JP4442303B2 - Engine starter - Google Patents

Description

  The present invention relates to an engine starting device.

Recently, in order to reduce fuel consumption and reduce CO2 emissions, the engine is automatically stopped when idle, and then restarted automatically when a restart condition such as a start operation is established. A starting device has been developed. As a technique, for example, as disclosed in Patent Document 1, after a cylinder is in a compression stroke at the time of stop, fuel is injected at the time of engine start and the crankshaft is once reversely rotated, and then in an expansion stroke at the time of stop. It is known to inject fuel into a cylinder and rotate it forward to start the engine. Further, as described in Patent Document 2, fuel is injected into the cylinder that was in the compression stroke at the time of stop and stopped before the bottom dead center, and then fuel is injected into the cylinder that was in the expansion stroke at the time of stop. It is known that the engine is rotated forward and the engine is started.
WO 01/38726 A1 WO 01/81759 A1

  As described above, when the engine is restarted only by the combustion of the cylinder (hereinafter, such restart is referred to as “direct start”), the load when two compression strokes are reached is the largest. However, after changing the second compression stroke, the engine speed is likely to increase more rapidly than is necessary (so-called blowing up). As for the blow-up, since the intake pressure (pressure downstream from the throttle valve) during the automatic stop period is substantially atmospheric pressure, the combustion energy in each cylinder immediately after the start is compared with the combustion energy during normal idle operation It is a phenomenon that occurs when it becomes temporarily larger. When this blow-up occurs, the rotational speed rapidly increases to about 1000 rpm, which is not desirable because an acceleration shock may occur and the driver may feel uncomfortable.

  This invention is made | formed in view of the said malfunction, and makes it the subject to prevent the blowing up after restart.

According to a first aspect of the present invention, there is provided an automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops the fuel supply automatically when a predetermined engine stop condition is satisfied, and the engine stop. An engine exhaust path comprising an engine starter comprising start control means for restarting the engine by burning at least a cylinder that was in an expansion stroke when the engine was stopped when a predetermined restart condition was established later. Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the cylinder, air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio, and timing for igniting a specific cylinder that starts combustion and ignition control means for controlling, from the phase of the crankshaft, the exhaust cylinder that was in an exhaust stroke during automatic stop of the at least engine strokes And a cylinder specifying means for specifying a cylinder, past the top dead center of the plurality of cylinders is burned start cylinder that was in the expansion stroke, and in lower than the rotational speed at the idle speed of the engine, combustion When determining the combustion condition of the specific cylinder to be started, when the catalyst is in a relatively high temperature state that is equal to or higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to be started to be greater than the stoichiometric air-fuel ratio. The ignition control means ignites the cylinder after the set fuel is injected. When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means starts combustion. that the target air-fuel ratio of the specific cylinder and sets below the stoichiometric air-fuel ratio, the ignition control means is for igniting the delayed after compression top dead center of the ignition timing, the air- The ratio control means and the ignition control means, characterized in that after the combustion of the cylinder that was in the expansion stroke is started, and performs control based on the temperature state of the catalyst from the first combustion of the exhaust stroke cylinder The engine starting device.

  In the present invention, the combustion conditions of a specific cylinder to start combustion in a state where the combustion of the cylinders in the expansion stroke is started and the top dead center of a plurality of cylinders is passed and the engine rotation speed is lower than the rotation speed at the time of idling. When determining the air-fuel ratio, the air-fuel ratio can be controlled under a certain condition to prevent the blow-up.

  Particularly in the present invention, when the temperature state of the catalyst is equal to or higher than the activation temperature, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the stoichiometric air-fuel ratio. The generated torque is reduced and the fuel consumption is improved. On the other hand, when the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the theoretical air-fuel ratio, and the ignition control means sets the ignition timing. Since ignition is delayed after the compression top dead center, the generated torque is reduced due to the ignition timing delay, while the fuel injected in excess of the stoichiometric air-fuel ratio reacts with the catalyst and burns As a result, not only can the torque be reduced, but the temperature of the catalyst can be increased and the filter performance of the catalyst can be improved. In other words, when the target air-fuel ratio is equal to or higher than the stoichiometric air-fuel ratio, ignition is performed without delaying the ignition timing.

Further, in the present invention, cylinder specifying means for specifying at least a cylinder that has been in the exhaust stroke when the engine is automatically stopped as an exhaust stroke cylinder from the phase of the crankshaft is provided, and the air-fuel ratio control means and the ignition control means include the above after combustion had been cylinder expansion stroke is started, and to perform based rather control the temperature state of the catalyst from the first combustion of the exhaust stroke cylinder.

As a result, control for preventing the blow-up from the initial combustion of the exhaust stroke cylinder is performed. After the so-called direct start is adopted, the exhaust stroke cylinder sucks air close to the atmospheric pressure and shifts to the compression stroke. Therefore, the initial combustion causes a very rapid torque generation. Therefore, in this aspect, the generated torque is suppressed by the control as described above.

Further, the second invention is equipped with an automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine, stops the fuel supply automatically when a predetermined engine stop condition is satisfied, and stops the engine automatically. An engine starter comprising start control means for restarting the engine by burning at least a cylinder in an expansion stroke when the engine is stopped when a predetermined restart condition is satisfied after the engine is stopped. Catalyst temperature estimation means for estimating the temperature state of the catalyst provided in the exhaust path, air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio, and ignition for the specific cylinder where combustion starts intake and ignition control means for controlling the timing, from the phase of the crankshaft, a cylinder that was in an intake stroke in the automatic stop of the at least engine A cylinder identifying means for identifying a stroke cylinder, past the top dead center of the plurality of cylinders is burned start cylinder that was in the expansion stroke, and in lower than the rotational speed at the idle speed of the engine, When determining the combustion condition of the specific cylinder where combustion is started, when the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder where combustion is started from the stoichiometric air-fuel ratio. And the ignition control means ignites the cylinder after the set fuel is injected. When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means starts combustion. In addition to setting the target air-fuel ratio of the specific cylinder to be equal to or lower than the theoretical air-fuel ratio, the ignition control means ignites the ignition timing by delaying it after the compression top dead center, Serial ignition control means, regardless of the temperature state of the catalysts, the ignition timing at engine starting system, characterized in that ignite delays after a compression top dead center of the intake stroke cylinder.

In the present invention , since the ignition timing is retarded regardless of the temperature state of the catalyst, the torque is reduced and the blow-up is prevented, and the piston surely exceeds the compression top dead center at the timing when the engine speed decreases most. Since it is ignited at the place, reverse torque is also prevented. Incidentally, the fuel injection at the time of the first combustion to the intake stroke cylinder is preferably rich in a state where it is delayed at a predetermined timing. In that case, it is possible to reduce the pressure (load) when the intake stroke cylinder is compressed.

Further, the third aspect of the invention is an automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine, stops fuel supply when a predetermined engine stop condition is satisfied, and automatically stops the engine, An engine starter comprising start control means for restarting the engine by burning at least a cylinder in an expansion stroke when the engine is stopped when a predetermined restart condition is satisfied after the engine is stopped. Catalyst temperature estimation means for estimating the temperature state of the catalyst provided in the exhaust path, air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio, and ignition for the specific cylinder where combustion starts Ignition control means for controlling the timing to perform the combustion, the combustion of the cylinder in the expansion stroke is started, the top dead center of a plurality of cylinders has passed, and the When determining the combustion condition of the specific cylinder to start combustion in a state where the rotational speed of the gin is lower than the rotational speed during idling, when the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means, The target air-fuel ratio of a specific cylinder to start combustion is set to be larger than the stoichiometric air-fuel ratio, and the ignition control means ignites the cylinder after the set fuel is injected, and the catalyst is lower than the active state. When the engine is in a low temperature state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means delays the ignition timing after the compression top dead center. is intended to ignite Te, the ignition control means, when the air-fuel ratio control means was set larger than the stoichiometric air-fuel ratio the target air-fuel ratio of a specific cylinder that starts the combustion A starting device of the engine, characterized in that ignite before the compression top dead center of the cylinder.

In the present invention , it is possible to achieve both improvement in fuel consumption and prevention of blow-up.

According to a fourth aspect of the present invention, there is provided an automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine, and that automatically stops the engine by stopping fuel supply when a predetermined engine stop condition is satisfied; An engine starter comprising start control means for restarting the engine by burning at least a cylinder in an expansion stroke when the engine is stopped when a predetermined restart condition is satisfied after the engine is stopped. Catalyst temperature estimation means for estimating the temperature state of the catalyst provided in the exhaust path, air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio, and ignition for the specific cylinder where combustion starts and ignition control means for controlling the timing of a rotation speed detecting means for detecting a rotational speed of the engine, the expansion stroke in the automatic stop of the engine The engine rotation speed at the inspection timing set after the lapse of a predetermined time from the start of the combustion of the given cylinder is used as the engine rotation speed at the time of inspection to receive input from the engine rotation speed detection means, thereby determining whether the engine has started or not. A start / fail judgment means for judging, and combustion starts in a state where combustion of the cylinders in the above expansion stroke is started and the top dead center of a plurality of cylinders is passed and the engine speed is lower than the idling speed. When determining the combustion conditions of the specific cylinder to be performed, if the catalyst is in a relatively high temperature state equal to or higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the stoichiometric air-fuel ratio. The ignition control means is for igniting the cylinder after the set fuel injection, and the catalyst is lower than the active state. In the state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means performs ignition by delaying the ignition timing after the compression top dead center. is intended to be, the combustion conditions of the specific cylinder that starts the combustion, and characterized in that it is determined after the test when the engine rotational speed is determined to be required engine rotational speed than required for successful restarting It is a starting device for the engine .

In the present invention , the engine rotational speed at the inspection timing set after a lapse of a predetermined time from the start of combustion of the cylinder in the expansion stroke is received from the engine rotational speed detecting means as the engine rotational speed at the time of inspection. Thus, since the engine start / failure determination means for determining the engine start / failure is provided, it is possible to predict whether or not the engine will restart in the second compression stroke with the largest load at the time of restart.

According to a fifth aspect of the present invention, there is provided an automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and that automatically stops the engine by stopping fuel supply when a predetermined engine stop condition is satisfied, An engine starter comprising start control means for restarting the engine by burning at least a cylinder in an expansion stroke when the engine is stopped when a predetermined restart condition is satisfied after the engine is stopped. Catalyst temperature estimation means for estimating the temperature state of the catalyst provided in the exhaust path, air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio, and ignition for the specific cylinder where combustion starts and ignition control means for controlling the timing of, and an intake pressure detecting means for detecting the intake air pressure supplied to the engine, the expansion stroke near When determining the combustion conditions of a specific cylinder to start combustion in a state where the combustion of the cylinders has started and the top dead center of multiple cylinders has passed and the engine speed is lower than the idling speed, the catalyst is activated. When the temperature is relatively high, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the stoichiometric air-fuel ratio, and the ignition control means When the cylinder is ignited after injection and the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio. the ignition control means is for igniting the delayed after compression top dead center of the ignition timing, the combustion condition of the specific cylinder to be started the combustion, said intake pressure is idle A starting device for an engine characterized in that it is determined higher than the intake pressure during rolling.

Since the blow-up occurs when the intake pressure is higher than the intake pressure during idle operation, in the present invention , the intake pressure detection means determines whether the intake pressure is higher than the intake pressure during idle operation. To do. When it is determined that the intake pressure is high, control for reducing the torque is performed based on the temperature state of the catalyst.

In the first aspect of the invention , the driver of the vehicle does not receive a sudden shock after performing a direct start by preventing the wind-up. Moreover, in order to prevent the blow-up, control for reducing the torque is performed based on the temperature state of the catalyst, so not only the blow-up is prevented, but also the temperature state rise of the catalyst is promoted as necessary. In addition, it is possible to promote the purification of exhaust gas.

Also, the first combustion cylinder that was in an exhaust stroke during automatic stop of the engine, since the control for the Prevention of rising Fukiage performed, there is an advantage that sudden torque generation is reliably suppressed.

In the second invention , the initial ignition timing of the cylinder that was in the intake stroke when the engine was automatically stopped is retarded regardless of the temperature state of the catalyst. As a result, torque is reduced and blowing is prevented, and the piston is ignited when the engine speed drops most so that the compression top dead center is exceeded. It becomes possible to make it.

In the third aspect of the invention , when the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the stoichiometric air-fuel ratio, the ignition control means before the compression top dead center of the cylinder Since the ignition is performed, it is possible to achieve both improvement in fuel consumption and prevention of blow-up.

In the fourth aspect of the present invention, it is possible to predict whether or not the engine will restart in the second compression stroke with the largest load at the time of restart, and then prevent the engine from being blown up. After that, there is no sudden shock.

In the fifth aspect of the invention , the combustion condition is determined when it is determined that the intake pressure is higher than the intake pressure during idling when the specific cylinder is ignited.

  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 (# 1 cylinder 12A, # 2 cylinder 12B, # 3 cylinder 12C, and # 4 cylinder 12D), and a crankshaft 3 is provided in each cylinder 12A-12D. By inserting the connected piston 13, a combustion chamber 14 is formed above the piston 13.

  In the present embodiment, the cylinder that was in the compression stroke while the engine was automatically stopped is referred to as the compression stroke cylinder, and the cylinder that was in the expansion stroke is referred to as the expansion stroke cylinder (similarly, the cylinder that was in the intake stroke is referred to as the intake stroke cylinder, The cylinders in the exhaust stroke are referred to as exhaust stroke cylinders). However, these are not specific cylinders, but are referred to for convenience based on the strokes of the individual cylinders when the engine is automatically stopped. is there.

  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. The ignition plug 15 is provided with an ignition device 27 for generating an electric spark. A fuel injection valve 16 that directly injects fuel into the combustion chamber 14 is provided on the side of the combustion chamber 14. The fuel injection valve 16 incorporates a needle valve and a solenoid (not shown), and is driven for a time corresponding to the pulse width of the pulse signal input from the fuel injection control unit 41 of the ECU 2 to open the valve. An amount of fuel corresponding to the time 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 timing of the 12D intake valve 19 and the exhaust valve 20 is 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 a throttle valve 23 driven by an actuator 24 is provided in the common intake passage 21c. An air flow sensor 25 for detecting the intake air flow rate and an intake air temperature sensor 29 for detecting the intake air temperature are provided on the upstream side of the throttle valve 23, and the intake pressure (negative pressure) is detected on the downstream side of the throttle valve 23. An intake pressure sensor 26 is provided.

  On the other hand, as shown in FIGS. 1 and 2, a catalyst 37 for purifying the exhaust is disposed downstream of the collection portion of the exhaust passage 22 where the exhaust from each of the cylinders 12 </ b> A to 12 </ b> D collects. The catalyst 37 is, for example, a so-called three-way catalyst in which the purification rate of HC, CO, and NOx is extremely high when the air-fuel ratio of the exhaust is in the vicinity of the theoretical air-fuel ratio, and this has a relatively high oxygen concentration in the exhaust. It has an oxygen storage capacity for storing it in an oxygen-excess atmosphere, and releases the stored oxygen to react with HC, CO, etc. when the oxygen concentration is relatively low. Note that the catalyst 37 is not limited to a three-way catalyst, and may be any catalyst that has the above-described oxygen storage ability. For example, the catalyst 37 may be a so-called lean NOx catalyst that can purify NOx even in an oxygen-excess atmosphere.

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

  Further, the engine is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the engine rotation speed 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.

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

  Further, the crankshaft 3 is provided with a flywheel (not shown) and a ring gear 35 fixed to the flywheel concentrically with the center of rotation. The ring gear 35 is an input member of a starter motor 36 as a start assist device, and is configured to mesh with a pinion gear 37 of the starter motor 36 as will be described later.

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

  The pinion gear 36d of the starter motor 36 employed in the present embodiment is twisted like a screw and is easily disengaged from and disengaged from the ring gear 35 when the ring gear 35 is stopped. It is the specification which meshes | engages while rotating in the reverse direction at the speed of about 60 rpm.

  Referring to FIG. 1, ECU 2 is a control unit that comprehensively controls engine operation. The engine of the present embodiment automatically stops fuel injection by stopping fuel injection into each cylinder 12A to 12D at a predetermined timing when a preset automatic engine stop condition is satisfied. Then, the engine is configured to perform control (idle stop control) that automatically restarts the engine when a restart condition is satisfied, for example, when an accelerator operation is performed by the driver. Hereinafter, in the description of the ECU 2, the portion related to the idle stop control will be mainly described.

  The ECU 2 receives detection signals from the air flow sensor 25, the intake pressure sensor 26, the intake air temperature sensor 29, the crank angle sensors 30, 31, the cam angle sensor 32, the water temperature sensor 33, and the accelerator opening sensor 34, and The drive signals are output to the fuel injection valve 16, the actuator 24 of the throttle valve 23, the ignition device 27, the regulator circuit 28a of the alternator 28, and the starter motor 36, respectively. The ECU 2 includes a fuel injection control unit 41, an ignition control unit 42, an intake air flow rate control unit 43, a power generation amount control unit 44, a piston position detection unit 45 and an in-cylinder temperature estimation unit 46, an automatic stop control unit 47, a start control unit 48, A start / fail judgment unit 49, an air-fuel ratio control unit 50, an alternator control unit 51, and a catalyst temperature estimation unit 52 are functionally included.

  The fuel injection control unit 41 is fuel injection control means for setting the fuel injection timing and the fuel injection amount for each injection and outputting the signal to the fuel injection valve 16. In particular, in the present embodiment, as will be described later, fuel for the first combustion in the expansion stroke cylinder at the time of restart is supplied by split injection. The fuel injection control unit 41 also performs setting of the divided injection timing and fuel distribution.

  The ignition control unit 42 sets an appropriate ignition timing for each of the cylinders 12 </ b> A to 12 </ b> D and outputs an ignition signal to each ignition device 27.

  The intake flow rate control unit 43 sets an appropriate intake flow rate for each of the cylinders 12 </ b> A to 12 </ b> D, and outputs an opening degree signal of the throttle valve 23 corresponding to the intake flow rate to the actuator 24. In particular, in this embodiment, as will be described later, the opening degree of the throttle valve 23 is adjusted when the engine is automatically stopped, and control is performed so that the piston 13 stops in an appropriate stop range suitable for restart. The intake flow rate control unit 43 also adjusts the opening of the throttle valve 23 at that time.

The power generation amount control unit 44 sets an appropriate power generation amount of the alternator 28 and outputs the drive signal to the regulator circuit 28a. In particular, in the present embodiment, as will be described later, the load on the crankshaft 3 is changed by adjusting the power generation amount of the alternator 28 during the automatic stop of the engine, and the piston 13 is stopped in an appropriate range suitable for restart. It is carried out. At this time, the power generation amount control unit 44 also adjusts the power generation amount of the alternator 28. Further, at the time of restarting, control is performed to increase the engine load by generating more power than usual, and to prevent the engine from blowing up (raising the engine speed more rapidly than necessary).

  The piston position detector 45 detects the piston position based on the detection signals of the crank angle sensors 30 and 31. Since the piston position and the crank angle (° CA) have a one-to-one correspondence, the piston position is represented by the crank angle in this specification as is generally done. In this embodiment, as will be described later, the in-cylinder air amount is calculated based on the piston positions during the automatic stop of the expansion stroke cylinder and the compression stroke cylinder, and the combustion control of each cylinder at the time of restart is performed accordingly. Yes.

  The in-cylinder temperature estimation unit 46 uses each map 12A based on an engine water temperature detected by the water temperature sensor 33, an intake air temperature detected by the intake air temperature sensor 29, or the like using a map obtained in advance through experiments or the like. In-cylinder temperature estimation means for estimating the air temperature in the cylinder of -12D. In particular, in this embodiment, as will be described later, in-cylinder temperature estimation is performed in consideration of the engine stop time when the engine is restarted, and combustion control is performed based on the estimated value.

  As will be described later, the automatic stop control unit 47 is an automatic stop control unit that stops the fuel supply and stops the engine automatically when a predetermined engine stop condition is satisfied during idling.

  The start control unit 48 is start control means for automatically restarting the engine when the engine restart condition is satisfied after the automatic engine stop. When the stop position of the piston 13 is within a specific range (appropriate range) described later when the engine is restarted, fuel is supplied to at least the expansion stroke cylinder when the engine is stopped, and ignition and combustion are performed. In the present embodiment, first, the first combustion is performed on the compression stroke cylinder when the engine is stopped, the piston 13 is pushed down, and the in-cylinder pressure is increased by raising the piston of the expansion stroke cylinder. In contrast, control is performed so that fuel is injected to ignite and burn. That is, at the time of automatic engine restart, if the piston stop position is in an appropriate range, which will be described later, control is performed so that the engine is once reversely operated at the beginning of the start, and then the normal rotation operation is started. In the present embodiment, the start control unit 48 also serves as assist drive control means.

  The start / fail judgment unit 49 detects the engine speed using the engine speed at the test timing t12 (see FIG. 11) set after the elapse of a predetermined time from the start of combustion of the expansion stroke cylinder as the engine speed at the time of inspection. This is start / failure means for determining whether the engine has been started or not by receiving inputs from the sensors 30 and 31 serving as parts and the piston position detector 45.

  The air-fuel ratio control unit 50 is an air-fuel ratio control means for calculating the air-fuel ratio and determining the fuel distributed by the fuel injection control unit 41 and the intake flow rate controlled by the intake flow rate control unit 43.

  The alternator control unit 51 is an alternator control means for controlling the operation of the alternator 28 via the regulator circuit 28 a of the alternator 28.

  The catalyst temperature state estimation unit 52 estimates the temperature of the catalyst 37 by using a map obtained in advance through experiments or the like based on the intake air temperature detected by the intake air temperature sensor 29 or the like. It is. In particular, in this embodiment, as will be described later, when restarting the engine, the temperature state of the catalyst is estimated, and fuel injection and combustion control are performed based on the estimated value.

  When performing the idle stop control by the ECU 2 having the above-described configuration, when the engine is restarted, the combustion is first performed in the compression stroke cylinder, whereby the piston 13 is pushed down to slightly reverse the crankshaft 3. As a result, the piston 13 of the expansion stroke cylinder is once raised (closed to top dead center), and the air-fuel mixture (which becomes the air-fuel mixture after fuel injection) is compressed and ignited and burned. Thus, the engine is restarted by applying a driving torque in the forward direction to the crankshaft 3.

  In order to properly restart the engine simply by igniting the fuel injected into a specific cylinder without using the starter motor 36 or the like, the combustion energy obtained by burning the air-fuel mixture in the expansion stroke cylinder Therefore, the cylinder that reaches the compression top dead center (in this embodiment, the compression stroke cylinder and the intake stroke cylinder) must overcome the compression reaction force and exceed the compression top dead center. Don't be. Therefore, it is necessary to ensure a sufficient amount of air in the expansion stroke cylinder.

  Since the phases of the compression stroke cylinder and the expansion stroke cylinder are shifted from each other by 180 ° CA, the pistons 13 operate in opposite directions as shown in FIG.

  As shown in FIG. 4B, if the piston 13 of the expansion stroke cylinder is located 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 the crankshaft 3 is rotated in the reverse direction by the initial combustion at the time of restart. Therefore, sufficient combustion energy cannot be obtained.

  On the other hand, a predetermined range R slightly lower than the position where the crank angle after the compression top dead center is 90 ° CA, for example, the crank angle after the compression top dead center, is the stroke center of the expansion stroke cylinder. If the piston 13 can be stopped within a range R of 100 ° CA to 120 ° CA, a predetermined amount of air can be secured in the compression stroke cylinder, and the crankshaft 3 can be slightly reversed in the first combustion. A degree of combustion energy can be obtained. Moreover, by securing a large amount of air in the expansion stroke cylinder, it is possible to generate a sufficient amount of combustion energy for causing the crankshaft 3 to rotate in the forward direction and to restart the engine reliably (hereinafter referred to as this). The range R is set as the appropriate stop range R).

  Therefore, the ECU 2 (automatic stop control unit 47) performs the following control so as to stop the piston 13 within the proper stop range R.

  FIG. 5 is a time chart when the engine is automatically stopped by the automatic stop control unit 47, and shows the engine speed Ne, the boost pressure Bt (intake pressure), and the opening K of the throttle valve 23. FIG. 6 is an enlarged view after the timing t1 in FIG. 5, and shows a crank angle CA and a stroke transition chart of each cylinder in addition to FIG. For the sake of brevity, it is assumed that # 1 cylinder 12A is an expansion stroke cylinder, # 2 cylinder 12B is an exhaust stroke cylinder, # 3 cylinder 12C is a compression stroke cylinder, and # 4 cylinder 12D is an intake stroke cylinder. .

  The ECU 2 sets a target engine speed at a timing t0 when the engine automatic stop condition is satisfied, a value higher than a normal idle engine speed when the engine is not automatically stopped (hereinafter referred to as a normal idle engine speed), For example, in an engine in which the normal idle engine rotation speed is set to 650 rpm (the automatic transmission is in the drive (D) range), the target speed (idle engine rotation speed when the automatic stop condition is satisfied) is set to about 850 rpm (the automatic transmission is neutral). By setting (N) range), control is performed to stabilize the engine speed Ne at an engine speed slightly higher than the normal idle engine speed. Further, the opening K of the throttle valve 23 is adjusted so that the boost pressure Bt is stabilized at a relatively high predetermined value (about −400 mmHg).

  Then, the fuel injection is stopped at the timing t1 when the engine speed Ne is stabilized at the target speed, and the engine speed Ne is decreased. Further, at the fuel injection stop timing t1, which is the initial stage of the control operation for automatically stopping the engine, the opening degree K of the throttle valve 23 is set at the idling time when the cylinder air-fuel ratio is set to the excess air ratio λ = 1. The intake air flow rate is set to be higher than the intake air flow rate (minimum intake air flow rate necessary for continuing engine operation). That is, when the combustion state immediately before the timing t1 is set to an in-cylinder air-fuel ratio in the vicinity of the excess air ratio λ = 1 to near λ = 1 and homogeneous combustion is performed, the opening K of the throttle valve 23 is increased (for example, When the air-fuel ratio in the cylinder is set to lean and stratified combustion is performed, the opening K of the throttle valve 23 is maintained as it is (the relatively large opening during stratified combustion). . 5 and 6 show the former case.

  As a result of this control, the boost pressure Bt starts to increase slightly after the timing t1 (when the combustion just before the timing t1 is homogeneous combustion) or maintains a relatively high boost pressure Bt (when the combustion just before the timing t1 is stratified combustion). Exhaust gas scavenging is facilitated.

  Further, the ECU 2 temporarily stops the power generation of the alternator 28 at the timing t1. This reduces the rotational resistance of the crankshaft 3 so that the engine rotational speed Ne does not decrease too quickly.

  Thus, when the combustion injection is stopped at the timing t1, the engine rotational speed Ne starts to decrease, and the throttle valve 23 is closed at the timing t2 at which it is confirmed that the engine speed becomes a preset reference speed, for example, 760 rpm or less. Then, the boost pressure Bt starts to decrease slightly after the timing t2, and the intake flow rate sucked into each cylinder of the engine decreases. Air sucked between timing t1 and timing t2 when the throttle valve 23 is opened is guided to the branch intake passage 21a of each cylinder via the common intake passage 21c and the surge tank 21b. Then, the air is sucked in order from the cylinder that has reached the intake stroke. In the case shown in FIG. 6, the order is # 4 cylinder 12D, # 2 cylinder 12B, # 1 cylinder 12A, and # 3 cylinder 12C. Here, by setting the timing t1 and the timing t2 as described above, the # 1 cylinder 12A (expansion stroke cylinder) sucks more air than the # 3 cylinder 12C (compression stroke cylinder). become.

  After the timing t1, the engine rotates due to inertia, so the engine rotational speed Ne gradually decreases and eventually stops at the timing t5. This decrease in the engine rotational speed Ne is small, as shown in FIG. 5 and FIG. It goes down while repeating up / down (around 10 times for a 4-cylinder 4-cycle engine).

  In the time chart of the crank angle CA shown in FIG. 6, the solid line indicates the crank angle when the top dead center of the # 1 cylinder 12A and the # 3 cylinder 12C is 0 ° CA, and the alternate long and short dash line indicates the # 2 cylinder 12B and # 4. The crank angle when the top dead center of the cylinder 12D is 0 ° CA is shown. The solid line and the alternate long and short dash line are in opposite phases with respect to 90 ° CA. In a four-cylinder four-cycle engine, one of the cylinders reaches compression top dead center every 180 ° CA. Therefore, this time chart shows either at the top of the waveform indicated by a solid line or one-dot chain line (crank angle = 0 ° CA). This indicates that the cylinder passes the compression top dead center.

  The timing at which any one of these cylinders becomes the compression top dead center coincides with the valley timing at which the engine rotational speed Ne increases or decreases. In other words, the engine rotational speed Ne gradually decreases every time the cylinders sequentially reach the compression top dead center, and then gradually rises and falls again at a timing exceeding the compression top dead center. To do.

  In the compression stroke cylinder 12C that reaches the compression top dead center after the timing t4 when the final compression top dead center is passed, the air pressure increases as the piston 13 rises due to the inertial force, and the piston 13 is top dead due to the compression reaction force. The crankshaft 3 rotates in the reverse direction by being pushed back without exceeding the point. Since the air pressure of the expansion stroke cylinder 12A rises due to the reverse rotation direction of the crankshaft 3, the piston 13 of the expansion stroke cylinder 12A is pushed back to the bottom dead center side according to the compression reaction force, and the crankshaft 3 rotates forward again. Then, the reverse direction and the normal direction 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 intake resistance of the intake stroke cylinder 12D, the friction of the engine, and the like. It also changes depending on the rotational inertia of the engine at the timing t4 beyond the compression top dead center, that is, the level of the engine rotational speed Ne.

  Therefore, in order to stop the piston 13 of the expansion stroke cylinder 12A within the proper stop range R, first, the compression reaction forces of the expansion stroke cylinder 12A and the compression stroke cylinder 12C are sufficiently increased, and the compression of the expansion stroke cylinder 12A is performed. It is necessary to adjust the intake air flow rates for both cylinders so that the reaction force is greater than the compression reaction force of the compression stroke cylinder 12C by a predetermined value or more. For this purpose, a predetermined amount of air is sucked into both the expansion stroke cylinder 12A and the compression stroke cylinder 12C by opening the throttle valve 23 at the fuel injection stop timing t1 and increasing its opening K, and then a predetermined amount. The intake air amount is adjusted by closing the throttle valve 23 at the timing t2 when the time has elapsed and reducing the opening K thereof.

  By the way, in the process in which the engine is automatically stopped in this way and the engine rotational speed decreases, the engine rotational speed (top dead center engine rotational speed) ne when each of the cylinders 12A to 12D passes through the compression top dead center, There is a clear correlation between the piston stop position of the expansion stroke cylinder 12A. That is, the piston stop position of the expansion stroke cylinder 12A is properly stopped when the top dead center engine rotational speed Ne in each stage (second, third, fourth from the stop) is within a certain speed range. The probability of being within the range R is increased.

  Using this characteristic, in this embodiment, the top dead center engine rotational speed ne within a predetermined speed range within a predetermined stage (particularly important is the second before the stop (timing t3)) in the process of decreasing the engine rotational speed Ne. Such control is performed so that the piston 13 of the expansion stroke cylinder 12A is more reliably stopped within the proper stop range R. Specifically, the load (engine load) of the crankshaft 3 is adjusted by increasing or decreasing the power generation amount of the alternator 28, and the second top dead center engine rotational speed ne (timing t3) from before the stop is 350 ± 50 rpm. Within the range.

  When the engine rotational speed Ne further decreases and the final compression top dead center passage time (timing t4 shown in FIG. 6) has passed, none of the cylinders passes through the top dead center, and the stroke is not changed. The piston 13 tries to stop in the target proper stop range R while being damped and oscillated within the stroke (when the crank 13 moves in the reverse direction, the crankshaft 3 rotates in the reverse direction and the engine speed Ne becomes negative). However, at this time, the intake stroke cylinder 12D performs an intake operation, and if the intake resistance is large, the stop position of the piston 13 tends to vary. In particular, since the intake resistance acts so as to increase when the piston 13 moves toward the bottom dead center, the piston 13 tends to stop closer to the top dead center than the target. Since the piston 13 of the intake stroke cylinder 12D and the piston 13 of the expansion stroke cylinder 12A move in the same phase, the piston 13 of the expansion stroke cylinder 12A tends to stop near the top dead center rather than the target.

  Therefore, in the present embodiment, the opening degree K of the throttle valve 23 is increased to the opening degree K1 (for example, about K1 = 40%) shown in FIG. 6 almost simultaneously with the timing t4 (may be slightly delayed), and the intake stroke cylinder 12D. The intake resistance is reduced. This makes it easier for the piston 13 to stop at a target position corresponding to the balance without affecting the intake flow rate balance in the expansion stroke cylinder 12A and the compression stroke cylinder 12C.

  In order to perform such control, it is necessary to immediately determine that the timing t4 is a time when it passes the last compression top dead center, and the next compression top dead (in the compression stroke cylinder 12C). It must be predicted at time t4 that the point will not pass. Therefore, in the present embodiment, the ECU 2 determines the last top dead center passage time. The ECU 2 compares the engine rotational speed ne when passing through each top dead center with a predetermined engine rotational speed (for example, 260 rpm) obtained in advance through experiments or the like. It is determined that it is time to pass the compression top dead center. The higher the top dead center engine rotational speed ne at the time when it passes the last compression top dead center, the closer to the latter stage of the stroke (the piston stop position of the expansion stroke cylinder 12A is closer to the bottom dead center, and the top dead center in the compression stroke cylinder 12C is It becomes easier to stop at the side.

  Incidentally, the intake flow rate balance in the final intake stroke of the expansion stroke cylinder 12A and the compression stroke cylinder 12C immediately before the engine is stopped is also affected by the boost pressure Bt. In particular, the second compression top dead center passage timing (timing t3 in FIG. 6) from before the stop is the starting point of the final intake stroke in the compression stroke cylinder 12C, and the influence of the boost pressure Bt at this timing is large. That is, when the boost pressure Bt is low (vacuum side), the intake flow rate to the compression stroke cylinder 12C decreases, and as a result, the stop position of the piston 13 of the compression stroke cylinder 12C is close to top dead center (in the expansion stroke cylinder 12A). It tends to be near the bottom dead center). The reverse is true when the boost pressure Bt is high (atmospheric pressure side).

  Accordingly, when the top dead center engine rotational speed ne at the last top dead center passage time is high and the boost pressure Bt at the second compression top dead center passage time from before the stop is low, the piston 13 of the expansion stroke cylinder 12A is Conditions that are likely to stop near the end of the stroke overlap, and there is a high possibility of stopping at the target stop position (100 to 120 ° CA after top dead center). Under such conditions, if the control is performed to increase the opening of the throttle valve 23 to K1 at the timing t3, the piston stop position may be closer to the latter stage of the stroke and may be deviated from the target stop position. is there. Therefore, in this embodiment, in such a case, the opening degree of the throttle valve 23 at the timing t3 is set to an opening degree K2 (see FIG. 6) that is lower (or closed) than K1. By suppressing the increase, the piston stop position of the expansion stroke cylinder 12A is prevented from becoming too close to the bottom dead center.

  Thus, the piston 13 is completely stopped at the timing t5. By detecting the operation of the piston 13 immediately before the stop by the crank angle sensors 30 and 31, the piston position detection unit 45 of the ECU 2 detects the stop position of the piston 13. Is detected. FIG. 7 is a flowchart showing the piston stop position detection control operation. When this detection control is started, based on the first crank angle signal CA1 (signal from the crank angle sensor 30) and the second crank angle signal CA2 (signal from the crank angle sensor 31), when the first crank angle signal CA1 rises. It is determined whether or not the second crank angle signal CA2 is Low, or whether or not the second crank angle signal CA2 is High when the first crank angle signal CA1 falls (Step S41). As a result, it is determined whether the phase relationship between the signals CA1 and CA2 during the engine stop operation is as shown in FIG. 8 (a) or FIG. 8 (b). It is determined whether it is in the direction state or the reverse direction state.

  That is, when the engine is rotating in the forward direction, as shown in FIG. 8A, the second crank angle signal CA2 is generated with a phase delay of about a half pulse width with respect to the first crank angle signal CA1, so that the first crank angle The second crank angle signal CA2 becomes Low when the signal CA1 rises, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, when the engine rotates in the reverse direction, as shown in FIG. 8B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, thereby causing the engine to rotate forward. Contrary to the direction, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls.

  Therefore, if the determination in step S41 is YES, the CA counter for measuring the crank angle change in the forward rotation direction of the engine is increased (step S42). If the determination in step S41 is NO, the CA counter is increased. Down (step S43). Then, after stopping the engine, the piston stop position is obtained by examining the measured value of the CA counter (step S44).

  When the engine is completely stopped, the in-cylinder temperatures of the cylinders 12A to 12D change as shown in the temperature characteristics of FIG. FIG. 9 is a graph showing the relationship between the elapsed time from the engine stop and the in-cylinder temperature, and is an estimated value of the in-cylinder temperature change when the in-cylinder temperature is 80 ° C. when the engine is stopped (timing t5). is there.

  As shown in this characteristic, when the engine is completely stopped, the flow of the cooling water is stopped, so that the in-cylinder temperature rapidly rises immediately after the stop. Then, it peaks at about 10 seconds after the engine stops, and then gradually decreases. This characteristic varies depending on the temperature of the cooling water (engine water temperature), the outside air temperature (intake air temperature), and the like, and the in-cylinder temperature estimation unit 46 of the ECU 2 stores data in which the characteristic is mapped.

  Since scavenging is promoted by increasing the opening K of the throttle valve 23 during the engine stop operation period, a sufficient amount of fresh air is supplied to the catalyst 37. Therefore, the oxygen storage amount of the catalyst 37 is sufficiently large while the engine is stopped.

  Next, control during engine restart will be described. In the following description, the compression top dead center that each cylinder 12 reaches is referred to as TDC, and serial numbers are assigned based on the order after the start of restart. Further, in the vicinity of the top dead center, before the top dead center is represented by B, and after the top dead center is represented by A.

  At the time of restart, the ECU 2 (starting control unit 48) first causes the combustion in the compression stroke cylinder 12C as described above to rotate the engine once in reverse, and then performs combustion in the expansion stroke cylinder 12A. Turn in the forward direction. That is, once the engine is reversely rotated, the piston 13 of the expansion stroke cylinder 12A is raised, and after the compression pressure is increased, combustion in the cylinder is performed. When the piston stop position of the expansion stroke cylinder 12A is within the proper stop range R and a sufficient amount of air for combustion is secured, and the air is compressed in the reverse direction of the engine, large combustion energy is obtained. It is done. That is, the engine can be reliably rotated in the normal rotation direction and smoothly shifted to the subsequent continuous operation.

  However, the presence of sufficient air in the expansion stroke cylinder 12A hinders strong compression of the air. This is because the compression reaction force of the compressed air acts in the direction of pushing back the piston 13 of the expansion stroke cylinder 12A.

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

  FIG. 10 is a graph showing the relationship between the fuel injection timing to the expansion stroke cylinder 12A and the corresponding piston arrival point (position closest to the top dead center when not ignited), by delaying the fuel injection. Represents the effect. The horizontal axis in FIG. 10 represents the fuel injection timing for the initial combustion of the expansion stroke cylinder 12A in terms of the crank angle (ATDC after top dead center), and the vertical axis represents the piston arrival point of the expansion stroke cylinder 12A corresponding thereto. This is expressed in terms of crank angle (ATDC after top dead center). The smaller the crank angle at the piston arrival point (closer to TDC), the smaller the in-cylinder volume at the time of maximum compression (the air density is larger), and a larger energy can be obtained during combustion. The characteristics shown in FIG. 10 are obtained when the piston stop position of the expansion stroke cylinder 12A is 110 ° CA (ATDC). As shown in this characteristic, the piston reaching point when injected at the beginning of the reverse rotation direction operation (crank angle = 110 ° CA) is about 36.5 ° CA (ATDC), whereas the reverse rotation direction starts, When the piston 13 is injected when it moves to the top dead center side up to 70 ° CA (ATDC), the piston reaching point becomes about 33.5 ° CA (ATDC), and the compressed air density increases by about 3 ° CA. Can be achieved.

  However, if the fuel injection timing is delayed too much, the vaporization is delayed, and the piston 13 reaches the reaching point before the compression pressure is sufficiently lowered by the latent heat of vaporization. That is, the piston reaching point starts to decrease (in the example of FIG. 10, after 70 ° CA). After all, in order to obtain the maximum air density increasing effect, it is preferable to perform the fuel injection timing from the middle stage of the compression stroke of the expansion stroke cylinder 12A to the first half of the latter stage.

  On the other hand, delaying the fuel injection timing also shortens the time from fuel injection to ignition, which may result in insufficient vaporization during ignition. In order to sufficiently promote vaporization by the ignition timing, it is desirable to perform fuel injection at an early stage (for example, at the beginning of the reverse direction operation). That is, the increase in the air density and the promotion of vaporization of the ignition timing have conflicting demands regarding the fuel injection timing.

  Therefore, in this embodiment, the fuel is dividedly injected (divided into two parts), the first stage fuel injection is performed at the beginning of the reverse direction operation, and the second stage fuel injection is performed in the reverse direction operation (preferably 90 ° CA (ATDC) at the center of the stroke) The fuel injection is performed at a position closer to the top dead center than the injection timing of 70 ° CA (ATDC) in FIG. That is, vaporization is promoted by the first stage fuel injection that takes a relatively long time until the ignition timing, and the compressed air density is increased by the second stage fuel injection.

  The fuel injection control unit 41 of the ECU 2 determines the ratio (split ratio) of the injected fuel between the front stage and the rear stage and the fuel injection timing of the rear stage, the piston stop position of the expansion stroke cylinder 12A, and the in-cylinder air temperature at the start of the reverse rotation direction. Correction is made based on (estimated value) so that the combustion energy can be increased as much as possible while ensuring the vaporization performance. That is, when the piston stop position of the expansion stroke cylinder 12A is relatively close to the bottom dead center within the appropriate stop range R (relatively large in-cylinder air amount), it is relatively close to top dead center (relatively). The fuel injection amount ratio at the subsequent stage is increased as compared with the case where the in-cylinder air amount is small. This is because when the amount of air in the cylinder is relatively large, the compression reaction force also becomes large. Therefore, by increasing the fuel injection amount in the subsequent stage, the compression pressure is effectively reduced and the density of the compressed air is increased. It is. Further, the fuel injection amount ratio in the subsequent stage is also increased when the in-cylinder air temperature is relatively high. This is because when the in-cylinder air temperature is high, the fuel vaporization performance is high, so that it is not necessary to perform fuel injection in the previous stage to ensure the vaporization performance.

  Regarding the subsequent fuel injection timing, when the in-cylinder air temperature is relatively high, the subsequent fuel injection timing is delayed (however, the timing corresponding to the injection timing of 70 ° CA in FIG. 10 is set as the upper limit). In other words, when the in-cylinder air temperature is high, the fuel vaporization performance is high, so even if the subsequent fuel injection timing is delayed, it is easy to vaporize until ignition, and the fuel injection timing is delayed accordingly. Therefore, the compressed air density is further increased.

  Next, referring to FIG. 11, when so-called direct start is performed by restart control, when the direct start is successful, the expansion stroke cylinder 12A starts from the timing t11 when the expansion stroke cylinder 12A changes from reverse rotation to normal rotation. The next combustion following the first combustion in is combustion in the intake stroke cylinder 12D. While the intake stroke cylinder 12D transitions to the first compression top dead center (2TDC), the engine rotational speed Ne increases and decreases between about 550 rpm and 300 rpm, and after exceeding 2 TDC, is indicated by a broken line in FIG. In this way, it gradually approaches the idle speed while repeating undulations at a relatively high gradient.

  However, when the engine rotational speed Ne falls below the required rotational speed (for example, 200 rpm) at the timing up to 2TDC, the intake stroke cylinder 12D cannot exceed 2TDC, and as shown by the solid line in FIG. Will suddenly descend and turn in reverse. Therefore, in this embodiment, whether or not the direct start is successful by detecting the engine rotation speed Ne at the inspection timing t12 as the engine rotation speed at the time of inspection is set as the inspection timing t12. Is determined by the start / fail judgment unit 49 of the ECU 2.

  The control operation at the time of engine restart including the above control will be described based on the flowcharts shown in FIGS. First, it is determined whether or not a predetermined engine restart condition (e.g., when an accelerator operation for starting is performed from a stopped state, when the battery voltage is reduced, or when the air conditioner is activated, etc.) ( In step S101), when it is determined NO and it is confirmed that the engine restart condition is not satisfied, the process waits as it is. If it is determined YES in step S101 and it is confirmed that the engine restart condition is satisfied, the in-cylinder temperature estimation unit 46 determines the engine water temperature, the stop time (elapsed time from the automatic stop), the intake air temperature, and the like. From this, the in-cylinder temperature is estimated (step S102). Then, based on the stop position of the piston 13 detected by the piston position detector 45, 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, and when the engine is stopped, the engine is stopped after several revolutions after the fuel injection is stopped. Since the stroke cylinder 12A is also filled with fresh air, and the inside of the compression stroke cylinder 12C and the expansion stroke cylinder 12A is substantially atmospheric pressure while the engine is stopped, the amount of fresh air is calculated from the combustion chamber volume. It will be required.

  Next, it is determined whether or not the piston stop position is relatively at the bottom dead center BDC side within the proper stop range R (before the top dead center BTDC 60 to 80 ° CA) in the compression stroke cylinder 12C (step). S104).

  If YES is determined in step S104 and the air amount is relatively large, the process proceeds to step S105, where λ (excess air ratio)> 1 with respect to the air amount of the compression stroke cylinder 12C calculated in step S103. Fuel is injected so that the air-fuel ratio (for example, air-fuel ratio = about 20) is reached (first fuel injection). This air-fuel ratio is obtained from the compression stroke cylinder first-time air-fuel ratio map M1 set in advance according to the stop position of the piston. By setting the lean air-fuel ratio such that λ> 1, even when the amount of air in the compression stroke cylinder 12C is relatively large, the combustion energy for the reverse rotation direction is not excessive and the reverse rotation is excessive (the compression stroke). In the cylinder 12C, the piston 13 that has moved to the bottom dead center side is prevented from passing through the bottom dead center and reversely rotating to the intake stroke.

  On the other hand, if NO is determined in step S104 and the air amount is relatively small, the process proceeds to step S106, where the air-fuel ratio becomes λ ≦ 1 with respect to the air amount of the compression stroke cylinder 12C calculated in step S103. The fuel is injected as described above (first fuel injection). This air-fuel ratio is obtained from the first-time air-fuel ratio map M2 of the compression stroke cylinder 12C set in advance according to the stop position of the piston. By setting the stoichiometric air-fuel ratio of λ ≦ 1 or a richer air-fuel ratio, combustion energy for the reverse direction can be sufficiently obtained even when the amount of air in the compression stroke cylinder 12C is relatively small.

  Next, the process proceeds to step S107, and ignition is performed on the cylinder after elapse of a time set in consideration of the vaporization time from the first fuel injection to the compression stroke cylinder 12C (timing t10 in FIG. 11). 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 (rise or fall of the crank angle signal) have been detected within a predetermined time after ignition (step S108). .

  In this step S108, when it is determined NO and it is confirmed that the piston 13 has not moved due to misfire, re-ignition is repeatedly performed on the compression stroke cylinder 12C (step S109).

  On the other hand, referring to FIG. 12, when it is determined YES in step S108 and it is confirmed that the piston 13 has moved, the expansion stroke cylinder is determined based on the piston stop position and the in-cylinder temperature estimated in step S102. A division ratio of the divided fuel injection to 12A (ratio between the first-stage injection (first time) and the second-stage injection (second time)) is calculated (step S121). The later-stage injection ratio is increased as the piston stop position in the expansion stroke cylinder 12A is closer to the bottom dead center and 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 the expansion stroke cylinder air-fuel ratio map M3 set in advance according to the stop position of the piston.

  Next, based on the fuel injection amount to the expansion stroke cylinder 12A calculated in step S122 and the split ratio calculated in step S121, the first stage fuel injection amount for the expansion stroke cylinder 12A is calculated and injected. (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 in-cylinder air is compressed after the piston 13 starts moving toward the top dead center (in the reverse direction of the engine), and the vaporization latent heat of the injected fuel is compressed. It is set so that the pressure is effectively reduced (the piston 13 is as close to the top dead center as possible), and the time for the second injected fuel to evaporate by the ignition timing is 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 after a predetermined delay time has elapsed (timing t11 in FIG. 11) (step S127). The predetermined delay time is obtained from an expansion stroke cylinder ignition delay map M4 set in advance according to the stop position of the piston. By the initial combustion in the expansion stroke cylinder 12A by this ignition, the engine rotates from the reverse direction to the normal direction. Accordingly, the piston 13 of the compression stroke cylinder 12C moves to the top dead center side and starts to compress the internal gas (burned gas burned by the ignition in step S107).

  Next, taking the fuel vaporization time into consideration, the second 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. Due to the latent heat of vaporization of the injected fuel to the compression stroke cylinder 12C for the second time, the compression pressure in the vicinity of 1 TDC of the compression stroke cylinder 12C is reduced, so that the 1TDC can be easily exceeded.

  Note that the second fuel injection to the compression stroke cylinder 12C is performed only to reduce the compression pressure in the cylinder, and ignition and combustion are not performed on this (the richer than the combustible air-fuel ratio). So self-ignition does not occur.) This incombustible fuel then reacts with oxygen stored in the catalyst 37 in the exhaust passage 22 and is rendered harmless.

  Next, as described above, since the second injected fuel in the compression stroke cylinder 12C does not burn, the next combustion following the first combustion in the expansion stroke cylinder 12A is combustion in the intake stroke cylinder 12D. As energy for the piston 13 of the intake stroke cylinder 12D to exceed 2TDC, a part of the energy of the initial combustion in the expansion stroke cylinder 12A is allocated. That is, the energy of the initial combustion in the expansion stroke cylinder 12A is used both for the compression stroke cylinder 12C to exceed 1 TDC and for the intake stroke cylinder 12D to exceed 2 TDC thereafter.

  Therefore, for smooth starting, it is desirable that the load when the intake stroke cylinder 12D exceeds 2TDC is small. In that case, it can exceed 2TDC with small energy. The following flow is control for exceeding 2 TDC with as little energy as possible when performing combustion in the next intake stroke cylinder 12D.

  Referring to FIG. 14, first, in step S140, the in-cylinder air density is estimated, and the air amount of intake stroke cylinder 12D is calculated from the estimated value. Next, 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) is generated that pushes the piston 13 back to the bottom dead center before reaching 2TDC due to the combustion. This is undesirable because it consumes much energy to exceed 2TDC. Therefore, in order to suppress this reverse torque, the air-fuel ratio is corrected to a rich value close to lean so that self-ignition does not occur.

  Next, the fuel injection amount to the intake stroke cylinder 12D is calculated from 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. This fuel injection is delayed until the later stage of the compression stroke so that the compression pressure is reduced by the latent heat of vaporization (that is, the energy required to exceed 2TDC is reduced). (Step S143). The delay amount is calculated based on the engine automatic stop period, the intake air temperature, the engine water temperature, and the like.

  On the other hand, the start / fail judgment unit 49 of the ECU 2 calculates the inspection timing t12 from the timing at which the edges of the crank angle sensors 30, 31 are detected in step S108 (step S144), and waits until this timing t12 is reached. (Step S145).

  Next, it is determined whether or not the engine rotation speed (inspection engine rotation speed) Ne at the inspection timing t12 shown in FIG. 11 is lower than a predetermined required engine rotation speed (for example, 200 rpm) (step S146).

  In this determination, if the engine speed at the time of inspection is equal to or higher than the required engine speed, as indicated by the broken line in FIG. 11, it is determined that the control exceeds 2TDC. In this case, in this embodiment, in order to suppress the occurrence of reverse torque, the ignition timing for the intake stroke cylinder 12D is ignited with a delay of 2 TDC or later (step S148). By the above control, in the intake stroke cylinder 12D, the compression pressure is reduced up to 2TDC so as to easily exceed the top dead center, and the torque in the forward rotation direction by the combustion energy is generated at the timing when the top dead center is passed. Become.

  On the other hand, if the engine speed at the time of inspection is lower than the required engine speed as indicated by the solid line in FIG. 11, the control shifts to the starter motor combined drive subroutine (step S147), and step S148 is executed. Not.

  Referring to FIGS. 11 and 15, when the start / fail judgment unit 49 of the ECU 2 determines that the start assist is necessary, the start control unit 48 determines that the engine speed Ne is decelerated and t13 at which the engine speed Ne first becomes 0 is the crank angle. Waiting for detection from the sensor 30 (step S1471), the timing t13 is used as an assist start timing as a reference for calculation (step S1472).

  Next, with reference to the timing t13, after the engine speed Ne changes in the reverse direction and then in the normal direction again, the zero speed timing tp of the starter motor 36 that becomes 0 is calculated (step S1474), and further 0 Based on the speed timing tp, the meshing timing region Ts of the starter motor 36 is calculated (step S1474). The meshing timing area Ts is determined based on the specification data of the starter motor 36 stored in advance in the storage area of the ECU 2 based on the specification of the adopted starter motor 36. In the present embodiment, when the ring gear 35 is stopped, the drive motor 36a is meshed while driving the pinion gear 36d in the reverse direction at a speed of about 60 rpm in the reverse direction to the ring gear 35. Ts is set in a range where the engine rotation speed Ne is from 0 rpm to 60 rpm.

Furthermore, in this embodiment, the drive delay time Tdy of the starter motor 36 is calculated from the battery voltage (step S1475). In the present embodiment, the drive motor 36a is designed to mesh while driving the pinion gear 36d in the reverse direction. Drive delay time Tdy) occurs. Therefore, in step S1475, the timing t _out incorporating the drive delay time Tdy is calculated.

Thereafter, the start control unit 48 waits for timing t _out based on the above calculation (step S1477), and outputs a drive signal at timing t _out (step S1478). As a result, the pinion gear 36d of the starter motor 36 is driven by the drive motor 36a and meshes with the ring gear 35, and the crankshaft 3 is assisted by the driving force from the starter motor 36 and returns to the main flow.

  After 2 TDC has been exceeded from the start of the start by using the direct start or the starter motor together, the blow-up suppression control is further performed in steps S149 to S159 in this embodiment. In accordance with the temperature state of the catalyst 37, the air-fuel ratio is made lean (λ> 1) or the ignition timing is delayed, and control for suppressing this blow-up is performed.

  Referring to FIG. 16, in the blow-up suppression control, first, power generation of alternator 28 is started (step S149). The target current value is set higher than usual by the power generation amount control unit 44 of the ECU 2. Since the load (engine load) of the crankshaft 3 is increased by the power generation of the alternator 28, the blow-up is suppressed.

  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 idling stop is not performed (step S149). If YES is determined here, it is in a state in which the engine is likely to blow up. Therefore, the opening of the throttle valve 23 is made smaller than the throttle opening during normal idling operation (step S151), and the combustion energy is reduced. Reduce the amount generated.

  Next, it is determined whether or not the temperature of the catalyst 37 provided in the exhaust passage 22 is in a relatively low temperature state lower than the active state (step S152). If YES is determined, the target air-fuel ratio is made rich so that λ ≦ 1. The air-fuel ratio is set (step S153), and the ignition timing is delayed after top dead center (step S154). By doing so, 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.

  Going back, if NO is determined in step S152, the target air-fuel ratio is set to a lean air-fuel ratio satisfying λ> 1, and fuel is injected (step S158). In this case, combustion is performed without delaying the ignition timing (step S159). This lean combustion can suppress the amount of combustion energy generated while suppressing fuel consumption.

  After step S154 or step S159, the process returns to step S150, and the above control is repeated until NO is determined. If it is determined as NO in step S150, there is no longer a possibility that the engine will blow up, and the routine proceeds to normal control including the power generation amount of the alternator 28 (step S160).

  When the above restart control is executed, fuel injection and ignition are performed according to the procedure shown in FIGS. In the following description, a case where the direct start is successful in the flow of FIG. 14 by the determination in step S146 is shown.

  First, the first fuel injection J3 is performed in the compression stroke cylinder 12C (# 3 cylinder), and combustion ((1) in FIG. 17) is performed by ignition. With the combustion pressure (part a in FIG. 18) by 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, the combustion energy is moderate enough for reversing the engine, that is, the combustion energy that is sufficient to compress the air in the expansion stroke cylinder 12A but does not excessively reverse the compression top dead center. Can be obtained.

  The piston 13 of the expansion stroke cylinder 12A (# 1 cylinder) starts to move in the direction of the top dead center with the start of reverse rotation of the engine. Immediately thereafter, the first (previous) 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 is compressed, the second (second stage) fuel injection J2 is performed. Is called. The compression pressure is reduced by the latent heat of vaporization of the injected fuel, and the piston 13 is closer to the top dead center, so that the density of the compressed air (air mixture) increases (part b in FIG. 18).

  When the piston 13 of the expansion stroke cylinder 12A is sufficiently close to the top dead center, the cylinder 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. 17), and the engine is driven in the normal rotation direction by the combustion pressure (c portion in FIG. 18).

  Furthermore, fuel richer than the combustible air-fuel ratio is injected into the compression stroke cylinder 12C at an appropriate timing (J4) ((3) in FIG. 17). 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. 18). Thereby, the first combustion energy of the expansion stroke cylinder 12A consumed to exceed the compression top dead center (the first compression top dead center from the start of starting) can be 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 (for example, after the middle of the compression stroke) when the temperature in the cylinder and the compression pressure are reduced by the latent heat of vaporization of the fuel. Since it is set ((4) in FIG. 17), self-ignition in the compression stroke (before compression top dead center) of the intake stroke cylinder 12D is prevented. 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. 18). That is, the expansion consumed to exceed the compression top dead center (second compression top dead center from the start of starting) by reducing the compression pressure by the fuel injection (J5) and not performing the combustion before the compression top dead center. The initial combustion energy in the stroke cylinder 12A can be reduced.

  Thus, the first compression top dead center ((3) in FIG. 17) and the second compression top dead center ((3) in FIG. 17) and the second compression top dead center (in FIG. 17) by the energy of the initial combustion ((2) in FIG. 17) in the expansion stroke cylinder 12A. 17 (4)) in FIG. 17 can be exceeded, and smooth and reliable startability can be ensured.

  Subsequent fuel injection (after J6 in FIG. 18 and after ignition (6) in FIG. 17) makes the air-fuel ratio lean (λ> 1) or delays the ignition timing in accordance with the temperature state of the catalyst 37. In other words, the vehicle shifts to a normal operation while preventing the blow-up.

  As described above, in the present embodiment, by preventing the wind-up, the driver of the vehicle does not receive a sudden shock after performing a direct start. Moreover, in order to prevent the blow-up, the control for reducing the torque is performed based on the temperature state of the catalyst 37, so that not only the blow-up is prevented but also the temperature state of the catalyst 37 rises as necessary. It is also possible to promote exhaust gas purification.

  Further, in the present embodiment, since control for preventing blow-up is performed from the initial combustion of the exhaust stroke cylinder 12B, there is an advantage that rapid torque generation is reliably suppressed.

  In the present embodiment, the initial ignition timing of the intake stroke cylinder 12D is retarded regardless of the temperature state of the catalyst 37 (see e in FIG. 17). As a result, torque is reduced and blowing is prevented, and the piston is ignited when the engine speed drops most so that the compression top dead center is exceeded. It becomes possible to make it.

  In the present embodiment, when the air-fuel ratio control unit 50 sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio (for example, J6 in FIG. 18), the ignition control unit 42 Since ignition is performed before the compression top dead center of the cylinder (see ignition (5) in FIG. 17), it is possible to achieve both improvement in fuel consumption and prevention of blow-up.

  Moreover, in this embodiment, it is possible to predict whether or not the engine will restart in the second compression stroke where the load at the time of restarting is the largest, and then prevent the engine from blowing up. There is no sudden shock after the start.

  In the present embodiment, the combustion condition is determined when it is determined that the intake air pressure is higher than the intake air pressure during idling when the specific cylinder is ignited.

  In this embodiment, since the alternator 28 starts or increases the generated current when it is determined that the direct start is successful, a load is applied to the engine and the deterioration of fuel consumption due to ignition retard is suppressed. While blowing up, it becomes possible to prevent the blow-up.

  In the present embodiment, the alternator control unit 51 operates the alternator 28 when it is determined that the intake pressure detected by the intake pressure sensor 26 as the intake pressure detection means is higher than the intake pressure during idle operation. Thus, it is possible to surely prevent blowing up.

  On the other hand, when the intake pressure detected by the intake pressure sensor 26 falls below the intake pressure during idling, the alternator 28 is stopped or the generated current is reduced. When the pressure drops below the pressure, it is possible to quickly reduce at least the generated current and secure the starting torque.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to said embodiment, A various deformation | transformation is possible within the range of the invention described in the claim. For example, in this embodiment, the fuel injection for the initial combustion in the expansion stroke cylinder 12A at the restart is divided injection (J1 + J2), but this can reduce the compression pressure due to the latent heat of vaporization and ensure the vaporization performance. A timing (predetermined fuel injection timing) that can be achieved as much as possible may be determined by experiment or the like, and one fuel injection at the predetermined fuel injection timing may be performed.

  Although omitted in the present embodiment, at the time of engine restart, when a 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 a predetermined time after start-up). Even when the predetermined value is not reached, control with assistance by the starter motor 36 may be performed.

  The start assist device is preferably a starter motor 36 having a pinion gear meshing with a ring gear provided on the engine-side flywheel. However, in this aspect, the starter motor 36 is not limited to a starter motor that outputs power from the pinion gear. An expression may be adopted.

  Control for automatically stopping the engine is not limited to this embodiment, and may be set as appropriate. However, in order to improve the restartability, the stop position of the piston 13 in the expansion stroke cylinder 12A is slightly closer to the bottom dead center than the stroke center (in the compression stroke cylinder 12C, slightly closer to the top dead center than the stroke center). Control is desirable.

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 a partially broken cross-sectional schematic diagram which shows the structure of a starter motor. 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. FIG. 6 is a partially enlarged view of FIG. 5 and further a time chart showing a crank angle and a stroke transition of each cylinder. It is a flowchart which shows detection control operation | movement of a piston stop position. It is explanatory drawing which shows an output signal in a crank angle signal. It is a graph which shows the relationship between the elapsed time from an engine stop, and a cylinder temperature estimated value. It is a graph which shows the relationship between the crank angle at the time of the fuel injection for the expansion stroke cylinder at the time of restart to combust first, and the crank angle of the piston arrival point at that time. It is a graph which shows the relationship between engine rotation speed at the time of engine restart, a crank angle, and time. It is a flowchart which shows the control action at the time of engine restart. It is a flowchart which shows the control action at the time of engine restart. It is a flowchart which shows the control action at the time of engine restart. It is a flowchart which shows the control action at the time of engine restart. It is a flowchart which shows 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.

2 ECU
12A # 1 cylinder (expansion stroke cylinder)
12B # 2 cylinder (exhaust stroke cylinder)
12C # 3 cylinder (compression stroke cylinder)
12D # 4 cylinder (intake stroke cylinder)
13 piston 16 fuel injection valve 47 automatic stop control part (an example of automatic stop means)
48 Start control unit (an example of start control means)
49 Start / fail judgment unit (an example of start / fail judgment means)
50 Air-fuel ratio control unit (an example of air-fuel ratio control means)
52 Catalyst temperature estimation unit (an example of catalyst temperature estimation means)
CA crank angle t12 Inspection timing

Claims (5)

An automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops fuel supply when a predetermined engine stop condition is satisfied, and a predetermined restart after the engine stops In an engine starter comprising start control means for restarting the engine by burning a cylinder that was in an expansion stroke at least when the engine was stopped when the condition was satisfied,
Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the exhaust path of the engine;
Air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio;
Ignition control means for controlling the timing for igniting a specific cylinder to start combustion ;
Cylinder specifying means for specifying at least a cylinder in the exhaust stroke when the engine is automatically stopped as an exhaust stroke cylinder from the phase of the crankshaft. Combustion of the cylinder in the expansion stroke is started and a plurality of cylinders are dead. In determining the combustion condition of a specific cylinder to start combustion in a state where the point has passed and the engine speed is lower than the idling speed,
When the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio, and the ignition control means is set. The cylinder is ignited after fuel injection,
When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the theoretical air-fuel ratio, and the ignition control means compresses the ignition timing. It is ignited with a delay after top dead center ,
The air-fuel ratio control means and the ignition control means perform control based on the temperature state of the catalyst from the initial combustion of the exhaust stroke cylinder after the combustion of the cylinder in the expansion stroke is started. An engine starting device. An automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops fuel supply when a predetermined engine stop condition is satisfied, and a predetermined restart after the engine stops In an engine starter comprising start control means for restarting the engine by burning a cylinder that was in an expansion stroke at least when the engine was stopped when the condition was satisfied,
  Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the exhaust path of the engine;
  Air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio;
  Ignition control means for controlling the timing for igniting a specific cylinder to start combustion;
  Cylinder specifying means for specifying, as an intake stroke cylinder, at least a cylinder that was in the intake stroke when the engine was automatically stopped from the phase of the crankshaft;
  The combustion conditions of a specific cylinder that starts combustion in a state in which combustion of the cylinders in the expansion stroke is started, the top dead center of a plurality of cylinders is passed, and the rotational speed of the engine is lower than the rotational speed during idling In deciding
  When the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio, and the ignition control means is set. The cylinder is ignited after fuel injection,
  When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means compresses the ignition timing. It is ignited with a delay after top dead center,
  The engine starter characterized in that the ignition control means ignites the ignition timing with a delay after the compression top dead center of the intake stroke cylinder regardless of the temperature state of the catalyst. An automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops fuel supply when a predetermined engine stop condition is satisfied, and a predetermined restart after the engine stops In an engine starter comprising start control means for restarting the engine by burning a cylinder that was in an expansion stroke at least when the engine was stopped when the condition was satisfied,
  Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the exhaust path of the engine;
  Air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio;
  Ignition control means for controlling timing for igniting a specific cylinder that starts combustion; and
  The combustion conditions of a specific cylinder that starts combustion in a state in which combustion of the cylinders in the expansion stroke is started, the top dead center of a plurality of cylinders is passed, and the rotational speed of the engine is lower than the rotational speed during idling In deciding
  When the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio, and the ignition control means is set. The cylinder is ignited after fuel injection,
  When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means compresses the ignition timing. It is ignited with a delay after top dead center,
  The ignition control means ignites before the compression top dead center of the cylinder when the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio. The engine starting device. An automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops fuel supply when a predetermined engine stop condition is satisfied, and a predetermined restart after the engine stops In an engine starter comprising start control means for restarting the engine by burning a cylinder that was in an expansion stroke at least when the engine was stopped when the condition was satisfied,
  Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the exhaust path of the engine;
  Air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio;
  Ignition control means for controlling the timing for igniting a specific cylinder to start combustion;
  A rotational speed detecting means for detecting the rotational speed of the engine;
  The engine rotation speed at the inspection timing set after a lapse of a predetermined time from the start of combustion of the cylinder that was in the expansion stroke when the engine was automatically stopped is received as an engine rotation speed at the time of inspection from the engine rotation speed detection means. Start / fail judgment means for judging engine start / fail
  The combustion conditions of a specific cylinder that starts combustion in a state where the combustion of the cylinders in the expansion stroke is started, the top dead center of a plurality of cylinders is passed, and the rotational speed of the engine is lower than the rotational speed during idling In deciding
  When the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio, and the ignition control means is set. The cylinder is ignited after fuel injection,
  When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means compresses the ignition timing. It is ignited with a delay after top dead center,
  The engine start device characterized in that the combustion condition of the specific cylinder to start combustion is determined after it is determined that the engine speed at the time of inspection is equal to or higher than a necessary engine speed necessary for normal restart . An automatic stop control means that is mounted on a vehicle together with a multi-cylinder four-cycle engine and stops fuel supply when a predetermined engine stop condition is satisfied, and a predetermined restart after the engine stops In an engine starter comprising start control means for restarting the engine by burning a cylinder that was in an expansion stroke at least when the engine was stopped when the condition was satisfied,
  Catalyst temperature estimating means for estimating the temperature state of the catalyst provided in the exhaust path of the engine;
  Air-fuel ratio control means for controlling the air-fuel ratio of the cylinder that reaches compression top dead center to the target air-fuel ratio;
  Ignition control means for controlling the timing for igniting a specific cylinder to start combustion;
  Intake pressure detecting means for detecting intake pressure supplied to the engine;
  The combustion conditions of a specific cylinder that starts combustion in a state where the combustion of the cylinders in the expansion stroke is started, the top dead center of a plurality of cylinders is passed, and the rotational speed of the engine is lower than the rotational speed during idling In deciding
  When the catalyst is in a relatively high temperature state higher than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be larger than the theoretical air-fuel ratio, and the ignition control means is set. The cylinder is ignited after fuel injection,
  When the catalyst is in a relatively low temperature state lower than the active state, the air-fuel ratio control means sets the target air-fuel ratio of the specific cylinder to start combustion to be equal to or lower than the stoichiometric air-fuel ratio, and the ignition control means compresses the ignition timing. It is ignited with a delay after top dead center,
  The engine starter according to claim 1, wherein the combustion condition of the specific cylinder to start combustion is determined when the intake pressure is higher than the intake pressure during idle operation.

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