Hybrid vehicle control device

Abstract

To suppress wasteful power consumption caused by discontinuation resulting from a failure diagnosis, while avoiding overheat of a filter device being subjected to the failure diagnosis.SOLUTION: An electronic control unit 40 executes diagnostic processing for diagnosing the presence or absence of a failure of an air-fuel ratio sensor 26 while performing motoring control in which an internal combustion engine 11 is driven by a generator 12, and a fuel cut for the internal combustion engine 11 is performed. Further, the electronic control unit 40 calculates an F / C limit time as an upper limit value of the duration of the motoring control based on the temperature of a filter device 27 and an amount of PM accumulation. Then, the electronic control unit 40 executes the diagnostic processing on condition that a time required for the diagnostic processing is shorter than the F / C limit time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for a hybrid vehicle that performs failure diagnosis on components of an internal combustion engine. [Background technology]

[0002] Some fault diagnosis of components of an internal combustion engine, such as exhaust sensors that detect the state of the exhaust gas and filter devices for purifying the exhaust gas, is performed during fuel cut when the exhaust gas flowing through the exhaust passage is replaced with fresh air. In a hybrid vehicle that generates regenerative power while the vehicle is coasting, opportunities to perform fuel cut of the internal combustion engine are limited. In contrast, the control device for a hybrid vehicle described in Patent Document 1 ensures opportunities to perform fault diagnosis by performing fault diagnosis while implementing the following motoring control. Motoring control is a control that cuts fuel to the internal combustion engine while the internal combustion engine is driven by an electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-179712 A Summary of the Invention [Problem to be solved by the invention]

[0004] An exhaust purification device for an internal combustion engine is a filter device that collects particulate matter in the exhaust. In an internal combustion engine equipped with such a filter device, a large amount of oxygen is supplied to the filter device during motoring control. When a large amount of oxygen is supplied, the particulate matter accumulated in the filter device is oxidized. The oxidation generates heat, and the temperature of the filter device rises. If the temperature of the filter device is high at the start of the diagnosis or if a large amount of particulate matter has accumulated, the temperature of the filter device may reach an allowable upper limit during the fault diagnosis. In such a case, the fault diagnosis must be stopped midway in order to protect the filter device from a decrease in durability due to overheating. If the fault diagnosis is stopped, the power consumed for the motoring control is wasted. [Means for solving the problem]

[0005] A control device for a hybrid vehicle that solves the above problems is applied to a hybrid vehicle that includes an internal combustion engine in which a filter device that captures particulate matter in the exhaust is provided in an exhaust passage, and an electric motor that can drive the internal combustion engine. The control device performs a motoring control that cuts fuel to the internal combustion engine while the internal combustion engine is driven by the electric motor, while performing a diagnostic process that diagnoses whether or not components of the internal combustion engine have a failure, and a limit time calculation process that calculates a limit time that is an upper limit of the duration of the motoring control based on the temperature of the filter device so that the limit time is shorter when the temperature is high than when the temperature is low. Furthermore, the control device performs the diagnostic process on the condition that the duration of the motoring control required for the diagnostic process is shorter than the limit time.

[0006] When motoring control is started, a large amount of oxygen is supplied to the filter device, accelerating the oxidation of particulate matter accumulated in the filter device. The oxidation generates heat, which increases the temperature of the filter device. If the temperature of the filter device exceeds an allowable upper limit due to the increase in temperature, the fault diagnosis must be stopped.

[0007] On the other hand, the duration of motoring control until the temperature of the filter device reaches the allowable upper limit value becomes shorter as the temperature of the filter device at the start of motoring control becomes higher. Therefore, a time limit, which is the upper limit of the duration of motoring control, is set so that the duration is shorter when the temperature of the filter device is high than when it is low. Then, by executing motoring control within a range that does not exceed the time limit, overheating of the filter device during motoring control can be avoided.

[0008] In the control device, when the duration of the motoring control required for the diagnosis process exceeds the time limit, the diagnosis process is not executed. In other words, the control device executes the diagnosis process only when it is determined that the diagnosis process will prevent the filter device from overheating based on the current temperature of the filter device. Therefore, the filter device prevents the filter device from overheating during diagnosis, while reducing unnecessary power consumption due to the cancellation of the diagnosis.

[0009] Furthermore, in the control device for the hybrid vehicle, when the diagnostic process is incomplete, it is preferable to implement an output restriction for the internal combustion engine that reduces the maximum required output, which is the upper limit of the required output of the internal combustion engine, compared to when the diagnostic process is complete. The higher the output of the internal combustion engine, the easier it is for the temperature of the filter device to rise. Therefore, when the output restriction is implemented, the temperature of the filter device becomes less likely to rise. As a result, it becomes easier to set the limit time to a time longer than the duration of motoring control required for fault diagnosis. Therefore, by implementing the output restriction for the internal combustion engine in the above manner, it becomes easier to obtain an opportunity to perform fault diagnosis. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic configuration of a control device for a hybrid vehicle according to a first embodiment; [Diagram 2] 3 is a flowchart of a fault diagnosis routine executed by the control device. [Diagram 3] FIG. 13 is a graph showing the relationship between the PM accumulation amount, the filter bed temperature, and the F / C limit time. [Figure 4]10 is a flowchart of an output limiting process routine executed by a control device for a hybrid vehicle according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) Hereinafter, a first embodiment of a control device for a hybrid vehicle will be described in detail with reference to FIGS.

[0012] <Configuration of Hybrid Vehicle 10> First, the configuration of a hybrid vehicle 10 to which the control device of this embodiment is applied will be described with reference to Fig. 1. The hybrid vehicle 10 includes an internal combustion engine 11, a generator 12, and a motor 13 as drive sources. The generator 12 and the motor 13 each have a function as a generator that receives external power to generate electricity, and a function as an electric motor that receives electric power to generate power. The names of the generator 12 and the motor 13 here are derived from their main functions. Therefore, in the hybrid vehicle 10, the generator 12 may function as an electric motor, and the motor 13 may function as a generator, depending on the situation.

[0013] The internal combustion engine 11 and the generator 12 are each connected to a power split mechanism 14. The power split mechanism 14 is a planetary gear mechanism. One of three rotating elements of the planetary gear mechanism is connected to the internal combustion engine 11, and the other is connected to the generator 12. The remaining rotating element of the planetary gear mechanism is connected to wheels 16 via a reduction gear mechanism 15. The motor 13 is also connected to the reduction gear mechanism 15.

[0014] The generator 12 and the motor 13 are electrically connected to a battery 18 via an inverter 17. The inverter 17 adjusts the power exchanged between the generator 12 / motor 13 and the battery 18.

[0015] <Configuration of internal combustion engine 11> Next, the configuration of the internal combustion engine 11 will be described with reference to Fig. 1. The internal combustion engine 11 includes combustion chambers 20 for each cylinder, an intake passage 21 which is a passage for introducing intake air into the combustion chamber 20 of each cylinder, and an exhaust passage 22 which is a passage for discharging exhaust gas from the combustion chamber 20 of each cylinder.

[0016] An air flow meter 23 and a throttle valve 24 are provided in the intake passage 21. The air flow meter 23 is a sensor that detects the intake flow rate GA, which is the flow rate of the intake air flowing through the intake passage 21. The throttle valve 24 is an intake throttle valve for adjusting the intake flow rate GA.

[0017] Meanwhile, the exhaust passage 22 is provided with an air-fuel ratio sensor 26 that detects the air-fuel ratio of the mixture burned in the combustion chamber 20, and a filter device 27 that collects particulate matter in the exhaust. Also provided in the exhaust passage 22 are an inlet gas temperature sensor 28 and an outlet gas temperature sensor 29. The inlet gas temperature sensor 28 is a sensor that detects the inlet gas temperature TIN, which is the temperature of the exhaust gas flowing into the filter device 27. The outlet gas temperature sensor 29 is a sensor that detects the outlet gas temperature TOUT, which is the temperature of the exhaust gas flowing out from the filter device 27.

[0018] Furthermore, the internal combustion engine 11 is provided with an injector 30 and an ignition device 31 for each cylinder. The injector 30 is a fuel injection valve that injects fuel into the intake air flowing into the combustion chamber 20. The ignition device 31 is a spark generating device that ignites the mixture of intake air and fuel introduced into the combustion chamber 20 by spark discharge. The internal combustion engine 11 is also provided with an EGR (Exhaust Gas Recirculation) passage 32, which is a passage for exhaust gas recirculated from the exhaust passage 22 to the intake passage 21. The EGR passage 32 is provided with an EGR cooler 33 that cools the exhaust gas recirculated during the intake air, and an EGR valve 34 that is a valve for adjusting the amount of exhaust gas recirculated.

[0019] <Control device configuration> The hybrid vehicle 10 is equipped with an electronic control unit 40 that controls the hybrid vehicle 10. Detection signals of various sensors provided in various parts of the hybrid vehicle 10 are input to the electronic control unit 40. The various sensors here include the above-mentioned air flow meter 23, the air-fuel ratio sensor 26, the inlet gas temperature sensor 28, and the outlet gas temperature sensor 29. In addition, the various sensors also include an accelerator pedal sensor 41, a vehicle speed sensor 42, and a crank angle sensor 43. The accelerator pedal sensor 41 is a sensor that detects an accelerator pedal opening degree ACC, which is an amount of depression of the accelerator pedal. The vehicle speed sensor 42 is a sensor that detects a vehicle speed V, which is a traveling speed of the hybrid vehicle 10. The crank angle sensor 43 is a sensor that detects a crank angle, which is a rotation angle of a crankshaft of the internal combustion engine 11. In addition, detection signals of various sensors that detect state quantities of the internal combustion engine 11, the generator 12, the motor 13, and the battery 18, such as an intake pressure sensor that detects an intake pressure PM of the internal combustion engine 11, are input to the electronic control unit 40.

[0020] <Power control of hybrid vehicle 10> The electronic control unit 40 controls the power of the hybrid vehicle 10. Next, the basic flow of the power control of the hybrid vehicle 10 will be described.

[0021] During power control, the electronic control unit 40 first calculates a required driving force TP*, which is a required value of the driving force of the hybrid vehicle 10, based on the accelerator pedal opening ACC. The electronic control unit 40 also calculates a driver required output PDRV* based on the required driving force TP* and the vehicle speed V. The driver required output PDRV* indicates the output of the internal combustion engine 11 at which a driving force equivalent to the required driving force TP* is obtained with the torque of the motor 13 set to zero.

[0022] On the other hand, the electronic control unit 40 calculates the charge / discharge required output PB* based on the charging rate of the battery 18. The electronic control unit 40 controls the charge / discharge amount of the battery 18 so as to maintain the charging rate of the battery 18 at a value within a predetermined control target range. For example, when the charging rate of the battery 18 is higher than the upper limit of the control target range, the motor 13 receives power from the battery 18 and generates torque, thereby reducing the charging rate of the battery 18. At this time, the motor 13 receives power discharged from the battery 18 and generates torque. Also, when the charging rate of the battery 18 is lower than the lower limit of the control target range, the motor 13 generates power and sends the power to the battery 18, thereby increasing the charging rate of the battery 18. The charge / discharge required output PB* is calculated as a value obtained by converting the driving force generated by the motor 13 to the output of the internal combustion engine 11 in order to control the charge / discharge amount. Note that the charge / discharge required output PB* is a negative value when the motor 13 generates power using part of the output of the internal combustion engine 11.

[0023] Next, the electronic control unit 40 calculates the difference obtained by subtracting the charge / discharge required output PB* from the driver required output PDRV* as the value of the required output PE* of the internal combustion engine 11. That is, the output of the internal combustion engine 11 required to obtain a driving force equivalent to the required driving force TP* while the charge / discharge amount control is being performed is calculated as the value of the required output PE*. Note that a maximum required output PEMAX, which is an upper limit value, is set for the required output PE*. Therefore, when the output of the internal combustion engine 11 required to obtain a driving force equivalent to the required driving force TP* exceeds the maximum required output PEMAX, the maximum required output PEMAX is set as the value of the required output PE*.

[0024] Next, the electronic control unit 40 determines an operating point of the internal combustion engine 11 at which the internal combustion engine 11 can efficiently generate an output equivalent to the value of the required output PE*. Then, the electronic control unit 40 calculates the rotation speed NE and torque TE of the internal combustion engine 11 at the operating point as the values ​​of the target rotation speed NE* and target torque TE*, respectively.

[0025] Furthermore, the electronic control unit 40 calculates the rotation speed of the generator 12 required to set the rotation speed NE of the internal combustion engine 11 to the target rotation speed NE* as the value of the target rotation speed NM1* of the generator 12. Then, the electronic control unit 40 calculates the value of the command torque TM1* based on the target rotation speed NM1*. The calculation of the command torque TM1* here is performed so as to feedback control the torque of the generator 12 based on the deviation of the current rotation speed of the generator 12 from the target rotation speed NM1*. That is, the sum of the command torque TM1* value calculated in the previous calculation cycle and a feedback correction term corresponding to the deviation is calculated as the value of the command torque TM1* in the current calculation cycle.

[0026] Furthermore, the electronic control unit 40 calculates the torque transmitted from the internal combustion engine 11 to the reduction gear mechanism 15 in a state where the generator 12 is generating torque equivalent to the value of the command torque TM1* as the value of the direct torque TEQ. Then, the electronic control unit 40 calculates the torque of the motor 13 that provides a driving force equivalent to the required driving force TP* in a state where torque equivalent to the value of the direct torque TEQ is transmitted from the internal combustion engine 11 to the reduction gear mechanism 15 as the value of the command torque TM2* of the motor 13.

[0027] Then, the electronic control unit 40 operates the operation amounts of the internal combustion engine 11, such as the opening of the throttle valve 24, the fuel injection amount of the injector 30, the ignition timing of the ignition device 31, etc., based on the target rotation speed NE* and the target torque TE*. The electronic control unit 40 also operates the inverter 17 so that the generator 12 generates torque corresponding to the value of the command torque TM1* and the motor 13 generates torque corresponding to the value of the command torque TM2*. In this way, the electronic control unit 40 performs power control of the hybrid vehicle 10.

[0028] <Failure diagnosis of the air-fuel ratio sensor 26> During the running of the hybrid vehicle 10, the electronic control unit 40 performs a diagnostic process to diagnose whether or not the air-fuel ratio sensor 26 has a malfunction. In the diagnostic process, the electronic control unit 40 first starts a motoring control to cut fuel to the internal combustion engine 11 while the internal combustion engine 11 is driven by the generator 12. When the motoring control starts, the gas flowing through the exhaust passage 22 of the internal combustion engine 11 is replaced by fresh air instead of burnt gas, and the output of the air-fuel ratio sensor 26 changes to the lean side. When the air-fuel ratio sensor 26 has a malfunction and the responsiveness of the output is reduced, the time required for the output to change at this time is longer than when the air-fuel ratio sensor 26 is functioning normally. In the diagnostic process, the electronic control unit 40 measures the time from the start of the fuel cut to the time when the output of the air-fuel ratio sensor 26 stops changing and converges. Then, the electronic control unit 40 judges whether or not the measured time is equal to or longer than a predetermined malfunction judgment time.

[0029] 2 shows the procedure of a failure diagnosis routine executed by the electronic control unit 40 to diagnose a failure of the air-fuel ratio sensor 26. The electronic control unit 40 repeatedly executes this routine at predetermined control intervals while the hybrid vehicle 10 is running.

[0030] When this routine starts, first in step S100, the electronic control unit 40 acquires the filter temperature TF, which is the temperature of the filter device 27, and the PM accumulation amount Q, which is the amount of particulate matter accumulated in the filter device 27. In this embodiment, the electronic control unit 40 obtains the filter temperature TF by estimation based on the rotation speed NE and load factor KL of the internal combustion engine 11. In addition, the electronic control unit 40 in this embodiment obtains the PM accumulation amount Q by estimation based on the rotation speed NE of the internal combustion engine 11, the load factor KL, and the coolant temperature.

[0031] Next, in step S110, the electronic control unit 40 calculates the F / C limit time from the filter temperature TF and the PM accumulation amount Q. The F / C limit time is the upper limit of the duration of the fuel cut. The details of the F / C limit time will be described later.

[0032] Next, in step S120, the electronic control unit 40 determines whether or not the failure diagnosis of the air-fuel ratio sensor 26 has been completed for the current trip. If the failure diagnosis has been completed (YES), the electronic control unit 40 ends the current processing of this routine. That is, the failure diagnosis of the air-fuel ratio sensor 26 is performed once per trip. On the other hand, if the failure diagnosis has not been completed (NO), the electronic control unit 40 proceeds to step S130.

[0033] When the process proceeds to step S130, the electronic control unit 40 determines in step S130 whether or not the preconditions for diagnosis are met. The preconditions for diagnosis are, for example, that the warm-up of the internal combustion engine 11 has been completed and that it has been confirmed that there are no abnormalities in the sensors used in the diagnosis. If the preconditions are not met (NO), the electronic control unit 40 ends the process of this routine. On the other hand, if the preconditions are met (YES), the electronic control unit 40 proceeds to step S140.

[0034] When the process proceeds to step S140, the electronic control unit 40 determines in step S140 whether or not the F / C time limit is longer than the diagnosis required time. The diagnosis required time represents the duration of motoring control required for fault diagnosis of the air-fuel ratio sensor 26. In this embodiment, a predetermined constant is set as the value of the diagnosis required time. If the F / C time limit is equal to or shorter than the diagnosis required time (NO), the electronic control unit 40 ends the process of this routine. On the other hand, if the F / C time limit is longer than the diagnosis required time (YES), the electronic control unit 40 proceeds to step S150.

[0035] When the process proceeds to step S150, the electronic control unit 40 determines whether or not the required output PE* of the internal combustion engine 11 is zero or less in step S150. That is, at this time, the electronic control unit 40 determines whether or not the internal combustion engine 11 is in a situation where the combustion operation can be stopped. The value of zero or less is set as the required output PE* when the hybrid vehicle 10 is stopped or coasting.

[0036] When the required output PE* is greater than zero (NO), the electronic control unit 40 ends the processing of this routine as it is. On the other hand, when the required output PE* is zero or less (YES), the electronic control unit 40 proceeds to step S160. Then, in step S160, the electronic control unit 40 performs a failure diagnosis of the air-fuel ratio sensor 26 by performing motoring control.

[0037] <F / C limit time> Next, with reference to FIG. 3 as well, the details of the F / C limit time calculated by the electronic control unit 40 in step S110 of the above failure diagnosis routine will be described.

[0038] When the fuel cut of the internal combustion engine 11 is started, the gas flowing through the exhaust passage 22 is replaced with fresh air from the burnt gas, and a large amount of oxygen is supplied to the filter device 27. As a result, the oxidation of the particulate matter deposited in the filter device 27 is promoted. Therefore, when the fuel cut is started, the filter temperature TF rises due to heat generated by the oxidation of the particulate matter. On the other hand, the filter temperature TF has an allowable upper limit temperature for ensuring the durability of the filter device 27. In the following description, this upper limit temperature is referred to as the upper limit temperature TFMAX of the filter device 27. The F / C limit time represents the duration of the fuel cut from the start of the fuel cut until the filter temperature TF reaches the upper limit temperature TFMAX. When the fuel cut of the internal combustion engine 11 is performed, the electronic control unit 40 forcibly ends the fuel cut when the duration of the fuel cut reaches the F / C limit time. In this way, the electronic control unit 40 protects the filter device 27 from a decrease in durability due to overheating. The fuel cut of the internal combustion engine 11 is also performed during motoring control. Therefore, the F / C time limit is also the upper limit for the duration of motoring control.

[0039] FIG. 3 shows the relationship between the filter temperature TF and the PM accumulation amount Q and the F / C limit time in a calculation map used by the electronic control unit 40 to calculate the F / C limit time. The calculation map stores the F / C limit time for each combination of the filter temperature TF and the PM accumulation amount Q. The electronic control unit 40 stores such a calculation map in advance. The higher the filter temperature TF at the start of the fuel cut, the smaller the increase in the filter temperature TF required to reach the upper limit temperature TFMAX. Also, the higher the filter temperature TF, the more the oxidation reaction of the particulate matter is promoted. Therefore, the electronic control unit 40 calculates the F / C limit time to be shorter when the filter temperature TF is high than when the filter temperature TF is low. On the other hand, the greater the PM accumulation amount Q, the greater the amount of heat generated by the oxidation of the particulate matter during the fuel cut. Therefore, the electronic control unit 40 calculates the F / C limit time to be shorter when the PM accumulation amount Q is large than when it is small.

[0040] <Actions and Effects of the Embodiment> The operation and effects of this embodiment will be described. In this embodiment, the electronic control unit 40 calculates the F / C limit time from the filter temperature TF and the PM accumulation amount Q. The electronic control unit 40 limits the duration of the fuel cut to within the F / C limit time, thereby protecting the filter device 27 from a decrease in durability due to overheating. Note that, in the motoring control, fuel cut of the internal combustion engine 11 is performed while maintaining the rotation of the internal combustion engine 11 with the power of the generator 12. Therefore, the duration of the motoring control is also limited to within the F / C limit time.

[0041] On the other hand, the electronic control unit 40 performs a fault diagnosis of the air-fuel ratio sensor 26 after performing the motoring control. Therefore, if the fault diagnosis is not completed within the F / C limit time, the diagnosis is stopped at that point. In such a case, the fault diagnosis must be performed again from the beginning at the next opportunity. On the other hand, the driving of the internal combustion engine 11 by the generator 12 under the motoring control involves power consumption. Therefore, if the fault diagnosis of the air-fuel ratio sensor 26 is stopped due to the F / C limit time, the power consumed up to the time of the stop is wasted. In contrast, in this embodiment, the diagnosis process is performed only when the F / C limit time is longer than the diagnosis required time. Therefore, the diagnosis process of the air-fuel ratio sensor 26 is not stopped due to the limit on the duration of the motoring control by the F / C limit time.

[0042] According to the control device for the hybrid vehicle 10 of the present embodiment described above, the following effects can be achieved. (1) In this embodiment, the diagnostic process is performed on the condition that the time required for diagnosis is shorter than the F / C time limit. Therefore, the diagnostic process is not stopped due to the limit on the duration of motoring control by the F / C time limit. Therefore, overheating of the filter device 27 during the fault diagnosis is avoided, and unnecessary power consumption due to the interruption of the fault diagnosis is suppressed.

[0043] (2) In this embodiment, the F / C limit time is calculated from the filter temperature TF and the PM accumulation amount Q. Therefore, it is possible to set the F / C limit time to a time appropriate for protecting the filter device 27 from deterioration in durability due to overheating.

[0044] <Correspondence> In this embodiment, the electronic control unit 40 corresponds to a control device of the hybrid vehicle 10, and the generator 12 corresponds to an electric motor capable of driving the internal combustion engine 11. In this embodiment, step S110 of the failure diagnosis routine corresponds to the time limit calculation process, and step S160 corresponds to the diagnosis process. Furthermore, in this embodiment, the air-fuel ratio sensor 26 corresponds to a component of the internal combustion engine 11 that is diagnosed for the presence or absence of a failure in the diagnosis process.

[0045] Second embodiment Next, a second embodiment of a control device for a hybrid vehicle will be described in detail with reference to FIG. 4. In this embodiment, components common to the above-mentioned embodiments are given the same reference numerals and detailed description thereof will be omitted. The hardware configuration of the control device of this embodiment is common to the first embodiment. The control device of this embodiment also executes the power control of the hybrid vehicle 10 and fault diagnosis of the air-fuel ratio sensor 26 similar to the first embodiment. The control device of this embodiment also executes the output limiting process of the internal combustion engine 11 described below.

[0046] <Output diagnostic processing> FIG. 4 shows the procedure of the output limiting process routine executed by the electronic control unit 40 for the output limiting process. The electronic control unit 40 repeatedly executes this routine at every predetermined control period while the internal combustion engine 11 is operating. When this routine is started, the electronic control unit 40 first determines in step S200 whether or not the failure diagnosis of the air-fuel ratio sensor 26 has been completed in the current trip. If the failure diagnosis has been completed (YES), the electronic control unit 40 ends the processing of this routine. On the other hand, if the failure diagnosis has not been completed (NO), the electronic control unit 40 proceeds to step S210. Then, the electronic control unit 40 implements the output limit of the internal combustion engine 11 in step S210. Specifically, in step S210, the electronic control unit 40 sets the value of the maximum required output PEMAX, which is the upper limit value of the required output PE*, to a value smaller than that in the case where the failure diagnosis has been completed.

[0047] <Actions and Effects of the Embodiment> The filter temperature TF during combustion operation of the internal combustion engine 11 increases as the output of the internal combustion engine 11 increases. Therefore, when the output is limited, the filter temperature TF is less likely to rise. When the filter temperature TF is low, a longer time is set as the F / C limit time than when the filter temperature TF is high. On the other hand, as described above, the diagnosis process for the air-fuel ratio sensor 26 is executed on the condition that the diagnosis required time is shorter than the F / C limit time. Therefore, if the output of the internal combustion engine 11 is limited, an opportunity to execute the diagnosis process becomes more likely. Furthermore, the increase in the filter temperature TF is suppressed by the output limit, and therefore the deterioration of the durability of the filter device 27 due to overheating is suppressed.

[0048] During the output restriction of the internal combustion engine 11, the power performance of the hybrid vehicle 10 is reduced. However, after the fault diagnosis is completed, the output restriction of the internal combustion engine 11 is lifted, so the reduction in power performance is temporary. Even after the fault diagnosis is completed, the duration of the fuel cut is limited by the F / C limit time, so the filter device 27 can be protected from a decrease in durability due to overheating during fuel cut.

[0049] According to this embodiment, in addition to the above advantages (1) and (2), the following advantage (3) can be achieved. (3) In this embodiment, when the diagnostic process of the air-fuel ratio sensor 26 is incomplete, the output limiting process of the internal combustion engine 11 is executed to make the maximum required output PEMAX smaller than when the diagnostic process of the air-fuel ratio sensor 26 is complete. Therefore, it is possible to increase the number of opportunities to execute the diagnostic process of the air-fuel ratio sensor 26 while avoiding overheating of the filter device 27.

[0050] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0051] <About fault diagnosis> In the above embodiment, the diagnostic process performs a fault diagnosis on the air-fuel ratio sensor 26. However, the diagnostic process may perform a fault diagnosis on components of the internal combustion engine 11 other than the air-fuel ratio sensor 26, as long as the fault diagnosis is performed after motoring control is performed. Such fault diagnosis includes, for example, a fault diagnosis on the EGR valve 34 and a fault diagnosis on the filter device 27.

[0052] First, the fault diagnosis of the EGR valve 34 will be described. In the fault diagnosis of the EGR valve 34, first, motoring control is started, and then a command to change the opening degree of the EGR valve 34 is issued. For example, the electronic control unit 40 issues a command to change the opening degree from the fully closed opening degree to the fully open opening degree, and then issues a command to change the opening degree from the fully open opening degree to the fully closed opening degree. At this time, the EGR valve 34 is functioning normally, and the opening degree of the EGR valve 34 is actually changed in response to the command. Then, when the opening degree of the EGR valve 34 changes, the flow rate of the gas that is recirculated from the exhaust passage 22 to the intake passage 21 through the EGR passage 32 changes. Then, together with this change, the intake pressure PM also changes. On the other hand, if the EGR valve 34 is in a state in which the opening degree cannot be changed normally due to a valve sticking, the change in the intake pressure PM in response to the command to change the opening degree becomes smaller than in the normal state. Therefore, the presence or absence of an abnormality in the EGR valve 34 can be diagnosed based on the change in the intake pressure PM in response to the command to change the opening degree of the EGR valve 34. If the opening of the EGR valve 34 is changed significantly for fault diagnosis during combustion operation of the internal combustion engine 11, the flow rate of the exhaust gas recirculated to the intake passage 21 changes significantly, significantly affecting combustion and exhaust properties. For this reason, it is desirable to perform the above-mentioned fault diagnosis of the EGR valve 34 during motoring control in which combustion in the internal combustion engine 11 is temporarily interrupted.

[0053] Next, the fault diagnosis of the filter device 27 will be described. When the motoring control is started, the gas flowing through the exhaust passage 22 is replaced from the high-temperature burnt gas to low-temperature fresh air. The inlet gas temperature TIN, which is the temperature of the gas flowing into the filter device 27, drops immediately after the motoring control is started. On the other hand, the inside of the filter device 27 during the combustion operation of the internal combustion engine 11 is at a high temperature due to heat received from the burnt gas. And the inside of the filter device 27 is at a high temperature for a while even after the motoring control is started. The fresh air flowing into the filter device 27 at this time receives heat from the filter device 27 and flows out of the filter device 27. Therefore, the drop in the outlet gas temperature TOUT after the motoring control is started is slower than the drop in the inlet gas temperature TIN. Incidentally, the filter device 27 has a built-in filter substrate made of a porous material such as ceramics. Such a filter substrate may be damaged by an external impact or heat shock, and the exhaust gas may pass through the filter device 27. In such a case, the drop in the outlet gas temperature TOUT after the motoring control is started is faster than when no damage occurs. Therefore, by observing the change in the difference between the inlet gas temperature TIN and the outlet gas temperature TOUT after the start of motoring control, it is possible to diagnose whether or not the filter substrate is damaged.

[0054] <About output restriction processing> In the second embodiment, when the fault diagnosis is incomplete in the output limiting process, a value smaller than that when the fault diagnosis is completed is set as the maximum required output PEMAX of the internal combustion engine 11. The value of the maximum required output PEMAX that is set when the fault diagnosis is incomplete may be made variable depending on the filter temperature TF, the PM accumulation amount Q, etc.

[0055] <Acquisition of filter temperature TF and PM accumulation amount Q> In the above embodiment, the filter temperature TF is estimated from the rotation speed NE and the load factor KL of the internal combustion engine 11. The filter temperature TF may be estimated in other ways, for example, using the detection result of the outlet gas temperature sensor 29. Also, a sensor that directly detects the filter temperature TF may be provided, and the filter temperature TF may be obtained from the output of the sensor.

[0056] In addition, in the above-described embodiment, the PM deposition amount Q was obtained from the rotational speed NE, the load factor KL, and the coolant temperature of the internal combustion engine 11. In other aspects, the PM deposition amount Q may be acquired. For example, the differential pressure of the exhaust gas before and after passing through the filter device 27 may be measured, and the PM deposition amount Q may be estimated and obtained from the measurement result of the differential pressure.

[0057] <Regarding the diagnosis required time> The diagnosis required time varies depending on the type of fault diagnosis targeted. Therefore, when performing multiple types of fault diagnoses, it is advisable to change the diagnosis required time according to the type of fault diagnosis to be carried out. In addition, the diagnosis required time may change depending on the operating condition of the internal combustion engine 11 when performing the fault diagnosis. In such a case, it is advisable to variably set the diagnosis required time according to the operating condition of the internal combustion engine 11.

[0058] Note that depending on the type of fault diagnosis, pre-processing before the start of motoring control or post-processing after the end of motoring control may be required. In such a case, the continuous time of the motoring control required for the same diagnosis process becomes shorter than the required time of the entire diagnosis process. Therefore, in such a case, it is advisable to execute the diagnosis process on the condition that the continuous time of the motoring control required for the diagnosis process is shorter than the F / C limit time.

[0059] <Regarding the F / C limit time> In the above-described embodiment, the F / C limit time was calculated based on the filter temperature TF and the PM deposition amount Q. The PM deposition amount Q among these may be removed from the parameters used for calculating the F / C limit time. In addition, the outside air temperature and the like also affect the rising rate of the filter temperature TF after the start of motoring control. Therefore, parameters that affect such a rising rate may be added to the parameters used for calculating the F / C limit time.

[0060] In the above embodiment, it is assumed that fuel cut of the internal combustion engine 11 is performed for other than fault diagnosis. When the duration of fuel cut reaches the F / C limit time, the fuel cut is forcibly stopped. If fuel cut of the internal combustion engine 11 is not performed for other than fault diagnosis, the control logic related to the forcible stopping of fuel cut due to the F / C limit time can be omitted.

[0061] <Other changes> The control device may be configured to control a hybrid vehicle having a configuration different from that shown in FIG.

[0062] The power control of the hybrid vehicle 10 may be performed in a manner other than that described above. [Explanation of symbols]

[0063] 10. Hybrid vehicle 11...Internal combustion engine 12…Generator 13…Motor 14...Power split mechanism 15...Reduction mechanism 16...Wheel 17…Inverter 18…Battery 20…Combustion chamber 21…Intake passage 22...Exhaust passage 23...Air flow meter 24…Throttle valve 26...Air-fuel ratio sensor 27...Filter device 28...Inlet gas temperature sensor 29...Outlet gas temperature sensor 30…Injector 31...Ignition device 32...EGR passage 33…EGR cooler 34...EGR valve 40...Electronic control unit 41...Accelerator pedal sensor 42...Vehicle speed sensor 43...Crank angle sensor

Claims

1. A control device applied to a hybrid vehicle including an internal combustion engine having an exhaust passage provided with a filter device for trapping particulate matter in the exhaust, and an electric motor capable of driving the internal combustion engine, a diagnostic process for diagnosing whether or not a component of the internal combustion engine has a failure while performing a motoring control for cutting fuel of the internal combustion engine in a state where the internal combustion engine is driven by the electric motor; a time limit calculation process for calculating a time limit that is an upper limit of a duration of the motoring control based on a temperature of the filter device, so that the time limit is shorter when the temperature is high than when the temperature is low; and executing the diagnostic process on the condition that the duration of the motoring control required for the diagnostic process is shorter than the time limit. A control device for a hybrid vehicle.

2. 2. The control device for a hybrid vehicle as described in claim 1, wherein, when the diagnostic process is incomplete, an output limit of the internal combustion engine is implemented to make the maximum required output, which is the upper limit value of the required output of the internal combustion engine, smaller than when the diagnostic process is completed.

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