JP2005031431A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cleaning defects even in large-quantity continuous printing. <P>SOLUTION: In a cleaning device 260 wherein an edge of a cleaning blade abuts against the peripheral surface of a photoreceptor drum 211, a control part 250 controls a motor 261 which drives the photoreceptor drum, and reverses the photoreceptor drum in units of, for example, a previously set number of print sheets while the photoreceptor rotates forward to continuously print a plurality of output media, thereby putting the photoreceptor drum back into the forward rotation again. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus. In particular, the present invention is intended to satisfactorily remove paper dust adhering to a photosensitive member (for example, a photosensitive drum, a photosensitive belt, etc.) to improve printing quality.
[0002]
[Prior art]
The printing process in the image forming apparatus will be briefly described as follows. The image forming apparatus has a cylindrical photosensitive drum having a photosensitive member formed on the outer periphery. The photosensitive member changes the potential of the region irradiated with light, and can capture the change in the potential as an electrostatic image. An exposure apparatus that irradiates light outputs a laser beam whose light intensity is changed in accordance with image information, thereby forming an electrostatic image, that is, an image on the photosensitive drum. The electrostatic image formed on the photosensitive drum is visualized (developed) by supplying toner (developer) from the developing device, and converted into a toner image. The toner image on the photosensitive drum is transferred to a transfer belt. Next, the toner image on the transfer belt is transferred to a transfer material, that is, a sheet fed by the sheet feeding / conveying unit. The image transferred to the paper is fixed on the paper by passing through the fixing device.
[0003]
[Patent Document 1]
JP-A-8-123284 [0004]
[Patent Document 2]
JP-A-8-262949 [0005]
[Problems to be solved by the invention]
A cleaning device is disposed around the photosensitive drum, and the cleaning device removes unnecessary toner and paper dust adhering to the peripheral surface of the photosensitive drum.
[0006]
On the other hand, in recent years, the speed of image forming apparatuses has been increased, and a large number of continuous printing has been required for such image forming apparatuses. For example, a high-speed image forming apparatus capable of printing on 50 or more sheets per minute requires, for example, continuous printing of 5000 or more sheets. However, when continuous large-scale printing is performed at such a high speed, the influence of paper dust on the photosensitive drum collecting surface becomes large. In particular, when paper of poor quality is used, a large amount of paper dust is deposited on the edge of the cleaning blade of the cleaning device. As a result, paper dust passes through the blade or is sandwiched between the blades, resulting in poor cleaning. When the cleaning failure occurs, the print quality on the paper also deteriorates, and a black streak pattern appears on the paper.
[0007]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable image forming apparatus which reduces the occurrence of defective cleaning even during a large amount of continuous printing.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention controls a photosensitive pair, a cleaning device in which an edge of a cleaning blade is brought into contact with a peripheral surface of the photosensitive pair, and a motor for driving the photosensitive pair. While the photosensitive pair is rotating forward and continuously printing on a plurality of output media, the photosensitive pair is operated in reverse in units of the preset number of prints of the output medium, drum rotation speed, or continuous printing time. And a photosensitive pair control unit for returning to the normal rotation state again.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0010]
FIG. 1 is a schematic diagram showing an example of an image forming apparatus to which an embodiment of the present invention is applied. The image forming apparatus 1 includes an image reading unit 100, an image forming unit 200, a paper supply unit 300, an automatic duplex unit (ADU) 400, and an automatic document feeder (ADF) 500.
[0011]
The image reading unit 100 captures image information of a copy (reading) object as light contrast, and outputs a signal corresponding to the image information, that is, image data. The image forming unit 200 forms a copy image, that is, an output image, based on the image data generated by the image reading unit 100. The paper supply unit 300 feeds an output medium (paper) to the image forming unit 20. The automatic duplexing unit (ADU) 400 is a part that pulls in a sheet that has been printed on one side, reverses the front and back so that printing is performed on the other side, and sends the sheet back to the transfer unit. An automatic document feeder (ADF) 500 is a part that sequentially feeds sheets to the image reading unit 100.
[0012]
Image reading unit The image reading unit 100 includes a document table 111 that holds a copy (reading) object (not shown), an illumination device 112 that illuminates the object set on the document table 111, and an object illuminated by the illumination device 112. The first to third mirrors 113, 114, and 115 for sequentially guiding the reflected light, that is, the image light toward the subsequent CCD sensor, and the image light guided by the respective mirrors 113 to 115 have a predetermined imaging magnification. The lens 116 includes a CCD sensor 117 that receives image light given a predetermined imaging magnification by the lens 116 and outputs image data corresponding to the image light.
[0013]
An object to be copied (hereinafter referred to as an original) is set on the original table 111 by the ADF 500 or directly, and the start of copying is instructed from the operation panel 700 (see FIG. 2). Illumination light is emitted and the document O is illuminated. As a result, the reflected light including the image information of the document as light brightness is extracted. Hereinafter, this reflected light is referred to as image light.
[0014]
The image light is guided to the first to third mirrors 113 to 115 and the lens 116, passes through the lens 116, and forms an image on the CCD sensor 117. The image light imaged on the CCD sensor 17 is photoelectrically converted, converted into image data by the image processing unit 150 (see FIG. 2), and stored in the image memory 160 (see FIG. 2).
[0015]
Image Forming Unit The image forming unit 200 includes a photoconductor 221. The main charging device 222 gives a predetermined surface potential to the photoconductor 221. The exposure device 223 irradiates the photoconductor 221 with light having an intensity distribution corresponding to the image data. The photosensitive member 221 is irradiated with light corresponding to image data in a charged state in advance, so that an electrostatic image is generated and held.
[0016]
The black (first) developing device 224 selectively supplies black (Bk) toner to the latent image formed on the photoconductor 221. The color (second) developing device 225 selectively supplies C (cyan), M (magenta), and Y (yellow) toners to the electrostatic latent image formed on the photoreceptor 221 in a predetermined order. The transfer belt (intermediate transfer member) 226 can hold the BK, C, M, and Y toner images formed on the photosensitive member 221 in a stacked state. The transfer device 227 transfers the color toner image superimposed on the transfer belt 226 to a sheet (output medium). The fixing device 228 fixes (fixes) the color toner image transferred to the paper to the paper.
[0017]
The photoconductor 221 has a cylindrical shape (hereinafter referred to as a photoconductor drum). Further, as the output medium, the thickness of the sheet of ^{50g / m 2 ~250g / m 2} , a transparent resin sheet, various media adhesive typified coated sticker sheet, etc. are available.
[0018]
At a position where the photosensitive drum 221 and the transfer belt 226 are in contact with each other, an intermediate transfer device 229 that sequentially transfers the toner images formed on the photosensitive drum 221 to the transfer belt 226 is positioned.
[0019]
In the image forming unit 200 described above, a predetermined constant potential is applied to the surface of the photosensitive drum 221 by the charging device 222 at the timing of starting illumination of the document by the illumination device 112. Next, image light whose intensity has been changed based on the image data is irradiated from the exposure device 223 onto the surface of the photosensitive drum 221. The potential difference on the photosensitive drum 221 is held on the photosensitive drum 221 for a predetermined time as an electrostatic latent image.
[0020]
When the electrostatic latent image held on the photosensitive drum 221 is a latent image corresponding to a black (Bk) image, black toner is supplied from the Bk developing device 224 to the photosensitive drum 221 and development processing is performed. Thereby, the electrostatic latent image is visualized. When the electrostatic latent image held on the photosensitive drum 221 is a latent image corresponding to an image of any color component other than black, the next development process is added. Color toner is supplied to the photosensitive drum 221 from the developing unit of the color developing device 225, and development processing is performed. Thereby, the electrostatic latent image to which the color component is added is visualized.
[0021]
The color developing device 225 includes three developing units (25C, 25M, and 25Y) each independently containing toner capable of visualizing three color components separated based on a known subtractive color mixture, and a rotating shaft 25A. It is a revolver system that is formed to be rotatable around.
[0022]
The (single color) toner image formed on the photosensitive drum 221 is conveyed to an intermediate transfer position in contact with the transfer belt 226 by the rotation of the photosensitive drum 221, and is transferred to the transfer belt 226. This transfer is realized by applying a predetermined transfer bias voltage to the intermediate transfer device 229 inside the transfer belt 226.
[0023]
When the requested image output (hard copy) is in color, the C toner image, M toner image, and Y toner image formed by the color developing device 225 are further added to the Bk toner image formed by the black developing device 224. Are added in order and transferred.
[0024]
When the four color toner images are superimposed on the transfer belt 226, all toner images, that is, color toner images, are transferred from the transfer belt 226 to a sheet (output medium) at the position of the transfer device 227. At this time, an output transfer bias voltage is supplied to the transfer device 227.
[0025]
The paper is guided to the aligning roller 38 in advance at a predetermined timing, and is sent to the position of the transfer device 227 in accordance with the transfer processing timing.
[0026]
Note that the transfer device 227 can change contact / non-contact with the transfer belt 226 by an interval holding mechanism, and at the time of non-transfer, the toner image stacked on the transfer belt 226 is not attracted. It is positioned at a retracted position where a predetermined interval is given between the transfer belt 226 and the transfer belt 226.
[0027]
A toner image transferred to an output medium such as paper or an OHP sheet, that is, a color toner image, is guided to the fixing device 228 as the output medium is conveyed. The toner image guided to the fixing device 228 is heated by the heat from the fixing device 228 together with the output medium, melted, and fixed (fixed) to the output medium by providing a predetermined pressure.
[0028]
Here, a cleaning device 260 is provided for cleaning the rotating circumferential surface of the photoconductor (photosensitive drum 221) that has passed through the position of the transfer device 229. The cleaning device 260 includes a cleaning blade 26a, which will be described later. The photosensitive drum 221 is rotationally controlled by a drum motor 261 (see FIG. 2). The drum motor 261 and its controller will be described in detail later.
[0029]
Paper Supply Unit The paper supply unit 300 is provided with first and second slots 31a and 31b in which cassettes containing paper of any size (output medium) are mounted. One slot side will be described as a representative.
[0030]
A pick-up roller 32a is provided in the slot 31a, and the paper stored in the cassette can be fed out toward the paper transport path. The paper fed out by the pickup roller 32a is sandwiched between the paper feed roller 33a and the separation roller 34a, taken out one by one, and sent out. A sheet fed from an arbitrary cassette is fed toward the image forming unit 200 via a sheet conveying unit.
[0031]
The paper transport unit is provided with a first intermediate transport roller 36 and a second intermediate transport roller 37 that transport the paper toward the image forming unit 200. Further, an aligning roller 38 and the like for temporarily stopping the sheet upstream of the transfer device 227 and aligning the position of the color toner image superimposed on the intermediate transfer body 226 with the position of the sheet are provided.
[0032]
The sheet conveyed to the aligning roller 38 may collide with the aligning roller 38 whose rotation has been stopped, and may occur when the sheet is fed out from the sheet holding unit or conveyed on the sheet conveying path. The non-parallel component, that is, the inclination with respect to a certain conveyance direction is removed, and the operation is temporarily stopped.
[0033]
The manual feed unit paper transport unit is also provided with a connection unit that can guide the paper or OHP sheet set in the manual feed unit 600 toward the aligning roller 38.
[0034]
Automatic duplex unit 400
A copy receiving unit is prepared downstream of the fixing device 228. The output medium to which the color toner image is fixed by the fixing device 228 is discharged to a copy receiving unit that is a space between the image reading unit 100 and the image forming unit 200. Here, if necessary, an automatic duplex unit 400 (also referred to as a reversing unit) that reverses the front and back of a sheet (output medium) having a color toner image fixed on one side thereof is provided.
[0035]
A sheet for which duplex copying (reversing the front and back sides) is instructed is sent out to the automatic duplex unit 400 by the discharge / reverse roller 441 and guided to the automatic duplex unit 400 through a switch 442 for guiding the sheet.
[0036]
The automatic duplex unit 400 is provided with transport rollers 443,..., 443, and the like that transport the paper supplied to the automatic duplex unit 400 toward the aligning roller 38.
[0037]
FIG. 2 is an example of a control system of the color image forming apparatus described with reference to FIG. 1, and is a schematic diagram of a portion including a photosensitive member control unit (in this case, a photosensitive drum control unit).
[0038]
A document is set on the document table 111. When the operation panel 700 instructs to start copying, the image reading unit 100 reads a document image and obtains image data. The image data is processed by the image processing unit 150 in accordance with a predetermined image processing routine and stored in the image memory 160.
[0039]
Under the overall management of the main control unit 800, the paper supply unit 300 and the image forming unit 200 execute paper supply and printing in synchronization with the image reading unit 100. The main control unit 800 also manages an image formation control unit 250 for controlling each unit in the image forming unit 200.
[0040]
The image formation control unit 250 includes a CPU 2501, a RAM 2502 for temporarily storing data, a movable mechanism control unit 2503 for driving a movable mechanism such as a plunger, a motor control unit 2504 for controlling a motor, and a voltage control unit 2505 for controlling various bias voltages. Have The image forming unit 200 operates in accordance with control signals, bias voltages, timing pulses, and the like from the control blocks of the image forming control unit 250, and performs printing on paper.
[0041]
The movable mechanism control unit 2503 controls the position of the roller of the transfer device 227, for example. The motor control unit 2504 controls the rotation of the drum motor 261, the motor of the color developing device 225, and the like. The voltage control unit 2505 controls the bias voltage of the developing device 224 and the color developing device 225, the transfer voltage of the transfer devices 229 and 228, and the like.
[0042]
The apparatus of the present invention is particularly characterized by the apparatus and method for controlling the rotation of the photosensitive drum 221, and will be described below.
[0043]
FIG. 3 shows an operation flow when the image forming apparatus starts printing, for example, when the number of prints is designated. In particular, the operation of the photosensitive drum control unit is shown. When the number of prints is specified and the start button on the operation panel is pressed, the printing process starts. The set number-of-prints information is taken into the RAM 2502 (step SA1). Printing processing is started (exposure / development processing / paper feeding / transfer / drum rotation / transfer belt drive / fixing processing, etc.) (step SA2). Each time printing on one sheet is completed, the number of printed sheets is counted (step SA3). If the number of printed sheets becomes the same as the set number (step SA4), the process ends. If the number is different, the process proceeds to step SA5 to determine whether it is the drum reverse rotation timing (step SA5). When it is determined that it is the drum reverse rotation timing, reverse rotation control of the drum motor is performed (step SA6). Even in the reverse rotation control, the photosensitive drum is slightly rotated, for example, about 1 mm to 30 mm. If it is not the reverse rotation time, the process returns to step SA2. After the reverse rotation control of the drum motor, a standby state for rotating the drum motor in the normal rotation direction is entered, and the process proceeds to step SA2.
[0044]
That is, according to the present apparatus, the operation in which the photosensitive drum reverses in the middle of the print job and returns to the original print job is repeated. This reverse operation is extremely effective in preventing paper dust from being deposited on the edge of the cleaning blade 26a of the leaning device 260. It is extremely effective in reducing printing defects and improving the reliability that have occurred conventionally.
[0045]
4, 5, and 6 show various examples of the drum reverse rotation timing determination means in step SA5. The example of FIG. 4 is an example in which it is determined whether or not the number of printed sheets has reached 1000, and when it is reached, the reverse rotation time control counter (counting the number of printed sheets) is cleared and the process proceeds to step SA6. The example of FIG. 5 is an example in which the photosensitive drum is reversely controlled when the continuous printing time reaches a predetermined time. When the continuous printing time reaches a predetermined time, the clock for setting the reverse rotation time is reset, and the process proceeds to Step SA6. The example of FIG. 8 is an example in which the photosensitive drum is reversely controlled when the rotational speed of the photosensitive drum reaches a predetermined rotational speed. When the rotation number of the photosensitive drum reaches a predetermined number, the drum rotation number counter is cleared and the process proceeds to step SA6.
[0046]
As described above, parameters for setting the reverse rotation timing (number of printed sheets, continuous printing time, drum rotation speed, etc.) can be set or changed in advance by a service person.
[0047]
In the example of FIG. 4 described above, the information on the number of printed sheets set by the user is read, and it is determined in step SA5 whether the number of printed sheets has exceeded a predetermined number. However, the present invention is not limited to this example, and it may be determined at an early stage whether or not the number of sheets to be printed exceeds a predetermined number. In the case of a printing process of a predetermined number or less, the printing process may be executed by a simple routine.
[0048]
As shown in FIG. 7, step SA11 is provided between steps SA1 and SA2. In step SA11, it is determined from the number of printed sheets information whether the number of sheets to be printed exceeds a predetermined number. If it is less than or equal to the predetermined number, step SA22 (the same processing content as step SA2) and the routine proceeds to steps SA3 and SA4. If it exceeds the predetermined number, the process proceeds to steps SA2 and SA5.
[0049]
In the above description, as shown in FIGS. 4, 5, and 6, the description has been made in units of 1000 sheets, a predetermined time unit, and a predetermined rotation speed unit. However, the table parameters may be arbitrarily selected in units of 1000 sheets, 1500 sheets, and 2000 sheets according to the quality of the sheet. The same applies to the predetermined time unit, and it may be prepared as time T1, T2, T3,... So that the parameters of the table can be arbitrarily selected. Further, the same applies to the number of revolutions, and the number of revolutions N1, N2, N3,... May be prepared so that the table parameters can be arbitrarily selected.
[0050]
FIG. 8A shows the result of an experiment conducted with the apparatus of the present invention. The paper used was of poor quality.
[0051]
Repeated the process of printing 1000 sheets continuously, rotating the photosensitive drum reverse, printing 1000 sheets again, and rotating the photosensitive drum again, and performed 13 times, but there was no problem and there was no effect of paper dust It was. In other words, the printing state was good and unchanged from the beginning. However, when continuous printing was performed without the reverse operation of the photosensitive drum, printing failure occurred on about 2500 sheets.
[0052]
In the above description, parameters (such as the number of continuous prints, the continuous printing time, or the number of continuous drum rotations) for obtaining the timing for reversely controlling the photosensitive drum are described as being automatically set. However, the present invention is not limited to such a method. Of course, the user may determine the quality of the paper used for printing and arbitrarily set the above parameters. It is. Furthermore, it goes without saying that both the automatic setting of the parameters and the manual setting may be used separately.
[0053]
As described above, the present invention can avoid the accumulation of paper dust on the blade edge of the cleaning device, particularly when continuously printing on poor quality paper. As a result, the print quality can be maintained well, and the reliability of the apparatus can be improved.
[0054]
Although the present invention has been described as a color copying apparatus, the present invention is not limited to this. Of course, the present invention can be applied to various image forming apparatuses.
[0055]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the occurrence of defective cleaning even during a large amount of continuous printing, and to obtain high reliability of the apparatus.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining an overall outline of an image forming apparatus to which the invention is applied.
FIG. 2 is an explanatory view showing a part relating to the present invention in FIG.
FIG. 3 is an explanatory diagram shown for explaining an example of the operation of the present invention.
FIG. 4 is an explanatory diagram showing another example of a part of FIG. 3;
FIG. 5 is an explanatory diagram showing still another example of part of FIG. 3;
6 is an explanatory view showing still another example of part of FIG. 3; FIG.
FIG. 7 is an explanatory diagram for explaining another operation of the present invention.
FIG. 8 is an explanatory diagram showing experimental results of the apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Image reading part, 200 ... Image forming part, 300 ... Paper supply part, 400 ... Automatic duplex unit, 260 ... Cleaning unit, 221 ... Photoconductor.

Claims (5)

Photosensitive pair,
A cleaning device in which an edge of a cleaning blade is brought into contact with the peripheral surface of the photosensitive pair;
The motor that drives the photosensitive pair is controlled, and while the photosensitive pair is rotating forward and continuously printing on a plurality of output media, any one of the preset number of prints of the output medium, drum rotation speed, and continuous printing time is selected. An image forming apparatus, comprising: a photosensitive pair control unit that reversely operates the photosensitive pair and returns to the normal rotation state again. The image forming apparatus according to claim 1, wherein the photosensitive pair control unit is prepared with a plurality of pieces of information of different numbers of printed sheets, and can select any one number of pieces of information. The image forming apparatus according to claim 1, wherein the photosensitive pair control unit includes a plurality of pieces of information on different continuous printing times, and can select information on any one of the times. The image forming apparatus according to claim 1, wherein the photosensitive pair control unit includes a plurality of pieces of information on different drum rotation speeds, and can select one of the rotation speed information. 2. The image forming apparatus according to claim 1, wherein when the photosensitive pair is rotated in the reverse direction, the photosensitive pair control unit reverses the photosensitive member abutting position of the edge of the cleaning blade so as to reverse within a range of 1 mm to 30 mm. apparatus.

Images