JP2001182566A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve timing control device for an internal combustion engine compatible with both high responsiveness and convergence in controlling a cam phase to a target cam phase so as to improve fuel consumption and an exhaust gas characteristic. SOLUTION: This device is provided with a cam phase control means 2 for performing feedback control of a control signal value to a cam phase variable device when a deviation between the target cam phase CAINCMD and an actual cam phase CAIN is no more than #DCAINFF0, #DCAINFFR, #DCAINFFA while performing feedforward control when exceeding a specified value. The device also provided with a limit value storage means 2 for storing feedback control limit values #DVLMTHB, #DVLMTLB regulating a range of the control signal value in feedback control and feedforward control limit values #DVLMTH0, #DVLMTH, #DVLMTL set to a value different from the feedback control limit values for regulating the control signal value in feedforward control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control apparatus for an internal combustion engine for controlling the opening / closing timing of an intake valve and / or an exhaust valve by changing a cam phase of an intake cam and / or an exhaust cam with respect to a crankshaft. About.

[0002]

2. Description of the Related Art As a conventional valve timing control device of this type, a cam shaft is rotatable with respect to a cam pulley, and a relative angle of the cam shaft with respect to the cam pulley is controlled by a hydraulic control valve to supply hydraulic pressure. There is known a cam phase changing mechanism that changes the cam phase by changing the cam phase. The hydraulic control valve is configured by a duty solenoid valve, and by selectively controlling the duty ratio of the current of the solenoid to supply the hydraulic pressure to the advance chamber or the retard chamber of the cam phase variable mechanism, Advance or retard the cam phase. Also,
When the duty ratio is near the median, the hydraulic control valve enters a neutral state that closes the advance and retard chambers simultaneously, shuts off the supply of hydraulic pressure to the advance and retard chambers, and maintains the cam phase. I do. In this type of valve timing control device, the target cam phase is set according to the operating state of the engine, and the duty ratio of the hydraulic control valve is set according to the deviation between the target cam phase and the detected actual cam phase. In general, cam phase control is performed by feedback-controlling (for example, Japanese Utility Model Publication No. 6-10106).

[0003]

In the valve timing control device having the above-described structure, the change speed of the cam phase by the cam phase variable mechanism with respect to the change of the duty ratio is small at the median value of the duty ratio, and increases as the distance from the median value increases. It has the property of increasing. Therefore, in order to obtain high responsiveness in the feedback control, the duty ratio limit value must be set to a large value and the feedback constant must be set to a large value. However, such a setting causes a control delay when the feedback control is started from the upper limit or the lower limit of the duty ratio, leading to a shortage of engine torque and deterioration of exhaust gas characteristics, and a decrease in cam phase. Hunting occurs, and the convergence to the target cam phase is reduced, thereby causing torque fluctuation.

The present invention has been made to solve such a problem, and can achieve both high responsiveness and high convergence of cam phase control to a target cam phase. It is an object of the present invention to provide a valve timing control device for an internal combustion engine that can improve exhaust gas characteristics.

[0005]

In order to achieve this object, the invention according to claim 1 is achieved by changing a cam phase CAIN, which is a phase of at least one of the intake cam 6a and the exhaust cam 7a with respect to the crankshaft 9. And an actual cam phase detecting means for detecting a cam phase CAIN (hereinafter referred to as "the same in this section"). 2) ECU 2, cam angle sensor 28, crank angle sensor 2
9) and the target cam phase CAINCMD according to the operation state
And a cam phase variable device (cam phase variable mechanism 8, hydraulic control valve 10) that changes cam phase CAIN according to an input control signal value (duty ratio DOUTVT). The control signal value to be output to the cam phase variable device is set to the set target cam phase C
The deviation between AINCMD and the detected actual cam phase CAIN (cam phase deviation DCAINCMD) is a predetermined value (first to third F / F control determination values # DCAINFF0, #DCAIN).
FFR, #DCAINFFA) and a cam phase control means (ECU2) that performs feed-forward control when it exceeds a predetermined value while performing feedback control.
(Steps 20, 19, and 22 in FIG. 2) and a predetermined feedback control limit value (F / B control upper limit value #) that regulates the range of the control signal value during feedback control.
DVLMTHB, F / B control lower limit value #DVLM
TLB) and a predetermined value different from the feedback control limit value, and a predetermined feedforward control limit value (first F / F control upper limit value # DVLMTH0,
Second F / F control upper limit value #DVLMTH, F / F
And a lower limit storage means (ECU2) for storing the control lower limit value #DVLMTL).

According to this valve timing control device for an internal combustion engine, when the deviation between the target cam phase set according to the operating state and the detected actual cam phase is equal to or less than a predetermined value, the control signal of the cam phase variable device is controlled. While the value feedback control is performed, and when the value exceeds a predetermined value, feedforward control is performed. In addition, the limit value of the control signal value during the feedback control and the limit value of the control signal value during the feedforward control are separately set to different values. So, for example,
It is possible to set the limit value in the feedback control to a value smaller than the limit value in the feedforward control. Thereby, at the time of the feedforward control in which the deviation between the target cam phase and the actual cam phase is large, the change speed of the cam phase is increased by using a larger control signal value, so that the cam phase is shifted from the target cam phase to the target cam phase. The arrival time can be shortened, and the response can be improved. On the other hand, at the time of feedback control in which the deviation between the target cam phase and the actual cam phase is small, hunting of the cam phase can be prevented and convergence can be improved by using a control signal value restricted to a small value by the limit value. .

According to a second aspect of the present invention, in the valve timing control device according to the first aspect, the feedforward control limit value is a first feedrate that regulates a control signal value during the feedforward control immediately after the start of the cam phase control. The forward control limit value (first F / F control upper limit value # DVLMTH0) is set to a value different from the first feedforward control limit value, and the control signal value is set at the time of feedforward control other than immediately after the start of the cam phase control. The second feedforward control limit value to be regulated (second F / F control upper limit value #DVLMTH, F
/ F control lower limit value #DVLMTL).

According to this configuration, the limit value at the time of the feedforward control is used immediately after the start of the cam phase control, and is used other than immediately after the start of the cam phase control. The control limit values are separately set to different values. Therefore, for example, the first feedforward control limit value can be set to a value larger than the second feedforward control limit value. Thus, at the time of feedforward control immediately after the start of the cam phase control, by using a larger control signal value, the arrival time of the cam phase to the target cam phase can be shortened, and the responsiveness can be further improved. On the other hand, during feedforward control other than immediately after the start of the cam phase control, overshoot can be prevented by using a smaller control signal value to suppress the cam phase change speed.

Further, the invention according to claim 3 is based on claim 2
In the valve timing control device of the above, the cam phase control means sets a predetermined initial value (I term initial value) when the feedforward control immediately after the start of the cam phase control ends as an initial value of the control signal value at the start of the feedback control. #DV
ISEN) and feedback control initial value setting means (ECU 2 (step 15 in FIG. 2 and step 27 in FIG. 3) for setting a feedback control limit value when feedforward control other than immediately after the start of cam phase control ends. , 30)).

In this configuration, when the feedforward control executed immediately after the start of the cam phase control is completed,
A predetermined initial value is set as the initial value of the feedback control. At the end of this feedforward control,
Since this is executed immediately after the start of the cam phase control, the actual cam phase is relatively unstable with respect to the target cam phase. Therefore, the initial value of this feedback control is, for example, a median value between the upper and lower feedback control limit values so that the cam phase can be changed to the advance side and the retard side in a well-balanced manner. This can be performed without causing a control delay. On the other hand, when the feedforward control executed other than immediately after the start of the cam phase ends, a feedback control limit value is set as an initial value of the feedback control. At the end of the feedforward control, the actual cam phase is relatively stable with respect to the target cam phase as compared to the end of the feedforward control immediately after the start of the cam phase control. Therefore, by starting the feedback control from the feedback control limit value, it is possible to shift to the feedback control smoothly and early, and the convergence is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a valve timing control device (hereinafter, simply referred to as a “control device”) of an internal combustion engine to which the present invention is applied. As shown in FIG. 1, the control device 1 includes an ECU 2 (actual cam phase detection means, target cam phase setting means, cam phase control means, limit value storage means, feedback control initial value setting means).
The ECU 2 executes a cam phase control, which will be described later, according to the operating state of the internal combustion engine (hereinafter referred to as “engine”) 3.

The engine 3 is, for example, a four-cycle DOHC
A gasoline engine having an intake camshaft 6 and an exhaust camshaft 7. Intake camshaft 6
The exhaust camshaft 7 is connected to the crankshaft 9 via respective driven sprockets 6b, 7b and a timing belt (not shown), and is driven to rotate at a rate of one rotation for every two rotations of the crankshaft 9. You. The intake camshaft 6 and the exhaust camshaft 7 are integrally provided with a plurality of intake cams 6a and an exhaust cam 7a (only one is shown) for opening and closing the intake valve 4 and the exhaust valve 5, respectively.

The intake camshaft 6 is rotatably connected to a driven sprocket 6b within a predetermined angle range. By changing the relative angle of the intake camshaft 6 with respect to the driven sprocket 6b, the phase (hereinafter, simply referred to as "cam phase") CAIN of the intake cam 6a with respect to the crankshaft 9 is changed. Valve timing) is advanced or retarded. At one end of the intake camshaft 6, a cam phase variable mechanism 8 as a cam phase variable device and a hydraulic control valve 10 for controlling the cam phase CAIN are provided.

The variable cam phase mechanism 8 has an advance chamber and a retard chamber (both not shown) defined on both sides of a vane (not shown) integral with the intake camshaft 6. Hydraulic pressure of an oil pump (not shown) driven by the engine 3 is selectively supplied to the advance chamber or the retard chamber under the control of the hydraulic control valve 10 so that the intake camshaft 6 is driven by the driven sprocket 6b. Is configured to be rotationally driven in the advance direction or the retard direction.

The hydraulic control valve 10 comprises a solenoid and a duty solenoid valve provided with a spool driven by the solenoid. The hydraulic control valve 10 is connected to the ECU 2
Duty ratio DO of solenoid current by control signal from
By controlling the UTVT, the position of the spool is changed steplessly, and the advance chamber or the retard chamber of the cam phase variable mechanism 8 is opened and closed according to the position. Specifically, when the duty ratio DOUTVT is, for example, greater than 50%, the spool moves from the neutral position to one side to open the advance chamber, thereby supplying hydraulic pressure to the advance chamber and providing the cam phase CAIN. Is advanced. On the other hand, when the duty ratio DOUTVT is less than 50%, the spool moves from the neutral position to the other side to open the retard chamber, thereby supplying hydraulic pressure to the retard chamber and retarding the cam phase CAIN. It becomes a corner state. When the duty ratio DOUTVT is 50%, the spool is in the holding state in which the spool is located at the neutral position for simultaneously closing the advance chamber and the retard chamber, and the supply of the hydraulic pressure to the advance chamber and the retard chamber is cut off. The cam phase CAIN is maintained by integrating the intake camshaft 6 and the driven sprocket 6b.

Returning to FIG. 1, a cam angle sensor 28 is provided at the end of the intake camshaft 6 opposite to the cam phase variable mechanism 8. The cam angle sensor 28 includes, for example, a magnet rotor and an MRE pickup.
With the rotation of the intake camshaft 6, a pulse signal C
The ECU outputs the AM signal for each predetermined cam angle (for example, 1 °).
Output to 2. The crankshaft 9 is provided with a crank angle sensor 29. Crank angle sensor 2
9 is configured in the same manner as the cam angle sensor 28, and outputs a CRK signal which is a pulse signal to the ECU at every predetermined crank angle (for example, 1 °) with the rotation of the crankshaft 9.
Output to 2. The ECU 2 calculates (detects) the actual cam phase CAIN from the CRK signal and the CAM signal.
(Hereinafter, the cam phase actually detected in this manner is
“Actual cam phase CAIN” as appropriate). Further, the engine speed Ne is obtained based on the CRK signal.

A throttle valve 31 is provided in an intake pipe 30 of the engine 3. Downstream of the throttle valve 31, an injector 32, an intake air temperature sensor 33 composed of a thermistor, and a semiconductor pressure sensor are provided. The configured intake pressure sensor 34 is attached. The fuel injection time (fuel injection amount) TOUT of the injector 32 is expressed by EC
It is controlled by the drive signal from U2. The intake air temperature sensor 33 detects the intake air temperature T, which is the temperature of the intake air in the intake pipe 30.
A, the intake pressure sensor 34 detects the absolute pressure PB
A are detected, and their detection signals are sent to the ECU 2. Further, an engine water temperature sensor 35 constituted by a thermistor or the like is attached to the main body of the engine 3. The engine water temperature sensor 35 measures an engine water temperature TW which is a temperature of cooling water circulating in a cylinder block of the engine 3. Detects and sends the detection signal to ECU2.

Further, a three-way catalyst 37 for purifying HC, CO, NOx and the like in the exhaust gas is disposed in the exhaust pipe 36 of the engine 3. On the upstream side of the three-way catalyst 37, an LAF composed of zirconia and platinum electrodes and the like is provided.
A sensor 38 is provided. The LAF sensor 38 linearly detects the oxygen concentration LAF in the exhaust gas, and sends a detection signal to the ECU 2.

The ECU 2 has an I / O interface, C
It is configured by a microcomputer including a PU, a RAM, a ROM, and the like. The detection signals from the various sensors are input to the CPU after being subjected to A / D conversion and shaping by the I / O interface.

The CPU determines the operating state of the engine 3 according to these input signals. In addition, the CPU
In accordance with the control program and the like stored in M and the data stored in RAM and the like, the detected absolute pressure PBA in the intake pipe is detected.
Cam phase CA depending on the engine speed and engine speed Ne
Set INCMD. Further, as described below, the cam phase CAIN is controlled by calculating the duty ratio DOUTVT of the hydraulic control valve 10 and outputting a duty control signal based on the result to the hydraulic control valve 10.

FIGS. 2 and 3 show the duty ratio DOUTV of the hydraulic control valve 10 executed in the cam phase control.
T (hereinafter, simply referred to as “duty ratio DOUTVT”)
6 is a flowchart showing a calculation process of (1). This calculation process is executed every predetermined time (for example, 10 ms).

First, step 1 (shown as "S1").
The same applies hereinafter), the cam phase control permission flag F_VT
It is determined whether or not C is set to "1". The cam phase control permission flag F_VTC indicates the engine coolant temperature T
This is set to “1” when it is determined that the execution condition of the cam phase control is satisfied based on W, the engine speed Ne, and the like. When the answer to step 1 is NO, that is, when F_VTC = 0 and the execution condition of the cam phase control is not satisfied, the F / F control flag F_VT
After setting CFF to "0" (step 2), the current value DVININ (n) of the I term (integral term) of the PID feedback control described later is set to a value of 0 (step 3), and the current value of the operation duty ratio is set. The value DVIN (n) is set to the duty value DVLMTL0 outside the execution condition of the cam phase control, which is the value 0 or a value near the value 0 (step 4).
In the following step 5, the current value DV of the calculated duty ratio
IN (n) is set as the duty ratio DOUTVT, and the program ends. As described above, when the execution condition of the cam phase control is not satisfied, the duty ratio D
By setting OUTVT to substantially the value 0, the operation of the hydraulic control valve 10 is prohibited, and the cam phase CAIN is maintained at the most retarded state.

On the other hand, when the answer to the above step 1 is YES, that is, when F_VTC = 1 and the execution condition of the cam phase control is satisfied, the target cam phase CAINCMD
The difference between the actual cam phase CAIN and the cam phase deviation DCAI
This is calculated as NCMD (step 6), and the previous value CAIN (n-1) and the current value CAIN of the actual cam phase are calculated.
A deviation DCANIN from (n) is calculated (step 7).

Next, the cam phase control permission flag F_VT
It is determined whether or not C has changed from “0” to “1” this time (step 8). If the answer is YES, that is, if the current loop is a loop immediately after the execution condition of the cam phase control is satisfied, the cam phase deviation DCAINCMD calculated in step 6 is equal to the first F It is determined whether the value is greater than a / F control determination value # DCAINFF0 (for example, 8 ° corresponding to the crank angle) (step 9). When DCAINCMD># DCAINFF0, the target cam phase CAINCMD and the actual cam phase C
Assuming that the cam phase deviation DCAINCMD from AIN is large, the F / F control flag F_VTCFF is set to "1" (step 10), and the feedforward control is executed. That is, in the next step 11, the current value DV of the I term
IIN (n) is set to a value of 0, and
And the current value DVIN (n) of the calculation duty ratio is set to 90
%, The first upper limit F / F control upper limit value DVLMTH0 immediately after the start of the cam phase control, and then proceeds to step 5 to change the current value DVIN (n) of the set operation duty ratio to the duty ratio. DOUTVT.

On the other hand, when the answer to step 8 is NO,
That is, when the current loop is the second or subsequent loop in which the execution condition of the cam phase control is satisfied, step 1
3 to determine whether the F / F control flag F_VTCFF has been set to “1”, and F_VTCFF = 1
In the case of, the process proceeds to step 9 described above. Therefore, the cam phase deviation DCAINCMD immediately after the start of the cam phase control
Is larger than the first F / F control determination value # DCAINFF0 (step 9: YES), in the subsequent loop, the answer to step 8 is NO, and
Since the answer to 3 is YES, DCAINCMD>#DC
Steps 10 to 12 are executed as long as AINFF0 holds.

As described above, immediately after the start of the cam phase control, the target cam phase CAINCMD and the actual cam phase CA
When the cam phase deviation DCAINCMD from IN is large, the first F / F control upper limit value #D which is a large value
Feedforward control by VLMTH0 is executed. Thus, by increasing the change speed of the cam phase, the actual cam phase CAI to the target cam phase CAINCMD is increased.
The arrival time of N can be shortened, and its responsiveness can be improved. Also, the first F / F control determination value # DCAINFF0
Is a second F / F control determination value #DCAINFFR for cam phase control described later (for example, 10
°) is set to a smaller value. Therefore, it is easy to shift to the feedforward control immediately after the start of the cam phase control, and this can be started earlier, so that the responsiveness can be further improved.

The first upper limit F / F control value # DVLMTH0 is calculated by searching a table stored in the ROM. Although not shown, in this table, the # DVLMTH0 value indicates the engine coolant temperature T
It is set to increase as W increases. This is because, as the engine coolant temperature TW rises, the oil pressure rises due to the rise in the oil temperature, and the electric resistance tends to increase due to the rise in the coil temperature of the duty solenoid 15 of the hydraulic control valve 10. To do that. For the same reason, the F / B control upper limit value #DVLMTHB and the F / B control lower limit value #DVL, which will be described later.
The MTLB and the I term initial value #DVISEN are also set to larger values as the engine coolant temperature TW is higher, and are searched from respective tables (not shown).

If the answer to step 9 is NO, ie, from the beginning of the cam phase control or during the feedforward control, DCAINCMD ≦ # DCAINIFF
0 is satisfied, or the answer of the above step 13 is N
When O (F_VTCFF = 0), the process proceeds to step S14. In this step 14, it is determined whether or not the previous value DIIV (n-1) of the I term of the PID feedback control is 0. When DIIV (n-1) = 0, that is, when the current loop is a loop immediately after the start of the cam phase control or a loop immediately after the end of the feedforward control described above, the previous value DIIV (n-1) of the I term )
Was set to the I term initial value #DVISEN (step 1
5) After that, go to step 16. , This I term initial value #DV
ISEN determines the initial duty ratio DOUTVT at the start of the feedback control, and the hydraulic control valve 10
Is set to a value corresponding to the neutral position (for example, 50%). On the other hand, if the value of DIIV (n-1) is not 0 in step 14, the process skips step 15 and proceeds to step 16, where the F / F control flag F_VTCFF is set to "0".

In the following step 17, the cam phase deviation DC
AINCMD (positive value: target cam phase CAINCMD> actual cam phase CAIN) is larger than the first F / F control determination value # DCAINFF0 immediately after the start of the cam phase control, and the second F / F during the cam phase control. Control judgment value #D
It is determined whether it is larger than CAINFFR (for example, 10 degrees corresponding to the crank angle). When this answer is YES, that is, when DCAINCMD>#DCAINFFR,
Assuming that the deviation between the target cam phase CAINCMD and the actual cam phase CAIN is large, the current value DVININ (n) of the I term and the current value DVIN (n) of the calculation duty ratio are used as the first F / F for immediately after the start of the cam phase control. The second F / F control upper limit value DVLMTH (for example, 70) which is smaller than the control upper limit value DVLMTH0 and is used during cam phase control.
%) (Steps 18 and 19)
Thereafter, the process proceeds to step 5, where the current value DVIN (n) of the set operation duty ratio is set as the duty ratio DOUTVT.

Similarly, in step 20 executed when the answer to step 17 is NO, the cam phase deviation DCA
INCMD (negative value: in the case of target cam phase CAINCMD <actual cam phase CAIN) is equal to the second F / F control determination value #DCAINFFR.
/ F control determination value #DCAINFFA (for example, 10 degrees corresponding to the crank angle) is determined. If the answer is YES, that is, DCAINCMD>#DCAIN
At the time of FFA, it is assumed that the deviation between the target cam phase CAINCMD and the actual cam phase CAIN is large on the negative side, and the current value DVININ (n) of the I term and the current value DVIN (n) of the calculation duty ratio are determined during the cam phase control. After setting the F / F control lower limit value DVMTL (for example, about 30%) for each of the steps (steps 21 and 22), the process proceeds to step 5, and the current value DVI of the set operation duty ratio is set.
Let N (n) be the duty ratio DOUTVT.

As described above, during the feedback control,
When the cam phase deviation DCAINCMD exceeds the second and third F / F control determination values #DCAININFR, #DCAINFFA, the first F / F control upper limit value #DVLMT during feedforward control immediately after the start of cam phase control.
Second F / F control upper limit value #D smaller than H0
VLMTH or F / F control lower limit value #DVL
The feedforward control by the MTL is executed. Thereby, the changing speed of the cam phase can be suppressed, and the overshoot can be prevented.

As described above, the second and third F / Fs
Control determination values #DCAINFFR, #DCAININFA
Is set to a value larger than the first F / F control determination value # DCAINFF0 applied immediately after the start of the cam phase control. This makes it difficult to shift to the feedforward control except immediately after the start of the cam phase control, that is, the feedback control period is extended.

If the answer to step 17 or step 20 is NO, the cam phase deviation DCAINCMD is equal to the second F / F control determination value #DCAINFF for controlling the cam phase.
When the value falls within the range between R and the third F / F control determination value #DCAINFFA, the P-term gain KVP, the I-term gain KVI, and the D-term gain KVD are stored in respective tables (not shown) in order to perform PID feedback control. ) Was calculated by searching (step 23).
Thereafter, in step 24, the P term DVPIN and the I term DV
IIN and D-term DVDIN are respectively calculated by the following equations. DVPIN ← KVP * DCAINCMD DVIIN (n) ← KVI * DCAINCMD + DVI
IN (n-1) DVDIN ← KVD * DCAIN

Next, in steps 25 to 30, limit processing of the I term DVIIN calculated in step 24 is executed. That is, the current value DVIIN (n) of the I term
Is higher than the F / B control upper limit value #DVLMTHB (eg, 65%) smaller than the second F / F control upper limit value #DVLMTH for the cam phase control (step 25). (N)># D
In the case of VLMTHB, the current value DVIIN of the I term
(N) and the current value DVIN (n) of the operation duty ratio
Is set to the #DVLMTHB value (steps 26 and 27), and the process proceeds to step 5. Similarly,
In step 28, the current value DVIIN (n) of the I term
Is the lower limit value DV of the F / F control during the cam phase control.
F / B control lower limit value #DV larger than LMTL
It is determined whether it is smaller than LMTLB (for example, 35%), and when DVIIN (n) <# DVLMTLB,
After setting the current value DVININ (n) of the I term and the current value DVIN (n) of the calculation duty ratio to this #DVLMTLB value (steps 29 and 30), the process proceeds to step 5.

If the answer in steps 25 and 28 is NO, that is, # DVLMTLB≤DVIIN (n)
When ≦ # DVLMTHB, the current value DVIN (n) of the calculation duty ratio is changed to the P term DVPIN and the I term DVII.
It is calculated as the sum of the N and D terms DVDIN (step 31).

Next, in steps 32 and 33, a limit process of the present value DVIN (n) of the calculated duty ratio calculated in step 31 is executed. That is, the present value DVIN (n) of the calculation duty ratio is equal to the F
/ B control upper limit value #DVLMTHB is determined (step 32). If it is higher, the process proceeds to step 27, where the current value of the calculation duty ratio DVI
N (n) is F / B control upper limit value #DVLMTHB
Set to. Similarly, the current value DVI of the calculation duty ratio
N (n) is the F / B control lower limit value #DVLMT
It is determined whether or not LB is smaller than LB (step 33). If smaller than LB, the routine proceeds to step 30, where the present value DVIN (n) of the calculation duty ratio is set to the F / B control lower limit limit value #DVLMTLB. Step 32
Are NO, ie, #DVLMT
When LB ≦ DVIN (n) ≦ # DVLMTHB,
Proceeding to step 5, the current value DVIN (n) of the calculated duty ratio calculated in step 31 is used as the duty ratio DOUTVT, and the program ends.

As described above, the duty ratio DOUTVT at the time of feedback control is set between the upper and lower limit values of the F / B control #DVLMTHB and #DVLMTLB. Further, as described above, the F / B control upper limit value #DVLMTHB is smaller than the second F / F control upper limit value #DVLMTH during the feedforward control except immediately after the start of the cam phase control, and the F / B control lower limit value The value #DVLMTLB is larger than the F / F control lower limit value #DVMLTL. That is, in the feedback control, the interval between the upper and lower limit values is smaller than in the feedforward control, and the setting range of the duty ratio DOUTVT is reduced. Further, as described above, the second and third F / F control determination values #D
By setting CAINFFR and #DCAINFFA,
The feedback control period has been extended. That is,
The hunting of the cam phase CAIN can be prevented and the convergence can be improved by reducing the set range of the duty ratio DOUTVT at that time while expanding the feedback control period.

FIG. 4 shows an example of transition of the duty ratio DOUTVT according to the target cam phase CAINCMD and the actual cam phase CAIN obtained by the above-described control. In the figure, first, the execution condition of the cam phase control is satisfied at time t1 (F_VTC = 0 → 1), and the target cam phase CAINCMD and the actual cam phase CAIN immediately after that are executed.
Is larger than the first F / F control determination value # DCAINFF0 (step 9 in FIG. 2: YES), the first F / F control upper limit value #DVLM that increases the duty ratio DOUTVT is large.
The feedforward control to be TH0 is executed (steps 12 and 5 in FIG. 3). Thereby, the cam phase CAI
By increasing the change speed of N, the target cam phase CAI
The arrival time of the actual cam phase CAIN to the NCMD can be shortened, and the response can be improved. Also, the first F /
Since the F control determination value # DCAINFFF0 is set to a value smaller than the second F / F control determination value #DCAINFFR, it is easy to shift to the feedforward control, which can be started earlier, and the responsiveness can be further improved. it can.

Thereafter, as the actual cam phase CAIN increases, at time t2, the cam phase deviation DCAINC
When MD ≦ the first F / F control determination value # DCAINFF0 (Step 9 in FIG. 2: NO), PID feedback control of the duty ratio DOUTVT is executed with the initial value of the I term DVININ being #DVISEN (point A in FIG. 4). Is done. Thus, the feedback control is started from the state where the hydraulic control valve 10 is located at the neutral position. At this point, the first F / F control upper limit value # immediately before that point #
By the feedforward control by DVLMTH0, the change speed of the cam phase CAIN is large, and the cam phase deviation DCAINCMD has no margin, so that the actual cam phase CAINCMD is compared with the target cam phase CAINCMD.
Is in a relatively unstable state. Therefore, the initial value of this feedback control is set to the #DVISEN value, and the cam phase CAIN can be changed to both the advance side and the retard side in a well-balanced manner. Can be done without. The duty ratio DOUTVT during the feedback control is based on the upper / lower limit value #D of the F / B control.
Due to the regulation by the VLMTHB and #DVLMTLB, the hunting of the actual cam phase CAIN can be prevented and the convergence can be improved since the hunting of the actual cam phase CAIN is prevented.

Next, at time t3, the target cam phase CAIN
If the cam phase deviation DCAINCMD becomes larger than the second F / F control determination value #DCAINFFR due to an increase in CMD (step 17 in FIG. 2: YES), the duty ratio DOUTVT is increased to the second F / F control upper limit value #DVL.
Feedforward control for MTH is executed (steps 19 and 5 in FIG. 3). Thereby, the actual cam phase CA
IN is the first F / F control upper limit value #DVLMTH
It changes at a smaller change speed than in the case of the feedforward control by 0, and approaches the target cam phase CAINCMD in a short time and without overshooting.

Thereafter, at time t4, the cam phase deviation DCAINCMD ≦ the second F / F control determination #DCAINF
When FR is reached (step 17 in FIG. 2: NO), feedback control is executed with the F / B control upper limit value #DVLMTHB as an initial value (step 27 in FIG. 3 and point B in FIG. 4). At this time, the actual cam phase CAIN is relatively stable with respect to the target cam phase CAINCMD because the change speed of the actual cam phase CAIN is smaller than that at the end of the feedforward control based on the first F / F control upper limit value # DVLMTH0. And there is room for the cam phase deviation DCAINCMD. Therefore, the feedback control is performed using the F / B control upper limit value #DVLMT.
By starting from the HB, it is possible to smoothly and early shift to the feedback control, and the convergence is improved.

Next, at time t5, the target cam phase CAIN
Cam phase deviation DCAINCMD due to reduction of CMD
When (negative value) becomes larger than the third F / F control determination value #DCAINFFA (Step 20 in FIG. 2: YES), the duty ratio DOUTVT is reduced to the F / F control lower limit value #.
The feedforward control of DVMTL is executed (steps 22 and 5 in FIG. 3). Also in this case, the second F /
As in the feedforward control using the F control upper limit value #DVLMTH, the actual cam phase CAIN changes at a relatively small change speed, and approaches the target cam phase CAINCMD in a short time without overshooting. Then, as the actual cam phase CAIN decreases,
At time t6, when DCAINCMD ≦ # DCAINFFA (step 20: NO), the feedback control is executed with the F / B control lower limit value #DVLMTLB as an initial value (step 30 in FIG. 3, point C in FIG. 4). . Time t7 indicates a time when the execution condition of the cam phase control is not satisfied.

As described above, according to this embodiment, immediately after the start of the cam phase control, the target cam phase CAINC
Cam phase deviation DCAIN between MD and actual cam phase CAIN
When the CMD exceeds the first F / F control determination value # DCAINFF0, the first F / F control upper limit value #
The feedforward control by DVLMTH0 is executed. Except immediately after the start of the cam phase control, when the cam phase deviation DCAINCMD is equal to or less than the second and third F / F control determination values #DCAININFR and #DCAININFA, the feedback control is executed. , 2nd F / F control upper limit value #DVLMT
The feedforward control based on the H or F / F control lower limit value #DVLMTL is performed. In this manner, by performing feedforward control when the cam phase deviation DCAINCMD is large and performing feedback control when the cam phase deviation DCAINCMD is small, it is possible to achieve both responsiveness and convergence of the cam phase control.

In the feedforward control, the first,
Second F / F control upper limit value # DVLMTH0, #D
VLMTH and F / F control lower limit value #DVL
F / B control upper and lower limit values during feedback control with respect to MTL #DVLMTHB, #DVMLTL
B is separately held and set to a small value. Therefore, during the feed forward control, the cam phase CAIN
By increasing the change speed of the target cam phase CAIN
The arrival time of the actual cam phase CAIN to the CMD can be shortened,
Responsiveness can be improved. As a result, engine torque and exhaust gas characteristics can be improved.

Further, the second and third F / F control determination values #D
Since CAINFFR and #DCAINFFA are set to values larger than the first F / F control determination value # DCAINFF0, the feedback control period is extended, and at the time of feedback control, a small value F / F is used.
B control upper and lower limit values #DVLMTHB, #DV
Since the setting range of the duty ratio DOUTVT is reduced by LMTB, convergence can be improved. As a result, hunting of the cam phase CAIN can be prevented, and torque fluctuation can be suppressed. Further, for example, in feedback control, even if a large cam phase deviation DCAINCMD occurs due to a decrease in oil pressure at a high oil temperature, the duty ratio DOUTVT is stopped with the F / B control upper limit value #DVLMTHB being a small value as a limit. . Therefore, even if the oil pressure recovers due to an increase in the engine speed Ne, the cam phase CAIN does not overshoot, so that engine stall or the like can be prevented. As a result, normally, in consideration of such a problem at the time of high oil temperature, the lower limit engine speed which is set higher as the execution condition of the cam phase control can be set to the lower rotation side, and thereby, at the normal temperature, By expanding the range of the cam phase control described above, fuel efficiency and exhaust gas characteristics can be improved.

Also, the first F / F control upper limit value #D
VLMTH0 and second F / F control upper limit value #DV
The LMTHs are separately held and the former is set to a large value. Therefore, in the feedforward control immediately after the start of the cam phase control, the arrival time of the actual cam phase CAIN to the target cam phase CAINCMD can be shortened by increasing the change speed of the cam phase CAIN, and the responsiveness can be improved. In the feedforward control except immediately after the start of the cam phase control, the cam phase CA
By reducing the rate of change of IN, the actual cam phase CAI
N can be made close to the target cam phase CAINCMD in a short time and without overshooting. Further, since the first F / F control determination value # DCAINFF0 is set to a value smaller than the second F / F control determination value #DCAINFFR, it is easy to shift to feedforward control immediately after the start of the cam phase control. And the response can be further improved.

Further, in the feedback control executed at the end of the feedforward control immediately after the start of the cam phase control, the initial value is set to a predetermined initial value #DVISEN, and the control is performed from the state where the hydraulic control valve 10 is located at the neutral position. , The feedback control can be performed without causing a large control delay. On the other hand, in the feedback control executed at the end of the feedforward control other than immediately after the start of the cam phase control, the initial value is set to F
/ B control upper or lower limit value #DVLMTHB,
Since the control is started as #DVLMTLB, it is possible to shift to the feedback control smoothly and early, and the convergence is improved.

The present invention is not limited to the embodiments described above, but can be implemented in various modes.
For example, the limit values during the feedforward control and the feedback control described in the embodiment, and F /
The F control determination values and the magnitude relation between them are merely examples, and can be changed as appropriate. Further, the embodiment is an example in which the present invention is applied to a valve timing control device in which the intake cam phase is variable. However, it is needless to say that the present invention can be applied to a device in which the exhaust cam phase is variable.

[0049]

As described above, the valve timing control apparatus for an internal combustion engine according to the present invention can achieve both high responsiveness and high convergence of the cam phase control to the target cam phase, thereby improving fuel economy and This has the effect that the exhaust gas characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a valve timing control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a cam phase control process by the control device of FIG. 1;

FIG. 3 is a diagram showing the remaining part of the flowchart of FIG. 2;

FIG. 4 is a time chart showing an operation example according to the flowcharts of FIGS. 2 and 3;

[Explanation of symbols]

Reference Signs List 1 control device (valve timing control device) 2 ECU (actual cam phase detection means, target cam phase setting means, cam phase control means, limit value storage means, feedback control initial value setting means) 3 engine (internal combustion engine) 4 intake valve Reference Signs List 5 exhaust valve 6 intake camshaft 6a intake cam 7 exhaust camshaft 7a exhaust cam 8 cam phase variable mechanism (cam phase variable device) 9 crankshaft 10 hydraulic control valve (cam phase variable device) 28 cam angle sensor (actual cam phase detection) Means) 29 Crank angle sensor (actual cam phase detecting means) CAIN actual cam phase CAINCMD target cam phase DCAINCMD cam phase deviation (deviation) DOUTVT Duty ratio of hydraulic control valve (control signal value) DVLMTH0 First F / F control upper limit value ( 1st feed forward control limit DVLMTH second F / F control upper limit value (second
Feed forward control limit value DVLMTL F / F control lower limit value (second feed forward control limit value) DVLMTHB F / B control upper limit value (feedback control limit value) DVLMTLB F / B control lower limit value (feedback control limit value) DCAINFFF0 First F / F control determination value (predetermined value) DCAINFFR Second F / F control determination value (predetermined value) DCAINFFA Third F / F control determination value (predetermined value) DVISEN I term initial value (predetermined initial value)

Continued on front page F-term (reference) 3G084 BA23 DA02 DA07 DA08 DA10 EB14 EB15 FA02 FA11 FA20 FA29 FA33 FA38 3G092 AA01 AA11 DA01 DA02 DA09 DF09 DG05 DG09 EA01 EA04 EA09 EA14 EA22 EA28 EA29 EB03 FA08 EC08 HA04Z HA05Z HA13X HA13Z HD05Z HE01Z HE03Z HE08Z

Claims (3)

[Claims] A valve timing control device for an internal combustion engine that controls the opening / closing timing of at least one of an intake valve and an exhaust valve by changing a cam phase that is at least one of an intake cam and an exhaust cam with respect to a crankshaft. An actual cam phase detecting means for detecting a cam phase; a target cam phase setting means for setting a target cam phase according to an operation state; and a cam phase variable for changing a cam phase according to an input control signal value. A control signal value to be output to the variable cam phase device, the feedback control when a deviation between the set target cam phase and the detected actual cam phase is equal to or less than a predetermined value, and the predetermined value Cam phase control means for performing feedforward control when the pressure exceeds the control signal; and A predetermined feedback control limit value that regulates the value range, and a limit that is set to a value different from the feedback control limit value and stores a predetermined feedforward control limit value that regulates the control signal value during feedforward control. A valve timing control device for an internal combustion engine, comprising: value storage means. 2. The feedforward control limit value includes a first feedforward control limit value that regulates the control signal value at the time of the feedforward control immediately after the start of the cam phase control, a first feedforward control limit value, and a first feedforward control limit value. 2. The internal combustion engine according to claim 1, further comprising: a second feedforward control limit value that regulates the control signal value during a feedforward control other than immediately after the start of the cam phase control. Engine valve timing control device. 3. The cam phase control means sets a predetermined initial value as an initial value of the control signal value at the start of the feedback control when the feedforward control immediately after the start of the cam phase control ends. 3. The valve for an internal combustion engine according to claim 2, further comprising feedback control initial value setting means for setting the feedback control limit value when feedforward control other than immediately after the start of the cam phase control ends. Timing control device.