Development device and image forming apparatus

A development device comprising:

• a developer container that contains developer, having a supply port,
• rotatable first and second developer supply members that are arranged below the supply port so that the developer falling from the supply port reach the first and second developer supply members;
• a rotatable developer carrier that is arranged in contact with the first and second developer supply members so that the developer is supplied to the developer carrier from the first and second developer supply members;
• and
• a rotatable electrostatic latent image carrier that is arranged in contact with the developer carrier, forms an electrostatic latent image thereon, and develops the electrostatic latent image with the developer supplied from the developer carrier, wherein
• the second developer supply member is positioned at an upstream side from a contact point (CP) with respect to the first developer supply member in a rational direction of the developer carrier, the contact point being defined as a point where the developer carrier contacts the electrostatic latent image carrier,
• a nip amount is defined as a pressure amount that is measured from a contact position where the first and second developer supply members respectively contact the developer carrier to another position where the first and second developer supply members and the developer carrier are pushed each other with a predetermined pressure, a difference between a nip amount of a central portion and a nip amount of an end portion of the first developer supply member is defined as a first nip difference (N1dif), the first nip difference satisfies the follow:
• 0.1 mm≦N1dif≦0.3 mm,
• a difference between a nip amount of a central portion and a nip amount of an end portion of the second developer supply member is defined as a second nip difference (N2dif), the second nip difference satisfies the follow:
• 0.0 mm≦N2dif≦0.5 mm,
• an outer size of the central portion of the first developer supply member is smaller than an outer size of the end portion thereof, and an outer size of the central portion of the second developer supply member is equal to or greater than an outer size of the end portion thereof.