JPH0972225A - Continuously variable valve timing controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve degrees of an air-fuel ratio control and the like by setting a target valve overlap quantity according to an engine load so that a valve overlap quantity is set to be suitable for emission and fuel in a middle load range, and suitable for output in a high load range, and correcting the target valve overlap quantity according to the deposit adhering quantity. SOLUTION: A reference target valve timing displacement quantity tVTD according to an engine rotational speed NE and an intake air amount GN is calculated. A deposit learning value is taken in this controller, and a water temperature correcting amount Kdp according to the deposit learning value is calculated by referring to a map. Further, water temperature THW is corrected to be decreased on the basis of the Kdp, and also the map is referred on the basis of the corrected water temperature THW so that the tVTD correcting amount OTHW according to the water temperature THW is calculated. The reference target valve timing displacement quantity tVTD is corrected by the OTHW so as to calculate A controlled target valve timing displacement quantity tVTD. After that, when the tVTD is a negative value, the tVTD is set to be 0 so as to feedback-control a VVT mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing continuously variable mechanism (VV) capable of continuously changing the valve timing (valve opening / closing timing) of an intake valve or an exhaust valve.
The invention relates to a device (continuously variable valve timing control device) for setting a target valve timing and controlling the variable mechanism in an internal combustion engine (engine) having T).

[0002]

2. Description of the Related Art Conventionally, various variable mechanisms of a valve train have been put to practical use in an automobile engine in order to achieve an optimal valve timing according to an operating state. The main type of such a variable mechanism is a two-stage switching type, that is, an ON / OFF control type.
In recent years, in order to meet the demand for higher performance of the engine, it is possible to always set an optimum valve timing in place of the conventional two-stage switching type even in the variable valve timing mechanism. A continuously variable type is being developed. For example, Japanese Patent Laid-Open No. 4-1754
Japanese Unexamined Patent Publication No. 30 discloses a continuously variable valve timing control device capable of continuously changing the overlap period between the exhaust period and the intake period, that is, the valve overlap amount according to the operating state. In an internal combustion engine having a variable valve timing mechanism, the internal efficiency contributes to the improvement of output performance, the improvement of exhaust gas purification performance (emission) by reducing NO _x , and the improvement of fuel efficiency by reducing pumping loss. Exhaust gas recirculation (internal E
From the viewpoint of GR), the valve timing is controlled according to the engine operating state.

[0003]

However, the conventional continuously variable valve timing control device as described above does not consider the influence of deposits adhering to the wall surface of the intake system and the combustion chamber. Here, the deposit is mainly the engine oil that has fallen from above through the intake valve and is solidified by heat. If the deposit amount in the intake system increases,
Since the surface area increases, the amount of fuel adhering increases and the amount of intake air decreases. Further, when the amount of deposits deposited in the combustion chamber increases, the combustion state deteriorates. In such a state where the intake air amount and the like are affected, it is necessary to change the set value of the valve overlap amount of the VVT mechanism.

In view of the above situation, an object of the present invention is to provide a continuously variable valve timing control device capable of setting the optimum valve timing, that is, the valve overlap amount, in accordance with the increased deposit amount. It is intended to further improve the air-fuel ratio control accuracy, exhaust gas purification performance, fuel efficiency, drivability, output performance, etc. of the internal combustion engine by providing the above.

[0005]

In order to achieve the above object, the present invention adopts the technical constitution as described below. That is, the continuously variable valve timing control device according to the first invention of the present application is a continuously variable valve timing control device that changes the valve overlap amount according to the load of an internal combustion engine, and is at least an intake valve or an exhaust valve. A valve timing continuously variable mechanism that can continuously change one valve timing, and an engine load that is suitable for emissions and fuel consumption in the medium load range and a valve overlap amount suitable for output in the high load range. Setting means for setting a target valve overlap amount according to the setting means, control means for controlling the valve timing continuously variable mechanism so as to achieve the target valve overlap amount set by the setting means, and the target set by the setting means. Correction means for correcting the valve overlap amount in accordance with at least the deposit adhesion amount.

According to a second aspect of the invention, in the apparatus according to the first aspect of the invention, the correction means corrects the target valve overlap amount so that it decreases as the deposit amount increases.

According to a third aspect of the present invention, in the apparatus according to the first aspect of the present invention, the correction means reduces and corrects the target valve overlap amount based on the amount determined by the deposit amount and the combustion state. It

According to a fourth aspect, the apparatus according to the third aspect further comprises a correction limiting means for limiting the correction by the correction means only when the load is light.

According to a fifth aspect of the present invention, the apparatus according to the fourth aspect further comprises second correction means for increasing the correction amount as the engine speed decreases.

According to a sixth aspect of the present invention, in the apparatus according to the second aspect of the present invention, the correction means sets the target valve overlap amount based on the amount determined by the responsiveness of the valve timing continuously variable mechanism and the deposit adhesion amount. Is to be reduced and corrected.

According to a seventh aspect, the apparatus according to the second aspect further comprises a correction limiting means for limiting the correction by the correcting means only when the load is high.

According to the eighth invention, the apparatus according to the seventh invention further comprises third correcting means for increasing the correction amount as the engine speed increases.

According to a ninth aspect of the present invention, in the apparatus according to the first aspect, the correcting means increases and corrects the target valve overlap amount as the deposit amount increases.

According to a tenth aspect of the present invention, in the apparatus according to the ninth aspect, the correcting means increases and corrects the target valve overlap amount based on the amount determined by the residual exhaust gas amount in the combustion chamber and the deposit adhesion amount. To be done.

According to an eleventh aspect, the apparatus according to the tenth aspect further comprises a correction limiting means for limiting the correction by the correcting means only when the load is medium.

According to the twelfth invention, the apparatus according to the eleventh invention further comprises fourth correction means for increasing the correction amount as the engine speed increases.

In the continuously variable valve timing control device according to the first aspect of the present invention configured as described above, the target valve overlap is corrected in accordance with the deposit amount, so that the proper valve is applied regardless of the deposit amount. The overlap amount is set.

The larger the deposit amount, the greater the change in the amount of fuel wall adhesion on the transition. In the device according to the second aspect of the present invention, the valve overlap amount is corrected to be smaller as the deposit amount is larger, so that the fuel wall adhesion due to the intake blowback is reduced, and as a result, the air-fuel ratio is prevented from becoming rough. It

In the apparatus according to the third and fourth aspects of the present invention, the correction amount for improving the combustibility can be used. Particularly, in the device according to the fourth aspect of the present invention, combustion stability under light load can be obtained.

The influence of deterioration of combustion due to deposits is
The larger the low speed range, the larger. In the device according to the fifth aspect of the present invention, the correction amount is increased and the valve overlap amount is decreased in the lower rotation speed region, so that the fuel wall adhesion due to the intake blowback is reduced and combustion is improved.

When the target overlap amount suddenly changes at the time of shifting or starting, the actual valve overlap amount cannot follow the target value, and there is a possibility that combustion deterioration will occur. , The larger the deposit amount, the larger. In the device according to the sixth aspect of the present invention, since the decrease correction is made in accordance with the deposit amount so that the valve overlap amount that can be followed is made, such deterioration of combustion is prevented.

Although the intake air amount under high load decreases due to the increase in the deposit amount, in the device according to the seventh aspect of the present invention, the target overlap amount is corrected to be decreased, so that the output decrease under high load is prevented. It

The degree of decrease in the intake air amount due to the increase in the deposit amount increases as the rotation speed increases, but in the device according to the eighth aspect of the invention, the valve overlap amount decreases as the rotation speed increases. Therefore, it is possible to accurately prevent the output from decreasing when the load is high.

When the deposit amount increases, the blowback resistance to the intake air increases and the internal EGR amount decreases. In the devices according to the ninth, tenth, and eleventh inventions, the valve overlap amount is increased as the deposit amount is increased, and the decrease in the internal EGR amount is suppressed. In particular, the device according to the eleventh aspect of the invention satisfies the requirements for emission and fuel efficiency under medium load.

The degree of decrease of the internal EGR amount due to the increase of the deposit amount increases as the rotation speed increases, but in the device according to the twelfth invention, the valve overlap amount increases as the rotation speed increases. Therefore, the decrease in the internal EGR amount can be accurately suppressed.

[0026]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine equipped with a valve timing control device according to an embodiment of the present invention. Air required for combustion in the engine 20 is filtered by the air cleaner 2, passes through the throttle body 4, and is distributed to the intake pipe 7 of each cylinder at the surge tank (intake manifold) 6. The intake air amount is adjusted by the throttle valve 5 provided in the throttle body 4 and is measured as a mass flow rate by the thermal air flow meter 40. The intake air temperature is detected by an intake air temperature sensor 43. The intake pipe pressure is detected by a vacuum sensor 41.

The opening of the throttle valve 5 is detected by the throttle opening sensor 42. When the throttle valve 5 is in the fully closed state, the idle switch 52 is turned on, and the throttle fully closed signal output from the idle switch 52 becomes active. An idle speed control valve (ISCV) 66 for adjusting the air flow during idling is provided in the idle adjustment passage 8 that bypasses the throttle valve 5.
Is provided.

On the other hand, the fuel stored in the fuel tank 10 is pumped up by the fuel pump 11, and the fuel pipe 12
Then, the fuel is injected into the intake pipe 7 by the fuel injection valve 60.

In the intake pipe 7, air and fuel are mixed,
The air-fuel mixture is sucked into a combustion chamber 21 of an engine body, that is, a cylinder 20 via an intake valve 24. In the combustion chamber 21, the air-fuel mixture is compressed by the piston 23 and then ignited to explode and burn to generate power.
Such ignition depends on the igniter 62 receiving the ignition signal.
Controls the energization and interruption of the primary current of the ignition coil 63, and the secondary current is supplied to the spark plug 65 via the ignition distributor 64.

The ignition distributor 64 includes:
Its axis is, for example, 720 ° converted to crank angle (CA)
A reference position detection sensor 50 that generates a reference position detection pulse for each CA and a crank angle sensor 51 that generates a position detection pulse for each 30 ° CA are provided. The actual vehicle speed is detected by a vehicle speed sensor 53 that generates an output pulse representing the vehicle speed. The engine 20 is cooled by cooling water guided to the cooling water passage 22, and the temperature of the cooling water is detected by a water temperature sensor 44.

The combusted air-fuel mixture is discharged as exhaust gas to the exhaust manifold 30 via the exhaust valve 26, and is then guided to the exhaust pipe 34. The exhaust pipe 34 is provided with an O ₂ sensor 45 for detecting the oxygen concentration in the exhaust gas. Further, a catalytic converter 38 is provided in the exhaust system downstream thereof, and the catalytic converter 38 has
A three-way catalyst that simultaneously promotes oxidation of unburned components (HC, CO) and reduction of nitrogen oxides (NO _x ) in the exhaust gas is accommodated. The exhaust gas thus purified by the catalytic converter 38 is discharged into the atmosphere.

The opening / closing mechanism of the intake valve 24 and the exhaust valve 26 will be described. The piston 23 is connected to a crankshaft 81 via a connecting rod 80. A timing pulley 84 is provided at an end of the crankshaft 81. The intake valve 24 and the exhaust valve 26 are driven by cams 87 and 88 attached to camshafts 85 and 86. Further, timing pulleys 89 and 90 are provided at ends of the camshafts 85 and 86. Timing pulley 89
And 90 are connected to the above-mentioned timing pulley 84 via a timing belt 91. Thus, the camshafts 85 and 86 are driven to rotate by the crankshaft 81, and the intake valve 24 and the exhaust valve 26 are opened and closed at a constant crank angle. A magnetic body 82 is embedded in the crankshaft 81,
A reference pulse is output from the first magnetic sensor 54 arranged close to the crankshaft 81. Further, a magnetic body 93 is embedded in the camshaft 85 of the intake valve 24, and a reference pulse is output from the second magnetic sensor 55 disposed close to the camshaft 85.

In particular, a generally known valve timing continuously variable mechanism 92 is provided between the cam shaft 85 of the intake valve 24 and the timing pulley 89. This causes the cam shaft 85 and the timing pulley 89 to rotate relative to each other. More specifically, the valve timing continuously variable mechanism 92 uses the cam shaft 85 and the timing pulley 89 as external teeth, connects them via an intermediate gear having helical teeth, and moves the intermediate gear in the axial direction. , Realizes the relative rotation described above. The movement of the intermediate gear is performed, for example, by controlling the hydraulic pressure supplied from a hydraulic source, and a hydraulic control valve 68 is provided for controlling the hydraulic pressure.

Engine electronic control unit (engine EC
U) 70 is a microcomputer system that executes valve timing control according to the present invention in addition to fuel injection control, ignition timing control, idle speed control, etc.
The hardware configuration is shown in the block diagram of FIG. According to the programs and various maps stored in the read-only memory (ROM) 73, the central processing unit (C
PU) 71 receives signals from various sensors and switches as A
It is input through the D / D conversion circuit 75 or the input interface circuit 76, the arithmetic processing is executed based on the input signal, and the drive control circuits 77a to 77d based on the arithmetic result.
Control signals for various actuators are output via. The random access memory (RAM) 74 is used as a temporary data storage place in the operation / control processing. The backup RAM 79 is supplied with power by being directly connected to a battery (not shown), and stores data (for example, various learning values) to be held even when the ignition switch is off. Used for Each component in the ECU is connected by a system bus 72 including an address bus, a data bus, and a control bus.

The engine control processing of the ECU 70 executed in the internal combustion engine (engine) having the above hardware configuration will be described below.

The fuel injection control is basically performed by the engine 1.
Based on the intake air mass per rotation, the fuel injection amount that achieves a predetermined target air-fuel ratio, that is, the injection time by the fuel injection valve 60 is calculated, and drive control is performed to inject fuel when a predetermined crank angle is reached. The fuel injection valve 60 is controlled via the circuit 77a. It should be noted that the intake air mass per one revolution of the engine is the intake air mass flow rate measured by the thermal air flow meter 40 and the crank angle sensor 51.
It is calculated from the engine rotation speed obtained from When the fuel injection amount is calculated, the basic correction based on the signals from the throttle opening sensor 42, the intake air temperature sensor 43, the water temperature sensor 44 and the like, and the O ₂ sensor 45.
The air-fuel ratio feedback correction based on the signal from, and the air-fuel ratio learning correction for making the median of the feedback correction values the stoichiometric air-fuel ratio are added.

In the ignition timing control, the state of the engine is comprehensively judged by the engine speed obtained from the crank angle sensor 51 and signals from other sensors.
The optimum ignition timing is determined and an ignition signal is sent to the igniter 62 via the drive control circuit 77b.

In the idle speed control, the idle state is detected by the throttle fully closed signal from the idle switch 52 and the vehicle speed signal from the vehicle speed sensor 53, and a target determined by the engine cooling water temperature from the water temperature sensor 44 and the like. The rotation speed is compared with the actual engine rotation speed, the control amount is determined according to the difference so that the target rotation speed is obtained, and the ISC is passed through the drive control circuit 77c.
By controlling the V66 to adjust the amount of air, the optimum idle rotation speed is maintained.

In the valve timing control, the target valve timing (valve opening / closing timing) of the intake valve 24 is set in accordance with the operating state to control the valve timing continuously variable mechanism 92. The hydraulic control valve 6 is controlled based on the signals from the first magnetic sensor 54 and the second magnetic sensor 55 so that the camshaft 85 of the valve 24 maintains a desired rotational phase with respect to the crankshaft 81.
8 is feedback-controlled.

FIG. 3 is a valve timing chart showing the opening / closing timing of the intake valve 24 and the exhaust valve 26 by the crank angle. As shown in this figure, the exhaust valve 26 is opened at a fixed valve opening timing EVO (50 ° before exhaust bottom dead center in this embodiment), and a fixed valve closing timing EVC.
(In this embodiment, the valve is closed at 3 ° after exhaust top dead center). On the other hand, with respect to the intake valve 24, the valve opening period is constant, but the valve opening timing IVO and the valve closing timing IVC are variable, and the opening and closing timings on the most retarded side (IVOr and IVCr in the figure) are used as a reference. Both positions can be set at timings displaced by an arbitrary amount in the advance angle direction.
However, the maximum value of the valve timing displacement amount VTD is 60 ° in this embodiment. Then, the valve timing displacement amount VTD from the reference position is set as the control target amount.
Here, in the present embodiment, as the reference position, the reference valve opening timing IVOr is 3 ° after the exhaust top dead center and the reference valve closing timing IVCr is 65 ° after the intake bottom dead center. Therefore, in this case, when the valve timing displacement amount VTD is, for example, 30 ° CA (crank angle), IVO is 27 ° before exhaust top dead center and IVC is 35 ° after intake bottom dead center. In this embodiment, the reference valve opening timing I of the intake valve 24
Since both VOr and the valve closing timing EVC of the exhaust valve 26 are the same as 3 ° after the exhaust top dead center, the valve timing displacement amount VTD coincides with the valve overlap amount.

In a transient state such as during acceleration / deceleration, the amount of fuel adhering to the wall surface of the intake system changes as the intake pipe pressure changes, so the amount of fuel corresponding to the valve opening time of the fuel injection valve changes. It is not directly supplied to the combustion chamber. Therefore, during the transient operation, the fuel injection amount is corrected in consideration of the change in the intake system wall surface attachment amount. That is, during acceleration, the amount of adhered wall surface increases as the intake pipe pressure increases (negative pressure decreases), so the fuel injection amount increases, and during deceleration, the wall surface increases as the intake pipe pressure decreases (negative pressure increases). Since the adhered amount is reduced, the correction of reducing the fuel injection amount is executed.

The amount of fuel adhering to the intake wall surface varies depending on the amount of deposits described above. That is, as shown in FIG. 4, when the intake wall surface deposit adhesion amount increases, the surface area increases, so that the intake wall surface fuel adhesion amount also increases. As a result, the amount of fuel adhering to the wall surface during acceleration and the amount of fuel carried away from the wall surface during deceleration increase. Therefore, the rich shift during acceleration and the lean shift during deceleration become large. In the fuel injection control, a deposit learning is performed to grasp how much the deposit is attached according to the rich shift degree at the time of acceleration. Also in the fuel injection control according to this embodiment, such a deposit learning value KDPC is obtained and stored in the backup RAM 79. And this deposit learning value KDP
C is 1.0 when no deposit is attached,
It increases as the amount of adhesion increases.

On the other hand, the lower the water temperature is, the lower the vaporization rate of the fuel is, so that the intake wall surface fuel adhesion amount is increased as shown in FIG. Further, as the valve timing displacement amount, that is, the valve overlap amount, increases, the intake blowback amount increases, so that the intake wall surface fuel adhesion amount increases as shown in FIG. Therefore, the intake wall surface fuel adhesion amount is affected by the intake wall surface deposit deposit amount, the water temperature, and the valve overlap amount.

FIG. 7 shows the throttle opening during acceleration,
FIG. 6 is a diagram showing temporal changes in the amount of fuel adhering to the intake wall surface, the amount of fuel supplied to the combustion chamber, and the air-fuel ratio when the amount of fuel adhering to the intake wall surface is small (curve) and large (curve).
As can be easily understood from this figure, it is preferable that the intake wall fuel adhesion amount be reduced as much as possible from the viewpoint of air-fuel ratio control. Considering factors affecting the intake wall surface fuel adhesion amount, the intake wall surface deposit adhesion amount and the water temperature cannot be controlled, but the valve overlap amount is a controllable amount. In other words, the increase in the intake wall surface fuel adhesion amount due to the increase in the intake wall surface deposit adhesion amount can be absorbed by decreasing the valve overlap amount.

The first embodiment according to the first and second inventions is as follows.
The larger the deposit amount, the valve timing displacement amount V
By suppressing the expansion of TD (valve overlap amount), it is possible to absorb the increase in the intake wall fuel adhesion amount accompanying the increase in the deposit amount and prevent the deterioration of the air-fuel ratio in the transient state. Generally, in an engine equipped with an intake valve VVT, in order to improve startability, the VVT is operated at a low temperature.
Stop the operation of. That is, as shown in FIG. 8A, the correction amount OTHW according to the water temperature THW is introduced, and the target valve timing displacement amount tVTD (map value).
Is reduced and corrected by the calculation tVTD ← tVTD-OTHW, and tVTD after this correction is corrected.
Is the control target valve timing displacement amount. That is, depending on the water temperature THW, when THW ≤ A [° C], when VVT operation stop A [° C] <THW <B [° C], when VVT limit operation B [° C] ≤ THW , VVT control such as full VVT operation is performed.

In the first embodiment, when the deposit amount is large, as shown in FIG. 8B, a water temperature correction amount Kdp corresponding to the deposit amount is introduced to control the VVT operating condition to the high temperature side. This suppresses the expansion of the valve overlap amount. That is, the VVT operation condition is that when THW ≦ A + Kdp [° C], VVT operation stop A + Kdp [° C] <THW <B + Kdp [° C]
VT limit operation B + Kdp [° C] ≤ THW, V
The VT is fully activated.

The processing procedure of the VVT control routine according to the first embodiment is shown in the flowchart of FIG. This routine is configured to be executed at a predetermined cycle.
First, the current engine speed NE is detected based on the output of the crank angle sensor 51 (step 102). Next, the engine speed NE and the air flow meter 4
Based on the intake air flow rate (mass) GA obtained from 0, the intake air amount (mass) GN per engine revolution is calculated (step 104). Then, the NE obtained by referring to the map as shown in FIG.
And basic target valve timing displacement amount tV according to GN
TD is calculated (step 106). This map is stored in the ROM 73 in advance.

Next, the water temperature TH is measured by the water temperature sensor 44.
W is detected (step 108). Next, the deposit learning value KDP stored in the backup RAM 79
C is taken in (step 110). Next, the water temperature correction amount Kdp corresponding to the deposit learning value KDPC is determined by referring to the map as shown in FIG. 11 (step 112). This map is also stored in the ROM 73 in advance. Then, based on this Kdp, a calculation of THW ← THW-Kdp is executed, and the water temperature THW is reduced and corrected (step 114). Next, based on the corrected water temperature THW, by referring to the map shown in FIG. 8A, the tVTD correction amount OTHW corresponding to the water temperature THW is obtained.
Is calculated (step 116). This map is also stored in the ROM 73 in advance.

Next, the basic target valve timing displacement amount tVTD obtained in step 106 is set to this OTHW.
To correct. That is, the control target valve timing displacement amount tV is calculated by the calculation of tVTD ← tVTD-OTHW.
TD is calculated (step 118). Finally, tVTD
Is negative, tVTD is set to 0 (step 1
20, 122), and feedback-controls the VVT mechanism based on the final control target valve timing displacement amount tVTD (step 124).

As described above, in the first embodiment, the valve timing displacement amount VTD, that is, the valve overlap amount is decreased and the intake blowback is performed when the intake wall fuel adhesion amount tends to increase as the deposit amount increases. Since the amount decreases, the increase tendency of the intake wall surface fuel adhesion amount is suppressed, and the deterioration of the air-fuel ratio in the transient state is prevented. Although the first embodiment corrects the valve timing displacement amount only when the temperature is low by adding the engine cooling water temperature THW to the condition, it is of course possible to implement without adding the water temperature condition. .

Next, the second embodiment will be described. FIG.
As shown in FIG. 2, the amount of deposit attached to the intake wall surface and the amount of deposit attached to the combustion chamber are in a proportional relationship. If the deposit in the combustion chamber increases, the quench portion also increases, which causes a problem that combustion deteriorates as shown in FIG. In the second embodiment, first, according to the above-mentioned first, third and fourth inventions, in the light load region,
By reducing the valve timing displacement amount (valve overlap amount) according to the deposit learning value KDPC and reducing the amount of internal EGR accompanied by the combustion deterioration, the combustion deterioration due to the adherence of the combustion chamber deposit is offset.

Further, when the map of the valve timing displacement amount is determined based on the engine rotation speed NE and the intake air amount GN, the following problems occur. That is,
When the deposit is attached, the blowback resistance to the intake air is increased. Therefore, as shown in FIG. 14, even if the valve overlap amount is the same, as compared with the case where the deposit is not attached (curve), There is a problem that the EGR amount decreases (curve), and the generation of nitrogen oxides (NO _x ) cannot be suppressed sufficiently. In the second embodiment, according to the first, ninth, tenth, and eleventh inventions, the valve timing displacement amount (valve overlap amount) is increased according to the deposit learning value KDPC in the medium load range, and the internal EGR is performed. Correct the decrease (curve in FIG. 14).

Further, if the deposit adheres, the intake resistance increases, so that the intake air amount GN decreases. The curve in FIG. 15 is a graph obtained by extracting the relationship between the intake air amount GN and the valve timing displacement amount VTD at a certain constant engine speed NE. in, by increasing the internal EGR amount by increasing the valve overlap amount, NO _x
From the viewpoint of improving exhaust gas purification performance by reducing fuel consumption and improving fuel economy by reducing pumping loss,
VTD is gradually increased, and in the high load range,
VTD is defined from the viewpoint of improving output. Therefore, when the intake air amount GN decreases, even if the throttle is fully opened (WOT) and high output is required, the valve timing displacement amount is controlled to be larger than the valve timing displacement amount that satisfies the high output requirement. That is, it becomes an excessive advance angle. Therefore, in the second embodiment, according to the first, second and seventh inventions, in the high load range, the valve timing displacement amount (valve overlap amount) is reduced according to the deposit learning value KDPC, and the high load ( The deviation of the valve timing at the time of WOT) is corrected to prevent the output from decreasing.

In summary, in the second embodiment, as shown by the curve in FIG. 15, the valve timing displacement amount (valve overlap amount) is changed in accordance with the deposit learning value KDPC in the light load region (S region). ) And high load area (W
In the area), reduction correction is performed, and in the medium load area (P area), enlargement correction is performed.

The processing procedure of the VVT control routine according to the second embodiment is shown in FIGS. First, similarly to steps 102 and 104 (FIG. 9) of the first embodiment, the engine speed NE and the intake air amount (mass) GN per engine revolution are detected (steps 202, 20).
4). Next, the current throttle opening TA is detected based on the output of the throttle opening sensor 42 (step 2
06). Next, by referring to a map as shown in FIG. 18 based on the current engine speed NE, reference values KtaW and KtaP for performing high load determination and medium load determination based on the throttle opening TA are obtained (step 208). ). This map is stored in the ROM 73 in advance. Next, similarly to step 110 (FIG. 9) of the first embodiment, the deposit learning value KDPC is obtained (step 210).

In the next steps 212 to 226, a process for obtaining a correction coefficient Kdp for correcting the intake air amount GN according to the deposit amount is performed for each load region. That is,
When it is determined in step 212 that TA> KtaW is satisfied and it is determined that the load is high (WOT), the deposit learning value KD is referred to by referring to the relationship shown by the curve in FIG.
A high load deposit correction coefficient KdpW corresponding to the PC is obtained (step 214). The curves and contents of FIG. 19 are mapped and stored in the ROM 73 in advance. Next, the obtained high load deposit correction coefficient KdpW is set as the final deposit correction coefficient Kdp (step 216).

Further, in step 218 which is executed when the decision result in step 212 is NO, TA> Kta
When P is established and it is determined that the load is medium, by referring to the relationship shown by the curve in FIG. 19, a deposit correction coefficient KdpP for medium load according to the deposit learning value KDPC is obtained.
Is obtained (step 220). Next, the determined medium load deposit correction coefficient KdpP is set as the final deposit correction coefficient Kdp (step 222). Further, when the determination result in step 218 is NO, that is, when it is determined that the load is light, the light load deposit correction coefficient KdpS corresponding to the deposit learning value KDPC is obtained by referring to the relationship shown by the curve in FIG. (Step 22
4). Next, the obtained light load deposit correction coefficient KdpS is set as the final deposit correction coefficient Kdp (step 226).

In step 228, the intake air amount GN is corrected by executing a calculation of GN ← GN × Kdp based on the deposit correction coefficient Kdp thus determined according to the load. Next, based on the corrected GN and NE, the basic target valve timing displacement amount tVTD is calculated by referring to the map as shown in FIG. 10 described above (step 230), and this is finally controlled. The VVT mechanism is feedback-controlled based on this tVTD as the target valve timing displacement amount (step 232).

According to the above control, the following corrections are made. That is, as shown in FIG. 15, in the light load region (S region), the valve timing displacement amount VTD is an increasing function with respect to the intake air amount GN, and the light load deposit correction coefficient KdpS is less than 1. After all, VTD is reduced and corrected. Also,
In the medium load range (P range), the valve timing displacement amount VTD is an increasing function with respect to the intake air amount GN, and since the medium load deposit correction coefficient KdpP is larger than 1, VTD is eventually expanded and corrected. Becomes Further, in the high load region (W region), the valve timing displacement amount VTD is a decreasing function with respect to the intake air amount GN, and since the high load deposit correction coefficient KdpP is larger than 1, VTD is eventually reduced and corrected. The Rukoto.

As described above, in the second embodiment, the valve timing displacement amount (valve overlap amount) is reduced in accordance with the deposit learning value KDPC in the light load region.
Since the amount of internal EGR accompanied by combustion deterioration is reduced, the combustion deterioration due to the adherence of the combustion chamber deposit is offset. Also, in the medium load range, the deposit learning value KD
The valve timing displacement amount (valve overlap amount) is increased according to PC, and the internal EGR lowering amount due to the increase in the blowback resistance to the intake air is compensated. Further, in the high load region, the valve timing displacement amount (valve overlap amount) is reduced in accordance with the deposit learning value KDPC, the valve timing deviation due to the reduction of the intake air amount is corrected, and as a result, the output reduction is prevented. Will be done.

Next, the third embodiment will be described. The third embodiment is an improvement of the second embodiment in accordance with the fifth, eighth and twelfth inventions described above. First, considering the deterioration of combustion due to deposit adhesion, the degree of deterioration of combustion increases as the rotational speed becomes lower and the load becomes lighter. Therefore, in the third embodiment, a deposit correction coefficient Kdp for reducing and correcting GN to reduce the valve timing displacement amount (valve overlap amount) in the light load region.
In determining S (curve in FIG. 19), the correction amount is set to increase as the rotation speed becomes lower and the load becomes lighter.

Further, the degree of decrease of the intake blowback amount, that is, the internal EGR amount due to the deposit adhesion is larger as the rotational speed and the load are higher. Therefore, in the third embodiment,
In determining the deposit correction coefficient KdpP (curve in FIG. 19) for increasing and correcting the GN in order to increase the valve timing displacement amount (valve overlap amount) in the medium load range, the correction amount increases as the rotation speed increases and the load increases. To be made larger.

Further, since the intake resistance increases as the rotational speed increases, as shown in FIG. 20, the degree to which the intake air amount GN decreases due to deposits in the high load (WOT) region increases as the rotational speed increases. . Therefore, the third
In the embodiment, in determining the deposit correction coefficient KdpW (curve in FIG. 19) for increasing and correcting the GN in order to reduce the valve timing displacement amount (valve overlap amount) in the high load region, the higher the rotational speed, the more the correction amount. To be made larger.

Specifically, the processing procedure of the VVT control routine according to the third embodiment is shown in FIGS. 21 and 22.
Steps 302 to 312 are the second embodiment (FIGS. 16 and 1).
7) steps 202 to 212, step 318 to step 218, and steps 332 to 336 to step 2
28 to 232, and the description thereof will be omitted. That is, only the method of obtaining the deposit correction coefficient Kdp in each load region is different.

First, when it is determined that the engine load is high (WOT), the high-load deposit correction coefficient KdpW corresponding to the deposit learning value KDPC and the engine speed NE is referred to by referring to the map shown in FIG. Ask (step 314). As you can see from this figure, NE
The higher the value, the higher the value of KdpW, so GN
Of the valve timing displacement amount (valve overlap amount) is increased. Next, the obtained high load deposit correction coefficient KdpW is used as the final deposit correction coefficient Kdp.
(Step 316).

When it is determined to be in the medium load range, first, by referring to the map as shown in FIG. 24, the deposit learning value KDPC and the engine speed N
A medium-load deposit correction coefficient KdpPne corresponding to E is obtained (step 320). As you can see from this figure, NE
The higher the value, the larger KdpPne is, so G
The increase correction amount of N becomes large, so that the increase correction amount of the valve timing displacement amount (valve overlap amount) becomes large. Next, by referring to the map as shown in FIG. 25, the deposit learning value KDPC
Also, a deposit correction coefficient KdpPgn for medium load according to the intake air amount (load) GN is obtained (step 322). As can be seen from this figure, the higher the GN, the larger the value of KdpPgn. Therefore, the increase correction amount of the GN increases, and thus the increase correction amount of the valve timing displacement amount (valve overlap amount) increases. Will result. Then, the final deposit correction coefficient Kdp is obtained by the calculation Kdp ← KdpPne × KdpPgn (step 324).

When it is determined that the vehicle is in the light load range, first, by referring to the map shown in FIG. 26, the deposit learning value KDPC and the engine speed N
A light load deposit correction coefficient KdpSne corresponding to E is calculated (step 326). As you can see from this figure, NE
The lower is, the smaller KdpSne is, so G
The reduction correction amount of N becomes large, and therefore the reduction correction amount of the valve timing displacement amount (valve overlap amount) becomes large. Next, referring to the map as shown in FIG. 27, the deposit learning value KDPC
And a light load deposit correction coefficient KdpSgn corresponding to the intake air amount (load) GN (step 328). As can be seen from this figure, the lower the GN, the smaller the value of KdpSgn, and the larger the reduction correction amount of the GN becomes. Therefore, the reduction correction amount of the valve timing displacement amount (valve overlap amount) is increased. Will result. Then, the final deposit correction coefficient Kdp is obtained by the calculation Kdp ← KdpSne × KdpSgn (step 330).

As described above, in the third embodiment, since the engine speed and the engine load are taken into consideration in obtaining the correction amount of the valve timing displacement amount (valve overlap amount) according to the deposit, it is possible to improve the accuracy. High correction is possible.

Finally, a fourth embodiment according to the first, second and sixth inventions will be described. Normally, when the vehicle is started, the accelerator pedal is depressed and the engine speed increases to some extent before the clutch is engaged. However, the engine speed may drop sharply depending on how the clutch is engaged. In such a case,
A conventional VVT control device attempts to increase the valve overlap amount in response to the depression of the accelerator pedal and then to reduce the valve overlap amount in response to a rapid decrease in the engine rotation speed. Cannot keep up with such a momentary fluctuation of the engine rotation speed, and the internal EGR amount is maintained at a relatively large amount even though the engine rotation speed is reduced, resulting in deterioration of combustion. However, there is a problem that engine stalls easily occur.

Further, the state in which the deposit adheres to the combustion chamber causes deterioration of combustion as described above. Further, even if a deposit adheres to the intake wall surface, the air-fuel ratio becomes lean when starting or accelerating, resulting in deterioration of combustion. Therefore, the greater the deposit amount, the more serious the problem of deterioration of combustion due to the VVT responsiveness described above. Therefore, in the fourth embodiment, the valve timing displacement amount is reduced and corrected in accordance with the deposit amount so that the VVT mechanism can follow the valve timing displacement amount (valve overlap amount) at the time of starting.

The processing procedure of the VVT control routine according to the fourth embodiment is shown in FIG. Steps 402-406
Is the same as steps 102 to 106 of the first embodiment (FIG. 9), and the engine speed NE, the intake air amount GN, and the basic target valve timing displacement amount (map value) tVTD
Is required. Next, at step 408, the current vehicle speed SPD is detected from the output of the vehicle speed sensor 53. In the next step 410, it is determined whether SPD is less than 5 km / h, that is, whether the vehicle is starting, and if it is starting, the procedure proceeds to step 412, and if it is not starting, step 418.
Proceed to. In step 412, the backup RAM 79
The deposit learning value KDPC stored in is stored. Next, based on this KDPC, by referring to the map as shown in FIG. 29, the tVTD correction coefficient Kdp (<1.0) according to the deposit learning value KDPC.
Is calculated (step 414). Then, based on this Kdp, tVTD is reduced by a correction calculation of tVTD ← tVTD × Kdp (step 416). In step 418 executed after step 410 or 416, the VVT mechanism is feedback-controlled with tVTD as the final control target valve timing displacement amount.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, of course.
It will be easy for those skilled in the art to devise various embodiments.

[0074]

As described above, according to the present invention,
Provided is a continuously variable valve timing control device capable of setting the optimum valve timing, that is, the valve overlap amount, in accordance with the increase in the amount of deposited deposit. Therefore, the present invention contributes to further improvement of air-fuel ratio control accuracy, exhaust gas purification performance, fuel efficiency, drivability, output performance, etc. in an internal combustion engine.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine equipped with a continuously variable valve timing control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a hardware configuration of an engine ECU according to an embodiment of the present invention.

FIG. 3 is a valve timing chart in which opening / closing timings of intake valves and exhaust valves are represented by crank angles.

FIG. 4 is a characteristic diagram showing a relationship between an intake wall surface deposit amount and an intake wall surface fuel amount.

FIG. 5 is a characteristic diagram showing a relationship between engine cooling water temperature and intake wall surface fuel adhesion amount.

FIG. 6 is a characteristic diagram showing a relationship between a valve overlap amount (valve timing displacement amount) and an intake wall surface fuel adhesion amount.

FIG. 7 (A) throttle opening during acceleration, (B)
It is a figure which shows the time change of intake wall surface fuel adhesion amount, (C) combustion chamber supply fuel amount, and (D) air-fuel ratio about the case where intake wall surface fuel adhesion amount is small (curve) and large (curve).

FIG. 8 is a diagram showing a valve timing displacement amount subtraction correction amount OTHW depending on a water temperature THW, where (A) shows a case without deposit correction and (B) shows a case with deposit correction.

FIG. 9 is a flowchart showing a processing procedure of a VVT control routine according to the first embodiment.

FIG. 10 is a diagram showing a map for determining a basic target valve timing displacement amount tVTD according to an engine speed NE and an intake air amount (mass) GN per engine revolution.

FIG. 11 is a diagram showing a map for determining a water temperature correction amount Kdp according to a deposit learning value KDPC.

FIG. 12 is a characteristic diagram showing a relationship between an intake wall surface deposit amount and a combustion chamber deposit amount.

FIG. 13 is a characteristic diagram showing a relationship between a combustion chamber deposit amount and combustion stability.

FIG. 14 is a characteristic diagram showing a relationship between an intake air amount GN and an internal EGR amount.

FIG. 15: Intake air amount GN and valve timing displacement amount V
It is a characteristic view which shows the relationship with TD.

FIG. 16 is a flowchart (1/2) showing a processing procedure of a VVT control routine according to the second embodiment.

FIG. 17 is a flowchart (2/2) showing a processing procedure of a VVT control routine according to the second embodiment.

FIG. 18 is a diagram showing a map in which reference values KtaW and KtaP for making a high load determination and a medium load determination based on a throttle opening TA are determined according to an engine speed NE.

FIG. 19 is a diagram showing a map of a deposit correction coefficient Kdp (KdpW during high load, KdpP during medium load, KdpS during light load) for correcting the intake air amount GN according to the deposit learning value KDPC.

FIG. 20 is a characteristic diagram showing the relationship between the engine speed NE and the intake air amount GN at high load (WOT) when the deposit amount is small and when it is large.

FIG. 21 is a flowchart (1/2) showing a processing procedure of a VVT control routine according to the third embodiment.

FIG. 22 is a flowchart (2/2) showing the processing procedure of the VVT control routine according to the third embodiment.

FIG. 23 is a diagram showing a map of a deposit correction coefficient KdpW for correcting the intake air amount GN according to the engine speed NE and the deposit learning value KDPC in the high load range.

FIG. 24 is a diagram showing a map of a deposit correction coefficient KdpPne for correcting the intake air amount GN according to the engine speed NE and the deposit learning value KDPC in the medium load range.

FIG. 25 is a diagram showing a map of a deposit correction coefficient KdpPgn for correcting the intake air amount GN according to the intake air amount GN and the deposit learning value KDPC in the medium load range.

FIG. 26 is a diagram showing a map of a deposit correction coefficient KdpSne for correcting the intake air amount GN according to the engine speed NE and the deposit learning value KDPC in the light load region.

FIG. 27 is a diagram showing a map of a deposit correction coefficient KdpSgn for correcting the intake air amount GN according to the intake air amount GN and the deposit learning value KDPC in the light load region.

FIG. 28 is a flowchart showing a processing procedure of a VVT control routine according to the fourth embodiment.

FIG. 29 is a diagram showing a map of a deposit correction coefficient Kdp for correcting the basic target valve timing displacement amount tVDT according to the deposit learning value KDPC.

[Explanation of symbols]

2 ... Air cleaner 4 ... Throttle body 5 ... Throttle valve 6 ... Surge tank (intake manifold) 7 ... Intake pipe 8 ... Idle adjust passage 10 ... Fuel tank 11 ... Fuel pump 12 ... Fuel piping 20 ... Engine body (cylinder) 21 ... Combustion Chamber 22 ... Cooling water passage 23 ... Piston 24 ... Intake valve 26 ... Exhaust valve 30 ... Exhaust manifold 34 ... Exhaust pipe 38 ... Catalytic converter 40 ... Thermal air flow meter 41 ... Vacuum sensor 42 ... Throttle opening sensor 43 ... Intake temperature sensor 44 ... Water temperature sensor 45 ... O ₂ sensor 50 ... Reference position detection sensor 51 ... Crank angle sensor 52 ... Idle switch 53 ... Vehicle speed sensor 54 ... First magnetic sensor 55 ... Second magnetic sensor 60 ... Fuel injection valve 62 ... Igniter 63 ... Ignition coil 64 ... Ignition distribution 65 ... Spark plug 66 ... Idle speed control valve (ISCV) 68 ... Hydraulic control valve 70 ... Engine ECU 71 ... CPU 72 ... System bus 73 ... ROM 74 ... RAM 75 ... A / D conversion circuit 76 ... Input interface circuit 77a, 77b, 77c, 77d ... Drive control circuit 79 ... Backup RAM 80 ... Connecting rod 81 ... Crankshaft 82 ... Magnetic material 84 ... Timing pulley 85, 86 ... Camshaft 87, 88 ... Cam 89, 90 ... Timing pulley 91 ... Timing belt 92 ... Valve timing continuously variable mechanism 93 ... Magnetic material

Claims (12)

[Claims] 1. A continuously variable valve timing control device for changing a valve overlap amount according to a load of an internal combustion engine, which is capable of continuously changing valve timing of at least one of an intake valve and an exhaust valve. A continuously variable valve timing mechanism and setting means for setting the target valve overlap amount according to the engine load so that the valve overlap amount is suitable for emissions and fuel consumption in the medium load range and suitable for output in the high load range. A control unit for controlling the valve timing continuously variable mechanism so that the target valve overlap amount set by the setting unit is adjusted; and the target valve overlap amount set by the setting unit is corrected at least in accordance with the deposit amount. A continuously variable valve timing control device comprising: 2. The continuously variable valve timing control device according to claim 1, wherein the correction means corrects the target valve overlap amount so as to decrease as the deposit amount increases. 3. The continuously variable valve timing control device according to claim 1, wherein the correction means reduces and corrects the target valve overlap amount based on an amount determined by a deposit adhesion amount and a combustion state. 4. The continuously variable valve timing control device according to claim 3, further comprising a correction limiting unit that limits the correction by the correction unit only when the load is light. 5. The continuously variable valve timing control device according to claim 4, further comprising second correction means for increasing the correction amount as the engine speed decreases. 6. The continuous operation according to claim 2, wherein the correction means reduces the target valve overlap amount based on an amount determined by the responsiveness of the valve timing continuously changing mechanism and a deposit adhesion amount. Variable valve timing controller. 7. The continuously variable valve timing control device according to claim 2, further comprising a correction limiting unit that limits the correction by the correcting unit only when the load is high. 8. The continuously variable valve timing control device according to claim 7, further comprising third correcting means for increasing the correction amount as the engine speed increases. 9. The continuously variable valve timing control device according to claim 1, wherein the correction means increases and corrects the target valve overlap amount as the deposit adhesion amount increases. 10. The continuously variable valve according to claim 9, wherein the correction means increases and corrects the target valve overlap amount based on an amount determined by a combustion chamber residual exhaust gas amount and a deposit adhesion amount. Timing control device. 11. The continuously variable valve timing control device according to claim 10, further comprising a correction limiting unit that limits the correction by the correcting unit only when the load is medium. 12. The continuously variable valve timing control device according to claim 11, further comprising fourth correction means for increasing the correction amount as the engine speed increases.