JP2006299859A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device capable of shortening time until supercharging pressure converges in an upper limit value, when controlling the upper limit value of the supercharging pressure, in an internal combustion engine having a turbocharger. <P>SOLUTION: This control device of the internal combustion engine has the turbocharger 5, and controls the upper limit value of the supercharging pressure, by opening a waist gate valve 12 arranged in a waist gate passage 11 for bypassing a turbine 5b of the turbocharger of an engine exhaust system 3 when the supercharging pressure exceeds the upper limit value, and opening an air bypass valve 14 arranged in an air bypass passage 13 for bypassing a compressor 5a of the turbocharger on the upstream side of a throttle valve 7 in an engine intake system 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Internal combustion engines with a turbocharger are known. In such an internal combustion engine, when the supercharging pressure rises excessively, the combustion pressure or the intake pipe pressure may increase abnormally, possibly causing damage to the seal portion of the internal combustion engine. In addition, the compressor may be damaged due to excessive rotation. Thereby, the upper limit control of the supercharging pressure is performed. In the control of the upper limit value of the supercharging pressure, a waste gate valve (WGV) disposed in a waste gate passage that bypasses the turbine of the engine exhaust system is opened to reduce the turbine rotational speed of the turbocharger.

  Also, during deceleration from supercharging, the opening of the throttle valve is greatly reduced, and as it is, the intake pressure suddenly rises between the compressor and the throttle valve, causing the compressor to generate abnormal noise, There is a concern that the compressor or the like may be damaged. Therefore, an air bypass valve (ABV) disposed in an air bypass passage that bypasses the compressor of the engine intake system is opened. In the case where the ABV is provided in this way, it has been proposed that when the WGV breaks down, the upper limit control of the supercharging pressure is performed by the ABV (see, for example, Patent Document 1).

JP 2004-332613 A JP-A-8-61073

  In the supercharging pressure upper limit control of the WGV, excessive rotation of the turbine can be prevented by opening the WGV when the supercharging pressure exceeds the upper limit. However, the supercharging pressure greatly overshoots due to a response delay.

  Accordingly, an object of the present invention is to provide a control device capable of suppressing an overshoot with a large supercharging pressure when controlling an upper limit value of the supercharging pressure in an internal combustion engine equipped with a turbocharger.

  The control apparatus for an internal combustion engine according to claim 1 of the present invention is a control apparatus for an internal combustion engine including a turbocharger, and when the supercharging pressure exceeds an upper limit value, the turbocharger turbine of the engine exhaust system is controlled. The waste gate valve disposed in the bypass waste gate passage is opened, and the air bypass valve disposed in the air bypass passage bypassing the compressor of the turbocharger is opened upstream of the throttle valve in the engine intake system. Then, the upper limit value control of the supercharging pressure is performed.

  According to a second aspect of the present invention, there is provided the control device for an internal combustion engine according to the first aspect, wherein the supercharging pressure is between the compressor and the throttle valve of the engine intake system. When the engine is decelerating, the upper limit value control is not performed even if the boost pressure exceeds the upper limit value, and the air bypass is set when the boost pressure becomes a set pressure higher than the upper limit value. The valve is opened.

  According to the control apparatus for an internal combustion engine according to the first aspect of the present invention, in the control of the upper limit value of the supercharging pressure, not only the waste gate valve but also the air bypass valve is opened. When the boost pressure exceeds the upper limit value, the waste gate valve needs to be opened in order to suppress the turbine speed, but that alone will cause the boost pressure to overshoot due to a response delay. The valve is opened to suppress overshoot of the boost pressure.

  According to the control device for an internal combustion engine according to claim 2 of the present invention, in the control device for the internal combustion engine according to claim 1, the supercharging pressure is between the compressor and the throttle valve of the engine intake system. , That is, the pressure upstream of the throttle valve, and this pressure is monitored by actual measurement or estimation. At the time of engine acceleration, the pressure on the upstream side of the throttle valve and the boost pressure in the cylinder substantially coincide with each other due to the opening of the throttle valve. However, when the engine is decelerating, the pressure on the upstream side of the throttle valve suddenly increases due to the closing of the throttle valve, but the supercharging pressure in the cylinder does not become so high. When the valve is opened to lower the turbine speed, the turbine speed cannot be increased immediately to achieve supercharging at the next acceleration. As a result, upper limit control is not performed during engine deceleration.

  However, if the pressure upstream of the throttle valve increases abnormally, abnormal noise may be generated from the compressor, or the compressor etc. may be damaged. When the set pressure is higher than the pressure upper limit, the air bypass valve is opened to reduce the pressure upstream of the throttle valve. In the control apparatus for an internal combustion engine according to the second aspect, such control can be realized by monitoring only the pressure between the compressor and the throttle valve of the engine intake system.

  FIG. 1 is a schematic view showing an internal combustion engine controlled by a control device according to the present invention. In the figure, 1 is an engine body, 2 is an intake system, and 3 is an exhaust system. In the intake system 2, an air cleaner 4, a compressor 5 a of a turbocharger 5, an intercooler 6, a throttle valve 7, and the like are arranged from the upstream side, and communicate with each cylinder through an intake manifold 8.

  On the other hand, the exhaust system 3 is provided with a muffler (not shown), an exhaust purification device 9, a turbine 5b of the turbocharger 5 and the like from the downstream side, and communicates with each cylinder via an exhaust manifold 10.

  The internal combustion engine 1 is not particularly limited in its invention, but includes a first fuel injection valve for directly injecting fuel into each cylinder, and a second fuel injector arranged in each intake branch pipe of the intake manifold 8. A fuel injection valve for injecting fuel during the intake stroke (intake synchronous) or before the start of the intake stroke (intake asynchronous) by the second fuel injection valve, and also injecting fuel during the intake stroke by the first fuel injection valve Then, homogeneous combustion is performed to form a homogeneous mixture in the cylinder.

The air-fuel ratio of this homogeneous combustion is usually made leaner than the stoichiometric air-fuel ratio, reducing fuel consumption. In such lean combustion, an appropriate lean air-fuel ratio (for example, 20) is selected so that a large amount of NO _X is not generated, but a certain amount of NO _X is still generated. , for example, as _the NO _X storage reduction catalyst device, it is preferable to sufficiently reduce the atmospheric emissions of NO _X.

  The fuel injected from the second fuel injection valve is atomized by collision with the intake port wall surface between the intake branch pipe and the intake valve, and is supplied into the cylinder together with the intake air. It is advantageous to vaporize and form a well-homogenized homogeneous mixture. On the other hand, it is difficult to accurately supply a desired amount of fuel into the cylinder due to fuel adhering to the intake port wall surface or the like. On the other hand, the fuel injected from the first fuel injection valve must be atomized and vaporized in the cylinder, and it is difficult to vaporize a large amount of fuel before ignition, but the desired amount of fuel is accurately measured. Can be supplied into the cylinder.

  As a result, when the engine is under low load, where it is desired to supply the desired amount of fuel to the cylinder with a small amount of required fuel, the fuel is mainly injected by the first fuel injection valve, and the required fuel amount is compared. It is preferable to inject the fuel mainly by the second fuel injection valve at the time of the engine middle load where the amount of unburned fuel tends to increase due to the increase of the target. Further, when the engine load becomes higher and the engine is at a high load, the lean combustion cannot generate a sufficient engine output, and homogeneous combustion is performed at the stoichiometric air-fuel ratio. In order to purify the exhaust gas of this stoichiometric air-fuel ratio homogeneous combustion, a three-way catalyst device may be arranged in the engine exhaust system.

  Since the internal combustion engine 1 includes the turbocharger 5, a large amount of intake air can be supplied into the cylinder by supercharging, and the lean combustion range can be expanded to the high load side. However, if a large amount of intake air is supplied into the cylinder due to the supercharging pressure exceeding the design limit, the sealing portion of the internal combustion engine will be adversely affected, and if such supercharging pressure is provided, the turbocharger 5 Since there is a concern that the compressor 5a and the turbine 5b may be damaged due to excessive rotation, the supercharging pressure is controlled to an upper limit value with a margin with respect to the design limit.

  For this purpose, the exhaust system 3 is provided with a waste gate passage 11 that bypasses the turbine 5b of the turbocharger 5, and the waste gate valve (WGV) 12 disposed in the waste gate passage 11 is opened to open the turbine 5b. The upper limit control of the supercharging pressure is carried out by suppressing excessive rotation of the engine. Further, when the throttle valve 7 is closed due to deceleration from supercharging, the supercharging pressure in the cylinder does not increase so much, but between the throttle valve 7 of the intake system 2 and the compressor 5a of the turbocharger 5. There is a concern that the supercharging pressure of the compressor 5a suddenly rises and the compressor 5a generates noise or the compressor 5a and the like are damaged.

  Accordingly, an air bypass passage 13 for bypassing the compressor 5a is provided on the upstream side of the throttle valve 7 of the intake system 2, and the air bypass valve (ABV) 14 disposed in the air bypass passage 13 is opened, so that the throttle valve 7 is prevented from rapidly increasing between the compressor 7 and the compressor 5a (hereinafter, the throttle valve upstream turbocharging pressure). The WGV 12 controls the supercharging pressure via the turbine 5b and the compressor 5a, and the response to the supercharging pressure is not high. On the other hand, the ABV 14 directly controls the supercharging pressure and has high response to the supercharging pressure.

  The control device according to the present invention performs supercharging pressure upper limit control and throttle valve upstream supercharging pressure control during deceleration according to the flowchart shown in FIG. This flowchart is repeated every set time or every set crank angle. First, in step 101, it is determined whether or not the engine is decelerating by releasing the accelerator pedal or depressing the brake pedal. When this determination is negative, feedback control of the ABV 14 is started in step 102 in order to perform supercharging pressure upper limit control that lowers the supercharging pressure when the supercharging pressure exceeds the upper limit P1. .

This feedback control of the ABV 14 is performed when the throttle valve upstream supercharging pressure P _i monitored by the pressure sensor 15 disposed between the throttle valve 7 of the intake system 2 and the compressor 5a exceeds the upper limit value P1. and controls so as to increase the larger the ABV14 the opening difference between the valve upstream supercharging pressure P _i and the upper limit value P1. ABV14 is fully closed when the throttle valve upstream-side supercharging pressure P _i is less than the upper limit value P1.

Throttle valve upstream supercharging pressure P _i, when the opening degree of the throttle valve 7 such as during engine deceleration is small, but becomes a value different from the boost pressure in the cylinder, the throttle valve upstream side except in the time of engine deceleration when the supercharging pressure P _i is the upper limit value P1 near the high load and a throttle valve 7 is fully opened near, whereby the throttle valve upstream supercharging pressure P _i at this time is substantially cylinder The supercharging pressure can be set.

Next, at step 103, it is determined whether or not the flag F is 1. This flag F is reset to 0 when both the WGV 12 and the ABV 14 are kept fully closed for a relatively long time, and the upper limit control of the supercharging pressure is not substantially performed. Initially, this determination is denied and the routine proceeds to step 104. In step 104, whether the current throttle valve upstream supercharging pressure P _i is greater than the upper limit value P1 is determined. When this determination is negative, the WGV 12 is fully closed in step 104. At this time, as described above, the ABV 14 is also fully closed. On the other hand, when the determination in step 104 is affirmative, the supercharging pressure must be suppressed to the upper limit value P1, and in step 106, the WGV 12 is fully opened. At this time, as described above, the ABV 14 is opened by feedback control.

  FIG. 3 is a time chart showing changes in supercharging pressure. If the duty control that fully opens and closes only the WGV 12 is performed in the upper limit control of the boost pressure, as shown by the dotted line, the boost pressure exceeding the upper limit P1 at time t0 is When the WGV 12 is fully opened at time t0, the response delay increases and then decreases and reaches the upper limit value P1 at time t1 ′. As a result, the WGV 12 is fully closed at time t1 ', rises again after the response delay is lowered, and reaches the upper limit value P1 at time t2'. As a result, the WGV 12 is fully opened again at the time t2 ', falls after an increase in response delay, and reaches the upper limit value P1 at the time t3'. By the duty control of the WGV 12, overshoot and undershoot are repeated, and the magnitude of the overshoot and undershoot gradually decreases, and finally the supercharging pressure converges to the upper limit value P1. However, since a large overshoot occurs first, a relatively long time is required until convergence.

  On the other hand, according to the flowchart shown in FIG. 2, at time t0 when the supercharging pressure exceeds the upper limit value P1, the WGV 12 is fully opened, and at the same time, the ABV 14 having high responsiveness to the supercharging pressure is opened, Moreover, the larger the difference between the supercharging pressure and the upper limit value P1, the larger the valve opening of the ABV 14, that is, the ABV 14 is controlled in its opening degree following the difference between the supercharging pressure and the upper limit value P1, so that FIG. As shown by the solid line, the supercharging pressure overshoots, but the increase in response delay can be suppressed to a small level, and falls to the upper limit value P1 at time t1 earlier than time t1 ′ described above. Thereby, at time t1, the WGV 12 is fully closed and the ABV 14 is also fully closed. The subsequent undersheet becomes small because the previous overshoot is suppressed to be small, and as a result, rises to the upper limit value P1 at time t2 earlier than the above-described time t2 '.

  At this time t2, the WGV 12 is fully opened again, and the ABV 14 is also opened again by feedback control, and drops to the upper limit value P1 at time t3 earlier than the above-described time t3 '. Thus, by adding feedback control of the ABV 14, the magnitude of overshoot and undershoot generated in the duty control of the WGV 12 can be reduced, and the supercharging pressure can be converged to the upper limit value P1 at an early stage.

  In the upper limit control of the supercharging pressure, feedback control may be performed so that only the WGV 12 is opened as the difference between the supercharging pressure and the upper limit P1 increases. For the supercharging pressure exceeding P1, the opening degree of the WGV 12 is initially made considerably smaller than the fully open state, so that the supercharging pressure greatly overshoots exceeding the upper limit value, and again reaches the upper limit value P1. A relatively long time is required for convergence. Compared to this control, the supercharging pressure upper limit control in the flowchart of FIG. 2 can converge the supercharging pressure to the upper limit P1 in a short time.

  Also, in both the duty control and feedback control of the WGV12, since a large overshoot occurs, the upper limit value must be set in anticipation of a large margin, and the upper limit value control is performed with a relatively low boost pressure. However, although the performance of the turbocharger cannot be exhibited sufficiently, according to the flowchart of FIG. 2, overshooting of the supercharging pressure is suppressed, and this problem can be solved.

By the way, in the flowchart shown in FIG. 2, in step 107, it is determined whether or not the current throttle valve upstream supercharging pressure _Pi (supercharging pressure in the cylinder when not decelerating) is an overshoot peak value. . When this determination is negative, in step 109, the aforementioned flag F remains at 0. On the other hand, when the current throttle valve upstream supercharging pressure _Pi is an overshoot peak value, the determination in step 107 is affirmed and the routine proceeds to step 108. In step 108, it is determined whether or not the overshoot peak value P _i is greater than the upper limit value P1 + a.

  When the determination in step 108 is negative (for example, in the case of the peak value between times t0 and t1 in FIG. 3), the overshoot peak value has a large difference from the upper limit value P1, and the flag in step 109 Finish with F set to 0.

  However, when the determination in step 108 is affirmative (for example, in the case of the peak value between times t1 and t2 in FIG. 3), the difference between the overshoot peak value and the upper limit value P1 is small. At this time, the flag F is set to 1 in step 110, and in step 111, the WGV 12 is fully closed and the process ends.

  As a result, in the subsequent processing, the determination in step 103 is affirmed, the duty control of the WGV 12 in steps 104 to 106 is not performed, and only the feedback control of the ABV 14 in step 102 is performed. Thus, when the overshoot peak value is in the vicinity of the upper limit value P1, the WGV 12 is fully closed, and the supercharging pressure is converged to the upper limit value P1 by feedback control using only the ABV14. Thereby, the supercharging pressure can be reliably converged to the upper limit value P1 without causing undershoot.

  However, if the ABV 14 is fully opened by feedback control, the supercharging pressure cannot be reduced by the ABV 14, and therefore it is necessary to slightly open the fully closed WGV 12. If the ABV 14 still remains fully open, it is necessary to open the WGV 12 further. Thus, in step 112, as long as the ABV 14 is fully opened, the WGV opening degree control for gradually opening the WGV 12 is performed.

  Further, if the supercharging pressure is reduced due to a change in the engine operating state and the opening degree of the ABV 14 is reduced to about half-open by feedback control, if the WGV 12 is opened, the opening degree of the WGV 12 is slightly reduced. Can be closed. Further, the WGV 12 may be gradually closed as long as the opening of the ABV 14 is about half open. Such opening degree control can also be included in the WGV opening degree control in step 112.

By the way, at the time of engine deceleration, the determination of step 101 is affirmed. At this time, the opening degree of the throttle valve 7 is small, and the supercharging pressure in the cylinder does not increase so much. However, if the opening of the throttle valve 7 is rapidly reduced during deceleration from the supercharging operation, the supercharging pressure P _i on the upstream side of the throttle valve increases rapidly, and abnormal noise is generated from the compressor 5a. The compressor 5a and the like may be damaged, and this must be prevented.

However, in order to decrease the throttle valve upstream supercharging pressure P _i, when it is opened to lower the turbine speed to WGV As described above, in the next acceleration, immediately supercharging to increase the turbine speed Can not be carried out. As a result, when the determination in step 101 is affirmed during engine deceleration, the routine proceeds to step 113, where control different from the duty control of the WGV 12 and the feedback control of the ABV 14 described so far is performed.

Specifically, in step 113, the feedback control of the ABV 14 based on the upper limit value P1 is stopped. Next, at step 114, it is determined whether or not the current throttle valve upstream supercharging pressure P _i is higher than the set pressure P2 higher than the aforementioned upper limit value P1. When this determination is denied, there is no particular problem. In step 116, the ABV 14 is fully closed and the process ends. However, when the current throttle valve upstream supercharging pressure P _i is higher than the set pressure P2, the determination in step 114 is affirmed, ABV14 in step 115 is fully opened. Thus, to reduce the throttle valve upstream supercharging pressure P _i from the set pressure P2, thereby preventing damage to the abnormal noise and the compressor 5a and the like from the compressor 5a.

  By opening the valve of the ABV 14 as described above, the intake air amount is reduced, and thus the rotational speed of the turbine 5b is slightly reduced, but the WGV 12 is not opened, and the rotational speed of the turbine 5b is significantly reduced. There is no. Thereby, at the time of the next acceleration, it is possible to immediately increase the turbine speed and realize supercharging.

In the flowchart shown in FIG. 2, the upper limit control of the supercharging pressure and the throttle valve upstream supercharging pressure control during deceleration are performed based on the throttle valve upstream supercharging pressure P _i detected by the pressure sensor 15. Of course, the upper limit control of the supercharging pressure may be performed based on the output of the pressure sensor arranged on the downstream side of the throttle valve 7. However, in this case, pressure sensors are required on the upstream side and the downstream side of the throttle valve 7, respectively.

In the flowchart shown in FIG. 2, the throttle valve upstream supercharging pressure P _i may be estimated based on the opening of the throttle valve 7 without being actually measured by the pressure sensor 15. Also in this case, it is possible to simplify the estimation calculations as compared with the case where it is sufficient only to estimate the throttle valve upstream-side supercharging pressure P _i, also the estimated throttle valve downstream supercharging pressure.

In the flowchart shown in FIG. 2, the duty control of the WGV 12 is started when the throttle valve upstream supercharging pressure P _i exceeds the upper limit value P1 except when the engine is decelerating. valve upstream greater control for opening the higher pressure difference is large WGV12 the supercharging pressure P _i and the upper limit value P1) may be started. Even in this case, since feedback control of the ABV 14 is started simultaneously, overshoot of the supercharging pressure is suppressed, and the supercharging pressure can be converged to the upper limit value P1 in a relatively short time. Of course, the ABV 14 may be opened not by feedback control but by fully open and fully closed duty control.

In step 114, when the throttle valve upstream supercharging pressure P _i exceeds the set pressure P2 during engine deceleration, the ABV 14 is fully opened, but the throttle valve upstream supercharging pressure P _i and the set pressure P2 are set. The feedback control for opening the ABV 14 to a greater extent may be started as the differential pressure with the larger the pressure difference. Further, in the flowchart shown in FIG. 2, when the overshoot peak value is close to the upper limit value P1, the duty control of the WGV 12 is stopped and only the feedback control of the ABV 14 is performed. Only the feedback control of the ABV 14 may be performed when the difference from the peak value (the minimum boost pressure value in the undershoot) is equal to or less than the set value.

It is the schematic which shows the internal combustion engine controlled by the control apparatus by this invention. 7 is a flowchart for performing upper limit control of supercharging pressure and throttle valve upstream supercharging control during deceleration. It is a time chart which shows the change of the supercharging pressure in the upper limit control of supercharging pressure.

Explanation of symbols

1 Engine Body 2 Intake System 3 Exhaust System 5 Turbocharger 12 WGV
14 ABV

Claims (2)

  A control device for an internal combustion engine including a turbocharger, wherein when a supercharging pressure exceeds an upper limit value, a wastegate valve disposed in a wastegate passage that bypasses the turbine of the turbocharger of the engine exhaust system is opened. And an upper limit control of the supercharging pressure is performed by opening an air bypass valve disposed in an air bypass passage that bypasses the compressor of the turbocharger on the upstream side of the throttle valve in the engine intake system. A control device for an internal combustion engine.   The supercharging pressure is a pressure between the compressor of the engine intake system and the throttle valve, and at the time of engine deceleration, the upper limit value control is not performed even if the supercharging pressure exceeds the upper limit value. The control device for an internal combustion engine according to claim 1, wherein the air bypass valve is opened when a supercharging pressure becomes a set pressure higher than the upper limit value.

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