JP2018045129A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an optimal transfer voltage in a short time with respect to a plurality of primary transfer rollers.SOLUTION: A color printer 1 includes: a plurality of voltage application parts 22 for applying a voltage to a plurality of primary transfer rollers 7; a current detection part 23 for detecting a current value of each primary transfer roller 7; a first voltage calculation part 25 for calculating a transfer voltage value based on the current value detected for the primary transfer roller 7; and a second voltage calculation part 26 for calculating the transfer voltage value of the other primary transfer roller 7 from associated information of the transfer voltage value of one primary transfer roller 7 and the other primary transfer roller 7. The control part 20 calculates the transfer voltage value of each primary transfer roller 7 by the first voltage calculation part 25 and accumulates the associated information of the calculated result when a calculation mode of the transfer voltage value is a second mode, and calculates the transfer voltage value of one primary transfer roller 7 by the first voltage calculation part 25 when a calculation mode of the transfer voltage value is a first mode and calculates the transfer voltage value of the other primary transfer roller 7 by the second voltage calculation part 26.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus including a plurality of photosensitive drums along a transfer belt.

  Some electrophotographic image forming apparatuses include a plurality of photosensitive drums along a transfer belt, and a plurality of primary transfer rollers for each of the plurality of photosensitive drums. In order to supply an optimal transfer current to each primary transfer roller, it is necessary to apply a transfer voltage that matches the resistance of each primary transfer roller.

  For example, an image forming apparatus described in Patent Document 1 includes a transfer material carrier (photosensitive drum) that carries a transfer material, and a charging unit that abuts on the surface of the transfer material carrier and applies a predetermined bias to the transfer material. A transfer charging unit (primary transfer roller) that is provided downstream of the charging unit in the moving direction of the transfer material carrier and transfers a developer image to the transfer material, and a current that flows when a predetermined bias is applied to the charging unit or And a control unit that controls a transfer bias applied to the transfer charging unit based on a detection result of the detection unit. Then, the control means corrects the current flowing or the applied voltage when a predetermined bias is applied to the charging means detected by the detection means to a variable given as a control function, and the transfer bias according to the correction result. And a control function is set for each of the widths of the transfer material.

JP 2003-248384 A

  The transfer current flowing through the primary transfer roller is determined by the resistance value of the primary transfer roller and the applied transfer voltage. The resistance value of the primary transfer roller may change due to temperature change of the primary transfer roller, deterioration due to use over time, and toner adhesion. In order to pass a specified transfer current to the primary transfer roller, it is necessary to correct the transfer voltage in accordance with the change in the resistance value. For example, the current flowing when a predetermined voltage is applied to the primary transfer roller is detected, the resistance value of the primary transfer roller is calculated based on the voltage value and the current value, and the prescribed transfer current is calculated based on the calculation result. Feedback control for measuring the transfer voltage required for the transfer is performed.

  However, it takes time to perform feedback control for each of the plurality of primary transfer rollers. Therefore, it is conceivable to perform feedback control on one primary transfer roller and correct the transfer voltage of the other primary transfer roller using the difference (correction amount) between the measured transfer voltage and the original transfer voltage. However, there are variations in the applied voltages and measurement voltages of the plurality of primary transfer rollers, and the transfer voltages of the other primary transfer rollers are corrected based on the measurement results immediately before or for the one primary transfer roller. Is insufficient in accuracy and cannot measure the optimum transfer voltage for each primary transfer roller.

  In view of the above circumstances, an object of the present invention is to measure an optimum transfer voltage in a short time for a plurality of primary transfer rollers.

  The image forming apparatus of the present invention applies a voltage to each of a plurality of photosensitive drums, a plurality of primary transfer rollers arranged corresponding to each of the plurality of photosensitive drums, and the plurality of primary transfer rollers. A plurality of voltage application units; a current detection unit that detects a current value of a current flowing through each of the plurality of primary transfer rollers; a storage unit that stores a transfer voltage value for each of the plurality of primary transfer rollers; A control unit that switches a calculation mode of the transfer voltage value to either the first mode or the second mode according to a use state of the primary transfer roller, and the control unit includes the plurality of primary transfer rollers. A first voltage calculation unit that newly calculates and updates the transfer voltage value based on the current value detected by the current detection unit for the predetermined primary transfer roller; Related information that associates the transfer voltage value of one primary transfer roller of the transfer rollers with the transfer voltage value of a primary transfer roller other than the one primary transfer roller of the plurality of primary transfer rollers. A second voltage calculation unit that newly calculates and updates the transfer voltage value of the other primary transfer roller based on the first voltage calculation unit, in the second mode, by the first voltage calculation unit, The transfer voltage value of each of the plurality of primary transfer rollers is newly calculated and updated, and the transfer voltage value updated for the one primary transfer roller and the transfer updated for the other primary transfer roller. The related information associated with a voltage value is accumulated in the storage unit, and in the first mode, the first voltage calculating unit determines whether the one primary transfer roller is in the first mode. The serial transfer voltage value is updated by newly calculated, and updates to newly calculate the transfer voltage value of the other primary transfer roller by said second voltage calculation unit.

  The voltage application unit applies a plurality of voltages having a plurality of different voltage values to the predetermined primary transfer roller, and the current detection unit calculates a current value of a current flowing through the predetermined primary transfer roller. Detection is performed for each of the plurality of voltage values, and the first voltage calculation unit indicates characteristics of the predetermined primary transfer roller determined based on the plurality of voltage values and the current value for each of the plurality of voltage values. The transfer voltage value of the predetermined primary transfer roller may be calculated based on a current value of a specified transfer current using a characteristic line.

  By adopting such a configuration, the past transfer voltage values of the respective primary transfer rollers 7 are accumulated, and related information indicating the characteristics of the respective primary transfer rollers 7 is used. Thus, the transfer voltage value can be calculated quickly. Therefore, even when there are variations in the applied voltages and measurement voltages of the plurality of primary transfer rollers 7, the optimum transfer voltage value for each primary transfer roller 7 is highly accurate regardless of the difference in characteristics between the primary transfer rollers 7. Can be calculated. Therefore, it is possible to avoid the malfunction of each primary transfer roller 7 and perform image formation appropriately.

  The control unit switches the transfer voltage value calculation mode to any one of the first mode, the second mode, and the third mode according to the usage state of the plurality of primary transfer rollers, In the first mode or the second mode, one characteristic line indicating the characteristic of the one primary transfer roller used by the first voltage calculation unit is stored in the storage unit, and the voltage application unit In the third mode, a single voltage is applied to the one primary transfer roller, and in the third mode, the current detector corresponds to the voltage value of the single voltage. In the third mode, the control unit detects the current value of the current flowing through the one primary transfer roller by the first voltage calculation unit for the single primary transfer roller. One voltage voltage And calculating the transfer voltage value based on the current value corresponding to the voltage value of the single voltage, the characteristic line stored in the storage unit, and the current value of a specified transfer current. The transfer voltage value of the other primary transfer roller may be newly calculated and updated by the second voltage calculation unit.

  By adopting such a configuration, when the first characteristic line calculated in the past is stored for each primary transfer roller 7, a single voltage is not primary-transferred in the feedback control. Since it is applied to the roller 7, it is possible to calculate a transfer voltage value that matches the characteristics of the primary transfer roller 7 while shortening the time required for feedback control.

  The second voltage calculation unit may use an expression indicating a correlation of the related information accumulated in the storage unit when calculating the transfer voltage value for the other primary transfer roller.

  By adopting such a configuration, even when there are variations in the applied voltages and measurement voltages of the plurality of primary transfer rollers 7, the characteristics of the primary transfer rollers 7 are appropriately determined and transfer voltage values are calculated. can do.

  The second voltage calculation unit may use the most recent predetermined number of related information accumulated in the storage unit when calculating the transfer voltage value for the other primary transfer roller.

  By adopting such a configuration, it is possible to always calculate the transfer voltage value using new information, and it is possible to optimize the storage unit 21 by deleting related information exceeding the most recent predetermined number. .

  According to the present invention, it is possible to measure an optimum transfer voltage for a plurality of primary transfer rollers in a short time.

1 is a cross-sectional view illustrating a color printer according to an embodiment of the present invention. 1 is a schematic diagram illustrating an electrical configuration of a color printer according to an embodiment of the present invention. 6 is a graph illustrating an example of a relationship between a voltage value and a current value of a primary transfer roller in a color printer according to an embodiment of the present invention. It is a graph which shows an example of the relationship of the transfer voltage value between the primary transfer rollers in the color printer which concerns on one Embodiment of this invention. 6 is a flowchart illustrating a transfer voltage calculation operation of a primary transfer roller in a color printer according to an embodiment of the present invention. It is a graph which shows the characteristic of the voltage value and current value of a primary transfer roller in the color printer which concerns on other embodiment of this invention.

  First, an overall configuration of a color printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of explanation, the front side of the sheet in FIG.

  The color printer 1 includes a substantially box-shaped printer main body 2, and an annular intermediate transfer belt 3 that rotates in a predetermined direction is installed between a plurality of rollers at the center of the printer main body 2. Below the intermediate transfer belt 3, four image forming units 4 (4Y, 4C, 4M, and 4K) are provided for each toner color (for example, four colors of yellow, cyan, magenta, and black). Each image forming unit 4 corresponds to each color of yellow (Y), cyan (C), magenta (M), and black (K) in order from the upstream side (left side in the present embodiment) in the rotation direction of the intermediate transfer belt 3. doing. Hereinafter, unless otherwise specified, the symbols “Y”, “C”, “M”, and “K” are omitted for the portions corresponding to the color of the toner. A secondary transfer unit 5 is provided at the right end of the intermediate transfer belt 3, and the secondary transfer unit 5 includes a part on the right end side of the intermediate transfer belt 3 and a secondary transfer roller.

  Each image forming unit 4 includes a rotatable photosensitive drum 6, in other words, four photosensitive drums 6 (6 </ b> Y, 6 </ b> C, 6 </ b> M, and 6 </ b> K) are arranged along the lower side of the intermediate transfer belt 3. . Each image forming unit 4 includes a rotatable primary transfer roller 7. In other words, each of the four primary transfer rollers 7 (7 Y, 7 C, 7 M, and 7 K) includes four intermediate transfer belts 3. It is arranged to face the photosensitive drum 6 (6Y, 6C, 6M, 6K).

  In the image forming process of the color printer 1, each color image is formed in each image forming unit 4. At this time, in each image forming unit 4, first, each photosensitive drum 6 is charged by a charger. Thereafter, each photosensitive drum 6 is exposed by an exposure device based on image data input from an external computer (not shown) or the like, whereby an electrostatic latent image is formed on each photosensitive drum 6. The electrostatic latent image on each photosensitive drum 6 is developed into a toner image of each color by a developing device. The toner image on each photosensitive drum 6 is primarily transferred onto the surface of the intermediate transfer belt 3 by each primary transfer roller 7. By sequentially repeating the above operation by the four image forming units 4, a full-color toner image (hereinafter referred to as a color toner image) is formed on the intermediate transfer belt 3.

  In the image forming process of the color printer 1, the color toner image is supplied to the secondary transfer unit 5 by the rotation of the intermediate transfer belt 3. In the secondary transfer unit 5, paper is supplied from a paper cassette or the like in time with the color toner image, and the color toner image on the intermediate transfer belt 3 is secondarily transferred to the paper. Further, in the color printer 1, the color toner image on the paper is fixed by the fixing device, and the paper after the color toner image is fixed is discharged to a paper discharge tray. The residual toner on the intermediate transfer belt 3 is cleaned and collected by a cleaning device.

  Next, the electrical configuration of the color printer 1 will be described with reference to FIG. The color printer 1 includes a control unit 20, a storage unit 21, four voltage application units 22 (22Y, 22C, 22M, and 22K), a current detection unit 23, a mode switching unit 24, and a first voltage calculation unit 25. And a second voltage calculation unit 26.

  The control unit 20 includes a CPU and the like, and includes a storage unit 21, four voltage application units 22, a current detection unit 23, a mode switching unit 24, a first voltage calculation unit 25, a second voltage calculation unit 26, and other color printers 1. Are connected to each part, and each part can be controlled. For example, the control unit 20 can perform transfer voltage application control to the four primary transfer rollers 7 and calculation control of transfer voltage values of the four primary transfer rollers 7, and transfer voltage values of the four primary transfer rollers 7. The calculation modes include a first mode and a second mode. In the first mode, the transfer voltage value required for one primary transfer roller 7 serving as a reference (for example, the primary transfer roller 7K corresponding to black toner) is determined (calculated) by feedback control, and the other primary transfer rollers 7 are used. The transfer voltage values required for the primary transfer rollers 7Y, 7C, and 7M corresponding to the yellow, cyan, and magenta toners are determined (calculated) based on the feedback control result of one primary transfer roller 7. In the second mode, the transfer voltage values of the four primary transfer rollers 7 are all determined (calculated) by feedback control.

  The storage unit 21 includes a ROM, a RAM, and the like, and stores programs and data for realizing the image forming process of the color printer 1 and other various functions. In FIG. 2, the mode switching unit 24, the first voltage calculation unit 25, and the second voltage calculation unit 26 are illustrated separately from the storage unit 21, but are stored in the storage unit 21 and executed by the control unit 20. The program may be configured. Further, the storage unit 21, for example, a prescribed transfer current value (target current value) suitable for each of the four primary transfer rollers 7, 4 calculated by the first voltage calculation unit 25 and the second voltage calculation unit 26. The transfer voltage value of each of the primary transfer rollers 7 is stored. Further, the storage unit 21 includes a transfer voltage value of one primary transfer roller 7 (for example, the primary transfer roller 7K) serving as a reference among the four primary transfer rollers 7 and primary other than one primary transfer roller 7. Related information that associates the transfer voltage value of the transfer roller 7 (for example, the primary transfer rollers 7Y, 7C, and 7M) is stored. The storage unit 21 may store characteristic lines (first characteristic line and second characteristic line) indicating the characteristics of each primary transfer roller 7.

  The four voltage application units 22 are provided corresponding to each of the four primary transfer rollers 7. Each voltage application unit 22 is connected to each primary transfer roller 7 and applies a voltage to each primary transfer roller 7 in accordance with control by the control unit 20. For example, in the case of normal printing, each voltage application unit 22 applies a voltage having a transfer voltage value stored in the storage unit for each primary transfer roller 7 to each primary transfer roller 7.

  The four voltage application units 22 apply voltages to the four primary transfer rollers 7 according to each calculation mode (first mode and second mode) when calculating the transfer voltage values of the four primary transfer rollers 7. .

  For example, in the case of the first mode, the voltage application unit 22 (for example, the voltage application unit 22K) corresponding to one primary transfer roller 7 (for example, the primary transfer roller 7K) subjected to feedback control has a plurality of different ones. A plurality of voltages having a voltage value (multi-stage voltages, for example, 700 V, 1000 V, 1300 V) are applied as current detection voltages. At the same time, with respect to the other primary transfer rollers 7 (for example, the primary transfer rollers 7Y, 7C, and 7M), the corresponding voltage application unit 22 (for example, the voltage application units 22Y, 22C, and 22M) is 1/200. A weak voltage (for example, 50 to 100 V) or a zero voltage having a voltage value of 1/10 or less is applied as a voltage for current detection.

  In the second mode, the four primary transfer rollers 7 are sequentially subjected to feedback control, and the corresponding voltage application unit 22 applies a multi-stage voltage to the primary transfer roller 7 to be feedback controlled. A corresponding voltage application unit 22 applies a weak voltage or a zero voltage to the other primary transfer rollers 7.

  The current detection unit 23 is connected to the four voltage application units 22 and detects the current value of the current flowing through the four primary transfer rollers 7. The current detection unit 23 includes, for example, four primary transfer rollers at a calculation timing of transfer voltage values of the four primary transfer rollers 7 (timing at which a current detection voltage, weak voltage, or zero voltage is applied to the primary transfer roller 7). 7 detects the current flowing through the circuit 7. The current detection unit 23 detects a total current value (total current value) flowing through the four primary transfer rollers 7 as a current value detection circuit common to the four primary transfer rollers 7, and detects a current based on the detection result. The unit 23 or the control unit 20 detects the current value of each primary transfer roller 7.

  For example, the current detection unit 23 flows to the predetermined primary transfer roller 7 each time a plurality of voltages having a plurality of voltage values are applied to the predetermined primary transfer roller 7 by the corresponding voltage application unit 22. The current is detected, that is, the current value of the current flowing through the predetermined primary transfer roller 7 is detected for each of a plurality of voltage values.

  In this embodiment, an example in which one current detection unit 23 common to the four primary transfer rollers 7 is provided will be described, but the configuration of the current detection unit 23 is not limited to this example. For example, a current detection unit may be provided for each of the four primary transfer rollers 7, and each current detection unit 23 may detect a current flowing through each primary transfer roller 7.

  The mode switching unit 24 switches and sets the transfer voltage value calculation mode between the first mode and the second mode according to the usage state of the four primary transfer rollers 7. The mode switching unit 24 is one of the cases where a change in the resistance value of each primary transfer roller 7 is expected (when image formation is performed on a relatively large number of sheets, the environmental temperature and the relative humidity greatly vary). The calculation mode is set, and the control unit 20 performs calculation control of the transfer voltage value by setting the calculation mode. The color printer 1 is preferably provided with a temperature sensor that measures the environmental temperature and a humidity sensor that measures the relative humidity in the vicinity of the four primary transfer rollers 7. The mode switching unit 24 sets the first mode when the four primary transfer rollers 7 are in use with no time margin, and sets the second mode when there is a time margin. For example, when image formation on a relatively large number of sheets is being continuously executed, the mode switching unit 24 sets the first mode every time image formation on a predetermined number of sheets is completed, and images on all sheets After the formation is completed, the second mode is set.

  The first voltage calculation unit 25 newly calculates a transfer voltage value for the predetermined primary transfer roller 7 out of the four primary transfer rollers 7 by feedback control based on the current value detected by the current detection unit 23. . The first voltage calculation unit 25 updates the transfer voltage value by storing the newly calculated transfer voltage value instead of the transfer voltage value stored in the storage unit 21 for the predetermined primary transfer roller 7.

For example, when the current detection unit 23 detects the current value of the current flowing through the predetermined primary transfer roller 7 for each of a plurality of voltage values, the first voltage calculation unit 25 sets the plurality of voltage values and the plurality of voltage values. Based on the current value, a first characteristic line indicating the characteristics of the predetermined primary transfer roller 7 is determined. For the first characteristic line, the voltage value is set on the horizontal axis and the current value is set on the vertical axis, the coordinates for each of the plurality of voltage values are determined, and linear interpolation, the least square method, or the like is applied to these coordinates. Is required. For example, as shown in FIG. 3, when a plurality of voltage values V _K1 , V _K2 , and V _K3 are applied to the black primary transfer roller 7K, current values A _K1 , A _K2 , and A _K3 are detected. In this case, the first characteristic line L _1K is obtained. Further, when the current values A _Y1 , A _Y2 , and A _Y3 are detected when a plurality of voltage values V _Y1 , V _Y2 , and V _Y3 are applied to the yellow primary transfer roller 7Y, the first characteristic is obtained. Line _L1Y is obtained.

Then, the first voltage calculation unit 25 uses the first characteristic line to transfer the transfer voltage value based on the specified transfer current value (target current value) stored in the storage unit 21 for the predetermined primary transfer roller. Is calculated. The first characteristic line of predetermined primary transfer roller 7, wherein the correlation between the voltage and current values (e.g., linear formula _{I = a 1 × V + b} 1 of which has a predetermined slope a ₁₎ as demonstrated by, The transfer voltage value is calculated by calculating back the voltage value corresponding to the target current value from the expression of the first characteristic line. For example, as shown in FIG. 3, the voltage value V _KT corresponding to the target current value _AT can be obtained as the transfer voltage value on the first characteristic line L _1K of the black primary transfer roller 7K. Further, it is possible in the first characteristic line L _1Y of the yellow primary transfer roller 7Y, to obtain a voltage value V _YT1 corresponding to the target current value A _T as the transfer voltage.

  The second voltage calculation unit 26 uses the transfer voltage value of one primary transfer roller 7 (for example, the primary transfer roller 7K) that is feedback-controlled and the other primary transfer rollers (for example, the primary transfer rollers 7Y, 7C, and 7M). The related information associated with the transfer voltage value is read from the storage unit 21, and the transfer voltage value of the other primary transfer roller 7 is newly calculated based on the related information. The second voltage calculation unit 26 updates the transfer voltage value by storing the newly calculated transfer voltage value in place of the transfer voltage value stored in the storage unit 21 for the other primary transfer roller 7.

For example, the second voltage calculation unit 26 converts the past transfer voltage value of one primary transfer roller 7 and the past transfer voltage value of the other primary transfer roller 7 accumulated as related information of the other primary transfer roller 7. Based on this, a second characteristic line indicating the characteristics of the other primary transfer roller 7 is determined. The second characteristic line indicates that the past transfer voltage value of one primary transfer roller 7 is set on the horizontal axis and the past transfer voltage value of the other primary transfer roller 7 is set on the vertical axis. It is obtained by determining the coordinates for each and applying the least square method or the like to these coordinates. For example, as shown in FIG. 4, in the graph showing the related information of the yellow primary transfer roller 7Y, the transfer voltage values V _{K11 to} V _K19 previously applied to the black primary transfer roller 7K and the yellow primary transfer roller 7K are displayed. Coordinates respectively corresponding to transfer voltage values V _{Y11 to} V _Y19 applied in the past to the transfer roller 7Y are obtained. Although there are some variations in these coordinates (see the dotted lines in FIG. 4), the second characteristic line L _2Y is obtained by applying a least square method or the like based on the voltage values of these coordinates.

Then, the second voltage calculation unit 26 calculates the transfer voltage value using the second characteristic line of the other primary transfer roller 7 based on the transfer voltage value of one primary transfer roller 7 obtained by the feedback control. . The transfer voltage value of the other primary transfer roller 7 is obtained by reading a voltage value corresponding to the transfer voltage value of one primary transfer roller 7 on the second characteristic line. For example, as shown in FIG. 4, the voltage value V _YT2 corresponding to the transfer voltage value V _KT of one primary transfer roller 7 is obtained as the transfer voltage value on the second characteristic line L _2Y of the yellow primary transfer roller 7Y. Can do.

The second voltage calculation unit 26 uses the second characteristic line of the other primary transfer roller 7 as a correlation of related information (correlation between the transfer voltage value of one primary transfer roller 7 and the transfer voltage value of the other primary transfer roller). (Relationship) may be expressed as an expression. For example, the second characteristic line indicates that the transfer voltage value V _K of the black primary transfer roller 7K, the transfer voltage value V _{Y of} the yellow primary transfer roller 7Y, and constants a and b are used, and V _Y = a _Y × V _K It can be expressed by a polynomial such as + b _Y. The second voltage calculation unit 26 can calculate a transfer voltage value V _Y of the primary transfer roller 7Y yellow using this equation. In addition, the second voltage calculation unit 26 may use only the latest predetermined number of related information instead of all the related information accumulated in the storage unit 21. When the related information is less than the predetermined number (related information In some cases, the transfer voltage value may be calculated by the first voltage calculation unit 25.

  Next, the calculation operation of the transfer voltage value of each primary transfer roller 7 of this embodiment will be described with reference to the flowchart of FIG. In FIG. 5, the “primary transfer roller” is simply abbreviated as “roller”.

  First, in the color printer 1, the use state of each primary transfer roller 7 is monitored by the control unit 20 or the mode switching unit 24 (step S1). As a result of the monitoring, the resistance value of each primary transfer roller 7 varies. Is predicted, the mode switching unit 24 sets the first mode when there is no time margin as the usage state of each primary transfer roller 7 (step S1: first mode), and the time margin is sufficient. If there is, the second mode is set (step S1: second mode).

  When the second mode is set, the four voltage application units 22 sequentially apply a plurality of step voltages to the four primary transfer rollers 7 (step S2), and the current detection unit 23 applies the plurality of applied voltage values. Every time, the current flowing through the four primary transfer rollers 7 is detected.

  Next, the first voltage calculation unit 25 calculates, for each of the four primary transfer rollers 7, a first characteristic line indicating a relationship between a plurality of voltage values and a plurality of current values detected corresponding to them. Then, the first voltage calculation unit 25 calculates a new transfer voltage value corresponding to the target current value by feedback control using the first characteristic line of each primary transfer roller 7 (step S3), and is newly calculated. The transferred voltage value is stored in the storage unit 21 and updated (step S4).

  At this time, the first voltage calculation unit 25 associates the transfer voltage value of the black primary transfer roller 7K serving as a reference with the transfer voltage values of the other primary transfer rollers 7Y, 7C, and 7M of yellow, cyan, and magenta. The related information of the primary transfer rollers 7Y, 7C, and 7M of yellow, cyan, and magenta is accumulated in the storage unit 21 (step S5).

  When the first mode is set, the black voltage application unit 22K sequentially applies a plurality of step voltages to the black primary transfer roller 7K (step S6), and the current detection unit 23 applies the plurality of applied voltage values. Every time, the current flowing through the black primary transfer roller 7K is detected.

  Next, the first voltage calculation unit 25 calculates a first characteristic line indicating a relationship between a plurality of voltage values and a plurality of current values detected corresponding to the black primary transfer roller 7K. Then, the first voltage calculation unit 25 calculates a new transfer voltage value corresponding to the target current value by feedback control using the first characteristic line of the black primary transfer roller 7 (step S7).

  In addition, the second voltage calculation unit 26 acquires related information of the other primary transfer rollers 7Y, 7C, and 7M of other yellow, cyan, and magenta from the storage unit 21, and the primary transfer rollers 7Y, 7C, and yellow of the yellow, cyan, and magenta A second characteristic line of 7M is calculated. Then, the second voltage calculation unit 26 uses the second characteristic lines of the primary transfer rollers 7Y, 7C, and 7M of yellow, cyan, and magenta, and corresponds to the transfer voltage value of the primary transfer roller 7 for black, yellow, cyan, and magenta. New transfer voltage values of the magenta primary transfer rollers 7Y, 7C, and 7M are calculated (step S8). Then, the first voltage calculation unit 25 and the second voltage calculation unit 26 store and update the newly calculated transfer voltage value in the storage unit 21 (step S9).

  According to the present embodiment, as described above, the color printer 1 (image forming apparatus) is arranged corresponding to each of the four (plural) photosensitive drums 6 and the four photosensitive drums 6. Current values of the currents flowing through the four primary transfer rollers 7, the four voltage transfer units 22 that apply voltages to the four primary transfer rollers 7, and the four primary transfer rollers 7, respectively. The current detection unit 23 that detects the transfer voltage, the storage unit 21 that stores the transfer voltage value for each of the four primary transfer rollers 7, and the transfer voltage value calculation mode according to the use state of the four primary transfer rollers 7, A mode switching unit 24 (control unit 20) that switches between the first mode and the second mode is provided. The color printer 1 (control unit 20) newly calculates and updates the transfer voltage value for a predetermined primary transfer roller 7 out of the four primary transfer rollers 7 based on the current value detected by the current detection unit 23. Primary voltage other than the primary transfer roller 7 of the first voltage calculation unit 25, the transfer voltage value of the primary transfer roller 7 of the four primary transfer rollers 7, and the primary transfer roller 7 of the plurality of primary transfer rollers 7. And a second voltage calculation unit 26 that newly calculates and updates the transfer voltage value of the other primary transfer roller 7 based on the related information that associates the transfer voltage value of the transfer roller 7. In the case of the second mode, the control unit 20 newly calculates and updates the transfer voltage values of the four primary transfer rollers 7 by the first voltage calculation unit 25, and one primary transfer roller 7. Is stored in the storage unit 21 in association with the transfer voltage value updated with respect to the transfer voltage value updated with respect to the other primary transfer roller 7. In the first mode, the control unit 20 newly calculates and updates the transfer voltage value of one primary transfer roller 7 by the first voltage calculation unit 25, and another primary transfer by the second voltage calculation unit 26. The transfer voltage value of the roller 7 is newly calculated and updated.

  For example, the voltage application unit 22 applies a plurality of voltages having a plurality of different voltage values to the predetermined primary transfer roller 7. The current detection unit 23 detects the current value of the current flowing through the predetermined primary transfer roller 7 for each of a plurality of voltage values. Then, the first voltage calculation unit 25 uses the first characteristic line indicating the characteristics of the predetermined primary transfer roller 7 determined based on the plurality of voltage values and the current value for each of the plurality of voltage values, to thereby perform a predetermined transfer. Based on the current value of the current, the transfer voltage value of the predetermined primary transfer roller 7 is calculated.

  By adopting such a configuration, the past transfer voltage values of the respective primary transfer rollers 7 are accumulated, and related information indicating the characteristics of the respective primary transfer rollers 7 is used. Therefore, according to the characteristics of the respective primary transfer rollers 7. The transfer voltage value can be calculated quickly. Therefore, even when there are variations in the applied voltages and measurement voltages of the plurality of primary transfer rollers 7, the optimum transfer voltage value for each primary transfer roller 7 is highly accurate regardless of the difference in characteristics between the primary transfer rollers 7. Can be calculated. Therefore, it is possible to avoid the malfunction of each primary transfer roller 7 and perform image formation appropriately.

  For example, in the embodiment in which the transfer voltage values of the four primary transfer rollers 7 are calculated in the second mode at a predetermined first timing, a transfer voltage value of 1100 V is calculated for the black primary transfer roller 7K, and the yellow primary A transfer voltage value of 900 V was calculated for the transfer roller 7Y. At this time, the difference between the two transfer voltage values was 200V. In the embodiment in which the transfer voltage values of the four primary transfer rollers 7 are calculated in the second mode at another second timing, a transfer voltage value of 1100 V is calculated for the black primary transfer roller 7K, and the yellow primary transfer roller 7K is calculated. A transfer voltage value of 870 V was calculated for the transfer roller 7Y. At this time, the difference between the two transfer voltage values was 230V. As described above, the difference in the transfer voltage value between the primary transfer rollers 7 may differ depending on the timing (depending on the usage state of each primary transfer roller 7). Therefore, the transfer voltage of the primary transfer roller 7 using such a difference. If the value is estimated, it may be calculated incorrectly. However, in the present embodiment, as described above, the transfer voltage value is calculated in accordance with the characteristics of each primary transfer roller 7, so that the transfer voltage value is not erroneously calculated.

  Further, according to the present embodiment, when the second voltage calculation unit 26 calculates the transfer voltage value for the other primary transfer roller 7, the correlation (second characteristic) of the related information accumulated in the storage unit 21. A formula indicating a line) is used.

  Thereby, even when there are variations in the applied voltages and measurement voltages of the plurality of primary transfer rollers 7, it is possible to appropriately determine the characteristics of the primary transfer rollers 7 and calculate the transfer voltage value.

  Further, according to the present embodiment, the second voltage calculation unit 26 uses the latest predetermined number of related information accumulated in the storage unit 21 when calculating the transfer voltage value for the other primary transfer roller 7. .

  As a result, the transfer voltage value can always be calculated using new information, and the storage unit 21 can be optimized by deleting the latest related information exceeding the predetermined number.

  In the above-described embodiment, the mode switching unit 24 switches the transfer voltage value calculation mode to either the first mode or the second mode according to the usage state of the four primary transfer rollers 7. Although an example in which the transfer voltage value is calculated in the second mode has been described, the method for calculating the transfer voltage value is not limited to this. For example, in another embodiment, the mode switching unit 24 selects one of the first mode, the second mode, and the third mode as a transfer voltage value calculation mode according to the usage state of the four primary transfer rollers 7. It may be set by switching to. The mode switching unit 24 is configured in a case where one first characteristic line indicating the characteristic of one primary transfer roller 7 that is feedback controlled is stored in the storage unit 21 by the first mode or the second mode that has been operated in the past. The third mode may be set instead of the first mode. Since the transfer voltage value calculation method in the first mode and the second mode has been described above, the transfer voltage value calculation method in the third mode will be described below.

  In the third mode, a transfer voltage value required for one primary transfer roller 7 (for example, the black primary transfer roller 7K) serving as a reference is calculated by feedback control, and other primary transfer rollers 7 (for example, yellow, cyan, The transfer voltage value required for the magenta primary transfer rollers 7Y, 7C, and 7M) is calculated based on the feedback control result of one primary transfer roller 7. The feedback control method is different between the first mode and the third mode.

  In the case of the third mode, the voltage application unit 22 (22K) corresponding to one primary transfer roller 7 (for example, the black primary transfer roller 7K) that is feedback-controlled has a single voltage (for example, 1000 V). Is applied as a voltage for current detection. At the same time, with respect to the other primary transfer rollers 7 (for example, primary transfer rollers 7Y, 7C, 7M), the corresponding voltage application unit 22 (22Y, 22C, 22M) detects the weak voltage or zero voltage for current detection. The voltage is applied as follows.

  Even in the third mode, the current detector 23 detects the current flowing through each primary transfer roller 7 in the same manner as described above. For example, the current detection unit 23 detects a current that flows through one primary transfer roller 7 when a single voltage is applied to one primary transfer roller 7 by the corresponding voltage application unit 22. The current value of the current flowing through one primary transfer roller 7 corresponding to the voltage value of a single voltage is detected.

  In the third mode, the first voltage calculation unit 25 uses a single voltage value (single voltage value) and a single voltage for one primary transfer roller 7 (for example, the black primary transfer roller 7K). A new transfer voltage value is calculated and updated based on the current value corresponding to the value (single current value), the first characteristic line stored in the storage unit 21, and the current value of the specified transfer current. .

For example, the first characteristic line is represented by an expression of a correlation between the voltage value and the current value (for example, a linear expression I = a ₁ × V + b ₁ having a predetermined slope), that is, a predetermined primary transfer roller 7. Has a characteristic of a predetermined inclination a ₁ of the first characteristic line. Therefore, the first voltage calculation unit 25 sets a single voltage value on the horizontal axis and passes through the coordinates where the single current value is set on the vertical axis, and has a voltage value having a predetermined slope a ₁ of the first characteristic line. The correlation expression with the current value is calculated and updated as a new first characteristic line indicating the characteristics of the predetermined primary transfer roller 7. For example, as shown in FIG. 6, for the primary transfer roller 7K of black toner, the first characteristic line L ₁₁ of the most recent stored in the storage unit 21 has a predetermined inclination a _1, a single voltage value V _A single current value I _S is detected for _S. At this time, the new first characteristic line L ₁₂ of the primary transfer roller 7K passes through the coordinates of the single voltage value V _S and the single current value I _S and is calculated as an equation having a predetermined inclination a ₁ .

Then, the first voltage calculation unit 25 calculates the new first voltage calculated as described above based on the prescribed transfer current value (target current value) stored in the storage unit 21 for the predetermined primary transfer roller 7. A transfer voltage value is calculated using the characteristic line. For example, as shown in FIG. 6, in the first characteristic line L ₁₂ of the primary transfer roller 7K of black toner, it is possible to obtain a voltage value V ₁₂ corresponding to the target current value A _T as the transfer voltage.

  In other words, in the color printer 1 according to another embodiment, the mode switching unit 24 changes the transfer voltage value calculation mode between the first mode, the second mode, and the first mode according to the usage state of the four primary transfer rollers 7. Switch to one of the three modes. The control unit 20 stores one first characteristic line indicating the characteristic of one primary transfer roller 7 used by the first voltage calculation unit 25 in the storage unit 21 in the most recent first mode or second mode. The voltage application unit 22 applies a single voltage to one primary transfer 7 roller in the third mode, and the current detection unit 23 outputs a single voltage in the third mode. The current value of the current flowing through one primary transfer roller 7 is detected corresponding to the voltage value of. In the case of the third mode, the control unit 20 uses the first voltage calculation unit 25 to correspond to a single voltage value and a single voltage value for one primary transfer roller 7. The transfer voltage value is calculated and updated based on the current value, the first characteristic line stored in the storage unit 21, and the current value of the specified transfer current. The transfer voltage value of the transfer roller 7 is newly calculated and updated.

  Thereby, when the first characteristic line calculated in the past is stored for each primary transfer roller 7, a single voltage is applied to the primary transfer roller 7 instead of a multi-stage voltage in the feedback control. The transfer voltage value that matches the characteristics of the primary transfer roller 7 can be calculated while reducing the time required for feedback control.

  In the present embodiment, the case where the configuration of the present invention is applied to the color printer 1 has been described. However, in other different embodiments, other image forming apparatuses including a plurality of photosensitive drums, such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible to apply the configuration of the present invention to an apparatus.

1 Color printer (image forming device)
DESCRIPTION OF SYMBOLS 3 Intermediate transfer belt 4 Image forming part 5 Secondary transfer part 6 Photosensitive drum 7 Primary transfer roller 20 Control part 21 Storage part 22 Voltage application part 23 Current detection part 24 Mode switching part 25 First voltage calculation part 26 Second voltage calculation Part

Claims (5)

A plurality of photosensitive drums;
A plurality of primary transfer rollers arranged corresponding to each of the plurality of photosensitive drums;
A plurality of voltage application sections for applying a voltage to each of the plurality of primary transfer rollers;
A current detection unit for detecting a current value of a current flowing through each of the plurality of primary transfer rollers;
A storage unit for storing a transfer voltage value for each of the plurality of primary transfer rollers;
A control unit that switches the transfer voltage value calculation mode between the first mode and the second mode in accordance with the use state of the plurality of primary transfer rollers;
With
The controller is
A first voltage calculation unit that newly calculates and updates the transfer voltage value based on the current value detected by the current detection unit for a predetermined primary transfer roller of the plurality of primary transfer rollers;
The transfer voltage value of one primary transfer roller of the plurality of primary transfer rollers and the transfer voltage value of a primary transfer roller other than the one primary transfer roller of the plurality of primary transfer rollers. A second voltage calculation unit that newly calculates and updates the transfer voltage value of the other primary transfer roller based on the related information that is associated,
In the case of the second mode, the first voltage calculation unit newly calculates and updates the transfer voltage value of each of the plurality of primary transfer rollers,
Storing the related information in which the transfer voltage value updated for the one primary transfer roller and the transfer voltage value updated for the other primary transfer roller are associated with each other in the storage unit;
In the case of the first mode, the first voltage calculation unit newly calculates and updates the transfer voltage value of the one primary transfer roller,
The image forming apparatus, wherein the second voltage calculation unit newly calculates and updates the transfer voltage value of the other primary transfer roller. The voltage application unit applies a plurality of voltages having a plurality of different voltage values to the predetermined primary transfer roller,
The current detection unit detects a current value of a current flowing through the predetermined primary transfer roller for each of the plurality of voltage values;
The first voltage calculation unit uses a characteristic line indicating a characteristic of the predetermined primary transfer roller that is determined based on the plurality of voltage values and the current value for each of the plurality of voltage values. The image forming apparatus according to claim 1, wherein the transfer voltage value of the predetermined primary transfer roller is calculated on the basis of the current value. The control unit switches the transfer voltage value calculation mode to any one of the first mode, the second mode, and the third mode according to the use state of the plurality of primary transfer rollers.
Storing the one characteristic line indicating the characteristic of the one primary transfer roller used by the first voltage calculation unit in the storage unit in the first mode or the second mode most recently;
In the case of the third mode, the voltage application unit applies a single voltage to the one primary transfer roller,
In the third mode, the current detection unit detects a current value of a current flowing through the one primary transfer roller corresponding to a voltage value of the single voltage,
In the case of the third mode, the control unit corresponds to the voltage value of the single voltage and the voltage value of the single voltage for the one primary transfer roller by the first voltage calculation unit. Calculating and updating the transfer voltage value based on the current value, the characteristic line stored in the storage unit, and a current value of a specified transfer current,
The image forming apparatus according to claim 2, wherein the transfer voltage value of the other primary transfer roller is newly calculated and updated by the second voltage calculation unit.   The second voltage calculation unit uses an expression indicating a correlation of the related information accumulated in the storage unit when calculating the transfer voltage value for the other primary transfer roller. Item 4. The image forming apparatus according to any one of Items 1 to 3.   The said 2nd voltage calculation part uses the last predetermined number of the said relevant information accumulate | stored in the said memory | storage part, when calculating the said transfer voltage value about the said other primary transfer roller. The image forming apparatus according to any one of 1 to 4.

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