JP2010270708A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, suppressing the emission of hydrocarbon, and improving exhaust gas characteristics by properly controlling switching of combustion modes in response to the emission of hydrocarbon. <P>SOLUTION: In the control device 1 for an engine 3, HC emission HCPKM1 per unit distance discharged from a combustion chamber 3c is calculated in response to an engine speed NE and a fuel injection amount QINJ (Fig.5), and the combustion mode is switched between a diffusion combustion mode and a premixed compression ignition combustion mode in response to the calculated HC emission HCPKM1 (Steps 4, 6 of Fig.4). During the diffusion combustion mode, an HC emission HCEXPKM1 in the premixed compression ignition combustion mode liable to have a large HC emission is predicted (Fig.5), and switching to the premixed compression ignition combustion mode is allowed till the predicted HC emission HCEXPKM1 becomes a threshold HCEXREF or less (Steps 2, 6 of Fig.4). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine having a diffusion combustion mode and a premixed compression ignition combustion mode as combustion modes.

  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 a gasoline engine, and as a combustion mode, a spark-ignition combustion mode in which a mixture of fuel and air supplied to the combustion chamber is combusted by spark ignition by an ignition plug, and the mixture is combusted by compression ignition. It has a compression ignition combustion mode. The exhaust system is provided with a catalyst device for purifying the exhaust gas. In this control device, when the catalyst device is activated, the combustion mode is switched from the spark ignition combustion mode to the compression ignition combustion mode.

JP 2007-40233 A

  However, in this conventional control device for an internal combustion engine, the combustion mode is switched only in accordance with the active state of the catalyst device, so the hydrocarbon emission amount may increase depending on the temperature state of the internal combustion engine. For example, when the internal combustion engine is restarted, depending on the stop time until then, the temperature of the catalyst may still be at the active temperature, whereas the temperature of the combustion chamber or cylinder block may have already decreased. . In such a case, assuming that the catalyst device is in an active state, switching the combustion mode from the spark ignition combustion mode to the compression ignition combustion mode increases the ignition delay, so a relatively large amount of hydrocarbons are generated and discharged. As a result, hydrocarbons that could not be purified by the catalyst device would be discharged into the atmosphere.

  The present invention has been made to solve the above-described problems, and can appropriately control switching of the combustion mode according to the amount of hydrocarbon emissions, thereby suppressing the amount of hydrocarbon emissions, An object of the present invention is to provide a control device for an internal combustion engine that can improve exhaust gas characteristics.

  In order to achieve the above object, an invention according to claim 1 is a control device 1 for an internal combustion engine which is operated by switching a combustion mode between a diffusion combustion mode and a premixed compression ignition combustion mode, The operating state detecting means (crank angle sensor 22) for detecting the operating state 3 (engine speed NE) and the carbonization exhausted from the combustion chamber 3c of the internal combustion engine 3 according to the detected operating state of the internal combustion engine 3 Hydrocarbon emission calculation means (ECU2, FIG. 5, FIG. 7) for calculating hydrogen emission (HC emission per unit distance HCEXPKM1, HCEXPKM2), and the combustion mode according to the calculated hydrocarbon emission And combustion mode switching means (ECU 2, steps 4 and 6 in FIG. 4, steps 24 and 25 in FIG. 6).

  This internal combustion engine is operated by switching the combustion mode between a diffusion combustion mode and a premixed compression ignition combustion mode. Here, the diffusion combustion mode is a combustion mode in which fuel and air are burned while being diffused and mixed in the combustion chamber, and the premixed compression ignition combustion mode is burned by compression ignition in a state where the fuel and air are mixed in advance. This is the combustion mode to be performed. In the premixed compression ignition combustion mode, since the combustion temperature is lower than in the diffusion combustion mode, the emission amount of nitrogen oxide (NOx) can be suppressed, but the ignition timing is difficult to control. Until the warm-up operation is completed, the ignition delay may increase, and the amount of hydrocarbon emissions tends to increase as the ignition timing deviates from the optimal ignition timing. According to the present invention, the hydrocarbon emission amount is calculated according to the detected operating state of the internal combustion engine, and the combustion mode is switched according to the calculated hydrocarbon emission amount. The emission amount of hydrocarbons can be suppressed, and the exhaust gas characteristics can be improved.

  The invention according to claim 2 is the control apparatus 1 for the internal combustion engine according to claim 1, based on the fuel injection amount QINJ injected into the internal combustion engine 3 from the start time during the warm-up operation after the start of the internal combustion engine 3. And a total generated heat amount calculating means (ECU2, step 12 in FIG. 5) for calculating the total amount of heat generated from the start of combustion of the fuel as the total generated heat quantity Qt. The exhaust amount of hydrocarbons is calculated according to the total generated heat amount Qt (ECU 2, steps 15 to 17 in FIG. 5).

  When the premixed compression ignition combustion mode is performed during warm-up operation after starting the internal combustion engine, the combustion chamber temperature is still low. There is a tendency to increase. Further, when detecting the temperature state of the internal combustion engine using the temperature of the cooling water circulating inside the internal combustion engine or the temperature of the lubricating oil of the internal combustion engine, the temperature of the cooling water or the lubricating oil is the same (for example, 30 ° C.). However, the actual combustion chamber temperature may be different. For example, the temperature of the combustion chamber differs between when the internal combustion engine is started in a state where the temperature of the cooling water or the lubricating oil is 30 ° C. and when the internal combustion engine is started at a state of 10 ° C. and then reaches 30 ° C. This is because combustion of a plurality of cycles is performed in the combustion chamber until the temperature of the cooling water or the lubricating oil, which was 10 ° C. at the start of the internal combustion engine, then increases to 30 ° C. This is because there is a delay before the temperature of the water is reflected in the temperature of the cooling water or the lubricating oil. For this reason, in the above case, the temperature of the combustion chamber is higher in the case of starting from the state of 10 ° C. than in the case of starting from the state of 30 ° C. According to this configuration, since the total amount of heat generated from the start of fuel combustion is calculated as the total generated heat amount based on the fuel injection amount injected into the internal combustion engine, the calculated total generated heat amount is warm. The temperature state of the internal combustion engine during machine operation is well represented. Since the hydrocarbon emission amount is calculated according to the total heat generation amount, the combustion mode can be more appropriately switched according to the hydrocarbon emission amount that better reflects the temperature state of the internal combustion engine. The exhaust gas characteristics can be further improved.

  According to a third aspect of the present invention, the hydrocarbon emission amount calculation means calculates the hydrocarbon emission amount expected to be emitted when the combustion mode is switched to the premixed compression ignition combustion mode during the diffusion combustion mode. It is calculated according to the operating state of the engine 3 (ECU 2, FIG. 5, FIG. 7), and the combustion mode switching means diffuses when the calculated hydrocarbon emission amount is larger than a predetermined value (threshold value HCEXREF). Switching from the combustion mode to the premixed compression ignition combustion mode is prohibited (ECU 2, steps 2 and 4 in FIG. 4, steps 23 and 24 in FIG. 6).

  According to this configuration, during the diffusion combustion mode, the amount of hydrocarbons expected to be discharged when the combustion mode is switched to the premixed compression ignition combustion mode is calculated in advance according to the operating state of the internal combustion engine. . Further, when the predicted hydrocarbon emission amount is larger than a predetermined value, switching of the combustion mode from the diffusion combustion mode to the premixed compression ignition combustion mode is prohibited. As described above, during the diffusion combustion mode, the hydrocarbon emission amount in the premixed compression ignition combustion mode, which tends to increase the hydrocarbon emission amount, is predicted, and the predicted hydrocarbon emission amount becomes a predetermined value or less. After that, switching to the premixed compression ignition combustion mode is permitted. Therefore, in the premixed compression ignition combustion mode, it is possible to reliably avoid exhausting an amount of hydrocarbons exceeding a predetermined value, and to maintain good exhaust gas characteristics.

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 schematic diagram which shows schematic structure of a cam phase variable mechanism. It is a figure which shows the valve lift curve of an exhaust valve when a cam phase is set to the most retarded angle value (solid line) and the most advanced angle value (two-dot chain line) by the cam phase variable mechanism. It is a flowchart which shows the switching process of the combustion mode by 1st Embodiment. It is a flowchart which shows the calculation process of HC discharge | emission amount per unit distance by 1st Embodiment. It is a flowchart which shows the switching process of the combustion mode by 2nd Embodiment. It is a flowchart which shows the calculation process of HC discharge | emission amount per unit distance by 2nd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a control device 1 according to an embodiment of the present invention and an internal combustion engine (hereinafter referred to as “engine”) 3 to which the control device 1 is applied. As shown in the figure, the control device 1 includes an ECU 2, which performs various control processes for the engine 3 as will be described later.

  The engine 3 is a four-cylinder diesel engine (not shown) for a vehicle (not shown), and a combustion chamber 3c is formed between a piston 3a and a cylinder head 3b of each cylinder. A fuel injection valve 4 (hereinafter referred to as “injector 4”) is attached to the cylinder head 3b so as to face the combustion chamber 3c, and the fuel is directly injected into the combustion chamber 3c.

  The injector 4 is disposed at the center of the top wall of the combustion chamber 3c, and is connected to a common rail (not shown) via a fuel pipe (not shown). The fuel is boosted by a high-pressure pump (not shown), accumulated in the common rail, supplied to the injector 4, and injected from the injector 4.

  The opening / closing of the injector 4 is controlled by a control signal from the ECU 2, whereby the fuel injection timing corresponding to the valve opening timing and the fuel injection amount QINJ corresponding to the valve opening time are controlled.

  Further, the engine 3 includes an intake camshaft 6 and an exhaust camshaft 7. These intake and exhaust camshafts 6 and 7 have an intake cam 6a and an exhaust cam 7a for opening and closing the intake valve 8 and the exhaust valve 9, respectively. The intake and exhaust camshafts 6 and 7 are connected to the crankshaft 3e via a timing belt (not shown), and rotate once every two rotations of the crankshaft 3e.

  A cam phase varying mechanism 10 is provided at one end of the exhaust camshaft 7. The cam phase variable mechanism 10 operates by being supplied with hydraulic pressure, and advances or retards the phase of the exhaust cam 7a with respect to the crankshaft 3e (hereinafter referred to as "cam phase CAEX") steplessly, thereby enabling the exhaust valve 9 is changed. As a result, the valve overlap between the intake valve 8 and the exhaust valve 9 increases or decreases, thereby increasing or decreasing the internal EGR amount and changing the charging efficiency.

  As shown in FIG. 2, the cam phase varying mechanism 10 has an electromagnetic valve 10a. This solenoid valve 10a is a combination of a spool valve mechanism 10b and a solenoid 10c, and is connected to the advance chamber 15 and the retard chamber 16 via the advance oil passage 17a and the retard oil passage 17b, respectively. The hydraulic pressure POIL supplied from the hydraulic pump 11 is controlled and supplied to the advance chamber 15 and the retard chamber 16 as the advance hydraulic pressure Pad and the retard hydraulic pressure Prt, respectively. The solenoid 10c changes the advance hydraulic pressure Pad and the retard hydraulic pressure Prt by moving the spool valve body of the spool valve mechanism 10b within a predetermined range by the phase control input U_CAEX from the ECU 2.

  The hydraulic pump 11 is of a mechanical type connected to the crankshaft 3e. As the crankshaft 3e rotates, the hydraulic oil stored in the oil pan 3d of the engine 3 is sucked through the oil passage 11a and boosted. After that, the oil is supplied to the electromagnetic valve 10a through the oil passage 11a.

  In the cam phase variable mechanism 10 having the above-described configuration, while the hydraulic pump 11 is in operation, the solenoid valve 10a operates in accordance with the phase control input U_CAEX, so that the advance hydraulic pressure Pad is transferred to the advance chamber 15 and the retard hydraulic pressure Prt is changed. As a result, the above-described cam phase CAEX continuously changes between a predetermined maximum retardation value and a predetermined maximum advance angle value, whereby the valve of the exhaust valve 9 is supplied. The timing is changed steplessly between the most retarded timing shown by the solid line in FIG. 3 and the most advanced timing shown by the two-dot chain line.

  A cam angle sensor 24 is provided at the end of the exhaust camshaft 7 opposite to the cam phase variable mechanism 10. The cam angle sensor 24 is composed of, for example, a magnet rotor and an MRE pickup, and outputs a CAM signal, which is a pulse signal, to the ECU 2 every predetermined cam angle (for example, 1 °) as the exhaust camshaft 7 rotates. . The ECU 2 calculates the actual cam phase CAEX from this CAM signal and the CRK signal and TDC signal described later.

  On the other hand, the crankshaft 3e is provided with a crank angle sensor 22 composed of a magnet rotor 22a and an MRE pickup 22b. The crank angle sensor 22 outputs a CRK signal and a TDC signal, which are pulse signals, with the rotation of the crankshaft 3e.

  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 3a is in a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke in any cylinder, and the engine 3 has four cylinders as in this embodiment. In this case, it is output every 180 ° crank angle.

  A water temperature sensor 21 is provided in the main body of the engine 3. The water temperature sensor 21 is composed of a thermistor, detects an engine water temperature TW that is the temperature of cooling water circulating in a cylinder block (not shown) of the engine 3, and outputs a detection signal to the ECU 2.

  On the other hand, the intake pipe 12 of the engine 3 is provided with an intake shutter 13. An actuator 13 a is coupled to the intake shutter 13. The opening degree of the intake shutter 13 is controlled by the ECU 2 by controlling the actuator 13a according to the operating state of the engine 3, thereby controlling the amount of intake air taken into the combustion chamber 3c.

  An intake air temperature sensor 23 is provided on the downstream side of the intake shutter 13 of the intake pipe 12. The intake air temperature sensor 23 detects an intake air temperature TA (hereinafter referred to as “intake air temperature”) TA downstream of the intake shutter 13 and outputs a detection signal to the ECU 2.

  Further, the ECU 2 receives a detection signal indicating an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) of the vehicle from the accelerator opening sensor 25 from the vehicle speed sensor 26. Detection signals representing the vehicle speed (VP) are output.

  The ECU 2 includes a microcomputer (not shown) including a CPU 2a, a RAM 2b, a ROM 2c, an input / output interface (not shown), and the like. The detection signals of the sensors 21 to 25 described above are respectively input to the ECU 2, and after A / D conversion and shaping are performed by the input interface, are input to the CPU 2 a. In response to these detection signals, the CPU 2a executes various arithmetic processes according to a control program stored in the ROM 2c.

  For example, the ECU 2 executes a combustion mode switching process for switching the combustion mode between the diffusion combustion mode and the premixed compression ignition combustion mode.

  Here, the diffusion combustion mode is a combustion mode in which fuel and air are burned while being diffused and mixed in the combustion chamber. This diffusion combustion mode is performed by setting the fuel injection timing of the injector 4 to a more retarded side, for example, near TDC, and setting the valve timing of the exhaust valve 9 to the retarded side under the control of the ECU 2. For this reason, in the diffusion combustion mode, the internal EGR amount decreases and the combustion temperature increases, so that the generation of particulates such as hydrocarbons (HC) is suppressed, while the NOx emission tends to increase. is there.

  The premixed compression ignition combustion mode is a combustion mode in which combustion is performed by compression ignition in a state where fuel and air are mixed in advance. In this premixed compression ignition combustion mode, the fuel injection timing of the injector 4 is set to the advance side with respect to the diffusion combustion mode and the valve timing of the exhaust valve 9 is set to the advance side under the control of the ECU 2. Done. For this reason, in the premixed compression ignition combustion mode, the internal EGR amount increases and the combustion temperature decreases, so that the generation of NOx is suppressed, but the ignition timing is difficult to control, and particularly after the engine 3 is started, Until the warm-up operation is completed, the ignition delay increases, and the amount of hydrocarbon emissions tends to increase as the ignition timing deviates from the optimal ignition timing.

  In the present embodiment, the ECU 2 corresponds to a hydrocarbon emission amount calculating means, a combustion mode switching means, and a total generated heat amount calculating means.

  Next, the combustion mode switching process according to the first embodiment of the present invention, which is executed by the ECU 2, will be described with reference to FIG. This process is executed at a predetermined period ΔT.

  In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), the HC emission amount HCEXKM1 per unit distance is calculated. The HC emission amount HCEXPKM1 corresponds to the HC emission amount per unit distance (for example, 1 km) that is discharged when the combustion mode is the premixed compression ignition combustion mode. The calculation process of the HC emission amount HCEXKM1 will be described later.

  Next, in step 2, it is determined whether or not the calculated HC emission amount HCEXKM1 is larger than a predetermined threshold value HCEXREF for determining the combustion mode.

  If the answer to step 2 is YES and the HC emission amount HCEXPKM1 is larger than the threshold value HCEXREF, the timer value (hereinafter referred to as “delay timer value”) TMDC of the down-count type delay timer is set to a predetermined time TREF (for example, 30 sec). (Step 3), and since the HC emission amount when the combustion mode is set to the premixed compression ignition combustion mode is expected to be large, the premixed compression ignition combustion mode flag F_PCCI is set to “0” ( In step 4), the combustion mode is set to the diffusion combustion mode, and the present process is terminated.

  On the other hand, if the answer to step 2 is NO and the HC emission amount HCEXPKM1 is equal to or less than the threshold value HCEXREF, it is determined whether or not the delay timer value TMDC is 0 (step 5).

  If this answer is NO and the state of HC emission amount HCEXPKM1 ≦ threshold value HCEXREF does not continue for a predetermined time TREF, the state where the HC emission amount is small when the combustion mode is switched to the premixed compression ignition combustion mode. Since there is a possibility that it cannot be surely obtained, step 4 is executed, and the combustion mode is maintained in the diffusion combustion mode.

  On the other hand, if the answer to step 5 is YES and the state of HCEXPKM1 ≦ HCEXREF continues for a predetermined time TREF or more, even if the combustion mode is switched to the premixed compression ignition combustion mode, a state in which the HC emission amount is small is reliably obtained. As a result, the premixed compression ignition combustion mode flag F_PCCI is set to “1” (step 6) to switch the combustion mode to the premixed compression ignition combustion mode, and the present process is terminated.

  FIG. 5 shows the calculation process of the HC emission amount HCEXPKM1 executed in step 1 of FIG. In this process, first, in step 11, a reference HC emission amount HCEXbase is calculated by searching a predetermined map (not shown) according to the engine speed NE and the fuel injection amount QINJ. The reference HC emission amount HCEXbase corresponds to the HC emission amount corresponding to the current processing cycle, which is discharged when the engine water temperature TW is a predetermined reference temperature (for example, 30 ° C.). In this map, the reference HC emission amount HCEXbase is set to a larger value as the engine speed NE is higher and the fuel injection amount QINJ is smaller.

  Next, in step 12, the total amount of heat generated from the start of the engine 3 due to fuel combustion is calculated as the total generated heat amount Qt. The time when the engine 3 is started corresponds to the time when the engine 3 is cranked by the starter and complete explosion. The total heat generation amount Qt is calculated by multiplying the product of the fuel injection amount QINJ from the injector 4 and the engine speed NE by a predetermined conversion coefficient as a heat generation amount corresponding to one processing cycle and integrating the value. Is calculated by

  Next, in step 13, a warm-up correction coefficient Kqt is calculated by searching a predetermined map according to the calculated total heat generation amount Qt. In this map, the warm-up correction coefficient Kqt is set to a smaller value as the total generated heat amount Qt is larger. This is because it is estimated that the larger the total amount of generated heat Qt, the higher the temperature of the combustion chamber 3c due to heat reception, and the smaller the amount of HC emission.

  Next, in step 14, the temperature correction coefficient Kwa at the time of start is calculated by searching a predetermined map according to the engine water temperature TW and the intake air temperature TA detected at the time of starting the engine 3. In this map, the starting temperature correction coefficient Kwa is set to a larger value as the engine coolant temperature TW is lower and the intake air temperature TA is lower. This is presumed that when the total generated heat quantity Qt is the same, the lower the engine water temperature TW at the time of starting and the lower the intake air temperature TA, the lower the temperature of the combustion chamber 3c and the higher the HC emission amount HCEX. This is because that.

Next, in step 15, the HC emission amount HCEX corresponding to the current processing cycle is calculated by the following equation (1) using the reference HC emission amount HCEXbase, the warm-up correction coefficient Kqt, and the starting temperature correction coefficient Kwa.
HCEX = HCEXbase · Kqt · Kwa (1)

  Next, in step 16, the travel distance DRV of the vehicle corresponding to the current processing cycle is calculated by multiplying the vehicle speed VP detected by the vehicle speed sensor 26 by the execution cycle ΔT of this processing. Then, the HC discharge amount HCEXKM1 is calculated by dividing the HC discharge amount HCEX by the travel distance DRV (step 17), and this process is terminated.

  Next, the combustion mode switching process according to the second embodiment of the present invention will be described with reference to FIG. This second embodiment differs from the first embodiment described above mainly in the method of calculating the HC emission amount per unit distance, and more specifically, every time the vehicle travels a predetermined distance. The discharge amount HCEXKM2 is calculated.

  In this process, first, in step 21, the HC discharge amount HCEXKM2 per unit distance is calculated. This HC emission amount HCEXKM2 is the hydrocarbon emission amount per unit distance (for example, 1 km), which is discharged when the combustion mode is the premixed compression ignition combustion mode, similarly to the HC emission amount HCEXKM1 of the first embodiment described above. It corresponds to.

  FIG. 7 shows a process for calculating the HC emission amount HCEXPKM2. In this process, first, in step 31, as in steps 11 to 15 of the first embodiment, the reference HC emission amount HCEXbase, the warm-up correction coefficient Kqt, and the start-up temperature correction coefficient Kwa are used, and the above equation (1) is used. Then, the HC emission amount HCEX corresponding to the current processing cycle is calculated.

  Next, in step 32, the calculated HC emission amount HCEX is added to the previously calculated HC emission amount integrated value ΣHCEX, thereby calculating the HC emission amount integrated value ΣHCEX.

  Next, in step 33, the vehicle travel distance DRV corresponding to the current process cycle is calculated by multiplying the vehicle speed VP detected by the vehicle speed sensor 26 by the execution period ΔT of this process. In step 34, the calculated travel distance DRV is calculated by adding the calculated travel distance DRV to the travel distance integrated value ΣDRV calculated up to the previous time.

  Next, it is determined whether or not the calculated travel distance integrated value ΣDRV is equal to or greater than a predetermined distance DREF (for example, 0.3 km) (step 35). If the answer to this question is NO and the travel distance integrated value ΣDRV has not reached the predetermined distance DREF, the determination execution flag F_JCOM is set to “0” because it is not the timing for performing the combustion mode switching determination (step 36). Exit.

  On the other hand, when the answer to step 35 is YES and the travel distance integrated value ΣDRV reaches the predetermined distance DREF, the HC discharge amount per unit distance is divided by dividing the HC discharge amount integrated value ΣHCEX by the travel distance integrated value ΣDRV. HCEXPKM2 is calculated (step 37). Next, both the HC emission amount integrated value ΣHCEX and the travel distance integrated value ΣDRV are reset to the value 0 (step 38), and the determination execution flag F_JCOM is set to indicate that it is the timing for performing the combustion mode switching determination. “1” is set (step 39), and this process is terminated.

  Returning to FIG. 6, in step 22 following step 21, it is determined whether or not the determination execution flag F_JCOM is “1”. If the answer to this question is NO and it is not the timing for determining whether to switch the combustion mode, the present process is terminated and the combustion mode is maintained.

  On the other hand, when the answer to step 22 is YES, it is determined at step 23 whether or not the HC emission amount HCEXKM2 is larger than a predetermined threshold value HCEXREF for determining the combustion mode.

  If the answer is YES and the HC emission amount HCEXKM2 is larger than the threshold value HCEXREF, it is estimated that the HC emission amount HCEXKM2 when the combustion mode is set to the premixed compression ignition combustion mode is large. By setting the combustion mode flag F_PCCI to “0” (step 24), the combustion mode is set to the diffusion combustion mode, and this process is terminated.

  On the other hand, if the answer to step 23 is NO and the HC emission amount HCEXPKM2 is less than or equal to the threshold value HCEXREF, it is assumed that even if the combustion mode is switched to the premixed compression ignition combustion mode, a small HC emission amount can be obtained. Then, by setting the premixed compression ignition combustion mode flag F_PCCI to “1” (step 25), the combustion mode is switched to the premixed compression ignition combustion mode, and this process is terminated.

  As described above, in the second embodiment, every time the vehicle travels for the predetermined distance DREF, the HC emission amount HCEXKM2 per unit distance is calculated, and the combustion mode is calculated using the calculated HC emission amount HCEXKM2. Switching judgment is executed.

  As described above, according to the first and second embodiments, the HC emission amount HCEXPKM1 or HCEXPKM2 per unit distance discharged from the combustion chamber 3c is calculated according to the engine speed NE and the fuel injection amount QINJ. Since the combustion mode is switched according to the calculated HC emission amount HCEXPKM1,2, the HC emission amount actually discharged from the combustion chamber 3c can be suppressed, and the exhaust gas characteristics can be improved.

  Further, the calculation of the HC exhaust amount HCEXPKM1,2 is performed according to the total generated heat amount Qt calculated based on the fuel injection amount QINJ in addition to the engine speed NE and the fuel injection amount QINJ. The combustion mode can be switched more appropriately in accordance with the hydrocarbon emission amount that favorably reflects the temperature state of the engine 3, and the exhaust gas characteristics can be further improved.

  In addition, during the diffusion combustion mode, the HC emission amount HCEXPKM1,2 in the premixed compression ignition combustion mode in which the HC emission amount tends to increase is predicted, and the predicted HC emission amount HCEXKM1,2 is less than the threshold HCEXREF. After that, switching to the premixed compression ignition combustion mode is permitted. Therefore, in the premixed compression ignition combustion mode, it is possible to reliably avoid discharging an amount of hydrocarbons exceeding the threshold HCEXREF, and to maintain good exhaust gas characteristics.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the first and second embodiments, the fuel injection amount QINJ is used as a parameter for calculating the reference HC emission amount HCEXbase. However, instead of this, another appropriate parameter representing the load of the engine 3 is used. For example, the required torque calculated based on the engine speed NE and the accelerator pedal opening AP may be used.

  In the embodiment, the engine water temperature TW and the intake air temperature TA are used as parameters representing the starting temperature of the combustion chamber 3c. However, only one of them may be used, or instead of or in addition to these. The oil temperature of the engine oil may be used.

  In the embodiment, the HC emission amount per unit distance is used as the HC emission amount for performing the combustion mode switching determination. Instead, the HC emission amount per unit time, the engine 3 You may use the average value of HC discharge | emission amount corresponding to the total travel distance from the time of starting.

  The embodiment is an example in which the present invention is applied to a diesel engine mounted on a vehicle. However, the present invention is not limited to this, and an engine other than a vehicle, for example, an outboard with a crankshaft arranged vertically. It can also be applied to an engine for a marine propulsion device such as an aircraft. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 Intake control device 2 ECU (hydrocarbon amount calculation means, combustion mode switching means, total generated heat amount calculation means)
3 Engine (Internal combustion engine)
3c Combustion chamber 22 Crank angle sensor (operating state detection means)
NE engine speed (operating condition of internal combustion engine)
HCEXPKM1 HC emissions per unit distance (hydrocarbon emissions)
HCEXPKM2 HC emissions per unit distance (hydrocarbon emissions)
QINJ Fuel injection amount HCEXREF threshold (predetermined value)
Qt Total generated heat

Claims (3)

A control device for an internal combustion engine operated by switching a combustion mode between a diffusion combustion mode and a premixed compression ignition combustion mode,
An operating state detecting means for detecting an operating state of the internal combustion engine;
A hydrocarbon emission amount calculating means for calculating an emission amount of hydrocarbons discharged from the combustion chamber of the internal combustion engine according to the detected operating state of the internal combustion engine;
Combustion mode switching means for switching the combustion mode according to the calculated hydrocarbon emission amount;
A control device for an internal combustion engine, comprising: During the warm-up operation after the start of the internal combustion engine, based on the fuel injection amount injected from the start to the internal combustion engine, the total amount of heat generated from the start due to fuel combustion is calculated as the total generated heat amount A heat generation amount calculation unit;
2. The control device for an internal combustion engine according to claim 1, wherein the hydrocarbon emission amount calculating means calculates the hydrocarbon emission amount according to the calculated total generated heat amount. The hydrocarbon emission amount calculating means calculates the hydrocarbon emission amount that is expected to be emitted when the combustion mode is switched to the premixed compression ignition combustion mode during the diffusion combustion mode. Calculate according to the driving state,
The combustion mode switching means prohibits switching of the combustion mode from the diffusion combustion mode to the premixed compression ignition combustion mode when the calculated hydrocarbon emission amount is larger than a predetermined value. The control device for an internal combustion engine according to claim 1.

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