JP5610158B2 - Hybrid vehicle - Google Patents

Description

  The present invention relates to a control device for a hybrid vehicle including a motor and an engine (internal combustion engine) as a vehicle drive source, and more particularly to a failure determination of a device attached to the engine.

  In recent years, hybrid vehicles that drive a vehicle by combining the driving force of a motor and the driving force of an engine have been developed and put into practical use. Furthermore, the development and commercialization of plug-in hybrid vehicles capable of charging a battery for supplying power to an electric motor with an external commercial power source are also progressing.

  As such a hybrid vehicle, for example, a vehicle using a series system in which the vehicle is driven by the driving force of the motor and the engine is used as a power source of the generator, or the vehicle is driven by the driving force of both the engine and the motor. Some have adopted a parallel system. Further, in the case of a plug-in hybrid vehicle, the EV driving mode in which the vehicle is driven by the driving force of only the motor, the series driving mode to which the above series method is applied, or the parallel driving mode to which the above parallel method is applied are Some are switched according to the situation.

Conventionally, in a vehicle equipped with an engine, failure determination (diagnosis) of equipment attached to the engine, for example, an oxygen (O ₂ ) sensor provided behind the catalyst in the exhaust passage, an EGR device, or the like is predetermined. It is implemented at the timing. Such device failure determination is generally performed when the fuel supply to the engine is stopped (fuel cut) due to an accelerator off or the like. For example, when determining the failure of the oxygen sensor in the exhaust passage, it is determined whether or not there is a failure from the amount of change in the output value of the sensor within a predetermined period after the fuel cut is started.

  And the failure determination (diagnosis) of the apparatus attached to such an engine is implemented also in the hybrid vehicle (for example, refer patent document 1). In the invention according to Patent Document 1, in a hybrid vehicle configured with a power train in which an engine, a motor, and a generator are always rotated together, the motor is driven by the driving force of the motor when the fuel is cut, and the engine is rotated by a predetermined amount by the motor. Failure judgment is performed with the number maintained. By maintaining the rotation of the engine by the motor in this way, it is possible to frequently perform failure determination of equipment attached to the engine even in a hybrid vehicle.

JP 2010-179712 A

  However, the hybrid vehicle according to Patent Document 1 travels when the motor and the engine are driven together, and the engine operating conditions such as the engine speed at the time of fuel cut and the air-fuel ratio are the driving conditions of the vehicle. Dependent. That is, the amount of change in the output value of the sensor during a predetermined period after the fuel cut is started varies depending on the traveling state of the vehicle. Therefore, there is a possibility that the failure determination cannot be performed accurately depending on the traveling state of the vehicle.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a hybrid vehicle that can improve the accuracy of failure determination of devices such as sensors attached to an engine.

According to a first aspect of the present invention for solving the above-mentioned problems, an internal combustion engine driven by fuel supply, a generator having a rotating body connected to rotate in synchronization with a rotating element of the internal combustion engine, and the generator A battery for storing electric power; a motor for driving the vehicle driven by the electric power of the battery; a friction clutch provided between the internal combustion engine and a drive wheel of the vehicle; After the engine is driven, it is confirmed that the friction clutch cuts off the transmission of the driving force, the fuel supply to the internal combustion engine is stopped, the rotating element of the internal combustion engine is rotated by the generator, It comprises a failure determining means for performing failure judgment of the attached device in an exhaust system of an internal combustion engine, and a EV mode traveling the friction clutch as a drive source to the traction motor as well as the disconnection state, before A series travel mode in which the friction clutch is disengaged and the travel motor is driven as a drive source while the generator is operated by the internal combustion engine to charge the battery, and the failure determination means includes In the hybrid vehicle, the failure determination is performed when switching from the series travel mode to the EV travel mode .

  In the first aspect, when the friction clutch is disengaged, the operating conditions such as the engine speed do not depend on the traveling state of the vehicle. Therefore, it is possible to determine the failure of the device while rotating the engine under a certain condition or an arbitrary condition. Thereby, the accuracy of equipment failure determination can be improved.

According to a second aspect of the present invention, the failure determination means controls the generator so as to vary the rotational speed of the rotating element of the internal combustion engine in accordance with the type of equipment to be subjected to the failure determination. It is in the hybrid vehicle of the 1st mode.

  In the second aspect, it is possible to determine the failure of various devices under the optimum engine operating conditions according to the type of device. Therefore, the accuracy of failure determination is further improved.

  According to a third aspect of the present invention, the failure determination means changes the fuel supply amount and drives the internal combustion engine, and then stops the fuel supply so that the power generation is held constant when the fuel supply is stopped. The hybrid vehicle according to the first or second aspect is characterized by controlling the machine.

  In the third aspect, the accuracy of the failure determination is more reliably improved by performing the failure determination while rotating the engine at a desired rotational speed.

  According to a fourth aspect of the present invention, the failure determination means is supplied to the internal combustion engine before the fuel supply to the internal combustion engine is stopped when performing a failure determination of an oxygen sensor provided in the exhaust passage. In the hybrid vehicle according to any one of the first to third aspects, the fuel supply amount is temporarily increased.

  In the fourth aspect, the oxygen sensor failure can be reliably detected by enriching the exhaust gas around the oxygen sensor before the fuel cut. Note that “can be implemented reliably” does not mean accuracy, but frequency. If the exhaust gas is lean, there is a risk that failure detection cannot be performed and the process ends.

  In the present invention, when the friction clutch is in a disengaged state and the fuel supply to the engine is stopped while the vehicle is running, the failure determination of the device is performed. Under certain conditions, it is possible to carry out equipment failure determination. Therefore, the accuracy of failure determination can be improved. In addition, with the improvement of accuracy, it becomes possible to set severe conditions for failure determination. For example, failure determination time can be shortened and drivability can be improved.

1 is a schematic view of a hybrid vehicle according to the present invention. It is a graph showing an example of a change in the output value of the O ₂ sensor in the failure determination. Is a flowchart illustrating an example of the failure determination control of the O ₂ sensor according to the present invention. It is a graph which shows an example of the change of the output value of a pressure sensor in failure judgment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a hybrid vehicle (hereinafter, also simply referred to as “vehicle”) 10 according to the present embodiment includes a front motor (traveling motor) 11 and an engine (internal combustion engine) 12 for traveling the vehicle. It is provided as a drive source. The driving force of the front motor 11 is transmitted to the wheels 15 via the front drive transmission mechanism 13 and the axle 14. A battery 17 is connected to the front motor 11 via an inverter 16, and predetermined power is supplied from the battery 17 via the inverter 16 in accordance with a driver's pedal operation. The battery 17 is connected to a sub-battery (12 V battery) 19 for supplying power to the auxiliary machines via the DC / DC converter 18.

  The engine 12 is configured as a general internal combustion engine, and is driven by burning fuel supplied from the fuel tank 20. The engine 12 includes an intake manifold 21 and an exhaust manifold 22. The intake manifold 21 and the exhaust manifold 22 are connected by an EGR passage 23, and an EGR valve 24 is provided at a connection portion of the EGR passage 23 with the intake manifold 21. That is, the engine 12 includes an EGR device 25 that recirculates a part of the exhaust gas in the exhaust manifold (exhaust passage) 22 to the intake manifold (intake passage) 21 via the EGR passage 23. Note that the exhaust gas flow rate is adjusted by opening and closing the EGR valve 24. An exhaust pipe 26 connected to the exhaust manifold 22 is provided with a catalyst 27 for exhaust gas purification.

  Such an engine 12 is connected to a generator (generator) 29 via an output system 28. The generator 29 is connected to the battery 17 (and the front motor 11) via the generator inverter 30. The output system 28 is connected to the generator 29, and is also connected to the front drive transmission mechanism 13 via the friction clutch 31.

  When the engine 12 is started according to the driving state of the vehicle 10, the driving force of the engine 12 is first transmitted to the generator 29 via the output system 28. The generator 29 is operated by the driving force of the engine 12, and the electric power generated by the generator 29 is appropriately supplied to the front motor 11 and the battery 17. Further, when the driving mode is switched according to the driving state of the vehicle 10 and the friction clutch 31 is connected, the driving force of the engine 12 is transmitted to the wheels 15 via the front drive transmission mechanism 13 and the axle 14. It has become.

Further, the vehicle 10 is provided with a control device 50 that comprehensively controls various devices. The control device 50 also controls the engine 12 based on signals from various sensors. For example, the exhaust pipe 26 is provided with O ₂ sensors (oxygen sensors) 32 and 33 for detecting the air-fuel ratio (oxygen concentration) of the exhaust provided upstream and downstream of the catalyst 27. The state (air-fuel ratio) of the catalyst 27 is monitored by detecting the oxygen concentration of the exhaust gas with these O ₂ sensors 32 and 33. A linear air-fuel ratio sensor (LAFS) can be provided instead of the O ₂ sensor. Further, for example, a pressure sensor 34 that detects a pressure (intake manifold pressure) in the intake manifold 21 is provided. The control device 50 appropriately controls the engine 12 based on signals from various sensors including the O ₂ sensors 32 and 33 and the pressure sensor 34.

  In the vehicle 10 according to the present embodiment, the traveling mode is appropriately switched according to the traveling state of the vehicle 10 by appropriately controlling the front motor 11, the engine 12, and the like by the control device 50. More specifically, the EV traveling mode in which the friction clutch 31 is disengaged and the vehicle 10 is driven using the front motor 11 as a drive source, and the vehicle 10 is operated while the friction clutch 31 is disengaged and the front motor 11 is the drive source. A series running mode in which the generator 29 is operated by the engine 12 to charge the battery 17 while running, and a parallel running in which the vehicle 10 is driven by using both the front motor 11 and the engine 12 as drive sources with the friction clutch 31 in the engaged state. The travel mode is appropriately switched according to the travel state of the vehicle 10.

In addition, the control device 50 includes a failure determination unit 51 that performs failure determination of various devices attached to the engine 12, such as the above-described various sensors, the EGR device 25, the catalyst 27, and the like at a predetermined timing. When the fuel supply to the engine 12 is stopped while the vehicle 10 is traveling in the series travel mode, the failure determination means 51 is a device attached to the engine 12 in a state where the engine 12 is rotated using the generator 29 as a power source. Perform a failure judgment. For example, in the present embodiment, the failure determination unit 51 performs failure determination of the O ₂ sensor 33 provided on the downstream side of the catalyst 27 when switching from the series traveling mode to the EV traveling mode. During the series travel mode, the fuel cut is usually not temporarily performed.

  Here, when switching from the series travel mode to the EV travel mode, the engine 12 stops when the fuel is cut. However, when the failure determination is performed, the generator 29 is driven and the rotation of the engine 12 is maintained. For this reason, fresh air is supplied to the engine 12 even after the fuel is cut, and the air-fuel ratio (exhaust air-fuel ratio) changes rapidly in the lean direction after the fuel cut.

Therefore, if the function of the O ₂ sensor 33 is normal, the output value (voltage) of the O ₂ sensor 33 rapidly decreases after the fuel cut, as indicated by a solid line in FIG. On the other hand, when the function of the O ₂ sensor 33 is deteriorated (failed), the output value of the O ₂ sensor 33 gradually decreases as shown by a dotted line in FIG.

In the present embodiment, failure determination is performed based on the difference in the output value of the O ₂ sensor 33. That is, performing the failure determination of the O ₂ sensor 33 based on the change in the output value of the O ₂ sensor 33 in the predetermined time from the fuel cut (failure determination time). Specifically, when the fuel cut is performed, monitoring of the output value (change) of the O ₂ sensor 33 is started. When the output value of the O ₂ sensor 33 by the failure determination time T1 has elapsed is below a first threshold value V1, the O ₂ sensor 33 is determined to be normal. On the other hand, larger output value of the failure determination time T1 has elapsed O ₂ sensor 33 even than the first threshold value V1, the O ₂ sensor 33 is determined to be faulty (deterioration).

By the way, when the vehicle is driven by the driving force of the engine, the operating condition of the engine immediately before the failure determination is performed, for example, the engine speed is determined by the driving state of the vehicle and is not always constant. The amount of fresh air supplied to the engine after the fuel cut is performed depends on the engine speed. That is, the output value of the O ₂ sensor during the failure determination time also changes depending on the operating condition of the engine. Therefore, depending on the running state of the vehicle, it may not be possible to accurately determine the failure of the O ₂ sensor.

  However, in the present invention, when the fuel supply to the engine 12 is stopped while the vehicle 10 is traveling in the series travel mode, the failure determination means 51 determines the failure of the device. In the series travel mode, the engine speed does not depend on the traveling state of the vehicle, and therefore, the engine speed immediately before the failure determination is performed can be kept constant. Further, for example, the rotational speed of the engine 12 immediately before the failure determination is performed can be set to a desired rotational speed.

Therefore, when the fuel supply to the engine 12 is stopped while the vehicle 10 is traveling in the series travel mode, the failure determination of the O ₂ sensor 33 can be performed under a constant or desired condition, and the accuracy of the failure determination is improved. Greatly improved. In addition, with the improvement of accuracy, it is possible to set severe conditions for failure determination. For example, drivability can be improved by shortening the failure determination time.

FIG. 3 is a flowchart illustrating an example of failure determination control for the O ₂ sensor. Hereinafter, an example of the O ₂ sensor failure determination procedure will be described with reference to FIG.

As described above, in the present embodiment, when the vehicle 10 is traveling in the series travel mode, there is a fuel cut instruction (instruction to stop the engine 12), and a failure occurs when the travel mode is switched from the series travel mode to the EV travel mode. A failure determination of the O ₂ sensor 33 is performed by the determination unit 51. An instruction to stop the engine 12 is issued, for example, when the battery 17 is fully charged by charging by the generator 29, when the vehicle speed decreases, or when the driver selects the EV travel mode.

As shown in FIG. 3, when the stop instruction for the engine 12 is turned ON, the air-fuel ratio (cylinder air-fuel ratio) is first determined from the output value of the O ₂ sensor 33 while the fuel supply to the engine 12 is continued. It is determined whether it is below the threshold value (rich side) (step S1). That is, it is determined whether or not the output value of the O ₂ sensor 33 is greater than or equal to the second threshold value V2. When the vehicle 10 is traveling in the series travel mode, the engine 12 is normally feedback controlled with the stoichiometric air / fuel ratio (stoichiometric) as the target air / fuel ratio. Therefore, the air-fuel ratio of the engine 12 fluctuates between the lean side and the rich side around the theoretical air-fuel ratio.

Here, if it is determined that the air-fuel ratio is equal to or less than a predetermined threshold value (rich side), that is, the output value of the O ₂ sensor 33 is equal to or greater than the second threshold value V2 (step S1: YES), the process proceeds to step S2 and the engine The fuel supply from the fuel tank 20 to 12 is cut off. At this time, if the traveling mode of the vehicle 10 is the series traveling mode, the fuel cut is performed as it is. When the traveling mode of the vehicle 10 is the parallel traveling mode, the parallel traveling mode is switched to the series traveling mode, and the fuel cut is performed after a predetermined time has elapsed. Simultaneously with the fuel cut, power is supplied from the battery 17 to the generator 29, and the generator 29 is started. As the generator 29 rotates, the rotation of the engine 12 is maintained at the rotation speed at that time.

At this time, the rotational speed of the engine 12 (the rotational speed of the generator 29) is set to a rotational speed suitable for determining the failure of the O ₂ sensor 33. Further, before the fuel cut is performed, the rotational speed of the engine 12 may be changed in advance to a rotational speed suitable for determining the failure of the O ₂ sensor 33.

Next, response monitoring of the O ₂ sensor 33 is started in a state where the rotation of the engine 12 is continued (step S3). Specifically, monitoring of the output value of the O ₂ sensor 33 is started.

Note that the order of step 1 and step 2 described above may be reversed. That is, the fuel cut may be performed, and it may be determined whether to start the response monitor according to the magnitude of the output value of the O ₂ sensor 33 at that moment.

Next, in step S4, it is determined from the output value of the O ₂ sensor 33 whether or not the air-fuel ratio is equal to or greater than a predetermined threshold (lean side). Specifically, it is determined whether or not the output value of the O ₂ sensor 33 is equal to or less than the first threshold value V1 (see FIG. 2).

For example, when the output value of the O ₂ sensor 33 is larger than the first threshold value V1 immediately after the start of fuel cut (step S4: NO), the process proceeds to step S5, and the fuel cut duration time is a fixed time (failure determination). It is determined whether it is shorter than time T1). That is, it is determined whether or not the failure determination time T1 has elapsed since the start of fuel cut. Here, when the fuel cut duration is shorter than the failure determination time T1 (step S5: YES), the process returns to step S4.

Whether the output value of the O ₂ sensor 33 in step S4 is equal to or less than the first threshold value V1 is determined again, if the output value of the O ₂ sensor 33 has become less than the first threshold value V1 (step (S4: YES), it is determined that the response of the O ₂ sensor 33 is normal (step S6). That is, if the output value of the O ₂ sensor 33 is equal to or less than the first threshold value V1 before the fuel cut duration time has elapsed the failure determination time T1, it is determined that the response of the O ₂ sensor 33 is normal.

On the other hand, when it is determined again whether or not the output value of the O ₂ sensor 33 is equal to or smaller than the first threshold value V1 in step S4, the output value of the O ₂ sensor 33 is larger than the first threshold value V1. In step S5, the process proceeds again. That is, when the output value of the O ₂ sensor 33 in step S4 is judged to be larger than the first threshold value V1, until the fuel cut continuation time has elapsed the failure determination time T1, the determination of the output value of the O ₂ sensor 33 Repeated. When the output value of the O ₂ sensor 33 is larger than the first threshold value V1 (step S4: NO) and the fuel cut continuation time has passed the failure determination time T1 (step S5: NO), step Proceeding to S7, it is determined that a response failure of the O ₂ sensor 33 has occurred.

Thereafter, the flow advances to step S8, and ends the response monitor of the _{O 2} sensor 33. That is, the monitoring of the output value of the O ₂ sensor 33 is terminated. In step S9, the driving of the generator 29 is terminated and the rotation of the engine 12 is stopped. Thereby, the failure determination control of the O ₂ sensor 33 ends.

As described above, when the fuel cut is performed during the series travel mode, the failure determination of the O ₂ sensor 33 is performed, so that the failure determination can be performed under a constant or arbitrary condition (for example, the engine speed). it can. Therefore, the accuracy of failure determination can be greatly improved.

Further, when performing the failure determination, the failure determination means 51 may temporarily increase the fuel supply amount before the fuel supply to the engine 12 is stopped. That is, the target air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio, and the fuel injection amount is temporarily increased so that the air-fuel ratio is reliably made rich (the output value of the O ₂ sensor is set to the second threshold value V2 or higher). The failure determination may be executed in the state). By creating a rich state first and then performing a fuel cut, the failure detection of the O ₂ sensor can be performed reliably (frequency).

In the present embodiment, the failure determination of the device has been described using the O ₂ sensor 33 as an example. However, the device that is the target of the failure determination is not limited to the O ₂ sensor 33, and is, for example, the EGR device 25 or the catalyst 27. May be. The failure determination of the EGR device 25 and the catalyst 27 can also be performed when the fuel is cut during the series travel mode, thereby improving the accuracy.

  The failure determination of the EGR device 25 is performed based on, for example, the output value of the pressure sensor 34 (pressure in the intake manifold 21). Specifically, after the fuel cut is performed, the engine 12 is rotated for a predetermined time with the EGR valve 24 closed, and then the EGR valve 24 is opened, and the output value of the pressure sensor 34 during that time is monitored.

When the EGR device 25 is functioning normally, for example, as indicated by a solid line in FIG. 4, the output value (intake manifold pressure) of the pressure sensor 34 increases rapidly. On the other hand, when the EGR device 25 is abnormal and a predetermined amount of exhaust gas is not circulated, the output value of the pressure sensor 34 gradually increases as shown by the dotted line in FIG. Therefore, similarly to the O ₂ sensor 33, the failure determination of the EGR device 25 can be performed from the difference in the change in the output value. That is, the failure determination of the EGR device 25 can be performed based on whether or not the output value of the pressure sensor 34 is equal to or higher than the first threshold value P1 during the failure determination time T1. In this case as well, failure determination is performed when the output value of the pressure sensor 34 is equal to or smaller than the second threshold value P2 that is smaller than the first threshold value P1.

The failure determination (degradation determination) of the catalyst 27 is performed based on, for example, the O ₂ sensor 32 provided on the upstream side of the catalyst 27 and the output value of the O ₂ sensor 33 provided on the downstream side. Specifically, the difference between the time until the output value of the O ₂ sensor 32 changes by a certain amount and the time until the output value of the O ₂ sensor 33 changes by a certain amount is obtained, and this time difference is larger than the predetermined time. If it is short, it can be determined that there is a failure (deterioration) of the catalyst 27.

  The failure determination of the EGR device 25 and the catalyst 27 is also performed when the fuel is cut during the series travel mode, so that the failure determination can be performed in a state where the engine 12 is rotated at an arbitrary constant rotational speed. . Therefore, the accuracy of failure determination is greatly improved.

  In the case where failure determination is performed for such different types of devices at different timings, it is preferable that the rotational speed of the engine 12 in the failure determination is varied according to the type of device that is the target of failure determination. Also in this case, it is preferable to vary the rotational speed of the engine 12 before the fuel supply to the engine 12 is stopped as described above, and to keep the rotational speed of the engine 12 constant during failure determination. This can further improve the accuracy of failure determination.

  As mentioned above, although one embodiment of the present invention was described, of course, the present invention is not limited to this embodiment. The present invention can be modified as appropriate without departing from the spirit of the present invention. For example, in the above-described embodiment, the present invention has been described by taking as an example a hybrid vehicle capable of switching between the EV travel mode, the series travel mode, and the parallel travel mode. However, the present invention can travel in the series travel mode. Any hybrid vehicle can be applied.

  In the above-described embodiment, various devices including the front motor 11 and the engine 12 are controlled by one control device 50, but the configuration of the control device 50 is not particularly limited. For example, the control device 50 includes a motor control unit that controls the front motor 11 and an engine control unit that controls the engine 12, and the motor control unit and the engine control unit can communicate with each other. May be.

DESCRIPTION OF SYMBOLS 10 Vehicle 11 Front motor 12 Engine 13 Front drive transmission mechanism 14 Axle 15 Wheel 16 Inverter 17 Battery 18 DC / DC converter 19 Sub battery (12V battery)
20 Fuel Tank 21 Intake Manifold 22 Exhaust Manifold 23 EGR Passage 24 EGR Valve 25 EGR Device 26 Exhaust Pipe 27 Catalyst 28 Output System 29 Generator 30 Generator Inverter 31 Friction Clutch 32, 33 O ₂ Sensor 34 Pressure Sensor 50 Control Device 51 Failure Determination Means

Claims (4)

An internal combustion engine driven by fuel supply;
A generator having a rotating body connected to rotate in synchronization with a rotating element of the internal combustion engine;
A battery for storing the power of the generator;
A travel motor that is driven by the power of the battery and travels the vehicle;
A friction clutch that is provided between the internal combustion engine and the drive wheels of the vehicle and connects and disconnects transmission of driving force;
After the internal combustion engine is driven, it is confirmed that the friction clutch has cut off the transmission of the driving force, the fuel supply to the internal combustion engine is stopped, and the rotating element of the internal combustion engine is rotated by the generator. Failure determination means for determining a failure of equipment attached to the exhaust system of the internal combustion engine ,
An EV traveling mode in which the friction clutch is disengaged and the traveling motor is used as a drive source;
A series running mode in which the friction clutch is disengaged and running with the running motor as a drive source, and the generator is operated by the internal combustion engine to charge the battery;
The failure determination means includes
The hybrid vehicle , wherein the failure determination is performed when switching from the series travel mode to the EV travel mode . 2. The hybrid according to claim 1, wherein the failure determination unit controls the generator so as to vary a rotation speed of a rotating element of the internal combustion engine in accordance with a type of a device to be subjected to the failure determination. vehicle. The failure determination means controls the generator so as to keep the rotation speed of the internal combustion engine constant when the fuel supply is stopped after the fuel supply amount is changed and the internal combustion engine is driven. The hybrid vehicle according to claim 1 or 2. The failure determination means temporarily increases the amount of fuel supplied to the internal combustion engine before stopping the supply of fuel to the internal combustion engine when determining the failure of an oxygen sensor provided in the exhaust passage. The hybrid vehicle according to any one of claims 1 to 3, wherein:

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