JP2012002076A - Device for control of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for control of an internal combustion engine, capable of properly controlling combustion timing by compression ignition when a combustion mode is switched from an SI combustion mode to an HCCI combustion mode to thereby suppress combustion noise so that merchantability is improved.SOLUTION: In accordance with the control device, when a selected combustion mode is switched from an SI combustion mode to an HCCI combustion mode, an operation by the SI combustion mode is executed as a switching duration SI combustion operation. In the switching duration SI combustion operation, ignition timing IGLOG is controlled so as to be more retarded than basic ignition timing IGMP by a correction amount DIGRS2H (step 86). After the switching duration SI combustion operation, an operation by the HCCI combustion mode is executed, and valve-closing timing of an exhaust valve 5 at that time is controlled so as to be more advanced than valve-closing timing for the SI combustion mode (steps 42, 46).

Description

  The present invention relates to a control apparatus for an internal combustion engine that is operated by switching a combustion mode between an SI combustion mode in which an air-fuel mixture supplied to a combustion chamber is combusted by spark ignition and an HCCI combustion mode in which combustion is performed by compression ignition.

  As a control device for a conventional internal combustion engine, for example, one disclosed in Patent Document 1 is known. This internal combustion engine is operated by switching the combustion mode between the SI combustion mode in which the air-fuel mixture in the combustion chamber is combusted by spark ignition and the HCCI combustion mode in which combustion is performed by compression ignition, and when in a predetermined deceleration operation state Then, a fuel cut for stopping the fuel supply is executed. In this control device, when the fuel supply is resumed after the fuel cut, the operation in the SI combustion mode is executed for a predetermined period even if the internal combustion engine is supposed to be operated in the HCCI combustion mode. Such control prevents misfire caused by a temperature drop in the combustion chamber due to fuel cut.

  Moreover, what was disclosed by patent document 2 is known as another conventional internal combustion engine control apparatus. This internal combustion engine is mounted on a vehicle and is operated by switching the combustion mode between the SI combustion mode and the HCCI combustion mode. The intake pipe is provided with an electric supercharger for supercharging intake air flowing through the intake pipe. In addition to the internal combustion engine, the vehicle includes a motor as a power source. In this control device, when it is determined that the combustion mode should be switched from the SI combustion mode to the HCCI combustion mode, the internal combustion engine is stopped and the motor is driven, and then the supercharger is operated. Thereafter, the internal combustion engine is restarted, the motor is stopped, and the operation in the HCCI combustion mode is executed. Thus, before the operation in the HCCI combustion mode is executed, the pressure in the combustion chamber is controlled to a state suitable for the HCCI combustion mode by operating the supercharger.

JP 2007-56772 A JP 2004-176688 A

  In general, when the combustion mode of the internal combustion engine is switched between the SI combustion mode and the HCCI combustion mode, the temperature of the burned gas generated by the combustion of the air-fuel mixture is higher in the SI combustion mode than in the HCCI combustion mode. Become. For this reason, in the control device of Patent Document 1, when the combustion mode is switched from the SI combustion mode after fuel cut to the HCCI combustion mode, the temperature of the combustion chamber becomes higher than the temperature suitable for the HCCI combustion mode, and compression is performed. There is a possibility that the combustion timing due to ignition is too early than the optimal timing. In that case, the pressure of the combustion chamber rises rapidly, so that the combustion noise becomes loud and the merchantability is reduced.

  Further, in the control device of Patent Document 2, since the internal combustion engine is stopped when the combustion mode is switched to the HCCI combustion mode, the temperature of the combustion chamber is thereby lowered, so that the problem as in Patent Document 1 is unlikely to occur. However, while the internal combustion engine is stopped, supercharging is performed by the supercharger, and as a result, the temperature of the combustion chamber rises as the pressure rises. As a result, the temperature of the combustion chamber is not necessarily set to a temperature suitable for the HCCI combustion mode. I can't control it. For this reason, at the start of operation in the HCCI combustion mode, the combustion timing due to compression ignition may be earlier than the optimal timing, and in this case, the merchantability is reduced. In order to perform the control as described above, it is indispensable to provide a motor as a power source in addition to the internal combustion engine.

  The present invention has been made to solve such a problem, and when the combustion mode is switched from the SI combustion mode to the HCCI combustion mode, the combustion timing by compression ignition can be appropriately controlled, thereby It is an object of the present invention to provide a control device for an internal combustion engine that can suppress combustion noise and improve the merchantability.

  In order to achieve this object, in the invention according to claim 1 of the present application, the combustion mode is divided into the SI combustion mode in which the air-fuel mixture in the combustion chamber 3d is combusted by spark ignition, and the HCCI combustion mode in which combustion is performed by compression ignition. A control apparatus 1 for an internal combustion engine that is operated while being switched and in which the valve timing of an exhaust valve 5 can be changed, and a combustion mode selection means that selects one of an SI combustion mode and an HCCI combustion mode as a combustion mode (Embodiment) When the selected combustion mode is switched from the SI combustion mode to the HCCI combustion mode, the operation in the SI combustion mode is switched to the SI combustion operation at the time of switching. Switching-time SI combustion operation execution means (ECU2) to be executed as HCCI combustion after ignition timing control means (ECU2, step 86 in FIG. 12) for controlling IGLOG to be retarded from the normal ignition timing (basic ignition timing IGMP) for SI combustion mode, and SI combustion operation at the time of switching Exhaust valve timing control means (ECU 2, FIG. 8, FIG. 9) for controlling the valve closing timing of the exhaust valve 5 to the advance side with respect to the valve closing timing for the SI combustion mode when the operation in the mode is executed. It is characterized by providing.

  This internal combustion engine is operated by switching the combustion mode between an SI combustion mode in which the air-fuel mixture in the combustion chamber is combusted by spark ignition and an HCCI combustion mode in which combustion is performed by compression ignition. Further, according to this control device, when the selected combustion mode is switched from the SI combustion mode to the HCCI combustion mode, the operation in the SI combustion mode is executed as the switching-time SI combustion operation. In this switching SI combustion operation, the ignition timing of the internal combustion engine is controlled to be retarded from the normal ignition timing for the SI combustion mode. By controlling the ignition timing to the retard side as described above, the combustion end timing and the propagation speed are delayed, and the temperature of the exhaust gas is increased. For this reason, the amount of burnt gas remaining in the combustion chamber is reduced at the closing timing of the exhaust valve immediately after the ignition timing retarding control is performed. In addition, since the SI combustion mode has higher combustion stability than the HCCI combustion mode, even if the ignition timing is controlled to the retard side as described above, it hardly affects the stability of the combustion state. .

  Further, according to this control device, the operation in the HCCI combustion mode is executed after the switching SI combustion operation, and the closing timing of the exhaust valve at that time is controlled to the advance side from the closing timing for the SI combustion mode. To do. As a result, the amount of burned gas remaining in the combustion chamber increases, and the pressure and temperature of the combustion chamber increase. As described above, the burned gas remaining in the combustion chamber at the closing timing of the exhaust valve immediately after the ignition timing retarding control is performed by the retarding control of the ignition timing during the switching SI combustion operation. And the amount of fresh air in the combustion chamber at the subsequent valve closing timing of the intake valve increases. Therefore, if the fuel supply amount is the same, the air-fuel ratio can be made lean, whereby the compression ignition timing can be controlled to the retard side.

  As described above, while maintaining the stability of the combustion state at the time of switching from the SI combustion mode to the HCCI combustion mode, it is possible to appropriately control the combustion timing by the compression ignition in the HCCI combustion mode, thereby suppressing the combustion noise, Can be improved.

  According to a second aspect of the present invention, in the control device 1 for an internal combustion engine according to the first aspect, the valve closing timing for the HCCI combustion mode from the start of the control to the advance side of the valve closing timing by the exhaust valve timing control means. Control period calculation means (ECU2, steps 36 and 37 in FIG. 8) for calculating a period until the switching to the valve is completed as a valve closing timing control period (exhaust VT switching counter value CVTECEX), and exhaust valve timing control When the calculated valve closing timing control period is shorter than the switching time SI combustion operation execution period (retarding cycle number CSRDS2H), the end of the valve closing timing control period is the switching time SI combustion operation execution. The control of the valve closing timing is started later than the SI combustion operation at the time of switching so as to coincide with the end of the period (step 4 in FIG. 8). 46), the switching time SI combustion operation execution means controls the valve closing timing when the switching time SI combustion operation execution period is shorter than the valve closing timing control period. The SI combustion operation at the time of switching is started later than the valve closing timing control so as to coincide with the end of the period (step 84 in FIG. 12).

  According to this configuration, the period from the start of the control to the advance side of the valve closing timing to the completion of switching to the valve closing timing for the HCCI combustion mode is calculated as the control period of the valve closing timing. When the control period of the valve closing timing is shorter than the execution period of the SI combustion operation at switching, the control of the valve closing timing is started later than the SI combustion operation at switching, and the execution period of the SI combustion operation at switching Is shorter than the control period of the valve closing timing, the SI combustion operation at the time of switching is started later than the control of the valve closing timing, so that the execution period of the SI combustion operation at the time of switching ends and the valve closing timing is controlled. Make the end of the period coincide with each other.

  This is due to the following reason. When the switching to the valve closing timing for the HCCI combustion mode is completed first, the switching is performed in a state where the amount of burned gas remaining in the combustion chamber is large until the SI combustion operation at the time of switching ends. As a result of the SI combustion operation, the combustion state deteriorates. On the other hand, when the execution period of the SI combustion operation at the time of switching is shorter than the control period of the valve closing timing, the normal SI without the retard angle control is thereafter performed until the control to the advance side of the valve closing timing ends. As a result of the operation in the combustion mode, the temperature of the combustion chamber once lowered by the switching SI combustion operation will rise again. Therefore, as described above, by matching the end of the control period of the valve closing timing and the end of the execution period of the SI combustion operation at the time of switching, while maintaining the combustion state in the SI combustion operation at the time of switching well, the HCCI The state of the air-fuel mixture in the combustion chamber at the start of operation in the combustion mode can be controlled more appropriately.

  According to a third aspect of the present invention, in the internal combustion engine control apparatus 1 according to the first or second aspect, is the switching to the valve closing timing for the HCCI combustion mode completed based on the control period of the valve closing timing? First determination means (ECU 2, step 84 in FIG. 12) for determining whether or not, and combustion parameter detection means (in-cylinder pressure sensor 24) for detecting a combustion parameter (maximum in-cylinder pressure value PCYLMAX) representing the combustion state of the internal combustion engine And a second determination means (ECU2, FIG. 11) for determining whether or not the switching to the valve closing timing for the HCCI combustion mode is completed based on the detected combustion parameter. The combustion operation execution means completes the switching of the valve closing timing by the second determination means when it is determined by the first determination means that the switching of the valve closing timing has been completed. If it is determined not, characterized by continuing the switching SI combustion operation (step 81, 86 in FIG. 12).

  According to this configuration, it is determined whether or not the switching to the valve closing timing for the HCCI combustion mode has been completed based on the control period of the valve closing timing. Further, based on the combustion parameter representing the combustion state of the internal combustion engine, it is determined whether or not the switching to the valve closing timing for the HCCI combustion mode has been completed. And when it is determined that the switching of the valve closing timing is completed by the determination based on the control period of the valve closing timing, when it is determined that the switching of the valve closing timing is not completed by the determination based on the combustion parameter, The SI combustion operation is continued during switching. The control period of the valve closing timing changes due to individual differences of internal combustion engines and aging deterioration. Therefore, when the above two determination results are different from each other, priority is given to the determination based on the combustion parameter representing the actual combustion state of the internal combustion engine, and this determination determines that the switching of the valve closing timing is not completed. Sometimes, the switching SI combustion operation is continued. As a result, the operation in the HCCI combustion mode can be started in a state where the switching of the valve closing timing is surely completed, and thereby the state and pressure of the air-fuel mixture in the combustion chamber at the start of the operation in the HCCI combustion mode can be determined. It can be controlled more appropriately.

  According to a fourth aspect of the present invention, in the internal combustion engine control apparatus 1 according to any one of the first to third aspects, a rotational speed detection means (crank angle sensor) for detecting the rotational speed of the internal combustion engine 3 (engine rotational speed NE). 20), load detection means (crank angle sensor 20, accelerator opening sensor 22) for detecting the load (required torque PMCMD) of the internal combustion engine 3, and switching according to the detected rotational speed and load of the internal combustion engine 3. An execution period determining means (ECU 2, steps 38 and 39 in FIG. 8) for determining the execution period of the hour SI combustion operation is further provided.

  Generally, the temperature of a combustion chamber changes according to the rotation speed and load of an internal combustion engine. According to this configuration, since the execution period of the SI combustion operation at the time of switching is determined according to the detected rotational speed and load of the actual internal combustion engine, the temperature of the combustion chamber at the end can be appropriately reduced. In addition, the operation in the HCCI combustion mode can be started at an appropriate timing.

  According to a fifth aspect of the present invention, in the control device 1 for an internal combustion engine according to any one of the first to third aspects, load detection means (a crank angle sensor 20, an accelerator) that detects a load (required torque PMCMD) of the internal combustion engine 3 is provided. An opening sensor 22) and exhaust gas temperature detection means (exhaust temperature sensor 23) for detecting the temperature of exhaust gas (exhaust temperature TEX) of the internal combustion engine 3, and the ignition timing control means detects the detected internal combustion engine 3 The ignition timing retard amount (retard angle correction amount DIGRS2H) during the switching SI combustion operation is set according to the load and exhaust gas temperature (steps 85 and 86 in FIG. 12).

  Generally, when the load on the internal combustion engine is different, the amount of change in the temperature of the combustion chamber with respect to the retard amount of the ignition timing is different, and the ignition timing limit delay that can maintain the stability of the combustion state without causing misfire or the like. Angular amount is different. Further, since the temperature of the exhaust gas reflects the temperature of the combustion chamber, if the temperature of the exhaust gas is different, the amount of change in the temperature of the combustion chamber with respect to the retard amount of the ignition timing is also different. According to this configuration, the retard amount of the ignition timing during the switching SI combustion operation is set according to the detected actual load of the internal combustion engine and the temperature of the exhaust gas. While reliably maintaining stability, the temperature of the combustion chamber can be appropriately reduced at the end.

1 is a diagram schematically showing a control device for an internal combustion engine according to an embodiment of the present invention together with the internal combustion engine. It is a block diagram of a control apparatus. It is a figure which shows the valve lift curve of an intake valve and an exhaust valve according to the change of the valve timing by an intake VT switching mechanism and an exhaust VT switching mechanism. It is a flowchart which shows the control processing of an internal combustion engine. It is a flowchart which shows a combustion mode determination process. It is a figure which shows an example of the map used for determination of a driving | operation area | region. It is a flowchart which shows a valve timing control process. It is a flowchart which shows an exhaust valve timing control process. It is a flowchart which shows the remaining part of an exhaust valve timing control process. It is a flowchart which shows an exhaust valve timing determination process. It is a flowchart which shows an actual valve timing determination process. It is a flowchart which shows an ignition timing setting process. 13 is a map for calculating an ignition timing retardation correction amount used in the ignition timing setting process of FIG. It is a figure which shows the operation example obtained by the control processing of the internal combustion engine by embodiment. It is a figure which shows the other operation example obtained by the control processing of the internal combustion engine by embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. An internal combustion engine (hereinafter referred to as “engine”) 3 to which the fuel injection control device 1 according to the present embodiment shown in FIG. 1 is applied is, for example, a 4-cylinder gasoline engine mounted on a vehicle (not shown).

  An intake pipe 8 and an exhaust pipe 13 are connected to a cylinder head 3c of the engine 3 for each cylinder 3a, and an in-cylinder fuel injection valve 12 and a spark plug 10 are attached so as to face the combustion chamber 3d. (Only one is shown). The in-cylinder fuel injection valve 12 generates an air-fuel mixture by injecting fuel to the vicinity of the spark plug 10 in the combustion chamber 3d during the compression stroke when performing combustion by compression ignition. The valve opening time and the opening / closing timing of the in-cylinder fuel injection valve 12 are controlled by the ECU 2, thereby controlling the fuel injection amount and the fuel injection timing.

  The engine 3 also has an intake valve 4 and an exhaust valve 5 for each cylinder 3a, an intake VT switching mechanism 6 for opening / closing the intake valve 4 and switching a valve timing, and opening / closing the exhaust valve 5 and switching a valve timing. An exhaust VT switching mechanism 7 is provided.

  The intake VT switching mechanism 6 is a well-known mechanism that switches the valve timing of the intake valve 4 (hereinafter referred to as “intake valve timing”) into two stages of a high-speed valve timing and a low-speed valve timing, and is provided integrally with the intake camshaft. A low-speed cam and a high-speed cam (both not shown), a low-speed rocker arm and a high-speed rocker arm (both not shown) rotatably attached to the intake rocker arm shaft.

  The intake VT switching mechanism 6 is of a hydraulic type and is connected to a hydraulic pump (not shown) via an oil passage (not shown) and an intake VT control valve 6a (see FIG. 2). This hydraulic pump is connected to the crankshaft 3e, is driven by the engine 3, and supplies hydraulic pressure to an intake VT control valve 6a and an exhaust VT control valve 7a (see FIG. 2) described later.

  In the intake VT switching mechanism 6, the intake valve timing is set to the low speed valve timing when the hydraulic pressure is not supplied, and the intake valve timing is set to the high speed valve timing when the hydraulic pressure is supplied. The intake VT control valve 6a is a normally closed solenoid valve, which is closed when turned off by a control input signal from the ECU 2, and stops the supply of hydraulic pressure from the hydraulic pump to the intake VT switching mechanism 6 side. At the same time, the valve is opened when it is turned ON, and the hydraulic pressure from the hydraulic pump is supplied to the intake VT switching mechanism 6 side. With the above configuration, the operation mode of the intake VT switching mechanism 6 is switched between the high-speed valve timing mode and the low-speed valve timing mode according to ON / OFF of the intake VT control valve 6a.

  In the low-speed valve timing mode, the intake valve 4 is driven according to the low-speed cam as the intake camshaft rotates, so that the valve opens according to the valve lift curve shown by the solid line in FIG. Become. On the other hand, in the high-speed valve timing mode, the intake valve 4 is driven according to the high-speed cam as the intake camshaft rotates, so that the valve opens according to the valve lift curve shown by the broken line in FIG. It's time. As shown in the figure, at this high speed valve timing, the maximum lift of the intake valve 4 is larger than the low speed valve timing, and the opening timing of the intake valve 4 is earlier (advanced side) and closed. The valve opening period becomes longer as the valve timing becomes later (on the retard side). As a result, air is sucked into the cylinder 3a with higher charging efficiency.

  The exhaust VT switching mechanism 7 switches the valve timing of the exhaust valve 5 (hereinafter referred to as “exhaust valve timing”) into two stages of a high speed valve timing and a low speed valve timing. The structure is the same as that of the mechanism 6. Therefore, in the exhaust VT switching mechanism 7, the operation mode is switched between the high speed valve timing mode and the low speed valve timing mode according to the ON / OFF state of the exhaust VT control valve 7a.

  In the high-speed valve timing mode, the exhaust valve 5 is driven according to the high-speed cam as the exhaust camshaft rotates, so that the valve opens according to the valve lift curve indicated by the broken line in FIG. Become. On the other hand, in the low-speed valve timing mode, the exhaust valve 5 is driven according to the low-speed cam as the exhaust camshaft rotates, so that the valve opens according to the valve lift curve shown by the solid line in FIG. It's time.

  As shown in the figure, at the low speed valve timing, the maximum lift of the exhaust valve 5 becomes smaller and the opening timing of the exhaust valve 5 is delayed (at the retarded angle side) and closed as compared with the high speed valve timing. The valve opening period is shortened by the earlier timing (advanced side). In addition, the valve overlap with the intake valve 4 is eliminated, and as a result, the amount of burned gas remaining in the combustion chamber 3d, that is, the internal EGR amount increases.

  As will be described later, in the present embodiment, the exhaust valve timing is set to the low speed valve timing in the HCCI combustion mode, and the high speed valve timing in the SI combustion mode. The low speed valve timing is called “HCCI timing”, and the high speed valve timing is called “SI timing”.

  Further, the spark plug 10 sparks the air-fuel mixture generated by the fuel from the in-cylinder fuel injection valve 12 to generate a fire type for causing compression ignition. The ignition timing of the spark plug 10 is controlled by the ECU 2.

  An in-cylinder pressure sensor 24 is integrally attached to the in-cylinder fuel injection valve 12. The in-cylinder pressure sensor 24 is composed of a ring-shaped piezoelectric element, and outputs a detection signal indicating the amount of change in pressure in the cylinder 3a to the ECU 2. The ECU 2 calculates the pressure in the cylinder 3a (hereinafter referred to as “in-cylinder pressure”) PCYL based on this detection signal.

  On the other hand, a crank angle sensor 20 is provided on the crankshaft 3 e of the engine 3. The crank angle sensor 20 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b in any one of the cylinders 3a is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke. Output every 180 °.

  A port fuel injection valve 11 is provided for each cylinder 3 a in the intake manifold of the intake pipe 8. The port fuel injection valve 11 injects fuel toward the intake port 8a in the intake stroke when performing combustion by compression ignition. Further, the valve opening time and the opening / closing timing of the port fuel injection valve 11 are controlled by the ECU 2, thereby controlling the fuel injection amount and the fuel injection timing.

  The intake pipe 8 is provided with a throttle valve 9. The opening degree of the throttle valve 9 is controlled by driving a TH actuator (not shown) by a control signal from the ECU 2, thereby controlling the amount of intake air taken into the engine 3.

  An intake pressure sensor 25 is provided downstream of the throttle valve 9 in the intake pipe 8. The intake pressure sensor 25 detects a pressure (hereinafter referred to as “intake pressure”) PBA in the intake pipe 8 and outputs a detection signal to the ECU 2.

  Further, the ECU 2 receives from the water temperature sensor 21 a detection signal indicating the temperature TW of the cooling water of the engine 3 (hereinafter referred to as “engine water temperature”) TW from the accelerator opening sensor 22 to the opening of the accelerator pedal (not shown). A detection signal representing AP (hereinafter referred to as “accelerator opening”) and a detection signal representing the temperature TEX of exhaust gas discharged from the cylinder 3a (hereinafter referred to as “exhaust temperature”) TEX are output from the exhaust temperature sensor 23, respectively.

  The ECU 2 is composed of a microcomputer including an I / O interface, a CPU, a RAM, and a ROM (all not shown). The ECU 2 determines the operating state of the engine 3 according to the detection signals from the various sensors 20 to 25 described above, and executes various control processes of the engine 3 according to the determination result. In this embodiment, the ECU 2 performs the combustion mode selection means, the switching time SI combustion operation execution means, the ignition timing control means, the exhaust valve timing control means, the control period calculation means, the first determination means, the second determination means, and the execution. It corresponds to the period determining means.

  FIG. 4 shows a control process of the engine 3 executed by the ECU 2. This process is executed in synchronization with the generation of the TDC signal. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), the required torque PMCMD is calculated by searching a predetermined map (not shown) according to the engine speed NE and the accelerator pedal opening AP. To do.

  Next, in step 2, a combustion mode determination process is executed. This combustion mode determination process selects either the HCCI combustion mode or the SI combustion mode as the combustion mode to be executed, and FIG. 5 shows the subroutine.

  In this process, first, in step 10, it is determined whether or not the engine water temperature TW is higher than a predetermined temperature TWHCCI. The predetermined temperature TWHCCI is set to a lower limit value of the engine water temperature TW that can execute the HCCI combustion mode. When the answer is YES, in step 11, by searching the map shown in FIG. 6 according to the required torque PMCMD and the engine speed NE, an HCCI region in which the engine 3 should execute the HCCI combustion mode (hatched in the figure) It is determined whether it is in the area indicated by.

  When the answer is YES and the engine 3 is in the HCCI region, it is determined that the execution condition of the HCCI combustion mode is established, and the HCCI combustion mode should be executed. The combustion mode flag F_HCCI is set to “1”, and this process ends.

  On the other hand, when the answer to step 10 is NO and TW ≦ TWHCCI, or when the answer to step 11 is NO and the engine 3 is in the SI region, the execution condition of the HCCI combustion mode is not satisfied, and SI In order to determine that the combustion mode should be executed and to represent this, in step 13, the HCCI combustion mode flag F_HCCI is set to “0”, and this processing is terminated.

  Returning to FIG. 4, in step 3 following step 2, valve timing control processing is executed. This valve timing control process controls the intake valve timing and the exhaust valve timing in accordance with the combustion mode selected as described above, and details thereof will be described later.

  Next, in step 4, an exhaust valve timing (exhaust VT) determination process is executed. This exhaust valve timing determination process is to determine the exhaust valve timing according to the selected combustion modes and their transitions, and the details will be described later.

  Next, in step 5, an ignition timing setting process is executed, and this process is terminated. Details of the ignition timing setting process will be described later.

  Hereinafter, the valve timing control process executed in step 3 of FIG. 4 will be described with reference to FIG. In this process, first, in step 20, an intake valve timing (intake VT) control process is executed. In this intake valve timing control process, the ON / OFF state of the intake VT control valve 6a is controlled according to the engine speed NE, the required torque PMCMD, and the like, whereby the intake valve timing is set to the SI timing and the HCCI timing. Controlled on one side.

  Next, in step 21, exhaust valve timing control processing is executed. FIG. 8 shows the subroutine. In this process, first, in step 30, the exhaust VT setting flag F_VTECEXS set and stored at the previous time is shifted to its previous value F_VTECEXZ.

  Next, in step 31, it is determined whether or not the HCCI combustion mode flag F_HCCI is “1”. If the answer is NO and the SI combustion mode is selected, the retard cycle number CSRDS2H and the retard correction amount DIGRS2H, which will be described later, are both reset to 0 (steps 32 and 33) and the exhaust VT is set. The flag F_VTECEXS is set to “0” (step 34), and this process ends. When the exhaust VT setting flag F_VTECEXS is set to “0” in this way, the exhaust VT control valve 7a is turned OFF, thereby controlling the exhaust valve timing to the SI timing.

  On the other hand, if the answer to step 31 is YES and the HCCI combustion mode is selected, it is determined in step 35 whether or not the previous value F_HCCIZ of the HCCI combustion mode flag is “0”. If the answer is YES and the selected combustion mode is immediately after switching from the SI combustion mode to the HCCI combustion mode, a predetermined map (not shown) is determined in step 36 according to the engine speed NE and the engine water temperature TW. The map value CVTECEHM is calculated by searching for, and in step 37, the calculated map value CVTECEHM is set as the exhaust VT switching counter value CVTECEX. The exhaust VT switching counter value CVTECEX corresponds to the time required for switching the exhaust valve timing. In this map, the map value CVTECTHM is set to a larger value as the engine speed NE is lower and the engine coolant temperature TW is lower.

  Next, in step 38, a map value CSRDS2HM is calculated by searching a predetermined map (not shown) according to the engine speed NE and the required torque PMCMD, and in step 39, the calculated map value CSRDS2HM is calculated. Is set as the retard cycle number CSRDS2H. This retard cycle number CSRDS2H corresponds to an execution period of ignition timing retard correction control which will be described later. In this map, the map value CSRDS2HM is set to a larger value as the engine speed NE is higher and as the required torque PMCMD is larger.

  Next, in step 40, it is determined whether or not the exhaust VT switching counter value CVTECEX is equal to or greater than the retard cycle number CSRDS2H. If the answer is YES, it is determined that the control of the exhaust valve timing to the HCCI timing should be started. In step 41, the exhaust VT switching delay DVTECEX is set to 0, and in step 42, the exhaust VT setting flag F_VTECEXS is set. Set to “1”, and the process ends. When the exhaust VT setting flag F_VTECEXS is set to “1”, the exhaust VT control valve 7a is turned on, whereby the exhaust valve timing is controlled to the HCCI timing.

  On the other hand, if the answer to step 40 is NO and CVTECEX <CSRDS2H, it is determined that control of the exhaust valve timing to the HCCI timing is not started, and in step 43, the exhaust VT switching delay DVTECEX is set to the number of retarded cycles. The difference between CSRDS2H and the exhaust VT switching counter value CVTECEX is set (= CSRDS2H−CVTECEX), and this process is terminated.

  On the other hand, if the answer to step 35 is NO and the selected combustion mode is not immediately after switching from the SI combustion mode to the HCCI combustion mode, it is determined in step 44 whether the exhaust VT switching delay DVTECEX is zero. To do. When this answer is NO, it is determined that the control of the exhaust valve timing to the HCCI timing is not yet started, and in step 45, the exhaust VT switching delay DVTECEX is decremented, and this process is terminated.

  On the other hand, if the answer to step 44 is YES and DVTECEX = 0, it is determined that control of the exhaust valve timing to the HCCI timing should be started. In step 46, the exhaust VT setting flag F_VTECEXS is set to “1”. By setting to, the exhaust valve timing is controlled to the HCCI timing, and this processing ends.

  Next, the exhaust valve timing determination process executed in step 4 of FIG. 4 will be described with reference to FIG. In this process, first, in step 50, it is determined whether or not the exhaust VT setting flag F_VTECEXS is “0”. If the answer to this question is YES, it is determined in step 51 whether or not the previous value F_VTECEXZ of the exhaust VT setting flag is “1”.

  If the answer is YES and immediately after the control of the exhaust valve timing to the SI timing is started, a predetermined SI map (not shown) is displayed in step 52 according to the engine speed NE and the engine water temperature TW. By searching, the map value CVTECESM is calculated, and in step 53, the calculated map value CVTECESM is set as the exhaust VT switching counter value CVTECEX, and the process proceeds to step 54.

  On the other hand, when the answer to step 51 is NO and not immediately after the control of the exhaust valve timing to the SI timing is started, the above steps 52 and 53 are skipped and the process proceeds to step 54.

  In this step 54, it is determined whether or not the exhaust VT switching counter value CVTECEX is zero. If this answer is NO, the exhaust VT switching counter value CVTECEX is decremented in step 55, and the exhaust VT determination flag F_VTECEXF is set in step 56, assuming that the exhaust valve timing has not actually switched to the SI timing yet. Set to “1” and proceed to Step 64 described below.

  On the other hand, when the answer to step 54 is YES and the exhaust VT switching counter value CVTECEX = 0, the exhaust valve timing is actually switched to the SI timing, and in step 57, the exhaust VT determination flag F_VTECEXF is set to “0”. To step 64.

  As described above, when the time corresponding to the map value CVTECSM calculated in step 52 has elapsed after the control of the exhaust valve timing to the SI timing is started, the exhaust valve timing is switched to the SI timing. In order to represent that, the exhaust VT determination flag F_VTECEXF is set to “0”.

  On the other hand, if the answer to step 50 is NO, it is determined in step 58 whether or not the previous value F_VTECEXZ of the exhaust VT setting flag is “0”. If the answer is YES and immediately after the control of the exhaust valve timing to the HCCI timing is started, a predetermined HCCI map (not shown) is displayed in step 59 according to the engine speed NE and the engine water temperature TW. By searching, the map value CVTECTHM is calculated. In step 60, the calculated map value CVTECTHM is set as the exhaust VT switching counter value CVTECEX, and the process proceeds to step 61.

  On the other hand, if the answer to step 58 is NO and not immediately after the control of the exhaust valve timing to the HCCI timing is started, the above steps 59 and 60 are skipped and the process proceeds to step 61.

  In this step 61, it is determined whether or not the exhaust VT switching counter value CVTECEX is zero. When this answer is NO, the exhaust VT switching counter value CVTECEX is decremented in step 62, and the exhaust VT determination flag F_VTECEXF is set in step 63, assuming that the exhaust valve timing has not actually switched to the HCCI timing. Set to “0” and go to step 64.

  On the other hand, when the answer to step 61 is YES and the exhaust VT switching counter value CVTECEX = 0, it is determined that the exhaust valve timing is actually switched to the HCCI timing, and the above-described step 56 is executed to execute the exhaust VT determination flag. F_VTECEXF is set to “1”. As described above, when the time corresponding to the map value CVTICEHM calculated in step 59 has elapsed since the control of the exhaust valve timing to the HCCI timing is started, the exhaust valve timing is switched to the HCCI timing. The exhaust VT determination flag F_VTECEXF is set to “1” to determine that it has been completed and to indicate that.

  In step 64 following step 56, 57 or 63, an actual valve timing (actual VT) determination process is executed, and this process ends. In the control described above, it is determined whether or not the exhaust valve timing has actually been switched based on the exhaust VT switching counter value CVTECEX, whereas this actual valve timing determination processing is based on the detected in-cylinder pressure PCYL. The actual exhaust valve timing is determined in a confirming manner. FIG. 11 shows the subroutine.

  In this process, first, in step 70, it is determined whether or not the maximum value PCYLMAX of the in-cylinder pressure PCYL detected in the exhaust stroke is equal to or greater than a predetermined value PREF. When the answer is YES, since the maximum value PCYLMAX is large and the valve closing timing of the exhaust valve 5 is estimated to be early, it is determined that the actual exhaust valve timing is the HCCI timing. The VT determination flag F_VTECEXP is set to “1”, and this process ends.

  On the other hand, if the answer to step 70 is NO and PCYLMAX <PREF, it is determined that the actual exhaust valve timing is the SI timing. In step 72, the actual VT determination flag F_VTECEXP is set to “0”. The process ends.

  Next, the ignition timing setting process will be described with reference to FIG. In this process, first, in step 80, it is determined whether or not the exhaust VT determination flag F_VTECEXF is “1”. When the answer is NO, in step 83, it is determined whether or not the exhaust VT switching counter value CVTECEX is zero. When the answer is NO, in step 84, it is determined whether or not the exhaust VT switching counter value CVTECEX is equal to or less than the retard cycle number CSRDS2H.

  When this answer is YES, that is, when the control of the exhaust valve timing from the SI timing to the HCCI timing is being performed and the exhaust VT switching counter value CVTECEX is less than or equal to the retard cycle number CSRDS2H, the SI combustion operation at switching is performed. Then, the retard angle correction control of the ignition timing IGLOG is executed.

  Specifically, in step 85, the map value DIGRS2HM is calculated by searching the map shown in FIG. 13 according to the required torque PMCMD and the exhaust temperature TEX, and in step 86, the calculated map value DIGRS2HM is ignited. The delay angle correction amount DIGRS2H of the timing IGLOG is set, and the routine proceeds to step 87 described later. In this map, the map value DIGRS2HM is set to a larger value as the required torque BMEP is smaller and the exhaust temperature TEX is higher than the two required torques PMCMD (PMCMD1 <PMCMD2) and the exhaust temperature TEX. When requested torque PMCMD is other than the above two values, map value DIGRS2HM is calculated by interpolation calculation.

  On the other hand, in other cases, specifically, when the answer to step 80 is YES and it is determined that the exhaust valve timing is the HCCI timing based on the exhaust VT switching counter value CVTECEX, step 83 is performed. If the answer to step 84 is YES and the exhaust valve timing is not being controlled, or if the answer to step 84 is NO and the exhaust VT switching counter value CVTECEX is greater than the retard cycle number CSRDS2H, the process proceeds to step 81.

  In this step 81, it is determined whether or not the actual VT determination flag F_VTECEXP is “0”. If the answer is NO and it is determined that the actual exhaust valve timing is the HCCI timing based on the in-cylinder pressure PCYL, the retard correction amount DIGRS2H is set to 0 in step 82 and the routine proceeds to step 87. .

  On the other hand, when the answer to step 81 is YES and the actual exhaust valve timing is determined to be the SI timing, the routine proceeds to steps 85 and 86, where the retard correction amount DIGRS2H of the ignition timing IGLOG is set to the map value DIGRS2HM. Set to.

  In step 87 following step 82 or 86, a map value IGMAP is calculated by searching a predetermined map (not shown) according to the engine speed NE and the intake pressure PBA, and calculated in step 88. The map value IGMAP is set as the basic ignition timing IGMP.

  Next, at step 89, the ignition timing IGLOG is set to the difference (= IGMP−DIGRS2H) between the basic ignition timing IGMP and the retard correction amount DIGRS2H, and this process ends.

  FIG. 14 shows an operation example obtained by the control process of the engine 3 described so far in the case where the set value (= map value CVTICEHM) of the exhaust VT switching counter is larger than the retard cycle number CSRDS2H. In this example, since the execution condition of the HCCI combustion mode is not satisfied until time t1, the SI combustion mode is selected, the HCCI combustion mode flag F_HCCI is set to “0”, and the operation in the SI combustion mode is performed. Has been done. Further, as the exhaust valve timing is controlled to the SI timing, the exhaust VT setting flag F_VTECEXS is set to “0”, and the retardation correction amount DIGRS2H is set to 0.

  When the execution condition of the HCCI combustion mode is satisfied from this state (t1), the HCCI combustion mode flag F_HCCI is set to “1” in accordance with the selection of the HCCI combustion mode (step 12 in FIG. 5), and the exhaust VT. The switching counter value CVTECEX is set to the value CVTECTHM (step 37 in FIG. 8). At the same time, the exhaust VT setting flag F_VTECEXS is set to “1” (step 42 in FIG. 8), and control of the exhaust valve timing to the HCCI timing is started.

  Thereafter, when the exhaust VT switching counter value CVTECEX decreases and becomes equal to the retarding cycle number CSRDS2H (t2, step 84 in FIG. 12: YES), the SI combustion operation at the time of switching is started, and the retarding correction amount DIGRS2H is By setting the value DIGRS2HM (step 86 in FIG. 12), the ignition timing IGLOG is controlled to be retarded, and the ignition timing IGLOG is delayed by the retard correction amount DIGRS2H from the basic ignition timing IGMP so far. The angled value (= IGMP-DIGRS2H) is set (step 89 in FIG. 12).

  Thereafter, the exhaust VT switching counter value CVTECEX becomes 0 (step 83 in FIG. 12: YES), and when the exhaust valve timing is switched to the HCCI timing (t3), the exhaust VT determination flag F_VTECEXF is set to “1”. (Step 56 in FIG. 10), the retard correction amount DIGRS2H is returned to 0 (Steps 80 and 82 in FIG. 12), whereby the control of the ignition timing IGLOG toward the retard side is completed, and thereafter (after t3). Is operated in the HCCI combustion mode.

  FIG. 15 shows an operation example obtained by the control process of the engine 3 when the set value of the exhaust VT switching counter is larger than the retard cycle number CSRDS2H. Other conditions are the same as those in FIG. In this example, even if the execution condition of the HCCI combustion mode is satisfied (t11) and the HCCI combustion mode flag F_HCCI is set to “1” according to the selection of the HCCI combustion mode, the exhaust VT switching delay DVTECEX is Until it becomes 0 (t11 to t12), the control of the exhaust valve timing to the HCCI timing is not started (step 44 in FIG. 9: NO). On the other hand, the control to the retard side of the ignition timing IGLOG as the SI combustion operation at the time of switching is started simultaneously with the establishment of the execution condition of the HCCI combustion mode (step 84 in FIG. 12: YES).

  Thereafter, when the exhaust VT switching delay DVTECEX becomes 0 (t12, step 44 in FIG. 9: YES), the exhaust VT setting flag F_VTECEXS is set to “1” (step 46 in FIG. 9), and the exhaust valve timing is changed. Control to the HCCI timing is started, and the exhaust VT switching counter value CVTECEX starts to decrease (step 55 in FIG. 10). The subsequent operation (after t12) is the same as that in FIG. 14 (after t2).

  As described above, according to the present embodiment, when the HCCI combustion mode is selected during operation in the SI combustion mode, the ignition timing IGLOG is retarded by the retardation correction amount DIGRS2H from the basic ignition timing IGMP so far. Since the SI combustion operation at the time of switching controlled to the side is executed, the temperature of the combustion chamber 3d can be lowered as compared with the operation in the normal SI combustion mode so far. In addition, since the SI combustion mode has higher combustion stability than the HCCI combustion mode, the stability of the combustion state can be maintained even if the ignition timing IGLOG is controlled to the retard side as described above. .

  Further, according to this control apparatus, after the switching time SI combustion operation, the operation in the HCCI combustion mode is started, and the exhaust valve timing at that time is set to the HCCI in which the valve closing timing is on the advance side with respect to the SI timing. Control the timing. As a result, the in-cylinder pressure PCYL and the temperature of the combustion chamber 3d are increased, and the temperature of the combustion chamber 3d is once decreased by the SI combustion operation at the time of switching because the temperature of the combustion chamber 3d is once decreased at the start of the operation by HCCI combustion. Can be appropriately controlled without excessively increasing the value. Therefore, while maintaining the stability of the combustion state at the time of switching from the SI combustion mode to the HCCI combustion mode, it is possible to appropriately control the combustion timing by compression ignition in the HCCI combustion mode, thereby suppressing the combustion noise and the merchantability. Can be improved.

  Further, since the retard cycle number CSRDS2H corresponding to the execution time of the SI combustion operation at the time of switching is calculated according to the detected actual engine speed NE and the required torque PMCMD, the combustion at the end of the SI combustion operation at the time of switching is calculated. The temperature of the chamber 3d can be lowered appropriately, and the operation in the HCCI combustion mode can be started at an appropriate timing.

  Further, since the retard correction amount DIGRS2H of the ignition timing IGLOG is calculated according to the detected actual required torque PMCMD and the exhaust gas temperature TEX, the retard control of the ignition timing IGLOG can be appropriately performed. While reliably maintaining the stability of the combustion state in the SI combustion operation at the time of switching, the temperature of the combustion chamber 3d at the end can be appropriately reduced.

  Further, since the control of the exhaust valve timing to the HCCI timing is started prior to the start of operation in the HCCI combustion mode, the hydraulic exhaust VT switching mechanism 7 that is inherently low in response as in the embodiment is used. Even in this case, the operation in the HCCI combustion mode can be started in a state where the switching to the HCCI timing is completed.

  Further, based on the comparison result between the exhaust VT switching counter value CVTECEX and the retarding cycle number CSRDS2H, the end of switching of the exhaust valve timing to the HCCI timing and the end of the retarding control of the ignition timing IGLOG coincide with each other. Therefore, the temperature of the combustion chamber 3d at the start of the operation in the HCCI combustion mode can be more appropriately controlled while maintaining a good combustion state in the switching SI combustion operation.

  Even when the exhaust VT switching counter value CVTECEX becomes 0, the SI combustion operation at the time of switching is performed until it is determined that the actual exhaust valve timing is the HCCI timing based on the maximum value PCYLMAX of the in-cylinder pressure PCYL. Therefore, the operation in the HCCI combustion mode can be started in a state where the switching of the exhaust valve timing to the HCCI timing has been completed with certainty, whereby the combustion chamber 3d at the start of the operation in the HCCI combustion mode can be started. Temperature, in-cylinder pressure PCYL, etc. can be controlled more appropriately.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the retardation correction amount DIGRS2H is set to a constant value, but may be changed according to the elapsed time from the start of the SI combustion operation at the time of switching. The angle correction amount DIGRS2H may be decreased.

  In the embodiment, a hydraulic type is used as the exhaust VT switching mechanism, but an electric type may be used instead. Further, an exhaust VT switching mechanism that changes the phase of the exhaust camshaft relative to the crankshaft 3e may be used.

  In the embodiment, the maximum value PCYLMAX of the in-cylinder pressure PCYL is used as the combustion parameter for determining whether or not the switching to the valve closing timing for the HCCI combustion mode is completed. Other appropriate parameters representing the combustion state of the engine 3, for example, the temperature of the combustion chamber 3d or the exhaust gas temperature TEX may be used.

  In the embodiment, the required torque PMCMD and the exhaust gas temperature TEX are used as parameters for calculating the retardation correction amount DIGRS2H. In addition, other parameters correlated with the temperature of the combustion chamber 3d are used. For example, the engine speed NE may be used.

  The embodiment is an example in which the present invention is applied to a gasoline engine mounted on a vehicle, but the present invention is not limited to this, and may be applied to various engines such as a diesel engine other than a gasoline engine. Also, the present invention can be applied to engines other than those for vehicles, for example, engines for marine propulsion devices such as outboard motors having a crankshaft arranged vertically. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 ECU (Combustion mode selection means, SI combustion operation execution means at the time of switching, ignition timing control means, exhaust valve timing control means, control period calculation means, first determination means,
(Second determination means, execution period determination means)
3 Engine (Internal combustion engine)
3d Combustion chamber 5 Exhaust valve 20 Crank angle sensor (rotation speed detection means, load detection means)
22 Accelerator opening sensor (load detection means)
23 Exhaust temperature sensor (exhaust gas temperature detection means)
IGLOG ignition timing IGMP basic ignition timing (normal ignition timing for SI combustion mode)
CVTECEX Exhaust VT switching counter value (valve closing timing control period)
PCYLMAX Maximum cylinder pressure (combustion parameter)
CSRDS2H Delay cycle number (SI combustion operation execution period at switching)
NE engine speed (speed of internal combustion engine)
PMCMD required torque (load of internal combustion engine)
TEX exhaust temperature (exhaust gas temperature)
DIGRS2H Ignition timing retardation correction amount (ignition timing retardation amount)

Claims (5)

Control of an internal combustion engine that is operated by switching the combustion mode between an SI combustion mode in which the air-fuel mixture in the combustion chamber is combusted by spark ignition and an HCCI combustion mode in which combustion is performed by compression ignition and the valve timing of the exhaust valve can be changed A device,
A combustion mode selection means for selecting one of the SI combustion mode and the HCCI combustion mode as the combustion mode;
A switching time SI combustion operation executing means for executing the operation in the SI combustion mode as a switching time SI combustion operation when the selected combustion mode is switched from the SI combustion mode to the HCCI combustion mode;
In the switching SI combustion operation, ignition timing control means for controlling the ignition timing of the internal combustion engine to be retarded from the normal ignition timing for the SI combustion mode;
Exhaust valve timing control for controlling the valve closing timing of the exhaust valve to be more advanced than the valve closing timing for the SI combustion mode when performing the operation in the HCCI combustion mode after the SI combustion operation at the time of switching Means,
A control device for an internal combustion engine, comprising: The period from the start of the control to the advance side of the valve closing timing by the exhaust valve timing control means until the completion of switching to the valve closing timing for the HCCI combustion mode is calculated as the control period of the valve closing timing A control period calculating means for
When the calculated valve closing timing control period is shorter than the switching time SI combustion operation execution period, the exhaust valve timing control means sets the switching time SI combustion operation at the end of the valve closing timing control period. The control of the valve closing timing is started later than the switching SI combustion operation so as to coincide with the end of the execution period of
The switching time SI combustion operation execution means is configured such that when the switching time SI combustion operation execution period is shorter than the valve closing timing control period, the switching time SI combustion operation execution period ends at the end of the switching time SI combustion operation execution period. 2. The control device for an internal combustion engine according to claim 1, wherein the SI combustion operation at the time of switching is started later than the control of the valve closing timing so as to coincide with the end of the control period. First determination means for determining whether switching to the valve closing timing for the HCCI combustion mode is completed based on a control period of the valve closing timing;
Combustion parameter detection means for detecting a combustion parameter representing a combustion state of the internal combustion engine;
Second determination means for determining whether switching to the valve closing timing for the HCCI combustion mode is completed based on the detected combustion parameter;
The switching-time SI combustion operation execution means, when it is determined by the first determination means that the switching of the valve closing timing is completed, the switching of the valve closing timing is not completed by the second determination means. The control apparatus for an internal combustion engine according to claim 1 or 2, wherein, when judged, the switching time SI combustion operation is continued. A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Load detecting means for detecting a load of the internal combustion engine;
The execution period determining means for determining an execution period of the SI combustion operation at the time of switching according to the detected rotation speed and load of the internal combustion engine, further comprising: The control apparatus of the internal combustion engine described in 1. Load detecting means for detecting a load of the internal combustion engine;
An exhaust gas temperature detecting means for detecting the temperature of the exhaust gas of the internal combustion engine,
The ignition timing control means sets a retard amount of the ignition timing during the switching time SI combustion operation in accordance with the detected load of the internal combustion engine and exhaust gas temperature. 4. The control apparatus for an internal combustion engine according to any one of 3 above.

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