JP2017180195A - Control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To early solve turbo lag in a control device of an engine including a turbo supercharger.SOLUTION: A PCM 50 includes a VVT control portion 59 for controlling an overlap timing as a timing when both of an intake valve 22 and an exhaust valve 29 are opened through an exhaust VVT in an intake stroke of an engine 100. The VVT control portion 59 determines whether turbo lag occurs in a turbo supercharger 4 or not, and the VVT control portion 59 retards a closing timing of the exhaust valve 29 so that the overlap timing is extended when the occurrence of the turbo lag in the turbo supercharger 4 is determined.SELECTED DRAWING: Figure 9

Description

  The technology disclosed herein relates to an engine control device including a turbocharger.

  In an engine equipped with a turbocharger, a turbine is disposed in the exhaust passage and a compressor is disposed in the intake passage. When the turbine is rotationally driven by the exhaust, the compressor directly connected to the turbine is rotationally driven, and the mass of the intake air (hereinafter referred to as “filling amount”) taken into the cylinder from the intake system is increased.

  Conventionally, it is known that a delay in rising of the supercharging pressure, that is, a so-called turbo lag occurs under a predetermined situation. Turbo lag occurs due to the exhaust flow being insufficient when accelerating from, for example, low speed operation or idle operation, and thus the turbine is not sufficiently driven to rotate. In order to solve this problem, for example, Patent Document 1 discloses increasing the filling amount by adjusting the opening / closing timing of the intake valve during acceleration transient. If the filling amount increases, the exhaust amount for rotationally driving the turbine also increases according to the increase.

JP 2004-183512 A

  However, when configured as described above, the increase in the filling amount contributes to the increase in the supercharging pressure after the exhaust stroke after the increased amount of the air-fuel mixture burns. Therefore, there is room for improvement in eliminating the turbo lag at an early stage.

  The technology disclosed herein has been made in view of such a point, and an object of the technology is to quickly eliminate a turbo lag in an engine control device including a turbocharger.

  The technology disclosed herein relates to an engine control device that includes a turbocharger and a variable valve timing mechanism that changes the opening / closing timing of an exhaust valve. The control device includes a control unit that sets a closing timing of the exhaust valve and controls an overlap period, which is a period in which both the intake valve and the exhaust valve are opened, via the valve timing variable mechanism. . The control unit determines whether a turbo lag is generated in the turbocharger, and the control unit also determines that the turbo lag is generated in the turbocharger, and the overlap period is extended. As described above, the closing timing of the exhaust valve is retarded.

  The control unit controls an overlap period in which both the intake valve and the exhaust valve are opened. During the overlap period, the air taken into the cylinder from the intake system blows into the exhaust system.

  Turbo lag can occur during acceleration transients. During acceleration transition, the amount of charge sucked into the cylinder increases through the opening of the throttle valve or the like.

  According to the above configuration, when it is determined that the turbo lag has occurred, the control unit retards the closing timing of the exhaust valve so that the overlap period is extended. By extending the overlap period, the proportion of air that blows into the exhaust system out of the air that has increased as the filling amount increases, and the flow rate of air sent to the turbine increases according to the increase. . As a result, the turbine can be sufficiently driven to rotate.

  Furthermore, the above-described configuration can increase the flow rate of the air sent to the turbine before the air-fuel mixture is combusted and exhausted when air is sucked into the cylinder. Turbo lag can be eliminated early.

  Furthermore, according to the above-described configuration, the amount of oxygen in the exhaust system increases as the proportion of air blown into the exhaust system increases, so that so-called afterburning occurs as a result of oxygen reacting in the exhaust system. It tends to happen. Since the air that has blown into the exhaust system rises in temperature due to the afterburning, and then increases in pressure, it is advantageous in sufficiently driving the turbine to rotate.

  Further, the control unit delays the closing timing of the exhaust valve based on a fresh air blow-off rate, which is a ratio of fresh air sucked into the cylinder and blown into the exhaust system during the overlap period. The angular amount may be set.

  According to this configuration, the control unit can appropriately set the retardation amount. This is advantageous for reliably eliminating the turbo lag.

  The engine further includes a second valve timing variable mechanism controlled by the control unit so as to change the opening / closing timing of the intake valve, and the control unit sets the opening / closing timing of the intake valve. When it is determined that a turbo lag has occurred in the turbocharger, the charging amount of the intake air taken into the cylinder is increased by correcting the opening / closing timing of the intake valve, and the control unit During the correction of the opening / closing timing of the intake valve, the closing timing of the exhaust valve may be retarded.

  According to the above configuration, when it is determined that the turbo lag has occurred, the control unit increases the filling amount by correcting the opening / closing timing of the intake valve. Then, the control unit retards the closing timing of the exhaust valve as described above during correction of the opening / closing timing of the intake valve. According to this, it is possible to increase the flow rate of air that blows through during the overlap period by the amount of filling that increases due to the correction related to the intake valve. This is advantageous in sufficiently driving the turbine.

  In addition, the engine includes a throttle valve provided downstream of the turbocharger compressor in the intake passage, and the controller is configured to take in intake air into the cylinder based on a target boost pressure. Based on the intake air state in the downstream side passage which is at least a part of the downstream side of the throttle valve and the operating state of the engine. The volume efficiency or the filling amount predicted value when the intake air in the downstream passage is sucked into the cylinder is calculated, and the control unit also calculates the volume efficiency or the filling amount predicted value as the volume efficiency. Alternatively, when the charging amount is smaller than the target value, the opening / closing timing of the intake valve may be corrected.

  Generally, a throttle valve, a surge tank, etc. are provided between the compressor and the combustion chamber. Therefore, the filling amount is influenced not only by the supercharging pressure that is the pressure in the intake passage between the compressor and the throttle valve, but also by the opening degree of the throttle valve, the volume of the surge tank, and the like.

  On the other hand, the downstream passage is a portion on the downstream side of the throttle valve, and is a portion relatively close to the cylinder in the intake passage. Therefore, the control unit corrects the opening / closing timing of the intake valve based on the intake state in the downstream passage. Thereby, the control part can adjust the filling amount with high accuracy.

  Further, the charging amount is affected not only by the intake state but also by the operating state of the engine such as the engine speed and the opening / closing timing of the intake valve. Therefore, the control unit corrects the opening / closing timing of the intake valve based on the operating state of the engine. Thereby, the control part can adjust the filling amount with high accuracy.

  Further, as described above, the control unit predicts the volume efficiency or the filling amount when the intake air in the downstream passage is sucked into the cylinder based on the intake state in the downstream passage and the operating state of the engine. At the same time, the opening / closing timing of the intake valve is corrected based on the prediction result. According to this, the control unit can correct the opening / closing timing of the intake valve in advance by predicting the volumetric efficiency or the charging efficiency in advance. Thus, the control unit can adjust the filling amount at an early stage. In addition, since it is assumed that the intake air in the downstream passage will be sucked into the cylinder in the future, by predicting the future volumetric efficiency or filling amount based on the state of the intake air in the downstream passage, the control unit Can accurately predict the volumetric efficiency or the filling amount.

  In addition, as described above, the control unit corrects the opening / closing timing of the intake valve in consideration of not only the predicted value of the volumetric efficiency or the filling amount but also the target value of the volumetric efficiency or the filling amount. According to this, the control unit can correct the opening / closing timing early so that, for example, the predicted value and the target value are compared in advance so that the volumetric efficiency or the filling amount becomes the target value.

  Further, as described above, the control unit compares the predicted value with the target value in advance. Thereby, the control unit can advance the closing timing early so that the volumetric efficiency or the filling amount becomes the target value. Thus, the control unit can adjust the filling amount at an early stage.

  Further, as described above, the control unit calculates the target value of the volumetric efficiency or the filling amount based on the target supercharging pressure. According to this, the control unit can accurately adjust the filling amount during acceleration transient.

  Specifically, as described above, turbo lag can occur during acceleration transients. In order to eliminate the turbo lag, it is conceivable to increase the filling amount at an early stage. At that time, in order to achieve the target supercharging pressure with high accuracy, it is desired to adjust the filling amount with high accuracy.

  As described above, since the target value of volumetric efficiency or filling amount is set based on the target supercharging pressure, the filling amount during acceleration transient can be accurately adjusted. In addition, as described above, the opening / closing timing of the intake valve is corrected in advance based on the predicted value of the volumetric efficiency or the filling amount, so that the filling amount can be increased early and the target boost pressure can be realized. Time can be shortened. This is advantageous in eliminating the turbo lag at an early stage.

  As described above, according to the engine control apparatus, the turbo lag can be eliminated at an early stage.

FIG. 1 is a schematic configuration diagram of an engine. FIG. 2 is a functional configuration diagram of the PCM. FIG. 3 is a flowchart of processing related to torque base control. FIG. 4 is an explanatory diagram schematically showing a state in which the opening / closing timing of the intake valve is set to a basic value. FIG. 5 is an explanatory diagram schematically showing a state in which the opening / closing timing of the intake valve is advanced from the basic value. FIG. 6 is an explanatory diagram schematically showing a state in which the opening / closing timing of the exhaust valve is set to (a) a basic value at start-up, and (b) a state in which the exhaust valve is delayed from the basic value. FIG. 7 is a block diagram showing a method for controlling the intake VVT. FIG. 8 is a block diagram showing a method for controlling the exhaust VVT. FIG. 9 is a time chart illustrating the transition of (a) the accelerator opening, (b) the transition timing of the intake valve, and (c) the transition timing of the exhaust valve during acceleration acceleration.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

<Engine configuration>
FIG. 1 is a schematic configuration diagram of an engine to which a control device according to an embodiment is applied.

  As shown in FIG. 1, an engine 100 (for example, a gasoline engine) mainly includes an intake passage 10 through which intake air (air) introduced from the outside passes, intake air supplied from the intake passage 10, and a fuel injection valve described later. An engine main body 20 that drives the engine 100 by burning an air-fuel mixture supplied from the fuel 23, an exhaust passage (exhaust system) 30 through which exhaust gas generated by the combustion in the engine main body 20 is discharged, and the engine 100 And a PCM (Powertrain Control Module) 50 for controlling the whole.

  In the intake passage 10, in order from the upstream side, an air cleaner 2 that purifies intake air introduced from the outside, a compressor 4 a of the turbocharger 4 that boosts the intake air that passes through, and an intercooler 9 that cools the intake air that passes through. And a throttle valve 11 for adjusting the flow rate of the intake air passing therethrough, and an intake manifold 13 having a surge tank 13a for temporarily storing the intake air supplied to the engine body 20. The intake manifold 13 is connected to the intake port 14 of the engine body 20.

  The intake passage 10 is provided with an air bypass passage 6 for returning a part of the intake air supercharged by the compressor 4a to the upstream side of the compressor 4a. One end of the air bypass passage 6 is connected to the intake passage 10 downstream of the compressor 4a and upstream of the throttle valve 11, and the other end is connected to the intake passage 10 upstream of the compressor 4a. The air bypass passage 6 is provided with an air bypass valve 7 for controlling the flow rate of intake air flowing through the air bypass passage 6.

  In this specification, a portion from the upstream end portion of the air cleaner 2 to the downstream end portion of the intake port 14 is referred to as an intake passage 10. Further, at least a part of the intake passage 10 on the downstream side of the throttle valve 11 is referred to as a downstream passage 10a. In this embodiment, the downstream passage 10a is a passage extending from the surge tank 13a of the intake manifold 13 to the downstream end of the intake port 14 (portion surrounded by a broken line in FIG. 1).

  The engine body 20 mainly includes an intake valve 22 that opens and closes the intake port 14, a fuel injection valve 23 that injects fuel into the cylinder 21, and a mixture of intake air and fuel supplied into the cylinder 21. An ignition plug 24 that ignites, a piston 27 that reciprocates by combustion of the air-fuel mixture in the cylinder 21, a crankshaft 28 that is rotated by the reciprocation of the piston 27, and an exhaust valve 29 that opens and closes the exhaust port 31. .

  An intake camshaft and an exhaust camshaft (not shown) are drivingly connected to the crankshaft 28. The intake camshaft rotates in conjunction with the crankshaft 28 to drive the intake valve 22. By this driving, the intake valve 22 reciprocates so as to open and close the intake port 14 at a predetermined timing. Similarly, the exhaust camshaft rotates in conjunction with the crankshaft 28 to drive the exhaust valve 29. By this driving, the exhaust valve 29 reciprocates so as to open and close the exhaust port 31 at a predetermined timing.

  The engine body 20 includes a variable valve timing mechanism (intake VVT) 25 that advances or retards the phase of the intake camshaft and a second variable valve timing mechanism (exhaust VVT) that advances or retards the phase of the exhaust camshaft. 26).

  The intake VVT 25 continuously changes the opening timing and closing timing of the intake valve 22 between a predetermined most advanced timing and the most retarded timing by advancing or retarding the phase of the intake camshaft. . In this embodiment, the intake VVT 25 is configured using an electromagnetic valve as its control valve. Similarly, the exhaust VVT 26 continuously changes the opening timing and closing timing of the exhaust valve 29 by advancing or retarding the phase of the exhaust camshaft. In this embodiment, the exhaust VVT 26 is configured using a hydraulic solenoid valve as its control valve.

  The exhaust passage 30 is rotated by the exhaust passing therethrough in order from the upstream side, and the turbine 4b of the turbocharger 4 that rotates the compressor 4a by this rotation, and an exhaust purification catalyst 37 having an exhaust purification function, 38. The exhaust purification catalysts 37 and 38 are, for example, a NOx catalyst, a three-way catalyst, an oxidation catalyst, or the like.

  The upstream end portion of the exhaust pipe constituting the exhaust passage 30 has a branch pipe 30a connected to the exhaust port 31 and a collecting part where the branch pipes 30a gather. A part of the branch pipe 30a is constituted by an exhaust manifold.

  Further, an exhaust gas recirculation (EGR) passage 32 that recirculates exhaust gas to the intake passage 10 is connected to the exhaust passage 30. One end of the EGR passage 32 is connected to the exhaust passage 30 upstream of the turbine 4 b, and the other end is connected to the intake passage 10 downstream of the throttle valve 11. In addition, the EGR passage 32 is provided with an EGR cooler 33 that cools the exhaust gas to be recirculated and an EGR valve 34 that controls the flow rate of the exhaust gas flowing through the EGR passage 32.

  Further, the exhaust passage 30 is provided with a turbine bypass passage 35 for bypassing the turbine 4b of the turbocharger 4 for exhaust. The turbine bypass passage 35 is provided with a waste gate valve (hereinafter referred to as “WG valve”) 36 for controlling the flow rate of the exhaust gas flowing through the turbine bypass passage 35.

  Further, the engine 100 shown in FIG. 1 is provided with various sensors. Specifically, in the intake system of the engine 100, an air flow meter 61 that detects an intake air flow rate in an intake passage 10 on the downstream side of the air cleaner 2 (specifically, an intake passage 10 between the air cleaner 2 and the compressor 4a), A first temperature sensor 62 for detecting the intake air temperature is provided, and a first pressure sensor 63 for detecting a supercharging pressure is provided in the intake passage 10 between the compressor 4 a and the throttle valve 11, and the downstream of the throttle valve 11. A second pressure sensor 64 that detects an intake manifold pressure that is a pressure in the surge tank 13a is provided in the intake passage 10 on the side (specifically, in the surge tank 13a). The second pressure sensor 64 incorporates a temperature sensor that detects the intake manifold temperature, which is the temperature in the surge tank 13a.

  In the engine body 20, a crank angle sensor 69 for detecting the crank angle of the crankshaft 28, an intake side cam angle sensor 70 for detecting the cam angle of the intake camshaft, and an exhaust for detecting the cam angle of the exhaust camshaft. A side cam angle sensor 71 is provided.

Further, in the exhaust system of the engine 100, an EGR opening sensor 65 that detects the EGR opening that is the opening of the EGR valve 34, and a WG opening sensor that detects the WG opening that is the opening of the WG valve 36. 66, an O ₂ sensor 67 for detecting the oxygen concentration in the exhaust gas, and an exhaust temperature in an exhaust passage 30 downstream of the turbine 4b (specifically, an exhaust passage 30 between the turbine 4b and the exhaust purification catalyst 37). And an exhaust gas temperature sensor 68 for detecting the above.

  In addition, the engine 100 is provided with an atmospheric pressure sensor 60 that detects the atmospheric pressure, and an accelerator opening sensor 72 that detects an accelerator opening that is an opening of the accelerator pedal 81.

The air flow meter 61 supplies a detection signal S61 corresponding to the detected intake flow rate to the PCM 50, the first temperature sensor 62 supplies a detection signal S62 corresponding to the detected intake air temperature to the PCM 50, and the first pressure sensor 63 The detection signal S63 corresponding to the detected supercharging pressure is supplied to the PCM 50, the second pressure sensor 64 supplies the detection signal S64 corresponding to the detected intake manifold pressure and intake manifold temperature to the PCM 50, and the EGR opening degree sensor 65 is The detection signal S65 corresponding to the detected EGR opening is supplied to the PCM 50, the WG opening sensor 66 supplies the detection signal S66 corresponding to the detected WG opening to the PCM 50, and the O ₂ sensor 67 detects The detection signal S67 corresponding to the oxygen concentration is supplied to the PCM 50, and the exhaust temperature sensor 68 detects the detection signal S68 corresponding to the detected exhaust temperature. Is supplied to the PCM50. The crank angle sensor 69 supplies a detection signal S69 corresponding to the detected crank angle to the PCM 50. The intake side cam angle sensor 70 and the exhaust side cam angle sensor 71 supply detection signals S70 and S71 corresponding to the detected cam angle to the PCM 50, respectively. The atmospheric pressure sensor 60 supplies a detection signal S60 corresponding to the detected atmospheric pressure to the PCM 50. The accelerator opening sensor 72 supplies a detection signal S72 corresponding to the detected accelerator opening to the PCM 50.

  The PCM 50 includes a CPU, a ROM for storing various programs (including a basic control program such as an OS and an application program that is activated on the OS to realize a specific function) and various data executed on the CPU. It is comprised by the computer provided with internal memory like RAM. The PCM 50 performs various controls and processes based on the detection signals supplied from the various sensors described above. The PCM 50 is an example of a control device.

  FIG. 2 shows a functional configuration diagram of the PCM 50. More specifically, the PCM 50 includes a base setting unit 51 that performs torque base control for setting a basic value for control of each actuator, and a VVT control that controls the intake VVT 25 and the exhaust VVT 26 based on the basic values set by the base setting unit 51. Part 59. The VVT control unit 59 is an example of a control unit.

  The base setting unit 51 obtains a required output torque value (hereinafter referred to as “target torque”) based on the operating state of the engine 100, and based on the target torque, the opening of the throttle valve 11 and the WG valve 36. Basic values such as the opening, the ignition timing of the spark plug 24, the opening / closing timing of the intake valve 22, the opening / closing timing of the exhaust valve 29, and the injection amount of the fuel injection valve 23 are set. Each basic value is variously changed according to the target torque.

  The VVT control unit 59 includes an intake VVT control unit 53 that controls the intake VVT 25 and an exhaust VVT control unit 54 that controls the exhaust VVT 26. Basically, the intake VVT control unit 53 controls the intake VVT 25 so as to realize the opening / closing timing of the intake valve 22 set by the base setting unit 51, while the exhaust VVT control unit 54 is controlled by the base setting unit 51. The exhaust VVT 26 is controlled so as to realize the set opening / closing timing of the exhaust valve 29. Depending on the operating state of the engine 100, the opening / closing timing of the intake valve 22 and the opening / closing timing of the exhaust valve 29 are set so that the valve opening period of the intake valve 22 and the valve opening period of the exhaust valve 29 overlap during the intake stroke. May be. In such a case, the VVT control unit 59 performs valve overlap in which both the intake valve 22 and the exhaust valve 29 are opened via the intake VVT control unit 53 and the exhaust VVT control unit 54. By executing the valve overlap, the fresh air taken into the cylinder 21 through the intake port 14 is discharged from the exhaust port 31 as it is. For example, valve overlap is performed when it is desired to increase the turbine flow rate, when it is desired to decrease the temperature of the cylinder 21, and when it is desired to promote scavenging of the cylinder 21.

  The intake VVT control unit 53 corrects the intake valve opening / closing timing set by the base setting unit 51 (specifically, based on the intake state in the downstream passage 10a and the operating state of the engine 100). , Advance angle of opening and closing time). This correction is performed when a turbo lag is generated in the turbocharger 4, and this correction increases the filling amount of the intake air sucked into the cylinder 21.

  Further, the exhaust VVT control unit 54 controls an overlap period that is a period in which both the intake valve 22 and the exhaust valve 29 are open. Specifically, the exhaust VVT control unit 54 determines whether or not a turbo lag has occurred in the turbocharger 4, and retards the closing timing of the exhaust valve 29 when determining that the turbo lag has occurred. The exhaust VVT control unit 54 extends the overlap period according to the amount of retardation. By extending the overlap period, the flow rate of fresh air that blows into the exhaust passage 30 increases as will be described later.

<Torque base control>
First, processing related to torque base control will be described in detail with reference to the flowchart of FIG. FIG. 3 is a flowchart showing processing performed by the base setting unit 51 and processing performed by the VVT control unit 59.

  First, in step S <b> 1, the base setting unit 51 acquires the operating state of the engine 100. Specifically, the rotational speed of engine body 20 (hereinafter referred to as “engine speed”), the vehicle speed, the accelerator opening, the gear ratio, and the like are read as the operating state of engine 100. For example, the engine speed is acquired based on the detection result of the crank angle sensor 69.

  Then, the base setting part 51 calculates | requires target acceleration according to the acquired driving | running state (step S2). Moreover, the base setting part 51 calculates | requires the target torque required in order to implement | achieve a target acceleration (step S3).

  Further, in step S4, the base setting unit 51 obtains a target value of charging efficiency (hereinafter referred to as “target charging efficiency”) necessary for realizing the target torque. Specifically, the target charging efficiency is obtained based on the target torque, the engine speed, and the target value of the indicated mean effective pressure (hereinafter referred to as “target indicated mean effective pressure”). The target indicated mean effective pressure is obtained based on the target torque, the mechanical resistance that becomes torque loss, and the pump loss (pumping loss).

  In step S5, the base setting unit 51 sets the basic value of the opening / closing timing of the intake valve 22 and the basic value of the opening / closing timing of the exhaust valve 29 based on the target charging efficiency obtained as described above. The basic value of the opening / closing timing of the intake valve 22 is stored in the internal memory of the PCM 50 in an intake VVT map defined in association with the engine speed and the target charging efficiency and the opening / closing timing of the intake valve 22 corresponding thereto. Based on. Similarly, the basic value of the opening / closing timing of the exhaust valve 29 is an exhaust gas that is pre-stored in the internal memory of the PCM 50 and is defined in association with the engine speed and the target charging efficiency and the opening / closing timing of the exhaust valve 29 corresponding thereto. It is obtained based on the VVT map.

  FIG. 4 is an explanatory diagram schematically showing a state in which the opening / closing timing of the intake valve 22 is set to a basic value when the engine 100 is started. As shown in FIG. 4, the basic value of the opening / closing timing of the intake valve 22 is basically set so that the intake valve 22 opens in the middle of the intake stroke and closes in the middle of the compression stroke past the BDC. . That is, the intake valve 22 is set to a so-called “slow closing”. Further, the basic value of the opening / closing timing of the exhaust valve 29 is set so that the above-described valve overlap is executed depending on the engine speed and the target charging efficiency.

  After step S5, steps S6 to S9 and steps S10 to S15 are performed in parallel.

In step S6, the base setting unit 51 obtains a target value (hereinafter referred to as “target intake manifold air amount”) of the amount of intake air in the intake manifold 13 necessary for realizing the target charging efficiency. The target intake manifold air amount is based on the volumetric efficiency based on the intake density in the intake manifold 13, so-called intake manifold reference volumetric efficiency, the volume of the intake manifold 13 (hereinafter referred to as “intake manifold volume”) Vi, and the volume of the cylinder 21. Vc (hereinafter referred to as “cylinder volume”) and a target value (hereinafter referred to as “target cylinder air amount”) of a cylinder intake air amount Qcr that is the mass of intake air per stroke taken into the cylinder 21. Based on. Both the intake manifold volume Vi and the cylinder volume Vc are defined in advance, and are respectively stored in the internal memory of the PCM 50. The target cylinder air amount is obtained based on the target charging efficiency set in step S4, the cylinder volume Vc, and the standard atmospheric density ρ0. The standard atmospheric density ρ0 is the density of the atmosphere in a standard state (about 1.2 kg [kg / m ³ ]).

  In step S <b> 7, the base setting unit 51 obtains a target value of the flow rate of the intake air that passes through the throttle valve 11 (hereinafter referred to as “target throttle passage flow rate”) that is necessary for realizing the target intake manifold air amount. This target throttle passage flow rate is obtained by calculating the target charging efficiency obtained in step S4, the target intake manifold air amount obtained in step S5, and the estimated value of the current intake manifold air amount (hereinafter referred to as “actual intake manifold air amount”). Based on and. The actual intake manifold air amount is estimated based on the intake manifold pressure and the intake manifold temperature detected by the second pressure sensor 64. The actual intake manifold air amount may be estimated by calculating a balance between the amount of air flowing into the intake manifold 13 and the amount of air flowing out of the intake manifold 13 into the cylinder 21.

  In step S <b> 8, the base setting unit 51 sets a target value of the valve opening of the throttle valve 11 (hereinafter referred to as “target throttle opening”) that is necessary for realizing the target throttle passage flow rate. The target throttle opening is determined by the target throttle passage flow rate, the intake pressure (supercharging pressure) upstream of the throttle valve 11 detected by the first pressure sensor 63, and the throttle valve detected by the second pressure sensor 64. 11 and the intake pressure on the downstream side.

  In step S <b> 9, the base setting unit 51 also obtains basic values for the fuel injection valve 23 and the spark plug 24 based on an appropriate map stored in advance in the internal memory of the PCM 50. For example, the base setting unit 51 sets the injection amount of the fuel injection valve 23 based on the target charging efficiency, and sets the ignition timing of the spark plug 24 so as to achieve the target torque. Then, the base setting unit 51 outputs control signals corresponding to the respective control values (basic values) to the fuel injection valve 23 and the spark plug 24.

  On the other hand, in step S10, the base setting unit 51 obtains a target supercharging pressure that is a target value of the supercharging pressure that is necessary for realizing the target charging efficiency. The target supercharging pressure is stored in advance in the internal memory of the PCM 50. The supercharging pressure map is defined in association with the engine speed, the target charging efficiency, the opening / closing timing of the intake valve 22, and the target supercharging pressure corresponding thereto. Based on.

  In step S11, the base setting unit 51 obtains a target turbine flow rate that is a target value of the flow rate that passes through the turbine 4b, based on the target supercharging pressure. Specifically, the target turbine flow rate is obtained based on the target compressor driving force that is the target value of the compressor driving force, the engine speed, and the like. The target compressor driving force is obtained based on the target supercharging pressure.

  After step S11, steps S12 to S13 and steps S14 to S15 are performed in parallel.

  In step S12, the base setting unit 51 sets a target value of the valve opening of the WG valve 36 (hereinafter referred to as “target WG opening”) necessary to realize the calculated target turbine flow rate. . The target WG opening is obtained based on the target turbine flow rate and the total exhaust flow rate.

  In step S13, the base setting unit 51 outputs a control signal for driving the WG valve 36 so that the valve opening of the WG valve 36 becomes the target WG opening.

  On the other hand, in step S <b> 14, the VVT control unit 59 adjusts (corrects) the basic values of the opening / closing timings of the intake valve 22 and the exhaust valve 29 set by the base setting unit 51. Details of step S14 will be described later.

  In step S15, the PCM 50 outputs a control signal corresponding to each control value (basic value after correction) to the intake valve 22 and the exhaust valve 29.

  Note that the order of these steps is an example, and the order of the steps may be appropriately changed within a possible range, or a plurality of steps may be processed in parallel. For example, the steps that follow from step S6 to step S9 and the steps that follow from step S10 to step S13 may be processed one by one without being processed in parallel.

  Subsequently, a method of correcting the opening / closing timing of the intake valve 22 by the intake VVT control unit 53 in the process performed in step S14 will be described with reference to FIG. FIG. 7 is a block diagram showing a method of controlling the intake VVT 25. As shown in FIG.

<Intake VVT control>
As shown in FIG. 2, the intake VVT control unit 53 includes a target volume efficiency calculation unit 53 a that calculates a target value of volume efficiency (hereinafter referred to as “target volume efficiency”) Kvt, a predicted value of volume efficiency (hereinafter, referred to as “target volume efficiency”). Volume efficiency prediction unit 53b for calculating Kvs (referred to as “predicted volume efficiency”) and volume efficiency when the opening / closing timing of the intake valve 22 is advanced by a predetermined crank angle from the current basic value (hereinafter referred to as “virtual efficiency”). Based on the calculation results of the virtual volume efficiency calculation unit 53c for calculating Kvv, the target volume efficiency calculation unit 53a, the volume efficiency prediction unit 53b, and the virtual volume efficiency calculation unit 53c (referred to as volume efficiency). An intake air advance amount calculation unit 53d for calculating the advance amount of the timing. Note that the volumetric efficiency in this example is the volumetric efficiency (that is, filling efficiency) based on the intake state in the standard state. Basically, the filling amount increases as the volumetric efficiency increases, while the filling amount also decreases as the volumetric efficiency decreases.

-Target volume efficiency calculation unit-
As shown in FIG. 7, the target volume efficiency calculation unit 53a calculates a target volume efficiency Kvt based on the target turbine flow rate Qtt obtained by the base setting unit 51 and the standard atmospheric density ρ0. Specifically, the target volume efficiency Kvt is a target volume efficiency map that is pre-stored in the internal memory of the PCM 50 and is defined by associating the target turbine flow rate Qtt and the standard atmospheric density ρ0 with the target volume efficiency Kvt corresponding thereto. Based on. Here, the target volumetric efficiency Kvt corresponds to the volumetric efficiency necessary for realizing the target turbine flow rate Qtt and, consequently, the target supercharging pressure.

-Volumetric efficiency prediction unit-
The predicted volumetric efficiency Kvs indicates a predicted value of the volumetric efficiency when the current intake air in the downstream passage 10a is sucked into the cylinder 21, and the intake air state in the downstream passage 10a and the operating state of the engine 100 are shown. Based on the above, it is obtained by the volumetric efficiency prediction unit 53b. Specifically, as shown in FIG. 7, the volumetric efficiency predicting unit 53b predicts the predicted volumetric efficiency Kvs based on the engine speed, the intake manifold pressure, the atmospheric pressure, and the current opening / closing timing of the intake valve 22 and the exhaust valve 29. Is calculated. Here, the intake manifold pressure is an example of “the state of intake air”, and the intake air amount in the downstream passage 10a, and thus the predicted value of volumetric efficiency (predicted volumetric efficiency) Kvs is calculated via this intake manifold pressure. become. The intake manifold pressure is detected by the second pressure sensor 64. The engine speed, the current opening / closing timing of the intake valve 22, and the current opening / closing timing of the exhaust valve 29 are examples of “engine operating state”. The current opening / closing timings of the intake valve 22 and the exhaust valve 29 are obtained based on detection results by the crank angle sensor 69, the intake side cam angle sensor 70, and the exhaust side cam angle sensor 71, respectively.

-Virtual volumetric efficiency calculator-
The virtual volumetric efficiency calculation unit 53c sets both the opening timing and closing timing of the intake valve 22 to 5 deg. This corresponds to the predicted volume efficiency Kvs when the angle is advanced by CA (crank angle). Specifically, as shown in FIG. 7, the virtual volume efficiency calculation unit 53c uses the same values as those used for calculating the corresponding predicted volume efficiency Kvs for the engine speed, the intake manifold pressure, and the atmospheric pressure. The opening timing and closing timing of the intake valve 22 are 5 deg. From the values used for calculating the corresponding predicted volumetric efficiency Kvs. The value advanced by CA is used.

-Intake advance amount calculation part-
As shown in FIG. 7, the intake-advance amount calculation unit 53d has a target volume efficiency Kvt calculated by the target volume efficiency calculation unit 53a, a predicted volume efficiency Kvs calculated by the volume efficiency prediction unit 53b, and a virtual volume efficiency. Based on the virtual volume efficiency Kvv calculated by the calculation unit 53c, the intake offset amount Δθi indicating the advance amount of the intake valve 22 is calculated.

  Specifically, as shown in FIG. 7, the intake-advance amount calculating unit 53d subtracts the predicted volume efficiency Kvs from the target volume efficiency Kvt to thereby obtain a difference ΔKv1 between the target volume efficiency Kvt and the predicted volume efficiency Kvs ( = Kvt-Kvs). This difference ΔKv1 is an index indicating whether or not the filling amount can be insufficient. For example, when the difference ΔKv1 is greater than 0, that is, when the predicted volumetric efficiency Kvs is less than the target volumetric efficiency Kvt, the actual filling amount may be insufficient than the filling amount necessary to achieve the target supercharging pressure. It is shown that. This corresponds to a situation in which, for example, during the acceleration transition, the filling amount does not increase sufficiently and the target supercharging pressure is not achieved.

  On the other hand, as shown in FIG. 7, the intake advance amount calculation unit 53d subtracts the predicted volume efficiency Kvs from the virtual volume efficiency Kvv separately from the calculation of the difference ΔKv1, thereby calculating the virtual volume efficiency Kvv and the predicted volume efficiency. A difference ΔKv2 (= Kvv−Kvs) with respect to Kvs is calculated. This difference ΔKv2 indicates that the opening timing and closing timing of the intake valve 22 are 5 deg. The amount of increase in volumetric efficiency when the angle is advanced by CA is shown. For example, when the difference ΔKv2 is greater than 0, the opening / closing timing of the intake valve 22 is set to 5 deg. It is shown that the volumetric efficiency and hence the filling amount increase when the angle is advanced by CA.

  As shown in FIG. 7, the intake air advance amount calculation unit 53d divides the difference ΔKv1 by the difference ΔKv2 to obtain 5 deg. CA excess / deficiency rate Rv (= ΔKv1 / ΔKv2) is calculated. And 5 deg. For the excess / deficiency rate Rv. By multiplying by CA, the intake offset amount Δθi (unit of crank angle) is calculated. When the excess / deficiency rate Rv is greater than 1, the opening / closing timing of the intake valve 22 is set to 5 deg. Even if the angle is advanced by CA, the predicted volumetric efficiency Kvs does not increase to the target volumetric efficiency Kvt, indicating that the filling amount may still be insufficient. At this time, the intake offset amount Δθi is 5 deg. It is set larger than CA. On the other hand, when the excess / deficiency rate Rv is 1 or less, the opening / closing timing of the intake valve 22 is set to 5 deg. If the angle is advanced by CA, the predicted volumetric efficiency Kvs becomes larger than the target volumetric efficiency Kvt, indicating that the filling amount can be increased more than necessary. At this time, the intake offset amount Δθi is 5 deg. Set to less than CA.

  Specifically, the intake offset amount Δθi is calculated as a value that increases as the difference ΔKv1 increases from 0 and decreases as the difference ΔKv2 increases from 0.

  If the calculated intake offset amount Δθi is smaller than 0, the intake advance amount calculation unit 53d changes the intake offset amount Δθi to 0. That is, the intake offset amount Δθi is a value greater than or equal to zero. Whether the turbo lag has occurred is indirectly determined depending on whether the intake offset amount Δθi is 0 or larger than 0.

  Specifically, the negative value of the intake offset amount Δθi indicates that the filling amount is not insufficient, and that no turbo lag is generated. In such a situation, since it is not necessary to correct the opening / closing timing of the intake valve 22, when the calculated value of the intake offset amount Δθi is 0 or less, the intake advance amount calculating unit 53d sets the intake offset amount Δθi to 0. change. On the other hand, the positive value of the intake offset amount Δθi indicates that the filling amount is insufficient and that turbo lag is generated. In such a situation, the intake offset amount Δθi is not changed and is kept at the calculated value.

  Finally, the intake VVT controller 53 advances the opening / closing timing of the intake valve 22 by subtracting the intake offset amount Δθi from the current basic values of the opening timing and closing timing of the intake valve 22. As described above, the intake air offset amount Δθi takes a value larger than 0 when the turbo lag occurs. This indicates that the intake VVT control unit 53 advances the opening / closing timing of the intake valve 22 when a turbo lag occurs.

  In step S15 subsequent to step S14 in FIG. 3, the intake VVT control unit 53 controls the intake VVT 25 so as to realize the opening / closing timing after advance. Such control increases the filling amount. Specifically, in general, intake air is sucked into the cylinder 21 by the negative pressure generated when the piston 27 descends, but the piston 27 passes through the BDC (bottom dead center) and rises from the descending position. Even after turning, the intake air is introduced into the cylinder 21 due to the inertia of the intake air until slightly after the BDC (ABDC). As shown in FIG. 4, the filling amount depends on the integral amount of the valve lift amount in the section from TDC to ABDC (corresponding to the area of region A in FIG. 4). On the other hand, during the period in which the intake valve 22 is open in the section from the ABCD to the next TDC, a part of the intake air is discharged to the intake port 14. The amount of intake air discharged from the cylinder 21 to the intake port 14 depends on the integral amount of the valve lift amount of the intake valve 22 in the section from ABDC to the next TDC (corresponding to the area of region B in FIG. 4). The filling amount is determined by the balance between the area A and the area B. If the opening / closing timing of the intake valve 22 is changed, the area of the region A and the area of the region B are changed, so that the filling amount is changed. For example, as shown in FIG. 5, when the opening timing and closing timing of the intake valve 22 are advanced from the state of FIG. 4, the area of the region A increases and the area of the region B decreases. Thereby, the filling amount is increased from the state shown in FIG.

  The processing related to the advance angle of the intake valve 22 described above is repeatedly executed by the PCM 50 at a predetermined cycle.

  Next, of the processes performed in step S14 of FIG. 3, a method of correcting the opening / closing timing of the exhaust valve 29 by the exhaust VVT control unit 54 will be described with reference to FIG. FIG. 8 is a block diagram showing a method for controlling the exhaust VVT 26.

<Exhaust VVT control>
As shown in FIG. 2, the exhaust VVT control unit 54 includes a blow-through rate estimation unit 54 b that estimates a current fresh-air blow-through rate (hereinafter referred to as “current blow-through rate”) Fs, and a deficiency in the fresh-air blow-out rate ( (Hereinafter referred to as “blow-through rate deficient amount”) and a fresh air when the opening / closing timing of the exhaust valve 29 is delayed by a predetermined crank angle from the current basic value. The calculation results of the virtual blow-through rate calculation unit 54c for calculating the blow-through rate (hereinafter referred to as “virtual blow-through rate”) Fv, the blow-through rate estimation unit 54b, the blow-through rate shortage calculation unit 54a, and the virtual blow-through rate calculation unit 54c And an exhaust retard amount calculating section 54d for calculating the retard amount of the opening / closing timing of the exhaust valve 29. Here, the fresh air blow-through rate indicates a ratio of fresh air that is blown into the exhaust port 31 without staying in the cylinder 21 out of the fresh air sucked into the cylinder 21.

-Blowout rate estimator-
The blow-through rate estimation unit 54b estimates the current blow-through rate Fs based on the state of intake air in the downstream passage 10a and the operating state of the engine 100. Specifically, the blow-through rate estimation unit 54b reads the intake manifold pressure detected by the second pressure sensor 64 as the intake air state, and as the operating state of the engine 100, as shown in FIG. The atmospheric pressure detected by the atmospheric pressure sensor 60 and the current opening / closing timings of the intake valve 22 and the exhaust valve 29 are read. The blow-through rate estimation unit 54b estimates the current blow-through rate Fs based on the read parameters.

-Insufficient blowout rate calculation unit-
The blowout rate deficiency ΔF1 is a value obtained by subtracting the current fresh air blowout rate from the new blowout rate required to achieve the target turbine flow rate Qtt, and indicates the shortage of the new blowout rate. Yes. For example, when the blow-through rate deficiency amount ΔF1 is larger than 0, it indicates that the fresh air blow-through rate, and thus the flow rate of the air blown into the exhaust system and sent to the turbine 4b may be insufficient. As shown in FIG. 8, the blow-through rate shortage calculating unit 54a is short of the blow-through rate based on the target turbine flow rate Qtt obtained by the base setting unit 51 and the current blow-through rate Fs estimated by the blow-through rate estimating unit 54b. The amount ΔF1 is obtained.

-Virtual blowout rate calculator-
The virtual blow-through rate calculating unit 54c sets both the opening timing and closing timing of the exhaust valve 29 from the current opening / closing timing by 5 deg. A virtual blow-through rate Fv corresponding to the current blow-through rate Fs when retarded by CA (crank angle) is calculated. Specifically, as shown in FIG. 8, the virtual blow-through rate calculating unit 54c uses the same value as the value used for calculating the corresponding current blow-through rate Fs for the intake manifold pressure, the engine speed, and the atmospheric pressure. The opening timing and closing timing of the exhaust valve 29 are 5 deg. From the values used for calculating the corresponding current blow-through rate Fs. Use the value retarded by CA.

−Exhaust retard amount calculation unit−
As shown in FIG. 8, the exhaust retard amount calculation unit 54d, the current blow-through rate Fs calculated by the blow-through rate estimation unit 54b, the blow-through rate deficient amount ΔF1 obtained by the blow-through rate deficient calculation unit 54a, and the virtual Based on the virtual blow-through rate Fv calculated by the blow-through rate calculation unit 54c, an exhaust offset amount Δθe indicating the retard amount of the exhaust valve 29 is calculated.

  Specifically, as shown in FIG. 8, the exhaust retardation amount calculating unit 54d subtracts the current blow-through rate Fs from the virtual blow-through rate Fv to obtain a difference ΔF2 ( = Fv-Fs). This difference ΔF2 is assumed to be 5 deg. Between the opening timing and closing timing of the exhaust valve 29. The amount of increase in the fresh air blow-through rate when retarded by CA is shown. For example, when the difference ΔF2 is greater than 0, the opening / closing timing of the exhaust valve 29 is set to 5 deg. This shows that when the angle is advanced by CA, the fresh air blow-through rate, and hence the flow rate of air sent to the turbine 4b, increases.

  As shown in FIG. 8, the exhaust retardation amount calculating unit 54d divides the blow-through rate deficient amount ΔF1 by the difference ΔF2 to obtain 5 deg. CA excess / deficiency rate Rf (= ΔF1 / ΔF2) is calculated. And for this excess / deficiency rate Rf, 5 deg. By multiplying by CA, an exhaust gas offset amount Δθe (crank angle unit) is calculated. For example, when the excess / deficiency rate Rf is greater than 1, the opening / closing timing of the exhaust valve 29 is set to 5 deg. Even if retarded by CA, the shortage of the fresh air blow-through rate is not resolved, indicating that the flow rate of the air sent to the turbine 4b may still be insufficient. At this time, the exhaust offset amount Δθe is 5 deg. It is set larger than CA. On the other hand, when the excess / deficiency rate Rf is 1 or less, the opening / closing timing of the exhaust valve 29 is set to 5 deg. If the angle is delayed by CA, it indicates that the fresh air blow-through rate and consequently the flow rate of the air sent to the turbine 4b can be increased more than necessary. At this time, the exhaust offset amount Δθe is 5 deg. Set to less than CA.

  Specifically, the exhaust offset amount Δθe is calculated as a value that increases as the blow-through rate deficient amount ΔF1 increases from 0 and decreases as the difference ΔF2 increases from 0.

  Subsequently, the exhaust retard amount calculating unit 54d reads the intake offset amount Δθi (value changed according to the sign) calculated by the intake advance amount calculating unit 53d. The exhaust retard amount calculation unit 54d determines whether or not a turbo lag has occurred in the turbocharger 4 based on the value of the intake offset amount Δθi, and changes the exhaust offset amount Δθe based on the determination result. . As described above, it is indirectly determined whether or not a turbo lag has occurred depending on whether the intake offset amount Δθi is 0 or larger than 0. When the intake offset amount Δθi is 0, the exhaust retard amount calculation unit 54d determines that no turbo lag has occurred in the turbocharger 4, and changes the exhaust offset amount Δθe to 0. On the other hand, if the intake offset amount Δθi is greater than 0, the exhaust retard amount calculation portion 54d determines that a turbo lag has occurred, and keeps the exhaust offset amount Δθe as it is without changing.

  Finally, the exhaust VVT controller 54 retards the opening / closing timing of the exhaust valve 29 by adding the exhaust offset amount Δθe to the current basic values of the opening timing and closing timing of the exhaust valve 29. As described above, the exhaust gas offset amount Δθe is changed to 0 when it is determined that no turbo lag has occurred. This indicates that the exhaust VVT control unit 54 retards the opening / closing timing of the exhaust valve 29 when it is determined that a turbo lag has occurred.

  In step S15 following step S14 in FIG. 3, the exhaust VVT control unit 54 controls the exhaust VVT 26 so as to realize the opening / closing timing after being retarded. Such control increases the fresh air blow-through rate. Specifically, for example, when the opening / closing timing of the exhaust valve 29 is retarded from the state shown in FIG. 6A, valve overlap as shown in FIG. 6B is performed. The overlap period (O / L) at that time is extended as the exhaust offset amount Δθe increases, that is, as the opening / closing timing of the exhaust valve 29 is retarded. This increases the blow-through rate of fresh air, and consequently the amount of air sent to the turbine 4b during the intake stroke.

  The processing related to the retardation of the exhaust valve 29 described above is repeatedly executed by the PCM 50 at a predetermined cycle.

<VVT control example>
Hereinafter, control examples of the intake VVT 25 and the exhaust VVT 26 will be described.

  FIG. 9 is a time chart illustrating the transition of (a) the accelerator opening, (b) the transition of the closing timing of the intake valve 22, and (c) the transition of the closing timing of the exhaust valve 29 during acceleration transition. . Hereinafter, the transient operation in the supercharging region, particularly the operation at the time of acceleration transient will be exemplified.

  For example, when the engine 100 accelerates relatively slowly, the supercharging pressure is controlled to follow the target supercharging pressure. As shown by the broken line in FIG. 9A, when the accelerator pedal 81 is depressed relatively slowly (t = t0), both the intake offset amount Δθi and the exhaust offset amount Δθe are values of 0 or around 0. Thus, the opening and closing timings of the intake valve 22 and the exhaust valve 29 are set to the basic value set by the base setting unit 51 or a value near the basic value, respectively. In this case, as shown by the broken lines in FIGS. 9B and 9C (only the basic values are shown), the closing timings of the intake valve 22 and the exhaust valve 29 both change smoothly over time. It will be.

  On the other hand, as shown by the solid line in FIG. 9 (a), at the time of full-open acceleration from idle operation or low-speed operation (t = t0), a delay may occur in the rise of the supercharging pressure, that is, turbo lag is remarkable. It is known to appear in For example, in the idling operation, the opening of the throttle valve 11 is set in the vicinity of the fully closed state. Therefore, the intake air amount in the downstream portion of the throttle valve 11, that is, in the downstream passage 10a is relatively small. When accelerating from this state, even if the opening degree of the throttle valve 11 is fully opened, the filling amount does not increase sufficiently, and as a result, a delay occurs in securing the exhaust, and the turbine 4b and the compressor 4a are sufficiently driven. May not be. In that case, a significant delay occurs in increasing the supercharging pressure to the target supercharging pressure.

  According to the above configuration, whether the turbo lag is generated, that is, whether the filling amount is insufficient is reflected in the sign of the intake air offset amount Δθi. When the intake offset amount Δθi takes a positive value, as shown by the solid line in FIG. 9B, the VVT control unit 59 advances the opening / closing timing of the intake valve 22 by the intake offset amount Δθi (t0 <t <T1). Thereby, the filling amount of the intake air sucked into the cylinder 21 increases. The increase in the filling amount increases the flow rate of exhaust discharged through the combustion stroke and the flow rate of air blown into the exhaust system during the intake stroke, as will be described later.

  The VVT control unit 59 also retards the exhaust VVT 26 when the intake charge amount is increased (that is, when it is determined that the intake offset amount Δθi takes a positive value and a turbo lag has occurred). As shown by the solid line in FIG. 9C, the VVT control unit 59 retards the opening / closing timing of the exhaust valve 29 by the exhaust offset amount Δθe (t0 <t <t1). Thereby, the overlap period in which the valve overlap is performed is extended, and the fresh air blow-through rate, that is, the ratio of the fresh air blown into the exhaust system during the intake stroke is increased. Here, as described above, by increasing the intake charge amount via the intake VVT 25, the amount of air blown into the exhaust system increases according to the increase.

  Thus, in both the intake stroke and the subsequent exhaust stroke, the flow rate of the air sent to the exhaust system is increased, which can promote the rotational drive of the turbine 4b.

  Further, since the ratio of fresh air in the exhaust system 30 is increased, so-called afterburning that occurs when fresh air reacts in the exhaust system 30 is likely to occur. Since the air that has blown into the exhaust system 30 rises in temperature due to the afterburning, and further increases in pressure, the rotational drive of the turbine 4b can be further promoted.

  Although such processing is repeatedly executed at a predetermined cycle, the difference ΔKv1, the volume efficiency excess / deficiency rate is increased as the flow rate of air sent to the turbine 4b increases and the boost pressure increases toward the target boost pressure. Rv and the intake offset amount Δθi gradually decrease toward zero. As a result, the opening / closing timing of the intake valve 22 gradually approaches the basic value. When the intake offset amount Δθi decreases to 0 (t = t1), at the same time, the exhaust offset amount Δθe also becomes 0 (t = t1). Thereby, the correction of the opening / closing timing of the intake valve 22 and the exhaust valve 29 is completed.

(Summary)
As described above, the VVT control unit 59 controls the overlap period in which both the intake valve 22 and the exhaust valve 29 are opened. During the overlap period, air is blown from the intake system 10 to the exhaust system 30.

  Turbo lag can occur during acceleration transients. During acceleration transition, the amount of air charged into the cylinder 21 increases through the opening of the throttle valve 11 or the like.

  As described above, when the VVT control unit 59 determines that the turbo lag has occurred, the VVT control unit 59 retards the closing timing of the exhaust valve 29 so that the overlap period is extended. By extending the overlap period, the ratio of the air blown into the exhaust system 30 in the air increased as the filling amount increases, and the flow rate of the air sent to the turbine 4b increases according to the increase. become. As a result, the turbine 4b can be sufficiently driven to rotate.

  Further, the above-described configuration can increase the flow rate of air sent to the turbine 4b when air is sucked into the cylinder 21 and before the air-fuel mixture is combusted and exhausted. Thus, the turbo lag can be eliminated at an early stage.

  Furthermore, according to the above-described configuration, the flow rate of fresh air in the exhaust system 30 is increased by the amount of air blown into the exhaust system 30, so that fresh air reacts in the exhaust system 30. The so-called afterburn that occurs is likely to occur. Since the air blown into the exhaust system 30 rises in temperature due to the afterburning, and then rises in pressure, it is advantageous in sufficiently driving the turbine 4b to rotate.

  Further, since the VVT control unit 59 sets the retard amount of the closing timing of the exhaust valve 29 based on the fresh air blow-off rate, it becomes possible to set the retard amount appropriately. This is advantageous in reliably eliminating the turbo lag.

  Further, since the VVT control unit 59 retards the opening timing of the exhaust valve 29 during the correction of the opening / closing timing of the intake valve 22, it is possible to secure as much as possible the flow rate of the air that blows into the exhaust system 30. It becomes possible. This is advantageous in eliminating the turbo lag at an early stage.

  Further, when the VVT control unit 59 determines that a turbo lag has occurred, the VVT control unit 59 increases the filling amount by correcting the opening / closing timing of the intake valve 22. Then, the VVT control unit 59 retards the closing timing of the exhaust valve 29 as described above during correction of the opening / closing timing of the intake valve 22. According to this, it is possible to further increase the flow rate of air that blows through during the overlap period by the amount of filling that increases due to the correction related to the intake valve 22. This is advantageous in sufficiently driving the turbine 4b to rotate.

  The downstream passage 10 a is a portion on the downstream side of the throttle valve 11, and is a portion that is relatively close to the cylinder 21 in the intake passage 10. Therefore, the VVT control unit 59 corrects the opening / closing timing of the intake valve 22 based on the intake state in the downstream side passage 10a. Thereby, the VVT control unit 59 can adjust the filling amount with high accuracy.

  Further, the filling amount is influenced not only by the intake state but also by the operating state of the engine 100 such as the engine speed and the opening / closing timing of the intake valve 22. Therefore, the VVT control unit 59 corrects the opening / closing timing of the intake valve 22 based on the operating state of the engine. Thereby, the VVT control part 59 can adjust the filling amount with high accuracy.

  Further, the VVT control unit 59 is a predicted value of volumetric efficiency when the intake air in the downstream passage 10a is sucked into the cylinder 21 based on the intake state in the downstream passage 10a and the operating state of the engine 100. A certain volumetric efficiency Kvs is calculated, and the opening / closing timing of the intake valve 22 is corrected based on the calculation result. Accordingly, the VVT control unit 59 can correct the opening / closing timing of the intake valve 22 in advance by predicting the volumetric efficiency in advance. As a result, the VT control unit 59 can adjust the filling amount at an early stage. Further, the intake air in the downstream passage 10a is taken into the cylinder 21 in the future. Therefore, the volumetric efficiency can be accurately predicted by predicting the future volumetric efficiency based on the state of intake air in the downstream passage 10a.

  Further, the VVT control unit 59 corrects the opening / closing timing of the intake valve 22 in consideration of not only the predicted volume efficiency Kvs but also the target volume efficiency Kvt which is a target value of the volume efficiency. Specifically, when the predicted volumetric efficiency Kvs is smaller than the target volumetric efficiency Kvt, the VVT control unit 59 advances the opening / closing timing of the intake valve 22 so that the filling amount increases. According to this, the VVT control unit 59 corrects the opening / closing timing early so that the volume efficiency reaches the target volume efficiency Kvt by comparing the predicted volume efficiency Kvs and the target volume efficiency Kvt in advance. Can do. As a result, the VVT control unit 59 can adjust the filling amount at an early stage.

  Further, since the VVT control unit 59 is configured to acquire the target value of the volumetric efficiency necessary for realizing the target boost pressure as the target volumetric efficiency Kvt, the filling amount can be accurately set during acceleration transient. Can be adjusted.

  Specifically, in order to eliminate the turbo lag during acceleration transition, it is conceivable to increase the filling amount early. At that time, in order to achieve the target supercharging pressure with high accuracy, it is desired to adjust the filling amount with high accuracy.

  According to this configuration, the target volume efficiency Kvt is set based on the target boost pressure, so that the filling amount during acceleration transient can be adjusted with high accuracy. In addition, as described above, the opening and closing timing of the intake valve 22 is corrected in advance based on the predicted volumetric efficiency Kvs, so that the filling amount can be increased at an early stage and the time until the target supercharging pressure is realized is shortened. Will be able to. This is advantageous in eliminating the turbo lag.

  Further, the VVT control unit 59 can appropriately predict the volume efficiency by reading the intake manifold pressure as the intake state.

  Further, the VVT control unit 59 can appropriately predict the volume efficiency by reading the engine speed, the opening / closing timing of the intake valve 22 and the opening / closing timing of the exhaust valve 29 as the operating state of the engine.

  Further, the downstream passage may include an intake manifold and an intake port in the intake passage.

  According to this configuration, in correcting the opening / closing timing of the intake valve 22, the state of intake air in the intake manifold and the intake port is taken into consideration. As a result, the intake state in the immediate vicinity of the cylinder is taken into consideration, so that the filling amount can be adjusted with higher accuracy.

<Other embodiments>
As described above, the embodiment has been described as an example of the technique disclosed in the present application.
However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to illustrate the technology. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  The configuration of the engine 100 is an example, and is not limited to this configuration.

  For example, the PCM 50 extends the overlap period by simultaneously retarding the opening timing and closing timing of the exhaust valve 29 via the exhaust VVT control unit 54, but is not limited thereto. The PCM 50 may extend the overlap period by delaying only the closing timing of the exhaust valve 29.

  Similarly, the PCM 50 increases the filling amount by simultaneously advancing the opening timing and closing timing of the intake valve 22 via the intake VVT control unit 53, but is not limited thereto. The PCM 50 increases the filling amount by advancing only the closing timing of the intake valve 22 or advancing one of the opening timing and closing timing of the intake valve 22 and retarding the other. Also good.

  In the embodiment, the intake VVT control unit 53 is configured to correct the opening / closing timing of the intake valve 22 based on the target value Kvt and the predicted value Kvs of the volumetric efficiency. The opening / closing timing of the intake valve 22 may be corrected based on the target value and the predicted value of the quantity.

  In the embodiment, the volumetric efficiency predicting unit 53b is configured to predict the volumetric efficiency based on the intake manifold pressure, but is not limited thereto. Instead of this configuration, it may be predicted based on the temperature and density of the intake air in the downstream passage 10a, or may be predicted based on a combination thereof. The same applies to the blow-through rate estimation unit 54b.

  In the embodiment, the virtual volumetric efficiency calculation unit 53c sets the opening timing and closing timing of the intake valve 22 to 5 deg. The virtual volume efficiency Kvv corresponding to the predicted volume efficiency Kvs when advanced by CA is calculated, but the advance amount at this time can be changed within a possible range. The same applies to the virtual blow-through rate calculation unit 54c.

  Further, in the above-described embodiment, the intake advance amount calculation unit 53d subtracts the difference ΔKv1 obtained by subtracting the predicted volume efficiency Kvs from the target volume efficiency Kvt and the predicted volume efficiency Kvv from the virtual volume efficiency Kvv. The intake offset amount Δθi is calculated based on the ratio with the obtained difference ΔKv2, but is not limited to this. Instead of this configuration, various calculations are performed based on the ratio between the target volumetric efficiency Kvt and the predicted volumetric efficiency Kvs, or the intake air based on the magnitude of the value obtained by subtracting the difference ΔKv1 from the difference ΔKv2. The offset amount Δθi may be calculated. The same applies to the exhaust retard amount calculation unit 54d.

  Moreover, although the said embodiment illustrated the structure using the volume efficiency on the basis of standard volume density (rho) 0 as volume efficiency, it is not limited to this structure. For example, instead of the volumetric efficiency based on the standard volume density ρ0, the volumetric efficiency based on the intake density in the intake manifold 13, that is, the so-called intake manifold based volumetric efficiency may be used. In this case, in the block diagram shown in FIG. 7, when obtaining the target volume efficiency Kvt, the intake density (hereinafter referred to as “in-manifold density”) ρi is input instead of the standard volume density ρ0. Will be.

  The intake manifold density ρi is obtained from the following equation (1) based on the intake manifold volume Vi and the mass of intake air in the intake manifold 13 (hereinafter referred to as “intake manifold mass”) Mi.

    ρi = Mi / Vi (1)

  The intake manifold internal mass Mi is a cylinder intake air amount Qcr which is the mass of intake air per stroke taken into the cylinder 21, an intake manifold reference volume efficiency prediction value Kvi, and a ratio of the cylinder volume Vc to the intake manifold volume Vi. Based on a certain cylinder / intake manifold volume ratio Ri (= Vc / Vi), the following equation (2) is obtained.

    Mi = Qcr / (Kvi × Ri) (2)

  In Expression (2), the cylinder intake air amount Qcr is obtained based on the target charging efficiency, the cylinder volume Vc, and the current value of the atmospheric density. The current value of the atmospheric density is estimated based on the atmospheric pressure detected by the atmospheric pressure sensor 60 and the intake air temperature downstream of the air cleaner 2 detected by the first temperature sensor 62. The estimated value Kvi of the volume efficiency based on the intake manifold is obtained based on the engine speed, the intake manifold pressure, and the like, similarly to the predicted volume efficiency Kvs in the embodiment. The cylinder / intake manifold volume ratio Ri is stored in the internal memory of the PCM 50 in advance.

100 Engine 10 Intake passage 10a Downstream passage 11 Throttle valve 13 Intake manifold 14 Intake port 20 Engine body 21 Cylinder 22 Intake valve 25 Intake VVT (second variable valve timing mechanism)
26 Exhaust VVT (Variable valve timing mechanism)
29 Exhaust valve 30 Exhaust passage 4 Turbocharger 4a Compressor 4b Turbine 50 PCM (control device)
51 Base Setting Unit 53 Intake VVT Control Unit 54 Exhaust VVT Control Unit 59 VVT Control Unit (Control Unit)
Fs Current blowout rate Kvs Predicted volumetric efficiency Kvt Target volumetric efficiency Qtt Target turbine flow rate Δθi Intake offset amount Δθe Exhaust offset amount (retard amount)

Claims (4)

An engine control device comprising a turbocharger and a variable valve timing mechanism for changing the opening / closing timing of an exhaust valve,
A control unit that sets a closing timing of the exhaust valve and controls an overlap period that is a period during which both the intake valve and the exhaust valve are opened via the valve timing variable mechanism;
The control unit determines whether or not a turbo lag has occurred in the turbocharger;
The control unit also delays the closing timing of the exhaust valve so that the overlap period is extended when it is determined that a turbo lag is generated in the turbocharger. The engine control device according to claim 1,
The control unit is configured to retard the closing timing of the exhaust valve based on a fresh air blow-off rate that is a ratio of fresh air sucked into the cylinder and blown into the exhaust system during the overlap period. Set the engine control device. The engine control device according to claim 1 or 2,
The engine includes a second valve timing variable mechanism controlled by the control unit so as to change the opening / closing timing of the intake valve,
The control unit sets the opening / closing timing of the intake valve and, when determining that a turbo lag has occurred in the turbocharger, corrects the opening / closing timing of the intake valve, and sucks it into the cylinder. Increase the intake charge,
The control unit also controls the engine to retard the closing timing of the exhaust valve during correction of the opening / closing timing of the intake valve. The engine control device according to claim 3,
The engine includes a throttle valve provided downstream of a compressor of the turbocharger in the intake passage,
The control unit calculates a target value of volumetric efficiency or filling amount of intake air sucked into the cylinder based on a target boost pressure, and at least one downstream of the throttle valve in the intake passage. Based on the state of intake air in the downstream side passage that is a part and the operating state of the engine, the predicted value of the volumetric efficiency or filling amount when the intake air in the downstream side passage is drawn into the cylinder is calculated And
The control unit also corrects the opening / closing timing of the intake valve when the predicted value of the volumetric efficiency or filling amount is smaller than the target value of the volumetric efficiency or filling amount.