Information
-
Patent Grant
-
6385417
-
Patent Number
6,385,417
-
Date Filed
Friday, July 7, 200024 years ago
-
Date Issued
Tuesday, May 7, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
An image forming unit includes a photosensitive drum as an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing a developing material thereon to hold the image. The apparatus also includes a developing roller as a developing portion for supplying the developing material to develop the latent image held on the photosensitive drum to the image with the developing material. The apparatus further includes a gap regulating mechanism for setting bearings, disposed on both ends of a rotation drive shaft of the photosensitive drum, for rotatably fixing the photosensitive drum to a system main body frame and bearings, disposed on both ends of the developing roller, for rotatably supporting a rotation drive shaft of the developing roller by a developing portion main body. With such a unit, a peripheral surface of the photosensitive drum always maintains a constant gap from the peripheral surface of the developing roller.
Description
BACKGROUND OF THE INVENTION
The present invention relates to image forming systems such as a color plain paper copy machine (hereinafter referred to as PPC) and a printer for printing/recording information from image information supply apparatuses such as a personal computer (hereinafter referred to as PC) and a digital camera on a plain paper, OHP sheet or other types of paper sheets, and particularly, it relates to a structure for holding an image holding member while a constant fine gap is always maintained on an abutment surface between a photosensitive drum or another image holding member and a developing roller.
An image forming system for use in the aforementioned purpose is provided with an image forming unit for forming an image by using a developing material, a sheet supply portion for supplying a sheet to the image forming unit, a sheet conveying portion for conveying the supplied sheet, and a sheet supplying/conveying controller for controlling the supplying/conveying of the sheet to the image forming unit by the sheet supplying and conveying portions. The image forming unit is provided with an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing the developing material thereon to hold the image, a developing unit for developing the latent image held on the image holding member as the image with the developing material, a transferring unit for transferring the developed image to the sheet, and a fixing unit for fixing the transferred image.
In recent years, in a field of image forming system, various color developing/forming methods for forming color images have been proposed, and there are roughly a multiple transferring system and a multiple developing system. The multiple transferring system can be classified into a transferring drum system, a tandem system, an intermediate transferrer system, and the like, and the multiple developing system can be classified to a multiple rotation system and a one pass method. The transferring drum system comprises successively transferring respective color toners on a sheet wound around a transferring drum to obtain the image, and is characterized in that a positioning control is difficult but a degree of freedom in a process design is high. The tandem system is provided with image forming portions for four colors, successively transfers respective color toner images on a conveyed sheet to obtain the color image with one pass, and is high in cost and difficult in the positioning control, but is also provided with an advantage that image formation can be accelerated and a degree of freedom in process design is highest. The intermediate transferrer system comprises successively transferring respective color toner images on an intermediate transferrer, and subsequently collectively transferring the images to the sheet to obtain the color image, and is difficult in the positioning control and low in transfer ratio as compared with the other systems but has advantages that a transferring mechanism portion capacity is relatively small and that curvature separation is also possible.
Moreover, the multiple rotation system in the multiple developing system comprises rotating the photosensitive drum to superposing the respective color toners on the surface, and subsequently collectively transferring the toners to the sheet to obtain the color image, and requires a complicated process control, but is advantageous in miniaturization of a machine body and cost reduction, and has an advantage that the system is also advantageous for positioning. The one pass system is provided with the image forming portions for four colors around a photosensitive member, comprises superposing the toner images on the photosensitive member with one pass to obtain the color image, has difficulty in process arrangement around the photosensitive member and exposure positioning control, easily enlarges an apparatus size, and disadvantageously requires the complicated process control, but has an advantage that image formation can be performed at a high speed.
For the aforementioned image holding member for holding the image in an image forming process, in the aforementioned various image forming systems, concretely, there is one large-diameter photosensitive drum, or there are a plurality of relatively small-diameter photosensitive drums for respective colors in color copy or the like, but any member comprises a single photosensitive drum or a plurality of photosensitive drums as a constituting element of the image forming unit. The photosensitive drum is rotatably supported on a frame constituting a main body of the image forming system via a bearing or the like, and for the single photosensitive drum or the plurality of photosensitive drums a magnet roller for supplying the developing material is also disposed.
The developing magnet roller is disposed in parallel between a developing unit main body case and the photosensitive drum, and is used for attaching a toner as the developing material on an electrostatic pattern to form a visualized image after the electrostatic pattern is formed on the photosensitive drum charged with a static electricity by a charger in accordance with a document pattern by exposure by an optical unit. Therefore, by applying a bias potential of either a positive potential or a negative potential to the developing (magnet) roller to attach the developing material to the peripheral surface of the roller as an electromagnet and rotating the roller opposite to the photosensitive drum with a constant gap immediately before placing the roller in sliding contact with the peripheral surface of the drum, the toner is supplied to the surface of the rotating photosensitive drum which is charged in a predetermined document pattern and on which an electric latent image is formed.
As seen from the aforementioned description, since the photosensitive drum is disposed close to the developing roller to such an extent that the peripheral surfaces are nearly in the sliding contact with each other, a gap control is a big problem to secure an adequate supply amount of the developing material (toner). Particularly, in a recent technique it is a mainstream to integrally forming the photosensitive drum and developing (magnet) roller including the developing unit main body case, and it is very important to control the gap in arranging these components for every unit.
In the conventional image forming system, in order to control the gap between the peripheral surface of the photosensitive drum and the peripheral surface of the developing roller, an adjustment portion for the gap control is disposed in either edge of both ends avoiding a central portion for forming the image in the photosensitive drum, and a gap setting member fixed to a developing roller shaft is disposed opposite to the adjustment portion, and controlled by direct contact in such a manner that a constant distance is always held from the peripheral surface of the photosensitive drum (direct contact system). The gap setting member is provided with a disc shape or a thin cylindrical shape such that the peripheral surface abuts on the adjustment portion disposed on at least one edge of the peripheral surface of the photosensitive drum, and may be constituted, for example, by a bearing comprising an inner race fixed to the developing roller shaft and an outer race rotatably held via a plurality of rollers.
In the conventional image forming system constituted as described above, since the gap between the photosensitive drum and the developing roller is directly adjusted by the surface extended from the surface with the image to be formed thereon, distortion and rattling generated between a rotation drive shaft of the photosensitive drum and the rotation drive shaft of the developing roller, and disturbance forces such as cogging generated in a motor for rotating/driving both drive shafts are applied without being inhibited.
However, according to a conventional image forming device, collision of the peripheral surface of the photosensitive drum against the peripheral surface of the developing roller is avoided by the gap setting member coaxial with the developing roller and slightly larger in diameter than the developing roller, and the predetermined gap is always secured between the peripheral surface of the photosensitive drum and the peripheral surface of the developing roller, but a gap deviation between the peripheral surfaces of two rotating members is caused not by the peripheral surface itself, but by position deviations of the rotation shafts in two rotating members, and therefore the adjustment of the gap between both members by placing the gap setting member in sliding contact with the peripheral surface itself of the photosensitive drum cannot be said to be a direct way as a method of adjusting a gap fluctuation.
Moreover, the gap setting member is constituted by the bearing attached to the developing roller, and the outer race on the outer periphery of the gap setting member in sliding contact with the peripheral surface of the photosensitive drum is rotatable, but a part of the peripheral surface of the photosensitive drum is always in sliding contact with rotation in order to adjust the gap between both components, the peripheral surface edges are therefore worn, and as a result of long-time use a warp is generated between the peripheral surface on the center side of the photosensitive drum and the peripheral surface on the edge side in sliding contact with the gap setting member, which causes a problem that the gap between both components cannot accurately be adjusted.
Furthermore, for the position deviation of the peripheral surface between two rotating members having parallel rotation shafts, even when the gap adjustment is performed on one end side edge of the peripheral surface, with occurrence of a situation in which axial lines of the rotation shafts are not parallel to each other the constant gap can be maintained in the peripheral surface of one end side edge in sliding contact with the gap setting member, but the opposite peripheral surface in the other side edge is sometimes close to or apart from the predetermined gap, and it is difficult to maintain the predetermined gap over the entire area of the peripheral surface. To solve the problem it is also proposed to dispose the gap setting members on both ends of the developing roller, but even by a simple consideration two gap setting members are necessary, and the adjustment portion has to be also secured on the other edge opposite to the photosensitive drum, which therefore causes problems that manufacture cost increases and that a usable area of the photosensitive drum is narrowed.
SUMMARY OF THE INVENTION
The present invention has been developed to solve the aforementioned problems, and an object thereof is to provide an image forming system in which in order to adjust a gap between a photosensitive drum and a developing roller, instead of placing a gap setting member directly in sliding contact with a peripheral surface of the photosensitive drum, by allowing bearings of the photosensitive drum and developing roller to abut on each other to adjust the gap between both components in such a manner that a predetermined distance is maintained, gap adjustment is more precisely adjusted.
Another object is to provide an image forming system in which an accurate gap can be secured even after a long-time use without damaging the peripheral surface of the photosensitive drum in order to adjust the gap from the developing roller.
Further object of the present invention is to provide an image forming system which can accurately perform gap adjustment with respect the entire area of the peripheral surface without generating a gap fluctuation between both peripheral surfaces attributed to an axial line distortion or the like in two rotating members.
To achieve the aforementioned objects, according to a first basic constitution of the present invention there is provided an image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying the supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to the image forming unit by the medium supplying portion and the medium conveying portion; a transferring portion for transferring the image developed by the image forming unit to the image forming medium; and a fixing portion for fixing the transferred image, wherein the image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing the developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of the system; a developing roller disposed in the developing portion for supplying the developing material to develop the latent image held on the image holding surface to the image with the developing material, and provided with a rotation drive shaft for supplying the developing material to the image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding the support shaft of the image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of the image holding member, for holding the support shaft in the vicinity of the image holding member in an assisting manner, and a second bearing for rotatably holding the rotation drive shaft of the developing roller from the side of the developing portion and maintaining the distance between the image holding surface of the image holding member and the peripheral surface of the developing roller with the gap setting portion, and which sets a gap between two surfaces in such a manner that a constant fine gap is continued to be maintained between the gap setting portion and the second bearing.
In the image forming system according to the aforementioned first basic constitution, the gap regulating mechanism of the image forming unit according to a first middle constitution may be provided with: the first bearing and the gap setting portion laterally symmetrically disposed on both sides of the photosensitive drum as the image holding member; a coupling portion for coupling respective outer peripheral portions of the first bearing and gap setting portion; the second bearing having an outer peripheral surface opposite to the gap setting portion right close to both ends of the photosensitive drum via the outer periphery of the coupling portion and having its inner peripheral surface fitted into the rotation drive shaft of the developing roller; and an urging member for urging the developing roller in the direction of the image holding surface of the image holding member.
In the image forming system according to the first middle constitution, at least one of coupling members for coupling outer peripheral sides of the first bearing and the gap setting portion may be provided with a detail constitution by an elastic member for absorbing, by an elastic force, external action forces including deflection, distortion and eccentric action applied to the support shaft passed inside the diametric direction.
In the image forming system according to the detailed constitution, the elastic member may be formed of a thin member as compared with an ordinary coupling member, and elastically deformed to absorb the external action force when the external action force is applied around the support shaft to such an extent that the ordinary coupling member fails to be elastically deformed.
Moreover, in the image forming system according to the detailed constitution, the elastic member is constituted of a plurality of coupling pieces for bridging the first bearing and the gap setting portion, portions other than the plurality of coupling pieces are a plurality of openings which are lightened and opened, and the plurality of elastic pieces may be deformed to absorb the external action force when the external action force is applied around the support shaft to such an extent that the ordinary coupling member fails to be elastically deformed.
In the image forming system according to the first basic constitution, the gap regulating mechanism is provided with: the first bearing and the gap setting portion laterally symmetrically disposed on both sides of the photosensitive drum as the image holding member; a coupling portion for coupling respective outer peripheral portions of the first bearing and the gap setting portion; the second bearing having an outer peripheral surface opposite to the gap setting portion right close to both ends of the photosensitive drum via the outer periphery of the coupling portion and having its inner peripheral surface fitted into the rotation drive shaft of the developing roller; and an urging member for urging the developing roller in the direction of the image holding surface of the image holding member, and at least one of the first bearings may be formed by a positioning collar which is fitted into an attachment place of an image forming unit frame fixed on a main body side of the image forming system and which loosely supports the support shaft of the photosensitive drum inside the diametric direction to regulate a large displacement of the support shaft.
In the image forming system according to the first basic constitution, at least one of a pair of first bearings may be constituted by a bearing provided with an inner race into which the support shaft is fitted, an outer race which is fitted into the main body frame, and a ball sealed between the inner race and the outer race.
In the image forming system according to the first basic constitution, at least one of a pair of first bearings may be constituted by a sliding shaft bearing whose inner peripheral surface contacts the peripheral surface of the rotation drive shaft as the support shaft to support rotation of the rotation drive shaft.
In the image forming system according to the first basic constitution, at least one of a pair of gap setting portions may be constituted by a bearing provided with an inner race into which the support shaft is fitted, an outer race which is fitted into the main body frame, and a ball sealed between the inner race and the outer race.
In the image forming system according to the first basic constitution, at least one of the pair of gap setting portions may be constituted by a sliding shaft bearing whose inner peripheral surface contacts the peripheral surface of the rotation drive shaft as the support shaft to support rotation of the rotation drive shaft.
In the image forming system according to the first basic constitution, at least one of the pair of gap setting portions may be constituted by a fixing member, and one end of the fixing member abuts on the support shaft and the other end thereof abuts on the second bearing to set a gap between the image forming surface of the photosensitive drum supported by the support shaft and the outer surface of the developing roller.
In the image forming system according to the first basic constitution, the image forming unit is provided with a plurality of photosensitive drums as the image holding member, and a plurality of developing units as a developer for forming a pair with each of the photosensitive drums, at least the plurality of photosensitive drums are arranged in parallel in a tandem structure, and the plurality of photosensitive drums and a plurality of developing units may be assembled in one image forming unit case.
In the image forming system according to the first basic constitution, the image forming unit may have a transferring drum structure provided with a single photosensitive drum as the image holding member and a single developing roller as the developer.
In the image forming system according to the first basic constitution, the image forming unit may have an intermediate transferring structure provided with a single photosensitive drum as the image holding member, a plurality of developing rollers as the developer provided with different colors of developing materials disposed apart from one another via a predetermined angle around the photosensitive drum, and an intermediate transferrer for successively transferring the respective colors of developing materials formed on the photosensitive drum.
In the image forming system according to the first basic constitution, the image forming unit may have a multiple developing structure of one pass system which includes a single large-diameter photosensitive drum as the image holding member, and a plurality of developing rollers as the developer provided with different colors of developing materials apart from one another via a predetermined angle around the photosensitive drum, and which transfers a color image obtained by superposing the developing materials on the image holding surface of the photosensitive drum onto the sheet by passing the sheet as the image forming medium once to obtain the formed image.
In the image forming system according to the first basic constitution, the image forming unit may have a transferring drum structure which comprises at least a small-diameter rollershaped photosensitive member as the image holding member, a transferring drum provided with a large-diameter drum shape disposed on one side of the photosensitive member and the transferring portion on the peripheral surface of the drum shape, and a plurality of developing rollers for the respective developing materials disposed apart from one another via a constant angle on the peripheral surface of a large-diameter drum disposed on the other side of the photosensitive member, and which successively forms the images of the respective color developing materials on the image forming medium wound around the transferring drum to obtain a final color image.
In the image forming system according to the first basic constitution, the image forming unit may have a multiple rotation structure which comprises a large-diameter multiple-rotation photosensitive drum as the image holding member, and a plurality of developing rollers for the respective colors of developing materials disposed opposite to the image forming surface of the photosensitive drum and apart from one another by a predetermined angle, and which rotates the photosensitive drum multiple times to superpose the respective colors of developing materials on the image forming surface and then collectively transfers them to the image forming medium to obtain the color image.
According to a second basic constitution of the present invention there is provided an image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying the supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to the image forming unit by the medium supplying portion and the medium conveying portion; a transferring portion for transferring the image developed by the image forming unit to the image forming medium; and a fixing portion for fixing the transferred image, wherein the image forming unit comprises: a photosensitive drum for converting an optical image formed via an optical system into a latent image and subsequently depositing the developing material thereon to hold the image on an image holding surface, said photosensitive drum being provided with a support shaft movably fixed to a main body frame of the system; a developing roller provided with a rotation drive shaft for supplying the developing material to the image holding surface to develop the latent image held on the image holding surface as the image by the developing material; and a gap regulating mechanism which includes at least first shaft holding means for holding the support shaft of the image holding member, gap setting means, disposed at a predetermined distance from the first shaft holding means in a direction of the image holding member, for holding the support shaft in the vicinity of the image holding member in an assisting manner, coupling means for coupling the first shaft holding means and an outer peripheral portion of the gap setting means, second shaft holding means for rotatably holding the rotation drive shaft of the developing roller from the side of the developing means and maintaining a distance between the image holding surface of the image holding member and the peripheral surface of the developing roller between the second shaft holding means itself and the gap setting means, said second shaft holding means being provided with an outer peripheral surface opposite to the gap setting means right close to both ends of the photosensitive drum via an outer periphery of the coupling means and an inner peripheral surface fitted into the rotation drive shaft of the developing roller, and urging means for urging the developing roller in the direction of the image holding surface of the image holding member, and which sets a gap between two surfaces in such a manner that the first shaft holding means and the gap setting means are laterally symmetrically disposed on both sides of the photosensitive drum and a constant fine gap continues to be maintained between the gap setting means and the second shaft holding means.
According to a third basic constitution of the present invention there is provided an image forming system comprising: image forming means for forming an image by using a developing material; medium supplying means for supplying an image forming medium to the image forming means; medium conveying means for conveying the supplied image forming medium; a medium supplying/conveying control means for controlling the supplying/conveying of the image forming medium to the image forming means by the medium supplying means and the image forming medium conveying means; transferring means for transferring the image developed by the image forming means to the image forming medium; and fixing means for fixing the transferred image, wherein the image forming means comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing the developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of the system; a developing roller disposed in the developing means for supplying the developing material to develop the latent image held on the image holding surface to the image by the developing material, and provided with a rotation drive shaft for supplying the developing material to the image holding surface; and a gap regulating mechanism which includes at least first shaft holding means for holding the support shaft of the image holding member, gap setting means, disposed at a predetermined distance from the first shaft holding means in a direction of the image holding member, for holding the support shaft in the vicinity of the image holding member in an assisting manner, and second shaft holding means for rotatably holding the rotation drive shaft of the developing roller from the side of the developing means and maintaining the distance between the image holding surface of the image holding member and the peripheral surface of the developing roller with the gap setting means, and which sets a gap between two surfaces in such a manner that a constant fine gap continues to be maintained between the gap setting means and the second shaft holding means, the gap regulating mechanism comprises: coupling means for coupling the first shaft holding means and the gap setting means laterally symmetrically disposed on both sides of the photosensitive drum as the image holding member, and outer peripheral portions of the first shaft holding means and the gap setting means; the second shaft holding means provided with an outer peripheral surface opposite to the gap setting means right close to both ends of the photosensitive drum via an outer periphery of the coupling means and an inner peripheral surface fitted into the rotation drive shaft of the developing roller; and urging means for urging the developing roller in the direction of the image holding surface of the image holding member, and at least one of the first shaft holding means is formed by collar means which is fitted into an attachment place of the frame of the image forming unit fixed on a main body side of the image forming system and which loosely supports the support shaft of the photosensitive drum inside the diametric direction to position/regulate a large displacement alone of the support shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1
is a sectional view showing a tandem type image forming system according to a first embodiment of the present invention;
FIG. 2
is a sectional view showing a main part of the tandem type image forming system of
FIG. 1
in an enlarged manner;
FIG. 3
is a plan view showing a position relation between a photosensitive drum and a developing roller of the image forming system according to the first embodiment;
FIG. 4
is a sectional view showing a simplified model of a gap regulating mechanism disposed on a bearing portion of the photosensitive drum and developing roller of an image forming unit according to the first embodiment;
FIG. 5
is a perspective view showing a constitution of the gap regulating mechanism on a rear side in the image forming unit shown in
FIG. 4
;
FIG. 6
is a sectional view showing a simplified model of the image forming unit whose coupling portion is thinned as a modification example of
FIG. 4
;
FIG. 7
is a perspective view showing a constitution of the image forming unit whose coupling portion is lightened as a modification example of
FIG. 5
;
FIG. 8
is a sectional view showing a simplified model of the gap regulating mechanism in the image forming system according to a second embodiment of the present invention;
FIGS. 9A and 9B
are a sectional view and front view showing an attachment structure of an ordinary photosensitive drum bearing of
FIG. 8
to a frame, and
FIGS. 9C and 9D
are a sectional view and a front view showing the attachment structure of the photosensitive drum bearing to the frame using plastic deformation as a modification example;
FIG. 10
is a perspective view showing an appearance constitution of the gap regulating mechanism according to the second embodiment shown in
FIG. 8
;
FIG. 11
is a perspective view showing an appearance of the gap regulating mechanism in the image forming system of the second embodiment;
FIG. 12
is a perspective view showing an assembly state of the image forming unit to a main body side according to a third embodiment of the present invention;
FIG. 13
is a plan view showing an attachment state and enlarged state of the photosensitive drum and developing roller in the image forming unit according to the third embodiment;
FIG. 14
is a front view, as seen from a main body front side, of the attachment state of the photosensitive drum and developing roller in the image forming unit according to the third embodiment;
FIG. 15
is a sectional view of the image forming unit by a single photosensitive drum and a single developing roller;
FIG. 16
is a sectional view showing the single photosensitive drum and a plurality of developing rollers for use in an intermediate transferring system of a multiple transferring system;
FIG. 17
is a sectional view showing the single photosensitive drum and the plurality of developing rollers for use in a one pass system of a multiple developing system;
FIG. 18
is a sectional view showing a simplified model of a transferring drum structure of the multiple transferring system provided with a small-diameter photosensitive member, a large-diameter transferring drum and a rotary developing member provided with a plurality of developing rollers on a peripheral surface; and
FIG. 19
is a sectional view showing a simplified model of a multiple rotation structure of the multiple developing system provided with a large-diameter photosensitive drum and a plurality of developing rollers arranged on a peripheral surface of the drum.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of an image forming system according to the present invention will be described hereinafter in detail with reference to the accompanying drawings.
FIG. 1
is a sectional view showing the entire constitution of the image forming system provided with a tandem type image forming unit as one example of the image forming system according to the present invention. In
FIG. 1
, an image forming system
1
is provided with: an image input portion
2
, constituted, for example, of an optical system disposed on a top surface side of a main body, for reading a document; a sheet supply cassette device
3
, disposed in a main body lower part, for containing a plurality of types of sheets to supply a large number of sheets with the same size; a manual insertion sheet supply device
4
by which various sizes or types of sheets can manually be supplied; an image forming unit
10
for converting an optical image formed by the image input portion
2
into a latent image to hold the image and for developing the held latent image by a developing material to form the image; a transferring unit
20
for transferring the formed image to a supplied sheet P; and a fixing unit
5
for fixing the transferred image.
Since
FIG. 1
only schematically shows the entire constitution of the image forming system, a detailed constitution of the image forming system will be described with reference to a main part enlarged view of FIG.
2
. In
FIG. 2
, the image forming unit
10
constituted by applying the present invention to a tandem type copying machine comprises four pairs of basic structures in which four photosensitive drums
11
are combined with four developers
12
, respectively, and the developer
12
is, as shown by reference numerals on a rightmost end, provided with: a developer case
13
; a developing material containing portion
14
, disposed in the case
13
, for containing developing materials such as the toner; a developing roller
15
for supplying the toner as the developing material to the peripheral surface of the photosensitive drum
11
from the developing material containing portion
14
; and a registration sensor
16
for detecting a color registration error when an image to be formed is recorded on the sheet P.
On a lower side of the image forming unit
10
, a transferring unit
20
is disposed, and the transferring unit
20
is provided with a transferring belt
21
for transferring the image formed by an image forming device to the supplied sheet P and conveying the sheet P in an endless shape, a drive roller
22
for rotating/driving the transferring belt
21
, and four transferring rollers
23
for transferring the image formed on the corresponding photosensitive drum to the sheet P. Additionally, in
FIG. 2
, the sheet P is supplied from the right side in the drawing and supplied/conveyed between the image forming unit
10
and the transferring unit
20
to a left direction in the drawing, and the sheet P is discharged as shown by an arrow after fixing.
The image transferred onto the sheet P by the image forming unit
10
and transferring unit
20
is supplied to the fixing unit
5
and fixed. The fixing unit
5
is provided with: an upper heat roller
6
which is heated and rotated/driven; a press roller
7
which is heated and rotated/driven and which presses the sheet P against the heat roller
6
; a heat lamp
8
, disposed inside the heat roller
6
and press roller
7
, for heating these rollers
6
and
7
; and a temperature detecting sensor
9
for detecting temperatures of the rollers
6
and
7
.
FIG. 3
shows a plan view of the image forming unit
10
, and for convenience of description the drawing shows only a pair of the photosensitive drum
11
and developing roller
15
positioned closest to a discharge side among four photosensitive drums
11
and four developing rollers
15
constituting the image forming unit
10
. The image forming unit
10
comprises a housing frame
30
for incorporating four pairs of photosensitive drums
11
and developing rollers
15
, and the photosensitive drum
11
and developing roller
15
are attached to a predetermined position f the frame
30
. A rotation drive shaft
31
of the photosensitive drum
11
and a rotation drive shaft
32
of the developing roller
15
are rotatably supported on the side of the frame
30
by a gap regulating mechanism
33
which also serves as a bearing and are constituted in such a manner that a fine gap is always maintained as an equal distance between the peripheral surface of the photosensitive drum
11
and the peripheral surface of the developing roller
15
.
With reference to
FIG. 4
showing a simplified model of a bearing structure according to the present embodiment in addition to
FIG. 3
, a detailed constitution of the gap regulating mechanism
40
will be described. Additionally, in the subsequent description, an upper side of
FIG. 3
is sometimes referred to as a rear side, a lower side thereof is a front side, a right side thereof is a sheet supply side, and a left side thereof is a sheet discharge side.
FIG. 4
is a view of the sheet discharge side as seen from the sheet supply side, and in
FIG. 4
the right side is the rear side and the left side is the front side.
In
FIG. 4
, the image forming unit
10
is detachably attached to raised surfaces
30
a
,
30
b
(corresponding to
61
,
62
in
FIG. 12
) forward and backward in the housing-shaped frame as an attachment main body. Along a rail guide disposed to connect the front surface to the back surface of the main housing frame, left and right side stays of the frame on the side of the image forming unit
10
slide, and movement of the image forming unit is guided during attachment/detachment. This constitution will be described later in details as a third embodiment with reference to
FIGS. 12
to
14
.
In order to position the image forming unit attached to the main body, positioning portions (described later as a stud or an insertion hole together with front and rear side frames
61
,
62
in
FIG. 12
) are disposed on the raised surfaces
30
a
,
30
b
forward and backward in the frame
30
of the image forming unit
10
, and a corresponding constituting portion (hole or stud) is formed in a corresponding position of the main body housing frame. This stud has a sufficient length to function as a guide when a type of a shaft extended from the rear of the image forming unit described later or another main body bonding site is bonded to a corresponding main body bonding site. The stud is screwed to a main body front frame from the front side not to be detached after the image forming unit is attached to the main body.
On the raised surface
30
b
on the back surface side of the main body frame, a drum drive motor
33
, a power transmission shaft
34
for transmitting a power from the motor
33
to the side of the photosensitive drum
11
, a flywheel
35
attached to the transmission shaft
34
, and a power supply terminal (not shown) for giving a charging voltage are disposed, and the transmission shaft
34
is provided with a bond coupling
36
for connecting the rotation drive shaft
31
of the photosensitive drum to a tip end thereof. Illustration or description is omitted with respect to a periphery of a drive shaft of a developing roller drive motor but a constitution similar to a constitution for use in rotating/driving the photosensitive drum
11
is disposed, and a voltage supply terminal for each site necessary for an image forming process is further disposed. Also on the side of the image forming unit
10
, a drum shaft, developing drive transmission shaft and power supply terminal are disposed in corresponding positions during attachment. When the image forming unit
10
is attached to the raised surfaces
61
,
62
of the main body side frame
30
, the drum shaft, developing drive shaft and power supply terminal are all in an integral state on the side of the main body and image forming unit.
FIG. 5
is a perspective view showing a constitution of the gap regulating mechanism on a photosensitive drum side of the image forming system according to the first embodiment, a first bearing
41
is fixed to the housing frame whose main body side is shown on the right side of the drawing, and a gap setting portion
42
disposed in a position apart from the first bearing
41
at a constant position is fixed to the rotation drive shaft (not shown in
FIG. 5
) of the photosensitive drum. A coupling portion
43
is disposed between the first bearing
41
and the gap setting portion
42
to bridge both components. In this constitution the rotation drive shaft of the photosensitive drum is rotatably supported basically by the first bearing
41
on the main body side housing frame, the distance from the developing roller is adjusted by the second bearing
42
to be constant, and the fine gap between the outer peripheral surfaces of both components can always be set to a constant distance.
FIG. 6
is a sectional view showing a simplified model of the image forming unit in which the coupling portion
43
is thinned as a modification example of FIG.
4
. In
FIG. 6
, only the coupling portion
43
of a front side gap regulating mechanism
40
C has a thin shape, but the present invention is not limited to this and such modification may be added to a rear side gap regulating mechanism
40
B.
FIG. 7
is a perspective view showing a constitution of further modification example of the gap regulating mechanism according to the first embodiment. In the modification example of
FIG. 7
, the coupling portion
43
in the middle of an extended portion of a drum holder
40
D is placed in a lightened state, and structured to be further easily elastically deformed. When the drum holder
40
D is integrally formed on a metal plate frame of the image forming unit
10
, as a modification example of the second embodiment shown in
FIG. 9D
described later, a flange
37
is formed as a bearing holding portion connected via a thin piece bent in a V shape or a two-bend crank shape, and in an easily plastically deformed constitution by respective bent portions a follow-up (copy) property of the bearing
41
with respect to the rotation drive shaft
31
becomes satisfactory.
In the structure in which the follow-up property is enhanced by the modification, a holding distance of the rotation drive shaft
31
can be set to be long, positioning of the rotation drive shaft
31
of the photosensitive drum
11
is securely performed, but a perpendicular degree with respect to the rotation drive shaft is also satisfactorily maintained, holding of a portion necessary for gap management is provided with softness, the copy property can be enhanced, and a stress of error of the holding portion applied to the rotation drive shaft can considerably be reduced in the structure.
The inside of the image forming unit will next be described. The forward and backward drum holder
40
as the gap regulating mechanism is screwed/fixed to the image forming unit frame. The drum holder
40
is provided with: the first bearings
41
,
41
for holding the rotation drive shaft
31
of the photosensitive drum
11
on the frame raised surfaces
30
a
,
30
b
; the gap setting portion bearings
42
,
42
for holding the shaft in positions closest to both end surfaces of the photosensitive drum
11
; the coupling members
43
for connecting a pair of first and gap setting portion bearings
41
,
42
on the respective sides of the frame raised surfaces
30
a
,
30
b
; second bearings
44
for holding the rotation drive shaft
32
of the developing roller
15
on both sides of the developing roller
15
and abutting on the peripheral surface of the coupling member
42
by its outer peripheral surface to set a gap between the photosensitive drum
11
and the developing roller in such a manner that the fine gap is formed between the peripheral surfaces of the drum and roller; and levers or brackets
45
for supporting the bearing on the side of the developing roller
15
from the developer case main body
14
. Additionally, the second bearings
44
,
44
disposed on both ends are provided with a support plate
46
for bridging both components, and urging members
47
,
47
for urging the support plate
46
and developing roller
15
in a direction of the photosensitive drum
11
are disposed between the developer main body case
14
and the support plate
46
.
Illustration and detailed description are omitted, but the first bearing and gap setting portion bearings
41
,
42
are constituted of an inner race fixed to the shaft
31
of the photosensitive drum
11
, an outer race fixed to the frame raised surfaces
30
a
,
30
b
and coupling member
43
, and a rotatable ball sealed between the inner race and the outer race. Moreover, the second bearing
44
is constituted of the inner race fixed to the rotation drive shaft
32
of the developing roller, the outer race fixed to the support plate
46
, the outer race fixed to the support plate
46
, and the rotatable ball pressed between the inner race and the outer race.
Additionally, in the description of the aforementioned first embodiment, as the concrete constitution of the gap regulating mechanism
40
the use of bearings as the first and second bearings and the gap setting portion has been described, but the present invention is not limited to this and the concrete constitution of the gap regulating mechanism
40
may be a bearing structure other than a ball bearing, for example, an oil containing metal bearing or a sliding shaft bearing using plastic with a high sliding property.
Returning to the description with reference to
FIG. 4
, for the photosensitive drum
11
as the image holding member, while a drum main body is tentatively placed in the image forming unit, the drum shaft
31
is passed from the side of the raised surface
30
a
on the front side of the frame
30
through a gap regulating mechanism
40
A on the front side, main body of the photosensitive drum
11
, and the gap regulating mechanism
40
B on the back side and fitted into the coupling
36
fixed to the tip end of the output shaft
34
of the motor
33
disposed on the main body side, so that the image forming unit
10
is completed.
A protruded portion is partially formed on a front flange hole of the photosensitive drum
11
, and a groove for engaging with the portion is formed in the front part of the drum shaft
31
, which forms a constitution to drive the main body of the drum
11
with the drum shaft
31
.
For the developing unit
12
, for arrangement along the peripheral surface of the photosensitive drum
11
, the developing unit
13
is screwed/fixed on a frame side, that is, a drum holder top surface in order to facilitate a fixing operation in this embodiment.
In the developing unit
12
, the developing material is supplied from a supply cartridge portion (not shown), stirred by a screw-shaped auger (not shown) in the developing unit
12
and charged before the developing material is supplied to the developing roller (magnet roller)
15
disposed adjacent to the unit. In the developing roller
15
, a magnetic field is applied to the developing material supplied/attached to a developing roller sleeve with a magnetic roller built therein, and a magnetic carrier contained in the developing material forms a magnetic brush state. When the developing roller sleeve on the outer periphery rotates, a magnetic brush supplies the developing material to the drum surface in the structure.
The developing roller
12
can freely rotate within a range limited by the structure via the lever
45
rotatably supported by the developing unit, and urged to the side of the photosensitive drum
11
by the spring member
47
. Moreover, a doctor blade assembled together with the rotatable developing roller
15
and lever assembly block
45
regulates a height to be thin when the magnetic brush stands like ears of rice, and the developing material is supplied to the peripheral surface of the photosensitive drum
11
in the structure.
Therefore, in order to obtain a good-quality image, between the peripheral surface of the photosensitive drum
11
and the peripheral surface of the developing roller
15
, the fine gap needs to be maintained in accordance with an image forming process property. In a conventional case, as described above, on either one of both sides of the rotatable developing roller disposed along the photosensitive drum side (either one of forward and backward sides of the device in an attached state to the image forming device), a contact roller coaxial with a developing roller axis is disposed. Thereby, after the developing unit and photosensitive drum are assembled in the image forming unit, the contact roller disposed opposite to a portion deviating from an image forming area on the peripheral surface of the photosensitive drum abuts on the photosensitive drum and rotates with rotation of the photosensitive drum and developing roller, a distance between the outer peripheral surface of the photosensitive drum and the shaft of the developing roller is regulated, and the aforementioned gap between both peripheral surfaces is thereby maintained/managed in the structure.
In this conventional gap maintenance/adjustment, since the contact roller directly abuts on the outer peripheral surface of the photosensitive drum, external force disturbance in this abutment portion is immediately applied to the outer peripheral surface of the photosensitive drum. Even for impacts such as image quality deterioration which raise no problem in monochromatic printing, in color printing in which multi-color images are superposed, even a slight disturbance sometimes influences a hue, and as a result, jitter or color unevenness sometimes appears on the image formed on the sheet.
In the present invention, in order to solve the problem the maintenance/management of the gap between the photosensitive drum and the developing roller is not adjusted by direct abutment onto the peripheral surface, and as shown in
FIG. 4
, the adjustment is performed by the gap regulating mechanism disposed on the bearing of the photosensitive drum and the bearing of the developing roller.
Moreover, during the conventional gap adjustment between the peripheral surfaces of the photosensitive drum and developing roller, because of direct contact with the drum surface, the drum surface is shaved by long-time continuous use. The shaved site has no influence on image formation itself, but a part of the peripheral surface of the photosensitive drum is shaved, and as a result the gap is gradually narrowed. The photosensitive drum has a life by a photosensitive layer thickness, and in many cases changed before shaved to provide an inappropriate gap, no substantial large problem is raised, but in recent years, the life has been lengthened by improvement of the photosensitive drum, and a problem may possibly arise in future.
An inventive gap maintenance/management structure proposed by the present invention is constituted as follows. First, as shown in
FIG. 4
, separately from the first bearings
41
,
41
disposed on the main body side frame
30
to hold rotation of the rotation drive shaft
31
of the photosensitive drum
11
, the gap setting portion bearings
42
,
42
are disposed in the vicinity of the photosensitive drum
11
, and on the front and back sides of the main body the first bearing
41
is connected to the gap setting portion
42
by the coupling member
43
. The outer surfaces of the coupling members
43
,
43
abut on the outer peripheral surface of the outer race of the second bearing
44
for holding the rotation of the developing roller
15
, and this indirectly maintains the gap between the outer peripheral surface of the photosensitive drum
11
and the outer peripheral surface of the developing roller
15
at a predetermined gap.
In the present specification, for the sake of convenience the gap regulating mechanism
40
is also referred to as the drum holder, but the drum holder is characterized in that the holder is extended in an inner shaft direction to the vicinity of the flange of the photosensitive drum
11
and that the gap is indirectly regulated by the gap setting portion bearing
42
disposed on the extended site.
The gap setting portion bearing
42
holds the rotation drive shaft
31
in the vicinity of the photosensitive drum, and has a function of following the position of the shaft
31
and indirectly regulating the shaft position on the outer surface of the extended site of the drum holder
40
. Specifically, a position obtained by subtracting “thickness+bearing radius” from the outer surface of the drum holder
40
corresponds to a drum shaft center, the thickness of the drum holder
40
is set to obtain a relation represented by an equation:
target gap length={(drum holder thickness+drum holder side bearing radius)+contact roller radius}−{drum outer periphery radius+developing roller radius},
the contact roller formed by the second bearing
44
is placed in contact with the outer surface of the holder
40
of the photosensitive drum
11
, and the gap is managed/maintained.
Additionally, in the image forming system according to the aforementioned first embodiment, the constituting of all the first and second bearings and gap setting portion forming the gap regulating mechanism
40
by the ball bearings has been described, but the present invention is not limited to this, and these bearings and gap setting portion may be constituted by sliding bearings.
FIG. 8
is a sectional view showing the gap regulating mechanism in the image forming system according to the second embodiment of the present invention. As shown in
FIG. 8
, for either one of forward and backward drum holders, the first and second bearings
41
,
42
of the drum holder
40
B on the back side in the example shown in the drawing mainly hold the rotation drive shaft
31
of the photosensitive drum
11
, the position of the rotation drive shaft
31
of the photosensitive drum
11
and the perpendicular degree with respect to the main body side housing frame
30
are determined, in another drum holder
55
A only the second bearing
42
for gap management holds the rotation drive shaft
31
, and both side second bearings
42
,
42
a
for the gap management manage/regulates the gap between the outer peripheral surface of the photosensitive drum
11
and the outer peripheral surface of the developing roller
15
.
A detailed constitution of the gap regulating mechanism according to the second embodiment will be described with reference to FIG.
8
. Since the constitution of the drum holder
40
B on the main body rear side is the same as the constitution of the first embodiment described using
FIG. 4
, the same reference numerals are used and a detailed description is omitted. The drum holder
55
A on the front side of the main body is provided with the bearing
42
a
of substantially the same constitution as that of the gap setting portion bearing
42
of the drum holder
40
B, and a positioning collar
56
disposed opposite to the bearing
42
a,
fitted into the flange of the front side raised surface
30
a
of the frame
30
and also connected to the bearing
42
a.
In the second embodiment shown in
FIG. 8
, the positioning collar
56
is provided with a fixing portion
56
a
engaging with the flange of the raised surface
30
a
of the frame
30
, a bearing holding portion
56
b,
disposed opposite to the photosensitive drum
11
, for holding the bearing
42
a,
and a thin bridge portion
56
c
for bridging the fixing portion
56
a
and holding portion
56
b.
On the main body front side of the rotation drive shaft
31
of the photosensitive drum
11
a small diameter portion
57
is formed with a small diameter, and a center hole
58
formed on the center side of fixing portion
56
a
of the collar
56
is in a loose engagement state with the small-diameter portion
57
.
According to the holding structure of the photosensitive drum in the image forming unit according to the second embodiment constituted as described above, by removing the positioning bearing of the rotation drive shaft
31
of the photosensitive drum
11
of one drum holder
55
A, and lowering a sliding function by the ball bearing, the stress attributed to an error from a coaxial degree of the bearing
42
and applied to the rotation drive shaft of the photosensitive drum can be weakened.
FIGS. 9A and 9B
are a sectional view and front view showing details of the bearing structure of the photosensitive drum. The first bearing
41
constituting the drum holder
40
engages in the flange
37
disposed on the main body side housing frame
30
. When the first bearing
41
is constituted, for example, by the bearing, the outer race is fitted/fixed with the inner wall of the flange
37
, and on the center side of the inner race the rotation drive shaft
31
of the photosensitive drum is fitted/fixed in the structure.
Additionally, one characteristic of the constitution in which the drum holder
40
according to the present invention is used as the bearing on both ends of the front and back sides of the photosensitive drum
11
lies in that, for example, distortion or the like of the rotation drive shaft
31
during assembling of the photosensitive drum
11
to the image forming unit can be absorbed. Specifically, the rotation drive shaft
31
of the photosensitive drum
11
is supported at two points only by the main body side frame, while in the present invention at least the first and gap setting portion is disposed on both sides of the photosensitive drum
11
in the constitution, so that the distortion or the like of the rotation drive shaft
31
during attachment can be absorbed.
FIGS. 9C and 9D
are a sectional view and a front view showing the attachment structure of the photosensitive drum bearing to the frame using plastic deformation as a modification example of
FIGS. 9A and 9B
. A displacement absorbing portion
50
is disposed around the flange
37
of the frame
30
, and this displacement absorbing portion
50
is provided with four ¼ peripheral hole portions
51
a
to
51
d
and four coupling pieces
52
of various shapes described later.
Additionally, after the photosensitive drum
11
is assembled into one with the developing unit to constitute the image forming unit
10
, during attaching to the main body side the outer peripheral portion of the bearing portion of the photosensitive drum
11
is distorted with the corresponding portion on the main body side or sometimes impacted. As a constitution for absorbing such damage to the bearing portion, a constitution shown in
FIG. 9D
may be disposed. The displacement absorbing portion
50
for the unit frame of the image forming unit
10
shown in
FIG. 9D
is disposed to surround the flange
37
on the outer peripheral side of the flange
37
of the unit frame molded by synthetic resins such as plastic. As shown in
FIG. 9D
, in the displacement absorbing portion
50
, for example, the ¼ peripheral portions
51
a
,
51
b
,
51
c
,
51
d
are formed around the flange
37
of the frame
30
by integral molding. The notch portion
52
of a predetermined shape is formed between respective edges of the peripheral portions
51
a
to
51
d
. As a concrete shape of the notch portion
52
, there are a V-shaped notch portion
52
a
and a crank-shaped notch portion
52
b
, and either notch portion absorbs displacement by distortion of the rotation drive shaft
31
of the photosensitive drum during assembly or disassembly.
As described above, for the gap setting portion bearings
42
,
42
on the side of the photosensitive drum
11
in the drum holder
40
for the gap management, the holder disposed the forward and backward sides in the main body instead of only one side is constituted of a pair of
40
A,
40
B, and by constituting a pair of second bearings
44
,
44
opposite to the gap setting portion bearing
42
via the coupling member
43
, gap management with a higher precision is possible.
Additionally, in the structure of the first embodiment, the holding of the rotation drive shaft
31
of the photosensitive drum
11
is performed by four bearings
41
,
42
,
41
,
42
exceeding two bearings, and by the necessarily generated coaxial degree error between the bearings, not little stress of the diametric direction sometimes occurs in the drum shaft
31
. This stress results in a motor drive load, and there is a problem that rotation precision is deteriorated.
Therefore, in order to also solve this problem, a new structure for obtaining a satisfactory follow-up property of the drum holder
40
in the direction of the photosensitive drum
11
with respect to a position fluctuation of the extended portion in a radius direction of the rotation drive shaft
31
is provided as the second embodiment.
FIG. 10
is a perspective view showing attachment positions of the photosensitive drum and developing roller.
FIG. 10
does not show a particularly new constitution, and shows the assembly position of the photosensitive drum
11
and developing roller
15
to the main body side housing frame
30
. In
FIG. 10
, between the rotation drive shaft
31
of the photosensitive drum
11
and the rotation drive shaft
32
of the developing roller
15
, the drum holders
40
as the gap regulating mechanism are disposed on both ends (the front and back sides in a main body position relation).
FIG. 11
is a perspective view showing details of the gap regulating mechanism in the image forming system of the second embodiment.
FIG. 11
shows one side of the drum holder
40
shown in
FIG. 4
in a cutaway manner. In
FIG. 11
, the rotation drive shaft
31
of the photosensitive drum
11
is provided with the drum holder
40
. The drum holder
40
comprises the shaft tip positioning collar
56
and the gap setting portion bearing
42
a
, and the gap setting portion bearing
42
a
abuts on the outer peripheral surface of the second bearing
44
disposed on the side of the developing roller
15
via the coupling portion
56
c.
The gap regulating mechanism of the image forming unit according to a third embodiment of the present invention will next be described with reference to
FIGS. 12
to
14
. In the gap regulating mechanism according to the third embodiment, a constitution for assembling the image forming unit
10
provided with the gap regulating mechanism described in the first and second embodiments on the main body side of the tandem type image forming system, and a position relation when the photosensitive drum
11
and developing roller
15
are attached will particularly be described.
In
FIG. 12
, a plurality of, for example, four photosensitive drums
11
and four developing rollers
15
to form pairs with the drums are assembled in a unit frame
60
and inserted in a direction of a rear frame
62
via an insertion port
61
A of a front frame
61
on the main body side. During insertion, engagement places on the side of the unit frame
60
are fitted and inserted into a pair of guide rails
63
,
63
bridged between the front frame
61
and the rear frame
62
. In this case, two positioning studs
60
a
,
60
a
formed on the unit frame
60
are fitted into the front frame
61
, and positioning studs
64
,
64
disposed on the rear frame
62
are engaged with engagement holes formed in the rear side end surface of the unit frame
60
. Additionally, in
FIG. 12
, among four pairs of photosensitive drums
11
and developing rollers
15
only two pairs on both sides are shown, and inner two pairs are omitted.
By the positioning studs and engagement holes disposed on the side of the front fame
61
and rear frame
62
, after determining the attachment position of the unit frame
60
of the image forming unit, the unit frame
60
can be assembled to the front frame
61
and rear frame
62
, but in this case, some distortion, collision of the frame against the frame, and the like sometimes occur. Even in this case, by disposing the displacement absorbing portion as shown in
FIG. 9
, the displacement around the shaft can be absorbed to some degree.
On a dead end to which the unit frame
60
is inserted, a plurality of hole portions
65
in which the rotation drive shaft
31
of the photosensitive drum
11
of the image forming unit
10
, the rotation drive shaft
32
of the developing roller
15
and power supply portions are disposed are formed in corresponding places of the rear frame
62
. After assembling the unit frame
60
to the front frame
61
and rear frame
62
according to the constitution shown in
FIG. 12
, respective main places of the image forming unit
10
are fixed by means such as screwing to complete the assembling.
FIG. 13
is a side view showing a gap setting state between the photosensitive drum and the developing roller in the third embodiment, and in the drawing, the gap between the photosensitive drum
11
and the developing roller
15
is managed in such a manner that the predetermined gap is maintained by the gap regulating mechanism according to the constitution described in the first and second embodiments. Moreover, in the position opposite to the developing roller
15
, disposed is a doctor blade
67
which is structured to regulate a height to be thin when the magnetic brush stands like the ears of rice and to supply the developing material to the peripheral surface of the photosensitive drum
11
.
FIG. 14
is an explanatory view of a position relation between the photosensitive drum
11
and the developing roller
15
in the image forming system according to the third embodiment, and
FIG. 14
is a front view when the main body is viewed in a rear side direction from the front side of the main body. In
FIG. 14
, the photosensitive drum
11
is supported while the mutual position relation is regulated by the gap regulating mechanism
40
described in the first and second embodiments in such a manner that a fine gap
69
requiring management is maintained between the photosensitive drum and the developing roller
15
rotatably supported by the rotary lever
45
. Additionally, the developing material is continuously supplied to the developing roller
15
by the developing unit
14
.
Some examples of the image forming device to which the gap regulating mechanism of the image forming unit according to the present invention is attached will next be described. As described above, as shown in
FIG. 15
, the present invention can also be used when the gap in the attachment relation of the single large-diameter photosensitive drum to the single developing roller is set. In this case, since the photosensitive drum
11
has a large diameter, the outer peripheral portion of the drum holder may be enlarged in diameter only in a direction of position in the contact roller on the developing roller side, and abut on the contact roller. This can save an excessive space.
Alternatively, by attaching the contact roller with a slight large diameter to both ends of the developing roller
15
and thereby adjusting abutment state around the shaft of the photosensitive drum, the gap between the outer peripheral surfaces of the photosensitive drum
11
and developing roller
15
can be set to a desired distance. Additionally, in
FIG. 15
, numeral
17
denotes a charger for charging the photosensitive drum
11
, and after the photosensitive drum
11
charged by the charger
17
rotates substantially once, electricity is removed by an electricity removing lamp
17
, and charging is performed with respect to the next image again by the charger
17
.
FIG. 16
is an explanatory view showing a case in which the present invention is applied to the image forming device of a multiple transferring system and an intermediate transferring system, in
FIG. 16
, a plurality of developing rollers
15
are arranged on the outer peripheral side of the single large-diameter photosensitive drum
11
in a satellite manner, and the gap regulating mechanism described in the first and second embodiments is disposed between the respective rotation drive shafts of the developing roller and photosensitive drum. In the image forming device of the intermediate transferring system, after an intermediate transferrer
70
is once subjected to primary transferring by a transferring portion
71
, secondary transferring is performed by a transferring portion
72
to form the image on the sheet or the like, and even in the image forming device of the intermediate transferring system constituted as described above, the gap regulating mechanism according to the present invention can be used to set the gap between the outer peripheral surfaces of the photosensitive drum and developing roller to the desired distance.
FIG. 17
shows the image forming device of a multiple developing system and one pass system, and even in the image forming device of the multiple developing/one pass system the developing rollers
15
are arranged like satellites around the single large-diameter photosensitive drum
11
. The gap regulating mechanism according to the present invention is attached between the respective rotation drive shafts of the photosensitive drum
11
and developing roller
15
to constantly adjust the gaps between the outer peripheral surface of the photosensitive drum and the respective outer peripheral surfaces of a plurality of developing rollers. The sheet as the image forming medium is supplied and conveyed as shown a dotted line in the drawing, and the image is formed on the photosensitive drum
11
by the developing material and subsequently transferred to the sheet in a transferring portion
73
.
FIG. 18
shows the transferring drum structure of the multiple transferring system. In the image forming system by the transferring drum structure of the multiple transferring system, the image forming unit is provided with at least the small diameter roller-shaped photosensitive drum
11
as the image holding member, a transferring drum
75
provided with a large-diameter drum shape disposed on one side of the photosensitive drum
11
and provided with a transferring portion
76
on its peripheral surface, and a plurality of developing rollers
15
, for respective colors of developing materials, disposed apart from one another by constant angles on the peripheral surface of a large-diameter drum
77
disposed on the other side of the photosensitive drum
11
, and a final color image is obtained by successively forming the images of the respective color developing materials on the sheet as the image forming medium wound around the transferring drum
75
. Even in the image forming system of the multiple transferring system transferring drum structure, by attaching the gap regulating mechanism according to the present invention to the mutual shafts of the developing roller for rotating in a revolver manner to successively/continuously develop the image on the photosensitive drum and the photosensitive drum, a desired action/effect can be achieved. Additionally, in this example, since a plurality of developing rollers
15
are disposed on the drum
77
rotating in the revolver manner, the gap regulating mechanism is constituted to set an optimum gap when the developing roller abuts on the photosensitive drum
11
.
FIG. 19
shows the image forming system of a multiple rotation structure. The image forming unit in this system is provided with the large-diameter photosensitive drum
11
rotating multiple times as the image holding member, and a plurality of developing rollers
15
, for the respective colors of developing materials, disposed opposite to the image forming surface of the photosensitive drum
11
and apart from one another by a predetermined angle, and the color image is obtained by rotating the photosensitive drum
11
multiple times and superposing the respective colors of developing materials on the image forming surface to perform collective transferring to the image forming medium.
Even in this example, the gap regulating mechanism according to the present invention can be applied, but the photosensitive drum
11
has a large diameter, and the gap setting portion is therefore constituted by a member with a diameter larger than that of the drum
11
, and allowed to abut on the bearing on the side of the plurality of developing rollers
15
, so that the gap between both can be adjusted and set to a desired value.
As described above, the present invention is not limited to the tandem type image forming system described in the first to third embodiments, and the gap between the respective outer peripheral surfaces of the single large-diameter photosensitive drum and the single or the plurality of developing rollers can be adjusted by setting the position between the respective rotation drive shafts. However, the tandem type image forming system is a most adaptable image forming system for the application of the present invention, and in this meaning the application of the present invention to the tandem type image forming system for forming the multiple color image is a best mode of the present invention.
Claims
- 1. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, and wherein at least one of said first and second bearing is formed by a positioning collar which is fitted into an attachment place of the frame of an image forming unit fixed on a main body side of said image forming system and which loosely supports the support shaft of said photosensitive drum inside its diametric direction to regulate a large displacement alone of the support shaft.
- 2. The image forming system according to claim 1 wherein said gap regulating mechanism comprises: said first bearing and the gap setting portion laterally symmetrically disposed on both sides of a photosensitive drum as said image holding member; a coupling portion for coupling respective outer peripheral portions of said first bearing and the gap setting portion; said second bearing having an outer peripheral surface opposite to said gap setting portion right close to both ends of said photosensitive drum via the outer periphery of said coupling portion and having its inner peripheral surface fitted into the rotation drive shaft of said developing roller; and an urging member for urging said developing roller in the direction of said image holding surface of said image holding member.
- 3. The image forming system according to claim 1 wherein at least one of a pair of said gap setting portions is constituted by a fixing member, and one end of said fixing member abuts on said support shaft and the other end thereof abuts on said second bearing to set a gap between said image forming surface of said photosensitive drum supported by said support shaft and the outer surface of said developing roller.
- 4. The image forming system according to claim 1 wherein said image forming unit is provided with a plurality of photosensitive drums as said image holding member, and a plurality of developing units as a developer for forming a pair with each of the photosensitive drums, at least said plurality of photosensitive drums are arranged in parallel in a tandem structure, and the plurality of photosensitive drums and the plurality of developing units are assembled in one image forming unit case.
- 5. The image forming system according to claim 1 wherein said image forming unit has a transferring drum structure provided with a single photosensitive drum as said image holding member and a single developing roller as said developer.
- 6. The image forming system according to claim 1 wherein said image forming unit has an intermediate transferring structure provided with a single photosensitive drum as said image holding member, a plurality of developing rollers as the developer provided with different colors of developing materials disposed apart from one another via a predetermined angle around the photosensitive drum, and an intermediate transferrer for successively transferring the respective colors of developing materials formed on said photosensitive drum.
- 7. The image forming system according to claim 1 wherein said image forming unit has a multiple developing structure of one pass system which includes a single large-diameter photosensitive drum as said image holding member, and a plurality of developing rollers as said developer provided with different colors of developing materials apart from one another via a predetermined angle around the photosensitive drum, and which transfers a color image obtained by superposing the developing materials on the image holding surface of said photosensitive drum onto said sheet by passing the sheet as said image forming medium once to obtain the formed image.
- 8. The image forming system according to claim 1 wherein said image forming unit has a transferring drum structure which comprises at least a small-diameter roller-shaped photosensitive member as said image holding member, a transferring drum provided with a large-diameter drum shape disposed on one side of the photosensitive member and the transferring portion on the peripheral surface of the drum shape, and a plurality of developing rollers for the respective developing materials disposed apart from one another by a constant angle on the peripheral surface of a large-diameter drum disposed on the other side of said photosensitive member, and which successively forms the images of respective color developing materials on the image forming medium wound around said transferring drum to obtain a final color image.
- 9. The image forming system according to claim 1 wherein said image forming unit has a multiple rotation structure which comprises a large-diameter multiple-rotation photosensitive drum as said image holding member, and a plurality of developing rollers for respective colors of developing materials disposed opposite to said image forming surface of the photosensitive drum and apart from one another by a predetermined angle, and which rotates said photosensitive drum multiple times to superpose the respective colors of developing materials on said image forming surface and then collectively transferring them to the image forming medium to obtain the color image.
- 10. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, wherein said gap regulating mechanism comprises: said first bearing and the gap setting portion laterally symmetrically disposed on both sides of a photosensitive drum as said image holding member; a coupling portion for coupling respective outer peripheral portions of said first bearing and the gap setting portion; said second bearing having an outer peripheral surface opposite to said gap setting portion right close to both ends of said photosensitive drum via the outer periphery of said coupling portion and having its inner peripheral surface fitted into the rotation drive shaft of said developing roller; and an urging member for urging said developing roller in the direction of said image holding surface of said image holding member, and wherein at least one of said coupling portions for coupling outer peripheral sides of said first bearing and said gap setting portion is constituted by an elastic member for absorbing, by an elastic force, external action forces including deflection, distortion and eccentric action applied to said support shaft passed inside the diametric direction.
- 11. The image forming system according to claim 10 wherein said elastic member is formed of a thin member as compared with an ordinary coupling member, and elastically deformed to absorb the external action force when said external action force is applied around the support shaft to such an extent that the ordinary coupling member fails to be elastically deformed.
- 12. The image forming system according to claim 10 wherein said elastic member is constituted of a plurality of coupling pieces for bridging said first bearing and said gap setting portion, portions other than the plurality of coupling pieces are a plurality of openings which are lighted and opened, and said plurality of elastic pieces are deformed to absorb the external action force when said external action force is applied around said support shaft to such an extent that the ordinary coupling member fails to be elastically deformed.
- 13. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, wherein said gap regulating mechanism comprises: said first bearing and the gap setting portion laterally symmetrically disposed on both sides of a photosensitive drum as said image holding member; a coupling portion for coupling respective outer peripheral portions of said first bearing and the gap setting portion; said second bearing having an outer peripheral surface opposite to said gap setting portion right close to both ends of said photosensitive drum via the outer periphery of said coupling portion and having its inner peripheral surface fitted into the rotation drive shaft of said developing roller; and an urging member for urging said developing roller in the direction of said image holding surface of said image holding member, and at least one of said first bearings is formed by a positioning collar which is fitted into an attachment place of the frame of an image forming unit fixed on a main body side of said image forming system and which loosely supports the support shaft of said photosensitive drum inside its diametric direction to regulate a large displacement alone of the support shaft.
- 14. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, wherein a peripheral edge of a frame side holding portion of the image forming unit for holding the first bearing constituting said gap regulating mechanism includes a plurality of peripheral holes and a plurality of coupling pieces for coupling a frame between the respective peripheral holes, and has a plastically deformable displacement absorbing structure.
- 15. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, wherein at least one of a pair of said first bearings is constituted by a bearing provided with an inner race into which said support shaft is fitted, an outer race which is fitted into said main body frame, and a ball sealed between said inner race and said outer race.
- 16. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in a developing portion for supplying said developing material to develop said latent image held on said image holding surface as the image with said developing material, said developing roller being provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least a first bearing for holding said support shaft of said image holding member, a gap setting portion, disposed at a predetermined distance from the first bearing in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and a second bearing for rotatably holding said rotation drive shaft of said developing roller from the side of a developer and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second bearing itself and said gap setting portion, said gap regulating mechanism setting a gap between two surfaces in such a manner that a constant fine gap is always continued to be maintained between said gap setting portion and said second bearing, wherein at least one of a pair of said first bearings is constituted by a sliding shaft bearing whose inner peripheral surface contacts the peripheral surface of a rotation drive shaft as said support shaft to support the rotation of said rotation drive shaft.
- 17. An image forming system comprising: an image forming unit for forming an image by using a developing material; a medium supplying portion for supplying an image forming medium to the image forming unit; a medium conveying portion for conveying said supplied image forming medium; a medium supplying/conveying controller for controlling the supplying/conveying of the image forming medium to said image forming unit by said medium supplying portion and the medium conveying portion; a transferring portion for transferring said image developed by said image forming unit to said image forming medium; and a fixing portion for fixing the transferred image,wherein said image forming unit comprises: a photosensitive drum for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said photosensitive drum being provided with a support shaft movably fixed to a main body frame of said system; a developing roller provided with a rotation drive shaft for supplying said developing material to said image holding surface to develop said latent image held on said image holding surface as the image by said developing material; and a gap regulating mechanism which includes at least first shaft holding means for holding said support shaft of said image holding member, gap setting means, disposed at a predetermined distance from the first shaft holding means in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, coupling means for coupling outer peripheral portions of said first shaft holding means and said gap setting means, second shaft holding means for rotatably holding said rotation drive shaft of said developing roller from the side of said developing means and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between said second shaft holding means itself and said gap setting means, said second shaft holding means being provided with an outer peripheral surface opposite to said gap setting means right close to both ends of said photosensitive drum via an outer periphery of said coupling means and an inner peripheral surface fitted into the rotation drive shaft of said developing roller, and urging means for urging said developing roller in the direction of said image holding surface of said image holding member, and which sets a gap between two surfaces in such a manner that said first shaft holding means and said gap setting means are laterally symmetrically disposed on both sides of said photosensitive drum and a constant fine gap continues to be maintained between said gap setting means and said second shaft holding means, and wherein at least one of said first and second shaft holding means is formed by a positioning collar which is fitted into an attachment place of the frame of an image forming unit fixed on a main body side of said image forming system and which loosely supports the support shaft of said photosensitive drum inside its diametric direction to regulate a large displacement alone of the support shaft.
- 18. An image forming system comprising: image forming means for forming an image by using a developing material; medium supplying means for supplying an image forming medium to the image forming means; medium conveying means for conveying the supplied image forming medium; a medium supplying/conveying control means for controlling the supplying/conveying of the image forming medium to said image forming means by said medium supplying means and the image forming medium conveying means; transferring means for transferring said image developed by said image forming means to said image forming medium; and fixing means for fixing the transferred image,wherein said image forming means comprises: a an image holding member for converting an optical image formed via an optical system into a latent image and subsequently depositing said developing material thereon to hold the image on an image holding surface, said image holding member being provided with a support shaft movably fixed to a main body frame of said system; a developing roller disposed in said developing means for supplying said developing material to develop said latent image held on said image holding surface as the image by said developing material, and provided with a rotation drive shaft for supplying said developing material to said image holding surface; and a gap regulating mechanism which includes at least first shaft holding means for holding said support shaft of said image holding member, gap setting means, disposed at a predetermined distance from the first shaft holding means in a direction of said image holding member, for holding said support shaft in the vicinity of said image holding member in an assisting manner, and second shaft holding means for rotatably holding said rotation drive shaft of said developing roller from the side of said developing means and maintaining a distance between the image holding surface of said image holding member and the peripheral surface of said developing roller between the second shaft holding means itself and said gap setting means, and which sets a gap between two surfaces in such a manner that a constant fine gap always continues to be maintained between said gap setting means and said second shaft holding means, said gap regulating mechanism comprises: said first shaft holding means and said gap setting means laterally symmetrically disposed on both sides of a photosensitive drum as said image holding member; coupling means for coupling outer peripheral portions of said first shaft holding means and the gap setting means with each other; said second shaft holding means provided with an outer peripheral surface opposite to said gap setting means right close to both ends of said photosensitive drum via an outer periphery of said coupling means and an inner peripheral surface fitted into the rotation drive shaft of said developing roller; and urging means for urging said developing roller in the direction of said image holding surface of said image holding member, and at least one of said first shaft holding means is formed by a positioning collar which is fitted into an attachment place of the frame of an image forming unit fixed on a main body side of said image forming system and which loosely supports the support shaft of said photosensitive drum inside its diametric direction to regulate a large displacement alone of the support shaft.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4258372 |
Ishikawa |
Mar 1981 |
A |
5223893 |
Ikemoto et al. |
Jun 1993 |
A |
6173145 |
Chadani et al. |
Jan 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
8-286561 |
Nov 1996 |
JP |