is started is calculated. The map of the target engine rotation speed increase integrated value to be used is based on the engine status (starting cooling water temperature, number of combustions, cooling water temperature, intake pipe pressure, intake valve timing, engine load, Any one or two or more areas such as temperature are set and stored in the ROM of the ECU 29.

  After calculating the basic target engine rotational speed increase integrated value corresponding to the target air-fuel ratio, this basic target engine rotational speed increase integrated value is calculated as the engine state (starting cooling water temperature, number of combustions, cooling water temperature, intake pipe pressure). The final target engine rotation speed increase integrated value may be obtained by correcting according to intake valve timing, engine load, intake air temperature or the like.

  Thereafter, the process proceeds to step 205, where the torque fluctuation amount map shown in FIG. 7 is searched, and the torque fluctuation amount (appropriate torque) corresponding to the deviation between the engine rotational speed increase integrated value and the target engine rotational speed increase integrated value is searched. (Excess or deficiency of generated torque with respect to). The processing in step 205 serves as a torque fluctuation amount calculation means in the claims. The torque fluctuation map shown in FIG. 7 is based on test data, design data, and the like in advance such as engine conditions (starting cooling water temperature, number of combustions, cooling water temperature, intake pipe pressure, intake valve timing, engine load, intake air temperature, etc.). Any one or two or more areas) are set and stored in the ROM of the ECU 29.

  After calculating the basic torque fluctuation amount according to the deviation between the engine rotational speed increase integrated value and the target engine rotational speed increase integrated value, the basic torque fluctuation amount is calculated based on the engine state (starting coolant temperature, number of combustions, The final torque fluctuation amount may be obtained by correcting according to the coolant temperature, the intake pipe pressure, the intake valve timing, the engine load, the intake air temperature, or the like.

[Fuel injection correction amount calculation]
The fuel injection correction amount calculation program shown in FIG. 6 is a subroutine executed in step 105 of the start time torque correction control program shown in FIG. 4, and serves as fuel injection amount correction means in the claims. When this program is started, first, in step 301, the combustion air-fuel ratio map shown in FIG. 8 is searched to calculate the combustion air-fuel ratio (actual air-fuel ratio of the in-cylinder mixture) according to the torque fluctuation amount. . The combustion air-fuel ratio map shown in FIG. 8 is based on engine conditions (starting cooling water temperature, number of combustions, cooling water temperature, intake air temperature, previous combustion air-fuel ratio, previous combustion air-fuel ratio based on test data, design data, and the like. Any one or two or more areas such as deviations from the target air-fuel ratio) are set and stored in the ROM of the ECU 29.

  After calculating the basic combustion air-fuel ratio according to the amount of torque fluctuation, this basic combustion air-fuel ratio is determined based on the engine condition (starting coolant temperature, number of combustions, coolant temperature, intake air temperature, previous calculated air-fuel ratio, previous calculated air-fuel ratio). The final combustion air-fuel ratio may be obtained by correcting according to any one or two or more of deviations between the fuel ratio and the target air-fuel ratio.

  Thereafter, the process proceeds to step 302, and after calculating the deviation between the target air-fuel ratio and the combustion air-fuel ratio, the process proceeds to step 303, where the combustion air-fuel ratio becomes the target air-fuel ratio based on the deviation between the target air-fuel ratio and the combustion air-fuel ratio. By calculating the fuel injection correction amount as described above, the fuel injection amount is corrected so that the generated torque becomes an appropriate torque.

  In the present embodiment described above, the engine rotation speed increase amount is calculated for each combustion of the engine 11 during the rotation speed increase period immediately after the start of the engine 11, and the engine rotation speed increase amount is integrated. After calculating the torque fluctuation amount of the engine 11 based on the deviation between the amount integrated value and the target engine rotational speed increase integrated value (the amount of torque generated that is excessive or insufficient with respect to the appropriate torque), the generated torque is calculated based on the torque fluctuation amount. A fuel injection correction amount is calculated so as to obtain an appropriate torque corresponding to the target air-fuel ratio.

  As a result, as shown in FIG. 9, even when the combustion air-fuel ratio at the start of the engine deviates from the target air-fuel ratio due to the fuel properties of the fuel used, aging of the engine 11, etc., the rotation speed increase period immediately after the start of the engine 11 starts. From the time when the torque fluctuation amount is calculated, torque correction control can be started based on the torque fluctuation amount so that the generated torque becomes an appropriate torque, and the generated torque is accurately controlled to the appropriate torque early at the start. Thus, the engine 11 can be smoothly started with an appropriate rotational speed behavior, and the startability can be improved.

  In addition, in this embodiment, the torque fluctuation amount is calculated based on the deviation between the engine rotation speed increase integrated value and the target engine rotation speed increase integrated value, so the engine rotation speed increase calculated for each combustion is calculated. Even if the effect of combustion variation among cylinders is included in the engine, the influence of combustion variation between cylinders can be reduced by using the integrated value of the engine speed increase, improving the accuracy of torque fluctuation calculation. Can be made.

  In the present invention, the torque fluctuation amount may be calculated based on the deviation between the engine rotation speed increase amount and the target engine rotation speed increase amount, thereby simplifying the calculation process of the torque fluctuation amount.

  Alternatively, the torque fluctuation amount is calculated based on both the deviation between the engine rotational speed increase amount and the target engine rotational speed increase amount, and the deviation between the engine rotational speed increase integrated value and the target engine rotational speed increase integrated value. Thus, the torque fluctuation amount may be calculated with higher accuracy.

  In the above-described embodiment, the torque fluctuation amount is calculated using the engine rotation speed increase amount for each combustion. However, as information on the engine rotation speed increase amount for each combustion, The torque fluctuation amount may be calculated using angular acceleration.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a figure which shows the relationship between a combustion air fuel ratio and generated torque. It is a time chart for demonstrating starting torque correction control. It is a flowchart which shows the flow of a process of the torque correction control program at the time of starting. It is a flowchart which shows the flow of a process of a torque variation calculation program. It is a flowchart which shows the flow of a process of a fuel injection correction amount calculation program. It is a figure which shows notionally an example of the map of torque fluctuation amount. It is a figure which shows notionally an example of the map of a combustion air fuel ratio. It is a time chart which shows the execution example of torque correction control at the time of starting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 26 ... Cooling water temperature sensor, 28 ... Crank angle sensor, 29 ... ECU ( (Rotational speed increase amount calculating means, rotational speed increase amount integrating means, torque fluctuation amount calculating means, fuel injection amount correcting means)

Claims (3)

A rotational speed increase amount calculating means for calculating a rotational speed increase amount or information correlated therewith (hereinafter referred to as “rotational speed increase amount information”) for each combustion of the internal combustion engine in a rotational speed increase period immediately after the start of the internal combustion engine;
A rotational speed increase amount integrating means for integrating the rotational speed increase amount information calculated by the rotational speed increase amount calculating means;
The rotational speed increase information integrated value integrated by the rotational speed increase amount integration means is compared with the target rotational speed increase information integrated value corresponding to the target air-fuel ratio, and the deviation from the appropriate torque according to the target air-fuel ratio ( (Hereinafter referred to as “torque fluctuation amount”) for calculating torque fluctuation amount ,
A control apparatus for an internal combustion engine, wherein the generated torque of the internal combustion engine is corrected according to the torque fluctuation amount calculated by the torque fluctuation amount calculation means . A rotational speed increase amount calculating means for calculating a rotational speed increase amount or information correlated therewith (hereinafter referred to as “rotational speed increase amount information”) for each combustion of the internal combustion engine in a rotational speed increase period immediately after the start of the internal combustion engine;
A rotational speed increase amount integrating means for integrating the rotational speed increase amount information calculated by the rotational speed increase amount calculating means;
The rotation speed increase information calculated by the rotation speed increase calculation means is compared with the target rotation speed increase information corresponding to the target air-fuel ratio, and the rotation speed increase information integrated value integrated by the rotation speed increase integration means is calculated. Torque fluctuation amount calculating means for calculating a deviation amount from an appropriate torque corresponding to the target air-fuel ratio (hereinafter referred to as “torque fluctuation amount”) in comparison with a target rotational speed increase information integrated value corresponding to the target air-fuel ratio ; Prepared,
A control apparatus for an internal combustion engine, wherein the generated torque of the internal combustion engine is corrected according to the torque fluctuation amount calculated by the torque fluctuation amount calculation means . 3. The control apparatus for an internal combustion engine according to claim 1, further comprising fuel injection amount correction means for correcting the fuel injection amount based on the torque fluctuation amount calculated by the torque fluctuation amount calculation means.

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