JP2008052187A - Developer supply device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer supply device which more uniformly conveys and supplies developer by a traveling wave, and an image forming apparatus which includes the developer supply device, whereby the occurrence of density unevenness is effectively suppressed and an excellent image is formed. <P>SOLUTION: In the image forming apparatus, a toner electric field conveying body 132 configured to convey toner T in a toner conveying direction TTD by traveling-wave electric field is housed in a developing casing 131 constituting the casing of a developing device 130. The toner T is stored in the developing casing 131. The developing casing 131 includes a casing bottom board 131b configured to restrain the passage of the toner T and also having permeability. By making air blow into the developing casing 131 through the casing bottom board 131b, the toner T in the developing casing 131 is fluidized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developer supply device and an image forming apparatus.

  In an image forming apparatus, many mechanisms for conveying toner (developer) using a traveling wave electric field have been conventionally known (for example, Japanese Patent Laid-Open Nos. 63-13074 and 4-204570, JP-B-5-31146, JP-A-2002-351218, JP-A-2003-15417, JP-A-2004-157259, JP-A-2005-275127, etc.).

  As described above, the mechanism capable of transporting the charged developer by a traveling wave electric field (hereinafter referred to as “developer electric field transport device”) includes a casing and a developer transport member.

  The developer is accommodated in the casing. The developer conveying member is accommodated in the casing. The developer conveying member is provided with a large number of linear electrodes arranged in a line.

According to the developer electric field transport device having the above-described configuration, the developer is supplied little by little from the casing to the developer transport member. On the other hand, a traveling wave electric field is formed in the developer conveying member by sequentially applying a multiphase AC voltage to the multiple linear electrodes. By the action of the traveling wave electric field, the developer supplied to the developer transport member is transported in a predetermined direction.
JP 63-13074 A JP-A-4-204570 Japanese Patent Publication No. 5-31146 JP 2002-351218 A JP 2003-15417 A JP 2004-157259 A JP 2005-275127 A

  In the conventional developer electric field transport apparatus as described above, the developer may not be transported uniformly by the developer transport member. This is remarkable when the developer aggregates in the casing of the developer electric field transport device.

  Here, a stirring member such as a mixing paddle is usually provided in the casing. Then, the developer in the casing is stirred and mixed by rotating the stirring member.

  However, even with such a stirring member, the aggregation of the developer is not solved well. Therefore, the developer present in the vicinity of the developer conveying member may contain a lot of aggregated ones.

  Further, if the rotation of the stirring member is vigorously driven in an attempt to eliminate the aggregation of the developer, a large mechanical stress (compression force, shearing force, etc.) is applied to the developer in the casing, Heat is generated. Rather, this may further promote the aggregation of the developer.

  As described above, when the developer aggregates in the casing, the amount of the developer supplied to the developer transport member is uneven. As a result, unevenness occurs in the amount of the developer conveyed on the developer conveying member, and density unevenness also occurs in the formed image.

  The present invention has been made to solve such problems. That is, an object of the present invention is to provide a developer supply device that can carry out and supply a developer more uniformly by traveling waves, and to generate density unevenness by providing the developer supply device. It is an object of the present invention to provide an image forming apparatus capable of forming a good image while being suppressed.

  (1) An image forming apparatus of the present invention includes an electrostatic latent image carrier and a developer supply device.

  The electrostatic latent image carrier has a latent image forming surface. The latent image forming surface is configured such that an electrostatic latent image by a potential distribution can be formed. This latent image forming surface is formed in parallel with a predetermined main scanning direction. The electrostatic latent image carrier is configured such that the latent image forming surface can move along a sub-scanning direction orthogonal to the main scanning direction.

  The developer supply device is disposed to face the electrostatic latent image carrier. The developer supply device is configured to supply the developer to the latent image forming surface in a charged state. Specifically, the developer supply device includes a developer containing casing, a developer transport body, a plurality of transport electrodes, and a gas supply unit.

  The developer containing casing is a box-shaped member including a developing unit facing plate and a breathable bottom plate. An opening is formed at a position facing the electrostatic latent image carrier on the developing unit facing plate. The breathable bottom plate is configured so that the passage of the developer is suppressed and gas can pass therethrough. The developer accommodating casing is configured to accommodate the developer.

  The developer transport body has a developer transport surface parallel to the main scanning direction. The developer transport body is disposed in the developer containing casing such that the developer transport surface faces the electrostatic latent image carrier with the opening in the developing unit facing plate interposed therebetween. .

  The plurality of transport electrodes are provided along the developer transport surface so as to face the latent image forming surface. These transport electrodes are arranged along the sub-scanning direction. These transport electrodes are configured to transport the developer in a predetermined developer transport direction on the developer transport surface when a traveling wave voltage is applied.

  The gas supply unit is configured to fluidize the developer in the developer containing casing by blowing gas into the developer containing casing through the breathable bottom plate.

  The image forming apparatus of the present invention having such a configuration operates as follows during image formation.

  The electrostatic latent image based on the potential distribution is formed on the latent image forming surface of the electrostatic latent image carrier. The latent image forming surface on which the electrostatic latent image is formed moves along the sub-scanning direction.

  On the other hand, gas is blown into the developer containing casing through the breathable bottom plate by the gas supply unit. Thereby, the developer in the developer containing casing is fluidized.

  A predetermined traveling-wave voltage is applied to the plurality of transport electrodes arranged along the sub-scanning direction. Thereby, a predetermined electric field is formed in the vicinity of the developer transport surface of the developer transport body. This electric field is formed as a traveling-wave electric field that travels in a direction along the sub-scanning direction.

  Of the developer in the developer containing casing fluidized as described above, the developer in the vicinity of the developer transport surface is placed on the developer transport surface by the traveling wave electric field. Is conveyed in a predetermined developer conveying direction. The developer is supplied to a position (development position) where the latent image forming surface and the developer transport surface parallel to each other face each other.

  Thus, the developer supply device supplies the developer in a charged state to the latent image forming surface on which the electrostatic latent image is formed. Thereby, the electrostatic latent image is developed (visualized) by the developer.

  According to the image forming apparatus of the present invention having such a configuration, mechanical or thermal stress due to compressive force or shear force when the developer is fluidized becomes extremely small. Therefore, according to the present invention, the developer can be conveyed and supplied more uniformly by traveling waves.

  Therefore, according to the present invention, it is possible to provide an image forming apparatus capable of effectively forming density unevenness and forming a good image.

  The breathable bottom plate may be provided at least in the vicinity of the most upstream portion in the developer transport direction on the developer transport surface.

  Here, the above-mentioned “position in the vicinity of the most upstream portion in the developer transport direction of the developer transport surface” means that the breathable bottom plate is disposed so that the most upstream portion of the developer transport surface is The position is such that the opposing developer is fluidized well.

  That is, the breathable bottom plate can be provided at a position where the developer fluidized well by the inflow of gas from the breathable bottom plate can come into contact with the most upstream portion of the developer transport surface. .

  Specifically, for example, the breathable bottom plate can be provided at a position corresponding to the most upstream portion of the developer transport surface in the developer transport direction.

  That is, the breathable bottom plate can be provided at a position overlapping the most upstream portion of the developer transport surface in the horizontal direction or the vertical direction. Alternatively, the breathable bottom plate can be provided at a position facing the most upstream portion of the developer transport surface.

  In this configuration, gas is blown into the developer containing casing from the gas supply section through the breathable bottom plate. As a result, the developer in the developer containing casing at a position near the most upstream portion in the developer transport direction on the developer transport surface is fluidized.

  According to such a configuration, the developer can be supplied as uniformly as possible to the most upstream portion of the developer transport surface.

  Therefore, the developer is transported on the developer transport surface by a traveling wave, and the developer is supplied to the latent image forming surface on which the electrostatic latent image is formed more evenly and uniformly. obtain.

  The image forming apparatus may further include the following configuration: The image forming apparatus further includes an exhaust unit. The exhaust unit is configured to be able to exhaust the gas in the developer containing casing. In the developer containing casing, an exhaust port communicating with the exhaust unit is provided at a position different from the opening.

  In this configuration, when the developer in the developer containing casing is fluidized, gas is blown into the developer containing casing from the gas supply section through the breathable bottom plate. On the other hand, the gas in the developer containing casing is discharged by the exhaust unit through the exhaust port provided at a position different from the opening.

  According to the image forming apparatus of the present invention having such a configuration, the negative pressure is generated at a position different from the opening in the developer containing casing.

  Therefore, when the gas is blown into the developer housing casing from the gas supply unit through the breathable bottom plate, it is possible to effectively suppress the developer from being ejected together with the gas from the opening. That is, inadvertent leakage of the developer from the developer containing casing can be suppressed as much as possible.

  The exhaust port may be provided at a diagonal position with respect to the breathable bottom plate. Here, the “diagonal position” refers to a position that constitutes a positional relationship between one end side and the other end side in the vertical direction and the front-rear direction of the developer containing casing.

  For example, it goes without saying that one end of a diagonal line in the side sectional view of the developer containing casing and the vicinity thereof and the other end on the side different from the one end and the vicinity thereof are in a “diagonal position”.

  In this configuration, gas is blown into the developer containing casing from the gas supply section through the breathable bottom plate provided at a position corresponding to the most upstream portion in the developer transport direction on the developer transport surface. . Thereby, the developer in the developer containing casing is fluidized.

  On the other hand, the gas in the developer containing casing is exhausted by the exhaust unit through the exhaust port provided at a position different from the opening and diagonally to the breathable bottom plate.

  That is, in such a configuration, gas is blown into the developer containing casing from a position corresponding to the most upstream portion of the developer transport surface in the developer transport direction, but at a position different from the opening. Thus, the gas in the developer containing casing is discharged from a position that is diagonal to the position.

  According to the image forming apparatus of the present invention having such a configuration, a negative pressure is generated at a position in the developer containing casing away from the opening.

  Therefore, when the gas is blown into the developer housing casing from the gas supply unit through the breathable bottom plate, it is possible to effectively suppress the developer from being ejected together with the gas from the opening. That is, inadvertent leakage of the developer from the developer containing casing can be suppressed as much as possible.

  The image forming apparatus may further include the following configuration: The image forming apparatus further includes a gas circulation passage. The gas circulation passage is configured to connect the exhaust port and the breathable bottom plate outside the developer containing casing. And the said gas supply part and the said exhaust part are comprised from the pump interposed by the said gas circulation path.

  In such a configuration, the pump is driven when the developer in the developer containing casing is fluidized. Thereby, the gas in the developer containing casing is discharged from the exhaust port provided corresponding to the upstream end of the gas circulation passage in the gas flow direction.

  On the other hand, gas is blown into the developer containing casing from the breathable bottom plate provided corresponding to the downstream end of the gas circulation passage in the gas flow direction.

  According to this, the developer in the developer containing casing is fluidized using a very simple apparatus configuration, and the developer leaks inadvertently from the developer containing casing. It can be effectively suppressed.

  The air permeable bottom plate may be provided at a position corresponding to at least the lowest part of the developer containing casing.

  According to the image forming apparatus having such a configuration, even when the amount of the developer accommodated in the developer accommodating casing decreases, the developer at the bottom of the developer accommodating casing is fluidized well. obtain.

  Thereby, even in the above-described case, the developer can be favorably transported to a position facing the latent image forming surface. Therefore, according to such a configuration, even in the above case, good image formation can be performed with the developer.

  (2) The developer supply device of the present invention is configured so that the developer can be supplied along a predetermined developer transport direction in a charged state with respect to the developer carrying surface of the developer carrying member. . Here, the developer carrying surface is a surface parallel to a predetermined main scanning direction and capable of carrying the developer.

  The developer carrying member has the developer carrying surface and is configured so that the developer carrying surface can move along a sub-scanning direction orthogonal to the main scanning direction.

  As the developer carrying member, for example, an electrostatic latent image carrying member having a latent image forming surface configured to be able to form an electrostatic latent image by potential distribution can be used.

  Alternatively, as the developer carrying member, for example, a recording medium (paper) conveyed along the sub-scanning direction can be used.

  Alternatively, as the developer carrier, for example, the developer can be transferred onto the recording medium or the electrostatic latent image carrier by facing the recording medium or the electrostatic latent image carrier. A roller, sleeve, or belt-shaped member (developing roller, developing sleeve, intermediate transfer belt, etc.) constructed and arranged can be used.

  The developer supply apparatus of the present invention includes a developer containing casing, a developer transport body, and a plurality of transport electrodes.

  The developer containing casing is a box-shaped member including a developing unit facing plate and a breathable bottom plate.

  An opening is formed at a position facing the developer carrying member on the developing unit facing plate. The breathable bottom plate is configured so that the passage of the developer is suppressed and gas can pass therethrough. The developer accommodating casing is configured to accommodate the developer.

  The developer transport body has a developer transport surface parallel to the main scanning direction. The developer transport body is disposed in the developer containing casing such that the developer transport surface faces the developer carrier with the opening in the developing unit facing plate interposed therebetween.

  The plurality of transport electrodes are provided along the developer transport surface so as to face the developer carrying surface. These transport electrodes are arranged along the sub-scanning direction. These transport electrodes are configured to transport the developer in the developer transport direction on the developer transport surface when a traveling wave voltage is applied.

  In the developer supply apparatus of the present invention having such a configuration, gas can be blown into the developer containing casing through the breathable bottom plate. Thereby, the developer in the developer containing casing can be fluidized.

  A predetermined traveling-wave voltage is applied to the plurality of transport electrodes arranged along the sub-scanning direction. Thereby, a predetermined electric field is formed in the vicinity of the developer transport surface of the developer transport body. This electric field is formed as a traveling-wave electric field that travels in a direction along the sub-scanning direction.

  Of the developer in the developer containing casing fluidized as described above, the developer in the vicinity of the developer transport surface is placed on the developer transport surface by the traveling wave electric field. Is conveyed in a predetermined developer conveying direction. This developer is supplied to a position (development position) where the developer carrying surface and the developer transport surface parallel to each other face each other.

  In this way, the developer supply device supplies the developer in a charged state to the developer carrying surface that moves along the sub-scanning direction. As a result, the developer is carried on the developer carrying surface.

  According to the developer supply apparatus of the present invention having such a configuration, mechanical or thermal stress due to compressive force or shear force when fluidizing the developer is extremely reduced. According to the present invention, it is possible to provide a developer supply apparatus that can more uniformly transport and supply the developer by traveling waves.

  It is preferable that the breathable bottom plate is provided at least at a position corresponding to the most upstream portion of the developer transport surface in the developer transport direction.

  According to such a configuration, the developer can be supplied as uniformly as possible to the most upstream portion of the developer transport surface. Accordingly, the transport of the developer on the developer transport surface and the supply of the developer to the developer carrying surface can be performed more uniformly.

  The developer supply device may further include a gas supply unit. The gas supply unit is configured to fluidize the developer in the developer containing casing by blowing gas into the developer containing casing through the breathable bottom plate.

  In this configuration, gas is blown into the developer containing casing through the breathable bottom plate by the gas supply unit. Thereby, the developer in the developer containing casing is fluidized.

  The developer supply device may further include the following configuration: The developer supply device further includes an exhaust unit. The exhaust unit is configured to be able to exhaust the gas in the developer containing casing. Further, an exhaust port is provided at a position different from the opening in the developer containing casing. The exhaust part is provided so as to communicate with the exhaust port.

  In such a configuration, the gas in the developer containing casing can be discharged to the outside through the exhaust port. That is, a negative pressure can be generated at a position different from the opening in the developer containing casing.

  According to the developer supply device of the present invention having such a configuration, when the gas is blown into the developer containing casing through the breathable bottom plate, the developer is ejected together with the gas from the opening. Can be effectively suppressed. That is, inadvertent leakage of the developer from the developer containing casing can be suppressed as much as possible.

  The exhaust port may be provided at a diagonal position with respect to the breathable bottom plate.

  In such a configuration, gas can be blown into the developer containing casing through the breathable bottom plate from a position corresponding to the most upstream portion of the developer transport surface in the developer transport direction. The gas in the developer accommodating casing can be exhausted from the diagonal position through the exhaust port.

  That is, while gas can be blown into the developer containing casing, negative pressure can be generated at a position farther from the opening in the developer containing casing.

  According to the developer supply device of the present invention having such a configuration, when the gas is blown into the developer containing casing through the breathable bottom plate, the developer is ejected together with the gas from the opening. Can be effectively suppressed. That is, inadvertent leakage of the developer from the developer containing casing can be suppressed as much as possible.

  The developer supply device may further include the following configuration: The developer supply device further includes a gas circulation passage. The gas circulation passage is configured to connect the exhaust port and the breathable bottom plate outside the developer containing casing. And the said gas supply part and the said exhaust part are comprised from the pump interposed by the said gas circulation path.

  According to the developer supply device of the present invention having such a configuration, the fluidization of the developer in the developer containing casing and the suppression of inadvertent leakage of the developer have a very simple device configuration. Can be realized using.

  The air permeable bottom plate may be provided at a position corresponding to at least the lowest part of the developer containing casing.

  According to such a configuration, even when the amount of the developer accommodated in the developer accommodating casing is reduced, the developer at the bottom of the developer accommodating casing can be fluidized well.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

<Overall configuration of laser printer>
FIG. 1 is a side sectional view showing a schematic configuration of a laser printer 100 to which an embodiment of the present invention is applied.

  Here, in FIG. 1, a sheet conveyance path PP which is a conveyance path of the sheet P as a recording medium which is an image formation target is indicated by a two-dot chain line. The tangential direction of the paper transport path PP is referred to as a paper transport direction.

  Further, the x-axis direction in the figure is referred to as the front-rear direction. One end side (right side in the figure) of the laser printer 100 in the front-rear direction is referred to as “front” side. On the other hand, the other end side (left side in the figure) opposite to the one end side of the laser printer 100 is referred to as a “rear” side.

  Further, the height direction of the laser printer 100 (y-axis direction in the figure), the paper conveyance direction, and the direction orthogonal to the front-rear direction are defined as the paper width direction (z-axis direction in the figure) as the “width direction” in the present invention. ).

<< Main body >>
Referring to FIG. 1, a laser printer 100 as an image forming apparatus of the present invention includes a main body casing 112. The main body casing 112 is a member constituting an outer cover of the laser printer 100, and is integrally formed of a synthetic resin plate. A paper discharge port 112 a made up of a slit-shaped through hole is formed on the front side of the upper portion of the main body casing 112.

  A paper discharge tray 114 is mounted on the front side of the upper portion of the main body casing 112 at a position corresponding to the paper discharge port 112a. The paper discharge tray 114 is configured to receive the image-formed paper P discharged from the paper discharge port 112a.

<< Electrostatic latent image forming section >>
An electrostatic latent image forming unit 120 is accommodated in the main body casing 112. The electrostatic latent image forming unit 120 includes a photosensitive drum 121 as an electrostatic latent image carrier and a developer carrier of the present invention.

  The photosensitive drum 121 is a substantially cylindrical member, and is arranged so that the rotation center axis thereof is parallel to the paper width direction. The photosensitive drum 121 is configured to be driven to rotate clockwise in the drawing.

  Specifically, the photosensitive drum 121 includes a drum main body 121a and a photosensitive layer 121b.

  The drum body 121a is made of a metal tube such as an aluminum alloy. The photoconductor layer 121b is a positively chargeable photoconductive layer, and is formed on the outer periphery of the drum body 121a.

  The photosensitive drum 121 has an image carrying surface 121b1 that constitutes a latent image forming surface and a developer carrying surface of the present invention. The image carrying surface 121b1 is constituted by the peripheral surface of the photoreceptor layer 121b.

  The image carrying surface 121b1 is formed to be parallel to the paper width direction and the main scanning direction described later. The image carrying surface 121b1 is configured such that an electrostatic latent image can be formed by a potential distribution.

  That is, the photosensitive drum 121 is configured such that the image bearing surface 121b1 can move along a sub-scanning direction, which will be described later, orthogonal to the main scanning direction.

  The electrostatic latent image forming unit 120 includes a scanner unit 122 and a charger 123.

  The scanner unit 122 emits laser light LB having a predetermined wavelength modulated based on image information at a predetermined scanning position SP along a main scanning direction (z-axis direction in the drawing) parallel to the paper width direction. It is configured and arranged so that it can irradiate the image bearing surface 121b1 while scanning.

  The charger 123 is disposed upstream of the scan position SP in the moving direction of the image carrying surface 121b1 (the rotation direction of the photosensitive drum 121). The charger 123 is configured and arranged so that the image carrying surface 121b1 upstream in the direction from the scan position SP can be uniformly positively charged.

  The electrostatic latent image forming unit 120 irradiates the image carrying surface 121b1 uniformly positively charged by the charger 123 with the laser beam LB by the scanner unit 122, thereby static electricity due to the potential distribution (charge distribution). An electrostatic latent image can be formed on the image bearing surface 121b1.

  The electrostatic latent image forming unit 120 is configured to be able to move the image carrying surface 121b1 on which the electrostatic latent image is formed along the sub-scanning direction.

  Here, the “sub-scanning direction” is an arbitrary direction orthogonal to the main scanning direction. Usually, the sub-scanning direction is a direction intersecting the vertical line. Typically, the sub-scanning direction may be a direction along the front-rear direction (x-axis direction in the drawing) of the laser printer 100.

<< Developing device >>
A developing device 130 constituting the developer supply device of the present invention is accommodated in the main body casing 112. The developing device 130 is disposed so as to face the photosensitive drum 121 at a development facing position DP (developing position).

  The developing device 130 circulates the toner T, which is a fine-particle dry developer (powder developer), along the toner transport direction TTD as indicated by the arrows in the drawing while being accommodated therein. It is comprised so that it can convey.

  That is, the toner transport direction TTD is a tangential direction at an arbitrary point on the circulation transport path of the toner T in the developing device 130 formed in an oval shape in a side sectional view.

  Further, the developing device 130 is configured and configured as follows so that the toner T can be supplied in a charged state to the image carrying surface 121b1 on which the electrostatic latent image is formed in the vicinity of the development facing position DP. Has been placed. Note that the toner T in this embodiment is used for non-magnetic one-component development in an electrophotographic system.

  FIG. 2 is an enlarged side sectional view of the electrostatic latent image forming unit 120 and the developing device 130 shown in FIG.

  Referring to FIGS. 1 and 2, the developing device 130 is disposed below the photosensitive drum 121 so as to face the downstream image carrying surface 121b1 in the moving direction of the image carrying surface 121b1 with respect to the scan position SP. Yes.

<<< Development casing >>>
The developing casing 131 as the developer containing casing of the present invention is a box-shaped member, and is configured to accommodate the toner T so as not to leak to the outside.

  The developing portion facing plate 131a1, which is the rear side portion of the casing upper surface cover 131a constituting the top plate of the developing casing 131, is formed in a substantially J-shape when viewed from the side cross section.

  That is, the developing unit facing plate 131a1 includes a flat plate portion positioned below the photosensitive drum 121 and arranged substantially horizontally, and a half pipe portion connected to the rear end of the flat plate portion. . The lower end portion of the half pipe portion is formed in a sloped shape with a slope that descends forward and downward.

  The developing portion facing plate 131a1 is thinner than the other portions of the casing upper surface cover 131a. That is, a recess is formed on the inner side surface of the casing upper surface cover 131a at a position corresponding to the developing unit facing plate 131a1.

  A developing opening 131a2 as an opening of the present invention is formed in the flat plate portion of the developing portion facing plate 131a1. The development opening 131a2 is provided at the position facing the image carrying surface 121b1 on the development unit facing plate 131a1 so as to surround the development facing position DP.

  The casing bottom plate 131 b constituting the air permeable bottom plate of the present invention is a flat plate member constituting the bottom plate of the developing casing 131. The casing bottom plate 131b is configured so that the passage of the toner T is suppressed and air can pass well. Specifically, the casing bottom plate 131b is formed from porous ceramics.

  The average opening diameter of the porous ceramics constituting the casing bottom plate 131b is set to be smaller than a-2σ when the number average particle diameter of the toner T is a and the standard deviation is σ.

  That is, assuming that the particle size distribution of the toner T is a normal distribution, the toner T that can pass through the casing bottom plate 131b is calculated to be a very small amount (less than about 2.28%) of the total amount of the toner T. The casing bottom plate 131b is configured so as to be.

  (It is rare that pores in the porous ceramics communicate almost linearly along the plate thickness direction. Therefore, even if the opening diameter is as described above, the casing bottom plate 131b is practically used. (Toner T hardly leaks downward through this.)

  The rear end portion (the left end portion in the figure) of the casing bottom plate 131b is connected to the lower end of the above-described half pipe portion in the casing upper surface cover 131a. That is, the casing bottom plate 131b and the casing upper surface cover 131a are integrally formed at the rear end of the developing casing 131 so as to be smoothly connected in a substantially U shape.

  Both ends of the casing top cover 131a and the casing bottom plate 131b in the sheet width direction are closed by a pair of casing side plates 131c. Further, the front ends of the casing top cover 131a, the casing bottom plate 131b, and the pair of casing side plates 131c are closed by a casing front closing plate 131d.

  Referring to FIG. 2, the air-permeable closing plate 131d1, which is the upper part of the casing front closing plate 131d, is made of a porous ceramic plate material. The lower part of the casing front closing plate 131d and the portion other than the above-described air-permeable closing plate 131d1 are made of a synthetic resin plate material that is not porous.

  That is, the air outlet of the present invention is constituted by the air-permeable blocking plate 131d1, which is a porous ceramic portion formed on the upper portion of the casing front closing plate 131d. The air-permeable blocking plate 131d1 is formed at the uppermost position of the developing casing 131 and at the position farthest from the developing opening 131a2.

<<< Developer Electric Field Carrier >>>
Referring to FIG. 2, a toner electric field transport body 132 constituting the developer transport body of the present invention is accommodated inside the developing casing 131. That is, the toner electric field transport body 132 is covered with the developing casing 131.

  The toner electric field carrier 132 is disposed on the rear side in the space inside the developing casing 131 so as to face the image carrying surface 121b1 with the developing opening 131a2 interposed therebetween. That is, the toner electric field transport body 132 is provided so that the photosensitive drum 121 and the toner electric field transport body 132 are opposed to each other with the development opening 131a2 interposed therebetween.

  Both ends of the toner electric field transport body 132 are supported by a pair of casing side plates 131c so as to float from the casing bottom plate 131b while facing the developing portion facing plate 131a1 with a predetermined gap.

  FIG. 3 is an enlarged side cross-sectional view of a portion near the developing opening 131a2 in the toner electric field transport body 132 shown in FIG. Referring to FIGS. 2 and 3, the toner electric field transport body 132 includes a transport wiring board 133. The transport wiring substrate 133 is disposed so as to face the image carrying surface 121b1 with the development opening 131a2 interposed therebetween.

  Referring to FIG. 3, the transport wiring board 133 has a configuration similar to that of the flexible printed wiring board, and includes a plurality of transport electrodes 133a.

  These transport electrodes 133a are arranged along the toner transport surface 133b as the developer transport surface of the present invention.

  Here, the toner transport surface 133 b is a surface on the upper side of the transport wiring substrate 133 in the figure and is a surface on the side facing the photosensitive drum 121. The toner transport surface 133b is a surface of the transport wiring substrate 133 that faces the image carrying surface 121b1.

  The toner conveying surface 133b is formed in parallel with the main scanning direction (z direction in the figure). The toner conveying surface 133b and the image carrying surface 121b1 are closest to each other at the development facing position DP.

  The transport electrode 133a is disposed in the vicinity of the toner transport surface 133b.

  The transport electrode 133a is made of a copper foil having a thickness of about several tens of μm. The transport electrode 133a is formed as a linear wiring pattern having a longitudinal direction parallel to the main scanning direction (perpendicular to the sub-scanning direction).

  The plurality of transport electrodes 133a are arranged in parallel to each other. These transport electrodes 133a are arranged along the toner transport direction TTD (along the sub-scanning direction).

  A plurality of transport electrodes 133a arranged in the sub-scanning direction are connected to the same power supply circuit every third.

  That is, the transfer electrode 133a connected to the power supply circuit VA, the transfer electrode 133a connected to the power supply circuit VB, the transfer electrode 133a connected to the power supply circuit VC, the transfer electrode 133a connected to the power supply circuit VD, and the power supply circuit VA The connected transport electrodes 133a, the transport electrodes 133a connected to the power supply circuit VB, are sequentially arranged along the sub-scanning direction.

  The transport wiring substrate 133 also includes a transport electrode support substrate 133c and a transport electrode coating layer 133d.

  The transport electrode support substrate 133c is a flexible film and is made of an insulating synthetic resin such as a polyimide resin. A transport electrode 133a is provided on the upper surface of the transport electrode support substrate 133c.

  A transport electrode coating layer 133d is provided on the upper surface of the transport electrode support substrate 133c on which the transport electrode 133a is formed.

  The transport electrode coating layer 133d is provided so as to cover the transport electrode 133a. The transport electrode coating layer 133d is provided so as to form the toner transport surface 133b on a smooth surface by covering the transport electrode support substrate 133c and the transport electrode 133a.

  Referring to FIGS. 2 and 3, the toner electric field transport body 132 includes a transport substrate support member 134. The transport board support member 134 is provided so as to support the transport wiring board 133 from below.

  Referring to FIG. 2, the rear end of the transport substrate support member 134 is formed to be bent downward along the casing upper surface cover 131 a in the developing casing 131. The front end portion of the transport substrate support member 134 is also formed in the same shape as the rear end portion so as to be bent downward. The part between the above-mentioned both ends of the conveyance board | substrate support member 134 is formed in substantially flat form.

  That is, the transport substrate support member 134 is formed in an inverted U shape when viewed from the side.

  FIG. 4 is a graph showing waveforms of voltages generated by the power supply circuits VA to VD shown in FIG. As shown in FIG. 4, each of the power supply circuits VA to VD is configured to generate an AC voltage having substantially the same waveform.

  Here, the waveforms of the voltages generated by the power supply circuits VA to VD are different in phase by 90 °. That is, the power supply circuits VA to VD are controlled by a control circuit (not shown) so that the phase of the voltage is delayed by 90 ° in order from the power supply circuit VA to the power supply circuit VD.

  2 and 3, in the toner electric field transport body 132, a transport voltage as shown in FIG. 4 is applied to each transport electrode 133a in the transport wiring board 133, so that the toner transport direction TTD By generating a traveling wave-like electric field, the positively charged toner T can be transported in the toner transport direction TTD.

  Referring to FIGS. 1 and 2, a counter wiring substrate 135 is mounted in the above-described recess formed on the inner surface of the casing upper surface cover 131 a and at a position corresponding to the developing unit counter plate 131 a 1. That is, the counter wiring substrate 135 is supported by the inner wall surface of the developing unit facing plate 131a1 in which the developing opening 131a2 is formed so as to oppose the toner transport surface 133b with a predetermined gap therebetween.

  The counter wiring board 135 has the same configuration as the above-described transport wiring board 133.

  That is, referring to FIG. 3, the counter electrode 135a is made of a copper foil having a thickness of about several tens of μm. The counter electrode 135a is formed as a linear wiring pattern having a longitudinal direction parallel to the main scanning direction (perpendicular to the sub-scanning direction). The plurality of counter electrodes 135a are arranged in parallel to each other.

  These counter electrodes 135a are arranged along a predetermined toner transport direction TTD (along the sub-scanning direction). Further, every three counter electrodes 135a are connected to the same power supply circuit.

  The counter wiring substrate 135 also includes a counter electrode support substrate 135c and a counter electrode coating layer 135d.

  The counter electrode support substrate 135c is a flexible film and is made of an insulating synthetic resin such as a polyimide resin. A counter electrode 135a is provided on the lower surface of the counter electrode support substrate 135c in the figure.

  A counter electrode coating layer 135d is provided on a lower surface of the counter electrode support substrate 135c where the counter electrode 135a is formed.

  The counter electrode coating layer 135d is provided so as to cover the counter electrode 135a. The counter electrode coating layer 135d is provided to cover the counter electrode support substrate 135c and the counter electrode 135a so as to form the toner transport surface 135b on a smooth surface.

  Similar to the above-described transport wiring substrate 133, the counter wiring substrate 135 is applied with a predetermined voltage to the plurality of counter electrodes 135a and generates a traveling-wave electric field along the toner transport direction TTD. The charged toner T can be transported in the toner transport direction TTD.

  Referring to FIG. 2, in the present embodiment, the most upstream portion of the counter wiring substrate 135 in the toner transport direction TTD is provided so as to be adjacent to the casing bottom plate 131b having air permeability.

  That is, in the present embodiment, the casing bottom plate 131b having air permeability is provided so as to correspond to the most upstream part of the transport of the toner T by the counter wiring substrate 135 and the transport wiring substrate 133 using a traveling wave electric field. Yes.

<<< Air circulation device >>>
Referring to FIG. 2, the developing device 130 includes an air circulation device 136 as a gas supply unit and an exhaust unit of the present invention.

  The air circulation device 136 is configured to be able to fluidize the toner T in the developing casing 131 by blowing air into the developing casing 131 through the casing bottom plate 131b having air permeability.

  The air circulation device 136 is configured to discharge the air in the developing casing 131.

  Specifically, the air circulation device 136 includes an air circulation passage 136a and a pump 136b.

  The air circulation passage 136a as the gas circulation passage of the present invention is configured to connect the air-permeable blocking plate 131d1 and the casing bottom plate 131b in an airtight manner outside the developing casing 131. A pump 136b is interposed in the air circulation passage 136a.

  When the pump 136b is driven, the air circulation device 136 sucks out air in the developing casing 131 through the air-permeable blocking plate 131d1, and returns this air to the developing casing 131 through the air-permeable casing bottom plate 131b. It is configured to let you.

<< Transfer section >>
Referring to FIG. 1 again, the transfer unit 140 faces the image bearing surface 121b1 at a position downstream of the photosensitive drum 121 in the rotation direction with respect to the position where the photosensitive drum 121 and the developing device 130 face each other. Is provided.

  The transfer unit 140 is a roller-shaped member, and includes a metal rotation center shaft 141 and a semiconductive rubber layer 142 provided around the rotation center shaft 141.

  The rotation center axis 141 is disposed in parallel with the main scanning direction (z-axis direction in the figure). A high voltage power source is connected to the rotation center shaft 141. The semiconductive rubber layer 142 is configured to exhibit semiconductivity by kneading carbon black or the like into synthetic rubber.

  The transfer unit 140 is rotated counterclockwise in the drawing while a predetermined transfer voltage is applied to the drum body 121a of the photosensitive drum 121, whereby the toner T carried on the image carrying surface 121b1. Can be transferred onto the paper P.

<< paper cassette >>
The paper feed cassette 150 is disposed below the developing device 130.

  The paper feed cassette case 151 is a box-shaped member that constitutes the casing of the paper feed cassette 150 and is formed to open upward. The sheet feeding cassette case 151 is configured to accommodate a large number of sheet-like sheets P having a maximum A4 size (width 210 mm × length 297 mm) in a stacked state.

  A paper pressing plate 153 is disposed in the paper feed cassette case 151. The paper pressing plate 153 is supported by the paper feed cassette case 151 so that the rear end can swing along the vertical direction in the figure with the front end as the center. The rear end of the paper pressing plate 153 is urged upward by a spring (not shown).

<< Paper Conveying Section >>
In the main body casing 112, a paper transport unit 160 is accommodated.

  The paper transport unit 160 is configured to be able to supply the paper P to a transfer position TP where the transfer unit 140 and the image carrying surface 121b1 face each other in the closest state. The paper transport unit 160 includes a paper feed roller 161, a paper guide 163, and a paper transport guide roller 165.

  The paper feed roller 161 is composed of a rotation center axis parallel to the main scanning direction and a surrounding rubber layer. The paper feed roller 161 is disposed so as to face the most distal portion of the paper P placed on the paper pressing plate 153 in the paper feed cassette case 151 in the paper transport direction.

  The paper guide 163 and the paper transport guide roller 165 are configured to guide the paper P fed by the paper feed roller 161 to the transfer position TP.

<< Fixing part >>
A fixing unit 170 is accommodated in the main body casing 112. The fixing unit 170 is disposed at a position downstream of the transfer position TP in the paper transport direction.

  The fixing unit 170 can fix the image formed by the toner T formed on the paper P on the paper P by heating the paper P to which the toner T is adhered through the transfer position TP while applying pressure. It is configured. The fixing unit 170 includes a heating roller 172 and a pressure roller 173.

  The heating roller 172 includes a metal cylinder whose surface has been subjected to a mold release process, and a halogen lamp housed in the cylinder.

  The pressure roller 173 includes a metal rotation center shaft and a silicon rubber rubber layer provided around the rotation center shaft. The heating roller 172 and the pressure roller 173 are disposed so as to press each other with a predetermined pressure.

  The heating roller 172 and the pressure roller 173 are configured and arranged so that the paper P can be sent out toward the paper discharge port 112a while pressing and heating the paper P.

<Outline of image forming operation by laser printer>
Hereinafter, an outline of an image forming operation by the laser printer 100 having the above-described configuration will be described with reference to the drawings.

<< Paper feeding action >>
First, referring to FIG. 1, the paper P stacked on the paper pressing plate 153 is urged upward toward the paper feed roller 161 by the paper pressing plate 153. As a result, the uppermost sheet P stacked on the sheet pressing plate 153 comes into contact with the peripheral surface of the sheet feeding roller 161.

  The paper feed roller 161 is driven to rotate clockwise in the drawing, so that the leading edge of the paper P in the paper transport direction is sent toward the paper guide 163. Then, the paper P is fed to the transfer position TP by the paper guide 163 and the paper transport guide roller 165.

<< Carrying of toner image on image carrying surface >>
As described above, while the paper P is being conveyed toward the transfer position TP, an image of the toner T is carried on the image carrying surface 121b1 that is the circumferential surface of the photosensitive drum 121 as follows.

<<< Formation of electrostatic latent image >>>
First, the image carrying surface 121b1 of the photosensitive drum 121 is uniformly charged positively by the charger 123.

  Referring to FIG. 3, the image bearing surface 121b1 charged by the charger 123 is rotated to the scan position SP which is a position facing (directly facing) the scanner unit 122 by the clockwise rotation of the photosensitive drum 121 in the drawing. It moves along the sub-scanning direction.

  At the scan position SP, the laser beam LB modulated based on the image information is irradiated onto the image carrying surface 121b1 while being scanned along the main scanning direction. Depending on the modulation state of the laser beam LB, a portion where the positive charge on the image bearing surface 121b1 disappears is generated. As a result, an electrostatic latent image LI is formed on the image bearing surface 121b1 by an image-like distribution of positive charges.

  The electrostatic latent image LI formed on the image carrying surface 121b1 moves toward the development facing position DP by the clockwise rotation of the photosensitive drum 121 in the drawing.

<<< Toner fluidization >>>
Referring to FIG. 2, by driving the pump 136b provided in the air circulation device 136, an air flow from the air-permeable blocking plate 131d1 toward the casing bottom plate 131b is formed in the air circulation passage 136a.

  Accordingly, negative pressure is generated in the space on the front side (right side in the drawing) of the air-permeable blocking plate 131d1, that is, the most upstream portion in the air flow direction in the air circulation passage 136a. Due to this negative pressure, the air in the developing casing 131 is discharged to the air circulation passage 136a through the air-permeable blocking plate 131d1.

  On the other hand, air is sent out by pump 136b to the space below casing bottom board 131b, ie, the most downstream part in air circulation passage 136a. Thus, air is blown into the bottom of the space inside the developing casing 131 through the casing bottom plate 131b.

  In this manner, when air is blown from below the casing bottom plate 131b by the air circulation device 136, the toner T stored in the lower portion of the space inside the developing casing 131 is fluidized like a liquid. Such an aggregate of the toner T fluidized at the lower part of the developing casing 131 is hereinafter referred to as “toner reservoir”.

<<< Charged toner transport >>>
Referring to FIG. 2, by applying a predetermined voltage (similar to that shown in FIG. 4) to the counter wiring substrate 135, a predetermined traveling wave electric field is formed on the counter wiring substrate 135. . As a result, the sufficiently fluidized toner T at the rear end of the toner reservoir is the most upstream portion (lower left side in the figure) of the counter wiring substrate 135 in the toner transport direction TTD due to the traveling-wave electric field. To the position where the rear end of the transport wiring board 133 and the counter wiring board 135 face each other so as to rise up the inclined toner transport surface 135b.

  However, when the most upstream part is covered with the toner T (toner reservoir), the conveyance is started from the position where the conveyance wiring board 133 is exposed from the toner T (toner reservoir).

  The toner T between the transport wiring board 133 and the counter wiring board 135 is developed by a traveling wave electric field generated on the toner transport surface 133b of the transport wiring board 133 and the toner transport surface 135b of the counter wiring board 135. It is conveyed toward the facing position DP.

  The toner T that has passed the development facing position DP falls downward from the foremost end portion of the toner transport surface 133b, and thus returns to the toner reservoir.

  The toner T transport operation by the counter wiring substrate 135 is the same as the toner T transport operation by the transport wiring substrate 133. Therefore, the toner T transporting operation by the transport wiring board 133 will be described in detail below.

  FIG. 5 is an enlarged side sectional view showing the periphery of the toner transport surface 133b in the transport wiring board 133 shown in FIG. In FIG. 3, the transport electrode 133a connected to the power supply circuit VA is shown as the transport electrode 133aA in FIG. The same applies to the transport electrodes 133aB to 133aD.

  Referring to FIGS. 4 and 5, at time t1 in FIG. 4, as shown in FIG. 5A, at the position between AB, which is the position between the transport electrode 133aA and the transport electrode 133aB. The electric field EF1 is formed in the direction opposite to the toner transport direction TTD (the direction opposite to x in FIG. 5).

  On the other hand, an electric field EF2 in the same direction as the toner transport direction TTD (the x direction in FIG. 5) is formed at the inter-CD position between the transport electrode 133aC and the transport electrode 133aD.

  Further, the position between BC, which is a position between the transport electrode 133aB and the transport electrode 133aC, and the position between DA, which is a position between the transport electrode 133aD and the transport electrode 133aA, are arranged in the direction along the toner transport direction TTD. An electric field is not formed.

  That is, at time t1, the positively charged toner T receives an electrostatic force in the direction opposite to the toner transport direction TTD at the position between AB.

  Further, at the position between BC and the position between DA, the positively charged toner T receives almost no electrostatic force in the direction along the toner transport direction TTD.

  Further, at the position between the CDs, the positively charged toner T receives an electrostatic force in the same direction as the toner transport direction TTD.

  Therefore, at time t1, the positively charged toner T is collected at the position between the DAs.

  Similarly, at time t2, the positively charged toner T is collected at the position between AB. Next, at time t3, the positively charged toner T is collected at the position between BC. As described above, the region where the toner T is collected moves in the toner transport direction TTD along the toner transport surface 133b as time elapses.

<<< Development of electrostatic latent image >>>
Referring to FIG. 3, as described above, the positively charged toner T is supplied to the development facing position DP.

  In the vicinity of the development facing position DP, the toner T adheres to the portion on the image bearing surface 121b1 where the positive charge in the electrostatic latent image LI has disappeared. That is, the electrostatic latent image LI on the image bearing surface 121b1 of the photosensitive drum 121 is developed with the toner T. An image of the toner T is carried on the image carrying surface 121b1.

<< Transfer of toner image from image bearing surface to paper >>
Referring to FIG. 1, an image of toner T carried on the image carrying surface 121b1 of the photosensitive drum 121 as described above is transferred to the transfer position TP by rotating the image carrying surface 121b1 clockwise in the drawing. It is conveyed toward.

  At this transfer position TP, the image of the toner T is transferred onto the paper P from the image carrying surface 121b1.

<< Fixing / Ejecting >>
The paper P on which the image of the toner T is transferred at the transfer position TP is sent to the fixing unit 170 along the paper transport path PP.

  The paper P is heated while being pressed by being sandwiched between the heating roller 172 and the pressure roller 173. As a result, the image of the toner T is fixed on the surface of the paper P.

  Thereafter, the paper P is sent to the paper discharge port 112a and discharged onto the paper discharge tray 114 through the paper discharge port 112a.

<Operation / Effects of Configuration of Embodiment>
In the configuration of this embodiment, air is blown into the developing casing 131 from the bottom of the developing casing 131 through the casing bottom plate 131b having air permeability.

  Thereby, the toner T is fluidized. At this time, stress such as compressive force and shear force applied to the toner T is extremely small.

  Therefore, according to such a configuration, the toner T is more fluidized in the developing casing 131. As a result, the toner T can be more uniformly supplied to the toner transport surface 133b. Then, the toner T can be transported more uniformly on the toner transport surface 133b.

  Thus, according to the configuration of the present embodiment, the toner T on the toner transport surface 133b by the traveling wave electric field and the supply of the toner T to the development facing position DP can be more uniformly performed. Therefore, the occurrence of density unevenness is effectively suppressed, and good image formation becomes possible.

  In the configuration of this embodiment, the rear end portion of the casing bottom plate 131b having air permeability is provided in the vicinity of the most upstream portion in the toner transport direction TTD of the toner transport surface 133b. That is, in the configuration of the present embodiment, the casing bottom plate 131b having air permeability is provided so as to correspond to the most upstream portion in the toner transport direction TTD of the toner transport surface 133b.

  According to such a configuration, the toner T can be uniformly transported at the initial stage of transport of the toner T on the toner transport surface 133b by the traveling-wave electric field.

  In the configuration of the present embodiment, the rear end of the casing bottom plate 131b is adjacent to the most upstream portion of the counter wiring substrate 135 in the toner transport direction TTD.

  According to such a configuration, the toner T can be uniformly transported at the initial stage of transport of the toner T on the toner transport surface 135b by the traveling-wave electric field.

  Further, in the configuration of the present embodiment, the rear end portion of the casing bottom plate 131b having air permeability is the most upstream part of the transport of the toner T by the counter wiring substrate 135 and the transport wiring substrate 133 using a traveling wave electric field. And is adjacent.

  According to such a configuration, the toner T can be more uniformly transported at the initial stage of toner T transport by the traveling wave electric field.

  In the configuration of the present embodiment, the casing bottom plate 131b having air permeability is a space in which the toner T can be accommodated in the developing casing 131 as well as the position in the vicinity of the most upstream portion in the toner transport direction TTD of the toner transport surface 133b. It corresponds to almost the whole.

  According to such a configuration, almost the entire amount of the toner T in the developing casing 131 is favorably fluidized by blowing air. Therefore, the toner T in the developing casing 131 is used for transport on the toner transport surface 133b without being biased. Therefore, the deterioration of the part of the toner T due to the fact that only the part of the toner T is frequently transported on the toner transport surface 133b can be suppressed as much as possible.

  In the configuration of the present embodiment, air is blown into the developing casing 131 through the casing bottom plate 131b by the air circulation device 136, while from the air-permeable blocking plate 131d1 at a position different from the developing opening 131a2, Air is exhausted.

  According to such a configuration, a negative pressure is generated at a position in the developing casing 131 that is away from the developing opening 131a2.

  Therefore, when gas is blown into the developing casing 131 through the casing bottom plate 131b, it can be effectively suppressed that the toner T is ejected together with air from the developing opening 131a2. That is, inadvertent leakage of the toner T from the developing casing 131 can be suppressed as much as possible.

<Example of modification>
Note that, as described above, the above-described embodiments are merely examples of typical embodiments of the present invention that the applicant has considered to be the best at the time of filing of the present application. Therefore, the present invention is not limited to the above-described embodiment. Therefore, it goes without saying that various modifications can be made to the above-described embodiment without departing from the essential part of the present invention.

  Hereinafter, some modifications will be illustrated. In the following description of modifications, members having the same configuration and function as those described in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment. And about description of this member, the description in the above-mentioned embodiment shall be used in the range which is not technically consistent.

  Needless to say, the modifications are not limited to those listed below. In addition, a plurality of modified examples can be applied in a composite manner as appropriate within a technically consistent range.

  The present invention (especially those expressed functionally and functionally in each component constituting the means for solving the problems of the present invention) is described in the above-described embodiments and the following modifications. On the basis of it, it should not be interpreted in a limited way.

  Such a limited interpretation, while improperly harming the applicant's interests (rushing to file under an earlier application principle), improperly imitates the patent for the protection and use of the invention Contrary to the purpose of the law, it is not allowed.

  (1) The application target of the present invention is not limited to a monochromatic laser printer. For example, the present invention can be suitably applied to a so-called electrophotographic image forming apparatus such as a color laser printer or a monochromatic and color copying machine.

  Alternatively, the present invention can be suitably applied to an image forming apparatus of a system other than the above-described electrophotographic system (for example, an image forming apparatus of a toner jet system or an ion flow system that does not use a photoreceptor).

  (2) The configurations of the toner electric field transport body 132, the transport wiring board 133, and the counter wiring board 135 are not limited to those shown in the above embodiment.

  For example, the transport electrode 133a can be embedded in the transport electrode support substrate 133c so as not to protrude from the surface of the transport electrode support substrate 133c. Further, the transport electrode coating layer 133d can be omitted. Alternatively, the transport electrode 133 a can be formed directly on the transport substrate support member 134.

  For example, the counter electrode 135a may be embedded in the counter electrode support substrate 135c so as not to protrude from the surface of the counter electrode support substrate 135c. Further, the counter electrode coating layer 135d may be omitted. Alternatively, the counter electrode 135a can be formed directly on the inner wall surface of the developing casing 131.

  Further, the longitudinal direction of the transport electrode 133a and the counter electrode 135a may be parallel to the main scanning direction as in the above embodiment, or may intersect the main scanning direction. . The arrangement direction of the transport electrode 133a and the counter electrode 135a may be parallel to the sub-scanning direction in a plan view as in the above-described embodiment, or a direction intersecting the sub-scanning direction in a plan view. It may be.

  There are no particular limitations on the shape of the transport electrode 133a and the counter electrode 135a and the electrical connection configuration. For example, the transport electrode 133a and the counter electrode 135a may be formed in various shapes such as a V shape, an arc shape, a wave shape, and a jagged shape instead of the linear shape as in the above-described embodiment.

  The connection between the electrodes may be in various states such as every other one, every two, and not every three as in the above-described embodiment. In this case, the corresponding power supply circuit is not four types, and the phase shift of each voltage waveform can be appropriately changed to 180 °, 120 °, or the like. Further, various voltage waveforms such as a rectangular wave and a sine wave can be used.

  (3) The entire casing bottom plate 131b may not have air permeability.

  For example, a portion having air permeability may be formed at least at a position facing the toner electric field transport body 132.

  6 is a side sectional view showing a configuration of one modification of the developing device 130 shown in FIG. 2 (in FIG. 6, the illustration of the air circulation device 136 in FIG. 2 is omitted). The same applies to FIGS. 7 and 8 described later.)

  Referring to FIG. 6, in the present modification, the above-described half pipe portion, which is the rear end portion of the casing upper surface cover 131a (developing portion facing plate 131a1), is formed in a substantially semi-cylindrical shape.

  Further, a ventilation portion 131b1 is formed at a position on the rear side of the casing bottom plate 131b and facing the toner electric field transport body 132. A non-venting portion 131b2 is provided in a portion on the front side of the casing bottom plate 131b and other than the venting portion 131b1.

  The ventilation part 131b1 is comprised from the porous ceramics similarly to the above-mentioned embodiment. The front end of the ventilation portion 131b1 is provided to correspond to the front end of the toner electric field transport body 132. That is, the ventilation portion 131b1 is provided below the toner electric field transport body 132.

  Further, the rear end portion of the ventilation portion 131b1 is provided at a position slightly separated from the most upstream portion in the toner conveyance direction TTD of the toner conveyance surface 133b.

  FIG. 7 is a side sectional view showing the configuration of another modification of the developing device 130 shown in FIG.

  Referring to FIG. 7, in the present modified example, a slope with a slope in which the lower end portion on the rear side of the casing upper surface cover 131a is lowered frontward and downward toward the rear end portion of the casing bottom plate 131b in a side sectional view. It is formed in a shape. The ventilation portion 131b1 is provided at the rearmost end portion of the casing bottom plate 131b so as to be connected to the lower end portion on the rear side of the casing upper surface cover 131a.

  Referring to FIG. 8, in the present modification, the lower end portion on the rear side of the casing upper surface cover 131a is lowered rearward and downward toward the rear end portion of the casing bottom plate 131b in a side sectional view. It is formed in the shape of a slope. The ventilation portion 131b1 is provided at the rearmost end portion of the casing bottom plate 131b so as to be connected to the rear lower end portion of the casing upper surface cover 131a in the same manner as described above.

  That is, referring to FIGS. 7 and 8, in these modified examples, the ventilation portion 131b1 corresponds to the position corresponding to the most upstream portion in the toner transport direction TTD of the toner electric field transport body 132 (transport wiring board 133) (in the drawing). It is provided only at the lower left end).

  Specifically, the ventilation portion 131b1 is provided immediately below the most upstream portion of the toner electric field transport body 132 (transport wiring board 133) in the toner transport direction TTD. In FIG. 8, the ventilation portion 131b1 is provided at a position overlapping with the most upstream portion in the toner conveyance direction TTD of the toner conveyance surface 133b in the horizontal direction. Further, in FIG. 8, the ventilation portion 131b1 is provided so as to be opposed to the most upstream portion in the toner conveyance direction TTD of the toner conveyance surface 133b.

  In such a configuration, the toner T at a position corresponding to the most upstream portion of the toner conveyance surface 133b in the toner conveyance direction TTD is fluidized favorably. This well fluidized toner T is supplied to the most upstream portion of the toner conveying surface 133b. As a result, the transport state of the toner T at the most upstream portion of the toner transport surface 133b can be made uniform. Therefore, the conveyance of the toner T on the toner conveyance surface 133b and the supply of the toner T to the development facing position DP can be performed more evenly and uniformly.

  Moreover, in the structure of the modification shown in FIG.6 and FIG.7, the ventilation part 131b1 and the air permeable obstruction board 131d1 are provided in the diagonal position. That is, in the configuration shown in FIGS. 6 and 7, the air-permeable blocking plate 131d1 is provided at the upper right position in the drawing in the side sectional view of the developing casing 131, while the ventilation portion 131b1 is located at the lower left position in the drawing. In the position.

  According to the configurations of these modified examples, the negative pressure is generated at a position in the developing casing 131 that is further away from the developing opening 131a2. Therefore, when gas is blown into the developing casing 131 through the casing bottom plate 131b, it can be more effectively suppressed that the toner T is ejected together with air from the developing opening 131a2.

  The ventilation portion 131b1 may be provided at a position (for example, a diagonal position of the toner conveyance surface 133b) that is separated from the toner conveyance surface 133b and adjacent to the toner conveyance surface 135b.

  (4) As shown in FIG. 6, an agitator 137 as a stirring member may be provided in the developing casing 131. The agitator 137 is rotatably supported in the developing casing 131.

  In such a configuration, the toner T in the developing casing 131 can be fluidized satisfactorily without rotating the agitator 137 vigorously.

  As shown in FIG. 6, the agitator 137 can be preferably provided corresponding to the non-venting part 131 b 2 when the casing bottom plate 131 b has the non-venting part 131 b 2.

  According to such a configuration, when the amount of the toner pool on the ventilation portion 131b1 decreases, the toner T can be added to the toner pool little by little by rotating the agitator 137. Therefore, it is possible to suppress as much as possible the deterioration of the toner T due to the stirring of the excess toner T continuously stored in the developing casing 131.

  In order to reduce the maintenance frequency by increasing the excess amount of toner T, the developing casing 131 is formed sufficiently longer (for example, twice or more) than the toner electric field transport body 132 in the front-rear direction. obtain. In this case, a plurality of agitators 137 can be arranged.

  In the configuration of FIG. 6, four agitators 137 including an upstream agitator 137a, a first intermediate agitator 137b, a second intermediate agitator 137c, and a downstream agitator 137d are provided.

  In such a configuration, the driving states of the upstream agitator 137a, the first intermediate agitator 137b, the second intermediate agitator 137c, and the downstream agitator 137d can be appropriately controlled according to the degree of consumption of the toner T in the developing casing 131.

  For example, when the degree of consumption of the toner T is small, the upstream side agitator 137a, the first intermediate agitator 137b, and the second intermediate agitator 137c are always stopped, and only the downstream side agitator 137d is appropriately selected according to the degree of decrease in toner accumulation. Driven by rotation.

  As the degree of consumption of the toner T in the developing casing 131 increases, the number of agitators 137 that are rotationally driven when the toner accumulation decreases increases.

  That is, the rotationally driven agitator 137 becomes the second intermediate agitator 137c and the downstream side agitator 137d, then becomes the first intermediate agitator 137b, the second intermediate agitator 137c, and the downstream side agitator 137d. Driven by rotation.

  (5) The stirring member such as an agitator may be provided at a position different from the toner electric field transport body 132 as shown in FIG. 6, or a position corresponding to the toner electric field transport body 132 (toner electric field). It may also be provided in the lower part of the carrier 132.

  As shown in FIG. 7, apart from the agitator 137 provided at a position different from the toner electric field transport body 132, a sub-agitator 138 smaller than the agitator 137 corresponds to the toner electric field transport body 132. It may be provided at a position (below the toner electric field carrier 132).

  In this case, the sub-agitator 138 is preferably provided below the toner electric field transport body 132 on the downstream side in the toner transport direction TTD.

  As a result, the portion where the toner T has refluxed from the toner electric field transport body 132 on the downstream side in the toner transport direction TTD is well stirred. Then, the toner T in this portion can be satisfactorily supplied to the most upstream portion (lower end portion in the drawing) of the counter wiring substrate 135 in the toner transport direction TTD.

  Further, a plurality of sub-agitators 138 may be provided as shown in FIG. In the configuration of FIG. 7, three sub-agitators 138, that is, an upstream sub-agitator 138a, an intermediate sub-agitator 138b, and a downstream sub-agitator 138c are provided.

  The plurality of sub-agitators 138 can also be driven to rotate as appropriate according to the degree of reduction in the toner pool, as in the above example.

  Further, as shown in FIG. 7, when the ventilation portion 131b1 in the casing bottom plate 131b is formed only in the upstream portion in the toner conveyance direction TTD of the toner electric field conveyance body 132, the toner in the non-vention portion 131b2 The sub-agitator 138 may be provided at a lower portion of the electric field carrier 132, and the agitator 137 may be provided at a portion not corresponding to the toner electric field carrier 132 in the non-venting portion 131b2.

  According to such a configuration, the rotational drive of the agitator 137 and the sub-agitator 138 is finely controlled according to the amount of the toner T in the developing casing 131 and the amount of the above-described toner reservoir, whereby the toner electric field transport body 132. The supply state of the toner T to the toner can be further optimized.

  (6) The configurations of the breathable bottom plate and the exhaust port of the present invention are not limited to the above-described embodiments and modifications.

  For example, the opening diameters of the porous ceramics constituting the casing bottom plate 131b (venting portion 131b1) and the breathable blocking plate 131d1 are not limited to the above-described embodiment.

  Moreover, the material of the casing bottom plate 131b (ventilating portion 131b1) and the breathable blocking plate 131d1 is not limited to porous ceramics. Specifically, for example, instead of the porous ceramic casing bottom plate 131b (venting portion 131b1) and the air-permeable blocking plate 131d1, there are a through hole formed in the developing casing 131 and a filter that covers the through hole from the outside. May be used.

  Furthermore, the exhaust port of the present invention may be provided at the front end of the casing upper surface cover 131a.

  (7) The counter wiring substrate 135 may be omitted partially or entirely.

  In this case, as shown in FIG. 8, the most upstream end (the lower left end in the figure) of the toner electric field transport body 132 (transport wiring board 133) in the toner transport direction TTD is almost always a toner reservoir. It is preferable that it is provided so as to extend downward to a position where it can be immersed in

  (8) In addition, what is expressed functionally and functionally in each element constituting the means for solving the problems of the present invention is a specific structure disclosed in the above-described embodiment or modification. In addition, any structure capable of realizing the action / function is included.

1 is a side sectional view showing a schematic configuration of a laser printer to which an embodiment of the present invention is applied. FIG. 2 is an enlarged side sectional view of an electrostatic latent image forming unit and a developing device shown in FIG. 1. FIG. 3 is an enlarged side cross-sectional view of a portion in the vicinity of a developing opening in the developer electric field carrier shown in FIG. 2. FIG. 4 is a graph showing a waveform of a voltage generated by the power supply circuit shown in FIG. 3. FIG. 4 is an enlarged side cross-sectional view illustrating a periphery of a toner transport surface in the transport wiring board illustrated in FIG. 3. FIG. 5 is a side sectional view showing a configuration of one modification of the developing device shown in FIG. 2. FIG. 10 is a side sectional view showing a configuration of another modification of the developing device shown in FIG. 2. FIG. 10 is a side sectional view showing a configuration of another modification of the developing device shown in FIG. 2.

Explanation of symbols

100: Laser printer (image forming apparatus)
121 ... Photosensitive drum (electrostatic latent image carrier / developer carrier)
121a ... drum body 121b ... photoreceptor layer 121b1 ... image carrying surface (latent image forming surface / developer carrying surface)
130... Development device (developer supply device)
131... Development casing (developer housing casing)
131a ... casing upper surface cover 131a1 ... developing unit facing plate 131a2 ... developing opening (opening)
131b ... casing bottom plate (breathable bottom plate)
131b1 ... Ventilation part (breathable bottom plate)
131b2 ... Non-venting part 131c ... Casing side plate 131d ... Casing front closing plate 131d1 ... Breathable closing plate (exhaust port)
132. Toner electric field carrier (developer carrier)
133 ... Conveyance wiring board 133a ... Conveyance electrode 133b ... Toner conveyance surface (developer conveyance surface)
135... Counter wiring substrate 135 a... Counter electrode 135 b... Toner transport surface 136...
136a ... Air circulation passage (gas circulation passage)
136b ... Pump T ... Toner (Developer)
TTD: Toner transport direction (developer transport direction)

Claims (13)

A latent image forming surface that is formed in parallel with a predetermined main scanning direction and configured to form an electrostatic latent image by a potential distribution; and the latent image forming surface is a sub-surface orthogonal to the main scanning direction. An electrostatic latent image carrier configured to be movable along a scanning direction;
A developer supply device arranged to face the electrostatic latent image carrier and configured to supply the developer to the latent image forming surface in a charged state;
An image forming apparatus comprising:
The developer supply device includes:
A box-shaped member comprising: a developing unit facing plate having an opening formed at a position facing the electrostatic latent image carrier; and a breathable bottom plate through which gas can pass while suppressing the passage of the developer. A developer containing casing configured to contain the developer;
The developer containing casing having a developer carrying surface parallel to the main scanning direction, and the developer carrying surface facing the electrostatic latent image carrier with the opening in the developing unit facing plate interposed therebetween A developer carrier disposed in the interior;
The developer is provided along the developer transport surface so as to face the latent image forming surface, and the developer is applied in a predetermined developer transport direction on the developer transport surface by applying a traveling wave voltage. A plurality of transport electrodes configured to be transported and arranged along the sub-scanning direction;
A gas supply unit configured to fluidize the developer in the developer accommodating casing by blowing gas into the developer accommodating casing through the breathable bottom plate;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
2. The image forming apparatus according to claim 1, wherein the breathable bottom plate is provided in the vicinity of the most upstream portion of the developer transport surface in the developer transport direction. The image forming apparatus according to claim 1, wherein:
An exhaust part configured to be able to exhaust the gas in the developer containing casing,
An image forming apparatus, wherein an exhaust port communicating with the exhaust unit is provided at a position different from the opening in the developer containing casing. The image forming apparatus according to claim 3, wherein
The image forming apparatus according to claim 1, wherein the exhaust port is provided at a diagonal position with respect to the breathable bottom plate. The image forming apparatus according to claim 3 or 4, wherein:
A gas circulation passage configured to connect the exhaust port and the breathable bottom plate outside the developer containing casing;
The image forming apparatus, wherein the gas supply unit and the exhaust unit are configured by a pump interposed in the gas circulation passage. An image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the breathable bottom plate is provided at a position corresponding to at least a lowest portion of the developer containing casing. A developer carrying surface that is parallel to a predetermined main scanning direction and has a developer carrying surface on which the developer can be carried, and the developer carrying surface can move along a sub-scanning direction orthogonal to the main scanning direction. In a developer supply device configured to be able to be supplied along a predetermined developer transport direction in a state where the developer is charged to a body,
A box-shaped member comprising: a developing portion facing plate in which an opening is formed at a position facing the developer carrying member; and a breathable bottom plate through which gas can pass while suppressing the passage of the developer. A developer accommodating casing configured to accommodate the developer;
The developer containing casing has a developer carrying surface parallel to the main scanning direction, and the developer carrying surface faces the developer carrying member across the opening in the developing unit facing plate. An arranged developer carrier;
It is provided along the developer transport surface so as to face the developer carrying surface, and the developer is transported in the developer transport direction on the developer transport surface by applying a traveling wave voltage. A plurality of transport electrodes arranged along the sub-scanning direction,
A developer supply apparatus comprising: The developer supply device according to claim 7,
2. The image forming apparatus according to claim 1, wherein the breathable bottom plate is provided in the vicinity of the most upstream portion of the developer transport surface in the developer transport direction. In the developer supply device according to claim 7 or 8,
The apparatus further comprises a gas supply unit configured to fluidize the developer in the developer containing casing by blowing gas into the developer containing casing through the breathable bottom plate. Developer supplying device. In the developer supply apparatus according to claim 8 or 9,
An exhaust part configured to be able to exhaust the gas in the developer containing casing,
The developer supply apparatus, wherein an exhaust port communicating with the exhaust port is provided at a position different from the opening in the developer containing casing. The developer supply device according to claim 10,
The developer supply device according to claim 1, wherein the exhaust port is provided at a position diagonal to the breathable bottom plate. The developer supply device according to any one of claims 9 to 11,
A gas circulation passage configured to connect the exhaust port and the breathable bottom plate outside the developer containing casing;
The developer supply device according to claim 1, wherein the gas supply unit and the exhaust unit are configured by a pump interposed in the gas circulation passage. The developer supply device according to any one of claims 7 to 12,
The developer supply device according to claim 1, wherein the breathable bottom plate is provided at least at a position corresponding to a lowest part of the developer containing casing.

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