JP2013060863A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of improving fuel consumption performance by expanding an EGR operation region and of securing an engine torque during EGR operation.SOLUTION: In the engine having two intake valves for each cylinder, one intake valve is opened while a piston rises, other intake valve is closed at an engine upper dead center and thereafter, so that combustion gas in a combustion chamber is blown back to an upstream side of the one intake valve. Then, a period while combustion gas introduced into an intake port at an upstream side of the one intake valve is introduced into the combustion chamber is estimated from a blow-back gas amount Wm and flow speed AS of intake air, and by starting injection of a fuel injection valve after new air introduction is started after introduction of combustion gas into the combustion chamber, fuel is prevented from being mixed in the combustion gas.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a technique for controlling an injection start timing of a fuel injection valve that injects fuel into an intake passage.

  Conventionally, as an internal combustion engine that realizes EGR stratified combustion in which the combustion chamber is divided into an internal EGR gas layer and a combustible mixture layer, and the combustible mixture layer is ignited and burned, EGR gas is introduced into the first intake port on the upstream side through the valve, and EGR gas introduced into the first intake port during the intake stroke in which the piston descends from the top dead center is passed through the first intake valve. There has been an internal combustion engine that introduces fresh air in the second intake port on the upstream side into the combustion chamber through the second intake valve and introduces EGR stratified combustion through the second intake valve (see, for example, Patent Document 1). ).

JP 2008-255866 A

  By the way, if the internal EGR gas is introduced into the cylinder from one of the two intake valves and the fresh air is introduced into the cylinder from the other, the intake valve on one side may be expanded even if the EGR operation area is expanded to the high output side. Therefore, it is difficult to expand the EGR operation region to the high output side while securing the engine torque.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can improve the fuel consumption performance by expanding the EGR operation region and can secure the engine torque during the EGR operation.

  Therefore, according to the present invention, in an internal combustion engine having a fuel injection valve that injects fuel into the intake passage, the injection start timing by the fuel injection valve is set to a later timing as the amount of combustion gas introduced into the intake passage increases. In addition, as the flow rate of the intake air flowing through the intake passage is slower, the injection start timing is set to a later timing.

  According to the above invention, the injection start timing of the fuel injection valve can be set in accordance with the introduction timing of the fresh air introduced into the cylinder following the EGR gas, so that the injected fuel can be mixed with fresh air and the engine torque is improved. In addition, fuel efficiency can be improved by the EGR effect.

It is a block diagram of the engine in embodiment of this invention. It is a top view which shows the structure of the combustion chamber periphery of the engine in embodiment of this invention. It is a diagram which shows the characteristic of the variable valve mechanism (cam switching mechanism) in embodiment of this invention. It is a diagram which shows the characteristic of the variable valve mechanism (lift and operating angle variable mechanism) in embodiment of this invention. It is a flowchart which shows the calculation routine of the injection start time in embodiment of this invention. It is a time chart which shows the correlation with the passage gas amount of the 1st intake valve and injection timing in embodiment of this invention. It is a top view which shows the structure of the combustion chamber periphery of the engine in embodiment of this invention. It is a top view which shows the structure of the combustion chamber periphery of the engine which performs external EGR in embodiment of this invention. It is a flowchart which shows the calculation routine of the injection start time in the engine which performs external EGR in embodiment of this invention. It is a time chart which shows the correlation with the passage gas amount of the 1st intake valve and the injection timing in the engine which performs external EGR in the embodiment of the present invention. It is a time chart which shows the correlation with the passage gas amount of the 1st intake valve in the engine which performs external EGR in the embodiment of the invention in this application, and the time of split injection. It is a diagram which shows the correlation with the valve opening period of an intake valve and the frequency | count of division | segmentation of fuel injection in embodiment of this invention. It is a time chart which shows the correlation with the passage gas amount of the 1st intake valve in the engine which performs external EGR in the embodiment of the invention in this application, and the time of split injection.

Embodiments of a control device for an internal combustion engine according to the present invention will be described below.
FIG. 1 is a diagram showing a system configuration of a vehicle engine (internal combustion engine) to which a control device according to the present invention is applied.
The engine 101 shown in FIG. 1 is an in-line multi-cylinder internal combustion engine, but may be a V-type or a horizontally opposed internal combustion engine.

An intake pipe (intake passage) 102 for introducing air into each cylinder of the engine 101 is provided with an intake air amount sensor 103 that detects an intake air flow rate QA of the engine 101. As the intake air amount sensor 103, for example, a hot-wire flow meter that detects the mass flow rate of intake air can be used.
The intake air flow rate QA of the engine 101 is adjusted by an electronic control throttle 119 disposed in the intake pipe 102 on the downstream side of the intake air amount sensor 103.

As shown in FIG. 2, each combustion chamber 104 has two intake ports 115a and 115b, two intake ports 113a and 113b reaching each intake port 115a and 115b are provided for each cylinder, and each intake port Two intake valves 105a and 105b for opening and closing the ports 115a and 115b are provided. Further, a first fuel injection valve 106a for injecting fuel into the first intake port 113a and a first fuel injection valve 106a for injecting fuel into the second intake port 113b are provided.
The first intake port 113a on the upstream side of the first intake valve 105a and the second intake port 113b on the upstream side of the second intake valve 105b merge and are connected to the intake pipe 102.

The fuel injected from the fuel injection valves 106a and 106b is introduced into the combustion chamber 104 by opening the intake valves 105a and 105b in the intake stroke, and ignited and burned by spark ignition by the spark plug 107, and the pressure by the combustion is changed to the piston. The crankshaft 109 is rotationally driven by pushing down 108 toward the crankshaft 109.
As shown in FIG. 2, each combustion chamber 104 has two exhaust ports 117a and 117b and two exhaust valves 110a and 110b for opening and closing the exhaust ports 117a and 117b. The combustion gas (exhaust gas) is discharged to the exhaust pipe (exhaust passage) 111 by opening 110b in the exhaust stroke.
In the exhaust pipe 111, a catalytic converter 112 including a three-way catalyst is installed in order to purify the exhaust gas.

The intake valves 105a and 105b open as the intake camshaft (not shown) rotated by the crankshaft 109 is rotated, and the exhaust valves 110a and 110b are exhaust camshaft (rotated by the crankshaft 109). It opens with the rotation of (not shown).
The exhaust valves 110a and 110b open at a constant valve timing (open characteristic), but the valve timings (open timing IVO and close timing IVC) of the intake valves 105a and 105b are controlled by the variable valve mechanisms 114a and 114b. Variable.

The first variable valve mechanism 114a is a known mechanism that continuously changes the center phase of the valve operating angle of the intake valves 105a and 105b by changing the rotational phase of the intake camshaft with respect to the crankshaft 109.
On the other hand, the second variable valve mechanism 114b is a mechanism that makes the valve timing (opening characteristic) of the second intake valve 105b variable independently without changing the valve timing (opening characteristic) of the first intake valve 105a. The second variable valve mechanism 114b can change the valve timing (open characteristic) of the second intake valve 105b from the same timing as the first intake valve 105a to a different timing.

As the second variable valve mechanism 114b, for example, the maximum valve lift amount of the intake valve is continuously variable together with the valve operating angle by changing the angle of the control shaft disclosed in Japanese Patent Laid-Open No. 2008-255866. Cam switching for switching the cam used for driving the intake valve to one of a large operating angle cam and a small operating angle cam, which is also disclosed in Japanese Patent Application Laid-Open No. 2008-255866. A mechanism or the like can be used.
Here, when a cam switching mechanism is used as the second variable valve mechanism 114b, as shown in FIG. 3, when the large operating angle cam is selected, the valve lift amounts (maximum) of the first intake valve 105a and the second intake valve 105b are selected. The valve lift amount and the valve operating angle are substantially equal, and when the small operating angle cam is selected, the valve lift amount and valve operating angle of the second intake valve 105b are larger than the valve lift amount and valve operating angle of the first intake valve 105a. Is set to be smaller.

When a lift and operating angle variable mechanism is used as the second variable valve mechanism 114b, as shown in FIG. 4, the valve lift amount (maximum valve lift amount) and the valve operating angle of the second intake valve 105b are adjusted. The variable range includes at least the valve lift amount and the valve operating angle that are the same as the valve lift amount and the valve operating angle of the first intake valve 105b, and the valve lift amount and the valve operating angle when the small operating angle cam is selected. Set to.
As described above, the second variable valve mechanism 114b has the same valve opening characteristics as the first intake valve 105a and a smaller valve lift and valve operating angle than the first intake valve 105a. It is a mechanism that can be switched to one of the characteristics.

Each ignition plug 107 is directly attached with an ignition module 116 that supplies ignition energy to the ignition plug 107. The ignition module 116 includes an ignition coil and a power transistor that controls energization of the ignition coil.
The engine control device (engine control unit) 201 includes a computer including a CPU, a ROM, a RAM, etc., inputs signals from various sensors and switches, and performs arithmetic processing according to a program stored in advance, thereby injecting fuel. It is a device that calculates and outputs operation amounts of various devices such as the valve 106, the variable valve mechanisms 114a and 114b, and the ignition module 116, and has a function as a control device according to the present invention as described later.

Further, the engine control device 201 inputs the output signal of the intake air amount sensor 103, the crank angle sensor 203 that outputs the rotation angle signal POS of the crankshaft 109, and the depression amount (accelerator opening ACC) of the accelerator pedal 207. Accelerator opening sensor 206 for detecting, cam angle sensor 204 for outputting the rotation angle signal CAM of the intake camshaft, water temperature sensor 208 for detecting the temperature (engine temperature) TW of the engine 101, exhaust on the upstream side of the catalytic converter 112 An air-fuel ratio sensor 209 that is installed in the pipe 111 and detects the air-fuel ratio AF based on the oxygen concentration in the exhaust, a throttle sensor 210 that detects the opening TVO of the electronic control throttle 119, the electronic control throttle 119, and the intake valves 105a and 105b Negative pressure which is the pressure in the intake pipe (intake passage) 102 between (Boost) receives signals from such an intake air pressure sensor 121 for detecting a PB, further, inputs the signal of the ignition switch (IGN switch) 205 is a main switch of the operation and stopping of the engine 101.
Here, the engine control device 201 calculates the engine rotation speed NE based on the rotation angle signal POS output from the crank angle sensor 203.

Next, the control of the variable valve mechanisms 114a and 114b by the engine control device 201 will be schematically described.
For example, in an operation region where fuel efficiency is required, such as a low load low rotation region of the engine 101, the rotational phase of the intake camshaft is advanced by the first variable valve mechanism 114a and the second variable valve mechanism 114a 2 By making the valve operating angle of the intake valve 105b smaller than the first intake valve 105a, the opening timing IVO of the first intake valve 105a is set before the top dead center TDC, and the opening timing IVO of the second intake valve 105b is set. The timing is set substantially after the top dead center TDC, and the closing timing IVC of the first intake valve 105a and the closing timing IVC of the second intake valve 105b are set to substantially the same timing after the bottom dead center BDC.
The closing timing EVC of the exhaust valves 110a and 110b is set near the top dead center TDC.

As a result, the first intake valve 105a is opened during the exhaust stroke (before the top dead center TDC) while the piston is rising. When the first intake valve 105a is opened while the piston is rising, the combustion gas in the combustion chamber 104 ( The exhaust gas after combustion) is blown back to the first intake port 113a upstream of the first intake valve 105a.
Then, the combustion gas (internal EGR gas) blown back to the first intake port 113a before the piston reaches the top dead center TDC in the opened state of the first intake valve 105a causes the piston to descend from the top dead center TDC. By switching to the intake stroke, the air is sucked again into the combustion chamber 104, and fresh air is sucked into the combustion chamber 104 via the first intake valve 105a following the intake of the internal EGR gas (introduction of combustion gas). means).

On the other hand, the second intake valve 105b does not open during the exhaust stroke (before the top dead center TDC) while the piston is rising, and opens during the intake stroke after the piston reaches the top dead center TDC. No combustion gas blows back (internal EGR) into the second intake port 113b on the upstream side of the engine, and fresh air is drawn into the combustion chamber 104 through the second intake valve 105b.
In parallel with the operation of sucking the internal EGR gas and fresh air into the combustion chamber 104 via the first intake valve 105a, fresh air is sucked into the combustion chamber 104 via the second intake valve 105b. The formation of swirls (lateral intake vortex flow) in the combustion chamber 104 is suppressed.

As a result, the internal EGR gas sucked into the combustion chamber 104 at the initial stage of the intake operation via the first intake valve 105 a is suppressed from being mixed with fresh air, and the fresh air layer and the internal EGR gas are suppressed in the combustion chamber 104. The EGR stratified combustion can be carried out by stratifying into a stratified fuel, and by mixing the fuel with a large amount of internal EGR and fresh air, the combustion chamber 104 as a whole can greatly reduce the air-fuel ratio and improve fuel efficiency. it can.
However, if the fuel is mixed in the internal EGR gas, the stratification degree decreases, and the amount of internal EGR cannot be increased.

Therefore, the engine control device 201 uses the first intake valve 113a as the gas that has blown back the injection start timing of the first fuel injection valve 106a to the first intake port 113a in order to prevent the fuel from being mixed into the internal EGR gas. It is set to a timing after the fuel from the first fuel injection valve 106a is injected into the fresh air after being sucked into the combustion chamber 104 through 105a.
That is, at the beginning of the intake stroke immediately after the piston starts to descend, the internal EGR gas is sucked into the combustion chamber 104 via the first intake valve 105a. At this time, fuel injection by the first fuel injection valve 106a is performed. When it is performed, fuel is injected into the internal EGR gas, and the fuel is mixed with the internal EGR gas, so that the stratification degree decreases.

Therefore, the fuel injection by the first fuel injection valve 106a is performed so that the fuel injection by the first fuel injection valve 106a is performed in the fresh air intake state after the internal EGR is sucked through the first intake valve 105a. To start.
As a result, it is possible to prevent the fuel from being mixed into the internal EGR gas, and thus the degree of stratification between the fresh air (air mixture) in the combustion chamber 104 and the internal EGR gas is improved, so that the first intake valve 105a It is possible to increase the internal EGR amount by advancing the opening timing IVO, and to improve the fuel efficiency by increasing the internal EGR amount.

Here, the delay period from the top dead center TDC to the injection start timing by the first fuel injection valve 106a can be set in advance as a fixed value, but the amount of gas blown back to the first intake port 113a (internal EGR). The larger the gas amount), the longer it takes for the blown-back gas to be sucked into the combustion chamber 104, and the slower the intake air flow rate, the more the blown-back gas is taken into the combustion chamber 104. The time will be longer.
For this reason, even when the amount of blown-back gas (internal EGR amount, amount of combustion gas introduced into the intake passage) is the largest and the flow velocity of the intake air in the intake stroke is the slowest, the fuel in the internal EGR gas If a delay period from the top dead center TDC to the injection start timing by the first fuel injection valve 106a is set, the injection starts excessively when the amount of blowback gas is small and / or when the flow rate of the intake air is high The timing is delayed, the fuel vaporization time is shortened, the homogeneity of the combustion mixture is lowered, and the combustion stability is lowered.

Therefore, it is preferable to variably set the delay period from the top dead center TDC to the injection start timing of the first fuel injection valve 106a in accordance with the amount of blowback gas and the flow rate of the intake air. This will be described with reference to the flowchart of FIG.
In addition, since the return of combustion gas to the second intake port 113b where the second fuel injection valve 106b is disposed does not occur or is negligibly small, the start of injection for suppressing fuel from being mixed into the internal EGR It is not necessary to set the timing, and it is only necessary to set the optimal timing at which the fuel can be uniformly mixed with the fresh air introduced into the combustion chamber 104 via the second intake valve 105b. The fuel injection can be started at a time earlier than the injection start time (for example, intake TDC).

The flowchart of FIG. 5 shows the injection of the first fuel injection valve 106a performed by the engine control device 201 at regular intervals in the operation region where the combustion gas is introduced into the first intake port 113a during EGR stratified combustion. The setting routine of a start delay time (injection start time) is shown.
First, in step S1 (gas amount detection means), the blow back EGR gas amount Wm (cc) for the first intake port 113a is calculated. The blow-back EGR gas amount Wm is the amount of internal EGR gas and the amount of combustion gas introduced into the first intake port 113a.

The calculation of the blown back EGR gas amount Wm can be performed using, for example, an estimation unit disclosed in Japanese Patent Application Laid-Open No. 2004-045548.
Specifically, based on the valve lift amount within the valve operating angle of the first intake valve 105a and the opening timing IVO of the first intake valve 105b, the valve opening area AWm of the first intake valve 105a at the time of valve overlap is set. Based on this valve opening area AWm, a basic blowback amount Wm0 at the time of valve overlap is calculated.

Here, as the valve opening area AWm is larger, in other words, as the opening timing IVO of the first intake valve 105a is advanced and the valve overlap amount is larger, and as the valve lift amount of the intake valve 105a is larger, the basic The blowback amount Wm0 is calculated as a larger value.
Then, the basic blowback amount Wm0 is corrected according to the intake negative pressure PB and the engine speed NE at that time to calculate the blowback EGR gas amount Wm.
In the correction according to the intake negative pressure PB, the higher the intake pressure, which is the upstream pressure of the first intake valve 105a (the smaller the negative pressure), the smaller the blow back EGR gas amount Wm is corrected. Further, the higher the engine rotation speed Ne, the smaller the correction of the blow back EGR gas amount Wm.

  For simplicity, as the opening timing IVO (valve timing) of the first intake valve 105b is advanced, in other words, the valve overlap period between the first intake valve 105b and the exhaust valves 110a and 110b is expanded. As the blow-back EGR gas amount Wm increases, the blow-back EGR gas amount (internal EGR gas amount) Wm can be estimated.

In the next step S2 (flow velocity detection means), the flow velocity AS of the intake air flowing through the first intake port 113a in the intake stroke is detected.
The intake air flow rate AS can be estimated from the intake negative pressure PB detected by the intake pressure sensor 121, the combination of the throttle opening TVO and the engine speed NE, the output of the intake air amount sensor 103, and the like. Specifically, it can be estimated that the higher the flow rate side (high load side), the faster the flow rate of the intake air.

In step S3, the intake period TS of the internal EGR is calculated from the blown back EGR gas amount (internal EGR gas amount) Wm detected in step S1 and the flow velocity AS of the intake air flowing through the first intake port 113a detected in step S2. To do.
The intake period TS of the internal EGR is the time required for the EGR gas (internal EGR gas) blown back to the first intake port 113a to be sucked into the combustion chamber 104 after the intake stroke (after the intake TDC). The fresh air is sucked into the combustion chamber 104 after the intake period TS has elapsed.

Here, the intake period TS of the internal EGR is calculated as a longer time as the blow-back EGR gas amount (internal EGR gas amount) Wm is larger and as the intake air flow rate AS is slower.
That is, if the flow rate AS of the intake air is the same, the larger the blow back EGR gas amount (internal EGR gas amount) Wm, the more the internal EGR gas in the first intake port 113a is required to be sucked into the combustion chamber 104. If the time is long and the blowback EGR gas amount (internal EGR gas amount) Wm is the same, the slower the flow rate AS of the intake air, the more the internal EGR gas in the first intake port 113a is sucked into the combustion chamber 104. It takes longer time to be done.

Therefore, based on such characteristics, from the blow-back EGR gas amount (internal EGR gas amount) Wm and the intake air flow rate AS at that time, the intake period TS of the internal EGR, in other words, from the intake top dead center TDC, The time until the suction into the combustion chamber 104 is almost completed is estimated.
In step S4 (injection start timing setting means), the injection start timing of the first fuel injection valve 106a is set based on the suction period TS of the internal EGR calculated in step S3.

Here, the longer the intake period TS of the internal EGR, the later the timing from the intake top dead center TDC is set as the injection start timing of the first fuel injection valve 106a.
That is, the gas introduced into the combustion chamber 104 through the first intake valve 105a (intake valve # 1) is internal EGR gas immediately after the intake top dead center TDC, as shown in FIG. After the EGR gas (internal EGR gas) blown back to the intake port 113a is introduced into the combustion chamber 104, fresh air passes through the first intake valve 105a and is introduced into the combustion chamber 104.

Then, the fuel injected from the first fuel injection valve 106a is mixed with the internal EGR gas to suppress a decrease in stratification, and the fuel injected from the first fuel injection valve 106a is desired to be mixed with fresh air. The fuel injection by the first fuel injection valve 106a is started after the intake period TS of the gas amount (internal EGR gas amount) substantially elapses.
The injection start timing of the first fuel injection valve 106a is set within a set range including a timing at which the suction of the internal EGR gas in the first intake port 113a to the combustion chamber 104 is substantially completed. In the step S4, a range in which the mixing of the fuel into the internal EGR gas can be suppressed to maintain the stratification degree and the fuel can be uniformly mixed with the air sucked into the combustion chamber 104 is set. A characteristic for setting the injection start timing from the suction period TS of the internal EGR is set in advance.

Thus, if the injection start timing of the first fuel injection valve 106a is set, the internal EGR gas can be introduced even if fresh air is introduced into the combustion chamber 104 following the internal EGR gas via the first intake valve 105a. It is possible to suppress the fuel from being mixed with the fuel and to mix the fuel freshly.
Accordingly, fresh air is introduced into the combustion chamber 104 via the second intake valve 105b, and fresh air is also introduced into the combustion chamber 104 via the first intake valve 105a to generate high engine torque. In addition, since the fuel is not mixed with the internal EGR gas, the stratification degree in the EGR stratified combustion can be secured, the internal EGR amount can be increased, the fuel consumption performance can be improved, and the fuel can be mixed evenly with fresh air. High combustion stability.

  Further, the larger the blowback EGR gas amount (internal EGR gas amount) Wm, the longer the intake period TS of the internal EGR, and the slower the intake air flow rate AS, the longer the intake period TS of the internal EGR. Since the injection start timing by the first fuel injection valve 106a is variably set, the injection by the first fuel injection valve 106a is started even if the blowback EGR gas amount (internal EGR gas amount) Wm and / or the flow velocity of the intake air are different. It is possible to prevent the fuel from being mixed with the internal EGR gas because the timing is too early, and the injection start timing by the first fuel injection valve 106a is excessively delayed, causing variations in the air-fuel ratio in fresh air. Can be suppressed.

For simplicity, in step S3, a first EGR gas amount (internal EGR gas amount) Wm detected in step S1 and a flow velocity AS of the intake air flowing through the first intake port 113a detected in step S2 are calculated as follows. Calculation of the intake period TS of the internal EGR can be omitted by setting the injection start timing by the fuel injection valve 106a.
In addition, as shown in FIG. 7, as the fuel injection valve 106, fuel is injected toward the first intake port 113a (first intake valve 105a) and toward the second intake port 113b (second intake valve 105b). However, when one two-way injection valve for injecting fuel is provided, the fuel injection may be started at the injection start timing set in step S4. One two-way injection valve is provided for each cylinder. The above-described injection start time setting process can also be applied to the engine 101 provided.
Further, the ratio of the fuel injection amount by the first fuel injection valve 106a and the fuel injection amount by the second fuel injection valve 106b is set to the ratio of fresh air introduced into the combustion chamber 104 via the intake valves 105a and 105b. By combining, air-fuel ratio variation in the air-fuel mixture can be suppressed.

  Incidentally, in the above embodiment, the combustion gas is introduced into the first intake port 113a by performing the internal EGR in which the combustion gas blows back from the combustion chamber 104 into the first intake port 113a. As shown in FIG. 3, an exhaust gas recirculation passage 122 (combustion gas introduction means) for communicating the first intake port 113a downstream of the first fuel injection valve 106a and the exhaust pipe 111, and an exhaust gas return passage interposed in the exhaust gas recirculation passage 122. An engine 101 that includes an exhaust recirculation valve (electromagnetic valve) 123 that controls the flow rate (external EGR gas amount) and performs external EGR that recirculates (introduces) combustion gas from the exhaust pipe 111 to the first intake port 113a. By setting the injection start timing by the first fuel injection valve 106a from the EGR gas amount and the flow velocity AS of the intake air, the same operation as in the above embodiment is performed. Effect can be obtained.

In the case of the engine 101 that performs the above external EGR, it is not necessary to introduce the blow back gas (internal EGR) into the first intake port 113a by setting the opening timing IVO of the intake valves 105a and 105b. The valve timing can be made the same.
The flowchart of FIG. 9 shows the setting process of the injection start timing of the first fuel injection valve 106a performed by the engine control device 201 in the engine 101 that performs external EGR with the structure shown in FIG.

The routine shown in the flowchart of FIG. 9 is executed at regular intervals by the engine control apparatus 201. First, in step S21 (gas amount detection means), the routine is introduced into the first intake port 113a via the exhaust gas recirculation passage 122. The external EGR amount Wm1 (the amount of combustion gas introduced into the first intake port 113a) is calculated.
The calculation of the external EGR amount Wm1 is performed based on the differential pressure between the pressure in the exhaust pipe 111 and the pressure PB in the intake pipe 102. That is, the external EGR recirculates the combustion gas in the exhaust pipe 111 into the intake pipe 102 based on the differential pressure. The larger the differential pressure, in other words, the intake pipe than the pressure in the exhaust pipe 111. The lower the pressure PB in 102, the greater the amount of combustion gas that is recirculated.

Therefore, in step S21, it is estimated that the external EGR amount Wm1 increases as the differential pressure between the pressure in the exhaust pipe 111 and the pressure PB in the intake pipe 102 increases.
Here, the pressure PB in the intake pipe 102 can be detected from the output of the intake pressure sensor 121, and can be estimated from the throttle opening TVO and the engine rotational speed NE in the engine 101 that does not include the intake pressure sensor 121.

Further, the pressure in the exhaust pipe 111 can be estimated based on the throttle opening TVO and the engine rotational speed NE, and can be detected by a pressure sensor.
Further, since the pressure in the intake pipe 102 and the pressure in the exhaust pipe 111 can both be estimated based on the throttle opening TVO and the engine rotational speed NE, the differential pressure is estimated from the throttle opening TVO and the engine rotational speed NE. be able to.

When the exhaust recirculation valve (electromagnetic valve) 123 is controlled to be opened or closed, the external EGR amount Wm1 is estimated from the differential pressure across the exhaust recirculation valve (electromagnetic valve) 123 in the open state as described above. However, when adjusting the external EGR amount Wm1 by changing the opening degree of the exhaust gas recirculation valve (electromagnetic valve) 123, the external EGR value is determined from the opening degree of the exhaust gas recirculation valve (electromagnetic valve) 123 and the differential pressure. The amount Wm1 can be estimated.
Further, when the valve timings of the intake valves 105a and 105b are made variable by the variable valve mechanisms 114a and 114b, the valve timing (open timing IVO) is advanced and the valve overlap period increases, so that the internal EGR amount increases. Therefore, the external EGR amount Wm1 may be corrected to increase as the valve timing is advanced, and the external EGR amount Wm1 may be calculated as the gas amount included in the internal EGR amount.

  Further, instead of correcting the external EGR amount Wm1 according to the valve timing (valve overlap period), an intake period TS1 described later is increased and corrected according to the increase in the internal EGR amount accompanying the advance of the valve timing, The injection start time can be corrected to a later time.

In the next step S22 (flow velocity detection means), the flow velocity AS of the intake air flowing through the first intake port 113a in the intake stroke is detected in the same manner as in step S2.
In step S23, the external EGR intake period TS1 is calculated from the external EGR amount Wm1 detected in step S21 and the intake air flow velocity AS flowing in the first intake port 113a detected in step S22.

When the combustion gas is introduced into the first intake port 113a by the external EGR, the pressure in the first intake port 113a gradually increases from the intake top dead center TDC toward the intake bottom dead center BDC. The differential pressure between the pressure and the pressure PB in the intake pipe 102 gradually decreases.
For this reason, as shown in FIG. 10, the gas introduced into the combustion chamber 104 via the first intake valve 105a is mostly occupied by the external EGR at the beginning of the intake stroke, but thereafter the ratio occupied by the external EGR. Will gradually become smaller and the proportion of fresh air will be relatively higher.
Here, the intake period TS1 of the external EGR is calculated as, for example, a period from the intake top dead center TDC until the ratio occupied by the external EGR in the gas introduced into the combustion chamber 104 starts to decrease. Then, the external EGR intake period TS1 is calculated as a longer period as the external EGR amount Wm1 increases and as the intake air flow rate AS decreases.

In step S24 (injection start timing setting means), the injection start timing of the first fuel injection valve 106a is set based on the suction period TS1 of the external EGR calculated in step S23.
Here, the longer the intake period TS1 of the external EGR, the later the time from the intake top dead center TDC is set as the injection start timing of the first fuel injection valve 106a.

Thus, if the injection start timing of the first fuel injection valve 106a is set, the external EGR gas can be introduced even if fresh air is introduced into the combustion chamber 104 following the external EGR gas via the first intake valve 105a. Since the fuel injection by the first fuel injection valve 106a is started after the amount introduced into the combustion chamber 104 starts to decrease, it is possible to suppress the mixing of fuel with the external EGR gas and to mix the fuel with fresh air.
Accordingly, fresh air is introduced into the combustion chamber 104 via the second intake valve 105b, and fresh air is also introduced into the combustion chamber 104 via the first intake valve 105a to generate high engine torque. In addition, since the fuel is not mixed with the external EGR gas, the stratification degree in the EGR stratified combustion can be secured, the external EGR amount can be increased, the fuel consumption performance can be improved, and the fuel can be mixed evenly with fresh air. High combustion stability.

  Further, the first fuel injection valve corresponds to the fact that the external EGR intake period TS1 is longer as the external EGR gas amount Wm1 is larger, and the external EGR intake period TS1 is longer as the intake air flow rate AS is slower. Since the injection start timing by 106a is variably set, even if the external EGR gas amount Wm1 and / or the flow velocity AS of the intake air are different, the injection start timing by the first fuel injection valve 106a is too early and fuel is supplied to the external EGR gas. Mixing can be suppressed, and the occurrence of variations in the air-fuel ratio in fresh air due to the excessive delay in the injection start timing of the first fuel injection valve 106a can be suppressed.

For simplicity, in step S23, the injection by the first fuel injection valve 106a is performed from the external EGR gas amount Wm1 detected in step S21 and the flow velocity AS of the intake air flowing through the first intake port 113a detected in step S22. The calculation of the inhalation period TS1 of the external EGR can be omitted by setting the start time.
The fuel injection valve 106 injects fuel toward the first intake port 113a (first intake valve 105a) and also injects fuel toward the second intake port 113b (second intake valve 105b) 2. When one directional injection valve is provided, it is only necessary to start fuel injection at the injection start timing set in step S24. One directional injection valve is provided for each cylinder, and external EGR is performed. The above-described injection start time setting process can also be applied to the engine 101.

By the way, when external EGR is performed, as shown in FIG. 10, the external EGR amount gradually decreases during the intake stroke, and even after fresh air is introduced, the external EGR gas is changed along with the fresh air. One intake valve 105a is passed.
Therefore, if the penetration force of the fuel spray injected from the first fuel injection valve 106a is strong, even if the injection start timing is set after the start of suction of fresh air, it will enter the first intake port 113a via the exhaust gas recirculation passage 122. The fuel spray reaches the introduced external EGR gas, and the possibility that the fuel is mixed with the external EGR increases.

Therefore, in the engine 101 that performs the external EGR, the fuel injected by the first fuel injection valve 106a against the fresh air existing in the first intake port 113a before the location where the exhaust gas recirculation passage 122 joins is generated. In other words, in other words, the fuel spray of the first fuel injection valve 106a can be suppressed so that the fuel spray of the first fuel injection valve 106a reaches the downstream side of the location where the exhaust gas recirculation passage 122 joins. It is preferable to reduce the penetration force.
As means for weakening the penetration force, in addition to means for reducing the particle size of the fuel spray injected from the first fuel injection valve 106a, a plurality of fuel injections from the first fuel injection valve 106a are performed as shown in FIG. By performing the process dividedly, it is possible to use means for dividing the injection time per time (divided injection control means).

If the injection by the first fuel injection valve 106a is divided into a plurality of times and the injection time per time is shortened, the penetration force of the fuel spray is weakened, and the fuel spray reaches after the confluence of the exhaust gas recirculation passage 122. The fuel can be mixed with the fresh air before the junction of the exhaust gas recirculation passage 122, so that the fuel can be suppressed from mixing with the external EGR gas.
Here, if the number of divisions of fuel injection is increased and the injection time per one is shortened, the penetration force of fuel spray becomes weaker. However, as the number of divisions of fuel injection is increased, The sum of the interval time until the start of injection becomes longer, and the time until fuel injection is finally finished for the same fuel injection amount becomes longer.

Therefore, it is preferable to set the number of divisions in accordance with the valve opening time of the intake valve 105a, in other words, the length of the fuel injection possible time. For example, as shown in FIG. 12, the longer the valve opening time of the intake valve 105a, the greater the number of divisions, and the fuel injection pulse width TI is divided by the set number of divisions to inject the injection pulse width per time. The first injection start timing is set as the injection start timing determined according to the external EGR gas amount Wm1 and the intake air flow rate AS described above, and the second injection is started after a certain time after the first injection is completed. Finally, the injection is repeated for the set number of divisions.
The valve opening time of the intake valve 105a can be obtained from the operating angle of the intake valve 105a and the engine speed NE at that time.

Further, the amount of the external EGR gas that passes through the first intake valve 105a and is sucked into the combustion chamber 104 gradually decreases during the intake stroke, so that the latter half of the intake stroke (as it approaches the intake bottom dead center BDC). Even if the penetration force of the fuel spray becomes strong, it is possible to suppress the mixing of fuel with the external EGR, and if the divided injection pulse width (injection amount per one time) is made as large as possible, fresh air intake The period during which the fuel is not injected is reduced, and the fuel can be uniformly mixed with the fresh air.
Therefore, in divided injection, it is preferable that the injection pulse width (fuel injection amount) is increased and changed as the number of injections increases, as shown in FIG. Here, each time the number of injections increases, the injection pulse width may be increased from the previous time. For example, the injection pulse width in the second and subsequent injections is set to be the same, and the injection pulse in the second and subsequent injections is set. The width can be longer than the injection pulse width in the first injection.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the control device for an internal combustion engine according to any one of claims 1 to 3,
The intake passage includes a first intake port provided with a first intake valve for each cylinder and a second intake port provided with a second intake valve;
The fuel injection valve includes a first fuel injection valve that injects fuel into the first intake port, and a second fuel injection valve that injects fuel into the second intake port,
The combustion gas introduction means opens the first intake valve while the piston is raised, and opens the second intake valve after the piston top dead center, so that the combustion gas in the combustion chamber is opened to the first intake valve. In the port,
The injection start timing setting means is configured to change the first fuel in accordance with a fresh air introduction start timing after the combustion gas introduced into the first intake port is introduced into the combustion chamber via the first intake valve. A control device for an internal combustion engine that sets an injection start timing of an injection valve.

  In such a configuration, since fresh air is introduced into the combustion chamber from the first intake port following the introduction of the combustion gas (internal EGR gas), gas is introduced into the combustion chamber in parallel from the first intake port and the second intake port. EGR can be suppressed, swirl formation in the combustion chamber can be suppressed, EGR stratified combustion can be performed, and mixing of fuel with the internal EGR gas can be suppressed to improve the stratification degree. Fuel consumption performance can be improved by increasing the amount.

(B) In the control device for an internal combustion engine according to claim 3,
The split injection control means is a control device for an internal combustion engine that increases a fuel injection amount per time as the number of injections increases.
In such a configuration, when the fresh air ratio at the beginning of injection is small, the penetration amount of the fuel spray is weakened by suppressing the injection amount, the fuel is prevented from being mixed with the external EGR, and the fresh air ratio is increased. High combustibility can be realized by increasing the injection amount (injection pulse width) and improving the mixing of fuel with fresh air.

  DESCRIPTION OF SYMBOLS 101 ... Engine (internal combustion engine), 105a, 105b ... Intake valve, 106a, 106b ... Fuel injection valve, 107 ... Spark plug, 109 ... Crankshaft, 110a, 110b ... Exhaust valve, 113a, 113b ... Intake port, 114a, 114b ... Variable valve mechanism, 115 ... Ignition module, 201 ... Engine control device, 203 ... Crank angle sensor, 204 ... Cam angle sensor

Claims (3)

A control device for an internal combustion engine including a fuel injection valve for injecting fuel into an intake passage,
Combustion gas introduction means for introducing combustion gas into the intake passage;
A gas amount detecting means for detecting a combustion gas amount introduced into the intake passage by the combustion gas introducing means;
A flow velocity detecting means for detecting a flow velocity of the intake air flowing in the intake passage;
As the amount of combustion gas introduced into the intake passage increases, the injection start timing by the fuel injection valve is set to a later timing, and as the flow rate of the intake air is slower, the injection start timing is set to a later timing. Injection start time setting means to perform,
A control device for an internal combustion engine, including: The combustion gas introduction means variably controls a valve overlap period between the intake valve and the exhaust valve to control the amount of combustion gas introduced into the intake passage;
The gas amount detection means detects a larger amount of combustion gas introduced into the intake passage as the valve overlap period increases, so that the injection start timing setting means increases the valve overlap period. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the injection start timing is set to a later timing as the operation is performed. The combustion gas introduction means is external EGR means for recirculating combustion gas from an exhaust passage into an intake passage downstream of the fuel injection valve;
The internal combustion engine according to claim 1 or 2, further comprising split injection control means for performing injection by the fuel injection valve in a plurality of times, with the injection at the injection start time set by the injection start time setting means being the first time. Control device.