JP2012014054A - Transfer device and transfer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device and a transfer program, which can suppress generation of density unevenness in an axial direction of transfer means as compared with a case where the same transfer voltage is applied along an axial direction of a transfer roll.SOLUTION: A toner patch is formed along an axial direction of a photoreceptor drum 12. The toner patch formed on the photoreceptor drum 12 is transferred on an intermediate transfer belt 21 with a primary transfer roll 22. Density of the toner patch transferred on the intermediate transfer belt 21 is detected with a density detection sensor 26 at a plurality of positions along an axial direction of the primary transfer roll 22. Based on the detected density of the toner patch at the plurality of positions, a voltage value of auxiliary voltage for assisting the transfer voltage to be applied to the primary transfer roll 22 is set.

Description

  The present invention relates to a transfer apparatus and a transfer program.

  In Patent Document 1, a first step of transferring a first color toner onto an intermediate transfer member and detecting the toner density, a second step over the first color toner transferred to the intermediate transfer member. The toner of the first color is transferred to detect the density of the toner composed of the first color toner and the second color toner, and the toner density detected in the first step is detected in the second step. A third step of calculating the transfer efficiency when the two color toners are superimposed on the basis of the toner density, and a fourth step of determining a γ correction characteristic on the basis of the calculated transfer efficiency. A color correction method in an image forming apparatus is disclosed.

JP 2002-40745 A

  The present invention provides a transfer device and a transfer program that can suppress the occurrence of density unevenness in the axial direction of the transfer means, as compared with the case where the same transfer voltage is applied in the axial direction of the transfer roll. The purpose is to do.

  In order to achieve the above object, a first aspect of the present invention provides a toner forming means for forming a toner for measurement having a predetermined density on an image holding member along the axial direction of the image holding member, and the image holding A transfer roll for transferring the measurement toner formed on the body onto the transfer target; a transfer voltage applying means for applying a transfer voltage to the transfer roll; and an auxiliary voltage for assisting the transfer voltage applied to the transfer roll. Auxiliary voltage applying means for detecting the density of the measurement toner transferred onto the transfer medium or the measurement toner remaining on the image carrier at a plurality of positions along the axial direction of the transfer roll Density detecting means for setting, setting means for setting the auxiliary voltage corresponding to the predetermined density based on the density of the measurement toner at the plurality of positions detected by the density detecting means, and the predetermined When an image toner having a predetermined density is formed on the image carrier, control is performed such that an auxiliary voltage corresponding to the predetermined density is applied to a predetermined position at which the potential of the transfer roll decreases. Control means.

  According to a second aspect of the present invention, the setting unit calculates a density difference of the density of the measurement toner at the plurality of positions, and the auxiliary unit corresponding to the predetermined density based on the calculated density difference. Set the voltage.

  According to a third aspect of the present invention, the toner forming unit sequentially forms the measurement toners having a plurality of densities on the image holding member along the axial direction of the image holding member, and the density detecting unit includes a plurality of density detecting units. The measurement means sequentially detects the density of the measurement toner, and the setting means sets the auxiliary voltage for each of the plurality of density measurement toners.

  According to a fourth aspect of the present invention, the toner forming unit, the transfer voltage applying unit, the auxiliary voltage applying unit, and the density detecting unit are provided for each of a plurality of types of colors, and the setting unit sets the auxiliary voltage for each color. Set.

  According to a fifth aspect of the present invention, there is provided a step of forming a measurement toner having a predetermined density on the image carrier along the axial direction of the image carrier, and a measurement toner formed on the image carrier. A step of transferring onto the transfer member, a step of applying a transfer voltage to the transfer roll, a step of applying an auxiliary voltage to assist the transfer voltage to the transfer roll, and a plurality of steps along the axial direction of the transfer roll Detecting the density of the measurement toner transferred onto the transfer medium at the position or the density of the measurement toner remaining on the image holding body, and at the plurality of positions detected by the density detection means A step of setting the auxiliary voltage corresponding to the predetermined density based on the density of the measurement toner, and a case where the image toner having the predetermined density is formed on the image carrier. A transfer program for executing the steps of an auxiliary voltage corresponding to the predetermined concentration is controlled so that the potential of the transfer roll is applied to a predetermined position to decrease, the processing including the computer.

  According to the first aspect of the present invention, it is possible to suppress the occurrence of density unevenness in the axial direction of the transfer unit as compared with the case where the same transfer voltage is applied across the axial direction of the transfer roll. It has the effect.

  According to the second aspect of the present invention, it is possible to more effectively suppress the occurrence of density unevenness as compared with the case where the auxiliary voltage is set without considering the density difference of the density of the measurement toner at a plurality of positions. It has the effect that it can do.

  According to the third aspect of the present invention, there is an effect that uneven density can be effectively suppressed for each concentration as compared with the case where no auxiliary voltage is set for each of a plurality of concentrations.

  According to the fourth aspect of the present invention, it is possible to effectively suppress the density unevenness for each of the plurality of colors as compared with the case where the auxiliary voltage is not set for each of the plurality of colors.

  According to the fifth aspect of the present invention, it is possible to suppress the occurrence of density unevenness in the axial direction of the transfer unit as compared with the case where the same transfer voltage is applied across the axial direction of the transfer roll. It has the effect.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. (A) is a diagram showing how toner cannot be transferred during primary transfer, (B) is a plan view of toner formed on an intermediate transfer belt after primary transfer, and (C) is a view of a primary transfer roll in primary transfer. It is an electric potential profile of an axial direction. It is sectional drawing of a primary transfer roll. It is a schematic block diagram of a control part. It is a flowchart of the control routine performed by a control part. FIG. 6 is a diagram illustrating an example of a toner patch. It is a figure which shows an example of a table. It is a block diagram of the image forming apparatus which concerns on 2nd Embodiment. It is a block diagram of the image forming apparatus which concerns on 3rd Embodiment.

  (First embodiment)

  The first embodiment of the present invention will be described below.

  First, the image forming apparatus according to the present embodiment will be described. In this embodiment, an image forming apparatus equipped with an LED print head will be described as an example. As the exposure apparatus, a laser scanning writing apparatus that scans and exposes a photosensitive member with laser light corresponding to an image may be used instead of the LED print head.

  FIG. 1 is a schematic diagram illustrating an example of the configuration of the image forming apparatus 50. The image forming apparatus 50 is a so-called tandem digital color printer, and controls the operation of the image forming process unit 10 as an image forming unit that forms an image corresponding to the image data of each color and the operation of the image forming apparatus 50. And an image processing unit 40 that is connected to the image reading device 3 and an external device such as a personal computer (PC) 2 and performs predetermined image processing on image data received from these devices. ing.

  The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K that are arranged in parallel at regular intervals. Each of the image forming units 11Y, 11M, 11C, and 11K forms yellow (Y), magenta (M), cyan (C), and black (K) toner images. The image forming units 11Y, 11M, 11C, and 11K may be collectively referred to as “image forming unit 11”. In addition, for each member constituting each image forming unit, “Y”, “M”, “C”, and “K” at the end of the reference numerals may be omitted.

  Each of the image forming units 11 includes a photosensitive drum 12 as an image holding body that forms an electrostatic latent image and holds a toner image, and a charger 13 that uniformly charges the surface of the photosensitive drum 12 with a predetermined potential. , An LED print head (LPH) 14 as an exposure device for exposing the photosensitive drum 12 charged by the charger 13, a developing unit 15 for developing the electrostatic latent image obtained by the LPH 14, and the photosensitive drum 12 after transfer. A cleaner 16 for cleaning the surface is provided.

  The LPH 14 is a long print head having substantially the same length as the length of the photosensitive drum 12 in the axial direction. The LPH 14 is disposed around the photosensitive drum 12 so that the length direction thereof faces the axial direction of the photosensitive drum 12. In the present embodiment, in the LPH 14, a plurality of LEDs are arranged in an array (row shape) along the length direction.

  The image forming process unit 10 also intermediate-transfers each color toner image of each image forming unit 11 and the intermediate transfer belt 21 onto which the toner images of each color formed on the photosensitive drum 12 of each image forming unit 11 are transferred in a multiple manner. A primary transfer roll 22 that sequentially transfers (primary transfer) to the belt 21; a secondary transfer roll 23 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 21 to a sheet P that is a recording medium; and A fixing device 25 for fixing the secondary transferred image on the paper P is provided.

  Further, as shown in FIG. 1, the width direction of the intermediate transfer belt 21 (the primary transfer roll 22 of the primary transfer roll 22) is disposed on the intermediate transfer belt 21 on the downstream side in the rotation direction (arrow A direction) of the intermediate transfer belt 21 of the image forming unit 11 </ b> Y. A density detection sensor 26Y for detecting the density of the yellow toner patch formed along the axial direction is provided. Further, a density detection sensor 26M that detects the density of a magenta toner patch formed on the intermediate transfer belt 21 along the width direction is provided on the downstream side in the rotation direction of the intermediate transfer belt 21 of the image forming unit 11M. ing. A density detection sensor 26C that detects the density of cyan toner patches formed on the intermediate transfer belt 21 along the width direction is provided on the downstream side of the image forming unit 11C in the rotation direction of the intermediate transfer belt 21. ing. A density detection sensor 26K that detects the density of the black toner patch formed on the intermediate transfer belt 21 along the width direction is provided on the downstream side of the image forming unit 11K in the rotation direction of the intermediate transfer belt 21. ing. Each concentration detection sensor 26 is connected to the control unit 30.

  Next, an image forming operation of the image forming apparatus 50 will be described.

  First, the image forming process unit 10 performs an image forming operation based on a control signal such as a synchronization signal supplied from the control unit 30. At that time, the image data input from the image reading device 3 or the PC 2 is subjected to image processing by the image processing unit 40 and supplied to each image forming unit 11 via the interface.

  For example, in the yellow image forming unit 11Y, the surface of the photosensitive drum 12 uniformly charged at a predetermined potential by the charger 13 is emitted by the LPH 14 that emits light based on the image data obtained from the image processing unit 40. As a result of exposure, an electrostatic latent image is formed on the photosensitive drum 12. That is, each LED of the LPH 14 emits light based on the image data, so that the surface of the photoconductive drum 12 is main-scanned, and the photoconductive drum 12 is rotated and sub-scanned, and the photoconductive drum 12 is scanned on the photoconductive drum 12. An electrostatic latent image is formed. The formed electrostatic latent image is developed by the developing device 15, and a yellow toner image is formed on the photosensitive drum 12. Similarly, magenta, cyan, and black toner images are formed in the image forming units 11M, 11C, and 11K.

  Each color toner image formed by each image forming unit 11 is sequentially electrostatically attracted and transferred by the primary transfer roll 22 onto the intermediate transfer belt 21 rotating in the direction of arrow A in FIG. 1 (primary transfer). A superimposed toner image is formed on the intermediate transfer belt 21. The superimposed toner image is conveyed to a region (secondary transfer portion) where the secondary transfer roll 23 is disposed as the intermediate transfer belt 21 moves. When the superimposed toner image is conveyed to the secondary transfer unit, the paper P is supplied to the secondary transfer unit in accordance with the timing at which the toner image is conveyed to the secondary transfer unit.

  The superimposed toner images are collectively electrostatically transferred onto the conveyed paper P (secondary transfer) by the transfer electric field formed by the secondary transfer roll 23 in the secondary transfer portion. The sheet P on which the superimposed toner image has been electrostatically transferred is peeled off from the intermediate transfer belt 21 and conveyed to the fixing device 25 by the conveyance belt 24. The unfixed toner image on the paper P conveyed to the fixing device 25 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 25. The paper P on which the fixed image is formed is discharged to a discharge unit (not shown) of the image forming apparatus 50.

  By the way, the potential profile on the intermediate transfer belt 21 when the toner image formed on the photosensitive drum 12 is primarily transferred to the intermediate transfer belt 21 by the primary transfer roll 22 is constant in the width direction of the intermediate transfer belt 21. It is desirable. However, actually, even when a constant transfer voltage is applied to the primary transfer roll 22, the potential profile in the width direction on the intermediate transfer belt 21 is not constant due to the shape of the photosensitive drum 12 and the like. There is. In such a case, the toner image on the photosensitive drum 12 may remain on the photosensitive drum 12 without being transferred to the intermediate transfer belt 21 at a location where the potential is low.

  In FIG. 2A, the toner on the photosensitive drum 12 is transferred onto the intermediate transfer belt 21 in the width direction of the intermediate transfer belt 21, that is, at the three ends of the axial direction of the primary transfer roll 22. In this example, the photosensitive drum 12 is separated from the intermediate transfer belt 21. FIG. 2B shows an example of a plan view of a toner image formed on the intermediate transfer belt 21 after transfer. FIGS. 7A and 7B show a state where yellow toner 27Y is first primarily transferred to the intermediate transfer belt 21, and then magenta toner 27M is primarily transferred. FIG. 3C shows an example of the potential profile 28 on the intermediate transfer belt 21 at the time of primary transfer. In FIG. 2, the left-right direction corresponds to the axial direction of the primary transfer roll 22.

  As shown in FIG. 2A, at both ends in the axial direction of the primary transfer roll 22, after the toner on the photosensitive drum 12 is transferred to the intermediate transfer belt 21, the photosensitive drum 12 is moved from the intermediate transfer belt 21. When moving away from the intermediate transfer belt 21, a part of magenta toner 29 </ b> M remains on the photosensitive drum 12 without being transferred to the intermediate transfer belt 21, whereas at the central portion in the axial direction of the primary transfer roll 22, magenta. All of the toner 29M is transferred to the intermediate transfer belt 21 and does not remain on the photosensitive drum 12.

  This is because, as shown in FIG. 2C, the potential profile in the axial direction of the primary transfer roll 22 is not constant, and the potentials at both ends are low. In such a case, since the potentials at both ends are lower than those originally required for transfer, the toner image on the photosensitive drum 12 is not transferred to the intermediate transfer belt 21 but remains on the photosensitive drum 12. End up.

  In view of this, the primary transfer roll 22 according to the present embodiment compensates for the potential at both ends in the axial direction of the primary transfer roll 22 being low, so that the transfer voltage applied to both ends in the axial direction is the center in the axial direction. It is configured to be higher than the transfer voltage applied to the part.

  FIG. 3 shows the configuration of the primary transfer roll 22 having such a configuration. As shown in the figure, the primary transfer roll 22 includes, for example, a shaft 22A obtained by plating composite free-cutting steel with nickel (Ni), an insulating layer 22B made of a dielectric as an example, and a conductive layer made of a carbon resistor as an example. 22C and rubber 22D are covered in this order. The thickness of the insulating layer 22B and the conductive layer 22C is 10 μm as an example, and the length in the axial direction of the primary transfer roll 22 of the rubber 22D is 328 mm as an example. In addition, an insulating layer 22B is not provided in a part of the central portion in the axial direction of the primary transfer roll 22, and as an example, an Au (copper) layer 22E having a thickness of 3 μm is coated on the shaft 22A to prevent oxidation. ing. The length of the primary transfer roll 22 in the axial direction of the Au layer 22E is 100 μm as an example. With such a configuration, the conductive layer 22C and the shaft 22A are electrically connected via the Au layer 22E in the central portion in the axial direction of the primary transfer roll 22.

  The shaft 22A is connected to the positive side of a transfer voltage power supply 60 for applying a predetermined DC primary transfer transfer voltage. The positive side of the transfer voltage power supply 60 is connected to the negative side of the high-voltage floating power supply 62 for applying a DC bias voltage, and the positive side of the high-voltage floating power supply 62 is connected to the conductive layer 22C. . The voltage value of the bias voltage applied by the high voltage floating power source 62 is controlled by the control unit 30.

  With such a configuration, when the transfer voltage power source 60 applies the original transfer voltage for primary transfer to the shaft 22 </ b> A and the bias voltage is applied by the high voltage floating power source 62, the potential in the axial direction of the primary transfer roll 22. The profile is as follows.

  That is, since the conductive layer 22 </ b> C and the shaft 22 </ b> A are electrically connected at the central portion in the axial direction of the primary transfer roll 22, the potential is in accordance with the transfer voltage applied by the transfer voltage power supply 60. At both ends in the direction, the bias voltage applied by the high-voltage floating power supply 62 becomes a potential corresponding to the voltage biased to the transfer voltage. As a result, the potential at both ends in the axial direction of the primary transfer roll 22 is higher than that at the central portion in the axial direction, and therefore, the potential at both ends in the axial direction of the primary transfer roll 22 decreases as shown in FIG. Be compensated.

  The toner image on the photoconductive drum 12 is not completely transferred to the intermediate transfer belt 21, and the amount of toner remaining on the photoconductive drum 12 is not always constant, and may vary depending on the density of each color toner. .

  Therefore, in this embodiment, as will be described in detail later, a toner patch is formed on the intermediate transfer belt 21 along the axial direction of the primary transfer roll 22, and the toner patch is read by the density detection sensor 26, whereby the primary transfer roll. A density profile in the axial direction of 22 is acquired, and a process of setting a voltage value of a bias voltage applied by the high-voltage floating power supply 62 is performed for each color based on the acquired density profile. This process is executed by the control unit 30.

  FIG. 4 shows a block diagram when the control unit 30 is configured by a computer. As shown in FIG. 4, the control unit 30 includes a CPU (Central Processing Unit) 30A, a ROM (Read Only Memory) 30B, a RAM (Random Access Memory) 30C, a non-volatile memory 30D, and an input / output interface. (I / O) 30E is connected to each other via a bus 30F. The I / O 30E is connected to each of the image reading unit 3, the image processing unit 40, and the image forming process unit 10. The nonvolatile memory 30D stores a process control program to be described later, various table data, and the like. The control program stored in the nonvolatile memory 30D is read and executed by the CPU 30A. The control program may be provided by a recording medium such as a CD-ROM.

  Next, the bias voltage setting process executed by the control unit 30 will be described with reference to the flowchart shown in FIG. The control program for this process is executed at a predetermined timing. For example, the bias voltage adjustment processing may be executed when instructed by the PC 2 or the like, may be executed every time the image forming apparatus 50 is activated, or every time a predetermined period elapses. However, the present invention is not limited to this.

  First, in step 100, the color of the toner patch formed on the intermediate transfer belt 21 is set. For example, in the present embodiment, processing is executed in the order of Y, M, C, and K. Therefore, Y is initially set.

  In step 102, the density of the toner patch formed on the intermediate transfer belt 21 is set. In this embodiment, as an example, a toner patch having a density of 10% is formed on the intermediate transfer belt 21, and the processing described later is performed at each density. Therefore, for example, a concentration of 10% is initially set. Note that the percentage of toner patch formation is not particularly limited.

  In step 104, for example, a toner patch 70 as shown in FIG. 6A that is long in the width direction of the intermediate transfer belt 21 is formed on the intermediate transfer belt 21. As shown in FIG. 5B, toner patches 70A, 70B, and 70C may be formed at three locations in the middle and both ends of the intermediate transfer belt 21 in the width direction. The density of the toner patch 70 formed on the intermediate transfer belt 21 is detected by the density detection sensor 26.

  In step 106, the density profile in the width direction of the intermediate transfer belt 21 is acquired by acquiring the density of the toner patch 70 detected by the density detection sensor 26.

  In step 108, based on the density profile acquired in step 106, the density difference between the density at the center in the width direction of the intermediate transfer belt 21 and the density at both ends in the width direction is obtained. For example, the average value of the density at both ends in the width direction is obtained, and the density difference between this average value and the density at the center in the width direction is calculated. The method of obtaining the density difference is not limited to this, and the density difference between the density at any one of the both ends in the width direction and the density at the center in the width direction may be calculated.

  In step 110, the voltage value of the bias voltage applied by the high voltage floating power source 62 is set. Specifically, as shown in FIG. 7A, the density difference between the central portion in the width direction and both ends in the width direction of the intermediate transfer belt 21 and the high pressure so that the density difference falls within a predetermined allowable range. A table 72 showing a correspondence relationship with the bias voltage applied by the floating power supply 62 is stored in advance in the nonvolatile memory 30D. This table 72 is obtained in advance by experiments or the like. Then, a bias voltage corresponding to the density difference obtained in step 108 is obtained from the table 72. The density difference that is not in the table 72 may be obtained by interpolation from the bias voltage corresponding to the density difference before and after.

  In step 112, the correspondence between each density and the bias voltage to be applied by the high-voltage floating power source 62 when the toner of the color of the density is formed on the intermediate transfer belt 21 as shown in FIG. The bias voltage set in step 110 is written in the table 74 shown.

  In step 114, it is determined whether or not the above processing has been executed for all densities. If the above processing is not executed for all the densities, the process returns to step 102, and the same processing as described above is executed by changing the density. On the other hand, when the above processing is executed for all the concentrations, the process proceeds to step 116.

  In step 116, it is determined whether or not the above processing has been executed for all the colors Y, M, C, and K. If the above processing is not executed for all colors, the process returns to step 100, and the same processing as described above is executed by changing the color. On the other hand, when the above processing is executed for all colors, this routine is terminated.

  As described above, by executing the process of setting the bias voltages of all the densities for all the colors Y, M, C, and K, a table 74 as shown in FIG. 7B is created for each color.

  When executing the image forming process, a bias voltage is set from the table 74 in accordance with the density of the color formed on the intermediate transfer belt 21 and applied by the high voltage floating power source 62. In addition, what is necessary is just to interpolate from the bias voltage of the density before and behind about the density | concentration which is not in the table 74. As a result, the toner is not completely transferred to the intermediate transfer belt 21 at both end portions on the intermediate transfer belt 21, but remains on the photosensitive drum 12, and the occurrence of uneven density is suppressed.

  In this embodiment, the photosensitive drum 12 corresponds to the image carrier of the present invention, and the intermediate transfer belt 21 corresponds to the transfer target of the present invention.

  (Second Embodiment)

  Next, a second embodiment of the present invention will be described.

  FIG. 8 shows the configuration of the image forming apparatus 50A according to the present embodiment. The image forming apparatus 50A differs from the image forming apparatus 50 described in the first embodiment in that only one density detection sensor 26A is provided on the secondary transfer roll 23 side as shown in FIG. It is a point not provided on the roll 22 side.

  In the present embodiment, the potential profile in the axial direction of the secondary transfer roll 23 when the secondary transfer voltage is applied is not constant, similar to the primary transfer roll 22 described in the first embodiment. As shown in FIG. 2C, a case similar to the potential profile of the primary transfer roll 22 described in the first embodiment will be described. It is assumed that the potential profile of the primary transfer voltage in the axial direction of the primary transfer roll 22 is constant.

  Thus, when the potential profile when the secondary transfer voltage is applied to the secondary transfer roll 23 is low at both ends in the axial direction of the secondary transfer roll 23 as shown in FIG. At both ends, after the toner on the intermediate transfer belt 21 is transferred to the paper P, when the paper P moves away from the intermediate transfer belt 21, the toner cannot be completely transferred to the paper P and some of the toner is transferred to the intermediate transfer belt. 21 will remain.

  Therefore, the secondary transfer roll 23 according to the present embodiment is configured as shown in FIG. 3 in the same manner as the primary transfer roll 22 described in the first embodiment. That is, in order to compensate for the potential at both ends in the axial direction of the secondary transfer roll 23 being lowered, the transfer voltage applied to both ends in the axial direction is higher than the transfer voltage applied to the central portion in the axial direction. It is comprised so that it may become. The configurations of the transfer voltage power supply 60 and the high voltage floating power supply 62 are the same as those in the first embodiment.

  Next, the bias voltage setting process executed by the control unit 30 is the same as the flowchart shown in FIG. 5 described in the first embodiment. However, the table 72 shown in FIG. 7A may be a table obtained by an experiment of secondary transfer by the secondary transfer roll 23 or the like.

  As described above, the secondary transfer roll 23 is also set with a bias voltage in the same manner as in the first embodiment, and when the image forming process is executed, the bias voltage corresponding to the density is applied to perform the secondary transfer. The toner is not completely transferred onto the paper P at both ends in the axial direction of the transfer roll 23 and remains on the intermediate transfer belt 21, thereby suppressing uneven density.

  In the present embodiment, the intermediate transfer belt 21 corresponds to the image carrier of the present invention, and the paper P corresponds to the transfer target of the present invention.

  (Third embodiment)

  Next, a third embodiment of the present invention will be described.

  FIG. 9 shows the configuration of the image forming apparatus 50B according to the present embodiment. The image forming apparatus 50B is different from the image forming apparatus 50 described in the first embodiment in that only one density detection sensor 26A is provided on the secondary transfer roll 23 side as shown in FIG. is there.

  That is, in this embodiment, the primary transfer roll 22 is the same as that in the first embodiment, and the secondary transfer roll 23 is the same as in the second embodiment.

  Accordingly, the bias voltage is set for the primary transfer roll 22 by the same process as in the first embodiment, and the bias voltage is set for the secondary transfer roll 23 by the same process as in the second embodiment.

  Thereby, at the time of primary transfer, toner is prevented from remaining on the photosensitive drum 12 without being completely transferred to the intermediate transfer belt 21 at both axial ends of the primary transfer roll 22, and at the time of secondary transfer, The toner is prevented from remaining on the intermediate transfer belt 21 without being completely transferred to the paper P at both axial ends of the transfer roll 23.

  In each of the above-described embodiments, the case where the potential profiles in the axial direction of the primary transfer roll 22 and the secondary transfer roll 23 are such that the potential profile is low at both ends in the axial direction has been described. It is not limited. In this case, the potential is lowered so that the bias voltage applied in the axial direction of the primary transfer roll 22 or the secondary transfer roll 23 changes according to the potential profile in the axial direction, that is, with respect to the position where the potential is lowered. It may be configured to be able to apply a bias voltage that compensates for this.

  The configuration of the image forming apparatus described in this embodiment (see FIGS. 1, 8, and 9) is merely an example. Unnecessary parts are deleted or new parts are added without departing from the gist of the present invention. Needless to say, you can do it.

  For example, in each of the above embodiments, the case where the present invention is applied to an image forming apparatus that forms a color image has been described. However, the present invention is also applied to an image forming apparatus that includes a single image forming unit 11 that forms a monochrome image. Applies.

  In addition, the flow of processing of the control program described in the present embodiment (see FIG. 5) is also an example, and unnecessary steps are deleted or new steps are added within the scope not departing from the gist of the present invention. Needless to say, the processing order may be changed.

2 PC
3 Image Reading Device 10 Image Forming Process Unit 11 Image Forming Unit 12 Photosensitive Drum (Example of Image Holding Body)
21 Intermediate transfer belt (an example of a transfer medium and an image carrier)
22 Primary transfer roll (an example of a transfer roll)
23 Secondary transfer roll (an example of a transfer roll)
26 Concentration detection sensor (an example of concentration detection means)
30 control unit (an example of setting means and control means)
40 Image processing unit 50 Image forming apparatus 60 Transfer voltage power source (an example of transfer voltage applying means)
62 High-voltage floating power supply (an example of auxiliary voltage application means)
70 toner patch (example of toner for measurement)
72, 74 tables

Claims (5)

Toner forming means for forming a toner for measurement having a predetermined density on the image carrier along the axial direction of the image carrier;
A transfer roll for transferring the measurement toner formed on the image carrier onto the transfer target;
Transfer voltage applying means for applying a transfer voltage to the transfer roll;
An auxiliary voltage applying means for applying an auxiliary voltage for assisting the transfer voltage to the transfer roll;
Density detecting means for detecting the density of the measurement toner transferred onto the transfer target at a plurality of positions along the axial direction of the transfer roll or the measurement toner remaining on the image carrier;
Setting means for setting the auxiliary voltage corresponding to the predetermined density based on the density of the measurement toner at the plurality of positions detected by the density detection means;
When the image toner having the predetermined density is formed on the image carrier, an auxiliary voltage corresponding to the predetermined density is applied to a predetermined position where the potential of the transfer roll is lowered. Control means to control,
A transfer device. 2. The setting unit calculates a density difference of the density of the toner for measurement at the plurality of positions, and sets the auxiliary voltage corresponding to the predetermined density based on the calculated density difference. Transfer device. The toner forming means sequentially forms the measurement toners having a plurality of densities on the image carrier along the axial direction of the image carrier, and the density detection means The transfer device according to claim 1, wherein the density is sequentially detected, and the setting unit sets the auxiliary voltage for each of the measurement toners having a plurality of densities. The toner forming unit, the transfer voltage applying unit, the auxiliary voltage applying unit, and the density detecting unit are provided for each of a plurality of types of colors, and the setting unit sets the auxiliary voltage for each color. Item 4. The transfer device according to any one of Items 3 to 3. Forming a toner for measurement having a predetermined density on the image carrier along the axial direction of the image carrier;
Transferring the measurement toner formed on the image carrier onto a transfer medium;
Applying a transfer voltage to the transfer roll;
Applying an auxiliary voltage to assist the transfer voltage to the transfer roll;
Detecting the density of the measurement toner transferred onto the transfer object at a plurality of positions along the axial direction of the transfer roll or the measurement toner remaining on the image carrier;
Setting the auxiliary voltage corresponding to the predetermined density based on the density of the measurement toner at the plurality of positions detected by the density detection unit;
When the image toner having the predetermined density is formed on the image carrier, an auxiliary voltage corresponding to the predetermined density is applied to a predetermined position where the potential of the transfer roll is lowered. Step to control,
Transfer program for causing a computer to execute processing including

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