JP3075122B2 - Valve timing control device for internal combustion engine - Google Patents

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 that changes at least one of an intake valve and an exhaust valve in accordance with the operating state of the internal combustion engine. The present invention relates to a valve timing control device for an internal combustion engine that switches control of a valve timing mechanism from convergence control to holding control.

[0002]

2. Description of the Related Art Heretofore, a valve timing control apparatus for changing at least one of an intake valve and an exhaust valve (valve timing) in accordance with an operating state of an engine has been put to practical use. According to this valve timing control device, the period during which the intake valve and the exhaust valve are simultaneously opened (valve overlap period) can be set to an arbitrary period, so that the combustion efficiency in the combustion chamber can be improved.

That is, for example, in a high rotation range,
By increasing the valve overlap period by advancing the valve opening timing of the intake valve, it is possible to obtain intake inertia and the like and improve the efficiency of charging the intake air into the combustion chamber. On the other hand, in the low rotation range, the valve opening timing of the intake valve is retarded to shorten the valve overlap period, thereby preventing the intake air once drawn into the combustion chamber from flowing back to the intake passage, The filling efficiency can be improved.

[0004] As this type of valve timing control device, there is known a valve timing control device that changes a valve timing by changing a displacement angle of a camshaft with respect to a crankshaft. Here, JP-A-4-27
Japanese Patent Publication No. 9705 discloses a valve timing control device capable of continuously changing a valve timing (displacement angle) in accordance with an operating state of an engine. According to this valve timing control device, a linear valve timing according to the operating state of the engine can be realized in the entire region from the low rotation region to the high rotation region.

In such a valve timing control device, feedback control is performed in order to converge the actual valve timing (actual displacement angle) to a target valve timing (target displacement angle). Then, when the absolute value of the difference between the actual displacement angle and the target displacement angle becomes equal to or less than a predetermined value, from feedback control for displacing the displacement angle to valve timing retention control for retaining the actual displacement angle at the current displacement angle. Is determined.

As a result of the switching determination, if the absolute value of the difference between the actual displacement angle and the target displacement angle is determined to be equal to or less than a predetermined value, the control in the valve timing control device is changed from feedback control to valve timing holding control. The switching is performed, and the predetermined valve timing is maintained.

[0007]

However, simply,
When executing the switching determination from the feedback control to the valve timing holding control based on whether the absolute value of the difference between the actual displacement angle and the target displacement angle is equal to or less than a predetermined value, the following problem occurs. there were.

In general, the target displacement angle is calculated based on a three-dimensional map using the intake pressure PM and the engine speed NE or the engine load Q / F and the engine speed NE as parameters. There is a relationship between the angle and the intake pressure PM as shown in the two-dimensional map of FIG. Here, FIG. 11 shows a predetermined engine speed N.
5 is a two-dimensional map obtained by cutting the three-dimensional map in E and showing the relationship between the target displacement angle and the intake pressure PM.

As can be seen from this two-dimensional map, especially in the region where the intake pressure PM is low, the intake pressure PM
Is large (differential coefficient at a specific point of the characteristic curve), the target displacement angle greatly changes due to slight intake pressure PM fluctuation even in the steady operation state. Become.

In the valve timing control device, feedback control is performed so that the actual displacement angle converges to the target displacement angle. Since the actual displacement angle changes following a change in the target displacement angle, the intake control is performed. If the target displacement angle changes due to the fluctuation of the pressure PM, the actual displacement angle will also change. Further, the actual displacement angle varies due to a response delay of the variable valve timing mechanism.

Therefore, the fluctuation of these target displacement angles,
Alternatively, if the predetermined value of the switching determination is reduced without considering the fluctuation of the actual displacement angle, the switching determination from the feedback control to the valve timing holding control may be erroneously performed. As 2
It was necessary to use a large value such as 3 ° CA.

As a result, the allowable convergence range of the actual displacement angle with respect to the target displacement angle becomes large, so that appropriate valve timing control for the operating state of the engine cannot be executed. There was a problem that it became large.

Further, since the valve timing control accuracy is low, there is a problem that emission varies by the internal EGR difference, in particular NO _X concentration to vary greatly with only the crank angle is different from 3 °, a predetermined value of the switching determination It was not easy to determine.

Further, the amount of air taken into the combustion chamber is:
It changes depending on the valve timing and affects the engine output characteristics.However, if the valve timing control accuracy is low, the optimal intake air amount necessary for the current operation state cannot be supplied to the combustion chamber, and the engine output characteristics However, there is a problem in that variations occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to improve control accuracy of a variable valve timing mechanism, thereby reducing emission variations and output characteristics variations. And

[0016]

According to a first aspect of the present invention, there is provided a valve timing control apparatus for an internal combustion engine, comprising: an intake passage M3 and an exhaust passage M4 which communicate with a combustion chamber M2 of an internal combustion engine M1; An intake valve M5 and an exhaust valve M6 that respectively open and close, an operating state detecting means M7 for detecting an operating state of the internal combustion engine M1, and an operating state of the internal combustion engine M1 detected by the operating state detecting means M7. Target valve timing determining means M8 for determining the target valve timing, and smoothed target valve timing calculating means for calculating the smoothed target valve timing based on the target valve timing determined by the target valve timing determining means M8 M
9, a variable valve timing mechanism M10 for changing the valve timing of at least one of the intake valve M5 and the exhaust valve M6, and the actual valve timing of the valve on the side where the variable valve timing mechanism M10 is provided. , A smoothed actual valve timing calculating means M12 for calculating a smoothed actual valve timing based on the actual valve timing detected by the valve timing detecting means M11, A valve timing convergence control means M13 for controlling the valve timing mechanism M10 to cause the actual valve timing to converge on the target valve timing, and controlling the variable valve timing mechanism M10 so that the actual valve timing is adjusted to a predetermined valve timing. A valve timing holding control means M14 for holding the target by the timing, determining that an absolute value of a difference between the target valve timing and the smoothed target valve timing is equal to or less than a first predetermined value, and When it is determined that the absolute value of the difference between the valve timing and the smoothed actual valve timing is equal to or smaller than a second predetermined value that is smaller than the first predetermined value , the control for the variable valve timing mechanism M10 is performed. Valve timing control switching means M15 for switching from the convergence control by the valve timing convergence control means M13 to the holding control by the valve timing holding control means M14.

[0017]

According to the valve timing control apparatus for an internal combustion engine according to the first aspect of the present invention, the internal combustion engine M
1 starts, the intake valve M5 and the exhaust valve M6
Is driven at a predetermined timing, and opens and closes an intake passage M3 and an exhaust passage M4 communicating with the combustion chamber M2. And
The valve timing of at least one of the intake valve M5 and the exhaust valve M6 is changed by the variable valve timing mechanism M10.

The operating state detecting means M7 detects the operating state of the internal combustion engine M1, and the target valve timing determining means M8 varies according to the operating state of the internal combustion engine M1 detected by the operating state detecting means M7. The target valve timing of the valve on the side where the valve timing mechanism M10 is provided is determined. Further, the smoothed target valve timing calculating means M9 calculates the smoothed target valve timing based on the target valve timing determined by the target valve timing determining means M8.

The valve timing detecting means M11 detects the actual valve timing of the valve on the side where the variable valve timing mechanism M10 is provided. Further, the smoothed actual valve timing calculating means M12 calculates the smoothed actual valve timing based on the actual valve timing detected by the valve timing detecting means M11.

The valve timing convergence control means M13 includes:
The variable valve timing mechanism M10 is controlled so that the actual valve timing converges to the target valve timing.
Reference numeral 4 denotes a variable valve timing mechanism M1 for maintaining the actual valve timing at a predetermined valve timing.
Control 0.

The valve timing control switching means M
15 is an absolute value of a difference between the target valve timing and the smoothed target valve timing is equal to or less than a first predetermined value, and
It is determined whether the absolute value of the difference between the target valve timing and the actual valve timing is equal to or less than a second predetermined value. That is, it is determined whether or not the target valve timing is stable, the actual valve timing converges to the target valve timing, and the variable valve timing mechanism M10 is in a stable state.

When the condition for determining the control switching is satisfied, the control for the variable valve timing mechanism M10 is switched from the convergence control by the valve timing convergence control means M13 to the holding control by the valve timing holding control means M14. .

Since it is determined whether or not the absolute value of the difference between the target valve timing and the actual valve timing subjected to the annealing process is equal to or less than a second predetermined value, the internal combustion engine M1 Even if the operation state of the first valve temporarily fluctuates, the change of both valve timings is gradual, and is hardly affected by the variation of the operation state.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a valve timing control device for an internal combustion engine will be described below with reference to the drawings.

First, the configuration of a valve timing control device VC for an internal combustion engine according to this embodiment will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram showing a gasoline engine system to which the present embodiment is applied.

An engine 10 as an internal combustion engine includes a cylinder block 11 in which a plurality of cylinders are formed, and a cylinder head 1 connected to an upper portion of the cylinder block 11.
2 and a piston 13 that reciprocates up and down in each cylinder of the cylinder block 11. Further, a crankshaft 14 is connected to a lower end portion of the piston 13, and the crankshaft 14 is rotated by moving the piston 13 up and down.

Further, a crank angle sensor 40 is provided near the crankshaft 14. The crank angle sensor 40 includes a magnetic rotor (not shown) connected to the crankshaft 14 and an electromagnetic pickup (not shown). (Not shown). Here, equiangular teeth are formed on the outer periphery of the rotor, and every time the equiangular teeth of the rotor pass in front of the electromagnetic pickup, a pulse-like crank angle signal is generated and detected.

After a reference position signal is generated by a cylinder discriminating sensor 42, which will be described later, the number of generated crank angle signals from the crank angle sensor 40 is measured, whereby the rotation angle (crank angle) of the crankshaft 14 is detected. You.

The space defined by the inner wall of each cylinder block 11 and the cylinder head 12 and the top of the piston 13 functions as a combustion chamber 15 for burning an air-fuel mixture. Is provided with a spark plug 16 for igniting the air-fuel mixture so as to protrude into the combustion chamber 15.

Each ignition plug 16 is connected to a distributor 18 via a plug cord or the like (not shown), and the high voltage output from the igniter 19 is synchronized with the crank angle by the distributor 18 to each of the ignition plugs 16. It is distributed to the spark plug 16.

Further, the distributor 18 is connected to the exhaust side camshaft 33, and the crankshaft 1
An engine speed sensor 41 for detecting the speed of the engine 4 is provided.

The engine speed sensor 41 comprises a magnetic rotor (not shown) rotating in synchronization with the crankshaft 14 and an electromagnetic pickup (not shown). The electromagnetic pickup detects the rotation speed of the rotor. Thus, the rotation speed of the crankshaft 14 (engine speed NE) is detected. In addition, the distributor 18 receives the crankshaft 1 from the rotation of the rotor.
A cylinder discriminating sensor 42 for detecting the four reference positions at a predetermined ratio is provided.

The cylinder block 11 is provided with a water temperature sensor 43 for detecting the temperature (cooling water temperature) THW of the cooling water flowing through the cooling water passage. Cylinder head 1
2 has an intake port 22 and an exhaust port 32. The intake port 22 is connected to the intake passage 20, and the exhaust port 32 is connected to the exhaust passage 30. In addition, the intake port 22 of the cylinder head 12 includes:
An intake valve 21 is provided, and an exhaust port 31 is provided with an exhaust valve 31.

Above the intake valve 21, an intake camshaft 2 for opening and closing the intake valve 21 is provided.
The exhaust side camshaft 33 for opening and closing the exhaust valve 31 is disposed above the exhaust valve 31. At one end of each of the camshafts 23 and 33, an intake-side timing pulley 27 and an exhaust-side timing pulley 34 are mounted.
7 and 34 are connected to the crankshaft 14 via a timing belt 35.

Therefore, when the engine 10 is operating, each camshaft 2 is transmitted from the crankshaft 14 via the timing belt 35 and the timing pulleys 27 and 34.
The rotational driving force is transmitted to each of the camshafts 2 and 3.
The rotation of 3, 33 causes the intake valve 21 and the exhaust valve 31 to open and close. Each of these valves 21,
31 is the rotation of the crankshaft 14 and the piston 13
In synchronization with the vertical movement of
The engine 10 is driven at a predetermined opening / closing timing in synchronization with a series of four strokes of the engine 10 including an explosion / expansion stroke and an exhaust stroke.

Further, a cam angle sensor 44 for detecting the valve timing of the intake valve 21 is provided near the intake side camshaft 23. The cam angle sensor 44 is connected to the intake side camshaft 23. It is composed of a connected magnetic rotor (not shown) and an electromagnetic pickup (not shown). Further, a plurality of teeth are formed at equal angles on the outer circumference of the magnetic rotor, for example,
Before the compression TDC of the predetermined cylinder, a pulse-like cam angle signal (displacement timing signal) accompanying rotation of the intake-side camshaft 23 is detected between BTDC 90 ° to 30 °.

An air cleaner 24 is connected to the air intake side of the intake passage 20, and a throttle valve 26 which is opened and closed in conjunction with an accelerator pedal (not shown) is provided in the middle of the intake passage 20. ing. The intake air amount is adjusted by opening and closing the accelerator pedal.

In the vicinity of the throttle valve 26, a throttle sensor 4 for detecting the throttle opening TA is provided.
5 are provided. Further, a surge tank 2 for suppressing intake pulsation is provided downstream of the throttle valve 26.
5 are formed. And in the surge tank 25,
An intake pressure sensor 46 for detecting an intake pressure in the surge tank 25 is provided. An injector 17 for supplying fuel to the combustion chamber 15 is provided near the intake port 22 of each cylinder. Each injector 17 is an electromagnetic valve that is opened by energization, and each injector 17 is supplied with fuel pumped from a fuel pump (not shown).

Therefore, when the engine 10 is operating,
The air filtered by the air cleaner 24 is taken into the intake passage 20, and fuel is injected from each injector 17 toward the intake port 22 simultaneously with the intake of the air. As a result, an air-fuel mixture is generated at the intake port 22, and the air-fuel mixture is sucked into the combustion chamber 15 with the opening of the intake valve 21 that is opened during the intake stroke.

A catalytic converter 36 containing a three-way catalyst for purifying exhaust gas is disposed in the exhaust passage 30. In the middle of the exhaust passage 30, an oxygen sensor 47 for detecting the oxygen concentration in the exhaust gas is provided.

In the gasoline engine system according to the present embodiment, the variable valve timing mechanism 50 (hereinafter referred to as “VV”) driven by hydraulic pressure is used to change the opening / closing timing of the intake valve 21 to change the valve overlap amount.
T ". ) Are arranged. This VVT50 is
Crankshaft 14 (intake side timing pulley 27)
This is a mechanism for continuously changing the valve timing of the intake valve 21 by changing the displacement angle of the intake side camshaft 23 with respect to the rotation of the intake valve 21.

The system configuration of the VVT 50 will be described with reference to FIG. Here, FIG.
FIG. 5 is an explanatory diagram showing a cross section near the intake side camshaft 23 where 0 is disposed, and an entire control system of the VVT 50.

The control system of the VVT 50 is a VVT 5
0, an oil control valve 80 (hereinafter referred to as "OCV") for applying a driving force to the VVT 50, a cam angle sensor 44 for detecting a cam angle signal, and a cam angle sensor 44.
And an ECU 70 that controls the drive of the OCV 80 based on input signals from various sensors such as the above.

The VVT 50 is disposed between the intake camshaft 23 and the intake timing pulley 27.
The intake camshaft 23 is rotatably supported between the cylinder head 12 and the bearing cap 51. An intake-side timing pulley 27 is mounted in the vicinity of the distal end of the intake-side camshaft 23 so as to be relatively rotatable, and an inner cap 52 is provided with a hollow bolt 53 and a pin 54 at the distal end of the intake-side camshaft 23. Are attached so as to be integrally rotatable.

A housing 56 having a cap 55 is attached to the intake-side timing pulley 27 by bolts 57 and pins 58 so as to be integrally rotatable. With this housing 56, the tip of the intake-side camshaft 23 and the inner The entire cap 52 is covered. Further, on the outer periphery of the intake-side timing pulley 27, a number of external teeth 27a for mounting the timing belt 35 are formed.

The intake-side camshaft 23 and the intake-side timing pulley 27 are connected by a ring gear 59 interposed between the housing 56 and the inner cap 52. The ring gear 59 has a substantially annular shape, and is housed in a space S surrounded by the intake-side timing pulley 27, the housing 56, and the inner cap 52 so as to be able to reciprocate in the axial direction of the intake-side camshaft 23. . A large number of teeth 59 are provided on the inner and outer circumferences of the ring gear 59.
a, 59b are formed.

Correspondingly, the outer periphery of the inner cap 52 and the inner periphery of the housing 56 have a number of teeth 52a,
56b are formed. These teeth 59a, 59b,
Both 52a and 56b are helical teeth whose tooth traces intersect at a predetermined angle with respect to the axis of the intake-side camshaft 23. That is, the teeth 52a and the teeth 59a mesh with each other, and the teeth 56b and the teeth 59b mesh with each other to form a helical spline.

The rotation of the intake-side timing pulley 27 is transmitted to the intake-side camshaft 23 through the housing 56 and the inner cap 52 by the meshing of these. Also, each tooth 59a, 59b, 52a, 56
Since b is a helical tooth, when the ring gear 59 moves in the axial direction of the intake side camshaft 23, a twisting force is applied to the inner cap 52 and the housing 56, and the intake side camshaft 23 is attached to the intake side timing pulley 27. Move relative to

The space S has a first hydraulic chamber 60 at the distal end of the ring gear 59 and a second hydraulic chamber 61 at the proximal end of the ring gear 59 in order to move the ring gear 59 in the axial direction.
have. The bearing cap 51 has a first hydraulic pressure supply hole 51a and a second hydraulic pressure supply hole 51b. The first camshaft 23 has a first
A first hydraulic supply path 62 that connects the hydraulic supply hole 51a to the first hydraulic chamber 60 and a second hydraulic supply path 63 that connects the second hydraulic supply hole 51b to the second hydraulic chamber 61 are formed. .

The lubricating oil sucked up from the oil pan 65 by the hydraulic pump 64 is supplied to each of the hydraulic pressure supply holes 51a and 51b through the oil filter 66 at a predetermined pressure. In addition, each hydraulic supply path 60, 6
In order to selectively supply the hydraulic pressure to each of the hydraulic chambers 60 and 61 through the respective hydraulic pressure supply holes 51 a and 51 b, an OCV 8 is provided.
0 is connected.

The OCV 80 is a four-port directional control valve for switching the lubricating oil flow direction by reciprocally moving a spool 84 in a plunger 83 driven by an electromagnetic actuator 81 and a coil spring 82. Then, the electromagnetic actuator 81
However, the duty is controlled so that the opening degree is adjusted, and the magnitude of the hydraulic pressure supplied to each of the hydraulic chambers 60 and 61 is adjusted.

The casing 85 of the OCV 80 has a tank port 85t, an A port 85a, a B port 85b, and a reservoir port 85r. The tank port 85t is connected to the oil pan 65 via the hydraulic pump 64, and the A port 85a is connected to the first hydraulic supply hole 5
1a and the B port 85b are connected to the second hydraulic pressure supply hole 51b. The reservoir port 85r is connected to the oil pan 65.

The spool 84 is a cylindrical valve body.
It has four lands 84a for sealing the flow of the lubricating oil between the two ports, a passage 84b communicating between the two ports and allowing the flow of the lubricating oil, and two passages 84c.

In the VVT 50 having these configurations, OVT
When the drive of the CV 80 is controlled and the spool 84 is moved to the left in the drawing, the passage 84b
t and the A port 85a, and the first hydraulic pressure supply hole 51a
Is supplied with lubricating oil. Then, the first hydraulic pressure supply hole 51a
Is supplied to the first hydraulic chamber 60 via the first hydraulic pressure supply path 62, and the hydraulic pressure is applied to the distal end side of the ring gear 59.

At the same time, the passage 84c communicates between the B port 85b and the reservoir port 85r, and the lubricating oil in the second hydraulic chamber 61 is supplied to the second hydraulic supply passage 63, the second hydraulic supply hole 51b, and the OCV 80. Is discharged to the oil pan 65 through the B port 85b and the reservoir port 85r.

Therefore, the ring gear 59 is moved while rotating to the base end (right side in the drawing) by the hydraulic pressure applied to the front end, and twist is applied to the intake camshaft 23 via the inner cap 52. . As a result, the rotational phase (displacement angle) of the intake side camshaft 23 with respect to the intake side timing pulley 27 (crankshaft 14) is changed (displaced), and the intake side camshaft 23 is shifted from the most retarded angle to the most advanced angle. To the intake valve 21
Is advanced.

The intake valve 21 whose valve opening timing has been advanced in this way is opened while the exhaust valve 31 is open, so that the intake valve 21 and the exhaust valve 31 are simultaneously opened. The lap period is extended. The movement of the ring gear 59 to the proximal end side is restricted by the ring gear 59 abutting on the intake-side timing pulley 27. When the ring gear 59 abuts on the intake-side timing pulley 27 and stops, the intake valve 21 is stopped. The valve opening timing is the earliest.

On the other hand, when the drive of the OCV 80 is controlled and the spool 84 is moved rightward in the drawing, the passage 84
b communicates between the tank port 85t and the B port 85b,
Lubricating oil is supplied to the second hydraulic pressure supply hole 51b. And
The lubricating oil supplied to the second hydraulic pressure supply hole 51b is supplied to the second hydraulic pressure chamber 61 via the second hydraulic pressure supply passage 63, and the hydraulic pressure is applied to the base end side of the ring gear 59.

At the same time, the passage 84c communicates between the A port 85a and the reservoir port 85r, and the lubricating oil in the first hydraulic chamber 60 is supplied to the first hydraulic supply path 62, the first hydraulic supply hole 51a, and the OCV 80. Is discharged to the oil pan 65 through the A port 85a and the reservoir port 85r.

Accordingly, the ring gear 59 is moved while rotating to the distal end side (left side in the drawing) by the hydraulic pressure applied to the proximal end side, and the intake camshaft 23 is twisted in the opposite direction via the inner cap 52. Granted. As a result,
Intake side timing pulley 27 (crankshaft 14)
, The rotational phase (displacement angle) of the intake camshaft 23 is changed (displaced), and the intake camshaft 23 is displaced from the most advanced angle to the most retarded angle, and the valve opening timing of the intake valve 21 is changed. Is retarded.

Thus, by delaying the opening timing of the intake valve 21, the valve overlap period during which the intake valve 21 and the exhaust valve 31 are simultaneously opened is reduced or eliminated. The movement of the ring gear 59 toward the distal end is regulated by the contact of the ring gear 59 with the housing 56. When the ring gear 59 contacts the housing 56 and stops, the valve opening timing of the intake valve 21 becomes the latest. .

The valve timing of the intake valve 21 changed by the VVT 50 is calculated based on a cam angle signal output from the cam angle sensor 44 and a crank angle signal output from the crank angle sensor 40.

That is, for example, after the cam angle signal (displacement timing signal) is input to the ECU 70, the BTD
The time required until a crank angle signal (reference timing signal) of C30 ° is input is measured using the engine speed NE, and the time is converted into a displacement angle using the relationship between the known time and the crank angle. Thus, the actual displacement angle VTB of the intake camshaft 23 with respect to the crankshaft 14 is calculated.

Next, a control system of the valve timing control device VC for the internal combustion engine according to the present embodiment will be described with reference to a control block diagram shown in FIG. The control system of the valve timing control device VC of the internal combustion engine includes an electronic control unit 7
0 (hereinafter referred to as “ECU”). The ECU 70 implements valve timing control switching means, valve timing holding control means, valve timing convergence control means, smoothed actual valve timing calculation means, smoothed target valve timing calculation means, target valve timing determination means, and the like.

The ECU 70 executes VV as a main routine.
A control switching processing program for switching the control for T50 from feedback control (convergence control) to holding control after the switching determination, and a VVT displacement angle map for determining a displacement angle of the intake camshaft 23 corresponding to various conditions are stored. ROM 71 is provided. The ECU 70
In addition to the main routine, a smoothed target displacement angle calculation program for calculating a smoothed target displacement angle VTTSM based on the target displacement angle VTT, and a smoothed corrected actual displacement angle VTSM based on the corrected actual displacement angle VT are calculated. It has an annealing calibration actual displacement angle calculation program.

Further, the ECU 70 executes an arithmetic process based on the control program stored in the ROM 71.
The PU 72 has a RAM 73 for temporarily storing the calculation results of the CPU 72, data input from each sensor and the like, and a backup RAM 74 for holding various data stored in the RAM 73 when power supply is stopped.

Then, the CPU 72, the ROM 71, and the RAM
73 and a backup RAM 74 include a bidirectional bus 75
And the input interface 76 and the output interface 77.

The input interface 76 includes a crank angle sensor 40, an engine speed sensor 41, a cylinder discrimination sensor 42, a water temperature sensor 43, a cam angle sensor 44, a throttle sensor 45, an intake pressure sensor 46, and an oxygen sensor 47.
Etc. are connected. When the signal output from each sensor is an analog signal, an A / D (not shown)
After being converted into a digital signal by the converter, it is output to the bidirectional bus 75.

The output interface 77 is connected to external circuits such as the injector 17, the igniter 19, the OCV 80, and the like.
The operation is controlled based on the result of the calculation of the control program executed in.

Next, a control switching processing program, a smoothed target displacement angle calculation program, and a smoothed calibration actual displacement angle calculation program in the valve timing control device VC for an internal combustion engine according to the present embodiment having the above-described configuration are shown in FIG. This will be described with reference to flowcharts shown in FIGS.

Here, the control switching processing program is a program for determining the control switching condition and switching the control processing for the VVT 50 from the feedback control processing to the holding control processing.

Hereinafter, description will be made with reference to the flowchart of the control switching processing program shown in FIG. Note that “S” in the flowchart of each program indicates each step.

First, in S10, the target displacement angle VTT,
Calibrated actual displacement angle VT, smoothed target displacement angle VTTSM calculated by the smoothed target displacement angle calculation program,
Reading of the smoothed calibration actual displacement angle VTSM calculated by the smoothed actual displacement angle calculation program is performed.

Here, the smoothed target displacement angle calculation program for calculating the smoothed target displacement angle VTTSM read in this step will be described with reference to the flowchart shown in FIG.

First, the intake pressure PM detected by the intake pressure sensor 46 and the engine speed NE detected by the engine speed sensor 41 are read (S100). Subsequently, the V stored in the ROM 71
From the VT displacement angle map, the read intake pressure PM,
And a displacement angle corresponding to the engine speed NE is determined, and a target displacement angle VTT is determined (S110).

Next, the currently determined target displacement angle VTT
_i and the previously calculated averaged target displacement angle VTTSM
by using the _i-1, the raw time Shi target displacement angle VTTSM _i is calculated by the equation (1) (S120).

Equation (1) VTTSM _i = VTTSM _i−1 + (VTT _i −VTTSM _i−1 ) / n1 where n1 is a smoothing constant that determines the degree of smoothing. For example, n1 = 24 Used and VTTS
VTT ₀ is used for M ₀ . Here, the difference between the change in the smoothed target displacement angle VTTSM obtained from Equation (1) and the change in the target displacement angle VTT will be described with reference to FIG. Here, FIG. 9 is a time chart for explaining a difference in a change in the smoothed target displacement angle VTTSM with respect to a change in the target displacement angle VTT. The vertical axis indicates the displacement angle, and the horizontal axis indicates the time.

As can be seen from the figure, the target displacement angle VTT
The degree of change of the smoothed target displacement angle VTTSM with respect to time is small compared to the degree of change with respect to time, and even if the intake pressure PM or the like temporarily fluctuates and the target displacement angle VTT greatly changes, Less susceptible to change. This is because the target displacement angle VTT depends only on the engine condition at the time of calculation,
This is because the smoothed target displacement angle VTTSM _i depends on the previously calculated smoothed target displacement angle VTTSM _i-1 in addition to the engine condition at the time of calculation.

[0079] That is, as shown in the equation (1), annealing target displacement angle VTTSM _i have now determined target displacement angle VTT _i was and Do the previously calculated target displacement angle VT
This is because the value is calculated by adding a value obtained by dividing the difference from TSM _i-1 by the smoothing constant to the previously calculated smoothing target displacement angle VTTSM _i-1 .

Therefore, a steady engine condition can be reflected without being influenced by an engine condition, for example, a temporary fluctuation of the intake pressure PM.

Next, the smoothed calibration actual displacement angle calculation program for calculating the smoothed calibration actual displacement angle VTSM read in this step will be described with reference to the flowchart shown in FIG.

First, the reference timing signal detected by the crank angle sensor 40 and the displacement timing signal detected by the cam angle sensor 44 are read (S200). Subsequently, the calibration actual displacement angle VT is calculated in S210.
Is the displacement angle obtained by calibrating the actual displacement angle VTB with the most retarded learning value GVTFR,
First, the actual displacement angle VTB is calculated.

Here, the actual displacement angle VTB is the actual displacement angle of the intake side camshaft 23 with respect to the crankshaft 14, and is calculated as follows based on the reference timing signal and the displacement timing signal. The most retarded learning value GVTFR is a learned value obtained by learning the most retarded displacement angle of the intake camshaft 23 with respect to the crankshaft 14 as the reference displacement angle of the VVT 50.

First, after the displacement timing signal detected by the cam angle sensor 44 is input to the ECU 70,
A signal interval (pulse interval) until the reference timing signal detected by the crank angle sensor 40 is input to the ECU 70 is measured as time using the engine speed NE. Then, by using the known relationship between the crank angle and the time (engine speed NE), the measured time is converted into the actual displacement angle VTB as the displacement angle of the camshaft with respect to the crankshaft.

Next, the obtained actual displacement angle VTB is calibrated by the most retarded learning value GVTFR, and the calibrated actual displacement angle VT is calculated.
Is calculated. Subsequently, the calibration actual displacement angle V calculated this time
T _i and the previously calculated averaged actual displacement angle VTSM
_The smoothed calibration actual displacement angle VTSM _i at this time is calculated from equation (2) using _i-1 (S220).

Equation (2) VTSM_i= VTSM_i-1+ (VT_i-VTSM_i-1) / N2 Here, n2 determines the degree of smoothing similarly to n1.
This is a smoothing constant, for example, n2 = 8 is used.
VTSM₀VT₀Is used. From equation (2)
As you can see, this time the smoothing calibration actual displacement angle VTSM_i
Is the previously calculated smoothing calibration actual displacement angle VTSM_i-1
The actual displacement angle VT determined this time _iAnd last calculated
Realized calibration actual displacement angle VTSM_i-1Smoothing the difference with
It is calculated by adding a value obtained by dividing by a constant.

Therefore, even if the calibration actual displacement angle VT varies due to the deviation of the pulse detection by the cam angle sensor 44 or the response delay of the VVT 50, the smoothed calibration actual displacement angle VTSM calculated every time is , And can reflect a steady change in VVT50.

Returning to the flowchart shown in FIG. 5, the description of the control switching processing program will be continued. In S20, it is determined whether the target displacement angle VTT is stable. Specifically, the target displacement angle VTT and the smoothed target displacement angle VT
It is determined whether the absolute value of the difference from the TSM is equal to or less than a first predetermined value a. In addition, as the first predetermined value a, for example,
3 ° CA is appropriate.

Here, the relationship between the target displacement angle VTT and the smoothed target displacement angle VTTSM will be described with reference to FIG. FIG. 8 is a time chart showing the relationship between the target displacement angle VTT and the smoothed target displacement angle VTTSM, and the difference between the target displacement angle VTT and the smoothed target displacement angle VTTSM. The vertical axis indicates the displacement angle, and the horizontal axis indicates Indicates time.

Since the smoothed target displacement angle VTTSM changes following the change in the target displacement angle VTT while having a response delay, the difference between the target displacement angle VTT and the smoothed target displacement angle VTTSM is both positive and negative. Can take a value. Then, in S20, it is determined whether or not the absolute value of the difference between the two is equal to or less than the first predetermined value a, that is, whether or not the difference between the two described in the upper part of FIG. Is determined.

When it is determined that the absolute value of the difference between the target displacement angle VTT and the smoothed target displacement angle VTTSM is equal to or smaller than the first predetermined value a (S20: YES), the target displacement angle VTT is stable. And the process proceeds to S30 to determine the next switching condition. on the other hand,
If it is determined that the absolute value of the difference between the target displacement angle VTT and the smoothed target displacement angle VTTSM is larger than the first predetermined value a (S20: NO), the process proceeds to S50, and the control for the VVT 50 is performed. The feedback control process is continuously performed.

In the feedback control processing, it is determined whether or not the absolute value of the difference between the target displacement angle VTT and the calibration actual displacement angle VT is equal to or less than a predetermined value. If it is determined that the absolute value of the difference between the two is greater than a predetermined value,
Further, control is performed to move the spool 84 of the OCV 80 to the advance side or the retard side, and to displace the intake camshaft 23 toward the target displacement angle VTT. On the other hand, when it is determined that the absolute value of the deviation between the two is equal to or smaller than the predetermined value, the calibration actual displacement angle VT is set to the target displacement angle V
It is considered that TT has converged to TT, and control for further displacing the calibration actual displacement angle VT is not executed.

In S30, it is determined whether or not VVT 50 is in a stable operation state. Specifically, it is determined whether or not the absolute value of the difference between the smoothed target displacement angle VTTSM and the smoothed calibration actual displacement angle VTSM is equal to or smaller than a second predetermined value b. As the second predetermined value b, a value smaller than the first predetermined value a, for example, 0.3 ° CA can be used, and it is desirable to use it.

That is, as described above, it is desirable to use a determination value as small as possible in determining whether or not the conventionally-calibrated actual displacement angle VT has converged to the target displacement angle VTT. However, since the target displacement angle VTT, which tends to change due to variations in engine conditions, is used as it is as the convergence target value of the calibration actual displacement angle VT, if the determination value is too small, it may not be possible to determine convergence completion forever. was there.

On the other hand, in the present embodiment, whether or not the target displacement angle VTT is stable is determined in S20. If it is determined that the target displacement angle VTT is stable, the calibration actual The displacement angle VT does not vary under the influence of the variation of the target displacement angle VTT. Also, unlike the conventional case, the calibration actual displacement angle VT and the target displacement angle V
The convergence determination of the VVT 50 is performed using the smoothed target displacement angle VTTSM and the smoothed calibrated actual displacement angle VTSM that have a gradual change with respect to time as compared with TT.

This will be described with reference to FIG.
Here, FIG. 10 is a time chart showing a change in the smoothed calibration actual displacement angle VTSM with respect to a change in the smoothed target displacement angle VTTSM. The vertical axis shows the transition angle, and the horizontal axis shows time. As can be understood from this figure, the smoothed target displacement angle VTT corresponds to the degree of change of the target displacement angle VTT and the calibration actual displacement angle VT with respect to time.
The degree of change of the SM and the smoothed calibration actual displacement angle VTSM with respect to time is gradual. Therefore, the VVT50 is determined using a small value as the second predetermined value b for determining convergence.
Can be determined. By using the smaller second predetermined value b, the convergence of the VVT 50 can be determined with higher accuracy.

Then, the absolute value of the difference between the smoothed target displacement angle VTTSM and the smoothed calibration actual displacement angle VTSM is calculated as the second value.
If it is determined that the value is larger than the predetermined value b (S30: N
O), the step moves to S50, and the above-described feedback control processing is executed on the VVT 50. On the other hand, the smoothed target displacement angle VTTSM and the smoothed calibration actual displacement angle V
If it is determined that the absolute value of the difference from the TSM is equal to or smaller than the second predetermined value b (S30: YES), the process proceeds to S4.
0, and the holding control process is performed on the VVT 50.

The holding control process is a control for holding the displacement angle of the VVT 50, that is, the displacement angle of the intake camshaft 23, at a predetermined displacement angle.
In this embodiment, the smoothed calibration actual displacement angle VTSM
However, since the holding control is executed when the averaged target displacement angle VTTSM converges, the corrected actual displacement angle VT is held at the target displacement angle VTT at the time of convergence. Hereinafter, the holding control process will be briefly described.

When the VVT 50 is displaced to the target displacement angle VTT, the duty ratio DVT output to the OCV 80 becomes the duty ratio D that displaces the VVT 50.
Switching from VT to the holding duty ratio DVTH for stopping the displacement of the VVT 50 and holding the displacement angle is performed.
The holding duty ratio DVTH is predetermined as a duty ratio DVT corresponding to a position where the spool 84 of the OCV 80 closes the A port 85a and the B port 85b, and also eliminates errors due to component tolerance, aging, and the like. , Has been updated by learning.

When the holding duty ratio DVTH is output to the OCV 80, the spool 84 of the OCV 80
Is driven at a position where the A port 85a and the B port 85b are closed. As a result, the displacement angle of the VVT 50 is held at the displacement angle immediately before the start of the holding control, that is, the target displacement angle VTT, without being shifted to the advance side or the retard side.

As described above in detail with reference to each embodiment, the valve timing control device VC for an internal combustion engine according to the above embodiment has the absolute value of the difference between the smoothed target displacement angle VTTSM and the target displacement angle VTT set to the first value. Less than or equal to a predetermined value a,
When the absolute value of the difference between the smoothed target displacement angle VTTSM and the smoothed calibration actual displacement angle VTSM is equal to or smaller than the second predetermined value b, the control process for the VVT 50 is switched from the feedback control process to the holding control process. It has.

Therefore, in the switching from the feedback control processing to the holding control processing of the control processing for the VVT 50, the condition for determining the switching can be made strict, and the accuracy of the valve timing control can be improved. As a result, it is possible to suppress the emission, particularly, the variation of NO _X due to the internal EGR difference. Further, since the valve timing control appropriate for the engine condition can be executed, it is possible to supply the currently necessary optimum intake air amount to the combustion chamber, and it is possible to suppress variations in engine output characteristics.

That is, unlike the related art in which control switching is determined simply based on whether the absolute value of the difference between the target displacement angle VTT and the calibration actual displacement angle VT is equal to or smaller than a predetermined value, first, the target displacement angle VTT It is determined whether or not is stable. Therefore, when it is determined that the target displacement angle VTT is stable, the calibration actual displacement angle VT affected by the variation of the target displacement angle VTT is also stabilized, and the target displacement angle VTT and the calibration actual displacement angle VT The judgment value for judging the difference can be made a small value.

Further, control switching is not determined simply based on whether the difference between the target displacement angle VTT and the calibration actual displacement angle VT is equal to or less than a predetermined value, and the smoothing target displacement angle VTTSM and the smoothing calibration actual displacement angle VTSM are not determined. Is determined based on whether or not the difference is equal to or less than a second predetermined value.

Here, the target displacement angle VTT and the calibrated actual displacement angle VT are numerical values directly affected by the engine condition, and are affected by instantaneous variations in the engine condition at each moment. On the other hand, the smoothed target displacement angle VTTSM and the smoothed calibration actual displacement angle V
In the calculation, the TSM takes into account the previous engine condition and is not directly affected by the engine condition, so it can be said that the TSM indicates a more steady engine condition.

Therefore, even if a value smaller than the first predetermined value a is used as the second predetermined value b, the smoothed calibration actual displacement angle VTSM can be made to converge to the smoothed target displacement angle VTTSM. If a smaller value is used as the second predetermined value b, the switching from the feedback control processing of the control processing for the VVT 50 to the holding control processing can be performed with higher accuracy.

In the present invention, various modifications and improvements can be made without departing from the gist of the present invention. For example, in the above-described embodiment, a configuration is provided in which the valve overlap period is changed by variably controlling the valve timing of the intake valve 21. However, the valve overlap period may be changed by variably controlling the valve timing of the exhaust valve 31 or variably controlling the valve timing of the intake valve 21 and the exhaust valve 31.

In any case, the valve overlap period is changed, and the method may be adopted so that desired engine characteristics can be obtained. Further, in the above embodiment, the averaging process is performed on the target displacement angle VTT and the calibration actual displacement angle VT according to the equations (1) and (2), but the averaging process is performed using other equations. Is also good. Further, the annealing constants n1 and n2 are not limited to the numerical values exemplified in the above embodiment.

Further, although the actual displacement angle VTB detected by the cam angle sensor 44 is calibrated by the actual displacement angle VT calibrated by the maximum retardation learning value GVTFR, the actual displacement angle VTB is used in the VVT 50 where the maximum retardation angle learning is not performed. The displacement angle VTB may be used. In this case, the actual displacement angle VTB is still affected by the target displacement angle VTT.
This is because it is necessary to strictly determine the control switching.

Further, as the VVT 50, the intake side camshaft 23 with respect to the crankshaft 14 is
Is used to change the valve timing of the intake valve 21. However, the displacement angle of the intake camshaft 23 with respect to the crankshaft 14 may be displaced by another driving means such as a step motor.

That is, in any case, the feedback control process for displacing the displacement angle of the intake camshaft 23 to the target displacement angle VTT,
This is because the holding control process for holding the target displacement angle at the target displacement angle VTT is still executed, and it is necessary to improve the accuracy of the valve timing control.

The technical ideas other than the claims which can be understood from the above embodiments will be described below together with their effects. (1) In the valve timing control device for an internal combustion engine according to claim 1, the valve timing control switching means includes:
First, it is determined whether or not the absolute value of the difference between the target valve timing and the smoothed target valve timing is equal to or less than a first predetermined value. Next, the smoothed target valve timing and the smoothed actual valve timing are determined. The absolute value of the difference with the second
A valve timing control device for an internal combustion engine, which determines whether or not the value is equal to or less than a predetermined value.

In the case where such a configuration is provided, the valve timing control switching means first determines whether or not the absolute value of the difference between the target valve timing and the smoothed target valve timing is equal to or less than a first predetermined value. Next, it is determined whether or not the absolute value of the difference between the target valve timing and the actual valve timing is equal to or less than a second predetermined value. Therefore, after the target valve timing is stabilized, it is determined whether or not the actual valve timing has converged to the target valve timing, and the control accuracy for the variable valve timing mechanism can be further improved.

(2) In the valve timing control device for an internal combustion engine according to claim 1 or (1), the second predetermined value used in the valve timing control switching means is also used in the valve timing control switching means. A valve timing control device for an internal combustion engine, wherein the valve timing control device is set to a value smaller than a first predetermined value.

With this configuration, it can be determined more strictly whether or not the actual valve timing has converged to the target valve timing, and the control accuracy of the variable valve timing mechanism can be improved.

(3) In the valve timing control device for an internal combustion engine according to any one of (1), (1), and (2), the variable valve timing mechanism is a variable valve driven by hydraulic pressure. A valve timing control device for an internal combustion engine, which is a timing mechanism.

The provision of such a configuration has the advantage that the variable valve timing mechanism can be driven by using the lubricating oil of the internal combustion engine.

[0118]

As described above, according to the valve timing control apparatus for an internal combustion engine according to the first aspect of the present invention, control of the variable valve timing mechanism is converged using the smoothed target valve timing and the smoothed actual valve timing. A configuration is provided in which switching from control to holding control is determined, and switching is performed.

Therefore, the control accuracy of the variable valve timing mechanism can be improved, and the variation in emission and the variation in output characteristics can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram showing a basic conceptual configuration of a valve timing control device for an internal combustion engine according to the present invention.

FIG. 2 is a system configuration diagram showing a schematic configuration of a gasoline engine system to which the present invention is applied.

FIG. 3 is a schematic configuration diagram of a variable valve timing mechanism system.

FIG. 4 is a control block diagram in the valve timing device of the internal combustion engine.

FIG. 5 is a flowchart showing a main routine of a control switching program.

FIG. 6 is a flowchart of a smoothed target displacement angle VTTSM calculation program executed in another routine.

FIG. 7 is a flowchart of a smoothing actual displacement angle VTSM calculation program executed in another routine.

FIG. 8 shows a target displacement angle VTT and a smoothed target displacement angle V.
6 is a time chart showing a relationship with TTSM.

FIG. 9 is a time chart for explaining the behavior of the smoothed target displacement angle VTT with respect to the target displacement angle VTT.

FIG. 10 is a time chart showing a relationship between a target displacement angle VTT and a calibration actual displacement angle VT.

FIG. 11 is a map showing a relationship between an intake pressure and a target displacement angle VTT for determining a target displacement angle VTT of a variable valve timing mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Engine, 14 ... Crankshaft, 15 ... Combustion chamber, 20 ... Intake passage, 21 ... Intake valve, 22 ... Intake port, 23 ... Intake side camshaft, 26 ... Throttle valve, 30 ... Exhaust passage, 40 ... Crank angle Sensor, 44
... Cam angle sensor, 46 ... Intake pressure sensor, 50 ... VV
T, 70: ECU, 71: ROM, 73: RAM, M2
... combustion chamber, M5 ... intake side camshaft, M6 ... exhaust side camshaft, M8 ... target valve timing determination means, M
9: smoothed target valve timing calculating means, M10: variable valve timing mechanism, M11: valve timing detecting means, M12: smoothed actual valve timing calculating means,
M13: valve timing convergence control means, M14: valve timing holding control means, M15: valve timing control switching means, VC: valve timing control device for an internal combustion engine.

Claims (1)

(57) [Claims] 1. An intake valve and an exhaust valve for respectively opening and closing an intake passage and an exhaust passage leading to a combustion chamber of an internal combustion engine, an operating state detecting means for detecting an operating state of the internal combustion engine, and an operating state detecting means thereof Target valve timing determining means for determining a target valve timing according to the operating state of the internal combustion engine detected by the engine, and a smoothed target valve timing is calculated based on the target valve timing determined by the target valve timing determining means. A variable valve timing mechanism for changing at least one of the intake valve and the exhaust valve, and a variable valve timing mechanism on the side where the variable valve timing mechanism is disposed. For detecting the actual valve timing of the valve Controlling the variable valve timing mechanism, based on the actual valve timing detected by the valve timing detection means, and based on the actual valve timing detected by the valve timing detection means. Valve timing convergence control means for causing the actual valve timing to converge to the target valve timing; and valve timing holding control means for controlling the variable valve timing mechanism to hold the actual valve timing at a predetermined valve timing. Determining that the absolute value of the difference between the target valve timing and the smoothed target valve timing is equal to or less than a first predetermined value, and determining the difference between the smoothed target valve timing and the actual smoothed valve timing. Absolute value is greater than first predetermined value
If it is determined that the value is also equal to or smaller than the second predetermined value having a small numerical value, the valve timing for switching the control of the variable valve timing mechanism from the convergence control by the valve timing convergence control means to the holding control by the valve timing holding control means. A valve timing control device for an internal combustion engine, comprising: control switching means.