DEVELOPING DEVICE AND IMAGE FORMING APPARATUS THEREWITH

A developing device includes a developer container, a developer carrier, and a stirring/conveying member. The developer container includes: a lower housing having a first accommodating portion and a first edge portion formed in a top end portion of it; and an upper housing having a second accommodating portion and a second edge portion formed in a bottom end portion of it. The first edge portion has a depression extending along the first edge portion, a first contact face formed inward of the depression, and a first opposite face formed outward of the depression. The second edge portion has an elevation inserted in the depression, a second contact face making contact with the first contact face, and a second opposite face facing the first opposite face. When the first and second contact faces are in contact, the first and second opposite faces face each other across a predetermined interval.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2023-040523 filed on Mar. 15, 2023, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a developing device that stores developer containing toner and that develops latent images using the toner, and to an image forming apparatuses incorporating such a developing device.

Known developing devices used in image forming apparatuses employing electrophotography, such as copiers, printers, facsimile machines, and multifunction peripherals incorporating their functions, include those of a two-component development system that use a two-component developer containing toner and carrier, and those of a one-component development system that use a one-component developer containing toner alone. A developer container for storing developer is generally structured to include a lower housing that is open at the top and an upper housing (cover portion) that seals the opening in the lower housing. The upper housing is fixed to the lower housing with screws or adhesive.

When the upper and lower housings are bonded together with adhesive, the adhesive can overflow into the developer container. In this case, adhesive that has set in the developer container can, inconveniently, interfere with the rotation of a stirring/conveying member that stirs and conveys developer.

SUMMARY

According to one aspect of the present disclosure, a developing device includes a developer container, a developer carrier, and a stirring/conveying member. The developer container stores developer containing toner. The developer carrier is rotatably supported on the developer container, and carries developer on its outer circumferential face. The stirring/conveying member is rotatably supported in the developer container to stir and convey the developer stored in the developer container. The developer container includes: a lower housing that has a first accommodating portion concave so as to be open at the top and a first edge portion formed in a top end portion of the first accommodating portion; and an upper housing that is arranged above the lower housing and that has a second accommodating portion concave so as to be open at the bottom and a second edge portion formed in a bottom end portion of the second accommodating portion and placed on the first edge portion. The first edge portion has a depression that extends along the first edge portion and that is open at the top, a first contact face that is formed inward of the depression, and a first opposite face that is formed outward of the depression. The second edge portion has an elevation that is inserted in the depression, a second contact face that makes contact with the first contact face, and a second opposite face that faces the first opposite face. Of the developer container, at least the depression and the elevation are bonded together with adhesive. When the first and second contact faces are in contact with each other, the first and second opposite faces face each other across a predetermined interval.

DETAILED DESCRIPTION

Hereinafter, with reference to the accompanying drawings, embodiments of the present disclosure will be described.FIG.1is a schematic sectional view of an image forming apparatus mounted with a developing device according to one embodiment of the present disclosure. Here, a tandem-type color printer is illustrated. In the main body of the color printer100, four image forming portions, Pa, Pb, Pc and Pd are arranged in this order from the upstream side in the conveying direction (from the left side inFIG.1). These image forming portions Pa to Pd are provided so as to correspond to images of four different colors (yellow, magenta, cyan, and black) and sequentially form yellow, magenta, cyan, and black images through the processes of electrostatic charging, exposure, development, and transfer.

In these image forming portions Pa to Pd, photosensitive drums1a,1b,1c, and1dare respectively arranged which carry visible images (toner images) of the different colors. Furthermore, an intermediate transfer belt8which rotates counter-clockwise inFIG.1is provided adjacent to the image forming portions Pa to Pd. The intermediate transfer belt8is stretched around a tension roller10on the upstream side and a driving roller11on the downstream side. Downstream of the image forming portion Pd in the rotation direction of the intermediate transfer belt8, a blade-form belt cleaner19is arranged so as to face the driving roller11across the intermediate transfer belt8.

When image data is fed in from a host device such as a personal computer, first, a main motor (not shown) starts rotating the photosensitive drums1ato1d, and charging devices2ato2delectrostatically charge the surfaces of the photosensitive drums1ato1duniformly. Next, an exposure device5irradiates the photosensitive drums1ato1dwith light based on the image data to form on them electrostatic latent images reflecting the image data. A predetermined amount of two-component developer containing yellow, magenta, cyan, and black toner is charged to developing devices3ato3dfrom toner containers4ato4d. The developing devices3ato3dfeed the photosensitive drums1ato1dwith toner in the developer, which electrostatically adheres to the photosensitive drums1ato1d. In this way, toner images corresponding to the electrostatic latent images formed through exposure to light from the exposure device5are formed.

Then, by primary transfer rollers6ato6d, electric fields with a predetermined transfer voltage are applied between the primary transfer rollers6ato6dand the photosensitive drums1ato1d, and the yellow, magenta, cyan, and black toner images on the photosensitive drums1ato1dare primarily transferred to the intermediate transfer belt8. Toner and the like left on the surface of the photosensitive drums1ato1dafter the primary transfer is removed by cleaning devices7ato7d.

The transfer sheet P to which toner images are to be transferred is stored in a sheet cassette16arranged in a lower part of the color printer100and is conveyed via a sheet feeding roller12aand a pair of registration rollers12bto, with predetermined timing, a nip (secondary transfer nip) between a secondary transfer roller9provided adjacent to the intermediate transfer belt8and the intermediate transfer belt8. The transfer sheet P on which the toner images have been secondarily transferred is conveyed to a fixing portion13.

The transfer sheet P conveyed to the fixing portion13is heated and pressed by a pair of fixing rollers13a, and thereby the toner images are fixed on the surface of the transfer sheet P to form a predetermined full-color image. The transfer sheet P on which a full-color image has been formed is directly (or after being directed to a reversing conveying passage18by a branch portion14to have images formed on both its faces) discharged to a discharge tray17by a pair of discharge rollers15.

FIG.2is a side cross-sectional view the developing device3aincorporated in the color printer100. The following description deals with, as an example, the developing device3aarranged in the image forming portion Pa inFIG.1. The developing devices3bto3darranged in the image forming portions Pb to Pd have a structure basically similar to that of the developing device3a, and thus no overlapping description will be repeated.

As shown inFIG.2, the developing device3aincludes a developer container20that stores two-component developer (hereinafter also referred to simply as developer) containing magnetic carrier and toner. The developer container20is partitioned into a first conveying chamber20cand a second conveying chamber20dby a partition wall20b. In the first conveying chamber20cand the second conveying chamber20d, there are respectively rotatably arranged a stirring/conveying screw22and a feeding/conveying screw23which mix the toner fed from the toner container4a(seeFIG.1) with magnetic carrier and which stir the mixture and thereby electrostatically charge the toner in the mixture.

Then, the developer is, while being stirred by the stirring/conveying screw22and the feeding/conveying screw23, conveyed in the axial direction (the direction perpendicular to the plane ofFIG.2) and, via communication portions (not shown) formed in opposite end parts of the partition wall20b, circulates between the first conveying chamber20cand the second conveying chamber20d. Thus, the first conveying chamber20c, the second conveying chamber20d, and the communication portions form a circulation passage for developer inside the developer container20.

The developer container20extends obliquely to the upper right inFIG.2. To the upper right of the feeding/conveying screw23in the developer container20, a developing roller21is arranged. Part of an outer circumferential face of the developing roller21is exposed through an opening20ain the developer container20so as to face the photosensitive drum1aacross a predetermined interval (developing gap). The developing roller21rotates counter-clockwise inFIG.2(rotates so as to be trailed at a position opposite the photosensitive drum1a).

The developing roller21is composed of a cylindrical developing sleeve which rotates counter-clockwise inFIG.2and a magnet (not shown) which is fixed inside the developing sleeve and has a plurality of magnetic poles. Although a developing sleeve with a knurled surface is used here, any other developing sleeves can instead be used such as one with a number of recesses (dimples) formed on the surface, one with a blasted surface, or even one subjected to, in addition to knurling and recess formation, blasting or plating. The developing roller21is fed with, from a developing voltage power supply via a voltage control circuit (none of these are illustrated), a developing voltage having an alternating-current voltage superposed on a direct-current voltage.

To the developer container20, a regulating blade27is fixed along the longitudinal direction of the developing roller21(in the direction perpendicular to the plane ofFIG.2). A small gap is formed between a tip end portion of the regulating blade27and the outer circumferential face of the developing roller21. In this embodiment, as the regulating blade27, a stainless steel (SUS430) magnetic blade is used.

On the side face of the first conveying chamber20c, a toner concentration sensor29is arranged so as to face the stirring/conveying screw22. The toner concentration sensor29senses the concentration of toner in the developer (the mixture ratio of toner to carrier in the developer; T/C) in the developer container20. Used as the toner concentration sensor29is, for example, a magnetic permeability sensor which senses the magnetic permeability of the two-component developer containing toner and magnetic carrier inside the developer container20. According to the concentration of toner sensed by the toner concentration sensor29, the toner in the toner container4a(seeFIG.1) is supplied through a developer supply port (not shown) into the developer container20.

With a magnetic field generated between a regulating pole of the magnet and the regulating blade27in such a direction as to attract each other, a magnetic brush comprising chains of developer is formed between the regulating blade27and the developing roller21. While the magnetic brush passes the regulating blade27, its layer thickness is restricted to a desired height. Then, as the developing roller21rotates counter-clockwise, the magnetic brush is conveyed to a region (developing region) where the developing roller21and the photosensitive drum1aface each other. Then, a magnetic field is applied by the main pole of the magnet and the photosensitive drum1asuch that these attract each other, and thus the magnetic brush makes contact with the surface of the photosensitive drum1ato develop an electrostatic latent image.

When the developing roller21rotates further counter-clockwise, a magnetic field along the outer circumferential face of the developing roller21is now applied by a conveying pole of the magnet, and the magnetic brush is, together with the developer unused in toner image formation, collected onto the developing roller21. Furthermore, by a peeling pole having a polarity different from that of the conveying pole, the magnetic brush separates from the developing roller21to fall into the second conveying chamber20d. Then, after the developer is stirred and conveyed by the feeding/conveying screw23, a magnetic brush is again formed on the developing roller21by the magnetic field of the regulating pole.

FIG.3is a cross-sectional side view of the developer container20of the first embodiment used in the developing devices3ato3d, in a state separated into a lower housing30and an upper housing40.FIG.4is a part cross-sectional view of a first edge portion33of the lower housing30and a second edge portion43of the upper housing40in a state joined together. As shown inFIG.3, the developer container20includes the lower housing30and the upper housing40. The lower housing30and the upper housing40are formed of synthetic resin by injection molding.

In the lower housing30, a first accommodating portion31is formed that is concave so as to be open at the top and that extends in the longitudinal direction of the developer container20(the direction perpendicular to the plane ofFIG.3). The cross-section of the first accommodating portion31has a shape of two semicircular sections arrayed in the left-right direction, and, in the middle of it in the width direction perpendicular to the longitudinal direction, the partition wall20bis formed along the longitudinal direction. On opposite sides of the partition wall20b, the stirring/conveying screw22and the feeding/conveying screw23(seeFIG.2) are arranged respectively. That is, the first accommodating portion31constitutes the lower half of the first conveying chamber20cand the second conveying chamber20d.

On opposite ends of the lower housing30in the longitudinal direction, a pair of first bearing supporting portions32is formed in which are fitted bearings on the stirring/conveying screw22and the feeding/conveying screw23. In a top end portion (circumferential portion) of the first accommodating portion31, the first edge portion33is formed. In an upper part of the first edge portion33excluding the first bearing supporting portion32, a depression50that is open at the top is formed so as to extend along the first edge portion33.

In the upper housing40, a second accommodating portion41is formed that is concave so as to be open at the bottom and that extends along the developer container20in its longitudinal direction. In opposite end parts of the upper housing40in the longitudinal direction, a pair of second bearing supporting portions42is formed in which are fitted bearings on the stirring/conveying screw22and the feeding/conveying screw23. The second bearing supporting portions42, together with the first bearing supporting portions32, support the bearings on the stirring/conveying screw22and the feeding/conveying screw23. The second accommodating portion41constitutes the upper half of the first conveying chamber20cand the second conveying chamber20d.

Over one of the second bearing supporting portions42(the right one inFIG.3), a third bearing supporting portion44is formed in which is fitted a bearing on the developing roller21(seeFIG.2). To the right of the third bearing supporting portion44, an opening20ais formed. In a bottom end portion (circumferential portion) of the second accommodating portion41, the second edge portion43is formed. On a bottom part of the second edge portion43excluding the bearing supporting portion42, an elevation60is formed which extends along the second edge portion43so as to project downward.

As shown inFIG.4, in a part of the first edge portion33inward of the depression50(to its left inFIG.4), a first contact face51is formed. In a part of the first edge portion33outward of the depression50(to its right inFIG.4), a first opposite face52is formed. The depression50has an inner side face50a(a side face close to the first contact face51), an outer side face50b(a side face close to the first opposite face52), and a bottom face50c.

The elevation60is inserted in the depression50in the first edge portion33when the second edge portion43is placed on the first edge portion33. In a part of the second edge portion43inward of the elevation60, a second contact face61is formed which makes contact with the first contact face51. In a part of the second edge portion43outward of the elevation60, a second opposite face62is formed which faces the first opposite face52. The elevation60has an inner side face60a(a side face close to the second contact face61), an outer side face60b(a side face close to the second opposite face62), and a bottom face60c.

When the first edge portion33of the lower housing30is placed on the second edge portion43of the upper housing40, the first contact face51makes contact with the second contact face61. On the other hand, the depression50does not make contact with the elevation60, and a gap is formed between the depression50and the elevation60. The first opposite face52and the second opposite face62face each other across a predetermined interval.

FIG.5is a part cross-sectional view showing how, with adhesive G applied to the depression50in the first edge portion33, the elevation60on the second edge portion43is inserted in it. To assemble the developer container20, first, with the bearings on the stirring/conveying screw22and feeding/conveying screw23fitted in the first bearing supporting portions32in the lower housing30, adhesive G is applied to the depression50in the first edge portion33.

As shown inFIG.5, the second edge portion43of the upper housing40is placed on the first edge portion33of the lower housing30. At this time, the elevation60on the second edge portion43is inserted in the depression50in the first edge portion33, and adhesive G is pushed inward and outward along the inner side face50aand the outer side face50bof the depression50as well as along the inner side face60aand the outer side face60bof the elevation60. This spreads wet adhesive G across the entire surface of the depression50and the elevation60, and the first edge portion33of the lower housing30and the second edge portion43of the upper housing40are firmly bonded together.

In this embodiment, as shown inFIG.4, when the first contact face51inward of the depression50makes contact with the second contact face61inward of the elevation60, the first opposite face52outward of the depression50faces the second opposite face62outward of the elevation60across a predetermined interval. That is, a space is formed between the first opposite face52and the second opposite face62.

With this structure, even if an excessive amount of adhesive G is applied to the depression50, adhesive G is likely to be pushed outward of the depression50(toward the first opposite face52and the second opposite face62) where a larger space is available. Thus, adhesive G is less likely to overflow into the developer container20(toward the first contact face51and the second contact face61), and this makes it possible to prevent the adhesive that has overflowed into and solidified in the developer container20from causing failure of the rotation of the stirring/conveying screw22and the feeding/conveying screw23.

To make it easy for adhesive G to be pushed outward of the depression50, it is preferable that the interval d1between the first opposite face52and the second opposite face62be equal to or larger than one-half of the depth d2of the depression50.

The inner side face50aand the outer side face50bof the depression50as well as the inner side face60aand the outer side face60bof the elevation60are inclined faces that are inclined in directions away from each other upward. In this way, when the second edge portion43is placed on the first edge portion33, the elevation60is easily guided into the depression50along the inclined faces. This eases the assembly of the developer container20.

FIG.6is a part cross-sectional view of the developer container20in a modified example of the first embodiment, showing a state where the first edge portion33of the lower housing30and the second edge portion43of the upper housing40are joined together. In the modified example shown inFIG.6, the depression50has no outer side face50b, and the bottom face50cof the depression50is flush with the first opposite face52. That is, the interval between the first opposite face52and the second opposite face62equals the depth of the depression50. In other respects, the structure of the developer container20here is similar to that in the first embodiment shown inFIG.4.

With the structure inFIG.6, the space between the first opposite face52and the second opposite face62(outward of the depression50) is even larger than inFIG.4; thus, adhesive G pressed out by the elevation60spreads outward of the depression50even more easily.

FIG.7is a part cross-sectional view of a developer container20of a second embodiment used in the developing devices3ato3d, showing a state where the first edge portion33of the lower housing30and the second edge portion43of the upper housing40are joined together. In this embodiment, the first opposite face52of the first edge portion33makes contact with the second opposite face62of the second edge portion43. The space between the depression50and the elevation60is larger outward of the elevation60(between the outer side faces50band60b) than inward of the elevation60(between the inner side faces50aand60a).

With the structure inFIG.7, even if an excessive amount of adhesive G is applied to the depression50, adhesive G is likely to be pushed outward of the elevation60(between the outer side faces50band60b) where a larger space is available. Thus, as in the first embodiment, adhesive G is less likely to overflow into the developer container20, and this makes it possible to prevent adhesive that has overflowed into and solidified in the developer container20from causing failure of the rotation of the stirring/conveying screw22and the feeding/conveying screw23.

To make it easier for adhesive G to be pushed outward of the elevation60, it is preferable that the volume of the space outward of the elevation60(between the outer side faces50band60b) be at least twice the volume of the space inward of the elevation60(between the inner side faces50aand60a).

The first opposite face52makes contact with the second opposite face62; thus, no space is formed between the first and second edge portions33and43. Thus, as seen from the side of the developer container20, adhesive that has overflowed outward of the depression50is not visible, and this improves the appearance and design of the assembled developer container20.

The embodiments described above are in no way meant to limit the present disclosure, which thus allow for many modifications and variations within the spirit of the present disclosure. For example, while the above description deals with developing devices3ato3dof a two-component development system using a two-component developer containing magnetic carrier and toner as shown inFIG.2, the present disclosure is also applicable to developing devices of a one-component development system using a one-component developer containing magnetic toner or non-magnetic toner alone.

While the above embodiments deal with, as an example, a color printer100of a tandem type as an image forming apparatus incorporating the developing devices3ato3d, needless to say, the present disclosure can be applied also to, for example, monochrome or color copiers, digital multifunction peripherals, monochrome printers, and the facsimile machines.

The present disclosure is applicable to developing devices that accommodate developer containing toner and that develop latent images using the toner. Based on the present disclosure, it is possible to provide a developing device that can effectively suppress an overflow of adhesive into a developer container when the lower housing and upper housing of the developer container are fixed together by bonding, as well as to provide an image forming apparatus incorporating such a developing device.