Image forming device equipped with oblique motion prevention mechanism

An image forming device, comprising:

• an image formation unit;
• first, second and third rollers arranged such that axial directions of the first, second and third rollers are substantially parallel with each other, and such that a distance between the first roller and the third roller is greater than both a distance between the first roller and the second roller and a distance between the third roller and the second roller;
• an endless belt extending around the first, second and third rollers;
• a collar provided at an axial end of the first roller, configured to move along the axial direction of the first roller when pressed by the endless belt as the endless belt moves obliquely;
• a press arm that extends from the axial end of the first roller to an axial end of the second roller, configured to swing about a swing center and to displace the axial end of the second roller in a direction perpendicular to an axis of the second roller, wherein the axial end of the first roller is on a same side of the endless belt as the axial end of the second roller;
• and
• an oblique motion force conversion unit that includes a cam on which a slanting surface slanted with respect to the axial direction of the first roller is formed and a movable part which slidably contacts the slanting surface, configured to convert an oblique motion force of the endless belt to a force which causes the press arm to swing about the swing center,
• wherein when the collar is pressed by the endless belt, the axial end of the second roller displaces in a direction that increases tension of the belt, generating tension differences within the endless belt in a width direction, which causes the endless belt to move from a higher tension side in the width direction to a lower tension side in the width direction,
• wherein the slanting surface is slanted such that an end of the slanting surface farthest from an end of the endless belt in the width direction is closer to an axis of the first roller than an end of the slanting surface closest to the end of the endless belt in the width direction, and
• wherein the axial end of the second roller is displaced by the press arm via an elastic member.

An image forming device, comprising:

• an image formation unit;
• first, second and third rollers arranged such that axial directions of the first, second and third rollers are substantially parallel with each other, and such that a distance between the first roller and the third roller is greater than both a distance between the first roller and the second roller and a distance between the third roller and the second roller;
• an endless belt extending around the first, second and third rollers;
• a collar provided at an axial end of the first roller, configured to move along the axial direction of the first roller when pressed by the endless belt as the endless belt moves obliquely;
• a cam configured to move in the axial direction of the first roller as the collar moves in the axial direction of the first roller;
• a movable part configured to contact the cam and to recede from an axis of the first roller as the cam moves in the axial direction;
• a slanting surface formed on at least one of the cam and the movable part, the slanting surface configured such that an end of the slanting surface farthest from an end of the endless belt in a width direction is closer to the axis of the first roller than an end of the slanting surface closest to the end of the endless belt in the width direction;
• and
• a press arm that extends from the axial end of the first roller to an axial end of the second roller, configured to swing about a swing center and to displace the axial end of the second roller in a direction perpendicular to an axis of the second roller, wherein the axial end of the first roller is on a same side of the endless belt as the axial end of the second roller,
• wherein when the collar is pressed by the endless belt, the axial end of the second roller displaces in a direction that increases tension of the belt, generating tension differences within the endless belt in the width direction, which causes the endless belt to move from a higher tension side in the width direction to a lower tension side in the width direction.