Developing device and image forming apparatus including same

A developing device includes a developing roller, a toner supplying roller, a regulation blade, a casing, a toner receiver support member, a toner receiver member, and a vibration generator. The toner receiver member is disposed along a longitudinal direction of the toner receiver support member facing the developing roller, and has a toner receiving surface inclined downward from the image-carrier side toward the toner-supplying-roller side. The toner receiving surface is disposed to be inclined so as to rise from the toner-supplying-roller side toward the image-carrier side. The toner receiving surface has a plurality of grooves formed therein to be inclined to approach a center part of the toner receiving surface from each end side of the toner receiving surface in its longitudinal direction, from an edge of the toner receiving surface on the image-carrier side toward an edge of the toner receiving surface on the toner-supplying-roller side.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2015-180494 filed on Sep. 14, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a developing device that supplies developer to an image carrier and an electro-photographic image forming apparatus including the developing device.

In an electro-photographic image forming apparatus, an electrostatic latent image is formed by irradiating a circumferential surface of an image carrier (a photosensitive drum) with light based on information of an image read from a document image or based on information of an image transmitted from an external device such as a computer or the like. Toner is supplied from a developing device to the electrostatic latent image to form a toner image, which is then transferred onto a sheet. The sheet that has gone through the transfer process is then subjected to toner-image fixing processing, and discharged to outside.

In recent years, more and more complicated configurations have come to be adopted in image forming apparatuses along with progress in color printing and high-speed processing. In addition, for higher-speed processing, it is indispensable to achieve higher-speed rotation of a toner stirring member within the developing device. In particular, according to a development method in which a two-component developer containing magnetic carrier and toner is used, and in which a magnetic roller (a toner supplying roller) that carries the developer and a developing roller that carries only the toner are used, in an opposing portion where the developing roller and the magnetic roller face each other, a magnetic brush is formed on the magnetic roller, and by the magnetic brush, only the toner is carried on the developing roller, and further, the toner left unused for development is peeled off from the developing roller. This is liable to cause toner particles to float in the vicinity of the opposing portion where the developing roller and the magnetic roller face each other, and such floating toner particles accumulate around a trimming blade (a regulation blade). If the accumulated toner particles adhere to the developing roller in a condensed manner, they may eventually fall and cause an image defect.

As a solution to such a problem, for example, there is known a developing device in which a two-component developer containing magnetic carrier and toner is used, in which a magnetic roller that carries the developer and a developing roller that carries only the toner are used, and that further includes a toner receiver support member that faces the developing or magnetic roller, a toner receiver member that is disposed along a longitudinal direction of the toner receiver support member and receives toner fallen from the developing roller, and vibration generating means that vibrates the toner receiver member.

There is also known a developing device in which a sheet-shaped vibration adjusting member is disposed at both end parts of a toner receiver support member in its longitudinal direction to be spaced by a predetermined distance from a toner receiver member. In this developing device, when the toner receiver member vibrates, the toner receiver member comes into contact with the vibration adjusting member, whereby the toner receiver member is caused to vibrate in waves such that a free end of the toner receiver member moves warping in an arc, and thereby, toner accumulated on a free-end side of the toner receiver member is moved to a fulcrum side.

SUMMARY

According to an aspect of the present disclosure, a developing device includes a developing roller, a toner supplying roller, a regulation blade, a casing, a toner receiver support member, a toner receiver member, and a vibration generator. The developing roller is disposed to face an image carrier on which an electrostatic latent image is formed, and the developing roller is configured to supply toner to the image carrier in an opposing region where the developing roller and the image carrier face each other. The toner supplying roller is disposed to face the developing roller, and the toner supplying roller is configured to supply toner to the developing roller in an opposing region where the toner supplying roller and the developing roller face each other. The regulation blade is disposed to face the toner supplying roller with a predetermined space therebetween. The casing accommodates the developing roller, the toner supplying roller, and the regulation blade. The toner receiver support member is disposed inside the casing so as to face the developing roller or the toner supplying roller between the regulation blade and the image carrier. The toner receiver member is disposed along a longitudinal direction of the toner receiver support member, and has a toner receiving surface that receives toner falling from the developing roller. The vibration generator vibrates the toner receiver member. The toner receiving surface is disposed to be inclined so as to rise from a said-toner-supplying-roller side toward a said-image-carrier side. The toner receiving surface has a plurality of grooves formed therein to be inclined to approach a center part of the toner receiving surface from each end side of the toner receiving surface in a longitudinal direction thereof, from an edge of the toner receiving surface on the said-image-carrier side toward an edge of the toner receiving surface on the said-toner-supplying-roller side.

Further features and specific advantages of the present disclosure will become apparent from the following descriptions of preferred embodiments.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.FIG. 1is a schematic sectional view of an image forming apparatus incorporating developing devices3ato3dof the present disclosure, and the image forming apparatus shown herein is a tandem-type color printer. In a main body of a color printer100, four image forming portions Pa, Pb, Pc, and Pd are arranged in this order from an upstream side in a conveyance direction (a right side inFIG. 1). The image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and sequentially form images of cyan, magenta, yellow, and black through charging, exposure, developing, and transferring steps.

In the image forming portions Pa, Pb, Pc, and Pd, there are disposed photosensitive drums1a,1b,1c, and1d, respectively, each for carrying a visible image (toner image) of a corresponding color, and further, an intermediate transfer belt8that is rotated by driving means (not shown) in a clockwise direction inFIG. 1is disposed adjacent to the image forming portions Pa to Pd. The toner images formed on the photosensitive drums1ato1dare primarily transferred sequentially onto the intermediate transfer belt8, which moves in contact with the photosensitive drums1ato1d, and the toner images are superimposed one on another on the intermediate transfer belt8. Then, the toner images primarily transferred onto the intermediate transfer belt8are secondarily transferred onto a transfer paper sheet P as an example of a recording medium by operation of a secondary transfer roller9. Further, the transfer paper sheet P onto which the toner images have been secondarily transferred is discharged from a main body of the color printer100after the toner images are fixed thereon at a fixing portion13. An image forming process is performed with respect to the photosensitive drums1ato1dwhile rotating the photosensitive drums1ato1din a counterclockwise direction inFIG. 1.

Transfer paper sheets P onto each of which a toner image is to be secondarily transferred are accommodated in a sheet cassette16disposed in a lower part of the color printer100. A transfer paper sheet P is conveyed via a sheet feeding roller12aand a registration roller pair12bto a nip portion between the secondary transfer roller9and a later-described driving roller11provided for driving the intermediate transfer belt8. The intermediate transfer belt8is made of a dielectric resin sheet, and mainly formed as a (seamless) belt having no seam. Furthermore, for the purpose of removing toner and the like remaining on a surface of the intermediate transfer belt8, a blade-shaped belt cleaner19is disposed downstream of the secondary transfer roller9.

Next, the image forming portions Pa to Pd will be described. Provided around and below the rotatably disposed photosensitive drums1a,1b,1c, and1dare chargers2a,2b,2c, and2dthat charge the photosensitive drums1a,1b,1c, and1d, respectively, an exposure device5that exposes the photosensitive drums1ato1dwith light based on image information, developing devices3a,3b,3c, and3dthat form a toner image on the photosensitive drums1a,1b,1c, and1d, respectively, and cleaning portions7a,7b,7c, and7dthat remove residual developer (toner) and the like remaining on the photosensitive drums1a,1b,1c, and1d, respectively.

When image data is input from a host device such as a personal computer, the chargers2ato2dfirst charge surfaces of the photosensitive drums1ato1duniformly. Then, the exposure device5irradiates the photosensitive drums1ato1dwith light according to the image data, and thereby an electrostatic latent image is formed on each of the photosensitive drums1ato1daccording to the image data. The developing devices3ato3dare each filled with a predetermined amount of two-component developer containing cyan, magenta, yellow, or black toner. Note that the developing devices3ato3dare replenished with toner from toner containers4ato4dwhen the proportion of toner contained in the two-component developer in each of the developing devices3ato3dfalls below a regulation value after formation of toner images, which will be described below. The toner contained in the developer is supplied onto the photosensitive drums1ato1dby the developing devices3ato3d, respectively, and electrostatically adheres thereto, whereby toner images are formed according to the electrostatic latent images that have been formed by being exposed to light from the exposure device5.

Further, by primary transfer rollers6ato6d, an electric field is applied at a predetermined transfer voltage between the primary transfer rollers6a,6b,6c, and6dand the photosensitive drums1a,1b,1c, and1d, respectively, and the toner images of cyan, magenta, yellow, and black on the photosensitive drums1ato1dare primarily transferred onto the intermediate transfer belt8. The toner images of the four colors are formed with a predetermined positional relationship therebetween that is previously determined for forming a predetermined full-color image. Thereafter, in preparation for formation of new electrostatic latent images to be subsequently performed, toner and the like remaining on the surfaces of the photosensitive drums1ato1dare removed by the cleaning devices7ato7d.

The intermediate transfer belt8is wound around and between a driven roller10disposed on an upstream side and a driving roller11disposed on a downstream side. When the intermediate transfer belt8starts to rotate in the clockwise direction along with rotation of the driving roller11caused by a driving motor (not shown), the transfer paper sheet P is conveyed from the registration roller pair12bat a predetermined timing to a nip portion (a secondary transfer nip portion) between the driving roller11and the secondary transfer roller9disposed adjacent to the driving roller11. Then, the full color image on the intermediate transfer belt8is secondarily transferred onto the transfer paper sheet P. The transfer paper sheet P onto which the toner image has been transferred is then conveyed to the fixing portion13.

The transfer paper sheet P that has been conveyed to the fixing portion13is heated and pressurized by a fixing roller pair13a, whereby the toner image is fixed on a surface of the transfer paper sheet P, and thus a predetermined full-color image is formed. The transfer paper sheet P on which the full-color image has been formed is discharged onto a discharge tray17by a discharge roller pair15.

FIG. 2is a side sectional view of a developing device3aaccording to an embodiment of the present disclosure. Note thatFIG. 2illustrates a state in which the developing device3ais seen from a back side ofFIG. 1, and arrangement of components in the developing device3aappears to be left-right reversal to that illustrated inFIG. 1. Further, in the following description, only the developing device3aarranged in the image forming portion Pa ofFIG. 1will be dealt with as an example, and the developing devices3bto3darranged in the image forming portions Pb to Pd are not described. This is because each of the developing devices3bto3dhas basically the same structure as that of the developing device3a.

As illustrated inFIG. 2, the developing device3aincludes a developing container (a casing)20for storing a two-component developer (hereinafter, simply referred to as developer) composed of toner and magnetic carrier. The developing container20is partitioned by a partition wall20ainto a stirring-conveyance chamber21and a supply-conveyance chamber22. In the stirring-conveyance chamber21and the supply-conveyance chamber22, there are rotatably disposed a stirring-conveyance screw25aand a supply-conveyance screw25b, respectively, for mixing and stirring toner (positively charged toner) supplied from the toner container4a(seeFIG. 1) with carrier to charge the toner.

Then the developer is conveyed in an axial direction (a direction perpendicular to a surface of a sheet on whichFIG. 2is drawn) while being stirred by the stirring-conveyance screw25aand the supply-conveyance screw25b, and circulates between the stirring-conveyance chamber21and the supply-conveyance chamber22through a developer passage (not shown) formed at each end part of the partition wall20a. That is, inside the developing container20, a developer circulation path is formed with the stirring-conveyance chamber21, the supply-conveyance chamber22, and the developer passages.

The developing container20extends obliquely right upward inFIG. 2. In the developing container20, a toner supplying roller30(a developer carrier) is arranged above the supply-conveyance screw25b, and a developing roller31is arranged obliquely right above the toner supplying roller30so as to face the toner supplying roller30. The developing roller31faces the photosensitive drum1a(seeFIG. 1) on an opening side of the developing container20(right side inFIG. 2). The toner supplying roller30and the developing roller31are rotated in the counterclockwise direction inFIG. 2about rotation shafts thereof.

In the stirring-conveyance chamber21, a toner concentration detection sensor27is disposed to face the stirring-conveyance screw25a. The toner concentration detection sensor27detects a toner-to-carrier ratio (T/C) in the developer. Based on a detection result obtained by the toner concentration detection sensor27, toner is replenished from the toner container4ato the stirring-conveyance chamber21via an unillustrated toner replenishment port. Used as the toner concentration detection sensor27is, for example, a magnetic permeability sensor that detects magnetic permeability of the developer in the developing container20.

The toner supplying roller30is composed of a non-magnetic rotary sleeve that rotates in the counterclockwise direction inFIG. 2, and a stationary magnet body having a plurality of magnetic poles enclosed in the rotary sleeve.

The developing roller31is composed of a cylindrical developing sleeve that rotates in the counterclockwise direction inFIG. 2, and a developing-roller-side magnetic pole fixed in the developing sleeve. The toner supplying roller30and the developing roller31face each other with a predetermined gap therebetween at a facing position (an opposing position). The developing-roller-side magnetic pole has a polarity reverse to that of such one (a main pole) of the magnetic poles of the stationary magnet body as faces the developing-roller-side magnetic pole.

Further, the developing container20is provided with a trimming blade33attached thereto along a longitudinal direction of the toner supplying roller30(a direction perpendicular to the surface of the sheet on whichFIG. 2is drawn). The trimming blade33is positioned on an upstream side relative to the opposing position of the developing roller31and the toner supplying roller30, in a rotational direction of the toner supplying roller30(the counterclockwise direction inFIG. 2). A slight clearance (gap) is provided between an edge of the trimming blade33and a surface of the toner supplying roller30.

A direct-current voltage (hereinafter, referred to as Vslv(DC)) and an alternating-current voltage (hereinafter, referred to as Vslv(AC)) are applied to the developing roller31. A direct-current voltage (hereinafter, referred to as Vmag(DC)) and an alternating-current voltage (hereinafter, referred to as Vmag(AC)) are applied to the toner supplying roller30. These direct-current voltages and alternating-current voltages are applied to the developing roller31and the toner supplying roller30from a developing bias power source via a bias control circuit (neither of which is shown).

As described above, the developer circulates in the stirring-conveyance chamber21and the supply-conveyance chamber22in the developing container20while being stirred by the stirring-conveyance screw25aand the supply-conveyance screw25bto thereby charge the toner contained in the developer, and then the developer is conveyed from the supply-conveyance chamber22to the toner supplying roller30by the supply-conveyance screw25b. Then, a magnetic brush (not shown) is formed on the toner supplying roller30, the magnetic brush is regulated in layer thickness by the trimming blade33, and is then conveyed to the opposing portion of the toner supplying roller30and the developing roller31. In this manner, a thin layer of toner is formed on the developing roller31by making use of a potential difference ΔV between Vmag(DC) to be applied to the toner supplying roller30and Vslv(DC) to be applied to the developing roller31, and a magnetic field.

A thickness of the toner layer formed on the developing roller31depends on factors such as resistance of the developer and difference in rotation speed between the toner supplying roller30and the developing roller31, but the thickness of the toner layer is controllable by means of ΔV. A larger ΔV increases, and a smaller ΔV reduces, the thickness of the toner layer on the developing roller31. An appropriate range of ΔV at the time of development is generally a range of from approximately 100 V to 350 V.

The thin layer of toner formed on the developing roller31through contact with the magnetic brush formed on the toner supplying roller30is transported by the rotation of the developing roller31to an opposing portion (an opposing region) where the photosensitive drum1aand the developing roller31face each other. Since Vslv(DC) and Vslv(AC) are applied to the developing roller31, potential difference between the developing roller31and the photosensitive drum1acauses toner to fly from the developing roller31to the photosensitive drum1a, and the electrostatic latent image on the photosensitive drum1ais developed with the toner.

Toner left without being used for development is conveyed back to the opposing portion of the developing roller31and the toner supplying roller30, and is collected by the magnetic brush formed on the toner supplying roller30. Next, the magnetic brush is peeled off from the toner supplying roller30at a homopolar portion of the stationary magnet body, and then falls into the supply-conveyance chamber22.

After that, based on a result of detection conducted by the toner concentration detection sensor27, a predetermined amount of toner is replenished via the toner replenishment port (not shown), and circulates in the supply-conveyance chamber22and the stirring-conveyance chamber21, whereby the two-component developer is restored to an appropriate toner concentration, and uniformly charged. This developer is supplied again onto the toner supplying roller30by the supply-conveyance screw25bto form a magnetic brush, and conveyed to the trimming blade33.

In the vicinity of the developing roller31on a right side wall of the developing container20inFIG. 2, there is provided a toner receiver support member35that has a triangular shape in section and projects to an inside of the developing container20. As illustrated inFIG. 2, the toner receiver support member35is disposed along a longitudinal direction of the developing container20(a direction perpendicular to the surface of the sheet on whichFIG. 2is drawn). An upper surface of the toner receiver support member35forms a wall portion facing the toner supplying roller30and the developing roller31and inclined downward in a direction of from the developing roller31to the toner supplying roller30. To the upper surface of the toner receiver support member35, along its longitudinal direction, there is attached a toner receiver member37that receives toner peeled off and fallen from the developing roller31.

FIG. 3is a perspective view of the toner receiver support member35, which is used in the developing devices3ato3dof the present embodiment, as seen from the inside of the developing container20(a left side ofFIG. 2),FIG. 4is a perspective view of a support member main body36included in the toner receiver support member35,FIG. 5is a perspective view of the toner receiver member37to be attached to the toner receiver support member35as seen from the inside of the toner receiver support member35, andFIG. 6is an enlarged view of an end part (a left end part inFIG. 3) of a toner receiver member37. Note thatFIG. 4illustrates the support member main body36as seen from an attachment direction of the toner receiver member37.

The toner receiver support member35has the support member main body36made of resin, the toner receiver member37made of sheet metal and swingably supported by the support member main body36, and a vibration generator40attached to a substantially center part of the toner receiver member37in its longitudinal direction. In the support member main body36, there is formed an accommodation portion36ain which the vibration generator40is accommodated when the toner receiver member37is attached to the support member main body36.

Further, at an upper end of the support member main body36, there is provided a seal member44that has a film-like shape. The seal member44extends in a longitudinal direction of the support member main body36(a right-left direction inFIG. 3) such that an end part of the seal member44is in contact with a surface of the photosensitive drum1a. The seal member44has a function as a shield to prevent the toner inside the developing container20(seeFIG. 2) from leaking to the outside.

The toner receiver member37has a bent shape such that a bent portion37ais formed along its longitudinal direction. The toner receiver member37is divided into a toner receiving surface37bthat faces the developing roller31(seeFIG. 2) and a toner fall surface37cthat is substantially vertical and faces the toner supplying roller30, with the bent portion37abetween the toner receiving surface37band the toner fall surface37c. On one end side of the toner receiver member37in its longitudinal direction, there is formed an engagement portion38to which is engaged a contact spring48via which the toner receiver member37is grounded. A lower end part of the contact spring48contacts the trimming blade33(seeFIG. 2) via an electrically conductive spring receiver member (not shown). At a substantially center part of the toner receiver member37in its longitudinal direction, there is formed a holding portion39that has a pair of holding claws39afor holding the vibration generator40. A base45is fixed to the vibration generator40with a screw46, and on the base45, there are mounted a circuit for controlling driving of a vibration motor43(seeFIG. 7) and electronic components (not shown).

The toner receiving surface37bhas formed therein a plurality of (herein, a total of ten, five on each of two sides separated by a center part in a longitudinal direction) grooves60ato60ethat extend from an edge37e, which is an edge of the toner receiving surface37bin a direction perpendicular to its longitudinal direction, toward the bent portion37a. The grooves60ato60eare inclined so as to approach the center part of the toner receiving surface37bfrom each end side of the toner receiving surface37bin its longitudinal direction, from the edge37etoward the bent portion37a. The grooves60ato60eon the two sides separated by the center part of the toner receiving surface37bare symmetrically arranged with respect to the center part in the longitudinal direction. At an end of each of the grooves60ato60eon the bent-portion-37aside, there is formed an opening61that communicates with the toner fall surface37c. The grooves60ato60eare formed, for example, by drawing the toner receiver member37by press.

Sheet members41aand41bare bonded to surfaces (a surface facing the developing roller31and a surface facing the toner supplying roller30) of the toner receiver member37. The sheet members41aand41bare release layers provided for reducing adhesion of toner to the toner receiver member37, and they are made of a material to which toner is less likely to adhere than to a material of the toner receiver member37. Examples of the material for the sheet members41aand41binclude a fluororesin sheet, for example.

FIG. 7is a perspective view of the vibration generator40. Note thatFIG. 7shows a state where the base45(seeFIG. 5) has been removed from a motor mounting holder42so that an inside of the vibration generator40can be seen. The vibration generator40includes the motor mounting holder42and the vibration motor43. In the motor mounting holder42, there are formed a motor holding portion42athat holds the vibration motor43and a screw hole42binto which the screw46is to be screwed. An oscillating weight50is fixed to an output shaft43aof the vibration motor43. When the vibration generator40is attached to the toner receiver member37, it is fixed such that the output shaft43aof the vibration motor43lies along the longitudinal direction of the toner receiver member37. Further, to the motor mounting holder42, there is connected a lead wire (not shown) for supplying electric power to the vibration motor43.

FIG. 8is a front view of the vibration motor43, andFIG. 9is a side view of the vibration motor43as seen from a side on which the oscillating weight50is disposed. As seen from a direction of the output shaft43aof the vibration motor43(from a right side inFIG. 8), as illustrated inFIG. 9, the oscillating weight50is formed in a cam-like shape with a cut portion50aformed in part of a disc shape, and is asymmetric with respect to the output shaft43a. When the output shaft43arotates at a predetermined speed or faster, a smaller centrifugal force acts on the cut portion50athan on other parts, and thus an uneven centrifugal force is applied to the oscillating weight50. The uneven centrifugal force is transmitted to the output shaft43ato cause the vibration motor43to vibrate. The shape of the oscillating weight50is not limited to the cam-like shape, but any shape may be adopted as long as a center of gravity of the oscillating weight50can be shifted with respect to the output shaft43a.

FIG. 10is a side sectional view (taken along line XX′ inFIG. 3) showing, in section, a structure of, and around, the vibration motor43for the toner receiver support member35used in the developing device3aof the present embodiment, andFIG. 11is an enlarged view of a part of the toner receiver support member35illustrated inFIG. 10.

As illustrated inFIG. 10andFIG. 11, the toner receiver member37has only an edge37don a toner-supplying-roller-30side in contact with the support member main body36, and an edge37eon an opposite side (a photosensitive-drum-1aside) is a free end. And a substantially center part of the toner receiving surface37bin its width direction (a right-left direction inFIG. 10) is supported by the support member main body36via the vibration generator40. Thereby, the toner receiver member37is configured to be swingable about the edge37das a fulcrum. The vibration motor43is disposed such that the output shaft43ais substantially parallel to the longitudinal direction of the toner receiver member37.

The toner receiver member37is disposed such that the toner receiving surface37bfacing the developing roller31is so inclined as to rise from the toner-supplying-roller-30side toward the photosensitive-drum-1aside, and the toner fall surface37cfacing the toner supplying roller30is substantially vertical.

The sheet member41ais bonded so as to cover a front surface (the toner fall surface37c) of the toner receiver member37, including a trimming-blade-33side boundary between the support member main body36and the toner receiver member37. Further, the sheet member41bis bonded to entirely cover the toner receiving surface37b, including a seal-member-44side boundary between the support member main body36and the toner receiver member37, the engagement portion38, the holding portion39(seeFIG. 5), and the grooves60ato60e. The sheet members41aand41breduce adhesion of toner to the toner receiving surface37band the toner fall surface37c, and also prevent leakage of toner through the boundaries between the toner receiver support member35and the toner receiver member37, entry of toner to an inside of the toner receiver support member35, and operation defect of the vibration motor43caused by the entry of toner.

Here, the grooves60ato60eformed in the toner receiving surface37bmake the operation of bonding the sheet member41ba complicated operation. To avoid such a complicated bonding operation, instead of bonding the sheet member41b, a coating of a fluororesin or the like may be formed on the toner receiving surface37bas a release layer, to thereby reduce adhesion of toner to the toner receiving surface37b.

By rotating the output shaft43aat high speed (for example, approximately 10,000 rpm) during non-image formation when no image is being formed, the oscillating weight50is also rotated at high speed together with the output shaft43a. At this time, an uneven centrifugal force is applied to the oscillating weight50, and thus the vibration motor43and the motor mounting holder42vibrate via the output shaft43a. As a result, the toner receiver member37to which the vibration generator40is attached also vibrates. Specifically, the toner receiving surface37bof the toner receiver member37vibrates about the edge37das a fulcrum such that an amplitude of the vibration is larger toward the edge37e.

In the present embodiment, the output shaft43aof the vibration motor43is rotated in a direction (a counterclockwise direction inFIG. 11) in which such part of an outer circumferential surface of the output shaft43aas faces the toner receiver member37moves from the free end (the edge37e) of the toner receiver member37toward the fulcrum (the edge37d). By the rotation of the output shaft43ain this direction, the toner receiver member37is vibrated and thereby causes toner accumulated on the toner receiving surface37bto move from an edge-37eside to an edge-37dside.

On the other hand, if the output shaft43ais rotated in a reverse direction (a clockwise direction inFIG. 11), the vibration of the toner receiver member37causes the toner particles to move in such a manner as to rise from the edge-37dside to the edge-37eside, and thus the toner accumulated on the toner receiving surface37bdoes not slide down along the toner receiving surface37b. Thus, by rotating the output shaft43aof the vibration motor43in the manner as in the present embodiment, it is possible to allow the toner particles accumulated on the toner receiving surface37bto effectively fall along the downward slope into a region R.

Further, according to the present embodiment, the grooves60ato60eare formed that are inclined so as to approach the center part of the toner receiving surface37bfrom each end side of the toner receiving surface37bin its longitudinal direction, from the edge37etoward the bent portion37a. As shown inFIG. 11, such part of toner T accumulated on the toner receiving surface37bas has accumulated above the grooves60ato60e(in an area on the edge-37eside) is caused to fall into the grooves60ato60eby vibration of the toner receiving surface37b. Then, the toner T slides downward (in a direction indicated by a white arrow inFIG. 11) along the grooves60ato60efrom each end side toward the center part of the toner receiving surface37bin its longitudinal direction, and freely falls through the opening61into the region R, which is a region sandwiched by the substantially vertical toner fall surface37cand the toner supplying roller30.

That is, most of toner accumulated on the toner receiving surface37bslides downward along the grooves60ato60ewhile being collected from each end part toward the center part, and this helps reduce fall of toner onto each end part of the toner supplying roller30in its longitudinal direction. Thus, it is possible to effectively reduce degradation of image quality caused by toner fall that tends to frequently occur at each end of the photosensitive drums1ato1din their longitudinal directions.

Here, the grooves60ato60eformed in the toner receiving surface37bextend from the bent portion37ato the edge37ein the present embodiment, but the grooves60ato60edo not necessarily need to extend to the edge37e, but the grooves60ato60emay be formed starting from positions slightly inward (the bent-part-37aside) from the edge37e.

Further, according to the present embodiment, the opening61, which communicates with the toner fall surface37c, is formed at the bent-portion-37a-side end of each of the grooves60ato60e; however, the grooves60ato60emay be formed, as illustrated inFIG. 12, so as to extend from the edge37e, through the bent portion37a, and in the toner fall surface37cin an up-down direction, to reach the edge37d. In this case, in comparison with the case where the grooves60ato60eare formed only in the toner receiving surface37b, distortion is less likely to occur during the drawing, and thus the toner receiver member37can be formed more easily.

FIG. 13is a perspective view of a part of the grooves60bto60eformed in the toner receiving surface37b, andFIG. 14is a perspective view of a part of the groove60aformed in the toner receiving surface37b. As illustrated inFIG. 13, the grooves60bto60eeach have a constant depth, and an inclination θ2of a bottom surface63of each of the grooves60bto60ewith respect to a horizontal plane is substantially equal to that of the toner receiving surface37b. On the other hand, as illustrated inFIG. 14, the groove60ahas a depth that increases toward the bent-portion-37aside (a left side inFIG. 14) from the edge-37eside (a right side inFIG. 14). That is, in the groove60a, the bottom surface63has an inclination θ3that is larger than θ2. This allows toner to slide downward more easily along the groove60a, which receives toner accumulated on each end part of the toner receiving surface37bin its longitudinal direction, than along the grooves60bto60e.

Thus, even in a case where a small motor that generates a small amount of vibration is used as the vibration motor43, it is possible to secure vibration sufficient to cause toner particles accumulated over an entire area of the toner receiver member37in its longitudinal direction to fall. This makes it possible to improve compactness of the developing devices3ato3dand the image forming apparatus100while even more effectively reducing degradation of image quality caused by toner fall that tends to frequently occur at each end of the photosensitive drums1ato1din their longitudinal directions.

An inclination angle θ1(seeFIG. 3) of the grooves60ato60dwith respect to the bent portion37ais not particularly limited, but a smaller θ1makes it easier to collect toner accumulated on the toner receiving surface37bto the center part. If the inclinations θ2and θ3are too large, accumulated toner may fall, causing toner fall during image formation. On the other hand, if the inclinations θ2and θ3are too small, it becomes difficult for accumulated toner to fall when the vibration generator40is vibrated. In the present embodiment, θ1is set to 20°, θ2is set to 20°, and θ3is set to 30°.

Part of the toner that has fallen from the toner receiving surface37bto accumulate in the region R adheres to the magnetic brush formed on the toner supplying roller30. To deal with this, during non-image formation, the developing roller31and the toner supplying roller30are rotated (forwardly rotated) in a direction same as a direction (the counterclockwise direction inFIG. 10) in which they are rotated during image formation. By forwardly rotating the toner supplying roller30, the toner adhered to the magnetic brush on the toner supplying roller30rotates together with the magnetic brush along with the rotation of the toner supplying roller30, is peeled off from the toner supplying roller30at the homopolar portion of the stationary magnet body, and then falls into the supply-conveyance chamber22.

Here, when the developing roller31and the toner supplying roller30are forwardly rotated, part of the toner adhered to the magnetic brush on the toner supplying roller30moves onto the developing roller31. However, Vslv(DC) is not applied to the developing roller31during non-image formation, and thus potential difference between the developing roller31and the photosensitive drum1ais zero. Accordingly, there is no possibility for the toner to move to the photosensitive-drum-1aside even when the toner adhered to the surface of the developing roller31is caused, by the rotation of the developing roller31, to pass through the opposing portion of the developing roller31and the photosensitive drum1a.

Further, when vibrating the toner receiver member37, Vslv(DC) having the same polarity as the toner has may be applied to the developing roller31, without applying Vmag(DC) to the toner supplying roller30. In this way, a potential difference is generated in a direction in which the toner moves from the developing roller31to the toner supplying roller30, and this helps effectively reduce occurrence of a phenomenon in which toner shaken off from the toner receiver member37to adhere to the toner supplying roller30moves to the developing roller31.

Incidentally, for the purpose of returning the toner fallen into the region R to the supply-conveyance chamber22, it is also possible to rotate (reversely rotate) the developing roller31and the toner supplying roller30during non-image formation in a direction (the clockwise direction inFIG. 11) reverse to the direction in which they are rotated during image formation. By reversely rotating the toner supplying roller30, the toner fallen into the region R and accumulated on an end of the trimming blade33is scraped off by the magnetic bush formed on the toner supplying roller30. The toner scraped off in this manner rotates together with the surface of the toner supplying roller30to pass through a gap between the toner supplying roller30and the trimming blade33, and is peeled off from the toner supplying roller30at the homopolar portion of the stationary magnet body, to be then forcibly returned to the supply-conveyance chamber22.

In the case where the developing roller31and the toner supplying roller30are reversely rotated, it is possible to scrape off the toner accumulated on the end of the trimming blade33more effectively by so adjusting magnetic force and disposition of the magnetic poles (regulation poles) in the stationary magnet body facing the trimming blade33as to allow bristles of the magnetic brush formed on the toner supplying roller30to be long. Further, as has been mentioned above, there is a possibility that the reverse rotation of the developing roller31and the toner supplying roller30may be accompanied by leakage of the developer from inside the developing container20through the toner replenishment port, or noise of the toner concentration detection sensor27generated when the developer is maldistributed inside the developing container20. To address these, it is preferable to forwardly rotate the developing roller31and the toner supplying roller30for a predetermined time after reversely rotating the developing roller31and the toner supplying roller30.

As for a timing for vibrating the toner receiver member37, the vibration may be performed each time a printing operation is completed, or may be performed at a predetermined timing such as each time printing has been performed on a predetermined number of sheets or each time temperature of inside the developing device3areaches or exceeds a predetermined temperature. Further, the timing of vibrating the toner receiver member37and the timing of forwardly (or reversely) rotating the developing roller31and the toner supplying roller30may be the same or different. Further, by vibrating the toner receiver member37each time printing has been performed on a predetermined number of sheets, the toner receiver member37is automatically vibrated in accordance with the number of sheets printed. This accordingly eliminates need for users themselves to manually perform settings for the vibration of the toner receiver member37, and thus helps avoid erroneous setting, omission of setting, or performance of unnecessary vibration.

It should be understood that the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the present disclosure. For example, the shapes and configurations of the toner receiver support member35and the toner receiver member37of the above-described embodiments are merely examples, and are not particularly meant to limit the present disclosure. The shapes and configurations may be appropriately set in accordance with factors including apparatus configurations.

In the above embodiments, the present disclosure is applied to the developing devices3ato3dthat each use two-component developer, each form a magnetic brush on the toner supplying roller30, each move only toner from the toner supplying roller30to the developing roller31, and each supply the toner from the developing roller31to a corresponding one of photosensitive drums1ato1d; however, it is also possible to apply the present disclosure to a developing device in which the disposition of the developing roller31and the toner supplying roller30is opposite to that in the above embodiments as illustrated inFIG. 15. In this developing device, toner is supplied to each of the photosensitive drums1ato1dby means of a magnetic brush formed of the two-component developer and held on the surface of the developing roller31(which, in the present configuration, is a magnetic roller similar to the toner supplying roller30in the above embodiments). Then, toner held on the surface of the toner supplying roller30(which, in the present configuration, is configured similar to the developing roller31of the above embodiments) is supplied to the developing roller31, and excessive toner remaining on the surface of the developing roller31is collected by means of the toner supplying roller30. With this configuration, too, it is possible to effectively reduce an amount of toner fallen from the developing roller31and accumulating around the regulation blade33facing the toner supplying roller30.

The present disclosure is applicable to a developing device having a toner receiver member that faces a developing roller between a regulation blade and an opposing region of an image carrier and the developing roller. With use of the present disclosure, it is possible to provide a developing device capable of improving performance of recovering toner accumulated at each end part of a toner receiver member in a longitudinal direction thereof with a simple configuration, and an image forming apparatus provided with such a developing device.