that provides a rotation signal according to the sensing signal in this device the bearing and the mounting surface are integrally formed into the housing at a prescribed distance to secure an unchanged air gap distance application_number US 81976607 A description a rotation detecting device according to the first embodiment of the invention will be described with reference to fig1 4 and fig5 a 5f as shown in fig1 the rotation detecting device is comprised of a housing 10 a gear teeth type magnetic rotor member 20 a magnet sensing semiconductor chip 30 a biasing permanent magnet 40 and a cover 50 as shown in fig2 and 3 the housing 10 is made of an insulative resinous member that has a bearing portion 11 for supporting one end of a rotary shaft 21 of the rotor 20 and a chip mounting surface 10 a that is formed perpendicular to the rotary shaft 21 on an imaginary plane x extending through the axially middle portion of the rotor member 20 the semiconductor chip 30 which includes a magnetic sensor chip 31 and a signal processing chip 32 is directly fixed to the chip mounting surface 10 a because the bearing portion 11 and the chip mounting.