JP5130710B2 - Image forming apparatus and image forming method - Google Patents

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 in accordance with a 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. In the ATVC control, after performing a detection operation of detecting a voltage (detection voltage Vd) when a constant current is passed through the transfer roller as a substitute value of the electric resistance value, the detection voltage Vd, a preset table, and an arithmetic expression are used. Based on the above, the optimum transfer voltage is determined. A specific configuration of ATVC control is disclosed in, for example, Patent Document 1.
JP 2003-156916 A

  FIG. 7 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 made of an ion conductive material. As shown in FIG. 7, the detection voltage Vd becomes smaller as the ambient temperature is higher, particularly in a low humidity environment. Therefore, when continuous printing is performed, the ambient temperature in the apparatus increases as the number of sheets that have elapsed since the start of continuous printing increases, and the detected voltage Vd may significantly decrease as the temperature increases. Therefore, when continuously printing, in order to always apply an appropriate transfer voltage to the transfer roller, it is necessary to frequently perform an ATVC control detection operation.

  However, if the detection operation of the ATVC control is frequently executed during continuous printing, the print productivity is lowered.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus and an image forming method that can perform printing in a state where an appropriate transfer voltage is always applied to a transfer roller during continuous printing, and can improve print productivity.

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 that controls a detection operation for detecting an electric resistance value of the transfer roller or a substitute value of the electric resistance value to determine the transfer voltage during continuous printing at a predetermined detection interval; ,
The control unit
During continuous printing, the ATVC control for determining the transfer voltage at the time of printing is executed every time one sheet is printed.
In the ATVC control when performing the detection operation during continuous printing, the transfer voltage is determined based on the detection value detected by the detection operation,
In the ATVC control when not performing the detecting operation during the continuous printing, and calculates an estimated value estimated as the detection value to be detected when it is assumed that perform the detection operation, based on the estimated values the transfer voltage to determine Te,
The correction formula for calculating the estimated value is
A plurality is prepared according to the number of elapsed sheets from the start of continuous printing to the detection operation, and the estimated value is calculated according to the current elapsed number of sheets and the detection value detected in the immediately preceding detection operation. It is a function of the current number of configured passes,
The control unit
When calculating the estimated value, a correction formula corresponding to the number of sheets that has elapsed when the immediately preceding detection operation is performed is selected from the plurality of correction formulas, and the estimation is performed based on the selected correction formula. A value is calculated .

An image forming method according to the present invention includes:
Forming a toner image on the surface of the image carrier;
Determining the magnitude of the transfer voltage applied to the transfer roller in contact with the surface of the image carrier;
Applying the transfer voltage to the transfer roller;
Transporting a transfer material to a nip between the image carrier and the transfer roller;
Transferring the toner image on the image carrier to the transfer material,
An image forming method in which a detection operation of detecting an electric resistance value of the transfer roller or a substitute value of the electric resistance value for determining the transfer voltage at the time of continuous printing is performed at a predetermined detection interval,
During continuous printing, the ATVC control for determining the transfer voltage at the time of printing is executed every time one sheet is printed.
In the ATVC control when performing the detection operation during continuous printing, the transfer voltage is determined based on the detection value detected by the detection operation,
In the ATVC when not performing the detecting operation during the continuous printing, and calculates an estimated value estimated as a detection value to be detected when it is assumed that perform the detection operation, based on the estimated values the transfer voltage to determine,
The correction formula for calculating the estimated value is
A plurality is prepared according to the number of elapsed sheets from the start of continuous printing to the detection operation, and the estimated value is calculated according to the current elapsed number of sheets and the detection value detected in the immediately preceding detection operation. It is a function of the current number of configured passes,
When calculating the estimated value,
A correction formula corresponding to the number of elapsed sheets when the immediately preceding detection operation is performed is selected from the plurality of correction formulas, and the estimated value is calculated based on the selected correction formula. To do.

  According to the present invention, during continuous printing, even when the detection operation for detecting the electrical resistance value of the transfer roller or the substitute value of the electrical resistance value is not performed, the electrical resistance value of the transfer roller or the electrical resistance value The substitute value is estimated according to the detection value detected in the immediately preceding detection operation and the number of sheets or the elapsed time from the start of continuous printing, and the transfer voltage is determined based on this estimated value. Continuous printing can be performed in a state where a transfer voltage is applied to the transfer roller. In addition, since good transferability can be maintained even when the detection operation is not performed, the interval between the detection operations can be increased, and the print productivity during continuous printing can be improved.

  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 at a substantially central portion inside thereof. 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 (corresponding to an image carrier in claims) is disposed above the photosensitive member 4. 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. Specifically, for example, acrylonitrile butadiene rubber (NBR), epichlorohydrin rubber, 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.

  A control unit 66 that performs ATVC control for determining the magnitude of the transfer voltage Vt applied to the secondary transfer roller 40 is provided above the image forming apparatus 2. 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, after the transfer voltage determined by the ATVC control to be described later is applied to the secondary transfer roller 40, the four color toner images superimposed on the intermediate transfer belt 30 are transferred to the secondary transfer roller 40. The belt 30 is conveyed to the secondary transfer area 41. 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.

  ATVC control is control performed to determine an optimum transfer voltage Vt in response to a change in electrical resistance of the secondary transfer roller 40 accompanying a change in the temperature and humidity environment in the apparatus. It is executed during continuous printing. During continuous printing, ATVC control is executed for each print.

  With respect to ATVC control executed during continuous printing by the control unit 66, a specific example of the flow of each process 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 are read. In the next step 2, the atmospheric temperature is read. Based on the absolute humidity information calculated from the relative humidity information, the corresponding absolute humidity step is selected from a plurality of preset absolute humidity steps (15 in the embodiment).

  In the subsequent step 3, after the type of the recording medium 46 is read, the process proceeds to step 4.

  In step 4, information on the image forming mode is read. 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 the next step 5, the pause time of the image forming apparatus 2 before the start of continuous printing is read, and the process proceeds to step 6. Here, the pause time refers to the time elapsed from the end of the previous print operation until the start of the continuous print operation.

  In step 6, the number of sheets that have elapsed since the start of continuous printing, that is, the number of sheets of the recording medium 46 printed immediately before is read from the start of continuous printing, and the process proceeds to step 7.

  In step 7, it is determined whether or not a detection operation described later needs to be executed. The detection operation is performed at a predetermined detection interval. In the embodiment, the detection operation is performed when the number of sheets elapsed from the start of continuous printing is a predetermined number, specifically, for example, after the start of continuous printing, for example, before the first print is performed, and 50 sheets. , 200 sheets, 400 sheets and 800 sheets are printed. In step 6, it is determined that the elapsed number read in step 5 is the predetermined number (specifically, 0, 50, 200, 400, or 800), and it is necessary to execute the detection operation. Then, the process proceeds to step 8, and if it is determined that the elapsed number read in step 5 is other than the predetermined number and it is not necessary to perform the detection operation, the process proceeds to step 11.

  In step 8, a detection operation 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. Thus, the voltage when a constant current is applied to the secondary transfer roller 40 is detected as a substitute value for the electrical resistance value of the secondary transfer roller 40 by a voltmeter (not shown) or the like.

  In Step 9, after the detection voltage Vd (corresponding to the detection value in the claims) detected in the detection operation in Step 8 is read, the process proceeds to Step 10.

On the other hand, in step 11, the detection voltage Vd detected in the immediately preceding detection operation is read. For example, when the number of elapsed sheets from the start of continuous printing is greater than 50 and less than 200, the detection voltage Vd ₍₅₀₎ detected in the immediately preceding detection operation, that is, the detection operation when the number of elapsed sheets is 50 is read.

  In the following step 12, an appropriate value f is selected from a plurality of functions f (x) set in advance to calculate an estimated value Ve (an estimated value of a voltage to be detected when it is assumed that a detection operation is performed). After (x) is selected, the process proceeds to step 13. A variable x in the function f (x) represents the number of sheets that have elapsed since the start of continuous printing. A plurality of functions f (x) are set according to the type of the recording medium 46, the image forming mode (monochrome / color, single-sided / double-sided), the absolute humidity step, and the rest time of the image forming apparatus 2 before the start of continuous printing. ing. When selecting the function f (x), first, a corresponding table is selected from a plurality of tables set for each recording medium 46 based on information on the recording medium 46 (see FIG. 3). Subsequently, from among a plurality of functions f (x) prepared in the selected table, the image forming mode (monochrome / color, single side / double side), the absolute humidity step, and the image forming apparatus 2 before the start of continuous printing are performed. The corresponding function f (x) is selected based on the rest time information.

  The function f (x) necessarily depends on the type of the recording medium 46, the image forming mode (monochrome / color, single-sided / double-sided), the absolute humidity step, and the pause time of the image forming apparatus 2 before the start of continuous printing. At least one of the type of the recording medium 46, the image forming mode (monochrome / color, single-sided / double-sided), the absolute humidity step, or the pause time of the image forming apparatus 2 before the start of continuous printing. It may be set according to

In step 13, a correction formula that corrects the function f (x) according to the number of elapsed sheets is selected. The correction formula when the number of elapsed sheets from the start of continuous printing is x is expressed by the following formula (1) when the number of elapsed sheets when the immediately preceding detection operation is performed is a.
Ve = f (x) -f (a) + Vd _(a) (1)
As shown in FIG. 4, a plurality of correction formulas are prepared according to the number of elapsed sheets when the direct detection operation is performed. That is, a plurality of correction formulas that are corrected each time the detection operation is executed are prepared. When selecting a correction formula, a correction formula corresponding to the number of elapsed sheets is selected from a plurality of correction formulas. For example, when the number of elapsed sheets is 51 to 199, the following equation (2) is selected.
Ve = f (x) -f (50) + Vd ₍₅₀₎ (2)

  In the following step 14, the estimated value Ve of the voltage to be detected when the detection operation is assumed to be performed is calculated by the correction formula selected in step 13, and then the process proceeds to step 10. The estimated value Ve is estimated according to the detection voltage Vd detected in the immediately preceding detection operation and the number of elapsed sheets x since the start of continuous printing by being calculated by the correction equation (1). The estimated value Ve changes, for example, as shown in FIG. 5 as the number of elapsed sheets x increases. As described above, since the correction formula (1) is appropriately corrected according to the elapsed number of sheets x, as shown in FIG. 5, an increase in the deviation between the estimated value Ve and the detection voltage Vd as the number of elapsed sheets x increases. It is suppressed.

In step 10, the voltage derived from the information on the detection voltage Vd or the information on the estimated value Ve, a preset table (see FIG. 6), and the following equation (3) or (4) is determined as the transfer voltage Vt. Is done. Specifically, when the detection operation is performed, the transfer voltage Vt is determined from the information of the detection voltage Vd and the table and the expression (3). When the detection operation is not performed, the information of the estimated value Ve, The transfer voltage Vt is determined from the table and equation (4).
(Transfer voltage Vt) = (slope A) × (detection voltage Vd) + (offset B) (3)
(Transfer voltage Vt) = (slope A) × (estimated value Ve) + (offset B) (4)

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. 6 shows a table for printing on the first side of plain paper having a basis weight of 100 g / m ² or less.

  In each table, for example, as shown in FIG. 6, for each absolute humidity step, values of slope A and offset B when printing in the color mode and 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 thus determined are substituted into the above equation (3) or (4) together with the value of the detection voltage Vd or the estimated value Ve, thereby calculating the transfer voltage Vt. ATVC control ends.

  As described above, in the present invention, even when the detection operation is not performed during continuous printing, the estimated value Ve is calculated by the correction equation (1) using the preset function f (x). Since the transfer voltage Vt is determined based on the estimated value Ve, the printing operation can be performed with the appropriate transfer voltage Vt applied to the secondary transfer roller 40 even when the detection operation is not performed. Therefore, it is possible to perform continuous printing while maintaining good transferability of secondary transfer. In the present invention, good transferability can be maintained even when the detection operation is not performed. Therefore, the interval between the detection operations can be increased, and the print productivity during continuous printing can be improved.

  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 estimated value Ve to be detected when it is assumed that the detection operation is performed, the detection voltage Vd detected in the immediately previous detection operation, and the number of elapsed sheets x from the start of continuous printing However, the estimated value Ve can be estimated according to the detected voltage Vd detected in the immediately preceding detection operation and the elapsed time from the start of continuous printing.

  In the above-described embodiment, the configuration for determining the magnitude of the transfer voltage applied to the secondary transfer roller has been described. However, the present invention also applies to the case of determining the transfer voltage applied to the primary transfer roller. Applicable 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 the table used for determination of function f (x). It is a table | surface which shows the correction formula corresponding to the number of progress. It is a graph which shows the specific example of the estimated value Ve which changes according to the number of progress. It is a specific example of a table used for determination of transfer voltage Vt. 6 is a graph showing a relationship between an ambient temperature in the vicinity of a secondary transfer roller and a detection voltage.

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 that controls a detection operation for detecting an electric resistance value of the transfer roller or a substitute value of the electric resistance value to determine the transfer voltage during continuous printing at a predetermined detection interval; ,
The control unit
During continuous printing, the ATVC control for determining the transfer voltage at the time of printing is executed every time one sheet is printed.
In the ATVC control when performing the detection operation during continuous printing, the transfer voltage is determined based on the detection value detected by the detection operation,
In the ATVC control when not performing the detecting operation during the continuous printing, and calculates an estimated value estimated as a detection value to be detected when it is assumed that perform the detection operation, based on the estimated values the transfer voltage to determine Te,
The correction formula for calculating the estimated value is
A plurality is prepared according to the number of elapsed sheets from the start of continuous printing to the detection operation, and the estimated value is calculated according to the current elapsed number of sheets and the detection value detected in the immediately preceding detection operation. It is a function of the current number of configured passes,
The control unit
When calculating the estimated value, a correction formula corresponding to the number of sheets that has elapsed when the immediately preceding detection operation is performed is selected from the plurality of correction formulas, and the estimation is performed based on the selected correction formula. An image forming apparatus that calculates a value . The above function, the type of the transfer material, the image forming mode, cabin temperature and humidity environment, or it is a function which is set according to at least one of dwell time of continuous printing before the start of the image forming apparatus The image forming apparatus according to claim 1. Forming a toner image on the surface of the image carrier;
Determining the magnitude of the transfer voltage applied to the transfer roller in contact with the surface of the image carrier;
Applying the transfer voltage to the transfer roller;
Transporting a transfer material to a nip between the image carrier and the transfer roller;
Transferring the toner image on the image carrier to the transfer material,
An image forming method in which a detection operation of detecting an electric resistance value of the transfer roller or a substitute value of the electric resistance value for determining the transfer voltage at the time of continuous printing is performed at a predetermined detection interval,
During continuous printing, the ATVC control for determining the transfer voltage at the time of printing is executed every time one sheet is printed.
In the ATVC control when performing the detection operation during continuous printing, the transfer voltage is determined based on the detection value detected by the detection operation,
In the ATVC when not performing the detecting operation during the continuous printing, and calculates an estimated value estimated as a detection value to be detected when it is assumed that perform the detection operation, based on the estimated values the transfer voltage to determine,
The correction formula for calculating the estimated value is
A plurality is prepared according to the number of elapsed sheets from the start of continuous printing to the detection operation, and the estimated value is calculated according to the current elapsed number of sheets and the detection value detected in the immediately preceding detection operation. It is a function of the current number of configured passes,
When calculating the estimated value,
A correction formula corresponding to the number of elapsed sheets when the immediately preceding detection operation is performed is selected from the plurality of correction formulas, and the estimated value is calculated based on the selected correction formula. Image forming method. The above function, the type of the transfer material, the image forming mode, cabin temperature and humidity environment, or it is a function which is set according to at least one of dwell time of continuous printing before the start of the image forming apparatus The image forming method according to claim 3.

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