JP2012003113A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stabilizing an image quality, improving the durability of a blade and an image carrier, and suppressing unnecessary toner consumption.SOLUTION: This image forming apparatus includes: the image carrier; a brush roller coming into contact with the image carrier to form a nip section and cleaning residual toner remaining on the surface of the image carrier; a drive motor for actuating the brush roller; brush roller polishing force determination means for determining the polishing force of the brush roller; and printing area ratio acquisition means for acquiring a printing area ratio of an image of image data to be transferred to a recording medium. This image forming apparatus controls the mount of the toner stuck to a non-image section which is not transferred to the recording medium, based on the detection result of the brush roller polishing force determination means and the printing area ratio acquisition means.

Description

  The present invention relates to an image forming apparatus including a cleaning device for collecting deposits such as residual toner deposited on an image carrier such as a photoconductor and an intermediate transfer member.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile machine, a multi-function machine, or an MFP (multifunction peripheral) having an electrophotographic process, an electrostatic latent image formed on a photosensitive drum is used. The image can be developed by developing the image to form a toner image and transferring it directly to the recording paper, or by transferring the toner image on the photosensitive drum to the intermediate transfer member and then transferring it to the recording paper. Form.

  In such an image forming apparatus, a cleaning device is provided to remove toner adhering to an image carrier such as a photosensitive drum or an intermediate transfer member.

  For the purpose of improving the cleaning performance of this cleaning device, the toner or paper dust can be imaged by adding a lubricant to the toner or providing a lubricant application member to adhere the lubricant onto the image carrier. It is easy to remove from the carrier.

  In addition, as a cleaning technique for the image carrier, a method using a blade, a method using a brush roller, and a combination of a blade and a brush, and a brush roller that rotates before the toner on the image carrier is scraped off by the blade, are used. And a method of reducing the adhesion of toner.

  It is well known that a cleaning effect (abrasive force) is improved by bringing a blade or a brush into pressure contact with an image carrier and interposing a toner.

  In Patent Document 1, the driving current for driving the cleaning brush is detected, the toner input amount is controlled based on the driving current value and the information related to the occurrence of filming, and the pressure contact force of the cleaning brush to the image carrier is determined. The device is designed to improve the cleaning by controlling.

JP 2004-86107 A

  In a cleaning device using a brush roller, since the brush roller rotates in contact with the image carrier for a long period of time, “hair fall” occurs in which the brush fibers fall down along the rotation direction. The polishing power may be reduced, and the polishing power may vary due to variations in parts such as the thickness and length of the brush fibers and the density per unit area (number of flocks).

  In Japanese Patent Laid-Open No. 2004-228867, when the fall of the brush roller proceeds, it is erroneously determined that the decrease in the drive motor starting current value due to the fall of the brush roller is due to filming, and the toner is supplied to polish the image carrier. In order to prevent this, there is a region where the toner input to the cleaning unit becomes zero. If a document with a low print area ratio is printed at this time, the amount of residual toner supplied to the image carrier is insufficient, and the polishing power is insufficient, and excess lubricant or filming material on the image carrier is removed. Image defects due to wear of the cut surface of the blade cannot easily be removed and are liable to occur. Further, since a mechanism for changing the pressure contact force and the rotation direction of the brush roller is necessary to make up for the shortage of the polishing force, there remains a problem that the apparatus is enlarged and the cost is increased.

  When the amount of toner supplied to the nip portion between the brush roller and the image carrier is unnecessarily large when the brush roller has a strong polishing force, the polishing force (hereinafter referred to as the polishing force combined with the brush roller polishing force and the toner polishing force). , The overall polishing force) becomes too strong, and the lubricant on the image carrier is scraped unnecessarily or the surface roughness is promoted, so that defective cleaning tends to occur, and the durability of the image carrier is also shortened.

  The toner amount supplied to the nip portion between the brush roller and the image carrier is the sum of the residual toner amount according to the print area ratio of the image data for image formation and the toner amount attached to the non-image portion.

  When the polishing force of the brush roller is weak, if the amount of toner supplied to the nip between the brush roller and the image carrier is insufficient, the polishing force is insufficient and excess lubricant and filming material on the image carrier are removed. Failure to do so results in poor cleaning, image blurring, density unevenness, etc. due to blade cut surface wear.

  The present invention has been made to solve the above-described problems, and provides an image forming apparatus capable of stabilizing image quality and suppressing unnecessary toner consumption as well as improving durability of a blade and an image carrier. The purpose is to provide.

  The above object is achieved by the invention described below.

1. An image carrier and a brush roller that contacts the image carrier to form a nip portion and cleans residual toner remaining on the surface of the image carrier;
A driving motor for driving the brush roller; a brush roller polishing force determining means for determining the polishing force of the brush roller; and a printing area ratio acquiring means for acquiring a printing area ratio of an image of image data transferred to a recording medium. Have
An image forming apparatus that controls the amount of toner that adheres to a non-image portion that is not transferred to a recording medium based on detection results of the brush roller polishing force determination unit and the print area ratio acquisition unit.

  2. 2. The image forming apparatus according to claim 1, wherein the brush roller polishing force determination unit determines the polishing force based on a drive current value of the drive motor.

3. Drive torque detection means for detecting the drive torque of the drive motor;
2. The image forming apparatus according to 1, wherein the brush roller polishing force determination unit determines the polishing force based on the driving torque detected by the driving torque detection unit.

  The present invention has been made in order to solve the above-described problems, and it is possible to stabilize the image quality, and to suppress unnecessary toner consumption as well as high durability of the blade and the image carrier.

1 is an overall configuration diagram of an image forming apparatus. It is sectional drawing of the cleaning apparatus which used the blade and brush roller by general weight load together. It is a graph showing transition of polishing power and time of a brush roller. It is a conceptual diagram showing the relationship between the polishing force of the brush roller, the drive current value A of the drive motor that drives the brush roller, and the drive torque N · m of the brush roller. It is a flowchart of control which acquires a printing area rate. 6 is a flowchart for setting a toner amount to be adhered to a non-image portion. This is the specification of the brush roller used in the confirmation test. It is an example of the detection method of the driving torque of a brush roller. 6 is a graph in which the amount of toner attached to a non-image portion is changed according to the polishing force and the print area ratio.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the present embodiment, an electrophotographic image forming apparatus incorporating a cleaning device will be described as an example.
(Mechanical configuration of image forming apparatus)
FIG. 1 is an overall configuration diagram of an image forming apparatus GH including an image reading unit SC and an automatic document feeder DF.

  The illustrated image forming apparatus GH includes an image forming unit GK including an image carrier 1, a charging unit 2, an image exposing unit 3, a developing unit 4, a transfer unit 5, a charge removing unit 6, a separation claw 7, a cleaning device 100, and the like. The fixing unit 9 and a paper transport system YH are included.

  The paper transport system YH includes a first transport unit including a paper feed cassette 10, a first paper feed unit 11, a second paper feed unit 12, a transport unit 13, a paper discharge unit 14, and a manual paper feed tray 15, and a recording paper. It comprises a circulation refeeding section JK that circulates and refeeds P.

  The paper feed cassette 10 and the first paper feed means 11 are formed by a plurality of paper feed means (three stages in the figure), and accommodate and feed a plurality of types of recording paper P. The recording paper size is input by manual setting by the operation unit 21 or automatic recording paper size setting by the recording paper size detecting means.

  The recording paper P that has passed through the conveying means 13 and has been fixed by the fixing unit 9 is conveyed by the conveying path switching means 16 in the straight discharge path conveying path r1, the reverse discharging path conveying path r2, and the double-sided circulation path conveying. It is selected and transported to one of the paths r3.

  The recording paper P passing through the transport path r1 is discharged with the image forming surface facing up (face up). The recording paper P passing through the transport path r2 is transported to the transport paths r3 and r4 of the double-sided circulation path, then reversely transported, passes through the transport path r2, and discharged with the image forming surface down (face down). Is done.

  When forming an image on both sides of the recording paper P, the recording paper P image-formed by the image forming unit GK is branched by the transport path switching means 16 before the paper discharge means 14, and the recording paper P is circulated and re-feeded. , The recording paper P is reversed by the reverse conveying roller 17 in the middle of the circulation refeeding path, and then fed again to the image forming unit GK via the second paper feeding unit 12.

  The document d placed on the document table of the automatic document feeder DF is transported by the document feeding means, and one or both images of the document d are read by the optical system of the image reading unit SC. Is read. The analog signal photoelectrically converted by the image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing and the like in the image processing unit 20 and then sent to the image exposure unit 3.

  In the image forming unit GK, processes such as charging, exposure, development, transfer, separation, and cleaning are performed.

A toner image is transferred to the recording paper P fed from the paper feed cassette 10 and the manual paper feed tray 15 by the transfer means 5. The recording paper P carrying the image is fixed by the fixing unit 9 and discharged from the paper discharge means 14.
(Cleaning device)
FIG. 2 is a cross-sectional view of a cleaning device 100 that uses both a cleaning by a blade with a general weight load and a brush roller.

  In the cleaning device 100, a cleaning unit CL and a toner recovery unit TC are integrally connected in a cleaning case 110 in the vertical direction.

  In the toner recovery part TC, the cleaning blade 111 (hereinafter referred to as a blade) is used to clean the image carrier 1 with the polishing force of the brush roller 121 that is in contact with the circumferential surface of the image carrier 1 and rotates in the same direction by a drive motor (not shown). Before scraping off the residual toner, the adhesive force of the residual toner to the image carrier 1 is weakened and a part of the residual toner is removed.

  Also, it functions to collect toner that has fallen from the cleaning portion CL.

  The brush roller 121 can be applied with a bias voltage by mixing a conductive material such as carbon with a resin material such as acrylic and in contact with the grounded image carrier 1.

  The toner adhering to the brush roller 121 rotating in the direction of the arrow is scraped off by the scraper 124, and the dropped toner is moved to the developing unit 4 by the operation of the spiral toner conveying screw 123 provided at the bottom of the toner collecting unit TC. Recycled or transported to a waste toner box (not shown) and collected.

  In addition, a toner recovery sheet 125 is provided at the lower end opening of the cleaning case 110 to prevent the recovery toner from spilling outside.

  In the cleaning unit CL, the blade 111 is made of an elastic material, contacts the surface of the image carrier 1, and removes transfer residual toner remaining on the image carrier 1 after transfer from the image carrier 1. The tip of the blade 111 is pressed against the rotation direction of the image carrier 1 in the counter direction.

  The blade 111 is formed of polyurethane rubber or silicone rubber having moderate elasticity.

  The blade 111 is held by a cleaning blade support member 112 (hereinafter referred to as a blade support member). The blade 111 is pressed with a constant load by a weight member 113 fixedly attached to the blade support member 112 and is brought into pressure contact with the image carrier 1.

  The loading method may be a method using not only a weight but also an elastic material.

The untransferred toner peeled off by the blade 111 falls to the lower toner collecting portion TC.
(Brush roller polishing power)
Since the brush roller 121 is rotated in a state of being in contact with the image carrier for a long period of time, the “hair fall” that causes the brush fibers to fall along the rotation direction occurs and the polishing power decreases. Depending on variations in parts such as the thickness and length of the brush fibers and the density per unit area (number of flocks), the polishing force may also vary.

  FIG. 3 is a graph showing the transition of polishing force and time of the brush roller. The horizontal axis represents the rotational drive time of the brush roller, and the vertical axis represents the polishing force.

  The brush roller represented by the solid line has a large polishing force at the start of use, but thereafter, the polishing force rapidly decreases. The brush roller indicated by a broken line has a lower polishing force than the solid brush roller at the start of use, but the decrease in the polishing force is moderate. Further, the brush roller represented by a two-dot chain line has a low polishing power from the start of use, and the polishing power further decreases with the passage of the rotation drive time.

  As described above, although the degree of decrease in the polishing force due to the rotational drive time varies depending on the parts variation of the brush roller, it decreases with the rotational drive time.

  FIG. 4A is a conceptual diagram showing the polishing force of the brush roller and the drive current value A of the drive motor that drives the brush roller.

  When the polishing force of the brush roller is large, the drive current value A of the drive motor is large, and when the polishing force is reduced, the drive current value A of the drive motor is also small.

  As described above, the brush roller polishing force detecting means can function by detecting the driving current value A of the driving motor based on the relationship between the polishing force of the brush roller and the driving current value A of the driving motor.

  FIG. 4B is a conceptual diagram showing the polishing force of the brush roller and the driving torque N · m of the brush roller.

  As in FIG. 4A, when the polishing force of the brush roller is large, the driving torque N · m is large, and when the polishing force is reduced, the driving torque N · m is also small.

  The drive torque detecting means for detecting the drive torque N · m of the brush roller functions as a piezoelectric element having a strain gauge described later.

  When the amount of toner supplied to the nip portion between the brush roller and the image carrier 1 is unnecessarily large when the brush roller has a strong polishing force, the total polishing force is a combination of the brush roller polishing force and the toner polishing force. Becomes too strong, and the lubricant on the image carrier is scraped unnecessarily or the surface roughness is promoted, so that cleaning failure is liable to occur, and the durability of the image carrier is also shortened.

  Further, when the brush roller has a weak polishing force, if the amount of toner supplied to the nip portion between the brush roller and the image carrier 1 is insufficient, the polishing force is insufficient and excessive lubricant or filming on the image carrier is performed. Since the substance cannot be removed, cleaning failure, image blur, density unevenness, and the like due to cut surface wear of the blade 111 are likely to occur.

  Here, cleaning is performed by controlling the amount of toner supplied to the nip portion between the brush roller and the image carrier 1 based on information of detection results by the brush roller polishing force determination means and the print area ratio acquisition means according to the present invention. An explanation to avoid defects will be given.

  The amount of toner supplied to the nip portion between the brush roller and the image carrier 1 is the amount of toner remaining after transfer according to the print area ratio of the image portion of the region transferred to the recording paper P and the transfer region to the recording paper P. This is the total amount of toner that adheres to the outer non-image area.

  The amount of toner attached to the non-image area outside the transfer area is determined by the band-shaped area formed by the entire area in the main scanning direction of the image exposure unit 3 of the image carrier 1 and the distance in the rotation direction of the image carrier 1. Not only the method but also a method of determining the volume by adding the thickness of the surface of the image carrier 1 may be used.

  The conditions for attaching the toner to the image carrier 1 are the same as the conditions for forming an image on the recording paper, but a control method based on the charging conditions, exposure intensity, DC component of the developing bias, etc. may be used.

  When the polishing force of the brush roller decreases, the total polishing force can be maintained by increasing the amount of toner supplied to the nip portion between the brush roller and the image carrier 1.

  FIG. 5 is a flowchart for acquiring the print area ratio by the print area ratio acquisition means.

  The print area rate acquisition means is performed by a CPU (not shown) of the image forming apparatus GH, and a control unit configured by a circuit having ROM and RAM as main parts.

  In step 100, the ratio of the print area to the print area is obtained as the print area ratio from the number of print pixels of the image data sent to the image exposure unit 3.

  In step 110, an integrated value B of the printing area ratio on the recording paper P is calculated.

  In step 120, an average print area ratio C is calculated. For example, the average print area ratio for every 50 sheets or the average print area ratio for the past 30 seconds every 15 seconds may be obtained.

  FIG. 6 is a flowchart for setting the toner amount to be adhered to the non-image portion.

  In step 200, the average print area ratio C calculated in FIG. 5 is acquired.

  In step 210, the driving current value A of the driving motor or the driving torque N · m of the brush roller is detected.

  In step 220, the toner amount to be adhered to the non-image portion is set according to the drive current value A of the drive motor or the brush roller drive torque N · m together with the average print area ratio C.

  The brush roller polishing force determining means determines the brush roller polishing force from the driving current value A of the brush roller driving motor or the brush roller driving torque N · m.

  The actual amount of toner, average print area ratio C, drive motor drive current value A, and brush roller drive torque N · m will be described in the embodiments.

  Up to here, an image forming apparatus of a type in which a lubricant for the purpose of reducing the frictional resistance between the surface of the image carrier and the cleaning member and improving the releasability of the toner on the surface of the image carrier is added to the toner However, it may be an image forming apparatus having a lubricant application device that scrapes off a solid / powder lubricant with a brush or the like and deposits it on an image carrier.

  In an image forming apparatus having a lubricant application device, when printing image data with a small print area ratio, the amount of toner supplied to the image carrier is small, and it is possible to prevent a shortage of toner from scraping the lubricant. When printing image data having a large area ratio, it is possible to prevent the lubricant on the image carrier from being scraped off more than necessary due to the polishing action of a large amount of untransferred toner.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

  In an environment of temperature 25 ° C. and humidity 50%, a confirmation test of 500,000 sheets was performed using A4 size recording paper while changing the printing area ratio from 0% to 30%.

  The specification of the brush part of the brush roller used in the confirmation test is shown in FIG.

  The brush roller is a conductive fur brush roller in which conductive fibers are planted on the outer periphery of a conductive roller (core metal).

  FIG. 8 shows an example of a method for detecting the driving torque N · m of the brush roller.

  Using a piezoelectric element (load cell LTS-50GA manufactured by Kyowa Denki Co., Ltd.) with a built-in strain gauge, the output value received by the piezoelectric element is converted by the output device while a sheet metal of 10 mm x 12 mm is pressed against the brush roller. The brush roller driving torque is N · m.

  FIG. 9 is a graph in which the amount of toner attached to the non-image area is changed according to the polishing force and the printing area ratio when the recording paper is A4 size.

  Non-volatile memory (RAM) not shown in the data table of the drive current A, brush roller drive torque N · m, average print area ratio (%), and toner amount (mm) attached to the non-image area shown in this graph The amount of toner adhering to the non-image portion was controlled with reference to this table.

  The print area ratio was calculated from image data of the past 30 seconds every 15 seconds.

  The solid line shows the case where the drive current A of the drive motor is 0.7 A or more or the brush roller drive torque N · m is 0.3 N · m or more, and the alternate long and short dash line shows the drive current of 0.67 A or more and less than 0.7 A or brush The roller drive torque N · m is 0.27 N · m or more and less than 0.3 N · m. The broken line indicates that the drive current is less than 0.67 A or the brush roller drive torque N · m is less than 0.27 N · m. In this case, the toner amount is attached to the non-image area.

  When the drive current value A or the brush roller driving torque N · m when driving the drive motor is large (the polishing force of the brush roller is large), the amount of toner attached to the non-image portion is controlled to be small. When the drive current value A or the brush roller drive torque N · m is small (the brush roller's polishing power is small), the amount of toner attached to the non-image area is controlled to be large.

  For example, when the printing area ratio is 20%, if the motor drive current value A represented by a solid line is 0.7 A or more, the toner amount to be adhered to the non-image portion is set to a width of 0 mm (no toner is adhered). If the motor drive current value A expressed by the formula is 0.67 A or more and less than 0.7 A, the amount of toner to be attached is 6 mm wide, and if the motor drive current value A represented by the broken line is less than 0.67 A, non-image The amount of toner attached to the part is 12 mm wide.

  As a result of the confirmation test for 500,000 sheets, no cleaning failure or other problems occurred.

  Also, when the drive current of the drive motor is 0.7 A or more or the brush roller drive torque is 0.3 N · m or more, or when the drive current is 0.67 A or more and less than 0.7 A or the brush roller drive torque is 0.27 N · m. In the case of m or more and less than 0.3 N · m, the polishing power is larger than in the case where the drive current is less than 0.67 A or the brush roller drive torque is less than 0.27 N · m. If it exceeds the limit, the amount of toner deposited on the non-image area is reduced, so that unnecessary toner consumption can be suppressed.

  At the same time, by avoiding excessive polishing force due to unnecessary toner, it is possible to suppress wear of the image carrier, brush roller, blade, and the like.

  In this way, the printing area of the image portion of the area transferred to the recording paper P based on the polishing force of the brush roller determined from the driving current value A of the brush roller driving motor or the driving torque N · m of the brush roller. By controlling the amount of toner that adheres to the non-image area outside the transfer area to the recording paper P according to the rate, the image carrier can be properly cleaned, the image quality is stabilized, and the blade and the image carrier are made highly durable. At the same time, unnecessary toner consumption can be suppressed.

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging means 3 Image exposure part 4 Developing part 5 Transfer means 6 Electric discharge means 7 Separation claw 9 Fixing part 10 Paper feed cassette 11 First paper feed means 12 Second paper feed means 13 Conveyance means 14 Paper discharge means 15 Feed tray 20 Image processing unit 21 Operation unit 100 Cleaning device 110 Cleaning case 111 Cleaning blade 112 Cleaning blade support member 113 Weight member 121 Brush roller 123 Toner transport screw 124 Scraper 125 Toner recovery sheet A Drive current value B Integrated value C Average printing Area ratio CCD image sensor CL Cleaning unit d Document DF Automatic document feeding unit GH Image forming device GK Image forming unit Nm Driving torque P Recording paper SC Image reading unit TC Toner collection unit YH Paper transport system

Claims (3)

An image carrier and a brush roller that contacts the image carrier to form a nip portion and cleans residual toner remaining on the surface of the image carrier;
A driving motor for driving the brush roller; a brush roller polishing force determining means for determining the polishing force of the brush roller; and a printing area ratio acquiring means for acquiring a printing area ratio of an image of image data transferred to a recording medium. Have
An image forming apparatus that controls the amount of toner that adheres to a non-image portion that is not transferred to a recording medium based on detection results of the brush roller polishing force determination unit and the print area ratio acquisition unit.   The image forming apparatus according to claim 1, wherein the brush roller polishing force determination unit determines the polishing force based on a drive current value of the drive motor. Drive torque detection means for detecting the drive torque of the drive motor;
The image forming apparatus according to claim 1, wherein the brush roller polishing force determination unit determines the polishing force based on the driving torque detected by the driving torque detection unit.

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