JP6269389B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device having means capable of changing the closing timing of an intake valve.

  2. Description of the Related Art Conventionally, an engine that changes the valve timing of an intake valve by changing the phase of an intake camshaft that opens and closes the intake valve and the crankshaft of the engine has been used.

  As a device for changing the valve timing of the intake valve, 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 timing changing device, if the engine speed is low and the hydraulic pressure supplied from the pump is low, the vane rotor vibrates, 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. This locking mechanism fixes the vane rotor to the housing member when the hydraulic pressure supplied to the intake valve timing changing device becomes a predetermined value or less, and allows the movement of the vane rotor only when the hydraulic pressure is higher than the predetermined value. The vane rotor is prevented from vibrating when the engine speed is low.

Japanese Patent Laid-Open No. 9-60508

  From the viewpoint of fuel efficiency, it is preferable that the engine speed during idling, that is, the target idling speed is lower.

  However, the present inventors have disclosed that the intake valve timing changing device is a hydraulic type having the lock mechanism as described above, and that the hydraulic pressure supplied to the intake valve timing changing device including the lock mechanism is the engine rotation speed. If the target idle speed is simply kept low when the engine is generated with the engine, the engine speed cannot be maintained at the target idle speed when the atmospheric pressure falls below a predetermined value. I found out that the engine behavior may become unstable.

  Specifically, under operating conditions where the atmospheric pressure is greater than or equal to a predetermined value and the air density is sufficiently high, even if the load on the engine increases, the valve timing of the intake valve does not change, for example, in the intake passage The engine speed can be set to the target idle speed by changing the opening of the throttle valve provided. However, under the operating conditions where the atmospheric pressure is less than a predetermined value and the air density is low, the load on the engine becomes high, and the valve timing of the intake valve in order to maintain the engine speed at the target speed. In some cases, the closing timing of the intake valve must be changed. That is, in a state where the closing timing of the intake valve is not changed, the engine speed is lower than the target idle speed, so the intake amount is increased by changing the closing timing of the intake valve, As a result, it may be necessary to increase the engine speed. However, in the case where the intake valve timing changing means is configured as described above, since the engine speed is low, a sufficient hydraulic pressure cannot be supplied to the intake valve timing changing means, and the closing timing of the intake valve is not changed. The engine speed cannot be maintained at the target idle speed.

  The present invention has been made in view of the circumstances as described above, and provides an engine control device capable of stabilizing engine behavior even under operating conditions with low atmospheric pressure while ensuring fuel efficiency. With the goal.

In order to solve the above problems, the present invention includes a hydraulic intake valve timing changing means capable of changing at least the closing timing of an intake valve provided in an engine, and generating hydraulic pressure as the engine rotates. An engine control device comprising a hydraulic pressure supply means for supplying hydraulic pressure to the intake valve timing changing means, and when the engine is idling, the engine speed is set to a target idle speed that is a target value. The engine is provided with idle speed changing means for controlling each part of the engine including the intake valve timing changing means, and the intake valve timing changing means is configured to control the intake valve when the supplied oil pressure is less than a preset reference oil pressure. The valve closing timing of the intake valve is held at a predetermined timing, while when the hydraulic pressure exceeds the reference hydraulic pressure, the holding timing of the intake valve is released. The idle speed changing means can change the target idle speed based on the atmospheric pressure, and can calculate the target idle speed when the atmospheric pressure is lower than a preset reference pressure. The engine drives the hydraulic pressure supply means so that the hydraulic pressure supplied to the intake valve timing changing means becomes the reference hydraulic pressure higher than the target idle speed when the atmospheric pressure is equal to or higher than the reference pressure. The engine speed is set to a value that is larger than the engine speed (Claim 1).

  According to the present invention, when the intake valve timing changing means is a hydraulic type having a lock mechanism and the hydraulic pressure is generated by the engine, the engine behavior is unstable while ensuring fuel efficiency. Can be avoided more reliably.

Specifically, in the present invention, when the atmospheric pressure is high, the target idle speed, that is, the engine speed during idling can be kept low. Therefore, fuel consumption performance can be ensured. On the other hand, when the atmospheric pressure is low, the target idle speed, that is, the engine speed during idling, is set higher than a value that can ensure a hydraulic pressure that can release the hold of the intake valve closing timing . Therefore, when the atmospheric pressure is low and the air density is low and there is a high possibility that the opening timing of the intake valve needs to be changed to stabilize the engine behavior, the hydraulic pressure supplied to the intake valve timing changing means The engine behavior can be stabilized by releasing the holding of the closing timing of the intake valve by the lock mechanism and changing the closing timing of the intake valve.

  In the present invention, it is preferable that an atmospheric pressure detecting means for detecting an atmospheric pressure is provided, and the idle speed changing means changes the target idle speed based on a detection value of the atmospheric pressure detecting means. ).

  In this way, the atmospheric pressure is directly detected by the atmospheric pressure detecting means, and the target idle speed is changed according to the detected value, so that it is possible to more reliably avoid the unstable engine behavior. it can.

  In the present invention, it is preferable that the idling engine speed changing means increases the target idling engine speed as the atmospheric pressure decreases from a preset second reference pressure toward the reference pressure.

  In this way, the engine speed during idling changes gradually without a sudden change as the atmospheric pressure changes, so that the driver can avoid feeling uncomfortable due to this sudden change in the speed.

Here, particularly when the lock mechanism is configured to hold the closing timing of the intake valve at the most retarded timing among the possible closing timings of the intake valve. There is a high possibility that the engine behavior decreases and the engine behavior becomes unstable because the holding is not released and the closing timing of the intake valve cannot be changed. Therefore, it is more effective if the present invention is applied to such a configuration (claim 4 ).

In the present invention, an alternator that is driven by an engine to generate electric power is provided, and the idle speed changing means closes the intake valve by the intake valve timing changing means so that the engine speed becomes the target idle speed. in case of changing the timing valve, when the engine speed is insufficient or greater than a predetermined amount set in advance with respect to the target idle rotation speed, it is preferable to reduce the amount of power generated by the alternator (claim 5).

  In this way, even if the amount of engine speed deficient with respect to the target idle speed is large and the hydraulic pressure has not yet been sufficiently increased, even when the closing timing of the intake valve cannot be changed sufficiently, the alternator As a result, the engine can be rotated stably, and the behavior of the engine can be more reliably avoided.

  As described above, according to the engine control apparatus of the present invention, it is possible to more reliably avoid the engine behavior from becoming unstable while ensuring fuel consumption performance during idle operation.

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 graph which showed the relationship between atmospheric pressure and target idle speed. It is the graph which showed the relationship between intake valve closing timing, shaft torque, and atmospheric pressure. It is the flowchart which showed the flow of control of the idle speed which concerns on one Embodiment of this invention. It is the figure which showed the time change of each parameter when the conventional control is implemented. 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 graph which showed the other example of the relationship between atmospheric pressure and target idle speed.

(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 35 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 supply 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.

  An alternator 47 is connected to the crankshaft 15 via a belt or the like. The alternator 47 has a built-in regulator circuit that controls the current of the field coil to adjust the amount of power generation, and obtains the driving force from the crankshaft 15 based on the target value of the power generation amount set according to the operating conditions and the like. To generate alternating current.

  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 35. 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 timing changing means, hereinafter referred to as “Variable Valve Timing”). The valve opening start timing of 8 and the valve closing timing of the intake valve 8 are changed. In the present embodiment, the intake VVT 29 changes the valve opening start timing and the valve closing timing of the intake valve while keeping the valve opening period of the intake valve 8 constant.

  The intake VVT 29 is a hydraulic type and is driven by the hydraulic pressure supplied from the hydraulic pump 40, and the valve opening start timing and the valve closing timing (hereinafter referred to as opening / closing timing as appropriate) of the intake valve 8 are changed according to the hydraulic pressure. To do. The intake VVT 29 is provided with a lock mechanism that holds the closing timing (opening / closing timing) of the intake valve 8. The lock mechanism fixes (holds) the valve opening start timing of the intake valve 8 at a predetermined reference valve opening timing when the hydraulic pressure supplied to the lock mechanism (intake VVT 29) is less than a preset reference hydraulic pressure Poil_min and the intake valve. The valve closing time of 8 is fixed (held) at a predetermined reference time, and when the oil pressure becomes equal to or higher than the reference oil pressure Poil_min, the fixing is released. Therefore, in the present embodiment, the intake VVT 29 can change the closing timing (opening / closing timing) of the intake valve 8 only when the supplied hydraulic pressure is equal to or higher than the reference hydraulic pressure Poil_min.

  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, as a lock mechanism, a lock pin that fits into a lock hole formed in the shoe housing and fixes (locks) the vane rotor at a predetermined position (position where the closing timing of the intake valve 8 becomes the reference timing). A spring member is provided for biasing the lock pin in a direction in which the lock pin is fitted into the lock hole. In this lock mechanism, when a hydraulic pressure equal to or higher than the reference hydraulic pressure Poil_min is supplied, the lock pin comes out of the lock hole against the biasing force of the spring member, and the vane rotor can be moved.

  This locking mechanism avoids the problem that the vane rotor hits the housing member and generates noise under operating conditions where the engine speed is low, such as at the start, and the problem that the opening / closing timing of the intake valve 8 is not stable. Is to do. That is, when no lock mechanism is provided, the hydraulic pressure supplied from the hydraulic pump 40 is not stable under operating conditions where the engine speed is low, and the movement of the vane rotor is not stable. However, if the locking mechanism is provided, the vane rotor can be fixed to the housing member, and the above problem can be avoided.

  The reference timing, which is the fixed timing of the closing timing of the intake valve 8, may be appropriately set according to the startability and the like. That is, at the time of start-up, the closing timing of the intake valve 8 is fixed to this reference time by the lock mechanism. Therefore, the reference time may be set to a time that can ensure startability. In the present embodiment, this reference timing is set to the most retarded timing among the closing timings of the intake valve 8 that can be changed by the intake VVT 29, and the amount of air sucked into the engine body 1 (intake amount). ) Is set to a timing that is retarded from the closing timing of the intake valve 8 (for example, a timing that is retarded by a predetermined amount from the top dead center).

(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 valve closing timing (opening / closing timing) of the intake valve 8 is specified, and on the basis of this detection signal and the pulse signal from the crank angle sensor SN1, which cylinder is in what stroke is determined. Information is identified.

  An intake air amount sensor SN3 for detecting the amount of air introduced into each cylinder 2 is provided between the surge tank 32 and the throttle valve 34a in the intake passage 30.

  The vehicle is provided with an accelerator opening sensor SN4 (see FIG. 2) that detects an opening degree of an accelerator pedal (accelerator opening degree) that is operated by the driver. In addition, an atmospheric pressure sensor SN5 that detects atmospheric pressure is provided. In the present embodiment, the atmospheric pressure sensor SN5 is built in the ECU 50.

  The ECU 50 is electrically connected to these sensors SN1 to SN5, and based on signals input from the respective sensors, the above-described various information (engine speed, closing timing (opening / closing timing) of the intake valve 8). And cylinder information, intake air amount, accelerator opening, atmospheric pressure).

  And ECU50 controls each part of an engine, performing various determination, a calculation, etc. based on the input signal from said each sensor SN1-SN5. That is, the ECU 50 is electrically connected to the injector 12, the spark plug 13, the throttle valve 34a, the intake VVT 29 (OCV), and the alternator 47 (regulator circuit). Each outputs a control signal for driving.

(4) Idle rotation speed control The ECU 50 functionally includes an idle rotation speed control unit (idle rotation speed changing means) 51 in order to control the engine rotation speed during idle operation.

  The idle speed control unit 51 functionally includes a target idle speed determination unit 51a and an idle speed change unit 51b.

  The target idle speed determining unit 51a determines a target idle speed that is a target value of the engine speed during idling. The target idle speed determining unit 51a changes the target idle speed based on the atmospheric pressure, and the target idle speed when the atmospheric pressure Patm is smaller than a preset reference pressure Patm_L is the atmospheric pressure Patm. The value is higher than the target idle speed when the pressure is equal to or higher than the reference pressure Patm_L.

  In the present embodiment, the target idle speed determining unit 51a changes the target idle speed Nidle_trg according to the atmospheric pressure as shown in the graph of FIG. FIG. 3 is a graph in which the horizontal axis is the atmospheric pressure Patm and the vertical axis is the target idle speed Nidle_trg, and the horizontal axis becomes a lower pressure as it goes to the right.

  Specifically, when the atmospheric pressure Patm is lower than the reference pressure Patm_L, the target idle rotation speed determination unit 51a sets the target idle rotation speed Nidle_trg to be a low pressure idle rotation speed Nidle_trg_L constant and is higher than the reference pressure Patm_L. When the pressure is equal to or higher than Patm_H, the target idle speed Nidle_trg is set to be constant at the high pressure idle speed Nidle_trg_H. When the pressure is higher than the reference pressure Patm_L and lower than the second reference pressure Patm_H, the target idle speed Nidle_trg is decreased from the high-pressure idle speed Nidle_trg_H toward the low-pressure idle speed Nidle_trg_L, so that the atmospheric pressure Patm decreases. Decide to be higher.

  The low-pressure idle speed Nidle_trg_L is determined by the engine speed at which the hydraulic pressure supplied to the intake VVT 29 (specifically, the lock mechanism of the intake VVT 29) is the reference hydraulic pressure Poil_min, that is, the lock by the lock mechanism is released. The intake valve 8 is set to a value larger than the intake VVT operation start rotation speed N_oil, which is the engine rotation speed that enables the closing timing (opening / closing timing) of the intake valve 8 to be changed.

  Further, the reference pressure Patm_L is normal while the closing timing of the intake valve 8 is set to the most retarded timing (hereinafter, referred to as the most retarded timing as appropriate) even when the external load applied to the engine becomes maximum. It is set to a lower value than the lower limit pressure that is the lower limit value of the atmospheric pressure that can be operated.

  This will be specifically described with reference to FIG. In FIG. 4, the horizontal axis represents the closing timing (intake valve closing timing) IVC of the intake valve 8, and the vertical axis represents the shaft torque of the engine. These are shown when the atmospheric pressure is low and when the atmospheric pressure is high. Each relationship is shown. These lines are obtained when the throttle valve 34a is fully opened and the ignition timing is set to a timing at which the engine shaft torque becomes maximum. These lines are those when the engine speed is near the high-pressure idle speed Nidle_trg_H.

  As indicated by these lines, the intake amount increases and the shaft torque increases as the valve closing timing IVC of the intake valve 8 is advanced from the most retarded timing that is the reference timing.

  A line L1 in FIG. 4 shows a torque conversion amount when the load applied to the engine from the outside (alternator, compressor (air conditioner), torque converter, oil pump, etc. driven by the engine) becomes maximum. .

  As is clear from the comparison between the line L1 and the line L_H on the high atmospheric pressure side, when the atmospheric pressure is sufficiently high and the air density is high, the closing timing of the intake valve 8 is a reference time ( Even in the present embodiment, the most retarded angle) IVC_0, the shaft torque output from the engine is sufficiently larger than the maximum amount of the external load. Therefore, when the atmospheric pressure is sufficiently high, the engine can be stably rotated even when the closing timing of the intake valve 8 is set to the reference timing IVC_0 in a state where the external load is maximized.

  On the other hand, when the line L1 is compared with the line L_L on the low atmospheric pressure side, when the atmospheric pressure is low, the shaft torque output from the engine decreases with a decrease in the air density. When the timing is the reference timing IVC_0 (point A in FIG. 4), the engine shaft torque is smaller than the external load amount (line L1). Therefore, in this case, the engine cannot be stably rotated unless the closing timing of the intake valve 8 is advanced from the reference timing IVC_0. That is, as described above, the line L_L is a line when the throttle valve 34a and the ignition timing are controlled so that the engine shaft torque is maximized, and therefore the engine shaft torque is made larger than the maximum amount of the external load. In order to reliably rotate the engine, the closing timing of the intake valve 8 needs to be advanced from the reference timing IVC_0.

  Thus, the lower limit pressure is the upper limit value of the atmospheric pressure at which the engine body cannot be stably rotated unless the closing timing of the intake valve 8 is advanced from the reference timing IVC_0. The atmospheric pressure is such that the engine shaft torque and the maximum torque of the external load substantially coincide with each other when the valve timing is the reference timing IVC_0. The reference pressure Patm_L is set to a value slightly higher than the lower limit pressure.

  The idling engine speed changing unit 51 b controls the engine engine speed during idling to the target idling engine speed determined by the idling engine speed control unit 51.

  Here, as described above, when the atmospheric pressure is higher than the lower limit pressure, the target idle speed, and thus the engine speed, is smaller than the intake VVT operation start speed N_oil, and the closing timing of the intake valve 8 is reached. Is held at the reference time.

  Therefore, when the atmospheric pressure is equal to or higher than the lower limit pressure, the idling engine speed changing unit 51b performs the throttle valve opening (intake amount) and fuel injection in accordance with this so that the engine engine speed becomes the target idle engine speed. While changing the amount, the ignition timing is changed, and the closing timing (opening / closing timing) of the intake valve 8 is not changed.

  On the other hand, when the atmospheric pressure is less than the lower limit pressure, the target idle speed, and thus the engine speed, is equal to or higher than the intake VVT operation start speed N_oil, so that the closing timing (opening / closing timing) of the intake valve 8 is changed by the intake VVT 29. It becomes possible. Therefore, when the atmospheric pressure is equal to or lower than the reference pressure Patm_L, in addition to the throttle valve opening, the fuel injection amount, and the ignition timing, the intake valve 8 is closed so that the engine speed becomes the target idle speed. Change the valve timing (open / close timing).

  Specifically, the idle speed changing unit 51b sets the reference values of these parameters set in advance according to the target idle speed, that is, the reference opening of the throttle valve, the reference ignition timing, and the reference intake valve closing timing. (Reference intake opening and closing timing) is stored in a map, and a reference value corresponding to the target idle speed is extracted from this map, and this reference value is calculated based on the difference between the target idle speed and the actual engine speed. The final values of these parameters are determined in accordance with the above, and the commands corresponding to the final values are given to the injector 12, the throttle valve 34a (valve actuator 34b), the spark plug 13, and the intake VVT 29 (OCV). Output a signal.

  Further, in the present embodiment, when the idle speed changing unit 51b changes the closing timing (opening / closing timing) of the intake valve 8 by the intake VVT 29, the actual engine speed is a predetermined value with respect to the target idle speed. If it is lower than the above, the load applied to the engine from the alternator 29 is reduced while changing the closing timing (opening / closing timing) of the intake valve 8. This reduction in the alternator load is carried out until the closing timing of the intake valve 8 reaches the final closing timing (opening / closing timing) set as described above, and the opening timing (opening / closing of the intake valve 8). When the timing reaches the final valve closing timing (opening / closing timing), the alternator load reduction control is stopped, and the alternator 29 is driven according to the required power. Whether or not the closing timing (opening / closing timing) of the intake valve 8 has reached the final timing is determined based on the detection value of the cam angle sensor SN2 or the like. When the load of the alternator, that is, the amount of power generated by the alternator 47 is reduced, the reduced amount of power is supplemented by a battery or the like.

  The flow of the idle speed control by the idle speed control unit 51 is shown in the flowchart of FIG.

  First, in step S1, it is determined whether or not the accelerator opening is fully closed, that is, whether or not the engine is in an idling state. This determination is made based on the detection value of the accelerator pedal sensor SN4.

  If this determination is NO, step S1 is repeated, and if it is YES, the process proceeds to step S2.

  In step S2, the detection value of the atmospheric pressure sensor SN5 is read. That is, in the present embodiment, the detected value of the atmospheric pressure sensor SN5 is used as the atmospheric pressure for determining the target idle rotational speed by the idle rotational speed determination unit 51a. In step S2, the atmospheric pressure sensor The detection value of SN5 is read.

  Next, in step S3, the target idle speed is determined according to the atmospheric pressure that is the detection value of the atmospheric pressure sensor SN5 read in step S2. In the present embodiment, the map of the atmospheric pressure and the target idle speed shown in FIG. 3 is stored in the idle speed determining unit 51a, and a value corresponding to the atmospheric pressure is determined as the target idle speed from this map. . That is, when the atmospheric pressure Patm is less than the reference pressure Patm_L, the target idle speed Nidel_trg is determined from the intake VVT operation start speed N_oil that allows the intake VVT 29 to change the closing timing (opening / closing timing) of the intake valve 8. When the atmospheric pressure Patm is equal to or higher than the reference pressure Patm_H, the target idle speed Nidel_trg is set to a value lower than the low pressure idle speed Nidle_trg_L. Is done. In particular, when the atmospheric pressure Patm is equal to or higher than the second reference pressure Patm_L, the high-pressure idle rotational speed Nidle_trg_H set on the lower rotational speed side is set.

  Next, in step S4, the actual engine speed (actual engine speed) is read. Specifically, the engine speed specified based on the detected value of the crank angle sensor SN1 is read.

  Next, in step S5, it is determined whether the atmospheric pressure is equal to or higher than the lower limit pressure.

  When determination of step S5 is YES and atmospheric pressure is more than a lower limit pressure, it progresses to step S6. In step S6, the opening degree of the throttle valve 34a, the fuel injection amount, and the ignition timing are changed so that the engine speed becomes the target idle speed.

  On the other hand, if the determination in step S5 is NO and the atmospheric pressure is less than the lower limit pressure, the process proceeds to step S7. In step S7, the closing timing (opening / closing timing) of the intake valve 8 is changed in addition to the opening degree of the throttle valve 34a, the fuel injection amount, and the ignition timing so that the engine speed becomes the target idle speed.

  In step S8, which proceeds after step S7, the amount of rotation deficiency, that is, the difference between the target idle speed and the actual engine speed is equal to or greater than a predetermined value, and the closing timing (opening / closing timing) of the intake valve 8 is the target. It is determined whether or not the final time set to realize the idle speed has not been reached. If this determination is NO and the shortage of the rotation amount is less than the predetermined value, or if the closing timing (opening / closing timing) of the intake valve 8 has reached the final timing, the process proceeds to step S10. move on. On the other hand, if this determination is YES, the process proceeds to step S9, where the power generation amount of the alternator is reduced to reduce the alternator load applied to the engine.

  The above control is repeatedly performed while the accelerator opening is fully closed and the idle state continues. That is, after steps S6 and S9, the process returns to step S1 again.

(5) Operation, etc. As described above, in the present embodiment, when the atmospheric pressure Patm is equal to or higher than the reference pressure Patm_L, the engine speed during idling is controlled to a high pressure idle speed Nidle_trg_H that is a relatively low value. Therefore, excessive driving of the engine can be avoided to improve fuel efficiency, and when the atmospheric pressure Patm is lower than the reference pressure Patm_L, the engine speed during idling is such that the intake valve 8 is closed by the intake VVT 29. Since the low-pressure idle rotation speed Nidle_trg_L is set to a value higher than the intake VVT operation start rotation speed N_oil at which the valve timing (opening / closing timing) can be changed, the closing timing of the intake valve 8 by the intake VVT 29 ( If the engine speed decreases and the engine behavior becomes unstable due to the inability to change the opening and closing time) You can avoid the situation.

  This will be specifically described with reference to FIGS. These FIGS. 6 and 7 show the time change of each parameter during the idling operation when the atmospheric pressure is lower than the reference pressure. FIG. 6 shows a case where the idling speed control according to the present embodiment is not performed, and the target idling speed is set to a speed lower than the intake VVT operation start speed N_oil even at a low atmospheric pressure. FIG. 7 is a diagram when the idle speed control according to the present embodiment is performed.

  As shown in FIG. 6, even when the idle speed control according to the present embodiment is not performed and the target idle speed is set lower than the intake VVT operation start speed N_oil, it is not until time t1. When the external load that is a load applied to the engine from the outside (alternator or the like) is relatively small, the engine speed can be controlled to the target idle speed. However, when the target idle speed is set in this way, the hydraulic pressure supplied to the intake VVT 29 (lock mechanism) does not reach the reference hydraulic pressure Poil_min that can release the lock of the intake valve opening timing by the lock mechanism. Therefore, the closing timing (opening / closing timing) of the intake valve 8 by the intake VVT 29 cannot be changed. Therefore, when the external load increases at time t1, the opening of the throttle valve 34a is fully opened so as to maintain the engine speed at the target idle speed. However, since the atmospheric pressure is low and the air density is low, this throttle Only by changing the opening of the valve 34a and changing the ignition timing (not shown), the engine speed cannot be maintained, the engine speed decreases, and the engine behavior becomes unstable (for example, stops).

  On the other hand, as shown in FIG. 7, in the present embodiment, the target idle speed is set higher than the intake VVT operation start speed N_oil, so the hydraulic pressure supplied to the intake VVT 29 (lock mechanism) is increased. It is always possible to ensure the reference hydraulic pressure Poil_min or more. For this reason, even when the external load increases at time t1, the closing timing IVC of the intake valve 8 can be changed in conjunction with the change in the opening of the throttle valve 34a, etc. The engine can be rotated stably while avoiding the decrease.

  In addition, in the present embodiment, the alternator load is reduced when the rotation amount deficiency is equal to or greater than a predetermined value and the closing timing of the intake valve 8 has not reached the final closing timing. . Therefore, in a state where the closing timing of the intake valve 8 has not reached the final closing timing (for example, until time t2 in FIG. 7), an unexpected cause (combustion caused by fluctuations in the amount of water in the combustion chamber) Even if the engine speed decreases to less than the intake VVT operation start speed N_oil due to deterioration of the state, etc., the engine speed can be maintained at the intake VVT operation start speed N_oil or more by the decrease in the alternator load. Thus, the closing timing of the intake valve 8 can be more reliably changed to a predetermined timing. Therefore, it is possible to stabilize the engine behavior by more reliably controlling the engine speed to the target idle speed.

  Here, in the above embodiment, the case where the atmospheric pressure information for determining the target idle speed is obtained from the detection value of the atmospheric pressure sensor SN5 has been described, but a specific procedure for obtaining the atmospheric pressure information is described. Is not limited to this. For example, an intake pressure sensor that detects the pressure in the intake passage 30 may be provided in the intake passage 30, and the atmospheric pressure may be estimated based on the detected value of the intake pressure sensor. Moreover, you may estimate atmospheric pressure from the detected value using an altimeter. However, if the atmospheric pressure sensor SN5 is provided as described above and the atmospheric pressure is directly detected by the atmospheric pressure sensor SN5, the estimation procedure as described above becomes unnecessary, and the configuration can be simplified. It is possible to detect the atmospheric pressure more accurately and set the target idle speed more appropriately.

  Further, in the above embodiment, when the atmospheric pressure is higher than the reference pressure Patm_L and lower than the second reference pressure Patm_H, the target idle speed Nidle_trg is changed from the high pressure idle speed Nidle_trg_H to the low pressure idle speed Nidle_trg_L. The case where the atmospheric pressure Patm is determined to increase as the atmospheric pressure Patm decreases has been described. However, as illustrated in FIG. Nidle_trg_H may be configured to be constant. In this way, the engine speed during idling can be kept low in a wider driving range, and fuel efficiency can be improved. On the other hand, when configured in this manner, the engine speed during idling changes abruptly before and after the reference pressure Patm_L, and the driver may feel uncomfortable. Therefore, according to the above embodiment, it is possible to improve the drivability by avoiding the driver feeling uncomfortable.

  Moreover, although the said embodiment demonstrated the case where the valve closing timing of the intake valve 8 was fixed to the most retarded angle timing by the lock mechanism, this fixing timing is not restricted to this. However, in the case where the timing is fixed at the most retarded angle as described above, if the valve closing timing of the intake valve 8 is not changed, the intake air amount becomes insufficient as the atmospheric pressure decreases and the air density decreases. There is a high possibility that the behavior becomes unstable. Therefore, if the control according to the present embodiment is performed in such a case, it is more effective.

  Moreover, although the said embodiment demonstrated the example which applied the control apparatus of this invention to the gasoline engine, the form of the engine which can apply the control apparatus of this invention is not restricted to this. For example, other types of internal combustion engines such as diesel engines, ethanol fuel engines, and LPG engines may be targeted.

1 Engine Body 8 Intake Valve 9 Exhaust Valve 29 Intake VVT (Intake Valve Timing Changing Means)
40 Oil pump (hydraulic supply means)
34a Throttle valve 51 Idle speed controller (idle speed changing means)
SN5 atmospheric pressure sensor

Claims (5)

Hydraulic intake valve timing changing means capable of changing at least the closing timing of an intake valve provided in the engine, and hydraulic supply means for generating hydraulic pressure as the engine rotates and supplying hydraulic pressure to the intake valve timing changing means An engine control device comprising:
When the engine is idling, it comprises idle speed changing means for controlling each part of the engine including the intake valve timing changing means so that the engine speed becomes the target idle speed that is the target value.
The intake valve timing changing means maintains the intake valve closing timing at a predetermined timing when the supplied hydraulic pressure is less than a preset reference hydraulic pressure, while closing the intake valve when the hydraulic pressure exceeds the reference hydraulic pressure. It has a lock mechanism that releases the hold of the valve timing,
The idle rotation speed changing means can change the target idle rotation speed based on atmospheric pressure, and the target idle rotation speed when the atmospheric pressure is lower than a preset reference pressure, More than the target idle speed when the pressure is equal to or higher than the pressure, and the engine speed at which the engine can drive the hydraulic pressure supply means so that the hydraulic pressure supplied to the intake valve timing changing means becomes the reference hydraulic pressure. An engine control device characterized by a large value. The engine control device according to claim 1,
Equipped with atmospheric pressure detection means for detecting atmospheric pressure,
The engine control apparatus, wherein the idle speed changing means changes the target idle speed based on a detection value of the atmospheric pressure detecting means. The engine control apparatus according to claim 1 or 2,
The engine control device according to claim 1, wherein the idle speed changing means increases the target idle speed as the atmospheric pressure decreases from a preset second reference pressure toward the reference pressure. The engine control apparatus according to any one of claims 1 to 3,
The engine control device according to claim 1, wherein the lock mechanism holds the closing timing of the intake valve at the most retarded timing among the closing timings of the intake valve. The engine control apparatus according to any one of claims 1 to 4,
With an alternator driven by an engine to generate electricity
The idling engine speed changing means changes the engine speed to the target idling engine speed when the closing timing of the intake valve is changed by the intake valve timing changing means so that the engine engine speed becomes the target idling engine speed. On the other hand, an engine control device that reduces the power generation amount of the alternator when a predetermined amount greater than a predetermined amount is insufficient.

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