Fusing technology is a core technology incorporated in multifunctional devices and printers using the xerography process. This technology fixes images on paper by soaking toner into paper as follows: 1) heating and melting toner on paper, and 2) applying pressure from rolls on and under paper.
Color fusing yields solid colors and produces high gloss on the toner surface by applying enough heat and sufficiently melting toner. In the conventional two-roll fusing method (using a fuser roll and pressure roll), the area where toner contacts the fuser roll is created by the thick rubber layer of a larger-diameter roll when pressure is applied. This enables enough heat being applied to toner. One issue regarding the conventional method was how to reduce warm-up time (the time needed for recovery to prepare for the next printing). This is because a thick core (roll core) must be used in the large-diameter roll to ensure rigidity, and thereby the heat capacity of the entire roll including the thick rubber layer is large.
To solve this issue, Fuji Xerox employed a method using a pressure roll consisting of a belt and a pressure pad (Fig. 1). The area where toner contacts the fuser roll is widened by pressing the belt against the fuser roll. Heat capacity is also reduced by using a smaller-diameter fuser roll with a thin core and thin rubber layer. As a result, the warm-up time is significantly reduced.
This fusing method realized miniaturization and better energy consumption at the same time (Fig. 2).
The free belt nip fusing technology, which has earned an excellent reputation for realizing compactness and energy conservation, is applied in many Fuji Xerox products and continues to evolve. High-speed printing has been realized in recent years due to prolonged life span, improved product reliability, and better energy-saving technologies. From a technical point of view, a highly efficient heat lamp has been applied to improve heat efficiency. More even heat distribution has also been achieved in warm-up, standby and paper-feed modes by setting the lamp at an optimum location, resulting in lower power consumption. Moreover, a material with a low friction coefficient was newly developed for use as the sliding material in the fusing belt, thereby prolonging the belt's life span and reducing the power consumed by the drive motor.
This fusing technology is also employed in compact printers. Using a fuser roll of even smaller diameter takes the advantages of a short warm-up time and miniaturization. Although the durability of fuser roll's surface layer was considered an issue given the increased number of rotations per sheet of printing due to using a smaller-diameter roll, this issue was solved by strengthening the adhesiveness of the roll core and coating rubber, and by developing highly durable materials.