Image forming device

Abstract

To execute a reverse rotation mode for rotating an image carrier in a reverse direction efficiently without waste.SOLUTION: An image forming apparatus is provided with a photoreceptor drum 1 (image carrier) that rotates in a normal direction in an image formation period, and a cleaning blade 2a that removes untransferred toner attached to the surface of the photoreceptor drum 1. The image forming apparatus is further provided with image information acquisition means 7, 80 that acquire image information on an image formed on the surface of the photoreceptor drum 1, and sheet information acquisition means 80, 90 that acquire sheet information on a sheet P to which the image formed on the surface of the photoreceptor drum 1 is transferred. The image forming apparatus sets an execution condition when executing a reverse rotation mode for rotating the photoreceptor drum 1 in a reverse direction in a non-image formation period based on the image information acquired by the image information acquisition means 7, 80 and the sheet information acquired by the sheet information acquisition means 80, 90.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] Conventionally, in image forming devices such as copiers and printers, a technique has been known in which the image carrier is rotated in the reverse direction at a predetermined timing in order to remove adhesions such as paper dust trapped between the image carrier and the cleaning blade (see, for example, Patent Document 1).

[0003] More specifically, a cleaning blade installed in the cleaning device is in contact with the photosensitive drum (image carrier), and the cleaning blade removes untransferred toner from the photosensitive drum. However, when a sheet (paper) with a lot of paper dust is passed through, the paper dust separated from the sheet during the transfer process adheres to the photosensitive drum, and this paper dust accumulates between the photosensitive drum and the cleaning blade, causing poor cleaning. To solve this problem, the photosensitive drum is rotated in reverse at a predetermined timing when no image is being formed, to remove paper dust and other adhering matter caught between the photosensitive drum and the cleaning blade. Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional technology, the reverse rotation mode, which rotates the image carrier in the reverse direction, is uniformly executed at a predetermined timing regardless of whether paper dust or other adhesions are caught between the image carrier and the cleaning blade. As a result, the reverse rotation mode is sometimes executed unnecessarily even in conditions where no cleaning defects would occur.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide an image forming apparatus in which a reverse rotation mode in which an image carrier is rotated in the reverse direction is efficiently executed without waste. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes an image carrier that rotates in a forward direction during image formation, a cleaning device having a cleaning blade that contacts the surface of the image carrier to remove untransferred toner adhering to the surface of the image carrier, image information acquisition means that acquires image information related to an image formed on the surface of the image carrier, and sheet information acquisition means that acquires sheet information related to a sheet onto which the image formed on the surface of the image carrier is transferred, and sets execution conditions for executing a reverse rotation mode in which the image carrier rotates in a reverse direction during non-image formation, based on the image information acquired by the image information acquisition means and the sheet information acquired by the sheet information acquisition means. The sheet information is information regarding the amount of deposits that may move and adhere from the sheet to the surface of the image carrier during image formation, and the image information is information regarding the toner adhesion amount of the image formed on the surface of the image carrier. With the toner adhesion amount on the horizontal axis, a first threshold value M1 and a second threshold value M2 larger than the first threshold value M1 are predetermined, and with the amount of deposits on the vertical axis, a first threshold value N1 and a second threshold value N2 larger than the first threshold value N1 are predetermined. In a graph, when the coordinates of the toner adhesion amount and the amount of deposits are located within the region of a first region surrounded by the straight line connecting the first threshold value M1 and the first threshold value N1, the horizontal axis, and the vertical axis, the frequency of the reverse rotation mode is set to H1. When it is outside the region of the first region and within the region of a second region surrounded by the straight line connecting the second threshold value M2 and the second threshold value N2, the horizontal axis, and the vertical axis, the frequency of the reverse rotation mode is set to H2. When it is located outside the region of the second region, the frequency of the reverse rotation mode is set to H3, and a relationship of H1 < H2 < H3 holds. It is something. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an image forming apparatus in which a reverse rotation mode in which an image carrier is rotated in the reverse direction is efficiently executed without waste. [Brief explanation of the drawings]

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 100 will be described with reference to FIG. In Figure 1, 100 denotes a printer as an image forming device, 1 denotes a photosensitive drum on whose surface a toner image is formed, 6 denotes a process cartridge in which the photosensitive drum 1, a charging roller 4, a developing device 5, and a cleaning device 2 are integrated, and 7 denotes an exposure unit (writing unit) that irradiates the photosensitive drum 1 with exposure light L based on image information input from an input device such as a personal computer 200 (see Figure 3). Also, 9 indicates a transfer roller that transfers the toner image carried on the surface of the photosensitive drum 1 onto a sheet P transported to the transfer nip portion (transfer position), and 12 indicates a paper feed device (paper feed cassette) that stores sheets P such as paper. Also, 16 denotes a registration roller (timing roller) that transports the sheet P toward the transfer nip portion where the photosensitive drum 1 and the transfer roller 9 abut, 20 denotes a fixing device that fixes the unfixed image on the sheet P, 21 denotes a fixing roller installed in the fixing device 20, 22 denotes a pressure roller installed in the fixing device 20, and 90 denotes an operation display panel for displaying information related to the printing operation (image forming operation) and for performing operations.

[0011] Here, a charging roller 4, a developing device 5, a cleaning device 2, etc. are arranged around the photosensitive drum 1. These components (photosensitive drum 1, charging roller 4, developing device 5, and cleaning device 2) are integrated as a process cartridge 6, which is detachably (replaceably) installed in the image forming apparatus main body 100. When the process cartridge 6 reaches a predetermined replacement cycle or when maintenance is performed, it is removed from the image forming apparatus main body 100 and replaced with a new one (or one that has been maintained).

[0012] Referring to FIG. 1, the operation of image forming apparatus 100 during normal image formation will be described. First, when image information is sent from an input device such as a personal computer 200 (see Figure 3) to the exposure unit 7 of the image forming apparatus 100, exposure light L (laser light) based on the image information is emitted from the exposure unit 7 toward the surface of the photosensitive drum 1. Meanwhile, the photosensitive drum 1 receives drive from a drive motor 70 (see FIG. 3) installed in the image forming apparatus main body 100 and rotates in the forward direction (the direction of the arrow in FIGS. 1 to 3, i.e., clockwise). First, the surface of the photosensitive drum 1 is uniformly charged at the position facing the charging roller 4 (charging process). In this way, a charging potential (approximately −900 V) is formed on the photosensitive drum 1. Thereafter, the charged surface of the photosensitive drum 1 reaches the position irradiated with the exposure light L. Then, the potential of the portion irradiated with the exposure light L becomes a latent image potential (approximately 0 to −100 V), and an electrostatic latent image is formed on the surface of the photosensitive drum 1 (exposure process).

[0013] Thereafter, the surface of the photosensitive drum 1 on which the electrostatic latent image has been formed reaches a position facing the developing device 5. Then, toner is supplied from the developing device 5 onto the photosensitive drum 1, and the latent image on the photosensitive drum 1 is developed to form a toner image (this is the developing process). Thereafter, the surface of the photosensitive drum 1 after the development process reaches a transfer nip portion (transfer position) with the transfer roller 9. Then, at the transfer nip portion with the transfer roller 9, a transfer bias (a bias with a polarity different from that of the toner) is applied from a power supply unit to the transfer roller 9, whereby the toner image formed on the photosensitive drum 1 is transferred onto the sheet P conveyed by the registration roller 16 (transfer process).

[0014] After the transfer process, the surface of the photosensitive drum 1 reaches a position facing the cleaning device 2. At this position, untransferred toner remaining on the photosensitive drum 1 is mechanically removed by a cleaning blade 2a (see FIGS. 2 and 3) and collected in the cleaning device 2 (this is the cleaning process). Thus, a series of image forming processes on the photosensitive drum 1 is completed.

[0015] On the other hand, the sheet P conveyed to the transfer nip portion between the photosensitive drum 1 and the transfer roller 9 operates as follows. First, the uppermost sheet of the sheets P stored in the sheet feeding device 12 is fed by the sheet feeding roller 15 toward the conveyance path. Thereafter, the sheet P reaches the position of the registration rollers 16. Then, the sheet P that has reached the position of the registration rollers 16 is transported toward the transfer nip portion (the position where the transfer roller 9 and the photosensitive drum 1 contact each other) in time to be aligned with the image formed on the photosensitive drum 1.

[0016] After the transfer process, the sheet P passes through the transfer nip portion (transfer roller 9) and then travels through a conveying path to reach the fixing device 20. The sheet P that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, where the image is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22. The sheet P with the fixed image is sent out from between the fixing roller 21 and the pressure roller 22 (the fixing nip portion), and then discharged from the image forming apparatus main body 100 and placed on a paper output tray. In this way, a series of image forming processes is completed.

[0017] Next, the process cartridge 6 in the image forming apparatus will be described in more detail with reference to FIG. As shown in FIG. 2, the process cartridge 6 is made up of a photosensitive drum 1 as an image carrier, a charging roller 4 (charging device), a developing device 5, a cleaning device 2, and the like. The photosensitive drum 1 serving as an image carrier is a negatively charged organic photosensitive body, and receives a driving force from a drive motor 70 (see Figure 3) installed on the device main body 100 side, and is driven to rotate in the clockwise direction (positive direction) in Figure 2.

[0018] The charging roller 4 (charging device) is an elastic roller having a medium-resistance foamed urethane layer formed on a core metal, the foamed urethane layer being made of a mixture of urethane resin, carbon black as conductive particles, a sulfide agent, a foaming agent, etc. The medium-resistance layer of the charging roller 4 can be made of rubber materials such as urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, or isoprene rubber with conductive materials such as carbon black or metal oxide dispersed therein to adjust the resistance, or foamed versions of these materials. In this embodiment, the charging roller 4 is configured to contact the photosensitive drum 1, but it can also be configured so that the charging roller 4 does not contact the photosensitive drum 1.

[0019] The cleaning device 2 is equipped with a cleaning blade 2a that comes into sliding contact with the photosensitive drum 1, and mechanically removes and collects untransferred toner from the photosensitive drum 1. The cleaning blade 2a is a generally plate-shaped member made of an elastic material such as urethane rubber, and its free end comes into contact with the photosensitive drum 1 at a predetermined contact pressure and angle. 2 and 3, the cleaning device 2 is provided with an entrance seal 2b as a flexible sheet member that abuts against the photosensitive drum 1 (image carrier) upstream of the cleaning blade 2a in the rotation direction (upstream of the forward rotation direction). The entrance seal 2b (flexible sheet member) can be a substantially rectangular sheet member made of a resin material such as polyurethane and having a thickness of approximately 0.05 to 0.15 mm. The entrance seal 2b (flexible sheet member) has a free end that abuts against the photosensitive drum 1 and a fixed end that is attached to the case of the cleaning device 2. The provision of the entrance seal 2b reduces the risk of untransferred toner collected inside the cleaning device 2 leaking out of the device.

[0020] The developing device 5 is arranged so that a developing roller 51 serving as a developer carrier comes into contact with the photosensitive drum 1 with a predetermined pressure, and a developing area is formed between the two members 1 and 51 (developing nip). The developing device 5 contains toner T (a non-magnetic or magnetic one-component developer) serving as a developer. The developing device 5 develops the electrostatic latent image formed on the photosensitive drum 1 (to form a toner image).

[0021] The developing device 5 will be described in detail below with reference to FIG. 2, developing device 5 in this embodiment is a contact one-component developing device, and is installed as a process cartridge 6 together with other image forming members 1, 2, and 4 in an apparatus main body 100 so as to be detachable (replaceable). The developing device 5 is composed of a developing roller 51 as a developer carrier, a supply roller 52 as a developer supply member, a doctor blade 53 as a developer regulating member, an agitating member 54 for agitating the toner T in the device, and the like.

[0022] The developing roller 51 (developer carrier) is disposed so as to come into contact with the photosensitive drum 1, and rotates in a predetermined direction (counterclockwise in FIG. 2) while carrying toner, supplying the toner to the electrostatic latent image formed on the photosensitive drum 1. The developing roller 51 may be one having a roller portion made of an elastic material mounted on a rotating shaft portion (core metal) made of a conductive metal material such as stainless steel. A predetermined voltage (developing bias) is applied to the developing roller 51 from a power supply portion (not shown), which promotes electrostatic transfer of toner from the developing roller 51 to the photosensitive drum 1. The supply roller 52 (developer supply member) is disposed so as to be in sliding contact with the developing roller 51, and supplies toner to the developing roller 51. The supply roller 52 has a core metal on which a conductive foamed polyurethane layer (having an electrical resistance of 10 3 ~10 14 The supply roller 52 also has the function of removing from the developing roller 51 the toner on the developing roller 51 that has not been used in the developing process in the developing area with the photosensitive drum 1. The doctor blade 53 (developer regulating member) is disposed so that its tip contacts the outer peripheral surface of the developing roller 51 at a predetermined angle with a pressure of about 10 to 100 N / m, and regulates the amount of toner carried on the developing roller 51. In other words, the doctor blade 53 contacts the developing roller 51 to form a thin layer of toner carried on the developing roller 51. The doctor blade 53 can be a thin plate-like member made of a metal material such as stainless steel.

[0023] The developing device 5 configured as above operates as follows during a normal developing process. First, a portion of the toner contained in the developing device 5 is supplied to and carried by the supply roller 52. The toner carried by the supply roller 52 is frictionally charged at the contact point (contact position) with the developing roller 51, and then moves onto the developing roller 51 and is carried thereon. The toner carried on the developing roller 51 is then thinned, made uniform, and frictionally charged at the contact position with the doctor blade 53, before reaching the position facing the photosensitive drum 1 (development area). At this position, the toner is attracted to the latent image formed on the photosensitive drum 1 by the electric field (development electric field) formed in the development area. The electric field (development electric field) in the development area is formed by a predetermined voltage (development bias) applied to the development roller 51 by the development power supply and the surface potential (latent image potential) formed on the surface of the photosensitive drum 1 by the charging process and the exposure process.

[0024] The characteristic configuration and operation of image forming apparatus 100 according to this embodiment will be described in detail below. As previously described with reference to FIGS. 1 to 3, the photosensitive drum 1 and the cleaning device 2 are provided. The photosensitive drum 1 functions as an image carrier that rotates in the forward direction (the direction of the solid arrow (clockwise) in FIGS. 2 and 3) during image formation (printing operation). The cleaning device 2 is provided with a cleaning blade 2a that contacts the surface of the photosensitive drum 1 to remove untransferred toner adhering to the surface of the photosensitive drum 1, and an entrance seal 2b as a flexible sheet member that contacts the photosensitive drum 1 upstream of the cleaning blade 2a in the forward rotation direction. In this embodiment, the photosensitive drum 1 can be rotated in both the forward direction (the direction of the solid arrow in FIG. 3) and the reverse direction (the direction of the dashed arrow in FIG. 3) by controlling the drive motor 70 by the control unit 80. The drive motor 70 that drives the photosensitive drum 1 to rotate is a motor that can rotate forward and backward.

[0025] Here, the image forming apparatus 100 in this embodiment is provided with an image information acquiring means for acquiring image information relating to the image (toner image) formed on the surface of the photosensitive drum 1 (image carrier). Specifically, the "image information" acquired by the image information acquisition means is information relating to the "toner adhesion amount (development amount)" and "width direction position" of the image formed on the surface of the photosensitive drum 1. In addition, in this embodiment, the control unit 80 and the exposure unit 7 function as the image information acquisition means.

[0026] In this embodiment, this "toner adhesion amount" is calculated from the number of dots of the image formed on the surface of the photosensitive drum 1. This is because the "toner adhesion amount (development amount)" on the photosensitive drum 1 is proportional to the number of dots of the image. Specifically, the control unit 80 determines the number of dots in the latent image (image) (and the "widthwise position" described below) from the writing data of the exposure unit 7 (data for forming a latent image on the photosensitive drum 1).

[0027] It is preferable that the information regarding the "toner adhesion amount" be adjusted based on the process conditions during image formation (such as the magnitude of the development bias applied to the development roller 51). In particular, when process control is executed during warm-up of the device to adjust the process conditions, or when the user sets a preferred image density and adjusts the process conditions, it is preferable to correct (adjust) the image information ("toner adhesion amount") based on the adjusted process conditions. This is because even if the number of image dots is the same, the amount of toner adhesion (development amount) varies depending on the process conditions. Specifically, the amount of toner adhesion on the photosensitive drum 1 varies even for the same number of image dots due to factors such as environmental fluctuations and the state of the toner (developer) in the developing device 5. Therefore, process control is performed during warm-up, etc., to adjust the process conditions so that the desired amount of toner adhesion is obtained. The process conditions are also adjusted appropriately based on the user's image density setting. If the process conditions are adjusted in this way so that the amount of toner adhesion does not change for the same number of image dots, no correction is required for the "amount of toner adhesion" (image information) in the image information. However, if the adjustment is to increase the amount of toner adhesion, a correction is made to increase the "amount of toner adhesion" in the image information, and if the adjustment is to decrease the amount of toner adhesion, a correction is made to decrease the "amount of toner adhesion." By performing such control, even when the process conditions are adjusted appropriately, accurate image information can be obtained according to the adjusted contents.

[0028] In addition, in this embodiment, the "widthwise position" refers to one or more of the multiple regions W1 to W3 (see Figure 5) divided in the widthwise direction (the direction perpendicular to the paper surface of Figure 3, and the left-right direction in Figure 5). Specifically, as shown in Fig. 5, the image area (the maximum widthwise range in which an image can be formed) is divided into three areas W1 to W3. When an image G1 as shown in Fig. 5(A) is formed, all three areas W1 to W3 are recognized as being at "widthwise positions" by the image information acquisition means. In contrast, when an image G2 as shown in Fig. 5(B) is formed, only area W1 at one widthwise end is recognized as being at "widthwise position" by the image information acquisition means. In this embodiment, the image area is divided into three areas W1 to W3, but the image area can also be divided into two or four or more areas. Furthermore, in this embodiment, the "number of image dots (toner adhesion amount)" and "widthwise position" are obtained from the writing data of the exposure unit 7, but the number of image dots (toner adhesion amount) can also be obtained based on image information input to the control unit 80 from an input device such as the personal computer 200 (or a server).

[0029] Furthermore, the image forming apparatus 100 in this embodiment is provided with a sheet information acquiring means for acquiring sheet information about the sheet P onto which the image (toner image) formed on the surface of the photosensitive drum 1 (image carrier) is transferred. In detail, this "sheet information" is information regarding the amount of adhesion material X (mainly paper dust, additives, etc.) that may migrate from the sheet P to the surface of the photosensitive drum 1 (image carrier) and adhere thereto during image formation. As shown in Figure 3, this adhesion X is a foreign substance that is likely to accumulate (be caught) on the edge portion of the cleaning blade 2a (the contact portion between the cleaning blade 2a and the photosensitive drum 1), and can cause poor cleaning.

[0030] Specifically, in this embodiment, the sheet information acquisition means acquires "sheet information" linked to the input brand of sheet P. This is because the amount of attached material, such as paper dust and additives, varies depending on the brand (type) of sheet P. For example, even recycled paper, which is generally considered to have a lot of paper dust, differs between product a made by company A, product a' made by company A, and product b made by company B in the amount of paper dust and additives (amount of attached material). Therefore, the relationship between these sheet brands and the amount of attached material is converted into data and stored in advance in the memory of the control unit 80. Then, when the user operates the operation display panel 90 to input the sheet brand, the control unit 80 grasps the sheet information (amount of attached material) of the sheet P being passed. Therefore, the operation display panel 90 and the control unit 80 function as sheet information acquisition means.

[0031] In this embodiment, "sheet information (amount of adhesion)" is obtained in association with the brand of sheet P, but it is also possible to directly detect the amount of adhesion (the amount of paper dust, additives, etc. that separates from sheet P) on sheet P being transported to the transfer position, and obtain "sheet information (amount of adhesion)" based on the detection results. In this embodiment, the relationship between the sheet brand and the amount of adhesion is stored in advance in a storage unit of the control unit 80 as data, and the storage unit is accessed based on input information about the sheet brand. Alternatively, an input device such as the personal computer 200 or a server in which the relationship between the sheet brand and the amount of adhesion is stored as data may be accessed based on input information about the sheet brand.

[0032] Here, the image forming apparatus 100 in this embodiment sets (adjusts) the execution conditions for executing a "reverse rotation mode" in which the photosensitive drum 1 (image carrier) rotates in the reverse direction when not forming an image (when normal printing operations are not being performed, such as before printing starts, after printing ends, or between sheets during continuous paper feed), based on the image information acquired by the image information acquisition means 7, 80 and the sheet information acquired by the sheet information acquisition means 80, 90.

[0033] Referring to FIG. 3, the deposits X that have accumulated on the edge of the cleaning blade 2a are removed from the edge by rotating the photosensitive drum 1 in reverse (by executing the reverse rotation mode), thereby reducing the occurrence of cleaning failures. However, the amount (degree of retention) of the deposits X that accumulate on the edge of the cleaning blade 2a increases (deteriorates) as sheets P containing a lot of paper dust and additives are passed through, and untransferred toner easily slips through the accumulated areas, causing poor cleaning. Furthermore, the amount of deposits X remaining on the edge of the cleaning blade 2a increases (becomes worse) as the amount of toner attached to the image formed on the photosensitive drum 1 increases, and untransferred toner easily slips through the accumulated portion, causing cleaning defects. When cleaning defects occur in this way, abnormal images with vertical streaks appear. On the other hand, even if the amount of adhesion X (degree of adhesion) remaining on the edge of the cleaning blade 2a is the same, when the amount of toner adhesion of the image on the photosensitive drum 1 is large, the amount of untransferred toner that slips through the area where the adhesion X has accumulated will be greater than when the amount of toner adhesion is small, and the degree of cleaning failure (vertical streak image) will also be worse. Furthermore, even if the amount of toner adhesion throughout the image is the same, when image G2 is formed locally in a portion of the image area (area W1) as shown in FIG. 5(B), compared to when image G1 is formed over the entire image area (areas W1 to W3) as shown in FIG. 5(A), as the amount of toner adhesion per unit area increases, the amount of untransferred toner that slips through the area where adhesion X has accumulated increases, and the degree of cleaning failure (vertical streak image) also worsens.

[0034] In this way, the degree of cleaning failure (vertical streak image) varies greatly not only depending on the amount of material attached to the sheet P (amount of paper dust, additives, etc.), but also on the amount of toner attached to the image formed on the photosensitive drum 1 and its widthwise position. However, if the reverse rotation mode is uniformly executed at a predetermined timing, the reverse rotation mode may be executed unnecessarily even in a state where no cleaning failure would occur, or the reverse rotation mode may not be executed sufficiently even in a state where a cleaning failure would occur. In contrast to this, in this embodiment, the conditions for executing the reverse rotation mode are set based on the sheet information and image information, so that the reverse rotation mode can be executed efficiently without waste.

[0035] In detail, referring to Figure 4, in this embodiment, when the amount of adhesion is large in the sheet information acquired by the sheet information acquisition means 80, 90, the frequency of the reverse rotation mode is controlled to be higher than when the amount of adhesion is small. In addition, in this embodiment, when the amount of toner adhesion (development amount) of the image on the photosensitive drum 1 is large in the image information acquired by the image information acquisition means 7, 80, the frequency of the reverse rotation mode is controlled to be higher than when the amount of toner adhesion is small. Furthermore, in the image information acquired by the image information acquisition means 7, 80, when the width direction position W1 of the image G2 having the predetermined amount of toner adhesion Z on the photosensitive drum 1 is localized (see FIG. 5(B)), the frequency of the reverse rotation mode is controlled to be higher than when the width direction positions W1 to W3 of the image G1 having the predetermined amount of toner adhesion Z are not localized. Specifically, in this embodiment, when the area W1 where the image G2 is formed is small as shown in FIG. 5(B), the frequency of the reverse rotation mode is controlled to be higher than when the areas W1 to W3 where the image G1 is formed are large as shown in FIG. 5(A). In this specification, the "frequency" of the reverse rotation mode is defined as the proportion of time that the reverse rotation mode is executed in a certain period of time. Therefore, if the reverse rotation mode is executed for a long time or if the reverse rotation mode is executed many times in a certain period of time, the "frequency" of the reverse rotation mode will be high.

[0036] Specifically, in this embodiment, as shown in FIG. 4, two thresholds M1 and M2 are set with the amount of toner adhesion of the image on the photosensitive drum 1 as the horizontal axis, and two thresholds N1 and N2 are set with the amount of adhesion of the sheet P (amount of paper dust and additives) as the vertical axis. When the image information and sheet information fall within the region connecting the threshold M1 on the horizontal axis and the threshold N1 on the vertical axis, a slightly severe cleaning failure occurs, and the reverse rotation mode is performed for a fixed period of time once every 100 printed sheets. On the other hand, when the image information and sheet information fall outside the region connecting the threshold M1 on the horizontal axis and the threshold N1 on the vertical axis, but within the region connecting the threshold M2 on the horizontal axis and the threshold N12 on the vertical axis, a moderate cleaning failure occurs, and the reverse rotation mode is performed for a fixed period of time once every 50 printed sheets. Furthermore, when the area is outside the area connecting the threshold value M2 on the horizontal axis and the threshold value N2 on the vertical axis, the most severe cleaning failure occurs at "Level 3," and the reverse rotation mode is performed for a certain period of time at a frequency of once every 10 printed sheets.

[0037] In this embodiment, the frequency of the reverse rotation mode (execution frequency) is determined based on the image information and the sheet information. Time The interval (number of prints) for executing the reverse rotation mode once was set based on the image information and sheet information. However, the execution conditions for the reverse rotation mode set based on the image information and sheet information are not limited to this, and can also be at least one of the execution time of the reverse rotation mode, the number of times it is executed, the execution timing (before printing starts, after printing ends, between sheets, etc.), and the number of rotations (the rotation speed of the photosensitive drum 1). As described above, the greater the "execution time" and "number of executions" of the reverse rotation mode, the greater the effect of reducing cleaning defects. Furthermore, by increasing the "number of rotations" of the photosensitive drum 1, the time required for reverse rotation mode is shortened, thereby reducing the user's waiting time. Therefore, when the frequency of reverse rotation mode exceeds a predetermined value, control can be performed to increase the "number of rotations." In addition, regarding the "execution timing," it is possible to control the reverse rotation mode depending on the level at which poor cleaning occurs (see levels 1 to 3 in Figure 4), such that if the level is high, the reverse rotation mode is executed before the printing operation begins, and if the level is low, the reverse rotation mode is executed after the printing operation is completed.

[0038] In this embodiment, the reverse rotation mode can also be a control mode in which the photosensitive drum 1 (image carrier) is alternately rotated in the reverse direction and the forward direction. At this time, the time for which the photosensitive drum 1 is rotated in the reverse direction and the time for which the photosensitive drum 1 is rotated in the forward direction may be the same or different. In this way, by rotating the photosensitive drum 1 alternately in the reverse direction and the forward direction, the deposits X caught in the edge portion of the cleaning blade 2a are more easily removed than when the photosensitive drum 1 is rotated only in the reverse direction.

[0039] Also, referring to Figure 3, in this embodiment, the reverse rotation mode can also be a control mode in which the photosensitive drum 1 rotates in the reverse direction so that the position of the photosensitive drum 1 (image carrier) that was in contact with the cleaning blade 2a does not reach the contact position of the entrance seal 2b, which is a flexible sheet member. In other words, in this case, the photosensitive drum 1 does not rotate in the reverse direction beyond the angle θ in FIG. 3 in the reverse rotation mode. By controlling in this way, it is possible to prevent the problem that the deposit X caught in the edge portion of the cleaning blade 2a reaches the edge portion of the inlet seal 2b in the reverse rotation mode and damages the edge portion.

[0040] An example of control relating to the reverse rotation mode performed in image forming apparatus 100 according to the present embodiment will be described below with reference to FIG. 6, first, information about the brand of sheet used during printing is acquired (step S1). Then, based on the acquired information, the amount of adhesion (amount of paper dust and additives) of the sheet P to be used is determined by comparing it with data stored in the control unit 80 (step S2). That is, the sheet information (amount of adhesion) is acquired by the sheet information acquisition means 80, 90. Then, the image information acquiring means 7, 80 acquires image information (information relating to the amount of toner adhesion and width direction position of the image formed on the photosensitive drum 1) (step S3). Then, based on the sheet information acquired in steps S1 and S2 and the image information acquired in step S3, the execution conditions for the reverse rotation mode are determined (set) (step S4), and this flow ends. Thereafter, the reverse rotation mode is performed based on the execution conditions determined in step S4.

[0041] As described above, image forming apparatus 100 in this embodiment is provided with photosensitive drum 1 (image carrier) that rotates in the forward direction during image formation, and cleaning device 2 equipped with cleaning blade 2a that contacts the surface of photosensitive drum 1 to remove untransferred toner adhering to the surface of photosensitive drum 1. Also provided are image information acquisition means 7, 80 that acquire image information related to the image formed on the surface of photosensitive drum 1, and sheet information acquisition means 80, 90 that acquire sheet information related to sheet P onto which the image formed on the surface of photosensitive drum 1 is transferred. Based on the image information acquired by image information acquisition means 7, 80 and the sheet information acquired by sheet information acquisition means 80, 90, execution conditions are set for executing a reverse rotation mode in which photosensitive drum 1 rotates in the reverse direction during non-image formation. This allows the reverse rotation mode in which the photosensitive drum 1 is rotated in the reverse direction to be executed efficiently without waste.

[0042] In this embodiment, the present invention is applied to a case where the photosensitive drum 1 (image carrier), the developing device 5, the charging roller 4, and the cleaning device 2 are integrated together to form a process cartridge 6. However, the application of the present invention is not limited to this, and the present invention can also be applied to a case where some or all of these components 1, 2, 4, and 5 are configured as a single unit that is detachably attached to the image forming apparatus main body 100. Even in such a case, the same effects as those of the present embodiment can be obtained. In this application, a "process cartridge" is defined as a unit that is detachably installed in the image forming apparatus main body, and that integrates at least one of a charging device that charges an image carrier, a developing device that develops a latent image formed on the image carrier, and a cleaning device that cleans the image carrier, with the image carrier.

[0043] In this embodiment, the present invention is applied to an image forming apparatus 100 equipped with a developing device 5 of a one-component development system that performs a development process using a one-component developer (toner). However, the present invention can also be applied to an image forming apparatus equipped with a developing device of a two-component development system that performs a development process using a two-component developer (developer consisting of toner and carrier). In such cases, the same effect as that of this embodiment can be obtained.

[0044] Furthermore, in this embodiment, the present invention is applied to a monochrome image forming apparatus 100 in which a toner image is transferred to a sheet P by one image forming unit (process cartridge 6). However, the present invention can also be applied to a color image forming apparatus in which a toner image is primarily transferred to an intermediate transfer body such as an intermediate transfer belt by multiple image forming units, and then the toner image is secondarily transferred from the intermediate transfer body to a sheet. In that case, the present invention can also be applied to a reverse rotation mode in which an intermediate transfer body serving as an image carrier rotates in the reverse direction in order to reduce cleaning defects caused by a cleaning device that cleans the surface of the intermediate transfer body serving as an image carrier. In such a case, the same effect as that of this embodiment can be obtained.

[0045] It is clear that the present invention is not limited to the present embodiment, and that within the scope of the technical concept of the present invention, the present embodiment may be modified as appropriate in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components may be any number, position, shape, etc. that is suitable for implementing the present invention.

[0046] In this specification, the term "sheet" is defined to include not only ordinary paper (sheet of paper), but also all sheet-like recording media such as coated paper, label paper, OHP sheets, and film. [Explanation of symbols]

[0047] 1 Photosensitive drum (image carrier), 2 cleaning devices, 2a cleaning blade (cleaning member), 2b inlet seal (flexible sheet member), 7 exposure unit (image information acquisition means), 70 drive motor, 80 control unit (image information acquisition means, sheet information acquisition means), 90 Operation display panel (seat information acquisition means), 100 Image forming apparatus (image forming apparatus main body), T Toner, X Deposits. [Prior art documents] [Patent documents]

[0048] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-90820

Claims

1. an image carrier that rotates in a forward direction during image formation; a cleaning device including a cleaning blade that contacts the surface of the image carrier to remove untransferred toner adhering to the surface of the image carrier; image information acquiring means for acquiring image information relating to an image formed on the surface of the image carrier; a sheet information acquiring means for acquiring sheet information relating to a sheet onto which an image formed on the surface of the image carrier is to be transferred; Equipped with setting an execution condition for executing a reverse rotation mode in which the image carrier is rotated in a reverse direction during non-image formation based on the image information acquired by the image information acquisition means and the sheet information acquired by the sheet information acquisition means; The sheet information is information about an amount of adhering matter that may move from the sheet to the surface of the image carrier and adhere to the surface during image formation, the image information is information about the amount of toner adhesion of an image formed on the surface of the image carrier, In a graph in which a first threshold M1 and a second threshold M2 larger than the first threshold M1 are predefined with the amount of toner adhesion as the horizontal axis, and a first threshold N1 and a second threshold N2 larger than the first threshold N1 are predefined with the amount of adhesion as the vertical axis, the coordinates of the amount of toner adhesion and the amount of adhesion are When the rotation speed is within a first region surrounded by a line connecting the first threshold value M1 and the first threshold value N1, the horizontal axis, and the vertical axis, the frequency of the reverse rotation mode is set to H1, When the rotational speed is outside the first region and within a second region surrounded by a line connecting the second threshold value M2 and the second threshold value N2, the horizontal axis, and the vertical axis, the frequency of the reverse rotation mode is set to H2, When the rotational speed is outside the second region, the frequency of the reverse rotation mode is set to H3. H1<H2<H3 The image forming apparatus is characterized in that the following relationship holds:

2. The image forming device described in Claim 1, characterized in that the sheet information acquisition means acquires the sheet information by linking it to the brand of the input sheet.

3. An image forming apparatus as described in claim 1 or claim 2, characterized in that the image information is information regarding the amount of toner adhesion and the widthwise position of the image formed on the surface of the image carrier.

4. An image forming apparatus as described in Claim 3, characterized in that when the widthwise position of the image with a predetermined amount of toner adhesion is localized, the frequency of the reverse rotation mode is controlled to be higher than when the widthwise position of the image with a predetermined amount of toner adhesion is not localized.

5. The amount of toner adhesion is determined from the number of dots of an image formed on the surface of the image carrier, 5. The image forming apparatus according to claim 3, wherein the widthwise position is one or more of a plurality of regions divided in the widthwise direction.

6. The image forming apparatus described in Claim 5, characterized in that the information regarding the amount of toner adhesion is adjusted based on process conditions during image formation.

7. An image forming apparatus as described in any one of claims 1 to 6, characterized in that the execution condition is at least one of the execution time, number of executions, execution timing, and rotation speed of the reverse rotation mode.

8. An image forming apparatus as described in any one of claims 1 to 7, characterized in that the reverse rotation mode is a control mode in which the image carrier alternates between rotating in the reverse direction and rotating in the forward direction.

9. The cleaning device includes a flexible sheet member that contacts the image carrier upstream of the cleaning blade in a forward rotation direction, The image forming apparatus according to any one of claims 1 to 8, characterized in that the reverse rotation mode is a control mode in which the image carrier rotates in the reverse direction so that the position of the image carrier that was in contact with the cleaning blade does not reach the contact position of the flexible sheet member.

Images