JP2009299588A - Control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control system for an internal combustion engine by which, under accumulation control, gas pressure in an exhaust passage can be increased in order to increase in a short time the gas pressure in an accumulator tank for storing gas supplied to a turbine for assisting the supercharge. <P>SOLUTION: The internal combustion engine 10 provided with a supercharger 35 includes an accumulator tank 51 for accommodating the gas in the exhaust passage by introducing the gas therein. The control system, under the accumulator control, injects main combustion fuel from a fuel injection valve 22 so as to generate main combustion for the engine 10 to generate torque in a combustion chamber 21. Furthermore, under the accumulator control in the control system, the main-combustion fuel is injected, then fuel for secondary combustion is injected from the injection valve 22. Thus, secondary combustion following the main combustion is generated in the combustion chamber 21 to increase the pressure of the gas in the exhaust passage. As a result, the pressure of the gas in the accumulator tank 51 is rapidly increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine including a supercharger and supercharging assisting means for assisting rotation of the supercharger using gas in an exhaust passage.

  It is known to mount a turbocharger on an internal combustion engine for the purpose of improving the output of the internal combustion engine. The supercharger is formed by a turbine that is provided in the exhaust passage and is rotated by using a gas flow in the exhaust passage, and a compressor that rotates integrally with the turbine. The supercharger compresses the intake air by rotating the compressor and increases the amount of intake air (that is, performs supercharging).

Further, one of the conventional techniques includes a pressure accumulating tank that stores air discharged from the engine during the deceleration fuel cut operation. In this technique, for example, during acceleration operation, the air in the pressure accumulation tank is supplied to the upstream side of the turbine in addition to the exhaust gas. As a result, it is possible to shorten the time (so-called turbo lag) until the compressor speed reaches the “predetermined speed required for supercharging” after starting acceleration (see, for example, Patent Document 1). That is, the responsiveness of the supercharger can be improved.
Japanese Patent Laid-Open No. 2008-2276

  By the way, it is also conceivable that the exhaust gas of the engine is stored (that is, accumulated) in the accumulator tank (accumulator) other than during fuel cut so that the pressure in the accumulator tank is increased more quickly. However, pressure accumulation in the pressure accumulator tank must be performed during medium to low load operation where the engine operation state does not require supercharging (for example, during steady running or during deceleration operation other than during deceleration fuel cut operation). Absent. Therefore, since the gas pressure in the exhaust passage during pressure accumulation is relatively small, it is difficult to perform efficient pressure accumulation. For this reason, for example, if the acceleration operation that requires supercharging and the steady operation that does not require supercharging are alternately repeated within a short time, the pressure of the gas in the pressure accumulation tank does not become sufficiently large, The problem arises that the turbo lag cannot be shortened.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can perform efficient pressure accumulation by increasing the pressure of gas in an exhaust passage introduced into the pressure accumulation section.

  In order to achieve the above object, a control apparatus for an internal combustion engine according to the present invention includes a supercharger and supercharging assisting means.

  The turbocharger is disposed in an exhaust pipe that forms an exhaust passage that communicates with a combustion chamber of an internal combustion engine, and in an intake pipe that forms an intake passage that communicates with the combustion chamber. And a compressor that rotates with rotation.

  The supercharging assisting unit includes a pressure accumulating unit that accommodates the gas in a high pressure state by introducing the gas in the exhaust passage when a predetermined pressure accumulating condition is satisfied. Furthermore, the supercharging assistance means supplies the high-pressure gas accommodated in the pressure accumulating section to the turbine “to assist the rotation of the turbine” when a predetermined supercharging assistance condition is satisfied. Thereby, a turbo lag can be shortened and the responsiveness of a supercharger can be improved.

  Here, the predetermined pressure accumulation condition is established when it is not necessary to supply the gas in the pressure accumulation section to the turbine. That is, the pressure accumulation condition is satisfied, for example, during medium to low load operation. During medium to low load operation, the gas pressure in the exhaust passage during pressure accumulation is relatively small. Therefore, it is difficult to efficiently store the pressure in the pressure accumulating unit.

Therefore, the control device of the present invention further includes main combustion fuel injection means and sub-combustion fuel injection means.
The main combustion fuel injection means injects fuel for main combustion so that main combustion for generating torque by the engine can occur in the combustion chamber.
The sub-combustion fuel injection means is a combustion for increasing the pressure of the gas in the exhaust passage introduced into the pressure accumulator when the pressure accumulation condition is satisfied, and is a sub-combustion different from the main combustion. The sub-combustion fuel is injected so that combustion can occur in at least one of the combustion chamber and the exhaust passage.

  Thereby, when the pressure accumulation condition is satisfied, sub-combustion occurs, and therefore the pressure of the gas (the number of gas molecules and the gas temperature) in the exhaust passage introduced into the pressure accumulation section increases. Therefore, the pressure accumulation in the pressure accumulating section can be completed in a short time (the gas pressure in the pressure accumulating section is increased to a predetermined gas pressure). As a result, for example, even in a situation where acceleration operations frequently occur within a short time, the turbo lag can be shortened, so that a sense of acceleration according to the driver's request can be brought about.

In this case, the main combustion fuel injection means is
When the pressure accumulation condition is satisfied, the amount of the main combustion fuel is controlled so that the air-fuel ratio of the air-fuel mixture supplied to the main combustion matches the first air-fuel ratio that is an air-fuel ratio larger than the stoichiometric air-fuel ratio. Configured to determine,
It is preferable that the sub-combustion fuel injection means is configured to form an air-fuel mixture used for the sub-combustion using excess oxygen contained in the air-fuel mixture supplied for the main combustion.

  According to this, the air-fuel ratio of the air-fuel mixture provided for main combustion becomes a larger air-fuel ratio (first air-fuel ratio, lean air-fuel ratio) than the stoichiometric air-fuel ratio. Therefore, since the air-fuel mixture provided for main combustion contains excess oxygen, the excess oxygen remains even after the end of main combustion. The secondary combustion is performed using oxygen remaining after the main combustion. Thereby, oxygen used for subcombustion can be supplied without separately providing an oxygen supply source using subcombustion.

In this case, the control device for the internal combustion engine includes:
Intake air amount acquisition means for acquiring an intake air amount that is an amount of air supplied to the combustion chamber;
Requested torque parameter acquisition means for acquiring a required torque parameter representing a required torque required for the engine;
An intake air amount control means for controlling the intake air amount;
With
The main combustion fuel injection means is
The main combustion fuel based on the acquired intake air amount and the first air-fuel ratio so that the air-fuel mixture provided for the main combustion matches the first air-fuel ratio when the pressure accumulation condition is satisfied The amount of intake air acquired so as to make the air-fuel mixture provided for main combustion coincide with a second air-fuel ratio smaller than the first air-fuel ratio when the pressure accumulation condition is not satisfied. And controlling (determining) the amount of the main combustion fuel based on the second air-fuel ratio,
The intake air amount control means includes:
Whether or not the required torque and the pressure accumulation condition are satisfied so that the engine generates the required torque represented by the acquired required torque parameter (that is, when determining the amount of fuel for main combustion) It is preferable that the intake air amount be controlled in accordance with the air-fuel ratio used.

  In the present invention, when the pressure accumulation condition is satisfied, the main combustion is performed at the first air-fuel ratio, and when the pressure accumulation condition is not satisfied, the main combustion is performed at the second air-fuel ratio smaller than the first air-fuel ratio. However, when main combustion is performed with the first air-fuel ratio at the time of pressure accumulation, the output torque of the internal combustion engine is lower than when main combustion is performed with the second air-fuel ratio. As a result, the internal combustion engine may not be able to generate sufficient torque with respect to the required torque. On the other hand, according to the above configuration, the generated torque of the engine 10 can be prevented from changing. A required torque parameter representing a required torque for the internal combustion engine is acquired based on, for example, an accelerator pedal operation amount and an engine rotational speed. Then, the intake air amount and the main combustion fuel injection are controlled so that the internal combustion engine can output the required torque represented by the required torque parameter under each air-fuel ratio. As a result, torque required by the driver can be output even when main combustion is performed at the first air-fuel ratio during pressure accumulation. In other words, it is possible to prevent the generated torque of the engine from changing before and after the pressure accumulation condition is satisfied.

In this case, the main combustion fuel injection means is
The main combustion fuel is configured to be injected in a first period from an in-cylinder injection valve that directly injects fuel into the combustion chamber,
The auxiliary combustion fuel injection means includes
It is preferable that the sub-combustion fuel is injected from the in-cylinder injection valve in a second period that is retarded from the first period.

  According to this, the main combustion fuel injection and the sub-combustion fuel injection are performed by the same in-cylinder injection valve. Therefore, the auxiliary combustion can be generated without separately providing a fuel injection device for the auxiliary combustion. Further, the sub-combustion fuel injection is performed on the retard side of the main combustion fuel injection. Therefore, the air-fuel mixture for secondary combustion can be ignited by the residual heat or flame of the main combustion. As a result, the auxiliary combustion can be generated without separately providing a device for igniting the air-fuel mixture used for the auxiliary combustion.

  In this case, the control device for the internal combustion engine has the exhaust passage and the outside in order to prevent the gas in the exhaust passage from flowing out to the outside (that is, the atmosphere outside the engine) when the pressure accumulation condition is satisfied. It is preferable to have exhaust blocking means for blocking.

  According to this, the outflow of the gas in the exhaust passage can be prevented by closing the exhaust cutoff valve when the pressure accumulation condition is satisfied. Thereby, since the gas in the exhaust passage during pressure accumulation can be maintained at a high pressure, the time required for pressure accumulation can be shortened.

  In this case, it is preferable that the auxiliary combustion fuel injection means is configured not to inject the auxiliary combustion fuel when the pressure accumulation condition is not satisfied.

  According to this, when the pressure accumulation is not performed, the auxiliary combustion fuel injection is not performed. Therefore, fuel consumption can be suppressed.

  FIG. 1 shows an internal combustion engine control device (hereinafter also referred to as “control device”) according to an embodiment of the present invention in a spark ignition type, multi-cylinder (4 cylinders in this example), gasoline fuel, and internal combustion engine 10. The schematic configuration of the applied system is shown. The internal combustion engine 10 includes a main body 20, an intake system 30, an exhaust system 40, and an exhaust pressure accumulation system 50.

  The main body portion 20 includes a cylinder block portion and a cylinder head portion. The main body portion 20 includes a plurality (four) of combustion chambers 21 including a piston top surface, a cylinder wall surface, and a lower surface of the cylinder head portion. An intake port (not shown) for supplying air to each combustion chamber 21 and an exhaust port for discharging exhaust gas from each combustion chamber 21 are formed in the cylinder head portion. The intake port is opened and closed by an unillustrated intake valve, and the exhaust port is opened and closed by an unillustrated exhaust valve.

  A plurality of (four) spark plugs (not shown) are fixed to the cylinder head portion. Each spark plug is disposed so that its spark generating portion is exposed at the center of each combustion chamber 21 and in the vicinity of the lower surface of the cylinder head portion. Each spark plug is configured to generate a spark for ignition from a spark generating unit in response to an ignition signal. Further, a plurality (four) of fuel injection valves (injectors) 22 are fixed to the cylinder head portion. Each fuel injection valve 22 responds to the injection instruction signal and directly injects the fuel of the instruction injection amount included in the injection instruction signal into each combustion chamber 21.

  The intake system 30 includes an intake manifold 31, an intake pipe 32, a throttle valve 33 and a throttle valve actuator 33a, an intercooler 34, a compressor 35a of a supercharger 35, and an air filter 36.

The intake manifold 31 includes a plurality of branch portions connected to each intake port, and a surge tank portion in which the branch portions are gathered. The intake pipe 32 is connected to the surge tank portion. The intake manifold 31, the intake pipe 32, and the intake port constitute an intake passage. The air filter 36 is provided at the end of the intake pipe 32. The throttle valve 33 is rotatably attached to the intake pipe 32 at a position between the air filter 36 and the intake manifold 31. The throttle valve 33 changes the opening cross-sectional area of the intake passage formed by the intake pipe 32 by rotating. The throttle valve actuator 33a is a DC motor, and rotates the throttle valve 33 in response to an instruction signal (drive signal).
The intercooler 34 is disposed in the intake pipe 32 at a position upstream of the throttle valve 33. The intercooler 34 cools the intake air passing through the intake passage. Engine cooling water is guided to the intercooler 34 through a cooling water introduction path (not shown), and the intake air is cooled by the engine cooling water.

  The compressor 35 a of the supercharger 35 is disposed in the intake pipe 32 at an upstream position of the intercooler 34.

  The exhaust system 40 includes an exhaust manifold 41, an exhaust pipe 42, a catalyst 43, and an exhaust cutoff valve 44.

  The exhaust manifold 41 includes a plurality of branch portions connected to each exhaust port and a collective portion in which the branch portions are gathered. The exhaust pipe 42 is connected to a collecting portion of the exhaust manifold 41. The exhaust manifold 41, the exhaust pipe 42, and the exhaust port constitute an exhaust passage.

The turbine 35 b of the supercharger 35 is disposed in the exhaust pipe 42 at a position downstream of the exhaust manifold 41.
The turbine 35b is connected to the compressor 35a via a rotating shaft 35c. The turbine 35b is rotated by the gas in the exhaust passage. Thereby, the compressor 35a rotates and performs a supercharging operation for compressing the intake air.

  The catalyst 43 is a known three-way catalyst. The catalyst 43 is disposed in the exhaust pipe 42 at a downstream position of the turbine 35b.

  The exhaust cutoff valve 44 is disposed in the exhaust pipe 42 at a position between the turbine 35 b and the catalyst 43. The exhaust cutoff valve 44 is opened and closed by an instruction signal. When the exhaust cutoff valve 44 is closed, the exhaust gas passage between the upstream side of the exhaust cutoff valve 44 and the outside (atmosphere outside the engine) is shut off. Thereby, the exhaust cutoff valve 44 prevents the gas in the exhaust passage from flowing out. When the exhaust shut-off valve 44 is opened, it allows gas to flow between the exhaust passage upstream of the exhaust shut-off valve 44 and the outside. Thereby, the gas in the exhaust passage is discharged to the outside through the catalyst 43.

  The exhaust pressure accumulation system 50 includes a pressure accumulation tank 51, a pressure accumulation path constituting pipe 52, and an electromagnetic valve 53.

  The pressure accumulating tank (pressure accumulating portion) 51 is connected to the collecting portion of the exhaust manifold 41 through the pressure accumulating path constituting pipe 52. The electromagnetic valve 53 is disposed in the pressure accumulation path constituting pipe 52 at a position between the pressure accumulation tank 51 and the gathering portion of the exhaust manifold 41. The electromagnetic valve 53 is opened and closed by an instruction signal. When the solenoid valve 53 is closed, the gas flow between the pressure accumulating tank 51 and the exhaust manifold 41 is blocked. Thereby, the pressure in the pressure accumulation tank 51 is maintained. When the solenoid valve 53 is opened, the gas flow between the pressure accumulating tank 51 and the gathering portion of the exhaust manifold 41 is allowed. As a result, the gas in the pressure accumulation tank 51 is released into the exhaust manifold 41 or the gas in the exhaust manifold 41 is introduced into the pressure accumulation tank 51 and stored.

  Further, the control device includes a throttle valve position sensor 61, a hot-wire air flow meter 62, an engine speed sensor 63, a water temperature sensor 64, an accumulator tank pressure sensor 65, an accelerator opening sensor 66, an exhaust pressure sensor 67, and an electric control device 70. It has.

The throttle valve position sensor 61 detects the opening of the throttle valve 33 and outputs a signal representing the throttle valve opening TA.
The hot-wire air flow meter 62 detects the mass flow rate of the intake air flowing through the intake pipe 32 and outputs a signal representing the mass flow rate (intake air amount per unit time of the engine 10) GA.

  The engine rotational speed sensor 63 outputs a signal having a narrow pulse every time the intake camshaft rotates 5 ° and a wide pulse every time the intake camshaft rotates 360 °. A signal output from the engine rotational speed sensor 63 is converted into a signal representing the engine rotational speed NE by the electric control device 70. Further, the electric control device 70 acquires the crank angle (absolute crank angle) of the engine 10 based on a signal from the engine rotation speed sensor 63.

The water temperature sensor 64 detects the temperature of the cooling water for cooling the internal combustion engine, and outputs a signal representing the water temperature.
The pressure accumulation tank pressure sensor 65 acquires the pressure in the pressure accumulation tank 51 and outputs a signal Pin representing the pressure.
The accelerator opening sensor 66 detects the operation amount of the accelerator pedal AP operated by the driver, and outputs a signal representing the accelerator pedal operation amount Accp.

  The exhaust pressure sensor 67 detects the pressure of the gas discharged from each combustion chamber 21 and outputs a signal representing the pre-accumulation tank pressure Pbf.

  The electric control device 70 includes a CPU 71, a ROM 72, a RAM 73, a backup RAM 74 that stores data while the power is turned on and holds the stored data even when the power is shut off, an interface 75 including an AD converter, and the like This is a well-known microcomputer.

  The interface of the electric control device 70 is connected to the sensors 61 to 67, supplies signals from the sensors 61 to 67 to the CPU 71, and in accordance with instructions from the CPU 71, the spark plug, the fuel injection valve 22, and the throttle valve actuator 33a. An instruction signal (drive signal) is sent to the exhaust cutoff valve 44 and the electromagnetic valve 53.

Next, the operation of the control device configured as described above will be described separately.
First, the operation of the control device immediately after the engine 10 is started will be described. The CPU 71 of the electric control device 70 repeatedly executes the throttle valve control routine shown in FIG. 2 every elapse of a predetermined time.
Accordingly, the CPU 71 starts processing from step 200 at a predetermined timing.

  The CPU 71 proceeds to step 205 to acquire the required torque TQreq based on the current accelerator pedal operation amount Accp, the current engine speed NE, and the function f. The required torque TQreq is “torque to be generated by the engine 10” requested by the driver to the engine 10. The function f is stored in the ROM 72 in advance in a look-up table (map) format.

  Next, the CPU 71 proceeds to step 210 and determines whether or not the pressure accumulation condition establishment determination flag XL is “0”. When the value of the pressure accumulation condition establishment determination flag XL is “1”, the current operation state is control to increase the pressure in the pressure accumulation tank 51 by introducing the gas in the exhaust passage into the pressure accumulation tank 51 ( Hereinafter, it is also referred to as “accumulated pressure control”). When the value of the pressure accumulation condition establishment determination flag XL is “0”, it indicates that the current operation state is a state where it is not necessary to perform pressure accumulation control. As will be described later, while the pressure accumulation control is being executed, the air-fuel ratio of the air-fuel mixture supplied to the engine 10 (engine air-fuel ratio) is set to an air-fuel ratio (lean air-fuel ratio AL) larger than the stoichiometric air-fuel ratio Stoch. The While the pressure accumulation control is not being executed, the air-fuel ratio of the engine is set to the stoichiometric air-fuel ratio Stoich.

  This accumulation condition establishment determination flag XL is set to “0” in an initial routine (not shown) executed by the CPU 71 when an ignition key switch (not shown) of the vehicle on which the engine 10 is mounted is changed from OFF to ON. It is like that. Furthermore, the pressure accumulation condition establishment determination flag XL is changed by a routine shown in FIG.

  Since the current time is immediately after the engine 10 is started, the pressure accumulation condition establishment determination flag XL is set to “0” by the above-described initial routine. Accordingly, the CPU 71 determines “Yes” in step 210 and proceeds to step 215.

  The CPU 71 acquires the target throttle valve opening degree TAtgt based on the required torque TQreq and the current engine speed NE acquired in step 205 in step 215 and the function gS. In the function gS, when the pressure accumulation control is not executed (that is, when the air-fuel ratio of the engine is set to the stoichiometric air-fuel ratio Stoch), the amount of air required for the engine 10 to generate the required torque TQreq is burned. This is a function for determining the target throttle valve opening degree TAtgt to be supplied to the chamber 21. The function gS is stored in the ROM 72 in advance in a lookup table (map) format.

  Next, the CPU 71 proceeds to step 220 and sets the stoichiometric air-fuel ratio Stoich to the target air-fuel ratio Abfref.

  Next, the CPU 71 proceeds to step 225 to control the throttle valve actuator 33a so that the throttle valve opening degree TA coincides with the target throttle valve opening degree TAtgt. Next, the CPU 71 proceeds to step 295 to end the present routine tentatively.

  Further, the CPU 71 repeatedly executes the combustion injection control routine shown in FIG. 3 every time the crank angle of each cylinder matches a predetermined crank angle before compression top dead center (for example, BTDC 90 °). Hereinafter, a cylinder whose crank angle coincides with the predetermined crank angle before the compression top dead center is also referred to as a fuel injection cylinder. Accordingly, when the crank angle of any cylinder coincides with the predetermined crank angle before the compression top dead center, the CPU 71 starts the process from step 300, proceeds to step 305, and the pressure accumulation condition establishment determination flag XL is “0”. It is determined whether or not there is.

  According to the above assumption, the pressure accumulation condition establishment determination flag XL is currently set to “0”. Therefore, the CPU 71 determines “Yes” in step 305 and proceeds to step 310.

  Next, the CPU 71 acquires the in-cylinder intake air amount Mc in step 310. The in-cylinder intake air amount Mc is the amount (weight) of air that flows into the fuel injection cylinder during the current intake stroke of the fuel injection cylinder. The in-cylinder intake air amount Mc is determined based on the mass flow rate GA acquired from the hot-wire air flow meter 62 and the engine rotational speed NE.

  Next, the CPU 71 proceeds to step 315, and obtains the main combustion fuel injection amount (main combustion fuel injection time) TAUM by dividing the in-cylinder intake air amount Mc obtained in step 310 by the target air-fuel ratio Abfref. The target air-fuel ratio Abfref at this time is set to the stoichiometric air-fuel ratio Stoich by the process of step 220 in FIG. Accordingly, the main combustion fuel injection amount TAUM is a fuel injection amount for making the air-fuel ratio of the air-fuel mixture supplied to the fuel injection cylinder coincide with the stoichiometric air-fuel ratio Stoch.

  Next, the CPU 71 proceeds to step 320 and instructs the fuel injection valve 22 to open so that the fuel of the main combustion fuel injection amount TAUM is injected from the fuel injection valve 22 provided corresponding to the fuel injection cylinder. I do. As a result, the fuel of the main combustion fuel injection amount TAUM is injected from the timing at which the crank angle of the fuel injection cylinder coincides with the predetermined crank angle before the compression top dead center (the crank angle Qinj1 before the compression top dead center). The fuel injection at this timing is referred to as “main combustion fuel injection”. The CPU 71 executes an ignition timing control routine (not shown) to ignite the air-fuel mixture formed in the combustion chamber 21 by the main combustion fuel injection at a predetermined ignition timing near the compression top dead center. As a result, main combustion for the engine 10 to generate the required torque TQreq occurs in the combustion chamber 21 after the vicinity of the compression top dead center. Next, the CPU 71 proceeds to step 395 to end the present routine tentatively.

  By the way, the CPU 71 repeatedly performs the pressure accumulation condition establishment flag setting routine shown in FIG. 4 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 71 starts processing from step 400 and proceeds to step 405.

In step 405, the CPU 71 determines whether the pressure accumulation condition is satisfied. The pressure accumulation condition is satisfied when all of the following conditions 1 to 3 are satisfied.
(Condition 1) The accelerator pedal operation amount Accp (that is, the engine load) detected by the accelerator opening sensor 66 is within a predetermined range (low load threshold Accpthl ≦ Accp ≦ high load threshold Accpthh).
(Condition 2) The engine rotational speed NE detected by the engine rotational speed sensor 63 is within a predetermined range (low-side rotational speed NEthl ≦ NE ≦ high-side rotational speed NEthh).
(Condition 3) The pressure accumulation tank internal pressure Pin detected by the pressure accumulation tank pressure sensor 65 is a predetermined value Pinth1 or less (Pin ≦ first threshold value Pinth1).
Condition 2 and / or condition 3 may be omitted.

  This pressure accumulation condition is satisfied when the operating condition of the engine 10 is in an operating state that does not require supercharging. That is, the pressure accumulation condition is a condition that is satisfied when the load of the engine 10 is smaller than a predetermined high-side load threshold.

In the above condition 1, the condition that the accelerator pedal operation amount Accp is equal to or higher than the low-side load threshold value Accpthl is added to the condition that the exhaust pressure increases the pressure in the accumulator tank 51 when the intake air amount is excessively small. This is because it is not large enough to make it happen.
Condition 3 is a condition for avoiding wasteful accumulation control when the pressure in the accumulation tank 51 is sufficiently high.

  Since the present time is immediately after the start of the engine 10, the engine 10 is in an idling state. Therefore, since the accelerator pedal operation amount Accp becomes the minimum value, the accelerator pedal operation amount Accp is less than the low-side load threshold Accpthl. Further, in a state immediately after the engine 10 is started, the engine 10 is operated at a relatively low rotational speed (rotational speed equal to or lower than the low-side rotational speed NEthl) necessary for maintaining idling. Accordingly, the CPU 71 makes a “No” determination at step 405 to proceed to step 425.

  Next, the CPU 71 determines in step 425 whether the supercharging assistance condition is satisfied. This supercharging assistance condition is satisfied when the operating condition of the engine 10 is in an operating state requiring supercharging. That is, the supercharging assistance condition is a condition that is satisfied when the load of the engine 10 is larger than a predetermined supercharging required load threshold. This supercharging required load threshold is greater than the high side load threshold.

More specifically, the CPU 71 determines that the supercharging assistance condition is satisfied when both of the following condition 4 and condition 5 are satisfied in step 425.
(Condition 4) The accelerator opening degree Accp detected by the accelerator opening degree sensor 66 is equal to or greater than the supercharging required load threshold value Accptha.
(Condition 5) The pressure accumulation tank internal pressure Pin detected by the pressure accumulation tank pressure sensor 65 is not less than the second threshold Pinth2. The second threshold Pinth2 is selected to a value that enables supercharging assist control when the pressure accumulation tank internal pressure Pin is equal to or higher than the second threshold Pinth2. The supercharging assist control is a control for increasing the supercharging pressure by assisting the rotation of the compressor 35a by supplying the gas in the pressure accumulating tank 51 to the turbine 35b. The second threshold value Pinth2 is smaller than the first threshold value Pinth1.

  The current time is immediately after the engine 10 is started. Therefore, the accelerator pedal operation amount Accp is smaller than the supercharging required load threshold Accptha.

  Therefore, the CPU 71 makes a “No” determination at step 425 and proceeds to step 445 to close the solenoid valve 53. Thereby, the gas flow between the pressure accumulating tank 51 and the gathering portion of the exhaust manifold 41 is blocked.

  Next, the CPU 71 proceeds to step 450 and opens the exhaust cutoff valve 44. Thereby, the gas flow between the exhaust passage upstream of the exhaust cutoff valve 44 and the outside is allowed. As a result, the gas in the exhaust passage is discharged outside through the catalyst 43.

  Next, the CPU 71 proceeds to step 440, sets the pressure accumulation condition establishment determination flag XL to “0”, proceeds to step 495, and once ends this routine.

  Next, the operation of the control device when the operation of the engine 10 is continued and the above-described pressure accumulation control condition is satisfied will be described. In this case, when the CPU 71 starts processing from step 400 in FIG. 4, the CPU 71 determines “Yes” in step 405, proceeds to step 410, and opens the electromagnetic valve 53. As a result, the gas flow between the accumulator tank 51 and the aggregate portion of the exhaust manifold 41 is allowed. Therefore, the gas in the exhaust passage on the upstream side of the exhaust cutoff valve 44 is introduced into the pressure accumulation tank 51 and stored.

Next, the CPU 71 proceeds to step 415 to close the exhaust cutoff valve 44. As a result, the gas flow between the exhaust passage upstream of the exhaust cutoff valve 44 and the outside is shut off.
As a result, the outflow of the gas in the exhaust passage upstream of the exhaust shutoff valve 44 is prevented, so that the exhaust gas discharged from the engine 10 does not flow out. As a result, the pressure of the gas in the exhaust passage on the upstream side of the exhaust cutoff valve 44 is increased, so that the pressure in the pressure accumulating tank 51 is efficiently increased. That is, pressure accumulation in the pressure accumulation tank 51 is executed.

  Next, the CPU 71 proceeds to step 420 to store “1” in the pressure accumulation condition establishment determination flag XL, proceeds to step 495, and once ends this routine.

  In this state, when the CPU 71 starts processing from step 200 in FIG. 2, the CPU 71 proceeds to step 205 to acquire the required torque TQreq required for the engine 10. In this case, the pressure accumulation condition establishment determination flag XL is set to “1” by the process of step 420 described above. Therefore, the CPU 71 makes a “No” determination at step 210 to proceed to step 230.

  In step 230, the CPU 71 acquires the target throttle valve opening degree TAtgt based on the required torque TQreq acquired in step 205, the current engine speed NE, and the function gL. The function gL indicates that when the pressure accumulation control is executed (that is, when the air-fuel ratio of the engine 10 is set to the lean air-fuel ratio AL), the amount of air required for the engine 10 to generate the required torque TQreq is This is a function for determining the target throttle valve opening degree TAtgt to be supplied to the combustion chamber 21. The function gL is stored in the ROM 72 in advance in a lookup table (map) format. Next, the CPU 71 proceeds to step 235 to store the lean air-fuel ratio AL in the target air-fuel ratio Abfref.

  Next, the CPU 71 proceeds to step 225 to control the throttle valve actuator 33a so that the throttle valve opening degree TA coincides with the target throttle valve opening degree TAtgt. Next, the CPU 71 proceeds to step 295 to end the present routine tentatively.

  In this state, when the CPU 71 starts processing from step 300 in FIG. 3 and proceeds to step 305, the CPU 71 determines “No” in step 305 and proceeds to step 325.

  In step 325, the CPU 71 determines whether the crank angle of the fuel injection cylinder is a predetermined crank angle after compression top dead center (for example, crank after compression top dead center) from the fuel injection valve 22 provided corresponding to the fuel injection cylinder in step 325. The fuel injection valve 22 is instructed so that the fuel of the sub-combustion fuel injection amount (sub-combustion fuel injection time) TAUP is injected from the time coincident with the angle Qinj2). The fuel injection at this timing is referred to as “sub-combustion fuel injection”. The combustion of the air-fuel mixture formed based on the auxiliary combustion fuel is called “sub-combustion”.

  Next, the CPU 71 proceeds to step 310 to acquire the in-cylinder intake air amount Mc. Next, the CPU 71 proceeds to step 315 to acquire the main combustion fuel injection amount (main combustion fuel injection time) TAUM.

  Next, the CPU 71 proceeds to step 320 and instructs the fuel injection valve 22 to open so that the fuel of the main combustion fuel injection amount TAUM is injected from the fuel injection valve 22 provided corresponding to the fuel injection cylinder. I do. Next, the CPU 71 proceeds to step 395 to end the present routine tentatively. Thereby, the main combustion mentioned above occurs.

  Here, the main combustion and the sub-combustion during the pressure accumulation control (when the pressure accumulation condition establishment determination flag XL is “1”) will be described with reference to FIG. FIG. 5 is a diagram showing the timing of the main combustion fuel injection and the sub-combustion fuel injection with respect to the crank angle of the fuel injection cylinder. In FIG. 5, TDC is a compression top dead center, and BDC is an expansion bottom dead center.

3 is executed, the timing at which the crank angle of the fuel injection cylinder coincides with the first predetermined crank angle before compression top dead center (Qinj1 crank angle before compression top dead center) is reached. Fuel of the main combustion fuel injection amount TAUM is injected. That is, main combustion fuel injection is performed. At this time, an air-fuel mixture having a target air-fuel ratio AL (lean air-fuel ratio AL) in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio is formed in the fuel injection cylinder. The amount of air that forms this air-fuel mixture is adjusted so that the required torque TQreq is generated by burning the fuel of the main combustion fuel injection amount TAUM (see step 230 in FIG. 2).
The CPU 71 executes an ignition timing control routine (not shown) to ignite the air-fuel mixture formed in the combustion chamber 21 by the main combustion fuel injection at the ignition timing Aig near the compression top dead center.
Thereby, the main combustion starts from the vicinity of the compression top dead center. Main combustion continues to a predetermined crank angle SN after compression top dead center. As a result, the required torque TQreq is generated from the engine 10. At this time, the air-fuel ratio of the air-fuel mixture provided for main combustion is the lean air-fuel ratio AL. Accordingly, surplus oxygen remains in the combustion chamber 21.

  Thereafter, the processing at step 325 of FIG. 3 described above is executed, so that the crank angle of the fuel injection cylinder coincides with the second predetermined crank angle after compression top dead center (Qinj2 crank angle after compression top dead center). From this, the fuel of the auxiliary combustion fuel injection amount TAUP is injected. That is, sub-combustion fuel injection is performed. Thus, an air-fuel mixture (sub-combustion air-fuel mixture) is formed in the combustion chamber 21 including the fuel injected by the auxiliary combustion fuel injection and the oxygen remaining as a result of the main combustion. The sub-combustion mixture is ignited at a high temperature by heat generated by the main combustion. That is, secondary combustion occurs.

  Further, the exhaust valve of the fuel injection cylinder is opened at the exhaust valve opening timing EO in the vicinity of the expansion bottom dead center BDC. As a result, the high-temperature gas generated by the secondary combustion is discharged into the exhaust passage. Further, secondary combustion occurs in the exhaust passage. At this time, as described above, the exhaust cutoff valve 44 is closed. Therefore, the number of molecules of the gas in the exhaust passage upstream of the exhaust cutoff valve 44 and the temperature of the gas increase. In other words, the pressure of the gas in the exhaust passage upstream of the exhaust cutoff valve 44 rises quickly. Further, the electromagnetic valve 53 is opened. As a result, the pressure in the pressure accumulation tank 51 rises to the first threshold value Pinth1 within a short time. That is, the pressure accumulation in the pressure accumulation tank 51 can be completed in a short time. Note that the secondary combustion occurs in the vicinity of the expansion bottom dead center, so that the generated torque of the engine 10 is not increased.

  When such pressure accumulation control is executed, the pressure accumulation tank internal pressure Pin becomes larger than the first threshold value Pinth1. In this case, since the condition 3 is not satisfied, the pressure accumulation condition is not satisfied. Therefore, when the CPU 71 starts processing from step 400 in FIG. 4, the CPU 71 determines “No” in step 405 and proceeds to step 425. At this stage, if the supercharging assistance condition is not satisfied, the CPU 71 proceeds to step 445, step 450 and step 440. Accordingly, the engine 10 is controlled in the same manner as immediately after the engine is started.

  Next, when the driver depresses the accelerator pedal AP and the accelerator pedal operation amount Accp becomes equal to or greater than the supercharging required load threshold value Accptha which is larger than the high side load threshold value Accpthh, the above supercharging assist condition is satisfied. The operation of the control device will be described. In this case, when the CPU 71 starts the process from step 400 in FIG. 4, the CPU 71 determines “No” in step 405 and proceeds to step 425. Further, the CPU 71 determines “Yes” in step 425 and proceeds to step 430.

  Next, the CPU 71 opens the electromagnetic valve 53 in step 430. As a result, gas circulation between the pressure accumulating tank 51 and the exhaust manifold 41 is allowed. Therefore, the gas in the pressure accumulating tank 51 is supplied in addition to the exhaust gas from the engine 10 upstream of the turbine 35b. As a result, it is possible to shorten the time (turbo lag) until the rotational speed of the compressor 35a reaches a predetermined rotational speed required for supercharging after starting acceleration.

  Next, the CPU 71 proceeds to step 435 to open the exhaust cutoff valve 44. As a result, the gas in the exhaust passage is discharged outside through the catalyst 43.

  Next, the CPU 71 proceeds to step 440 to store “0” in the pressure accumulation condition establishment determination flag XL, proceeds to step 495, and once ends this routine.

  In this state, when the CPU 71 starts processing from step 200 in FIG. 2, the CPU 71 proceeds to step 205 to acquire the required torque TQreq required for the engine 10. In this case, the pressure accumulation condition establishment determination flag XL is set to “0” by the process of step 440 described above. Therefore, the CPU 71 determines “Yes” in step 210 and performs the processing in steps 215 to 225.

  As a result, the target throttle valve opening degree TAtgt is obtained based on the required torque TQreq, the current engine speed NE, and the function gS. The target air-fuel ratio Abfref is set to the stoichiometric air-fuel ratio Stoich. Further, the throttle valve actuator 33a is driven so that the throttle valve opening degree TA coincides with the target throttle valve opening degree TAtgt.

  Further, in this state, when the CPU 71 starts processing from step 300 in FIG. 3 and proceeds to step 305, the CPU 71 determines “Yes” in step 305, and performs the processing in steps 310 to 320 described above. As a result, the main combustion fuel injection amount TAUM for making the air-fuel ratio of the engine 10 coincide with the stoichiometric air-fuel ratio Stoch is determined, and the fuel of the main combustion fuel injection amount TAUM is supplied to the fuel injection cylinder. In addition, since the process of step 325 is not performed, subcombustion does not occur. Next, the CPU 71 proceeds to step 395 to end the present routine tentatively.

  FIG. 6 is a time chart for explaining the effect of the present control device. In FIG. 6, Mc is the cylinder intake air amount, Trq is the engine output torque, Pbf is the pre-accumulation tank pressure (pressure in the exhaust passage upstream from the turbine 35b), and Pin is the accumulator tank internal pressure. Further, a solid line L1 indicates the above values in the present control device. The broken line L2 indicates the above-described values in the control device (hereinafter referred to as “modified example”) according to a modified example of the embodiment of the present invention. An alternate long and short dash line L3 indicates the above values in the comparative example.

  Here, in the modified example, during the pressure accumulation control, the exhaust shut-off valve 44 is closed and the electromagnetic valve 53 is opened, and the air-fuel ratio of the air-fuel mixture supplied to the main combustion matches the lean air-fuel ratio AL. Then, the auxiliary combustion is performed by performing the auxiliary combustion fuel injection. However, in the modification, the in-cylinder intake air amount Mc is kept constant without changing the throttle valve opening TA before and after the start of the pressure accumulation control.

  In the comparative example, the exhaust cutoff valve 44 is closed and the electromagnetic valve 53 is opened during pressure accumulation control. However, in the comparative example, in the pressure accumulation control, the air-fuel ratio of the air-fuel mixture used for main combustion is maintained at the same stoichiometric air-fuel ratio before the start of pressure accumulation control, and no sub-combustion fuel injection is performed (that is, sub-combustion is not performed). Do not generate). Further, in the comparative example, the in-cylinder intake air amount Mc is kept constant without changing the throttle valve opening TA before and after the start of the pressure accumulation control.

  In the example shown in FIG. 6, the pressure accumulation condition is satisfied at time t1 (the pressure accumulation control is started). According to the comparative example, the cylinder intake air amount Mc and the air-fuel ratio of the air-fuel mixture supplied to the main combustion do not change before and after the pressure accumulation control is started. Accordingly, as indicated by the line L3, the in-cylinder intake air amount Mc and the output torque Trq do not change. However, since the exhaust shut-off valve 44 is closed and the electromagnetic valve 53 is opened, the pre-accumulation tank pressure Pbf slightly increases during the accumulation control. As a result, the pressure accumulation tank internal pressure Pin gradually increases and reaches the first threshold value Pinth1 at time t4.

  On the other hand, according to the modification, the in-cylinder intake air amount Mc is maintained constant before and after the pressure accumulation control is started, but the air-fuel ratio of the air-fuel mixture supplied to the main combustion is changed from the stoichiometric air-fuel ratio to the lean air-fuel ratio. Changed to AL. Therefore, as indicated by the line L2, the in-cylinder intake air amount Mc is constant, but the output torque Trq decreases during the pressure accumulation control. Even in this case, the exhaust cutoff valve 44 is closed and the electromagnetic valve 53 is opened. Further, secondary combustion is generated. Therefore, the pressure Pbf before the pressure accumulation tank during the pressure accumulation control is larger than that in the comparative example. As a result, the pressure accumulation tank internal pressure Pin increases more quickly than the comparative example, and reaches the first threshold value Pinth1 at time t3 before time t4.

  On the other hand, according to the present control device, before and after the pressure accumulation control is started, the air-fuel ratio of the air-fuel mixture used for main combustion is changed from the stoichiometric air-fuel ratio Stoch to the lean air-fuel ratio AL, and at the same time, The in-cylinder intake air amount Mc is increased so that the generated torque is constant (see line L1). In other words, the generated torque of the engine 10 does not change before and after the start of the pressure accumulation control (and before and after the end).

  Further, even in the case of this control device, the exhaust cutoff valve 44 is closed, the electromagnetic valve 53 is opened, and sub-combustion is generated. Accordingly, the pressure Pbf before the pressure accumulation tank during the pressure accumulation control is larger in the cylinder air amount than in the modified example, so that the pressure in the pressure accumulation tank Pin increases more quickly than in the modified example, and at time t2 before time t3. The first threshold value Pinth1 is reached.

  As described above, the present control device can complete the pressure accumulation in the pressure accumulation tank 51 in an extremely short time, and can also avoid the fluctuation in the torque generated by the engine 10 due to the execution of the pressure accumulation control. Play.

Thus, this control device
A supercharger (35);
When a predetermined pressure accumulation condition is satisfied, the gas storage section includes a pressure accumulation section that accommodates the gas in a high pressure state by introducing the gas in the exhaust passage, and when a predetermined supercharging assist condition is satisfied, Supercharging assistance means (pressure accumulation system 50, steps 405, 425, and 410 in FIG. 4) for supplying the contained high-pressure gas to the turbine so as to assist the rotation of the turbine;
Main combustion fuel injection means (fuel injection valve 22, step 220 of FIG. 2, FIG. 3) for injecting fuel for the main combustion so that main combustion for generating torque by the engine can occur in the combustion chamber Step 315 and step 320),
When the pressure accumulation condition is satisfied, combustion for increasing the pressure of the gas in the exhaust pipe introduced into the pressure accumulating section and sub-combustion different from the main combustion is performed in the combustion chamber and the exhaust pipe Sub-combustion fuel injection means (fuel injection valve 22, step 235 in FIG. 2 and step 325 in FIG. 3) for injecting fuel for the sub-combustion so that it can be generated in at least one of
Have

  The main combustion fuel injection means is configured to cause the air-fuel ratio of the air-fuel mixture supplied to the main combustion to coincide with the first air-fuel ratio that is an air-fuel ratio larger than the stoichiometric air-fuel ratio when the pressure accumulation condition is satisfied. It is configured to control the amount of fuel for combustion (step 235 in FIG. 2 and step 315 in FIG. 3). Further, the sub-combustion fuel injection means is configured to form an air-fuel mixture used for the sub-combustion using excess oxygen contained in the air-fuel mixture supplied for the main combustion.

In addition, this control device
Intake air amount acquisition means for acquiring an intake air flow rate that is the amount of air supplied to the combustion chamber (step 310 in FIG. 3);
Request torque parameter acquisition means for acquiring a request parameter representing a request torque required for the engine (step 205 in FIG. 2 and the like);
Intake air amount control means (throttle valve 33, throttle valve actuator 33a, etc.) for controlling the intake air amount.

The main combustion fuel injection means includes
When the pressure accumulation condition is satisfied (when XL = 1), based on the acquired intake air amount and the first air-fuel ratio so that the air-fuel mixture provided for the main combustion matches the first air-fuel ratio The amount of fuel for the main combustion is controlled (step 235 in FIG. 2, step 315 in FIG. 3, etc.), and the air-fuel mixture supplied to the main combustion when the pressure accumulation condition is not satisfied (when XL = 0) The amount of the main combustion fuel is controlled based on the acquired intake air amount and the second air-fuel ratio so as to match the second air-fuel ratio (theoretical air-fuel ratio) smaller than the first air-fuel ratio. (Step 220 in FIG. 2 and Step 315 in FIG. 3).

Further, the intake air amount control means includes:
The intake air amount is controlled according to whether the required torque and the pressure accumulation condition are satisfied so that the engine generates the required torque represented by the acquired required torque parameter. (See routine in FIG. 2).

Further, the main combustion fuel injection means includes
The main combustion fuel is injected from the in-cylinder injection valve (22) that directly injects fuel into the combustion chamber (21) in the first period (the main combustion fuel injection time TAUM has elapsed from the crank angle Qinj1 before compression top dead center). (Step 320 in FIG. 3).
The auxiliary combustion fuel injection means includes
The sub-combustion fuel is injected from the in-cylinder injection valve (22) into a second period (a sub-combustion fuel injection time TAUP elapses from the post-compression top dead center crank angle Qinj2) that is delayed from the first period. During the period) (step 325 in FIG. 3).

  Accordingly, the present control device can maintain the pressure-accumulation tank internal pressure Pin at a high value (can be quickly recovered) even in a situation where acceleration operations frequently occur within a short time, for example, so that supercharging by the gas in the pressure-accumulation tank 51 is performed. Assistance can be provided, and turbo lag can be shortened. Therefore, it is possible to provide an acceleration feeling according to the driver's request.

  The control device for an internal combustion engine according to the present invention is not limited to the above embodiment, and various modifications as described below can be adopted. For example, the start timing of the auxiliary combustion fuel injection may be during the combustion of the main combustion as long as the auxiliary combustion does not cause the engine 10 to generate torque. In this case, the air-fuel mixture for secondary combustion is ignited by the main combustion flame and the heat generated by the main combustion, so that the secondary combustion can be generated more reliably.

  Further, the auxiliary combustion may be generated only in the combustion chamber 21 or may be generated only in the exhaust passage.

  Further, the auxiliary combustion fuel injection means of the above embodiment injects the auxiliary combustion fuel using the fuel injection valve 22 (in-cylinder injection valve) that injects the fuel directly into the cylinder. On the other hand, a fuel injection valve may be separately provided in the exhaust manifold 41, and the auxiliary combustion fuel injection means may be configured to inject fuel for auxiliary combustion from the separately provided injection valve. Even in this case, it is desirable that the air-fuel ratio of the air-fuel mixture supplied to the main combustion during the pressure accumulation control is set to the lean air-fuel ratio AL. According to this, the surplus oxygen discharged from the combustion chamber 21 into the exhaust manifold 41 and the fuel injected into the exhaust manifold 41 form an air-fuel mixture for subcombustion in the exhaust manifold 41. The air-fuel mixture for secondary combustion is ignited by the exhaust heat of combustion. Therefore, the gas pressure in the exhaust passage can be increased while avoiding fluctuations in the torque generated by the engine 10 before and after the pressure accumulation control.

  Furthermore, the aspect in which the fuel for sub-combustion is injected from the fuel injection valve provided in the exhaust manifold 41 may include a spark plug for sub-combustion in the exhaust manifold 41. As a result, sub-combustion can be more reliably generated in the exhaust manifold 41.

  In addition, when the auxiliary combustion fuel injection means is configured to inject fuel for auxiliary combustion from the fuel injection valve disposed in the exhaust manifold 41, secondary air (fresh air) is separately supplied to the exhaust passage. A secondary air supply device for supplying may be provided. In this case, oxygen for auxiliary combustion is supplied by the secondary air supply device. Therefore, the air-fuel ratio of the air-fuel mixture used for main combustion during the pressure accumulation control can be set to the stoichiometric air-fuel ratio Stoich.

  In the above embodiment, gas is supplied from the pressure accumulation tank 51 to the turbine 35b through the pressure accumulation path constituting pipe 52 when the supercharging assist condition is satisfied. On the other hand, in addition to the pressure accumulation path constituting pipe 52, a communication pipe that communicates the pressure accumulation tank 51 and the turbine 35b and an electromagnetic valve that opens and closes the passage of the communication pipe may be provided. In this case, the solenoid valve is opened only when the supercharging assist condition is satisfied, whereby gas is supplied to the turbine 35b through the communication pipe. According to this, the gas in the pressure accumulation tank 51 can be directly supplied to the turbine 35b. Therefore, the pressure of the gas supplied to the turbine 35b can be made higher than when the gas in the pressure accumulating tank 51 is supplied to the turbine 35b via the exhaust passage. As a result, the turbo lag can be further shortened.

  Moreover, in the said embodiment, supply of the gas from the pressure accumulation tank 51 at the time of supercharging assistance conditions satisfaction may be performed with respect to the auxiliary turbine of the auxiliary supercharger provided separately. That is, the auxiliary supercharger has an auxiliary turbine that is rotated by the gas supplied from the pressure accumulation tank 51. Furthermore, the auxiliary supercharger is rotated in accordance with the rotation of the auxiliary turbine, and has an auxiliary compressor disposed in the intake passage downstream or upstream of the compressor 35a. Thus, when the supercharging assistance condition is satisfied, the auxiliary turbine and the auxiliary compressor are rotated by the gas supplied from the pressure accumulation tank 51. As a result, the intake air is compressed by the auxiliary compressor in addition to the compressor 35a, and the intake efficiency can be further improved.

  In the above embodiment, the auxiliary combustion fuel injection amount TAUP injected from the fuel injection valve 22 is constant. On the other hand, the auxiliary combustion fuel injection amount TAUP injected from the fuel injection valve 22 may be variable. That is, for example, when the control controller performs pressure accumulation control, if the pressure accumulation tank internal pressure is low, the injection amount of the auxiliary combustion fuel injection amount TAUP is increased. The pressure of the gas supplied to the pressure accumulation tank 51 can be increased as the pressure accumulation tank internal pressure Pin is lower. As a result, the pressure accumulation tank internal pressure Pin increases rapidly, and the time for reaching the first threshold value Pinth1 is shortened.

1 is a schematic diagram of an internal combustion engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. 2 is a flowchart showing a throttle valve control routine executed by a CPU shown in FIG. 2 is a flowchart showing a fuel injection control routine executed by a CPU shown in FIG. 2 is a flowchart showing a pressure accumulation condition establishment flag setting routine executed by a CPU shown in FIG. It is the figure which showed the timing of the main combustion fuel injection, the subcombustion fuel injection, etc. with respect to the crank angle of a fuel injection cylinder. It is a figure showing the time change of the amount of intake air at the time of pressure accumulation, generated torque, pressure in a pressure accumulation tank, and pressure in a pressure accumulation tank.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Main part, 21 ... Combustion chamber, 22 ... Fuel injection valve, 30 ... Intake system, 31 ... Intake manifold, 32 ... Intake pipe, 33 ... Throttle valve, 33a ... Throttle valve actuator, 35 ... Excess 35a ... compressor, 35b ... turbine, 40 ... exhaust system, 41 ... exhaust manifold, 42 ... exhaust pipe, 44 ... exhaust shut-off valve, 50 ... accumulator system, 50 ... exhaust accumulator system, 51 ... accumulator tank, 52 ... Pressure accumulating path constituting pipe, 53 ... Solenoid valve, 61 ... Throttle valve position sensor, 62 ... Hot wire air flow meter, 63 ... Engine rotational speed sensor, 65 ... Accumulated tank pressure sensor, 66 ... Accelerator opening sensor, 67 ... Exhaust pressure sensor 70 ... electric control device, 75 ... interface.

Claims (6)

A compressor disposed in an intake pipe that forms an intake passage communicating with the turbine and a turbine disposed in an exhaust pipe that forms an exhaust passage communicating with the combustion chamber of the internal combustion engine, and that rotates as the turbine rotates A turbocharger having
When a predetermined pressure accumulation condition is satisfied, the gas storage section includes a pressure accumulation section that accommodates the gas in a high pressure state by introducing the gas in the exhaust passage, and when a predetermined supercharging assist condition is satisfied, Supercharging assisting means for supplying a gas in a high-pressure state accommodated to the turbine so as to assist the rotation of the turbine;
Main combustion fuel injection means for injecting fuel for the main combustion so that main combustion for generating torque by the engine can occur in the combustion chamber;
When the pressure accumulation condition is satisfied, combustion for increasing the pressure of the gas in the exhaust passage introduced into the pressure accumulating portion, and sub-combustion different from the main combustion is performed in the combustion chamber and the exhaust Sub-combustion fuel injection means for injecting fuel for sub-combustion so that it can be generated in at least one of the passages;
A control apparatus for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
The main combustion fuel injection means is configured to cause the air-fuel ratio of the air-fuel mixture supplied to the main combustion to coincide with the first air-fuel ratio that is an air-fuel ratio larger than the stoichiometric air-fuel ratio when the pressure accumulation condition is satisfied. Configured to control the amount of fuel for combustion;
The sub-combustion fuel injection means is configured to form an air-fuel mixture provided for the secondary combustion using excess oxygen contained in the air-fuel mixture provided for the main combustion.
Control device for internal combustion engine. A control device for an internal combustion engine according to claim 2,
Intake air amount acquisition means for acquiring an intake air amount that is an amount of air supplied to the combustion chamber;
Request torque parameter acquisition means for acquiring a request parameter representing a request torque required for the engine;
An intake air amount control means for controlling the intake air amount;
With
The main combustion fuel injection means is
The main combustion fuel based on the acquired intake air amount and the first air-fuel ratio so that the air-fuel mixture provided for the main combustion matches the first air-fuel ratio when the pressure accumulation condition is satisfied When the pressure accumulation condition is not satisfied, the air-fuel mixture provided for the main combustion is equal to the acquired intake air amount so as to coincide with the second air-fuel ratio smaller than the first air-fuel ratio. 2 is configured to control the amount of the main combustion fuel based on the air-fuel ratio;
The intake air amount control means includes:
The intake air amount is controlled according to whether the required torque and the pressure accumulation condition are satisfied so that the engine generates the required torque represented by the acquired required torque parameter. ,
Control device for internal combustion engine. A control device for an internal combustion engine according to any one of claims 1 to 3,
The main combustion fuel injection means is
The main combustion fuel is configured to be injected in a first period from an in-cylinder injection valve that directly injects fuel into the combustion chamber,
The auxiliary combustion fuel injection means includes
The sub-combustion fuel is injected from the in-cylinder injection valve in a second period that is retarded from the first period.
Control device for internal combustion engine. A control device for an internal combustion engine according to any one of claims 1 to 4,
When the pressure accumulation condition is satisfied, the exhaust passage has a means for shutting off the exhaust passage and the outside in order to prevent the gas in the exhaust passage from flowing out to the outside.
Control device for internal combustion engine. The control device for an internal combustion engine according to any one of claims 1 to 5,
The control device for an internal combustion engine, wherein the sub-combustion fuel injection means is configured not to inject the sub-combustion fuel when the pressure accumulation condition is not satisfied.

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