Regulating member and developing device

A regulating member for regulating a layer thickness of a developer includes a base portion, a regulating portion extending along a longitudinal direction of the base portion and projecting from a first surface of the base portion to regulate a layer thickness of a developer, and a rib formed along the longitudinal direction and configured to project from a second surface opposite from the first surface of the base portion. In addition, a through hole structure is provided at each end of the base portion with respect to the longitudinal direction, and configured with a through hole that passes through the base portion. The rib is provided adjacently to each through hole with respect to a direction perpendicular to the longitudinal direction, and the rib stands along each through hole in a cross-section which crosses the through hole and is perpendicular to the longitudinal direction of the base portion.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a regulating member, including a layer thickness regulating portion for regulating a layer thickness of a developer carried on a developer carrying member, extended between bearing members for supporting the developer carrying member at end portions of the developer carrying member, and relates to a developing device including the regulating member. Specifically, the present invention relates to a structure in which an opposing gap between the developer carrying member and an image bearing member is visible.

An image forming apparatus in which an electrostatic image is developed by the developing device to form a toner image on the image bearing member, and the toner image on the image bearing member is transferred onto a recording material directly or via an intermediary transfer member, and then the toner image is fixed as an image on the recording material by heating and pressing the recording material to which the toner image is transferred has been widely used. The developing device regulates the layer thickness of the developer, carried on the developer carrying member, at a constant level by a layer thickness regulating member (doctor blade) with rotation of the developer carrying member, and feeds the developer subjected to the layer thickness regulation to an opposing portion to the image bearing member with rotation of the developer carrying member.

When the developer passes through an opposing gap between the layer thickness regulating member and the developer carrying member and is subjected to the layer thickness regulation, the layer thickness regulating member is deformed toward a direction the layer thickness regulating member is moved away from the developer carrying member by being subjected to application of pressure of the developer. In the case where the layer thickness regulating member is mounted relative to the developer carrying member while being extended between bearing members for supporting the developer carrying member at end portions of the developer carrying member, a longitudinal central portion of the layer thickness regulating member is moved away from the developer carrying member, so that there is a possibility that the layer thickness of the developer is larger at the longitudinal central portion than at longitudinal end portions. With downsizing of the image forming apparatus, when section modulus of the regulating member becomes small, a degree of flexure (bending) of the regulating member supported at the longitudinal end portions becomes large, so that a difference in developer layer thickness between the longitudinal central portion and each of the longitudinal end portions further becomes large.

In Japanese Laid-Open Patent Application (JP-A) 2002-214886, a layer thickness regulating member formed of a metal plate is provided with ribs by a drawing process, so that the section modulus of the layer thickness regulating member is enhanced. In JP-A 2009-175360, a supporting portion for a layer thickness regulating member is added to a longitudinal central portion where a degree of flexure of the layer thickness regulating member supported at longitudinal end portions is liable to increase, so that the degree of flexure of the layer thickness regulating member as a whole is decreased.

In JP-A 2012-247757, a layer thickness regulating member for regulating a layer thickness on a developer carrying member is fixed to a beam portion extended in a beam shape between a pair of supporting portions for rotatably supporting the developer carrying member at end portions of the developer carrying member, so that a degree of flexural stress acting on the layer thickness regulating member is alleviated compared with those in JP-A 2002-214886 and JP-A 2009-175360. In JP-A 2012-247757, the developer carrying member, the pair of supporting portions and the layer thickness regulating member are integrally assembled into a unit, and the units is detachably mounted to a developing device.

A gap (spacing) where the image bearing member and the developer carrying member oppose each other is an important parameter largely relating to a developing performance of the developing device. When the developer carrying member is obliquely assembled with the image bearing member, a difference in developing performance is generated between end portions of the developer carrying member with respect to a rotational axis direction of the developer carrying member, so that an image density largely varies. Even when the developer carrying member is assembled in parallel with the developer carrying member, if an interval (distance) of the gap between the image bearing member and the developer carrying member varies every developing device, the image density of an output image for each of the image forming apparatuses changes. For that reason, in the image forming apparatus, after the developer carrying member is assembled with the image bearing member, the interval of the gap between the image bearing member and the developer carrying member is required to be measured and adjusted to a standard value.

Incidentally, for example, as described in JP-A 2012-247757, in a constitution in which the developer carrying member, the pair of supporting portions, the beam portion and the layer thickness regulating member are exchangeable (replaceable) as a unit, it was proposed that the number of components was reduced by integrally assembling the layer thickness regulating member with the beam portion from the start. A constitution in which a layer thickness regulating portion as a separate member is fixed in advance to the beam portion to be extended between the supporting portions for supporting the end portions of the developer carrying member and a constitution in which the layer thickness regulating portion and the beam portion are integrally formed of the same material are employed (FIG. 8).

In these cases, in order to enhance flexural rigidity of the member obtained by integrally assembling the beam portion and the layer thickness regulating portion into a unit, it would be considered that a cross-section of the beam portion (member) is expanded toward the image bearing member along a cross-section perpendicular to an axis (shaft) of the developer carrying member. In this case, it would be considered that an overhang-like portion, of the layer thickness regulating portion, expanded toward the image bearing member covers the gap between the developer carrying member and the image bearing member, so that it is difficult to observe a state of the gap after the assembling.

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide a regulating member permitting visual recognition of a gap (interval) between an image bearing member and a developer carrying member from an outside in an assembled state even in the case where a cross-section thereof is expanded to a close position to the image bearing member.

Another object of the present invention is to provide a developing device including the regulating member.

According to an aspect of the present invention, there is provided a regulating member for regulating a layer thickness of a developer carried on a developer carrying member, comprising: a regulating portion for regulating the layer thickness of the developer carried on the developer carrying member; an opposing portion provided integrally with the regulating portion at an opposing position to the developer carrying member, wherein the opposing portion is provided so as to cover a rectilinear line passing through a developing gap formed, when the regulating member is mounted relative to the developer carrying member, with a predetermined interval between the developer carrying member and an image bearing member on which a latent image to be developed by the developer carrying member is formed; and an opening provided on the rectilinear line passing through the developing gap at the opposing portion.

According to another aspect of the present invention, there is provided a developing device comprising: a developer carrying member for carrying a developer; a regulating member for regulating a layer thickness of the developer carried on the developer carrying member; an opposing portion provided integrally with the regulating member at an opposing position to the developer carrying member, wherein the opposing portion is provided so as to cover a rectilinear line passing through a developing gap formed, when the regulating member is mounted relative to the developer carrying member, with a predetermined gap between the developer carrying member and an image bearing member on which a latent image to be developed by the developer carrying member; an opening provided on the rectilinear line passing through the developing gap of the opposing portion; a casing including an accommodating space for accommodating the developer carrying member and the regulating member in an integrally assembled state; an adjusting mechanism capable of adjusting a distance between a center of the image bearing member and a center of the developer carrying member; and a cap member, connected with the casing, capable of opening a part of the accommodating space, wherein the predetermined gap is visible through the opening from an opening portion of the casing from which the cap member is dismounted.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1is an illustration of a structure of an image forming apparatus100. As shown inFIG. 1, the image forming apparatus100is an intermediary transfer type full color printer of a tandem type in which image forming portions60Y,60M,60C and60Bk are arranged along a downward surface of an intermediary transfer belt61.

At the image forming portion60Y, a yellow toner image is formed on a photosensitive drum1Y and then is transferred onto the intermediary transfer belt61. At the image forming portion60M, a magenta toner image is formed on a photosensitive drum1M and then is transferred onto the intermediary transfer belt61. At the image forming portions60C and60Bk, cyan and black toner images are formed on photosensitive drums1C and1Bk, respectively, and then are transferred onto the intermediary transfer belt61.

The four color toner images transferred on the intermediary transfer belt61are conveyed to a secondary transfer portion T2 and are secondary-transferred onto the recording material S. A separation roller63separates sheets of the recording material S, one by one, pulled out from a recording material cassette62, and then feeds the recording material S to a registration roller pair65. The registration roller pair65sends the recording material S to the secondary transfer portion T2 while being timed to the toner images on the intermediary transfer belt61. The recording material P on which the four color toner images are secondary-transferred is pressed and heated by a fixing device9, so that the toner images are fixed on a surface of the recording material S.

In the case of one-side image formation, the recording material S on which surface the toner image is fixed is discharged onto an upper tray601through a discharging roller69. On the other hand, in the case of double-side image formation, the recording material S is fed until a trailing end thereof passes through a switching flapper602, and thereafter a leading end and the trailing end are changed and the recording material S is fed to a feeding path603again by a feeding roller pair604. Then, the recording material S is fed to the secondary transfer portion T2 by the registration roller pair65, and then image formation on the back surface of the recording material S is carried out.

The image forming portions60Y,60M,60C and60Bk have the substantially same constitution except that colors of toners used in developing devices3are yellow, magenta, cyan and black, respectively, which are different from each other. In the following, the image forming portion60Bk is described, and redundant explanation about other image forming portions60Y,60M and60C will be omitted.

The image forming portion60Bk includes, at a periphery of the photosensitive drum1Bk, a charging device2, an exposure device68, the developing device3, a transfer roller4and a drum cleaning device5. The photosensitive drum1Bk is prepared by forming a photosensitive layer on an outer peripheral surface of an aluminum cylinder, and is rotated at a predetermined process speed.

The charging device2electrically charges a surface of the photosensitive drum1Bk to a negative potential uniformly by applying, to a charging roller rotated by the photosensitive drum1Bk, an oscillating voltage in the form of a negative(-polarity) DC voltage biased with an AC voltage. The exposure device68scans the surface of the photosensitive drum1K with a laser beam, obtained by ON-OFF modulation of a scanning line image signal developed from an associated color image, through a rotating mirror, so that an electrostatic image for an image is written (formed) on the surface of the photosensitive drum1Bk. The developing device3develops the electrostatic image into a toner image by transferring the toner onto the photosensitive drum1Bk. A fresh toner in an amount corresponding to an amount of the toner consumed in the developing device3by image formation is supplied from a toner cartridge605, set in the image forming apparatus100, to the developing device3via an unshown toner feeding path.

The transfer roller4presses the intermediary transfer belt61to form a transfer portion between the photosensitive drum1Bk and the intermediary transfer belt61. By applying a positive DC voltage to the transfer roller4, the negative toner image carried on the photosensitive drum1Bk is transferred onto the intermediary transfer belt61. The drum cleaning device5removes a transfer residual toner deposited on the surface of the photosensitive drum1Bk by sliding a cleaning blade on the surface of the photosensitive drum1Bk.

The intermediary transfer belt61is extended around and supported by a tension roller6, a driving roller66also functioning as a secondary transfer opposite roller, and stretching rollers7aand7b, and is driven by the driving roller66to be rotated in an arrow C direction. A secondary transfer roller67contacts the intermediary transfer belt61supported at an inside surface thereof by the driving roller66to form the secondary transfer portion T2. By applying a positive DC voltage to the secondary transfer roller67, the toner image on the intermediary transfer belt61is transferred onto the recording material S. A belt cleaning device8collects the transfer residual toner on the surface of the intermediary transfer belt61by rubbing the intermediary transfer belt61with a cleaning blade.

As shown inFIG. 2, a developing sleeve70as an example of a developer carrying member carries the developer and rotates with a predetermined gap from the photosensitive drum1as an example of an image bearing member. A developing container30as an example of a casing includes an accommodating space for accommodating a developing sleeve70, sleeve bearing members11aand11band a regulating member37in an integrally assembled state. A cover76as an example of a cap member is connected with the developing container30by using screws77, and thus is capable of opening a part of the accommodating space.

As shown inFIG. 3, with respect to the sleeve bearing members11aand11bas an example of a supporting member and the regulating member37, the sleeve bearing members11aand11bas an example of a pair of bearing members rotatably support the developing sleeve70at end portions. An opening80is positioned outside a developing region (image formable region) and is disposed so as to oppose an SD gap at each of end portions of the regulating member37.

As shown in (a) ofFIG. 4, the regulating member37as an example of a regulating member includes a layer thickness regulating portion36for regulating a layer thickness of the developer carried on the developing sleeve70, and is fixed to the sleeve bearing members11aand11bat end portions thereof. The layer thickness regulating portion36is integrally formed with the regulating member37by using the same material. The regulating member37has a cross-section shape, expanded (extended) toward a downstream side of the layer thickness regulating portion36with respect to a rotational direction of the developer carrying member, so as to cover the above-described predetermined gap in a cross-section perpendicular to an axis of the developing sleeve70.

As shown in (b) ofFIG. 4, the regulating member37as an example of at least one of the bearing member and the regulating member is provided with the opening80, as an example of an opening, formed so as to permit penetration therethrough of a phantom rectilinear line passing through the predetermined gap. The opening80is formed at a portion where the cross-section shape of the regulating member37is extended toward the downstream side of the rotational direction of the developer carrying member. From an opening portion of the developing container30(FIG. 2) from which the cover76(FIG. 2) is removed, the predetermined gap is visible (visually recognizable) through the opening80.

As shown inFIG. 5, the image forming portion60Bk (FIG. 1) as an example of a process cartridge includes an adjusting ring53as an example of an adjusting mechanism. The adjusting ring53is capable of individually adjusting a distance between a center of the developing sleeve70and a center of the photosensitive drum1at each of the end portions of the developing sleeve70.

FIG. 2is an illustration of a structure of the developing device3in Embodiment 1. As shown inFIG. 2, in the developing device3, a two-component developer containing a (non-magnetic) toner and a (magnetic) carrier in mixture is used to visualize the electrostatic image on the photosensitive drum1Bk. The developing device3electrically charges the developer stored in the developing container30, and then develops the electrostatic image on the photosensitive drum1Bk into the toner image while carrying the charged developer on the surface of the developing sleeve70.

The developing device3includes the developing sleeve70at an opening toward the photosensitive drum1Bk. The developing sleeve70is supported rotatably relative to the developing container30at end portions thereof. Below the developing sleeve70, a first feeding screw33and a second feeding screw34are provided. The developing sleeve70and the first and second feeding screws33and34are rotationally driven integrally by being connected with gear trains provided at associated shaft ends outside the developing container30.

The developing container30is partitioned into a first feeding chamber31and a second feeding chamber32by a partition wall30h. The first and second feeding chambers31and32communicate with each other through an opening, of the partition wall30h, formed at each of longitudinal end portions of the partition wall30h. The first feeding screw33is disposed in the first feeding chamber31, and the second feeding screw34is disposed in the second feeding chamber32. By driving the first and second feeding screws33and34, the developer is delivered through the openings of the partition wall30h, so that the developer is circulated between the first and second feeding chambers31and32. In a process in which the developer is fed while being stirred by the first and second feeding screws33and34, the carrier and the toner in the developer are triboelectrically charged to the positive polarity and the negative polarity, respectively.

The developing sleeve70is supported rotatably around a magnet portion71supported non-rotatably, and opposes the second feeding screw34with respect to a circumferential direction. The second feeding screw34supplies the developer to the developing sleeve70while feeding the developer in the second feeding chamber32. The developer supplied from the second feeding screw34is carried on the surface of the developing sleeve70by a magnetic force of the magnet portion71and is fed in an arrow D direction.

The magnet portion71generates a desired magnetic field for magnetically carrying the developer on the surface of the developing sleeve70by forming a desired magnetic pattern on the surface of the rotating developing sleeve70. Magnetic poles of the magnet portion71are fixed at predetermined phase positions with respect to the circumferential direction and are supported non-rotatably, and therefore magnetic pole patterns of the magnet portion71are fixed at predetermined phases with respect to the circumferential direction. Around the magnet portion71, only a sleeve pipe72constituting an outer shell of the developing sleeve70is supported rotatably. The carrier and the toner in the developer are carried in an erected chain shape on the surface of the developing sleeve70in a deposited state by triboelectric charge at associated magnetic polarity positions of the magnet portion71.

The layer thickness regulating member (sleeve holder frame)37is disposed so that a free end of the layer thickness regulating portion36opposes the surface of the developing sleeve70. The erected chain-shaped developer deposited by the magnetic field of the developing sleeve70is carried and fed toward the layer thickness regulating portion36. A gap between the free end surface of the layer thickness regulating portion36and the surface of the developing sleeve70is set in a desired range, and therefore the erected chain-shaped developer forms a uniform thickness coating layer by passing through the layer thickness regulating portion36.

As shown inFIG. 1, each of the image forming portions60Y,60M,60C and60Bk is the process cartridge, as an exchangeable (replaceable) unit for the associated one of the colors, obtained by integrally assembling constituent images from which the exposure device68and the transfer roller4are removed. Each of the image forming portions60Y,60M,60C and60Bk is detachably mounted to an apparatus main assembly frame of the image forming apparatus100. The transfer roller4is incorporated in an intermediary transfer unit including an intermediary transfer belt61. The image forming portion60Bk including the developing device3is integrally constituted as a unit and is made detachably mountable to the image forming apparatus100.

Incidentally, depending on the image forming apparatus, a drum cleaning device5is constituted as an independent exchangeable unit is some cases. There is also the case where the drum cleaning device5and the charging device2are constituted as an independent exchangeable unit, and the photosensitive drum1Bk and the developing device3are constituted as a single process cartridge.

FIG. 3is an illustration of a structure of a sleeve holder unit in Embodiment 1. InFIG. 4, (a) and (b) are illustrations of an assembled state of the sleeve holder unit and the photosensitive drum. InFIG. 4, (a) shows an operation during image formation in a cross-section in an image region, and (b) shows an operation during the image formation in a cross-section in a region outside the image region.

As shown inFIG. 2, the regulating member (sleeve holder frame)37uniformizes the layer thickness of the developer on the surface of the developing sleeve70and thus realizes stable developer supply onto the photosensitive drum1Bk. The regulating member37integrally includes a developer rectifying portion35and the layer thickness regulating portion36, and causes a free end portion of the layer thickness regulating portion36to oppose the surface of the developing sleeve70. The developer rectifying portion35functions as a guide at the time of feeding the developer in the upstream side of the layer thickness regulating portion36, and guides the developer, deposited on the surface of the developing sleeve70and carried by the developing sleeve70, to the opposing interval (gap) between the developing sleeve70and the layer thickness regulating portion36while placing the developer in a substantially uniform pressure state with respect to a longitudinal direction. The layer thickness regulating portion36cuts a magnetic chain of the developer, deposited on the surface of the developing sleeve70, in a predetermined length. The magnetic chain of the developer formed by the magnetic field of the developing sleeve70constitutes a coating layer having a uniform thickness by passing through the opposing interval (SB gap G shown inFIG. 4) between the developing sleeve70and the layer thickness regulating portion36.

As shown inFIG. 3, the developing sleeve70, the sleeve bearing members11aand11band the regulating member37which are formed as separate members are adjusted and assembled to constitute a sleeve holder unit10. The regulating member37supports the developing sleeve70by the sleeve bearing members11aand11bprovided at end portions thereof.

The regulating member37is formed of a metal material, such as aluminum, which is non-magnetic and which has strength. At the end portion of the regulating member37is a front side, the sleeve bearing member11aincluding a bearing for supporting rotatably the front-side end portion of the developing sleeve70is fixed by welding. At the end portion of the regulating member37in a rear side, the sleeve bearing member11bincluding a bearing for supporting rotatably the rear-side end portion of the developing sleeve70is fixed by welding. The developing sleeve70is rotatably supported by the sleeve bearing members11aand11b.

As shown in (a) ofFIG. 4, a gap at a closest portion where the developing sleeve70and the layer thickness regulating portion oppose each other is referred to as a SB gap G. The SB gap G is defined at the free end portion of the layer thickness regulating portion36, and is required to be set in a desired range in order to obtain an optimum developed image density. With respect to the SB gap G, accuracy of about ±30-50 μm is required to be ensured over an entire longitudinal direction. Further, longitudinal straightness of a regulating surface of the layer thickness regulating portion36is required to be ensured with accuracy of, e.g., 30 μm or less in order to uniformize a coating amount of the developer on the surface of the developing sleeve70. Further, the regulating member37is required to have sufficient rigidity such that the regulating member37is not flexed (bent) by reaction force, from the developer generated when the coating amount of the developer on the surface of the developing sleeve70is uniformed. In a state in which such high accuracy is imparted to the SB gap G, a positional relationship among the developing sleeve70, the sleeve bearing members11aand11band the regulating member37is fixed invariantly.

As shown in (a) ofFIG. 4, during the image formation, the regulating member37is subjected to application of reaction force F1 at the layer thickness regulating portion36. The reaction force F1 is generated by collision when the developer deposited on the surface of the developing sleeve70is rotated and fed together with the developing sleeve70. The direction of the reaction force F1 varies depending on a shape of the developer rectifying portion35, but roughly coincides with a tangential direction at an outer circumference point70aof the developing sleeve70opposing the layer thickness regulating portion36. In order to provide strength against the reaction force F1, the regulating member37is formed by extending the cross-section shape so as to elongate in a direction L1 in parallel to a direction of the reaction force F1.

As shown in (a) ofFIG. 4, during the image formation, the regulating member37is subjected to application of reaction force F2 at the layer thickness regulating portion36. The reaction force F2 is reaction force of pressure applied when the developer passes through the gap between the layer thickness regulating portion36and the developing sleeve70. The direction of the reaction force F2 varies depending on a shape of the developer rectifying portion35, but roughly coincides with a diameter direction perpendicular to a tangential direction at an outer circumference point70aof the developing sleeve70opposing the layer thickness regulating portion36. In order to provide strength against the reaction force F2, the regulating member37is formed by extending the cross-section shape so as to elongate in a direction L2 in parallel to a direction of the reaction force F2.

In this embodiment, an angle70bformed between a line segment connecting rotation centers of the developing sleeve70and the photosensitive drum1and a line segment connecting the outer circumference point70aopposing the layer thickness regulating portion36and the center of the developing sleeve70is approximately 90 degrees. For this reason, the elongation (extension) direction L1 of the cross-section of the regulating member37is substantially parallel to the line segment connecting the centers of the developing sleeve70and the photosensitive drum1. As a result, the cross-section of the regulating member37largely projects toward the photosensitive drum1to prevent a gap (SD gap) between the developing sleeve70and the photosensitive drum1from being visually recognized from above.

As shown inFIG. 3, at each of the end portions of the regulating member37, the opening80for permitting visual recognition of the gap (SD gap) between the developing sleeve70and the photosensitive drum1from above while penetrating through the regulating member37is provided. The opening80is provided in the regulating member37correspondingly to a non-image region of the photosensitive drum1.

As shown in (b) ofFIG. 4, in a cross-section H2 of the regulating member37in the non-image region, the opening80ranging in an arrow 81 direction in which a sight line to the SD gap between the developing sleeve70and the photosensitive drum1is ensured. The shapes of the cross-sections H2 at the front-side end portion and the rear-side end portion of the developing sleeve70are formed in a symmetrical manner. For this reason, the shape of the cross-section H2 at the front-side end portion is described and will be omitted from redundant description.

The cross-section H2 of the regulating member37in the non-image region has the substantially same outer configuration as the cross-section H1 of the regulating member37in the image (formable) region, and therefore the regulating member37ensures sufficient cross-sectional area and rigidity at the end portions thereof for being connected with the sleeve bearing members11aand11b. The opening80is larger in width than the SD gap.

As shown inFIG. 3, adjustment of the SB gap G is made by moving the regulating member37relative to the sleeve bearing members11aand11bassembled with the developing sleeve70by being supported on an unshown supporting table when the sleeve holder unit10is adjusted and assembled. The cross-section of the regulating member37is positioned so that the opposing interval between the developing sleeve70and the layer thickness regulating portion36falls within a predetermined dimensional range, and then the regulating member37and the sleeve bearing members11aand11bare integrally welded.

The opposing interval between the developing sleeve70and the layer thickness regulating portion36is shot by a digital camera or the like, and then a shot image is (image-)processed, so that a value of the SB gap G can be obtained. Alternatively, the value of the SB gap G can be obtained by gap measurement with laser light.

In a state in which only the regulating member37and the developing sleeve70are disposed, the regulating member37and the sleeve bearing members11aand11bare integrally fixed by using a precision jig (tool). The SB gap G is adjusted so that a value thereof falls within a desired range at each of the longitudinal end portions of the regulating member37, and then the sleeve bearing members11aand11bare bonded to the regulating member37, thus being integrally fixed. The regulating member37is fixed to the sleeve bearing members11aand11bwhile maintaining accuracy of the SB gap G by the adjustment.

When an external force is strongly applied when the regulating member37is fixed to the sleeve bearing members11aand11b, there is a possibility of generation of permanent deformation due to bending and distortion of the regulating member37. For this reason, the bonding of the end portions of the regulating member37to the sleeve bearing members11aand11bmay desirably be made by a stress-free method, such as laser welding or UV bonding, carried out in a normal-temperature environment. The bonding and the welding is cited as an example of a stress-free bonding method at a normal temperature. As far as Embodiment 1 is concerned, screw fastening is not desirable because there is a possibility of generation of distortion of the regulating member37during the fastening. As far as Embodiment 1 is concerned, arc welding and gas welding are not desirable because there is a possibility that they cause deformation at high temperatures and flexure due to residual stress.

(Adjustment of SD Gap)

FIG. 5is an illustration of adjustment of the opposing interval (gap) between the developing sleeve70and the photosensitive drum1. As shown in (b) ofFIG. 4, in a state in which a positional relationship between the developing sleeve70and the regulating member37is fixed, the sleeve holder unit10and the photosensitive drum1are connected with each other. The opposing interval between the developing sleeve70and the photosensitive drum1is referred to as a SD gap H. In order to obtain a good image, it is important to precisely adjust the SD gap H at a predetermined value over the entire image (formable) region along the developing sleeve70. For this reason, the interval between the photosensitive drum1and the developing sleeve70is actually measured, and then adjustment and assembling between the photosensitive drum1and the developing sleeve70are carried out.

A gap gage of 300 μm in thickness is inserted into the SD gap in the arrow 81 direction through the opening80provided at each of the end portions of the developing sleeve70. A center distance between the photosensitive drum1and the developing sleeve70, i.e., a distance between the center of the photosensitive drum1and the center of the developing sleeve70, is adjusted by using the gap gage as a spacer. The SD gap H is adjusted at a desired value by abutment of the developing sleeve70and the photosensitive drum1with the gap gage inserted therebetween. The same operation is performed in each of the front and rear sides of the photosensitive drum1, so that the developing sleeve70and the photosensitive drum1are assembled in substantially parallel to each other with a predetermined interval.

Incidentally, scanning is made by irradiation with laser light through the opening80to detect reflected light, and thus the SD gap H may also be measured. It is possible to adjust the center distance between the photosensitive drum1and the developing sleeve70at a predetermined opposing interval while conducting the measurement.

As shown inFIG. 3, the sleeve bearing members11aand11bare provided with abutting portions12aand12b, respectively, for defining a distance between a rotation shaft of the developing sleeve70and the surface of the photosensitive drum1. To each of the sleeve bearing members11aand11b, a swingable shaft13for swingably mounting the sleeve holder unit10relatively to the developing container (FIG. 2) is mounted.

As shown inFIG. 5, the sleeve holder unit10is connected with the developing container30by the swingable shafts13. An urging spring52presses a whole of the sleeve holder unit10toward the photosensitive drum1. In this state, the abutting portions12aand12babut against the adjusting ring53, so that the SD gap H is ensured between the photosensitive drum1and the developing sleeve70. The adjusting ring53has an eccentric peripheral surface relative to the rotation center of the photosensitive drum1, and is mounted to the developing container30in a manually rotatable manner. By manually rotating the adjusting ring53disposed at each of the end portions of the developing container30, in each of the front and rear sides of the developing sleeve70, the center between the photosensitive drum1and the developing sleeve70is adjustable.

In the developing device3in Embodiment 1, even when the regulating member (sleeve holder frame)37is formed of an inexpensive material having low rigidity, necessary rigidity can be ensured by the cross-section shape projecting toward the photosensitive drum1. In the developing device3in Embodiment 1, the SB gap G which is the interval between the developing sleeve70and the layer thickness regulating portion36is held and fixed with high accuracy, and thereafter the SD gap H which is the interval between the photosensitive drum1and the developing sleeve70can be adjusted and assembled with high accuracy.

In the developing device3in Embodiment 1, the SG gap G and the SD gap H can be set precisely and stably with high reproducibility, and therefore it is possible to provide a further downsized process cartridge. The developing device3in Embodiment 1 is capable of compatibly realizing reductions in size and weight of the process cartridge and stabilization of image density.

In the developing device in Embodiment 1, the regulating member37is provided with the gap80correspondingly to the non-image region of the photosensitive drum1, and therefore even when the surface of the photosensitive drum1is damaged during insertion and removal of the gap gage, an image quality is not impaired.

As shown inFIG. 6, the sleeve bearing members11aand11band the regulating member37are integrally bonded to each other. Each of reinforcing ribs84is a rib extending in the rotational axis direction of the developing sleeve70. Reinforcing ribs82are a pair of ribs each extending in the rotational direction of the developer carrying member (developing sleeve70). The regulating member37is integrally molded by using a resin material so that a box-like shape in which a side opposite from an opposing surface to the developing sleeve70is open is formed by connecting the reinforcing ribs84with the reinforcing ribs82. Each of the reinforcing ribs82also functions as a wall, of the opening80, in a side closer to a center side with respect to the rotational axis direction.

FIG. 6is an illustration of a structure of a sleeve holder unit in Embodiment 2. InFIG. 7, (a) and (b) are illustrations of an assembled state of the sleeve holder unit and the photosensitive drum. InFIG. 7, (a) shows an operation during image formation in a cross-section in an image region, and (b) shows an operation during the image formation in a cross-section in a region outside the image region. A developing device3B in this embodiment is constituted and operated similarly as in Embodiment 1 except that the regulating member37is resin-molded in a shape such that the reinforcing ribs are provided. For this reason, inFIGS. 6 and 7, constituent elements common to Embodiments 1 and 2 are represented by the same reference numerals or symbols as those inFIGS. 1 to 5, and will be omitted from redundant description.

As shown inFIG. 6, the developing sleeve70, the sleeve bearing members11aand11band a regulating member137which are formed as separate members are integrally assembled to constitute a sleeve holder unit10. The regulating member137rotatably supports the developing sleeve70by the sleeve bearing members11aand11bprovided at end portions thereof. The regulating member137is formed of a resin material by injection molding using a metal mold.

As shown in (a) ofFIG. 7, in a cross-section H3 ofFIG. 6, reaction forces F1 and F2 act on the layer thickness regulating portion36during the image formation. For this reason, the regulating member136is provided with the reinforcing rib84for reducing a degree of deformation of the layer thickness regulating portion36against the reaction forces F1 and F2.

As shown inFIG. 6, with respect to the image (formable) region of the photosensitive drum1, the three reinforcing ribs84each having a rib shape continuously extending in a longitudinal direction of the regulating member137are formed as a part of the regulating member137. At each of the end portions of the reinforcing ribs84, in a non-image region outside the image region, a reinforcing rib83perpendicular to the longitudinal direction is connected, so that large geometrical moment of inertia of the regulating member137is ensured.

As shown in (a) ofFIG. 7, the reinforcing ribs84positioned in the image region are disposed at positions where the reinforcing ribs84do not adversely affect accuracy of injection molding. The positions of the reinforcing ribs84are somewhat deviated from the back-side position of the layer thickness regulating portion36in the upstream side and the downstream side, respectively, with respect to the feeding develop. The reinforcing ribs84are disposed in parallel to the longitudinal direction of the regulating member137, and do not cross the back-side position of the layer thickness regulating portion36. For this reason, the deformation and a lowering in straightness of the layer thickness regulating portion36due to resin contraction after the injection molding are not readily generated.

The cross-section of each of the reinforcing ribs84projecting in the back side of the layer thickness regulating portion36is invariant at any longitudinal position. For this reason, warpage of the regulating member137due to the resin contraction after the injection molding is not readily generated. Each of the reinforcing ribs84has a cross-sectional shape, perpendicular to the longitudinal direction, which is extended in an L4 direction parallel to a direction of the reaction force F2, so that rigidity of the regulating member137against the reaction force F2 is enhanced. With respect to the regulating member137, a cross-sectional shape perpendicular to the longitudinal direction is extended in an L3 direction parallel to a direction of the reaction force F1, so that rigidity of the regulating member137against the reaction force F1 is enhanced. The regulating member137is integrally formed with a developer rectifying portion35, so that the rigidity of the regulating member137against the reaction force F1 is enhanced.

As shown inFIG. 6, in the non-image region of the regulating member137, the pair of reinforcing ribs82extending in the toner feeding direction are connected, and a pair of reinforcing ribs83and outer wall ribs83bperpendicular to the pair of reinforcing ribs82are disposed. The pair of reinforcing ribs83are disposed so as to connect between the reinforcing rib82for forming a bonding surface to the sleeve bearing member11aand the reinforcing rib82connected with the reinforcing rib84positioned in the image region. The reinforcing ribs82are provided in the non-image region, and therefore even when a local lowering in straightness of the layer thickness regulating portion36is generated in the back side of the reinforcing ribs82, the reinforcing ribs82do not influence an output image.

The reinforcing ribs82, the reinforcing ribs83and the outer wall ribs83bconstitute a box-like shape formed of the resin in the non-image region. The reinforcing ribs82are provided outside the image formable region of the regulating member137to form the box-like shape at each of the end portions, of the regulating member137, which are the non-image regions. The reinforcing ribs83inside the box-like shape are formed along a line-of-sight direction of the SD gap through between the photosensitive drum1and the developing sleeve70. The reinforced box-like shape realizes sufficient rigidity and accuracy capable of withstanding the reaction forces F1 and F2 of the developer.

As shown in (b) ofFIG. 7, in a cross-section H4 ofFIG. 6, the pair of reinforcing ribs83are provided in parallel to the line-of-sight direction of the SD gap H which is the gap between the developing sleeve70and the photosensitive drum1. One of the pair of reinforcing ribs83constitutes a wall surface of the opening80and penetrates through the regulating member137. For that reason, an inclined surface of the reinforcing rib83functions as a guiding surface when the gap gage is inserted into the SD gap H as described in Embodiment 1. Through the opening80, measurement of the SD gap H by laser light can be made.

The developing device3B in Embodiment 2 has the cross-sectional shape extending in the longitudinal direction and the toner feeding direction as described above, and therefore each of the reinforcing ribs84in the image (formable) region and the reinforcing ribs83in the non-image region can be extended in a most effective direction. By providing the reinforcing rib82between the reinforcing rib84and the reinforcing rib83, even in the case where the reinforcing rib84and the reinforcing rib83cannot provided on the same line, it is possible to ensure rigidity required for the regulating member137.

The developing device3B in Embodiment 2 is provided with the gap80, in the non-image region as each of the end portions of the regulating member137, capable of ensuring a sight line to the SD gap H from above. For this reason, in a state in which the photosensitive drum1, the regulating member137and the developing sleeve70are incorporated in the developing device3B, the SD gap H can be accurately adjusted without damaging the photosensitive drum1in the image region. The developing device3B in Embodiment 2 is capable of providing a stable image density of the output image since the gap between the photosensitive drum1and the developing sleeve70can be adjusted with high accuracy.

In the developing device3B in Embodiment 2, the regulating member137including the layer thickness regulating portion36is a molded product obtained by the injection molding of the resin material, and therefore a component cost of the image forming apparatus can be reduced by forming the regulating member137inexpensively compared with Embodiment 1. In the developing device3B in Embodiment 2, while employing a simple and inexpensive constitution of the regulating member137, by providing the reinforcing ribs83, it is possible to ensure sufficient flexural rigidity of the regulating member137with respect to the toner feeding direction and a diameter direction of the developing sleeve70.

In the developing device3B in Embodiment 2, the regulating member137has the sufficient flexural rigidity with respect to the toner feeding direction and the diameter direction of the developing sleeve70and therefore a degree of variation in image density with respect to the longitudinal direction of the photosensitive drum1is decreased. In the developing device3B in Embodiment 2, the straightness of the layer thickness regulating portion36can be set with high accuracy, and therefore the image density of the output image is stabilized, so that also a degree of variation in image density between the image forming apparatuses becomes small. In developing device3B in Embodiment 2, by using the regulating member137which is the resin-molded product having high accuracy and high rigidity, it is possible to stably regulate the amount of the developer on the developing sleeve70in the simple and inexpensive constitution.

The present invention can be carried out also in other embodiments in which a part or all of constituent elements in the above-described embodiments are replaced with alternative constituent elements thereof so long as the regulating member form regulating the layer thickness of the developer is provided with the through hole through which the SD gap is visually recognizable. Accordingly, the present invention is not limited to the developing device using the two-component developer, but may also be carried out in a developing device using a one-component developer. The present invention is not limited to the developing device in the form of the process cartridge, but may also be carried out in a developing device capable of being mounted and dismounted alone for exchange. The present invention is not limited to the full-color image forming apparatus, but may also be carried out in a monochromatic image forming apparatus including the developing device or the process cartridge.

Constituent elements, other than the developing device, integrally assembled as the process cartridge may be arbitrarily selected. The process cartridge may also be prepared by integrally assembling the plurality of image forming portions into a unit. Further, in the above-described embodiments, only a principal portion relating to toner image formation and transfer is described, but the present invention can be carried out in image forming apparatuses, having various uses, such as printers, various printing machines, copying machines, facsimile machines, and multi-function machines, by adding necessary equipment, devices and casing structures.

Comparison Example 1

FIG. 8is an illustration of a structure of a developing device3E in Comparison Example 1. As shown inFIG. 8, in the developing device3E in Comparison Example 1, a doctor blade73is formed of a metal material in a plate shape, and is fixed to a developer rectifying member75with fixing screws74. A magnetic force of a magnet portion71deposits the developer on the surface of a developing sleeve70. The doctor blade73uniformizes a layer thickness of the developer on the surface of the developing sleeve70, so that stable developer supply to an electrostatic image on a photosensitive drum1is realized.

In the developing device3E in Comparison Example 1, the doctor blade73is deformed by a force generated when the doctor blade73uniformizes a developer coating amount on the surface of the developing sleeve70in the SB gap G. The SB gap G is displaced in a remote direction from the developing sleeve70at a longitudinal central portion of the developing sleeve70, and therefore the developer coating amount with respect to the longitudinal direction of the developing sleeve70cannot become uniform, thus causing image density non-uniformity.

In recent years, the developing device3E is required to be reduced in weight and the number of components. Therefore, the doctor blade73, of the metal material, which has been used as a single layer thickness regulating member is required to be integrally formed of the resin material with the developer rectifying member35.

Comparison Example 2

FIG. 9is an illustration of a structure of a developing device3F in Comparison Example 2. As shown inFIG. 9, in the developing device3F Comparison Example 2, a regulating member37is formed as a molded product of a resin material as a whole, and is provided with a layer thickness regulating portion36for regulating a layer thickness of a developer by defining an SB gap G with a developing sleeve70.

In the back side of the layer thickness regulating portion36, as a reinforcing means for the regulating member37, reinforcing ribs83continuously extending in the longitudinal direction of the regulating member37. Each of the reinforcing ribs83is, in order to ensure rigidity against a force Fc applied from the developer to the layer thickness regulating portion36when the developer passes through the layer thickness regulating portion36, disposed over an entire area with respect to the longitudinal direction, so that a large cross-sectional area is ensured.

The regulating member37formed of the resin material is prepared by assembling respective components at a high density for the purpose of realizing a large cross-sectional area and downsizing of the developing device, and therefore it is difficult to ensure a line-of-sight space for measuring an SD gap H.

According to the developing device of the present invention, through the opening newly added in the present invention, the gap where the image bearing member and the developer carrying member oppose each other can be visually recognized from the outside of the regulating member. Accordingly, even in the case where the cross-section of the layer thickness regulating beam member is extended to the position close to the image bearing member, in a state in which the layer thickness regulating member is assembled with the developing device, it is possible to check and adjust the gap between the image bearing member and the developer carrying member.

This application claims priority from Japanese Patent Application No. 166633/2013 filed Aug. 9, 2013, which is hereby incorporated by reference.