DEVELOPING DEVICE AND IMAGE FORMING APPARATUS

• US 20110229209A1
• Filed: 03/18/2011
• Published: 09/22/2011
• Est. Priority Date: 03/19/2010
• Status: Active Grant

• Current Assignee: Konica Minolta Inc.
• Original Assignee: Konica Minolta Business Technologies Incorporated (Konica Minolta Inc.)
• Inventors: MAEDA, Osamu, TAKAYA, Shunichi
• Granted Patent: US 8,818,245 B2
• Time in Patent Office: Days
• US Class Current: 399/257
• CPC Class Codes: G03G 15/0844 Arrangements for purging used developer from the developing unit
• CPC Class Codes: G03G 15/0893 in a closed loop within the sump of the developing device
• CPC Class Codes: G03G 2215/0607 two-component
• CPC Class Codes: G03G 2215/0827 Augers
• CPC Class Codes: G03G 2215/0838 Circulation of developer in a closed loop within the sump of the developing device

Abstract

A developing device having a housing that houses two-component developer containing carrier and toner, replenishing replenishment carrier to the housing while gradually ejecting developer to outside from an outlet. The developing device includes: transport passage provided in the housing so that developer is transported therein; transport member provided in the housing and rotates to transport the developer; ejection passage having diverged from the transport passage so that a part of the developer transported in the transport passage is conveyed therein to the outlet; and restriction unit configured to restrict an amount of ejected developer so that a first amount of developer is ejected from the outlet when the transport member rotates at a first speed, and a second amount of developer is ejected when it rotates at a second speed. The second amount is smaller than the first amount. The second speed is higher than the first speed.

Claims

1. A developing device having a housing that houses a two-component developer containing a carrier and a toner, replenishing a replenishment carrier to the housing while gradually ejecting the developer to outside from an outlet, the developing device comprising:

a transport passage provided in the housing so that the developer is transported therein;

a transport member provided in the housing and configured to rotate to transport the developer;

an ejection passage having diverged from the transport passage so that a part of the developer transported in the transport passage is conveyed therein to the outlet; and

a restriction unit configured to restrict an amount of ejected developer so that a first amount of developer is ejected from the outlet when the transport member rotates at a first speed, and a second amount of developer is ejected from the outlet when the transport member rotates at a second speed, the second amount being smaller than the first amount, the second speed being higher than the first speed.

2. The developing device of claim 1, wherein

the restriction unit includes:

a shutter configured to move and close the outlet by covering thereof; and

a moving mechanism configured to move the shutter so that the outlet is opened for a first time period per rotation of the transport member when the transport member rotates at the first speed, and the outlet is opened for a second time period per rotation of the transport member when the transport member rotates at the second speed, the second time period being shorter than the first time period.

3. The developing device of claim 2, wherein

the ejection passage is composed of a first cylindrical member,

the outlet is provided in a circumferential surface of the first cylindrical member,

the shutter is composed of a second cylindrical member whose circumferential surface has a hole, and the shutter is fixed on the first cylindrical member to be rotatable in a circumferential direction relative to the first cylindrical member, is disposed at a position where at least part of the hole overlaps with the outlet in an axis direction of the first cylindrical member, and closes the outlet when the shutter is, by rotation, at a position where the hole does not overlap with the outlet, and

the moving mechanism causes the shutter to rotate in a same direction as a rotation of the transport member in coordination with the transport member.

4. The developing device of claim 3, wherein

the transport passage includes:

a first straight passage; and

a curved passage being one of two passages into which the straight passage diverges at a downstream end in a developer transport direction, the curved passage being curved relative to the first straight passage,

the ejection passage includes;

a second straight passage being another of the two passages and extending in a same direction as the developer transport direction of the first straight passage,

wherein the transport member is inserted in the first straight passage and the second straight passage,

the shutter is a cylindrical member whose one end in the axis direction is opened and another end in the axis direction has a bottom, and a portion of the shutter on a side of the opened end is fixed on the first cylindrical member, and

the bottom is engaged with a rotation shaft of the transport member, and a rotational driving force of the transport member is conveyed to the shutter via the bottom thereof engaged with the rotation shaft, so that the shutter rotates in coordination with the transport member.

5. The developing device of claim 1, wherein

the restriction unit includes:

a shutter configured to move and close the outlet by covering thereof; and

a moving mechanism configured to move the shutter so that an opening area of the outlet is a first size when a rotation speed of the transport member is the first speed, and an opening area of the outlet is a second size when the rotation speed of the transport member is the second speed, the second size being smaller than the first size.

6. The developing device of claim 5, wherein

the shutter is supported to be rotatable around the rotation shaft of the transport member,

the moving mechanism includes:

a connection member connecting the shutter with the rotation shaft of the transport member, the connection member being rotatable around the rotation shaft of the transport member, and conveying a driving force in a rotation direction that is generated by a frictional force that is generated by a contact between the connection member and the rotation shaft; and

an urging member configured to apply an urging force to the shutter in a reverse direction of the rotation direction of the transport member,

wherein the shutter is rotated by a rotational driving force that is conveyed via the connection member when the transport member rotates, against the urging force applied by the urging member, by an angle corresponding to the rotation speed in the rotation direction.

7. The developing device of claim 6, wherein

the transport passage includes:

a first straight passage; and

a curved passage being one of two passages into which the straight passage diverges at a downstream end in a developer transport direction, the curved passage being curved relative to the first straight passage,

the ejection passage includes;

a second straight passage being composed of a first cylindrical member, being another of the two passages, and extending in a same direction as the developer transport direction of the first straight passage,

wherein the outlet is provided in a circumferential surface of the first cylindrical member,

the shutter is composed of a second cylindrical member whose circumferential surface has a hole and whose one end in the axis direction is opened and another end in the axis direction has a bottom, and a portion of the shutter on a side of the opened end is fixed on the first cylindrical member to be rotatable in a circumferential direction relative to the first cylindrical member, and is disposed at a position where at least part of the hole overlaps with the outlet in an axis direction of the first cylindrical member, and closes the outlet when the shutter is, by rotation, at a position where the hole does not overlap with the outlet,

the transport member is inserted in the first straight passage and the second straight passage, the rotation shaft of the transport member is fitted in an engaging hole provided in the bottom of the shutter, and

the bottom of the shutter doubles as the connection member.

8. The developing device of claim 1 further comprising:

a bypass connecting a first part of the ejection passage with a second part of the transport passage, the second part being on a downstream of a position where the transport passage diverges to the ejection passage in a developer transport direction, the bypass guiding the developer transported in the ejection passage from the first part of the ejection passage to the second part of the transport passage.

9. The developing device of claim 8, wherein

the transport passage includes:

a first straight passage; and

a curved passage being one of two passages into which the straight passage diverges at a downstream end in a developer transport direction, the curved passage being curved relative to the first straight passage,

the ejection passage includes;

a second straight passage being another of the two passages and extending in a same direction as the developer transport direction of the first straight passage,

wherein the first part is connected with the second straight passage, and is higher in position than the rotation shaft of the transport member.

10. An image forming apparatus comprising a developing device for developing an electrostatic latent image held by an image holder by using a developer, the developing device having a housing that houses a two-component developer containing a carrier and a toner, replenishing a replenishment carrier to the housing while gradually ejecting the developer to outside from an outlet, the developing device including:

a transport passage provided in the housing so that the developer is transported therein;

a transport member provided in the housing and configured to rotate to transport the developer;

an ejection passage having diverged from the transport passage so that a part of the developer transported in the transport passage is conveyed therein to the outlet; and

a restriction unit configured to restrict an amount of ejected developer so that a first amount of developer is ejected from the outlet when the transport member rotates at a first speed, and a second amount of developer is ejected from the outlet when the transport member rotates at a second speed, the second amount being smaller than the first amount, the second speed being higher than the first speed.

11. An image forming apparatus comprising:

a developing device;

a driver configured to drive a transport member included in the developing device; and

a controller configured to control the driver to stop the transport member from rotating, to be in a state in which an outlet of an ejection passage in the developing device is closed by a shutter provided in the developing device,

wherein the developing device has a housing that houses a two-component developer containing a carrier and a toner, replenishes a replenishment carrier to the housing while gradually ejecting the developer to outside from the outlet, the developing device including;

a transport passage provided in the housing so that the developer is transported therein;

the transport member provided in the housing and configured to rotate to transport the developer;

the ejection passage having diverged from the transport passage so that a part of the developer transported in the transport passage is conveyed therein to the outlet; and

a restriction unit configured to restrict an amount of ejected developer so that a first amount of developer is ejected from the outlet when the transport member rotates at a first speed, and a second amount of developer is ejected from the outlet when the transport member rotates at a second speed, the second amount being smaller than the first amount, the second speed being higher than the first speed,

wherein the restriction unit includes;

a shutter configured to move and close the outlet by covering thereof; and

a moving mechanism configured to move the shutter so that the outlet is opened for a first time period per rotation of the transport member when the transport member rotates at the first speed, and the outlet is opened for a second time period per rotation of the transport member when the transport member rotates at the second speed, the second time period being shorter than the first time period,

wherein the ejection passage is composed of a first cylindrical member,

the outlet is provided in a circumferential surface of the first cylindrical member,

the shutter is composed of a second cylindrical member whose circumferential surface has a hole, and the shutter is fixed on the first cylindrical member to be rotatable in a circumferential direction relative to the first cylindrical member, is disposed at a position where at least part of the hole overlaps with the outlet in an axis direction of the first cylindrical member, and closes the outlet when the shutter is, by rotation, at a position where the hole does not overlap with the outlet, and

the moving mechanism causes the shutter to rotate in a same direction as a rotation of the transport member in coordination with the transport member.