A developing cartridge which is detachably mountable in an apparatus main body of an image forming apparatus, the developing cartridge comprising:
- a housing including a first side wall and a second side wall which are provided to oppose each other, the housing configured to accommodate developer therein;
- a receiving member provided at an outer side of the first side wall to be rotatable about a first axis which extends in an opposing direction of the first side wall and the second side wall, the receiving member configured to couple with a driving force output member provided in the apparatus main body to receive a driving force from the driving force output member;
- a developing roller provided between the first side wall and the second side wall to be rotatable about a second axis which extends in parallel to the first axis with a space therebetween, the developing roller configured to rotate by the driving force received by the receiving member;
- a first rotary member provided at the outer side of the first side wall to be rotatable about a third axis which extends in parallel to the first axis with a space therebetween, the first rotary member configured to rotate by the driving force received by the receiving member;
- a second rotary member provided at the outer side of the first side wall to be rotatable about a fourth axis which extends in parallel to the third axis with a space therebetween, the second rotary member configured to take a driven position where the second rotary member rotates by the driving force transmitted from the first rotary member and a non-driven position where the transmission of the driving force from the first rotary member is cut off;
- a detected member provided at the outer side of the first side wall and configured to move in association with the rotation of the second rotary member and function as a detection target to be detected by a detection member provided in the apparatus main body;
- and
- a first engagement portion provided at the outer side of the first side wall in a position separated from a fifth axis which extends in parallel to the first axis with a space therebetween, the first engagement portion configured to rotate about the fifth axis by the driving force received by the receiving member,
- wherein the second rotary member includes a second engagement portion which is provided in a position separated from the fourth axis,
- wherein when the second rotary member is in the non-driven position, the second engagement portion is provided on a rotating locus drawn by the first engagement portion, and
- wherein the first engagement portion is configured to engage with the second engagement portion as the first engagement portion rotates after the first rotary member has rotated for a predetermined amount, so that the second engagement portion moves rotationally about the fourth axis by a force received from the first engagement portion, whereby the second rotary member rotates from the non-driven position to the driven position.