Developing cartridge and electrophotographic image forming apparatus employing same

1. A developing cartridge comprising:

a photosensitive unit including a photosensitive drum;

a developing unit including a developing roller, the developing unit coupled to the photosensitive unit to be movable to:

a release position at which the developing roller is spaced apart from the photosensitive drum, and

a developing position at which the developing roller contacts the photosensitive drum to form a developing nip;

an elastic member to provide an elastic force in a direction to maintain the developing unit at the developing position;

a movable member including a gear portion, the movable member movable to:

a first position to cause the developing unit to move to the release position, and

a second position to cause the developing unit to move to the developing position;

a driving gear rotatable in a first direction and a second direction; and

a switching member connected to the driving gear, the switching member to switch between:

a third position at which the switching member engages the gear portion to transmit power from the driving gear to the movable member from the second position to the first position, as the driving gear rotates in the first direction, and

a fourth position at which the switching member disengages the gear portion to allow the movable member to move from the first position to the second position, as the driving gear rotates in the second direction.

2. The developing cartridge of claim 1 , further comprising a return spring to apply a spring elastic force to the movable member, in a direction to move the movable member to the second position.

3. The developing cartridge of claim 2 , further comprising a locking member to lock the movable member at the first position.

4. The developing cartridge of claim 3 , wherein

the locking member includes first and second coupling portions respectively provided on

the movable member and

one of the developing unit and/or the photosensitive unit on which the movable member is provided, and

the first and second coupling portions are elastically coupled to each other when the movable member is at the first position.

5. The developing cartridge of claim 1 , wherein the switching member includes a swing gear

to engage the driving gear to be connected to the driving gear, to swing to the third position or the fourth position as the driving gear rotates in the first direction or the second direction, and

to engage with the gear portion at the third position to be connected to the gear portion.

6. The developing cartridge of claim 5 , wherein

the movable member is provided on the developing unit and is slidable between the first position and the second position, and

the gear portion includes a rack gear.

7. The developing cartridge of claim 6 , further comprising:

a coupler to receive driving power; and

a developing roller gear to be rotated by the coupler and coupled to a rotation shaft of the developing roller,

wherein the driving gear engages with the developing roller gear to rotate together with the developing roller gear.

8. The developing cartridge of claim 5 , wherein

the movable member is provided on the photosensitive unit and is slidable between the first position and the second position, and

the gear portion includes a rack gear.

9. The developing cartridge of claim 5 , wherein the movable member is provided on the developing unit and movable between the first position and the second position.

10. The developing cartridge of claim 1 , wherein

the driving gear includes a first helical gear portion, and

the switching member includes:

a first rotary member including

a first latch portion and

a pinion gear portion engaging with the gear portion; and

a second rotary member including

a second latch portion and

a second helical gear portion engaging with the first helical gear portion, the second rotary member being provided coaxially with the first rotary member,

wherein, as the driving gear rotates in the first direction and the second direction, the second rotary member reciprocates in an axial direction and switches between

the third position at which the second latch portion engages with the first latch portion, to be connected to the gear portion to move the movable member from the second position to the first position, as the driving gear rotates in the first direction, and

the fourth position at which the second latch portion is spaced apart from the first latch portion, to be disconnected from the gear portion to allow the movable member to move from the first position to the second position, as the driving gear rotates in the second direction.

11. The developing cartridge of claim 1 , wherein the switching member includes:

a first rotary member including

a pinion gear portion engaging with the gear portion,

a latch portion, and

a long hole portion having an arc shape;

a second rotary member provided coaxially with the first rotary member and engaging with the driving gear to rotate with the driving gear, the second rotary member including an inner gear portion; and

a latch gear engaging with the inner gear portion and being provided in the long hole portion,

the latch gear to, according to a rotation direction of the driving gear, be moved:

to the third position at which the latch gear engages with the latch portion such that the first rotary member rotates together with the first rotary member, or

to the fourth position at which the latch gear is separate from the latch portion.

12. The developing cartridge of claim 11 , wherein

the first rotary member includes a partial gear portion, and

the partial gear portion engages with the driving gear when the first rotary member moves the movable member from the second position to the first position and is separate from the driving gear when the movable member is completely moved from the second position to the first position.

13. An image forming apparatus comprising:

a main body; and

a developing cartridge including:

a photosensitive unit including a photosensitive drum;

a developing unit including a developing roller, the developing unit coupled to the photosensitive unit to be movable to:

a release position at which the developing roller is spaced apart from the photosensitive drum, and

a developing position at which the developing roller contacts the photosensitive drum to form a developing nip;

an elastic member to provide an elastic force in a direction to maintain the developing unit at the developing position;

a movable member including a gear portion, the movable member movable to:

a first position to cause the developing unit to move to the release position, and

a second position to cause the developing unit to move to the developing position;

a driving gear rotatable in a first direction and a second direction; and

a switching member connected to the driving gear, the switching member to switch between:

a third position at which the switching member engages the gear portion to transmit power from the driving gear to move the movable member from the second position to the first position, as the driving gear rotates in the first direction, and

a fourth position at which the switching member disengages the gear portion to allow the movable member to move from the first position to the second position, as the driving gear rotates in the second direction.

14. The image forming apparatus of claim 13 , wherein the switching member includes a swing gear

to engage with the driving gear and swing to the third position or the fourth position according to a rotation direction of the driving gear, and

to engage with the gear portion at the third position.

15. The image forming apparatus of claim 13 , wherein

the switching member includes:

a first rotary member; and

a second rotary member provided coaxially with the first rotary member,

wherein, as the driving gear is rotated in the first and second directions, the second rotary member switches between

the third position at which the first rotary member engages with the second rotary member and

the fourth position at which the first rotary member disengages the second rotary member.