Image forming apparatus comprising a detection member and tension applying member facing each other

An image forming apparatus comprising:

• an endless belt that travels circularly by a drive member and has an outer peripheral surface on which an image is formed;
• a tension applying member around which the endless belt is trained and that applies tension to the endless belt by pressing an inner peripheral surface of the endless belt;
• a detection member that detects the image formed on the outer peripheral surface of the endless belt, and wherein the detection member is disposed at a position facing the tension applying member;
• a support member to which the detection member is attached and that movably supports the detection member in accordance with the movement of the tension applying member, the support member comprises a groove section into which a shaft of the tension applying member is fitted and that has an opening in a mounting/dismounting direction of the belt unit;
• a positioning member that positions the detection member with respect to the outer peripheral surface of the endless belt at a portion pressed by the tension applying member;
• a keeping member that keeps the support member so that the opening of the groove section formed at the support member faces the mounting/dismounting direction of the belt unit in a case in which the belt unit is mounted on and dismounted from the apparatus main body;
• and
• a belt unit that comprises the endless belt and the tension applying member and that is mounted on and dismounted from the apparatus main body.

An image forming apparatus comprising:

• an endless belt that travels circularly by a drive member and has an outer peripheral surface on which an image is formed;
• a tension applying member around which the endless belt is trained and that applies tension to the endless belt by pressing an inner peripheral surface of the endless belt;
• a detection member that detects the image formed on the outer peripheral surface of the endless belt, and wherein the detection member is disposed at a position facing the tension applying member;
• a support member to which the detection member is attached and that movably supports the detection member in accordance with the movement of the tension applying member;
• a positioning member that positions the detection member with respect to the outer peripheral surface of the endless belt at a portion pressed by the tension applying member;
• a holding member that movably and rotatably support the support member;
• and
• coil springs disposed between a bottom section of the support member and a bottom section of the holding member side by side in an axial direction.