JP2009019577A - Control device for internal combustion engine - Google Patents

Abstract

An amount of air exhausted from an engine (amount of oxygen) can be reduced during a period from when a request to stop operation of the engine (engine stop request) occurs until the rotation of the engine stops. A control device for an internal combustion engine is provided.
When an engine stop request is generated (XAD = 1), the control device performs combustion while setting the ignition timing to an over-advanced ignition timing that is advanced from the optimal ignition timing θmbt by an over-advance amount θadv. Continue, thereby reducing the engine speed (step 320). When the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the fuel supply is cut off and the ignition is stopped (step 335). Since the rotational speed decreases while the air-fuel mixture is combusted and the fuel supply is stopped after the rotational speed becomes equal to or lower than the threshold rotational speed, the amount of rotation due to the inertia of the engine until the engine stops is small. Therefore, a large amount of air is not discharged from the engine.
[Selection] Figure 3

Description

  The present invention relates to a control device for an internal combustion engine that controls the internal combustion engine (hereinafter simply referred to as “engine”) when the engine is stopped.

  Conventionally known general engine control devices are designed to immediately stop the supply of fuel to an engine when a request to stop the operation of the engine (hereinafter also referred to as “engine stop request”) occurs. It has become. However, the engine does not stop simultaneously with the stop of the fuel supply, but stops after several revolutions due to inertia. For this reason, a large amount of oxygen (air containing a large amount of oxygen) flows into the catalyst disposed in the exhaust passage of the engine. Therefore, the catalyst is in a state where a large amount of oxygen is retained. When the engine is restarted in such a state, the catalyst cannot efficiently purify NOx flowing into the catalyst. Therefore, the conventional control device increases the amount of fuel so as to control the air-fuel ratio of the air-fuel mixture supplied to the engine at the time of restart to an air-fuel ratio richer than the stoichiometric air-fuel ratio. The amount of NOx that is sometimes discharged is suppressed.

When such control is performed, the amount of fuel consumed at the time of restart increases. Therefore, one of the conventional control devices is that when a vehicle equipped with an engine is a “hybrid vehicle” that includes not only the engine but also an electric motor as a power source of the vehicle, the engine is immediately sent to the engine when a request to stop the engine is generated. The fuel supply is stopped and the engine is braked by an electric motor. According to this control, the engine becomes difficult to rotate due to inertia and stops rotating within a short period of time, so the amount of air exhausted from the engine is reduced. Therefore, the amount of oxygen flowing into the catalyst can be reduced. As a result, the increase in fuel at the time of restart can be reduced, so that it is possible to reduce NOx emissions and improve fuel efficiency (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2002-130001

  However, even if the rotation of the engine is braked by an electric motor to stop the operation of the engine, the engine rotates to some extent due to inertia. Therefore, a considerable amount of air is still exhausted from the engine, so that a large amount of oxygen flows into the catalyst. As a result, it is eventually necessary to control the air-fuel ratio of the air-fuel mixture to be considerably richer than the stoichiometric air-fuel ratio by relatively increasing the amount of fuel at the time of restart. Furthermore, if the vehicle is a normal vehicle that is not a hybrid vehicle (a vehicle equipped with only an engine as a power source), the above-described conventional control device cannot be applied.

  From the above, one of the objects of the present invention is to increase the amount of air discharged from the engine (the amount of oxygen) during the period from when the request to stop the operation of the engine occurs until the engine stops. An object of the present invention is to provide a control device for an internal combustion engine that can be reduced.

A control device for an internal combustion engine according to the present invention that achieves the above-described object,
An internal combustion engine control device applied to an internal combustion engine comprising ignition means for generating sparks in a combustion chamber, fuel supply means for supplying fuel to the combustion chamber, and a catalyst disposed in an exhaust passage,
Engine stop request determining means for determining whether or not an engine stop request for stopping operation of the engine has occurred;
After the time when it is determined that the engine stop request has been generated, torque is generated by the engine to reduce the rotational speed of the engine while burning the air-fuel mixture in the combustion chamber of the engine (decreasing the engine rotational speed). Stop control means for controlling the ignition means and the fuel supply means so that the engine itself generates a torque to be generated while the engine itself burns the air-fuel mixture;
It has.

  In other words, the ignition means and the fuel supply means continue to supply fuel after the time point when it is determined that an engine stop request has occurred, and the mixture formed in the combustion chamber of the engine by the supplied fuel is reduced. While burning by spark ignition, torque is generated in the engine that reduces the rotational speed of the engine.

  Accordingly, since the engine speed can be reduced while the air-fuel mixture is burned, air containing a large amount of oxygen is not discharged from the engine during the period until the engine speed decreases. Further, if the fuel supply is stopped after the rotational speed of the engine is reduced, even if the engine rotates due to inertia, the amount of rotation can be made very small. As a result, the amount of air discharged from the engine and flowing into the catalyst is very small. Therefore, even if the air-fuel ratio of the air-fuel mixture supplied to the engine at the time of restart is not made richer than before (that is, even if the amount of fuel is reduced than before), the NOx emission amount can be suppressed. , Fuel economy can be improved. Furthermore, since the fuel amount at the time of restart can be reduced as compared with the conventional case, the in-cylinder fuel adhesion amount can be reduced. As a result, the amount of PM (particulate matter, SOF, soot and other particulates) that tends to be generated in large quantities due to insufficient bonding with oxygen when the amount of fuel in the cylinder is large is reduced. It can also be reduced. In addition, since the amount of air flowing into the catalyst that is at a high temperature when the operation of the engine is stopped can be reduced, it is possible to suppress deterioration of the catalyst function due to sintering of the noble metal supported on the catalyst. .

In this case, the stop control means is
The ignition means is controlled so that the ignition timing of the engine becomes an over-advanced ignition timing advanced from an optimal ignition timing that causes the engine to generate a maximum torque after the time when it is determined that the engine stop request is generated. Ignition timing control means for
The supply of the fuel is continued from the time when it is determined that the engine stop request is generated until the time when the predetermined control end condition is satisfied, and the supply of the fuel is stopped after the time when the control end condition is satisfied. A fuel supply control means for controlling the fuel supply means;
Is preferably included.

  Usually, in order to improve fuel consumption, the ignition timing of the engine is set to the optimum ignition timing (MBT) that generates the maximum torque in the engine. In other words, the torque generated by the engine is lower than when the ignition timing is the optimal ignition timing, regardless of whether the ignition timing shifts to either the advance side or the retard side from the optimal ignition timing. If the ignition timing is set to an over-advanced ignition timing that is more advanced than the optimal ignition timing, combustion starts at a crank angle well before the compression top dead center (explosion top dead center). As compared with the case where is set to the retarded ignition timing that is retarded from the optimal ignition timing, it is possible to generate torque in the engine that can more effectively reduce the rotational speed of the engine. Therefore, according to the above configuration, it is possible to shorten the time from when the engine stop request is generated until the rotation of the engine is stopped.

In this engine control device, when the engine includes an auxiliary machine driven by the engine,
The stop control means further includes
In a “predetermined period” that does not include the time when the “torque for reducing the rotational speed of the engine generated by the combustion of the air-fuel mixture” becomes maximum after it is determined that the engine stop request has occurred. And auxiliary load control means for controlling the auxiliary machine so as to increase the torque required for the engine to drive the auxiliary machine (hereinafter also referred to as “load drive required torque”). Is preferred.

  The torque that decreases the rotational speed of the engine that occurs with the combustion of the air-fuel mixture increases every time combustion of the air-fuel mixture occurs and fluctuates with the rotation of the engine. Therefore, as in the above-described configuration, the “load driving necessary torque” is increased in a “predetermined period” that does not include a time when “torque for reducing the engine speed generated by combustion of the air-fuel mixture” becomes maximum. As a result, it is possible to reduce fluctuations in torque that functions to reduce the rotational speed of the engine. That is, the load driving required torque in the “predetermined period” is made larger than the load driving required torque in the “period other than the predetermined period”. As a result, the torque that functions to reduce the rotational speed of the engine is flattened, so that vibration when the engine is stopped (that is, when the rotational speed of the engine is reduced) can be reduced.

  In this case, the auxiliary machine may be, for example, a generator (alternator) driven by an engine, a compressor of an air conditioner, or the like. Further, when the control device is mounted on a hybrid vehicle including an internal combustion engine and an electric motor as a vehicle drive source, the electric motor may be caused to function as the auxiliary device by causing the electric motor to generate electric power.

  By the way, when the ignition timing is set to the over-advanced ignition timing by the ignition timing control means, the stop control means further immediately before the determination is made after the time when it is determined that the engine stop request is generated. It is more preferable to provide a combustion speed increasing means for increasing the combustion speed of the air-fuel mixture in the combustion chamber of the engine.

  When the ignition timing is set to the over-advanced ignition timing, ignition is performed when the air-fuel mixture is in a low compression state, that is, when the ignitability of the air-fuel mixture (that is, ease of ignition) is not good ( Sparks are generated). For this reason, the air-fuel mixture may be misfired. On the other hand, when the combustion speed of the air-fuel mixture increases, the optimal ignition timing shifts to the retard side. Therefore, by increasing the combustion speed of the air-fuel mixture, it becomes possible to shift the ignition timing in the case of overadvance control to the retard side. Therefore, if the combustion speed of the air-fuel mixture is increased by the combustion speed increasing means as in the above configuration, the time when the air-fuel mixture is compressed to some extent and the ignitability is good (higher than when the fuel speed is not increased). The air-fuel mixture can be ignited (spark is generated from the ignition means) at the time when it is in a compressed state and the ignitability is improved). As a result, even when the ignition timing is set to the over-advanced ignition timing, the air-fuel mixture can be ignited (combusted) more reliably.

  The combustion speed of the air-fuel mixture controls, for example, an intake control valve for generating a tumble flow (tumble control valve, TCV), an intake control valve for generating swirl (swirl control valve, SCV), etc. Thereby, it can be increased by generating vortices such as tumble flow and swirl in the combustion chamber. Further, in an engine having two or more intake ports in each cylinder, the same intake valve is set so that the intake valve of one of the intake ports is not operated (maintains a closed state). Can also be increased, for example, by controlling the pressure and thereby generating an air flow in the combustion chamber.

  In addition, when the ignition timing is set to the over-advanced ignition timing by the ignition timing control means, the stop control means further makes the same determination after the time when it is determined that the engine stop request is generated. Provided with “ignition delay time shortening means” that shortens the “ignition delay time” from “when a spark is generated in the combustion chamber of the engine” to “when the air-fuel mixture is ignited” than before. Is preferred.

  The air-fuel mixture is ignited after a predetermined delay time (ignition delay time) has elapsed from the ignition timing (spark generation start timing), and combustion by flame propagation is started. Therefore, when the ignition timing is set to the over-advanced ignition timing, if the ignition delay time is long, the ignition timing has to be considerably shifted to the advanced angle side. For this reason, since the spark generation start time is a time when the air-fuel mixture is in a further low compression state, the possibility that the air-fuel mixture will misfire increases. Therefore, by reducing the ignition delay time of the air-fuel mixture by the ignition delay time shortening means, the over-advanced ignition timing is set to “when the air-fuel mixture is compressed to a certain degree and the ignitability is good (the ignition delay time is shortened). If not, it is possible to set the over-advanced ignition timing that is retarded relative to the over-advanced ignition timing). As a result, the air-fuel mixture can be ignited (combusted) more reliably.

  The ignition delay time shortening means may be ignition energy increasing means for increasing the ignition energy generated by the ignition means during one spark generation operation period. It is considered that the success or failure of ignition of the air-fuel mixture in a spark ignition internal combustion engine is determined by the energy balance of the ignition means (ignition plug portion) at the time of ignition. The energy balance of the ignition means is the sum of energy transfer to the flame kernel. If the energy density received by the flame nuclei is much higher than the energy density taken away from the flame nuclei, the flame nuclei will grow relatively fast and consequently the mixture will ignite. The energy received by the flame kernel greatly depends on the energy input by ignition (ignition energy). Therefore, if the ignition energy is increased by the ignition energy increasing means, the ignition delay time can be shortened, and the air-fuel mixture can be ignited (combusted) more reliably.

  Further, when the ignition timing is set to the over-advanced ignition timing by the ignition timing control means, the stop control means is more than immediately before the determination is made after the time when it is determined that the engine stop request is generated. It is preferable to provide a compression ratio increasing means for increasing the actual compression ratio of the engine.

  The higher the actual compression ratio is set, the more the compressed state of the air-fuel mixture at a predetermined over-advance angle ignition timing (spark generation start time) can be made higher. Can improve sex. Therefore, if the actual compression ratio is increased by the actual compression ratio increasing means, the air-fuel mixture can be ignited (combusted) more reliably.

  The actual compression ratio is simply increased by, for example, bringing the closing timing of the intake valve at a predetermined crank angle after the intake bottom dead center (compression bottom dead center) close to the intake bottom dead center in normal operation. Can do. In a variable compression ratio engine having a known compression ratio changing mechanism, the actual compression ratio may be increased by changing the mechanical compression ratio by the compression ratio changing mechanism.

On the other hand, when such a control device includes an electric motor capable of generating torque for braking the rotation of the engine (for example, a control device mounted on a hybrid vehicle including an internal combustion engine and an electric motor as a vehicle drive source). Case), the stop control means further comprises:
In a "predetermined period" that does not include the time when the "torque for reducing the rotational speed of the engine generated by the combustion of the air-fuel mixture" becomes maximum after it is determined that the engine stop request has occurred. It is preferable to provide an electric motor control means for controlling the electric motor so that the electric motor generates a torque for braking the rotation of the engine.

  As described above, the torque that decreases the rotational speed of the engine that occurs with the combustion of the air-fuel mixture increases each time combustion of the air-fuel mixture occurs, and fluctuates with the rotation of the engine. Therefore, as in the above-described configuration, the rotation of the engine is braked by the electric motor during a “predetermined period” that does not include the time when the “torque for reducing the rotational speed of the engine generated by the combustion of the air-fuel mixture” becomes maximum. By controlling the electric motor so as to generate a torque to be generated (hereinafter also referred to as “motor torque”), it is possible to reduce fluctuations in torque that functions to reduce the rotational speed of the engine. That is, the control device generates the “motor torque” in the “predetermined period” and does not generate the “motor torque” in the “period other than the predetermined period”. As a result, the torque that functions to reduce the rotational speed of the engine is flattened, so that vibration when the engine is stopped (that is, when the rotational speed of the engine is reduced) can be reduced.

  The “motor torque” is generated by rotationally driving the motor at a rotational speed (rotational speed including “0”) that is the same rotational direction as the rotational direction of the engine and smaller than the rotational speed of the engine. The motor may be rotationally driven so that rotational torque in the direction opposite to the rotational direction of the engine is applied to the engine (that is, the motor is rotationally driven so that torque in the direction of reverse rotation of the engine is applied to the engine). May be generated.

  On the other hand, instead of setting the ignition timing to the over-advanced ignition timing, the ignition timing is retarded from the optimal ignition timing, or retarded from the ignition timing when it is determined that an engine stop request has occurred. The above-mentioned problem can also be dealt with by setting to the retarded ignition timing.

More specifically, when the control device for the internal combustion engine includes an auxiliary machine driven by the engine, the stop control means further includes:
After the time when it is determined that the engine stop request has occurred, the ignition timing of the engine is retarded from the optimal ignition timing that causes the engine to generate maximum torque, or the engine stop request is Ignition timing control means for controlling the ignition means so that the ignition timing is retarded from the ignition timing at the time when it is determined to have occurred,
The supply of the fuel is continued from the time when it is determined that the engine stop request is generated until the time when the predetermined control end condition is satisfied, and the supply of the fuel is stopped after the time when the control end condition is satisfied. A fuel supply control means for controlling the fuel supply means;
Auxiliary machine load control means for controlling the auxiliary machine so as to increase the torque required for the engine in order to drive the auxiliary machine after the time when it is determined that the engine stop request has occurred;
Is preferably included.

  According to this, the ignition timing after the time when it is determined by the ignition timing control means that the engine stop request has occurred is the retarded ignition timing that is retarded from the optimum ignition timing, or the engine stop request is The ignition timing is set to a retarded ignition timing that is more retarded than the ignition timing at the time when it is determined to have occurred. As a result, the torque generated with the combustion of the air-fuel mixture decreases (than before the time point when it is determined that the engine stop request has occurred). That is, the engine generates torque that lowers the rotational speed of the engine while burning the air-fuel mixture. Further, the load driving necessary torque is increased by the auxiliary load control means after the time when it is determined that the engine stop request is generated (than before the determination is made). As a result, the rotational speed of the engine decreases relatively quickly. Then, when a predetermined control end condition (for example, a condition that the engine speed is equal to or lower than a predetermined value) is satisfied, the fuel supply control unit stops the fuel supply.

  Accordingly, since the engine speed can be reduced while the air-fuel mixture is burned, air containing a large amount of oxygen is not discharged from the engine during the period until the engine speed decreases. Further, since the fuel supply is stopped after the rotational speed of the engine is reduced, even if the engine rotates due to inertia, the amount of rotation can be made very small. As a result, the amount of air discharged from the engine and flowing into the catalyst is very small. Therefore, as described above, fuel consumption can be improved while suppressing NOx and PM emissions during restart. Furthermore, deterioration of the catalyst function can be suppressed.

Similarly, when the control device for the internal combustion engine includes an electric motor capable of generating torque for braking the rotation of the engine, the stop control means further includes:
After the time when it is determined that the engine stop request has been generated, the ignition timing of the engine is retarded from the optimal ignition timing at which the engine generates maximum torque or at the time when it is determined that the engine stop request has occurred. Ignition timing control means for controlling the ignition means so as to become a retarded ignition timing that is retarded from the ignition timing;
The supply of the fuel is continued from the time when it is determined that the engine stop request is generated until the time when the predetermined control end condition is satisfied, and the supply of the fuel is stopped after the time when the control end condition is satisfied. A fuel supply control means for controlling the fuel supply means;
Electric motor control means for controlling the electric motor so as to generate torque for braking the rotation of the engine after the time when it is determined that the engine stop request is generated;
Is preferably included.

  According to this, the ignition timing after the time when it is determined by the ignition timing control means that the engine stop request has occurred is the retarded ignition timing that is retarded from the optimum ignition timing, or the engine stop request is The ignition timing is set to a retarded ignition timing that is more retarded than the ignition timing at the time when it is determined to have occurred. As a result, the torque required for the engine to continue to rotate decreases. That is, the engine generates torque that lowers the rotational speed of the engine while burning the air-fuel mixture. Further, the electric motor control means generates torque for braking the rotation of the engine from the electric motor after the time point when it is determined that the engine stop request is generated. As a result, the rotational speed of the engine quickly decreases. Then, when a predetermined control end condition (for example, a condition that the engine speed is equal to or lower than a predetermined value) is satisfied, the fuel supply control unit stops the fuel supply.

  Accordingly, since the engine speed can be reduced while the air-fuel mixture is burned, air containing a large amount of oxygen is not discharged from the engine during the period until the engine speed decreases. Further, since the fuel supply is stopped after the rotational speed of the engine is reduced, even if the engine rotates due to inertia, the amount of rotation can be made very small. As a result, the amount of air discharged from the engine and flowing into the catalyst is very small. Therefore, as described above, fuel consumption can be improved while suppressing NOx and PM emissions during restart. Furthermore, deterioration of the catalyst function can be suppressed.

Hereinafter, an internal combustion engine control apparatus according to each embodiment of the present invention will be described with reference to the drawings.
<First Embodiment>
(Constitution)
FIG. 1 shows a spark reciprocating spark-ignition multi-cylinder (four-cylinder) engine control device for an internal combustion engine according to a first embodiment of the present invention (hereinafter also referred to as “first control device”). 1 shows a schematic configuration of a system applied to a four-cycle internal combustion engine 10. 1 shows only a cross section of a specific cylinder, other cylinders have the same configuration as the illustrated cylinder.

  The internal combustion engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and a gasoline mixture to the cylinder block portion 20. An intake system 40 for supplying and an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside are included.

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

  The cylinder head unit 30 includes an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake valve control device 33 that opens and closes the intake valve 32, an exhaust port 34 that communicates with the combustion chamber 25, an exhaust An exhaust valve 35 that opens and closes the port 34, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37, an ignition coil 37a that generates a high voltage applied to the ignition plug 37, an igniter 38, and fuel are injected into the intake port 31. An injector 39 is provided. The spark plug 37, the ignition coil 37 a, the igniter 38, and the like constitute ignition means for generating a spark in the combustion chamber 25. The injector 39 constitutes fuel supply means (fuel injection means) that supplies fuel supplied from a fuel tank (not shown) to a combustion chamber 25 by a fuel pump (not shown).

  The intake valve control device 33 has a known configuration that adjusts and controls the relative rotation angle (phase angle) between an intake cam shaft and an intake cam (not shown) by hydraulic pressure, and opens the intake valve 32 (intake valve). The valve opening time IO) can be changed. In this example, the valve opening period (the valve opening crank angle width) of the intake valve is constant. Therefore, when the intake valve opening timing IO is advanced or retarded by a predetermined angle, the intake valve closing timing IC is also advanced or retarded by the predetermined angle. Further, the opening timing and closing timing of the exhaust valve 35 are constant.

  The intake system 40 includes an intake pipe 41 including an intake manifold that communicates with the intake ports 31 of each cylinder and forms an intake passage together with the intake ports 31, an air filter 42 provided at an end of the intake pipe 41, and a throttle valve 43. A throttle valve actuator 43a, a tumble control valve (hereinafter referred to as "TCV") 44, and a TCV actuator (TCV driving means) 44a. The throttle valve 43 is rotatably supported with respect to the intake pipe 41 so that the opening cross-sectional area of the intake passage can be made variable. The throttle valve actuator (throttle valve driving means) 43a is a DC motor, and drives (rotates) the throttle valve 43.

  In fact, two intake ports 31 are formed in each cylinder. The TCV 44 is instructed to rotate at one of the two ports. The TCV 44 is driven by a TCV actuator 44a to open and close the intake port 31 provided with the TCV 44. The two intake ports 31 provided in each cylinder are configured to generate a tumble flow (longitudinal vortex) in the combustion chamber 25 when the intake port 31 on the side where the TCV 44 is provided is closed. .

  The exhaust system 50 includes an exhaust manifold 51 communicating with the exhaust port 34 of each cylinder, an exhaust pipe (exhaust pipe) 52 connected to the exhaust manifold 51, a three-way catalyst 53 on the upstream side, and a three-way catalyst 54 on the downstream side. ing. The upstream catalyst 53 is disposed in the exhaust pipe 52. The downstream catalyst 54 is disposed in the exhaust pipe 52 downstream of the upstream catalyst 53. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, a throttle position sensor 62, a cam position sensor 63, a crank position sensor 64, a cooling water temperature sensor 65, an air-fuel ratio sensor 66 disposed in an exhaust passage upstream of the catalyst 53, a catalyst. An air-fuel ratio sensor 67 and an accelerator opening sensor 68 are provided in the exhaust passage downstream of 53 and upstream of the catalyst 54.

The hot-wire air flow meter 61 detects the mass flow rate per unit time of the intake air flowing through the intake pipe 41 and outputs a signal representing the mass flow rate Ga.
The throttle position sensor 62 detects the opening of the throttle valve 43 and outputs a signal representing the throttle valve opening TA.
The cam position sensor 63 outputs one pulse every time the intake camshaft rotates 90 degrees, 90 degrees, and 180 degrees from a predetermined angle. This signal is also referred to as a G2 signal.

  The crank position sensor 64 outputs a pulse every time the crankshaft 24 rotates 10 degrees. The pulse output from the crank position sensor 64 is converted into a signal representing the engine rotational speed NE. Further, based on signals from the cam position sensor 63 and the crank position sensor 64, the crank angle of the engine 10 (for example, an absolute crank angle in which a crank angle at which a certain cylinder is an intake top dead center is 0 ° CA) is determined. It has come to be required.

  The upstream air-fuel ratio sensor 66 and the downstream air-fuel ratio sensor 67 detect upstream and downstream air-fuel ratios of the catalyst 53 and output signals representing the upstream and downstream air-fuel ratios, respectively. The accelerator opening sensor 68 detects the operation amount of the accelerator pedal 91 operated by the driver, and outputs a signal indicating the operation amount Accp of the accelerator pedal 91.

  The system further includes an ignition key switch 71, a generator (alternator) 72, and an air conditioner compressor 73.

  An ignition key switch (hereinafter referred to as an “IG switch”) 71 is operated by the driver so that any one of a shut-off position (off position), a connection position (on position, accessory position), and a start position is selected. And a signal representing each position is output.

  The generator 72 is driven by the engine 10 to generate electric power, charge a battery (not shown), and supply electric power to an electric load (not shown). The generator 72 constitutes an auxiliary machine driven by the engine 10. The generator 72 includes a regulator circuit (not shown). The regulator circuit can control the generated voltage of the generator 72 by controlling the field current (excitation current) of the generator according to the instruction signal. The torque required for the engine 10 to drive the generator 72 (load drive required torque) increases as the generated voltage of the generator 72 increases.

  The compressor 73 of the air conditioner includes an electromagnetic clutch 73a. The electromagnetic clutch 73a is in a state where power can be transmitted in accordance with the instruction signal, and the compressor 73 is driven by the engine 10. Therefore, the compressor 73 also constitutes an auxiliary machine driven by the engine 10. The electromagnetic clutch 73 a becomes incapable of transmitting power in response to the instruction signal, disconnects the compressor 73 from the output shaft of the engine 10, and prevents the compressor 73 from being driven by the engine 10. When the compressor 73 is driven by the engine 10, the torque for the engine 10 to drive the compressor 73 (load drive required torque) naturally increases as compared to when the compressor 73 is not driven by the engine 10. .

  The electric control device 80 includes a CPU 81, a ROM 82, a RAM 83, a backup RAM 84 for storing data while the power is turned on and holding the stored data even when the power is shut off, an interface 85 including an AD converter, and the like. This is a well-known microcomputer.

The interface 85 is connected to the sensors 61 to 68 and the IG switch 71 and the like, and supplies signals from these sensors and switches to the CPU 81.
The interface 85 is connected to the intake valve control device 33, the igniter 38, the injector 39, the throttle valve actuator 43a, the TCV actuator 44a, the generator 72, the electromagnetic clutch 73a of the compressor 73, and the like, and sends a drive signal or an instruction signal thereto. It is like that.

(Operation)
Next, the contents of control (particularly control when stopping the operation of the engine 10, that is, control when the engine is stopped) performed by the control device (first control device) of the internal combustion engine 10 configured as described above will be described. To do.

<During normal operation>
When the engine 10 is started by a starter (not shown) by moving the IG switch 71 from the off position to the start position, the engine is in normal operation. At this time, the CPU 81 is configured to execute the routines shown in the flowcharts of FIGS. 2 and 3 every elapse of a predetermined time.

  Therefore, the CPU 81 starts processing from step 200 in FIG. 2 at a predetermined timing, and whether or not a request for stopping the operation of the engine (engine stop request) is generated in step 205 (that is, an engine stop request is generated). Whether or not it is immediately after. In this example, the engine stop request is generated when the IG switch 71 is changed from the on position to the off position by the driver while the engine 10 is operating.

  At this time, the engine is in normal operation and no engine stop request has been issued. Accordingly, the CPU 81 makes a “No” determination at step 205 to proceed to step 295 to end the present routine tentatively.

  Further, the CPU 81 starts processing from step 300 in FIG. 3 at a predetermined timing, proceeds to step 305, and determines whether or not the value of the stop time control flag XAD is “1”. When the value of the stop time control flag XAD is “1”, it indicates that the advance angle control described later is being executed, and when the value is “0”, the advance angle control is not being executed. Indicates. The value of the stop time control flag XAD is set to “0” in an initial routine (not shown) executed when the IG switch 71 is moved from the off position to the start position. Accordingly, the CPU 81 makes a “No” determination at step 305 to proceed to step 310.

  In step 310, the CPU 81 determines whether or not the value of the fuel cut flag XFC is “1”. When the value of the fuel cut flag XFC is “1”, it indicates that the fuel cut when the engine is stopped, which will be described later, is to be executed. When the value of the fuel cut flag XFC is “0”, the fuel cut when the engine is stopped is determined. Indicates that the state is not to be executed. The fuel cut flag XFC value is also set to “0” in the initial routine described above. Accordingly, the CPU 81 makes a “No” determination at step 310 to proceed to step 315 to execute normal operation control, and then proceeds to step 395 to end the present routine tentatively.

  The normal operation control executed by the CPU 81 in step 315 is as follows.

(1) The CPU 81 determines a target value (target throttle valve opening) of the throttle valve 43 according to the accelerator pedal operation amount Accp and the rotational speed NE. The CPU 81 sends an instruction signal to the throttle valve actuator 43a so that the opening degree of the throttle valve 43 coincides with the determined target value.

(2) The CPU 81 obtains the in-cylinder intake air amount Mc that each cylinder of the engine 10 sucks in one intake stroke based on the mass flow rate Ga, the engine rotational speed NE, etc., and the mixture gas supplied to the engine 10 The fuel injection amount is determined so that the air-fuel ratio matches a predetermined target air-fuel ratio (for example, the theoretical air-fuel ratio or the lean air-fuel ratio). Then, the CPU 81 executes a fuel injection execution routine (fuel supply routine) (not shown) to inject the fuel of the determined fuel injection amount from the injector 39 provided for the cylinder that reaches the intake stroke.

(3) The CPU 81 includes a basic ignition timing table (map) that defines the relationship among the load of the engine 10 (for example, the in-cylinder intake air amount Mc), the engine rotational speed NE, and the optimum ignition timing θmbt, and the actual in-cylinder intake air. The optimum ignition timing θmbt is determined based on the amount Mc and the actual engine speed NE. The optimum ignition timing θmbt is usually a crank angle before the compression top dead center TDC. The in-cylinder intake air amount Mc and the engine rotational speed NE are variables representing the operating state of the engine 10. The optimum ignition timing θmbt is an ignition timing at which the engine 10 can generate the maximum torque for each operating state of the engine 10. The basic ignition timing table is determined in advance by experiments or the like and stored in the ROM 72. Each value related to the ignition timing is expressed by a crank angle (crank angle magnitude) before the compression top dead center TDC.

  Then, the CPU 81 executes an ignition execution routine (not shown) so that a spark is generated from the spark plug 37 of the cylinder when the crank angle of the cylinder in the compression process coincides with the optimal ignition timing. An instruction signal is sent to the igniter 38. As a result, a spark is generated from the spark plug 37 at the optimal ignition timing, and the air-fuel mixture is ignited and burned.

(4) When a predetermined condition (for example, a lean combustion operation condition such as a light load operation state) is established, the CPU 81 sends an instruction signal to the TCV actuator 44a so as to close the TCV 44. As a result, a tumble flow is generated in the combustion chamber 25. The CPU 81 sends an instruction signal to the TCV actuator 44a so that the TCV 44 is opened at least when the throttle valve opening degree TA is “0”. As a result, when the throttle valve opening degree TA is “0”, no tumble flow is generated in the combustion chamber 25.

(5) As shown in FIG. 10A described in detail later, the CPU 81 determines that the intake valve closing timing IC is greater than the intake bottom dead center (compression bottom dead center) BDC by a predetermined crank angle θ2 (θ2> 0). ) Is sent to the intake valve control device 33 so that the crank angle (normal valve closing timing ICn) is retarded. As a result, the intake valve 32 is closed at the normal closing timing ICn.
(6) The CPU 81 controls the generator 72 so that the voltage generated by the generator 72 matches the normal target voltage.
(7) The CPU 81 controls the state of the electromagnetic clutch 73a based on an air conditioning setting signal from an air conditioner (not shown).

<When an engine stop request occurs (when an engine stops)>
Next, a case where the driver changes the IG switch 71 from the on position to the off position in order to stop the operation of the engine 10 during the normal operation will be described. In this case, an engine stop request is generated. Therefore, when the CPU 81 proceeds to step 205 in FIG. 2, it determines “Yes” in step 205 and proceeds to step 210, where the throttle valve opening TA is set to “0” as to whether or not the current time is the idling operation state. It is determined based on whether or not.

  Assuming that the engine is idling, the CPU 81 makes a “Yes” determination at step 210 and proceeds to step 215. Then, the CPU 81 sets the value of the stop time control flag XAD to “1” in step 215, proceeds to step 295, and once ends this routine.

  When the CPU 81 starts processing from step 300 in FIG. 3 in this state, the CPU 81 makes a “Yes” determination at step 305 and proceeds to step 320 to execute the over-advance control described below.

(1) The CPU 81 determines the optimal ignition timing θmbt in the same way as during normal operation.
(2) The CPU 81 determines the overtravel angle amount θadv (θadv> 0) based on the overtravel angle table defining the relationship between the engine speed NE and the overtravel angle amount θadv and the actual engine speed NE. . The over-advance angle table is determined in advance by experiments or the like and stored in the ROM 72. Based on the over-advance angle table of this example, the over-advance angle amount θadv is determined to increase as the engine speed NE increases.

(3) The CPU 81 obtains the over-advanced ignition timing θig by adding the obtained over-advanced amount θadv to the obtained optimum ignition timing θmbt. The over-advance ignition timing θig is a timing obtained by advancing the optimum ignition timing θmbt by the over-advance amount θadv. Then, the CPU 81 executes an ignition execution routine (not shown) so that a spark is generated from the spark plug 37 of the cylinder when the crank angle of the cylinder in the compression process coincides with the over-advanced ignition timing θig. Then, an instruction signal is sent to the igniter 38 of the cylinder. As a result, a spark is generated from the spark plug 37 at the over-advanced ignition timing θig, and the air-fuel mixture is ignited and burned.
(4) On the other hand, the CPU 81 continues the fuel supply (fuel injection) by executing a fuel injection execution routine (not shown). Even in this case, the fuel injection amount is determined so that the air-fuel ratio of the air-fuel mixture supplied to the engine matches the stoichiometric air-fuel ratio.

  As a result, since the actual ignition timing coincides with the over-advanced ignition timing θig, the engine 10 generates a torque that reduces the rotational speed NE at that time by the combustion based on the spark ignition at the over-advanced ignition timing θig. appear. Accordingly, the rotational speed NE of the engine 10 gradually decreases. At this time, since the combustion of the air-fuel mixture is continued in the combustion chamber 25, the exhaust gas is discharged from the engine 10. In other words, air containing a large amount of oxygen is not discharged from the engine 10. Therefore, a large amount of oxygen does not flow into the catalyst 53 and the catalyst 54. Combustion is continued while setting the ignition timing to an over-advanced ignition timing that is advanced from the optimal ignition timing, thereby generating a torque that lowers the rotational speed of the engine 10 by the engine 10. The control for reducing the engine speed is referred to as “over-advance angle control”.

  Next, the CPU 81 proceeds to step 325 and determines whether or not the rotational speed NE has become equal to or lower than the threshold rotational speed NEth. That the rotational speed NE is equal to or lower than the threshold rotational speed NEth is a control end condition for over-advance angle control. The threshold rotational speed NEth is set to a speed that is slightly larger than the lower limit speed of the rotational speeds of the engine that can burn the air-fuel mixture. That is, for example, if the normal idle rotation speed is about 700 rotations / minute, the threshold rotation speed NEth is about 400 rotations / minute. In other words, the threshold rotational speed NEth is greatly rotated by inertia when the supply of fuel is stopped when the actual rotational speed NE has decreased to the threshold rotational speed NEth (that is, when combustion is stopped). The rotation speed can be set immediately without stopping.

  Since the present time is the time when the over-advance control in step 320 is started, the rotational speed NE is higher than the threshold rotational speed NEth. Accordingly, the CPU 81 makes a “No” determination at step 325 to proceed to step 395 to end the present routine tentatively.

  Thereafter, when the CPU 81 starts processing from step 200 in FIG. 2, the CPU 81 makes a “No” determination at subsequent step 205 and proceeds directly to step 295. Therefore, the value of the stop time control flag XAD is maintained at “1”. Thereby, the CPU 81 determines “Yes” in step 305 following step 300 in FIG. 3, and continues the over-advance angle control in step 320.

  As a result, when a predetermined time elapses, the rotational speed NE becomes equal to or less than the threshold rotational speed NEth. In this case, when the CPU 81 proceeds to step 325, it determines “Yes” at step 325, proceeds to step 330, sets the value of the stop time control flag XAD to “0”, and sets the fuel cut flag XFC. The value is set to “1”, and the routine proceeds to step 395 to end the present routine tentatively.

  As a result, when the CPU 81 starts processing from step 300 next, the CPU 81 determines “No” in step 305, determines “Yes” in step 310, and proceeds to step 335. In step 335, the CPU 81 executes fuel cut (stops fuel supply) and stops generating sparks from the spark plug 37 (stops ignition). Thereafter, the CPU 81 proceeds to step 395 to end the present routine tentatively. Thereby, the engine 10 stops.

  When the engine stop request is generated and the engine 10 is not in the idle operation state (for example, when the throttle valve opening TA is not “0”), the CPU 81 continues to step 200 and step 205 in FIG. When the routine proceeds to step 210, “No” is determined at step 210 and the routine proceeds to step 220 where the value of the fuel cut flag XFC is set to “1”. As a result, the CPU 81 determines “No” in step 305 following step 300 in FIG. 3 and determines “Yes” in step 310, and then proceeds to step 335. Therefore, when the engine stop request is generated and the engine 10 is not in the idle operation state, the fuel cut is immediately performed without performing the over-advance control, and the engine 10 is stopped.

  As described above, when the engine 10 is in the idle operation state at the time when the engine stop request is generated, the first control device determines that the excessive advance angle until the rotational speed NE becomes equal to or less than the threshold rotational speed NEth. Take control. As a result, the first control device causes the engine 10 to generate torque that decreases the rotational speed NE while continuing to burn the air-fuel mixture. Then, the first control device stops the fuel supply when the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth (when the control end condition is satisfied).

  Therefore, air containing a large amount of oxygen is not discharged from the engine 10 during the period from when the engine stop request is generated until the engine rotational speed NE decreases to the threshold rotational speed NEth. Further, since the fuel supply is stopped after the rotational speed NE is reduced, even if the engine 10 rotates due to inertia, the amount of rotation is very small. As a result, when the rotation of the engine is stopped, the amount of air discharged from the engine 10 and flowing into the catalyst 53 and the catalyst 54 becomes very small. Therefore, even if the air-fuel ratio of the air-fuel mixture supplied to the engine 10 at the time of restart is not greatly enriched (that is, even if the amount of fuel is not increased so much), the NOx emission amount can be suppressed. Fuel consumption can be improved. Furthermore, since the fuel amount at the time of restart can be reduced as compared with the conventional case, the in-cylinder fuel adhesion amount can be reduced. As a result, the amount of PM (particulate matter, SOF, soot and other particulates) that tends to be generated in large quantities due to insufficient bonding with oxygen when the amount of fuel in the cylinder is large is reduced. It can also be reduced. In addition, since the amount of air flowing into the catalyst 53 and the catalyst 54 that are at a high temperature when the operation of the engine 10 is stopped can be reduced, the function of the catalyst due to sintering of the noble metal supported on these catalysts can be reduced. Deterioration can also be suppressed.

(Second Embodiment)
Next, a control device according to a second embodiment of the present invention (hereinafter also referred to as “second control device”) will be described. When the second control device is performing the over-advance control after the time point when it is determined that the engine stop request has been generated, the second control device is more in the combustion chamber 25 than immediately before it is determined that the engine stop request has been generated. It is different from the first control device only in that a combustion speed increasing means for increasing the combustion speed of the air-fuel mixture is provided. An example of the combustion speed increasing means is means for generating a tumble flow in the combustion chamber 25 by closing the TCV 44.

  When the ignition timing is set to the over-advanced ignition timing, ignition is performed when the air-fuel mixture is in a low compression state. For this reason, since the ignitability of the air-fuel mixture becomes poor, there is a risk that the air-fuel mixture will misfire (it will not ignite or burn).

  FIG. 4 is a graph showing the relationship between the ignition timing and the torque generated by the engine 10 for each combustion speed. As is apparent from this graph, the optimal ignition timing shifts to the retard side as the combustion speed increases (see θmbt1, θmbt2, and θmbt3). Therefore, by increasing the combustion speed, it becomes possible to shift the ignition timing (over-advanced ignition timing) in the case of performing the advanced angle control to the retarded angle side. If the over-advanced ignition timing can be set to the retarded angle side, the mixture is compressed to a certain extent and the ignitability is good (the ignitability is improved because the compression state is higher than when the combustion speed is not increased). The air-fuel mixture can be ignited at the time. As a result, the air-fuel mixture can be ignited (combusted) more reliably.

  Hereinafter, the operation of the second control device will be described. The CPU 81 of the second control device executes the routine shown by the flowchart in FIG. 2 and FIG. 5 instead of FIG. Of the steps shown in FIG. 5, the same steps as those shown in FIG. 3 are denoted by the same reference numerals as the steps given in FIG.

<During normal operation>
During normal operation, the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, so the CPU 81 proceeds to step 505 following step 500, step 305, and step 310 in FIG. Then, control for setting the combustion speed of the air-fuel mixture to a normal speed (combustion speed normal control) is executed. In this example, the CPU 81 does not generate a tumble flow in the combustion chamber 25 by opening the TCV 44 in step 505. Then, the CPU 81 proceeds to step 315 and executes normal operation control similar to that of the first control device except for the control in step 505 of the TCV 44.

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the time is in the idling operation state, the CPU 81 performs step 215 in FIG. The value of the stop time control flag XAD is set to “1”.

  As a result, the CPU 81 makes a “Yes” determination at step 305 following step 500 in FIG. 5 and proceeds to step 510 to execute control (combustion speed increase control) for increasing the combustion speed more than during normal combustion speed control. . That is, the CPU 81 closes the TCV 44 in step 510 to generate a tumble flow in the combustion chamber 25. As a result, the combustion speed increases from the normal speed. Thereafter, the CPU 81 proceeds to step 320 to execute over-advance angle control, and continues over-advance angle control until it is determined “Yes” at step 325.

  As a result, the engine 10 generates a torque that reduces the rotational speed NE, so that the engine rotational speed NE becomes equal to or less than the threshold rotational speed NEth when a predetermined time elapses. Therefore, the CPU 81 determines “Yes” at step 325 and executes the process of step 330. As a result, the value of the stop time control flag XAD is set to “0”, and the value of the fuel cut flag XFC is set to “1”.

  As a result, when the CPU 81 starts processing from step 500 next, the CPU 81 determines “No” in step 305 and “Yes” in step 310, and executes the fuel cut in step 335 described above. At the same time, the ignition by the spark plug is stopped. Thereby, the engine 10 stops rotating.

  In addition, when it determines with "No" in step 210 of FIG. 2 (when it is not an idle driving state at the time of an engine stop request | requirement), CPU81 sets the fuel cut flag XFC to "1". Therefore, when the CPU 81 starts the process from step 500 in FIG. As a result, fuel cut is executed and ignition is stopped.

  As described above, when the engine 10 is in the idle operation state at the time when the engine stop request is generated, the second control device is in an over-advanced angle until the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth. Control is executed, and then fuel cut is executed. Therefore, the second control device can naturally exhibit the same effect as the first control device. Further, the second control device increases the combustion speed of the air-fuel mixture during the over-advance control compared to during normal operation. As a result, the over-advanced ignition timing is set to a retarded ignition timing than when the combustion speed is not increased. Therefore, a spark can be generated from the spark plug 37 when the air-fuel mixture is compressed to a certain degree and the ignitability is good. As a result, even when the ignition timing is set to the over-advanced ignition timing, the air-fuel mixture can be ignited (combusted) more reliably.

  The second control device controls the combustion speed of the air-fuel mixture, for example, an intake control valve (swirl control valve, SCV) for generating a swirl in the combustion chamber 25 and the like to control the swirl in the combustion chamber 25. It may be configured to increase by generating. Further, the second control device makes the combustion speed of the air-fuel mixture not operate the intake valve of one of the intake ports provided in each cylinder (maintains the valve closed state). It may be increased by controlling the intake valve to thereby generate an air flow in the combustion chamber. In addition, the second control device may increase the combustion speed of the air-fuel mixture by enriching the air-fuel ratio of the air-fuel mixture supplied to the engine.

(Third embodiment)
Next, a control device according to a third embodiment of the present invention (hereinafter also referred to as “third control device”) will be described. When the third control device is executing the over-advance control after the time point when it is determined that the engine stop request is generated, the “ignition delay time” is immediately before the determination that the engine stop request is generated. This is different from the first control device only in that an ignition delay time shortening means for shortening is provided. The ignition delay time is the time from when a spark is generated in the combustion chamber 25 until the air-fuel mixture in the combustion chamber 25 is ignited.

  As described above, when the ignition timing is set to the over-advanced ignition timing, since the spark is generated when the air-fuel mixture is in a low compression state and the ignitability is not good, the air-fuel mixture misfires (ignition)・ Do not burn). Furthermore, if the “ignition delay time” from when a spark is generated to when substantial combustion starts is long, the ignition timing has to be shifted considerably to the advance side. For this reason, since the spark generation start time is the time when the air-fuel mixture is in a further low compression state, the possibility that the air-fuel mixture will misfire increases.

  Therefore, the third control device shortens the ignition delay time of the air-fuel mixture by the ignition delay time shortening means. As a result, the over-advanced ignition timing is determined as “when the air-fuel mixture is compressed to a certain degree and the ignitability is good (the over-advanced ignition timing is set to be greater than the over-advanced ignition timing set when the ignition delay time is not reduced) It is possible to set the ignition timing). As a result, the air-fuel mixture can be ignited (combusted) more reliably. The ignition delay time shortening means in this example is means for increasing the ignition energy.

  6 is a circuit diagram of the ignition plug 37, the ignition coil 37a, and the igniter 38 shown in FIG. The ignition coil 37a includes a primary side coil 37p and a secondary side coil 37s. The igniter 38 includes a switching element 38a that is a power transistor and an energization control circuit 38b. The primary side coil 37p is energized by turning on the switching element 38a. When the switching element 38a is cut off at the ignition timing, a high voltage is generated in the secondary coil 37s and a large current flows. As a result, the spark plug 37 generates a spark.

  FIG. 7 shows the current flowing through the primary coil 37p (primary coil current), the current flowing through the secondary coil 37s (secondary coil current), and the voltage (secondary side) generated in the secondary coil 37s. It is the time chart which showed the relationship of the coil voltage. (A) of FIG. 7 shows each value when the energization time to the primary coil prior to ignition is set to time T1, and (B) of FIG. 7 shows the energization time to the primary coil that is longer than time T1. Each value when set to T2 is shown. As understood from FIGS. 7A and 7B, when the energization period to the primary side coil 37p is lengthened, the primary side coil current is increased, and thereby the secondary side coil current and the secondary side coil are increased. Both coil voltages increase. The ignition energy is a time integral value of the product of the secondary side coil current and the secondary side coil voltage. Therefore, the ignition energy can be controlled to increase by extending the energization period to the primary side coil 37p.

  Hereinafter, the operation of the third control device will be described. The CPU 81 of the third control device executes the routine shown by the flowchart in FIG. 2 and FIG. 8 instead of FIG. Of the steps shown in FIG. 8, the same steps as those shown in FIG. 3 are denoted by the same reference numerals as the steps given in FIG. 3.

<During normal operation>
During normal operation, the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, so the CPU 81 proceeds to step 805 following step 800, step 305 and step 310 in FIG. Then, control (ignition delay time normal control) for setting the ignition delay time to a normal time (first ignition delay time) is executed.

  More specifically, the CPU 81 sends an instruction signal to the igniter 38 in step 805, and executes “energization of the ignition coil 37a to the primary coil 37p” executed prior to ignition to execute ignition. Time (hereinafter referred to as “energization time”. This energization time is also referred to as a closing angle) is set to a normal time (first energization time). This energization time control is referred to as “ignition delay time normal control”. As a result, the ignition energy released by the spark plug 37 when a spark is generated becomes the first energy. Then, the CPU 81 proceeds to step 315 and executes normal operation control similar to that of the first control device.

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the current state is the idle operation state, the CPU 81 stops at step 215. The value of the hour control flag XAD is set to “1”.

  As a result, the CPU 81 makes a “Yes” determination at step 305 following step 800 in FIG. 8 and proceeds to step 810 to execute control for shortening the ignition delay time compared with the normal control of the ignition delay time (ie, the ignition delay). Execute time reduction control. As a result, the ignition delay time becomes a second ignition delay time shorter than the first ignition delay time.

  More specifically, the CPU 81 sets the “energization time” to a second energization time longer than the first energization time in step 805. As a result, the ignition energy released by the spark plug 37 when a spark is generated becomes a second energy larger than the first energy. Thereafter, the CPU 81 proceeds to step 320 to execute over-advance angle control, and continues over-advance angle control until it is determined “Yes” at step 325.

  Thereafter, the third control device operates in the same manner as the first control device. That is, the CPU 81 causes the engine 10 to generate a torque that lowers the rotational speed NE while burning the air-fuel mixture. When the engine rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 executes fuel cut and stops ignition by the spark plug. . Thereby, the engine 10 stops rotating.

  Further, when it is determined “No” in step 210 in FIG. 2 (when the engine stop request is generated and the engine is not in the idling state), the CPU 81 proceeds to step 220 and sets the fuel cut flag XFC to “1”. . Therefore, when the CPU 81 starts the process from step 800 of FIG. 8, it immediately executes the process of step 335. As a result, fuel cut is executed and ignition is stopped.

  As described above, when the engine 10 is in the idle operation state at the time when the engine stop request is generated, the third control device performs the over-advanced angle until the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth. Control is executed, and then fuel cut is executed. Therefore, the third control device can naturally exhibit the same effect as the first control device. Further, the third control device shortens the ignition delay time by increasing the ignition energy during the over-advance control. As a result, the over-advanced ignition timing is set to a retarded ignition timing as compared with the case where the ignition delay time is not shortened. Therefore, a spark can be generated from the spark plug 37 when the air-fuel mixture is compressed to a certain degree and the ignitability is good. Further, the ignition energy is increased during the over-advance control. From the above, even when the ignition timing is set to the over-advanced ignition timing, the air-fuel mixture can be ignited (combusted) more reliably.

(Fourth embodiment)
Next, a control device according to a fourth embodiment of the present invention (hereinafter also referred to as “fourth control device”) will be described. The fourth control device performs the actual compression of the engine 10 more than immediately before the determination that the engine stop request has occurred when the over-advance control is executed after the time when it is determined that the engine stop request has occurred. It is different from the first control device only in that a compression ratio increasing means for increasing the ratio is provided.

  When the ignition timing is set to the over-advanced ignition timing, ignition is performed when the air-fuel mixture is in a low compression state. For this reason, since the ignitability of the air-fuel mixture becomes poor, there is a risk that the air-fuel mixture will misfire (it will not ignite or burn). Therefore, the fourth control device increases the actual compression ratio by the compression ratio increasing means during the over-advance control. As a result, since the compressed state of the air-fuel mixture at the over-advanced ignition timing can be set to a relatively high compression state, the air-fuel mixture can be ignited (combusted) more reliably. The compression ratio increasing means in this example increases the actual compression ratio by bringing the intake valve closing timing closer to the intake bottom dead center (ie, compression bottom dead center).

  Hereinafter, the operation of the fourth control device will be described. The CPU 81 of the fourth control device executes the routines shown in the flowcharts in FIG. 2 and FIG. 9 instead of FIG. Note that, among the steps shown in FIG. 9, the same steps as those shown in FIG. 3 are denoted by the same reference numerals as the steps given in FIG.

<During normal operation>
During normal operation, the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, so the CPU 81 proceeds to step 905 following step 900, step 305 and step 310 of FIG. Then, the actual compression ratio normal control for setting the actual compression ratio to the normal compression ratio is executed.

  More specifically, in step 905, the CPU 81 sets the intake valve closing timing IC to the normal valve closing timing ICn shown in FIG. The normal valve closing timing ICn is a crank angle that is retarded from the intake bottom dead center BDC by the crank angle θ2 (θ2> 0). As a result, the air-fuel mixture starts to be compressed from the crank angle ICn. The intake valve opening timing is the crank angle IOn that is advanced from the intake top dead center by the crank angle θ1 (θ1> 0). The intake valve opening angle IVopen (crank angle width from the intake valve opening timing IOn to the intake valve closing timing ICn) is constant. Thereafter, the CPU 81 proceeds to step 315 and executes normal operation control similar to that of the first control device.

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the current state is the idle operation state, the CPU 81 stops at step 215. The value of the hour control flag XAD is set to “1”.

  As a result, the CPU 81 makes a “Yes” determination at step 305 following step 900 in FIG. 9 and proceeds to step 910 to execute control for increasing the actual compression ratio as compared to during actual compression ratio normal control (ie, actual compression ratio). (Specific increase / decrease control) is executed.

  More specifically, in step 910, the CPU 81 sets the intake valve closing timing IC to the first actual compression ratio increasing valve closing timing ICi1 shown in FIG. The first actual compression ratio increasing valve closing timing ICi1 is a crank angle that is retarded from the intake bottom dead center BDC by the crank angle θ2a (θ2a> 0). The crank angle θ2a is smaller than the aforementioned crank angle θ2. In other words, the CPU 81 brings the intake valve closing timing IC closer to the intake bottom dead center BDC than the intake valve closing timing IC (= ICn) during actual compression ratio normal control.

  Therefore, the air-fuel mixture starts to be compressed from the crank angle ICi1 that is more advanced than the crank angle ICn. As a result, the combustion chamber volume at the time when the air-fuel mixture starts to be compressed is increased, and the actual compression ratio is increased. Since the intake valve opening angle IVopen is constant, the intake valve opening timing IO is an intake valve opening timing IOi1 that is advanced from the normal intake valve opening timing IOn.

  Thereafter, the fourth control device operates in the same manner as the first control device. That is, the CPU 81 causes the engine 10 to generate a torque that lowers the rotational speed NE while burning the air-fuel mixture. When the engine rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 executes fuel cut and stops ignition by the spark plug. . Thereby, the engine 10 stops rotating.

  Further, when it is determined “No” in step 210 in FIG. 2 (when the engine stop request is generated and the engine is not in the idling state), the CPU 81 proceeds to step 220 and sets the fuel cut flag XFC to “1”. . Therefore, when the CPU 81 starts the process from step 900 of FIG. 9, it immediately executes the process of step 335. As a result, fuel cut is executed and ignition is stopped.

  As described above, if the engine 10 is in the idle operation state at the time when the engine stop request is generated, the fourth control device performs the over-advanced angle until the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth. Control is executed, and then fuel cut is executed. Accordingly, the fourth control device can naturally exhibit the same effect as the first control device. Further, the fourth control device increases the actual compression ratio during the over-advance angle control more than the actual compression ratio during the normal operation. Thereby, the ignitability of the air-fuel mixture at the over-advanced ignition timing is improved. As a result, even when the ignition timing is set to the over-advanced ignition timing, the air-fuel mixture can be ignited (combusted) more reliably.

  In the fourth control device, the valve opening period (intake valve opening crank angle width) IVopen of the intake valve 32 was constant. On the other hand, as shown in FIG. 10C, the intake valve opening crank angle width IVopen may be changed. That is, the CPU 81 sets the intake valve opening timing IO and the intake valve closing timing IC as shown in FIG. 10A during the actual compression ratio normal control, and the intake air during the actual compression ratio increase control. The valve closing timing IC may be set to the crank angle ICi1 and the intake valve opening timing IO may be set to the crank angle IOn during the actual compression ratio normal control.

  Further, in a variable compression ratio engine having a known compression ratio changing mechanism, the actual compression ratio during the actual compression ratio increase control is changed during the actual compression ratio normal control by changing the mechanical compression ratio by the compression ratio changing mechanism. The actual compression ratio may be increased. An example of such a variable compression ratio engine is an engine that moves a cylinder block and a cylinder head fixed to the cylinder block along the axial direction of the cylinder with respect to the crankcase (for example, JP-A-2006-283730, (See JP-A-2006-283730, JP-A-2005-113738, etc.). Further, regarding other variable compression ratio engines, for example, Japanese Patent Laid-Open No. 2006-257876, Japanese Patent Laid-Open No. 2001-140666, Japanese Patent Laid-Open No. 8-284702, Japanese Patent Laid-Open No. 2003-65090, and International Publication Pamphlet See WO92 / 09799 and the like.

(Fifth embodiment)
Next, a control device according to a fifth embodiment of the present invention (hereinafter also referred to as “fifth control device”) will be described. The fifth control device generates a “reducing the rotational speed of the engine 10 when the engine 10 is accompanied by the combustion of the air-fuel mixture when performing the over-advance control after the time when it is determined that the engine stop request is generated. It differs from the first control device only in that it has auxiliary load control means for controlling the auxiliary machine so as to increase the load drive required torque during the “predetermined period” that does not include the time when “torque to be maximized” is maximum. is doing. As described above, the “load drive necessary torque” is a torque necessary for the engine 10 to drive auxiliary equipment such as the generator 72 and the compressor 73.

  During the over-advance angle control, the torque that decreases the rotational speed of the engine 10 generated by the combustion of the air-fuel mixture increases every time combustion of the air-fuel mixture occurs and fluctuates with the rotation of the engine. Therefore, by increasing the “load driving necessary torque” in the “predetermined period” that does not include the time when such torque becomes maximum, the torque that reduces the rotation of the engine by the auxiliary machine in the “predetermined period”. It can be given to the engine 10. As a result, it is possible to reduce torque fluctuations for reducing the rotational speed of the engine. In other words, since the torque that functions to lower the rotational speed of the engine is flattened, it is possible to reduce vibration when the engine 10 is stopped by over-advance control.

  Hereinafter, the operation of the fifth control device will be described. In addition to the routines shown in FIGS. 2 and 3, the CPU 81 of the fifth control device further executes a routine shown by a flowchart in FIG. In the following description, the CPU 81 increases the required load driving torque by increasing the target value (target power generation voltage) of the power generation voltage of the power generator 72 and thereby increasing the power generation voltage of the power generator 72. .

<During normal operation>
During normal operation, the CPU 81 operates in the same manner as the CPU 81 of the first control device. That is, since the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, the CPU 81 executes normal operation control in step 315 of FIG.

  Further, the CPU 81 starts processing from step 1100 of FIG. 11 at a predetermined timing, and determines “No” in step 1105 for determining whether or not the value of the stop time control flag XAD is “1”. Proceeding to step 1110, normal auxiliary machine control is executed. That is, the CPU 81 sets the target generated voltage of the generator 72 to the normal voltage during normal operation. That is, the CPU 81 sends an instruction signal to the generator 72 so that the generated voltage of the generator 72 is maintained at the normal voltage. As a result, the load drive required torque becomes a normal magnitude torque (normal torque).

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the current state is the idle operation state, the CPU 81 stops at step 215. The value of the hour control flag XAD is set to “1”. As a result, the CPU 81 executes “over-advance angle control” by performing the process of step 320 in FIG.

  On the other hand, when the CPU 81 starts processing from step 1100 in FIG. 11 and proceeds to step 1105, the value of the stop time control flag XAD is set to “1”, so that “Yes” is determined in step 1105. Then, the process proceeds to Step 1115. In step 1115, the CPU 81 determines that the current crank angle θ increases from the 30 ° crank angle before the explosion top dead center (compression top dead center) of any cylinder (that is, the explosion BTDC 30 ° CA). It is determined whether or not it is within a range up to 90 ° crank angle after dead center (that is, explosion ATDC 90 ° CA).

  When over-advance control is performed, the air-fuel mixture ignited at the over-advance ignition timing is combusted during the period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA, and the combustion reduces the engine speed. Torque is generated. In other words, the “torque for reducing the rotational speed of the engine” generated by the engine 10 by the over-advanced angle control takes a maximum value within the period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA.

  In this case, if the current time is within the “period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA”, the CPU 81 makes a “Yes” determination at step 1115 to proceed to step 1120 to execute normal auxiliary machine control. To do. As a result, the load drive required torque becomes a normal magnitude torque (normal torque). Thereafter, the CPU 81 proceeds to step 1195 to end the present routine tentatively.

  On the other hand, if the current time is not within the “period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA” (that is, if the current time is within the “predetermined period”), the CPU 81 determines “No” in step 1115. It progresses to step 1125 and performs load drive required torque increase control. More specifically, the CPU 81 sets the target generated voltage of the generator 72 to “a higher voltage higher than the normal voltage”. That is, the CPU 81 sends an instruction signal to the generator 72 so that the generated voltage of the generator 72 is maintained at the high side voltage. As a result, the load drive required torque is increased to a “vibration reducing torque” larger than the “normal torque”. Thereafter, the CPU 81 proceeds to step 1195 to end the present routine tentatively.

  During the period that is not “the period from the explosion BTDC 30 ° CA of any cylinder to the explosion ATDC 90 ° CA”, the engine 10 is generated by the combustion of the air-fuel mixture by the over-advance angle control. This is a “predetermined period” that does not include the time when the “torque to be reduced” is maximized. That is, according to the fifth control device, the load driving required torque in the “predetermined period” is increased more than the load driving required torque in the “period other than the predetermined period”.

  Thereafter, the fifth control device operates in the same manner as the first control device except that the load driving torque is changed in steps 1120 and 1125. That is, the CPU 81 causes the engine 10 to generate a torque that lowers the rotational speed NE while burning the air-fuel mixture. When the engine rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 executes fuel cut and stops ignition by the spark plug. . Thereby, the engine 10 stops rotating.

  As described above, when the engine 10 is in the idle operation state at the time when the engine stop request is generated, the fifth control device performs the advance angle until the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth. Control is executed, and then fuel cut is executed. Accordingly, the fifth control device can naturally exhibit the same effect as the first control device. Furthermore, the fifth control device drives the load during a “predetermined period” that does not include the time when the “torque for reducing the rotational speed of the engine 10” generated with the combustion of the air-fuel mixture during the over-advance control is maximum. The required torque is increased by increasing the power generation amount of the generator 72. As a result, the torque that functions to reduce the rotational speed of the engine is temporally flattened, so that vibrations when the engine 10 is stopped by over-advance angle control can be reduced.

  In addition, the 5th control apparatus increased / decreased load drive required torque by changing the electric power generation voltage of the generator 72. FIG. Instead, the fifth control device changes the electromagnetic clutch 73a to a power transmission enabled state in step 1125 to drive the compressor 73 of the air conditioner in the engine 10 to increase the load drive required torque, and in step 1120. By changing the electromagnetic clutch 73a to the state in which power cannot be transmitted, the load drive required torque may be reduced so that the engine 10 does not drive the compressor 73 of the air conditioner. Further, in the fifth control device, a vehicle on which the engine 10 is mounted can drive the vehicle by both the engine 10 and the electric motor, and can cause the electric motor to generate electric power by the engine 10 depending on conditions. In the case of a hybrid vehicle (for example, the hybrid vehicle shown in the next sixth embodiment), the fifth control device can also use the electric motor as “an auxiliary device for increasing the load driving torque”.

(Sixth embodiment)
Next, a control device according to a sixth embodiment of the present invention (hereinafter also referred to as “sixth control device”) will be described. The engine 10 controlled by the sixth control device is mounted on the “hybrid vehicle 100” shown in FIG.

  The hybrid vehicle 100 is well known, and is the same engine 10 as the engine 10, a front electric motor (motor / generator) 101, a power switching unit 102, a power transmission unit 103, an inverter 104, a battery 105, and a rear electric motor (motor). A rear transaxle 106 including a generator) and a differential is provided.

The electric motor 101 has both functions of a motor that generates rotational torque and a generator that generates electric power by being rotationally driven.
The power switching unit 102 transmits the output torque of the engine 10 to the power transmission unit 103 and transmits the output torque of the electric motor 101 to the power transmission unit 103 as described in, for example, Japanese Patent Application Laid-Open No. 2003-291691. Various states such as a state in which the motor 101 is driven by the engine 10 and a state in which the engine 10 is driven by the motor 101 are achieved. Accordingly, the electric motor 101 uses a power switching unit 102 to generate a force for braking the rotation of the engine 10 based on the torque generated by the electric motor 100 itself (hereinafter referred to as “engine braking torque” or “motor torque”). It is comprised so that it can provide to the engine 10 via.

The power transmission unit 103 includes a continuously variable transmission and a differential. The power transmission unit 103 converts the torque transmitted from the power switching unit 102 into torque for rotating the front wheel axle.
The inverter 104 generates a three-phase alternating current that is energized to the three-phase winding of the stator coil of the electric motor 101 based on the electric power applied from the battery 105 in order to rotate the electric motor 101. When the electric motor 101 is generating electric power, the inverter 104 converts an AC signal applied from the electric motor 101 into a DC voltage and charges the battery 105.
The rear transaxle 106 converts the torque generated by the rear motor into torque for rotating the rear axle.

  The sixth control device is configured such that when the engine 10 is mounted on the hybrid vehicle and over-advance control is being executed after the time when it is determined that the engine stop request has occurred, the engine 10 Electric motor control means for controlling the electric motor 101 so as to generate the “engine braking torque” in a “predetermined period” that does not include a time when the “torque for reducing the rotational speed of the engine 10” generated along with combustion becomes maximum; In the point provided, it differs from the 1st control device. The “engine braking torque” is a rotational speed (a rotational speed including “0”) that is lower than the rotational speed of the engine 10 when the power switching unit 102 is used to drive the engine 10 by the motor 101. ), The motor 101 is caused to generate a force that causes the motor 101 to stop, or the motor 101 generates a force that rotates the engine 10 in a direction opposite to the rotation direction of the engine 10. It can be generated by rotating 101 or the like (for example, see Japanese Patent No. 3094859).

  During the over-advance angle control, the torque that decreases the rotational speed of the engine 10 generated by the combustion of the air-fuel mixture increases every time combustion of the air-fuel mixture occurs and fluctuates with the rotation of the engine. Therefore, the motor control means causes the motor 101 to generate “engine braking torque” in a “predetermined period” that does not include the time when such torque becomes maximum. As a result, it is possible to reduce torque fluctuations for reducing the rotational speed of the engine. In other words, since the torque that functions to lower the rotational speed of the engine is flattened, it is possible to reduce vibration when the engine 10 is stopped by over-advance control.

  Hereinafter, the operation of the sixth control device will be described. The CPU 81 of the sixth control device executes a routine shown by a flowchart in FIG. 13 in addition to the routines shown in FIGS. Of the steps shown in FIG. 13, the same steps as those shown in FIG. 11 are denoted by the same reference numerals as the steps given in FIG. 11.

<During normal operation>
During normal operation, the CPU 81 operates in the same manner as the CPU 81 of the first control device. That is, since the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, the CPU 81 executes normal operation control in step 315 of FIG.

  Further, the CPU 81 starts processing from step 1300 in FIG. 13 at a predetermined timing, and determines “No” in step 1105 for determining whether or not the value of the stop time control flag XAD is “1”. Proceeding to step 1305, normal motor control is executed. That is, the CPU 81 performs electric motor control for generating vehicle driving force from the electric motor 101 or charging the battery 105 in accordance with the driving state of the hybrid vehicle 100.

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the current state is the idle operation state, the CPU 81 stops at step 215. The value of the hour control flag XAD is set to “1”. As a result, the CPU 81 executes “over-advance angle control” by performing the process of step 320 in FIG.

  On the other hand, when the CPU 81 starts processing from step 1300 in FIG. 13 and proceeds to step 1105, the value of the stop time control flag XAD is set to “1”, so the CPU 81 determines “Yes” in step 1105. To proceed to step 1115. In step 1115, the CPU 81 determines whether or not the current time is within the range of the period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA.

  In this case, if the current time is within the “period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA”, the CPU 81 makes a “Yes” determination at step 1115 to proceed to step 1310, where “engine braking by the motor 101 is performed. Control (braking torque generation stop control) to set “torque” to “0” is executed. For example, in this state, the electric motor 101 is disconnected from the engine 10 (that is, the engine 10 and the electric motor 101 cannot transmit power to each other). Thereafter, the CPU 81 proceeds to step 1395 to end the present routine tentatively.

  On the other hand, if the current time is not within the “period from the explosion BTDC 30 ° CA to the explosion ATDC 90 ° CA” (that is, if the current time is within the “predetermined period”), the CPU 81 determines “No” in step 1115. In step 1315, the motor 101 and the power switching unit 102 are controlled so as to generate the “engine braking torque”. As a result, the engine braking torque is increased (generated). Thereafter, the CPU 81 proceeds to step 1395 to end the present routine tentatively.

  During the period that is not “the period from the explosion BTDC 30 ° CA of any cylinder to the explosion ATDC 90 ° CA”, the “torque that reduces the rotational speed of the engine 10” that occurs along with combustion of the air-fuel mixture by over-advance control “Predetermined period” that does not include the time when “ That is, according to the sixth control device, the engine braking torque in the “predetermined period” is increased more than the engine braking torque in the “period other than the predetermined period”.

  Thereafter, the sixth control device operates in the same manner as the first control device except for the control of the electric motor 101. That is, the CPU 81 causes the engine 10 to generate a torque that lowers the rotational speed NE while burning the air-fuel mixture. When the engine rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 executes fuel cut and stops ignition by the spark plug. . Thereby, the engine 10 stops rotating.

  As described above, when the engine stop request is generated, if the engine 10 is in the idle operation state, the sixth control device determines that the over-advance angle until the rotational speed NE becomes equal to or less than the threshold rotational speed NEth. Control is executed, and then fuel cut is executed. Therefore, the sixth control device can naturally exhibit the same effect as the first control device. Further, the sixth control device performs engine braking in a “predetermined period” that does not include a time when the “torque for reducing the rotational speed of the engine 10” generated during combustion of the air-fuel mixture during over-advance control is maximized. Torque (motor torque) is generated using the motor 101. As a result, the torque that functions to reduce the rotational speed of the engine is temporally flattened, so that vibrations when the engine 10 is stopped by over-advance angle control can be reduced.

(Seventh embodiment)
Next, a control device according to a seventh embodiment of the present invention (hereinafter also referred to as “seventh control device”) will be described. The seventh control device performs the following control after the time point when it is determined that the engine stop request has occurred.
(1) The seventh control device sets the ignition timing to a retarded ignition timing that is retarded from the optimal ignition timing, thereby reducing the torque of the engine 10 while burning the air-fuel mixture (that is, the engine 10 A retard control is performed in which the engine 10 generates a torque that reduces the rotation speed. If the ignition timing at which it is determined that the engine stop request has occurred is an ignition timing that is retarded from the optimal ignition timing, the seventh control device further ignites the ignition timing from the retarded ignition timing. Delay the time. That is, the seventh control device sets the ignition timing to the retarded ignition timing that is retarded from the ignition timing at the time when it is determined that the engine stop request has occurred.

(2) The seventh controller increases the load driving force torque that increases the torque required for the engine 10 to drive the auxiliary machine (that is, the above-described “load driving necessary torque”) during the retard control. Increase control is executed.
(3) When the rotational speed NE becomes lower than the threshold rotational speed NEth (when a predetermined control end condition is satisfied), the seventh control device executes fuel cut.

  Hereinafter, the operation of the seventh control device will be described more specifically. The CPU 81 of the seventh control device executes the routines shown in the flowcharts in FIG. 2 and FIG. 14 instead of FIG. Of the steps shown in FIG. 14, the same steps as those shown in FIG. 3 are denoted by the same reference numerals as the steps given in FIG.

<During normal operation>
During normal operation, the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, so the CPU 81 proceeds to step 315 following step 1400, step 305 and step 310 of FIG. The normal operation control similar to that of the first control device is executed. Next, the CPU 81 proceeds to step 1405 to execute normal auxiliary machine control. That is, the CPU 81 sets the target generated voltage of the generator 72 to the normal voltage during normal operation. In other words, the CPU 81 sends an instruction signal to the generator 72 so that the generated voltage of the generator 72 is maintained at the normal voltage. As a result, the load drive required torque becomes a normal magnitude torque (normal torque).

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the time is in the idling operation state, the CPU 81 performs step 215 in FIG. The value of the stop time control flag XAD is set to “1”. As a result, the CPU 81 makes a “Yes” determination at step 305 in FIG. 14 and proceeds to step 1410 to execute “retard angle control” described below.

(1) The CPU 81 determines the optimal ignition timing θmbt in the same way as during normal operation.
(2) The CPU 81 determines the retard amount θrtd (θrtd> 0) based on the retard amount table that defines the relationship between the engine speed NE and the retard amount θrtd and the actual engine speed NE. The retardation amount table is determined in advance by experiments or the like and stored in the ROM 72. Based on the retard amount table of this example, the retard amount θrtd is determined to decrease as the engine speed NE increases.

(3) The CPU 81 obtains the retarded ignition timing θig by subtracting the retarded amount θrtd obtained from the obtained optimum ignition timing θmbt. That is, the retarded ignition timing θig is a timing obtained by retarding the optimum ignition timing θmbt by the retard amount θrtd. Then, the CPU 81 executes an ignition execution routine (not shown) so that a spark is generated from the ignition plug 37 of the cylinder when the crank angle of the cylinder in the compression process coincides with the retard ignition timing θig. An instruction signal is sent to the igniter 38 of the cylinder. As a result, a spark is generated from the spark plug 37 at the retarded ignition timing θig, and the air-fuel mixture is ignited and burned.

  Note that the CPU 81 is at a time point when it is determined that the engine stop request has occurred (a time point immediately before the value of the stop time control flag XAD is set to “1” and determined “Yes” in step 305). If the ignition timing is the ignition timing θd that is retarded from the optimal ignition timing θmbt, in step 1410, the ignition timing is further retarded by θrtd from the retarded ignition timing θd. That is, the CPU 81 may set the ignition timing to a retard ignition timing that is retarded from the ignition timing at the time when it is determined that the engine stop request has occurred.

(4) On the other hand, the CPU 81 continues the fuel supply (fuel injection) by executing a fuel injection execution routine (not shown). Even in this case, the fuel injection amount is determined so that the air-fuel ratio of the air-fuel mixture supplied to the engine matches the stoichiometric air-fuel ratio.

  As a result, since the actual ignition timing coincides with the retarded ignition timing θig, the output torque of the engine 10 is lower than the output torque immediately before the engine stop request is generated when the ignition timing is set to the optimal ignition timing θmbt. That is, the engine 10 generates a torque that reduces the rotational speed NE at that time while continuing combustion. As a result, the rotational speed NE of the engine 10 gradually decreases. At this time, since the combustion of the air-fuel mixture is continued in the combustion chamber 25, the exhaust gas is discharged from the engine 10. In other words, air containing a large amount of oxygen is not discharged from the engine 10. Therefore, a large amount of oxygen does not flow into the catalyst 53 and the catalyst 54. “Control that continues combustion while setting the ignition timing to the retarded ignition timing that is retarded from the optimal ignition timing (or the ignition timing immediately before the engine stop request is generated), thereby lowering the engine speed” Is called “retard angle control”.

  Next, the CPU 81 proceeds to step 1415 to execute load drive necessary torque increase control. More specifically, the CPU 81 sets the target generated voltage of the generator 72 to “a higher voltage higher than the normal voltage”. That is, the CPU 81 sends an instruction signal to the generator 72 so that the generated voltage of the generator 72 is maintained at the high side voltage. Thereby, the load drive required torque is increased to a torque larger than the “normal torque”.

  Thereafter, the CPU 81 proceeds to step 325 to determine whether or not the rotational speed NE has become equal to or lower than the threshold rotational speed NEth. If the rotational speed NE is greater than the threshold rotational speed NEth, the process proceeds directly to step 1495 to end the present routine tentatively. On the other hand, when the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 proceeds to step 330 and sets the value of the stop time control flag XAD to “0” and sets the value of the fuel cut flag XFC to “1”. Then, the process proceeds to step 1495 to end the present routine tentatively.

  As a result, the CPU 81 performs the retard control and the load driving torque for a period from the time when the engine stop request is generated until the time when the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth (that is, until a predetermined control end condition is satisfied). Increase control is executed. Further, when the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth, the CPU 81 proceeds to step 335 in FIG. 14 to execute fuel cut and stop ignition by the spark plug. Thereby, the engine 10 stops rotating.

  As described above, the seventh control device sets the ignition timing after the time when it is determined by the ignition timing control means (step 1410) that the engine stop request has occurred to the “retarded ignition timing”. As a result, the torque generated with the combustion of the air-fuel mixture decreases. In other words, the engine 10 generates torque that lowers the rotational speed of the engine 10 while burning the air-fuel mixture. Further, the auxiliary load control means (step 1415) increases the load drive required torque after the time when it is determined that the engine stop request has been generated (as compared to immediately before the determination). As a result, the rotational speed of the engine 10 decreases relatively quickly. When a predetermined control end condition (condition that the engine rotational speed NE is equal to or lower than the predetermined value NEth) is satisfied, the fuel supply control means (step 335) stops the fuel supply.

  Therefore, since the rotational speed of the engine 10 can be reduced while the air-fuel mixture is burned, air containing a large amount of oxygen is not discharged from the engine 10 during the period until the rotational speed of the engine 10 is reduced. Furthermore, since the fuel supply is stopped after the rotational speed of the engine 10 is reduced, even if the engine 10 rotates due to inertia, the amount of rotation can be made very small. As a result, the amount of air discharged from the engine 10 and flowing into the catalyst 53 and the catalyst 54 becomes very small. Therefore, as described above, fuel consumption can be improved while suppressing NOx and PM emissions during restart. Furthermore, it is possible to suppress the deterioration of the catalytic functions of the catalyst 53 and the catalyst 54.

(Eighth embodiment)
Next, a control device according to an eighth embodiment of the present invention (hereinafter also referred to as “eighth control device”) will be described. The eighth control device is applied when the engine 10 is mounted on the hybrid vehicle 100 as in the sixth control device.

  Further, the eighth control device executes “motor normal control” instead of the normal auxiliary machine control (step 1405 in FIG. 14) by the seventh control device, and the load drive necessary torque increase control by the seventh control device. It differs from the seventh control device in that “braking torque generation control” by the electric motor 101 is executed instead of (step 1415 in FIG. 14).

  More specifically, the CPU 81 of the eighth control apparatus executes the routines shown in the flowcharts in FIG. 2 and FIG. 15 instead of FIG. Of the steps shown in FIG. 15, the same steps as those shown in FIG. 3 are denoted by the same reference numerals as the steps given in FIG. 3.

<During normal operation>
During normal operation, the value of the stop time control flag XAD and the value of the fuel cut flag XFC are both maintained at “0”, so the CPU 81 proceeds to step 315 following step 1500, step 305 and step 310 in FIG. The normal operation control similar to that of the first control device is executed. Next, the CPU 81 proceeds to step 1505 and executes normal motor control. That is, the CPU 81 performs electric motor control for generating vehicle driving force from the electric motor 101 or charging the battery 105 in accordance with the driving state of the hybrid vehicle 100.

<When an engine stop request occurs (when an engine stops)>
During the normal operation, when the engine stop request is generated when the IG switch 71 is changed from the on position to the off position, and the time is in the idling operation state, the CPU 81 performs step 215 in FIG. The value of the stop time control flag XAD is set to “1”. As a result, the CPU 81 proceeds from step 305 to step 1510 in FIG. 15 to execute “retard angle control”. The processing in step 1510 is the same as the processing in step 1410 shown in FIG. That is, the CPU 81 sets the ignition timing to the retarded ignition timing (θmbt−θrtd) that is retarded by the retard amount θrtd from the optimal ignition timing θmbt, thereby delaying the torque of the engine 10 while burning the air-fuel mixture. Execute angle control.

  The CPU 81 determines the ignition timing at the time when it is determined that the engine stop request has occurred (when the value of the stop time control flag XAD is set to “1” and “Yes” is determined in step 305). Is the ignition timing θd retarded from the optimal ignition timing θmbt, in step 1510, the ignition timing is further retarded by θrtd from the retarded ignition timing θd. That is, the CPU 81 may set the ignition timing to a retard ignition timing that is retarded from the ignition timing at the time when it is determined that the engine stop request has occurred.

  Next, the CPU 81 proceeds to step 1515 to perform braking torque generation control. That is, the CPU 81 controls the electric motor 101 and the power switching unit 102 so as to generate the “engine braking torque” by performing the same process as the process of step 1315 of FIG.

  Furthermore, the CPU continues the “retard angle control” and “braking torque generation control” until the rotational speed NE becomes equal to or lower than the threshold rotational speed NEth by the processing of Step 325 and Step 330, and the rotational speed NE is equal to or lower than the threshold rotational speed NEth. In step 335, the fuel cut and ignition are stopped.

  As described above, the eighth control device sets the ignition timing after the time when it is determined by the ignition timing control means (step 1510) that the engine stop request has occurred to the “retarded ignition timing”. As a result, the torque generated with the combustion of the air-fuel mixture decreases. In other words, the engine 10 generates torque that lowers the rotational speed of the engine 10 while burning the air-fuel mixture. Further, the engine control torque (step 1515) increases the engine braking torque by the motor 101 after the time point when it is determined that the engine stop request is generated. As a result, the rotational speed of the engine 10 decreases relatively quickly. When a predetermined control end condition (condition that the engine rotational speed NE is equal to or lower than the predetermined value NEth) is satisfied, the fuel supply control means (step 335) stops the fuel supply.

  Therefore, since the rotational speed of the engine 10 can be reduced while the air-fuel mixture is burned, air containing a large amount of oxygen is not discharged from the engine 10 during the period until the rotational speed of the engine 10 is reduced. Furthermore, since the fuel supply is stopped after the rotational speed of the engine 10 is reduced, even if the engine 10 rotates due to inertia, the amount of rotation can be made very small. As a result, the amount of air discharged from the engine 10 and flowing into the catalyst 53 and the catalyst 54 becomes very small. Therefore, as described above, fuel consumption can be improved while suppressing NOx and PM emissions during restart. Furthermore, it is possible to suppress the deterioration of the catalytic functions of the catalyst 53 and the catalyst 54.

  As described above, according to the control apparatus for an internal combustion engine according to each embodiment of the present invention, after the engine stop request is generated, the rotational speed of the engine 10 is reduced to the engine 10 itself while the air-fuel mixture is burned. Generate torque. When the engine speed NE reaches the threshold speed NEth, the fuel supply is stopped and the ignition is stopped to stop the engine 10 from rotating. Accordingly, since the amount of air exhausted from the engine (the amount of oxygen) can be reduced during the period from when the engine stop request is generated until the engine stops, the fuel consumption can be improved and the NOx emission amount Various effects such as reduction, reduction of PM emission, and suppression of catalyst deterioration can be realized.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, the “engine stop request” is generated when the driver changes the IG switch 71 from the on position to the off position. Alternatively, or in addition, the “engine stop request” may be automatically generated when the operation state of the vehicle on which the engine 10 is mounted is in an operation state in which the engine may be stopped. Good. When the driving state of the vehicle is in a driving state where the engine may be stopped, for example, when the vehicle on which the engine 10 is mounted is in a driving state in which idle driving continues for a predetermined time or more in a signal waiting state, and This is the case when the hybrid vehicle equipped with the engine 10 is in an operating state in which the driving force of the vehicle is generated only by the electric motor 101.

  In addition, the control content according to each embodiment that executes the over-advance angle control can be used in appropriate combination with the control content of the other embodiments that execute the over-advance angle control. That is, for example, the combustion rate increase control according to the second embodiment and the ignition delay time reduction control according to the third embodiment may be used in combination. Further, the injector 39 in each of the above embodiments is arranged to inject fuel into the intake passage, but it may be an “in-cylinder injector” that injects fuel directly into the combustion chamber 25. In addition, after the predetermined control end condition (NE ≦ NEth) is satisfied, the fuel supply is stopped, but the execution of ignition (spark generation) may be continued. Further, the control end condition in step 325 or the like in FIG. 3 may be set to a condition that is satisfied when a predetermined time or a predetermined crank angle has elapsed since the start of “over-advance angle control” or “retard angle control”. .

1 is a schematic view of an internal combustion engine to which a control device according to a first embodiment of the present invention is applied. It is the flowchart which showed the routine which CPU shown in FIG. 1 performs. It is the flowchart which showed the routine which CPU shown in FIG. 1 performs. It is the graph which showed the relationship between the ignition timing and the torque which an engine generate | occur | produces according to the combustion speed. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on 2nd Embodiment of this invention performs. FIG. 2 is a circuit diagram of a spark plug, an ignition coil, and an igniter shown in FIG. 1. (A) is a time chart showing the primary coil current, the secondary coil current, and the secondary coil voltage shown in FIG. 6 when the energization time of the primary coil is set to a short time. (B) is a time chart showing the relationship between the primary side coil current, the secondary side coil current, and the secondary side coil voltage when the energization time of the primary side coil is set to a long time. . It is the flowchart which showed the routine which CPU of the control apparatus which concerns on 3rd Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on 4th Embodiment of this invention performs. It is a figure for demonstrating the intake valve opening timing and intake valve closing timing which are set in 4th Embodiment of this invention. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on 5th Embodiment of this invention performs. It is a schematic system diagram of a vehicle to which a control device of a sixth embodiment of the present invention is applied. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on 6th Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control device which concerns on 7th Embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control device which concerns on 8th Embodiment of this invention performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 22 ... Piston, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 33 ... Intake valve control device, 37 ... Spark plug, 37a ... Ignition coil, 38 ... Igniter, 39 ... injector (fuel injection means), 43 ... throttle valve, 53 ... upstream catalyst (first catalyst), 54 ... downstream catalyst (second catalyst), 71 ... ignition key switch, 72 ... generator, 73 ... Air conditioner compressor, 73a ... electromagnetic clutch, 80 ... electric control device, 100 ... hybrid vehicle, 101 ... electric motor.

Claims (11)

An internal combustion engine control device applied to an internal combustion engine comprising ignition means for generating sparks in a combustion chamber, fuel supply means for supplying fuel to the combustion chamber, and a catalyst disposed in an exhaust passage,
Engine stop request determining means for determining whether or not an engine stop request for stopping operation of the engine has occurred;
The ignition means and the fuel so that the engine generates a torque that lowers the rotational speed of the engine while burning the air-fuel mixture in the combustion chamber of the engine after it is determined that the engine stop request is generated. Stop control means for controlling the supply means;
The control apparatus of the internal combustion engine provided with. A control device for an internal combustion engine according to claim 1,
The stop control means includes
The ignition means is controlled so that the ignition timing of the engine becomes an over-advanced ignition timing advanced from an optimal ignition timing that causes the engine to generate a maximum torque after the time when it is determined that the engine stop request is generated. Ignition timing control means for
The supply of the fuel is continued from the time when it is determined that the engine stop request is generated until the time when the predetermined control end condition is satisfied, and the supply of the fuel is stopped after the time when the control end condition is satisfied. A fuel supply control means for controlling the fuel supply means;
A control device for an internal combustion engine, including: A control device for an internal combustion engine according to claim 2,
An auxiliary machine driven by the engine,
The stop control means further includes
After the time when it is determined that the engine stop request has been generated, the auxiliary machine is driven for a predetermined period that does not include the time when the torque that decreases the rotational speed of the engine generated by the combustion of the air-fuel mixture becomes maximum. A control device for an internal combustion engine comprising auxiliary load control means for controlling the auxiliary machine so as to increase the torque required for the engine. A control apparatus for an internal combustion engine according to claim 2 or claim 3,
The stop control means further includes
A control apparatus for an internal combustion engine, comprising combustion speed increasing means for increasing the combustion speed of the air-fuel mixture in the combustion chamber of the engine after the time when it is determined that the engine stop request is generated, immediately before the determination is made. A control device for an internal combustion engine according to any one of claims 2 to 4,
The stop control means further includes
The ignition delay time from the time when the spark is generated in the combustion chamber of the engine to the time when the air-fuel mixture in the combustion chamber is ignited is more than just before the determination is made after the determination that the engine stop request is generated. A control device for an internal combustion engine comprising means for shortening an ignition delay time to shorten. A control device for an internal combustion engine according to claim 5,
The control device for an internal combustion engine, wherein the ignition delay time shortening means is ignition energy increasing means for increasing ignition energy generated by the ignition means in one spark generation operation period. A control device for an internal combustion engine according to any one of claims 2 to 6,
The stop control means further includes
A control apparatus for an internal combustion engine, comprising compression ratio increasing means for increasing the actual compression ratio of the engine more than immediately before the determination is made after the time when it is determined that the engine stop request is generated. A control device for an internal combustion engine according to any one of claims 2 to 7,
An electric motor capable of generating a torque for braking the rotation of the engine;
The stop control means further includes
After the time when it is determined that the engine stop request is generated, the electric motor is supplied to the electric motor in a predetermined period that does not include a time when the torque that decreases the rotation speed of the engine that occurs due to combustion of the air-fuel mixture becomes maximum. A control apparatus for an internal combustion engine, comprising an electric motor control means for controlling the electric motor so as to generate a torque for braking the rotation of the engine. A control device for an internal combustion engine according to claim 1,
An auxiliary machine driven by the engine,
The stop control means includes
After the time when it is determined that the engine stop request has been generated, the ignition timing of the engine is retarded from the optimal ignition timing at which the engine generates maximum torque or at the time when it is determined that the engine stop request has occurred. Ignition timing control means for controlling the ignition means so as to become a retarded ignition timing that is retarded from the ignition timing;
The supply of the fuel is continued from the time when it is determined that the engine stop request is generated until the time when the predetermined control end condition is satisfied, and the supply of the fuel is stopped after the time when the control end condition is satisfied. A fuel supply control means for controlling the fuel supply means;
Auxiliary machine load control means for controlling the auxiliary machine so as to increase the torque required for the engine in order to drive the auxiliary machine after the time when it is determined that the engine stop request has occurred;
A control device for an internal combustion engine, including: A control device for an internal combustion engine according to claim 1,
An electric motor capable of generating a torque for braking the rotation of the engine;
The stop control means further includes
After the time when it is determined that the engine stop request has been generated, the ignition timing of the engine is retarded from the optimal ignition timing at which the engine generates maximum torque or at the time when it is determined that the engine stop request has occurred. Ignition timing control means for controlling the ignition means so as to become a retarded ignition timing that is retarded from the ignition timing;
The fuel supply is continued from the time when it is determined that the engine stop request is generated until the predetermined end condition is satisfied, and the fuel supply is stopped after the end condition is satisfied. Fuel supply control means for controlling the fuel supply means;
Electric motor control means for controlling the electric motor so as to generate torque for braking the rotation of the engine after the time when it is determined that the engine stop request is generated;
A control device for an internal combustion engine, including: The control apparatus for an internal combustion engine according to any one of claims 1 to 10,
The control apparatus for an internal combustion engine, wherein the control end condition is determined to be satisfied when a rotation speed of the engine becomes a predetermined rotation speed or less.

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