Hybrid vehicle and control method thereof

A hybrid vehicle, having an internal combustion engine capable of outputting power for driving the hybrid vehicle and equipped in an exhaust system with a catalytic conversion unit including a purifying catalyst for purifying exhaust, a motor constructed to input and output power for driving the hybrid vehicle, a battery unit including at least one secondary battery designed to transmit electric power to and from the motor, and a charger connected to an external power supply in a system shutdown state of the hybrid vehicle to charge the secondary battery of the battery unit with electric power from the external power supply, the hybrid vehicle being capable of motor travel where the hybrid vehicle is driven only with input and output power to and from the motor and hybrid travel where the hybrid vehicle is driven with output power from the internal combustion engine and with the input and output power to and from the motor, the hybrid vehicle comprising:

• an accumulated charge ratio calculation module configured to calculate an accumulated charge ratio that is a ratio of an accumulated charge amount in the at least one secondary battery of the battery unit to a whole capacity of the at least one secondary battery of the battery unit;
• a mode setting module configured to, when the calculated accumulated charge ratio is at least larger than a first preset ratio at system startup of the hybrid vehicle, set a motor travel priority mode where the motor travel is prioritized for driving the hybrid vehicle until the calculated accumulated charge ratio becomes less than a second preset ratio that is less than the first preset ratio during vehicle travelling, while setting a hybrid travel priority mode where the hybrid travel is prioritized for driving the hybrid vehicle when the motor travel priority mode is not set;
• and
• a control module configured to, when the calculated accumulated charge ratio becomes less than a third preset ratio that is smaller than the first preset ratio and larger than the second preset ratio in a state that the purifying catalyst is not at a temperature where the purifying catalyst is activated during vehicle travelling upon setting the motor travel priority mode to prioritize the motor travel, control the internal combustion engine and the motor so that the internal combustion engine is started up and the hybrid vehicle is driven with the motor travel priority mode while the internal combustion engine is operated in an appropriate state to warming up the purifying catalyst.