Patent ID: 8385763

Claim:
A heating fixer, comprising: a fixing member configured to heat and melt a toner image; a pressure member configured to contact the fixing member upon application of pressure to form a nip; a pressure member controller comprising a cam, configured to vary the pressure of the pressure member against the fixing member with rotation of the cam to set the nip to at least three different widths; a drive motor configured to drive the cam; and at least two position detectors configured to detect a rotational position of the cam, each of the position detectors including a corresponding fixed transmission sensor and a corresponding blocking filler coaxially rotating with the cam in a body, the blocking fillers of the position detectors comprising a corresponding blocking blade capable of blocking light received by the transmission sensor, the blocking blades of the blocking fillers having phases different from one another, the blocking blades cutting across the light received by the transmission sensor to switch on and off signals of the transmission sensor as the blocking filler rotates, and the rotational position of the cam controlled by switching the signals of the transmission sensor.