Seat belt system with comfort control

摘要

A rotatable spool has seat belt webbing wound around the spool. A motor, when actuated, rotates the spool in the belt withdrawal direction. A spring has a biasing force which rotates the spool to wind the belt webbing onto the spool. A worm gear mechanism is located between the motor and the spool and is selectively drivingly connectable with the spool. When drivingly connected with the spool, the worm gear mechanism prevents the biasing force of the spring from winding the belt webbing onto the spool. A clutch, when engaged, connects the spool and the worm gear mechanism. The clutch is disengaged and the motor is deactuated when a belt tension signal is below a lower predetermined threshold value. The clutch is engaged and the motor is actuated when the belt tension signal is above an upper predetermined threshold value which is greater than the lower predetermined threshold value. The clutch is engaged and the motor is deactuated when the belt tension signal is between the upper and lower predetermined threshold values. A pressure sensor provides the belt tension signal which continuously varies in magnitude as the amount of tension in the belt webbing continuously varies.