JP3264177B2 - Valve characteristic 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 characteristic control for an internal combustion engine having a variable valve timing mechanism, which eliminates a problem that occurs when fuel is deposited on a deposit that accumulates in an intake system of the engine. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection type internal combustion engine (engine), a mixture supplied to the engine is optimized in order to optimize various performances such as output performance, exhaust characteristics, and drivability according to various operating conditions. It has been practiced to control the ratio of air to fuel, that is, the air-fuel ratio.
This control is performed by controlling the amount of fuel supplied to the engine such that the actual air-fuel ratio matches a target air-fuel ratio that can vary according to the engine speed, load condition, warm-up 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. In practice, a part of the injected fuel adheres to an intake port, an intake valve, a piston, etc. of an intake system downstream of the injector. The amount of fuel adhesion depends on the state of the intake system, and in particular, deposit is one of the major factors.
The deposit is a substance such as carbon fine particles that accumulate in the intake system due to blow-by gas, lubricating oil, and the like, and has a property of adsorbing fuel.

Incidentally, a variable valve timing mechanism (VVT) for changing valve characteristics (valve timing, valve lift amount, etc.) of an intake valve or an exhaust valve in accordance with an operating state (load, rotation speed, etc.) of an internal combustion engine (engine). It has been known. By VVT, the amount of air taken into the combustion chamber through the intake passage becomes optimal according to the operating state of the engine, and the fuel efficiency, output, and emission of the engine can be improved over a wide range of changes in the operating state. In the internal combustion engine equipped with such a mechanism, the following problems occur due to the deposit.

[0005] (1) In particular, when the VVT valve characteristic is abruptly changed as in the transient operation of the acceleration and deceleration operation of the engine, the volumetric efficiency also changes abruptly. However, when the amount of fuel adsorbed by the deposit is large, the supply of fuel to compensate for the adsorbed amount is delayed, and the fuel cannot follow a rapid change in volumetric efficiency, becomes locally lean, and knocking easily occurs.

(2) When deposits accumulate in the piston or the combustion chamber, the volume of the combustion chamber decreases, and the compression ratio becomes higher than when no deposits accumulate. Therefore,
Knocking is likely to occur without any treatment. In this case, the knock can be suppressed by detecting the knock with the knock sensor and shifting the ignition timing of the spark plug, but the fuel consumption is rather deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a VVT valve for an internal combustion engine equipped with a VVT when fuel adheres to a deposit that accumulates in an intake system of the engine. The characteristics are changed in accordance with the amount of deposit to enable good combustion of the internal combustion engine.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a variable valve timing mechanism capable of adjusting an 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 exhaust gas discharged from the internal combustion engine to the exhaust system, the operating state detecting means, and concentration detecting Means for calculating an air-fuel ratio during transient operation of the air-fuel mixture supplied into the internal combustion engine based on the detection result with the means, and learning an estimated amount of deposits in the intake system based on the result. And an opening / closing characteristic changing unit configured to change the opening / closing characteristic of the variable valve timing mechanism based on a learning value of the deposit amount learning unit. Therefore, the deposit amount learning means learns the estimated deposit amount of the deposit based on the detection results of the operating state detecting means and the concentration detecting means. The opening / closing characteristic changing means changes the opening / closing characteristics of the variable valve timing mechanism using the learning value as a correction value.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the target displacement angle of the variable valve timing mechanism is shifted to the retard side based on the learning value updated by the deposit amount learning means. It was configured to change. Therefore, the volume of the combustion chamber is reduced due to the accumulation of deposits, and the compression ratio is increased.However, 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.

According to the third aspect of the present invention, the first or second aspect is provided.
In addition to the configuration of the invention, the advance angle 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 accelerated operation state in which the volume efficiency is sharply increased, the fuel is adsorbed on the deposit and the supply is delayed, so that the fuel cannot follow the increase in the volume efficiency, and the air-fuel ratio becomes locally lean. Accordingly, by delaying the advancing speed using the learning value learned by the deposit amount learning means as a correction value, it is possible to follow a rapid increase in volumetric efficiency.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which a valve characteristic control device for an internal combustion engine according to the present invention is embodied in a gasoline engine system of an automobile will be described below in detail 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 includes a cylinder block 2a and a cylinder head 2b. The pistons 3 provided in the respective cylinders 2 are connected to the crankshaft 1a and can move up and down in the respective cylinders 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
Operate based on the rotation of different camshafts 10, 11. Timing pulleys 12, 13 provided at the tips of the camshafts 10, 11, respectively, are connected to the crankshaft 1a via a timing belt 14.

During operation of the engine 1, the rotational force of the crankshaft 1a is applied to the timing belt 14 and each pulley 1
The power is transmitted to the respective camshafts 10 and 11 via the second and third camshafts. The valves 8 and 9 are operated by 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.

An air cleaner 15 provided at the entrance of the intake passage 6 purifies 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, when the ignition plug 5 is operated, the air-fuel mixture explodes and burns. As a result, the piston 3 operates, the crankshaft 1a rotates, and an output is obtained in the engine 1. The exhaust gas after combustion is exhausted by an exhaust valve 9 during an exhaust stroke.
When a is opened, it is drawn out of the combustion chamber 4 and is drawn out to the exhaust passage 7. Then, the catalyst 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 the intake air. Air cleaner 15
The intake air temperature sensor 71 provided near the intake air temperature THA
And outputs a signal corresponding to the detected value. Throttle sensor 7 provided near throttle valve 17
2 detects the opening degree (throttle opening degree) 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
And outputs a signal corresponding to the detected value. Cylinder block 2
a is provided with a water temperature sensor 74. 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. In the middle of the exhaust passage 7, an oxygen sensor 7 as a concentration detecting means is provided.
5 are provided. The oxygen sensor 75 detects the concentration Ox of the oxygen remaining in the exhaust gas and outputs a signal corresponding to the detected concentration.

The distributor 21 includes an 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 the camshaft 11 which 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 discriminating 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 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 makes two rotations, the rotation speed sensor 76 outputs one pulse signal 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 an oil pressure to advance 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 engine 1
0 and the like constitute a lubricating device for lubricating each part of the engine 1. This lubrication device supplies hydraulic pressure to the VVT 25 to drive the same. Oil control valve (OC
V) 55 allows the hydraulic pressure supplied to the VVT 25 to be adjusted. When the oil pump 29 operates in conjunction with the operation of the engine 1, the lubricating oil sucked 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 camshaft 10 is rotatably supported by the cylinder head 2b. A pulley 12 is provided on the camshaft 10.
The pulley 12 is rotatable relative to the camshaft 10. A cylindrical cover 35 with a bottom fixed to the pulley 12 has a flange 39 on its outer periphery.
And a hole 40 at the bottom center. 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.

The hollow bolt 46 and the pin 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
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 a pulley 1 of the camshaft 10.
2 and the pulley 12 of the crankshaft 1a.
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 via the ring gear 48 to rotate.
And the camshaft 10 rotates integrally with the pulley 12.

Here, the first hydraulic chamber 4
By supplying the oil pressure to the ring 9, the oil pressure is applied to the ring gear 48. Based on the oil pressure, the ring gear 48
Rotates in the axial direction of the camshaft 10 while moving to the right in the drawing. 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 advances more than that of the pulley 12. As a result, the phase of the valve timing of the intake valve 8 leads the rotation 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 becomes relatively large. As described above, by controlling the oil pressure supplied to the first hydraulic chamber 49, the ring gear 48 shown in FIG. 2 can be moved to the terminal 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 rightward in the drawing, the hydraulic pressure is applied to the ring gear 48 by supplying the hydraulic pressure to the second hydraulic chamber 50 through the oil passage 53. 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 rotational 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. As described above, by controlling the oil pressure supplied to the second hydraulic chamber 50, the ring gear 48 shown in FIG.
5 can be moved to the end position approaching. When the ring gear 48 reaches the end position, the valve timing of the intake valve 8 is the most delayed.

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

Here, an ECU (Electronic Control Unit) 80 receives 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 these input signals.

As shown in the block diagram of FIG.
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. CPU 81 is R
The control program stored in the OM 82 is executed. RO
M82 stores a predetermined control program, function data, and the like in advance, and stores, 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 sensor 71 to 78 described above
Is connected to the external input circuit 85. Each member 1 described above
6, 22, and 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 the OCV to activate fuel injection control, ignition timing control,
Execute valve timing control and the like.

Next, among 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 the present embodiment, the amount of the deposit increasing with time is learned in a state where the engine is in an acceleration state and the air-fuel ratio A / F is leaner than the target air-fuel ratio. The CPU 81 executes this routine periodically at predetermined time intervals. The deposit amount learning value KDPC is set to 0 as an initial value.

In step 100, the CPU 81 determines whether or not the engine 1 is accelerating. That is, the CPU 81 determines the acceleration state of the engine 1 by the throttle opening T detected by the sensors 72, 73, 76.
The determination is made based on values such as A, the intake pressure PM, and the engine speed NE. When the CPU 81 determines that the vehicle is in the acceleration state, the process proceeds to step 110. In step 110, the CPU 81 determines whether the air-fuel ratio A / F is lean based on the value of the oxygen concentration Ox detected by the oxygen sensor 75, in comparison with the target air-fuel ratio.

If 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
Is not lean, the previous value is retained without updating the deposit amount learning value KDPC. In the present embodiment, the CPU 81 that executes the processing of the “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 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.
The CPU 81 executes this routine periodically at predetermined time intervals.

In step 200, the CPU 81
It is determined whether the VT target displacement angle has changed. Here, the VVT target displacement angle is a value calculated 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, and the like as parameters.

If the CPU 81 determines that the VVT target displacement angle has changed, that is, that the operating conditions have changed, step 21 is executed.
At 0, it is determined whether or not the deposit amount learning value KDPC is larger than a threshold value n. Here, the threshold value n is a value that can be ignored if the deposit amount learning value KDPC is equal to or less than this. The threshold value n is variable and may be zero. The CPU 81 calculates a deposit amount learning value KDPC.
Is greater than the threshold value n,
At 0, it is determined whether the engine 1 is accelerating. This determination conforms to the processing of step 100 of the above-mentioned “deposit amount learning routine”. When determining that the engine 1 is accelerating, the CPU 81 determines in step 230 that the VVT advance angle (VVTSP) to the VVT target displacement angle has been reached.
The value of D) is calculated according to the following equation.

VVTSPD = VVTSP0 * 1 / KDPC That is, the CPU 81 sets the VVTPS to the previous VVT target displacement angle.
By multiplying the reciprocal of the latest deposit amount learning value KDPC updated to the VT advance speed 0, the current VVT advance speed corrected for the deposit amount is calculated. here,
The VVT advance angle speed is a speed until a new VVT target displacement angle is reached when the operating conditions are changed, for example, when the operation shifts from a low load operation state to a high load operation state.

On the other hand, at step 220, the engine 1
Is not in the accelerated state, the CPU 81 determines in step 240 whether or not it is in the steady operation state. C
When determining that the PU 81 is in the steady operation state, the PU 81 proceeds to step 250.
, A VVT target displacement angle (VVTB) is calculated according to the following equation.

VVTB = VVTB0 * 1 / KDPC That is, the CPU 81 multiplies the previous VVT target displacement angle 0 by the reciprocal of the latest deposit amount learning value KDPC updated to correct the deposit amount this time.
A VT target displacement angle is calculated. The CPU 81 proceeds to step 26
At 0, the current VVT advance velocity 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 that the current VVT target displacement angle and the VVT
The control is executed based on the value of the advance angle speed. In the present embodiment, the CPU 81 executing 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 correction based on the conventional deposit amount learning value KDPC is not performed in a certain operating state.
The concept of T control is shown by a solid line in FIG. In other words, in this conventional VVT control, the target VVT displacement angle of P1 is (T1−
T0) The vehicle is driven for a steady operation for a time. Next, the vehicle shifts to an acceleration operation state under a predetermined load, and after (T2−T1) time, P
The VVT target displacement angle of 2 is reached, and the vehicle shifts to the steady operation running again with the load maintained.

Incidentally, during the acceleration operation, the VVT advance angle rapidly changes to increase the valve overlap amount. That is, the volumetric efficiency of the engine 1 accompanying the VVT advance angle increases, and the fuel supply amount also increases. In this conventional VVT control, the CPU performs VVT according to a predetermined load.
The advance angle speed t1 is calculated based on various parameters. However, when deposits are deposited, fuel is adsorbed to the deposits, and the balance between the fuel supply speed corresponding to the volumetric efficiency and the VVT advance speed 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 locally becomes lean. Therefore,
In some cases, the required ignition timing of the spark plug is deviated to cause knocking.

When deposits accumulate in the piston or the combustion chamber, the volume of the combustion chamber decreases, and the compression ratio becomes higher than when no deposits accumulate. In particular, in recent engines, the ignition timing of the spark plug is advanced to near the limit where knocking occurs in order to improve the output and fuel efficiency. Therefore, in the conventional VVT control in which the increase in the compression ratio based on the accumulation of the deposit is not taken into consideration, knocking occurs beyond the limit.

On the other hand, the concept of the VVT control of this embodiment, which is corrected by the deposit amount learning value KDPC under the operating condition under the same conditions, is shown by a broken line in FIG. In the VVT advancement speed t2 in the VVT control of the present embodiment, step 2
By the process of 30, the delay is made in comparison with the VVT advance speed t1. That is, although the displacement amount is almost the same as that of the conventional VVT control until the VVT target displacement angle is reached, the displacement time is longer by (T3-T2) time. Therefore, the VVT advance angle speed 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 during acceleration operation and knocking is less likely to occur.

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

On the other hand, the CPU 81 determines in step 200 that VV
If it is determined that the T target displacement angle has not changed, the previous VVT advance velocity and VVT target displacement angle are held in step 280, and the process proceeds to step 260. Also, CPU
In step 210, when it is determined in step 210 that the deposit amount learning value KDPC is equal to or smaller than the threshold value N, the process proceeds to step 280 in the same manner. When it is determined in step 240 that the vehicle is not in the steady operation state, that is, in the case of the deceleration operation state, the CPU 81 performs another process in step 290.
In the present embodiment, the CPU 81 that executes the processing of the “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 reduces the VVT advance speed based on the deposit amount learning value KDPC during the acceleration operation, the CPU 81 can perform optimal control on the VVT 25 in accordance with the amount of deposit adhesion. The occurrence of knocking is prevented. Also, the CPU 81 changes the VVT target displacement angle based on the deposit amount learning value KDPC during the steady operation, so that the VV
Optimal control according to the deposit amount can be performed for T25, and occurrence of knocking, which has been a conventional problem, is prevented. In particular, for the amount of deposit
The latest learning value KDPC is always obtained by the deposit amount learning routine ranging from 00 to 130, and the optimum learning value KDPC according to the estimated amount of deposit amount can be used as a correction value.

(2) The deposit amount learning value KDPC is always updated from the previous learning value KDPC and the backup RAM 8
Therefore, even if the engine 1 is temporarily stopped, it can be controlled by the latest learning value KDPC at the next operation.

(3) In step 210, the control is performed so that the deposit amount learning value KDPC is not a parameter up to the threshold value n. Therefore, if a certain amount of deposit does not accumulate, it is possible to perform control ignoring the deposit amount.

The present invention can be embodied in another embodiment as follows. 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 velocity and the VVT target displacement angle corrected on the basis of are stored in the backup RAM 84 in step 260. This is stored in the backup RAM 8
4 may be directly executed without being stored. By doing so, the processing speed of the CPU 82 is improved.

(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. When changing the valve lift, the ROM 8
2, a plurality of function data maps are set based on the magnitude of the deviation of the actual valve lift amount from the target valve lift amount with reference to the function data map in the state where the target valve lift amount and the actual valve lift amount match. You. With these configurations, the operating state of the engine 1 can be adjusted over a wider range.

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

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

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

(B) The valve characteristic control device for an internal combustion engine according to claim 1, wherein the transient operation is particularly an acceleration operation. In this configuration, the rate of change of the volumetric efficiency during the acceleration operation becomes slower, and the fuel supply can follow the change, so that the VVT control based on the fuel adsorption by the deposit does not occur.

[0055]

According to the first aspect of the invention, since the opening / closing characteristic of the variable valve timing mechanism is set as a correction parameter using a deposit amount learning value obtained by learning an estimated deposit amount of the deposit, an optimum VVT according 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 effects 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 of the deposit amount, the compression ratio is reduced and knocking is prevented from occurring.

According to the invention described in claim 3, according to claim 1
Or, in addition to the effect of the invention described in 2 above, the rate of change in volumetric efficiency in the accelerated operation state is slowed and the fuel supply can follow the change, so that occurrence of knocking is prevented.

[Brief description of the 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 a change 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: rotational speed sensor, (72 to 76)
Constitutes operating state detecting means. ), 81 ... CPU (8
Reference numeral 1 denotes a deposit amount learning unit and an opening / closing characteristic changing unit. ), 84 ... Backup RAM as storage means.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 13/02 F01L 13/00 301 F02D 41/04 320 F02D 41/04 330 F02D 45/00 340

Claims (3)

(57) [Claims] 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 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 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. A deposit amount learning means for calculating an air-fuel ratio at the time of operation and learning an estimated amount of deposits in the intake system based on the result; and the variable valve timing mechanism based on a learning 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 an opening / closing characteristic of the engine. 2. The valve characteristic control device for an internal combustion engine according to claim 1, wherein a target displacement angle of the variable valve timing mechanism is changed to a retard side based on a 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 an advance speed of the variable valve timing mechanism in an acceleration operation state is delayed based on a learning value updated by the deposit amount learning unit.