Rotation angle detection device

1. A rotation angle detection device, having a magnet installed on a rotating shaft, which magnetically detects a rotation angle of the rotating shaft, the device comprising:

a magnetizing body having a magnet installed onto the valve shaft, which rotates together therewith, and a magnetic sensor that magnetically detects the rotation angle of the valve shaft, the magnetic sensor having a magneto-electric conversion element mounted onto a substrate and being structured to detect a magnetic field of the magnet and output the detection signal to a control device;

a plate member having a predetermined thickness which is fastened and fixed to one end of the rotating shaft,

wherein the magnet is molded to the plate member into a cylindrical shape having a height larger than the predetermined thickness and is fixed to the rotating shaft via the plate member.

2. The rotation angle detection device according to claim 1 , wherein the plate member includes an outer edge portion which is buried in an inner circumferential surface of the magnet.

3. The rotation angle detection device according to claim 1 , wherein the magnet includes a first extending portion extending to one surface side of the plate member, and a second extending portion extending to the other surface side of the plate member.

4. The rotation angle detection device according to claim 3 , wherein the plate member is fastened and fixed to the one end of the rotating shaft by a bolt inserted from the one surface side, and

the first extending portion extends to at least a head portion of the bolt protruding to the one surface side of the plate member.

5. The rotation angle detection device according to claim 3 , wherein the second extending portion extends so as to be larger than the first extending portion.

6. The rotation angle detection device according to claim 1 , wherein the plate member is formed of a non-magnetic metal material.