JP2007199129A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a polishing process which is necessary and enough for the periphery of an a-Si photoreceptor according to a status while restraining a waste of consumption of toner during a polishing mode for the periphery of the a-Si photoreceptor. <P>SOLUTION: In the polishing mode for the photoreceptor drum 101, toner is supplied to the periphery of the photoreceptor drum so as to satisfy a condition expressed by (VO-Vdc1)>(VO-Vdc2), wherein VO is the surface potential when the periphery of the photoreceptor drum 101 is not exposed, Vdc1 is a DC bias voltage applied to a developing roller 1031 in a developing section 103 in a regular image formation mode, and Vdc2 is a bias voltage applied to the developing roller 1031 in the developing section103 in the polishing mode for the photoreceptor drum 101. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer provided with a photoconductor, and more particularly to an image forming apparatus configured so that a peripheral surface of the photoconductor can be cleaned by polishing.

  Usually, in an image forming apparatus such as a copying machine or a printer, a charging process is performed on the peripheral surface of the photosensitive member by discharging with a charger performed in the vicinity of the peripheral surface of the photosensitive member (photosensitive drum) rotating around an axis. It is made to give. Light based on image information is irradiated from the exposure device to the peripheral surface of the photoreceptor subjected to the charging process, and an electrostatic latent image is formed by disappearance of the charged state of the portion irradiated with the light. By supplying toner from the developing device toward the electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive member, and the toner image is transferred to a sheet.

  By the way, when an amorphous silicon (a-Si) layer having a characteristic that it is extremely smooth and has high hardness but high hygroscopicity is formed on the peripheral surface of the photoreceptor (hereinafter, such a layer is formed). The photosensitive member is referred to as an a-Si photosensitive member), and water-soluble discharge products (for example, oxides of NOx, ozone, etc.) generated by the discharge of the charger are highly hygroscopic, so that the peripheral surface of the a-Si photosensitive member It becomes easy to adhere to.

  When this discharge product remains attached to the peripheral surface of the a-Si photosensitive member, a so-called “image flow” occurs in which the toner image on the peripheral surface of the a-Si photosensitive member flows laterally. This causes a problem peculiar to the a-Si photoreceptor. Incidentally, when a normal organic photoreceptor (OPC) is used, the peripheral surface of the photoreceptor is easily scraped by sliding contact with the following polishing roller even if a discharge product adheres, so that a new surface is easily formed. Such problems are unlikely to occur.

  Therefore, conventionally, a polishing roller is provided so that the peripheral surface is in contact with the peripheral surface of the a-Si photosensitive member, and the periphery of the a-Si photosensitive member is driven by the abrasive contained in the toner by driving rotation of the polishing roller. Polishing the surface is periodically performed, and those described in Patent Documents 1 to 3 are known as such polishing processing.

  First, in the device disclosed in Patent Document 1, the polishing roller is forcibly driven during the operation in the polishing mode, while the polishing roller is driven by the photosensitive member during the normal image forming mode. It is described in Patent Document 1 that it is possible to prevent the occurrence of jitter (temporal fluctuation) during image formation while ensuring the cleaning process of the peripheral surface of the photoreceptor.

  Also, the one disclosed in Patent Document 2 is based on the temperature and humidity of the formation time of a solid image (a so-called solid image having the same color on the entire surface) to be formed on the peripheral surface of the a-Si photoconductor during the polishing mode operation. Various changes are made. It is described in Patent Document 2 that a polishing process suitable for the amount of the discharge product according to the temperature and humidity is realized.

Further, in Patent Document 3, not only the solid image formation time to be formed on the peripheral surface of the a-Si photosensitive member during operation in the polishing mode but also the number of repetitions of solid image formation is changed by temperature and humidity. Yes. Patent Document 3 discloses that this makes it possible to obtain necessary and sufficient toner for polishing according to temperature and humidity, and to suppress wasteful consumption of toner.
JP 2000-81820 A JP 2002-14589 A JP 2003-330319 A

  However, in the polishing process of the a-Si photosensitive member described in Patent Documents 1 to 3, the light from the exposure device is applied to the entire peripheral surface of the a-Si photosensitive member charged by the charger in the polishing mode. The toner is supplied from the developing device to the peripheral surface of the photosensitive member whose entire charged state has been eliminated. Accordingly, a solid image is formed on the peripheral surface of the a-Si photosensitive member with a large amount of toner uniformly attached over the entire surface.

  Since this large amount of toner is used as a polishing material for the polishing process by the polishing roller in the polishing mode, the amount of the peripheral surface of the a-Si photoreceptor exceeds the necessary and sufficient amount of the polishing process, which wastes the toner. Inconveniences such as being consumed or running out of toner during the polishing process have occurred.

  The present invention has been made in view of such a conventional situation. In the present invention, wasteful consumption of toner is suppressed in the polishing mode of the peripheral surface of the a-Si photosensitive member, and the a-Si photosensitive member is used depending on the situation. An object of the present invention is to provide an image forming apparatus capable of performing necessary and sufficient polishing treatment on a peripheral surface.

  According to a first aspect of the present invention, a predetermined development is performed on an electrostatic latent image formed by exposure processing based on predetermined image information from a predetermined exposure device on a peripheral surface of a photoreceptor rotating around an axis in an image forming mode. A toner image formed by supplying toner from the apparatus via a developing roller is transferred to a sheet, while toner supplied to the peripheral surface of the photosensitive member rotating around the axis in the polishing mode is used as a polishing agent. An image forming apparatus configured to perform a polishing process on the peripheral surface by rotation around the axis of a polishing roller, in which the charging process is performed by a predetermined charging device and the exposure process is not performed. The surface potential of the peripheral surface of the photosensitive member is V0, the DC bias voltage applied to the developing roller in the developing device in the image forming mode is Vdc1, and the current potential in the developing device in the polishing mode. When the bias voltage applied to the roller is Vdc2, voltage applying means for applying a voltage to the developing roller is provided under the condition satisfying (V0−Vdc1)> (V0−Vdc2) in the polishing mode. It is a feature.

  According to this configuration, when the polishing process is performed on the peripheral surface of the photoconductor, toner containing an abrasive is supplied from the developing device to the peripheral surface of the photoconductor while the photoconductor is rotated about the axis. In this state, by rotating the polishing roller whose peripheral surface is in contact with the peripheral surface of the photosensitive member around the axis, the peripheral surface of the photosensitive member is polished and adhered by sliding contact with the toner of the polishing roller. The discharged discharge product etc. are removed and cleaned.

  In this polishing process, the surface potential when the peripheral surface of the photoconductor is not exposed is V0, the DC bias voltage applied to the developing roller in the developing device in the normal image forming mode is Vdc1, and the photoconductor is polished. When the bias voltage applied to the developing roller in the developing device in the mode is Vdc2, the toner is applied to the peripheral surface of the photosensitive member under the condition satisfying (V0−Vdc1)> (V0−Vdc2) in the polishing mode of the photosensitive member. Therefore, the potential difference between the peripheral surface of the photoreceptor and the developing roller is set to be smaller when the polishing process is performed than when the normal image forming process is performed. Yes. Therefore, when the peripheral surface of the photoconductor and the toner have the same charge, during the polishing process, the potential difference between the photoconductor and the photoconductor is smaller than that during the image forming process, so that a uniform and small amount of toner is used. Can be directed to the circumferential surface of the photoreceptor. This has been confirmed as a result of various tests.

  Accordingly, when the potential of the developing roller in the polishing mode is set to be the same as that at the time of image formation and the potential is lowered by exposing the peripheral surface of the photosensitive member as in the conventional case, A large amount of toner unnecessary for the polishing of the peripheral surface is supplied to the peripheral surface of the photoconductor in the polishing mode, which wastes toner and increases the maintenance cost. Inconvenience that the toner may run out and the polishing process cannot be completed may occur. In the present invention, the occurrence of such an inconvenience is effectively suppressed, and the necessary and sufficient toner for the polishing process is obtained. Supplied to the peripheral surface of the photoreceptor.

  According to a second aspect of the present invention, in the first aspect of the present invention, the voltage applying unit is configured to change the value of (V0−Vdc2) corresponding to one or both of temperature and humidity. It is characterized by being.

  According to such a configuration, the toner is supplied to the photoconductor in an optimum state according to one or both of temperature and humidity, and thereby, an optimum polishing process with the toner is performed on the peripheral surface of the photoconductor. As for the change of the value of (V0−Vdc2) corresponding to one or both of temperature and humidity, as a result of various confirmation tests, it becomes difficult to move to the toner photoconductor according to the temperature and humidity. This is because it was confirmed by various tests, and the DC bias voltage Vdc2 is varied in accordance with the temperature and humidity based on the test results.

  According to a third aspect of the present invention, in the first aspect of the present invention, driving means for driving the polishing roller and the photosensitive drum is provided, and the driving means corresponds to one or both of temperature and humidity. Thus, the peripheral speed ratio between the polishing roller and the photosensitive member can be changed.

  According to this configuration, the optimum polishing process is always performed on the peripheral surface of the photoconductor by changing the peripheral speed ratio between the polishing roller and the photoconductor corresponding to one or both of temperature and humidity. .

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the driving means is configured to change a polishing time for the photosensitive member by the polishing roller according to the peripheral speed ratio. It is a feature.

  According to such a configuration, finer control over the polishing of the peripheral surface of the photoconductor by changing the polishing time for the photoconductor by the polishing roller in accordance with the peripheral speed ratio between the polishing roller and the photoconductor. Is realized.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the photoconductor is an amorphous silicon photoconductor drum in which an amorphous silicon layer is laminated on a peripheral surface. Is.

  According to such a configuration, the amorphous silicon layer has an extremely smooth surface and high hardness. Therefore, the photosensitive drum on which the amorphous silicon layer is formed is used to form an electrostatic latent image or a toner image. It becomes suitable.

  According to the first aspect of the present invention, the surface potential when the peripheral surface of the photosensitive member is not exposed is V0, the DC bias voltage applied to the developing roller in the developing device in the normal image forming mode is Vdc1, and the photosensitive member. When the bias voltage applied to the developing roller in the developing device in the body polishing mode is Vdc2, the circumference of the photosensitive member is satisfied under the condition that (V0−Vdc1)> (V0−Vdc2) is satisfied in the photosensitive member polishing mode. Since the toner is supplied to the surface, the potential of the developing roller in the polishing mode is set to be the same as that at the time of image formation and the potential is lowered by exposing the peripheral surface of the photoconductor as in the past. In this case, a large amount of toner that is unnecessary for the polishing process of the peripheral surface of the photoconductor is supplied to the peripheral surface of the photoconductor in the polishing mode, which wastes toner and raises the maintenance cost. In addition, there may be a problem that the toner runs out during the polishing process and the polishing process cannot be completed. In the present invention, the occurrence of such a problem is effectively suppressed, and the polishing is always performed. By supplying sufficient and necessary toner to the peripheral surface of the photoreceptor, the cost of the polishing process can be reduced.

  According to the second aspect of the present invention, the toner is supplied to the photoconductor in an optimum state in accordance with one or both of temperature and humidity, and thus the peripheral surface of the photoconductor is optimally polished with the toner. Can be applied.

  According to the third aspect of the present invention, the optimum polishing process is always performed on the peripheral surface of the photosensitive member by changing the peripheral speed ratio between the polishing roller and the photosensitive member corresponding to one or both of temperature and humidity. Can be applied.

  According to the fourth aspect of the present invention, the polishing time for the photosensitive member by the polishing roller is changed according to the peripheral speed ratio between the polishing roller and the photosensitive member. It is possible to achieve finer grain control over the.

  According to the invention described in claim 5, since the amorphous silicon layer laminated on the peripheral surface of the photosensitive drum is extremely smooth and has a high hardness, the photosensitive drum on which the amorphous silicon layer is formed. Can be made suitable for forming an electrostatic latent image or a toner image.

  FIG. 1 is a front sectional view for explaining an outline of an internal configuration of a copying machine 1 which is an example of an image forming apparatus according to the present invention. As shown in FIG. 1, the copying machine 1 includes an image forming unit 100, a document reading unit 300, and a paper feeding unit 400 inside a main body unit 10, and a document feeding unit 200 provided above the main body unit 10. It has a basic configuration. The image forming unit 100 is formed in the central portion of the main body unit 10, and a document reading unit 300 is provided at an upper position of the main body unit 10 via a later-described in-body discharge tray 131. A paper feed unit 400 is formed on the front side. An operation display unit 500 is provided at the upper front position of the main body unit 10.

  The document reading unit 300 reads a document and generates image data corresponding to the document. The document reading unit 300 includes a CCD (charge coupled device) image sensor that generates image data from an optically acquired document image, a scanner 301 including an exposure lamp, and the like. A first platen glass 302 on which a document to be read is placed and a second platen glass 303 for ADF (automatic document reader) of the document feeder 200 are provided.

  The document reading unit 300 acquires image data acquired while scanning a document placed on the first platen glass 302 or a document automatically fed to the second platen glass 303 by the document feeding unit 200, which will be described later. Output to the main control unit 20.

  The document feeding unit 200 including the ADF feeds the document to the document reading position of the second platen glass 303 and discharges the document read by the document reading unit 300 to the discharge unit of the document feeding unit 200. It is like that. The document feeding unit 200 is configured to be tiltable with respect to the upper surface of the document reading unit 300 with the back side of the apparatus as a rotation fulcrum (rotation center axis), and the first and second platen glasses 302 and 303. The upper surface of the first platen glass 302 can be placed on the upper surface of the first platen glass 302. For example, a book document such as a book that has been opened can be placed.

  The paper feeding unit 400 is for feeding paper for transfer processing to the image forming unit 100. The sheet feeding unit 400 is a manual sheet feeding unit including sheet feeding cassettes 401 and 402 that store sheets of various sizes (recording sheets), a manual feed tray 4031 that can be opened and closed on one side of the main body unit 10, and the like. Unit 403.

  The sheet feeding unit 400 includes a conveyance path 404 that conveys sheets from the respective sheet feeding cassettes 401 and 402 to the image forming unit 100, and a conveyance path 405 that conveys sheets from the manual sheet feeding unit 403 to the image forming unit 100. ing. Each of the paper feed cassettes 401 and 402 and the manual paper feed unit 403 includes pickup rollers 406, 407, and 408 for taking out the stored paper, and paper feed rollers 409 and 410 that feed the paper one by one to each transport path. 411. The transport path 404 is provided with transport rollers 412 and 413 for transporting paper, and registration rollers 414 for waiting the transported paper in front of the image forming unit 100. Note that the transport path 405 joins the transport path 404 between the transport roller 413 and the registration roller 414.

  The image forming unit 100 transfers a predetermined formed image onto the sheet conveyed by the sheet feeding unit 400. The image forming unit 100 includes a drum unit 110 and a fixing unit 120. Details of the drum unit 110 will be described later.

  The fixing unit 120 fixes the toner image transferred to the sheet in the drum unit unit 110. The fixing unit 120 includes a heat roller 121 and a pressure roller 122 having a circumferential surface opposed to the circumferential surface of the heat roller 121, and a sheet is supplied to a nip portion between the heat roller 121 and the pressure roller 122. Thus, the toner image on the paper is melted by obtaining heat from the heat roller 121 and fixed on the paper.

  An in-body discharge tray 131 is provided between the main body unit 10 and the document reading unit 300, and an out-of-machine discharge tray 132 is provided on the left side in FIG. The received sheets are discharged toward the target discharge trays 131 and 132 by discharge rollers 133 and 134, respectively. The paper transport direction can be switched by a discharge branch guide 135 between a discharge roller 133 for the in-body discharge tray 131 and a discharge roller 134 for the external discharge tray 132.

  The operation display unit 500 performs a predetermined instruction input according to a user operation. The operation display unit 500 includes a start key 501 for a user to input a print execution instruction, a numeric keypad 502 for inputting the number of copies to be printed, operation guide information for inputting various copying operation settings, and the like. And a display 503 including a liquid crystal display (LCD) on which various operation buttons and the like are displayed.

  FIG. 2 is an explanatory diagram of a front cross-sectional view for explaining an outline of an embodiment of the drum unit 110 configured as a unit. As shown in FIG. 2, the drum unit 110 includes a photosensitive drum 101, a charging unit 102, and a developing unit (developing device) 103 that are sequentially arranged around the photosensitive drum 101 from a position immediately above in a clockwise direction. And a cleaning unit 104, an exposure unit 105, a transfer unit 106, a charge removal unit 107, and a DC bias voltage storage unit 108.

  A photosensitive drum (photosensitive member) 101 is supported so as to be rotatable around an axis in the direction of an arrow shown in the figure. In this embodiment, an amorphous silicon drum (a-Si drum) in which amorphous silicon (a-Si) is laminated on the peripheral surface is used as the photosensitive drum 101. Such an a-Si drum is obtained by laminating an amorphous silicon film (for example, a film thickness of 20 μm) on the surface of a predetermined drum-shaped cylindrical body by vapor deposition or the like. This a-Si film has a very high hardness, for example, about 1500 to 2000 in terms of Vickers hardness. The peripheral surface of the photosensitive drum 101 is uniformly charged to about +250 V by the charging unit 102, and an electrostatic latent image corresponding to image information is formed on the peripheral surface by irradiation of light from the exposure unit 105. . The photosensitive drum 101 is driven and rotated at a speed (drum linear speed) of about 210 mm / sec.

  The charging unit 102 uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. The charging unit 102 includes a charging wire 1021 disposed opposite to the peripheral surface of the photosensitive drum 101, and a predetermined voltage is applied to the charging wire 1021, so that the peripheral surface ( That is, a uniform charge is applied to the a-Si layer.

  The developing unit 103 exposes (develops) the electrostatic latent image by attaching toner onto the electrostatic latent image formed on the peripheral surface of the photosensitive drum 101 by irradiation of light from the exposure unit 105. . The developing unit 103 includes a developing roller 1031 that is disposed to face the photosensitive drum 101 with a slight gap, a toner storage unit 1032 that stores toner, and a layer regulating blade that is disposed immediately above the developing roller 1031. 1033.

  The layer regulating blade 1033 regulates the amount of toner so that the amount of toner supplied from the toner storage unit 1032 onto the developing roller 1031 becomes an appropriate amount, that is, a thin layer of toner is formed.

  In the developing unit 103, toner is made positive by applying an AC bias voltage of 1.6 kV and a DC bias voltage Vdc of 180 V, for example, at a frequency of about 6.0 kHz to the developing roller 1031 in the normal image forming mode. The toner is charged, and the toner is adsorbed from the developing roller 1031 to the exposed portion of the peripheral surface of the photosensitive drum 101 (the portion of the electrostatic latent image from which charges have been removed by exposure). As a result, the electrostatic latent image is replaced with a real image of toner, and a toner image is formed on the peripheral surface of the developing roller 1031.

  The cleaning unit 104 includes a cleaning roller (polishing roller) 1041, a cleaning blade 1042, and the like, and the toner (transferring) remaining on the peripheral surface of the photosensitive drum 101 after the transfer of the image onto the sheet is completed. The remaining toner) is cleaned (cleaning treatment) and the drum peripheral surface is neutralized. Specifically, the cleaning roller 1041 is made of, for example, an EPDM (ethylene propylene rubber) material, rotates while being slidably ground on the photosensitive drum 101, and removes discharge products on the drum peripheral surface. The cleaning blade 1042 presses the lower edge 1043 to the circumferential surface of the photosensitive drum 101, and mechanically removes residual toner on the circumferential surface of the photosensitive drum 101.

  The exposure unit 105 irradiates the peripheral surface of the photosensitive drum 101 with an exposure laser 1051 based on image data transmitted from the image storage unit 30 and the like described later, and scans the peripheral surface with a laser beam for exposure. Thus, an electrostatic latent image is formed on the circumferential surface of the photosensitive drum 101.

  The transfer unit 106 is for transferring the toner image formed on the photosensitive drum 101 to a sheet, and is disposed to face the peripheral surface of the photosensitive drum 101 and applies a voltage having a potential opposite to that of the toner image. The transfer roller 1061 is provided. Then, the sheet conveyed in the direction of arrow A is pressed against the photosensitive drum 101 by the transfer roller 1061, so that the toner image that is made visible on the photosensitive drum 101 in the developing unit 103 is formed on the sheet. It is peeled off electrostatically and transferred. In the present embodiment, the exposed toner image on the peripheral surface of the photosensitive drum 101 is transferred onto the sheet by the transfer roller 1061 at a transfer bias of −2.5 kV.

  The charge removal unit 107 discharges the peripheral surface of the photosensitive drum 101 by irradiating the peripheral surface of the photosensitive drum 101 with a neutralizing light beam such as LED light (that is, erases residual charges). .

  In the present invention, the peripheral surface of the photosensitive drum 101 that rotates about the axis in the polishing mode specifically set for the operation of the copying machine 1 for polishing the peripheral surface of the photosensitive drum 101 is A cleaning process is performed by rotating around the axis of the cleaning roller 1041 using toner containing abrasive supplied from the developing roller 1031 of the developing unit 103 to the peripheral surface.

  Therefore, in the polishing mode, after the charging process by the charging wire 1021 on the circumferential surface of the photosensitive drum 101 is performed, the exposure process from the exposure unit 105 to the circumferential surface of the photosensitive drum 101 is stopped. The toner is supplied from the developing roller 1031 toward the toner 101. Since the exposure process is not performed on the peripheral surface of the photosensitive drum 101, there is no electrostatic latent image formed on the peripheral surface of the photosensitive drum 101 by erasing the charged state. If the voltage condition of the developing roller 1031 is the voltage condition in the image forming mode, the toner in the toner storage portion 1032 does not fly from the peripheral surface of the developing roller 1031 toward the peripheral surface of the photosensitive drum 101. It becomes impossible to secure toner for polishing treatment on the peripheral surface of the photosensitive drum 101.

  Therefore, in the present invention, the surface potential of the peripheral surface of the photosensitive drum 101 after the charging process by the charging unit 102 and not exposed by the exposure unit 105 is V0, and the surface potential in the normal image forming mode is set. When the DC bias voltage Vdc1 applied to the toner in the developing unit 103 via the developing roller 1031 is Vdc2 and the DC bias voltage applied to the toner in the developing unit 103 via the developing roller 1031 in the polishing mode is set to Vdc2. In the polishing mode in which the peripheral surface of the body drum 101 is subjected to a polishing process, each voltage is set so as to satisfy the following expressions (i) to (iii).

V0> Vdc1 (i)
V0> Vdc2 (ii)
(V0-Vdc1)> (V0-Vdc2) (iii)
In other words, the expressions (i) to (iii) mean that the potential difference between the peripheral surface of the photosensitive drum 101 and the peripheral surface of the developing roller 1031 is the image forming mode in the polishing mode. It is set to be smaller than the time. By doing so, in the polishing mode, the toner can be directed toward the peripheral surface of the photosensitive drum 101 by a smaller potential difference from the photosensitive drum 101 than in the image forming mode.

  That is, if the DC bias voltage Vdc2 applied to the developing roller 1031 in the polishing mode is the same potential as the DC bias voltage Vdc1 applied to the developing roller 1031 in the image forming mode as in the prior art (that is, Vdc2 = Vdc1 ( If V0−Vdc1 = V0−Vdc2), toner does not fly from the developing roller 1031 toward the photosensitive drum 101 unless the photosensitive drum 101 is exposed by the exposure unit 105 in the polishing mode.

  In this case, the toner for polishing processing cannot be secured on the peripheral surface of the photosensitive drum 101. Therefore, the DC bias voltage Vdc2 in the polishing mode is set higher than the DC bias voltage Vdc1 in the image forming mode, and the photosensitive drum. The surface potential V0 of the developing drum 1031 is approached (that is, the evacuation force between the positive charging of the peripheral surface of the photosensitive drum 101 and the positive charging of the toner is weakened). The toner can be transferred toward the peripheral surface of the body drum 101.

  However, the DC bias voltage Vdc2 of the toner in the polishing mode does not exceed the surface potential V0 of the photosensitive drum 101 according to the condition of the above formula (ii). This is because if the DC bias voltage Vdc2 of the toner is greater than the surface potential V0 of the photosensitive drum 101, the toner is actively moved toward the peripheral surface of the photosensitive drum 101 by electrostatic force. (That is, the same as when the peripheral surface of the photosensitive drum 101 is exposed in terms of the potential difference between the two), so that a large amount of toner is exposed from the developing unit 103 as in the conventional case. Since it is supplied to the body drum 101, the condition of the equation (ii) is set to eliminate such inconvenience.

  In the present invention, the toner amount of the solid image formed on the peripheral surface of the photosensitive drum 101 in the polishing mode is set by performing voltage control so as to satisfy the conditions of the expressions (i) to (iii). The amount of toner in the conventional solid image can be reduced.

  Therefore, as in the prior art, the potential of the developing roller 1031 in the polishing mode is set to be the same as that in the image forming mode, and exposure processing by the exposure unit 105 is performed on the peripheral surface of the photosensitive drum 101. In this case, due to a large potential difference between the peripheral surface of the developing roller 1031 and the peripheral surface of the photosensitive drum 101, a large amount of toner that is unnecessary for the polishing process of the peripheral surface of the photosensitive drum 101 is generated during the polishing mode. As a result, the toner is unnecessarily consumed and the maintenance cost increases, and the toner runs out during the polishing process, which makes it impossible to complete the polishing process. However, in the present invention, such inconvenience is effectively suppressed.

  Furthermore, in the present invention, as a result of various tests, the potential difference between the surface potential V0 in the state where the peripheral surface of the photosensitive drum 101 is not exposed and the DC bias voltage Vdc2 applied to the developing roller 1031 in the polishing mode. (The right side of the equation (iii)), that is, the value of Vd in the following equation (iv) is changed according to temperature and humidity.

Vd = V0−Vdc2 (iv)
This is done for the following reason. That is, it was confirmed by various tests that the image flow increases as the temperature and humidity increase. In this embodiment, the surface potential V0 of the photosensitive drum 101 is not changed, and the DC bias voltage Vdc2 (that is, the toner voltage) applied to the developing roller 1031 is variously changed according to temperature and humidity.

  FIG. 3 is a block diagram for explaining operation control by the main control unit 20 of the copying machine 1 shown in FIG. The copying machine 1 includes a main control unit 20 composed of a microcomputer for controlling the operation of the entire apparatus as shown in FIG. The main control unit 20 is a central processing unit (CPU) that performs control based on a program input in advance for various operations of the copier 1, and a ROM (read only) that stores a control program for the copier 1. memory), RAM (random access memory) that temporarily stores data, etc., and predetermined instruction information input on the operation display unit 500, etc., and detection signals from various sensors provided in various places Accordingly, the entire apparatus is controlled.

  For example, when the copying machine 1 is not used, that is, when the copying operation is not performed, the main control unit 20 controls each part of the copying machine 1 to shift to a driving state in a so-called sleep mode, or the user performs copying. Control to automatically return from the sleep mode to the normal print mode at the time of execution is also performed. The main control unit 20 also includes the image forming unit 100, the document feeding unit 200, the document reading unit 300, the paper feeding unit 400, the operation display unit 500, the image storage unit 30, and the formed image. Is provided to obtain a detection signal for performing voltage control on the peripheral surface of the photosensitive drum 101 and the developing roller 1031 in the polishing mode. It is electrically connected to the temperature / humidity measuring unit 600 or the like.

  The temperature / humidity measuring unit 600 is a temperature / humidity sensor configured to simultaneously and integrally measure the temperature and humidity in the copying machine 1. The temperature / humidity measuring unit 600 is provided at a predetermined position in the copying machine 1 (a position where the temperature and humidity of the environment around the developing roller 1031 can be measured more accurately). Note that the temperature / humidity measurement unit 600 may include a temperature sensor and a humidity sensor as separate bodies that separately measure temperature and humidity.

  The image storage unit 30 is a memory that temporarily stores image data of a document read by the document reading unit 300 and image data transmitted from an external device via a network I / F unit (not shown). .

  The image processing unit 40 performs various image processing on the image data, such as gamma processing and enlargement / reduction processing. In the image processing unit 40, for example, A / D conversion of image data is performed on a document image read by the document reading unit 300, and the various images are used using image data based on digital data obtained by the A / D conversion. Processing is performed. Note that the image forming unit 100 includes the DC bias voltage storage unit 108. The DC bias voltage storage unit 108 stores a table in which a voltage to be applied to the developing roller 1031 is set according to temperature and humidity in the polishing mode.

  The main control unit 20 determines whether or not the timing for performing the polishing process on the photosensitive drum 101 has arrived, and the polishing timing determination unit 21 determines whether the polishing timing has arrived. If it is determined, the value of the DC bias voltage Vdc2 to be applied to the developing roller 1031 is set, and a DC bias that outputs a control signal toward a predetermined power supply device 19 (FIG. 2) that applies a voltage to the developing roller 1031. And a voltage setting unit 22.

  In order for the polishing timing discriminating unit 21 to discriminate the polishing timing with respect to the peripheral surface of the photosensitive drum 101, a number sensor 18 (see FIG. 5) detects the number of sheets subjected to image forming processing at an appropriate position in the main body unit 10. 1) is provided, and the timing sheet number storage unit 109 provided in the image forming unit 100 stores the upper limit number of sheets to be used as a reference for polishing the peripheral surface of the photosensitive drum 101. Has been.

  Then, each time the number sensor 18 detects a sheet subjected to image forming processing, the polishing timing determination unit 21 accumulates the number of sheets and stores the accumulated value, and the accumulated value and the timing number storage unit 109 The stored upper limit number of sheets is compared, and when the integrated value exceeds the upper limit number of sheets, it is determined that it is time to change the mode from the image forming mode to the polishing mode. The determination result is output toward the DC bias voltage setting unit 22.

  When the DC bias voltage setting unit 22 receives a determination result indicating that it is time to change the mode to the polishing mode from the polishing timing determination unit 21, the copying machine 1 is based on a predetermined signal from the operation display unit 500. After confirming that the image forming process is not being executed, a control signal indicating that the mode is changed from the image forming mode to the polishing mode is output to the related parts. The mode is automatically changed to the polishing mode.

  Instead of this, when a determination result indicating that it is time to change the mode to the polishing mode is input from the polishing timing determination unit 21, a display output indicating that the mode conversion time has arrived is performed toward the operation display unit 500. Alternatively, the mode conversion from the image forming mode to the polishing mode may be performed by the operator pressing a predetermined key based on the display output.

  When the mode conversion from the image forming mode to the polishing mode is performed, the DC bias voltage setting unit 22 outputs a control signal for preventing the exposure unit 105 from performing light irradiation (that is, to the exposure unit 105). And the DC bias voltage storage unit 108 based on the temperature and humidity detected by the temperature / humidity measuring unit 600 toward the developing roller 1031 with respect to the power supply device 19. A control signal to which the DC bias voltage Vdc2 having a value selected from the stored table is to be applied is output. Incidentally, in the present embodiment, the DC bias voltage setting unit 22 and the power supply device 19 constitute voltage applying means according to the present invention.

  Therefore, the power supply device 19 that has received the control signal outputs the DC bias voltage Vdc2 having an optimum value corresponding to the temperature and humidity at that time to the developing roller 1031. Therefore, the DC bias voltage Vdc2 is applied. An appropriate amount of toner is supplied from the developing roller 1031 toward the peripheral surface of the photosensitive drum 101.

  The DC bias voltage setting unit 22 is provided with a timer, while the image forming unit 100 is provided with a polishing time storage unit 1091 for storing a polishing process time (set time) in the polishing mode.

  Then, the DC bias voltage setting unit 22 starts a timer at the start of the polishing mode, compares the time measured by the timer with the set time for the polishing process stored in the polishing time storage unit 1091, and measures the time measured by the timer When the set time elapses, a control signal for stopping the voltage application to the developing roller 1031 is output to the power supply device 19 and a signal for changing the mode from the polishing mode to the image forming mode is output to the related parts. It is designed to output.

  Hereinafter, the flow of the polishing process for the peripheral surface of the photosensitive drum 101 in the polishing mode will be described with reference to FIG. FIG. 4 is a flowchart showing an embodiment of a flow of polishing processing of the circumferential surface of the photosensitive drum 101 in the polishing mode. In this flowchart, the state in which the copying machine 1 is set to the image forming mode is set as the start time.

  First, it is determined by the polishing timing determination unit 21 whether or not the cumulative number of sheets processed in step S1 exceeds the upper limit number stored in the timing number storage unit 109 (YES in step S1). In this case, it is determined that the time to polish the peripheral surface of the photoconductive drum 101 has already come.

  Next, after it is determined that the time for the polishing process has come, the copying machine 1 is set to the sleep mode in order to determine whether the photosensitive drum 101 is in a state that does not hinder the polishing process. (Step S2), and if the sleep mode is not set (NO in step S2), the current image forming mode continues without mode conversion from the image forming mode to the polishing mode. (Step S3). Therefore, even if the cumulative number of sheets exceeds the upper limit, the image forming process is continued beyond the upper limit until the sleep mode is entered.

  If it is determined in step S2 that the sleep mode is set (YES in step S2), a control signal for changing the current image forming mode to the polishing mode is output from the DC bias voltage setting unit 22 to the related device. As a result, the copying machine 1 is in a polishing mode and is ready to perform a polishing process on the photosensitive drum 101 (specifically, the photosensitive drum 101 and the cleaning roller 1041 are driven and rotated while the charging wire 1021 is corona A state in which electric charges having a surface potential V0 are formed on the peripheral surface of the photosensitive drum 101 by discharging is performed (step S4).

  In this state, the DC bias voltage setting unit 22 sets the voltage to be applied to the developing roller 1031 according to the temperature and humidity stored in the timing number storage unit 109 based on the detection signal from the temperature / humidity measurement unit 600. The DC bias voltage Vdc2 is selected and set with reference to the table, and this DC bias voltage Vdc2 is applied to the developing roller 1031 via the power supply device 19 (step S5). As a result, a polishing process is performed by driving the cleaning roller 1041 using toner as an abrasive on the peripheral surface of the photosensitive drum 101 (step S6).

  Next, in step S7, the DC bias voltage setting unit 22 compares the preset polishing time stored in the polishing time storage unit 1091 with the time measured by the timer, and the time measured becomes the set polishing time. When exceeded (YES in step S7), the mode is changed from the polishing mode to the image forming mode (step S8), and the polishing process on the peripheral surface of the photosensitive drum 101 is completed.

  As described above in detail, the copying machine 1 according to the present invention uses the toner containing the abrasive applied from the developing unit 103 to the peripheral surface of the photosensitive drum 101 that rotates about the axis. The surface is polished by rotation around the axis of a cleaning roller 1041 serving as a polishing roller that is in contact with the peripheral surface of the photosensitive drum 101, so that the cleaning process can be performed.

  According to this configuration, when the polishing process is performed on the circumferential surface of the photosensitive drum 101, the developing unit 103 rotates the photosensitive drum 101 around the axial center to the circumferential surface of the photosensitive drum 101. By supplying toner containing an abrasive and rotating the cleaning roller 1041 whose peripheral surface is in contact with the peripheral surface of the photosensitive drum 101 in this state, the peripheral surface of the photosensitive drum 101 is cleaned by the cleaning roller 1041. Thus, the peripheral surface of the photosensitive drum 101 is cleaned by removing the attached discharge products and the like.

  In this polishing process, the surface potential when the peripheral surface of the photosensitive drum 101 is not exposed is V0, the DC bias voltage applied to the developing roller 1031 in the developing unit 103 in the normal image forming mode is Vdc1, When the bias voltage applied to the developing roller 1031 in the developing unit 103 in the polishing mode of the photosensitive drum 101 is Vdc2, (V0−Vdc1)> (V0−Vdc2) is satisfied in the polishing mode of the photosensitive drum 101. Since toner is supplied to the peripheral surface of the photosensitive drum 101 under the above conditions, the potential difference between the peripheral surface of the photosensitive drum 101 and the peripheral surface of the developing roller 1031 is greater when the polishing process is performed. It is set to be smaller than that during normal image forming processing, whereby the peripheral surface of the photosensitive drum 101 and the toner are set. If the toner has the same charge, the toner may be directed toward the peripheral surface of the photosensitive drum 101 in the polishing process because the potential difference with the photosensitive drum 101 is smaller than in the image forming process. it can.

  That is, if the DC bias voltage Vdc2 applied to the developing roller 1031 in the polishing mode is the same potential as the DC bias voltage Vdc1 applied to the developing roller 1031 in the image forming mode as in the prior art (that is, Vdc2 = Vdc1 ( If V0−Vdc1 = V0−Vdc2), the toner does not fly toward the photosensitive drum 101 unless the photosensitive drum 101 is exposed in the polishing mode. Since it cannot be secured on the peripheral surface of the photosensitive drum 101, the DC bias voltage Vdc2 in the polishing mode is made higher than the DC bias voltage Vdc1 in image formation so as to approach the surface potential V0 of the photosensitive drum 101. (In other words, positive charging of the peripheral surface of the photosensitive drum 101 and positive toner Photoelectrically repulsive force is weakened with), whereby with each other to such may transfer the toner toward the circumferential surface of the photosensitive drum 101 from the circumferential surface of the developing roller 1031.

  Accordingly, when the potential of the developing roller 1031 in the polishing mode is set to be the same as that at the time of image formation and the peripheral surface of the photosensitive drum 101 is exposed to lower the potential as in the prior art, A large amount of toner unnecessary for the polishing process of the peripheral surface of the photoconductive drum 101 is supplied to the peripheral surface of the photoconductive drum 101 in the polishing mode, which wastes toner and raises the maintenance cost. In addition, there may be a problem that the toner runs out during the polishing process and the polishing process cannot be completed. In the present invention, the occurrence of such a problem is effectively suppressed, and the polishing is always performed. By supplying sufficient and necessary toner to the peripheral surface of the photosensitive drum 101, the cost of the polishing process can be reduced.

  In the above embodiment, since the value of (V0−Vdc2) is changed in accordance with the temperature and humidity, the toner is in the optimum state according to the change in temperature and humidity. 101, and thus the peripheral surface of the photosensitive drum 101 can be optimally polished with the toner.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the copying machine 1 has been described as an example of the image forming apparatus. However, the present invention is not limited to the copying machine 1 being an image forming apparatus. The image forming apparatus may be a facsimile apparatus that forms an image based on image information transmitted from the printer, or a printer that executes an image forming process based on image information from an external device such as a computer.

  (2) In the above embodiment, the value of (V0−Vdc2) is changed according to the temperature and humidity. Instead, the cleaning roller 1041 and the photosensitive drum are changed according to the temperature and humidity. The peripheral speed ratio with 101 may be changed. That is, since various tests have confirmed that the image flow increases as the temperature and humidity values increase, the peripheral speed between the cleaning roller 1041 and the photosensitive drum 101 depends on the temperature and humidity to compensate for this. Increase the ratio. By doing so, the optimum polishing process can always be performed on the peripheral surface of the photosensitive drum 101.

  (3) In the above embodiment, the value of (V0−Vdc2) is changed corresponding to the temperature and humidity. However, for example, in the environment where the copying machine 1 is installed, the temperature is always substantially reduced by temperature control. When the humidity is controlled to be constant or the humidity is always controlled to be substantially constant by humidity control, the value of (V0−Vdc2) may be changed according to only one side of temperature and humidity. Good.

  (4) In the above-described embodiment, the image forming apparatus (copier 1) provided with the voltage applying unit according to the present invention is exemplified as one for monochrome printing. The image forming apparatus (so-called color machine) capable of color printing is not limited to the one for monochrome printing.

  In order to confirm the effect of the present invention, the toner is actually driven by driving the cleaning roller 1041 after variously changing the DC bias voltage Vdc2 applied to the developing roller 1031 via the developing roller 1031 according to changes in temperature and humidity. Then, the peripheral surface of the photosensitive drum 101 was polished, and the actual image forming process was subsequently performed. Then, the image forming state was inspected by visually observing the transfer-treated paper obtained as a result of the image forming process.

  The photosensitive drum 101 employed in the copying machine 1 used in this test has a diameter of 30 mm and a thickness of the a-Si layer of 20 μm. The peripheral surface of the photosensitive drum 101 was discharged from the charging wire 1021, and the surface potential V0 was set to 300V.

  Further, this type of developing roller 1031 has a diameter of 20 mm, and a gap dimension between the layer regulating blade 1033 and the developing roller 1031 peripheral surface is 0.55 mm. The gap between the peripheral surface of the developing roller 1031 and the peripheral surface of the photosensitive drum 101 is set to 0.50 mm.

  The developing roller 1031 is applied with an AC bias voltage having a frequency of 6 kHz and a DC bias voltage Vdc1 of 180 V in the image forming mode. In this test, an AC bias voltage is also applied. A value (V0−Vdc2) shown in Table 1 obtained by subtracting the value of the DC bias voltage Vdc2 applied to the developing roller 1031 from the condition set in advance according to the temperature and humidity, that is, the value of the surface potential V0 of the photosensitive drum 101. Under such conditions, only the DC bias voltage Vdc2 was applied to the developing roller 1031 for 20 seconds. In Table 1, the value of “V0−Vdc2” is shown, and in particular, the value of the DC bias voltage Vdc2 is shown in parentheses.

  Then, after performing a polishing process for 20 seconds on the photosensitive drum 101 for each temperature and humidity, an image forming process is actually executed by the copying machine 1 in each temperature and humidity environment, and an image of the printed paper is obtained. Although it observed visually, it was able to confirm that it was a favorable image with no image flow about all.

  Next, instead of increasing the peripheral speed ratio between the cleaning roller 1041 and the photosensitive drum 101 from 1.2 in the first embodiment to 2.0, the polishing time is decreased from 20 seconds to 10 seconds, and the other The conditions were set in the same manner as in Example 1, and the photosensitive drum 101 was polished.

  Then, after performing a polishing process for 10 seconds on the photosensitive drum 101 for each temperature and humidity, an image forming process is actually executed by the copying machine 1 in each temperature and humidity environment, and an image of the printed paper is obtained. Although it observed visually, it was able to confirm that it was a favorable image with no image flow about all.

  In the third embodiment, the temperature and humidity conditions are divided as in the first embodiment, and the cleaning roller 1041 and the photosensitive drum 101 are replaced with the DC bias voltage Vdc2 applied to the preceding developing roller 1031 in each division. The peripheral speed ratio is set variously as shown in Table 2, while the DC bias voltage Vdc2 applied to the developing roller 1031 is set to a constant value of 200V. Other conditions are the same as in the first embodiment.

  Then, after polishing the photosensitive drum 101 for 20 seconds at each peripheral speed ratio for each temperature and humidity, the image forming process is actually executed by the copying machine 1 in each temperature and humidity environment, and printing is performed. The images of the printed paper were visually observed, and it was confirmed that all of them were good images with no image flow.

  In Example 3, the polishing time may be further changed according to the peripheral speed ratio between the photosensitive drum 101 and the cleaning roller 1041. By doing so, it is possible to realize the polishing process of the peripheral surface of the photosensitive drum 101 with finer grain.

FIG. 2 is a front sectional view for explaining an outline of an internal configuration of a copying machine that is an example of the image forming apparatus according to the present invention. It is explanatory drawing of front sectional view for demonstrating the outline | summary of one Embodiment of the drum unit part comprised by the unit. FIG. 2 is a block diagram for explaining operation control by a main control unit of the copier shown in FIG. 1. 3 is a flowchart illustrating an embodiment of a flow of polishing processing of a circumferential surface of a photosensitive drum in a polishing mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier 10 Main-body part 100 Image formation part 101 Photosensitive drum (photosensitive body)
DESCRIPTION OF SYMBOLS 102 Charging part 1021 Charging wire 103 Developing part (developing device) 1031 Developing roller 1032 Toner storage part 1033 Layer regulating blade 104 Cleaning part 1041 Cleaning roller (polishing roller)
1042 Cleaning blade 1043 Lower edge 105 Exposure unit 1051 Exposure laser 106 Transfer unit 1061 Transfer roller 107 Static elimination unit 108 DC bias voltage storage unit 109 Timing number storage unit 1091 Polishing time storage unit 110 Drum unit unit 120 Fixing unit 121 Heat roller 122 Pressure roller 131 In-body discharge tray 132 Out-of-machine discharge tray 133 Discharge roller 134 Discharge roller 135 Discharge branch guide 18 Number of sheets sensor 19 Power supply (voltage applying means)
20 Main control unit 21 Polishing timing discrimination unit 22 DC bias voltage setting unit (voltage applying means)
DESCRIPTION OF SYMBOLS 30 Image memory | storage part 40 Image processing part 200 Document feeding part 300 Document reading part 301 Scanner 302 Platen glass 303 Platen glass 400 Paper feed part 401 Paper feed cassette 403 Paper feed part 404 Transport path 405 Transport path 406 Pickup roller 409 Feed roller 412 Conveying roller 413 Conveying roller 414 Registration roller 500 Operation display unit 501 Start key 502 Numeric keypad 503 Display 600 Humidity measuring unit 4031 Manual feed tray I Network V0 Surface potential Vdc1 of photoconductive drum DC bias voltage applied to developing roller in image forming mode DC bias voltage applied to the developing roller in the Vdc2 polishing mode

Claims (5)

In the image forming mode, toner is applied from a predetermined developing device via a developing roller to an electrostatic latent image formed by exposure processing based on predetermined image information from a predetermined exposure device on the peripheral surface of the photosensitive member rotating about the axis. The toner image formed by supplying the toner image is transferred to a sheet, and the toner supplied to the peripheral surface of the photosensitive member rotating around the axis in the polishing mode is used as an abrasive to rotate around the axis of a predetermined polishing roller. An image forming apparatus configured to be able to perform a polishing process on the peripheral surface,
DC bias applied to the developing roller in the developing device in the image forming mode when the surface potential of the peripheral surface of the photoconductor is charged by a predetermined charging device and the exposure processing is not performed is V0. When the voltage is Vdc1 and the bias voltage applied to the developing roller in the developing device in the polishing mode is Vdc2, the voltage is applied to the developing roller under the condition that (V0−Vdc1)> (V0−Vdc2) is satisfied in the polishing mode. An image forming apparatus comprising a voltage applying means for applying a voltage.   The image forming apparatus according to claim 1, wherein the voltage application unit is configured to change the value of (V0−Vdc2) corresponding to one or both of temperature and humidity. .   Drive means for driving the polishing roller and the photoconductor is provided, and the drive means can change a peripheral speed ratio between the polishing roller and the photoconductor corresponding to one or both of temperature and humidity. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as described above.   The image forming apparatus according to claim 3, wherein the driving unit is configured to change a polishing time for the photosensitive member by the polishing roller according to the peripheral speed ratio.   5. The image forming apparatus according to claim 1, wherein the photoconductor is an amorphous silicon photoconductor drum in which an amorphous silicon layer is laminated on a peripheral surface.

Images