Four-wheel drive vehicle and control device for four-wheel drive vehicle

A control device that is mounted on a four-wheel drive vehicle, in which

• the four-wheel drive vehicle in configured to be switched between a two-wheel drive mode and a four-wheel drive mode and includes:
• a pair of right and left main drive wheels to which a driving force of a driving source is transmitted in the two-wheel drive mode and the four-wheel drive mode,
• a pair of right and left auxiliary drive wheels to which the driving force of the driving source is transmitted in the four-wheel drive mode,
• a drive shaft that transmits the driving force to the auxiliary drive wheels,
• a first clutch configured to cut off transmission of the driving force from the driving source to the drive shaft,
• a second clutch configured to cut off transmission of the driving force from the drive shaft to the auxiliary drive wheels, and
• a first actuator that actuates the first clutch,
• a second actuator that actuates the second clutch, the second actuator including an electric motor,
• the control device controls the first and second actuators, and
• the first clutch is a dog clutch that transmits a rotational force when a projection engages with a recess, and the second clutch is a friction clutch that transmits the rotational force when friction members are caused to frictionally contact each other by a pressing force received from the second actuator, the control device comprising:
• a first control device that, when the four-wheel drive vehicle is in the two-wheel drive mode in which the driving force is transmitted only to the pair of right and left main drive wheels, cuts off transmission of the rotational force via the dog clutch and the friction clutch to stop rotation of the drive shaft;
• a second control device that, when at least one of the pair of right and left main drive wheels slips in the two-wheel drive mode, causes the projection and the recess of the dog clutch to engage with each other after rotating the drive shaft by the rotational force transmitted via the friction clutch to synchronize the dog clutch;
• and
• a third control device that, if a predetermined condition is satisfied when the pair of right and left main drive wheels are not slipping in the two-wheel drive mode, causes the projection and the recess of the dog clutch to engage with each other after rotating the drive shaft by the rotational force transmitted via the friction clutch to synchronize the dog clutch, wherein
• time required to synchronize the dog clutch by the third control device is set to be longer than that required to synchronize the dog clutch by the second control device, and
• a first electric current that drives the electric motor when controlled by the second control device is greater than a second electric current that drives the electric motor when controlled by the third control device.