JP2013080034A - Exhaust mechanism and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust mechanism configured to maintain exhaust performance for a long time in discharging air to the outside, without enlarging the installation space of a collection part.SOLUTION: A discharge container 200 equipped with a filter 202 having a collection surface of magnetic powder includes a movable magnet 203 which is arranged on a side opposite the collection surface of the filter 202 and configured to cross the collection surface. On the basis of a predetermined time or the time corresponding to a change in toner density, the movable magnet 203 is moved along the collection surface toward a position off the collection surface, thereby collecting the powder deposited on the collection surface by use of magnetic restraint of the movable magnet to remove it from the collection surface.

Description

  The present invention relates to an exhaust mechanism and an image forming apparatus. More specifically, the present invention relates to a purification mechanism for an exhaust mechanism used when air-conveying a two-component developer.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.

As a developer used for development, there is a two-component developer obtained by mixing a toner and a carrier in addition to a one-component developer containing only a magnetic or non-magnetic toner.
A two-component developer is composed of a toner that forms a powder body and a carrier that carries the powder. The toner is charged by a frictional charging action that occurs during agitation and mixing, and is applied to the electrostatic latent image on the photoreceptor. Thus, it can be electrostatically attracted.

  The two-component developer used in the developing device is a magnetic pole built in a developing sleeve used for the developer carrying member in a state where, for example, a developing device using a magnetic developing system is maintained in a charged state by stirring and mixing. By bringing the magnetic brush formed on the surface into contact with the surface of the photoconductor by the above action, the toner in the magnetic brush is electrostatically attracted to the latent image carrier on the photoconductor to perform visible image processing.

In order to stabilize the toner density in the developer contained in the developing device and the image density on the photosensitive member, and to stabilize the image quality, it is necessary to maintain high mixing and mixing in the developing device. It becomes.
Conventionally, two screws that can move the developer while stirring are provided in the developing device, one screw is in the developer supply space, and the other screw is a collection space for collecting the developer after development. There is known a configuration in which the developer is moved in opposite directions after being arranged in each.
The recovered developer mentioned above means a developer that is repelled from the developing sleeve and introduced into the recovery space by the action of the repulsive magnetic pole disposed in the developing sleeve carrying the magnetic brush.

  However, in the configuration described above, since the developer is stirred and mixed by the rotation of the two screws, if the toner balance is large, such as a rapid increase in toner consumption, the limited stirring and mixing of the developing device. In the space, the replenished toner may not be sufficiently dispersed. For this reason, the charge amount of the toner is not sufficient, and there is a possibility of causing stains on the peripheral portion due to background dirt or scattered toner.

In order to solve such problems, a configuration is known in which a stirring unit is provided at a position different from the developing device, and the stirred developer is supplied to the developing device using a conveying screw.
In addition to the developing unit having the above-described configuration, an agitation unit having a configuration for replenishing new toner using a gas such as air is connected by a circulation unit, and the agitation unit performs the agitation according to the state of the developer. A configuration has been proposed in which a developer whose toner density and charge amount are appropriately adjusted is supplied to the developing unit and circulated from the developing unit to the stirring unit (for example, Patent Documents 1 to 4).

When airflow conveyance is used, air is introduced from the outside using an air pump or the like, so that the internal pressure increases in the developer conveyance system.
When the internal pressure rises in the transport system, the pressure is discharged from the externally open portion in the transport path, that is, from the joint portion of each component upstream and downstream of the developing sleeve. For this reason, there is a possibility that air whose pressure has increased is ejected from the exhaust pressure section, causing the inside of the apparatus to be contaminated due to ejection of toner and developer.

  Therefore, the suction device generates a negative pressure in the developing device and conveys the scattered toner generated in the developing device to a collecting unit provided at a position different from the developing device, and the air passes through a filter. A configuration for discharging to the outside has also been proposed (Patent Document 5).

When the air is discharged to the outside of the apparatus, as disclosed in Patent Document 5, powders such as toner and carrier contained in the air are collected by using a filter.
However, since the developer is stored in the recovery unit, the air discharge function decreases as the recovery amount increases.
For this reason, it is necessary to replace the collection unit when the predetermined amount is reached. Therefore, in order to reduce the replacement frequency, the volume of the collection unit must be increased. As a result, the space for arranging the collection unit is increased, which leads to an increase in the size of the image forming apparatus.
In addition, the replacement of the collection unit has a problem that the developer, which is attracting attention as an environmental problem, cannot be reused.

  An object of the present invention is to provide a long-term exhaust capability when exhausting air to the outside without causing an increase in the installation space of the recovery unit in view of the problems in the above-described conventional developing device, particularly a developer circulation mechanism using an air stream. It is an object of the present invention to provide an exhaust mechanism having a configuration that can be maintained over a long period of time and an image forming apparatus using the exhaust mechanism.

In order to achieve the above object, the present invention provides an exhaust mechanism including a filter for collecting powder and discharging only air in an air exhaust part used for airflow conveyance of powder,
For at least one of the powders, a magnetic substance is used as a target,
On the opposite side of the powder collecting surface of the filter to which the powder adheres, a movable magnet capable of crossing the powder collecting surface is provided,
The movable magnet is in an exhaust mechanism characterized by sweeping the powder toward a position off the powder collecting surface after traversing the powder collecting surface.

  According to the present invention, by providing a movable magnet that traverses the powder collecting surface of the filter, the powder that is collected on the powder collecting surface is collected in accordance with the sweeping of the movable magnet. Move to a position outside the body collection surface. As a result, the increase in the amount of powder stored on the powder collecting surface is eliminated, and the exhaust function is maintained.

1 is an overall configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic diagram for explaining a configuration of a developing device used in the image forming apparatus shown in FIG. 1. FIG. 3 is a diagram for explaining a configuration of a developer supply mechanism for the developing device shown in FIG. 2. FIG. 4 is a development view of the supply mechanism shown in FIG. 3. It is an external view which shows the structure of the exhaust mechanism used for the supply mechanism shown in FIG. It is a figure for demonstrating the structure of the movable magnet used for the exhaust mechanism shown in FIG. It is a figure for demonstrating the effect | action of the exhaust mechanism shown in FIG. FIG. 6 is a timing chart for explaining a change in pressure due to the action of the exhaust mechanism shown in FIG. 5. It is a figure for demonstrating the structure and effect | action of a principal part modification for the exhaust mechanism shown in FIG. FIG. 6 is a diagram for explaining the relationship between the toner concentration and the toner dust collection amount, which is one of the requirements for setting the operation frequency of the exhaust mechanism shown in FIG. 5.

Hereinafter, embodiments for carrying out the present invention will be described with reference to illustrated embodiments.
FIG. 1 is a diagram showing an image forming apparatus to which a developing device using an exhaust mechanism is applied. The image forming apparatus will be described as follows before explanation of exhaust return. The image forming apparatus shown in FIG. 1 is a tandem full-color printer. However, the present invention is not limited to this, and can be applied to a copying machine, a facsimile machine, and the like.

  In the image forming apparatus shown in FIG. 1, each color (yellow, magenta, cyan, black) faces the lower surface of an intermediate transfer belt 10A as an unfixed image carrier provided in the intermediate transfer unit 10 in the apparatus main body 100. ) Corresponding to the image forming units 6Y, 6M, 6C, and 6K.

These image forming units 6Y, 6M, 6C, and 6K have the same structure except that the color of the toner used in the image forming process is different. In the following description, only the numerical symbols common to the image forming units will be described, and the alphabetic symbols indicating the toner colors will be omitted.
Each image forming unit 6 includes a photosensitive drum 1 as a latent image carrier, a charging unit 2, a developing device 3, a cleaning unit 4 and the like disposed around the photosensitive drum 1.
An image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1.
The photosensitive drum 1 is rotationally driven in the clockwise direction in the drawing by a driving unit (not shown), and the surface is uniformly charged at the position of the charging means 2 (charging process).

The surface of the photosensitive drum 1 reaches an irradiation position of a laser beam emitted from an exposure unit (not shown), and an electrostatic latent image is formed by exposure scanning at this position (exposure process). When the position reaches this position, the visible image is processed with the toner contained in the developer supplied therefrom, and the development process is executed.
The surface of the photosensitive drum 1 carrying the toner image that has been subjected to the visible image processing in the development process reaches a position facing the intermediate transfer belt 10A and the primary transfer bias roller 5, and at this position on the photosensitive drum 1. The toner image is transferred onto the intermediate transfer belt 10A (primary transfer step).

After the transfer, the surface of the photosensitive member 1 reaches a position facing the cleaning unit 4, and untransferred toner remaining on the photosensitive drum 1 is collected at this position (cleaning step). After cleaning, the potential of the surface of the photosensitive drum 1 is initialized by a neutralizing roller (not shown). By passing through such steps, a series of image forming processes performed on the photosensitive drum 1 is completed.
The image forming process described above is performed at the time of forming a single image of only a monochrome image and at the time of forming a full color image. At the time of forming a full color image, each of the four image forming units 6Y, 6M, 6C, and 6K shown in FIG. Each step is performed. That is, a laser beam based on image information from an exposure unit (optical writing device) (not shown) disposed below the image forming unit is applied to the photosensitive drums of the image forming units 6Y, 6M, 6C, and 6K. Irradiated toward. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 10A in an overlapping manner. Thus, a color image is formed on the intermediate transfer belt 10A.

The four primary transfer bias rollers 5Y, 5M, 5C, and 5K respectively sandwich the intermediate transfer belt 10A with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. The primary transfer bias rollers 5Y, 5M, 5C, and 5K are applied with a transfer bias having a polarity opposite to the polarity of the toner.
The intermediate transfer belt 10A travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 5Y, 5M, 5C, and 5K. Thus, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 10A.
The intermediate transfer belt 10A onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 7 as a secondary transfer unit. The color toner image formed on the intermediate transfer belt 10A is collectively transferred onto a transfer sheet P as a recording medium conveyed to the secondary transfer nip position.

A plurality of transfer sheets P are stored in a paper supply unit 8 disposed in the lower part of the apparatus main body 100, and are separated and fed one by one by a paper supply roller 9. The fed transfer paper P is temporarily stopped by the registration roller pair 10, and after the oblique deviation is corrected, it is conveyed toward the secondary transfer nip by the registration roller pair 10 at a predetermined timing. As described above, a desired color image is transferred onto the transfer paper P at the secondary transfer nip.
The transfer paper P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing unit 11 where the color image transferred to the surface is fixed by heat and pressure generated by the fixing roller and the pressure roller. The
After the fixing, the transfer sheet P is discharged as an output image to the paper discharge unit 100A formed on the upper surface of the apparatus main body 100 by the paper discharge roller pair 12 and stacked. Thus, a series of image forming processes in the image forming apparatus is completed. In FIG. 1, reference numeral 13 denotes a cleaning device for the intermediate transfer belt 10A.

FIG. 2 shows the developing device 3, and the developing device 3 shown in FIG. 2 is used as a developing unit in the image forming unit.
Inside the developer tank 30, there are a developer supply unit 30A and a developer recovery unit 30B, in which a developer supply member 3A and a developer recovery member 3B, each consisting of two conveying screws arranged in the vertical direction, are arranged. Is provided.
A developer sleeve 3C, which is a developer carrying member, faces the developer supply member 3A, and the developer supplied from the developer supply member 3A is supplied after a layer thickness is defined by the doctor blade 3D. It is like that.
The rotation direction of the developer supply member 3A and the developer recovery member 3B is set in the opposite direction, and the developer is conveyed in the opposite direction during rotation.
The developer supply unit 30A and the developer recovery unit 30B are arranged at positions included in the circulation unit in the configuration shown in the developer supply mechanism shown in FIG.

FIG. 3 shows the overall configuration of the developer supply mechanism.
The developer supply mechanism is provided with the following members.
A developing tank 30 that can store a developer for developing an electrostatic latent image on the photosensitive drum 1, and a new toner that matches the developer collected from the developing tank 30 and a consumed toner at a position away from the developing tank 30. A developer container 40 that stirs and mixes the toner, a toner supply part 60 that replenishes new toner toward the developer container 40, and a rotary for transporting the developer after stirring and mixing discharged from the developer container 40. The feeder 50 and the developer correspond to a developer circulation drive source for constituting a so-called air flow conveying mechanism that transports the developer toward the developing tank 30 by a gas such as air (hereinafter, described in the case of air for convenience). An air pump 51 is provided as a main part.
In FIG. 3, the developing tank 30 is configured in a cartridge shape. In FIG. 3, for convenience, the developer supply member 3 </ b> A and the developer recovery member 3 </ b> B are shown with reference numerals for these rotation axes.

  The developer tank 30 and the developer container 40 are connected to the developer recovery channel 41 and the rotary feeder 50 connected to the developer recovery part 30B in the developer tank 30 and the developer supply part 30A in the developer tank 30. The developer supply flow path 42 constitutes a developer circulation path, and a circulation section including members provided in the circulation path is formed.

  The developer supply flow path 42 connected to the developer tank 30 is one end in the axial direction of the developer supply member 3A, specifically, the developer conveyance start position side corresponding to the upstream side in the developer conveyance direction by the developer supply member 3A. It is connected to face. Further, the developer recovery flow path 41 corresponds to the developer discharge position on the downstream side in the transport direction of the developer by the developer recovery member 3B in the axial direction of the developer recovery member 3B provided in the developer tank 30. Connected.

  The developer accommodating portion 40 has an appearance like a silo with an upper portion being cylindrical and a lower portion having a downward conical shape, and a stirring member described in detail in FIG. 4 is provided inside.

In FIG. 4, a drive motor 40 </ b> A and a reduction gear group GR that form a drive unit for the stirring member are provided on the upper part of the developer container 40.
The developer agitated and mixed in the developer container 40 is fed to a rotary feeder 50 that is provided with a paddle that can adjust the supply amount and is driven to rotate by a drive motor 50A, and the supply amount is adjusted at this position. The developer is conveyed toward the developing tank 30 by the air flow generated by the air pump 51.

  In FIG. 3, the toner supply unit 60 includes a toner tank 61, a replenishment toner conveyance path 62 connected between the toner tank 61 and the developer container 40, and toner replenished in the replenishment toner conveyance path 62. And a drive motor 63 that drives a conveying screw (not shown) disposed in the supply path.

The developed developer is transported to the developer container 40 from a developer recovery channel 41 (see FIG. 3) connected to the end of the developer recovery member 3B equipped in the developer recovery unit 30B. The
On the most downstream side in the developer moving direction by the developer collecting member 3B, a toner density detecting means (not shown) is installed, and new toner is replenished from the toner tank 61 based on the signal. As described above, the toner is replenished by airflow conveyance by the air pump 63 connected to the replenishment toner conveyance path 62.

The details of the developer container 40 shown in FIG. 3 are shown in FIG.
In FIG. 4, a container 43 having a funnel-like shape with a cylindrical upper portion and a downwardly conical shape is used for the developer accommodating portion 40, and the discharge port having the smallest diameter located at the lowermost portion is used. 400 communicates with the rotary feeder 50.

  In the internal space of the developer container 40, a screw 44A that is integrated with a rotating shaft 44 that is suspended from the drive motor 40A as a stirring member and that moves the developer in the direction opposite to the flow direction of the developer, A stirring blade 45A having an end plate 45 that can be interlocked with the output gear of the reduction gear group GR driven by the rotating shaft 44 is provided. The stirring blade 45A has a configuration in which a plurality of slits are formed in a plate-like member parallel to the radial direction of the end plate 45 so that the remaining developer can be pushed and stirred while passing a part of the developer. .

  The rotary feeder 50 connected to the discharge port 400 positioned at the bottom of the container 43 is provided to control the developer discharge amount in accordance with the rotation amount of the motor 50A (see FIG. 3). A rotary valve member 50B having a plurality of blades 50B1 that are fixed to the rotation shaft of 50A and extend radially is provided.

The characteristics of the present embodiment will be described as follows with the above configuration as an object.
A feature of the present embodiment is that it includes an exhaust mechanism that exhausts air when the pressure at a location where air used for transporting the developer acts in the developer circulation path by airflow transport increases, and the exhaust mechanism It is characterized in that a mechanism for cleaning the filter used in the above is provided.

Hereinafter, this feature will be described.
3 and 4, the top plate positioned above the developer surface of the developer accommodating portion 40 has an exhaust pipe line 201 communicating with the discharge container 200 forming the exhaust portion, in addition to the developer recovery channel 41. It is connected. In FIG. 4 and FIG. 7 to be described later, an arrow indicates the moving direction of the developer.

  As the discharge container 200, a box-shaped container is used in which a communication portion 200A configured by an opening communicating with the outside is provided at at least one location on the outer periphery. The discharge container 200 has a space used as a volume expansion part inside, and can exhibit a function of reducing the pressure of the introduced air.

The communication portion 200A is covered with a filter 202 that can prevent the discharge of the developer and discharge only the air to the outside. The communication portion 101A and the filter 202 have a mesh mesh structure, and contain the developer. The area and the number of air that can be set to be equal to or lower than the pressure generated in the airflow transport mechanism are set so that the pressure of the air introduced from the section 40 into the pipe line 201 is set.
In the case of a mesh-like mesh structure, for example, as with punching metal, since the surface is not uneven, the toner does not get into the fiber, unlike the filter with a structure in which the fiber is knitted. It becomes easy to bring.

  On the other hand, FIG. 5 is an enlarged view of only the discharge container 200 extracted. In FIG. 5, the filter 202 provided in the discharge container 200 includes toner that is a substance that can fly by airflow conveyance and this. A cleaning mechanism for the filter 202, which is a member for collecting magnetic carriers having magnetism in the developer, is provided.

5, in the vicinity of the discharge container 100, a movable magnet 203 that can horizontally traverse the filter 202 that forms a powder collecting surface such as toner and magnetic carrier in FIG.
The movable magnet 203 includes a collection surface sweeping magnet 203 </ b> A facing the collection surface of the filter 202, and a bottom sweeping magnet 203 </ b> B facing the bottom of the discharge container 200. Therefore, the collection surface sweeping magnet 203A facing the collection surface is disposed on the opposite side of the collection surface of the filter 202 to which powder such as toner and magnetic carrier adheres.

  The mechanism for traversing the movable magnet 203 on the side opposite to the collection surface of the filter 202 includes a drive screw 204 having an axial length up to a position outside the occupied area of the filter 202 in the transverse direction, and a drive motor that rotationally drives the drive screw 204. As will be described later, the drive motor 205 is configured to set the rotation timing in accordance with the toner density in the developing device. In FIG. 5, reference numeral 206 indicates a movable table that supports the movable magnet 203.

A magnet used as the movable magnet 203 has a magnetic pole configuration shown in FIG.
As shown in FIG. 6A, the movable magnet 203 is formed of a single-pole magnet whose end facing the collection surface of the filter 202 is uniformly magnetized with either the N or S pole.
As a result, the collecting force can be increased by causing the lines of magnetic force to be perpendicular to the collecting surface of the filter 202.
FIG. 6B shows a case where the magnet end portions are positioned along the collecting surface, and the magnetic poles at the respective end portions are set as N and S poles along the collecting surface. In such a magnetic pole configuration, magnetic lines of force are generated along the collecting surface of the disadvantage 202, in other words, parallel to the collecting surface, so that the magnetic lines passing through the inside of the collecting surface are weak and the collecting force is reduced. I can't strengthen it.

  The area of the collection surface of the filter 202 from which the toner and magnetic carrier are removed when the movable magnet 203 traverses is an area obtained by adding an area capable of obtaining a necessary exhaust capacity to the projected area of the movable magnet 203 at the time of traversing. Is set. In other words, even if the movable magnet 203 exists on the collection surface, an area where the exhaust capability when the movable magnet 203 is not present is obtained can be secured.

The operation of the above configuration will be described as shown in FIG.
In FIG. 7, when the state where the toner and the magnetic carrier that have been conveyed to the collection surface of the filter 202 are collected and only the air is discharged is continued, the toner and the magnetic carrier are gradually collected on the collection surface. Deposits (state shown in FIG. 7A).
The operation time of the movable magnet 203 is set in advance according to the operation time of the image forming apparatus or the number of prints, and the movable base 203 is moved by the movable magnet 203 via the drive motor 205 and the drive screw 204 linked thereto. Then, the movable magnet is traversed on the side opposite to the collection surface of the filter 202. When the movable magnet 203 crosses the collecting surface, toner is also swept away by using the movement of the developer, that is, the magnetic carrier, restrained by the magnetic force of the movable magnet 203 (the state shown in FIG. 7B). .
When the movable magnet 203 moves to a position outside the area occupied by the filter 202, the magnetic force applied to the toner and the magnetic carrier is weakened, and the swept toner and developer that are released from the restriction of the magnetic force are collected at the end of the discharge container. (The state shown in FIG. 7C).

FIG. 8 is a diagram illustrating a result of comparing the pressure change between the case where the filter 202 is cleaned by the movable magnet 203 and the case where the filter 202 is not cleaned.
In the same figure, when the filter 202 is not cleaned, the pressure in the discharge container 200 increases with the accumulation of toner and developer on the collecting surface of the filter 202 over time as indicated by the broken line. However, this causes a pressure increase in the developer transport system.
On the other hand, when the above configuration is used, as shown by the solid line, the pressure rise is eliminated by cleaning.

Next, a modification of the main part of the above configuration will be described.
The filter 202 is detachably attached to the support frame of the filter 202 corresponding to the discharge container 200 so that the filter 202 can be replaced.
On the other hand, as shown in FIG. 9, in the communication part 200 </ b> A of the discharge container 200, a holding part 207 that constitutes a space capable of storing a magnetic carrier that is powder is provided on the crossing start side of the movable magnet 203. .
The holding unit 207 is provided on the side of the crossing start position of the movable magnet, and has a space volume in which the flying magnetic carrier can easily enter.
The holding portion 207 is used as a portion that can introduce and store a part of the magnetic carrier using magnetic restraint when the movable magnet 203 returns to the crossing start side.
Accordingly, when a large amount of toner is scattered on the collection surface of the filter 202, magnetic restraint on the toner does not function effectively even if the movable magnet 203 is traversed, but the magnetic material stored in the holding portion 207 As the carrier moves on the collecting surface as the movable magnet 203 starts to cross, the toner captured by the magnetic carrier is swept across the collecting surface.

Further, in the communicating portion 200A of the discharge container 200, the toner and the magnetic carrier, which are powders that are swept together with the moving movement of the movable magnet 203 and adhered to each other at the position on the transverse end side of the movable magnet 203. The peeling part 208 which peels is provided.
The peeling portion 208 is formed by a piece extending inward from the inner wall surface of the discharge container 200 and parallel to the transverse direction, and the piece enters between the bulky toner moving on the collecting surface and the magnetic carrier. It can be done.

In the above configuration, when a large amount of toner is scattered on the collection surface of the filter 202, the collection surface is efficiently cleaned. That is, as shown in FIG. 9A, when a large amount of toner is scattered on the collection surface of the filter 202, the magnetic carrier accumulated in the holding unit 207 moves on the collection surface as the movable magnet 203 starts moving. Moving.
When the magnetic carrier moves on the collection surface, the toner scattered on the collection surface is also swept away (as shown in FIG. 9B), and the toner and magnetic carrier that have become agglomerated into the peeling portion 208 enter. To do.
The toner and the magnetic carrier that have reached the peeling unit 208 are collected separately by separating one part of the peeling unit 208 into the mass of the toner and the magnetic carrier so that the powder of the toner and the magnetic carrier is peeled off.
The above-described operation has been described for the case where only the toner is mainly attached to the collecting surface of the filter 202 and collected, but the same applies to the case of a magnetic carrier instead of the toner.

  As described above, the drive motor 205 of the movable magnet 203 does not have the operation time set according to the preset operation time of the image forming apparatus or the number of prints, but the amount of toner collected by the filter 202, In other words, it is possible to start up according to the toner concentration that affects the dust collection amount.

FIG. 10 is a graph showing the amount of collected toner per unit time with respect to the toner concentration.
As shown in the figure, as the toner concentration increases, the amount of collected toner increases, and a large amount of toner adheres to the collecting surface of the filter 202.
Based on such a phenomenon, when the toner concentration of the developer in the developing device is high, the frequency is increased to suppress the performance deterioration of the filter 202. Conversely, when the toner concentration is low, the frequency is decreased and the excess sweeping is performed. It is also possible to set the drive timing of the drive motor 205 so as to reduce the operation.
As described above, since the frequency of the agent sweeping operation by the movable magnet 203 is changed depending on the toner concentration of the developer in the developing device, no extra operation is performed, so that power saving can be achieved.

  In the above embodiment, the filter replacement frequency can be reduced by cleaning the collecting surface of the filter 202 provided in the discharge container 200. Thereby, it is not necessary to enlarge the collection surface such as a filter in order to reduce the replacement frequency, and an increase in the size of the apparatus can be avoided. Further, as a matter of course, since the collection surface of the filter is cleaned, the exhaust function can be maintained over a long period of time by suppressing the deterioration of the exhaust function.

DESCRIPTION OF SYMBOLS 3 Developing apparatus 30 Developing tank 40 Developer accommodating part 41 Developer collection flow path 42 Developer supply flow path 100 Image forming apparatus main body 200 Discharge container 201 Pipe line 202 Filter 203 Movable magnet 204 Drive screw 205 Drive motor 207 Holding part 208 Peeling Part

Patent 3733496 Japanese Patent No. 3349286 Japanese Patent Laid-Open No. 11-143196 JP 2008-003561 A JP 2003-215918 A

Claims (9)

In an exhaust mechanism equipped with a filter for collecting powder and discharging only air to an air exhaust part used for airflow conveyance of powder,
For at least one of the powders, a magnetic substance is used as a target,
On the opposite side of the powder collecting surface of the filter to which the powder adheres, a movable magnet capable of crossing the powder collecting surface is provided,
An exhaust mechanism, wherein the movable magnet sweeps the powder toward a position off the powder collection surface after traversing the powder collection surface.   As a mechanism for sweeping the powder, a part of the powder collecting surface includes a rotating shaft extending along the powder collecting surface, and the movable magnet is attached to the rotating shaft and the rotating shaft The exhaust mechanism according to claim 1, wherein the exhaust mechanism is movable to a position off the powder collecting surface in accordance with the rotation direction of the powder.   2. The movable magnet is a single-pole magnet whose end facing the powder collecting surface of the filter is uniformly magnetized to either an N pole or an S pole. 2. The exhaust mechanism according to 2.   The exhaust mechanism according to claim 1, wherein the filter has a mesh-like mesh structure.   The filter is detachably attached to a support frame, and the support frame wall on the transverse start side of the movable magnet in the support frame has a powder collecting surface side to which the powder adheres. The exhaust mechanism according to any one of claims 1 to 4, further comprising a holding portion that constitutes a holding space capable of storing magnetic powder.   In the support frame, the support frame wall portion on the crossing end side of the movable magnet enters between the swept powder while adhering to each other in conjunction with the transverse movement of the movable magnet, and the powder is separated. 6. The exhaust mechanism according to claim 1, further comprising a peeling portion.   The area of the filter is set to an area obtained by adding an area for obtaining a necessary exhaust capacity to a projected area of the movable magnet when the movable magnet crosses the powder collecting surface. The exhaust mechanism according to claim 1. An image forming apparatus that performs visible image processing on an electrostatic latent image formed on a latent image carrier by a developing device using a two-component developer using toner and a magnetic carrier,
The developing device transports the developer in an air flow between a developing unit that supplies the developer to the latent image carrier and a developer stirring unit provided separately from the developing unit, and the developing unit includes an exhaust mechanism. An image forming apparatus using the exhaust mechanism according to any one of claims 1 to 7 as the exhaust mechanism.   The image forming apparatus according to claim 8, wherein the frequency of the sweeping operation of the movable magnet in the exhaust mechanism is set according to the toner concentration of the developing device in the developing device.

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