Control apparatus for four-wheel drive vehicle, four-wheel drive vehicle, and control method

A four-wheel drive vehicle that is capable of switching a state of drive between a two-wheel drive state in which the vehicle travels by transmitting power provided by a drive force source only from a main drive shaft to main driving wheels and a four-wheel drive state in which the vehicle travels by transmitting the power to the main driving wheels, and also by transmitting the power from the main drive shaft to an auxiliary drive shaft by putting into a connected state a first power connection/disconnection device capable of connecting and disconnecting a power transmission path between the main drive shaft and the auxiliary drive shaft, and by transmitting the power from the auxiliary drive shaft to auxiliary driving wheels by putting into the connected state a second power connection/disconnection device capable of connecting and disconnecting a power transmission path between the auxiliary drive shaft and the auxiliary driving wheels, the four-wheel drive vehicle comprising

• a control apparatus that puts both the first power connection/disconnection device and the second power connection/disconnection device into a disconnected state when the state of drive is switched to the two-wheel drive state, a control portion temporarily switches only one of the first power connection/disconnection device and the second power connection/disconnection device into the connected state when a count value concerning a travel of the vehicle in the two-wheel drive state becomes equal to or greater than a predetermined value.

A method of controlling a four-wheel drive vehicle, the method comprising:

• switching a state of drive between a two-wheel drive state in which the vehicle travels by transmitting power provided by a drive force source only from a main drive shaft to main driving wheels and a four-wheel drive state in which the vehicle travels by transmitting the power to the main driving wheels, and also by transmitting the power from the main drive shaft to an auxiliary drive shaft by putting into a connected state a first power connection/disconnection device capable of connecting and disconnecting a power transmission path between the main drive shaft and the auxiliary drive shaft, and by transmitting the power from the auxiliary drive shaft to auxiliary driving wheels by putting into the connected state a second power connection/disconnection device capable of connecting and disconnecting a power transmission path between the auxiliary drive shaft and the auxiliary driving wheels, wherein both the first power connection/disconnection device and the second power connection/disconnection device are put into a disconnected state when the state of drive is switched to the two-wheel drive state;
• detecting a count value concerning a travel of the vehicle in the two-wheel drive state;
• and
• temporarily switching only one of the first power connection/disconnection device and the second power connection/disconnection device into the connected state when the count value becomes equal to or greater than a predetermined value.