JP3945423B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic system such as a printer, a copying machine, a facsimile, and the like, and more particularly, to a countermeasure for environment dependency of a photoconductor that forms a toner image on an image carrier.
[0002]
[Prior art]
An image forming apparatus that forms a toner image on an image carrier having a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and the like, and electrostatically transfers the toner image to a recording medium such as a transfer material. Are known.
[0003]
In general, a drum type is mainly used as an image carrier because of advantages such as manufacturing and downsizing of an apparatus, and a type in which an OPC (organic photoconductor) is recently laminated on the surface of the image carrier is mainly used. 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 photosensitive member laminated on the surface of the image carrier (hereinafter referred to as the photosensitive drum) varies depending on the temperature and humidity of the atmosphere in which the photosensitive member is present, and the surface of the photosensitive member accordingly. The potential fluctuates.
[0005]
During normal printing operation, the effect is hardly recognized, but when the device is in a standby state, the change in temperature and humidity is limited to the image formation immediately after resuming the printing operation, especially in the halftone image. This phenomenon cannot be ignored as described below.
[0006]
Among the parts surrounding the photosensitive drum, the developing unit and the cleaning unit, which are responsible for supplying and collecting toner, respectively, shield the entire photosensitive member layer on the drum surface in order to prevent scattering of minute toner by supplying and collecting. The enclosed space including each is formed independently.
[0007]
For this reason, when the apparatus enters a standby state, other than the developing unit and the cleaning unit described above immediately adapt to the standby environment. However, the developing unit and the cleaning unit that form a previously closed space are in 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 maintained with low humidity, the sensitivity of the photosensitive member around the photosensitive drum in that part is lowered, and in this state When the photosensitive member surface is exposed to light, the surface potential drop due to light attenuation does not fall to a predetermined potential, and the amount of toner adhered during development decreases.
[0009]
For this reason, in the halftone image formation, white corresponding to the width of each opening in the width direction of the photosensitive drum (90-degree direction with respect to the transfer material conveyance surface direction) facing the photosensitive drum surface of the developing unit and the cleaning unit. It becomes a belt-like image density unevenness and is transferred onto the transfer material.
[0010]
On the other hand, if the environment between the developing unit and the cleaning unit described above is maintained with a high humidity, black belt-shaped image density unevenness having a width in the width direction of the photosensitive drum is generated on the transfer material. Will be transcribed.
[0011]
Further, for example, when the environmental humidity greatly changes 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 when the apparatus is on standby, the surface of the photosensitive drum of the developing unit is in the NN state. The sensitivity remains in the NN state because it is in contact with the moisture-absorbed toner, and the cleaning unit retains the residual toner that has absorbed moisture in the NN state in a closed space that shields the scattering of the toner from the blade. The sensitivity remains NN.
[0012]
When printing is performed in this state, the drum surface other than the cleaning unit and the developing unit is LL, so the sensitivity is low, and the halftone image portion facing the cleaning unit and the developing unit becomes a black belt-like image density unevenness and the transfer material It will be transferred to the top.
[0013]
On the other hand, when the environmental humidity changes greatly from LL to NN, the halftone image portion facing the cleaning unit and the developing unit becomes a white band-like image density unevenness and is transferred onto the transfer material.
[0014]
Conventionally, in order to solve such a problem, the moving amount of the photosensitive drum during standby of the image forming apparatus is at a constant interval so that it is at least the interval between the openings of the cleaning unit facing the surface of the photosensitive drum. Image density unevenness is prevented from occurring in an image forming apparatus in which a photosensitive drum is rotated and transferred onto a transfer material (for example, Patent Document 1).
[0015]
[Patent Document 1]
JP 2000-75567 A (paragraph number 0042, FIG. 5)
[0016]
[Problems to be solved by the invention]
However, in this case, there are the following problems.
[0017]
That is, (a) humidity dependence of the photoreceptor is one of the fundamental problems, but there is no technical response to this. (B) The method is limited to the cleaning unit only, and there is no other method for dealing with the sealed closed space for processing the toner disposed around the photosensitive drum. (C) Since the photosensitive drum is rotated at regular intervals, there is a lot of unnecessary rotation, and the tip of the cleaning blade that is in sliding contact with the photosensitive drum surface is rubbed against the photosensitive drum surface. Time is wasted and the life of the cleaning blade is reduced.
[0018]
Therefore, an object of the present invention is to provide an image forming apparatus that 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, a charging unit for charging the image carrier, an image exposure unit for forming an electrostatic latent image on the charged image carrier, and a toner charged on the electrostatic latent image A developing means for supplying and developing the image; a transfer means for transferring the visualized toner image on the image carrier onto a transfer material; and a cleaning means for removing the toner remaining on the image carrier after the transfer. And a control means, and a detection means for detecting the humidity of the atmosphere around the image carrier,
  The developing means has a closed space sealed by a developing unit storage container, an opening surface facing the image carrier and a toner scattering prevention member,
  The cleaning means includes a closed space sealed 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, respectively. ,
  The control means opposes the image carrier to the image carrier constituting the closed space of the cleaning unit according to the humidity detected by the detection means when the image carrier is waiting for image formation. Corresponds to the wider of the width of the gap of the opening surface and the width of the gap of the opening surface facing the image carrier constituting the closed space of the developing unit.widthThe image forming apparatus is controlled so as to be rotated.
[0022]
  (2)Detected by detection meansHumidity is 40% or lessSometimes the control means rotates the image carrier(1)The image forming apparatus described.
[0023]
  (3) Supplying at least an image carrier, a charging unit for charging the image carrier, an image exposure unit for forming an electrostatic latent image on the charged image carrier, and a toner charged to the electrostatic latent image. Developing means for visualizing; transfer means for transferring the visualized toner image on the image carrier onto a transfer material; cleaning means for removing toner remaining on the image carrier after transfer; Control means and detection means for detecting the humidity of the atmosphere around the image carrier,
  The developing means has a closed space sealed by a developing unit storage container, an opening surface facing the image carrier and a toner scattering prevention member,
  The cleaning means includes a closed space sealed 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, respectively. ,
  When the image carrier is waiting for image formation, the control unit causes the image carrier to form the closed space of the cleaning unit according to a change in humidity per unit time detected by the detection unit. This corresponds to the wider of the width of the gap of the opening surface facing the body and the width of the gap of the opening surface facing the image carrier constituting the closed space of the developing unit.widthAn image forming apparatus, wherein the image forming apparatus is controlled so as to be rotated.
[0025]
  (4The humidity change per hour in the atmosphere around the image carrierWithin 8 hours from previous image formation20% or moreSometimes the image carrier is rotatedIt is characterized by (The image forming apparatus according to 3).
[0026]
  (5(1) to (1), which are color image forming apparatuses4The image forming apparatus according to any one of the above.
[0030]
DETAILED DESCRIPTION OF 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 the 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 that the rotation of the photosensitive drum is controlled. FIG. 4 is a flowchart for controlling the rotation of the photosensitive drum, and FIG. 5 is a schematic diagram showing a contact state of the cleaning blade to 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 called 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 paper feeding / conveying unit 21, and A document image reading device SC is disposed above the main body A of the image forming apparatus.
[0034]
An image forming unit 10Y that forms a yellow image includes a charging unit 2Y that is a charging unit and an exposure unit 3Y that is an exposure unit disposed around a drum-shaped photoconductor (hereinafter referred to as a photoconductor drum) 1Y. 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 are included.
[0035]
The image forming unit 10M that forms a magenta image includes a photosensitive drum 1M, a charging unit 2M, an exposure 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 that forms a cyan image includes a photosensitive drum 1C, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, and a cleaning unit 6C.
[0037]
An image forming apparatus 10K that forms a black image includes a photosensitive drum 1K, a charging unit 2K, an exposure 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 a semiconductive endless belt-shaped endless belt-shaped intermediate transfer body 70 (hereinafter referred to as an intermediate transfer body) that is wound around a plurality of rollers 71, 72, 73, 74 and is rotatably supported. A transfer belt).
[0039]
Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the intermediate transfer belt 70 rotated by the primary transfer rollers 5Y, 5M, 5C, and 5K, and the combined color image. Is formed.
[0040]
The transfer material P as a recording medium housed in the paper feed cassette 20 is fed by the paper feed / conveying unit 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D and a registration roller 23, and a secondary transfer unit. The color image is transferred onto the transfer material P at a time.
[0041]
The transfer material P onto which the color image has been transferred is fixed by the fixing device 24, sandwiched between the paper discharge rollers 25, and placed on the paper discharge tray 26.
[0042]
The above describes the state in which the image is formed on one side of the transfer material P. However, in the case of double-sided copying, the paper discharge switching member 27 is switched, the paper guide portion 28 is opened, and the transfer material P is indicated by an arrow. It is conveyed in the direction a.
[0043]
Further, the transfer material P is transported downward by the transport mechanism 29, switched back by the paper reversing unit 30, and transported into the duplex copying paper supply unit 31 with the rear end portion of the transfer material P serving as the leading end portion. .
[0044]
The transfer material P moves the conveyance guide 32 provided in the double-sided copy paper supply unit 31 in the paper supply direction, and re-feeds the transfer material P with the paper supply rollers 33A, 33B, 33C, 33D. To the transport path R.
[0045]
In this manner, as described above, the transfer material P is again conveyed to the secondary transfer position, the toner image is transferred to the back surface of the transfer material P, fixed by the fixing device 24, and then discharged to the discharge tray 26. To do.
[0046]
Further, after the color image is transferred to 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 correspond to the photosensitive drums 1Y, 1M, and 1C, respectively, only during color image formation. Press contact.
[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 body unit 7 is arranged on the left side of the photosensitive drums 1Y, 1M, 1C, and 1K in the drawing.
[0049]
The endless belt-shaped intermediate transfer body unit 7 includes an intermediate transfer belt 70 that can be rotated by winding 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.
When the photosensitive drum drive motor (not shown) is started by starting image recording, the photosensitive drum 1Y of the yellow (Y) image forming unit 10Y is rotated counterclockwise as indicated by the arrow in FIG. Application of a potential to the Y photosensitive drum 1Y is started by the charging action of the portion 2Y.
[0051]
After the Y photoconductor drum 1Y is applied with an electric potential, the Y exposure unit 3Y starts image writing using an electric signal corresponding to the first color signal, that is, the Y image data, and the surface of the Y photoconductor drum 1Y. 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 the developing roller 4Y1 of the Y developing unit 4Y, and yellow (Y) toner is formed on the photosensitive drum 1Y according to the rotation of the Y photosensitive drum 1Y. An image is formed.
[0053]
The Y toner image formed on the Y photosensitive drum 1Y by the above image forming process is intermediated by the Y primary transfer roller 5Y serving as the first transfer means in the Y transfer area (not indicated). The image is transferred onto the transfer belt 70.
[0054]
Next, the Y toner image on the intermediate transfer belt 70 is synchronized, and a potential is applied by the charging action of the M charging unit 2M by the magenta (M) image forming unit 10M. The image writing is performed by the electrical signal corresponding to the color signal, that is, 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 of the M developing unit 4M by the developing roller 4M1 is the M primary in the M transfer area (not indicated). By the transfer roller 5M, an M toner image is superimposed on the Y toner image.
[0056]
By a similar process, the Y and M superimposed toner images are synchronized, and the C image by the third color signal formed on the C photosensitive drum 1C by the cyan (C) image forming unit 10C. A C toner image corresponding to the data is formed by superimposing the Y and M toner images on the Y and M toner images by the C primary transfer roller 5 </ b> C in the C transfer region (no symbol).
[0057]
Further, K image data based on the fourth color signal, which is synchronized with the superimposed toner images of Y, M, and C and is formed on the K photosensitive drum 1K by the black (K) image forming unit 10K. A K toner image corresponding to is formed by superimposing the Y, M, and C toner images on the Y transfer area (not indicated) by the K primary transfer roller 5K, and the intermediate transfer belt. 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 photosensitive drums 1Y, 1M, 1C, and 1K for each color after transfer is the photosensitive drums 1Y, 1M, and 1C of the cleaning units 6Y, 6M, 6C, and 6K for the respective colors. The cleaning blade is cleaned by being rubbed by a cleaning blade (see FIG. 2, indicated as a cleaning blade 6Y1 constituting the image forming unit 10Y) that is in contact with 1K.
[0059]
In synchronization with the formation of the superimposed color toner image on the intermediate transfer belt 70, the transfer material P separated and conveyed one by one from the paper feed cassette 20 as transfer material storage means is a timing roller 23 as transfer material feeding means. The intermediate transfer belt 70 is transferred onto the intermediate transfer belt 70 by the secondary transfer roller 5A, which is conveyed to the transfer area (no sign) of the secondary transfer roller 5A, which is the second transfer means, and to which a DC voltage having the opposite polarity to the toner is applied. The superimposed color toner images are collectively retransferred onto the transfer material P.
[0060]
The transfer material P onto which the color toner image has been transferred is neutralized by a neutralizing electrode (not shown) as a separating means, conveyed to the fixing device 24, and heat and pressure between the fixing roller 24A and the pressure roller 24B. As a result, the toner image on the transfer material P is fixed, and then discharged onto the discharge tray 26 by the discharge roller 25.
[0061]
The transfer residual toner remaining on the peripheral surface of the intermediate transfer belt 70 after the transfer is brought into contact with the intermediate transfer belt 70 provided to face the cleaning counter roller 6A2 with the intermediate transfer belt 70 sandwiched by the intermediate transfer belt cleaning unit 6A. The intermediate transfer member cleaning blade 6A1, which is an intermediate transfer member cleaning member in contact, is rubbed and cleaned.
[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 color image forming apparatus.
[0063]
In addition, since M, C, and K other than Y have the same configuration, function, and size, the following description will be made on Y.
[0064]
The photosensitive drum 1Y of this embodiment uses aluminum as a drum base, uses an OPC (organic photoconductor) photosensitive body as a photosensitive body on the base, and adopts a function-separated type laminated type. It rotates at a peripheral speed of 220 mm / s in the direction of the arrow with a drum diameter of φ60 mm.
[0065]
In the laminated OPC photoreceptor, an undercoat layer is formed on a drum substrate, and a charge carrier generation layer (CGL) and a charge carrier transport layer (CTL) are laminated and applied thereon. The thickness of the photosensitive layer is 25 μm.
[0066]
Although there are belts and seats as the substrate, the drum type is mainly used at present.
[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 this embodiment, a non-contact charging device using a band electrode is used. Yes.
[0068]
The image exposure unit 3Y uses a laser scanning type semiconductor laser (LD), and its output power is 300 μW. The laser beam is emitted to scan and expose the uniformly charged surface of the photosensitive drum 1Y, and electrostatically A latent image is formed.
[0069]
A potential sensor SP that measures the potential of the surface of the photoreceptor is provided downstream of the image exposure unit 3Y and upstream of the developing unit 4Y. The potential of the non-image part of the photoreceptor is based on the detection potential of the potential sensor SP. Feedback control.
[0070]
The developing unit 4Y develops the electrostatic latent image on the photosensitive 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 toner and carrier as developers. The two-component developer thus used is used, and the toner concentration in the developing portion 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, an image can be formed with high resolution, stable density, and extremely low fog generation.
[0072]
The primary transfer roller 5Y is a rotating member-shaped contact charging member having an elastic layer. In this embodiment, the roller diameter is 20 mm, and the resistance is 1 × 10.⁶An Ω foam rubber roller, made of NBR (nitrile butadiene rubber), with a hardness of 30 degrees (Asker C scale), pressed against the photoreceptor with a load of 500 g, and a transfer nip (transfer) between the photoreceptor drum 1Y Position) N is formed.
[0073]
The surface of the photosensitive drum 1Y after the transfer of the toner image transferred onto the intermediate transfer belt 70 is cleaned of residual transfer toner by the cleaning unit 6Y. In this embodiment, a cleaning blade 6Y1 made of urethane rubber is used. The cleaning blade 6Y1 is a counter type that is rubbed against the peripheral surface of the photosensitive drum 1Y for cleaning.
[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-charge exposure (PCL) unit (not shown) to reduce the residual potential and proceed to the next image forming cycle. And migrate.
[0075]
The developing unit 4Y of the image forming unit according to the present embodiment will be described in more detail. In FIG. 2, from the developing unit frame 4Y8, a developer carrier 4Y1 composed of a developing roller, a regulating unit 4Y6 composed of a panicle plate, and a screw. The feeding / conveying unit 4Y4 is composed of a stirring / conveying unit 4Y5 composed of a screw, a conveying roller 4Y2, and a collecting unit 4Y3 composed of a screw.
[0076]
The developer carrier 4Y1 is disposed to face the photosensitive drum 1Y and is rotatably supported. The developer carrier 4Y1 rotates as indicated 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 developer carrier 4Y1, a conveying roller 4Y2, a lower frame 4Y9 that supports the supply / conveyance unit 4Y4 and the agitation / conveyance 4Y5, and a developing unit that supports a regulation unit 4Y6 and a collection unit 4Y3, each of which includes a cutting plate It is comprised from the part frame 4Y8.
[0079]
The lower frame 4Y9 accommodates a supply / conveyance unit 4Y4 and a stirring / conveyance unit 4Y5.
[0080]
The developing unit frame 4Y8 and the lower frame 4Y9 constitute a storage container that covers the entire developing unit.
[0081]
To meet the recent demand for higher image quality, it is essential to reduce the particle size of the toner, and resolution and sharpness can be improved.
[0082]
However, when a toner having a small particle diameter is used for two-component magnetic brush development, the electrostatic force is weak, so that a large amount of toner scatters, which easily causes in-machine contamination and color mixing.
[0083]
In order to prevent toner scattering from the developing unit 4Y, the tip of the developing unit frame 4Y8 that faces the photosensitive drum 1Y is visualized by the developing unit 4Y and attached to the surface of the photosensitive drum on the photosensitive drum 1Y by electrostatic force. It is arranged close to the last position that does not impair the power.
[0084]
Further, the photosensitive drum 1Y is arranged such that the front end of the shielding sheet 4Y7 made of PET (polyethylene terephthalate) is in contact with the outer periphery of the photosensitive drum 1Y with the panning plate 4Y6 sandwiched between the front end of the lower frame 4Y9 on the photosensitive drum 1Y side. Are attached to at least a part involved in image formation.
[0085]
The tip of the shielding sheet 4Y7 is disposed in contact with the outer peripheral surface of the photosensitive drum 1Y with a pressing force that does not damage the photosensitive member laminated on the surface of the photosensitive drum 1Y, and mainly in the developing unit 4Y. It prevents the stir / convey that occurs from around the developer carrying member 4Y1 and the scattering of toner at the time of trimming, and the scattering of toner not adhered to the photosensitive member to the outside of the developing unit 4Y.
[0086]
Note that both ends of the developing section 4Y in the width direction of the photosensitive drum 1Y (perpendicular to the feeding direction of the intermediate transfer belt 70) (which constitutes both ends of the developing frame 4Y8 and the lower frame 4Y9) are also covered. is doing.
[0087]
As described above, the developing unit 4Y is a part of the outer periphery of the photosensitive drum 1Y {the 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}. It forms an almost enclosed space including
[0088]
For this reason, the environment (humidity) in the developing section 4Y affects the photoconductor on the outer peripheral portion U1 on the photoconductor drum 1Y side.
[0089]
Further, since a closed space is formed in the developing unit 4Y, there is a difference in response to changes in the humidity of the atmosphere around the photosensitive drum 1Y.
[0090]
Further, a cleaning unit 6Y which is another embodiment of the present invention in FIG. 2 will be described in more detail.
[0091]
The cleaning unit 6Y is provided with a urethane rubber cleaning blade 6Y1 that rubs the surface of the photosensitive drum 1Y 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 includes a toner recovery unit 6Y6. In the cleaning unit 6Y, the support member 6Y4 to which the cleaning blade 6Y1 having an elastic plate shape is attached has the other weight due to the weight of the weight 6Y3 on one side. The side support shaft 6Y2 is urged to rotate clockwise with the fulcrum as a fulcrum.
[0094]
As a result, the edge portion at the tip of the cleaning blade 6Y1 is brought into contact with the circumferential surface of the photosensitive drum 1Y, and the residual toner on the circumferential surface is peeled off and dropped to the lower toner collecting portion 6Y6.
[0095]
On the other hand, in the toner collecting unit 6Y6, the toner dropped from the cleaning unit 6Y is collected and recycled to the developing unit 4Y by the operation of the toner conveying screw 6Y7.
[0096]
Generally, the toner adhering to the surface of the photoconductor is not completely transferred, and about 20% remains on the surface of the photoconductor.
[0097]
If the residual toner is carried over to the next copy cycle, the residual toner may block the photodischarge of the photoconductor in the step of exposing the photoconductor, which may cause an image defect in the next image formation.
[0098]
In order to prevent toner scattering from the cleaning unit 6Y, the tip A of the cleaning unit storage container 6Y8 facing the photoconductive drum 1Y is disposed close to the last position where the photoconductive surface on the photoconductive drum 1Y is not damaged. It is.
[0099]
Further, PET (polyethylene terephthalate) having one end fixed to the cleaning unit storage container 6Y8 at the tip B of the other cleaning unit storage container 6Y8 so that the toner peeled off by the cleaning blade 6Y1 is not scattered outside the cleaning unit 6Y. A shield sheet 6Y5 made of metal is attached so that the other end is in contact with the photosensitive drum 1Y, and has a width of at least a part related to image formation of the entire width of the photosensitive drum 1Y.
[0100]
The tip of the shielding sheet 6Y5 is attached in contact with a pressing force that does not impair the photoreceptors stacked on the outer peripheral surface of the photoreceptor drum 1Y, and prevents the cleaning blade 6Y1 from scattering out of the cleaning unit 6Y due to toner peeling. is doing.
[0101]
Note that both ends of the cleaning unit 6Y in the width direction of the photosensitive drum 1Y (perpendicular to the feeding direction of the intermediate transfer belt 70) (which constitutes both ends of the cleaning unit storage container 6Y8) 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 enclosed space.
[0103]
For this reason, the environment (humidity) in the cleaning unit 6Y affects the photoreceptor on the outer peripheral portion U2 on the photoreceptor drum 1Y side.
[0104]
Further, since the sealed portion 6Y forms a sealed closed space, a deviation of the response to the environmental change in the humidity of the atmosphere around the other photosensitive drum 1Y occurs.
[0105]
In addition, there is a structure in which the cleaning unit storage container 6Y8 does not have the tip 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 showing rotation control of the photosensitive drum during standby of the image forming apparatus.
[0107]
The photosensitive drum rotation control shown in this block diagram is the same for each color Y, M, C, and K, and will be described below.
[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 in the vicinity of the photosensitive drum 1M.
[0109]
In the case where four or more photosensitive drums are provided as in this apparatus, the sensor S is provided with a sensor S for detecting humidity in the vicinity of the photosensitive drum showing the lowest detected humidity. It is.
[0110]
When the image forming apparatus is in a 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 is specified to be equal to or lower than the humidity K stored in the memory 1 in advance. In this case, it is determined that the humidity on the photosensitive drum surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K is equal to or lower than the humidity K.
[0111]
Further, in the standby state, when the change width L of the detected humidity of the sensor S per time is larger than the change width of the humidity stored in the memory 2 in advance, the photosensitive drums 1Y, 1M, 1C, It is determined that the change width of the humidity of each 1K photoconductor surface is larger than the change width L set in advance.
[0112]
Next, based on the determination, the control unit 100 sends signals to the drive circuits (Y), (M), (C), and (K), thereby driving the drive sources (Y), (M), (C), and (K). ), The photosensitive drums 1Y, 1M, 1C, and 1K connected to the drive source are rotated (counterclockwise), and the control unit 100 determines that a predetermined rotation amount has been reached. Sends signals to the drive circuits (Y), (M), (C), (K), stops the drive sources (Y), (M), (C), (K), and the photosensitive drums 1Y, 1M. The rotation of 1C and 1K is stopped.
[0113]
The intermediate transfer belt 70 may be rotated clockwise at the same timing as the photosensitive drum rotation and stopped at the same timing.
[0114]
The humidity K and the change width L described above were determined based on the following experiments described in the examples.
[0115]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.
[0116]
Example 1
Based on the image forming apparatus of FIG. 1, an image forming experiment was performed under the following setting conditions.
[0117]
Process speed (photosensitive drum peripheral speed): 220 mm / s
Photosensitive drum: diameter 60 mm. The organic semiconductor layer is coated with phthalocyanine pigment dispersed in polycarbonate. The film thickness of the photoreceptor layer including the charge transport layer is 25 μm.
[0118]
Exposure: Laser scanning method. Semiconductor laser (LD) power is 300μW.
Development: Two-component development method. Development nip width 20 mm. The toner density in the developer is 7 mass
%.
[0119]
Cleaning part: Counter type blade.
Intermediate transfer body: 100 μm thick PI (polyimide) seamless belt
Under the above conditions, the in-machine humidity sensor detects 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, and after waiting for 20 minutes, the entire halftone image was output for each color, and when this series of operations was repeated 10 times, all the halftone images were uniform with no white bands. This was the case when the humidity was 40% or more.
[0121]
When the humidity was 40% or less, white belt-like density unevenness occurred at a pitch corresponding to the development portion and the cleaning portion of the photosensitive drum in the halftone image.
[0122]
In order to solve this problem, when the photosensitive drum was rotated 31 mm (60 degrees, a width facing the outer periphery of the photosensitive drum in the developing unit) while the apparatus was on standby, the above-described white band-like density unevenness disappeared.
[0123]
For this reason, the humidity K of the photosensitive member surface was defined as 40%.
The running pattern is a character pattern printed at 5% for each color, and the entire halftone is 600 dpi (number of pixels per inch) and PWM (pulse width modulation) is 30%.
[0124]
(Example 2)
Furthermore, with the same apparatus configuration as in the first embodiment, the in-machine humidity sensor detects humidity every 5 minutes during standby, and the detected humidity change width is 10%, 20%, 30%, 40%, and 50%. The image was output while changing the installation environment 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%, after entering the standby state, reducing the humidity to 25 ° C and 50% in 8 hours, collecting a halftone sample on the entire surface, outputting 500 prints, and waiting 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 is 20% or more, black belt-like density unevenness occurs 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 31 mm (60 degrees, the width facing the outer periphery of the photosensitive drum in the developing unit) while the apparatus was on standby, the above black band-like density unevenness disappeared.
[0128]
From this, the humidity change width L per hour on the surface of the photoconductor is defined as 2.5% (20% change in 8 hours) or more, and the humidity difference at the previous image output is defined as 20% or more.
[0129]
FIG. 4 shows a photosensitive drum against 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, 1K.
[0130]
The control unit 100 (see FIG. 3) checks whether the image forming apparatus is in a standby state (in idling or energy saving mode) 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 inside the apparatus detects the humidity of the atmosphere around the photosensitive drums 1Y, 1M, 1C, and 1K every 5 minutes. The control unit 100 checks whether or not the humidity is 40% or less compared to the humidity K = 40% defined in 1 (S12).
[0132]
When it is determined that the humidity is 40% or less, the drive circuits (Y), (M), (C), and (K) of the photosensitive drums 1Y, 1M, 1C, and 1K (see FIG. 3) , The drive sources (Y), (M), (C), and (K) (see FIG. 3) are activated, and the photosensitive drums 1Y, 1M, 1C, and 1K connected to the drive sources are rotated. The movement is started (S14).
[0133]
On the other hand, when it is determined that the humidity is not less than 40%, the humidity change width per time is defined as the humidity change width L = 20% defined in advance in the memory 2 (see FIG. 3) (from the previous image output time). The control unit 100 checks whether or not the humidity change width is 20% or more (within 8 hours) (S13).
[0134]
When it is determined that the humidity change width is 20% or more within 8 hours after the previous image output, the drive circuits (Y), (M), and the photosensitive drums 1Y, 1M, 1C, and 1K Signals are sent to (C) and (K), the drive sources (Y), (M), (C) and (K) are activated, and the drive sources (Y), (M), (C) and (K) ) Start to rotate (S14).
[0135]
When it is determined that the humidity change width is not 20% or more, the humidity detection is performed again.
[0136]
The rotation of the photosensitive drums 1Y, 1M, 1C, and 1K is executed, and the control unit 100 checks whether or not the rotation amount of the photosensitive drums 1Y, 1M, 1C, and 1K defined in advance is reached (S15). ).
[0137]
When it is determined that the rotation amount of the photosensitive drums 1Y, 1M, 1C, and 1K has reached a predetermined amount, the control unit 100 drives the photosensitive drums 1Y, 1M, 1C, and 1K drive circuits (Y), (M), (C), a signal is sent to (K), the operation of the drive sources (Y), (M), (C), (K) is stopped, and at the same time, the drive 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 vehicle is in the standby state, the sensor S that detects the humidity inside the apparatus is detected again.
[0140]
When it is determined that the image forming apparatus is not in the standby state, this 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 varies.
[0142]
In addition, since M, C, and K other than Y have the same configuration, function, and size, Y will be described below.
[0143]
The photoconductor laminated on the photoconductor drum 1Y is an organic photoconductor, and is known to cause a decrease in sensitivity, a decrease in surface potential, and the like due to low humidity. The toner adhesion amount is reduced.
[0144]
For this reason, when the image forming apparatus is in the standby state, the image forming apparatus is easily affected by the previous operating state.
[0145]
Each processing means is provided around the photosensitive drum 1Y for image formation. Among them, the developing unit 4Y and the cleaning unit 6Y for stirring, transporting, and peeling the toner prevent scattering of the toner during processing. In order to do this, it is composed of a substantially closed space.
[0146]
In the standby state of the image forming apparatus described above, the ambient atmosphere around the photosensitive drum 1Y becomes familiar with the humidity during standby in the machine from the humidity of the operating state before standby as the standby time elapses.
[0147]
For this reason, the humidity of the photosensitive surface in the open state excluding the photosensitive surface facing the developing unit 4Y and the cleaning unit 6Y disposed around the photosensitive drum 1Y in the apparatus is also adjusted to the in-machine humidity during standby. come.
[0148]
However, since the developing unit 4Y and the cleaning unit 6Y are configured in a substantially sealed space, the humidity on the surface of the photoreceptor facing each closed space is familiar with the humidity of the atmosphere in the closed space, and is open. The humidity on the surface of the photoreceptor is different.
[0149]
When shifting from standby to operation in this state, when the humidity is 40% or less, the toner adhesion amount on the developing unit 4Y to the opened photosensitive member surface decreases, and the developing unit to the photosensitive member surface facing the developing unit 4Y and the cleaning unit 6Y. This is different from the toner adhesion amount in 4Y. In particular, in the case of a halftone image, noticeably black belt-like image density unevenness occurs in two places (the photosensitive member surface facing the developing unit 4Y and the cleaning unit 6Y). .
[0150]
Further, when the toner adhesion amount is reversed, white belt-like image density unevenness occurs in two places.
[0151]
In order to prevent this, the humidity during standby is detected by the sensor S, and when the humidity around the photosensitive drum 1Y in the apparatus becomes a low humidity of 40% or less, each of the developing unit 4Y and the cleaning unit 6Y is provided. The photosensitive drum 1Y is rotated during standby so that the humidity of the opposing photosensitive surfaces U1 and U2 is the same as the humidity of the opened photosensitive surface.
[0152]
Accordingly, it is possible to eliminate the humidity difference between the entire circumferential surface of the photoreceptor by exposing the photoreceptor surfaces U1 and U2 of the developing unit 4Y and the cleaning unit 6Y to the same atmospheric humidity as the opened photoreceptor surface. It is possible to prevent the occurrence of white belt-like or black belt-like image density unevenness.
[0153]
The rotation amount of the photosensitive drum 1Y is determined by comparing the width W1 of the developing unit 4Y facing the photoreceptor surface U1 and the width W2 of the cleaning unit 6Y facing the photoreceptor surface U2, at least the circumference of the longer photoreceptor surface. It can be seen that the rotation amount corresponding to the length may be set.
[0154]
Similarly, even when the humidity change width per 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 on the entire circumference of the photosensitive surface. By eliminating the difference, it is possible to prevent the occurrence of white belt-like or black belt-like image density unevenness.
[0155]
Further, the cleaning blade 6Y1 is always in contact with the photosensitive drum 1Y with a prescribed 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 constant time interval during standby except when the copy is in operation. In the present invention, the specified humidity (humidity of 40% or less and humidity change width per hour) 20 during standby is used. It has been confirmed that the amount of wear at the tip of the cleaning blade 6Y1 in contact with the photosensitive surface of the cleaning blade 6Y1 is reduced and the life is extended.
[0157]
This is specifically shown below.
(Reference example)
In the same apparatus configuration as in Example 1 (see page 15), (b) after 100 continuous prints (printing rate of 5% image), repeated stop operation 1000 times, (b) continuous 100 printings (printing rate of 5% image) ) After that, a series of operations for rotating the photosensitive drum 1Y by 60 degrees is repeated 35 times. (C) After 100 continuous prints (printing rate 5% image), the photosensitive drum 1Y is rotated by 60 degrees. The operation of repeating the series of operations 100 times was performed 1000 times.
[0158]
When the effects of the cleaning blade 6Y1 were compared and checked, the blade tip wear amount was (b) 10 μm, (b) 12 μm, (c) 17 μm, and (b) and (b) had no problem with the cleaning function. However, in (C), toner slip-through was observed from the 700th time.
[0159]
From this, the relationship between the wear of 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 wound 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 swung (the part indicated by the arrow b in FIG. 5B). The contact state of the cleaning blade 6Y1 indicates that the edge of the tip of the cleaning blade 6Y1 is damaged or the wear of the tip of the cleaning blade 6Y1 increases.
[0160]
In addition, (b) is assumed to be 1/3 of the environment where the humidity is 30% or less at high temperature and high pressure, normal temperature and normal pressure, and low temperature and low pressure as the installation environment. Carried out in a state.
[0161]
Under the above experimental conditions, in general, a copying machine has a replacement life of a photosensitive drum and a cleaning blade of 100,000 prints, and is operated for about 200 days as 500 print processes per day.
[0162]
As a copying machine having an average processing capacity, the actual operation (printing) per day is 10 minutes at 50 prints / minute, and the remaining 470 minutes out of 8 hours per day is the standby time.
[0163]
If the waiting time interval is 5 minutes and the photosensitive member has a diameter of 60 mm and is rotated 60 degrees per rotation, the photosensitive drum will be rotated 564 times a day and approximately 110,000 rotations in 200 days, and the cleaning blade wears out. It can be seen that the effects on the environment cannot be ignored.
[0164]
【The invention's effect】
While waiting for image formation of the image forming apparatus, the photosensitive drum is rotated in accordance with the humidity change of the atmosphere around the photosensitive drum, thereby eliminating the non-uniformity of the humidity on the surface of the photosensitive drum. It is possible to prevent the occurrence of image density unevenness in the white belt shape or the black belt shape due to the sensitivity change.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an 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.
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 view showing a contact state of a cleaning blade to a photosensitive drum.
[Explanation of symbols]
1Y Photosensitive drum (Y)
2Y Charging part (Y)
3Y exposure part (Y)
4Y Development part (Y)
4Y7 shielding sheet
4Y8 Development unit frame
4Y9 Lower frame
6Y Cleaning section (Y)
6Y1 Cleaning blade (Y)
6Y5 shielding sheet
6Y8 Cleaning unit storage container
10Y Image forming unit (Y)
100 control unit
S sensor

Claims (5)

At least an image carrier, a charging unit for charging the image carrier, an image exposure unit for forming an electrostatic latent image on the charged image carrier, and a toner charged to the electrostatic latent image are supplied and developed. A developing unit that forms an image; a transfer unit that transfers the toner image on the image carrier that has been visualized onto a transfer material; a cleaning unit that removes toner remaining on the image carrier after the transfer; and a control Means and detecting means for detecting the humidity of the atmosphere around the image carrier,
The developing means has a closed space sealed by a developing unit storage container, an opening surface facing the image carrier and a toner scattering prevention member,
The cleaning means includes a closed space sealed 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, respectively. ,
The control means opposes the image carrier to the image carrier constituting the closed space of the cleaning unit according to the humidity detected by the detection means when the image carrier is waiting for image formation. Control is performed so that the opening is rotated by a width corresponding to the wider one of the width of the opening surface and the width of the opening surface facing the image carrier that forms the closed space of the developing unit. An image forming apparatus. 2. The image forming apparatus according to claim 1 , wherein when the humidity detected by the detection unit is 40% or less, the control unit rotates the image carrier . At least an image carrier, a charging unit for charging the image carrier, an image exposure unit for forming an electrostatic latent image on the charged image carrier, and a toner charged to the electrostatic latent image are supplied and developed. A developing unit that forms an image; a transfer unit that transfers the toner image on the image carrier that has been visualized onto a transfer material; a cleaning unit that removes toner remaining on the image carrier after the transfer; and a control Means and detecting means for detecting the humidity of the atmosphere around the image carrier,
The developing means has a closed space sealed by a developing unit storage container, an opening surface facing the image carrier and a toner scattering prevention member,
The cleaning means includes a closed space sealed 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, respectively. ,
When the image carrier is waiting for image formation, the control unit causes the image carrier to form the closed space of the cleaning unit according to a change in humidity per unit time detected by the detection unit. And a width corresponding to the wider of the width of the gap of the opening surface facing the body and the width of the gap of the opening surface facing the image carrier constituting the closed space of the developing unit. An image forming apparatus that controls the image forming apparatus. 4. The image carrier is rotated when the humidity change per hour in the atmosphere around the image carrier is 20% or more within 8 hours from the previous image formation. Image forming apparatus. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus.

Images