Fixing device having a cooling device for a pressure member

摘要

A fixing device includes a heating roller, a fixing roller, an endless fixing belt, a pressure roller, a temperature gauge, and a cooling device. The fixing belt is stretched between the heating roller and the fixing roller. The pressure roller includes a core rod and an elastic layer formed on an outer circumferential surface of the core rod, and is pressed against the fixing roller via the fixing belt to form a nip portion to thermally fix an image on a recording medium passed through the nip portion. The temperature gauge measures the surface temperature of the pressure roller. The cooling device includes plural cooling units arranged parallel to a rotation axis of the pressure roller, and cools the pressure roller while adjusting the amount of cooling for each of the cooling units in accordance with the surface temperature of the pressure roller measured by the temperature gauge.

主权项

1. A fixing device comprising:
a heating roller; a fixing roller; an endless fixing belt stretched between the heating roller and the fixing roller; a pressure roller including a core rod and an elastic layer formed on an outer circumferential surface of the core rod, and pressed against the fixing roller via the fixing belt to form a nip portion between the pressure roller and the fixing belt to thermally fix an image on a recording medium passed through the nip portion; a plurality of temperature sensors configured to measure the surface temperature of the pressure roller; and a cooling device including a plurality of cooling units and a plurality of blowers arranged parallel to a rotation axis of the pressure roller, and to perform a cooling operation to cool the pressure roller while adjusting the amount of cooling for each of the cooling units in accordance with the surface temperature of the pressure roller measured by the plurality of temperature sensors, and to adjust an amount of cooling air blown per unit time or a duration of blowing of the cooling air in accordance with a temperature of the cooling air after blowing a constant amount of cooling air upon start of the fixing device, wherein each of the blowers includes a sensor to detect temperature or humidity of the cooling air, and wherein the cooling operation suppress uneven change in an outer diameter of the pressure roller due to the change in temperature so that the pressure roller maintains a constricted shape in a direction of the rotation axis.