JP2004264647A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which does not produce white beltlike and black beltlike image density unevenness of the images outputted when image formation under standby is switched to image formation in the environment of drastically changing humidity. <P>SOLUTION: A photoreceptor drum is so controlled as to be rotationally moved according to the humidity or humidity change per hour detected by a detecting means while the photoreceptor drum is under standby for the image formation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic method, such as a printer, a copying machine, and a facsimile, and more particularly, to a countermeasure for environmental dependency of a photoconductor for forming a toner image on an image carrier.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus that forms a toner image on an image carrier having a charging unit, an exposure unit, a development unit, a transfer unit, a cleaning unit, and the like on its periphery and electrostatically transfers the toner image to a recording medium such as a transfer material is known. Are known.
[0003]
Generally, a drum type is mainly used as an image carrier due to advantages such as manufacturing and miniaturization of an apparatus, and a type in which an OPC (organic photoreceptor) is laminated as a photoreceptor on the surface has recently become mainstream. In addition, the charging unit, the exposure unit, the developing unit, the transfer unit, the cleaning unit, and the like are arranged around the drum in the order of processing.
[0004]
In such an image forming apparatus, the sensitivity of the photoconductors laminated on the surface of an image carrier (hereinafter, referred to as a photoconductor drum) fluctuates depending on the temperature and humidity of the atmosphere in which the photoconductors are present, and the surface of the photoconductor is accordingly changed. The potential fluctuates.
[0005]
During a normal printing operation, the influence is hardly recognized, but when the apparatus is in a standby state, the change in temperature and humidity is not affected when an image is formed immediately after the printing operation is restarted, particularly in a halftone image. This is a phenomenon that cannot be ignored as described below.
[0006]
Of the sections surrounding the photosensitive drum, the developing section and the cleaning section, which respectively supply and collect the toner, block the entire photosensitive layer on the drum surface in order to shield the whole in order to prevent minute toner scattering due to supply and collection. Each closed space including the space is formed independently.
[0007]
Therefore, when the apparatus is in the standby state, the environment other than the developing unit and the cleaning unit immediately adapts to the environment at the time of standby. The environment formed during the previous continuous printing is maintained.
[0008]
For this reason, when the environment between the developing unit and the cleaning unit forming the closed space is kept at a low humidity, the sensitivity of the photoconductor around the photoconductor drum in that portion decreases, and in that state, When the photoreceptor surface is exposed, the decrease in surface potential due to light attenuation cannot be reduced to a predetermined potential, and the amount of toner adhered during development decreases.
[0009]
For this reason, in the halftone image formation, in the width direction of the photoconductor drum (in the direction of 90 degrees with respect to the transfer material conveying surface direction), white corresponding to the width of each opening of the development unit and the cleaning unit facing the photoconductor drum surface. A band-like image density unevenness is transferred onto the transfer material.
[0010]
On the other hand, if the environment between the developing unit and the cleaning unit is maintained at a high humidity, the black band-shaped image density unevenness having a certain width in the width direction of the photosensitive drum causes unevenness in image density on the transfer material. Will be transcribed.
[0011]
Further, for example, when the ambient humidity changes significantly from normal temperature and normal humidity (hereinafter, referred to as NN) to low temperature and low humidity (hereinafter, referred to as LL) during a certain period of time while the apparatus is on standby, the photosensitive drum surface of the developing unit is in the NN state. The sensitivity remains in the NN state because the toner is in contact with the moisture-absorbed toner, and the residual toner absorbed in the NN state remains in the cleaning section in the closed space that shields the blade and toner scattering. Means that the sensitivity remains NN.
[0012]
When printing is performed in this state, the sensitivity is reduced because the drum surface other than the cleaning unit and the developing unit is LL, and the halftone image portion facing the cleaning unit and the developing unit becomes a black band-like image density unevenness, and the transfer material is changed. It will be transcribed on top.
[0013]
On the other hand, if the above-mentioned environmental humidity greatly changes from LL to NN, the halftone image portion facing the cleaning unit and the developing unit is transferred to the transfer material as white band-shaped image density unevenness.
[0014]
Conventionally, in order to solve such a problem, the amount of movement of the photosensitive drum at the time of standby of the image forming apparatus is set to be at least equal to the distance between the openings of the cleaning unit opposed to the surface of the photosensitive drum. The image forming apparatus in which the photosensitive drum is rotated to transfer the image on the transfer material prevents image density unevenness from occurring (for example, Patent Document 1).
[0015]
[Patent Document 1]
JP-A-2000-75567 (paragraph number 0042, FIG. 5)
[0016]
[Problems to be solved by the invention]
However, in that case, there are the following problems.
[0017]
That is, (a) the humidity dependence of the photoconductor sensitivity fluctuation is one of the fundamental problems, but there is no technical countermeasure for this. (B) The method is limited to only the cleaning section, and there is no other method for dealing with a closed space other than the above, which processes toner disposed around the photosensitive drum. (C) Since the photoconductor drum is rotated at a fixed interval, there is a lot of unnecessary rotation, and the tip of the cleaning blade rubbing the photoconductor surface of the photoconductor drum rubs against the photoconductor surface. Time is wasted and the cleaning blade life is shortened.
[0018]
Therefore, an object of the present invention is to provide an image forming apparatus which does not cause such a problem.
[0019]
[Means for Solving the Problems]
The above object is achieved by the following image forming apparatus of the present invention.
[0020]
(1) At least an image carrier, charging means for charging the image carrier, image exposure means for forming an electrostatic latent image on the charged image carrier, and supplying a charged toner to the electrostatic latent image Developing means for visualizing the image, transfer means for transferring the toner image on the image carrier to a transfer material, cleaning means for removing toner remaining on the image carrier after the transfer, and control means And detecting means for detecting the humidity of the atmosphere around the image carrier, wherein the control means controls the image carrier according to the humidity detected by the detecting means when the image carrier is waiting for image formation. An image forming apparatus characterized by controlling so as to rotate.
[0021]
(2) The image forming apparatus according to (1), wherein the image carrier has humidity dependency.
[0022]
(3) The image forming apparatus according to (1) or (2), wherein the humidity is 40% or less.
[0023]
(4) At least an image carrier, charging means for charging the image carrier, image exposure means for forming an electrostatic latent image on the charged image carrier, and supplying charged toner to the electrostatic latent image Developing means for visualizing the image, transfer means for transferring the toner image on the image carrier to a transfer material, cleaning means for removing toner remaining on the image carrier after the transfer, and control means And detecting means for detecting the humidity of the atmosphere around the image carrier, wherein the control means responds to a change in humidity per time detected by the detecting means when the image carrier is waiting for image formation. An image forming apparatus that controls the image carrier to rotate.
[0024]
(5) The image forming apparatus according to (4), wherein the image carrier has humidity dependency.
[0025]
(6) The image forming apparatus according to (4) or (5), wherein the humidity change per hour in the atmosphere around the image carrier is 20% or more.
[0026]
(7) The developing means constitutes a closed space which is hermetically closed by a developing unit storage container, an opening surface facing the image carrier, and a toner scattering prevention member. The image forming apparatus according to claim 1.
[0027]
(8) The cleaning means constitutes a closed space which is hermetically closed by a cleaning unit storage container, an opening surface facing the image carrier, a cleaning blade in contact with the image carrier surface, and a toner scattering prevention member. The image forming apparatus according to any one of (1) to (7), wherein:
[0028]
(9) The amount of rotation of the image carrier is determined by a distance between an opening surface facing the image carrier constituting the closed space of the cleaning unit and an opening facing the image carrier constituting a closed space of the developing unit. (8) The image forming apparatus according to (8), wherein the width of the image forming apparatus is equal to or larger than the width of the surface.
[0029]
(10) The image forming apparatus according to any one of (1) to (9), which is a color image forming apparatus.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an embodiment according to the present invention will be described below with reference to the drawings.
[0031]
FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus, FIG. 2 is a schematic diagram showing a set of image forming units constituting the image forming apparatus, and FIG. 3 shows controlling rotation of a photosensitive drum. FIG. 4 is a flowchart for controlling the rotation of the photosensitive drum, and FIG. 5 is a schematic diagram showing a state in which the cleaning blade contacts the photosensitive drum.
[0032]
FIG. 1 shows an embodiment of a color image forming apparatus as an image forming apparatus of the present invention.
[0033]
This color image forming apparatus is referred to as a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7, a sheet feeding and conveying unit 21, A document image reading device SC is arranged above the main body A of the image forming apparatus.
[0034]
The image forming unit 10Y that forms a yellow image includes a charging unit 2Y that is a charging unit disposed around a drum-shaped photoconductor (hereinafter, referred to as a photoconductor drum) 1Y, an exposure unit 3Y that is an exposure unit, The image forming apparatus includes a developing unit 4Y as a developing unit, a primary transfer roller 5Y as a primary transfer unit, and a cleaning unit 6Y as a cleaning unit.
[0035]
The image forming unit 10M that forms a magenta image has a photosensitive drum 1M, a charging unit 2M, an exposing unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, and a cleaning unit 6M.
[0036]
The image forming unit 10C for forming a cyan image has a photosensitive drum 1C, a charging unit 2C, an exposing unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, and a cleaning unit 6C.
[0037]
The image forming apparatus 10K for forming a black image has a photosensitive drum 1K, a charging unit 2K, an exposing unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit 6K.
[0038]
The endless belt-shaped intermediate transfer body unit 7 is wound around a plurality of rollers 71, 72, 73, and 74, and is a semiconductive endless belt-shaped endless belt-shaped intermediate transfer body 70 (hereinafter referred to as intermediate) supported rotatably. Transfer belt).
[0039]
Images of each color formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer belt 70 that is rotated by the primary transfer rollers 5Y, 5M, 5C, and 5K, and are combined into a color image. Is formed.
[0040]
A transfer material P as a recording medium stored in a paper feed cassette 20 is fed by a paper feed / conveyance unit 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D, a registration roller 23, and a secondary transfer unit. 5A, and a color image is collectively transferred onto the transfer material P.
[0041]
The transfer material P to which the color image has been transferred is subjected to a fixing process by a fixing device 24, and is held by a sheet discharging roller 25 and placed on a sheet discharging tray 26.
[0042]
The above is a description of a state in which image formation is performed on one side of the transfer material P. However, in the case of double-sided copying, the discharge switching member 27 is switched, the paper guide unit 28 is opened, and the transfer material P is indicated by an arrow. It is transported in the direction of a.
[0043]
Further, the transfer material P is transported downward by the transport mechanism 29, is switched back by the sheet reversing unit 30, and is transported into the double-sided copy paper feed unit 31 with the rear end of the transfer material P serving as the leading end. .
[0044]
The transfer material P is moved in the sheet feeding direction by the conveyance guide 32 provided in the sheet feeding unit 31 for duplex copying, and the transfer material P is fed again by the sheet feeding rollers 33A, 33B, 33C, and 33D. To the transport path R.
[0045]
As described above, the transfer material P is again conveyed to the secondary transfer position as described above, the toner image is transferred to the back surface of the transfer material P, and is fixed by the fixing device 24, and then discharged to the discharge tray 26. I do.
[0046]
After the color image is transferred onto the transfer material P by the secondary transfer unit 5A, the residual toner is removed by the cleaning unit 6A from the intermediate transfer belt 70 from which the transfer material P is separated by curvature.
[0047]
During the image forming process, the primary transfer roller 5K is always in pressure contact with the photosensitive drum 1K, and the other primary transfer rollers 5Y, 5M, and 5C are respectively associated with the corresponding photosensitive drums 1Y, 1M, and 1C only during color image formation. Press against
[0048]
The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction, and an endless belt-shaped intermediate transfer unit 7 is arranged on the left side of the photosensitive drums 1Y, 1M, 1C, and 1K.
[0049]
The endless belt-shaped intermediate transfer body unit 7 includes an intermediate transfer belt 70 that can rotate around rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5K, and a cleaning unit 6A.
[0050]
Next, the image forming process will be described with reference to FIG.
By starting a photosensitive drum drive motor (not shown) at the start of image recording, the photosensitive drum 1Y of the yellow (Y) image forming unit 10Y is rotated counterclockwise as indicated by the arrow in FIG. The application of a potential to the Y photoconductor drum 1Y is started by the charging action of the section 2Y.
[0051]
After the potential is applied to the Y photoconductor drum 1Y, the Y exposure unit 3Y starts image writing by the first color signal, that is, an electric signal corresponding to the Y image data, and the surface of the Y photoconductor drum 1Y Then, an electrostatic latent image corresponding to the Y image of the original image is formed.
[0052]
The latent image is reversely developed in a contact or non-contact state by a developing roller 4Y1 of a Y developing unit 4Y, and a yellow (Y) toner is formed on the photosensitive drum 1Y in accordance with the rotation of the Y photosensitive drum 1Y. An image is formed.
[0053]
The Y toner image formed on the Y photoreceptor drum 1Y by the above-described image forming process is intermediately transferred by a Y primary transfer roller 5Y as a first transfer unit in a Y transfer area (no sign). The image is transferred onto the transfer belt 70.
[0054]
Next, synchronization is established with the Y toner image on the intermediate transfer belt 70, a potential is applied by the charging action of the M charging section 2M by the magenta (M) image forming section 10M, and the second potential is applied by the M exposing section 3M. , That is, an electric signal corresponding to the M image data.
[0055]
Subsequently, the M toner image formed on the M photoconductor drum 1M by the contact or non-contact reversal development by the developing roller 4M1 of the M developing unit 4M is transferred to the M primary area in the M transfer area (no symbol). By the transfer roller 5M, an M toner image is superimposed on the Y toner image.
[0056]
By the same process, the image of C is synchronized with the superposed toner image of Y and M, and is formed on the photosensitive drum 1C of C by the cyan (C) image forming unit 10C by the third color signal. The C toner image corresponding to the data is formed by being superimposed on the Y and M toner images by the C primary transfer roller 5C in the C transfer area (no symbol).
[0057]
Further, the image data of K is synchronized with the superposed toner image of Y, M, and C and formed on the photosensitive drum 1K of K by the black (K) image forming unit 10K by the fourth color signal. Is formed in a K transfer area (no symbol) by the K primary transfer roller 5K so as to be superimposed on the Y, M, and C toner images, and an intermediate transfer belt is formed. A superimposed color toner image of Y, M, C and K is formed on 70.
[0058]
The transfer residual toner remaining on the peripheral surfaces of the photoconductor drums 1Y, 1M, 1C, and 1K for each color after the transfer is transferred to the photoconductor drums 1Y, 1M, and 1C of the cleaning units 6Y, 6M, 6C, and 6K for each color. The cleaning member is in contact with 1K, and is rubbed and cleaned by a cleaning blade (see FIG. 2, shown as a cleaning blade 6Y1 constituting the image forming section 10Y).
[0059]
Transfer materials P separated and conveyed one by one from a paper feed cassette 20 serving as a transfer material storage means in synchronization with the formation of the superimposed color toner image on the intermediate transfer belt 70 are transferred to a timing roller 23 as a transfer material feed means. Is transferred to the transfer area (no symbol) of the secondary transfer roller 5A, which is the second transfer means, and the secondary transfer roller 5A to which a DC voltage having a polarity opposite to that of the toner is applied. The superimposed color toner images are collectively retransferred onto the transfer material P.
[0060]
The transfer material P to which the color toner image has been transferred is neutralized by a neutralizing electrode (not shown) as a separating unit, transported to the fixing device 24, and heat and pressure are applied between the fixing roller 24A and the pressure roller 24B. Is applied, the toner image on the transfer material P is fixed, and then discharged to the discharge tray 26 by the discharge roller 25.
[0061]
The untransferred toner remaining on the peripheral surface of the intermediate transfer belt 70 after the transfer is applied to the intermediate transfer belt 70 provided opposite to the cleaning opposing roller 6A2 with the intermediate transfer belt 70 sandwiched by the intermediate transfer belt cleaning unit 6A. The cleaning member is rubbed and cleaned by an intermediate transfer member cleaning blade 6A1, which is an intermediate transfer member cleaning member in a contact state.
[0062]
FIG. 2 is a schematic cross-sectional view showing a set of image forming units (Y is shown as an example) constituting the tandem-type color image forming apparatus.
[0063]
Since M, C, and K other than Y also have the same configuration, function, and size, they will be described below as Y.
[0064]
The photoreceptor drum 1Y of this embodiment mainly uses aluminum for the drum base, uses an OPC (organic photoconductor) photoreceptor as the photoreceptor on the base, and adopts a function-separated type lamination type. It rotates at a peripheral speed of 220 mm / s in the direction indicated by the arrow at a drum diameter of φ60 mm.
[0065]
The laminated type OPC photoreceptor has an undercoat layer on a drum substrate, and a charge carrier generation layer (CGL) and a charge carrier transport layer (CTL) laminated and coated thereon. The photosensitive layer has a thickness of 25 μm.
[0066]
In addition, as a base, there is a belt or a sheet, but a drum type is currently mainly used.
[0067]
The charging unit 2Y uniformly charges the periphery of the rotating photosensitive drum 1Y to a predetermined polarity and potential by corona discharge. In the present embodiment, a non-contact charging device using a band electrode is used. I have.
[0068]
The image exposure unit 3Y uses a semiconductor laser (LD) based on a laser scanning method, has an output power of 300 μW, emits a laser beam, scans and exposes the uniformly charged surface of the photosensitive drum 1Y, Form a latent image.
[0069]
A potential sensor SP for measuring the potential of the photoconductor surface is provided downstream of the image exposure unit 3Y and upstream of the development unit 4Y, and the potential of the non-image portion of the photoconductor is based on the detection potential of the potential sensor SP. Feedback control is performed.
[0070]
The developing unit 4Y develops the electrostatic latent image on the photoreceptor drum 1Y as a toner image, and development by contact or non-contact is performed by a combination of image exposure and reversal development, and includes a toner and a carrier as a developer. The used two-component developer is used, and the toner concentration in the developing unit 4Y is maintained at 7% by mass.
[0071]
As the toner, a polymerized toner having a volume average particle diameter of 3 to 8 μm is preferable. By using the polymerized toner, it is possible to form an image having a high resolving power, a stable density, and extremely low fogging.
[0072]
The primary transfer roller 5Y is a contact member in the form of a rotary member having an elastic layer. In this embodiment, the roller diameter is 20 mm and the resistance is 1 × 10 5. ⁶ Ω foam rubber roller, NBR (nitrile butadiene rubber) is used as the material, hardness is 30 degrees (Asker C scale), 500 g load is applied to the photoreceptor, and the transfer nip (transfer) between the photoreceptor drum 1Y Position) N is formed.
[0073]
After transfer of the toner image transferred onto the intermediate transfer belt 70, the surface of the photosensitive drum 1Y is cleaned by a cleaning unit 6Y to remove residual toner. In the present embodiment, a cleaning blade 6Y1 made of urethane rubber is used. The cleaning blade 6Y1 performs cleaning by rubbing the peripheral surface of the photosensitive drum 1Y in a counter type.
[0074]
The peripheral surface of the photosensitive drum 1Y whose surface has been cleaned by passing through the cleaning unit 6Y is irradiated by a pre-charging exposure (PCL) unit (not shown) to reduce the residual potential and proceed to the next image forming cycle. And migrate.
[0075]
The developing section 4Y of the image forming section according to the present embodiment will be described in more detail. In FIG. 2, a developing section frame 4Y8, a developer carrying member 4Y1 composed of a developing roller, a regulating section 4Y6 composed of a cutting board, and a screw And a stirring / transporting unit 4Y5 composed of a screw, a conveying roller 4Y2, a collecting unit 4Y3 composed of a screw, and the like.
[0076]
The developer carrying member 4Y1 is disposed to face the photoreceptor drum 1Y and is rotatably supported. The developer carrying member 4Y1 rotates as shown by an arrow to convey and carry the developer to form a layer necessary for development. .
[0077]
The developer carrier 4Y1 includes a rotatable rotating member (sleeve) 4YA, and a cylindrical magnet body 4YB housed inside the rotating member 4YA and fixed to the developing unit frame 4Y8.
[0078]
The developing unit 4Y includes a lower frame 4Y9 that supports the developer carrier 4Y1, the conveying roller 4Y2, the supply / conveying unit 4Y4, and the stirring / conveying 4Y5, and a developing unit that supports the cutting unit 4Y6 and the collecting unit 4Y3. And a frame 4Y8.
[0079]
The lower frame 4Y9 contains a supply / transport unit 4Y4 and a stirring / transport unit 4Y5.
[0080]
Note that the developing unit frame 4Y8 and the lower frame 4Y9 constitute a storage container that covers the entire developing unit.
[0081]
In response to recent demands for higher image quality, a reduction in the particle size of the toner is an essential condition, and an improvement in resolution and sharpness can be obtained.
[0082]
However, when a small particle size toner is used for the two-component magnetic brush development, the electrostatic force is weak, so that a large amount of toner scatters, which easily causes stains and color mixing in the apparatus.
[0083]
In order to prevent toner scattering from the developing unit 4Y, the tip of the developing unit frame 4Y8 facing the photosensitive drum 1Y is developed by the developing unit 4Y on the photosensitive member surface on the photosensitive drum 1Y and adhered by electrostatic force. It is located close to the last minute position that does not impair.
[0084]
Further, a photoconductive drum 1Y is provided at the front end of the lower frame 4Y9 on the photoconductor drum 1Y side such that the front end of a PET (polyethylene terephthalate) shielding sheet 4Y7 is in contact with the outer periphery of the photoconductor drum 1Y with the ear cutting plate 4Y6 interposed therebetween. Is attached to at least a portion involved in image formation.
[0085]
The leading end of the shielding sheet 4Y7 is disposed in contact with the outer peripheral surface of the photoconductor drum 1Y with a pressing force that does not damage the photoconductor laminated on the surface of the photoconductor drum 1Y. The toner scattered around the developer carrying member 4Y1 at the time of agitation / transportation or ear cutting is prevented, and the toner not adhered to the photoconductor is scattered outside the developing unit 4Y.
[0086]
Both ends of the developing unit 4Y in the width direction of the photosensitive drum 1Y (in a direction perpendicular to the feed direction of the intermediate transfer belt 70) (constituting both ends of the developing frame 4Y8 and the lower frame 4Y9) are also covered. are doing.
[0087]
As described above, the developing unit 4Y is a part of the outer periphery of the photosensitive drum 1Y {a circumferential length (arc) U1 (not shown) on the photosensitive drum 1Y side corresponding to the width W1 on the developing unit 4Y side in FIG. 2}. And a substantially closed space including the above.
[0088]
For this reason, the environment (humidity) in the developing unit 4Y affects the photoreceptor in the outer peripheral portion U1 on the photoreceptor drum 1Y side.
[0089]
Further, since the inside of the developing section 4Y forms a closed space, the reaction of the atmosphere around the photosensitive drum 1Y other than that to the environmental change of humidity changes.
[0090]
Further, the cleaning section 6Y as another embodiment of the present invention in FIG. 2 will be described in further detail.
[0091]
The cleaning section 6Y is provided with a cleaning blade 6Y1 made of urethane rubber for rubbing the surface of the photosensitive drum 1Y in order to remove residual toner on the rotating photosensitive drum 1Y.
[0092]
In some cases, a cleaning auxiliary means including a conductive roller or a conductive brush roller located upstream of the cleaning blade 6Y1 and below the cleaning blade 6Y1 may be provided.
[0093]
Further, the cleaning unit 6Y has a built-in toner collecting unit 6Y6. In the cleaning unit 6Y, the supporting member 6Y4 to which the cleaning blade 6Y1 having an elastic plate shape is attached is driven by the weight of the weight 6Y3 on one side to the other. It is urged to rotate clockwise about the side support shaft 6Y2.
[0094]
As a result, the edge portion of the tip of the cleaning blade 6Y1 is brought into contact with the peripheral surface of the photosensitive drum 1Y, and the residual toner on the peripheral surface is peeled off and falls to the lower toner collecting section 6Y6.
[0095]
On the other hand, in the toner collecting section 6Y6, the toner dropped from the cleaning section 6Y is collected and is recycled to the developing section 4Y by the operation of the toner conveying screw 6Y7.
[0096]
Generally, not all of the toner adhering to the photoconductor surface is transferred, and about 20% of the toner remains on the photoconductor surface.
[0097]
If the residual toner is carried over to the next copy cycle, in the step of exposing the photoconductor, the residual toner blocks the photodischarge of the photoconductor and may cause image defects in the next image formation.
[0098]
In order to prevent toner scattering from the cleaning unit 6Y, the leading end A of the cleaning unit storage container 6Y8 facing the photoconductor drum 1Y is disposed close to a bare position on the photoconductor drum 1Y without damaging the photoconductor surface. It is.
[0099]
Further, at the tip B of the other cleaning unit storage container 6Y8, PET (polyethylene terephthalate) having one end fixed to the cleaning unit storage container 6Y8 so that the toner separated by the cleaning blade 6Y1 does not scatter outside the cleaning unit 6Y. A shielding sheet 6Y5 is attached so that the other end thereof is in contact with the photosensitive drum 1Y, and has a width of at least a portion related to image formation of the entire width of the photosensitive drum 1Y.
[0100]
The leading end of the shielding sheet 6Y5 is attached in contact with the pressing force without damaging the laminated photoreceptor on the outer peripheral surface of the photoreceptor drum 1Y, thereby preventing the cleaning blade 6Y1 from scattering out of the cleaning unit 6Y due to toner peeling. are doing.
[0101]
In addition, both ends of the cleaning unit 6Y (constituting both ends of the cleaning unit storage container 6Y8) in the width direction of the photoconductor drum 1Y (the direction perpendicular to the feed direction of the intermediate transfer belt 70) are also covered.
[0102]
As described above, the cleaning unit 6Y includes a part of the outer periphery of the photosensitive drum 1Y (the outer periphery (arc) U2 (not shown) on the photosensitive drum 1Y side corresponding to the width W2 on the cleaning unit 6Y side in FIG. 2). It forms an almost closed space.
[0103]
For this reason, the environment (humidity) in the cleaning unit 6Y affects the photoconductor on the outer circumference U2 on the photoconductor drum 1Y side.
[0104]
Further, since the inside of the cleaning unit 6Y forms a closed space, the reaction of the atmosphere around the photosensitive drum 1Y other than that to the environmental change of the humidity occurs.
[0105]
Note that there is also a structure in which the cleaning unit storage container 6Y8 does not have the front end A, and the opening width between the shielding sheet 6Y5 and the cleaning blade 6Y1 is W2.
[0106]
Next, FIG. 3 is a block diagram illustrating rotation control of the photosensitive drum during standby of the image forming apparatus.
[0107]
The photosensitive drum rotation control shown in the block diagram is the same for each of the colors Y, M, C, and K, and will be described together.
[0108]
A sensor S (see FIG. 1) for detecting the humidity of the atmosphere around the photosensitive drums 1Y, 1M, 1C, and 1K constituting the image forming units 10Y, 10M, 10C, and 10K is provided near the photosensitive drum 1M.
[0109]
When four or more photosensitive drums are provided as in the present apparatus, a sensor S for detecting humidity is provided near the photosensitive drum having the lowest detected humidity. It is.
[0110]
When the image forming apparatus is in the standby state, the control unit 100 as a control unit checks the detected humidity of the sensor S every 5 minutes, and the detected humidity falls below the predetermined humidity K stored in the memory 1 in advance. In this case, it is determined that the humidity of each photoreceptor surface of the photoreceptor drums 1Y, 1M, 1C, and 1K is lower than the humidity K.
[0111]
In the standby state, when the change width L per unit time of the detected humidity of the sensor S is larger than the change width of the humidity previously defined and stored in the memory 2, the photosensitive drums 1Y, 1M, 1C,. It is determined that the change width of the humidity of each photoconductor surface of 1K is larger than a predetermined change width L.
[0112]
Next, based on the determination, the control unit 100 sends a signal to the drive circuits (Y), (M), (C), and (K) to thereby drive the drive sources (Y), (M), (C), (K). ) Is started, and the photosensitive drums 1Y, 1M, 1C, and 1K connected to the drive source are rotated (counterclockwise). Sends signals to the drive circuits (Y), (M), (C), and (K) to stop the drive sources (Y), (M), (C), and (K), and the photosensitive drums 1Y, 1M , 1C and 1K are stopped.
[0113]
The intermediate transfer belt 70 may be rotated clockwise at the same timing as the rotation of the photosensitive drum, and stopped at the same timing.
[0114]
The humidity K and the change width L described above were determined based on the following experiment described in Examples.
[0115]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto.
[0116]
(Example 1)
An image forming experiment was performed based on the image forming apparatus shown in FIG. 1 under the following conditions.
[0117]
Process speed (photosensitive drum peripheral speed): 220 mm / s
Photoconductor drum: diameter 60 mm. An organic semiconductor layer coated with a phthalocyanine pigment dispersed in polycarbonate. The thickness of the photoconductor layer including the charge transport layer is 25 μm.
[0118]
Exposure: Laser scanning method. Semiconductor laser (LD) power is 300 μW.
Development: Two-component development system. Development nip width 20 mm. The toner concentration in the developing device is 7% by mass.
[0119]
Cleaning unit: Counter type blade.
Intermediate transfer member: PI (polyimide) seamless belt with a thickness of 100 μm
Under the above conditions, the in-machine humidity sensor detects the humidity every 5 minutes during standby, and changes the installation environment so that the detected humidity becomes 10%, 20%, 40%, 60%, and 80%. Output.
[0120]
The image output was 1000 copies, after which the entire halftone image was output for each color after waiting for 20 minutes, and this series of operations was repeated ten times. As a result, no white band was generated in any halftone image, and the entire surface was uniform. This was the case when the humidity was 40% or more.
[0121]
When the humidity was 40% or less, white band-shaped density unevenness occurred at a pitch corresponding to the developing portion and the cleaning portion of the photosensitive drum in the halftone image.
[0122]
To solve this problem, when the photosensitive drum was rotated by 31 mm (60 degrees, the width facing the outer periphery of the photosensitive drum of the developing unit) while the apparatus was on standby, the white band-like density unevenness was eliminated.
[0123]
For this reason, the humidity K on the photoreceptor surface was specified to be 40%.
The running pattern is a character pattern of 5% printing for each color, and the entire halftone is 600 dpi (the number of pixels per inch) and PWM (pulse width modulation) is 30%.
[0124]
(Example 2)
Further, with the same device configuration as in the first embodiment, the in-machine humidity sensor detects the humidity every 5 minutes during standby, so that the detected humidity change ranges are 10%, 20%, 30%, 40%, and 50%. The image was output with the installation environment changed at a time interval of 8 hours or less.
[0125]
For image output, for example, after running (5000 prints) in an installation environment of 25 ° C. and 80%, enter a standby state, reduce the humidity to 25 ° C. and 50% in 8 hours, collect a halftone sample of the entire surface, output 500 prints, and wait for 20 minutes. Thereafter, the entire halftone image was output again for each color, and this series of operations was repeated five times.
[0126]
As a result, when the humidity change width was 20% or more, black band-shaped density unevenness occurred at a pitch corresponding to the developing portion and the cleaning portion of the photosensitive drum in the halftone image.
[0127]
In order to solve this problem, when the photosensitive drum was rotated by 31 mm (60 degrees, the width facing the outer periphery of the photosensitive drum of the developing unit) while the apparatus was on standby, the black band-shaped density unevenness was eliminated.
[0128]
From this, it was specified that the humidity change width L per hour on the photoreceptor surface was 2.5% or more (20% change in 8 hours) and the humidity difference at the previous image output was 20% or more.
[0129]
FIG. 4 illustrates a photosensitive drum with respect to a change in humidity when the image forming apparatus is in a standby state.
It is a flowchart which shows rotation control of 1Y, 1M, 1C, and 1K.
[0130]
The control unit 100 (see FIG. 3) checks whether the image forming apparatus is in a standby state (idling, energy saving mode, or the like) from the copy state (S11).
[0131]
When it is determined that the apparatus is in the standby state, the sensor S for detecting the humidity in the apparatus detects the humidity of the atmosphere around the photosensitive drums 1Y, 1M, 1C, and 1K in the apparatus every 5 minutes. The controller 100 checks whether or not the humidity is 40% or less as compared with the humidity K = 40% specified in S1 (S12).
[0132]
When it is determined that the humidity is 40% or less, the drive circuits (Y), (M), (C), and (K) for the photosensitive drums 1Y, 1M, 1C, and 1K (see FIG. 3). And the drive sources (Y), (M), (C), and (K) (see FIG. 3) operate, and the photosensitive drums 1Y, 1M, 1C, and 1K connected to the drive source rotate. The movement is started (S14).
[0133]
On the other hand, when it is determined that the humidity is not 40% or less, the humidity change width per hour is set to the humidity change width L = 20% (from the time of the previous image output) specified in the memory 2 (see FIG. 3) in advance. (Within 8 hours), the control unit 100 checks whether or not the humidity change width is 20% or more (S13).
[0134]
If it is determined within 8 hours from the previous image output that the humidity change width is 20% or more, the drive circuits (Y), (M), (M), and (M) of the photosensitive drums 1Y, 1M, 1C, and 1K Signals are sent to (C) and (K), and the driving sources (Y), (M), (C) and (K) operate, and the driving sources (Y), (M), (C) and (K) ), The photoreceptor drums 1Y, 1M, 1C, and 1K start rotating (S14).
[0135]
When it is determined that the humidity change width is not more than 20%, the humidity detection is performed again.
[0136]
The rotation of the photoconductor drums 1Y, 1M, 1C, and 1K is performed, and the control unit 100 checks whether or not the predetermined rotation amount of the photoconductor drums 1Y, 1M, 1C, and 1K has been reached (S15). ).
[0137]
When it is determined that the rotation amounts of the photosensitive drums 1Y, 1M, 1C, and 1K have reached the specified amounts, the control unit 100 drives the driving circuits (Y), (M), (M), and (M) of the photosensitive drums 1Y, 1M, 1C, and 1K. (C) and (K) are sent to stop the driving sources (Y), (M), (C) and (K), and at the same time, the driving sources (Y), (M), (C), The rotation of the photosensitive drums 1Y, 1M, 1C and 1K connected to (K) is stopped (S16).
[0138]
Next, the control unit 100 checks whether or not the image forming apparatus is in a standby state (S17).
[0139]
When it is determined that the apparatus is in the standby state, the detection of the sensor S for detecting the inside humidity is executed again.
[0140]
When it is determined that the image forming apparatus is not in the standby state, the flow is stopped (end) until the image forming apparatus enters the next standby state.
[0141]
As described above, when the internal environment changes rapidly, the humidity of the atmosphere around the photosensitive drums 1Y, 1M, 1C, and 1K also changes.
[0142]
Since M, C, and K other than Y also have the same configuration, function, and size, they will be described below as Y.
[0143]
The photoreceptor laminated on the photoreceptor drum 1Y is an organic photoconductor, and is known to cause a decrease in sensitivity and a decrease in surface potential due to low humidity. The amount of toner adhesion is reduced.
[0144]
Therefore, when the image forming apparatus is in the standby state, the image forming apparatus is likely to be affected by the previous operating state.
[0145]
Around the photoreceptor drum 1Y, various processing means for image formation are arranged. In this, a developing unit 4Y and a cleaning unit 6Y for stirring, transporting and peeling the toner prevent scattering of the toner during the processing. In order to achieve this, it is configured as a substantially closed space.
[0146]
In the standby state of the above-described image forming apparatus, the atmosphere around the photosensitive drum 1Y adapts from the humidity in the operating state before the standby to the humidity in the standby state in the apparatus as the standby time elapses.
[0147]
For this reason, the humidity of the photoconductor surface in an open state except for the photoconductor surface opposite to the developing unit 4Y and the cleaning unit 6Y disposed around the photoconductor drum 1Y in the machine also adjusts to the in-machine humidity during standby. come.
[0148]
However, since the developing unit 4Y and the cleaning unit 6Y are configured as substantially closed enclosed spaces, the humidity of the photoconductor surface facing each closed space is adapted to the humidity of the atmosphere in the closed space. The humidity of the photoconductor surface.
[0149]
When the operation shifts from standby to operation in this state, when the humidity is 40% or less, the amount of toner adhering to the developing unit 4Y on the photoconductor surface in the open state decreases, and the developing unit on the photoconductor surface facing the developing unit 4Y and the cleaning unit 6Y. This is different from the toner adhesion amount in 4Y, and particularly in the case of a halftone image, remarkably black band-like image density unevenness occurs in two places (the photosensitive member surface facing the developing unit 4Y and the cleaning unit 6Y). .
[0150]
When the toner adhesion amount is opposite, white band-like image density unevenness occurs at two places.
[0151]
In order to prevent this, the humidity at the time of standby is detected by the sensor S, and when the humidity of the atmosphere around the photoconductor drum 1Y in the apparatus becomes low humidity of 40% or less, the humidity is applied to each of the developing unit 4Y and the cleaning unit 6Y. The photoreceptor drum 1Y is rotated even during standby so that the humidity of the opposing photoreceptor surfaces U1 and U2 becomes the same as the humidity of the open photoreceptor surface.
[0152]
Thus, by exposing each of the photoconductor surfaces U1 and U2 of the developing unit 4Y and the cleaning unit 6Y to the humidity of the same atmosphere as the opened photoconductor surface, it is possible to eliminate the difference in humidity on the entire peripheral surface of the photoconductor. It is possible to prevent the occurrence of white band-like or black band-like image density unevenness.
[0153]
The rotation amount of the photoconductor drum 1Y is determined by comparing the width W1 of the developing unit 4Y facing the photoconductor surface U1 and the width W2 of the cleaning unit 6Y facing the photoconductor surface U2, at least the circumference of the longer photoconductor surface. It can be seen that it is sufficient to set the rotation amount to the length.
[0154]
Similarly, even when the change in humidity per unit time during standby of the image forming apparatus is 20% or more (within 8 hours from the previous image output), the photosensitive drum 1Y is rotated, and the humidity around the photosensitive member surface is changed. By eliminating the difference, it is possible to prevent the occurrence of white band-like or black band-like image density unevenness.
[0155]
Further, the cleaning blade 6Y1 is always in contact with the photosensitive drum 1Y with a predetermined pressing force for separating the toner remaining after the transfer from the surface of the photosensitive drum 1Y.
[0156]
Conventionally, the photosensitive drum 1Y is rotated at a fixed time interval during standby except when the copying operation is performed. However, in the present invention, the specified humidity during standby (40% or less of humidity and a humidity change width per hour of 20%) is set. % Or more), it is only necessary to rotate the photosensitive drum 1Y, and it has been confirmed that the amount of wear at the tip of the cleaning blade 6Y1 that contacts the photosensitive member surface is reduced and the life is extended.
[0157]
The details are shown below.
(Reference example)
With the same apparatus configuration as in Example 1 (see page 15), (a) after 100 continuous printings (printing rate 5% image), stop repeated operation 1000 times, (b) continuous 100 printings (printing rate 5% image) ) After that, a series of operations of rotating the photosensitive drum 1Y by 60 degrees is repeated 35 times 1000 times (c) After continuous 100 prints (printing rate 5% image), the photosensitive drum 1Y is rotated by 60 degrees. An operation of repeating a series of operations 100 times was performed 1000 times.
[0158]
When the effect of the cleaning blade 6Y1 was compared and checked, the wear amount of the blade tip was (a) 10 μm, (b) 12 μm, (c) 17 μm, and (a) and (b) did not cause any problem in the cleaning function. In (c), however, toner slippage was observed from the 700th time.
[0159]
Therefore, the relationship between the wear of the cleaning blade 6Y1 and the tip of the cleaning blade 6Y1 that is in contact with the photosensitive drum 1Y is that the tip of the cleaning blade 6Y1 is caught in the rotating direction of the photosensitive drum 1Y as the photosensitive drum 1Y rotates. In order to repeat the operation of returning to the original state when the photosensitive drum 1Y is stopped, the cleaning blade 6Y1 is turned up {arrow b in FIG. 5 (b), and (a) indicates the normal state of the photosensitive drum 1Y. The mark を indicating the contact state of the cleaning blade 6Y1 damages the edge of the tip of the cleaning blade 6Y1 or increases the wear of the tip of the cleaning blade 6Y1.
[0160]
In (b), the environment in which the humidity is 30% or less at high temperature and high pressure, normal temperature and normal pressure, and low temperature and low pressure is estimated to be 1/3, and the number of repetitions is set to 1/3 for (c). It was carried out in the state.
[0161]
Under the above experimental conditions, in general, the replacement life of the photosensitive drum and the cleaning blade of the copying machine is 100,000 prints, and 500 prints per day are operated for about 200 days.
[0162]
As a copying machine with an average processing capacity, at 50 prints / minute, the actual operation (print) per day is 10 minutes, and the remaining 470 minutes out of the use of 8 hours a day is a standby time.
[0163]
If the time interval during standby is 5 minutes and the photoreceptor is rotated 60 degrees at φ60 mm per time, the photoreceptor drum rotates 60 degrees at 564 times a day and about 110,000 times in 200 days, and the cleaning blade wears. It can be seen that the effect on the water cannot be ignored.
[0164]
【The invention's effect】
By rotating the photosensitive drum according to a change in the humidity of the atmosphere around the photosensitive drum during standby for image formation by the image forming apparatus, unevenness in humidity on the photosensitive member surface of the photosensitive drum is eliminated, and the humidity is reduced. It is possible to prevent the occurrence of white band-shaped or black band-shaped image density unevenness caused by a change in sensitivity.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating the overall configuration of an image forming apparatus.
FIG. 2 is a schematic diagram illustrating a set of image forming units included in the image forming apparatus.
FIG. 3 is a block diagram illustrating control of rotation of a photosensitive drum.
FIG. 4 is a flowchart for controlling rotation of a photosensitive drum.
FIG. 5 is a schematic diagram showing a state in which a cleaning blade contacts a photosensitive drum.
[Explanation of symbols]
1Y photoreceptor drum (Y)
2Y charging unit (Y)
3Y exposure part (Y)
4Y development part (Y)
4Y7 shielding sheet
4Y8 developing unit frame
4Y9 Lower frame
6Y Cleaning unit (Y)
6Y1 Cleaning blade (Y)
6Y5 shielding sheet
6Y8 cleaning unit storage container
10Y Image forming unit (Y)
100 control unit
S sensor

Claims (10)

At least an image carrier, charging means for charging the image carrier, image exposure means for forming an electrostatic latent image on the charged image carrier, and supplying the charged toner to the electrostatic latent image to visualize the image. Developing means for transferring, a transfer means for transferring the visualized toner image on the image carrier onto a transfer material, a cleaning means for removing toner remaining on the image carrier after transfer, a control means, Detecting means for detecting the humidity of the atmosphere around the carrier, wherein the control means rotates the image carrier according to the humidity detected by the detecting means when the image carrier is waiting for image formation. An image forming apparatus, wherein the image forming apparatus controls the image forming apparatus to perform the control. The image forming apparatus according to claim 1, wherein the image carrier has humidity dependency. The image forming apparatus according to claim 1, wherein the humidity is 40% or less. At least an image carrier, charging means for charging the image carrier, image exposure means for forming an electrostatic latent image on the charged image carrier, and supplying the charged toner to the electrostatic latent image to visualize the image. Developing means for transferring, a transfer means for transferring the visualized toner image on the image carrier onto a transfer material, a cleaning means for removing toner remaining on the image carrier after transfer, a control means, Detecting means for detecting the humidity of the atmosphere around the carrier, wherein the control means controls the image carrier in accordance with a change in humidity per time detected by the detecting means when the image carrier is waiting for image formation. An image forming apparatus for controlling a body to rotate. The image forming apparatus according to claim 4, wherein the image carrier has humidity dependency. The image forming apparatus according to claim 4, wherein the change in humidity per hour in the atmosphere around the image carrier is 20% or more. 7. The developing device according to claim 1, wherein the developing unit forms a closed space which is closed by an opening surface facing the image carrier and a toner scattering preventing member. 5. The image forming apparatus according to claim 1. The cleaning unit forms a closed space that is closed by a cleaning unit storage container, an opening surface facing the image carrier, a cleaning blade in contact with the image carrier surface, and a toner scattering prevention member. The image forming apparatus according to claim 1. The rotation amount of the image carrier is a distance between an opening surface facing the image carrier constituting a closed space of the cleaning unit, and a distance between the opening surfaces facing the image carrier constituting a closed space of the developing unit. The image forming apparatus according to claim 8, wherein the width of the image forming apparatus is greater than or equal to a larger one. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus.

Images