Developing device and image forming apparatus including same

A developing device for forming a toner image by developing an electrostatic latent image formed on an electrostatic image support using a developer, the device comprising:

• a housing that stores the developer;
• a developer support that is opposed to the electrostatic image support and rotates while supporting the developer supplied from the housing, thereby feeding the developer to a developing area opposed to the electrostatic image support;
• a guide member that is disposed downstream of a supply space in the housing from which the developer is supplied, in the rotational direction of the developer support, so as to be opposed to the developer support with a gap therefrom, such that the developer supported on the developer support passes through the gap;
• a regulating member that is disposed downstream of the guide member in the rotational direction, so as to be opposed to the developer support at a distance therefrom and with a gap from the developer support, thereby regulating the amount of the developer that has passed through the gap between the guide member and the developer support;
• and
• a magnet assembly that is fixed inside the developer support and has a plurality of magnetic poles, at least including a catch pole, a feeding pole, and a regulating pole arranged from upstream to downstream in the rotational direction, wherein,
• the catch pole is approximately opposed to the supply space so as to attract the developer from the supply space onto the developer support,
• the feeding pole is disposed in a position opposed to the guide member, so as to be adjacently upstream of the regulating pole in the rotational direction,
• a peak of the regulating pole is approximately opposed to the regulating member,
• the guide member has an upstream end disposed downstream of a position where the magnetic flux density of the catch pole peaks, in the rotational direction, and upstream of or at a position where the feeding pole has a magnetic flux density of substantially zero, in the rotational direction, and a magnetic attractive force applied at the upstream end is lower than a magnetic attractive force in the gap between the developer support and the regulating member.

A developing device for forming a toner image by developing an electrostatic latent image formed on an electrostatic image support using a developer, the device comprising:

• a housing that stores the developer;
• a developer support that is opposed to the electrostatic image support and rotates while supporting the developer supplied from the housing, thereby feeding the developer to a developing area opposed to the electrostatic image support;
• and
• a magnet assembly that is fixed inside the developer support and has a plurality of magnetic poles, at least including a catch pole, a charging pole, a regulating pole, and a developing pole, wherein,
• the catch pole is opposed to a supply space in the housing from which the developer is supplied, so as to attract the developer from the supply space onto the developer support,
• the charging pole is disposed downstream of the catch pole in a rotational direction of the developer support,
• the regulating pole is disposed downstream of the charging pole in the rotational direction,
• the developing pole is disposed downstream of the regulating pole in the rotational direction so as to be opposed to the developing area,
• the developing device further includes:
• a guide member that is disposed downstream of the supply space in the rotational direction, so as to be opposed to the charging pole with a gap from the developer support, thereby creating a guide channel through which the developer supported on the developer support is fed;
• and
• a regulating member that is disposed downstream of the guide member in the rotational direction, so as to be opposed to the regulating pole with a gap from the developer support, thereby regulating the amount of the developer that has passed through the guide channel,
• the guide member further creates a reflux channel in a gap from an inner surface of the housing,
• the reflux channel is connected to the guide channel via a communication channel such that the developer regulated by the regulating member returns toward an upstream end of the guide member against the rotational direction, and
• the developing device further includes a shear force applying unit for applying a shear force to a top of the developer in the guide channel that is caused to spike by a magnetic force from the charging pole.