JP6046918B2 - Valve timing control device - Google Patents

Description

  The present invention relates to a valve timing control device that controls the opening timing of an intake valve of a four-stroke engine, and more particularly to a device that can obtain good drivability even when a supercharging response delay exists.

In a 4-stroke engine, an intake valve and an exhaust valve are each opened and closed by a valve drive system such as a camshaft.
Further, in recent years, a variable valve timing mechanism that can change the valve opening timing and valve closing timing of each valve by advancing and retarding the phase of the camshaft or switching the cam profile according to the operating state of the engine. Is popular.

As a conventional technique related to such valve timing control, for example, in Patent Document 1, in order to improve output at high altitude and high load, the engine load value is corrected based on atmospheric pressure, and the corrected load and engine are corrected. It is described that the control target value of the intake valve valve timing displacement amount is obtained based on the rotational speed.
Further, Patent Document 2 discloses that the transient state and the steady state are discriminated based on the intake air amount or the fluctuation of the intake pipe pressure in order to achieve both the transient response of the variable valve timing control and the steady state stability. In addition, switching of feedback gain in valve timing control is described.
Further, in Patent Document 3, in an engine having a variable valve lift mechanism, even if the air density of the outside air changes due to a change in atmospheric pressure, a stable performance is always generated for the accelerator operation. It is described that the target valve lift amount is corrected based on the above.

Japanese Patent Laid-Open No. 9-41999 JP 2001-303990 A JP 2008-115754 A

In an engine equipped with a variable valve timing mechanism, the intake valve is slowly opened and closed during normal driving to give a mirror cycle (Atkinson cycle) to give priority to fuel efficiency. When high torque is required, the intake valve is opened early. It has been proposed to perform control to increase the overlap by increasing the overlap (the state in which both the exhaust valve and the intake valve are open or the period thereof), and increasing the charging efficiency.
However, in the case of an engine that performs turbocharging, since there is a delay in response to turbocharging (turbo lag), the intake pressure is low relative to the exhaust pressure immediately after the throttle valve is opened. When the lap is enlarged, the amount of internal EGR is increased, and the torque is reduced instead, so that drivability (ease of driving) is impaired. Such a phenomenon becomes prominent particularly in highlands.
An object of the present invention is to provide a valve timing control device that can obtain good drivability even when a supercharging response delay exists.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is a valve timing control device for changing the opening timing of the intake valve with respect to the crank angle position in accordance with the operating state of the engine, the intake air amount detecting means for detecting the intake air amount of the engine; And an intake pressure detecting means for detecting an intake pressure in the vicinity of the intake port and a required torque determining means for determining the required torque, and when the required torque is less than a predetermined value, according to an increase in the intake air amount The first valve opening timing control for advancing the valve opening timing of the intake valve is performed, and when the required torque is equal to or greater than a predetermined value, the valve opening of the intake valve is increased according to an increase in the intake pressure. A valve timing control device that performs second valve opening timing control for advancing the timing.

  The invention according to claim 2 is a valve timing control device for changing the opening timing of the intake valve with respect to the crank angle position in accordance with the operating state of the engine, the intake air amount detecting means for detecting the intake air amount of the engine; An intake pressure detecting means for detecting an intake pressure in the vicinity of the intake port, an exhaust pressure estimating means for estimating an exhaust pressure in the vicinity of the exhaust port, and a required torque determining means for determining the required torque, wherein the required torque is a predetermined value. When the required torque is less than the predetermined value, the first valve opening timing control for advancing the valve opening timing of the intake valve according to the increase in the intake air amount is performed and the required torque is equal to or greater than a predetermined value. And a second valve opening timing control for advancing the valve opening timing of the intake valve in accordance with an increase in relative pressure of the intake pressure with respect to the exhaust pressure. A timing controller.

According to the present invention, when the required torque is high and it is necessary to perform output priority control, the valve opening timing of the intake valve is controlled based on the intake pressure or the relative pressure of the intake pressure to the exhaust pressure. In a state where the intake pressure is lower than the exhaust pressure due to a delay in supercharging response, the valve opening timing of the intake valve is delayed to reduce the overlap, and torque reduction due to an increase in internal EGR can be suppressed.
On the other hand, in a state where the boost pressure has increased and the intake pressure has become sufficiently high, the opening timing of the intake valve can be advanced to increase the overlap, thereby increasing the charging efficiency and increasing the torque. .
In particular, by performing such control based on the absolute pressure or relative pressure of the intake pressure, it is possible to perform highly accurate control, for example, for control based on the intake air amount.
As described above, according to the present invention, it is possible to provide a valve timing control device that can obtain good drivability even when a supercharging response delay exists.

It is a figure which shows the structure of the engine which has Example 1 of the valve timing control apparatus to which this invention is applied. It is a figure which shows the structure of the valve timing variable mechanism in the engine of FIG. It is a graph which shows an example of transition of the pressure in an intake manifold after shifting an accelerator from a fully closed state to a fully opened state in a standard atmospheric state and a highland.

  It is an object of the present invention to provide a valve timing control device that can obtain good drivability even when there is a supercharging response delay when performing driver-priority valve timing control with a driver requested torque exceeding a predetermined value. The intake valve opening timing is controlled according to the absolute pressure of the pressure in the intake pipe (intake pressure) or relative pressure to the exhaust pressure. The problem was solved by suppressing torque reduction due to an increase in EGR.

Embodiment 1 of a valve timing control apparatus to which the present invention is applied will be described below.
The valve timing control device of the embodiment is provided in a DOHC horizontally opposed gasoline engine mounted on an automobile such as a passenger car, for example, and changes the phase of the intake camshaft and the exhaust camshaft with respect to the phase of the crankshaft (advance / retard). )

FIG. 1 is a diagram illustrating a configuration of an engine having a valve timing control device according to a first embodiment.
The engine 1 includes a crankshaft 10, a cylinder block 20, a cylinder head 30, a turbocharger 40, an intake system 50, an exhaust system 60, an engine control unit (ECU) 70, an intake valve timing variable mechanism 100, an exhaust valve timing variable mechanism 200, and the like. It is comprised.

The crankshaft 10 is a rotating shaft that serves as an output shaft of the engine 1.
A piston is connected to the crankshaft 10 via a connecting rod (not shown).
A crank angle sensor 11 that detects the angular position of the crankshaft is provided at the end of the crankshaft 10.
The output of the crank angle sensor 11 is transmitted to the ECU 70.

The cylinder block 20 is configured in two parts so as to sandwich the crankshaft 10 from the left-right direction.
Inside the cylinder block 20 is formed a cylinder in which a piston is inserted and reciprocates inside.

The cylinder head 30 is provided at the end (left and right end) of the cylinder block 20 on the side opposite to the crankshaft 10.
The cylinder head 30 includes a combustion chamber 31, a spark plug 32, an intake port 33, an exhaust port 34, an intake valve 35, an exhaust valve 36, and the like.
The combustion chamber 31 is formed by denting a portion facing the piston crown surface of the cylinder head 30.
The spark plug 32 is provided in the center of the combustion chamber 31 and ignites the air-fuel mixture in response to an ignition signal from the ECU 70.
The intake port 33 is a flow path for introducing combustion air (fresh air) into the combustion chamber 31.
The exhaust port 34 is a flow path for discharging burned gas (exhaust gas) from the combustion chamber 31.
The intake valve 35 and the exhaust valve 36 open and close the intake port 33 and the exhaust valve 34 at a predetermined timing.
The intake valve 35 and the exhaust valve 36 are opened / closed by an intake camshaft and an exhaust camshaft (not shown) that are driven by a timing chain and rotate at a half speed of the crankshaft 10.
The intake camshaft and exhaust camshaft cam sprockets include a variable intake valve timing mechanism 100 that changes the valve opening timing and valve closing timing by advancing and retarding the phase of each camshaft, and exhaust valve timing. A variable mechanism 200 is provided.
These will be described in detail later.

The turbocharger 40 is a supercharger that supercharges fresh air using the exhaust energy of the engine 1.
The turbocharger 40 includes a turbine 41, a compressor 42, and the like.
The turbine 41 is rotationally driven by the exhaust gas of the engine 1.
The compressor 42 is coaxially attached to the turbine 41 and is rotationally driven by the turbine 41 to compress fresh air.

The intake system 50 introduces fresh air and introduces it into the intake port 33.
The intake system 50 includes an intake duct 51, a chamber 52, an air cleaner 53, an air flow meter 54, an intercooler 55, a throttle valve 56, an intake manifold 57, an intake pressure sensor 58, an injector 59, and the like.
The intake duct 51 introduces outside air and introduces it into the intake port 33.
The chamber 52 is a space provided in communication with the vicinity of the inlet of the intake duct 51.
The air cleaner 53 is provided on the downstream side of the intake duct 51 where it communicates with the chamber 52, and filters fresh air to remove dust and the like.
The air flow meter 54 is provided in the vicinity of the outlet of the air cleaner 53 and measures the flow rate of air passing through the intake duct 51.
The output of the air flow meter 54 is transmitted to the ECU 70.
The compressor 42 of the turbocharger 40 is provided on the downstream side of the air flow meter 54.

The intercooler 55 is a heat exchanger that is provided on the downstream side of the compressor 42 in the intake duct 51 and cools fresh air that has been compressed and heated by heat exchange with the traveling wind.
The throttle valve 56 is a butterfly valve that is provided downstream of the intercooler 55 in the intake duct 51 and controls the output of the engine 1 by adjusting the flow rate of fresh air.
The throttle valve 56 is opened and closed by a throttle actuator (not shown) in response to an accelerator pedal operation (not shown) by the driver.
Further, the throttle valve 56 is provided with a throttle sensor for detecting the opening degree, and its output is transmitted to the ECU 70.
The intake manifold 57 is a branch pipe that is provided downstream of the throttle valve 56 and distributes fresh air to the intake port 33 of each cylinder.
The intake pressure sensor 58 detects the pressure of fresh air (intake pressure) in the intake manifold 57.
The output of the intake pressure sensor 58 is transmitted to the ECU 70.
The injector 59 is provided at the end of the intake manifold 57 on the cylinder head 30 side, and injects fuel into the intake port 33 in response to a valve opening signal generated by the ECU 70 to form an air-fuel mixture.

The exhaust system 60 discharges exhaust gas discharged from the exhaust port 34 to the outside.
The exhaust system 60 includes an exhaust manifold 61, an exhaust pipe 62, a catalytic converter 63, a silencer 64, and the like.
The exhaust manifold 61 is a collecting pipe that collects exhaust gas discharged from the exhaust port 34 of each cylinder.
The turbine 41 of the turbocharger 40 is disposed on the downstream side of the exhaust manifold 61.
The exhaust pipe 62 is a conduit that discharges the exhaust gas emitted from the turbine 41 to the outside.
The catalytic converter 63 is provided in an intermediate portion of the exhaust pipe 62 and includes a three-way catalyst that purifies HC, NOx, CO, and the like in the exhaust gas.
The silencer 64 is provided in the vicinity of the outlet of the exhaust pipe 62, and reduces the acoustic energy of the exhaust gas.

The engine control unit (ECU) 70 comprehensively controls the engine 1 and its accessories.
The ECU 70 includes information processing means such as a CPU, storage means such as RAM and ROM, an input / output interface, a bus connecting these, and the like.
Further, the ECU 70 is provided with an accelerator pedal sensor 71 that detects the amount of depression of an accelerator pedal (not shown) by the driver.
The ECU 70 has a function of calculating the driver request torque based on the output of the accelerator pedal sensor 71.

In addition, an intake valve timing variable mechanism 100 and an exhaust valve timing variable mechanism 200 that advance or retard the angular position of each camshaft are provided in the cam sprocket portions of the intake camshaft and the exhaust camshaft.
Hereinafter, the intake valve timing variable mechanism 100 will be described, but the exhaust valve timing variable mechanism 200 has substantially the same configuration.
FIG. 2 is a diagram showing the configuration of the intake valve timing variable mechanism 100.
The intake valve timing variable mechanism 100 includes a housing 110, a rotor 120, a cam angle control valve 130, a lock mechanism 140, a cam angle sensor 150, and the like.

The housing 110 is a member that is fixed to the intake cam sprocket and rotates at a half rotation speed of the crankshaft 10. The intake cam sprocket is driven by a timing chain spanned between the crank sprocket fixed to the crankshaft 10.
The rotor 120 is a member inserted into the inner diameter side of the housing 110 and fixed to the intake camshaft.
The rotor 120 is rotatable relative to the housing 110 about the center axis of the intake camshaft. By this relative rotation, the phase of the intake camshaft is changed, and the opening timing and closing timing of the intake valve 35 are changed. It is possible to advance and retard infinitely.

As shown in FIG. 2, the housing 110 is formed with a fan-shaped space 111 formed by denting an inner peripheral surface portion facing the outer peripheral surface of the rotor 120 to the outer diameter side.
On the other hand, the rotor 120 is formed with a vane portion 121 that protrudes from the outer peripheral surface portion and is inserted into the fan-shaped space portion 111.
The rotor 120 is rotatable relative to the housing 110 within a range in which the vane portion 121 can move in the fan-shaped space 111.
The fan-shaped space 111 is divided into two by a vane portion 121 into an advance chamber 111a (advanced hydraulic chamber) and a retard chamber 111b (retarded hydraulic chamber).

The cam angle control valve 130 selectively transmits hydraulic pressure supplied from an oil pump (not shown) to the advance chamber 111a and the retard chamber 111b.
The cam angle control valve 130 is a spool valve configured by inserting a spool 132 into a sleeve 131 formed with a plurality of ports.
At each port of the sleeve 131, a hydraulic pressure supply line 134 that supplies hydraulic pressure into the sleeve 131 via the check valve 133, an advance hydraulic pressure supply line 135 that supplies hydraulic pressure to the advance chamber 111a, and an oil pressure to the retard chamber 111b. Are connected to a retarding hydraulic pressure supply line 136 and a drain line 137 for discharging unnecessary hydraulic fluid from the sleeve 131.
The cam angle control valve 130 is provided with a solenoid 138 that drives the spool 132 in one direction, and a return spring 139 that biases the spool 132 in a direction opposite to the driving direction of the solenoid 138 when the solenoid 138 is turned off. Yes.
Solenoid 138 operates in response to a control signal from ECU 70.
The cam angle control valve 130 changes the valve timing by switching the hydraulic pressure supply to the advance chamber 111a and the retard chamber 111b by driving the spool 132 forward and backward with respect to the sleeve 131 by the solenoid 138 and the return spring 139. Is.

The lock mechanism 140 locks the valve timing at a predetermined position when the supply hydraulic pressure is low, such as when the engine is started.
The lock mechanism 140 includes a lock pin 141, a flange 142, an unlock cylinder 143, a hydraulic passage 144, a spring 145, and the like.
The lock pin 141 is provided at a portion where the rotor 120 is opposed to the housing 110, and a protruding end portion is inserted into a recess 112 formed in the housing 110 to lock the valve timing.
The lock pin 141 is formed in a cylindrical shape and is held so as to be relatively movable with respect to the rotor 120 along the axial direction of the lock pin 141.
The flange 142 is formed to project from the base side of the lock pin 141 to the outer diameter side in a flange shape.
The unlock cylinder 143 is a cylindrical portion into which the flange 142 is inserted, and the outer peripheral edge portion of the flange 142 is slidably in contact with the inner peripheral surface of the unlock cylinder 143.
The hydraulic passage 144 introduces the hydraulic pressure extracted from the retarding hydraulic pressure supply line 136 into the unlock cylinder 143.
The spring 145 urges the lock pin 141 in the feeding direction.
With the above-described configuration, when the hydraulic pressure supplied from the hydraulic passage 144 is equal to or greater than a predetermined value, the hydraulic oil in the unlock cylinder 143 pushes the flange 142, whereby the lock pin 141 is extracted from the recess 112, and the lock is Canceled.
When the hydraulic pressure supplied from the hydraulic circuit 144 is smaller than a predetermined value, the lock pin 141 is extended by the urging force of the spring 145 and inserted into the recess 112 to lock the valve timing.

The cam angle sensor 150 is a sensor that detects the angular position of the intake camshaft.
The output of the cam angle sensor 150 is transmitted to the ECU 70.
The solenoid 138 is feedback-controlled by the ECU 70 using the detection value of the cam angle sensor 150 so that the advance angle amount and the retard angle amount of the intake camshaft become predetermined control target values.

  The variable exhaust valve timing mechanism 200 is also substantially the same housing (not shown), rotor (not shown), cam angle control valve 230, lock mechanism (not shown), cam, and cam as the intake valve timing variable mechanism 100 described above. An angle sensor 250 and the like are provided.

Hereinafter, the intake valve timing control in the first embodiment will be described.
In the first embodiment, when the driver request torque calculated based on the output of the accelerator pedal sensor 71 is less than a predetermined threshold value, the fuel efficiency emphasis control that gives priority to the fuel efficiency is performed at the expense of the output, and the driver request torque Is greater than or equal to a predetermined threshold, output-oriented control is performed with priority on output (torque) performance at the expense of fuel efficiency.

表１に示すように、燃費重視吸気バルブタイミングマップにおいては、特に低回転、低負荷の領域において、吸気バルブタイミングを遅角させ、吸気バルブのいわゆる遅開き、遅閉じを行うことによって、実効圧縮比に対して膨張比を大きくし、ミラーサイクル化して熱効率の改善を図っている。 In fuel efficiency-oriented control, the target advance of the intake valve timing is calculated from the intake air amount of the engine 1 calculated based on the output of the air flow meter 54 and the rotational speed of the engine 1 calculated based on the output of the crank angle sensor 11. A fuel-consumption-oriented intake valve timing map that requires angle and retardation is used.
An example of this fuel efficiency-oriented intake valve timing map is shown in Table 1.

As shown in Table 1, in the fuel efficiency-oriented intake valve timing map, effective compression is achieved by retarding the intake valve timing and so-called slow opening and closing of the intake valve, particularly in the region of low rotation and low load. The expansion ratio is increased relative to the ratio, and the mirror cycle is used to improve the thermal efficiency.

表２に示すように、出力重視吸気バルブタイミングマップにおいては、基本的には吸気バルブタイミングを進角させてバルブオーバーラップを拡大し、充填効率を高めることによってトルクアップを図っているが、ターボチャージャ４０の過給応答遅れによってインテーク内マニホールド内圧力が低い領域では、進角量を小さくするか、あるいは実質的に進角させないことによって、バルブオーバーラップを小さくし、内部ＥＧＲの増加によるトルクダウンを防止している。 On the other hand, in the output emphasis control, the intake pressure in the intake manifold 57 (absolute pressure of the intake manifold boost) detected by the intake pressure sensor 58 and the rotational speed of the engine 1 calculated based on the output of the crank angle sensor 11 are An output-oriented intake valve timing map in which the target advance / retard amount of intake valve timing is obtained is used.
An example of this output-oriented intake valve timing map is shown in Table 2.

As shown in Table 2, in the output-oriented intake valve timing map, the torque is basically increased by advancing the intake valve timing to increase the valve overlap and increase the charging efficiency. In a region where the pressure in the intake manifold is low due to a delay in the supercharging response of the charger 40, the valve overlap is reduced by reducing the advance amount or not substantially advanced, and the torque is reduced by increasing the internal EGR. Is preventing.

According to the first embodiment described above, when the driver request torque is high and it is necessary to perform output priority control, by controlling the valve opening timing of the intake valve 35 based on the absolute pressure in the intake manifold, In a state where the intake pressure is lower than the exhaust pressure due to the delay in the supercharging response, the valve opening timing of the intake valve 35 is delayed to reduce the overlap, and the torque down due to the increase in internal EGR can be suppressed. In particular, such an effect becomes remarkable in a highland where the atmospheric pressure is relatively low.
On the other hand, in a state where the boost pressure has increased and the intake pressure has become sufficiently high, the opening timing of the intake valve 35 can be advanced to increase the overlap, thereby increasing the charging efficiency and increasing the torque. it can.
In particular, by performing such control based on the intake pressure, it is possible to perform control with high accuracy, for example, for control based on the intake air amount.

FIG. 3 is a graph showing an example of the transition of the pressure in the intake manifold after the accelerator is shifted from the fully closed state to the fully opened state in the standard atmospheric state (atmospheric pressure 760 mmHg) and high altitude (atmospheric pressure 500 mmHg).
As shown in FIG. 3, in the standard atmospheric condition, the pressure in the intake manifold is equivalent to atmospheric pressure immediately after the accelerator is started, so the charging efficiency is improved by expanding the valve overlap, and the torque It is possible to up.
However, at high altitudes, the turbocharger is not supercharged immediately after the start of the accelerator depression due to the time response delay of the turbocharger, so that the state where the pressure in the intake manifold is low continues for a predetermined period. At this time, if the valve overlap is enlarged, the internal EGR is increased and the torque is reduced.
In this regard, according to the first embodiment, the valve overlap is not expanded until the pressure inside the intake manifold is improved after the supercharging pressure starts to be applied, thereby suppressing the torque reduction due to the increase in the internal EGR and the supercharging. After starting, the valve overlap can be expanded to improve the filling efficiency and increase the torque.

Next, a second embodiment of the valve timing control apparatus to which the present invention is applied will be described.
In addition, about the location which is substantially common with Example 1 mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted and a difference is mainly demonstrated.
In the second embodiment, in the output-oriented control, the intake pressure (relative pressure) in the intake manifold 57 relative to the exhaust pressure in the exhaust manifold 61 (in the exhaust port) is used instead of the absolute pressure in the intake manifold 57 in the first embodiment. ) To control the intake valve timing.
The exhaust pressure can be estimated using, for example, a map created in advance by experiments or calculations from the engine speed and the intake air amount.
In the second embodiment described above, in addition to the effects substantially similar to the effects of the first embodiment described above, the intake valve timing is controlled using the relative pressure of the intake pressure with respect to the exhaust pressure, thereby providing high accuracy. Control becomes possible, and an even higher effect can be obtained.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configurations of the engine and its accessories are not limited to the above-described embodiments, and can be changed as appropriate. For example, the engine of the embodiment is a horizontally opposed gasoline engine, but the present invention is not limited to this, and can be applied to an engine of another cylinder layout such as an inline engine or a V-type engine. Is not particularly limited. Moreover, if it is a 4-stroke engine, it is applicable also to the thing using fuels other than a diesel engine and gasoline.
(2) The method for detecting or estimating the intake pressure and the exhaust pressure is not limited to the above-described embodiment.
(3) The method of changing the valve opening timing of the intake valve is not limited to the method in which the phase of the camshaft is advanced or retarded by hydraulic pressure as in the above-described embodiment, and can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Engine 10 Crankshaft 11 Crank angle sensor 20 Cylinder block 30 Cylinder head 31 Combustion chamber 32 Spark plug 33 Intake port 34 Exhaust port 35 Intake valve 36 Exhaust valve 40 Turbocharger 41 Turbine 42 Compressor 50 Intake system 51 Intake duct 52 Chamber 53 Air cleaner 54 Air Flow Meter 55 Intercooler 56 Throttle Valve 57 Intake Manifold 58 Intake Manifold Sensor 59 Injector 60 Exhaust System 61 Exhaust Manifold 62 Exhaust Pipe 63 Catalytic Converter 64 Silencer 70 Engine Control Unit (ECU)
71 Accelerator pedal sensor 100 Intake valve timing variable mechanism 110 Housing 111 Fan-shaped space 111a Advance chamber 111b Delay chamber 112 Recess 120 Rotor 121 Vane portion 130 Cam angle control valve 131 Sleeve 132 Spool 133 Check valve 134 Hydraulic supply line 135 Advance Hydraulic supply line 136 Hydraulic delay supply line 137 Drain line 138 Solenoid 139 Return spring 140 Lock mechanism 141 Lock pin 142 Flange 143 Unlock cylinder 144 Hydraulic passage 145 Spring 150 Cam angle sensor 200 Exhaust valve timing variable mechanism 230 Cam angle control Valve 250 Cam angle sensor

Claims (2)

A valve timing control device that changes a valve opening timing of an intake valve with respect to a crank angle position according to an operating state of an engine,
Intake air amount detection means for detecting the intake air amount of the engine;
An intake pressure detecting means for detecting an intake pressure in the vicinity of the intake port;
A required torque determining means for determining the required torque, and
When the required torque is less than a predetermined value, a first valve opening timing control for advancing the valve opening timing of the intake valve according to an increase in the intake air amount is performed, and the required torque is a predetermined value. In the case described above, the valve timing control device performs second valve opening timing control for advancing the valve opening timing of the intake valve in accordance with an increase in the intake pressure. A valve timing control device that changes a valve opening timing of an intake valve with respect to a crank angle position according to an operating state of an engine,
Intake air amount detection means for detecting the intake air amount of the engine;
An intake pressure detecting means for detecting an intake pressure in the vicinity of the intake port;
Exhaust pressure estimating means for estimating the exhaust pressure in the vicinity of the exhaust port;
A required torque determining means for determining the required torque, and
When the required torque is less than a predetermined value, a first valve opening timing control for advancing the valve opening timing of the intake valve according to an increase in the intake air amount is performed, and the required torque is a predetermined value. In the case of the above, the valve timing control is characterized in that second valve opening timing control is performed to advance the valve opening timing of the intake valve in accordance with an increase in the relative pressure of the intake pressure to the exhaust pressure. apparatus.

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