JP6222000B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control apparatus capable of automatic stop and automatic restart.

  Conventionally, an engine that changes the phase of the intake camshaft that drives the intake valve to open and close and the crankshaft of the engine to change the valve opening timing of the intake valve (intake valve opening timing) has been used. .

  As a device that changes the intake valve opening timing, a hydraulic device that changes the phase by receiving the supply of hydraulic pressure from a pump that generates hydraulic pressure as the engine rotates is widely used.

  For example, Patent Document 1 includes a housing member connected to a crankshaft and a vane rotor connected to an intake camshaft, and a hydraulic chamber in which hydraulic oil is supplied from a pump is formed between the housing member and the vane. A device that changes the phase of the vane rotor and the housing member, that is, the phase of the intake camshaft and the crankshaft, by changing the hydraulic pressure in the oil chamber is disclosed.

  Here, in such a hydraulic intake valve opening timing change device, when the engine speed is low at the time of starting or the like and the hydraulic pressure supplied from the pump is low, the vane rotor vibrates and the intake valve The valve opening time is not stable, which is not preferable. Therefore, in such an apparatus, as disclosed in Patent Document 1, when the engine speed is low, a lock mechanism for fixing the vane rotor to the housing member is provided, thereby prohibiting the movement of the vane rotor. Has been done.

  Patent Document 2 uses a hydraulic intake valve opening timing changing device having a lock mechanism as described above for a vehicle having a so-called idle stop function for automatically stopping the engine.

  In the vehicle of Patent Document 2, when a predetermined condition for automatically stopping the engine is satisfied, the fuel supply and ignition are stopped so that the restart is performed in a state where the opening timing of the intake valve is held by the lock mechanism. Thus, the intake valve is moved toward the time when it is held by the lock mechanism while the engine speed is decreased.

Japanese Patent Laid-Open No. 9-60508 JP 2013-96376 A

  As described above, in the vehicle of Patent Document 2, when a predetermined condition for automatically stopping the engine is satisfied, the fuel supply and ignition are stopped to reduce the engine speed, and the time when the intake valve is held by the lock mechanism. The engine speed is decreased and the intake valve is moved simultaneously.

  As a result, the engine stops before the intake valve opening timing shifts to the timing held by the lock mechanism, and the engine is restarted in a state where the intake valve opening timing is not held. The intake valve opening timing may become unstable during startup.

  Specifically, in the device that changes the intake valve opening timing by receiving hydraulic pressure supplied from the pump that generates hydraulic pressure as the engine rotates as described above, the intake valve opening timing is set when the engine rotation decreases. It cannot be changed. Therefore, as described in Patent Document 2, when the engine speed reduction and the intake valve movement are started at the same time, it is supplied to a device that changes the valve opening timing of the intake valve as the engine speed decreases. The hydraulic pressure is reduced, and the opening timing of the intake valve cannot be changed, and the opening timing of the intake valve cannot be shifted to the timing held by the lock mechanism.

  In order to solve this, for example, it is conceivable to limit the opening timing of the intake valve in advance, but this causes a decrease in engine performance.

  The present invention has been made in view of the circumstances as described above, and the engine behavior is unstable when the engine is restarted by shifting the opening timing of the intake valve to a predetermined timing when the engine is automatically stopped. It is an object of the present invention to provide an engine control device that can more reliably avoid the occurrence of the engine.

In order to solve the above problems, the present invention provides an automatic stop control means for automatically stopping and restarting the engine, a hydraulic pressure generating means for generating a hydraulic pressure as the engine rotates, and a hydraulic pressure from the hydraulic pressure generating means. The hydraulic intake valve opening timing includes a mechanism that changes the opening timing of the intake valve provided in the engine in response to the supply of the engine and a lock mechanism that holds the opening timing of the intake valve at a predetermined reference timing Change means, hydraulic control means for controlling the hydraulic pressure supplied to the intake valve opening timing change means, automatic stop determination means for determining whether or not an automatic stop condition that is a condition for automatically stopping the engine is satisfied, Lock state determination means for determining whether or not the intake valve is in a state that can be held at the reference time by the lock mechanism, and the hydraulic control means satisfies the automatic stop condition. Is determined, the hydraulic pressure for setting the intake valve opening start timing to the reference timing is supplied to the intake valve opening timing changing means, and the automatic stop means satisfies the automatic stop condition, and Then, after the lock state determination means determines that the intake valve is in a state that can be held at the reference time, the engine is automatically stopped, and the lock state determination means If the difference from the reference time is equal to or less than a preset determination value, it is determined that the intake valve is in a state where it can be held at the reference time, and the determination value is determined that the automatic stop condition is satisfied. The higher the engine speed at that time, the larger the value is set (claim 1).

  According to the present invention, even when an automatic stop condition, which is a condition for automatically stopping the engine, is satisfied, after the opening timing of the intake valve is held at the reference time by the lock mechanism, the engine Since the automatic stop of the intake valve is started, it is possible to reliably hold the opening timing of the intake valve based on the reference timing during the automatic stop of the engine. The behavior of can be stabilized. Further, since the opening timing of the intake valve is not limited in advance, engine performance can be ensured.

  In the present invention, it is provided with a target intake valve opening timing determining means for determining a target intake valve opening timing that is a target value of the opening timing of the intake valve according to the operating conditions, and the lock state determining means is determined If the difference between the target intake valve opening timing and the reference timing, and the difference between the intake valve opening start timing and the reference timing are less than or equal to a predetermined determination value, the intake valve is It is preferable to determine that the state has been maintained at the reference time (claim 2).

  In this way, the engine can be automatically stopped earlier, and fuel efficiency can be improved.

  Here, in the present invention, the reference timing is set to the most retarded timing in the range of the intake valve opening start timing changed by the intake valve opening timing changing means, and the engine speed is The intake valve opening start timing in the middle-rotation load region in which the engine load is set to a region between the predetermined first rotation speed and the second rotation speed and the engine load is set between the predetermined first load and the second load. Is particularly effective in the case where it is set on the advance side more than a predetermined time set in advance with respect to the reference time.

  In other words, in the present invention, the engine is automatically stopped after the intake valve opening start timing is maintained at the reference timing, so that the engine is in the middle rotation near the low rotation and low load region where the engine is automatically stopped. In the load region, the opening timing of the intake valve is set to a timing that is more than the predetermined timing than the reference timing, and the intake valve opening start timing is shifted to the reference timing as the load and rotation decrease thereafter. Even when the time required for the engine becomes longer, the intake valve opening start timing can be more reliably shifted to the reference timing when the engine is automatically stopped, and the engine behavior can be stabilized during restart. it can.

  Further, according to the present invention, the intake valve opening timing changing means changes the intake valve opening start timing over a range of 50 crank angles or more according to operating conditions, and the reference timing is changed to the intake valve opening timing. This is also effective in the case where the most retarded timing is set in the range of the intake valve opening start timing changed by the means (claim 4).

  In other words, according to the present invention, the opening timing of the intake valve can be more reliably maintained at the reference timing when the engine is automatically stopped. Therefore, the opening timing of the intake valve is within a wide range of 50 crank angles or more. Even if it is changed and the reference time is set to the most retarded time, the engine behavior can be stabilized at the time of restart.

  As described above, according to the engine control apparatus of the present invention, the start timing of the intake valve is shifted to and maintained at a predetermined time when the engine is automatically stopped, and the engine behavior is not improved when the engine is restarted. It can be avoided more reliably that it becomes stable.

It is a schematic diagram of an engine system concerning one embodiment of the present invention. It is the block diagram which showed the control system concerning one Embodiment of this invention. It is the figure which showed the example of the map of target intake valve opening time. It is the flowchart which showed the flow of the engine automatic stop control. It is the figure which showed the time change of each parameter when the control which concerns on one Embodiment of this invention is implemented. It is the figure which showed the time change of each parameter when the conventional control is implemented.

(1) Overall Configuration of Engine System FIG. 1 is a diagram showing an embodiment of an engine system to which a control device of the present invention is applied. The engine shown in the figure is a 4-cycle multi-cylinder gasoline engine mounted on a vehicle as a power source for traveling. Specifically, this engine includes an engine body 1 having a plurality of cylinders 2 (only one is shown in FIG. 1), an intake passage 30 for introducing air into the engine body 1, and the engine body 1. And an exhaust passage 39 for exhausting the exhaust gas generated in the above.

  The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper side of the cylinder block 3, a cam cap 5 provided on the upper side of the cylinder head 4, and a cylinder 2. And a piston 11 slidably inserted.

  A combustion chamber 10 is formed above the piston 11, and a fuel mainly composed of gasoline injected from an injector 12 (see FIG. 2) described later is supplied to the combustion chamber 10. The supplied fuel burns in the combustion chamber 10, and the piston 11 pushed down by the expansion force due to the combustion reciprocates in the vertical direction.

  The piston 11 is connected to a crankshaft 15 that is an output shaft of the engine body 1 via a connecting rod 14, and the crankshaft 15 rotates about the central axis in accordance with the reciprocating motion of the piston 11. Yes.

  An oil pump (hydraulic pressure generating means) 40 is connected to the crankshaft 15. The oil pump 40 is for supplying hydraulic pressure to an intake air VVT 29 and the like which will be described later. The oil pump 40 is driven in accordance with the rotation of the crankshaft 15, that is, the rotation of the engine body 1, and generates a hydraulic pressure corresponding to the rotation amount. An adjustment valve 41 (hereinafter referred to as OCV (Oil Control Valve)) for adjusting the hydraulic pressure is provided between the oil pump 40 and the intake VVT 29. The final hydraulic pressure supplied to the intake VVT 29 by the OCV 41 is provided. However, it is changed within the range below the discharge pressure of the oil pump 40.

  The cylinder head 4 has an injector 12 that injects fuel (gasoline) toward the combustion chamber 10 of the cylinder 2, and an ignition that supplies ignition energy by spark discharge to a mixture of fuel and air injected from the injector 12. A plug 13 is provided.

  In the cylinder head 4, the intake port 6 for introducing the air supplied from the intake passage 30 into the combustion chamber 10 of each cylinder 2 and the exhaust gas generated in the combustion chamber 10 of each cylinder 2 are supplied to the exhaust passage 39. An exhaust port 7 for deriving, an intake valve 8 for opening and closing the opening of the intake port 6 on the combustion chamber 10 side in order to control the introduction of intake air through the intake port 6, and gas exhaust from the exhaust port 7 are controlled. For this purpose, an exhaust valve 9 for opening and closing the opening of the exhaust port 7 on the combustion chamber 10 side is provided. In this embodiment, two intake ports 6 and intake valves 8 are provided for each cylinder 2, and two exhaust ports 7 and exhaust valves 9 are provided for each cylinder 2. .

  The intake passage 30 is connected in common to the independent intake passage 31 that communicates with the two intake ports 6 of each cylinder 2 and to the upstream end of each independent intake passage 31 (the upstream end in the intake flow direction). A surge tank 32 and one intake pipe 33 extending upstream from the surge tank 32 are provided.

  An openable / closable throttle valve 34 a for adjusting the flow rate of intake air introduced into the engine body 1 is provided in the middle of the intake pipe 33. The intake pipe 33 is provided with a valve actuator 34b for driving the throttle valve 34a. The throttle valve 34a is opened and closed by the valve actuator 34b. An air cleaner 35 is provided in a portion of the intake pipe 33 upstream of the throttle valve 34a.

(2) Intake valve drive mechanism Next, a mechanism for opening and closing the intake valve 8 will be described.

  The cylinder head 4 includes an intake camshaft 28a for opening and closing the intake valve 8, and an intake cam valve mechanism (not shown) provided so as to rotate integrally with the intake camshaft 28a. 28 is provided. The intake camshaft 28a is configured to rotate in conjunction with the rotation of the crankshaft 15, and the intake valve 8 is periodically lowered by the intake cam portion when the intake camshaft 28a rotates as the crankshaft 15 rotates. Is opened and closed.

  In the present embodiment, the intake side valve mechanism 28 is provided with an intake valve timing variable mechanism 29 (intake valve opening timing changing means, hereinafter referred to as an intake VVT (variable valve timing)). The valve opening start timing of the valve 8 (hereinafter referred to as intake valve opening timing as appropriate) is changed. In the present embodiment, the intake VVT 29 changes the intake valve opening start timing in a state in which the valve opening period of the intake valve 8 is kept constant.

  The intake VVT 29 is a hydraulic type and is driven when a hydraulic pressure equal to or higher than a predetermined reference hydraulic pressure Poil_min is supplied from the hydraulic pump 40, and the intake valve opening start timing is changed according to the supplied hydraulic pressure. The intake VVT 29 is provided with a lock mechanism that holds the intake valve opening timing.

  As such an intake VVT 29, for example, what is disclosed in Japanese Patent Laid-Open No. 9-60508 may be applied, and only a brief description of the structure will be given here.

  The intake VVT 29 includes a housing member that rotates integrally with the crankshaft via a chain and a chain sprocket, and a vane rotor that is disposed inside the housing member and rotates integrally with the camshaft. The housing member is provided with a vane rotor and a shoe facing the rotation direction thereof, and a hydraulic chamber to which hydraulic oil is supplied is defined between the shoe and the vane rotor. The vane rotor rotates with respect to the shoe and the shoe housing in accordance with the hydraulic pressure of the hydraulic oil supplied to the hydraulic chamber, thereby changing the phase between the crankshaft and the vane rotor, that is, the camshaft.

  The intake VVT 29 has a lock pin that locks the vane rotor at a predetermined position (a position at which the intake valve opening timing becomes the reference timing) by fitting into a lock hole formed in the shoe housing as a lock mechanism, and the lock And a spring member that urges the pin in a direction to fit the lock hole. In this lock mechanism, when a hydraulic pressure higher than a predetermined pressure is supplied, the lock pin comes out of the lock hole against the urging force of the spring member, and the vane rotor can be moved.

  This locking mechanism is for avoiding the problem that the vane rotor hits the housing member and generates noise under the operating condition where the engine speed is low, such as at the time of starting, and the problem that the intake valve opening timing is not stable. belongs to. That is, when the lock mechanism is not provided, the movement of the vane rotor is not stable due to the low hydraulic pressure supplied from the hydraulic pump 40 under the operating condition where the engine speed is low. There is a problem of hitting the housing member, there is a possibility that the intake valve opening timing is not stable and combustion may become unstable, but if the lock mechanism is provided, the vane rotor can be fixed to the housing member, The above problem can be avoided.

  The reference timing, which is the fixed timing of the intake valve opening timing, may be set as appropriate according to the startability and the like. That is, at the time of start-up, the intake valve opening timing is fixed to this reference time by the lock mechanism, and therefore, the reference time may be set to a time at which startability can be ensured. In the present embodiment, this reference timing is set to the most retarded timing among the intake valve opening timings that can be changed by the intake VVT 29.

(3) Control system Next, an engine control system will be described. Each part of the engine of the present embodiment is centrally controlled by an ECU (engine control unit) 50 shown in FIGS. 1 and 2. As is well known, the ECU 50 is a microprocessor including a CPU, a ROM, a RAM, and the like.

  The engine and the vehicle are provided with a plurality of sensors for detecting the state quantities of the respective parts, and information from each sensor is input to the ECU 50.

  For example, the cylinder block 3 is provided with a crank angle sensor SN1 that detects a rotation angle (crank angle) and a rotation speed of the crankshaft 15. The crank angle sensor SN1 outputs a pulse signal in accordance with the rotation of the crank plate that rotates integrally with the crankshaft 15. Based on this pulse signal, the rotation angle and rotation speed of the crankshaft 15, that is, engine rotation. Numbers are to be specified.

  The cam cap 5 is provided with a cam angle sensor SN2. The cam angle sensor SN2 outputs a pulse signal according to the passage of teeth of a signal plate that rotates integrally with the intake camshaft 28a, and detects the phase difference between the intake camshaft 28a and the crankshaft. Based on this detection signal, the intake valve opening timing is specified, and cylinder discrimination information indicating which cylinder is in what stroke is specified based on this detection signal and the pulse signal from the crank angle sensor SN1.

  An intake air amount sensor SN3 for detecting the amount of air introduced into each cylinder 2 is provided between the air cleaner 35 and the throttle valve 34a in the intake passage 30.

  The engine body is provided with a water temperature sensor SN4 (see FIG. 2) that detects the temperature of the engine cooling water.

  The vehicle includes an accelerator opening sensor SN5 (see FIG. 2) for detecting the opening degree of an accelerator pedal (accelerator opening degree) operated by a driver (see FIG. 2), a vehicle speed sensor SN6 (see FIG. 2) for detecting the vehicle speed, and the like. Is provided.

  The ECU 50 is electrically connected to these sensors SN1 to SN6, and based on signals input from the respective sensors, the above-described various information (engine speed, intake valve opening timing and cylinder information, intake amount, Water temperature, accelerator opening, vehicle speed).

  And ECU50 controls each part of an engine, performing various determination, a calculation, etc. based on the input signal from each said sensor SN1-SN6. That is, the ECU 50 is electrically connected to the injector 12, the spark plug 13, the throttle valve 34a, and the intake VVT 29 (OCV). Based on the result of the above calculation and the like, a drive control signal is sent to each of these devices. Output.

(4) Automatic stop control The vehicle according to the present embodiment is configured such that the engine is automatically stopped (so-called idle stop) for the purpose of improving fuel efficiency. That is, when a predetermined condition is met, automatic stop is performed in which combustion in each cylinder is stopped and the engine is automatically stopped regardless of the driver's operation (such as an operation of turning off the ignition key).

  The ECU 50 includes an automatic stop determination unit (automatic stop determination unit) 51, a lock state determination unit (lock state determination unit) 52, and an automatic stop unit (automatic stop unit) 53 as functional elements related to the automatic stop control of the engine. Have.

  Further, the ECU 50 includes a target intake valve opening timing determination unit (target intake valve opening timing determination unit) 54 and an intake valve opening timing change unit (hydraulic control unit) 55 as functional elements related to the control of the intake valve. ing.

  The target intake valve opening timing determination unit 54 determines a target intake valve opening timing which is a target value of the intake valve opening timing (intake valve opening start timing).

  The target intake valve opening timing determination unit 54 determines the target intake valve opening timing according to the engine speed and the engine load during normal operation in which an automatic stop condition described later is not satisfied. Specifically, the target intake valve opening timing determining unit 54 stores a target intake valve opening timing with respect to a preset engine speed and engine load as a map, and according to the engine speed and engine load. The target intake valve opening timing is extracted from this map. In this embodiment, as shown in FIG. 3, the target intake valve opening timing is such that the engine speed is not less than the first speed N1 and not more than the second speed N2, and the engine load is not less than a predetermined first load Ce1 and not less than the second load. It is set to be the most advanced side in the middle rotation middle load region A1 set in the region of the load Ce2 or less, and from the region A1 so that the engine rotational speed and the engine load become smaller, and the larger the value becomes, the slower the side becomes. ing. The difference between the most retarded time and the most advanced time is set to a relatively wide range of about 50 ° CA. That is, the valve opening start timing of the intake valve in the middle rotational load region A1 is set to be about 50 ° CA or more advanced than the reference timing which is the most retarded timing.

  On the other hand, the target intake valve opening timing determination unit 54 determines the target intake valve opening timing as a reference timing (most retarded timing) held by the lock mechanism when an automatic stop condition described later is satisfied. That is, in this embodiment, when the engine is automatically stopped, the intake valve opening timing is set to the reference timing, and the intake valve opening timing is held at the reference timing by the lock mechanism. This is because the vane rotor collides with the housing member as described above, and noise occurs when the engine is restarted after the engine is automatically stopped, and the intake valve opening timing is not stable. In order to avoid this problem, in this embodiment, the vane rotor is fixed to the housing member by the lock mechanism and the intake valve opening timing is held at the reference timing even during restart.

  The intake valve opening timing changing unit 55 controls the intake VVT 29 so that the intake valve opening timing becomes the target intake valve opening timing. In the present embodiment, as described above, the intake valve opening timing is changed by the OCV, and the intake valve opening timing changing section 55 supplies the intake VVT 29 with the hydraulic pressure that realizes the target intake valve opening timing. The OCV is controlled as follows.

  The automatic stop determination unit 51 determines whether or not an automatic stop condition that is a condition for automatically stopping the engine is satisfied. In the present embodiment, the automatic stop determination unit 51 is configured such that the engine water temperature is equal to or higher than a predetermined temperature, the engine is warmed up, the accelerator opening is fully closed, and the vehicle speed is equal to or lower than a predetermined value (for example, 4 km / h). If all the certain conditions are satisfied, it is determined that the automatic stop condition is satisfied.

  The lock state determination unit 52 determines whether or not the intake valve opening timing can be maintained at the reference timing by the lock mechanism of the intake VVT 29.

  Here, the state in which the intake valve opening timing can be maintained at the reference timing does not mean the state in which the vane rotor is completely fixed and held in the housing member, but is not yet completely fixed and held. Including a state in which it is surely fixed and held naturally thereafter. That is, in the present embodiment, as described above, the lock pin of the lock mechanism is fitted into the lock hole so that the vane rotor is fixed and the intake valve opening timing is maintained. When approaching the lock hole to some extent, the lock pin is securely fitted into the lock hole by the biasing force and inertia of the spring member. Therefore, in this embodiment, the state where the distance between the vane rotor and the lock hole is close, that is, the state where the intake valve opening timing is close to the reference time is also the state where the vane rotor is fixed to the housing member and It is included in the state where the intake valve opening timing is maintained at the reference timing.

  Specifically, the lock state determination unit 52 is in a state where the vane rotor can be fixed to the housing member when the difference between the intake valve opening timing and the reference time is equal to or less than a predetermined determination time (determination value), that is, the intake air It is determined that the valve opening timing can be maintained at the reference timing. The determination time is set to approximately 3 ° CA, for example. As described above, the intake valve opening timing is specified based on the detection value of the cam angle sensor SN2.

  The automatic stop unit 53 performs control for automatically stopping the engine. The automatic stop unit 53 automatically stops the engine by stopping fuel injection from the injector 12 and stopping ignition by the spark plug 13.

  Here, in the present embodiment, the automatic stop unit 53 does not start the automatic engine stop only when the automatic stop condition is satisfied, the automatic stop condition is satisfied, and the lock state determination unit 52 performs the intake air intake. Only when it is determined that the valve opening timing can be maintained at the reference timing, the engine is automatically stopped. That is, the automatic stop unit 53 continues the fuel injection from the injector 12 and ignites when it is determined that the automatic stop condition is satisfied while the intake valve opening timing is not in a state that can be held at the reference time. Ignition by the plug 13 is maintained. Then, after it is determined that the intake valve opening timing is maintained at the reference timing, fuel injection from the injector 12 is stopped, and ignition by the spark plug 13 is stopped.

  It is implemented by the ECU 50. FIG. 4 shows a control flow for automatically stopping the engine.

  First, in step S1, the water temperature (engine coolant temperature) detected by the water temperature sensor SN4, the accelerator opening sensor SN5, and the vehicle speed sensor SN6, the accelerator opening, the vehicle speed, and the like are read.

  Next, in step S2, it is determined whether or not an automatic stop condition is satisfied. If this determination is NO, the process returns to step S1. On the other hand, if this determination is YES, the process proceeds to step S3.

  In step S3, the target intake valve opening timing is set to the reference timing, and a command is issued to the OCV so that the intake valve opening timing becomes the reference timing.

  In step S4, which proceeds after step S3, it is determined whether the vane rotor is fixed to the housing member and whether the intake valve opening timing can be maintained at the reference timing. As described above, in this embodiment, if the difference between the target intake valve opening timing and the actual intake valve opening start timing and the reference timing is equal to or less than the determination timing, the intake valve opening timing can be maintained at the reference timing. It is determined that it has become.

  If the determination in step S4 is NO, the process returns to step S3, and the intake valve opening timing is retarded toward the reference timing.

  On the other hand, if the determination in step S4 is YES and the difference between the target intake valve opening timing and the actual intake valve opening start timing and the reference timing is equal to or less than the determination timing, the process proceeds to step S5. In step S5, the engine is automatically stopped. That is, the fuel injection from the injector 12 is stopped, and the ignition by the spark plug 13 is stopped.

(5) Operation, etc. As described above, in this embodiment, even when an automatic stop condition that is a condition for automatically stopping the engine is satisfied, the vane rotor can be fixed to the housing member by the lock mechanism of the intake VVT 29, and the intake air Since the engine stops automatically only after the valve opening timing can be maintained at the reference timing, the vane rotor is securely fixed to the housing member by the lock mechanism during the automatic engine stop, and the intake air The valve opening start time can be reliably held by the reference time. Therefore, it is possible to stabilize the behavior of the vane rotor and the start timing of intake valve opening at the time of restart, avoid vibrations caused by the vane rotor hitting the housing member, and engine behavior due to unstable combustion. It is possible to avoid becoming unstable.

  This will be specifically described with reference to FIGS. FIG. 5 and FIG. 6 are diagrams showing the time change of each parameter when the engine automatically stops from a predetermined operating condition and then restarts. 5 and 6, the automatic stop flag is a flag that is 1 when the automatic stop condition is satisfied, and is 0 when the automatic stop condition is not satisfied. Further, in FIG. 5, the lock determination flag is a flag that becomes 1 when the intake valve opening timing can be held at the reference timing by the lock mechanism of the intake VVT 29, and becomes 0 in other cases. FIG. 5 is a diagram when the control according to the present embodiment is performed, and FIG. 6 is a diagram when the conventional control is performed, that is, when the automatic stop of the engine is started as soon as the automatic stop condition is satisfied. It is.

  In FIG. 6, when the automatic stop condition is satisfied at time t1, the automatic engine stop is started almost simultaneously. Therefore, the engine speed starts to decrease from time t1, and similarly, the hydraulic pressure supplied to intake VVT 29 starts to decrease from time t1. Here, when the automatic stop condition is satisfied at time t1, the intake VVT 29 opens the intake valve to fix the vane rotor to the housing member by the lock mechanism and keep the intake valve opening timing at the most retarded timing (reference timing). Start changing the timing toward the most retarded angle (reference time). However, in the case shown in FIG. 6, as described above, the hydraulic pressure supplied to the intake VVT 29 starts to decrease from time t1 as the automatic engine stop is started at time t1. Therefore, at time t21 until the intake valve opening timing reaches the most retarded timing (reference timing), the hydraulic pressure supplied to the intake VVT 29 is lower than a predetermined reference hydraulic pressure Poil_min that can operate the intake VVT 29. Thus, after time t21, the intake valve opening timing cannot be changed. Therefore, in the case shown in FIG. 6, the engine is automatically stopped in a state where the intake valve start timing is not held at the most retarded timing (reference timing) by the lock mechanism and the vane rotor is not fixed to the housing member.

  When the engine is automatically stopped in this way, as shown in FIG. 6, after the engine is restarted at time t3, the hydraulic pressure supplied to the intake VVT 29 when the engine speed reaches a predetermined speed is Until the time t22 when the reference hydraulic pressure Poil_min is reached, the movement of the vane rotor is not stable, and the intake valve opening timing varies. When the intake valve opening timing fluctuates in this way, the amount of air taken into each cylinder 2 is not stable and combustion becomes unstable.

  In FIG. 6, the idling operation is performed until time t4 after restart, and from time t22 to time t4, the hydraulic pressure supplied to the intake VVT 29 is secured, so that the intake valve opening timing is the most retarded timing. (Reference time) will be changed. After time t4, the intake valve opening timing is changed to a timing set according to the operating conditions.

  On the other hand, as shown in FIG. 5, in this embodiment, even if the automatic stop condition is satisfied at time t1, the automatic stop of the engine is not started. First, the intake valve opening timing is the most retarded timing (reference Time). This change is started from time t1, and at time t1, the target intake valve opening timing is changed to the most retarded timing (reference timing), and the intake VVT 29 changes the intake valve opening timing so as to be the target intake valve opening timing. To start. Then, at time t2, the difference between the actual intake valve opening timing and the most retarded timing (reference timing) becomes the above-described determination timing, and after the lock determination flag becomes 1, automatic engine stop is started. That is, the engine speed and the hydraulic pressure supplied to the intake VVT 29 begin to decrease for the first time after time t2.

  Therefore, in this embodiment, at the time t3 restart, the vane rotor is fixed to the housing member by the lock mechanism and the intake valve opening timing is held at the most retarded timing timing (reference timing), and then restarted at time t3. Even when the hydraulic pressure supplied to the intake VVT 29 is low at the time of restart, the vane rotor can be prevented from vibrating and the intake valve opening timing is set to the most retarded timing (reference timing). Thus, the amount of air sucked into each cylinder 2 and the combustion in each cylinder 2 can be stabilized.

  In the present embodiment, as described above, the difference between the target intake valve opening timing and the most retarded timing (reference timing) and the difference between the actual intake valve opening timing and the most retarded timing (reference timing) are 0. When the time becomes equal to or less than the determination time set to a larger value, it is determined that the intake valve opening time can be maintained at the most retarded time (reference time), and automatic engine stop is started. Therefore, the engine can be automatically stopped earlier while the intake valve opening timing shifts to the most retarded timing (reference timing), and fuel efficiency can be improved.

  Here, the range of the intake valve opening timing changed by the intake VVT 29, that is, the difference between the most retarded angle side timing and the most advanced angle side timing is not limited to about 50 ° CA. However, in the present embodiment, the intake valve opening timing can be reliably held at the reference timing when the engine is automatically stopped regardless of the difference between the intake valve opening timing when the automatic stop condition is satisfied and the reference timing. Therefore, if the range of the intake valve opening timing is set to at least 30 ° CA or more in this way, the intake valve opening timing is held at the reference timing when the engine is automatically stopped, and deterioration of combustion stability at the time of restart is suppressed. Further, the engine performance can be improved by appropriately controlling the intake valve opening timing in accordance with the operating conditions.

  In the above embodiment, the case where the reference timing is set to the most retarded timing and the intake valve opening timing is set to the most advanced timing in the mid-rotation load region A1 has been described. The specific intake valve opening timing is not limited to this. However, if the time period is set as described above and the configuration according to the present embodiment is applied, the engine behavior at the time of restart can be more effectively stabilized.

  Specifically, in the above-described embodiment, basically, the engine is often automatically stopped in a low rotation and low load region (an operation region in which the engine speed and the engine load are lower than predetermined values). However, for example, when an external load such as an air conditioner is large and the engine is automatically stopped during traveling, the engine may be automatically stopped in the middle rotation load region A1. Therefore, in the case where each timing is set as described above and the engine is automatically stopped in the middle rotation load region A1, the conventional control (automatic engine stop and intake air opening shown in FIG. 6) is performed. If the control for starting the change of the valve timing to the reference timing at the same time is performed, the intake valve opening timing does not reach the reference timing, and the engine behavior is likely to become unstable at the time of restart. On the other hand, with the configuration according to the present embodiment, each time is set as described above, and even when the engine is automatically stopped in the middle rotation load region A1, Since the intake valve opening timing can reach the reference timing, the engine behavior at the time of restart can be stabilized.

  Here, as described above and as shown in FIG. 3, in the above embodiment, the intake valve opening timing is retarded as the engine speed and the engine load from the region A1 become smaller and larger. In the operating region around this region A1, the intake valve opening timing is a timing more advanced than the most retarded timing by a predetermined timing or more. Therefore, not only when the engine is automatically stopped in the region A1, but also when the engine is automatically stopped in the region around the region A1, of course, the present embodiment is applied, The engine behavior at the time of restart can be stabilized. That is, the present invention is not limited to the case where the intake valve opening timing is set to the most advanced timing in the middle rotation load region A1, but the intake valve opening timing is the most retarded timing (reference) in the middle rotation load region A1. This is also effective when the valve is set to the advance side by a predetermined time or more than (time), and the intake valve opening time in the mid-rotation load region A1 may be set in this way. In this case, the predetermined time is set longer than at least the determination time.

  Further, in the above embodiment, a case has been described in which it is determined that the intake valve opening timing is in a state that can be held at the reference timing when the difference between the intake valve opening timing and the reference timing is equal to or less than a predetermined determination timing. However, other procedures, for example, a procedure for determining that the intake valve opening timing can be maintained at the reference timing when the actual value of the intake valve opening timing is equal to or less than the predetermined timing (a retarded side from the predetermined timing). May be adopted.

  Further, the predetermined timing to be compared with the determination timing or the actual value of the intake valve opening timing is set according to the engine speed before the engine is automatically stopped (for example, when the automatic stop condition is satisfied). It may be changed. That is, the higher the engine speed, the higher the hydraulic pressure supplied to the intake VVT 29, and the time until the hydraulic pressure drops to the reference hydraulic pressure Poil_min, that is, the change in the intake valve opening timing by the intake VVT 29 after the engine is stopped. The time until it becomes impossible, in other words, the time during which the intake valve opening timing can be moved to the reference timing even after the engine is stopped becomes longer. Therefore, the determination timing may be set to be on the advance side as the engine speed before the engine is automatically stopped is higher. In this way, it is possible to quickly determine that the intake valve opening timing can be maintained at the reference timing, and it is possible to automatically stop the engine earlier and improve fuel efficiency.

1 Engine body 8 Intake valve 29 Intake VVT (Intake valve opening timing change means)
40 Oil pump (hydraulic pressure generating means)
51 Automatic stop determination unit (automatic stop determination means)
52 Lock state determination unit (lock state determination means)
53 Automatic stop (automatic stop means)
54 Target intake valve opening timing determining section (target intake valve opening timing determining means)
55 Intake valve opening timing change section (hydraulic control means)

Claims (4)

Automatic stop control means for automatically stopping and restarting the engine;
Hydraulic pressure generating means for generating hydraulic pressure as the engine rotates;
Oil pressure including a mechanism that receives the supply of oil pressure from the oil pressure generating means and changes the opening start timing of the intake valve provided in the engine, and a lock mechanism that holds the opening start timing of the intake valve at a predetermined reference time A means for changing the intake valve opening timing of the formula,
Hydraulic control means for controlling the hydraulic pressure supplied to the intake valve opening timing changing means;
Automatic stop determination means for determining whether or not an automatic stop condition that is a condition for automatically stopping the engine is satisfied;
Lock state determination means for determining whether or not the intake valve is in a state that can be held at the reference time by the lock mechanism,
When it is determined that the automatic stop condition is satisfied, the hydraulic control means supplies the intake valve opening timing changing means with a hydraulic pressure for setting the opening timing of the intake valve to the reference timing,
The automatic stop means starts automatic engine stop after the automatic stop condition is satisfied and the lock state determination means determines that the intake valve is in a state that can be held at the reference time ,
The lock state determination means determines that the intake valve is in a state that can be held at the reference time if the difference between the opening timing of the intake valve and the reference time is equal to or less than a predetermined determination value. ,
The engine control apparatus , wherein the determination value is set to a larger value as the engine speed is higher when it is determined that the automatic stop condition is satisfied . The engine control device according to claim 1,
A target intake valve opening timing determining means for determining a target intake valve opening timing that is a target value of the opening timing of the intake valve according to the operating conditions,
The lock state determination means determines whether a difference between the determined target intake valve opening timing and the reference timing and a difference between the intake valve opening start timing and the reference timing are set in advance. If the value is equal to or less than the value, it is determined that the intake valve is in a state capable of being held at the reference time. The engine control apparatus according to claim 1 or 2,
The reference timing is set to the most retarded timing in the range of the opening timing of the intake valve that is changed by the intake valve opening timing changing means,
In the region of the mid-rotation load region in which the engine speed is set to a range between a predetermined first speed and a second speed, and the engine load is set to a range between the predetermined first load and the second load, the intake valve The engine control device is characterized in that the valve opening start time is set to an advance side by a predetermined time or more than the reference time. The engine control apparatus according to any one of claims 1 to 3,
The intake valve opening timing changing means changes the valve opening start timing of the intake valve over a range of 50 crank angles or more according to operating conditions,
2. The engine control apparatus according to claim 1, wherein the reference time is set to the most retarded time in a range of the opening timing of the intake valve that is changed by the intake valve opening timing changing means.

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