Internal combustion engine fault detection device

Abstract

To provide an internal combustion engine and a failure determination device for the internal combustion engine capable of making a failure determination including detachment failure of piping having a differential pressure sensor of an exhaust gas recirculation device by using a simple configuration.SOLUTION: An internal combustion engine 1 includes: an intake passage 20; a throttle valve 26; an exhaust passage 30; an exhaust gas recirculation device 4 having an exhaust gas recirculation passage 40 connecting an upstream side of the throttle valve 26 in the intake passage 20 and the exhaust passage 30, an exhaust gas recirculation valve 42 provided in the exhaust gas recirculation passage 40, a first passage 50a extending from an upstream side of the exhaust gas recirculation valve 42 in the exhaust gas recirculation passage 40, a second passage 50b extending from a downstream side of the exhaust gas recirculation valve 42, and a differential pressure sensor 51 provided between the first passage 50a and the second passage 50b; a third passage 60 that connects a downstream side of the throttle valve 26 in the intake passage 20 and the first passage 50a, the second passage 50b or the exhaust gas recirculation passage 40; and a valve 61 provided in the third passage 60.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a failure determination device for a combustion engine equipped with an exhaust gas recirculation device. inside

Background Art

[0002] In an internal combustion engine, an exhaust gas recirculation device (EGR: Exhaust Gas Recirculation, hereinafter also referred to as an "EGR device") is installed to reduce the emission of NOx and soot in the exhaust gas and improve fuel efficiency. The EGR device includes an exhaust gas recirculation passage (EGR passage) that connects the upstream side of the throttle in the intake passage of the internal combustion engine and the exhaust passage, an exhaust gas recirculation cooler (EGR cooler) interposed in the EGR passage, and an exhaust gas recirculation valve (EGR valve) interposed on the downstream side (intake passage side) of the EGR cooler in the EGR passage. There is a low-pressure exhaust gas recirculation device (low-pressure EGR device).

[0003] In this low-pressure EGR device, there is a device provided with a bypass passage that connects the upstream side of the EGR valve in the EGR passage and the downstream side of the EGR valve, and a differential pressure sensor is provided in this bypass passage. In this device, for example, the EGR valve and the like can be controlled based on the differential pressure between the upstream and downstream of the EGR valve detected by the differential pressure sensor.

[0004] However, in a device provided with a differential pressure sensor in the bypass passage, when an abnormality (failure) occurs in the differential pressure sensor or the like, appropriate engine control cannot be implemented. Therefore, an abnormality detection technique for a differential pressure sensor or the like has been developed. For example, Patent Document 1 discloses a technique for calculating the differential pressure (differential pressure calculation value) between the upstream side and the downstream side of the EGR valve, and determining that the differential pressure sensor is abnormal when the difference between this differential pressure calculation value and the differential pressure (differential pressure sensor value) detected by the differential pressure sensor is equal to or greater than a determination threshold value.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-176565 [Overview of the project] [Problems that the invention aims to solve]

[0006] By the way, failures of differential pressure sensors and the like include not only malfunctions of the differential pressure sensors themselves, but also failures where the connection between the piping constituting the bypass passage and the piping constituting the EGR passage becomes disconnected (disconnection failure). Therefore, there is a demand for a system that can detect disconnection failures of piping equipped with differential pressure sensors with the simplest possible configuration.

[0007] This invention was devised in light of the above-mentioned issues, and with a simple configuration, it is possible to perform fault detection, including faults in the piping equipped with a differential pressure sensor for exhaust gas recirculation devices. inside One of the objectives is to provide a combustion engine failure detection device. However, this objective is not limited to this, and another objective of this invention is to achieve effects and benefits that cannot be obtained by conventional technology, which are derived from each configuration shown in the embodiments for carrying out the invention described later. [Means for solving the problem]

[0008] Disclosure of internal combustion engines Fault detection device This can be realized as Embodiment 1 (Example of Application) disclosed below, and solves at least some of the above problems. . condition Mr. 2 ~4 Each of these embodiments is an additional embodiment that can be appropriately selected, and each of these embodiments is an embodiment that can be omitted. Embodiment 2 ~4 None of the embodiments disclosed hereby disclose any embodiments or configurations that are essential to this case.

[0009] Appearance 1. Disclosed internal combustion engine Fault detection device It comprises an intake passage, a throttle valve provided in the intake passage, and an exhaust passage. A fault detection device for an internal combustion engine, wherein the internal combustion engine is equipped with:An exhaust recirculation device having: an exhaust recirculation passage connecting the upstream side of the throttle valve in the intake passage to the exhaust passage; an exhaust recirculation valve provided in the exhaust recirculation passage; a first passage extending from upstream of the exhaust recirculation valve in the exhaust recirculation passage; a second passage extending from downstream of the exhaust recirculation valve; and a differential pressure sensor provided between the first passage and the second passage; and a third passage connecting the downstream side of the throttle valve in the intake passage to the first passage, the second passage, or the exhaust recirculation passage; and a valve provided in the third passage. A fault determination unit is provided, and the fault determination device determines faults in the exhaust recirculation passage and the auxiliary members of the exhaust recirculation passage. Equipped with The fault determination unit opens the valve when there is negative pressure downstream of the throttle valve in the intake passage, and determines that there is a fault in either the exhaust recirculation passage or the auxiliary member if the differential pressure detected by the differential pressure sensor at the time of opening is less than a preset first threshold. ru.

[0010] Embodiment 2. In Embodiment 1 described above, the exhaust gas recirculation device has an exhaust gas recirculation cooler provided in the exhaust gas recirculation passage, the exhaust gas recirculation valve is provided downstream of the exhaust gas recirculation cooler in the exhaust gas recirculation passage, the first passage extends from downstream of the exhaust gas recirculation cooler and upstream of the exhaust gas recirculation valve in the exhaust gas recirculation passage, and the third passage preferably connects the downstream side of the throttle valve in the intake passage to the downstream side of the exhaust gas recirculation cooler in the second passage or the exhaust gas recirculation passage.

[0011] Embodiment 3. In Embodiment 1 or 2 described above, it is preferable that the third passage connects the intake passage downstream of the throttle valve to the second passage.

[0013] manner 4 . In any one of the above embodiments 1 to 3, the fault determination unit, when the opening occurs, The differential pressure sensor Detected Differential pressure and, The aforementioned The system compares a first threshold with a second threshold that is smaller than the first threshold. If the differential pressure is less than the first threshold and greater than or equal to the second threshold, it is determined that there is a possibility of a malfunction on the exhaust gas return passage side of the connection between the first passage and the third passage. If the differential pressure is less than the second threshold, it is determined that there is a possibility of a malfunction on the differential pressure sensor side of the connection. Preferably . [Effects of the Invention]

[0014] Disclosure inside According to the failure determination device of the internal combustion engine, it is possible to perform failure determination including disconnection failure of a pipe equipped with a differential pressure sensor with a simple configuration.

Brief Description of the Drawings

[0015] [Figure 1] It is a schematic configuration diagram of an intake / exhaust system of an internal combustion engine and a failure determination device of the internal combustion engine according to the first embodiment. [Figure 2] It is a time chart for explaining failure determination by the failure determination device shown in FIG. 1. [Figure 3] It is a flowchart for explaining failure determination by the failure determination device shown in FIG. 1. [Figure 4] It is a schematic configuration diagram of an intake / exhaust system of an internal combustion engine and a failure determination device of the internal combustion engine according to the second embodiment. [Figure 5] It is a schematic configuration diagram of an intake / exhaust system of an internal combustion engine and a failure determination device of the internal combustion engine according to the third embodiment.

Modes for Carrying Out the Invention

[0016] Referring to the drawings, the internal combustion engine and the failure determination device of the internal combustion engine will be described as embodiments. The embodiments shown below are merely examples, and there is no intention to exclude various modifications and applications of technologies not explicitly shown in the following embodiments. Each configuration of the embodiments can be implemented with various modifications without departing from their gist. Also, it can be selectively adopted as necessary, or appropriately combined.

[0017] [1. First Embodiment] [1-1. Configuration of Intake / Exhaust System of Internal Combustion Engine] First, referring to the schematic configuration diagram of FIG. 1, the configuration of the intake / exhaust system of the internal combustion engine 1 according to the present embodiment will be described. In the present embodiment, the internal combustion engine 1 is described as being equipped on a vehicle, but it may be an internal combustion engine mounted on a machine tool, a ship, a generator, various test devices, etc. Also, the internal combustion engine 1 of the present embodiment is a gasoline engine.

[0018] The internal combustion engine 1 in this case is an engine capable of performing fuel cut control, which temporarily stops fuel injection from an injector (not shown). The conditions for performing fuel cut control include, for example, the following conditions, and fuel cut control is performed when at least one (preferably all) of these conditions are met. • The engine speed (rotational velocity) is above a predetermined lower limit and below a predetermined upper limit. • The throttle opening is fully closed (below a predetermined opening). • The vehicle speed is above the specified lower limit and below the specified upper limit. • The temperature of the internal combustion engine 1 is above a specified temperature. • A motor is required to rotate the internal combustion engine 1 using the output of the motor.

[0019] As shown in Figure 1, the internal combustion engine 1 comprises an engine body 10 which includes cylinders (not shown), an intake manifold, an exhaust manifold, etc., an intake passage 20 connected to the intake manifold of the engine body 10, and an exhaust passage 30 connected to the exhaust manifold of the engine body 10.

[0020] The intake passage 20 is equipped with, in order from upstream, an air cleaner 21, a compressor 23 of the turbocharger 22, an intercooler 25, and a throttle valve 26. The outside air taken into the intake passage 20 is purified by the air cleaner 21, pressurized by the compressor 23, cooled by the intercooler 25, and then supplied to the cylinders of the engine body 10 from the intake manifold after passing through the throttle valve 26.

[0021] The exhaust passage 30 is equipped with an exhaust catalytic converter 31 (simply referred to as "catalyst 31") consisting of, in order from the upstream side, the turbine 24 of the turbocharger 22 and a three-way catalytic converter for purifying the exhaust. The high-pressure exhaust discharged from the engine body 10 into the exhaust passage 30 rotates the turbine 24, is purified by the catalyst 31, and then discharged.

[0022] The internal combustion engine 1 is equipped with an exhaust gas recirculation device 4 (hereinafter also referred to as "EGR device 4"). The EGR device 4 is a low-pressure exhaust gas recirculation device (low-pressure EGR device) equipped with an exhaust gas recirculation passage 40 (hereinafter also referred to as "EGR passage 40") that connects the upstream side of the throttle valve 26 in the intake passage 20 (specifically, between the air cleaner 21 and the compressor 23) and the downstream side of the catalyst 31 in the exhaust passage 30. The EGR passage 40 is equipped with an exhaust gas recirculation cooler 41 (hereinafter also referred to as "EGR cooler 41") and an exhaust gas recirculation valve 42 (hereinafter also referred to as "EGR valve 42") in that order from the upstream side (exhaust passage 30 side).

[0023] The internal combustion engine 1 is equipped with a bypass passage 50 as an accessory member of the EGR passage 40, which has a first passage 50a extending from downstream of the EGR cooler 41 and upstream of the EGR valve 42 in the EGR passage 40, and a second passage 50b extending from downstream of the EGR valve 42, and a differential pressure sensor 51 provided between the first passage 50a and the second passage 50b for detecting the pressure difference between the first passage 50a and the second passage 50b, that is, the pressure difference between the upstream and downstream sides of the EGR valve 42 (hereinafter also referred to as "EGR differential pressure" or simply "differential pressure"). The value detected by the differential pressure sensor 51 can be used, for example, for controlling the EGR valve 42.

[0024] Furthermore, the internal combustion engine 1 is equipped with a third passage 60 as an accessory to the EGR passage 40, which connects the intake passage 20 downstream of the throttle valve 26 to the bypass passage 50 or the EGR passage 40, and a solenoid valve 61 (valve) provided in the third passage 60. In the case where the EGR cooler 41 is provided upstream of the EGR valve 42 as in this embodiment, the third passage 60 connects the intake passage 20 downstream of the throttle valve 26 to the bypass passage 50 or the EGR passage 40 downstream of the EGR cooler 41.

[0025] In this embodiment, the third passage 60 connects the section of the intake passage 20 directly downstream of the throttle valve 26 to the second passage 50b. In Figure 1, the added third passage 60 is decorated with patterns such as hatching or dots. In this embodiment, a solenoid valve 61 is used as the valve, but any valve that can be opened and closed may be used, for example, a butterfly valve.

[0026] [1-2. Outline of the Control System Configuration] The vehicle of this embodiment is equipped with a control device 7 that controls various parts of the internal combustion engine 1. The control objects of the control device 7 include, for example, the open / closed state (opening degree) of the throttle valve 26, EGR valve 42, and solenoid valve 61 of the intake and exhaust system of the internal combustion engine 1, as well as the fuel injection amount and injection timing from injectors (not shown). The control device 7 is an ECU (electronic control unit) equipped with input / output devices (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, a central processing unit (CPU), a timer counter, etc.

[0027] The control device 7 is provided with a fault detection unit 71 that determines a failure in the EGR device 4. The fault detection unit 71 may be implemented by an electronic circuit (hardware), programmed as software, or some of these functions may be provided as hardware and the other parts as software. The fault detection device 6 for the internal combustion engine 1 according to this embodiment has the internal combustion engine 1 described above and this fault detection unit 71. In this embodiment, the fault detection unit 71 is provided as a functional element within the control device 7 that comprehensively controls the internal combustion engine 1, but the fault detection unit 71 may also be provided in a separate (dedicated) control device (ECU) from the control device 7.

[0028] Vehicles equipped with the above-mentioned internal combustion engine 1 are engine-powered vehicles equipped with the internal combustion engine 1 as a power source, or hybrid vehicles or plug-in hybrid vehicles equipped with the internal combustion engine 1 as a power source, a motor, a generator as a power generation device, and a battery as an energy storage device. A plug-in hybrid vehicle refers to a hybrid vehicle that can be externally charged to the battery or receive power from the battery. Plug-in hybrid vehicles and electric vehicles are equipped with a charging port (inlet) for inserting a charging cable that receives power from an external charging facility, and an outlet for external power supply.

[0029] [1-3. Internal Combustion Engine Fault Detection Device] Next, we will describe the fault detection device 6 that determines the failure of the EGR device 4 of the internal combustion engine 1. The fault detection device 6 uses the differential pressure sensor 51 installed in the EGR device 4, the third passage 60, and the solenoid valve 61 installed in the third passage 60 to determine a fault.

[0030] The failure types to be determined here include abnormalities in the piping that constitutes the bypass passage 50, such as the occurrence of cracks or the disconnection of the connection part of the piping connected to the EGR passage 40 (pipe detachment). Also included are abnormalities in the differential pressure sensor 51 installed in the bypass passage 50 (for example, failure of the sensor itself or communication failure, etc.) and abnormalities in the solenoid valve 61 installed in the third passage 60.

[0031] The fault determination unit 71 performs fault determination when the fuel supply to the internal combustion engine 1 is cut off, by closing the EGR valve 42 and opening the solenoid valve 61 of the third passage 60, and based on the EGR differential pressure detected by the differential pressure sensor 51 at the time of opening. Specifically, when the solenoid valve 61 is opened (fault determination time), the fault determination unit 71 determines that the system is "normal" or "no fault" if the EGR differential pressure is above a preset first threshold, and determines that the system is "abnormal" or "fault present" if the EGR differential pressure falls below the first threshold.

[0032] This determination principle will be explained with reference to Figure 2. Since the EGR passage 40 downstream of the EGR valve 42 is in communication with the intake passage 20 upstream of the throttle valve 26, if the solenoid valve 61 is closed (when the third passage 60 is not provided), the internal pressure in this part (downstream of the EGR valve 42) will be approximately atmospheric pressure. Also, the internal pressure upstream of the EGR valve 42 in the EGR passage 40 will basically always be positive pressure (approximately atmospheric pressure or higher), regardless of whether the EGR valve 42 is open or closed.

[0033] In contrast, when the fuel supply to the internal combustion engine 1 is cut off (e.g., when the accelerator is released), the EGR valve 42 and the throttle valve 26 are closed, resulting in negative pressure downstream of the throttle valve 26 in the intake passage 20. Therefore, when the solenoid valve 61 is opened (time t2) after the start of fuel cut-off (time t1), the area downstream of the throttle valve 26 in the intake passage 20 and the second passage 50b are connected via the third passage 60, and the second passage 50b also becomes negative pressure. Consequently, the EGR differential pressure increases compared to when the solenoid valve 61 is closed, as shown by the solid line in Figure 2. After fault detection is complete, the solenoid valve 61 is closed (time t3).

[0034] However, if there is a leak due to a pipe disconnection or the like in the downstream region A1 (shown as hatched in Figure 1) below the connection point of the second passage 50b to the third passage 60, the negative pressure downstream (intake side) of the differential pressure sensor 51 when the solenoid valve 61 is opened will decrease, and the EGR differential pressure will also decrease, as shown by the dashed line in Figure 2. Note that this change in EGR differential pressure can also be caused by a malfunction (abnormality) of the EGR valve 42 (e.g., stuck open), in addition to a malfunction (abnormality) due to a pipe disconnection.

[0035] Furthermore, if there is a leak due to pipe disconnection or the like at the connection point of the bypass passage 50 with the third passage 60, or in the upstream region A2 (shown as a shaded area in Figure 1) above this connection point, the area downstream of the differential pressure sensor 51 will remain at atmospheric pressure even if the solenoid valve 61 is opened. In this case, the EGR differential pressure will remain approximately zero and will not increase, as shown by the dotted line in Figure 2.

[0036] [1-4. Flowchart] Figure 3 is an example flowchart illustrating the fault detection described above, and it is assumed that this process is repeated at a predetermined control cycle. Furthermore, the solenoid valve 61 is normally in the closed state (except during fault detection).

[0037] As shown in Figure 3, the fault detection unit 71 determines whether or not fuel cut-off is being performed (step S10). If fuel cut-off is not being performed, the processing for the current control cycle is terminated. On the other hand, if it is determined in step S10 that fuel cut-off is being performed, the solenoid valve 61 is opened (step S20). Note that the EGR valve 42 remains closed from the start to the end of fuel cut-off. The EGR differential pressure is then read (step S30), and the read EGR differential pressure is compared with a first threshold to determine whether or not the EGR differential pressure is less than the first threshold (differential pressure < first threshold) (step S40).

[0038] If the determination in step S40 is found to be below the first threshold, it is determined that there is a fault in the piping or other components constituting the bypass passage 50 (step S50). On the other hand, if the determination is found that the EGR differential pressure is not below the first threshold (i.e., the EGR differential pressure is equal to or greater than the first threshold), it is determined that the piping or other components constituting the bypass passage 50 are normal (no fault) (step S60).

[0039] Although not shown in the flow chart in Figure 3, if a fault is detected in the piping, etc., in step S50, a second threshold value smaller than the first threshold (a very small value close to zero) may be set in advance, and the EGR differential pressure may be compared with the second threshold value to further classify the fault in the piping, etc.

[0040] In other words, if the EGR differential pressure is above the second threshold, it is determined that there is a leak due to a pipe disconnection or the like in region A1 (see Figure 1) downstream of the connection point between the bypass passage 50 and the third passage 60, or that there is a malfunction in the EGR valve 42. Note that in this case, a pipe disconnection includes a pipe disconnection at the connection point downstream of the EGR valve 42 in the bypass passage 50.

[0041] On the other hand, if the EGR differential pressure is below the second threshold (i.e., the EGR differential pressure is near zero), it is determined that there is a leak due to pipe disconnection or the like at the connection point of the bypass passage 50 with the third passage 60 and the upstream region A2 (see Figure 1) above this connection point, or that the solenoid valve 61 is stuck in the closed position.

[0042] [1-5. Action and Effects] As described above, the internal combustion engine 1 and its fault detection device 6 according to this embodiment include a third passage 60 connecting the intake passage 20 downstream of the throttle valve 26 to the first passage 50a, the second passage 50b, or the EGR passage 40, and a valve (solenoid valve 61) provided in the third passage 60. Therefore, when the fuel of the internal combustion engine 1 is cut off, the solenoid valve 61 is opened, causing the negative pressure downstream of the throttle valve 26 to act on the differential pressure sensor 51, and fault detection can be performed based on the EGR differential pressure obtained from the differential pressure sensor 51.

[0043] Specifically, by comparing the EGR differential pressure obtained with the solenoid valve 61 in the open state with a first threshold, if the EGR differential pressure is less than the first threshold, it can be determined that there is a fault in the EGR passage 40 or its associated components (bypass passage 50, EGR valve 42, third passage 60, or solenoid valve 61). Therefore, with a simple configuration, fault detection, including detachment of piping constituting the bypass passage 50 equipped with the differential pressure sensor 51, can be performed.

[0044] In the internal combustion engine 1 and its fault detection device 6 according to this embodiment, the third passage 60 connects the part of the intake passage 20 directly downstream of the throttle valve 26 to the second passage 50b. As a result, negative pressure acts on the downstream part of the throttle valve 26 downstream of the differential pressure sensor 51, and a differential pressure corresponding to the action of this negative pressure is generated between the upstream and downstream parts of the throttle valve 26, thereby enabling more accurate fault detection.

[0045] Furthermore, a second threshold can be set, and the EGR differential pressure can be compared with this second threshold to classify (determine) the type of failure. Specifically, if the EGR differential pressure obtained with the solenoid valve 61 open is equal to or greater than the second threshold, it can be determined that there is a leak in the downstream region A1 due to pipe disconnection or the like. On the other hand, if the EGR differential pressure is less than the second threshold, it can be determined that there is a leak in the upstream region A2 due to pipe disconnection or the like, or that the solenoid valve 61 is stuck in the closed position.

[0046] [2. Second Embodiment] [2-1. Structure] Next, the configuration of the intake and exhaust system of the internal combustion engine 1A according to the second embodiment will be described with reference to the schematic configuration diagram in Figure 4. The internal combustion engine 1A of this embodiment differs from the internal combustion engine 1 of the first embodiment in that the connection destination of the third passage 60A is different, but the other configurations are the same as in the first embodiment. Hereinafter, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted. In this embodiment, as in the first embodiment, the internal combustion engine 1 is assumed to be mounted on a vehicle.

[0047] In this embodiment, the third passage 60A is connected to the downstream side of the throttle valve 26 in the intake passage 20 and to the downstream side of the point where the second passage 50b is connected in the EGR passage 40. Furthermore, the fault detection device 6A in this embodiment includes a control device 7 similar to that in the first embodiment, and the control device 7 is provided with a fault detection unit 71A that determines a fault in the EGR device 4. In other words, the fault detection device 6A of the internal combustion engine 1A according to this embodiment includes the internal combustion engine 1A and the fault detection unit 71A. Note that a dedicated control unit (ECU) may be used for the fault detection unit 71A.

[0048] The fault detection device 6A uses the differential pressure sensor 51 equipped on the EGR device 4, the third passage 60A, and the solenoid valve 61 equipped on the third passage 60A to determine the fault. However, in this embodiment, the position of the connection part on one end of the third passage 60A is different from that of the first embodiment, and as a result, there are differences in the determination of the fault type.

[0049] The fault determination unit 71A performs fault determination when the fuel supply to the internal combustion engine 1A is cut off, by opening the solenoid valve 61 of the third passage 60A, and based on the EGR differential pressure detected by the differential pressure sensor 51 at the time of opening. In other words, in this embodiment as well, when the solenoid valve 61 is opened (fault determination time), the fault determination unit 71A determines that the system is "normal" or "no fault" if the EGR differential pressure is above the first threshold, and determines that the system is "abnormal" or "fault present" if the EGR differential pressure falls below the first threshold. The determination principle is the same as in the first embodiment.

[0050] However, in the first embodiment, since the third passage 60A is connected to the middle of the second passage 50b, it was possible to classify failures in the downstream region A1 and the upstream region A2 from the connection point between the second passage 50b and the third passage 60A. In this embodiment, however, since one end of the third passage 60A is connected to the downstream side of the point where the second passage 50b is connected in the EGR passage 40, such classification is not possible.

[0051] [2-2. Mechanism of Action and Effects] In the internal combustion engine 1A and its fault detection device 6A according to this embodiment, one end of the third passage 60A is connected to the downstream side of the connection point of the second passage 50b in the EGR passage 40. Therefore, it is possible to determine if there is a fault in either the solenoid valve 61 or the bypass passage 50. In other words, although it is not possible to specifically identify a detachment of the bypass passage 50 piping as in the first embodiment, it is possible to determine, for example, whether there is a leak in the bypass passage 50 due to a detachment of the piping, whether the solenoid valve 61 is stuck closed, or whether there is an abnormality in the EGR valve 42 itself. Thus, it becomes possible to perform fault detection, including detachment of piping constituting the bypass passage 50 equipped with a differential pressure sensor 51, with a simple configuration.

[0052] [3. Third Embodiment] [3-1. Structure] Finally, with reference to the schematic diagram in Figure 5, the configuration of the intake and exhaust system of the internal combustion engine 1B according to the third embodiment will be described. The internal combustion engine 1B of this embodiment differs from the internal combustion engine 1 of the first embodiment in that the connection destination of the third passage 60B is different, but the other configurations are the same as in the first embodiment. Hereinafter, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted. In this embodiment, as in the first embodiment, the internal combustion engine is assumed to be mounted on a vehicle.

[0053] In this embodiment, the third passage 60B is connected to the intake passage 20 downstream of the throttle valve 26 and to the first passage 50a. Furthermore, the fault detection device 6B in this embodiment includes a control device 7 similar to that in the first embodiment, and the control device 7 is provided with a fault detection unit 71B that determines a fault in the EGR device 4. In other words, the fault detection device 6B of the internal combustion engine 1B according to this embodiment includes the internal combustion engine 1B and the fault detection unit 71B. Note that a dedicated control unit (ECU) may be used for the fault detection unit 71B.

[0054] The fault detection device 6B uses the differential pressure sensor 51 installed in the EGR device 4, the third passage 60B, and the solenoid valve 61 installed in the third passage 60B to determine the fault. The failures to be determined here include disconnections of the connections of the piping constituting the bypass passage 50, which is connected to both ends of the EGR passage 40, and failures of the differential pressure sensor 51 provided in the bypass passage 50. However, in this embodiment, the connection at one end of the third passage 60B is different from that in the first and second embodiments, and as a result, there are differences in how the failure type is determined.

[0055] The fault determination unit 71B performs fault determination when the fuel supply to the internal combustion engine 1B is cut off, by opening the solenoid valve 61 of the third passage 60B, and based on the EGR differential pressure detected by the differential pressure sensor 51 at the time of opening. In other words, in this embodiment as well, when the solenoid valve 61 is opened (fault determination time), the fault determination unit 71B determines that the system is "normal" or "no fault" if the EGR differential pressure is above the first threshold, and determines that the system is "abnormal" or "fault present" if the EGR differential pressure falls below the first threshold.

[0056] In this embodiment, the determination principle is the same as in the first and second embodiments. However, in this embodiment, when the solenoid valve 61 is opened during fuel cut-off, the downstream side of the throttle valve 26 and the first passage 50a are connected, and the negative pressure downstream of the throttle valve 26 is introduced into the first passage 50a. As a result, while the second passage 50b is at approximately atmospheric pressure, the first passage 50a becomes negative, and a differential pressure opposite to that in the first and second embodiments is generated. In other words, the EGR differential pressure (= pressure upstream of the EGR valve 42 - pressure downstream of the EGR valve 42) becomes a negative value.

[0057] [3-2. Action and Effects] In the internal combustion engine 1B and its fault detection device 6B according to this embodiment, one end of the third passage 60B is connected to the first passage 50a. Therefore, when the solenoid valve 61 is opened during fuel cut-off, if the value detected by the differential pressure sensor 51 is negative, it can be determined to be "normal".

[0058] On the other hand, when the solenoid valve 61 is opened during fuel cut-off, if the value detected by the differential pressure sensor 51 is negative but its absolute value is smaller than a preset third threshold, it can be determined to be "abnormal." The third threshold can be preset based on the EGR differential pressure under normal conditions.

[0059] In the case of an abnormality detection, if the value detected by the differential pressure sensor 51 is negative but its absolute value is smaller than the third threshold, it can be inferred that sufficient negative pressure is not acting on the upstream side of the differential pressure sensor 51. It can be assumed that the piping of the bypass passage 50 has become detached at the connection point with the bypass passage 50 (the part connected to the EGR passage 40 downstream of the EGR cooler 41 and upstream of the EGR valve 42). An abnormality of the EGR valve 42 is also a possibility. Therefore, it becomes possible to perform fault detection, including detachment failures of the piping constituting the bypass passage 50 equipped with the differential pressure sensor 51, with a simple configuration.

[0060] In particular, when an EGR cooler 41 is provided as in this embodiment, the third passage 60B is configured to connect the intake passage 20 downstream of the throttle valve 26 with the bypass passage 50 or the EGR passage 40 downstream of the EGR cooler 41 and upstream of the differential pressure sensor 51. As a result, the EGR cooler 41 acts as a wall partitioning the downstream space, and the negative pressure from the downstream part of the throttle valve 26 effectively acts on the upstream side of the differential pressure sensor 51. Therefore, the accuracy of fault detection can be improved.

[0061] [4. Others] The configurations of the internal combustion engines 1, 1A, and 1B described above are examples and are not limited to those described above. For example, the internal combustion engines 1, 1A, and 1B in each of the above embodiments are equipped with a turbocharger 22, but this is not essential. Furthermore, while the EGR device 4 in each of the above embodiments includes an EGR cooler 41, this is not essential. In addition, the air cleaner 21 and intercooler 25 are also not essential.

[0062] However, as in the third embodiment, when one end of the third passage 60B is connected to the first passage 50a between the EGR cooler 41 and the differential pressure sensor 51, the EGR cooler 41 acts like a wall that partitions the space where negative pressure acts, thereby improving the accuracy of fault detection using negative pressure. Therefore, depending on the connection method of the third passage 60B, it is effective to equip the EGR cooler 41.

[0063] Furthermore, although not mentioned in the fault detection devices 6, 6A, and 6B of the above embodiments, if the abnormality detection of the differential pressure sensor 51 and the open / stuck detection of the solenoid valve 61 are performed by other methods, and fault detection is performed by the fault detection devices 6, 6A, and 6B assuming that there is no abnormality in the differential pressure sensor 51 and that there is no open / stuck detection of the solenoid valve 61, then a detachment fault in the piping constituting the bypass passage 50 can be detected with high accuracy.

[0064] Furthermore, the connection points of the third passages 60, 60A, and 60B on the intake passage 20 side are limited to the downstream side of the throttle valve 26 of the intake passage 20. However, the connection points of the third passages 60, 60A, and 60B on the EGR passage 40 side can be any downstream of the EGR cooler 41 if one is present, and if there is no EGR cooler 41, they can be either upstream or downstream of the EGR valve 42 in the EGR passage 40, or upstream or downstream of the differential pressure sensor 51 in the third passage 60. The internal combustion engines 1, 1A, and 1B applicable to each of the above embodiments may also be diesel engines. However, even in the case of a diesel engine, a throttle valve must be provided in the intake passage. [Explanation of Symbols]

[0065] 1,1A,1B Internal Combustion Engine 4. Exhaust gas recirculation (EGR) system 6,6A,6B Failure determination device 7 Control device 20 Intake passage 26 Throttle valve 30 Exhaust passage 40 Exhaust recirculation passage (EGR passage) 41 Exhaust Recirculation Cooler (EGR Cooler) 42 Exhaust Recirculation Valve (EGR Valve) 50 Bypass passage 50a First aisle 50b Second aisle 51 Differential pressure sensor 60,60A,60B Third aisle 61 Solenoid valve (valve) 71,71A,71B Failure determination section

Claims

1. A fault detection device for an internal combustion engine comprising an intake passage, a throttle valve provided in the intake passage, and an exhaust passage, The aforementioned internal combustion engine includes: An exhaust recirculation device comprising: an exhaust recirculation passage connecting the upstream side of the throttle valve in the intake passage to the exhaust passage; an exhaust recirculation valve provided in the exhaust recirculation passage; a first passage extending from upstream of the exhaust recirculation valve in the exhaust recirculation passage; a second passage extending from downstream of the exhaust recirculation valve; and a differential pressure sensor provided between the first passage and the second passage; A third passage connecting the intake passage downstream of the throttle valve to the first passage, the second passage, or the exhaust return passage, A valve is provided in the third passage, The fault detection device is The system includes a fault determination unit that determines a fault in the exhaust gas recirculation passage and its auxiliary members, The fault determination unit opens the valve when there is negative pressure downstream of the throttle valve in the intake passage, and determines that there is a fault in either the exhaust recirculation passage or the auxiliary member if the differential pressure detected by the differential pressure sensor at the time of opening is less than a preset first threshold. A device for determining the failure of an internal combustion engine, characterized by the above features.

2. The exhaust gas recirculation device has an exhaust gas recirculation cooler provided in the exhaust gas recirculation passage, The exhaust gas return valve is provided downstream of the exhaust gas return cooler in the exhaust gas return passage. The first passage extends from the side downstream of the exhaust gas recirculation cooler and upstream of the exhaust gas recirculation valve in the exhaust gas recirculation passage. The third passage connects the intake passage downstream of the throttle valve and the second passage or the exhaust recirculation passage downstream of the exhaust recirculation cooler. A fault detection device for an internal combustion engine according to claim 1, characterized in that...

3. The third passage connects the intake passage downstream of the throttle valve to the second passage. A fault detection device for an internal combustion engine according to claim 1, characterized in that...

4. The fault determination unit compares the differential pressure detected by the differential pressure sensor when the opening is performed with the first threshold and a second threshold that is smaller than the first threshold, and if the differential pressure is less than the first threshold and greater than or equal to the second threshold, it determines that there is a possibility that the exhaust return passage side is faulty more than the connection between the first passage and the third passage. If the differential pressure is less than the second threshold, it is determined that there is a possibility that the differential pressure sensor is malfunctioning rather than the connection part. A fault detection device for an internal combustion engine according to claim 1, characterized in that...

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