Rotary damper

A rotary damper for limiting a movement of a viscous fluid to generate a damping torque in reaction to a rotating force applied, the rotary damper comprising:

• a casing having a circular cylindrical chamber filled by the viscous fluid;
• a partition in a shape of substantial open fan, placed in the circular cylindrical chamber and partitioning an inside of the circular cylindrical chamber;
• a rotor configured to rotate due to the rotating force applied and comprising a rotor body and a vane, the rotor body contained in the circular cylindrical chamber rotatably relative to the circular cylindrical chamber and placing an outer peripheral surface close to an inner peripheral surface of the partition, the vane formed along a center line of the circular cylindrical chamber and radially outwardly from the outer peripheral surface of the rotor body to place a front end face close to an inner peripheral surface of the circular cylindrical chamber;
• a lid attached to an opening section of the circular cylindrical chamber and sealing the rotor along with the viscous fluid within the circular cylindrical chamber;
• and
• a bypass passage having a groove longer than a thickness of the vane in a rotational direction of the rotor, the groove being located on a lower side of the lid;
• upon faces that form both ends of the vane in the rotational direction of the rotor being located inside of a range of the bypass passage, an area upstream and an area downstream from the vane against the rotational direction of the rotor being communicated with each other through the bypass passage, out of the areas in the circular cylindrical chamber partitioned by the vane and the partition, and the viscous fluid in the area upstream and in the area downstream becoming movable through the bypass passage;
• and
• upon at least one of the faces that form the both ends of the vane in the rotational direction of the rotor being located outside of the range of the bypass passage, the bypass passage providing no communication between the area upstream and the area downstream from the vane and the viscous fluid in the area upstream and in the area downstream becoming immovable through the bypass passage.

A rotary damper for limiting a movement of a viscous fluid to generate a damping torque in reaction to a rotating force applied, the rotary damper comprising:

• a casing having a circular cylindrical chamber filled by the viscous fluid;
• a partition in a shape of substantial open fan, placed in the circular cylindrical chamber and partitioning an inside of the circular cylindrical chamber;
• a rotor configured to rotate due to the rotating force applied and comprising a rotor body and a vane, the rotor body contained in the circular cylindrical chamber rotatably relative to the circular cylindrical chamber and placing an outer peripheral surface close to an inner peripheral surface of the partition, the vane formed along a center line of the circular cylindrical chamber and radially outwardly from the outer peripheral surface of the rotor body to place a front end face close to an inner peripheral surface of the circular cylindrical chamber;
• a lid attached to an opening section of the circular cylindrical chamber and sealing the rotor along with the viscous fluid within the circular cylindrical chamber;
• and
• a bypass passage having a groove longer than a thickness of the vane in a rotational direction of the rotor, the groove being located on an inner peripheral surface side of the circular cylindrical chamber;
• upon faces that form both ends of the vane in the rotational direction of the rotor being located inside of a range of the bypass passage, an area upstream and an area downstream from the vane against the rotational direction of the rotor being communicated with each other through the bypass passage, out of the areas in the circular cylindrical chamber partitioned by the vane and the partition, and the viscous fluid in the area upstream and in the area downstream becoming movable through the bypass passage;
• and
• upon at least one of the faces that form the both ends of the vane in the rotational direction of the rotor being located outside of the range of the bypass passage, the bypass passage providing no communication between the area upstream and the area downstream from the vane and the viscous fluid in the area upstream and in the area downstream becoming immovable through the bypass passage.