Image forming apparatus

Abstract

To prevent separation, from a conveyance path, of a recording medium conveyed between a secondary transfer unit and a secondary transfer unit arranged side by side in a conveyance direction.SOLUTION: An image forming apparatus 10 comprises: a conveying belt 21 that conveys a recording sheet along a conveyance direction while in contact with one face of the recording sheet; a plurality of intermediate transfer belt bodies 40, 60 that are arranged side by side in the conveyance direction on a side of the other surface of the recording sheet on the conveyance path, and to which toner images formed in a plurality of image forming units 32, 52 are primarily transferred; secondary transfer units 74, 76 that are arranged side by side in the conveyance direction, and secondarily transfer the toner images on a plurality of intermediate transfer belts 21 to the other surface of the recording sheet conveyed by the conveying belt 21; and conveying rolls 110, 120 that are in contact, on peripheral surfaces 110A, 120A, with the other surface of the recording medium sheet conveyed by the conveying belt 21 between one secondary transfer unit 74 and the other secondary transfer unit 76 arranged side by side in the conveyance direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] Patent Document 1 discloses a technique related to an image forming apparatus such as an electrophotographic copying machine and a printer, and particularly relates to an improvement in a duplex image forming apparatus capable of forming a duplex image. In this prior art, an air conveyance means disposed on at least one side of a recording material conveyance path between the most downstream transfer means and the fixing means, a recording material detection means for detecting information on the conveyed recording material, and an air flow rate control means for controlling the air flow rate of the air conveyance means based on the detection result from the recording material detection means are provided. Further, one or a plurality of rows of star wheels are rotatably provided on at least one side of the recording material conveyance path in the conveyance direction of the recording material. Further, an interim fixing means capable of interim fixing an unfixed image on at least one side of the recording material is provided, and the interim fixed recording material is guided to the fixing means by a recording material guiding member.

[0003] Patent Document 2 discloses a technique related to an image forming apparatus, particularly an image forming apparatus capable of forming a developer image based on image information. In this prior art, a color printer capable of forming a developer image based on image information includes a main body having a plurality of first image forming units, a first transfer belt, and an elastic roller. The first image forming unit is a unit capable of forming an image of each color based on image information. The first transfer belt is where the images formed by the first image forming units are respectively transferred. The intermediate transfer roller has at least a surface formed of an elastic member, and the image is transferred from the first transfer belt and then transferred to the paper. The main body can house the first image forming unit, the first transfer belt, and the intermediate transfer roller therein, and has a shutter portion disposed near the intermediate transfer roller and capable of being opened and closed.

[0004] Patent Document 3 discloses a color image duplication system in which a developed image is transferred from an image forming member to a receiving material via at least one intermediate transfer member. This prior art includes two toner image acquisition devices, toner, and first and second toner image acquisition devices each having toner. The first toner image acquisition device transfers the toner to the second toner image acquisition device, and the second toner image acquisition device transfers the toner to the receiving material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-44973 [Patent Document 2] Japanese Patent Publication No. 2009-3236 [Patent Document 3] Japanese Patent Publication No. 2014-13388 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In an image forming apparatus that sequentially transfers toner images from multiple intermediate transfer bodies, onto a transported recording medium, to superimpose the toner images, there is a risk that the recording medium being transported between the secondary transfer units, which are aligned in the transport direction, may deviate from the transport path.

[0007] The object of the present invention is to suppress the separation of the recording medium from the transport path when it is transported between secondary transfer units aligned in the transport direction, compared to a case where there are no members in contact with the surface on which the toner image of the recording medium is transferred when it is transported between secondary transfer units aligned in the transport direction. [Means for solving the problem]

[0008] The first embodiment is an image forming apparatus comprising: a transport means for transporting a recording medium along a transport path in contact with one surface of the recording medium; a plurality of intermediate transfer bodies provided in the transport direction on the other surface side of the recording medium along the transport path, on which toner images formed by a plurality of image forming units are primary transferred; a plurality of secondary transfer units arranged in the transport direction for secondary transfer of the toner images of the plurality of intermediate transfer units to the other surface of the recording medium being transported by the transport means; and one or more rotating bodies whose circumferential surfaces contact the other surface of the recording medium being transported by the transport means between one of the secondary transfer units and the other secondary transfer unit arranged in the transport direction.

[0009] The second embodiment is an image forming apparatus according to the first embodiment, wherein the circumferential surface of the rotating body is insulating, and the apparatus is equipped with a charging member that charges the circumferential surface of the rotating body with the same polarity as the toner image.

[0010] The third embodiment is an image forming apparatus according to the second embodiment, wherein the rotating body is a conveyor roll with an insulating circumferential surface, the conveying means is a conveyor belt stretched in the conveying direction, and comprises an opposing roll positioned opposite the conveyor roll and the conveyor belt, the circumferential surface of the conveyor roll is adjusted to a surface potential set by the charging member, and the opposing roll is set to a potential that forms an electric field in which the electrostatic force acting on the toner image is directed toward the recording medium, relative to the surface potential of the conveyor roll.

[0011] The fourth embodiment is the image forming apparatus according to the third embodiment, wherein the opposing roll is grounded.

[0012] The fifth embodiment is an image forming apparatus according to any one of the first to fourth embodiments, wherein the circumferential surface of the rotating body is made of resin.

[0013] The sixth embodiment is an image forming apparatus according to the first embodiment, wherein the rotating body is a conveying roll with a conductive circumferential surface, the conveying means is a conveying belt stretched in the conveying direction, and comprises an opposing roll positioned opposite the conveying roll and the conveying belt, and the circumferential surface of the conveying roll and the opposing roll are set to a potential that forms an electric field in which the electrostatic force acting on the toner image is directed toward the recording medium.

[0014] The seventh embodiment is the image forming apparatus according to the sixth embodiment, wherein the circumferential surface of the conveying roll or the opposing roll is grounded.

[0015] The eighth embodiment is an image forming apparatus according to the sixth or seventh embodiment, wherein an insulating layer is formed on the circumferential surface of the conductive transport roll.

[0016] The ninth embodiment is an image forming apparatus according to any one of the first, sixth, and seventh embodiments, wherein the circumferential surface of the rotating body is made of metal.

[0017] The tenth embodiment is an image forming apparatus according to any one of the first to ninth embodiments, further comprising a cleaning member for cleaning the circumferential surface of the rotating body.

[0018] The eleventh aspect is the image forming apparatus according to the tenth aspect, wherein the cleaning member is a blade that contacts the circumferential surface of the rotating body.

[0019] The twelfth embodiment is an image forming apparatus according to the eleventh embodiment, which has a mode for attaching toner to the rotating body at a set timing.

[0020] The thirteenth embodiment is an image forming apparatus according to any one of the first to twelfth embodiments, wherein the distance between the secondary transfer unit and the rotating body is set to be less than or equal to the minimum width in the transport direction of the recording medium on which an image can be formed.

[0021] The fourteenth aspect is the image forming apparatus according to the thirteenth aspect, in which a plurality of the rotating bodies are provided, and the distance between one of the rotating bodies arranged in the conveyance direction and the other rotating body is set to be equal to or less than the width in the conveyance direction of the smallest recording medium on which image formation is possible.

[0022] The fifteenth aspect is the image forming apparatus according to any one of the first to fourteenth aspects, in which one or more of the image forming units are arranged between the intermediate transfer bodies arranged in the conveyance direction.

Advantages of the Invention

[0023] According to the first aspect, compared with the case where there is no member that contacts the other surface of the recording medium conveyed between the secondary transfer portions arranged in the conveyance direction, the separation from the conveyance path of the recording medium conveyed between the secondary transfer portions arranged in the conveyance direction is suppressed.

[0024] According to the second aspect, compared with the case where the circumferential surface of the rotating body is charged with the opposite polarity to the toner of the toner image, the adhesion of the toner to the conveyance roll is suppressed.

[0025] According to the third aspect, compared with the case where the electrostatic force acting on the toner image is set to a potential that forms an electric field directed toward the conveyance roll side, the adhesion of the toner to the conveyance roll is suppressed.

[0026] According to the fourth aspect, it is less costly compared with the case where a voltage is applied to the opposing roll.

[0027] According to the fifth aspect, compared with the case where the circumferential surface of the rotating body is rubber, the adhesion of the toner to the rotating body is suppressed.

[0028] According to the sixth aspect, compared with the case where the electrostatic force acting on the toner image is set to a potential that forms an electric field directed toward the conveyance roll side, the adhesion of the toner to the conveyance roll is suppressed.

[0029] According to the seventh aspect, it is less costly compared with the case where a voltage is applied to both the conveyance roll and the opposing roll.

[0030] According to the eighth embodiment, the electrical leakage resistance of the conveying roll is improved compared to the case in which an insulating layer is not formed on the circumferential surface of the conductive conveying roll.

[0031] According to the ninth embodiment, toner adhesion to the rotating body is suppressed compared to the case where the circumferential surface of the rotating body is made of rubber.

[0032] According to the tenth embodiment, compared to the case where the circumferential surface of the rotating body is not cleaned, the adhesion of toner attached to the rotating body to the recording medium is suppressed.

[0033] According to the eleventh embodiment, this method is less expensive than the method used to electrically clean the circumferential surface of a rotating body with a brush.

[0034] According to the twelfth embodiment, compared to the case where no toner is applied to the rotating body at all, the peeling of the blade is suppressed.

[0035] According to the thirteenth embodiment, compared to the case where the distance between the secondary transfer unit and the transport roll is greater than the width in the transport direction of the smallest image-forming recording medium, the separation of the smallest image-forming recording medium from the transport path, which is transported between secondary transfer units aligned in the transport direction, is suppressed.

[0036] According to the fourteenth embodiment, compared to the case where the distance between the rotating bodies is greater than the width in the transport direction of the smallest image-forming recording medium, the separation of the smallest image-forming recording medium from the transport path, which is transported between secondary transfer units aligned in the transport direction, is suppressed.

[0037] According to the fifteenth embodiment, by positioning one or more image forming units between intermediate transfer bodies, even if the distance between secondary transfer units aligned in the transport direction widens, the separation from the transport path that transports the secondary transfer units aligned in the transport direction is suppressed by the rotating body. [Brief explanation of the drawing]

[0038] [Figure 1]This is a diagram showing the configuration of the image forming apparatus in the first embodiment. [Figure 2] This is an enlarged view of the main part of Figure 1. [Figure 3] This is a diagram showing the configuration of the conveyor belt device according to the first embodiment. [Figure 4] Figure 3 is a schematic diagram of the main part. [Figure 5] Block diagram showing the configuration of control devices, etc. [Figure 6] This is a diagram showing the configuration of the conveyor belt device according to the second embodiment. [Figure 7] Figure 6 is a schematic diagram of the main part. [Figure 8] This is a schematic diagram of the main part of a modified example of the second embodiment. [Modes for carrying out the invention]

[0039] <First Embodiment> An image forming apparatus according to a first embodiment of the present invention will be described.

[0040] In Figure 1, the width direction of the image forming apparatus 10 is denoted as the X direction, the height direction as the Y direction, and the depth direction as the Z direction, indicated by arrows X, Y, and Z, respectively. When it is necessary to distinguish between one side and the other side in the X, Y, and Z directions, the right side of the image forming apparatus 10 shown in Figure 1 is described as the +X side, the left side as the -X side, the top side as the +Y side, the bottom side as the -Y side, the front side as the +Z side, and the rear side as the -Z side. In this embodiment, recording paper P is used as an example of a recording medium, and the upstream side in the transport direction in which the recording paper P is transported is called the "transport direction upstream side," and the downstream side in the transport direction is called the "transport direction downstream side." In this embodiment, the image forming apparatus 10 is a so-called single-pass system, and printing is performed by the recording paper P passing in front of the image forming unit 30 and the image forming unit 50, which will be described later, only once each.

[0041] [Overall structure] First, I will explain the overall configuration of the image forming apparatus.

[0042] As shown in Figure 1, the image forming apparatus 10 includes a storage unit 12 in which recording paper P (see also Figure 4) as an example of a recording medium is stored, a transport unit 11 that transports the recording paper P along a transport path 19, and image forming units 30 and 50 that form toner images to be transferred to the recording paper P. The "transport direction" is the direction in which the recording paper P is transported along the transport path 19.

[0043] The storage section 12 is retractable from the main body 10A of the image forming apparatus 10, and stores the recording paper P inside.

[0044] The transport unit 11 includes, in order from the upstream side in the transport direction, a discharge roll 13, a transport roll 14, a pair of resist rolls 15, a transport belt unit 20, a fixing device 18, and a discharge roll 17.

[0045] The discharge roll 13 sends the recording paper P stored in the storage unit 12 to the transport path 19 that constitutes the transport unit 11. The transport roll 14 transports the recording paper P along the transport path 19.

[0046] The resist roll pair 15 transports the recording paper P, which has been transported by the transport roll 14, to the upstream secondary transfer position TJ2, which will be described later. The resist roll pair 15 sandwiches the recording paper P between the resist roll 15A and the pinch roll 15B and transports the recording paper P downstream in the transport direction.

[0047] The conveyor belt unit 20 transfers the toner image formed by the image forming units 30 and 50 onto the recording paper P, while simultaneously conveying the recording paper P downstream along the conveyor path 19. Details of the conveyor belt unit 20 will be described later.

[0048] The fixing device 18 has a pair of fixing rolls 16, and heats and pressurizes the recording paper P on which the toner image has been transferred as it passes between the pair of fixing rolls 16, thereby fixing the toner image to the recording paper P.

[0049] The discharge roll 17 discharges the recording paper P, on which the toner image has been fixed by the fixing device 18, to the discharge unit 9.

[0050] The image forming unit 30 and the image forming unit 50 are arranged side by side in the vertical direction. In this embodiment, the image forming unit 50 is positioned above the image forming unit 30. From another perspective, the image forming unit 50 is positioned downstream of the image forming unit 30 in the transport direction.

[0051] As shown in Figure 2, the image forming unit 30 comprises multiple image forming units 32, four in this embodiment, and an endless intermediate transfer belt 40. The intermediate transfer belt 40, as an example of an intermediate transfer body, is mounted so as to be rotatable counterclockwise when viewed from the front in Figure 2, and onto which the toner image formed by the four image forming units 32 is transferred.

[0052] The image forming unit 32 comprises an image forming unit 32W that forms a white toner image, an image forming unit 32M that forms a magenta toner image, an image forming unit 32C that forms a cyan toner image, and an image forming unit 32Y that forms a yellow toner image. These four image forming units 32 are arranged in the order of image forming unit 32Y, image forming unit 32M, image forming unit 32C, and image forming unit 32W, starting from the upstream side (closer to the support roll 44, which will be described later) in the rotational direction of the intermediate transfer belt 40. Note that Y, M, C, and W are omitted in the description when it is not necessary to distinguish between them.

[0053] Furthermore, in the following, the upstream side of the intermediate transfer belt 40 in the direction of rotation will be referred to as the "upstream side in the direction of rotation," and the downstream side in the direction of rotation will be referred to as the "downstream side in the direction of rotation." In other words, in the image forming unit 32, the image forming unit 32W is located on the furthest downstream side in the direction of rotation.

[0054] The image forming unit 32 includes a photoreceptor 33, a photoreceptor charging member 34 that charges the peripheral surface of the photoreceptor 33, an exposure device 35 that irradiates the charged photoreceptor 33 with exposure, and a developing device 36 that develops the electrostatic latent image formed by the exposure and visualizes it as a toner image.

[0055] The developing apparatus 36 has developing rolls 39Y, 39M, 39C, and 39W, and each has a developing bias applied by the power supply unit 99 (see Figure 5).

[0056] Furthermore, primary transfer rolls 37Y, 37M, 37C, and 37W are positioned opposite each photoreceptor 33 across the intermediate transfer belt 40 to transfer the toner image formed by the image forming unit 32 to the intermediate transfer belt 40. The intermediate transfer belt 40 is wrapped around a support roll 44 that supports the intermediate transfer belt 40 and a backup roll 42 that is positioned in the upstream secondary transfer unit 74, which will be described later. The primary transfer unit 70 is composed of the photoreceptor 33, the primary transfer rolls 37, and the intermediate transfer belt 40. The positions between the photoreceptors 33Y, 33M, 33C, and 33W and the intermediate transfer belt 40 are designated as primary transfer positions TY1, TM1, TC1, and TW1, respectively.

[0057] The image forming unit 50 has the same configuration as the aforementioned image forming unit 30, except that it forms images of different colors.

[0058] The image forming unit 50 comprises multiple image forming sections 52, or four in this embodiment, and an intermediate transfer belt 60. The intermediate transfer belt 60, as an example of an intermediate transfer body, is mounted so as to be rotatable counterclockwise when viewed from the front in Figure 2, and onto which the toner image formed by the four image forming sections 52 is transferred.

[0059] Furthermore, the image forming section 52 has the same configuration as the image forming section 32 of the image forming unit 30, except that the color being formed is different. Also, the intermediate transfer belt 60 and the primary transfer roll 57, which will be described later, have the same configuration as the intermediate transfer belt 40 and primary transfer roll 37 of the image forming unit 30. In addition, the other components constituting the image forming unit 50 are the same as those of the image forming unit 30.

[0060] The image forming unit 52 includes an image forming unit 52K that forms a black toner image, an image forming unit 52G that forms a gold toner image, an image forming unit 52S that forms a silver toner image, and an image forming unit 52T that forms a transparent toner image. Note that T, S, G, and K are omitted in descriptions where it is not necessary to distinguish between them.

[0061] The four image forming units 52 are arranged in the following order from the upstream side in the rotation direction (the side closer to the support roll 64, which will be described later): image forming unit 52T, image forming unit 52S, image forming unit 52G, and image forming unit 52K. In other words, in the image forming unit 52, image forming unit 52K is located furthest downstream in the rotation direction, image forming unit 52G and image forming unit 52S are located upstream of image forming unit 52K in the rotation direction, and image forming unit 52T is located furthest upstream in the rotation direction.

[0062] The image forming unit 52 includes a photoreceptor 53, a photoreceptor charging member 54, an exposure device 55, and a developing device 56.

[0063] The developing apparatus 56 has developing rolls 59T, 59S, 59G, and 59K, and each has a developing bias applied by the power supply unit 99 (see Figure 5).

[0064] Furthermore, primary transfer rolls 57T, 57S, 57G, and 57K are positioned opposite each photoreceptor 53 across the intermediate transfer belt 60. The intermediate transfer belt 60 is wound around a support roll 64 and a backup roll 62 located in the downstream secondary transfer section 76, which will be described later. The primary transfer section 72 is composed of the photoreceptors 53, primary transfer rolls 57, and the intermediate transfer belt 60. The positions between the photoreceptors 53T, 53S, 53G, and 53K and the intermediate transfer belt 60 are designated as primary transfer positions TT1, TS1, TG1, and TK1, respectively.

[0065] Furthermore, the developing devices 36 of each color image forming section 32 of the image forming unit 30 and the developing devices 56 of each color image forming section 52 of the image forming unit 50 are connected via supply lines to multiple toner cartridges (not shown) each containing toner corresponding to each color. The toner contained in each toner cartridge is supplied to the respective color developing devices 36 and 56 via the supply lines as needed when a supply device (not shown) provided in the supply lines is activated.

[0066] Furthermore, in this embodiment, since each image forming section 52 of the image forming unit 50 is located below the intermediate transfer belt 60, each image forming section 52 is positioned between the intermediate transfer belt 40 and the intermediate transfer belt 60.

[0067] [Conveyor Roll Unit] Next, we will describe the details of the conveyor belt unit 20.

[0068] As shown in Figures 2 and 3, the conveyor belt unit 20 includes an endless conveyor belt 21, a support roll 22 that supports the conveyor belt 21, a drive roll 23 that rotates the conveyor belt 21, secondary transfer rolls 24 and 25 positioned opposite the backup rolls 42 and 62 with the intermediate transfer belts 40 and 60 in between, the conveyor rolls 110 and 120 of the conveyor roll unit 100 (described later), and opposing rolls 111 and 121 positioned opposite the conveyor rolls 110 and 120 with the conveyor belt 21 in between.

[0069] As an example of a conveying means, the conveyor belt 21 is stretched by support rolls 22 and drive rolls 23, which are spaced apart in the direction of conveying the recording paper P (see Figures 1 and 4), and in this embodiment, in the vertical direction (Y direction). The drive rolls 23 rotate by a drive mechanism (not shown), causing the endless conveyor belt 21 to rotate. The support rolls 22 rotate in conjunction with the rotation of the conveyor belt 21.

[0070] In this embodiment, the transport direction of the recording paper P transported by the transport belt unit 20 is the Y direction.

[0071] The secondary transfer roll 24, with the recording paper P (see Figures 1 and 4) and the transport belt 21 sandwiched between it and the backup roll 42, transfers the toner image TZ (see Figure 4) formed on the intermediate transfer belt 40 of the image forming unit 30 to the surface PA (see Figure 4) of the recording paper P being transported by the transport belt 21. Similarly, the secondary transfer roll 25, with the recording paper P and the transport belt 21 sandwiched between it and the backup roll 62, transfers the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 to the surface PA (see Figure 4) of the recording paper P.

[0072] As shown in Figure 4, the side of the recording paper P on which the toner image TZ is transferred is referred to as surface PA, and the side in contact with the transport belt 21 is referred to as surface PB.

[0073] As shown in Figures 2 and 3, the secondary transfer section 74 is composed of a backup roll 42, a secondary transfer roll 24, and an intermediate transfer belt 40. Furthermore, the secondary transfer section 76 is composed of a backup roll 62, a secondary transfer roll 25, and an intermediate transfer belt 60.

[0074] The secondary transfer rolls 24 and 25 rotate in conjunction with the rotation of the conveyor belt 21. Furthermore, a transfer bias is applied to the secondary transfer rolls 24 and 25 by the power supply unit 99 (see Figure 5).

[0075] The secondary transfer position TJ2 is defined as the space between the intermediate transfer belt 40 and the transport belt 21 of the image forming unit 30, and the secondary transfer position TK2 is defined as the space between the intermediate transfer belt 60 and the transport belt 21 of the image forming unit 50. Note that the secondary transfer position TK2 is the furthest downstream secondary transfer position.

[0076] Furthermore, the conveyor belt unit 20 is equipped with a belt cleaning device (not shown) for cleaning the conveyor belt 21. The belt cleaning device (not shown) cleans the conveyor belt 21 on the downstream side in the rotational direction of the furthest downstream secondary transfer position TK2 and on the upstream side in the rotational direction of the furthest upstream secondary transfer position TJ2.

[0077] As an example of a transport means, on the side of the record paper P on the transport belt 21 (see Figure 4), a transport roll unit 100 is provided between the image forming units 30 and 50, which are spaced apart vertically in the transport direction.

[0078] The transport roll unit 100 has multiple transport rolls, two in this embodiment: 110 and 120. Recording paper P (see Figure 4) and a transport belt 21 are placed between the transport rolls 110 and 120, which are examples of rotating bodies, and the opposing rolls 111 and 121, and the recording paper P is transported downstream in the transport direction. The transport rolls 110 and 120 are configured to rotate by a drive mechanism (not shown).

[0079] Note that the conveyor rolls 110 and 120 and the surrounding components are the same components, differing only in their position in the conveying direction. Therefore, in the schematic diagram of Figure 4, they are not shown separately.

[0080] As shown in Figures 3 and 4, the conveyor rolls 110 and 120 are composed of cylindrical metal shafts 112 and 122, and roll body portions 114 and 124 made of insulating resin with a circular cross-sectional shape perpendicular to the axial direction, formed around the shafts 112 and 122. In this embodiment, the roll body portions 114 and 124 are made of fluororesin. Furthermore, the static friction coefficient of the circumferential surfaces 110A and 120A of the conveyor rolls 110 and 120 with respect to the recording paper P (see Figures 1 and 4) is 0.3 or less. In this case, the recording paper P is ordinary paper.

[0081] Here, the minimum width LS is defined as the width in the transport direction of the smallest recording paper PS in the image forming apparatus 10 (see Figure 1). In this embodiment, the minimum width LS is the width of the shorter side of an A5 size recording paper PS when it is fed horizontally. In other words, in this embodiment, the minimum width LS is the width of the shorter side of an A5 size.

[0082] As shown in Figure 3, the distance L1 between the upstream conveyor roll 110 and the secondary transfer section 74 in the conveying direction is less than or equal to the minimum width LS. Similarly, the distance L3 between the downstream conveyor roll 120 and the secondary transfer section 76 in the conveying direction is less than or equal to the minimum width LS. Furthermore, the distance L2 between the upstream conveyor roll 110 and the downstream conveyor roll 120 in the conveying direction is less than or equal to the minimum width LS. Note that the distances L1, L2, and L3 are the distances between the axes of the conveyor rolls 110 and 120 and the secondary transfer rolls 24 and 25 of the secondary transfer sections 74 and 76.

[0083] Furthermore, it is desirable that the distance L1 between the upstream conveyor roll 110 and the secondary transfer section 74 is smaller than the minimum width LS. Similarly, it is desirable that the distance L3 between the downstream conveyor roll 120 and the secondary transfer section 76 is smaller than the minimum width LS. Moreover, it is desirable that the distance L2 between the upstream conveyor roll 110 and the downstream conveyor roll 120 is smaller than the minimum width LS.

[0084] As shown in Figures 3 and 4, the transport roll units 100 and 200 are provided with charging rolls 130 and 140, which are examples of charging members for the transport rolls 110 and 120 that contact the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 and rotate in a driven manner. The charging rolls 130 and 140 consist of metal shafts 132 and 142, and semiconductive rubber parts 134 and 144 formed around the shafts 132 and 142, with a circular cross-sectional shape perpendicular to the axial direction. A roll charging bias is applied to the metal shafts 132 and 142 of the charging rolls 130 and 140 by a power supply unit 99 (see Figure 5), and the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are charged to a set potential.

[0085] Specifically, the toner image TZ (see Figure 4) is charged with the same polarity, and in this embodiment, with a negative polarity. Note that the potential due to the charging of the peripheral surfaces 110A and 120A of the transport rolls 110 and 120 in this embodiment is -300 to -600V, but this is just an example and is not limited to this potential.

[0086] Cleaning rolls 136 and 146, each consisting of a spirally wound sponge as an example of a cleaning material, are in contact with the electrostatically charged rolls 130 and 140. The cleaning rolls 136 and 146 rotate in contact with the circumferential surfaces of the electrostatically charged rolls 130 and 140, cleaning their surfaces. The toner and other debris cleaned by the cleaning rolls 136 and 146 are transported to a waste toner box (not shown) for collection.

[0087] Furthermore, cleaning blades 150 and 160, which are examples of cleaning members, come into contact with the circumferential surfaces 110A and 120A of the transport rolls 110 and 120, cleaning the circumferential surfaces 110A and 120A. The toner and other attached materials cleaned by the cleaning blades 150 and 160 are stored in the storage sections 152 and 162 (see Figure 3) and then transported to a waste toner box (not shown) for collection.

[0088] The aforementioned opposing rolls 111 and 121 are composed of cylindrical metal shafts 113 and 123, and rubber roll bodies 115 and 125 with a circular cross-section perpendicular to the axial direction, formed around the shafts 113 and 123. The metal shafts 113 and 123 are grounded via resistors 117 and 127 (see Figure 4). Therefore, the potential of the opposing rolls 111 and 121 is 0V.

[0089] Furthermore, when the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are charged to -300 to -600V by the charged rolls 130 and 140, an electrostatic force is generated in the negatively charged toner image TZ (see Figure 4) in the direction toward the transport belt 21 and the recording paper P due to the electric field formed between the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 and the opposing rolls 111 and 121.

[0090] Here, the opposing rolls 111 and 121 can be switched by the power supply unit 99 (see Figure 5) from a grounded state to a state in which a potential greater than the absolute value of the potential of the transport rolls 110 and 120 is applied. In this state, an electrostatic force is generated in the direction toward the transport rolls 110 and 120 by the electric field formed between the circumferential surfaces 110A and 120 of the transport rolls 110 and 120 and the opposing rolls 111 and 121.

[0091] [Control device] Next, using Figure 5, we will describe the control device 80 that controls the operation of the image forming apparatus 10.

[0092] As shown in Figure 5, the control device 80 is electrically connected to the image forming unit 30, the image forming unit 50, the communication unit 90, the non-volatile memory 92, and the power supply unit 99, among others.

[0093] The control unit 80 has a CPU 81 (Central Processing Unit), ROM 82 (Read Only Memory), RAM 83 (Random Access Memory), and an input / output interface (I / O 84) connected via a bus.

[0094] Here, ROM 82 stores an image formation control program (not shown) that is to be executed by CPU 81. The CPU 81 then reads the image formation control program (not shown) from ROM 82 and loads it into RAM 83, thereby executing the printing process according to the image formation control program (not shown).

[0095] Furthermore, the I / O 84 is connected to the image forming unit 30, the image forming unit 50, the communication unit 90, and the non-volatile memory 92. The communication unit 90 is an interface for data communication between the image forming apparatus 10 and a terminal device such as a personal computer (not shown). The non-volatile memory 92 stores information necessary for the image forming apparatus 10 to perform image forming operations.

[0096] The control device 80 performs various controls to form toner images on the intermediate transfer belt 40 (see Figure 2, etc.) using the image forming sections 32 (see Figure 2, etc.) of each color of the image forming unit 30. Similarly, the control device 80 performs various controls to form toner images on the intermediate transfer belt 60 (see Figure 2, etc.) using the image forming sections 52 (see Figure 2, etc.) of each color of the image forming unit 50.

[0097] Furthermore, the control device 80 controls the development bias applied to the development rolls 39Y, 39M, 39C, 39W, 59T, 59S, 59G, and 59K (see Figure 2, etc.) of the development units 36 and 56 by the power supply unit 99. In addition, the control device 80 controls the transfer bias applied to the secondary transfer rolls 24 and 25 (see Figure 2, etc.) by the power supply unit 99.

[0098] Furthermore, the control device 80 controls the roll charging bias applied to the charged rolls 130 and 140 of the transport roll unit 100 by the power supply device 99.

[0099] Here, while the recording paper P is being transported by the transport roll unit 100, the control device 80 charges the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 of the transport roll unit 100 to -300 to -600V using the charged rolls 130 and 140.

[0100] Furthermore, the control device 80 performs control to apply toner to the transport rolls 110 and 120 of the transport roll unit 100 at pre-set intervals, for example, every 4,000 printed pages.

[0101] Specifically, a patch image is formed using toner in one of the image forming sections 32 of the image forming unit 30 and transferred to the transport belt 21. The power supply unit 99 switches the opposing rolls 111 and 121 from a grounded state to a state where a potential greater than the absolute value of the potential of the transport rolls 110 and 120 is applied, causing the patch image to adhere to the transport rolls 110 and 120. The patch image that has adhered to the transport rolls 110 and 120 is then cleaned by the cleaning blades 150 and 160.

[0102] [Image forming process] Next, an overview of the image forming process in the image forming apparatus 10 will be described.

[0103] First, the control device 80 controls each image forming unit 32 so that a toner image is formed on the intermediate transfer belt 40 of the image forming unit 30. Similarly, it controls each image forming unit 52 so that a toner image is formed on the intermediate transfer belt 60 of the image forming unit 50.

[0104] Specifically, the control device 80 applies a voltage to the photoreceptor charging members 34 and 54, and charges the circumferential surfaces of the photoreceptors 33 and 53 to a predetermined potential using the voltage applied to the photoreceptor charging members 34 and 54. Subsequently, based on the image data acquired via the communication unit 90, the control device 80 irradiates the circumferential surfaces of the photoreceptors 33 and 53, which have been charged by the photoreceptor charging members 34 and 54, with exposure devices 35 and 55 to form an electrostatic latent image. As a result, an electrostatic latent image corresponding to the image data is formed on the circumferential surfaces of the photoreceptors 33 and 53.

[0105] Next, the control device 80 develops the electrostatic latent image formed by the exposure devices 35 and 55 using the developing devices 36 and 56, and visualizes it as a toner image. Furthermore, the control device 80 uses the primary transfer rolls 37 and 57 to transfer the toner images formed on the circumferential surfaces of the photoreceptors 33 and 53 of each color onto the intermediate transfer belts 40 and 60.

[0106] In this way, the image forming unit 30 forms a toner image TZ (see Figure 4) on the intermediate transfer belt 40 by superimposing, for example, yellow (Y), magenta (M), cyan (C), and white (W) toners. Similarly, the image forming unit 50 forms a toner image on the intermediate transfer belt 60 by superimposing, for example, black (K), gold (G), silver (S), and transparent (T) toners.

[0107] Here, the recording paper P, which has been sent from the storage unit 12 to the transport path 19 by the delivery roll 13, is sent to the secondary transfer position TJ2 upstream in the transport direction after the transport timing is adjusted by the register roll pair 15 based on the control of the control device 80. At this secondary transfer position TJ2, the recording paper P is transported between the backup roll 42 and the secondary transfer roll 24, and the toner image on the outer surface of the intermediate transfer belt 40 is transferred to the recording paper P. Then, the recording paper P with the transferred toner image is transported downstream in the transport direction to the secondary transfer position TK2 downstream in the transport direction.

[0108] At this time, the control device 80 adjusts the timing of starting image formation so that the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 is superimposed and transferred onto the toner image on the recording paper P that has been transported from the upstream side in the transport direction.

[0109] The recording paper P, on which the toner images of each color formed by the image forming unit 30 and the image forming unit 50 are superimposed and transferred, is fixed by the fixing roll pair 16 of the fixing device 18, and then discharged by the discharge roll 17 to the discharge section 9 located at the top of the main body 10A of the image forming device.

[0110] Here, as the recording paper P is transported from the secondary transfer section 74 on the upstream side in the transport direction to the secondary transfer section 76 on the downstream side in the transport direction, the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 of the transport roll unit 100, which are charged to -300 to -600V, come into contact with the surface PA on the recording paper P to which the toner image TZ (see Figure 4) has been transferred, thereby transporting the recording paper P downstream in the transport direction.

[0111] [Effect] Next, the operation of this embodiment will be described.

[0112] As the recording paper P is transported from the secondary transfer section 74 on the upstream side in the transport direction to the secondary transfer section 76 on the downstream side in the transport direction, the circumferential surfaces 110A and 120A of the transport roll unit 100 come into contact with the surface PA on which the toner image TZ of the recording paper P has been transferred, thereby transporting the recording paper P downstream in the transport direction.

[0113] Therefore, compared to the case where there are no members in contact with the surface PA of the recording paper P being transported between the two secondary transfer units 74 and 76 aligned in the transport direction, the separation of the recording paper P from the transport path 19 between the two secondary transfer units 74 and 76 aligned in the transport direction is suppressed. Thus, the misalignment of the toner image in the secondary transfer unit 76 caused by the separation of the recording paper P from the transport path 19 between the two secondary transfer units 74 and 76 aligned in the transport direction is suppressed.

[0114] Furthermore, since the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are charged with the same polarity as the toner image TZ, i.e., negative polarity, by the charged rolls 130 and 140, the adhesion of the negatively charged toner image TZ to the transport rolls 110 and 120 is suppressed compared to the case where the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are charged with the opposite polarity to the toner image TZ.

[0115] Furthermore, the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are charged to -300V to -600V by the charged rolls 130 and 140, while the opposing rolls 111 and 121 are at 0V. Therefore, an electrostatic force is generated in the charged toner image TZ in the direction toward the transport belt 21 and the recording paper P due to the electric field formed between the circumferential surfaces 110A and 120 of the transport rolls 110 and 120 and the opposing rolls 111 and 121. Consequently, compared to the case where the electrostatic force acting on the toner image TZ is set to a potential that forms an electric field toward the transport rolls 110 and 120, the adhesion of toner to the transport rolls 110 and 120 is suppressed.

[0116] Furthermore, since the opposing rolls 111 and 121 are grounded via resistors 117 and 127 to set their potential to 0V, this method is less costly compared to the case where voltage is applied to the opposing rolls 111 and 121.

[0117] Furthermore, the circumferential surfaces 110A and 120A of the conveyor rolls 110 and 120 are made of resin and have a low coefficient of friction. Therefore, compared to the case where the circumferential surfaces 110A and 120A are made of rubber, which has a high coefficient of friction, adhesion to the conveyor rolls 110 and 120 is suppressed.

[0118] Furthermore, since the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 are cleaned by the cleaning blades 150 and 160, the adhesion of toner adhering to the transport rolls 110 and 120 to the recording paper P is suppressed compared to cases where the circumferential surfaces 110A and 120A are not cleaned.

[0119] Furthermore, it is less expensive compared to electrically cleaning the surrounding surfaces (110A, 120A) with a brush.

[0120] Furthermore, since toner is applied to the circumferential surfaces 110A and 120A of the transport rolls 110 and 120 at the set timing, the peeling of the cleaning blades 150 and 160 is suppressed compared to the case where no toner is applied at all.

[0121] Furthermore, the distance L1 between the transport roll 110 on the upstream side in the transport direction and the secondary transfer unit 74 is less than or equal to the minimum width LS in the transport direction in which an image can be formed. Therefore, when recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 110 and the secondary transfer unit 74.

[0122] Similarly, since the distance L3 between the transport roll 120 and the secondary transfer section 76 on the downstream side in the transport direction is less than or equal to the minimum width LS, when a recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 120 and the secondary transfer section 76.

[0123] Therefore, compared to the case where the distance between the secondary transfer sections 74 and 76 and the transport rolls 110 and 120 is greater than the minimum width LS, the separation of the recording paper PS from the transport path 19 is suppressed.

[0124] Furthermore, since the distance L2 between the transport roll 110 and the transport roll 120 is less than or equal to the minimum width LS, when the recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 110 and the transport roll 120. Therefore, compared to the case where the distance L2 between the transport roll 110 and the transport roll 120 is greater than the minimum width LS, the separation of the recording paper PS from the transport path 19 is suppressed.

[0125] Furthermore, since each image forming unit 52 is positioned between the intermediate transfer belt 40 and the intermediate transfer belt 60, there is a limit to how narrow the gap between the two secondary transfer units 74 and 76, which are aligned in the transport direction, can be. As a result, the gap between them is wide, making it easy for the recording paper P to separate from the transport path 19. However, the transport rolls 110 and 120 suppress the separation of the recording paper P from the transport path 19.

[0126] <Second Embodiment> Next, an image forming apparatus according to the second embodiment of the present invention will be described. Note that the configuration is the same as the first embodiment, except for the transport roll unit. Therefore, explanations other than those of the transport roll unit will be omitted or simplified.

[0127] [Conveyor Roll Unit] As shown in Figure 6, in this embodiment, a transport roll unit 200 is provided between the image forming units 30 and 50, which are spaced apart in the transport direction on the side of the recording paper P (see Figure 7) of the transport belt 21, as an example of a transport means, and in the vertical direction.

[0128] The conveyor roll unit 200 has multiple conveyor rolls, two in this embodiment: 210 and 220. Recording paper P (see Figure 7) and a conveyor belt 21 are sandwiched between the conveyor rolls 210 and 220, which are examples of rotating bodies, and the opposing rolls 111 and 121, and the recording paper P is conveyed downstream in the conveying direction. The conveyor rolls 210 and 220 are configured to rotate by a drive mechanism (not shown).

[0129] Note that the conveyor rolls 210 and 220 and the surrounding components are the same components, differing only in their position in the conveying direction. Therefore, they are not distinguished in the schematic diagram of Figure 7.

[0130] As shown in Figures 6 and 7, the conveying rolls 210 and 220 are solid metal rolls with a circular cross-sectional shape perpendicular to the axial direction. In this embodiment, the conveying rolls 210 and 220 are made of SUS304.

[0131] The static friction coefficient between the circumferential surfaces 210A and 220A of the transport rolls 210 and 220 and the recording paper P (see Figure 7) is approximately 2.0. In this case, the recording paper P is plain paper.

[0132] As shown in Figure 6, the distance L1 between the upstream conveyor roll 210 and the secondary transfer section 74 in the conveying direction is less than or equal to the minimum width LS. Similarly, the distance L3 between the downstream conveyor roll 220 and the secondary transfer section 76 in the conveying direction is less than or equal to the minimum width LS. Furthermore, the distance L2 between the upstream conveyor roll 210 and the downstream conveyor roll 220 in the conveying direction is less than or equal to the minimum width LS. Note that the distances L1, L2, and L3 are the distances between the axes of the conveyor rolls 210 and 220 and the secondary transfer rolls 24 and 25 of the secondary transfer sections 74 and 76.

[0133] Furthermore, it is desirable that the distance L1 between the upstream conveyor roll 210 and the secondary transfer section 74 in the conveying direction be smaller than the minimum width LS. Similarly, it is desirable that the distance L3 between the downstream conveyor roll 220 and the secondary transfer section 76 in the conveying direction be smaller than the minimum width LS. Moreover, it is desirable that the distance L2 between the upstream conveyor roll 210 and the downstream conveyor roll 220 in the conveying direction be smaller than the minimum width LS.

[0134] A roll bias is applied to the metal transport rolls 210 and 220 by the power supply unit 99 (see Figure 5), setting the transport rolls 210 and 220 to have the same polarity as the toner image TZ (see Figure 7), and in this embodiment, a negative polarity potential. Note that the potential of the transport rolls 210 and 220 in this embodiment is -300V to -600V, but this is just an example and not limited to this potential.

[0135] Furthermore, if the transport rolls 210 and 220 are -300 to -600V, an electrostatic force is generated in the negatively charged toner image TZ (see Figure 7) in the direction toward the transport belt 21 and the recording paper P due to the electric field formed between the transport rolls 210 and 220 and the opposing rolls 111 and 121.

[0136] Here, the opposing rolls 111 and 121 can be switched by the power supply unit 99 (see Figure 5) from a grounded state to a state where a potential greater than the absolute value of the potential of the transport rolls 210 and 220 is applied. In this state, an electrostatic force is generated in the direction toward the transport rolls 210 and 220 by the electric field formed between the circumferential surfaces 210A and 220 of the transport rolls 210 and 220 and the opposing rolls 111 and 121.

[0137] The control device 80 sets the voltage of the transport rolls 210 and 220 of the transport roll unit 100 to -300 to -600V while the recording paper P is being transported by the transport roll unit 100.

[0138] Furthermore, the control device 80 controls the attachment of toner to the transport rolls 210 and 120 of the transport roll unit 200 at pre-set intervals, for example, every 4,000 printed pages.

[0139] Specifically, a patch image is formed using toner in one of the image forming sections 32 of the image forming unit 30 and transferred to the transport belt 21. The power supply unit 99 switches the opposing rolls 111 and 121 from a grounded state to a state where a potential greater than the absolute value of the potential of the transport rolls 210 and 220 is applied, causing the patch image to adhere to the transport rolls 210 and 220. The patch image that has adhered to the transport rolls 210 and 220 is then cleaned by the cleaning blades 150 and 160.

[0140] [Effect] Next, the operation of this embodiment will be described.

[0141] As the recording paper P is transported from the secondary transfer section 74 on the upstream side in the transport direction to the secondary transfer section 76 on the downstream side in the transport direction, the circumferential surfaces 210A and 220A of the transport rolls 210 and 220 of the transport roll unit 200 come into contact with the surface PA on which the toner image TZ of the recording paper P has been transferred, thereby transporting the recording paper P downstream in the transport direction.

[0142] Therefore, compared to the case where there are no members in contact with the surface PA of the recording paper P being transported between the two secondary transfer units 74 and 76 aligned in the transport direction, the separation of the recording paper P from the transport path 19 between the two secondary transfer units 74 and 76 aligned in the transport direction is suppressed. Thus, the misalignment of the toner image in the secondary transfer unit 76 caused by the separation of the recording paper P from the transport path 19 between the two secondary transfer units 74 and 76 aligned in the transport direction is suppressed.

[0143] Furthermore, the potential of the transport rolls 210 and 220 is -300V to -600V, while the potential of the opposing rolls 111 and 121 is 0V. Therefore, an electrostatic force is generated on the negatively charged toner image TZ in the direction toward the transport belt 21 and the recording paper P due to the electric field formed between the circumferential surfaces 210A and 220A of the transport rolls 210 and 220 and the opposing rolls 111 and 121. Consequently, compared to the case where the electrostatic force acting on the toner image TZ is set to a potential that forms an electric field toward the transport rolls 210 and 220, the adhesion of toner to the transport rolls 210 and 220 is suppressed.

[0144] Furthermore, since the opposing rolls 111 and 121 are grounded via resistors 117 and 127 to a potential of 0V, this method is less expensive compared to the case where voltage is applied to the opposing rolls 111 and 121.

[0145] Furthermore, the circumferential surfaces 210A and 220A of the conveyor rolls 210 and 220 are made of metal and have a low coefficient of friction. Therefore, compared to the case where the circumferential surfaces 210A and 220A are made of rubber, which has a high coefficient of friction, the adhesion of toner to the conveyor rolls 210 and 220 is suppressed.

[0146] Furthermore, since the circumferential surfaces 210A and 220A of the transport rolls 210 and 220 are cleaned by the cleaning blades 150 and 160, the adhesion of toner adhering to the transport rolls 210 and 220 to the recording paper P is suppressed compared to cases where the circumferential surfaces 210A and 220A are not cleaned.

[0147] Furthermore, it is less expensive compared to electrically cleaning the surrounding surfaces (210A, 220A) with a brush.

[0148] Furthermore, since toner is applied to the circumferential surfaces 210A and 220A of the transport rolls 210 and 220 at a set timing, the peeling of the cleaning blades 150 and 160 is suppressed compared to the case where toner is not applied.

[0149] Furthermore, the distance L1 between the transport roll 210 on the upstream side in the transport direction and the secondary transfer unit 74 is less than or equal to the minimum width LS in the transport direction in which an image can be formed. Therefore, when recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 210 and the secondary transfer unit 74.

[0150] Similarly, since the distance L3 between the transport roll 220 and the secondary transfer unit 76 on the downstream side in the transport direction is less than or equal to the minimum width LS, when the recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 220 and the secondary transfer unit 76.

[0151] Therefore, compared to the case where the distance between the secondary transfer sections 74 and 76 and the transport rolls 210 and 220 is greater than the minimum width LS, the separation of the recording paper PS from the transport path 19 is suppressed.

[0152] Furthermore, since the distance L2 between the transport roll 210 and the transport roll 220 is less than or equal to the minimum width LS, when the recording paper PS of the minimum width LS is being transported, the recording paper PS is covered by both the transport roll 210 and the transport roll 220. Therefore, compared to the case where the distance L2 between the transport roll 210 and the transport roll 220 is greater than the minimum width LS, the separation of the recording paper PS from the transport path 19 is suppressed.

[0153] Furthermore, since each image forming unit 52 is positioned between the intermediate transfer belt 40 and the intermediate transfer belt 60, there is a limit to how narrow the gap between the two secondary transfer units 74 and 76, which are aligned in the transport direction, can be. As a result, the gap between them is wide, making it easy for the recording paper P to separate from the transport path 19. However, the transport rolls 210 and 220 suppress the separation of the recording paper P from the transport path 19.

[0154] [Differentiation] Next, a modified example of this embodiment will be described.

[0155] The modified conveyor rolls 212 and 222 shown in Figure 8 are solid metal rolls 210 and 220 with a circular cross-sectional shape perpendicular to the axial direction, and insulating resin coating layers 211 and 221 are formed on the circumferential surfaces 210A and 220A of these rolls.

[0156] In this embodiment, the metal rolls 210 and 220 are the same as the conveyor rolls 210 and 220 described above, and are made of SUS304. Therefore, they are given the same reference numerals 210 and 220.

[0157] Furthermore, in this embodiment, the resin coating layers 211 and 221, which are examples of insulating layers, are made of fluororesin.

[0158] As described above, the modified transport rolls 212 and 222 shown in Figure 8 are the same as those in the second embodiment except that resin coating layers 211 and 221 are formed on the aforementioned transport rolls 210 and 220, so no further explanation is provided.

[0159] Since the conductive transport rolls 212 and 222 have insulating resin coating layers 211 and 221 formed on them, their electrical leakage resistance is improved compared to cases where no resin coating layer is formed.

[0160] <Other> Furthermore, the present invention is not limited to the embodiments described above.

[0161] For example, in the above embodiment, the charge potentials of the transport rolls 110 and 120 were the same, but this is not limited to this. The charge potentials of the transport roll 110 and the transport roll 120 may be different.

[0162] Similarly, in the above embodiment, the potentials of the conveyor rolls 210 and 220 were the same, but this is not limited to this. The potentials of the conveyor roll 210 and the conveyor roll 220 may be different.

[0163] Furthermore, for example, in the above embodiment, the opposing rolls 111 and 121 were grounded, but this is not limited to this. Voltage may be applied to the opposing rolls 111 and 121. If voltage is applied to the opposing rolls 111 and 121, the transport rolls 210 and 210 may also be grounded.

[0164] The transport rolls 110, 120, 210, and 220 may be grounded or electrically isolated.

[0165] Furthermore, for example, in the above embodiment, the conveyor roll unit 100 had two conveyor rolls 110 and 120, and the conveyor roll unit 200 had two conveyor rolls 210 and 220, but it is not limited to this. A conveyor roll unit may have only one conveyor roll, or it may have three or more conveyor rolls.

[0166] Furthermore, for example, in the above embodiment, the roll body portions 114, 124 of the conveyor rolls 110, 120 and the resin coating layers 211, 221 of the conveyor rolls 212, 222 were made of fluororesin, but the invention is not limited to this.

[0167] Furthermore, although the conveying rolls 210 and 220 in the above embodiment were made of SUS304, they are not limited to this. Other metals may be used, such as SUM24L. Moreover, conductive materials other than metals may be used, such as urethane foam. Conductivity refers to a volume resistivity of 10. 6 ~10 12It refers to anything less than Ω.

[0168] Furthermore, the coefficient of static friction between the circumferential surfaces 110A, 120A, 210A, and 220A of the transport rolls 110, 120, 210, and 210 and the recording paper P is approximately 0.3 or less, but is not limited to this. However, a smaller coefficient of friction on the circumferential surface of the transport rolls is desirable.

[0169] Furthermore, for example, in the above embodiment, the conveyor rolls 110, 120, 210, and 220 were driven to rotate at the same speed as the conveyor belt 21, but this is not limited to this configuration. The conveyor rolls 110, 120, 210, and 220 may be configured to rotate in a manner that is driven by the conveyor belt 21.

[0170] Furthermore, for example, in the above embodiment, the charging members that charge the transport rolls 110 and 120 were the charging rolls 130 and 140, but the system is not limited to these. Other charging members besides the charging rolls 130 and 140 may be used, such as a charging brush or a scorotron.

[0171] Furthermore, for example, in the above embodiment, the cleaning members for cleaning the conveyor rolls 110, 120, 210, and 220 were cleaning blades 150 and 160, but the invention is not limited to these. Other cleaning members besides the cleaning blades 150 and 160 may be used, such as a cleaning brush.

[0172] Furthermore, although the image forming units 30 and 50 in the above embodiment each had four image forming sections 32 and 52, they are not limited to this. An image forming unit only needs to have two or more image forming sections.

[0173] Furthermore, in the above embodiment, for example, the image forming apparatus 10 was equipped with two image forming units, an image forming unit 30 and an image forming unit 50, but it is not limited to this. An image forming apparatus may be equipped with three or more image forming units.

[0174] If the system includes three or more image forming units, it will have three or more secondary transfer sections that sequentially transfer images from the intermediate transfer belt of each image forming unit to the recording paper P. It is desirable, but not limited to, a transport roll unit between all secondary transfer sections.

[0175] Furthermore, while the recording medium in the above embodiment was, for example, recording paper P such as plain paper, it is not limited to this. The recording medium can be any sheet-like material to which a toner image, such as an OHP, can be transferred and fixed.

[0176] In this embodiment, the transport direction of the recording paper P transported by the transport belt unit 20 is the Y direction, but it is not limited to this. The transport direction may be the X direction, the Z direction, or an oblique direction.

[0177] Furthermore, in the above embodiment, for example, the conveying means that contacts and conveys one side of the recording medium was a conveying belt 21, but it is not limited to this. The conveying means may be something other than a belt, such as a drum.

[0178] Furthermore, in the above embodiment, for example, the intermediate transfer body to which the toner image is first transferred was the intermediate transfer belt 40, 60, but it is not limited to this. The intermediate transfer body may be something other than a belt, such as a drum.

[0179] Furthermore, in the above embodiment, for example, the rotating body whose circumferential surface contacts the other surface of the recording medium was the conveyor rolls 110, 120, 210, and 220, but it is not limited to these. The rotating body may be other than a roll, for example, a drum or a belt.

[0180] Furthermore, in the above embodiment, for example, the application of toner to the transport rolls 110, 120, 210, and 220 of the transport roll units 100 and 200, which is performed every predetermined number of printed pages, for example every 4000 pages, was done by switching the opposing rolls 111 and 121 from a grounded state to a state where a potential greater than the absolute value of the potential of the transport rolls 110, 120, 210, and 220 was applied, but this is not limited to this. The toner may be applied to the transport rolls 110, 120, 210, and 220 by any method. For example, the opposing rolls 111 and 121 may remain grounded, and the toner may be applied by changing the potential of the transport rolls 110, 120, 210, and 220.

[0181] Furthermore, the configuration of the image forming apparatus is not limited to the configuration of the above embodiment, and various configurations are possible. Multiple embodiments and modifications may be implemented in combination. Moreover, the present invention can be implemented in various forms without departing from the spirit of the invention. [Explanation of Symbols]

[0182] 10 Image forming apparatus 19. Transport Route 21. Conveyor belt (an example of a conveying means) 32 Image forming unit 40. Intermediate transfer belt (an example of an intermediate transfer material) 52 Image forming unit 60 Intermediate Transfer Belt (An example of an intermediate transfer material) 74 Secondary transfer section 76 Secondary transfer section 110 Conveyor Roll (Example of a Rotating Body) 110A circumferential surface 111 Opposite Roll 120 Conveyor Roll (Example of a Rotating Body) 120A circumferential surface 130 Electrostatic Roll (Example of an electrostatic component) 140 Electrostatic Roll (Example of an electrostatic component) 150 Cleaning blade (an example of a cleaning component) 160 Cleaning blade (an example of a cleaning component) 210 Conveyor Roll (Example of a Rotating Body) 210A circumferential surface 212 Conveyor Roll (Example of a Rotating Body) 220 Conveyor Roll (Example of a Rotating Body) 220A circumferential surface 222 Conveyor Roll (Example of a Rotating Body) P Recording sheet (an example of a recording medium) PA surface (the other surface) PB side (one side) PS recording paper (an example of the smallest recording medium capable of forming an image)

Claims

1. A transport means for transporting a recording medium along a transport path while in contact with one side of the recording medium, A plurality of intermediate transfer bodies are provided on the other side of the recording medium in the transport path, arranged in the transport direction, and to which toner images formed by a plurality of image forming units are first transferred. A plurality of secondary transfer units arranged in the transport direction for secondary transfer of the toner image of a plurality of intermediate transfer bodies onto the other surface of the recording medium transported by the transport means, One or more rotating bodies whose circumferential surface contacts the other surface of the recording medium being transported by the transport means between one secondary transfer section and the other secondary transfer section arranged in the transport direction, A charging member that charges the circumferential surface of the rotating body with the same polarity as the toner image, Equipped with, The rotating body is a conveying roll with an insulating circumferential surface. The conveying means is a conveying belt stretched in the conveying direction, The system further comprises opposing rolls positioned opposite each other, with the conveying roll and the conveying belt in between. The circumferential surface of the transport roll is adjusted to a surface potential set by the charging member. The opposing roll is set to a potential that forms an electric field with respect to the surface potential of the transport roll such that the electrostatic force acting on the toner image is directed toward the recording medium. The opposing roll is grounded, Image forming apparatus.

2. The circumferential surface of the rotating body is made of resin. The image forming apparatus according to claim 1.

3. The rotating body is A conductive roll body, An insulating layer formed on the outer circumference of the roll body and constituting the circumferential surface, The conveying roll is said to have the following: The image forming apparatus according to claim 1 or claim 2.

4. A transport means for transporting a recording medium along a transport path while in contact with one side of the recording medium, A plurality of intermediate transfer bodies are provided on the other side of the recording medium in the transport path, arranged in the transport direction, and to which toner images formed by a plurality of image forming units are first transferred. A plurality of secondary transfer units arranged in the transport direction for secondary transfer of the toner image of a plurality of intermediate transfer bodies onto the other surface of the recording medium transported by the transport means, One or more rotating bodies whose circumferential surface contacts the other surface of the recording medium being transported by the transport means between one secondary transfer section and the other secondary transfer section arranged in the transport direction, Equipped with, The rotating body has a conductive conveying roll on its circumferential surface. The conveying means is a conveying belt stretched in the conveying direction, The system further comprises opposing rolls positioned opposite each other, with the conveying roll and the conveying belt in between. The circumferential surface of the transport roll and the opposing roll are set to a potential that forms an electric field in which the electrostatic force acting on the toner image is directed toward the recording medium. The circumferential surface of the conveying roll or the opposing roll is grounded. Image forming apparatus.

5. The circumferential surface of the rotating body is made of metal. The image forming apparatus according to claim 4.

6. A transport means for transporting a recording medium along a transport path while in contact with one side of the recording medium, A plurality of intermediate transfer bodies are provided on the other side of the recording medium in the transport path, arranged in the transport direction, and to which toner images formed by a plurality of image forming units are first transferred. A plurality of secondary transfer units arranged in the transport direction for secondary transfer of the toner image of a plurality of intermediate transfer bodies onto the other surface of the recording medium transported by the transport means, One or more rotating bodies whose circumferential surface contacts the other surface of the recording medium being transported by the transport means between one secondary transfer section and the other secondary transfer section arranged in the transport direction, Equipped with, The circumferential surface of the rotating body is made of metal. Image forming apparatus.

7. A cleaning member for cleaning the circumferential surface of the rotating body, The image forming apparatus according to any one of claims 1 to 6.

8. The cleaning member is a blade that contacts the circumferential surface of the rotating body. The image forming apparatus according to claim 7.

9. Having a mode for attaching toner to the rotating body at a set timing, The image forming apparatus according to claim 8.

10. The distance between the secondary transfer unit and the rotating body is set to be less than or equal to the minimum width in the transport direction of the recording medium on which an image can be formed. The image forming apparatus according to any one of claims 1 to 9.

11. The rotating body is provided in multiple locations, The distance between one of the rotating bodies and the other, which are aligned in the transport direction, is set to be less than or equal to the minimum width of the transport direction of the recording medium on which an image can be formed. The image forming apparatus according to claim 10.

12. A transport means for transporting a recording medium along a transport path while in contact with one side of the recording medium, A plurality of intermediate transfer bodies are provided on the other side of the recording medium in the transport path, arranged in the transport direction, and to which toner images formed by a plurality of image forming units are first transferred. A plurality of secondary transfer units arranged in the transport direction for secondary transfer of the toner image of a plurality of intermediate transfer bodies onto the other surface of the recording medium transported by the transport means, One or more rotating bodies whose circumferential surface contacts the other surface of the recording medium being transported by the transport means between one secondary transfer section and the other secondary transfer section arranged in the transport direction, Equipped with, The distance between the secondary transfer unit and the rotating body is set to be less than or equal to the minimum width in the transport direction of the recording medium that can form an image. Multiple rotating bodies are provided, The distance between one of the rotating bodies and the other, which are aligned in the transport direction, is set to be less than or equal to the minimum width of the transport direction of the recording medium on which an image can be formed. Image forming apparatus.

13. One or more of the image forming units are arranged between the intermediate transfer bodies and the intermediate transfer bodies that are aligned in the transport direction. An image forming apparatus according to any one of claims 1 to 12.

Images