Drive mechanism and image forming apparatus

A drive mechanism used in an image forming apparatus, the drive mechanism comprising:

• a rotatable drive member having a first engagement portion;
• a coupling member having a second engagement portion engaged with the first engagement portion and a drive transmitting portion, the coupling member being constituted to be rotatable by receiving a drive force from the drive member in the second engagement portion and movable between a first position and a second position in a rotation axis direction of the drive member;
• a biasing member disposed between the drive member and the coupling member in the rotation axis direction, the biasing member biasing the coupling member from the second position toward the first position;
• and
• a driven member having a first drive transmitted portion capable of contacting with the drive transmitting portion which moves along the first rotation direction in a case where the coupling member is at the first position and the drive member rotates in a first rotation direction, the driven member being constituted to be rotatable in the first rotation direction by receiving the drive force from the coupling member in the first drive transmitted portion, wherein
• the first engagement portion includes:
• a first contact portion capable of contacting with the second engagement portion in a case where the coupling member is at the first position and the drive member rotates in the first rotation direction;
• a second contact portion capable of contacting with the second engagement portion in a case where the coupling member is at the second position and the drive member rotates in the first rotation direction;
• and
• a third contact portion capable of contacting with the second engagement portion so as to regulate movement of the coupling member from the second position to the first position in the rotation axis direction in a case where the coupling member is at the second position and the second contact portion and the coupling member are in a contact state by rotation of the drive member in the first rotation direction.