Belt transmission system

A belt transmission system comprising:

• a first pulley transmitting a first power;
• a second pulley transmitting a second power;
• an endless belt wrapped between the first pulley and the second pulley;
• and
• an automatic tensioner including a first tension pulley applying tension to a portion of the endless belt located between the first pulley and the second pulley on a slack side of the first pulley during normal operation, a second tension pulley applying tension to a portion of the endless belt located between the first pulley and the second pulley on a tension side of the first pulley during normal operation, a fixing member, and an arm provided on the fixed member in a manner capable of oscillating in an axial rotation direction of the fixed member,
• wherein
• the first tension pulley and the second tension pulley both are supported on the arm, force from the endless belt makes the first tension pulley and the second tension pulley rotate in the same direction, and
• when the first tension pulley rotates in a direction tensioning the endless belt, the second tension pulley also rotates in the direction tensioning the endless belt, and
• a T/S ratio determined by the equation
• {L1×sin(θ1/2)×sin(α1)}/{L2×sin(θ2/2)×sin(α2)}
• is bigger than 1, where a first arm length from a pivotal center of the arm to a center of the second tension pulley is L1, a belt wrap angle at the second tension pulley is θ1, and a hub load angle at the second tension pulley is α1, and where a second arm length from a pivotal center of the arm to a center of the first tension pulley is L2, a belt wrap angle at the first tension pulley is θ2, and a hub load angle at the first tension pulley is α2.