JP2005282466A - Control device for premixed compression self-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a two cycle premixed compression self ignition internal combustion engine capable of suppressing fluctuation of combustion conditions between cycles due to combustion conditions of previous cycle. <P>SOLUTION: This control device sends out drive signal to a drive circuit 38 to make an air supply valve 32 open by an air supply valve drive mechanism 32a when cylinder pressure detected by a cylinder pressure sensor 63 provided in a combustion chamber 25 becomes reference cylinder pressure predetermined according to operation conditions of an internal combustion engine 10 or less. Consequently, fluctuation of combustion gas quantity remaining in the combustion chamber 25 and air quantity introduced in the combustion chamber 25 between cycles can be made small and fluctuation of combustion conditions between cycles can be suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a two-cycle premixed compression self-ignition internal combustion engine that performs premixed compression self-ignition combustion in which a mixed gas formed in a combustion chamber is compressed and self-ignited.

  It is known that the amount of NOx generated by combustion in an internal combustion engine (NOx generation amount) depends on the combustion period in which the combustion chamber is at a high temperature, and decreases when this period becomes shorter. In the combustion by the spark ignition that ignites the mixed gas by using the spark plug, the flame propagates from the ignition point near the spark plug and the combustion proceeds. Therefore, the combustion period becomes relatively long, and as a result, a large amount of NOx is generated. On the other hand, in the combustion by self-ignition in which the mixed gas formed in the combustion chamber is compressed to ignite the mixed gas, the compressed mixed gas (compressed mixed gas) is almost simultaneously distributed at many scattered positions. Ignite. For this reason, combustion by self-ignition is completed within a shorter period than combustion by spark ignition, and as a result, the amount of NOx generated is relatively small. From the above, a premixed compression self-ignition internal combustion engine is considered useful as an internal combustion engine that can reduce the amount of NOx produced. Further, in a premixed compression self-ignition internal combustion engine, knocking is unlikely to occur even when the mixed gas is compressed higher than an internal combustion engine using spark ignition. Therefore, an improvement in fuel consumption is expected by burning a higher-compressed mixed gas.

  In order to burn the mixed gas by self-ignition, the mixed gas needs to have a high temperature. For this reason, the temperature of the mixed gas is increased by allowing the combustion gas of the previous cycle to remain in the combustion chamber or by circulating the combustion gas from the exhaust system and introducing it again into the combustion chamber (for example, Patent Documents). 1). At this time, when the time interval between a certain combustion stroke and the next combustion stroke in a certain cylinder is shorter, the temperature of the mixed gas can be increased efficiently because the combustion gas is less likely to be cooled. Therefore, a two-cycle internal combustion engine having a shorter time interval between successive combustion strokes than a four-cycle internal combustion engine is considered suitable for premixed compression auto-ignition combustion. Further, the two-cycle internal combustion engine is also considered suitable for premixed compression auto-ignition combustion in that combustion gas tends to remain in the combustion chamber.

  Here, a combustion cycle of a general two-cycle premixed compression self-ignition internal combustion engine will be described with reference to FIG. In this internal combustion engine, when the crank angle is in the vicinity of the top dead center TDC, the compressed mixed gas self-ignites and the expansion stroke starts. At this stage, both the air supply valve that opens and closes the air supply port and the exhaust valve that opens and closes the exhaust port are closed. Next, when the crank angle reaches a predetermined crank angle EO (exhaust valve opening timing EO) between the top dead center TDC and the bottom dead center, the exhaust valve is opened, and the exhaust period starts. During the exhaust period, the combustion gas confined at a high pressure in the combustion chamber is discharged from the exhaust port.

  Subsequently, when the crank angle reaches a predetermined crank angle IO (supply valve opening timing IO) between the exhaust valve opening timing EO and the bottom dead center, the supply valve is opened. As a result, the scavenging period in which the exhaust period ends and both the air supply valve and the exhaust valve are opened is started. During this scavenging period, air flows into the combustion chamber through the air supply port, and the combustion gas remaining in the combustion chamber is pushed out from the exhaust port by the inflowing air. Subsequently, when the crank angle is near the bottom dead center, fuel is injected into the combustion chamber.

When the crank angle reaches a predetermined crank angle EC (exhaust valve closing timing EC) between the bottom dead center and the next top dead center TDC, the exhaust valve is closed and the scavenging period ends. Thereafter, when the crank angle reaches a predetermined crank angle IC (supply valve closing timing IC) between the exhaust valve closing timing EC and the next top dead center TDC, the intake valve is closed and the compression stroke starts. . The exhaust valve opening timing EO, the intake valve opening timing IO, the exhaust valve closing timing EC, and the intake valve closing timing IC described above are determined in advance according to the operating state of the internal combustion engine. The above is the combustion cycle of the conventional two-cycle premixed compression self-ignition internal combustion engine (see, for example, Patent Document 2).
JP 2001-214741 A (Claim 2, FIGS. 1 to 2) Japanese Patent Laid-Open No. 07-026964 (FIG. 2)

  However, the conventional internal combustion engine has a combustion state (combustion state represented by an ignition timing, a combustion period, a combustion temperature, etc.) in one combustion of a certain cylinder, even when the operating state does not change, There is a problem that the combustion state in the next combustion of the same cylinder is likely to change, and as a result, a relatively large torque fluctuation occurs for each combustion.

  This factor is estimated as follows. Now, it is assumed that the operating state has not changed, but the ignition timing is delayed from the scheduled ignition timing due to some factor. The in-cylinder pressure changes with a delay after the ignition timing is delayed from the scheduled ignition timing. On the other hand, the air supply valve is opened at a predetermined air supply valve opening timing according to the operating state of the internal combustion engine. For this reason, the in-cylinder pressure at the supply valve opening timing becomes higher than the planned pressure. Therefore, since the high-pressure combustion gas existing in the combustion chamber at the opening timing of the intake valve inhibits the flow of air into the combustion chamber during the scavenging period, the amount of low-temperature air in the mixed gas used for the next combustion is relatively The amount of high-temperature combustion gas is relatively increased.

  As a result, the compressed mixed gas used for the next combustion becomes a high temperature at an early stage, so that the ignition timing is earlier than the scheduled timing. As a result, the pressure in the combustion chamber at the time of opening the next air supply valve is lowered, so that the amount of air in the mixed gas used for the next combustion is relatively increased and the amount of combustion gas is relatively decreased. . Therefore, the ignition timing of the next combustion is later than the scheduled ignition timing. As described above, in the two-cycle premixed compression self-ignition internal combustion engine, the case where the ignition timing is earlier or later than the scheduled timing is likely to occur repeatedly.

  The present invention has been made to address the above-described problems, and its purpose is to perform two-cycle premixed compression capable of suppressing the cycle-to-cycle variation of the combustion state caused by the combustion state of the previous cycle. An object of the present invention is to provide a control device for a self-ignition internal combustion engine. In order to achieve this object, the control device of the present invention is a period during which the air supply valve that opens and closes the air supply port formed in the cylinder head for supplying air into the combustion chamber and the air supply port is open. An air supply valve driving means for opening the air supply valve at the start timing of the air supply valve opening period and closing the air supply valve at the end timing of the air supply valve opening period; and combustion in the combustion chamber An exhaust valve that opens and closes an exhaust port formed in the cylinder head to discharge gas from the combustion chamber, and a period that is earlier than the start time of the intake valve opening period and that opens the exhaust port The exhaust valve is opened at the start timing of the exhaust valve opening period, and the exhaust valve is opened at a timing later than the start timing of the supply valve opening period and at the end timing of the exhaust valve opening period. Exhaust valve driving means for closing the valve, A control device for controlling a two-cycle premixed compression self-ignition internal combustion engine that performs premixed compression self-ignition combustion that compresses and self-ignites a mixed gas formed in a combustion chamber, and acquires an operating state of the internal combustion engine Storing in advance a relationship between an operating state acquisition unit that performs the operation, an in-cylinder pressure acquisition unit that acquires an in-cylinder pressure that is a pressure in the combustion chamber, and a reference in-cylinder pressure that is a reference value of the in-cylinder pressure Reference in-cylinder pressure storage means, and reference in-cylinder pressure acquisition means for acquiring a reference in-cylinder pressure according to the acquired operating state based on the acquired operating state and the relationship stored in the reference in-cylinder pressure storage unit And the air supply valve driving means to open the air supply valve and start the air supply valve opening period when the acquired in-cylinder pressure becomes equal to the acquired reference in-cylinder pressure. Supply valve control means for controlling Made with a.

  According to this, the reference in-cylinder pressure corresponding to the acquired operating state is acquired based on the acquired operating state and the relationship stored in the reference in-cylinder pressure storage means, the exhaust valve is opened, and the exhaust gas is exhausted. After the valve opening period starts (exhaust valve opening timing) and when the acquired in-cylinder pressure becomes equal to the acquired in-cylinder pressure, the intake valve opens and the intake air The valve opening period begins.

  As a result, since the in-cylinder pressure at the intake valve opening timing always matches the reference in-cylinder pressure corresponding to the operating state of the internal combustion engine, the amount of combustion gas remaining in the combustion chamber and the amount of air introduced into the combustion chamber are reduced. Variations between cycles can be reduced. Thereby, the cycle-to-cycle variation of the temperature of the mixed gas formed in the combustion chamber is reduced and the cycle-to-cycle variation of the ignition timing is suppressed, so that the cycle-to-cycle variation of the combustion state can be suppressed.

  In this case, the control device for the premixed compression self-ignition internal combustion engine is in a period in which the supply valve and the exhaust valve are both open during the operating state of the internal combustion engine and the supply valve opening period. Based on the basic scavenging period storage means for storing in advance the relationship between the basic scavenging period and the basic scavenging period, and the acquired operating state and the relation stored in the basic scavenging period storage means A basic scavenging period acquisition means for acquiring a basic scavenging period according to the operated state, and when the acquired basic scavenging period has elapsed from a supply valve opening timing which is a start timing of the supply valve opening period. And an exhaust valve control means for controlling the exhaust valve driving means so that the exhaust valve opening period is ended by closing the exhaust valve.

  According to this, the basic scavenging period corresponding to the acquired operating state is acquired based on the acquired operating state and the relationship stored in the basic scavenging period storage means, and the start of the intake valve opening period When the basic scavenging period elapses from the intake valve opening timing, which is the timing, the exhaust valve is closed and the exhaust valve opening period ends.

  As a result, a scavenging period corresponding to the operating state of the internal combustion engine is always ensured regardless of the supply valve opening timing, so that the cycle-to-cycle variation of the combustion gas amount and the air amount can be further reduced. Therefore, fluctuations in the combustion state between cycles can be further suppressed.

  In this case, the exhaust valve control means closes the exhaust valve at the same time as the closing timing of the intake valve at least earlier or later than the closing timing of the intake valve, which is the end timing of the intake valve opening period. Thus, it is preferable to control the exhaust valve driving means.

  According to this, the exhaust valve closes earlier than the supply valve closing timing, which is the end timing of the supply valve opening period, or simultaneously with the supply valve closing timing.

  As a result, the exhaust valve is opened even though the supply valve is closed, so that the unburned mixed gas newly formed in the combustion chamber for the next combustion is discharged through the exhaust port. Can be prevented. Also, the actual compression ratio (ratio of the combustion chamber volume at the timing when both the supply valve and the exhaust valve close to the combustion chamber volume when the crank angle becomes top dead center) is determined only by the closing timing of the supply valve. Control can be performed. Therefore, it is possible to ensure the actual compression ratio according to the operating state only by determining the air supply valve closing timing according to the operating state of the internal combustion engine. The gas temperature) can be made higher than the temperature required for self-ignition. As a result, misfire in which the mixed gas does not ignite can be prevented, and the mixed gas can be combusted stably.

  In this case, the control device for the premixed compression self-ignition internal combustion engine includes an ignition timing estimating means for estimating an ignition timing of the immediately preceding combustion, a reference ignition timing that is a reference value of the operating state of the internal combustion engine and the ignition timing, The reference ignition timing storage means for storing the relationship in advance, and the reference ignition timing according to the acquired operating state based on the acquired operating state and the relationship stored in the reference ignition timing storage means It is preferable to include a reference scavenging period acquisition unit that corrects the acquired basic scavenging period so that the estimated ignition timing is later than the acquired reference ignition timing. It is.

  According to this, the reference ignition timing corresponding to the acquired operating state is acquired based on the acquired operating state and the relationship stored in the reference ignition timing storage means, and the estimated ignition timing is acquired. The basic scavenging period is corrected so as to be later than the reference ignition timing.

  As a result, when the ignition timing becomes earlier than the reference ignition timing, the temperature of the mixed gas can be lowered by increasing the ratio of the air amount to the combustion gas amount in the mixed gas formed in the combustion chamber. Therefore, premature ignition can be prevented. Thereby, a fuel consumption can be improved and the combustion noise which is an excessive sound accompanying combustion can be suppressed.

  Instead of the means for correcting the basic scavenging period according to the ignition timing, the control device for the premixed compression auto-ignition internal combustion engine has a maximum pressure increase rate that is a maximum value of a rate at which the in-cylinder pressure increases during the immediately preceding combustion period. A maximum pressure increase rate acquisition means for acquiring, a reference maximum pressure increase rate storage means for preliminarily storing a relationship between an operating state of the internal combustion engine and a reference maximum pressure increase rate that is a reference value of the maximum pressure increase rate; Reference maximum pressure increase rate acquisition means for acquiring a reference maximum pressure increase rate according to the acquired operation state based on the acquired operation state and the relationship stored in the reference maximum pressure increase rate storage means; It is also preferable to comprise basic scavenging period correction means for correcting the acquired basic scavenging period so that the acquired maximum pressure increase rate is smaller than the acquired reference maximum pressure increase rate.

  According to this, the reference maximum pressure increase rate corresponding to the acquired operation state is acquired based on the acquired operation state and the relationship stored in the reference maximum pressure increase rate storage means, and the acquired maximum The basic scavenging period is corrected so that the pressure increase rate is smaller than the acquired reference maximum pressure increase rate.

  As a result, when the maximum pressure increase rate is equal to or higher than the reference maximum pressure increase rate, the temperature of the mixed gas is increased by increasing the ratio of the air amount to the combustion gas amount in the mixed gas formed in the combustion chamber. Since it can be lowered, rapid combustion can be prevented. Thereby, the combustion noise which generate | occur | produces by the rapid raise of the pressure in a combustion chamber can be suppressed.

  Hereinafter, embodiments of a control device for a premixed compression self-ignition internal combustion engine according to the present invention will be described with reference to the drawings. FIG. 2 shows a schematic configuration of a system in which the control device according to the first embodiment is applied to a two-cycle premixed compression self-ignition internal combustion engine. FIG. 2 shows only a cross section of the specific cylinder, but the other cylinders have the same configuration.

  The internal combustion engine 10 supplies air to a cylinder block portion 20 including a cylinder block, a cylinder block lower case and an oil pan, a cylinder head portion 30 fixed on the cylinder block portion 20, and the cylinder block portion 20. And an exhaust system 50 for releasing the exhaust gas from the cylinder block 20 to the outside.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an air supply port 31 communicating with the combustion chamber 25, an air supply valve 32 for opening and closing the air supply port 31, an air supply valve driving mechanism 32a as an air supply valve driving means for driving the air supply valve 32, An exhaust port 33 communicating with the combustion chamber 25, an exhaust valve 34 for opening and closing the exhaust port 33, an exhaust valve driving mechanism 34a as an exhaust valve driving means for driving the exhaust valve 34, a spark plug 35, and a high voltage applied to the spark plug 35 An igniter 36 including an ignition coil to be generated, an injector 37 that injects fuel into the combustion chamber 25, a pressure accumulation chamber 37a that supplies high pressure fuel to the injector 37, and a fuel pump 37b that pressure-feeds the fuel to the pressure accumulation chamber 37a are provided. The supply valve drive mechanism 32 a and the exhaust valve drive mechanism 34 a are connected to a drive circuit 38.

  The air supply system 40 communicates with the air supply port 31 and has an intake manifold including an intake manifold that forms an air supply passage with the air supply port 31, a surge tank 42 communicated with the air supply pipe 41, and one end connected to the surge tank 42. The air supply duct 43, the air filter 44, the compressor 91a of the turbocharger 91, and the bypass flow rate adjusting valve disposed in the air supply duct 43 in this order from the other end of the air supply duct 43 toward the downstream side (the air supply pipe 41). 45, an intercooler 46 and a throttle valve 47 are provided.

  The air supply system 40 further includes a bypass passage 48. One end of the bypass passage 48 is connected to the bypass flow rate adjustment valve 45, and the other end is connected to the air supply duct 43 at a position between the intercooler 46 and the throttle valve 47. The bypass flow rate adjusting valve 45 changes the valve opening degree (not shown) in response to the drive signal, so that the air amount flowing into the intercooler 46 and the air amount bypassing the intercooler 46 (the air amount flowing into the bypass passage 48). ) And can be adjusted.

  The intercooler 46 is a water-cooled type, and cools the air passing through the air supply duct 43. The intercooler 46 is connected to a radiator 46a that releases heat of the cooling water in the intercooler 46 to the atmosphere, and a circulation pump 46b that circulates the cooling water between the intercooler 46 and the radiator 46a.

  The throttle valve 47 is rotatably supported by the air supply duct 43, and is driven by a throttle valve actuator 47a so that the opening cross-sectional area of the air supply passage is variable.

  The exhaust system 50 bypasses the exhaust pipe 51 including an exhaust manifold that communicates with the exhaust port 33 and forms an exhaust passage together with the exhaust port 33, the turbine 91b of the turbocharger 91 disposed in the exhaust pipe 51, and the turbine 91b. Thus, both ends are arranged in a wastegate passage 52 communicated with the exhaust pipe 51 upstream and downstream of the turbine 91b, a supercharging pressure adjustment valve 52a disposed in the wastegate passage 52, and an exhaust pipe 51 downstream of the turbine 91b. A three-way catalyst device 53 is provided.

  With such an arrangement, the turbine 91b of the turbocharger 91 is rotated by the energy of the exhaust gas, whereby the compressor 91a of the air supply system 40 is rotated to compress the air. Thereby, the turbocharger 91 supercharges air to the internal combustion engine 10. The supercharging pressure adjustment valve 52a adjusts the amount of exhaust gas flowing into the turbine 91b in response to the drive signal, thereby adjusting the pressure (supercharging pressure) in the air supply pipe 41. The supercharging pressure is controlled by the supercharging pressure adjustment valve 52a so as to coincide with a target supercharging pressure determined by the load (for example, accelerator pedal operation amount Accp) of the internal combustion engine 10 and the engine speed NE. It has become.

  On the other hand, this system includes an air flow meter 61, a crank position sensor 62, an in-cylinder pressure sensor 63 as an in-cylinder pressure acquisition means, and an accelerator opening sensor 64. The air flow meter 61 outputs a signal representing the amount of air taken in. The crank position sensor 62 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °. This signal represents the engine speed NE. The in-cylinder pressure sensor 63 outputs a signal representing the pressure (in-cylinder pressure) P in the combustion chamber 25. The in-cylinder pressure sensor 63 may be provided in the cylinder head portion 30 above the combustion chamber 25. The accelerator opening sensor 64 outputs a signal indicating the operation amount Accp of the accelerator pedal 65 operated by the driver.

  The electric control device 70 is a CPU 71 connected to each other by a bus, a ROM 72 pre-stored with programs executed by the CPU 71, tables (lookup tables, maps), constants, and the like, and the CPU 71 temporarily stores data as necessary. The microcomputer includes a RAM 73, a backup RAM 74 that stores data while the power is turned on, and retains the stored data while the power is shut off, an interface 75 including an AD converter, and the like. The interface 75 is connected to the sensors 61 to 64, supplies signals from the sensors 61 to 64 to the CPU 71, and according to instructions from the CPU 71, the drive circuit 38, the igniter 36, the injector 37, the fuel pump 37b, the throttle valve. Drive signals are sent to the actuator 47a, the bypass flow rate adjustment valve 45 and the supercharging pressure adjustment valve 52a.

  Next, an outline of the operation of the control device configured as described above will be described.

  The control device acquires the exhaust valve opening timing EO based on the operating state of the internal combustion engine 10, and opens the exhaust valve 34 at the acquired exhaust valve opening timing EO. Further, the control device acquires the in-cylinder pressure, and opens the air supply valve 32 when the acquired in-cylinder pressure becomes equal to or lower than a reference in-cylinder pressure that is predetermined according to the operating state of the internal combustion engine 10.

  Next, the control device acquires a scavenging period according to the operating state of the internal combustion engine 10, and closes the exhaust valve 34 when the scavenging period elapses from when the air supply valve 32 is opened. Thereafter, the control device acquires the supply valve closing timing IC according to the operating state of the internal combustion engine 10, and closes the supply valve 32 at the acquired supply valve closing timing IC.

  Thus, the air supply valve 32 opens when the in-cylinder pressure becomes equal to or lower than the reference in-cylinder pressure, so that the in-cylinder pressure at the intake valve opening timing IO is not affected by the ignition timing. Therefore, the cycle-to-cycle variation in the amount of combustion gas remaining in the combustion chamber 25 and the amount of air introduced into the combustion chamber 25 is reduced, and the variation in the combustion state between cycles is suppressed.

  Further, this control device estimates the ignition timing for the purpose of improving fuel consumption and suppressing combustion noise, and corrects the basic scavenging period so that the estimated ignition timing is later than the reference ignition timing.

  Hereinafter, the details of the operation of this control device will be described from the time when the crank angle becomes the top dead center TDC. These operations are executed by the CPU 71 every time a predetermined minute crank angle is increased. The exhaust valve opening timing control routine, the intake valve opening timing control routine, the exhaust valve closing timing control routine, This is accomplished by a valve closing timing control routine and an ignition timing estimation routine, and an exhaust valve control end flag initialization routine executed by the CPU 71 each time the crank angle reaches the top dead center TDC.

(Before opening the exhaust valve)
When the crank angle reaches a predetermined crank angle immediately after top dead center TDC, the CPU 71 starts the processing of the exhaust valve opening timing control routine shown by the flowchart in FIG. 3 from step 300 and proceeds to step 310 to open the exhaust valve. It is determined whether or not the value of the valve flag Xeo is “0” and the value of the exhaust valve control end flag Xef is “0”.

  Here, the exhaust valve opening flag Xeo is a flag indicating whether or not the exhaust valve 34 is open. If the value is “1”, the valve is open, and if it is “0”, the valve is closed. Indicates that he is speaking. As will be described later, the value of the exhaust valve opening flag Xeo is set to “1” immediately after the exhaust valve 34 is opened in this routine (see step 370 in FIG. 3), and the exhaust valve closing timing control routine is performed. Immediately after the exhaust valve 34 is closed, it is set to “0” (see step 540 in FIG. 5). Since the current time is immediately after the crank angle becomes the top dead center TDC, the exhaust valve 34 is closed. Therefore, the value of the exhaust valve opening flag Xeo is “0”.

  The exhaust valve control end flag Xef is a flag indicating whether or not the opening / closing control of the exhaust valve 34 is ended in the current cycle. If the value is “1”, the exhaust valve control end flag Xef is ended. Indicates that it has not ended. As will be described later, the value of the exhaust valve control end flag Xef is set to “1” immediately after the exhaust valve 34 is closed in the exhaust valve closing timing control routine (see step 550 in FIG. 5), and the crank angle. Is set to “0” in the exhaust valve control end flag initialization routine executed when the top dead center TDC is reached (see step 710 in FIG. 7). Since the current time is immediately after the crank angle becomes the top dead center TDC, the value of the exhaust valve control end flag Xef is “0”.

  Accordingly, the CPU 71 makes a “Yes” determination at step 310 to proceed to step 320 and read the accelerator pedal operation amount Accp, and at the next step 330 read the engine speed NE. The accelerator pedal operation amount Accp and the engine rotational speed NE represent the operating state of the internal combustion engine 10. Next, the CPU 71 proceeds to step 340, and acquires the exhaust valve opening timing EO based on the map shown in step 340 and the read accelerator pedal operation amount Accp and engine rotation speed NE.

  Next, the CPU 71 proceeds to step 350 and compares the current crank angle (the crank angle at the start of the routine) with the acquired exhaust valve opening timing EO. Since the current crank angle is in the vicinity of the top dead center TDC, the crank angle is before the exhaust valve opening timing EO. Accordingly, the CPU 71 makes a “No” determination at step 350 to proceed to step 399 to end the present routine tentatively. In this case, the exhaust valve 34 does not open.

  On the other hand, the CPU 71 starts the processing of the supply valve opening timing control routine shown in the flowchart of FIG. 4 from step 400, proceeds to step 402, and the value of the exhaust valve opening flag Xeo is “1” and the supply air It is determined whether or not the value of the valve opening flag Xio is “0”.

  Here, the air supply valve opening flag Xio is a flag indicating whether or not the air supply valve 32 is open. If the value is “1”, the valve is open, and if it is “0”. Indicates that the valve is closed. As will be described later, the value of the air supply valve opening flag Xio is set to “1” immediately after the air supply valve 32 is opened in this routine (see step 418 in FIG. 4), and the air supply valve is closed. Immediately after the air supply valve 32 is closed in the timing control routine, it is set to “0” (see step 640 in FIG. 6). Since the current time is immediately after the crank angle becomes the top dead center TDC, the air supply valve 32 is closed. Therefore, the value of the supply valve opening flag Xio is “0”.

  In this case, since the value of the exhaust valve opening flag Xeo is “0”, the CPU 71 determines “No” in step 402, proceeds to step 499, and ends this routine once.

  Further, the CPU 71 starts the processing of the exhaust valve closing timing control routine shown in the flowchart of FIG. 5 from step 500, proceeds to step 510, and the value of the exhaust valve opening flag Xeo is “1” and the air supply valve It is determined whether or not the value of the valve opening flag Xio is “1”. Since the value of the exhaust valve opening flag Xeo is “0” and the value of the air supply valve opening flag Xio is also “0” at this time, the CPU 71 determines “No” in step 510, and step 599. Proceed to to end the present routine.

  In addition, the CPU 71 starts the processing of the air supply valve closing timing control routine shown in the flowchart of FIG. 6 from step 600 and proceeds to step 610 to check whether the value of the air supply valve opening flag Xio is “1”. Determine whether or not. Since the value of the air supply valve opening flag Xio is “0” at this time, the CPU 71 determines “No” in step 610, proceeds to step 699, and ends this routine once.

  The above processing for the exhaust valve opening timing control routine, the air supply valve opening timing control routine, the exhaust valve closing timing control routine, and the air supply valve closing timing control routine is performed in step 350 in the exhaust valve opening timing control routine. It is repeatedly executed until it is determined as “Yes”. On the other hand, the high-pressure combustion gas in the combustion chamber 25 pushes down the piston 22 during this time.

(Exhaust valve open)
The crank angle increases with time and coincides with the exhaust valve opening timing EO. At this time, when the CPU 71 starts the processing of the exhaust valve opening timing control routine of FIG. 3, the CPU 71 determines “Yes” when it proceeds to step 350, and proceeds to step 360.

  In step 360, the CPU 71 sends a drive signal for opening the exhaust valve 34 to the drive circuit 38 via the interface 75. As a result, the exhaust valve 34 is opened by the exhaust valve drive mechanism 34a. As a result, high-pressure combustion gas begins to be discharged from the combustion chamber 25 through the exhaust port 33.

  Next, the CPU 71 proceeds to step 370 to set the value of the exhaust valve opening flag Xeo to “1”, and in the subsequent step 399, this routine is once ended. Thus, the exhaust valve 34 is opened at the exhaust valve opening timing EO. Further, since the value of the exhaust valve opening flag Xeo is set to “1”, when the CPU 71 subsequently proceeds to step 310, it determines “No” in step 310 and proceeds directly to step 399. become.

(Before opening the air supply valve)
At this time, the value of the exhaust valve opening flag Xeo is “1” and the value of the air supply valve opening flag Xio is “0”. Therefore, when the CPU 71 starts the processing of the air supply valve opening timing control routine of FIG. 4, the CPU 71 determines “Yes” when it proceeds to step 402, proceeds to step 404, reads the accelerator pedal operation amount Accp, In step 406, the engine speed NE is read. Next, the CPU 71 proceeds to step 408, and acquires the reference in-cylinder pressure A based on the map shown in step 408, the read accelerator pedal operation amount Accp, and the engine speed NE.

  As will be described later, the air supply valve 32 opens when the acquired in-cylinder pressure P becomes equal to or less than the reference in-cylinder pressure A. Therefore, when the reference in-cylinder pressure A is larger than the supercharging pressure controlled according to the operating state of the internal combustion engine 10, the combustion gas in the combustion chamber 25 flows out to the air supply port 31. The outflowing combustion gas flows into the combustion chamber 25 again from the air supply port 31 as the in-cylinder pressure P decreases, and then air flows into the combustion chamber 25. As a result, the amount of air in the mixed gas used for the next combustion decreases, and the amount of combustion gas increases.

  On the other hand, when the reference in-cylinder pressure A is smaller than the supercharging pressure, the combustion gas in the combustion chamber 25 hardly flows into the air supply port 31, and air flows into the combustion chamber 25 from the air supply port 31. As a result, the amount of air in the mixed gas used for the next combustion increases, and the amount of combustion gas decreases.

  From the above, the reference in-cylinder pressure A is set so that the air amount and the combustion gas amount in the mixed gas formed in the combustion chamber 25 become the desired amounts. In this example, the reference in-cylinder pressure A is set to a value that is smaller than the in-cylinder pressure P at the exhaust valve opening timing EO and substantially equal to the supercharging pressure that is controlled according to the operating state of the internal combustion engine 10. The ROM 72 storing the map shown in step 408 constitutes a reference in-cylinder pressure storage means. Furthermore, the execution of the processing of step 408 corresponds to the achievement of the function of the reference in-cylinder pressure acquisition means.

  Next, the CPU 71 proceeds to step 410 and reads the in-cylinder pressure P based on the signal output from the in-cylinder pressure sensor 63. Then, the CPU 71 proceeds to step 412 to compare the in-cylinder pressure P with the acquired reference in-cylinder pressure A. Since the current time is immediately after the exhaust valve 34 is opened, the in-cylinder pressure P is greater than the acquired reference in-cylinder pressure A. Accordingly, the CPU 71 makes a “No” determination at step 412 to proceed to step 499, and once ends the routine at step 499. In this case, the air supply valve 32 is not opened.

  Further, the CPU 71 starts the processing of the exhaust valve closing timing control routine of FIG. At this time, the value of the exhaust valve opening flag Xeo is “1”. On the other hand, since the value of the air supply valve opening flag Xio is “0”, the CPU 71 determines “No” when it proceeds to step 510, proceeds to step 599, and ends this routine once.

  In addition, the CPU 71 starts the process of the air supply valve closing timing control routine of FIG. At this time, since the value of the air supply valve opening flag Xio is “0”, the CPU 71 determines “No” when it proceeds to step 610, proceeds to step 699, and ends this routine once.

  The above processing for the air supply valve opening timing control routine, the exhaust valve closing timing control routine, and the air supply valve closing timing control routine is performed in step 412 in the air supply valve opening timing control routine. The process is repeatedly executed until it is determined as “Yes” when the reference in-cylinder pressure A or less is reached. On the other hand, high-pressure combustion gas continues to be discharged from the combustion chamber 25 through the exhaust port 33 during this period.

(Air supply valve open)
As a result, the in-cylinder pressure P decreases with time and becomes equal to or less than the acquired reference in-cylinder pressure A. At this time, when the CPU 71 starts the processing of the air supply valve opening timing control routine of FIG. 4, the CPU 71 determines “Yes” when it proceeds to step 412, and proceeds to step 414.

  In step 414, the CPU 71 sends a drive signal for opening the air supply valve 32 to the drive circuit 38 via the interface 75. As a result, the air supply valve 32 is opened by the air supply valve drive mechanism 32a. As a result, air flows into the combustion chamber 25 through the air supply port 31, and a scavenging period in which the combustion gas remaining in the combustion chamber 25 is discharged from the exhaust port 33 by the inflowing air starts. Note that the execution of the processing of step 412 and step 414 corresponds to the achievement of the function of the air supply valve control means.

  Next, the CPU 71 proceeds to step 416 and sets the supply valve opening timing IO to the current crank angle. Then, the CPU 71 proceeds to step 418 to set the value of the intake valve opening flag Xio to “1”, and in the subsequent step 420, the map shown in the step 420, the read accelerator pedal operation amount Accp, and the engine rotation are read. The basic scavenging period Y is acquired based on the speed NE. The ROM 72 storing the map shown in step 420 constitutes a basic scavenging period storage unit. Further, the execution of the process of step 420 corresponds to the achievement of the function of the basic scavenging period acquisition means.

  Next, the CPU 71 proceeds to step 422 and acquires the reference ignition timing B and the basic scavenging period correction coefficient K based on the map shown in the step 422 and the read accelerator pedal operation amount Accp and engine rotational speed NE. Here, the reference ignition timing B is determined in advance according to the operating state of the internal combustion engine 10 so that the fuel efficiency is not deteriorated excessively or excessive combustion noise is not generated. The ROM 72 storing the map shown in step 422 constitutes a reference ignition timing storage means. Furthermore, the execution of the process of step 422 corresponds to the achievement of the function of the reference ignition timing acquisition means.

  Then, the CPU 71 proceeds to step 424 and compares the immediately preceding combustion ignition timing T estimated in the ignition timing estimation routine of FIG. 8 described later with the acquired reference ignition timing B. Here, the ignition timing T and the reference ignition timing B are represented by a crank angle (BTDC) in which the top dead center TDC is the origin and the direction opposite to the rotation direction of the crankshaft 24 is positive.

  If the ignition timing T is earlier than the acquired reference ignition timing B (greater than BTDC), the CPU 71 determines “Yes” in step 424 and proceeds to step 426. In step 426, the CPU 71 calculates a basic scavenging period correction amount by multiplying the difference between the ignition timing T and the acquired reference ignition timing B by the acquired basic scavenging period correction coefficient K. The basic scavenging period is corrected by adding the corrected amount to the basic scavenging period Y, and the scavenging period Yf is set to the corrected basic scavenging period. Thereby, the scavenging period Yf becomes longer than the basic scavenging period Y.

  On the other hand, if the ignition timing T coincides with the acquired reference ignition timing B or is later than the reference ignition timing B (small in BTDC), the CPU 71 determines “No” in step 424 and determines in step 428. Proceed to and set the scavenging period Yf to the basic scavenging period Y. Note that the execution of the processing of step 424, step 426, and step 428 corresponds to the achievement of the function of the basic scavenging period correction means in the first embodiment.

  Next, the CPU 71 proceeds to step 430, sets the exhaust valve closing timing EC to a value obtained by adding the scavenging period Yf to the above-described set air supply valve opening timing IO, and then continues to step 432 in step 432. The air supply valve closing timing IC is acquired based on the map shown and the read accelerator pedal operation amount Accp and the engine speed NE.

  Then, the CPU 71 proceeds to step 434 and compares the exhaust valve closing timing EC with the air supply valve closing timing IC. When the exhaust valve closing timing EC becomes a crank angle after the air supply valve closing timing IC, the CPU 71 determines “Yes” at step 434 and proceeds to step 436 to proceed to the exhaust valve closing timing. EC is set to the supply valve closing timing IC. Therefore, the exhaust valve closing timing EC is determined so as not to have a crank angle after the supply valve closing timing IC. In other words, the exhaust valve 34 closes at the same time as the air supply valve closing timing IC at the latest or later than the air supply valve closing timing IC. Next, the CPU 71 proceeds to step 499 to end the present routine tentatively. Note that the processing of each step from step 430 to step 436 corresponds to the achievement of part of the function of the exhaust valve control means.

  On the other hand, if the exhaust valve closing timing EC coincides with the air supply valve closing timing IC or if the crank angle is earlier than the air supply valve closing timing IC, the CPU 71 determines “No” in step 434. And the routine proceeds to step 499 to end this routine once without changing the exhaust valve closing timing EC. As described above, the exhaust valve closing timing EC and the supply valve closing timing IC are determined.

(Before closing the exhaust valve)
At this time, the value of the air supply valve opening flag Xio is set to “1” in the previous step 418. Accordingly, when the CPU 71 proceeds to step 402 thereafter, it is determined as “No” in step 402 and the process immediately proceeds to step 499. Further, since the value of the exhaust valve opening flag Xeo is maintained at “1”, when the CPU 71 starts the processing of the exhaust valve closing timing control routine of FIG. If “Yes” is determined, the process proceeds to step 520 to compare the current crank angle with the exhaust valve closing timing EC.

  Since the present time is immediately after the intake valve 32 is opened, the current crank angle is a crank angle before the exhaust valve closing timing EC. Therefore, the CPU 71 makes a “No” determination at step 520 to proceed to step 599 to end the present routine tentatively. In this case, the exhaust valve 34 is not closed.

(Before closing the air supply valve)
Further, when the CPU 71 starts the processing of the air supply valve closing timing control routine of FIG. The valve closing timing IC is compared.

  Since the present time is immediately after the supply valve 32 is opened, the current crank angle is a crank angle before the supply valve closing timing IC. Therefore, the CPU 71 makes a “No” determination at step 620 to proceed to step 699 to end the present routine tentatively. In this case, the supply valve 32 does not close.

(Exhaust valve closed)
Thereafter, the crank angle increases with time and coincides with the exhaust valve closing timing EC. At this time, when the CPU 71 starts the processing of the exhaust valve closing timing control routine of FIG. 5, the CPU 71 determines “Yes” when it proceeds to step 520, and proceeds to step 530.

  In step 530, the CPU 71 sends a drive signal for closing the exhaust valve 34 to the drive circuit 38 via the interface 75. As a result, the exhaust valve 34 is closed by the exhaust valve drive mechanism 34a, and the air supply stroke starts. In addition to the steps from step 430 to step 436 in FIG. 4, the execution of the processing of step 520 and step 530 corresponds to the achievement of the function of the exhaust valve control means.

  Next, the CPU 71 proceeds to step 540, sets the value of the exhaust valve opening flag Xeo to “0”, and sets the value of the exhaust valve control end flag Xef to “1” in the subsequent step 550. Next, the CPU 71 proceeds to step 599 to end the present routine tentatively.

  Thus, the exhaust valve 34 is closed at the exhaust valve closing timing EC. Further, the value of the exhaust valve opening flag Xeo is set to “0”, and the value of the exhaust valve control end flag Xef is set to “1”. Accordingly, when the CPU 71 subsequently proceeds to step 510, it determines “No” in step 510 and immediately proceeds to step 599.

  At this stage, when the CPU 71 starts the processing of the exhaust valve opening timing control routine of FIG. 3, the CPU 71 determines “No” when it proceeds to step 310, proceeds to step 399, and once ends this routine. The above processing for this routine is repeatedly executed until the value of the exhaust valve control end flag Xef is set to “0” in step 710 in the exhaust valve control end flag initialization routine described later.

(Air supply valve closed)
Thereafter, the crank angle increases with time, and coincides with the supply valve closing timing IC. At this time, when the CPU 71 starts the process of the air supply valve closing timing control routine of FIG. 6, the CPU 71 determines “Yes” when it proceeds to step 620, and proceeds to step 630.

  In step 630, the CPU 71 sends a drive signal for closing the air supply valve 32 to the drive circuit 38 via the interface 75. As a result, the air supply valve 32 is closed by the air supply valve drive mechanism 32a, and a compression stroke in which the mixed gas in the combustion chamber 25 is compressed is started.

  Next, the CPU 71 proceeds to step 640 to set the value of the intake valve opening flag Xio to “0”, and at the subsequent step 650 to set the value of the ignition timing estimation completion flag Xig to “0”. Proceed to end this routine.

  Here, the ignition timing estimation completion flag Xig is a flag indicating whether or not the estimation of the ignition timing has been completed in the current cycle. If the value is “1”, the ignition timing is estimated. “0” indicates that it has not been estimated. The value of the ignition timing estimation completion flag Xig is set to “1” immediately after the ignition timing is estimated in an ignition timing estimation routine described later (see step 870 in FIG. 8).

  Thus, the supply valve 32 is closed at the supply valve closing timing IC. Further, the value of the supply valve opening flag Xio is set to “0”, and the value of the ignition timing estimation completion flag Xig is also set to “0”. Therefore, when the CPU 71 proceeds to step 610 thereafter, it is determined as “No” in step 610 and the process immediately proceeds to step 699.

(Initialization of exhaust valve control end flag)
Thereafter, when the crank angle becomes the next top dead center TDC, the CPU 71 starts the processing of the exhaust valve control end flag initialization routine shown in the flowchart of FIG. The value of the control end flag Xef is set to “0”. Next, the CPU 71 proceeds to step 799 to end the present routine tentatively.

  As described above, since the value of the exhaust valve control end flag Xef is set to “0”, when the CPU 71 starts the processing of the exhaust valve opening timing control routine of FIG. 3 at this time, the CPU 71 proceeds to step 310. At this time, it is determined as “Yes”, and processing for controlling the exhaust valve opening timing in the next cycle is performed.

(Ignition timing estimation)
As described above, in this example, the basic scavenging period Y is corrected based on the immediately preceding combustion ignition timing T, and the scavenging period Yf is determined. The ignition timing is a timing when the mixed gas is ignited in the combustion chamber 25, and combustion starts from this timing. FIG. 9 is a graph conceptually showing a temporal change in the in-cylinder pressure P in a period including the vicinity of the ignition timing. As shown in FIG. 9, since the in-cylinder pressure P rapidly increases when combustion starts, the ignition timing T can be estimated from the temporal change in the in-cylinder pressure P.

  In this example, the ignition timing T is estimated to be the time when the pressure increase rate Rp in the combustion chamber 25 exceeds a predetermined threshold value Rpth. The above estimation of the ignition timing T is achieved by the CPU 71 executing an ignition timing estimation routine every time a predetermined minute crank angle is increased. Note that the execution of the ignition timing estimation routine corresponds to the achievement of the function of the ignition timing estimation means. Hereinafter, the estimation of the ignition timing T will be described with time from immediately after the supply valve 32 is closed in the supply valve closing timing control routine of FIG.

  The CPU 71 starts the processing of the ignition timing estimation routine shown in the flowchart of FIG. 8 from step 800, proceeds to step 810, and determines whether or not the value of the ignition timing estimation completion flag Xig is “0”.

  At this time, the value of the ignition timing estimation completion flag Xig is set to “0” in step 650 in the supply valve closing timing control routine of FIG. Accordingly, the CPU 71 determines “Yes” at step 810 and proceeds to step 820 to read the in-cylinder pressure P based on the signal output from the in-cylinder pressure sensor 63.

  Next, the CPU 71 proceeds to step 830 and sets the pressure increase rate Rp to the difference between the in-cylinder pressure P and the past in-cylinder pressure Pold set in step 840 described later when this routine was executed last time. Since this routine is executed for every increase of a predetermined minute crank angle, the amount of change in the in-cylinder pressure with respect to the increment of the predetermined crank angle is set as the pressure increase rate Rp. Then, the CPU 71 proceeds to step 840 and sets the past in-cylinder pressure Pold to the in-cylinder pressure P at the time of execution of this routine.

  Next, the CPU 71 proceeds to step 850 and determines whether or not the pressure increase rate Rp is larger than a predetermined threshold value Rpth of the pressure increase rate. Since the present time is immediately after the air supply valve 32 is closed, the mixed gas is not ignited, and the pressure increase rate Rp is equal to or less than the threshold value Rpth. Accordingly, the CPU 71 makes a “No” determination at step 850 to proceed to step 899 to end the present routine tentatively. The above processing for this routine is repeated until “Yes” is determined in step 850 of the routine. On the other hand, the mixed gas in the combustion chamber 25 is compressed during this time.

  Thereafter, combustion starts when the temperature of the mixed gas rises. As the combustion progresses, the pressure increase rate Rp increases and becomes larger than the threshold value Rpth. When the CPU 71 starts processing of the ignition timing estimation routine at this time, the CPU 71 determines “Yes” when it proceeds to step 850, and proceeds to step 860.

  Next, in step 860, the CPU 71 sets the ignition timing T to the current crank angle, and in the subsequent step 870, sets the value of the ignition timing estimation completion flag Xig to “1”. Then, the CPU 71 proceeds to step 899 to end the present routine tentatively. Thus, the ignition timing T is estimated. Further, since the value of the ignition timing estimation completion flag Xig is set to “1”, when the CPU 71 subsequently proceeds to step 810, it is determined as “No” in step 810 and the process immediately proceeds to step 899. become.

  Thereafter, the estimated ignition timing T is used to correct the basic scavenging period Y in step 424 and step 426 in the supply valve opening timing control routine of FIG. When the time further elapses, the value of the ignition timing estimation completion flag Xig is set to “0” in step 650 after the supply valve 32 is closed in the supply valve closing timing control routine of FIG. As a result, when the CPU 71 starts processing of the ignition timing estimation routine, the CPU 71 determines “Yes” when the routine proceeds to step 810, and proceeds to step 820 to estimate the ignition timing of the next cycle.

  As described above, in the first embodiment of the control device for a two-cycle premixed compression self-ignition internal combustion engine according to the present invention, the in-cylinder pressure is equal to or lower than a reference in-cylinder pressure that is predetermined according to the operating state of the internal combustion engine 10. When the air supply valve 32 is opened, the air supply valve 32 is opened. Thereby, the cycle-to-cycle variation of the amount of combustion gas remaining in the combustion chamber 25 and the amount of air introduced into the combustion chamber 25 can be reduced, and the cycle-to-cycle variation of the combustion state can be suppressed. .

  Further, in the first embodiment, the exhaust valve 34 is closed when the scavenging period has elapsed from the supply valve opening timing. Thereby, the scavenging period according to the operating state of the internal combustion engine 10 is always ensured regardless of the supply valve opening timing, and the fluctuation of the combustion state between cycles can be further suppressed.

  In the first embodiment, the exhaust valve 34 is closed by the air supply valve closing timing at the latest. Thereby, it is possible to prevent the unburned mixed gas newly formed in the combustion chamber for the next combustion from being discharged through the exhaust port. In addition, since the actual compression ratio according to the supply valve closing timing determined according to the operating state of the internal combustion engine 10 is always maintained, misfire can be prevented and the mixed gas is combusted stably. be able to.

  Further, in the first embodiment, the ignition timing is estimated, and the basic scavenging period is corrected so that the estimated ignition timing is later than the reference ignition timing to determine the scavenging period. Thereby, since premature ignition is prevented, fuel consumption can be improved and combustion noise can be suppressed.

  In the first embodiment, the pressure increase rate Rp is a change amount of the in-cylinder pressure P with respect to a predetermined crank angle increment. By multiplying the change amount by the engine rotational speed NE, the in-cylinder pressure for a predetermined time is obtained. The amount of change of P may be used. As a result, the pressure increase rate Rp is acquired as a value that does not depend on the engine speed NE.

  Next, a control apparatus for a two-cycle premixed compression self-ignition internal combustion engine according to a second embodiment of the present invention will be described. The second embodiment is the same as the first embodiment described above except that the basic scavenging period correction method is different. In the first embodiment, the basic scavenging period is corrected so that the ignition timing is later than the reference ignition timing. However, in the second embodiment, the maximum pressure increase rate that is the maximum value of the rate at which the in-cylinder pressure increases is the reference. The basic scavenging period is corrected to be smaller than the maximum pressure increase rate. Thereby, the rapid rise of the pressure in the combustion chamber 25 is suppressed, and combustion noise is suppressed.

  Hereinafter, the second embodiment will be described focusing on differences from the first embodiment. In the second embodiment, the CPU 71 replaces the processing from step 422 to step 428 shown in FIG. 4 with the processing from step 1022 to step 1028 shown in FIG. Execute.

  Now, the CPU 71 executes the air supply valve opening timing control routine of FIG. 4, and immediately after the air supply valve 32 is opened, the process up to acquiring the basic scavenging period Y in step 420 is completed. Suppose that it is time. At this time, the CPU 71 performs the reference maximum based on the map shown in step 1022 following step 420 and the accelerator pedal operation amount Accp read in step 404 and the engine speed NE read in step 406. Acquire pressure rise rate C and basic scavenging period correction coefficient L. Here, the reference maximum pressure increase rate C is determined in advance according to the operating state of the internal combustion engine 10 so that excessive combustion noise is not generated. Note that the ROM 72 storing the map shown in step 1022 constitutes a reference maximum pressure increase rate storage means. Furthermore, the execution of the processing of step 1022 corresponds to the achievement of the function of the reference maximum pressure increase rate acquisition means.

  Next, the CPU 71 compares the maximum pressure increase rate Rpmax within the immediately preceding combustion period acquired in the maximum pressure increase rate acquisition routine described later in step 1024 with the acquired reference maximum pressure increase rate C.

  If the maximum pressure increase rate Rpmax is greater than the acquired reference maximum pressure increase rate C, the CPU 71 determines “Yes” in step 1024 and proceeds to step 1026. In step 1026, the CPU 71 calculates the correction amount of the basic scavenging period by multiplying the difference between the maximum pressure increase rate Rpmax and the acquired reference maximum pressure increase rate C by the acquired basic scavenging period correction coefficient L. Then, the basic scavenging period is corrected by adding the calculated correction amount to the basic scavenging period Y, and the scavenging period Yf is set to the corrected basic scavenging period.

  On the other hand, if the maximum pressure increase rate Rpmax is equal to or less than the acquired reference maximum pressure increase rate C, the CPU 71 determines “No” in step 1024 and proceeds to step 1028 to set the scavenging period Yf to the basic scavenging period. Set to Y. Note that the execution of the processing of step 1024, step 1026, and step 1028 corresponds to the achievement of the function of the basic scavenging period correction means in the second embodiment.

  Next, the CPU 71 proceeds to the steps after step 430, determines the exhaust valve closing timing EC as described above, acquires the supply valve closing timing IC, and then ends this routine once.

  Further, when executing the above-described air supply valve closing timing control routine of FIG. 6, the CPU 71 performs the processing of step 1150 shown in FIG. 11 instead of the processing of step 650 shown in FIG.

  Now, it is assumed that the CPU 71 executes the supply valve closing timing control routine of FIG. 6 to close the supply valve 32 and start the compression of the mixed gas in the combustion chamber 25. At this time, the CPU 71 sets the maximum pressure increase rate Rpmax to “0” in step 1150 following step 640. As a result, the maximum pressure increase rate Rpmax is initialized simultaneously with the start of the compression stroke, so that the maximum pressure increase rate within the next combustion period can be acquired by the maximum pressure increase rate acquisition routine described later. . Next, the CPU 71 proceeds to step 699 to end the present routine tentatively.

  In addition, the CPU 71 executes a maximum pressure increase rate acquisition routine shown by a flowchart in FIG. 12 instead of the ignition timing estimation routine shown in FIG. Note that the execution of the maximum pressure increase rate acquisition routine corresponds to the achievement of the function of the maximum pressure increase rate acquisition means.

  The CPU 71 starts processing of the maximum pressure increase rate acquisition routine from step 1200, proceeds to step 1210, and reads in-cylinder pressure P based on a signal output from the in-cylinder pressure sensor 63. Next, the CPU 71 proceeds to step 1220 and sets the pressure increase rate Rp to the difference between the in-cylinder pressure P and the past in-cylinder pressure Pold set in step 1230 described later when this routine was executed last time. Since this routine is executed for every increase of a predetermined minute crank angle, the amount of change in the in-cylinder pressure with respect to the increment of the predetermined crank angle is set as the pressure increase rate Rp. Then, the CPU 71 proceeds to step 1230 and sets the past in-cylinder pressure Pold to the in-cylinder pressure P at the time of execution of this routine.

  Next, the CPU 71 proceeds to step 1240 and sets the maximum pressure increase rate Rpmax to the larger of the pressure increase rate Rp and the maximum pressure increase rate Rpmax up to the present time. Here, the function MAX is a function that compares the values of two arguments and returns the larger one as a return value. Thus, the maximum pressure increase rate Rpmax is set to the maximum pressure increase rate from when the maximum pressure increase rate Rpmax is initialized in the processing of step 1150 in the supply valve closing timing control routine to the present time. It will be. Next, the CPU 71 proceeds to step 1299 to end the present routine tentatively.

  As described above, in the second embodiment of the control device for a two-cycle premixed compression self-ignition internal combustion engine according to the present invention, the in-cylinder pressure is determined in advance according to the operating state of the internal combustion engine 10, as in the first embodiment. The air supply valve 32 is opened when the reference internal cylinder pressure or lower is reached. Thereby, the cycle-to-cycle variation of the amount of combustion gas remaining in the combustion chamber 25 and the amount of air introduced into the combustion chamber 25 can be reduced, and the cycle-to-cycle variation of the combustion state can be suppressed. .

  Furthermore, in the second embodiment, the exhaust valve 34 is closed when the scavenging period has elapsed from the supply valve opening timing, as in the first embodiment. Thereby, the scavenging period according to the operating state of the internal combustion engine 10 is always ensured regardless of the supply valve opening timing, and the fluctuation of the combustion state between cycles can be further suppressed.

  In the second embodiment, similarly to the first embodiment, the exhaust valve 34 is closed by the air supply valve closing timing at the latest. Thereby, it is possible to prevent the unburned mixed gas newly formed in the combustion chamber for the next combustion from being discharged through the exhaust port. In addition, since the actual compression ratio according to the supply valve closing timing determined according to the operating state of the internal combustion engine 10 is always maintained, misfire can be prevented and the mixed gas is combusted stably. be able to.

  In the second embodiment, the maximum pressure increase rate is acquired, and the basic scavenging period is corrected so that the acquired maximum pressure increase rate is smaller than the reference maximum pressure increase rate, and the scavenging period is determined. Thereby, the rapid rise of the pressure in the combustion chamber 25 can be suppressed, and combustion noise can be suppressed.

  In the second embodiment, the rate of pressure increase Rp is the amount of change in the in-cylinder pressure P with respect to a predetermined crank angle increment. By multiplying the change amount by the engine speed NE, the in-cylinder pressure for a predetermined time is obtained. The amount of change of P may be used. As a result, the pressure increase rate Rp is acquired as a value that does not depend on the engine speed NE.

  The present invention is not limited to the above embodiments, and various modifications can be employed within the scope of the present invention. For example, the map for the reference in-cylinder pressure, the basic scavenging period, the reference ignition timing, or the reference maximum pressure increase rate can be different for each cylinder so that the difference between the cylinders in the combustion state is suppressed. Thereby, the temporal torque fluctuation as the whole internal combustion engine is reduced, and a stable engine output can be obtained.

  Further, the map for the exhaust valve opening timing or the intake valve closing timing may be determined in advance based on the target torque determined from the accelerator pedal operation amount and the engine rotation speed and the engine rotation speed.

It is the figure which showed the time when the supply valve and the exhaust valve in a general 2 cycle internal combustion engine open and close. 1 is a schematic configuration diagram of a system in which a control device according to the present invention is applied to a two-cycle premixed compression self-ignition internal combustion engine. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to open an exhaust valve. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to open an air supply valve. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to close an exhaust valve. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to close an air supply valve. 3 is a flowchart showing a program executed by the CPU shown in FIG. 2 to initialize an exhaust valve control end flag. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to estimate ignition timing. It is the graph which showed notionally the time change of the pressure in a combustion chamber in the period including the ignition timing vicinity. FIG. 5 is a flowchart showing a process executed by the CPU shown in FIG. 2 in place of a part of the program shown in FIG. 4 in order to correct the basic scavenging period based on the maximum pressure increase rate. 7 is a flowchart showing processing executed by the CPU shown in FIG. 2 in place of a part of the program shown in FIG. 6 in order to correct the basic scavenging period based on the maximum pressure increase rate. It is the flowchart which showed the program which CPU shown in FIG. 2 performs in order to acquire the maximum pressure increase rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 31 ... Supply port, 32 ... Supply valve, 32a ... Supply valve drive mechanism, 33 ... Exhaust port, 34 ... Exhaust valve, 34a ... Exhaust valve drive mechanism, 38 ... Drive Circuit 63 ... In-cylinder pressure sensor 70 ... Electric control device

Claims (5)

An air supply valve that opens and closes an air supply port formed in the cylinder head for supplying air into the combustion chamber;
A supply valve that opens the supply valve at the start timing of the supply valve opening period, which is a period during which the supply port is open, and closes the supply valve at the end timing of the supply valve opening period. A valve driving means;
An exhaust valve that opens and closes an exhaust port formed in a cylinder head for discharging the combustion gas in the combustion chamber from the combustion chamber;
The exhaust valve is opened at the start timing of the exhaust valve opening period, which is a period earlier than the start timing of the supply valve opening period and the exhaust port is open, and the supply valve is opened. Exhaust valve driving means for closing the exhaust valve at a timing later than the start timing of the valve period and at the end timing of the exhaust valve opening period;
A control apparatus for a two-cycle premixed compression self-ignition internal combustion engine that performs premixed compression self-ignition combustion that compresses and self-ignites the mixed gas formed in the combustion chamber,
Operating state acquisition means for acquiring the operating state of the internal combustion engine;
In-cylinder pressure acquisition means for acquiring an in-cylinder pressure that is a pressure in the combustion chamber;
Reference in-cylinder pressure storage means for preliminarily storing a relationship between an operating state of the internal combustion engine and a reference in-cylinder pressure serving as a reference value of the in-cylinder pressure;
Reference in-cylinder pressure acquisition means for acquiring a reference in-cylinder pressure according to the acquired operation state based on the acquired operation state and the relationship stored in the reference in-cylinder pressure storage means;
When the acquired in-cylinder pressure becomes equal to the acquired reference in-cylinder pressure, the intake valve driving means is controlled to open the intake valve and start the intake valve opening period. A supply valve control means;
A control device for a premixed compression self-ignition internal combustion engine. A control device for a premixed compression self-ignition internal combustion engine according to claim 1,
The relationship between the operating state of the internal combustion engine and the basic scavenging period, which is the basis of the scavenging period during which the air supply valve and the exhaust valve are both open during the air supply valve opening period, Basic scavenging period storage means for storing;
Basic scavenging period acquisition means for acquiring a basic scavenging period according to the acquired operating state based on the acquired operating state and the relationship stored in the basic scavenging period storage means;
The exhaust valve is closed when the acquired basic scavenging period has elapsed from the supply valve opening timing, which is the start timing of the supply valve opening period, and the exhaust valve opening period ends. Exhaust valve control means for controlling the exhaust valve drive means;
A control device for a premixed compression self-ignition internal combustion engine. The control device for a premixed compression self-ignition internal combustion engine according to claim 2,
The exhaust valve control means is configured to close the exhaust valve at the same time as the air supply valve closing timing at the earliest or later than the air supply valve closing timing, which is the end timing of the air supply valve opening period. A control device for a premixed compression self-ignition internal combustion engine for controlling exhaust valve driving means. A control device for a premixed compression self-ignition internal combustion engine according to claim 2 or 3,
Ignition timing estimating means for estimating the ignition timing of the immediately preceding combustion,
Reference ignition timing storage means for storing in advance a relationship between the operating state of the internal combustion engine and a reference ignition timing which is a reference value of the ignition timing;
Reference ignition timing acquisition means for acquiring a reference ignition timing according to the acquired operation state based on the acquired operation state and the relationship stored in the reference ignition timing storage means;
Basic scavenging period correction means for correcting the acquired basic scavenging period so that the estimated ignition timing is later than the acquired reference ignition timing;
A control device for a premixed compression self-ignition internal combustion engine. A control device for a premixed compression self-ignition internal combustion engine according to claim 2 or 3,
Maximum pressure increase rate acquisition means for acquiring a maximum pressure increase rate that is the maximum value of the rate at which the in-cylinder pressure increases during the immediately preceding combustion period;
Reference maximum pressure increase rate storage means for storing in advance a relationship between the operating state of the internal combustion engine and a reference maximum pressure increase rate which is a reference value of the maximum pressure increase rate;
Reference maximum pressure increase rate acquisition means for acquiring a reference maximum pressure increase rate according to the acquired operation state based on the acquired operation state and the relationship stored in the reference maximum pressure increase rate storage means; ,
Basic scavenging period correction means for correcting the acquired basic scavenging period so that the acquired maximum pressure increase rate is smaller than the acquired reference maximum pressure increase rate;
A control device for a premixed compression self-ignition internal combustion engine.

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