JP2010255603A - Control device for internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the torque of an internal combustion engine while introducing an EGR gas with a sufficient gas flow rate in a high rotation high load region, in a control device for an internal combustion engine with a supercharger. <P>SOLUTION: The control device includes a first exhaust valve 28a for switching a first exhaust passage 14a leading to a turbine 18b, and a second exhaust valve 28b for switching a second exhaust passage 14b not leading to the turbine 18b. An HPL 40 is provided for connecting the upstream side of the turbine 18b in the first exhaust passage 14a and an intake passage 12. A high pressure side EGR valve 46 is provided for adjusting the exhaust gas flow rate passing through the HPL 40. An exhaust variable valve system 30 is provided for changing the valve opening characteristics of the second exhaust valve 28b. In the case the flow rate of the exhaust gas returned to the intake passage 12 via the HPL 40 is same as or higher than a predetermined value in a high rotation high load region of the internal combustion engine 10, the second exhaust valve 28b is stopped in a closed state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Conventionally, for example, Patent Document 1 discloses a turbocharger that includes, for each cylinder, a first exhaust valve that opens and closes a first exhaust passage that communicates with a turbine, and a second exhaust valve that opens and closes a second exhaust passage that does not pass through a turbine. An internal combustion engine (so-called independent exhaust engine) is disclosed. More specifically, in this conventional internal combustion engine, a lean NOx catalyst is disposed downstream of the turbine in the first exhaust passage. An EGR passage to the intake system is connected between the turbine and the lean NOx catalyst in the first exhaust passage.

JP-A-11-210449

  By the way, in an internal combustion engine with a supercharger provided with EGR means for recirculating a part of exhaust gas to an intake passage via an EGR passage connecting the upstream side of the turbine and the intake passage, There are the following problems when performing EGR control. That is, if the EGR gas flow rate is increased in the high rotation and high load region, the exhaust gas flow rate (exhaust energy amount) supplied to the turbine decreases. As a result, there is a concern that the supercharging capability is reduced and the torque of the internal combustion engine is reduced.

  The present invention has been made in order to solve the above-described problems, and is capable of improving the torque of an internal combustion engine while introducing EGR gas at a sufficient gas flow rate in a high rotation and high load region. An object of the present invention is to provide a control device for an internal combustion engine with a feeder.

1st invention is a control apparatus of the internal combustion engine with a supercharger,
A turbocharger that supercharges intake air;
A first exhaust passage leading to a turbine of the turbocharger;
A first exhaust valve for opening and closing the first exhaust passage;
A second exhaust passage not passing through the turbine;
A second exhaust valve for opening and closing the second exhaust passage;
An exhaust variable valve mechanism capable of changing a valve opening characteristic of the second exhaust valve;
An EGR passage connected to the upstream side of the turbine in the first exhaust passage and toward the intake passage;
An EGR valve that adjusts the flow rate of gas flowing through the EGR passage;
A high rotation high load external EGR control means for controlling the EGR valve so that exhaust gas is recirculated to the intake passage through the EGR passage in a high rotation high load region;
In the high rotation and high load region, the exhaust variable valve mechanism is used to increase the flow rate of exhaust gas flowing to the turbine when the flow rate of exhaust gas recirculated to the intake passage is a predetermined value or more. Second exhaust valve control means for controlling a valve opening characteristic of the second exhaust valve;
It is characterized by providing.

The second invention is the first invention, wherein
An exhaust bypass passage that branches off from the first exhaust passage at a portion upstream of the turbine and rejoins the first exhaust passage at a portion downstream of the turbine;
A wastegate valve responsible for opening and closing the exhaust bypass passage;
A turbine upstream pressure control means for increasing the degree of opening of the wastegate valve when the exhaust pressure in the first exhaust passage on the upstream side of the turbine is equal to or higher than a predetermined value in the high rotation high load region;
Is further provided.

The third invention is the first or second invention, wherein
When the exhaust pressure in the first exhaust passage on the upstream side of the turbine is greater than or equal to a predetermined value in the high rotation and high load region, the lift amount of the second exhaust valve is adjusted using the exhaust variable valve mechanism. And turbine upstream pressure control means for increasing at least one of the operating angles.

  According to the first invention, when it is recognized that the EGR gas flow rate is not less than a predetermined value in the high rotation and high load region, the flow rate of the exhaust gas flowing to the turbine using the adjustment of the valve opening characteristic of the second exhaust valve. Is controlled to increase. Thereby, the turbine rotation speed can be secured high. For this reason, it is possible to increase the intake air amount while introducing the EGR gas. As described above, according to the present invention, it is possible to improve the torque of the internal combustion engine while introducing the EGR gas at a sufficient gas flow rate in the high rotation and high load region.

  According to the second invention, when the exhaust pressure in the first exhaust passage on the upstream side of the turbine becomes a predetermined value or more during the adjustment of the second exhaust valve in the high rotation and high load region. The opening of the waste gate valve is corrected so as to increase. As a result, the flow rate of exhaust gas that bypasses the turbine increases, so that the exhaust pressure can be lowered to a value within an appropriate range. Thereby, the internal EGR gas amount can be controlled to an appropriate value, and knocking can be suppressed.

  According to the third invention, when the exhaust pressure in the first exhaust passage on the upstream side of the turbine becomes a predetermined value or more during the execution of the adjustment of the second exhaust valve in the high rotation and high load region. The second exhaust valve is corrected so that at least one of the lift amount and the operating angle is increased. As a result, the flow rate of exhaust gas that bypasses the turbine increases, so that the exhaust pressure can be lowered to a value within an appropriate range. Thereby, the internal EGR gas amount can be controlled to an appropriate value, and knocking can be suppressed.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. FIG. 2 is a diagram for explaining an EGR introduction region in the internal combustion engine shown in FIG. 1. It is a figure for demonstrating the subject at the time of EGR introduction | transduction in a high rotation high load area | region. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is the figure which represented the change of the intake air amount with respect to the change of the EGR gas flow rate introduce | transduced by HPL, and the change of turbine speed according to the presence or absence of the valve stop of a 2nd exhaust valve. It is a figure showing the change of the turbine upstream pressure (back pressure) and the internal EGR gas flow rate with respect to the throttle opening change. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure showing the change of the turbine upstream pressure (back pressure) and the external EGR gas flow rate with respect to the throttle opening change. It is a flowchart of the routine performed in Embodiment 4 of this invention.

Embodiment 1 FIG.
[System configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a spark ignition type internal combustion engine 10. The internal combustion engine 10 is mounted on a vehicle and used as a power source. The internal combustion engine 10 includes an intake passage 12 for taking air into the cylinder and an exhaust passage 14 for discharging exhaust gas from the cylinder.

  In the vicinity of the inlet of the intake passage 12, an air flow meter 16 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 12 is provided. A compressor 18 a of the turbocharger 18 is disposed downstream of the air flow meter 16. The turbocharger 18 includes a turbine 18b that is integrally connected to the compressor 18a and that is operated by exhaust gas exhaust energy. The compressor 18a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 18b.

  An intercooler 20 that cools the air compressed by the compressor 18a is disposed in the intake passage 12 on the downstream side of the compressor 18a. Further, a throttle valve 22 for adjusting the amount of air flowing through the intake passage 12 is disposed downstream of the intercooler 20. The throttle valve 22 is an electronically controlled valve that is driven by a throttle motor (not shown). A surge tank 24 is disposed downstream of the throttle valve 22. The surge tank 24 is provided with an intake pressure sensor 26 for detecting intake pressure (supercharging pressure).

  The exhaust passage 14 shown in FIG. 1 includes a first exhaust passage 14a that communicates with the turbine 18b and a second exhaust passage 14b that does not communicate with the turbine 18b. Each cylinder of the internal combustion engine 10 is provided with a first exhaust valve (Ex1) 28a for opening and closing the first exhaust passage 14a and a second exhaust valve (Ex2) 28b for opening and closing the second exhaust passage 14b. .

  Further, the internal combustion engine 10 shown in FIG. 1 includes an exhaust variable valve mechanism 30 for driving the exhaust valves 28a and 28b. More specifically, the exhaust variable valve mechanism 30 is a mechanism capable of stopping the second exhaust valve 28b in a closed state independently of the first exhaust valve 28a, although a detailed description thereof is omitted. And

  Further, an exhaust pressure sensor 32 for detecting an exhaust pressure (turbine upstream pressure) at that portion is attached to the first exhaust passage 14a upstream of the turbine 18b. Furthermore, a catalyst (S / C) 34 for purifying exhaust gas is provided in the post-merging exhaust passage 14c after joining the first exhaust passage 14a and the second exhaust passage 14b.

  The first exhaust passage 14a is connected to an exhaust bypass passage 36 that bypasses the turbine 18b and connects the inlet side and the outlet side of the turbine 18b. An electric waste gate valve 38 that opens and closes the exhaust bypass passage 36 is disposed in the middle of the exhaust bypass passage 36.

  The system shown in FIG. 1 includes a high pressure exhaust gas recirculation passage (HPL: High Pressure Loop) 40. The HPL 40 is configured to communicate the first exhaust passage 14a upstream of the turbine 18b and the intake passage 12 downstream of the compressor 18a. In the middle of the HPL 40, an EGR catalyst 42, an EGR cooler 44, and a high pressure side EGR valve 46 are arranged in this order from the upstream side of the flow of the recirculated exhaust gas (EGR gas). The high pressure side EGR valve 46 is a valve responsible for opening and closing the HPL 40.

  Further, the system shown in FIG. 1 includes a low pressure exhaust gas recirculation passage (LPL: Low Pressure Loop) 48. The LPL 48 is configured to communicate the combined exhaust passage 14c downstream of the turbine 18b and downstream of the catalyst 34 with the intake passage 12 upstream of the compressor 18a. In the middle of the LPL 48, a low pressure side EGR valve 50 is disposed. The low pressure side EGR valve 50 is a valve responsible for opening and closing the LPL 48. The specific configuration of the low-pressure exhaust gas recirculation passage is not limited to the configuration of the LPL 48, and for example, the high-pressure exhaust gas recirculation passage 40 and the intake passage 12 upstream of the compressor 18a are communicated. It may be what was done.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 60. The input of the ECU 60 includes the air flow meter 16, the intake pressure sensor 26, the exhaust pressure sensor 32, and the crank angle sensor 62 for detecting the engine speed and the turbine speed sensor for detecting the speed of the turbine 18b. Various sensors for detecting the operating state of the internal combustion engine 10 such as 64 are connected. In addition to the throttle valve 22 and the EGR valves 46 and 50 described above, various actuators for controlling the operation state of the internal combustion engine 10 such as the fuel injection valve 66 and the spark plug 68 are connected to the output of the ECU 60. .

FIG. 2 is a view for explaining an EGR introduction region in the internal combustion engine 10 shown in FIG.
According to the system of the present embodiment configured as described above, the flow rate of the EGR gas returning to the intake passage 12 through the HPL 40 is adjusted by adjusting the opening degree (valve lift amount) of the high-pressure side EGR valve 46. can do. Further, by adjusting the opening degree (valve lift amount) of the low pressure side EGR valve 50, the flow rate of the EGR gas flowing back to the intake passage 12 through the LPL 48 can be adjusted.

  As shown in FIG. 2, in the present embodiment, EGR control with a small amount using the LPL 48 is performed in almost the entire operation region of the internal combustion engine 10. The EGR control using the HPL 40 is performed from the low rotation / low load region to the middle / middle load region and the high rotation / high load region.

  In the system according to the present embodiment, in the high-rotation and high-load region, the exhaust gas from the intake side through the combustion chamber is ensured by ensuring a valve overlap period between the intake valve (not shown) and the second exhaust valve 28b. It is possible to sufficiently scavenge the in-cylinder residual gas by using the gas blow-through to the cylinder. According to such scavenging (scavenging), the engine output can be effectively increased in a high rotation and high load region.

  However, when the above scavenging is performed, the engine output can be improved satisfactorily, while the combustion pressure (Pmax) and the combustion temperature rise. Measures on the hardware configuration of the internal combustion engine 10, such as temperature measures such as jet reinforcement, are required. Taking such measures leads to an increase in the friction loss of the internal combustion engine 10 and results in a deterioration in fuel consumption in the normal operation region.

  Therefore, in the present embodiment, as described above, the EGR gas sufficiently cooled by the EGR cooler 44 using the HPL 40 is introduced in the high rotation and high load region. As a result, the combustion temperature can be lowered, so that the combustion pressure (Pmax) is not increased too much, and the fuel consumption can be improved without the above measures. Further, knocking can be suppressed.

FIG. 3 is a diagram for explaining a problem at the time of EGR introduction in a high rotation and high load region.
EGR control using the HPL 40 is a method for extracting exhaust gas from the upstream side of the turbine 18b. For this reason, if the EGR gas flow rate introduced by the EGR control is increased, the amount of exhaust energy supplied to the turbine 18b is reduced, so that the turbine rotational speed is lowered as shown in FIG. Moreover, since the supercharging capability of the compressor 18a is reduced accordingly, the intake air amount is reduced, and the torque of the internal combustion engine 10 may be reduced.

  Therefore, in the present embodiment, when the EGR gas flow rate is equal to or higher than a predetermined value in the high rotation and high load region in which EGR control using the HPL 40 is performed, the exhaust variable valve mechanism 30 is used to bypass the turbine 18b. The second exhaust valve 28b on the side is stopped in a closed state (that is, the lift amount is made zero). More specifically, the turbine rotational speed and the intake air amount are monitored in the high rotational speed and high load region, and when the turbine rotational speed or the intake air amount becomes a predetermined value (a first predetermined value described later) or less, The second exhaust valve 28b is stopped in a closed state when a tendency to decrease the parameter is observed.

FIG. 4 is a flowchart of a routine executed by the ECU 60 in the first embodiment in order to realize the above function. Note that this routine is periodically executed at predetermined time intervals.
In the routine shown in FIG. 4, first, it is determined whether or not the current operating region of the internal combustion engine 10 is a high rotation high load region (see FIG. 2) in which EGR is introduced using the HPL 40 (step 100).

  If it is determined in step 100 that the region is in the high rotation / high load region, it is determined whether the intake air amount or the turbine speed is lower than a first predetermined value (step 102). The predetermined value of the intake air amount and the first predetermined value of the turbine speed in step 102 are in a situation where the EGR gas flow rate by EGR using the HPL 40 is higher than a predetermined value at which the torque reduction of the internal combustion engine 10 is a concern. It is a value for judging whether or not.

  If it is determined in step 102 that the intake air amount or the turbine rotational speed is lower than the first predetermined value, the side directly connected to the catalyst (S / C) 34 (that is, the turbine 18b is bypassed). A process of stopping the second exhaust valve (Ex2) 28b on the side in a closed state is executed (step 104).

  Next, it is determined whether or not the intake air amount or the turbine rotational speed is higher than a second predetermined value that is larger than the first predetermined value (step 106). The predetermined value of the intake air amount and the second predetermined value of the turbine speed in this step 106 are the viewpoints for securing the torque of the internal combustion engine 10 in accordance with the valve closing stop processing of the second exhaust valve (Ex2) 28b in the above step 104. This is a value for judging whether the intake air amount or the turbine rotational speed has increased to a level where there is no problem.

  If it is determined in step 106 that the intake air amount or the turbine rotational speed is higher than the second predetermined value, the second exhaust valve (Ex2) 28b on the side directly connected to the catalyst (S / C) 34 The valve closing stop process is canceled (step 108).

FIG. 5 is a diagram showing changes in the intake air amount and the turbine rotational speed with respect to changes in the EGR gas flow rate introduced by the HPL 40, depending on whether the second exhaust valve 28b is stopped or not.
According to the routine shown in FIG. 4 described above, the EGR gas flow rate is equal to or higher than a predetermined value (the intake air amount or the turbine speed is the first predetermined value) in the high-rotation and high-load region where EGR is introduced using the HPL 40. 2), the second exhaust valve 28b is stopped in a closed state.

  As a result, the flow rate of the exhaust gas flowing through the first exhaust passage 14a to the turbine 18b increases, so that the turbine speed can be secured high. For this reason, as shown in FIG. 5, it is possible to increase the intake air amount while introducing the EGR gas by the HPL 40. Thus, according to the control of the present embodiment, the torque of the internal combustion engine 10 can be improved while introducing the EGR gas at a sufficient gas flow rate in the high rotation and high load region.

  By the way, in the first embodiment described above, when the EGR gas flow rate is equal to or higher than a predetermined value in the high-rotation and high-load region where EGR is introduced using the HPL 40, the second exhaust valve 28b is stopped in a closed state. I try to let them. However, the present invention is not limited to such a method as long as the opening characteristic of the second exhaust valve is changed to increase the flow rate of the exhaust gas flowing through the turbine in such a case. That is, in the case described above, when the exhaust variable valve mechanism that enables at least one of the lift amount and the operating angle of the second exhaust valve to be continuously changed is provided, the lift amount of the second exhaust valve Further, at least one of the working angles may be reduced.

  In the first embodiment described above, the HPL 40 corresponds to the “EGR passage” in the first invention, and the high pressure side EGR valve 46 corresponds to the “EGR valve” in the first invention. Further, when the ECU 60 executes EGR control using the HPL 40 in the high rotation / high load region shown in FIG. 2, the “high rotation / high load external EGR control means” in the first aspect of the present invention is the above steps 102 and 104. By executing the process, the “second exhaust valve control means” in the first invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 6 and FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 7 described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG.

FIG. 6 is a diagram showing changes in the turbine upstream pressure (back pressure) and the internal EGR gas flow rate with respect to changes in the throttle opening.
According to the control of the second exhaust valve 28b of the first embodiment described above, the torque of the internal combustion engine 10 is increased while introducing the EGR gas at a sufficient gas flow rate in the high rotation and high load region as described above. Can be improved. However, when the above control is executed, the flow rate of the exhaust gas flowing to the turbine 18b increases, so that the side where the throttle opening is large (that is, the side where the load is high) within the high rotation and high load region is shown in FIG. As such, the back pressure (turbine upstream pressure) increases. As a result, the amount of exhaust gas remaining in the cylinder (so-called internal EGR gas amount) increases, and knocking is likely to occur.

  Therefore, in this embodiment, when the back pressure (turbine upstream pressure) on the turbine 18b side becomes a certain level or higher during execution of the control of the second exhaust valve 28b of the first embodiment described above, the waste gate valve. 38 was opened by a predetermined amount.

  FIG. 7 is a flowchart of a routine executed by the ECU 60 in the second embodiment in order to realize the above function. In FIG. 7, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 7, after the processing for stopping the second exhaust valve 28 b in the closed state in the high rotation / high load region at step 104 is executed, the back pressure (turbine on the EGR / T / C side) is It is determined whether or not (upstream pressure) is within a predetermined range (step 200). As a result, when it is determined that the turbine upstream pressure is within the predetermined range (within an appropriate range), the processing after step 106 is executed.

  On the other hand, if it is determined in step 200 that the turbine upstream pressure is not within the predetermined range, then whether or not the turbine upstream pressure is higher than the predetermined range (from the upper limit value of the predetermined range). Is higher or lower than the lower limit value of the predetermined range) (step 202).

  When it is determined in step 202 that the turbine upstream pressure is higher than the upper limit value of the predetermined range, control for opening the waste gate valve 38 by a predetermined amount is executed (step 204). Specifically, the wastegate valve 38 is normally controlled in a state opened to a predetermined opening. In this step 204, the opening degree is controlled to the opening side with respect to such a predetermined opening degree.

  On the other hand, when it is determined in step 202 that the turbine upstream pressure is lower than the lower limit value of the predetermined range, control for closing the waste gate valve 38 by a predetermined amount is executed (step 206).

  According to the routine shown in FIG. 7 described above, when the turbine upstream pressure becomes a certain level or more during execution of the valve stop control of the second exhaust valve 28b in the high rotation and high load region, the wastegate valve 38 is used. Is opened by a predetermined amount. As a result, the flow rate of the exhaust gas that bypasses the turbine 18b increases, so that the turbine upstream pressure can be lowered to a value within an appropriate range. Thereby, the internal EGR gas amount can be controlled to an appropriate value, and knocking can be suppressed.

  Further, according to the above routine, when the turbine upstream pressure is below a certain level, the wastegate valve 38 is closed by a predetermined amount. As a result, the flow rate of the exhaust gas that bypasses the turbine 18b decreases, so that the turbine upstream pressure can be increased to a value within an appropriate range.

  In the second embodiment described above, the “turbine upstream pressure control means” according to the second aspect of the present invention is realized by the ECU 60 executing the processing of steps 202 and 204 described above.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 8 described later instead of the routine shown in FIG. 7 using the hardware configuration shown in FIG.

  In the first and second embodiments described above, when the EGR gas flow rate is greater than or equal to a predetermined value in the high rotation and high load region, the second exhaust valve 28b is closed to increase the flow rate of the exhaust gas flowing to the turbine 18b. It stops in the valve state. However, when the second exhaust valve 28b is stopped for a long time by such control, the flow of the exhaust gas in the second exhaust passage 14b stops, so the temperature of the second exhaust passage 14b decreases, Along with this, the wall surface temperature of the combustion chamber decreases. As a result, the cooling loss increases and the fuel consumption may deteriorate.

  Therefore, in the present embodiment, when the EGR gas flow rate is a predetermined value or higher in the high rotation and high load region, the second exhaust valve 28b is not stopped in order to increase the exhaust gas flow rate flowing to the turbine 18b. The lift amount of the second exhaust valve 28b is lowered by a predetermined amount. Further, when the turbine upstream pressure deviates from the predetermined range during the control of the lift amount of the second exhaust valve 28b, the turbine upstream pressure is adjusted by adjusting the lift amount of the second exhaust valve 28b. To do.

  FIG. 8 is a flowchart of a routine executed by the ECU 60 in the third embodiment in order to realize the above function. In FIG. 8, the same steps as those shown in FIG. 7 in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 8, when it is determined in step 102 that the intake air amount or the turbine rotational speed is lower than the first predetermined value, the lift amount of the second exhaust valve (Ex2) 28b is decreased by a predetermined amount. Processing is performed (step 300). If it is determined in step 106 that the intake air amount or the turbine speed is higher than the second predetermined value, a process of increasing the lift amount of the second exhaust valve (Ex2) 28b by a predetermined amount is executed. (Step 302).

  Further, in the routine shown in FIG. 8, when it is determined in step 202 that the turbine upstream pressure is higher than the upper limit value of the predetermined range, a process of increasing the lift amount of the second exhaust valve 28b by a predetermined amount is performed. It is executed (step 304). On the other hand, if it is determined in step 202 that the turbine upstream pressure is lower than the lower limit value of the predetermined range, a process of lowering the lift amount of the second exhaust valve 28b by a predetermined amount is executed (step 306). ).

  According to the routine shown in FIG. 8 described above, the lift amount of the second exhaust valve 28b is determined when the EGR gas flow rate is equal to or higher than a predetermined value in the high-rotation and high-load region where EGR is introduced using the HPL 40. Only a fixed amount can be lowered. As a result, the flow rate of the exhaust gas flowing through the first exhaust passage 14a to the turbine 18b is increased, so that the turbine rotational speed can be secured high and the intake air amount can be prevented from decreasing. Also according to the method of the present embodiment, the torque of the internal combustion engine 10 can be improved while introducing the EGR gas at a sufficient gas flow rate in the high rotation and high load region.

  In addition, in this embodiment, in the above case, the second exhaust valve 28b is not stopped in a closed state, but the lift amount is lowered by a predetermined amount. Thereby, even during the control of the second exhaust valve 28b, the circulation of the exhaust gas in the second exhaust passage 14b is continued, so that an increase in cooling loss can be suppressed and deterioration in fuel consumption can be suppressed.

  In addition, according to the above routine, when the turbine upstream pressure is out of the predetermined range during the control of the lift amount of the second exhaust valve 28b in the high rotation and high load region, the lift amount of the second exhaust valve 28b is set. By controlling, the turbine upstream pressure can be adjusted to a value within an appropriate range. Also by such a method, the amount of internal EGR gas can be controlled to an appropriate value, and knocking can be suppressed.

  By the way, in Embodiment 3 mentioned above, the lift amount of the 2nd exhaust valve 28b is adjusted as needed. However, the method for changing the valve opening characteristic of the second exhaust valve in the present invention is not limited to this. That is, when the variable exhaust valve mechanism that can change the operating angle of the second exhaust valve without changing the lift amount is provided, the operating angle of the second exhaust valve is adjusted as necessary. Also good.

  In the third embodiment described above, the “turbine upstream pressure control means” according to the third aspect of the present invention is realized by the ECU 60 executing the processing of steps 202 and 304 described above.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. 9 and FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 10 described later instead of the routine shown in FIG. 8 using the hardware configuration shown in FIG.

FIG. 9 is a diagram showing changes in the turbine upstream pressure (back pressure) and the external EGR gas flow rate with respect to changes in the throttle opening. FIG. 9 shows a waveform when the opening degree of the high-pressure side EGR valve 46 is a constant opening degree.
According to the control of the third embodiment described above, the turbine upstream pressure excess is adjusted by adjusting the lift amount of the second exhaust valve 28b to the optimum opening degree when the external EGR gas is introduced in the high rotation / high load region. External EGR can be introduced while preventing the rise. However, if the lift amount of the second exhaust valve 28b is made variable as in the above control, the turbine upstream pressure changes. When the turbine upstream pressure changes, as shown in FIG. 9, the pressure difference between the upstream and downstream of the HPL 40 changes, so the external EGR gas flow rate changes. Further, as shown in FIG. 9, the change in the external EGR gas flow rate due to such a change in the turbine upstream pressure is larger on the side where the throttle opening is large (high load side).

  As described above, if the external EGR gas flow rate changes in association with making the lift amount of the second exhaust valve 28b variable, there is a possibility that the EGR gas flow rate will be excessive or insufficient. Further, when the EGR gas flow rate is insufficient, knocking is likely to occur. On the other hand, if the EGR gas flow rate is excessive, misfire is likely to occur.

  Therefore, in the present embodiment, when the second exhaust valve 28b in the third embodiment described above is controlled, the EGR gas flow rate is based on the pressure difference between the upstream and downstream of the HPL 40 and the opening degree of the high pressure side EGR valve 46. Was estimated. When an excess or deficiency in the EGR gas flow rate (EGR rate) is recognized, the opening degree of the high pressure side EGR valve 46 is adjusted (feedback controlled) so as to eliminate such excess or deficiency.

  FIG. 10 is a flowchart of a routine executed by the ECU 60 in the fourth embodiment in order to realize the above function. 10, the same steps as those shown in FIG. 8 in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 10, after adjusting the lift amount of the second exhaust valve 28b by the process of step 304 or 306, it is next determined whether or not the EGR rate (EGR gas flow rate) of the HPL 40 is excessive or insufficient. (Step 400). In this step 400, the EGR gas flow rate by the HPL 40 is calculated using the relationship of the following equation (1), and then the EGR rate is calculated. Then, by comparing the calculated EGR rate with a predetermined value, it is determined whether or not the current EGR rate is excessive or insufficient.
EGR gas flow rate Ｅ EGR system flow coefficient × √ (intake pipe pressure-back pressure) (1)

  In the above equation (1), the EGR flow rate coefficient is a value that correlates with the pressure loss of HPL 40 (the passage length of HPL 40, the opening degree of high-pressure side EGR valve 46, etc. are influential factors). According to the relationship of the above expression (1), the passage length of the HPL 40 is known, and therefore the current opening degree of the high-pressure side EGR valve 46, the intake pipe pressure, and the back pressure (turbine upstream pressure) are used as the intake pressure sensor 26. Etc., the current EGR gas flow rate can be calculated. Then, when the EGR gas flow rate Ge is obtained using the relationship of the above equation (1), the EGR rate by HPL is set to (Ge / (Ga + Ge)), and the intake air flow rate measured by the EGR gas flow rate Ge and the air flow meter 16 It can be calculated using Ga.

  If the EGR rate is insufficient in step 400, a process of increasing the lift amount (opening) of the high-pressure side EGR valve 46 by a predetermined amount is executed in order to eliminate the shortage of the EGR rate ( Step 402). On the other hand, when an excessive EGR rate is recognized, a process of lowering the lift amount (opening) of the high pressure side EGR valve 46 by a predetermined amount is executed in order to eliminate the excessive EGR rate (step 404). .

  According to the routine shown in FIG. 10 described above, when an excess or deficiency in the EGR gas flow rate (EGR rate) is recognized as a result of the control of the second exhaust valve 28b in the third embodiment described above, The opening degree of the high-pressure side EGR valve 46 is adjusted so as to eliminate excess and deficiency. As a result, when the torque of the internal combustion engine 10 is improved while introducing the EGR gas at a sufficient gas flow rate in the high rotation and high load region, knocking and misfire due to excessive or insufficient EGR gas flow rate are improved. Can be prevented.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 14a 1st exhaust passage 14b 2nd exhaust passage 14c Exhaust passage after merge 16 Air flow meter 18 Turbocharger 18a Compressor 18b Turbine 22 Throttle valve 26 Intake pressure sensor 28a First exhaust valve (Ex1) )
28b Second exhaust valve (Ex2)
30 Exhaust variable valve mechanism 32 Exhaust pressure sensor 36 Exhaust bypass passage 38 Wastegate valve 40 High pressure exhaust gas recirculation passage (HPL)
46 High pressure side EGR valve 48 Low pressure exhaust gas recirculation passage (LPL)
50 Low pressure side EGR valve 60 ECU (Electronic Control Unit)
62 Crank angle sensor 64 Turbine rotational speed sensor

Claims (3)

A turbocharger that supercharges intake air;
A first exhaust passage leading to a turbine of the turbocharger;
A first exhaust valve for opening and closing the first exhaust passage;
A second exhaust passage not passing through the turbine;
A second exhaust valve for opening and closing the second exhaust passage;
An exhaust variable valve mechanism capable of changing a valve opening characteristic of the second exhaust valve;
An EGR passage connected to the upstream side of the turbine in the first exhaust passage and toward the intake passage;
An EGR valve that adjusts the flow rate of gas flowing through the EGR passage;
A high rotation high load external EGR control means for controlling the EGR valve so that exhaust gas is recirculated to the intake passage through the EGR passage in a high rotation high load region;
In the high rotation and high load region, the exhaust variable valve mechanism is used to increase the flow rate of exhaust gas flowing to the turbine when the flow rate of exhaust gas recirculated to the intake passage is a predetermined value or more. Second exhaust valve control means for controlling a valve opening characteristic of the second exhaust valve;
A control device for an internal combustion engine with a supercharger. An exhaust bypass passage that branches off from the first exhaust passage at a portion upstream of the turbine and rejoins the first exhaust passage at a portion downstream of the turbine;
A wastegate valve responsible for opening and closing the exhaust bypass passage;
A turbine upstream pressure control means for increasing the degree of opening of the wastegate valve when the exhaust pressure in the first exhaust passage on the upstream side of the turbine is equal to or higher than a predetermined value in the high rotation high load region;
The control device for an internal combustion engine with a supercharger according to claim 1, further comprising:   When the exhaust pressure in the first exhaust passage on the upstream side of the turbine is greater than or equal to a predetermined value in the high rotation and high load region, the lift amount of the second exhaust valve is adjusted using the exhaust variable valve mechanism. 3. The control device for an internal combustion engine with a supercharger according to claim 1, further comprising a turbine upstream pressure control means for increasing at least one of the operating angle and the operating angle.

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