Developing apparatus with separable multiple developer layers and image forming apparatus incorporating same

A developing apparatus comprising:

• a developer container which contains a first developer provided with a first charging polarity and a second developer provided with a second charging polarity opposite to the first charging polarity;
• a developer bearing member which bears the first and the second developers;
• layer forming means which forms a first layer, which substantially includes the first developer, on the developer bearing member and forms a second layer, which includes the first and the second developers, on the first layer;
• and
• a regulating member which is provided on a downstream side of the layer forming means and on an upstream side of a developing position in a developer bearing and conveying direction of the developer bearing member and regulates thickness of a layer of a developer on the developer bearing member, the regulating member including an inflected part in a developer regulating part,
• wherein a curvature radius of the inflected part is 0.5 mm or less, and a contacting pressure of the regulating member and the developer bearing member is 5 gf/cm or more and 100 gf/cm or less.

An image forming apparatus comprising:

• a plurality of developing apparatuses, each of the plurality of developing apparatuses comprising:
• a developer container which contains a first developer of a first color provided with a first charging polarity and a second developer of a second color provided with a second charging polarity opposite to the first charging polarity;
• a developer bearing member which bears the first and the second developers;
• layer forming means which forms a first layer, which substantially includes the first developer, on the developer bearing member and forms a second layer, which includes the first and the second developers, on the first layer;
• and
• separating means which is provided on a downstream side of the layer forming means and on an upstream side of a developing position in a developer carrying and conveying direction of the developer bearing member and separates the second layer from the developer carrying member.