JP4853376B2 - Internal combustion engine control system - Google Patents

Description

  The present invention relates to a system for controlling a spark ignition type internal combustion engine.

  There is known a control system that maintains an idling engine speed at a target engine speed during idling of an internal combustion engine. In this control system, there are a case where the idle speed is feedback-controlled by the intake air amount and a case where the idle speed is feedback-controlled by the ignition timing.

  Here, for example, when performing feedback control of the idling engine speed based on the intake air amount, if combustion deteriorates and the idling engine speed decreases, the throttle valve is opened to increase the intake air amount and increase the engine speed. An operation to increase the degree is performed. However, when the combustion deteriorates due to insufficient fuel vaporization at the intake port, increasing the throttle valve opening decreases the intake pipe negative pressure on the downstream side of the throttle valve. In some cases, the fuel in the fuel becomes more difficult to vaporize, and the deterioration of combustion is amplified.

  On the other hand, when the feedback control of the idling speed based on the ignition timing is continued, problems such as deterioration of emission may occur particularly immediately after the cold start. That is, if the combustion speed deteriorates and the engine speed decreases during feedback control of the idle speed by the ignition timing, the exhaust temperature decreases because the ignition timing is advanced to increase the engine speed. . For this reason, if the feedback control of the idling engine speed by the ignition timing continues, the warm-up of the exhaust purification catalyst is delayed, and there is a problem that the emission at the cold start deteriorates.

  On the other hand, when the engine combustion state deteriorates, the idle speed feedback control based on the intake air amount is stopped, and the idle speed feedback control based on the ignition timing is performed. During this control, the ignition timing advance correction amount Has been proposed that the engine combustion state is determined to be improved and the feedback control of the idling engine speed based on the intake air amount is resumed when a state where the engine pressure is below a predetermined value continues for a predetermined time ( For example, Patent Document 1). In this technology, the warm-up delay of the exhaust purification catalyst can be suppressed.

  However, in the above-described prior art, if the in-cylinder temperature is low immediately after the cold start, the amount of HC discharged from the internal combustion engine during idle operation may increase. Then, even if the warm-up delay of the exhaust purification catalyst is suppressed, there is a possibility that the emission during the cold start as a whole may be deteriorated.

On the other hand, in the conventional spark ignition type internal combustion engine, the ignition timing is advanced to the front of MBT (Minimum spark advance for Best Torque), thereby promoting the temperature rise of the cooling water, thereby increasing the warm-up property of the internal combustion engine. There is known a technique for improving the above (see, for example, Patent Document 2). However, in this prior art, the warm-up property of the internal combustion engine is considered, but the exhaust emission is not considered.
JP 2001-82226 A JP 2000-240547 A JP 2003-293833 A JP 11-343915 A JP 2005-344656 A JP 2000-227043 A JP 2002-357151 A

  The present invention has been made in view of the above circumstances, and its purpose is to suppress the discharge of unburned fuel components from the internal combustion engine during idle operation after cold start of the spark ignition internal combustion engine, It is to provide technology that can suppress the deterioration of emissions.

  In order to solve the above-described problem, the present invention provides an internal combustion engine ignition timing in a case where the combustion chamber of the internal combustion engine is at a low temperature lower than a predetermined temperature when the idle speed of the internal combustion engine is feedback controlled by the ignition timing. It is the greatest feature that the feedback control is performed after setting the angle to the advance side of the MBT.

More specifically, an exhaust purification catalyst that is provided in an exhaust passage of a spark ignition type internal combustion engine and purifies exhaust that passes through the exhaust passage;
Idle speed control means for controlling an ignition timing related to spark ignition of the internal combustion engine and causing the idle speed of the internal combustion engine to converge to a target speed by feedback control;
In-cylinder temperature acquisition means for acquiring the in-cylinder temperature in the cylinder of the internal combustion engine;
With
During the feedback control, when the in-cylinder temperature acquired by the in-cylinder temperature acquisition unit is lower than a predetermined temperature, the idle speed control unit controls the ignition timing on the advance side from the MBT. Features.

  Here, during the idling operation of the internal combustion engine, when the ignition speed of the internal combustion engine is controlled to converge the idle speed to the target speed by feedback control, for example, when the intake air amount increases, the engine speed is decreased. Therefore, the ignition timing shifts to the retard side. As a result, the in-cylinder temperature is low during idling, and the peak value of the combustion chamber temperature in the internal combustion engine during combustion decreases due to the retard of the ignition timing, so that the unburned fuel component discharged from the combustion chamber ( For example, the amount of HC (hereinafter abbreviated as “HC”) may increase. As a result, during the idling operation of the internal combustion engine, the exhaust purification catalyst is often not fully warmed up, so that the emission may be deteriorated due to an increase in the HC emission amount.

  On the other hand, it has been found that when the ignition timing is advanced before MBT in the spark ignition type internal combustion engine, the HC discharged from the cylinder is remarkably reduced. This is because when the ignition timing is advanced before MBT, the amount of the air-fuel mixture combusted before the compression top dead center increases, so that the boosting / heating effect due to the combustion of the air-fuel mixture is due to the upward movement of the piston. In addition to the pressure increase / temperature increase effect, the peak value during combustion of the pressure in the cylinder (hereinafter also referred to as “in-cylinder pressure”) and the in-cylinder temperature is increased, and vaporization and oxidation of HC remaining in the cylinder are promoted. It is thought to be due to this.

  In the control system for an internal combustion engine according to the present invention, this phenomenon is noted. Then, the in-cylinder temperature of the internal combustion engine is acquired during the idling operation of the internal combustion engine, and when the acquired in-cylinder temperature is lower than the predetermined temperature, the ignition timing of the internal combustion engine is shifted from the MBT to the advance side. The idle speed was converged to the target speed by feedback control.

Then, in a state where the in-cylinder temperature is low and the HC emission amount is likely to increase, the peak value of the combustion chamber temperature at the time of combustion can be increased, and an increase in the HC emission amount can be suppressed. In the above, the predetermined temperature is the in-cylinder temperature as a threshold value that does not significantly increase the HC emission amount even if the ignition timing of the internal combustion engine is retarded from the MBT when the in-cylinder temperature is higher than this, Required by experiments. Further, the in-cylinder temperature acquired by the in-cylinder temperature acquisition means does not mean a peak value during combustion, but means an average in-cylinder temperature related to the warm-up state of the cylinder.

  In the present invention, during the feedback control, when the in-cylinder temperature acquired by the in-cylinder temperature acquisition unit is equal to or higher than the predetermined temperature, the idle speed control unit sets the ignition timing from the MBT. Control may be performed on the retard side.

  In this case, since the in-cylinder temperature is equal to or higher than the predetermined temperature, the HC emission amount does not increase even when the ignition timing of the internal combustion engine is retarded from the MBT. Further, the exhaust gas temperature can be made higher by setting the ignition timing of the internal combustion engine to the retard side of the MBT. Therefore, warming up of the exhaust purification catalyst can be promoted.

  Further, in the present invention, during the feedback control, when the idle speed control means shifts the ignition timing from either the advance side or the retard side from the MBT to the other, The ignition timing may be determined so that the torque of the internal combustion engine before and after the transition becomes equal.

  Then, when the in-cylinder temperature of the internal combustion engine reaches the predetermined temperature, the ignition timing shifts from the advance side to the retard side of MBT (or from the retard side to the advance side of MBT). The torque fluctuation can be suppressed, and the occurrence of a torque shock can be suppressed.

Further, in the present invention, a fuel injection valve that is provided in an intake port of the internal combustion engine and injects fuel to be used for combustion in the internal combustion engine;
The fuel injection by the fuel injection valve is performed by intake synchronous injection in which the fuel injection is synchronized with the opening timing of the intake valve of the internal combustion engine, or the intake asynchronous injection in which the fuel injection is not synchronized with the opening timing of the intake valve Injection selecting means for selecting whether to perform
Combustion deterioration detecting means for detecting deterioration of combustion in the internal combustion engine;
Further comprising
When the combustion deterioration detection means detects the deterioration of combustion in the internal combustion engine during the feedback control, the injection selection means selects to perform the combustion injection by the intake synchronous injection. Also good.

  Here, a case where combustion in an internal combustion engine deteriorates is considered. In this case, combustion often deteriorates due to the influence of the fuel properties of the fuel injected from the fuel injection valve of the internal combustion engine. For example, when the fuel property is heavy fuel with poor volatility, when fuel is injected from the fuel injection valve provided in the intake port, the injected fuel is stably supplied from the intake port to the combustion chamber. Since it does not flow in, the air-fuel ratio in the combustion chamber becomes unstable, and combustion worsens.

  When combustion is deteriorated due to heavy fuel properties in this way, if the fuel injection is synchronized with the opening timing of the intake valve of the internal combustion engine and the intake synchronous injection is performed, the fuel properties are heavy Even so, the fuel can flow stably into the combustion chamber. However, this time, heavy fuel that has flowed into the combustion chamber without vaporizing into the combustion chamber is increased, which may deteriorate the combustion.

In contrast, in the present invention, when the in-cylinder temperature is lower than the predetermined temperature, control is performed after the ignition timing of the internal combustion engine is shifted from the MBT to the advance side, and the idle speed is controlled by feedback control. Since the rotation speed is converged, the peak value at the time of combustion of the in-cylinder temperature can be increased, and the vaporization of the heavy fuel flowing into the combustion chamber can be promoted.

  Further, in the present invention, when the in-cylinder temperature is equal to or higher than the predetermined temperature, the idle speed control means controls the ignition timing on the retard side from the MBT. Since the temperature is higher due to warm-up, the heavy fuel that has flowed into the combustion chamber can be vaporized without any problem and used for combustion.

  As described above, in the present invention, when the deterioration of combustion is detected by the combustion deterioration detecting means, the fuel injection is performed by the intake synchronous injection, so that the deterioration of the combustion due to the heavy fuel is more reliably improved. be able to.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  ADVANTAGE OF THE INVENTION According to this invention, at the time of the idle operation after the cold start of a spark ignition type internal combustion engine, discharge | emission of the unburned fuel component from an internal combustion engine can be suppressed, and the deterioration of an emission can be suppressed.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine control system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. The cylinder 2 of the internal combustion engine 1 is connected to the intake passage 30 through the intake port 3 and is connected to the exhaust passage 40 through the exhaust port 4.

  The intake port 3 is provided with a fuel injection valve 5 that injects fuel into the cylinder 2. The intake passage 30 is provided with a throttle valve 6 that controls the amount of air flowing through the intake passage 30. An intake pressure sensor 7 that measures the pressure (intake pressure) in the intake passage 30 is provided in the intake passage 30 downstream of the throttle valve 6. An air flow meter 8 that measures the amount of air flowing through the intake passage 30 is provided in the intake passage 30 upstream of the throttle valve 6.

  On the other hand, an exhaust purification device 9 is disposed in the exhaust passage 40. The exhaust purification device 9 includes a three-way catalyst, an NOx storage reduction catalyst (hereinafter simply referred to as “catalyst”), and purifies exhaust when it is in a predetermined activation temperature range. Note that the catalyst provided in the exhaust purification device 9 corresponds to an exhaust purification catalyst in this embodiment.

  Further, the internal combustion engine 1 is provided with an intake valve 10 that opens and closes an open end of the intake port 3 facing the cylinder 2 and an exhaust valve 11 that opens and closes an open end of the exhaust port 4 facing the cylinder 2. The intake valve 10 and the exhaust valve 11 are driven to open and close by an intake camshaft 12 and an exhaust camshaft 13, respectively.

  A spark plug 14 for igniting the air-fuel mixture in the cylinder 2 is disposed at the upper part of the cylinder 2. A piston 15 is slidably inserted into the cylinder 2. The piston 15 is connected to the crankshaft 17 via a connecting rod 16.

A crank position sensor 18 that detects a rotation angle of the crankshaft 17 is disposed in the vicinity of the crankshaft 17. Furthermore, a water temperature sensor 19 for measuring the temperature of the cooling water circulating through the internal combustion engine 1 is attached to the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 20. The ECU 20 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like. The ECU 20 is electrically connected to various sensors such as the intake pressure sensor 7, the air flow meter 8, the crank position sensor 18, and the water temperature sensor 19 described above, and can input measurement values of the various sensors.

  The ECU 20 electrically controls the fuel injection valve 5, the throttle valve 6, the spark plug 14, and the like based on the measured values of the various sensors described above.

  Here, conventional control of the ignition timing at the time of cold start of the internal combustion engine 1 will be described. When the internal combustion engine 1 is cold started, the exhaust purification device 9 needs to be warmed up quickly in order to reduce the amount of HC or the like released from the internal combustion engine 1 to the outside at an early stage. For this reason, the ignition timing at the time of cold start of the internal combustion engine 1 is controlled to be retarded from the normal, and the control for increasing the temperature of the exhaust gas has been performed. However, when this control is performed, the position of the piston 15 at the time of completion of combustion in the cylinder 2 becomes relatively low, so that the peak value and the in-cylinder pressure at the time of combustion of the in-cylinder temperature of the cylinder 2 are relatively To drop. As a result, the amount of fuel that does not completely burn in the cylinder 2 increases, and the amount of HC discharged from the internal combustion engine 1 may increase.

  In such a state, since the warm-up of the catalyst in the exhaust purification device 9 has not been completed, the HC discharged from the internal combustion engine 1 may be discharged outside without being purified by the exhaust purification device 9. It was. If it does so, there existed a possibility that the emission might be deteriorated rather in the initial stage at the time of cold start.

  On the other hand, it has been found that the peak value at the time of combustion, such as the in-cylinder pressure of the cylinder 2 and the in-cylinder temperature, can be particularly increased by advancing the ignition timing of the spark plug 14 from the MBT.

  FIG. 2 is a graph showing how the relationship between various parameters in the cylinder 2 and the crank angle changes depending on the ignition timing in the cylinder 2. The horizontal axis represents the crank angle of the internal combustion engine 1, and the vertical axis represents each parameter in the cylinder 2. In FIG. 2, the graph when the ignition of the spark plug 14 is advanced before MBT is a solid line, the graph when the ignition is performed at MBT is a broken line, and the ignition is at compression top dead center (TDC). A graph in the case of being performed is indicated by a one-dot chain line.

  When the ignition timing is over-advanced, the air-fuel mixture burned before the compression top dead center is compared to when the ignition timing is set to MBT and when the ignition timing is set to compression top dead center (TDC). The amount of increases. For this reason, the peak of heat energy generated by the combustion of the air-fuel mixture (see the heat generation rate, generated heat amount, and combustion mass ratio in FIG. 2) shifts to before the compression top dead center.

  Therefore, in-cylinder pressure during the period from the compression stroke to the expansion stroke is obtained by a synergistic effect of the temperature increase / pressure increase effect due to the combustion of the air-fuel mixture and the compression effect due to the piston ascending operation (operation from the bottom dead center toward the top dead center). And the peak value at the time of combustion of the in-cylinder temperature increases significantly.

  In the present embodiment, the above-described phenomenon is utilized to advance the ignition timing of the internal combustion engine 1 further than the MBT when the internal combustion engine 1 is cold started. Then, the ignition timing is controlled within the advance side of the MBT, and the idle speed is converged to the target speed by feedback control. As a result, the temperature peak in the cylinder 2 during the idling operation is raised to promote the vaporization and oxidation of the HC remaining in the cylinder 2 and to reduce the amount of HC discharged from the internal combustion engine 1.

  FIG. 3 shows a graph of the relationship between the ignition timing and torque in the cylinder 2 and the maximum in-cylinder temperature. The horizontal axis represents the ignition timing of the spark plug 14, and the vertical axis represents the torque and the maximum temperature in the cylinder. As can be seen from FIG. 3, the torque generated in the internal combustion engine 1 is greatest when the ignition timing is MBT. As the ignition timing is advanced to the front of MBT, the torque decreases while the in-cylinder maximum temperature increases and reaches the highest in ST1.

  In this embodiment, the wall surface temperature of the cylinder 2 in the internal combustion engine 1 is estimated. When the estimated wall surface temperature reaches the ignition timing switching temperature TC, the ignition timing is shifted from the advance side of MBT to the retard side of MBT. As a result, the exhaust temperature can be positively increased this time, and warming up of the exhaust purification device 9 can be promoted.

  That is, in the present embodiment, in the cold start state where the wall surface temperature of the cylinder 2 is lower than the ignition timing switching temperature TC, the ignition timing of the spark plug 14 is set to the advance side of the MBT, and the HC discharged from the internal combustion engine 1 Reduce the amount. When the wall surface temperature of the cylinder 2 becomes equal to or higher than the ignition timing switching temperature TC, the ignition timing of the spark plug 14 is shifted to the retard side from the MBT, and the exhaust gas temperature is increased, thereby increasing the exhaust gas purification device 9. Promote warming up.

  In the present embodiment, as described above, when the wall surface temperature of the cylinder 2 reaches the ignition timing switching temperature TC, the ignition timing of the spark plug 14 is switched from the advance side to the retard side of the MBT. At this time, as shown in FIG. 4, the ignition timing is switched so that the same torque can be obtained before and after the switching. If it does so, the torque shock at the time of switching from the control which gives priority to the reduction | decrease of HC discharge | emission amount at the time of the cold start of the internal combustion engine 1 to the control which gives priority to the warming-up of the exhaust gas purification apparatus 9 can be suppressed. It is possible to suppress deterioration of the ability.

  FIG. 5 shows a start idle speed control routine in the present embodiment. This routine is a program stored in the ROM of the ECU 20 and is executed by the ECU 20 at predetermined intervals while the internal combustion engine 1 is in operation.

  When this routine is executed, first, in S101, it is determined whether or not the wall surface temperature of the cylinder 2 is lower than the ignition timing switching temperature TC. Specifically, the wall surface temperature of the cylinder 2 is estimated from the integrated value after the start of the intake air amount detected by the air flow meter 8, and the estimated wall surface temperature is compared with a predetermined ignition timing switching temperature TC. It is determined by. If it is determined that the wall surface temperature of the cylinder 2 is lower than the ignition timing switching temperature TC, the process proceeds to S102. On the other hand, when it is determined that the wall surface temperature of the cylinder 2 is equal to or higher than the ignition timing switching temperature TC, the process proceeds to S103.

  In S102, the ignition timing of the spark plug 14 is set to an advance side from the MBT, and the idle speed feedback control based on the ignition timing is performed in the advance side of the MBT. At this time, when the ignition timing of the spark plug 14 is switched from the retarded side to the advanced side of the MBT, the ignition timing at which the torque is equivalent before and after the switching is selected.

  On the other hand, in S103, the ignition timing of the spark plug 14 is retarded from the MBT, and idle speed feedback control based on the ignition timing is performed in the retarded region of the MBT. In this case as well, when the ignition timing of the spark plug 14 is switched from the advance side to the retard side of the MBT, the ignition timing at which the torque is equivalent before and after the switching is selected. When the process of S102 or S103 is completed, this routine is temporarily ended.

As described above, in the present embodiment, when the wall surface temperature of the cylinder 2 is lower than the ignition timing switching temperature TC, the idle speed feedback control by the ignition timing is performed in the region where the ignition timing is advanced from the MBT. When the wall surface temperature of the cylinder 2 is equal to or higher than the ignition timing switching temperature TC, idle speed feedback control based on the ignition timing is performed in a region where the ignition timing is retarded from the MBT.

  Therefore, in the initial stage of the cold start, it is possible to suppress the emission of HC from the internal combustion engine 1 by increasing the peak value during combustion of the in-cylinder temperature of the cylinder 2 and to suppress the deterioration of the emission. . Further, in the later stage of the cold start, the temperature of the exhaust gas from the cylinder 2 can be increased, and warming up of the exhaust gas purification device 9 can be promoted.

  In this embodiment, when the wall surface temperature of the cylinder 2 reaches the ignition timing switching temperature TC, the ignition timing of the spark plug 14 is switched from the advance side to the retard side of the MBT. Since the ignition timing that can obtain the same torque before and after the switching is selected, the occurrence of torque shock can be suppressed.

  Next, changes in parameters related to the internal combustion engine 1 during cold start when the start idle speed control routine is executed will be described using the time chart of FIG. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the value of each parameter.

  In FIG. 6, it is assumed that the start of the internal combustion engine 1 is started at time t1. If it does so, an engine speed will once increase rapidly after the time t1. At this time, the ignition timing of the spark plug 14 is controlled to a predetermined initial value. Then, at a time point t2 when a predetermined feedback start waiting time has elapsed from the time point t1, the feedback control of the idle speed based on the ignition timing is started.

  At this time t2, since the wall surface temperature of each cylinder 2 is lower than the ignition timing switching temperature TC, the ignition timing on the advance side of MBT is selected as the ignition timing of the spark plug 14, and the ignition timing on the advance side of MBT. The feedback control of the engine (idle) speed is started in the region. As a result, the engine speed converges to the target speed. Further, at this time, the catalyst warm-up control is started to increase the throttle opening and increase the exhaust flow rate to promote the warm-up of the catalyst. Further, after the time point t2, the cylinder wall surface temperature starts to increase rapidly, and the catalyst temperature also starts to increase.

  Here, from the time point t2 to a time point t3 described later, the ignition timing on the advance side of the MBT is selected as described above, so that the peak value during combustion of the temperature in the cylinder 2 is maintained at a high temperature. Thus, the discharge of HC from the internal combustion engine 1 is suppressed.

  Since the state as described above is maintained after time t2, the wall surface temperature in the cylinder 2 rises. At the time point t3, the wall surface temperature in the cylinder 2 reaches the ignition timing switching temperature TC.

  Then, the ignition timing shifts to the retard side from MBT. At that time, the ignition timing shifts to the ignition timing on the retarded side of the MBT at which a torque equivalent to the torque obtained before time t3 is obtained, so that there is no step in the torque and the engine speed, and the torque Shock is suppressed.

  After the time point t3, the feedback control of the idling speed based on the ignition timing is continued in the region where the ignition timing is retarded from the MBT. Accordingly, even at this time, the idle speed is converged to the target speed. Further, after the time point t3, the ignition timing is retarded from the MBT, so that the exhaust temperature rises, the warming up of the exhaust purification device 9 is promoted, and the rising gradient of the catalyst temperature becomes steeper.

  Then, when the temperature of the exhaust purification device 9 reaches the activation temperature TA of the catalyst, the opening degree of the throttle valve 6 decreases, and the catalyst warm-up control ends.

  As described above, in the present embodiment, after the cold start of the internal combustion engine 1, until the wall surface temperature of the cylinder 2 reaches the ignition timing switching temperature TC, in the ignition timing region on the advance side from the MBT, Implements feedback control of the idling speed based on the ignition timing. Therefore, HC emission from the internal combustion engine 1 can be suppressed, and deterioration of emissions at the initial cold start can be suppressed.

  On the other hand, when the temperature of the combustion chamber becomes equal to or higher than the ignition timing switching temperature TC, the feedback control of the idling engine speed by the ignition timing is performed in the ignition timing region retarded from the MBT. Therefore, in this case, the exhaust temperature from the internal combustion engine 1 can be raised, and warming up of the catalyst in the exhaust purification device 9 can be promoted.

  In addition, when the ignition timing use range in the idle speed feedback control is switched from the advance side to the retard side from the MBT, the ignition timing is switched so that the torque becomes equal before and after the switching. Torque shock due to switching can be suppressed.

  In S102 and S103 of the starting idle speed control routine of the present embodiment, the ECU 20 that performs control for controlling the ignition timing and converging the idle speed to the target speed by feedback control is performed in the present embodiment. It corresponds to number control means. In S101, the ECU 20 that estimates the wall surface temperature of the cylinder 2 from the integrated value after the start of the intake air amount constitutes in-cylinder temperature acquisition means. In this embodiment, the ignition timing switching temperature TC corresponds to a predetermined temperature.

  Next, a second embodiment of the present invention will be described. In the present embodiment, in addition to the control described in the first embodiment, a control for switching the timing of fuel injection when the combustion of the internal combustion engine 1 deteriorates will be described. The internal combustion engine, its intake / exhaust system, and control system in this embodiment are the same as those described in FIG.

  In this embodiment, when the combustion of the internal combustion engine 1 deteriorates, it is determined that the property of the fuel introduced into the cylinder 2 is heavy, so that even heavy fuel can be easily introduced into the combustion chamber. The injection is synchronized with the opening timing of the intake valve.

  FIG. 7 shows a flowchart of the starting idle speed control routine 2 in the present embodiment. The difference between this routine and the starting idle speed control routine described in the first embodiment is that the processing of S201 to S203 is executed after the processing of S102 or S103. Hereinafter, only the difference between this routine and the starting idle speed control routine will be described.

  In S201 in this routine, it is determined whether or not the deterioration of combustion is detected in the cylinder 2. Specifically, in the feedback control of the idle speed based on the ignition timing, the deterioration of combustion may be detected by determining whether or not the actual idle speed is abnormally lower than the target speed. . More specifically, for example, it may be determined whether the idle speed is 80% or less of the target speed.

  If it is determined in S201 that the deterioration of combustion is detected in the cylinder 2, the process proceeds to S202. On the other hand, when it is determined that no deterioration in combustion is detected in the cylinder 2, the process proceeds to S203.

  In S202, intake synchronous injection is executed. That is, fuel injection by the fuel injection valve 5 is executed in synchronization with the opening timing of the intake valve 10. Thereby, even if the fuel injected from the fuel injection valve 5 is heavy fuel, it can be stably introduced into the cylinder 2.

  In S203, intake asynchronous injection is executed. That is, the fuel injection by the fuel injection valve 5 is executed at a timing before the opening timing of the intake valve 10. In this case, since the fuel injected from the fuel injection valve 5 is a non-heavy fuel, even the intake asynchronous injection can be stably introduced into the cylinder 2.

  As described above, in this embodiment, whether the ignition timing in the feedback control of the idling engine speed by the ignition timing is advanced or retarded from the MBT according to the cylinder wall surface temperature during cold start. When the combustion state deteriorates due to the heavy fuel property, the fuel injection timing is changed to intake synchronous injection to improve the combustion state. As a result, the idling engine speed can be more reliably converged to the target engine speed during cold start.

  In particular, according to this embodiment, the peak value during combustion of the temperature in the cylinder 2 is maintained at a high temperature by setting the ignition timing in the internal combustion engine 1 to the advance side from the MBT from the initial stage of cold start. Therefore, when the heavy fuel is directly introduced into the cylinder 2 by the intake synchronous injection, the heavy fuel can be vaporized more reliably, and the combustion stability can be more reliably ensured.

  In addition, ECU20 which performs the process of S201 in the starting idle speed control routine 2 of a present Example comprises a fuel deterioration detection means. Moreover, ECU20 which performs the process of S201, S202, and S203 comprises an injection selection means.

  Next, Embodiment 3 of the present invention will be described. In the present embodiment, when performing the feedback control of the idling speed based on the ignition timing described in the first embodiment, when the combustion deterioration is detected, the intake synchronous injection is performed and the ignition timing is forcibly set. The control set in the advance side area from the MBT will be described.

  In FIG. 8, the flowchart about the combustion improvement routine in a present Example is shown. This routine is a program stored in the ROM of the ECU 20, and is executed at predetermined intervals by the ECU 20 during the operation of the internal combustion engine 1 independently or in parallel with the start-up idle speed control routine described in the first embodiment. Is done.

  When this routine is executed, it is first determined in S301 whether or not the cooling water temperature is less than 60 ° C. Here, the cooling water temperature is acquired by reading the output of the water temperature sensor 19 into the ECU 20. When the cooling water temperature is 60 ° C. or higher, the internal combustion engine 1 is sufficiently warmed up and the fuel can be sufficiently vaporized, so that even if deterioration of combustion is detected, it is caused by the fuel properties Otherwise, the process proceeds to S305. On the other hand, when the cooling water temperature is lower than 60 ° C., it is determined that the combustion may be deteriorated depending on the fuel properties and the fuel vaporization state, and the process proceeds to S302.

In S302, it is determined whether or not deterioration of combustion is detected. Specifically, the determination may be made based on whether or not the idling engine speed has decreased to 80% or less of the target engine speed due to deterioration of combustion. Here, when combustion deterioration is not detected, it progresses to S305. On the other hand, if combustion deterioration is detected, it is determined that there is a high possibility that the fuel property is heavy, and the process proceeds to S303.

  In S303, it is determined whether or not the A / F control stabilization time ts has elapsed since the start of A / F feedback control. Here, the A / F control stabilization time ts is a time required from the start of A / F feedback control until the control itself is stably executed. Therefore, when it is determined that the A / F control stabilization time ts has elapsed after the start of A / F feedback control, the A / F is stabilized at the target value even if the fuel property is heavy and the volatility is low. Therefore, the process proceeds to S305. On the other hand, when it is determined that the elapsed time after the start of the A / F feedback control is less than the A / F control stabilization time ts, it is determined that the A / F feedback control itself is not stable. Proceed to

  In S304, intake-synchronized injection is executed, and the ignition timing of the spark plug 14 is forcibly advanced from the MBT, and feedback control of the idle speed is performed. Therefore, even if the fuel property is heavy, fuel injection is performed in synchronization with the opening timing of the intake valve 10, so that the fuel is introduced into the cylinder 2 satisfactorily. Further, since the peak value during combustion of the in-cylinder temperature of the cylinder 2 can be increased, it is introduced into the cylinder 2 even in a disadvantageous situation where the coolant temperature is low and the A / F feedback control is not stabilized. The vaporization of heavy fuel can be promoted and combustion can be stabilized. When the process of S304 ends, this routine is temporarily ended.

  In S305, the intake asynchronous injection is executed, and the fuel injection timing is set to a normal timing earlier than the opening timing of the intake valve 10. When the processing of S305 ends, this routine is temporarily ended. Since this routine is executed independently or in parallel with the start-up idle speed control routine, the ignition timing when S305 is performed is the ignition timing determined by the start-up idle speed control routine. May be.

  In FIG. 9, the time chart which shows the change after starting of each parameter which concerns on the internal combustion engine 1 at the time of performing the combustion improvement routine in a present Example is shown. When the combustion improvement routine is executed independently or in parallel with the start-up idle speed control routine at the time of cold start, the internal combustion engine 1 starts to start at time t1 and the engine (idle) speed rapidly increases. . Here, the cooling water temperature is less than 60 ° C., but since the idling engine speed is 80% or more of the target engine speed, deterioration of combustion has not yet been detected, and the fuel injection timing from the fuel injection valve 5 is the intake air. Asynchronous injection is selected. Thereafter, when the fuel is heavy, the engine (idle) rotational speed is decreased as it is, and falls below 80% of the target rotational speed at time t5.

  Then, it is determined that the combustion has deteriorated. At this time point, since the A / F control stabilization time ts has not elapsed since the A / F feedback control was started, the fuel injection timing is switched to the intake synchronous injection. Furthermore, after the ignition timing of the internal combustion engine 1 is set to a region on the more advanced side than MBT, idle speed feedback control based on the ignition timing is executed. As a result, even if the fuel is heavy, the fuel can be introduced into the cylinder 2 satisfactorily, and the peak value during combustion of the in-cylinder temperature of the cylinder 2 is increased, so that the heavy fuel in the cylinder 2 is vaporized. Is promoted and combustion is improved. As a result, the engine (idle) rotational speed converges to the target value.

  Next, A / F feedback control is started at time t6. At a time t7 when a predetermined A / F control stabilization time ts has elapsed from the start of the A / F feedback control, the A / F feedback control itself is stable, so regardless of the state of the fuel in the cylinder 2. Since it is determined that the combustion can be stabilized, the fuel injection timing is returned to the intake asynchronous injection, and the idling engine speed feedback control by the ignition timing using the advance side with respect to the MBT is canceled.

  Note that this routine is executed for the stability of combustion of the internal combustion engine 1, and the start idle speed control routine described in the first embodiment is executed for both HC reduction and catalyst warm-up. Considering this, when the control of this routine and the control of the ignition timing of the spark plug 14 in the control of the starting idle speed control routine are batting, the control of this routine is prioritized. After the idle speed feedback control based on the ignition timing using the advance side of the MBT is canceled at time t7, the ignition timing in the internal combustion engine 1 is the ignition in the start-time idle speed control routine as described above. You may make it follow the control of time.

  As described above, when the deterioration of combustion occurs in the cylinder 2, there is a high possibility that the fuel property is heavy. On the other hand, in this embodiment, when deterioration of combustion in the cylinder 2 is detected, the fuel injection is set to the intake-synchronous injection, so that even if it is heavier fuel, the fuel can be stabilized in the cylinder 2. Can be introduced. Thereby, deterioration of combustion can be improved.

  Further, in this embodiment, when the deterioration of combustion in the cylinder 2 is detected, the ignition timing of the internal combustion engine 1 is forcibly advanced from the MBT, and the feedback of the idling speed based on the ignition timing is performed. Since the control is continued, the peak value during combustion of the in-cylinder temperature is increased, and the heavy fuel introduced into the cylinder 2 can be vaporized more efficiently. Therefore, combustion can be improved more reliably and HC emissions can be suppressed.

  Further, when S304 is executed in a situation where the cause of the actual combustion deterioration is not the fuel property, normal fuel is directly introduced into the combustion chamber by the intake synchronous injection, but even in this case, the ignition plug After the ignition timing of 14 is advanced from the MBT, feedback control of the idle speed is performed by the ignition timing, so that the peak value at the time of combustion of the in-cylinder temperature rises and adheres to the cylinder 2 Normal fuel can be vaporized more efficiently, and HC emissions can be suppressed.

  It should be noted that the technical idea in the combustion improvement routine described in the present embodiment, that is, when combustion deterioration is detected, intake-synchronized injection is performed and the ignition timing is forcibly set to an advance side region from MBT. The idea itself can be applied not to the idle speed feedback control based on the ignition timing but also to the idle speed feedback control based on the intake air amount.

  In the idle speed feedback control based on the intake air amount, if combustion deteriorates due to the heaviness of the fuel and the engine speed decreases, the intake air amount is increased to increase the engine speed, and the throttle valve 6 is opened. The degree is increased. If it does so, there exists the characteristic that intake pipe negative pressure falls and it becomes difficult to vaporize heavy fuel further. Therefore, in the idle speed feedback control based on the intake air amount, when combustion deteriorates due to the heaviness of the fuel, the intake synchronous injection is performed and the ignition timing is forcibly set to the advance side region from the MBT. If the routine technical idea is applied, the effect that the heavy fuel can be introduced into the cylinder 2 more reliably and the fuel in the cylinder 2 can be vaporized more reliably can be used more efficiently.

  In the combustion improvement routine according to this embodiment, the ECU 20 that executes the process of S302 constitutes a fuel deterioration detection unit. Moreover, ECU20 which performs the process of S304 and S305 comprises an injection selection means.

It is a figure which shows schematic structure of the internal combustion engine in the Example of this invention, its intake-exhaust system, and a control system. It is a graph which shows the relationship between the ignition timing in the cylinder which concerns on the Example of this invention, and the state in a cylinder. It is a graph which shows the relationship between the ignition timing in the cylinder which concerns on the Example of this invention, the torque of an internal combustion engine, and the highest in-cylinder temperature. It is a graph for demonstrating the relationship of the torque before and after ignition timing switching in Example 1 of this invention. It is a flowchart about the starting idle speed control routine which concerns on Example 1 of this invention. It is a time chart which shows change of each parameter after starting of an internal-combustion engine concerning Example 1 of the present invention. It is a flowchart about the starting idle speed control routine 2 which concerns on Example 2 of this invention. It is a flowchart which shows the combustion improvement routine in Example 3 of this invention. It is a time chart which shows the change of each parameter after starting of the internal combustion engine in Example 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Intake port 4 ... Exhaust port 5 ... Fuel injection valve 6 ... Throttle valve 7.・ ・ ・ ・ Intake pressure sensor 8 ・ Air flow meter 9 ・ Exhaust gas purification device 10 ・ ・ ・ ・ Intake valve 11 ・ ・ ・ ・ Exhaust valve 12 ・ ・ ・ ・ Intake side camshaft 13 ・ ・・ ・ Exhaust camshaft 14 ・ ・ ・ ・ Spark plug 15 ・ ・ ・ ・ Piston 16 ・ ・ ・ ・ Connecting rod 17 ・ ・ ・ ・ Crankshaft 18 ・ ・ ・ ・ Crank position sensor 19 ・ ・ ・ ・ Water temperature sensor 20 ・... ECU
30 ... Intake passage 40 ... Exhaust passage

Claims (2)

An exhaust purification catalyst provided in an exhaust passage of a spark ignition type internal combustion engine for purifying exhaust gas passing through the exhaust passage;
Idle speed control means for controlling an ignition timing related to spark ignition of the internal combustion engine and causing the idle speed of the internal combustion engine to converge to a target speed by feedback control;
In-cylinder temperature acquisition means for acquiring the in-cylinder temperature in the cylinder of the internal combustion engine;
With
During the feedback control, when the in-cylinder temperature acquired by the in-cylinder temperature acquisition unit is less than a predetermined temperature, the idle speed control unit controls the ignition timing on the advance side from the MBT ,
During the feedback control, when the in-cylinder temperature acquired by the in-cylinder temperature acquisition unit is equal to or higher than the predetermined temperature, the idle speed control unit controls the ignition timing on the retard side from the MBT,
During the feedback control, when the idle speed control means shifts the ignition timing from either the advance side or the retard side from the MBT to the other, the ignition timing after the transition is A control system for an internal combustion engine, characterized in that the torque of the internal combustion engine in is determined to be equal. A fuel injection valve that is provided at an intake port of the internal combustion engine and injects fuel to be used for combustion in the internal combustion engine;
The fuel injection by the fuel injection valve is performed by intake synchronous injection in which the fuel injection is synchronized with the opening timing of the intake valve of the internal combustion engine, or the intake asynchronous injection in which the fuel injection is not synchronized with the opening timing of the intake valve Injection selecting means for selecting whether to perform
Combustion deterioration detecting means for detecting deterioration of combustion in the internal combustion engine;
Further comprising
During the feedback control, when the deterioration of combustion in the internal combustion engine is detected by the combustion deterioration detection means, the injection selection means selects to perform the combustion injection by the intake synchronous injection. The control system for an internal combustion engine according to claim 1 .

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