Steering apparatus

A steering apparatus comprising:

• a rotation transmitting apparatus for transmitting an operation of a steering wheel of a vehicle to a steering mechanism, the rotation transmitting apparatus including:
• a differential mechanism having a first shaft and a second shaft arranged so as to be freely rotatable and linked with each other so as to rotate interlockingly, the first shaft being at a steering wheel side, and the second shaft being at a steering mechanism side;
• and
• a first electric motor for driving a part of the differential mechanism,
• wherein the differential mechanism is arranged to have a torque ratio (T2/T1) of a torque (T2) applied to the second shaft to a torque (T1) applied to the First shaft ranging from 1/0.7 to 1/0.9, and
• wherein the differential mechanism includes a first sun gear joined to the first shaft so as to rotate interlockingly, a second sun gear joined to the second shaft so as to rotate interlockingly, a first planetary gear meshed with the first sun gear, a second planetary gear rotating with the first planetary gear and meshed with the second sun gear, and a carrier supporting the first and second planetary gears and arranged to be driven by the first electric motor, wherein the number of teeth of each of the first and second sun gears and the first and second planetary gears is determined so as to satisfy the torque ratio, and
• wherein the torque ratio is obtained from the following formula:
• (Z1/Z2)×(Z3/Z4),
• where Z1 is the number of teeth of the first sun gear, Z2 is the number of teeth of the first planetary gear, Z3 is the number of teeth of second planetary gear, and Z4 is the number of teeth of the second sun gear.

A steering apparatus comprising:

• a rotation transmitting apparatus for transmitting an operation of a steering wheel of a vehicle to a steering mechanism, the transmitting apparatus including:
• a differential mechanism having a first shaft and a second shaft arranged so as to be freely rotatable and linked with each other so as to rotate interlockingly, the first shaft being at a steering wheel side, and the second shaft being at a steering mechanism side;
• a first electric motor for driving a part of the differential mechanism, the differential mechanism being arranged to have a torque ratio (T2/T1) of a torque (T2) applied to the second shaft to a torque (T1) applied to the first shaft ranging from 1/0.7 to 1/0.9;
• and
• a second electric motor for applying a desired torque to the first shaft in response to the torque applied to the second shaft.