Image forming unit

1. An image forming unit detachably mountable to an image forming apparatus, the image forming unit comprising:

a main assembly that includes an image bearing member and is insertable into the image forming apparatus;

a cover portion engageable with the main assembly of the image forming unit to cover the image bearing member; and

a locking portion movably provided on the cover portion and configured to lock the cover portion to the image forming apparatus,

wherein, in a case that the main assembly is between (i) an initial position in which the main assembly is positioned when the setting of the cover portion to said image forming apparatus is completed and (ii) a first position in which the main assembly is inserted into the image forming apparatus from the initial position by a first amount, the locking portion is positioned in an unlocked position in which the locking portion unlocks the cover portion from the image forming apparatus, and

wherein, in a case that the main assembly is between the first position and a second position in which the main assembly is inserted into the image forming apparatus from the initial position by a second amount that is larger than the first amount, the locking portion is positioned in a locked position in which the locking portion locks the cover portion to the image forming apparatus.

2. An image forming unit according to claim 1 , further comprising:

a moving mechanism configured to move the locking portion between the locked position and the unlocked position when the main assembly slides relative to the cover portion, and

wherein the moving mechanism moves the locking portion in the locked position to the unlocked position when the main assembly takes the initial position as a result of movement thereto from a predetermined position between the first position and the second position.

3. An image forming unit according to claim 1 , wherein the locking portion includes a locking engaging portion configured to lock the cover portion by engagement with the image forming apparatus.

4. An image forming unit according to claim 1 , wherein the locking portion is provided with a projection, and the image forming unit further comprises a guide portion configured to engage with the projection to guide said the projection, and

wherein the locking portion is guided by the guide portion between the locked position and the unlocked position along with the inserting of the main assembly into the image forming apparatus.

5. An image forming unit according to claim 1 , wherein the second amount is not less than a distance from a downstream end of the main assembly with respect to an inserting direction of the main assembly to a center of gravity of the main assembly.

6. An image forming unit according to claim 1 , wherein the first amount is less than a distance from a downstream end of the main assembly with respect to an inserting direction of the main assembly to a center of gravity of the main assembly.

7. An image forming unit according to claim 1 , further comprising an engaging portion engageable with the image forming apparatus to lock the main assembly with the image forming apparatus when the main assembly is mounted to the image forming apparatus, and a releasing portion for breaking engagement of the engaging portion.

8. An image forming unit according to claim 1 , further comprising an inserting portion provided on the cover portion for insertion into the image forming apparatus,

wherein the locking portion is provided on the inserting portion.

9. An image forming unit according to claim 1 , wherein the locking portion is a first locking portion and the image forming unit further comprises a second locking portion movably provided on the cover portion and configured to lock the cover portion to the main assembly, and

wherein the first locking portion and the second locking portion are integral with each other.

10. An image forming unit according to claim 9 , wherein the second locking portion is movable to a position to release locking between the main assembly and the cover portion with a mounting operation of the cover portion to the image forming apparatus.

11. An image forming unit according to claim 1 , wherein when the main assembly is inserted into the image forming apparatus from the initial position by the second amount, the main assembly is set in the image forming apparatus.

12. An image forming unit according to claim 1 , wherein, in a case that the main assembly is the second position, the locking portion is positioned in the unlocked position.

13. An image forming unit detachably mountable to an image forming apparatus, the image forming unit comprising:

a main assembly that includes an image bearing member and is insertable into the image forming apparatus;

a cover portion engagable with the main assembly to cover the image bearing member;

a locking portion movably provided on the cover portion and configured to lock the cover portion to the image forming apparatus; and

a moving mechanism configured (i) to move the locking portion between a locked position in which the locking portion locks the cover portion to the image forming apparatus and an unlocked position in which the locking portion unlocks the cover portion from the main assembly,

wherein the locking portion moves from the unlocked position to the locked position when the main assembly moves to a first position in which the main assembly is inserted into the image forming apparatus by a first amount from an initial position in which the main assembly is positioned when the setting of the cover portion to the image forming apparatus is completed, and

wherein the locking portion moves from the locked position to the unlocked position when the main assembly moves from the first position to a second position in which the main assembly is inserted into the image forming apparatus from the initial position by a second amount that is larger than the first amount.

14. An image forming unit according to claim 13 , wherein, when the main assembly is inserted into the image forming apparatus from the initial position by the second amount, the main assembly is set in the image forming apparatus.

15. An image forming unit detachably mountable to an image forming apparatus, the image forming unit comprising:

a main assembly that includes an image bearing member and is insertable into the image forming apparatus;

a cover portion engaging with the main assembly to cover the image bearing member;

a first locking portion movably provided on the cover portion and configured to lock the cover portion to the image forming apparatus;

a second locking portion movably provided on the cover portion and configured to lock the cover portion to the main assembly, wherein the second locking portion is movable to a position to release locking between the main assembly and the cover portion with a mounting operation of the cover portion to the image forming apparatus; and

a moving mechanism configured to move the first locking portion between a locked position in which the first locking portion locks the cover portion to the image forming apparatus and an unlocked position in which the first locking portion unlocks the cover portion from the image forming apparatus when the main assembly slides relative to the cover portion,

wherein the first locking portion and the second locking portion are integral with each other.

16. An image forming unit detachably mountable to an image forming apparatus, the image forming unit comprising:

a main assembly that includes an image bearing member and is insertable into the image forming apparatus;

a cover portion engaging with the main assembly to cover the image bearing member;

a first locking portion movably provided on the cover portion and configured to lock the cover portion to the image forming apparatus;

a second locking portion movably provided on the cover portion and configured to lock the cover portion to the main assembly, wherein the second locking portion is movable to a position to release locking between the main assembly and the cover portion with a mounting operation of the cover portion to the image forming apparatus; and

a moving mechanism configured to move the first locking portion between a locked position in which the first locking portion locks the cover portion to the image forming apparatus and an unlocked position in which the first locking portion unlocks the cover portion from the image forming apparatus when the main assembly slides relative to the cover portion,

wherein, when the second locking portion moves to the position to release locking between the main assembly and the cover portion with the mounting operation of the cover portion to the image forming apparatus, the first locking portion is the unlocked position,

wherein, when the main assembly moves relative to the cover portion by a first amount as the main assembly is inserted into the image forming apparatus, the first locking portion in the unlocked position moves to the locked position, and

wherein, when the main assembly moves relative to the cover portion by a second amount that is larger than first amount as the main assembly is inserted into the image forming apparatus, the first locking portion in the locked position moves to the unlocked position.

17. A drum unit detachably mountable to an image forming apparatus, the drum unit comprising:

a drum cartridge that includes a photosensitive drum and is insertable into the image forming apparatus;

a cover member engageable with the drum cartridge to cover the photosensitive drum; and

an engaging portion provided on the covering member and engageable with the image forming apparatus so as to prevent the cover member from disengaging from the image forming apparatus when the cover member is set at a predetermined position in the image forming apparatus and then the drum cartridge moves toward a set position in the image forming apparatus by a predetermined distance.

18. A drum unit according to claim 17 , wherein the engaging portion is released from the image forming apparatus when the drum cartridge is returned to the cover member after the engaging portion is engaged with the image forming apparatus.

19. A drum unit according to claim 17 , wherein the engaging portion is released from the image forming apparatus when the drum cartridge is moved toward the set position by a second predetermined distance after the engaging portion is engaged with the image forming apparatus.

20. A drum unit according to claim 17 , further comprising a second engaging portion provided on the cover member and engageable with the drum cartridge so as to prevent the cover member from disengaging from the drum cartridge before the cover member is set in the image forming apparatus,

wherein the second engaging portion is released from the drum cartridge when the cover member is set in the image forming apparatus.

21. A drum unit according to claim 20 , wherein the first and second engaging portion are integral with each other.