Developing device and image forming apparatus

1. A developing device comprising:

a static latent image supporting member having a photosensitive layer and being arranged to be rotatable;

a developer supporting member arranged to be rotatable for developing a static latent image formed on the static latent image supporting member using developer to form an image;

a developer supplying member arranged to contact with the developer supporting member and be rotatable for supplying developer; and

a drive transmission unit disposed on a side of same end portions of the developer supporting member and the developer supplying member for rotating the developer supporting member and the developer supplying member in a same rotational direction,

wherein said developer supplying member is formed so that an outer diameter thereof on a side of the drive transmission unit becomes smaller than an outer diameter thereof on an opposite side.

2. The developing device according to claim 1 , wherein said drive transmission unit includes a first gear disposed at one end portion of the developer supporting member, a second gear disposed at one end portion of the developer supplying member, and a third gear disposed between the first gear and the second gear to engage with the first gear and the second gear so that a drive force is transmitted from the first gear to the second gear.

3. The developing device according to claim 1 , wherein said developer supplying member includes a surface layer formed of a conductive foamed layer.

4. The developing device according to claim 1 , wherein said developer supplying member is formed in a shape so that outer diameters φD1, φD2, and φD3 thereof at points D1, D2, and D3 satisfy a condition of φD1>φD2>φD3 under a condition in which a contact pressure between the developer supplying member and the developer supporting member is less than 0.10 kgf/cm 2 ,

said developer supplying member has a total length of 220.0 mm in a rotational axis direction thereof,

said point D1 is located at a position 5.0 mm away from an end portion of the developer supplying member on the opposite side toward the side of the drive transmission unit,

said point D2 is located at a position away from the end portion by 110.0 mm,

said point D3 is located at a position away from the end portion by 215.0 mm,

a difference between φD1 and φD2 is between 0.1 mm and 0.2 mm, and

a difference between φD2 and φD3 is between 0.1 mm and 0.2 mm.

5. The developing device according to claim 1 , wherein said developer supplying member is formed in a shape so that outer diameters φD1, φD2, and φD3 thereof at points D1, D2, and D3 satisfy a condition of φD1≈φD2>φD3 under a condition in which a contact pressure between the developer supplying member and the developer supporting member is equal to or greater than 0.10 kgf/cm 2 , or equal to or smaller than 0.15 kgf/cm 2 ,

said developer supplying member has a total length of 220.0 mm in a rotational axis direction thereof,

said point D1 is located at a position 5.0 mm away from an end portion of the developer supplying member on the opposite side toward the side of the drive transmission unit,

said point D2 is located at a position away from the end portion by 110.0 mm,

said point D3 is located at a position away from the end portion by 215.0 mm,

a difference between φD1 and φD2 is ±0.05 mm, and

a difference between φD2 and φD3 is between 0.4 mm and 0.6 mm.

6. The developing device according to claim 1 , wherein said developer supplying member is formed in a shape so that outer diameters φD1, φD2, and φD3 thereof at points D1, D2, and D3 satisfy a condition of φD2>φD1>φD3 under a condition in which a contact pressure between the developer supplying member and the developer supporting member is equal to or greater than 0.15 kgf/cm 2 , or equal to or smaller than 0.20 kgf/cm 2 ,

said developer supplying member has a total length of 220.0 mm in a rotational axis direction thereof,

said point D1 is located at a position 5.0 mm away from an end portion of the developer supplying member on the opposite side toward the side of the drive transmission unit,

said point D2 is located at a position away from the end portion by 110.0 mm,

said point D3 is located at a position away from the end portion by 215.0 mm,

a difference between φD1 and φD2 is between 0.1 mm and 0.3 mm, and

a difference between φD2 and φD3 is between 0.4 mm and 0.6 mm.

7. An image forming apparatus, comprising:

a static latent image supporting member having a photosensitive layer and being arranged to be rotatable;

a developer supporting member arranged to be rotatable for developing a static latent image formed on the static latent image supporting member using developer to form an image;

a developer supplying member arranged to contact with the developer supporting member and be rotatable for supplying developer; and

a drive transmission unit disposed on a side of same end portions of the developer supporting member and the developer supplying member for rotating the developer supporting member and the developer supplying member in a same rotational direction,

wherein said developer supplying member is formed so that an outer diameter thereof on a side of the drive transmission unit becomes smaller than an outer diameter thereof on an opposite side.