JP2005049672A - Method for forcedly consuming color toner in color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To forcedly consume color toner without soiling a transfer member and soiling the back side of paper which is a recording medium. <P>SOLUTION: The color toner forced consumption method of a color printer equipped with a plurality of photoreceptor drums 102 and so on provided so as to correspond to each color and developing units 108 and so on is provided. At an image forming time, an electrostatic latent image is formed in an area corresponding to the printing part of black toner in addition to an electrostatic latent image corresponding to the printing part of the color toner at the photoreceptor drum corresponding to the color toner other than the black toner, so that color toner forced consumption processing by which development with the color toner is performed at the developing part of the black toner is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for forcibly consuming color toner used in an electrophotographic color image forming apparatus such as a color printer or a color copying machine.

An electrophotographic color printer is configured to perform color printing by subtractive color mixing using yellow toner, magenta toner, cyan toner, and black toner. The ratio is relatively high. As a result, the printing rate of color toners other than black toner, in other words, the consumption is extremely small, or the idling state of the toner carrier of the developing device containing some color toners may continue for a long time. is there. If such a state continues for a long time, toner replacement in the developing device is reduced, and problems such as a decrease in toner density and fogging due to overcharging of the toner occur.

By the way, when the printing rate of the toner is smaller than the predetermined printing rate, the toner is conveyed so as to form, for example, a checkerboard pattern on the electrostatic latent image carrier at a timing when the image is not transferred to the recording medium. A method of forcibly consuming the toner conveyed to the electrostatic latent image carrier by collecting it with a cleaning device is already known (see Patent Documents 1 and 2). However, in this method, a forcibly consumed toner image is formed in an appropriate region of the electrostatic latent image carrier during non-image formation. Therefore, when contact transfer is performed, the transfer member is soiled or the recording medium is used. There was a problem that the back side of a certain paper was soiled.

Prior art information relating to the present application includes the following.
JP-A-4-68370 JP-A-4-204986

The object of the present invention is to allow color toner to be forcibly consumed without contaminating the transfer member or the back surface of the recording medium, even in a color image forming apparatus using contact transfer. It is an object of the present invention to provide a color toner forced consumption method for a novel color image forming apparatus.

According to the present invention, a plurality of electrostatic latent image carriers provided corresponding to the respective colors including black, and electrostatic latent image carriers are each electrostatically charged with a corresponding color toner. In a color image forming apparatus including a developer including a developer carrier that develops an electrostatic latent image formed on a latent image carrier, the color toner other than black toner can be used when an image is formed on a recording medium. In addition to the electrostatic latent image corresponding to the color toner printing portion, an electrostatic latent image is formed on the electrostatic latent image carrier in an area corresponding to the black toner printing portion, thereby forming the color toner. A color toner forcible consumption method for a color image forming apparatus is provided, wherein color toner forced consumption processing for developing a black toner at a developing portion of the black toner is performed.
When the image formation on the recording medium is a single recording medium or the last recording medium of continuous printing, the printing rate of each color toner other than the black toner to be printed on the recording medium is higher than the predetermined printing rate. It is preferable to carry out the above-described forced color consumption process for the color toner determined to be low.
When image formation on a recording medium is continuously performed for a predetermined number or more, an average printing rate of each color toner other than the black toner over a predetermined number of sheets is calculated, and the average printing rate is a predetermined printing rate. It is preferable to carry out the above-mentioned forced color toner consumption process for the color toner determined to be lower than the above.

Hereinafter, embodiments of the present invention will be described. FIG. 1 illustrates a main part of an embodiment of a color printer (hereinafter simply referred to as a printer) which is an electrophotographic color image forming apparatus capable of carrying out the method of forced color toner consumption according to the present invention. Yes. The illustrated printer includes an intermediate transfer belt 2 constituting an endless belt-shaped intermediate transfer member. The intermediate transfer belt 2 is supported by being wound around three support rollers 4, 6 and 8, and is rotated clockwise in FIG. 1 by a driving means (not shown). The support rollers 4 and 6 are arranged at intervals in the horizontal direction, and the support roller 8 is arranged below the support roller 4. The intermediate transfer belt 2 extends horizontally between the support rollers 4 and 6, and a plurality of intermediate transfer belts 2 are disposed above the horizontally extending region of the intermediate transfer belt 2 along the rotational direction of the intermediate transfer belt 2. In the embodiment, four photoconductor units, that is, a black photoconductor unit 100K, a yellow photoconductor unit 200Y, a cyan photoconductor unit 300C, and a magenta photoconductor unit 400M are arranged in this order.

The black photoconductor unit 100K includes a photoconductor drum 102 which is an electrostatic latent image carrier, and a region extending horizontally of the intermediate transfer belt 2 is opposed to the lowermost surface of the photoconductor drum 102. Has been placed. Around the photosensitive drum 102, a charger 104, an exposure unit 106, a developing unit 108, a cleaning unit 110, and a charge removal unit 112 are arranged. Note that the photosensitive drum 100, the charger 104, the exposure unit 106, the cleaning unit 110, and the static elimination unit 106 are integrally accommodated in the photosensitive unit 100K. The developing device 108 includes a developing sleeve 108a that is a developer carrying member, and a stationary permanent magnet (not shown) is disposed in the developing sleeve 108a. The developing unit 108 contains a two-component developer in which black toner and a magnetic carrier are mixed. The mixing ratio of the magnetic carrier and the toner is 100: 5. The cleaning unit 110 includes a cleaning blade 110a.

The other photoconductor units 200Y, 300C, and 400M are configured in substantially the same manner as the photoconductor unit 100K. That is, each of the photoconductor units 200Y, 300C, and 400M includes photoconductor drums 202, 302, and 402 that are electrostatic latent image carriers, and is opposed to the lowermost surface of the photoconductor drums 202, 302, and 402. A region extending horizontally of the intermediate transfer belt 2 is disposed. Around the photosensitive drums 202, 302, and 402, the chargers 204, 304, and 404, the exposure units 206, 306, and 406, the developers 208, 308, and 408, the cleaning units 210, 310, and 410, and the static elimination, respectively. Units 212, 312, and 412 are arranged. Each of the developing devices 208, 308, and 408 includes developing sleeves 208a, 308a, and 408a that are developer carriers, and stationary permanent magnets (not shown) are disposed in the developing sleeves 208a, 308a, and 408a, respectively. . In the developing devices 208, 308, and 408, two-component developers obtained by mixing yellow toner, cyan toner, magenta toner, and magnetic carrier are accommodated, respectively. The mixing ratio of the magnetic carrier and the toner is the same as that of the black toner. The cleaning units 210, 310, and 410 include cleaning blades 210a, 310a, and 410a, respectively. In addition, the code | symbol which illustrates each of these component was described only about the component especially required in order to avoid complication of drawing. In the following description, black toner may be abbreviated as K, yellow toner as Y, cyan toner as C, and magenta toner as M.
In order to carry out the present invention, it is essential that the black photoconductor unit 100K is disposed on the most upstream side in the rotation direction of the transfer belt. By concealing the color toner other than black that has been forcibly consumed by the black toner, the color toner can be forcibly consumed without impairing the color of the image.

Primary transfer rollers 114, 214, 314, and 414 are arranged to face the photosensitive drums 102, 202, 302, and 402, respectively, and a horizontal extension region of the intermediate transfer belt 2 is sandwiched therebetween. . A secondary transfer roller 10 is disposed on the downstream side of the intermediate transfer belt 2 in the rotation direction, on the lower left side in FIG. The intermediate transfer belt 2 is sandwiched between the support roller 8 and the secondary transfer roller 10, and the toner image (primary transfer image) on the intermediate transfer belt 2 is a recording medium by the secondary transfer roller 10 as described later. Transferred to P (secondary transfer). A fixing unit 20 is disposed downstream of the secondary transfer roller 10, which is downstream of the conveyance direction of the paper P. The fixing unit 20 includes a heat roller 22 and a pressure roller 24, and the secondary transfer image transferred onto the paper P is pressed and heated by the heat roller 22 and the pressure roller 24 of the fixing unit 20 to be fixed.

A cleaning blade 26 is disposed opposite the support roller 4, and the toner remaining on the intermediate transfer belt 2 is cleaned by the cleaning blade 26.

Next, a specific operation (printing operation) of the printer shown in FIG. 1 will be described with reference to one embodiment. In the black photoconductor unit 100K, the positively charged single-layer OPC photoconductor drum 102 rotates in the counterclockwise direction in FIG. 1 to form an image. The surface of the photosensitive drum 102 is uniformly charged to +460 V by the scorotron charger 104, and an electrostatic latent image is formed on the photosensitive member by the exposure unit 104 including an LED head based on image data sent from a computer (not shown). Form. At this time, the wavelength of light of the LED is 780 nm, the exposure amount is 0.9 μJ / cm ² , and the photoreceptor surface potential after exposure is about + 30V. A developing sleeve 108a of a developing device 108 containing a developer composed of a non-magnetic toner (black) and a magnetic carrier is supplied with a DC voltage of 350 V, an AC rectangular wave having a frequency of 3.6 kHz, an amplitude of 1.0 kV, and a DUTY ratio of 50%. Is applied to cause the toner on the developing sleeve 108a to fly to the electrostatic latent image formed on the photosensitive drum 102, and the electrostatic latent image is developed into a toner image. This black toner image is transferred onto the intermediate transfer belt 2 by a primary transfer roller 114 to which a transfer bias by constant current control of 10 μA is applied. Residual toner on the photosensitive drum 102 is recovered by being cleaned by the cleaning unit 110 with a cleaning blade (counter blade 110a) set to a linear pressure of 15 g / cm. The electricity is removed by the electricity removing unit composed of the LED, wherein the wavelength of the light of the LED is 630 nm and the exposure amount is 4.0 μJ / cm ² .

Subsequently, in the yellow photoconductor unit 200Y, the cyan photoconductor unit 300C, and the magenta photoconductor unit 400M, in the same manner as in the black photoconductor unit 100K, the photoconductor drum 202, The yellow toner image, cyan toner image, and magenta toner image formed on 302 and 402 are primarily transferred onto the intermediate transfer belt 2 in the above order, and finally, four color toners are formed on the intermediate transfer belt 2. Multiple images are transferred. The color toner image multiplex-transferred onto the intermediate transfer belt 2 is transferred to the secondary transfer roller 10 while the paper P conveyed at a predetermined timing passes through the pressure contact portion between the support roller 8 and the secondary transfer roller 10. As a result, the sheet P is secondarily transferred onto the sheet P by charging the sheet P with the opposite polarity to the color toner image. The sheet P on which the color toner image is secondarily transferred is conveyed leftward in FIG. 1 and fixed as a full color image by the fixing unit 20.

The printer includes a controller (not shown). The controller is composed of a microcomputer, and includes a central processing means (CPU) that performs arithmetic processing according to a control program, a storage means (memory) having a ROM for storing the control program and a RAM for storing various data, an input / output interface, a counter, and a timer. The printer is controlled such as image formation (printing) and color toner forced consumption mode to be described later. The controller also includes a counting unit that counts the number of pages of paper on which images are formed, a printing rate processing unit that counts a printing rate corresponding to an image for each color toner including black and color toner, and a black And an average printing rate processing means for calculating the printing rate corresponding to the image for each toner including all color toners for each page to obtain an average printing rate. For example, in the yellow photoconductor unit 200Y, the print rate processing means uses the number of yellow dots (paper for forming an electrostatic latent image corresponding to the image on the photoconductor drum 202 from image data transmitted from a computer (not shown) to the printer. The number of yellow dots actually used in one page) is counted for each page, and the printing rate is calculated by the ratio to the number of dots when the entire image forming area of one page of paper is yellow solid.

The controller also includes the color toner when the image printing rate of the color toner (for example, cyan toner) other than the black toner is lower than a predetermined printing rate at the time of forming the image to be transferred to the paper P. In addition to the electrostatic latent image corresponding to the color toner printing portion, the photosensitive drum 302 facing the developing sleeve 308a to which the component developer is conveyed is electrostatically placed in an area corresponding to the black toner printing portion. By forming the latent image, the color toner is forcibly consumed by forcibly printing the color toner on the black toner printing unit in addition to the color toner printing unit.

Hereinafter, an embodiment of the color toner forced consumption method will be described with reference to the flowchart shown in FIG. When the printer receives image data to be printed, the controller stores the image data in a memory. The accumulated image data is converted into printing data for one page. When the conversion processing for the first page is completed, a printing operation (image forming operation) is started. It is determined from the stored image data whether there is a next page at the time of starting the printing operation (step S1). If it is determined that there is no next page, it is determined whether the Y, M, and C printing rates A of the page are less than a predetermined printing rate, for example, less than 4% (step S2). If the printing rates A for Y, M, and C are not all less than 4%, the normal printing operation is performed, and it is determined that one, two, or all of the printing rates A of Y, M, and C are less than 4%. If the color toner is detected, the color toner forced consumption process is performed only for the color toner (step S3). The forced consumption of Y, M, and C is preferably 4% -α%, assuming that the actual printing rate is α%.

In addition to the electrostatic latent image corresponding to the cyan toner printing portion, an area corresponding to the black toner printing portion on the developing sleeve 308a to which the color toner having a printing rate A of less than 4%, for example, cyan toner is conveyed By forming an electrostatic latent image therein, the cyan toner is forcibly consumed by forcibly printing not only the cyan toner printing portion but also the black toner printing portion. One page of color toner forced consumption processing is performed, and when the development by all the developing units is completed for the one page, the discharge counter is reset (step S4), and the predetermined printing operation is ended. The discharge counter is reset for the developing units (excluding the K developing unit 108) that have undergone the color toner forced consumption processing. In step S2, it is determined whether the printing rate of the page to be printed is lower than a predetermined printing rate, and the color toner forced consumption process is performed for the color toner determined to be low (step S2). The reason why S3) performs the color toner forced consumption process for the page based on the printing rate of the page to be printed is as follows. That is, when performing a single printing operation, the ratio of the time required to develop the exposed portion of the photosensitive member in the rotation time of the developer carrying member is particularly short compared to continuous printing. This is because there is a high possibility that the toner becomes excessively charged. Further, after printing the last recording medium of continuous printing, the developer is used for the purpose of stirring the toner supplied to the developing device and the developer present in the developing device for a predetermined time after the recording medium is discharged out of the apparatus. Since it is normal to rotate the carrier, there is a high possibility that the color toner will be overcharged. This is because, when the next printing operation is performed in a state in which an excessively charged toner exists on the developer carrying member at the end of the printing operation, problems such as a decrease in image density may occur as described above.

If it is determined in step S1 that there is a next page, it is determined whether or not the discharge counter has counted 10 sheets (10 pages) (step S5). This counting is performed based on the end of development of one sheet. If the discharge counter does not count 10 sheets, the discharge counter continues counting (step S6), and if the discharge counter counts 10 sheets, each of Y, M, and C averages of 10 sheets It is determined whether the printing rate X is a predetermined printing rate, for example, less than 3%. If the average printing rates X of Y, M, and C are not all less than 3%, a normal printing operation is performed and the discharge counter is reset (step S9). When it is determined that one, two, or all of the average print ratios X of Y, M, and C are less than 3%, the color toner forced consumption process as described above is performed for the color toner ( Step S8). The color toner forced consumption process is performed, and when the development for all the developing units for the one page is completed, the discharge counter is reset (step S9), and the printing operation is continued.

According to the color toner forced consumption method according to the present invention, the color toner that does not reach the predetermined printing rate simultaneously with the image forming operation is forcibly consumed using the black toner printing portion. Even in a color image forming apparatus, it is possible to forcibly consume color toner without contaminating the transfer member or the back surface of the recording medium. The present invention can be applied to cases other than the case where the printing rate is low. For example, when the mixing ratio of the toner to the carrier in the two-component developer becomes excessively large, the present invention can be applied when the toner is forcibly consumed.

1 is a schematic cross-sectional view showing a main part of an embodiment of an image forming apparatus according to the present invention. 5 is a flowchart illustrating toner forced consumption processing according to the present invention.

Explanation of symbols

2: Intermediate transfer belt 10: Secondary transfer roller 100K: Photoconductor unit for black 200Y: Photoconductor unit for yellow 300C: Photoconductor unit for cyan 400M: Photoconductor unit for magenta 102, 202, 302, 402: Photoconductor drum 108, 208, 308, 408: developing units 108a, 208a, 308a, 408a: developing sleeves 114, 214, 314, 414: primary transfer roller P: paper (recording medium)

Claims (3)

A plurality of electrostatic latent image carriers provided corresponding to each color including black, and each of the electrostatic latent image carriers is formed on the electrostatic latent image carrier using the corresponding color toner. And a developing device including a developer carrier for developing the electrostatic latent image, and an electrostatic latent image carrier corresponding to a color toner other than black toner when an image is formed on a recording medium. In addition to the electrostatic latent image corresponding to the color toner printing portion, an electrostatic latent image is formed in an area corresponding to the black toner printing portion, whereby the color toner is moved to the black toner. A color toner compulsory consumption method for a color image forming apparatus, wherein color toner compulsory consumption processing for developing the developing unit is also performed. When the image formation on the recording medium is a single recording medium or the last recording medium of continuous printing, the printing rate of each color toner other than the black toner to be printed on the recording medium is higher than the predetermined printing rate. 2. A color toner compulsory consumption method for a color image forming apparatus according to claim 1, wherein said color toner compulsory consumption processing is carried out for a color toner judged to be low. When image formation on a recording medium is continuously performed for a predetermined number or more, an average printing rate of each color toner other than the black toner over a predetermined number of sheets is calculated, and the average printing rate is a predetermined printing rate. 2. The color toner forced consumption method of a color image forming apparatus according to claim 1, wherein the color toner forced consumption processing is performed on a color toner determined to be lower than the color toner.

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