JP2015007666A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to prevent transfer failure to be caused by a change in resistance value of a transfer member.SOLUTION: When the number of sheet members P to which a toner image has been transferred sequentially reaches a predetermined threshold and a detection result of a resistance detection unit 82 decreases below a predetermined threshold, a control unit 84 derives a transfer voltage to be applied to an auxiliary roll 50 on the basis of a correction reference line F different from a derivation reference line E. A transfer failure to be caused by a change in resistance value of a secondary transfer roll 22 can be prevented, accordingly.

Description

  The present invention relates to an image forming apparatus.

  The image forming apparatus described in Patent Document 1 includes an environmental sensor that measures an environmental condition in the apparatus when the power is turned on, and a time required until the environmental condition in the image forming apparatus becomes a steady state based on a measurement result by the environmental sensor. The transfer condition in the secondary transfer device is changed according to the elapsed time from power-on or the number of images formed until the required time obtained by the required time predicting means and the required time estimated means elapses. Transfer condition changing means.

JP 2002-55535 A

  An object of the present invention is to suppress transfer defects caused by a change in resistance value of a transfer member.

  An image forming apparatus according to a first aspect of the present invention includes a semiconductive layer containing an ionic conductive agent, sandwiches a recording medium between the electrodes, and records a toner image by a potential difference generated between the electrodes. A transfer member that is transferred to the transfer member, a detection member that detects a resistance value of the transfer member, and a transfer voltage that is supplied to the transfer member or the electrode based on a derivation criterion that is predetermined according to a detection result of the detection member Alternatively, when the transfer current is changed and the number of recording media onto which the toner images are continuously transferred by the transfer member reaches a predetermined threshold value, and the detection result falls below a predetermined threshold value, A control member that changes a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a correction criterion different from the derivation criterion according to a detection result of the detection member. To.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with an electrode, and recording a toner image by a potential difference generated between the electrode and the recording medium. A transfer member to be transferred to, a detection member for detecting a resistance value of the transfer member,
A fixing member that can be operated in a low-temperature fixing mode and a high-temperature fixing mode and that fixes the toner image transferred to the recording medium to the recording medium by heat, and a derivation standard determined in advance according to the detection result of the detection member The transfer voltage or transfer current supplied to the transfer member or the electrode is changed based on the number of recording media onto which the toner image is continuously transferred by the transfer member while the fixing member is operating in the high-temperature fixing mode. When the predetermined threshold value is reached and the detection result falls below a predetermined threshold value, the transfer member or the transfer member based on a correction criterion different from the derivation criterion according to the detection result of the detection member And a control member that changes a transfer voltage or a transfer current supplied to the electrode.

  According to a third aspect of the present invention, there is provided an image forming apparatus comprising a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with an electrode, and recording a toner image by a potential difference generated with the electrode. A transfer member that is transferred to the transfer member, a detection member that detects a resistance value of the transfer member, and a transfer voltage that is supplied to the transfer member or the electrode based on a derivation criterion that is predetermined according to a detection result of the detection member Alternatively, when the transfer current is changed, the number of recording media onto which the toner images are continuously transferred on both sides by the transfer member reaches a predetermined threshold value, and the detection result falls below a predetermined threshold value And a control member that changes a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a correction criterion different from the derivation criterion according to a detection result of the detection member. And features.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus having a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with an electrode, and recording a toner image by a potential difference generated with the electrode. A transfer member that transfers to the recording medium, a detection member that detects a resistance value of the transfer member, and a low-temperature fixing mode and a high-temperature fixing mode. The toner image transferred to the recording medium is fixed to the recording medium by heat. The fixing member is operated in a high-temperature fixing mode by changing a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a derivation criterion determined in advance according to a detection result of the fixing member and the detection member. In this state, the number of recording media on which the toner images are continuously transferred on both sides by the transfer member has reached a predetermined threshold value, and the detection result has decreased to a predetermined threshold value or less. And a control member that changes a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a correction criterion different from the derivation criterion according to a detection result of the detection member. .

  According to the image forming apparatus of the first aspect of the present invention, compared to the case where the transfer voltage or the transfer current supplied to the transfer member or the electrode is always derived based on the same reference, the resistance value of the transfer member is reduced. Transfer defects due to the change can be suppressed.

  According to the image forming apparatus of the second aspect of the present invention, compared to the case where the transfer voltage or the transfer current supplied to the transfer member or the electrode is always derived based on the same reference, the resistance value of the transfer member is reduced. Transfer defects due to the change can be suppressed.

  According to the image forming apparatus of the third aspect of the present invention, compared to the case where the transfer voltage or the transfer current supplied to the transfer member or the electrode is always derived based on the same reference, the resistance value of the transfer member is reduced. Transfer defects due to the change can be suppressed.

  According to the image forming apparatus of the fourth aspect of the present invention, the resistance value of the transfer member is smaller than that in the case where the transfer voltage or the transfer current supplied to the transfer member or the electrode is always derived based on the same reference. Transfer defects due to the change can be suppressed.

FIG. 3 is a side view showing a secondary transfer roll, an auxiliary roll, and the like used in the image forming apparatus according to the first embodiment of the present invention. 3 is a diagram illustrating a graph used to explain control of a control unit used in the image forming apparatus according to the first embodiment of the present invention. 3 is a diagram illustrating a graph used to explain control of a control unit used in the image forming apparatus according to the first embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. It is the side view which showed the secondary transfer roll, the auxiliary | assistant roll, etc. which were used for the image forming apparatus concerning 2nd Embodiment of this invention. It is the side view which showed the secondary transfer roll, the auxiliary | assistant roll, etc. which were used for the image forming apparatus which concerns on 3rd Embodiment of this invention. It is the figure which showed the graph used for demonstrating control of the control part used for the image forming apparatus which concerns on 3rd Embodiment of this invention. It is the side view which showed the secondary transfer roll, the auxiliary | assistant roll, etc. which were used for the image forming apparatus concerning 4th Embodiment of this invention.

<First Embodiment>
An example of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS. In the figure, an arrow V indicates the vertical direction and indicates the vertical direction of the apparatus, and an arrow H indicates the horizontal direction and indicates the horizontal direction of the apparatus.

(overall structure)
As shown in FIG. 4, an image processing unit 12 that performs image processing on input image data is provided inside the apparatus main body 10 </ b> A of the image forming apparatus 10.

  The image processing unit 12 processes input image data into gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K).

  At the center side of the apparatus main body 10A, four image forming units 16Y, 16M, 16C, and 16K of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in the horizontal direction. Are arranged at intervals in the inclined direction, and can be attached to and detached from the apparatus main body 10A. These image forming units 16Y, 16M, 16C, and 16K form toner images of respective colors. If there is no need to distinguish between Y, M, C, and K, Y, M, C, and K may be omitted.

  On the other hand, a primary transfer unit 18 is provided above the image forming unit 16 of each color in the vertical direction, and the toner images formed by the image forming unit 16 of each color are transferred in multiple layers. Further, on the side of the primary transfer unit 18 (on the left side in the drawing), multiple transfer onto the primary transfer unit 18 is performed on a sheet member P as a recording medium conveyed along a conveyance path 60 by a supply conveyance unit 30 described later. A secondary transfer roll 22 is provided as an example of a transfer member that transfers the toner image.

  The toner image transferred to the sheet member P is transferred to the sheet member P by heat and pressure downstream of the secondary transfer roll 22 in the conveyance direction of the sheet member P (hereinafter simply referred to as “sheet conveyance direction”). A fixing device 24 is provided as an example of a fixing member for fixing. Further, on the downstream side in the sheet conveying direction with respect to the fixing device 24, a discharge roller 28 for discharging the sheet member P on which the toner image is fixed to a discharge portion 26 provided on the upper portion of the apparatus main body 10A of the image forming apparatus 10. Is provided.

  On the other hand, a supply and conveyance unit 30 that supplies and conveys the sheet member P is provided below and to the side of the image forming unit 16 of each color in the vertical direction.

[Image forming unit]
First, the image forming unit 16 will be described.

  The image forming units 16 for the respective colors are all configured similarly. Each color image forming unit 16 includes a rotating columnar image carrier 34 and a charging member 36 that charges the surface of the image carrier 34.

  Further, each color image forming unit 16 includes an LED head 32 that irradiates the surface of the charged image carrier 34 with exposure light, and an electrostatic latent image formed by image exposure of the LED head 32 as a developer (this embodiment). , A developing unit 38 that develops the toner image with a toner charged on the negative electrode and visualizes it as a toner image, and a cleaning blade (not shown) that cleans the surface of the image carrier 34 are provided. The charging member 36, the LED head 32, the developing device 38, and the cleaning blade are arranged in this order from the upstream side to the downstream side in the rotation direction of the image carrier 34 so as to face the surface of the image carrier 34. Has been.

[Transfer section (primary transfer unit, secondary transfer roll)]
Next, the primary transfer unit 18 and the secondary transfer roll 22 will be described.

  The primary transfer unit 18 is disposed above the image forming unit 16 of each color in the vertical direction. The primary transfer unit 18 includes an endless intermediate transfer belt 42, a drive roll 46 around which the intermediate transfer belt 42 is wound and rotationally driven to rotate the intermediate transfer belt 42 in the direction of arrow A, and the intermediate transfer belt 42 is wound around the primary transfer unit 18. A tension applying roll 48 that is applied to apply tension to the intermediate transfer belt 42, an auxiliary roll 50 that is disposed above the tension applying roll 48 in the vertical direction and that rotates following the intermediate transfer belt 42, and intermediate transfer A primary transfer roll 52 disposed on the opposite side of the image carrier 34 of each color with the belt 42 interposed therebetween.

  As a result, the yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the image carrier 34 of each color image forming unit 16 are transferred to the primary transfer of each color. Multiple rolls are transferred onto the intermediate transfer belt 42 by the roll 52.

  Further, a cleaning blade 56 that contacts the surface of the intermediate transfer belt 42 and cleans the surface of the intermediate transfer belt 42 is disposed on the opposite side of the drive roll 46 with the intermediate transfer belt 42 interposed therebetween.

  Further, on the opposite side of the auxiliary roll 50 across the intermediate transfer belt 42, a secondary transfer roll 22 for transferring the toner image transferred on the intermediate transfer belt 42 to the conveyed sheet member P is provided. .

  As shown in FIG. 1, the secondary transfer roll 22 is grounded, and the auxiliary roll 50 forms a counter electrode of the secondary transfer roll 22. The auxiliary roll 50 has a secondary transfer voltage. Is applied.

  Here, when a secondary transfer voltage (negative voltage) is applied to the auxiliary roll 50 and a potential difference is generated between the auxiliary roll 50 and the secondary transfer roll 22, the secondary transfer roll 22 and the intermediate transfer belt 42 are The toner image on the intermediate transfer belt 42 is secondarily transferred to a sheet member P conveyed (contacted between the secondary transfer roll 22 and the auxiliary roll 50) to the contact portion.

  Details of the secondary transfer roll 22 and the auxiliary roll 50 will be described later.

[Supply transport unit]
Next, the supply conveyance unit 30 that supplies and conveys the sheet member P will be described.

  As shown in FIG. 4, the supply conveyance unit 30 includes a sheet feeding member 62 that is disposed below the image forming unit 16 in the vertical direction in the apparatus main body 10 </ b> A and on which a plurality of sheet members P are stacked. ing.

  Further, the supply and conveyance unit 30 includes a sheet feeding roll 64 that feeds the sheet member P stacked on the sheet feeding member 62 to the conveyance path 60 and a separation roll that separates the sheet member P fed by the sheet feeding roll 64 one by one. 66 and an alignment roll 68 for adjusting the conveyance timing of the sheet member P. And each roll is arrange | positioned in this order toward the downstream from the upstream of a sheet conveyance direction.

  With this configuration, the sheet member P supplied from the sheet feeding member 62 is set at a timing determined by the rotating alignment roll 68 to the contact portion (secondary transfer position) between the intermediate transfer belt 42 and the secondary transfer roll 22. It is to be sent out.

  Further, the supply conveyance unit 30 forms the toner image on the other surface without discharging the sheet member P, on which the toner image is fixed on one surface by the fixing device 44, to the discharge unit 26 by the discharge roll 28 as it is. For this purpose, a double-sided conveyance device 70 is provided.

  The double-sided conveyance device 70 includes a double-sided conveyance path 72 through which the sheet member P is conveyed so as to reverse the front and back of the sheet member P from the discharge roll 28 toward the alignment roll 68, and the sheet member along the double-sided conveyance path 72. A transport roll 74 and a transport roll 76 for transporting P are provided.

(Operation of the overall configuration)
With this configuration, an image is formed on the sheet member P as follows.

  First, gradation data of each color is sequentially output from the image processing unit 12 to the LED head 32 of each color. Then, the exposure light emitted from the LED head 32 according to the gradation data is applied to the surface of the image carrier 34 charged by the charging member 36. Thereby, an electrostatic latent image is formed on the surface of the image carrier 34. The electrostatic latent image formed on the image holding member 34 is developed by each color developing device 38, and is formed as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K). Visualized.

  Further, the yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the image carrier 34 circulate by the primary transfer roll 52 of the primary transfer unit 18. Multiple transfer is performed on the intermediate transfer belt 42.

  The toner images of each color transferred onto the circulating intermediate transfer belt 42 in a multiple manner are conveyed from the sheet feeding member 62 along the conveyance path 60 by the sheet feeding roll 64, the separation roll 66, and the alignment roll 68. Secondary transfer is performed on P at the secondary transfer position by the secondary transfer roll 22.

  Further, the sheet member P to which the toner image has been transferred is conveyed to the fixing device 44. Then, the toner image is fixed on the sheet member P by the fixing device 44. The sheet member P on which the toner image is fixed is discharged to the discharge unit 26 by the discharge roll 28.

  On the other hand, when images are formed on both surfaces of the sheet member P, the sheet member P on which the toner image is fixed on one surface (front surface) by the fixing device 44 is not directly discharged to the discharge unit 26 by the discharge roll 28. The conveyance direction of the sheet member P is switched by reversing the discharge roll 28. And this sheet member P is conveyed along the double-sided conveyance path | route 72 by the conveyance rolls 74 and 76. FIG.

  The sheet member P conveyed along the double-sided conveyance path 72 is conveyed to the alignment roll 68 again with the front and back reversed. This time, after the toner image is transferred and fixed on the other surface (back surface) of the sheet member P, the sheet member P is discharged to the discharge portion 26 by the discharge roll 28.

(Main part configuration)
Next, the secondary transfer roll 22, the auxiliary roll 50, etc. will be described.

  The secondary transfer roll 22 has an elastic layer, and this elastic layer is made of a semiconductive material containing an ion conductive agent. The auxiliary roll 50 is a stainless steel shaft having no elastic layer. Examples of the ionic conductive agent include epichlorohydrin rubber, quaternary ammonium salts (for example, lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, modified fatty acid, dimethylethylammonium, etc. Perchlorate, chlorate, borofluoride, sulfate, ethosulphate salt, benzyl halide salt (benzyl bromide, benzyl chloride, etc.), aliphatic sulfonate, higher alcohol sulfate Salt, higher alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide addition phosphate ester salt, various betaines, higher alcohol ethylene oxide, poly Chi glycol fatty acid esters, polyhydric alcohol fatty acid esters.

  In addition, the image forming apparatus 10 includes a voltage application unit 80 that applies a voltage to the auxiliary roll 50 as shown in FIG. The voltage application unit 80 detects the transfer voltage for secondary transfer of the toner image formed on the intermediate transfer belt 42 to the auxiliary roll 50 and the resistance of the secondary transfer roll 22. And a detection voltage for application.

  Further, the image forming apparatus 10 controls the resistance detection unit 82 as an example of a detection member that detects the resistance value of the secondary transfer roll 22 and the voltage application unit 80 according to the detection result of the resistance detection unit 82. And a control unit 84 that changes the transfer voltage described above. Further, the image forming apparatus 10 includes a counter 86 that stores the number of sheet members P onto which the toner image has been continuously transferred by the secondary transfer roll 22.

(Resistance detector)
The resistance detector 82 detects the resistance value of the secondary transfer roll 22 from the current flowing between the auxiliary roll 50 and the secondary transfer roll 22 by applying a detection voltage from the voltage application unit 80 to the auxiliary roll 50. It has become.

  The timing at which the resistance detection unit 82 detects the resistance value of the secondary transfer roll 22 is the sheet member P on which the toner image is transferred by the secondary transfer roll 22 when the image forming apparatus 10 is turned on (during setup). And when the sheet member P does not exist between the auxiliary roll 50 and the secondary transfer roll 22 (for example, during inter-image).

〔counter〕
As described above, the counter 86 stores the number of sheet members P onto which the toner images are continuously transferred by the secondary transfer roll 22. Specifically, when the time between the previous sheet member P to which the toner image is transferred by the secondary transfer roll 22 and the subsequent sheet member P is within one hour, the counter 86 The sheet member P and the subsequent sheet member P memorize that the toner image has been transferred by the secondary transfer roll 22 continuously.

  When the secondary transfer roll 22 transfers the toner image to the front and back surfaces of the A4 size sheet member P, the counter 86 stores two sheets. That is, when the toner image is transferred to the front and back surfaces of the A3 size sheet member P, the counter 86 stores four sheets.

(Control part)
The control unit 84 changes the transfer voltage by controlling the voltage application unit 80 based on the derivation standard shown in FIG. 2 according to the detection result of the resistance detection unit 82.

  The horizontal axis of the graph shown in FIG. 2 indicates the resistance value [MΩ] of the secondary transfer roll 22, and the vertical axis indicates the transfer voltage [V]. The control unit 84 derives a transfer voltage based on a derivation reference line E (an example of derivation criteria) in a graph derived from a predetermined relational expression. The derived line E has a certain slope. Further, the control unit 84 applies a transfer voltage derived by controlling the voltage application unit 80 to the auxiliary roll 50.

  Here, the control unit 84 is configured to receive information on the number of sheet members P onto which the toner image has been continuously transferred by the secondary transfer roll 22 from the counter 86.

  Then, when the number of sheet members P onto which the toner images are continuously transferred reaches a predetermined threshold value, and the detection result by the resistance detection unit 82 falls below a predetermined threshold value, the control unit 84. Is configured to derive a transfer voltage applied to the auxiliary roll 50 based on a correction reference line F (an example of a correction reference) different from the derivation reference line E.

  As shown in FIG. 2, the correction reference line F indicates the relationship between the resistance value of the secondary transfer roll 22 below a [MΩ] (an example of a threshold value) and the transfer voltage [V]. The slope of the derived reference line E is maintained and the voltage is lowered by a certain value.

  The reason why the control unit 84 derives the transfer voltage applied to the auxiliary roll 50 from the correction reference line F instead of the derivation reference line E when the above-described conditions are satisfied will be described with reference to FIG. To do.

  The horizontal axis of the graph shown in FIG. 3 indicates the number of sheet members P on which toner images are continuously transferred to one side by the secondary transfer roll 22 in terms of A4 size, and the vertical axis indicates the resistance of the secondary transfer roll 22. The value is shown. The speed at which the toner image is transferred onto one side of the A4 size sheet member P by the secondary transfer roll 22 is 70 sheets / minute.

  As can be seen from this graph, the detection result by the resistance detection unit 82 decreases below the threshold until the number of sheet members P onto which the toner images are continuously transferred to one side by the secondary transfer roll 22 reaches about 800 sheets. After that, the resistance value is flat.

  This is because the secondary transfer roll 22 has an ion conductive elastic layer whose resistance value changes with temperature, and the number of sheet members P onto which the toner image has been transferred is about 800. Until then, the temperature of the secondary transfer roll 22 rises, and after that, the temperature rise of the secondary transfer roll 22 becomes slow.

  Then, from the actual machine evaluation, when the number of sheet members P onto which the toner images are continuously transferred reaches a certain number and the detection result by the resistance detection unit 82 falls below the threshold value, the derivation reference line E It has been found that when a transfer voltage derived based on the above is applied to the auxiliary roll 50, transfer failure may occur. This was the same defect as that caused by the high transfer voltage.

(Summary)
However, in the first embodiment, as described above, the number of sheet members P onto which the toner images are continuously transferred reaches the predetermined threshold value, and the detection result by the resistance detection unit 82 is determined in advance. The controller 84 derives the transfer voltage applied to the auxiliary roll 50 based on the correction reference line F different from the derivation reference line E. As described above, the correction reference line F maintains the inclination of the derived reference line E and lowers the transfer voltage by a certain value.

  Thereby, transfer failure due to a change in the resistance value of the secondary transfer roll 22 is suppressed.

  In addition, since the transfer failure due to the change in the resistance value of the secondary transfer roll 22 is suppressed, the quality degradation of the output image output from the image forming apparatus 10 is suppressed.

Second Embodiment
Next, an example of an image forming apparatus according to the second embodiment of the present invention will be described with reference to FIG. In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected, the description is abbreviate | omitted, and a different part from 1st Embodiment is mainly demonstrated.

  The fixing device 24 according to the second embodiment is operable in a low temperature fixing mode and a high temperature fixing mode. For example, when fixing a toner image on plain paper, the fixing device 24 operates in a low-temperature fixing mode, and when fixing a toner image on thick paper, the fixing device 24 operates in a high-temperature fixing mode. Yes.

  Further, as illustrated in FIG. 5, the image forming apparatus 10 includes a control unit 100 that controls the voltage application unit 80 and changes the transfer voltage according to the detection result of the resistance detection unit 82.

  Specifically, the number of sheet members P onto which toner images are continuously transferred in a state where the fixing device 24 is operating in the high-temperature fixing mode reaches a predetermined threshold value, and the detection result by the resistance detection unit 82 is When the voltage drops below a predetermined threshold, the control unit 100 derives a transfer voltage applied to the auxiliary roll 50 based on a correction reference line F different from the derivation reference line E. As described above, when the control unit 100 derives the transfer voltage, it is considered that the temperature of the secondary transfer roll 22 increases due to the heat generated by the fixing device 24.

  Thereby, transfer failure due to a change in the resistance value of the secondary transfer roll 22 is suppressed.

  The time between the previous sheet member P to which the toner image is transferred by the secondary transfer roll 22 and the subsequent sheet member P is within one hour, and the previous sheet member P and the subsequent sheet When the toner image is fixed on the member P by the fixing device 24 in the high-temperature fixing mode, the counter 86 transfers the toner image continuously by the secondary transfer roll 22 between the previous sheet member P and the subsequent sheet member P. Remember that it was done.

<Third Embodiment>
Next, an example of an image forming apparatus according to the third embodiment of the present invention will be described with reference to FIGS. In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected, the description is abbreviate | omitted, and a different part from 1st Embodiment is mainly demonstrated.

  As shown in FIG. 6, the image forming apparatus 10 according to the third embodiment includes a control unit 110 that controls the voltage application unit 80 and changes the transfer voltage in accordance with the detection result of the resistance detection unit 82. ing.

  The counter 112 stores the number of sheet members P onto which the toner image has been transferred on both sides by the secondary transfer roll 22. Specifically, the time between the sheet member P to which the toner image is transferred onto both sides by the secondary transfer roll 22 and the sheet member P after the toner image is transferred to both sides is within one hour. At this time, the counter 86 stores the fact that the first sheet member P and the subsequent sheet member P are continuously transferred to the both surfaces by the secondary transfer roll 22.

  Then, the control is performed when the number of sheet members P onto which the toner images are continuously transferred on both sides reaches a predetermined threshold value and the detection result by the resistance detection unit 82 falls below a predetermined threshold value. The unit 110 derives a transfer voltage applied to the auxiliary roll 50 based on a correction reference line F different from the derivation reference line E. As described above, when the control unit 110 derives the transfer voltage, the sheet member P heated by the fixing device 24 to fix the toner image on one side (surface) is again transferred to the secondary transfer roll 22 and the auxiliary roll 50. It is considered that the temperature of the secondary transfer roll 22 is increased by passing between the two.

  Thereby, transfer failure due to a change in the resistance value of the secondary transfer roll 22 is suppressed.

  The horizontal axis of the graph shown in FIG. 7 indicates the number of sheet members P onto which the toner images are continuously transferred on both sides by the secondary transfer roll 22 in terms of A4 size, and the vertical axis indicates the secondary transfer roll 22. The resistance value is shown. The speed at which the toner image is transferred onto one side of the A4 size sheet member P by the secondary transfer roll 22 is 70 sheets / minute.

  As described in the first embodiment, the detection result by the resistance detection unit 82 until the number of sheet members P onto which the toner images are continuously transferred on both sides by the secondary transfer roll 22 reaches about 800 from this graph. Falls below a predetermined threshold value, and thereafter, the resistance value remains flat. However, since the sheet member P heated by the fixing device 24 to fix the toner image on one side (front surface) passes again between the secondary transfer roll 22 and the auxiliary roll 50, the resistance of the secondary transfer roll 22 is increased. About the fall range of a value, it becomes large compared with the case of 1st Embodiment.

<Fourth embodiment>
Next, an example of an image forming apparatus according to the fourth embodiment of the present invention will be described with reference to FIG. In addition, about the same member as 3rd Embodiment, the same code | symbol is attached | subjected, the description is abbreviate | omitted, and a different part from 3rd Embodiment is mainly demonstrated.

  The fixing device 24 according to the fourth embodiment can be operated in a low temperature fixing mode and a high temperature fixing mode. For example, when fixing a toner image on plain paper, the fixing device 24 operates in a low-temperature fixing mode, and when fixing a toner image on thick paper, the fixing device 24 operates in a high-temperature fixing mode. Yes.

  Further, as illustrated in FIG. 8, the image forming apparatus 10 includes a control unit 120 that controls the voltage application unit 80 and changes the transfer voltage according to the detection result of the resistance detection unit 82.

  Specifically, when the fixing device 24 operates in the high-temperature fixing mode, the number of sheet members P onto which the toner images are continuously transferred on both sides reaches a predetermined threshold value, and the detection by the resistance detection unit 82 is performed. When the result falls below a predetermined threshold, the control unit 120 derives the voltage applied to the auxiliary roll 50 based on the correction reference line F different from the derivation reference line E. . As described above, when the control unit 120 derives the transfer voltage, it is considered that the temperature of the secondary transfer roll 22 increases due to the heat generated by the fixing device 24.

  Thereby, transfer failure due to a change in the resistance value of the secondary transfer roll 22 is suppressed.

  The time between the previous sheet member P to which the toner image is transferred by the secondary transfer roll 22 and the subsequent sheet member P is within one hour, and the previous sheet member P and the subsequent sheet When the toner image is fixed on the member P by the fixing device 24 in the high-temperature fixing mode, the counter 112 continuously transfers the toner image by the secondary transfer roll 22 between the previous sheet member P and the subsequent sheet member P. Remember that it was done.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments can be taken within the scope of the present invention. This will be apparent to those skilled in the art. For example, in the above-described embodiment, the present embodiment has been described using the secondary transfer roll 22 that transfers the toner image transferred to the intermediate transfer belt 42 to the sheet member P. However, the present embodiment is placed on the image carrier. The formed toner image may be used for a transfer roll or the like for directly transferring the toner image to the sheet member P (direct transfer).

  In the above embodiment, the case where the transfer voltage is applied (supplied) to the auxiliary roll 50 has been described as an example. However, a transfer current may be supplied to the auxiliary roll.

  In the above embodiment, the case where the transfer voltage is applied (supplied) to the auxiliary roll 50 has been described as an example. However, the transfer voltage may be applied to the secondary transfer roll, and further, the transfer voltage may be transferred to the secondary transfer roll. An electric current may be supplied.

  In the above embodiment, the correction reference line F maintains the inclination of the derivation reference line E and reduces the voltage by a certain value. However, the inclination of the derivation reference line E may be changed.

  Further, although not particularly described in the above embodiment, the mode provided in each embodiment may be selectively usable by one image forming apparatus.

  In the above embodiment, the reference for deriving the transfer voltage is changed in order to suppress the transfer failure caused by the secondary transfer roll 22 becoming hot and the resistance value of the secondary transfer roll 22 changing. In order to suppress the temperature rise of the secondary transfer roll 22, a fan for cooling the secondary transfer roll 22 may be operated as appropriate to suppress the temperature rise of the secondary transfer roll 22. In addition, the amount of heat transferred from the sheet member P to the secondary transfer roll 22 can be reduced by increasing the time between the timing of fixing the toner image on the front surface and the timing of fixing the toner image on the back surface. In general, when transferring the toner image on both sides, only the resistance value of the secondary transfer roll 22 measured after the toner image is transferred to the back surface of the sheet member P is used to transfer the transfer image applied to the auxiliary roll 50. It may derive.

10 Image forming apparatus 22 Secondary transfer roll (an example of a transfer member)
24 Fixing device (an example of a fixing member)
50 Auxiliary roll (example of electrode)
82 Resistance detection unit (an example of a detection member)
84 Control part (an example of a control member)
100 control unit (an example of a control member)
110 Control Unit (Example of Control Member)
120 control unit (an example of a control member)

Claims (4)

A transfer member having a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with the electrode, and transferring a toner image to the recording medium by a potential difference generated between the electrode;
A detection member for detecting a resistance value of the transfer member;
A recording in which a toner image is continuously transferred by the transfer member by changing a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a derivation criterion predetermined according to a detection result of the detection member. When the number of media reaches a predetermined threshold and the detection result falls below a predetermined threshold, based on a correction criterion different from the derivation criterion depending on the detection result of the detection member A control member for changing a transfer voltage or a transfer current supplied to the transfer member or the electrode;
An image forming apparatus comprising: A transfer member having a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with the electrode, and transferring a toner image to the recording medium by a potential difference generated between the electrode;
A detection member for detecting a resistance value of the transfer member;
A fixing member that is operable in a low-temperature fixing mode and a high-temperature fixing mode, and fixes the toner image transferred to the recording medium to the recording medium by heat;
The transfer voltage or transfer current supplied to the transfer member or the electrode is changed on the basis of a derivation criterion determined in advance according to the detection result of the detection member, and the transfer is performed while the fixing member is operating in a high-temperature fixing mode. When the number of recording media onto which the toner images are continuously transferred by the member reaches a predetermined threshold value and the detection result falls below a predetermined threshold value, the detection result of the detection member is A control member that changes a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a correction criterion different from the derivation criterion;
An image forming apparatus comprising: A transfer member having a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with the electrode, and transferring a toner image to the recording medium by a potential difference generated between the electrode;
A detection member for detecting a resistance value of the transfer member;
A transfer voltage or a transfer current supplied to the transfer member or the electrode is changed based on a derivation criterion determined in advance according to a detection result of the detection member, and a toner image is continuously transferred to both surfaces by the transfer member. When the number of recording media reaches a predetermined threshold value and the detection result falls below a predetermined threshold value, the correction criterion differs from the derivation criterion according to the detection result of the detection member. A control member for changing a transfer voltage or a transfer current supplied to the transfer member or the electrode,
An image forming apparatus comprising: A transfer member having a semiconductive layer containing an ionic conductive agent, sandwiching a recording medium with the electrode, and transferring a toner image to the recording medium by a potential difference generated between the electrode;
A detection member for detecting a resistance value of the transfer member;
A fixing member that is operable in a low-temperature fixing mode and a high-temperature fixing mode, and fixes the toner image transferred to the recording medium to the recording medium by heat;
The transfer voltage or transfer current supplied to the transfer member or the electrode is changed on the basis of a derivation criterion determined in advance according to the detection result of the detection member, and the transfer is performed while the fixing member is operating in a high-temperature fixing mode. The detection result of the detection member when the number of recording media onto which the toner images are continuously transferred on both sides by the member reaches a predetermined threshold value and the detection result falls below a predetermined threshold value And a control member that changes a transfer voltage or a transfer current supplied to the transfer member or the electrode based on a correction criterion different from the derivation criterion,
An image forming apparatus comprising:

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