JP2008304654A - Image forming apparatus and image forming program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of maintaining high image quality over a long period of time by suppressing an image density change in image formation processing due to the secular deterioration in an image carrier. <P>SOLUTION: The drive time of the image carrier 16 is stored in an HDD 27, the toner density of the image carrier 16 is detected by a toner density detecting sensor 29 and the detection result is stored in the HDD 27. When the drive time of the image carrier 16 elapses by a predetermined time, a predetermined number of toner density detection results before and after the elapse of the predetermined time are compared. When a toner density difference before and after the elapse of the predetermined time exceeds a threshold, a control circuit 23 correction-controls the electric potential of an electrifying part 17 and the erase light quantity of a static eliminating part 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a charging unit that uniformly charges an image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and an exposure unit that exposes the image carrier. A developing unit that visualizes the electrostatic latent image into a toner image, a transfer unit that transfers the toner image visualized in the developing unit to a transfer medium, and a static elimination unit that neutralizes the image carrier after the transfer. The present invention relates to an image forming apparatus and an image forming program.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction machine equipped with these functionally, an image carrier such as a photosensitive drum is uniformly charged by a charging unit, and after being charged by an exposure unit. The image bearing member is exposed to form an electrostatic latent image, the developed electrostatic latent image is visualized as a toner image by the developing unit, and the toner image is transferred to a transfer medium such as transfer paper by the transfer unit, and the charge is eliminated. It is well known to repeat the step of discharging the image bearing member after transfer for the next image forming process.

  At this time, the image carrier undergoes image formation processing repeatedly to cause surface degradation over time. When the degree of surface degradation of the image carrier over time increases, the image carrier undergoes the image formation process. There is a possibility that the balance with the parameters is lost, and it is difficult to perform image forming processing with good image quality.

  For example, as the cumulative number of rotations of the image carrier increases, wear occurs on the surface of the image carrier, and the photosensitivity of the image carrier tends to gradually decrease according to the driving time.

  Therefore, even if the image carrier is exposed with the same amount of light, the surface potential of the exposed portion varies depending on the cumulative number of rotations of the image carrier, resulting in inconvenience that the density of the transferred image is not stable.

Therefore, a technique is known in which the number of image forming processes on the image carrier is counted, and the applied voltage of the exposure unit is increased as the count number increases (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 08-278686

  However, in the image forming apparatus configured as described above, in the configuration in which the sensitivity of the image carrier is corrected by increasing the voltage applied to the exposure unit as the count of the number of processed images increases, Although tone density reproducibility is improved, there is a problem that high tone density reproducibility, that is, a problem occurs in which adjacent dots are enlarged and tone characteristics are lowered.

  For example, in the case of multilevel 256 gradations, there is almost no peak in the color image until the gradation output of 0 to 255, and each output value has almost the same appearance frequency. However, in a monochrome image, image data is concentrated on 0 to 64 gradation output corresponding to characters and the like, and there is a peak in the vicinity of 255 gradation output that is white of the background.

  In view of the above circumstances, the present invention provides an image forming apparatus capable of suppressing fluctuations in image density during image forming processing accompanying aging degradation of an image carrier and maintaining high image quality for a long period of time. The purpose is to provide.

  An image forming apparatus according to the present invention includes a charging unit that uniformly charges an image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and the exposure unit. A developing unit that visualizes the electrostatic latent image exposed in step 1 into a toner image, a transfer unit that transfers the toner image visualized in the developing unit to a transfer medium, and a charge eliminating unit that neutralizes the image carrier after the transfer. In the image forming apparatus, the driving time storage unit that stores the driving time of the image carrier, the toner density detector that detects the toner density of the image carrier, and the detection result of the toner density detector The comparison between the toner density storage unit to be stored, the comparison unit that compares the detection results of the toner density detection means for a predetermined number of times before and after the drive time of the image carrier has passed a predetermined time, and the comparison unit The toner density difference before and after the specified time has exceeded the threshold Wherein the can and a control unit for correcting the erase light intensity of the static eliminator and the charging potential of the charging unit when that.

  At this time, one or more toner density detection means are installed in the print area of the image carrier, and the control means erases the amount of erase light from the neutralization unit when at least one of the toner density detection means exceeds the threshold. Is preferably corrected in a state of being divided into a plurality along the scanning direction of the image carrier. The threshold is preferably set to 0.1.

  The image forming program of the present invention includes a drive time storage step for storing the drive time of the image carrier, a toner concentration detection step for detecting the toner concentration of the image carrier, and a toner concentration storage for storing the toner density detection result. A step, a comparison step for comparing the toner density detection results for a predetermined number of times before and after the drive time of the image carrier has passed a predetermined time, and a toner density difference before and after the predetermined time has exceeded a threshold value And a correction step of correcting the charging potential of the charging unit and the erase light quantity of the charge eliminating unit.

  The image forming apparatus of the present invention can improve the temperature management accuracy of the image carrier without adversely affecting the image forming process by the image carrier.

  Next, an image forming apparatus according to an embodiment of the present invention is applied to a color printer and will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a color printer as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a main part of the color printer as an image forming apparatus according to an embodiment of the present invention. It is.

  As shown in FIG. 1, a printer 1 as an image forming apparatus according to an embodiment of the present invention includes a paper feed cassette 3 that can be pulled out from one surface (for example, the front surface) of a printer main body 2, and one surface of the printer main body 2. A manual paper feed tray 4 that can be turned upside down, a transport path 5 that transports transfer paper (not shown) set in the paper feed cassette 3 or the manual paper feed tray 4, and an upstream end of the transport path 5 Forming a toner transfer image on the surface of the transfer paper in cooperation with the secondary transfer roller 7 serving as a transfer unit disposed in the middle of the conveyance path 5 and the secondary transfer roller 7 disposed in the middle of the conveyance path 5 An endless belt-shaped intermediate transfer member 8 and a plurality of toner supply units 9 for transferring toner of each color (for example, yellow, magenta, cyan, and black) as a toner image to the surface of the intermediate transfer member 8 as necessary, Of transport path 5 A fixing unit 10 which is arranged near the edge and fixes a toner transfer image formed on the surface of the transfer paper, and discharges the fixed transfer paper from the downstream end of the conveyance path 5 to the paper discharge tray 11 of the printer body 2. And a discharge unit 12 for performing the above operation.

  In this embodiment, the toner supply units 9 are arranged at four locations along the conveyance direction (see the arrow) of the intermediate transfer body 8, and basically the same configuration is arranged. The toner supply unit 9 includes a toner cartridge 13 that stores toner of each color, a supply unit 14 that supplies toner stored in the toner cartridge 13, and a primary image formation processing unit that primarily transfers a toner image to the intermediate transfer body 8. 15.

  As shown in FIG. 2, the primary image forming processing unit 15 includes a drum-shaped image carrier 16, a charging unit 17 that charges the surface of the image carrier 16, and a predetermined electrostatic latent image on the surface of the image carrier 15. An exposure unit 18 that forms an image, a developing roller 19 that constitutes part of the supply unit 14 and supplies toner from the supply unit 14 to the image carrier 16, and the image carrier 16 across the intermediate transfer member 8. The primary transfer roller 20 disposed, a cleaning unit 21 that removes residual toner and the like adhering to the surface of the image carrier 16, and a charge removal unit 22 that removes the charge of the image carrier 16 for the next image forming process. Are provided in this order (process order). The image carrier 16, the charging unit 17, the exposure unit 18, and the charge removal unit 22 are controlled to be driven by a control circuit 23.

  The control circuit 23 is provided, for example, on a control circuit board 24 (see FIG. 1) disposed near the bottom surface of the apparatus main body 2. The control circuit 23 controls the image carrier 16, the charging unit 17, the exposure unit 18, the charge eliminating unit 22, and the like based on various control programs related to the entire image forming process stored in the ROM 25.

  The ROM 25 also stores a control program related to the image carrier control of the present invention, and a microcomputer is configured with the control circuit 23 that executes the image carrier control program. Note that image data and the like when executing the image forming process are temporarily stored in a storage unit such as the RAM 26 or the HDD 27 different from the ROM 25.

  Further, the control circuit 23 causes the timer 28 to measure the driving time of the image carrier 16 (any of the operation time, the number of rotations, and the number of image forming processes), and stores the measurement time in the RAM 26 or the HDD 27. Further, the control circuit 23 stores the detection result from the toner detection sensor 29 that detects the toner density on the surface of the intermediate transfer body 8 in the RAM 26 or the HDD 27.

  Next, an example of image carrier control by the control circuit 17 of the present invention will be described based on the flowchart of FIG.

(Step S1)
In step S1, the control circuit 17 causes the timer 28 to measure the driving time of the image carrier 16, and stores the total driving time in the RAM 26 or the HDD 27, and proceeds to step S2.

(Step S2)
In step S2, the control circuit 17 causes the toner density detection sensor 29 to detect the toner density, for example, every time the number of image forming processes on the transfer paper or every rotation of the image carrier 16 (or the intermediate transfer body 8). The density detection value is stored in the RAM 26 or HDD 27 for each detection, and the process proceeds to step S3.

(Step S3)
In step S3, the control circuit 17 monitors the total drive time of the image carrier 16 stored in the RAM 26 or HDD 27 to determine whether or not the predetermined time has elapsed. If the predetermined time has elapsed, the control circuit 17 proceeds to step S4. If the predetermined time has not elapsed, the process loops to step S1.

  For example, as shown in the graph of FIG. 4, the predetermined time includes a peak Z at which the image quality maintenance decreases with the deterioration of the image carrier 16, and the size, rotational speed, material, It can be set based on past experience values in consideration of the toner type and the like.

  At this time, like the printer 1 of the present invention, in the case of color, the driving time of the image carrier 16 is set and controlled independently for each color.

(Step S4)
In step S4, when the image forming process is continuously executed after a predetermined time has elapsed, the control circuit 17 performs every image forming process on the transfer paper or every rotation of the image carrier 16 (or the intermediate transfer member 8). Then, the toner density detection sensor 29 detects the toner density, the toner density detection value is stored in the RAM 26 or the HDD 27 for each detection, and the process proceeds to step S5.

(Step S5)
In step S5, after a predetermined time has elapsed, the control circuit 17 determines whether the number of image forming processes for the transfer paper or the number of rotations of the image carrier 16 (or the intermediate transfer body 8) associated with execution of the continuous image forming process is a predetermined number of times (for example, (10 sheets or 10 rotations) is monitored. If the predetermined number of times has been reached, the process proceeds to step S6. If the predetermined number has not been reached, the process loops to step S4.

(Step S6)
In step S6, the control circuit 17 detects the toner density detection value of the toner density detection sensor 29 before the predetermined time has passed a predetermined number of times (for example, 10 sheets or 10 rotations) and the toner density detection after the predetermined time has passed. The detected value of the toner density detected by the sensor 29 is compared with the detected value for a predetermined number of times (for example, 10 sheets or 10 rotations), and the process proceeds to step S7.

(Step S7)
In step S 6, the control circuit 17, for example, based on the average value A of the toner density detection value for a predetermined number of times before a predetermined time elapses and the average value B of the toner density detection value for a predetermined number of times after a predetermined time elapses. In the case of (A−B) /B≧0.1, it is determined that the control accompanying the deterioration of the image carrier 16 is necessary, and the process proceeds to Step S8, where (A−B) / B <0.1. In this case, after a predetermined time with respect to the drive time of the image carrier 16 is extended (for example, 10 minutes) in step S9, the process loops to step S1.

  The predetermined number of times before and after the elapse of the predetermined time is not limited to the above ten times, but is the same number before and after. If (A−B) / B <0.1 is determined after the comparison result, the predetermined time is extended and then the process loops to step S1 and the predetermined number of times before and after the predetermined time elapses. And you may loop to step S6.

(Step S8)
In step S8, the control circuit 17 corrects the charging potential of the charging unit 17 and the erase light amount of the charge eliminating unit 22 and terminates this routine, assuming that the image carrier 16 has deteriorated over time.

  As a specific correction amount of the control circuit 17, as shown in the graph of FIG. 5, when the threshold value 0.1 is exceeded, the change rate of the charging potential of the image carrier 16 is X, and Correction control is performed with the change rate of the erase light quantity as Y.

  Also, a plurality of toner density detection sensors 29 are installed in the printing region of the intermediate transfer body 8 (depth direction perpendicular to the paper surface = scanning direction in FIG. 2), and any one or more of the toner density detection sensors 29 is a threshold value. If (0.1) is exceeded, the erase light amount correction is performed in the scanning direction.

  Specifically, when the toner density detection sensors 29 are installed at the center and three positions on the left and right in the scanning direction, and the output values of the toner density detection sensors 29 show different values X in FIG. In order to select Y for the value, the light amount correction can be performed in the center, left and right divisions in the longitudinal direction of the erase.

  By performing such division control, it is possible to correct for potential unevenness in the scanning direction, and a uniform image without density unevenness can be obtained.

  As described above, in the printer 1 as the image forming apparatus of the present invention, by performing the potential correction of the image carrier 16 and the erase light amount correction, it is possible to prevent a gradation defect due to film scraping of the image carrier 16. Can respond.

FIG. 3 is an explanatory diagram of a color printer as an image forming apparatus according to an embodiment of the present disclosure. FIG. 2 is an enlarged explanatory view of a main part of a color printer as an image forming apparatus according to an embodiment of the present invention. 4 is a flowchart of a control routine of a control circuit in the image forming apparatus according to the embodiment of the present disclosure. FIG. FIG. 6 is a graph showing the relationship between the drive time of the image carrier and the sensitivity VL (half sensitivity) in the image forming apparatus according to an embodiment of the present invention. 6 is a graph showing a relationship between an image carrier potential change rate X and an erase light quantity change rate Y with respect to a calculation result of a toner density detection sensor output value in the image forming apparatus according to the embodiment of the present invention. FIG.

Explanation of symbols

1 ... Printer (image forming apparatus)
8 ... Intermediate transfer member 16 ... Image carrier 17 ... Charging unit 22 ... Static elimination unit 23 ... Control circuit (control unit / comparison unit)
27. HDD (storage unit)
29 ... Toner density detection sensor

Claims (4)

A charging unit that uniformly charges the image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and an electrostatic latent image that is exposed by the exposure unit An image forming apparatus comprising: a developing unit that visualizes a toner image; a transfer unit that transfers a toner image visualized by the developing unit to a transfer medium; and a static elimination unit that neutralizes the image carrier after the transfer. ,
A driving time storage unit that stores the driving time of the image carrier, a toner density detection unit that detects a toner density of the image carrier, a toner concentration storage unit that stores a detection result of the toner density detection unit, and A comparison unit that compares the detection results of the toner concentration detection means for a predetermined number of times before and after the drive time of the image carrier has elapsed, and a toner density difference before and after the predetermined time compared by the comparison unit An image forming apparatus comprising: a control unit that corrects a charging potential of the charging unit and an erase light amount of the neutralizing unit when the voltage exceeds a threshold value.   One or more toner density detectors are installed in the print area of the image carrier, and the control unit determines the erase light amount of the charge eliminating unit when at least one of the toner density detectors exceeds the threshold. The image forming apparatus according to claim 1, wherein the correction is performed in a state of being divided into a plurality along the scanning direction of the carrier.   The image forming apparatus according to claim 1, wherein the threshold value is 0.1.   A drive time storage step for storing the drive time of the image carrier, a toner density detection step for detecting the toner density of the image carrier, a toner concentration storage step for storing the toner density detection result, and a drive time of the image carrier. A comparison step for comparing the toner density detection results for a predetermined number of times before and after the predetermined time has passed, and when the toner density difference before and after the predetermined time has exceeded a threshold value, An image forming program for causing a computer to execute a correction step for correcting an erase light amount.

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