Torque distribution control apparatus for four-wheel drive vehicle and four-wheel drive vehicle having the same

A torque distribution control apparatus for a four-wheel drive vehicle, comprising:

• vehicle-speed detection means for detecting a vehicle speed of the four-wheel drive vehicle which includes:
• right and left main driving wheels to which a driving torque output from a driving source is directly transmitted;
• and
• right and left sub-driving wheels to which the driving torque is transmitted via right and left torque distribution clutches;
• wheel-speed detection means for detecting wheel speeds of the main driving wheels and the sub-driving wheels;
• sub-driving-wheel distribution-torque calculation means for calculating a sub-driving-wheel distribution torque in accordance with a rotation speed difference between the main driving wheels and the sub-driving wheels calculated based on an output from the wheel-speed detection means;
• torque limiting means for limiting an upper limit of the sub-driving-wheel distribution torque when the sub-driving-wheel distribution torque calculated by the sub-driving-wheel distribution-torque calculation means is higher than or equal to a first predetermined value, both a rotation speed difference of the left torque distribution clutch and a rotation speed difference of the right torque distribution clutch are larger than or equal to a second predetermined value, and the vehicle speed detected by the vehicle-speed detection means is lower than or equal to a third predetermined value;
• and
• controlling means for controlling the sub-driving-wheel distribution torque to be transmitted to the right and left sub-driving wheels by the right and left torque distribution clutches in accordance with a driving state of the vehicle.

A four-wheel drive vehicle comprising:

• right and left main driving wheels to which a driving torque output from a driving source is directly transmitted;
• right and left sub-driving wheels to which the driving torque is transmitted via right and left torque distribution clutches;
• and
• a torque distribution control apparatus comprising:
• a vehicle-speed detector configured to detect a vehicle speed of the four-wheel drive vehicle;
• a wheel-speed detector configured to detect wheel speeds of the main driving wheels and the sub-driving wheels;
• a sub-driving-wheel distribution-torque calculator configured to calculate a sub-driving-wheel distribution torque in accordance with a rotation speed difference between the main driving wheels and the sub-driving wheels calculated based on an output from the wheel-speed detector;
• a torque limiter configured to limit an upper limit of the sub-driving-wheel distribution torque when the sub-driving-wheel distribution torque calculated by the sub-driving-wheel distribution-torque calculator is higher than or equal to a first predetermined value, both a rotation speed difference of the left torque distribution clutch and a rotation speed difference of the right torque distribution clutch are larger than or equal to a second predetermined value, and the vehicle speed detected by the vehicle-speed detector is lower than or equal to a third predetermined value;
• and
• a controller configured to control the sub-driving-wheel distribution torque to be transmitted to the right and left sub-driving wheels by the right and left torque distribution clutches in accordance with a driving state of the vehicle.