Image forming apparatus

An image forming apparatus comprising:

• a driven member;
• a driving source configured to generate a driving force for rotationally driving the driven member;
• a first rotatable member configured to be rotated by input of the driving force from the driving source thereto;
• a second rotatable member provided coaxially with the first rotatable member and configured to transmit the driving force toward the driven member by being rotated through transmission thereto the driving force from the driving source by the first rotatable member, the second rotatable member being rotatable relative to the first rotatable member so that a phase which is a position of the second rotatable member relative to the first rotatable member with respect to a rotational direction of the first rotatable member changes from a first phase toward a second phase different from the first phase;
• detecting means capable of detecting that the second rotatable member is in the second phase;
• and
• restricting means configured to restrict the phase,
• wherein the first rotatable member and the second rotatable member are configured so as to change the phase with a change in rotational load torque of the driven member from a first torque to a second torque larger than the first torque so that the first rotatable member and the second rotatable member are rotated in a state in which the second rotatable member is in the first phase in a case where the rotational load torque of the driven member is the first torque and so that the first rotatable member and the second rotatable member are rotated in a state in which the second rotatable member is in the second phase in a case where the rotational load torque of the driven member is the second torque, and
• wherein in a case where the phase changes from the first phase to the second phase, even when the rotational load torque of the driven member lowers from the second torque toward the first torque, the restricting means restricts that the phase returns from the second phase to the first phase.