JP2005055741A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of carrying out stable image formation over a long period of time by suppressing the deterioration of a photoreceptor by keeping down the accumulated quantity of a discharge current from an electrifying member to the photoreceptor. <P>SOLUTION: The image forming apparatus is provided with a photoreceptor 202 and an electrifying member 250 for electrifying the photoreceptor 202 in image formation, and transfers a toner image formed on the photoreceptor 202 to a sheet either directly or through an intermediate transfer body 205. The quantity of a discharge current by the electrifying member 250 is controlled according to the relation between the rotation position of the photoreceptor 202, the position of the toner image and the position of the sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an image forming apparatus such as an electrophotographic system or an electrostatic recording system, and various types of color copying such as a multicolor electrophotographic copying apparatus and a recording apparatus constituting an output unit of a facsimile or a computer. The present invention relates to an image forming apparatus that can be suitably embodied in a color machine, a color printer, or the like. Of course, the image forming apparatus of the present invention is not limited to the above-described multicolor electrophotographic copying apparatus.

There are cases where the rotation speed of the intermediate transfer member when the toner image is formed on the intermediate transfer member and the rotation speed of the intermediate transfer member when the formed toner image is transferred to the sheet are different depending on the type of the sheet. In an image forming apparatus (see, for example, Patent Document 1), since the discharge from the charging member to the photosensitive member has been continued while waiting for the transfer timing to the sheet, the integrated amount of the discharge current has increased rapidly. Tended to be. The amount of abrasion on the surface of the photoconductor that causes deterioration of the photoconductor increases in proportion to the amount of discharge current, and as a result, the life of the photoconductor is shortened.
JP-A-6-337568

  The present invention has been made paying attention to the above-mentioned points. When the rotational speed of the intermediate transfer member is decelerated during image formation, the charging current amount is reduced in accordance with the shift timing of the intermediate transfer member. An object of the present invention is to provide an image forming apparatus capable of suppressing deterioration of a photoconductor by controlling and enabling stable image formation over a long period of time.

Also, various problems caused by discharge products such as O ₃ and NO _x due to discharge of the charger, that is, generation of image unevenness due to product adhesion to the discharge electrode, deterioration of the photosensitive drum due to the discharge products, and discharge products An object of the present invention is to provide an image forming apparatus capable of reducing problems such as environmental pollution and increase in power consumption by performing control so as to create a state in which the charging high voltage setting value of the charger is lowered. .

  This invention can solve the said subject by providing the following structure.

  (1) A system that includes a photosensitive member and a charging member that charges the photosensitive member along with image formation, and that transfers a toner image formed on the photosensitive member directly or via an intermediate transfer member to a sheet In the image forming apparatus, a speed control unit that controls a rotation speed of the photosensitive member or the intermediate transfer body and a conveyance speed of the sheet, and a discharge that discharges the charging member in accordance with the control content of the speed control unit. An image forming apparatus comprising: a discharge current amount control unit that controls a current amount.

  (2) The image forming apparatus according to (1), wherein the speed control unit changes a rotation speed of the photosensitive member or the intermediate transfer member and a conveyance speed of the sheet depending on a sheet type.

  (3) The image forming apparatus according to (1), wherein the speed control unit changes a rotation speed of the photoconductor or the intermediate transfer body and a conveyance speed of the sheet according to a sheet size.

  (4) The speed control means changes the rotational speed of the photoconductor or the intermediate transfer body and the conveyance speed of the sheet according to the number of toner images simultaneously formed on the photoconductor or the intermediate transfer body. The image forming apparatus according to item (1).

  (5) When the toner image is formed on the photosensitive member and when the toner image on the photosensitive member is transferred onto the intermediate transfer member, the amount of discharge current of the charging member is I1, The image forming apparatus according to (1), wherein a relationship of I1> I2 is established, where I2 is a discharge current amount of the charging member when the toner image is transferred to the sheet.

  (6) A system that includes a photosensitive member and a charging member that charges the photosensitive member in association with image formation, and transfers a toner image formed on the photosensitive member to a sheet directly or via an intermediate transfer member In this image forming apparatus, when the rotational speed of the photoconductor or the intermediate transfer body and the sheet conveyance speed are changed, the amount of discharge current for controlling the amount of discharge current discharged by the charging member at a predetermined timing after the change is made. An image forming apparatus comprising a control unit.

  According to the present invention, when the rotational speed of the intermediate transfer member is decelerated during image formation, the deterioration of the photosensitive member is suppressed by controlling the charging current amount in a direction that decreases in accordance with the shift timing of the intermediate transfer member. Therefore, it is possible to provide an image forming apparatus that enables stable image formation over a long period of time.

Also, various problems caused by discharge products such as O ₃ and NO _x due to discharge of the charger, that is, generation of image unevenness due to product adhesion to the discharge electrode, deterioration of the photosensitive drum due to the discharge products, and discharge products It is possible to provide an image forming apparatus capable of reducing problems such as environmental pollution and increase in power consumption by performing control so as to create a state where the charging high voltage setting value of the charger is lowered.

  Embodiments of the present invention will be described below using examples.

  Hereinafter, a color image forming apparatus 50 according to an embodiment of the present invention will be described with reference to the accompanying drawings. In each figure, the member which attached | subjected the same reference number represents the same member, and duplication description is abbreviate | omitted.

  FIG. 1 is a schematic cross-sectional view of a color image forming apparatus 50.

  The image forming apparatus 50 has a color image reader unit 1 (hereinafter referred to as “reader unit 1”) in the upper part and a color image printer unit 2 (hereinafter referred to as “printer part 2”) in the lower part.

  First, the configuration of the reader unit 1 will be described.

  Reference numeral 100 denotes a control unit that controls the color image forming apparatus 50 as a whole, 101 is a platen glass (platen), 102 is an automatic document feeder (ADF), and a specular pressure plate is used instead of the automatic document feeder 102. Alternatively, a configuration in which a white pressure plate (not shown) is attached may be used. Reference numerals 103 and 104 denote light sources that illuminate the original, and use light sources such as halogen lamps, fluorescent lamps, and xenon lamps. Reference numerals 105 and 106 denote reflectors for condensing the light from the light sources 103 and 104 on the document, 107, 108, and 109 mirrors, and 110 a reflected light or projection light from the document to a CCD (Charge Coupled Device) image sensor (hereinafter referred to as a CCD) (Referred to as CCD) 111 is a lens for condensing light on 111, and 111 is a CCD. Reference numeral 112 denotes a substrate on which the CCD 111 is mounted, and 113 denotes a digital image processing unit, which includes a portion excluding the CCD 111 in FIG. 4 and portions 401 and 402 in FIG. A carriage 114 accommodates the light sources 103 and 104, the reflectors 105 and 106, and the mirror 107. A carriage 115 accommodates the mirrors 108 and 109. The carriage 114 is moved at a speed V and the carriage 115 is moved at a speed V / 2 in the sub-scanning direction Y orthogonal to the electrical scanning direction (main scanning direction X) of the CCD 111. Scan the entire surface. Reference numeral 116 denotes an external interface (I / F) unit with another device.

  Next, the configuration of the color printer unit 2 will be described.

  Reference numeral 200 denotes a rotation shaft, 201 denotes a laser scanner, 202 denotes a photosensitive drum as a photosensitive member, 203 denotes a rotary color developing device, 205 denotes an intermediate transfer member, 206 denotes a transfer belt, 207a denotes a fixing roller (also referred to as fixing R), and 207b is a pressure roller (also referred to as pressure R), 208 is an upper cassette, 209 is a lower cassette, 211 and 212 are pickup rollers (also referred to as pickup R), and 213 is an upper paper feed roller (also referred to as upper paper feed R). , 214 is a lower feed roller (also referred to as lower feed R), 215 is a transport roller (also referred to as transport R), 216 is a manual feed roller (also referred to as MPFR), and 217 is a face-up discharge. Paper mouth, 218 is a printer control I / F, 219 is a registration roller (also referred to as registration R), 221 is a black developing device, and 222 is a yellow developing device. 223 magenta developing device, 224 is a cyan developer.

  The rotating color developing unit 203 is configured by disposing developing units 221, 222, 223, and 224 corresponding to the respective colors of black, yellow, magenta, and cyan around the rotating shaft 200.

  Reference numeral 230 denotes a cleaning roller (also referred to as cleaning R), reference numeral 231 denotes a waste toner box, and reference numeral 250 denotes a charger as a charging member.

  Reference numeral 280 denotes fixing paper discharge R, 281 denotes FUR, 282 denotes reverse R, 283 denotes DR, and 284 denotes double-sided R.

  P is a laser irradiation position and Q is a visualization position.

  S1 is no upper sheet S, S2 is no upper second sheet S, S3 is no lower sheet S, S4 is no lower second sheet S, S5 is a refeed S, S6 is an MP trailing edge detection S, S7 S is MPF paper absence, S8 is the middle plate position S, S9 is S before registration, S10 is separation jam S, S11 is fixed discharge S, S12 is reverse S, and S13 is double-sided S.

  The image forming apparatus according to the present exemplary embodiment includes a motor that is a speed change member that changes the rotation speed of the photosensitive drum 202 and the intermediate transfer body 205 and the sheet conveyance speed, although not shown in the drawing.

  The printer unit 2 receives a control signal from a CPU 301 of the control unit 100 described later by the printer control I / F 218 and operates based on the control signal from the printer control I / F 218.

  An electrostatic latent image is formed on the photosensitive drum 202 by rotating the photosensitive drum 202 counterclockwise and irradiating the laser irradiation position P with laser light by the laser scanner 201. Then, in order to form a toner image on the photosensitive drum 202, the rotary color developing device 203 is rotated about the rotation shaft 200 by the rotation of a stepping motor (not shown). The developing units 221 to 224 of the respective colors are selectively brought close to (or in contact with) the photosensitive drum 202 in accordance with the separated colors to be developed, and development is performed at the visualization position Q. From the developing units 221 to 224, an amount of toner corresponding to the charge on the photosensitive drum 202 is supplied, and the electrostatic latent image on the photosensitive drum 202 is developed.

  In the present embodiment, the developing units 221 to 224 are configured to be easily detachable from the rotating color developing unit 203. In the rotating color developing unit 203, the installation positions corresponding to the respective colors of black, yellow, magenta, and cyan are designated in the clockwise direction, and the developing units 221 to 224 of the respective colors are mounted at the designated color positions. The

  When developing a black monochromatic image, only the black developing unit 221 is used, and the rotating color developing unit 203 is rotated to a position where a sleeve (not shown) of the black developing unit 221 faces the photosensitive drum 202, and the toner. Supply. When developing a full-color image, all of the developing devices 221 to 224 are used, and in the order of yellow, magenta, cyan, and black, the color of the developing device is rotated to the visualization position Q where the sleeve of the developing device faces the photosensitive drum 202. The container 203 is rotated to supply toner.

  The toner image formed on the photosensitive drum 202 is transferred to the intermediate transfer member 205 that rotates in the clockwise direction by the rotation of the photosensitive drum 202 in the counterclockwise direction. The transfer to the intermediate transfer member 205 is completed with one rotation of the intermediate transfer member 205 in the case of a black single-color image and four rotations in the case of a full-color image. The intermediate transfer member 205 can form two-sided images on the intermediate transfer member 205 when forming an image having a specific sheet size, for example, A4 size or smaller. So-called two-sheet pasting.

  On the other hand, the sheet (recording paper) is picked up by the pickup roller 211 from the upper cassette 208 or by the pickup roller 212 from the lower cassette 209. Then, the paper is conveyed by a paper feed roller 213 or 214, and further conveyed by a conveyance roller 215 to a registration roller (registration R) 219. Then, at the timing when the transfer to the intermediate transfer member 205 is completed, the sheet is conveyed by the registration roller 219 between the intermediate transfer member 205 and the transfer belt 206. Thereafter, the sheet is conveyed by the transfer belt 206 and pressed against the intermediate transfer member 205, and the toner image on the intermediate transfer member 205 is transferred onto the sheet. The toner image transferred onto the sheet is transported between the fixing roller 207a and the pressure roller 207b, and is fixed on the sheet by being heated and pressed. The sheet on which the toner image is fixed is discharged to the face-up discharge port 217.

  The residual toner on the intermediate transfer member 205 that remains without being transferred to the sheet is cleaned by post-processing control. In the post-processing control, the residual toner on the intermediate transfer member 205 after the transfer is finished is charged as a waste toner to the reverse polarity of the original toner polarity by the cleaning roller 230 in FIG. It is transcribed again. In the photosensitive drum unit, the reverse polarity residual toner is scraped off from the drum surface by a blade (not shown) and conveyed to a waste toner box 231 integrated in the photosensitive drum unit. In this way, the residual toner on the intermediate transfer member 205 is completely cleaned, and the post-processing control ends.

  Next, the configuration of the laser scanner will be described with reference to FIG.

  FIG. 2 is a diagram showing a schematic configuration of the laser scanner 201.

  Reference numeral 601 denotes a laser driver circuit board, 602 denotes a collimator lens, 603 denotes a cylindrical lens, 604 denotes a polygon mirror, 605 denotes a polygon mirror driving motor, 606 denotes an imaging lens, 607 denotes a reflecting mirror, and 608 denotes a BD circuit board.

  A laser beam emitted from a laser driver circuit board 601 corresponding to an image data signal and converted into parallel light by a collimator lens 602 and a cylindrical lens 603 is rotated at a constant speed by a polygon mirror drive motor 605. The light enters the mirror 604. Laser light reflected from the polygon mirror 604 passes through an imaging lens 606 and a reflection mirror 607 arranged in front of the polygon mirror 604, scans in the main scanning direction, and is irradiated to the laser irradiation position P of the photosensitive drum 202. .

  Next, the configuration around the control unit will be described with reference to FIG.

  FIG. 3 is a block diagram showing a main configuration around the control unit 100.

  Reference numeral 301 denotes a CPU which is a speed control means and a discharge current amount control means, 302 is a memory, 303 is an operation unit, 304 is a ROM, and 305 is a RAM.

  The control unit 100 includes a CPU 301, an operation unit 303, and a memory 302 having an I / F that exchanges information for performing control with the digital image processing unit 113, the printer control I / F 218, and the external I / F 116. Has been. The memory 302 includes a RAM 305 that provides a work area to the CPU 301 and a ROM 304 that stores a control program for the CPU. The ROM 304 executes various operation modes such as an automatic color selection (ACS) mode for automatically switching between color image formation and monochrome image formation, which will be described later, a color image formation mode (also referred to as color mode), and a monochrome image formation mode. And a control program for controlling the entire image forming apparatus 50 are stored. The operation unit 303 includes a liquid crystal with a touch panel for inputting processing execution contents by the operator, information on processing for the operator, notification of warnings, and the like.

  The CPU 301 controls the rotation speed of the photosensitive drum 202 and the intermediate transfer member 205 and the sheet conveyance speed via a motor (not shown) depending on the type of sheet.

  Further, the CPU 301 can control the amount of discharge current discharged by the charger 250 in accordance with the speed control content.

  That is, the image forming apparatus according to the present exemplary embodiment includes a photosensitive drum 202, a charger 250 that charges the photosensitive drum 202 when the image is formed, and an intermediate transfer member 205, and a toner image formed on the photosensitive drum 202. Is transferred to the intermediate transfer member 205, and the toner image on the intermediate transfer member 205 is transferred to the sheet in synchronism with the sheet conveyance. The CPU 301 uses the rotation speed of the intermediate transfer member 205 and the sheet Further, the CPU 301 controls the amount of discharge current discharged by the charger 250 in accordance with the control content.

  The control content of the speed control means is generally a specific target speed, and includes an acceleration (deceleration) instruction in which the target speed is not determined and an acceleration (deceleration) instruction limited to a certain time.

  For example, correspondence is determined in advance by a table or the like such as which control content corresponds to which discharge current amount, and the discharge current amount can be controlled in accordance with the control content of the speed control means.

  In this embodiment, the CPU 301 serves as both speed control means and discharge current amount control means. However, the present invention is not limited to this, and the speed control means and discharge current amount control means are individually provided. Needless to say, it may be prepared.

  In this case, with respect to the discharge current amount control means, a signal is directly received from the speed control means, a sensor for detecting the speed of the intermediate transfer member 205 is separately provided, and a signal is received therefrom, etc. The control content of the speed control means can be obtained.

  Next, the configuration of the digital image processing unit will be described with reference to FIG.

  FIG. 4 is a block diagram showing a detailed configuration of the digital image processing unit 113.

  Reference numeral 502 denotes a clamp & AMP & S / H & A / D unit, 503 a shading unit, 504 a connection & MTF correction & document detection unit, 505 an input masking unit, 506 a selector, 507 a color space compression & background removal & LOG conversion unit, and 508 A delay unit, 509 a moire removal unit, 510 a scaling process unit, 511 a UCR & masking & black character reflection unit, 512 a γ correction unit, 513 a filter unit, 514 a background removal unit, and 515 a black character determination unit.

  The document on the platen glass 101 reflects light from the light sources 103 and 104, and the reflected light is guided to the CCD 111 and converted into an electrical signal (when the CCD 111 is a color sensor, the RGB color filter is a one-line CCD. It may be one that is inlined in RGB order, or a three-line CCD with R filters, G filters, and B filters arranged for each CCD. The filters are on-chip or the filters are separate from the CCD. It does not matter if it is configured). The electric signal (analog image signal) is input to the digital image processing unit 113.

  In the digital image processing unit 113, first, the clamp & AMP & S / H & A / D unit 502 samples and holds (S / H), clamps the dark level of the analog image signal to the reference potential, and amplifies it to a predetermined amount (the above processing order is A / D conversion is performed, for example, and converted into a digital signal of 8 bits for each of RGB. The RGB signal is subjected to shading correction and black correction by a shading unit 503.

  Thereafter, in the connection & MTF correction & document detection unit 504, for example, when the CCD 111 is a three-line CCD, since the reading position between the lines is different in the connection processing, the delay amount for each line is adjusted according to the reading speed. The signal timing is corrected so that the reading positions are the same. In the MTF correction, since the reading MTF changes depending on the reading speed and magnification, the change is corrected, and the original detection recognizes the original size by scanning the original on the original table glass 101.

  The digital signal whose reading position timing is corrected corrects the spectral characteristics of the CCD 111 and the spectral characteristics of the light sources 103 and 104 and the reflectors 105 and 106 by the input masking unit 505.

  The output of the input masking unit 505 is input to a selector 506 that can be switched to an external I / F signal.

  The signal output from the selector 506 is input to the color space compression & background removal & LOG conversion unit 507 and the background removal unit 514.

  After the background is removed, the signal input to the background removal unit 514 is input to the black character determination unit 515 that determines whether the document is a black character in the document, and generates a black character signal from the document.

  In the color space compression & background removal & LOG conversion unit 507 to which the output of another selector 506 is input, the color space compression determines whether or not the read image signal is within a range that can be reproduced by the printer. If not, the image signal is corrected so that it can be reproduced by the printer. Then, background removal processing is performed, and the LOG conversion unit converts the RGB signal into the YMC signal.

  Then, in order to correct the signal and timing generated by the black character determination unit 515, the timing of the output signal of the color space compression & background removal & LOG conversion unit 507 is adjusted by the delay unit 508.

  The moire removal unit 509 removes the moire from the two types of signals, and the scaling processing unit 510 performs scaling processing in the main scanning direction.

  Next, the signal processed by the scaling processing unit 510 is generated by the UCR & masking & black character reflecting unit 511, and the YMCK signal is generated from the YMC signal by UCR processing, and the masking processing unit corrects the signal to the output signal of the printer. At the same time, the determination signal generated by the black character determination unit 515 is fed back to the YMCK signal.

  The signal processed by the UCR & masking & black character reflecting unit 511 is subjected to density adjustment by the γ correction unit 512 and then smoothed or edge processed by the filter unit 513. The processed signal is transmitted to the printer control I / F 218 and further transmitted to the printer unit 2 and the like.

  Next, reception of a signal processed by the digital image processing unit at the printer unit will be described with reference to FIG.

  FIG. 5 is a diagram illustrating processing in which the printer unit 2 receives a signal processed by the digital image processing unit.

  401 is a binary conversion unit, and 402 is a delay unit.

  The binary conversion unit 401 and the delay unit 402 constitute a printer control I / F 218.

  The 8-bit multilevel signal received from the digital image processing unit 113 is converted into a binary signal by the binary conversion unit 401.

  The conversion method at this time may be a dither method, an error diffusion method, an improved error diffusion method, or the like.

  The converted binary signal is transmitted to the delay unit 402 and the external I / F 116.

  The external I / F 116 transmits the received signal to an external output device such as a FAX (not shown) as necessary. The delay unit 402 adjusts the transmission timing to the laser scanner 201 in order to correct the received signal and the laser emission timing of the laser scanner 201. Then, a signal is transmitted to the laser scanner 201.

  Next, the discharge current amount control of the charging member, which is a feature of the present invention, will be described.

  First, the discharge current amount control of the charging member when the sheet type is plain paper will be described with reference to FIGS.

  FIG. 6 is a timing chart of full-color image formation when the sheet type is plain paper, and FIG. 8 is a flowchart showing image formation of this embodiment.

  Reference numeral 701 denotes a motor timing indicating a speed change of a motor (not shown) for driving the photosensitive drum 202 and the intermediate transfer transfer member 205, 702 denotes a laser timing for irradiating laser light, and 703 is formed on the photosensitive drum 202. Is a primary transfer timing at which the toner image is transferred to the intermediate transfer member 205, 704 is a development rotary timing for rotating the rotary color developing device 203, 705 is a charging high-pressure timing, and 706 is transferred onto the intermediate transfer member 205. A secondary transfer high-pressure timing 707a for transferring the toner image to the sheet is a series of controls.

  First, the type of sheet is detected by various sensors, input from the operation unit 303, or the like (S801 in FIG. 8). Note that the sheet type detection S801 is not necessarily performed first, and may be performed at any timing as long as it is before the control of the motor rotation speed and the sheet conveyance speed (before S804 in FIG. 8).

  Next, as shown in the motor timing 701 of FIG. 6, when outputting plain paper, the motor is rotated at the speed V1 for producing plain paper, and in this state, the voltage of the charger 250 is shown as shown in the charging high voltage timing 705. The surface of the photosensitive drum 202 is charged to −300 to −900 V by E1 (S802 in FIG. 8). Then, as indicated by the laser timing 702, electrostatic latent images are formed on the photosensitive drum 202 in the order of YMCK. Here, two images corresponding to A4 size are formed at the same time, and YA, MA, CA, and KA are pasted on the first sheet, YB, MB, C -B and K-B indicate the second image.

  Then, the electrostatic latent image is developed in accordance with the development rotary timing 704 (to be a toner image), and primary transfer is performed to the intermediate transfer member 205 as indicated by the primary transfer timing 703 (S803 in FIG. 8).

  Next, the motor rotation speed and the sheet conveyance speed are controlled according to the type of sheet (S804 in FIG. 8). Here, since the sheet type is plain paper, deceleration control or the like is not performed.

  Next, the CPU 301 determines whether or not the vehicle has decelerated (S805 in FIG. 8).

  Since the plain paper is not decelerated (NO in S805 in FIG. 8), secondary transfer is performed as shown in the secondary transfer high-pressure timing 706 while the charging high voltage is kept at E1 (FIG. 8). S807).

  When the number of formed images is three or more, a series of control 707a is repeated.

  In the case of a black monochromatic image, only the KA laser timing and primary transfer timing and the secondary transfer high-pressure timing A in the secondary transfer high-pressure timing 706 are included in the laser timing 702 and the primary transfer timing 703. It becomes control of.

  Next, the discharge current amount control of the charging member when the sheet type is thick paper will be described with reference to FIGS.

  FIG. 7 is a diagram illustrating a timing chart of full-color image formation when the sheet type is thick paper.

  Reference numeral 707b denotes a series of controls.

  Until the primary transfer end timing, it is the same as the control timing of plain paper.

  That is, first, the type of sheet is detected by an input from a sensor or an operation unit (S801 in FIG. 8). The sheet type detection S801 is not limited to this timing, and may be performed at any timing as long as it is before the control of the motor rotation speed and the sheet conveyance speed (S804 in FIG. 8).

  Next, the motor is rotated at the speed V1, and the surface of the photosensitive drum 202 is charged by the voltage E1 of the charger 250 (S802 in FIG. 8). Then, electrostatic latent images are formed on the photosensitive drum 202 in the order of YMCK.

  Then, the electrostatic latent image is developed (made as a toner image), and primary transfer is performed to the intermediate transfer member 205 (S803 in FIG. 8).

  After the completion of the primary transfer, as shown in the motor timing 701, the motor is decelerated to the speed V2 (= V1 / 2) for cardboard production (S804 in FIG. 8) (YES in S805 in FIG. 8), and the charging high pressure As shown in timing 705, the setting of the charging high voltage is lowered to E2 (= E1 / 10 (1/10 at the time of primary transfer)) (S806 in FIG. 8).

  Therefore, when the toner image is formed on the photosensitive drum 202 and when the toner image on the photosensitive drum 202 is transferred onto the intermediate transfer member 205, the amount of discharge current of the charger 250 is I1, and the toner image on the intermediate transfer member 205 is transferred to the intermediate transfer member 205. When the discharge current amount of the charger 250 when transferring the toner image to the sheet is I2, the relationship is I1> I2.

The reason for this control is that even if the charging high voltage is set to the same setting E1 as in the primary transfer, the secondary transfer control is not affected, but the charger 250 is operated in a high output state. Various problems due to discharge products such as O ₃ and NO _x due to discharge, that is, generation of image unevenness due to product adhesion to the discharge electrode, deterioration of the photosensitive drum due to discharge products, contamination of the environment due to discharge products, This is because problems such as excessive power consumption increase. Therefore, control is performed to reduce the output in order to alleviate such problems.

  After the motor speed is stabilized at the speed V2, the secondary transfer 706 is performed at the timing when the toner image on the intermediate transfer member 205 and the leading edge of the conveyed sheet coincide (S807 in FIG. 8).

  When the number of images formed is three or more, after the B image is transferred at the secondary transfer high pressure timing 706, the sheet type is detected (S801 in FIG. 8), and the motor speed is accelerated again to V1, The setting of the charging high voltage timing 705 is returned to E1 (setting value at the time of primary transfer) (S802 in FIG. 8).

  Then, a series of control 707b is repeated.

  In the case of a black monochrome image, at the laser timing 702 and the primary transfer timing 703, only the KA laser and primary transfer and the secondary transfer of A in the secondary transfer high-pressure timing 706 are controlled. .

  When a full-color image is formed and the sheet size is A4 size or larger in the sub-scanning direction and only one sheet can be formed on the intermediate transfer body 205 at the same time, at the laser timing 702 and the primary transfer timing 703, Only the laser and primary transfer of YA, MA, CA, and KA and the secondary transfer of A in the secondary transfer high-pressure timing 706 are controlled.

  In this embodiment, the system for decelerating the motor speed to V2 when the sheet type is thick paper has been described, but the relationship between the sheet type and the motor speed is not limited to the above, A system in which each motor speed corresponding to the sheet type may be prepared.

  For example, the CPU 301 may change the rotation speed of the intermediate transfer member 205 and the sheet conveyance speed depending on the type of sheet such as cardboard, film, or label paper.

  Further, the rotational speed of the intermediate transfer member 205 and the sheet conveyance speed may be changed depending on not only the sheet type but also the sheet size.

  Further, the rotational speed of the intermediate transfer body 205 and the sheet conveyance speed may be changed according to the number of toner images simultaneously formed on the intermediate transfer body 205. The number of toner images formed at the same time is the number of toner images held simultaneously. For example, the rotation speed of the intermediate transfer member 205 and the sheet conveyance speed are set when there is one image and when two images are pasted. It may be changed.

  Further, in the present embodiment, a system has been described in which the charging high voltage is set to E1 to E2 and reduced to 1/10 when the motor speed is reduced from V1 to V2. The setting values are not limited to 10, and set values may be prepared according to various environmental conditions, sheet types, sheet sizes, and the like.

  Further, even during image formation at a motor speed of V1, if there is a predetermined time or more from the end of the secondary transfer to the start of laser exposure of the next image, a system that performs control to lower the setting of the charging high voltage may be used.

  That is, the CPU 301 controls the amount of discharge current discharged by the charger 250 at a predetermined timing after the rotation speed of the intermediate transfer member 205 and the sheet conveyance speed are changed.

  As a result, the amount of excess discharge current can be further reduced.

  In this embodiment, the intermediate transfer member 205 has a drum shape. However, the intermediate transfer member 205 is not limited to a drum shape, and may be a belt shape.

  In the present embodiment, the toner image on the photosensitive drum 202 is transferred to the intermediate transfer member 205 and transferred to the sheet. However, the toner image on the photosensitive drum 202 can be transferred without the intermediate transfer member 205. It can be applied even if it is configured to transfer directly to a sheet.

1 is a schematic cross-sectional view showing an overall schematic configuration of a color image forming apparatus according to an embodiment of the present invention. The perspective view which shows the principal part structure of an optical writing optical system Block diagram showing the main part configuration around the control unit The figure which shows the principal part structure of a digital image processing part Block diagram showing the main configuration of the printer processing unit Diagram showing timing chart of plain paper image formation Diagram showing timing chart for cardboard image formation Flow chart showing image formation of this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color image reader part 2 Color image printer part 100 Control part 202 Photosensitive drum (electrostatic carrier)
205 Intermediate transfer member 206 Transfer belt 215 Conveying roller 250 Charger 301 CPU
302 Memory P Laser irradiation position Q Visualization position

Claims (6)

An image forming method comprising: a photosensitive member; and a charging member that charges the photosensitive member in association with image formation, and transferring a toner image formed on the photosensitive member to a sheet directly or via an intermediate transfer member. In the device
A speed control means for controlling the rotational speed of the photoconductor or the intermediate transfer body and the conveyance speed of the sheet;
An image forming apparatus comprising: a discharge current amount control unit that controls a discharge current amount discharged from the charging member in accordance with the control content of the speed control unit.   The image forming apparatus according to claim 1, wherein the speed control unit changes a rotation speed of the photosensitive member or the intermediate transfer member and a conveyance speed of the sheet according to a type of the sheet.   The image forming apparatus according to claim 1, wherein the speed control unit changes a rotation speed of the photoconductor or the intermediate transfer body and a conveyance speed of the sheet according to a size of the sheet.   The speed control unit is configured to change a rotation speed of the photoconductor or the intermediate transfer body and a conveyance speed of the sheet according to the number of toner images simultaneously formed on the photoconductor or the intermediate transfer body. Item 2. The image forming apparatus according to Item 1. When the toner image is formed on the photosensitive member and when the toner image on the photosensitive member is transferred onto the intermediate transfer member, the discharge current amount of the charging member is I1,
When the discharge current amount of the charging member when transferring the toner image on the intermediate transfer member to a sheet is I2,
2. The image forming apparatus according to claim 1, wherein I1> I2 is satisfied. An image forming method comprising: a photosensitive member; and a charging member that charges the photosensitive member in association with image formation, and transferring a toner image formed on the photosensitive member to a sheet directly or via an intermediate transfer member. In the device
Discharge current amount control means for controlling a discharge current amount discharged from the charging member at a predetermined timing after the change is made when the rotation speed of the photosensitive member or the intermediate transfer member and the conveyance speed of the sheet are changed. An image forming apparatus.

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