Sheet conveyance apparatus and image forming apparatus

A sheet conveyance apparatus comprising:

• a conveyance member configured to convey a sheet;
• a drive source configured to generate a driving force;
• a first member including a first ratchet portion and being configured to be rotationally driven in a predetermined rotational direction about an axis by the driving force, wherein the first ratchet portion has a first transmission surface and a first guide surface;
• a second member opposing the first member in an axial direction of the axis, the second member including a second ratchet portion and being configured to rotate about the axis to transmit the driving force received from the first member to the conveyance member, wherein the second ratchet portion has a second transmission surface and a second guide surface;
• and
• an urging portion configured to urge one of the first member and the second member toward another of the first member and the second member in the axial direction,
• wherein the one of the first member and the second member is movable in the axial direction between an engaged position where the first transmission surface is engaged with the second transmission surface, and a separated position where the first transmission surface is separated from the second transmission surface in the axial direction,
• wherein during a drive transmission period in which the first member is rotationally driven in the rotational direction by the driving force of the drive source, the second member rotates in the rotational direction together with the first member in a state in which (i) the one of the first member and the second member is positioned in the engaged position, and (ii) a contact portion between the first transmission surface and the second transmission surface is formed,
• wherein during an idling period in which the conveyance member is rotated in a state in which the drive source is stopped, the first guide surface and the second guide surface slide on each other such that the one of the first member and the second member is retracted from the engaged position to the separated position against an urging force of the urging portion, and thus the second member is allowed to rotate in the rotational direction with respect to the first member, and
• wherein in a rotational radius direction of the first member, at least part of the contact portion during the drive transmission period is at a more outward position than a sliding surface between the first guide surface and the second guide surface during the idling period.

A sheet conveyance apparatus comprising:

• a conveyance member configured to convey a sheet;
• a drive source configured to generate a driving force;
• a first member including a first ratchet portion and configured to be rotationally driven in a predetermined rotational direction about an axis by the driving force, wherein the first ratchet portion includes a first outer claw portion and a first inner claw portion disposed at a more inward position than the first outer claw portion in a rotational radius direction of the first member;
• a second member opposing the first member in an axial direction of the axis, the second member including a second ratchet portion and being configured to rotate about the axis to transmit the driving force received from the first member to the conveyance member, wherein the second ratchet portion includes a second outer claw portion and a second inner claw portion disposed at a more inward position than the second outer claw portion in the rotational radius direction of the first member;
• and
• an urging portion configured to urge one of the first member and the second member toward another of the first member and the second member in the axial direction,
• wherein the one of the first member and the second member is movable in the axial direction between an engaged position where the first outer claw portion and the first inner claw portion are respectively engaged with the second outer claw portion and the second inner claw portion, and a separated position where the first outer claw portion and the first inner claw portion are respectively separated from the second outer claw portion and the second inner claw portion in the axial direction,
• wherein during a drive transmission period in which the first member is rotationally driven in the rotational direction by the driving force of the drive source, the second member and the first member rotate together in the rotational direction in a state in which the one of the first member and the second member is positioned at the engaged position,
• wherein during an idling period in which the conveyance member is rotated in a state in which the drive source is stopped, a third guide surface provided on the first outer claw portion and the first inner claw portion and a fourth guide surface provided on the second outer claw portion and the second inner claw portion slide on each other such that the one of the first member and the second member is retracted from the engaged position to the separated position against an urging force of the urging portion, and thus the second member is allowed to rotate in the rotational direction with respect to the first member,
• wherein at least one of the first outer claw portion and the second outer claw portion has a first holding surface,
• wherein at least one of the first inner claw portion and the second inner claw portion has a second holding surface, and
• wherein after the one of the first member and the second member has retracted from the engaged position to the separated position during the idling period, the sheet conveyance apparatus switches to a state in which the one of the first member and the second member is held at the separated position by the first holding surface and a state in which the one of the first member and the second member is held at the separated position by the second holding surface.