JP2006316689A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately control crank angle at a time of engine stop to target crank angle suitable for engine restart. <P>SOLUTION: In a control device for an internal combustion engine provided with a fuel injection valve 21 injecting fuel directly into a cylinder and a spark plug 20 igniting air fuel mixture in the cylinder and restarting the internal combustion engine by performing fuel injection and ignition in a cylinder in a middle of expansion stork during engine stop when an engine restart condition is established during engine stop, a cylinder charged air quantity adjustment means adjusting cylinder charged air quantity to make cylinder charge air quantities different between in a compression stroke cylinder which is in a middle of compression stroke and an expansion stroke cylinder which is in a middle of expansion stroke at a time of engine stop by reducing pressure in at least one cylinder right before engine stop or after engine stop is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

In recent years, for the purpose of reducing fuel consumption and reducing CO ₂ emissions, the internal combustion engine is automatically stopped when the vehicle equipped with the internal combustion engine is stopped, and the internal combustion engine is automatically activated when the vehicle starts again. A control device for an internal combustion engine that performs control to be restarted (hereinafter referred to as “eco-run control”) has been developed. During such eco-run control, for example, when the vehicle is stopped and the amount of depression of the accelerator pedal by the driver is zero, the engine stop condition is satisfied, and the fuel supply from the fuel injection valve or the spark plug The ignition due to is stopped, and the rotation of the internal combustion engine is stopped. Thereafter, the engine restart condition is satisfied, for example, when the accelerator pedal is depressed, and the internal combustion engine is rotated again.

  When such an eco-run control is performed, if the starter motor is always used to restart the internal combustion engine when the engine restart condition is satisfied, the starter motor is used many times and the life of the starter motor is shortened. Shorter. Further, since the battery charge / discharge load increases with the increase in use of the starter motor, a large capacity battery is required.

  Therefore, in the apparatus described in Patent Document 1, fuel injection and ignition are performed on a cylinder in the middle of an expansion stroke while the engine is stopped, and the internal combustion engine is started without using a starter motor by combustion of the air-fuel mixture accompanying this. I try to let them. This reduces the number of times the starter motor is used and eliminates the need for a large capacity battery.

  In particular, in the apparatus described in Patent Document 1, the throttle valve opening is increased as the fuel injection and ignition are stopped after the engine stop condition is satisfied, so that the in-cylinder charged air amount is increased for each cylinder. . As a result, the cylinder in the middle of the compression stroke when the engine is stopped (hereinafter referred to as “compression stroke cylinder”) and the cylinder in the middle of the expansion stroke (hereinafter referred to as “expansion stroke cylinder”) in large quantities and substantially the same amount. Therefore, when the engine is stopped, the piston is located near the middle position of the stroke.

JP 2004-124754 A JP 2002-39038 A

  Incidentally, in the device of Patent Document 1, the crank angle at which the piston of the expansion stroke cylinder is near the middle position of the stroke and close to the bottom dead center (that is, the cylinder volume of the expansion stroke cylinder is the compression stroke). The crank angle when the engine is stopped is controlled with the aim of a crank angle that is larger than the cylinder volume of the cylinder) to improve the restartability. Such control of the crank angle when the engine is stopped is performed by adjusting the opening of the throttle valve so that the in-cylinder charged air amount in the compression stroke cylinder is larger than the in-cylinder charged air amount in the expansion stroke cylinder. Has been done by.

  However, in general, since there is a certain distance from the throttle valve to each cylinder, the amount of air flowing into each cylinder does not decrease at the same time as the opening of the throttle valve is reduced. Therefore, it is difficult to accurately control the in-cylinder charged air amount to the expansion stroke cylinder and the in-cylinder charged air amount to the compression stroke cylinder by adjusting the opening of the throttle valve. Also, if the cylinder charge air amount to the compression stroke cylinder is small from the time when the intake valve is closed, the force acting in the direction opposite to the rotation direction of the internal combustion engine caused by the compressed air in the compression stroke cylinder is small, so the internal combustion engine is compressed. The stroke cylinder may rotate beyond the compression top dead center. Therefore, it has been difficult to accurately control the crank angle when the engine is stopped to the target crank angle.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can accurately control the crank angle when the engine is stopped to a target crank angle suitable for engine restart.

In order to solve the above-described problem, the first invention includes a fuel injection valve that directly injects fuel into the cylinder, and an ignition plug that ignites the air-fuel mixture in the cylinder. In an internal combustion engine controller that restarts an internal combustion engine by injecting and igniting a cylinder in the middle of an expansion stroke while the engine is stopped when the engine restart condition is satisfied, immediately before or after the engine is stopped, By reducing the in-cylinder pressure of at least one of the cylinders, the in-cylinder charged air amount is different between the compression stroke cylinder that is in the middle of the compression stroke and the expansion stroke cylinder that is in the middle of the expansion stroke when the engine is stopped. Further, a cylinder filling air amount adjusting means for adjusting the cylinder filling air amount is further provided.
According to the first aspect of the invention, since the cylinder charge air amount is adjusted by reducing the cylinder pressure, the cylinder charge air amount of the compression stroke cylinder or the expansion stroke cylinder can be accurately controlled. become.

  According to a second invention, in the first invention, the internal combustion engine has four cylinders, and the in-cylinder charged air amount adjusting means has a crank angle at a time when the engine is stopped of 105 to 105 based on a compression top dead center of the expansion stroke cylinder The in-cylinder charged air amount is adjusted to be 125 degrees.

  According to a third invention, in the first invention, the internal combustion engine has six cylinders, and the cylinder charge air amount adjusting means has a crank angle at the time of engine stop of 60 to 60 based on a compression top dead center of the expansion stroke cylinder. The in-cylinder charged air amount is adjusted to be 70 degrees.

  According to a fourth invention, in any one of the first to third inventions, the at least one cylinder is a compression stroke cylinder, and the in-cylinder charged air amount adjusting means is provided in the cylinder of the compression stroke cylinder. By reducing the pressure, the in-cylinder charged air amount is adjusted so that the in-cylinder charged air amount of the compression stroke cylinder becomes smaller than the in-cylinder charged air amount of the expansion stroke cylinder.

  According to a fifth aspect, in the fourth aspect, the cylinder charge air amount adjusting means reduces the cylinder pressure of the compression stroke cylinder when the internal combustion engine is rotating in reverse before the engine is stopped.

  According to a sixth aspect, in the fourth aspect, the in-cylinder charged air amount adjusting means is configured such that the compression stroke is performed when the internal combustion engine is stationary while trying to shift from forward rotation to reverse rotation. Reduce cylinder pressure in cylinder.

  According to a seventh invention, in the sixth invention, there is further provided a stationary crank angle adjusting means for adjusting an operating parameter of the internal combustion engine so that a crank angle when the internal combustion engine is temporarily stationary becomes a predetermined crank angle. To do.

  In an eighth invention, in any one of the first to fourth inventions, the reduction of the in-cylinder pressure of at least one of the cylinders is performed after the engine is stopped and in the cylinders of the compression stroke cylinder and the expansion stroke cylinder. Performed when the pressure is higher than atmospheric pressure.

  According to a ninth invention, in any one of the first to eighth inventions, an intake valve and an exhaust valve are further provided, and the in-cylinder pressure of the at least one cylinder is reduced by opening the intake valve or the exhaust valve. By valve.

  According to a tenth invention, in the first to eighth inventions, there is provided an auxiliary valve for reducing the in-cylinder pressure separately from the intake valve and the exhaust valve, and assists in reducing the in-cylinder pressure of at least one of the cylinders This is done by opening the valve.

  In an eleventh aspect of the invention, in the first to tenth aspects of the invention, retard control is performed to retard the opening / closing valve timings of the intake valve and the exhaust valve after the engine is stopped.

  According to the present invention, the cylinder charge air amount of the compression stroke cylinder or the expansion stroke cylinder can be accurately controlled, so that the crank angle when the engine is stopped is accurately controlled to a target crank angle suitable for engine restart. Will be able to.

  Hereinafter, the control device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an entire internal combustion engine in which the control device of the first embodiment of the present invention is used.

  Referring to FIG. 1, the engine body 1 includes a plurality of, for example, four cylinders 1a. Each cylinder 1 a is connected to a surge tank 3 via a corresponding intake branch pipe 2, and the surge tank 3 is connected to an air cleaner 5 via an intake duct 4. A throttle valve 7 driven by an actuator 6 is disposed in the intake duct 4. Each cylinder 1 a is connected to a catalytic converter 11 having an exhaust purification catalyst 10 built in via an exhaust manifold 8 and an exhaust pipe 9. In the internal combustion engine shown in FIG. 1, combustion is performed in the order of # 1- # 3- # 4- # 2.

  Referring to FIG. 2 showing details of each cylinder 1a, 12 is a cylinder block, 13 is a cylinder head fixed on the cylinder block 12, 14 is a piston reciprocating in the cylinder block 12, and 15 is a piston 14 and cylinder head 13. , 16 is a pair of intake ports, 17 is a pair of intake valves, 18 is a pair of exhaust ports, and 19 is a pair of exhaust valves. A spark plug 20 is arranged at the center of the inner wall surface of the cylinder head 13, and a fuel injection valve 21 is arranged around the inner wall surface of the cylinder head 13.

  The intake valve 17 of each cylinder is driven to open and close by an intake valve drive device 22. The intake valve drive device 22 includes a camshaft and a switching mechanism for selectively switching the rotation angle of the camshaft with respect to the crank angle between the advance side and the retard side. When the rotation angle of the camshaft is advanced, as shown by AD in FIG. 3, the valve opening timing VO and the valve closing timing VC of the intake valve 17 are advanced, and accordingly the opening / closing valve timing is advanced. On the other hand, when the rotation angle of the camshaft is retarded, the valve opening timing VO and the valve closing timing VC of the intake valve 17 are retarded as indicated by RT in FIG. In this case, the phase angle (open / close valve timing) is changed while the lift amount and operating angle (open / close valve period) of the intake valve 17 are maintained. In the internal combustion engine shown in FIG. 1, the rotation angle of the camshaft is switched to the advance side or the retard side according to the engine operating state. Note that the present invention can also be applied when the valve opening timing of the intake valve 17 is continuously changed, or when the lift amount or the operating angle is changed.

  Further, the exhaust valve 18 of each cylinder is driven to open and close by an exhaust valve driving device 23. Similarly to the intake valve drive device 22, the exhaust valve drive device 23 includes a camshaft and a switching mechanism. The exhaust valve drive device 23 changes the phase angle of the exhaust valve 19 in the same manner as the intake valve 17.

  Further, an auxiliary exhaust port 24 that communicates with the combustion chamber 15 and the exhaust port 18 is formed in the cylinder head 13, and an auxiliary exhaust valve 25 that opens and closes the auxiliary exhaust port 24 is provided in the auxiliary exhaust port 24. The auxiliary exhaust valve 25 is driven to open and close by an auxiliary exhaust valve driving device 26. The auxiliary exhaust valve driving device 26 is formed of an electromagnetic actuator, and can open and close the auxiliary exhaust valve 25 regardless of the rotation of the camshaft.

  Referring to FIG. 1 again, an electric motor 28 can be connected to the crankshaft 27 via a clutch (not shown). The electric motor 28 can be formed of, for example, a so-called starter motor, or can be formed of an electric motor having a power generation function for generating electric power by being rotationally driven by the crankshaft 27.

  The electronic control unit (ECU) 30 is a digital computer, and is connected to a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, and a power source that are connected to each other via a bidirectional bus 31. B-RAM 35 (backup RAM), an input port 36, and an output port 37.

  In addition, an accelerator depression amount sensor 41 that generates an output voltage representing the depression amount of the accelerator pedal is attached to an accelerator pedal (not shown). The output signal of the accelerator depression amount sensor 41 is input to the input port 36 via the corresponding AD converter 38. A crank angle sensor 42 for detecting the crank angle is attached to the crankshaft 27, and the crank angle sensor 42 is connected to the input port 36. In the ECU 30, the engine speed is calculated based on the output of the crank angle sensor 42. Further, an ignition (IG) switch 43 that generates an output pulse that indicates being turned on and a key switch 44 that generates an output pulse that is turned on are connected to the input port 36. . The ignition switch 43 and the key switch 44 are operated by a driver of a vehicle equipped with an internal combustion engine. On the other hand, the output port 37 is connected to the actuator 6, spark plug 20, fuel injection valve 21, various valve drive devices 22, 23, 26 and electric motor 28 via corresponding drive circuits 39.

  The internal combustion engine of the present embodiment, during normal operation, injects fuel during the intake stroke, makes the air-fuel ratio of the air-fuel mixture substantially uniform over the entire combustion chamber 15, and then ignites the air-fuel mixture, Operation can be performed in two combustion modes: a stratified combustion mode in which fuel is injected during the compression stroke immediately before ignition and fuel is ignited only in the vicinity of the spark plug. These operation modes are selected based on the engine load and the engine speed. For example, in the operation region where the engine load is low and the engine speed is low, the engine is operated in the stratified combustion mode, and the engine load is high and the engine speed is low. In the operation region where the number is high, the operation is performed in the homogeneous combustion mode.

  FIG. 4 shows the opening / closing valve timing of the intake valve 17 of each cylinder, the opening / closing valve timing of the exhaust valve 19, the fuel injection timing and the ignition timing with respect to the crank angle when the operation is performed in the homogeneous combustion mode during the normal operation. FIG. In particular, FIG. 4 shows the opening / closing valve timing of the intake valve 17 (white arrow) and the opening / closing valve timing (hatched) of the exhaust valve 19 with respect to the change in crank angle when the compression top dead center of the first cylinder # 1 is set to 0 degree. Arrows), fuel injection timing (protrusion), and ignition timing (black arrows) are shown.

  As shown in the drawing, during normal operation of the internal combustion engine (that is, when the engine is not stopped by eco-run control, which will be described later), as the crankshaft 27 rotates, the intake stroke, compression stroke, The expansion stroke and the exhaust stroke are sequentially repeated. To explain with reference to the fourth cylinder, the intake valve 17 is opened during and before and after the intake stroke, and air is sucked into the cylinder during the intake stroke. In the embodiment shown in FIG. 4, fuel is injected from the fuel injection valve 21 during the intake stroke, and an air-fuel mixture is formed in the cylinder during the intake stroke. Next, the air-fuel mixture is compressed in the compression stroke, and the ignition plug 20 is ignited near the compression top dead center, whereby the air-fuel mixture is combusted. The piston 14 is pushed down in the next expansion stroke by the explosive force due to this combustion. Next, the exhaust valve 19 is opened during and before and after the exhaust stroke, and the exhaust gas in the cylinder during the exhaust stroke is discharged.

  In the above description, the case where the internal combustion engine is operated in the homogeneous combustion mode is described. However, when the internal combustion engine is operated in the stratified combustion mode, the fuel is not generated during the intake stroke but during the compression stroke. Fuel injection by the injection valve 21 is performed.

  Further, in the internal combustion engine of the present embodiment, when the ignition switch 43 is turned on by the driver, the internal combustion engine is started by the electric motor 28, and when the key switch 44 is turned off by the driver, the rotation of the internal combustion engine ( That is, the rotation of the crankshaft 27 is stopped.

  Further, in the internal combustion engine of the present embodiment, even when the key switch 44 is not turned off by the driver, the fuel injection from the fuel injection valve 21 is automatically performed when the predetermined engine stop condition is satisfied. The ignition by the spark plug 20 is stopped, and as a result, the rotation of the internal combustion engine is stopped. Thereafter, when the engine restart condition is satisfied, the rotation of the internal combustion engine is automatically started again (that is, the crankshaft 27 of the internal combustion engine is rotated again). In this way, even when the key switch is not turned off by the driver, the control automatically stops and restarts the internal combustion engine under certain conditions (hereinafter, such control is referred to as “eco-run control”). In addition, reduction of fuel consumption and suppression of deterioration of exhaust emission can be realized.

  Here, the engine stop condition is satisfied when the engine load is zero (that is, the accelerator depression amount detected by the accelerator depression amount sensor 41 is zero) and the engine speed is low, or in addition to the above conditions This is the case where the speed of the vehicle equipped with the internal combustion engine is zero, and specifically includes the case where the vehicle is decelerating rapidly, the case where the vehicle is stopped, and the like. Therefore, the success or failure of the engine stop condition is detected based on the accelerator depression amount sensor 41, the crank angle sensor 28, the vehicle speed sensor (not shown) for detecting the speed of the vehicle equipped with the internal combustion engine, and the depression amount of the brake pedal by the driver. The ECU 30 makes a determination based on the output of a brake depression amount sensor (not shown) or the like.

  On the other hand, the case where the engine restart condition is satisfied is a case where the engine load is no longer zero or a case where the engine load is expected not to be zero. Specifically, the driver depresses the accelerator pedal. And when the brake pedal is depressed by the driver, the clutch pedal depressing operation or shift position is changed from N (neutral) or P (parking) to D (drive). This includes the case where a change operation is performed. Therefore, the success or failure of the engine restart condition is determined by the accelerator depression amount sensor 41, the vehicle speed sensor, the brake depression amount sensor, the clutch sensor (not shown) for detecting the depression of the clutch pedal by the driver, and the shift position sensor (not shown). ) And the like based on the output.

  In the present embodiment, when the engine restart condition is satisfied after the rotation of the internal combustion engine is stopped by the eco-run control, the restart of the rotation of the internal combustion engine is performed without applying external force to the internal combustion engine, that is, the driving force by the electric motor 28. Without being added, fuel injection and ignition are performed on a cylinder in the middle of an expansion stroke while the engine is stopped (hereinafter referred to as “expansion stroke cylinder when stopped”). Thus, energy consumption can be reduced by resuming the rotation of the internal combustion engine.

  The resumption of rotation of the internal combustion engine performed without applying external force will be specifically described with reference to FIG. FIG. 5 is a view similar to FIG. 4 and shows the opening / closing valve timing of the intake valve 17 of each cylinder when the engine restart condition is satisfied while the engine is stopped.

  When the engine stop condition is satisfied, fuel injection and ignition are stopped for all the cylinders, the rotational speed of the internal combustion engine (that is, the rotational speed of the crankshaft 27) gradually decreases, and finally the internal combustion engine rotates at a certain crank angle. Therefore, each cylinder stops in the middle of each stroke.

  In the example shown in FIG. 5, the rotation of the internal combustion engine stops when the crank angle is at a certain crank angle θx. In this case, the first cylinder (# 1) stops in the middle of the expansion stroke, the third cylinder (# 3) stops in the middle of the compression stroke, and the fourth cylinder (# 4) stops in the middle of the intake stroke. The second cylinder (# 2) is stopped during the exhaust stroke.

  Next, when the engine restart condition is satisfied, the fuel injection valve 21 injects fuel into the cylinder of the expansion stroke cylinder at the time of stop (the first cylinder in the example of FIG. 5) with the rotation of the internal combustion engine stopped at the crank angle θx. The injected fuel forms an air-fuel mixture with the air in the cylinder. Next, the air-fuel mixture is ignited by the spark plug 20, and the air-fuel mixture is ignited and combusted. When the air-fuel mixture is ignited and combusted in the expansion stroke cylinder at the time of stop, rotation of the internal combustion engine is started by the driving force obtained by this combustion. Note that when fuel injection is performed as described above, fuel injection is performed in a situation where the in-cylinder pressure is atmospheric pressure or the temperature of the air in the cylinder is at an atmospheric temperature. Is difficult to ignite. For this reason, in this embodiment, the ignition action by the spark plug 20 is performed a plurality of times.

  Further, when the engine restart condition is satisfied, in addition to the fuel injection and ignition for the stop-time expansion stroke cylinder as described above, a cylinder in the middle of the compression stroke while the engine is stopped (hereinafter referred to as “stop-time compression stroke cylinder”). Fuel injection is performed from the fuel injection valve 21 into the cylinder of the third cylinder in the example of FIG. Such fuel injection is performed immediately after the engine restart condition is satisfied or after the engine restart condition is satisfied and immediately after the rotation of the internal combustion engine is started. Thereafter, as described above, when the internal combustion engine is rotated by the driving force due to combustion in the stop expansion stroke cylinder and the crank angle is at the compression top dead center for the stop compression stroke cylinder or immediately after the compression top dead center is exceeded. Ignition by the spark plug 20 is performed in the cylinder. Thus, following the combustion in the stop expansion stroke cylinder described above, combustion is also performed in the stop compression stroke cylinder, and the operation of the internal combustion engine is started more reliably.

  As described above, when combustion is performed for the stop expansion stroke cylinder and the stop compression stroke cylinder, the combustion is sequentially performed in each cylinder as usual. In particular, when the engine is restarted, in order to stabilize the operation of the internal combustion engine, the operation is performed in the homogeneous combustion mode, so that fuel injection is performed in the intake stroke. Accordingly, a cylinder in which normal combustion is performed next to combustion in the stop expansion stroke cylinder and the stop compression stroke cylinder, that is, a cylinder in the middle of the intake stroke while the engine is stopped (hereinafter referred to as a “stop intake stroke cylinder”). For the fourth cylinder in the example of Fig. 5, fuel injection is performed immediately after the engine restart condition is satisfied or after the engine restart condition is satisfied and immediately after the rotation of the internal combustion engine is started. Become.

  When restarting the engine, it is preferable to retard the opening / closing valve timings of the intake valve 17 and the exhaust valve 19. That is, when the closing timing of the intake valve 17 is retarded, the amount of air charged in the cylinders of the stop compression stroke cylinder and the stop intake stroke cylinder is reduced, and the crank angle is the stop compression stroke cylinder and the stop intake stroke. It becomes easy to exceed the compression top dead center of the cylinder. Further, since the opening timing of the exhaust valve 19 is retarded, the energy generated by the combustion performed in the stop expansion stroke cylinder and the stop compression stroke cylinder can be efficiently transmitted to the piston 14. The driving force of the internal combustion engine can be increased.

  By the way, as described above, even if fuel injection and ignition are performed, the rotation of the internal combustion engine cannot always be resumed. Depending on the crank angle when the engine is stopped, the rotation of the internal combustion engine can be performed even if the fuel injection and ignition are performed. Cannot be resumed. This will be described with reference to FIGS. FIG. 6 is a diagram showing the relationship between the position of the piston in the expansion stroke cylinder and the position of the piston in the compression stroke cylinder when the engine is stopped. FIG. 6 shows, as an example, the case where the first cylinder is in the middle of the expansion stroke when the engine is stopped. In the figure, # 1 and # 3 indicate the position of the piston of the first cylinder and the position of the piston of the third cylinder, respectively. ing. FIG. 7 is a graph showing changes in crank angle and in-cylinder pressure after the engine restart condition is established. FIG. 7 shows an example in which the first cylinder is in the middle of the expansion stroke when the engine is stopped.

  In general, when the engine is stopped, air flows out from the combustion chamber 15 through a joint portion of a piston ring 14a (see FIG. 2) provided on the piston 14, and therefore, when the engine is restarted, the in-cylinder pressure in all cylinders Is often at atmospheric pressure. Therefore, the cylinder air charge amount of each cylinder at the time of engine restart is proportional to the volume of the combustion chamber 15 of that cylinder.

  As shown in FIG. 6A, when the engine is stopped and the position of the piston 14 of the stop expansion stroke cylinder is close to the upper end position of the stroke (the position corresponding to the compression top dead center TDC), the stop compression stroke is performed. The position of the piston 14 of the cylinder is away from the upper end position of the stroke. Therefore, in such a case, the volume of the combustion chamber 15 of the expansion stroke cylinder at the time of stop (corresponding to the region Ve in FIG. 6) during the engine stop is the volume of the combustion chamber 15 of the compression stroke cylinder at the time of stop (in FIG. 6). Therefore, the in-cylinder charged air amount in the stop expansion stroke cylinder is small and the in-cylinder charged air amount in the stop compression stroke cylinder is large.

  If the internal combustion engine is stopped at such a crank angle, even if the air-fuel mixture is burned by injecting and igniting the fuel in the stop expansion stroke cylinder to restart the rotation of the internal combustion engine, Since the amount of air is small, sufficient driving force cannot be obtained. On the other hand, since the amount of air in the stop compression stroke cylinder is large, the in-cylinder pressure in the stop compression stroke cylinder becomes very large as the piston 14 rises toward the upper end position of the stroke. The in-cylinder pressure of the compression stroke cylinder becomes a great resistance against the rotation of the internal combustion engine. For this reason, as shown in FIG. 7A, the internal combustion engine cannot rotate beyond the compression top dead center of the compression stroke cylinder at the time of stop, that is, it rotates 180 degrees or more from the crank angle when the engine is stopped. The internal combustion engine rotates in reverse before that, and then stops.

  As shown in FIG. 6C, when the position of the piston 14 of the stop expansion stroke cylinder is away from the upper end position of the stroke when the engine is stopped, the position of the piston 14 of the stop compression stroke cylinder is the stroke. It is close to the upper end position. Therefore, in such a case, the volume of the combustion chamber 15 of the stop expansion stroke cylinder (corresponding to Ve) when the engine is stopped is larger than the volume of the combustion chamber 15 of the stop compression stroke cylinder (corresponding to Vc). The cylinder charge air amount in the stop expansion stroke cylinder is large, and the cylinder charge air amount in the stop compression stroke cylinder is small.

  When the internal combustion engine is stopped at such a crank angle, when the mixture is burned by injecting and igniting the fuel in the expansion stroke cylinder at the stop in order to restart the rotation of the internal combustion engine, Since the distance from the position of the piston 14 of the expansion stroke cylinder to the lower end position (position corresponding to the bottom dead center BDC) of the stroke is short and the piston 14 is pushed down slightly by the combustion of the air-fuel mixture, such combustion Therefore, a sufficient driving force cannot be obtained. On the other hand, since the amount of air in the stop compression stroke cylinder is small, the increase in the in-cylinder pressure accompanying the rise of the piston 14 toward the upper end position of the stroke in the stop compression stroke cylinder is small. The in-cylinder pressure of the cylinder does not become a great resistance to the rotation of the internal combustion engine. Therefore, as shown in FIG. 7C, the internal combustion engine can rotate beyond the compression top dead center of the compression stroke cylinder at the time of stop.

  However, since the air amount in the compression stroke cylinder at the time of stop is small, even if the air-fuel mixture is burned in the cylinder after the compression top dead center of the cylinder is exceeded, sufficient driving force can be obtained by such combustion. I can't. For this reason, as shown in FIG. 7 (c), the internal combustion engine cannot rotate beyond the compression top dead center of the next stop-time intake stroke cylinder, that is, 360 from the crank angle when the engine is stopped. The engine cannot be rotated more than once, and the internal combustion engine rotates in reverse before that, and then stops.

  On the other hand, as shown in FIG. 6 (b), the position of the piston 14 of the stop expansion stroke cylinder when the engine is stopped is between the position shown in FIG. 6 (a) and the position shown in FIG. 6 (c). When the engine is stopped, the volume of the combustion chamber 15 of the stop expansion stroke cylinder is slightly larger than the volume of the combustion chamber 15 of the stop compression stroke cylinder, so that the cylinder charge air amount in the stop expansion stroke cylinder is It is slightly larger than the cylinder air charge amount in the stop compression stroke cylinder.

  If the internal combustion engine is stopped at such a crank angle, when the mixture is burned by injecting and igniting the fuel in the expansion stroke cylinder at the stop in order to start the rotation of the internal combustion engine, A relatively large driving force can be obtained, and thus the internal combustion engine can rotate beyond the compression top dead center for the stop-time compression stroke cylinder, as shown in FIG.

  Further, since the amount of air in the stop-time compression stroke cylinder is relatively large, a sufficient driving force can be obtained by combustion of the air-fuel mixture performed in the stop-time compression stroke cylinder after the compression top dead center is exceeded. For this reason, as shown in FIG. 7 (b), the internal combustion engine can rotate beyond the compression top dead center of the next intake stop-stroke intake cylinder, and combustion is sequentially performed thereafter, so that the internal combustion engine Operation starts.

  FIG. 8 shows a crank angle based on the compression top dead center of the stop expansion stroke cylinder when the engine is stopped (hereinafter referred to as “stop crank angle”), and the stop expansion stroke cylinder and the stop compression as described above. It is the figure which showed the relationship with the angle which an internal combustion engine can rotate by performing fuel injection and ignition to a stroke cylinder. As shown in FIG. 8 (a), when the stop crank angle is small, particularly in the case of 0 to 100 degrees, the internal combustion engine is the first time as described with reference to FIGS. 6 (a) and 7 (a). Cannot be rotated beyond the top dead center (that is, the compression top dead center for the compression stroke cylinder when stopped). On the other hand, when the stop crank angle is large, particularly when the stop crank angle is 130 to 180 degrees, the internal combustion engine has a second top dead center (that is, stop) as described with reference to FIGS. 6 (c) and 7 (c). It is not possible to rotate beyond the compression top dead center) for the hour intake stroke cylinder. On the other hand, when the stop crank angle is medium, particularly when it is 105 to 125 degrees, the internal combustion engine rotates beyond the second top dead center as described in FIGS. 6 (b) and 7 (b). can do. Therefore, in order to restart the rotation of the internal combustion engine by fuel injection and ignition to the stop expansion stroke cylinder and the stop compression stroke cylinder, it is necessary to stop the internal combustion engine so that the stop crank angle is 105 to 125 degrees. .

  In the above description, a four-cylinder internal combustion engine is targeted. However, in the case of an internal combustion engine having four or more cylinders, the rotation of the internal combustion engine is restarted by fuel injection and ignition to the stop expansion stroke cylinder and the stop compression stroke cylinder. In addition, the stop crank angle suitable for resuming the rotation of the internal combustion engine by fuel injection and ignition to the stop expansion stroke cylinder and the stop compression stroke cylinder varies depending on the number of cylinders. FIG. 8 (b) shows a view similar to FIG. 8 (a) in a 6-cylinder internal combustion engine. From this figure, in the 6-cylinder internal combustion engine, fuel injection to the stop expansion stroke cylinder and the stop compression stroke cylinder. It can be seen that in order to restart the rotation of the internal combustion engine by ignition and the ignition, it is necessary to stop the internal combustion engine so that the stop crank angle becomes 60 to 70 degrees.

  Therefore, in the present embodiment, at a stop crank angle (hereinafter referred to as “target stop crank angle”) suitable for resuming the rotation of the internal combustion engine by fuel injection and ignition to the stop expansion stroke cylinder and the stop compression stroke cylinder. The internal combustion engine is controlled so that the internal combustion engine stops. Hereinafter, engine stop control for stopping the internal combustion engine at the target stop crank angle will be described.

  In this embodiment, when the engine stop condition is satisfied, fuel injection and ignition are stopped for all the cylinders, the opening degree of the throttle valve 7 is increased, and the closing timing of the intake valve 17 is advanced. When the opening degree of the throttle valve 7 is increased, the intake resistance caused by the throttle valve 7 is reduced, the air easily flows into each cylinder, and the closing timing of the intake valve 17 is advanced toward the bottom dead center. In other words, the intake valve 17 is closed when the volume of the combustion chamber 14 is large. As a result, after the engine stop condition is satisfied, the in-cylinder charged air amount to each cylinder becomes large.

  In this way, by increasing the amount of in-cylinder charged air into each cylinder when the engine is stopped, the internal combustion engine piston 14 is positioned near the middle position of its stroke unless the pressure in the cylinder is adjusted. It can be stopped at a proper crank angle. That is, in general, the resistance to rotation of the internal combustion engine (hereinafter referred to as “rotational resistance”) after the stop of fuel injection and ignition is mainly due to the mechanical friction and compression stroke in the internal combustion engine. Is a force (hereinafter referred to as “repulsive force”) that acts in the direction opposite to the rotational direction of the internal combustion engine due to the in-cylinder pressure. Therefore, if the amount of air filled in each cylinder is small when the engine is stopped, the repulsive force does not become a large rotational resistance, but only mechanical friction becomes the main rotational resistance. The stop crank angle is determined solely by mechanical friction. However, it is difficult to control the stop crank angle of the internal combustion engine by controlling mechanical friction.

  On the other hand, if the cylinder air charge amount in each cylinder is large when the engine is stopped, the repulsive force becomes a large resistance to the rotation of the internal combustion engine, so the repulsive force is not the main friction but the main rotational resistance. Therefore, the stop crank angle of the internal combustion engine is mainly determined by the repulsive force. Therefore, if the cylinder air charge amount to each cylinder is large, the stop crank angle of the internal combustion engine can be appropriately controlled by appropriately controlling the repulsive force. In particular, the cylinder charge air amount in the cylinder that is in the middle of the compression stroke when the engine is stopped (hereinafter referred to as “compression stroke cylinder”) and in the cylinder that is in the middle of the expansion stroke (hereinafter referred to as “expansion stroke cylinder”) is If the closing timings of the intake valves 17 are the same, they are almost the same. In such a case, the internal combustion engine is stopped so that the in-cylinder pressures are equal for both cylinders. Therefore, unless the pressure in the cylinder is particularly adjusted, the internal combustion engine stops at a crank angle at which the piston 14 is located near the middle position of the stroke. As in this embodiment, in a four-cylinder internal combustion engine, the stop crank angle is approximately 90 degrees.

FIG. 9 is a diagram showing transitions of the crank angle and the in-cylinder pressure immediately before the engine is stopped, and particularly shows a case where the internal combustion engine is stopped when the first cylinder (# 1) is in the middle of the expansion stroke. When the fuel injection and ignition to the internal combustion engine are stopped due to the establishment of the engine stop condition, the engine speed gradually decreases, and the rotation angle of the internal combustion engine that progresses per unit time becomes gradually small. In the example shown in FIG. 9, when the compression top dead center (0 degree) of the expansion stroke cylinder is exceeded at time t ₁ , the in-cylinder pressure of the first cylinder rapidly decreases, The in-cylinder pressure of the third cylinder (# 3) that reaches the compression top dead center suddenly increases. At time t ₂ , the repulsive force due to the in-cylinder pressure of the third cylinder becomes greater than the rotational inertia force of the internal combustion engine, whereby the rotation of the internal combustion engine is temporarily stopped, and then the internal combustion engine is reversely rotated.

When the internal combustion engine rotates in the reverse direction, the in-cylinder pressure of the first cylinder decreases and simultaneously the in-cylinder pressure of the first cylinder increases again. When the internal combustion engine rotates to some extent, the force acting in the forward rotation direction of the internal combustion engine due to the in-cylinder pressure of the first cylinder causes the inertial force in the reverse rotation direction of the internal combustion engine and the repulsive force due to the in-cylinder pressure of the third cylinder. The rotation of the internal combustion engine once stops, and then the internal combustion engine rotates forward again (time t ₃ ). In this way, the internal combustion engine repeats forward rotation and reverse rotation, and finally stops at a crank angle (about 90 degrees in the example shown in FIG. 9) such that the piston 14 is located near the middle position of the stroke.

  Here, in order to stop the internal combustion engine at the target stop crank angle described above, the in-cylinder pressure is reduced for at least one of the cylinders, and the in-cylinder charge air amount of the expansion stroke cylinder is reduced to the in-cylinder charge of the compression stroke cylinder. It is conceivable to increase the air amount. Since the internal combustion engine basically stops so that the in-cylinder pressure of the expansion stroke cylinder becomes equal to the in-cylinder pressure of the compression stroke cylinder, the internal combustion engine is appropriately reduced by appropriately reducing the in-cylinder pressure for any one of the cylinders. Can be stopped at the target stop crank angle described above. In particular, in this embodiment, as described above, if the in-cylinder pressure is not reduced for any cylinder, when the internal combustion engine stops, the in-cylinder charged air amount in the expansion stroke cylinder and the in-cylinder charged air amount in the compression stroke cylinder are reduced. Since they are substantially equal, the internal combustion engine can be stopped at the target stop crank angle by reducing the in-cylinder pressure of the compression stroke cylinder, that is, by appropriately letting out air from the compression stroke cylinder.

  Here, the timing for reducing the in-cylinder pressure of the compression stroke cylinder becomes a problem. That is, depending on the time when the cylinder pressure of the compression stroke cylinder is reduced, the internal combustion engine may not be stopped at the target stop crank angle.

FIG. 10 is a view similar to FIG. 9, and shows changes in the crank angle and the in-cylinder pressure when the in-cylinder pressure of the cylinder is reduced while the in-cylinder pressure of the compression stroke cylinder increases as the piston 14 rises. Is shown. As can be seen from the figure, when the in-cylinder pressure of the third cylinder is increasing and the crank angle of the internal combustion engine is at the target stop crank angle θt, the in-cylinder pressure of the third cylinder is reduced (time t ₄ ). Since the repulsive force due to the in-cylinder pressure of the third cylinder is almost lost, the internal combustion engine rotates beyond the compression top dead center (# 3 TDC in the figure) of the third cylinder due to the inertial force of the internal combustion engine. Then, after exceeding the compression top dead center of the third cylinder, the repulsive force due to the in-cylinder pressure of the fourth cylinder becomes the rotational resistance, and thus the rotation of the internal combustion engine is stopped. In this case, as can be seen from the figure, the crank angle when the internal combustion engine is stopped is about 220 degrees, that is, the crank angle (stop crank angle) based on the compression top dead center of the third cylinder is about 40 degrees. Therefore, the internal combustion engine stops at a crank angle far away from the target stop crank angle.

  Therefore, in this embodiment, the in-cylinder pressure of the compression stroke cylinder is reduced immediately after the internal combustion engine is temporarily stopped and the reverse rotation is started by the repulsive force due to the in-cylinder pressure of the compression stroke cylinder.

  FIG. 11 is a view similar to FIGS. 8 and 9 and shows changes in the crank angle and the in-cylinder pressure when the in-cylinder pressure of the compression stroke cylinder is reduced during the reverse rotation of the internal combustion engine. As can be seen from the figure, when the in-cylinder pressure of the compression stroke cylinder (the third cylinder in the example of FIG. 11) is reduced immediately after the internal combustion engine starts reverse rotation, the repulsive force due to the in-cylinder pressure of the compression stroke cylinder becomes small. In addition, since the inertial force in the reverse rotation direction of the internal combustion engine is still small when the pressure is reduced, the reverse rotation of the internal combustion engine is stopped immediately after the in-cylinder pressure is reduced. Therefore, in this embodiment, the internal combustion engine is reduced in the cylinder pressure of the compression stroke cylinder when the internal combustion engine is rotating in reverse and before or when the crank angle reaches the target stop crank angle. I am trying to stop at.

  Further, the crank angle at which the reduction of the cylinder pressure of the compression stroke cylinder is started is determined according to the crank angle when the internal combustion engine changes from forward rotation to reverse rotation (hereinafter referred to as “reverse crank angle”). That is, when the reverse crank angle is close to the compression top dead center of the compression stroke cylinder, the crank angle at the start of the reduction of the in-cylinder pressure is moved to the compression top dead center side of the compression stroke cylinder, and the reverse crank angle is compressed. When it is away from the compression top dead center of the stroke cylinder, the crank angle when starting to reduce the in-cylinder pressure is also moved to the side away from the compression top dead center of the compression stroke cylinder. This is because if the angle from the reverse crank angle to the crank angle when starting the reduction of the in-cylinder pressure is large, the inertial force in the reverse rotation direction of the internal combustion engine increases during that time, and after reducing the in-cylinder pressure, the internal combustion engine This is because the angle at which the internal combustion engine rotates until the engine is completely stopped increases.

  In the present embodiment, the in-cylinder pressure is reduced by opening the auxiliary exhaust valve 25. In addition, since it is preferable to retard the opening / closing valve timings of the intake valve 17 and the exhaust valve 19 when the engine is restarted as described above, in this embodiment, after the internal combustion engine is completely stopped, the intake valve 17 and the exhaust valve 19 The opening / closing valve timing is retarded.

  FIG. 12 is a flowchart of a control routine for executing the engine stop control described above. First, in step 101, it is determined whether or not an engine stop condition is satisfied based on the outputs of the accelerator depression amount sensor 41, the crank angle sensor 28, and the like. If it is determined that the engine stop condition is not satisfied, the control routine is terminated. On the other hand, if it is determined that the engine stop condition is satisfied, the routine proceeds to step 102.

  In steps 102 to 104, fuel injection and ignition are stopped, and the throttle opening of the throttle valve 7 is increased and the intake valve 17 is advanced in order to increase the amount of in-cylinder charged air into each cylinder. The Next, at step 105, it is determined whether or not the internal combustion engine has started reverse rotation. If it is determined in step 105 that the internal combustion engine has not started reverse rotation, that is, if the internal combustion engine is still rotating forward, step 105 is repeated. On the other hand, if it is determined in step 105 that the internal combustion engine has started reverse rotation, the routine proceeds to step 106 where the crank angle when the internal combustion engine starts reverse rotation by the crank angle sensor 42, that is, the reverse crank angle. Acr is detected.

  Next, at step 107, a depressurization start crank angle Act for starting depressurization of the in-cylinder pressure is calculated based on the reverse rotation crank angle Ac detected at step 106. More specifically, the relationship between the reverse rotation crank angle and the decompression start crank angle at which decompression is to be started is obtained in advance experimentally or by calculation, stored as a map in the ROM 32 of the ECU 30, and the decompression start crank angle is based on this map. Act is calculated. Next, it is determined in step 108 whether or not the current crank angle Ac detected by the crank angle sensor 42 is the decompression start crank angle Act. If the crank angle Ac is different from the decompression start crank angle Act, Step 108 is repeated. On the other hand, if it is determined in step 108 that the crank angle Ac is the same as the target crank angle Act, the routine proceeds to step 109. In step 109, the auxiliary exhaust valve 25 of the compression stroke cylinder is opened, the in-cylinder pressure of the compression stroke cylinder is reduced, and then the internal combustion engine is stopped.

  Next, the control apparatus of 2nd embodiment of this invention is demonstrated. In the present embodiment, the configurations of the internal combustion engine and the control device are basically the same as those in the first embodiment. However, in the second embodiment, the timing for reducing the in-cylinder pressure of the compression stroke cylinder is different from the timing in the first embodiment. In the second embodiment, the internal combustion engine changes from normal rotation to reverse rotation. The cylinder pressure of the compression stroke cylinder is reduced when it is temporarily stopped to change (hereinafter referred to as “at rest”).

  FIG. 13 is a view similar to FIGS. 9 to 11, and shows the crank angle and the cylinder when the cylinder pressure of the compression stroke cylinder is reduced when the internal combustion engine is stopped once trying to change from forward rotation to reverse rotation. It shows the transition of internal pressure. As can be seen from the figure, when the in-cylinder pressure of the compression stroke cylinder (the third cylinder in the example of FIG. 11) is reduced when the internal combustion engine is stationary, the repulsive force due to the in-cylinder pressure of the compression stroke cylinder is reduced and the pressure is reduced. At that time, there is no rotational inertia force of the internal combustion engine, so that the internal combustion engine is stopped as it is when the in-cylinder pressure is reduced or slightly reversely rotated thereafter. Thus, in this embodiment, the internal combustion engine is stopped at the target stop crank angle by reducing the in-cylinder pressure of the compression stroke cylinder when the internal combustion engine is stationary.

  However, in order to stop the internal combustion engine at the target stop crank angle in this way, the stationary position must be near the target stop crank angle. Therefore, in this embodiment, the opening degree of the throttle valve 7 or the opening / closing valve timing of the intake valve 17 is adjusted when the engine stop condition is satisfied or immediately after the engine stop condition is satisfied so that the internal combustion engine is stopped near the target stop crank angle. Yes.

  FIG. 14 shows the transition of the crank angle or the like immediately before the engine is stopped according to the closing timing of the intake valve 17, and FIG. 14 (a) shows the case where the closing timing of the intake valve 17 is advanced. 14 (c) shows a case where the closing timing of the intake valve 17 is retarded. FIG. 14 (b) shows a case where the closing timing of the intake valve 17 is shown in FIG. 14 (a) and FIG. 14 (c). Each case is shown in the middle of the case shown.

  As described above, when the closing timing of the intake valve 17 is advanced, the in-cylinder charged air amount to each cylinder increases. For this reason, as shown in FIG. 14A, the in-cylinder pressures of the compression stroke cylinder and the expansion stroke cylinder are considerably high, and thus the repulsive force due to the in-cylinder pressure is large. Accordingly, when the closing timing of the intake valve 17 is advanced, the crank angle vibrates with a large amplitude immediately before the engine stops, and accordingly, in the example shown in FIG. It stops at a crank angle of 170, 40, 140, 70 degrees.

  On the other hand, when the closing timing of the intake valve 17 is retarded, the in-cylinder charged air amount to each cylinder is small. For this reason, as shown in FIG. 14C, the in-cylinder pressures of the compression stroke cylinder and the expansion stroke cylinder are not so high, and the repulsive force due to the in-cylinder pressure is small. Therefore, when the closing timing of the intake valve 17 is retarded, the crank angle vibrates with a small amplitude immediately before the engine is stopped, and in accordance with this, in the example shown in FIG. It stops at a crank angle of 140, 50 degrees.

  When the closing timing of the intake valve 17 is in the middle of these, as shown in FIG. 14B, the in-cylinder charged air amount to each cylinder is medium, and therefore the repulsive force due to the in-cylinder pressure is also medium. is there. Accordingly, in this case, the crank angle vibrates with a medium amplitude immediately before the engine stops, and in accordance with this, the internal combustion engine stops at crank angles of 160, 50, 120, and 80 degrees in order in the example shown in FIG. To do.

  Thus, by adjusting the valve closing timing of the intake valve 17, the crank angle at which the internal combustion engine stops can be controlled. Therefore, in this embodiment, the closing timing of the intake valve 17 is adjusted so that the internal combustion engine stops at the target stop crank angle, and the in-cylinder pressure of the compression stroke cylinder is reduced when the internal combustion engine stops. Yes. For example, when the target stop crank angle is 160 degrees, the closing timing of the intake valve 17 is made medium, and the auxiliary exhaust valve 25 is opened when the internal combustion engine is stationary.

  The stationary position of the internal combustion engine can be similarly adjusted by adjusting the opening degree of the throttle valve 7 when the engine stop condition is satisfied or immediately after that. That is, when the opening degree of the throttle valve 7 is increased, the amount of air charged in the cylinder increases, the crank angle of the internal combustion engine changes as shown in FIG. 14A, and conversely, when the opening degree of the throttle valve 7 is reduced. The in-cylinder charged air amount decreases, and therefore the crank angle of the internal combustion engine changes as shown in FIG.

  Moreover, even if the opening degree of the throttle valve 7 and the closing timing of the intake valve 17 are appropriately controlled, the stationary position of the internal combustion engine may not reach the target stop crank angle. These control devices may be used in combination with the control device of the first embodiment. That is, when the internal combustion engine stationary position does not reach the target stop crank angle, the cylinder pressure of the compression stroke cylinder is not reduced when the internal combustion engine rotates in reverse, rather than reducing the cylinder pressure of the compression stroke cylinder when the internal combustion engine is stationary. The internal pressure may be reduced to stop the internal combustion engine at the target stop crank angle.

  In the above embodiment, the auxiliary exhaust valve 25 is used as a means for reducing the in-cylinder pressure of the compression stroke cylinder, but other means may be used. For example, an auxiliary intake port that communicates with the combustion chamber 15 and the intake port 16 and an auxiliary intake valve that opens and closes the auxiliary intake port is provided as means for reducing the in-cylinder pressure of the compression stroke cylinder. Also good. Or you may use the intake valve 17 and the exhaust valve 19 instead of these, without providing an auxiliary port and an auxiliary port. In this case, for example, the intake valve 19 of the compression stroke cylinder can be opened in order to reduce the in-cylinder pressure of the compression stroke cylinder by retarding the closing timing of the intake valve 19. Further, when the intake valve driving device 22 or the exhaust valve driving device 23 is formed of an electromagnetic actuator, the in-cylinder pressure of the compression stroke cylinder is reduced by transmitting a valve opening signal to the electromagnetic actuator. Also good.

  Furthermore, in the above embodiment, the internal combustion engine is stopped at the target crank angle by reducing the in-cylinder pressure of the compression stroke cylinder before the internal combustion engine is completely stopped. However, the in-cylinder pressure of the compression stroke cylinder or the expansion stroke cylinder is reduced when the internal combustion engine is completely stopped or just after that and when the in-cylinder pressure of the compression stroke cylinder and the expansion stroke cylinder is not reduced to the atmospheric pressure. Then, after the internal combustion engine is completely stopped, the internal combustion engine may be slightly rotated by the differential pressure between the compression stroke cylinder and the expansion stroke cylinder to stop the internal combustion engine at the target crank angle. As described above, the internal combustion engine often stops at a crank angle such that the piston 14 is positioned near the intermediate position of the stroke. In this case, the compression stroke cylinder is either immediately stopped or immediately after the internal combustion engine is completely stopped. In-cylinder pressure is reduced.

  In the above description, the restart when the engine is stopped when the key switch 44 is turned on has been described. Therefore, the restart when the rotation of the internal combustion engine is stopped by turning the key switch 44 off is described. Starting is basically performed by an electric motor. This is because when the key switch 44 is turned off, the crank angle of the internal combustion engine may change between when the rotation of the internal combustion engine stops and when it is restarted. However, if the crank angle of the internal combustion engine does not change while the key switch 44 is turned off, the key switch 44 is turned on after the rotation of the internal combustion engine is stopped by turning the key switch 44 off. The same control may be performed when restarting.

  In the above description, the “expansion stroke cylinder” is described as a cylinder that is in the middle of the expansion stroke when the engine is stopped. However, more specifically, in any cylinder, when the pressure in the cylinder is not reduced, the engine This means cylinders that are expected to be in the middle of the expansion stroke when the engine is stopped, and cylinders that are actually in the middle of the expansion stroke when the engine is stopped. Similarly, the “compression stroke cylinder” refers to the cylinder pressure in any cylinder. This means a cylinder that is expected to be in the middle of the compression stroke when the engine is stopped when decompression is not performed, and a cylinder that is actually in the middle of the compression stroke when the engine is stopped.

1 is an overall view of an internal combustion engine to which the present invention is applied. It is a schematic sectional drawing of each cylinder. It is a figure which shows the on-off valve timing of an intake valve. It is a figure which shows the cycle of each cylinder at the time of normal driving | operation, fuel injection timing, and ignition timing. It is a figure which shows the fuel-injection period, ignition timing, the opening / closing valve period of an intake valve, and the opening / closing valve period of an exhaust valve when the engine restart conditions are satisfied during an engine stop. It is a figure which shows the relationship between the position of the piston in an expansion stroke cylinder, and the position of the piston in a compression stroke cylinder. It is a figure which shows transition of the crank angle and cylinder pressure after engine restart conditions are satisfied. It is the figure which showed the relationship between a stop crank angle and the angle which can be rotated when it is going to restart an internal combustion engine from the stop crank angle. It is a figure which shows transition of the crank angle and cylinder pressure in the case of an engine stop. It is a figure which shows transition of the crank angle and cylinder pressure when the cylinder pressure of the said cylinder is reduced during the raise of cylinder pressure of a compression stroke cylinder. It is a figure which shows transition of a crank angle at the time of reducing the cylinder pressure of a compression stroke cylinder during reverse rotation of an internal combustion engine, and cylinder pressure. It is a flowchart of the control routine which performs engine stop control. It is a figure which shows transition of the crank angle and cylinder pressure when the cylinder pressure of a compression stroke cylinder is pressure-reduced, when an internal combustion engine is once stopped still trying to change from normal rotation to reverse rotation. It is a figure which shows transition of the crank angle etc. just before the engine stop according to the valve closing time of an intake valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 1a Cylinder 15 Combustion chamber 17 Intake valve 19 Exhaust valve 20 Spark plug 21 Fuel injection valve 22 Intake valve drive device 23 Exhaust valve drive device 25 Auxiliary exhaust valve 26 Auxiliary exhaust valve drive device 27 Crankshaft 28 Electric motor 30 ECU

Claims (11)

A fuel injection valve that directly injects fuel into the cylinder, and an ignition plug that ignites the air-fuel mixture in the cylinder, and expands when the engine is restarted when the engine restart condition is met In a control device for an internal combustion engine that restarts the internal combustion engine by injecting and igniting a cylinder in the middle of a stroke,
By reducing the in-cylinder pressure of at least one of the cylinders immediately before the engine stop or after the engine stop, between the compression stroke cylinder that is in the middle of the compression stroke and the expansion stroke cylinder that is in the middle of the expansion stroke when the engine is stopped A control device for an internal combustion engine, further comprising a cylinder filling air amount adjusting means for adjusting the cylinder filling air amount so that the cylinder filling air amount is different.   The internal combustion engine has four cylinders, and the in-cylinder charged air amount adjusting means adjusts the in-cylinder charged air amount so that the crank angle when the engine is stopped is 105 to 125 degrees with reference to the compression top dead center of the expansion stroke cylinder. The control apparatus for an internal combustion engine according to claim 1, wherein the control is performed.   The internal combustion engine has 6 cylinders, and the in-cylinder charged air amount adjusting means adjusts the in-cylinder charged air amount so that the crank angle when the engine is stopped is 60 to 70 degrees with reference to the compression top dead center of the expansion stroke cylinder. The control apparatus for an internal combustion engine according to claim 1, wherein the control is performed.   The at least one cylinder is a compression stroke cylinder, and the cylinder charge air amount adjusting means reduces the cylinder pressure of the compression stroke cylinder so that the cylinder charge air amount of the compression stroke cylinder is expanded. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the in-cylinder charged air amount is adjusted so as to be smaller than the in-cylinder charged air amount of the cylinder.   5. The control device for an internal combustion engine according to claim 4, wherein the in-cylinder charged air amount adjusting means reduces the in-cylinder pressure of the compression stroke cylinder when the internal combustion engine rotates in reverse immediately before the engine is stopped.   The in-cylinder charged air amount adjusting means reduces the in-cylinder pressure of the compression stroke cylinder when the internal combustion engine is stationary while trying to shift from forward rotation to reverse rotation. The control apparatus of the internal combustion engine described in 1.   The control of the internal combustion engine according to claim 6, further comprising a stationary crank angle adjusting means for adjusting an operation parameter of the internal combustion engine so that a crank angle when the internal combustion engine is temporarily stationary becomes a predetermined crank angle. apparatus.   The in-cylinder pressure of at least one of the cylinders is reduced when the in-cylinder pressure of the compression stroke cylinder and the expansion stroke cylinder is higher than the atmospheric pressure after the engine is stopped. The control device for an internal combustion engine according to claim 1.   The internal combustion engine according to any one of claims 1 to 8, further comprising an intake valve and an exhaust valve, wherein the in-cylinder pressure of the at least one cylinder is reduced by opening the intake valve or the exhaust valve. Control device.   9. An auxiliary valve for reducing the in-cylinder pressure separately from the intake valve and the exhaust valve, and reducing the in-cylinder pressure of at least one of the cylinders by opening the auxiliary valve. The control device for an internal combustion engine according to claim 1.   The control device for an internal combustion engine according to any one of claims 1 to 10, wherein retard control is performed to retard the opening / closing valve timing of the intake valve and the exhaust valve after the engine is stopped.

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