Fixing device including mechanism for varying pressure at nip region between rotary body and pressure body

A fixing device comprising:

• a rotary body;
• a pressure body configured to form a nip region in cooperation with the rotary body;
• a frame supporting the rotary body;
• and
• a pressure varying mechanism configured to provide a nip pressure to be applied to the nip region formed between the rotary body and the pressure body, the pressure varying mechanism comprising:
• a first spring configured to apply a first urging force to one of the rotary body and the pressure body, the first urging force acting in a first urging direction;
• and
• a second spring configured to apply a second urging force to the one of the rotary body and the pressure body, the second urging force acting in a second urging direction opposite to the first urging direction,
• the pressure varying mechanism being configured to vary the nip pressure to be applied to the nip region between a first nip pressure and a second nip pressure smaller than the first nip pressure,
• the first nip pressure being applied to the nip region while the first urging force of the first spring is applied to the one of the rotary body and the pressure body without application of the second urging force of the second spring to the one of the rotary body and the pressure body, and
• the second nip pressure being applied to the nip region while both of the first urging force of the first spring and the second urging force of the second spring are applied to the one of the rotary body and the pressure body.