Fault judgment device

Abstract

To improve accuracy of a failure determination of an EGR system while maintaining combustion stability of an engine in a failure determination device.SOLUTION: A failure determination device 20 is for an EGR system 6 applied to an engine 1 outputting driving force for causing a generator 2 to generate electric power. The failure determination device includes: first calculation means 21 for calculating engine torque A transmitted from the engine 1 to the generator 2; second calculation means 22 for calculating absorption torque B converted into electric power by the generator 2; and determination means 23 for executing a failure determination of an EGR valve 7 interposed in an exhaust recirculation flow passage of the EGR system 6 by comparing the engine torque A with the absorption torque B.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a failure determination device for an EGR system that is applied to an engine that outputs driving force for causing a generator to generate electricity. [Background technology]

[0002] Conventionally, as an example of a device to which an engine is applied to output a driving force for a generator to generate electricity, a series-parallel hybrid vehicle equipped with an engine, a motor, and a generator is known (see Patent Document 1). In this type of hybrid vehicle, the driving sources are used separately or in combination depending on the driving state. For example, when starting or running at low speed, only the motor with large torque at low revolutions is used (EV mode). On the other hand, when the battery charging rate is low or during acceleration, the vehicle runs using the driving force of the motor while generating electricity in the generator using the driving force of the engine (series mode). Also, during high-speed running when the engine is efficient, the driving force of the engine is used as the main force, and the driving force of the motor is used as a supplementary force (parallel mode, ENG mode).

[0003] Regarding failure judgment of the EGR system applied to the engine as described above, a technique is known to detect sticking of the EGR valve from the change in intake pressure when the EGR valve is opened and closed. For example, it has been proposed to calculate the change in intake pressure when the opening degree of the EGR valve is changed, and to judge that the EGR valve is stuck if the amount of change is smaller than a threshold value (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-088070 A [Patent Document 2] JP 2010-196684 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to improve the accuracy of failure judgment based on the change in intake pressure, it is necessary to recirculate a large amount of EGR gas. Therefore, depending on the operating state of the engine, there is a problem that performing failure judgment may easily reduce combustion stability. In particular, in series-parallel hybrid vehicles, changes in the combustion state of the engine may cause the amount of power generated by the generator to become unstable, which may adversely affect the accuracy of predicting the battery charge amount and the estimation accuracy of the cruising range. It is not limited to the above-mentioned hybrid vehicles, but it is desirable to avoid reducing the stability of engine combustion as much as possible when judging failures in the EGR system.

[0006] One of the objectives of the present invention, which has been devised in light of the above-mentioned problems, is to provide a failure determination device that can improve the accuracy of failure determination of an EGR system while maintaining the combustion stability of the engine. Note that this is not the only objective, but another objective of the present invention is to achieve effects derived from the configurations shown in the "Description of Embodiments" described later, which cannot be obtained by conventional techniques. [Means for solving the problem]

[0007] The present invention can be realized as the following disclosed aspects or application examples. The disclosed failure determination device solves at least a part of the above-mentioned problems. The disclosed failure determination device is A failure determination device for an EGR system applied to an engine that outputs a driving force for causing a generator to generate electricity. When the EGR system is normal, transmitted from the engine to the generator It is estimated that A first calculation means for calculating an engine torque; corresponds to the actual value transmitted from the engine to the generator. A second calculation means for calculating an absorption torque converted into electric power by the generator; 、 a determination means for performing a failure determination of an EGR valve provided in an exhaust gas recirculation passage of the EGR system by comparing the engine torque with the absorption torque; The determination means determines that there is a possibility that the EGR valve has an open malfunction, that is, the EGR valve does not close in response to a close command, when an absolute value of a deviation between the engine torque and the absorption torque is equal to or larger than a predetermined deviation in a state in which the EGR valve is in a fully closed state. Effect of the Invention

[0008] According to the disclosed failure determination device, it is possible to improve the accuracy of failure determination in the EGR system while maintaining the combustion stability of the engine. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram for explaining a failure determination device as an embodiment; [Diagram 2] 4 is a graph for explaining the principle of failure determination. [Diagram 3] 4 is a flowchart (diagnosis flow) relating to failure determination. [Figure 4] 11 is a flowchart (continuation of the diagnosis flow) relating to failure determination. [Diagram 5] 11 is a flowchart (continuation of the diagnosis flow) relating to failure determination. [Figure 6] 6 is a modified example of the flowchart shown in FIG. 5. [Figure 7] 13 is a flowchart (second diagnosis flow) relating to another failure determination. [Figure 8] 13 is a flowchart (continuation of the second diagnosis flow) relating to another failure determination. [Figure 9] 13 is a flowchart (continuation of the second diagnosis flow) relating to another failure determination. [Figure 10] 10 is a modified example of the flowchart shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [1. Vehicle] A failure determination device 20 as an embodiment is applied to a vehicle 10 shown in Fig. 1. The vehicle 10 is a plug-in hybrid vehicle (hybrid vehicle) that can run using an engine 1 and a motor 3 as drive sources. The engine 1 is an internal combustion engine such as a gasoline engine or a diesel engine, and drives a rotating shaft by combusting a mixture of fuel and air in a combustion chamber. The engine 1 is also capable of outputting a driving force for causing a generator 2 to generate electricity and a driving force for running the vehicle 10.

[0011] The generator 2 is a generator that generates electricity using the driving force of the engine 1. The motor 3 is an electric motor / generator that has both the function of driving the drive wheels with the power of the battery 4 and the function of charging the battery 4 with regenerative power generated by utilizing the inertial rotation of the drive wheels. The engine 1, the generator 2, and the motor 3 are connected via a transaxle 5. For example, a speed change gear, a clutch device, etc. are built into the transaxle 5. The operating states of the engine 1, the generator 2, and the motor 3 are selected according to the running state of the vehicle 10 and the operation of the driver, or are used in combination.

[0012] The engine 1 and the generator 2 are connected to the motor 3 and drive wheels via a clutch. The vehicle 10 can select a series mode in which the engine 1 and the generator 2 are disconnected from the motor 3 and drive wheels (the clutch is disengaged) and the vehicle runs. The EV mode is realized by stopping the engine 1 and the generator 2 with the clutch disengaged. Also, by engaging the clutch, the parallel mode or the ENG mode can be realized.

[0013] The power generated by the generator 2 and the motor 3 is charged into the battery 4. The battery 4 is a secondary battery such as a lithium-ion secondary battery or a nickel-metal hydride battery, and can be charged by an external charging facility (external charging). A converter 11 that converts power between direct current and alternating current is connected to the battery 4. The converter 11 has a function of converting AC power supplied from a charging port 12 during external charging into DC power to charge the battery 4, and a function of converting DC power stored in the battery 4 into AC power to supply it to an in-vehicle outlet 13. The in-vehicle outlet 13 can output, for example, AC power of 100 [V] at a frequency of 50 to 60 [Hz]. This allows the battery 4 to be charged using power supplied from a household outlet, and allows general home appliances to be connected to the in-vehicle outlet 13 for use.

[0014] An EGR system 6 is applied to the engine 1. The EGR system 6 is a system that recirculates a portion of the exhaust gas discharged from the cylinders of the engine 1 to the intake system. By applying the EGR system 6 to the engine 1, it becomes possible to reduce the oxygen concentration and combustion temperature in the cylinders, thereby improving fuel efficiency and exhaust gas performance. The EGR system 6 of this embodiment has an EGR valve 7 interposed in an exhaust recirculation passage (EGR passage) that communicates the exhaust system and the intake system. By changing the opening degree of the EGR valve 7, it is possible to adjust the flow rate (EGR amount) of exhaust gas (EGR gas) introduced from the exhaust system to the intake system.

[0015] [2. Failure determination device] The failure determination device 20 is a computer (ECU, Electronic Control Unit) having at least the function of determining a failure of the EGR valve 7. The failure determination device 20 has built-in a processor (central processing unit), memory (main memory), storage device, interface device, etc. (not shown), which are communicably connected to each other via an internal bus. The contents of the determination and control performed by the failure determination device 20 are recorded and saved in the memory as firmware or an application program. When a program is executed, the contents of the program are expanded in the memory space and executed by the processor.

[0016] 1, the engine 1, the generator 2, the motor 3, the battery 4, the EGR valve 7, the engine speed sensor 14, the airflow sensor 15, the generator speed sensor 16, and the current sensor 17 are connected to the failure determination device 20 of this embodiment. The failure determination device 20 determines a failure of the EGR valve 7 based on information transmitted from these various devices. The engine speed sensor 14 is a sensor that detects the engine speed (the number of revolutions per unit time, the rotation speed of the engine 1), and the airflow sensor 15 is a sensor that detects the amount of intake air of the engine 1. The generator speed sensor 16 is a sensor that detects the generator speed (the number of revolutions per unit time, the rotation speed of the generator 2), and the current sensor 17 is a sensor that detects the generated current of the generator 2.

[0017] The failure determination device 20 determines a failure based on two principles. The first principle is that by increasing the EGR amount without fixing the throttle opening, the specific heat ratio in the cylinder changes, and the combustion torque generated by the engine 1 increases. As shown in FIG. 2, the increase rate of the engine torque increases as the EGR rate increases (as the EGR amount increases). Therefore, by observing the change in the absorption torque of the generator 2 when a command is issued to change the opening of the EGR valve 7, the actual fluctuation in the EGR rate can be estimated, and the presence or absence of a failure (close failure or open failure) of the EGR valve 7 can be determined. Note that an open failure means a failure in which the EGR valve 7 does not close in response to a close command, and a close failure means a failure in which the EGR valve 7 does not open in response to an open command. An open failure includes, for example, a failure in which the valve does not close beyond a predetermined opening due to sticking, and a failure in which the valve remains open. Similarly, a close failure includes, for example, a failure in which the valve does not open beyond a predetermined opening due to sticking, and a failure in which the valve remains closed.

[0018] The second principle is that by increasing the EGR amount with the throttle opening fixed, the ratio of fresh air in the intake air decreases, thereby reducing the combustion torque generated in the engine 1. In other words, by observing the change in the absorption torque of the generator 2 when a command is issued to change the opening of the EGR valve 7 with the throttle opening fixed, the actual fluctuation in combustion torque can be estimated and the presence or absence of a malfunction of the EGR valve 7 (close malfunction or open malfunction) can be determined.

[0019] The failure determination device 20 is provided with a first calculation means 21, a second calculation means 22, and a determination means 23. The first calculation means 21 calculates an engine torque A transmitted from the engine 1 to the generator 2 when the generator 2 generates electricity using the driving force of the engine 1. The engine torque A is calculated based on, for example, the engine speed and the intake amount. Note that the method of calculating the engine torque A is not limited to this. For example, it may be calculated based on the vehicle speed, the accelerator opening, etc., or may be calculated taking into account the fuel injection amount and the air-fuel ratio.

[0020] The second calculation means 22 calculates the absorption torque B that is converted into electric power by the generator 2 (i.e., recovered as charging power for the battery 4) when the generator 2 is generating power using the driving force of the engine 1. The absorption torque B is calculated based on, for example, the generator rotation speed and the generated current. Note that the method of calculating the absorption torque B is not limited to this. For example, it may be calculated based on the current value and voltage value charged from the generator 2 to the battery 4, or may be calculated taking into account the generator temperature and the battery temperature.

[0021] The determination means 23 executes a failure determination of the EGR valve 7 by comparing at least the engine torque A and the absorption torque B. The determination means 23 is provided with an initial determination means 24, a first determination means 25, and a second determination means 26. The initial determination means 24 determines whether or not there is a possibility that the EGR valve 7 interposed in the exhaust gas recirculation path of the EGR system 6 has a failure. When the possibility of a failure of the EGR valve 7 is recognized, the first determination means 25 closely examines the possibility and determines whether or not there is a failure of the EGR valve 7. Furthermore, when the first determination means 25 determines that the EGR valve 7 has a failure (is broken), the second determination means 26 determines whether the failure state is an open failure or a closed failure.

[0022] In the initial determination means 24, for example, based on a deviation C which is a value obtained by subtracting the engine torque A from the absorption torque B, the following failure determination is performed. Judgment 1: If the absolute value of the deviation C is equal to or greater than the specified deviation C0, It is determined that the EGR valve 7 may be malfunctioning. Judgment 2: If the absolute value of the deviation C is less than the specified deviation C0, It is determined that the EGR valve 7 is not malfunctioning (normal).

[0023] These failure determinations are performed at least when the engine 1 drives the generator 2 (for example, in the series mode, parallel mode, or ENG mode). Preferably, the failure determinations are performed when the engine 1 starts during external power feeding of the vehicle 10. External power supply means power supply to a home appliance connected to the in-vehicle outlet 13. For example, a hot plate may be connected to the in-vehicle outlet 13 of the vehicle 10 parked at a campsite, and the hot plate may be used with power from the battery 4. In this case, when the charge level of the battery 4 decreases, the engine 1 operates, power generation by the generator 2 starts, and a failure determination is performed.

[0024] When the initial determination means 24 determines that there is a possibility of a malfunction in the EGR valve 7, the first determination means 25 performs a malfunction determination based on the deviation C, for example, as follows. Judgment 3: When the absolute value of the deviation C is equal to or greater than the specified deviation C0 in the fully closed state, It is determined that there is a high possibility that the EGR valve 7 has an open valve malfunction. Judgment 4: When the absolute value of the deviation C is less than the specified deviation C0 in the fully closed state, It is determined that there is a high possibility that the EGR valve 7 has a closed malfunction.

[0025] These failure judgments are preferably made with the ignition timing of the engine 1 retarded compared to when the initial judgment means 24 judges the failure. For example, the ignition timing of the engine 1 is controlled based on an ignition timing map used when the EGR system 6 is not in operation (when EGR is off). In general, the ignition timing of the engine 1 when the EGR system 6 is in operation is controlled to be more advanced compared to when the EGR system 6 is not in operation. Therefore, by setting the ignition timing of the engine 1 with reference to the ignition timing map used when the EGR system 6 is not in operation, the ignition timing of the engine 1 is given a retarded tendency.

[0026] When it is determined that the EGR valve 7 is highly likely to have an open valve malfunction, the second determination means 26 executes a malfunction determination for the EGR valve 7 based on the amount of change in the absorption torque B caused by changing the EGR opening in a stepwise manner. At this time, the throttle opening is held at a constant value and the intake amount of the engine 1 is controlled to be constant. Here, the absorption torque before changing the EGR opening is set to B1, and the absorption torque after changing the EGR opening is set to B2. The second determination means 26 executes the following malfunction determination based on the amount of change D obtained by subtracting B1 from B2. Decision 5: If the absolute value of the change amount D is less than the predetermined change amount D0, It is determined that the EGR valve 7 has an open valve malfunction. Decision 6: If the absolute value of the change amount D is equal to or greater than the predetermined change amount D0, It is determined that the previous judgment was an incorrect judgment (no malfunction).

[0027] On the other hand, when it is determined that the EGR valve 7 is highly likely to have a closed fault, the second determination means 26 outputs an instruction to open the EGR valve 7 to a predetermined opening degree. After that, the second determination means 26 recalculates the deviation C and performs the following fault determination. Judgment 7: If the absolute value of the deviation C is equal to or greater than the specified deviation C0, It is determined that the EGR valve 7 has a closed malfunction. Judgment 8. If the absolute value of the deviation C is less than the predetermined deviation C0, It is determined that the previous judgment was an incorrect judgment (no malfunction).

[0028] As described above, the conditions for judging an open fault in the second judging means 26 (conditions for judgments 5 and 6) are different from the conditions for judging a close fault in the second judging means 26 (conditions for judgments 7 and 8). By using different judgment conditions in this way, the accuracy of judging an open fault and a close fault is improved.

[0029] [3. Flowchart] (A) Flowchart of Figures 3 to 5 3 to 5 are flowcharts (diagnosis flow) relating to the failure determination performed by the failure determination device 20. This flow can be repeatedly executed at a predetermined calculation period inside the failure determination device 20. The operating state (operating point) of the engine 1 for executing this flow is not important, and failure determination can be made independent of the engine speed or the magnitude of the load.

[0030] In step A1, it is determined whether or not the engine 1 has started during external power feeding of the vehicle 10. In addition, in step A2, it is determined whether or not the engine 1 is driving the generator 2 (for example, in a series mode with the clutch disengaged). If any of the conditions is met, the process proceeds to step A3, and if neither of the conditions is met, the process ends (returns). In step A3, the first calculation means 21 calculates the engine torque A, and the second calculation means 22 calculates the absorption torque B. In the following step A4, the determination means 23 calculates the deviation C obtained by subtracting the engine torque A from the absorption torque B.

[0031] In step A5, in the initial determination means 24, the absolute value |C| of the deviation C is compared with a predetermined deviation C0 set in advance. Here, if |C| < C0, the process proceeds to step A6, and it is determined that there is no failure in the EGR valve 7 (EGR system 6), and this flow ends. On the other hand, if |C| ≥ C0, it is determined that there may be some kind of failure, and the process proceeds to step A7, and the failure determination by the first determination means 25 continues.

[0032] In step A7, the ignition timing map for setting the ignition timing of the engine 1 is fixed to the map at the time of EGR off (when the EGR valve 7 is fully closed). In the subsequent step A8, the EGR opening degree is set to 0% (fully closed), and the control command is instructed from the failure determination device 20 to the EGR valve 7. Thereafter, in step A9, the engine torque A is calculated by the first calculation means 21, and the absorption torque B is calculated by the second calculation means 22. In the subsequent step A10, in the determination means 23, the deviation C obtained by subtracting the engine torque A from the absorption torque B is calculated.

[0033] In step A11, in the first determination means 25, the absolute value |C| of the deviation C is compared with the predetermined deviation C0. Here, if |C| < C0, it is determined that there is a high possibility that the EGR valve 7 has a closed failure, and the process proceeds to step A12 shown in FIG. 4. On the other hand, if |C| ≥ C0, it is determined that there is a high possibility that the EGR valve 7 has an open failure, and the process proceeds to step A18 shown in FIG. 5.

[0034] Steps A12 to A17 shown in FIG. 4 are a flow for examining the closed failure of the EGR valve 7. In step A12, the EGR opening degree is set to a predetermined K% (open), and the control command is instructed from the failure determination device 20 to the EGR valve 7. The opening degree set here may be 100% (fully open) or may be less than 100%. Thereafter, in step A13, the engine torque A is calculated by the first calculation means 21, and the absorption torque B is calculated by the second calculation means 22. In the subsequent step A14, in the determination means 23, the deviation C obtained by subtracting the engine torque A from the absorption torque B is calculated.

[0035] In step A15, in the second determination means 26, the absolute value |C| of the deviation C is compared with a predetermined deviation C0. Here, if |C| < C0, the process proceeds to step A16, and the previous determination (the determination in step A11) is canceled on the assumption that it was a false determination (that is, there is no failure), and this flow ends. On the other hand, if |C| ≥ C0, the process proceeds to step A17, and it is determined that the EGR valve 7 is closed and malfunctioning, and this flow ends.

[0036] Steps A18 to A25 shown in FIG. 5 are a flow for examining an open failure of the EGR valve 7. In step A18, the value of the absorption torque B at this time is substituted into B1. In step A19, the throttle opening is fixed (held at a constant value), and the intake air amount of the engine 1 is controlled to be constant. In step A20, similar to step A12, the EGR opening is set to a predetermined K% (open), and its control command is instructed from the failure determination device 20 to the EGR valve 7. The opening set here may be 100% (fully open), or may be an opening smaller than 100%. Also, it does not have to be the same as the instruction value in step A12.

[0037] In step A21, the absorption torque B is calculated by the second calculation means 22, and its value is substituted into B2. In the subsequent step A22, in the determination means 23, the change amount D of the absorption torque B (subtracting B1 from B2) is calculated. In step A23, in the second determination means 26, the absolute value |D| of the change amount D is compared with a predetermined change amount D0. Here, if |D| < D0, the process proceeds to step A24, and it is determined that the EGR valve 7 is open and malfunctioning, and this flow ends. On the other hand, if |D| ≥ D0, the process proceeds to step A25, and the previous determination (the determination in step A11) is canceled on the assumption that it was a false determination (that is, there is no failure), and this flow ends.

[0038] (B) Flowchart of FIG. 6 The flowchart shown in FIG. 6 is a modified example of the flowchart shown in FIG. 5 (with steps A26 to A28 added). In this flowchart, the presence or absence of an opening failure is determined based on the change amount D of the absorption torque B when the EGR opening is gradually opened, and the opening degree of the opening failure is determined.

[0039] The EGR opening set in step A20 of FIG. 6 is not at least 100%, but is, for example, 10%. Thereafter, if |D| < D0 in step A23, the process proceeds to step A24, and it is determined that the EGR valve 7 has an opening failure at an opening of 10%. That is, the opening degree at the time when the condition of step A23 is satisfied (the time when |D| < D0) is determined as the opening degree of the opening failure. On the other hand, if |D| ≥ D0, the process proceeds to step A26, and it is determined whether the EGR opening is fully open (100%). This condition is initially not satisfied, and the process proceeds to step A27.

[0040] In step A27, the value of the absorption torque B at this time is substituted into B1. In the subsequent step A28, the EGR opening is set to be even larger, for example, 20%. Thereafter, in step A21, the value of the absorption torque B is substituted into B2, in step A22, the change amount D of the absorption torque B is calculated, and in step A23, its absolute value |D| is compared with the predetermined change amount D0. Here, if |D| < D0, the process proceeds to step A24, and it is determined that the EGR valve 7 has an opening failure at an opening of 20%.

[0041] On the other hand, if |D| ≥ D0, the EGR opening is gradually opened until it is fully open (100%), and the determination in step A23 is repeated. If the condition of step A23 remains unsatisfied even though the EGR opening is fully open (100%), in step A25, the previous determination (the determination in step A11) is determined to be a false determination (that is, there is no failure), and the determination is cancelled, and this flow ends.

[0042] (C) Flowcharts of FIGS. 7 to 9 7 to 9 are flowcharts (second diagnosis flow) relating to another failure determination. This flow can be repeatedly executed at a predetermined calculation period inside the failure determination device 20. The failure determination in this flow is performed with the throttle opening of the engine 1 fixed, and the operating state (operating point) of the engine 1 is limited.

[0043] In step B1, it is determined whether the engine 1 has started during external power feeding of the vehicle 10. In addition, in step B2, it is determined whether the engine 1 is driving the generator 2. If either of the conditions is satisfied, the process proceeds to step B3, and if neither of the conditions is satisfied, the flow ends. In step B3, it is determined whether the EGR rate is greater than 0% (i.e., the EGR system 6 is in operation). Here, if the EGR system 6 is in operation, the process proceeds to step B4, where the EGR opening is set to 0% (fully closed), and a control command for this is sent from the failure determination device 20 to the EGR valve 7, and then the process proceeds to step B5. In addition, if the EGR system 6 is not in operation, the process proceeds directly to step B5.

[0044] In step B5, the throttle opening is fixed (kept at a constant value) and the intake amount of the engine 1 is controlled to be constant. In step B6, the ignition timing map for setting the ignition timing of the engine 1 is fixed to the map for when EGR is off (when the EGR valve 7 is fully closed). In the following step B7, the second calculation means 22 calculates the absorption torque B, and this value is substituted for B3. In step B8, the EGR opening is set to a predetermined K1% (open), and a control command for this is issued from the failure determination device 20 to the EGR valve 7. The opening K1 set here is larger than 0% (fully closed) and smaller than 100% (fully open).

[0045] In step B9, the absorption torque B is calculated again by the second calculation means 22, and the value is substituted into B4. In step B10, the determination means 23 calculates the change amount D of the absorption torque B (the result of subtracting B3 from B4). In step B11, the first determination means 25 compares the absolute value |D| of the change amount D with a predetermined change amount D0. Here, if |D| < D0, it is determined that the EGR valve 7 is likely to have a closed failure, and the process proceeds to step B12 shown in FIG. 8. On the other hand, if |D| ≥ D0, it is determined that the EGR valve 7 is likely to have an open failure, and the process proceeds to step B18 shown in FIG. 9.

[0046] Steps B12 to B17 shown in FIG. 8 are a flow for inspecting the closed failure of the EGR valve 7. In step B12, the EGR opening is set to 0% (fully closed), and the control command is instructed from the failure determination device 20 to the EGR valve 7. Thereafter, in step B13, the engine torque A is calculated by the first calculation means 21, and the absorption torque B is calculated by the second calculation means 22. In the subsequent step B14, the determination means 23 calculates the deviation C obtained by subtracting the engine torque A from the absorption torque B.

[0047] In step B15, the second determination means 26 compares the absolute value |C| of the deviation C with a predetermined deviation C0. Here, if |C| < C0 (that is, when the engine torque A and the absorption torque B are substantially equal), the process proceeds to step B16, and it is determined that the EGR valve 7 has a closed failure, and this flow ends. On the other hand, if |C| ≥ C0, the process proceeds to step B17, and the previous determination (the determination in step B11) is canceled as a misjudgment (that is, there is no failure), and this flow ends.

[0048] Steps B18 to B23 shown in FIG. 9 are a flow for inspecting an open failure of the EGR valve 7. In step B18, the EGR opening degree is set to a predetermined K2% (open), and its control command is instructed from the failure determination device 20 to the EGR valve 7. The opening degree K2 set here is, for example, a larger opening degree than the opening degree K1 set in step B8. In step B19, the absorption torque B is calculated by the second calculation means 22, and its value is substituted into B5. In the subsequent step B20, the determination means 23 calculates the change amount E of the absorption torque B (the result of subtracting B4 from B5).

[0049] In step B21, the second determination means 26 compares the absolute value |E| of the change amount E with a predetermined change amount E0. Here, if |E| < E0, the process proceeds to step B22, and it is determined that the EGR valve 7 has an open failure, and this flow ends. On the other hand, if |E| ≧ E0, the process proceeds to step B23, and the determination is canceled assuming that the previous determination (the determination in step B11) was a false determination (that is, there is no failure), and this flow ends.

[0050] (D) Flowchart of FIG. 10 The flowchart shown in FIG. 10 is a modified example of the flowchart shown in FIG. 9 (steps B24 to B26 are added). In this flowchart, the presence or absence of an open failure is determined based on the change amount E of the absorption torque B when the EGR opening degree is gradually opened, and the opening degree of the open failure is determined.

[0051] The EGR opening degree set in step B18 of FIG. 10 is larger than the opening degree K1 set in step B8 and is an opening degree that is at least not 100% (for example, 30%). Thereafter, if |E| < E0 in step B21, the process proceeds to step B22, and it is determined that the EGR valve 7 has an open failure at an opening degree of 30%. That is, the opening degree at the time when the condition of step B21 is satisfied (the time when |E| < E0) is determined as the opening degree of the open failure.

[0052] On the one hand, when |E| ≥ E0 in step B21, the process proceeds to step B24, and it is determined whether the EGR opening is fully open (100%). This condition is initially not satisfied, and the process proceeds to step B25. In step B25, the value of the absorption torque B at this time is substituted into B4. In the subsequent step B26, the EGR opening is set to be even larger (for example, to 40%). Thereafter, in step B19, the value of the absorption torque B is substituted into B5, in step B20, the change amount E of the absorption torque B is calculated, and in step B21, its absolute value |E| is compared with the predetermined change amount E0.

[0053] Here, when |E| < E0, the process proceeds to step B22, and it is determined that the EGR valve 7 is open-failed at an opening of 40%. On the other hand, when |E| ≥ E0, the EGR opening is gradually opened until it is fully open (100%), and the determination in step B21 is repeated. If the condition in step B21 remains unsatisfied even though the EGR opening is fully open (100%), the determination in step B23 is cancelled assuming that the previous determination (the determination in step B11) was a false determination (that is, there is no failure), and this flow ends.

[0054] [4. Effects] (1) The failure determination device 20 according to the above embodiment includes a first calculation means 21, a second calculation means 22, and a determination means 23. The first calculation means 21 calculates the engine torque A transmitted from the engine 1 to the generator 2. The second calculation means 22 calculates the absorption torque B that is converted into electric power by the generator 2. The determination means 23 compares the engine torque A and the absorption torque B and executes a failure determination of the EGR valve 7 interposed in the exhaust gas recirculation passage of the EGR system 6. With such a configuration, the failure of the EGR valve 7 can be determined without recirculating a large amount of EGR gas. Therefore, the failure determination accuracy of the EGR system 6 can be improved while maintaining the combustion stability of the engine 1.

[0055] (2) The above-mentioned determination means 23 (first determination means 25) determines that there is a possibility (high possibility) that the EGR valve 7 has an open malfunction when the absolute value |C| of the deviation C between the engine torque A and the absorption torque B is equal to or larger than a predetermined deviation C0 in a state in which the EGR valve 7 is in a fully closed state (No route of step A11 in FIG. 3 and FIGS. 5 and 6). With this configuration, it is possible to accurately detect the possibility of an open malfunction of the EGR valve 7, and it is possible to improve the accuracy of malfunction determination of the EGR system 6.

[0056] (3) The above-mentioned determination means 23 (first determination means 25) determines that there is a possibility (high possibility) that the EGR valve 7 has a closed malfunction when the absolute value |C| of the deviation C between the engine torque A and the absorption torque B is less than a predetermined deviation C0 in a state in which the EGR valve 7 is in a fully closed state (Yes side route of step A11 in FIG. 3 and FIG. 4). With this configuration, it is possible to accurately detect the possibility of a closed malfunction of the EGR valve 7, and it is possible to improve the accuracy of malfunction determination of the EGR system 6.

[0057] (4) When |C|≧C0, the above-mentioned determination means 23 (second determination means 26) executes a failure determination for the EGR valve 7 based on the amount of change D in the absorption torque B caused by changing the EGR opening degree (steps A22, A23 in FIG. 5 and FIG. 6). With this configuration, the presence or absence of an open failure of the EGR valve 7 can be accurately determined, and erroneous detection can be reduced. Therefore, the accuracy of failure determination for the EGR system 6 can be improved.

[0058] (5) When determining whether or not the EGR valve 7 has a malfunction based on the amount of change D in the absorption torque B, the determination means 23 (second determination means 26) changes the EGR opening while maintaining the throttle opening (step A19 in Figs. 5 and 6). With this configuration, the reduction in the combustion torque of the engine 1 caused by an increase in the EGR amount can be accurately grasped. Therefore, the presence or absence of an open malfunction of the EGR valve 7 can be accurately determined, and the accuracy of malfunction determination of the EGR system 6 can be improved.

[0059] (6) When determining whether the EGR valve 7 has an open circuit malfunction based on the amount of change D in the absorption torque B, the determination means 23 (second determination means 26) determines that the EGR valve 7 has an open circuit malfunction if the absolute value |D| of the amount of change D is less than a predetermined amount of change D0 (steps A23 and A24 in FIGS. 5 and 6). With this configuration, it is possible to accurately determine whether the EGR valve 7 has an open circuit malfunction, and it is possible to improve the accuracy of determining a malfunction in the EGR system 6.

[0060] (7) When the above-mentioned determination means 23 (second determination means 26) determines that the EGR valve 7 has a failure based on the amount of change D in the absorption torque B, if the absolute value |D| of the amount of change D is equal to or larger than a predetermined amount of change D0, it cancels the immediately preceding failure determination as an erroneous determination (steps A23, A25 in Figs. 5 and 6). With this configuration, it is possible to accurately determine an erroneous detection of an open failure of the EGR valve 7 (i.e., that the EGR valve 7 is not at fault), and it is possible to improve the accuracy of failure determination for the EGR system 6.

[0061] (8) The above-described failure determination device 20 is applied to a plug-in hybrid vehicle 10 equipped with an engine 1 and a generator 2. Furthermore, the determination means 23 forcibly executes a failure determination for the EGR valve 7 when the engine 1 starts during external power supply to the vehicle 10 (step A1 in FIG. 3). With this configuration, it is possible to determine a failure in the EGR valve 7 without adversely affecting the running state and drivability (the driving operation and the comfort and responsiveness of the ride that the occupants feel in the vehicle 10) of the vehicle 10, and it is possible to improve the accuracy of failure determination for the EGR system 6.

[0062] (9) The engine 1 and generator 2 are mounted on a hybrid vehicle 10 that is connected to the motor 3 and drive wheels via a clutch. The hybrid vehicle 10 can select a series mode in which the engine 1 and generator 2 can be disconnected from the motor 3 and drive wheels to run, and fault diagnosis can be performed during the series mode. In other words, fault diagnosis can be performed while driving the drive wheels with the motor 3 without transmitting the driving force of the engine 1 to the drive wheels. Therefore, even if the operating condition of the engine 1 is changed for fault diagnosis, fault diagnosis can be performed without adversely affecting drivability.

[0063] [5.Other] The above embodiment is merely illustrative, and is not intended to exclude various modifications or application of techniques not specified in the embodiment. Each configuration of the embodiment can be modified in various ways without departing from the spirit of the embodiment. Furthermore, each configuration of the embodiment can be selected or combined as necessary.

[0064] In the above embodiment, the failure determination device 20 applied to a plug-in hybrid vehicle is exemplified, but the application of the present invention is not limited to this type of vehicle 10. If the EGR system 6 is applied to at least the engine 1 that outputs driving force for causing the generator 2 to generate electricity, the same control as in the above embodiment can be applied. Specifically, the present invention can be applied to ships, plants, power generation facilities, etc. in which the generator 2 can be driven by the engine 1 to which the EGR system 6 is applied. Even in these application targets, a failure of the EGR valve 7 can be accurately detected by comparing the engine torque A and the absorption torque B, and the accuracy of failure determination of the EGR system 6 can be improved while maintaining the combustion stability of the engine 1. [Explanation of symbols]

[0065] 1 Engine 2. Generator 3 Motor 4 Battery 5 Transaxle 6. EGR system 7. EGR valve 10 Vehicles (plug-in hybrid vehicles, hybrid vehicles) 11 Converter 12 Charging port 13 Car power outlet 14 Engine speed sensor 15 Airflow Sensor 16 Generator RPM Sensor 17 Current Sensor 20 Failure determination device 21 First calculation means 22 Second calculation means 23 Judgment means 24 Initial determination means 25 First determination means 26 Second determination means A. Engine torque B Absorption torque C deviation C0 specified deviation D. Amount of change D0 specified change amount E change amount E0 specified change amount

Claims

1. A failure determination device for an EGR system applied to an engine that outputs a driving force for causing a generator to generate electricity, comprising: a first calculation means for calculating an engine torque estimated to be transmitted from the engine to the generator when the EGR system is normal; a second calculation means for calculating an absorption torque that corresponds to an actual value transmitted from the engine to the generator and is converted into electric power by the generator; a determination means for performing a failure determination of an EGR valve provided in an exhaust gas recirculation path of the EGR system by comparing the engine torque with the absorption torque; Equipped with When an absolute value of a deviation between the engine torque and the absorption torque is equal to or greater than a predetermined deviation in a state in which the EGR valve is instructed to be fully closed, the determining means determines that there is a possibility that the EGR valve has an open malfunction, that is, the EGR valve does not close in response to a close command. A failure determination device comprising:

2. When an absolute value of a deviation between the engine torque and the absorption torque is less than the predetermined deviation in a state in which the EGR valve is instructed to be fully closed, the determining means determines that there is a possibility that the EGR valve has a closing failure, that is, the EGR valve does not open in response to an opening command.

2. The failure determination device according to claim 1 .

3. When the condition recited in claim 1 is satisfied, the determining means performs a failure determination of the EGR valve based on an amount of change in the absorption torque caused by changing an EGR opening degree.

2. The failure determination device according to claim 1 .

4. The determination means changes the EGR opening while maintaining the throttle opening when making the failure determination as set forth in claim 3.

4. The failure determination device according to claim 3.

5. In the malfunction determination according to claim 4, the determining means determines that the EGR valve has an open malfunction when the absolute value of the amount of change is less than a predetermined amount of change.

5. The failure determination device according to claim 4,

6. In the fault determination as set forth in claim 4, when the absolute value of the amount of change is equal to or greater than a predetermined amount of change, the determining means cancels the fault determination previously performed as an erroneous determination.

6. The failure determination device according to claim 4 or 5.

7. The engine and the generator are mounted on a hybrid vehicle, The determination means forcibly performs a failure determination of the EGR valve when the engine is started during external power supply to the hybrid vehicle. The failure determination device according to any one of claims 1 to 6.

8. the engine and the generator are mounted on a hybrid vehicle connected to a motor and drive wheels via a clutch, the hybrid vehicle is capable of selecting a series mode in which the engine and the generator are separated from the motor and the drive wheels; The determination means executes the failure determination during the series mode. The failure determination device according to any one of claims 1 to 7.

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