JP3661450B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a facsimile, and a copying machine that forms an image using electrophotographic technology.
[0002]
[Prior art]
In general, an image forming apparatus using an electrophotographic technique has a photosensitive member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a charging unit that is uniformly charged by the charging unit. An exposure unit that selectively exposes the outer peripheral surface to form an electrostatic latent image, and a toner that is a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image (toner image). Developing means, transfer means for transferring the toner image developed by the developing means to a transfer medium such as paper, and a cleaning blade for removing the developer remaining on the outer peripheral surface of the photoreceptor after transfer. .
[0003]
As the photosensitive member, a hard photosensitive drum having a photosensitive layer formed on the outer peripheral surface and a flexible photosensitive belt having a photosensitive layer formed on the surface are generally known.
[0004]
Further, as the developing means, a roller-shaped one that is brought into contact with the surface of the photosensitive member is known, and as the roller, a hard one and a soft rubber are known.
[0005]
When a hard photosensitive drum is used as the photosensitive member, and a developing roller that is in contact with the photosensitive drum is used hard, there is a limit to the production of the photosensitive drum and the hard roller with high accuracy. Because of this, it is difficult to bring them into uniform contact. If the two do not contact evenly, there arises a problem that gaps are locally generated and uneven development occurs, or the photosensitive drum and the developing roller are damaged by being pressed more strongly than necessary.
[0006]
Therefore, it is not usually done to make both the photosensitive member and the developing roller in contact with the photosensitive member hard. When a hard photosensitive drum is used as the photosensitive member, the developing roller is made of soft rubber. When a hard developing roller is used, a photosensitive belt having flexibility is used as the photosensitive member.
[0007]
However, when the developing roller in contact with the photosensitive member is made of soft rubber, conductive particles such as carbon are dispersed in order to impart conductivity to the developing roller. There is a problem that the rubber hardness changes due to variations, the hardness on the roller surface varies, and a good adhesion state to the photoreceptor cannot be obtained. On the other hand, if the amount of carbon dispersion is reduced in order to obtain a good adhesion to the photoreceptor, there is a problem that the conductivity varies and causes uneven development.
[0008]
Such a problem can be solved by using a hard developing roller and using a flexible photosensitive belt as the photosensitive member.
[0009]
However, when a photoconductor belt is used as the photoconductor, at least two support rollers are required to support the photoconductor belt, so that not only the structure becomes complicated but also the apparatus becomes large. there were.
[0010]
Therefore, it is desired to solve such problems at the same time.
[0011]
Conventionally, a photoreceptor driving device described in Japanese Patent Laid-Open No. 4-188164 has been known as an attempt to meet such a demand.
[0012]
5A and 5B are diagrams showing the photosensitive member driving device, where FIG. 5A is a side view and FIG. 5B is a perspective view.
[0013]
This photoconductor driving device has a photoconductor belt 20 formed as a cylindrical thin film sheet, an outer diameter circumference shorter than the inner diameter circumference of the photoconductor belt 20, and is located inside the photoconductor belt 20. The friction coefficient between the driving roller 21 that rotationally drives the photosensitive belt 20 and the photosensitive belt 20 is set to be smaller than the friction coefficient between the driving roller 21 and the photosensitive belt 20, and the circumferential direction of the driving roller 21 is A pressing member 22 that slidably presses the photosensitive belt 20 while keeping the photosensitive belt 20 in close contact with the driving roller 21 within a predetermined range is provided. In FIG. 5, 24 is a charger, 25 is an exposure device, 26 is a developing roller, 27 is a transfer charger, and 28 is a cleaning roller.
[0014]
According to such a photosensitive member driving device, the photosensitive belt 20 is driven in a state of being in close contact with the surface of the driving roller 21 by the pressing member 22. The deflection 23 is formed by the difference in circumference.
[0015]
For this reason, the photosensitive belt 20 can be used as a hard material in the contact portion by the pressing member 22 because the hardness is simulated by the hardness of the driving roller 21, and in the portion without the pressing member 22. Since the deflection 23 is formed, it can be used as an elastic body.
[0016]
Therefore, according to this apparatus, the cleaning roller 28 made of an elastic body can be brought into contact with the contact portion of the photosensitive belt 20 with the pressing portion 22, and the developing roller 26 made of a hard material at the deflection 23 portion. Can be contacted.
[0017]
The contact of the developing roller 26 is stably performed with a sufficient nip width and a low pressure contact force even when the developing roller 26 is made of a hard material because the deflection 23 acts as an elastic body.
[0018]
That is, according to this apparatus, even if a hard developing roller is used, the photosensitive member and the developing roller are not damaged, and an increase in the size of the apparatus can be prevented.
[0019]
An apparatus similar to this apparatus is also disclosed in JP-A-6-27859, JP-A-6-258989, and the like.
[0020]
However, in the above-described photoreceptor driving device (see FIG. 5) described in Japanese Patent Laid-Open No. 4-188164, the photoreceptor belt 20 is guided by the pressing member 22 partially provided on the peripheral edge of the photoreceptor belt 20. Therefore, when the photoreceptor belt 20 enters the pressing member 22, bending stress is likely to be generated at the peripheral portion (edge portion) of the photoreceptor belt 22 at the entrance portion 22 a, and thereby the photoreceptor belt 20. There is a problem that the end edge portion is likely to be broken or cracked or the photosensitive layer is peeled off (inferior in durability). As a result, there is a problem that the photosensitive belt 20 may be broken from the edge portion or may not cause destruction but may cause a serious image defect.
[0021]
Further, the photosensitive belt 20 must be handled alone until it is incorporated into the apparatus in the state shown in FIG. However, since the photosensitive belt 20 is formed as a cylindrical thin film sheet as described above and does not have sufficient rigidity, there is a problem that it is difficult to handle it.
[0022]
Further, in the above apparatus, since the deflection 23 is formed in the portion where the pressing member 22 that presses both ends of the photosensitive belt 20 is not provided, in the portion where the deflection 23 is formed, in the both ends. An opening 29 is formed between the photosensitive belt 20 and the driving roller 21.
[0023]
For this reason, foreign matters such as toner, toner external additives, and paper dust floating in the apparatus are likely to enter between the photosensitive belt 20 and the driving roller 21 through the openings 29 and 29, and the entry of these foreign matters. There is a problem that the frictional force between the photosensitive belt 20 and the driving roller 21 decreases, and the photosensitive belt 20 may not be driven.
[0024]
Therefore, it is possible to solve the various problems as described above, and to obtain a reliable and stable contact state between the image carrier, the developing roller, and the cleaning blade. An image carrier unit (and an image forming apparatus) that can reliably drive the carrier has already been proposed in Japanese Patent Laid-Open No. 10-239934.
[0025]
FIG. 6 is a partially omitted front sectional view showing the image carrier unit, and FIG. 7 is a partial side view showing a state in which the image carrier unit is incorporated in the image forming apparatus.
[0026]
As shown in FIG. 6, the image carrier unit 1 includes a shaft 2 that does not rotate by itself, a pair of disk-like members 3 and 3 that are rotatably attached to the shaft 2, and a pair of these members. Both ends are supported and fixed by the disk-shaped members 3 and 3, and the flexible thin-walled cylindrical image carrier 4 that is rotationally driven together with the disk-shaped members 3 and 3. Attached to the shaft 2 by side plates 17 and 17, the image carrier 4 is supported from the inside at a contact position where the cleaning blade 11 (see FIG. 7) abuts the image carrier 4 from the outside. The backup roller 5 is provided.
[0027]
Further, as shown in FIG. 7, the image forming apparatus is configured to uniformly charge the image carrier unit 1, the charging roller 6 that uniformly charges the outer peripheral surface of the image carrier 4, and the charging roller 6. An exposure means (not shown) that selectively exposes the outer peripheral surface thus formed to form an electrostatic latent image, and a toner that is a developer is applied to the electrostatic latent image formed by the exposure L to form a visible image. A developing device 8 (Y, M, CK) having a developing roller 7 as a (toner image), a transfer roller 10 for transferring a toner image developed by the developing roller 7 to an intermediate transfer belt 9, and an image carrier 4 And a cleaning blade 11 for removing the toner remaining on the outer peripheral surface of the image carrier 4 after the transfer.
[0028]
Reference numeral 12 denotes a backup roller for the charging roller 6, and reference numeral 13 denotes a backup roller for the transfer roller 10.
[0029]
In FIG. 6, 14 is a driving gear fixed to one disk-shaped member 3, 15 is an interlocking means for transmitting the driving force to the other disk-shaped member and interlocking the disk-shaped members 3 and 3. is there.
[0030]
In this conventional apparatus, each of the backup rollers 5, 12, and 13 is provided by the side plates 17 and 17 so that the outer peripheral surface thereof is in light contact with or extremely close to the inner peripheral surface of the image carrier 4. It was supported.
[0031]
According to the image forming apparatus described in Japanese Patent Laid-Open No. 10-239934, the following effects can be obtained.
[0032]
(A) In the image carrier unit 1, both ends of a thin cylindrical image carrier 4 are supported and fixed by a pair of disk-like members 3 and 3 that are rotatably attached to the shaft 2. Therefore, when the disk-shaped members 3 and 3 are rotationally driven, the image carrier 4 is reliably rotationally driven.
[0033]
Further, since both end portions of the image carrier 4 are supported and fixed by the pair of disc-like members 3 and 3, the durability is excellent.
[0034]
(B) Since the image carrier 4 has a thin cylindrical shape having flexibility and both ends thereof are supported by the disk-like members 3 and 3, the image carrier 4 has a disk shape. The central portion 4a not supported by the members 3 and 3 can be deformed inward.
[0035]
Therefore, a portion of the central portion 4a of the image carrier 4 that is not supported from the inside by the backup roller can be used as a pseudo soft material. Even with a hard roller or the like, a reliable and stable contact state can be obtained, and an image can be reliably formed on the image carrier 4 or an image can be carried.
[0036]
On the other hand, a cleaning blade 11 that removes the developer remaining on the outer peripheral surface of the image carrier 4 is brought into contact with the image carrier 4. Therefore, the cleaning blade 11 can be reliably brought into contact.
[0037]
(C) In the image carrier unit 1, both ends of the image carrier 4 are supported and fixed by a pair of disk-like members 3 and 3 rotatably attached to the shaft 2, and the image carrier 4 Since the back-up roller is unitized by being attached to the shaft 2 by the side plates 17, 17, the image carrier unit 1 itself can be easily handled.
[0038]
That is, according to the image forming apparatus described in JP-A-10-239934, it is possible to obtain a reliable and stable contact state between the image carrier, the developing roller, and the cleaning blade. It is excellent in handleability, and an effect that the image carrier can be reliably driven can be obtained.
[0039]
[Problems to be solved by the invention]
There is a limit to manufacturing the components of the image carrier unit 1 with high accuracy, and an error necessarily occurs. Therefore, the distance between the inner peripheral surface of the image carrier 4 and the outer surface of the backup roller facing the inner surface is small. However, the image carrier unit varies.
[0040]
For this reason, the image forming apparatus described in JP-A-10-239934 has the following problems.
[0041]
That is, the backup roller 5 in the conventional apparatus should be arranged such that the outer peripheral surface thereof is in light contact with or very close to the inner peripheral surface of the image carrier 4. As a result, as shown in FIG. 8, the gap g between the inner surface 4a of the image carrier 4 and the outer surface 5a of the backup roller 5 may become too large at the position where the cleaning blade 11 is to come into contact. is there. FIG. 8 depicts a state in which the cleaning blade 11 is in contact and the image carrier 4 is supported from the inside by the backup roller 5 at the contact position. Although the outer surface 5a of the roller 5 is in contact, the interval g indicates the interval between the inner surface 4a of the image carrier 4 and the outer surface 5a of the backup roller 5 before the cleaning blade 11 is in contact. .
[0042]
If the gap g is excessively large, the end 11a of the cleaning blade 11 is located at the both ends 11a of the cleaning blade 11 (only one is shown) compared to the central portion 11b. As a result of the large deformation along the shape, the contact force between the end portion 11a and the image carrier 4 becomes too large, and as a result, the cleaning blade 11 may turn over from the end portion 11a.
[0043]
An object of the present invention is to solve the above problems and prevent the cleaning blade from turning up.
[0044]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 includes a shaft that does not rotate by itself, a pair of disk-shaped members that are rotatably attached to the shaft, and a pair of disk-shaped members. A flexible thin-walled cylindrical image carrier that is supported and fixed at both ends by a member and rotated together with the disk-like member, and is attached to the shaft inside the image carrier and is attached to the image carrier. An image carrier unit comprising a backup member that supports the image carrier from the inside at the contact position where the cleaning blade comes into contact from the outside;
An image forming apparatus comprising a cleaning blade that contacts the image carrier of the image carrier unit from the outside and removes the developer remaining on the outer peripheral surface of the image carrier,
At the contact position, the backup member protrudes the image carrier outward, and the backup member has an outer diameter slightly smaller than the inner diameter of the image carrier, On the other hand, it is characterized by comprising a backup drum that is rotatably supported via an eccentric bearing .
[0045]
The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the backup member has an outer diameter slightly smaller than an inner diameter of the image carrier, and an eccentric bearing is provided with respect to the shaft. It is characterized by comprising a backup drum that is rotatably supported through the support drum.
[0046]
[Function and effect]
According to the image forming apparatus of the first aspect, the following effects can be obtained.
[0047]
A shaft that does not rotate by itself, a pair of disk-shaped members that are rotatably attached to the shaft, and both ends are supported and fixed by the pair of disk-shaped members and are rotationally driven together with the disk-shaped members. A thin cylindrical image carrier having flexibility, and an abutting position where the cleaning blade is abutted against the image carrier from the outside by being attached to the shaft inside the image carrier. An image carrier unit provided with a backup member for supporting the image carrier from the inside, and the development remaining on the outer peripheral surface of the image carrier in contact with the image carrier of the image carrier unit from the outside The cleaning blade for removing the agent is provided, so that the same effect as the above-described (a) to (c), that is, reliable and stable contact between the image carrier, the developing roller and the cleaning blade. The state can be obtained, the durability and handling of the image carrier are excellent, and the effect of being able to drive the image carrier reliably is obtained.
[0048]
Further, according to the image forming apparatus of the first aspect, the backup member is configured to protrude the image carrier toward the outside at the contact position. Even if there are some manufacturing errors in the component parts, no gap is formed between the inner peripheral surface of the image carrier and the outer surface of the backup member facing the image carrier.
[0049]
Therefore, the end of the cleaning blade is not greatly deformed along the shape of the image carrier compared to the central portion, and the contact force between the cleaning blade and the image carrier at both end positions of the cleaning blade is large. As a result, it is possible to prevent the cleaning blade from being turned over.
[0050]
According to the image forming apparatus of claim 1, in the image forming apparatus of claim 1, the backup member has an outer diameter slightly smaller than an inner diameter of the image carrier, and is eccentric with respect to the axis. Since it is composed of a backup drum that is rotatably supported via a bearing, the following effects can be obtained.
[0051]
That is, since the backup drum is configured to be rotatably supported with respect to the shaft via the eccentric bearing, the structure is simple and can be easily assembled. Therefore, it can be created with high accuracy.
[0052]
Further, the backup drum has an outer diameter that is slightly smaller than the inner diameter of the image carrier, and is supported rotatably with respect to the shaft via an eccentric bearing. From the inside, the image carrier can be supported over a wide range at the contact position where the cleaning blade comes into contact. Therefore, the developer is removed more reliably by the cleaning blade.
[0053]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0054]
FIG. 1 is a transverse cross-sectional view (partially omitted II cross-sectional view in FIG. 3) showing an image carrier unit in an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is an image incorporating the image carrier unit. FIG. 3 is a schematic partial side view of the forming apparatus, and FIG. 3 is a partially enlarged view of FIG.
[0055]
As shown in FIGS. 1 and 3, the image carrier unit 100 includes a shaft 110 that does not rotate by itself, a pair of disk-like members 120 and 120 that are rotatably attached to the shaft 110, and A thin cylindrical image carrier 140 having both ends supported and fixed by a pair of disk members 120, 120 and rotating together with the disk members 120, 120, and the inside of the image carrier 140 A backup drum 150 as a backup member that is attached to the shaft 110 and supports the image carrier 140 from the inside at a contact position where the cleaning blade 210 contacts the image carrier 140 from the outside; ing.
[0056]
The pair of disk-shaped members 120 and 120 are both rotatably provided on the shaft 110 via bearings 114, and both ends of the image carrier 140 are supported by the outer peripheral surfaces 121 and 121 of the disk-shaped members 120 and 120. The part 141 is supported. Both end portions 141 of the image carrier 140 are fixed to the outer peripheral surfaces 121 and 121 by an appropriate means such as adhesion. A driving gear (not shown) is fixed to the outer surface of at least one of the disk-shaped members 120.
[0057]
The image carrier 140 is configured as a photoconductor in this embodiment, and is configured by forming a photosensitive layer on the surface (outer peripheral surface) of a flexible thin cylindrical substrate. As a base material, the nickel seamless pipe produced by the electroforming method, the aluminum pipe by impact processing, etc. can be used, for example. The photosensitive layer can be formed by so-called OPC (organic photoreceptor) by dipping. Such flexibility, that is, softness of the photoconductor 140 can be determined by adjusting the thickness and diameter of the base material, and therefore can be appropriately set according to the image forming apparatus used. Is possible. For example, the thickness is appropriately set in the range of a base material thickness of 20 to 200 μm and a base material diameter of 10 to 300 mm. Since OPC is mainly made of resin, it is excellent in flexibility. However, in order to ensure adhesion with the base material and to take measures against interference of laser light, an undercoat layer is provided between the base material and the OPC. It is desirable to form. As the undercoat layer, a layer in which particles capable of absorbing laser light such as zinc oxide and titanium oxide are dispersed in a resin such as nylon resin is preferable.
[0058]
The backup drum 150 includes a pair of side plates 151 and 151 and a cylindrical member 152 having both ends fixed by outer peripheral surfaces of the side plates 151 and 151. The outer diameter D1 of the cylindrical member 152 is slightly smaller than the inner diameter D2 of the image carrier 140. A bearing hole 153 is provided in the side plate 151, and an eccentric bearing 154 is interposed between the bearing hole 153 and the shaft 110. Therefore, the backup drum 150 is rotatably supported with respect to the shaft 110 via the eccentric bearing 154. As shown in FIG. 3, the eccentric bearing 154 is eccentric by an eccentric amount E on the contact position side (right side in FIG. 3) with which the cleaning blade 210 and the charging roller 220 are contacted. A part of the outer peripheral surface 150 (the outer peripheral surface of the cylindrical member 152) supports the image carrier 140 from the inside over a relatively wide range at the contact position.
[0059]
Since the backup drum 150 is rotatably supported with respect to the shaft 110 via an eccentric bearing 154, as shown in FIG. 3, the cylindrical member 152 is at least at the contact position of the cleaning blade 210 and the charging roller 220. The outer peripheral surface 152a of the photosensitive member 140 abuts on the inner peripheral surface 140a of the photosensitive member 140 and rotates following the photosensitive member 140.
[0060]
As shown in FIG. 2, the image carrier unit 100 as described above is incorporated in the image forming apparatus, and a driving gear (not shown) of the image forming apparatus main body is connected to a driving gear (not shown) provided on the disk-shaped member 120. The image carrier (photosensitive member) 140 is rotationally driven in the direction of the arrow.
[0061]
In FIG. 2, L is a laser beam for selectively exposing the surface of the photoreceptor 140, 300 (Y, M, C, K) is a developing device, 210 is the above-described cleaning blade, and 220 is the above-described charging roller.
[0062]
The charging roller 220 is in contact with the outer peripheral surface of the photoreceptor 140 so as to uniformly charge the outer peripheral surface. The charging roller 220 is incorporated in the sub case 240, is pressed against the photoconductor 140 by a compression spring 221 (see FIG. 3), and rotates following the photoconductor 140.
[0063]
The laser beam L is emitted from an exposure unit (not shown), and selectively exposes the surface of the photoconductor 140 to form an electrostatic latent image on the surface of the photoconductor 140.
[0064]
Each developing device 300 (Y, M, C, K) contains toners of yellow, magenta, cyan, and black, respectively. Each developing device 300 is configured to be able to come into contact with and separate from the photoreceptor 140, and only one of the developing devices can come into contact with the photoreceptor 140 during image formation. Reference numeral 310 (Y, M, C, K) denotes a developing roller that comes into contact with the photosensitive member 140, and is composed of a metal roller whose surface is roughened or a hard resin roller.
[0065]
The intermediate transfer belt 400 is brought into contact with the photoreceptor 140, and this contact position forms the primary transfer portion T1. The intermediate transfer belt 400 is wound around a driving roller 410, a tension roller 420, a backup roller 430 for the secondary transfer roller 460, a backup roller 440 for the cleaning blade 470, and a positioning roller 450 for forming the primary transfer portion T1. The drive roller 410 is driven to circulate in the direction of the arrow shown in the figure. In the process in which the intermediate transfer belt 400 is circulated, the toner image on the photoconductor 140 is transferred onto the intermediate transfer belt 400 at the primary transfer portion T1, and the toner image transferred onto the intermediate transfer belt 400 is transferred to the secondary transfer belt 400. The image is transferred to a recording medium (not shown) such as paper supplied between the transfer roller 460 and the intermediate transfer belt 400.
[0066]
As shown in FIG. 3, the upper part of the cleaning blade 210 is fixed to the blade holder 211. The blade holder 211 is a plate-like body extending in a direction orthogonal to the paper surface of FIG. 3, and arms 212 (only one is shown) provided at both ends of the blade holder oscillate with respect to the side portion 241 of the sub case 240 by the shaft 213. It is attached as possible. A blade urging spring (compression coil spring) 242 is provided between the sub case 240 and the blade holder 211. The tip of the cleaning blade 210 is urged by the urging force of the blade urging spring 242 and the elastic force of the blade 210 itself. The portion (edge) is brought into pressure contact with the surface of the photoreceptor 140.
[0067]
The sub case 240 is formed with a receiving portion 243 that receives the toner scraped off by the blade 210.
[0068]
A scoop sheet 244 is provided below the tip of the cleaning blade 210. The base of the rake sheet 244 is fixed to the sub case 240, and the leading edge of the rake sheet 244 is pressed against the surface of the photoreceptor 140 by the elastic force of the sheet 244 itself, and is in sliding contact with the surface of the photoreceptor 140. The toner scraped off at 210 is prevented from leaking downward.
[0069]
A toner conveying screw 245 is provided in the sub case 240, and the toner is conveyed toward a waste toner tank (not shown) by the toner conveying screw 245.
[0070]
The sub case 240 incorporating the cleaning blade 210 and the like can be combined with the image carrier unit 100 to form a single unit.
[0071]
The image forming apparatus as described above is an apparatus that can form a full-color image using toners of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and its operation. Is as follows.
[0072]
(I) When a print command signal (image formation signal) is input from a host computer (such as a personal computer) (not shown), the photoreceptor 140 and the intermediate transfer belt 400 are driven to rotate.
[0073]
(Ii) The outer peripheral surface of the photoreceptor 140 is uniformly charged by the charging roller 220.
[0074]
(Iii) On the outer peripheral surface of the uniformly charged photoreceptor 140, selective exposure L corresponding to image information of the first color (for example, yellow) is performed by an exposure unit (not shown), and an electrostatic latent image for yellow is formed. It is formed.
[0075]
(Iv) Only the developing roller 310Y of the developing device 300Y for the first color (for example, yellow) contacts the photoconductor 140, whereby the electrostatic latent image is developed, and the toner for the first color (for example, yellow) An image is formed on the photoreceptor 140.
[0076]
(V) The toner image formed on the photoreceptor 140 is transferred onto the intermediate transfer belt 400 between the primary transfer portion T1, that is, between the photoreceptor 140 and the primary transfer roller 230. At this time, the secondary transfer roller 460 is separated from the intermediate transfer belt 400.
[0077]
(Vi) After the toner remaining on the photosensitive member 140 is removed by the cleaning blade 210, the photosensitive member 140 is discharged by a discharging means (not shown).
[0078]
(Vii) The operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated according to the content of the print command signal, and the toner images according to the content of the print command signal are superimposed on the intermediate transfer belt 400 to be intermediate. It is formed on the transfer belt 400.
[0079]
(Viii) A recording medium such as paper is supplied to the secondary transfer portion T2 (contact portion between the intermediate transfer belt 400 and the secondary transfer roller 460) at a predetermined timing, and the toner image (basically, the intermediate transfer belt 400). Is a full-color image) is transferred onto a recording medium.
[0080]
By the way, in the image forming apparatus as described above, for example, the shaft 110, the disk-shaped member 120, the image carrier 140, and the backup drum 150, which are components of the image carrier unit 100, are naturally manufactured with high accuracy. There is a limit and an error always occurs. In particular, when a nickel seamless tube produced by electroforming is used as the base material of the image carrier 140, it is necessary to refresh the electroforming matrix in order to normally produce the base material. Since the inner diameter (D2) of the base material gradually decreases as the outer diameter of the matrix decreases, each image carrier 140 tends to vary in the inner diameter.
[0081]
Therefore, the distance between the inner peripheral surface of the image carrier 140 and the outer surface of the backup member facing the image carrier 140 also varies depending on each image carrier unit.
[0082]
In such a situation, if no measures are taken, there is a problem as described above with reference to FIG. 8, that is, the cleaning blade may turn over from its end. Arise.
[0083]
Therefore, in this embodiment, even if there are some manufacturing errors in the components of the image carrier unit 100, the backup drum 150 is placed at the contact position of the cleaning blade 210 as shown in FIG. Is projected outward (radially outward).
[0084]
Specifically, even if there are some manufacturing errors in the components of the image carrier unit 100 (in the state where the tolerance is taken into consideration),
(D1 / 2) + E> (D2 / 2)
The eccentric amount E, the backup drum 150, and the image carrier 140 are configured so that the following condition is satisfied.
[0085]
According to the image forming apparatus as described above, the following effects can be obtained as compared with the image forming apparatus described in JP-A-10-239934 described above.
[0086]
(1) As shown in FIG. 4, since the backup member 150 is configured to protrude the image carrier 140 outward at the contact position of the cleaning blade 210, the configuration of the image carrier unit 100. Even if there are some manufacturing errors in the parts, there is no gap formed between the inner peripheral surface 140a of the image carrier 140 and the outer surface 152a of the backup member 150 facing the inner peripheral surface 140a.
[0087]
Therefore, the end portion 210a of the cleaning blade 210 is not greatly deformed in a curved shape along the shape of the image carrier compared to the central portion (see FIG. 8), and the contact force between the cleaning blade 210 and the image carrier 140 is eliminated. Is substantially uniform in the length direction of the cleaning blade 210. In other words, the contact force between the cleaning blade 210 and the image carrier 140 at both end positions 210a of the cleaning blade 210 is not excessively increased. As a result, the cleaning blade 210 is prevented from being turned over. It is done.
[0088]
As described above, according to the image forming apparatus of this embodiment, it is possible to obtain a reliable and stable contact state between the image carrier 140 and the developing roller 310, the cleaning blade 210, and the like. In addition to the operational effect that the image carrier 140 can be driven reliably, the operational effect of preventing the cleaning blade 210 from being turned up is obtained.
[0089]
(2) Since the backup drum 150 is rotatably supported with respect to the shaft 110 via the eccentric bearing 154, the structure of the image carrier unit 100 is simple and can be easily assembled. Therefore, it can be created with high accuracy.
[0090]
(3) Since the backup drum 150 has an outer diameter D1 that is slightly smaller than the inner diameter D2 of the image carrier 140 and is rotatably supported by the shaft 110 via an eccentric bearing 154, the image carrier The image carrier 140 can be supported over a wide range from the inside at the contact position where the cleaning blade 210 is in contact with 140 from the outside (see FIGS. 2 and 3). Accordingly, the toner is removed more reliably by the cleaning blade 210.
[0091]
Further, since the backup drum 150 contacts the image carrier 140 over a wide range and is reliably driven and rotated with respect to the image carrier 140, the image is driven by a driving gear provided on one disk-like member 120. When the carrier 140 is configured to be driven from one end side, the backup drum 150 transmits the driving force acting from the one end side of the image carrier 140 to the image carrier 140 at the support portion for the image carrier 140. The role as a member is surely fulfilled, and the image carrier 140 is driven well.
[0092]
(4) Since the backup drum 150 is configured to protrude the image carrier 140 outward at the contact position of the cleaning blade 210, the contact position of the cleaning blade 210 and the upstream thereof. On the side (upstream side with respect to the rotation direction of the image carrier 140), the image carrier 140 is along the backup drum 150, whereby the shape or behavior of the image carrier 140 is stabilized.
[0093]
Therefore, good cleaning characteristics can be obtained.
[0094]
【Example】
The axis | shaft 110 is comprised with a metal axis | shaft.
[0095]
The side plate 151 and the cylindrical member 152 of the backup drum 150 are made of aluminum.
[0096]
The positional accuracy of the backup drum 150 in the radial direction is preferably about ± 100 μm. The positional accuracy in the circumferential direction (the rotation direction of the image carrier 140) is preferably within ± 1 °.
[0097]
The amount of contact of the charging roller 220 and the developing roller 310 with respect to the image carrier 140 (the amount of depression of the image carrier 140) is preferably 0.5 mm or less.
[0098]
Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments or examples, and can be appropriately modified within the scope of the gist of the present invention.
[0099]
For example, in the above embodiment, the image carrier unit is described as the photosensitive unit. However, the image carrier unit of the present invention is not limited to this and can be configured as an intermediate transfer medium unit. In this case, the image carrier is a thin cylindrical intermediate transfer medium.
[0100]
【The invention's effect】
According to images forming apparatus according to claim 1 Symbol mounting, it can be obtained reliable and stable contact state between the image carrier and the developing roller and the cleaning blade, excellent in durability and handling properties of the image bearing member, In addition to the operational effect that the image carrier can be reliably driven, the operational effect is also obtained that the cleaning blade is prevented from turning over.
[0101]
further,
According to the image forming apparatus of the first aspect , the structure is simple and can be easily assembled, and can be produced with high accuracy, and the developer can be more reliably removed by the cleaning blade.
[0102]
[Brief description of the drawings]
FIG. 1 is a transverse cross-sectional view (partially omitted II cross-sectional view in FIG. 3) showing an image carrier unit in an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a schematic partial side view of an image forming apparatus incorporating the image carrier unit.
FIG. 3 is a partially enlarged view of FIG. 2;
4 is a schematic diagram showing a state where the image carrier and the backup member are in contact with each other at the end position of the cleaning blade, and corresponds to a partially enlarged view of FIG.
FIGS. 5A and 5B are explanatory diagrams of the prior art.
FIG. 6 is an explanatory diagram of a conventional technique.
FIG. 7 is an explanatory diagram of a conventional technique.
FIG. 8 is a conceptual diagram for explaining a problem.
[Explanation of symbols]
100 image carrier unit 110 shaft 120 disc-like member 140 photoconductor (image carrier)
150 Backup drum (backup member)
154 Eccentric bearing 210 Cleaning blade 310 Developing roller

Claims (1)

A shaft that does not rotate by itself, a pair of disk-shaped members that are rotatably attached to the shaft, and both ends are supported and fixed by the pair of disk-shaped members and are rotationally driven together with the disk-shaped members. A thin cylindrical image carrier having flexibility, and an abutting position where the cleaning blade is abutted against the image carrier from the outside by being attached to the shaft inside the image carrier. An image carrier unit comprising a backup member for supporting the image carrier from the inside;
An image forming apparatus comprising a cleaning blade that contacts the image carrier of the image carrier unit from the outside and removes the developer remaining on the outer peripheral surface of the image carrier,
At the contact position, the backup member protrudes the image carrier outward, and the backup member has an outer diameter slightly smaller than the inner diameter of the image carrier, An image forming apparatus comprising: a backup drum rotatably supported via an eccentric bearing .

Images