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A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus includes first and second end covers, first and second bottom-surface portions to be guided by first and second main assembly guide portions, first, second, and third portions to be position

A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus includes first and second end covers, first and second bottom-surface portions to be guided by first and second main assembly guide portions, first, second, and third portions to be positioned by first, second, and third main assembly positioning portions, and a driving force receiving portion partly exposed through the first end cover between the first and third portions to be positioned and engaging with a main assembly driving force transmitting portion to rotate a process-cartridge developing member when the process cartridge is mounted to the apparatus.

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What is claimed is: 1. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on said electr

What is claimed is: 1. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on said electrophotographic photosensitive drum; a first end cover portion provided at one longitudinal end of said electrophotographic photosensitive drum; a second end cover portion provided at the other longitudinal end of said electrophotographic photosensitive drum; a first portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a first main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a second main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a first portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said first end cover portion, said first portion to be positioned being positioned by a first main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said second end cover portion, said second portion to be positioned being positioned by a second main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a third portion to be positioned provided to project parallel to the lengthwise direction of said process cartridge from said first end cover portion at a position downstream of said first portion to be positioned with respect to a mounting direction in which said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, said third portion to be positioned being positioned by a third main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through said first end cover portion between said first portion to be positioned and said third portion to be positioned with respect to the mounting direction, said driving force receiving portion, when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in the main assembly of the electrophotographic image forming apparatus to receive a driving force for rotating said developing member from the main assembly driving force transmitting portion. 2. A process cartridge according to claim 1, wherein said third portion to be positioned is disposed at a position out of a movement path along which said driving force receiving portion moves to engage with the main assembly driving force transmitting portion. 3. A process cartridge according to claim 1 or 2, wherein said third portion to be positioned is in the form of a circular column and is disposed below a movement path along which said driving force receiving portion moves to engage with the main assembly driving force transmitting portion. 4. A process cartridge according to claim 3, wherein said third portion to be positioned is molded integrally with said first end cover portion. 5. A process cartridge according to claim 1 or 2, wherein said first portion to be positioned and said second portion to be positioned include bearings configured and positioned to rotatably support a drum shaft of said electrophotographic photosensitive drum. 6. A process cartridge according to claim 1 or 2, wherein a helical gear of said driving force receiving portion, a circular column of said third portion to be positioned, and a bearing of said first portion to be positioned configured and positioned to support a drum shaft of said electrophotographic photosensitive drum, are positioned in the order named in a longitudinal direction of said electrophotographic photosensitive drum from the inside to the outside thereof. 7. A process cartridge according to claim 1, further comprising a third portion to be guided provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said second end cover portion at a position downstream of said second portion to be positioned with respect to the mounting direction, said third portion to be guided being guided by a third main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus. 8. A process cartridge according to claim 7, wherein said third portion to be guided is disposed above said third portion to be positioned in a vertical direction when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus. 9. A process cartridge according to claim 1 or 8, wherein said process cartridge further includes: a first unit containing said electrophotographic photosensitive drum, a charging member configured and positioned to electrically charge said electrophotographic photosensitive drum, a cleaning member configured and positioned to remove a residual developer remaining on said electrophotographic photosensitive drum and a removed developer accommodating portion configured and positioned to accommodate the developer removed from said cleaning member; and a second unit containing said developing member and a developer accommodating portion configured and positioned to accommodate the developer to be used by said developing member to develop the electrostatic latent image, wherein said first and second units are rotatably coupled with each other such that said developing member is urged to said electrophotographic photosensitive drum by an elastic force of a first elastic member, wherein said first end cover portion, said second end cover portion, said first portion to be guided, said first portion to be positioned, said second portion to be positioned and said third portion to be positioned are provided in said first unit, and wherein said second portion to be guided is provided in said second unit. 10. A process cartridge according to claim 9, wherein when said process cartridge is set in the main assembly of the electrophotographic image forming apparatus, an upper surface of said first unit is urged in the mounting direction by an elastic force of a second elastic member, which is provided in the main assembly of the electrophotographic image forming apparatus. 11. A process cartridge according to claim 1 or 8, wherein said first portion to be positioned and second portion to be positioned are urged in the mounting direction by an elastic force of an elastic member provided in the main assembly of the electrophotographic image forming apparatus. 12. A process cartridge according to claim 7 or 8, wherein said third portion to be guided is in the form of a circular column and is integrally molded with said second end cover portion. 13. A process cartridge according to claim 1, further comprising a grip portion projected in the direction opposite the mounting direction. 14. An electrophotographic image forming apparatus for forming an image on a recording material, and having a main assembly to which a process cartridge is detachably mountable, said apparatus comprising: (a) a first main assembly guide portion and a second main assembly guide portion; (b) a first main assembly positioning portion, a second main assembly positioning portion and a third main assembly positioning portion; and (c) a mounting portion configured and positioned to detachably mount the process cartridge, the process cartridge including: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on the electrophotographic photosensitive drum; a first end cover portion provided at one longitudinal end of the electrophotographic photosensitive drum; a second end cover portion provided at the other longitudinal end of the electrophotographic photosensitive drum; a first portion to be guided provided on a bottom surface of the process cartridge so as to be guided by said first main assembly guide portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a second portion to be guided provided on a bottom surface of the process cartridge so as to be guided by said second main assembly guide portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a first portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the first end cover portion, the first portion to be positioned being positioned by said first main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a second portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the second end cover portion, the second portion to be positioned being positioned by said second main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a third portion to be positioned provided to project parallel to the lengthwise direction of the process cartridge from the first end cover portion at a position downstream of the first portion to be positioned with respect to a mounting direction in which the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, the third portion to be positioned being positioned by said third main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through the first end cover portion between the first portion to be positioned and the third portion to be positioned with respect to the mounting direction, the driving force receiving portion, when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in said main assembly of said electrophotographic image forming apparatus to receive a driving force for rotating the developing member from said main assembly driving force transmitting portion. 15. A process cartridge according to claim 14, wherein the driving force receiving portion includes a helical gear, and the third portion to be positioned is in the form of a circular column and is disposed at a position out of a movement path along which the driving force receiving portion moves to engage with the main assembly driving force transmitting portion. 16. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on said electrophotographic photosensitive drum; a first end cover portion provided at one longitudinal end of said electrophotographic photosensitive drum; a second end cover portion provided at the other longitudinal end of said electrophotographic photosensitive drum; a first portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a first main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a second main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a first portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said first end cover portion, said first portion to be positioned being positioned by a first main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said second end cover portion, said second portion to be positioned being positioned by a second main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a third portion to be positioned provided to project parallel to the lengthwise direction of said process cartridge from said first end cover portion at a position downstream of said first portion to be positioned with respect to a mounting direction in which said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, said third portion to be positioned being positioned by a third main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through said first end cover portion between said first portion to be positioned and said third portion to be positioned with respect to the mounting direction, said driving force receiving portion, when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in the main assembly of the electrophotographic image forming apparatus to receive a driving force for rotating said developing member from the main assembly driving force transmitting portion, wherein said driving force receiving portion includes a helical gear, and said third portion to be positioned is in the form of a circular column and is disposed at a position out of a movement path along which said driving force receiving portion moves to engage with the main assembly driving force transmitting portion, wherein said third portion to be positioned is also disposed below the movement path along which said driving force receiving portion moves to engage with the main assembly driving force transmitting portion, and wherein said first portion to be positioned and said second portion to be positioned include bearings configured and positioned to rotatably support a drum shaft of said electrophotographic photosensitive drum. 17. A process cartridge according to claim 16, wherein said helical gear of said driving force receiving portion, said third portion to be positioned in the form of a circular column, and one of said bearings configured and positioned to rotatably support a drum shaft of said electrophotographic photosensitive drum, are provided in the order named in a longitudinal direction of said electrophotographic photosensitive drum from an inside to outside of thereof. 18. A process cartridge according to claim 16 or 17, further comprising a third portion to be guided provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said second end cover portion at a position downstream of said second portion to be positioned with respect to the mounting direction, said third portion to be guided being guided by a third main assembly guiding portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus. 19. A process cartridge according to claim 18, wherein said process cartridge further includes: a first unit containing said electrophotographic photosensitive drum, a charging member configured and positioned to electrically charge said electrophotographic photosensitive drum, a cleaning member configured and positioned to remove a residual developer remaining on said electrophotographic photosensitive drum and a removed developer accommodating portion configured and positioned to accommodate the developer removed from said cleaning member; and a second unit containing said developing member and a developer accommodating portion configured and positioned to accommodate the developer to be used by said developing member to develop the electrostatic latent image, wherein said first and second units are rotatably coupled with each other such that said developing member is urged to said electrophotographic photosensitive drum by an elastic force of a first elastic member, wherein said first end cover portion, said second end cover portion, said first portion to be guided, said first portion to be positioned, said second portion to be positioned and said third portion to be positioned are provided in said first unit, and wherein said second portion to be guided is provided in said second unit. 20. A process cartridge according to claim 19, wherein said first portion to be positioned and second portion to be positioned are urged in the mounting direction by the elastic force of a second elastic member provided in the main assembly of the electrophotographic image forming apparatus. 21. A process cartridge according to claim 20, wherein when said process cartridge is set in the main assembly of the electrophotographic image forming apparatus, an upper surface of said first unit is urged in the mounting direction by the elastic force of the second elastic member provided in the main assembly of the electrophotographic image forming apparatus. 22. An electrophotographic image forming apparatus for forming an image on a recording material, and having a main assembly to which a process cartridge is detachably mountable apparatus, said apparatus comprising: (a) a first main assembly guide portion and a second main assembly guide portion; (b) a first main assembly positioning portion, a second main assembly positioning portion, and a third main assembly positioning portion; and (c) a mounting portion configured and positioned to detachably mount the process cartridge, the process cartridge including: an electrophotographic photosensitive drum; a developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; a first end cover portion provided at one longitudinal end of the electrophotographic photosensitive drum; a second end cover portion provided at the other longitudinal end of the electrophotographic photosensitive drum; a first portion to be guided provided on a bottom surface of the process cartridge so as to be guided by said first main assembly guide portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a second portion to be guided provided on a bottom surface of the process cartridge so as to be guided by said second main assembly guide portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a first portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the first end cover portion, the first portion to be positioned being positioned by said first main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a second portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the second end cover portion, the second portion to be positioned being positioned by said second main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a third portion to be positioned provided to project parallel to the lengthwise direction of the process cartridge from the first end cover portion at a position downstream of the first portion to be positioned with respect to a mounting direction in which the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, the third portion to be positioned being positioned by said third main assembly positioning portion provided in said main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through the first end cover portion between the first portion to be positioned and the third portion to be positioned with respect to the mounting direction, the driving force receiving portion, when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in said main assembly of said electrophotographic image forming apparatus to receive a driving force for rotating the developing member from the main assembly driving force transmitting portion, wherein the driving force receiving portion includes a helical gear, and the third portion to be positioned is in the form of a circular column and is disposed at a position out of a movement path along which the driving force receiving portion moves to engage with the main assembly driving force transmitting portion, wherein the third portion to be positioned is also disposed below the movement path along which the driving force receiving portion moves to engage with the main assembly driving force transmitting portion, and wherein the first portion to be positioned and the second portion to be positioned include bearings configured and positioned to rotatably support a drum shaft of the electrophotographic photosensitive drum. 23. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on said electrophotographic photosensitive drum; an end cover portion provided at one longitudinal end of said electrophotographic photosensitive drum; a first cartridge portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said end cover portion, said first cartridge portion to be positioned being positioned by a first positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second cartridge portion to be positioned provided to project parallel to the lengthwise direction of said process cartridge from said end cover portion at a position downstream of said first cartridge portion to be positioned with respect to a mounting direction in which said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, said second cartridge portion to be positioned being positioned by a second positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through said end cover portion between said first cartridge portion to be positioned and said second cartridge portion to be positioned with respect to the mounting direction, said driving force receiving portion, when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in the main assembly of the electrophotographic image forming apparatus to receive a driving force for rotating said developing member from the main assembly driving force transmitting portion, wherein said driving force receiving portion has an axis which is different from an axis of said electrophotographic photosensitive drum. 24. A process cartridge according to claim 23, wherein said second cartridge portion to be positioned is disposed at a position out of a movement path along which said driving force receiving portion moves to engage with the main assembly driving force transmitting portion. 25. A process cartridge according to claim 23 or 24, wherein said driving force receiving portion comprises a helical gear, wherein said second cartridge portion to be positioned comprises a circular column, wherein said first cartridge portion to be positioned comprises a bearing that is configured and positioned to rotatably support a drum shaft of said electrophotographic photosensitive drum, and wherein said helical gear, said circular column, and said bearing are positioned in this order in a longitudinal direction of said electrophotographic photosensitive drum from the inside to the outside thereof. 26. An electrophotographic image forming apparatus for forming an image on a recording material, and having a main assembly to which a process cartridge is detachably mountable, said apparatus comprising: (a) a first positioning portion provided in said main assembly and a second positioning portion provided in said main assembly; and (b) a mounting portion configured and positioned to detachably mount the process cartridge, the process cartridge including: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on the electrophotographic photosensitive drum; an end cover portion provided at one longitudinal end of the electrophotographic photosensitive drum; a first cartridge portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the end cover portion, the first cartridge portion to be positioned being positioned by said first positioning portion when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; a second cartridge portion to be positioned provided to project parallel to the lengthwise direction of the process cartridge of the electrophotographic photosensitive drum from the end cover portion at a position downstream of the first cartridge portion to be positioned with respect to a mounting direction in which the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, the second cartridge portion to be positioned being positioned by said second positioning portion when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus; and a driving force receiving portion provided to be partly exposed through the end cover portion between the first cartridge portion to be positioned and the second cartridge portion to be positioned with respect the mounting direction, the driving force receiving portion, when the process cartridge is mounted to said main assembly of said electrophotographic image forming apparatus, engaging in the mounting direction with a main assembly driving force transmitting portion provided in said main assembly of said electrophotographic image forming apparatus to receive a driving force for rotating the developing member from the main assembly driving force transmitting portion, wherein the driving force receiving portion has an axis which is different from an axis of the electrophotographic photosensitive drum. 27. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive drum; a developing member configured and positioned to develop an electrostatic latent image formed on said electrophotographic photosensitive drum; a drum unit supporting said electrophotographic photosensitive drum; a developing unit supporting said developing member; a first portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said drum unit, said first portion to be positioned being positioned by a first main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, wherein said first portion to be positioned rotatably supports a drum shaft of said electrophotographic photosensitive drum; a second portion to be positioned which is coaxial with said electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said drum unit, said second portion to be positioned being positioned by a second main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, wherein said second portion to be positioned rotatably supports the drum shaft; a third portion to be positioned provided to project parallel to the lengthwise direction of said process cartridge from said drum unit at a position downstream of said first portion to be positioned with respect to a mounting direction in which said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, said third portion to be positioned being positioned by a third main assembly positioning portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a cartridge coupling provided at one longitudinal end of the drum shaft, configured and positioned to receive a driving force for rotating said electrophotographic photosensitive drum from the main assembly when said process cartridge is mounted to the main assembly; and a helical gear provided to be partly exposed through said drum unit between said first portion to be positioned and said third portion to be positioned with respect to the mounting direction, said helical gear being disposed at one longitudinal end of said developing unit, and when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus, said helical gear receives a driving force for rotating said developing member from a main assembly driving force transmitting portion provided in the main assembly of the electrophotographic image forming apparatus. 28. A process cartridge according to claim 27, wherein said third portion to be positioned is disposed at a position out of a movement path along which said helical gear moves to engage with the main assembly driving force transmitting portion. 29. A process cartridge according to claim 27 or 28, wherein said third portion to be positioned is in the form of a circular column and is disposed below a movement path along which said helical gear moves to engage with the main assembly driving force transmitting portion. 30. A process cartridge according to claim 29, wherein said third portion to be positioned is molded integrally with said drum unit. 31. A process cartridge according to claim 27 or 28, wherein said helical gear, a circular column of said third portion to be positioned, and a bearing of said first portion to be positioned configured and positioned to support the drum shaft, are positioned in the order named in a longitudinal direction of said electrophotographic photosensitive drum from the inside to the outside thereof. 32. A process cartridge according to claim 27, further comprising: a first end cover portion provided at one longitudinal end of said electrophotographic photosensitive drum; a second end cover portion provided at the other longitudinal end of said electrophotographic photosensitive drum; a first portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a first main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; a second portion to be guided provided on a bottom surface of said process cartridge so as to be guided by a second main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus; and a third portion to be guided provided to project longitudinally outwardly of said electrophotographic photosensitive drum from said drum unit at a position downstream of said second portion to be positioned with respect to the mounting direction, said third portion to be guided being guided by a third main assembly guide portion provided in the main assembly of the electrophotographic image forming apparatus when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus. 33. A process cartridge according to claim 32, wherein said third portion to be guided is disposed above said third portion to be positioned in a vertical direction when said process cartridge is mounted to the main assembly of the electrophotographic image forming apparatus. 34. A process cartridge according to claim 32 or 33, wherein said third portion to be guided is in the form of a circular column and is integrally molded with said drum unit. 35. A process cartridge according to claim 33, wherein said drum unit contains said electrophotographic photosensitive drum, a charging member configured and positioned to electrically charge said electrophotographic photosensitive drum, a cleaning member configured and positioned to remove a residual developer remaining on said electrophotographic photosensitive drum, and a removed developer accommodating portion configured and positioned to accommodate the developer removed from said cleaning member, and wherein said developing unit contains said developing member and a developer accommodating portion configured and positioned to accommodate the developer to be used by said developing member to develop the electrostatic latent image, wherein said drum and developing units are rotatably coupled with each other such that said developing member is urged to said electrophotographic photosensitive drum by an elastic force of a first elastic member, wherein said first portion to be guided, said first portion to be positioned, said second portion to be positioned, and said third portion to be positioned are provided in said drum unit, and wherein said second portion to be guided is provided in said developing unit. 36. A process cartridge according to claim 35, wherein when said process cartridge is set in the main assembly of the electrophotographic image forming apparatus, an upper surface of said drum unit is urged in the mounting direction by an elastic force of a second elastic member, which is provided in the main assembly of the electrophotographic image forming apparatus. 37. A process cartridge according to claim 27 or 33, wherein said first portion to be positioned and second portion to be positioned are urged in the mounting direction by an elastic force of an elastic member provided in the main assembly of the electrophotographic image forming apparatus. 38. A process cartridge according to claim 27, further comprising a grip portion projecting in the direction opposite from the mounting direction. 39. An electrophotographic image forming apparatus for forming an image on a recording material, and having a main assembly to which a process cartridge is detachably mountable, said apparatus comprising: (a) a first main assembly positioning portion, a second main assembly positioning portion and a third main assembly positioning portion; and (b) a mounting portion configured and positioned to detachably mount the process cartridge, the process cartridge including an electrophotographic photosensitive drum, a developing member configured and positioned to develop an electrostatic latent image formed on the electrophotographic photosensitive drum, a drum unit supporting the electrophotographic photosensitive drum, a developing unit supporting the developing member, a first portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the drum unit, the first portion to be positioned being positioned by said first main assembly positioning portion provided in the main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to the main assembly of said electrophotographic image forming apparatus, wherein the first portion to be positioned rotatably supports a drum shaft of the electrophotographic photosensitive drum, a second portion to be positioned which is coaxial with the electrophotographic photosensitive drum and which is provided to project longitudinally outwardly of the electrophotographic photosensitive drum from the drum unit, the second portion to be positioned being positioned by said second main assembly positioning portion provided in the main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to the main assembly of said electrophotographic image forming apparatus, wherein the second portion to be positioned rotatably supports the drum shaft, a third portion to be positioned provided to project parallel to the lengthwise direction of the process cartridge from the drum unit at a position downstream of the first portion to be positioned with respect to a mounting direction in which the process cartridge is mounted to the main assembly of said electrophotographic image forming apparatus, the third portion to be positioned being positioned by said third main assembly positioning portion provided in the main assembly of said electrophotographic image forming apparatus when the process cartridge is mounted to the main electrophotographic image forming apparatus, a cartridge coupling provided at one longitudinal end of the drum shaft, configured and positioned to receive a driving force for rotating the electrophotographic photosensitive drum from the main assembly when the process cartridge is mounted to the main assembly, and a helical gear provided to be partly exposed through the drum unit between the first portion to be positioned and the third portion to be positioned with respect to the mounting direction, the helical gear being disposed at one longitudinal end of the developing unit, wherein the helical gear, when the process cartridge is mounted to the main assembly of said electrophotographic image forming apparatus, receives a driving force for rotating the developing member from a main assembly drive force transmitting portion provided in the main assembly of said electrophotographic image forming apparatus.