JP2001312121A - Image forming device and image carrier unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly shave the surface of an image carrier such as a photoreceptor by a gap controlling member. SOLUTION: A pair of rollers 18 whose outside diameter D2 is larger than the outside diameter D1 of a conductive rubber roller part 17 are attached at both end parts of the core bar 16 of an electrifying roller 14, and are respectively abutted on noncoated parts 62 formed of a material harder than the coated part 61 of the photoreceptive drum 5, so that a very small gap G is formed between the conductive rubber roller part 17 of the electrifying roller 14 and the coated part 61 of the photoreceptive drum 5. Thus, wear due to the roller 18 of the surface of the photoreceptive drum 5 is reduced as compared with the case that each roller 18 is brought into contact with the coated part 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image bearing member having a coated portion for forming a photosensitive layer and non-coated portions formed on both sides of the coated portion with a material harder than the coated portion. The present invention relates to an image forming apparatus including a charging unit having a charging member for charging a coating unit, and an image carrier unit mounted on the image forming apparatus.

[0002]

2. Description of the Related Art Heretofore, a charging member having an effective width of a charging member has been arranged close to the surface of a photosensitive member as an image carrier, and a voltage has been applied between the charging member and the photosensitive member to apply a voltage to the photosensitive member. There is a non-contact type charging device that charges the surface of the device. In such a charging device, there is an advantage that the charging member is less likely to be stained because the portion of the effective charging width of the charging member does not contact the surface of the photoconductor.

In such a non-contact type charging device, for example, a convex portion is formed by attaching tape members to both ends of a roller portion of a charging roller which is a charging member, thereby removing the both ends of the charging roller. Is made non-contact with the surface of the photoreceptor as the image carrier. FIG. 9 shows an example of the charging roller. The charging roller 114 is provided with an elastic portion 117 having conductivity, for example, on the outer periphery of a cored bar 116 made of stainless steel.
7, resin tape members 118, 118 for forming a gap at both ends are wound in the circumferential direction and fixed integrally.

[0004] Both ends of the cored bar 116 are pressed by the pressing springs 119, 119 to the photosensitive drum 105 side through sliding bearings 130, 130 with a predetermined pressing force. As a result, the charging roller 114 has the tape members 118 on both sides in contact with the surface of the photosensitive drum 105, and the charging effective width Wac of the elastic portion 117 is not in contact with the surface of the photosensitive drum 105. Contact (a gap G corresponding to the thickness of the tape member 118 is formed).

[0005]

However, by bringing the gap management members formed of the tape members for forming the gaps provided at both ends of the charging roller into contact with the photosensitive drum as described above, the charging is performed in the portion of the effective charging width. In a non-contact type charging device in which a predetermined gap is formed between the roller and the surface of the photoconductor drum, inconvenience may occur depending on the position where the gap management member contacts the photoconductor drum. .

That is, if the gap G shown in FIG. 9 is too wide, a predetermined charging performance cannot be obtained. Therefore, the gap G needs to be extremely small, for example, about 100 μm or less. is there. Therefore, when the gap management member is brought into contact with a coated portion (a portion where the photosensitive layer is formed) having a lower hardness than the non-coated portion of the photosensitive drum, the contact portion of the photosensitive drum becomes the gap management member. , The portion of the effective charging width of the charging roller comes into contact with the surface of the photosensitive drum (the gap becomes zero).

In such a case, since residual toner and the like on the photosensitive drum are transferred to a portion of the effective charging width of the charging roller, poor charging may occur due to the contamination. In particular,
In the case where roller-shaped gap management members are provided at both ends of the charging roller to form the gap G, the rollers may easily remove the coated portion of the photosensitive drum. The present invention has been made in view of the above problems, and has as its object to make it difficult for the surface of an image carrier such as a photoconductor to be scraped by a gap management member.

[0008]

In order to achieve the above object, the present invention has a coated portion for forming a photosensitive layer and non-coated portions formed on both sides of the coated portion with a material harder than the coated portion. In an image forming apparatus including an image carrier and charging means having a roller-shaped charging member for charging the coating portion of the image carrier, the coating of the charging member is performed at both ends of the charging member. A roller-shaped gap management member formed with an outer diameter larger than the outer diameter of the portion facing the portion is provided, and the gap management member is brought into contact with the non-coated portions on both sides of the image carrier to thereby charge the charging member. A minute gap is formed between the coating portion and the coating portion of the image carrier.

In the above image forming apparatus, a transfer member for transferring a visible image formed on the surface of the image carrier to a transfer material is provided, and the effective transfer width of the transfer member is made larger than the effective charge width of the charging means. It is good to make it narrow. Further, the non-coating portions may be formed outside the effective charging width of the charging means.

The image forming apparatus further includes a developing device that develops a latent image on the image carrier with a developer to make the image visible, wherein a developing width of the developing device is larger than an effective charging width of charging means. It is good to make it narrow. Further, in the image forming apparatus in which the effective transfer width of the transfer member is smaller than the effective charge width of the charging unit, the image forming apparatus further includes a developing device that develops a latent image on the image carrier with a developer to make the latent image visible. It is preferable that the developing width by the developing device is smaller than the effective transfer width.

Further, in any of the above image forming apparatuses, it is preferable to provide a cleaning means for slidably contacting the surface of the image carrier with a predetermined cleaning width, and to make the cleaning width wider than the effective charging width of the charging means. . Then, the cleaning width is preferably smaller than the coating width of the portion where the coating portion is formed.

Further, in the image forming apparatus, there is provided a cleaning member oscillating mechanism for oscillating the cleaning member of the cleaning means in a direction orthogonal to a sliding contact direction of the cleaning member with respect to the image carrier, and the cleaning member oscillating mechanism is provided. The width of the cleaning oscillating area of the cleaning member oscillated by the above is preferably the cleaning width. An image carrier unit mounted on any one of the image forming apparatuses, wherein the image carrier and the charging member are integrally provided.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a charging roller and a photosensitive drum provided in an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a front view for explaining the detailed configuration of the charging roller. 3 is an overall configuration diagram showing a small color printer which is also the image forming apparatus.

The color small printer as the image forming apparatus shown in FIG. 3 is a four-drum full-color electrophotographic image forming apparatus, and a photoconductor as four image carrier units is provided in the apparatus main body 1. Units 2A, 2B, 2C and 2
D are detachably attached to the apparatus main body 1. In this small-sized printer, a transfer belt 3 is mounted at a substantially center in the apparatus main body 1 so as to be rotatable between a plurality of rollers in a direction indicated by an arrow A.

Then, the photosensitive drums 5 provided in the four photosensitive units 2A, 2B, 2C and 2D are brought into contact with the upper surface of the transfer belt 3 in FIG. Units 2A to 2D are provided respectively. The developing device 1 uses a different toner color for each of the photoreceptor units 2A to 2D.
0A to 10D are provided.

A writing unit 6 is provided above the photosensitive units 2A to 2D, and a duplex unit 7 is provided below the photosensitive units 2A to 2D. Further, this small printer is equipped with a reversing unit 8 for reversing and discharging the transfer paper P after image formation and conveying it to the duplex unit 7 on the left side of the apparatus main body 1 in FIG.

Between the transfer belt 3 and the reversing unit 8, there is provided a fixing device 9 for fixing the image of the transfer paper on which the image has been transferred. On the downstream side of the fixing device 9 in the transfer paper transport direction, a reverse transport path 20 is formed by branching, and the transfer paper P transported there is allowed to be discharged onto a paper discharge tray 26 by a paper discharge roller pair 25. .

In the lower part of the apparatus main body 1, a paper feed cassette 1 capable of storing transfer papers P of different sizes in two upper and lower stages is provided.
1 and 12 are provided respectively. Further, a manual tray 13 is provided on the right side of the apparatus main body 1 so as to be openable and closable in the direction of arrow B, and the manual tray 13 is opened so that manual paper can be fed therefrom.

The photoconductor units 2A to 2D are units having the same configuration. The photoconductor unit 2A forms an image corresponding to yellow, the photoconductor unit 2B forms an image corresponding to magenta, The photoconductor unit 2C forms an image corresponding to cyan, and the photoconductor unit 2D
Forms an image corresponding to the black color. Then, they are arranged at intervals in the transport direction of the transfer paper.

As shown in FIG. 4, each of the photoreceptor units 2A to 2D has a charging roller 14 included in a charging device 4 serving as a charging unit, and the surface thereof is charged by the charging roller 14. The photosensitive drum 5 which is an OPC drum type image carrier to be formed, and a cleaning blade 47 and a brush roller 15 which constitute a cleaning device (cleaning means) for cleaning the surface of the photosensitive drum 5 are integrated into an integrated unit. Make up,
This is detachable from the apparatus main body 1 shown in FIG.

As shown in FIG. 2, the charging device 4 is arranged such that the effective charging width Wac of the charging roller 14 as a charging member is brought closer to the charged surface (surface) of the photosensitive drum 5 in a configuration described later. Then, a voltage is applied between the charging roller 14 and the photosensitive drum 5 to charge the charged surface of the photosensitive drum 5.

The charging roller 14 of the charging device 4 is a metal shaft 16 having an outer diameter of 9 mm formed by, for example, SUM-Ni plating (steel surface is finished with nickel plating).
For example, the wall pressure is 1.5 m
The conductive rubber roller portion 17 is formed of an epichlorohydrin rubber having a volume resistivity of 1 × 10 ³ to 1 × 10 ⁸ Ω · cm. In addition,
The conductive rubber roller portion 17 has a rubber hardness of the old JIS-JIS.
A is about 77 degrees and the test piece hardness of rubber itself is 5
Use the one with 0 degrees or more.

A pair of rollers 18, 18 which are gap management members, are attached to both ends of the cored bar 16. The roller 18 is made of rubber, for example, and has an outer diameter D as shown in FIG.
It is larger than the outer diameter D ₁ of the conductive rubber roller portion 17 which faces ₂ to coated portion 61 (described later) of the photosensitive drum 5 of the charging roller 14.

The pair of rollers 18, 18 are provided on both sides of a coating portion 61 forming the photosensitive layer of the photosensitive drum 5, and are formed of a material harder than the coating portion 61. And the outer diameter D of the conductive rubber roller portion 17 of the charging roller 14.
The difference between ₁ and the outer diameter D ₂ of each roller 18 to form a minute gap G (e.g., 100μm or less) between the conductive rubber roller portion 17 and the coated portion 61 of the photosensitive drum 5.

As shown in FIG. 2, the charging roller 14 has both ends of the metal core 16 sliding on the photosensitive drum 5 via sliding bearings 30, 30 by pressurizing springs 19, 19 with a predetermined pressing force. Pressurized. The charging roller 14
Alternatively, the rollers 18 on both sides may be brought into contact with the non-coated portions 62 on both ends of the photosensitive drum 5 by their own weight without using the pressure spring 19, respectively.

A driving gear (not shown) is fixed to one end of the core 16 of the charging roller 14 on the right side in FIG. 2, and a driving force from a motor is transmitted to the driving gear to make the charging roller 14 the same as the photosensitive drum 5. It rotates at the linear velocity. The voltage is applied to the charging roller 14 by applying, for example, DC-700V to the cored bar 16 with constant voltage control and applying an AC voltage with constant current control.

On the other hand, the photosensitive drum 5 is rotationally driven in the direction of arrow C in FIG. 4 by a motor which is rotationally driven via a drum driving timing belt, a drum driving pulley (both not shown) and the like. Each of the photoreceptor units 2A to 2D provided with the photoreceptor drum 5 slides the leading end thereof into a coating portion 61 on the surface of the photoreceptor drum 5 to transfer the transfer residue adhered to the coating portion 61. A cleaning blade 4 for scraping off toner and the like and cleaning with a predetermined cleaning width
7, the toner scraped off by the cleaning blade 47 is moved to the toner conveying auger 48 side by the brush roller 15, and the waste toner collected by rotating the toner conveying auger 48 is removed to a predetermined waste toner. It is transported to the storage unit.

The photosensitive units 2A to 2D are
Also on the surface of the conductive rubber roller portion 17 of the charging roller 14,
For example, when a charging roller cleaner 49 made of a sponge is brought into contact with the conductive rubber roller 17, even if toner, dust, or the like floating in the apparatus adheres to the surface of the conductive rubber roller 17, it can be cleaned.

The photoconductor units 2A to 2D are provided with a positioning main reference portion 51 as a reference for attaching and detaching the photoconductor units to and from the apparatus main body 1 (see FIG. 3).
The near side positioning reference part 52 and the back side positioning reference part 5
When the photoconductor units 2A to 2D are mounted on the apparatus main body 1, the photoconductor units 2A to 2D can be reliably positioned at predetermined mounting positions by their reference portions. Like that.

Each of the photosensitive drums 5 of the photosensitive units 2A to 2D rotates in the direction of arrow C as described above, and their linear speeds are monochrome speed priority mode, monochrome image quality priority mode, and color speed priority. 185mm / sec, 125mm / sec depending on several modes such as mode, color image quality priority mode, thick paper / OHP passing mode
c, it can be adjusted in three stages of 62.5 mm / sec. In addition, this photoconductor unit
The brush roller 15 may be removed from the configuration, and the charging roller 14 and the photosensitive drum 5 may be configured as an integrated unit.

The developing devices 10A to 10D shown in FIG.
The configurations are all the same, and they differ only in the color of the toner used. The developing device 10A uses a yellow toner, the developing device 10B uses a magenta toner, the developing device 10C uses a cyan toner, and the developing device 10D uses a black toner. .

The writing unit 6 shown in FIG. 5 is a laser diode (LD) type one-color, monochromatic two-beam writing unit of a one-polygon motor having two six-sided rotating polygon mirrors 22a and 22b. The writing unit 6 includes yellow scanning light and magenta scanning light and cyan scanning light by rotating polygon mirrors 22 a and 22 b emitted from a laser diode (not shown) serving as a light source and rotated by a polygon motor 21. And the scanning light for black are reflected right and left separately.

The scanning light for yellow and the scanning light for magenta pass through the two-layer fθ lens 23, respectively, and the scanning light for yellow is reflected by the mirror 27 to form a long WTL 24.
Through the mirror unit 28 via the mirrors 28 and 29
A is irradiated on the photosensitive drum 5 of A. The scanning light for magenta is reflected by the mirror 31, passes through the long WTL 32, and passes through the mirrors 33 and 34 to the photosensitive unit 2 </ b> B.
Is irradiated on the photosensitive drum 5.

Further, the scanning light for cyan and the scanning light for black pass through the two-layer fθ lens 35, respectively, and the scanning light for cyan is reflected by the mirror 36 to form a long WTL 37.
Through the photoreceptor unit 2 via mirrors 38 and 39
C is irradiated onto the photosensitive drum 5. The scanning light for black is reflected by the mirror 41, passes through the long WTL 42, and passes through the mirrors 43 and 44 to the photosensitive unit 2D.
Is irradiated on the photosensitive drum 5.

The duplex unit 7 shown in FIG. 3 comprises a pair of transport guide plates 45a and 45b and a pair (four in this example) of transport rollers 46 for forming images on both sides of the transfer paper. In the double-sided image forming mode, the transfer paper P on which an image is formed on one side and conveyed to the reversing conveyance path 54 of the reversing unit 8 and conveyed by switchback is received, and the photoconductor units 2A to 2D are provided. Is re-conveyed to the current image forming unit.

The reversing unit 8 is composed of a plurality of pairs of transport rollers and a plurality of pairs of transport guide plates. The reversing unit 8 reverses the transfer paper P for forming a double-sided image as described above, and forms a double-sided unit. 7 and discharges the transfer paper P after image formation to the outside of the apparatus in the same direction, or reverses the front and back to discharge the transfer paper P to the outside of the apparatus. Separating sheet feeding sections 55 and 56 for separating and feeding the transfer sheets P one by one are provided in the sheet feeding sections provided with the sheet feeding cassettes 11 and 12.
Are provided respectively.

This small printer employs a roller curvature separation system using the transfer belt 3.
Inside, are provided four transfer brushes 57 corresponding to the four photosensitive drums 5, respectively.

In this small printer, when the image forming operation is started, each photosensitive drum 5 rotates clockwise in FIG. Then, the surface of each photosensitive drum 5 is
When a voltage is applied between the photosensitive drum 5 and the charging roller 14 of each charging device, charging is performed uniformly. Then, the writing unit 6 irradiates the charged surface of the photosensitive drum 5 of the photosensitive unit 2A with a laser beam corresponding to a yellow image.

The writing unit 6 applies a laser beam corresponding to a cyan image to the charged surface of the photosensitive drum 5 of the photosensitive unit 2B, and a magenta laser to the charged surface of the photosensitive drum 5 of the photosensitive unit 2C. A laser beam corresponding to the color image is irradiated on the charged surface of the photoconductor drum 5 of the photoconductor unit 2D, and a laser beam corresponding to the black image is irradiated thereon, and a latent image corresponding to each color is formed thereon. Is done. Then, when the respective latent images reach the positions of the developing devices 10A, 10B, 10C and 10D by the rotation of the photosensitive drum 5, the latent images there are yellow, magenta,
The toner images are developed with cyan and black toners to form four color toner images.

On the other hand, the transfer paper P is fed from the selected paper feed tray in the paper feed cassette 11 or 12 by the separation paper feed unit 55 or 56, and is fed to the photosensitive unit 2A.
The registration roller pair 59 provided immediately before
At an accurate timing coincident with the toner image formed on each photoconductor drum 5, it is conveyed between the photoconductor drum 5 of the photoconductor unit 2 </ b> A and the transfer belt 3.

At this time, the transfer paper P is charged to a positive polarity by the paper suction roller 58 disposed near the entrance of the transfer belt 3, and is thereby electrostatically attracted to the surface of the transfer belt 3. . Then, while the transfer paper P is attracted to the transfer belt 3 and conveyed in the same direction by the rotation of the transfer belt 3 in the direction of arrow A, yellow, magenta, cyan, and cyan The black toner images are sequentially transferred, and when passing through the photoreceptor unit 2D, a full-color toner image of four colors is formed.

The transfer paper P is melted and fixed by applying heat and pressure to the transfer paper P in the fixing device 9, and thereafter passes through a paper discharge system according to a designated mode, and is discharged to the upper part of the apparatus main body. The sheet is inverted and discharged to the paper tray 26, or is straightly discharged from the fixing device 9 and passes through the inside of the reversing unit 8.

Alternatively, when the two-sided image forming mode is selected, the sheet is fed back to the reversing conveyance path 54 in the reversing unit 8 and then switched back and conveyed to the two-sided unit 7 where it is fed again. In the image forming unit provided with the photoconductor units 2A to 2D, the image is discharged after an image is formed on the back surface. Thereafter, when an instruction to form two or more images is given, the above-described image forming process is repeated.

In this small printer, as shown in FIG. 1, a pair of rollers 18, 18 attached to both ends of a metal core 16 of the charging roller 14 is applied to the coating portion 6 of the photosensitive drum 5.
Non-coated portions 62, 62 formed of a material harder than 1
, So that the portion of the charging effective width Wac of the charging roller 14 forms a small gap G between the charging roller 14 and the photosensitive drum 5.

Therefore, the wear of the surface of the photosensitive drum 5 can be reduced as compared with the case where each roller 18 is in contact with the coating portion 61 which is softer than the non-coating portion 62. Therefore, even if the above-mentioned gap G between the charging roller 14 and the surface of the photoconductor drum 5 is set to 100 μm or less so that good charging performance can be obtained, the gap G of the roller 18 of the photoconductor drum 5 does not contact. Since the coating portion 62 is not easily worn, the gap G 'between the charging roller 14 and the non-coating portion 62 of the photosensitive drum 5 can be maintained at the set value for a long time.

On the other hand, the coating portion 61 of the photosensitive drum 5
Since the cleaning blade 47 is in sliding contact as described with reference to FIG. 4, the area of the cleaning width is worn over time. Therefore, when the coating portion 61 wears to a certain amount with time, the photosensitive drum 5 reaches the end of its life.

At this time, in this small printer, the uncoated portion 62 of the photosensitive drum 5 is
8, the gap G 'is maintained over time, and only the gap G between the charging roller 14 and the portion of the photosensitive drum 5 cut by sliding contact with the cleaning blade 47 increases. . Then, if the increase in the gap G reaches an amount at which charging failure occurs, a good image cannot be obtained. Therefore, in this small-sized printer, it is possible to judge that the life of the photosensitive drum 5 (the coating section 61 has been cut down until the life is reached) has reached the end of its life by utilizing the timing when the charging failure occurs. it can.

FIG. 6 is a schematic diagram showing a relative comparison of the width relationship of each part constituting the image forming system of the small printer of FIG. Each part constituting the image forming system of the small printer shown in FIG. 3 has a width relationship as shown in FIG. 6 and a total width Wdo in the longitudinal direction of the photosensitive drum 5 and a coating portion 61 of the photosensitive drum 5. Coating width W
t, the uncoated width Wnt of the uncoated portion 62 of the photosensitive drum 5
And the effective charging width Wac of the charging device 4 and the developing device 10A
-10D, an effective transfer width Wte of the transfer device having the transfer belt 3, and a cleaning blade 4
7 (see FIGS. 3 and 4).
See also).

That is, the transfer belt 3 (which is a transfer member that is in contact with the coating portion 61 of the photosensitive drum 5 and transfers a visible image formed on the surface of the photosensitive drum 5 to transfer paper (transfer material)). The effective transfer width Wte according to FIG. 3) is smaller than the effective charge width Wac of the charging device 4. As a result, the charging potential becomes unstable near the outer ends of both ends of the effective charging width Wac on the surface of the photosensitive drum 5, so that the developer easily adheres.
By making the width narrower, it is possible to prevent the developer (toner and carrier in the case of a two-component developer) attached to the vicinity of the outside of both ends of the effective charging width Wac from being transferred to the transfer belt 3.

Further, the developing width Wde of each of the developing devices 10A to 10D which develops the latent image on the photosensitive drum 5 with a developer to form a visible image is made smaller than the effective charging width Wac. Further, the uncoated portions 62 on both sides of the photosensitive drum 5 (FIG. 6)
Are formed outside the effective charging width Wac of the charging device 4, and the rollers 18 of the charging roller 14 are respectively in contact therewith.

As a result, it is possible to prevent the developer from adhering to the vicinity of both ends of the effective charging width Wac on the photosensitive drum 5, and to allow the developer to be transferred to the roller 1 described with reference to FIG.
It is possible to prevent the gap G from being enlarged by entering between the photosensitive drum 5 and the non-coated portion 62 of the photosensitive drum 5.

The developing width Wde is smaller than the effective transfer width Wte. This makes it more difficult for the developer to adhere to the vicinity of both ends of the effective charging width Wac on the photosensitive drum 5. When the developer is a two-component developer using a toner and a carrier, both the toner and the carrier can be prevented from adhering to the vicinity of both ends of the effective charging width Wac on the photosensitive drum 5.

Further, as described above, the uncoated portions 6 on both sides
2, 62 (portion indicated by uncoated width Wnt in FIG. 6)
Are formed outside the effective charging width Wac of the charging means, so that both ends in the axial direction of the charging roller 14 (the left end and the right end of the effective charging width Wac in FIG. 6) are indicated by the non-coating width Wnt. As shown in the drawing, the non-coating portions 62 are located inside the non-coating portions 62, 62, respectively. Therefore, even when the non-coating portions 62, 62 are formed of a conductor such as a metal, the non-coating portions 62 Leakage to the parts 62, 62 can be prevented.

Further, the cleaning width Wc is set wider than the effective charging width Wac. Thereby, even if the deposit such as the developer adheres to the portions located at both ends of the effective charging width Wac on the photosensitive drum 5, the portions can be cleaned by the cleaning blade 47 (see FIG. 4). Therefore, it is possible to prevent adverse effects due to the deposits.

Further, the cleaning width Wc is set to
Is narrower than the coating width Wt of the portion where is formed. As a result, the cleaning blade 47 always comes into sliding contact with the inside of the coating portion 61, and comes into contact with a stepped portion of the seam portion between the coating portion 61 and the non-coating portion 62, or a part of the cleaning blade 47 is on the non-coating portion 62. As a result, it is possible to prevent the blade from being turned up due to an increase in the frictional force.

Further, when the cleaning width Wc reaches the position of the non-coating portion 62 where the roller 18 as the gap management member is in contact, transfer residual toner collected from the photosensitive drum 5 by the cleaning blade 47 is removed. When the cleaning blade 47 spills from both ends and adheres to the roller 18 after attaching again to the photosensitive drum 5, a gap between the photosensitive drum 5 and the charging roller 14 (see a gap G in FIGS. 1 and 2). ) May be large.

However, if the cleaning width Wc is made smaller than the coating width Wt as described above, the collected toner and the like spilled from the cleaning blade 47 falls to a portion inside the position where the roller 18 is located. Roller 1
8, the gap can be prevented from increasing. Note that the effective charging width Wac in this embodiment corresponds to the entire width of the conductive rubber roller portion 17 of the charging roller 14 in the axial direction as shown in FIG.

FIG. 7 is a schematic diagram similar to FIG. 6, in which the width relationship of each part of the image forming system in the different embodiments of the image forming apparatus according to the present invention is relatively compared. The small-sized printer as the image forming apparatus in this embodiment is different from the embodiment described in FIG. 6 in that the cleaning blade 47 shown in FIG. The only difference is that Other components are shown in FIG.
6 to FIG. 6, the illustration and description of the entire small printer are omitted.

In this embodiment, as shown in FIG. 8, the cleaning blade 47, which is a cleaning member of the cleaning means, is swung in the direction indicated by the arrow F perpendicular to the direction in which the cleaning blade 47 slides on the photosensitive drum 5. A cleaning member swinging mechanism 70 is provided.

The cleaning member swinging mechanism 70 includes a blade holding member 71 which holds the cleaning blade 47 and is swingably supported in the direction indicated by the arrow F, and a protrusion formed on the left end of the blade holding member 71. A cam 72 having a cam surface slidably in contact with a hemispherical portion at the tip of 71a; a compression coil spring 73 for urging the blade holding member 71 so as to press the hemispherical portion at the tip of the protruding portion 71a against the cam surface of the cam 72; , And a motor 74 for rotating the cam 72.

When the cam 72 is rotated once, the cleaning blade 47 swings together with the blade holding member 71 to make one reciprocation. Then, the cleaning swing area width Wsc of the cleaning blade 47 formed at the cleaning blade width Wcb swung by the cleaning member swing mechanism 70 is defined as the cleaning width, and the cleaning width is the coating portion 61 of the photosensitive drum 5. It is located within. In addition, the movement limit positions on both sides of the cleaning blade 47 oscillated by the cleaning member oscillating mechanism 70 are respectively located outside the effective charging width Wac.

According to this embodiment, the cleaning blade 47 shown in FIG.
As the cleaning blade 47 swings in the direction indicated by arrow F in FIG.
Even when paper dust or the like is caught between the photoconductor drum 5 and the photosensitive drum 5, it is possible to prevent the paper dust or the like from continuing to be caught. Also in this embodiment, the cleaning blade 47 includes the coating portion 61 of the photosensitive drum 5 and the non-coating portion 6.
Since the seam portion 2 and the non-coated portion 62 do not come into sliding contact with each other, it is possible to prevent the cleaning blade 47 from being turned up and to prevent the cleaning blade 47 from being worn out early.

The movable limit positions (left and right ends of the cleaning oscillating region width Wsc) on both sides of the cleaning blade 47 oscillated by the cleaning member oscillating mechanism 70 are outside the effective charging width Wac. Therefore, even if the deposit such as the developer adheres to the portions located at both ends of the effective charging width Wac on the photosensitive drum 5, it can be cleaned by the cleaning blade 47. As a result, it is possible to prevent adverse effects due to the deposits.

Further, since the cleaning swing region width Wsc is within the coating width Wt and inside the non-coating width Wnt, the transfer residual toner and the like collected from the photosensitive drum 5 by the cleaning blade 47 are spilled. Therefore, even if it adheres to the photosensitive drum 5, there is almost no possibility that the transfer residual toner or the like enters between the roller 18 and the non-coating portion 62. (See gap G in FIGS. 1 and 2) can be prevented from becoming large.

[0065]

As described above, according to the present invention, the following effects can be obtained. According to the image forming apparatus of the present invention, the charging member is formed by bringing the roller-shaped gap management member into contact with the non-coating portions on both sides formed of a material harder than the coating portion of the image carrier. Since a minute gap is formed between the image carrier and the coating portion of the image carrier to charge the coating portion of the image carrier, the portion of the image carrier that is in contact with the gap management member is not easily scraped.

For this reason, the coating portion of the image bearing member on which the photosensitive layer is formed is liable to wear over time due to sliding contact with a sliding member such as a cleaning means that slides thereon. Even when the image carrier reaches the end of its life, the portion of the non-coated portion of the image carrier that is in contact with the gap management member is hardly scraped. Accordingly, a charging failure occurs due to an increase in the gap between the surface of the roller-shaped charging member and the surface worn by the above-mentioned sliding contact of the coating portion of the image carrier, and the timing of occurrence of the charging failure is utilized. Thus, it can be determined that the life of the image carrier has reached the end of its life.

According to the image forming apparatus of the second aspect, the charge potential is generally unstable near the outer ends of both ends of the effective charge width of the surface of the image carrier, so that the developer easily adheres to the area. By making the effective transfer width of the transfer member narrower than the effective charge width of the charging means, even if the developer adheres to the vicinity of both ends of the effective charge width, it is prevented from transferring to the transfer member. Can be.

According to the image forming apparatus of the third aspect, the non-coating portion is formed outside the effective charging width of the charging means, and the roller-shaped charging member is located further inside than the non-coating portion. Therefore, even when the non-coated portion of the image carrier is formed of a conductor such as a metal, it is possible to prevent leakage from the charging member to the non-coated portion.

According to the fourth aspect of the present invention, since the developing width of the developing device is narrower than the effective charging width of the charging means, the developer adheres to the vicinity of both ends of the effective charging width on the image carrier. Can be prevented. Further, since the non-coating portion with which the gap management member is in contact is located outside the effective charging width, the developer enters between the gap management member and the surface of the image carrier to increase the gap. Can be prevented.

According to the image forming apparatus of the present invention, the developing width is narrower than the effective transfer width, and the effective transfer width is smaller than the effective charging width. Is difficult to adhere near both ends.

According to the image forming apparatus of the present invention, even if the deposits such as the developer adhere to the portions of the image carrier which are located at both ends of the effective charging width, the portions are cleaned by the cleaning means. Therefore, it is possible to prevent adverse effects due to the attached matter.

According to the image forming apparatus of the present invention, since the cleaning width is smaller than the coating width of the portion where the coating portion is formed, the cleaning means is a cleaning blade which slides on the surface of the image carrier. However, the cleaning blade always slides inside the coated part, contacts the stepped part of the seam between the coated part and the non-coated part, or a part of the blade slides on the non-coated part. As a result, it is possible to prevent the blade from being turned up due to an increase in the frictional force.

Further, since the cleaning width is narrower than the coating width, the transfer residual toner and the like collected from the image carrier by the cleaning means may spill out from both ends of the cleaning means and adhere to the image carrier again. Even if this occurs, the dropped transfer residual toner and the like do not adhere to the gap management member that is in contact with the non-coating portion located away from the drop position. Therefore,
It is possible to prevent an increase in the gap between the charging member and the surface of the image carrier due to the transfer residual toner or the like entering between the gap management member and the surface of the image carrier.

According to the image forming apparatus of the present invention, since the cleaning member swings, it is possible to prevent paper dust and the like from being continuously caught between the cleaning member and the surface of the image carrier. Also, since the cleaning width, which is the width of the cleaning swinging area of the cleaning means, is smaller than the coating width, the cleaning means always slides inside the coating part, and there is a step at the seam between the coating part and the non-coating part. There is no contact with the part or part of the sliding contact on the non-coated part.

Therefore, even if the cleaning means is of a blade shape which slides on the surface of the image carrier, it is possible to prevent the blade from being turned up due to an increase in the frictional force with the image carrier. Further, even when an adhered substance such as a developer adheres to the portions located at both ends of the effective charge width on the image carrier, the adhered substance can be cleaned by the cleaning member, thereby preventing adverse effects due to the adhered substance. be able to.

According to the image carrier unit of the ninth aspect, since the image carrier is formed in the image carrier unit integral with the charging member, the workability when replacing the image carrier and the charging member or performing maintenance. Can be improved.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a charging roller and a photosensitive drum included in an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a front view for explaining the detailed configuration of the charging roller.

FIG. 3 is an overall configuration diagram showing a color small printer as the image forming apparatus.

FIG. 4 is a configuration diagram showing a photosensitive unit provided in the small printer.

FIG. 5 is a configuration diagram showing a writing unit provided in the small printer of FIG. 3;

FIG. 6 is a schematic diagram in which the width relations of respective units constituting the image forming system of the small printer of FIG. 3 are relatively compared.

FIG. 7 is a schematic diagram similar to FIG. 6, in which the width relationship of each part of an image forming system in different embodiments of the image forming apparatus according to the present invention is relatively compared.

FIG. 8 is a schematic diagram for explaining a cleaning member swing mechanism of the image forming apparatus.

FIG. 9 is a front view showing an example of a charging roller used in a conventional non-contact type charging device.

[Explanation of symbols]

2A, 2B, 2C, 2D: Photoconductor unit (image carrier unit) 3: Transfer belt (transfer member) 4: Charging device (charging means) 5: Photoconductor drum (image carrier) 10A, 10B, 10C, 10D : Developing device 14: charging roller (charging member) 18: roller (gap management member) 47: cleaning blade (cleaning means) 61: coating section 62: non-coating section 70: cleaning member swing mechanism

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ugitsu Ugitsu 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Hitoshi Ishibashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Iwasakisaki Yukiko 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. Masami Hiramatsu 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H003 BB07 BB11 CC05 DD03 EE19 2H032 AA05 BA01 BA23 2H034 AA06 BE03 BF01 2H077 AD06 BA08 BA09 GA13

Claims (9)

[Claims] 1. An image bearing member having a coating portion for forming a photosensitive layer and non-coating portions formed on both sides of the coating portion with a material harder than the coating portion, and the coating portion of the image bearing member. An image forming apparatus comprising: a charging unit having a roller-shaped charging member for charging; forming an outer diameter at both ends of the charging member to be larger than an outer diameter of a portion of the charging member opposed to the coating section; Roller-shaped gap management members are provided, and the gap management members are respectively brought into contact with the non-coating portions on both sides of the image carrier, so that the gap between the charging member and the coating portion of the image carrier is formed. An image forming apparatus, wherein a minute gap is formed in the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein
Image forming, wherein a transfer member for transferring a visible image formed on the surface of the image carrier to a transfer material is provided, and an effective transfer width of the transfer member is smaller than an effective charge width of the charging unit. apparatus. 3. The image forming apparatus according to claim 1, wherein the non-coating portions are formed outside an effective charging width of the charging unit. 4. The image forming apparatus according to claim 3, wherein
An image forming apparatus comprising: a developing device that develops a latent image on the image carrier with a developer to form a visible image, wherein a developing width of the developing device is smaller than an effective charging width of the charging unit. apparatus. 5. The image forming apparatus according to claim 2, wherein
An image forming apparatus, comprising: a developing device that develops a latent image on the image carrier with a developer to convert the latent image to a visible image, wherein a developing width of the developing device is narrower than an effective transfer width. 6. The image forming apparatus according to claim 1, further comprising a cleaning unit that slides on a surface of the image bearing member and performs cleaning with a predetermined cleaning width. An image forming apparatus characterized in that the width is wider than the effective charging width of the charging means. 7. The image forming apparatus according to claim 6, wherein the cleaning width is smaller than a coating width of a portion where the coating portion is formed. 8. The image forming apparatus according to claim 7, wherein
A cleaning member oscillating mechanism for oscillating the cleaning member of the cleaning means in a direction perpendicular to a sliding direction of the cleaning member with respect to the image carrier; and a cleaning member oscillating mechanism oscillated by the cleaning member oscillating mechanism. An image forming apparatus, wherein a width of a cleaning swing area is the cleaning width. 9. An image carrier unit mounted on the image forming apparatus according to claim 1, wherein:
An image carrier unit in which the image carrier and the charging member are integrally provided.