Developing device and image forming apparatus using the same

摘要

A developing device includes a first developing unit, a second developing unit, a rotating member, a magnetic pole forming member, a first separating pole, a second separating pole, a developer supplying unit, and a path formation member. The developing device is provided with a magnetic structure, in which, when a value of a magnetic flux density at which the developer is separated is a reference separation value, at a side of the first separating pole at the separation area of the second developing unit, a position where a magnetic flux density of a vertical component of a magnetic force becomes less than or equal to the reference separation value is disposed downstream in the direction of rotation of the rotating member of a position where a magnetic flux density of a horizontal component of the magnetic force becomes less than or equal to the reference separation value.

主权项

1. A developing device comprising:
a first developing unit that performs development to form a toner image using developer; a second developing unit that is disposed above the first developing unit and that performs development to form the toner image using the developer; a rotating member that is rotatably provided at an outer periphery of the second developing unit; a magnetic pole forming member that is provided at an inner side of the rotating member, the magnetic pole forming member having separating poles that include a first separating pole and a second separating pole, the separating poles defining a separation area where the developer is separated; the first separating pole that defines a starting point of the separation area; the second separating pole that is disposed downstream of the first separating pole in a direction of rotation of the rotating member, the second separating pole defining an end point of the separation area; a developer supplying unit that supplies the developer to the first developing unit and the second developing unit; and a path formation member that is disposed with an end portion thereof being out of contact with the outer periphery of the second developing unit, the path formation member forming a path for returning residual developer remaining on the second developing unit without being used in the development to the developer supplying unit, wherein a magnetic structure is provided, in which, when a value of a magnetic flux density at which the developer is separated is a reference separation value, at a side of the first separating pole at the separation area of the second developing unit, a position where a magnetic flux density of a vertical component of a magnetic force becomes less than or equal to the reference separation value is disposed downstream in the direction of rotation of the rotating member of a position where a magnetic flux density of a horizontal component of the magnetic force becomes less than or equal to the reference separation value.