BACKGROUND

1. Field

The following description relates to a vehicle controller configured to control a vehicle that includes an internal combustion engine capable of transmitting rotational power of a crankshaft to a driven wheel, a catalyst arranged in an exhaust passage of the internal combustion engine, a heater that generates heat by consuming electric power with the catalyst as a subject to be heated, a driving circuit that supplies the heater with electric power of a battery, and an electric generator that converts the rotational power of the crankshaft into electric power and supplies the driving circuit with the electric power.

2. Description of Related Art

Japanese Laid-Open Patent Publication No. 2009-227038 discloses an example of a vehicle including a controller. In the electric power generated by the motor generator, the controller controls the amount of electric power supplied to a heater that heats a catalyst (electrically heated catalyst: EHC).

When an anomaly has occurred in the controller, the motor generator and the EHC are constantly energized and the EHC and the battery, which charges the electric power generated by the motor generator, are constantly energized. In this case, the EHC and a member located proximate to the EHC, such as the catalyst, may excessively increase in temperature.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Example 1: A vehicle controller is configured to control a vehicle. The vehicle includes an internal combustion engine capable of transmitting rotational power of a crankshaft to a driven wheel, a catalyst arranged in an exhaust passage of the internal combustion engine, a heater configured to generate heat by consuming electric power with the catalyst as a subject to be heated, a driving circuit configured to supply the heater with electric power of a battery, a breaking circuit configured to break an electrical path between the battery and the driving circuit, and an electric generator configured to convert the rotational power of the crankshaft into electric power and supply the driving circuit with the electric power. The vehicle controller is configured to execute an anomaly determination process of determining whether an anomaly where power is constantly supplied from the battery to the heater has occurred in the driving circuit and a breaking process of breaking the electrical path by operating the breaking circuit when determining that the anomaly has occurred in the driving circuit. The vehicle controller is also configured to execute a duty cycle control process of alternately repeating an electric power generation execution period, during which the electric generator generates power, and an electric power generation stop period, during which the electric generator does not generate power, and controlling a duty cycle, which is a ratio of the electric power generation execution period to a single cycle of repeated cycles, when determining that the anomaly has occurred in the driving circuit, and the duty cycle control process includes at least one of two processes, which are a process of setting the duty cycle to be larger when a member in an overheatable region, in which overheating is possibly performed by the heater, has a low temperature than when the member has a high temperature and a process of setting the duty cycle to be larger when the internal combustion engine has a large intake air amount than when the internal combustion engine has a small intake air amount.

When an anomaly where power is constantly supplied from the battery to the heater has occurred in the driving circuit, the supply of power from the battery cannot be controlled. Thus, the amount of heat generated by the heater may not be able to be controlled. Consequently, this may excessively increase the temperature in the member located proximate to the heater such as the catalyst, which is subject to heating. Thus, in the above-described configuration, when an anomaly has occurred in the driving circuit, the electrical path between the battery and the heater is broken. This prevents the constant supply of electric power from the battery to the heater. Thus, as compared to when the electrical path is not broken, an excessive increase is limited in the temperature of the member located proximate to the heater. However, when the electric generator stops generating electric power, auxiliary devices such as the heater, which has the battery as the power supply, cannot supply electric power. Thus, when the breaking process is executed, the supply of electric power may be inadequate.

In the above-described configuration, the electric generator controls the generation of electric power to change the duty cycle in accordance with the intake air amount and the temperature of the member located proximate to the heater. The flow rate of fluid in the exhaust passage that takes heat from the member located proximate to the heater is larger when the intake air amount is large than when the intake air amount is small. This increases the upper limit value electric power that can be supplied to the heater. Further, the temperature of the member located proximate to the heater is more sufficient when the temperature of the member located proximate to the heater is low than when the temperature is high. This increases the upper limit value of electric power that can be supplied to the heater. Accordingly, setting the duty cycle in accordance with the intake air amount increases the amount of electric power generated by the electric generator while limiting an excessive increase in the temperature of the member located proximate to the heater.

Example 2: In the vehicle controller according to example 1, the battery is a high-voltage battery. The vehicle includes a low-voltage battery having a lower terminal voltage than the high-voltage battery and a step-down converter configured to step down an output voltage at the electric generator and apply the output voltage to the low-voltage battery. The step-down converter is capable of outputting electric power to the low-voltage battery when a terminal voltage at the electric generator is greater than or equal to an operation ensuring lower limit voltage. The duty cycle control process includes setting the duty cycle such that the output voltage at the electric generator in the electric power generation execution period is greater than or equal to the operation ensuring lower limit voltage.

In the above-described configuration, the output voltage of the electric generator during the electric power generation execution period is set to be greater than or equal to the operation ensuring lower limit voltage. This allows the step-down converter to supply the low-voltage battery with generated electric power.

Example 3: In the vehicle controller according to example 1 or 2, the vehicle includes a torque converter connected to the crankshaft and provided with a lock-up clutch. The vehicle controller is configured to execute a disengagement process of setting the lock-up clutch to a disengaged state when determining that the anomaly has occurred in the driving circuit.

For example, in a case in which the power of the crankshaft drives the driven wheel, when the lock-up clutch is set to the disengaged state, the rotational speed of the crankshaft tends to increase by an amount of slipping of the crankshaft toward the output side of the torque converter. Thus, in the above-described configuration, when it is determined that an anomaly has occurred in the driving circuit, the lock-up clutch is set to the disengaged state. In this case, as compared to when the lock-up clutch is set to the engaged state, control of intending to increase the rotational speed of the crankshaft is performed. The flow rate of fluid in the exhaust passage that takes the heat of the member located proximate to the heater increases to a larger extent when the rotational speed is high than when the rotation speed is low. Thus, as compared to when the disengagement process is set to the engaged state, the electric generator generates a large amount of electric power.

Example 4: In the vehicle controller according to example 3, the vehicle controller is configured to execute a fuel cut-off process of stopping combustion control in the internal combustion engine on a condition that an accelerator operation amount is zero and a stop process of stopping the disengagement process in a case in which the fuel cut-off process has been executed even when determining that the anomaly has occurred in the driving circuit.

When the fuel cut-off process is executed, the rotational speed of the crankshaft decreases. The speed decrease occurs at a higher pace when the lock-up clutch is disengaged than when the lock-up clutch is engaged. In the above-described configuration, when the fuel cut-off process is executed, the disengagement process is stopped to limit a decrease in the rotational speed of the crankshaft and limits a decrease in the flow rate of exhaust gas that takes the heat of the member located proximate to the heater. Thus, as compared to when the disengagement process is continued, the electric generator generates a large amount of electric power.

Example 5: In the vehicle controller according to any one of examples 1 to 4, the vehicle controller is configured to execute an idling process of controlling a rotational speed of the crankshaft of the internal combustion engine to a target rotational speed when an accelerator operation amount is zero. The vehicle controller is also configured to execute a setting process of setting the target rotational speed to be a larger value when determining that the anomaly has occurred in the driving circuit than when determining that the anomaly has not occurred in the driving circuit. The vehicle controller is further configured to execute an amount decreasing process of decreasing an amount of fuel injected from a fuel injection valve of the internal combustion engine to a larger extent in a case in which the idling process is stopped to switch to control corresponding to the accelerator operation amount when determining that the anomaly has occurred in the driving circuit than in a case in which the idling process is stopped to switch to control corresponding to the accelerator operation amount when determining that the anomaly has not occurred in the driving circuit.

The flow rate of exhaust gas that takes heat from the member located proximate to the heater is smaller when the idling process is executed than when the idling process is not executed. In the above-described configuration, when it is determined that an anomaly has occurred in the driving circuit, the target rotational speed is set to a large value to maximize the flow rate of exhaust gas that takes heat from the member located proximate to the heater. Thus, as compared to when the target rotational speed is not increased, the electric generator generates a large amount of electric power.

However, the driving force of the vehicle is larger when the idling process is not performed in a case in which the target rotational speed is increased than in which the target rotational speed is not increased. This may make the user feel strange. In the above-described configuration, the amount decreasing process is performed to set a small amount of fuel when the idling process is not performed. As compared to the normal time, this limits an increase in the driving force of the vehicle when the idling process is not performed.

Example 6: In the vehicle controller according to any one of examples 1 to 5, the internal combustion engine includes an EGR passage configured to cause exhaust gas discharged to the exhaust passage to flow into an intake passage and an EGR valve configured to adjust a cross-sectional flow area of the EGR passage. The catalyst is a selective catalytic reduction catalyst. The vehicle includes a urea solution addition valve configured to add urea solution to exhaust gas in a section located at an upstream side of the catalyst. The vehicle controller is configured to execute a valve operation process of operating the EGR valve in order to set an EGR ratio to be smaller when determining that the anomaly has occurred in the driving circuit than when determining that the anomaly has not occurred in the driving circuit and an amount increasing process of increasing an amount of the urea solution added from the urea solution addition valve to a larger extent when the valve operation process is executed than when the valve operation process is not executed.

In the above-described configuration, when it is determined that an anomaly has occurred in the driving circuit, the concentration of NOx in exhaust gas is increased by reducing the EGR ratio. This increases the amount of urea solution in which NOx should be reduced in the catalyst. Thus, the amount increasing process is executed. This allows the urea solution to take the heat generated by the heater and thus limits an excessive increase in the temperature of the member located proximate to the heater. Accordingly, as compared to when the amount increasing process is not performed, the electric generator generates a large amount of electric power.

Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

