JP2015190379A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deviation of the quantity of cylinder inflow air at a time of restarting an internal combustion engine with a turbocharger from a temporary stop.SOLUTION: In an internal combustion engine 10 including a turbocharger that includes a turbine 32 and a compressor 22, a control device estimates the number of revolutions of the turbine 32 during stop of the engine 10 if a request to stop the engine 10 is issued. The control device estimates the current number of revolutions of the turbine 32 based on the number of revolutions of the turbine 32 during the engine stop and engine stop time when the engine 10 is restarted. If the current number of revolutions of the turbine 32 is higher than a predetermined threshold, the control device corrects a manipulated variable of an air related actuator such as a throttle 26, an ABV 28 or an IN-VVT so as to reduce a quantity of cylinder inflow air.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine provided with a turbocharger.

  Conventionally, for example, Japanese Patent Application Laid-Open No. 2013-245595 discloses a technique for suppressing deterioration of drivability after starting an engine in a hybrid vehicle including an engine having a supercharger. More specifically, in this hybrid vehicle, when the engine stop is requested, when the idling operation or the motoring operation is performed, the supercharging pressure of the supercharger is reduced than when the engine is not performed. Then, the engine stop process is performed. Thereby, generation | occurrence | production of the vehicle vibration accompanying a stop of an engine is suppressed.

JP 2013-245595 A JP 2010-14071 A JP 2013-184554 A

  By the way, in an internal combustion engine equipped with a turbocharger, when an engine stop request is issued during high load traveling, the turbine may continue to rotate even after the engine is stopped. If an engine restart request is issued again in such a state, the amount of fresh air flowing into the cylinder at the time of starting becomes larger than the target value, so that the desired torque cannot be realized, and the emission deteriorates. May happen.

  The present invention has been made in view of the above-described problems. In an internal combustion engine equipped with a turbocharger, the displacement of the inflow into the cylinder when the internal combustion engine restarts from a temporary stop is suppressed. It is an object of the present invention to provide a control device for an internal combustion engine that can be used.

In order to achieve the above object, a first invention provides a control device for an internal combustion engine including a turbocharger including a turbine disposed in an exhaust passage and a compressor disposed in an intake passage.
First estimation means for estimating a turbine rotational speed at the time of stop when a request to stop the internal combustion engine is issued;
Second estimation means for estimating the current turbine speed based on the turbine speed at the time of stop and the stop time of the internal combustion engine when the internal combustion engine is restarted;
Correction means for correcting the operation amount of the air actuator in a direction to decrease the in-cylinder inflow air amount when the current turbine rotation speed is larger than a predetermined threshold;
It is characterized by providing.

  According to the first invention, when a stop request for the internal combustion engine is issued, the turbine speed at the time of stop is estimated, and the turbine at the time of restart is based on the turbine speed and the stop time at the time of stop. The number of revolutions is estimated. Then, when the estimated turbine rotational speed at restart is larger than a predetermined reference value, the air system actuator is controlled in a direction in which the amount of air flowing into the cylinder decreases. For this reason, according to the present invention, an increase in the in-cylinder inflow air amount due to the influence of the turbine rotation at the time of restart can be suppressed, so that a problem that a desired torque cannot be realized and emission deteriorates occurs. Can be suppressed.

It is a block diagram which shows the system configuration | structure of the hybrid vehicle applied to Embodiment 1 of this invention. It is a block diagram for demonstrating the system configuration | structure of the engine by Embodiment 1 of this invention. It is a flowchart which shows the routine for the control at the time of the engine stop performed by ECU50 in Embodiment 1 of this invention. It is a flowchart which shows the routine for the control at the time of the engine restart performed by ECU50 in Embodiment 1 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

[Configuration of Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a system configuration of a hybrid vehicle applied to the first embodiment of the present invention. A hybrid vehicle 1 includes a motor 2, a transmission mechanism 3, a power split mechanism 5, a generator 6, a battery 9, an internal combustion engine (engine) 10, and the like. The motor 2 constitutes a power source of the vehicle 1 together with the engine 10, and the output side of the motor 2 is connected to the wheel 4 via a transmission mechanism 3 including a speed reduction mechanism and the like. The output side of the engine 10 is connected to the transmission mechanism 3 and the generator 6 via the power split mechanism 5. The generator 6 is connected to a battery 9 via an inverter 7 and a boost converter 8.

  Power split device 5 adjusts the ratio of driving force transmitted from engine 10 to transmission mechanism 3 and generator 6. Thereby, in the hybrid vehicle, the battery 9 can be charged by the generator 6 while the power split mechanism 5 controls the ratio of the driving force of the motor 2 and the engine 10 transmitted to the wheels 4. While the vehicle 1 is traveling, both the engine traveling that travels by the driving force of the engine 10 while the motor 2 is stopped and the motor traveling that travels by the driving force of the motor 2 while the engine 10 is stopped are both. Hybrid traveling that travels using the driving force is realized. These vehicle controls are executed by an ECU 50 described later.

  Next, the configuration of the engine 10 will be described with reference to FIG. FIG. 2 is a configuration diagram for explaining a system configuration of the engine according to the first embodiment of the present invention. The engine 10 shown in FIG. 2 is a spark ignition type 4-stroke reciprocating engine. The engine 10 has a configuration of an intake system for supplying air into the combustion chamber of each cylinder, an exhaust system for discharging exhaust gas, and a control system for controlling the operation of the engine 10. Hereinafter, each of these configurations will be described in detail.

  The intake system of the engine 10 includes an intake passage 12. An air cleaner 14 is attached to the inlet side of the intake passage 12. An air flow meter (AFM) 16 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 12 is attached to the intake passage 12 downstream of the air cleaner 14. The outlet side of the intake passage 12 is connected to the combustion chamber of each cylinder 20 via a surge tank 18 and an intake valve. The intake valve is provided with a variable valve timing mechanism (IN-VVT) for variably setting the valve timing. Further, the surge tank 18 is provided with a pressure sensor 52 for detecting the intake pipe pressure (supercharging pressure) Pim.

  A turbocharger compressor 22 is disposed downstream of the air flow meter 16 in the intake passage 12. An intercooler 24 for cooling the intake air compressed by the compressor 22 is disposed in the intake passage 12 on the downstream side of the compressor 22. A throttle 26 for adjusting the amount of air supplied into the engine 10 is disposed in the intake passage on the downstream side of the intercooler 24.

  The intake passage 12 is provided with an air bypass valve (hereinafter also referred to as “ABV”) 28 for allowing air to flow through the compressor 22. The air bypass valve 28 is configured by, for example, an electrically controlled air bypass valve for active control that realizes an arbitrary opening degree. The air bypass valve 28 is opened when the throttle 26 is suddenly closed, thereby suppressing the occurrence of a surge and the compressor 22. Protect.

  The exhaust system of the engine 10 includes an exhaust passage 30. One end side of the exhaust passage 30 is connected to the combustion chamber of each cylinder 20 via an exhaust valve. The exhaust valve is provided with a variable valve timing mechanism (EX-VVT) for variably setting the valve timing.

  A turbocharger turbine 32 is arranged in the middle of the exhaust passage 30. A start catalyst (hereinafter referred to as “S / C”) 34 is disposed in the exhaust passage 30 on the downstream side of the turbine 32. S / C 34 is a so-called three-way catalyst that efficiently purifies the three components of HC, CO, and NOx contained in the exhaust gas in the vicinity of the theoretical air-fuel ratio.

  The exhaust passage 30 is provided with a waste gate valve (hereinafter also referred to as “WGV”) 36 for allowing the exhaust gas to flow by bypassing the turbine 32. A pressure sensor 54 for detecting the exhaust pressure Pex is provided on the upstream side of the turbine 32 in the exhaust passage 30.

  The engine 10 of the present embodiment includes an ECU (Electronic Control Unit) 50 as its control system. In addition to the throttle 26, ABV 28, WGV 36, and IN-VVT, various actuators such as a spark plug (not shown) are connected to the output side of the ECU 50. On the input side of the ECU 50, in addition to the air flow meter 16 and the pressure sensors 52 and 54, a crank angle sensor and an air-fuel ratio sensor (both not shown) for outputting a signal corresponding to the rotation angle of a crankshaft (not shown). Etc.) are connected. The ECU 50 operates each actuator provided in the engine according to a predetermined control program based on the output of each sensor provided in the engine.

[Operation of Embodiment 1]
Next, the operation of the first embodiment will be described. In a hybrid vehicle, the engine is stopped when there is no torque request. Here, when the engine is stopped from a high load running in an engine equipped with a turbocharger, the turbine continues to rotate for a while even after the engine is stopped. For this reason, when the accelerator pedal is stepped on immediately after the engine is stopped, the engine is restarted in a state of being supercharged by the rotation of the turbine. It will flow into. In this case, since the in-cylinder air-fuel ratio becomes lean, there is a risk that a desired torque cannot be realized or the emission deteriorates.

  Therefore, in the system of the present embodiment, the turbine rotational speed when the engine is restarted is estimated, and the throttle 26 is adjusted so that the amount of air flowing into the cylinder does not exceed the target. Hereinafter, control at the time of engine stop and control at the time of engine restart executed in the present embodiment will be described with reference to flowcharts.

  The flowchart of FIG. 3 shows a routine for control at the time of engine stop executed by the ECU 50 in the present embodiment. In this routine, it is first determined whether an engine stop request has been issued (step S100). As a result, when the engine stop request has not been issued, this routine is immediately terminated. On the other hand, when an engine stop request is issued, the process proceeds to the next step and the engine is stopped (step S102).

  Next, it is determined whether or not it is in the turbine speed estimation operation region (step S104). Specifically, it is determined whether or not the engine load factor and engine speed before engine stop are equal to or greater than a threshold value. As the threshold value, predetermined values are used as an engine load factor and an engine speed at which the turbine rotates even after the engine is stopped. As a result, when it is determined that it is not in the turbine rotation speed estimation operation region, it is determined that there is no influence by the turbine rotation at the time of restart, and this routine is ended. On the other hand, when it is determined that it is in the turbine rotation speed estimation operation region, the process proceeds to the next step, and the estimated turbine rotation speed is calculated (step S106). Specifically, the exhaust pressure Pex detected by the pressure sensor 54, the intake pipe pressure (supercharging pressure) Pim detected by the pressure sensor 52, and the opening degree of the WGV 36 are acquired. Based on the turbine turning force calculated from the exhaust pressure Pex, the exhaust amount flowing into the turbine calculated from the opening of the WGV 36, and the compressor flow rate calculated from the supercharging pressure Pim, the estimated turbine rotation before the engine stops A number is calculated. When this step is finished, the control at the time of engine stop by this routine is finished.

  The flowchart of FIG. 4 shows a routine for control at the time of engine restart executed by the ECU 50 in the present embodiment. In this routine, it is first determined whether an engine restart request has been issued (step S200). As a result, when the engine restart request has not been issued, this routine is immediately terminated. On the other hand, when an engine restart request is issued, the process proceeds to the next step, and the engine stop time from when the engine is stopped to when it is restarted is calculated (step S202).

  Next, based on the estimated turbine speed calculated in step S106 and the engine stop time calculated in step S202, a current estimated speed that is the current turbine speed is calculated (step S204). After the engine stops, the turbine speed is attenuated by friction. Specifically, the attenuation rate is estimated from the engine stop time. Then, the current estimated rotational speed is calculated based on the attenuation rate and the estimated turbine rotational speed.

  Next, it is determined whether or not the currently estimated rotational speed is greater than a predetermined threshold (step S206). As the threshold value, a predetermined value is used as a value for determining whether or not the in-cylinder inflow air amount deviates from the target air amount. As a result, when it is not recognized that the current estimated rotational speed> the threshold value is not established, it is determined that the adjustment of the air amount is unnecessary, and this routine is immediately terminated.

  On the other hand, if it is determined in step S206 that the current estimated rotational speed> threshold value is established, the process proceeds to the next step. In the next step, the operation amount of the throttle 26 is corrected in a direction to decrease the in-cylinder inflow air amount, and the in-cylinder inflow air amount is adjusted to the target air amount (step S208). Here, specifically, when the currently estimated rotational speed is large, the opening degree of the throttle 26 is corrected to the closed side.

  As described above, according to the system of the first embodiment, the turbine rotational speed (currently estimated rotational speed) when the engine is stopped and restarted is calculated, so that the turbine can be used without using the rotational speed sensor. The number of rotations can be acquired. Further, since the operation amount of the throttle 26 is corrected based on the currently estimated rotational speed, the in-cylinder air amount at the time of restart is controlled to the control target value even in a state of being supercharged by the rotation of the turbine. Can do.

  By the way, in the system of Embodiment 1 mentioned above, in the hybrid vehicle, it demonstrated as control performed when an engine is restarted, However, The system which can apply the control of this invention is restricted to the system of a hybrid vehicle. Absent. That is, for example, in a vehicle system using only an engine with a turbocharger as a power source, the control of the present invention may be applied when the engine is stopped and then restarted during idle operation.

  Further, in the system of the first embodiment described above, the operation amount of the throttle 26 is corrected when the present estimated rotational speed> threshold is established. However, the correction target is not limited to the operation amount of the throttle 26, and the operation amount of other air system actuators such as ABV 28 and IN-VVT may be corrected instead of or in addition to the operation amount of the throttle 26. . In this case, when the currently estimated rotational speed is large, the opening degree of the ABV 28 may be corrected to the open side, and IN-VVT may be corrected to the late closing side.

  In the control device of the first embodiment described above, the current estimated rotational speed is the “current turbine rotational speed” of the first invention, and the estimated turbine rotational speed is the “turbine rotational speed at stop” of the first invention. Respectively. In the control device of the first embodiment described above, the ECU 50 executes the processes of steps S100 to S106, so that the “first estimating means” of the first invention causes the ECU 50 to perform the processes of steps S200 to S204. When executed, the “second estimating means” of the first invention and the “correcting means” of the first invention are realized by the ECU 50 executing the processing of steps S206 to S208.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Motor 3 Transmission mechanism 5 Power split mechanism 6 Generator 7 Inverter 8 Boost converter 9 Battery 10 Internal combustion engine (engine)
12 Intake passage 14 Air cleaner 16 Air flow meter (AFM)
18 Surge tank 20 Cylinder 22 Compressor 24 Intercooler 26 Throttle 28 Air bypass valve (ABV)
30 Exhaust passage 32 Turbine 34 Start catalyst (S / C)
36 Wastegate valve (WGV)
50 ECU (Electronic Control Unit)
52,54 Pressure sensor

Claims (1)

In an internal combustion engine including a turbocharger configured by a turbine disposed in an exhaust passage and a compressor disposed in an intake passage,
First estimation means for estimating a turbine rotational speed at the time of stop when a request to stop the internal combustion engine is issued;
Second estimation means for estimating the current turbine speed based on the turbine speed at the time of stop and the stop time of the internal combustion engine when the internal combustion engine is restarted;
When the current turbine speed is greater than a predetermined threshold, correction means for correcting the operation amount of the air system actuator in a direction to decrease the in-cylinder inflow air amount;
A control device for an internal combustion engine, comprising:

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