JP2000230437A - Valve timing control device for internal combustion engine - Google Patents

Abstract

(57) Abstract: A valve timing control device for an internal combustion engine controls valve operation timing with high controllability in any operating state of the engine. An electronic control unit (27) controls a duty of a hydraulic control valve (19) to control a variable valve timing mechanism (20).
To make the valve timing of the engine 1 variable. The electronic control unit 27 further appropriately learns a duty ratio command value output to the hydraulic control valve 27 as a holding duty so as to hold the valve timing at a predetermined value. The holding duty is learned separately in a cold region immediately after the start of the engine, which is defined based on the cooling water temperature, and a warm region after the warm-up is completed.In a middle region between the cold region and the warm region, Interpolation is performed based on the holding duties learned during the cold state and the warm state, respectively.

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 which controls the operation timing of intake valves and exhaust valves of each cylinder during operation of the internal combustion engine. The present invention relates to an embodiment of a control structure that is useful for further enhancement.

[0002]

2. Description of the Related Art Conventionally, as this type of valve timing control device, for example, a device described in Japanese Patent Application Laid-Open No. 8-338271 is known.

As described in the same publication, such a valve timing control device for an internal combustion engine is generally provided on a camshaft and is drivingly connected to a crankshaft of the engine (internal combustion engine) by a chain or a belt. By dividing the first rotating portion fixed to the timing pulley and the second rotating portion fixed to the camshaft and changing the phase of both rotating portions, the operation timing of the valve can be reduced. Change continuously.

In order to change the phase of both rotating parts, a helical spline type or vane type variable valve timing mechanism described below is often used. In a valve timing control device that employs a helical spline type variable valve timing mechanism, for example, as in the device described in the above publication, a movable piston having a helical spline formed on the inner and outer circumferences is provided between the two rotating parts, The phases of both rotating parts are shifted by moving the movable piston in the axial direction by hydraulic pressure.

On the other hand, in the vane type variable valve timing mechanism, a part of one of the two rotating parts is formed as a housing, and a part of the other rotating part is formed as an internal rotor. The housing is provided with a plurality of protrusions projecting from the inner peripheral surface toward the rotation axis, while the inner rotor is provided with a plurality of protrusions (vanes) radially projecting from the outer peripheral surface. With such a combination of the housing and the internal rotor, the space between the protrusions of the housing is partitioned by the vanes of the internal rotor, and hydraulic chambers are formed on the left and right of each vane. Then, by appropriately changing the hydraulic pressure supplied to the left and right hydraulic chambers, the phases of both rotating parts are shifted.

That is, regardless of the helical spline type or vane type variable valve timing mechanism, the first
The above operation for shifting the phase of the second rotating portion is performed by hydraulic distribution through a hydraulic control valve, and the advance amount or the retard amount of the valve timing is determined according to the hydraulic distribution amount. You.

The hydraulic control valve is further controlled by an electronic control device that controls the operation of the engine, and the amount of hydraulic distribution is determined through duty control by the electronic control device.

Thus, the phase of the camshaft with respect to the crankshaft is continuously controlled according to the operating state of the engine. On the other hand, in the duty control for determining the hydraulic distribution amount, the feedback control for sequentially changing the duty command value so that the actual phase of the normal camshaft follows the target phase, and the actual phase of the camshaft coincides with the target phase. The holding control for holding the state as it is when it is performed is selectively performed as appropriate.

In this holding control, the duty command value is controlled to a predetermined value so that the oil pressure acting for the retarding operation of the valve timing and the oil pressure acting for the advance operation are balanced.

[0010]

By the way, the duty command value (hereinafter referred to as holding duty) for maintaining the actual phase of the camshaft constant is determined by the aging of parts.
It fluctuates momentarily due to the nature of the hydraulic oil, temperature conditions, and the like.

In particular, since the temperature of each part of the engine fluctuates (rises) transiently from the start of the engine to the warm-up operation period, the viscosity of the hydraulic oil and the components between the members constituting the variable valve timing mechanism are changed. The clearance greatly fluctuates, and the duty command value suitable for the holding duty also changes rapidly.

[0012] However, in general, including the above-mentioned conventional valve timing control device, learning control for appropriately updating the holding duty during operation of the engine is performed.
Actually, no appropriate control for applying an accurate holding duty is performed from the start of the engine to the warm-up operation period as described above. Therefore, sufficient stability and reliability cannot be obtained in the valve timing control from the start of the engine to the warm-up operation period.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a valve timing control for an internal combustion engine capable of controlling the operation timing of the valve with high controllability in any operating state of the engine. It is intended to provide a device.

[0014]

In order to achieve the above object, an invention according to claim 1 is to displace the rotation phase of a camshaft with respect to the rotation phase of an output shaft of an internal combustion engine to at least one of an intake valve and an exhaust valve. A variable valve timing mechanism for varying the operation timing of the valve, actual valve timing calculation means for calculating the actual operation valve timing of the valve based on the phase difference between the rotation phase of the engine output shaft and the rotation phase of the camshaft, Target valve timing calculating means for calculating a target operation timing of the valve based on an operation state of the engine; and a control gain of the variable valve timing mechanism based on the calculated values, such that the actual valve timing matches the target valve timing. Control means for setting the actual operation valve timing and the target operation type. When the ring and is sufficiently approximate,
And a holding control gain calculating means for calculating a holding control gain for holding the actual operation valve timing at that time. Means, a holding control gain learning means for learning a holding control gain obtained by the holding control gain calculating means for a plurality of learning areas set based on the detected temperature parameters, and Holding control gain interpolating means for performing an interpolation calculation of a holding control gain suitable for the intermediate region based on the holding control gains learned in the learning regions before and after the region when in the intermediate region of the region. I do.

According to this configuration, under the transient condition of the engine temperature, even when the clearance between the members of the engine including the components of the variable valve timing mechanism and the viscosity of the hydraulic oil fluctuate greatly, the holding control is not performed. High controllability can be maintained.

According to a second aspect of the present invention, in the valve timing control apparatus for an internal combustion engine according to the first aspect, the plurality of learning regions include a learning region set based on a temperature parameter at the time of starting the engine. The gist is to include at least a learning region set based on the temperature parameter after the warm-up is completed.

According to the above configuration, after warm-up, which is the most general and stable engine temperature range among all engine operation ranges,
At the start of the engine where the temperature parameter difference is most remarkable compared to after the end of the warm-up, the holding control gain is obtained,
These holding control gains can be used as a reference, so that the holding control gains in the intermediate region can be accurately interpolated.

According to a third aspect of the present invention, in the valve timing control device for an internal combustion engine according to the first or second aspect, the temperature parameter is a cooling water temperature of the internal combustion engine.

According to this configuration, the control accuracy and the simplicity are improved by applying the engine cooling water temperature which has a high correlation with the engine temperature and is easily obtained. According to a fourth aspect of the present invention, in the valve timing control device for an internal combustion engine according to any one of the first to third aspects, in the intermediate region between any two learning regions among the plurality of learning regions, A control gain correcting unit that compares the interpolated holding control gain and the holding control gain, and corrects the holding control gain learned in the two learning regions when the difference between the two values exceeds a predetermined value. The gist is to further provide

According to the above configuration, even if a deviation occurs in the holding control gain to be subjected to the interpolation calculation, the deviation is accurately corrected,
As a result, the reliability of the control in the intermediate region can always be suitably maintained.

According to a fifth aspect of the present invention, in the valve timing control apparatus for an internal combustion engine according to the fourth aspect, the control gain correcting means is configured to determine the two control parameters based on the temperature parameter at the time of the comparison. The gist is to determine the correction amount of each holding control gain learned in the learning region.

According to a sixth aspect of the present invention, in the valve timing control apparatus for an internal combustion engine according to the fifth aspect, the amount of correction of each holding control gain learned in the two learning regions is such that the holding control gain is The gist is that the temperature parameter of the learned learning area is set to be larger as the temperature parameter at the time of the comparison is approximated.

If the holding control gain deviates from the true value, the learning value in the learning region in which the temperature parameter corresponding to the holding control gain for which the deviation has been recognized is close, of the two learning regions for interpolating the holding control gain. Has a greater effect on the shift. Thus, a temperature parameter corresponding to the holding control gain for which the deviation has been recognized,
The distance from the temperature parameter in the two learning regions reflects the degree of relative contribution to the deviation due to the learning values in the respective learning regions. In this regard, according to the configuration of the invention described in claim 5 or 6, the degree of contribution to the deviation is reflected in the correction of the learning value, so that the accuracy of the correction can be further increased.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described in detail. FIG. 1 shows a schematic configuration of an engine (internal combustion engine) provided with a valve timing control device according to the present embodiment.

A piston 30 provided reciprocally in the cylinder block 3 of the engine 1 is connected to a crankshaft 5 which is an output shaft of the engine 1 via a connecting rod 31. The crankshaft 5 is rotated based on the reciprocating motion of the piston 30. A crank pulley 10 is provided at the tip of the crankshaft 5.
A crank angle rotor 11 for detecting a crank angle is provided. Further, teeth are provided on the outer periphery of the crank angle rotor 11 at regular intervals. Crank angle sensor 12
Outputs a pulse-like electric signal to the electronic control unit 27 each time the tooth passes by its side. The teeth on the outer periphery of the crank angle rotor 11 are missing one tooth, and the electronic control unit 27 grasps the rotation phase of the crankshaft 5 based on the number of pulses from the missing tooth. Further, the electronic control unit 27 calculates the rotational speed (engine speed) NE of the engine 1 based on the output of the crank angle sensor 12.

Further, at the tip of the crankshaft 5,
Oil pump 16 that operates based on the rotation of the shaft 5
Is provided. The oil pump 16 sucks oil stored in the oil pan 4 and supplies the oil to a lubricating unit and the like of the internal combustion engine 1 as lubricating oil. Part of the oil supplied from the oil pump 16 is also used as hydraulic oil for the valve timing control device. This valve timing control device is a device that varies the relative rotation phase between the crankshaft 5 and the intake camshaft 6 based on hydraulic control, and details thereof will be described later.

Part of the oil pressurized and discharged from the oil pump 16 is supplied to a hydraulic control valve 19 through a supply oil passage 21 formed in the cylinder block 3, the cylinder head 2, and the like. The hydraulic control valve 19 is a variable valve timing mechanism mounted at the tip of the intake camshaft 6 via a retard oil passage 23 and an advance oil passage 22 formed in the cylinder head 2 and the intake camshaft 6. The hydraulic oil is supplied to 20.

The crank pulley 10 is drivingly connected to an intake cam pulley 13 and an exhaust cam pulley 14 via a timing belt 15. This crank pulley 10
Gear ratio with the intake cam pulley 13 or the exhaust cam pulley 14 is 1: 2,
During the rotation, the intake cam pulley 13 or the exhaust cam pulley 14 makes one rotation. The intake cam pulley 13 is provided with a variable valve timing mechanism 20 at the tip of the intake camshaft 6.
Is mounted so as to be relatively rotatable with respect to the intake camshaft 6. That is, while the exhaust camshaft 7 is rotated in synchronization with the crankshaft 5, the relative rotation phase between the intake camshaft 6 and the crankshaft 5 is made variable by the variable valve timing mechanism 20.

A cam angle rotor 1 for detecting the rotational phase of the intake camshaft 6 is provided on the intake camshaft 6.
7 is provided, and a cam angle sensor 18 composed of an electromagnetic pickup is provided in the vicinity thereof. One tooth is formed on the outer periphery of the cam angle rotor 17, and the cam angle sensor 18 controls the pulse-shaped electric signal every time the tooth passes by the electronic control, similarly to the crank angle sensor 12. Output to the device 27.

The electronic control unit 27 controls the cam angle sensor 1
8, the rotation phase of the intake camshaft 6 is detected. The crankshaft 5 and the intake camshaft 6 are compared with the rotational phase of the crankshaft 5 obtained from the output signal of the crank angle sensor 12.
, That is, the operating angle of the variable valve timing mechanism 20. In the present embodiment, the operating angle of the variable valve timing mechanism 20 has a larger value as the valve timing advances.

A plurality of intake cams 8 and exhaust cams 9 are provided on the intake camshaft 6 and the exhaust camshaft 7, respectively, so as to be integrally rotatable. These intake cams 8
The exhaust cam 9 opens and closes the intake valve 28 and the exhaust valve 29 based on the pressing. That is, in the engine 1, the valve timing of the exhaust valve 29 is fixed with respect to the rotation phase of the crankshaft 5, and the valve timing of the intake valve 28 is variable.

The electronic control unit 27 includes, in addition to the output signals from the crank angle sensor 12 and the cam angle sensor 18 described above, cooling water circulating in a passage (not shown) formed in the cylinder block 3. In addition to a water temperature sensor 24 for detecting a temperature (cooling water temperature) THW, an intake pressure sensor 25 for detecting a pressure (intake pressure) PM in an intake passage (not shown) of the engine 1, and a throttle valve provided in the intake passage Output signals from various sensors, such as a throttle sensor 26 that detects an opening (throttle opening) TA of a not-shown illustration, are input.

Next, the valve timing control device will be described in detail. Note that the valve timing control device mainly includes a variable valve timing mechanism 20 that is operated based on hydraulic control, and a hydraulic control system that supplies hydraulic oil to the variable valve timing mechanism 20.

FIG. 2 shows a side sectional structure of the variable valve timing mechanism 20 and a schematic configuration of a hydraulic control system. FIG. 3 shows a front sectional structure of the variable valve timing mechanism 20. As shown in FIG. 2, the internal rotor 40 is fixed to a tip of the intake camshaft 6 by a center bolt 46 so that the internal rotor 40 can rotate integrally with the intake camshaft 6. As shown in FIG. 3, a plurality of (four in the present embodiment) vanes 41 are radially formed on the outer periphery of the internal rotor 40.

A housing 42 is provided to cover the outer periphery of the internal rotor 40, and a cover 45 is further provided to cover the front surface thereof. The housing 42 and the cover 45 are fixed to the intake cam pulley 13 by a plurality of mounting bolts 54 so that they can rotate integrally with the intake cam pulley 13. On the inner periphery of the housing 42, as shown in FIG. 3, the same number of protrusions 44 as the vanes 41 of the internal rotor 40 are formed, and in the recesses 43 formed between the adjacent protrusions 44. A vane 41 is accommodated.

The tip of the vane 41 is in sliding contact with the inner periphery of the concave portion 43, and the tip of the convex portion 44 is in sliding contact with the outer periphery of the internal rotor 40. As a result, the internal rotor 40 and the intake camshaft 6, and the intake cam pulley 13, the housing 42, and the front cover 45 are relatively rotatable about the same axis.

Further, two spaces 47 and 48 are formed in the recess 43 by being partitioned by the vanes 41. Hereinafter, of these two spaces 47 and 48, the space 47 on the rotation direction side of the intake camshaft 6 with respect to the vane 41 is referred to as a retard hydraulic pressure chamber, and the space 48 on the opposite side is referred to as an advance hydraulic pressure chamber. The variable valve timing mechanism 20
Are operated based on pressure control (hydraulic control) of the hydraulic oil supplied into each of the hydraulic chambers 47 and 48.

Next, the configuration of a hydraulic control system for controlling the pressure of the hydraulic oil supplied into the hydraulic chambers 47 and 48 will be described with reference to FIG.
It will be described based on. As described above, the oil pump 16
The operation is performed based on the rotation of the crankshaft 5, sucks the hydraulic oil in the oil pan 4, and supplies the hydraulic oil to the hydraulic control valve 19 via the supply oil passage 21.

The hydraulic control valve 19 is a four-port valve whose opening is controlled based on duty control.
1 and two discharge oil passages 32 for returning hydraulic oil to the oil pan 4, a retard oil passage 23 connected to the retard hydraulic chamber 47 of the variable valve timing mechanism 20, and an advance hydraulic pressure. The advance oil passage 22 connected to the chamber 48 is connected.
The hydraulic control valve 19 is provided with a spool 3 slidably disposed in a reciprocating manner.
5 and a coil spring 34 for urging the spool 35
And an electromagnetic solenoid 33 that attracts the spool 35 when a voltage is applied.

The voltage applied to the electromagnetic solenoid 33 is:
The duty is controlled by the electronic control unit 27.
The attractive force generated by the electromagnetic solenoid 33 changes according to the duty ratio of the applied voltage. The position of the spool 35 is determined by the balance between the attraction force generated by the electromagnetic solenoid 33 and the urging force of the coil spring 34.

As the spool 35 moves, the amount of communication between the retard oil passage 23 and the advance oil passage 22 and the supply oil passage 21 and the discharge oil passage 23 changes, and the retard oil passage 23 and the advance oil passage 23 change. The amount of hydraulic oil supplied to the passage 22 or the amount of hydraulic oil discharged from these oil passages 23 and 22 changes. The hydraulic control valve 19 of the present embodiment is configured such that the larger the duty ratio of the voltage applied to the electromagnetic solenoid is,
2, the hydraulic pressure supply amount to the retard oil passage 23 increases as the duty ratio decreases. By adjusting the hydraulic pressure in the retard hydraulic chamber 47 and the advance hydraulic chamber 48 in this manner, the variable valve timing mechanism 20 is operated.

Next, the operation control of the variable valve timing mechanism 20 will be described. Electronic control unit 27
Is a target value of the operating angle (valve timing) of the variable valve timing mechanism 20 (hereinafter referred to as “target valve timing”) based on the operating state of the engine 1 obtained from the detection results of various sensors such as the crank angle sensor 12.
Calculate vtt. The electronic control unit 27 calculates the actual operating angle (actual operating valve timing) vt of the variable valve timing mechanism 20 obtained from the output signals of the crank angle sensor 12 and the cam angle sensor 18 and the target valve timing vtt. The duty ratio command value is calculated based on the comparison. Further, the electronic control unit 27 applies a command signal having a duty ratio according to the calculated duty command value to the electromagnetic solenoid 33 of the hydraulic control valve 19. By adjusting the opening degree of the hydraulic control valve 19 in this manner, the hydraulic pressure in each of the hydraulic chambers 47 and 48 of the variable valve timing mechanism 20 is appropriately adjusted, and the mechanism 20 is operated. In the above-described manner, the electronic control unit 27 controls the operation of the variable valve timing mechanism 20 and thereby controls the change of the valve timing of the intake valve 28.

Further, the valve timing control includes a holding control and a learning control for the holding control in addition to a normal feedback control for causing the actual operating valve timing vt to converge to the target valve timing. The holding control is a control for setting a duty command value for driving the hydraulic control valve 19 to a predetermined value (holding duty) so as to hold the valve timing at a predetermined phase. This is a control in which a result obtained by the control is evaluated, and an accurate holding duty is sequentially updated and stored.

As described above, since the temperature of each part of the engine fluctuates (increases) transiently from the start of the engine 1 to the warm-up operation period, the viscosity of the hydraulic oil and the valve timing variable mechanism are varied. , The clearance between the members constituting the above fluctuates greatly, and the duty command value suitable for the holding duty also changes rapidly.

For this reason, as described above, sufficient stability and reliability were not obtained in the valve timing control during the warm-up operation period from the start of the engine. Therefore, in the device of the present embodiment, by adopting the following control structure for such valve timing control, the valve timing control can be performed at the time of starting the engine and during the warm-up operation period.
Control stability and reliability are improved when the engine is in a low temperature state or in a transition state from a low temperature to a high temperature.

First, the outline of the valve timing control performed by the electronic control unit 27 in the present embodiment will be described. The electronic control unit 27 calculates the actual operation valve timing of the intake valve (the actual phase angle of the camshaft).
vt converges to a target value (target valve timing) vtt, and the actual operating valve timing vt
Is sufficiently close to the target valve timing vtt, the holding control is performed so that the actual operating valve timing vt at that time is held.

That is, first, the actual operating valve timing v
In the control for converging t to the target valve timing vtt, the electronic control unit 27 grasps the deviation | vtt-vt | between the actual operation valve timing vt and the target valve timing vtt in the above-described manner, and this deviation | vtt. If -vt | is equal to or greater than the predetermined value β, the duty command value for driving the hydraulic control valve 19 is changed to perform feedback control so that the actual operating valve timing vt approaches the target valve timing vtt.

On the other hand, when the deviation | vtt-vt | is less than the predetermined value β, it is considered that the actual operation valve timing vt is sufficiently close to the target valve timing vtt, and the actual operation valve timing vt is held at the current value. Control and learning control thereof.

In the holding control and the learning control thereof, a value for holding the valve timing at an arbitrary phase angle among the duty command values for driving the hydraulic control valve 19 is recognized as the holding duty gdvth and learned. That is, when the deviation | vtt-vt | is maintained within a certain range with the predetermined duty ratio as a command value, the electronic control device 27 learns the duty ratio at that time as the holding duty gdvth.

In this embodiment, the holding duty g
The value of dvth is stored and updated for each learning region divided based on the cooling water temperature THW. The learning area is
(1) The cold learning region from the start of the engine to the determination of the cooling water temperature at the start, (2) the warm learning region after the completion of the warm-up operation, and (3) the termination of the warm-up operation from the determination of the cooling water temperature at the start. It consists of three areas of the intermediate (interpolated) area up to the hour.

Hereinafter, how the holding duty gdvth is stored and updated in each of the learning areas (1) to (3) will be described in detail with reference to the drawings.

FIG. 4 shows the relationship between the cooling water temperature THW and the holding duty dgvth. For example, when the engine 1 starts, the electronic control unit 27 sets the cooling water temperature THW at the time of starting.
In order to determine the holding duty gdvth that conforms to the above, a new learning value is determined using the learning value stored in the previous engine start, that is, the learning value stored in the cold learning region (1) as an initial value. Here, the learning value of the holding duty gdvth stored in the cold learning area is changed to the holding duty g during cold.
dvthc. The electronic control unit 27 learns the cooling water temperature THW when the cold holding duty gdvthc is newly updated and stored as the starting cooling water temperature THWst. The holding duty gdvth corresponding to the start-up cooling water temperature THWst, ie, the cold holding duty g
dvthc is shown as point P1 in FIG.

On the other hand, in the warm learning region (2) after the end of the warm-up operation, the holding duty gd which is appropriately updated is maintained.
vth is learned as the warm-time holding duty gdvthh. As shown in FIG. 4, a region where the cooling water temperature THW exceeds a predetermined water temperature C is set as a warm learning region. Incidentally, when the cooling water temperature THW exceeds the predetermined water temperature C, a thermostat (not shown) provided in a radiator (not shown) of the engine 1 opens a circulation path of the cooling water and causes the cooling water to start releasing heat. Therefore, after the warm-up operation is completed, the normal cooling water temperature THW becomes stable around the predetermined water temperature C. As shown as point P2 in FIG.
The holding duty gdvth corresponding to the predetermined water temperature C corresponds to the holding duty gdvthh during the warm period. Strictly speaking, the holding duty during the warm period depends on the cooling water temperature THW that repeatedly fluctuates delicately around the predetermined water temperature C. Repeat the update until it stops.

In FIG. 4, points P1 and P2
The region between the above corresponds to an intermediate (interpolated) region (3) from the time of determining the cooling water temperature at the time of starting to the time of finishing the warm-up operation. The determination of the holding duty gdvth in the intermediate region is performed as follows.

That is, when the cold maintenance duty gdvthc is newly updated after the engine is started, the electronic control unit 27 stores the updated cooling water temperature THW as the starting cooling water temperature THWst. As you did. Next, the warm holding duty gdvthh stored at the end of the previous operation of the engine is set as an initial value of the warm holding duty gdvthh corresponding to the predetermined temperature C. Here, if a one-dimensional map for uniquely calculating the holding duty gdvth from the cooling water temperature THW is set basically in the same manner as the relationship diagram of FIG.
1 and the point P2 are defined. Therefore, the temperature range between these two points is defined as an intermediate area of the holding duty gdvth, and in this intermediate area, the holding duty gdvth corresponding to the cooling water temperature THW is set as a line segment connecting the points P1 and P2 (hereinafter referred to as an interpolation reference line). Is determined (interpolated).

Further, when the electronic control unit 27 determines that the valve timing is not held accurately even by the holding duty gdvth interpolated in the intermediate region, the electronic control unit 27 changes the points P1 and P2. In other words, by changing the cold holding duty gdvthc and the warm holding duty gdvthh, the interpolation reference line set on the map is corrected.

In the intermediate region, the electronic control unit 27 corrects the cold maintenance duty gdvthc as the cooling water temperature THW becomes closer to the starting cooling water temperature when it is determined that the valve timing is not accurately maintained. Is set large, and the correction amount of the warm-time holding duty gdvthh is set small. On the other hand, as the cooling water temperature THW at the time of the determination is closer to the predetermined water temperature C, the cold maintenance duty gdvt
The correction amount of hc is set small,
The correction amount of dvthh is set to be large. In the present embodiment, a parameter called the holding duty update reflection rate kgdv is applied to the change of the correction amount. However, regarding a method of calculating the holding duty update reflection rate kgdv, a specific control procedure described later is used. (routine)
This will be described in detail.

The valve timing control device of the present embodiment basically learns and updates the holding duty gdvth in the two learning regions divided based on the cooling water temperature THW and the intermediate region in the manner described above. Accordingly, stability and reliability of the valve timing control are ensured under all temperature conditions including a transient state.

Next, a specific control procedure of the electronic control unit 27 with respect to the above-described valve timing holding control and its learning control will be described with reference to a flowchart.

The routine shown in FIGS. 5 and 6 is a flowchart showing a control procedure for updating and learning the holding duty gdvth. This routine is started at the same time as the start of the engine through the electronic control unit 27, and is periodically executed at predetermined time intervals.

When the process proceeds to this routine, the electronic control unit 27 first determines in step 101 (FIG. 5) whether or not the cold hold duty learning completion flag xgdv is set to "1". The holding duty learning completion flag xgdv is a flag that has been released to “0” as an initial state when the engine is started. Same flag x
gdv is the cold maintenance duty g described with reference to FIG.
When dvthc is newly updated after the engine is started, that is, when the point P1 is determined, it is set to “1”.
Incidentally, the setting is performed in step 115 (FIG. 6) described later.
It is performed in. Here, the affirmative determination in step 101 means that the starting cooling water temperature THWst
Means that the cold holding duty gdvthc corresponding to the above is temporarily completed after the engine 1 is started, and the electronic control unit 27 shifts the processing to step 102. On the other hand, a negative determination in the step means that the cold maintenance duty gdvthc has not been newly determined after the start of the engine 1, in other words, it is still learning, The electronic control unit 27 shifts the processing to step 103.

In step 102, the target valve timing vtt is calculated based on parameters indicating the operating state of the engine 1, such as the engine speed NE, the throttle opening TA, the intake pressure PM, and the like.

On the other hand, in step 103, the current cooling water temperature THW is set as the starting cooling water temperature THWst. In step 104, the target valve timing vt
t is set to a predetermined value α.

That is, the target valve timing vtt is
During the learning period of the holding duty gdvthc during cold (xg
dv = “0”), it remains fixed at the predetermined value α (step 104), and the learning is completed (xgdv =
Only after “1” is changed (step 1)
02). This is for accurately learning the initial value of the cold maintenance duty gdvthc (point P1), which is the starting point of the interpolation reference line (see FIG. 4), so that stable and reliable maintenance control can be performed. .

Next, step 102 and step 1
After passing through any of steps 04, the process proceeds to step 105. In step 105, the target valve timing v determined in step 102 or 104 is used.
The difference dlvtt between tt and the actual operation valve timing vt is calculated. The actual operation valve timing vtt is obtained from the output signals of the crank angle sensor 12 and the cam angle sensor 18 as described above. The difference dlvtt calculated in step 105 is equal to the current actual operating valve timing v
This means to what extent t converges to the target valve timing vtt.

In the following step 106, the gradual change value vttsm of the target valve timing vtt and the gradual change value vtsm of the actual operation valve timing vt are obtained in accordance with the following arithmetic expressions (i) and (ii), respectively. ), The difference dlvttsm between them is calculated.

Vttsm = vttsmo + k × (vtt−vttsmo) (i) where vttsmo: vttsm k calculated last time: gradually changing constant (0 <k <1) vtsm = vtsmo + K × (vt-vtsmo). Here, vtsmo: previously calculated vtsmo K: gradual change constant (0 <K <1) dlvttsm = vttsm-vtsm (iii) As is clear from the above arithmetic expressions (i) and (ii), the gradual change value vttsm And vtsm are values intermediate between the previous value and the current value of the target valve timing vtt and the actual operation valve timing vt, respectively. In other words, it can be said that the gradual change values vttsm and vtsm are parameters that follow the target valve timing vtt and the actual operation valve timing vt while reflecting past histories thereof.

Therefore, the electronic control unit 27 recognizes that the actual operation valve timing vt is sufficiently close to the target valve timing vtt if the difference dltt calculated in step 105 is within a predetermined range in the subsequent processing. In addition, if the difference dlttsm between the gradually changing values calculated in step 106 is within a predetermined range, it is recognized that the sufficiently approximated state is maintained substantially constant.

That is, after the processing in step 106, in the subsequent step 107,
Absolute value | dlvt of the difference dlvtt between the target valve timing vtt calculated in step 5 and the actual operation valve timing vt
t | is determined as the difference between the two, and it is determined whether the difference is smaller than a predetermined value β. If the determination is negative, the routine once exits. By the way, as long as the determination in step 107 is negative, the electronic control unit 2
7 always executes a well-known feedback control for converging the actual operation valve timing vt toward the target valve timing vtt sequentially updated in the previous step 102 or 104 through a separate routine. A detailed description of the feedback control of the actual operation valve timing vt is omitted here.

On the other hand, if the determination in step 107 is affirmative, the process proceeds to step 108, recognizing that the actual operating valve timing vt is at least sufficiently close to the target valve timing vtt.

In step 108, the holding duty update reflection rate kgdv is obtained. When the interpolation reference line (see FIG. 4) is modified, the holding duty update reflection rate (hereinafter, simply referred to as “reflection rate”) kgdv is the cold holding duty gdvthc and the warm holding duty gdvth.
h is a parameter for adjusting the correction amount. Reflection rate kgd
v is the current cooling water temperature THW and the starting cooling water temperature THW.
It is determined by referring to a preset map on the basis of st.
The relationship on the map between the reflection rate kgdv and the cooling water temperature THW when it is determined that the correction is to be performed is as shown in FIG. As shown in FIG. 7, for example, when it is determined that the interpolation reference line is to be corrected, as the cooling water temperature THW increases and approaches the predetermined water temperature C, the reflection rate kgdv is set to be larger, and “1” at the predetermined water temperature C is set to an upper limit. The value becomes constant (kgdv = 1) at higher temperatures. The lower limit of the reflection rate kgdv is “0” corresponding to the water temperature THWst at the time of starting. After calculating the reflection rate kgdv, the electronic control unit 27 shifts the processing to step 109 (FIG. 6).

In a series of processes from step 109 to step 113, the difference dlvtt between the gradual change value vttsm of the target valve timing vtt and the gradual change value vtsm of the actual operation valve timing vt obtained in the above step 106.
Recognize one of the following cases: when sm is within a predetermined range (case 1), above the upper limit of the predetermined range (case 2), or below the lower limit of the predetermined range (case 3). Then, processing corresponding to each case is performed.

That is, in step 109, it is determined whether or not the difference dlvttsm exceeds a predetermined value d (d> 0).
It moves to 10. Here, the predetermined value d corresponds to the upper limit of the predetermined range, and if the determination in step 109 is affirmative, it corresponds to the “case 2”. In this case, in order to correct the interpolation reference line (see FIG. 4), step 11 is performed.
At 0, the update amounts dlgdvthc, dlgdvthhh to be added this time to the cold maintenance duty gdvthc and the warm maintenance duty gdvthh, respectively, are calculated. The update amount dlgdvthc is a value obtained by multiplying the preset reference update amount e by the reflection rate kgdv obtained in step 108, and the update amount dlgdvthh is a value obtained by subtracting the reflection rate kgdv from “1” (step in FIG. 6). 110). That is, the larger the one update amount dlgdvthc is set, the larger the update amount dlgdvthc corresponds to the magnitude of the reflection rate kgdv
The other update amount dlgdvthh is set to be small. Naturally, the smaller the one update amount dlgdvthc is set, the larger the other update amount dlgdvthh is set. After step 110, the electronic control unit 27 shifts the processing to step 113.

On the other hand, if the determination in step 109 is negative, the process proceeds to step 111.
In step 111, it is determined whether or not the difference dlvttsm is smaller than a predetermined value -d. If the determination is affirmative, the process proceeds to step 112. Here, the predetermined value -d
Corresponds to the lower limit of the above-mentioned predetermined range. That is, if the determination in step 111 is affirmative, it corresponds to the above “Case 3”. In this case, the interpolation reference line (see FIG. 4)
In step 111, the cold maintenance duty gdvthc and the warm maintenance duty gd
vthh, the update amount dlgdvth to be added this time
c, dlgdvthh is calculated. Update amount dlgdvt
Arithmetic expressions for obtaining hc and dlgdvthh are substantially the same as those in step 110 described above. However, the respective update amounts dlgdvthc and dlgdvthh obtained in step 111 are the same as those in step 11
The difference from the one obtained with 0 is that the signs are opposite. Thereafter, the electronic control unit 27 executes the processing in step 1
Go to step 13.

On the other hand, if the determination in step 111 is negative, this corresponds to the above “Case 1”. In this case, the process proceeds directly to step 113. That is, if the determination in step 111 is negative, step 11
If it is 0 or after step 112, the process proceeds to step 113 in any case.

In step 113, the update amount d obtained this time
The interpolation reference line (see FIG. 4) is corrected by adding lgdvthc and dlgdvthh to the previous cold holding duty gdvthc and the hot holding duty gdvthh, respectively. However, the previous step 11
If the determination in 1 is negative, the update amount dlgdvth
c and dlgdvthh are both set to “0”. That is, the gradual change value v of the target valve timing vtt
ttsm and gradual change value vt of actual operating valve timing vt
Since the difference dlvttsm between sm is within a predetermined range (case 1), it is recognized that the actual operating valve timing vt is maintained sufficiently close to the target valve timing vtt, and the interpolation reference line ( The modification of FIG. 4) is not performed.

In the following step 114, it is determined whether or not the difference dlvttsm is within a range from a predetermined value -d to a predetermined value d. In other words, it is determined whether or not the relationship between the gradually changing value vttsm of the target valve timing vtt and the gradually changing value vtsm of the actual operating valve timing vt corresponds to Case 1. If the determination is affirmative, in step 115, the holding duty learning completion flag xgdv is set to “1”, and then in step 11
Move to 6. On the other hand, if the determination in step 114 is negative, the process directly jumps to step 116.

In step 116, the latest interpolation reference line (see FIG. 4) is determined from the cold holding duty gdvthc and the warm holding duty gdvthh calculated in step 113 this time. Then, the holding duty gdvth corresponding to the current cooling water temperature THW is determined on the map corresponding to FIG. However, when the current cooling water temperature is out of the intermediate region in FIG. 4, the cold holding duty gdvthc or the warm holding duty is respectively corresponding to the cold learning region or the warm learning region. gdvthh is directly applied as the holding duty gdvth.

Based on the above processing procedure, this routine
After the engine 1 is started, the update and the learning of the holding duty gdvth are executed in each learning region defined by the cooling water temperature THW.

Here, in the conventional valve timing control device, even when the engine 1 is started, or during a transitional period of the engine temperature such as a subsequent warm-up operation period, no special consideration is given to the learning of the holding duty. The same learning mode with the same holding duty as in the later normal operation has been applied.

For this reason, especially in the operation range from the start of the engine to the warm-up operation period, the viscosity of the hydraulic oil due to the transient fluctuation of the temperature of each part of the engine and the like between the members constituting the variable valve timing mechanism. , The controllability for obtaining an appropriate holding duty is impaired.

In this regard, according to the valve timing control apparatus of the present embodiment which performs the valve timing control in the above-described manner, the learning area of the holding duty gdvth is used to make the cooling water temperature THW of the engine 1 highly correlated with the fluctuation of the holding duty.
, The optimum holding duty gdvth can be obtained in each region where the viscosity of the hydraulic oil and the clearance between the members constituting the variable valve timing mechanism 20 are different.

In particular, in the control device according to the present embodiment, immediately after the engine 1 is started, first, the cold maintenance duty gdvthc corresponding to the cooling water temperature THWst at the time of the start is learned, and then the last learned after the warm-up. The holding duty in the intermediate region is interpolated together with the warm holding duty gdvthh. For this reason, even at the time of starting the engine where the viscosity of the hydraulic oil and the clearance between the members of the variable valve timing mechanism 20 are the most different from those in the warm state, a highly reliable holding duty gdvth can be obtained.
Even during the subsequent engine temperature transition period (intermediate region), accurate interpolation of the holding duty gdvth can be performed.

Further, in this embodiment, the accuracy of the holding duty gdvth is constantly monitored even in the intermediate area, and the interpolation reference line (see FIG. 4) is rewritten (corrected) as necessary. Therefore, the reliability of the holding duty gdvth to be interpolated in the intermediate area is appropriately maintained.

Further, in correcting the interpolation reference line, each point P is adjusted according to the cooling water temperature for which the correction is determined.
Since the correction amount (update reflection rate kgdv) required to correct 1, P2 (see FIG. 4) is changed, the accuracy of the correction is further improved.

As described above, according to the valve timing control device of the present embodiment, the following effects can be obtained. (1) An optimal holding duty gdvth can always be obtained regardless of the temperature of the engine in any temperature state including a low temperature state when the engine is started.

(2) Even in the transient state of the engine temperature corresponding to the transition period (intermediate region) from cold to warm, the holding control is performed accurately. (3) Also, even if a deviation occurs in the accuracy of the holding duty during the transition period, the deviation can be accurately corrected.

In the present embodiment, two learning regions for learning the holding duty, such as a cold learning region at the start and a warm learning region after the warm-up is completed, and an intermediate region between them (interpolation). Area), but in addition to this,
For example, depending on the specifications of the cooling device for adjusting the cooling water temperature THW, by setting a larger number of engine temperature ranges, three or more types of learning regions according to the respective engine temperature ranges, and intermediate regions between these learning regions. (Interpolation area) can also be set.

In this embodiment, the interpolation reference line applied in the intermediate area (see FIG. 4) is a straight line (linear function of cooling water temperature THW) having both ends of points P1 and P2.
However, other approximate expressions and functions can be set based on data obtained by experiments and the like.

Further, the effect according to the present embodiment can be obtained without rewriting (correcting) the interpolation reference line once set in the intermediate area. Further, in the present embodiment, the cooling water temperature THW of the engine 1 is employed as a temperature parameter for defining the learning region, but the engine temperature may be represented by, for example, the operating oil temperature or the integrated amount of the engine intake air after the start. Other parameters may be employed.

The variable valve timing mechanism 20 includes:
A configuration may be provided on the exhaust camshaft 7 side instead of the intake camshaft 6 side, or on both the intake camshaft 6 and the exhaust camshaft 7.

In this embodiment, a valve timing control device having a so-called vane type variable valve timing mechanism 20 has been described. However, a variable valve timing mechanism based on other operating principles, such as a helical spline type variable valve timing mechanism, etc. In the valve timing control device including the above, the same control mode as described above can be applied as long as the device performs the same valve timing control based on the hydraulic pressure control.

[0093]

According to the first aspect of the present invention, when the engine temperature changes rapidly, the clearance between members of each part of the engine including the components of the variable valve timing mechanism, the viscosity of the hydraulic oil, and the like fluctuate greatly under the transient condition of the engine temperature. In any case, the controllability of the holding control can be maintained at a high level.

According to the second aspect of the present invention, it is possible to accurately interpolate the holding control gain in the intermediate region where the change in the engine temperature is transient. According to the third aspect of the invention, the accuracy and simplicity of control are improved by applying the engine cooling water temperature which has a high correlation with the engine temperature and is easily obtained.

According to the fourth aspect of the present invention, even if a deviation occurs in the holding control gain to be interpolated, the deviation is accurately corrected, so that the reliability of the control in the intermediate region is always suitably maintained. Will be able to

According to the invention described in claim 5 or 6,
By reflecting the degree of relative contribution to the deviation of the holding control gain in the intermediate region in the correction of each of the two learning values as the reference value, the accuracy of the correction can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an engine provided with a valve timing control device according to an embodiment of the present invention.

FIG. 2 is a sectional view mainly showing a side sectional structure of the variable valve timing mechanism;

FIG. 3 is a sectional view showing a front sectional structure of the variable valve timing mechanism.

FIG. 4 is a graph showing a relationship between a cooling water temperature and a holding duty.

FIG. 5 is a flowchart showing a valve timing control procedure of the embodiment.

FIG. 6 is a flowchart showing a valve timing control procedure of the embodiment.

FIG. 7 is a graph showing a relationship between a cooling water temperature and a holding duty update reflection ratio.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Cylinder block, 4 ... Oil pan, 5 ... Crankshaft, 6 ... Intake camshaft, 7 ... Exhaust camshaft, 8 ... Intake cam, 9 ... Exhaust cam, 10 ... Crank pulley , 11 ... crank angle rotor, 12 ... crank angle sensor, 13 ... crank pulley, 14 ... exhaust cam pulley, 16 ... oil pump, 17 ... cam angle rotor, 18 ... cam angle sensor, 19 ...
Hydraulic control valve, 20 ... variable valve timing mechanism, 21 ...
Supply oil passage, 22 ... advance oil passage, 23 ... retard oil passage, 24 ... water temperature sensor, 25 ... intake pressure sensor, 26 ... throttle sensor, 27 ... electronic control unit, 28 ... intake valve, 29 ... exhaust valve, Reference numeral 30: piston, 31: connecting rod, 33: electromagnetic solenoid, 34: coil spring,
35: spool, 40: internal rotor, 41: vane, 4
2 ... housing, 43 ... concave, 44 ... convex, 45 ... cover, 46 ... center bolt, 47 ... retard side hydraulic chamber, 48 ...
Advance hydraulic chamber, 54 mounting bolts.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA08 AA19 BA03 BA06 BA22 BA28 BA38 BB04 DA06 DA22 DA23 GA07 3G084 BA23 CA01 CA02 DA05 DA22 EB13 EB18 EB20 EC06 FA10 FA11 FA20 FA33 FA38 3G092 AA11 DA01 DA02 DA09 DG05 DG05 EA05 EA22 EA25 EB06 EB08 EC02 EC05 EC08 EC10 FA09 FA48 GA01 GA02 HA05Z HA06Z HA13X HA13Z HE01Z HE04Z HE08Z

Claims (6)

[Claims] 1. A variable valve timing mechanism for displacing a rotation phase of a camshaft with respect to a rotation phase of an output shaft of an internal combustion engine to vary an operation timing of at least one of an intake valve and an exhaust valve, and a rotation phase of the engine output shaft. Actual valve timing calculating means for calculating the actual operating valve timing of the valve based on the phase difference between the rotation phase of the camshaft and target valve timing calculating for calculating the target operating timing of the valve based on the operating state of the engine Means, and control means for setting a control gain of the variable valve timing mechanism based on the calculated values so that the actual valve timing matches the target valve timing. When approximated, the actual operating valve timing at that time A valve timing control device for an internal combustion engine, comprising: a holding control gain calculating means for calculating a holding control gain for holding; a temperature parameter detecting means for detecting a temperature parameter relating to an engine temperature of the internal combustion engine; and the detected temperature. Holding control gain learning means for learning a holding control gain obtained by the holding control gain calculating means for a plurality of learning areas set based on the parameters; andwhen the engine temperature is in an intermediate area between the plurality of learning areas, A valve timing control device for an internal combustion engine, comprising: a holding control gain interpolating means for performing an interpolation calculation of a holding control gain suitable for the intermediate region based on the holding control gains learned in the learning regions before and after them. . 2. The valve timing control device for an internal combustion engine according to claim 1, wherein the plurality of learning regions include a learning region set based on a temperature parameter at the time of starting the engine, and a temperature parameter after completion of warm-up. A valve timing control device for an internal combustion engine, comprising at least a learning region set based on 3. The valve timing control device for an internal combustion engine according to claim 1, wherein the temperature parameter is a cooling water temperature of the internal combustion engine. 4. The valve timing control device for an internal combustion engine according to claim 1, wherein the interpolation calculation is performed in an intermediate region between any two of the plurality of learning regions. The apparatus further includes a control gain correction unit that compares the hold control gain with the hold control gain, and when the difference between the two values exceeds a predetermined value, corrects the hold control gain learned in the two learning regions. A valve timing control device for an internal combustion engine, comprising: 5. The valve timing control device for an internal combustion engine according to claim 4, wherein said control gain correcting means learns each of said two learning regions based on said temperature parameter when said comparison is performed. A valve timing control device for an internal combustion engine, which determines a correction amount of a holding control gain. 6. The valve timing control device for an internal combustion engine according to claim 5, wherein the correction amount of each of the holding control gains learned in the two learning regions is a temperature parameter of the learning region in which the holding control gain is learned. Is set so as to be closer to the temperature parameter at the time of the comparison.