WO2020055738A1 - Imaging system - Google Patents

Imaging system Download PDF

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Publication number
WO2020055738A1
WO2020055738A1 PCT/US2019/050187 US2019050187W WO2020055738A1 WO 2020055738 A1 WO2020055738 A1 WO 2020055738A1 US 2019050187 W US2019050187 W US 2019050187W WO 2020055738 A1 WO2020055738 A1 WO 2020055738A1
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WO
WIPO (PCT)
Prior art keywords
toner
station
imaging system
prei
tma
Prior art date
Application number
PCT/US2019/050187
Other languages
French (fr)
Inventor
Koji Yamaguchi
Shinya Nakasha
Yasushi Koshimura
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP2018168870A priority Critical patent/JP2020042139A/en
Priority to JP2018-168870 priority
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Publication of WO2020055738A1 publication Critical patent/WO2020055738A1/en

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/06Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/065Arrangements for controlling the potential of the developing electrode
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/01Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0105Details of unit
    • G03G15/0126Details of unit using a solid developer
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/50Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control
    • G03G15/5054Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt
    • G03G15/5058Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the characteristics of an intermediate image carrying member or the characteristics of an image on an intermediate image carrying member, e.g. intermediate transfer belt or drum, conveyor belt using a test patch

Abstract

An imaging system includes a first station and a second station. The first station has a first image carrier and a first developing device to supply toner to the first image carrier, and the second station has a second image carrier and a second developing device to supply toner to the second image carrier. A control unit determines a first developing voltage applied to the first developing device of the first station and a second developing voltage applied to the second developing device of the second station. Additionally, the control unit determines Vcur2 corresponding to the second developing voltage used in a current density control of the second station. The control unit outputs the Vcur2 to the second developing device based on Vpre1 corresponding to a previous developing voltage of the first station, based on Vcur1 corresponding to a current developing voltage of the first station, and based on Vpre2 corresponding to a previous developing voltage of the second station. The second developing device communicates with the control unit to receive the Vcur2 and to supply toner to the second image carrier in response to the Vcur2.

Description

IMAGING SYSTEM
BACKGROUND
[0001] An image forming system may include a developing apparatus which develops a toner image on a photosensitive member and a transfer device which transfers the toner image of the photosensitive member to a printing medium such as a sheet. In the image forming system, the density of the toner image may change due to a change in environmental conditions or due to the extended use of the photosensitive member or the developing apparatus. The toner density may be controlled in the image forming system. A toner patch for the density control is formed on a transfer belt of the transfer device and a toner adhesion amount of the toner patch is detected by a sensor. Then, the density control of the toner image is performed by setting a developing voltage to the developing apparatus in response to the toner adhesion amount detected by the sensor. BRIEF DESCRIPTION OF DRAWINGS
[0002] FIG. 1 is a schematic diagram illustrating an example imaging system.
FIG. 2 is a schematic diagram illustrating the example imaging system of FIG. 1 including a station, a sensor, and a control unit.
FIG. 3 is a schematic diagram illustrating an example sensor of FIG.
2.
FIG. 4 is a flowchart illustrating an example density control flow of the imaging system of FIG. 1.
FIG. 5 is a flowchart illustrating an example developing voltage calculation process. FIG. 6 is a graph illustrating an example of a time-series change of a toner charge amount and a toner adhesion amount.
FIG. 7 is a graph illustrating an example relationship between a toner adhesion amount and an output of a diffused and reflected light sensor.
FIG. 8 is a graph illustrating an example relationship between a toner adhesion amount and an output of a regular reflected light sensor.
FIG. 9 is a graph illustrating an example relationship between a toner adhesion amount and a signal-to-noise ratio.
FIG. 10 is a schematic diagram illustrating an example transfer device and an example photosensitive member.
DETAILED DESCRIPTION
[0003] In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. An imaging system may include all or part of an imaging apparatus including a developing device and a transfer device and various components for forming an image.
[0004] As illustrated in FIG. 1 , an example imaging system 1 may form a color image by using yellow, magenta, cyan, and black colors. The imaging system 1 includes, for example, a recording medium conveying device 10, a transfer device 30, a fixing device 50, and first to fourth stations 2A, 2B, 2C, and 2D. Each of the stations 2A, 2B, 2C, and 2D includes a developing device 20 and a photosensitive member 40.
[0005] The recording medium conveying device 10 conveys a printing medium P. The printing medium P is paper as an example. The recording medium conveying device 10 includes a feeding roller 11 which conveys the printing medium P forming an image thereon, as an example, along a conveying route R1. The printing medium P is stacked and accommodated on a cassette C and is picked up and conveyed by the feeding roller 11. The feeding roller 11 is provided, for example, in the vicinity of the outlet of the printing medium P in the cassette C. The recording medium conveying device 10 allows the printing medium P to reach a secondary transfer region R2 through the conveying route R1 at a timing in which the transferred toner image reaches the secondary transfer region R2.
[0006] The transfer device 30 secondarily transfers a toner image to the printing medium P. The fixing device 50 fixes the toner image to the printing medium P. The transfer device 30 receives, for example, toner from each of the stations 2A to 2D and forms the toner image (e.g., composite toner image). As an example, the transfer device 30 includes a transfer belt 31 , suspension rollers 32a, 32b, 32c, and 32d, a primary transfer roller 33, and a secondary transfer roller 34.
[0007] The transfer belt 31 is suspended on, for example, the suspension rollers 32a to 32d. The primary transfer roller 33 is provided to correspond to, for example, each of the stations 2A to 2D. Each primary transfer roller 33 sandwiches the transfer belt 31 along with the photosensitive member 40 of each of the stations 2A to 2D. The secondary transfer roller 34 sandwiches the transfer belt 31 along with the suspension roller 32d. The transfer belt 31 is, for example, an endless belt which moves in a circulating manner by the suspension rollers 32a to 32d. Each primary transfer roller 33 presses each photosensitive member 40 from the inner peripheral side of the transfer belt 31. The secondary transfer roller 34 presses the suspension roller 32d from the outer peripheral side of the transfer belt 31.
[0008] The fixing device 50 fixes, for example, the toner image secondarily transferred from the transfer belt 31 to the printing medium P to the printing medium P. As an example, the fixing device 50 includes a heating roller 51 which fixes the toner image to the printing medium P while heating the printing medium P and a pressing roller 52 which presses the heating roller 51 . Both the heating roller 51 and the pressing roller 52 are formed in, for example, a cylindrical shape. A nip portion N which is a fixing region of the printing medium P is provided between the heating roller 51 and the pressing roller 52. When the printing medium P passes through the nip portion N, the toner image is heated and fixed (e.g., fused) to the printing medium P.
[0009] As an example, the imaging system 1 may include a secondary fixing device which is provided at the downstream side of the fixing device 50 of the conveying route of the printing medium P so as to smooth the toner and produce a gloss finish of the image of the printing medium P. Further, the imaging system 1 may include discharging rollers 12 and 13 which discharge the printing medium P having the toner image fixed thereto to the outside of the imaging system 1.
[0010] The color of the toner T of the first station 2A may include a color other than black. As an example, the color of the toner T of the first station 2A is yellow, the color of the toner T of the second station 2B is black, the color of the toner T of the third station 2C is magenta, and the color of the toner T of the fourth station 2D is cyan. In some examples, the first station 2A, the third station 2C, the fourth station 2D, and the second station 2B are disposed in order from the upstream side in the movement route of the transfer belt 31.
[0011] Each of the stations 2A to 2D may include a process cartridge integrally including the developing device 20, the photosensitive member 40, a charging device 42, and a cleaning device 43. For example, the imaging system 1 includes a casing 3 to which the stations 2A to 2D are attached. The stations 2A to 2D are separately attached to the casing 3, for example, in such a manner that a door of the casing 3 is opened and the station is inserted into and extracted from the casing 3.
[0012] Each of the first to fourth stations 2A to 2D may be provided for each color of the toner T. In each of the first to fourth stations 2A to 2D, the photosensitive member 40 forms an electrostatic latent image and the developing device 20 develops the electrostatic latent image formed on the photosensitive member 40. The photosensitive member 40 may include a photosensitive drum and may be an organic photosensitive member (OPC: Organic Photo Conductor). In some examples, the first to fourth stations 2A to 2D are arranged along the movement direction of the transfer belt 31. Additionally, the developing device 20, an exposure unit 41 , the charging device 42, and the cleaning device 43 may face the outer peripheral surface of each photosensitive member 40.
[0013] The charging device 42 may be configured to uniformly charge the outer peripheral surface of the photosensitive member 40 to a predetermined potential. The charging device 42 may include a charging roller which rotates to follow the rotation of the photosensitive member 40. The exposure unit 41 exposes the outer peripheral surface of the photosensitive member 40 charged by the charging device 42 in response to an image formed on the printing medium P. A potential of a portion exposed by the exposure unit 41 in the outer peripheral surface of the photosensitive member 40 changes, so that an electrostatic latent image is formed on the outer peripheral surface of the photosensitive member 40.
[0014] Each of the stations 2A to 2D is disposed to face, for example, the toner tank 25. The toner T is supplied from each toner tank 25 to each developing device 20 of the stations 2A to 2D. Each developing device 20 forms a toner image by developing the electrostatic latent image of the outer peripheral surface of the photosensitive member 40 using the supplied toner T. The photosensitive member 40 is an example of an image carrier forming a toner image thereon.
[0015] Each developing device 20 receives a developing voltage from a control unit 70 (see FIG. 2) and supplies the toner T to the photosensitive member 40 in response to the developing voltage. The toner image formed on the outer peripheral surface of the photosensitive member 40 is initially transferred to the transfer belt 31. For example, the transfer belt 31 may be an image carrier forming a toner image thereon. The toner T remaining on the outer peripheral surface of the photosensitive member 40 after the primary transfer operation is removed by the cleaning device 43.
[0016] Each developing device 20 of the stations 2A to 2D includes a developing roller 21 which carries toner on the photosensitive member 40. In the developing device 20, for example, the toner and the carrier are adjusted to a predetermined mixing ratio and a developing agent including the toner and the carrier is mixed and agitated to uniformly disperse the toner. The developing agent is carried on the developing roller 21 and the developing roller 21 rotates so that the developing agent is conveyed to a region facing the photosensitive member 40. Then, the toner in the developing agent carried on the developing roller 21 moves to the electrostatic latent image of the photosensitive member 40 to develop the electrostatic latent image.
[0017] Example imaging methods will be described with reference to the imaging system 1. In an example printing process, when an image signal of a recording target image is input to the imaging system 1 , the feeding roller 11 rotates so that the printing medium P stacked on the cassette C is picked up and the printing medium P is conveyed along the conveying route R1. Additionally, the charging device 42 uniformly charges the outer peripheral surface of the photosensitive member 40 to a predetermined potential. The exposure unit 41 irradiates a laser beam to the outer peripheral surface of the photosensitive member 40 so as to form an electrostatic latent image on the outer peripheral surface of the photosensitive member 40 based on the image signal.
[0018] Subsequently, the developing device 20 forms a toner image on the photosensitive member 40 and develops the toner image. For example, in each of the stations 2A to 2D, the toner image is initially transferred from each photosensitive member 40 to the transfer belt 31 in a region in which each photosensitive member 40 faces the transfer belt 31. The toner images formed on the photosensitive members 40 of the first to fourth stations 2A to 2D are sequentially superimposed on the transfer belt 31 so that one composite toner image is formed. The composite toner image is secondarily transferred to the printing medium P conveyed from the recording medium conveying device 10 in the secondary transfer region R2 in which the suspension roller 32d and the secondary transfer roller 34 face each other.
[0019] The printing medium P to which the composite toner image is secondarily transferred is conveyed from the secondary transfer region R2 to the fixing device 50. For example, the fixing device 50 fuses or otherwise fixes the composite toner image to the printing medium P as a result of the printing medium P passing through the nip portion N while heat and pressure are applied to the printing medium P. The printing medium P to which the composite toner image is fixed may be discharged from the discharging rollers 12 and 13 to the outside of the imaging system 1.
[0020] FIG. 2 is a schematic diagram illustrating a configuration in the periphery of the example stations 2A to 2D and the transfer device 30. In the imaging system 1 , the density control of the toner T initially transferred to the transfer belt 31 is performed. The density control may be performed, for example, at least either during the printing process on the printing medium P or before the printing process on the printing medium P.
[0021] For example, the imaging system 1 includes a sensor 60 which measures the adhesion amount of the toner T with respect to the transfer belt 31 , the control unit 70 which receives an output from the sensor 60 to calculate the adhesion amount of the toner T and determines the developing voltage to the developing device 20 of each of the stations 2A to 2D, and a cleaning blade 80 which scrapes off the residual toner of the transfer belt 31. The cleaning blade 80 removes the toner T remaining on the transfer belt 31 after passing through the secondary transfer region R2 from the transfer belt 31 .
[0022] FIG. 3 is a schematic diagram of a detailed example of the sensor 60. As illustrated in FIG. 3, for example, the sensor 60 includes an irradiation unit 61 which irradiates light L1 to a surface 31 a of the transfer belt 31 having the toner T adhering thereto, a regular reflected light sensor 62 which detects regular reflected light L2 from the transfer belt 31 , and a diffused and reflected light sensor 63 which detects diffused and reflected light L3 from the transfer belt 31. The particle diameter of the toner T is 5.8 pm as an example. Further, the output of each of the regular reflected light sensor 62 and the diffused and reflected light sensor 63, that is, the output of the measured toner adhesion amount (hereinafter, also referred to as the "toner adhesion amount") is transmitted to the control unit 70.
[0023] In some examples, the irradiation unit 61 includes an LED which irradiates visual light. The regular reflected light sensor 62 detects, for example, the regular reflected light L2 specularly reflected from the transfer belt 31 by the irradiation of the light L1 from the irradiation unit 61. The regular reflected light sensor 62 is disposed at a position to receive the regular reflected light L2 specularly reflected from the transfer belt 31 as a result of the irradiation of the light L1 of the irradiation unit 61. In some examples, the intensity of the regular reflected light L2 increases as the adhesion amount of the toner T with respect to the transfer belt 31 decreases, such that the output of the regular reflected light sensor 62 increases. Additionally, since the intensity of the regular reflected light L2 decreases as the adhesion amount of the toner T with respect to the transfer belt 31 increases, the output of the regular reflected light sensor 62 decreases.
[0024] The control unit 70 calculates the adhesion amount of the toner T from the output of the regular reflected light sensor 62. However, when the toner T of a predetermined amount or more (for example, two layers or more) is superimposed on the transfer belt 31 , the intensity of the regular reflected light L2 does not change and the output of the regular reflected light sensor 62 does not change even when the amount of the toner T further increases. Thus, when the toner T of a predetermined amount or more is superimposed on the transfer belt 31 , the output of the regular reflected light sensor 62 may not be readily accessible when calculating the adhesion amount of the toner T.
[0025] The diffused and reflected light sensor 63 can use the output of the diffused and reflected light sensor 63 for the measurement of the adhesion amount of the toner T since the intensity of the diffused and reflected light L3 increases and the output of the diffused and reflected light sensor 63 increases even when the toner T of a predetermined amount or more is superimposed on the transfer belt 31. In some examples, the intensity of the diffused and reflected light L3 is large in the toner T other than black as compared with the black toner T, such that the adhesion amount of the toner T may be more accurately measured as compared to black. However, in some examples the output of the diffused and reflected light sensor 63 with respect to the adhesion amount of the toner T is not calibrated. In still further examples, the output of the diffused and reflected light sensor 63 can be calibrated with high accuracy.
[0026] FIG. 4 is a flowchart illustrating an example density control flow of the toner T with respect to the transfer belt 31. In some examples, one or more operations of the flow chart may be added, deleted, or changed. The irradiation of the light L1 of the irradiation unit 61 is adjusted at operation S1. At this time, for example, the output of the irradiation unit 61 may be calibrated so that the output of the light L1 of the irradiation unit 61 falls within a predetermined range.
[0027] At operation S2, the developing voltage (developing bias) and the charging voltage (charging bias) with respect to each of the stations 2A to 2D are set. In some examples, the values of the developing voltage of the developing device 20 and the charging voltage of the charging device 42 at the time of forming a toner patch are set. The charging voltage set at this time may correspond to a photosensitive member surface voltage or a charging voltage at the time of first performing a uniform charging operation.
[0028] At operation S3, the toner patch is formed. In some examples, the development of the developing device 20 is performed by the developing voltage and the charging voltage set as described above and the toner patch is transmitted from the photosensitive member 40 to the transfer belt 31. At operation S4, the sensor 60 reads the toner patch on the transfer belt 31 , and the control unit 70 calculates and corrects the developing voltage at operation S5.
[0029] FIG. 5 is a flowchart illustrating example processes of operation S5. As illustrated in FIGS. 4 and 5, the sensor 60 first measures the adhesion amount TMACUri of the toner T from the first station 2A (operation S 11 ). In operation S11 , for example, the density of the toner T of the first station 2A is corrected. Further, the control unit 70 acquires a ratio Aouh between the adhesion amount TMAouh of the toner T and the developing voltage VCun of the first station 2A from Equation (1 ) by receiving the diffused and reflected light L3 generated by the irradiation of the light L1 of the irradiation unit 61 using the diffused and reflected light sensor 63 (operation S12).
Acurl = TMAcurlA/cur1 ... (1 )
[0030] Next, a ratio Apre between the adhesion amount TMAprei of the toner T of the first station 2A and the developing voltage Vprei of the first station 2A at the previous density correction (for example, several days ago) is acquired from Equation (2) at operation S13.
Aprel = TMAprelA/pre1 . . . (2)
[0031] In some examples, the density of the image due to the toner T has a correlation with the charge amount Q/M of the toner T. The charge amount Q/M indicates a ratio between the charge amount (Q) and the mass (M) of the toner T. The charge amount Q/M of the toner T decreases with the lapse of time. Additionally, when the developing voltage is constant and the charge amount Q/M of the toner T decreases, the adhesion amount of the toner T increases. Accordingly, when the toner patch is formed at the same developing voltage as that of the previous density correction in a state in which the charge amount Q/M decreases, the density of the toner patch increases. Since the density of the toner T cannot be read by the regular reflected light sensor 62 when the density of the toner patch increases, the preparation and detection of the toner patch may be repeated.
[0032] The value of (ACun/Aprei ) indicates a ratio of the charge amount Q/M that decreases with the lapse of time. In some examples, the developing voltage is corrected by using the value of (Acun/APrei ) in the station 2B handling the black toner T. For example, the developing voltage is set to a low value by integrating the value of (Acun/APrei ) with the developing voltage VPre2 at the previous density correction of the station 2B. The control unit 70 may perform the density control before a printing state and after a stop state of the developing device 20 and may calculate the value of VCUr2 to be low in response to the charge amount Q/M of the toner decreasing with the lapse of time. In addition to preventing an increase in density of the toner patch, the frequency of repeating the preparation and detection of the toner patch may be reduced or prevented by correcting the developing voltage in consideration of a change in the charge amount Q/M.
[0033] In some examples, the developing voltage VCUr2 for the density control of the second station 2B is calculated from (Acun/APrei) and the developing voltage Vpre2 for the previous density control of the second station 2B by Equation (3) described below (operations S14 and S15).
Vcur2 = (Acurl/APre1 ) VPre2 ... (3)
The toner patch is written by the black toner T using the developing voltage VCUr2, and the detection of the sensor 60 is performed (operation S16).
[0034] When the developing voltage VCUr2 is output to the second station 2B handling the black toner T, the toner patch can be written at the same density degree as that of the black toner T of the previous density correction. Thus, in addition to preventing the black toner T from being dark, the density of the toner T may also be read by the regular reflected light sensor 62. Additionally, the frequency of repeating the preparation and detection of the toner patch may be suppressed or limited to, for example, a case in which the initial correction is performed, a case in which the toner is exchanged, or a case in which a change in the charge amount Q/M cannot be predicted. Therefore, the density control may be efficiently realized.
[0035] The developing voltage VCUr2 may be determined by the density control when a difference between the toner consumption rate TCnsl from the previous time to the current time of the first station 2A and the toner consumption rate TCns2 from the previous time to the current time of the second station 2B is 10% or less. Furthermore, a relationship of the toner consumption rate TCnsl = (the toner consumption amount from the previous time to the current time of the first station) / (the average toner amount of the first station) and a relationship of the toner consumption rate TCns2 = (the toner consumption amount from the previous time to the current time of the second station) / (the average toner amount of the second station) may be established.
[0036] The toner consumption rate TCnsl may be calculated from a toner replenishment amount from the previous time to the current time of the first station 2A. Additionally, the toner consumption rate TCns2 may be calculated from the toner replenishment amount from the previous time to the current time of the second station 2B. Since the toner amount inside the developing device 20 including the average toner amount is monitored by, for example, a TC sensor and a predetermined amount of toner is replenished when the toner amount inside the developing device 20 is smaller than a reference value, the toner replenishment amount may be calculated by measuring the number of replenishment times. Further, the toner consumption rate TCnsl may be calculated from the sum of the print dot signals from the previous time to the current time of the first station 2A and the toner consumption rate TCns2 may be calculated from the sum of the print dot signals from the previous time to the current time of the second station 2B.
[0037] FIG. 6 illustrates example time-series data of the charge amount of the toner T and the adhesion amount of the toner T when performing the above-described density control, and when performing the comparative example without the above-described density control. As illustrated in FIG. 6, when the non-operational state of the imaging system 1 is allowed to continue, the charge amount of the toner T decreases over time. In the case of the comparative example without the above-described correction of the developing voltage, the toner adhesion amount may increase when the toner patch is formed after a predetermined time elapses. As an example, when the density correction is performed after ten hours from the previous density correction, the toner adhesion amount was increased from about 250 (mg/cm2 c 100) to 300 (mg/cm2 c 100) in the comparative example. On the other hand, when the developing voltage was corrected to a low value, the toner adhesion amount was 250 (mg/cm2 x 100) equal to that of the previous density correction.
[0038] Further, when twenty hours or thirty hours elapse from the previous density correction, in the case of the comparative example, the toner adhesion amount becomes about 350 (mg/cm2 c 100) or 370 (mg/cm2 c 100) so that the adhesion amount exceeds 320 (mg/cm2 c 100) which is an example allowable upper-limit adhesion amount. When the toner adhesion amount exceeds the allowable upper-limit adhesion amount, the preparation and detection of the toner patch may be repeated. However, in some examples, the toner adhesion amount may be maintained at 250 (mg/cm2 c 100) and an increase in density may be prevented even when twenty hours or thirty hours elapse from the previous density correction.
[0039] FIG. 7 is a graph illustrating an example relationship between the toner adhesion amount and the output of the diffused and reflected light sensor 63. The output of the diffused and reflected light sensor 63 increases substantially in a linear function as the toner adhesion amount increases. For example, a solid line and a dashed line in FIG. 7 indicate a relationship between the output of the diffused and reflected light sensor 63 and the toner adhesion amount TMA obtained by measurement values. Although these lines are illustrated as curves in FIG. 7, these lines can be expressed by the approximation as Equation (4) below. In this case, when the toner adhesion amount is indicated by TMA and the output of the diffused and reflected light sensor 63 is indicated by S, the control unit 70 may calculate a by using Equation (4) of S = a c TMA and may calibrate the output of the diffused and reflected light sensor 63 by using a.
[0040] g illustrated in FIG. 7 may be a ratio between a ratio B between the upper-limit measurement value of the tolerance of the output of the diffused and reflected light sensor 63 and the toner adhesion amount, and a ratio A between the lower-limit measurement value of the tolerance of the output of the diffused and reflected light sensor 63 and the toner adhesion amount. In this case, a gradient B may be set such that the upper-limit measurement value of the tolerance of the diffused and reflected light sensor 63 is Y1 and the toner adhesion amount is X1. Additionally, a gradient A may be set such that the lower-limit measurement value of the tolerance of the diffused and reflected light sensor 63 is Y2 and the toner adhesion amount is X2, and g may be B/A.
[0041] In some examples, g illustrated in FIG. 7 may be expressed by a ratio between the output (S_Std) of the diffused and reflected light sensor 63 as the reference characteristic and the actual output S of the diffused and reflected light sensor 63, that is, g = S_Std/S. Furthermore, S_Std may be a value measured in advance or may be a value calculated from a previously stored table. As described above, g can be calculated according to various methods.
[0042] As illustrated in FIG. 7, the value g becomes constant when the toner adhesion amount is large to a certain degree, but when the toner adhesion amount is about 0, there is a tendency that the value noticeably decreases and becomes unstable as the toner adhesion amount increases. Thus, when there is no limitation in the toner adhesion amount, the value g changes to about 20%. For this reason, when g is used to correct the density, a density error of about 20% may occur. Therefore, , a range may be provided for the toner adhesion amount to suppress the above-described density error, as will be described in further detail.
[0043] FIG. 8 is a graph illustrating an example relationship between the toner adhesion amount and the output of the regular reflected light sensor 62. FIG. 9 is a graph illustrating an example relationship between the toner adhesion amount and the S/N ratio of the regular reflected light sensor 62. As illustrated in FIGS. 8 and 9, the output of the regular reflected light sensor 62 substantially does not change, for example, when the toner adhesion amount is 3.0 g/m2 or more. Thus, the output of the regular reflected light sensor 62 may not be readily usable when the toner adhesion amount is 3.0 g/m2 or more.
[0044] When the toner adhesion amount is 3.0 g/m2 or more, the light receiving amount of the regular reflected light sensor 62 may not change even when the toner adhesion amount increases and the S/N ratio of the output of the regular reflected light sensor 62 becomes unstable. Additionally, the S/N ratio may be maintained at 5 dB, for example, when the average particle diameter of the toner is 5.8 pm and the toner adhesion amount is 2.5 g/m2 or less. In some examples, when the average particle diameter of the toner is set to d (pm), the S/N ratio may be maintained at 5 dB when the toner adhesion amount is 2.5 c d/5.8 (g/m2). [0045] In some examples, a change in the above-described value g can be suppressed to be 2% or less when the toner adhesion amount is 1 .8 g/m2 or more. Additionally, when the toner adhesion amount is 1.8 g/m2 or more and 2.5 c d/5.8 (g/m2) or less, the S/N ratio may be stabilized and a change in value g can be suppressed. In some examples, the toner patch is selected within a specified range (a range in which the toner adhesion amount is 1.8 g/m2 or more and 2.5 c d/5.8 (g/m2) or less) after forming a plurality of toner patches and g is calculated from the data of the selected toner patch. Since the range of the toner adhesion amount is set to 1.8 g/m2 or more and 2.5 c d/5.8 (g/m2) or less, a density error of the toner patch can be suppressed. Further, the control unit 70 may control the toner adhesion amount so that a range in which the value of g changes becomes 5% or less of the output S of the diffused and reflected light sensor 63. Also in this case, the density error of the toner patch can be similarly suppressed.
[0046] FIG. 10 is a schematic diagram illustrating an example configuration for forming the toner patch. For example, the positions of the toner patches T1 and T2 may be set to the positions for dividing the period of the photosensitive member 40 (as an example, the phase angles Q1 and Q2) and the average value of the measurement values of the toner patches T1 and T2 of the sensor 60 may be calculated by the control unit 70. In the case of this example, performance of the density correction of the toner patches T 1 and T2 may reduce the influence of the cyclic unevenness of the photosensitive member 40 due to the minute eccentricity or the like of the photosensitive member 40.
[0047] In some examples, the toner patches T1 and T2 may be disposed at a position in which the phase of the patch position equals the period of the photosensitive member 40 divided by the number of toner patches. As an example, Q1 = 0° and Q2 = 180°. In other examples, when the period of the photosensitive member 40 is 90 mm and three toner patches are formed, the position of the first toner patch may be 0 mm (the phase angle is 0°), the position of the second toner patch may be 30 mm (the phase angle is 120°), and the position of the third toner patch may be 60 mm (the phase angle is 240°).
[0048] As still other examples including a time interval and in which the development voltage is different for each toner patch, the position of the first toner patch may be 0 mm (the phase angle is 0°), the position of the second toner patch may be 60 mm (the phase angle is 240°), and the position of the third toner patch may be 30 mm (the phase angle is 120°). Further, the number of toner patches may be some number other than three, and the positions of the toner patches may be deviated from each other by a value calculated from the period of the photosensitive member 40 divided by the number of toner patches.
[0049] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail.
[0050] In some examples, the sensor 60 measures the adhesion amount TMAcuri of the toner T of the first station 2A and the control unit 70 measures a ratio between the adhesion amount TMAouh and the developing voltage Vcun by Equation (1 ). Additionally, the control unit 70 may determine the developing voltage VCun so that the current toner adhesion amount TMAouh of the first station 2A becomes the same as the previous toner adhesion amount TMAprei. Further, the sensor 60 may measure the toner adhesion amount of at least one of the second station 2B, the third station 2C, and the fourth station 2D and the control unit 70 may use an average value of the toner adhesion amount thereof. Further, the control unit 70 may use the developing voltage of at least one of the second station 2B, the third station 2C, and the fourth station 2D.
[0051] In some examples, the control unit 70 may perform the calculation of the above-described value of (Acun/APrei) also for the third station 2C and the fourth station 2D and may calculate VCUr2 for the density control by integrating Vpre2 with the average value of (ACun/APrei) of the first station 2A, (Acun/APrei) of the third station 2C, and (ACun/APrei) of the fourth station 2D. In this case, the density correction may be performed by also considering all color toner states other than black. Furthermore, the control unit 70 may calculate the above-described values by an Equation other than Equations (1 ) to (4).
[0052] In some examples, the color of the toner T of the first station 2A was yellow, the color of the toner T of the second station 2B was black, the color of the toner T of the third station 2C was magenta, and the color of the toner T of the fourth station 2D was cyan. However, the color of the toner T of the first station 2A, the color of the toner T of the second station 2B, the color of the toner T of the third station 2C, and the color of the toner T of the fourth station 2D may vary. Further, the number of stations may be three or less or five or more.

Claims

1. An imaging system comprising:
a first station including a first image carrier and a first developing device to supply toner to the first image carrier;
a second station including a second image carrier and a second developing device to supply toner to the second image carrier; and
a control unit to determine a first developing voltage applied to the first developing device of the first station and a second developing voltage applied to the second developing device of the second station,
the control unit to determine VCUr2 corresponding to the second developing voltage used in a current density control of the second station and to output the VCUr2 to the second developing device based on Vprei corresponding to a previous developing voltage of the first station, based on Vcun corresponding to a current developing voltage of the first station, and based on Vpre2 corresponding to a previous developing voltage of the second station, and
the second developing device to communicate with the control unit to receive the VCUr2 and to supply toner to the second image carrier in response to the VCUr2.
2. The imaging system according to claim 1 , comprising:
a sensor to measure a toner adhesion amount of toner adhering to at least one image carrier selected from the group consisting of the first image carrier and the second image carrier,
the control unit to determine Aprei and Aouh and to calculate the VCUr2 by integrating the Vpre2 to a value of (Acun/APrei),
wherein the Aprei indicates a ratio between TMAprei and Vprei, wherein the TMAprei indicates the toner adhesion amount previously measured by the sensor,
wherein the Aouh indicates a ratio between TMAouh and VCun , and wherein the TMAouh indicates the toner adhesion amount currently measured by the sensor.
3. The imaging system according to claim 2,
the control unit to calculate Aoup from TMAoup currently measured by the sensor and VCun corresponding to the current developing voltage by Equation (1 ) of Aouh = TMAcunA/cun, to calculate Aprei from TMAprei previously measured by the sensor and Vprei corresponding to the previous developing voltage by Equation (2) of Aprei = TMApreiA/Prei , and to calculate VCur2 from VPre2 corresponding to the previous developing voltage of the second station by Equation (3) of VCUr2 = (ACun/APrei) c Vpre2.
4. The imaging system according to claim 2,
wherein the sensor includes an irradiation unit to irradiate light to the at least one image carrier, a regular reflected light sensor to detect regular reflected light from the at least one image carrier, and a diffused and reflected light sensor to detect diffused and reflected light from the at least one image carrier,
the control unit to calibrate an output of the diffused and reflected light sensor by an output of the regular reflected light sensor, and
the control unit to calculate a from an adhesion amount TMA of toner adhering to the at least one image carrier and an output S of the diffused and reflected light sensor by Equation (4) of S = a c TMA and to perform the calibration by using the a.
5. The imaging system according to claim 4,
wherein the toner adhesion amount TMA is 1.8 g/m2 or more.
6. The imaging system according to claim 4,
wherein when an average particle diameter of the toner is set to d (pm), the toner adhesion amount TMA is 2.5 c d/5.8 (g/m2) or less.
7. The imaging system according to claim 4,
wherein at least one of the first station and the second station includes a photosensitive drum, and
the control unit to form a plurality of toner patches corresponding to a rotation position of the photosensitive drum on the at least one image carrier and to obtain an average value of the toner adhesion amount TMA of the plurality of toner patches.
8. The imaging system according to claim 2, comprising:
a third station and a fourth station,
the control unit to perform the calculation of the value of the (Acun/Aprei) for the third station and the fourth station and to calculate the VCur2 by integrating the Vpre2 with an average value of the (Acun/APrei ) of the first station, the third station, and the fourth station.
9. The imaging system according to claim 1 ,
the control unit to calculate the value of VCUr2 to be low in response to a toner charge amount decreased with the lapse of time at the time of performing the density control before a printing state and after a stop state of the first developing device of the first station and the second developing device of the second station.
10. The imaging system according to claim 1 ,
the control unit to determine VCun so that a current toner adhesion amount TMAouh of the first station becomes the same as a previous toner adhesion amount TMAprei in the density control.
11. The imaging system according to claim 1 ,
wherein when a difference between a toner consumption rate TCnsl from a previous time to a current time of the first station and a toner consumption rate TCns2 from a previous time to a current time of the second station is 10% or less, the VCUr2 is determined by the density control, wherein the toner consumption rate TCnsl = (a toner consumption amount from a previous time to a current time of the first station) / (an average toner amount of the first station), and
wherein the toner consumption rate TCns2 = (a toner consumption amount from a previous time to a current time of the second station) / (an average toner amount of the second station).
12. The imaging system according to claim 11 ,
wherein the toner consumption rate TCnsl is calculated from a toner replenishment amount from a previous time to a current time of the first station, and
wherein the toner consumption rate TCns2 is calculated from a toner replenishment amount from a previous time to a current time of the second station.
13. The imaging system according to claim 11 ,
wherein the toner consumption rate TCnsl is calculated from a sum of print dot signals from a previous time to a current time of the first station, and
wherein the toner consumption rate TCns2 is calculated from a sum of print dot signals from a previous time to a current time of the second station.
14. The imaging system according to claim 1 ,
wherein a color of the toner stored in the second station is black, and
wherein a color of the toner stored in the first station is a color other than black.
PCT/US2019/050187 2018-09-10 2019-09-09 Imaging system WO2020055738A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3903042B2 (en) * 2003-12-26 2007-04-11 キヤノン株式会社 Image forming apparatus
CN101504521B (en) * 2008-02-07 2012-01-11 株式会社理光 Image forming apparatus and image density control method
JP5979475B2 (en) * 2012-03-05 2016-08-24 株式会社リコー Image forming apparatus
JP2017138546A (en) * 2016-02-05 2017-08-10 キヤノン株式会社 Image forming apparatus and image forming method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3903042B2 (en) * 2003-12-26 2007-04-11 キヤノン株式会社 Image forming apparatus
CN101504521B (en) * 2008-02-07 2012-01-11 株式会社理光 Image forming apparatus and image density control method
JP5979475B2 (en) * 2012-03-05 2016-08-24 株式会社リコー Image forming apparatus
JP2017138546A (en) * 2016-02-05 2017-08-10 キヤノン株式会社 Image forming apparatus and image forming method

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