JP6877935B2 - Engine control unit - Google Patents

Description

The present invention relates to an engine control device, particularly a device capable of suppressing an excessive increase in engine speed immediately after starting and improving fuel efficiency.

For example, in a gasoline engine for automobiles, in order to ensure good startability even if there are variations in fuel properties or individual differences in the engine, the crankshaft rotation speed is generally once higher than the target idle speed. It is common to control the engine to converge by decreasing it to the target idle speed after increasing it to.
However, in a vehicle equipped with an idle stop system (ISS) that automatically stops the engine when the vehicle is stopped and automatically restarts the engine when a predetermined restart condition is satisfied, the transmission is in a running state ( Since the engine is started in the D range), if the amount of increase in the crankshaft rotation speed at the time of restart is excessively large, the driver feels a strong feeling of popping out when starting from the restart, which is unpleasant. You may feel it.

As a conventional technique relating to control at the time of restarting the engine, for example, in Patent Document 1, restarting after the engine is stopped by idle stop is performed by in-cylinder fuel injection and ignition to an expansion stroke cylinder or the like, and at the time of restarting. It is described that the fuel is dividedly injected at a predetermined time and distribution.
Patent Document 2 describes the fuel injection amount for each of a plurality of regions defined by the engine speed and the pressure in the intake pipe for the purpose of optimizing the fuel injection amount at the time of restarting the internal combustion engine after the idle stop. It is described that the fuel injection amount is determined by referring to the learned value when the engine transitions to the same operating region again after the learning.
Patent Document 3 describes a change in engine speed after the stop control is executed when a restart condition is satisfied for the purpose of avoiding deterioration of fuel efficiency at restart at idling stop and deterioration of exhaust gas performance. It is described that the fuel injection amount at the time of starting is corrected according to the speed, and the deterioration of fuel efficiency and the deterioration of the quality of exhaust gas due to the injection of more fuel than necessary at the time of restarting are prevented.
In Patent Document 4, in the automatic start control after the automatic stop control of a diesel engine that controls torque according to the fuel injection amount, an upper limit value of the amount of depression of the accelerator pedal is set to prevent sudden start at the time of restart, and the occupant. It is described that the fuel injection amount is such that a torque that does not give a feeling of strangeness such as popping out can be obtained.

Japanese Unexamined Patent Publication No. 2006-161676 Japanese Unexamined Patent Publication No. 2015-08623 Japanese Unexamined Patent Publication No. 2012-154279 Japanese Unexamined Patent Publication No. 2004-218606

Ignition timing is immediately after the judgment of complete explosion (a state in which the air-fuel mixture is normally ignited in each cylinder) in order to prevent the crankshaft rotation speed from rising excessively when the engine is restarted by idle stop control. May be controlled to significantly retard (retard) the engine during normal operation, worsen combustion, and suppress the generated torque.
However, such ignition timing retard deteriorates the thermal efficiency of the engine and causes a loss from the viewpoint of effective use of the energy generated by the supplied fuel, and the effect of improving fuel efficiency by idle stop control is achieved. It will reduce some of them.
In view of the above-mentioned problems, an object of the present invention is to provide an engine control device capable of suppressing an excessive increase in engine speed immediately after starting and improving fuel efficiency.

The present invention solves the above-mentioned problems by the following solutions.
The invention according to claim 1 is an engine control device for controlling an engine, wherein a complete explosion determining means for determining complete explosion after the engine is started and a predetermined period after the complete explosion determining means determines complete explosion. The rotation change detecting means for detecting the amount of change in the rotation speed of the output shaft in the above, and when the amount of change in the rotation speed is equal to or greater than a predetermined threshold value, the number of fuel cuts is increased according to the increase in the amount of change in the rotation speed. The engine control device is characterized by comprising a fuel injection control means for stopping fuel injection of at least one cylinder for the number of fuel cuts after setting and then restarting fuel injection.
According to this, the ignition timing is set while fuel injection is performed by suppressing an excessive increase in the rotation speed of the output shaft after the engine is completely detonated by using torque reduction due to the stoppage of fuel injection (fuel cut). Fuel consumption can be suppressed compared to the existing technology of retarding and reducing torque.
In addition, by determining the necessity of fuel cut according to the amount of change in the rotational speed, an appropriate rotational increase history (even if there are variations in fuel properties, environmental factors, individual differences in the engine, etc.) Rotational profile) can be obtained.

Further , by extending the fuel cut period according to the increase in the amount of change in the rotational speed, an appropriate effect of suppressing the increase in rotation according to the amount of change in the rotational speed can be obtained, and the ascending speed of rotation can be controlled more appropriately. Can be done.

According to the second aspect of the present invention, the engine has a plurality of cylinders, and when the fuel injection control means stops the fuel injection, the fuel injection of all the cylinders is performed after the fuel injection of only a part of the cylinders is stopped. The engine control device according to claim 1, wherein the engine control device is shifted to a stopped state.
According to this, it is possible to suppress a sudden decrease in the engine output torque when starting the fuel cut, and to prevent the occurrence of a shock due to a sudden change in the rotation speed.

According to the third aspect of the present invention, the engine has a plurality of cylinders, and the fuel injection control means is among the cylinders in which fuel injection is stopped when the fuel cut period ends and fuel injection is restarted. The engine control device according to claim 1 or 2 , wherein the fuel injection of only some cylinders is restarted and then the fuel injection of all cylinders is restarted.
According to this, it is possible to suppress a sudden increase in the engine output torque when returning from the fuel cut, and to prevent the occurrence of a shock due to a sudden change in the rotation speed.

The invention according to claim 4, wherein the fuel injection control means, the number of resume cylinders subsequent fuel injection is stopped the fuel injection over prior Symbol fuel cut number increases with the increase of the rotation speed variation The engine control device according to claim 1, wherein the engine control device is characterized by the above.
According to this, by executing the fuel cut only for some cylinders when the amount of change in the rotation speed is relatively small, it is possible to prevent the increase in the rotation speed from suddenly decelerating and to make the increase speed of the rotation more appropriate. Can be controlled.

As described above, according to the present invention, it is possible to provide an engine control device capable of suppressing an excessive increase in engine speed immediately after starting and improving fuel efficiency.

It is a figure which shows the structure of the engine which comprises Example 1 of the engine control device to which this invention is applied. It is a flowchart which shows the fuel injection control at the time of engine restart in the engine control apparatus of Example 1. FIG. It is a figure which shows an example of the transition of the rotation speed, the ignition timing, and the fuel injection signal at the time of restarting an engine in the engine control device which is a comparative example of this invention. It is a figure which shows an example of the transition of the rotation speed, ignition timing, and a fuel injection signal at the time of restarting an engine in the engine control device of Example 1. It is a figure which shows an example of the transition of the rotation speed, the ignition timing, and the fuel injection signal at the time of restarting an engine in Example 2 of the engine control device to which this invention is applied. It is a flowchart which shows the fuel injection control at the time of engine restart in Example 3 of the engine control apparatus to which this invention was applied. It is a figure which shows an example of the transition of the rotation speed, ignition timing, and a fuel injection signal at the time of restarting an engine in the engine control device of Example 3.

Hereinafter, Example 1 of a fuel injection device to which the present invention is applied will be described.
The engine control device of the embodiment is provided in, for example, a gasoline direct injection engine mounted as a power source for traveling in an automobile such as a passenger car, and controls the engine and its accessories in an integrated manner.

FIG. 1 is a diagram showing a configuration of an engine including the engine control device of the first embodiment.
The engine 1 is, for example, a 4-stroke horizontally opposed 4-cylinder gasoline engine.
The rotational output of a crankshaft (not shown), which is the output shaft of the engine 1, is, for example, a transmission such as a continuously variable transmission (CVT) having a variator, a torque converter, etc., and an AWD transfer, a propeller shaft, a final reduction gear, and the like. It is transmitted to the drive wheels of the vehicle via a drive force transmission mechanism (not shown) having a differential, a drive shaft, or the like.

The engine 1 has a first cylinder 10, a second cylinder 20, a third cylinder 30, and a fourth cylinder 40 that are sequentially arranged from the front end side (opposite side of the transmission) of a crankshaft (not shown).
For example, in the engine 1, the crankshafts are arranged vertically along the front-rear direction of the vehicle, and the first cylinder 10 and the third cylinder 30 are arranged in the right bank, the second cylinder 20, and the second cylinder on the right side in the vehicle width direction. The 4-cylinder 40 is housed in a left bank arranged on the left side in the vehicle width direction.
The first cylinder 10 and the second cylinder 20, the third cylinder 30 and the fourth cylinder 40 are arranged so as to substantially face each other with the crankshaft sandwiched in a state where the offset amount of the crankpin of each cylinder is shifted. ..
The firing order (explosion order) in the engine 1 is set in the order of the first cylinder 10, the third cylinder 30, the second cylinder 20, and the fourth cylinder 40, and ignites at substantially equal intervals at every 180 ° in the crank angle. It is supposed to (explode).

Each cylinder 10 to 40 includes a cylinder, a piston, a combustion chamber, an intake / exhaust port, an intake / exhaust valve, a valve drive mechanism, etc., as well as injectors 11, 21, 31, 41, spark plugs 12, 22, 32, 42, etc. Has.
The cylinder has a tubular cylinder sleeve into which the piston is inserted so that it can reciprocate.
The piston is a member that receives the pressure of the combustion gas and is connected to the crank pin of the crankshaft via a connecting rod.
The combustion chamber is formed by recessing a surface portion of the cylinder head facing the piston crown surface, and forms a part of a space portion in which the air-fuel mixture burns.
The intake port is a flow path for introducing fresh air into the combustion chamber.
The exhaust port is a flow path for discharging exhaust gas (burned gas) from the combustion chamber.
The intake valve, the exhaust valve, the intake port and the exhaust port are opened and closed at predetermined valve timings.
The valve drive mechanism is a mechanism for driving an intake / exhaust valve, and includes a camshaft or the like that rotates synchronously at half the rotation speed of the crankshaft.

The injectors 11 to 41 are injection devices that inject atomized gasoline into the combustion chamber of each cylinder.
The fuel (gasoline) stored in the fuel tank (not shown) is conveyed to the high-pressure pump linked with the camshaft of the engine 1 by the feed pump provided in the fuel tank, boosted by the high-pressure pump, and then the injectors 11 to 1 of each cylinder. It is supplied to 41.
The injectors 11 to 41 inject the fuel accumulated at high pressure over the valve opening period of the solenoid valve.
The fuel injection amount and the fuel injection timing of the injectors 11 to 41 are controlled by the engine control unit 100 according to the operating state of the engine 1.

During normal operation, the engine control unit 100 calculates the basic injection amount based on the output value of the air flow meter that detects the intake air amount (fresh air flow rate) of the engine, and the air-fuel ratio sensor provided in the exhaust system. The target fuel injection amount is calculated by performing various corrections such as air-fuel ratio feedback using the output, and a fuel injection signal is generated.
The engine control unit 100 gives a fuel injection signal, which is a pulse signal, to the injectors 11 to 41 of each cylinder.
The pulse width of the fuel injection signal correlates with the valve opening time of the injectors 11 to 41, and the engine control unit 100 sets the pulse width according to the target fuel injection amount.

The spark plugs 12 to 42 ignite the air-fuel mixture formed in each cylinder by an electric spark.
The ignition timing of the spark plugs 12 to 42 is controlled by the engine control unit 100.
The ignition timing of the spark plugs 12 to 42 is set near the ignition timing (MBT) at which the maximum torque is obtained during the normal operation of the engine 1.
In addition to these, the engine 1 has an intake device 50 that introduces fresh air (combustion air) into each cylinder, an exhaust device (not shown), an exhaust gas aftertreatment device, a supercharging device, a valve timing variable device, a cooling device, a lubrication device, and an EGR. It is configured to have equipment and the like.

The intake device 50 introduces fresh air into the engine 1.
The intake device 50 includes a throttle valve 51, a throttle actuator 52, an intake manifold 53, and the like.
The throttle valve 51 is a butterfly valve that controls the flow rate of combustion air (fresh air) introduced through an air cleaner (not shown) and adjusts the output of the engine 1.
The throttle actuator 52 is an electric actuator that opens and closes and drives the throttle valve 51.
The throttle actuator 52 is feedback-controlled so that the actual opening degree of the throttle valve 51 detected by the throttle opening degree sensor (not shown) approaches the target opening degree set by the engine control unit 100.
The intake manifold 53 is a branch pipe that distributes fresh air that has passed through the throttle valve 51 and introduces the fresh air into the intake ports of the cylinders 10 to 40.

The engine 1 further includes a crank angle sensor 60, a starter motor 70, and the like.
The crank angle sensor 60 sequentially detects the angular position of the crankshaft.
The crank angle sensor 60 includes a sensor plate 61, a position sensor 62, and the like.
The sensor plate 61 is a disk-shaped member fixed to the front end of the crankshaft, and has a sprocket-like shape formed by radially projecting a plurality of vanes (teeth) at predetermined angular intervals on the outer peripheral edge. It has become.
The position sensor 62 is a magnetic pickup arranged so as to face the outer peripheral edge of the sensor plate 61, and has a magnet, a core, a coil, a terminal, and the like.
The position sensor 62 outputs a predetermined pulse signal when the vane of the sensor plate 61 passes immediately before.
The engine control unit 100 can calculate the rotation speed (crankshaft rotation speed) of the engine 1 based on the output of the crank angle sensor 60.

The starter motor 70 is an electric actuator that rotationally drives the crankshaft when the engine 1 is started.
The starter motor 70 has a pinion gear that drives a gear portion formed on the outer peripheral edge of a flywheel (not shown), and a starter relay that switches energization on / off in response to a command from the engine control unit 100. The crankshaft is rotationally driven at a speed of, for example, about 200 rpm.

The engine control unit (ECU) 100 comprehensively controls the engine 1 and its accessories.
The engine control unit 100 includes, for example, an information processing device such as a CPU, a storage device such as a RAM or ROM, an input / output interface, and a bus connecting these.
The engine control unit 100 includes the opening degree of the throttle valve 51, the fuel injection amount of the injectors 11 to 41, the fuel injection timing, and the spark plugs 12 to 42 according to the required torque set based on, for example, the accelerator operation of the driver. Control ignition timing, valve timing, etc.
The output value of the accelerator pedal sensor 110 that detects the operation amount (stepping stroke) of the accelerator pedal by the driver is transmitted to the engine control unit 100, and the engine control unit 100 sets the required torque based on this output value.

Further, an idle stop system control unit (ISS control unit) 120 is connected to the engine control unit 100.
The idle stop system control unit 120 automatically stops the engine 1 when a predetermined idle stop condition is satisfied when the vehicle is stopped, and automatically stops the engine 1 when a predetermined restart condition is satisfied. Idle stop control is performed to restart the engine.

In the idle stop system control unit 120, for example, the vehicle stop determination is established, the traveling range (D range) is selected in the automatic transmission, the air conditioning load of the air conditioner is equal to or less than a predetermined value, and the starter motor 70 is powered. The SOC of the battery to be supplied is equal to or higher than the predetermined value, the steering angle of the steering system is equal to or lower than the predetermined value, the engine cooling water temperature is equal to or higher than the predetermined value (warm-up completed), and the brake master cylinder hydraulic pressure is equal to or higher than the predetermined value. Yes, and if no abnormality is detected in the system function by the self-diagnosis function, it is determined that the idle stop condition is satisfied.
Further, the idle stop system control unit 120 determines that the restart condition is satisfied when the above-mentioned idle stop condition is not satisfied.
For example, if the master cylinder hydraulic pressure falls below a predetermined value due to the driver loosening the pedal effort of the brake pedal in an attempt to restart the vehicle or releasing the foot from the brake pedal, the restart condition is satisfied. Then, the idle stop system control unit 120 instructs the engine control unit 100 to restart the engine 1.

Further, the engine control unit 100 functions as an engine control device for preventing the rotation speed (rotation speed) of the crankshaft from excessively increasing immediately after the complete explosion at the start of the engine 1.
The engine control unit 100 has functions as a complete explosion determining means, a rotation change detecting means, and a fuel injection controlling means according to the present invention.
This function will be described in detail below.

FIG. 2 is a flowchart showing fuel injection control at the time of engine restart in the engine control device of the first embodiment.
The control described in FIG. 2 is started in a state where the engine 1 is automatically stopped based on the idle stop condition determination of the idle stop system control unit 120.
Hereinafter, each step will be described step by step.

<Step S01: Judgment that the idle stop system restart condition is satisfied>
The engine control unit 100 determines whether or not the restart condition is satisfied (satisfied) in the idle stop system control unit 120.
If the restart condition is satisfied, the process proceeds to step S02, and in other cases, step S01 is repeated.

<Step S02: Start engine start>
The engine control unit 100 starts starting the engine 1.
The engine control unit 100 instructs the starter motor 70 to be energized and drives the crankshaft to rotate at a rotation speed of, for example, about 200 rpm.
Further, the engine control unit 100 gives an injection signal to the injectors 11 to 41 to start fuel injection, and also gives an ignition signal to the spark plugs 12 to 42 to start ignition.
In the normal operation of the engine 1, the fuel injection amount is set by the closed loop control using the output of the air flow meter, the air-fuel ratio sensor, etc. as described above, but such control is performed immediately after the start. Therefore, the open loop control is used to inject a preset starting fuel injection amount.
This starting fuel injection amount is set so as to be fuel-rich with respect to the stoichiometric air-fuel ratio for the purpose of ensuring ignition even if there are variations in fuel properties and individual differences in the engine. There is.
Then, the process proceeds to step S03.

<Step S03: Judgment of engine speed>
The engine control unit 100 detects the rotation speed (rotational speed) of the crankshaft, which is the output shaft of the engine 1, based on the output of the crank angle sensor 60.
Then, when the current rotation speed is equal to or higher than a predetermined threshold value (500 rpm as an example) sufficiently higher than the drive rotation speed by the starter motor (200 rpm in this case), the air-fuel mixture is normally mixed in each cylinder. It is determined that the engine 1 has been ignited and the start of the engine 1 has been completed, and the process proceeds to step S04.
The energization of the starter motor 70 is stopped when the determination of the complete explosion state is established.
On the other hand, in other cases, it is determined that the explosion is not yet complete, and step S03 is repeated.

<Step S04: Detection of change in rotation speed at 30 msec>
The engine control unit 100 detects a change amount (rotational speed change amount) of the crankshaft rotation speed in a predetermined period (30 msec as an example) based on the output history of the crank angle sensor 60.
Then, the process proceeds to step S05.

<Step S05: Judgment of rotation speed change amount>
The engine control unit 100 compares the amount of change in rotational speed detected in step S04 with a preset threshold value (200 rpm / 30 msec as an example).
If the amount of change in the rotational speed is equal to or greater than the threshold value, it is considered necessary to execute the fuel cut in order to suppress an excessive increase in the rotational speed, and the process proceeds to step S06.

燃料カット回数の設定後、ステップＳ０７に進む。 <Step S06: Setting the number of fuel cuts>
The engine control unit 100 sets the number of times (the number of cycles) to cut the fuel according to the amount of change in the rotational speed detected in step S04.
At this time, the number of fuel cuts is set to increase (the fuel cut period is extended) according to the increase in the amount of change in the rotational speed.
Table 1 shows an example of setting the number of fuel cuts.

After setting the number of fuel cuts, the process proceeds to step S07.

<Step S07: Return to normal injection control after fuel cut>
The engine control unit 100 stops the fuel injection of each cylinder for the number of times (number of cycles) set in step S06, and then restarts the fuel injection.
After resuming fuel injection, a preset start-up fuel injection amount is injected by open-loop control over a predetermined period, and then the normal fuel injection control in which the above-mentioned closed-loop control is performed is restored.
After that, a series of processes is completed.

<Step S08: Normal injection control execution>
The engine control unit 100 injects a preset starting fuel injection amount over a predetermined period by open loop control without performing fuel cut, and then returns to the normal fuel injection control in which closed loop control is performed.
After that, a series of processes is completed.

Hereinafter, the effect of Example 1 will be described in comparison with the engine control device of the comparative example of the present invention described below.
FIG. 3 is a diagram showing an example of changes in the engine speed, ignition timing, and fuel injection signal when the engine is restarted in the engine control device which is a comparative example of the present invention.
In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates engine speed (upper is high rotation), ignition timing (upper is advance angle), and fuel injection signal pulse width (upper is valve opening time length). ing. (The same applies to FIGS. 4, 5, and 7.)

In the engine control device of the comparative example, the torque is reduced by significantly retarding the ignition timing with respect to the normal operation in order to suppress an excessive increase in rotation immediately after the complete explosion.
At this time, the fuel injection is continued at a predetermined starting fuel injection amount.
If the ignition timing is not retarded, as shown by the broken line in FIG. 3, the engine speed rises once exceeding the target speed, then falls, and converges.
In the comparative example, it is possible to suppress an excessive increase in rotation and prevent the user from feeling a pop-out feeling by reducing the torque due to the retard of the ignition timing.
However, since the ignition timing is retarded and the torque that the fuel can originally generate is controlled to be intentionally reduced, the thermal efficiency is lowered and a part of the energy of the supplied fuel is wasted. ..
In particular, since the fuel injection amount at start-up is set to be increased compared to normal operation so that the fuel injection amount is considerably richer than that of stoichiometric fuel consumption, the effect of improving fuel efficiency by idle stop is diminished and fuel efficiency is deteriorated. There is concern about letting them do it.

FIG. 4 is a diagram showing an example of transitions in the engine speed, ignition timing, and fuel injection signal when the engine is restarted in the engine control device of the first embodiment.
In the first embodiment, the excessive rotation rise immediately after the complete explosion is suppressed by the fuel cut, and the ignition timing is substantially maintained in the vicinity of the MBT.
For example, in the example shown in FIG. 4, the fuel injection is restarted after the fuel is cut for 3 cycles from the 1st cylinder 10 to the 4th cylinder 40 in the firing order.

According to the first embodiment described above, fuel is consumed for a technique of retarding the ignition timing while injecting fuel by cutting the fuel when the amount of change in the rotational speed immediately after the complete explosion is equal to or more than a predetermined value. The amount can be suppressed.
In addition, by determining the necessity of fuel cut according to the amount of change in the rotation speed, an appropriate rotation increase form (rotation) even when there are variations in fuel properties, environmental factors, individual differences in the engine, etc. Profile) can be obtained.
Further, when fuel is cut, by increasing the fuel cut period (the number of fuel cut cycles) according to the increase in the amount of change in the rotation speed, it is possible to obtain an appropriate effect of suppressing the increase in rotation according to the amount of change in the rotation speed. And the rotation profile can be controlled more appropriately.

Next, the second embodiment of the engine control device to which the present invention is applied will be described.
In each of the examples described below, the parts substantially the same as those in the above-described first embodiment are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

FIG. 5 is a diagram showing an example of transitions in the engine speed, ignition timing, and fuel injection signal when the engine is restarted in the engine control device of the second embodiment.
In the engine control device of the second embodiment, at the start of the fuel cut immediately after the start, the fuel is cut only in some cylinders, and the fuel is injected in the other cylinders, and then the fuel is cut in all the cylinders. Is supposed to do.
Further, at the end of the fuel cut, the fuel injection is restarted only in some cylinders, and after the fuel cut is performed in the other cylinders, the fuel injection is restarted in all the cylinders.

In the example shown in FIG. 5, at the start of the fuel cut, the fuel cut of the first cylinder and the second cylinder is started first, and the fuel cut of the third cylinder and the fourth cylinder is started from the next cycle.
Further, at the end of the fuel cut, the fuel injection of the first cylinder and the second cylinder is restarted first, and the fuel injection of the third cylinder and the fourth cylinder is restarted from the next cycle.

According to the second embodiment described above, in addition to substantially the same effect as that of the first embodiment described above, the start of the fuel cut and the restart of the fuel injection are performed stepwise for each cylinder group. The output torque of the engine 1 can be changed stepwise to prevent the output torque from suddenly changing and causing a shock.

Next, Example 3 of the engine control device to which the present invention is applied will be described.
The engine control device of the third embodiment is characterized in that the number of cylinders for fuel cutting is changed according to the amount of change in the rotational speed of the crankshaft immediately after the complete explosion.
FIG. 6 is a flowchart showing fuel injection control at the time of engine restart in the engine control device of the third embodiment.
Hereinafter, each step will be described step by step.

<Step S11: Judgment that the idle stop system restart condition is satisfied>
The engine control unit 100 determines whether or not the restart condition is satisfied (satisfied) in the idle stop system control unit 120.
If the restart condition is satisfied, the process proceeds to step S12, and in other cases, step S11 is repeated.

<Step S12: Start engine start>
The engine control unit 100 starts starting the engine 1 in the same manner as in step S02 described above.
Then, the process proceeds to step S13.

<Step S13: Judgment of engine speed>
The engine control unit 100 detects the rotation speed of the crankshaft in the same manner as in step S03 described above.
When the current rotation speed exceeds a predetermined threshold value (500 rpm as an example), the process proceeds to step S14, and in other cases, step S13 is repeated.

<Detection of rotation speed change amount in step S14: 30 msec>
Similar to step S04 described above, the engine control unit 100 detects the amount of change in the crankshaft rotation speed during a predetermined period (30 msec as an example).
Then, the process proceeds to step S15.

<Step S15: Judgment of rotation speed change amount>
The engine control unit 100 compares the amount of change in rotational speed detected in step S14 with a preset threshold value.
If the amount of change in the rotational speed is equal to or greater than the threshold value, it is considered necessary to execute the fuel cut in order to suppress an excessive increase in the rotational speed, and the process proceeds to step S16. In other cases, the process proceeds to step S19.

<Step S16: Setting the number of fuel cut cylinders>
The engine control unit 100 sets the number of cylinders for fuel cut according to the amount of change in rotational speed detected in step S14, and sets some or all of the cylinders as fuel cut execution cylinders.
The number of cylinders for which fuel is cut is set to increase as the amount of change in rotational speed increases.
Then, the process proceeds to step S17.

<Step S17: Setting the number of fuel cuts>
The engine control unit 100 sets the number of times the fuel is cut according to the amount of change in the rotational speed detected in step S14.
Then, the process proceeds to step S18.

<Step S18: Return to normal injection control after fuel cut>
In the cylinder set as the fuel cut execution cylinder in step S16, the engine control unit 100 stops the fuel injection of each cylinder for the number of times (number of cycles) set in step S17, and then restarts the fuel injection.
After resuming fuel injection, a preset start-up fuel injection amount is injected by open-loop control over a predetermined period, and then the normal fuel injection control in which the above-mentioned closed-loop control is performed is restored.
After that, a series of processes is completed.

<Step S19: Normal injection control execution>
The engine control unit 100 injects a preset starting fuel injection amount over a predetermined period by open loop control without performing fuel cut, and then returns to the normal fuel injection control in which the above-mentioned closed loop control is performed.
After that, a series of processes is completed.

FIG. 7 is a diagram showing an example of changes in the engine speed, ignition timing, and fuel injection signal when the engine is restarted in the engine control device of the third embodiment.
In the example shown in FIG. 7, the amount of change in the rotational speed immediately after the complete explosion is smaller (the slope of the graph is gentler) than in the cases of FIGS. 4 and 5 in Examples 1 and 2.
For this reason, when fuel is cut in all cylinders as in Examples 1 and 2, there is a concern that the rotation speed will decrease with respect to the target rotation speed, in addition to suppressing an excessive increase in rotation speed. To.
In this regard, in the third embodiment, for example, in the case of FIG. 7, fuel is cut only for the first cylinder 10 and the second cylinder 20, and the fuel injection is continued for the third cylinder 30 and the fourth cylinder 40. I have a good rotation profile.

According to the third embodiment described above, in addition to the effect substantially the same as the effect of the first embodiment described above, the number of cylinders for which fuel cut is executed is made different according to the amount of change in the rotational speed immediately after the complete explosion. As a result, it is possible to perform optimum torque reduction with respect to the amount of change in rotation speed, increase the degree of freedom in setting the rotation profile, and perform more appropriate rotation rise suppression control.

(Modification example)
The present invention is not limited to the above-described embodiments, and various modifications and modifications are possible, and these are also within the technical scope of the present invention.
(1) The configurations of the engine and the engine control device can be appropriately changed without being limited to the above-described embodiments.
For example, in each embodiment, the engine is, for example, a horizontally opposed 4-cylinder engine of gasoline direct injection, but the cylinder layout and the number of cylinders are not limited to this, and can be changed as appropriate.
Further, the present invention is applicable not only to a direct injection (in-cylinder injection) engine but also to a port injection engine, and further, the fuel is not limited to gasoline as long as it is a spark ignition type engine.
Further, the presence / absence of a supercharger and the type of the supercharger are not particularly limited.
(2) In each embodiment, the cylinder for which the fuel is cut is configured to continuously stop the fuel injection over a continuous cycle, but the present invention is not limited to this, and the fuel may be cut intermittently. Good.
For example, the cycle of fuel injection and the cycle of fuel cut may be sequentially switched.
(3) Each embodiment is described by taking automatic restart from the idle stop state as an example, but the present invention is not limited to this, and can be applied to engine start from a state other than the idle stop state.
For example, it can be applied to engine start according to a user's engine start operation at the start of vehicle operation, and to engine start from a motor running state in an engine-electric hybrid vehicle.

1 Engine 10 1st cylinder 11 Injector 12 Ignition plug 20 2nd cylinder 21 Injector 22 Ignition plug 30 3rd cylinder 31 Injector 32 Ignition plug 40 4th cylinder 41 Injector 42 Ignition plug 50 Injector 51 Throttle valve 52 Throttle actuator 53 Intake manifold 60 Crank angle sensor 61 Sensor plate 62 Position sensor 70 Starter motor 100 Engine control unit (ECU)
110 Accelerator pedal sensor 120 Idle stop system control unit

Claims (4)

An engine control device that controls the engine
A complete explosion determination means for determining complete explosion after the engine is started,
A rotation change detecting means for detecting the amount of change in the rotation speed of the output shaft in a predetermined period after the complete explosion determining means determines the complete explosion.
When the amount of change in rotational speed is equal to or greater than a predetermined threshold value, the number of fuel cuts is set to increase according to the increase in the amount of change in rotational speed, and then fuel injection of at least one cylinder is stopped over the number of fuel cuts. An engine control device including a fuel injection control means for restarting fuel injection thereafter. The engine has multiple cylinders
The engine according to claim 1, wherein when the fuel injection control means is stopped, the fuel injection of only a part of the cylinders is stopped and then the fuel injection of all the cylinders is stopped. Control device. The engine has multiple cylinders
When the fuel cut period ends and the fuel injection is restarted, the fuel injection control means restarts the fuel injection of all the cylinders after restarting the fuel injection of only a part of the cylinders in which the fuel injection is stopped. The engine control device according to claim 1 or 2, wherein the engine control device shifts to the above-mentioned state. Said fuel injection control means, according to claim 1 which before Symbol number resume cylinders subsequent fuel injection is stopped the fuel injection over the fuel cut number, and characterized by increasing according to an increase of the rotation speed variation The engine control device described in.

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