JP4656222B2 - Ignition control system for internal combustion engine - Google Patents

Description

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

2. Description of the Related Art Conventionally, in a spark ignition type internal combustion engine, a technique for promoting the temperature rise of cooling water by advancing the ignition timing from MBT (Minimum spark advance for Best Torque) and thereby improving the warming-up performance of the internal combustion engine. It is known (see, for example, Patent Document 1).
JP 2000-240547 A JP 2006-242109 A JP-A-5-302535 JP 2006-112329 A JP-A-10-318111 JP 2002-195141 A JP 2006-112365 A

  By the way, although the above-mentioned conventional technology considers the warming-up property of the internal combustion engine, it does not consider exhaust emission, so it may not be able to fully adapt to exhaust emission regulations.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique suitable for reducing exhaust emission in an ignition control system of a spark ignition internal combustion engine capable of advancing ignition timing from MBT. It is in.

  In order to solve the above-described problems, the present invention reduces the exhaust emission by using a technology for advancing the ignition timing from the MBT in an ignition control system for an internal combustion engine that can advance the ignition timing from the MBT. I tried to figure it out.

  When the temperature in the cylinder (hereinafter abbreviated as “in-cylinder temperature”) is low as in the case where the internal combustion engine is in a cold state, the fuel tends to adhere to the wall surface in the cylinder. Most of the fuel adhering to the wall surface in the cylinder (hereinafter referred to as “adhered fuel”) is discharged from the cylinder without being burned without being used for combustion. At this time, if the catalyst disposed in the exhaust system of the internal combustion engine is in an inactive state, the unburned fuel is discharged into the atmosphere without being purified by the catalyst.

  In particular, when the internal combustion engine is started at an extremely low temperature, the period from the start of the internal combustion engine to the activation of the catalyst becomes longer and the amount of attached fuel increases, so that the amount of unburned fuel released into the atmosphere increases. There is concern that the amount will be excessive.

On the other hand, as a result of intensive experiments and verifications by the present inventor, when the ignition timing is advanced before MBT in a spark ignition internal combustion engine, unburned fuel discharged from the cylinder (for example, HC) was found to be significantly 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 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 boosting / heating effect, the peak of the cylinder pressure (hereinafter abbreviated as “in-cylinder pressure”) and cylinder temperature is increased, and the fuel adhering to the cylinder wall and / or the cylinder wall This is thought to be due to the accelerated vaporization and combustion of the fuel before it adheres.

  Therefore, as a first means for solving the above-described problems, an ignition control system for an internal combustion engine according to the present invention is attached to an over-advance angle means for advancing the ignition timing from MBT and a wall surface in a cylinder of the internal combustion engine. An acquisition means for acquiring the fuel amount and a control means for operating the over-advance angle means when the amount of attached fuel acquired by the acquisition means is equal to or greater than a predetermined amount are provided.

  According to this configuration, since the ignition timing is advanced from the MBT when the amount of attached fuel exceeds a predetermined amount, it is possible to reduce the unburned fuel discharged from the cylinder. Therefore, even under conditions where the catalyst is in an inactive state, less unburned fuel is released into the atmosphere. As a result, the exhaust emission of the internal combustion engine is reduced.

  The control means may increase the advance amount by the over-advance means as the amount of adhered fuel acquired by the acquisition means increases.

  According to the knowledge of the present inventors, the amount of unburned fuel discharged from the cylinder decreases as the ignition timing is advanced with respect to MBT. For this reason, if the advance amount of the ignition timing is increased as the amount of attached fuel increases, the amount of unburned fuel released into the atmosphere can be suitably reduced even under conditions where the amount of attached fuel increases.

  However, if the ignition timing is excessively advanced from the MBT, the combustion of the air-fuel mixture starts before the temperature rise / pressure increase effect due to the upward movement of the piston is sufficiently obtained, so the combustion becomes slow and the heat loss increases. Become. Furthermore, since the heat energy generated by the combustion of the air-fuel mixture hinders the upward movement of the piston, the torque of the internal combustion engine may be significantly reduced.

  On the other hand, when changing the advance amount of the ignition timing according to the amount of adhered fuel, the control means may limit the advance amount so that the ignition timing is after a predetermined time.

  Examples of the predetermined timing include an ignition timing at which the combustion end timing of the air-fuel mixture is near the compression top dead center, an ignition timing at which the in-cylinder pressure peaks near the compression top dead center, or an in-cylinder temperature near the compression top dead center. Examples of the ignition timing at the peak can be given.

  When the advance amount of the ignition timing by the over-advance means is thus limited, it is possible to increase the in-cylinder pressure and the peak of the in-cylinder pressure as much as possible while suppressing an increase in heat loss and an excessive decrease in torque. It becomes possible.

  Note that the control means may determine the advance amount of the over-advance means so that the ignition timing becomes the above-mentioned predetermined timing regardless of the amount of attached fuel acquired by the acquisition means. In this case, the peak values of the in-cylinder temperature and the in-cylinder pressure can be increased as much as possible within a range in which an increase in heat loss and an excessive decrease in torque can be suppressed. As a result, the amount of unburned fuel discharged from the cylinder can be minimized.

  The predetermined time described above changes according to the combustion speed of the air-fuel mixture. For example, if the combustion speed changes even if the ignition timing is constant, the crank angle at the end of combustion of the air-fuel mixture varies. Therefore, the aforementioned predetermined time may be retarded as the combustion speed increases and advanced as the combustion speed decreases.

  However, if the engine speed is different even if the combustion speed is constant, the crank angle at the end of combustion will be different. For this reason, the predetermined time is preferably determined based on the relative relationship between the combustion speed and the engine speed.

  Further, the control means is (1) when the internal combustion engine is in a state before the start is completed, (2) when the air-fuel ratio of the air-fuel mixture used for combustion in the internal combustion engine is lean, or (3) When the load is higher than the predetermined load, the operation of the over-advance angle means may be prohibited.

  If the over-advance means is operated before the start of the internal combustion engine is completed, a decrease in ignitability, an increase in cranking torque, and the like are induced, and it may be difficult to start the internal combustion engine quickly. Therefore, when the internal combustion engine is in a state before the start is completed, the startability can be prevented from being deteriorated by prohibiting the operation of the advance angle means.

  The “start completion” condition here may be the occurrence of a complete explosion, but may be the occurrence of an initial explosion when the amount of advance by the excessive advance means is small.

  When the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder is lean, the amount of unburned fuel discharged from the cylinder decreases, and the unburned fuel and oxygen in the exhaust gas react with each other in the catalyst. The temperature of the catalyst is quickly raised to the active temperature range. Therefore, it is possible to reduce the exhaust emission even if the over-advance means is not operated.

  When the load of the internal combustion engine is equal to or greater than a predetermined load, the generated torque of the internal combustion engine may fall below the required torque when the over-advance angle means is activated. Therefore, when the load on the internal combustion engine is equal to or higher than the predetermined load, the internal combustion engine can generate the torque as required by prohibiting the operation of the over-advance angle means.

  In the internal combustion engine in which the fuel injection valve is configured to inject fuel into the intake port, the control means synchronizes the fuel injection timing of the fuel injection valve with the intake stroke when operating the over-advance angle means. It is good also as timing (intake synchronous injection).

  When the in-cylinder temperature is lowered, the temperature in the intake port is also considered to be lowered. When the cylinder injection temperature and the intake port temperature are low, if the fuel injection timing is asynchronous with the intake stroke (intake asynchronous injection), in addition to the amount of fuel adhering to the cylinder wall, it adheres to the intake port wall The amount of fuel to be increased also increases.

  On the other hand, if the fuel injection valve performs intake-synchronized injection when the over-advance angle means operates, the amount of fuel adhering to the wall surface of the intake port is reduced without increasing the amount of unburned fuel discharged from the cylinder. Can be made.

  It is desirable that the switching timing from the intake asynchronous injection to the intake synchronous injection is after the start of the operation of the over-advance means.

  When the intake synchronous injection is performed, the fuel adhering to the wall surface in the intake port is reduced compared to the time when the intake asynchronous injection is performed, but the fuel adhering to the wall surface in the cylinder is likely to increase. Further, since the in-cylinder temperature is low immediately after the start of the operation of the over-advance angle means, if the amount of fuel adhering to the wall surface in the cylinder becomes excessive, it may be difficult to vaporize and burn all the adhering fuel.

  Therefore, when switching from the intake asynchronous injection to the intake synchronous injection is performed simultaneously with the start of the operation of the over-advance angle means, it may be difficult to effectively reduce the unburned fuel discharged from the cylinder.

On the other hand, when the switching timing from the intake asynchronous injection to the intake synchronous injection is set after the start of the operation of the over-advance angle means, the switching from the intake asynchronous injection to the intake synchronous injection is performed after the in-cylinder temperature rises to some extent. Therefore, the amount of fuel adhering to the wall surface in the cylinder is unlikely to be excessive, and all the adhering fuel is easily vaporized and burned.

  Therefore, if switching from the intake asynchronous injection to the intake synchronous injection is performed after the operation of the over-advance angle means is started, the unburned fuel discharged from the cylinder can be effectively reduced.

  As a second means for solving the above-described problem, an ignition control system for an internal combustion engine according to the present invention includes an over-advance angle means for advancing the ignition timing from MBT, an acquisition means for acquiring the amount of attached fuel, Control means for changing the amount of advance by the over-advance means according to the amount of attached fuel acquired by the acquisition means.

  When the ignition timing is advanced from MBT, there is a considerable decrease in torque and deterioration in fuel consumption. For this reason, when the amount of attached fuel is small, it is preferable to reduce the advance amount of the ignition timing as much as possible.

  On the other hand, if the advance amount of the ignition timing by the over-advance means is changed according to the amount of adhered fuel, unburned fuel discharged from the cylinder is reduced while minimizing torque reduction and fuel consumption deterioration. It becomes possible to decrease.

  As described above, since the excessive advance of the ignition timing causes an increase in heat loss and a decrease in torque, the advance amount is limited in the second means so that the ignition timing is after the predetermined timing. It may be. In this case, the predetermined timing includes an ignition timing at which the combustion end timing of the air-fuel mixture is near the compression top dead center, an ignition timing at which the in-cylinder pressure peaks near the compression top dead center, or an in-cylinder temperature near the compression top dead center. The ignition timing that peaks at can be illustrated.

  Further, the control means is (1) when the internal combustion engine is in a state before the start is completed, (2) when the air-fuel ratio of the air-fuel mixture used for combustion in the internal combustion engine is lean, or (3) When the load is higher than the predetermined load, the operation of the over-advance angle means may be prohibited.

  Further, when the fuel injection valve of the internal combustion engine is configured to inject fuel into the intake port, the control means synchronizes the fuel injection timing of the fuel injection valve with the intake stroke when operating the over-advance angle means. It is good also as the timing.

  As a third means for solving the above-described problem, an ignition control system for an internal combustion engine according to the present invention includes an over-advance means for advancing the ignition timing from the MBT, and a combustion end timing of the air-fuel mixture is compression dead. And control means for determining the advance amount by the over advance means so as to be in the vicinity of the point.

  According to such a configuration, when the over-advance angle means operates, the combustion end timing of the air-fuel mixture is necessarily near the compression top dead center. For this reason, the peak values of the in-cylinder pressure and the in-cylinder temperature can be increased as much as possible while suppressing an increase in heat loss and an excessive decrease in torque. Therefore, unburned fuel discharged from the cylinder is minimized.

  Further, the control means is (1) when the internal combustion engine is in a state before the start is completed, (2) when the air-fuel ratio of the air-fuel mixture used for combustion in the internal combustion engine is lean, or (3) When the load is higher than the predetermined load, the operation of the over-advance angle means may be prohibited.

  Further, when the fuel injection valve of the internal combustion engine is configured to inject fuel into the intake port, the control means synchronizes the fuel injection timing of the fuel injection valve with the intake stroke when operating the over-advance angle means. It is good also as the timing.

  As a fourth means for solving the above-described problem, an ignition control system for an internal combustion engine according to the present invention includes an over-advance angle means for advancing the ignition timing from MBT, and an over-advance angle means after completion of starting of the internal combustion engine. And a control means for actuating.

  According to such a configuration, the over-advance means does not operate before the start of the internal combustion engine is completed. As a result, a decrease in startability due to the ignition timing being advanced from the MBT is suppressed.

  The over-advance means may be inevitably operated after the start of the internal combustion engine is completed, or may be operated only when the amount of attached fuel may increase. In any case, unburned fuel released from the internal combustion engine into the atmosphere during the period from the completion of the start of the internal combustion engine to the activation of the catalyst can be extremely reduced.

  Examples of cases where the amount of fuel adhering in the cylinder may increase include cases where the temperature of the cooling water is low in addition to the case where the amount of adhering fuel acquired by the acquisition means as described above exceeds a predetermined value. can do.

  The advance amount of the ignition timing by the over-advance means may be changed according to the amount of attached fuel, or may be determined so that the ignition timing becomes the aforementioned predetermined timing.

  Further, the control means operates (1) when the air-fuel ratio of the air-fuel mixture supplied for combustion in the internal combustion engine is lean, or (2) when the load of the internal combustion engine is higher than a predetermined load, May be prohibited.

  Further, when the fuel injection valve of the internal combustion engine is configured to inject fuel into the intake port, the control means synchronizes the fuel injection timing of the fuel injection valve with the intake stroke when operating the over-advance angle means. It is good also as the timing.

  According to the present invention, exhaust emission can be suitably reduced in an ignition control system for a spark ignition type internal combustion engine that can advance the ignition timing from MBT.

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

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an ignition control system for an internal combustion engine according to the present invention.

  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, and the like, and purifies exhaust when it is in a predetermined activation temperature range.

  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, and the spark plug 14 based on the measurement values of the various sensors described above. For example, the ECU 20 performs attached fuel reduction control for reducing the fuel attached to the wall surface in the cylinder 2.

  Hereinafter, the adhered fuel reduction control in this embodiment will be described.

  When the in-cylinder temperature is low, such as when the internal combustion engine 1 is in a cold state, fuel tends to adhere to the wall surface in the cylinder. Most of the fuel adhering to the wall surface in the cylinder (adhered fuel) is discharged from the cylinder without being burned without being used for combustion. At that time, if the exhaust purification device 9 is not heated to the activation temperature range, the above-mentioned unburned fuel is discharged into the atmosphere without being purified.

  In particular, when the internal combustion engine 1 is started at an extremely low temperature, etc., the period from the start of the internal combustion engine 1 to the activation of the exhaust purification device 9 becomes longer and the amount of attached fuel increases. There is a risk that the amount of unburned fuel will be excessive.

  On the other hand, in the adhered fuel reduction control, the ECU 20 reduces the adhered fuel amount by advancing the operation timing (ignition timing) of the spark plug 14 from the MBT when the adhered fuel amount increases. The amount of unburned fuel discharged from inside 2 was reduced.

  According to the inventor's earnest experiment and verification, when the ignition timing is advanced from the MBT, as shown in FIG. 2, the unburned gas discharged from the cylinder 2 increases as the advance amount increases. It has been clarified that the amount of fuel (HC) is reduced.

  Although this mechanism has not been clearly clarified, it is thought to be due to the following mechanism.

FIG. 3 shows a case where the ignition timing is advanced (hereinafter referred to as “over-advance angle”) before MBT (ST1 in FIG. 3) and a case where the ignition timing is set to MBT (in FIG. 3). It is a figure which shows the result of having measured the state in the cylinder 2 in each of the case where the ignition timing is set to the compression top dead center (TDC) (ST3 in FIG. 3). The solid line in FIG. 3 shows the case where the ignition timing is over-advanced, the broken line shows the case where the ignition timing is set to MBT, and the dashed line shows the case where the ignition timing is set to compression top dead center (TDC). Yes.

  In FIG. 3, when the ignition timing is over-advanced, combustion occurs before the compression top dead center, 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 air-fuel mixture produced increases. For this reason, the peak of the 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. 3) 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 bottom dead center to top dead center) In addition, the peak value of the in-cylinder temperature increases significantly. As a result, it is considered that the fuel attached to the wall surface in the cylinder is vaporized and / or vaporized before being attached to the wall surface in the cylinder and used for combustion.

  Therefore, the ECU 20 acquires the amount of attached fuel, and when the acquired amount of attached fuel is equal to or greater than a predetermined amount, the ignition timing is over-advanced.

  As a method for obtaining the amount of attached fuel, a method for optically measuring the thickness of the liquid film in the cylinder 2 and actually measuring it, and a sensor for measuring the conductivity in the cylinder 2 are provided. The method of converting the measured value into the amount of attached fuel, or the method of estimating the amount of attached fuel from the operating conditions of the internal combustion engine 1 (hereinafter abbreviated as “engine operating conditions”) can be exemplified.

  When estimating the amount of attached fuel from the engine operating conditions, the ECU 20 determines the measured value of the water temperature sensor 19 (cooling water temperature thw), the measured value of the intake pressure sensor 7 (intake pressure pm), and the start time of the internal combustion engine 1. From the start of the internal combustion engine 1 to the current time (ΣQinj), the fuel injection amount (Qinj), and the air-fuel ratio (A / F) of the air-fuel mixture The amount of attached fuel may be estimated using at least one of the above as a parameter.

  For example, when the internal combustion engine 1 is started (hereinafter abbreviated as “engine start”), it can be considered that the coolant temperature thw is substantially equal to the wall surface temperature in the cylinder 2. The amount of attached fuel increases as the wall surface temperature in the cylinder 2 decreases. Therefore, the ECU 20 can estimate the amount of attached fuel from the coolant temperature thw at the time of engine start and the map shown in FIG.

  Since the wall surface temperature in the cylinder 2 at the time of starting the engine is substantially equal to the temperature of the atmosphere, when the internal combustion engine 1 includes an intake air temperature sensor, an intake air temperature sensor is used instead of the cooling water temperature thw at the time of starting the engine. May be used.

  By the way, after the internal combustion engine 1 is started, the wall surface temperature in the cylinder 2 increases as the operation time elapses. The amount of temperature rise at that time correlates with the integrated amount ΣQinj of the fuel used for combustion in the cylinder 2, in other words, the integrated amount ΣGa of the air used for combustion in the cylinder 2. Therefore, the ECU 20 can also estimate the amount of adhering fuel from the accumulated intake air amount ΣGa (or accumulated fuel injection amount ΣQinj) from the time of engine startup to the present time and the map shown in FIG.

  Further, the amount of attached fuel decreases as the in-cylinder pressure decreases (in other words, the negative pressure in the cylinder 2 increases). The in-cylinder pressure correlates with the intake pressure pm downstream from the throttle valve 6 (for example, the intake pressure pm during the intake stroke). Therefore, the ECU 20 can also estimate the amount of attached fuel from the intake pressure pm and the map shown in FIG.

  Further, the amount of attached fuel also tends to increase as the amount of fuel injected from the fuel injection valve 5 (fuel injection amount Qinj) increases. Therefore, the ECU 20 can also estimate the amount of attached fuel from the fuel amount Qinj injected from the fuel injection valve 5 and the map shown in FIG.

  Furthermore, the amount of attached fuel also tends to increase as the air-fuel ratio A / F of the mixture decreases. Therefore, the ECU 20 may estimate the amount of attached fuel from the air-fuel ratio A / F of the air-fuel mixture and the map shown in FIG.

  In addition, ECU20 can also raise the estimation precision of the amount of adhesion fuel by combining the map of FIGS. 4-8 as much as possible. However, since the air-fuel ratio A / F of the air-fuel mixture correlates with the fuel injection amount Qinj, the attached fuel amount Dpfuel is determined from the cooling water temperature thw, the intake pressure pm, the integrated intake air amount ΣGa, and the fuel injection amount Qinj at the time of engine start. May be calculated.

  When the amount of attached fuel is acquired by the various methods described above, the ECU 20 determines whether or not the amount of attached fuel is greater than or equal to a predetermined amount. The aforementioned predetermined amount may be determined such that the total amount of unburned fuel discharged from all the cylinders 2 of the internal combustion engine 1 is less than the regulated amount.

  When the ECU 20 determines that the amount of attached fuel is equal to or greater than the predetermined amount, the ECU 20 causes the ignition timing of the spark plug 14 to advance forward before MBT. The advance amount at that time (for example, the advance amount from MBT) is preferably determined so that the combustion end timing of the air-fuel mixture in the cylinder 2 is in the vicinity of the compression top dead center.

  From the experiments and verifications of the present inventor, it is known that the amount of unburned fuel discharged from the cylinder 2 decreases as the ignition timing is advanced with respect to MBT. However, if the ignition timing is advanced excessively from MBT, the following contradiction occurs.

  (1) If the ignition timing is excessively advanced with respect to MBT, combustion of the air-fuel mixture starts before the temperature rise / pressure increase effect by the ascending operation of the piston 15 is sufficiently obtained, so the combustion becomes slow. Heat loss increases.

  (2) If the ignition timing is excessively advanced with respect to MBT, the heat energy generated by the combustion of the air-fuel mixture hinders the upward movement of the piston 15, so the torque of the internal combustion engine 1 is significantly reduced and drivability is reduced. Induces a decrease and deterioration of fuel consumption.

  (3) When the ignition timing is advanced excessively with respect to MBT, the fuel entering the gap (clevis volume) between the piston 15, the piston ring, and the cylinder bore wall surface increases. The fuel that has entered the clevis volume is easily discharged from the cylinder 2 without being used for combustion. For this reason, if the ignition timing is advanced excessively with respect to MBT, the amount of unburned fuel discharged from the cylinder 2 may increase.

  In contrast, when the advance amount of the ignition timing is determined so that the combustion end timing of the air-fuel mixture is in the vicinity of the compression top dead center, the cylinder pressure and the cylinder are within a range in which excessive increase in the above-described contradiction can be suppressed. The peak of the internal temperature can be increased as much as possible. As a result, unburned fuel discharged from the cylinder 2 is minimized.

By the way, in order to synchronize the combustion end timing of the air-fuel mixture in the vicinity of the compression top dead center, it is necessary to grasp the combustion time of the air-fuel mixture, in other words, the combustion speed of the air-fuel mixture. The combustion speed of the air-fuel mixture is affected by the in-cylinder temperature, the amount of gas charged in the cylinder 2 (hereinafter abbreviated as “in-cylinder gas amount”), the air-fuel ratio A / F of the air-fuel mixture, and the like. Further, the combustion end timing (crank angle) of the air-fuel mixture becomes slower as the engine speed Ne becomes higher, and becomes earlier as the engine speed Ne becomes lower, even if the combustion speed is constant.

  Therefore, the ECU 20 may determine the advance amount of the ignition timing based on the in-cylinder temperature, the in-cylinder gas amount, the air-fuel ratio A / F, and the engine speed Ne. Immediately after the internal combustion engine 1 is started (that is, during warm-up operation), the fuel injection amount is controlled so that the air-fuel ratio A / F is suitable for the coolant temperature thw, so the air-fuel ratio A / F is cooled. It can be said that it correlates with the water temperature thw. The in-cylinder temperature is also correlated with the cooling water temperature thw.

  Therefore, the ECU 20 may determine the advance amount of the ignition timing based on the in-cylinder temperature, the in-cylinder gas amount, and the engine speed Ne. For example, the ECU 20 may determine the advance amount of the ignition timing based on maps as shown in FIGS.

  FIG. 9 is a map showing the relationship between the ignition timing advance amount and the coolant temperature thw. In the map of FIG. 9, the advance amount of the ignition timing increases as the cooling water temperature thw decreases and decreases as the cooling water temperature thw increases.

  FIG. 10 is a map showing the relationship between the ignition timing advance amount and the in-cylinder gas amount. In the example of FIG. 10, the load factor KL of the internal combustion engine 1 is used instead of the in-cylinder gas amount. In the map of FIG. 10, the advance amount of the ignition timing increases as the load factor KL decreases (as the in-cylinder gas amount decreases), and decreases as the load factor KL increases (as the in-cylinder gas amount increases). Is done.

  FIG. 11 is a diagram showing the relationship between the advance amount of the ignition timing and the engine speed Ne. In the map of FIG. 11, the advance amount of the ignition timing decreases as the engine speed Ne decreases and increases as the engine speed Ne increases.

  When the advance amount of the ignition timing is determined based on the maps as shown in FIGS. 9 to 11 described above, the combustion end timing of the air-fuel mixture becomes the vicinity of the compression top dead center regardless of the operating state of the internal combustion engine 1. Become. As a result, it is possible to minimize the amount of unburned fuel discharged from the cylinder 2 while minimizing an increase in heat loss, a decrease in torque, or a deterioration in fuel consumption.

  Next, an execution procedure of the attached fuel reduction control in this embodiment will be described with reference to FIGS. FIG. 12 is a flowchart showing an over-advance angle execution determination routine for determining whether or not the over-advance angle of the ignition timing should be executed, and FIG. 7 is a flowchart showing an advance amount determination routine for determining (time).

  The routines of FIGS. 12 and 13 are routines stored in the ROM of the ECU 20 in advance, and are periodically executed by the ECU 20. Further, when the ECU 20 executes the routines of FIGS. 12 and 13, the acquisition means, over-advance angle means, and control means according to the present invention are realized.

  First, in the over-advance angle execution determination routine, the ECU 20 determines whether or not the internal combustion engine 1 is being started in S101, for example, whether an ignition switch (not shown) is turned on, or whether a starter switch is turned on. Is determined.

  If an affirmative determination is made in S101, the ECU 20 reads the measured value of the water temperature sensor 19 in S102 and stores the measured value in the RAM as the cooling water temperature thw at the time of engine start. If a negative determination is made in S101, the process of S102 is skipped and the process proceeds to S103.

  In S103, the ECU 20 reads the measured value of the intake pressure sensor 7, and stores the measured value in the RAM as the in-cylinder pressure.

  In S104, the integrated intake air amount ΣGa from the start of the internal combustion engine 1 to the current time is calculated, and the calculation result is stored in the RAM. In S104, instead of the cumulative intake air amount ΣGa, the cumulative fuel injection amount ΣQinj from the start of the internal combustion engine 1 to the current time may be used.

  In S105, the fuel injection amount Qinj is read. The fuel injection amount Qinj at that time may be the fuel injection amount of the cylinder 2 from which fuel injection will be performed from now on, or may be the fuel injection amount of the cylinder 2 that has already been injected and before ignition is performed. Good.

  In S106, the ECU 20 calculates the adhered fuel amount Dpfuel using the various values obtained in S102 to S105 and the maps shown in FIGS.

  In S107, it is determined whether or not the attached fuel amount Dpfuel calculated in S106 is a predetermined amount or more.

  If an affirmative determination is made in S107, the ECU 20 proceeds to S108 and sets “1” in the over-advance angle execution flag. The over-advance angle execution flag is a storage area set in advance in the RAM or the like.

  On the other hand, if a negative determination is made in S107, the ECU 20 proceeds to S109 and resets the over-advance angle execution flag to “0”.

  Next, in the advance amount determination routine of FIG. 13, the ECU 20 first determines whether or not “1” is set to the over-advance angle execution flag in S201. If a negative determination is made in S201, the ECU 20 ends the execution of this routine. On the other hand, when a positive determination is made in S201, the ECU 20 proceeds to S202.

  In S202, the ECU 20 reads the measured value (cooling water temperature) thw of the water temperature sensor 19. In S203, the ECU 20 calculates the load factor KL of the internal combustion engine 1. In S204, the ECU 20 acquires the engine speed Ne.

  In S205, the ECU 20 uses the various values obtained in S202 to S204 and the maps shown in FIGS. 9 to 11 to advance the amount of advancement at which the combustion end timing of the air-fuel mixture is near the compression top dead center. ΔSa is calculated.

  In S206, the ECU 20 determines the ignition timing It for each cylinder 2 based on the advance amount ΔSa obtained in S205.

  When the ignition timing It is determined as described above, the fuel end timing of the air-fuel mixture in each cylinder 2 becomes near the compression top dead center. As a result, the peak values of the in-cylinder pressure and the in-cylinder temperature are highest within a range where the above-described contradiction falls within an allowable range. As a result, unburned fuel discharged from the cylinder 2 is suitably reduced, and the amount of unburned fuel released into the atmosphere is also reduced.

  In this embodiment, the example in which the ignition timing It at the time of over-advancement is determined in consideration of the combustion speed of the air-fuel mixture and the engine speed Ne has been described, but the over-advance angle is determined by the following simple method. The ignition timing It may be determined.

  As shown in FIG. 14, the MBT is determined so that the heat generation rate when the air-fuel mixture burns peaks near the compression top dead center. Further, the waveform of the heat release rate is substantially symmetric with respect to the peak.

  Therefore, the ECU 20 obtains the crank angle difference (ΔIt in FIG. 14) between the compression stroke top dead center (TDC) and MBT, and cranks twice the crank angle difference ΔIt from the compression top dead center (TDC). The timing (TDC−ΔIt * 2) at which the angle (= ΔIt * 2) is advanced may be used as the ignition timing It (see FIG. 15). According to such a method, it is possible to make the combustion end timing of the air-fuel mixture substantially near the compression top dead center while keeping the calculation load of the ECU 20 low.

  Further, the excessive advance angle of the ignition timing may be prohibited when the load of the internal combustion engine 1 is higher than a predetermined load (for example, during acceleration operation). This is because if the ignition timing is excessively advanced when the load of the internal combustion engine 1 is higher than the predetermined load, the internal combustion engine 1 cannot generate torque as requested by the driver, which may give the driver a sense of incongruity. Because there is.

<Example 2>
Next, a second embodiment of the ignition control system for an internal combustion engine according to the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In this embodiment, an example will be described in which the over-advanced ignition timing is prohibited when the air-fuel ratio A / F of the air-fuel mixture used for combustion in the cylinder 2 is lean.

  When the air-fuel ratio of the air-fuel mixture used for combustion in the cylinder 2 is lean, the amount of unburned fuel discharged from the cylinder 2 is reduced, and unburned fuel and oxygen in the exhaust gas are removed from the exhaust purification device 9. It is possible to quickly raise the temperature of the exhaust purification device 9 to the activation temperature range by reacting with the above. Further, when the ignition timing is excessively advanced, the combustion of the air-fuel mixture is performed earlier than usual, so that the exhaust temperature tends to be low.

  Therefore, if the advance angle of the ignition timing is prohibited when the air-fuel ratio A / F of the air-fuel mixture is lean, a decrease in the exhaust temperature is suppressed, so that the reaction between the unburned fuel and oxygen in the exhaust purification device 9 Promoted. As a result, the exhaust purification device 9 is activated early.

  Hereinafter, the execution procedure of the adhered fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 16 is a flowchart showing an over-advance angle execution determination routine. In the flowchart of FIG. 16, the same reference numerals are assigned to the same processes as those in the above-described over-advance execution determination routine (see FIG. 12) of the first embodiment.

  The ECU 20 proceeds to S1101 after executing S105, and acquires the air-fuel ratio A / F. This air-fuel ratio A / F may be calculated from the measured value of the air flow meter 8 and the fuel injection amount Qinj, or may be the measured value of an air-fuel ratio sensor (not shown) attached to the exhaust passage 40. Good.

  Subsequently, the ECU 20 proceeds to S1102, and determines whether or not the air-fuel ratio A / F acquired in S1101 is lean. If a negative determination is made in S1102, the ECU 20 executes the processes after S106. On the other hand, if an affirmative determination is made in S1102, the process proceeds to S109, where the over-advance angle execution flag is reset to “0” to prohibit the execution of the over-advance angle.

  According to the embodiment described above, since the exhaust purification device 9 can be activated at an early stage, the exhaust emission can be reduced by utilizing the purification capability of the exhaust purification device 9.

<Example 3>
Next, a description will be given of a third embodiment of the ignition control system for the internal combustion engine according to the present invention. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In this embodiment, an example of optimizing the fuel injection timing when the ignition timing is excessively advanced will be described.

  When the internal combustion engine 1 is started or warmed up, the fuel injection timing may be set asynchronously with the intake stroke of each cylinder 2 (intake asynchronous injection). In that case, a large amount of fuel tends to adhere to the wall surface in the intake port 3 in addition to the wall surface in the cylinder 2. The fuel adhering to the wall surface in the intake port 3 may flow into the exhaust passage 40 while remaining unburned during the valve overlap period of the intake / exhaust valves 10 and 11.

  On the other hand, when the fuel injection timing is set to a timing (intake synchronous injection) synchronized with the intake stroke of each cylinder 2, the amount of fuel adhering to the wall surface in the intake port 3 can be reduced. If the amount of fuel adhering to the wall surface in the intake port 3 decreases, the amount of fuel adhering to the wall surface in the cylinder 2 may increase. However, the fuel adhering to the wall surface in the cylinder 2 is reduced by the excessive advance angle of the ignition timing.

  Therefore, if the fuel injection timing is switched from the intake asynchronous injection to the intake synchronous injection when the ignition timing is excessively advanced, it adheres to the wall surface in the intake port 3 in addition to the fuel amount attached to the wall surface in the cylinder 2. The amount of fuel to be reduced can also be reduced. As a result, the amount of unburned fuel discharged from the cylinder 2 of the internal combustion engine 1 can be further reduced.

  The timing for switching from intake asynchronous injection to intake synchronous injection may be when the ignition timing over-advanced angle is started, but after a predetermined period after the ignition timing over-advanced angle is started (for example, 1 to 2 cycles later).

  When intake synchronous injection is performed, the fuel adhering to the wall surface in the intake port 3 decreases, but the fuel adhering to the wall surface in the cylinder 2 tends to increase. On the other hand, the in-cylinder temperature (the wall surface temperature or the atmospheric temperature in the cylinder 2) is lowered immediately after the ignition timing over-advanced angle is started. For this reason, when the amount of fuel adhering to the wall surface in the cylinder 2 increases, it becomes difficult to vaporize and burn all the adhering fuel.

  Therefore, if the fuel injection timing is switched after a predetermined period from when the ignition timing over-advanced angle is started, the cylinder temperature at the time of fuel injection timing switching is high, so that it adheres to the wall surface of the intake port 3. Even if a minute amount of fuel flows into the cylinder 2, almost all of the fuel can be vaporized and burned.

<Example 4>
Next, a fourth embodiment of the ignition control system for an internal combustion engine according to the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the present embodiment, an example will be described in which the ignition timing is gradually changed when the ignition timing over-advance angle is started and ended.

If the ignition timing changes rapidly when the ignition timing over-advance angle is started, combustion fluctuations and torque fluctuations may occur. For this reason, the ECU 20 gradually changes the ignition timing at the start and end of the over-advance angle.

  For example, when starting the over-advance angle of the ignition timing, as shown in FIG. 17, the ECU 20 starts after the over-advance angle starts from the ignition timing before the start of the over-advance angle (the normal time ignition timing in FIG. 17). The ignition timing is advanced in a plurality of times until the ignition timing (over-advance point ignition timing in FIG. 17).

  At this time, the advance amount per one time may be a fixed amount that is defined in advance, and a variable value (for example, a difference) that is changed in accordance with the difference between the normal timing and the over-advance timing. The value may be increased as the value of becomes larger.

  In addition, when the ECU 20 ends the ignition timing over-advanced angle, the ECU 20 may delay the ignition timing in a plurality of times as in the case of the over-advanced angle start (see FIG. 18).

  As described above, when the ignition timing is gradually changed when the ignition timing over-advance angle is started or ended, it is possible to suppress the occurrence of combustion fluctuations and torque fluctuations.

  As shown in FIG. 19, when the ignition timing St1 that can generate the same torque as the normal time ignition timing exists before the MBT, the ECU 20 sets the ignition timing to the normal time ignition when starting the over-advanced angle. It is also possible to change the timing from the ignition timing St1 once and then gradually change the ignition timing from the ignition timing St1 to the over-advance point ignition timing.

  According to such a method, it is possible to shorten the time required until the ignition timing shifts from the normal timing fire timing to the over-advance timing timing. Furthermore, when the ignition timing over-advanced angle is terminated, if the ignition timing is switched by the same method, the ignition timing can be quickly returned from the over-advanced angle ignition timing to the normal ignition timing.

  Further, the ECU 20 may change the ignition timing from the normal timing fire timing to the over-advance timing timing at one time, and suppress the torque fluctuation by adjusting the intake air amount.

  For example, as shown in FIG. 20, the ECU 20 obtains a torque equivalent to the current time (when the ignition timing is set to the normal time ignition timing) when the ignition timing is changed to the over-advance timing ignition timing. The intake air amount Ga2 required for the operation is specified. Next, the ECU 20 controls the throttle valve 6 so that the intake air amount becomes the intake air amount Ga2 at the same time that the ignition timing is changed from the normal ignition timing to the over-advance ignition timing.

  According to such a method, the ignition timing can be quickly changed from the normal timing fire timing to the over-advance timing timing, and torque fluctuations at that time can be suppressed. Further, when the ignition timing over-advanced angle is terminated, if the ignition timing is switched and the intake air amount is adjusted by the same method, the ignition timing is normally set from the over-advanced ignition timing while suppressing torque fluctuation. It is possible to return to the ignition timing early.

<Example 5>
Next, a fifth embodiment of the ignition control system for an internal combustion engine according to the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the present embodiment, an example will be described in which the ignition timing at the time of over advance is limited so that the peak of the in-cylinder pressure is after the compression top dead center.

When the ignition timing is excessively advanced, the air-fuel mixture burns while the piston 15 is moving up during the compression stroke. For this reason, the ascending operation of the piston 15 is hindered by the combustion pressure of the air-fuel mixture, and the torque of the internal combustion engine 1 is reduced considerably.

  At this time, if the peak of the in-cylinder pressure is before the compression top dead center, the total pressure received by the piston 15 during the expansion stroke (hereinafter referred to as “first total pressure”) is the pressure received by the piston 15 during the compression stroke. May be equal to or less than the total sum (hereinafter referred to as “second total pressure”).

  By the way, friction acts on the movable part of the internal combustion engine 1. Therefore, in order for the internal combustion engine 1 to generate positive torque, the first total pressure needs to exceed the sum of the second total pressure and the friction. However, if the first total pressure becomes equal to or less than the second total pressure, the internal combustion engine 1 cannot overcome the above-described friction, and thus the internal combustion engine 1 may not be able to generate positive torque.

  FIG. 21 is a diagram showing a result of measuring the in-cylinder pressure when the ignition timing is set so that the peak of the in-cylinder pressure becomes the compression top dead center.

  In FIG. 21, the first total pressure (corresponding to the area of region A in FIG. 21) is the thermal expansion of the combustion gas compared to the second total pressure (corresponding to the area of region B in FIG. 21). The difference (a value obtained by subtracting the second total pressure from the first total pressure) is sufficiently larger than the friction of the internal combustion engine 1.

  Therefore, in the attached fuel reduction control of this embodiment, the ECU 20 determines the ignition timing at which the peak of the in-cylinder pressure becomes the compression top dead center as an upper limit value (hereinafter referred to as “torque limit ignition timing”), and the over-advance point The fire timing is limited after the torque limit ignition timing.

  Specifically, the ECU 20 determines the ignition timing (hereinafter referred to as “reference ignition timing”) obtained by the advance amount determination routine (see FIG. 13) described in the first embodiment and the torque limit. Compare the ignition timing.

  When the reference ignition timing is later than the torque limit ignition timing (retarding side), the ECU 20 performs over-advance using the reference ignition timing as the over-advance time point fire timing. On the other hand, when the reference ignition timing is earlier than the torque limit ignition timing (advance angle side), the ECU 20 performs overadvance using the torque limit ignition timing as the overadvance time point fire timing.

  The torque limit ignition timing described above may be experimentally obtained in advance, or may be specified using an in-cylinder pressure sensor.

  When the torque limit ignition timing is specified using the in-cylinder pressure sensor, the ECU 20 first sets the over-advanced ignition timing as the reference ignition timing, and the in-cylinder pressure peaks from the measured value of the in-cylinder pressure sensor at that time. Find the timing (crank angle). Subsequently, the ECU 20 continues the over-advance angle based on the reference ignition timing if the peak timing of the in-cylinder pressure is after the compression top dead center, and if the timing is before the compression top dead center, You may make it retard from reference ignition timing.

  Hereinafter, the execution procedure of the attached fuel reduction control in this embodiment will be described with reference to FIG. FIG. 22 is a flowchart showing an advance amount determination routine. In the flowchart of FIG. 22, the same processes as those in the advance amount determination routine (see FIG. 13) of the first embodiment are denoted by the same reference numerals.

In the advance amount determination routine, when the ignition timing (reference ignition timing) It is determined in S206, the ECU 20 proceeds to S2201, and uses the ignition timing (reference ignition timing) It as an over-advance time point ignition timing. To start.

  In S2202, the ECU 20 specifies the timing (peak timing) at which the in-cylinder pressure peaks based on the measured value of the in-cylinder pressure sensor.

  In S2203, the ECU 20 determines whether or not the peak timing specified in S2202 is after the compression top dead center (TDC). If an affirmative determination is made in S2203, the ECU 20 continues the over-advanced angle with the ignition timing (reference ignition timing) It as the over-advanced point ignition timing.

  On the other hand, if a negative determination is made in S2203, the ECU 20 advances to S2204. In S2204, the ECU 20 corrects the over-advanced time point fire timing by retarding. The correction amount at that time may be a predetermined fixed value, or a variable value that is changed based on the difference between the peak timing of the in-cylinder pressure and the compression top dead center TDC (for example, as the difference increases). (Value to be increased).

  When the ECU 20 finishes executing the process of S2204, it executes the processes after S2202 again. That is, the ECU 20 repeatedly performs the retardation correction of the over-advanced ignition timing until an affirmative determination is made in S2203.

  According to the embodiment described above, it is possible to reduce the amount of unburned fuel discharged from the cylinder 2 while generating the minimum necessary torque in the internal combustion engine 1.

  In the present embodiment, an example is described in which the ignition timing at the time of overtravel is limited in consideration of only the torque generated by the internal combustion engine 1. However, the present invention is not limited to this example. Considering this, the ignition timing at the time of excessive advance may be limited.

  For example, the ECU 20 determines, based on the relationship between the magnitude of combustion fluctuation and the ignition timing as shown in FIG. 23, the earliest ignition timing (hereinafter referred to as “variation limit”) within the ignition timing range in which the combustion fluctuation is less than or equal to the allowable limit value. (Referred to as “ignition timing”). Then, the ECU 20 compares the reference ignition timing, the torque limit ignition timing, and the fluctuation limit ignition timing, and determines the latest (retard side) ignition timing as the over-advance timing ignition timing among these ignition timings. Also good.

  Further, the ECU 20 may calculate the combustion fluctuation rate from the measured value of the in-cylinder pressure sensor, and correct the over-advance point ignition timing so that the calculation result is equal to or less than a predetermined threshold value. In this case, the ECU 20 can determine the over-advance timing fire timing according to the advance amount determination routine as shown in FIG.

  In the advance amount determination routine of FIG. 24, when the ECU 20 acquires the peak timing of the in-cylinder pressure in S2202, the process proceeds to S2301. In S2301, the ECU 20 calculates the combustion fluctuation rate from the measured value of the in-cylinder pressure sensor.

  Subsequently, in S2203, the ECU 20 determines whether or not the peak timing of the in-cylinder pressure acquired in S2202 is after the compression top dead center. If an affirmative determination is made in S2203, the ECU 20 proceeds to S2302, and determines whether or not the combustion fluctuation rate calculated in S2301 is equal to or less than a threshold value.

If an affirmative determination is made in S2302, the ECU 20 continues the over-advanced angle without correcting the over-advanced angle fire timing. On the other hand, if a negative determination is made in S2203 or S2302, the ECU 20 performs the process after S2202 again after correcting the retard of the over-advanced ignition timing in S2204.

  When the over-advance point ignition timing is determined in this way, it is possible to reduce the amount of unburned fuel discharged from the cylinder 2 while suppressing combustion fluctuations and excessive torque reduction.

<Example 6>
Next, a sixth embodiment of the ignition control system for an internal combustion engine according to the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In this embodiment, an example in which the advance amount of the ignition timing is made variable according to the amount of fuel adhering to the wall surface in the cylinder 2 (attached fuel amount Dpfuel) when the ignition timing is excessively advanced is described.

  When the ignition timing is over-advanced, the peak of the heat energy generated when the air-fuel mixture burns (in other words, the peak of the heat generation rate) shifts before the compression top dead center. No. 1 torque reduction and fuel consumption deterioration occur.

  The above-described contradiction becomes more prominent as the ignition timing advance amount increases. Therefore, when the amount of adhering fuel Dpfuel is small, it is preferable to minimize torque advancement and fuel consumption deterioration by reducing the advance amount of the ignition timing.

  Therefore, in the attached fuel reduction control of the present embodiment, the ECU 20 increases the advance amount of the ignition timing as the attached fuel amount Dpfuel increases, and decreases the advance amount of the ignition timing as the attached fuel amount Dpfuel decreases. I made it.

  Hereinafter, the execution procedure of the attached fuel reduction control in the present embodiment will be described with reference to FIG. FIG. 25 is a flowchart showing an advance amount determination routine in the present embodiment. In the flowchart of FIG. 25, processing similar to that of the advance amount determination routine (see FIG. 13) of the first embodiment described above is denoted by the same reference numeral.

  In the advance amount determination routine of FIG. 25, if the ECU 20 determines in S201 that the excessive advance execution flag is set to “1”, the ECU 20 proceeds to S2401. In S2401, the ECU 20 reads the attached fuel amount Dpfuel calculated in the over-advance angle execution determination routine (see FIG. 12) of the first embodiment described above.

  In S2402, the ECU 20 determines the ignition timing It1 at the time of over-advance based on the attached fuel amount Dpfuel. At that time, the ignition timing It1 at the time of over-advance may be determined based on a map as shown in FIG. The map shown in FIG. 26 is a map that defines the amount of attached fuel that can be removed (vaporization and combustion) at each ignition timing, and is obtained experimentally in advance.

  When the ignition timing It1 at the over-advance angle is determined in this way, the advance amount of the ignition timing is suppressed to the necessary minimum, so that the reduction in torque and the deterioration of fuel consumption are suppressed to the minimum while the cylinder 2 is in the cylinder 2. It becomes possible to reduce the amount of unburned fuel discharged from the fuel.

The attached fuel reduction control of this embodiment can be combined with at least one of the attached fuel reduction controls of the second to fourth embodiments described above. For example, when the air-fuel mixture that is used for combustion in the cylinder 2 is lean, the advance angle of the ignition timing may be prohibited. Further, when the ignition timing is excessively advanced, the fuel injection timing may be set to the intake synchronous injection. Furthermore,
The ignition timing may be gradually changed when the ignition timing over-advanced angle starts and ends.

  In the adhered fuel reduction control of this embodiment, the ignition timing at the time of over-advance may be limited as described in the fifth embodiment. That is, the ignition timing at the excessive advance angle may be limited after a predetermined timing.

  For example, as shown in FIG. 27, when the adhered fuel amount Dpfuel is less than the first predetermined amount, the ignition timing is fixed to MBT, and when the adhered fuel amount Dpfuel is greater than or equal to the first predetermined amount and less than the second predetermined amount. The ignition timing may be advanced according to the attached fuel amount Dpfuel, and when the attached fuel amount Dpfuel exceeds the second predetermined amount, the ignition timing may be fixed at the predetermined time.

  The first predetermined amount may be the same as the predetermined amount described in the first embodiment, or may be an amount smaller than the predetermined amount. The second predetermined amount corresponds to the amount of attached fuel that can be removed when the ignition timing is set to the predetermined timing in the map shown in FIG.

  The predetermined timing may be one of (1) a reference ignition timing, (2) a torque limit ignition timing, and (3) a fluctuation limit ignition timing, or (1) to ( It may be the latest ignition timing among at least two ignition timings of 3).

  When the ignition timing at the over-advance angle is thus limited, the ECU 20 may determine the ignition timing at the over-advance angle according to the advance amount determination routine as shown in FIG.

  In the advance angle determination routine of FIG. 28, if the ECU 20 determines in S201 that the excessive advance execution flag is set to “1”, the ECU 20 proceeds to S2401 and reads the attached fuel amount Dpfuel.

  Subsequently, the ECU 20 proceeds to S2501, and determines whether or not the attached fuel amount Dpfuel is equal to or greater than a first predetermined amount. If a negative determination is made in S2501 (Dpfuel <first predetermined amount), the ECU 20 proceeds to S2505 and sets the ignition timing to MBT.

  On the other hand, if a positive determination is made in S2501 (Dpfuel ≧ first predetermined amount), the ECU 20 proceeds to S2502. In S2502, the ECU 20 determines whether or not the attached fuel amount Dpfuel is equal to or smaller than a second predetermined amount.

  If an affirmative determination is made in S2502 (Dpfull ≦ second predetermined amount), the ECU 20 proceeds to S2503, and determines the ignition timing based on the attached fuel amount Dpfuel and the above-described map of FIG.

  In this case, since the advance amount of the ignition timing is an advance amount corresponding to the amount of adhered fuel, it is possible to minimize a decrease in torque and a deterioration in fuel consumption.

  If a negative determination is made in S2502 (Dpfull> second predetermined amount), the ECU 20 proceeds to S2504 and fixes the ignition timing to a predetermined timing. That is, the ECU 20 selects at least one of (1) a reference ignition timing, (2) a torque limit ignition timing, and (3) a variation limit ignition timing, or (1) to (3). Of these, the latest ignition timing is set as the ignition timing at the time of overtravel.

  In this case, since excessive advance of the ignition timing is prevented, it is possible to prevent excessive decrease in torque and excessive decrease in combustion fluctuation.

<Example 7>
Next, a seventh embodiment of the ignition control system for an internal combustion engine according to the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In this embodiment, an example will be described in which the ignition timing is advanced excessively after the start of the internal combustion engine 1 is completed.

  When the ignition timing is excessively advanced, the upward movement of the piston 15 is hindered by the combustion pressure of the air-fuel mixture. Therefore, if the ignition timing is excessively advanced before the start of the internal combustion engine 1 is completed, a starter (for example, a starter) is generated by a combustion pressure (hereinafter referred to as “negative torque”) that hinders the upward movement of the piston 15. Operation of a motor, motor generator, etc.) may be hindered.

  If the operation of the starter is hindered as described above, it is difficult to start the internal combustion engine 1 quickly, and there is a possibility that the engine cannot be started.

  On the other hand, if the ignition timing is excessively advanced after the start of the internal combustion engine 1 is completed, the above-described problem can be prevented.

  The “start completion” condition here may be the occurrence of a complete explosion, but may be the occurrence of an initial explosion when the advance amount of the ignition timing is small.

  Hereinafter, the execution procedure of the attached fuel reduction control in this embodiment will be described with reference to FIG. FIG. 29 is a flowchart showing an over-advance angle execution determination routine in the present embodiment. In the flowchart of FIG. 29, processing similar to that of the above-described over-advance angle execution determination routine (see FIG. 12) of the first embodiment is denoted by the same reference numeral.

  The ECU 20 proceeds to S1201 after executing S102, and determines whether or not the internal combustion engine 1 has been started. As this determination method, a method of determining that the start of the internal combustion engine 1 is completed on condition that the engine speed Ne calculated based on the output signal of the crank position sensor 18 is equal to or higher than a predetermined speed is illustrated. Can do.

  If an affirmative determination is made in S1201, the ECU 20 executes the processes after S103. In this case, the ignition timing over-advance is performed on condition that the adhered fuel amount Dpfuel is equal to or greater than a predetermined amount.

  On the other hand, if a negative determination is made in S1201, the ECU 20 proceeds to S109 and resets the over-advance angle execution flag to “0”. In this case, the excessive advance angle of the ignition timing is prohibited regardless of the adhered fuel amount Dpfuel.

  According to the embodiment described above, the ignition timing over-advanced angle is not performed before the completion of the start-up of the internal combustion engine 1, so that the startability deterioration due to the ignition timing over-advanced angle is prevented.

  The attached fuel reduction control of the present embodiment can be combined as much as possible with the above-described attached amount reduction control of the second to sixth embodiments. In this case, it is possible to efficiently reduce the amount of unburned fuel discharged from the cylinder 2 while minimizing various contradictions due to the excessive advance angle of the ignition timing.

It is a figure showing the schematic structure of the ignition control system of the internal-combustion engine concerning the present invention. It is a figure which shows the relationship between the unburned fuel (HC) discharged | emitted from the inside of a cylinder, and ignition timing. It is a figure which shows the relationship between an ignition timing and the state in a cylinder. It is a figure which shows the relationship between the cooling water temperature at the time of engine starting, and the amount of adhesion fuel. It is a figure which shows the relationship between a cylinder pressure and the amount of adhesion fuel. It is a figure which shows the relationship between the integrated intake air amount from the time of engine starting, and the amount of adhesion fuel. It is a figure which shows the relationship between the amount of fuel injection, and the amount of adhesion fuel. It is a figure which shows the relationship between the air fuel ratio of the air-fuel | gaseous mixture supplied for combustion within a cylinder, and the amount of adhesion fuel. It is a figure which shows the relationship between cooling water temperature and the amount of advance at the time of an excessive advance. It is a figure which shows the relationship between the load factor of an internal combustion engine, and the advance amount at the time of an excessive advance angle. It is a figure which shows the relationship between an engine speed and the advance amount at the time of an excessive advance angle. 3 is a flowchart illustrating an over-advance angle execution determination routine in the first embodiment. 6 is a flowchart illustrating an advance amount determination routine in the first embodiment. It is a figure which shows the relationship between the heat release rate and crank angle when ignition timing is set to MBT. It is a figure which shows the relationship between the heat release rate and crank angle when ignition timing is advanced by 2 times of MBT. 7 is a flowchart illustrating an over-advance angle execution determination routine according to the second embodiment. It is a figure which shows the change procedure of the ignition timing at the time of the excessive advance start of ignition timing. It is a figure which shows the change procedure of the ignition timing at the time of completion | finish of the excessive advance angle of ignition timing. It is a figure which shows the other change procedure of the ignition timing at the time of the advance advance of ignition timing. It is a figure which shows the other change procedure of the ignition timing at the time of the advance advance of ignition timing. It is a figure which shows the result of having measured in-cylinder pressure when ignition timing is set so that the peak of in-cylinder pressure may become the compression top dead center vicinity. 12 is a flowchart illustrating an advance angle determination routine in the fifth embodiment. It is a figure which shows the relationship between a combustion fluctuation | variation and ignition timing. 12 is a flowchart illustrating another example of an advance amount determination routine in the fifth embodiment. 18 is a flowchart illustrating an advance angle determination routine in the sixth embodiment. It is a figure which shows the relationship between ignition timing and the amount of adhesion fuel which can be removed at each ignition timing. It is a figure which shows the relationship between the ignition timing when the restriction | limiting is added to the advance amount of ignition timing, and the amount of adhesion fuel. 18 is a flowchart illustrating another example of the advance amount determination routine in the sixth embodiment. 18 is a flowchart showing an over-advance angle execution determination routine in Embodiment 7.

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 14 ... Spark plug 15 ... Piston 16 ... Connecting rod 17 ... Crank Shaft 18 ... Crank position sensor 19 ... Water temperature sensor 20 ... ECU
30 ... Intake passage 40 ... Exhaust passage

Claims (6)

Over-advance means for advancing the ignition timing of the spark ignition internal combustion engine from MBT;
Obtaining means for obtaining an amount of fuel adhering to a wall surface in a cylinder of the internal combustion engine;
The over-advance means is operated when the amount of attached fuel acquired by the acquisition means is a predetermined amount or more, and the operation of the over-advance means is prohibited before the start of the internal combustion engine is completed. Control means;
With
Before SL control means, an internal combustion engine ignition control system, wherein a mixture combustion end timing of the cylinder determines the advance angle amount by the over-advanced means such that the vicinity of the compression top dead center. Over-advance means for advancing the ignition timing of the spark ignition internal combustion engine from MBT;
Obtaining means for obtaining an amount of fuel adhering to a wall surface in a cylinder of the internal combustion engine;
The over-advance means is operated when the amount of attached fuel acquired by the acquisition means is a predetermined amount or more, and the operation of the over-advance means is prohibited before the start of the internal combustion engine is completed. Control means;
With
Before SL control means, an internal combustion engine ignition control system, wherein the pressure in the cylinder determines the advance angle amount by the over-advanced means to indicate the maximum value in the vicinity of the compression top dead center. Over-advance means for advancing the ignition timing of the spark ignition internal combustion engine from MBT;
Obtaining means for obtaining an amount of fuel adhering to a wall surface in a cylinder of the internal combustion engine;
The advance amount by the over-advance means is changed according to the amount of attached fuel acquired by the acquisition means, and the operation of the over-advance means is prohibited before the start of the internal combustion engine is completed. Control means;
With
Before SL control means, such mixture combustion end timing of the cylinder is top dead center or later vicinity compression, internal combustion engine ignition control system, characterized in that to limit the advance angle amount by the over-advanced means . The ignition control system for an internal combustion engine according to claim 3, wherein the control means increases the advance amount by the over-advance means as the amount of attached fuel acquired by the acquisition means increases.
Stem. Over-advance means for advancing the ignition timing of the spark ignition internal combustion engine from MBT;
Obtaining means for obtaining an amount of fuel adhering to a wall surface in a cylinder of the internal combustion engine;
The advance amount by the over-advance means is changed according to the amount of attached fuel acquired by the acquisition means, and the operation of the over-advance means is prohibited before the start of the internal combustion engine is completed. Control means;
With
Before SL control means, so that the pressure in the cylinder becomes maximum at the compression top dead center after the neighborhood, an internal combustion engine ignition control system, characterized in that to limit the advance angle amount by the over-advanced means. 6. The ignition control system for an internal combustion engine according to claim 5, wherein the control means increases the advance amount by the over-advance angle means as the amount of attached fuel acquired by the acquisition means increases.

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