JP4500232B2 - Control device for compression ignition internal combustion engine - Google Patents

Description

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

  In the internal combustion engine, when the injector is disposed near the intake port in front of the intake valve, the injected fuel adheres to the wall surface in the vicinity thereof. Since the fuel transportation delay due to the wall adhesion becomes a disturbance in the air-fuel ratio control, it is necessary to correct the fuel injection amount by estimating the wall adhesion amount. Further, when the intake valve is variably controlled, the wall surface adhesion amount is also affected by the change of the valve timing. Therefore, for example, as in the technique described in Patent Document 1, the model parameters of the deposition rate and the evaporation rate are calculated for the deposited fuel in the vicinity of the combustion chamber and the deposited fuel at a position away from the combustion chamber, and the valve overlap amount is calculated. It has been proposed that a model parameter is calculated from the change state of the internal EGR gas accompanying the change of the air to correct the deviation of the air-fuel ratio.

  By the way, recently, in an internal combustion engine using gasoline as fuel, a compression ignition (Homogeneous Charge Compression Ignition) operation (HCCI operation) is performed to compress and ignite an air-fuel mixture supplied to a combustion chamber in a predetermined operation region. (Nitrogen oxide) Emission reduction and improvement of thermal efficiency or fuel efficiency, and so-called compression self-ignition, which performs spark ignition (Spark Ignition) operation in which the air-fuel mixture is spark-ignited and combusted via spark plugs in other operating regions Various internal combustion engines have been proposed. The present applicant has also proposed this type of technology as shown in Patent Document 2 below. In such an internal combustion engine, the compression ratio can be increased as compared with the spark ignition engine, and the thermal efficiency or fuel efficiency can be improved.

As an internal combustion engine operation method (more precisely, a kind of heat engine), there is an operation method called an Atkinson cycle (or Miller cycle) in which the intake valve is delayed and closed to reduce the pumping loss.
JP 2003-20965 A Japanese Patent Laid-Open No. 2005-09324

  In the compression ignition internal combustion engine described in Patent Document 2, when the Atkinson cycle operation is performed while spark-igniting the air-fuel mixture in the combustion chamber, the intake valve is not closed immediately even after entering the compression stroke, and remains open. Therefore, the fuel that was injected before the previous control cycle and adhered to the wall surface near the intake port may be aspirated suddenly into the combustion chamber. Furthermore, the fuel injected in the control cycle this time once flows into the combustion chamber and then blown back into the intake port, so that the amount of adhesion may seem to increase.

  Therefore, as in the technique described in Patent Document 1, the fuel injection amount is calculated by calculating the wall adhesion amount of the injected fuel based on the valve timing of the intake valve, that is, the opening / closing angle of the intake valve. Specifically, as a result of calculating the fuel injection amount so as to decrease in accordance with the adhesion amount, in some cases, the fuel injection amount may become a lower limit value near zero. Therefore, the required cylinder intake fuel amount cannot be controlled, the air-fuel ratio deviates from the target value, combustion becomes unstable, torque fluctuation occurs, drivability decreases, and exhaust emission performance may deteriorate. .

  Such inconvenience becomes particularly noticeable when switching from the spark ignition operation of the Atkinson cycle to the compression ignition operation in the compression ignition internal combustion engine.

  Accordingly, an object of the present invention is to solve the above-described problems, and includes a mechanism for variably adjusting an intake valve, performing a compression ignition operation and a spark ignition operation, and performing a spark ignition operation in an Atkinson cycle. In the control device, even when the fuel injection amount becomes a lower limit value near zero, the compression ignition internal combustion engine in which the actual injection amount is made to coincide with the required injection amount to avoid the decrease in drivability or the deterioration of the exhaust emission performance. It is to provide a control device.

In order to solve the above-mentioned object, according to claim 1, at least a variable valve mechanism for variably adjusting an intake valve and an ignition means for igniting an air-fuel mixture in a combustion chamber are provided, and the combustion is performed in a predetermined operation region. Performing a compression ignition operation in which the air-fuel mixture supplied to the chamber is subjected to compression ignition combustion, and performing a spark ignition operation in which the air-fuel mixture is subjected to spark ignition combustion through the ignition means in an operation region other than the predetermined operation region; In a control apparatus for a compression ignition internal combustion engine that performs the spark ignition operation in an Atkinson cycle, an intake valve opening / closing angle calculating means that calculates an opening / closing angle of the intake valve according to an operating state of the internal combustion engine, and the combustion chamber in a certain cycle Of the fuel injected into the combustion chamber in the cycle, and a direct rate indicating the proportion of fuel sucked into the combustion chamber in the cycle, and the intake valve injected before the cycle Based on the calculated opening / closing angle of the intake valve, the take-off rate indicating the proportion of the fuel that has been adhering to the wall of the intake port to be placed and the like is sucked into the combustion chamber in the cycle. And a wall surface adhering amount calculating means for calculating a wall surface adhering amount of the injected fuel based on the calculated direct rate and take-off rate, and opening and closing of the intake valve calculated using the calculated wall surface adhering amount. A fuel injection amount calculating means for calculating a fuel injection amount for correcting an angle , and a change in the opening / closing angle of the intake valve when the calculated fuel injection amount is at or near a lower limit value. Intake valve opening / closing angle correcting means for correcting the calculated intake valve opening / closing angle is provided.

In the control apparatus for a compression ignition internal combustion engine according to claim 1, the opening / closing angle of the intake valve is calculated according to the operating state of the internal combustion engine, and is injected into the combustion chamber in a certain cycle based on the calculated opening / closing angle of the intake valve. Of the generated fuel, the direct ratio indicating the proportion of fuel sucked into the combustion chamber in the cycle, and the fuel that was injected before the cycle and attached to the wall of the intake port where the intake valve is disposed Of these, the removal rate indicating the ratio of the fuel sucked into the combustion chamber in the cycle is calculated, and the wall adhesion amount of the injected fuel is calculated based on the calculated direct rate and the removal rate. A fuel injection amount for correcting the calculated opening / closing angle of the intake valve is calculated using the wall surface adhering amount, and when the calculated fuel injection amount is at or near the lower limit value, the opening / closing angle of the intake valve is calculated . change As limited to, the opening and closing angle of the calculated intake valve and configured to correct, in other words, since the actual injection amount so as to correct gradually closing angle of the intake valve while a small amount, the actual injection It becomes easy to make the amount coincide with the required injection amount, so that the air-fuel ratio can be made coincident with the target value, and the change in the opening / closing angle of the intake valve can be limited so that the combustion becomes stable. As a result, torque fluctuations can be removed, drivability can be avoided, and exhaust emission performance can be prevented from deteriorating.

  The best mode for carrying out a control apparatus for a compression ignition internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram generally showing a control apparatus for a compression ignition internal combustion engine according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a four-cylinder four-cycle internal combustion engine (only one cylinder is shown; hereinafter referred to as “engine”) using gasoline as fuel. In the engine 10, air (intake air) drawn from the air cleaner 12 and passing through the intake pipe 14 is adjusted in flow rate by the throttle valve 16, flows through the intake manifold 20, and two intake valves (only one is shown) 22 are opened. When it is done, it flows into the combustion chamber 24.

  An injector 26 is disposed near the intake port in front of the intake valve 22. Gasoline fuel stored in a fuel tank (not shown) is pumped to the injector 26 via a fuel supply pipe (not shown). The injector 26 is connected to an ECU (Electronic Control Unit) 30 through a drive circuit (not shown).

  The injector 26 opens when a drive signal indicating the valve opening time is supplied from the ECU 30 through the drive circuit, and injects gasoline fuel corresponding to the valve opening time into the intake port. The injected gasoline fuel is mixed with the inflowing air to form an air-fuel mixture (pre-air mixture), and flows into the combustion chamber when the intake valve 22 is opened.

  An ignition plug (ignition means) 32 is disposed in the combustion chamber 24. The spark plug 32 is connected to the ECU 30 via an ignition device (ignition means, not shown) such as an igniter. When an ignition signal is supplied from the ECU 30, a spark discharge is generated between the electrodes facing the combustion chamber. The air-fuel mixture is thereby ignited and burned, driving the piston 34 downward.

  The engine 10 is operated between a compression ignition (Homogeneous Charge Compression Ignition) operation in which an air-fuel mixture is compressed and ignited in a predetermined operation region, and a spark ignition operation in which spark ignition combustion is performed through an ignition plug 32 or the like. It is configured as a compression ignition engine (internal combustion engine) that can be switched.

  Exhaust gas (exhaust gas) generated by combustion flows to the exhaust manifold 40 when two exhaust valves (only one is shown) 36 are opened.

  The exhaust valve 36 and the intake valve 22 are provided with solenoid solenoids 36a and 22a for valve closing, electromagnetic solenoids 36b and 22b for valve opening, springs 36c and 22c, and springs 36d and 22d attached to the stem. The solenoid valve is configured to operate by the electromagnetic force of the solenoids 36a, 22a, 36b, and 22b. Specifically, the exhaust valve 36 and the intake valve 22 are closed by exciting the solenoid solenoids 36a and 22a for closing and demagnetizing the solenoid solenoids 36b and 22b for opening, and the solenoid solenoid for closing the valve. The valves 36a and 22a are demagnetized and the valve opening electromagnetic solenoids 36b and 22b are excited to open the valves. In this way, the exhaust valve 36 and the intake valve 22 are excited and demagnetized by the mounted electromagnetic solenoids 36a, 22a, 36b, 22b, so that the valve is independent of the rotation angle of the crankshaft (not shown). It is configured as a variable valve mechanism 38 that variably adjusts (open / close) timing.

  The exhaust manifold 40 gathers downstream to form an exhaust system gathering portion, to which an exhaust pipe 42 is connected. Exhaust gas flows from the exhaust manifold 40 through the exhaust pipe 42. A catalyst device 44 made of a three-way catalyst is disposed in the exhaust pipe (exhaust system) 42. When the catalyst device 44 is in an active state, the exhaust gas is discharged into the atmosphere outside the engine after removing harmful components such as HC, CO, and NOx.

  The exhaust pipe 42 is connected to the intake pipe 14 via the EGR pipe 46 in the vicinity of the downstream of the position where the throttle valve 16 is disposed. An EGR valve 46 a is inserted in the EGR pipe 46. The EGR valve 46a is electrically connected to the ECU 30 and, when driven, opens the EGR pipe 46 to recirculate a part of the exhaust gas to the intake system (external EGR).

  A turbocharger 50 is provided upstream of the catalyst device 44 in the exhaust pipe 42. As schematically shown in FIG. 1, the turbocharger 50 is disposed in the exhaust pipe 42, and is disposed in the intake pipe 14 while being connected to the turbine 50a and being rotated by the exhaust gas passing therethrough. The compressor 50b is driven by a rotational force and supercharged. A variable nozzle (not shown) is provided in the vicinity of the turbine 50a, and adjusts the flow rate and speed of the exhaust gas flowing through the impeller (not shown) of the turbine 50a.

  A throttle actuator (such as a pulse motor) 52 is connected to the throttle valve 16 disposed in the intake pipe 14 and is opened and closed by the throttle actuator 52. That is, the throttle valve 16 is mechanically disconnected from the accelerator pedal 54 disposed on the driver's seat floor of a vehicle (not shown) on which the engine 10 is mounted, and the throttle valve 16 is operated by the accelerator pedal 54. And a DBW (Drive By Wire) mechanism 56 that opens and closes independently.

  The reciprocating motion of the piston 34 rotates a crankshaft (not shown) via the connecting rod 34a. The engine 10 is connected to an automatic transmission 58 (shown as “A / T” in the figure) composed of five forward speeds and one reverse speed. The rotation of the engine 10 input through the rotation of the crankshaft is shifted by the automatic transmission 58 and transmitted to drive wheels (not shown) to drive the vehicle.

  A crank angle sensor 60 is disposed in the vicinity of the crankshaft of the engine 10 and is obtained by subdividing a cylinder discrimination signal, a TDC signal indicating a TDC (top dead center) of each cylinder or a crank angle in the vicinity thereof, and a TDC signal. A crank angle signal is output. Those outputs are input to the ECU 30.

  The ECU 30 includes a microcomputer, and includes a CPU, ROM, RAM, A / D conversion circuit, input / output circuit, and counter (all not shown). The ECU 30 counts the crank angle signal in the input signal and calculates (detects) the engine speed (ENG speed) NE.

  An air flow meter 62 having a temperature detecting element is disposed in the vicinity of the air cleaner 12 and outputs a signal corresponding to a flow rate (indicating engine load) Gair and temperature TA of air (intake air) drawn from the air cleaner 12.

  A MAP sensor 64 is disposed downstream of the throttle valve 16 in the intake pipe 14 to output a signal indicating the intake pipe pressure PBA in absolute pressure, and a throttle opening sensor 66 is disposed in the throttle valve 16. A signal corresponding to the position (throttle opening) TH is output. A rotary encoder 70 is disposed in the throttle actuator 52 and outputs a signal corresponding to the drive amount (rotation amount) of the throttle actuator 52.

  A water temperature sensor 72 is disposed in a cooling water passage (not shown) of the engine 10 and outputs a signal corresponding to the engine cooling water temperature TW.

  An accelerator opening sensor 74 is provided in the vicinity of the accelerator pedal 54, and outputs a signal corresponding to an accelerator opening (indicating engine load) AP indicating the amount of depression of the accelerator pedal of the driver.

  In the exhaust system, a wide area air-fuel ratio sensor 76 is disposed in the vicinity of the downstream portion of the collection portion of the exhaust manifold 40, and outputs a signal proportional to the oxygen concentration (that is, air-fuel ratio) of the exhaust gas flowing through that portion, and the turbocharger 50. A variable nozzle position sensor 80 is disposed in the vicinity of the variable nozzle disposed in the vicinity of the turbine 50a, and outputs a signal corresponding to the position of the variable nozzle.

  An ATF temperature sensor 82 is disposed at an appropriate position of an oil passage or an oil pan (not shown) for supplying hydraulic oil (Automatic Transmission Fluid) to the automatic transmission 58, and generates an output TATF proportional to the ATF temperature.

  The output of the sensor group described above is also input to the ECU 30. Based on the input value, the ECU 30 functions as a control device that executes control such as switching permission from the spark ignition operation to the compression ignition operation, as will be described later in accordance with a command stored in the ROM.

  Next, the operation of the control device shown in FIG. 1 will be described.

  FIG. 2 is a flowchart showing the operation, specifically, the operation of the ECU 30. The illustrated program is activated by a time interrupt every predetermined time (for example, 10 msec).

  In the following, A / D conversion values such as the accelerator opening AP, the intake pipe absolute pressure PBA, and the intake air temperature TA detected through the sensor group in S10 are sampled, and the calculated engine speed NE is read.

Next, in S12, the required torque PMCMD (engine load) is calculated. Since the engine 10 according to this embodiment is controlled by the DBW mechanism 56, the required torque PMCMD is calculated as follows.
PMCMD = CONST / PSE / NE

  In the above, CONST is a constant. PSE is a required output of the engine 10 obtained by searching a preset map (characteristic not shown) from the accelerator opening AP and the engine speed NE. Specifically, the PSE is set to increase as the accelerator pedal opening AP is larger or the engine speed NE is higher.

  Next, in S14, a compression ignition (hereinafter referred to as “HCCI”) operable region determination is performed. That is, it is determined whether the engine 10 is in an area where HCCI operation is possible.

  FIG. 3 is a sub-routine flowchart showing the processing.

  Explaining below, it is determined whether or not the engine coolant temperature TW detected in S100 exceeds a predetermined water temperature TWHCCI. If the determination is negative, the process proceeds to S102, and the engine 10 is in the spark ignition (hereinafter referred to as “SI”) operation region. And the bit of the flag F_HCCI is reset to 0.

  When the result is affirmative in S100, the process proceeds to S104, where it is determined whether the detected intake air temperature TA exceeds the predetermined intake air temperature TAHCCI. When the result is negative, the process proceeds to S102, and when the result is affirmative, the process proceeds to S106. It is determined whether the temperature TEX exceeds a predetermined exhaust temperature TEXHCCI.

  The exhaust temperature TEX is calculated from the engine speed NE, the fuel injection amount Tout (or the required torque PMCMD), the target in-cylinder gas temperature TempCYL, and the like. However, since calculation of these target in-cylinder gas temperature TempCYL and exhaust gas temperature TEX is described in Patent Document 2, detailed description thereof is omitted.

  When the result in S106 is negative, the process proceeds to S102, and when the result is affirmative, the process proceeds to S108 to determine whether the HCCI is within a possible range. This is done by searching a map showing the characteristics in FIG. 4 from the required torque PMCMD and the engine speed NE. As shown in FIG. 4, the middle and low load regions are within the HCCI possible range.

  When the result in S108 is negative, the process proceeds to S102, and when the result is affirmative, the process proceeds to S110, in which the engine 10 determines that it is in an area where HCCI operation is possible, and sets the bit of the flag F_HCCI to 1.

  Returning to the description of the flow chart of FIG. 2, the process then proceeds to S16, where the VT (valve timing) of the exhaust valve 36, that is, the opening / closing angle, and the intake air are determined from the engine speed NE, the required torque PMCMD, and the target internal EGR amount nEGR. The VT (valve timing) of the valve 22, that is, the opening / closing angle (temporary value) is calculated. Since the opening / closing angle of the intake valve 22 is corrected as will be described later with reference to the flow chart of FIG. 2, the opening / closing angle calculated here is assumed to be a temporary value.

  The target internal EGR amount nEGR is calculated from the target in-cylinder gas temperature TempCYL and the intake pipe absolute pressure PBA by calculating the total filling amount nCYLGAS in the combustion chamber 24 (adding fresh air and the EGR amount). Although it is calculated from the amount nCYLGAS, the target in-cylinder gas temperature TempCYL, the intake air temperature TA, and the exhaust gas temperature TEX, since this is also described in Patent Document 2, detailed description thereof is omitted.

  FIG. 5 is an explanatory diagram showing a calculation example of VT (valve timing) of the intake valve 22 and the exhaust valve 36.

  In FIG. 5, the intake valve 22 is indicated as In-valve, and the exhaust valve 36 is indicated as Ex-valve. Since the engine 10 is operated in the Atkinson cycle, the intake valve In-valve is controlled to be closed late (at the crank angle) as indicated by a solid line. In addition, the characteristic shown with a broken line shows the case where an Atkinson cycle driving | operation is not performed.

  Further, the exhaust valve Ex-valve is controlled as indicated by a solid line in the SI operation, and is controlled so as to close late because internal EGR is performed as described later in the HCCI operation.

  Returning to the description of the flow chart of FIG. 2, the process then proceeds to S18 to calculate the fuel injection amount TOUTmin (n).

  The fuel injection amount TOUTmin calculated in S18 is a value for correcting the opening / closing angle (temporary value) of the intake valve 22 unlike the value calculated in the original fuel injection amount calculation cycle. When the fuel injection amount is at or near the lower limit value, a value for correcting the calculated opening / closing angle (temporary value) of the intake valve 22, more precisely, the calculated opening / closing angle (temporary value) of the intake valve 22. Value) is a value that is intentionally calculated so as to be at or near the lower limit value. Specifically, the lower limit value is zero. The original fuel injection amount is calculated in the vicinity of the TDC of each cylinder, that is, in the TDC cycle.

  FIG. 6 is a sub-routine flowchart showing the processing.

  In the following description, first, the fuel injection amount TOUTmin1 is calculated in S200, the process proceeds to S202, the fuel injection amount TOUTmin2 is calculated, the process proceeds to S204, the fuel injection amount TOUTmin3 is calculated, and the same processing is performed until S20n. N fuel injection amounts up to the amount TOUTmin (n) are calculated.

  FIG. 7 is a sub-routine flow chart showing in detail the fuel injection amount calculation process such as S200 in FIG.

  In the following description, in S300, a characteristic set appropriately from VTn of the intake valve 22 is searched, the direct rate AFW (n) and the carry-off rate BFW (n) are searched, and the adhesion amount Fw is calculated according to the equation shown in the figure.

  VTn is a value when it is assumed that the crank angle is changed by a predetermined crank angle, for example, every 5 degrees, with the opening / closing angle (temporary value) of the intake valve 22 as a center, and therefore the direct rate AFW (n) and the carry-off rate BFW. (N) is a value obtained corresponding to the corresponding opening / closing angle. K is a discrete sample time, more specifically, a program loop time in the flowchart of FIG.

  Note that only the VT of the intake valve 22 is used because, as described at the beginning, when the Atkinson cycle operation is performed, the intake valve 22 is slowly closed, so that the adhering fuel is aspirated rapidly into the combustion chamber 24. When more fuel than required by the engine 10 flows into the engine 24 and the operation is switched to HCCI operation, the deviation of the air-fuel ratio affects the ignition timing of the HCCI, knocking occurs and drivability is deteriorated, and exhaust emission performance is deteriorated. Because there is a risk of doing.

  In the above, the direct rate AFW is the proportion of the fuel injected into the combustion chamber 24 in the fuel injected in a certain cycle (TDC cycle), and the carry-off rate BFW is injected before that cycle. Of the fuel adhering to the wall surface of the intake port, the ratio of the fuel sucked into the combustion chamber 24 in that cycle is shown.

Next, in S302, the calculated fuel injection amount TOUTmin (n) is calculated according to the equation shown using the calculated adhesion amount Fw (n) and the like. In the expression shown, Tcyl is the required injection amount of the engine 10 and is calculated as follows.
Tcyl = Ti × KCMD × KTT + KT

  In the above, Ti: engine excluding basic fuel injection amount obtained by map search from engine speed NE and engine load (for example, fresh air amount detected by air flow meter 62), KCMD: air-fuel ratio correction coefficient, KTT: engine excluding KCMD A multiplication correction term based on the cooling water temperature TW or the like, and KT: a residual addition correction term. The fuel injection amount is specifically defined by the valve opening time of the injector 26.

  6 and 7, the fuel injection amount TOUTmin when the opening / closing angle (temporary value) of the intake valve 22 is changed for each predetermined crank angle around the temporary value is 1, 2, 3. . . Up to n are calculated.

  Returning to the description of the flow chart of FIG. 2, the process then proceeds to S20, where the VT (opening / closing angle) upper limit value of the intake valve 22 is calculated based on the fuel injection amount TOUTmin (n) calculated in S18.

  FIG. 8 is a sub-routine flowchart showing the processing.

  In the following, it is determined whether or not the fuel injection amount TOUTmin1 calculated in S400 exceeds the lower limit value TOUTHCL. The lower limit value TOUTHCL is set to zero or a value near it, more specifically, a value corresponding to the invalid stroke of the injector 26.

  When the result in S400 is affirmative, the routine proceeds to S402, where the opening / closing angle VT1 of the intake valve 22 is set as the VT upper limit value. On the other hand, when the fuel injection amount TOUTmin1 calculated in S400 is a negative value, the determination in S400 is denied and the process proceeds to S404, and it is determined whether or not the calculated fuel injection amount TOUTmin2 exceeds the lower limit value TOUTHCL.

  When the result in S404 is affirmative, the program proceeds to S406, in which the opening / closing angle VT2 of the intake valve 22 is set as the VT upper limit value. On the other hand, when the fuel injection amount TOUTmin2 is a negative value, the determination in S404 is denied and the process proceeds to S408, and it is determined whether or not the calculated fuel injection amount TOUTmin3 exceeds the lower limit value TOUTHCL. When the result in S408 is affirmative, the program proceeds to S410, in which the opening / closing angle VT3 of the intake valve 22 is set as the VT upper limit value.

  When the result in S408 is negative, the process proceeds to S412 while repeating the same processing, and it is determined whether or not the calculated fuel injection amount TOUTmin (n) exceeds the lower limit value TOUTHCL. When the result is affirmative, the process proceeds to S414. The opening / closing angle VT (n) of the intake valve 22 at this time is set as the VT upper limit value. If the result in S412 is negative, the process proceeds to S416, and an appropriately set value VTHH is set as the VT upper limit value.

  Returning to the description of the flowchart of FIG. 2, the process then proceeds to S22, where the opening / closing angle (temporary value) is corrected based on the calculated VT upper limit value, that is, the opening / closing angle (temporary value) of the intake valve 22 is calculated. VT upper limit value. In response to this, the opening and closing of the intake valve 22 is adjusted in the variable valve mechanism 38.

  The above will be described with reference to FIGS.

  FIG. 9 is a time chart when the control according to this embodiment is not performed, and FIG. 10 is a time chart showing the opening / closing operation of the intake valve 22 when the control according to this embodiment is performed. In the case shown in FIG. 9, since the control accuracy of the air-fuel ratio is poor, a torque step is generated, resulting in the disadvantages described above.

  On the other hand, in the control according to this embodiment, the opening / closing angle of the intake valve 22 is calculated according to the operating state such as the rotational speed NE of the engine 10 and the required torque, and the injection is performed based on the calculated opening / closing angle of the intake valve. A fuel wall adhesion amount FW is calculated, and a fuel injection amount is calculated using the calculated wall surface adhesion amount. When the calculated fuel injection amount is at or near the lower limit value TOUTHCL, the calculated intake valve 22 is calculated. It was configured to correct the opening and closing angle of the

  In other words, since the opening / closing angle of the intake valve is gradually corrected while the actual injection amount is made small, as shown in FIG. 10, the opening / closing angle (temporary value) of the intake valve 22 is centered on the temporary value as shown in FIG. The fuel injection amount TOUTmin when it is assumed that the angle is changed for each angle is set to 1, 2, 3,. . . Calculate up to n. Specifically, by calculating the fuel injection amount TOUTmin (n) so as to gradually change from a negative value to a positive value, the calculated intake valve when the fuel injection amount is at or near the lower limit value. More precisely, so as to correct the opening / closing angle (temporary value) of 22, in order to correct the calculated opening / closing angle (temporary value) of the intake valve 22, it is intentionally calculated to be at or near the lower limit value. can do.

  Since the fuel injection amount at that time is very small, it is easy to make the actual injection amount coincide with the required injection amount, thereby making the air-fuel ratio coincide with the target value and stabilizing the combustion. It is possible to limit the change in the opening / closing angle. Accordingly, it is possible to eliminate torque fluctuations, thereby avoiding a decrease in drivability and avoiding a deterioration in exhaust emission performance.

  FIG. 11 is a flowchart similar to FIG. 2 showing the operation of the control apparatus for the compression ignition internal combustion engine according to the second embodiment of the present invention.

  The following description focuses on the differences from the first embodiment. After performing the same processing as in the first embodiment from S500 to S504, the process proceeds to S506, where the VT (valve of the exhaust valve 36 and the intake valve 22 is set. Timing), that is, an opening / closing angle is calculated. In the second embodiment, since the opening / closing angle of the intake valve 22 is not corrected, the calculated opening / closing angle of the intake valve 22 is not a temporary value.

  Next, in S508, a leaning coefficient is calculated.

  FIG. 12 is a subroutine flowchart showing the processing.

  Explained below, in S600, the characteristics set as appropriate are searched from the VT of the intake valve 22 calculated in S506, the direct rate AFW and the carry-off rate BFW are searched, and the adhesion amount Fw (k) is calculated according to the equation shown in the figure. .

  Next, in S602, using the calculated adhesion amount Fw (n) or the like, the minimum required injection amount TCYLmin of the engine 10 is calculated according to the equation shown in the figure. Note that TOUTHCL in the equation is the lower limit value (zero or a value in the vicinity thereof) used in the first embodiment.

  Next, in S604, the temporarily required cylinder inflow fuel amount TCYLP of the engine 10 is calculated according to the equation shown in the figure. Tout in the equation is the fuel injection amount calculated in S302 of the flowchart of FIG. 7 of the first embodiment.

  Next, in S606, a ratio obtained by dividing the calculated minimum required injection amount by the temporary required cylinder inflow fuel amount is set as a leaning coefficient KLEANHC (calculated). Next, the process proceeds to S608, where it is determined whether or not the calculated leaning coefficient KLEANHC exceeds 1.0. If the determination is affirmative, the process proceeds to S610, where it is limited to 1.0.

  Returning to the description of the flowchart of FIG. 11, the process proceeds to S510, and the fuel injection amount Tout is calculated. This calculation is the same as that shown in S302 of the flowchart of FIG. 7 of the first embodiment. At this time, the leaning coefficient KLEANHC is multiplied by the basic fuel injection amount Ti to correct it, similarly to the air-fuel ratio correction coefficient KCMD used when calculating the required injection amount Tcyl.

  Here, the leaning coefficient KLEANHC calculated in the processing from S600 to S606 of FIG. 12 is set to a lower limit value for the required injection amount calculated based on the wall surface adhesion amount determined according to the opening / closing angle of the intake valve 22. Since the leaning coefficient KLEANHC is calculated as the ratio of the required injection amount to be set, in other words, the lean air-fuel ratio is set in accordance with the calculated wall surface adhesion amount so that the fuel injection amount does not fall below the lower limit value. This corresponds to an air-fuel ratio correction coefficient that corrects the direction.

As described above, in the second embodiment, the opening / closing angle of the intake valve 22 is calculated according to the operating state such as the rotational speed NE of the engine 10 and the required torque PMCMD, and the injection is performed based on the calculated opening / closing angle of the intake valve. A leaning coefficient (air-fuel ratio correction coefficient) KLEANHC for calculating the fuel wall surface adhesion amount Fw and correcting the air-fuel ratio in the lean direction according to the calculated wall surface adhesion amount so that the fuel injection amount does not fall below the lower limit value TOUTHCL. And the fuel injection amount T out is calculated using the calculated leaning coefficient.

Accordingly, the actual injection amount can be reduced by correcting the air-fuel ratio in the lean direction. As a result, it becomes easy to make the actual injection amount coincide with the required injection amount, and thus make the air-fuel ratio coincide with the target value. And combustion can be stabilized. As a result, torque fluctuations can be removed, drivability can be avoided, and exhaust emission performance can be prevented from deteriorating.

  The remaining configuration and effects are the same as in the first embodiment.

As described above, in the first embodiment, at least the variable valve mechanism 38 for variably adjusting the intake valve 22 and the ignition means (ignition plug 32 or the like) for igniting the air-fuel mixture in the combustion chamber 24 are provided. A spark ignition (HCCI) operation is performed in which the air-fuel mixture supplied to the combustion chamber is subjected to compression ignition combustion, and the air-fuel mixture is spark-ignited and combusted via the ignition means in an operation region other than the predetermined operation region. In a control apparatus for a compression ignition internal combustion engine (engine) 10 that performs an ignition (SI) operation and further performs the spark ignition (SI) operation in an Atkinson cycle, the operation state of the internal combustion engine (engine) 10 (more specifically, Intake valve opening / closing angle calculating means for calculating the opening / closing angle (temporary value) of the intake valve 22 in accordance with the engine speed NE, the required torque PMCMD, etc. CU30, S16), a direct rate AFW indicating the proportion of fuel injected into the combustion chamber 24 in the cycle in a certain cycle (TDC cycle), and before the cycle Of the fuel that has been injected and adhered to the wall surface of the intake port where the intake valve 22 is disposed, the carry-off rate BFW indicating the proportion of fuel that is drawn into the combustion chamber 24 in the cycle is calculated. Wall surface adhesion amount calculation means (ECU 30, S18, S200) that calculates the wall surface adhesion amount Fw of the injected fuel based on the calculated direct rate AFW and carry-off rate BFW. etc., S300) and the fuel injection amount for correcting the opening and closing angle of the intake valve 22 the calculated using the calculated wall deposit quantity TOUTmin ( ) Such as fuel injection amount calculating means (ECU 30, S18, S200 to calculate a, and S302), and when the fuel injection amount the calculated is in the lower limit TOUTHCL or near, the change of the opening and closing angle of the intake valve 22 Intake valve opening / closing angle correcting means (ECU 30, S20, S22, S400 to S416) for correcting the calculated opening / closing angle of the intake valve so as to limit the engine is configured.

In the second embodiment, at least a variable valve mechanism 38 that variably adjusts the intake valve 22 and ignition means (such as a spark plug 32) for igniting the air-fuel mixture in the combustion chamber 24 are provided. A spark ignition (HCCI) operation in which the air-fuel mixture supplied to the combustion chamber is subjected to compression ignition combustion is performed, and the air-fuel mixture is subjected to spark ignition combustion via the ignition means in an operation region other than the predetermined operation region. SI) In the control device for the compression ignition internal combustion engine (engine) 10 that performs the operation and further performs the spark ignition (SI) operation in the Atkinson cycle, the opening / closing angle of the intake valve 22 is calculated according to the operation state of the internal combustion engine. an intake valve closing angle calculating means for (ECU 30, S506), among the fuel injected into the combustion chamber at a certain cycle (TDC cycle), before Of the direct rate AFW indicating the proportion of fuel sucked into the combustion chamber 24 in the cycle, and the fuel injected before the cycle and attached to the wall of the intake port where the intake valve 22 is disposed, etc. A take-off rate BFW indicating the ratio of fuel sucked into the combustion chamber 24 in the cycle is calculated based on the calculated opening / closing angle of the intake valve 22, and the calculated direct rate AFW and take-off rate BFW are calculated. the wall adhesion amount calculating means for calculating a wall deposit quantity FW of injected fuel based on the bets (ECU 30, S508, S600), so the fuel injection amount does not fall below the lower limit, depending on the wall deposit quantity of the calculated An air-fuel ratio correction coefficient calculating means (ECU 30, S508, S602 to S610) for calculating an air-fuel ratio correction coefficient KLEANHC for correcting the air-fuel ratio in the lean direction; Fuel injection amount calculating means for calculating the fuel injection amount using the air-fuel ratio correction coefficients (ECU 30, S510) and was composed as comprising a.

  In the above description, the VT characteristics of the intake valve 22 and the exhaust valve 36 shown in FIG. 5 are examples, and are not limited thereto. Further, although the intake valve 22 and the exhaust valve 36 are composed of electromagnetic valves and the VT is variably controlled, it may be variably controlled using other mechanisms.

  Further, although the internal EGR is executed in the HCCI operation, the external EGR for returning a part of the exhaust gas to the intake system via the EGR pipe 46 may be executed together with the internal EGR.

    Further, although the exhaust gas temperature TEX is estimated by calculation, as shown by an imaginary line in FIG. 1, a temperature sensor 100 may be provided in the exhaust system and the exhaust gas temperature TEX may be directly measured.

  Although the present invention has been described by taking as an example a configuration in which fuel is injected into the intake port in front of the intake valve 22 using the engine 10 as an example, the present invention is also applicable to a direct injection engine that directly injects fuel into the combustion chamber 24. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an overall control apparatus for a compression ignition internal combustion engine according to a first embodiment of the present invention. It is a flowchart explaining operation | movement of the apparatus shown in FIG. FIG. 3 is a sub-routine flow chart showing a compression ignition operation possible region determination process of FIG. 2. FIG. It is explanatory drawing which shows the characteristic of the map used for the compression ignition possible range determination of FIG. FIG. 3 is an explanatory diagram illustrating a calculation example of VT (valve timing) of an intake valve and an exhaust valve calculated in the process of FIG. 2. FIG. 3 is a sub-routine flow chart showing a fuel injection amount calculation process of FIG. 2. FIG. FIG. 3 is a sub-routine flow chart showing in detail a fuel injection amount calculation process of FIG. 2. FIG. FIG. 3 is a sub-routine flowchart showing a calculation process of a VT (opening / closing angle) upper limit value of the intake valve of FIG. 2. It is a time chart which shows the opening / closing operation | movement of the intake valve, etc. when not performing the control according to this embodiment. It is a time chart which shows the opening / closing operation | movement of the intake valve, etc. at the time of performing the control which concerns on this Example. FIG. 6 is a flow chart similar to FIG. 2 showing the operation of the control apparatus for a compression ignition internal combustion engine according to the second embodiment of the present invention. 12 is a sub-routine flowchart showing the leaning coefficient calculation process of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Compression ignition internal combustion engine (engine), 22 Intake valve, 26 Injector, 30 ECU (electronic control unit), 32 Spark plug (ignition means), 36 Exhaust valve, 38 Variable valve mechanism, 44 Catalytic device, 50 Turbocharger, 56 DBW mechanism, 60 crank angle sensor, 62 air flow meter, 72 water temperature sensor, 74 accelerator opening sensor, 100 temperature sensor

Claims (1)

At least a variable valve mechanism for variably adjusting the intake valve and an ignition means for igniting the air-fuel mixture in the combustion chamber, and performing a compression ignition operation for compressing and combusting the air-fuel mixture supplied to the combustion chamber in a predetermined operation region In addition, in a control apparatus for a compression ignition internal combustion engine that performs a spark ignition operation for spark ignition combustion of the air-fuel mixture via the ignition means in an operation region other than the predetermined operation region, and further performs the spark ignition operation in an Atkinson cycle An intake valve opening / closing angle calculating means for calculating an opening / closing angle of the intake valve in accordance with an operating state of the internal combustion engine, and fuel injected into the combustion chamber in a certain cycle is sucked into the combustion chamber in the cycle. The direct rate that indicates the proportion of fuel that is injected and the fuel that was injected before the cycle and attached to the wall of the intake port where the intake valve is located A take-off rate indicating a ratio of fuel sucked into the combustion chamber in the cycle based on the calculated opening / closing angle of the intake valve, and calculating the direct rate and the take-off rate. And a fuel injection amount for calculating a fuel injection amount for correcting the calculated opening / closing angle of the intake valve using the calculated wall surface adhesion amount. And an intake valve that corrects the calculated opening / closing angle of the intake valve so as to limit a change in the opening / closing angle of the intake valve when the calculated fuel injection amount is at or near a lower limit value. A control apparatus for a compression ignition internal combustion engine, comprising an opening / closing angle correction means.

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