JP2009086234A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can avoid deterioration in total productivity due to the period that it cannot perform general image formation due to separately carrying out of process control operation and cleaning member turn-over preventing and that increases that much. <P>SOLUTION: This image forming apparatus has an imaging device to form images to be developed with a dry developing agent, a turning image holder having a holding surface to hold the images formed in the image forming apparatus, a cleaning member to remove the developing agent adhering to the image holding surface of the image holder in a state in contact with it, and a control means to form an image in the imaging device to supply to the area of the cleaning member in contact with the image holding surface and to hold it on this image holding surface when carrying out a control including the operation to form an inspection image in the imaging device and to hold it on the image holding surface of the image holder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Some image forming apparatuses such as printers, copiers, and facsimiles form an image to be developed with a dry developer and finally form an image on a recording medium such as recording paper.

  In such an image forming apparatus, from the viewpoint of stabilizing the image quality of the image, the developer forms an inspection image for control inspection having a specific pattern shape by the developer, and rotates a photosensitive member, an intermediate transfer member, etc. It is known that, after being held on the surface (holding surface) of the image holding body, control related to the process of image forming operation, so-called process control, is executed as needed based on information obtained by detecting the inspection image. (For example, Patent Document 1).

  Further, in such an image forming apparatus, there is provided a cleaning member such as a cleaning blade that removes deposits such as developer remaining on the holding surface of the image holding member while being in contact with the holding surface. The contact portion of the cleaning member with the holding surface may turn up carelessly due to factors such as frictional resistance with the holding surface, and the original cleaning performance may not be sufficiently obtained. For this reason, as a countermeasure, for example, a belt-shaped (replenishment) image composed of a developer is formed on the image holding member, and the image is supplied so as to be conveyed to a contact portion with the holding surface of the cleaning member. It is known to perform a so-called turning-up preventing operation of the cleaning member as necessary (for example, Patent Document 2).

  In the image forming apparatus configured to perform both the process control operation and the turning-up prevention operation of the cleaning member, each operation is performed individually because the purpose of each operation and the timing for executing the operation are different. Yes.

JP 2003-337458 A Japanese Patent Laid-Open No. 7-334012

  According to the present invention, the process control operation and the cleaning member curl prevention operation as described above are performed separately, and accordingly, the time during which a general image forming operation cannot be performed is increased, and the overall productivity is lowered. An object of the present invention is to provide an image forming apparatus that can avoid the above.

  The image forming apparatus of the present invention (A1) has an image forming apparatus for forming an image developed with a dry developer, and a holding surface for holding an image formed by the image forming apparatus, and rotating image holding And a cleaning member that removes the developer attached to the holding surface of the image holding member in contact with the holding surface, and an inspection image is formed by the image forming device and held on the holding surface of the image holding member Control means for performing an operation of forming a supply image to be supplied to a contact portion in contact with the holding surface of the cleaning member by the image forming device and holding the supply image on the holding surface at a time of executing a control operation including the operation of It has.

  In the image forming apparatus according to the present invention (A2), in the image forming apparatus according to the aforementioned invention A1, the control means forms the supply image simultaneously with the inspection image.

  Further, in the image forming apparatus of the invention (A3), in the image forming apparatus of the invention A1 or A2, the control means displays the supply image and the inspection image in the region in the rotation axis direction of the image carrier. It is formed so as to be held in at least a part of the area portion excluding the area to be held.

  The image forming apparatus according to the present invention (A4) further includes a measuring unit that accumulates and measures the number of rotations of the image carrier in the image forming apparatus according to any one of the above-described inventions A1 to A3. The operation of forming the supply image is executed when the measurement result of the measuring means exceeds a set value.

  The image forming apparatus according to the invention (A5) is the image forming apparatus according to the invention A4, wherein the control means changes the set value to an increased value every time the measurement result reaches the set value. is there.

  The image forming apparatus according to the present invention (A6) includes a detecting means for detecting an increase in power for rotating the image carrier in the image forming apparatus according to any one of the inventions A1 to A3, and the control means. However, when the detection result of the detection means exceeds a set value, the operation of forming the supply image is executed.

  The image forming apparatus according to the invention (A7) is the image forming apparatus according to the invention A1, A4 or A6, which individually accommodates a plurality of developers having different colors, and individually images each developer of each color. The control unit selects at least one of the plurality of developers to form the supply image.

  The image forming apparatus according to the present invention (A8) is the image forming apparatus according to the invention A7, wherein the number of image pixels formed by the image forming device is individually accumulated for each color image and measured. And the control unit forms the supply image using a developer having a color having the smallest cumulative pixel number among the measurement results of the pixel measurement unit.

  Further, the image forming apparatus of the present invention (A9) has a detecting means for detecting the inspection image held on the holding surface of the image holding member at a position facing the holding surface in the image forming apparatus of the invention A1. The control unit forms the supply image at a time until the inspection image held on the holding surface is detected by the detection unit and finishes passing.

  According to the image forming apparatus of the invention A1, compared to the case where the configuration of the present invention is not provided, there is less chance that a general image forming operation cannot be performed, and the productivity of the entire apparatus is reduced accordingly. Can be avoided.

  In the invention A2, the supply image can be efficiently formed as compared with the case where the configuration is not provided, and it is possible to more reliably avoid the decrease in the overall productivity.

  In the invention A3, as compared with the case where the configuration is not provided, the supply image is formed by thinning out at least the inspection image, so that it is possible to reduce the consumption of the developer required for forming the supply image.

  In the invention A4, a supply image is formed when necessary as compared with the case where the configuration is not provided, and the consumption of the developer required for forming the supply image can be reduced.

  In the invention A5, as compared with the case where the configuration is not provided, as the cumulative number of rotations of the image carrier increases, the interval at which the formation time of the supply image determined based on the set value arrives becomes longer. The consumption of the developer required for formation can be reduced.

  In the invention A6, a supply image is formed when necessary as compared with the case where the configuration is not provided, and the consumption of the developer required for forming the supply image can be reduced.

  In the invention A7, the consumption of the developer can be adjusted by appropriately selecting the developer used for forming the supply image, as compared with the case where the configuration is not provided.

  In the invention A8, the supplied image is formed with the least consumed developer at the time of general image formation as compared with the case without the configuration, and only a part of the plurality of developers is provided. There is no risk of consuming much only for the formation of the supply image.

  In the invention A9, as compared with the case where the configuration is not provided, it is possible to reliably prevent the supply image from being formed at the time when the control operation is performed and to reduce the overall productivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic explanatory diagram illustrating a main part of the image forming apparatus according to the first embodiment. The image forming apparatus 1 is configured as a color printer, for example, and has toner (colored fine powder) as a dry developer based on input image information in a housing (not shown). A plurality of image forming apparatuses 10 that form toner images developed by the image forming apparatus, a sheet conveying apparatus 20 that conveys a sheet 9 to which the toner images formed by the respective image forming apparatuses 10 are transferred, and the sheet conveying apparatus 20 A fixing device 30 for fixing the toner image by passing the paper 9 after the toner image is transferred is mainly installed. A one-dot chain line with an arrow in the figure indicates a main conveyance path of the paper 9.

  The image forming apparatus 10 can form and transfer a toner image to be developed with toner as a dry developer using, for example, a known electrophotographic method, electrostatic recording method or the like. In this embodiment, four image forming devices (10Y, 10M, 10C, 10C, 10M, 10C, 10K), and the image forming devices are arranged in series.

  Each image forming device (10Y, 10M, 10C, 10K) has a substantially common configuration as shown below. Each of these image forming apparatuses 10 basically includes a photosensitive drum 12 that is driven to rotate in the direction of arrow A (the clockwise direction in the drawing), and around the photosensitive drum 12 is as follows. Each device is mainly arranged. The main devices are a charging device 13 provided with a charging roll for uniformly charging the surface (image holding surface) of the photosensitive drum 12, and image information (signal) on the surface of the photosensitive drum 12 after charging. , An exposure device 14 including an LED array, a laser scanning device, and the like that forms an electrostatic latent image having a potential difference (for each color) by irradiating light based on the above, and each color (Y, M, C, K) a developing device 15 (Y, M, C, K) that performs development for transferring and adhering the toner to a visible image, and the toner image is conveyed by the paper conveying device 20 (the paper conveying belt 21). A transfer device 16 provided with a transfer roll or the like for transferring to the paper 9 to be transferred, and a drum cleaning device 17 for removing toner remaining on the surface of the photosensitive drum 12 after transfer.

  The photosensitive drum 12 is obtained by forming an image holding surface having a photoconductive layer (photosensitive layer) made of an organic photosensitive material on a cylindrical base material to be grounded. In the exposure device 14, image information input from a device such as a document reading device, a storage medium reading device, or a personal computer that is mounted on or connected to the image forming apparatus 1 is processed by an image processing device (not shown). And an image signal for each color component obtained after the processing is input. Further, the charging device 12, the developing device 15 (the developing roll 15a), and the transfer device 16 are supplied with a charging voltage, a developing voltage, and a transfer voltage at predetermined times from a power supply device (not shown) at the time of image formation. Applied.

  The paper transport device 20 includes a paper transport belt 21 that rotates in the direction of arrow B (counterclockwise in the drawing) while passing between the photosensitive drum 12 of the image forming device 10 and the transfer device 16 (transfer position). A plurality of support rolls 22 and 23 that support the paper transport belt 21 in a desired state so as to rotate freely, and paper 9 fed one by one from a paper feeding device (not shown) are provided on the outer peripheral surface of the paper transport belt 21. It mainly comprises an attracting roll 25 that electrostatically attracts and a belt cleaning device 26 that removes unnecessary toner and paper dust adhering to the outer peripheral surface of the paper transport belt 21.

  As the paper transport belt 21, for example, a material formed in a form of an endless belt having a predetermined thickness using a material in which a resistance adjusting agent such as carbon is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. Is done. The support roll 22 is configured as a drive roll, and rotates by rotational power transmitted from a rotary drive device 28 including a motor and the like. A sheet suction voltage is applied to the suction roll 25 at a time when the sheet 9 is sucked from a power supply device (not shown).

  The belt cleaning device 26 includes a cleaning blade 27 that is installed in contact with the outer peripheral surface of the paper transport belt 21 at a predetermined pressure and angle, and is attached with toner or the like scraped and removed by the blade 27. The kimono is collected in the storage case. The cleaning blade 27 is a plate having a length that contacts almost the entire region in the width direction of the paper transport belt 21 (a direction substantially parallel to the direction of the rotation axis), and is made of urethane rubber or the like. Things are used. In this embodiment, the cleaning blade 27 is inclined at a predetermined angle to the downstream side in the belt rotation direction B with respect to the outer peripheral surface of the paper transport belt 21 portion whose tip is supported by the support roll 23. It is arranged so as to come into contact with the posture.

  The fixing device 30 includes a heating roll 31 that is rotated in the direction of the arrow and heated by heating means so that the surface temperature is maintained at a predetermined temperature in a dedicated housing (not shown). A pressurizing rotator 32 such as a roll type or a belt type that is driven to rotate in contact with a predetermined pressure so as to substantially follow the axial direction is installed. Fixing by the fixing device 30 is performed when the sheet 9 on which the toner image is transferred is introduced into a contact portion where the heating roll 31 that rotates in a heated state and the pressing rotator 32 are in contact with each other and passes through the contact portion. It is performed by heating and pressurizing.

  As shown in FIG. 2, the image forming apparatus 1 is controlled by a control device 5 for various operations in the entire apparatus. The control device 5 is mainly composed of a central processing unit, storage means, control means, and the like. In addition, the control device 1 includes a central control unit 51 that comprehensively controls the whole, and each operation (rotation operation, charging, exposure, exposure) of the four image forming devices 10 (Y, M, C, K). An image forming control unit 52 (Y, M, C, K) for controlling development and transfer process operations, and a sheet conveyance control unit for controlling each operation (rotation operation, sheet adsorption operation, etc.) of the sheet conveyance device 20. 53, a control unit such as a fixing control unit (not shown) for controlling each operation (rotation operation, heating operation, etc.) of the fixing device 30 and a control unit for controlling the operation of the image processing apparatus. ing.

  The control device 5 is connected to an operation display unit, an input / output unit, a detection unit, and the like (not shown), and inputs and outputs (including display) necessary information. The control operation by the control device 5 is executed in accordance with various control programs and data stored in the storage means while taking in various necessary input information.

  Such an image forming operation (hereinafter also referred to as “printing operation”) by the image forming apparatus 1 is performed as follows. Here, a basic printing operation when a full-color image is formed on one side of the paper 9 will be described.

  When the control device 5 receives a print operation start command, the control device 5 controls the photosensitive drum 12 of the image forming device 10 (Y, M, C, K) and the paper transport belt 21 of the paper transport device 20. While starting to rotate, each charging device 13 in the image forming device 10 charges the outer peripheral surface of each photosensitive drum 12 to a predetermined polarity and potential. Subsequently, the exposure device 14 performs exposure based on an image signal on the outer peripheral surface of the charged photosensitive drum 12 to form an electrostatic latent image having a predetermined potential difference. A toner charged with an electrostatic latent image with a predetermined polarity is supplied from the developing roll 15a and developed to be visualized as a toner image. As a result, a toner image of each color (Y, M, C, K) is formed exclusively on the photosensitive drum 12 of each image forming device 10 (Y, M, C, K).

  On the other hand, in accordance with the image forming operation timing of the toner image, the sheet 9 having a desired size and type is supplied toward the sheet conveying device 20, and the suction roll 25 is applied to the outer peripheral surface of the rotating sheet conveying belt 21. It is adsorbed by the electrostatic action. When the sheet 9 is conveyed by the sheet conveying belt 21 and passes the transfer position of each image forming device 10 (Y, M, C, K), the toner image on the photosensitive drum 12 in each image forming device 10 is transferred. The images are transferred in such a manner that they are sequentially superposed on the paper 9 side under the electrostatic action of the transfer device 16. The surface of the photosensitive drum 12 after the transfer is completed is cleaned by a drum cleaning device 17.

  Subsequently, the sheet 9 on which the toner image has been transferred is peeled off from the sheet conveying belt 21 and then conveyed toward the fixing device 30 and introduced. In the fixing device 30, the toner of the toner image is melted and heated on the paper 9 by heating and pressurizing the paper 9 on which the toner image is transferred through the contact portion between the heating roll 31 and the pressurizing rotating body 32. Let it settle. The paper 9 after the fixing is completed is discharged and accommodated in a paper discharge section (not shown) when only image formation on one side is performed. As a result, the basic printing operation for one sheet is completed. Further, when there are continuous print instructions for a plurality of sheets, the series of operations described above are similarly repeated for the number of sheets instructed.

  In the image forming apparatus 1, when a predetermined time comes, the control device 5 executes a density control operation for performing control for correcting the image density by forming a patch image for control inspection described below. At the time of executing the control operation, a blade turning prevention operation for forming a supply image to be supplied to the contact portion of the cleaning blade 28 with the paper conveying belt 21 is executed.

  In the density control, the four image forming devices 10 form patch images Tp (Y, M, C, K) of the respective colors (Y, M, C, K), respectively, and transfer them to the paper transport belt 21; An operation of reading each patch image transferred to the conveyance belt 21 by the density detection sensor 6, and an operation of determining a correction amount of the density-related condition based on information on the density detection result of each patch image read by the density detection sensor 6. Is included. The predetermined time when such control operation is executed is, for example, when the number of formed images reaches a set number, or when the temperature and humidity in the apparatus reach set values. Also, when this control operation is executed, the normal image forming operation is prohibited or temporarily interrupted.

  As shown in FIG. 3, the patch image Tp is formed as a rectangular toner image (predetermined density) having a predetermined dimension (for example, 10 mm × 10 mm). This patch image Tp is, for example, a size that occupies a part of the area in the rotation axis direction (C, D) of the outer peripheral surface (strictly speaking, the area corresponding to image formation) of the sheet conveying belt 21, and is almost in the rotation axis direction. It is formed so as to be located in the center or the like. The formation position of the patch image Tp in the rotation axis direction is also determined by the relationship with the effective reading range of the density detection sensor 6. A reference numeral 27 a indicated by a dotted line in FIG. 3 exaggerates the region where the cleaning blade 27 is in contact with the paper transport belt 21.

  In this image forming apparatus 1, a patch image Tp is formed by the same process as a normal toner image in each production device 10, then directly transferred onto the paper transport belt 21, and held on the paper transport belt 21. The patch image Tp is read by the density detection sensor 6. FIG. 4 shows the operation timing at the time of patch image formation executed in each production device 10 (Y, M, C, K). In FIG. 4, charging, development, and transfer indicate the charging voltage, the developing voltage (actually, the developing bias applied to the developing roll 15a), and the timing (ON state) at which the transfer voltage is applied. In FIG. 4, exposure indicates exposure timing (ON state) when forming an electrostatic latent image of each color patch image Tp.

  The density detection sensor 6 includes an illumination unit (light emitting element or the like) that illuminates the patch image Tp on the paper transport belt 21, and a reading unit (light receiving element) that receives necessary light reflected by the patch image Tp and reads it as an electrical signal. ) And a sensor control unit 62 that controls the operation of the detection element unit and calculates the concentration state from the electrical signal obtained by the reading unit (see FIG. 2). The sensor control unit 62 is connected to the central control unit 51 of the control device 5, and transmits the detection result of the concentration detection sensor 6 to the central control unit 51.

  In this embodiment, the density detection sensor 6 is further downstream in the rotational direction B from the transfer position of the black image forming device 10K arranged at the most downstream position in the rotational direction B of the paper transport belt 21. It is installed at a position (for example, a position facing the belt portion supported by the drive roll 22) that is close to and opposed to the outer peripheral surface portion of the sheet conveying belt 21. Further, the density detection sensor 6 operates at the timing shown in FIG. 4 during the density control operation. That is, when the execution timing of the density control operation comes, the illumination unit of the detection element unit in the density detection sensor 6 emits light and starts illumination, and the reading unit of the detection element unit has four colors (Y, M, C, K). The light receiving operation (reading) is performed at a time in accordance with (a passage time of the patch image Tp). The passage time is determined by, for example, the relationship between the transfer timing, the separation distance from the transfer position to the reading unit, and the rotation speed of the paper transport belt 21.

  When transmitted from the sensor control unit 62, the central control unit 51 determines a correction amount for a density-related condition determined in advance based on information on the density detection result of each patch image at that time. For example, a comparison table of detection results and setting values of conditions corresponding to the detection results can be prepared, and the correction amount of the density related condition can be determined based on the table. Further, the density-related condition can be adopted as long as it is a target that can adjust the density of the toner image formed by each image forming device 10 by changing a set value, for example, the exposure amount of the exposure device 14, This is a setting value such as a developing bias of the developing device 15. The central control unit 51 transmits the determined set value after correction to the corresponding image formation control unit 52 and applies it to the image forming operation (process operation) to be executed thereafter.

  The blade turning prevention operation includes an operation in which the supply image Ts is formed in the image forming apparatus 10 at the time when the above-described density control operation is performed, and is directly transferred to the paper transport belt 21, and the supply image Ts is transferred to the paper transport belt 21. The operation includes conveying and supplying the cleaning blade 27 of the belt cleaning device 26 to the contact portion 27a with the belt by rotation.

  Among the turning-up preventing operations, the supply image Ts is formed within the time when the density control operation is executed. In this embodiment, the supply image Ts is formed at the same time as the patch image Tp.

  The execution time of the density control operation is, for example, as shown in FIG. 4, from the time point PS when the illumination unit of the density detection sensor 6 is turned on (start point) PS to the time point when the illumination unit is turned off (end). Point) It can be between PE. Incidentally, all the formation of the patch image Tp as the detection target and the reading of the patch image Tp by the density detection sensor 6 are performed until the illumination unit is turned off.

  As shown in FIG. 5, the supply image Ts is transferred and held in the rotation axis directions C and D of the paper transport belt 21 from the viewpoint of not overlapping the formation area of the patch image Tp that is formed simultaneously. It is formed so as to be transferred onto a region portion excluding the region Ea to be transferred (in this embodiment, two regions Eb and Ec exist on both sides of the region Ea).

  In this embodiment, the supply image Ts is formed with black color (K) toner in the image forming apparatus 10K, and the length of the patch image Tp (K) (the dimension in the belt rotation direction B) is used as the supply image Ts. ) A shape having the same length as L1 and a predetermined width (dimensions in the rotation axis directions C and D) w1 and w2 over almost the entire area of the two regions Eb and Ec in the rotation axis directions C and D excluding the patch image Tp. It is set to form a thing (Ts1, Ts2). The supply image Ts may be formed with the same density as the patch image Tp. However, from the viewpoint of reducing toner consumption, the supply image Ts may be formed with a density lower than that.

  The formation of the supply image Ts is set so as to be performed when the accumulated number of rotations of the sheet conveying belt 21 exceeds a set value (M) that is a threshold (when the density control operation is performed). ing. The accumulated number of rotations of the sheet conveying belt 21 is measured by a reading sensor 29 arranged at a position where the reference mark (not shown) formed at a fixed position of the sheet conveying belt 21 can be read. This is performed by accumulating and counting the detection results by the rotation counter 55 provided in the central control unit 51 of the control device 5. The set value (M) of the number of rotations is set to 1000 times, for example. The central control unit 51 determines whether or not the number of rotations exceeds the set value (M).

  Hereinafter, the density control operation and the blade turning prevention operation will be described.

  For example, when the predetermined number of image formations is reached and the execution timing of the density control operation comes, after the accumulated number of rotations of the sheet conveying belt 21 is read from the rotation counter 55 in the central control unit 51 as shown in FIG. (Step 10: S10), it is determined whether or not the number of rotations is within a set value M (S11).

  If the number of rotations does not exceed the set value M, the central controller 51 determines that only the patch image Tp (K) is formed in the image forming device 10K (S12), and thereafter only the density control operation is performed. Executed.

  That is, in each image forming device 10 (Y, M, C, K), the charging, exposure, and development process operations by the charging device 13, the exposure device 14, and the developing device 15 are the same as the conditions for the current image forming operation ( (Only the pattern conditions of the latent image formed by exposure are different), and each color patch image Tp (Y, M, C, K) is formed on each photosensitive drum 12, and then the transfer process by the transfer device 16 is performed. And the patch images Tp (Y, M, C, K) are respectively transferred to the paper transport belt 21 at intervals (S13, FIG. 3).

  Subsequently, each patch image Tp transferred and held on the paper conveyance belt 21 is read by the density detection sensor 6 when being conveyed by the rotation of the belt 21 and passing through the density detection sensor 6 (S14). The detection result read by the density detection sensor 6 is sent to the central control unit 51 through the sensor control unit 62, and the central control unit 51 determines the correction amount of the density related condition based on the information on the density detection result of each patch image Tp. It is determined (S15). Each patch image Tp (Y, M, C, K) after passing through the density detection sensor 6 is cleaned by the cleaning blade 27 of the belt cleaning device 26 installed downstream of the sensor 6 in the belt rotation direction B. Removed.

  On the other hand, if the number of rotations exceeds the set value M in step S11, the central controller 51 determines that the image forming device 10K forms the patch image Tp (K) and the supply image Ts (K) ( S16) After that, the density control operation and the blade turning prevention operation are executed.

  In this case, the patch images Tp of the respective colors (Y, M, C, K) are respectively formed as described above in the respective image forming devices 10 (Y, M, C, K), and at the same time, in particular, the image forming device 10K. In step S13, an electrostatic latent image of the supply image Ts (K) and its toner image are formed through the exposure and development processes.

  Since the electrostatic latent image of the supply image Ts (K) at this time is formed simultaneously with the black patch image Tp (K), it is not displayed so as to be particularly identifiable in the time chart of FIG. The patch image Tp (K) is exposed and formed at the same timing. In the development process, the electrostatic latent image of the supply image Ts (K) is developed with black (K) toner together with the electrostatic latent image of the patch image Tp (K).

  Subsequently, the patch images Tp (Y, M, C, K) of the respective colors are respectively transferred to the paper transport belt 21 at intervals, and at the same time, the supply image Ts together with the patch image Tp (K) in the image forming apparatus 10K. (K) is also transferred to the paper transport belt 21. As a result, as shown in FIG. 5, in addition to the patch images Tp (Y, M, C, K) of the respective colors, the sheet conveying belt 21 has both the patch images Tp (K) in the rotation axis directions C, D. The supply image Ts (K) is transferred to the side.

  Thereafter, each patch image Tp and supply image Ts (K) transferred and held on the paper conveyance belt 21 are conveyed by the rotation of the belt 21 and pass through the density detection sensor 6, and only the patch images Tp. Is read by the concentration detection sensor 6 (S14). When the detection result is transmitted to the central control unit 51, the central control unit 51 determines the correction amount of the density related condition based on the information of the density detection result of each patch image Tp (S15).

  Each patch image Tp (Y, M, C, K) and supply image Ts (K) after passing through the density detection sensor 6 are both removed by the cleaning blade 27 of the belt cleaning device 26. At this time, the contact portion of the cleaning blade 27 is formed as a lump of toner in which the black patch image Tp (K) and the supply image Ts (K) existing on both sides of the black patch image Tp (K) are grouped into one band in the rotation axis directions C and D. 27a is supplied to the entire area (see FIG. 5). As a result, the black toner is present between the entire area of the contact portion 27a of the blade 27 and the sheet conveying belt 21, and the blade 27 is prevented from being turned up.

  In this image forming apparatus 1, the blade turning prevention operation is executed within the execution timing of the density control operation as described above, and is not separately executed at a time different from the execution timing of the density control operation. Further, the supply image Ts (K) formed by the blade curling prevention operation is formed in a state excluding (thinned out) the patch image Tp (K), so that it is originally formed in the formation region of the patch image Tp (K). There is no need to form a portion of the supply image to be provided, and toner is not consumed correspondingly.

[Other Embodiments]
In the first embodiment, for example, as shown in FIG. 7, instead of forming a supply image composed of a full-color toner image as illustrated in FIG. 5 as the supply image Ts (K). In addition, supply images Ts3 and Ts4 composed of a plurality of line-shaped toner images extending in the rotation axis directions C and D with a predetermined interval with respect to the rotation direction B of the sheet conveying belt 21 are formed. It can also be configured.

  In the supply image Ts formed by the blade turning prevention operation, in addition to the amount of toner supplied to the contact portion 27a of the cleaning blade 27 by the patch image Tp, the amount of toner supplied by the supply image Ts prevents the cleaning blade 27 from turning up. If it becomes an effective amount, the pattern shape to be formed is not particularly limited. For example, the supply image Ts is not limited to being formed in a continuous state with respect to the rotation axis direction, and can be formed in a scattered pattern.

  In addition, the supply image Ts depends on the relationship with the formation position of the patch image Tp in the rotation axis directions C and D on the paper transport belt 21 (for example, when the supply image Ts is formed at a position shifted to one end side). It is also possible to form the supply image Ts in only one of the regions without forming the supply image Ts in the regions on both sides of the patch image Tp.

  In the first embodiment, the formation of the supply image Ts (blade turning prevention operation) is performed only when the accumulated number of rotations of the sheet conveying belt 21 exceeds the set value M when executing the density control operation. However, if necessary, the density control operation may be performed whenever it is executed.

  In the first embodiment, the same set value M is used as a threshold value when the supply image Ts is formed based on the number of rotations of the sheet conveyance belt 21. For example, FIG. As shown in FIG. 8, a plurality of set values (M1, M2,..., M5) are sequentially changed and used, and the formation time of the supply image Ts is determined based on the different set values. Good.

  In this case, the plurality of set values M are set to values obtained by gradually increasing the first set value M1 used first to the smallest value (for example, about 10 sheets) and thereafter setting values M2 to M5. Use what you set for each. For example, the second set value M2 is about 100 sheets, the third set value M3 is about 500 sheets, the fourth set value M4 is about 1000 sheets, and the fifth set value M5 is about 3000 sheets.

  In addition, when the blade turning prevention operation is executed in this case, as shown in FIG. 9, when the density control operation is executed, the accumulated number of rotations of the sheet conveying belt 21 is the set value M (initially the first set value M1). ), It is determined that the patch image Tp and the supply image Ts are to be formed (S16), and then the count value of the rotation counter 55 is cleared to zero and used thereafter. What is necessary is just to add and perform the process (S17) which changes the setting value M into the setting value (M2, M3, ...) which consists of the next increased value. Steps S10 to S16 in FIG. 9 are the same as the respective steps (S10 to S16) shown in the flowchart (FIG. 6) of the density control operation and the blade turning prevention operation in the first embodiment.

  Such a configuration that is used while changing a plurality of set values M that increase in value is effective when applied to the following cases. That is, since the paper conveying belt 21 has no frictional material such as toner (debris) on the outer peripheral surface of the belt at the initial stage of use, the friction resistance with the cleaning blade 27 is the largest, and the blade While turning is likely to occur, when the period of use increases (as the number of rotations increases), the amount of toner that adheres to the outer peripheral surface of the belt increases, so the frictional resistance gradually increases. This is a case where the blade is small and the blade is hardly turned over. In other words, when applied to such a case, in the initial stage of use of the paper transport belt 21, the turning-up preventing operation is executed in a relatively short period of time to form the supply image Ts. Blade turning that tends to occur is appropriately prevented. On the other hand, when the use of the paper transport belt 21 is increased, the interval at which the curling prevention operation is performed becomes gradually longer. However, since the blade curling phenomenon is less likely to occur compared to the initial stage of use, the curling prevention is prevented. It is not necessary to perform the operation frequently, and the amount of toner consumption is reduced accordingly.

  Furthermore, in the first embodiment, the number of rotations of the sheet conveying belt 21 is applied as the determination information for determining the timing for forming the supply image Ts. However, other information may be used. A state in which the power for rotating the belt 21 increases and fluctuates (increasing fluctuation of the rotational power) may be applied.

  In this case, the increase fluctuation of the rotational power of the paper transport belt 21 may be detected by measuring the fluctuation of the current supplied to the motor in the rotary drive device 28 that transmits the rotational power to the drive roll 22 of the paper transport belt 21. . Specifically, the sheet conveyance control unit 53 measures and detects the power by a power supply control unit (such as an ammeter) 56 for controlling a power supply device that supplies a current (voltage) to the motor of the rotation drive device 28 (see FIG. 2). The power control unit 56 is configured to transmit the detection result to the central control unit 51.

  Further, in this case, the determination for determining the timing for forming the supply image Ts is that the set value (Q) as the threshold value is determined by detecting the increase fluctuation of the current measured by the power control unit 56 as the increase amount of the rotational power. (FIG. 10), and the current increase fluctuation (rotational power increase amount) is determined depending on whether or not the set value Q has been reached. That is, as shown in FIG. 10, only the patch image Tp is formed when the amount of increase in rotational power is less than the set value Q, and the supply image Ts is formed together with the patch image Tp when the increase value exceeds the set value Q. Set to.

  When the density control operation is executed in the case where the number of rotations of the sheet conveying belt 21 is applied as the determination information for determining the formation time of the supply image Ts, as shown in FIG. After the increase amount (detection result) of the rotational power of the sheet conveying belt 21 is read (S20), it is determined whether or not the increase amount has reached the set value Q (S21).

  As a result, when the increase amount does not reach the set value Q, as shown in FIG. 11, it is decided to form only the patch image Tp (S22), and then the case of the first embodiment (FIG. 11). (Steps S13 to S15 in FIG. 6) Formation of only the patch image Tp, reading of the patch image Tp by the density detection sensor 6, and determination of the correction amount of the density related condition in the central control unit 51 are performed ( S23 to S25). On the other hand, when the increase amount has reached the set value Q, it is decided to form the patch image Tp and the supply image Ts (S26), and then in the case of the first embodiment (steps S13 to S13 in FIG. 6). Similar to S15), the patch image Tp and the supply image Ts are formed, the patch image Tp is read, and the correction amount of the density-related condition is determined (S23 to S25).

  In the first embodiment, the supply image Ts is always formed by the image forming apparatus 10K using the black (K) toner. However, any of the four color (Y, M, C, K) toners may be used. Alternatively, the supply image Ts may be formed while being selected.

  In this case, the toner used for forming the supply image Ts is selected, for example, by a pixel (pixel) of an image (latent image) divided into each color component formed by each image forming device 10 (Y, M, C, K). ) Is accumulated and measured, and the color toner having the smallest number of accumulated images may be set. The cumulative count of the number of pixels of each color component is performed by, for example, a pixel counter 52 (Y, M, C, K) installed in each image formation control unit 52. The pixel counter 52 may be disposed in the central control unit 51, the image processing apparatus, or the like.

  When executing the density control operation in this case, as shown in FIG. 12, when it is determined that the accumulated number of rotations of the sheet conveying belt 21 exceeds the set value M (S10 to S11), the patch image and the supply are supplied. After deciding to form an image (S16), the central control unit 51 reads the accumulated count value of each color pixel and selects the color toner having the smallest accumulated pixel number (S18). It is done in addition. After this selection, the patch image Tp and the supply image Ts are formed, and the formation of the supply image Ts at this time is performed in the image forming apparatus 10 using the selected color toner. At this time, operations other than the added process are performed in the same manner as in the case of the first embodiment (steps S10 to S16 in FIG. 6).

  Furthermore, in the first embodiment, the supply image Ts is formed at the same time as the patch image Tp. However, the supply image Ts may be formed at other timings as long as the density control operation is performed.

  In this case, for example, as shown in FIG. 13, the supply image Tss can be formed after the patch images Ts of four colors are formed and transferred to the paper transport belt 21. The supply image Tss may be formed at a time until the last patch image Tp (K) is read by the density detection sensor 6 and finishes passing. The supply image Tss at this time is actually formed after the electrostatic latent image of the last patch image Tp (K) is formed (exposure K) in the image forming apparatus 10K, as indicated by a dotted line in FIG. This is performed by forming an electrostatic latent image (exposure K) of the image Tss.

  Such a supply image Tss can be formed in a strip shape that is substantially continuous over the entire area in the rotation axis directions C and D of the paper transport belt 21, but from the viewpoint of suppressing toner consumption, As in the case of the above embodiment (configuration in which the supply image Ts is formed simultaneously with the patch image Tp), the area excluding the area Ea where the patch image Tp is transferred and held in the rotation axis directions C and D of the paper transport belt 21 It is good to form so that it may be transcribe | transferred to the part (at least one part) (FIG. 13). Incidentally, when the supply image Tss is formed by the black color image forming device 10K arranged on the most downstream side, until the time point PEt (FIG. 4) when the transfer operation of the image forming device 10K in the density control operation is turned off. The supply image Tss may be formed on the surface.

  In addition, in the first embodiment, the case where the blade turning prevention operation is performed at the execution timing of the density control operation has been described. However, the blade turning prevention operation is not limited to the density control operation and is different from a general image forming operation. It is also possible to configure so as to be performed within the execution time of other control operations performed at the time. Other control operations include, for example, a misregistration correction control operation (in this case, performed to correct misregistration that becomes apparent when the toner images respectively formed by the image forming devices 10 are transferred and superimposed) (A special patch image for inspecting misalignment is formed).

  Further, the image forming apparatus is not limited to the type illustrated in the first embodiment, and other types of image forming apparatuses that form a control patch image and a supply image for preventing the cleaning blade from turning over. It may be. As another type of image forming apparatus, for example, toner images formed by a plurality of image forming apparatuses 10 are once transferred to an intermediate transfer body (image holding body) in a belt form or a drum form, and finally transferred onto a sheet at the end. And an image forming apparatus of a type that needs to form a control patch image and a blade turning prevention supply image on the intermediate transfer member. As another type of image forming apparatus, it is necessary to form a patch image for control and a supply image for preventing blade turn-up on a photosensitive drum or belt (image holding member), not on a paper conveyance belt or an intermediate transfer member. A type of image forming apparatus can also be applied. From this viewpoint, the image forming apparatus is not limited to an image forming apparatus that forms a color image, and may be an image forming apparatus that forms a single color image (for example, a black and white image).

  When such other types of image forming apparatuses are employed, the determination information for determining the timing for performing the curl prevention operation includes, for example, the number of rotations of the intermediate transfer member, the photosensitive drum or the belt, and the rotational power of the rotation. An increase amount may be applied.

1 is a schematic explanatory diagram illustrating a main part of an image forming apparatus according to an embodiment. FIG. 2 is an explanatory diagram illustrating a configuration of a control system in the image forming apparatus of FIG. 1. It is a schematic explanatory drawing which shows a state when only a patch image is formed. It is a time chart which shows the state of patch image formation (and supply image formation) and reading at the time of density control operation. It is a schematic explanatory drawing which shows a state when a patch image and a supply image are formed simultaneously. It is a flowchart which shows the structural example of density | concentration control operation | movement and a blade turning prevention operation | movement. It is a schematic explanatory drawing which shows the other example of the formation pattern of a supply image. It is explanatory drawing which shows the relationship between the several setting value regarding the frequency | count of rotation, and the image to form. It is a flowchart which shows the structural example of the density | concentration control operation | movement in case a some setting value is used, and a blade turning-up prevention operation | movement. It is explanatory drawing which shows the relationship between the setting value regarding the increase amount of rotational power, and the image to form. It is a flowchart which shows the structural example of the density | concentration control operation | movement in case the setting value regarding the increase amount of rotational power is used, and a blade turning prevention operation | movement. 6 is a flowchart illustrating a configuration example of a density control operation and a blade turning prevention operation in a case where a processing step of selecting toner for forming a supply image is included. It is a schematic explanatory drawing which shows a state when a supply image is formed after forming a patch image.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 5 ... Control apparatus (control means), 6 ... Density detection sensor (detection means), 10 ... Image forming apparatus, 15 ... Developing apparatus which accommodates developer, 21 ... Paper conveyance belt (image holding body) , 27 ... Cleaning blade (cleaning member), 55 ... Rotation counter (measurement means), 56 ... Power supply control unit (detection means), 57 ... Pixel counter (pixel measurement means), Tp ... Patch image (inspection image), Ts ... Supply image, C, D ... Rotational axis direction, Ea ... Area where a patch image is held, Eb, Ec ... A region part excluding an area where a patch image is held.

Claims (9)

An image forming apparatus for forming an image to be developed with a dry developer;
An image holder having a holding surface for holding an image formed by the image forming device and rotating;
A cleaning member that removes the developer adhering to the holding surface of the image holding member in contact with the holding surface;
A supply image to be supplied to a contact portion that contacts the holding surface of the cleaning member at a time when a control operation including an operation of forming an inspection image by the image forming device and holding the inspection image on the holding surface of the image holding member is executed. An image forming apparatus comprising: a control unit that executes an operation of forming the image forming apparatus and holding the image forming apparatus on the holding surface.   The image forming apparatus according to claim 1, wherein the control unit forms the supply image simultaneously with the inspection image.   The said control means is formed so that the said supply image may be hold | maintained so that it may hold | maintain in at least one part of the area | region part except the area | region where the said test | inspection image is hold | maintained in the rotating shaft direction of the said image holding body. Image forming apparatus. Measuring means for accumulating and measuring the number of rotations of the image carrier;
The image forming apparatus according to claim 1, wherein the control unit performs an operation of forming the supply image when a measurement result of the measurement unit exceeds a set value.   The image forming apparatus according to claim 4, wherein the control unit changes the set value to an increased value every time the measurement result reaches the set value. Detecting means for detecting an increase variation in power for rotating the image carrier;
The image forming apparatus according to claim 1, wherein the control unit performs an operation of forming the supply image when a detection result of the detection unit exceeds a set value. The image forming apparatus is an apparatus that individually accommodates a plurality of developers having different colors and can individually form an image for each developer of each color.
The image forming apparatus according to claim 1, wherein the control unit selects at least one of the plurality of developers to form the supply image. Pixel measuring means for accumulating and measuring the number of pixels of the image formed by the image forming device individually for each color image;
The image forming apparatus according to claim 7, wherein the control unit forms the supply image using a developer having a color having the smallest cumulative number of pixels among the measurement results of the pixel measurement unit. Detecting means for detecting an inspection image held on the holding surface of the image holding body at a position facing the holding surface;
The image forming apparatus according to claim 1, wherein the control unit forms the supply image at a time until the inspection image held on the holding surface is detected by the detection unit and finishes passing.

Images