JP2007270805A - Control device of multicylinder 4-cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent a warm lock, when simultaneously using an electric driving means, when requiring restarting, in an automatic stopping system. <P>SOLUTION: This control device is provided with the electric driving means capable of at least starting and assisting a stopping engine. A piston stopping position discriminating means is arranged for discriminating a piston stopping position of respective cylinders in automatic stopping. A determination is made on whether or not a piston of the respective cylinders discriminated by the piston stopping position discriminating means is fit for combustion restarting by combustion in a stopping time expansion stroke cylinder. A means is arranged for correcting a piston position of a stopping time compression stoke cylinder to the front half side of a compression stroke by the combustion in the stopping time expansion stroke cylinder, when a stopping time compression stroke cylinder put in the compression stroke in warm stopping is in the first half of the compression stroke, when determined as improper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a multi-cylinder four-cycle engine, and more particularly to a control device for a multi-cylinder four-cycle engine suitable for an automatic stop system using electric drive means.

  For example, as disclosed in Patent Documents 1 to 3, an engine control system (automatic stop system) is known in which an engine is automatically stopped during idling for the purpose of reducing fuel consumption and suppressing CO2 emission. Yes.

  In such an automatic stop system, the engine must be started immediately in response to an engine restart request such as a start operation. However, as disclosed in Patent Document 1, in a general starting method in which the engine is started through cranking by the electric drive means, there is a tendency that the starting time becomes slightly longer. In addition, there was a problem that the noise accompanying the cranking and the engine blow-up (rapid increase in engine speed more than necessary) give a sense of incongruity.

  Furthermore, if the engine is assisted and restarted every time when the engine is in an idle state, the number of start-ups is much higher than in a normal system that starts only when the ignition switch is operated. Therefore, the electric drive means is required to have extremely high durability, and there is a problem that unnecessary cost increases.

Therefore, in recent years, for example, in-cylinder direct injection engines disclosed in Patent Documents 2 and 3, electric drive means is provided by injecting fuel into a cylinder in an expansion stroke in a stopped state, and igniting and burning the cylinder. The one that started the engine with its own power without borrowing the power of has been developed.
JP 2004-100616 A JP-A-2005-42677 JP-A-2005-180208

  By the way, in the automatic stop system as described above, sufficient combustion torque cannot be obtained depending on the stop position of the piston, and there are many cases in which electric drive means must be used in combination. However, if there is a fuel leak from the fuel injection valve to the combustion chamber, if the in-cylinder temperature of the engine at the time of the restart request is high, when the engine is driven by a predetermined amount by the electric drive means, the compression stroke is reduced. There is a possibility that self ignition (Auto Ignition) occurs in the greeted cylinder and the engine reverses to lock the electric drive means. Such a lock phenomenon (so-called warm lock) is likely to occur particularly when the piston position is inappropriate. On the other hand, it is conceivable that the piston position is simply displaced by the electric drive means, but in that case, a serious noise is generated. In addition, in the case of a 4-cycle engine, in the process where the piston of the cylinder in the first half of the compression stroke moves in the second half of the compression stroke, the intake valve of the cylinder in the intake stroke and the exhaust valve in the exhaust stroke are interlocked, The reaction force for a plurality of cylinders is received together with the compression reaction force, which may lock the electric drive means.

  The present invention has been made in view of the above-described problems, and in an automatic stop system, a multi-cylinder 4 that can reliably prevent a warm lock when using an electric drive means when a restart request is made. An object is to provide a control device for a cycle engine.

  In order to solve the above-described problems, the present invention restarts an engine by combustion in a stop-time expansion stroke cylinder that was in an expansion stroke at least when the engine was stopped when a condition for restarting the engine after automatic stop was satisfied. In a control device for a multi-cylinder four-cycle engine to be operated, an electric drive means capable of assisting at least starting a stopped engine, an operating state detecting means capable of estimating an in-cylinder temperature of the engine at the time of a restart request, The piston stop position identifying means for identifying the piston stop position of each cylinder at the time, and the piston of each cylinder identified by the piston stop position identifying means is suitable for combustion restart by combustion in the stop-time expansion stroke cylinder The combustion restart determination means for determining whether or not the combustion restart is inappropriate by the combustion restart determination means If it is determined that there is a stop compression stroke cylinder in the compression stroke at the time of a warm stop and is in the first half of the compression stroke, the piston of the stop compression stroke cylinder due to combustion in the stop expansion stroke cylinder A stop position correcting means for correcting the position to the first half of the compression stroke; and an electric drive control means for controlling the start of the electric drive means after each piston position is corrected by the stop position correcting means. This is a control device for a multi-cylinder four-cycle engine. In this aspect, when the restart condition is satisfied when the engine is stopped, whether the stop state of each cylinder is suitable for restart due to combustion of the stop-stroke expansion stroke cylinder (referred to as “combustion restart” in this specification). It is determined whether or not. If it is determined that the stop state of each cylinder is not suitable for combustion restart, and the stop-time compression stroke cylinder is in the first half of the compression stroke when warm, combustion occurs in the stop-time expansion stroke cylinder. Is called. As a result, each cylinder rotates forward by a predetermined amount. This normal rotation moves to a position suitable for starting the engine by the electric drive means. Here, in this embodiment, each piston position of the engine is corrected by combustion in the stop expansion stroke cylinder, and therefore, by this correction operation, the stop compression stroke cylinder and the stop intake stroke cylinder that are prone to self-ignition are likely to occur. As a result of returning to the atmospheric pressure in the cylinder, after driving the electric drive means, it is possible to suppress an excessive pressure increase in these cylinders, and to effectively prevent self-ignition. become. The timing at which the stop position correcting means burns the expansion stroke cylinder at the stop is preferably when the engine is stopped after the automatic stop condition is satisfied and before the restart condition is satisfied. However, since the restart condition may be satisfied before the engine stops after the automatic stop condition is satisfied, the stop-time expansion stroke cylinder may be combusted after the restart condition is satisfied.

  In a preferred embodiment, fuel injection control means for injecting fuel into the cylinder that was in the compression stroke when the engine was stopped is provided at least when the electric drive means is operated. In this aspect, when the engine is restarted by the electric drive means, the fuel is injected into the cylinder in the compression stroke, so that the in-cylinder pressure of the cylinder in the compression stroke is reduced by the latent heat of vaporization, and more reliably. It becomes possible to prevent self-ignition.

  In a preferred aspect, the stop position correcting means is the case where the combustion restart determining means determines that the combustion restart is inappropriate and the stop-time compression stroke cylinder is in the first half of the compression stroke. When it is determined that the operating state detecting means is cold when the temperature is less than the predetermined temperature, combustion for correcting the piston position in the stop-time expansion stroke cylinder is stopped. In this aspect, combustion in the expansion stroke cylinder at the time of stop is executed only during the warm operation where the warm lock is relatively likely to occur, so that the warm lock is surely prevented and the warm lock is difficult to occur. By performing normal combustion restart or assist drive by electric drive means, it is possible to realize quick and reliable restart.

  In a preferred embodiment, at the time of restarting combustion, an engine start control means is provided that reverses the engine once by combustion in a stop-time compression stroke cylinder and then forwardly rotates the engine by combustion in the stop-time expansion stroke cylinder. The electric drive control means stops the reverse combustion in the stop compression stroke cylinder when the stop position correction means corrects the piston position by the combustion in the stop expansion stroke cylinder. The engine is normally rotated by operating the electric drive means. In this aspect, even when so-called reverse combustion restart is executed, it is possible to reliably prevent self-ignition and perform a quick restart.

  In a preferred aspect, the electric drive means includes a ring gear provided in the engine, a pinion gear that is detachably engaged with the ring gear, and drive means that drives engagement / disengagement of the pinion gear with the ring gear. And a drive source for inputting torque to the ring gear via the pinion gear.

  As described above, according to the present invention, when the restart is executed after the engine is stopped, the electric drive means is driven after the piston position is corrected by the combustion in the stop expansion stroke cylinder under a predetermined condition. Since the restart is executed, self-ignition can be prevented when the electric drive means is used together, and the reaction force acting on the electric drive means can be suppressed by correcting the piston position by combustion. As a result, there is a remarkable effect that a warm restart can be surely prevented and a quick restart can be realized without causing noise.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an engine control system according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing configurations of an intake system and an exhaust system of the engine control system.

  Referring to the drawings, the engine control system includes an engine body 1 including a cylinder head 10 and a cylinder block 11, and a control unit (ECU) 2 for controlling the engine body 1.

  The engine body 1 is provided with four cylinders 12A to 12D. As shown in FIG. 1, pistons 13 connected to the crankshaft 3 are inserted into the cylinders 12A to 12D, respectively. Thus, a combustion chamber 14 is formed above the piston 13 in each of the cylinders 12A to 12D.

  In general, in a multi-cylinder four-cycle engine, each cylinder performs a combustion cycle including intake, compression, expansion, and exhaust strokes with a predetermined phase difference. In the case of the four-cylinder engine of the present embodiment, the first cylinder 12A, the second cylinder 12B, the third cylinder 12C, and the fourth cylinder 12D from the one end side in the cylinder row direction are referred to as the first cylinder (# 1) and the third cylinder. (# 3) Combustion is performed with a phase difference of 180 degrees in crank angle in the order of the fourth cylinder (# 4) and the second cylinder (# 2). Further, in this embodiment, a cylinder that was in the compression stroke during the automatic engine stop is referred to as a stop compression stroke cylinder, and a cylinder that was in the expansion stroke is referred to as a stop expansion stroke cylinder (similarly, the cylinder that was in the intake stroke is stopped). The cylinder in the intake stroke and the exhaust stroke is referred to as a stop exhaust stroke cylinder).

  Referring to FIG. 1, an ignition plug 15 for igniting and burning an air-fuel mixture in the combustion chamber 14 is provided at the top of each combustion chamber 14 of each of the cylinders 12A to 12D. The electrode at the tip of each spark plug 15 is disposed so as to face the combustion chamber 14. Further, a fuel injection valve 16 is provided on the side of the combustion chamber 14 (rightward in FIG. 1) with the nozzle hole at the tip facing the combustion chamber 14. The fuel injection valve 16 includes a needle valve and a solenoid (not shown) and is driven to open for a time corresponding to the pulse width in response to the input of a pulse signal from the control unit 2. The fuel is injected directly into the cylinders into the cylinders 12A to 12D. The fuel injection direction is adjusted so as to be directed to the vicinity of the electrode of the spark plug 15.

  Although not shown, fuel is supplied to the fuel injection valve 16 via a fuel supply passage or the like by a fuel pump, and the fuel supply pressure is in the middle of the compression stroke of each cylinder 12A to 12D. Thereafter, the pressure is set higher than the pressure in the combustion chamber 14 so that fuel can be injected into the high-pressure in-cylinder combustion chamber 14.

  An intake port 17 and an exhaust port 18 that open toward the combustion chamber 14 are provided in the upper part of the combustion chamber 14 of each of the cylinders 12A to 12D. An intake valve 19 and an exhaust valve 20 are disposed in these ports 17 and 18, respectively. The intake valve 19 and the exhaust valve 20 are driven by a valve operating mechanism including a camshaft (not shown). The opening timings of the intake valve 19 and the exhaust valve 20 by the valve operating mechanism are set for each of the cylinders 12A to 12D so that the cylinders 12A to 12D perform a combustion cycle with a predetermined phase difference.

  As shown in FIG. 2, an intake passage 21 and an exhaust passage 22 communicate with the intake port 17 and the exhaust port 18, respectively. The downstream side of the intake passage 21 close to the intake port 17 forms a branched intake passage 21a independent for each of the cylinders 12A to 12D, and the upstream end of each branched intake passage 21a communicates with the surge tank 21b. . The intake passage 21 upstream of the surge tank 21b is a common intake passage 21c common to the cylinders 12A to 12D. In this common air passage 21c, for example, a throttle valve 23 for restricting the intake flow by adjusting the passage sectional area by a butterfly valve and an actuator 24 for driving the throttle valve 23 are disposed. Further, an air flow sensor 25 for detecting the intake air amount and an intake pressure sensor 26 for detecting the intake air pressure (negative pressure) are disposed upstream and downstream of the throttle valve 23.

  Next, an alternator 28 that is drivingly connected to the crankshaft 3 by a belt or the like is attached to the engine body 1. The alternator 28 includes a regulator circuit 28a that changes the output voltage by controlling the current of the field coil and thereby adjusts the amount of power generation. A control command from the control unit 2 is supplied to the regulator circuit 28a. By inputting (for example, voltage), basically, the amount of power generation is controlled according to the electric load of the vehicle electrical component and the in-vehicle battery voltage. When the power generation amount of the alternator 28 is changed in this way, the driving force, that is, the magnitude of the external load of the engine body 1 changes accordingly.

  Next, as shown in FIGS. 1 and 2, a catalyst 37 for purifying exhaust gas is disposed downstream of the collecting portion of the exhaust passage 22 of each cylinder 12 </ b> A to 12 </ b> D. The catalyst 37 is, for example, a so-called three-way catalyst in which the purification rate of HC, CO, and NOx is extremely high when the air-fuel ratio of the exhaust gas is in the vicinity of the theoretical air-fuel ratio, and this is a relatively high oxygen concentration in the exhaust gas. It has an oxygen storage capacity for storing it in a high oxygen excess atmosphere. When the oxygen concentration is relatively low, the stored oxygen is released and reacted with HC, CO and the like. Note that the catalyst 37 is not limited to a three-way catalyst, and may be any catalyst as long as it has an oxygen storage capacity as described above. For example, the catalyst 37 may be a so-called lean NOx catalyst that can purify NOx even in an oxygen-excess atmosphere.

  Next, the engine body 1 is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the engine rotation speed Ne is determined based on the detection signal output from one crank angle sensor 30. The rotation direction and phase of the crankshaft 3 are detected on the basis of detection signals out of phase output from the crank angle sensors 30 and 31 as well as being detected.

  Next, the engine body 1 is provided with a cam angle sensor 32 for detecting a specific rotational position for cylinder identification provided on the camshaft, and a water temperature sensor 33 for detecting the coolant temperature of the engine. Is provided with an accelerator opening sensor 34 for detecting the accelerator opening corresponding to the accelerator operation amount of the driver.

  Further, the crankshaft 3 is provided with a flywheel (not shown) and a ring gear 35 fixed to the flywheel concentrically with respect to the center of rotation. The ring gear 35 is an input member of a starter motor 36 as electric drive means, and is configured to mesh with a pinion gear 36d of the starter motor 36, as will be described later.

  FIG. 3 is a partially broken schematic cross-sectional view showing the configuration of the starter motor.

  Referring to FIG. 3, a starter motor 36 includes a motor 36a, an electromagnetically driven plunger 36b arranged in parallel with the motor 36a, and a shift lever 36c by the plunger 36b on the output shaft of the motor 36a. And a pinion gear 36d that reciprocates in a state in which relative rotation is impossible. When the engine is restarted, the pinion gear 36d is moved from the standby position indicated by the solid line in FIG. , The crankshaft 3 is rotationally driven to restart the engine.

  The pinion gear 36d of the starter motor 36 employed in the present embodiment is twisted like a screw and is easy to disengage from the ring gear 35 when the ring gear 35 is stopped. The ring gear 35 is meshed while rotating in the reverse direction at a speed of about 60 rpm.

  Referring to FIG. 1, the control unit 2 is a microprocessor that comprehensively controls the operation of the engine. The engine according to this embodiment is configured to automatically stop the fuel by stopping fuel injection into each cylinder 12A to 12D at a predetermined timing (fuel cut) when a preset automatic stop condition is satisfied ( (Idle stop control) and a control (combustion restart control) that automatically restarts the engine when a restart condition is satisfied, for example, when the driver performs an accelerator operation after the engine is automatically stopped. It is configured as follows. In order to realize such control, the control unit 2 includes an air flow sensor 25, an intake pressure sensor 26, an intake air temperature sensor 29, crank angle sensors 30, 31, a cam angle sensor 32, a water temperature sensor 33, and an accelerator opening sensor 34. Are output to the fuel injection valve 16, the actuator 24 of the throttle valve 23, the ignition device 27, the regulator circuit 28a of the alternator 28, and the starter motor 36, respectively. Thereby, the control unit 2 functionally constitutes an electric drive control means, an operation state detection means, a piston stop position identification means, a stop position correction means, a fuel injection control means, and an ignition control means.

  FIG. 4 is an explanatory diagram showing piston stop positions of the stop expansion stroke cylinder and the stop compression stroke cylinder for automatic engine stop control, and FIG. 5 shows the stop expansion stroke cylinder, the stop compression stroke cylinder, and the air amount. It is explanatory drawing which shows these relationships.

  Referring to FIG. 4 and FIG. 5, the memory of the control unit 2 stores the bottom dead center limit (θ1 of the compression stroke cylinder 12A when stopped, θ4 of the expansion stroke cylinder when stopped) and the upper limit that can be restarted by combustion. A combustion restartable range A determined by the dead point limit (θ4 of the compression stroke cylinder 12A at the stop, θ1 of the expansion stroke cylinder at the stop) is determined. The piston 13 stops within the combustion restartable range A based on the above-described control. Among the combustion restart range, the stop compression stroke cylinder is from 90 ° CA before top dead center. However, it is preferable to stop in the slightly upper range. In the example of this embodiment, as indicated by θ2 to θ3 in FIG. 4, the compression stroke cylinder at the stop is 60 ° CA to 80 ° CA before top dead center (therefore, the expansion cylinder at stop is 100 ° CA after top dead center). From the single combustion stop range R to the top dead center side of the single combustion stop range R to θ1 in FIG. 4 (the bottom dead center side in the case of a stop expansion stroke cylinder). And the control unit 2 determines the predetermined range on the bottom dead center side (top dead center side in the case of the expansion stroke cylinder at the time of stop) as the combined combustion stop range and the remaining range as non-combustible restart ranges NG1 and NG2. The standard is set.

  The single combustion stop range R refers to a stop position in which the engine body 1 can be restarted only by combustion without using the starter motor 36 at the time of restart. When the piston 13 of the stop expansion stroke cylinder is in the single combustion stop range R, the amount of air in the cylinder increases and sufficient combustion energy is obtained. Further, since the scavenging is promoted by increasing the opening K of the throttle valve 23 during the engine stop operation period, a sufficient amount of fresh air is supplied to the catalyst 37. Therefore, the oxygen storage amount of the catalyst 37 is sufficiently large while the engine is stopped. Further, a predetermined amount of air is secured in the compression stroke cylinder at the time of stop, and combustion energy is obtained to such an extent that the crankshaft 3 can be slightly reversed in the first combustion. In addition, by securing a large amount of air in the expansion stroke cylinder at the time of stop, it is possible to generate sufficient combustion energy for causing the crankshaft 3 to rotate in the forward direction and to reliably restart the engine.

  Therefore, in the present embodiment, when the engine body 1 is automatically stopped at the time of idling, first, the fuel is cut at a predetermined rotational speed slightly higher than the idle rotational speed so that the scavenging of each cylinder 12A to 12D is sufficiently performed. At the same time, the throttle valve 23 is opened for a predetermined period thereafter, and control is performed to achieve a preset opening degree. The throttle valve 23 is closed at an appropriate timing set in advance. As a result, the amount of air drawn into the stop-time expansion stroke cylinder 12B and the stop-time compression stroke cylinder 12A is sufficiently increased, and the amount of air in the expansion stroke cylinder 12B is slightly larger than that of the compression stroke cylinder 12A. As a result, the piston 13 of the expansion stroke cylinder 12B is suitable for restarting somewhat closer to the bottom dead center from the center of the stroke due to the balance of the compression pressure of the air in the two cylinders 12A and 12B driven at the time of restart. It stops within the combustion stop range R.

  Next, the combined combustion stop ranges A1 and A2 are stop ranges that can be restarted by using the starter motor 36 at the time of restart.

  Further, the combustion restart impossible range NG1, NG2 refers to a stop range where reverse rotation restart by combustion is not possible.

  In the following description, subscripts 1 and 2 are attached to the first half and the second half of the stroke in the combined combustion stop ranges A1 and A2 and the combustion restart impossible range NG1 and NG2, respectively.

These stop range R, A1, A2, NG1, NG2, after the control unit 2 estimates the stop range, is identified by the stop range determining flag F _ST is set, then the restart control engine body 1 to be described The restart control is executed according to each case. Further, in the present embodiment, when the piston 13 of the compression stroke cylinder 12A at the time of stop is before the compression top dead center from the single combustion stop range R in the combined combustion stop ranges A1 and A2, the piston position forcing described later is forced. By executing the process, the position of the piston 13 is forced prior to the restart process.

  In the present embodiment, when the fuel is restarted in the middle of the compression stroke at the time of the combustion restart control, it is executed when the piston of the compression stroke cylinder 12A is in the range of θ2 to θ3 in FIG. It has come to be.

  Next, control for automatically stopping the engine body 1 by the control unit 2 will be described.

  FIG. 6 corresponds to changes in engine speed Ne, crank angle, and stroke of each cylinder 12A to 12D during the period from the fuel cut until the engine body 1 rotating with inertia stops (hereinafter also referred to as a stop operation period). It is explanatory drawing which shows typically the control of the throttle opening performed in the meantime, and the change of the intake pressure (intake pipe negative pressure) by this. FIG. 7 is a diagram showing the correlation between the rotational speed ne (described later) at the top dead center of the engine body 1 whose rotation gradually decreases during the stop operation period, and the piston stop position in the expansion stroke cylinder 12 after the stop. It is.

  As shown in FIG. 6, when a fuel cut is performed at a predetermined set rotational speed (800 rpm in the illustrated example) during operation of the engine body 1 (timing t0), the motion of the motion part such as the crankshaft 3 at that time Energy is consumed by mechanical friction or pump work of each cylinder 12A to 12D, the engine rotational speed Ne gradually decreases, and the engine body 1 stops after several revolutions due to inertia. Specifically, while the engine body 1 rotates with inertia, the engine rotational speed Ne is temporarily reduced greatly when the compression top dead center (top dead center) of each of the cylinders 12A to 12D is reached. It rises again when it exceeds the dead point, and goes down while repeating up and down. For example, when the fuel is cut at about 800 rpm as shown in the figure, the top dead center is usually exceeded 8 or 9 times, and after the last top dead center (timing t3), the next top dead center. Can no longer be exceeded, leading to a stop (timing t4 to t6). In this process, the pistons 13 of the cylinders 12A to 12D are reciprocated several times and then stopped by the compression reaction forces acting in opposite directions on the pistons 13 of the compression stroke cylinder 12 and the expansion stroke cylinder 12, respectively. (Timing t6), the stop position is roughly determined by the balance of the compression reaction forces of the compression and expansion stroke cylinders 12, and is finally top dead before the stop due to the influence of the friction of the engine body 1 and the like. It changes in accordance with the rotational inertia of the engine body 1 when the point is exceeded, that is, the engine rotational speed Ne when the top dead center is finally exceeded. Therefore, in order to stop the piston 13 of the stop expansion stroke cylinder 12B within the single combustion stop range R suitable for restarting, first, the compression reaction force of the stop expansion stroke cylinder 12 and the stop compression stroke cylinder 12 is applied. Need to be adjusted so that the compression reaction force of the expansion stroke cylinder 12 is a predetermined balance larger than the compression stroke cylinder 12 and larger than the compression stroke cylinder 12. is there. For this reason, in the present embodiment, the throttle valve 23 (timing t1) opened immediately after the fuel cut is closed after a predetermined period (timing t2), and the intake pipe negative pressure is temporarily reduced (intake amount increases). Thus, a required amount of air is sucked into the compression and expansion stroke cylinders 12 when stopped.

  However, in the actual engine body 1, there are individual variations in the shape of the throttle valve 23 itself, the intake port 17, the branch intake passage 21a, etc., and the behavior of the air flow that circulates there may change, so Since the amount of air flowing into each of the cylinders 12A to 12D varies to some extent during the stop operation period, even if the opening / closing control of the throttle valve 23 as described above is performed, the compression stroke or It is difficult to keep the piston stop position of the cylinder 12 in the expansion stroke within the single combustion stop range R that is accurately targeted.

  In this regard, in this embodiment, as shown in an example in FIG. 7, the engine when each of the cylinders 12A to 12D sequentially passes the top dead center in the process in which the engine rotation speed Ne gradually decreases during the stop operation period. Note that there is a clear correlation between the rotational speed Ne (hereinafter also referred to as the rotational speed ne at the top dead center) and the piston stop position of the cylinder 12 in the expansion stroke after the engine is stopped. As shown in FIG. 5, the engine speed Ne at each top dead center is detected every 180 ° CA in the process of decreasing the engine speed Ne, and the engine speed is controlled by controlling the power generation amount of the alternator 28 according to the detected value. I am trying to adjust the degree of falling.

  In the example shown in FIG. 7, as described above, when the engine speed Ne is approximately 800 rpm, the fuel is cut, and the throttle valve 23 is kept open for a predetermined period thereafter, so that the engine body rotates with inertia. Each time one of the cylinders 12A to 12D exceeds the top dead center, the rotational speed ne at the top dead center is measured, and the piston position of the expansion stroke cylinder 12 after the stop is checked to determine the piston position. The vertical axis represents the rotational speed ne at the top dead center and the horizontal axis represents the relationship between the two. By repeating such work a predetermined number of times, as shown in FIG. 7, there is a correlation between the rotational speed ne at the top dead center during the engine stop operation period and the piston stop position in the expansion stroke cylinder 12 after the stop. Is obtained.

  In the example of FIG. 7, the rotational speed when the last top dead center before the engine stops is not shown, and the rotational speed at the top dead center immediately after the fuel cut (in the example of FIG. The data from the first) ne to the last previous top dead center rotational speed ne (second one counted from the last) is shown. The rotation speed ne at the 9th to 2nd top dead center from the last is distributed in a lump, and as clearly shown in the 6th to 2nd ones shown in the figure, the rotation speed at the top dead center. If the speed ne is in a certain range (range shown by hatching in the figure), the piston stop position is the single combustion stop range R suitable for restart (in the example shown in the figure, compression of the expansion stroke cylinder 12B at the time of stop). It can be seen that it enters 100 to 120 ° CA after top dead center.

  As described above, the specific range of the rotational speed ne at the top dead center at which the piston 13 of the expansion stroke cylinder 12 stops in the single combustion stop range R suitable for restarting the engine body 1 will be described below. Then, it shall call an appropriate rotational speed range. In this embodiment, when the engine rotational speed Ne decreases while repeating up and down, the rotational speed ne at the top dead center for each of the cylinders 12A to 12D is detected, and the detected value and the appropriate rotational speed range are detected. And the power generation amount of the alternator 28 is controlled according to the speed deviation between the two.

  First, during a predetermined period immediately after the fuel cut, the throttle valve 23 is opened relatively large for scavenging the cylinders 12A to 12D. Even if the throttle opening is further adjusted, the pump work of the cylinder 12 is not increased. Since it does not change so much, it is difficult to adjust the engine rotational speed Ne. Therefore, during this time, the alternator 28 is intentionally operated to generate power, and the amount of power generation is changed and controlled to change the magnitude of the power generation driving force, thereby adjusting the degree of decrease in the engine rotational speed Ne. At this time, the power generation amount of the alternator 28 is controlled to be large so that the rotational speed ne at the top dead center is close to the lower limit of the appropriate rotational speed range, that is, the engine rotation is slightly lowered.

  As described above, the degree of decrease in the engine rotational speed Ne is adjusted by the power generation control of the alternator 28, and the rotational speed ne at the top dead center falls within the appropriate rotational speed range before passing the last top dead center at the latest. By doing so, the kinetic energy possessed by the moving parts such as the crankshaft 3 or the piston 13 or the connecting rod at this time, the potential energy possessed by the high-pressure air of the compression stroke cylinder 12, etc. are commensurate with the friction acting thereafter. Thus, the piston 13 of the cylinder 12 in the expansion stroke when the engine body 1 is stopped can be stopped within the single combustion stop range R suitable for the restart.

  Next, a specific control example of automatic stop will be described with reference to FIGS.

  8 and 9 are flowcharts showing the procedure of stop control.

  Referring to FIG. 8, control unit 2 determines whether or not an automatic stop condition (idle stop condition) is satisfied at a predetermined timing during engine operation (step S1). This determination is made based on the vehicle speed, the operating condition of the brake, the engine water temperature, and the like. For example, the vehicle speed is smaller than a predetermined speed, the brake is operating, the engine water temperature is within a predetermined range, and the engine body 1 If there is no particular inconvenience in stopping the operation, it is assumed that the automatic stop condition is satisfied.

  When the automatic stop condition is satisfied in step S1 (in the case of YES), the control unit 2 specifies any one cylinder 12 (for example, the first cylinder 12A) and the predetermined condition for stopping the engine body 1 is satisfied. It is determined whether or not it has been performed (step S2). In this control, it is determined whether or not the engine rotational speed Ne is a fuel cut set rotational speed (approximately 800 rpm in this embodiment), whether or not the specified cylinder 12 is in a preset stroke (for example, an intake stroke), and the like. Is done. If the conditions of Steps S1 and S2 are satisfied and it is determined YES, the control unit 2 stops fuel injection to each of the cylinders 12A to 12D (Step S3).

  Next, as shown by t1 in FIG. 6, the throttle valve 23 is opened so as to reach the set opening degree (step S4). As a result, the amount of intake air to each of the cylinders 12A to 12D increases, and sufficient scavenging is performed, and a large amount of fresh air is also supplied to the catalyst 37 disposed in the exhaust passage 22. The amount of oxygen stored in 37 is sufficiently increased.

  Subsequently, the control unit 2 determines whether or not the rotational speed ne at the top dead center obtained from the signal from the crank angle sensor 30 is within an appropriate rotational speed range (step S5).

  If the determination in step S5 is YES, the control unit 2 determines whether or not the engine rotational speed Ne is equal to or lower than a predetermined rotational speed (step S6). This predetermined rotational speed takes into account the transport delay of the intake air, as shown in FIG. 6, the intake air amount to the stop expansion stroke cylinder (# 2 cylinder in the illustrated example) 12B is the compression stroke cylinder (the illustrated example). (# 1 cylinder) is for closing the throttle valve 23 at a timing higher than 12A, and corresponds to the timing t2 in the figure, and in this embodiment, for example, it is set in the range of about 500 to 600 rpm. Yes. Then, the control unit 2 closes the throttle valve 23 (step S7) when the engine rotational speed Ne becomes equal to or lower than the predetermined rotational speed (when the determination in step S8 is YES), and the engine rotational speed Ne is higher than the predetermined rotational speed. If it is higher (NO), the process returns to step S5.

  In step S5, when it is determined that the top dead center rotational speed is out of the appropriate rotational speed range (in the case of NO), the control unit 2 determines the rotational speed between the top dead center rotational speed and the appropriate rotational speed range. The power generation amount of the alternator 28 is calculated based on the deviation (step S8). This power generation amount is read from a map set in advance according to, for example, the engine rotation speed Ne, the speed deviation from the appropriate rotation speed range, and the current power generation amount. For example, the top dead center rotation speed is the upper limit of the appropriate rotation speed range. Is higher, the power generation amount of the alternator 28 is increased so that the load on the engine body 1 is increased. On the other hand, when the top dead center rotational speed is lower than the lower limit of the appropriate rotational speed range, the load on the engine body 1 is decreased. It reduces power generation. In the map, the target value of the power generation amount is set to be large so that the top dead center rotational speed is near the lower limit of the appropriate rotational speed range. Next, the control unit 2 outputs a control command to the regulator circuit 28a of the alternator 28 according to the calculation result in step S6 (step S9). By adjusting the load of the engine main body 1 by the power generation operation of the alternator 28, the locus of the rotational speed of the engine main body 1 rotating by inertia is shifted to either the high rotation side or the low rotation side, and gradually becomes the target. Go closer to the trajectory. Then, if the engine rotational speed Ne becomes equal to or lower than the predetermined rotational speed in step S6 (in the case of YES), the control unit 2 proceeds to step S7 and closes the throttle valve 23.

  On the other hand, by controlling the alternator 28 as described above, the degree of decrease in the engine rotational speed Ne after the fuel cut is adjusted, so that the engine rotational speed Ne gradually decreases while repeating up and down as shown in FIG. The trajectory is gradually corrected so that it can be within the proper rotational speed range by the latest top dead center at the latest. Therefore, in this embodiment, after the actuator 24 of the throttle valve 23 is driven, the process proceeds to step S23.

  Thereafter, the cylinders are rotated several times in the forward and reverse directions by the compression reaction forces of the two cylinders 12A and 12B in the compression stroke and the expansion stroke, respectively, and then stopped. Therefore, referring to FIG. 9, control unit 2 proceeds to step S <b> 24 and predicts a stop position of engine body 1 based on signals from crank angle sensors 30 and 31.

At this time, the control unit 2 determines whether or not the stop position of the piston 13 is within the single combustion stop range R (step S25), and if the estimated stop position is within the single combustion stop range R. If it is determined, the control unit 2 sets the stop position determination flag _FST from the initial value 0 to 1 (step S26). On the other hand, if it is determined in step S25 that the estimated stop position is out of the proper range, the control unit 2 further determines that the piston 13 of the stop-time compression stroke cylinder 12A is in the combined combustion stop range A1. It is determined whether or not to stop within A2 (step S27). If it is within the combined combustion stop ranges A1 and A2, the control unit 2 further determines whether the stop position is the first half or the second half of the compression stroke (step S28), and if it is the first half, the stop position determination flag. _{FST is set} to 2 (step S29), and if it is the second half, it is set to 3 (step S30). On the other hand, when it is determined in step S27 that the piston 13 of the stop-time compression stroke cylinder 12A stops outside the allowable range, the control unit 2 further determines whether the stop position is the first half or the second half of the compression stroke. (Step S31), if it is the first half, the stop position determination flag _{FST is set} to 4 (Step S32), if it is the second half, it is set to 5 (Step S33), and the value of each stop position determination flag _FST is set. Store in the memory of the control unit 2 to complete the engine stop control.

Here, the stop position determination flag _FST is listed in Table 1 described later.

  Next, a description will be given of a case where the engine body 1 that has been automatically stopped at the time of idling is automatically restarted.

  When the engine main body 1 is forcibly stopped as described above, if self-ignition occurs in a cylinder that reaches the compression stroke (mainly the intake stroke cylinder at the stop) after burning the expansion stroke cylinder at the time of stop, A large reaction force causes knocking and fails to restart. In particular, when restart must be performed using the starter motor 36 together, if self-ignition occurs when the pinion gear 36d of the starter motor 36 and the ring gear 35 of the engine body 1 are engaged, both gears 35 are caused by the reverse torque. , 36d may be locked. Therefore, in this embodiment, various measures are taken in order to prevent self-ignition at the time of restarting combustion.

  FIG. 10 is a graph showing the relationship between the elapsed time from the engine stop and the in-cylinder temperature, and is an estimated value of the in-cylinder temperature change when the in-cylinder temperature is 80 ° C. when the engine is stopped (timing t5). is there. Referring to FIG. 10, when the engine is completely stopped, the in-cylinder temperatures of cylinders 12A to 12D change with the temperature characteristics shown in FIG.

  First, as one of the countermeasures for self-ignition, there is management of the in-cylinder temperature. That is, after the engine main body 1 is automatically stopped, when the engine main body 1 is completely stopped, the flow of the cooling water is also stopped, so that the in-cylinder temperature rapidly increases immediately after the stop. Then, it peaks at about 10 seconds after the engine stops, and then gradually decreases. Although this characteristic varies depending on the temperature of the cooling water (engine water temperature), the outside air temperature (intake air temperature), etc., it can be determined by experiment for each specification of the engine body 1. Data in which the characteristics of FIG. 10 are mapped for each specification of the main body 1 is stored, and a range of about 10 seconds after the engine is stopped is set as a predetermined stop time range. In this predetermined stop time range, the intake air of the engine main body 1 is stored. It is determined that the predetermined warm state is determined when the air temperature of the passage rapidly rises, and that the in-cylinder temperature is determined to be higher as the restart time is closer to the predetermined stop time range. Therefore, measures are taken to prevent self-ignition.

  FIG. 11 is a graph showing the relationship between the stop position of the automatically stopped engine and the timing of occurrence of self-ignition.

  Next, referring to FIG. 11, in the warm state (warm-up: for example, when the detected value of the intake air temperature sensor 29 is 100 ° C. or higher), the stop position of the stop-time compression stroke cylinder 12A is before the top dead center. When there is unburned fuel in the compression stroke cylinder 12A at the time of stop when it is at the bottom dead center side than 90, the self-compression cylinder 12A at the stop compression stroke after the combustion of the expansion stroke cylinder 12B at the stop is almost independent of the air-fuel ratio. As a result of experiments conducted by the present inventors, it became clear that ignition tends to occur. For this reason, in the present embodiment, when the piston 13 exists in the allowable range of the piston stop position shown in FIG. 4 beyond θ3 to θ4, the engine body 1 is forced after forcing the piston position. To restart. In addition, after the combustion in the stop expansion stroke cylinder 12B is completed, the fuel is injected into the stop compression stroke cylinder 12A, thereby reducing the in-cylinder pressure by atomization of the injected fuel. However, in certain cases, the fuel injection is stopped, or additional fuel is injected to prevent self-ignition so as to prevent self-ignition in the stop-time compression stroke cylinder 12A. ing.

  Next, fuel injection timing at restart will be described.

  FIG. 12 is a schematic diagram showing an engine starting procedure in the engine control system.

  Referring to FIG. 12, when the engine is restarted, the engine main body 1 is started by itself without borrowing the force of the starter motor 36. In this embodiment, FIG. 12 (A) to FIG. As schematically shown in FIG. 12 (D), first, the first combustion is performed in the compression stroke cylinder 12A when stopped, and the piston 13 is pushed down, so that the crankshaft 3 is slightly reversed (FIG. 12 (A)). Thus, the piston 13 of the expansion stroke cylinder 12B at the time of stop is raised, and the air-fuel mixture in the cylinder 12B is compressed (see FIG. 12B). Then, the air-fuel mixture in the stop expansion stroke cylinder 12B, which has been compressed in this way and whose temperature and pressure are increased, is ignited and burned, thereby giving the crankshaft 3 torque in the forward direction, and The main body 1 is started. In order to start the engine main body 1 by itself, the torque in the forward rotation direction is applied to the crankshaft 3 as much as possible by the combustion of the expansion stroke cylinder 12B at the stop, and as shown in FIG. The stop compression stroke cylinder 12A must overcome the compression reaction force (compression pressure) and exceed the top dead center. Therefore, in order to reliably start the engine body 1, it is necessary to ensure sufficient air for combustion in the stop-time expansion stroke cylinder 12B. On the other hand, the presence of considerable air in the expansion stroke cylinder 12B at the time of restart prevents the air from being strongly compressed during reverse rotation. This is because the compression reaction force of the compressed air acts in the direction of pushing back the piston 13 of the expansion stroke cylinder 12B at the time of stop.

  Therefore, in the present embodiment, control is performed to increase the compression amount (increase the density) of the air in the stop expansion stroke cylinder 12B by delaying the fuel injection timing to the stop expansion stroke cylinder 12B. When the fuel injection timing is delayed, the fuel is injected into the cylinder in which the cylinder air is compressed to some extent, and the compression pressure is reduced by the latent heat of vaporization. Therefore, if the energy is in the same engine reverse direction, the piston 13 can move closer to the top dead center (increase in piston stroke), and the density of compressed air can be further increased.

  Next, after the normal rotation, the reaction force of the burned gas remaining in the compression stroke cylinder at the stop time can cause a decrease in the torque after the normal rotation. For this reason, in the present embodiment, after combustion in the stop expansion stroke cylinder, fuel is injected into the stop compression stroke cylinder 12A, thereby reducing the pressure in the stop compression stroke cylinder 12A after reverse rotation due to latent heat of vaporization. The reduction in torque is suppressed (see FIG. 12C).

  Further, in the stop-time intake stroke cylinder 12C that reaches the compression stroke after combustion in the stop-time expansion stroke cylinder 12B, the ignition timing is retarded after compression top dead center to prevent so-called blow-up (FIG. 12D). )reference).

  Next, the start control procedure will be described. In the following description, control is executed using a flag based on Table 1. These flags are logically constructed for explaining the operation of the present embodiment, and do not necessarily need to be set on the program.

The stop position determination flag _FST indicates a stop state when the engine body 1 is automatically stopped. In the case of 1, the stop position determination flag _FST indicates that the piston 13 is stopped in the single combustion stop range R. In this case, it indicates that the engine is stopped within the combined combustion stop range A1 in the first half of the stroke, and in the case of 3, it indicates that the engine is stopped within the combined combustion stop range A2 in the latter half of the stroke. Indicates that the piston 13 is stopped in the combustion restart impossible range NG1 in the first half of the stroke. In the case of 5, the piston 13 is stopped in the combustion restart impossible range NG2 in the second half of the stroke. Is shown. The initial value is set to 1.

The correction determination flag F _EXP indicates a case where the piston stop position is corrected by the combustion of the stop-time expansion stroke cylinder 12B. When the correction determination flag F _EXP is 0, there is no correction processing (that is, the piston 13 is in an unburned state). In some cases, the correction process is executed in the case of 1, and the correction operation is successful. In the case of 2, the correction process is executed and the correction fails (misfire). The initial value is set to 0.

The reverse rotation determination flag F _REV is a flag for identifying whether or not the reverse rotation operation by the combustion of the stop-time compression stroke cylinder 12A has been successful. In the case of 0, the reverse rotation operation is not performed. When the operation is successful, the case of 2 indicates a case where a reverse operation is performed and a misfire occurs. The initial value is set to 0.

The restart determination flag F _RS is a flag for determining whether or not the cylinder that has reached the second compression stroke after the restart has exceeded the compression top dead center. Is the state in which ignition for the reverse rotation from the reverse rotation is successful in the stop expansion stroke cylinder, in the case of 02, the ignition failure for the reverse rotation in the expansion stroke cylinder at the stop is in the case of 11 Is the state in which the engine speed Ne detected at a predetermined timing is equal to or higher than the required speed after completion of the combustion in the expansion stroke cylinder at the time of stop (that is, the state in which the first compression top dead center can be exceeded), Is a state in which the engine speed Ne detected at a predetermined timing is less than a required speed after the combustion in the expansion stroke cylinder at the time of stop (that is, a state in which the first compression top dead center cannot be exceeded), If on the first compression After the point is exceeded, the engine body 1 has exceeded the second compression top dead center at a predetermined determination timing. In the case of 22, the first compression top dead center is exceeded, and then at a predetermined determination timing, 2 The case where the second compression top dead center was not exceeded is shown. The initial value is 0.

  FIG. 13 is a flowchart showing a main flow of restart control.

  Referring to FIG. 13, the restart control of the engine main body 1 according to the present embodiment is based on starting the engine main body 1 by itself as described above, but the starter motor 36 is also used as a fail-safe function. Not only the case but also the case where the starter motor 36 is used together from the beginning is included.

In this flow, the control unit 2 first determines whether or not a restart condition is satisfied (step S60). The restart condition is when the brake is released to start from a stopped state, when an accelerator operation or the like is performed, or when the engine needs to be operated for the operation of an air conditioner or the like. When the restart condition is satisfied, it is determined whether or not the engine body 1 is stopped (step S61). If the accelerator is depressed while the engine is not stopped, it is determined whether or not the engine rotational speed Ne at that time has reached a predetermined allowable rotational speed Ne _min (step S62). If the engine does not reach the predetermined rotational speed in this flow, the flowcharts shown in FIGS. 8 and 9 are executed, wait for the engine to stop, and if it exceeds the allowable rotational speed, it is normal. The operation is switched to operation (step S63), and the process is terminated.

Next, when it is determined in step S61 that the engine body 1 is stopped, the control unit 2 reads the stop position determination flag _FST from the memory and identifies the stop state of the engine body 1 (step S64).

If the value of the stop position determination flag _FST is 1, it is determined whether or not the operation state requires further start assist (step S65). Based on this determination, the combustion restart control subroutine (step S65) is determined. S110), the assist combined use restart control subroutine (S120) is executed. When the value of the stop position determination flag _FST is other than 1, the control unit 2 immediately executes the assist combined use restart control subroutine S120.

  14 to 16 are flowcharts showing the combustion restart control subroutine S110.

  First, the control unit 2 estimates the in-cylinder temperatures of the cylinders 12A to 12D from the water temperature, the stop time, the intake air temperature, and the like (step S1101). Then, the control unit 2 calculates the amount of air in the stop compression stroke cylinder 12A and the stop expansion stroke cylinder 12B based on the detected stop position of the piston 13 (step S1102). That is, the combustion chamber volumes of the stop compression stroke cylinder 12A and the stop expansion stroke cylinder 12B are obtained from the stop position of the piston 13, and when the engine is stopped, after the engine has been rotated several times after the fuel injection is stopped. Since the engine is stopped, the stop expansion stroke cylinder 12B is also filled with fresh air, and the inside of the stop compression stroke cylinder 12A and the stop expansion stroke cylinder 12B is substantially at atmospheric pressure while the engine is stopped. The amount of fresh air is obtained from the combustion chamber volume.

Next, the control unit 2, by reading the value of the restart ID flag F _ST, the piston stop position, alone combustion stop range R in the stop-state compression-stroke cylinder 12A (BTDC 60-80 ° CA) Of these, it is determined whether or not it is relatively at the bottom dead center side (step S1103).

  If the air amount is relatively large and it is determined as YES in step S1103, the control unit 2 proceeds to step S1104 and λ (air) with respect to the air amount of the stop-time compression stroke cylinder 12A calculated in step S1102. The fuel is injected so that the air-fuel ratio (excess ratio)> 1 (for example, air-fuel ratio = about 20) (first fuel injection). This air-fuel ratio is obtained from the compression stroke cylinder first-time air-fuel ratio map M1 set in advance according to the stop position of the piston. By setting the lean air-fuel ratio to be λ> 1, even when the air amount in the compression stroke cylinder 12A at the time of stop is relatively large, the combustion energy for the reverse direction does not become excessive, and the reverse rotation is excessive ( In the stop compression stroke cylinder 12A, the piston 13 that has moved to the bottom dead center side passes through the bottom dead center and is prevented from reversing to the intake stroke).

  On the other hand, if the air amount is relatively small and it is determined NO in step S1103, the control unit 2 proceeds to step S1105 and λ ≦ the air amount in the stop-time compression stroke cylinder 12A calculated in step S1102. The fuel is injected so that the air-fuel ratio becomes 1 (first fuel injection). This air-fuel ratio is obtained from the first-time air-fuel ratio map M2 of the stop-time compression stroke cylinder 12A set in advance according to the stop position of the piston. By setting the stoichiometric air-fuel ratio of λ ≦ 1 or a richer air-fuel ratio, sufficient combustion energy for the reverse direction can be obtained even when the amount of air in the compression stroke cylinder 12A at the time of stop is relatively small. it can.

Next, the control unit 2 proceeds to step S1106, and ignites the cylinder after elapse of a time set in consideration of the vaporization time from the first fuel injection into the stop-time compression stroke cylinder 12A. Then, depending on whether or not the ignition to the crank angle sensor 30, 31 within a predetermined time T _LT from the edge (rising or falling edge of the crank angle signal) is detected, whether the control unit 2 the piston 13 is moved Determination is made (step S1107).

In step S1107, if it is determined as YES and it is confirmed that the piston 13 has moved, the control unit 2 updates the reverse rotation determination flag F _REV to 1 (step S1108), and proceeds to the next step.

On the other hand, if it is determined as NO in step S1107 and it is confirmed that the piston 13 has not moved due to misfire, the control unit 2 determines whether or not the elapsed time T after ignition has elapsed by a predetermined time _TLT . (Step S1109), and if it has not elapsed, reignition is repeatedly performed on the compression stroke cylinder 12A at the time of stop (step S1110). On the other hand, when the elapsed time T after ignition has passed the predetermined time in step S1109, the routine proceeds to the starting normal rotation control subroutine S220 in the assist combined restart of step S120.

Referring to FIG. 15, when it is determined as YES in step S1107 and it is confirmed that the piston 13 has moved, and the reverse rotation determination flag F _REV is updated, the control unit 2 estimates at the piston stop position and step S1101. Based on the in-cylinder temperature, a split ratio of the split fuel injection to the stop-time expansion stroke cylinder 12B (ratio between the front stage injection (first time) and the rear stage injection (second time)) is calculated (step S1112). The later-stage injection ratio is increased as the piston stop position in the expansion stroke cylinder 12B during the stop is closer to the bottom dead center and the in-cylinder temperature is higher.

  Next, the control unit 2 calculates the fuel injection amount so that a predetermined air-fuel ratio (λ ≦ 1) is obtained with respect to the air amount in the stop-time expansion stroke cylinder 12B calculated in step S1102 (step S1113). The air-fuel ratio at this time is obtained from the expansion stroke cylinder air-fuel ratio map M3 set in advance according to the stop position of the piston.

  Next, the control unit 2 uses the division ratio calculated in step S1112 and the fuel injection amount to the stop expansion stroke cylinder 12B calculated in step S1113 to perform the first stage for the stop expansion stroke cylinder 12B. A fuel injection amount is calculated and injected (step S1114).

  Next, the control unit 2 calculates the subsequent (second) fuel injection timing for the stop-time expansion stroke cylinder 12B based on the in-cylinder temperature estimated in step S1101 (step S1115). This second injection timing is a time when the in-cylinder air is compressed after the piston 13 starts moving toward the top dead center (in the reverse direction of the engine), and the vaporization latent heat of the injected fuel is compressed. It is set so that the pressure is effectively reduced (the piston 13 is as close as possible to the top dead center) and the time for the second injected fuel to evaporate by the ignition timing is as long as possible. The

  Next, the control unit 2 calculates the fuel injection amount at the second injection timing calculated in step S1115, and causes the fuel injection valve 16 to inject the calculated amount of fuel (step S1116). After the second fuel injection into the stop-time expansion stroke cylinder 12B, the control unit 2 drives the spark plug 15 after a predetermined delay time has elapsed (steps S1117 and S1118). The predetermined delay time is obtained from an expansion stroke cylinder ignition delay map M4 set in advance according to the stop position of the piston. Due to the initial combustion in the expansion stroke cylinder 12B at the time of stop by this ignition, the engine turns from the reverse rotation direction to the normal rotation direction. Therefore, the piston 13 of the stop-time compression stroke cylinder 12A moves to the top dead center side and starts to compress the internal gas (burned gas burned by ignition in step S1106).

After ignition in the stop-state expansion-stroke cylinder 12B in step S1118, the control unit 2, again, the edge of the crank angle sensor 30, 31 from the ignition within a predetermined time T _LT (rising or falling edge of a crank angle signal) It is determined whether or not the piston 13 has moved according to whether or not it has been detected (step S1119). In this step S1118, if it is determined as YES to confirm that the piston 13 is moved, the control unit 2 sets the 01 restart ID flag F _ST, the process proceeds to the next step (step S1120).

On the other hand, if it is determined NO in step S1119 and it is confirmed that the piston 13 has not moved due to misfire, the control unit 2 determines whether or not the elapsed time T after ignition has elapsed by the predetermined time T _LT . Is determined (step S1121), and if not, reignition is repeatedly performed on the compression stroke cylinder 12A at the time of stop (step S1122). Here, in step S1121, when the elapsed time T after ignition has passed a predetermined time, the control unit 2 sets the stop position determination flag _FST to 02, and restarts with the assist combined use in step S120. The routine proceeds to the starting normal rotation control subroutine S220.

  Next, referring to FIG. 16, when it is determined YES in step S1119 and it is confirmed that the piston 13 has moved, the control unit 2 considers the fuel vaporization time for the stop-time compression stroke cylinder 12A. The second amount of fuel put in the fuel is injected into the fuel injection valve 16 (step S1124). The fuel injection amount at this time is such that the overall air-fuel ratio based on the total amount with the first injection amount becomes richer (for example, about 6) than the combustible air-fuel ratio (lower limit is 7 to 8). It is obtained from the second air-fuel ratio map M5 for the stop-time compression stroke cylinder 12A set in advance according to the stop position. The compression pressure near the first compression top dead center of the stop-time compression stroke cylinder 12A is reduced by the latent heat of vaporization of the second injection fuel to the stop-time compression stroke cylinder 12A. Can be easily exceeded.

  Note that the second fuel injection into the compression stroke cylinder 12A at the time of stop is performed exclusively for reducing the compression pressure in the cylinder, and ignition and combustion are not performed for this (from the combustible air-fuel ratio) Because it is rich, self-ignition does not occur.) This incombustible fuel then reacts with oxygen stored in the catalyst 37 in the exhaust passage 22 and is rendered harmless.

  Next, as described above, since the second injected fuel in the stop-time compression stroke cylinder 12A does not burn, the next combustion following the first combustion in the stop-time expansion stroke cylinder 12B is the stop-time intake stroke cylinder 12C. It is burning in. As energy for the piston 13 of the stop-time intake stroke cylinder 12C to exceed the second compression top dead center, a part of the initial combustion energy in the stop-time expansion stroke cylinder 12B is used. That is, the energy of the first combustion in the stop expansion stroke cylinder 12B is that the stop compression stroke cylinder 12A exceeds the first compression top dead center, and then the stop intake stroke cylinder 12C is in the second compression top dead center. For both crossing over and over.

  Therefore, for smooth start-up, it is desirable that the load when the intake stroke cylinder 12C during the stop exceeds the second compression top dead center is small. In that case, the second compression top dead center can be exceeded with small energy. The following flow is control for exceeding the second compression top dead center with as little energy as possible when performing combustion in the next stop intake stroke cylinder 12C.

  First, the control unit 2 estimates the in-cylinder air density, and calculates the air amount in the stop-time intake stroke cylinder 12C from the estimated value (step S1125). Next, the control unit 2 calculates an air-fuel ratio correction value for preventing self-ignition based on the in-cylinder temperature estimated in step S1101 (step S1126). That is, when self-ignition occurs, a force (reverse torque) is generated that pushes the piston 13 back to the bottom dead center side before reaching the second compression top dead center due to the combustion. This is undesirable because it consumes a lot of energy for exceeding the second compression top dead center. Therefore, in order to suppress this reverse torque, the air-fuel ratio is corrected to a rich value close to lean so that self-ignition does not occur.

  Next, the control unit 2 uses the air amount in the stop-intake stroke cylinder 12C calculated in step S1125 and the air-fuel ratio in consideration of the air-fuel ratio correction value calculated in step S1126 to supply fuel to the stop-in intake stroke cylinder 12C. The injection amount is calculated (step S1127).

  Then, fuel injection to the stop-time intake stroke cylinder 12C is executed. This fuel injection is delayed until the later stage of the compression stroke so that the compression pressure is reduced by the latent heat of vaporization (that is, the energy required for exceeding the second compression top dead center is reduced) (step) S1128). The delay amount is calculated based on the engine automatic stop period, the intake air temperature, the engine water temperature, and the like.

  On the other hand, the control unit 2 calculates the inspection timing from the timing at which the edges of the crank angle sensors 30 and 31 are detected in step S1119 (step S1129), and waits until this timing is reached (step S1130).

Next, it is determined whether or not the engine rotation speed Ne (inspection engine rotation speed Ne) Ne at the calculated inspection timing is less than a predetermined required engine rotation speed Ne (for example, 200 rpm) (step S1130). In this determination, when the engine speed Ne at the time of inspection is equal to or higher than the required engine speed Ne (YES in step S1131), the control unit 2 determines that the second compression top dead center is exceeded, and the restart determination flag F The value of _RS is updated to 11 (step S1132). On the other hand, in the judgment of step S1130, if it is determined that less than required engine rotational speed Ne is, proceeds to update the restart determination flag F _RS 12 (step S1133), the starter motor combination drive subroutine (Step S220) To do.

Next, referring to FIG. 17, the control unit 2 waits for the engine to exceed the second compression top dead center (step S1134). In this step, if it exceeds the second compression top dead center, the control unit 2 updates the value of the restart determination flag F _RS 21 (step S1135), sparks the spark plug 15 at a predetermined timing (Step S1136). On the other hand, if the engine cannot exceed the second compression top dead center despite the determination based on the rotational speed, the control unit 2 updates the value of the restart determination flag _FRS to 22. (Step S1137), the process proceeds to a starter motor combined drive subroutine (Step S220). As described above, in this embodiment, since the ignition timing for the stop-time intake stroke cylinder 12C is delayed after the second compression top dead center, it is possible to suppress the occurrence of reverse torque. In the intake stroke cylinder 12C at the time of stop, the compression pressure is reduced to easily exceed the top dead center until the second compression top dead center, and the torque in the forward direction due to the combustion energy is generated at the timing when the top dead center is passed. To occur. In the second transition to the compression top dead center, the stop-time exhaust stroke cylinder 12D reaches the compression stroke after the restart is started. With respect to the control of the transition to the exhaust stroke cylinder 12D at the time of stop, a return to the main routine is performed, fuel is injected in the intake stroke by normal control, and ignition is performed before the compression top dead center has elapsed, thereby obtaining a high torque. .

  Next, the assist combined restart control subroutine will be described with reference to FIG.

First, the control unit 2, in the assisted-restart control subroutine, refer to restart ID flag F _ST (step S1201). When the value of the stop position determination flag _FST is an initial value (= 1), the control unit 2 executes a start reverse rotation control subroutine (step S210). This starting reverse rotation control subroutine (step S210) is a reverse rotation operation before the engine body 1 is rotated forward, and the contents thereof omit the processing (steps S1109 and S1111) for using the starter motor 36 together. Others are substantially the same from step S1101 to step S1108 in the combustion restart control subroutine (step S110) described above, and a detailed description thereof will be omitted.

On the other hand, in step S1201, if the value of the restart ID flag F _ST is other than 1 the initial value (= 0), the control unit 2, the engine coolant temperature, (the elapsed time from the automatic stop) the stop time, the intake air temperature The in-cylinder temperature is estimated from the above (step S1202), and whether the estimated in-cylinder temperature is equal to or higher than a predetermined temperature, that is, whether it is warm (warm-up) or cold (cold-start). Is determined (step S1203). In If step S1203, when the operating state of the engine body 1 is determined to be in warm, the control unit 2 further refers to the restart ID flag F _ST (step S1204), the value of the restart ID flag F _ST Is determined to be 2, the control unit 2 executes a piston position correction control subroutine (step S200), and then executes a start-up normal rotation control subroutine (step S220) to return to the main routine and return to the normal routine. Execute operation control.

  On the other hand, if it is determined in step S1203 that the engine is cold, or if it is determined in step S1204 that the stop position determination flag is 3 to 5, the control unit 2 bypasses the piston position correction control 200. Then, the starting normal rotation control subroutine (step S220) is executed.

  FIG. 19 is a flowchart of the piston position correction control subroutine S210.

  As described above, if the stop position of the piston 13 is inappropriate, self-ignition tends to occur in the cylinder that reaches the compression stroke. On the other hand, if the piston 13 can be corrected prior to the restart control, the restart control can be successful without causing self-ignition. Here, as a method of correcting the stop position of the piston 13, it is conceivable to directly drive the engine body 1 with the starter motor 36. However, in that case, noise when driving the stopped engine main body 1 is increased, and there is a possibility that the operator feels uncomfortable. In addition, if the piston of the compression stroke cylinder at the time of stop, which is stopped at the bottom dead center side, is driven to the top dead center side, the starter motor 36 may be locked due to the reaction force of the cams of the intake valve 19 and the exhaust valve 20. There is also. Therefore, in this embodiment, the position of the piston 13 is changed by burning the stop-time expansion stroke cylinder 12B to prevent self-ignition.

  Referring to FIG. 19, when this subroutine S200 is executed, control unit 2 sets the fuel injection amount for stop-time expansion stroke cylinder 12B based on control map M20 in accordance with the stop position (step S2001). .

Next, the control unit 2 injects fuel into the stop-time expansion stroke cylinder 12B (step S2002). Thereafter, the stop-time expansion stroke cylinder 12B is ignited after elapse of a predetermined time considering the fuel vaporization time (step S2003). Here, in the stop-time expansion stroke cylinder 12B, multipoint ignition is executed in order to accelerate the combustion speed. Therefore, in this embodiment, the number of ignition times N _Ig is counted (step S2004), it is determined whether the counted number of ignition times N _Ig has reached a predetermined required number of ignition times N _{Ig_end} (step S2005), and the required number of ignition times. If you do not reach the N _{Ig_end} is to re-ignite (step S2006) and returns to step S2004, in the case that led to necessary number of ignitions N _{Ig_end} the crank angle since the last ignition within a predetermined time T _LT It is determined whether or not the piston 13 has moved to an appropriate range based on whether or not the edges of the sensors 30 and 31 (rise or fall of the crank angle signal) have been detected (step S2007). If YES is determined in step S2007, the value of the correction determination flag F _EXP is changed to 1 (step S2008), and the process returns to the main routine.

On the other hand, if it is determined NO in step S2007 and it is confirmed that the piston 13 has not moved due to misfire, the control unit 2 determines whether the elapsed time T after ignition has elapsed by a predetermined time _TLT . It is further judged whether or not (step S2009), and if not, re-ignition is repeatedly performed on the stop-time expansion stroke cylinder 12B (step S2010). On the other hand, when the elapsed time T after ignition has passed the predetermined time in step S2009, the control unit 2 changes the value of the correction determination flag F _EXP to 2 (step S2011) and returns to the main routine. To do.

  20 and 21 are flowcharts showing the starting normal rotation control subroutine S220.

  Referring to FIG. 20, when start-up normal rotation control subroutine S220 is executed in start-assist combined restart control subroutine S120, starter motor drive control subroutine S240 is executed in parallel.

In parallel with this starter motor drive control subroutine S240, the control unit 2, based on the restart ID flag F _ST, determines whether the combustion for the stop-state expansion-stroke cylinder 12B (Step S2201). Specifically, when reading the value of the restart ID flag F _ST, the process proceeds to the next step S2202 in the case of either the value is 1, 3 or 4, which does not correspond to any of these, stop The combustion in the time expansion stroke cylinder 12B and the combustion in the stop time intake stroke cylinder 12C are also stopped (steps S2203 and S2206).

However, the control unit 2 refers to the value of the reversal determination flag F _REV after stopping the fuel injection to the expansion stroke cylinder 12B at the stop in step S2203, and whether the value of the reversal determination flag F _REV is other than 2. It is determined whether or not (step S2204).

Even when the piston position is appropriate and the reverse rotation operation is executed, if the reverse operation causes a misfire and step S1111 is executed (when the reverse rotation determination flag F _REV is 2), unburned fuel remains in the compression stroke at the time of stoppage. Therefore, if the forward rotation operation is executed as it is, there is a risk that self-ignition occurs in the stop-time compression stroke cylinder 12A when warm. Therefore, referring to the value of the reverse determination flag F _REV in step S2204 and the value of the reverse determination flag F _REV is 2, even when the combustion in the stop-time expansion stroke cylinder 12B is stopped, The additional fuel is injected into the stop-time compression stroke cylinder 12A, and the air-fuel ratio of the stop-time compression stroke cylinder 12A is set to overrich to prevent self-ignition.

In step S2201, when the value of the stopping position determination flag F _ST is 1, the control unit 2, when the automatic stop, the piston 13 is in a single combustion stop range R, after the reverse operation, performs a forward operation Therefore, at this time, the expansion stroke cylinder 12B at the time of stop needs to be burned. When the value of the stop position determination flag _FST is 3, the piston 13 is in the combined combustion stop ranges A1 and A2, and the starter motor 36 drives the engine body 1 to cause combustion in the stop expansion stroke cylinder 12B. If possible. When the value of the stop position determination flag _FST is 4, although the piston 13 is in the combustion non-restartable range NG1, NG2, the piston 13 is displaced to an appropriate stop position by driving the engine body 1 with the starter motor 36. Thereafter, combustion is possible in the expansion stroke cylinder 12B at the time of stop. Therefore, in these cases, by satisfying other conditions, fuel is injected into the stop-time expansion stroke cylinder 12B to obtain torque due to combustion.

In contrast, in step S2201, if the value of the restart ID flag F _ST is 2, the piston position correction control subroutine described above (step S200) is performed, the combustion in the stop-state expansion-stroke cylinder 12B Do not run. Further, when the value of the stop position determination flag _FST is 5, since the piston 13 is between θ0 and θ1 shown in FIG. 4, vaporization atomization occurs even when fuel is injected into the stop-time expansion stroke cylinder 12B. By this time, the exhaust valve 20 is opened, and torque cannot be obtained. Therefore, even in this case, the combustion in the stop-time expansion stroke cylinder 12B is not executed, and the wasteful fuel injection / ignition operation is avoided.

Next, in step S2201, when any value of the restart ID flag F _ST is 1, 3 or 4, the control unit 2 refers to the restart determination flag F _RS (step S2202). In step S2202, when the value of non-zero value of the restart determination flag F _RS, the stop-state expansion-stroke cylinder 12B, the combustion restart control subroutine S110, whether already combustion is performed, if a misfire has occurred It is. When the stop-time expansion stroke cylinder 12B is burned, even if fuel is injected and ignited, there is no fresh air, so combustion that can output torque cannot be executed. In addition, when misfire occurs in the expansion stroke cylinder 12B at the time of stop, even if fuel is repeatedly injected, the fuel becomes overrich, so there is a high risk of misfire. Therefore, when the value of the restart determination flag _{FRS is} a value other than 0, the combustion in the cylinder is stopped.

  If the determination in step S2202 is YES, a combustion control subroutine S230 in the stop expansion stroke cylinder 12B is executed. On the other hand, when the determination in step S2202 is NO, the combustion in the stop-time expansion stroke cylinder 12B is stopped. The execution contents of the combustion control subroutine S230 are such that the fuel injection timing comes after the piston 13 is driven by the starter motor 36, and the processing for using the starter motor 36 (steps S1121 and S1123) is omitted. The rest is substantially the same as the fuel injection control of the stop-time expansion stroke cylinder 12B described with reference to FIG.

When step S230 is executed, or when the value of the reverse determination flag F _REV is 2 in step S2204, the control unit 2 takes fuel into the stop-time compression stroke cylinder 12A in consideration of the fuel vaporization atomization time. Inject (step S2207).

On the other hand, when the fuel injection into the stop-state compression-stroke cylinder 12A is discontinued at step S2205, the control unit 2, again, referring to the value of the restart ID flag F _ST (step S2208). When the value of the referred stop position determination flag _FST is 12 or 22, the control unit 2 also stops the fuel injection to the stop-time intake stroke cylinder 12C (step S2209). This is because when the value of the stop position determination flag _FST is 12 or 22, combustion in the stop-time intake stroke cylinder 12C has already been executed.

  Referring to FIG. 21, next, when fuel is injected into stop-time compression stroke cylinder 12A by executing step S2207, or fuel injection in stop-time intake stroke cylinder 12C is before execution in step S2208. If it is determined, the control unit 2 estimates the in-cylinder air density of the stop-time intake stroke cylinder 12C, and calculates the air amount of the stop-time intake stroke cylinder 12C from the estimated value (step S2220). Next, an air-fuel ratio correction value for preventing self-ignition is calculated based on the in-cylinder temperature estimated in step S2101 (step S2221).

  Next, the fuel injection amount to the stop-time intake stroke cylinder 12C is calculated from the air amount of the stop-time intake stroke cylinder 12C calculated in step S2220 and the air-fuel ratio considering the air-fuel ratio correction value calculated in step S2221. (Step S2222).

  Then, fuel injection to the intake stroke cylinder 12C at the time of stop is performed. This fuel injection is delayed until the latter stage of the compression stroke so that the compression pressure is reduced by the latent heat of vaporization (steps S2223 and S2224). The delay amount is calculated based on the engine automatic stop period, the intake air temperature, the engine water temperature, and the like.

Next, the control unit 2 refers to the restart determination flag F _RS and determines whether or not the value is 22 (step S2225). If the value of the restart determination flag _FRS is 22 when the stop-time intake stroke cylinder 12C first reaches the compression stroke, the restart control has already been executed in the combustion restart control S110. As a result, the second compression top dead center could not be exceeded (see FIG. 17). In this case, the self-ignition prevention measure is taken in the intake stroke cylinder 12C at the time of the stop when the self-ignition is most likely to occur. It is necessary to take. As a measure for preventing such self-ignition, in this embodiment, consideration is given to the influence of the rotation speed. That is, when the rotational speed is low, the heat conduction time becomes long, and at the time of warm restart, the cylinder inside the intake stroke cylinder 12C at the time of stop becomes a high temperature state, and the fuel injection timing is delayed as described above. Even so, self-ignition is likely to occur.

  Therefore, in this embodiment, a cranking air-fuel ratio and rotational speed map M14 is stored in the memory of the control unit 2, and the air-fuel ratio is rich according to the engine rotational speed Ne while referring to this map M14. (Step S2226), the timing at which the pinion gear 36d of the starter motor 36 meshes with the ring gear 35 is detected (step S2227), and is added to the stop intake stroke cylinder 12C at the time of meshing. Fuel is to be injected (step S2228). As will be described later, when the pinion gear 36d of the starter motor 36 meshes with the ring gear 35, the crankshaft 3 is reversed without the piston 13 exceeding the top dead center, and then the engine rotational speed Ne drops to zero. Since it is the time immediately after, by injecting additional fuel at this timing, vaporization atomization in the stop-time intake stroke in the compression stroke is promoted again, and self-ignition can be avoided.

  Thereafter, it is determined whether or not the stop-time intake stroke cylinder 12C has exceeded the compression top dead center (step S2229), and if exceeded, the stop-time compression stroke cylinder 12A is ignited (step S2230). Return to routine.

  As described above, in the assist combined restart control subroutine (step S220), when the combustion restart control (step S110) cannot be executed, or during the execution of the combustion restart control (step S110), the combustion restart fails. In the case of, the control is performed as shown in Table 2.

Referring to Table 2, first, when the value of the stop position determination flag _FST is 5, since the piston 13 is between θ0 and θ1 shown in FIG. 4, the fuel is injected into the stop expansion cylinder 12B. Even so, the exhaust valve 20 is opened before vaporization and atomization, and torque cannot be obtained. Therefore, in this case, the combustion in the stop-time expansion stroke cylinder 12B is not executed to avoid useless fuel injection / ignition operations.

Next, when the reverse rotation determination flag F _REV is 2, this is a case where misfire occurs during reverse rotation after restart (see FIG. 14). In this case, fuel for preventing self-ignition in the intake stroke cylinder 12A at the time of stop. So as to avoid the so-called warm lock (see FIG. 20).

In the case of restart determination flag F value of _RS is 02, since a failure in the combustion in the stop-state expansion-stroke cylinder 12B (Step S1123 of FIG. 15), the control of FIG. 20 in this case, While fuel injection (and hence ignition) into the stop-time expansion stroke cylinder 12B is stopped in step S2202, fuel for reducing the in-cylinder pressure during start-up by the starter motor 36 is applied to the stop-time compression stroke cylinder 12A. Is injected, and fuel injection is performed on the intake stroke cylinder 12C when stopped.

In the case of restart ID flag F value of _ST 12, despite successful combustion in the stop-state expansion-stroke cylinder 12B, a case where torque is not output sufficiently (step S1133 in FIG. 16). In this case, combustion in the stop expansion stroke cylinder 12B has already been completed and fuel injection to the stop compression stroke cylinder 12A has been executed, but reverse rotation control (steps S1101 to S1111) is executed. Therefore, in the stop-time compression stroke cylinder 12A, the problem of self-ignition cannot occur and there is no possibility that warm lock will occur. Accordingly, the fuel injection to the stop expansion stroke cylinder 12B and the stop compression stroke cylinder 12A is stopped by the determination in step S2202 of FIG. 20, and the fuel injection to the stop intake stroke cylinder 12C is determined in step S2208. Is also canceled (see FIG. 20).

Further, when the value of the stop position determination flag _FST is 22, it is a case where the combustion in the stop expansion stroke cylinder 12B was successful, but the second compression top dead center could not be exceeded (see FIG. 16 step S1133). In this case, combustion in the stop expansion stroke cylinder 12B has already been completed, and fuel injection into the stop compression stroke cylinder 12A and the stop intake stroke cylinder 12C has been executed, so the determination in step S2202 of FIG. Thus, the fuel injection to the stop expansion stroke cylinder 12B and the stop compression stroke cylinder 12A is stopped, and the fuel injection to the stop intake stroke cylinder 12C is also stopped by the determination in step S2208.

  Next, the starter motor drive control subroutine S240 will be described with reference to FIGS.

  FIG. 22 is a flowchart of the starter motor drive control subroutine S240, and FIG. 23 is a timing chart when the subroutine is executed.

  With reference to the drawings, when the control unit 2 executes the starter motor drive control subroutine S240, first, the current engine speed Ne is detected and it is determined whether or not it is 0 (step S2401). If the engine rotational speed Ne is 0, the control unit 2 immediately determines the timing tout at which the starter motor 36 should be driven (step S2402).

On the other hand, when the engine rotational speed Ne is not 0, the control unit 2 waits for detection of the crank angle CA0 at which the engine rotational speed Ne is decelerated and first becomes 0 (step S2403). Next, starting from the crank angle CA0 when the engine rotational speed Ne is 0, the crank angle CA waits until it reaches a predetermined crank angle CA1 at which the engine rotational speed Ne subsequently decreases (step S2403). This is because when the engine rotation speed Ne changes from normal rotation to reverse rotation and becomes 0, it becomes difficult to detect the signal, so the rotation speed Ne becomes 0 and then rotates in the reverse direction. Reliable control is _achieved by using the detectable timing T _CA1 as a reference.

When the crank angle CA reaches CA1, the control unit 2 uses the timing T _CA1 when the position of the piston 13 reaches _CA1 as an assist calculation timing as a reference for calculation (step S2404).

Next, the 0-speed timing tp of the starter motor 36 that is 0 after the engine rotation speed Ne changes in the reverse direction and then in the normal direction again from the assist reference timing T _CA1 is calculated (step S2405). Further, the meshing timing region Ts of the starter motor 36 is calculated based on the 0 speed timing tp (step S2406). The meshing timing area Ts is determined based on the specification data of the starter motor 36 stored in advance in the storage area of the control unit 2 based on the specification of the adopted starter motor 36. In the present embodiment, when the ring gear 35 is stopped, the drive motor 36a is meshed while driving the pinion gear 36d in the reverse direction at a speed of about 60 rpm in the reverse direction to the ring gear 35. The meshing timing region Ts is set in a range where the engine speed Ne is from 0 rpm to 60 rpm.

  Furthermore, in this embodiment, the drive delay time Tdy of the starter motor 36 is calculated from the battery voltage (step S2407). In the present embodiment, since the drive motor 36a is configured to mesh while driving the pinion gear 36d in the reverse direction, a time lag (i.e., between the input of the drive signal and the meshing of the gears 35, 36a) Drive delay time Tdy) occurs. Therefore, in step S2407, the timing tout incorporating the drive delay time Tdy is calculated.

  After step S2407, the control unit 2 calculates timing tout based on the above calculation (step S2408). In the calculation in step S2402, the same calculation as in steps S2405 to 2408 is performed with the rotation speed set to zero.

  After step S2402 or step S2408, the control unit 2 outputs a drive signal at the timing tout to drive the starter motor 36 (step S2409). As a result, the pinion gear 36d of the starter motor 36 is driven by the drive motor 36a and meshes with the ring gear 35, and the crankshaft 3 is assisted by the driving force from the starter motor 36 and returns to the main flow.

  After the second compression top dead center from the start of the start by starting combustion or using the starter motor together, it is detected whether or not the rotational speed has exceeded a predetermined rotational speed (step S2410). If detected, the drive of the starter motor 36 is released and the process is terminated (step S2411).

  As described above, in the present embodiment, when the restart condition is satisfied when the engine body 1 is stopped, it is determined whether or not the stop state of each of the cylinders 12A to 12D is suitable for combustion restart. If it is determined that the stop state of each of the cylinders 12A to 12D is not suitable for restarting combustion, and the stop-time compression stroke cylinder 12A is in the first half of the compression stroke when warm, the stop-time expansion stroke cylinder Combustion is performed at 12B. As a result, each cylinder 12A-12D rotates forward by a predetermined amount. Due to this normal rotation, the engine body 1 moves to a position suitable for starting the engine by the starter motor 36. Here, in the present embodiment, each piston position of the engine body 1 is corrected by combustion in the stop expansion stroke cylinder 12B. Therefore, the correction operation during the stop compression stroke cylinder 12A or the stop cylinder is likely to cause self-ignition. As a result of the return of the inside of the hour intake stroke cylinder 12C to the atmospheric pressure, after the starter motor 36 is driven, it is possible to suppress an excessive pressure rise in the cylinders 12A and 12C, and self-ignition Can be effectively prevented.

  As described above, the timing at which the control unit 2 burns the stop-time expansion stroke cylinder 12B is preferably when the engine body 1 is stopped after the automatic stop condition is satisfied and before the restart condition is satisfied. However, since the restart condition may be satisfied before the engine body 1 stops after the automatic stop condition is satisfied, the stop-time expansion stroke cylinder 12B may be combusted after the restart condition is satisfied.

  In this embodiment, at least when the starter motor 36 is operated, fuel is injected into the cylinder 12A that was in the compression stroke when the engine body was stopped. For this reason, in this embodiment, when the engine body 1 starts restarting by the starter motor 36, fuel is injected into the cylinder in the compression stroke, so that the in-cylinder pressure of the cylinder in the compression stroke decreases due to the latent heat of vaporization. As a result, self-ignition can be prevented more reliably.

  Further, in the present embodiment, when the control unit 2 determines that the combustion restart is inappropriate, and when the stop-time compression stroke cylinder 12 </ b> A is in the first half of the compression stroke, it is in a cold state that does not reach the predetermined temperature. If it is determined that there is, the combustion in the stop-time expansion stroke cylinder 12B is stopped. For this reason, in this embodiment, combustion in the stop expansion stroke cylinder 12B is executed only during warm operation where warm lock is relatively likely to occur, and warm lock is reliably prevented and warm lock is unlikely to occur. When cold, normal combustion restart or assist drive by the starter motor 36 is executed, so that quick and reliable restart can be realized.

  In the present embodiment, when the combustion is restarted, the engine body 1 is once reversely rotated by the combustion in the stop-time compression stroke cylinder 12A, and then the engine body 1 is normally rotated by the combustion in the stop-time expansion stroke cylinder 12B. When the correction of the piston position by the combustion in the stop expansion stroke cylinder 12B is executed, the combustion in the stop compression stroke cylinder 12A is stopped and the starter motor 36 is operated. For this reason, in this embodiment, even when performing so-called reverse combustion restart, it is possible to execute a quick restart in a state in which self-ignition is reliably prevented.

  As described above, according to the present embodiment, in the automatic stop system, when the restarter is requested, the multi-cylinder four-cycle engine main body 1 that can reliably prevent the warm lock when the starter motor 36 is used together. There is a remarkable effect that a control device can be provided.

  The above-described embodiments are merely preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  For example, the present invention is not limited to an engine control system in which the engine body 1 is first slightly rotated reversely to compress the air-fuel mixture in the stop-stroke expansion stroke cylinder 12 and then ignited, as in this embodiment. The present invention can also be applied to an engine in which the expansion cylinder 12 at the time of stop is ignited so that the engine body 1 is restarted.

  In addition, the starter motor may be an assist unit that applies torque at the time of restart, or may be a driving motor for a motor driving vehicle.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

1 is a schematic configuration diagram of an engine control system according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the intake system and exhaust system of the said engine control system. It is a partially broken cross-sectional schematic diagram which shows the structure of a starter motor. It is the schematic which shows the suitability of the piston stop range at the time of a stop. It is explanatory drawing about an engine automatic stop control, (A) is a piston stop position of a stop expansion stroke cylinder and a stop compression stroke cylinder, (B) is a stop expansion stroke cylinder, a stop compression stroke cylinder, and air quantity It is explanatory drawing which shows the relationship. It is explanatory drawing which shows typically the change of an engine speed, a crank angle, throttle opening, and an intake pressure in an engine stop period. It is a distribution map showing the correlation between the rotational speed at the compression top dead center during the engine stop period and the piston position after engine stop. It is a flowchart figure which shows the procedure of stop control. It is a flowchart figure which shows the procedure of stop control. It is a graph which shows the relationship between the elapsed time after an engine stop and in-cylinder temperature, and is an estimated value of in-cylinder temperature change when the in-cylinder temperature at the time of an engine stop is 80 degreeC. It is a graph which shows the relationship between the stop position of the engine which stopped automatically, and self-ignition generation | occurrence | production timing. It is a schematic diagram which shows the starting procedure of the engine in the said engine control system. It is a flowchart which shows the main flow of restart control. It is a flowchart which shows a combustion restart control subroutine. It is a flowchart which shows a combustion restart control subroutine. It is a flowchart which shows a combustion restart control subroutine. It is a flowchart which shows a combustion restart control subroutine. It is a flowchart which shows an assist combined use restart control subroutine. It is a flowchart of a piston position correction control subroutine. It is a flowchart which shows the normal rotation control subroutine at the time of starting. It is a flowchart which shows the normal rotation control subroutine at the time of starting. It is a flowchart of a starter motor drive control subroutine. It is a timing chart when the subroutine is executed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Control unit 3 Crankshaft 12A Stop compression stroke cylinder 12B Stop expansion stroke cylinder 12C Stop intake stroke cylinder 12D Stop exhaust stroke cylinder 13 Piston 14 Combustion chamber 15 Spark plug 16 Fuel injection valve 25 Air flow sensor 26 Suction Atmospheric pressure sensor 27 Ignition device 28 Alternator 29 Intake air temperature sensor 30, 31 Crank angle sensor 32 Cam angle sensor 33 Water temperature sensor 34 Accelerator opening sensor 35 Ring gear 36 Starter motor 36a Drive motor 36d Pinion gear

Claims (5)

In a control apparatus for a multi-cylinder four-cycle engine that restarts the engine by combustion in a stop-time expansion stroke cylinder that was in an expansion stroke at least when the engine was stopped when a condition for restarting the engine after automatic stop was satisfied,
Electric drive means capable of at least starting assisting the stopped engine;
An operating state detecting means capable of estimating an in-cylinder temperature of the engine at the time of at least a restart request;
Piston stop position identifying means for identifying the piston stop position of each cylinder at the time of automatic stop;
Combustion restart determining means for determining whether the piston of each cylinder identified by the piston stop position identifying means is suitable for combustion restart due to combustion in the stop expansion stroke cylinder;
When it is determined that the combustion restart is inappropriate by the combustion restart determination means, and the stop-time compression stroke cylinder in the compression stroke at the time of warm stop is in the first half of the compression stroke, Stop position correction means for correcting the piston position of the compression stroke cylinder at the time of stop by combustion in the expansion stroke cylinder to the first half of the compression stroke;
An electric drive control means for starting and controlling the electric drive means after each piston position is corrected by the stop position correction means. A control device for a multi-cylinder four-cycle engine. The control device for a multi-cylinder four-cycle engine according to claim 1,
A control apparatus for a multi-cylinder four-cycle engine, comprising fuel injection control means for injecting fuel into a cylinder that was in a compression stroke when the engine was stopped at least when the electric drive means was operated. The control device for a multi-cylinder four-cycle engine according to claim 1 or 2,
The stop position correcting means is the operation state detecting means when the combustion restart determining means determines that the combustion restart is inappropriate and the stop-time compression stroke cylinder is in the first half of the compression stroke. Control of a multi-cylinder four-cycle engine characterized by stopping combustion for correcting the piston position in the stop-time expansion stroke cylinder when it is determined that the engine is cold when the temperature is less than a predetermined temperature. apparatus. The control device for a multi-cylinder four-cycle engine according to any one of claims 1 to 3,
At the time of combustion restart, engine start control means is provided to reverse the engine by combustion in the stop-time compression stroke cylinder and then forwardly rotate the engine by combustion in the stop-time expansion stroke cylinder;
The electric drive control means, when the stop position correction means performs correction of the piston position by combustion in the stop expansion stroke cylinder, stops the reverse combustion in the stop compression stroke cylinder, A control device for a multi-cylinder four-cycle engine, characterized in that the electric drive means is operated to cause the engine to rotate normally.   5. The control device for a multi-cylinder four-cycle engine according to claim 1, wherein the electric drive means includes a ring gear provided in the engine and a pinion gear that is detachably engaged with the ring gear. A multi-cylinder four-cycle system comprising: drive means for driving engagement / disengagement of the pinion gear with the ring gear; and a drive source for inputting torque to the ring gear through the pinion gear. Engine control device.

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