JP2009167871A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which estimates an air-fuel ratio before an air-fuel ratio sensor in starting or the like of the engine is activated and controls so as to suppress a torque variation. <P>SOLUTION: The control device of the internal combustion engine is equipped with an air-fuel ratio detection means, a torque variation value calculation means, a torque variation determination means for determining whether or not the torque variation value is a torque variation limit value or more, and an ignition timing control means for calculating and correcting a delay angle guard value. The control device of the internal combustion engine which calculates and corrects the delay angle guard value based on the air-fuel ratio detected by the air-fuel ratio detection means is equipped with an air-fuel ratio estimation means for estimating the air-fuel ratio based on the operation state of the engine, and calculates the delay angle guard value based on the air-fuel ratio estimated by the air-fuel estimation means, the torque variation limit value, and the operation state of the engine before the air-fuel detection means is brought into a usable state in starting of the engine. When the torque variation value is a torque variation limit value or more, the delay angle guard value is corrected so that the torque variation value is less than the torque variation limit value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  In order to reduce the variation in the generated torque caused by the variation in the combustion state between the cylinders, for example, there is a control device for an internal combustion engine described in Patent Document 1. This control device first detects in-cylinder pressure for each cylinder, and calculates an in-cylinder pressure integrated value in a predetermined crank angle range after compression top dead center and an in-cylinder pressure integrated value in a predetermined crank angle range before compression top dead center. The deviation or ratio is calculated as a parameter indicating the generated torque for each cylinder. Then, the generated torque for each cylinder is compared with the average value for all cylinders, and the ignition timing is corrected to advance for a cylinder with a generated torque smaller than the average value, and for a cylinder with a generated torque larger than the average value, Ignition timing is corrected to retard.

Japanese Patent Laid-Open No. 9-209814

  Incidentally, the torque is determined by controlling the air amount, the fuel amount, the ignition timing, and the like. However, for example, when the engine is started, the air-fuel ratio sensor that detects the ratio of the air amount and the fuel amount, that is, the air-fuel ratio, is not activated, so that the accurate air-fuel ratio cannot be measured. Therefore, there is a problem that torque fluctuation occurs and drivability deteriorates because accurate engine control cannot be performed and a stable combustion state cannot be obtained.

  In view of the above problems, the present invention provides a control device for an internal combustion engine that estimates an air-fuel ratio before activation of an air-fuel ratio sensor at the time of engine startup or the like and controls to suppress torque fluctuations based on the air-fuel ratio. The purpose is to provide.

  In order to solve the above problem, according to the first aspect of the present invention, the in-cylinder pressure detecting means for detecting the in-cylinder pressure, the air-fuel ratio detecting means for detecting the air-fuel ratio, the torque is calculated based on the in-cylinder pressure, and A torque fluctuation value calculating means for calculating a torque fluctuation value based on the torque, a torque fluctuation determining means for determining whether the torque fluctuation value is equal to or greater than a predetermined torque fluctuation limit value, and a retard limit of the ignition timing. An ignition timing control means having a retarding guard value for limiting and calculating and correcting the retarding guard value, and calculating and correcting the retarding guard value based on the air-fuel ratio detected by the air-fuel ratio detecting means In the control device for the internal combustion engine, the air-fuel ratio estimation means for estimating the air-fuel ratio based on the engine operating state is further provided, and before the air-fuel ratio detection means becomes usable when the engine is started, A retard guard value is calculated based on the air-fuel ratio estimated by the air-fuel ratio estimating means, the torque fluctuation limit value, and the engine operating state, and when the torque fluctuation value is equal to or greater than the torque fluctuation limit value, There is provided a control device for an internal combustion engine that corrects the retardation guard value so that the torque fluctuation value is less than the torque fluctuation limit value.

  According to the first aspect of the present invention, it is possible to estimate the air-fuel ratio before the air-fuel ratio sensor is activated at the time of starting the engine or the like, and to control the torque fluctuation based on the air-fuel ratio. There is an effect.

  Hereinafter, an internal combustion engine control apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an overall view of an internal combustion engine having an engine body having a plurality of cylinders on which a control device of the present invention is mounted.

  Referring to FIG. 1, for example, 1 is an engine body having four cylinders, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an intake valve, 7 is an intake port, and 8 is an exhaust. A valve, 9 is an exhaust port, and 10 is a spark plug. The intake port 7 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an air cleaner 14 via an intake duct 13. An air flow meter 15 for detecting the intake air flow rate and a throttle valve 17 driven by a step motor 16 are arranged in the intake duct 13. An electrically controlled fuel injection valve 18 that injects fuel into the intake port 7 is disposed in the intake port 7.

  Furthermore, the intake valve 6 and the exhaust valve 8 are respectively provided with variable valve mechanisms 19 and 20 that change their valve opening operations. Here, the valve opening operation is determined, for example, by one or more of the lift amount, the valve opening period (working angle), and the valve opening start timing, and any known mechanism can be used as the mechanism of this embodiment. It will not be described in detail.

  On the other hand, the exhaust port 9 is connected to a small capacity three-way catalyst 22 via an exhaust manifold 21. An air-fuel ratio sensor 23 for detecting the air-fuel ratio is attached to the upstream exhaust passage of the three-way catalyst 22. A water temperature sensor 24 for detecting the engine cooling water temperature is attached to the engine body 1, and an in-cylinder pressure sensor 25 for detecting the cylinder internal pressure of the combustion chamber 5 is attached to the cylinder head 3.

  The electronic control unit (ECU) 40 is a digital computer and includes a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45, An output port 46 is provided. The accelerator pedal 49 is connected to a load sensor 50 for detecting the depression amount of the accelerator pedal 49. Here, the depression amount of the accelerator pedal 49 represents a required load.

  Output signals of the air flow meter 15, the air-fuel ratio sensor 23, the water temperature sensor 24, the in-cylinder pressure sensor 25, and the load sensor 50 are input to the input port 45 via the corresponding AD converters 47, respectively. Further, the input port 45 is connected to a crank angle sensor 51 that generates an output pulse every time the crankshaft rotates, for example, 30 °. The CPU 44 calculates the engine speed based on the output pulse of the crank angle sensor 51.

  On the other hand, the output port 46 is connected to the spark plug 10, the step motor 16, the fuel injection valve 18, and the variable valve mechanisms 19 and 20 through corresponding drive circuits 48, which are output signals from the electronic control unit 40. Controlled based on. Further, the output port is connected to the warning device 52. The warning device 52 lights or blinks the lamp based on the output signal from the electronic control unit 40 when the vehicle information should be transmitted to the driver.

  The three-way catalyst 22 has an oxygen storage capacity, so that when the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 22 is lean, it stores oxygen in the exhaust gas and flows into the three-way catalyst 22. When the air-fuel ratio of the exhaust gas is rich, the stored oxygen is released to oxidize and purify HC and CO contained in the exhaust gas.

  When the temperature of the three-way catalyst 22 has not reached the activation temperature, such as when the engine is started, the ignition timing is retarded to cause the high-temperature exhaust gas to flow into the three-way catalyst 22 so that the temperature rises quickly. I do. On the other hand, if the ignition timing is retarded excessively, the variation in crankshaft torque fluctuation becomes large, resulting in a problem that drivability deteriorates. For this reason, it is desirable to perform the control that retards the ignition timing the most with the torque fluctuation suppressed, because the temperature of the three-way catalyst 22 can be raised quickly without affecting the drivability. However, if the air-fuel ratio sensor 23 is not activated as described above, accurate air-fuel ratio cannot be measured, and it is difficult to perform such desirable control.

  Therefore, in this embodiment, control is performed so that the ignition timing is most retarded in a state where torque fluctuation is suppressed, and the air-fuel ratio estimated from the operating state is used as the air-fuel ratio used at that time. This makes it possible to maintain good drivability and raise the temperature of the three-way catalyst 22 at an early stage.

  Hereinafter, the flowchart of the operation of the present embodiment will be described. FIG. 2 is a flowchart showing the engine control operation when the engine is started. This operation is performed as a routine that is executed by interruption every set time predetermined by the electronic control unit (ECU) 40.

  First, in step 101, the operation state is read for each cylinder, and the process proceeds to step 102. Here, the operating state refers to, for example, the fuel injection amount, the engine speed, the intake air amount, the advance amount of the valve opening timing by the variable valve mechanism, the engine cooling water temperature, the basic ignition timing, and the like.

  Next, at step 102, it is determined whether the air-fuel ratio sensor 23 is activated. Whether the air-fuel ratio sensor 23 is activated is determined based on, for example, the engine coolant temperature, the integrated value of the intake air amount after startup, the number of fuel injections described after startup, and the like. If it is determined in step 102 that the air-fuel ratio sensor 23 is activated, the routine is terminated without performing the engine control according to the present embodiment. On the other hand, if it is determined in step 102 that the air-fuel ratio sensor 23 has not been activated, the routine proceeds to step 103.

  Next, at step 103, an estimated air-fuel ratio AFest, which is an estimated value of the air-fuel ratio, is calculated, and the routine proceeds to step 104. The estimated air-fuel ratio AFest is based on the operation state read in step 101 and the estimated value of the wall surface adhesion amount by the adhesion model of the fuel injected from the fuel injection valve 18 to the wall surface, that is, the wall surface adhesion amount estimated value. It is obtained from a map or a calculation formula obtained in advance by experiments or the like.

Ｔ＝Ｗ／４π …（２） Next, at step 104, the in-cylinder pressures of all cylinders for a predetermined cycle or predetermined time are detected, and a torque fluctuation value is calculated based on the detected in-cylinder pressure, and the routine proceeds to step 105. The calculation of the torque fluctuation value will be described. Here, in the internal combustion engine having four cylinders, the in-cylinder pressure is measured in the section of the crank angle of 360 ° in the compression stroke and the expansion stroke, and one is calculated from the in-cylinder pressure based on the following equation (1). The amount of work W performed on the crankshaft by the cylinder in one compression stroke and expansion stroke is calculated. Then, when the work amount W is divided by 4π in one cycle, the torque T is calculated as shown in Expression (2).

T = W / 4π (2)

  The torque fluctuation value obtained by quantifying the torque T fluctuation thus obtained is a torque fluctuation value, which can be defined by various methods. In the present embodiment, for example, it is possible to calculate the standard deviation of the torque T of all the cylinders calculated during a predetermined in-cylinder pressure measurement time, and calculate the torque fluctuation value using the standard deviation. What is calculated in step 104 is a torque fluctuation value of all cylinders in consideration of the total torque output from each cylinder.

  Next, in step 105, it is determined whether or not the torque fluctuation values of all cylinders calculated in step 104 are equal to or greater than the torque fluctuation limit values of all cylinders. “Torque fluctuation limit value or more” means exceeding the allowable range of the torque fluctuation value, and the torque fluctuation limit value is obtained in advance by experiments or the like. If it is determined in step 105 that the torque fluctuation value of all cylinders is equal to or greater than the torque fluctuation limit value of all cylinders, the process proceeds to step 106. On the other hand, if it is determined in step 105 that the torque fluctuation value of all the cylinders is less than the torque fluctuation limit value of all the cylinders, the routine is terminated.

  Next, at step 106, a torque fluctuation value for each cylinder is calculated, and the routine proceeds to step 107. That is, since the torque fluctuation value calculated in step 104 is considered for all cylinders, even if the torque fluctuation is large only in a specific cylinder, it cannot be determined. Therefore, in this step, the torque fluctuation value for each cylinder is calculated by the same method as that used in step 104.

  Next, in step 107, based on the operation state read in step 101, the torque fluctuation limit value, and the estimated air-fuel ratio AFest calculated in step 103, the cylinder or cylinder is calculated from a map or calculation formula obtained in advance through experiments or the like. Every time, a correction amount from the current value of the retard guard value set to limit the retard limit value of the ignition timing or the retard guard value itself is obtained. Thereafter, the process proceeds to step 108.

  Next, in step 108, it is determined for each cylinder whether or not the torque fluctuation value calculated in step 106 is equal to or greater than the torque fluctuation limit value of all cylinders used in the determination in step 105. Then, only for the cylinders determined to be equal to or greater than the torque fluctuation limit value of all cylinders, the ignition timing is corrected so that the torque fluctuation value is less than the torque fluctuation limit value, and the correction amount or the correction guard value obtained in step 107 Is further corrected to finally determine and correct the retard guard value. Then, the corrected retardation guard value is learned, and the learned retardation guard value is used as an initial value at the next engine start. Then the routine ends. Here, the correction of the ignition timing of the cylinder determined that the torque fluctuation value is equal to or greater than the torque fluctuation limit value is obtained from a map or a calculation formula of the torque fluctuation value with respect to the ignition timing obtained in advance through experiments or the like.

  FIG. 3 is another flowchart showing the engine control operation at the time of starting the engine. Step 201 to step 208 are substantially the same as step 101 to step 108 in FIG. However, if it is determined in step 205 corresponding to step 105 in the flowchart of FIG. 2 that the torque fluctuation limit value of all the cylinders is less than the routine, the routine is not terminated and the routine returns to step 209 as in step 208. move on.

  In step 209, a torque fluctuation value for each cylinder is calculated, and the process proceeds to step 210. That is, since the ignition timing is corrected in step 208, the torque fluctuation value may fluctuate. If it is determined in step 205 that the torque fluctuation value of all cylinders is less than the torque fluctuation limit value of all cylinders, the torque fluctuation value for each cylinder is not calculated. Therefore, in this step, the torque fluctuation value for each cylinder is calculated by the same method as that used in step 204.

  Next, in step 210, it is determined for each cylinder whether or not the torque fluctuation value for each cylinder calculated in step 209 is equal to or greater than the torque fluctuation limit value for each cylinder. The torque fluctuation limit value for each cylinder is also obtained in advance by experiments or the like. If it is determined that the torque fluctuation value of any cylinder is equal to or greater than the torque fluctuation limit value, the process proceeds to step 211. On the other hand, when it is determined that the torque fluctuation value of any cylinder is less than the torque fluctuation limit value, the routine is terminated.

  Next, in step 211, only the cylinders determined to be equal to or greater than the torque fluctuation limit value in step 210 are based on the estimated value of the wall surface adhesion amount based on the adhesion model of the fuel injected from the fuel injection valve 18 to the wall surface. Then, the fuel shortage due to the wall surface adhesion amount and the fuel injection amount are increased so that the torque fluctuation value becomes less than the torque fluctuation limit value.

  Further, instead of or in addition to the increase due to the amount of fuel adhering to the wall surface, when the engine cooling water temperature is low, the injected fuel is calculated from the water temperature and fuel increase map or calculation formula obtained in advance through experiments or the like. The amount may be increased. Further, instead of or in combination with these, even when the air is excessive, the amount of fuel shortage may be increased. Then the routine ends.

  FIG. 4 is still another flowchart showing the engine control operation at the time of engine start. Steps 301 to 311 are substantially the same as steps 201 to 211 in FIG. However, if it is determined in step 310 corresponding to step 210 in the flowchart of FIG. 3 that the torque variation limit value for each cylinder is less than the routine, the routine is not ended, and step 312 is performed as in step 311. move on.

  In step 312, the torque for each cylinder is calculated using equations (1) and (2) as in step 304, and the process proceeds to step 313. Next, in step 313, a torque lower limit value for each cylinder estimated based on the operation state for each cylinder is calculated, and the process proceeds to step 314.

  Next, in step 314, it is determined whether the torque for each cylinder calculated in step 312 is equal to or greater than the torque lower limit value for each cylinder calculated in step 313. If it is determined that the torques of all the cylinders calculated in step 312 are equal to or greater than the torque lower limit value calculated in step 313, the routine is terminated.

  On the other hand, if it is determined in step 314 that the torque of any cylinder calculated in step 312 is less than the torque lower limit value calculated in step 313, the process proceeds to step 315.

  Next, in step 315, the warning device 52 is turned on or blinked for the cylinder determined to be less than the torque lower limit value in step 314, and the cylinder number is notified to the driver. That is, with respect to such a cylinder, there is a possibility that the valve clearance is increased due to deterioration of the intake / exhaust valve over time. This is because air leaks in the compression stroke, and it is considered that good combustion cannot be obtained and the torque is smaller than the estimated value. Then the routine ends.

  The engine control operation at the time of starting each engine described in the above flowchart is performed until the air-fuel ratio sensor 23 is activated. After the air-fuel ratio sensor 23 is activated, the actual air-fuel ratio is measured using it. Then, the offset ΔAF with the estimated air-fuel ratio AFest used in the operation is learned. That is, in the engine control operation at the time of engine start at the next engine start, for example, a value obtained by adding the offset ΔAF to the estimated air-fuel ratio AFest calculated from the operating state or the like in step 103 of FIG. The accuracy of estimation of the air-fuel ratio AFest is improved.

It is a figure of the whole internal combustion engine in which the control apparatus of this invention is used. It is a flowchart which shows engine control operation at the time of engine starting. 7 is another flowchart showing an engine control operation at the time of engine start. 7 is still another flowchart showing an engine control operation at the time of engine start.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 6 Intake valve 8 Exhaust valve 15 Air flow meter 18 Fuel injection valve 22 Three-way catalyst 23 Air-fuel ratio sensor 24 Water temperature sensor 25 In-cylinder pressure sensor 40 Electronic control unit (ECU)
52 Warning device

Claims (1)

  In-cylinder pressure detecting means for detecting in-cylinder pressure; air-fuel ratio detecting means for detecting air-fuel ratio; torque fluctuation value calculating means for calculating torque based on the in-cylinder pressure and calculating torque fluctuation value based on the torque; Torque fluctuation determination means for determining whether or not the torque fluctuation value is equal to or greater than a predetermined torque fluctuation limit value, and a retard guard value for limiting the retard limit of the ignition timing, and calculation and correction of the retard guard value And an ignition timing control means for performing an ignition timing control means for calculating and correcting a retard guard value based on the air-fuel ratio detected by the air-fuel ratio detection means. An air-fuel ratio estimating means for estimating the air-fuel ratio and the torque variation estimated by the air-fuel ratio estimating means before the air-fuel ratio detecting means becomes usable when the engine is started. A retard guard value is calculated based on the limit value and the engine operating state, and when the torque fluctuation value is equal to or greater than the torque fluctuation limit value, the torque fluctuation value is less than the torque fluctuation limit value. A control device for an internal combustion engine that corrects the retardation guard value.

Images