JP6554988B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming program.

  Patent Document 1 is an image forming apparatus that forms a multicolor image by superimposing at least two monochrome images and having at least two colors for each color to form a single color image. A means for forming an image of a predetermined correction pattern, an image position detecting means for detecting the position of the correction pattern that has been imaged, and a position for forming an image of the monochrome image based on the detection result of the image position detecting means The image forming apparatus is characterized in that the correction pattern for each color can be formed under an image forming condition different from that of the single-color image.

  Patent Document 2 controls a plurality of image forming units including an image carrier and image writing means, storage means for preliminarily storing generation information of quality deterioration factors during image formation, and controls each unit and the storage means. An image forming apparatus comprising: a control unit, wherein generation of the quality deterioration factor is suppressed by optical control of the image writing unit.

  Patent Document 3 discloses an image forming unit that writes an electrostatic latent image on a photoconductor and develops the electrostatic latent image to form a toner image, and transfers the formed toner image to a sheet; A drive source that is controlled to rotate at a preset rotation speed that drives a pair of conveyance rollers provided on a conveyance path of a sheet to be transferred in a section, and the photosensitive member and the conveyance roller pair An image control unit that corrects at least the density of the image, and a correction value determination unit that determines a correction value used to correct the density of the image by the image control unit, The image control unit is configured to write an electrostatic latent image on the photosensitive member with respect to an image to be formed after the leading edge of the sheet enters the nip portion of the conveying roller pair or the trailing edge of the sheet is removed. The When the difference between the rotational speed of the drive source (hereinafter referred to as “variable rotational speed”) and the set rotational speed is greater than or equal to a predetermined level, the variable rotational speed of the drive source deviates from the set rotational speed. Drive source speed fluctuation density correction is performed to correct the density of an image to be formed within a rotation speed fluctuation period until the set rotation speed is converged, and the fluctuation rotation speed of the drive source and the set rotation speed are When the difference is less than a predetermined level, the drive source speed fluctuation density correction is not performed within the rotation speed fluctuation period, and the correction value determination unit is configured so that the image control unit is not in the rotation speed fluctuation period. When the drive source speed fluctuation density correction is performed, a correction value for correcting the image density to be dark when the fluctuation rotation speed is faster than the set rotation speed is determined, and the fluctuation rotation speed is Discloses an image forming apparatus, wherein when slower than the set rotational speed is to determine a correction value for correcting thin density of the image.

JP 2004-126528 A Japanese Patent Laying-Open No. 2005-062324 JP 2013-020180 A

  In general, the image forming apparatus discharges the toner in the developing device at a predetermined timing, thereby preventing deterioration in image quality formed on the recording medium. In the image forming apparatus, for example, a toner image in which the toner amount is abruptly changed by the toner discharged from the developing device is formed outside the image forming area of the intermediate transfer member.

The present invention provides an image forming equipment which suppresses the toner image formed on the intermediate transfer member by toner discharged from the developing device is thus cause speed variations in the photoreceptor.

In order to achieve the above object, an image forming apparatus according to claim 1 is arranged in a predetermined direction, each of which forms a toner image on a photosensitive member, and a predetermined direction. are moved, and an intermediate transfer member the toner image formed on the photosensitive member of the plurality of image forming units are transferred, the toner amount in the axial direction of the photosensitive member, the moving direction of the intermediate transfer member A toner image that is incremented by a predetermined amount or less in the opposite direction, the toner image having a predetermined amount of toner along the circumferential direction of the photoconductor for the entire area in the axial direction of the photoconductor , And a control unit that controls at least one of the plurality of image forming units so as to be transferred outside the image forming region of the intermediate transfer member.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit includes an image forming unit excluding the most downstream image forming unit in the moving direction of the intermediate transfer body among the plurality of image forming units. To control.

An image forming apparatus according to a third aspect is the image forming apparatus according to the first or second aspect, wherein the control unit controls an image forming unit that forms a toner image with toner containing metal particles among the plurality of image forming units. .

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to any one of the first to third aspects, wherein the control unit transfers a toner image transferred outside an image forming area of the intermediate transfer body to a width of the intermediate transfer body. The image forming unit is controlled so as to be inclined from the central portion in the direction toward both ends or inclined from the both ends in the width direction toward the central portion.

  The image forming apparatus according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, wherein the control unit moves a toner image formed outside an image forming area of the intermediate transfer member to the intermediate transfer member. The image forming unit is controlled so as to form a line-symmetric shape with respect to a line along the direction.

The image forming apparatus according to a sixth aspect is the image forming apparatus according to any one of the first to fifth aspects, wherein the toner image formed outside the image forming area of the intermediate transfer member has a predetermined size and a predetermined size. the amount of toner in the toner block as a unit, the number of the toner blocks in the width direction of the intermediate transfer body is formed is increased in a direction opposite to the moving direction of the intermediate transfer body.

An image forming apparatus according to claim 7, in any one of claims 6 請 Motomeko 1, the amount less the amount of toner the predetermined, the intermediate transfer member in the toner image transferred to the intermediate transfer member The amount of change in toner along the moving direction is less than the amount of change that causes speed fluctuations in the photoconductor in contact with the toner image .
An image forming apparatus according to an eighth aspect is the image forming apparatus according to any one of the first to seventh aspects, wherein the toner image is connected from one end side to the other end side in the width direction of the intermediate transfer member.

According to the first aspect of the present invention, there is an effect that the toner image generated by the toner discharged from the developing device is restrained from causing speed fluctuations on the photosensitive member.

  According to the second aspect of the present invention, there is an effect that the toner image generated by the toner discharged from the developing device suppresses the speed fluctuation on the downstream side of the photosensitive member in the moving direction of the intermediate transfer belt. According to the third aspect of the present invention, there is an effect that the speed fluctuation on the photosensitive member is suppressed by the toner image formed by the toner containing the metal particles discharged from the developing device.

  According to the fourth aspect of the present invention, there is an effect that the change in the frictional force generated in the axial direction of the photosensitive member is suppressed by the toner image generated by the toner discharged from the developing device. According to the fifth aspect of the present invention, there is an effect that the change in the frictional force generated in the axial direction of the photosensitive member is suppressed by the toner image generated by the toner discharged from the developing device.

  According to the sixth aspect of the present invention, it is possible to easily suppress the speed fluctuation on the photosensitive member due to the toner image generated by the toner discharged from the developing device.

(A) is a plan view schematically showing a toner band according to the present embodiment, and (B) is a diagram showing an integrated value of the toner amount of the toner band and a change in the integrated value according to the present embodiment. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment. It is a schematic block diagram of an image forming unit. It is a schematic block diagram of an apparatus control part. FIG. 3 is a plan view of a main part of an intermediate transfer belt showing an example of an image area and an interval area. It is a flowchart which shows an example of a band creation process. (A) is a side view of the main part along the axial direction of the photosensitive drum showing the intermediate transfer belt and the photosensitive drum, and (B) is a plan view schematically showing a conventional toner band. (A) is a plan view schematically showing toner bands for two colors, and (B) is a diagram showing an integrated value of the toner amount of the toner band of (A) and a change in the integrated value. (A) is a plan view schematically showing a toner band according to Modification 1, and (B) is a diagram showing an integrated value of the toner amount of the toner band according to Modification 2 and a change in the integrated value. (A) is a plan view schematically showing a toner band according to Modification Example 2, and (B) is a diagram showing an integrated value of the toner amount of the toner band according to Modification Example 2 and a change in the integrated value. (A) is a plan view schematically showing toner bands for two colors including a toner band according to Modification 2, and (B) is an integrated value of the toner amount of the toner band of (A) and a change in the integrated value. FIG. (A) is a plan view schematically showing another example of the toner band according to Modification Example 2, and (B) is a diagram showing the integrated value of the toner amount of the toner band of (A) and the change of the integrated value. . (A) is a plan view schematically showing a toner band according to Modification 3, and (B) is a diagram showing an integrated value of the toner amount of the toner band according to Modification 3 and a change in the integrated value. (A) is a plan view schematically showing a toner band according to Modification Example 4, and (B) is a diagram showing an integrated value of the toner amount of the toner band according to Modification Example 4 and changes in the integrated value. (A) is a plan view schematically showing a toner band according to Modification Example 5, and (B) is a diagram showing an integrated value of the toner amount of the toner band according to Modification Example 5 and a change in the integrated value.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows a configuration of a main part of the image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 forms an image on a recording medium 12 such as a recording sheet by applying an electrophotographic method.

  Image data of an image to be formed on the recording medium 12 is input to the image forming apparatus 10. The image data may be input via a communication line such as a dedicated or public network line to which the image forming apparatus 10 is connected. The image forming apparatus 10 may be configured to be connected to an image reading apparatus that reads an image recorded on a document, and the image reading apparatus reads the image recorded on the document and acquires image data to be output. Further, the image forming apparatus 10 may be connected to a storage medium reading device that reads data stored in a portable storage medium, and may read image data stored in the portable storage medium by the storage medium reading device.

  The image forming apparatus 10 includes a storage unit 14 that stores a recording medium 12, an image forming unit 16 that forms a toner image on the recording medium 12, and a fixing unit 18 that fixes the toner image on the recording medium 12. The storage unit 14 stacks and stores a plurality of recording media 12 and sequentially takes out the stored recording media 12 from the upper layer.

  In the image forming apparatus 10, for example, a plurality of pairs of transport rolls 20 and a transport belt 22 form a transport path 24 from the storage unit 14 to the secondary transfer position of the image forming unit 16 and the fixing unit 18 to a discharge unit (not shown). Has been. In the image forming apparatus 10, the transport roll 20 and the transport belt 22 are rotated by a driving force of a driving source (not shown), and the recording medium 12 taken out from the storage unit 14 is transported along the transport path 24.

  The image forming unit 16 includes an intermediate transfer belt 26 and a plurality of image forming units 30. The image forming unit 16 forms a toner image by each of the plurality of image forming units 30 and transfers the toner image on the intermediate transfer belt 26. Further, the image forming unit 16 transfers the toner image on the intermediate transfer belt 26 to the recording medium 12 in the secondary transfer device 48 provided at the secondary transfer position. In the present embodiment, the intermediate transfer belt 26 functions as an example of an intermediate transfer member, and the image forming unit 30 functions as an example of an image forming unit.

  The intermediate transfer belt 26 has an endless shape, and is wound around a plurality of rolls 28 so as to form, for example, a triangular shape in which the lower side (the lower side in the drawing in FIG. 2) has one corner. The intermediate transfer belt 26 is rotated at a predetermined speed in the direction of arrow A in FIG. 2 when the driving force of a driving source (not shown) is transmitted to the roll 28.

  The image forming unit 16 includes image forming units 30Y, 30M, 30C, and 30K that use toners (pigments) of Y, M, C, and K colors (process colors) as the image forming unit 30. As the C, M, Y, and K toners, general process color toners are used. Further, the toner used in the image forming apparatus 10 may have an external additive such as silica (Si) or zinc stearate (ZnSt) added thereto.

  The image forming unit 16 includes an image forming unit 30 that uses toner having a color different from the process color. As the toner different from the process color, the so-called special color toner different from the process color, the toner different in saturation from the process color, the transparent toner that improves the gloss of the image, the foaming toner for braille, the fluorescent color toner, and the metal color And the like. The image forming unit 16 applies a metallic toner (toner including a metallic pigment) as an example of a toner having a color different from the process color, and an image using a gold toner as the image forming unit 30 that uses the metallic toner. A forming unit 30V and an image forming unit 30W using silver toner are provided.

  The metal pigment improves the reproducibility of the metal color. The metal pigment may be particulate (spherical), or may be a flat pigment (flat pigment) that provides a higher gloss than the particulate. Metallic pigments (metallic toner) such as gold and silver are blended with pigments (powder) such as metallic aluminum powder in addition to synthetic resins such as styrene and acrylic, colorants, and compounding agents, for example. Thus, it is formed into a scale-like (disk-like) flat shape or spherical shape. The metallic toner is not limited to the one in which metallic aluminum powder or the like is blended. For example, a flat pigment (flaky pigment) in which a thin film made of titanium dioxide is coated on a flaky inorganic crystalline substrate is used. You may use the toner mix | blended with the coloring agent. Further, as the metal color toner, a toner blended with the metal itself in a flat flake may be used.

  In the image forming unit 16, a plurality of image forming units 30 are arranged along one side of the triangular transfer belt 26 (side on the upper side in FIG. 2). In this embodiment, as an example, the image forming units 30W, 30V, 30Y, 30M, 30C, and 30K are arranged in this order from the upstream side in the circumferential direction of the intermediate transfer belt 26. The image forming units 30Y, 30M, 30C, 30K, 30V, and 30W use different toners, but have the same basic configuration. In the following description, when distinguishing between the toners to be used, Y, M , C, K, V, and W are given codes, and the codes are omitted if the toners are not distinguished.

  FIG. 3 shows an example of the image forming unit 30. The image forming unit 30 includes a photosensitive drum 32. In the present embodiment, the photosensitive drum 32 functions as an example of a photosensitive member. The photosensitive drum 32 is formed in a cylindrical shape as an example, and holds an electrostatic latent image on the outer peripheral surface. The image forming unit 30 is arranged so that the photosensitive drum 32 is in contact with the intermediate transfer belt 26. Further, in the image forming unit 30, the photosensitive drum 32 is rotated at a predetermined rotation speed in a direction (in the direction of arrow R in FIG. 3) according to the rotation direction of the intermediate transfer belt 26 by a driving force of a driving source (not shown). It is rotated at a speed (according to the circumferential speed of the intermediate transfer belt 26).

  As an example, the image forming unit 30 includes a charger 34, an exposure device 36, a developing device 38, a cleaning device 40, and a static eliminator 42 around the photosensitive drum 32 in order along the rotation direction of the photosensitive drum 32. Each of them is opposed to the outer peripheral surface of the photosensitive drum 32. Further, the photosensitive drum 32 is in contact with the intermediate transfer belt 26 on the downstream side of the developing unit 38 (upstream side of the cleaning unit 40). In the image forming unit 16, the position where the photosensitive drum 32 of the image forming unit 30 is in contact with the intermediate transfer belt 26 is the primary transfer position.

  As the charger 34, for example, a corotron or a scorotron is used, and a predetermined charging voltage is applied to charge the outer peripheral surface of the opposing photosensitive drum 32. The exposure device 36 exposes the charged outer surface of the photosensitive drum 32 by, for example, irradiating it with a light beam. The image forming apparatus 10 performs predetermined image processing on the image data, and performs color separation on the image data that has been subjected to the image processing. As exposure data for each recording medium 12, for example, raster data of each color (Bitmap data) is generated. The exposure device 36 irradiates a light beam corresponding to the exposure data while scanning the outer peripheral surface of the photosensitive drum 32, and forms an electrostatic latent image corresponding to the exposure data on the outer peripheral surface of the photosensitive drum 32.

  For example, the toner is mixed with a magnetic carrier or the like and contained in the developer. For example, the developing unit 38 agitates the developer to charge the toner and the magnetic carrier, and supplies the toner to the outer peripheral surface of the photosensitive drum 32. As a result, the electrostatic latent image is developed on the photosensitive drum 32 by the toner supplied from the developing device 38, and a toner image corresponding to the electrostatic latent image is formed. The image forming unit 16 forms toner images of each color of Y, M, C, K, gold, and silver by using the image forming units 30Y, 30M, 30C, 30K, 30V, and 30W.

  As shown in FIGS. 2 and 3, in the image forming unit 16, a primary transfer roll 44 is disposed at each primary transfer position of the image forming unit 30 so as to face the photosensitive drum 32. The intermediate transfer belt 26 is sandwiched between the photosensitive drum 32 and the primary transfer roll 44 at each primary transfer position. In the image forming unit 30, a primary transfer voltage having a predetermined polarity and magnitude is applied between the photosensitive drum 32 sandwiching the intermediate transfer belt 26 and the primary transfer roll 44. As a result, the toner image on the photosensitive drum 32 is transferred to the intermediate transfer belt 26.

  The image forming unit 16 forms a full-color toner image on the surface (outer peripheral surface) of the intermediate transfer belt 26 by transferring the toner images of each color of Y, M, C, and K while being superimposed on the intermediate transfer belt 26. . Further, the image forming unit 16 transfers the toner images of each color of silver, gold, Y, M, C, and K onto the surface of the intermediate transfer belt 26, so that the intermediate transfer belt 26 has a color containing gold and silver. A toner image is formed.

  As shown in FIG. 3, the cleaning device 40 includes, for example, a blade 46 whose tip is in contact with the outer peripheral surface of the photosensitive drum 32. The cleaning device 40 scrapes and removes the toner remaining on the photosensitive drum 32 when the surface of the photosensitive drum 32 that has passed the primary transfer position contacts the blade 46. The static eliminator 42, for example, irradiates the outer peripheral surface of the photosensitive drum 32 with light, erases the charging history of the outer peripheral surface of the photosensitive drum 32, and when charged by the charger 34, The occurrence of uneven charging in 32 is suppressed.

  The image forming unit 30 has a charger 34, an exposure device 36, a developing device 38, a cleaning device 40, and a static eliminator 42 arranged in this order around the photosensitive drum 32, so that the photosensitive drum 32 is Charging, exposure, development, transfer, cleaning, and charge removal processes are executed in parallel.

  As shown in FIG. 2, in the image forming unit 16, a secondary transfer device 48 is disposed at a triangular lower end (lower corner) formed by the intermediate transfer belt 26. In the image forming unit 16, a cleaning device 54 is disposed opposite to the intermediate transfer belt 26 on the downstream side of the secondary transfer device 48 in the moving direction of the intermediate transfer belt 26.

  The secondary transfer device 48 includes a backup roll 50 around which the intermediate transfer belt 26 is wound, and a secondary transfer roll 52 that sandwiches the intermediate transfer belt 26 with the backup roll 50. In the image forming unit 16, the secondary transfer position is between the backup roll 50 and the secondary transfer roll 52.

  In the image forming unit 16, the recording medium 12 conveyed through the conveyance path 24 is sent to the secondary transfer position in accordance with the timing at which the toner image transferred to the intermediate transfer belt 26 reaches the secondary transfer position. The secondary transfer device 48 applies a secondary transfer voltage having a predetermined polarity and a predetermined magnitude between the backup roll 50 and the secondary transfer roll 52, so that the toner image on the intermediate transfer belt 26 is obtained. Is transferred to the recording medium 12. As a result, a toner image corresponding to the image data is transferred to the recording medium 12.

  In addition, the secondary transfer device 48 is applied between the backup roll 50 and the secondary transfer roll 52 with a voltage (reverse bias voltage) having a reverse polarity to the secondary transfer voltage. When a reverse bias voltage is applied to the secondary transfer device 48, the toner image on the intermediate transfer belt 26 passes through the secondary transfer position while being held by the intermediate transfer belt 26 and reaches the cleaning device 54. The cleaner 54 includes, for example, a blade 54A whose tip is in contact with the surface (outer peripheral surface) of the intermediate transfer belt 26, and scrapes off the toner remaining on the intermediate transfer belt 26 that has passed through the secondary transfer position with the blade 54A. Remove.

  The fixing unit 18 is disposed, for example, facing the heating roll 56 whose outer peripheral surface is heated to a predetermined temperature (fixing temperature) and the heating roll 56, and applies a predetermined pressure (fixing pressure). A pressure roll 58 is provided. The recording medium 12 that has passed the secondary transfer position is fed between the heating roll 56 and the pressure roll 58 of the fixing unit 18. The fixing unit 18 heats and pressurizes the toner image on the recording medium 12 by sandwiching the recording medium 12 between the heating roll 56 and the pressure roll 58 to melt and fix the recording medium 12 on the recording medium 12. The image forming apparatus 10 forms an image of toner on the recording medium 12 by fusing and fixing the toner image at the fixing unit 18.

  Note that the image forming apparatus 10 may be provided with an intermediate conveyance path (not shown) that returns the recording medium 12 that has passed through the fixing unit 18 onto the conveyance path 24 closer to the storage unit 14 than the secondary transfer position. The image forming apparatus 10 is provided with an intermediate conveyance path. For example, after an image using gold and silver toner is formed on the recording medium 12, image formation using Y, M, C, and K toners is performed. It may be done. Further, the intermediate conveyance path may be provided with a reversing mechanism for determining the front and back of the recording medium 12, whereby the image forming apparatus 10 performs so-called double-sided printing in which images are formed on both the front and back sides of the recording medium 12.

  FIG. 4 shows an example of a device control unit 60 that controls image formation in the image forming apparatus 10. The device control unit 60 includes a controller 62. In the apparatus control unit 60, the storage unit 14, the image forming unit 30, the secondary transfer device 48, the fixing unit 18, and the driving unit 64 are connected to the controller 62. The controller 62 includes a microcomputer (not shown) having a general configuration in which nonvolatile memories such as a CPU, ROM, RAM, and HDD are connected by a bus. In the controller 62, the CPU executes the programs stored in the ROM, the HDD, and the like, thereby operating the storage unit 14, the image forming unit 30, the secondary transfer unit 48, the fixing unit 18, the driving unit 64, and the like. Control. For example, the controller 62 controls the removal of the recording medium 12 stored in the storage unit 14.

  The controller 62 controls the charging, exposure, development, transfer, cleaning, and charge removal in each of the image forming units 30 by the CPU executing the image forming program, and controls the secondary transfer in the secondary transfer unit 48. Then, the fixing of the toner image in the fixing unit 18 is controlled. In the present embodiment, the controller 62 functions as an example of a control unit. The image control program executed by the CPU may be stored in advance in a ROM, an HDD, or the like, but is not limited thereto, and is provided by being stored in a portable storage medium such as a CD-ROM (Compact Disk Read Only Memory). It may be a form or a form provided via a network.

  The drive unit 64 includes drive sources (not shown) such as conveyance of the recording medium 12, circumferential movement of the intermediate transfer belt 26, and rotation of the respective photosensitive drums 32 of the image forming unit 30. The controller 62 controls the operation of the drive unit 64 so that the recording medium 12 is conveyed, the intermediate transfer belt 26 rotates and the photosensitive drums 32 of the image forming unit 30 so as to have a predetermined speed. Control the rotation of

  The controller 62 includes an image processing unit 66. When the image processing unit 66 reads the image data input to the image forming apparatus 10, for example, shading correction, misregistration correction, brightness correction, color space conversion, gamma correction, and frame erasure are performed on the image data in advance. The predetermined image processing or editing processing is executed. The image processing unit 66 generates exposure data for C, M, Y, K, gold, and silver by performing color separation processing on image data, for example. To do.

  The controller 62 controls each exposure unit 36 of the image forming unit 30 based on the exposure data of each color generated by the image processing unit 66, thereby causing the electrostatic latent image corresponding to the exposure data on the photosensitive drum 32. Form. The image forming unit 30 develops the electrostatic latent image on the photosensitive drum 32 with toner, so that a toner image corresponding to the exposure data is formed.

  The controller 62 is provided with a creation determination unit 68 and a pattern setting unit 70. The image forming apparatus 10 discharges toner from the developing device 38 of the image forming unit 30 at a predetermined timing. In the image forming apparatus 10, the toner is discharged from the developing device 38, thereby suppressing the deterioration of the toner used for image formation and the occurrence of unevenness in the toner supplied to the photosensitive drum 32.

  The toner is discharged from the developing device 38 by forming a toner image that is not transferred to the recording medium 12. The toner is discharged from the developing unit 38 so that a predetermined amount of toner is discharged over the entire area along the axial direction of the photosensitive drum 32. The controller 62 forms an electrostatic latent image on the photosensitive drum 32 from which a toner image having a predetermined image density is obtained in order to discharge toner from each developing device 38. Further, the electrostatic latent image formed on the photosensitive drum 32 is formed so that the toner amount becomes a predetermined amount for the entire area in the axial direction of the photosensitive drum 32. Note that the entire area in the axial direction of the photosensitive drum 32 indicates the entire area of the toner image forming range in the axial direction on the photosensitive drum 32.

  The toner image formed on the photosensitive drum 32 by the toner discharged from the developing unit 38 is transferred to the intermediate transfer belt 26 at the primary transfer position. As a result, a toner image is formed on the intermediate transfer belt 26 by the toner discharged from the developing device 38. In the following description, a toner image formed on the intermediate transfer belt 26 by discharging toner from the developing device 38 is referred to as a toner band. The toner band is created in order to discharge toner from the developing unit 38 as an example.

  Part of the toner that forms the toner band remains on the photosensitive drum 32 without being transferred, and the remaining toner is removed by the blade 46 of the cleaner 40. When silica and zinc stearate are added as external additives to the toner, silica (Si) added to the toner reaching the blade 46 promotes wear of the outer peripheral surface of the photosensitive drum 32, and stearic acid is added. Zinc (ZnSt) acts to suppress wear. As a result, the outer circumference of the photosensitive drum 32 is controlled and the blade 46 is prevented from being bent or chipped.

  The image forming apparatus 10 creates a toner band at a predetermined timing. The creation determination unit 68 determines whether it is time to create a toner band. As a timing for creating the toner band, when the image forming apparatus 10 starts up after the power is turned on, every time the operation time of the image forming apparatus 10 reaches a predetermined time, an image is recorded on a predetermined number of recording media 12. Each time it is formed, and when the average density of the image formed on the recording medium 12 is less than a predetermined threshold value, etc. are applied. The pattern setting unit 70 stores a predetermined toner band pattern. The toner band pattern indicates an arrangement of toner images, and is stored, for example, as image data or exposure data of the toner band.

  The toner band pattern stored in the pattern setting unit 70 is determined such that the amount of toner along the axial direction of the photosensitive drum 32 increases by a predetermined amount or less. Thus, a toner band is formed on the intermediate transfer belt 26 in which the toner amount along the width direction of the intermediate transfer belt 26 is increased by a predetermined amount from the downstream side to the upstream side of the intermediate transfer belt 26. Is done.

  Further, the toner band is determined so that the toner amount along the circumferential direction becomes a preset amount for the entire region of the photosensitive drum 32 in the axial direction. When the creation determination unit 68 determines that the timing for creating the toner band has been reached, the toner band pattern recorded in the pattern setting unit 70 is read, and a setting is made so that the toner band is formed based on the read pattern. To do.

  The image processing unit 66 generates exposure data based on the toner band set by the creation determination unit 68. The controller 62 forms a toner band at a timing different from that for forming a toner image (toner image based on image data) to be transferred to the recording medium 12. That is, the controller 62 controls the image forming unit 30 so that a toner band is formed on the intermediate transfer belt 26 outside the image forming area that is an area outside the image forming area corresponding to the recording medium 12.

  When the toner band is formed on the intermediate transfer belt 26, the controller 62 applies a reverse bias voltage to the secondary transfer device 48 at the timing when the formed toner band reaches the secondary transfer position. As a result, the toner band on the intermediate transfer belt 26 is held by the intermediate transfer belt 26 without being transferred to the recording medium 12, and is removed from the intermediate transfer belt 26 by the cleaner 54. When the cleaning device 54 has a restriction on the removal ability of the toner removed from the intermediate transfer belt 26, the controller 62 creates a toner band having a toner amount that does not exceed the removal ability of the cleaning device 54.

  FIG. 5 shows a main part of the intermediate transfer belt 26 when images are sequentially formed on a plurality of recording media 12. In the following description, the width direction of the intermediate transfer belt 26 is indicated by an arrow X, and the upstream side in the moving direction of the intermediate transfer belt 26 is indicated by an arrow Y. In the present embodiment, the arrow X direction corresponds to the axial direction of the photosensitive drum 32, and the arrow Y direction corresponds to the circumferential direction of the photosensitive drum 32.

  When the image forming apparatus 10 forms an image on the recording medium 12, a toner image to be transferred to the recording medium 12 is formed in an area on the intermediate transfer belt 26 where the recording medium 12 is overlapped at the secondary transfer position. In the present embodiment, an area on the intermediate transfer belt 26 on which the recording medium 12 is overlaid is an image area 72. In the present embodiment, the image area 72 functions as an example of an image forming area.

  The controller 62 forms a toner band for one color or a plurality of colors in an area outside the image area 72 on the intermediate transfer belt 26. In the following description, an area outside the image area 72 is referred to as an interval area 74. In the present embodiment, a toner band is formed in the interval region 74. In the present embodiment, the interval area 74 functions as an example outside the image forming area.

1A shows a toner band 76 according to the present embodiment, and FIG. 1B shows a horizontal axis as a position along the moving direction on the intermediate transfer belt 26, and a vertical axis as an integrated value of toner amount. As T _Dy , the integrated value T _Dy of the toner amount T of the toner band 76 and the change line Q1 of the integrated value T _Dy are indicated by solid lines.

  In this embodiment, as an example, the toner band 76 is formed as a toner band formed by the image forming units 30 </ b> W and 30 </ b> V using the metallic toner on the upstream side of the intermediate transfer belt 26 among the plurality of image forming units 30. Apply. In the present embodiment, the toner band 76 functions as an example of a toner image formed outside the image forming area, and the toner amount increases by a predetermined amount or less as it goes upstream in the moving direction of the intermediate transfer belt 26. It functions as an example of a toner image. The toner band formed by the image forming units 30Y, 30M, 30C, and 30K on the downstream side of the image forming units 30W and 30V may be the toner band 76, or a toner band having a general configuration that will be described later. It may be applied.

  In the following, in order to simplify the description, the interval region 74 on the intermediate transfer belt 26 is divided into a plurality along the width direction, and from the downstream side to the upstream side along the movement direction of the intermediate transfer belt 26. Thus, a plurality of rectangular regions 78 are determined by dividing the length into predetermined lengths. As shown in FIG. 1A, in this embodiment, as an example, the image is divided into 11 (rows A to K) along the width direction of the intermediate transfer belt 26. In this embodiment, the position Dy along the moving direction of the intermediate transfer belt 26 (for example, the center position of the region 78) Dy is determined as positions D1, D2,... Sequentially from the downstream side in the moving direction. The position D0 is a predetermined position on the downstream side of the intermediate transfer belt 26 from the tip of the toner band 76. Note that an arbitrary size can be applied as the size of the region 78 formed by the division. For example, a pixel unit or the like can be applied as the minimum size. The division of the interval area 74 is not limited to this, and an arbitrary number of divisions can be applied. For example, the interval area 74 may be determined based on the size of the area 78, and along the width direction of the intermediate transfer belt 26. The number of divisions is not limited to an odd number and may be an even number.

  In the toner band 76, a toner image having a predetermined toner density is formed in a region 78 at a predetermined position. Hereinafter, the toner image formed in the region 78 is referred to as a toner block 80. As an example, the toner band 76 is formed by arranging a plurality of toner blocks 80 in a predetermined pattern. In the present embodiment, the toner block 80 functions as an example of a toner block. An arbitrary size is applied to the toner block 80 (region 78 where the toner image is formed). In the present exemplary embodiment, a rectangular toner block 80 will be described as an example. However, the toner block is not limited to the rectangular shape, and various predetermined shapes such as a circular shape are applied.

  The toner amount of the toner image changes according to the toner concentration of the toner image. When the toner concentration is high, the toner amount is larger than when the toner concentration is low. In the present embodiment, toner density is applied as an example of an index of toner amount. The toner amount T of the toner block 80 is, for example, a toner amount T = 100 when the toner concentration is 100%, a toner amount T = 50 when the toner concentration is 50%, and a toner when the toner concentration is 0% (no toner). Let the amount T = 0.

  In the toner band 76, the toner density (toner amount T) of the toner block 80 is determined so that a predetermined amount of toner is discharged over the entire region (each of the rows A to K) along the width direction of the intermediate transfer belt 26.

For the toner amount in the axial direction of the photosensitive drum 32, an integrated value _TDy of the toner amount T of the toner block 80 at the position Dy of the intermediate transfer belt 26 is applied. Further, the toner amount in the entire area in the axial direction of the photosensitive drum 32 in the toner band 76 or the like is the integrated value T _S (the toner amount T of the toner block 80 along the moving direction of the intermediate transfer belt 26 in each of the rows A to K. T _{SA to} T _SK ) are applied. In the present embodiment, the toner amount integrated value T _Dy functions as an example of the toner amount along the axial direction of the photoconductor, and the toner amount integrated value TS _is the toner amount along the circumferential direction of the photoconductor drum 32. It functions as an example.

  As shown in FIG. 1A, in the toner band 76, one toner block 80 is arranged at the center portion (row F) in the width direction at the position D1 that is the downstream end portion of the intermediate transfer belt 26 in the moving direction. Then, at the next position D2, three toner blocks 80 (rows E, F, G) are arranged. In the toner band 76, two toner blocks 80 (rows D, E, G, and H) are arranged at a position D3 with one region 78 (row F) not forming a toner image (toner block 80) interposed therebetween. Is done. Further, in the toner band 76, two toner blocks 80 are arranged after the position D4, and the number of regions 78 in which the toner blocks 80 are not formed between the two toner blocks 80 is sequentially increased. As a result, the toner block 80 is arranged so that the tip of the toner band 76 is directed to the downstream side in the moving direction of the intermediate transfer belt 26 and an arrow shape without the “pattern” is formed.

The toner band 76 is formed such that an integrated value T _{SA to} T _SK of the toner amount T of the toner block 80 along the moving direction of the intermediate transfer belt 26 in each of the rows A to K becomes a predetermined toner amount. In the toner band 76, for example, the toner amount T of each toner block 80 is 50 (T = 50), and each of the integrated values T _{SA to} T _SK is 100 (T _{SA to} T _SK = 100). .

As shown in FIG. 1B, the toner band 76 has an integrated value T _D1 = 50 at position _D1 , an integrated value T _D2 = 150 at position TD2, and an integrated value T _D3 = 200 at position TD3. Therefore, in the toner band 76, the toner amount along the axial direction of the photosensitive drum 32 is gradually increased along the moving direction of the intermediate transfer belt 26 corresponding to the circumferential direction of the photosensitive drum 32.

In the change line Q1, for example, the inclination from the position D0 to the position D1 is indicated by the ratio of the change amount (T _D1 -T _D0 ) of the integrated value T _{Dy to} the length along the moving direction of the intermediate transfer belt 26. That is, the inclination of the change line Q1 is determined by the change amount (degree of change) of the integrated value T _Dy of the toner amount per unit length along the moving direction of the intermediate transfer belt 26.

In the toner band 76, the amount of change in the toner amount integrated value _TDy increases as the slope of the change line Q1 increases. In the toner band 76, the toner block 80 is arranged so that the inclination of the change line Q1 of the integrated value _TDy of the toner amount is smaller than the predetermined inclination, whereby the toner amount is less than the predetermined amount. It is formed to increase.

  Hereinafter, as an operation of the present exemplary embodiment, a band creation process for forming a toner band in the image forming apparatus 10 will be described. The band creation process may be performed individually for each of the image forming units 30Y, 30M, 30C, 30K, 30V, and 30W, or may be performed collectively. Further, when the toner bands are formed by the plurality of image forming units 30, if the toner bands do not fit in one interval area 74, for example, the toner bands may be formed in a plurality of interval areas 74. Further, as an example, the image forming apparatus 10 uses an image forming unit 30Y, 30M, 30C, 30K, 30V, and 30W that uses toner containing metal particles on the upstream side in the moving direction of the intermediate transfer belt 26. The toner band 76 is applied to the toner band formed by the forming units 30V and 30W. The toner band formed by the image forming units 30Y, 30M, 30C, and 30K may be a toner band 76 pattern or a general pattern.

  FIG. 6 shows an example of band creation processing. This flowchart is executed during the operation of the image forming apparatus 10, and in the first step 100, it is confirmed whether or not a condition for forming a toner band is satisfied. That is, it is confirmed whether it is time to create a toner band.

  The image processing unit 66 generates exposure data for each color, and an average density for each recording medium 12 is obtained from the exposure data for each color. For example, in the image forming apparatus 10, the amount of toner supplied from the developing unit 38 to the photosensitive drum 32 is small when the average density in one or a plurality of recording media 12 is less than a predetermined threshold value. Therefore, density unevenness may occur. In the image forming unit 30, if the amount of toner supplied from the developing unit 38 to the photosensitive drum 32 continues to be small, a part of the toner stays in the developing unit 38 for a long time and deteriorates. Sometimes.

  For example, if the average density of the image formed on the recording medium 12 does not reach the threshold value or the images whose average density does not reach the threshold value continue, the controller 62 needs to create a toner band. In step 100, an affirmative determination is made, and the process proceeds to step 102. In step 102, a toner band to be created is set.

  The controller 62 sets the image forming units 30 </ b> V and 30 </ b> W to create the toner band 76 using the pattern stored in the pattern setting unit 70. In the toner band, the toner density is set based on the amount of toner discharged from the developing device 38. A predetermined toner concentration may be applied as the toner concentration. Further, for example, when the average toner density of the image formed on the recording medium 12 is less than a predetermined threshold value, a density at which the average toner density including the toner band exceeds the threshold value may be set.

  When the toner band is set, in step 104, the operation of each image forming unit 30 is controlled so that the toner band is formed in the interval area 74 outside the image area 72 on the intermediate transfer belt 26. That is, the controller 62 controls the operation of each image forming unit 30 so as to form a toner band on the intermediate transfer belt 26 at a timing when a toner image to be transferred to the recording medium 12 is not formed. As a result, the intermediate transfer belt 26 forms a toner band in the interval region 74. The controller 62 controls the toner band formed on the intermediate transfer belt 26 to apply a reverse bias voltage having a polarity opposite to that of the secondary transfer voltage at a timing when the toner band passes through the secondary transfer device 48, and the toner band is cleaned. It is removed from the intermediate transfer belt 26 by 54.

By the way, the coefficient of friction between the photosensitive drum 32 and the intermediate transfer belt 26 is reduced by the presence of toner, and the amount of toner in contact with the photosensitive drum 32 (the toner along the axial direction of the photosensitive drum 32). In this embodiment, as the toner amount integrated value T _Dy ) increases, the friction coefficient decreases. In addition, since the metal color toner contains metal particles, the friction coefficient between the photosensitive drum 32 and the intermediate transfer belt 26 is smaller than that of a toner not containing metal particles (for example, process color toner). Get smaller.

  FIG. 7A shows a toner band of the intermediate transfer belt 26 and the photosensitive drum 32, and FIG. 7B shows a toner band 82 as an example of a general toner band.

  As shown in FIG. 7A, the toner bands (for example, toner bands 76 and 82) formed on the intermediate transfer belt 26 by the upstream image forming unit 30 are moved downstream as the intermediate transfer belt 26 moves. In contact with the photosensitive drum 32 of the image forming unit 30. When the photosensitive drum 32 is changed in a direction in which the toner amount of the toner band in contact decreases, the friction coefficient increases, and the frictional force increases as the friction coefficient increases. When the photosensitive drum 32 is changed in the direction in which the frictional force is increased, the speed fluctuation is less likely to occur.

  However, the coefficient of friction of the photosensitive drum 32 decreases as the toner amount of the toner band in contact with the photosensitive drum 32 increases. When the photosensitive drum 32 changes in a direction in which the friction coefficient decreases, the frictional force decreases and slipping occurs.

As shown in FIG. 7B, the toner band 82 has a predetermined amount of toner in the entire width direction of the intermediate transfer belt 26 and a predetermined amount of toner along the moving direction of the intermediate transfer belt 26. It is formed to be a quantity. In the toner band 82, for example, the integrated values T _{SA to} T _SK of the respective toner amounts in the rows A to K along the axial direction of the photosensitive drum 32 are 100 (T _{SA to} T _SK = 100). Further, in the toner band 82, the integrated values T _D1 and T _D2 of the toner amounts at the positions D1 and _D2 are 550 (T _D1 and T _D2 = 550). Accordingly, as shown by a broken line in FIG. 1B, when the toner band 82 is formed on the intermediate transfer belt 26, the integrated value T _Dy of the toner amount on the intermediate transfer belt 26 is formed at the tip of the formed toner band 82. However, it increases from 0 to 550, and the slope of the change line Q0 is relatively large.

  In addition, the toner contains metal particles, so that the friction coefficient is smaller than when the toner does not contain metal particles. When the toner band 82 is formed of toner containing metal particles (for example, gold or silver toner), the photoconductor drum 32 is formed without any problem when the toner band 82 is formed of toner containing no metal particles. The contact with the toner band 82 further reduces the frictional force. When the frictional force is greatly reduced, the photosensitive drum 32 undergoes speed fluctuation due to slippage. In the image forming unit 30, charging, exposure, development, transfer, cleaning, and charge removal are performed in parallel with respect to the photosensitive drum 32, and the speed fluctuation of the photosensitive drum 32 is caused by charging of the photosensitive drum 32. Affects exposure and development.

  In the toner band 76 applied to the present embodiment, the toner amount along the width direction of the intermediate transfer belt 26 increases by a predetermined amount or less along the moving direction of the intermediate transfer belt 26. The image forming apparatus 10 applies a toner band 76 as a toner band to be formed on the intermediate transfer belt 26 by the image forming units 30V and 30W using toner containing metal particles.

The amount of change in the integrated amount _TDy of the toner amount that causes the speed fluctuation in the photosensitive drum 32 is determined by the inertial force of the photosensitive drum 32, the surface condition of the photosensitive drum 32 and the intermediate transfer belt 26, and the toner amount with respect to the photosensitive drum 32. It affects depending on factors such as friction characteristics. Therefore, from these factors, a change amount (upper limit of the change amount) of the toner amount integrated value _TDy that does not cause the speed fluctuation in the photosensitive drum 32 is determined. The toner band 76 has a toner amount integrated value T _Dy that does not cause a speed fluctuation in the photosensitive drum 32 as a predetermined amount (hereinafter referred to as a predetermined amount ΔT _D ). The toner amount T (toner density) of the toner block 80 and the arrangement of the toner block 80 are determined so as to increase by a predetermined amount ΔT _D or less.

As a result, the slope of the change line Q1 of the toner band 76 shown in FIG. 1B increases by a change amount (predetermined toner amount) of the integrated value T _Dy of the toner amount that does not cause the speed fluctuation in the photosensitive drum 32. It is more gradual than the case (not shown). Further, the toner band 76 has a smaller inclination of the change line Q1 than the inclination of the change line Q0 of the toner band 82, and the integrated value of the toner amount from the downstream side to the upstream side in the moving direction of the intermediate transfer belt 26. _TDy is formed so as to increase gradually. Accordingly, the image forming apparatus 10 is configured so that the photosensitive drum 32 is in contact with the toner band 76 formed by the image forming unit 30W even if the photosensitive drums 32 of the downstream image forming units 30V, 30Y, 30M, 30C, and 30K are in contact with each other. The occurrence of speed fluctuation is reduced to 32. Further, in the image forming apparatus 10, the toner band 76 is formed by the image forming unit 30 </ b> V, so that the speed fluctuations occur in the photosensitive drums 32 of the image forming units 30 </ b> Y, 30 </ b> M, 30 </ b> C, and 30 </ b> K on the downstream side of the image forming unit 30 </ b> V. It is prevented from occurring.

  Further, as shown in FIG. 1A, the toner band 76 has a shape in which toner blocks 80 are arranged so as to spread from the central portion in the width direction of the intermediate transfer belt 26 toward both outer sides. . That is, the toner band 76 is formed such that the toner blocks 80 are arranged in a shape that can be said to be line-symmetric with respect to the symmetry line CL, and the symmetry line CL is along the moving direction of the intermediate transfer belt 26. As a result, when the photosensitive drum 32 comes into contact with the toner band 76, the frictional force along the axial direction changes symmetrically, and the change in the frictional force along the axial direction cancels the photosensitive drum 32.

On the other hand, when the toner band 76 is formed by each of the image forming units 30V and 30W in one interval region 74, the integrated amount T _Dy of the toner amount by the two toner bands 76 increases by a predetermined amount ΔT _D or less. You can do that. FIG. 8A shows an example of an arrangement of the toner band 76V formed by the image forming unit 30V and the toner band 76W formed by the image forming unit 30W in the interval region 74 of the intermediate transfer belt 26. FIG. 8B shows a change in the integrated value T _Dy of the toner amount in FIG.

  As shown in FIG. 8A, as an example, the toner band 76W includes a toner block 80W having a toner amount T = 50, and the toner band 76V includes a toner block 80V having a toner amount T = 50. When the two toner bands 76V and 76W are formed in the interval region 74, the toner band 76V and the toner band 76W may be continuous along the moving direction of the intermediate transfer belt 26, or a predetermined interval may be provided. FIG. 8A shows an example in which the toner band 76V is formed with an interval of one area 72 next to the toner band 76W.

As shown in FIG. 8B, in the toner bands 76V and 76W, the slope of the change line Q2 becomes gentler than the slope Q0 of the toner band 82 in the region where the integrated value T _Dy of the toner amount increases. cage, and has a gentler than the slope when and in increments predetermined amount [Delta] T _D. Therefore, even if the photosensitive drums 32 of the image forming units 30Y, 30M, 30C, and 30K come into contact with the toner bands 76V and 76W formed on the intermediate transfer belt 26, the occurrence of speed fluctuations is reduced.

In the above description, the toner band 76 to which the toner blocks 80 are arranged so that the arrow-shaped has been described as an example, the toner band, the amount [Delta] T _D by following the change in the integrated value T _Dy of the toner amount is set in advance As long as the toner blocks are arranged so as to increase, an arbitrary shape (array pattern) is applied. A toner band as a modified example will be described below. The toner band to be described below, the slope of the change line integrated value T _Dy of the toner amount, has a gentler than the slope of the time in increments amount [Delta] T _D with predetermined integrated value T _Dy amount of toner .

[Modification 1]
FIG. 9A shows a toner band 86 according to the first modification. FIG. 9B shows a toner band 86 in which the horizontal axis is a position on the intermediate transfer belt 26 and the vertical axis is an integrated value T _Dy of the toner amount. The integrated value _TDy and change line Q3 of the toner amount of the band 86 are shown. In the following description of the modified examples, in the graph showing the toner amount integrated value _TDy and the change line, the horizontal axis is a position along the moving direction of the intermediate transfer belt 26, and the vertical axis is the toner amount integrated value T. _Dy .

  In the toner band 86 shown in FIG. 9A, the toner blocks 80 are arranged obliquely from the widthwise both ends of the intermediate transfer belt 26 toward the widthwise center, and the arrow shape of the toner band 76 is directed in the reverse direction. It has a different shape. That is, in the toner band 86, toner blocks 80 are arranged at both ends in the width direction of the intermediate transfer belt 26 at the position D1, and two toner blocks 80 are arranged at both ends in the width direction of the intermediate transfer belt 26 at the position D2. It is arranged. Also. As the toner band 86 changes to positions D3, D4, and D5, the number of empty areas 78 where no toner image is formed between the two toner blocks 80 is reduced. Further, in the toner band 86, three toner blocks 80 are continuously arranged at the center portion in the width direction of the intermediate transfer belt 26 at the position D6, and one toner block 80 is disposed at the center portion in the width direction at the rear end position D7. Is arranged.

As shown in FIG. 9B, in the toner band 86, the toner amount integrated value T _Dy gradually increases by a predetermined amount ΔT _D or less on the downstream side in the moving direction of the intermediate transfer belt 26. As a result, in the toner band 86, the inclination of the change line Q3 is gentler than the inclination of the change line Q0 of the toner band 82.

  Therefore, the toner band 86 formed by the image forming units 30V and 30W reduces the occurrence of speed fluctuations on the photosensitive drums 32 of the image forming units 30V, 30Y, 30M, 30C, and 30K.

  The toner band 86 is formed such that the toner blocks 80 are arranged in a shape that can be said to be line-symmetric with respect to the symmetry line CL, and the symmetry line CL is along the moving direction of the intermediate transfer belt 26. Thereby, even if the photosensitive drum 32 contacts the toner band 86, the change in the frictional force along the axial direction is canceled.

[Modification 2]
FIG. 10A shows a toner band 88 according to Modification 2, and FIG. 10B shows a toner amount integrated value T _Dy and a change line Q4 of the toner band 88. As shown in FIG. 10A, the toner block 80 is arranged so that the toner band 88 has a triangular shape with the tip directed downstream in the moving direction of the intermediate transfer belt 26. That is, in the toner band 88, one toner block 80 is disposed at the center in the width direction of the intermediate transfer belt 26 at the position D1, and the position Dy changes toward the upstream side in the moving direction of the intermediate transfer belt 26. Along with this, the number of toner blocks 80 is increased.

As shown in FIG. 10B, in the toner band 88, the integrated amount T _Dy of the toner amount gradually increases by a predetermined amount ΔT _D or less on the downstream side in the moving direction of the intermediate transfer belt 26. As a result, in the toner band 88, the inclination of the change line Q4 is gentler than the inclination of the change line Q0 of the toner band 82 (indicated by a broken line in FIG. 10B). Therefore, even if the photosensitive drum 32 contacts the toner band 88 formed on the intermediate transfer belt 26, the occurrence of speed fluctuation is reduced. Further, the toner band 88 is formed such that the toner blocks 80 are arranged in a shape that can be said to be line symmetric with respect to the symmetry line CL, and the symmetry line CL is formed along the moving direction of the intermediate transfer belt 26. Thereby, even if the photosensitive drum 32 contacts the toner band 88, the change in the frictional force along the axial direction is canceled.

In FIG. 11A, the toner band 88 is formed by the image forming unit 30W, and the toner band 82V to which the pattern of the toner band 82 is applied by the image forming unit 30V is continued along the moving direction of the intermediate transfer belt 26. In FIG. 10B, the toner amount integrated value T _Dy and the change line Q5 in FIG. 11A are shown.

As shown in FIG. 11A, in the toner band 88, the integrated value TDy of the toner amount on the upstream side in the moving direction of the intermediate transfer belt 26 is large. Accordingly, even if the toner band 88 is formed by the image forming unit 30W and the toner band 88V to which the pattern of the toner band 82 is applied is formed by the image forming unit 30V, the increase amount of the toner amount integrated value T _Dy is increased. It can be suppressed. The toner band 82V uses silver toner as an example, and toner blocks 80B having a toner amount T of 50 (T = 50) are arranged.

As shown in FIG. 11B, when the toner band 88 and the toner band 82V are continuously formed, even if the toner band 82V is formed continuously with the toner band 88, the integrated amount T _Dy of the toner amount change in the integrated value T _Dy of the toner amount is more than the amount [Delta] T _D a predetermined. Therefore, even if the change line Q5 includes the toner band 82V, the inclination is suppressed, and even when the toner band 88 and the toner band 82V are in continuous contact with each other, the occurrence of speed fluctuation is reduced. Is done.

12A shows the toner band 88A using the shape of the toner band 88, and FIG. 12B shows the integrated value T _Dy and change line Q6 of the toner amount of the toner band 88A. In FIG. 12B, the change line Q4 of the toner band 88 is indicated by a two-dot chain line.

In the toner band 88 shown in FIG. 10A, since toner blocks 80 having a predetermined toner amount T (toner density) are arranged, an integrated value T _S (for example, the central portion in the width direction of the intermediate transfer belt 26) The integrated values T _{SD to} T _SH ) are larger than the integrated value T _S (for example, the integrated values T _SA and T _SK ) of the toner amount at both ends.

  On the other hand, in the toner band 88A shown in FIG. 12A, as an example, a part of the toner block 80 is replaced with a toner block 80A in which the toner amount T is smaller than the toner block 80 (toner density is low). Yes. As an example, the toner band 88A uses a toner block 80 having a toner amount T = 50 and a toner block 80A having a toner amount T = 25, and the toner block 80 arranged in a triangular shape inside the toner band 88 is used as a toner block 80A. Replaced.

As shown in FIG. 12B, in the toner band 88A, the inclination of the change line Q6 is further gentler than the inclination of the change line Q4 of the toner band 88. A change in the integrated value _TDy is further suppressed.

As shown in FIG. 12A, the toner band 88A uses a toner block 80A having a toner amount T smaller than that of the toner block 80, so that the integrated value T at the center in the width direction of the intermediate transfer belt 26 is used. _S (for example, integrated values T _{SD to} T _SH ) is suppressed. Therefore, as shown in FIGS. 10A and 12A, the toner band 88A has an integrated value T _S (for example, an integrated value) at the center in the width direction of the intermediate transfer belt 26 as compared with the toner band 88. T _{SD to} T _SH ) A difference from the integrated value T _S (for example, integrated values T _SA , T _SK ) at both ends in the width direction is reduced, and toner consumption is suppressed as compared with the case where the toner band 88 is used.

[Modification 3]
FIG. 13A shows a toner band 90 according to Modification 3, and FIG. 13B shows an integrated value T _Dy of toner amount of toner band 90 and a change line Q7. In the toner band 90 shown in FIG. 13A, when the toner blocks 80 are arranged in a halftone dot pattern, the number of the toner blocks 80 is reduced on the downstream side in the moving direction of the intermediate transfer belt 26, and the number on the upstream side. Has been increased. As an example, the toner band 90 has four regions 78 at the position D1, and toner blocks 80 are arranged at the center and both ends in the width direction of the intermediate transfer belt 26, and one at each position D2. Five toner blocks 80 are arranged with an area 78 therebetween. In the toner band 80, two toner blocks 80 are arranged between two toner blocks 80 with one area 78 being provided. Further, in the toner band 90, at the position D4, three toner blocks 80 are arranged with a single area 78, and one toner block 80 is arranged with a single area 78, and a position D5. 11, 11 toner blocks 80 are continuously arranged.

  Further, as an example, in the toner band 90, the arrangement of the toner blocks 80 is line symmetric with the center in the width direction of the intermediate transfer belt 26 as a symmetric line. That is, the toner band 90 is formed so that the toner blocks 80 are arranged in a shape that can be said to be line-symmetric with respect to the symmetry line CL, and the symmetry line CL is along the moving direction of the intermediate transfer belt 26.

As a result, as shown in FIG. 13B, the toner band 90 has a toner amount integrated value T _{Dy that} is equal to or less than a predetermined amount ΔT _D from the downstream side to the upstream side in the moving direction of the intermediate transfer belt 26. Has been gradually increased. Further, in the toner band 90, the inclination of the change line Q7 is gentler than the inclination of the change line Q0 of the toner band 82. Therefore, even if the photosensitive drum 32 contacts the toner band 90, the occurrence of speed fluctuation is reduced.

[Modification 4]
FIG. 14A shows a toner band 92 according to Modification 4, and FIG. 14B shows a toner amount integrated value T _Dy and a change line Q8 of the toner band 90. As shown in FIG. 14A, the toner band 92 has a toner density higher than that of the toner block 80 and the toner block 80 so as to be continuous from one end side to the other end side along the width direction of the intermediate transfer belt 26. A low toner block 80A is arranged. At this time, the toner band 92 is shifted in order along the moving direction of the intermediate transfer belt 26 by sequentially shifting the positions of the toner blocks 80 or the toner blocks 80 and 80A arranged in each of the rows A to K. A belt-like shape that is inclined toward the upstream side in the moving direction of the intermediate transfer belt 26 with respect to the width direction of the belt.

  That is, in the toner band 92, one toner block 80, 80A is arranged on one end side in the width direction of the intermediate transfer belt 26 at the position D1, and three toner blocks 80 and one toner block are arranged at the next position D2. 80A is arranged. In the toner band 92, one toner block 80A on each side of the three toner blocks 80 is sequentially shifted in the width direction of the intermediate transfer belt 26 from the position D3 to the position D5. Further, the toner band 92 includes three toner blocks 80 and one toner block 80A at a position D6, and one toner block 80 and 80A at a position D7 on the other end side in the width direction of the intermediate transfer belt 26. They are arranged side by side.

Accordingly, as shown in FIG. 14B, the toner band 92 has a toner amount integrated value T _{Dy that} is equal to or less than a predetermined amount ΔT _D from the downstream side in the moving direction of the intermediate transfer belt 26 toward the upstream side. As a result, the slope of the change line Q8 is gentler than the slope of the change line Q0 of the toner band 82. Therefore, even if the toner band 92 contacts the photosensitive drum 32, the occurrence of speed fluctuation is reduced.

[Modification 5]
FIG. 15A shows a toner band 94 according to the modified example 5, and FIG. 15B shows an integrated value T _Dy and a change line Q9 of the toner amount of the toner band 94.

In order to reduce the occurrence of speed fluctuation in the photosensitive drum 32, the toner amount of the toner image formed in each region 78 is not limited to the arrangement of the regions 78 in which the toner blocks 80 and the like are provided (toner images are formed). (Toner concentration) may be changed stepwise or continuously. That is, the toner amount T (toner density) is changed so as to increase gradually by increasing the integrated value T _{Dy of the} toner amount along the moving direction of the intermediate transfer belt 26 by a predetermined amount ΔT _D or less. May be.

  A toner band 94 shown in FIG. 15A changes the toner amount T of the toner image formed in the region 78 so as to gradually increase from the downstream side to the upstream side in the moving direction of the intermediate transfer belt 26. . That is, the toner band 94 gradually increases the toner density from the downstream side to the upstream side of the intermediate transfer belt 26. For example, the toner band 94 includes toner blocks 96A having a toner amount T1, toner blocks 96B having a toner amount T2, toner blocks 96C having a toner amount T3, and toner blocks having a toner amount T4 at positions D1, D2, D3, D4, and D5. A toner block 96E having a toner amount 96D and a toner amount T5 is arranged in the entire width direction of the intermediate transfer belt 26. At this time, the toner band 94 has T1 = 10, T2 = 20, T3 = 30, T4 = 40, and T5 = 50 so that T1 <T2 <T3 <T4 <T5.

As a result, as shown in FIG. 15B, the toner band 94 has a toner amount integrated value T _Dy less than or equal to a predetermined amount ΔT _D from the downstream side in the moving direction of the intermediate transfer belt 26 to the upstream side. Has been increased. Further, in the toner band 94, the inclination of the change line Q8 is gentler than the inclination of the change line Q0 of the toner band 82. Therefore, even if the photosensitive drum 32 contacts the toner band 94, the occurrence of speed fluctuation is reduced.

Further, the toner band 94 is arranged so that each of the toner blocks 96A, 96B, 96C, 96D, and 96E is line symmetric with the center line of the central portion along the width direction of the intermediate transfer belt 26 as a symmetric line CL. ing. Therefore, even if the photosensitive drum 32 contacts the toner band 94, the change in the frictional force along the axial direction is canceled. As described above, the toner band is obtained by changing at least one of the toner block arrangement and the toner amount (toner density) of the toner block along the moving direction of the intermediate transfer belt 26, thereby integrating the toner amount integrated value T _Dy. However, it may be increased by a predetermined amount ΔT _D or less.

As described above, in the image forming apparatus 10 applied to the present embodiment, the integrated value T _{DY of the} toner amount gradually increases in the interval region 74 along the circumferential direction of the photosensitive drum 32 by the image forming units 30V and 30W. An increasing toner band 76 and the like are formed. Therefore, even if the photosensitive drum 32 comes into contact with the toner band 76 of the intermediate transfer belt 26 formed by the image forming units 30V and 30W, the image forming apparatus 10 may cause uneven charging or development on the photosensitive drum 32, or Disturbance of the electrostatic latent image formed on the photosensitive drum 32 is prevented.

  As a technique for suppressing the speed fluctuation of the photosensitive drum 32, there is a technique for increasing the inertial force by attaching a flywheel to the photosensitive drum 32 or increasing the mass of the flywheel. The method of suppressing the speed fluctuation of the photosensitive drum 32 using the flywheel causes an increase in component weight and an increase in cost of the image forming unit 30 and the image forming apparatus 10.

  On the other hand, the image forming apparatus 10 uses the toner band 76 or the like that is symmetric with respect to the symmetry line along the moving direction of the intermediate transfer belt 26, so that the photosensitive drum 32 can be used without using a flywheel. The occurrence of speed fluctuations in the photosensitive drum 32 is reduced. Therefore, the image forming apparatus 10 does not cause an increase in component weight or cost in order to prevent fluctuations in the speed of the photosensitive drum 32.

  In the present embodiment, the toner band 76 or the like is used as the toner image formed in the interval region 74 by the image forming units 30V and 30W using the toner including the metal particles. The present invention may be applied to a toner image formed in the interval region 74 by the image forming units 30Y, 30M, and 30C excluding the most downstream image forming unit 30K.

  In the present embodiment, as an example, the toner band is formed in the interval region 74 so as to form the toner band in the entire width direction of the intermediate transfer belt 26. However, the present invention is not limited to this, and the toner image formed in a part in the width direction. You may apply to.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Recording medium 16 Image forming part 26 Intermediate transfer belt 30 (30W, 30V, 30Y, 30M, 30C, 30K) Image forming unit 32 Photosensitive drum 36 Exposure unit 38 Developer 48 Secondary transfer unit 54 Cleaner 60 Device control unit 62 Controller 66 Image processing unit 68 Creation determination unit 70 Pattern setting unit 76 (76V, 76W), 86, 88, 90, 92, 94 Toner band 80, 80A, 80V, 80W, 96A to 96E Toner block 82 Toner band

Claims (8)

A plurality of image forming units arranged in a predetermined direction and each forming a toner image on the photoreceptor;
An intermediate transfer member that is moved in the predetermined direction and onto which the toner images formed on the photosensitive members of the plurality of image forming units are transferred;
A toner image obtained by increasing a toner amount along the axial direction of the photosensitive member by a predetermined amount or less in a direction opposite to the moving direction of the intermediate transfer member, and for the entire region in the axial direction of the photosensitive member, At least one of the plurality of image forming units is controlled so that a toner image having a predetermined amount of toner along the circumferential direction of the photoconductor is transferred outside the image forming area of the intermediate transfer member. A control unit;
An image forming apparatus including:   The image forming apparatus according to claim 1, wherein the control unit controls an image forming unit excluding the most downstream image forming unit in the moving direction of the intermediate transfer member among the plurality of image forming units. Wherein the control unit, the plurality of the image forming unit, an image forming apparatus according to claim 1 or claim 2, wherein controlling the image forming unit for forming a toner image by a toner containing metal particles.   The controller is configured to incline the toner image transferred outside the image forming area of the intermediate transfer member from the central portion in the width direction of the intermediate transfer member toward both ends, or from the both ends in the width direction to the central portion. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming unit is controlled to have a shape inclined toward the surface.   The control unit is configured to form the toner image formed outside the image forming area of the intermediate transfer member in a shape that is symmetrical with respect to a line along the moving direction of the intermediate transfer member. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled. The toner image formed outside the image forming area of the intermediate transfer member has a predetermined size and a toner amount of a predetermined toner amount as a unit, and the toner block in the width direction of the intermediate transfer member is a unit. 6. The image forming apparatus according to claim 1, wherein the number is increased in a direction opposite to a moving direction of the intermediate transfer member. When the toner amount is equal to or less than the predetermined amount, the amount of change in the toner along the moving direction of the intermediate transfer member in the toner image transferred to the intermediate transfer member causes speed fluctuations in the photosensitive member that contacts the toner image. any one image forming equipment according to claims 1 to 6 is an amount less than the amount of change to be. The image forming apparatus according to claim 1, wherein the toner image is connected from one end side to the other end side in the width direction of the intermediate transfer member.