JP2020042139A - Image forming system - Google Patents

Abstract

To provide an image forming system.SOLUTION: An image forming system comprises: a first station 2A and a second station 2B including image carriers and developing devices supplying toner to the image carriers; and a control unit 70 for determining a development voltage applied to the respective developing devices in the first station and second station. The control unit determines Vwhich is a previous development voltage of the first station, Vwhich is a current development voltage of the first station, and Vwhich is a development voltage used fur current density control of the second station on the basis of Vwhich is a previous development voltage of the second station, and outputs Vto the developing device in the second station. The developing device in the second station can communicate with the control unit to receive Vand supplies toner to the image carrier according to V.SELECTED DRAWING: Figure 2

Description

  The image forming system includes a developing device that develops a toner image on a photoconductor, and a transfer device that transfers the toner image on the photoconductor to a printing medium such as paper. In an image forming system, the density of a toner image may change due to a change in environmental conditions, a long-term use of a photoconductor or a developing device, or the like. Therefore, in the image forming system, toner density control is performed. In the toner density control, a toner patch for density control is formed on a transfer belt of a transfer device, and a sensor detects the amount of toner attached to the toner patch. The density control of the toner image is executed by determining the developing voltage to the developing device according to the amount of toner adhesion detected by the sensor.

1 is a schematic diagram of an exemplary imaging system that can be used to implement the various examples disclosed herein. FIG. 2 is a diagram schematically illustrating an exemplary station, a sensor, and a control unit of the image forming system in FIG. 1. FIG. 3 is a diagram schematically illustrating an example of the sensor in FIG. 2. 3 is a flowchart illustrating each step of an exemplary density control flow in the image forming system of FIG. 1. 5 is a flowchart illustrating an example of each step of a developing voltage calculation process among the steps in FIG. 4. 5 is a graph illustrating an example of a time-series change of a toner charge amount and a toner adhesion amount. 6 is a graph illustrating an example of a relationship between a toner adhesion amount and an output of a diffuse reflection light sensor. 5 is a graph illustrating an example of a relationship between a toner adhesion amount and an output of a regular reflection light sensor. 5 is a graph illustrating an example of a relationship between a toner adhesion amount and a signal-to-noise ratio. FIG. 9 is a diagram schematically illustrating a transfer device and a photoconductor according to a modified example.

  Hereinafter, various examples of the image forming system will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements have the same reference characters allotted, and redundant description will not be repeated. The drawings may be simplified or exaggerated to illustrate the examples more clearly. First, an exemplary image forming system will be described. The image forming system may include the entire image forming apparatus including the developing device and the transfer device described above, or may include only a part of the image forming device, and includes various configurations related to image formation.

  As shown in FIG. 1, the image forming system 1 as an example forms a color image using each color of yellow, magenta, cyan, and black. The image forming system 1 includes, for example, a recording medium transport device 10, a transfer device 30, a fixing device 50, and first to fourth stations 2A, 2B, 2C, 2D. Each of the stations 2A, 2B, 2C, and 2D includes a developing device 20 and a photoconductor 40.

  The recording medium transport device 10 transports the print medium P. The print medium P is paper as an example. The recording medium transport device 10 includes, for example, a paper feed roller 11 that transports a print medium P on which an image is formed along a transport path R1. The print medium P is stacked and accommodated in the cassette C, and is picked up and transported by the paper feed roller 11. The paper feed roller 11 is provided, for example, near the exit of the print medium P in the cassette C. The recording medium transport device 10 causes the print medium P to reach the secondary transfer area R2 via the transport path R1 at the timing when the transferred toner image reaches the secondary transfer area R2.

  The transfer device 30 secondarily transfers the toner image to the print medium P. The fixing device 50 fixes the toner image on the print medium P. The transfer device 30 receives toner from each of the stations 2A to 2D, and forms a toner image (laminated toner image). The transfer device 30 includes, for example, a transfer belt 31, suspension rollers 32a, 32b, 32c, 32d, a primary transfer roller 33, and a secondary transfer roller.

  The transfer belt 31 is suspended by, for example, suspension rollers 32a to 32d. The primary transfer roller 33 is provided, for example, corresponding to each of the stations 2A to 2D. Each primary transfer roller 33 holds the transfer belt 31 together with the respective photoconductors 40 of the stations 2A to 2D. The secondary transfer roller 34 sandwiches the transfer belt 31 together with the suspension roller 32d. The transfer belt 31 is, for example, an endless belt that is circulated by the suspension rollers 32a to 32d. Each primary transfer roller 33 presses each photoconductor 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.

  The fixing device 50 fixes the toner image secondarily transferred from the transfer belt 31 to the print medium P, for example, to the print medium P. The fixing device 50 includes, for example, a heating roller 51 that heats the printing medium P and fixes a toner image on the printing medium P, and a pressing roller 52 that presses the heating roller 51. The heating roller 51 and the pressure roller 52 are, for example, both formed in a cylindrical shape. Between the heating roller 51 and the pressure roller 52, a nip portion N which is a fixing area of the printing medium P is provided. As the print medium P passes through the nip N, the toner image is fused and fixed to the print medium P.

  As an example, the image forming system 1 may include a secondary fixing device that smoothes the toner on the downstream side of the fixing device 50 in the transport path of the print medium P to output the gloss of the image of the print medium P. Further, the image forming system 1 may include discharge rollers 12 and 13 for discharging the print medium P on which the toner image is fixed to the outside of the image forming system 1.

  For example, the color of the toner T in the first station 2A is a color other than black. As an example, the color of the toner T in the first station 2A is yellow, the color of the toner T in the second station 2B is black, the color of the toner T in the third station 2C is magenta, The color of the toner T in the station 2D is cyan. For example, in the moving path of the transfer belt 31, a first station 2A, a third station 2C, a fourth station 2D, and a second station 2B are arranged in order from the upstream side.

  As an example, each of the stations 2A to 2D is a process cartridge integrally including the developing device 20, the photoconductor 40, the charging device 42, and the cleaning device 43. For example, the image forming system 1 includes a housing 3 to which stations 2A to 2D are mounted. The stations 2 </ b> A to 2 </ b> D are detachable from the housing 3 by, for example, opening the door of the housing 3 and inserting and removing the stations 3.

  Each of the first to fourth stations 2A to 2D is provided for each color of the toner T, for example. In each of the first to fourth stations 2A to 2D, the photoconductor 40 forms an electrostatic latent image, and the developing device 20 develops the electrostatic latent image formed on the photoconductor 40. The photoconductor 40 is, for example, a photoconductor drum, and may be an organic photoconductor (OPC: Organic Photo Conductor). For example, the first to fourth stations 2A to 2D are arranged side by side along the moving direction of the transfer belt 31. For example, the developing device 20, the exposure unit 41, the charging device 42, and the cleaning device 43 face the outer peripheral surface of each photoconductor 40.

  For example, the charging device 42 uniformly charges the outer peripheral surface of the photoconductor 40 to a predetermined potential. The charging device 42 is, for example, a charging roller that rotates following the rotation of the photoconductor 40. The exposure unit 41 exposes the outer peripheral surface of the photoconductor 40 charged by the charging device 42 according to an image formed on the print medium P. The potential of the portion of the outer peripheral surface of the photoconductor 40 exposed to the exposure unit 41 changes, whereby an electrostatic latent image is formed on the outer peripheral surface of the photoconductor 40.

  In each of the stations 2A to 2D, for example, a toner tank 25 is disposed so as to face each other. The toner T is supplied from each toner tank 25 to each of the developing devices 20 of the stations 2A to 2D. Each developing device 20 develops an electrostatic latent image on the outer peripheral surface of the photoconductor 40 with the supplied toner T to form a toner image. The photoconductor 40 is an example of an image carrier on which a toner image is formed.

  Each developing device 20 receives a developing voltage from a control unit 70 (see FIG. 2) described later, and supplies the toner T to the photoconductor 40 according to the developing voltage. The toner image formed on the outer peripheral surface of the photoconductor 40 is primarily transferred to the transfer belt 31. For example, the transfer belt 31 may be an image carrier on which a toner image is formed. The toner T remaining on the outer peripheral surface of the photoconductor 40 after the primary transfer is removed by the cleaning device 43.

  Each of the developing devices 20 of the stations 2 </ b> A to 2 </ b> D includes a developing roller 21 that carries a toner on the photoconductor 40. In the developing device 20, for example, the toner and the carrier are adjusted to have a predetermined mixing ratio, and the developer containing the toner and the carrier is mixed and stirred to uniformly disperse the toner. The developer is carried on the developing roller 21, and the developing roller 21 rotates to transport the developer to a region facing the photoconductor 40. Then, the toner in the developer carried on the developing roller 21 moves to the electrostatic latent image on the photoconductor 40, and the electrostatic latent image is developed.

  Next, an example of an image forming method by the image forming system 1 will be described. First, an example of a printing process performed by the image forming system 1 will be described. For example, when an image signal of an image to be recorded is input to the image forming system 1, the paper feed roller 11 rotates to pick up the print medium P stacked on the cassette C and move the print medium P along the transport path R1. Conveyed. On the other hand, the charging device 42 uniformly charges the outer peripheral surface of the photoconductor 40 to a predetermined potential. Then, based on the image signal, the exposure unit 41 irradiates the outer peripheral surface of the photoconductor 40 with laser light to form an electrostatic latent image on the outer peripheral surface of the photoconductor 40.

  Subsequently, the developing device 20 forms a toner image on the photoconductor 40 and performs development. For example, in each of the stations 2A to 2D, a toner image is primarily transferred from each photoconductor 40 to the transfer belt 31 in a region where each photoconductor 40 and the transfer belt 31 face each other. On the transfer belt 31, the toner images formed on the respective photoconductors 40 of the first to fourth stations 2A to 2D are sequentially laminated to form one laminated toner image. The laminated toner image is secondarily transferred to the print medium P conveyed from the recording medium conveyance device 10 in the secondary transfer region R2 where the suspension roller 32d and the secondary transfer roller 34 face each other.

  The print medium P on which the laminated toner image has been secondarily transferred is transported from the secondary transfer area R2 to the fixing device 50. The fixing device 50 fixes the laminated toner image on the print medium P by, for example, passing the print medium P through the nip portion N while applying heat and pressure to the print medium P. The print medium P on which the laminated toner image has been melt-fixed is discharged to the outside of the image forming system 1 from the discharge rollers 12 and 13, for example.

  FIG. 2 is a diagram schematically illustrating a configuration around the exemplary stations 2A to 2D and the transfer device 30. In the image forming system 1, the density control of the toner T primarily transferred to the transfer belt 31 is performed. This density control may be performed, for example, at least during intervals between printing on the print medium P and before printing on the print medium P.

  For example, the image forming system 1 includes a sensor 60 that measures the amount of toner T attached to the transfer belt 31, calculates the amount of toner T attached by receiving an output from the sensor 60, and develops each of the stations 2 </ b> A to 2 </ b> D. The control unit 70 determines a developing voltage to be applied to the transfer belt 20 and a cleaning blade 80 that scrapes off residual toner on the transfer belt 31. The cleaning blade 80 removes the toner T remaining on the transfer belt 31 from the transfer belt 31 after passing through the secondary transfer region R2.

  FIG. 3 is a diagram schematically illustrating an example of details of the sensor 60. As shown in FIG. 3, for example, the sensor 60 includes an irradiation unit 61 that irradiates the light 31 onto the surface 31 a of the transfer belt 31 to which the toner T adheres, and a regular reflection that detects the regular reflection light L2 from the transfer belt 31. It includes an optical sensor 62 and a diffuse reflection light sensor 63 that detects diffuse reflection light L3 from the transfer belt 31. The particle size of the toner T is, for example, 5.8 μm. Further, the respective outputs of the regular reflection light sensor 62 and the diffuse reflection light sensor 63, that is, the output of the measured toner adhesion amount (hereinafter, also referred to as “toner adhesion amount”) are transmitted to the control unit 70. You.

  As an example, the irradiation unit 61 is an LED that emits visible light. The regular reflection light sensor 62 detects, for example, regular reflection light L2 that is specularly reflected from the transfer belt 31 by irradiation of the light L1 from the irradiation unit 61. The regular reflection light sensor 62 is arranged at a position where regular reflection light L2 which is regularly reflected from the transfer belt 31 by the irradiation of the light L1 from the irradiation unit 61 reaches. For example, the smaller the amount of the toner T adhered to the transfer belt 31, the larger the amount of the regular reflection light L2. Therefore, the output of the regular reflection light sensor 62 increases, and the larger the amount of the toner T adhered to the transfer belt 31, the more positive. Since the amount of the reflected light L2 decreases, the output of the regular reflection light sensor 62 decreases.

  The controller 70 calculates the amount of toner T attached from the output of the regular reflection light sensor 62. However, when a certain amount or more (for example, two or more layers) of the toner T is stacked on the transfer belt 31, even if the toner T further increases, the amount of the regular reflection light L2 does not change and the output of the regular reflection light sensor 62 is changed. It does not change. Therefore, when a certain amount or more of the toner T is stacked, it may be difficult to use the output of the regular reflection light sensor 62 to calculate the amount of toner T attached.

  The diffuse reflection light sensor 63 increases the output of the diffuse reflection light sensor 63 by increasing the amount of the diffuse reflection light L3 even if a certain amount or more of the toner T is stacked on the transfer belt 31. The output of the diffuse reflection light sensor 63 can be used for measurement. For example, since the amount of the diffuse reflection light L3 is larger in the non-black toner T than in the black toner T, the amount of the non-black toner T attached can be measured more accurately. However, the diffuse reflection light sensor 63 may not be able to calibrate its output and the amount of toner T attached. In an example described later, it is possible to accurately calibrate the output of the diffuse reflection light sensor 63.

  FIG. 4 is a flowchart illustrating an example of the flow of controlling the density of the toner T on the transfer belt 31. Note that the steps in the flowchart of FIG. 4 are merely examples, and steps may be added, deleted, or changed. First, the emission of the light L1 of the irradiation unit 61 is adjusted (step S1). At this time, for example, the calibration of the output of the irradiation unit 61 may be performed, and the calibration may be performed such that the output of the light L1 of the irradiation unit 61 falls within a predetermined range.

  Next, a developing voltage (developing bias) and a charging voltage (charging bias) are set for each of the stations 2A to 2D (step S2). For example, the value of the developing voltage in the developing device 20 and the value of the charging voltage in the charging device 42 when the toner patch is created are set. The charging voltage set at this time may be equivalent to a charging voltage for initially performing uniform charging, or a photoconductor surface voltage.

  Subsequently, a toner patch is formed (Step S3). Specifically, the development of the developing device 20 and the transfer of the toner patch from the photoreceptor 40 to the transfer belt 31 are performed with the development voltage and the charging voltage set as described above. Thereafter, the sensor 60 reads the toner patch on the transfer belt 31 (Step S4), the control unit 70 calculates and corrects the developing voltage (Step S5), and ends a series of processes.

FIG. 5 is a flowchart illustrating an example of each step of step S5. As shown in FIGS. 4 and 5, first, the sensor 60 measures the amount of adhesion TMA _cur1 of the toner T from the first station 2A (step S11). In step S11, for example, the density correction of the toner T in the first station 2A is performed. Further, by diffuse reflection light sensor 63 diffuse reflection light L3 with the irradiation of the light L1 of the irradiating unit 61 is received, the developing voltage _V of the control unit 70 and the deposition amount _{TMA cur1} of toner T first station 2A _cur1 the ratio _{a cur1} of obtaining from equation (1) (step S12).
A _cur1 = TMA _cur1 / V _cur1 (1)

Next, the ratio A _pre between the adhesion amount TMA _pre1 of the toner T of the first station 2A at the time of the previous density correction (for example, several days ago) and the developing voltage V _pre1 of the first station 2A is obtained from Expression (2). (Step S13).
A _pre1 = TMA _pre1 / V _pre1 (2)

  Incidentally, the density of an image formed by the toner T has a correlation with the charge amount Q / M of the toner T. The charge amount Q / M indicates the ratio between the charge amount (Q) of the toner T and the mass (M). The charge amount Q / M of the toner T decreases over time. By the way, when the developing voltage remains unchanged and the charge amount Q / M of the toner T decreases, the amount of toner T attached increases. Therefore, if the toner patch is formed at the same developing voltage as that at the time of the previous density correction in a state where the charge amount Q / M has been reduced, the density of the toner patch may be increased. If the density of the toner patch becomes high, the density of the toner T cannot be read by the regular reflection light sensor 62, so that there may be a problem that the retry of toner patch creation and detection is likely to occur.

The value of (A _cur1 / A _pre1 ) indicates the ratio of the charge amount Q / M that decreases with the passage of time. In the following example, the value of (A _cur1 / A _pre1 ) is treated as the black toner T. By using the station 2B, the developing voltage is corrected. That is, the value of (A _cur1 / A _pre1 ) is integrated with the developing voltage V _pre2 at the previous density correction in the station 2B, and the developing voltage is set to a low value. In other words, the control unit 70 calculates the value of _Vcur2 low according to the toner charge amount Q / M that decreases with the passage of time when the density control is performed after the developing device 20 is stopped and before printing. Is also good. As a result, it is possible to suppress the density of the toner patch from increasing, and it is possible to reduce the frequency of retries. That is, the retry can be suppressed by correcting the developing voltage in consideration of the variation of the charge amount Q / M.

That is, the previous density correction when the developing voltage _{V pre2} the second station 2B with _(A cur1 _{/ A pre1)} developing voltage _{V cur2} for density control of the second station 2B using Equation (3) described later from It is calculated (steps S14, S15).
V _cur2 = (A _cur1 / A _pre1 ) × V _pre2 (3)
Thereafter, the writing of the toner patch with the black toner T and the detection by the sensor 60 are performed using the developing voltage _Vcur2 (step S16), and the series of steps is ended.

By _{outputting the} above-described developing voltage _Vcur2 to the second station 2B that handles the black toner T, it is possible to write a toner patch with the same density as the black toner T at the time of the previous density correction. Therefore, the density of the black toner T can be suppressed, and the density of the toner T can be read by the regular reflection light sensor 62, so that the occurrence of the retry described above can be suppressed. That is, the occurrence of the retry is limited to, for example, the first correction execution, the toner replacement, or the case where the change in the charge amount Q / M cannot be predicted. According to the above example, since the frequency of occurrence of retries can be reduced, the density control with high productivity can be realized.

Regarding the determination of V _cur2 , the difference between the toner consumption rate TCns1 of the first station 2A from the previous time to the current time and the toner consumption rate TCns2 of the second station 2B from the previous time to the current time is 10% or less. In this case, V _cur2 which is a developing voltage may be determined by density control. Note that the toner consumption rate TCns1 = (the toner consumption amount of the first station from the previous time to the present time) / (the average toner amount of the first station), and the toner consumption rate TCns2 = (the previous time of the second station and the present time) Toner consumption amount) / (average toner amount of the second station).

  The toner consumption rate TCns1 described above is calculated from the toner supply amount of the first station 2A from the previous time to the present time, and the toner consumption rate TCns2 is calculated from the toner supply amount of the second station 2B from the previous time to this time. Is also good. The toner amount in the developing device 20 including the average toner amount is monitored by, for example, a TC sensor. When the toner amount in the developing device 20 becomes smaller than a reference value, a fixed amount of toner is supplied. The toner supply amount may be calculated by measuring the number of times of the supply. The toner consumption rate TCns1 is calculated from the sum of the print dot signals of the first station 2A from the previous time to the present time, and the toner consumption rate TCns2 is the sum of the print dot signals of the second station 2B from the previous time to this time. May be calculated from

FIG. 6 shows time-series data of the charge amount of the toner T and the adhesion amount of the toner T in the embodiment in which the above-described density control is performed and the comparative example in which the above-described density control is not performed. As shown in FIG. 6, for example, if the state in which the image forming system 1 is not operating continues, the charge amount of the toner T decreases with time. In the case of the comparative example in which the above-described correction of the developing voltage is not performed, it can be seen that if a toner patch is created after a certain period of time, the amount of toner adhesion increases. As an example, when density correction is performed 10 hours after the previous density correction, in the comparative example, the toner adhesion amount increased from 250 (mg / cm ² × 100) to about 300 (mg / cm ² × 100). On the other hand, in the embodiment, since the developing voltage was corrected to a low value, the toner adhesion amount was 250 (mg / cm ² × 100), which was the same as that at the time of the previous density correction.

Further, when 20 hours or 30 hours have passed since the previous density correction, in the case of the comparative example, the toner adhesion amount is about 350 (mg / cm ² × 100) or about 370 (mg / cm ² × 100), respectively. The adhesion amount exceeded the allowable upper limit adhesion amount of 320 (mg / cm ² × 100). If the amount of toner adhered exceeds the allowable upper limit, a retry is required. However, in the case of the embodiment, even if 20 hours or 30 hours have passed since the previous density correction, the toner adhesion amount can be maintained at 250 (mg / cm ² × 100), and the density becomes high. Was found to be able to be suppressed.

FIG. 7 is a graph showing an example of the relationship between the toner adhesion amount and the output of the diffuse reflection light sensor 63. The output of the diffuse reflection light sensor 63 increases in a substantially linear function as the toner adhesion amount increases. Specifically, both the solid line and the broken line in FIG. 7 are the relationship between the toner adhesion amount TMA obtained from the actually measured value and the output of the diffuse reflection light sensor 63, and are shown in a curved shape in FIG. By approximation, it can be expressed as the following equation (4). In this case, when the toner adhesion amount is TMA and the output of the diffuse reflection light sensor 63 is S, the control unit 70 calculates α using Expression (4),
S = α × TMA (4)
The output of the diffuse reflection light sensor 63 may be calibrated using α.

  7 exemplarily indicates the upper limit of the tolerance of the output of the diffuse reflection light sensor 63 and the ratio B of the toner adhesion amount, and the lower limit actual measurement of the output of the diffuse reflection light sensor 63 and the ratio A of the toner adhesion amount. May be used. In this case, when the upper limit of the actual tolerance of the diffuse reflection light sensor 63 is Y1, the slope when the toner adhesion amount is X1 is B, and the lower limit actual measurement of the tolerance of the diffuse reflection light sensor 63 is Y2, and the toner adhesion amount is X2. May be A, and γ may be B / A.

Further, for example, γ shown in FIG. 7 is a ratio of the output (S_Std) of the diffuse reflection light sensor 63 as the reference characteristic to the actual output S of the diffuse reflection light sensor 63,
γ = S_Std / S
May be represented by Note that S_Std may be a value measured in advance or calculated from a table stored in advance. As described above, the calculation of γ can be performed by various methods.

  As exemplarily shown in FIG. 7, the value of γ is constant when the toner adhesion amount is large to some extent, but decreases significantly as the toner adhesion amount increases when the toner adhesion amount is close to 0. Tend to be unstable. Therefore, when there is no limitation on the amount of adhered toner, the value of γ fluctuates by about 20%, and if γ is used for density correction, a density error of about 20% may occur. Therefore, in an example described later, the above-described density error is suppressed by providing a range for the toner adhesion amount.

FIG. 8 is a graph showing the relationship between the toner adhesion amount and the output of the regular reflection light sensor 62. FIG. 9 is a graph showing the relationship between the toner adhesion amount and the S / N ratio of the regular reflection light sensor 62. As shown in FIGS. 8 and 9, the output of the regular reflection light sensor 62 hardly fluctuates, for example, when the toner adhesion amount is 3.0 g / m ² or more. Therefore, it is difficult to use the output of the regular reflection light sensor 62 when the toner adhesion amount is 3.0 g / m ² or more.

When the toner adhesion amount is 3.0 g / m ² or more, the light reception amount of the regular reflection light sensor 62 does not change even if the toner adhesion amount increases, and the S / N ratio of the output of the regular reflection light sensor 62 Becomes unstable. On the other hand, for example, when the average particle size of the toner is 5.8 μm and the toner adhesion amount is 2.5 g / m ² or less, the state where the S / N ratio becomes 5 dB can be maintained. . In other words, if the average particle diameter of the toner is d (μm) and the amount of toner adhered is 2.5 × d / 5.8 (g / m ² ), the S / N ratio is 5 dB. Can be maintained.

For example, when the toner adhesion amount is 1.8 g / m ² or more, the fluctuation of the above-mentioned value of γ can be suppressed to 2% or less. According to the above example, when the toner adhesion amount is 1.8 g / m ² or more and 2.5 × d / 5.8 (g / m ² ) or less, the S / N ratio becomes stable and γ Can be suppressed. For example, after forming a plurality of toner patches, toner patches within a specified range (toner adhesion amount is 1.8 g / m ² or more and 2.5 × d / 5.8 (g / m ² ) or less) are selected, γ is calculated from the data of the selected toner patch. By specifying the range of the toner adhesion amount to be 1.8 g / m ² or more and 2.5 × d / 5.8 (g / m ² ) or less, the density error of the toner patch can be suppressed. Further, the control unit 70 may control the amount of toner adhesion so that the variation range of the value of γ is 5% or less of the output S of the diffuse reflection light sensor 63. In this case, similarly, the density error of the toner patch can be suppressed.

  FIG. 10 is a diagram schematically showing a modification of the configuration for creating a toner patch. For example, the positions of the toner patches T1 and T2 are set to positions obtained by dividing the cycle of the photoconductor 40 (eg, the phase angles θ1 and θ2), and the average value of the measured values of the toner patches T1 and T2 by the sensor 60 is determined by the control unit. 70 may be calculated. In the case of this example, it is possible to execute the density correction of the toner patches T1 and T2 in which the influence of the uneven period of the photoconductor 40 due to the minute eccentricity of the photoconductor 40 is reduced.

As an example, the toner patches T1 and T2 are
It may be arranged at a position where the phase of the patch position = the period of the photoconductor 40 / the number of toner patches. In this case, as an example, θ1 = 0 ° and θ2 = 180 °. As another example, when the period of the photoconductor 40 is 90 mm and three toner patches are formed, the position of the first toner patch is 0 mm (the phase angle is 0 °), and the position of the second toner patch is The position 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 °).

  As another example, when a time interval is required, for example, when the developing voltage is different for each toner patch, the position of the first toner patch is set to 0 mm (the phase angle is 0 °), and the second toner patch is set. 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 °). Furthermore, the number of toner patches need not be three, and the positions of the toner patches may be shifted from each other by (period of photoconductor 40 / number of toner patches).

  It is to be understood that not all aspects, advantages, and features described herein are necessarily achieved or included by any particular example. Indeed, while various examples have been presented herein, it should be apparent that the structure, arrangement and details can be modified or varied in various examples.

In the above-described example, the sensor 60 measures the adhesion amount TMA _cur1 of the toner T by the first station 2A, and the control unit 70 _obtains the ratio between the adhesion amount TMA _cur1 and the developing voltage V _cur1 by Expression (1). For example, the control unit 70 may determine the developing voltage V _cur1 such that the current toner adhesion amount TMA _{cur1 of} the first station 2A becomes the same as the previous toner adhesion amount TMA _pre1 . The sensor 60 measures the amount of toner adhered to at least one of the second station 2B, the third station 2C, and the fourth station 2D, and the controller 70 averages the amount of adhered toner. A value may be used. 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.

The control unit 70 calculates the value of the above-mentioned _(A cur1 _/ A _pre1), also performed on the third station 2C and the fourth station 2D, the first station 2A _{(A cur1} / a _pre1), the third station _{2C (a cur1 / a pre1)} , and a fourth station 2D of _(a cur1 _/ a _pre1) to averaged value by integrating _{V pre2 V cur2} for density control May be calculated. In this case, density correction can be performed in consideration of the state of all color toners other than black. Further, the control unit 70 may calculate each value using an expression other than Expressions (1) to (4).

  In the above example, the color of the toner T in the first station 2A is yellow, the color of the toner T in the second station 2B is black, the color of the toner T in the third station 2C is magenta, The color of the toner T in the fourth station 2D was cyan. However, the color of the toner T in the first station 2A, the color of the toner T in the second station 2B, the color of the toner T in the third station 2C, and the color of the toner T in the fourth station 2D are as described above. May be different colors. Further, the number of stations may be less than three or more than five.

  Thus, all modifications and variations that fall within the spirit and scope of the claimed subject matter are claimed. In addition, all and part of the above-described example can be expressed by closing described later, but are not limited to the following description.

[Close 1]
A first station and a second station including an image carrier on which a toner image is formed, and a developing device for supplying toner to the image carrier;
A control unit that determines a developing voltage to be applied to the developing device of each of the first station and the second station;
With
The control unit includes:
V _pre1 which is the previous developing voltage of the first station,
It said first V _cur1 a time of said developing voltage _stations, and the developing voltage used for this density control of the second station based on the V _pre2 a last of said developing voltage of the second station V _cur2 is determined, and V _cur2 is output to the developing device of the second station.
Wherein the developing device of the second station is capable of communicating to the controller to receive the V _cur2, supplying toner to the image carrier in accordance with the V _cur2,
Image forming system.
[Close 2]
A sensor for measuring the amount of toner attached to the image carrier,
Wherein the control _{unit, A pre1,} and thereby determine the _{A cur1,} calculate the _{V cur2} by integrating _{V pre2} the value of _(A cur1 _/ A _pre1),
A _pre1 is the ratio of TMA _pre1 to V _pre1 ,
TMA _pre1 is the toner adhesion amount measured by the sensor last time,
A _cur1 is the ratio between TMA _cur1 and V _cur1 ,
TMA _cur1 is the toner adhesion amount measured this time by the sensor.
The image forming system according to claim 1.
[Close 3]
The control unit includes:
A _cur1 is calculated by equation (1) from TMA _cur1 measured this time by the sensor and V _cur1 which is the current development voltage,
A _cur1 = TMA _cur1 / V _cur1 (1)
A _pre1 is calculated according to equation (2) from TMA _pre1 measured last time by the sensor and V _pre1 which is the previous development voltage,
A _pre1 = TMA _pre1 / V _pre1 (2)
Calculating V _cur2 from equation (3) using V _pre2 which is the previous developing voltage of the second station;
V _cur2 = (A _cur1 / A _pre1 ) × V _pre2 (3)
The image forming system according to Crow 2.
[Close 4]
The controller controls the V in accordance with the amount of charge of the toner that has decreased with time when the density control is performed after the developing devices of the first station and the second station are stopped and before printing is performed. _lower the value of _cur2 ,
The image forming system according to any one of Closes 1 to 3.
[Close 5]
The control unit determines V _cur1 in the density control such that the current toner adhesion amount TMA _cur1 of the first station is the same as the previous toner adhesion amount TMA _pre1 .
An image forming system according to any one of claims 1 to 4.
[Close 6]
When the difference between the toner consumption rate TCns1 of the first station from the previous time to the present time and the toner consumption rate TCns2 of the second station from the previous time to the present time is 10% or less, the density control is performed. Determine _Vcur2 ,
Here, the toner consumption rate TCns1 = (the toner consumption amount of the first station from the previous time to the present time) / (the average toner amount of the first station).
Toner consumption rate TCns2 = (toner consumption amount of the second station from the previous time to the present time) / (average toner amount of the second station)
The image forming system according to any one of claims 1 to 5.
[Close 7]
The toner consumption rate TCns1 is calculated from the toner supply amount of the first station from the previous time to the present time,
The toner consumption rate TCns2 is calculated from the toner supply amount of the second station from the previous time to the present time.
7. The image forming system according to Crow 6.
[Close 8]
The toner consumption rate TCns1 is calculated from the total sum of print dot signals from the last time to the present time of the first station,
The toner consumption rate TCns2 is calculated from the sum total of the print dot signals from the previous time to the present time of the second station.
The image forming system according to claim 6 or 7.
[Close 9]
The color of the toner contained in the second station is black,
The color of the toner contained in the first station is a color other than black.
The image forming system according to any one of claims 1 to 8.
[Close 10]
An irradiating unit that irradiates the image carrier with light; a regular reflection light sensor that detects regular reflection light from the image carrier; and a diffuse reflection light that detects diffuse reflection light from the image carrier. And a sensor,
The control unit calibrates the output of the diffuse reflection light sensor by the output of the regular reflection light sensor,
The control unit calculates the expression (4) from the adhesion amount TMA of the toner adhered to the image carrier and the output S of the diffuse reflection light sensor.
S = α × TMA (4)
Is used to calculate α, and the calibration is performed using the α.
The image forming system according to Crow 2.
[Close 11]
The adhesion amount TMA of the toner is 1.8 g / m ² or more;
The image forming system according to claim 10.
[Close 12]
When the average particle diameter of the toner is d (μm), the adhesion amount TMA of the toner is 2.5 × d / 5.8 (g / m ² ) or less.
12. The image forming system according to claim 10 or 11.
[Close 13]
At least one of the first station and the second station has a photosensitive drum,
The control unit forms a plurality of toner patches corresponding to the rotation position of the photoconductor drum on the image carrier, and averages the toner adhesion amounts TMA of the plurality of toner patches.
The image forming system according to any one of claims 10 to 12.
[Close 14]
A third station and a fourth station,
The control unit also calculates the value of (A _cur1 / A _pre1 ) for the third station and the fourth station, and calculates the value of (A _cur1 / A _pre1 ) for the first station, the third station, and the third station. 4 of each of the stations the value of _(a cur1 _/ a _pre1) by integrating the _{V pre2} the averaged value to calculate the _{V cur2,}
The image forming system according to Crow 2.

Claims (14)

A first station and a second station including an image carrier on which a toner image is formed, and a developing device for supplying toner to the image carrier;
A control unit that determines a developing voltage to be applied to the developing device of each of the first station and the second station;
With
The control unit includes:
V _pre1 which is the previous developing voltage of the first station,
It said first V _cur1 a time of said developing voltage _stations, and the developing voltage used for this density control of the second station based on the V _pre2 a last of said developing voltage of the second station V _cur2 is determined, and V _cur2 is output to the developing device of the second station.
Wherein the developing device of the second station is capable of communicating to the controller to receive the V _cur2, supplying toner to the image carrier in accordance with the V _cur2,
Image forming system. A sensor for measuring the amount of toner attached to the image carrier,
Wherein the control _{unit, A pre1,} and thereby determine the _{A cur1,} calculate the _{V cur2} by integrating _{V pre2} the value of _(A cur1 _/ A _pre1),
A _pre1 is the ratio of TMA _pre1 to V _pre1 ,
TMA _pre1 is the toner adhesion amount measured by the sensor last time,
A _cur1 is the ratio between TMA _cur1 and V _cur1 ,
TMA _cur1 is the toner adhesion amount measured this time by the sensor.
The image forming system according to claim 1. The control unit includes:
A _cur1 is calculated by equation (1) from TMA _cur1 measured this time by the sensor and V _cur1 which is the current development voltage,
A _cur1 = TMA _cur1 / V _cur1 (1)
A _pre1 is calculated according to equation (2) from TMA _pre1 measured last time by the sensor and V _pre1 which is the previous development voltage,
A _pre1 = TMA _pre1 / V _pre1 (2)
Calculating V _cur2 from equation (3) using V _pre2 which is the previous developing voltage of the second station;
V _cur2 = (A _cur1 / A _pre1 ) × V _pre2 (3)
The image forming system according to claim 2. The controller controls the V in accordance with the amount of charge of the toner that has decreased with time when the density control is performed after the developing devices of the first station and the second station are stopped and before printing is performed. _lower the value of _cur2 ,
The image forming system according to claim 1. The control unit determines V _cur1 in the density control such that the current toner adhesion amount TMA _cur1 of the first station is the same as the previous toner adhesion amount TMA _pre1 .
The image forming system according to claim 1. When the difference between the toner consumption rate TCns1 of the first station from the previous time to the present time and the toner consumption rate TCns2 of the second station from the previous time to the present time is 10% or less, the density control is performed. Determine _Vcur2 ,
Here, the toner consumption rate TCns1 = (the toner consumption amount of the first station from the previous time to the present time) / (the average toner amount of the first station).
Toner consumption rate TCns2 = (toner consumption amount of the second station from the previous time to the present time) / (average toner amount of the second station)
The image forming system according to claim 1. The toner consumption rate TCns1 is calculated from the toner supply amount of the first station from the previous time to the present time,
The toner consumption rate TCns2 is calculated from the toner supply amount of the second station from the previous time to the present time.
The image forming system according to claim 6. The toner consumption rate TCns1 is calculated from the total sum of print dot signals from the last time to the present time of the first station,
The toner consumption rate TCns2 is calculated from the sum total of the print dot signals from the previous time to the present time of the second station.
The image forming system according to claim 6. The color of the toner contained in the second station is black,
The color of the toner contained in the first station is a color other than black.
The image forming system according to claim 1. An irradiating unit that irradiates the image carrier with light; a regular reflection light sensor that detects regular reflection light from the image carrier; and a diffuse reflection light that detects diffuse reflection light from the image carrier. And a sensor,
The control unit calibrates the output of the diffuse reflection light sensor by the output of the regular reflection light sensor,
The control unit calculates the expression (4) from the adhesion amount TMA of the toner adhered to the image carrier and the output S of the diffuse reflection light sensor.
S = α × TMA (4)
Is used to calculate α, and the calibration is performed using the α.
The image forming system according to claim 2. The adhesion amount TMA of the toner is 1.8 g / m ² or more;
The image forming system according to claim 10. When the average particle diameter of the toner is d (μm), the adhesion amount TMA of the toner is 2.5 × d / 5.8 (g / m ² ) or less.
The image forming system according to claim 10. At least one of the first station and the second station has a photosensitive drum,
The control unit forms a plurality of toner patches corresponding to the rotation position of the photoconductor drum on the image carrier, and averages the toner adhesion amounts TMA of the plurality of toner patches.
The image forming system according to claim 10. A third station and a fourth station,
The control unit also calculates the value of (A _cur1 / A _pre1 ) for the third station and the fourth station, and calculates the value of (A _cur1 / A _pre1 ) for the first station, the third station, and the third station. 4 of each of the stations the value of _(a cur1 _/ a _pre1) by integrating the _{V pre2} the averaged value to calculate the _{V cur2,}
The image forming system according to claim 2.

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