Patent ID: 7151991

Claim:
A driving-force distribution control system for a four-wheel-drive vehicle comprising: a friction clutch through which a driving force produced by a driving power source is delivered to primary drive wheels and to secondary drive wheels at a distribution ratio based on an operating condition of the vehicle; and a four-wheel-drive vehicle controller configured to be electronically connected to the friction clutch for automatically controlling the distribution ratio, the four-wheel-drive vehicle controller comprising: (a) a torque threshold value setting section that sets a lower limit torque, above which noise and vibrations take place within the friction clutch when an input direction of torque inputted into the friction clutch is reversed, as a predetermined torque threshold value; (b) an input-torque past-history condition decision section that determines whether a past-history condition that a clutch input torque has been greater than or equal to the predetermined torque threshold value is satisfied when a command torque for the friction clutch is greater than or equal to the predetermined torque threshold value during a time period from a time when the command torque begins to rise from a zero torque level to a current execution cycle of the driving-force distribution control system; (c) a command torque condition decision section that determines whether a command torque condition that a current value of the command torque, produced at the current execution cycle, is greater than or equal to the predetermined torque threshold value is satisfied; (d) a reversal-of-torque condition decision section that determines whether a reversal-of-torque condition that an input direction of torque inputted into the friction clutch is reversed is satisfied; (e) a countermeasure-of-noise command torque calculation section that calculates a countermeasure-of-noise command torque obtained by decreasingly compensating for the current value of the command torque when the past-history condition, the command torque condition, and the reversal-of-torque condition are all satisfied; and (f) a clutch command torque control section that outputs a command signal corresponding to the countermeasure-of-noise command torque to the friction clutch, when the past-history condition, the command torque condition, and the reversal-of-torque condition are all satisfied.