JP3758448B2 - Control device for variable valve engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for a variable valve engine including a variable valve apparatus that can arbitrarily control the opening / closing operation of an intake valve.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a variable valve device, for example, an electromagnetic drive device, which drives an intake valve and an exhaust valve and arbitrarily controls their opening / closing operations (see Japanese Patent Laid-Open No. 10-311231).
[0003]
The engine that changes the valve timing by the variable valve system and controls the cylinder intake air amount aims to improve fuel efficiency by non-throttle operation, so basically boost wants to drive at atmospheric pressure, but blowby, In order to deal with a case where there is a demand for negative pressure, such as for evaporative purge, brake master back, etc., operation is performed while generating a desired boost using an electric throttle valve or the like.
[0004]
However, it is difficult to establish a high rotation / low load region (reducing torque in the high rotation region) due to the limitation of the driving speed of the variable valve operating device.
That is, in order to reduce the torque, it is necessary to reduce the intake air amount by shortening the opening period of the intake valve. However, even if the intake valve is opened and immediately closed, the driving speed is constant (spring constant) Therefore, in the high speed range, the minimum open period as seen from the crank angle becomes large, and there is a great limitation on the torque drop due to the reduction of the intake air amount. is there.
[0005]
For this reason, in a region where the intake air amount cannot be controlled by the variable valve device due to restrictions on the minimum opening period of the intake valve by the variable valve device (minimum operating angle region typified by a high rotation and low load region), the valve It is necessary to control the intake air amount by fixing the timing and controlling the opening degree of the electric throttle valve.
[0006]
[Problems to be solved by the invention]
However, in the normal operation region, while controlling the intake manifold with the electronic throttle valve to the target negative pressure, the intake valve closing timing is controlled by the variable valve operating device according to the operating conditions, while the intake air amount is controlled. The intake valve closing timing is fixed to the operating conditions in the region where the intake air amount cannot be controlled by the variable valve device (minimum operating angle region) due to the restriction of the minimum opening period of the intake valve by the variable valve device. Accordingly, when the intake air amount is controlled by controlling the opening of the electric throttle valve, there are the following problems.
[0007]
When the intake valve closing timing is fixed in the vicinity of the minimum intake air amount position (the earliest closing side) in the minimum operating angle region, and the intake air amount is controlled by the electronic throttle valve, the intake valve is closed by the variable valve system. Since the cylinder intake volume per intake is extremely small compared to a normal engine, the cylinder for the throttle operation is relatively increased by relatively increasing the volume of the intake manifold (including the collector). The responsiveness of the intake air amount is remarkably deteriorated, and this causes the drivability to deteriorate.
[0008]
Therefore, in the minimum operating angle region, it is considered that the intake valve closing timing is fixed to the vicinity of the maximum intake air amount position (latest closing side) as in a normal engine, and the intake air amount control is performed by the electric throttle valve. It is done.
[0009]
However, in this case, when switching from the normal operation range (variable valve control with constant boost) to the minimum operating angle range (throttle control), the intake valve closing timing is switched from the earliest side to the latest side. As a result of such switching, the amount of intake air in the cylinder is greatly changed, resulting in a torque step.
[0010]
That is, since a boost change occurs at the time of switching, in order to perform switching without changing the cylinder intake air amount, PV is constant, so V (cylinder intake volume due to intake valve closing timing) in accordance with P (boost). It is because it is necessary to change.
[0011]
In view of such a situation, the present invention achieves good drivability without causing a torque step when switching from the normal operation region (variable valve control with constant boost) to the minimum operation angle region (throttle control). The purpose is to be able to.
[0012]
[Means for Solving the Problems]
Therefore, in the invention according to claim 1, as shown in FIG. 1, in the normal operation region, the throttle valve that can arbitrarily control the opening degree is used to control the intake manifold to the target negative pressure and Accordingly, in a control apparatus for a variable valve engine having first intake air amount control means for controlling the intake air amount by controlling the intake valve closing timing by the variable valve device, the variable valve device performs minimum opening of the intake valve. The intake valve closing timing is set to the maximum intake air in the region where the amount of intake air cannot be controlled by the variable valve operating device due to the limitation of the period (specifically, the low rotation high load region shown in the invention according to claim 2 ). A second intake air amount control means that controls the intake air amount by controlling the opening degree of the throttle valve according to the operating condition, and is provided with the first intake air amount control means and the first intake air amount control means; 2 intake air amount control means (Especially in the invention according to claim 3, wherein the first intake air amount control means only when switching to the second intake air amount control means) in-over, the intake valve closing timing having the characteristics of the first-order lag And an intake valve closing timing switching means for changing the intake valve closing timing, the time constant of the primary delay in the intake valve closing timing switching means is set to the target intake air amount, the engine speed, and the intake valve closing timing during the primary delay control. It sets based on .
[0014]
【The invention's effect】
According to the first aspect of the present invention, when switching from the normal operation region (variable valve control with constant boost) to the minimum operating angle region (throttle control), the intake valve closing timing is fixed near the maximum intake air amount position. However, by changing the intake valve closing timing with a first-order lag characteristic, the change characteristic of the intake valve closing timing can be matched to the boost changing characteristic, and the cylinder intake air amount is kept constant (PV = Constant), switching can be performed, so that drivability can be improved without generating a torque step during switching.
[0015]
In addition, when the minimum operating angle region is reached, the responsiveness of the cylinder intake air amount to the throttle operation is changed by changing the intake valve closing timing to the vicinity of the maximum intake air amount position and switching to normal engine level control. Further, it is possible to prevent deterioration in combustion efficiency due to low compression ratio operation in a state where boost is developed in the minimum operating angle region.
[0016]
In addition, by setting the time constant of the primary delay of the intake valve closing timing at the time of switching based on the target intake air amount, the engine speed, and the intake valve closing timing during the primary delay control, Effects can be obtained.
[0017]
When the intake manifold volume is constant and the cylinder intake volume is constant, the time constant may be determined by the target intake air amount and the engine speed. However, the boost change characteristic in the present invention is that the intake manifold volume is constant. However, since the intake valve closing timing changes, the cylinder intake volume changes, and the boost change characteristic changes depending on the intake valve closing timing.
[0018]
Therefore, in order to always match the boost change characteristic, it is necessary to change the time constant of the first-order lag according to the intake valve closing timing that changes transiently.
For this reason, by adopting a configuration in which the first-order lag time constant is changed according to the intake valve closing timing, it is possible to have a first-order lag time constant that matches the intake valve closing timing that changes transiently. Even if the valve closing timing changes transiently, switching can be performed with the equal cylinder intake air amount (PV = constant), and the torque step can be further reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 2 is a system diagram of a variable valve engine showing an embodiment of the present invention.
[0020]
The combustion chamber 3 defined by the piston 2 of each cylinder of the engine 1 is provided with an electromagnetically driven intake valve 5 and an exhaust valve 6 so as to surround the spark plug 4. 7 is an intake passage and 8 is an exhaust passage.
[0021]
FIG. 3 shows the basic structure of an electromagnetic drive device (variable valve operating device) for the intake valve 5 and the exhaust valve 6. A plate-like movable element 22 is attached to the valve shaft 21 of the valve body 20, and the movable element 22 is biased to a neutral position by springs 23 and 24. A valve opening electromagnetic coil 25 is disposed below the mover 22, and a valve closing electromagnetic coil 26 is disposed above the movable element 22.
[0022]
Therefore, when opening the valve, after energization of the upper valve closing electromagnetic coil 26 is stopped, by energizing the lower valve opening electromagnetic coil 25 and attracting the mover 22 downward, The valve body 20 is lifted and opened. Conversely, when closing the valve, by energizing the lower valve opening electromagnetic coil 25 and then energizing the upper valve closing electromagnetic coil 26 to attract the mover 22 upward, The valve body 20 is seated on the seat portion and closed.
[0023]
Returning to FIG. 2, an electric throttle valve 9 is provided in the intake passage 7 upstream of the intake manifold.
The intake passage 7 is also provided with an electromagnetic fuel injection valve 10 for each cylinder in each branch portion of the intake manifold.
[0024]
Here, the operation of the intake valve 5, the exhaust valve 6, the electric throttle valve 9, the fuel injection valve 10 and the spark plug 4 is controlled by the control unit 11, and the control unit 11 has a crank in synchronization with the engine rotation. A crank angle sensor 12 that outputs an angle signal and can detect the engine speed Ne together with the crank angle position, an accelerator pedal sensor that detects an accelerator opening (accelerator pedal depression amount) APO (an idle switch that is turned on when the accelerator is fully closed) 13), an air flow meter 14 for detecting the intake air amount Qa upstream of the throttle valve 9 in the intake passage 7, a water temperature sensor 15 for detecting the engine cooling water temperature Tw, and the like.
[0025]
In this engine 1, in the normal operation region, the opening / closing operation of the electromagnetically driven intake valve 5 and the exhaust valve 6 is controlled for the purpose of improving the fuel consumption by reducing the pump loss. The intake air amount is controlled by variably controlling the closing timing IVC of the intake valve 5 and substantially non-throttle operation is performed. In this case, the electric throttle valve 9 controls the opening degree for the purpose of obtaining a target negative pressure required downstream of the intake valve 7 (in the intake manifold).
[0026]
On the other hand, in the region where the amount of intake air cannot be controlled by the variable valve device due to restrictions on the minimum opening period of the intake valve 5 by the variable valve device (minimum operating angle region typified by a high rotation and low load region), The closing timing IVC of the valve 5 is fixed in the vicinity of the bottom dead center near the maximum intake air amount position, and the intake air amount is controlled by variably controlling the opening degree TVO of the electric throttle valve 9.
[0027]
The fuel injection timing and the fuel injection amount of the fuel injection valve 10 are controlled based on the engine operating conditions. The fuel injection amount is basically determined based on the intake air amount Qa detected by the air flow meter 14. It controls so that it may become the air fuel ratio.
[0028]
The ignition timing by the spark plug 4 is controlled to MBT (optimum ignition timing on torque) or a knock limit based on engine operating conditions.
Next, the control of the intake valve 5 (particularly the intake valve closing timing IVC) and the electric throttle valve 9 (throttle opening TVO) will be described in more detail with reference to the flowcharts of FIGS.
[0029]
FIG. 4 is a flowchart of the main routine, which is executed every predetermined time or every predetermined rotation.
In step 1 (denoted as S1 in the figure, the same applies hereinafter), the accelerator opening APO and the engine speed Ne are read.
[0030]
In step 2a, the accelerator opening APO is converted to an opening area equivalent value AAPO with reference to the table, and in the next step 2b, the opening torque equivalent value AAPO and the engine speed Ne are used to obtain the required torque by the following equation. The target intake air amount TQH0 is calculated.
[0031]
TQH0 = (AAPO / V) / Ne
V is the displacement (constant).
However, during idle operation (idle switch ON), based on the deviation ΔNe = Ne−Nidle between the engine speed Ne and the target idle speed Nidle, when the deviation is on the negative side, the increase direction, the positive side In this case, the target intake air amount TQH0 is corrected in the decreasing direction.
[0032]
The target intake air amount TQH0 is calculated as a target volume flow rate ratio. Regarding the volume flow rate ratio QH0 (target volume flow rate ratio TQH0), when QH0 = 1, when viewed statically, the intake valve closing timing IVC is at the bottom dead center, that is, the cylinder intake stroke volume is the maximum. Further, when QH0 = 0.7, the cylinder intake stroke volume is 70% of the maximum stroke volume.
[0033]
In step 3, the time constant FLOADM for the first-order lag processing is calculated according to the time constant FLOADM calculation subroutine of FIG. The calculation method will be described in detail later.
[0034]
In step 4, the target intake air amount TQH0 is subjected to a first-order lag process by the following equation to calculate a target intake air amount FQH0 after the first-order lag process corresponding to the actual negative pressure change.
FQH0 = TQH0 × FLOADM + FQH0z × (1-FLOADM)
FQH0z is the previous value of FQH0. Also, 0 <FLOADM <1.
[0035]
In step 5, the target intake air amount FQH0 after the first-order lag process corresponding to the actual negative pressure change is compared with a predetermined threshold value, and the variable valve control region (normal operation region) or the throttle control region (minimum operating angle). Region). That is, when FQH0 ≧ threshold, it is determined as a variable valve control region (normal operation region), and when FQH0 <threshold, it is determined as a throttle control region (minimum operating angle region). Therefore, this portion corresponds to the operation region determination means.
[0036]
In the case of the variable valve control region, the process proceeds to step 6 and after setting the flag FTH = 0, in step 7, variable valve control is performed according to the variable valve control subroutine of FIG. 5, and this routine is terminated. .
[0037]
In the case of the throttle control region, the routine proceeds to step 8, and after setting the flag FTH = 1, in step 8, the throttle control is performed according to the throttle control subroutine of FIG. 6, and this routine is terminated.
[0038]
FIG. 5 is a flowchart of the variable valve control subroutine executed in step 7, which corresponds to the first intake air amount control means.
In step 11, the throttle opening TVO is calculated from the target negative pressure TBOOST and the target intake air amount FQH0 so as to obtain the target negative pressure TBOOST, and the electronic throttle valve 9 is controlled.
[0039]
In step 12, the intake valve closing timing IVC is calculated so as to obtain the target intake air amount (in-cylinder intake stroke volume FQH0EM) from the target intake air amount TQH0 and the target negative pressure TBOOST, and the electromagnetically driven intake valve 5 is calculated. To control.
[0040]
FIG. 6 is a flowchart of the throttle control subroutine executed in step 9, which corresponds to the second intake air amount control means.
In step 21, the electromagnetic intake valve 5 is controlled so that the intake valve closing timing IVC is fixed at the maximum intake air amount position MAXIVC (near bottom dead center).
[0041]
At this time, at the time of switching from intake air amount control using a variable valve to intake air amount control using a throttle, the in-cylinder intake stroke volume FQH0EM at the current intake valve closing timing IVC is first-order delayed so as to be equal to the intake manifold boost change. Is calculated using the first-order delay time constant FLOADM so that the in-cylinder intake stroke volume corresponding to the maximum intake air amount is obtained, and the intake air becomes the calculated in-cylinder intake stroke volume FQH0EM. Control to valve closing timing IVC.
[0042]
FQH0EM =
TQH0 × FLOADM + FQH0EMz × (1-FLOADM)
FQH0EMz is the previous value of FQH0EM.
[0043]
In step 22, the throttle opening TVO is calculated from the target intake air amount TQH0 and the engine speed Ne so as to obtain the target intake air amount TQH0, and the electric throttle valve 9 is controlled.
[0044]
FIG. 7 is a flowchart of the time constant FLOADM calculation subroutine executed in step 3.
In step 31, it is determined whether or not the throttle control is currently being performed (FTH = 1). If the throttle valve control is not being performed but the variable valve control is being performed (FTH = 0), the routine proceeds to step 32, where the primary delay occurs. In order to calculate the constant, the maximum value (MAXIVC) can be referred to the in-cylinder intake stroke volume ratio for calculating the intake valve closing timing (IVC position), and a time constant equivalent to the conventional engine can be obtained.
[0045]
Here, the time constant FLOADM calculation map has each time constant based on the IVC calculation cylinder intake stroke volume ratio FQH0EM2 and the target intake air amount TQH0 for each rotation. Therefore, the time constant corresponding to the conventional engine is the time constant at the time of MAXIVC where the IVC position is the same as that of the conventional engine, that is, the maximum intake air amount can be obtained.
[0046]
When the throttle control is in progress (FTH = 1), the routine proceeds to step 33, where the current intake valve is set to the in-cylinder intake stroke volume ratio for calculating the intake valve closing timing (IVC position) in order to calculate the first-order lag time constant. Reference is made to the in-cylinder intake stroke volume ratio for calculating the closing timing (IVC position). This is because IVC is fixed at the MAXIVC position during steady state during throttle control, so IVC does not change regardless of the calculated time constant, but at the time of switching from variable valve control to throttle control (minimum) In the process in which the boost develops in a constant boost state (operating angle → MAXIVC), it is possible to realize the movement of the IVC (movement of the intake stroke volume in the cylinder) in accordance with the development of the boost.
[0047]
In step 34, a map is selected from the current engine speed Ne, and the time constant of the first-order lag is selected based on the current intake closing timing (IVC position) and the target intake air amount TQH0 from the selected map. Search for FLOADM. Since a map for each engine speed Ne is used, interpolation calculation is performed between the engine speeds.
[0048]
Here, the higher the engine speed Ne, the higher the response of the negative pressure change to the change in the target intake air amount TQH0. Therefore, the higher the engine speed Ne, the larger the time constant FLOADM is set.
[0049]
Also, the greater the target intake air amount TQH0, the lower the response of the negative pressure change to the change. Therefore, the larger the target intake air amount TQH0, the larger the time constant FLOADM, and the smaller the target intake air amount TQH0, the smaller the time constant FLOADM. Set smaller.
[0050]
Further, the earlier the intake valve closing timing (IVC position), the lower the response of the negative pressure change to the change in the target intake air amount TQH0. Therefore, the earlier the intake valve closing timing (IVC position), the smaller the time constant FLOADM. The time constant FLOADM is set so as to increase.
[0051]
FIG. 8 is a time chart for switching from the normal operation region (variable valve control with constant boost) to the minimum operating angle region (throttle control).
In the figure, APO represents the accelerator opening, TQH0 represents the target intake air amount, IVC represents the intake valve closing timing, TVO represents the throttle opening, BOOST represents the negative pressure, and Qcyl represents the change in the cylinder intake air amount.
[0052]
In the case of switching from the normal operation region (variable valve control with constant boost) to the minimum operating angle region (throttle control), as shown in FIG. 8, FQH0 obtained by first-order lag processing of the target intake air amount TQH0 When the value crosses the threshold value, the variable valve control is switched to the throttle control.
[0053]
By this switching, the intake valve closing timing IVC is controlled to be fixed at the maximum intake air amount position MAXIVC. At this time, the in-cylinder intake stroke volume used for calculating the intake valve closing timing IVC is changed to the actual boost change primary delay characteristic. By changing it, the change characteristic of the intake valve closing timing IVC can be matched with the change characteristic of the boost, and switching can be performed while the cylinder intake air amount is constant (PV = constant). It is possible to improve drivability without generating torque steps.
[0054]
Further, in the throttle control in the minimum operating angle region, the intake valve closing timing IVC is changed from the minimum operating angle MINIVC to the maximum intake air amount position MAXIVC, and is switched to the control equivalent to that of a normal engine. Responsiveness of the intake air amount can be ensured, and deterioration of combustion efficiency due to low compression ratio operation in a state where boost is developed in the minimum operating angle region can be prevented.
[0055]
Further, by adopting a configuration in which the first-order lag time constant FLOADM is changed according to the intake valve closing timing IVC, it is possible to have a first-order lag time constant FLOADM in accordance with the intake valve closing timing IVC that changes transiently. Therefore, even if the intake valve closing timing IVC changes transiently, switching can be performed with the equal cylinder intake air amount (PV = constant), and the torque step can be further reduced.
[0056]
In the present embodiment, an electromagnetically driven type is used as the variable valve operating device, but a hydraulically driven type can also be used.
[Brief description of the drawings]
1 is a functional block diagram showing the configuration of the present invention. FIG. 2 is a system diagram of a variable valve engine showing an embodiment of the present invention. FIG. 3 is a basic structural diagram of an electromagnetic drive device for intake and exhaust valves. Flow chart of main routine [FIG. 5] Flow chart of variable valve control subroutine [FIG. 6] Flow chart of throttle control subroutine [FIG. 7] Flow chart of time constant calculation subroutine [FIG. 8] Time for switching variable valve control → throttle control Chart [Explanation of symbols]
1 Engine 4 Spark plug 5 Electromagnetically driven intake valve 6 Electromagnetically driven exhaust valve 7 Intake passage 8 Exhaust passage 9 Fuel injection valve 10 Electric throttle valve 11 Control unit 12 Crank angle sensor 13 Accelerator pedal sensor 14 Air flow meter

Claims (3)

While equipped with a variable valve system that can arbitrarily control the opening and closing operation of the intake valve and a throttle valve that can be controlled to an arbitrary opening provided upstream of the intake manifold, the intake manifold is controlled by the throttle valve in the normal operation region. Control of a variable valve engine provided with first intake air amount control means for controlling the intake air amount by controlling the intake valve closing timing by a variable valve device in accordance with operating conditions while controlling the inside to a target negative pressure In the device
In the area where the intake valve cannot be controlled by the variable valve system due to the restrictions on the minimum opening period of the intake valve by the variable valve system, the intake valve closing timing is fixed near the maximum intake air volume position and In response, a second intake air amount control means for controlling the intake air amount by controlling the opening of the throttle valve is provided,
An intake valve closing timing switching means for changing the intake valve closing timing with a first-order lag characteristic when switching between the first intake air amount control means and the second intake air amount control means ;
A variable valve that sets a primary delay time constant in the intake valve closing timing switching means based on a target intake air amount, an engine speed, and an intake valve closing timing during primary delay control. Engine control device. 2. The variable motion according to claim 1, wherein the region in which the amount of intake air cannot be controlled by the variable valve device due to the restriction on the minimum opening period of the intake valve by the variable valve device is a high rotation / low load region. Valve engine control device. The intake valve closing timing switching means changes the intake valve closing timing with a first-order lag characteristic only when switching from the first intake air amount control means to the second intake air amount control means. 3. The control apparatus for a variable valve engine according to claim 1 , wherein the control apparatus is a variable valve engine.

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