JP2010242617A - Abnormality detection system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for determining the generation of leakage in an intake system and an exhaust system in an internal combustion engine having a low pressure EGR device. <P>SOLUTION: An abnormality detection system detects that any abnormality occurs in an intake system or an exhaust system in the case in which a low pressure EGR valve is fully open during fuel cut, an exhaust throttle valve provided downstream of the branch portion of a low pressure EGR passage is fully closed, the measurement Pim of an intake air pressure by a pressure sensor provided in an intake air passage is equal to or smaller than a predetermined reference value Pimth, and the measured value Ga of air amount by an air flow sensor is equal to or larger than a predetermined reference value Gath. When an abnormality is detected, the detected abnormality is determined as an exhaust air leakage in the case where the low pressure EGR valve is fully closed, and the measured value Pex of an exhaust air pressure by a pressure sensor provided in an exhaust air passage is equal to or smaller than a predetermined reference value Pexth. The detected abnormality is determined as an intake air leakage in the other cases. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an abnormality detection system for an internal combustion engine.

  A method has been proposed for determining the occurrence of leakage in the intake system and exhaust system of an internal combustion engine. For example, Patent Document 1 describes a technique for determining that there is a leak in the intake system when the intake pipe pressure during idling is greater than a predetermined value. Patent Document 2 describes a technique for determining that a leak has occurred in the intake system when the intake pipe pressure when the exhaust brake device is operated is larger than a predetermined value.

  There is known an internal combustion engine including an EGR device that returns a part of exhaust gas to an intake system. Patent Document 3 discloses a low-pressure EGR device that returns a part of exhaust gas to an intake system via a low-pressure EGR passage that connects an exhaust passage downstream of a turbocharger turbine and an intake passage upstream of a compressor, and upstream of the turbine. And a high-pressure EGR device that returns a part of the exhaust gas to the intake system via a high-pressure EGR passage that communicates the exhaust passage with the intake passage downstream of the compressor.

JP 2004-150302 A JP 2001-193500 A JP 2008-051022 A JP 2008-248729 A

  An object of the present invention is to provide a technique for accurately determining the occurrence of leakage in an intake system and an exhaust system in an internal combustion engine equipped with a low pressure EGR device.

In order to solve the above-described problem, an abnormality detection system for an internal combustion engine according to the present invention includes:
A turbocharger having a turbine provided in the exhaust passage of the internal combustion engine and a compressor provided in the intake passage of the internal combustion engine;
A low pressure EGR passage that communicates an exhaust passage downstream of the turbine and an intake passage upstream of the compressor;
A low pressure EGR valve that changes a flow path area of the low pressure EGR passage;
An exhaust throttle valve that is provided in the exhaust passage downstream of the connection portion of the low-pressure EGR passage and changes the flow passage area of the exhaust passage;
An intake pressure measuring means provided in an intake passage downstream of the throttle valve for measuring the pressure of the intake air;
An exhaust pressure measuring means for measuring the pressure of exhaust gas provided in the exhaust passage upstream of the connecting portion of the low pressure EGR passage or the low pressure EGR passage;
An air flow sensor that is provided in an intake passage upstream of a connection portion of the low-pressure EGR passage and measures a flow rate of intake air flowing through the intake passage;
During the fuel cut control of the internal combustion engine, the low pressure EGR valve is fully opened and the exhaust throttle valve is fully closed, and the intake pressure measured by the intake pressure measuring means at that time is a predetermined intake pressure reference value. An abnormality detection means for detecting an abnormality in the internal combustion engine when the intake flow rate measured by the air flow sensor is equal to or higher than a predetermined intake flow rate reference value;
When an abnormality is detected by the abnormality detecting means, the low pressure EGR valve is fully closed, and when the exhaust pressure measured by the exhaust pressure measuring means at that time is below a predetermined exhaust pressure reference value, It is determined that the detected abnormality is an exhaust leak that has occurred in the exhaust passage or the low-pressure EGR passage, and if not, the abnormality determination that determines that the detected abnormality is an intake leak that has occurred in the intake passage Means,
It is characterized by providing.

  The variation in the measured value by the air flow sensor tends to increase as the flow rate of the intake air passing through the air flow sensor increases.

  The abnormality detection of the internal combustion engine by the abnormality detection means of the present invention is performed based on the measurement value by the air flow sensor, but when the measurement by the air flow sensor is performed, the exhaust throttle valve is fully closed and the low pressure EGR valve is fully opened. Therefore, the measurement by the air flow sensor can be performed in a state where the amount of the low-pressure EGR gas is increased and the flow rate of the air passing through the air flow sensor is decreased. Therefore, a highly accurate measurement value with little variation can be obtained, so that an abnormality of the internal combustion engine can be detected with high accuracy.

  Further, the abnormality detection means of the present invention detects an abnormality based on the measurement values by the air flow sensor and the intake pressure measurement means, and the abnormality determination means of the present invention determines the abnormality based on the measurement values by the exhaust pressure measurement means. However, each of these measuring means is a general component normally provided in an internal combustion engine control system. Therefore, according to the present invention, it is not necessary to add a new component such as a sensor for abnormality detection and abnormality determination, and an abnormality detection system for an internal combustion engine can be configured at a low cost. It can also be determined whether the abnormality is an intake leak or an exhaust leak.

  According to the present invention, in an internal combustion engine equipped with a low pressure EGR device, it is possible to accurately determine the occurrence of leakage in the intake system and the exhaust system.

It is a figure which shows typically the schematic structure of the internal combustion engine which concerns on an Example, its intake system, and an exhaust system. It is a flowchart showing the abnormality detection process of the internal combustion engine which concerns on an Example.

  Hereinafter, embodiments of the present invention will be described in detail. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a diagram schematically showing a schematic configuration of an internal combustion engine and its intake system and exhaust system according to the present embodiment. In FIG. 1, the engine 1 includes four cylinders 2, and each cylinder 2 includes a fuel injection valve 29 that directly injects fuel into the cylinder. The engine 1 is provided with a crank angle sensor 22 that measures the rotation angle of the crankshaft of the engine 1 and an accelerator opening sensor 27 that measures the amount of depression of an accelerator pedal (not shown). Each cylinder 2 communicates with an intake manifold 5 and an exhaust manifold 6.

The intake manifold 5 is provided with an intake pressure sensor 24 that measures the pressure (supercharging pressure) of intake air in the intake manifold 5. An intake passage 3 is connected to the intake manifold 5. Connected to the intake passage 3 is a high-pressure EGR passage 9 that guides part of the exhaust gas in the exhaust manifold 6 to the intake passage 3 at high temperature and pressure. The intake passage 3 upstream of the connecting portion of the high pressure EGR passage 9 is provided with a throttle valve 23 that can change the flow passage area of the intake passage 3. The intake passage 3 upstream of the throttle valve 23 is provided with an intercooler 11 that cools the intake air. The intake passage 3 upstream of the intercooler 11 is provided with a supercharger compressor 7. Connected to the intake passage 3 upstream of the compressor 7 is a low-pressure EGR passage 12 that guides part of the exhaust gas in the exhaust passage 4 to the intake passage 3 at a low temperature and low pressure. An air flow sensor 25 that measures the amount of air flowing into the intake passage 3 is provided in the intake passage 3 upstream of the connection portion of the low pressure EGR passage 12. The intake passage 3 upstream of the air flow sensor 25 is provided with an air cleaner 26 for removing foreign substances in the air.

  The above-described high pressure EGR passage 9 is connected to the exhaust manifold 6, and the exhaust manifold 6 and the intake passage 3 are communicated with each other. An exhaust passage 4 is connected to the exhaust manifold 6. The exhaust passage 4 is provided with a turbocharger turbine 8. An exhaust gas purification device 17 is provided in the exhaust passage 4 on the downstream side of the turbine 8. The exhaust gas purification device 17 includes a filter 18 that collects particulate matter (PM) in the exhaust gas and an NOx storage reduction catalyst 19. The low-pressure EGR passage 12 described above branches off from the exhaust passage 4 at the branch portion 30 in the exhaust passage 4 on the downstream side of the exhaust purification device 17. An exhaust throttle valve 20 capable of changing the flow area of the exhaust passage 4 is provided in the exhaust passage 4 on the downstream side of the branch portion 30 of the low pressure EGR passage 12.

  The high pressure EGR passage 9 is provided with a high pressure EGR valve 10 that changes the flow area of the high pressure EGR passage 9. By changing the opening degree of the high pressure EGR valve 10, the flow rate of the exhaust gas (hereinafter referred to as high pressure EGR gas) recirculated to the intake passage 3 through the high pressure EGR passage 9 can be adjusted. The low pressure EGR passage 12 is provided with a low pressure EGR valve 14 that changes the flow area of the low pressure EGR passage 12. By changing the opening degree of the low pressure EGR valve 14, the flow rate of the exhaust gas (hereinafter referred to as low pressure EGR gas) recirculated to the intake passage 3 via the low pressure EGR passage 12 can be adjusted. A low-pressure EGR cooler 13 that cools the low-pressure EGR gas is provided in the low-pressure EGR passage 12 upstream of the low-pressure EGR valve (that is, the exhaust passage 4 side). The low pressure EGR passage 12 upstream of the low pressure EGR cooler 13 is provided with an exhaust pressure sensor 21 that measures the pressure (back pressure) of the exhaust gas in the low pressure EGR gas passage 12. In addition, it replaces with the exhaust pressure sensor 21 in a present Example, and is equipped with the sensor which measures the pressure of the exhaust_gas | exhaustion in the position near the branch part 30 in the upstream of the branch part 30 or the branch part 30 of the low pressure EGR path 12 in the exhaust passage 4. You may do it.

  The engine 1 is provided with an ECU 28 that is a computer for controlling the operation of the engine 1. The ECU 28 is connected to the crank angle sensor 22, the airflow sensor 25, the accelerator opening sensor 27, the intake pressure sensor 24, and the exhaust pressure sensor 21 described above, and measurement data from these sensors is input to the ECU 28. The ECU 28 is connected to the fuel injection valve 29, the high pressure EGR valve 10, the low pressure EGR valve 14, the throttle valve 23, and the exhaust throttle valve 20 described above, and the operation of these devices is controlled by commands from the ECU 28. The The ECU 28 has a known configuration including a CPU, a memory, an input / output interface, and the like, acquires the operating state of the engine 1 and the driver's request from measurement data input from each of the connected sensors, and based on that The control target value of each device is calculated, and the operation of each device is controlled.

  Processing for detecting abnormalities in intake air leakage and exhaust air leakage occurring in the intake system and exhaust system of the engine 1 having the above-described configuration will be described with reference to FIG. FIG. 2 is a flowchart illustrating the abnormality detection process according to the present embodiment. The processing represented by this flowchart is periodically executed by the ECU 28 during operation of the engine 1.

In step S101, the ECU 28 determines whether or not fuel cut control is being executed in the engine 1. If an affirmative determination is made in step S101, the abnormality detection process of steps S102 to S109 is executed, and if a negative determination is made in step S101, the abnormality detection process is not executed and normal engine control is executed ( Step S110). Thereby, the abnormality detection process can be executed without affecting the operating state of the engine 1.

  In step S102, the ECU 28 fully opens the low pressure EGR valve 14, fully opens the throttle valve 23, and fully closes the exhaust throttle valve 20, and in the subsequent step S103, the measured value Ga of the air amount by the air flow sensor 25 and the intake pressure sensor. 24, the measured value Pim of the intake pressure is obtained.

  In step S104, the ECU 28 determines whether or not the air amount Ga acquired in step S103 is equal to or greater than a predetermined air amount reference value Gath, and the intake pressure Pim acquired in step S103 is equal to or less than a predetermined intake pressure reference value Pimth. Determine. If an affirmative determination is made in step S104, that is, if the intake air pressure is below the reference value even though the air amount is above the reference value, it is determined that some abnormality has occurred in the intake system or the exhaust system. Then, the process proceeds to processing (step S105 to step S109) for determining where the abnormality occurs in the intake system and the exhaust system. When a negative determination is made in step S104, it is determined that no abnormality has occurred in the intake system and the exhaust system, and normal engine control is executed (step S110).

  In step S105, the ECU 28 fully closes the low pressure EGR valve 14, and in subsequent step S106, the exhaust pressure measurement value Pex obtained by the exhaust pressure sensor 21 is acquired.

  In step S107, the ECU 28 determines whether or not the exhaust pressure Pex acquired in step S106 is equal to or less than a predetermined exhaust pressure reference value Pexth.

  If a positive determination is made in step S107, the ECU 28 determines that an abnormality has occurred in the exhaust system. As an abnormality of the exhaust system in this case, exhaust leakage in the low pressure EGR cooler 13 is suspected. Therefore, the ECU 28 turns on the MIL to notify the driver of the fact (step S108).

  If a negative determination is made in step S107, the ECU 28 determines that an abnormality has occurred in the intake system. As an abnormality in the intake system in this case, intake air leakage in the intercooler 11 is suspected. Therefore, the ECU 28 turns on the MIL to notify the driver of the fact (step S109).

  By detecting the abnormality of the intake system and the exhaust system of the engine 1 by the abnormality detection process described above, the following excellent effects can be obtained.

  First, the variation included in the measurement value by the air flow sensor 25 tends to increase as the flow rate of air passing through the air flow sensor 25 increases. Therefore, when an abnormality is detected based on the measurement value by the air flow sensor 25, it is preferable that the flow rate of air passing through the air flow sensor 25 is reduced. According to the abnormality detection process of the present embodiment, as described above, measurement is performed by the air flow sensor 25 with the exhaust throttle valve 20 fully closed and the low pressure EGR valve 14 fully opened (steps S102 to S103). ), The amount of low-pressure EGR gas increases, and the amount of fresh air decreases. Therefore, the measurement by the air flow sensor 25 can be performed in a state where the flow rate of the air passing through the air flow sensor 25 is small. As a result, a highly accurate measurement value of the air amount with little variation can be obtained, so that accurate abnormality detection can be performed based on the measurement value of the air amount.

  Secondly, the abnormality detection process of the present embodiment is performed based on the measured values by the air flow sensor 25, the intake pressure sensor 24, and the exhaust pressure sensor 21, and these sensors are often already installed in a normal engine system. It is a general sensor. That is, it is not necessary to additionally install a new sensor in order to execute the abnormality detection process according to the present embodiment, and it is possible to configure an abnormality detection system at a low cost. In addition, according to the abnormality detection process according to the present embodiment, it is possible not only to detect the occurrence of abnormality, but also to determine whether the abnormality is intake leakage or exhaust leakage. Therefore, there is no need to separately install an intake air leak detection system and an exhaust air leak detection system, which can further contribute to cost reduction and simplification of the system.

  The above-described embodiment is an example for explaining the present invention, and various modifications can be made to the above-described embodiment without departing from the gist of the present invention. For example, the above embodiment is an embodiment in which the present invention is applied to an internal combustion engine having an EGR system having both the high pressure EGR passage 9 and the low pressure EGR passage 12, but the EGR system having only the low pressure EGR passage 12 is provided. The present invention can also be applied to internal combustion engines. In such a system, a configuration in which there is no throttle valve 23 provided for metering the high-pressure EGR gas amount is conceivable, but in that case, the process of fully opening the throttle valve 23 in the processing contents of step S102 is omitted. Just do it.

1 Engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Intake manifold 6 Exhaust manifold 7 Compressor 8 Turbine 9 High pressure EGR passage 10 High pressure EGR valve 11 Intercooler 12 Low pressure EGR passage 13 Low pressure EGR cooler 14 Low pressure EGR valve 17 Exhaust purification device 18 Filter 19 NOx storage reduction catalyst 20 Exhaust throttle valve 21 Exhaust pressure sensor 22 Crank angle sensor 23 Throttle valve 24 Intake pressure sensor 25 Air flow sensor 26 Air cleaner 27 Accelerator opening sensor 28 ECU
29 Fuel Injection Valve 30 Branch

Claims (1)

A turbocharger having a turbine provided in the exhaust passage of the internal combustion engine and a compressor provided in the intake passage of the internal combustion engine;
A low pressure EGR passage that communicates an exhaust passage downstream of the turbine and an intake passage upstream of the compressor;
A low pressure EGR valve that changes a flow path area of the low pressure EGR passage;
An exhaust throttle valve that is provided in the exhaust passage downstream of the connection portion of the low-pressure EGR passage and changes the flow passage area of the exhaust passage;
An intake pressure measuring means provided in an intake passage downstream of the throttle valve for measuring the pressure of the intake air;
An exhaust pressure measuring means for measuring the pressure of exhaust gas provided in the exhaust passage upstream of the connecting portion of the low pressure EGR passage or the low pressure EGR passage;
An air flow sensor that is provided in an intake passage upstream of a connection portion of the low-pressure EGR passage and measures a flow rate of intake air flowing through the intake passage;
During the fuel cut control of the internal combustion engine, the low pressure EGR valve is fully opened and the exhaust throttle valve is fully closed, and the intake pressure measured by the intake pressure measuring means at that time is a predetermined intake pressure reference value. An abnormality detection means for detecting an abnormality in the internal combustion engine when the intake flow rate measured by the air flow sensor is equal to or higher than a predetermined intake flow rate reference value;
When an abnormality is detected by the abnormality detecting means, the low pressure EGR valve is fully closed, and when the exhaust pressure measured by the exhaust pressure measuring means at that time is below a predetermined exhaust pressure reference value, It is determined that the detected abnormality is an exhaust leak that has occurred in the exhaust passage or the low-pressure EGR passage, and if not, the abnormality determination that determines that the detected abnormality is an intake leak that has occurred in the intake passage Means,
An abnormality detection system for an internal combustion engine, comprising:

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