JP3565119B2 - Variable valve control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device that adjusts the torque of a variable valve engine having an intake / exhaust valve that can variably control the opening / closing timing, such as an electromagnetic drive type.
[0002]
[Prior art]
Conventional general engines control the amount of intake air by the opening degree of a throttle valve.In recent years, however, an electromagnetically driven intake / exhaust valve has been provided, and the intake air amount is mainly controlled by controlling the closing timing of the intake valve. The following has been proposed (see Japanese Patent Application Laid-Open No. 10-37727).
[0003]
In this type of intake air amount control, when the throttle valve is not provided, the intake pressure is maintained at approximately the atmospheric pressure, and when the throttle valve is used together, the intake pressure corresponding to the opening degree of the throttle valve is closed. By controlling the volume of the cylinder intake air according to the effective intake stroke determined by the timing, it is possible to control so as to obtain the target air amount according to the required torque.
[0004]
[Problems to be solved by the invention]
However, to be precise, the intake valve closing timing for obtaining the target air amount changes according to the residual gas amount in the combustion chamber, and as the residual gas amount increases, the closing timing approaches the intake bottom dead center to increase the effective intake stroke. There is a need to. Therefore, it is possible to calculate the closing timing of the intake valve in consideration of the closing timing of the exhaust valve and the opening timing of the intake valve which determine the residual gas amount (more precisely, also considering the opening timing of the exhaust valve). Required.
[0005]
In this case, if the control of each valve timing of the intake and exhaust valves is performed equally, for example, in response to a change in the residual gas amount, the exhaust valve closing timing and the intake valve opening timing other than the intake valve closing timing, and further, the exhaust valve If the control other than the intake valve closing timing, including the opening timing of the intake valve, is performed with higher responsiveness than the control of the intake valve closing timing, the transient operation until the intake valve closing timing is controlled to the target value is performed. , The deviation of the torque became large, and good operability could not be secured.
[0006]
For example, when performing control to increase the intake air amount while maintaining the internal EGR rate constant, the intake air amount is changed while changing the opening timing of the intake valve, the closing timing of the exhaust valve, and the opening timing of the exhaust valve. In consideration of the increase in the internal EGR amount (residual gas amount), control is performed to delay the closing timing of the intake valve. However, the opening timing of the intake valve, the closing timing of the exhaust valve, and the opening of the exhaust valve are controlled. If the change of the closing timing of the intake valve is delayed with respect to the change of the timing, the intake air amount becomes insufficient with respect to the increase of the residual gas amount, and the torque becomes insufficient, so that the operability is greatly reduced.
[0007]
That is, the opening timing and exhaust of the intake valve for determining the internal EGR amount (residual gas amount) so that the optimum air amount (fresh air amount) can always be ensured by following the change in the internal EGR amount (residual gas amount). It is necessary to make the responsiveness of the control of the closing timing of the valve, and further, the opening timing of the exhaust valve, lower than the responsiveness of the control of the closing timing of the intake valve.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has a variable dynamic range in which good transient performance can be obtained by appropriately setting the response of each valve timing of the intake and exhaust valves. An object of the present invention is to provide an air volume control device for a valve.
[0009]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is
In a variable valve control device that variably controls the opening / closing timing of an intake / exhaust valve of an engine to be a set target value, the target value of each target value at the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve is determined. The change speed is set to a value smaller than the change speed of the target value when the intake valve is closed.
[0010]
According to the first aspect of the invention,
When the target values of the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve are changed, the target value of the closing timing of the intake valve is also changed according to the change in the residual gas amount according to the change. The rate of change of the target value of the opening timing of the intake valve, the timing of the opening timing of the exhaust valve, and the target value of the closing timing related to the change of the residual gas amount other than the closing timing are controlled to be smaller than the rate of change of the target value of the closing timing of the intake valve. .
[0011]
As a result, control can be performed to maintain the target air amount at an optimum value following changes in the amount of residual gas, and high-precision intake air amount control and, consequently, torque control can be performed even during a transient, and a sudden torque Changes can be avoided and good driving performance can be maintained.
[0012]
The invention according to claim 2 is
An upper limit value is set for the change speed of the target value at the opening timing of the intake valve and the opening timing and the closing timing of the exhaust valve.
[0013]
According to the invention according to claim 2,
Opening timing of the intake valve, the change rate of the target value of the opening timing and closing timing of the exhaust valve, by being restricted by the upper limit value is controlled to be smaller than the change rate of the target value of the closing timing of the intake valve.
[0014]
The invention according to claim 3 is:
The upper limit provided for the target value changing speed at the intake valve opening timing, the exhaust valve opening timing and the closing timing is smaller than the upper limit provided at the target value changing speed at the intake valve closing timing. I do.
[0015]
According to the invention according to claim 3,
Opening timing of the intake valve, the change rate of the target value of the opening timing and closing timing of the exhaust valve, the upper limit value provided for the rate of change in these target values to the change rate of the target value of the closing timing of the intake valve By setting it smaller than the upper limit provided, it is controlled to be smaller than the change speed of the target value of the closing timing of the intake valve.
[0016]
The invention according to claim 4 is
The weight for the past value when calculating the target value of the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve by the weighted average calculation, when calculating the target value of the intake valve closing timing by the weighted average calculation. It is characterized in that it is made larger than the weight for past values .
[0017]
According to the invention of claim 4,
When weighted averaging is performed on the control target value to avoid transient fluctuations due to noise and the like, there is a delay in convergence to the target value, and the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve , By making the past weight of the weighted average calculation in the calculation of the target value larger than the past weight of the weighted average calculation in the calculation of the target value of the intake valve closing timing, the delay of the convergence to the target value is increased.
[0018]
Thus, the changing speed of the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve can be made smaller than the changing speed of the intake valve closing timing.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a system diagram of an engine including a variable valve control device according to an embodiment of the present invention.
[0020]
A combustion chamber 3 defined by a 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 an ignition plug 4. 7, an intake passage; and 8, an exhaust passage.
[0021]
FIG. 2 shows a basic structure of an electromagnetic drive device for the intake valve 5 and the exhaust valve 6 (which constitutes a variable valve together with the intake and exhaust valves). A plate-shaped mover 22 is attached to a valve shaft 21 of the valve body 20, and the mover 22 is urged to a neutral position by springs 23 and 24. A valve opening electromagnetic coil 25 is disposed below the movable element 22, and a valve closing electromagnetic coil 26 is disposed above the movable element 22.
[0022]
Before the start of the engine 1, the valve-opening electromagnetic coil 25 and the valve-closing electromagnetic coil 26 are alternately energized to resonate the mover 22, and when the amplitude becomes sufficiently large, the movable member 22 is moved to one of the electromagnetic coils. The child 22 is held by suction.
[0023]
Thereafter, when the valve is opened from the closed state, the energization of the upper valve closing electromagnetic coil 26 that is attracting the mover 22 is stopped, and then the mover 22 is moved downward by the urging force of the spring 23. By energizing the valve opening electromagnetic coil 25 from a position sufficiently close to the lower valve opening electromagnetic coil 25 to attract the mover 22, the valve body 20 is lifted to open the valve.
[0024]
Conversely, when the valve is to be closed from the open state, after the energization of the lower valve-opening electromagnetic coil 25 that is attracting the mover 22 is stopped, the mover 22 is moved upward by the urging force of the spring 24. The valve closing electromagnetic coil 26 is energized from a position sufficiently close to the upper valve closing electromagnetic coil 26 to attract the movable element 22, thereby seating the valve body 20 on the seat portion and closing the valve. .
[0025]
Returning to FIG. 1, an electromagnetic fuel injection valve 9 is provided in the intake passage 7 at an intake port portion for each cylinder.
Here, the operations of the intake valve 5, the exhaust valve 6, the fuel injection valve 9 and the ignition plug 4 are controlled by a control unit 10, which outputs a crank angle signal in synchronization with the engine rotation. Signals are input from a crank angle sensor 11 that can detect an engine rotation speed, an accelerator pedal sensor 12 that detects an accelerator opening (depression amount of an accelerator pedal), and the like.
[0026]
Then, a target torque is generated based on operating conditions of the engine such as an accelerator opening and an engine rotation speed, and the internal EGR amount is controlled to an appropriate amount according to the operating conditions in order to reduce exhaust emissions, particularly NOx emissions. Thus, the target opening / closing timing of the intake valve 5 and the exhaust valve 6 is set, and the opening / closing timing of the intake valve 5 and the exhaust valve 6 is controlled so as to obtain the target opening / closing timing.
[0027]
The intake air amount is detected based on the values detected by the various sensors, and the fuel injection amount from the fuel injection valve 9 is controlled based on the intake air amount. Hereinafter, a first embodiment of the intake / exhaust valve opening / closing timing control according to the present invention will be described in detail with reference to the flowchart of FIG.
[0028]
In step 1, the operation state of the engine 1 is detected by reading the accelerator opening detected by the accelerator pedal sensor 12, the engine rotation speed detected by the crank angle sensor 11, and the like.
[0029]
In step 2, a target air amount QA corresponding to the required torque is calculated based on the detected operating state.
In step 3, a basic value IVCo of the closing timing of the intake valve 5 for obtaining the target air amount QA is set. The basic value IVCo is set as a value that does not consider the internal EGR amount (residual gas amount).
[0030]
In step 4, the closing timing EVC of the exhaust valve 6 and the opening timing IVO of the intake valve 5, which determine the valve overlap amount to control the internal EGR amount to an appropriate amount, are set based on the detected operating state, Further, the opening timing EVO of the exhaust valve 6 is set such that a necessary opening period of the exhaust valve 6 is secured in accordance with the closing timing EVC of the exhaust valve 6. The opening timing EVO of the exhaust valve 6 also affects the internal EGR amount in relation to the exhaust (scavenging) efficiency.
[0031]
In step 5, limit processing is performed to limit the amounts of change of the IVO, EVC, and EVO from the previously set values so that the amounts of change ΔIVO, ΔEVC, and ΔEVO do not exceed the upper limit value Δmax.
[0032]
In step 6, a closing timing IVC is set by correcting the basic value IVCo of the closing timing of the intake valve 5 in consideration of the internal EGR amount according to the operating state.
In step 7, the closing timing IVC of the intake valve 5 set as described above, the opening timing EVO and the closing timing EVC of the exhaust valve 6 subjected to the limit processing, and the opening timing IVO of the intake valve 5 (finally set) A control signal corresponding to the target value of the opening / closing timing is output to control the opening / closing timing of the intake and exhaust valves.
[0033]
In this manner, the opening timing EVO and the closing timing EVC of the exhaust valve 6 and the opening timing IVO of the intake valve 5 related to the internal EGR amount are changed to the closing timing IVC of the intake valve 5 by the limit processing using the upper limit value Δmax. The change speed is controlled to be slower than that.
[0034]
FIG. 4 shows a control example at the time of acceleration / deceleration. During acceleration, the opening timing EVO and the closing timing EVC of the exhaust valve 6 are retarded by 5 °, and the opening timing IVO of the intake valve 5 is advanced by 5 °, and valve over is performed. The control is performed to increase the lap amount by 10 ° and to retard the closing timing IVC of the intake valve 5 by 20 °, and thereafter, the valve timing is returned to the value before acceleration and deceleration is performed.
[0035]
As shown by the solid line in the drawing, the change speed of the closing timing IVC of the intake valve 5 is made larger than the change speed of the other valve timings IVO, EVC, and EVO, so that the change of IVO, EVC, and EVO even in the transient state. The IVC can converge to the final target value while satisfactorily following. Also, even if the change in the closing timing IVC of the intake valve 5 having a large torque sensitivity during the transition may be earlier than the change in each valve timing having the other small torque sensitivity, the change coincides with the increasing / decreasing direction of the required torque. There is no sense of incompatibility because it is only slightly larger in the direction. Conversely, if the change in the closing timing IVC of the intake valve 5 during the transition is later than the other changes in the valve timings IVO, EVC, and EVO, the control is once performed in the direction opposite to the increasing / decreasing direction of the required torque. Therefore, a sense of discomfort is large (see the dashed line in the figure). In particular, it is a serious problem that the control of the intake valve closing timing is delayed due to the increase in the residual gas and the actual torque is reduced despite the increase in the required torque. Problems can be avoided.
[0036]
Next, FIG. 5 shows a flow of the second embodiment of the opening / closing timing control of the intake / exhaust valve according to the present invention. Steps 1 to 6 are the same as those in FIG. 3 except that in step 11, the change amount ΔIVC of the closing timing of the intake valve 5 set in step 6 with respect to the previous setting value also exceeds the upper limit value Δmax2. A limit process is performed to limit the amount of change so that there is no change, but the upper limit value Δmax2 of ΔIVC is set to a value larger than the upper limit value Δmax set for the change amounts ΔIVO, ΔEVC, and ΔEVO in step 5. It is.
[0037]
As described above, even when the upper limit value Δmax2 of ΔIVC> ΔIVO, ΔEVC, and the upper limit value Δmax of ΔEVO, the changing speed of the valve timing other than the closing timing of the intake valve 5 can be controlled to be smaller than the changing speed of the closing timing of the intake valve 5. Therefore, high-accuracy torque control can be performed even during a transient period, and by limiting the ΔIVC, it is possible to suppress a sudden change in torque and ensure smooth driving performance.
[0038]
Also, the target value of the valve timing is set at each valve timing so that the convergence of the closing timing IVC of the intake valve 5 to the target value and the convergence of the other valve timings IVO, EVC, and EVO to the target value are performed substantially simultaneously. A configuration may be adopted in which the upper limit value is set proportionally to the amount of change.
[0039]
FIG. 6 shows a flow of the third embodiment of the opening / closing timing control of the intake / exhaust valve according to the present invention.
In this embodiment, instead of the limit process, the opening timing IVO of the intake valve 5 and the closing timing EVC and the opening timing EVO of the exhaust valve 6 are calculated in step 4 ′, and the internal EGR amount in step 6 is calculated. In step 21 after the correction of the closing timing IVC of the intake valve 5, a weighted average calculation process is performed in order to avoid a transient fluctuation due to noise or the like, but the opening timing IVO of the intake valve 5, the closing timing EVC of the exhaust valve 6, and The degree of averaging (the degree of smoothing) in the calculation of the opening timing EVO is made larger than the degree of averaging in the calculation of the closing timing IVC of the intake valve 5 (in the case of the weighted average calculation, the weight for the past value is made larger).
[0040]
When the averaging process is performed in this manner, there is a delay in convergence to the target value, and the averaging degree of the calculation of the opening timing IVO of the intake valve 5, the opening timing EVO of the exhaust valve 6, and the closing timing EVC is determined by the intake valve. 5, the delay in the convergence to the target value is increased, and the changing speed of the opening timing IVO of the intake valve 5, the opening timing EVO of the exhaust valve 6, and the closing timing EVC is increased. , Can be made smaller than the change speed of the intake valve 5 closing timing IVC, and the same effects as those of the first and second embodiments can be obtained.
[Brief description of the drawings]
FIG. 1 is a system diagram of an engine including a variable valve control device according to an embodiment of the present invention.
FIG. 2 is a basic structural diagram of an electromagnetic drive device for intake and exhaust valves.
FIG. 3 is a flowchart of a first embodiment of opening / closing timing control of intake and exhaust valves.
FIG. 4 is a time chart showing the state of each valve timing during acceleration / deceleration control.
FIG. 5 is a flowchart of a second embodiment of opening / closing timing control of intake and exhaust valves.
FIG. 6 is a flowchart of a third embodiment of opening / closing timing control of intake and exhaust valves.
[Explanation of symbols]
Reference Signs List 1 engine 5 intake valve 6 exhaust valve 8 exhaust passage 9 fuel injection valve 10 control unit 11 crank angle sensor 12 accelerator pedal sensor

Claims (4)

In a variable valve control device that variably controls the opening / closing timing of an intake / exhaust valve of an engine to be a set target value, the target value of each target value at the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve is determined. the change speed control device of the variable valve, characterized in that set in the change rate value smaller than the target value in the closing timing of the intake valve. 2. The variable valve control device according to claim 1, wherein an upper limit value is provided for a change speed of a target value at the opening timing of the intake valve and the opening timing and the closing timing of the exhaust valve. The upper limit provided for the target value changing speed at the intake valve opening timing, the exhaust valve opening timing and the closing timing is smaller than the upper limit provided at the target value changing speed at the intake valve closing timing. The variable valve control device according to claim 1. The weight for the past value when calculating the target value of the opening timing of the intake valve, the opening timing and the closing timing of the exhaust valve by the weighted average calculation, when calculating the target value of the intake valve closing timing by the weighted average calculation. The variable valve control device according to claim 1, wherein the weight is set to be larger than a weight for a past value .

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