JP2008144609A - Failure determining method of egr system and failure determining system of egr system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure determining method of an EGR system, and a failure determining system of the EGR system, capable of determining the existence of failure in an EGR cooler and the existence of failure due to a sticking bypass control valve for adjusting the flow rate ratio of EGR gas flowing in the EGR cooler and a bypass passage bypassing the EGR cooler, in the EGR system. <P>SOLUTION: The temperatures Tm1 and Tm2 of gas of an EGR passage 13 or an intake system passage 12 on the downstream side of a confluent part 13b of the bypass passage 15 and the EGR passage 13 are measured. The temperature Ts of the gas in a position for measuring the temperature of the EGR gas is estimated based on a state detected in a vehicle. The existence of failure of the EGR system 10 is determined based on the measured temperatures Tm1 and Tm2 and the estimated temperature Ts. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the EGR system, it is possible to determine whether or not there is a failure in the EGR cooler and whether or not there is a failure due to sticking of a bypass control valve that adjusts the flow rate ratio of the EGR gas flowing into the bypass passage that bypasses the EGR cooler and the EGR cooler. The present invention relates to a failure determination method for an EGR system and a failure determination system for an EGR system.

  In an internal combustion engine mounted on a vehicle, a part of the exhaust gas is recirculated to the intake side and mixed with intake air in order to reduce NOx (nitrogen oxide) in the exhaust gas and improve fuel efficiency. Therefore, EGR (Exhaust Gas Recirculation) is performed in which the oxygen concentration in the combustion chamber is suppressed, the combustion is moderated, and the combustion temperature is lowered. This reduction in combustion temperature can reduce NOx generated during high temperature combustion.

  In this EGR system, an EGR passage is provided for flowing EGR gas that is a part of exhaust gas from the exhaust system passage to the intake system passage, and an EGR cooler and an amount of EGR gas for cooling the EGR gas are provided in the EGR passage. An EGR valve for adjusting (EGR rate) is provided. The EGR cooler is usually composed of a large number of microtubes, and EGR gas is allowed to flow through the microtubes, and a cooling medium (air or cooling water) is allowed to flow outside to cool the EGR gas.

  In recent EGR systems, in order to prevent overcooling of the EGR gas by the EGR cooler, a bypass passage that bypasses the EGR cooler and a bypass control valve are provided, and the EGR cooler is controlled by opening and closing the valve of the bypass control valve. The ratio of the flowing EGR gas is adjusted to adjust the temperature of the EGR gas.

  However, if this bypass control valve malfunctions due to sticking or the like in the exhaust gas, the EGR gas temperature cannot be adjusted after the engine warms up, for example, the EGR gas temperature cannot be adjusted, and the combustion state of the internal combustion engine There is a problem that the exhaust gas condition deteriorates. Further, since the EGR cooler is also formed of microtubules, there is a possibility that eyes are clogged. Therefore, it is necessary to detect failure of these bypass control valves and failure of the EGR cooler.

  As a method of detecting the sticking of the bypass control valve, when the intake throttle valve and the EGR valve are fully open, the bypass control valve is controlled so as to fully open and close the bypass passage, There has been proposed an EGR mechanism for an internal combustion engine that determines that the bypass control valve is fixed when the intake air intake amount during the fully closed control is substantially equal (see, for example, Patent Document 1).

However, this determination method assumes that there is exhaust pressure loss in both the bypass passage and the EGR cooler, and is used when the exhaust passage loss on the EGR cooler side is increased to make the exhaust pressure loss equal to the bypass passage. There is a problem that you can not. In addition, when the intake throttle valve and the EGR valve are fully open, the bypass control valve is controlled so as to fully open and close the bypass passage. Since the passage and the EGR cooler are switched, there is a problem that the exhaust sound changes and the impression to the driver is deteriorated.
Japanese Patent Laid-Open No. 2003-247459

  The present invention has been made to solve the above-described problems, and the object of the present invention is to use the EGR system even when the exhaust gas pressure loss of the EGR cooler and the bypass passage is equal, and when the engine is normal, the EGR cooler is used. To provide a failure determination method for an EGR system and a failure determination system for an EGR system that can determine whether or not there is a failure in an EGR cooler and whether or not there is a failure due to adhesion of a bypass control valve without switching between the bypass passage and the bypass passage. .

  In order to achieve the above object, a failure determination method for an EGR system according to the present invention includes an EGR cooler that cools EGR gas into an EGR passage that recirculates EGR gas that is part of exhaust gas from an exhaust system of an internal combustion engine to an intake system. EGR system failure determination including a bypass control valve that adjusts the flow rate of EGR gas flowing through the bypass passage, and a valve control unit that controls the bypass control valve. In the method, the temperature of the gas in the EGR passage or the intake system passage downstream from the joining portion of the bypass passage and the EGR passage is measured, and the temperature of the gas is measured based on a state detected by the vehicle. A gas position at a position to be operated is estimated, and based on the control signal for opening and closing the bypass control valve, the measured temperature, and the estimated temperature, the EGR And judging the presence or absence of failure systems out.

  Based on the state detected by this vehicle means that the estimated temperature is calculated by the outside air temperature, the exhaust temperature, the intake pressure, the opening degree of the EGR valve, etc., in other words, the estimated temperature by a function having these as arguments. Is calculated.

  According to this failure determination method, when the valve control unit outputs a control signal to the bypass control valve so that the EGR cooler flows into the exhaust gas, by monitoring the temperature of the EGR gas or the mixed gas, EGR cooler failure and bypass control valve sticking are detected, so it can be used even when the exhaust passage area on the EGR cooler side is increased to make the exhaust pressure loss equal to the bypass passage. A failure of the EGR cooler can also be detected.

  In addition, it monitors whether the temperature of the EGR gas or mixed gas after passing through the EGR cooler, which is the purpose of mounting the EGR cooler, is the intended temperature, eliminating the need for preconditions such as opening the intake valve and EGR valve. A failure can be easily determined during operation of the EGR system.

  Furthermore, it is not necessary to operate a bypass control valve for switching between passages having different exhaust pressures, that is, a passage having an EGR cooler and a bypass passage only for failure determination. Therefore, since there is no switching to a passage with a different exhaust pressure loss, there is no change in the exhaust sound due to this switching, and it is inadvertently inferior compared with a failure determination system that performs failure determination by switching the bypass control valve. No change in exhaust noise.

  This failure determination method is not based on actual opening / closing of the bypass control valve, but based on a control signal for opening / closing the bypass control valve of the valve control unit. Therefore, when the bypass control valve is out of order, it is possible that the valve control unit outputs a valve opening / closing control signal, but the bypass control valve itself does not operate. In this failure determination, the failure determination of this bypass control valve is also performed.

  In the EGR system failure determination method, the measured temperature and the estimated temperature when the valve control unit outputs a control signal to the bypass control valve so that EGR gas flows to the EGR cooler side are compared, When the measured temperature is higher than the estimated temperature by a predetermined first determination value or more, it is determined that the EGR system is faulty. The time when the control signal is output refers to a period from when the operation signal for the bypass control valve is output until the next operation signal is output.

  By comparing the measured temperature with the estimated temperature, it can be seen that the EGR system is malfunctioning. That is, the EGR cooler has failed or the bypass control valve should be controlled so that the EGR gas passes through the EGR cooler, but the bypass control that the gas flows to the bypass passage side that does not pass through the EGR cooler. From the possibility of any of the valve failures, it is possible to focus on EGR cooler failures. The predetermined first determination value can be set through experiments or calculations performed in advance.

  In the EGR system failure determination method, the valve control unit outputs a control signal to the bypass control valve so that EGR gas flows to the EGR cooler side, and the valve control unit When the absolute value of the measured temperature difference from the measured temperature when the control signal is output to the bypass control valve so that EGR gas flows to the passage side is equal to or smaller than the predetermined second determination value, there is an abnormality in the bypass control valve. Judge that there is.

  From the measured temperature difference when the two control signals are output, it can be determined that the bypass control valve has failed. In other words, even if the EGR cooler fails and is not functioning normally, the EGR gas that passes through is cooled to some extent due to the structure of the EGR cooler, so if the bypass control valve is operating normally A temperature difference equal to or greater than a predetermined second determination value is generated between the EGR gas that has passed through the EGR cooler and the EGR gas that has passed through the bypass passage without the EGR cooler. Therefore, when the difference between the two measured temperatures is equal to or smaller than the predetermined second determination value, it can be determined that the bypass control valve is limited to failure. The predetermined second determination value can be set through experiments or calculations performed in advance.

  In the failure determination method of the EGR system, the measured temperature when the valve control unit outputs a control signal to the bypass control valve so that EGR gas flows to the bypass passage side is set to a predetermined value from the estimated temperature. 3 When the value is lower than the determination value, it is determined that the bypass control valve is abnormal.

  Since the amount of the EGR gas cooled in the bypass passage is small, it is considered that the EGR gas passes through the EGR cooler regardless of the control signal when it is lower than the estimated temperature by a predetermined third judgment value or more. Therefore, it can be determined that there is an abnormality in the bypass control valve. The predetermined third determination value can be set through experiments or calculations performed in advance.

  An EGR system failure determination system for achieving the above object includes an EGR cooler that cools EGR gas in an EGR passage that recirculates EGR gas that is part of exhaust gas from an exhaust system of an internal combustion engine to an intake system. The EGR system is provided with a bypass passage that is installed, bypasses the EGR cooler, adjusts the flow rate of EGR gas flowing through the bypass passage, and a valve control unit that controls the bypass control valve. A temperature sensor that measures the temperature of the gas is disposed in the EGR passage or the intake system passage on the downstream side of the joining portion of the passage and the EGR passage, and the temperature sensor is arranged based on a state detected by the vehicle. A temperature estimation unit that estimates the temperature of the gas at the position, a control signal for opening and closing the bypass control valve, a measured temperature measured by the temperature sensor, Serial based on the estimated temperature and estimated by the temperature estimation unit configured to include failure determination section determines the presence or absence of a failure of the EGR system.

  In the EGR system failure determination system, the measurement is performed when the failure determination unit outputs a control signal to the bypass control valve so that the valve control unit causes EGR gas to flow to the EGR cooler side. The temperature is compared with the estimated temperature, and when the measured temperature is higher than the estimated temperature by a predetermined first determination value or more, the EGR system is determined to be faulty.

  Further, in the failure determination system of the EGR system, the failure determination unit may measure a temperature when the valve control unit outputs a control signal to the bypass control valve so that the EGR gas flows to the EGR cooler side. When the absolute value of the measured temperature difference from the measured temperature when the valve control unit outputs a control signal to the bypass control valve so as to flow EGR gas to the bypass passage side is equal to or smaller than a predetermined second determination value In addition, it is configured to determine that there is an abnormality in the bypass control valve.

  Further, in the failure determination system for the EGR system, the measured temperature when the failure determination unit outputs a control signal to the bypass control valve so that the valve control unit causes EGR gas to flow to the bypass passage side is obtained. The bypass control valve is determined to be abnormal when it is lower than the estimated temperature by a predetermined third determination value or more.

  In the failure determination system of the EGR system, the failure determination unit outputs the control signal to the bypass control valve so that the valve control unit causes EGR gas to flow to the EGR cooler side, and the measured temperature An estimated temperature is compared, and the EGR system is determined to be faulty when the measured temperature is higher than the estimated temperature by a predetermined first determination value or more.

  In the failure determination system of the EGR system, the failure determination unit is configured to output a control signal to the bypass control valve so that the valve control unit causes EGR gas to flow to the EGR cooler side; When the absolute value of the measured temperature difference from the measured temperature when the valve control unit sends a control signal to the bypass control valve so that EGR gas flows to the bypass passage side is equal to or less than a predetermined second determination value, The bypass control valve is configured to determine that there is an abnormality.

  According to these configurations, the above-described failure determination method for the EGR system can be implemented, and the same effects can be achieved.

  According to the failure determination method of the EGR system and the failure determination system of the EGR system of the present invention, it can be used even when the exhaust pressure loss of the EGR cooler and the bypass passage is equal, and it is easy and careless during operation of the EGR system. It is possible to determine both the presence / absence of a failure of the EGR cooler and the presence / absence of a failure due to the adhering of the bypass control valve without performing an operation of switching between the EGR cooler and the bypass passage accompanying the occurrence of a change in exhaust sound.

  Moreover, it is possible to detect whether the failure is on the EGR cooler side or the bypass control valve side by outputting a switching control signal to the bypass control valve after detecting an abnormality in the entire EGR system.

  Hereinafter, an EGR system failure determination method and an EGR system failure determination system according to embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an EGR system 10 provided with an EGR system failure determination system 1 according to an embodiment of the present invention includes an exhaust system passage 11 such as an exhaust manifold 11 a and an exhaust pipe 11 b of an engine (internal combustion engine) E. The EGR passage 13 for returning EGR gas Ge (= G1-G2), which is a part of the exhaust gas G1, is provided to the intake system passage 12 such as the intake manifold 12a and the intake pipe 12b. An EGR cooler 14 that cools the gas Ge1 and a bypass passage 15 that bypasses the EGR cooler 14 are provided. Further, a bypass control valve 16 for adjusting the flow rate of the EGR gas Ge2 flowing through the bypass passage 15, an EGR valve 17 for controlling the entire EGR gas amount Ge (= Ge1 + Ge2), and the bypass control valve 16 and the EGR valve 17 are controlled. The valve control unit 31 is configured.

  The EGR valve 17 has an EGR passage 13 on the downstream side of a joining portion (position of the bypass control valve 16 in the configuration of FIG. 1) 13b between the bypass passage 15 and the EGR passage 13 so that the low-temperature EGR gas Ge passes therethrough. Is provided. Further, in the embodiment of FIG. 1, the bypass control valve 16 is disposed in the joining portion 13 b of the EGR passage 13 and the bypass passage 15 downstream of the EGR cooler 14, but is upstream of the EGR cooler 14. The EGR passage 13 and the bypass passage 15 of the EGR passage 13 may be a branch portion 13a, or the EGR passage before and after the EGR cooler 14 between the branch portion 13a of the bypass passage 15 and the merge portion 13b in the EGR passage 13 may be used. 13 parts may be sufficient. And the valve control part 31 is provided in the engine control apparatus (ECU) 30 which controls the engine E whole.

  The failure determination system 1 of the EGR system measures the temperature of the EGR gas in the EGR passage 13 or the intake system passage 12 downstream of the joining portion 13b of the bypass passage 15 and the EGR passage 13 in the EGR system 10. A temperature sensor 18 (or (18)) is arranged. Further, a temperature measurement unit 21 for obtaining a measurement temperature Tm from a detection value of the temperature sensor 18 and a gas Ge (or temperature sensor) at a position where the temperature sensor 18 is arranged based on a state detected by a vehicle equipped with the engine E. A temperature estimation unit 22 that estimates the temperature of the mixed gas Gm (= A + Ge) in which fresh air (intake air) A and EGR gas Ge are mixed at the position where (18) is disposed, and opening and closing of the bypass control valve 16 A failure determination that determines the presence or absence of a failure in the EGR system 10 based on the control signal, the measured temperature Tm measured by the temperature sensor 18 and obtained by the temperature measurement unit 21, and the estimated temperature Ts estimated by the temperature estimation unit 22 The unit 23 is provided.

  These temperature measurement unit 21, temperature estimation unit 22, and failure determination unit 23 are normally provided in an engine control unit (ECU) 30 as shown in FIG. 1, but valves in the engine control unit (ECU) 30 are provided. You may provide in the failure determination apparatus which can input the control signal of the control part 31, and the temperature detection signal of the temperature sensor 18. FIG. By providing this failure determination device separately from the engine control device 30, it can be easily added to an existing vehicle. Further, it is possible to connect only at the time of failure diagnosis at the time of vehicle inspection and to remove it after failure diagnosis.

  Next, a failure determination method in the failure determination unit 23 will be described. This failure determination is executed according to the control flow illustrated in FIGS. The control flow in FIGS. 2 and 3 is called and executed from an advanced control flow, for example, a main control flow for controlling the engine, when failure determination of the EGR system is necessary. It is shown as something to do.

  When the engine key is turned on (ON) and the engine is started, it is called as necessary from the engine control program or from a failure determination device separated from the overall engine control. 2 control flow starts. By this start, the control signal of the valve control unit 31 to the bypass control valve 16 is checked at step S11. That is, it is checked whether or not this control signal is a control signal for flowing the EGR gas Ge to the EGR cooler 14 side.

  In the control signal check to the bypass control valve 16 in step S11, if the control signal is a control signal for flowing EGR gas Ge to the EGR cooler 14 side (YES), the measured temperature Tm1 by the temperature sensor 18 is input in step S12. In the next step S13, the estimated temperature Ts is calculated. This estimated temperature Ts is calculated by a function having the outside air temperature, the exhaust gas temperature, the intake pressure, the EGR valve opening degree and the like as arguments. This function is obtained in advance by experiments or calculations and stored. The calculation may be performed using map data instead of the function.

  Regarding the calculation of the estimated temperature Ts, for example, in the case of calculating the estimated intake air temperature, for example, the base temperature of the intake air temperature is calculated from the outside air temperature, the intake temperature, the water temperature, etc. at the time of starting the engine, The temperature rise is calculated from the engine speed, the fuel injection amount, and the elapsed time. Furthermore, the temperature decrease is calculated from the exhaust temperature, ON / OFF of the bypass control valve 16, vehicle speed, engine temperature (water temperature, combustion temperature), outside air temperature, ON / OFF of the indoor heater, etc. and elapsed time information. The estimated temperature Ts is calculated from “base temperature + temperature rise + temperature drop”.

  In the next step S14, the measurement temperature Tm1 is checked. That is, the measured temperature Tm1 is compared with a determination value (Ts + Tc1) obtained by adding a predetermined first determination value Tc1 to the estimated temperature Ts. If the measured temperature Tm1 is less than the determination value (Ts + Tc1) in step S14 of this comparison (NO), the process goes to step S15. In step S15, it is determined that the EGR cooling system of the EGR system 10 is normal, the failure determination is terminated, and the process returns. If the failure determination is necessary again, the control flow of FIG. 2 is called and started.

  If the measured temperature Tm1 is equal to or higher than the determination value (Ts + Tc1) in the comparison in step S14 (YES), the process goes to step S16. In step S16, the EGR system of the EGR system 10 determines in more detail that the EGR cooling system is out of order, and performs processing when the EGR cooling system is abnormal. In other words, an error code (diagnostic code at the time of valve abnormality) is output, backup processing such as saving of various data at the time of abnormality occurs, exhaust gas processing capacity decreases, output is limited and a warning lamp is displayed . Then, the process goes to the determination of the abnormal part in the next step S20.

  In step S20, as shown in the control flow of FIG. 3, the measured temperature Tm1 is input in the first step S21. The measured temperature Tm1 is a measured temperature when the valve control unit 31 is outputting a control signal so that the EGR gas Ge flows through the bypass control valve 16 to the EGR cooler 14 side. In the next step S22, a control signal is issued so that EGR gas flows from the valve control unit 31 to the bypass control valve 16 to the bypass passage 15 side. That is, the control signal is switched. In step S23, the measurement temperature Tm2 is input. The measured temperature Tm2 is a measured temperature when the valve control unit 31 is outputting a control signal so that the EGR gas Ge flows to the bypass control valve 16 on the bypass passage 15 side.

  In the next step S24, the absolute value of the difference (Tm2−Tm1) between these measured temperatures Tm1 and Tm2 is compared with a predetermined second determination value Tc2. If the absolute value (| Tm2-Tm1 |) of the measured temperature difference (Tm2-Tm1) is equal to or smaller than the predetermined second determination value Tc2 (YES) in step S24, the process goes to step S25 and the bypass control valve 16 Is determined to be malfunctioning, the process when the bypass control valve is abnormal is performed, and step S20 is terminated. In this abnormal process, the energization to the bypass control valve 16 is stopped, or the energization is periodically performed for diagnosis so that the return can be made when the stack (fixation) is corrected.

  If the absolute value (| Tm2−Tm1 |) of the measured temperature difference (Tm2−Tm1) is greater than or equal to the predetermined second determination value Tc2 (NO) in the comparison in step S24, the process goes to step S26 to perform bypass control. It is determined that the valve 16 has not failed, that is, it is determined that a portion other than the bypass control valve 16 (for example, the EGR cooler 14) has failed, the normal processing of the bypass control valve is performed, and step S20 is performed. finish. In this normal processing, when the valve is abnormal and normal, the normal operation is performed or the diagnostic code at the time of valve abnormality is deleted. When step S20 ends, the process returns to the control flow of FIG. 2, ends the failure determination, and returns. If the failure determination is necessary again, the control flow of FIG. 2 is called and started.

  In the control signal check to the bypass control valve 16 in step S11, if the control signal is not a control signal for flowing the EGR gas Ge to the EGR cooler 14 side (NO), the measured temperature Tm2 by the temperature sensor 18 is input in step S31, In the next step S32, an estimated temperature Ts is calculated. This estimated temperature Ts is calculated by a function with the outside air temperature, the exhaust gas temperature, the intake pressure, the EGR valve opening, etc. as arguments, as in step S13.

  In the next step S33, the measurement temperature Tm2 is checked. That is, the measured temperature Tm2 is compared with a determination value (Ts−Tc3) obtained by subtracting a predetermined third determination value Tc3 from the estimated temperature Ts.

  In step S33 of this comparison, if the measured temperature Tm2 is equal to or higher than the determination value (Ts−Tc3) (YES), the process goes to step S15. In step S15, it is determined that the EGR cooling system of the EGR system 10 is normal, the failure determination is terminated, and the process returns. If the failure determination is necessary again, the control flow of FIG. 2 is called and started.

  If the measured temperature Tm2 is lower than the determination value (Ts−Tc3) (NO) in step S33, the process goes to step S34. In step S34, it is determined that the bypass control valve 16 is in failure, and processing is performed when the bypass control valve is abnormal. In other words, an error code is output or backup processing is performed. Then, the failure determination is finished and the process returns. If the failure determination is necessary again, the control flow of FIG. 2 is called and started.

  According to this failure determination method for the EGR system, the measured temperature Tm1 and the estimated temperature Ts when the valve control unit 31 outputs a control signal to the bypass control valve 16 so that EGR gas flows to the EGR cooler 14 side are compared. When the measured temperature Tm1 is higher than the estimated temperature Ts by a predetermined first determination value Tc1, it is determined that the EGR system is malfunctioning (S16).

  Further, the measured temperature Tm1 when the valve control unit 31 outputs a control signal to the bypass control valve 16 so that EGR gas flows to the EGR cooler 14 side, and the valve control unit 31 flows EGR gas to the bypass passage 15 side. When the absolute value (| Tm2−Tm1 |) of the measured temperature difference from the measured temperature Tm2 when the control signal is output to the bypass control valve 16 is equal to or smaller than the predetermined second determination value Tc2, the bypass control valve It is determined that there is an abnormality (S25).

  Further, the measured temperature Tm2 when the valve control unit 31 outputs a control signal to the bypass control valve 16 so that EGR gas flows to the bypass passage 15 side is lower than the estimated temperature Ts by a predetermined third determination value Tc3 or more. In this case, it is determined that the bypass control valve 16 is abnormal (S34).

  Therefore, according to the failure determination method of the EGR system and the failure determination system 1 of the EGR system of the present invention, the EGR system can be used even when the exhaust gas pressure loss in the EGR cooler 14 and the bypass passage 15 are equal, and can be easily used while the EGR system 10 is in operation. Without the switching operation between the EGR cooler 14 and the bypass passage 15, which is accompanied by the occurrence of an unpleasant exhaust noise change, the presence or absence of the EGR cooler 14 and the failure due to the adhering bypass control valve 16 Both can be determined.

  In addition, it is possible to detect whether the failure is on the EGR cooler 14 side or the bypass control valve 16 side by outputting a switching control signal to the bypass control valve 16 after detecting an abnormality in the entire EGR system 10. . That is, in the failure determination of the EGR system 10, the failure of the bypass control valve 16 and the failure caused by others can be separated.

It is a figure which shows the structure of the failure determination system of the EGR system and EGR system of embodiment which concerns on this invention. It is a figure which shows an example of the control flow of the failure determination method of the EGR system of embodiment which concerns on this invention. It is a figure which shows the control flow of determination of the abnormal part of FIG.

Explanation of symbols

E engine 1 EGR system failure determination system 10 EGR system 11 exhaust system passage 12 intake system passage 13 EGR passage 13a branching portion 13b confluence portion 14 EGR cooler 15 bypass passage 16 bypass control valve 17 EGR valve 18 temperature sensor 21 temperature measuring unit 22 Temperature estimation unit 23 Failure determination unit 30 Engine control unit (ECU)
31 Valve control part A Fresh air (intake air)
G1, G2 exhaust gas Ge, Ge1, Ge2 EGR gas Gm mixed gas Tm, Tm1. Tm2 Measurement temperature Ts Estimated temperature Tc1 Predetermined first determination value Tc2 Predetermined second determination value Tc3 Predetermined third determination value

Claims (8)

An EGR cooler that cools the EGR gas is installed in an EGR passage that recirculates EGR gas that is part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system, and a bypass passage that bypasses the EGR cooler is provided. In a failure determination method for an EGR system comprising a bypass control valve for adjusting the flow rate of flowing EGR gas and a valve control unit for controlling the bypass control valve,
The temperature of the gas in the EGR passage or the intake system passage on the downstream side of the joining portion of the bypass passage and the EGR passage is measured, and the gas temperature is measured based on the state detected by the vehicle. Estimate the temperature of the gas,
A failure determination method for an EGR system, wherein the presence or absence of a failure in the EGR system is determined based on a control signal for opening and closing the bypass control valve, the measured temperature, and the estimated temperature.   The measured temperature is compared with the estimated temperature when the valve control unit sends a control signal to the bypass control valve so that EGR gas flows to the EGR cooler side, and the measured temperature is higher than the estimated temperature. 2. The failure determination method for an EGR system according to claim 1, wherein when the EGR system is higher than a predetermined first determination value, it is determined that the EGR system is defective.   The measured temperature when the valve control unit sends a control signal to the bypass control valve so that EGR gas flows to the EGR cooler side, and the valve control unit causes the EGR gas to flow to the bypass passage side. It is determined that there is an abnormality in the bypass control valve when the absolute value of the measured temperature difference from the measured temperature when the control signal is output to the bypass control valve is equal to or smaller than a predetermined second determination value. Item 3. An EGR system failure determination method according to Item 1 or 2.   When the measured temperature when the valve control unit outputs a control signal to the bypass control valve so that EGR gas flows to the bypass passage side is lower than the estimated temperature by a predetermined third determination value or more, the bypass 4. The failure determination method for an EGR system according to claim 1, wherein the control valve is determined to be abnormal. An EGR cooler that cools the EGR gas is installed in an EGR passage that recirculates EGR gas that is part of the exhaust gas from the exhaust system of the internal combustion engine to the intake system, and a bypass passage that bypasses the EGR cooler is provided. An EGR system including a bypass control valve that adjusts the flow rate of flowing EGR gas and a valve control unit that controls the bypass control valve,
A temperature sensor that is disposed in the EGR passage or the intake system passage on the downstream side of the joining portion of the bypass passage and the EGR passage, and measures the temperature of the gas;
A temperature estimation unit that estimates the temperature of the gas at the position where the temperature sensor is arranged based on the state detected by the vehicle;
A failure determination unit that determines whether or not there is a failure in the EGR system based on a control signal for opening and closing the bypass control valve, a measured temperature measured by the temperature sensor, and an estimated temperature estimated by the temperature estimation unit; A failure determination system for an EGR system, comprising:   The failure determination unit compares the measured temperature with the estimated temperature when the control signal is output to the bypass control valve so that the valve control unit causes EGR gas to flow to the EGR cooler side, and the measured temperature 6. The EGR system failure determination system according to claim 5, wherein the EGR system determines that the EGR system is in failure when the temperature is higher than the estimated temperature by a predetermined first determination value or more.   The failure determination unit has a measured temperature when the valve control unit outputs a control signal to the bypass control valve so that EGR gas flows to the EGR cooler side, and the valve control unit performs EGR on the bypass passage side. When the absolute value of the measured temperature difference from the measured temperature when the control signal is output to the bypass control valve so as to flow gas is equal to or smaller than a predetermined second determination value, it is determined that the bypass control valve is abnormal. The failure determination system for an EGR system according to claim 5 or 6.   The measured temperature when the failure determination unit outputs a control signal to the bypass control valve so that the valve control unit causes EGR gas to flow to the bypass passage side is a predetermined third determination value or more than the estimated temperature. 8. The failure determination system for an EGR system according to claim 5, 6 or 7, wherein when it is low, it is determined that the bypass control valve is abnormal.

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