JP2006299895A - EGR device for internal combustion engine - Google Patents

Abstract

An EGR device for an internal combustion engine is provided that can appropriately perform abnormality determination of a bypass valve without adding a dedicated sensor or the like for abnormality determination.
An EGR passage, an EGR valve provided in the EGR passage, an EGR cooler that cools EGR gas, a bypass passage that bypasses the EGR cooler, and a bypass that adjusts the flow rate ratio of the EGR gas. A valve 13, a bypass valve driving means 13 a that drives the bypass valve 13, an intake throttle valve 8, a pressure sensor 33 that detects a pressure PBA of the intake system downstream of the intake throttle valve 8, and an intake throttle valve 8. Intake system pressures P2, P1, respectively detected when the throttle valve and the EGR valve 10 are opened to a predetermined opening degree and the bypass valve drive means drives the bypass valve 13 to open and close. Bypass valve abnormality determining means 2 for determining abnormality of the bypass valve 13 using ΔPBA as a parameter.
[Selection] Figure 2

Description

  The present invention relates to an EGR device for an internal combustion engine that recirculates a part of exhaust gas discharged from the internal combustion engine as EGR gas to an intake system.

  As a conventional EGR device for this type of internal combustion engine, for example, one disclosed in Patent Document 1 is known. In this EGR device, an EGR cooler that cools EGR gas and a bypass passage that bypasses the EGR cooler are provided in an EGR passage that connects the exhaust pipe and the intake pipe. A bypass valve for adjusting the flow rate ratio of EGR gas flowing through these passages is provided at a branch portion between the EGR passage and the bypass passage. The EGR passage is provided with an EGR valve that adjusts the amount of EGR gas downstream of the junction with the bypass passage. The intake pipe is provided with an air cleaner, an air flow meter for detecting the intake air amount, and an intake throttle valve for adjusting the intake air amount in order from the upstream side.

  In this EGR device, the abnormality determination of the bypass valve is performed as follows during the deceleration operation of the internal combustion engine. First, the intake throttle valve and the EGR valve are both controlled to be fully open, and the bypass valve is controlled to be fully open, thereby closing the EGR passage and opening the bypass passage. As a result, the EGR gas recirculates to the intake pipe via the bypass passage, and the detected value of the air flow meter at this time is obtained as the actual intake air amount Gaop when fully opened. Next, by controlling the bypass valve to a fully closed state, the EGR passage is opened and the bypass passage is shut off. As a result, the EGR gas is cooled by the EGR cooler and then recirculated to the intake pipe, and the detected value of the air flow meter at this time is obtained as a fully closed actual intake air amount Gacl.

  Further, according to the rotational speed NE of the internal combustion engine, the intake air amount when the bypass valve is fully open and fully closed when the bypass valve is normal, the normal fully open intake air amount Baseop and the normal fully closed intake air amount Each is calculated as Basel. The fully opened actual intake air amount Gaop and the fully closed actual intake air amount Gacl are different from each other, and the fully opened actual intake air amount Gaop, the normal fully opened intake air amount Baseop, and the fully closed actual intake air amount Gacl are normal. When the time fully closed intake air amount Bascl is substantially equal to each other, it is determined that the bypass valve is normal, and in other cases, the bypass valve is fixed in any of the fully open, fully closed, or intermediate position, It is determined that an abnormality has occurred.

  However, the amount of air actually sucked into the intake pipe varies depending not only on the amount of EGR gas but also on the clogging of the air cleaner. On the other hand, in the conventional EGR device, the abnormality determination of the bypass valve is executed based on the fully opened actual intake air amount Gaop and the fully closed actual intake air amount Gacl. For this reason, for example, although the bypass valve is normal, the actual intake air amount Gaop when fully opened may become equal to the actual intake air amount Gacl when fully closed due to the influence of the clogging of the air cleaner described above. In this case, it is erroneously determined that an abnormality has occurred in the bypass valve. On the contrary, the actual intake air amount Gaop when fully opened may differ from the actual intake air amount Gacl when fully closed despite the occurrence of an abnormality in the bypass valve. In this case, the bypass valve is normal. It is misjudged that it is.

  Further, in this EGR device, the abnormality determination of the bypass valve is executed in a state where the intake throttle valve is fully opened during the deceleration operation of the internal combustion engine. For this reason, when a catalyst is provided in the exhaust pipe, the catalyst is cooled by a large amount of air sucked through the intake throttle valve, leading to deterioration of emissions.

  Further, as another method for determining the abnormality of the bypass valve, for example, it is conceivable to directly detect the open / closed state of the bypass valve with a sensor or a switch. In that case, a dedicated sensor for determining the abnormality is considered. Etc. need to be added, which increases the manufacturing cost. In addition, since it is necessary to make an abnormality determination for the added sensor or the like, the determination becomes complicated.

  The present invention has been made to solve such a problem, and it is possible to appropriately determine the abnormality of the bypass valve without adding a dedicated sensor or the like for determining the abnormality. An object is to provide an apparatus.

Japanese Patent Laid-Open No. 2003-247459

  In order to achieve this object, the invention according to claim 1 is configured such that a part of the exhaust gas discharged from the internal combustion engine 3 is used as EGR gas in the intake system (the intake pipe 4 in the embodiment (hereinafter the same in this section)). An EGR device 1 for an internal combustion engine 3 for recirculation, which is provided in an EGR passage 9 for recirculating EGR gas, an EGR passage 9, an EGR valve 10 for adjusting the amount of EGR gas, and an EGR passage 9 The EGR cooler 11 for cooling the EGR gas flowing through the EGR passage 9, the bypass passage 12 that branches from the upstream side of the EGR cooler 11 of the EGR passage 9, bypasses the EGR cooler 11, and the EGR passage 9 and the bypass A bypass valve 13 for adjusting the flow rate ratio of the EGR gas flowing through the passage 12 and a bypass valve driving means (bypass valve actuator) for driving the bypass valve 13 And an intake throttle valve 8 provided in the intake system for adjusting the intake air amount QA, and arranged downstream of the intake throttle valve 8 to detect the pressure of the intake system (intake pressure PBA). Driven by the bypass valve driving means to open and close the bypass valve 13 with the pressure sensor (intake pressure sensor 33) and the intake throttle valve 8 being throttled and the EGR valve 10 being opened to a predetermined opening degree. Bypass valve abnormality determining means (ECU2, ECU2) for determining abnormality of the bypass valve 13 using as parameters the intake system pressure (full opening pressure P2, total closing pressure P1 and intake pressure change amount ΔPBA) detected by the pressure sensor when Steps 25, 26, and 28) of FIG.

  According to the EGR device of the internal combustion engine, the amount of EGR gas recirculated to the intake system is adjusted by the EGR valve provided in the EGR passage, and the bypass valve is driven by the bypass valve driving means, so that the EGR passage and the bypass The flow rate ratio of the EGR gas flowing through the passage is adjusted. When the EGR gas flows through the EGR passage, it passes through the EGR cooler provided in the EGR passage and then returns to the intake system. When the EGR gas flows through the bypass passage, it returns to the intake system without passing through the EGR cooler. . An intake throttle valve is provided in the intake system, and a pressure sensor for detecting the pressure of the intake system is provided downstream of the intake throttle valve. Then, the bypass valve abnormality determining means throttles the intake throttle valve, and when the EGR valve is opened to a predetermined opening, the bypass valve driving means drives the bypass valve to open and close the pressure. Abnormality of the bypass valve is determined using the pressure of the intake system detected by the sensor as a parameter.

  According to the above configuration, when the bypass valve is closed, when EGR gas passes through the EGR cooler, pressure loss occurs due to the ventilation resistance of the EGR cooler, so the pressure in the intake system becomes relatively small. On the other hand, when the bypass valve is opened, the EGR gas does not pass through the EGR cooler, so the pressure loss is reduced and the pressure in the intake system is increased. For this reason, if the bypass valve is normal, the pressure of the intake system changes within a predetermined range according to the opening / closing drive of the bypass valve. According to the present invention, the abnormality of the bypass valve is determined using the pressure of the intake system when the bypass valve is driven by the bypass valve driving means as a parameter. Accordingly, when the pressure in the intake system does not change within a predetermined range, it can be determined that there is an abnormality.

  In addition, since the abnormality determination is performed with the intake throttle valve throttled, the bypass valve opening / closing drive is performed while eliminating the influence on the intake system pressure from the upstream side of the intake throttle valve, for example, the influence of clogging of the air cleaner. The abnormality determination can be performed with high accuracy using the change in the pressure of the intake system associated with the parameter as a parameter. Further, the intake system negative pressure is increased by restricting the intake throttle valve. For this reason, since the change in the intake pressure accompanying the opening / closing drive of the bypass valve is large and appears clearly, abnormality determination can be performed accurately. On the other hand, when the intake throttle valve is fully opened as in the conventional EGR device, the change in the intake pressure accompanying the opening / closing drive of the bypass valve is extremely small, so that the abnormality determination cannot be performed accurately. Further, as a pressure sensor, for example, an existing pressure sensor that is usually provided for controlling an internal combustion engine can be used, and thus a dedicated sensor or the like for abnormality determination needs to be added. Therefore, the manufacturing cost can be reduced.

  According to a second aspect of the present invention, in the EGR device 1 for the internal combustion engine 3 according to the first aspect, the deceleration operation determining means (ECU2, step 1 of FIG. 2) for determining whether or not the internal combustion engine 3 is performing the deceleration operation. ), And the bypass valve abnormality determining means executes the abnormality determination when it is determined that the internal combustion engine 3 is decelerating.

  According to this configuration, the abnormality determination of the bypass valve is executed during the deceleration operation of the internal combustion engine, so that it is possible to reliably eliminate the influence on the pressure due to the change in the temperature and amount of the EGR gas accompanying the combustion. The abnormality determination can be performed with higher accuracy by using the pressure change of the intake system accompanying the opening / closing drive of as a parameter. Even if the abnormality determination is executed during the deceleration operation in this way, the intake throttle valve is throttled, so that the inflow of cold air to the exhaust system can be suppressed. Therefore, even when a catalyst is provided in the exhaust system, it is possible to suppress the cooling of the catalyst, thereby preventing the emission from deteriorating.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an EGR device 1 according to an embodiment of the present invention and an internal combustion engine to which the EGR device 1 is applied. The internal combustion engine (hereinafter referred to as “engine”) 3 is, for example, a four-cylinder (only one is shown) diesel engine mounted on a vehicle (not shown).

  A combustion chamber 3c is formed between the piston 3a of the engine 3 and the cylinder head 3b. An intake pipe 4 (intake system) and an exhaust pipe 5 are connected to the cylinder head 3b, and a fuel injection valve (hereinafter referred to as “injector”) 6 is attached so as to face the combustion chamber 3c.

  The injector 6 is disposed at the center of the top wall of the combustion chamber 3c, and is connected in turn to a high-pressure pump and a fuel tank (both not shown) via a common rail. The fuel injection amount and the injection timing that are the valve opening time of the injector 6 are controlled by a drive signal from the ECU 2.

  A magnet rotor 30a is attached to the crankshaft 3d of the engine 3, and the crank angle sensor 30 is constituted by the magnet rotor 30a and the MRE pickup 30b. The crank angle sensor 30 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3d rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3a of each cylinder is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the 4-cylinder type, every crank angle of 180 °. Is output.

  The intake pipe 4 is provided with a water-cooled intercooler 7 and an intake throttle valve 8 for adjusting the intake air amount in order from the upstream side. The intercooler 7 cools the intake air when the temperature of the intake air rises due to a supercharging operation of a supercharging device (not shown). The intake throttle valve 8 is connected to an actuator 8a made of, for example, a DC motor. The opening degree of the intake throttle valve 8 is controlled by controlling the duty ratio of the current supplied to the actuator 8a by the ECU 2.

  The intake pipe 4 is provided with an air flow sensor 31 upstream of the intercooler 7 and an intake air temperature sensor 32 and an intake pressure sensor 33 (pressure sensor) downstream of the intake throttle valve 8. . The air flow sensor 31 detects the intake air amount QA, the intake air temperature sensor 32 detects the intake air temperature (hereinafter referred to as “intake air temperature”) TA, and the intake air pressure sensor 33 absolutely calculates the intake air pressure PBA (intake system pressure). The detected signals are output to the ECU 2.

  An EGR passage 9 is connected between the intake pipe 4 and the exhaust pipe 5. The EGR passage 9 is connected so as to connect the exhaust pipe 5 and the intake throttle valve 8 downstream of the intake pipe 4. A part of the exhaust gas of the engine 3 is recirculated to the intake pipe 4 as EGR gas through the EGR passage 9, thereby reducing the combustion temperature in the combustion chamber 3 c, thereby reducing NOx in the exhaust gas. .

  The EGR passage 9 is provided with an EGR valve 10 and an EGR cooler 11 for cooling the EGR gas in order from the upstream side. The EGR valve 10 is composed of a linear electromagnetic valve, and the amount of recirculation of EGR gas (hereinafter referred to as “EGR amount”) is controlled by controlling the valve lift amount with a duty-controlled drive signal from the ECU 2. Be controlled. The EGR cooler 11 is a water-cooled type that uses the cooling water of the engine 3.

  The EGR passage 9 is provided with a bypass passage 12. The bypass passage 12 has one end branched from the EGR valve 10 of the EGR passage 9 and the EGR cooler 11, and the other end joined to the downstream side of the EGR cooler 11 of the EGR passage 9. 11 is bypassed. Further, a bypass valve 13 is provided at a branch portion between the EGR passage 9 and the bypass passage 12, and a bypass valve actuator 13a (bypass valve driving means) for driving the bypass valve 13 is connected to the bypass valve 13. . The opening degree of the bypass valve 13 is variably controlled between the fully closed opening degree and the fully open opening degree via the bypass valve actuator 13a by a duty-controlled drive signal from the ECU 2, and thereby the EGR passage 9 and The flow rate ratio of EGR gas flowing through the bypass passage 12 is adjusted.

  By the control of the bypass valve 13 described above, when the EGR gas is passed through the EGR passage 9, it is cooled by the EGR cooler 11 and then passed through the bypass passage 12 without being cooled. It returns to the intake pipe 4.

  Further, a catalyst device 14 is provided on the exhaust pipe 5 downstream of the EGR passage 9. The catalyst device 14 is a combination of a three-way catalyst and a NOx catalyst (both not shown). The three-way catalyst is a high-temperature active state, and the exhaust gas can be contained in exhaust gas under a stoichiometric atmosphere. Exhaust gas is purified by oxidizing HC and CO and reducing NOx. On the other hand, when the oxygen concentration is high, the NOx catalyst purifies the exhaust gas by capturing NOx in the exhaust gas and reducing the captured NOx.

  Further, the ECU 2 receives from the water temperature sensor 34 a detection signal representing the temperature (hereinafter referred to as “engine water temperature”) TW of the coolant circulating in the cylinder block (not shown) of the engine 3 from the accelerator opening sensor 35. , Detection signals representing the amount of operation of an accelerator pedal (not shown) (hereinafter referred to as “accelerator opening AP”) are output.

  The ECU 2 (bypass valve abnormality determination means and deceleration operation determination means) is composed of a microcomputer comprising an I / O interface, CPU, RAM, ROM and the like. The detection signals from the various sensors 30 to 35 described above are each input to the CPU after A / D conversion and shaping by the I / O interface.

  In response to these input signals, the CPU determines the operating state of the engine 3 in accordance with a control program stored in the ROM and the like, and determines the EGR valve 10 and the bypass valve actuator 13a of the bypass valve 13 according to the determined operating state. By outputting the drive signal, the EGR amount and the flow rate ratio of the EGR gas flowing through the EGR passage 9 and the bypass passage 12 are respectively controlled, and an abnormality determination process for the bypass valve 13 is executed.

  2 and 3 show a flowchart of the abnormality determination process for the bypass valve 13. This process is executed every predetermined time. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), it is determined whether or not the engine 3 is decelerating. Specifically, when both the fuel injection amount of the injector 6 and the accelerator opening AP are 0, it is determined that the engine 3 is in a decelerating operation. If the determination result is NO and the engine 3 is not decelerating, the present process is terminated without performing abnormality determination. As described above, the abnormality determination is performed on condition that the engine 3 is in a decelerating operation.

  On the other hand, if the determination result in step 1 is YES and the engine 3 is in a decelerating operation, it is determined whether or not another execution condition for abnormality determination is satisfied (step 2). It is determined that this execution condition is satisfied when the detected engine speed NE, intake air temperature TA, engine water temperature TW, and intake air pressure PBA are all within predetermined ranges. If the determination result is NO and the execution condition is not satisfied, the present process is terminated. On the other hand, when the determination result in Step 2 is YES, it is determined whether or not the in-determination flag F_BPA is “1”, assuming that an abnormality determination execution condition is satisfied (Step 3). This in-determination flag F_BPA is set to “1” during execution of abnormality determination, as will be described later.

  When the determination result of step 3 is NO, that is, when this time corresponds to the first loop after the abnormality determination execution condition is satisfied, the intake throttle valve 8 is controlled to be fully closed (step 4), The EGR valve 10 is controlled to be fully opened (step 5). Then, in order to indicate that the abnormality determination is being performed, the determination flag F_BPA is set to “1” (step 6), and then the process proceeds to step 7. Further, in the second and subsequent loops in which the abnormality determination execution condition is satisfied, the determination result of Step 3 becomes YES by execution of Step 6, and in this case, the process proceeds directly to Step 7.

  In this step 7, it is determined whether or not the fully closed mode end flag F_BP is “1”. If the determination result is NO, it is determined whether or not the bypass valve fully closed flag F_BPC is “1”. (Step 8).

  When the determination result is NO, in step 9, by outputting a drive signal to the bypass valve actuator 13a, the bypass valve 13 is controlled to be fully closed (hereinafter referred to as “fully closed control”) and the bypass valve is fully closed. The flag F_BPC is set to “1”, and the bypass valve full open flag F_BPO is set to “0” (step 10). Next, an up-counting timer (not shown) for measuring the elapsed time (hereinafter referred to as “full closing time”) TBPC after starting the fully closed control of the bypass valve 13 was started (step 11). Then, this process is terminated. In addition, after step 10 is executed, the determination result in step 8 is YES. In this case, the process proceeds to step 12, and the fully closed time TBPC is set to the first predetermined time TREF1 (for example, 5 seconds or less (more It is preferably determined whether it is 1 to 2 seconds)) or more.

  When this determination result is NO and TBPC <TREF1, that is, when the first predetermined time TREF1 has not elapsed after the start of the fully-closed control of the bypass valve 13, it is determined that the intake pressure PBA is not yet stable and this processing is performed. Exit.

  On the other hand, if the determination result in step 12 is YES and TBPC ≧ TREF1, it is determined that the intake pressure PBA has become stable, and the intake pressure PBA at this time is stored as a fully closed pressure P1 (parameter) (step 13). ). Then, in order to indicate that the fully closed mode has ended, the fully closed mode end flag F_BP is set to “1” (step 14), and this processing is ended.

  After step 14 is executed, the determination result of step 7 is YES. In this case, the process proceeds to step 15 to determine whether or not the bypass valve fully open flag F_BPO is “1”. . When the determination result is NO, in step 16, by outputting a drive signal to the bypass valve actuator 13a, the bypass valve 13 is controlled to be fully open (hereinafter referred to as “fully open control”), and the bypass valve fully open flag F_BPO is set. The bypass valve fully closed flag F_BPC is set to “0” at “1” (step 17). Next, an up-counting timer for measuring the elapsed time (hereinafter referred to as “full opening time”) TBPO after starting the full opening control of the bypass valve 13 is started (step 18), and then this processing is ended. .

  After step 17 is executed, the determination result in step 15 is YES. In this case, the process proceeds to step 19 where the fully open time TBPO is a second predetermined time TREF2 (for example, 5 seconds or less (more preferably Is 1 to 2 seconds)) or more.

  If the determination result is NO and TBPO <TREF2, it is determined that the intake pressure PBA is not yet stable, and this process is terminated. On the other hand, if the determination result in step 19 is YES and TBPO ≧ TREF2, it is determined that the intake pressure PBA is in a stable state, and the intake pressure PBA at this time is stored as a fully open pressure P2 (parameter) (step 20). Then, the fully closed mode end flag F_BP is set to “0” (step 21).

  Next, the difference (= P2−P1) between the fully open pressure P2 stored in step 20 and the fully closed pressure P2 stored in step 13 is calculated as an intake pressure change amount ΔPBA (parameter) (step 22). Next, a water temperature correction coefficient KTW and an intake air amount correction coefficient KQA are calculated (step 23). These calculations are performed by searching a table (both not shown) according to the engine water temperature TW and the intake air amount QA. Next, the corrected intake pressure change amount ΔPBAC is calculated by multiplying the intake pressure change amount ΔPBA by the water temperature correction coefficient KTW and the intake air amount correction coefficient KQA (step 24).

  This correction is for converting the intake pressure change amount ΔPBA into values when the engine water temperature TW and the intake air amount QA are in a predetermined reference state. In other words, the higher the engine water temperature TW and the larger the intake air amount QA, the higher the combustion temperature and the higher the EGR gas pressure, so the intake pressure PBA becomes higher. Therefore, in the above table, the water temperature correction coefficient KTW is set to a smaller value as the engine water temperature TW is higher, and the intake air amount correction coefficient KQA is set to a smaller value as the intake air amount QA is larger. ing.

  The correction coefficient corresponding to the above KTW × KQA may be obtained by mapping in advance according to the engine water temperature TW and the intake air amount QA and searching this map according to the actual TW value and QA value. Good.

  Next, it is determined whether or not the corrected intake pressure change amount ΔPBAC calculated in step 24 is greater than or equal to a predetermined reference value PLMT (step 25). This reference value PLMT is the intake pressure between when the bypass valve 13 is fully closed and when it is fully open when the bypass valve 13 is normal and the engine water temperature TW and the intake air amount QA are in a predetermined reference state. It is set based on the amount of change.

  When the determination result is YES and ΔPBAC ≧ PLMT, it is determined that the bypass valve 13 is normal because the intake pressure PBA greatly changes between when the bypass valve 13 is fully closed and when fully opened. The bypass valve abnormality flag F_BPNG is set to “0” (step 26). Then, in order to indicate that the abnormality determination has ended, the determination-in-progress flag F_BPA is set to “0” (step 27), and this processing is ended.

  On the other hand, when the determination result of step 25 is NO and ΔPBAC <PLMT, the intake pressure PBA must change greatly between when the bypass valve 13 is fully closed and when it is fully open, Therefore, it is determined that an abnormality has occurred in the bypass valve 13. Then, in order to indicate that, the bypass valve abnormality flag F_BPNG is set to “1” (step 28), and then the step 27 is executed, and this process is terminated.

  In the above example, the detected intake pressure change amount ΔPBA is corrected according to the engine water temperature TW and the intake air amount QA, while the reference value PLMT to be compared with it is set to a predetermined value. Conversely, the reference value PLMT may be corrected using the intake pressure change amount ΔPBA as it is. In this case, for example, when the bypass valve 13 is normal, a fully closed intake pressure map and a fully open intake pressure map are set in advance according to the engine water temperature TW and the intake air amount QA, and the detected engine water temperature is detected. In accordance with TW and intake air amount QA, intake pressure PBA when fully closed and fully open is obtained from these intake pressure maps, and reference value PLMT may be set based on the difference between the latter and the former. Alternatively, based on the difference between the intake pressure PBA between the fully opened state and the fully closed state as described above, it is set as a map of the reference value PLMT according to the intake air amount QA and the engine water temperature TW. The reference value PLMT may be obtained by searching a map according to the actual QA value and TW value.

  As described above, according to the present embodiment, the intake pressure PBA (fully closed pressure P1) when the bypass valve 13 is fully closed is controlled while the EGR valve 10 is held fully open during the deceleration operation of the engine 3. Next, the intake pressure PBA (full open pressure P2) when the bypass valve 13 is fully opened is obtained, and basically the intake pressure change ΔPBA (= P2−P1), which is the difference between the two, is compared with the reference value PLMT. By doing so, abnormality determination of the bypass valve 13 is performed. If the bypass valve 13 is normal, the EGR gas has a pressure loss due to the ventilation resistance of the EGR cooler when the bypass valve 13 is fully closed, so that the intake pressure PBA is within a predetermined range in accordance with the opening / closing control of the bypass valve 13. Will change. Therefore, when the intake pressure change amount ΔPBA is smaller than the reference value PLMT, it can be determined that an abnormality has occurred in the bypass valve 13.

  Further, by executing the abnormality determination while the engine 3 is decelerating, the influence on the intake pressure PBA due to fluctuations in the temperature and amount of EGR gas due to combustion can be surely eliminated, and the abnormality determination is performed. Is controlled in a fully closed state, the influence on the intake pressure PBA from the upstream side of the intake throttle valve 8, for example, the influence of clogging of the air cleaner can be surely eliminated, so that the abnormality determination is performed with higher accuracy. be able to. Furthermore, since the negative pressure of the intake pipe 4 is increased by controlling the intake throttle valve 8 to be fully closed, the change in the intake pressure PBA between the fully closed control and the fully open control of the bypass valve 13 is large. It will appear clearly, so that the abnormality determination can be performed accurately.

  In addition, since the existing intake pressure sensor 33 for controlling the engine 3 is used, it is not necessary to add a dedicated sensor or the like for abnormality determination, thereby reducing manufacturing costs. Further, since the corrected intake pressure change amount ΔPBAC obtained by correcting the intake pressure change amount ΔPBA in accordance with the engine water temperature TW and the intake air amount QA is compared with the reference value PLMT, the EGR cooler 11 is controlled when the bypass valve 13 is fully closed. The abnormality determination can be performed with higher accuracy while reflecting the degree of pressure loss caused by the ventilation resistance.

  Even if the abnormality determination is executed during the deceleration operation of the engine 3 as described above, the intake throttle valve 8 is controlled to be fully closed, so that the flow of cold air into the exhaust pipe 5 is suppressed, and the catalyst device 14 is controlled. Cooling can be suppressed, thereby preventing emission from deteriorating.

  FIG. 4 shows the first half of a variation of the abnormality determination process for the bypass valve 13. Note that the execution contents of the latter half part following FIG. 4 of this modification are exactly the same as those of FIG. 3 of the embodiment, so the drawings are omitted. As can be seen from the comparison between FIG. 4 and FIG. 2, in the abnormality determination process of the embodiment, the abnormality determination is executed during the deceleration operation of the engine 3, whereas in this process, the abnormality determination is performed in the idle operation of the engine 3. There is a big difference in what to do during or during cruise driving. Therefore, in the following description, the same execution number as the abnormality determination process of the embodiment will be described with the same step number attached to the drawings, and different execution contents will be mainly described.

  In this process, first, in step 31, it is determined whether or not the engine 3 is in idle operation or cruise operation. If the determination result is NO and the engine 3 is not in idle operation or cruise operation, the present process is terminated without executing abnormality determination.

  On the other hand, if the determination result in step 31 is YES and the engine 3 is in idle operation or cruise operation, another execution condition for abnormality determination is satisfied (step 2: YES), and the determination flag F_BPA is “1”. If not (step 3: NO), the intake throttle valve 8 is controlled to a predetermined opening in a half-open state (step 34). This is to ensure combustion of the engine 3 during idle operation or cruise operation. Other execution contents are the same as in the embodiment.

  As described above, according to the modified example, during the idling operation or the cruise operation of the engine 3, the EGR valve 10 is fully opened and the intake throttle valve 8 is held half open, and the bypass valve 13 is fully closed. The abnormality of the bypass valve 13 is determined by comparing the intake pressure change amount ΔPBA (= P2−P1) at the time of full open control with the reference value PLMT. Therefore, the abnormality of the bypass valve 13 can be determined appropriately, and the same effect as the embodiment can be obtained.

  Further, during idle operation or during cruise operation, the operating state of the engine 3 is relatively stable, so that even if the intake throttle valve 8 is held at a predetermined opening degree in a half-open state, the operation is hindered. In addition, since the temperature and amount of EGR gas are relatively stable, abnormality determination can be performed with high accuracy.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the intake pressure (the fully closed pressure P1 and the fully opened pressure P2) when the EGR valve 10 is fully opened and the bypass valve 13 is fully closed and fully opened is used as a parameter. In addition, the intake pressure P0 when the EGR valve 10 is fully closed may be used as a parameter to compare these pressures. In this case, for example, when the bypass valve 13 is malfunctioning in a state where it is fixed to the closed side, the EGR gas passes through the EGR cooler 11 when the EGR valve 10 is fully opened regardless of the opening / closing control of the bypass valve 13. Therefore, when P0> P1≈P2 holds, it is possible to specify that the failure of the bypass valve 13 is a closed-side failure. On the other hand, in the case where the bypass valve 13 is stuck on the open side and fails, the EGR gas bypasses the EGR cooler 11 when the EGR valve 10 is fully opened regardless of the opening / closing control of the bypass valve 13. Therefore, when P0≈P1≈P2 holds, it can be determined that the failure of the bypass valve 13 is an open-side failure.

  In addition, the bypass valve 13 of the embodiment is of a type whose opening degree is variable between fully closed and fully open, but may be of a type that simply opens and closes the bypass passage 12. Furthermore, in the embodiment, when the abnormality is determined, the bypass valve 13 is fully opened and then fully opened, but it goes without saying that the order may be reversed. Further, the abnormality determination according to the present invention can be performed not only when the vehicle is running, but also when the vehicle is being maintained or at the time of factory shipment.

  Furthermore, the present invention can be applied not only to a diesel engine mounted on a vehicle but also to a gasoline engine. In addition, the present invention can be applied to various industrial internal combustion engines including a marine vessel propulsion engine such as an outboard motor having a crankshaft arranged in a vertical direction. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 is a diagram showing a schematic configuration of an EGR device of the present invention and an internal combustion engine to which the EGR device is applied. FIG. It is a flowchart which shows the abnormality determination process of a bypass valve. 3 is a flowchart showing a continuation of FIG. It is a flowchart which shows the modification of the abnormality determination process of a bypass valve.

Explanation of symbols

1 EGR device 2 ECU (bypass valve abnormality determination means and deceleration operation determination means)
3 Engine (Internal combustion engine)
4 Intake pipe (intake system)
8 Intake throttle valve 9 EGR passage 10 EGR valve 11 EGR cooler 12 Bypass passage 13 Bypass valve 13a Bypass valve actuator (bypass valve driving means)
33 Intake pressure sensor (pressure sensor)
PBA Intake pressure (Intake system pressure)
QA Intake air volume P1 Total closing pressure (parameter)
P2 Full open pressure (parameter)
ΔPBA Intake pressure change (parameter)

Claims (2)

An EGR device for an internal combustion engine that recirculates a part of exhaust gas discharged from the internal combustion engine as EGR gas to an intake system,
An EGR passage for refluxing the EGR gas;
An EGR valve provided in the EGR passage for adjusting the amount of EGR gas;
An EGR cooler provided in the EGR passage for cooling EGR gas flowing through the EGR passage;
A bypass passage that branches from an upstream side of the EGR cooler of the EGR passage and bypasses the EGR cooler;
A bypass valve for adjusting a flow ratio of EGR gas flowing through the EGR passage and the bypass passage;
Bypass valve driving means for driving the bypass valve;
An intake throttle valve provided in the intake system for adjusting the amount of intake air;
A pressure sensor that is disposed downstream of the intake throttle valve and detects the pressure of the intake system;
When the intake throttle valve is throttled and the EGR valve is opened to a predetermined opening, the bypass sensor is detected by the pressure sensor when the bypass valve is driven to open and close the bypass valve. Bypass valve abnormality determining means for determining abnormality of the bypass valve, using the pressure of the intake system as a parameter,
An EGR device for an internal combustion engine, comprising: Further comprising a deceleration operation determining means for determining whether or not the internal combustion engine is in a deceleration operation;
2. The EGR device for an internal combustion engine according to claim 1, wherein the bypass valve abnormality determination unit executes the abnormality determination when it is determined that the internal combustion engine is decelerating. 3.

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