Patent ID: 8165498

Claim:
An image forming device, comprising: an image carrying unit that, while rotating, carries an image; an image forming unit that forms the image on a surface of the image carrying unit; a transfer unit that transfers the image formed on the surface of the image carrying unit to a recording sheet while rotating and being in contact with the image carrying unit; a conveyance unit that conveys the recording sheet to a nipping portion between the image carrying unit and the transfer unit; a determination unit that determines whether a thickness of the recording sheet conveyed by the conveyance unit is greater than a set threshold value; and a cam member that rotates with respect to a rotational axis of the transfer unit, and enlarges or reduces a gap of the nipping portion between the image carrying unit and the transfer unit according to a rotational position of the cam member, the cam member includes a first portion having a first external radius and a second portion having a second external radius, the first external radius being greater than a radius of the transfer unit with the rotational axis of the transfer unit as a center, the second external radius being equal to or less than the radius of the transfer unit with the rotational axis of the transfer unit as a center, wherein an outside surface of the cam member includes a surface of the first portion, a surface of the second portion, and an inclined surface joining an end of the surface of the first portion and an end of the surface of the second portion, the inclined surface portion is formed from an elastic material having low resilience, and wherein when the determination unit determines that the thickness of the recording sheet is greater than the set threshold value, the cam member rotates so that the gap of the nipping portion is enlarged.