JP5206514B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  In order to reduce the amount of nitrogen oxides in the exhaust gas of an internal combustion engine (engine), an exhaust gas recirculation device that joins part of the exhaust gas to the intake side is employed. Patent Document 1 discloses an apparatus having a high pressure EGR path and a low pressure EGR path in order to use exhaust gas recirculation (hereinafter referred to as “EGR”) in a wider operating range of the engine.

JP 2004-150319 A

  The amount of EGR in the low-pressure EGR path is determined by the means for pushing the exhaust gas by increasing the pressure on the exhaust side by the exhaust throttle valve provided in the exhaust passage and the pressure on the intake side by the intake throttle valve provided in the intake passage. It is adjusted by means for lowering and sucking exhaust gas.

  However, the exhaust throttle valve provided in the exhaust passage is exposed to high-temperature, high-pressure, and high-humidity environments, and galling, rust, deformation, shaft misalignment, and the like occur, so that the clearance is increased. For this reason, it is difficult to perform highly accurate control due to the disturbance of the clearance change.

  Therefore, an object of the present invention is to control the amount of EGR with high accuracy against disturbance.

An exhaust gas recirculation device for an internal combustion engine according to the present invention that solves such a problem includes a turbocharger having a turbine in an exhaust passage of the internal combustion engine, a compressor in an intake passage of the internal combustion engine, and a downstream of the turbine in the exhaust passage. A low pressure passage for connecting a portion of the exhaust gas from the internal combustion engine to the intake passage, an upstream side of the exhaust passage from the turbine and the intake passage. A high-pressure passage connected to the downstream side of the compressor and returning a part of the exhaust gas from the internal combustion engine to the intake passage, and an upstream side connected to the low-pressure passage of the intake passage, An intake throttle valve that changes a passage area; an exhaust throttle valve that is disposed downstream of the exhaust passage to which the low-pressure passage is connected; and an exhaust throttle valve that changes an exhaust passage area; If introduced into the gas passage, the intake throttle valve based on the exhaust gas flow through the low-pressure passage which is acquired from the flow rate sensor, and closed-loop control, and a control means for open loop control of the exhaust throttle valve It is characterized by that.

  With this configuration, it is possible to adjust the general EGR amount with the exhaust throttle valve and perform fine adjustment with the intake throttle valve. Thereby, the amount of EGR can be controlled with high accuracy. In the present invention, since the intake throttle valve performs closed loop control, that is, feedback control, it is resistant to disturbance. Further, the open-loop control of the exhaust throttle valve by the control means may be performed based on the engine speed and the engine load.

  When exhaust gas is introduced into the low-pressure passage using an exhaust throttle valve in an area where the turbocharger pressure is increased, such as during acceleration, the turbine expansion ratio decreases and the turbocharger response decreases. . If the responsiveness of the turbocharger is lowered, it is possible that the emission is deteriorated.

  According to the present invention, in the exhaust gas recirculation apparatus for an internal combustion engine, the control means can stop the control of the exhaust throttle valve when the amount of change in the accelerator opening exceeds a threshold value.

  With such a configuration, it is possible to control the supercharger with good responsiveness by introducing exhaust gas into the low-pressure passage even in a region where the supercharging pressure is increased, such as during acceleration. By controlling the turbocharger with good responsiveness, it is possible to suppress the deterioration of emissions.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention controls the EGR introduction amount with high resistance to disturbance and high accuracy by adjusting the general EGR introduction amount with the exhaust throttle valve and finely adjusting with the intake throttle valve. Can do.

It is explanatory drawing which showed schematic structure of the internal combustion engine incorporating the exhaust gas recirculation apparatus. It is the flow which showed the control at the time of introduce | transducing exhaust gas to an intake pipe through a low pressure passage.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine 2 in which an exhaust gas recirculation device 1 according to this embodiment is incorporated. The internal combustion engine 2 is a water-cooled diesel engine having four cylinders.

  An intake pipe 4 and an exhaust pipe 5 are connected to the internal combustion engine 2. A compressor 61 of the turbocharger 6 is disposed in the middle of the intake pipe 4. This turbocharger 6 is the supercharger of the present invention. An intake throttle valve 7 is disposed upstream of the compressor 61 in the intake pipe 4. The intake throttle valve 7 changes the flow area of the intake air that passes through the intake pipe 4 and adjusts the flow rate of the intake air flowing through the intake pipe 4. An intercooler 8 is disposed downstream of the compressor 61 in the intake pipe 4.

  On the other hand, a turbine 62 of the turbocharger 6 is provided in the middle of the exhaust pipe 5. A filter 9 carrying an NOx storage reduction catalyst is disposed downstream of the turbine 62 in the exhaust pipe 5. Further, an exhaust throttle valve 10 is disposed downstream of the filter 9 in the exhaust pipe 5. The exhaust throttle valve 10 changes the flow area of the exhaust gas passing through the exhaust pipe 5 and adjusts the flow rate of the exhaust gas flowing through the exhaust pipe 5.

  The exhaust circulation device 1 is provided with a low pressure passage 11 for recirculating a part of the exhaust gas flowing through the exhaust pipe 5 to the intake pipe 4 at a low pressure. This low pressure passage 11 connects between the filter 9 of the exhaust pipe 5 and the exhaust throttle valve 10 and between the intake throttle valve 7 of the intake pipe 4 and the compressor 61. That is, the intake throttle valve 7 is disposed on the intake pipe 4 on the upstream side to which the low pressure passage 11 is connected, and the exhaust throttle valve 10 is on the exhaust pipe 5 on the downstream side to which the low pressure passage 11 is connected. It will be arranged. When the exhaust flow passage area in the exhaust pipe 5 is narrowed by the exhaust throttle valve 10, the pressure on the upstream side of the exhaust throttle valve 10 increases and the flow rate of the exhaust gas flowing into the low pressure passage 11 increases. Further, when the intake air flow path area in the intake pipe 4 is narrowed by the intake throttle valve 7, the pressure on the downstream side of the intake throttle valve 7 is reduced to a negative pressure, and the flow rate of the exhaust gas flowing into the low pressure passage 11 is increased. . Further, an EGR cooler 12 and a low-pressure EGR valve 13 are arranged in this order from the exhaust pipe 5 side in the low-pressure passage 11. A flow rate sensor 14 is disposed between the EGR cooler 12 and the low pressure EGR valve 13 in the low pressure passage 11.

  Further, the exhaust circulation device 1 is provided with a high-pressure passage 15 for recirculating a part of the exhaust gas flowing through the exhaust pipe 5 to the intake pipe 4 at a high pressure. The high-pressure passage 15 connects the upstream side of the turbine 62 in the exhaust pipe 5 and the downstream side of the intercooler 8 in the intake pipe 4. The high pressure passage 15 is provided with a high pressure EGR valve 16.

  Further, the exhaust gas circulation device 1 includes an ECU (Electronic Control Unit) 17. The ECU 17 is electrically connected to the flow sensor 14 and acquires the flow rate of the exhaust gas passing through the low pressure passage 11. The ECU 17 is electrically connected to the rotation sensor 18 and the accelerator position sensor 19, and calculates the engine rotation speed and the engine load from the engine rotation speed and the accelerator position acquired by these sensors. The ECU 17 is electrically connected to each of the intake throttle valve 7, the exhaust throttle valve 10, the low pressure EGR valve 13, and the high pressure EGR valve 16, and controls these valves.

  The ECU 17 controls the high-pressure EGR valve 16 to introduce the exhaust gas into the intake pipe 4 through the high-pressure passage 15 when the internal combustion engine 2 is operated in the low-medium speed and low-medium load region. Further, the ECU 17 controls the low pressure EGR valve 13 to assist the exhaust gas to be introduced into the intake pipe 4 through the low pressure passage 11. At this time, premixed combustion is performed in the cylinder of the internal combustion engine 2. When the internal combustion engine 2 is operated in the low, medium speed and high load range, the ECU 17 controls the low pressure EGR valve 13 to introduce the exhaust gas into the intake pipe 4 through the low pressure passage 11. At this time, normal combustion is performed in the cylinder of the internal combustion engine 2. Further, when the internal combustion engine 2 is operated at a high speed, the EGR 17 controls the high pressure EGR valve 16 to introduce the exhaust gas into the intake pipe 4 through the high pressure passage 15. At this time, normal combustion is performed in the cylinder of the internal combustion engine 2.

  When the ECU 17 controls the low pressure EGR valve 13 and sends exhaust gas to the intake pipe 4 through the low pressure passage 11, the ECU 17 controls the intake throttle valve 7 and the exhaust throttle valve 10. The ECU 17 calculates the engine speed and the engine load from the engine speed and the accelerator position acquired from the rotation sensor 18 and the accelerator position sensor 19, and based on the calculated engine speed and the engine load, the exhaust throttle valve 10 Open loop control. Further, the ECU 17 performs the closed loop control, that is, feedback control, on the intake throttle valve 7 based on the exhaust gas flow rate passing through the low pressure passage 11 acquired from the flow rate sensor 14.

  From the above, when exhaust gas is sent to the intake pipe 4 through the low pressure passage 11, the exhaust gas recirculation device 1 roughly adjusts the amount of exhaust gas introduced into the low pressure passage 11 by the exhaust throttle valve 10, and the internal combustion engine 2 by the intake throttle valve 7. Fine adjustment is performed so that the exhaust gas introduction amount required based on the operating state is obtained. By performing such control, even if there is a disturbance that changes the clearance of the exhaust throttle valve 7, the intake throttle valve 7 finely adjusts the exhaust gas introduction amount, so that the EGR introduction amount is controlled with high accuracy. be able to.

  Next, in the present embodiment, the control for increasing the supercharging pressure of the turbocharger 6 during acceleration or the like will be described. FIG. 2 is a flow showing control at the time of exhaust gas introduction by the low pressure passage 11. This control is executed by the ECU 17. This control is performed when exhaust gas is introduced into the low pressure passage 11.

  The ECU 17 determines whether or not the amount of change in the accelerator opening exceeds the threshold value x in step S1. The threshold value x is a change amount that can be determined to be during rapid acceleration. When the ECU 17 determines Yes in step S1, that is, when the change amount of the accelerator opening exceeds the threshold value x, the process proceeds to step S2.

  The ECU 17 controls the intake throttle valve 7 in step S2. At this time, the ECU 17 stops the control of the exhaust throttle valve 10, and the exhaust throttle valve 10 stops in a state where the flow passage area is expanded. When the exhaust throttle valve 10 is controlled to reduce the exhaust passage area, the pressure on the downstream side of the turbine 62 increases, and the responsiveness of the turbocharger 6 decreases. In step S2, in order to stop the control of the exhaust throttle valve 10, the responsiveness of the turbocharger 6 is suppressed from decreasing, and the emission is prevented from deteriorating.

  If the ECU 17 determines No in step S1, that is, if the change amount of the accelerator opening is equal to or less than the threshold value x, the process proceeds to step S3. The ECU 17 executes both the control of the intake throttle valve 7 and the control of the exhaust throttle valve 10 in step S3. That is, when the supercharging pressure of the turbocharger 6 does not change suddenly, the exhaust throttle valve 10 is controlled.

  By such a control process, the response deterioration of the turbocharger 6 is suppressed, and the emission deterioration is suppressed.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

DESCRIPTION OF SYMBOLS 1 Exhaust gas recirculation apparatus 2 Engine 4 Intake pipe 5 Exhaust pipe 6 Turbocharger 61 Compressor 62 Turbine 7 Intake throttle valve 10 Exhaust throttle valve 11 Low pressure passage 13 Low pressure EGR valve 15 High pressure passage 16 High pressure EGR valve 17 ECU

Claims (2)

A turbocharger having a turbine in the exhaust passage of the internal combustion engine and having a compressor in the intake passage of the internal combustion engine;
A low pressure passage for connecting a portion of the exhaust passage downstream of the turbine and a portion of the intake passage upstream of the compressor, and returning a part of the exhaust from the internal combustion engine to the intake passage;
A high-pressure passage that connects an upstream side of the turbine of the exhaust passage and a downstream side of the compressor of the intake passage, and returns a part of the exhaust from the internal combustion engine to the intake passage;
An intake throttle valve disposed on the upstream side to which the low-pressure passage of the intake passage is connected to change an intake passage area;
An exhaust throttle valve that is disposed downstream of the exhaust passage to which the low-pressure passage is connected, and changes an exhaust passage area;
When exhaust gas is introduced into the intake passage through the low pressure passage, the exhaust throttle valve is controlled in an open loop, and the intake throttle valve is closed loop based on an exhaust gas flow rate passing through the low pressure passage obtained from a flow rate sensor. Control means for controlling;
An exhaust gas recirculation device for an internal combustion engine. The exhaust gas recirculation device for an internal combustion engine according to claim 1,
The exhaust gas recirculation apparatus for an internal combustion engine, wherein the control means stops the control of the exhaust throttle valve when a change amount of an accelerator opening exceeds a threshold value.

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