Developing device, process cartridge and electrophotographic image forming apparatus

A process cartridge which is detachably mounted on a main body of an electrophotographic image forming apparatus, said process cartridge comprising:

• (a) an electrophotographic photosensitive member;
• (b) a developing device including a developer container having a developing portion for containing a developer and provided with a developer bearing member for feeding the developer to said electrophotographic photosensitive member, and a hopper portion for containing the developer and supplying the developer to said developing portion, in order to develop an electrostatic latent image formed on said electrophotographic photosensitive member;
• and
• (c) a developer residual amount detecting electrode pair having first and second electrodes disposed to interpose said developing portion and said hopper portion therebetween in order to detect the residual amount of developer by said main body of the electrophotographic image forming apparatus,
• wherein said developer residual amount detecting electrode pair are shaped such that a space region defined between said first and second electrodes includes substantially 20% or more of a space in said developing portion and said hopper portion which is filled with the developer.

An electrophotographic image forming apparatus for forming an image on a recording medium, said electrophotographic image forming apparatus comprising:

• (a) an electrophotographic photosensitive member;
• (b) electrostatic latent-image forming means for forming an electrostatic latent image on said electrophotographic photosensitive member;
• (c) a developing device including a developer container having a developing portion for containing a developer and provided with a developer bearing member for feeding the developer to said electrophotographic photosensitive member, and a hopper portion for containing the developer and supplying the developer to said developing portion, in order to develop the electrostatic latent image formed on said electrophotographic photosensitive member;
• (d) a developer-residual-amount detecting electrode pair having first and second electrodes disposed to interpose said developing portion and said hopper portion therebetween in order to detect the residual amount of developer by a main body of the electrophotographic image forming apparatus;
• (e) bias voltage applying means for applying an alternate bias voltage to at least said first electrode;
• and
• (f) developer-amount detecting means for measuring the capacitance between said developer-residual-amount detecting electrode pair to determine the amount of developer,
• wherein said developer-residual-amount detecting electrode pair are shaped such that a space region defined between said first and second electrodes includes substantially 20% or more of a space in said developing portion and said hopper portion that is filled with the developer.

An electrophotographic image forming apparatus for forming an image on a recording medium, to which a process cartridge is detachably mountable, said electrophotographic image forming apparatus comprising:

• (a) mounting means for detachably mounting the process cartridge, the process cartridge comprising:
• (i) an electrophotographic photosensitive member;
• and
• (ii) a developing device including a developer container having a developing portion for containing a developer and provided with a developer bearing member for feeding the developer to said electrophotographic photosensitive member, and a hopper portion for containing the developer and supplying the developer to said developing portion, in order to develop an electrostatic latent image formed on said electrophotographic photosensitive member;
• (b) a developer-residual-amount detecting electrode pair having first and second electrodes disposed to interpose said developing portion and said hopper portion therebetween in order to detect the residual amount of developer by a main body of the electrophotographic image forming apparatus;
• (c) electrostatic latent-image forming means for forming the electrostatic latent image on said electrophotographic photosensitive member;
• (d) bias voltage applying means for applying an alternate bias voltage to at least said first electrode;
• and
• (e) developer-amount detecting means for measuring the capacitance between said developer-residual-amount detecting electrode pair to determine the amount of developer,
• wherein said developer-residual-amount detecting electrode pair are shaped such that a space region defined between said first and second electrodes includes substantially 20% or more of a space in said developing portion and said hopper portion that is filled with the developer.

An electrophotographic image forming apparatus for forming an image on a recording medium, said electrophotographic image forming apparatus comprising:

• (a) an electrophotographic photosensitive member;
• (b) electrostatic latent image forming means for forming an electrostatic latent image on said electrophotographic photosensitive member;
• (c) a plurality of developing devices each including a developer container having a developing portion for containing a developer and provided with a developer bearing member for feeding the developer to said electrophotographic photosensitive member, and a hopper portion for containing the developer and supplying the developer to said developing portion, in order to develop the electrostatic latent image formed on said electrophotographic photosensitive member;
• (d) a support member for detachably mounting said plurality of developing devices to move each of said plurality of developing devices to a developing position opposite to said electrophotographic photosensitive member;
• (e) a developer-residual-amount detecting electrode pair having first and second electrodes disposed to interpose said developing portion and said hopper portion therebetween in order to detect the residual amount of developer in each of said plurality of developing devices by a main body of the electrophotographic image forming apparatus;
• (f) bias voltage applying means for applying an alternate bias voltage to at least said first electrode;
• and
• (g) developer amount detecting means for measuring the capacitance between said developer-residual-amount detecting electrode pair to determine the amount of developer,
• wherein said developer-residual-amount detecting electrode pair are shaped such that a space region defined between said first and second electrodes includes substantially 20% or more of a space in said developing portion and said hopper portion that is filled with the developer.