Image forming apparatus and rotation control method

Abstract

To provide an image forming apparatus and a rotation control method that can prevent the occurrence of an image defect.SOLUTION: An image forming apparatus comprises: an image carrier (photoreceptor drum) that can carry a toner image to be formed on a sheet; a cleaning unit (cleaning blade) that removes a foreign substance attached to the surface of the image carrier; a developing roller that forms the toner image on the image carrier; and a control unit that controls the rotation speed of the developing roller according to a cleaning power of the cleaning unit for the surface of the image carrier.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a rotation control method.

Background Art

[0002] Conventionally, an electrophotographic image forming apparatus that forms an image on a sheet of paper is known. In such an apparatus, an electrostatic latent image formed on a photoreceptor drum (photoreceptor) is developed with toner to form a toner image, the formed toner image is transferred onto a sheet of paper (recording medium), and the transferred toner image is heat-fixed.

[0003] In such an image forming apparatus, there is provided an image forming apparatus including a cleaning unit that cleans toner (hereinafter referred to as "residual toner") remaining on the photoreceptor drum after the toner image has been transferred onto the sheet of paper. As such a cleaning unit, there are provided a cleaning brush that rotates while contacting the surface of the photoreceptor drum to clean foreign matter (including residual toner) adhering to the surface, and a cleaning blade that is disposed downstream of the cleaning brush in the rotation direction of the photoreceptor drum and contacts the surface of the photoreceptor drum to clean foreign matter (including residual toner) adhering to the surface.

[0004] Citation Document 1 discloses a technique for removing discharge products adhering to the surface of a photoreceptor drum over a long period of time by using a member including at least fibers subjected to a crimping process as a toner holding member and causing the toner holding member to hold a large amount of toner. According to the technique described in Citation Document 1, it is possible to prevent the occurrence of "Deletion" in which white spots appear in an image and "rain-drop-shaped Filming" that occurs due to the use of a rotary brush cleaner to prevent the occurrence of such "Deletion".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Incidentally, when an image is formed on paper, external additives (silica contained in toner) and fillers (such as calcium carbonate contained in paper dust generated from the paper) accumulate at the contact point between the cleaning blade and the photoreceptor drum. This provides a refreshing effect by lightly scraping the surface (surface layer) of the photoreceptor drum to clean (very lightly polish) any deposits (silica, toner, lubricant, and discharge products, etc.) on that surface. Typically, the specifications of the cleaning blade and cleaning brush, such as material, hardness, and density, are determined so that a predetermined cleaning power is achieved when the recommended paper is used for image formation.

[0007] However, if paper with very little paper dust or filler contained in the paper dust is used as the paper used to form the image, the amount of filler accumulated on the cleaning blade decreases. As a result, the cleaning power obtained by the external additives and fillers accumulated at the contact point between the cleaning blade and the photoreceptor drum becomes lower than the predetermined cleaning power. Consequently, the surface deposits of the photoreceptor drum cannot be sufficiently removed, resulting in image defects such as white spots (granular noise) in the photoreceptor drum diameter period.

[0008] The present invention aims to provide an image forming apparatus and a rotation control method that can suppress the occurrence of image defects. [Means for solving the problem]

[0009] The image forming apparatus according to the present invention is An image carrier capable of supporting a toner image formed on paper, A cleaning unit for cleaning foreign matter adhering to the surface of the image carrier, A developing roller that forms the toner image on the image carrier, A control unit controls the rotation speed of the developing roller according to the cleaning force of the cleaning unit on the surface of the image carrier, A cleaning brush that rotatably contacts the surface of the image carrier and cleans foreign matter adhering to the surface of the image carrier, Equipped with, The control unit controls the rotation speed of the developing roller and cleaning brush according to the cleaning force. The control unit increases the rotational speed in response to the decrease in cleaning force, and decreases the rotational speed in response to the increase in cleaning force. The control unit can perform two modes: a first mode in which the rotational speed of both the developing roller and the cleaning brush is increased, and a second mode in which the rotational speed of the developing roller is increased without increasing the rotational speed of the cleaning brush. .

[0010] The rotation control method according to the present invention is An image carrier capable of holding a toner image formed on paper, a cleaning unit for cleaning foreign matter adhering to the surface of the image carrier, and a developing roller for forming the toner image on the image carrier, A cleaning brush that rotatably contacts the surface of the image carrier and cleans foreign matter adhering to the surface of the image carrier, and a control unit that controls the rotation speed of the developing roller according to the cleaning force of the cleaning unit on the surface of the image carrier. A rotation control method in an image forming apparatus comprising: The rotational speed is increased in accordance with the decrease in the cleaning force, while the rotational speed is decreased in accordance with the increase in the cleaning force. It is possible to perform two modes: a first mode in which the rotational speed of both the developing roller and the cleaning brush is increased, and a second mode in which the rotational speed of the developing roller is increased without increasing the rotational speed of the cleaning brush. . [Effects of the Invention]

[0011] According to the present invention, the occurrence of image defects can be suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] This is a control block diagram of the image forming apparatus in this embodiment. [Figure 2] This figure shows the specific configuration near the image forming section in this embodiment. [Figure 3] This diagram shows the configuration of the paper dust amount detection unit in this embodiment. [Figure 4] This flowchart shows an example of rotation control operation of the image forming apparatus in this embodiment. [Figure 5] This flowchart shows an example of rotation control operation of the image forming apparatus in this embodiment. [Figure 6] This flowchart shows an example of rotation control operation of the image forming apparatus in this embodiment. [Figure 7]It is a flowchart showing an example of the rotation control operation of the image forming apparatus in the present embodiment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The image forming apparatus 100 shown in FIG. 1 forms an image on a sheet by an electrophotographic process. As shown in FIG. 1, the image forming apparatus 100 includes a document reading unit 110, an operation display unit 120, an image processing unit 130, an image writing unit 135, an image forming unit 140, a conveyance unit 150, a fixing unit 160, a toner amount detection unit 180, an image reading unit 190, and a control unit 200.

[0014] The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, etc. The CPU 201 reads a program corresponding to the processing content from the ROM 202 and expands it in the RAM 203, and centrally controls the operations of each block of the image forming apparatus 100 in cooperation with the expanded program. At this time, various data stored in the storage unit 172 is referred to. The storage unit 172 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0015] The control unit 200 performs transmission and reception of various data with an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 171. The control unit 200, for example, receives image data transmitted from an external device and forms an image on a sheet based on this image data (input image data). The communication unit 171 is composed of, for example, a communication control card such as a LAN card.

[0016] The document scanning unit 110 optically scans the document transported onto the contact glass, and images the reflected light from the document onto the light-receiving surface of the CCD (Charge Coupled Device) sensor to read the document. Although the document is transported onto the contact glass by an automatic document feeder (ADF), the document may also be placed onto the contact glass manually.

[0017] The operation display unit 120 has a touch panel screen. Various instructions and settings can be input by the user via the touch panel screen. This instruction and setting information is handled by the control unit 200 as job information. Job information includes paper size, number of prints, etc. When a print job is instructed via the operation display unit 120, the control unit 200 records the number of prints included in the job information corresponding to that print job in the storage unit 172.

[0018] The image processing unit 130 includes a circuit for analog-to-digital (A / D) conversion processing and a circuit for digital image processing. The image processing unit 130 generates digital image data from the analog image signal acquired by the CCD sensor of the document reading unit 110 through A / D conversion processing and outputs it to the image writing unit 135.

[0019] The image writing unit 135 emits laser light based on the digital image data generated by the image processing unit 130, and irradiates the photoreceptor drum of the image forming unit 140 with the emitted laser light to form an electrostatic latent image on the photoreceptor drum (exposure process).

[0020] In addition to the exposure process described above, the image forming unit 140 is configured to perform a charging process before the exposure process, a developing process after the exposure process, a transfer process after the developing process, and a cleaning process after the transfer process. In the charging process, the image forming unit 140 uniformly charges the surface of the photoreceptor drum by corona discharge from a charging device. In the developing process, the image forming unit 140 forms a toner image on the photoreceptor drum by adhering toner contained in the developer in the developing device to the electrostatic latent image on the photoreceptor drum.

[0021] In the transfer process, the image forming unit 140 transfers the toner image on the photoreceptor drum to the paper transported by the transport unit 150 by applying a transfer voltage from a voltage application unit (not shown). In the cleaning process, the image forming unit 140 removes foreign matter (including residual toner) adhering to the photoreceptor drum after the transfer process by bringing a cleaning device such as a cleaning brush into contact with the photoreceptor drum.

[0022] The fixing unit 160 includes a fixing roller and a pressure roller. The pressure roller is positioned in a state of pressure contact with the fixing roller in the area in contact with the fixing roller. A fixing nip is formed at the pressure contact area between the fixing roller and the pressure roller. The fixing unit 160 fixes the toner image on the paper to the paper by applying heat and pressure (heat fixing) to the toner image introduced into the fixing nip (fixing process). As a result, a fixed toner image is formed on the paper. The paper that has been heat-fixed by the fixing unit 160 is discharged to the outside of the image forming apparatus 100.

[0023] Next, the specific configuration near the image forming unit 140 will be explained with reference to Figure 2. In Figure 2, 1 is a photoreceptor drum capable of carrying the toner image formed on the paper P (functioning as the "image carrier" of the present invention), and along the rotation direction (arrow direction) of this photoreceptor drum 1, there is a charging device 2, an image writing unit 135, a developing device 4, a transfer transport path 5 that guides the paper P to the transfer area, a transfer belt 6 that transfers the toner image formed on the photoreceptor drum 1 to the paper P, and a cleaning device 7 that removes foreign matter (including residual toner) adhering to the photoreceptor drum 1. Furthermore, downstream of the transfer belt 6 in the paper transport direction, there is a fixing unit 160 that fixes the toner image on the paper P.

[0024] The developing unit 4 receives toner from the toner cartridge via the toner hopper. The developing unit 4 also receives carriers via the carrier hopper. The developing unit 4 agitates the supplied toner and carriers with an agitation screw to charge the toner. After agitation, the developer (toner and carriers) is supplied to the developing roller 4A by the supply screw.

[0025] In the developing roller 4A, the developing sleeve rotates around a fixed magnetic roller, and developer is supplied to the outer surface of the developing sleeve by a supply screw. As the developer supplied to the outer surface of the developing sleeve moves along its outer surface, the magnetic force of the magnetic poles on the magnetic roller causes the carrier to form a magnetic brush. The toner adhering to the magnetic brush adheres to the electrostatic latent image on the photoreceptor drum 1. In other words, the electrostatic latent image on the photoreceptor drum 1 is developed by the toner, forming a toner image on the photoreceptor drum 1.

[0026] The cleaning device 7 comprises a cleaning brush 7A that rotates while in contact with the surface of the photoreceptor drum 1 to clean foreign matter (including residual toner) adhering to the surface, and a cleaning blade 7B (functioning as the "cleaning unit" of the present invention) which is positioned downstream of the cleaning brush 7A in the rotational direction of the photoreceptor drum 1 and contacts the surface of the photoreceptor drum 1 to clean foreign matter (including residual toner) adhering to the surface.

[0027] The transfer belt 6 is stretched between the driven roller 61, the drive roller 62, and other rollers, and is positioned below the photoreceptor drum 1 such that the surface of the transfer belt 6 is in contact with a portion of the outer surface of the photoreceptor drum 1. That is, a transfer nip is formed between the transfer belt 6 and the photoreceptor drum 1 as a transfer area. The paper P is conveyed while being pressed against the photoreceptor drum 1 by the transfer belt 6 in the transfer nip.

[0028] A backup roller 63 capable of applying a transfer voltage to the transfer belt 6 is positioned inside the transfer belt 6, which is in contact with a portion of the outer surface of the photoreceptor drum 1. A voltage application unit (not shown), which serves as a power source for applying the transfer voltage to the transfer belt 6, is connected to the backup roller 63. The control unit 200 controls the voltage to be applied by the voltage application unit so that a predetermined current flows from the backup roller 63 to the voltage application unit.

[0029] The paper P is stored in the paper feed cassette 9 and is supplied to the transfer transport path 5 via the paper feed transport path 90. Downstream of the fuser unit 160, a gate 91 is provided to switch between ejecting the paper P to the outside and feeding the paper to the double-sided transport path 92 for double-sided copying. Once the paper P enters the double-sided transport path 92, it first proceeds to the reversal transport path 93, where it is reversed and joins the transfer transport path 5 via the re-feed transport path 94.

[0030] A paper dust detection unit 180 is provided on the upstream side of the transfer nip in the paper transport direction to detect the amount of paper dust generated from the paper P being transported. The paper dust detection unit 180 may be provided at any position as long as it is in a position that can detect the amount of paper dust generated from the paper P being transported.

[0031] Figure 3 shows the configuration of the paper dust amount detection unit 180 in this embodiment. As shown in Figure 3, the paper dust amount detection unit 180 includes a pair of transport rollers (lower transport roller 181, upper transport roller 182), a paper dust removal brush roller 183, a paper dust removal and collection roller 184, a light source 185, and a light receiving sensor 186.

[0032] The paper dust removal brush roller 183 is a cleaning brush roller in which multiple elastic conductive fibers (e.g., acrylic resin) are implanted on the surface of a rotating member, for example. The paper dust removal brush roller 183 is rotatably positioned in contact with the upper transport roller 182 and removes paper dust that adheres to the upper transport roller 182 as the paper P is transported by the transport roller pair. In order to suitably remove paper dust from the upper transport roller 182, the paper dust removal brush roller 183 is driven to rotate in a counter-direction relative to the upper transport roller 182 by a control signal from the control unit 200.

[0033] The paper dust collection roller 184 is a cylindrical roller in which an acrylic UV-curing resin layer (resistive layer) is coated on the surface of a core metal made of, for example, stainless steel. The paper dust collection roller 184 is a roller for collecting paper dust adhering to the surface of the paper dust collection brush roller 183. Therefore, the paper dust collection roller 184 is rotatably positioned so that a part of its outer surface is in contact with the conductive fibers of the paper dust collection brush roller 183. The surface of the paper dust collection roller 184 may be plated or otherwise treated to improve its smoothness and durability. The paper dust collection roller 184 is rotationally driven in the counter-direction relative to the paper dust collection brush roller 183 by a control signal from the control unit 200.

[0034] The light source 185 illuminates the paper dust 187 scattered from the surface of the paper dust removal brush roller 183. The light source 185 is, for example, made of a light-emitting diode (LED). The light receiving sensor 186 captures the light diffusely reflected from the paper dust 187 illuminated by the light source 185 and detects its amount (diffuse reflected light amount). The light receiving sensor 186 outputs the detected diffuse reflected light amount to the control unit 200. Experiments have shown that the diffuse reflected light amount increases monotonically as the amount of paper dust 187 scattered from the surface of the paper dust removal brush roller 183 increases. Therefore, the output signal level of the light receiving sensor 186 is approximately proportional to the incident diffuse reflected light amount (and thus the paper dust concentration).

[0035] Downstream of the fixing unit 160 in the paper transport direction (whether inside or outside the image forming apparatus 100), there is an image reading unit 190 that reads the image formed on the paper P (see Figure 2). The image reading unit 190 is a line sensor that has a width greater than or equal to the maximum width of the paper P used in the image forming apparatus 100 in a direction perpendicular to the transport direction of the paper P (main scanning direction), and reads the image formed on the paper P.

[0036] The image reading unit 190 has multiple reading elements arranged in a line in a direction perpendicular to the transport direction of the paper P, and each reading element outputs an output value to the control unit 200 corresponding to the reflected light reflected from the image on the paper P.

[0037] Incidentally, when the process of forming an image on paper P is performed, external additives (silica contained in toner) and fillers (such as calcium carbonate contained in paper dust generated from paper P) accumulate at the contact point between the cleaning blade 7B and the photoreceptor drum 1. This provides a refreshing effect by lightly scraping the surface (surface layer) of the photoreceptor drum 1 and cleaning (very lightly polishing) the deposits (silica, toner, lubricant, and discharge products, etc.) on the surface. Typically, the specifications of the cleaning blade 7B and cleaning brush 7A, such as material, hardness, and density, are determined so that a predetermined cleaning force is obtained when the recommended paper is used as the paper P on which the image is formed.

[0038] However, if paper with very little paper dust or filler contained in the paper dust is used as the paper P for forming the image, the amount of filler accumulated on the cleaning blade 7B will decrease. As a result, the cleaning power obtained by the external additives and fillers accumulated at the contact point between the cleaning blade 7B and the photoreceptor drum 1 will be lower than the predetermined cleaning power. Consequently, it may not be possible to sufficiently remove the deposits on the surface of the photoreceptor drum 1, which may result in image defects such as white spots (granular noise) in the photoreceptor drum diameter period.

[0039] Therefore, in this embodiment, from the viewpoint of suppressing the occurrence of image defects, the control unit 200 controls the rotation speed of the developing roller 4A and the cleaning brush 7A according to the cleaning force of the cleaning blade 7B on the surface of the photoreceptor drum 1. Specifically, the control unit 200 increases the rotation speed of the developing roller 4A and the cleaning brush 7A in response to a decrease in the cleaning force of the cleaning blade 7B, while decreasing the rotation speed of the developing roller 4A and the cleaning brush 7A in response to an increase in the cleaning force of the cleaning blade 7B.

[0040] By increasing the rotation speed of the developing roller 4A, the number of contacts between the magnetic brush (carrier and toner bristles) formed on the developing roller 4A and the photoreceptor drum 1 can be increased, thereby increasing the refreshing effect of the photoreceptor drum 1 obtained through contact between the developing roller 4A and the photoreceptor drum 1. Similarly, by increasing the rotation speed of the cleaning brush 7A, the number of contacts between the cleaning brush 7A and the photoreceptor drum 1 can be increased, thereby increasing the refreshing effect of the photoreceptor drum 1 obtained through contact between the cleaning brush 7A and the photoreceptor drum 1. As a result, even if paper with very little paper dust or filler contained in the paper dust is used as the paper P for forming the image, and the cleaning power of the cleaning blade 7B decreases, the refreshing effect of the photoreceptor drum 1 that is lost due to this decrease is compensated for by the refreshing effect of the photoreceptor drum 1 obtained through contact between the developing roller 4A and the cleaning brush 7A and the photoreceptor drum 1. Therefore, the occurrence of image defects such as white spots (granular noise) in the photoreceptor drum diameter period can be suppressed.

[0041] Figure 4 is a flowchart showing an example of rotation control operation of the image forming apparatus 100 in this embodiment. The process in step S100 begins when the image forming apparatus 100 is powered on and started up.

[0042] First, the control unit 200 reads the paper setting information stored in the storage unit 172 (step S100). The paper setting information indicates the settings for the rotation speed of the developing roller 4A and the cleaning brush 7A for each type of paper P. For example, for paper P with very little paper dust or filler contained in the paper dust, it is estimated that the cleaning power of the cleaning blade 7B will be greatly reduced and the desired refresh effect cannot be obtained. Therefore, the execution of the refresh (strong) mode is set to increase the rotation speed of both the developing roller 4A and the cleaning brush 7A to compensate for the refresh effect of the photoreceptor drum 1 that cannot be obtained due to the reduction in cleaning power. Also, for paper with little paper dust or filler contained in the paper dust, it is estimated that the cleaning power of the cleaning blade 7B will be reduced and the desired refresh effect cannot be obtained. Therefore, the execution of the refresh (medium) mode is set to increase the rotation speed of the developing roller 4A to compensate for the refresh effect of the photoreceptor drum 1 that cannot be obtained due to the reduction in cleaning power.

[0043] Next, the control unit 200 refers to the paper setting information read in step S100 and determines whether or not the refresh (strong) mode is set for the paper P on which the image is formed (step S120). If the determination shows that the refresh (strong) mode is set (step S120, YES), the control unit 200 increases the rotation speed of the developing roller 4A (step S140).

[0044] Next, the control unit 200 increases the rotation speed of the cleaning brush 7A (step S160). Upon completion of step S160, the image forming apparatus 100 terminates the process shown in Figure 4.

[0045] On the other hand, if the execution of the refresh (strong) mode is not set (step S120, NO), the control unit 200 refers to the paper setting information read in step S100 and determines whether the execution of the refresh (medium) mode is set for the paper P on which the image is to be formed (step S180). If the result of the determination is that the execution of the refresh (medium) mode is set (step S180, YES), the control unit 200 increases the rotation speed of the developing roller 4A (step S200). Upon completion of the process in step S200, the image forming apparatus 100 terminates the process shown in Figure 4.

[0046] On the other hand, if the refresh (medium) mode is not set (step S180, NO), the image forming apparatus 100 does not use paper P with little paper dust or filler contained in the paper dust, and therefore terminates the process shown in Figure 4 without increasing the rotation speed of the developing roller 4A and the cleaning brush 7A.

[0047] Figure 5 is a flowchart showing a modified example of the rotation control operation of the image forming apparatus 100 in this embodiment. The process in step S300 begins when the image forming apparatus 100 is powered on and started up.

[0048] First, the control unit 200 reads the paper feed tray setting information stored in the storage unit 172 (step S300). The paper feed tray setting information indicates the settings for the rotation speed of the developing roller 4A and the cleaning brush 7A for each paper feed tray into which the paper P is fed. For example, for a paper feed tray into which paper P is fed with very little paper dust or filler contained in the paper dust, it is estimated that when paper P is fed using that paper feed tray, the cleaning power of the cleaning blade 7B will be greatly reduced and the desired refresh effect will not be obtained. Therefore, the execution of a refresh (strong) mode is set to increase the rotation speed of both the developing roller 4A and the cleaning brush 7A to compensate for the refresh effect of the photoreceptor drum 1 that is not obtained due to the reduction in cleaning power. Furthermore, for paper feed trays that feed paper P with little paper dust or filler contained in the paper dust, it is presumed that when paper P is fed using such a paper feed tray, the cleaning power of the cleaning blade 7B will decrease and the desired refresh effect will not be obtained. Therefore, a refresh (medium) mode is set to be executed, which increases the rotation speed of the developing roller 4A to compensate for the refresh effect of the photoreceptor drum 1 that is not obtained due to the decrease in cleaning power.

[0049] Next, the control unit 200 refers to the paper tray setting information read in step S300 and determines whether or not the refresh (strong) mode is set to execute on the paper tray for the paper P on which the image is to be formed (step S320). If the result of the determination is that the refresh (strong) mode is set to execute (step S320, YES), the control unit 200 increases the rotation speed of the developing roller 4A (step S340).

[0050] Next, the control unit 200 increases the rotation speed of the cleaning brush 7A (step S360). Upon completion of step S360, the image forming apparatus 100 terminates the process shown in Figure 5.

[0051] On the other hand, if the refresh (strong) mode is not set (step S320, NO), the control unit 200 refers to the paper setting information read in step S300 and determines whether the refresh (medium) mode is set for the paper tray that feeds the paper P for forming the image (step S380). If the determination shows that the refresh (medium) mode is set (step S380, YES), the control unit 200 increases the rotation speed of the developing roller 4A (step S400). Upon completion of the process in step S400, the image forming apparatus 100 terminates the process shown in Figure 5.

[0052] On the other hand, if the refresh (medium) mode is not set (step S380, NO), the image forming apparatus 100 does not feed paper P using a paper feed tray that feeds paper P with less paper dust or filler contained in the paper dust. Therefore, the image forming apparatus 100 terminates the process shown in Figure 5 without increasing the rotation speed of the developing roller 4A and the cleaning brush 7A.

[0053] Figure 6 is a flowchart showing a modified example of the rotation control operation of the image forming apparatus 100 in this embodiment. The process in step S500 begins when the image forming apparatus 100 is powered on and started up.

[0054] First, the control unit 200 acquires the detection result from the paper dust amount detection unit 180 (specifically, the light receiving sensor 186) (step S500).

[0055] Next, the control unit 200 determines the amount of paper dust from the detection result (paper dust concentration) obtained in step S500 and determines whether the amount of paper dust is less than the first threshold (step S520). If the determination result is that the amount of paper dust is less than the first threshold (step S520, YES), it is estimated that the cleaning power of the cleaning blade 7B will be greatly reduced and the desired refreshing effect will not be obtained, so the control unit 200 increases the rotation speed of the developing roller 4A (step S540).

[0056] Next, the control unit 200 increases the rotation speed of the cleaning brush 7A (step S560). Upon completion of step S560, the image forming apparatus 100 terminates the process shown in Figure 6.

[0057] On the other hand, if the amount of paper dust is not below the first threshold (step S520, NO), the control unit 200 determines whether the amount of paper dust, as determined from the detection result (paper dust concentration) obtained in step S500, is below the second threshold which is greater than the first threshold (step S580). If the determination shows that the amount of paper dust is below the second threshold (step S580, YES), the control unit 200 increases the rotation speed of the developing roller 4A because it is estimated that the cleaning power of the cleaning blade 7B will decrease and the desired refreshing effect cannot be obtained (step S600). Upon completion of the process in step S600, the image forming apparatus 100 terminates the process shown in Figure 6.

[0058] On the other hand, if the amount of paper dust is greater than the second threshold (step S580, NO), it is presumed that paper P with little paper dust or filler contained in the paper dust is not being used, and therefore the image forming apparatus 100 terminates the process in Figure 6 without increasing the rotation speed of the developing roller 4A and the cleaning brush 7A.

[0059] Figure 7 is a flowchart showing a modified example of the rotation control operation of the image forming apparatus 100 in this embodiment. The process in step S700 begins when the image forming apparatus 100 is powered on and started up.

[0060] First, the control unit 200 acquires the image reading result from the image reading unit 190 (step S700).

[0061] Next, the control unit 200 refers to the reading result obtained in step S700 and determines whether or not image defects such as white spots (granular noise) in the photoreceptor drum diameter period have occurred (step S720). If the determination result is that no image defects have occurred (step S720, NO), the image forming apparatus 100 terminates the process shown in Figure 7 without increasing the rotation speed of the developing roller 4A and the cleaning brush 7A.

[0062] On the other hand, if an image defect occurs (step S720, YES), the control unit 200 determines whether the frequency of image defects is above a threshold (step S740). If the determination shows that the frequency of image defects is above a threshold (step S740, YES), it is estimated that the cleaning force of the cleaning blade 7B has decreased significantly and the desired refreshing effect is not being obtained, so the control unit 200 increases the rotation speed of the developing roller 4A (step S760).

[0063] Next, the control unit 200 increases the rotation speed of the cleaning brush 7A (step S780). Upon completion of step S780, the image forming apparatus 100 terminates the process shown in Figure 7.

[0064] On the other hand, if the frequency of image defects is not above a threshold (step S740, NO), it is presumed that the cleaning force of the cleaning blade 7B has decreased and the desired refreshing effect has not been obtained, so the control unit 200 increases the rotation speed of the developing roller 4A (step S800). Upon completion of the process in step S800, the image forming apparatus 100 terminates the process shown in Figure 7.

[0065] As described in detail above, in this embodiment, the image forming apparatus 100 includes a photoreceptor drum 1 (image carrier) capable of carrying a toner image to be formed on the paper P, a cleaning blade 7B (cleaning unit) for cleaning foreign matter adhering to the surface of the photoreceptor drum 1, a developing roller 4A for forming a toner image on the photoreceptor drum 1, and a control unit that controls the rotational speed of the developing roller 4A according to the cleaning force of the cleaning blade 7B on the surface of the photoreceptor drum 1.

[0066] In this embodiment, the rotational speed of the developing roller 4A and cleaning brush 7A is controlled according to the cleaning force of the cleaning blade 7B on the surface of the photoreceptor drum 1. Specifically, the rotational speed of the developing roller 4A and cleaning brush 7A is increased in response to a decrease in the cleaning force of the cleaning blade 7B, while the rotational speed of the developing roller 4A and cleaning brush 7A is decreased in response to an increase in the cleaning force of the cleaning blade 7B.

[0067] By increasing the rotation speed of the developing roller 4A, the number of contacts between the magnetic brush (carrier and toner bristles) formed on the developing roller 4A and the photoreceptor drum 1 can be increased, thereby increasing the refreshing effect of the photoreceptor drum 1 obtained through contact between the developing roller 4A and the photoreceptor drum 1. Similarly, by increasing the rotation speed of the cleaning brush 7A, the number of contacts between the cleaning brush 7A and the photoreceptor drum 1 can be increased, thereby increasing the refreshing effect of the photoreceptor drum 1 obtained through contact between the cleaning brush 7A and the photoreceptor drum 1. As a result, even if paper with very little paper dust or filler contained in the paper dust is used as the paper P for forming the image, and the cleaning power of the cleaning blade 7B decreases, the refreshing effect of the photoreceptor drum 1 that is lost due to this decrease is compensated for by the refreshing effect of the photoreceptor drum 1 obtained through contact between the developing roller 4A and the cleaning brush 7A and the photoreceptor drum 1. Therefore, the occurrence of image defects such as white spots (granular noise) in the photoreceptor drum diameter period can be suppressed.

[0068] It should be noted that the above embodiments are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its gist or its main features. [Explanation of Symbols]

[0069] 1. Photoconductor drum 2. Charging device 4. Developing device 4A developing roller 5 Transfer transport path 6 Transfer belt 7 Cleaning device 7A Cleaning Brush 7B Cleaning Blade 9 Paper feed cassette 61 Driven roller 62 drive rollers 63 Backup Roller 90 Paper feed transport path Gate 91 92 Double-sided transport path 93 Reversal transport path 94 Re-feed conveyance path 100 Image forming apparatus 110 Manuscript Reading Unit 120 Operation display section 130 Image Processing Unit 135 Image writing section 140 Image forming unit 150 Conveying section 160 Fixing section 171 Communications Department 180 Paper dust amount detection unit 190 Image reading unit 200 Control Unit 201 CPU 202 ROM 203 RAM

Claims

1. An image carrier capable of supporting a toner image formed on paper, A cleaning unit for cleaning foreign matter adhering to the surface of the image carrier, A developing roller that forms the toner image on the image carrier, A control unit controls the rotation speed of the developing roller according to the cleaning force of the cleaning unit on the surface of the image carrier, A cleaning brush that rotatably contacts the surface of the image carrier and cleans foreign matter adhering to the surface of the image carrier, Equipped with, The control unit controls the rotation speed of the developing roller and cleaning brush according to the cleaning force. The control unit increases the rotational speed in response to the decrease in cleaning force, and decreases the rotational speed in response to the increase in cleaning force. The control unit is capable of executing a first mode in which the rotational speed of both the developing roller and the cleaning brush is increased, and a second mode in which the rotational speed of the developing roller is increased without increasing the rotational speed of the cleaning brush. Image forming apparatus.

2. The control unit executes the second mode when forming an image on paper with more paper dust than when the first mode is executed, or when forming an image on paper with more filler contained in the paper dust than when the first mode is executed. The image forming apparatus according to claim 1.

3. The paper dust removal brush roller, which removes paper dust adhering to the rollers that transport the paper, is equipped with a paper dust amount detection unit that detects the amount of paper dust by irradiating the paper dust scattered from the surface of the roller with a light source. The control unit executes the first mode when the detected amount of paper dust is less than a first threshold, and executes the second mode when the detected amount of paper dust is greater than the first threshold but less than a second threshold. The image forming apparatus according to claim 1.

4. The system includes an image reading unit that reads an image formed on the aforementioned paper, The control unit refers to the reading results obtained by the image reading unit and executes the first mode if it determines that the frequency of image defects is above a threshold, and executes the second mode if it determines that the frequency of image defects is below a threshold. The image forming apparatus according to claim 1.

5. A rotation control method for an image forming apparatus comprising: an image carrier capable of carrying a toner image formed on paper; a cleaning unit for cleaning foreign matter adhering to the surface of the image carrier; a developing roller for forming the toner image on the image carrier; a cleaning brush that rotatably contacts the surface of the image carrier and cleans foreign matter adhering to the surface of the image carrier; and a control unit that controls the rotation speed of the developing roller according to the cleaning force of the cleaning unit on the surface of the image carrier, wherein The rotational speed is increased in accordance with the decrease in the cleaning force, while the rotational speed is decreased in accordance with the increase in the cleaning force. The system can perform two modes: a first mode in which the rotational speed of both the developing roller and the cleaning brush is increased, and a second mode in which the rotational speed of the developing roller is increased without increasing the rotational speed of the cleaning brush. Rotation control method.

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