JP5109994B2 - Control device for an internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine with a supercharger.

  Conventionally, for example, Patent Document 1 discloses an internal combustion engine including a so-called twin entry turbocharger. In an internal combustion engine equipped with this twin-entry turbocharger, a first exhaust passage that guides exhaust gas discharged from one cylinder to the turbine, and a second exhaust passage that guides exhaust gas discharged from the other cylinder to the turbine And an exhaust passage. Further, a passage communication control valve is provided for switching between a state in which the first exhaust passage and the second exhaust passage communicate with each other and a state in which the first exhaust passage and the second exhaust passage are blocked. In this conventional internal combustion engine, the passage communication control valve is opened during low output torque operation or high rotational speed operation.

JP-A-2005-330836 JP 2008-106725 A

  By the way, an internal combustion engine that includes an EGR passage that connects an exhaust passage and an intake passage and an EGR valve that opens and closes the EGR passage and performs so-called external EGR control is known. In such an internal combustion engine that performs external EGR control, when the twin entry turbocharger and the passage communication control valve (exhaust switching valve) are provided, the exhaust gas is exhausted in the operating region in which external EGR control is performed. When the switching valve is opened, the back pressure of the internal combustion engine decreases, and the differential pressure between the back pressure (exhaust pressure) and the intake pressure decreases. As a result, the external EGR rate decreases, and it becomes difficult to effectively improve the fuel consumption by effectively using the external EGR control.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine equipped with a twin-entry turbocharger, it is possible to more reliably improve fuel efficiency in an operation region where external EGR gas is introduced. An object of the present invention is to provide a control device for an internal combustion engine with a supercharger.

1st invention is a control apparatus of the internal combustion engine with a supercharger,
A turbocharger provided with an exhaust passage having a turbine operated by exhaust energy of the internal combustion engine;
Exhaust gas including a first exhaust passage that guides exhaust gas discharged from one cylinder of the internal combustion engine to the turbine, and a second exhaust passage that guides exhaust gas discharged from the other cylinder of the internal combustion engine to the turbine. A passage,
An exhaust switching valve that switches between a state in which the first exhaust passage and the second exhaust passage communicate with each other and a state in which the first exhaust passage and the second exhaust passage are blocked;
An EGR passage connecting at least one of the first exhaust passage and the second exhaust passage and an intake passage of the internal combustion engine;
An EGR valve disposed in the middle of the EGR passage and responsible for opening and closing the EGR passage;
EGR control means for controlling the EGR valve so that exhaust gas is recirculated to the intake passage through the EGR passage in a predetermined operating region of the internal combustion engine;
Switching valve control means for controlling the exhaust switching valve to be closed in the operating region;
It is characterized by providing.

The second invention is the first invention, wherein
The internal combustion engine is mounted on a hybrid vehicle including the internal combustion engine and an electric motor as a power source,
In the hybrid vehicle, during steady running, control is performed to shift the operating point of the internal combustion engine to an operating point on the high engine speed and low load side that maintains the same engine output as the current operating point,
The switching valve control means controls to open the exhaust switching valve when the operating point of the internal combustion engine in the operating region is shifted to the operating point on the high engine speed and low load side. It includes an hour valve control means.

The third invention is the first or second invention, wherein
The switching valve control means includes pressure change time valve control means for controlling the exhaust switching valve to open when the exhaust pressure is higher than the intake pressure by a predetermined value or more in the operating region.

Moreover, 4th invention is set in 3rd invention,
An exhaust bypass passage that branches off from the exhaust passage at a portion upstream of the turbine and merges with the exhaust passage again at a portion downstream of the turbine;
A waste gate valve disposed in the middle of the exhaust bypass passage and responsible for opening and closing the exhaust bypass passage;
The switching valve control means includes a second valve control means during pressure change for controlling the waste gate valve to open when the exhaust pressure is higher than the intake pressure by a predetermined value or more in the operating region. .

  According to the first invention, the back pressure of the internal combustion engine is easily secured in the operation region (external EGR introduction region) in which the exhaust gas is controlled to recirculate to the intake passage through the EGR passage. As a result, it becomes easy to ensure the differential pressure between the exhaust pressure and the intake pressure, so that the external EGR rate can be sufficiently high in the external EGR gas introduction region. Thereby, it becomes possible to improve the fuel consumption in the external EGR introduction region more reliably.

  If control is performed to shift the operating point of the internal combustion engine to an operating point on the high engine speed and low load side, the intake pressure (supercharging pressure) decreases, so the exhaust pressure does not depend on the control to close the exhaust switching valve. An environment where it is easy to ensure a differential pressure between the intake pressure and the intake pressure is obtained. For this reason, it becomes easier to secure external EGR gas than before the transition. In addition, according to the second aspect of the present invention, when such an operating point transition control is performed, the exhaust switching valve is opened, so that the back pressure is lowered and the amount of internal EGR gas is reduced. Therefore, knocking can be suppressed. As a result, it is possible to suppress the execution of ignition timing retard and the like, so that the internal combustion engine can be operated with high efficiency (fuel consumption). As described above, according to the present invention, it is possible to improve the fuel efficiency by suppressing knocking while improving the efficiency of the entire vehicle and securing the external EGR gas during steady running.

  According to the third aspect of the present invention, the back pressure can be lowered under a situation where the exhaust gas pressure is higher than the intake pressure by a predetermined value or more and the EGR gas amount may be excessive, and the exhaust pressure (back pressure) The differential pressure from the intake pressure can be made as small as possible. Thereby, it can suppress that the amount of EGR gas becomes excessive.

  According to the fourth invention, when the exhaust pressure is higher than the intake pressure by a predetermined value or more, in addition to the exhaust switching valve, the waste gate valve is also opened. The back pressure can be reduced more effectively. Thereby, it becomes possible to suppress more effectively that the amount of EGR gas is excessive.

Embodiment 1 FIG.
[Configuration of HV system]
FIG. 1 is a diagram showing a schematic configuration of a drive system for a hybrid vehicle to which the present invention is applied. The drive system 10 includes an internal combustion engine 12 and a vehicle drive motor (hereinafter simply “motor”) 14 as a power source of the vehicle. The drive system 10 also includes a generator 16 that receives power and generates electric power. The internal combustion engine 12, the motor 14, and the generator 16 are connected to each other via a power split mechanism 18. A reduction gear 20 is connected to the rotating shaft of the motor 14 connected to the power split mechanism 18. The speed reducer 20 connects the rotation shaft of the motor 14 and the drive shaft 24 connected to the drive wheels 22. The power split mechanism 18 is a device that splits the driving force of the internal combustion engine 12 into the generator 16 side and the speed reducer 20 side. The distribution of the driving force by the power split mechanism 18 can be arbitrarily changed.

  The drive system 10 further includes an inverter 26, a converter 28, and a high voltage battery 30. Inverter 26 is connected to generator 16 and motor 14, and is also connected to high-voltage battery 30 via converter 28. The electric power generated by the generator 16 can be supplied to the motor 14 via the inverter 26, or the high voltage battery 30 can be charged via the inverter 26 and the converter 28. Further, the electric power charged in the high voltage battery 30 can be supplied to the motor 14 via the converter 28 and the inverter 26.

  According to the drive system 10 described above, the motor 14 can be stopped and the drive wheels 22 can be rotated only by the drive force of the internal combustion engine 12 based on a predetermined condition. Conversely, the internal combustion engine 12 is stopped. Thus, the driving wheel 22 can be rotated only by the driving force of the motor 14. Furthermore, both the motor 14 and the internal combustion engine 12 can be operated, and the driving wheels 22 can be rotated by both driving forces. Further, according to the drive system 10, the motor 14 can also function as a starter for the internal combustion engine 12. That is, when the internal combustion engine 12 is started, the internal combustion engine 12 can be cranked by inputting a part or all of the driving force of the motor 14 to the internal combustion engine 12 via the power split mechanism 18.

  The drive system 10 of this embodiment is controlled by an ECU (Electronic Control Unit) 40. The ECU 40 comprehensively controls the entire drive system 10 including the internal combustion engine 12, the motor 14, the generator 16, the power split mechanism 18, the inverter 26, the converter 28, and the like.

[System configuration of internal combustion engine]
FIG. 2 is a diagram for explaining a system configuration of the internal combustion engine 12 shown in FIG. Here, it is assumed that the explosion order of the internal combustion engine 12 is # 1 → # 3 → # 4 → # 2. The internal combustion engine 12 includes an intake passage 42 for taking air into the cylinder. An air cleaner 44 is provided near the inlet of the intake passage 42. A compressor 46 a of the turbocharger 46 is disposed in the intake passage 42 on the downstream side of the air cleaner 44. The turbocharger 46 includes a turbine 46b that is operated by exhaust energy of exhaust gas. The compressor 46a is integrally connected to the turbine 46b and is driven to rotate by exhaust energy of exhaust gas input to the turbine 46b.

  An intercooler 48 for cooling the intake air compressed by the compressor 46a is disposed in the intake passage 42 on the downstream side of the compressor 46a. An electronically controlled throttle valve 50 driven by a throttle motor (not shown) is disposed downstream of the intercooler 48. The intake air that has passed through the throttle valve 50 is distributed by the intake manifold 52 and flows into each cylinder. Further, an air flow meter 54 for detecting the intake air amount is installed near the downstream of the air cleaner 44, and an intake pressure sensor 56 for detecting intake pressure is installed near the downstream of the throttle valve 50.

  The internal combustion engine 12 includes an exhaust passage 58 through which exhaust gas discharged from the cylinder flows. The exhaust passage 58 includes a first exhaust passage 58a that guides exhaust gas discharged from one cylinder (# 1 and # 4) of the internal combustion engine 12 to the turbine 46b, and the other cylinder (# 2 and # 3) of the internal combustion engine 12. And a second exhaust passage 58b for guiding the exhaust gas discharged from the turbine 46b to the turbine 46b. The turbocharger 46 has the first cylinder (# 1 and # 4) and the other cylinder (# 2 and # 4) through the first exhaust passage 58a and the second exhaust passage 58b thus configured. It is a turbocharger that is supplied with exhaust gas independently from 3), that is, a so-called twin entry turbocharger.

  As shown in FIG. 2, the first exhaust passage 58a and the second exhaust passage 58b have portions close to each other. An exhaust switching valve for switching between a state in which the first exhaust passage 58a and the second exhaust passage 58b communicate with each other and a state in which the first exhaust passage 58a and the second exhaust passage 58b are blocked are connected to the portion. 60 is arranged. According to such a configuration, the exhaust system volume can be adjusted by controlling the opening and closing of the exhaust switching valve 60 as necessary. More specifically, by closing the exhaust switching valve 60, the first exhaust passage 58a and the second exhaust passage 58b are shut off, so that the flow volume through which the exhaust gas discharged from each cylinder passes respectively. Can be reduced. Then, by opening the exhaust switching valve 60 from that state, the first exhaust passage 58a and the second exhaust passage 58b are in communication with each other, so that the passage volume through which the exhaust gas discharged from each cylinder passes is increased. Thus, the average back pressure can be lowered. Thus, the back pressure of the internal combustion engine 12 can be adjusted by controlling the opening and closing of the exhaust gas switching valve 60.

  Further, a catalyst 62 for purifying exhaust gas is disposed in the exhaust passage 58 on the downstream side of the turbine 46b. Further, the exhaust system of the internal combustion engine 12 is provided with an exhaust bypass passage 64 that bypasses the turbine 46b. The exhaust bypass passage 64 branches from both the first exhaust passage 58a and the second exhaust passage 58b at a portion upstream of the turbine 46b, and joins the exhaust passage 58 again at a portion downstream of the turbine 46b. It is configured.

  Further, an electric waste gate valve (hereinafter referred to as “WGV”) that opens and closes the exhaust bypass passage 64 is provided in the middle of the exhaust bypass passage 64, more specifically, at an upstream end portion of the exhaust gas in the exhaust bypass passage 64. (Abbreviated as “Waste Gate Valve”) 66 is installed. According to the configuration including the exhaust bypass passage 64 and the WGV 66, when the WGV 66 is closed, the entire amount of exhaust gas flowing through the exhaust passages 58a and 58b passes through the turbine 46b, while the WGV 66 is opened. In the state, a part of the exhaust gas flowing through the exhaust passages 58a and 58b passes through the turbine 46b, and the remaining part of the exhaust gas flows out of the turbine 46b through the exhaust bypass passage 64.

  In addition, one end of an EGR passage 68 is connected to the first exhaust passage 58a and the second exhaust passage 58b located on the upstream side of the turbine 46b. The other end of the EGR passage 68 is connected to the intake passage 42. In this system, it is possible to perform so-called external EGR (Exhaust Gas Recirculation) control through which the exhaust gas is recirculated to the intake passage 42 through the EGR passage 68.

  An EGR cooler 70 is provided in the middle of the EGR passage 68. Furthermore, an EGR valve 72 that opens and closes the EGR passage 68 is provided in the EGR passage 68 on the downstream side of the EGR cooler 70. The EGR valve 72 has a stepping motor (not shown) as a drive source. When the EGR valve 72 is opened, a part of the exhaust gas is returned to the intake passage 42 through the EGR cooler 70. Under the same exhaust pressure and intake pressure conditions, the exhaust gas amount (external EGR rate) passing through the EGR passage 68 can be increased as the opening degree of the EGR valve 72 is increased.

  The ECU (Electronic Control Unit) 40 includes various sensors for detecting the operating state of the internal combustion engine 12 such as a crank angle sensor 74 for detecting the engine speed, in addition to the air flow meter 54 and the like. And various actuators for controlling the operating state of the internal combustion engine 12 such as a fuel injection valve 76 for supplying fuel to the internal combustion engine 12 in addition to the exhaust switching valve 60 and WGV 66 described above. Has been. The ECU 40 controls the operating state of the internal combustion engine 12 based on those sensor outputs.

[Characteristic control of the first embodiment]
FIG. 3 is a diagram for explaining characteristic control in the first embodiment of the present invention. More specifically, FIG. 3 is a diagram showing the relationship between the torque (TRQ) of the internal combustion engine 12 and the engine speed. A curve represented by a thick solid line in FIG. 3 indicates an operation line obtained by connecting operating points at which the internal combustion engine 12 can operate most efficiently (fuel consumption). Such an operation line can be obtained by increasing both the torque and the engine speed after greatly increasing the load (torque) without significantly increasing the engine speed from the low speed and low load operation state. It is an operation line, and is an operation line used in a hybrid vehicle in order to improve fuel consumption. When the vehicle is not a hybrid vehicle, the operation line of the internal combustion engine is generally located on the lower load (low torque) side than the operation line. Further, a line labeled “WOT” in FIG. 3 is a torque curve when the internal combustion engine 12 is in a full load state.

(Basic control of exhaust switching valve in the external EGR area)
As described above, in the system including the twin entry type turbocharger 46 having the exhaust switching valve 60, the back pressure can be adjusted by controlling the exhaust switching valve 60. In order to effectively introduce the external EGR gas, it is desirable that the exhaust pressure is sufficiently increased with respect to the intake pressure. Nevertheless, if the exhaust gas switching valve 60 is opened in the external EGR introduction region, the average back pressure in the exhaust passages 58a and 58b is reduced, and the differential pressure between the exhaust pressure and the intake pressure is reduced. As a result, the external EGR rate decreases, and it becomes difficult to improve fuel efficiency using external EGR introduction.

  Therefore, in the present embodiment, the exhaust gas switching valve 60 is closed in the operation region in which external EGR control is performed by adjusting the opening degree of the EGR valve 72. In FIG. 3, the area surrounded by the trapezoidal shape indicates the external EGR introduction area. Specifically, as shown in FIG. 3, the operation region corresponding to the external EGR introduction region corresponds to a low load to medium load region and a low rotation number to medium rotation number region.

  In FIG. 3, a solid line with a symbol “A” indicates that effective external EGR gas can be introduced when the control of the present embodiment (control to close the exhaust gas switching valve 60 in the external EGR introduction region) is performed. The upper limit torque is shown. On the other hand, the broken line with the symbol “B” in FIG. 3 indicates the upper limit torque at which effective EGR gas can be introduced when the exhaust gas switching valve 60 is open. As described above, when the exhaust gas switching valve 60 is opened in the external EGR introduction region, the region where the external EGR gas can be introduced becomes the lower load side region, and in the operation line on the high load side used in the hybrid vehicle. Therefore, it becomes difficult to improve fuel efficiency using external EGR control.

  On the other hand, according to the control of the present embodiment, it is easy to ensure the back pressure, and thus it is easy to ensure the differential pressure between the exhaust pressure and the intake pressure. As a result, the external EGR rate can be secured sufficiently high in the external EGR introduction region. Thereby, it becomes possible to improve the fuel consumption in the external EGR introduction region more reliably. Further, according to the control of the present embodiment, the external EGR introduction region can be secured even in the operation region on the higher load side. As a result, even in a hybrid vehicle in which a relatively high load operation region is frequently used from the low rotation speed region, the external EGR introduction region can be sufficiently ensured, and fuel consumption can be further improved.

FIG. 4 is a flowchart of a routine executed by the ECU 40 in the first embodiment to realize the above function.
In the routine shown in FIG. 4, first, it is determined whether or not the current operation region of the internal combustion engine 12 is the external EGR introduction region (step 100). More specifically, the ECU 40 determines the external EGR introduction region as shown in FIG. 3 above using the torque (load) and the engine speed, which are parameters for defining the operation region of the internal combustion engine 12. A map (not shown) is stored. In this step 100, whether or not the current operation region is the external EGR introduction region, using the current sensor outputs such as the air flow meter 54 and the crank angle sensor 74 for detecting the operation state of the internal combustion engine 12 and the above map. Judgment is made.

  If it is determined in step 100 that the current operation region is the external EGR introduction region, the opening degree of the EGR valve 72 is controlled so that an external EGR rate that is a control target is obtained (step 102). ).

  Next, it is determined whether or not the exhaust gas switching valve 60 is currently open (step 104). As a result, when the exhaust gas switching valve 60 is open, the exhaust gas switching valve 60 is controlled to be closed (step 106).

(Control of the exhaust switching valve during high-speed steady operation)
Also, the operating point marked with “C” in FIG. 3 represents one point on the operating line (thick line) where the efficiency (fuel consumption) as the internal combustion engine 12 is the best. 3 is an operating point on an iso-output line at which the internal combustion engine 12 can generate an engine output equal to that at the time of operation at the operating point C. The operating point on the high rotation and low load side than C is shown. In a state where the internal combustion engine 12 is accelerating or decelerating (transient state), for example, the operating point on the operating line with the best efficiency (fuel consumption) as the internal combustion engine 12 is used, such as the operating point C. The overall efficiency is also good. However, when the vehicle is performing high-speed steady operation (steady travel), considering the efficiency of the entire hybrid system, the operating point D on the high rotation and low load side than the operating point C on the operating line is used. However, although the efficiency of the internal combustion engine 12 alone is slightly lowered, the efficiency of the entire system is preferable.

  Therefore, in the present embodiment, the operating region of the internal combustion engine 12 on the higher output (higher rotation and higher load) side than the equal output line denoted by “E” in FIG. ), When the vehicle is in steady running, the control for shifting the operating point of the internal combustion engine 12 from the operating point on the operating line indicated by the bold line to the operating point on the high rotation and low load side is This is performed by cooperative control with the power split mechanism 18. In addition, in this embodiment, even in the external EGR introduction region, the exhaust gas switching valve 60 is opened in the region on the higher output side than the equal output line E.

  As described above, when the control for shifting the operating point of the internal combustion engine 12 to the operating point on the high-rotation low-load side is performed, the intake pressure (supercharging pressure) decreases, so that the control for closing the exhaust switching valve 60 is not relied on. An environment in which a differential pressure between the exhaust pressure and the intake pressure is easily secured can be obtained. For this reason, it becomes easier to secure external EGR gas than before the transition. In addition, since the exhaust gas switching valve 60 is opened by the control of the present embodiment, the back pressure is lowered and the internal EGR gas amount can be reduced. When the amount of internal EGR gas is reduced, the hot end gas is reduced, so that the compression end temperature is lowered. For this reason, knocking can be suppressed. As a result, it is possible to prevent the ignition timing from being retarded, and the like, so that the internal combustion engine 12 can be operated with high efficiency (fuel consumption).

  As described above, in the present embodiment, the exhaust switching valve 60 is opened when the control for shifting the operating point as described above is performed, so that the efficiency of the entire vehicle can be improved during high-speed steady traveling. While increasing and securing external EGR gas, it becomes possible to suppress knocking and improve fuel efficiency.

FIG. 5 is a flowchart of a routine executed by the ECU 40 in the first embodiment in order to realize the above function.
In the routine shown in FIG. 5, first, it is determined based on the output of a vehicle speed sensor (not shown) whether or not the current driving state of the vehicle is during high-speed steady driving (step 200).

  If it is determined in step 200 that the high-speed steady operation is being performed, it is determined whether or not the exhaust gas switching valve 60 is closed (step 202). As a result, when the exhaust gas switching valve 60 is closed, the exhaust gas switching valve 60 is controlled to open (step 204).

In the first embodiment described above, the ECU 40 executes the processes of steps 100 and 102, so that the “EGR control means” in the first invention performs the processes of steps 100, 104, and 106. By executing this, the “switching valve control means” in the first aspect of the present invention is realized.
Further, in the first embodiment described above, the “steady travel valve control means” in the second aspect of the present invention is realized by the ECU 40 executing the processing of steps 200 to 204.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment is realized by causing the ECU 40 to execute the routine shown in FIG. 7 described later together with the routine shown in FIG. 4 (and the routine shown in FIG. 5) using the hardware configuration shown in FIG. It is something that can be done.

[Control of exhaust selector valve during deceleration]
FIG. 6 is a diagram showing how the operating point changes when the internal combustion engine 12 operating in the external EGR introduction region is decelerated.
Also in the system of the present embodiment, in the external EGR introduction region, the exhaust switching valve 60 is basically controlled to close except during high-speed steady running. When the accelerator pedal is turned off during operation at the operating point F and the internal combustion engine 12 is decelerated, the operating point of the internal combustion engine 12 rapidly changes to the operating point G on the low load side as shown in FIG. . More specifically, at the start of deceleration, the vehicle speed itself does not change abruptly, so the engine speed does not change suddenly, but the throttle valve 50 is immediately closed as the accelerator pedal is turned off, so that the intake The amount of air decreases rapidly and the engine torque decreases rapidly. As a result, the operating point suddenly changes from F to G as shown in FIG.

  When the change in the operating point as described above occurs, the intake pressure rapidly decreases, so that the differential pressure between the exhaust pressure and the intake pressure increases, and the external EGR gas is easily introduced. In such a case, control is performed to close the EGR valve 72 at the start of deceleration in order to prevent the external EGR gas amount from rapidly increasing. However, in general, since the control speed of the EGR valve 72 is lower than the control speed of the throttle valve 50, the amount of external EGR gas may temporarily be excessive when the internal combustion engine 12 is decelerated while the external EGR is introduced. Concerned. Further, there is a concern that misfire may occur in the internal combustion engine 12 when such an excessive amount of EGR gas occurs.

  Therefore, in this embodiment, the exhaust gas switching valve 60 is opened when the internal combustion engine 12 is operating in the external EGR introduction region with the exhaust gas switching valve 60 closed. Furthermore, in this embodiment, the WGV 66 is opened during the deceleration.

FIG. 7 is a flowchart of a routine executed by the ECU 40 in the second embodiment in order to realize the above function.
In the routine shown in FIG. 7, first, based on the output of an accelerator opening sensor (not shown), it is determined whether or not the accelerator pedal is turned off (step 300). As a result, when it is recognized that the accelerator pedal is turned off and it is determined that the vehicle is decelerating, it can be determined that the differential pressure between the exhaust pressure and the intake pressure is large. In this case, it is determined whether or not the exhaust gas switching valve 60 is closed (step 302). Then, in step 300, in order to more accurately determine the degree of change in the differential pressure between the exhaust pressure and the intake pressure, the magnitude of the accelerator opening before the change and the magnitude of the change rate of the accelerator opening are determined. May be evaluated.

  If it is determined in step 302 that the exhaust gas switching valve 60 is closed, the exhaust gas switching valve 60 is controlled to open (step 304). In this case, the WGV 66 is also controlled to open (step 306).

  Next, it is determined whether or not the intake air amount is stabilized during deceleration (step 308). More specifically, in step 308, it is determined whether the amount of change in the intake air amount is below a predetermined threshold based on the output of the air flow meter 54. As a result, when it is determined that the intake air amount is stable, it can be considered that the deceleration operation of the internal combustion engine 12 has been completed, so that the exhaust gas switching valve 60 is closed in preparation for the next acceleration (step 310). ) And the WGV 66 is closed (step 312).

  On the other hand, even when it is determined in step 308 that the intake air amount is not yet stable (that is, when it can be determined that the vehicle is decelerating), the accelerator pedal is depressed again in step 314. If detected, the exhaust selector valve 60 and the WGV 66 are immediately closed in preparation for subsequent acceleration (steps 310 and 312).

  By executing the routine shown in FIG. 7 described above in parallel with the routine shown in FIG. 4 of the first embodiment described above, during operation in the external EGR introduction region with the exhaust switching valve 60 closed, When the deceleration of the internal combustion engine 12 is started, the exhaust switching valve 60 and the WGV 66 are opened. In such a case, the back pressure is reduced by opening the exhaust gas switching valve 60 at the start of deceleration. As a result, the pressure difference between the exhaust pressure (back pressure) and the intake pressure can be made as small as possible under a situation where the intake pressure decreases with deceleration. For this reason, it is possible to temporarily suppress an excessive amount of EGR gas during deceleration. Furthermore, since the WGV 66 is opened at the start of deceleration, the back pressure can be reduced more effectively. As a result, it is possible to more effectively suppress an excessive amount of EGR gas temporarily.

FIG. 8 is a time chart for explaining the effects associated with the execution of the routine shown in FIG.
As shown in FIG. 8A, when the accelerator pedal is closed at time t0, the throttle valve 50 is also closed as shown in FIG. 8B. As a result, as shown in FIG. 8C, the intake pressure decreases. In the present embodiment, as shown in FIG. 8D, the EGR valve 72 is closed in conjunction with a decrease in the intake pressure in order to suppress a temporary excessive amount of EGR gas during deceleration even when the EGR valve 72 is controlled. It will be.

  In FIG. 8E and the like, the waveform represented by a thin solid line is a case where the exhaust switching valve 60 and the WGV 66 of the present embodiment are not controlled during deceleration. On the other hand, in FIG. 8 (E) and the like, the waveform represented by a thick solid line is a case where only the exhaust gas switching valve 60 is controlled to open when the accelerator pedal is turned off, and is represented by a broken line. The waveform is obtained when the exhaust switching valve 60 and the WGV 66 are controlled to be opened together with the accelerator pedal being turned off. As shown in FIGS. 8E and 8F, the back pressure is reduced by performing the valve opening control of the exhaust gas switching valve 60 as compared with the case where the exhaust gas switching valve 60 and the WGV 66 are not controlled. Thus, it can be seen that the pressure difference between the exhaust pressure and the intake pressure becomes small. Further, it can be seen that by adding the valve opening control of the WGV 66 to the control of the exhaust gas switching valve 60, the back pressure is more effectively reduced and the pressure difference is further reduced.

  As a result, as shown in FIG. 8G, the EGR rate during deceleration is achieved by performing the valve opening control of the exhaust gas switching valve 60 as compared with the case where the exhaust gas switching valve 60 and the WGV 66 are not controlled. However, a margin is recognized for the EGR rate under the combustion limit condition of the internal combustion engine 12. Furthermore, by adding the valve opening control of the WGV 66 to the control of the exhaust gas switching valve 60, the margin for the EGR rate during deceleration with respect to the EGR rate under the combustion limit condition is increased.

  As shown in FIG. 8 (G), the EGR rate that is the control target usually has a margin with respect to the EGR rate under the combustion limit condition in consideration of a temporary increase in the EGR rate at the time of deceleration or the like. Is set. According to the control of the exhaust gas switching valve 60 of the present embodiment, an increase in the EGR rate during deceleration can be suppressed. Therefore, as shown in FIG. 8 (H), the control target EGR rate is brought closer to the EGR rate under the combustion limit condition by the margin of the EGR rate generated by the control of the exhaust gas switching valve 60 of the present embodiment. It becomes possible to set. As a result, it is possible to operate with good efficiency (fuel consumption) by making full use of the external EGR control. Further, as shown in FIG. 8 (I), such an effect becomes more remarkable when the control of the WGV 66 is performed simultaneously with the control of the exhaust gas switching valve 60 during deceleration.

In the second embodiment described above, the “pressure change time valve control means” according to the third aspect of the present invention is realized by the ECU 40 executing the processing of steps 300 to 304.
In the second embodiment described above, the “second valve control means during pressure change” according to the fourth aspect of the present invention is implemented when the ECU 40 executes the processing of steps 300 and 306.

  In the first and second embodiments described above, the exhaust bypass passage 64 is configured to branch from both the first exhaust passage 58a and the second exhaust passage 58b. Thereby, when the WGV 66 is opened, both the exhaust passages 58a and 58b are simultaneously opened to the exhaust bypass passage 64. However, the exhaust bypass passage according to the present invention does not necessarily include the first exhaust passage and the exhaust passage when control is performed so that the exhaust switching valve is always opened when the waste gate valve is opened. It may not be configured to branch from both of the second exhaust passages, and may be configured to branch from one of the first exhaust passage and the second exhaust passage.

1 is a diagram showing a schematic configuration of a drive system for a hybrid vehicle to which the present invention is applied. It is a figure for demonstrating the structure of the system of the internal combustion engine shown in FIG. It is a figure for demonstrating the characteristic control in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure showing the mode of change of the operating point when the internal combustion engine in operation within the external EGR introduction region is decelerated. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a time chart for demonstrating the effect accompanying execution of the routine shown in FIG.

DESCRIPTION OF SYMBOLS 10 Drive system 12 Internal combustion engine 14 Motor 18 Power split mechanism 40 ECU (Electronic Control Unit)
42 Intake passage 46 Twin entry turbocharger 46a Compressor 46b Turbine 54 Air flow meter 56 Intake pressure sensor 58 Exhaust passage 58a First exhaust passage 58b Second exhaust passage 60 Exhaust switching valve 64 Exhaust bypass passage 66 Waste gate valve (WGV)
68 EGR passage 72 EGR valve 74 Crank angle sensor 76 Fuel injection valve

Claims (4)

A turbocharger provided with an exhaust passage having a turbine operated by exhaust energy of the internal combustion engine;
Exhaust gas including a first exhaust passage that guides exhaust gas discharged from one cylinder of the internal combustion engine to the turbine, and a second exhaust passage that guides exhaust gas discharged from the other cylinder of the internal combustion engine to the turbine. A passage,
An exhaust switching valve that switches between a state in which the first exhaust passage and the second exhaust passage communicate with each other and a state in which the first exhaust passage and the second exhaust passage are blocked;
An EGR passage connecting at least one of the first exhaust passage and the second exhaust passage and an intake passage of the internal combustion engine;
An EGR valve disposed in the middle of the EGR passage and responsible for opening and closing the EGR passage;
EGR control means for controlling the EGR valve so that exhaust gas is recirculated to the intake passage through the EGR passage in a predetermined operating region of the internal combustion engine;
Switching valve control means for controlling the exhaust switching valve to be closed in the operating region;
A control device for an internal combustion engine with a supercharger. The internal combustion engine is mounted on a hybrid vehicle including the internal combustion engine and an electric motor as a power source,
In the hybrid vehicle, during steady running, control is performed to shift the operating point of the internal combustion engine to an operating point on the high engine speed and low load side that maintains the same engine output as the current operating point,
The switching valve control means controls to open the exhaust switching valve when the operating point of the internal combustion engine in the operating region is shifted to the operating point on the high engine speed and low load side. The control apparatus for an internal combustion engine with a supercharger according to claim 1, further comprising an hour valve control means.   The switching valve control means includes pressure change time valve control means for controlling the exhaust switching valve to open when the exhaust pressure is higher than the intake pressure by a predetermined value or more in the operating region. 3. A control device for an internal combustion engine with a supercharger according to 1 or 2. An exhaust bypass passage that branches off from the exhaust passage at a portion upstream of the turbine and merges with the exhaust passage again at a portion downstream of the turbine;
A waste gate valve disposed in the middle of the exhaust bypass passage and responsible for opening and closing the exhaust bypass passage;
The switching valve control means includes a second valve control means during pressure change for controlling the waste gate valve to open when the exhaust pressure is higher than the intake pressure by a predetermined value or more in the operating region. The control device for an internal combustion engine with a supercharger according to claim 3.

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