JP2011141352A - Image-forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-forming device which prevents an increase in running cost and outputs a print image of high-quality without reducing productivity. <P>SOLUTION: The image-forming device cleaning the toner adhered on an image carrier has a cleaning blade whose end is in contact with the image carrier to remove the toner adhered on the image carrier, a replenishing member which is located on the upstream side of the cleaning blade and replenishes the image carrier with the toner removed by the cleaning blade, a sensor which detects the amount of toner carried to a slide-contact part at which the cleaning blade is in slide contact with the image carrier, and a control part which starts supplying the toner when the sensor detects that the toner is insufficient in quantity, and stops supplying the toner when the sensor detects that the toner is sufficient in quantity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to cleaning of an image carrier.

  There is known an image forming apparatus provided with a cleaning unit having a cleaning blade for scraping off residual toner remaining on an image carrier.

  Since such a cleaning unit slides the cleaning blade against the relatively moving image carrier to scrape off residual toner, the amount of toner adhering to the image carrier is reduced, and the image carrier and the cleaning blade are in sliding contact. It is known that when the toner is removed from the portion, the friction coefficient increases, and the cleaning blade is caught in the image carrier due to friction, and the cleaning blade is turned up or worn.

  In order to prevent the cleaning blade from turning over or wearing, a sensor is provided to detect the toner held at the tip of the cleaning blade.When the detected value of the sensor falls below a predetermined value, a patch is formed on the photoconductor, There is known a technique in which a cleaning blade is mounted on a portion where the cleaning blade is not transferred and replenished to the tip of the cleaning blade to reduce the friction coefficient (see, for example, Patent Document 1).

  In order to prevent the cleaning blade from turning up and wearing, it detects the space formed by the intermediate transfer belt, the roller slidably contacting the intermediate transfer belt, and the holding plate slidably contacting the roller, and the amount of toner accumulated in the space. A sensor that holds the toner scraped off by the cleaning blade in the space and re-supplies it to the tip of the cleaning blade. When the sensor for detecting the amount of the held toner falls below a predetermined value, the intermediate transfer belt A patch is formed, and the patch is not transferred onto a sheet but is carried up to a cleaning blade installation portion to replenish the space (see, for example, Patent Document 2).

JP 2004-170605 A JP-A-2005-275219

  However, since the cleaning unit described in Patent Document 1 detects toner held at the tip of the cleaning blade, the held toner sometimes drops, adheres to the surface, rises, or rises. The shape of the toner is unstable, the toner amount cannot be detected stably, and even if the toner held at the tip of the cleaning blade is insufficient, it may not be replenished or even if there is toner.

  For this reason, there is a possibility that the image quality may be deteriorated because a constant cleaning cannot be performed, and an unnecessary patch is formed, resulting in a decrease in productivity and an increase in usage amount of toner, that is, an increase in running cost. There was a problem.

  Further, since the cleaning unit described in Patent Document 2 holds and detects the toner scraped off by the cleaning blade in the space, the held toner is offset (accumulated), swelled, or soared. There is a possibility that the shape may become unstable, and when the toner amount cannot be detected stably, there is a possibility that a constant cleaning cannot be performed and the image quality may be deteriorated.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of preventing an increase in running cost and outputting a high-quality print image without reducing productivity.

  The above object is achieved by the following configuration.

1. In an image forming apparatus capable of cleaning toner adhering to an image carrier,
A cleaning blade that removes toner adhering to the image carrier by contacting a tip of the image carrier and replenishing the image carrier with toner that is located upstream of the cleaning blade and removed by the cleaning blade A replenishment member that detects the amount of toner that is carried to the sliding contact portion between the cleaning blade and the image carrier;
And a control unit that starts supplying toner when the sensor detects that the toner amount is insufficient, and stops supplying toner when the sensor detects that the toner amount is sufficient. Forming equipment.

  2. 2. The image forming apparatus according to claim 1, wherein the sensor is a sensor that detects an amount of toner attached to the image carrier passing through a section sandwiched between the cleaning blade and the replenishing member. .

  3. 3. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer belt, and the sensor detects the amount of toner on the intermediate transfer belt.

  4). The control unit forms a patch image on the image carrier when the sensor detects that the toner amount is insufficient and conveys the patch image to the sliding contact portion. When the sensor detects that the toner amount is sufficient, the control unit 4. The image forming apparatus according to any one of 1 to 3, wherein the formation is stopped.

  5. The control unit forms a patch image on the image carrier and conveys it to the slidable contact portion when the output value of the sensor becomes less than a preset threshold value 1 indicating insufficient toner amount, and outputs the sensor. 5. The image forming apparatus according to item 4, wherein the formation of a patch image is stopped when a value becomes equal to or larger than a threshold value 2 indicating a satisfaction of the preset amount of toner larger than the threshold value 1.

  6). The controller increases the replenishment amount of toner to the image carrier when the sensor detects that the toner amount is insufficient, and when the sensor detects that the toner amount is sufficient, the control unit increases the amount of toner to the replenishment member. 4. The image forming apparatus according to any one of items 1 to 3, wherein the replenishment amount of the toner to the carrier is restored.

  7). The image forming apparatus according to any one of 1 to 6, wherein the sensor is a photoelectric detector.

  8). The image forming apparatus according to any one of claims 1 to 7, wherein the replenishing member is a replenishing roller that adheres the toner removed by the cleaning blade to the image carrier.

9. The replenishing member is a replenishing roller for adhering the toner removed by the cleaning blade to the image carrier;
When the sensor detects a shortage of the toner amount, the control unit sets a rotation speed of the replenishment roller from a preset first rotation speed to a preset second rotation that is earlier than the first rotation speed. Any of the above 6 to 8, wherein the amount of toner supplied to the image carrier is increased by increasing the number of toners, and when the sensor detects that the amount of toner is satisfied, the sensor returns to the first rotational speed. The image forming apparatus according to claim 1.

  According to the above invention, it is possible to provide an image forming apparatus capable of preventing an increase in running cost and outputting a high-quality print image without reducing productivity.

FIG. 3 is a cross-sectional view of the image forming apparatus viewed from the side. It is sectional drawing of a cleaning part. It is a flowchart which concerns on the 1st cleaning method of the cleaning part. FIG. 6 is a flowchart according to a first toner supply mode. FIG. 5 is an explanatory diagram showing a relationship between an output of a sensor 94 and image formation when the first cleaning method described in FIGS. 3 and 4 is performed. It is a flowchart which concerns on the 2nd cleaning method of a cleaning part. It is explanatory drawing which shows the relationship between the output of the sensor 94 at the time of performing the 2nd cleaning method demonstrated in FIG. 6, and image formation. It is explanatory drawing which shows the relationship between the output of a sensor 94, and the rotation speed of a replenishment roller. It is explanatory drawing when a cleaning part is applied to a secondary transfer part.

  FIG. 1 is a cross-sectional view of the image forming apparatus as viewed from the side.

  Explain the wording before entering the concrete explanation. The upstream relating to the flow of paper refers to the direction in which the paper flows, and the downstream refers to the direction in which the paper flows. Further, the upstream relating to the intermediate transfer belt refers to the direction in which one point of the circulating intermediate transfer belt moves, and the downstream refers to the direction in which one point of the intermediate transfer belt moves. Note that the rotation means that the intermediate transfer belt suspended on the roller rotates.

  The image forming apparatus A is called a tandem color image forming apparatus, and a document image reading apparatus B that reads image information of a document is installed on the upper part of the image forming apparatus A.

  The document image reading device B scans a document image by the optical system of the document image scanning unit, and outputs image information corresponding to the document image to the image forming apparatus A.

  The image forming apparatus A is formed on the photosensitive member 1 and an exposure unit 2 (2Y, 2M, 2C, 2K) that forms a latent image on the photosensitive member 1 (1Y, 1M, 1C, 1K) based on the image information. A developing unit 3 (3Y, 3M, 3C, 3K) for visualizing the latent image, a charging unit and a cleaning unit (not shown) arranged around the photosensitive drum, and a photosensitive member 1 (1Y, 1M). 1C, 1K), a primary transfer portion 5 (5Y, 5M, 5C, 5K) for transferring the toner image carried on the intermediate transfer belt 4 and a toner image carried on the intermediate transfer belt 4 serving as an image carrier. A secondary transfer unit 6 that transfers the toner image transferred onto the paper P, a fixing unit 7 that fixes the toner image transferred onto the paper P, a paper feeding unit 8 that has a plurality of paper cassettes 81 and supplies paper from the paper cassette, A cleaning unit 9 for removing toner remaining on the intermediate transfer belt 4; The has.

  Note that Y, M, C, and K attached to each part indicate colors. For example, 1Y, 1M, 1C, and 1K are for yellow (Y), magenta (M), cyan (C), and black (K) colors. Refers to each photoconductor. Hereinafter, for example, the photoconductors (1Y, 1M, 1C, 1K) are simply referred to as photoconductors 1 unless they are related to a specific color.

  Each configuration will be described below.

  The image information (analog signal) read by the document image reading apparatus B is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then a digital image information signal. To the exposure unit 2.

  The exposure unit 2 modulates and scans the laser beam based on the digital image information signal to form a latent image on the surface of the photoreceptor 1.

  The developing unit 3 visualizes the latent image on the surface of the photosensitive member 1 with a two-component developer composed of a small particle size toner of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. A toner image is formed.

  The primary transfer unit 5 sequentially transfers (primary transfer) the toner image formed on the surface of the photoreceptor 1 to the intermediate transfer belt 4 by the primary transfer roller 51, and synthesizes a color image on the surface of the intermediate transfer belt 4. .

  The intermediate transfer belt 4 is a semiconductive and endless belt, and is suspended by a drive roller 41, driven rollers 42 and 43, and a backup roller 44 that constitutes a part of the secondary transfer unit 6. Driven by the drive roller 41 in the direction of the arrow.

  The secondary transfer unit 6 faces the backup roller 44, the transfer roller 61 that can nip the intermediate transfer belt 4 and the paper P, the transfer power source 62, and the transfer roller 61 facing the backup roller 44. The toner image carried on the intermediate transfer belt 4 is transferred onto the paper P at the nip portion n.

  The paper feed unit 8 has a plurality of paper cassettes 81 and picks up the paper P stored in the paper cassette 81 by the paper feeder 82. The picked up paper P is transported to the nip portion n by transport rollers 83, 84, 85, 86 and resist rollers 87 that transport the paper.

  The fixing unit 7 includes a heating roller 72 and a pressure roller 73 in which a heater lamp 71 as a heating source is housed. The paper P on which the toner image is transferred is heated and pressed, and the toner image is fixed on the paper P. Is done.

  Then, the fixed paper P is sandwiched between the paper discharge rollers 88 and discharged to the lift paper discharge tray 89.

  The intermediate transfer belt 4 transfers the toner image onto the paper P and then separates the curvature of the paper P, and the toner remaining on the intermediate transfer belt 4 is removed by a cleaning unit 9 described later.

  FIG. 2 is a cross-sectional view of the cleaning unit.

  The cleaning unit 9 has a cleaning blade 91 that removes toner adhering to the intermediate transfer belt 4 with its tip abutting against the intermediate transfer belt 4 that is an image carrier, and a toner positioned on the upstream side of the cleaning blade 91 that transfers toner to the intermediate transfer belt. 4, a replenishing roller 92 that is a replenishing member, a storage plate 93 that temporarily contacts the peripheral surface of the replenishing roller 92 and that has been scraped off by the cleaning blade 91, a cleaning blade 91, and an intermediate transfer And a sensor 94 for detecting the amount of toner carried to the sliding contact portion with the belt 4.

  A region (shaded portion) surrounded by the storage plate 93 and the peripheral surface of the replenishing roller 92 forms a storage portion 95 that temporarily stores the toner scraped off by the cleaning blade 91.

  The cleaning unit 9 can remove the toner remaining on the intermediate transfer belt 4 by the edge portion 911 of the cleaning blade 91 being in sliding contact with the surface of the intermediate transfer belt 4. A very small amount of toner is present in the sliding contact portion 912 like an oil film, and a thin film of toner such as this oil film enables smooth sliding contact between the intermediate transfer belt 4 and the cleaning blade 91.

  When the toner thin film is interrupted, the frictional resistance between the intermediate transfer belt 4 and the cleaning blade 91 increases, making smooth sliding contact difficult, and the edge portion 911 of the cleaning blade 91 increases the frictional force on the intermediate transfer belt 4. There is a problem in that the cleaning blade 91 is turned up and worn.

  In the present invention, the amount of toner adhering to the intermediate transfer belt 4 is positioned on the upstream side of the sliding contact portion 912 so that a thin film of toner can be always formed at the sliding contact portion 912 between the edge portion 911 and the intermediate transfer belt 4. When the toner amount is small, a patch toner image is formed, the formed toner image is scraped off by a cleaning blade, and the scraped toner is attached to the intermediate transfer belt 4 by the rotation of the replenishing roller 92, and the sliding contact portion The amount of toner replenished to 912 is increased.

  Further, when the amount of toner detected by the sensor is small, the amount of toner attached to the intermediate transfer belt 4 is increased by increasing the rotation of the replenishing roller 92 so that the amount of toner replenished to the sliding contact portion 912 is increased. It is a thing.

  The cleaning blade 91 is supported by a support member 913, and the support member 913 is rotatably attached to the housing of the cleaning unit 9 via a support shaft 914. As a result, the edge portion 911 of the cleaning blade 91 supported by the support member 913 can come into contact with the surface of the intermediate transfer belt 4.

  The cleaning blade 91 is plate-shaped and can be adjusted by a pressure urging mechanism 915 (for example, a spring) so that the edge portion 911 contacts the intermediate transfer belt 4 with uniform pressure.

  As the material of the cleaning blade 91, rubber, metal or the like is used, but rubber which is an elastic body is preferably used. As the rubber material, urethane rubber, silicon rubber, fluorine rubber, chloropyrene rubber, butadiene rubber, and the like are known. Of these, urethane rubber is preferable because it has excellent wear characteristics compared to other rubbers. .

  Further, a backup roller 45 is provided on the opposite side of the cleaning blade 91 from the intermediate transfer belt 4 so that the urging force of the cleaning blade 91 toward the intermediate transfer belt 4 is stably received.

  As described above, the edge portion 911 of the cleaning blade 91 having elasticity comes into contact with the surface of the intermediate transfer belt 4 with a predetermined urging force, so that the toner remaining on the intermediate transfer belt 4 can be removed.

  The replenishing roller 92 is a replenishing member that is located upstream of the cleaning blade 91 and replenishes the toner removed by the cleaning blade 91 to the intermediate transfer belt 4, and is formed of nitrile rubber (NBR) having an Asker C hardness of about 30 °. The intermediate transfer belt 4 is supported so as to be in contact with the surface of the intermediate transfer belt 4. The peripheral speed of the driving unit (not shown) that drives the replenishing roller 92 is the same as or slightly faster than the speed of the intermediate transfer belt 4 and rotates in the direction of the arrow q.

  Then, the toner stored in the storage portion 95 (shaded portion) is transported to the contact position with the intermediate transfer belt 4 by the rotation in the direction of the arrow q, and the transported toner is adhered to the intermediate transfer belt 4.

  The storage plate 93 is attached to the housing of the cleaning unit 9, and one end 931 of the storage plate 93 is in contact with the surface of the supply roller 92.

  Then, the toner remaining after the transfer or the toner forming the patch toner image is scraped off by the cleaning blade 91, and the falling toner (dotted line in the drawing) is stacked on the surface of the storage plate 93 (storage unit 95). The accumulated toner adheres to the replenishing roller 92, and is removed from the contact portion between the storage plate 93 and the replenishing roller 92 by the rotation of the replenishing roller 92 and conveyed to the intermediate transfer belt 4. The toner is conveyed to the sliding contact portion 912 by the intermediate transfer belt 4.

  The storage plate 93 has a plate shape, and polyethylene terephthalate (PET) or the like is used.

  Even if a large amount of toner is scraped off by the cleaning blade 91, the amount of toner that accumulates on the surface of the storage plate 93 falls one after another when the limit is exceeded, so that a substantially constant volume is maintained.

  The sensor 94 detects the amount of toner carried to the sliding contact portion 912 as described above, and the toner adhering to the intermediate transfer belt 4 passing through the section 46 sandwiched between the cleaning blade 91 and the replenishing roller 92. Detect the amount.

  The sensor 94 has a small sensor output when the toner amount is small, and a large sensor output when the toner amount is large. In addition, a photoelectric detector can be used. If the intermediate transfer belt 4 is transparent, a transmissive photoelectric detector can be used. If the intermediate transfer belt 4 is opaque and has a high light reflectance, a reflective photoelectric detector can be used. A detector can be used.

  Here, when the amount of toner is small, the sensor 94 has a large amount of transmitted light (reflected light amount) and a large output of a photoelectric element (not shown), and when the amount of toner is large, the amount of transmitted light (reflected light amount) is small and the output of the photoelectric element is small. However, the sensor amplifier built in the sensor 94 reverses the sensor output so that the sensor output decreases when the toner amount is small and the sensor output increases when the toner amount is large.

  A sensor 94 using a transmissive photoelectric detector is composed of a light projector and a light receiver, and a light projector or light receiver is provided on one side (inside the cleaning unit 9) with the intermediate transfer belt 4 interposed therebetween, and a light receiver or light projector on the opposite side. Is provided. The light projector or light receiver provided in the cleaning unit 9 is disposed at a position away from the falling toner (dotted line in the drawing) in order to prevent erroneous detection due to toner adhesion.

  For the same reason, a transparent portion of the cleaning portion 9 may be provided at the optical axis position of the sensor 94 and one of them may be provided outside.

  The wavelength of light emitted from the sensor 94 is not particularly limited because the toner often used in the image forming apparatus is black toner. For example, a sensor that emits near-infrared light can be used.

  As described above, the amount of toner carried to the sliding contact portion 912 by directly detecting the amount of toner adhering to the intermediate transfer belt 4 passing through the section 46 sandwiched between the cleaning blade 91 and the replenishing roller 92. As a result, the problem that the toner amount cannot be detected stably as described in the problem to be solved by the invention can be solved.

  The image forming apparatus A has a control unit (not shown) that controls the entire image forming apparatus A, and the cleaning unit 9 will be described with reference to the flowcharts of FIGS. 1, 2, 3, 4, and 6. A control method will be described. The program according to the flowchart is stored in the storage unit of the control unit, and is sequentially read and executed by the CPU.

  FIG. 3 is a flowchart according to the first cleaning method of the cleaning unit.

1. Generation of image data Step S101
For example, image data (normal image data) based on image information read by the document image reading apparatus B is generated, and the process proceeds to the next step.

2. Execution of image formation Step S102
Image formation (normal image formation) is performed based on the generated normal image data, and the process proceeds to the next step. Note that when the first toner replenishment mode in step S106 is executed and the paper supply and the secondary transfer are prohibited, both are canceled to enable the paper supply and the secondary transfer.

3. Job completion confirmation Step S103
Check whether the number of images formed at the time of job setting has been reached or not. If it has reached (Y), it is determined that the job has ended and the process proceeds to the end. If it has not reached (N) the job has ended It judges that it has not carried out, and progresses to the next step.

4). Toner adhesion amount detection Step S104
In order to grasp the amount of toner conveyed to the sliding contact portion 912 between the cleaning blade 91 and the intermediate transfer belt 4, the output of the sensor 94 is read and the process proceeds to the next step. This step is for detecting the toner adhesion amount during normal image formation.

5. Determination of toner adhesion amount Step S105
When the sensor 94 detects an insufficient amount of toner conveyed to the sliding contact portion 912 (Y), the process proceeds to the next step. If the sensor 94 does not detect a shortage of toner amount (N), the process proceeds to step S109.

  Here, the shortage of the toner amount refers to a situation in which the amount of toner conveyed to the sliding contact portion 912 is reduced and the smooth sliding contact between the intermediate transfer belt 4 and the cleaning blade 91 is disabled.

  For example, the threshold value 1 stored in advance in the storage unit is read, and the threshold value 1 is compared with the read output of the sensor 94. If the read output of the sensor 94 decreases to less than the threshold value 1 (Y), it is determined that the amount of toner carried to the sliding contact portion 912 has decreased, and the process proceeds to the next step to replenish the sliding contact portion 912 with toner. . If the read output of the sensor 94 is greater than or equal to the threshold 1 (N), the process proceeds to step S109.

  Note that the threshold value 1 is such that when the toner adhesion amount decreases and decreases further, the frictional resistance between the intermediate transfer belt 4 and the cleaning blade 91 increases, and smooth sliding contact becomes impossible and the edge portion 911 is caught in the intermediate transfer belt 4. This is the same value as the output value of the sensor 94 corresponding to the toner adhesion amount obtained by adding a marginal adhesion amount to the toner adhesion amount immediately before the cleaning blade 91 is turned over or worn. It is.

6). First toner supply mode execution Step S106
A first toner supply mode described later is executed, and the process proceeds to the next step.

7). Toner adhesion amount detection Step S107
Since it is the same as that in step S104, the description is omitted. In this step, the toner adhesion amount after the first toner replenishment is detected, and the process proceeds to step S108.

8). Determination of toner adhesion amount Step S108
If the sensor 94 does not detect that the amount of toner carried to the sliding contact portion 912 is sufficient (N), the process proceeds to step S106, and steps S106 to S108 are repeated until the satisfaction of the amount of toner is detected. If the toner amount is satisfied (Y), the process proceeds to step S102.

  Here, the satisfaction of the amount of toner refers to a situation in which the amount of toner conveyed to the sliding contact portion 912 increases and smooth sliding contact between the intermediate transfer belt 4 and the cleaning blade 91 is possible.

  For example, the threshold value 2 stored in advance in the storage unit is read, and the threshold value 2 is compared with the read output of the sensor 94. If the read output of the sensor 94 is less than the threshold value 2 (N), the process proceeds to step S106 to continue the first toner replenishment mode, and step S106 is performed until the read output of the sensor 94 becomes equal to or greater than the threshold value 2 (Y). Repeat step S108.

  When the read output of the sensor 94 is equal to or greater than the threshold value 2 (Y), the process proceeds to step S102 to resume image formation.

  Note that the threshold value 2 is larger than the threshold value 1, and the toner adhesion amount increases to reduce the frictional resistance between the intermediate transfer belt 4 and the cleaning blade 91, thereby enabling smooth sliding contact and the edge portion 911 to the intermediate transfer belt 4. The value is the same as the output value of the sensor 94 corresponding to the amount of toner that does not get caught and does not turn over or wear the cleaning blade 91.

9. Determination of toner adhesion amount Step S109
Since it is the same as that of step S108, description is abbreviate | omitted.

  FIG. 4 is a flowchart according to the first toner supply mode.

  In this mode, toner is supplied to the intermediate transfer belt 4. For example, a patch image is formed on the intermediate transfer belt 4 and toner is supplied to the sliding contact portion.

1. Generation of first patch image data Step S201
Solid image data, that is, first patch image data over the entire surface of the paper is generated by toner of any one of Y, M, C, and K, preferably black toner, and the process proceeds to the next step.

2. Toner image formation using first patch image data Step S202
The generated first patch image data is sent to the exposure unit 2, a latent image of the first patch image is formed on the photosensitive member 1, the formed latent image is developed by the developing unit 3, and the process proceeds to the next step.

3. Conveying the first patch toner image to the cleaning unit by prohibiting the paper supply and the secondary transfer Step S203
The driving of the intermediate transfer belt is continued, and the developed first patch toner image is primarily transferred to the intermediate transfer belt 4 by the operation of the primary transfer unit 5. At the same time, the operation of the paper feeder 82 is stopped to prohibit paper supply, and the operation of the transfer power supply 62 and the urging device 63 is stopped to transfer the first patch toner image transferred to the intermediate transfer belt 4 to the secondary transfer. Instead, it is conveyed to the cleaning unit 9 and proceeds to the end (return to step S106).

  In the first cleaning method and the first toner replenishment mode, the width of the first patch toner image in both the main and sub scanning directions has a length corresponding to one sheet to be used. Further, the width in the sub-scanning direction may be a continuous length from when the output of the sensor 94 becomes less than the threshold value 1 until it becomes equal to or more than the threshold value 2.

  In the above flowchart, the relationship between the output of the sensor 94 and image formation will be described below with reference to FIGS.

  FIG. 5 is an explanatory diagram showing the relationship between the output of the sensor 94 and image formation when the first cleaning method described in FIGS. 3 and 4 is performed.

  In FIG. 5, the horizontal axis represents time t, and the vertical axis represents the output of the sensor 94.

  PG indicates a toner image formed on the intermediate transfer belt 4 according to the output of the sensor 94. A white square indicates a normal toner image PG1 based on image information read by a normal document image reading device, for example, and a black (hatched) square indicates a first patch toner based on the first patch image data described above. An image PG2 is shown.

  In period 1, a normal toner image PG1 is formed on the intermediate transfer belt 4 on the basis of image information read by a normal document image reading device, for example, and transferred to a sheet by a secondary transfer unit. The toner remaining without being transferred is removed by the cleaning unit. At this time, the sensor 94 detects the amount of toner carried to the sliding contact portion between the cleaning blade and the intermediate transfer belt to obtain a sensor output.

  Usually, the toner image PG1 is generally a character image, and the printing rate (toner adhesion amount per unit area) at this time is lower than the printing rate of an image such as a picture. As a result, the amount of toner remaining in 4 also decreases, and as a result, the amount of toner stored in the storage unit 95 shown in FIG. 2 also decreases, and the output of the sensor 94 gradually decreases each time the normal toner image PG1 is formed. .

  In the period 2, when the shortage of the amount of toner conveyed to the sliding contact portion 912 is detected, for example, when the output of the sensor 94 becomes less than the threshold value 1 (Sh1), the first toner supply mode is activated. As a result, the formation of the normal toner image PG1 is interrupted, the solid image data, that is, the first patch toner image PG2 is formed on the intermediate transfer belt 4, and the first patch toner image PG2 reaches the cleaning unit without being secondarily transferred. It is scraped off.

  Thereafter, the formation of the first patch toner image PG2 is repeated, and the scraped-off toner is stored in the storage unit 95 shown in FIG. 2 and supplied to the intermediate transfer belt 4 by the supply roller 92. The toner adhesion amount of the intermediate transfer belt 4 in the section 46 sandwiched between the supply rollers 92 increases.

  Then, when the sensor 94 detects the increased toner adhering to the surface of the intermediate transfer belt 4 and detects that the amount of toner carried to the sliding contact portion 912 is sufficient, for example, when the output of the sensor 94 becomes equal to or greater than the threshold 2 (Sh2), The first toner supply mode is stopped.

  Thereafter, the period 1 and the period 2 are repeated according to the amount of toner carried to the sliding contact portion 912, for example, the output of the sensor 94.

  With the configuration and method described above with reference to FIGS. 1 to 5, a toner thin film can always be formed at the sliding contact portion between the edge portion of the cleaning blade and the intermediate transfer belt, and as a result, the blade is prevented from being turned or worn. High-quality image formation is possible.

  FIG. 6 is a flowchart according to the second cleaning method of the cleaning unit.

1. Generation of image data Step S301
Since it is the same as the above-mentioned step S101, description is abbreviate | omitted.

2. Execution of image formation Step S302
Image formation is performed based on the generated normal image data, and the process proceeds to the next step.

3. Job completion confirmation Step S303
The description is omitted because it is similar to step S103 described above.

4). Toner adhesion amount detection Step S304
Since it is the same as step S104 described above, description thereof is omitted.

5. Determination of toner adhesion amount Step S305
Since it is the same as the above-mentioned step S105, description is abbreviate | omitted. If the read output of the sensor 94 is greater than or equal to the threshold 1 (N), the process proceeds to step S310.

6). Addition of second patch data to image data Step S306
A second patch between the nth normal toner image and the n + 1th normal toner image after the output of the sensor 94 becomes less than the threshold 1 with respect to the normal image data generated in step S301. The second patch image data is added to proceed to the next step so that the toner image is formed.

  The second patch toner image is a toner image having a short width in the sub-scanning direction formed between the nth normal toner image and the (n + 1) th normal toner image formed on the intermediate transfer belt. The length is equal to or shorter than the interval between the front and rear normal toner images formed on the intermediate transfer belt 4.

  In addition, since the second patch toner image is not transferred, the transfer voltage switching time and the transfer roller release / removal time are determined based on the interval between the normal toner images, not simply the length of the interval between the normal toner images before and after the second patch toner image. It is preferable to set a length obtained by subtracting a length corresponding to one or both of the crimping operation times.

7). Executing Patched Toner Image Formation / Normal Image Formation Step S307
Based on the image data formed by adding the second patch image data to the normal image data formed in step S306, a patched toner image (normal toner image and second patch toner image) is formed on the intermediate transfer belt 4.

  Of the toner images formed on the intermediate transfer belt 4, the normal toner image based on the normal image data is transferred to the paper, and the second patch toner image based on the second patch data added in step S306 is transferred to the paper. Without carrying out, it conveys to the cleaning part 9, and progresses to the next step.

8). Toner adhesion amount detection Step S308
Since it is the same as step S104 described above, description thereof is omitted.

9. Determination of toner adhesion amount Step S309
Since it is the same as the above-mentioned step S108, description is abbreviate | omitted. If the read output of the sensor 94 is less than the threshold value 2 (N), the process proceeds to step S307, and steps S307 to S309 are repeated until the read output of the sensor 94 becomes equal to or greater than the threshold value 2.

  If the read output of the sensor 94 is equal to or larger than the threshold 2 (Y), the second patch image data added in step S306 is deleted, and the process proceeds to step S311 to continue image formation.

10. Determination of toner adhesion amount Step S310
The description is omitted because it is similar to step S109 described above. If the read output of the sensor 94 is greater than or equal to the threshold 2 (Y), the process proceeds to step S302, and if it is less than the threshold 2 (N), the process proceeds to step S306.

11. Deletion of second patch data Step S311
The second patch data added in step S306 is deleted, and the process proceeds to step S302.

  FIG. 7 is an explanatory diagram showing the relationship between the output of the sensor 94 and image formation when the second cleaning method described in FIG. 6 is performed.

  In FIG. 7, the horizontal axis represents time t, and the vertical axis represents the output of the sensor 94.

  PG indicates a toner image formed on the intermediate transfer belt 4 according to the output of the sensor 94. The white square indicates a normal toner image PG1 based on image information read by a normal document image reading device, for example, and the black (hatched) square indicates a second patch toner based on the second patch image data described above. An image PG3 is shown.

  In period 1, a normal toner image PG1 is formed on the intermediate transfer belt 4 on the basis of image information read by a normal document image reading device, for example, and transferred to a sheet by a secondary transfer unit. The toner remaining without being transferred is removed by the cleaning unit. At this time, the sensor 94 detects the amount of toner carried to the sliding contact portion between the cleaning blade and the intermediate transfer belt to obtain a sensor output.

  Usually, the toner image PG1 is generally a character image, and the printing rate (toner adhesion amount per unit area) at this time is lower than the printing rate of an image such as a picture. As a result, the amount of toner stored in the storage unit 95 shown in FIG. 2 also decreases, and the output of the sensor 94 gradually decreases each time the normal toner image PG1 is formed.

  In the period 3, when the shortage of the amount of toner conveyed to the sliding contact portion 912 is detected, for example, when the output of the sensor 94 becomes less than the threshold value 1 (Sh1), the second image is transferred to the intermediate transfer belt 4 between the normal toner image PG1. A second patch toner image PG3 is formed based on the patch image data. Then, the normal toner image PG1 is subjected to secondary transfer, and the second patch toner image PG3 reaches the cleaning unit without being subjected to secondary transfer, and is scraped off.

  Thereafter, the formation of the normal toner image PG1 and the second patch toner image PG3 is repeated, and the toner scraped off from the second patch toner image PG3 is stored in the storage unit 95 shown in FIG. The intermediate transfer belt 4 is replenished. For this reason, the toner adhesion amount of the intermediate transfer belt 4 in the section 46 sandwiched between the cleaning blade 91 and the supply roller 92 increases.

  Then, when the sensor 94 detects the increased toner adhering to the surface of the intermediate transfer belt 4 and detects that the amount of toner carried to the sliding contact portion 912 is sufficient, for example, when the output of the sensor 94 becomes equal to or greater than the threshold 2 (Sh2), The formation of the second patch toner image PG3 is stopped.

  Thereafter, the period 1 and the period 3 are repeated according to the amount of toner carried to the sliding contact portion 912, for example, according to the output of the sensor 94.

  With the configuration and method described above with reference to FIGS. 1 and 2 and FIGS. 6 and 7, a toner thin film can always be formed at the sliding contact portion between the edge portion of the cleaning blade and the intermediate transfer belt. Prevents curling and wear and enables high-quality image formation.

  FIG. 8 is an explanatory diagram showing the relationship between the output of the sensor 94 and the rotation speed of the replenishing roller.

  In FIG. 8, the horizontal axis indicates time t, and the vertical axis indicates the output of the sensor 94 and the rotation speed of the replenishing roller 92.

  In period 1, a normal toner image PG1 is formed on the intermediate transfer belt 4 on the basis of image information read by a normal document image reading device, for example, and transferred to a sheet by a secondary transfer unit. The toner remaining without being transferred is removed by the cleaning unit. At this time, the sensor 94 detects the amount of toner carried to the sliding contact portion between the cleaning blade and the intermediate transfer belt to obtain a sensor output.

  Usually, the toner image PG1 is generally a character image, and the printing rate (toner adhesion amount per unit area) at this time is lower than the printing rate of an image such as a picture. As a result, the amount of toner stored in the storage unit 95 shown in FIG. 2 also decreases, and the output of the sensor 94 gradually decreases each time the normal toner image PG1 is formed.

  In the period 1 until the output value of the sensor becomes less than the preset threshold value 1, the rotation speed of the replenishing roller 92 is the first rotation speed whose peripheral speed is equal to or slightly faster than the speed of the intermediate transfer belt 4. The rotation speed Lo is set to a certain level, and the toner is replenished to the intermediate transfer belt 4 with a normal amount.

  If an insufficient amount of toner conveyed to the sliding contact portion 912 is detected in the period 2, for example, even if the output of the sensor 94 becomes less than the threshold value 1 (Sh1), the normal toner image PG1 is continuously formed to perform the secondary transfer. I do. In period 2, since the replenishment roller 92 increases the amount of toner replenished to the intermediate transfer belt 4, the rotation speed of the replenishment roller 92 is faster than the rotation speed Lo, for example, the second rotation speed that is 10 to 50% faster. Is set to the rotation speed Hi. The first rotation speed and the second rotation speed are obtained and set in advance by experiments or the like.

  When the shortage of the amount of toner conveyed to the sliding contact portion 912 is detected, increasing the rotation speed of the replenishment roller 92 to increase the amount of toner conveyed to the sliding contact portion 912 is equivalent to the rotation speed of the replenishment roller 92, There is a correlation between the amount of toner that adheres to the replenishing roller 92 and moves from the storage unit 95 toward the intermediate transfer belt 4, and the amount of toner that adheres to and moves on the replenishing roller 92 and adheres to the intermediate transfer belt 4. This is based on the fact that there is a correlation with the amount of toner to be used.

  Accordingly, when the shortage of the amount of toner conveyed to the sliding contact portion 912 is detected, for example, when the output value of the sensor 94 becomes less than the threshold value 1, the rotation speed of the replenishing roller 92 is changed from the first rotation speed to the second rotation speed. When the toner supply amount to the intermediate transfer belt 4 can be increased by increasing the speed and the satisfaction of the amount of toner carried to the sliding contact portion 912 is detected, for example, the output value of the sensor 94 becomes a threshold value 2 or greater, which is larger than the threshold value 1. It is possible to restore the toner replenishment amount to the intermediate transfer belt 4 by decelerating to the first rotation speed. Accordingly, until the amount of toner conveyed to the sliding contact portion 912 is insufficient and satisfied, for example, until the output value of the sensor 94 decreases to the threshold value 1 and increases to the threshold value 2 or more, the sliding roller slided by the accelerated replenishing roller 92 The amount of toner replenished to the contact portion 912 can be increased.

  Thereafter, the period 1 and the period 2 are repeated according to the amount of toner carried to the sliding contact portion 912, for example, the output of the sensor 94.

Note that the rotation speed of the replenishment roller 92 may be changed according to the output of the sensor 94 while the output of the sensor 94 is less than the threshold value 1 (Sh1) and then the threshold value 2 (Sh2) or more (period 2) In this case, for example, a direct current motor or the like that can change the number of rotations according to the output of the sensor 94 is used for the driving portion of the replenishing roller 92. (If the amount of transmitted light is large, it is detected that the sensor output is large and the amount of toner is small, and the speed is increased in the direction of increasing the rotation speed or vice versa.)
Further, as described above, the rotation speed of the replenishing roller 92 may be changed in accordance with the output of the sensor 94 during the entire period.

  As described above, by increasing the rotation speed of the replenishing roller 92, the amount of toner conveyed from the storage unit 95 to the sliding contact portion 912 via the replenishing roller 92 and the intermediate transfer belt 4 can be increased. A toner thin film can always be formed at the sliding contact portion between the edge portion and the intermediate transfer belt. As a result, the blade is prevented from being turned over or worn, thereby enabling high-quality image formation.

  FIG. 9 is an explanatory diagram when the cleaning unit is applied to the secondary transfer unit.

  The secondary transfer unit is a belt-type transfer unit, and the transfer belt 64 is suspended by a plurality of rollers 65 and is driven to rotate by a drive unit (not shown). One of the plurality of rollers 65 is connected to a transfer power supply (not shown), and the toner image carried on the intermediate transfer belt 4 is transferred onto the paper P at the nip portion n ′.

  Toner may adhere to the transfer belt 64 due to image formation over a long period of time, and the attached toner may be further transferred to the paper P to deteriorate image quality. To prevent this, the toner attached to the transfer belt 64 is scraped off. Cleaning means is required.

  The cleaning unit 9 ′ scrapes off the toner adhering to the transfer belt 64 and has the same configuration as the cleaning unit 9 described above.

  When the cleaning unit 9 ′ is provided on the transfer belt 64, the toner adhering to the transfer belt 64 is slightly less than the toner remaining on the intermediate transfer belt 4, so that the transfer belt 64 and the cleaning blade are removed when the toner thin film is interrupted. Smooth sliding contact with 91 becomes impossible, and the edge portion of the cleaning blade 91 may be wound around the transfer belt 64 and turn over or wear.

  Therefore, as described with reference to FIGS. 2 and 3, toner is supplied to the sliding contact portion so that a thin film of toner can always be formed at the sliding contact portion between the transfer belt 64 and the cleaning blade 91.

  The image forming apparatus (tandem type color image forming apparatus) having the belt-shaped image carrier has been described above as an example, but the image forming apparatus (monochrome image forming apparatus) having the cylindrical image carrier (photosensitive body) has been described. Needless to say, the present invention can also be applied. In this case, the cleaning unit is disposed on the downstream side of the transfer unit for transferring the toner image carried on the photosensitive member to the sheet, and is provided inside the cleaning unit. A sensor detects the amount of residual toner adhering to the surface of the photoreceptor.

4 Intermediate transfer belt 9 Cleaning unit 91 Cleaning blade 92 Replenishment roller 93 Storage plate 94 Sensor 95 Storage unit 95
911 Edge portion 912 Sliding contact portion A Image forming apparatus P Paper PG1 Normal toner image PG2 First patch image PG3 Second patch image

Claims (9)

In an image forming apparatus capable of cleaning toner adhering to an image carrier,
A cleaning blade that removes toner adhering to the image carrier by contacting a tip of the image carrier and replenishing the image carrier with toner that is located upstream of the cleaning blade and removed by the cleaning blade A replenishment member that detects the amount of toner that is carried to the sliding contact portion between the cleaning blade and the image carrier;
And a control unit that starts supplying toner when the sensor detects that the toner amount is insufficient, and stops supplying toner when the sensor detects that the toner amount is sufficient. Forming equipment.   The image forming apparatus according to claim 1, wherein the sensor is a sensor that detects an amount of toner attached to the image carrier passing through a section sandwiched between the cleaning blade and the replenishing member. .   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer belt, and the sensor detects a toner amount on the intermediate transfer belt.   The control unit forms a patch image on the image carrier when the sensor detects that the toner amount is insufficient and conveys the patch image to the sliding contact portion. When the sensor detects that the toner amount is sufficient, the control unit The image forming apparatus according to claim 1, wherein the formation is stopped.   The control unit forms a patch image on the image carrier and conveys it to the slidable contact portion when the output value of the sensor becomes less than a preset threshold value 1 indicating insufficient toner amount, and outputs the sensor. 5. The image forming apparatus according to claim 4, wherein the patch image formation is stopped when a value becomes equal to or greater than a threshold value 2 indicating a satisfaction of the preset amount of toner larger than the threshold value 1.   The controller increases the replenishment amount of toner to the image carrier when the sensor detects that the toner amount is insufficient, and when the sensor detects that the toner amount is sufficient, the control unit increases the amount of toner to the replenishment member. The image forming apparatus according to claim 1, wherein the replenishment amount of toner with respect to the carrier is restored.   The image forming apparatus according to claim 1, wherein the sensor is a photoelectric detector.   The image forming apparatus according to claim 1, wherein the replenishing member is a replenishing roller that adheres the toner removed by the cleaning blade to the image carrier. The replenishing member is a replenishing roller for adhering the toner removed by the cleaning blade to the image carrier;
When the sensor detects a shortage of the toner amount, the control unit sets a rotation speed of the replenishment roller from a preset first rotation speed to a preset second rotation that is earlier than the first rotation speed. The number of toners to be replenished to the image bearing member is increased by increasing the number of toners, and when the sensor detects that the toner amount is sufficient, the first rotational speed is restored. The image forming apparatus according to claim 1.

Images