Patent ID: 8757365

Claim:
An image forming apparatus configured to form an image of recording agent on a recording medium, the image forming apparatus comprising: a plurality of rollers having respective axes parallel to each other; an endless belt wound around the plurality of rollers, the endless belt being configured to be driven to turn and convey one of the recording medium and the recording agent; a strip-shaped guide provided to a first-side portion of the endless belt with respect to a middle point of a contact portion of a predetermined one of the plurality of rollers that turns in contact with the endless belt in an axial direction of the plurality of rollers, the guide being configured to continuously protrude from an inner circumferential surface of the endless belt; a groove formed on at least one of the plurality of rollers, the groove being configured to regulate movement of the endless belt in the axial direction in a state where the guide is fitted into the groove; and urging members provided at a first end and a second end of at least one of the plurality of rollers in the axial direction, the urging members being configured to urge the at least one roller in such a tensile direction as to apply a tension to the endless belt, the urging members comprising: a first urging member configured to apply, to the first end of the predetermined one roller, a first moment about the middle point of the contact portion of the predetermined one roller in the axial direction; and a second urging member configured to apply, to the second end of the predetermined one roller, a second moment about the middle point in the axial direction, the second moment and the first moment being adapted such that the first-side portion of the endless belt with respect to the middle point in the axial direction is extended in the tensile direction by a same length as a second-side portion of the endless belt with respect to the middle point in the axial direction under predetermined conditions of use for the image forming apparatus, based on a first load required for a unit extension rate in the tensile direction of the first-side portion and a second load required for a unit extension rate in the tensile direction of the second-side portion, the first load determined based on a cross-sectional area and a Young's modulus of each element included in the first-side portion, the second load determined based on a cross-sectional area and a Young's modulus of each element included in the second-side portion.