Rotation angle detection device

A rotation angle detection device for a steering of a vehicle, the rotation angle detection device comprising:

• a correction-object driven gear that is a driven gear meshing with a main driving gear that is provided to a pinion shaft so as to be integrally rotatable with the pinion shaft that is linked to steering wheels;
• a first sensor that is configured to generate an electrical signal based on rotation of the correction-object driven gear;
• an electronic control unit that is configured to compute a driven-side rotation angle, which is a rotation angle of the correction-object driven gear, based on the electrical signal generated by the first sensor, wherein
• the number of teeth of the correction-object driven gear is the number of teeth obtained by dividing the number of teeth of the main driving gear by an integer,
• the electronic control unit is configured to store a correction angle used to correct the driven-side rotation angle when computing the driven-side rotation angle, and
• the correction angle is a predetermined deviation in a predetermined angle domain obtained as an average value in which deviations of a number equal to the integer and corresponding to the same relative rotation angle is averaged, so as to be deviation in an angle domain of 0 to 360 degrees, the predetermined deviation is a deviation obtained in the predetermined angle domain and is deviation between the driven-side rotation angle and an actual rotation angle of the correction-object driven gear, and the driven-side rotation angle is obtained over a full angle domain when the correction-object driven gear is rotated for a number of times equal to the integer;
• a correction-exempt driven gear that meshes with the main driving gear and is a different driven gear from the correction-object driven gear;
• and
• a second sensor that is configured to generate an electrical signal based on rotation of the correction-exempt driven gear, wherein
• the numbers of teeth of the correction-object driven gear and the correction-exempt driven gear are different from each other,
• the electronic control unit is configured to compute a rotation angle of the correction-exempt driven gear based on the electrical signal generated by the second sensor, and is configured not to perform correction of the rotation angle of the correction-exempt driven gear based on the correction angle, and
• the electronic control unit is configured to compute the number of rotations of the correction-object driven gear based on an angle difference between the rotation angle of the correction-object driven gear and the rotation angle of the correction-exempt driven gear.