INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-163379 filed on Aug. 31, 2018 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle, and a control method for a vehicle.

2. Description of Related Art

Disclosed in Japanese Patent Application Publication No. 2011-231710 (JP 2011-231710 A) is a hybrid vehicle including an internal combustion engine and an electric motor as a power source, with an electrically-heated catalyst (EHC) device provided in an exhaust passage of the internal combustion engine. The electrically-heated catalyst device is configured to be able to heat a catalyst carried on a base material, the base material being retained inside the exhaust passage to generate heat upon being energized. When the electrically-heated catalyst device is provided, the catalyst device can be warmed up before the internal combustion engine is started up.

In JP 2011-231710 A, when the base material made of a porous body is heated in the state where water is contained in the base material, bumping may occur inside the base material, so that vapor may be generated. The generated vapor may rapidly increase the pressure inside the base material and cause deterioration of the base material. Accordingly, when water is contained in the base material, low electric power control is performed at the time of heating the base material so as to supply electric power, which is lower than usual, to the base material. The low electric power control is considered to achieve slow and gradual evaporation of the water contained in the base material, and thereby prevent deterioration of the base material due to the bumping.

SUMMARY

When the base material is heated in the state where water is present on the surface or inside of the base material, that is, in the state where water is present inside the catalyst device, there is a possibility of deterioration of the base material attributed to generation of temperature difference inside the base material, in addition to the deterioration of the base material attributed to bumping.

The present disclosure provides a vehicle and a control method for a vehicle that restrain deterioration of a base material which occurs when the base material is heated in the state where water is present inside a catalyst device.

A first aspect of the present disclosure relates to a vehicle. The vehicle includes an internal combustion engine, an electrically-heated catalyst device provided in an exhaust passage of the internal combustion engine, and an electronic control unit. The electrically-heated catalyst device includes a conductive base material that generates heat upon being energized, and a catalyst heated through the conductive base material. The electronic control unit is configured to control base material electric power supply that is supplied to the conductive base material. The electronic control unit is configured to determine whether or not the conductive base material is in a stagnant period where temperature of the conductive base material partially stagnates in a prescribed temperature zone, the stagnant period occurring when water is present inside the electrically-heated catalyst device in a process of increase in temperature of the conductive base material. When determining that the conductive base material is in the stagnant period, the electronic control unit is configured to control the base material electric power supply to be lower than when determining that the conductive base material is not in the stagnant period.

In the vehicle, the electronic control unit may be configured to calculate an internal water content that is a water content present inside the electrically-heated catalyst device. The electronic control unit may be configured to determine that the conductive base material is in the stagnant period, when the internal water content is larger than zero, or equal to or more than a prescribed water content, and the temperature of the conductive base material is equal to or more than a prescribed temperature that allows determination that the water present inside the electrically-heated catalyst device is evaporated.

In the vehicle, when determining that the conductive base material is in the stagnant period, the electronic control unit may be configured to control the base material electric power supply to be lower than when determining that the conductive base material is not in the stagnant period, based on the internal water content. When the internal water content is large, the electronic control unit may be configured to control the base material electric power supply to be lower than when the internal water content is small.

In the vehicle, when determining that the conductive base material is in the stagnant period, the electronic control unit may be configured to control the base material electric power supply, for a prescribed time, to be a prescribed electric power that is lower than a prescribed normal electric power supply that is supplied to the conductive base material when determining that the conductive base material is not in the stagnant period. When the internal water content is large, the electronic control unit may be configured to set the prescribed time longer than when the internal water content is small.

In the vehicle, the prescribed water content may be a water content where a temperature difference, generated between a region where water is present and a region where water is not present in the conductive base material in the process of increase in temperature of the conductive base material when the electronic control unit controls the base material electric power supply to be the prescribed normal electric power supply, becomes equal to or more than a prescribed temperature difference, the prescribed normal electric power supply being supplied to the conductive base material when the electronic control unit determines that the conductive base material is not in the stagnant period.

In the vehicle, the electronic control unit may be configured to determine that the conductive base material is in the stagnant period irrespective of whether or not water is present inside the electrically-heated catalyst device, when the temperature of the conductive base material becomes equal to or more than the prescribed temperature that allows determination that the water present inside of the electrically-heated catalyst device is evaporated. When determining that the conductive base material is in the stagnant period, the electronic control unit may be configured to control the base material electric power supply, for a prescribed time, to be a prescribed electric power that is lower than a prescribed normal electric power supply that is supplied to the conductive base material when determining that the conductive base material is not in the stagnant period.

The vehicle may further include a traveling motor as a driving source of the vehicle. The electronic control unit may be configured to control the base material electric power supply by energizing the conductive base material during traveling of the vehicle with drive power of the traveling motor before starting up the internal combustion engine.

A second aspect of the present disclosure relates to a control method for a vehicle. The vehicle includes an internal combustion engine, an electrically-heated catalyst device provided in an exhaust passage of the internal combustion engine, and an electronic control unit. The electrically-heated catalyst device includes a conductive base material that generates heat upon being energized, and a catalyst heated through the conductive base material. The control method includes: controlling, by the electronic control unit, base material electric power supply that is supplied to the conductive base material; determining, by the electronic control unit, whether or not the conductive base material is in a stagnant period where temperature of the conductive base material partially stagnates in a prescribed temperature zone, the stagnant period occurring when water is present inside the electrically-heated catalyst device in a process of increase in temperature of the conductive base material; and controlling, by the electronic control unit, when the electronic control unit determines that the conductive base material is in the stagnant period, the base material electric power supply to be lower than when determining that the conductive base material is not in the stagnant period.

The above configuration can restrain deterioration of the base material caused when the base material is heated in the state where water is present inside the electrically-heated catalyst device.

