Fixing device and image forming apparatus provided with same

摘要

A fixing device includes a heat source, a fixing roller, a pressure roller, an elastic layer, a pressing portion, a restricting portion and a driving unit. The fixing roller is heated by the heat source. The pressure roller is held in contact with the fixing roller and forms a fixing nip portion through which a sheet is to be passed. The elastic layer is formed on an inner layer of the fixing roller. The pressing portion presses one roller of the fixing roller and the pressure roller against the other roller while compressing the elastic layer. The restricting portion restricts a compression amount of the elastic layer lest the compression amount should exceed a preset compression amount when the pressing portion presses the roller. The driving unit drives and rotates one of the fixing roller and the pressure roller in a state where the compression amount is restricted.

主权项

1. A fixing device comprising:
a heat source; a fixing roller that is heated by the heat source; a first housing that rotatably supports the fixing roller; a pressure roller that is held in contact with the fixing roller so that a fixing nip portion is formed between the pressure roller and the fixing roller and through which a sheet is to be passed; a second housing that rotatably supports the pressure roller; an elastic layer formed on a circumferential surface or an inner layer of the fixing roller or the pressure roller; a pressing portion that presses one roller of the fixing roller and the pressure roller against the other roller by biasing one of the first and second housings toward the other while compressing the elastic layer; a restricting portion that restricts a compression amount of the elastic layer lest the compression amount should exceed a preset compression amount when the pressing portion presses the roller, the restricting portion restricting the compression amount of the elastic layer by restricting an inter-axis distance between the fixing roller and the pressure roller lest the inter-axis distance should become equal to or shorter than a preset distance, the restricting portion including a contact portion arranged on one of the first and second housings and a contacted portion arranged on the other of the first and second housings different from the one on which the contact portion is arranged, the inter-axis distance being restricted by contact of the contact portion with the contacted portion, the contact portion is separated from the contacted portion by thermal expansion of the elastic layer when the fixing roller is heated to a preset temperature by the heat source; and a driving unit that drives and rotates one of the fixing roller and the pressure roller in a state where the compression amount is restricted by the restricting portion.