JP2011174381A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can reduce an emission amount of PM at restart after automatic stop even though idle stop is executed. <P>SOLUTION: In a control device applied to an internal combustion engine directly injecting fuel in a combustion chamber of each cylinder in the internal combustion engine 1 with an injector 12, purge control is executed until the internal combustion engine stops after the establishment of an automatic stop (idle stop) condition formation. At automatic start (restart), fuel amount of purge gas supplied by the purge control is reduced from a basic injection amount to calculate a final injection amount from the injector 12. Thus, an emission amount of PM at restart can be suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control apparatus applied to an internal combustion engine having an idle stop function for automatically stopping and automatically starting the internal combustion engine during idling.

  In recent years, some internal combustion engines mounted on vehicles employ an automatic stop / start device (idle stop device) for the purpose of reducing fuel consumption (for example, Patent Document 1).

JP-A-2005-299445

  However, at the time of restart after automatic stop, more fuel is injected from the injector than when stoichiometric combustion is realized in order to ensure startability. Therefore, PM (particulate matter) discharged from the internal combustion engine can be eliminated during the stop period of the internal combustion engine, but there has been a problem that PM discharged at the time of restarting temporarily increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can reduce the PM emission amount at the time of restart after an automatic stop even if an idle stop is performed.

  In order to solve the above problem, the invention according to claim 1 is a control device applied to an internal combustion engine in which fuel is directly injected into a combustion chamber of each cylinder of the internal combustion engine by an injector, and satisfies a predetermined automatic stop condition. The internal combustion engine is automatically stopped when the engine is stopped, and the automatic stop start control means for automatically starting the internal combustion engine when a predetermined automatic start condition is satisfied, and the purge gas from the canister connected to the fuel tank is supplied with air through the purge pipe. Purge control means for executing the purge control to be discharged to each cylinder of the internal combustion engine and executing the purge control after the automatic stop condition is established until the internal combustion engine is stopped, and the purge gas supplied into the combustion chamber. Purge gas residual fuel amount calculating means for determining the amount of fuel to be generated and the purge gas from the basic injection amount required for restart when the internal combustion engine is automatically started Characterized in that it comprises a injection amount calculating means for calculating the final injection amount by weight loss distillate fuel amount.

  According to the above configuration, the purge control means supplies the purge gas to each cylinder after the automatic stop condition is established and before the internal combustion engine is stopped. The purge gas residual fuel calculating means obtains the amount of fuel contained in the purge gas supplied into the combustion chamber by the purge control means. Then, the injection amount calculation means determines the final injection amount by reducing the fuel amount contained in the purge gas from the basic injection amount at the time of automatic start.

  Here, since the purge gas is in a state where the fuel is evaporated (vaporized), PM is less likely to be generated than the fuel atomized by the injector. Therefore, according to the above configuration, the purge gas in which PM is not easily generated at the time of automatic start can be used as the fuel at the start, and the amount of fuel injected from the injector can be reduced. The amount can be reduced.

  The purge gas control means calculates the in-cylinder target purge gas amount to be supplied to the combustion chamber of the internal combustion engine based on the outside air temperature when the automatic stop condition is satisfied and the cooling water temperature when the automatic stop condition is satisfied. It is characterized by.

  The state of the fuel contained in the purge gas changes depending on the ambient temperature. For example, when the ambient temperature is low, a part of the fuel contained in the purge gas is liquefied and becomes liquid, and when the ambient temperature is high, a part of the fuel contained in the purge gas is vaporized and becomes gas. Therefore, the purge gas state can be estimated by using the parameters of the outside air temperature and the cooling water temperature, and the in-cylinder target purge gas amount to be supplied into the combustion chamber can be set appropriately.

  The invention according to claim 3 is characterized in that the purge gas control means increases the in-cylinder target purge gas amount as the outside air temperature when the automatic stop condition is satisfied and the cooling water temperature when the automatic stop condition is satisfied.

  As described above, when the ambient temperature is low, that is, when the outside air temperature or the cooling water temperature decreases, a part of the fuel contained in the purge gas gradually liquefies. When purge control is performed at such a low temperature, a part of the fuel in the purge gas is liquefied, so that it adheres to the inner wall of the intake pipe, or the purge gas comes into contact with the low-temperature intake pipe so that the amount of fuel contained in the purge gas is reduced. Liquefaction is promoted. Therefore, the amount of purge gas that reaches the combustion chamber is reduced, and it is not possible to supply an appropriate purge gas to the in-cylinder target purge gas amount. On the other hand, in the invention of claim 3, the in-cylinder target purge gas amount is increased as the outside air temperature and the cooling water temperature are lowered. That is, the in-cylinder target purge gas amount is determined in consideration of the decrease amount of the purge gas amount that reaches the combustion chamber. For this reason, even if the outside air temperature and the cooling water temperature are lowered, an appropriate purge gas can be supplied.

  According to a fourth aspect of the present invention, the purge gas residual fuel amount calculation means calculates the purge gas residual fuel amount of the cylinder stopped in the compression stroke of the internal combustion engine (hereinafter referred to as “compression stroke stop cylinder”) as the in-cylinder target purge gas amount. It is characterized in that it is estimated from the cooling water temperature at the time of automatic stop and the cooling water temperature at the time when the automatic start condition is established.

  The purge gas supplied into the combustion chamber before the internal combustion engine is stopped is also affected by the temperature in the combustion chamber. Specifically, the temperature in the combustion chamber gradually decreases between automatic stop and restart. As the temperature decreases, the fuel contained in the purge gas gradually liquefies, and the purge gas contributing to combustion decreases. As a result, an accurate purge gas residual fuel amount that contributes to combustion cannot be calculated.

  On the other hand, in the invention of claim 4, the purge gas that decreases due to the temperature change in the combustion chamber is estimated using the coolant temperature at the time of automatic stop and the coolant temperature at the time when the automatic start condition is satisfied. Then, by subtracting this decrease amount from the in-cylinder target purge gas amount, the purge gas residual fuel amount in the compression stroke stopped cylinder is estimated. As a result, an accurate purge gas residual fuel amount that contributes to combustion can be estimated.

  According to a fifth aspect of the present invention, the purge gas residual fuel amount calculating means calculates the residual purge gas amount of a cylinder stopped in the intake stroke of the internal combustion engine (hereinafter referred to as “intake stroke stop cylinder”) as the in-cylinder target purge gas amount. It is characterized in that it is estimated from the cooling water temperature at the time of automatic stop, the cooling water temperature at the time when the automatic start condition is established, and the stop time.

  In order to estimate the remaining amount of purge gas in the intake stroke stopped cylinder, the stop time is used in addition to the coolant temperature at the time of automatic stop and the coolant temperature at the time when the automatic start condition is satisfied. The use of the cooling water temperature at the time of automatic stop and automatic start condition as a parameter corresponds to the liquefaction of the purge gas in the combustion chamber described above. The reason for using the stop time as a parameter is as follows. In the intake stroke stop cylinder, the intake valve is stopped in an open state. That is, since the combustion chamber is not closed, the purge gas supplied until the internal combustion engine is stopped moves to the intake pipe side through the intake valve. Correspondingly, the movement amount of the purge gas through the intake valve is estimated using the stop time as a parameter. Thereby, the amount of fuel remaining in the purge gas in the intake stroke stopped cylinder can be estimated by reducing the amount of movement due to the liquefaction accompanying the temperature drop and the stop time from the in-cylinder target purge gas amount. As a result, it is possible to estimate the purge gas residual fuel amount in the intake stroke stopped cylinder.

  The invention described in claim 6 is characterized in that the purge gas control means does not execute the purge control when the cooling water temperature is equal to or higher than a predetermined value even when the automatic stop condition is satisfied.

  According to the above configuration, the purge control is prevented from being executed when the cooling water temperature is equal to or higher than the predetermined value, that is, the temperature in the combustion chamber is high. As a result, it is possible to prevent a phenomenon (pre-ignition) in which the purge gas is supplied and spontaneous ignition occurs in a state where the temperature in the combustion chamber is high.

  According to a seventh aspect of the present invention, there is provided an internal combustion engine in which fuel is directly injected into a combustion chamber of each cylinder of the internal combustion engine by an injector, a canister connected to the fuel tank and storing purge gas generated in the fuel tank, and an internal combustion engine A purge pipe for supplying purge gas together with air to the connected intake pipe, a purge control valve arranged between the canister and the intake pipe for adjusting the supply amount of the purge gas, and each cylinder of the internal combustion engine from the intake pipe An intake valve for taking air and purge gas into the combustion chamber and a control device for controlling the internal combustion engine and the purge control valve are provided, and the control device automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied. An automatic stop / start control means for controlling the internal combustion engine to automatically start when a predetermined automatic start condition is satisfied, and a cartridge connected to the fuel tank. Purge control means for performing purge control for discharging purge gas from the star together with air to the intake pipe of the internal combustion engine through the purge pipe, and for performing purge control after the automatic stop condition is established until the internal combustion engine is stopped; A purge gas residual fuel amount calculating means for determining the amount of fuel contained in the purge gas supplied into the combustion chamber, and at the time of automatic start of the internal combustion engine, the final injection amount is reduced by reducing the purge gas residual fuel amount from the basic injection amount upon restart And a purge pipe is provided with a purge gas introduction port for introducing purge gas into each cylinder.

  According to the above configuration, the purge gas inlet for introducing the purge gas is formed in each cylinder. Therefore, when purge control is performed, the purge gas can be released from a position close to the intake valve, and the purge gas can be reliably introduced into the combustion chamber after the automatic stop condition is established until the internal combustion engine is stopped. . In addition, the purge gas can be prevented from remaining in the intake pipe.

Schematic configuration diagram of the entire engine control system The flowchart which shows the control procedure at the time of the automatic stop performed with ECU Flow chart showing control procedure at the time of automatic start performed by ECU It is a time chart which shows the transition state of various controls corresponding to the processing of FIG.2 and FIG.3. The figure which shows the PM reduction effect by this invention

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of the entire engine control system. As shown in FIG. 1, an air cleaner 3 is provided at the most upstream portion of an intake pipe 2 of an engine 1 that is a cylinder injection type internal combustion engine. A throttle valve 5 whose opening degree is adjusted by a DC motor 4 is provided on the downstream side of the air cleaner 3. The DC motor 4 is driven based on an output signal from an engine control device 6 (hereinafter referred to as “ECU”), whereby the opening degree (throttle opening degree) of the throttle valve 5 is controlled, and the throttle opening degree is determined according to the throttle opening degree. Thus, the intake air amount to each cylinder is adjusted. A throttle sensor 7 for detecting the throttle opening is provided in the vicinity of the throttle valve 5.

  A surge tank 8 is provided on the downstream side of the throttle valve 5, and an intake manifold 9 for introducing air into each cylinder of the engine 1 is connected to the surge tank 8. An intake port 10 is formed in the intake manifold 9 of each cylinder, and the intake port 10 is connected to an intake valve 11 formed in each cylinder of the engine 1.

  An injector 12 for directly injecting fuel into the combustion chamber of each cylinder is attached to the upper part of each cylinder of the engine 1. In order to inject fuel directly into the combustion chamber, the pressure of the fuel needs to be higher than the pressure in the combustion chamber. Therefore, the fuel sucked up by the fuel pump 14 disposed in the fuel tank 13 is pressurized by the high-pressure pump 15 a provided in the fuel pipe 15 and is pumped to the delivery pipe 16. The pressurized high pressure fuel (for example, a predetermined pressure in the range of 2 to 10 MPa) is distributed to the injectors 12 of the respective cylinders by the delivery pipe 16. High-pressure fuel is injected from the injector 12 into the combustion chamber and mixed with intake air supplied from the intake port 10 to form an air-fuel mixture.

  The air-fuel mixture in the combustion chamber is ignited by a spark plug (not shown) attached to the cylinder head of the engine 1. The spark plug is attached to each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug.

  Exhaust gas discharged from the engine exhaust valve 17 merges into one exhaust pipe 19 via the exhaust manifold 18. The exhaust pipe 19 is connected to a three-way catalyst 20 that purifies exhaust gas near the stoichiometric air-fuel ratio. In addition, oxygen sensors 21 and 22 are provided before and after the three-way catalyst 20 to detect the oxygen concentration of the exhaust gas and output it to the ECU 6. The ECU 6 adjusts the fuel injection amount of the injector 12 so that combustion is performed at an optimal air-fuel ratio based on this oxygen concentration.

  The fuel tank 13 is connected to a canister 23 that adsorbs evaporated fuel (also referred to as evaporation). The evaporative fuel is the fuel in the fuel tank 13 that is vaporized by stirring the fuel due to temperature changes in the fuel tank 13 or vibration during traveling. The evaporated fuel adsorbed in the canister 23 is discharged to the intake side of the engine 1 together with air as a purge gas. Specifically, the air is guided to the intake side of the engine 1 by a purge pipe 24 that connects the canister 23 and the intake manifold 9. A purge control valve 25 is disposed between the intake side of the engine 1 and the canister 23. The purge control valve 25 is opened and closed by an output signal from the ECU 6 to adjust the supply amount of purge gas.

  The purge pipe 24 is provided with a purge gas inlet 26 for introducing purge gas into the intake port 10 of each cylinder on the intake pipe side of the purge control valve 25. Specifically, the purge pipe 24 is branched and connected to the intake manifold 9 branched for each cylinder, and a purge gas inlet 26 is provided so that purge gas is discharged toward the intake port 10 side.

  Here, various sensors other than the throttle sensor 7 and the oxygen sensors 21 and 22 described above will be described. The cylinder discrimination sensor 27 generates an output pulse when a specific cylinder reaches top dead center, and the ECU 6 performs cylinder discrimination. The crank angle sensor 28 generates an output pulse every time a crankshaft (not shown) of the engine 1 rotates by a certain crank angle (for example, 30 ° C. A). The crank angle and the engine speed are detected by this output pulse. The water temperature sensor 29 and the outside air temperature sensor 30 detect the cooling water temperature and the outside air temperature of the engine 1, respectively, and output them to the ECU 6. The coolant temperature is used as a parameter representing the temperature of the engine 1.

  Output signals from the various sensors described above are input to the ECU 6. The ECU 6 is mainly composed of a microcomputer, and based on various sensor outputs in accordance with a control program and a control map stored in a built-in ROM (storage medium), the above-described DC motor 4, injector 12, spark plug, purge control The valve 25 is controlled.

  Here, the automatic stop / starting means provided in the ECU 6 will be described. The automatic stop / start means means that when the engine 1 satisfies a predetermined automatic stop condition during idle operation, the fuel injection from the injector 12 and ignition of the spark plug are stopped, and the engine 1 is automatically stopped. When a predetermined automatic start condition (hereinafter referred to as “restart condition”) is satisfied during automatic stop, automatic start (hereinafter referred to as “restart”) is performed.

  Further, the ECU 6 issues a purge control that outputs a drive signal to the purge control valve 25 based on the outputs from the oxygen sensors 21 and 22 and releases the purge gas from the canister 23 together with air to the intake side of the engine 1 through the purge pipe 24. Purge control means is provided.

  Below, the control which ECU6 performs is demonstrated based on FIGS.

  First, the control performed by the ECU 6 during automatic stop will be described with reference to FIG. First, in step 100, it is determined whether an automatic stop condition is satisfied. Here, the automatic stop condition is that the brake switch is “ON”, the vehicle speed is “0 (zero) [km / h]”, and the three-way catalyst 20 is in an active state by depressing the brake pedal.

  When the automatic stop condition is satisfied at step 100, the fuel injection is stopped and the spark plug is stopped, and the routine proceeds to step 101. In step 101, it is determined whether a purge gas introduction condition is satisfied. The purge gas introduction conditions are that the purge control valve 25 is not broken, that it is after learning the purge gas concentration (hereinafter referred to as “PGden”), and that the cooling water temperature is a predetermined value (for example, 90 ° C.) or less. .

  PGden changes the purge rate so that the air-fuel ratio detected by the oxygen sensors 21 and 22 is in a predetermined region, and changes the purge rate before and after the purge rate and the change amount of the air-fuel ratio. Detected. Here, the purge rate is a ratio of the fuel amount contained in the purge gas out of the fuel amount obtained by adding the fuel amount injected from the injector 12 and the fuel amount contained in the purge gas. The purge gas concentration learning is a state in which PGden is detected during traveling and the value is stored in the ECU 6.

  When the cooling water temperature is equal to or higher than a predetermined value, the purge control is not executed because the temperature in the combustion chamber is high. The reason is that when the purge control is performed in a state where the temperature in the combustion chamber is high, there is a possibility that preignition in which the purge gas supplied in the combustion chamber spontaneously ignites may occur.

  If the purge gas introduction condition is not satisfied in step 101, the purge gas is not supplied for the reason described above, and the routine proceeds to step 105, where the engine 1 is stopped, that is, waits until the engine speed becomes 0 (zero). End the routine.

  On the other hand, when the purge gas introduction condition is satisfied, the routine proceeds to step 102 where the in-cylinder target purge gas amount (hereinafter referred to as “PGtrgm”) supplied into the combustion chamber is calculated. PGtrgm is obtained from a map stored in the ROM of the ECU 6 based on the outside air temperature detected by the outside air temperature sensor 30 and the cooling water temperature detected by the water temperature sensor 29.

  At this time, when the outside air temperature and the cooling water temperature are low, a part of the purge gas supplied from the canister 23 is liquefied, so that it adheres to the wall surface in the intake manifold 9 or the purge gas contacts the low temperature intake pipe. As a result, the liquefaction of the fuel contained in the purge gas is promoted. Therefore, the purge gas that reaches the combustion chamber of each cylinder decreases. On the other hand, a map is stored that is set such that the in-cylinder target purge gas amount increases as the outside air temperature and the cooling water temperature decrease.

  Next, the process proceeds to step 103, and a purge DUTY for controlling the opening degree and the valve opening time of the purge control valve 25 is calculated based on the PGtrgm calculated in step 102.

  Then, the purge control valve 25 is energized based on the purge DUTY calculated in step 104, and purge gas is supplied into the combustion chamber. When the purge gas is supplied, the routine proceeds to step 105, and when it is detected that the engine 1 has stopped, the purge control at the time of automatic stop is terminated. Here, the engine stop means that the engine speed becomes 0 (zero).

  Next, a control procedure at the time of automatic start performed by the ECU 6 will be described with reference to FIG.

  First, in step 200, it is determined whether a restart condition is satisfied. When the restart condition is satisfied, the routine proceeds to step 201, where the basic injection amount required for restart is calculated. Here, the basic injection amount is the amount of fuel required when purge gas is not supplied into the combustion chamber, that is, when the purge gas is zero. The basic injection amount includes a basic injection amount (hereinafter referred to as “Q1 cmp”) for a compression stroke stop cylinder stopped in the compression stroke of the engine 1 and a basic injection amount (hereinafter referred to as “Q1int” for an intake stroke stop cylinder stopped in the intake stroke. Are calculated separately. The basic injection amount is calculated from a control map stored in the ROM of the ECU 6 based on the coolant temperature when the restart condition is established.

  After calculating the basic injection amount, in step 202, it is determined whether or not purge gas is introduced before the engine is stopped. If the purge gas has been introduced before the engine is stopped, the process proceeds to step 203 to estimate the amount of fuel contained in the purge gas supplied to the compression stroke stopped cylinder and the remaining amount of purge gas (hereinafter referred to as “Qcmp”). To do. Since combustion is not performed when the engine 1 is stopped, the temperature in the combustion chamber gradually decreases. The purge gas supplied into the combustion chamber is liquefied due to a decrease in temperature, and the purge gas contributing to combustion is reduced. Thereby, PGtrgm supplied before the automatic stop decreases as the temperature in the combustion chamber decreases. Qcmp is calculated using a water temperature correction term in which the influence of the temperature change in the combustion chamber is estimated from the cooling water temperature at the time of automatic stop and the cooling water temperature when the restart condition is satisfied. The water temperature correction term is obtained by the ratio of the cooling water temperature at the time of automatic stop and the cooling water temperature at the time when the restart condition is satisfied. Further, the water temperature correction term can be obtained not by the ratio but also by storing a map of the cooling water temperature at the time of automatic stop and the cooling water temperature at the time when the restart condition is satisfied in the ECU 6.

  Next, the routine proceeds to step 204 where the amount of fuel contained in the purge gas supplied to the intake stroke stopped cylinder and the amount of residual purge gas (hereinafter referred to as “Qint”) are calculated. Qint must consider the influence of the engine stop time in addition to the temperature change in the combustion chamber described above. The reason is that, in the intake stroke stop cylinder, unlike the compression stroke cylinder, since the intake valve is stopped in an open state, the purge gas supplied to the combustion chamber moves to the intake pipe side through the intake valve. It is. For this reason, the movement amount of the purge gas is estimated by the stop time correction term estimated from the stop time and the water temperature at the time of automatic stop, and Qint is calculated.

  On the other hand, when the purge gas is not supplied before the engine is stopped, the routine proceeds to step 205 where Qcmp = 0 and Qint = 0.

  Then, after each purge residual fuel amount is calculated in step 203 and step 204 or step 205, the process proceeds to step 206, and the final injection amount (hereinafter referred to as “Qcmpfin”) of the compression stroke stopped cylinder is calculated. . Qcmpfin is obtained by reducing (subtracting in this embodiment) the Qcmp calculated in step 203 from Q1cmp calculated in step 201. Next, the routine proceeds to step 207, where the final injection amount (hereinafter referred to as “Qintfin”) of the intake stroke stopped cylinder is calculated. Qintfin is obtained by reducing (subtracting in this embodiment) the Qint calculated in step 204 from Q1int calculated in step 201. In step 208, Qcmpfin and Qintfin are injected from the injector 12 into each cylinder, and the engine 1 is started through ignition by a spark plug. This routine is completed.

  Next, transition states of various controls corresponding to the control procedure at the time of automatic stop and automatic start / start described above will be described with reference to FIG.

  In FIG. 4, (a) shows the fuel cut, (b) shows the purge DUTY, and (c) shows the engine speed.

  In the initial state (t0), (a) fuel cut “OFF”, (b) purge DUTY “OFF”, and (c) engine speed is low. 2 is established (t1), the fuel cut is “ON”, the fuel injection from the injector 12 is stopped, and the engine speed starts to gradually decrease. When the purge gas introduction condition is satisfied in step 101, the processing of step 102 to step 104 described above is executed, and the purge DUTY is turned “ON”. Then, the supply of purge gas is started, and PGtrgm is supplied to each cylinder until the engine speed reaches 0 (zero) (t1 to t2). When the engine speed becomes 0 (zero) (t2), the engine 1 is stopped and the purge DUTY is turned “OFF”, and the purge control is stopped.

  The engine is stopped until the engine restart condition of step 200 in FIG. 3 is satisfied (t3). Here, the period from t2 to t3 when the restart condition is satisfied after this automatic stop (engine speed is 0) is referred to as a stop time. Then, when the restart condition is satisfied, the control of Step 201 to Step 207 described above is executed, and the final injection amount is calculated. Then, the fuel cut is “OFF”, the fuel is supplied, and the engine 1 is started.

  Next, the effect of this embodiment is demonstrated.

  Since the purge gas is in a state where the fuel is vaporized, it is easier to burn than the fuel atomized by the injector 12. That is, if the amount of fuel injected from the injector 12 is large, incomplete combustion occurs, so PM contained in the exhaust gas increases.

  Further, it is known that PM is generated by combustion of hydrocarbons contained in gasoline. Hydrocarbons are classified as aromatic hydrocarbons according to their bonding structure. Among the aromatic hydrocarbons, it has been confirmed by experiments by the inventors that those having a structure called polycyclic aromatic hydrocarbon (for example, naphthalene, anthracene, etc.) cause the generation of PM.

  And many polycyclic aromatic hydrocarbons are contained when gasoline is a liquid. On the other hand, even if it is the same gasoline, the amount of polycyclic aromatic hydrocarbons contained in the purge gas evaporated in the fuel tank 13 is extremely small compared to the case where it is liquid. That is, a large amount of polycyclic aromatic hydrocarbons is contained in gasoline (liquid) injected from the injector 12, and a very small amount is contained in the purge gas.

  Therefore, according to the above configuration, the amount of fuel injected from the injector can be reduced by the purge gas supplied by the purge control. That is, since the amount of fuel injected from the injector 12 that is less flammable than the purge gas and contains a large amount of polycyclic aromatic hydrocarbons and causes PM generation can be reduced, the PM emission amount can be reduced. As shown in FIG. 5, it can be seen that the PM discharged increases as the purge rate increases, that is, the amount of fuel by the purge gas increases and the amount of fuel injected from the injector 12 decreases.

  In the present embodiment, based on this idea, the purge gas is positively used as the fuel at the time of restart, thereby reducing the amount of liquid fuel (injected fuel amount of the injector 12) that causes PM generation. ing. As a result, the amount of PM contained in the exhaust gas can be reduced.

  In addition, parameters such as the outside air temperature and the cooling water temperature are used for setting PGtrgm in step 102. The state of the fuel contained in the purge gas changes depending on the ambient temperature. As described above, when the outside air temperature or the cooling water temperature is low, a part of the fuel contained in the purge gas is liquefied, so that the supply amount of the purge gas through the purge pipe 24 changes or the amount of the purge gas contributing to combustion is reduced. Or drop. Therefore, by using the parameters of the outside air temperature and the cooling water temperature, the influence on the purge gas due to the temperature change can be estimated, and an appropriate in-cylinder target purge gas amount can be set.

  Further, the in-cylinder target purge gas amount is increased as the outside air temperature and the cooling water temperature decrease. That is, the in-cylinder target purge gas amount is set in consideration of the purge gas amount that decreases as the ambient temperature decreases (the outside air temperature and the cooling water temperature decrease). For this reason, even if the outside air temperature and the cooling water temperature are lowered, an appropriate purge gas can be supplied.

  In step 203, Qcmp is estimated from PGtrgm, the cooling water temperature at the time of automatic stop, and the cooling water temperature when the restart condition is satisfied. Specifically, Qcmp is estimated by correcting PGtrgm using a water temperature correction term calculated from the cooling water temperature at the time of automatic stop and the cooling water temperature at the time when the automatic start condition is satisfied.

  As described above, the temperature in the combustion chamber gradually decreases between automatic stop and restart. Due to this temperature decrease, a part of the fuel contained in the purge gas is gradually liquefied, and the purge gas contributing to combustion is reduced. A decrease amount of the purge gas due to the temperature change in the combustion chamber is estimated by a water temperature correction term, and is reduced from the in-cylinder target purge gas amount. As a result, it is possible to estimate an accurate purge gas residual fuel amount that contributes to combustion.

  Further, Qint is estimated from PGtrgm, the cooling water temperature at the time of automatic stop, the cooling water temperature when the restart condition is satisfied, and the stop time. Specifically, Qint is estimated by correcting PGtrgm using a water temperature correction term calculated from the cooling water temperature at the time of automatic stop and the cooling water temperature when the restart condition is satisfied, and the stop time correction term. .

  As described above, the cooling water temperature at the time of automatic stop and when the automatic start condition is satisfied corresponds to the liquefaction of the purge gas in the combustion chamber. The stop time parameter is used in the intake stroke stop cylinder in which the intake valve 11 is open and stopped. That is, since the combustion chamber is not closed, the purge gas supplied until the internal combustion engine is stopped moves to the intake pipe side through the intake valve 11. Correspondingly, since the stop time is used as a parameter, the remaining amount of purge gas in the intake stroke stopped cylinder can be appropriately estimated.

  Further, the purge gas control means does not execute the purge control when the cooling water temperature is equal to or higher than the predetermined value even when the automatic stop condition is satisfied. The purge control is prevented from being executed when the cooling water temperature is equal to or higher than a predetermined value, that is, the temperature in the combustion chamber is high. Thereby, it is possible to prevent a phenomenon (pre-ignition) in which the purge gas is supplied and spontaneously ignites when the temperature in the combustion chamber is high.

  The purge pipe 24 is provided with a purge gas inlet 26 for introducing purge gas into each cylinder on the intake side of the purge control valve 25.

  As a known configuration, there is a configuration in which a purge pipe is connected to a surge tank which is a collecting portion of air to be sucked and a purge inlet is provided only at one place. In such a configuration, since the distance from the purge gas inlet to the intake valve is long, the supplied purge gas remains in the surge tank or the intake pipe, or the target amount is shortly after the automatic stop condition is established until the engine stops. The purge gas cannot be supplied.

  On the other hand, according to the above configuration, the purge gas can be supplied from a position close to the intake valve 11, so that the purge gas remains in the intake pipe 2 and the surge tank 8 and is supplied in a short time. be able to.

  As described above, according to the present embodiment, it is possible to provide a control device for an internal combustion engine that can reduce the PM emission amount at the restart after the automatic stop even if the idle stop is performed.

[Other Embodiments]
In the first embodiment, PGtrgm, Q1 cmp, Q1 int, Qcmp, and Qint are estimated using the temperature of the cooling water as a parameter indicating the temperature of the engine 1 and the temperature in the combustion chamber. Even if the combustion temperature, the exhaust temperature, or the like is used, the same effects as those of the above-described embodiment can be obtained.

  In the first embodiment, when the engine speed is 0 (zero), the purge control is executed from when the automatic stop condition is satisfied until the engine is stopped, but the engine speed becomes 0. The purge control may be executed before and after, that is, from a low rotation or 0 rotation to a predetermined time.

  In the first embodiment, the opening degree of the purge control valve 25 is “ON” and “OFF”, that is, fully opened and fully closed, but the opening degree of the purge control valve 25 is adjusted (0 to 100%). It may be configured.

1 engine (internal combustion engine)
6 ECU
DESCRIPTION OF SYMBOLS 11 Intake valve 12 Injector 13 Fuel tank 23 Canister 24 Purge piping 25 Purge control valve 29 Water temperature sensor 30 Outside temperature sensor

Claims (7)

In a control device applied to an internal combustion engine in which fuel is directly injected into a combustion chamber of each cylinder of the internal combustion engine by an injector,
Automatic stop start control means for automatically stopping the internal combustion engine when a predetermined automatic stop condition is satisfied, and automatically starting the internal combustion engine when a predetermined automatic start condition is satisfied;
Purge control is performed to release purge gas from the canister connected to the fuel tank together with air to each cylinder of the internal combustion engine via a purge pipe, and the purge control is stopped after the automatic stop condition is satisfied. Purge control means to be executed between
A purge gas residual fuel amount calculating means for obtaining a fuel amount contained in the purge gas supplied into the combustion chamber;
And an injection amount calculating means for calculating a final injection amount by subtracting the purge gas residual fuel amount from a basic injection amount required for restart at the time of the automatic start of the internal combustion engine. apparatus.   The purge gas control means calculates an in-cylinder target purge gas amount to be supplied to a combustion chamber of the internal combustion engine based on an outside air temperature when the automatic stop condition is satisfied and a cooling water temperature when the automatic stop condition is satisfied. Item 2. A control device for an internal combustion engine according to Item 1.   3. The control device for an internal combustion engine according to claim 2, wherein the purge gas control means increases the in-cylinder target purge gas amount as the outside air temperature and the cooling water temperature when the automatic stop condition is satisfied are lowered.   The purge gas residual fuel amount calculation means calculates the purge gas residual fuel amount of a cylinder stopped in the compression stroke of the internal combustion engine (hereinafter referred to as “compression stroke stop cylinder”), the in-cylinder target purge gas amount, and the automatic stop time. The control apparatus for an internal combustion engine according to claim 2 or 3, wherein the temperature is estimated from a cooling water temperature of the engine and a cooling water temperature when the automatic start condition is satisfied.   The purge gas residual fuel amount calculation means calculates the purge gas residual fuel amount of a cylinder stopped in the intake stroke of the internal combustion engine (hereinafter referred to as “intake stroke stop cylinder”), the in-cylinder target purge gas amount, and the automatic stop time. The control apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the controller is estimated from a cooling water temperature, a cooling water temperature when the automatic start condition is established, and a stop time.   The purge gas control means does not execute the purge control when the cooling water temperature is equal to or higher than a predetermined value even when the automatic stop condition is satisfied. A control apparatus for an internal combustion engine according to claim 1. An internal combustion engine in which fuel is directly injected into the combustion chamber of each cylinder of the internal combustion engine by an injector;
A canister connected to a fuel tank and storing purge gas generated in the fuel tank;
A purge pipe for supplying purge gas together with air to an intake pipe connected to the internal combustion engine;
A purge control valve disposed between the canister and the intake pipe to adjust the supply amount of the purge gas;
An intake valve for taking air and the purge gas into the combustion chamber of each cylinder of the internal combustion engine from the intake pipe;
A control device for controlling the internal combustion engine and the purge control valve;
The control device automatically stops and starts the internal combustion engine when a predetermined automatic stop condition is satisfied, and automatically stops and starts the internal combustion engine when the predetermined automatic start condition is satisfied. When,
The purge control is performed to release the purge gas from the canister connected to the fuel tank together with air to the intake pipe of the internal combustion engine through the purge pipe, and the purge control is performed after the automatic stop condition is established. Purge control means executed until the internal combustion engine stops;
A purge gas residual fuel amount calculating means for obtaining an amount of fuel contained in the purge gas supplied into the combustion chamber;
An injection amount calculating means for calculating a final injection amount by reducing the purge gas residual fuel amount from a basic injection amount during restart at the time of the automatic start of the internal combustion engine;
The control system for an internal combustion engine, wherein the purge pipe is provided with a purge gas inlet for introducing the purge gas into each cylinder.

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