| CPC G03G 15/1615 (2013.01) | 12 Claims |
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1. An image forming apparatus comprising:
an image bearing member configured to bear a toner image;
a first belt to which the toner image is transferred from the image bearing member;
a first transfer roller provided in contact with an inner surface of the first belt and configured to form a nip portion where the toner image borne by the image bearing member is transferred to a recording material;
an upstream roller provided adjacently upstream of the first transfer roller with respect to the rotational direction of the first belt and configured to stretch the first belt while in contact with the inner surface of the first belt;
a second belt configured to form the nip portion while in contact with an outer surface of the first belt and to convey the recording material;
a second transfer roller configured to form the nip portion between the second transfer roller and the first transfer roller through the second belt and to transfer the toner image borne by the first belt to the recording material;
a first stretching roller provided adjacently downstream of the second transfer roller with respect to a rotational direction of the second belt and configured to stretch the second belt while in contact with an inner surface of the second belt; and
a second stretching roller provided adjacently upstream of the second transfer roller with respect to the rotational direction of the second belt and configured to stretch the second belt while in contact with the inner surface of the second belt,
wherein when a line perpendicular to a line connecting a center of the first transfer roller and a center of the second transfer roller and passing through a center of the nip portion is defined as a nip line L1, a tangential line of the first stretching roller passing through the center of the nip portion and formed along the second belt is defined as a tangential line L3, a tangential line of the second stretching roller passing through the center of the nip portion and formed along the second belt is defined as a tangential line L2, an angle formed by the nip line L1 and the tangential line L2 is defined as φ1, an angle formed by the nip line L1 and the tangential line L3 is defined as φ2, and an angle formed between the first belt, which is stretched between the first transfer roller and the upstream roller, and the tangential line L2 is defined as φ3,
the first stretching roller, the second stretching roller, and the second transfer roller are disposed so as to satisfy φ1≤30°, φ2≤30°, and φ3<φ1, and
wherein the first stretching roller includes parts, at both end portions in a rotational axis direction, of which a diameter is less than a diameter of a central portion in the rotational axis direction in an area where the second belt is stretched, and the second stretching roller includes parts, at both end portions in the rotational axis direction, of which a diameter is greater than a diameter of a central portion in the rotational axis direction in an area where the second belt is stretched.
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