Rotary angle detecting device

A rotary angle detecting device comprising:

• a main driving gear configured to be rotateable when directly or indirectly connected to a detection target rotating about a predetermined axis;
• a driven gear configured to be rotateable when meshed with the main driving gear;
• a magnet provided at a center of the driven gear;
• a holder member including a first insertion hole sized and dimensioned so that the detection target is insertable therethrough such that a surface of the first insertion hole rotatably supports the main driving gear;
• the holder member having a support portion to rotatably support the driven gear, and an opening of the support portion faces the magnet;
• a first cover member including a second insertion hole sized and dimensioned so that the detection target is insertable therethrough;
• the first cover member and a first side of the holder member spaced apart to form a first space when the first cover member is assembled to first side of the holder member, so that the main driving gear and the driving gear are disposed therebetween, and a part of the main driving gear disposed in the first space;
• a magnetic detection element, disposed to face the magnet with the opening of the support portion interposed therebetween, so as to detect a variation in magnetic field in accordance with a rotation of the magnet;
• a circuit board having the magnetic detection element mounted thereon;
• and
• a second cover member including a third insertion hole sized and dimensioned so that the detection target is insertable therethrough, the second cover member and the holder member spaced apart to form a second space to accommodate the circuit board when the second cover member is attached to a second side of the holder member,
• wherein the opening in the support portion of the holder member is closed by the circuit board.