JP3724312B2 - 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]
In an engine in which the valve timing is changed by a variable valve system and the intake air amount in the cylinder is controlled, the purpose is to improve fuel efficiency by non-throttle operation. Therefore, boost is basically operated at atmospheric pressure. However, for the purpose of blow-by, evaporation purge, brake master back, etc., in order to cope with a negative pressure request, an electric throttle valve is used to generate a desired boost.
[0004]
On the other hand, when the target intake air amount becomes large in the fully open region, open the throttle valve and change the boost to the atmospheric pressure side while keeping the valve timing fixed at the time when the maximum intake air amount is reached. It is necessary to control the intake air amount.
[0005]
[Problems to be solved by the invention]
However, when switching between the intake air amount control by the variable valve operating device and the intake air amount control by the throttle valve, if switching is performed only with the target intake air amount, the actual negative pressure is controlled by the variable valve operating device. Switching is performed even when the target negative pressure does not coincide with the current target negative pressure, and there is a problem that a torque step is generated at the time of switching.
[0006]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to eliminate a torque step at the time of switching and to obtain good drivability.
[0007]
[Means for Solving the Problems]
For this reason, in the invention according to claim 1, as shown in FIG. 1, the intake valve closing timing is controlled by the variable valve device while the intake passage is controlled to the target negative pressure by the throttle valve, and the intake air amount is controlled. The first intake air amount control means for controlling, the second intake air amount control means for controlling the intake air amount by fixing the intake valve closing timing and controlling the opening degree of the throttle valve, and the engine operating range And a switching means for selectively actuating the first and second intake air amount control means. The variable valve engine control device further comprises an actual negative pressure detection means for detecting the actual negative pressure in the intake passage. The switching means is switched when the actual negative pressure detected by the actual negative pressure detecting means coincides with the target negative pressure after the switching command based on the engine operating range determined by the engine speed and the required torque. Specially configured To.
[0008]
The invention according to claim 2 is characterized in that the actual negative pressure detecting means is means for estimating the actual negative pressure with a first-order lag characteristic with respect to a change in the target intake air amount.
The invention according to claim 3 is characterized in that the first-order lag time constant is set based on the target intake air amount and the engine speed.
[0009]
The invention according to claim 4 is characterized in that the actual negative pressure detecting means is a negative pressure sensor for directly detecting the actual negative pressure in the intake passage.
The invention according to claim 5 is characterized in that the throttle valve is an electric throttle valve.
[0010]
【The invention's effect】
According to the first aspect of the present invention, when switching between the intake air amount control by the variable valve operating device and the intake air amount control by the throttle valve, the actual negative pressure becomes the target negative pressure after the switching command by the engine operating region. Since the switching is performed at the time of coincidence, the switching can be performed without generating a torque step, and the drivability can be improved.
[0011]
According to the second aspect of the present invention, the actual negative pressure is estimated with a first-order lag characteristic with respect to a change in the target intake air amount, so that it can be implemented easily and inexpensively without using a negative pressure sensor.
[0012]
According to the invention of claim 3, by setting the time constant of the first-order lag based on the target intake air amount and the engine speed, it is possible to satisfactorily change the response depending on the target intake air amount and the engine speed. It can cope and can improve estimation accuracy.
[0013]
According to the invention of claim 4, the control accuracy can be improved by directly detecting the actual negative pressure in the intake passage by the negative pressure sensor.
According to the invention which concerns on Claim 5, controllability improves by using an electrically controlled throttle valve.
[0014]
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 a first embodiment of the present invention.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
Returning to FIG. 2, the intake passage 7 is provided with an electrically controlled throttle valve 9 at a common portion common to all cylinders.
The intake passage 7 is also provided with an electromagnetic fuel injection valve 10 at the intake port portion of each cylinder.
[0019]
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.
[0020]
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 in the intake passage 7.
[0021]
On the other hand, in the fully open vicinity region (WOT region), the closing timing IVC of the intake valve 5 is fixed near the bottom dead center, and the opening degree TVO of the electric throttle valve 9 is variably controlled to control the intake air amount.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
In step 2, the target intake air amount TQH0 corresponding to the required torque is calculated from the accelerator opening APO and the engine speed Ne with reference to a map. However, in idling 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.
[0026]
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.
[0027]
In step 3, the actual negative pressure is estimated by an actual negative pressure estimation subroutine shown in FIG.
Specifically, at step 21 in FIG. 5, a first-order delay time constant FLOAD is calculated from the engine speed Ne and the target intake air amount TQH0 with reference to a map.
[0028]
Then, in the next step 22, the target intake air amount TQH0 is subjected to a first-order lag process by the following equation to calculate an actual negative pressure estimated value FQH0.
FQH0 = TQH0 × FLOAD + FQH0z × (1-FLOAD)
FQH0z is the previous value of FQH0.
[0029]
Since the actual negative pressure estimated value FQH0 is obtained by subjecting the target intake air amount TQH0 to a first-order lag process, the negative pressure is small (atmospheric pressure side) when FQH0 is large, and the negative pressure is large when FQH0 is small. .
[0030]
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 FLOAD and the larger the target intake air amount TQH0. Since the response of the negative pressure change to the change is higher, the time constant FLOAD is set larger as the target intake air amount TQH0 is larger.
[0031]
In step 4, it is determined whether the variable valve control region (normal operation region) or the throttle control region (near full open region). This region determination is performed based on the engine speed Ne and torque (target intake air amount TQH0).
[0032]
In the case of the variable valve control region, the process proceeds to step 5 to determine whether or not the flag FTH = 0 (currently during variable valve control). If YES, the process proceeds to step 9 to continue the variable valve control. .
[0033]
If the determination in step 5 is No, that is, if the throttle control is currently being performed and the switch command to the variable valve control is given, the process proceeds to step 6.
In step 6, the actual negative pressure estimated value FQH0 obtained in step 3 is compared with a threshold value corresponding to the target negative pressure, and the actual negative pressure estimated value FQH0 ≦ threshold value (actual negative pressure BOOST ≧ target negative pressure TBOOST). ) Is determined, and if No, the process proceeds to step 11 to continue the throttle control.
[0034]
If the determination in step 6 is Yes, that is, if the actual negative pressure estimated value FQH0 ≦ the threshold value (actual negative pressure BOOST ≧ target negative pressure TBOOST) after the command to switch to variable valve control, step Proceed to 9 to switch to variable valve control.
[0035]
If the determination in step 4 is in the throttle control region, the process proceeds to step 7 to determine whether or not the flag FTH = 1 (currently during throttle control). If yes, the process proceeds to step 11 to continue the throttle control. .
[0036]
If the determination in step 7 is No, that is, if the variable valve control is currently being performed and the switch command to throttle control is issued, the process proceeds to step 8.
In step 8, the actual negative pressure estimated value FQH0 obtained in step 3 is compared with a threshold corresponding to the target negative pressure, and the actual negative pressure estimated value FQH0 ≧ threshold (actual negative pressure BOOST ≦ target negative pressure TBOOST). ) Is determined, and in the case of No, the process proceeds to step 9 to continue the variable valve control.
[0037]
If the determination in step 8 is Yes, that is, if the actual negative pressure estimated value FQH0 ≧ threshold value (actual negative pressure BOOST ≦ target negative pressure TBOOST) after the command to switch to throttle control, the process proceeds to step 11. Go ahead and switch to throttle control.
[0038]
The variable valve control in step 9 and the throttle control in step 11 will be described later, but after the variable valve control in step 9, the routine is ended with flag FTH = 0 in step 10, After the throttle control in step 11, the routine is terminated in step 12 with the flag FTH = 1.
[0039]
Here, the step 3 corresponds to the actual negative pressure detection means (actual negative pressure estimation means), and the steps 4 to 8 correspond to the switching means including the operation region determination means (step 4).
[0040]
FIG. 6 is a flowchart of the variable valve control subroutine executed in step 9, which corresponds to the first intake air amount control means.
In step 31, the throttle opening TVO is calculated from the target negative pressure TBOOST and the target intake air amount TQH0 so as to obtain the target negative pressure TBOOST, and the electric throttle valve 9 is controlled.
[0041]
In step 32, the intake valve closing timing IVC is calculated from the target intake air amount TQH0 and the target negative pressure TBOOST so as to obtain the target intake air amount TQH0, and the electromagnetically driven intake valve 5 is controlled.
[0042]
FIG. 7 is a flowchart of the throttle control subroutine executed in step 11 and corresponds to the second intake air amount control means.
In step 41, the electromagnetic intake valve 5 is controlled so that the intake valve closing timing IVC is fixed near the bottom dead center.
[0043]
In step 42, 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. 8 is a time chart of switching from the fully open vicinity region (throttle control) to the normal operation region (variable valve control), and FIG. 9 is from the normal operation region (variable valve control) to the fully open region (throttle control). It is a time chart of switching.
[0045]
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.
[0046]
In the case of switching from the fully open vicinity region (throttle control) to the normal operation region (variable valve control), as shown in FIG. 8, the actual negative pressure estimation value obtained by subjecting the target intake air amount TQH0 to the primary delay processing When FQH0 crosses the threshold value corresponding to the target negative pressure, that is, when the actual negative pressure BOOST becomes the target negative pressure TBOOST, the throttle control is switched to the variable valve control.
[0047]
Conversely, in the case of switching from the normal operation region (variable valve control) to the fully open region (throttle control), as shown in FIG. 9, the actual negative value obtained by subjecting the target intake air amount TQH0 to the first-order lag process. When the estimated pressure value FQH0 crosses the threshold corresponding to the target negative pressure, that is, when the actual negative pressure BOOST becomes the target negative pressure TBOOST, the variable valve control is switched to the throttle control.
[0048]
As described above, when switching between the intake air amount control by the variable valve device and the intake air amount control by the electric throttle valve, the actual negative pressure during the switching transition is calculated using the primary delay by the intake manifold. Then, switching can be performed without a torque step by switching at the time when the target negative pressure coincides with the intake air amount control by the variable valve device.
[0049]
At the time of switching, the control of the previous area is continued until the actual negative pressure matches the target negative pressure, so that the area of the cylinder intake air can be switched with a response equivalent to that of the conventional engine and without a torque step. Can do.
[0050]
Next, a second embodiment of the present invention will be described.
FIG. 10 is a system diagram of the variable valve engine in the second embodiment.
In the second embodiment, a negative pressure sensor 16 that directly detects the actual negative pressure BOOST is provided downstream of the throttle valve 9 in the intake passage 7, and the signal is input to the control unit 11.
[0051]
FIG. 11 is a flowchart of the main routine in the second embodiment. The processing contents of steps 3, 6, and 8 are different from the flow of FIG.
In step 3, the actual negative pressure BOOST is detected based on the signal from the negative pressure sensor 16.
[0052]
In step 6, the actual negative pressure BOOST detected in step 3 is compared with the target negative pressure TBOOST, and it is determined whether or not the actual negative pressure BOOST ≧ target negative pressure TBOOST. As a result, when the actual negative pressure BOOST ≧ the target negative pressure TBOOST is satisfied after the switching command to the variable valve control, the routine proceeds to step 9 to switch to the variable valve control.
[0053]
In step 8, the actual negative pressure BOOST detected in step 3 is compared with the target negative pressure TBOOST to determine whether or not the actual negative pressure BOOST ≦ target negative pressure TBOOST. As a result, when the actual negative pressure BOOST ≦ the target negative pressure TBOOST is satisfied after the command for switching to the throttle control, the routine proceeds to step 11 to switch to the throttle control.
[0054]
In the second embodiment, the need for the negative pressure sensor 16 increases the cost, but since the actual negative pressure is detected directly, the control accuracy is improved.
In the above 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]
FIG. 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 a first embodiment of the present invention. 4) Main routine flowchart [FIG. 5] Actual negative pressure estimation subroutine flowchart [FIG. 6] Variable valve control subroutine flowchart [FIG. 7] Throttle control subroutine flowchart [FIG. 8] Throttle control → Variable valve control switching FIG. 9 is a time chart of switching from variable valve control to throttle control. FIG. 10 is a system diagram of a variable valve engine in the second embodiment. FIG. 11 is a flowchart of a main routine in the second embodiment. [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 15 Water temperature Sensor 16 Negative pressure sensor

Claims (5)

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 arbitrarily control the opening provided in the intake passage, the throttle valve controls the inside of the intake passage to a target negative pressure. On the other hand, the first intake air amount control means for controlling the intake air amount by controlling the intake valve closing timing by the variable valve device, and the intake valve closing timing is fixed, and the throttle valve opening is controlled to control the intake air. A control apparatus for a variable valve engine, comprising: a second intake air amount control means for controlling the amount; and a switching means for selectively operating the first and second intake air amount control means according to the engine operating range. In
An actual negative pressure detecting means for detecting the actual negative pressure in the intake passage is provided,
The switching means is switched when the actual negative pressure detected by the actual negative pressure detecting means coincides with the target negative pressure after a switching command based on the engine operating range determined by the engine speed and the required torque. A control apparatus for a variable valve engine characterized in that it is configured.   2. The control apparatus for a variable valve engine according to claim 1, wherein the actual negative pressure detecting means is means for estimating the actual negative pressure with a first-order lag characteristic with respect to a change in the target intake air amount. .   3. The control apparatus for a variable valve engine according to claim 2, wherein the time constant of the first-order lag is set based on the target intake air amount and the engine speed.   2. The control apparatus for a variable valve engine according to claim 1, wherein the actual negative pressure detecting means is a negative pressure sensor that directly detects the actual negative pressure in the intake passage.   The control apparatus for a variable valve engine according to any one of claims 1 to 4, wherein the throttle valve is an electric throttle valve.

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