JP2007040310A - Control method for cylinder injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a cylinder injection internal combustion engine capable of effectively reducing HC and NOx exhausted from a combustion chamber during the time from starting the engine to stopping the engine. <P>SOLUTION: The control device comprises an external EGR passage 11 for recirculating part of exhaust gas from an exhaust pipe 10 to an intake pipe 5, an external EGR control valve 12 for controlling the amount of exhaust gas to be recirculated to the external EGR passage 11, and valve timing varying mechanisms 9A, 9B for varying an opening/closing timing of at least one of an intake valve and an exhaust valve. In an operation region requiring exhaust gas recirculation, an ECU 100 always controls the valve timing varying mechanism 9A, 9B to recirculate internal EGR. When an EGR amount required depending on an operated condition is not enough for an internal EGR amount with the valve timing varying mechanisms 9A, 9B, it controls the external EGR control valve 12 to recirculate the exhaust gas while combining internal EGR with external EGR. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a direct injection internal combustion engine, and more particularly to a control device for a direct injection internal combustion engine suitable for use in controlling a direct injection internal combustion engine equipped with an exhaust gas recirculation device.

  As a control device for a cylinder injection internal combustion engine equipped with a conventional exhaust gas recirculation device, for example, as described in Japanese Patent Laid-Open No. 2-245460, the internal combustion engine is controlled in a low load region. It is known that only EGR is refluxed and external EGR is refluxed in a high load range.

  Further, for example, Japanese Patent Laid-Open No. 6-323201 discloses a first EGR in which the air-fuel ratio is controlled so that the air surplus rate is larger in the low load region than in the high load region, and the high temperature exhaust gas is recirculated to the combustion chamber. In the internal combustion engine provided with the device and the second EGR device that recirculates the low-temperature exhaust gas, the high-temperature exhaust gas and the low-temperature exhaust gas are recirculated together in the low load range, and in the low load range, to the exhaust combustion chamber compared to the high load range. It is known to reduce the total reflux rate.

  As described above, when exhaust gas is recirculated to the combustion chamber, the maximum temperature in the cylinder is lowered, so that NOx can be reduced. In particular, when the external EGR, which is a low-temperature exhaust gas, is recirculated to the combustion chamber, the effect is remarkable, and NOx decreases as the external EGR amount increases.

  In addition, when the internal EGR that is high-temperature exhaust gas is recirculated to the combustion chamber, the temperature inside the cylinder becomes high, so the NOx reduction effect is reduced, but the atomization of fuel spray is promoted or the fuel adhering to the combustion chamber wall surface By promoting vaporization, it is possible to reduce HC simultaneously with NOx reduction. Thus, the internal EGR can reduce both HC and NOx.

JP-A-2-245460 JP-A-6-323201

  However, as described in JP-A-2-245460 and JP-A-6-323201, when external EGR that is low-temperature exhaust gas is recirculated to the combustion chamber, it is contrary to NOx reduction. , HC tends to increase. When excess EGR is recirculated, a large amount of HC is discharged from the combustion chamber, and the combustion becomes unstable.

  Further, in order to effectively reduce NOx discharged from the combustion chamber by the internal EGR, a large amount of internal EGR is required. However, if the variable valve is controlled so as to increase the internal EGR, combustion instability or The problem of engine torque drop occurs. Further, when the engine performs stratified combustion when it is cold, there is a problem that a large amount of HC is discharged due to the injected fuel adhering to the combustion chamber wall surface.

  An object of the present invention is to provide a control apparatus for a direct injection internal combustion engine that can effectively reduce HC and NOx discharged from a combustion chamber from the start of the engine to the stop of the engine.

  To achieve this object, the present invention provides an external EGR passage for recirculating a part of exhaust gas from an exhaust pipe to an intake pipe, and an external EGR control for controlling the amount of exhaust gas recirculated to the external EGR passage. In a spark ignition type in-cylinder injection internal combustion engine having a valve timing variable mechanism that varies the opening and closing timing of at least one of an intake valve and an exhaust valve, in the operation region that requires exhaust gas recirculation, Control the timing variable mechanism to constantly recirculate the internal EGR, and control the external EGR control valve when the EGR amount required according to the operating state is insufficient with the internal EGR amount by the valve timing variable mechanism. Thus, the internal EGR is used in combination with the external unit GR, and control means for recirculating the exhaust gas is provided. With this configuration, it is possible to effectively reduce HC and NOx discharged from the combustion chamber from when the engine is started to when the engine is stopped.

  According to the present invention, it is possible to effectively reduce HC and NOx discharged from the combustion chamber from when the engine is started to when the engine is stopped.

Hereinafter, the configuration and operation of a control apparatus for a direct injection internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS.
First, the overall configuration of the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 1 is an overall configuration diagram of a direct injection internal combustion engine according to an embodiment of the present invention.

  In the cylinder injection internal combustion engine according to the present embodiment, a fuel injection valve 2 is disposed on the side surface of the combustion chamber 1, and a spark plug 3 is disposed in the center of the upper surface of the combustion chamber 1. The fuel injection valve 2 can inject fuel into the combustion chamber 1 at any timing regardless of the operation of the intake valve 4.

  At the time of stratified combustion, which is a feature of the in-cylinder injection type, the opening degree of the electronic control throttle 6 provided in the middle of the intake pipe 5 is greatly opened, and the intake air amount is increased and the air-fuel ratio is secured, compared with the case of homogeneous combustion. .

  Further, the ECU 100 receives a number of signals such as a crank angle sensor signal Sca, an accelerator opening sensor Sap, and an intake air amount signal Sia from an airflow sensor 7 that measures the intake air amount. Based on these signals, ECU 100 controls the engine according to operating conditions.

  Furthermore, the valve timing variable mechanisms 9A and 9B vary the opening / closing timings of the intake valve 4 and the exhaust valve 8 in order to further improve the exhaust and torque. The variable valve timing mechanisms 9A and 9B are controlled based on a command from the ECU 100. The external EGR passage 11 is a passage for recirculating a part of the exhaust from the exhaust pipe 10 to the intake pipe 5. The external EGR control valve 12 is a control valve for controlling the amount of exhaust gas recirculated to the external EGR passage 11. The external EGR control valve 12 is used to reduce NOx when the engine is warm, and is controlled based on a command from the ECU 100.

Next, the contents of control by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 2 is a flowchart showing the control contents of the control device for the direct injection internal combustion engine according to the embodiment of the present invention.

  In step s100, the ECU 100 reads the engine coolant temperature based on the output of the water temperature sensor provided in the engine.

  Next, in step s110, the ECU 100 determines whether the engine coolant temperature has reached a predetermined value, for example, 80 ° C. When the engine cooling water temperature is 80 ° C. or lower, the process proceeds to step s120, and when the engine cooling water temperature is higher than 80 ° C., the process proceeds to step s150.

  If the engine coolant temperature is 80 ° C. or lower, in step s120, the ECU 100 controls the valve timing variable mechanism 9B to perform early closing control of the exhaust valve 8.

Here, the contents of the early closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 3 is an explanatory diagram of the early closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention.

  FIG. 3 is an enlarged view of the intake / exhaust valve cam profile near the intake top dead center in the exhaust valve early closing control. The solid lines C-1 and C-2 in FIG. 3 indicate the opening and closing timing of the normal intake valve 4 and exhaust valve 8. As indicated by the solid line C-1, the closing timing of the exhaust valve is normally set near the intake top dead center (TDC). Further, as indicated by a solid line C-2, the opening timing of the intake valve is normally set near the intake top dead center (TDC).

  On the other hand, as shown by the dotted line A-1 in the figure, in the case of the exhaust valve early closing, the ECU 100 controls the valve timing variable mechanism 9B to set the closing timing of the exhaust valve 8 to the normal exhaust valve. The exhaust valve is closed while the piston is moving up earlier than the closing timing. As a result, the exhaust discharged to the exhaust pipe normally until the piston top dead center is confined in the combustion chamber, and internal EGR can be realized. By realizing the internal EGR, it is possible to reduce NOx and HC in the exhaust gas when the water temperature is low at the time of starting or the like. The method for realizing the internal EGR is not particularly limited as long as it is a means for returning the internal EGR by variable control of the intake valve and the exhaust valve, in addition to the early closing control of the exhaust valve.

  Next, in step s130, the ECU 100 determines whether or not the catalyst temperature is higher than 250 ° C., for example. If it is 250 ° C. or lower, the process proceeds to step s140. If it is higher than 250 ° C., step s140 is skipped. Here, the temperature (250 ° C.) that is a criterion is for determining whether or not the catalyst is activated, and does not necessarily have to be 250 ° C. The activation of the catalyst at other temperatures. It may be determined whether or not there is.

  When the catalyst temperature is, for example, 250 or less, in step s140, the ECU 100 controls the valve timing variable mechanism 9B to perform quick opening control of the exhaust valve 8.

Here, the contents of the quick opening control of the exhaust valve by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 4 is an explanatory diagram of the control for quickly opening the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 4 is an enlarged view of the exhaust valve cam profile and the in-cylinder temperature (T) in the exhaust valve early opening control.

  A solid line C-1 in FIG. 4 indicates a normal opening timing of the exhaust valve 8. On the other hand, the dotted line A-1 shows the opening timing when the quick opening control of the exhaust valve according to the present embodiment is performed. A solid line D indicates the in-cylinder temperature in the expansion stroke. By quickly opening the exhaust valve, the in-cylinder temperature is increased to T2 during the early opening control of the exhaust valve as compared to the in-cylinder temperature T1 at the normally set exhaust valve opening timing indicated by the solid line C-1, and the temperature is increased. Exhaust is discharged into the exhaust pipe. As a result, the engine is in a cold state, and particularly during the period until the catalyst is activated, high-temperature exhaust gas can be supplied to the catalyst, and the time until catalyst activation can be shortened. Further, this control may be performed only during the period from the start to the time when the temperature of the catalyst reaches a predetermined value.

  However, in this case, since there is a concern about a decrease in torque due to high-temperature exhaust discharge, it is desirable to increase the injected fuel corresponding to the torque decrease in advance.

  Thereby, simultaneously with the effect of reducing HC and NOx discharged from the combustion chamber, it is possible to obtain the effect of the initial activation of the catalyst without being accompanied by a decrease in torque.

  In order to detect the catalyst temperature, it is necessary to newly install a catalyst temperature sensor. In order to avoid an increase in cost due to the installation of the catalyst temperature sensor, step s140 may be executed immediately after step s120 without performing the determination in step s130. As a result of the determination in step s110, the fact that the water temperature is 80 ° C. or lower often reduces the catalyst temperature as in the case of starting or the like, and therefore step s130 can be omitted.

  Further, in the case of a direct injection internal combustion engine using a phase difference type intake / exhaust valve, in order to execute the step s120, in order to perform the exhaust valve early closing, it is necessary to perform the exhaust valve early opening in step s140. Steps s140 and s120 are executed at the same time.

  Next, when the engine coolant temperature is higher than 80 ° C. in the determination in step s110 of FIG. 2, in step s150, the ECU 100 determines whether the current combustion mode is homogeneous combustion or stratified combustion, Determine by. For example, when F = 0 and homogeneous combustion, the process proceeds to step s160, and when F = 1 and stratified combustion, the process proceeds to step s170. Here, the ECU 100 determines in advance whether to perform stratified combustion or homogeneous combustion based on the engine speed and required torque, and controls the fuel injection amount and timing based on the determination result. . Accordingly, the determination result of whether to perform stratified combustion or homogeneous combustion is held as flag F, where F = 0 is homogeneous combustion and F = 1 is stratified combustion. By F, the current combustion state can be determined.

  At the time of homogeneous combustion, in step 160, the ECU 100 controls the variable valve timing mechanisms 9A and 9B to perform early closing control of the intake valve 4 and late closing control of the exhaust valve 8.

Here, the content of the early closing of the intake valve and the late closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 5 is an explanatory view of the early closing control of the intake valve and the late closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 5 is an enlarged view of the intake / exhaust valve cam profile near the intake top dead center in the early closing control of the intake valve and the late closing control of the exhaust valve.

  The solid lines C-1 and C-2 in FIG. 5 indicate the normal opening and closing timings of the intake valve 4 and the exhaust valve 8 as in FIG. As indicated by the solid line C-1, the closing timing of the exhaust valve is normally set near the intake top dead center (TDC). Further, as indicated by a solid line C-2, the opening timing of the intake valve is normally set near the intake top dead center (TDC).

  On the other hand, as shown by the dotted line A-1 in the figure, in the case of the exhaust valve early closing, the ECU 100 controls the valve timing variable mechanism 9B to set the closing timing of the exhaust valve 8 to the normal exhaust valve. The exhaust valve is closed while the piston is moving up earlier than the closing timing. As a result, the exhaust discharged to the exhaust pipe normally until the piston top dead center is confined in the combustion chamber, and internal EGR can be realized. The method for realizing the internal EGR is not particularly limited as long as it is a means for returning the internal EGR by variable control of the intake valve and the exhaust valve, in addition to the early closing control of the exhaust valve.

  On the other hand, when the intake valve is closed late and the intake valve is opened early, the ECU 100 controls the valve timing variable mechanism 9A so that the closing timing of the intake valve 4 is set to normal exhaust as shown by the dotted line B-1. The opening timing of the exhaust valve 8 is set earlier than the opening timing of the normal intake valve, as shown by the dotted line B-2. As a result, the amount of overlap during the open period of the intake valve and the exhaust valve increases. That is, when the intake valve is quickly opened B-2, a part of the exhaust gas is injected back into the intake pipe and is again sucked into the combustion chamber after the piston top dead center. The exhaust once exhausted into the exhaust pipe is sucked again, and internal EGR is realized.

  Next, in step s170, the ECU 100 reads the engine speed and the target torque based on the pulse interval of the crank angle sensor signal Sca obtained from the crank angle sensor.

  Next, in step s180, the ECU 100 calculates a required EGR amount by a map search or the like from the engine speed and the target torque obtained in step s160.

  Next, in step s190, the ECU 100 determines an internal EGR amount (a variable amount of intake and exhaust valves) that does not cause combustion deterioration or torque reduction from the engine speed and the target torque, and the required EGR amount calculated in step s180. Judge whether you are satisfied. If the internal EGR amount satisfies the required EGR amount, the process proceeds to step s150, and the early closing control of the intake valve and the late closing control of the exhaust valve are executed. If the internal EGR amount does not satisfy the required EGR amount, the process proceeds to step s200.

  In step s200, the ECU 10O recirculates the corresponding external EGR by controlling the external EGR control valve 12 so as to compensate for the shortage of internal EGR for the request EGR.

  During engine operation, a series of operations from step s100 to step s200 can be repeated to reduce HC and NOx discharged from the combustion chamber.

  As described above, in the present embodiment, as understood from the control contents of steps s160 and s200 based on the determination of step s190, when the internal EGR is sufficient, only the internal EGR is executed, When EGR is insufficient, external EGR is used together.

Here, the combined use state of the internal EGR and the external EGR and the exhaust gas reducing effect during the control by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS.
First, the combined use state of the internal EGR and the external EGR at the time of control by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS.
FIG. 6 is an explanatory view showing a combined state of the internal EGR and the external EGR when the engine speed N is N1 during control by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 8 is an explanatory diagram showing a combined state of internal EGR and external EGR when the engine speed N during control by the control device for a direct injection internal combustion engine according to an embodiment of the present invention is N2, FIG. It is explanatory drawing which shows the combined state of internal EGR and external EGR when the engine speed N at the time of control by the control apparatus of the direct injection internal combustion engine by one Embodiment of this invention is N3. The horizontal axis indicates the target torque TT, and the vertical axis indicates the EGR amount. The engine speed N has a relationship of N1>N2> N3. A region X indicates a region using the internal EGR, and a region Y indicates a region using the external EGR.

  In step s170 of FIG. 2, the engine speed and the target torque are read, and in step s180, the required EGR amount is calculated. When the engine speed N is relatively high at N1, the required EGR amount also increases. Therefore, as shown in FIG. 6, in a region where the target torque TT is as small as TT2, for example, the required EGR amount increases, and the internal EGR alone is not sufficient, so the external EGR is used together. However, in a region where the target torque TT is large, for example, TT1, the required EGR amount is small. Therefore, the internal EGR alone is sufficient, and only the internal EGR is used.

  On the other hand, when the engine speed N is relatively low such as N2 and N3, the required EGR amount also decreases. Therefore, as shown in FIGS. 7 and 8, only the internal EGR is sufficient, and only the internal EGR is used.

Next, the effect of reducing exhaust gas during control by the control device for a direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS. 9 and 10.
FIG. 9 is an explanatory view of the effect of reducing exhaust gas in a region where the target torque is large during control by the control device for a direct injection internal combustion engine according to one embodiment of the present invention, and FIG. 10 is one embodiment of the present invention. It is explanatory drawing of the reduction effect of the exhaust gas in the area | region where the target torque at the time of control by the control apparatus of the direct injection internal combustion engine by a form is small. The horizontal axis represents the HC emission amount, and the vertical axis represents the NOx emission amount.

  For example, in the example shown in FIG. 6, when the target torque TT is TT1, only the internal EGR is used in this embodiment. In the example shown in FIG. 9, point Z1 indicates the exhaust gas emission amount when neither internal EGR nor external EGR is performed, the HC emission amount is HC1, and the NOx emission amount is NOx1. is there. Here, as in the present embodiment shown in FIG. 6, when the target torque TT1, the exhaust gas is reduced to the point Z2 by performing the internal EGR. That is, the HC emission amount is reduced from HC1 to HC2, and the NOx emission amount is reduced from NOx1 to NOx2.

  On the other hand, at the target torque TT1, if the external EGR is performed as in the conventional case, the exhaust gas changes to the point Z3. That is, the HC emission amount increases from HC1 to HC3, and the NOx emission amount decreases from NOx1 to NOx2.

  That is, by performing EGR, if the EGR amount is the same, the reduction amount of NOx is approximately the same. However, by performing internal EGR, HC can be reduced in external EGR, while HC can be reduced. That is, in the present embodiment, both NOx and HC can be reduced basically by using the internal EGR. This is the same because only the internal EGR is used at the low speed side shown in FIG. 7 and FIG.

  On the other hand, in the example shown in FIG. 6, when the target torque TT is TTO, in this embodiment, the internal EGR and the external EGR are used in combination. In the example shown in FIG. 10, the point Z4 indicates the exhaust gas emission amount when neither internal EGR nor external EGR is performed, the HC emission amount is HC3, and the NOx emission amount is NOx3. is there. Here, as in this actual embodiment shown in FIG. 6, when the target torque TT0 is used, by using the internal EGR and the external EGR together, the NOx in the exhaust gas goes to the introduction hole of the internal EGR, Reduce to point Z5. That is, the HC emission amount is reduced from HC3 to HC4, and the NOx emission amount is reduced from NOx3 to NOx4. As the target torque TT increases, NOx and HC decrease as indicated by the solid line Z6.

  On the other hand, if only the external EGR is performed as in the prior art, the exhaust gas changes from the point Z4 to the solid line Z6. That is, although NOx and HC emissions are reduced, the effect of reducing HC is particularly small compared to the case where the internal EGR and external EGR indicated by the solid line Z5 are used in combination. That is, in this embodiment, both NOx and HC can be effectively reduced by basically using the internal EGR.

Next, the configuration of the direct injection internal combustion engine according to the present embodiment will be described with reference to FIG.
FIG. 11 is a perspective view of a direct injection internal combustion engine according to an embodiment of the present invention. In addition, although the structure of the cylinder injection type internal combustion engine shown in figure is a preferable structure for controlling with the control apparatus by this embodiment, it is not limited to this. The same reference numerals as those in FIG. 1 indicate the same parts.

  An air flow generation plate 13 is provided in the intake pipe 5 so that the intake pipe 5 is vertically divided into two. An air flow control valve 14 is disposed upstream of the air flow generation plate 13. By closing the air flow control valve 14, the air sucked during the intake stroke forms a vertical air flow (tumble) 15 in the combustion chamber 1.

  A groove 16 for storing the tumble 15 is formed on the crown surface of the piston 16. During stratified combustion, the fuel injected from the fuel injection valve 2 in the second half of the compression stroke is guided toward the spark plug 3 by the tumble 15.

Next, the configuration of the fuel injection valve used in the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS.
FIG. 12 is an overall side view of a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 13 is an enlarged cross-sectional view of a main part of a fuel injection valve used in an in-cylinder internal combustion engine according to an embodiment of the present invention. FIG. 14 is a bottom view of the main part of the fuel injection valve used in the direct injection internal combustion engine according to the embodiment of the present invention. The configuration of the illustrated fuel injection valve is a preferable configuration for use in the internal combustion engine controlled by the control device according to the present embodiment, but is not limited thereto.

  FIG. 12 shows a side configuration of the fuel injection valve 2 according to the present embodiment. FIG. 13 is an enlarged view of the region X surrounded by the broken line at the tip of the fuel injection valve 2.

  As shown in FIG. 12, the nozzle portion 17 of the fuel injection valve 2 includes a ball valve 18, a rod 19 connected to the ball valve 18, a swirler 20 that gives a turning force to the spray, an injection port 21, and an axial direction. A groove 22 and a radial groove 23 are provided. In the present embodiment, the injection port 21 provided at the tip of the nozzle portion 17 is not symmetrical, and a notch 21a is provided in a part thereof. In the illustrated example, the notch 21a is provided in a range of 180 degrees.

  When the ball valve 18 is opened, fuel flows through the axial groove 22 and the radial groove 23, a turning force is applied, and the fuel is injected from the injection port 21. Since the notch 21a is provided in the injection port 21, as will be described later with reference to FIGS. 10 and 11, a lead spray and an ignition spray are formed.

  In the example shown in FIG. 14, the arrow IGN-P direction is the spark plug side, and the arrow PSTN direction is the piston side. That is, the lead spray is sprayed in the direction of the ignition plug by installing the fuel injection valve 21 so that the notch 21a of the injection port 21 faces the ignition plug.

Next, the shape of the fuel spray injected from the fuel injection valve used in the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS. 15 and 16.
FIG. 15 is a side view showing the shape of fuel spray injected from a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. 16 is a cross-sectional view taken along the line AA in FIG.

  As shown in FIG. 15, the shape of the fuel spray sprayed from the injection port 21 of the fuel injection valve 2 is not symmetrical because a cutout is provided in the injection port. The spray angle θ1 of the lead spray 24 with respect to the center line of the fuel injection valve 2 is, for example, 30 degrees. The spray angle θ2 of the ignition spray 25 with respect to the center line of the fuel injection valve 2 is, for example, 20 degrees.

  Further, as shown in FIG. 16, the cross-sectional shape of the fuel spray becomes a shape having a gap 24 </ b> A in a part of the spray due to the notch provided in the injection port 21. Further, the flow density of the lead spray 24 directed to the spark plug 3 is higher than that of the ignition spray 25. Therefore, the spray reach distance of the lead spray 24 becomes longer than the ignition spray 25.

  The spray angle θ1 of the lead spray 24 and the spray angle θ2 of the ignition spray 25 can be variously changed depending on the shape of the notch provided in the injection port 21. The spray angle θ1 of the lead spray 24 and the spray angle θ2 of the ignition spray 25 can be variously changed depending on the shape of the notch provided in the injection port 21. The configuration of the fuel injection valve is not limited to that described above, and a fuel injection valve having means for generating a reed fluid such as a porous body can also be used.

  As described above, since the spray penetration force in the spark plug direction increases, the fuel spray can be conveyed to the spark plug even at a high rotation speed, and the stratified combustion operation becomes possible. This reduces the HC emission rate by promoting the vaporization of fuel spray at the initial stage of injection while reducing the HC emission rate while maintaining the combustion stability by suppressing the mixing of the burnt gas and the soot, and further reducing NOx by the effect of exhaust gas recirculation And

Next, the spray behavior in the cylinder during stratified combustion in the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS. 17 and 18.
FIG. 17 is an explanatory diagram of spray behavior in a cylinder before fuel injection at the time of stratified combustion in a direct injection internal combustion engine according to an embodiment of the present invention, and FIG. 18 is a cylinder according to an embodiment of the present invention. It is explanatory drawing of the spraying behavior in the cylinder after the fuel injection at the time of stratified combustion in an internal injection type internal combustion engine.

  As shown in FIG. 17, in the case of stratified combustion, a tumble 15 having a strength corresponding to the engine speed and target torque is formed in the cylinder before fuel injection by controlling the opening of the air flow generation valve. Has been.

  On the other hand, as shown in FIG. 18, after fuel injection, for example, the fuel injection valve 2 that can form the structure and the fuel spray shape as described in FIGS. Since the fluid flow supplied toward the spark plug 3 can be generated prior to the subsequent ignition spray 25 by the movement of 24, the fluid generated by the lead spray 24 is led, The air-fuel mixture vaporized from the ignition spray 25 at the ignition timing can be more reliably guided to the spark plug 3.

Next, the fuel injection control method by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS.
First, the contents of control of the fuel injection control method by the control device for a direct injection internal combustion engine according to the present embodiment will be described with reference to FIG. This control method is performed until the catalyst is activated.
FIG. 19 is a flowchart showing the control contents of the fuel injection control method by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention.

  In step s200, the ECU 100 reads the catalyst temperature using a catalyst temperature sensor provided in the engine.

  Next, in step s210, the ECU 100 determines whether the catalyst temperature has reached a predetermined value, for example, 250 ° C. When the catalyst temperature is 250 ° C. or higher, the control process before catalyst activation is terminated, and normal fuel injection control is executed. In normal fuel injection control, fuel injection is performed once during the compression stroke. On the other hand, when the catalyst is not activated, fuel is injected twice during the compression stroke.

Here, the control content of the fuel injection control method by the control device for the direct injection internal combustion engine according to the present embodiment will be described with reference to FIGS.
FIG. 20 is an explanatory diagram of the control contents of the fuel injection control method based on the control concealment of the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 21 is an explanatory diagram of the state of fuel spray during fuel injection control after catalyst activation by the control device for a direct injection internal combustion engine according to one embodiment of the present invention, and FIG. 22 is one embodiment of the present invention. It is explanatory drawing of the state of the fuel spray at the time of the fuel-injection control before catalyst activation by the control apparatus of the cylinder injection type internal combustion engine by a form.

  As shown in FIG. 20 (A), after the catalyst is activated, fuel injection is performed once during the compression stroke (COM). On the other hand, as shown in FIG. 20B, before the catalyst is activated, the fuel injections 1NJ1 and 1NJ2 are divided and injected twice during the compression stroke (COM). During the period until the catalyst is activated, the exhaust gas purification efficiency of the catalyst is insufficient, so that most of the HC discharged from the combustion chamber is released to the atmosphere. Therefore, during the period until the catalyst is activated, combustion is required so that HC is not discharged from the combustion chamber. In particular, the fuel adhering to the wall surface of the combustion chamber when the engine is cold, such as before the activation of the catalyst, is discharged as unburned HC that is difficult to vaporize because the wall surface of the combustion chamber is cold.

  Therefore, during the period until the catalyst is activated, as shown in FIG. 17, the two-time injection in which the fuel spray arrival distance L <b> 2 is shorter than the fuel spray arrival distance L <b> 1 at the time of one-time injection as shown in FIG. This suppresses the fuel adhesion to the piston. In combination with the fuel spray evaporation promoting effect by the internal EGR, the unburned HC discharged from the combustion chamber can be greatly reduced.

  The specific control will be described. When the catalyst temperature is lower than 250 ° C., the process proceeds to step s220 in FIG.

  In step s220, the ECU 100 reads the target torque and the target equivalent ratio.

  Next, in step s230, the FCU 100 calculates the first fuel injection pulse width Ti1 and the second fuel injection pulse width Ti2 corresponding to the required fuel amount by map search or the like from the target torque and target equivalence ratio obtained in step s220. To do.

  Next, in step S240, the ECU 100 reads the engine speed obtained from the pulse interval from the crank angle sensor.

  Next, in step s250, the ECU 100 calculates the first fuel injection timing IT1 and the second fuel injection timing IT2 based on the engine speed obtained in step s240.

  The control from step s220 to s250 is repeated until the catalyst temperature reaches 250 ° C.

As described above, according to the present embodiment, it is possible to effectively reduce HC and NOx extracted from the combustion chamber from the start of the engine to the stop of the engine.

FIG. 1 is an overall configuration diagram of a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 2 is a flowchart showing the control contents of the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 3 is an explanatory diagram of the early closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of the control for quickly opening the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 5 is an explanatory view of the early closing control of the intake valve and the late closing control of the exhaust valve by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 6 is an explanatory diagram showing a combined state of the internal EGR and the external EGR when the engine speed N is N1 during control by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 7 is an explanatory diagram showing a combined state of the internal EGR and the external EGR when the engine speed N is N2 during control by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 8 is an explanatory diagram showing a combined state of the internal EGR and the external EGR when the engine speed N is N3 during control by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 9 is an explanatory diagram of the exhaust gas reduction effect in a region where the target torque is large during control by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 10 is an explanatory diagram of the effect of reducing exhaust gas in a region where the target torque is small during control by the pasting device for a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 11 is a perspective view of a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 12 is an overall side view of a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 13 is an enlarged cross-sectional view of a main part of a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 14 is a bottom view of an essential part of a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. FIG. 15 is a side view showing the shape of fuel spray injected from a fuel injection valve used in a direct injection internal combustion engine according to an embodiment of the present invention. 16 is a cross-sectional view taken along the line AA in FIG. FIG. 17 is an explanatory diagram of the spray behavior in the cylinder before fuel injection during stratified combustion in the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 18 is an explanatory diagram of the spray behavior in the cylinder after fuel injection during stratified combustion in the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 19 is a flowchart showing the control contents of the fuel injection control method by the control unit for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 20 is an explanatory diagram of the control contents of the fuel injection control method by the control device for the direct injection internal combustion engine according to the embodiment of the present invention. FIG. 21 is an explanatory diagram of the state of fuel spray during fuel injection control after catalyst activation by the control device for a direct injection internal combustion engine according to one embodiment of the present invention. FIG. 22 is an explanatory diagram of the state of fuel spray during fuel injection control before catalyst activation by the control device for a direct injection internal combustion engine according to one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 ... Intake pipe 9A, 9B ... Variable valve timing mechanism 10 ... Exhaust pipe 11 ... External EGR passage 12 ... External EGR control valve 100 ... ECU

Claims (6)

An external EGR passage for recirculating part of the exhaust from the exhaust pipe to the intake pipe;
An external EGR control valve for controlling the amount of exhaust gas recirculated to the external EGR passage;
In a spark ignition in-cylinder injection internal combustion engine having a valve timing variable mechanism that varies the opening and closing timing of at least one of an intake valve or an exhaust valve,
In the operation region that requires exhaust gas recirculation, the above valve timing variable mechanism is controlled to constantly recirculate the internal EGR,
When the EGR amount required according to the operating state is insufficient with the internal EGR amount by the variable valve timing mechanism, the external EGR control valve is controlled, and the external EGR is used together with the internal EGR to recirculate the exhaust gas. A control device for a direct injection internal combustion engine, comprising: The control apparatus for a direct injection internal combustion engine according to claim 1,
The control device for a direct injection internal combustion engine, wherein when the engine water temperature is equal to or lower than a predetermined value, only the internal EGR is recirculated. The control apparatus for a direct injection internal combustion engine according to claim 1,
The control device for a direct injection internal combustion engine, wherein the control means recirculates only the internal EGR when the temperature of the catalyst is equal to or lower than a predetermined value. The control apparatus for a direct injection internal combustion engine according to claim 1,
When the combustion mode is homogeneous combustion, the control means recirculates only the internal EGR, and the control device for a direct injection internal combustion engine, The control apparatus for a direct injection internal combustion engine according to claim 1,
The in-cylinder injection internal combustion engine generates a reed fluid that generates a fluid flow that is supplied in the direction of the spark plug prior to the subsequent ignition fuel, in addition to the air flow supplied to the combustion chamber by the intake port. With means,
A control apparatus for a direct injection internal combustion engine, wherein the air-fuel mixture, which is led by the fluid generated by the lead fluid generating means and vaporized from the ignition fuel spray at the ignition timing, is supplied to the spark plug. The control apparatus for a direct injection internal combustion engine according to claim 1,
A control device for a cylinder injection internal combustion engine, wherein the control means divides fuel injection into two during the compression stroke until the catalyst at the time of starting is activated.

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