JP2016098801A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a shock in timing for switching from a drive state to a driven state, when reducing generation torque of an internal combustion engine according to the establishment of a fuel cut execution condition.SOLUTION: When a fuel cut execution condition is established, before executing the fuel cut, in the case where output torque of an engine is reduced, demand torque for each cycle is set according to engine output torque at start time of a torque holding control period including the timing for the engine switching from a drive state to a driven state, and target torque of the engine at the finish time of the torque holding control period. Ignition timing of an ignition plug is controlled so that the demand torque set corresponding to the cycle can be acquired for each cycle. Thereby, even when actual torque becomes low with respect to the demand torque by an intake amount reducing greatly and the like during the torque holding period, proper demand torque with respect to the next time cycle can be acquired.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device for an internal combustion engine.

  In general, in a vehicle having an internal combustion engine as a drive source, when a predetermined fuel cut execution condition is satisfied when the accelerator pedal depression amount by the driver (driver) becomes “0” or the like, the fuel to the internal combustion engine is satisfied. A so-called fuel cut for stopping the supply is performed. As a result, fuel consumption is reduced. However, when the fuel cut is started from a state in which the generated torque of the internal combustion engine is relatively large, the generated torque is greatly reduced in a short time, and a torque shock due to the torque step is generated. End up.

  As a control of the internal combustion engine for the purpose of reducing the torque shock, when the fuel cut execution condition is satisfied, the generated torque of the internal combustion engine is decreased by gradually retarding the ignition timing (hereinafter also referred to as attenuation). After that, it is known to start a fuel cut (see, for example, Patent Document 1). According to the control of the internal combustion engine, the torque step when the fuel cut is started is reduced, and the torque shock can be reduced.

  By the way, as described above, when the generated torque of the internal combustion engine is reduced by gradually retarding the ignition timing, the internal combustion engine is in a driving state (a state in which driving wheels are driven by the generated torque of the internal combustion engine) at a certain point in time. To the driven state (the state in which the internal combustion engine is driven by the torque input from the driving wheels). When switching from this driving state to the driven state, there is a problem that the backlash direction caused by the backlash between the gears provided in the power transmission system is reversed and a shock (so-called shock due to rattling) occurs.

JP 2013-142307 A

  As a control for reducing the shock when the internal combustion engine is switched from the driving state to the driven state, a timing for switching from the driving state to the driven state is included in the period in which the generated torque of the internal combustion engine is reduced. In a predetermined period, the reduction amount per unit time of the torque generated by the internal combustion engine is particularly reduced. Hereinafter, this period is referred to as a torque holding control period. In addition, during the period before and after the torque holding control period, the amount of reduction per unit time of the torque generated by the internal combustion engine is increased. This shortens the period from when the fuel cut execution condition is satisfied to when the fuel cut is started.

  Then, as the control in the torque holding control period, the required torque at the next processing timing is instructed based on the actual torque at the present time at every predetermined processing timing (for example, every cycle of the engine) (for example, the required torque is obtained). Instructing the ignition timing). In other words, the next time so as to connect the actual torque at the current time and the target torque at the end of the torque holding control period (so that the torque reduction speed between the actual torque and the target torque at the current time is constant) The required torque at the processing timing is obtained, and control at the next processing timing is performed so that the required torque is obtained.

  However, when the amount of intake air is greatly reduced by the control of the VVT (Variable Valve Timing) mechanism or the control of the throttle valve opening when the accelerator pedal depression amount becomes “0” during the torque holding control period. In some cases, the actual torque may be lower than the required torque by the amount of decrease in the intake air amount. In such a situation, since the required torque at the next processing timing is determined based on the actual torque that is lower than the required torque, the actual torque is obtained as an appropriate torque (the required torque). Compared to the case, the required torque at the next processing timing is obtained as a low value.

  FIG. 6 shows an example of the target torque Tt, the actual torque Tn at each processing timing, and the required torque Tr in this case. When the actual torque Tnb at the timing tb decreases with respect to the required torque Trb due to a significant decrease in the intake air amount (see the arrow I in the figure), the actual torque Tnb and the target torque at the timing tb The required torque Trc at the next processing timing (timing tc) is obtained so as to connect Tt. The required torque Trc at the timing tc obtained here is lower than the required torque Trc ′ required when the actual torque at the timing tb is properly obtained (when the required torque Trb is obtained). . If the situation where the intake air amount greatly decreases continues, such an operation is repeated at each processing timing (every time the required torque Tr is obtained, it is affected by the actual torque Tn that is low at the previous processing timing. As a result, the required torque Tr is determined as a low value), and the accumulation of the difference between the required torque Tr and the actual torque Tn increases, and the rate of decrease in the output torque of the internal combustion engine becomes extremely high. End up. As a result, the torque change at the timing when the internal combustion engine is switched from the driving state to the driven state becomes large, and there is a possibility that the shock due to the reverse of the backlash direction due to the backlash between the gears described above may increase.

  The present invention has been made in view of such a point, and an object of the present invention is to change the internal combustion engine from a driven state to a driven state when the generated torque of the internal combustion engine is reduced as the fuel cut execution condition is satisfied. An object of the present invention is to provide a control device for an internal combustion engine that can reduce shock at the timing of switching.

  According to another aspect of the present invention, there is provided a control device for an internal combustion engine that stops fuel supply to the internal combustion engine after reducing an output torque of the internal combustion engine when a predetermined fuel cut execution condition is satisfied. Assuming With respect to the control device for the internal combustion engine, a predetermined period including a timing at which the internal combustion engine is switched from the driving state to the driven state is obtained from the period in which the output torque of the internal combustion engine is reduced. The required torque for each cycle of the internal combustion engine during this predetermined period is set according to the engine output torque and the target torque of the internal combustion engine at the end of this predetermined period, and each cycle corresponds to that cycle Thus, the control value of the control parameter of the internal combustion engine is instructed so as to obtain the set required torque.

  Due to this specific matter, as control when the fuel cut execution condition is satisfied, the output torque of the internal combustion engine at the start of the predetermined period including the timing at which the internal combustion engine switches from the driven state to the driven state, and at the end of the predetermined period The required torque for each cycle of the internal combustion engine during this predetermined period is set according to the target torque of the internal combustion engine at. Then, for each cycle, the control value of the control parameter of the internal combustion engine is instructed so that the required torque set corresponding to the cycle is obtained. With this control, even if the actual torque becomes lower than the required torque due to a significant decrease in the intake air amount during the predetermined period, in the next cycle (for example, the cycle in which the next combustion stroke is reached), the predetermined Control is performed using the control value of the control parameter instructed so as to obtain the required torque set according to the output torque of the internal combustion engine at the start of the period and the target torque of the internal combustion engine at the end of the predetermined period. It will be. In this way, the control value of the control parameter is instructed so that the required torque in the next cycle set without being affected by the decrease in the actual torque is obtained. Therefore, an increase in the difference between the required torque and the actual torque is avoided, and the reduction speed of the output torque of the internal combustion engine does not become extremely high. As a result, it is possible to avoid an increase in torque change at the timing when the internal combustion engine switches from the driven state to the driven state, and to reduce the shock.

  In the present invention, the output torque of the internal combustion engine at the start of the predetermined period including the timing at which the internal combustion engine switches from the driving state to the driven state and the target torque of the internal combustion engine at the end of the predetermined period are set. The control value of the control parameter of the internal combustion engine is instructed so that the required torque for each cycle is obtained. Therefore, an increase in the difference between the required torque and the actual torque is avoided, and the reduction rate of the output torque of the internal combustion engine does not become extremely high, so that the internal combustion engine is changed from the driven state to the driven state. Shock at the time of switching to can be reduced.

1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment. It is a figure which shows schematic structure of an engine. It is a timing chart figure showing an example of change of the amount of intake air, ignition timing, and engine output torque at the time of fuel cut execution. It is a flowchart figure which shows the procedure of torque holding | maintenance control. It is a figure which shows an example of the target torque in a torque holding control period, the actual torque in each cycle, and a request torque. It is a figure which shows an example of the target torque in a prior art, the actual torque in each cycle, and a request torque.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the case where the control device for an internal combustion engine according to the present invention is applied to an FR (Front engine Rear drive) vehicle equipped with an automatic transmission will be described.

-Vehicle configuration-
As shown in FIG. 1, a vehicle 1 according to the present embodiment includes an engine 2 that is an internal combustion engine, a torque converter 3 that amplifies output torque output from the engine 2, and a rotational speed of an output shaft of the torque converter 3. The speed change mechanism 5 that rotates the output shaft 4 at the changed rotational speed, the differential gear 7 that transmits the rotational force of the output shaft 4 of the speed change mechanism 5 to the drive shafts 6L and 6R, and the drive shafts 6L and 6R are rotated. Drive wheels 8L and 8R driven by The torque converter 3 and the transmission mechanism 5 constitute an automatic transmission 9.

  Further, the vehicle 1 electrically connects an engine electronic control unit (hereinafter referred to as “EG-ECU”) 10 that controls the engine 2, a hydraulic control circuit 11 that controls the automatic transmission 9 by hydraulic pressure, and a hydraulic control circuit 11. And an automatic transmission electronic control unit (hereinafter referred to as “TM-ECU”) 12 that automatically controls.

  As shown in FIG. 2, the engine 2 includes a cylinder block 20, a cylinder head 21 attached to an upper portion of the cylinder block 20, and an oil pan 22 for storing lubricating oil. Thus, a plurality of cylinders are formed.

  The engine 2 according to the present embodiment is an in-line four-cylinder engine. However, the present invention is not limited to various types such as an in-line six-cylinder engine, a V-type six-cylinder engine, a V-type twelve-cylinder engine, and a horizontally opposed six-cylinder engine. Applicable to engine. FIG. 2 shows one of the four cylinders arranged in series.

  A piston 24 is accommodated in each cylinder so as to be able to reciprocate, and a combustion chamber 25 for each cylinder is formed by the cylinder block 20, the cylinder head 21, and the piston 24. The engine 2 according to the present embodiment is a four-stroke one-cycle engine that performs a series of four strokes including an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke while the piston 24 reciprocates twice.

  Pistons 24 housed in the cylinders are connected to a crankshaft 27 via connecting rods 26. The connecting rod 26 converts the reciprocating motion of the piston 24 into the rotational motion of the crankshaft 27.

  Therefore, the engine 2 reciprocates the piston 24 by burning the fuel / air mixture in the combustion chamber 25 and rotates the crankshaft 27 via the connecting rod 26, thereby supplying power to the torque converter 3. To communicate.

  In addition, although the fuel used for the engine 2 is gasoline, it may replace with gasoline and the alcohol fuel which mixed alcohol, such as ethanol, and gasoline.

  The engine 2 is provided with an intake pipe 30 connected to the cylinder head 21 for introducing air into the combustion chamber 25. The intake pipe 30 includes an air cleaner 31 that cleans air flowing from outside the vehicle, an air flow sensor 32 that detects a flow rate of air introduced into the combustion chamber 25, that is, an intake air amount, and a throttle valve that adjusts the intake air amount. 33 is provided.

  The air flow sensor 32 is provided on the upstream side of the throttle valve 33 and outputs a detection signal indicating the intake air amount to the EG-ECU 10.

  The throttle valve 33 is provided with a throttle valve actuator 34 and adjusts the intake air amount in accordance with a command signal from the EG-ECU 10.

  Further, the engine 2 is provided with an exhaust pipe 35 connected to the cylinder head 21 in order to exhaust the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 25. The exhaust pipe 35 is provided with a catalyst (three-way catalyst) 36 for purifying harmful substances in the exhaust gas.

  The cylinder block 20 is formed with a water jacket 37 through which cooling water circulates, and a water temperature sensor 38 that detects the temperature of the cooling water circulated through the water jacket 37. The cylinder head 21 is formed with an intake port 40 for communicating the intake pipe 30 and the combustion chamber 25 and an exhaust port 41 for communicating the combustion chamber 25 and the exhaust pipe 35.

  The cylinder head 21 includes an intake valve 42 for controlling the introduction of intake air from the intake pipe 30 to the combustion chamber 25, and an exhaust valve for controlling discharge of exhaust gas from the combustion chamber 25 to the exhaust pipe 35. 43, an injector 44 for injecting fuel toward the combustion chamber 25, and a spark plug 45 for igniting the air-fuel mixture in the combustion chamber 25.

  When the solenoid coil is energized by the EG-ECU 10, the injector 44 opens the needle valve and injects fuel toward the combustion chamber 25.

  The spark plug 45 is discharged when the electrode is energized by the EG-ECU 10 and ignites the air-fuel mixture in the combustion chamber 25.

  As shown in FIG. 1, on the input side of the EG-ECU 10, in addition to the crank angle sensor 61 for calculating the engine speed of the engine 2, the air flow sensor 32, and the water temperature sensor 38, the opening degree of the accelerator pedal 90 is set. An accelerator opening sensor 91 that detects the accelerator opening that is represented and a vehicle speed sensor 92 that detects the vehicle speed are connected.

  The accelerator opening sensor 91 is configured by, for example, an electronic position sensor using a Hall element. When the accelerator pedal 90 is operated by the driver, the accelerator opening sensor 91 outputs a signal indicating the accelerator opening indicating the opening of the accelerator pedal 90 to the EG-ECU 10. The vehicle speed sensor 92 detects the rotation angles of the drive shafts 6L and 6R, averages the detected rotation angles of the drive shafts 6L and 6R, and outputs the average to the EG-ECU 10.

  The EG-ECU 10 communicates with other ECUs such as the TM-ECU 12 via the high-speed CAN, and exchanges various control signals and data with the other ECUs such as the TM-ECU 12. .

  For example, the EG-ECU 10 controls the fuel injection control for the injector 44, the ignition control for the spark plug 45, and the intake air amount for the throttle valve actuator 34 based on detection signals input from various sensors that detect the operating state of the engine 2. While performing operation control of the engine 2 such as adjustment control, data related to the operation state of the engine 2 is output to the TM-ECU 12 as necessary.

  Further, the engine 2 of the present embodiment is provided with a VVT mechanism (not shown) for adjusting the opening / closing timing of the intake valve 42 and the exhaust valve 43, and the EG-ECU 10 corresponds to the operating state of the engine 2. The VVT mechanism is controlled to adjust the opening / closing timing of the intake valve 42 and the exhaust valve 43.

  A shift position sensor 94 that detects the shift position selected by the shift lever 93 is connected to the input side of the TM-ECU 12.

  The TM-ECU 12 communicates with other ECUs such as the EG-ECU 10 via the high-speed CAN, and exchanges various control signals and data with the other ECUs such as the EG-ECU 10. .

  For example, the TM-ECU 12 controls the hydraulic control circuit 11 based on the shift position detected by the shift position sensor 94 and the operating state of the engine 2 output from the EG-ECU 10, so Is established, and information indicating the speed established by the speed change mechanism 5 is output to the EG-ECU 10.

-Fuel cut control-
Hereinafter, fuel cut control executed by the EG-ECU 10 will be described. The EG-ECU 10 executes a fuel cut that stops the fuel supply to the engine 2 after reducing the output torque of the engine 2 when the fuel cut execution condition is satisfied.

  Specifically, as shown in FIG. 3, when the EG-ECU 10 detects that the accelerator pedal position 90 is “0”, that is, the accelerator is OFF, by the accelerator position sensor 91 at time t0, The output torque of the engine 2 is estimated in a predetermined delay section, for example, at a time t1 when about 100 ms to 200 ms have elapsed, on condition that the engine speed of 2 is equal to or higher than a predetermined speed.

  The ROM of the EG-ECU 10 stores a map in which the output torque of the engine 2 is previously associated with the engine speed, the intake air amount, and the ignition timing for the spark plug 45 by experiments. Yes.

  The EG-ECU 10 determines the engine speed of the engine 2 obtained from the signal output from the crank angle sensor 61, the intake air amount obtained from the air flow sensor 32, and the ignition timing instructed to the spark plug 45. The output torque of the engine 2 is estimated by specifying the output torque of the engine 2 associated with the map.

  Further, the EG-ECU 10 reduces the output torque of the engine 2 so that the operating state of the engine 2 is a driving state where driving force is generated (a state where the driving wheels 8L and 8R are driven by the generated torque of the engine 2). ) To the driven state (the state in which the engine 2 is driven by the torque input from the drive wheels 8L and 8R) that receives the driving force due to the inertial force or the like of the vehicle 1 (hereinafter referred to as “drive switching”). Torque TQex ”).

  Here, in the ROM of the EG-ECU 10, the vehicle speed, the gear stage established by the transmission mechanism 5, the differential ratio of the differential gear 7, the loads of auxiliary equipment such as an air conditioner, an alternator, and an oil pump, A map in which the drive switching torque TQex is previously associated with the resistance, the engine torque, and the coolant temperature of the engine 2 by an experiment is stored.

  The EG-ECU 10 compensates for the vehicle speed of the vehicle 1 obtained from the vehicle speed sensor 92, the gear position of the transmission mechanism 5 obtained from the TM-ECU 12, the preset differential ratio, and the operating state of each auxiliary machine. It is obtained from the water temperature sensor 38, the running resistance obtained based on the vehicle load, the vehicle running state (command torque value, vehicle body longitudinal acceleration, road surface inclination, etc.), the engine torque obtained based on the operating state of the engine 2. The drive switching torque TQex is estimated by specifying the drive switching torque TQex associated with the map with respect to the water temperature.

  At time t1 in FIG. 3, the EG-ECU 10 sets the output torque of the engine 2 to a target torque (starting torque holding control) that is a torque TQex + TQm that is higher than the drive switching torque TQex by a minute torque TQm that is a predetermined number N · m Torque), the output torque of the engine 2 is reduced.

  Specifically, EG-ECU 10 has a damping rate ΔTQ lower than a predetermined damping rate θ and is a natural number times the natural vibration period of the power transmission system interposed between engine 2 and drive wheels 8L and 8R. Over time, output torque attenuation control is executed to reduce (attenuate) the output torque of the engine 2 to a target torque (torque holding control start torque).

  Here, the damping rate θ is a damping rate at which a shock starts to occur in the vehicle 1 when the damping rate of the output torque of the engine 2 is significantly reduced, and is determined in advance by experiments. In addition, the natural vibration period of the power transmission system interposed between the engine 2 and the drive wheels 8L and 8R is determined in advance by experiment for each gear stage established by the transmission mechanism 5.

  In the present embodiment, as shown in FIG. 3, the EG-ECU 10 reduces the output torque of the engine 2 by changing the intake air amount and ignition timing for the engine 2.

  Further, the EG-ECU 10 starts the output torque attenuation control at time t1, and when the output torque of the engine 2 reaches the torque holding control start torque (TQex + TQm) at time t2, the torque holding control period (from time t2) is determined. During the period until time t3), the output torque attenuation rate of the engine 2 is reduced to a level that does not become negative. Hereinafter, the period from time t1 to time t2 is referred to as a first output torque decay period.

  Here, the torque holding control period includes a period in which the operating state of the engine 2 is switched from a driving state in which driving force is generated to a driven state in which driving force such as inertial force of the vehicle 1 is received. That is, this torque holding control period corresponds to the “predetermined period including the timing at which the internal combustion engine switches from the driving state to the driven state” in the present invention. During the torque holding control period, the EG-ECU 10 decreases the output torque of the engine 2 from a torque TQex + TQm that is higher than the drive switching torque TQex by a minute torque TQm to a torque TQex-TQm that is lower than the drive switching torque TQex by a minute torque TQm. It is supposed to let you.

  The length of this torque holding control period is set according to the gear stage established in the transmission mechanism 5 and the like. For example, the longer the gear position is on the low gear side (the higher the gear ratio), the longer the torque holding control period is set. Further, the minute torque TQm is reduced from the driving state to the driven state when the output torque of the engine 2 is decreased at a constant rate from TQex + TQm to TQex−TQm during the set torque holding control period. It is set in advance by experiment or simulation so that a shock due to the reverse of the backlash direction caused by the backlash between the gears does not occur at the timing of switching to the state or the shock falls within an allowable range. Specifically, the minute torque TQm is 2.5 N · m. This value is not limited to this, and is appropriately set as described above.

  Further, the EG-ECU 10 decreases the output torque of the engine 2 from time t2, and stops the fuel supply to the engine 2 when the output torque of the engine 2 becomes torque TQex-TQm (torque holding control end torque) at time t3. The output torque attenuation control is executed with the torque TQfc of the engine 2 as the target torque (fuel cut execution torque).

  Further, the EG-ECU 10 starts output torque attenuation control at time t3, and controls the injector 44 so that fuel is not injected when the output torque of the engine 2 reaches the target torque (fuel cut execution torque) at time t4. It has become. Hereinafter, the period from time t3 to time t4 is referred to as a second output torque decay period.

  As described above, the EG-ECU 10 performs the output torque attenuation control (the natural vibration period of the power transmission system interposed between the engine 2 and the drive wheels 8L and 8R) in the first output torque attenuation period from time t1 to time t2. The control for reducing the output torque of the engine 2 is executed over a natural number times the time. As a result, the vehicle 1 is shocked by the squealing (vibration in the front-rear direction of the vehicle) that occurs due to a significant decrease in the damping rate of the output torque of the engine 2 during the torque holding control period from time t2 to time t3. It is configured to suppress without causing it.

  Further, the EG-ECU 10 switches the operating state of the engine 2 from the driving state to the driven state by significantly reducing the attenuation rate of the output torque of the engine 2 during the torque holding control period from time t2 to time t3. It is configured to reduce the shock that sometimes occurs in the power transmission system. Details of the control of the output torque during this torque holding control period will be described later.

  In addition, the EG-ECU 10 performs the output torque attenuation control (the natural vibration cycle of the power transmission system interposed between the engine 2 and the drive wheels 8L and 8R during the second output torque attenuation period from time t3 to time t4. (Control for reducing the output torque of the engine 2) is executed over several times. As a result, the squealing that occurs due to the stop of fuel injection by the injector 44 at time t4 is suppressed without causing a shock to the vehicle 1.

  As described above, in the first output torque decay period and the second output torque decay period, it takes a natural number times the natural vibration period of the power transmission system interposed between the engine 2 and the drive wheels 8L and 8R. The output torque attenuation control for reducing the output torque of the engine 2 to the target torque is executed. The reason why the squealing can be suppressed by performing such output torque attenuation control is as disclosed in, for example, Japanese Patent Application Laid-Open No. 2013-151900.

-Torque control during torque holding control period-
Next, torque control (torque retention control) performed during the torque retention control period (period from time t2 to time t3), which is a feature of the present embodiment, will be described. First, the outline of this torque holding control will be described.

  In the torque holding control period, the required torque at the next processing timing is obtained so as to connect the actual torque at the present time and the target torque at the end of the torque holding control period, and the next processing is performed so that the required torque can be obtained. In the case of conventional control in which control is performed at timing, there are the following problems.

  In other words, if the intake air amount has decreased significantly due to the control of the VVT mechanism or the throttle valve opening when the accelerator pedal depression amount becomes "0", the required torque is reduced by the amount of decrease in the intake air amount. The actual torque may be lower than that. In such a situation, if the required torque at the next processing timing is obtained based on the actual torque that is lower than the required torque, as described above with reference to FIG. As compared to the case where the torque is obtained as the torque, the required torque at the next processing timing is obtained as a low value. Then, if the situation in which the intake air amount greatly decreases continues, such an operation will be repeated at each processing timing, and the accumulation of the difference between the required torque and the actual torque will increase. The decrease rate of the output torque becomes extremely high. As a result, there is a possibility that the torque change at the timing when the engine is switched from the driving state to the driven state becomes large and a shock occurs. In particular, in an engine with a relatively small intake volume (such as an engine with a supercharger or an engine mounted on a hybrid vehicle), the rate of decrease in intake air tends to be high, and this situation occurs remarkably.

  In view of this point, in the present embodiment, the output torque of the engine 2 at the start of the torque holding control period (the torque holding control start torque) and the target torque of the engine 2 at the end of the torque holding control period (the above-mentioned Torque holding control end torque), the required torque for each cycle of the engine 2 during this torque holding control period is set, and the required torque set corresponding to that cycle is obtained for each cycle. Thus, the ignition timing (control value of the control parameter of the internal combustion engine) of the spark plug 45 is instructed.

  As a result, even during the torque holding control period, even if the actual torque becomes lower than the required torque due to a significant decrease in the intake air amount, the torque holding control will be performed in the next cycle (the cycle that reaches the next combustion stroke). It is instructed to obtain the required torque set according to the output torque of the engine 2 at the start of the period and the target torque of the engine 2 at the end of the torque holding control period (the torque holding control end torque). The ignition timing is controlled. In this way, the ignition timing is instructed so that the required torque in the next cycle set without being affected by the decrease in the actual torque can be obtained. Therefore, an increase in the difference between the required torque and the actual torque is avoided, and the output torque reduction rate of the engine 2 does not become extremely high. As a result, it is possible to avoid an increase in torque change at the timing when the engine 2 is switched from the driving state to the driven state, and to reduce the shock.

  Hereinafter, a specific procedure of the torque holding control in this torque holding control period will be described along the flowchart of FIG. The torque holding control shown in this flowchart is executed in the EG-ECU 10 from the time when the fuel cut execution condition is satisfied.

  First, in step ST1, it is determined whether or not it is time to start the torque holding control period. This determination is to determine whether or not the output torque of the engine 2 has decreased to the torque holding control start torque (TQex + TQm).

  If the output torque of the engine 2 has not decreased to the torque holding control period start torque (TQex + TQm) and the determination is NO in step ST1, the output torque of the engine 2 is determined to be still in the first output torque decay period. Waits for the torque holding control period start torque (TQex + TQm) to drop.

  On the other hand, if the output torque of the engine 2 decreases to the torque holding control period start torque (TQex + TQm) and YES is determined in step ST1, the process proceeds to step ST2, and the current actual torque (torque holding control start torque; TQex + TQm) and the torque holding control end torque (TQex−TQm), a torque line in this torque holding control period is set. This torque line is a line for defining the transition of the required torque from the start point to the end point of the torque holding control period, and the torque decreasing speed from the start point to the end point of the torque holding control period is It is set to be constant.

  FIG. 5 is a diagram showing an example of the target torque, the actual torque and the required torque in each cycle during the torque holding control period. Timings T1 to T7 in FIG. 5 are timings for defining the required torque in each cycle, for example, timing when the torque becomes maximum in the combustion stroke of each cycle (or timing when the piston 24 is at the compression top dead center). To a predetermined period (for example, timing on the retard side by a crank angle of 30 °). Specifically, for example, in the engine 2 that reaches the combustion stroke in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, the cylinder that first reaches the combustion stroke in the torque holding control period is In the case of the first cylinder, timings T1 and T5 are timings at which the torque is maximized in the combustion stroke of the first cylinder, and timings T2 and T6 are timings at which the torque is maximized in the combustion stroke of the third cylinder. Timings T3 and T7 are timings when the torque becomes maximum in the combustion stroke of the fourth cylinder, and timings T4 and t3 are timings when the torque becomes maximum during the combustion stroke of the second cylinder. Further, FIG. 5 shows a case where the torque holding control period is set as a length for executing the eight cycles. That is, the case where the torque holding control period is set on the assumption that the crankshaft 27 rotates four times during the torque holding control period is shown.

  The straight line L in FIG. 5 is the torque line (a line for defining the transition of the required torque from the start point to the end point of the torque holding control period). By setting the torque line L in this way, the required torques Tr1 to Tr7 are defined for each cycle.

  The required torques Tr1 to Tr7 defined here are set so that the torque reduction rate from the start point to the end point of the torque holding control period is constant as described above. Therefore, the required torque deviation dTQ between the cycles is calculated by the following equation (1).

dTQ = 2TQm / Ns (1)
Here, dTQ is a torque deviation with respect to the required torque of the previous cycle, and Ns is the number of cycles during the torque holding control period.

  For example, the required torque Tr1 set for the timing T1 in FIG. 5 is obtained by subtracting the torque deviation dTQ from the torque holding control period start torque (TQex + TQm). The required torque Tr2 set for the timing T2 is obtained by subtracting the torque deviation dTQ from the required torque Tr1 set for the timing T1. The required torques Tr3 to Tr7 set for other timings T3 to T7 are obtained in the same manner.

  The required torques Tr1 to Tr7 thus defined are assigned to each cycle and stored in the RAM of the EG-ECU 10.

  After setting the torque line L in this way, the process moves to step ST3, and the required torque assigned to the next cycle (the cycle that reaches the next combustion stroke) is read. For example, if the current time is the start time (timing t2) of the torque holding control period, the timing corresponding to the next cycle is the timing T1 in FIG. 5, and therefore the timing is the required torque of the next cycle (the cycle that reaches the next combustion stroke). The required torque Tr1 at T1 is read out.

  Thereafter, the process proceeds to step ST4, and the ignition timing at which the required torque in the next cycle is obtained is calculated. For example, an ignition timing map that defines the relationship between the output torque of the engine 2 and the ignition timing when the control parameters other than the ignition timing are constant in the current engine operating state is stored in the ROM of the EG-ECU 10. From the ignition timing map, the ignition timing at which the required torque in the next cycle is obtained is obtained.

  After the ignition timing is calculated in this way, the process proceeds to step ST5, and it is determined whether or not the timing of the set ignition timing has been reached. That is, it is determined whether or not the timing of the ignition timing in the next cycle has been reached. In this determination, the rotational angle position of the crankshaft 27 is detected based on the signal output from the crank angle sensor 61, and it is determined whether or not this rotational angle position coincides with the timing of the ignition timing in the next cycle. It is.

  Then, NO is determined in step ST5 until the ignition timing timing is reached, and the process waits until the ignition timing timing is reached. When the ignition timing has been reached and the determination in step ST5 is YES, the process proceeds to step ST6, where ignition of the spark plug 45 is performed. As a result, ignition is performed at the ignition timing at which the required torque is obtained.

  Thereafter, the process proceeds to step ST7, where it is determined whether or not the required torque (the required torque read out in step ST3) coincides with the torque holding control end torque (TQex−TQm). That is, when the required torque matches the torque holding control end torque, the torque holding control period ends and the second output torque decay period starts. In this step ST7, the torque holding control ends. It is determined whether or not the timing has come.

  If the requested torque has not yet coincided with the torque holding control end torque and a NO determination is made in step ST7, the process returns to step ST3, and the requested torque for the next cycle is read again. For example, if the current cycle is a cycle in which the torque becomes maximum at timing T1 in FIG. 5, the required torque Tr2 in the cycle in which the torque becomes maximum at timing T2 is read as the required torque for the next cycle. become. Then, similarly to the case described above, the ignition timing at which the required torque in the next cycle is obtained is calculated (step ST4), and ignition of the spark plug 45 is executed when the ignition timing is reached (YES determination in step ST5). (Step ST6).

  Such an operation is repeated, and the ignition timing control is performed so that the required torques Tr1 to Tr7 set corresponding to the respective timings are obtained at the respective timings T1 to T7 in FIG. Thereafter, in step ST7, the required torque (the required torque read in step ST3) coincides with the torque holding control end torque (TQex−TQm). Torque holding control ends. Thereafter, the output torque of the engine 2 is decreased during the second output torque decay period, and when the output torque becomes the fuel cut execution torque TQfc, the fuel injection from the injector 44 is stopped.

  Since such torque holding control is performed, the control device for the internal combustion engine according to the present invention is configured by the EG-ECU 10. This control device senses the output value of the engine 2 (engine speed, intake air amount, etc. of the engine 2) and the sense value (estimated vehicle speed and shift speed) for estimating the drive switching torque TQex. Or auxiliary load) is received as an input signal. The control device is configured to output an ignition timing command signal of the spark plug 45 as an output signal.

  As described above, in this embodiment, as the torque holding control in the torque holding control period when the fuel cut execution condition is satisfied, the output torque of the engine 2 at the start of the torque holding control period and the torque holding In accordance with the target torque of the engine 2 at the end of the control period (torque holding control end torque), a required torque for each cycle of the engine 2 during this torque holding control period is set, and for each cycle, the cycle The ignition timing of the spark plug 45 is instructed so that the required torque set corresponding to the above is obtained. With this control, even if the actual torque becomes lower than the required torque due to a significant decrease in the intake air amount during the torque holding control period (see arrow II in FIG. 5), the next cycle (next time In the cycle that reaches the combustion stroke), the output torque of the engine 2 at the start of the torque holding control period and the target torque (torque holding control end torque) of the engine 2 at the end of the torque holding control period are set. Control based on the ignition timing of the spark plug 45 instructed to obtain the required torque (refer to the required torque Tr3 in FIG. 5) is performed. In this way, the ignition timing is instructed so that the required torque in the next cycle set without being affected by the decrease in the actual torque can be obtained. Therefore, an increase in the difference between the required torque and the actual torque is avoided, and the output torque reduction rate of the engine 2 does not become extremely high. As a result, it is possible to avoid an increase in torque change at the timing when the engine 2 is switched from the driving state to the driven state, and to reduce the shock.

-Other embodiments-
In the embodiment described above, the ignition plug 45 ignition timing is used as the control value of the control parameter of the engine 2 during the torque holding control period. The present invention is not limited to this, and other control parameters may be controlled, or a plurality of control parameters may be controlled. For example, when the present invention is applied to a diesel engine, the output torque of the engine is reduced by changing the fuel injection amount.

  In the embodiment, the required torques Tr1 to Tr7 for all the cycles are set when the torque holding control period is started. The present invention is not limited to this, and when the combustion stroke in a certain cycle is executed, the torque deviation dTQ is subtracted from the required torque set in that cycle, and the next cycle (the cycle in which the next combustion stroke is reached). The required torque may be calculated sequentially.

  In the above embodiment, the example in which the control device for an internal combustion engine according to the present invention is applied to the vehicle 1 having the stepped automatic transmission 9 is described. You may apply to the vehicle provided with the manual transmission, and may apply to the vehicle provided with the continuously variable transmission.

  In the above embodiment, an example in which the control device for an internal combustion engine according to the present invention is applied to an FR vehicle has been described. However, the control device for an internal combustion engine according to the present invention is applied to an FF (Front engine Front drive) vehicle. It may be applied to a four-wheel drive vehicle.

  The control device for an internal combustion engine according to the present invention may be applied to a power split type hybrid vehicle. In this case, the output power of the engine is reduced by changing the power consumed by the rotating electrical machine to which the power generated by the engine is distributed.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  The present invention is applicable to a control device for an internal combustion engine that executes fuel cut after reducing the output torque of the internal combustion engine when the fuel cut execution condition is satisfied.

2 Engine (Internal combustion engine)
10 EG-ECU
44 Injector 45 Spark plug

Claims (1)

In a control device for an internal combustion engine that stops fuel supply to the internal combustion engine after reducing an output torque of the internal combustion engine when a predetermined fuel cut execution condition is satisfied,
Of the period during which the output torque of the internal combustion engine is reduced, a predetermined period including the timing at which the internal combustion engine switches from the driving state to the driven state is obtained, the output torque of the internal combustion engine at the start of the predetermined period, and the predetermined period The required torque for each cycle of the internal combustion engine during the predetermined period is set according to the target torque of the internal combustion engine at the end of the period, and the required torque set corresponding to the cycle is set for each cycle. A control apparatus for an internal combustion engine, characterized in that the control value of the control parameter of the internal combustion engine is instructed so as to be obtained.

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