JPH09303165A - Valve characteristic control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform excellent combustion of an internal combustion engine by a method wherein when fuel is adhered on a deposit accumulated on the intake system of an engine, the valve characteristics of a VVT(Variable Valve Timing mechanism) is varied according to a deposit amount, in an internal combustion engine having the VVT. SOLUTION: An ECU 80 detects the operation state of an engine 1 by a throttle sensor 72 and an intake air sensor 7, the concentration of oxygen in exhaust gas is detected by an oxygen sensor 75. Based on the detecting value, an air-fuel ratio during acceleration operation of air-fuel mixture fed in the engine 1 is computed at a given timing, and an estimated adhesion amount of deposit is learned. The ECU 80 varies the target displacement angle of a variable valve timing mechanism 25 to the angle of lag side and an angle of lead speed is delayed. This constitution prevents the occurrence of knocking due to adhesion of the deposit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine equipped with a variable valve timing mechanism, which is intended to solve the problem that occurs when fuel adheres to a deposit accumulated in the intake system of the engine. It relates to the device.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection type internal combustion engine (engine), in order to optimize various performances such as output performance, exhaust characteristics, drivability, etc. according to various operating conditions, a mixture supplied to the engine is mixed. The air-fuel ratio, that is, the air-fuel ratio, is controlled.
This control is performed by controlling the fuel supply amount to the engine so that the actual air-fuel ratio matches a target air-fuel ratio that can change depending on the engine speed, load condition, warm air condition, and the like.

[0003]

However, in such an engine, not all of the fuel injected from the fuel injection valve (injector) is taken into the combustion chamber. Actually, a part of the injected fuel adheres to the intake port, intake valve, piston, etc. of the intake system downstream of the injector. The amount of fuel adhered depends on the state of the intake system, and the deposit is one of the major factors.
The deposit is a substance such as carbon fine particles derived from blow-by gas or lubricating oil and deposited in the intake system, and has a property of adsorbing fuel.

By the way, a variable valve timing mechanism (VVT) for changing valve characteristics (valve timing, valve lift amount, etc.) of an intake valve or an exhaust valve according to an operating state (load, rotational speed, etc.) of an internal combustion engine (engine). It has been known. The VVT makes it possible to optimize the amount of air taken into the combustion chamber through the intake passage in accordance with the operating condition of the engine, and improve the fuel efficiency, output and emission of the engine over a wide range of changes in the operating condition. In an internal combustion engine equipped with such a mechanism, the following problems occur due to the deposit.

(1) Especially when the VVT valve characteristic is drastically changed, such as during transient operation of engine acceleration and deceleration, the volumetric efficiency is also drastically changed. However, if the amount of fuel adsorbed in the deposit is large, the fuel supply for compensating for the adsorbed amount is delayed, a rapid change in volume efficiency cannot be followed, and the engine becomes lean locally and knocking easily occurs.

(2) When deposits are accumulated in the piston and the combustion chamber, the volume of the combustion chamber is reduced, and the compression ratio becomes higher than that when the deposits are not accumulated. Therefore,
If there is no treatment, knocking will occur easily. In this case, it is possible to suppress it by detecting the knock with the knock sensor and shifting the ignition timing of the spark plug, but on the contrary, the fuel consumption deteriorates.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is an internal combustion engine equipped with a VVT and a valve of the VVT when fuel adheres to a deposit accumulated in an intake system of the engine. The characteristics are changed according to the amount of deposit to enable good combustion of the internal combustion engine.

[0008]

In order to achieve the above object, according to the invention of claim 1, a variable valve timing mechanism capable of adjusting the operation timing of at least one of an intake valve and an exhaust valve, and an internal combustion engine. Operating state detecting means for detecting the operating state of the engine, concentration detecting means for detecting the concentration of a specific component of the exhaust gas discharged from the internal combustion engine to the exhaust system thereof, the operating state detecting means and the concentration detecting A deposit amount learning means for calculating the air-fuel ratio during transient operation of the air-fuel mixture supplied to the internal combustion engine based on the detection result of the means, and learning the estimated deposit amount of the deposit in the intake system based on the result. And an opening / closing characteristic changing means for changing the opening / closing characteristic of the variable valve timing mechanism based on the learning value of the deposit amount learning means. Therefore, the deposit amount learning unit learns the estimated deposit amount of deposit based on the detection results of the operating state detecting unit and the concentration detecting unit. The opening / closing characteristic changing means changes the opening / closing characteristic of the variable valve timing mechanism using the learned value as a correction value.

Further, in the invention of claim 2, in addition to the configuration of the invention of claim 1, the target displacement angle of the variable valve timing mechanism is retarded based on the learning value updated by the deposit amount learning means. I configured it to change. Therefore, although the volume of the combustion chamber decreases due to the accumulation of deposits and the compression ratio becomes high, the target displacement angle is changed to the retard side by using the learning value learned by the deposit amount learning means as a correction value to lower the compression ratio. And make adjustments.

Further, in the invention of claim 3, the invention of claim 1 or 2
In addition to the configuration of the present invention, the advance angle speed of the variable valve timing mechanism in the acceleration operation state is delayed based on the learning value updated by the deposit amount learning means. That is, in the acceleration operation state where the volumetric efficiency rapidly increases, the fuel is adsorbed by the deposit and the supply is delayed, so that the increase in the volumetric efficiency cannot be followed and the air-fuel ratio becomes locally lean. Therefore, the learning speed learned by the deposit amount learning means is used as a correction value to delay the advance speed to follow the rapid increase in the volumetric efficiency.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment in which the valve characteristic control device for an internal combustion engine according to the present invention is embodied in a gasoline engine system for an automobile will be described in detail below with reference to FIGS.

FIG. 1 is a schematic configuration diagram showing a gasoline engine system according to a valve characteristic control device of this embodiment. The engine 1 as an internal combustion engine includes a plurality of cylinders 2. The cylinder 2 is composed of a cylinder block 2a and a cylinder head 2b. A piston 3 provided in each cylinder 2 is connected to a crankshaft 1a and is vertically movable in each cylinder 2. In each cylinder 2, the upper side of the piston 3 forms a combustion chamber 4. The ignition plugs 5 provided for each of the combustion chambers 4 ignite a mixture of air and fuel introduced into the combustion chambers 4. Each of the intake port 6a and the exhaust port 7a provided corresponding to each combustion chamber 4 constitutes a part of the intake passage 6 and the exhaust passage 7. Each of the intake valve 8 and the exhaust valve 9 provided in each combustion chamber 4 selectively opens and closes each port 6a, 7a. These valves 8, 9
Each of which operates based on the rotation of a different camshaft 10, 11. The timing pulleys 12 and 13 provided at the tips of the camshafts 10 and 11 are connected to the crankshaft 1 a via a timing belt 14.

When the engine 1 is in operation, the torque of the crankshaft 1a is generated by the timing belt 14 and the pulleys 1.
It is transmitted to the camshafts 10 and 11 via 2 and 13. The valves 8 and 9 are operated in accordance with the rotation of the camshafts 10 and 11. Each of the valves 8 and 9 is operable in synchronization with the rotation of the crankshaft 1a, that is, at a predetermined valve timing and a valve lift corresponding to the vertical movement of each piston 3.

The air cleaner 15 provided at the inlet of the intake passage 6 cleans the outside air taken into the passage 6.
The injectors 16 provided near the respective intake ports 6a inject fuel toward the intake ports 6a.
During operation of the engine 1, outside air is taken into the intake passage 6 via the air cleaner 15. Further, the air-fuel mixture explodes and burns when the spark plug 5 is activated. As a result, the piston 3 operates, the crankshaft 1a rotates, and an output is obtained for the engine 1. The exhaust gas after combustion is exhausted by the exhaust valve 9 through the exhaust port 7 in the exhaust stroke.
When a is opened, it is led out of the combustion chamber 4 and led to the exhaust passage 7. Then, it is purified by the catalyst 19 and discharged to the outside.

The throttle valve 17 provided in the intake passage 6 operates in conjunction with the operation of an accelerator pedal (not shown). By adjusting the opening of the valve 17, the amount of outside air taken into the intake passage 6, that is, the intake air amount QA is adjusted. A surge tank 18 is provided downstream of the throttle valve 17. The surge tank 18 smoothes the pulsation of intake air. Air cleaner 15
The intake air temperature sensor 71 provided near the
And outputs a signal corresponding to the detected value. Throttle sensor 7 provided near the throttle valve 17
Reference numeral 2 detects the opening (throttle opening) TA of the valve 17 and outputs a signal corresponding to the detected value. The intake pressure sensor 73 provided in the surge tank 18 is
The pressure (intake pressure) PM of the intake air at is detected, and a signal corresponding to the detected value is output. Cylinder block 2
A water temperature sensor 74 is provided in a. Water temperature sensor 7
4 is the temperature TH of the cooling water for cooling the cylinder block 2a
W is detected and a signal corresponding to the detected temperature is output. An oxygen sensor 7 as a concentration detecting means is provided in the middle of the exhaust passage 7.
5 are provided. The oxygen sensor 75 detects the concentration Ox of oxygen remaining in the exhaust gas and outputs a signal corresponding to the detected concentration.

The distributor 21 is the igniter 2
The high voltage output from 2 is distributed to the spark plugs 5 to activate each spark plug 5. Therefore, the timing at which each ignition plug 5 is operated is determined by the timing at which the igniter 22 outputs a high voltage.

A rotor (not shown) built in the distributor 21 is rotated by a camshaft 11 that rotates in synchronization with the crankshaft 1a. Rotation speed sensor 76 provided in distributor 21
Detects the engine rotation speed NE based on the rotation of the rotor and outputs the detected value as a pulse signal. The cylinder discrimination sensor 78 provided in the distributor 21 detects the reference position GP of the crank angle CA at a predetermined rate according to the rotation of the rotor, and also outputs the predetermined value as a pulse signal. In this embodiment, the crankshaft 1a makes two rotations for a series of four strokes of the engine 1. While the crankshaft 1a rotates twice, the rotation speed sensor 76 outputs a signal of 1 pulse at 30 ° CA.
The cylinder discrimination sensor 77 outputs a signal of one pulse every 360 ° CA.

A cam sensor 78 provided on the camshaft 10 detects an actual displacement angle (actual displacement angle) VT related to the rotation of the camshaft 10 and outputs a signal corresponding to the detected value. The cam sensor 78 includes a plurality of projections arranged at equal angular intervals on the camshaft 10, and a pickup coil arranged to be able to face each projection.
When the camshaft 10 rotates and each projection crosses the pickup coil, the coil generates an electromotive force.
The cam sensor 78 outputs the electromotive force as a pulse signal indicating the actual displacement angle VT.

The variable valve timing mechanism (hereinafter referred to as "VVT") 25 of the present invention provided on the timing pulley 12 is driven by hydraulic pressure to advance the valve timing as a valve characteristic of the intake valve 8. Or delay. Oil pan 28, oil pump 29, and oil filter 3 provided in the engine 1
0 and the like constitute a lubricating device for lubricating each part of the engine 1. This lubricating device supplies hydraulic pressure to the VVT 25 in order to drive the VVT 25. Oil control valve (OC
V) 55 makes it possible to adjust the hydraulic pressure supplied to the VVT 25. By operating the oil pump 29 in conjunction with the operation of the engine 1, the lubricating oil sucked up from the oil pan 28 is discharged by the oil pump 29. The discharged lubricating oil passes through the oil filter 30, is selectively pumped by the OCV 55, and is supplied to the VVT 25.

FIG. 2 is a sectional view showing the structure of the VVT 25. The cam shaft 10 is rotatably supported by the cylinder head 2b. Pulley 12 on camshaft 10
Is mounted, and the pulley 12 is rotatable relative to the camshaft 10. The bottomed cylindrical cover 35 fixed to the pulley 12 has a flange 39 on its outer periphery.
And has a hole 40 in the center of the bottom. Multiple bolts 41
And the pin 42 fixes the flange 39 to one side surface of the pulley 12. The lid 43 attached to the hole 40 is removable. The cover 35 has internal teeth 35a on its inner periphery.

Hollow bolts 46 and pins 47 fix the inner cap 45 to the tip of the camshaft 10. The cap 45 has external teeth 45a on its outer periphery. Cover 35
And the ring gear 48 interposed between the cap 45 and
Both are relatively rotatable with respect to 35 and 45. The ring gear 48 has internal teeth 48a and external teeth 48b formed of helical splines on its inner circumference and outer circumference, respectively. The internal teeth 48a mesh with the external teeth 45a of the cap 45, and the external teeth 48b mesh with the internal teeth 35a of the cover 35.

Inside the cover 35, the ring gear 4
The first hydraulic chamber 49 and the second hydraulic chamber 50 formed on the left and right sides of FIG. 8 respectively communicate with oil passages 51 and 53 formed inside the camshaft 10.

The belt 14 is the pulley 1 of the camshaft 10.
2 and the pulley 12 of the crankshaft 1a are connected.
As the crankshaft 1a rotates, the belt 1
The pulley 12 rotates via 4 and the like. The rotation of the pulley 12 causes the cap 45 to pass through the ring gear 48.
And the camshaft 10 rotates integrally with the pulley 12.

Here, through the oil passage 51, the first hydraulic chamber 4
By supplying the hydraulic pressure to 9, the hydraulic pressure is applied to the ring gear 48. Based on the hydraulic pressure, the ring gear 48
Rotates while moving to the right in the drawing in the axial direction of the camshaft 10. At this time, the rotation phase changes relatively between the camshaft 10 and the pulley 12. in this case,
The rotation phase of the camshaft 10 leads that of the pulley 12. As a result, the valve timing phase of the intake valve 8 leads the rotational phase of the crankshaft 1a.

In this case, as shown in FIG. 3B, the valve timing of the intake valve 8 is relatively advanced, and the valve overlap in the intake stroke is relatively large. In this way, by controlling the hydraulic pressure supplied to the first hydraulic chamber 49, the ring gear 48 shown in FIG. 2 can be moved to the end position approaching the timing pulley 12. When the ring gear 48 reaches its end position,
The valve timing of the intake valve 8 is the most advanced, and the valve overlap is the largest.

On the other hand, when the ring gear 48 is moved to the right in the drawing, the hydraulic pressure is supplied to the second hydraulic chamber 50 through the oil passage 53, so that the hydraulic pressure is applied to the ring gear 48. The ring gear 48 moves leftward in the axial direction of the camshaft 10 based on the hydraulic pressure. At this time, the rotation phase between the camshaft 10 and the pulley 12 relatively changes in the opposite direction. In this case, the rotation phase of the camshaft 10 lags behind that of the pulley 12. As a result, the valve timing of the intake valve 8 lags behind the rotation phase of the crankshaft 1a.

In this case, as shown in FIG. 3A, the valve timing of the intake valve 8 is relatively delayed, and the valve overlap in the intake stroke is relatively small. In this way, by controlling the hydraulic pressure supplied to the second hydraulic chamber 50, the ring gear 48 shown in FIG.
It can be moved to the end position approaching 5. When the ring gear 48 reaches the end position, the valve timing of the intake valve 8 is delayed most.

In this embodiment, the OCV 55 controls the supply of hydraulic pressure to the hydraulic chambers 49, 50. Here, the ring gear 48 moves to the left side of the drawing or the right side of the drawing by appropriately controlling the balance of the hydraulic pressures in the hydraulic chambers 49 and 50. Alternatively,
At the intermediate position on the moving stroke, the ring gear 4
8 is retained. As a result, the VVT 25 is appropriately controlled and the valve timing of the intake valve 8 is continuously (stepless) from the position shown in FIG. 3A to the position shown in FIG. 3B.
Can be changed to That is, by operating the VVT 25, the phase of the intake valve 8 can be changed within the range of 0 to 60 ° CA. In this embodiment, the valve timing is controlled by controlling the OCV 55 based on the value of the required drive duty ratio DVT.

Here, the ECU (electronic control unit) 80 inputs signals output from the various sensors 71 to 78 described above. The ECU 80 controls the injector 16, the igniter 22, the OCV and the like based on those input signals.

As shown in the block diagram of FIG. 4, the ECU 8
0 is a central processing unit (CPU) 81, a read only memory (ROM) 82 and a random access memory (RAM)
83, a backup RAM 84 and the like. ECU80
Constitutes a logical operation circuit in which these units 81 to 83, an external input circuit 85 including an A / D converter, an external output circuit 85 and the like are connected by a bus 86. CPU81 is R
The control program stored in the OM 82 is executed. RO
M82 stores in advance a predetermined control program, function data, etc., for example, a control program for controlling valve timing. The RAM 83 temporarily stores the calculation result of the CPU 81 and the like. Each of the above-mentioned sensors 71 to 78
Is connected to the external input circuit 85. Each member 1 described above
6, 22, 55 are connected to the external output circuit 86. The backup RAM 84 stores various data in the RAM 83 so that the data is not erased even when the power supply to the ECU 80 is stopped. The CPU 81 reads the signals of the sensors 71 to 78 input via the external input circuit 85 as input values. Then, the injector 16 and the igniter 2
2 and OCV are operated to control fuel injection, ignition timing,
Executes valve timing control, etc.

Next, of various processes executed by the CPU 81, a "deposit amount learning routine" for calculating the deposit amount learning value KDPC will be described with reference to FIG. In this embodiment, the amount of deposit increasing with time is learned in a lean state in which the engine is in an accelerating state and the air-fuel ratio A / F is compared with the target air-fuel ratio. The CPU 81 periodically executes this routine at predetermined time intervals. Further, the deposit amount learning value KDPC is set to 0 as an initial value.

In step 100, the CPU 81 determines whether the engine 1 is in an accelerating state. That is, the CPU 81 determines the acceleration state of the engine 1 by the throttle opening T detected by the sensors 72, 73 and 76.
The determination is made based on the values of A, the intake pressure PM, the engine speed NE, and the like. When the CPU 81 determines that the vehicle is in the accelerated state, it shifts the processing to step 110. In step 110, the CPU 81 determines whether the air-fuel ratio A / F is lean by comparing with the target air-fuel ratio based on the value of the oxygen concentration Ox detected by the oxygen sensor 75.

When the air-fuel ratio A / F is lean, the CPU 81 increments the deposit amount learning value KDPC by "1" in step 120.
Then, in step 120, the updated deposit amount learning value KDPC is stored in the backup memory 84.
On the other hand, when it is determined in step 100 that the vehicle is not in the acceleration state, or in step 110, the air-fuel ratio A / F
When it is determined that is not lean, the deposit amount learning value KDPC is not updated and the previous value is held. In the present embodiment, the CPU 81 that executes the processing of this "deposit amount learning routine" corresponds to the deposit amount learning means of the present invention.

On the other hand, the CPU 81 controls the VVT by using the deposit amount learning value KDPC updated in the deposit amount learning routine of FIG. 5 as a correction parameter. The “VVT control routine” will be described with reference to FIGS. 6 and 7.
The CPU 81 periodically executes this routine at predetermined time intervals.

In step 200, the CPU 81 sets V
It is determined whether the VT target displacement angle has changed. Here, the VVT target displacement angle is a value calculated in order to optimize the valve overlap according to the operating state of the engine 1. The CPU 81 refers to the map stored in the ROM 82, and calculates the VVT target displacement angle using the throttle opening TA, the intake pressure PM, the engine speed NE, etc. as parameters.

When the CPU 81 determines that the VVT target displacement angle has changed, that is, the operating conditions have changed, step 21
At 0, it is determined whether the deposit amount learning value KDPC is larger than the threshold value n. Here, the threshold value n is a value that can be ignored if the deposit amount learning value KDPC is less than this. The threshold value n is variable and may be zero. CPU81 is a deposit amount learning value KDPC
Is greater than the threshold n, step 22
At 0, it is determined whether the engine 1 is in the acceleration state. This determination is based on the process of step 100 of the "deposit amount learning routine". When it is determined that the engine 1 is accelerating, the CPU 81 determines in step 230 that the VVT advance rate (VVTSP) to the VVT target displacement angle.
The value of D) is calculated according to the following formula.

VVTSPD = VVTSPD0 * 1 / KDPC That is, the CPU 81 sets V to the previous VVT target displacement angle.
By multiplying VT advance velocity 0 by the reciprocal of the updated latest deposit amount learning value KDPC, the current VVT advance velocity with the corrected deposit amount is calculated. here,
The VVT advance speed is a speed until a new VVT target displacement angle is reached when the operating condition is changed, for example, when the low load operating state is changed to the high load operating state.

On the other hand, in step 220, the engine 1
If it is determined that is not in the acceleration state, the CPU 81 determines in step 240 whether it is in the steady operation state. C
If the PU 81 determines that it is in a steady operation state, step 250
In, the VVT target displacement angle (VVTB) is calculated according to the following formula.

VVTB = VVTB0 * 1 / KDPC That is, the CPU 81 multiplies the previous VVT target displacement angle 0 by the reciprocal of the updated latest deposit amount learning value KDPC to correct the deposit amount V for this time.
Calculate the VT target displacement angle. CPU81 is step 26
At 0, the current VVT advance rate and the VVT target displacement angle obtained in steps 230 and 250 are stored in the backup RAM 84. Then, the CPU 81 determines in step 270 the current VVT target displacement angle and VVT.
The control is executed based on the value of the advance speed. In the present embodiment, the CPU 81 that executes the processing of step 220 and step 240 corresponds to the transient state detecting means of the present invention.

Here, VV in the case where the conventional deposit amount learning value KDPC is not corrected in a certain operating state
The concept of T control is shown by the solid line in FIG. That is, in this conventional VVT control, at the VVT target displacement angle P1 (T1-
T0) Run for steady operation for a time. Next, under a predetermined load, the acceleration operation state is entered, and after (T2-T1) time, P
When the VVT target displacement angle of 2 is reached and the load is maintained, the vehicle shifts to the steady operation traveling again.

By the way, during acceleration operation, the VVT advance rate changes abruptly in order to increase the valve overlap amount. That is, the volumetric efficiency of the engine 1 increases with the advance of the VVT, and the fuel supply amount also increases. In this conventional VVT control, the CPU controls the VVT corresponding to a predetermined load.
The advance speed t1 is calculated based on various parameters. However, when the deposit is accumulated, the fuel is adsorbed to the deposit, and the balance between the fuel supply rate according to the volume efficiency and the VVT advance rate calculated by the CPU is lost. That is, the air-fuel mixture supplied to the combustion chamber with respect to the target air-fuel ratio becomes locally lean. Therefore,
There was a case where the ignition timing of the required spark plug was displaced and knocking occurred.

Further, when the deposit is accumulated in the piston or the combustion chamber, the volume of the combustion chamber is reduced, and the compression ratio becomes higher than that in the case where the deposit is not accumulated. Especially in recent engines, the ignition timing of the spark plug is advanced to near the limit at which knocking occurs in order to improve high output and fuel efficiency. Therefore, in the conventional VVT control in which the increase in the compression ratio due to the accumulation of deposits is not taken into consideration, knocking occurs beyond the limit.

On the other hand, the concept of the VVT control of the present embodiment corrected by the deposit amount learning value KDPC under the operating condition under the same conditions is shown by the broken line in FIG. In the VVT advance rate t2 in the VVT control of the present embodiment, step 2 is performed.
By the processing of 30, the VVT advance angular velocity t1 is compared and delayed. That is, although the displacement amount is almost the same as that of the conventional VVT control until the target VVT displacement angle is reached, the displacement time is lengthened by (T3-T2) time. Therefore, the VVT advance rate is also delayed in accordance with the fuel supply speed delay due to the adsorption of fuel to the deposit, so that the air-fuel ratio A / F does not become lean and knocking hardly occurs during the acceleration operation.

Further, by the processing of step 250, VV
The T target displacement angle changes from P1 to p1 during the (T1-T0) time, and from P2 to p2 after the (T3 + n) time.
Is changed to the retard side. Therefore, since the compression ratio decreases, knocking is prevented from occurring during steady operation. In the VVT control of this embodiment, (T2-T
1) Since the processing of step 240 is performed by the acceleration in time and the VVT target displacement angle is delayed from the previous time, strictly speaking, (P1-p1)> (P2-p2).

On the other hand, the CPU 81 sends VV in step 200.
When it is determined that the T target displacement angle has not changed, the previous VVT advance angular velocity and the VVT target displacement angle are held in step 280, and the process proceeds to step 260. Also, CPU
81, when it is determined in step 210 that the deposit amount learning value KDPC is equal to or less than the threshold value N, the process proceeds to step 280 similarly. If it is determined in step 240 that the operation is not in the steady operation state, that is, if it is in the deceleration operation state, the CPU 81 performs other processing in step 290.
In the present embodiment, the CPU 81 that executes the processing of this "deposit amount learning routine" corresponds to the opening / closing characteristic changing means of the present invention.

As described above, the valve characteristic control device for an internal combustion engine according to the present embodiment has the following effects. (1) Since the CPU 81 slows down the VVT advancing speed on the basis of the deposit amount learning value KDPC during the acceleration operation, it is possible to perform optimum control on the VVT 25 according to the deposit amount, which is a conventional problem. It prevents the occurrence of knocking. Further, since the CPU 81 changes the VVT target displacement angle based on the deposit amount learning value KDPC during the steady operation, the VV
It is possible to perform optimum control on T25 according to the deposit adhesion amount, and prevent the occurrence of knocking, which has been a problem in the past. Especially for deposit amount, step 1
The latest learning value KDPC is always obtained by the deposit amount learning routine from 0 to 130, and the optimum learning value KDPC corresponding to the estimated deposit amount is used as the correction value.

(2) The learning amount KDPC of the deposit amount is constantly updated from the previous learning value KDPC and the backup RAM 8
Even if the engine 1 is once stopped, it can be controlled with the latest learning value KDPC at the next operation because it is stored in No. 4.

(3) The deposit amount learning value KDPC is controlled not to be a parameter up to the threshold value n in step 210. Therefore, if a certain amount of deposit is not accumulated, control that ignores the deposit amount is also possible.

The present invention can be embodied in the following other embodiments. In the following another embodiment, the same operation and effect as the above embodiment can be obtained. (1) In the above embodiment, the deposit amount learning value KDPC
The VVT advance rate and the VVT target displacement angle corrected based on the above are stored in the backup RAM 84 in step 260. This is the backup RAM8
It may be executed directly without being stored in the memory 4. This improves the processing speed of the CPU 82.

(2) In the above embodiment, the valve timing of the intake valve 8 is changed as the valve characteristic. On the other hand, only the valve timing of the exhaust valve 9 may be changed, or the valve timing of both valves 8 and 9 may be changed. Further, the valve lift of the intake valve 8 or the exhaust valve 9 may be changed. ROM8 when changing the valve lift amount
Based on the function data map in the state where the target valve lift amount and the actual valve lift amount are coincident with 2, the multiple function data maps are set according to the size of the deviation of the actual valve lift amount from the target valve lift amount. It With these configurations, the operating state of the engine 1 can be adjusted in a wider range.

(3) In the above-described embodiment, the VVT 25 provided with the ring gear 48 that meshes with the inner cap 45 and the cover 35 for both 45 and 35 is used. On the other hand, the present invention may be embodied as a rotary type variable mechanism.

(4) In the above embodiment, the oxygen sensor 75
The specific component in the exhaust gas detected by was oxygen Ox. However, a specific component other than oxygen Ox may be detected.

Furthermore, it will be described below, together with the effect, that the above embodiment includes the following embodiments according to the technical idea described in the claims. (A) In the inventions of claims 1 to 3, storage means having a backup function for the current learned value learned by the deposit amount learning means (backup R in the above embodiment).
AM84) valve characteristic control device for internal combustion engine. With this configuration, even if the engine is stopped once, the engine can be controlled with the latest learned value KDPC in the next operation.

The valve characteristic control device for an internal combustion engine according to claim 1, wherein (b) the transient operation is an acceleration operation. With this configuration, the rate of change of the volumetric efficiency during acceleration operation becomes slower, and the fuel supply can follow the change, so that no problem occurs in VVT control based on fuel adsorption due to deposits.

[0055]

According to the first aspect of the present invention, the opening / closing characteristic of the variable valve timing mechanism uses the deposit amount learning value obtained by learning the estimated deposit amount of the deposit as the correction parameter, so that the optimum VVT corresponding to the deposit is obtained. It is possible to control.

According to the invention described in claim 2, according to claim 1
In addition to the effect of the invention described in (1), since the target displacement angle of the variable valve timing mechanism is changed to the retard side based on the learning value for deposit amount learning, the compression ratio is lowered and the occurrence of knocking is prevented.

According to the invention described in claim 3, according to claim 1
Alternatively, in addition to the effect of the invention described in 2, the rate of change of the volumetric efficiency in the acceleration operation state becomes slower and the fuel supply can follow the change, so that knocking is prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a VVT of the present invention.

FIG. 3 is an explanatory diagram showing changes in valve overlap.

FIG. 4 is a block diagram showing a configuration of an ECU.

FIG. 5 is a flowchart showing a “deposit amount learning routine”.

FIG. 6 is a flowchart showing a “VVT control routine”.

FIG. 7 is a graph showing a relationship between a target displacement angle and time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 4 ... Combustion chamber, 6 ... Intake passage, 7 ... Exhaust passage, 8 ... Intake valve, 9 ... Exhaust valve, 16 ... Injector as fuel injection means, 25 ...
Variable valve timing mechanism (VVT), 72 ... Throttle sensor, 73 ... Intake pressure sensor, 74 ... Water temperature sensor, 7
5 ... Oxygen sensor, 76 ... Rotation speed sensor, (72-76
Constitutes an operating state detecting means. ), 81 ... CPU (8
Reference numeral 1 constitutes a deposit amount learning means and an opening / closing characteristic changing means. ), 84 ... A backup RAM as a storage means.

Claims (3)

[Claims] 1. A variable valve timing mechanism capable of adjusting an operation timing of at least one of an intake valve and an exhaust valve, an operating state detecting means for detecting an operating state of an internal combustion engine, and the internal combustion engine Concentration detection means for detecting the concentration of a specific component of the exhaust gas discharged to the exhaust system, and a transient of the air-fuel mixture supplied into the internal combustion engine based on the detection results of the operating state detection means and the concentration detection means. And a deposit amount learning means for computing an air-fuel ratio during operation and learning an estimated deposit amount in the intake system based on the result, and the variable valve timing mechanism based on the learned value of the deposit amount learning means. A valve characteristic control device for an internal combustion engine, comprising: an opening / closing characteristic changing means for changing the opening / closing characteristic of the valve. 2. The valve characteristic control device for an internal combustion engine according to claim 1, wherein the target displacement angle of the variable valve timing mechanism is changed to a retard side based on the learning value updated by the deposit amount learning means. 3. The valve characteristic control device for an internal combustion engine according to claim 1, wherein the advance angle speed of the variable valve timing mechanism in an accelerating operation state is delayed based on the learned value updated by the deposit amount learning means.