DYNAMIC NIP WIDTH DETERMINATION WITH FRS SENSOR
Original Publication Date: 1990-Dec-31
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
An electrophotographic printing machine uses a fusing device to permanently fix a toner powder image to a copy sheet. One type of fusing device frequently employed includes a heated fuser roller and a pressure roller. The fuser roller and pressure roller define a nip through which the copy sheet with the toner powder image thereon passes. For best fusing results it is desirable to have close control over the temperature and pressure exerted at the nip. An improved design of a tool for measuring fuser roll nip pressure is realized by incorporating short force sensing resistors (FRS) that measure the nip width by noting the duration of resistance change and comparing this value with fuser speed. Fuser speed is determined by the time interval between the resistance change pulses and the known geometry of the sensor. The device consists of a wide strip of FRS placed over metallic conductors constructed in an interdigitated or alternating finger pattern that is mounted between two polyimide sheets, as shown in the Figure. The connection of the interdigitated network to a measurement device is via two metallic strips that run the entire length of the device on the outside of the polyimide sheets. The polyimide material used is a commercial polymer. A working example follows: the strip sensor device is fed into a hand held ohm meter where contact is made with the external conductors and the resistance between the finger pattern is measured. The strip is then presented to a fuser nip and fed through while the resistance of the long finger area and the timing of the pulses from the short bar area are measured.