JP2002235593A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve timing device capable of performing a stable combustion even if an ignition timing is delayed. SOLUTION: This controller is explained according to a flow chart shown in Fig. 6. In step 301, it is judged whether the requirements for execution of catalyst premature warming-up are satisfied or not. When the requirements are satisfied, it is judged in step 302 whether an intake valve 8 is set to a target open position or not. When the intake valve is not at the target open position, in step 303, the intake valve 8 is set to the target open position where a sufficient intake air flow velocity can be obtained, and this routine is terminated. Thus, since the intake valve 8 is set to the target open position where the sufficient intake flow velocity can be obtained, fuel adhered to an intake passage can be evaporated and, since mixture in a combustion chamber can be agitated sufficiently, an air/fuel ratio is prevented from being disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine having a variable valve timing mechanism.

[0002]

2. Description of the Related Art In recent years, there has been developed a technique for activating a catalyst at an early stage after an internal combustion engine is started in response to a request for emission regulation. In this technique, in order to activate the catalyst at an early stage, a high-temperature gas of incomplete combustion is intentionally discharged by retarding the ignition, thereby achieving an early temperature rise of the three-way catalyst.

[0003] As a technique relating to early temperature rise of a three-way catalyst,
In the technology disclosed in JP-A-6-117348,
When the ignition timing is retarded for early warm-up of the catalyst, the intake valve is opened during a period from the top dead center to the bottom dead center of the piston during the period from the exhaust stroke to the intake stroke of the internal combustion engine. Is controlled. According to this, the combustion speed is reduced due to the ignition retardation, so that the combustion gas may flow back into the intake pipe at the timing when the normal intake valve is opened, and backfire may occur. By performing the control, the backflow of the combustion gas into the intake pipe is prevented, and the backfire that occurs when the ignition is retarded is prevented.

[0004]

However, Japanese Patent Laid-Open No. 6-1173 / 1994
In the technique of JP-A-48-48, the backfire that occurs when the ignition is retarded is prevented, but there is no description about stabilizing combustion.

Accordingly, an object of the present invention is to provide a variable valve timing device capable of performing stable combustion even when ignition retard is performed.

[0006]

According to the first aspect of the present invention,
In an internal combustion engine that performs ignition timing retard control to warm up the catalyst early, the internal combustion engine includes a retard control unit that retards the opening timing of the intake valve when the start of the internal combustion engine is a cold start. The fuel injection control means performs fuel injection control according to the delayed opening timing of the intake valve.

[0007] By delaying the opening timing of the intake valve as described above, the state where the intake valve is closed is maintained even when the piston of the internal combustion engine moves from the top dead center to the bottom dead center. Thus, the pressure in the combustion chamber becomes relatively lower than the pressure in the intake pipe. Since the intake valve is opened in this state, the flow rate of intake air is improved by the pressure difference between the pressure in the intake pipe and the pressure in the combustion chamber.

When the intake valve starts to open, since the area for the intake air to flow into the fuel chamber is small, and particularly the intake flow velocity is improved, the fuel is drawn into the combustion chamber at this timing. By controlling the injection,
Atomization of the fuel is promoted and good combustion is obtained. Further, by performing these controls at the time of a cold start, the amount of fuel adhering to the intake passage can be reduced by improving the intake flow velocity, and the emission of HC gas and the like due to the adhering fuel can be reduced.

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the retard control means determines that a difference between the pressure in the intake passage and the pressure in the combustion chamber is equal to or greater than a predetermined value. Thus, the opening timing of the intake valve is retarded.

[0010] Thus, the intake flow velocity when the intake valve is opened can reduce the amount of fuel adhering to the wall surface of the intake passage, and the fuel injected by the fuel injection control can have an improved intake flow velocity. This promotes atomization and stabilizes combustion.

The predetermined value is preferably a differential pressure capable of obtaining an intake air flow rate at which sufficient injection fuel is atomized. For example, about 30 KPa or more is a preferable value for obtaining a sufficient intake air flow rate.

According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the first or second aspect, the retard control means is blown back into the intake passage when the intake valve is opened. The opening timing of the intake valve is retarded so that the gas amount becomes equal to or more than a predetermined value.

Thus, the gas in the combustion chamber having a relatively high temperature is blown back to the intake pipe, so that the intake passage can be warmed up, and the fuel adhering to the intake passage can be positively evaporated. .

According to a fourth aspect of the present invention, in the control apparatus for an internal combustion engine according to any one of the first to third aspects, the retard control means determines that the internal combustion engine has been started by the start determination means. When the determination is made, the opening timing of the intake valve is retarded from a predetermined opening timing regulated by the intermediate holding mechanism when the internal combustion engine is started.

Thus, at the time of starting, the start timing of the internal combustion engine can be ensured by maintaining the opening timing of the intake valve at a timing suitable for starting, and when it is determined that the internal combustion engine has started, it is delayed. Since the opening timing of the intake valve is retarded by the angle control means, it is possible to atomize the injected fuel controlled by the fuel injection control means and reduce the amount of fuel adhering to the intake passage, thereby reducing the emission of HC gas. can do.

According to a fifth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to fourth aspects, the fuel injection control means includes: When this is done, the fuel injection amount is reduced and corrected.

When the retard control is performed, the fuel adhering to the intake passage flows into the combustion chamber in order to increase the intake flow velocity. For this reason, it is possible to prevent the air-fuel ratio from being disturbed by reducing and correcting the amount of the attached fuel flowing into the combustion chamber.

According to a sixth aspect of the present invention, in the control apparatus for an internal combustion engine according to any one of the first to fifth aspects, the fuel injection control means includes an advance angle control means for setting the intake valve to an advance angle. When this is done, the fuel injection amount is increased and corrected.

If the opening timing of the intake valve is set after the top dead center, a pressure difference occurs between the intake passage and the combustion chamber. Is larger than when it opens. Further, even after the top dead center, the intake flow velocity changes depending on the opening timing of the intake valve, so that the degree of evaporation of the fuel attached to the intake pipe also differs. Therefore, as described above, when the advance timing of the intake valve is advanced by the advance angle control means, the fuel injection amount is controlled to increase in accordance with the advance angle, thereby controlling in consideration of the fuel adhering to the intake pipe. Therefore, it is possible to prevent the air-fuel ratio from being disturbed.

According to a seventh aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to sixth aspects, the second valve timing control means for setting the closing timing of the exhaust valve is provided. A period during which the intake valve is retarded by retard control means for early catalyst warm-up,
The exhaust valve is advanced by the second valve timing control means.

Thus, the amount of exhaust gas remaining in the combustion chamber is increased by advancing the closing timing of the exhaust valve. Since this is performed when the opening timing of the intake valve is retarded, the exhaust gas remaining in the combustion chamber can be further agitated by the improvement of the intake flow velocity, so that deterioration of combustion can be reduced.

According to an eighth aspect of the present invention, in the control apparatus for an internal combustion engine according to the fourth aspect, when it is detected that the internal combustion engine is in a semi-warmed state at the time of starting the internal combustion engine, the internal combustion engine is started. Sometimes the intake valve is retarded. Thereby, the atomization of the fuel is promoted by the improvement of the intake flow velocity, and the startability of the internal combustion engine can be improved.

According to the ninth aspect of the present invention, in the control device for an internal combustion engine according to the eighth aspect, when the catalyst is not warmed up and the internal combustion engine is almost warmed up, the internal combustion engine is activated. It is determined that it is in a semi-warmed state. Here, the state in which the internal combustion engine is almost warmed up is a state in which the internal combustion engine is restarted before the cooling water temperature starts decreasing after the engine stops.

In such a case, the startability is more stable than at the time of the cold start. Therefore, when the opening timing of the intake valve is retarded, the engine can be started sufficiently even if the charging efficiency is deteriorated. Further, the intake air flow rate is increased, and the atomization of the fuel is improved, so that the combustion state of the fuel is improved, and the emission at the time of starting can be improved.

Further, since the opening timing of the intake valve is already retarded at the time of starting, ignition retard control for early warm-up of the catalyst can be executed immediately after starting.

According to a tenth aspect of the present invention, in the control apparatus for an internal combustion engine according to the ninth aspect, the temperature of the internal combustion engine is set to be half-warmed, the cooling water temperature of the internal combustion engine, the elapsed time after starting the internal combustion engine, and the intake air temperature. By using at least one of the integrated values of the internal combustion engine speed, it is possible to accurately detect the semi-warmed state of the internal combustion engine.

According to the eleventh aspect of the present invention, the second valve timing control means controls the exhaust valve according to the opening timing of the intake valve while the opening timing of the intake valve is delayed by the retarding control means. Control the closing timing.

Thus, when the opening timing of the intake valve is retarded, the optimal closing timing of the exhaust valve can be set according to the opening timing of the intake valve. Normally, a slight gap is created between the exhaust valve and the cylinder for a predetermined period even when the exhaust valve is closed. When a negative pressure is generated in the cylinder by retarding the opening timing of the intake valve as in the present invention, the influence of this gap is greatly affected.

Therefore, according to the present invention, the closing timing of the exhaust valve is set so that the intake valve opens after a predetermined crank angle has elapsed after the closing of the exhaust valve. Since the exhaust valve and the cylinder can be reliably sealed, a negative pressure can be efficiently generated in the cylinder by delaying the closing timing of the intake valve.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the valve timing control device for an internal combustion engine according to each invention described above is embodied in a gasoline engine will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an internal combustion engine (engine) provided with a valve timing control device according to a first embodiment of the present invention. Engine 1 consisting of a plurality of cylinders
A piston 3 is provided in the cylinder 2 of each cylinder so as to be movable up and down, and a combustion chamber 4 is provided above the piston 3.

Each combustion chamber 4 is provided with a spark plug 5. In addition, each combustion chamber 4 is provided with an intake passage 6 and an exhaust passage 7 through an intake port 6a and an exhaust port 7a.
Are provided respectively. Downstream of the exhaust passage 7, H
A three-way catalyst 19 capable of purifying C gas is provided.

The catalyst disposed downstream of the exhaust passage 7 is not limited to the three-way catalyst 19 but may be any catalyst capable of adsorbing or occluding HC gas. For example, an HC adsorbing catalyst may be used. A plurality of these catalysts may be provided in combination.

The intake port 6a and the exhaust port 7
a includes an intake valve 8 for opening and closing the intake port 6a.
And an exhaust valve 9 for opening and closing the exhaust port. The intake valve 8 and the exhaust valve 9 are connected to the intake camshaft 10 and the exhaust camshaft 1.
It is driven by one rotation. Also, each camshaft 10,
At one end of 11, an intake-side timing pulley 12 and an exhaust-side timing pulley 13 are provided. Further, each of the timing pulleys 12 and 13 is drivingly connected to a crankshaft (not shown) via a timing belt 14.

Therefore, when the engine 1 is operating, rotational power is transmitted from the crankshaft to the camshafts 10 and 11 via the timing belt 14 and the timing pulleys 12 and 13, and the rotation of the camshafts 10 and 11 causes intake air to rotate. The valve 8 and the exhaust valve 9 are driven to open and close. The intake valve 8 and the exhaust valve 9 are synchronized with the rotation of the crankshaft, that is, in synchronization with a series of four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke.
It is driven at a predetermined opening / closing timing. In the vicinity of the intake port 6a for each cylinder, an injector 16 as a fuel injection valve for fuel injection is provided for each cylinder.

In the middle of the intake passage 6, there is provided a throttle valve 17 which is electrically controlled to open and close based on operation of an accelerator pedal (not shown). When the throttle valve 17 is opened and closed, the intake passage 6 is opened.
The intake amount of outside air into the air, that is, the intake air amount is adjusted.
A surge tank 18 for smoothing intake pulsation is provided downstream of the throttle valve 17.
In the vicinity of the throttle valve 17, a throttle sensor 74 for detecting the throttle opening TA is provided.

Further, the engine 1 is provided with a water temperature sensor 75 for detecting the temperature of the cooling water (cooling water temperature) THW.

The high voltage distributed by the distributor 21 is applied to each ignition plug 5. The distributor 21 has a built-in rotor (not shown) connected to the exhaust-side camshaft 11 and rotated in synchronization with rotation of the crankshaft. The distributor 21 is provided with a rotation speed sensor 76 for detecting the rotation speed (engine rotation speed per minute) Ne of the engine 1 from the rotation of the rotor. Further, a cylinder discrimination sensor 77 for detecting a crank angle reference position GP of the engine 1 at a predetermined ratio according to the rotation of the rotor is attached to the distributor 21. In this embodiment, assuming that the crankshaft makes two rotations for a series of four strokes of the engine 1, the rotation speed sensor 76 detects the crank angle at a rate of 30 ° CA per pulse. Also, the cylinder discrimination sensor 77 uses 3 per pulse.
The crank angle is detected at a rate of 60 ° CA.

In this embodiment, the intake-side timing pulley 12 is similarly provided with a hydraulically operated intake-side variable valve timing mechanism 25a driven by oil pressure to make the opening and closing timing of the intake valve 8 variable. The exhaust-side timing pulley 13 has an exhaust-side variable valve timing mechanism 25 for making the opening / closing timing of the exhaust valve 9 variable.
b is provided.

The oil pan 28 and the oil pump 29 constitute an engine lubrication system of the present embodiment. The oil pump 29 pumps up the oil in the oil pan 28, and the pumped-up oil is supplied to the intake-side variable valve timing mechanism 25a through an oil path 90 via an oil filter 30. Here, the first oil control valve 56a provided in the middle of the oil passage 90 adjusts the pressure of the oil supplied to the advance chamber and the retard chamber (not shown) of the intake-side variable valve timing mechanism 25a, and The opening timing of the valve 8 is controlled to be advanced or retarded.

The oil passage 90 branches off downstream of the oil filter, and the intake-side variable valve timing mechanism 25
Similarly to the case a, the second oil control valve 56b adjusts the pressure of the oil supplied to the advance chamber and the retard chamber (not shown) of the exhaust-side variable valve timing mechanism 25b to advance the opening timing of the exhaust valve 9. Side, retard side.

First and second oil control valves 5
Each of 6a and 56b is constituted by a solenoid type electromagnetically driven valve, and determines the spool amount according to the duty ratio of the applied voltage. By changing the spool amounts of the first and second oil control valves 56a and 56b, the intake-side and exhaust-side variable valve timing mechanisms 25a and 25
By adjusting the oil pressure supplied to b, the valve timing can be adjusted to the advance side or the retard side. As the oil control valves 56a and 56b, conventionally known hydraulic control valves may be used. The detailed description of the oil control valve is omitted.

Each of the variable valve timing mechanisms 25a and 25b on the intake side and the exhaust side has a vane in a housing (not shown), and a hydraulic pressure (not shown) for urging the vane to advance and retard. The variable valve timing mechanisms 25a and 25b on the intake side and the exhaust side are independently advanced and retarded by applying voltage to the chamber and the retard chamber. In addition,
Not only the conventionally known vane type variable valve timing mechanism but also a conventionally known helical type variable valve timing mechanism may be used. Further, a valve that can set the opening and closing timing of the valve by setting the lift amount variably may be used, or a valve that can freely set the valve timing and the lift amount by electromagnetic driving may be used. good. A detailed description of the valve timing mechanism will be omitted.

Intake side and exhaust side valve timing mechanism 25
The first and second oil control valves 56a and 56b for advancing or retarding the a.25b are controlled by an ECU.
80 is electrically connected. The ECU 80 includes:
The spool amount of the second oil control valves 56a and 56b is controlled.

FIG. 2 shows the configuration of the ECU 80. A schematic configuration of the ECU 80 will be described with reference to FIG. ECU
The 80 is electrically connected to a throttle sensor 74, a water temperature sensor 75, a rotation speed sensor 76, a cylinder discrimination sensor 77, cam rotation angle sensors 78a and 78b, and an oil temperature sensor 79, respectively. The ECU 80 controls each of these sensors 74
The drive of each injector 16, the igniter 22, and the first and second oil control valves 56a and 56b is appropriately controlled based on output signals output from the devices 79 to 79 and the like.

Next, an electrical configuration related to the ECU 80 will be described. The ECU 80 includes a CPU 81 as a central processing unit, a read-only memory (ROM) 82 in which a predetermined control program and the like are stored in advance, a random access memory (RAM) 83 for temporarily storing the calculation results of the CPU 81, and the like. A backup RAM 84 for storing the data. The components 81 to 84, the external input circuit 85 including the analog / digital converter, and the external output circuit 86 transmit and receive signals via the bus 87.

The external input circuit 85 includes a throttle sensor 74, a water temperature sensor 75, a rotation speed sensor 76, a cylinder discrimination sensor 77, a cam rotation angle sensor 78, and an oil temperature sensor 79.
Are connected respectively. On the other hand, the external output circuit 86
Each injector 16, the igniter 22 and the first,
The second oil control valves 56a and 56b are respectively connected.

The CPU 81 reads detection signals from the sensors 74 to 79 and various sensors (not shown) input via the external input circuit 85 as input values at each time, and
It is stored in a predetermined area of the AM 83. Further, the CPU 81 controls the fuel injection amount, the ignition timing, and the like based on the input values read from the sensors 74 to 79 and various sensors (not shown).
In order to execute idle speed control, valve timing control, etc., each injector 16 and igniter 2
2 and the first and second oil control valves 56a
56b and the like are appropriately controlled.

In addition to the above configuration, a circuit configuration is adopted in which power is applied to each circuit even after the key switch is turned off in order to control valve timing and the like after turning off the ignition switch SW.

That is, the external output circuit 86 is connected to the base terminal of the transistor TR. The emitter terminal of the transistor TR is connected to the input terminal of the power holding circuit 88, and the collector terminal is grounded. The other input terminal of the power supply holding circuit 88 is connected to a power supply circuit 89 including a battery via a switch SW. A resistor R1 is connected between the ignition switch SW and the power holding circuit 88, and a negative terminal of the resistor R1 is grounded via a resistor R2. The output terminal of the power holding circuit 88 is connected to the power circuit 89. The power supply circuit 89 is connected to various electric circuits mounted on the vehicle and supplies power stably. The power supply circuit 89 is operated by a High signal from the power supply holding circuit 88 and is stopped by a Low signal.

When the ignition switch SW is turned on, the power supply holding circuit 88 outputs a high level signal from the output terminal.
h signal is output. When a drive signal from the external output circuit 86 is output to the transistor TR, the transistor TR operates and a High signal is output from the output terminal of the power holding circuit 88. The power holding circuit 88 is disclosed in
No. 166705, page 5, upper left column, line 19 to upper right column, first
This can be realized by an OR gate and a relay described in two lines.

Next, among the various processing contents executed by the ECU 80, the processing contents according to the present invention will be described.

FIG. 3 is a flowchart showing the control of the ignition timing performed to warm up the three-way catalyst 19 early. First, at step 101, the engine speed N
e, the intake pipe pressure PM, the engine coolant temperature Thw, and the like are read. Here, the engine rotation speed Ne and the intake pipe pressure P
M and the engine water temperature Thw are read out in a later step. The engine rotation speed Ne and the intake pipe pressure PM are parameters for calculating the basic ignition timing θBSE, and the engine water temperature Thw is a retard correction value for the basic ignition timing θBSE. This is because it is a parameter for calculating θCLD.

Next, in step 102, step 101
It is determined from the detected engine speed Ne whether or not the engine is started. For example, 1000 rpm is set as the engine rotation speed Ne for determining the start time. That is, after the cranking, if the engine rotation speed Ne exceeds 1000 rpm even once, it is determined that the start is completed. Of course, the start may be determined using another known method. Further, the engine speed for determining the start may be other than 1000 rpm.
It may be set to 00 rpm.

In this step 102, it is determined whether or not the engine is to be started, because the ignition timing is not retarded at the time of starting to give priority to combustion stabilization, while the catalyst is quickly warmed after the start. This is because the ignition timing is retarded in order to operate.

If it is determined in step 102 that the engine is in the starting state, the routine proceeds to step 108, where the fixed ignition timing at which the combustion is stabilized is stored at a predetermined address, and this routine is terminated. On the other hand, if it is determined in step 102 that it is not the time of starting, the process proceeds to step 103, and it is determined whether or not the operating state of the internal combustion engine is idling. If it is determined in step 103 that the engine is in the idling operation state, the routine proceeds to step 105, where the basic ignition timing θBSE is calculated from the engine speed Ne and the engine coolant temperature Thw.
Proceed to step 106. On the other hand, if it is determined that the operation state of the internal combustion engine is not the idle operation state, step 10
The program proceeds to step S4, where the basic ignition timing θBSE is calculated from the intake pipe pressure PM, the engine coolant temperature Thw, and the engine rotation speed Ne.

In step 106, the engine coolant temperature Thw
The retardation correction value θCLD is calculated from Thus, in steps 104 to 106, the basic ignition timing θBS
After calculating E and the retard correction value θCLD, step 10
7, the ignition timing θig is calculated (θig = θBSE−θC).
LD) and store it at a predetermined address. Thereafter, this routine ends.

Next, the fuel injection amount TAU according to the ignition timing
Is described with reference to FIG.

In step 201, the engine speed N
e, engine water temperature Thw, intake pipe pressure PM, intake temperature Th
Read a. Then, the routine proceeds to step 202, where it is determined whether or not the operating state of the internal combustion engine is the operating state at the time of starting. If it is determined that the operating state is the time of starting, the routine proceeds to step 205, where the fuel injection amount TAUSTA at the time of starting is calculated from the engine water temperature Thw read in step 201, and the routine proceeds to step 206. In step 206, the starting fuel injection amount TAUSTA is corrected based on the intake air temperature Thw and the engine rotation speed Ne read in step 201, and the routine ends.

On the other hand, if it is determined in step 202 that the operating state is not at the time of starting, the process proceeds to step 203,
A basic injection amount Tp as a base is calculated from the engine rotation speed Ne and the intake pipe pressure PM. And step 204
It is determined whether two seconds or more have elapsed since the start. If more than 2 seconds have passed since startup, step 2
Proceed to 10. On the other hand, if two seconds have not elapsed after the start, the processing of steps 207 to 209 is performed.

First, in step 207, step 20
A fuel increase coefficient FASE after the start is calculated from the engine coolant temperature Thw read in step 1. The fuel increase coefficient FASE at the time of starting from the engine water temperature Thw is calculated such that the air-fuel ratio gradually goes to the lean side at the moment of exit from the time of starting to after the starting, so that the fuel injection amount is gradually increased from the time of starting to after the starting. Is to be attenuated.

Next, at step 208, a correction coefficient α is calculated from the retardation correction value θCLD calculated at step 106 of the ignition timing calculation routine of FIG. Then, the fuel increase coefficient FASB after the start is calculated from the calculated fuel increase coefficient FASE and the correction coefficient α (FASE = FASE
× α), and proceeds to step 210.

In step 210, the warm-up increase coefficient FWL is calculated from the engine coolant temperature Thw read in step 201.
Is calculated, and the routine proceeds to step 211. In step 211, another correction coefficient β is calculated, and the process proceeds to step 212. In step 212, a correction coefficient γ corresponding to the opening timing (opening timing) of the intake valve 8 is calculated. Control of the opening timing of the intake valve will be described later. As a method of calculating the correction coefficient γ, for example, a method of calculating using the map shown in FIG. In FIG. 5, the opening timing of the intake valve is determined by BTDC (before top dead ce).
(nter) crank angle. Therefore, the negative value indicates that the opening timing of the intake valve is more retarded.
In the map of FIG. 5 of the intake valve, the correction coefficient γ is set so that the fuel injection amount decreases as the opening timing is retarded.

The calculated basic injection amount T
The final fuel injection amount TAU is calculated from p and various correction coefficients (TAU = Tp × (1 + FASE + FWL) × β ×
γ), and terminates this routine.

Next, control of the opening timing of the intake valve 8, which is a feature of the present invention, will be described with reference to the flowchart of FIG. First, at step 300, it is determined whether or not the engine speed Ne is equal to or higher than a predetermined value. Since the variable valve timing mechanism is driven by hydraulic pressure, the predetermined value is set to 1000 rpm in consideration of sufficient driving.
It is preferable to set m or more. If it is determined that the engine 1 has not been started by such a determination, step 3
Proceed to 10. When it is determined that the rotation speed is equal to or more than 1000 rpm, the process proceeds to step 301, and it is determined whether or not the condition for executing the catalyst early warm-up is satisfied.

The condition for executing the early catalyst warm-up is determined based on the rotational speed Ne, the engine water temperature Thw, and the fuel control. Here, if the execution condition is not satisfied, the routine proceeds to step 310, where normal control is performed. In the normal control, the ignition valve is not retarded.
, And the closing timing control of the exhaust valve 9 is performed.

On the other hand, if the condition for executing the early catalyst warm-up is satisfied in step 301, it is determined in step 302 whether the intake valve 8 is at the target open position. If the intake valve is not at the target open position, the routine proceeds to step 303,
The intake valve 8 is set to the target open position, and this routine ends.

The control of the target opening position of the intake valve 8 is described in FIG.
This will be described with reference to the timing charts shown in FIGS.

In FIG. 7A, the solid line shows the opening / closing timing of the intake valve 8 and the exhaust valve 9 in the normal state, and the dotted line shows the opening / closing timing of the intake valve 8 after retarding.
That is, the target open position is shown. This target opening position is set based on the in-cylinder volume and the in-cylinder pressure in the combustion chamber shown in FIGS. 7 (b) to 7 (c). In the in-cylinder volume of FIG. 7B, the volume indicated by hatching in the figure is a predetermined value or more.
At the in-cylinder (combustion chamber) pressure of (c), the target opening position of the intake valve 8 is set such that the deviation between the in-cylinder pressure and the intake pipe pressure is equal to or greater than a predetermined value.

The condition for setting the target opening position of the intake valve 8 may be determined only from the cylinder volume shown in FIG. 7B, or may be determined from the cylinder pressure and the intake pipe shown in FIG. It may be determined only from the deviation from the pressure. Further, for the purpose of stabilizing combustion, the target opening position may be set based on the intake air flow velocity. More specifically, this is performed based on the characteristic diagrams shown in FIGS. FIG. 8 shows the intake flow rate with respect to the target open position of the intake valve 8, and the intake valve 8 is set to the target open position where an intake flow rate sufficient to agitate the air-fuel mixture in the combustion chamber can be obtained.

In the characteristic diagram of FIG. 8, the intake flow velocity increases as the target opening position of the intake valve 8 is more retarded. Further, in the characteristic diagram of FIG. 9, the intake pipe temperature increases as the target opening position of the intake valve 8 is more retarded. From this relationship, the target opening position of the intake valve 8 obtained by the characteristic shown in FIG. 8 may be corrected. Similarly, the characteristic diagram of FIG. 10 shows the relationship between the intake air flow rate and the engine exhaust HC. From FIG. 10, it can be seen that the higher the flow rate of the intake air, the lower the amount of HC gas generated by the engine, and the higher the temperature in the intake passage, the lower the amount of HC gas discharged by the engine. . The intake valve 8 obtained by the characteristic shown in FIG.
May be corrected. As described above, the target opening position of the intake valve 8 is controlled to the optimal opening timing by using the above-described relationship while paying attention to the in-cylinder pressure and the intake flow velocity. At this time, the optimal target opening position of the intake valve 8 is set. However, the target position of the intake valve 8 may be corrected to the advance side according to the above-described characteristic diagram, and the target position of the intake valve 8 is set to the retard side relative to the intake TDC. In this case, the means for correcting to the advance angle side according to these characteristic diagrams corresponds to the advance angle control means.

If it is determined in step 302 that the intake valve 8 has reached the target open position, the process proceeds to step 304, where it is determined whether or not a peak at the time of the first explosion has been detected from the engine speed Ne. . If the peak at the first explosion has not been detected, the routine proceeds to step 305, where the exhaust valve 9 is set to the target closed position, and this routine ends.

At step 304, the engine speed N
When the peak at the time of the first explosion of e is detected, the routine proceeds to step 306, where the target ignition timing for the early catalyst warm-up calculated in the ignition timing calculation routine of FIG. It is determined whether or not the target ignition timing has reached the target ignition timing. If the target ignition timing has not been reached, the routine proceeds to step 307, where ignition timing control for early catalyst warm-up is performed, and this routine ends.

On the other hand, if it is determined that the ignition timing has reached the target ignition timing, the routine proceeds to step 308, where it is determined whether a predetermined period has elapsed since the ignition timing reached the target ignition timing. . If the predetermined period has not elapsed, the process proceeds to step 311 to determine whether or not the idle operation state has been turned off. If a negative determination is made here, that is, if it is determined that the idle operation state is continued, the process proceeds to step 312.

In step 312, it is determined whether or not the ND shift has been performed. If it is determined that the ND shift has not been performed, this routine is terminated. On the other hand, if any one of the determination processes of step 308, step 311 and step 312 is determined as yes, step 30
Then, the routine returns to step S9, where the intake valve 8 and the exhaust valve 9 are returned to the positions suitable for the normal operation state, and the routine ends. It is preferable to return the exhaust valve 9 to a position suitable for a normal operation state, and then return the intake valve 8 to a position suitable for a normal operation state.

Here, the reason why the exhaust valve 9 is returned to a position suitable for a normal operation state and then the intake valve 8 is returned to a position suitable for a normal operation state will be described.

Since the amount of exhaust gas remaining in the combustion chamber is increased by advancing the closing timing of the exhaust valve, there is a possibility that the combustion state may deteriorate in the normal case. However, in the present embodiment, the exhaust valve 9 is advanced when the opening timing of the intake valve is retarded, so that the exhaust gas remaining in the combustion chamber can be further agitated by improving the intake flow velocity.

As described above, by returning the exhaust valve 9 to a position suitable for a normal operation state and then returning the intake valve 9 to a position suitable for a normal operation state, combustion by exhaust gas remaining in the combustion chamber is achieved. Deterioration can be reduced. In addition, since the exhaust gas can contribute to combustion again, fuel consumption can be reduced.

The timing chart of this embodiment is shown in FIG.
This will be described with reference to FIGS. FIG.
(A) shows the engine rotation speed Ne. When the ignition switch is turned on (indicated as IG-ON in the figure), a starter (not shown) is driven, and the rotation speed Ne is increased by the starter. Then, the rotation speed Ne is set to, for example, 100
When it exceeds 0 rpm, it is determined that the engine has started.

At this time, as shown in FIG. 11C, the opening timing of the intake valve 8 is retarded to generate a differential pressure between the pressure in the intake passage and the pressure in the combustion chamber, thereby improving the intake flow velocity. Let it. Fig. 11
As shown in (e), the fuel arrival timing is retarded.
The fuel arrival timing indicates the timing at which the fuel injected into the combustion chamber reaches the fuel by the fuel injection of the injector 16. Therefore, the fuel arrival timing can be adjusted by changing the fuel injection timing. Note that when the intake valve 8 is retarded from the intake TDC and the advance angle is corrected by the advance control means in accordance with the above-described characteristic diagram, the intake flow velocity becomes slow. For this reason, atomization of the fuel in the combustion chamber is reduced. Therefore, it is preferable that the fuel injection amount be increased and corrected. In this case, the exhaust valve 9 is advanced so that a large amount of exhaust gas remains in the combustion chamber, and the deterioration of combustion is reduced by utilizing the fact that the intake flow velocity is improved by retarding the intake valve 8.

When the control of the fuel injection timing of the intake valve 8 and the injector 16 is performed, the closing timing of the exhaust valve 9 is advanced as shown in FIG. By advancing the exhaust valve 9 more than the closing timing at the time of starting, a part of the exhaust gas generated by combustion can remain in the combustion chamber. By retarding the intake valve 8, the intake flow velocity is improved, so that the exhaust gas remaining in the combustion chamber is stirred in the combustion chamber, and the unburned gas component contained in the exhaust gas again contributes to combustion. . Thus, even if the exhaust valve 9 is advanced, deterioration of combustion can be prevented, and effects such as reduction of fuel consumption can be obtained.

When the engine speed reaches a peak after the initial explosion, the ignition timing is retarded for early warming up of the catalyst as shown in FIG. 11B. When the ignition timing reaches the target ignition timing, the timing between the intake valve 8 and the exhaust valve 9 is continued until a predetermined period has elapsed therefrom. After a lapse of a predetermined period, the exhaust valve 9 is returned to the start timing, and then the opening timing of the intake valve 8 is returned to the start timing.

By performing such control, good combustion can be obtained, and it is possible to prevent the A / F from being disturbed as shown in FIG.

In this embodiment, the start determination means is in step 300 of FIG. 6, the retard control means is in FIG. 3, the fuel injection control means is in FIG. 4, and the first valve timing control means is in step 303 of FIG. In addition, the retarded fuel control means is a means for delaying the fuel arrival timing in accordance with the improvement of the intake flow velocity,
The second valve timing control means is provided in step 30 of FIG.
In FIG. 5, the water temperature detecting means corresponds to and functions as the water temperature sensor 75 in FIG.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

First, in the second embodiment, the closing timing of the exhaust valve 9 is controlled according to the opening timing of the intake valve 8. Specifically, during a period in which the opening timing of the intake valve 8 is retarded, after the exhaust valve 9 is closed, the exhaust valve 9 is opened such that the intake valve opens after a predetermined crank angle (for example, 20 ° CA) has elapsed. It is characterized in that the closing timing is set.

Normally, even when the exhaust valve is closed, a slight gap is formed between the exhaust valve and the cylinder for a predetermined period. By controlling in this manner, the exhaust valve and the cylinder are securely sealed. Because you can create a state
By delaying the closing timing of the intake valve, a negative pressure can be efficiently generated in the cylinder.

The details will be described below. Overall configuration, ECU
Is the same as that of the first embodiment, and a description thereof will be omitted. First, the contents of the program for the control of this embodiment will be described using the flowchart of FIG. This program is started every predetermined crank angle of a crankshaft (not shown) of the engine 1. First, in step S401, it is determined whether or not the engine 1 has been driven after the engine 1 has been driven by cranking. The start completion is determined, for example, when the engine rotation speed Ne is 400 rpm or 1 as a predetermined rotation speed.
The determination condition is whether the rotation speed exceeds 000 rpm. If the engine speed Ne does not exceed 400 rpm, the process proceeds to step S402. In step S402,
As control at the time of starting, the closing timing of the exhaust valve 9 is set to the advance side, and a fixed position is set as the opening timing of the intake valve 8. In the case of the present embodiment, an intermediate position stopper (not shown) is provided in the intake variable valve timing mechanism 25a, and the opening timing of the intake valve 8 is mechanically fixed to, for example, the intake BTDC 5 ° CA.

The reason why the closing timing of the exhaust valve 9 is set to the advanced side is as follows. Since the intake valve 8 and the exhaust valve 9 are simultaneously opened, the exhaust passage 7
Control for supplying the combustion gas discharged to the combustion chamber again is known. This control is so-called EGR control for causing the combustion gas discharged into the exhaust passage to contribute to combustion again. However, the re-intake combustion gas amount by the EGR control is determined by the differential pressure between the pressure in the intake passage and the pressure in the exhaust passage. In an operating state where pressure cannot be obtained, sufficient combustion gas cannot be re-inhaled into the combustion chamber, and the EGR effect of causing unburned HC gas contained in the combustion gas to contribute to combustion again cannot be obtained. For this reason, at the time of starting in which a large negative pressure cannot be obtained as the pressure in the intake passage, the closing timing of the exhaust valve 9 is changed to the intake TDC.
It is intended to obtain the EGR effect by confining the combustion gas in the combustion chamber by setting it to the more advanced side. At this time, a normal ignition timing is set as the ignition timing at the time of starting, and this routine ends.

On the other hand, if it is determined in step S401 that the start has been completed, the process proceeds to step S403. In step S403, it is determined whether the condition for executing the early catalyst warm-up is satisfied. This execution condition is whether the engine water temperature Thw is within a predetermined temperature range. As the predetermined temperature range, for example, a temperature range of, for example, −10 ° C. as a non-extremely low cooling water temperature to 80 ° C. in a warm-up state is preferable. If the early warm-up execution condition is satisfied, the process proceeds to step S404. Step S404
Now, set a value to retard the ignition timing by a predetermined amount,
Proceed to step S405. In step S405, it is determined whether it is within a predetermined time since the start of the engine 1. Here, the predetermined time is a period during which combustion is improved and post-burning occurs.

The condition for post-burning is that the exhaust gas temperature is not less than a predetermined temperature, for example, 800 ° C. or more, and the air-fuel ratio is not less than a predetermined lean, for example, 15 or more. The fuel injection control will be described later. When such a condition is satisfied, since high oxygen concentration and high temperature exist in the exhaust passage, the unburned HC gas contained in the combustion gas discharged to the exhaust passage is purified by causing an oxidation reaction. You.

Here, if it is within the predetermined period, the process proceeds to step S406, and the overlap control is executed. The overlap control is a control for obtaining the EGR effect, and is the same control as the above-described EGR control. That is, by setting a period during which the intake valve 8 and the exhaust valve 9 are simultaneously opened, the combustion gas once discharged into the exhaust passage is again sucked into the combustion chamber. It is possible to suppress the deterioration of the emission by causing the unburned HC gas contained in the combustion gas to contribute to the combustion again by re-inhaling the combustion gas once discharged into the combustion chamber. In particular, when the engine water temperature Thw is in a cold operation state, combustion is unstable because the temperature in the combustion chamber is low, and a large amount of unburned HC gas is generated. When the three-way catalyst 19 has not yet been warmed up, the unburned HC gas is directly discharged to the atmosphere because the purification rate of harmful gas components is low. Also from this, it is possible to suppress unburned HC discharged to the atmosphere by the EGR effect, and to suppress deterioration of emission.

Next, a specific setting method of the intake valve 8 and the exhaust valve 9 will be described below. First, the intake valve 8
As the target opening timing, the opening timing set at the start is continuously set. On the other hand, the closing timing of the exhaust valve 9 is, for example,
Intake ATDC is set to 10 ° CA. That is, here, since the pressure in the intake passage becomes a negative pressure necessary for obtaining the EGR effect by the overlap, the EGR effect by retarding the exhaust valve 9 and setting the overlap amount is used. I have. The ignition timing is retarded as described above until the predetermined time elapses after the start, and the closing timing of the exhaust valve 9 is retarded in consideration of the amount of overlap. Thereby, the unburned HC contained in the combustion gas can be reduced by the EGR effect, so that deterioration of the emission can be suppressed.

On the other hand, if the predetermined time has elapsed, the afterburning condition is satisfied, and the unburned HC gas contained in the combustion gas in the exhaust passage is purified by the oxidation reaction.
The effect of reducing the unburned HC gas by the effect is not required. Therefore, the process proceeds to step S409, and underlap control is executed. The flowchart shown in FIG. 13 is a subroutine of the underlap control, and is a program called every time the process of step S409 is executed.
In this control, the timing between the intake valve 8 and the exhaust valve 9 is set based on the target underlap amount for the following reason.

First, when the after-burning condition is satisfied after a predetermined period has elapsed, it is necessary to make the air-fuel ratio lean. However, if the air-fuel ratio is controlled to be lean during execution of the EGR control due to the overlap, the rotation is fluctuated because the combustion is not stable. Therefore, in order to stabilize combustion in the combustion chamber, the opening timing of the intake valve is set to a more retarded side than the intake TDC. As described above, by delaying the target closing timing of the intake valve 8, a pressure difference is generated between the pressure in the intake passage and the pressure in the combustion chamber. By generating this differential pressure, the flow rate of the intake air when the intake valve 8 is opened can be improved, so that the atomization of the fuel injected by the injector 16 is promoted and the combustion is improved. Therefore, even if the combustion air-fuel ratio is set to lean by the fuel injection control described later, it is possible to prevent the combustion stability from deteriorating.

Further, the closing timing of the exhaust valve 9 is set based on the target underlap. Even if the opening timing of the intake valve 8 is retarded to improve the intake flow velocity, if the closing timing of the exhaust valve is close to the closing timing, there is a possibility that the closed state between the exhaust valve 9 and the cylinder wall surface may not be ensured. Therefore, there is a problem that the pressure difference between the combustion chamber and the intake passage cannot be sufficiently secured. Therefore, by setting the predetermined amount of underlap, it is possible to secure a sufficient differential pressure between the combustion chamber and the intake passage.

The underlap control process will be described below with reference to the flowchart of FIG. First, the process of step S501 is performed. This step S501
In this process, the intake pressure PM, the engine rotation speed Ne, the cooling water temperature Thw, and the like are called from the RAM in the ECU 80 as the engine load. In step S502, the target opening timing VT2 is calculated as the opening timing VT of the intake valve 8 based on the map shown in FIG. According to this map, the target opening timing VT2 is set to the retard side as the absolute pressure is higher as the intake pressure PM,
The smaller the absolute pressure is, the more the advance is set. That is, in this map, as a differential pressure between the combustion chamber and the intake passage,
For example, the retard amount of the opening timing of the intake valve 8 is set to be 600 mmHg.

Next, in step S503, the target underlap amount ULT is calculated. As described above, the target underlap amount may sufficiently improve the intake flow velocity because the combustion chamber may not be sufficiently sealed when the opening timing of the intake valve 8 and the closing timing of the exhaust valve 9 are close as described above. There is a possibility that the combustion may be deteriorated without being performed. Therefore, in setting the target underlap amount ULT, the fact that the combustion stability is deteriorated due to the rotation fluctuation ΔNe as shown in the map in FIG. 17 is substituted. That is, when the rotation fluctuation ΔNe becomes large, the position of the opening timing of the intake valve 8 and the position of the closing timing of the exhaust valve 9 are close to each other, so that the combustion chamber cannot be sufficiently sealed. The differential pressure is not enough. Therefore, it is determined that the combustion is deteriorated without increasing the intake flow velocity. For this reason, when ΔNe becomes large, the target underlap amount ULT is set large, and when ΔNe is small, it is judged that the combustion chamber is sufficiently sealed, and the small target underlap amount ULT is determined.
Set LT.

Further, a predetermined coefficient 1 may be set according to the air-fuel ratio as shown in a map shown in FIG. This coefficient 1
Is a correction coefficient for the target underlap amount ULT set according to the aforementioned rotational speed fluctuation ΔNe. FIG.
According to this, the coefficient 1 is set to a larger value as the air-fuel ratio is leaner, while it is set to a smaller value as the air-fuel ratio is richer. That is, the leaner the air-fuel ratio is, the worse the combustion stability is. Therefore, by setting the underlap amount ULT to be large, even if the airtightness in the cylinder is increased as compared with the case where the air-fuel ratio is rich. good.

As shown in the map of FIG. 19, the coefficient 2 may be set based on the amount of retardation of the intake valve 8 from the intake TDC. Is set to a small value, and the larger the retard amount, the larger the coefficient 2 is set. The coefficient 2 is also a correction coefficient for correcting the target underlap amount ULT similarly to the coefficient 1. When the coefficient 2 is used as the opening timing of the intake valve 8, the greater the amount of retardation from the intake TDC, the greater the pressure in the cylinder becomes to a negative pressure, so that it is necessary to ensure the tightness of the cylinder. Therefore, the coefficient 2 may be set according to the retard amount as described above.

Incidentally, the coefficient 1 and / or the coefficient 2 are used as correction coefficients for the target underlap amount ULT set in FIG. 17, and in the actual calculation, these coefficients are multiplied or added to obtain the target underlap amount ULT. May be calculated.

Then, at the target opening timing VT2 of the intake valve 8 set at step S502, the target underlap amount UL set at step S503 is set.
By adding T, the target closing timing VH2 obtained by the above-described calculation is set as the closing timing VH of the exhaust valve 9, and the routine ends.

The underlap control called at step S409 in FIG. 12 is performed at step S403.
In step S40, catalyst early warm-up has not been executed.
The control is also executed when the combustion is deteriorated at 7 or when the combustion stabilization control is being executed. For example, in the case where the combustion air-fuel ratio is controlled near the lean limit, the rotation speed of the engine tends to fluctuate at a lean air-fuel ratio because the torque fluctuation is large. Therefore, in the combustion stabilization control, in order to stabilize the combustion, the fuel injection amount, the ignition timing, and the like are controlled so as to suppress the rotation speed fluctuation. That is, when the combustion deteriorates, or during the execution of the above-described combustion deterioration control, the ignition timing is set in step S408, the underlap control is executed in step S409, and the routine ends.

On the other hand, if the combustion has not deteriorated and the combustion deterioration control has not been executed, the determination in step S407 is negative (NO), and the routine proceeds to step S410. In step S410, it is determined whether the early warm-up control of the catalyst has been performed. Here, if it is determined that the early and early warm-up control has not been executed, the determination in step S410 is negative (N
O) Then, the process proceeds to step S412, executes normal control after starting, and ends this routine. On the other hand, if it is determined that the early warm-up control has been executed, the process proceeds to step S411,
It is determined whether the return control from the early warm-up control to the normal control has been completed. If the return control has been completed, the determination in step S411 is affirmed (YES), and step S4
Proceed to 12.

The normal control after starting shown in step S412 is control for calculating the opening timing of the intake valve 8 and the closing timing of the exhaust valve 9 using the maps shown in FIGS. 14 and 15, respectively. First, in the method of setting the target opening timing VT1 of the intake valve 8, FIG.
The target opening timing VT1 is set according to the map shown in FIG. According to this map, the target opening timing VT1 of the intake valve 8 according to the operating state can be set.
Further, in the method of setting the target closing timing VH1 of the exhaust valve 9, similarly to the setting method of the intake valve 8, the target closing timing VH1 is determined in advance by using a map shown in FIG. Set. Similarly, in this map, the target closing timing VH1 can be set as the optimal closing timing VH according to the driving state. The ignition timing is set by a conventionally known method of setting the ignition timing after the engine is warmed up. As a specific method of setting the ignition timing,
The ignition timing at which the most torque is generated is set according to the operating state, and in a region where the knock occurs, the ignition timing is retarded by a predetermined angle based on the occurrence of the knock, and thereafter, the knock is conventionally advanced. Control is also performed at the same time.

On the other hand, if the return control from the early warm-up to the normal operation is not completed in step S411, the determination in step S411 is negative (NO), and step S4
Proceed to 13 to perform the return control. In the return control, the ignition timing and the intake valve set in the normal control after starting from the target close timing VH2 as the ignition timing at the time of early warm-up of the catalyst, the target opening timing VT2 of the intake valve 8, and the closing timing VH of the exhaust valve 9. The control for gradually switching the target opening timing VT1 and the target closing timing VH1 of the exhaust valve 9 is performed. Specifically, a target value during return to normal control after starting is set by adding or subtracting a predetermined value to or from each of the target values before switching to reach the target value after switching. End the routine.

Next, the fuel injection control according to the present embodiment will be described with reference to the flowchart shown in FIG. The routine shown in FIG. 20 shows processing of a program for calculating the fuel injection time TAU and the fuel injection timing. First,
In step S601, it is determined whether the start has been completed. As the determination of the completion of the start, it is determined whether or not the engine rotation speed Ne has reached a predetermined rotation speed, for example, 400 rpm or 1000 rpm. Here, for example, if it is determined that the startup has not been completed, that is, it is at the time of startup, the process proceeds to step S602. In step S602, a fixed value is set for the fuel injection timing and the fuel injection time TAU in consideration of the startability at the start, and the routine ends.

On the other hand, when it is determined that the engine has been completely started, the determination in step S601 is affirmed (YES), and the flow advances to step S603. In step S603, the operating state includes, for example, the intake air amount Q and the engine rotational speed Ne.
Based on this, the basic injection time Tp is calculated using, for example, a map, and the process proceeds to step S604. Similarly, in step S604, the fuel injection end timing is calculated from a map or the like based on the intake air amount Q and the engine rotation speed Ne, and the process proceeds to step S605. In step S605, it is determined whether the early warm-up control of the catalyst is being performed. If it is determined that the catalyst early warm-up control is being executed, the process proceeds to step S.
Proceeding to 606, it is determined whether it is within a predetermined time after the start of the engine is completed. The predetermined time is the same as step S405 in the flowchart of FIG.

If it is within the predetermined time, the fuel injection time TAU during the early catalyst warm-up control is calculated in step S607. The fuel injection time TAU is obtained by multiplying the basic fuel injection time Tp calculated in step S603 by a correction coefficient based on the engine coolant temperature Thw and the like. At the same time, the fuel injection end timing and the fuel injection time TAU are determined, so that the fuel injection start timing is finally set and the fuel injection control is executed.

On the other hand, if it is determined that the predetermined time has elapsed since the completion of the start of the engine is determined, the process proceeds to step S606. In step S606, since the predetermined time has elapsed, that is, the after-burning condition is satisfied, the opening timing of the intake valve 8 is retarded, so that a pressure difference occurs between the combustion chamber and the intake passage. For this reason, the intake flow velocity is improved as compared with the normal opening timing of the intake valve. Therefore,
The fuel injection start timing is set according to the opening timing of the intake valve 8. Specifically, the fuel injection end timing set in step S604 is changed based on the target timing of the intake valve 8, and the process proceeds to step S609.

In step S609, the fuel injection time TAU after the post-burning condition is satisfied is calculated. In the calculation of the injection time TAU, the basic injection time Tp calculated in step S603 is multiplied by a correction coefficient such as the engine coolant temperature Thw, and the fuel injection amount is corrected so that the combustion air-fuel ratio becomes lean. This routine is completed after multiplying by the leaning correction coefficient. As described above, after the predetermined time has elapsed, the fuel injection time TAU is set to a value smaller than the normal time, the combustion air-fuel ratio is controlled to be lean, and the fuel injection start timing is determined based on the opening timing of the intake valve 8. With this setting, atomization of the fuel injected by the injector is promoted, and combustion is stabilized. Further, when the exhaust gas temperature is higher than a predetermined temperature (800 ° C.) and the air-fuel ratio is lean, the unburned HC gas component discharged by combustion in the exhaust passage is consumed by the oxidation reaction. , EG
Even if the R control (overlap control) is not performed, it is possible to suppress the emission from deteriorating.

On the other hand, if it is determined that the early warm-up control of the catalyst has not been executed, the process in step S605 is negative (N
O) and the process proceeds to step S610. Step S60
In the process 1, it is determined whether the early warm-up control has been executed. Here, when the early warm-up is not executed, the determination in step S610 is denied (NO) and step S6 is performed.
The routine proceeds to 12, where the normal fuel injection time TAU after the start is calculated, and this routine ends. In the calculation of the fuel injection time TAU, the basic injection time T calculated in step S603 is used.
The fuel injection time TAU is calculated by multiplying p by a correction coefficient such as the engine cooling water temperature Thw.

If it is determined that the early warm-up control has been executed, the determination in step S610 is affirmed (YES), and the flow advances to step S611 to determine whether or not the return control is being executed. Here, the return control refers to step S41 in FIG.
This is the same as the return control executed in step 4, and if the above-described return control has not been executed, the process proceeds to step S612, where the normal fuel injection time TAU after the start is calculated, and this routine ends. On the other hand, when it is determined that the return control is being performed, the determination in step S611 is negative (NO), and the process in step S613 is executed. In step S613, FIG.
In accordance with the target opening timing of the intake valve 8 set in the return control of 2, the fuel injection timing is gradually changed to be the normal fuel injection timing after starting, and the process proceeds to step S614.

In step S614, the fuel injection time TAU at the time of return is calculated. In this calculation, the fuel injection time TAU is set so as to gradually follow the normal fuel injection time TAU after starting from the fuel injection time TAU at the lean air-fuel ratio set in step S609, and this routine ends. I do.

Next, the target opening timing of the intake valve 8, the target closing timing of the exhaust valve 9, the ignition timing control, and the fuel injection control controlled as described above are shown in FIG.
This will be described below with reference to the time chart of FIG.

First, when cranking is started by the driver at time t0, the engine speed Ne explodes for the first time.
The engine rotation speed Ne increases. At this time, the ignition timing and the opening timing VT of the intake valve 8 are set to fixed values in consideration of startability. On the other hand, the exhaust valve 9 reduces the unburned HC gas component by the EGR effect, but burns the combustion gas even when the overlap amount is set because the differential pressure between the pressure in the intake passage and the atmospheric pressure is small at the time of starting. It is difficult to re-inhale into the room. Therefore, when the exhaust valve 9 is started, the closing timing VH is advanced more than the intake TDC so that the combustion gas is confined in the combustion chamber, so that the EGR is performed.
The effect has been obtained. The closing timing VH of the exhaust valve 9 is set based on the opening timing VT of the intake valve 8 and the target underlap amount ULT.

The engine rotation speed Ne is, for example, 4
At 00 rpm, it is determined at time t1 that the engine has been completely started. If it is determined that the start of the engine has been completed and the engine coolant temperature Thw is within a predetermined temperature range, the condition for executing the catalyst early warm-up control is satisfied. When the condition for executing the catalyst early warm-up control is satisfied at time t1, the ignition timing θig is retarded from the intake TDC and set to ATDC10 ° CA. When the ignition timing θig is retarded, the combustion becomes slower and the peak becomes smaller than the normal combustion temperature peak. However, even if the exhaust valve 9 is opened, the combustion temperature becomes lower than the normal combustion temperature. Is maintained high, the temperature of the combustion gas in the exhaust passage can be increased.

The opening timing VT of the intake valve is set to a fixed value at the time of starting.
At H, since the pressure in the intake passage has reached the predetermined negative pressure after time t1, the combustion gas can be re-inhaled into the combustion chamber by setting the overlap amount. Therefore,
The closing timing VH of the exhaust valve 9 is set to be more retarded than the opening timing VT of the intake valve 8. At this time,
The closing timing VH of the exhaust valve 9 sets the target underlap amount ULT to −15 ° CA, that is, sets an overlap amount of 15 ° CA to obtain the EGR effect.

At a time t3 after a lapse of a predetermined time from the start of the engine, the temperature of the combustion gas in the exhaust passage becomes 800 ° C.
Therefore, the fuel injection amount is reduced and corrected to control the air-fuel ratio lean. This eliminates the need for EGR control because the unburned HC gas in the exhaust passage undergoes an oxidation reaction with oxygen in the exhaust passage. Therefore, in order to stabilize the combustion from the time t3 to the time t4, the opening timing VT of the intake valve 8 is set.
Is retarded from the intake TDC. This is because, when the piston descends from TDC after the intake stroke, the pressure in the combustion chamber becomes large negative pressure because the intake valve 8 is closed. Therefore, when the intake valve 8 is opened,
Since a large pressure difference is generated between the intake passage and the combustion chamber, the intake flow velocity is improved. In the present embodiment, since the fuel injection timing is set at a timing at which the intake flow velocity is high in accordance with the opening timing of the intake valve 8, the atomization of the fuel injected by the injector is promoted and the combustion can be stabilized.

At this time, the closing timing V of the exhaust valve 9
H is set based on the opening timing VT of the intake valve 8 and the target underlap amount ULT. Intake valve 8
The opening timing VT is retarded from the intake TDC, so that the pressure in the combustion chamber is greatly reduced. However, the closing timing VH of the exhaust valve 9 is changed to the opening timing VH of the intake valve 8.
If the temperature is close to T, the hermeticity of the combustion chamber cannot be maintained, and the pressure in the combustion chamber cannot be greatly reduced. Therefore, the target underlap amount ULT is set to 20 ° CA as a predetermined crank angle, and the exhaust valve 8
Is set. Thereby, the combustion chamber can be hermetically closed, the improvement of the intake flow velocity can be maintained, and the deterioration of combustion stability can be prevented.

When the early warm-up control of the catalyst is completed at time t5, the ignition timing θig is gradually returned to the normal ignition timing by time t6. Note that the opening timing VT of the intake valve 8 and the closing timing VH of the exhaust valve 9 are at time t5.
In FIG. 21, the control may be returned to the normal control stepwise as shown in the time chart of FIG. 21, or may be gradually returned to the normal control by the return control.

In the fuel injection control of this embodiment, as shown by A / F in FIG. 21, the air-fuel ratio is gradually made lean from the completion of the start, and the time t at which the early warm-up control of the catalyst ends.
At 5, the target air-fuel ratio may be controlled to the stoichiometric air-fuel ratio.

In this embodiment, the intake correspondence control means is provided as shown in FIG.
Corresponds to step S503.

(Other Embodiments) In this embodiment, the first and second embodiments
In the second embodiment, a warm-up state detecting means for detecting a warm-up state is provided, and when the warm-up state detecting means detects that the internal combustion engine is in a semi-warmed state at the time of starting the internal combustion engine, Opening timing V of intake valve 8 when starting
T may be delayed more than intake TDC.

The warm-up state detecting means detects that the internal combustion engine is in a semi-warmed state when the three-way catalyst 19 is not warmed up and the internal combustion engine is almost warmed up. I do. As a specific method, it is preferable to detect the half-warmed state based on at least one of the engine water temperature Thw, the elapsed time after the engine is started, the intake air temperature Tha, and the integrated value of the engine rotation speed Ne.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of an ECU and the like according to the first embodiment.

FIG. 3 is a flowchart illustrating ignition timing control according to the first embodiment.

FIG. 4 is a flowchart illustrating fuel injection control according to the first embodiment.

FIG. 5 is a map for calculating a fuel injection amount correction value according to an opening position of an intake valve in the first embodiment.

FIG. 6 is a main flowchart of the first embodiment.

FIG. 7 is a timing chart for setting a target open position of the intake valve according to the first embodiment.

FIG. 8 is a diagram showing a relationship between an open position of an intake valve and an intake flow velocity.

FIG. 9 is a characteristic diagram showing a relationship between an opening position of an intake valve and a temperature in an intake pipe.

FIG. 10 is a characteristic diagram showing a relationship between an intake air flow rate and HC gas discharged from an engine.

FIG. 11 is a timing chart of the first embodiment.

FIG. 12 is a main flowchart of the second embodiment.

FIG. 13 is a flowchart for setting an underlap amount ULT according to the second embodiment.

FIG. 14 is a map for setting the intake valve opening timing according to the intake passage pressure and the rotation speed according to the second embodiment.

FIG. 15 is a map for setting the closing timing of the exhaust valve according to the pressure and the rotation speed of the intake passage according to the second embodiment.

FIG. 16 is a map for setting the opening timing of the intake valve according to the pressure of the intake passage according to the second embodiment.

FIG. 17 is a map for setting a target underlap amount set according to a rotation speed variation of the second embodiment.

FIG. 18 is a map for setting a coefficient 1 for correcting a target underlap amount according to an air-fuel ratio according to the second embodiment.

FIG. 19 is a map for setting a coefficient 2 for correcting the target underlap amount according to the retard amount of the intake valve according to the second embodiment.

FIG. 20 is a flowchart illustrating fuel injection control according to a second embodiment.

FIG. 21 is a time chart showing a control operation of the second embodiment.

[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 25a ... Intake side variable valve timing mechanism 25b ... Exhaust side variable valve timing mechanism 56a: first oil control valve, 56b: second oil control valve, 74: throttle sensor, 75: water temperature sensor, 76: rotation speed sensor, 78: rotation angle sensor, 79: oil temperature sensor, 80: ECU , 89 ... power supply circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 13/02 F02D 13/02 H J41 / 06 320 41/06 320 330 330A 41/32 41/32 C 45/00 364 45/00 364D F02N 11/08 F02N 11/08 G F02P 5/15 F02P 5/15 EF term (reference) 3G022 CA02 DA02 EA01 GA02 GA05 GA06 GA08 GA09 3G084 BA13 BA17 BA23 BA26 CA01 CA02 DA09 DA10 DA11 EB12 EB16 EC02 FA07 FA10 FA20 FA33 FA39 3G091 AA02 AA17 AA23 AA28 AB03 AB10 BA00 BA03 BA14 BA15 BA19 BA32. FB12 FC04 FC07 GA06 HA08 HB05 3G092 AA01 AA11 AB02 BA09 BB01 DA01 DA02 DA03 DA10 DA12 DC03 DE01Y DG10 EA02 EA04 EA08 EA16 EA22 EA29 EB02 EC 01 EC10 FA18 FA31 GA01 GA02 HA06Y HA13X HB01Z HC09X HD10X HE01Z HE04Z HE08Z 3G301 HA01 HA19 JA21 JA23 JA26 KA01 KA02 KA05 LA07 LB01 LC01 LC08 MA14 NA06 NA07 NC02 ND04 NE06 NE12 NE20 NE24 PA11Z PE01Z PE04Z PE08Z08

Claims (12)

[Claims] 1. An internal combustion engine that performs ignition timing retard control for warming up a catalyst early, a fuel injection valve arranged to inject fuel, and fuel injected by the fuel injection valve. Fuel injection control means for controlling an injection amount; an intake valve for opening and closing an intake passage of an internal combustion engine; a first valve capable of arbitrarily setting an opening timing of the intake valve
A variable valve timing mechanism, and first valve timing control means for setting the opening timing of the intake valve, wherein the first valve timing control means is configured to open the intake valve after a cold start of the internal combustion engine. The fuel injection control means includes retard fuel control means for controlling a fuel injection amount based on the opening timing of the intake valve controlled by the retard control means. A control device for an internal combustion engine, comprising: 2. The method according to claim 1, wherein the retard control means delays the opening timing of the intake valve such that a difference between a pressure in the intake passage and a pressure in a combustion chamber of the internal combustion engine becomes a predetermined value or more. The control device for an internal combustion engine according to claim 1, wherein 3. The retard control means delays the opening timing of the intake valve such that the amount of gas blown back into the intake passage when the intake valve is opened becomes a predetermined amount or more. The control device for an internal combustion engine according to claim 1 or 2, wherein 4. An engine control apparatus comprising: a start determining means for determining whether to start the internal combustion engine; and an intermediate holding mechanism for restricting an opening timing of the intake valve to a predetermined timing suitable for starting when the internal combustion engine is started. Means for delaying the opening timing of the intake valve from the predetermined opening timing regulated by the intermediate holding mechanism when the internal combustion engine is started, when the starting determination means determines that the internal combustion engine has been started. The control device for an internal combustion engine according to any one of claims 1 to 3, characterized in that: 5. The fuel control device according to claim 1, wherein the retarded fuel control means reduces the fuel injection amount when the intake valve is retarded by the retard control means.
The control device for an internal combustion engine according to any one of claims 4 to 4. 6. An advance control means for advancing an opening timing of the intake valve, wherein the fuel injection control means adjusts the fuel injection amount when the intake valve is advanced by the advance control means. The control device for an internal combustion engine according to any one of claims 1 to 5, further comprising advanced fuel control means for increasing the amount of fuel. 7. An exhaust valve for opening and closing an exhaust passage of an internal combustion engine, and a second valve capable of arbitrarily setting a closing timing of the exhaust valve.
A variable valve timing mechanism, and second valve timing control means for setting the closing timing of the exhaust valve. The second valve timing control means delays the opening timing of the intake valve by the retard control means. The control device for an internal combustion engine according to any one of claims 1 to 6, further comprising an advancing angle control means for advancing the closing timing of the exhaust valve during the horned period. 8. A warm-up state detecting means for detecting a warm-up state of the internal combustion engine, wherein the retard control means sets the internal combustion engine to a half-warmed state by the warm-up state detecting means when the internal combustion engine is started. 5. The control device for an internal combustion engine according to claim 4, wherein when the occurrence is detected, the intake valve is retarded when the internal combustion engine is started. 9. The warm-up state detecting means detects that the internal combustion engine is in a semi-warmed state when the catalyst is not warmed up and the internal combustion engine is almost warmed up. The control device for an internal combustion engine according to claim 8, wherein: 10. The semi-warming-up of the internal combustion engine based on at least one of a cooling water temperature of the internal combustion engine, an elapsed time after starting the internal combustion engine, an intake air temperature, and an integrated value of a rotation speed of the internal combustion engine. The control device for an internal combustion engine according to claim 9, wherein the state is detected. 11. An exhaust valve for opening and closing an exhaust passage of an internal combustion engine, and a second valve capable of arbitrarily setting a closing timing of the exhaust valve.
And a second valve timing control means for setting the closing timing of the exhaust valve. The second valve timing control means delays the opening timing of the intake valve by the retard control means. 7. The control device for an internal combustion engine according to claim 1, further comprising: intake control means for controlling the closing timing of the exhaust valve in accordance with the opening timing of the intake valve during the squaring period. 12. The intake response control means opens the intake valve after a predetermined crank angle elapses after closing the exhaust valve during a period in which the opening timing of the intake valve is delayed by the retard control means. 2. The closing timing of the exhaust valve is set to open.
2. The control device for an internal combustion engine according to claim 1.