JP2007328175A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of achieving the high durability of a cleaning blade and photoreceptor drum, by relaxing the contact pressure between the cleaning blade and the photoreceptor drum. <P>SOLUTION: The image forming apparatus includes the photoreceptor that forms an electrostatic latent image and holds a toner image having the electrostatic latent image developed with toner; a detection means for detecting the current value of a motor that drives the photoreceptor, in an image non-forming area where toner is not attached; and a control means for controlling the supply of the toner to the photoreceptor in the image non-forming area, when the current value detected by the detecting means exceeds a predetermined value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that employs an electrophotographic system, an electrostatic system, or the like, and more particularly to an image forming apparatus that can clean the surface of a photosensitive drum, which is an image carrier, using a blade.

  The toner image formed on the surface of the photosensitive drum of the electronic copying machine is not completely transferred onto the transfer paper, and untransferred toner remains. In order to perform the copying operation continuously, it is necessary to remove the residual toner and clean it. Many conventional cleaning devices use a configuration in which a blade as a cleaning member is brought into contact with a photosensitive drum and scrapes off residual toner at an edge thereof, and an elastic body such as polyurethane is used for the blade. . In order to clean the toner remaining on the photosensitive drum, it is necessary to apply a load of a certain level or more, and as a result, the blade gradually and permanently deforms. For this reason, in the conventional cleaning device, the blade is brought into contact with the photosensitive drum during the copying operation, is isolated after the copying operation is completed, and thereafter the load is completely released.

  Further, the blades require periodic replacement in order to prevent cleaning failures due to edge wear and wear. This blade replacement is usually performed by a maintenance worker, but if the replacement operation is performed for each blade, the replacement cycle becomes too short. For this reason, those equipped with a plurality of blades have also been proposed, and these cleaning devices employ a configuration in which the blade support shaft for fixing the plurality of blades is rotated for a predetermined operation or every predetermined time and replaced with another blade. ing.

  Furthermore, a blade that supports the blade as it abuts the photoconductor to automatically adjust the pressure contact force of the blade in response to changes in the ambient temperature and to obtain a stable cleaning performance without overwearing or turning the photoconductor. It has been devised that the holder is composed of at least two members having different coefficients of thermal expansion, and the coefficient of thermal expansion of the blade holder is selected so as to move in the direction of pressing the photoreceptor as the temperature of the blade end increases.

Further, an image carrier surface detection means for detecting the surface state of the image carrier or a storage means for previously storing the time-dependent change data of the surface state of the image carrier is provided and obtained by the image carrier surface detection means or the storage means. In some cases, the cleaning state of the image carrier by the cleaning device is controlled as needed according to the surface state of the image carrier.
JP-A-7-181865 JP-A-6-148974 JP-A-6-214493 Japanese Patent Laid-Open No. 8-11525 JP 2000-172026

  However, after the copying operation is completed, the load is completely released after that, and after the copying operation, a considerable amount of toner is present on the contact surface of the blade with the photosensitive drum, that is, on the upstream portion of the blade edge. May have accumulated. A lot of paper dust is also mixed in this. Therefore, if the blade is completely removed after the copying operation is completed, the paper dust adhering to the blade or the paper dust remaining on the photosensitive drum is removed from the blade when contacting the photosensitive drum during the next copying operation. There is a possibility of being caught at the edge. In such a portion where the paper dust is sandwiched, the blade is not in close contact with the photosensitive drum, so that the toner cannot be cleaned, resulting in poor cleaning.

  Also, it can move between the position where the blade abuts against the photosensitive drum and the position where the blade is isolated, and replaces the used blade with a new blade when the blade is in the isolated position. However, a considerable amount of toner is present at the contact point between the blade and the photosensitive drum, and the toner contains a lot of paper dust adhering to the photosensitive drum during transfer. Therefore, when replacing a used blade with a new blade, when the blade is in an isolated position, it remains on the photosensitive drum when it is replaced with a new blade and brought into contact with the photosensitive drum. In some cases, paper dust mixed in the toner is caught. As described above, when paper dust is sandwiched, since the blade does not adhere to the photosensitive drum in the portion where the paper dust is sandwiched, the toner cannot be cleaned, resulting in poor cleaning.

  Further, when the blade replacement means for replacing the blade performs the blade replacement by rotating the blade support shaft, the blade support shaft may have backlash in the rotation direction. If the rotation direction and the rotation direction of the photosensitive drum are the same, the blade support shaft moves when the rotation of the photosensitive drum starts or stops, and the contact point and contact angle of the blade change.

  Furthermore, the contact point and contact angle of the blade change, so that the paper dust can easily enter between the blade and the photosensitive drum, and the blade is in close contact with the photosensitive drum where the paper dust is sandwiched. Therefore, the toner cannot be cleaned, resulting in poor cleaning.

  In addition, for a blade that replaces a used blade and a new blade by rotating the blade support shaft, it is possible that the toner is attached to the new blade that is mounted in advance for replacement. When the blade support shaft is rotated for replacement, the toner attached to the new blade may be scattered.

  In addition, a blade holder that supports one end of the blade and supports the blade as if the other end is in contact with the photosensitive member is composed of at least two members having different coefficients of thermal expansion. As for the one that selects the coefficient of thermal expansion of the two members as they move in the direction of pressing the body, the number of members increases, the configuration becomes complicated, and the cost increases.

  Further, when the torque fluctuation measuring means is attached as a mechanical mechanism, there may be problems such as an increase in the number of parts and an increase in the size of the apparatus itself. In addition, depending on the surface state of the image carrier required by the surface detection means or storage means of the image carrier, the consumption of the black belt increases for those that form a black belt, so color copying In the case of a machine, there is a problem that black toner is replenished more than other colors.

  In order to solve the above problems, an image forming apparatus according to claim 1 of the present invention is a photoconductor that forms an electrostatic latent image and holds a toner image obtained by developing the electrostatic latent image with toner. Detecting means for detecting a current value of a motor for driving the photosensitive member in a non-image portion where no toner adheres, and when the current value detected by the detecting means exceeds a predetermined value, in the non-image portion An image forming apparatus comprising control means for controlling the toner to supply the toner.

  In order to solve the above problem, in the image forming apparatus according to claim 2 of the present invention, the detection means detects the current value after a predetermined time has elapsed since the motor driving the photoconductor is started. The image forming apparatus is controlled.

  In order to solve the above problem, in the image forming apparatus according to claim 3 of the present invention, the detection means starts detection of a current value after a predetermined time from the start of the motor that drives the photosensitive member, The image forming apparatus is controlled to detect a current value based on an average value of a current until the motor stops.

  In order to solve the above problem, the image forming apparatus according to claim 4 of the present invention controls the supply amount of the toner in accordance with an increase from a predetermined value of the current value detected by the detection unit. An image forming apparatus comprising toner control means for controlling.

  In order to solve the above problems, an image forming apparatus according to claim 5 of the present invention includes a cleaning unit provided with a cleaning blade that contacts the photosensitive member and removes residual toner, and the non-image portion includes the cleaning unit. Even when control is performed so that the toner is supplied to the photoconductor, when the current value detected by the detection means exceeds a predetermined value, the blade is pressed against the surface of the photoconductor to remove residual toner. An image forming apparatus comprising blade pressure control means for controlling the pressure in a releasing direction.

  In order to solve the above problem, the image forming apparatus according to claim 6 of the present invention is detected by the detection unit even when the toner is supplied to the photoconductor in a non-image portion. In the image forming apparatus, a warning unit is displayed on an operation screen of the image forming apparatus when the current value exceeds a predetermined value.

  In order to solve the above problem, the image forming apparatus according to claim 7 of the present invention is detected by the detection unit even when the toner is supplied to the photoconductor in a non-image portion. When the measured current value exceeds a predetermined value, a warning unit is displayed on the operation screen of the image forming apparatus, and a blade pressure setting unit for setting a blade pressure is controlled to be displayed on the operation screen. An image forming apparatus including a control unit.

  In order to solve the above problem, the image forming apparatus according to claim 8 of the present invention is characterized in that the toner supplied to the photosensitive member is at least one of black, cyan, magenta, and yellow. Forming device.

  In order to solve the above problems, the image forming apparatus according to claim 9 of the present invention is configured to remove the toner having the largest amount of toner by the toner remaining amount detecting unit that detects the remaining amount of toner. There is provided an image forming apparatus that is controlled to be supplied to the image forming apparatus.

  According to the present invention, by detecting the current value of the motor that drives the photoconductor, when the detected current value exceeds a predetermined value, control is performed so that toner is supplied to the photoconductor in the non-image area. This makes it possible to relieve the contact pressure between the photosensitive member and the cleaning blade, so that high durability of the cleaning blade and the photosensitive member can be realized.

  In addition, by detecting the current value of the motor that drives the photoconductor, the amount of toner supplied to the photoconductor is controlled in accordance with the increment from the detected current value, so that the toner consumption is minimized. It becomes possible to suppress.

  Further, even when control is performed so that toner is supplied to the photoconductor in the non-image area, when the current value detected by the detection unit exceeds a predetermined value, control is performed so that the pressure of the cleaning blade is released. As a result, high durability of the cleaning blade and the photoreceptor can be realized.

  Further, even when control is performed so that toner is supplied to the photoconductor in the non-image area, a warning display or an error display is displayed on the operation screen when the current value detected by the detection unit exceeds a predetermined value. As a result, defects around the photosensitive member can be detected at an early stage, so that the defects can be corrected before image defects occur.

  Furthermore, the toner consumption can be balanced by selecting the toner to be supplied to the photoconductor with at least one color of black, cyan, magenta, and yellow and having the largest amount of toner remaining.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of an image forming apparatus of the present invention. The color image forming apparatus includes an image reading unit 100R and an image output unit 100P. The image reading unit 100R optically reads a document image, converts it into an electrical signal, and sends it to the image output unit 100P. Its configuration is well known and has no particular relationship with the present invention, and therefore will not be described in detail.

  The image output unit 100P is roughly divided into an image forming unit 110 in which four stations a, b, c, and d are arranged in parallel (the basic configuration of each station a to d is the same), a paper feeding unit 120, an intermediate transfer unit. 130, a fixing unit 140, a cleaning unit 150, and a control unit 170.

  Each unit will be described in detail. Each station a, b, c, and d of the image forming unit 110 has photosensitive drums 111a, 111b, 111c, and 111d as image carriers, and the photosensitive drums 111a to 111d are pivotally supported at the centers thereof, and in the direction of the arrows. Driven by rotation. Opposing to the outer peripheral surfaces of the photosensitive drums 111a, 111b, 111c, and 111d, primary chargers 112a, 112b, 112c, and 112d, optical systems 113a, 113b, 113c, and 113d, folding mirrors 116a, 116b, 116c, 116d and developing devices 114a, 114b, 114c, and 114d are disposed.

  A toner image is formed on the photosensitive drum 111 (111a to 111d) by an image forming process. First, the surface of the photosensitive drum 111 is given a uniform charge amount by the primary charger 112 (112a to 112d), and then modulated according to the recording image signal generated by the optical system 113 (113a to 113d), for example. A light beam such as a laser beam is exposed on the photosensitive drum 111 through the folding mirror 116 (116a to 116d), and an electrostatic latent image is formed on the surface of the photosensitive drum 111.

  The electrostatic latent image on the photosensitive drum 111 is developed by the developing device 114 (114a to 114d) and visualized as a toner image. The developing devices 114a, 114b, 114c, and 114d contain four color developers (toners) of black, magenta, cyan, and yellow, and latent images on the respective photosensitive drums 111 are developed into black, magenta, and cyan by development. A yellow toner image is formed.

  Under the photosensitive drums 111a, 111b, 111c, and 111d, primary transfer areas Ta, Tb, Tc, and Td are formed in which the intermediate transfer belt 131 abuts and the toner image on the photosensitive drum is transferred to the intermediate transfer belt 131. Yes. Primary transfer chargers 135a, 135b, 135c, and 135d are disposed on the back side (inner side) of the intermediate transfer belt 131 in the primary transfer region. Cleaning devices 115a, 115b, 115c, and 115d are installed downstream of the primary transfer areas Ta, Tb, Tc, and Td in the rotation direction of the photosensitive drums 111a, 111b, 111c, and 111d, and are not transferred to the intermediate transfer belt 131. The surface of the photosensitive drum 111 is cleaned by scraping off the untransferred toner remaining on each photosensitive drum 111.

  The paper feeding unit 120 includes cassettes 121a and 121b and manual feed trays 127 that store the recording material P, pickup rollers 122a, 122b, and 126 that feed the recording material P one by one in the cassettes 121a and 121b or from the manual feed tray 127, and each pickup roller. The recording material P fed from the sheet feeding roller pair 123 and the paper feeding guide 124 for conveying the recording material P to the registration rollers 125a and 125b, and the recording material P fed to the secondary transfer region Te in accordance with the image forming timing of the image forming unit. The registration rollers 125a and 125b.

  The intermediate transfer unit 130 includes a plurality of rollers, that is, a driving roller 132 that transmits driving to the belt 131, and a tension roller that applies an appropriate tension to the belt 131 by urging by a spring (not shown). 133 and a secondary transfer counter roller 134 facing the secondary transfer region Te with the belt 131 interposed therebetween, and a primary transfer plane A is formed between the drive roller 132 and the tension roller 133. The intermediate transfer belt 131 is made of a material such as polyethylene terephthalate (PET) or polyvinylidene fluoride (PVdF).

  The driving roller 132 is coated on the surface of a metal roller with rubber (urethane rubber or chloroprene rubber) having a thickness of several millimeters to prevent a slip portion with the belt 131. The driving roller 132 is a pulse motor (not shown). )).

  A secondary transfer roller 136 is disposed opposite to the secondary transfer counter roller 134 with the intermediate transfer belt 131 interposed therebetween, and the secondary transfer roller 136 is pressed against and brought into contact with the intermediate transfer belt 131 with an appropriate pressure. The secondary transfer region Te is formed by the contact nip portion. A cleaning unit 150 that cleans the surface (image forming surface) of the intermediate transfer belt 131 is installed downstream of the secondary transfer region Te of the intermediate transfer belt 131, and this unit 150 is a blade that contacts the surface of the belt 131. 151 and a waste toner box 152 that accommodates toner removed from the surface of the belt 131 by the blade 151.

  The fixing unit 140 includes a fixing roller 141 provided with a heat source such as a halogen heater therein, a pressure roller 142 that is pressed against the fixing roller 141 (the pressure roller 142 may also be provided with a heat source), and a roller pair 141. 142, the guide 143 for guiding the recording material P to the contact nip portion, the fixing heat insulating covers 146, 147 for confining the heat in the unit 140, and the recording material P discharged from the pair of rollers 141, 142 further outside the unit 140. A paper discharge tray 148 on which the recording material P output from the unit 140 is stacked is installed outside the image forming apparatus main body on the extension thereof.

  Next, an image forming operation of the image forming apparatus will be described. When an image forming operation start signal is issued from the CPU 501 of the control unit 170, the recording material is fed from a cassette corresponding to the selected paper size or the like. For example, a case where paper is fed from the upper cassette 121a will be described. The recording material P is fed one by one from the cassette 121a by the pickup roller 122a and guided between the paper feed guides 124 by the paper feed roller pair 123. The recording material P is conveyed to the registration rollers 125 (125a and 125b). At that time, the registration roller 125 is stopped, the leading edge of the recording material P hits the nip portion of the registration roller 125, and then the registration roller 125 starts rotating at a predetermined timing with respect to the start of image formation in the image forming unit. As for the rotation timing of the registration roller 125, toner images of the respective colors are formed on the respective photosensitive drums 111, and the toner images of the respective colors are primarily transferred while being superimposed on the intermediate transfer belt 131. When the toner image reaches the secondary transfer area Te, the recording material P sent to the registration roller 125 is set to reach the secondary transfer area Te.

  In the image forming unit, when an image forming operation start signal is issued, a toner image is formed on the photosensitive drum 111d of the station d, which is the most upstream in the rotational direction of the intermediate transfer bell 131, by the image forming process described above. The toner image is primarily transferred to the intermediate transfer belt 131 in the primary transfer region Td by the action of the primary transfer charger 135d to which a high voltage is applied. The primarily transferred toner image is conveyed to the primary transfer region Tc of the next station c as the intermediate transfer belt 131 moves. At the station c, image formation is performed with a delay of the time during which the toner image is conveyed between the stations d and c, and the next toner image is transferred with the position (resist) aligned on the previous toner image. . Thereafter, the same process is repeated at the stations b and a, so that the four color toner images are finally transferred onto the intermediate transfer belt 131 in a superimposed manner.

  Thereafter, when the recording material P enters the secondary transfer region Te and comes into contact with the intermediate transfer belt 131, a high voltage is applied to the secondary transfer roller 136 in accordance with the passing timing of the recording material P. Then, the four-color toner images formed on the intermediate transfer belt 131 by the above-described process are secondarily transferred collectively onto the surface of the recording material P. The recording material P onto which the toner image has been secondarily transferred is accurately guided to the roller nip portion of the fixing unit 140 by the conveyance guide 149, and the toner image is transferred to the surface of the recording material P by heat and pressure from the fixing roller 141 and the pressure roller 142. To form a four-color full-color permanent image. Thereafter, the recording material P is conveyed outside the apparatus by the internal and external paper discharge rollers 144 and 145 and is stacked on the paper discharge tray 148.

  The image forming apparatus includes a registration correction device including photosensors 200 and 201 as pattern detection means and a control unit 170. The photo sensors 200 and 201 are disposed close to the belt at both ends in the width direction perpendicular to the moving direction of the intermediate transfer belt 131 at a position downstream of the final color image forming station a. Each color registration pattern (registration correction pattern) formed along the belt moving direction at two positions on both ends of the intermediate transfer belt 131 in the width direction is detected and read, and the resist correction control is performed by the correction unit of the control unit 170. Is going.

  Here, a method for detecting the current of the photosensitive drum 111 will be described. The photosensitive drum 111 is controlled to rotate by a DC motor (not shown). As shown in FIG. 2, a cleaning device 115 is arranged on the downstream side in the rotation direction of the photosensitive drum 111, and the transfer residual toner that is not transferred to the intermediate transfer belt 131 and remains on each photosensitive drum 111 is scraped off to be photosensitive. The surface of the drum 111 is cleaned. The cleaning device 115 has a cleaning blade 117 and a blade holder 118. The drive current of the photosensitive drum 111 is detected in a state where the surface of the photosensitive drum 111 is cleaned.

  As a drive current detection circuit for the photosensitive drum 111, a circuit as shown in FIG. 4 is generally used. First, the drive current Io (A) is converted into a voltage, the voltage is amplified by the operational amplifier IC 106, and the load state of the photosensitive drum 111 is determined by comparing with the reference voltage Vref (V) via the sample hold circuit. I can do it. However, if the starting current of the motor is larger than the load load state setting value Iref (A), a limiter is provided for the starting current of the motor, or current detection is not performed when the motor is started as shown in FIG. That is, it is necessary to start current detection after T (ms) after the motor is started. In the normal case, as shown in FIG. 3, the detected current value is lower than the reference value. However, in the case of a heavy load, the detected current value is higher than the reference value. The detected current value Io (A) is expressed as an average value from T (ms) after startup to motor operation stop or a predetermined time after motor rotation.

As shown in FIG. 3, when the detected current value Io (A) is larger than the load load state setting value Iref (A), it is considered that some load load state has occurred. Therefore, the detected current value Io (A) is amplified after current-voltage conversion, and the difference between the voltage Vo (V) via the sample-and-hold circuit and Vref (V) obtained by current-voltage conversion of the load state setting value Iref (A). A value TNR proportional to (ΔV = Vo−Vref)
TNR = αΔV = α (Vo−Vref)
Only the toner band is controlled on the photosensitive drum 111. With respect to the toner band to be supplied, in the case of a color copying machine, control is performed so that at least one color toner having the largest remaining amount is supplied according to the remaining amount of toner detected by a remaining amount detecting unit (not shown).

  Even when the toner band is applied on the photosensitive drum 111 by the amount corresponding to TNR, if the detected current value Io (A) is larger than the load weight state setting value Iref (A), the blade holder 118 is moved as shown in FIG. Control is performed so as to be separated from the photosensitive drum 111. The movement of the blade holder 118 is performed by driving means such as a motor (not shown). The movement amount is controlled to operate for a predetermined number of pulses or for a predetermined time.

  Further, even when the toner band is hit on the photosensitive drum 111 by the amount corresponding to TNR and the blade holder 118 is controlled to be separated from the photosensitive drum 111, the detected current value Io (A) is the load load state setting value Iref (A Is larger than), problems other than the contact pressure between the cleaning blade 117 and the photosensitive drum 111 may be considered, so that a warning is displayed on an operation unit (not shown) of the image forming apparatus main body.

  Next, a control flow representing the present invention will be described with reference to FIG. In the non-image portion, the photosensitive drum 111 drive motor (DC motor) is rotated (S501). The detected current value Io (A) of the photosensitive drum 111 drive motor is compared with a preset reference current value Iref (A) (S502). If the detected current value Io of the photosensitive drum 111 drive motor is smaller than the reference current value Iref, the process ends normally (S509). When the detected current value Io of the photosensitive drum 111 drive motor is larger than the reference current value Iref, control is performed so that toner is evenly placed on the photosensitive drum 111 by α (Io−Iref) (S503). In the one-drum type color copying machine, the toner remaining amount detecting means for each color is controlled to supply the largest remaining amount of toner to at least one color drum according to the detected remaining toner amount. Again, Io and Iref are compared with toner on the photosensitive drum 111 (S504). If Io> Iref, control is performed to display a warning on the operation screen of the image forming apparatus (S505). If Io <Iref in S504, the process ends normally (S509). If Io> Iref in S504, when the blade holder 118 is moved in S506, Io and Iref are compared again (S507). If Io <Iref, the process ends normally (S509). If Io> Iref despite the separation of the blade holder 118 from the photosensitive drum 111 in S507, the process is terminated by displaying an error on the operation screen of the image forming apparatus (S509).

1 is a cross-sectional view illustrating an image forming apparatus embodying the present invention. It is the schematic of a photosensitive drum and a cleaning apparatus. It is a figure which shows the comparison waveform at the time of normal and abnormal in the photosensitive drum drive motor detection current. It is a figure which shows a photosensitive drum motor drive current detection circuit. It is a follow chart showing the present invention.

Claims (9)

An electrostatic latent image is formed, and a current value of a motor that drives the photosensitive member in a non-image portion where no toner adheres and a photosensitive member that holds the toner image obtained by developing the electrostatic latent image with toner is detected. And a control unit that controls to supply the toner to the photoconductor in a non-image portion when the current value detected by the detection unit exceeds a predetermined value. Image forming apparatus. The image forming apparatus according to claim 1, wherein the detection unit is controlled so as to detect a current value after a predetermined time has elapsed since a motor that drives the photoconductor is activated. 2. The image forming apparatus according to claim 1, wherein the detection unit starts detecting the current value after a predetermined time from the start of the motor that drives the photoconductor, and the current value is an average value until the motor stops or operates for the predetermined time. And an image forming apparatus controlled to detect the image. The image forming apparatus according to claim 1, further comprising: a toner control unit configured to control a supply amount of the toner according to an increase from a predetermined value of the current value detected by the detection unit. apparatus. 2. The image forming apparatus according to claim 1, further comprising a cleaning unit provided with a cleaning blade that contacts the photosensitive member and removes residual toner. When the current value detected by the detection means exceeds a predetermined value, there is provided a blade pressure control means for controlling in a direction to release the pressure of the blade that presses against the surface of the photoconductor to remove residual toner. An image forming apparatus. 6. The image forming apparatus according to claim 5, wherein even when control is performed so that the toner is supplied to the photoconductor in a non-image portion, image formation is performed when the current value detected by the detection unit exceeds a predetermined value. An image forming apparatus that displays a warning on an operation screen of the apparatus. The image forming apparatus according to claim 4, wherein the current value detected by the detection means is a predetermined value even when the pressure of the blade that presses against the surface of the photoconductor to remove residual toner is controlled to be released. An image forming apparatus characterized by displaying an error on an operation screen of the image forming apparatus when exceeding the limit. The image forming apparatus according to claim 1, wherein the toner supplied to the photosensitive member is at least one of black, cyan, magenta, and yellow. 9. The image forming apparatus according to claim 8, wherein the toner remaining amount detecting means for detecting the remaining amount of toner is controlled to supply the toner having the largest remaining amount of toner to the photosensitive member. .

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