JP2003035167A - Variable valve control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve engine starting and the precision of air/fuel ratio control, after the start of the engine. SOLUTION: During engine start (cranking), the closing timing of an intake valve 13 is controlled near the bottom dead center of air intake to enhance an effective compression ratio, and by controlling the opening timing of the intake valve 13 near the top dead center of air intake, a valve overlap amount with an exhaust valve is made to be approximately zero to lessen an inside EGR amount (remaining gas amount), thus improving the ignitability and combustibility at engine start. During warming up after start finishing, the working angle and lifting amount of intake valve 13 are made smaller than those at a normal operation to lessen the opening period of intake valve 13 and the cross section of intake air flow path. Further, by controlling the opening timing of intake valve 13 to the vicinity of or more advance angle side than the top dead center of intake air, the intake valve 13 is opened at a stage, when the difference between an intake pipe pressure and cylinder internal pressure is small. Thereby, the rapid intake of wet fuel immediately, after opening the intake valve, is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve control device for an internal combustion engine, which has an improved open / close control method for intake valves of the internal combustion engine.

[0002]

2. Description of the Related Art In recent years, an increasing number of internal combustion engines mounted on a vehicle employ a variable valve control device for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. Many of the variable valve control devices that are currently in practical use change the valve timing of the intake valve. For example, by advancing the valve timing of the intake valve during partial load to increase the valve overlap amount, The internal EGR amount (residual gas amount) is increased to reduce pumping loss and improve fuel efficiency.

[0003]

However, in the conventional general variable valve timing control device, as shown in FIG. 3B, the working angle of the intake valve (intake valve opening period) is high. -Fixed at a large working angle (for example, 240 ° C) so that sufficient intake performance can be obtained at full load,
Moreover, in order to minimize the valve overlap amount at the time of starting, the advance amount of the valve timing of the intake valve is set to almost 0 (the opening timing of the intake valve is near the intake top dead center). The valve closing timing is much retarded from the bottom dead center of suction (generally ABDC40
It shifts to the retard angle side from ℃). Therefore, the compression of the in-cylinder gas must be started until the piston has risen to a certain extent from the bottom dead center of the suction, and as shown in FIG. The internal temperature cannot be raised sufficiently. As a result, the ignitability and combustibility at the time of start-up are lowered, and particularly during cold start during cold weather, this effect becomes prominent and the startability may be deteriorated.

Further, at the cold start when the engine is started in a cold state, a large amount of fuel (wet fuel) adheres to the inner wall of the intake port, etc., so that as shown in FIG.
During warm-up after cold start, if the working angle of the intake valve is fixed to a large working angle so that sufficient intake performance can be obtained at high rotation and full load, the engine speed will rapidly increase immediately after the start is completed. As a result, the intake air amount rapidly increases, and a large amount of wet fuel rapidly flows into the cylinder due to the flow of the intake air, and as shown by the dotted line in FIG. 5, the air-fuel ratio increases from the target air-fuel ratio to the rich direction. There is also a drawback in that the air-fuel ratio control accuracy after starting deteriorates due to deviation.

Incidentally, in Japanese Patent Laid-Open No. 8-218833,
By reducing the lift amount of the intake valve at startup, the intake flow velocity at startup (during cranking) is increased to improve fuel intake performance, and the lift amount of the intake valve is set to a normal large lift amount immediately after completion of startup. I'm suggesting to bring it back,
In this case as well, since the lift amount of the intake valve is increased immediately after the completion of the start, a large amount of wet fuel easily flows into the cylinder immediately after the completion of the cold start, and again, the accuracy of the air-fuel ratio control immediately after the completion of the start is deteriorated. There is a drawback to

The present invention has been made in consideration of these circumstances, and a first object thereof is to provide a variable valve control device for an internal combustion engine, which can improve the starting performance of the internal combustion engine. A second object is to provide a variable valve control device for an internal combustion engine that can improve the air-fuel ratio control accuracy after starting.

[0007]

In order to achieve the above-mentioned first object, the variable valve control device for an internal combustion engine according to claim 1 of the present invention sucks the closing timing of the intake valve at the time of starting by the valve control means. The valve control is performed at the time of starting to control near the bottom dead center. If you set the closing timing of the intake valve near the intake bottom dead center at startup,
Since the effective compression ratio at startup can be increased to raise the in-cylinder temperature sufficiently, it is possible to improve the ignitability and combustibility at startup, and to make a good start even during cold startup during cold weather. It is possible to secure the sex.

In this case, if the valve overlap amount of the intake valve and the exhaust valve is large, the internal EGR amount (residual gas amount) is increased and the amount of fresh air introduced into the cylinder is reduced, resulting in ignitability and combustibility. The effect of improving is reduced.

Therefore, as in claim 2, during the valve control at the time of starting, it is preferable to control so that the working angle of the intake valve is reduced to reduce or eliminate the valve overlap amount with the exhaust valve. With this configuration, the internal EGR amount (residual gas amount) can be reduced and the inside of the cylinder can be filled with fresh air during the valve control at the time of starting, and the ignitability and the combustibility at the time of starting can be further improved. it can.

In order to achieve the second object,
As described in claim 3, the warm-up valve control may be performed during the warm-up operation after starting so as to control the working angle and / or the lift amount of the intake valve to be smaller than that during the normal operation. In other words, during cold start, a large amount of fuel (wet fuel) adheres to the inner wall of the intake port, etc., but during warm-up operation after cold start, the working angle of the intake valve is reduced to increase the intake valve open period. By shortening or reducing the lift of the intake valve to reduce the flow passage cross-sectional area of the intake air when the intake valve is opened, a large amount of wet fuel can get into the cylinder during warm-up operation after cold start. The wet fuel can be gradually introduced while suppressing the sudden inflow, and the air-fuel ratio can be prevented from shifting in the rich direction.

In this case, it is preferable that the throttle opening correction means corrects the opening of the throttle valve to the open side during normal warm-up operation than during normal idle operation. By doing so, even if the working angle and / or the lift amount of the intake valve are controlled to be small during the warm-up operation after the start, the throttle opening is opened so as to compensate for the decrease in the intake air amount. Because it is corrected to the side,
The amount of intake air can be secured. Thereby, pumping loss can be reduced and fuel consumption can be improved.

Further, as in claim 5, the fuel injection amount may be increased and corrected by the fuel injection amount correcting means during the warm-up operation valve control so as to compensate for the torque decrease. By doing so, the fuel injection amount is increased and corrected to compensate for the decrease in torque due to the control that the working angle and / or the lift amount of the intake valve are controlled to be small during the warm-up operation after starting. The engine speed can be stabilized by suppressing torque fluctuation during warm-up operation.

Further, if the operating angle of the intake valve is made too small and the valve opening timing of the intake valve is shifted too far behind the intake top dead center, the piston descends from the intake top dead center and the cylinder pressure increases. Since the intake valve is opened after it has dropped considerably below the intake pipe pressure, the intake air in the intake pipe is suddenly sucked into the cylinder immediately after the intake valve is opened, and the intake of wet fuel The suppression effect is reduced.

As a countermeasure against this, it is preferable to control the valve opening timing of the intake valve near the intake top dead center or on the advance side of the intake valve during the warm-up operation valve control. In this way, the intake valve can be opened at a stage where the pressure difference between the intake pipe pressure and the in-cylinder pressure is small, and a rapid air intake (a sudden wet fuel intake) immediately after the intake valve is opened. ) Can be avoided, and the effect of suppressing the intake of wet fuel can be further improved.

When the engine temperature rises, the intake port temperature rises and the amount of wet fuel decreases. In consideration of this point, the working angle and / or the lift amount of the intake valve are changed according to the engine temperature or a parameter (for example, cooling water temperature, elapsed time after start, etc.) that correlates with the engine temperature. You may do it. In this way, the working angle and lift amount of the intake valve can be increased in response to the decrease in the wet fuel amount as the engine temperature (intake port temperature) rises. It is possible to prevent the intake performance from being deteriorated by controlling the angle and the lift amount to be smaller than necessary.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIG. First, the schematic configuration of the engine will be described with reference to FIG. An electromagnetically driven intake valve 13 is provided at an intake port 12 of each cylinder of an engine 11 that is an internal combustion engine, and an exhaust port 14 of each cylinder is provided at an exhaust port 14.
An electromagnetically driven exhaust valve 15 is provided. The intake valve 13 and the exhaust valve 15 are driven by electromagnetic actuators 16 and 17, respectively. A fuel injection valve 1 for injecting fuel is provided near the intake port 12 of each cylinder.
8 is attached, and a spark plug 22 is attached to the cylinder head of each cylinder. On the other hand, the engine 11
A water temperature sensor 19 for detecting the cooling water temperature and a crank angle sensor 20 for detecting the engine rotation speed are attached to the cylinder block.

Outputs of various sensors such as the water temperature sensor 19 and the crank angle sensor 20 are input to the engine control circuit 21. The engine control circuit 21 is mainly composed of a microcomputer and has a built-in ROM.
By executing various engine control programs stored in the (storage medium), the fuel injection amount of the fuel injection valve 18 and the ignition timing of the ignition plug 22 are controlled according to the engine operating state.

The engine control circuit 21 also functions as valve control means for controlling the electromagnetic actuators 16 and 17 of the valves 13 and 15 to control the opening / closing operations of the valves 13 and 15. At that time, the engine control circuit 21
By executing the intake valve control program of FIG. 2 stored in the ROM, as shown in FIG. 3A, when the engine is started, the valve control at the time of starting is executed to control the closing timing of the intake valve 13. The intake valve 13 is controlled near the intake bottom dead center (intake BDC), for example, in the range of intake BDC ± 20 ° C, and the operating angle of the intake valve 13 is reduced to make the valve overlap amount with the exhaust valve 15 almost zero. Then, as shown in FIG. 4 (a), during warm-up operation after starting, valve control during warm-up operation is carried out, and the intake valve 13
The valve opening timing of the intake valve 13 is controlled near the intake TDC or on the advance side of the intake valve 13 while controlling the operating angle and the lift amount thereof to be smaller than those during normal operation.

The specific processing contents of the intake valve control program of FIG. 2 executed by the engine control circuit 21 will be described below. This program is repeatedly executed every predetermined time or every predetermined crank angle after the ignition switch (not shown) is turned on. When this program is started,
First, in step 101, it is determined whether or not the start is completed, for example, based on whether or not the engine speed exceeds a complete explosion determination value.

Before starting is completed, that is, during starting (during cranking), the routine proceeds to step 102, where valve control at starting is carried out. In this valve control at the time of starting, as shown in FIG. 3A, the closing timing of the intake valve 13 is set to the intake BD.
The exhaust valve 15 is controlled by controlling near C (for example, in the range of intake BDC ± 20 ° C.) to increase the effective compression ratio at the time of starting, and by controlling the opening timing of the intake valve 13 near intake TDC. The valve overlap amount with is made almost zero, and the internal EGR amount (residual gas amount) is reduced.

After that, at step 101, when it is determined that the start-up is completed, the routine proceeds to step 103, where it is determined whether or not the warm-up operation execution condition is satisfied depending on whether or not the cooling water temperature is lower than the predetermined temperature α. To do. If the warm-up operation execution condition is not satisfied, the routine proceeds to step 106, where normal intake valve control is performed, and the opening / closing operation of the intake valve 13 is controlled based on the engine operating state.

On the other hand, when the warm-up operation execution condition is satisfied and the warm-up operation is executed, the routine proceeds to step 104, where the warm-up operation valve control is executed. In the valve control during warm-up operation, as shown in FIG. 4A, the operating angle and lift amount of the intake valve 13 are controlled to be smaller than those during normal operation, and the opening period of the intake valve 13 and When the flow passage cross-sectional area of the intake air is made small and the valve opening timing of the intake valve 13 is controlled near the intake TDC or at the advance side thereof, when the differential pressure between the intake pipe pressure and the in-cylinder pressure is small. The intake valve 13 is opened.

Further, during the valve control during the warm-up operation, as shown in FIG. 4 (a), in order to compensate for the decrease in the intake air amount due to the decrease in the working angle and the lift amount of the intake valve 13, By correcting the opening of the throttle valve to the open side as compared with the normal idle operation, the intake air amount is secured and pumping loss is reduced. This function plays a role corresponding to the throttle opening correction means in the claims.

After this, the routine proceeds to step 105, where it is judged whether or not the warm-up operation end condition is satisfied, based on whether or not the cooling water temperature is equal to or higher than a predetermined temperature α, or whether or not the idle operation is ended. To do. During the period when the warm-up operation end condition is not satisfied, that is, during the warm-up operation, the valve control during the warm-up operation is continued.

Thereafter, if it is determined in step 105 that the cooling water temperature is equal to or higher than the predetermined temperature α, or if the idle operation has been completed, it is determined that the warm-up operation end condition is satisfied, and the routine proceeds to step 106. , Shift to normal intake valve control.

A control example when the intake valve control of the present embodiment described above is executed will be described with reference to FIG. During the start-up period from when the ignition switch is turned on to when the start-up is completed, the start-time valve control [see FIG. 3 (a)] is performed to control the closing timing of the intake valve 13 near the intake BDC. As a result, the effective compression ratio at the time of starting can be increased to sufficiently raise the in-cylinder temperature, and the ignitability and combustibility at the time of starting can be improved. As a result, good startability can be ensured even during cold start during cold weather.

During the valve control at the time of starting, the intake valve 1
If the valve overlap amount of 3 and the exhaust valve 15 is large, the internal EGR amount (residual gas amount) increases, the amount of fresh air introduced into the cylinder decreases, and the effect of improving ignitability and combustibility decreases. However, in the present embodiment, the valve overlap timing with the exhaust valve 15 is set to almost 0 by controlling the opening timing of the intake valve 13 near the intake TDC during the valve control at the start, so By reducing the EGR amount (residual gas amount), the cylinder can be filled with fresh air,
The ignitability and flammability at the time of starting can be further improved.

Thereafter, during the warm-up operation period from the completion of the start-up until the gear position is switched to the D range and the traveling of the vehicle is started, the valve control during the warm-up operation [see FIG. 4 (a)].
Is performed to control the working angle and the lift amount of the intake valve 13 to be smaller than those during normal operation. This allows
During the warm-up operation after the cold start in which the amount of wet fuel adhering to the inner wall of the intake port 12 and the like increases, the opening period of the intake valve 13 and the flow passage cross-sectional area of the intake air at the time of opening the intake port 13 are reduced to make a large amount of wet It is possible to prevent the fuel from rapidly flowing into the cylinder and gradually allow the wet fuel to flow. Therefore, the deviation of the air-fuel ratio due to the inflow of the wet fuel into the cylinder can be corrected by the air-fuel ratio feedback control,
The air-fuel ratio can be stabilized near the target air-fuel ratio, and the air-fuel ratio control accuracy can be improved.

During the valve control during the warm-up operation, if the working angle of the intake valve 13 is made too small and the opening timing of the intake valve 13 is shifted too far behind the intake TDC [Fig. 4 (a)]. [Refer to the dotted line], since the piston descends from the top dead center of the intake TDC and the in-cylinder pressure drops significantly below the intake pipe pressure, the intake valve 13 is opened. The intake air is sucked into the cylinder all at once, and the effect of suppressing wet fuel intake is reduced.

In this regard, in the present embodiment, the intake valve opening timing of the intake valve 13 is set to the intake timing T during the valve control during the warm-up operation.
Near DC or on the advance side (see the chain double-dashed line in Fig. 5)
Therefore, the intake valve 13 can be opened when the pressure difference between the intake pipe pressure and the in-cylinder pressure is small, and rapid intake of air immediately after the intake valve 13 is opened (a sudden increase in wet fuel (Inhalation) can be avoided, and the effect of suppressing wet fuel inhalation can be further improved.

Further, during the valve control during the warm-up operation, the throttle opening is corrected to the open side so as to compensate for the decrease in the intake air amount by reducing the working angle and lift amount of the intake valve 13. It is possible to secure the amount of intake air,
It is possible to reduce pumping loss and improve fuel efficiency.

During the warm-up valve control, the fuel injection amount may be increased and corrected so as to compensate for the torque decrease amount caused by reducing the working angle and the lift amount of the intake valve 13. With this configuration, the torque decrease amount due to the valve control during warm-up operation can be compensated by the increase correction of the fuel injection amount, so that the torque fluctuation during warm-up operation can be suppressed and the engine rotation speed can be stabilized.

In this embodiment, both the working angle and the lift amount of the intake valve 13 are reduced during the valve control during warm-up operation. Only one of them may be made smaller.

The working angle and the lift amount of the intake valve 13 during the valve control during the warm-up operation may be fixed values set in advance, but the wet fuel amount may be increased as the engine temperature (the intake port 12 temperature) rises. Corresponding to the decrease of the above, the working angle and the lift amount of the intake valve 13 may be increased by a map or the like. In this way, the intake valve 1
It is possible to avoid that the working angle and the lift amount of 3 become unnecessarily small and the intake performance is impaired.

In this case, the engine temperature (or the intake port 12
Temperature) may be detected by a temperature sensor, but the cooling water temperature, the elapsed time after the start, the cumulative engine speed after the start,
It may be estimated from parameters such as the cumulative intake air amount after starting and the cumulative fuel injection amount, which are correlated with the engine temperature. Alternatively, instead of the engine temperature, the intake valve 1 may be mapped according to a parameter that correlates with the engine temperature.
The working angle and lift amount of 3 may be variable.

Further, in the above embodiment, the working angle and lift amount of the intake valve 13 are changed by the electromagnetic actuator, but in the present invention, the intake valve 13 is controlled by controlling the operation of the cam mechanism or the like by the hydraulic circuit. It may be applied to a variable valve control device in which the working angle and / or the lift amount of the variable valve are varied stepwise or continuously.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of processing of an intake valve control program.

FIG. 3A is a diagram showing a valve operating characteristic at the time of starting of the present embodiment, and FIG. 3B is a diagram showing a conventional valve operating characteristic at the time of starting.

FIG. 4A is a diagram showing a valve operating characteristic during warm-up operation of the present embodiment, and FIG. 4B is a diagram showing a valve operating characteristic during conventional warm-up operation.

FIG. 5 is a time chart showing a control example of the present embodiment.

FIG. 6 is a diagram showing a relationship between a closing timing of an intake valve and a cylinder pressure.

[Explanation of symbols]

11 ... Engine (internal combustion engine), 13 ... Intake valve, 14
... Exhaust valves, 16, 17 ... Electromagnetic actuators, 18
... fuel injection valve, 21 ... engine control circuit (valve control means, throttle opening correction means, fuel injection amount correction means).

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/06 370 F02D 41/06 370 43/00 301 43/00 301H 301K 301Z F term (reference) 3G018 AB08 BA38 CA11 DA70 EA02 EA17 EA21 FA01 FA08 FA26 GA11 3G084 BA23 CA01 CA02 DA04 DA05 DA09 EA11 FA02 FA33 3G092 AA01 AA11 AB02 BA01 DA01 DA02 DA03 DA07 DA12 DE01S DG09 DG10 KA01 LA00 LA03 HA01 HA01 HA01 HA03 HA01 HE01 GA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA01 FA03 FA01 FA03 FA31 FA01 FA03 FA31 FA01 FA03 FA08 LB02 LC01 MA01 MA11 ND04 ND12 NE01 NE11 NE12 NE13 PE01Z PE08Z

Claims (7)

[Claims] 1. A variable valve control device for an internal combustion engine, comprising: a valve control means for controlling an opening / closing operation of an intake valve of an internal combustion engine, wherein the valve control means has a valve closing timing of the intake valve at the time of starting. A variable valve control device for an internal combustion engine, characterized in that valve control at start-up is performed to control the vicinity of a point. 2. The valve control means controls during the valve control at the time of start-up to reduce the working angle of the intake valve to reduce or eliminate the valve overlap amount with the exhaust valve. A variable valve control device for an internal combustion engine according to claim 1. 3. A variable valve control device for an internal combustion engine, comprising: a valve control means for controlling an opening / closing operation of an intake valve of an internal combustion engine, wherein the valve control means has a working angle of the intake valve during a warm-up operation after starting. And / or a variable valve control device for an internal combustion engine, which performs valve control during warm-up operation for controlling the lift amount to be smaller than during normal operation. 4. The throttle opening correction means for correcting the opening of the throttle valve to the open side during normal warm-up during valve control during warm-up operation. A variable valve control device for an internal combustion engine as set forth in. 5. The fuel injection amount correcting means for increasing and correcting the fuel injection amount so as to compensate for the torque decrease during the warm-up operation valve control is provided. Variable valve control device for internal combustion engine. 6. The valve control means controls the valve opening timing of the intake valve near the intake top dead center or on the advance side of the intake valve during the warm-up operation valve control. Item 6. A variable valve control device for an internal combustion engine according to any one of items 3 to 5. 7. The valve control means varies the working angle and / or the lift amount of the intake valve according to the engine temperature or a parameter correlated with the engine temperature. A variable valve control device for an internal combustion engine as set forth in.