JP2011090114A - Image forming apparatus and voltage control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the wear of a photoreceptor drum. <P>SOLUTION: The image forming apparatus includes: a plurality of electrostatic latent image holding means; a plurality of DC electrifying means electrifying the electrostatic latent image holding means respectively; a plurality of developing means developing electrostatic latent images formed on the surfaces of the electrostatic latent image holding means by using developer respectively; a power supply means in which at least a part of a power supply circuit supplying a voltage to the DC electrifying means or the plurality of developing means is made common; a calculation means calculating a developing contrast bias voltage Vcnt required in each developing means; and a control means performing control so as to make a voltage Vcf except the developing means requiring most the developing contrast bias voltage Vcnt smaller than the voltage Vcf of the developing means requiring most the developing contrast bias voltage Vcnt, on the basis of the calculation result. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus and a voltage control program.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a color printer or a multi-function machine adopting an electrophotographic system, four image forming units for forming single color toner images such as yellow, magenta, cyan, and black (YMCK) are arranged in parallel. The single-color toner images of yellow, magenta, cyan, and black that are arranged and sequentially formed by each of these image forming units are once transferred in multiple onto the intermediate transfer belt, and the recording medium such as printing paper is transferred from the intermediate transfer belt. Some are configured to form a color image by transferring them all together and fixing a toner image on a recording medium.

  By the way, in the so-called tandem engine in which a plurality of image forming units are mounted as described above, it is necessary to individually prepare a high voltage power source for supplying a bias voltage to the developing device and the charger.

  For this reason, there has been a problem that the size of the entire power supply circuit is hindered from being reduced in size and the cost is increased due to an increase in the number of parts.

  In order to solve such a problem, various techniques relating to common use of power sources in image forming apparatuses have been proposed.

  An example of such a technique is JP-A-2002-162801.

  Japanese Patent Laid-Open No. 2002-162801 discloses an image forming apparatus that can reduce the size and cost of a power supply circuit by sharing a power supply circuit that supplies voltages to a plurality of charging units or a plurality of developing units. A detection means for detecting a parameter caused by the density of an image developed by a plurality of developing means, and a control means for controlling an image forming condition based on the detection result. An image forming apparatus configured to share at least a part of a power supply circuit that supplies a voltage to a developing unit or a plurality of charging units is disclosed.

JP 2002-162801 A

  An object of the present invention is to provide an image forming apparatus and a voltage control program capable of suppressing wear of a photosensitive drum (electrostatic latent image holding unit).

  In order to solve the above problems, an image forming apparatus according to a first aspect of the present invention includes a plurality of electrostatic latent image holding means for holding an electrostatic latent image formed based on image information, and the plurality of electrostatic latent images. A plurality of DC charging means provided corresponding to the image holding means and charging each electrostatic latent image holding means; and each electrostatic latent image holding means provided corresponding to the plurality of electrostatic latent image holding means. A power supply in which at least a part of a plurality of developing means for developing the electrostatic latent image formed on the surface of the toner using a developer and a power supply circuit for supplying a voltage to the DC charging means or the plurality of developing means are made common A supplying means; a toner density detecting means for detecting the toner density of the developer; a cleaning means for cleaning the developer remaining in each electrostatic latent image holding means; Required development contrast vias in the tool A calculation means for calculating a voltage Vcnt (Vcnt = Vb−Vl, where Vb is a developing bias voltage and Vl is an exposure potential (potential of the electrostatic latent image holding means at the time of exposure)), and calculation by the calculation means Based on the result, the cleaning field voltage (DC component of the cleaning bias applied to the cleaning unit) other than the developing unit that requires the development contrast bias voltage Vcnt most (Vcf = Vh−Vb, where Vh is applied) The charging potential as a difference between the voltage Vdc and the discharge start voltage Vα, where Vb is the developing bias voltage) is controlled to be smaller than the cleaning field voltage Vcf of the developing unit that requires the developing contrast bias voltage Vcnt. And a control means.

  A voltage control program according to a second aspect of the present invention is provided corresponding to a plurality of electrostatic latent image holding means, and a plurality of developments for developing the electrostatic latent image formed on the surface of each electrostatic latent image holding means. Based on the calculation process for calculating the required development contrast bias voltage Vcnt (Vcnt = Vb−Vl where Vb is the development bias voltage and Vl is the exposure potential) in the means, and the calculation result, the most development contrast bias voltage A cleaning field voltage Vcf other than the developing unit that requires Vcnt (Vcf = Vh−Vb, where Vh is a charging potential as a difference between the applied voltage Vdc and the discharge start voltage Vα, and Vb is a developing bias voltage). Smaller than the cleaning field voltage Vcf of the developing means requiring the most development contrast bias voltage Vcnt. Characterized in that to execute a control process for controlling the Kunar so the arithmetic means.

  According to the present invention, the following effects can be obtained.

  That is, according to the image forming apparatus of the first aspect of the invention, it is possible to obtain an excellent effect of suppressing wear of the electrostatic latent image holding unit due to an increase in Vh (applied voltage). Further, the increase in fog toner of the electrostatic latent image holding means suppresses the cleaning blade composing the cleaning means, and the cleaning blade itself from being chipped or squeaked due to friction between the electrostatic latent image holding means and the cleaning blade. The secondary effect is obtained.

  According to the voltage control program of the second aspect of the invention, in the image forming apparatus, it is possible to suppress wear of the electrostatic latent image holding unit due to an increase in Vh (applied voltage).

1 is an overall configuration diagram showing a configuration of an image forming apparatus PR1 according to an embodiment. 2 is a configuration diagram showing an image forming unit U. FIG. 2 is a functional block diagram showing a functional configuration of an image forming apparatus PR1 according to an embodiment. FIG. 3 is a block diagram illustrating a configuration example of a control circuit of the image forming apparatus PR1 according to the embodiment. FIG. It is a graph which shows the conventional electric potential setting method. It is a graph which shows the electric potential setting method in image forming apparatus PR1 which concerns on embodiment. 3 is a control block diagram illustrating a configuration example of a control system capable of realizing voltage control in the image forming apparatus PR1 according to the embodiment. FIG. It is a flowchart which shows the example of the process sequence of a voltage control process.

  Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  An image forming apparatus PR1 according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a tandem type full-color printer as an image forming apparatus PR1 according to an embodiment of the present invention.

  In FIG. 1, an image forming unit U for forming a full-color image and an electrostatic latent image holding unit of the image forming unit U are roughly divided into a printer main body M composed of a resin casing or the like. Of the four photosensitive drums 11, 12, 13, and 14, and the developing devices (examples of developing means) 41, 42, 43, and 44 of the respective colors of the image forming unit U. Four toner cartridges 04Y, 04M, 04C, and 04K that supply toner, a paper feed cassette 05 that supplies printing paper P as a recording medium to the image forming unit U, and printing with a toner image transferred from the image forming unit U The fixing device 06 that performs the fixing process on the paper P, and the printing paper P on which the image is fixed on one side by the fixing device 06 are again formed in an image form with the front and back sides reversed. It is composed of a double-sided conveyance path 07 for conveying to the transfer unit of the unit U, a manual paper feeding means 08 for feeding a desired printing paper P from the outside of the printer main body M, and a microcomputer for controlling the operation of the printer. Controller (an example of a control unit) 09 and an electric circuit 10 including an image processing circuit that performs image processing on an image signal, a high-voltage power supply circuit (common power supply device 200; an example of a power supply unit), and the like. ing.

  Reference numeral T denotes a discharge toilet that discharges the printing paper P on which an image is formed. The discharge toilet T is integrally disposed on the upper portion of the printer main body M.

  The exposure device 03 disposed in the printer main body M is four lighted and driven based on image data corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). The semiconductor laser is constituted by an f-θ lens, a polygon mirror, or a plurality of reflection mirrors for deflecting and scanning four laser beams emitted from these four semiconductor lasers.

  Next, the configuration of the image forming unit U will be described with reference to FIG.

  As shown in FIG. 2, the image forming unit U includes image forming units 11, 12, 13, and 14 for yellow (Y), magenta (M), cyan (C), and black (K). U1, U2, U3, U4, and primary charging chargers (contact type charger; an example of DC charging means) 21, 23, 23, 24 that are in contact with the respective photosensitive drums 11, 12, 13, 14; An exposure device 03 (see FIG. 1) that irradiates laser beams 31, 32, 33, and 34 of yellow (Y), magenta (M), cyan (C), and black (K) colors, and photosensitive drums 11 and 12 , 13, 14 to develop the electrostatic latent images with toners of yellow (Y), magenta (M), cyan (C), and black (K). And four photosensitive drums 11, 12, 13, The first primary intermediate transfer drum (intermediate transfer body) 51 in contact with two of the four photosensitive drums 11 and 12 and the second primary intermediate transfer drum (in contact with the other two photosensitive drums 13 and 14). An intermediate transfer member) 52, a secondary intermediate transfer drum (intermediate transfer member) 53 in contact with the first and second primary intermediate transfer drums 51 and 52, and a final transfer roll (in contact with the secondary intermediate transfer drum 53). Transfer member) 60.

  The photoconductor drums 11, 12, 13, and 14 are arranged at regular intervals so as to have a common tangential plane 150.

  A signal corresponding to the image information for each color is rasterized by an image processing circuit disposed in the electric circuit 10 (see FIG. 1) and input to the exposure apparatus 03.

  In this exposure apparatus 03, yellow (Y), magenta (M), cyan (C), and black (K) laser beams 31, 32, 33, and 34 are modulated, and the corresponding photosensitive drums 11, 12, 13, and 14 are irradiated.

  Each of the developing devices 41, 42, 43, and 44 is provided with toner concentration sensors S1 to S4 (an example of toner concentration detecting means) configured by a magnetic permeability sensor or the like.

  Also, cleaning blades C1 to C4 are provided in the vicinity of the photosensitive drums 11, 12, 13, and 14 as cleaning means for cleaning the developer remaining on the surfaces of the photosensitive drums 11, 12, 13, and 14. It has been.

  The cleaning blades C1 to C4 remove toner remaining on the surfaces of the photosensitive drums 11, 12, 13, and 14 by applying a cleaning bias.

  Further, as shown in FIG. 3, the image forming apparatus PR1 according to the present embodiment has a required development contrast bias voltage Vcnt (Vcnt = Vb−Vl where Vbnt is Vb) in each of the developing devices 41, 42, 43, and 44. Is a development bias voltage, and Vl is a development contrast bias voltage Vcnt calculation unit 201 (an example of a calculation unit) that calculates an exposure potential (respective photosensitive drums 11, 12, 13, and 14 at the time of exposure).

  Based on the calculation result of the Vcnt calculation unit 201, the above-described control device 09 uses a cleaning field voltage other than the developing device that most requires the developing contrast bias voltage Vcnt (cleaning applied to the cleaning units C1 to C4). DC bias component) Vcf (where Vcf = Vh−Vb, where Vh is a charging potential as a difference between the applied voltage Vdc and the discharge start voltage Vα, and Vb is a developing bias voltage). Control is performed so that Vcnt is smaller than the cleaning field voltage Vcf of the developing device that requires it. The detailed processing procedure will be described later.

  As a result, the wear of the photosensitive drums 11, 12, 13, and 14 due to an increase in Vh (applied voltage) can be suppressed.

  Further, as the fog toner on the photosensitive drums 11, 12, 13, and 14 increases, the cleaning blades C1 to C4 constituting the cleaning unit are swung, and the photosensitive drums 11, 12, 13, and 14 and the cleaning blades C1 to C4 are cleaned. The secondary effect of suppressing the squeal due to friction with the is obtained.

  Next, the control circuit of the image forming apparatus PR1 will be briefly described with reference to the block diagram of FIG.

  In FIG. 4, reference numeral 300 denotes a control circuit including a CPU that controls image forming conditions such as a developing bias voltage based on the detection result of the optical density sensor 100, and reference numeral 301 denotes charging based on an output signal from the control circuit 300. A voltage control circuit that directly controls the applied voltage Vdc to the devices 21, 22, 23, and 24 and the developing bias voltage Vb to the developing devices 41, 42, 43, and 44. Reference numeral 302 denotes the chargers 21, 22, 23, A high voltage power supply for a charger (common power supply device) as a common power supply circuit that applies a predetermined voltage to 24, reference numerals 303Y, 303M, 303C, and 303K are predetermined development bias voltages to the developing devices 41, 42, 43, and 44, respectively. A high-voltage power supply for the developing device that individually applies Vb, and reference numeral 304 denotes each developing device 41, 42, 4, based on an output signal from the control circuit 300 Shows the toner concentration control circuit for controlling the toner supply from the toner cartridge to 44, respectively.

  Here, an outline of the image forming process for each color by the electrophotographic method performed using each of the photosensitive drums 11, 12, 13, and 14 will be described.

  First, the photosensitive drums 11, 12, 13, and 14 are rotationally driven at a predetermined rotational speed.

  As shown in FIG. 2, the surfaces of the photosensitive drums 11, 12, 13, and 14 are applied with, for example, a DC voltage (DC voltage) of about −840 V to the chargers 21, 22, 23, and 24, for example. It is charged to about -300V.

  Thereafter, laser light 31 and 32 corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is applied to the surfaces of the photosensitive drums 11, 12, 13, and 14 by the exposure device 03. , 33 and 34 are formed, and electrostatic latent images corresponding to input image information for each color are formed. When the electrostatic latent image is written by the exposure device 03, the surface potential of the image exposure portion of the photosensitive drums 11, 12, 13, and 14 is neutralized to about −60V or less.

  Further, the electrostatic latent images corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 correspond. The toner is developed by the color developing devices 41, 42, 43, and 44, and the toners of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are formed on the photosensitive drums 11, 12, 13, and 14. Visualized as an image.

  In this embodiment, a magnetic brush contact type two-component developing method is used as the developing devices 41, 42, 43, and 44.

  The developing devices 41, 42, 43, and 44 are filled with a yellow (Y), magenta (M), cyan (C), and black (K) toner, and a developer.

  As shown in FIG. 1, when toner is supplied from the corresponding color toner cartridges 04Y, 04M, 04C, and 04K to the developing devices 41, 42, 43, and 44, the supplied toner is augered. At 404, the carrier is sufficiently agitated and frictionally charged.

  Inside the developing roll 401, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is fixed.

  The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. Yes.

  A developing bias voltage Vb is applied to the developing roll 401, and the toner on the developing roll 401 is developed into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14, thereby forming a toner image. Is done.

  Next, the toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the respective photosensitive drums 11, 12, 13, and 14 are the first primary intermediate. The secondary transfer is electrostatically performed on the transfer drum 51 and the second primary intermediate transfer drum 52.

  The yellow (Y) and magenta (M) color toner images formed on the photoconductive drums 11 and 12 are formed on the first primary intermediate transfer drum 51 and cyan (on the photoconductive drums 13 and 14). C) and black (K) toner images are respectively transferred onto the second primary intermediate transfer drum 52.

  Accordingly, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed.

  In addition, similar single-color images and double-color images are formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.

  The surface potential necessary for electrostatically transferring the toner image from the photosensitive drums 11, 12, 13, and 14 onto the first and second primary intermediate transfer drums 51 and 52 is about +250 to 500V.

  This surface potential is set to an optimum value in consideration of the charged state of the toner, the ambient temperature, and the humidity.

  The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 are electrostatically and tertiary-transferred onto the secondary intermediate transfer drum 53.

  Therefore, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the secondary intermediate transfer drum 53. Will be.

  The surface potential necessary for electrostatically transferring the toner image from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200V.

  The surface potential is the same as when the toner is transferred from the photoconductor drums 11, 12, 13, 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Is set to an optimum value in consideration of the above.

  Also, since what is necessary for the transfer is a potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 52 have different potentials. The value is set according to the surface potential.

  Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is tertiary transferred by the final transfer roll 60 onto the printing paper P passing through the paper conveyance path. .

  The printing paper P passes through the paper transporting roll 90 through a paper feeding process, and is fed into the nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60.

  After this final transfer step, the final toner image formed on the printing paper P is fixed by the fixing device 70, and a series of image forming processes is completed.

  Next, before describing the voltage control processing procedure according to the basis of the present invention, problems and the like of a conventional technique (for example, a technique disclosed in Japanese Patent Laid-Open No. 2002-162801) as a comparison target will be described.

  Japanese Patent Application Laid-Open No. 2002-162801 discloses a technique for reducing the cost by sharing a high-voltage power supply on either the developing side or the charging side.

  Here, it should be applied to a charger necessary for obtaining desired Vh (p) = {Vh (y), Vh (m), Vh (c), Vh (k)} in DC charging (direct current charging). The voltage Vdc is expressed as Vh = Vdc−Vα (Expression 1) using the discharge start voltage Vα.

  The discharge start voltage Vα is a function that varies mainly depending on the photoreceptor film thickness (T), environment (temperature t, humidity h), and BCR resistance (resistance of the charging roll) (R). By measuring the contribution, it is possible to adjust the applied voltage Vdc to obtain a desired Vh (note that the detailed procedure is known and will not be described).

  By the way, in the technique disclosed in Japanese Patent Laid-Open No. 2002-162801, it is disclosed that the charging-side Vdc power supply is shared, but the discharge start voltage Vα (T, t, h, R) does not operate in each engine. When used in a range that changes, there is a disadvantage that it is difficult to make common.

  However, if the four drum cartridges are replaced almost at the same time and a small engine has a small difference in temperature and humidity between the engines, the conventional technology can cope with it.

  Therefore, here, a technique for reducing the cost by using a common high-voltage power source on the developing side instead of the charging side will be described.

  Among the development bias voltages Vb (p) = {Vb (y), Vb (m), Vb (c), Vb (k)}, the YMC side is used as a common power supply.

Vb (y) = Vb (m) = Vb (c) (Formula 2)
The relationship is always maintained.

  Even in this case, a desired density is obtained, which is called an electric field peeling phenomenon (BCO: bead-carry-out), and an image deterioration phenomenon in which an electrostatic force acts on a charged carrier and is transferred onto the surface of the photosensitive member). In addition, it is required to perform control so as to avoid defects such as fogging (a phenomenon in which a small amount of toner is transferred to a white background portion of a printing paper that should not be printed and the white background portion is slightly dirty and looks gray).

  First, in order to obtain the density, it is necessary to control the development toner density control (TC control) so that the target toner density (here, 8%) is as much as possible.

  For this purpose, a reading value from an ATC sensor (toner density sensor; a sensor that outputs a detection value for detecting two or more types of apparatus states including the remaining amount of toner) is fed back or consumed due to an increase in printing density or the like. By predicting the toner amount and rotating an appropriate amount of the dispense motor that sends the toner to the developing device, a substantially appropriate target toner density is maintained (note that the detailed procedure is known and will not be described).

  During normal use, the toner density fluctuation range is within ± 1 to 2%.

  However, when the toner cartridge is empty, that is, when empty is detected, since toner cannot be supplied, the toner density may be reduced to about 5%.

  When the toner density is lower than the target, it is difficult to obtain the image density. Therefore, by creating a control patch on the predictive control or intermediate transfer belt (IBT), measuring the density, and reflecting it in the potential setting conditions. The target concentration is maintained (note that the detailed procedure is known and will not be described).

  To obtain the density, the exposure potential Vl (p) = {Vl (y), Vl (m), Vl (c), Vl (k)} obtained by exposing from Vh with the exposure device 03, and the developing voltage ( The development contrast bias voltage Vcnt (p) = {Vcnt (y), Vcnt (m), Vcnt (c), Vcnt (k)}, which is the difference from the development bias voltage Vb, can be increased to suppress the density. You can make this smaller.

  Vcnt = Vb−Vl (Formula 3)

  Here, the exposure potential Vl is often set as low as possible because the DC charging cannot obtain a high Vh and the stability of the Vh is disadvantageous compared to the AC charging (AC charging).

  That is, exposure is performed to near RP (limit point) where sensitivity is lost on PIDC (exposure attenuation curve of the photosensitive member), and exposure potential Vl = 40 to 60 [V].

  By doing so, a relatively stable exposure potential Vl can be obtained even if there is a large variation in Vh or a large variation in the light amount distribution in the axial direction of the exposure apparatus.

  Therefore, within the normal toner density control range, the development contrast bias voltage Vcnt can be finely adjusted by adjusting only the exposure potential Vl while the development bias voltage Vb is fixed, thereby obtaining an appropriate density.

  However, it can be seen that the development contrast bias voltage Vcnt at the exposure potential Vl has a small adjustment margin (adjustment range) for the above reasons.

  In this case, when the toner density is greatly interrupted by toner empty detection or the like, the exposure potential Vl is stuck to the lower limit, but the density does not come out, so it is necessary to increase the developing bias voltage Vb. Come.

  In this case, if the high-voltage power supply on the development side is independent for each engine, the development bias voltage Vb of each engine may be simply increased. However, if the high-voltage power supply on the development side is shared, Since the relationship 2) is maintained, the unnecessary development bias voltage Vb of the engine must also be increased.

  For example, the development contrast bias voltage Vcnt required for each of the Y, M, and C engines is Vcnt (y) = 300 [V], Vcnt (m) = 350 [V], and Vcnt (c) = 280 [V]. Think of a case.

  If the development high-voltage power supplies are independently variable, Vl = 40V, Vb (y) = 340 [V], Vb (m) = 390 [V], Vb (c) = 320 [V]. The relationship of (Formula 3) is satisfied.

  However, when a high-voltage power supply having the relationship of (Equation 2) is used, Vb (y) = Vb (m) = Vb (c) = 390 in accordance with the M engine that most requires the development contrast bias voltage Vcnt. [V] must be set.

  The conventional potential setting method as described above is exemplified as shown in FIG.

  On the other hand, in the case described above, the M engine performs maximum exposure, the exposure potential Vl (m) = 40V, and the other Y and C engines stop the exposure, and Vl (y) = 90 [V], Vl ( (Equation 3) is satisfied respectively as c) = 110 [V].

  According to the studies by the present inventors, it has been found that density control can be maintained even when the development voltage is made common by performing voltage control by devising as described above.

  Furthermore, regarding the setting of the charging potential Vh, this is simply the cleaning field Vcf (p) = {Vcf (y), Vcf (m), Vcf (c), which is the difference between the charging potential Vh and the developing bias voltage Vb. It is only necessary to set Vcf (k)} to be maintained at about 90 to 110 [V]. The lower limit is fogging, and the upper limit is background BCO (electric field peeling phenomenon).

  Vcf = Vh−Vb (Formula 4)

  In this example, when the cleaning field Vcf = 100 [V], when the developing power supply is independently variable, Vh (y) = 440 [V], Vh (m) = 490 [V], Vh (c) = Although it may be 420 [V], when the development power source is common, it is necessary to set Vh (y) = Vh (m) = Vh (c) = 490 [V].

  In the case of DC charging (direct current charging), it is known that the higher the charging potential Vh setting, the worse the wear rate of the photosensitive drums 11, 12, 13, 14.

  In the case of the present embodiment, the charging potential Vh of the Y and C engines that share the power source also increases due to the detection of the toner empty of the M engine, and the wear of the photosensitive drums 11, 12, 13, and 14 is accelerated. It turns out that it will be done.

  If the Y, M, and C drum cartridges are replaced at the same time, this may be used. However, if the drum cartridges are not replaced at the same time, the drum cartridges will be consumed due to the influence of other engines, which increases the cost and operation. It is not preferable.

  Therefore, the present invention proposes a control technique that eliminates the need to increase the charging potential Vh as much as possible even in the above-described case.

  In the present invention, with respect to an engine in which the development bias voltage Vb increases due to an engine that requires the development contrast bias voltage Vcnt, the cleaning field Vcf is set to be small, and control for suppressing an increase in the charging potential Vh is performed.

  Although the fog is deteriorated by lowering the cleaning field Vcf, the toner density is often lowered in an engine that requires Vcnt, and since the fog amount is small in the first place, the total fog amount is hardly deteriorated.

  Thereby, the influence on other engines is reduced.

  Continuing with the previous example, if development contrast bias voltage Vcnt (y) = 300 [V], Vcnt (m) = 350 [V], and Vcnt (c) = 280 [V] are required, Vb (y ) = Vb (m) = Vb (c) = 390 [V] must be set.

  At this time, Vl (y) = 90 [V], Vl (m) = 40 [V], and Vl (c) = 110 [V] were set.

  In this case, since the conventional control method requires the cleaning field Vcf = 100 [V], Vh (y) = Vh (m) = Vh (c) = 490 [V] is set. However, in the present invention, the cleaning field Vcf of the engine other than the engine is set low.

  That is, Vcf (y) = 60 [V], Vcf (m) = 100 [V], and Vcf (c) = 60 [V].

  As a result, the charging potential Vh becomes Vh (y) = 390 + 60 = 450 [V], Vh (m) = 390 + 100 = 490 [V], and Vh (c) = 390 + 60 = 450 (V), respectively, which is 40 compared to the conventional case. It is set low near [V] (see FIG. 6).

  When the developing power source is independently variable, Vh (y) = 440 [V] and Vh (c) = 420 [V] should suffice. Although not lowered so far, the effect of suppressing the charging potential Vh can be achieved. Was obtained.

  In this case, the fogging tendency tends to be worse in the Y and C engines where the cleaning field Vcf is lowered (G0-1 is G1-2), but conversely, the fogging is improved in the M engine where the toner concentration is lowered. Therefore, the total fog level does not deteriorate so much.

  Here, the reason why the cleaning field Vcf of the M engine in which the toner concentration is lowered is not lowered is that, when the toner empty is detected, the toner concentration is lowered in the first place, so that the toner is not consumed as much as possible.

  On the other hand, if the amount of fog toner of the M engine with the toner density decreased is small, damage to the cleaning blades C1 to C4 will be large, and depending on the conditions, there will be a problem such as chipping or squealing of the cleaning blade. If the number is large, there is an advantage that toner is supplied to the cleaning blades C1 to C4 by retransfer such as a transfer belt. However, this effect does not appear when the toner density of the Y engine is low.

  FIG. 7 shows a configuration example (control block diagram) of a control system capable of realizing the voltage control as described above.

  The configuration example of FIG. 7 shows the relationship between the image formation control unit 500, the image formation unit (hardware) 600, and the image formation conditions.

  In this configuration example, the image formation control unit 500 includes a toner density control unit 501 that controls the target toner density to be 8%, a density control unit 502 that controls the image density to be constant, and a cleaning field. The Vh control unit 503 controls the Vcf to be constant.

  The toner density control unit 501 is connected to ATC sensors (toner density sensors) S1 to S4, a dispense motor 601 for controlling the toner supply amount, and the like.

  The density controller 502 is connected to an ADC sensor (density sensor) 602, an exposure device 03 for controlling the amount of light, a development high voltage power source 603 for controlling the development bias voltage Vb, and the like.

  The Vh control unit 503 is connected to an environmental sensor 604 that detects temperature, humidity, and the like, a memory (CRUM) 605 provided in the toner cartridge, a power failure high-voltage power source 606 that controls the charging voltage, and the like.

  Based on various information (toner density information, density information, development bias setting information, in-machine environment information, etc.) as the image forming condition 700, the voltage control as described above is performed.

  Next, with reference to the flowchart shown in FIG. 8, an example of the processing procedure of the voltage control processing executed in the image forming apparatus PR1 according to the present embodiment will be described.

  When this process is started, engine determination (determination of which engine is YMCK) is first performed in step S10. If Y, M, or C, the process proceeds to step S11. Moves to step S12.

  In step S11, it is determined whether or not the toner density of the other color engine other than that determined in step S10 has decreased. If “Yes”, the process proceeds to step S16, where the high developing bias voltage is reached. After calculating the cleaning field Vcf (for example, Vcf = 50 to 70 [V]), the process proceeds to step S13.

  On the other hand, if “No” is determined in step S11, the process proceeds to step S12, the normal cleaning field Vcf is calculated (for example, Vcf = 90 to 110 [V]), and then the process proceeds to step S13. .

  In step S11, whether or not the “toner replacement time” warning is issued in conjunction with the toner empty detection of the toner density sensors S1 to S4 may be used as a determination condition.

  In step S13, Vh is calculated from Vh = Vb + Vcf, and the process proceeds to step S14.

  In step S14, a subroutine for calculating the applied voltage Vdc is executed. Specifically, an appropriate applied voltage Vdc is calculated based on environmental conditions such as temperature and humidity, film thickness conditions of the photosensitive drums 11, 12, 13, and 14.

  That is, the applied voltage Vdc may be calculated based on Vdc = Vh + Vα (however, the discharge start voltage Vα is predicted and calculated from environmental conditions such as temperature and humidity).

  Next, the process proceeds to step S15, where the development high-voltage power supply 603 (see FIG. 7) is controlled based on the calculation result of step S14, and the process is terminated.

  As a result, the wear of the photosensitive drums 11, 12, 13, and 14 due to an increase in Vh (applied voltage) can be suppressed.

  Further, the increase in fog toner on the photosensitive drums 11, 12, 13, and 14 causes the cleaning blades C1 to C4 constituting the cleaning unit to be swung, and the photosensitive drums 11, 12, 13, and 14 and the cleaning blades C1 to C4. The secondary effect of suppressing chipping and squealing due to friction with the surface is obtained.

  Although the invention made by the present inventor has been specifically described based on the embodiments, the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed technology. Should not be considered. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above embodiment, but should be construed according to the description of the scope of claims. All modifications that fall within the scope of the claims and the equivalent technology are included.

  When using a program, it can be provided via a network or stored in a recording medium such as a CD-ROM.

  That is, the predetermined program including the image processing program is not limited to being recorded in a storage device such as a hard disk as a recording medium, and the predetermined program can be provided as follows.

  For example, a predetermined program may be stored in the ROM, and the CPU may load the predetermined program from the ROM to the main storage device and execute it.

  The predetermined program may be stored in a computer-readable recording medium such as a DVD-ROM, a CD-ROM, an MO (magneto-optical disk), a flexible disk, and distributed.

  Further, the image forming apparatus or the like is connected to a server apparatus or a host computer via a communication line (for example, the Internet), and after the predetermined program is downloaded from the server apparatus or the host computer, the predetermined program is executed. You may do it. In this case, examples of the download destination of the predetermined program include a memory such as a RAM and a storage device (recording medium) such as a hard disk.

  The image forming apparatus and the voltage control program according to the present invention can be applied to a full-color printer, a multifunction machine, and the like.

PR1 Image forming apparatus M Printer main body 03 Exposure device 04 Toner cartridge 05 Paper feed cassette 06 Fixing device 07 Double-sided transport path 08 Paper feed means 09 Control device 10 Electrical circuits 11-14 Photoconductor drums 21-24 Charger 31 Laser light 41 44 Developing device 51 Primary intermediate transfer drum 52 Primary intermediate transfer drum 53 Secondary intermediate transfer drum 60 Final transfer roll 70 Fixing device 90 Paper transport roll 100 Optical density sensor 150 Tangent plane 200 Common power supply device 201 Development contrast bias voltage Vcnt calculation Unit 300 control circuit 401 developing roll 404 auger 500 image formation control unit 501 toner density control unit 502 density control unit 503 control unit 601 dispense motor 603 development high voltage power source 604 environment sensor 606 power failure high voltage power source 700 image forming conditions C1 4 cleaning blade S1~S4 toner concentration sensor P printing paper T discharged Toilet

Claims (2)

A plurality of electrostatic latent image holding means for holding an electrostatic latent image formed based on image information;
A plurality of DC charging means provided corresponding to the plurality of electrostatic latent image holding means and charging each electrostatic latent image holding means;
A plurality of developing means provided corresponding to the plurality of electrostatic latent image holding means, and for developing the electrostatic latent image formed on the surface of each electrostatic latent image holding means using a developer;
A power supply means sharing at least a part of a power supply circuit for supplying a voltage to the DC charging means or the plurality of developing means;
A toner density detecting means provided in each of the developing means for detecting a toner density of the developer;
Cleaning means for cleaning the developer remaining in each electrostatic latent image holding means;
The required development contrast bias voltage Vcnt (where Vcnt = Vb−Vl, where Vb is the development bias voltage and Vl is the exposure potential (the potential of the electrostatic latent image holding means during exposure)) is calculated for each of the development units. Calculating means for
Based on the calculation result of the calculating means, the cleaning field voltage (DC component of the cleaning bias applied to the cleaning means) Vcf (Vcf = Vh−Vb) other than the developing means that most requires the development contrast bias voltage Vcnt. However, Vh is a charging potential as a difference between the applied voltage Vdc and the discharge start voltage Vα, and Vb is a developing bias voltage), which is smaller than the cleaning field voltage Vcf of the developing means requiring the developing contrast bias voltage Vcnt. Control means for controlling so that
An image forming apparatus comprising: Necessary development contrast bias voltage Vcnt (provided in the plurality of developing means provided for the plurality of electrostatic latent image holding means and for developing the electrostatic latent image formed on the surface of each electrostatic latent image holding means (note that Vcnt = Vb−Vl where Vb is the developing bias voltage and Vl is the exposure potential)
Based on the calculation result, the cleaning field voltage Vcf other than the developing means that requires the development contrast bias voltage Vcnt most (Vcf = Vh−Vb, where Vh is a charge as a difference between the applied voltage Vdc and the discharge start voltage Vα. A control process for controlling the electric potential, Vb is a developing bias voltage) to be smaller than the cleaning field voltage Vcf of the developing means that most requires the developing contrast bias voltage Vcnt;
A voltage control program for causing a calculation means to execute.

Images