JP4341477B2 - Engine starter - Google Patents

Description

  The present invention relates to an engine starting device, and when an engine automatic stop condition set in advance in an engine idling state or the like is satisfied, the engine is automatically stopped and a restart condition is satisfied in this state. The present invention relates to an engine starter configured to automatically restart the engine.

Recently, in order to reduce fuel consumption and CO ₂ emissions, the engine is automatically stopped once during idle operation, etc., and then restart conditions such as starting the vehicle are established. Technology for automatic engine stop control (so-called idle stop control) that automatically restarts the engine has been developed. The restart during the idle stop control requires a smooth start of the engine in accordance with the vehicle starting operation or the like, but the engine output shaft is driven by a starter motor as is generally done conventionally. According to the method of restarting the engine through cranking for driving the motor, there are problems that the starter motor is frequently operated and a large noise is generated and the life of the starter motor is shortened.

  Therefore, it is desirable to immediately start the engine with the combustion energy by injecting fuel into a cylinder that is in a stopped state in the expansion stroke to ignite and burn the cylinder. However, when the piston stop position of the cylinder that is in the stopped state in the expansion stroke as described above is inappropriate, for example, when the piston is stopped at a position very close to top dead center or bottom dead center, There is a possibility that the engine cannot be started normally due to the fact that the amount of air is so small that combustion energy cannot be obtained sufficiently or the stroke of the combustion energy acting on the piston is too short.

As a countermeasure against such a problem, for example, as shown in Patent Document 1 below, a braking device is provided for the crankshaft of the engine, and the piston of the cylinder that is stopped in the expansion stroke stops at an appropriate position during the stroke. If it is determined that the engine automatic stop condition is satisfied, as shown in Patent Document 2 below, the lean air-fuel ratio injection mode is selected and the intake pressure is increased as shown in Patent Document 2 below. The compression pressure is increased so that the piston of the cylinder that is stopped in the expansion stroke can be stopped at a predetermined position.
Japanese Utility Model Publication No. 60-128975 JP 2001-173473 A

  According to the engine starting device disclosed in Patent Document 1, it is necessary to provide a device for braking the crankshaft of the engine separately from the braking device for the vehicle, and the piston of the cylinder that is stopped in the expansion stroke is provided. In order to stop at an appropriate position, the braking device must be controlled with high accuracy, and there is a problem that this control is difficult.

  On the other hand, as disclosed in Patent Document 2, even when the engine pressure is increased and the compression pressure is increased when the automatic engine stop condition is satisfied, the fuel injection is stopped after the fuel injection is stopped. When the degree of decrease in engine rotation speed changes, there is a problem that the piston stop position fluctuates and it is difficult to properly stop the piston at a position suitable for engine restart.

  In particular, in a vehicle having a deceleration fuel cut control means for stopping fuel injection when the vehicle is decelerating, when an automatic stop condition is satisfied, for example, when the vehicle is stopped during execution of this deceleration fuel cut, it remains as it is. When the engine is automatically stopped, the fuel injection stop state continues for a long time and the temperature of the exhaust gas purification catalyst provided in the exhaust passage decreases, so that the exhaust gas purification performance is sufficient when the engine is restarted. There is a problem that it can not be demonstrated.

  In order to prevent the temperature of the exhaust gas purification catalyst from lowering, when the automatic stop condition is satisfied after the fuel injection is restored when the engine speed is reduced to a predetermined value during execution of the deceleration fuel cut control. Although it is conceivable to execute the automatic engine stop control, in this case, the fuel economy improvement effect by executing the deceleration fuel cut control and the automatic engine stop control cannot be sufficiently obtained, and the automatic engine There is a problem that the scavenging performance at the time of stoppage tends to be lowered.

  In view of the above circumstances, the present invention provides a piston for a cylinder that undergoes an expansion stroke when the engine is stopped without causing problems such as a reduction in exhaust gas purification performance due to execution of automatic engine stop control. An engine starter capable of appropriately executing automatic stop control for stopping the engine at a position suitable for restart is provided.

According to the first aspect of the present invention, when a preset automatic engine stop condition is satisfied, the fuel supply for continuing the operation of the engine is stopped and the engine is automatically stopped. Engine start configured to automatically restart the engine by injecting fuel into at least the cylinders stopped in the expansion stroke to cause ignition and combustion when the engine restart condition is established And a decelerating fuel cut control means for stopping fuel injection when decelerating and a piston of a cylinder that is in an expansion stroke when the engine is stopped even when the engine automatic stop condition is satisfied during execution of the decelerating fuel cut control and an automatic stop control means for executing automatic stop control for stopping the position suitable to restart the engine during the deceleration fuel cut control When automatically stopping, as well as the exhaust gas recirculation passage in an open state, after reducing the intake air flow introduced into the cylinders, as well as the exhaust gas recirculation passage and a closed state at a predetermined timing, it is introduced into each cylinder This is to increase the intake flow rate .

According to a second aspect of the present invention, in the engine starter according to the first aspect of the present invention, after the intake air flow rate is increased during execution of the deceleration fuel cut control, the engine is introduced into a cylinder that becomes an expansion stroke when the engine is stopped. The intake air flow rate is decreased at a timing such that the intake air flow rate is greater than the intake air flow rate introduced into the cylinder that is in the compression stroke.

According to a third aspect of the present invention, in the engine starting device according to the first aspect, it is determined that the temperature of the exhaust gas purification catalyst is equal to or lower than a preset reference temperature during execution of the deceleration fuel cut control. In this case, the exhaust gas recirculation passage is opened and the intake air flow rate introduced into each cylinder is reduced.

According to a fourth aspect of the present invention, in the engine starting device according to the first aspect, it is determined that the temperature of the exhaust gas purifying catalyst is higher than a preset reference temperature during execution of the deceleration fuel cut control. In this case, the exhaust gas recirculation passage is closed and the intake air flow rate reduction control is suppressed.

The present invention according to claim 5, in the starting device of the engine according to any one of the preceding claims 1-4, wherein, when the engine rotational speed at an execution point of the deceleration fuel cut control is high, exhaust Kikae When the flow passage is opened and the engine speed at the above time is low, the reduction control of the intake flow rate is suppressed.

According to the sixth aspect of the present invention, when a preset engine automatic stop condition is satisfied, the fuel supply for continuing the operation of the engine is stopped to automatically stop the engine, and the automatic stop state Engine start configured to automatically restart the engine by injecting fuel into at least the cylinders stopped in the expansion stroke to cause ignition and combustion when the engine restart condition is established And a decelerating fuel cut control means for stopping fuel injection when decelerating and a piston of a cylinder that is in an expansion stroke when the engine is stopped even when the engine automatic stop condition is satisfied during execution of the decelerating fuel cut control And an automatic stop control means for executing an automatic stop control for stopping the engine at a position suitable for restarting, and exhaust gas during execution of the deceleration fuel cut control When it is confirmed that the temperature of the activation catalyst is lower than the value corresponding to the activation temperature, the engine automatic stop control is executed after returning the fuel injection, and the temperature of the exhaust gas purification catalyst becomes the activation temperature. When it is confirmed that the value is higher than the corresponding value, the automatic engine stop control is executed without returning the fuel injection.

According to a seventh aspect of the present invention, in the engine starter according to the sixth aspect , the temperature of the exhaust gas purification catalyst is higher than a value corresponding to the activation temperature during execution of the deceleration fuel cut control, and is set in advance. When it is determined that the temperature is lower than the reference temperature, the exhaust gas recirculation passage is opened and the intake air flow rate introduced into each cylinder is decreased.

The present invention according to claim 8 is the engine start device according to claim 6 or 7 , wherein the temperature of the exhaust gas purification catalyst is lower than a value corresponding to the activation temperature during execution of the deceleration fuel cut control. When the determination is made, the exhaust gas recirculation passage is closed after the fuel injection is restored, and the intake flow rate introduced into each cylinder is increased.

The present invention according to claim 9 is the engine starter according to any one of claims 6 to 8, wherein the temperature of the exhaust gas purifying catalyst corresponds to the activation temperature during execution of the deceleration fuel cut control. If the exhaust gas recirculation passage is closed when it is determined that the exhaust gas recirculation passage is closed and the intake air flow rate is higher than the preset reference temperature, the intake air flow rate introduced into each cylinder is increased.

The present invention according to claim 1 0, in the starting device of the engine according to the claim 6, the temperature of the exhaust gas purifying catalyst is determined to be lower than the value corresponding to the activation temperature during the deceleration fuel cut control Thus, when the fuel injection is restored, the air-fuel ratio in the cylinder is set richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio.

Determining the present invention according to claim 1 1, in the starting device of the engine according to the claim 1 0, and the temperature of the exhaust gas purifying catalyst during execution of the deceleration fuel cut control is less than the value corresponding to the activation temperature When the fuel injection is restored, the exhaust gas recirculation passage is closed and the ignition timing is retarded.

According to the invention of claim 1, when automatically stopping the engine during deceleration fuel cut control, as well as the exhaust gas recirculation passage and an open state, the Rukoto reducing the intake air flow introduced into the cylinders Then, after executing the control that effectively suppresses the temperature drop caused by the supply of low-temperature air to the installation part of the exhaust gas purification catalyst while ensuring sufficient scavenging performance of the engine, the exhaust gas is discharged at a predetermined timing. There is an advantage that the automatic stop control of the engine can be appropriately executed by closing the recirculation passage and increasing the intake flow rate introduced into each cylinder to reduce the pumping loss .

In the invention according to claim 2 , when the engine is automatically stopped during execution of the deceleration fuel cut control, the exhaust recirculation passage is closed and the control for increasing the intake flow rate introduced into each cylinder is executed. By reducing the intake air flow rate at a predetermined timing, the piston of the cylinder that is in the expansion stroke when the engine is stopped is positioned at a position suitable for restarting the engine, that is, slightly lower than the center of the stroke. Since it comprised, the combustion energy obtained by making it burn with an expansion stroke cylinder at the time of engine restart can fully be ensured, and an engine can be restarted effectively.

According to the invention of claim 3, when it is determined that the temperature of the exhaust gas purifying catalyst is equal to or lower than a preset reference temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is opened. By reducing the intake flow rate introduced into each cylinder, it is possible to effectively reduce the catalyst temperature due to low-temperature air being supplied to the exhaust gas purification catalyst installation part while maintaining the scavenging performance of the engine. Can be suppressed.

According to the fourth aspect of the present invention, when it is determined that the temperature of the exhaust gas purification catalyst is higher than the preset reference temperature, the exhaust gas recirculation passage is closed and the intake flow rate reduction control is performed. By suppressing the exhaust gas purification catalyst, a sufficient amount of air can be supplied to the installation portion of the exhaust gas purification catalyst to effectively cool the exhaust gas purification catalyst, so that the temperature of the exhaust gas purification catalyst becomes excessively high. Can be prevented and its reliability can be ensured.

According to the invention of claim 5, high engine rotational speed at an execution point of the deceleration fuel cut control, when the time until the engine is stopped is in the long trend was opened exhaust Kikae passage In this state, by stopping the fuel injection for a long period of time, it is possible to effectively improve fuel efficiency, while ensuring sufficient scavenging performance of the engine, while low-temperature air is introduced into the exhaust gas purification catalyst installation part. It is possible to effectively suppress the temperature decrease due to the supply. In addition, when the engine speed at the time of execution of the deceleration fuel cut control is low and the time until the engine is stopped tends to be short, a sufficient amount for each cylinder is suppressed by suppressing the intake flow rate reduction control. By introducing the intake air, it is possible to effectively improve the scavenging performance of the engine and properly execute automatic stop control for stopping the piston at a position suitable for restarting the engine with reduced pumping loss. There are advantages.

According to the sixth aspect of the present invention, when it is confirmed that the temperature of the exhaust gas purification catalyst is lower than the value corresponding to the activation temperature during execution of the deceleration fuel cut control, after the fuel injection is restored By executing the automatic engine stop control, the temperature reduction caused by the supply of low-temperature air to the exhaust gas purification catalyst installation section is effectively suppressed, and the exhaust purification performance during engine restart is improved. There is an advantage that it can be maintained. If it is confirmed that the temperature of the exhaust gas purification catalyst is higher than the value corresponding to the activation temperature during the execution of the deceleration fuel cut control, the engine automatic stop control is executed without returning the fuel injection. By doing so, there is an advantage that fuel injection can be effectively improved by continuing the stopped state of fuel injection for a long time, and the scavenging performance of the engine can be sufficiently secured.

According to the seventh aspect of the present invention, when it is determined that the temperature of the exhaust gas purification catalyst is equal to or lower than a preset reference temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is opened. At the same time, by executing the control to reduce the intake flow rate introduced into each cylinder, the temperature drop caused by the supply of low-temperature air to the exhaust gas purification catalyst installation portion is effectively suppressed, and the engine The exhaust purification performance at the time of restart can be maintained.

According to the eighth aspect of the present invention, when it is determined that the temperature of the exhaust gas purification catalyst is lower than the value corresponding to the activation temperature during execution of the deceleration fuel cut control, the exhaust gas is recovered after the fuel injection is restored. Since the recirculation passage is closed and the intake air flow rate introduced into each cylinder is increased, the scavenging performance when the automatic engine stop control is subsequently executed can be effectively improved.

According to the ninth aspect of the present invention, when it is confirmed that the temperature of the exhaust gas purification catalyst is higher than the activation temperature by a predetermined value or more during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is closed. At the same time, the exhaust gas purification catalyst is cooled by increasing the intake air flow rate introduced into each cylinder and increasing the amount of low-temperature air supplied to the exhaust gas purification catalyst installation portion. Is advantageous in that it can be prevented from becoming excessively high and its reliability can be effectively secured.

According to the invention of claim 1 0, in the cylinder in a case where low and is determined to restore the fuel injection than the value the temperature corresponding to the activation temperature of the deceleration fuel cut control of the exhaust gas purifying catalyst during execution By setting the air-fuel ratio to be richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, the temperature of the exhaust gas led out to the exhaust passage can be raised and the exhaust gas purification catalyst can be activated early.

According to the invention of claim 1 1, in the cylinder in a case where low and is determined to restore the fuel injection than the value the temperature corresponding to the activation temperature of the deceleration fuel cut control of the exhaust gas purifying catalyst during execution The air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, and the exhaust gas recirculation passage is closed so that the ignition timing is sufficiently retarded without causing misfire after the fuel injection is restored. There is an advantage that the exhaust gas purification catalyst can be activated quickly by effectively raising the temperature of the gas.

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine having an engine starter according to the present invention. The engine includes an engine main body 1 having a cylinder head 10 and a cylinder block 11 and an ECU 2 for engine control. The engine body 1 is provided with four cylinders 12A to 12D, and a piston 13 connected to the crankshaft 3 is fitted into each of the cylinders 12A to 12D so that a combustion chamber 14 is provided above the cylinder 13. Is formed.

  A spark plug 15 is installed at the top of the combustion chamber 14 of each of the cylinders 12 </ b> A to 12 </ b> D so that the plug tip faces the combustion chamber 14. A fuel injection valve 16 that directly injects fuel into the combustion chamber 14 is provided on the side of the combustion chamber 14. This fuel injection valve 16 incorporates a needle valve and a solenoid (not shown), and is driven and opened for a time corresponding to the pulse width of the pulse signal input from the ECU 2, and has an amount corresponding to the valve opening time. The fuel is injected toward the vicinity of the electrode of the spark plug 15.

  In addition, an intake port 17 and an exhaust port 18 that open toward the combustion chamber 14 are provided above the combustion chamber 14 of each of the cylinders 12A to 12D, and an intake valve 19 and an exhaust gas are connected to these ports 17 and 18, respectively. Each valve 20 is equipped. The intake valve 19 and the exhaust valve 20 are driven by a valve operating mechanism having a camshaft (not shown), so that each cylinder 12A to 12D performs a combustion cycle with a predetermined phase difference. The opening / closing timings of the 12D intake / exhaust valves 19, 20 are set.

  An intake passage 21 and an exhaust passage 22 are connected to the intake port 17 and the exhaust port 18. As shown in FIG. 2, the downstream side of the intake passage 21 close to the intake port 17 is an independent branch intake passage 21a corresponding to each of the cylinders 12A to 12D. The upstream ends of the branch intake passages 21a are respectively It communicates with the surge tank 21b. A common intake passage 21c is provided upstream of the surge tank 21b, and an intake flow rate adjusting means including a throttle valve 23 driven by an actuator 24 is disposed in the common intake passage 21c. An air flow sensor 25 for detecting the intake flow rate and an intake pressure sensor 26 for detecting the intake pressure (boost pressure) are disposed on the upstream side and the downstream side of the throttle valve 23, respectively.

  Further, an exhaust gas purification catalyst 37 is disposed downstream of the collection portion of the exhaust passage 22 where exhaust from each of the cylinders 12A to 12D collects. The exhaust gas purification catalyst 37 is constituted by, for example, a three-way catalyst having a very high purification rate of HC, CO, and NOx when the air-fuel ratio of the exhaust is in the vicinity of the stoichiometric air-fuel ratio, and the oxygen concentration in the exhaust gas is It has a function of storing oxygen in a relatively high oxygen-excess atmosphere, releasing oxygen stored when the oxygen concentration is relatively low, and reacting with HC, CO, and the like. In FIG. 2, reference numeral 38 denotes an exhaust gas recirculation passage for recirculating the exhaust gas led out to the exhaust passage 22 to the intake air passage 21. The exhaust gas recirculation passage 38 has an EGR valve 39 for adjusting the recirculation amount of the exhaust gas. Is provided.

  The engine body 1 is provided with an alternator (generator) 28 connected to the crankshaft 3 by a timing belt or the like. The alternator 28 includes a regulator circuit 28a that adjusts a target generated current by controlling an output voltage by controlling a current of a field coil (not shown), and an output signal of the ECU 2 that is input to the regulator circuit 28a. Based on the above, the control of the target generated current corresponding to the electric load of the vehicle and the voltage of the in-vehicle battery, etc. is executed at normal times.

  Further, the engine is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the rotation speed of the engine is detected based on a detection signal output from one crank angle sensor 30. In addition, as will be described later, the rotation direction and the rotation angle of the crankshaft 3 are detected based on detection signals out of phase output from the crank angle sensors 30 and 31.

  In addition, a cam angle sensor 32 that detects a specific rotational position for cylinder identification provided on the camshaft, a water temperature sensor 33 that detects the coolant temperature of the engine, and an accelerator opening corresponding to the accelerator operation amount of the driver. Each detection signal output from the accelerator sensor 34 to be detected and the brake sensor 35 to detect that the driver has performed a brake operation is input to the ECU 2.

  The ECU 2 receives detection signals from the sensors 25, 26, 30 to 35, outputs a control signal for controlling the fuel injection amount and injection timing to the fuel injection valve 16, and performs ignition. By controlling the ignition timing with respect to the ignition device 27 attached to the plug 15, the combustion control means 41 for executing the combustion control corresponding to the operating state of the engine and the actuator 24 of the throttle valve 23 to open the throttle. Intake flow rate control means 42 for controlling the intake flow rate by outputting a control signal for controlling the speed, and deceleration fuel cut control means 43 for stopping fuel injection when the vehicle is decelerating are provided.

  Further, the ECU 2 automatically stops fuel injection by stopping fuel injection to each of the cylinders 12A to 12D at a predetermined timing when a preset automatic engine stop condition is satisfied. At the same time, an automatic stop control means 44 for executing a control for automatically restarting the engine when a restart condition is satisfied, for example, when an accelerator operation is performed by the driver, and a target generated current of the alternator 28 are set. A generated current control means 45 and an exhaust gas recirculation control means 46 for driving the EGR valve 39 to open and close the exhaust gas recirculation passage 38 are provided.

  The combustion control means 41 and the intake flow rate control means 42 are configured to execute combustion control in which the air-fuel ratio in the cylinders 12A to 12D is set to a value corresponding to the operating state. Further, the deceleration fuel cut control means 43 executes deceleration fuel cut control by stopping fuel injection when the engine rotation speed is about 1100 rpm or more, for example, while the vehicle is running at a reduced speed, and the engine rotation speed. When the engine speed is reduced to about 900 rpm, the deceleration fuel cut control is stopped and the fuel injection is restarted except when the automatic stop control means 44 executes the automatic engine stop control.

  The automatic stop control means 44 pushes down the piston 13 to slightly reverse the crankshaft 3 by causing the first combustion in the compression stroke cylinder in which the piston 13 is stopped during the compression stroke when the engine is automatically stopped. When the engine is automatically stopped, the piston 13 of the expansion stroke cylinder in which the piston 13 is stopped in the middle of the expansion stroke is temporarily raised, and the air-fuel mixture in the cylinder is compressed and ignited and burned. Thus, a control for applying a driving torque in the forward rotation direction to the crankshaft 3 to restart the engine is executed.

  In order to ignite the fuel injected into a specific cylinder and restart the engine properly without using a restart motor or the like as described above, the air-fuel mixture in the expansion stroke cylinder is burned. The obtained combustion energy must be sufficiently secured, and the cylinder that reaches the compression top dead center must overcome the compression reaction force and exceed the compression top dead center. Therefore, it is necessary to ensure a sufficient amount of air in the expansion stroke cylinder in which the piston 13 is in the middle of the expansion stroke when the engine is automatically stopped.

  That is, as shown in FIGS. 3A and 3B, in the cylinders that are in the expansion stroke and the compression stroke when the engine is stopped, the phases are shifted by 180 ° CA. If the piston 13 of the expansion stroke cylinder is positioned on the bottom dead center side of the stroke center, the amount of air in the cylinder increases and sufficient combustion energy is obtained. However, when the piston 13 of the expansion stroke cylinder is extremely positioned on the bottom dead center side, the amount of air in the compression stroke cylinder becomes too small and sufficient combustion energy for reversing the crankshaft 3 is obtained. Disappear.

  In contrast, the center of the stroke of the expansion stroke cylinder, that is, a predetermined range slightly lower than the position where the crank angle after compression top dead center is 90 ° CA, for example, the crank angle after compression top dead center is 100 If the piston 13 can be stopped within an appropriate range R of 120 ° CA, a predetermined amount of air is secured in the compression stroke cylinder, and the crankshaft 3 can be slightly reversed by the initial combustion. Combustion energy can be obtained. In addition, by securing a large amount of air in the expansion stroke cylinder, sufficient combustion energy for normal rotation of the crankshaft 3 can be obtained, and the engine can be reliably restarted.

  Therefore, in this embodiment, it is determined that the automatic stop control means 44 provided in the ECU 2 can execute the automatic engine stop control, and the engine rotation speed does not automatically stop the engine. The engine automatic stop control is executed when it is confirmed that the engine speed is higher than the normal idling speed. For example, in an engine in which a normal idle rotation speed is set to 650 rpm (the automatic transmission is in the drive range), the target value of the engine rotation speed is set to about 860 rpm (the automatic transmission is in the neutral range). As shown, the fuel injection is stopped and the engine rotational speed Ne is decreased at the time t1 when the engine rotational speed Ne becomes equal to or higher than the target value.

  Further, at the fuel injection stop time t1, which is the initial stage of the control operation for automatically stopping the engine, the opening K of the throttle valve 23 is increased to, for example, an opening of about 30% of the full opening to increase the boost pressure (intake pressure). By increasing Bt, the intake air flow sucked into the cylinders 12A to 12D of the engine is set to be larger by a predetermined amount than the minimum intake air flow required for continuing the engine operation, thereby improving the scavenging performance of the engine. The control to ensure is executed in the intake flow rate control means 42, and the control to reduce the rotational resistance of the crankshaft 3 by reducing the target power generation current Ge of the alternator 28 at the fuel injection stop time t1 is performed. It is configured to be executed in the current control means 45.

  In addition, when the fuel injection is stopped at the time point t1, the throttle valve 23 is detected at the time point t2 when it is confirmed that the engine rotational speed Ne has decreased to a reference speed N2 (for example, 790 rpm) or less. Is set to 0% and the throttle valve 23 is closed. The boost pressure Bt starts to decrease from the time t2 when the throttle valve 23 is closed, and the intake flow rate introduced into the cylinders 12A to 12D of the engine decreases. The air introduced into the common intake passage 21c passes through the surge tank 21b and the branch intake passage 21a, and thereby reaches the intake stroke of the fourth cylinder 12D, the second cylinder 12B, the first cylinder 12A, and the third cylinder 12C. Introduced in sequence with a predetermined transport delay. In consideration of the intake transport delay, the opening time t1 and the closing time t2 of the throttle valve 23 are set to appropriate times, so that more air expands than the third cylinder 12C, which is in the compression stroke when the engine is stopped. It will be introduced into the first cylinder 12A, which is the stroke.

  Further, at the time t2 when it is confirmed that the engine rotational speed Ne has decreased to the reference speed N2 or less, the target generated current Ge of the alternator 28 is temporarily increased, and the engine is rotated at the top dead center as described later. At the time t3 when the speed ne is within the predetermined range, the target generated current Ge of the alternator 28 is adjusted to a value corresponding to the degree of decrease in the engine rotational speed Ne, and is set based on the results of experiments conducted in advance. Control is performed to reduce the engine speed Ne along the reference line.

  When the engine is automatically stopped as described above, the kinetic energy of the crankshaft 3, the flywheel, etc. from the fuel injection stop time t1 is caused by mechanical loss due to frictional resistance or pump work of each cylinder 12A to 12D. When consumed, the crankshaft 3 of the engine is rotated several times by inertia, and in a 4-cylinder 4-cycle engine, it stops after reaching the compression top dead center of about 10 times. Specifically, as shown in FIG. 4, after the engine rotational speed Ne temporarily drops each time the cylinders 12 </ b> A to 12 </ b> D reach compression top dead center, they again when the compression top dead center is exceeded. The engine rotation speed Ne gradually decreases while repeating up and down.

  In the cylinder 12C that reaches the compression top dead center after the time t5 when the last compression top dead center is exceeded before the engine is stopped, the air pressure increases as the piston 13 rises due to the inertial force, and the compression reaction force causes the piston to 13 is pushed back, and the crankshaft 3 is reversely rotated. Due to the reverse rotation of the crankshaft 3, the air pressure of the expansion stroke cylinder 12 </ b> A that becomes the expansion stroke when the engine is stopped increases, so that the piston 13 of the expansion stroke cylinder 12 </ b> A is pushed back toward the bottom dead center according to the compression reaction force. Thus, the crankshaft 3 starts to rotate forward again, and the reverse rotation and forward rotation of the crankshaft 3 are repeated several times to stop the piston 13 after reciprocating. The stop position of the piston 13 is substantially determined by the balance of the compression reaction force in the compression stroke cylinder 12C and the expansion stroke cylinder 12A, and is influenced by the frictional resistance of the engine and exceeds the last compression top dead center. It also changes depending on the rotational inertia of the engine at the time t5, that is, the level of the engine rotational speed Ne.

  Accordingly, in order to stop the piston 13 of the expansion stroke cylinder 12A in the expansion stroke within the appropriate range R suitable for restart when the engine automatically stops, first, the compression of the expansion stroke cylinder 12A and the compression stroke cylinder 12C is performed. It is necessary to adjust the intake air flow rates for both cylinders 12A and 12C so that the reaction force becomes sufficiently large and the compression reaction force of the expansion stroke cylinder 12A is larger than the compression reaction force of the compression stroke cylinder 12C by a predetermined value or more. is there. For this reason, in the present embodiment, a predetermined amount of air is supplied to both the expansion stroke cylinder 12A and the compression stroke cylinder 12C by setting the opening K of the throttle valve 23 to a large value at the fuel injection stop time t1. After inhalation, the throttle valve 23 is closed to reduce its opening K at a time t2 when it is confirmed that the engine rotational speed Ne has decreased to a preset reference speed N2 (for example, 790 rpm) or less. Thus, the intake air amount is adjusted.

  That is, in FIG. 5, as described above, the fuel injection is stopped at the time t1 when the rotational speed Ne of the engine becomes a predetermined speed, and the throttle valve 23 is kept open for a predetermined period thereafter. The piston 13 provided in each cylinder 12A to 12D of the engine that rotates due to inertia measures the top dead center rotational speed ne when the piston 13 passes through the compression top dead center, and the piston position of the expansion stroke cylinder 12A when the engine is stopped. The piston position is plotted on the vertical axis, and the top dead center rotational speed ne of the engine is plotted on the horizontal axis, and the relationship between the two is graphed. By repeating this operation, a distribution map showing the correlation between the top dead center rotational speed ne during the engine stop operation period and the piston stop position in the expansion stroke cylinder 12A is obtained.

  From the above distribution map, a predetermined correlation is found between the top dead center rotational speed ne during the engine stop operation period and the piston stop position in the expansion stroke cylinder 12A. In the example shown in FIG. 5, the engine is stopped. If the top dead center rotational speed ne at the sixth to second before the state is within the range indicated by hatching, the stop position of the piston 13 is within a range R suitable for restarting the engine (after the compression top dead center). 100 ° to 120 ° CA). Particularly, regarding the second top dead center rotational speed ne before the engine is stopped, as shown in FIG. 6, the top dead center rotational speed ne is in the range of about 280 rpm to 380 rpm, and about On the low rotation side below 320 rpm, the piston stop position gradually changes closer to the top dead center as the top dead center rotation speed ne decreases. On the other hand, on the high rotation side where the top dead center rotational speed ne is 320 rpm or higher, the stop position of the piston 13 becomes substantially constant and falls within the substantially appropriate range R regardless of the top dead center rotational speed ne. I understand.

  The characteristic distribution tendency as described above can be seen when the engine top dead center rotational speed ne is on the high rotation side of 320 rpm or more, which is sufficient for the expansion stroke cylinder 12A and the compression stroke cylinder 12C when the engine is stopped. It is considered that this is because a large amount of air is filled and the piston stop position is concentrated toward the center of the stroke due to the compression reaction force of the air. It should be noted that the piston stop position is distributed to the lower left side at the low rotation side of 320 rpm or less, after the piston 13 reciprocating in each cylinder 12A to 12D is reversed on the compression top dead center side, and then the frictional resistance, etc. This is considered to be because the vehicle cannot be returned to the center of the stroke by being decelerated by the stop and stops.

  On the other hand, if the throttle valve 23 is kept closed without opening the fuel injection after the fuel injection is stopped, as shown by the broken line in FIG. The stop position of the piston 13 changes according to the height of the top dead center rotational speed ne. This is because if the throttle valve 23 is kept closed, the intake negative pressure is maintained at a high level (the intake pressure is low), and the compression reaction of the cylinders that become the expansion stroke cylinder 12A and the compression stroke cylinder 12C after the engine is stopped. This is because the influence of the rotational speed (rotational inertia) of the engine and the frictional resistance becomes relatively large because the force becomes small.

  Therefore, in order to sufficiently secure the scavenging performance of the engine while suppressing the influence of the rotational inertia and the frictional resistance, as shown in FIG. 4, until a predetermined time elapses from the time t1 when the fuel injection is stopped, that is, Until the engine speed Ne drops to a reference speed (for example, about 790 rpm) N2 or less, it is necessary to set the opening K of the throttle valve 23 to a relatively large value (for example, 30% of full opening). . Further, in order to maintain the engine speed Ne at a speed at which the piston 13 can be controlled to stop at an appropriate position, the target generated current Ge of the alternator 28 is set to 0, for example, at the fuel injection stop time t1. It is preferable.

  Then, at the time t2 when the engine speed Ne is decreased to the reference speed N2 or less, the opening K of the throttle valve 23 is reduced, and the target power generation current Ge of the alternator 28 is increased to a preset initial value. After the execution, at the time t3 when the engine top dead center rotational speed ne falls within the predetermined range, the target power generation current Ge of the alternator 28 is decreased to a value corresponding to the decreased state of the engine rotational speed Ne, and the crankshaft 3 By adjusting the rotational resistance of the engine and changing the engine external load in accordance with the degree of decrease in the engine rotational speed Ne, the engine rotational speed Ne is decreased along a reference line set based on experiments conducted in advance. It becomes possible to make it.

  Specifically, the engine top dead center rotational speed ne is detected in the process in which the engine rotational speed Ne decreases along the reference line, and the top dead center rotational speed ne falls within, for example, 480 rpm to 540 rpm. Based on the top dead center rotational speed ne at the time point t3 when it is determined that the engine has passed through the fourth compression top dead center before the engine is stopped, as shown in FIG. As described above, the higher the engine top dead center rotational speed ne is, the larger the value of the target generated current Ge is read from the map where the target generated current Ge corresponding to the detected value of the top dead center rotational speed ne is read. The alternator 28 has a target generated current Ge corresponding to the value.

  Further, the initial value when the target generated current Ge of the alternator 28 is increased at the time point t2 when the engine rotation speed Ne is reduced to the reference N2 speed or less is larger than the maximum value of the target generated current Ge read from the map. The target generated current Ge that has been set and increased to the initial value at the time t2 is decreased at the time t3, so that the target generated current Ge of the alternator 28 is changed based on the detected value of the top dead center rotational speed ne. Configured to control. For example, when the target generated current Ge read from the map is set to 0 to 50A, the initial value is set to a value higher than 50A that is the maximum value, for example, 60A. Then, after the target generated current Ge is set to 60 A at the time point t2, the amount of decrease in the target generated current Ge is set based on the value read from the map at the time point t3, and based on this value. Thus, control for reducing the target generated current of the alternator 28 is executed.

  By controlling the generated current of the alternator 28 as described above, the crankshaft 3, the flywheel, the piston 13, and the connecting rod at the time t5 when the final compression top dead center is passed in the normal operation state. The kinetic energy of the air compressed by the cylinder 12C and the potential energy of the air compressed in the compression stroke cylinder 12C, etc. are commensurate with the frictional resistance loss that acts thereafter, and the piston 13 of the cylinder 12A that is in the expansion stroke when the engine is stopped. It becomes possible to stop within the range R suitable for restarting the engine.

  When the automatic stop control unit 44 determines that the automatic engine stop condition is satisfied during execution of the fuel cut control by the deceleration fuel cut control unit 43, in principle, without returning the fuel injection, By controlling the opening of the throttle valve 23, the generated current of the alternator 28, and the opening of the EGR valve 39, the piston 13 of the cylinder 12A, which is in the expansion stroke when the engine is stopped, is stopped at a position suitable for restarting the engine. The engine is configured to perform automatic stop control.

  That is, when the vehicle decelerates, as shown in FIG. 8, the deceleration fuel cut control for stopping the fuel injection is executed at the time t0 when it is determined that the engine rotational speed Ne is in a state equal to or higher than a certain value (for example, 1100 rpm) At the same time, it is determined whether or not the temperature of the exhaust gas purifying catalyst 37 is lower than a preset reference temperature during execution of the deceleration fuel cut control. If it is confirmed that the temperature is low, the EGR valve 39 By setting the opening degree E to the fully open state and opening the exhaust gas recirculation passage 38, the opening degree K of the throttle valve 23 is set to 0% to reduce the intake flow rate, thereby reducing the low temperature introduced to the exhaust passage 22. Control for circulating air through the intake passage 21 is executed.

  Then, at the time t1 ′ when the rotational speed Ne of the engine is reduced to, for example, 900 rpm or less, it is determined whether or not the temperature of the exhaust gas purification catalyst 37 is in the state of the activation temperature or more, and it is the activation temperature or more. If it is confirmed, the opening E of the EGR valve 39 is set to be fully closed to close the exhaust gas recirculation passage 38, and the opening K of the throttle valve 23 is set to 30% to increase the intake flow rate. In addition, by setting the opening K of the throttle valve 23 to 0% at a predetermined timing t2, the piston 13 of the cylinder 12A that is in the expansion stroke when the engine is stopped is within the range R suitable for restarting the engine. The automatic stop control means 44 executes control for stopping.

  A control operation when the engine is automatically stopped by the automatic stop control means of the ECU 2 will be described based on the flowcharts shown in FIGS. When this control operation is started, it is determined whether or not an automatic stop permission flag F indicating whether or not the engine is in an operating state capable of executing the automatic stop control is ON (step S1). This automatic stop permission flag F satisfies all the conditions such as the vehicle speed is a predetermined value (for example, 10 km / h) or more, the steering angle is a predetermined value or less, the battery voltage is a reference value or more, and the air conditioner is in an OFF state. In such a case, it is determined that the engine is in a state where it is possible to execute the automatic engine stop control, and an ON state is set.

  If YES is determined in step S1, it is determined whether or not the accelerator sensor 34 is in an OFF state (step S2), and YES is determined and it is confirmed that the vehicle is in a predetermined deceleration state. In this case, it is determined whether or not the engine rotational speed Ne is larger than a reference value FC · ON for deceleration fuel cut that is set to about 1100 rpm in advance (step S3). Determines whether or not the brake sensor 35 is in the ON state (step S4), and if NO is determined, the process returns to step S1.

  When it is determined YES in step S4 and it is confirmed that the brake sensor 35 is in the ON state, the target value N1 of the engine speed is a value higher than the normal idle speed (650 rpm) by a predetermined amount. For example, after setting to 860 rpm (step S5), it is determined whether or not the engine rotational speed Ne is in a stable state at the target value N1 or more (step S6). If it is determined NO in step S6, the process returns to step S1 and the above control operation is repeated.

  EGR provided in the EGR passage to improve the scavenging performance of the engine at the time t1 when it is determined YES in Step S6 and it is confirmed that the engine rotational speed Ne is stable at the target value N1 or more. By closing the valve 38 and closing the exhaust gas recirculation passage 39 (step S7), setting the shift range of the automatic transmission to neutral and setting it to the no-load state (step S8), and stopping the fuel injection The engine automatic stop control is started (step S9).

  Further, the target power generation current Ge of the alternator 28 is set to 0 to stop power generation (step S10), and the throttle valve 23 is opened, and the opening degree K is set to about 30%, for example (step S11). . Thereafter, whether or not a predetermined time has elapsed from the time point t1 when the fuel injection is stopped in the above step S9, that is, the combustion of the fuel injected before reaching the two compression top dead centers after the fuel injection is stopped. It is determined whether or not the process has been completed (step S12), and after the ignition by the ignition device 27 is stopped when determined as YES (step S13), the process proceeds to the following step S31.

  As described above, in step S1, it is confirmed that the engine automatic stop permission flag F is in the ON state when the vehicle speed is higher than 10 km / h, and in step S2, the vehicle is decelerated (the brake sensor 35 is When it is confirmed that the engine target rotational speed N1 is stabilized at a predetermined value corresponding to the combustion state of the engine, the engine rotational speed Ne is set to a normal idle speed. Before the speed is reduced to 650 rpm, automatic engine stop control is executed.

  If it is determined YES in step S3 and it is confirmed that the engine rotational speed Ne is larger than the reference fuel value FC • ON for deceleration fuel cut, the fuel cut during deceleration is performed at this time t0. (FC) is executed (step S14), and the temperature of the exhaust gas purification catalyst 37 is set in advance to a value higher than the activation temperature by a predetermined value (a temperature at which the exhaust gas purification catalyst 37 is sufficiently activated), for example. It is determined whether the temperature is equal to or lower than the reference temperature T1 (step S15). If YES is determined in step S15, the opening degree E of the EGR valve 39 is set to be fully open to open the exhaust gas recirculation passage 38, and the opening degree K of the throttle valve 23 is set to 0%. The intake flow rate is decreased (step S16). As a result, the air led out from the cylinders 12A to 12D to the exhaust passage 22 is circulated to the cylinders 12A to 12D and gradually warmed.

  If it is determined NO in step S15 and it is confirmed that the temperature of the exhaust gas purification catalyst 37 is higher than the reference temperature, the opening E of the EGR valve 39 is set to fully closed and the exhaust gas recirculation is performed. The passage 38 is closed, and the opening K of the throttle valve 23 is set to 30% to increase the intake air flow (step S17). As a result, the low-temperature air introduced from the intake passage 21 to the cylinders 12 </ b> A to 12 </ b> D is directly led to the installation portion of the exhaust gas purification catalyst 37 through the exhaust passage 22.

  Next, it is determined whether or not the engine rotational speed Ne has decreased to a fuel return determination reference value FC · OFF that is set in advance to approximately 900 rpm (step S18). It is determined whether or not the sensor 34 is turned on (step S19). If YES is determined in step S19, the opening E of the EGR valve 39 is set to be fully closed (step S20), and fuel cut (FC) control at the time of deceleration is completed (step S21). To return.

  If it is determined YES in step S18 and it is confirmed that the engine speed Ne has decreased below the fuel return determination reference value FC · OFF set to about 900 rpm in advance, the brake sensor 35 is detected. Is determined to be continued in the ON state (step S22). If NO is determined, the process proceeds to step S20 and the opening degree E of the EGR valve 39 is set to fully closed, and then the speed is reduced. End fuel cut (FC) control.

  If it is determined as YES in step S22 and it is confirmed that the brake sensor 35 is kept in the ON state, it is determined whether or not the exhaust gas purification catalyst 37 is equal to or higher than the temperature T0 corresponding to the activation temperature. If the determination is NO (step S23) and the determination is NO, the fuel cut (FC) control is terminated by setting the air-fuel ratio in the cylinder to the theoretical air-fuel ratio (λ = 1) and returning the fuel injection. At the same time (step S24), the ignition timing is retarded by a predetermined amount (step S25), and the process returns to step S1.

  If it is determined NO in step S23 and it is confirmed that the temperature of the exhaust gas purification catalyst 37 is lower than the value T0 corresponding to the activation temperature during execution of the deceleration fuel cut control, the cylinders 12A to 12D. The air-fuel ratio in the engine may be set to be richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio to return the fuel injection, and the exhaust gas recirculation passage 38 may be closed. According to this configuration, the ignition timing can be sufficiently retarded without causing misfire by ensuring a sufficient amount of fresh air introduced into each of the cylinders 12A to 12D. There is an advantage that the exhaust gas purification catalyst 37 can be activated more rapidly by increasing the efficiency.

  If it is determined YES in step S23 and it is confirmed that the exhaust gas purification catalyst 37 is equal to or higher than the temperature T0 corresponding to the activation temperature, the shift range of the automatic transmission is set to neutral. A load state is set (step S26), and the target power generation current Ge of the alternator 28 is set to 0 to stop power generation (step S27). Further, the EGR valve 38 is closed and the exhaust gas recirculation passage 39 is closed (step S28), and the throttle valve 23 is opened and its opening degree K is set to about 30%, for example (step S29). ), The process proceeds to the following step S31.

  Then, by determining whether or not the engine rotational speed Ne has become equal to or lower than a reference speed N2 set to about 790 rpm in advance (step S31), the engine rotational speed Ne is decreased by stopping the fuel injection. It is determined whether or not it has started, and at time t2 when it is determined YES, the throttle valve 23 is closed and its opening degree K is set to 0% (step S32). As a result, the boost pressure Bt that has risen so as to approach the atmospheric pressure when the throttle valve 23 is opened in steps S11 and S29 starts to decrease with a predetermined time difference in accordance with the closing operation of the throttle valve 23.

  Further, the power generation control for operating the alternator 28 is started by setting the target power generation current Ge of the alternator 28 to an initial value set to about 60 A in advance (step S33). Note that the engine top dead center is replaced with the above embodiment in which the throttle valve 23 is closed at the time t2 when it is determined in step S31 that the engine rotational speed Ne has become equal to or lower than the reference speed N2. For example, when it is determined that the rotational speed ne is equal to or lower than the reference speed N2 set to about 790 rpm, for example, the throttle valve 23 is closed and power generation control of the alternator 28 is started. Good.

  Next, it is determined whether or not the engine top dead center rotational speed ne is within the first predetermined range (step S34). This first predetermined range is a time point t3 when the engine passes through the fourth compression top dead center before the engine is stopped, for example, in the process in which the engine rotational speed Ne decreases along a preset reference line. Is a value set based on the top dead center rotational speed ne, and specifically, is set within the range of 480 rpm to 540 rpm.

  When it is determined YES in step S33 and it is confirmed that the engine top dead center rotational speed ne is within the predetermined range (480 rpm to 540 rpm), it corresponds to the top dead center rotational speed ne at that time t3. The target generated current Ge of the generated alternator 28 is set (step S35). That is, as shown in FIG. 7, the higher the engine top dead center rotational speed ne is, the higher the engine top dead center rotational speed ne is read from the map where the target power generation current Ge is set to a larger value, and the target power generation current Ge corresponding to the top dead center rotational speed ne is read. Based on this value, control is performed to reduce the target generated current Ge of the alternator 28 from the initial value (60A) to the value read from the map.

  Next, the engine top dead center rotational speed ne is within a second predetermined range set based on the top dead center rotational speed ne at the time t4 when the engine passes the second compression top dead center before the engine stops, for example, 260 rpm to It is determined whether it is within the range of 400 rpm (step S36). The fuel injection amount increases as the engine top dead center rotational speed ne increases at time t4 when it is determined YES in step S36 and it has been confirmed that the second compression top dead center before the engine stop has passed. From the map (not shown) set to, the fuel injection amount for the cylinder 12C that is in the compression stroke when the engine is stopped is set, and fuel is injected in the latter half of the compression stroke of the cylinder 12C (step S37). When the fuel injected into the cylinder 12C is vaporized, the temperature in the cylinder is lowered, and the increase in the internal pressure is suppressed.

  Then, it is determined whether or not the engine top dead center rotational speed ne is equal to or less than a predetermined value N3 (step S38). This predetermined value N3 is a value corresponding to the top dead center rotational speed ne when exceeding the last compression top dead center in the process in which the engine rotational speed Ne is decreasing along a preset reference line, For example, it is set to about 260 rpm. Further, the boost pressure Bt at each time when each of the cylinders 12A to 12D sequentially passes the compression top dead center is detected, and the value is stored.

  If it is determined YES in step S38 and the engine top dead center rotational speed ne is equal to or lower than the predetermined value N3, that is, if it is confirmed that the engine has passed the last compression top dead center, At time t5, the boost pressure Bt at the time of passing through the previous compression top dead center is read, and this value is set as the boost pressure Bt at the second compression top dead center (TDC) before engine stop (step). S39).

  The top dead center rotational speed ne at the time t5 when the engine reaches the final compression top dead center (hereinafter referred to as the final top dead center rotational speed ne1) and the boost pressure Bt at the second compression top dead center before the engine stops. Based on (hereinafter referred to as boost pressure Bt2), it is determined whether or not the piston 13 tends to stop at a later position in each stroke (a position closer to the bottom dead center in the expansion stroke cylinder 12A) (step S40). . Specifically, when the final top dead center rotational speed ne1 is equal to or higher than a predetermined rotational speed N4 (for example, N4 = 200 rpm) and the boost pressure Bt2 is equal to or lower than a predetermined pressure P2 (for example, P2 = −200 mmHg) (vacuum side) ), The piston stop position in the expansion stroke cylinder 12A is 100 ° to 120 ° CA after the compression top dead center with respect to the appropriate range R. Since the tendency to stop at a position close to 120 ° CA is large, YES is determined in step S339.

  When it is determined NO in step S40, the engine does not tend to stop at a position near the latter stage of the stroke as described above, and the position at a relatively earlier stage of the stroke, that is, in the expansion stroke cylinder 12A. There is a possibility that the piston stop position may stop at a position close to 100 ° CA or 100 ° CA or less with respect to an appropriate range R of 100 ° to 120 ° CA after compression top dead center. Therefore, in order to stop the piston 13 within the appropriate range R more reliably, the throttle valve 23 is opened. For example, the throttle valve 23 is opened so that the opening degree K of the throttle valve 23 is set to the first opening degree K1 set to about 40% of full opening (step S41), and the intake air flow rate is increased to thereby increase the intake stroke. The intake resistance of the cylinder 12D is reduced. As a result, the engine is likely to stop at a later position in the stroke, and as a result, the stop position of the piston 13 in the expansion stroke cylinder 12A is prevented from exceeding the lower limit (100 ° CA) within the appropriate range R. become.

  On the other hand, if YES is determined in step S40, the rotational inertia of the engine is large, the intake air flow rate in the final intake stroke to the compression stroke cylinder 12C is small, and the compression reaction force is small. There is already a condition where 13 is likely to stop at a later stage of the stroke. Therefore, the throttle valve 23 is operated so that the opening degree K of the throttle valve 23 becomes the second opening degree K2 set to about 5%, for example (step S42). The second opening K2 may be a smaller opening or a closed state according to engine characteristics and the like. In this way, an appropriate intake resistance is generated in the intake stroke cylinder 12D, and the occurrence of a situation where the stop position of the piston 13 exceeds the appropriate range R and is further on the late stage is effectively prevented.

  Next, it is determined whether or not the engine is stopped (step S43). When it is determined YES, the shift range of the automatic transmission is returned from the neutral state to the drive state (D range) (step S44). ) After turning off the automatic stop permission flag F (step S45), the control operation is terminated.

  A control operation for restarting the engine that has been automatically stopped as described above will be described based on the flowcharts shown in FIGS. 12 to 14 and the time charts shown in FIGS. 15 and 16. First, it is determined whether or not a predetermined engine restart condition is satisfied (step S101). If YES is determined, for example, if an accelerator operation for starting from a stopped state is performed, the battery voltage is When the air temperature decreases or when the air conditioner is activated, the in-cylinder temperature is estimated based on the engine water temperature, the elapsed time since the automatic stop, the intake air temperature, and the like (step S102).

  Based on the stop position of the piston 13 detected when the engine is automatically stopped, the amount of air in the compression stroke cylinder 12C and the expansion stroke cylinder 12A is calculated (step S103). That is, the combustion chamber volumes of the compression stroke cylinder 12C and the expansion stroke cylinder 12A are obtained from the stop position of the piston 13. When the engine is automatically stopped, the engine is stopped after several revolutions after the fuel injection is stopped. Therefore, the expansion stroke cylinder 12A is also filled with fresh air, and the compression stroke cylinder 12C and the expansion cylinder 12C are expanded while the engine is stopped. Since the inside of the stroke cylinder 12A is at substantially atmospheric pressure, the amount of fresh air is obtained from the combustion chamber volume.

  Next, the stop position of the piston 13 detected according to the output signals of the crank angle sensors 30 and 31 is within the proper stop range R (before BTDC 60 ° CA to 80 ° CA) in the compression stroke cylinder 12C. Then, it is determined whether or not it is close to the bottom dead center BDC (step S104). When it is determined YES in step S104 and it is confirmed that the air amount in the compression stroke cylinder 12C is relatively large, the air amount in the compression stroke cylinder 12C calculated in step S103 is λ ( The first fuel injection is performed so that the air-fuel ratio (air excess ratio)> 1 (for example, air-fuel ratio = about 20) (step S105). This air-fuel ratio is obtained from the first air-fuel ratio map M1 for the first time of the compression stroke cylinder 12C set in advance according to the stop position of the piston 13, and is set to a lean air-fuel ratio of λ> 1. This prevents excessive combustion energy for reverse rotation even when the amount of air in the compression stroke cylinder 12C is relatively large.

  On the other hand, when it is determined NO in step S104 and the air amount in the compression stroke cylinder 12C is relatively small, the air-fuel ratio satisfying λ ≦ 1 with respect to the air amount in the compression stroke cylinder 12C calculated in step S103. The first fuel injection is performed so as to become (step S106). This air-fuel ratio is obtained from the first-time second air-fuel ratio map M2 of the compression stroke cylinder 12C set in advance according to the stop position of the piston 13, and satisfies λ ≦ 1 (theoretical air-fuel ratio or richer air-fuel ratio). By setting, even when the amount of air in the compression stroke cylinder 12C is small, sufficient combustion energy for reverse rotation can be obtained.

  Next, the cylinder 12C is ignited after the elapse of a predetermined time set in consideration of the vaporization time from the first fuel injection to the compression stroke cylinder 12C (step S107). Then, it is determined whether or not the piston 13 has moved based on whether or not the edges of the crank angle sensors 30 and 31, that is, the rising or falling edge of the crank angle signal, have been detected within a certain time after ignition (step S108). If it is determined as NO and it is confirmed that misfire has occurred and the piston 13 has not moved, the compression stroke cylinder 12C is re-ignited (step S109).

  If it is determined YES in step S108 and it is confirmed that the piston 13 has moved, the split fuel injection split for the expansion stroke cylinder 12A is based on the stop position of the piston 13 and the in-cylinder temperature estimated in step S102. The ratio (the ratio between the first pre-injection and the second post-injection) is calculated (step S121). The latter injection ratio is set to a larger value as the piston stop position in the expansion stroke cylinder 12A is closer to the bottom dead center or as the in-cylinder temperature is higher.

  Next, the fuel injection amount is calculated so that a predetermined air-fuel ratio (λ ≦ 1) is obtained with respect to the air amount of the expansion stroke cylinder 12A calculated in step S103 (step S122). The air-fuel ratio at this time is obtained from an air-fuel ratio map M3 for the expansion stroke cylinder 12A set in advance according to the stop position of the piston 13. Further, based on the fuel injection amount to the expansion stroke cylinder 12A calculated in step S122 and the division ratio calculated in step S121, the first stage fuel injection amount for the expansion stroke cylinder 12A is calculated, and the fuel is Injecting (step S123).

  Next, based on the in-cylinder temperature estimated in step S102, the subsequent (second) fuel injection timing for the expansion stroke cylinder 12A is calculated (step S124). This second injection timing is a timing when the air in the cylinder is compressed after the piston 13 starts moving toward the top dead center (reverse rotation of the engine), and the latent heat of vaporization of the injected fuel is compressed. The pressure is set to be reduced effectively, that is, the piston 13 is set to approach the top dead center, and the time for the second injected fuel to evaporate by the ignition timing is set to be as long as possible. The

  Next, the subsequent (second) fuel injection amount for the expansion stroke cylinder 12A is calculated based on the fuel injection amount for the expansion stroke cylinder 12A calculated in step S122 and the split ratio calculated in step S121 (step S125). ), And is injected at the second injection timing calculated in step S124 (step S126).

  After the second fuel injection into the expansion stroke cylinder 12A, ignition is performed when a predetermined delay time has elapsed (step S127). This delay time is obtained from the ignition map M4 for the expansion stroke cylinder 12A set in advance according to the stop position of the piston 13. Due to the initial combustion in the expansion stroke cylinder 12A by the ignition, the engine turns from reverse rotation to normal rotation. Therefore, the piston 13 of the compression stroke cylinder 12C moves to the top dead center side, and the gas in the cylinder (burned gas combusted by the ignition in step S107) starts to be compressed.

  Next, taking into account the fuel vaporization time, the second time fuel is injected into the compression stroke cylinder 12C (step S128). The fuel injection amount at this time is such that the entire air-fuel ratio based on the total injection 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 compression stroke cylinder 12C set in advance according to the stop position of the piston 13. The compression top dead center can be easily exceeded by reducing the compression pressure in the vicinity of the compression top dead center of the compression stroke cylinder 12C according to the latent heat of vaporization caused by the second injection fuel in the compression stroke cylinder 12C. It becomes.

  Note that the second fuel injection into the compression stroke cylinder 12C is performed exclusively to reduce the compression pressure in the cylinder, and ignition and combustion are not performed on this, and it is richer than the combustible air-fuel ratio. Therefore, self-ignition does not occur, and the non-combustible fuel is made harmless by reacting with oxygen stored in the exhaust gas purification catalyst 37 in the exhaust passage 22 thereafter.

  Since the fuel injected for the second time in the compression stroke cylinder 12C does not burn as described above, the next combustion following the first combustion in the expansion stroke cylinder 12A is the intake stroke cylinder 12D, that is, as shown in FIG. This is the first combustion in the fourth cylinder that was in the intake stroke when stopped. As energy for the piston 13 of the intake stroke cylinder 12D to exceed the compression top dead center, a part of the initial combustion energy in the expansion stroke cylinder 12A is used, and the initial combustion energy in the expansion stroke cylinder 12A is compressed. The stroke cylinder 12C is used both for overcoming the compression top dead center and for the intake stroke cylinder 12D for exceeding the compression top dead center.

  Therefore, for smooth start-up, it is desirable that the energy required for the intake stroke cylinder 12D to exceed the compression top dead center is small. For this reason, the air density in the intake stroke cylinder 12D is estimated, and the intake air is estimated from the estimated value. After calculating the air amount of the stroke cylinder 12D (step S140), an air-fuel ratio correction value for preventing self-ignition is calculated based on the in-cylinder temperature estimated in step S102 (step S141). That is, when self-ignition occurs, a force (reverse torque) that pushes the piston 13 back to the bottom dead center before the compression top dead center is generated by the combustion, and much energy is required to exceed the compression top dead center. Since it is consumed, it is not desirable. Therefore, in order to suppress the reverse torque, the air-fuel ratio is corrected to the lean side so that compression self-ignition does not occur.

  Next, the fuel injection amount to the intake stroke cylinder 12D is calculated based on the air amount of the intake stroke cylinder 12D calculated in step S140 and the air-fuel ratio in consideration of the air-fuel ratio correction value calculated in step S141 ( Step S142). Then, fuel is injected into the intake stroke cylinder 12D. In this fuel injection, the compression pressure is reduced by the latent heat of vaporization, that is, the energy required to exceed the compression top dead center is reduced. The process is delayed until the later stage of the compression stroke (step S143), and the delay amount is calculated based on the automatic engine stop period, the intake air temperature, the engine water temperature, and the like.

  Further, in order to suppress the occurrence of the reverse torque, ignition is performed with a delay after the top dead center (step S144). By executing the above control, in the intake stroke cylinder 12D, the compression pressure is reduced until the compression top dead center, and it is easy to exceed the top dead center. Directional torque will be generated.

  After step S144, the control state may be shifted to a normal control state, but in this embodiment, control for further suppressing the increase in engine speed is performed. This increase in engine rotation speed means that the engine rotation speed suddenly increases more than necessary after the initial combustion in the intake stroke cylinder 12D, which causes an acceleration shock or gives the driver a feeling of strangeness. This is not desirable. The increase in the engine rotation speed is immediately after starting (after the first combustion in the intake stroke cylinder 12D) because the intake pressure (pressure downstream of the throttle valve 23) during the automatic stop period is substantially atmospheric pressure. It is generated when the combustion energy in each of the cylinders 12A to 12D temporarily becomes larger than the combustion energy during normal idle operation. For this purpose, in steps S145 to S158 described below, control for suppressing the engine speed from rising is performed.

First, by setting the target current value of the alternator 28 in higher than usual started power generation (step S145), the engine rotational speed by increasing the rotational resistance of the crankshaft 3 (external load of the engine) by a generator of the alternator 28 Suppresses the rising of. Next, it is determined whether or not the intake pressure detected by the intake pressure sensor 26 is higher than the intake pressure during normal idling when the engine is not automatically stopped (step S150). Since the engine speed is likely to rise, the amount of combustion energy generated is reduced by making the opening of the throttle valve 23 smaller than the throttle opening during normal idle operation (step S151). Suppress.

When the temperature of the exhaust gas purification catalyst 37 provided in the exhaust passage 22 is equal to or less than the activation temperature (step S152), it is judged as YES, the target air-fuel ratio in the cylinder A rich air-fuel ratio satisfying λ ≦ 1 is set (step S153), and the ignition timing is delayed after top dead center (step S154). Thereby, the temperature increase of the catalyst 37 is promoted, and the amount of combustion energy generated is suppressed by the delay of the ignition timing.

  On the other hand, if it is determined NO in step S152 and it is confirmed that the temperature of the exhaust gas purification catalyst 37 is higher than the activation temperature, the target air-fuel ratio in the cylinder is set to a lean air-fuel ratio with λ> 1. The stratified lean combustion state is set (step S158). This lean combustion suppresses fuel consumption and suppresses the amount of combustion energy generated.

  The process returns to step S150 through step S154 or step S158 until the intake pressure is confirmed to be lower than that in normal idling when it is determined NO in step S150 and the engine is not automatically stopped. The control operation is repeated. If it is determined NO in step S150, there is no possibility that the engine speed will increase any more, so that the normal control state including the generated current of the alternator 28 is entered (step S160).

  By executing the restart control, as shown in FIGS. 15 and 16, first, the first fuel injection J3 is performed in the compression stroke cylinder 12C (third cylinder), and combustion is performed by the ignition (FIG. 15). (1)) is performed. With the combustion pressure (part a in FIG. 16) due to this combustion (1), the piston 13 of the compression stroke cylinder 12C is pushed down to the bottom dead center side, and the engine is driven in the reverse direction. Here, the first fuel injection J3 of the compression stroke cylinder 12C becomes a lean air-fuel ratio (λ> 1) when the air amount is relatively large, and a stoichiometric air-fuel ratio or a rich air-fuel ratio (λ ≦ 1) when it is small. Therefore, an appropriate combustion energy for reversing the engine, that is, a combustion energy that does not excessively reverse the compression top dead center while sufficiently compressing the air in the expansion stroke cylinder 12A. Obtainable.

  As the engine starts reverse rotation, the piston 13 of the expansion stroke cylinder 12A (first cylinder) starts to move in the direction of the top dead center. Immediately thereafter, the first fuel injection J1 in the expansion stroke cylinder 12A is performed and vaporization starts. Then, when the piston 13 of the expansion stroke cylinder 12A moves to the top dead center side (preferably closer to the top dead center from the stroke center) and the air in the cylinder 12A is compressed, the second (rear stage) fuel injection J2 is performed. Is done. The compression pressure is reduced by the latent heat of vaporization of the injected fuel, and the piston 13 comes closer to the top dead center, so that the density of the compressed air (air mixture) increases (part b in FIG. 16).

  When the piston 13 of the expansion stroke cylinder 12A is sufficiently close to top dead center, the cylinder 12A is ignited, and the first injected fuel (J1) and the second injected fuel (J2) whose vaporization is promoted are promoted. ) Are combusted ((2) in FIG. 15), and the engine is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 16).

  In addition, fuel richer than the combustible air-fuel ratio is injected into the compression stroke cylinder 12C at an appropriate timing (J4) ((3) in FIG. 15), but the compression stroke cylinder 12C is not combusted, The compression pressure of the compression stroke cylinder 12C is reduced by the latent heat of vaporization caused by fuel injection (part d in FIG. 16), and accordingly, the compression top dead center (the first compression top dead center from the start of starting) is exceeded. The initial combustion energy of the consumed expansion stroke cylinder 12A is reduced.

  Furthermore, the timing of fuel injection (J5) in the intake stroke cylinder 12D, which is the next combustion cylinder, is set to an appropriate timing ((4) in FIG. 15) for reducing the temperature in the cylinder and the compression pressure by the vaporization latent heat of the fuel. As shown, for example, after the middle stage of the compression stroke), self-ignition before the compression top dead center is prevented in the compression stroke of the intake stroke cylinder 12D. Further, in combination with the ignition timing of the intake stroke cylinder 12D being set after the compression top dead center, combustion before the compression top dead center is prevented (part e in FIG. 16). That is, by reducing the compression pressure by the fuel injection (J5) and not performing the combustion before the compression top dead center, the energy of the first combustion in the expansion stroke cylinder 12A becomes the compression top dead center (the second compression from the engine start start time). It is possible to suppress consumption to exceed the top dead center.

  Thus, the first compression top dead center ((3) in FIG. 15) after the start of restart and the second compression by the energy of the first combustion ((2) in FIG. 15) in the expansion stroke cylinder 12A. The top dead center ((4) in FIG. 15) can be exceeded, and smooth and reliable startability can be ensured, and thereafter ((5), (6) in FIG. ) Makes the air-fuel ratio lean (λ> 1) according to the temperature of the catalyst 37, or delays the ignition timing, thereby shifting to normal operation while preventing the engine speed from rising.

  When the preset engine automatic stop condition is satisfied as described above, the fuel injection for continuing the operation of the engine is stopped to automatically stop the engine, and the engine restart condition in the automatic stop state. In the engine starter configured to restart the engine by injecting fuel into at least the cylinder 12A that is stopped in the expansion stroke to cause ignition and combustion when The decelerating fuel cut control means 43 for stopping the engine and the piston 13 of the cylinder 12A that is in the expansion stroke when the engine is stopped even when the engine automatic stop condition is satisfied during the execution of the decelerating fuel cut control are suitable for restarting. And automatic stop control means 44 for executing automatic stop control for stopping at a position, and exhausting during execution of deceleration fuel cut control Since the engine automatic stop control is executed while the flow passage 38 is opened and the intake flow rate introduced into the cylinders 12A to 12D is reduced, the deceleration fuel cut control and the engine automatic control are executed. By appropriately executing the stop control, the fuel efficiency is effectively improved, and the scavenging performance of the engine is sufficiently secured, and the low temperature air is supplied to the installation portion of the exhaust gas purification catalyst 37. There is an advantage that the temperature reduction can be effectively suppressed and the exhaust purification performance can be maintained when the engine is restarted.

  That is, the engine automatic stop control is executed during the deceleration fuel cut control so that the fuel injection stop state is continued for a long period of time. A sufficient scavenging property can be secured. Moreover, since the EGR valve 38 is opened and the throttle valve 23 is closed during the execution of the deceleration fuel cut control, cold air is supplied from the intake passage 22 into the cylinders 12A to 12D. Can be effectively suppressed, and the air led out from each of the cylinders 12A to 12D can be recirculated into the cylinders 12A to 12D by the exhaust gas recirculation passage 38 to be warmed. Therefore, it is possible to effectively suppress a temperature decrease due to low temperature air being supplied to the installation portion of the exhaust gas purification catalyst 37, maintain exhaust purification performance when the engine is restarted, and expand when the engine is stopped. There is an advantage that automatic stop control for stopping the piston 13 of the cylinder 12A in the stroke at a position suitable for restarting can be properly executed.

Further, when the engine is automatically stopped during the execution of the deceleration fuel cut control as described above, the exhaust gas recirculation passage 39 is opened, and the intake flow rate introduced into each of the cylinders 12A to 12D is reduced. After executing the control to effectively suppress the temperature drop caused by the low temperature air being supplied to the installation portion of the exhaust gas purification catalyst 37, the EGR valve 38 is closed and the exhaust gas recirculation passage 39 is closed. In addition, since the throttle valve 23 is opened to increase the intake air flow rate introduced into the cylinders 12A to 12D, the engine is kept in a state where the pumping loss is reduced while sufficiently securing the scavenging performance of the engine. When a predetermined amount of air is introduced into each of the cylinders 12A to 12D when the engine is stopped, the piston 13 is stopped at a position suitable for restarting the engine (near the center of the stroke). Control to be able to properly perform.

  In particular, after the intake flow rate introduced into each of the cylinders 12 to 12D is increased when the engine is automatically stopped during execution of the deceleration fuel cut control as described above, the intake flow rate is introduced into the cylinder that becomes the expansion stroke when the engine is stopped. When the throttle valve 23 is closed to reduce the intake air flow rate at a timing such that the intake air flow rate to be increased is larger than the intake air flow rate introduced into the cylinder that is in the compression stroke, the engine restart condition is It is possible to effectively restart the engine by injecting fuel into the cylinder 12A that is established and in the expansion stroke to perform ignition and fuel.

  That is, in the above embodiment, at the time t2 when it is confirmed that the engine rotational speed Ne has dropped below the reference speed (790 rpm), the throttle valve 23 is closed to reduce the intake air flow rate, and with a predetermined transport delay. By adjusting the flow rate of the intake air introduced into the cylinders 12A to 12D at an appropriate timing, the piston 13 of the cylinder 12A that becomes the expansion stroke when the engine is stopped is positioned slightly above the center of the stroke, and the cylinder that becomes the compression stroke Since more intake air than the inner 12C is introduced into the expansion stroke cylinder 12A, there is an advantage that a driving torque necessary for restarting the engine can be sufficiently generated.

  In the above embodiment, when it is determined that the temperature of the exhaust gas purification catalyst 37 is equal to or lower than the preset reference temperature T1 during execution of the deceleration fuel cut control, the EGR valve 38 is closed and the exhaust gas recirculation is performed. The passage 39 is opened, and the throttle valve 23 is opened to reduce the intake flow rate introduced into the cylinders 12A to 12D, so that the air derived from the cylinders 12A to 12D enters the cylinders 12A to 12D. Since it is configured to recirculate, it is possible to effectively suppress the temperature of the exhaust gas purification catalyst 37 from being lowered due to the supply of low temperature air to the installation portion of the exhaust gas purification catalyst 37, and restart the engine. The exhaust gas purification performance at the time can be maintained.

  Further, in the above embodiment, the temperature of the exhaust gas purification catalyst 37 is set to a predetermined value rather than a preset reference temperature, that is, a value corresponding to the activation temperature of the exhaust gas purification catalyst 37 during execution of the deceleration fuel cut control. The exhaust gas recirculation passage 39 is closed when it is determined that the temperature is higher than the temperature T1 that is set to a higher value, and the reduction control of the intake flow rate is suppressed. By supplying a sufficient amount of air to the installation portion to cool the exhaust gas purification catalyst 37, it is possible to prevent the temperature of the exhaust gas purification catalyst 37 from becoming excessively high. Therefore, there is an advantage that it is possible to effectively prevent the occurrence of a situation in which the exhaust gas purification catalyst 37 is burned and its reliability is lowered.

When it is determined that the temperature of the exhaust gas purification catalyst 37 is lower than the preset reference temperature T1 during execution of the deceleration fuel cut control, the exhaust gas recirculation passage 39 is opened and each cylinder 12 is opened. When the intake air flow rate introduced into -12D is reduced and it is determined that the intake air flow rate is higher than the reference temperature T1, the exhaust gas recirculation passage 39 is closed and the intake air flow rate reduction control is suppressed. instead of the embodiment, when the engine rotational speed Ne is higher at an execution point t0 deceleration fuel cut control, the exhaust Kikae flow passage 39 opened, when the engine rotational speed at the time t0 of the low, the intake air flow Reduction control may be suppressed.

  According to the above configuration, the exhaust gas recirculation passage 39 is opened when the engine rotational speed Ne is high at the execution time t0 of the deceleration fuel cut control and the time until the engine is stopped tends to be long. In this state, by stopping the fuel injection for a long period of time, the fuel efficiency is effectively improved and the air scavenging performance of the engine is sufficiently ensured, and the low temperature air is supplied to the installation portion of the exhaust gas purification catalyst 37. It is possible to effectively suppress the temperature decrease due to the On the other hand, when the engine rotational speed Ne at the execution time t0 of the deceleration fuel cut control is low and the time until the engine is stopped tends to be shortened, the valve closing operation amount of the throttle valve 23 is reduced. By suppressing the reduction control of the intake flow rate, a sufficient amount of intake air is introduced into each of the cylinders 12A to 12D to effectively improve the scavenging performance of the engine and reduce the pumping loss. There is an advantage that the automatic stop control for stopping the piston 13 at a position suitable for the restart can be properly executed.

  In the above embodiment, during the execution of the deceleration fuel cut control by the deceleration fuel cut control means 43, it is determined whether or not the temperature of the exhaust gas purification catalyst 37 is higher than the value T0 corresponding to the activation temperature. When it is confirmed that the value is lower than the value T0 corresponding to the control temperature, the fuel injection is restored, so that the temperature drop caused by the low temperature air being supplied to the installation portion of the exhaust gas purification catalyst 37 is reduced. There is an advantage that it can be effectively suppressed. When it is confirmed that the temperature of the exhaust gas purification catalyst 37 is higher than the value corresponding to the activation temperature during execution of the deceleration fuel cut control, the automatic engine stop control is executed without returning the fuel injection. Thus, there is an advantage that the fuel injection can be effectively improved by continuing the stopped state of the fuel injection for a long time and the scavenging performance of the engine can be sufficiently secured.

  In the above embodiment, when the engine is automatically stopped, a predetermined time elapses after the engine rotation speed Ne becomes the preset reference speed N2 and fuel injection is stopped. At time t3 when it is confirmed that the fourth compression top dead center has been reached, the top dead center rotational speed ne is detected, and the target generated current Ge corresponding to this top dead center rotational speed ne is shown in FIG. When the top dead center rotation speed ne is read out from the map, the reduction amount of the target generated current Ge of the alternator 28 is set to a larger value than when it is high. Thus, the target generated current Ge of the alternator 28 can be appropriately controlled so as to reduce the engine rotational speed Ne. Thus, the fourth top dead center before the engine is stopped so that the second top dead center speed ne before the engine is stopped is within the range indicated by hatching in FIG. By adjusting the target power generation current Ge of the alternator 28 based on the number of times speed ne and changing the rotational resistance of the engine, the piston 13 of the cylinder that is in the expansion stroke when the engine is stopped is brought into a position suitable for restarting the engine. Can be stopped.

  In order to stop the piston 13 of the cylinder 12A, which is in the expansion stroke when the engine is stopped, at a position suitable for restarting the engine, the crankshaft is controlled by controlling the power generation current of the alternator 28 immediately before the engine is stopped. It is desirable to adjust the rotational resistance of 3. However, immediately before the engine is stopped, the engine rotational speed Ne becomes low, and the power generation function of the alternator 28 is not fully exhibited. Even if the target power generation current Ge is changed, the rotational resistance of the crankshaft 3 Therefore, it is difficult to accurately adjust the reduced state of the engine rotational speed Ne. Therefore, in order to stop the piston 13 of the cylinder 12A, which is in the expansion stroke when the engine is stopped, at an appropriate position, the target generated current Ge of the alternator 28 is increased to a preset initial value after the fuel injection is stopped. The target of the alternator 28 is set to a value corresponding to the degree of decrease in the engine speed at the middle stage of the process of decreasing the engine speed Ne (for example, when the fourth to sixth compression top dead centers before the engine stops). It is desirable to execute control for reducing the generated current Ge.

  That is, the alternator 28 can accurately adjust the rotational resistance of the crankshaft 3 over a wide range by adjusting the target generated current Ge to an arbitrary value from about 0 A to about 60 A, for example, as shown in FIG. Thus, it is known that when the target power generation current Ge is set from a small current value of about 10 A to a large current value of about 60 A and the generated current is increased, it takes about 0.1 sec. On the other hand, when the target generated current Ge of the alternator 28 is set to a small current value of about 10 A from a large current value of about 60 A, for example, the generated current can be instantaneously changed. .

  Therefore, at the initial stage of the operation for automatically stopping the engine, the target power generation current Ge of the alternator 28 is increased to an initial value of about 60 A so that the power generation function of the alternator 28 can be sufficiently exerted, and then the piston 13 The engine top dead center rotational speed ne when passing through the compression top dead center is detected at a predetermined timing. When the top dead center rotational speed ne is low, the amount of decrease in the target generated current Ge is higher than when it is high. Is set to a large value so that the rotational resistance of the crankshaft 3 is adjusted in response to a decrease in the engine rotational speed Ne to stop the piston 13 of the expansion stroke cylinder 12A at a position suitable for restarting the engine. It is desirable to perform.

  In addition, while detecting the top dead center rotational speed ne when the piston 13 passes through the compression top dead center, the reduction amount of the target generated current Ge is controlled based on the top dead center rotational speed ne. Instead of the above-described embodiment, the crank angle at the time when the piston 13 passes the center position of the stroke is set as the detection angle, and the target power generation is performed based on the engine speed Ne detected at the time when the detection angle is reached. It is also possible to set a reduction amount of the current Ge. However, when the piston 13 passes through the center position of the stroke, the engine rotational speed Ne is in a significantly fluctuating state, and it is difficult to accurately determine the reduced state of the engine rotational speed Ne. As shown in the embodiment, based on the engine top dead center rotational speed ne when the piston 13 in which the engine rotational speed Ne is temporarily stabilized passes the compression top dead center, the target generated current Ge of the alternator 28 is It is desirable to set the amount of decrease.

  In particular, in the above-described embodiment, the intake flow rate introduced into the cylinders 12A to 12D is sufficiently secured by reducing the intake throttle amount in a region where the engine rotational speed Ne is sufficiently high at the initial stage of the operation of automatically stopping the engine. At the same time, the target generated current Ge of the alternator 28 is set to 0, for example, so that the target generated current Ge is temporarily reduced, so that the scavenging performance of the engine can be effectively improved. At the same time, both the rotational resistance of the crankshaft 3 and the pumping loss can be reduced. Therefore, at the initial stage of the operation of automatically stopping the engine, while preventing the engine speed Ne from significantly decreasing, the target generated current Ge of the alternator 28 is increased to the initial value at a predetermined timing thereafter. There is an advantage that the power generation function of the alternator 28 can be quickly and sufficiently exhibited to adjust the external load of the engine to an appropriate value.

  Further, as shown in the above-described embodiment, at the initial stage of the operation of automatically stopping the engine, the automatic transmission is set to the neutral state and the fuel injection is stopped to suppress the rotation of the engine while the fluctuation of the engine rotational speed Ne due to disturbance is suppressed. When it is configured to reduce the speed Ne, there is an advantage that automatic stop control for stopping the piston 13 at a position suitable for restarting the engine can be appropriately executed.

  Furthermore, in the above embodiment, it is determined whether or not the piston 13 tends to stop at a position near the latter half of the stroke based on the top dead center rotational speed ne1 at the time t5 when the piston 13 reaches the last compression top dead center. Since the opening degree K of the throttle valve 23 is adjusted according to the determination result, the stroke amount of the piston 13 immediately before the engine is stopped is appropriately adjusted to be within a range R suitable for restarting the engine. The automatic stop control for stopping the piston 13 can be appropriately executed.

  For example, does the piston 13 tend to stop at a position near the latter half of the stroke depending on whether or not the final top dead center rotational speed ne1 is 200 rpm or more and the boost pressure Bt2 satisfies the condition that P2 = −200 mmHg or less? If NO is determined, the opening degree K of the throttle valve 23 is set to a first opening degree set in advance to about 40% to reduce the intake resistance of the intake stroke cylinder 12D. Thus, it is possible to effectively prevent the position of the piston 13 of the expansion stroke cylinder 12A from exceeding the lower limit of the appropriate range R. On the other hand, if the determination result is YES, the opening degree K of the throttle valve 23 is set to a second opening degree of about 5%, and an appropriate intake resistance is generated in the intake stroke cylinder 12D, whereby the piston 13 There is an advantage that it is possible to prevent the stop position from exceeding the appropriate range R and further toward the later stage.

  When the deceleration fuel cut control by the deceleration fuel cut control means 43 is executed, the exhaust gas recirculation passage 39 is opened in principle and the intake flow rate introduced into each cylinder 12A to 12D is reduced. When it is confirmed that the temperature of the exhaust gas purification catalyst 37 corresponds to the activation temperature and is lower than the value T0, instead of the above embodiment configured to return the fuel injection, during the execution of the deceleration fuel cut control Before the exhaust recirculation passage 39 is opened and the control for reducing the intake flow rate introduced into the cylinders 12A to 12D is executed, the temperature of the exhaust gas purification catalyst 37 is lower than the value T0 corresponding to the activation temperature. It may be configured to execute the control corresponding to the determination result.

  That is, if it is determined YES in step S3 of the flowcharts shown in FIGS. 17 and 18, and it is confirmed that the engine speed Ne is larger than the determination reference value FC • ON for fuel cut during deceleration, step S3 is performed. After the fuel cut (FC) at the time of deceleration is executed in S14, the process proceeds to step S18 to determine whether or not the deceleration fuel cut control should be terminated, and the control in steps S19 to S22 is performed according to the determination result. Execute. If it is determined in step S22 that the brake sensor 35 is in the ON state and it is confirmed that the automatic engine stop condition is satisfied during execution of the deceleration fuel cut control, the exhaust gas purification is performed at this time. It is determined whether or not the catalyst 37 has a temperature T0 or higher corresponding to the activation temperature (step S23).

  If it is determined NO in step S23 and it is confirmed that the exhaust gas purification catalyst 37 is lower than the temperature T0 corresponding to the activation temperature, the air-fuel ratio in the cylinder is set to the stoichiometric air-fuel ratio (λ = 1). The fuel cut (FC) control is completed by setting and returning the fuel injection (step S24), and the ignition timing is retarded by a predetermined amount (step S25). Further, after closing the EGR valve 38 and closing the exhaust gas recirculation passage 39 (step S50), the process returns to step S1.

  When it is determined YES in Step S23 and it is confirmed that the temperature of the exhaust gas purification catalyst 37 is equal to or higher than the temperature T0 corresponding to the activation temperature, the temperature of the exhaust gas purification catalyst 37 is the above temperature. It is determined whether or not the temperature is equal to or lower than a reference temperature T1 set to a value higher than T0 by a predetermined temperature (step S51). If YES is determined, the opening E of the EGR valve 39 is set to fully open. Then, the exhaust gas recirculation passage 38 is opened, and the opening K of the throttle valve 23 is set to 0% to reduce the intake flow rate (step S52). As a result, the air led out from the cylinders 12A to 12D to the exhaust passage 22 is circulated to the cylinders 12A to 12D and gradually warmed.

  When it is determined NO in step S51 and it is confirmed that the temperature of the exhaust gas purification catalyst 37 is lower than the reference temperature T1, the opening E of the EGR valve 39 is set to be fully closed and the exhaust gas is exhausted. The low-temperature air introduced into the cylinders 12A to 12D from the intake passage 21 by executing the control for increasing the intake flow rate by setting the opening degree K of the throttle valve 23 to 30% while closing the reflux passage 38. Is led to the installation part of the exhaust gas purification catalyst 37 (step S53), and then the process proceeds to step S31 of the flowchart shown in FIG. 11 through steps S26 to S29 of the flowchart shown in FIG.

  As described above, during the execution of the deceleration fuel cut control by the deceleration fuel cut control means 43, it is determined whether or not the temperature of the exhaust gas purification catalyst 37 is higher than the value T0 corresponding to the activation temperature, and the activation temperature is set. When it is confirmed that the fuel injection is resumed when it is confirmed that the value is lower than the corresponding value T0, the exhaust gas purification catalyst is caused by the fact that the stop state of the fuel injection is continued for a long time. There is an advantage that the temperature reduction of 37 can be effectively suppressed and the exhaust purification performance at the time of resumption of fuel injection can be maintained. When it is confirmed that the temperature of the exhaust gas purification catalyst 37 is higher than the value T0 corresponding to the activation temperature during the execution of the deceleration fuel cut control, the automatic engine stop control is performed without returning the fuel injection. Therefore, there is an advantage that the fuel injection can be effectively improved by continuing the stopped state of fuel injection for a long period of time, and the scavenging performance of the engine can be sufficiently secured.

  In the above embodiment, the temperature of the exhaust gas purification catalyst 37 is set higher than the value T0 corresponding to the activation temperature and higher than the value T0 by a predetermined temperature during execution of the deceleration fuel cut control. When it is determined that the temperature is equal to or lower than the reference temperature T1, the exhaust gas recirculation passage 38 is opened, and the control for reducing the intake flow rate introduced into each of the cylinders 12A to 12D is executed. By effectively suppressing the temperature drop caused by the low temperature air being supplied to the installation portion of the gas purification catalyst 37, it is possible to maintain the exhaust purification performance when the engine is restarted.

  Further, in the above embodiment, when it is determined that the temperature of the exhaust gas purification catalyst 37 is lower than the value T0 corresponding to the activation temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation is performed after the fuel injection is restored. Since the passage 39 is closed and the intake air flow rate introduced into the cylinders 12A to 12D is increased, scavenging performance can be effectively improved when the automatic engine stop control is subsequently executed. There is an advantage that you can.

  Further, when it is confirmed that the temperature of the exhaust gas purification catalyst 37 is higher than the value T0 corresponding to the activation temperature and higher than the reference temperature T1 during the execution of the deceleration fuel cut control, the exhaust gas recirculation is performed. When the passage 39 is closed and the intake flow rate introduced into the cylinders 12A to 12D is increased, the exhaust gas purification catalyst 37 is installed from the intake passage 21 via the cylinders 12A to 12D. By increasing the amount of low-temperature air supplied to the section, the exhaust gas purification catalyst 37 can be cooled and the temperature of the exhaust gas purification catalyst 37 can be prevented from becoming excessively high. Therefore, by effectively preventing the occurrence of a situation in which the exhaust gas purification catalyst 37 is burned and its reliability is reduced, the reliability can be effectively ensured and the deceleration fuel cut control is performed. By executing the automatic engine stop control without returning the fuel injection during execution, there are advantages that the fuel efficiency can be effectively improved and the scavenging performance of the engine can be sufficiently secured.

  Further, in the above embodiment, in the cylinders 12A to 12D when the temperature of the exhaust gas purification catalyst 37 is determined to be lower than the value T0 corresponding to the activation temperature during the execution of the deceleration fuel cut control and the fuel injection is returned. Since the air-fuel ratio of the exhaust gas is set to be richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, the exhaust gas purification catalyst 37 can be activated early by effectively increasing the temperature of the exhaust gas led to the exhaust passage 22. it can.

  Further, as shown in the above embodiment, the cylinder 12A in the case where it is determined that the temperature of the exhaust gas purification catalyst 37 is lower than the value T0 corresponding to the activation temperature during the execution of the deceleration fuel cut control and the fuel injection is returned. The air-fuel ratio in .about.12D is set richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, and the exhaust gas recirculation passage 38 is closed, so that fresh air introduced into each cylinder 12A-12D. By securing the amount, the ignition timing can be sufficiently retarded without causing misfire. Therefore, there is an advantage that the exhaust gas purification catalyst 37 can be activated quickly by increasing the temperature of the exhaust gas more effectively.

  When the air-fuel ratio in the cylinders 12A to 12D is set richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio and the exhaust gas recirculation passage 38 is opened when the fuel injection is restored, the air-fuel ratio feedback is performed. Although the controllability tends to deteriorate, the air fuel ratio feedback controllability can be ensured to some extent by calculating the intake charge amount based on the intake pressure detected by the intake pressure sensor 27. For this reason, when the exhaust gas purification catalyst 37 is in an inactive state and the fuel injection is returned in a state where the NOx purification performance is insufficient, the exhaust gas recirculation passage 38 is opened to thereby generate NOx. It may be suppressed to prevent the emission from deteriorating.

  In the above-described embodiment, the example in which the intake flow rate to the cylinders 12A to 12D is adjusted by the intake flow rate adjusting means including the throttle valve 23 disposed on the upstream side of the surge tank 21b has been described. The present invention is not limited to this, and a known variable valve mechanism that changes the lift amount of the intake valve 19 provided in each of the cylinders 12A to 12D is provided to adjust the intake flow rate to each of the cylinders 12A to 12D. Alternatively, the intake flow rate to each of the cylinders 12A to 12D is adjusted using a multiple throttle valve in which a valve body is individually provided in the branch intake passage 21a connected to each of the cylinders 12A to 12D. You may comprise as follows.

  Further, in the above-described embodiment, at the time t2 when the engine rotational speed Ne is lower than the reference speed N2 set in advance to about 790 rpm after the stop of fuel injection, the operation of decreasing the opening K of the throttle valve 23; Although the operation of increasing the target generated current Ge of the alternator 28 is simultaneously performed, it is not always necessary to match the operation time points of the two, and the opening time of the throttle valve 23 is decreased according to the increase timing of the target generated current Ge of the alternator 28. You may make it shift slightly back and forth from the time t2.

  Further, in the engine starter in the above embodiment, when the engine in the automatic stop state is restarted, the crankshaft 3 is slightly reversed first by causing the compression stroke cylinder 12C to perform the first combustion. Although the ignition is performed after rotating and compressing the air-fuel mixture in the expansion stroke cylinder 12A, the engine starter according to the present invention is not limited to this, and the expansion stroke cylinder 12A is first ignited. May be configured to restart the engine.

  Furthermore, in the above embodiment, when the engine is restarted, the fuel injection for the initial combustion in the expansion stroke cylinder 12A is divided injection (J1 + J2). This is achieved by reducing the compression pressure due to the latent heat of vaporization and ensuring the vaporization performance. It is also possible to formulate a timing (predetermined fuel injection timing) that can be compatible with the above as much as possible through experiments or the like, and to perform one fuel injection at the predetermined fuel injection timing. Further, the divided fuel injection performed for the first combustion in the expansion stroke cylinder 12A when the engine is restarted may be divided into three or more as required.

  Although omitted in the above embodiment, when the engine is restarted, when the predetermined condition is satisfied, for example, when the piston stop position is not within the proper stop range R, or when the engine rotation speed is increased by the predetermined time after the start. You may make it perform control accompanied by the assist by a starter motor, when it does not reach a predetermined value.

1 is a schematic cross-sectional view of an engine provided with a starter according to the present invention. It is explanatory drawing which shows the structure of the intake system and exhaust system of an engine. It is explanatory drawing which shows the relationship between the piston stop position and air quantity of the cylinder which becomes an expansion stroke and a compression stroke at the time of an engine stop. It is a time chart which shows the change state etc. of the engine speed at the time of an engine stop. It is a distribution map which shows the correlation with the engine speed at the time of an engine stop, and a piston stop position. It is a distribution map which shows the correlation with the top dead center rotational speed and piston stop position in the 2nd before an engine stop. It is a graph which shows an example of the map for setting the target electric power generation current of an alternator according to the rotational speed of an engine. It is a time chart which shows the change state etc. of the throttle opening degree corresponding to an engine speed, and an EGR valve opening degree. It is a flowchart which shows the first half of the engine automatic stop control operation. It is a flowchart which shows the middle part of an engine automatic stop control operation | movement. It is a flowchart which shows the second half part of the engine automatic stop control operation. It is a flowchart which shows the first half of the control action at the time of engine restart. It is a flowchart which shows the middle part of control action at the time of engine restart. It is a flowchart which shows the latter half part of the control action at the time of engine restart. It is a time chart which shows the combustion operation etc. at the time of engine restart. It is a time chart which shows the change state etc. of the engine speed at the time of engine restart. It is a flowchart which shows another example of the first half of the engine automatic stop control operation. It is a flowchart which shows another example of the middle part of an engine automatic stop control operation | movement. It is a time chart which shows the change state of the electric power generation current of an alternator.

Explanation of symbols

12A-12D Cylinder 22 Exhaust passage 23 Throttle valve (Intake flow rate adjusting means)
37 Exhaust gas purification catalyst 38 EGR valve 39 Exhaust gas recirculation passage 41 Combustion control means 42 Intake flow rate control means 43 Deceleration fuel cut control means 44 Automatic stop control means 46 Exhaust gas recirculation control means

Claims (11)

When the preset automatic engine stop condition is satisfied, the fuel supply for continuing the engine operation is stopped to automatically stop the engine, and the restart condition for the engine in the automatic stop state is satisfied. An engine starter configured to automatically restart the engine by injecting fuel into at least the cylinder stopped in the expansion stroke to cause ignition and combustion, and injecting fuel during deceleration The deceleration fuel cut control means for stopping the engine and the piston of the cylinder that is in the expansion stroke when the engine is stopped even when the engine automatic stop condition is satisfied during execution of the deceleration fuel cut control is stopped at a position suitable for restart. and an automatic stop control means, the engine during deceleration fuel cut control when automatically stopping executing the automatic stop control to, exhaust With the recirculation passage and an open state, after reducing the intake air flow introduced into the cylinders, as well as the exhaust gas recirculation passage and a closed state at a predetermined timing, to increasing the intake air flow introduced into the cylinders An engine starting device. After increasing the intake air flow rate introduced into each cylinder during execution of the deceleration fuel cut control, the intake air flow rate introduced into the cylinder that becomes the expansion stroke when the engine is stopped is introduced into the cylinder that becomes the compression stroke. 2. The engine starter according to claim 1, wherein the intake flow rate is reduced at a timing that is greater than the flow rate . When it is determined that the temperature of the exhaust gas purification catalyst is equal to or lower than a preset reference temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is opened, and the intake flow rate introduced into each cylinder is reduced. 2. The engine starting device according to claim 1 , wherein the starting device is reduced. When it is determined that the temperature of the exhaust gas purification catalyst is higher than a preset reference temperature during the execution of the deceleration fuel cut control, the exhaust gas recirculation passage is closed and the reduction control of the intake flow rate is suppressed. The engine starting device according to claim 1. When the engine rotational speed definitive execution time of deceleration fuel cut control is high, the exhaust gas recirculation passage and an open state, when the engine rotational speed at the time of the is low, characterized by suppressing the reduction control of the intake air flow rate The engine starting device according to claim 1. When the preset automatic engine stop condition is satisfied, the fuel supply for continuing the engine operation is stopped to automatically stop the engine, and the restart condition for the engine in the automatic stop state is satisfied. An engine starter configured to automatically restart the engine by injecting fuel into at least the cylinder stopped in the expansion stroke to cause ignition and combustion, and injecting fuel during deceleration The deceleration fuel cut control means for stopping the engine and the piston of the cylinder that is in the expansion stroke when the engine is stopped even when the engine automatic stop condition is satisfied during execution of the deceleration fuel cut control is stopped at a position suitable for restart. And an automatic stop control means for executing the automatic stop control, and the temperature of the exhaust gas purifying catalyst is activated while the deceleration fuel cut control is being executed. If it is confirmed that the value is lower than the value corresponding to the value, the engine automatic stop control is executed after returning the fuel injection, and it is confirmed that the temperature of the exhaust gas purification catalyst is higher than the value corresponding to the activation temperature. In such a case, the engine start device performs automatic engine stop control without returning the fuel injection . When it is determined that the temperature of the exhaust gas purification catalyst is higher than the value corresponding to the activation temperature and lower than the preset reference temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is opened. The engine start device according to claim 6, wherein an intake flow rate introduced into each cylinder is reduced . When it is determined that the temperature of the exhaust gas purification catalyst is lower than the value corresponding to the activation temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is closed after the fuel injection is restored, and engine starting system according to claim 6 or 7, characterized in that to increase the intake air flow introduced into the cylinders. If it is determined that the temperature of the exhaust gas purification catalyst is higher than the value corresponding to the activation temperature and higher than the preset reference temperature during execution of the deceleration fuel cut control, the exhaust gas recirculation passage is closed. The engine start device according to any one of claims 6 to 8 , wherein an intake air flow rate introduced into each cylinder is increased. When it is determined that the temperature of the exhaust gas purifying catalyst is lower than the value corresponding to the activation temperature during execution of the deceleration fuel cut control and the fuel injection is returned, the air-fuel ratio in the cylinder is set to the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio. The engine starter according to any one of claims 6 to 9 , wherein the engine starter is also set to be rich . When it is determined that the temperature of the exhaust gas purification catalyst is lower than the value corresponding to the activation temperature during execution of the deceleration fuel cut control and the fuel injection is returned, the exhaust gas recirculation passage is closed and the ignition timing is retarded. starting apparatus according to claim 1 0, wherein the engine, characterized in that to.

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