JP2008152166A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform image forming operation in such a state that appropriate transfer voltage is applied to a transfer roller while decreasing frequency of performing detecting operation of ATVC (automatic transfer voltage control). <P>SOLUTION: The image forming apparatus is equipped with: the transfer roller 40 interposing a material 46 to be transferred with an image carrier 30 in order to transfer the toner image on the image carrier 30 to the material 46; a transfer voltage applying device 24 applying the transfer voltage Vt to the transfer roller 40; and a control part 66 performing the detecting operation of the electric resistance value of the transfer roller 40 or the substitutive value of the electric resistance value and then performing the ATVC control for deciding the optimum transfer voltage Vt in accordance with the electric resistance value or the substitutive value. In the image forming apparatus, the control part 66 sets so that the detecting operation of the ATVC control may be performed at a predetermined detecting interval A during consecutive printing, and sets a plurality of detecting intervals A in accordance with the electric resistance value of the secondary transfer roller 40 or the substitutive value thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method, and more particularly, to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having these functions combined, and these image forming apparatuses. The present invention relates to an image forming method for forming an image using the image forming method.

  As a color image forming apparatus, a so-called 4-cycle type or so-called tandem type image forming apparatus is known. In these color image forming apparatuses, the toner image formed on the surface of the electrostatic latent image carrier is transferred to the intermediate transfer member passing through the nip portion at the nip portion between the electrostatic latent image carrier and the primary transfer roller. (Primary transfer), and a four-color toner image is superimposed on the intermediate transfer member by the primary transfer, thereby forming a full-color image. The full-color image is transferred (secondary transfer) to a transfer material such as paper passing through the nip portion at the nip portion between the intermediate transfer member and the secondary transfer roller.

  During primary transfer, an electric field is formed between the electrostatic latent image carrier and the primary transfer roller to move the toner from the electrostatic latent image carrier to the intermediate transfer member. A transfer voltage having the opposite polarity is applied. Similarly, during secondary transfer, an electric field that moves toner from the intermediate transfer member to the transfer material is formed between the intermediate transfer member and the secondary transfer roller. A transfer voltage having the opposite polarity is applied.

  For this reason, conductive rollers are used as the primary transfer roller and the secondary transfer roller, and in recent years, ion conductive rollers having excellent uniformity in electrical resistance are often used. When the ion conductive roller is used as a primary transfer roller or a secondary transfer roller, high transfer performance can be obtained, so that the image quality can be improved.

  However, since the electric resistance value of the ion conductive roller greatly changes due to the change in the temperature and humidity environment in the machine, the optimum transfer voltage to be applied to the roller also changes as the electric resistance value changes. Therefore, when an ion conductive roller is used as the primary transfer roller or the secondary transfer roller, it is necessary to control the magnitude of the transfer voltage applied to the roller according to the change in the electrical resistance value of the roller.

As one method for controlling the transfer voltage, ATVC (Auto Transfer Voltage Control) control has been proposed. The ATVC control is optimized based on the detected voltage, a preset table and an arithmetic expression after performing a detection operation of detecting a voltage when a constant current is passed through the transfer roller as a substitute value of the electric resistance value. The transfer voltage is determined. The ATVC control is a control used for both the transfer voltage of the primary transfer roller and the transfer voltage of the secondary transfer roller. For example, Patent Document 1 discloses a specific configuration of ATVC control for the primary transfer roller. It is disclosed.
JP 2003-156916 A

  By the way, when an ion conductive roller is used as the secondary transfer roller, a temperature / humidity sensor is installed in the vicinity of the secondary transfer roller in order to cope with a change in the electrical resistance of the secondary transfer roller accompanying an increase in the internal temperature during continuous printing. A technique has been proposed in which an ATVC control detection operation is performed in response to a change in the internal environment near the secondary transfer roller.

  However, when the temperature / humidity sensor is used, there are problems such as an increase in cost and a difficulty in positioning the temperature / humidity sensor for accurately detecting the in-machine environment near the secondary transfer roller.

  In view of such a problem, a technique has been proposed in which the detection operation of ATVC control is performed every certain number of prints during continuous printing.

  However, in the setting that the ATVC control detection operation is performed every certain number of prints during continuous printing, in order to always apply an appropriate transfer voltage to the secondary transfer roller during continuous printing, the detection operation of ATVC control is performed. It is necessary to set so that it is frequently executed at a short interval, and print productivity decreases.

  Therefore, the present invention provides an image forming apparatus and an image forming method capable of executing an image forming operation in a state where an appropriate transfer voltage is applied to a transfer roller while reducing the frequency with which an ATVC control detection operation is performed. For the purpose.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A transfer roller for clamping the transfer material together with the image carrier to transfer the toner image on the image support to the transfer material;
A transfer voltage applying device for applying a transfer voltage to the transfer roller;
A controller for performing ATVC control for determining an optimum magnitude of the transfer voltage corresponding to the magnitude of the electrical resistance value or the substitute value after the operation of detecting the electrical resistance value of the transfer roller or the substitute value of the electrical resistance value An image forming apparatus comprising:
The control unit is set so that the detection operation of the ATVC control is executed at predetermined detection intervals during continuous printing, and the detection interval is the magnitude of the electric resistance value or the substitute value. It is characterized in that a plurality are set according to the above.

An image forming method according to the present invention includes:
A transfer roller for clamping the transfer material together with the image carrier to transfer the toner image on the image support to the transfer material;
Using an image forming apparatus provided with a transfer voltage applying device that applies a transfer voltage to the transfer roller,
Image formation for performing ATVC control for determining the optimum transfer voltage magnitude according to the magnitude of the electrical resistance value or the substitute value after the operation of detecting the electrical resistance value of the transfer roller or the substitute value of the electrical resistance value A method,
During continuous printing, the detection operation of the ATVC control is performed at predetermined detection intervals,
A plurality of the detection intervals are set according to the magnitude of the electric resistance value or the substitute value so as to increase as the electric resistance value decreases.

  According to the present invention, during continuous printing, the detection operation of ATVC control is performed at a predetermined detection interval, and the detection interval depends on the magnitude of the electric resistance value of the transfer roller or the substitute value of the electric resistance value. Multiple settings are made. Therefore, when the change amount of the electrical resistance value of the transfer roller is small, the frequency of the detection operation of the ATVC control can be reduced by setting the detection interval to be large according to the electrical resistance value of the transfer roller or a substitute value thereof. On the other hand, when the amount of change in the electrical resistance value of the transfer roller is large, the ATVC control is performed at an appropriate frequency by setting the detection interval relatively small in accordance with the electrical resistance value of the transfer roller or its substitute value. An appropriate transfer voltage can be applied. Therefore, the image forming operation can be executed in a state where an appropriate transfer voltage is applied to the transfer roller while reducing the frequency of ATVC control according to the electric resistance value of the transfer roller or a substitute value thereof.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, terms indicating a specific direction and position (for example, “up”, “down”, “right”, “left” and other terms including those terms) are used as necessary. These terms are used for easy understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms.

  FIG. 1 shows a schematic configuration of an image forming apparatus 2 according to an embodiment of the present invention.

  The image forming apparatus 2 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-function machine having a combination of these functions. Currently, various types of electrophotographic image forming apparatuses have been proposed. The illustrated image forming apparatus is a so-called four-cycle color image forming apparatus. However, the present invention is not applied only to this type of image forming apparatus, and other forms of image forming apparatuses such as a so-called tandem color image forming apparatus or a monochrome apparatus having only one developing device. The present invention is equally applicable to image forming apparatuses.

  The image forming apparatus 2 includes a photoconductor 4 as an image carrier at a substantially central portion inside. The photoreceptor 4 is rotationally driven in the clockwise direction in the drawing by a drive motor (not shown).

  Around the photoconductor 4, a charging device (a scorotron charger in the example in the figure) 8 for uniformly charging the surface of the photoconductor 4 in order along the rotation direction (clockwise direction in the drawing), and the photoconductor 4. An exposure device 10 for sequentially forming an electrostatic latent image of each color on the upper surface, a developing device 12 for sequentially supplying toner of each color to the photoconductor 4 and thereby revealing the electrostatic latent image, and on the photoconductor 4 In order to transfer the toner image to an intermediate transfer belt 30 described later, a primary transfer roller 14 that sandwiches the intermediate transfer belt 30 together with the photoreceptor 4 and a photoreceptor cleaning blade 16 are disposed.

  The developing device 12 includes four developing units 18 (18Y, 18M, 18C, and 18K) containing yellow (Y), magenta (M), cyan (C), and black (K) toners in the clockwise direction in the drawing. The components are sequentially attached to the developing device rack 20 while being shifted by 90 °, and can be rotated in the counterclockwise direction in FIG. In the developing device 12, each time an electrostatic latent image of each color is formed on the photoconductor 4, the corresponding developing roller 22 (22 </ b> Y, 22 </ b> M, 22 </ b> C, 22 </ b> K) of the developing device 18 approaches or contacts the photoconductor 4. Rotate to move to development position. A predetermined developing bias voltage is appropriately applied to the developing roller 22 from a power source (not shown).

  Each developing device 18 contains one-component toner or two-component toner. Although not shown in the drawings, each developing device 18 regulates the supply roller that supplies toner to the developing roller 22 and the layer thickness of the toner carried on the developing roller 22, and the toner layer has a predetermined charge amount. It has a regulating member that charges the battery.

  The photosensitive member cleaning blade 16 is in contact with the surface of the photosensitive member 4 at the tip, and the blade 16 scrapes off toner remaining on the surface of the photosensitive member 4 after the primary transfer.

  An intermediate transfer belt 30 is disposed above the photoconductor 4 as an intermediate transfer member. The intermediate transfer belt 30 is supported on the outer peripheral portions of the plurality of rollers 14, 32, 34, 36, and 38 and is driven to rotate counterclockwise in the drawing. The roller 32 is connected to a drive motor (not shown), and the remaining rollers 14, 34, 36 and 38 are driven to rotate as the roller 32 rotates.

  The image forming apparatus 2 has a color mode in which a color image is formed by superimposing and transferring four color toner images on the intermediate transfer belt 30, and a monochrome mode by transferring only a black toner image on the intermediate transfer belt 30. It is possible to switch between a monochrome mode for forming an image.

  Inside the intermediate transfer belt 30, the above-described primary transfer roller 14 is disposed to face the photoconductor 4 with the intermediate transfer belt 30 interposed therebetween. The primary transfer roller 14 is provided in a state in which it is always in pressure contact with the intermediate transfer belt 30.

  A secondary transfer roller 40 and an intermediate transfer belt cleaning blade 42 are disposed outside the intermediate transfer belt 30.

  The secondary transfer roller 40 can be switched between a state where it is pressed against a portion of the intermediate transfer belt 30 supported by the roller 32 and a state where it is separated from the intermediate transfer belt 30. As the secondary transfer roller 40, a material having ion conductivity is used, and specifically, for example, epichlorohydrin rubber, acrylonitrile butadiene rubber (NBR), or the like is used.

  A nip portion between the secondary transfer roller 40 and the intermediate transfer belt 30 forms a secondary transfer region 41, and a recording medium 46 such as a sheet passing through the secondary transfer region 41 is transferred to the intermediate transfer belt 30 and the secondary transfer roller. 40.

  A power supply 24 (corresponding to a transfer voltage applying device in claims) is connected to the secondary transfer roller 40 via the control circuit 26, and a transfer voltage is applied to the secondary transfer roller 40 by the power supply 24. .

  The intermediate transfer belt cleaning blade 42 can be switched between a state in which the tip thereof is in contact with a portion of the intermediate transfer belt 30 supported by the roller 36 and a state in which the intermediate transfer belt 30 is separated from the intermediate transfer belt 30. When the edge of the intermediate transfer belt cleaning blade 42 is in contact with the intermediate transfer belt 30, the toner remaining on the surface of the intermediate transfer belt 30 after the secondary transfer is scraped off by the blade 42.

  A paper feed cassette 44 is detachably disposed below the image forming apparatus 2. The recording medium 46 loaded and accommodated in the paper feeding cassette 44 is changed from the top one by the rotation of the paper feeding member 48 disposed at a position facing the vicinity of the front end of the recording medium 46 loaded in the paper feeding cassette 44. Each sheet is sent out to the conveyance path 50.

  The conveyance path 50 passes from the paper feed cassette 44 through the nip portion of the timing roller pair 52, the secondary transfer region 41, the nip portion of the fixing roller pair 56, and the nip portion of the paper discharge roller pair 60 to the image forming apparatus 2. It extends to the paper discharge unit 64 provided on the top of the paper.

  On the upper part of the image forming apparatus 2, a control unit 66 that performs ATVC control for determining an optimum magnitude of the transfer voltage Vt applied to the secondary transfer roller 40 after a predetermined detection operation is provided. However, the position where the control unit 66 is arranged in the image forming apparatus 2 is not particularly limited. ATVC control will be described later.

  Next, an image forming operation in the color mode of the image forming apparatus 2 will be described.

  First, when the control unit 66 receives a print signal transmitted from an external terminal or an operation unit, the photosensitive member 4 and the intermediate transfer belt 30 start to rotate at a predetermined timing.

  Subsequently, a charging process for stabilizing the charged potential on the surface of the photoconductor 4 is started, and the developing device rack 20 is driven to rotate so that the developing device 18Y containing yellow toner is disposed opposite to the photoconductor 4. The

  Thereafter, the photosensitive member 4 is exposed at a predetermined timing, and the driving of the developing unit 18Y containing yellow toner is started. Further, a transfer voltage is applied to the primary transfer roller 14 at a predetermined timing.

  When the photosensitive member 4 is exposed, an electrostatic latent image for a yellow image is formed on the photosensitive member 4, and the electrostatic latent image is made visible by yellow toner supplied from the developing unit 18Y. When the yellow toner image formed on the photoconductor 4 in this way reaches the primary transfer region facing the primary transfer roller 14 with the intermediate transfer belt 30 interposed therebetween due to the rotation of the photoconductor 4, Primary transfer is performed on the intermediate transfer belt 30.

  After the primary transfer, the toner remaining on the photoconductor 4 is scraped off at the edge of the cleaning blade 16 when reaching the contact portion between the photoconductor 4 and the cleaning blade 16.

  The developing device 18Y containing yellow toner is stopped driving at a predetermined timing, and the development and primary transfer of the yellow image are completed. Thereafter, the charging process of the photosensitive member 4 is performed again, and the developing device rack 20 is rotationally driven, so that the developing device 18M containing magenta toner is disposed to face the photosensitive member 4.

  Subsequently, as in the case of forming a yellow toner image, development and primary transfer of a magenta image, and cleaning of the surface of the photoreceptor 4 by a cleaning blade are performed. The magenta toner image is superimposed and transferred onto the yellow toner image on the intermediate transfer belt 30 during the primary transfer.

  Similarly, the cyan and black toner images are also sequentially transferred onto the intermediate transfer belt 30 and the four color toner images are superimposed on the intermediate transfer belt 30.

  On the other hand, the controller 66 performs ATVC control, which will be described later, and after the transfer voltage determined by the ATVC control is applied to the secondary transfer roller 40, the four color toner images superimposed on the intermediate transfer belt 30 are intermediate. It is conveyed to the secondary transfer area 41 by the transfer belt 30. Further, the recording medium 46 accommodated in the paper feed cassette 44 is conveyed to the secondary transfer area 41 in accordance with the timing.

  Subsequently, in the secondary transfer region 41, the four color toner images are transferred from the intermediate transfer belt 30 to the recording medium 46. The recording medium 46 to which the toner image has been transferred is conveyed further downstream in the conveying path 50, and after the toner image is fixed to the recording medium 46 by the fixing roller 56, it is sent out to the paper discharge unit 64 by the paper discharge roller 60. .

  Thereafter, the application of the transfer voltage to the secondary transfer roller 40 is stopped at a predetermined timing, and the intermediate transfer belt cleaning blade 42 is brought into pressure contact with the intermediate transfer belt 30 at a predetermined timing. The toner remaining on the transfer belt 30 is scraped off by the blade 42.

  Next, ATVC control for determining the transfer voltage of the secondary transfer roller 40 will be described.

  The ATVC control is a control performed to determine an optimum transfer voltage Vt in response to a change in the electrical resistance of the secondary transfer roller 40 that changes with a change in the internal environment. It is executed during continuous printing.

  A specific example of the flow of each process in the ATVC control executed during continuous printing will be described with reference to the flowchart shown in FIG.

  First, in step 1, the atmospheric temperature and the relative humidity in the apparatus detected by a temperature / humidity sensor (not shown) installed for the purpose of detecting the wetness of the recording medium 46, etc. are read by the controller 66, and the next step 2, the absolute humidity step corresponding to the preset absolute humidity step among a plurality (15 in the embodiment) of absolute humidity steps based on the absolute humidity information calculated from the atmospheric temperature and relative humidity information by the control unit 66. Is selected.

  In subsequent step 3, information on the image forming mode is read by the control unit 66. Specifically, information indicating whether the mode is the monochrome mode or the color mode and information indicating whether the mode is single-sided printing or double-sided printing are read.

  In step 4, the detection operation of ATVC control is performed. Specifically, a voltage is applied to the secondary transfer roller 40 by the power supply 24 in a state where there is no recording medium 46 in the secondary transfer area 41. At this time, the control circuit 26 controls so that the current supplied to the secondary transfer roller 40 becomes a constant current having a predetermined magnitude.

  In step 5, the constant current voltage applied to the secondary transfer roller 40 by the detection operation in step 4 is detected as a substitute value for the electrical resistance value of the secondary transfer roller 40 by a voltmeter or the like (not shown), and is controlled by the controller 66. It is read as the detection voltage Vd.

In subsequent step 6, the control unit 66 determines the voltage derived from the information of the detection voltage Vd, a preset table (see FIG. 3), and the following equation (1) as the transfer voltage Vt.
(Transfer voltage Vt) = (slope A) × (detection voltage Vd) + (offset B) (1)

Two tables are set for each type of the recording medium 46: printing on the first surface of the recording medium 46 and printing on the second surface of the recording medium 46. Therefore, when determining the transfer voltage Vt, the corresponding table is selected from a plurality of tables prepared in advance based on the type of the recording medium 46 and information on the surface to be printed (first surface or second surface). Selected. For example, FIG. 3 shows a table for printing on the first surface of plain paper having a basis weight of 100 g / m ² or less.

  In each table, for example, as shown in FIG. 3, for each absolute humidity step, the values of slope A and offset B when printing in the color mode and the values of slope A and offset B when printing in the monochrome mode are prepared. Has been. Accordingly, when the table is selected, the corresponding value of the slope A and the value of the offset B are determined based on the information on the absolute humidity step and the information on the image forming mode (color mode or monochrome mode). The value of the slope A and the value of the offset B determined in this way are substituted into the above equation (1) together with the value of the detection voltage Vd, whereby the transfer voltage Vt is calculated, and the ATVC control is finished.

  In step 7, the control unit 66 determines whether or not the continuous print number is equal to or less than a preset detection interval A (sheets). The detection interval A will be described later.

  If it is determined in step 7 that the number of continuous prints is equal to or smaller than the detection interval A, the process proceeds to step 8, and after all the continuous prints are executed in step 8, the process ends. On the other hand, if it is determined in step 7 that the number of continuous prints is greater than the detection interval A, the process proceeds to step 9.

  In step 9, continuous printing of A sheets is executed in a state where the transfer voltage Vt determined by the ATVC control is applied to the secondary transfer roller 40.

  In the subsequent step 10, the detection operation of the secondary transfer roller 40 is performed as in step 4. In the next step 11, the detection voltage Vd is read in the same manner as in step 5, and in the subsequent step 12, the transfer voltage Vt is determined in the same manner as in step 6, and the process proceeds to step 13.

  In step 13, it is determined whether or not the remaining number of prints is equal to or less than the detection interval A.

  If it is determined in step 13 that the remaining number of prints is equal to or smaller than the detection interval A, the process proceeds to step 8, and after the continuous printing of all remaining sheets is performed in step 8, the process ends.

  On the other hand, if it is determined in step 13 that the remaining number of prints is larger than the detection interval A, the process returns to step 9, and after continuous printing of A sheets is executed again in step 9, the transfer is performed from the detection operation (step 10). After a series of operations up to the determination of the voltage Vt (step 12), the process proceeds to step 13. Such a series of operations is repeated until the remaining number of prints is equal to or less than the detection interval A.

  Subsequently, after describing the relationship between the internal environment in the vicinity of the secondary transfer roller 40 and the detection voltage Vd, the detection interval A representing the frequency of the detection operation of the ATVC control will be described.

  FIG. 4 is a graph showing the relationship between the ambient temperature and the detection voltage Vd when the absolute humidity is assumed to be constant with respect to the in-machine environment near the secondary transfer roller 40. As shown in FIG. 4, the detection voltage Vd increases as the ambient temperature is lower, particularly in a low humidity environment. Further, the amount of change in the detection voltage Vd increases as the ambient temperature is low, and decreases as the ambient temperature is high. That is, the amount of change in the detection voltage Vd increases as the detection voltage Vd increases, and decreases as the detection voltage Vd decreases. Therefore, when the detection voltage Vd is relatively small, the amount of change in the detection voltage Vd is relatively small, so that good secondary transfer can be performed without frequently performing the detection operation of the ATVC control. However, when the detection voltage Vd is relatively large, since the amount of change in the detection voltage Vd is relatively large, it is preferable that the frequency of the detection operation of the ATVC control be relatively high.

  In view of such a viewpoint, the control unit 66 sets a plurality of different detection intervals A according to the magnitude of the detection voltage Vd. In the embodiment, the detection interval A is defined by the number of prints during continuous printing. However, in the present invention, the detection interval can also be defined by the elapsed time after the start of continuous printing.

  The lower part of FIG. 5 and FIG. 6 shows the setting of the detection interval A according to the embodiment.

  Here, the thick line on the left side of FIG. 6 indicates the relationship between the detection voltage Vd and the transfer voltage Vt, and the area indicated by the arrow on the left side of FIG. "Transfer OW"). The solid line on the right side of FIG. 6 shows a specific example of the relationship between the ambient temperature in the vicinity of the secondary transfer roller 40 and the detection voltage Vd, and the region between the upper and lower broken lines in the right side of FIG. It shows the range of variation. In the lower part of FIG. 6, specific numerical values (the numerical values described in FIG. 5) of the detection interval A set in accordance with the detection voltage Vd are shown corresponding to the detection voltage Vd.

  As shown in the left part of FIG. 6, the transfer voltage Vt is determined according to the magnitude of the detection voltage Vd. Therefore, for example, when the detection voltage Vd decreases from 3500 V to 3000 V as the ambient temperature near the secondary transfer roller 40 increases, the range of the transfer OW changes as the detection voltage Vd decreases. Vt becomes a predetermined magnitude within the range of the transfer OW before and after the detection voltage Vd decreases, and secondary transfer can be performed satisfactorily.

  As shown by the upper broken line in the right part of FIG. 6, when the change amount of the detection voltage Vd accompanying the change in the ambient temperature of the secondary transfer roller 40 is remarkably large, if the detection interval A is constant as in the conventional case, When the detection voltage Vd is large, the frequency of the detection operation of the ATVC control is remarkably insufficient, and there is a possibility that the image forming operation is executed with an inappropriate transfer voltage applied to the secondary transfer roller 40. On the other hand, when the amount of change in the detection voltage Vd accompanying the change in the ambient temperature of the secondary transfer roller 40 is remarkably small as indicated by the broken line on the lower side of the right part of FIG. For example, particularly when the detection voltage Vd is small, the frequency of the detection operation of the ATVC control becomes excessive, and the print productivity during continuous printing is significantly reduced.

  As shown in FIGS. 5 and 6, the detection interval A according to the present embodiment is set individually for printing in the monochrome mode and for printing in the color mode. Specifically, the detection interval A is set smaller in the color mode than in the monochrome mode. This is because when printing in the color mode, the range of the transfer OW is narrower than when printing in the monochrome mode, and therefore it is preferable that the frequency of the ATVC control detection operation be higher than that in the monochrome mode.

  In addition, the detection interval A is individually set for single-sided printing and double-sided printing in each of the monochrome mode and the color mode. Specifically, the detection interval A is set smaller for double-sided printing than for single-sided printing. When performing double-sided printing, the range of transfer OW is narrower than that for single-sided printing, and the ambient temperature in the machine rises faster than for single-sided printing. Therefore, the frequency of ATVC control detection operations is higher than in monochrome mode. This is because a higher value is preferable.

  5 and 6, each numerical value of the detection interval A at the time of double-sided printing is a numerical value obtained by counting that one sheet is printed when both sides are printed.

  In each image forming mode (monochrome / color, single side / double side), the detection interval A is set to be larger as the detection voltage Vd is smaller.

  Specifically, when single-sided printing is performed in monochrome mode, the detection interval A is 12 sheets when the detection voltage Vd is 3500 V or more, 24 sheets when the detection voltage Vd is 3000 V or more and less than 3500 V, and the detection voltage Vd is 2500 V or more and 3000 V. 36 sheets when the detection voltage Vd is 2000V or more and less than 2500V, 96 sheets when the detection voltage Vd is 1500V or more and less than 2000V, and 182 sheets when the detection voltage Vd is 1000V or more and less than 1500V. When the voltage Vd is less than 1000 V, it is set to 182 sheets.

  When performing duplex printing in monochrome mode, the detection interval A is 6 when the detection voltage Vd is 3500 V or more, 12 when the detection voltage Vd is 3000 V or more and less than 3500 V, and when the detection voltage Vd is 2500 V or more and less than 3000 V. 18 sheets, 24 sheets when the detection voltage Vd is 2000 V or more and less than 2500 V, 48 sheets when the detection voltage Vd is 1500 V or more and less than 2000 V, 96 sheets when the detection voltage Vd is 1000 V or more and less than 1500 V, and the detection voltage Vd is 1000 V When the number is less than 96, the number is set to 96.

  When printing on one side in the color mode, the detection interval A is 4 when the detection voltage Vd is 3500 V or more, 8 when the detection voltage Vd is 3000 V or more and less than 3500 V, and when the detection voltage Vd is 2500 V or more and less than 3000 V. 12 sheets, 16 sheets when the detection voltage Vd is 2000 V or more and less than 2500 V, 32 sheets when the detection voltage Vd is 1500 V or more and less than 2000 V, 64 sheets when the detection voltage Vd is 1000 V or more and less than 1500 V, and the detection voltage Vd is 1000 V If it is less than 64, the number is set to 64.

  When performing duplex printing in the color mode, the detection interval A is 2 when the detection voltage Vd is 3500 V or more, 4 when the detection voltage Vd is 3000 V or more and less than 3500 V, and when the detection voltage Vd is 2500 V or more and less than 3000 V. 6 sheets, 8 sheets when the detection voltage Vd is 2000 V or more and less than 2500 V, 16 sheets when the detection voltage Vd is 1500 V or more and less than 2000 V, 32 sheets when the detection voltage Vd is 1000 V or more and less than 1500 V, and the detection voltage Vd is 1000 V If it is less than 32, it is set to 32 sheets.

  Therefore, the smaller the detection voltage Vd, the lower the frequency of ATVC control detection operation. When the detection voltage Vd is relatively small, it is possible to maintain good print productivity during continuous printing. Further, as described above, when the detection voltage Vd is small, the amount of change in the detection voltage Vd is small, so that the secondary transfer can be performed satisfactorily even if the detection operation frequency of the ATVC control is low.

  On the contrary, the detection interval A is set to be smaller as the detection voltage Vd is larger. Therefore, the detection operation frequency of the ATVC control is higher as the detection voltage Vd is larger. Therefore, when the detection voltage Vd is relatively large and the amount of change in the detection voltage Vd is large, the detection operation of the ATVC control is performed relatively frequently, so that the secondary transfer can be performed satisfactorily.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, in the above-described embodiment, the case where a plurality of detection intervals A are set according to the magnitude of the detection voltage Vd that is a substitute value of the electrical resistance value of the secondary transfer roller 40 has been described. A may be set in plural according to the magnitude of the electrical resistance value of the secondary transfer roller 40. In this case, the detection interval A is set to be larger as the electrical resistance value of the secondary transfer roller 40 is smaller. Is preferred.

  In the above-described embodiment, the configuration of the ATVC control for determining the magnitude of the transfer voltage applied to the secondary transfer roller has been described. However, the present invention describes the ATVC control for determining the transfer voltage applied to the primary transfer roller. The same applies to.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows the flow of the process of ATVC control performed during continuous pudding. It is a specific example of a table used for determination of ATVC control. 6 is a graph showing a relationship between an ambient temperature in the vicinity of a secondary transfer roller and a detection voltage. It is a table | surface which shows the specific numerical value of the detection interval A. It is a graph which shows the numerical value of the detection interval A shown in FIG. 5 corresponding to the detection voltage Vd.

Explanation of symbols

2: Image forming apparatus,
24: Transfer voltage application device (power supply),
30: Image carrier (intermediate transfer belt),
40: transfer roller (secondary transfer roller),
46: Transfer material (recording medium),
66: Control unit.

Claims (4)

A transfer roller for clamping the transfer material together with the image carrier to transfer the toner image on the image support to the transfer material;
A transfer voltage applying device for applying a transfer voltage to the transfer roller;
A controller for performing ATVC control for determining an optimum magnitude of the transfer voltage corresponding to the magnitude of the electrical resistance value or the substitute value after the operation of detecting the electrical resistance value of the transfer roller or the substitute value of the electrical resistance value An image forming apparatus comprising:
The control unit is set so that the detection operation of the ATVC control is executed at predetermined detection intervals during continuous printing, and the detection interval is the magnitude of the electric resistance value or the substitute value. A plurality of image forming apparatuses are set in accordance with the image forming apparatus.   2. The image forming apparatus according to claim 1, wherein in the control unit, the detection interval is set to be larger as the electrical resistance value is smaller.   The image forming apparatus according to claim 1, wherein the detection interval is defined by the number of prints during continuous printing. A transfer roller for clamping the transfer material together with the image carrier to transfer the toner image on the image support to the transfer material;
Using an image forming apparatus provided with a transfer voltage applying device that applies a transfer voltage to the transfer roller,
Image formation for performing ATVC control for determining the optimum transfer voltage magnitude according to the magnitude of the electrical resistance value or the substitute value after the operation of detecting the electrical resistance value of the transfer roller or the substitute value of the electrical resistance value A method,
During continuous printing, the detection operation of the ATVC control is performed at predetermined detection intervals,
An image forming method, wherein a plurality of the detection intervals are set according to the magnitude of the electric resistance value or the substitute value so as to increase as the electric resistance value decreases.

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