Image forming device

Abstract

The present invention provides an image forming apparatus. The image forming apparatus comprises: an image holding unit that holds a toner image transferred to a sheet of paper, the sheet of paper contacting and passing through the image holding unit; a peeling unit that peels the sheet of paper from the image holding unit; and a removal unit that contacts the image holding unit and removes toner remaining after passing through the peeling unit. The image forming apparatus forms a non-transferred toner image that is not transferred to the sheet of paper within a range of the image holding unit where the peeling unit is not present.

Description

Technical Field

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

[0002] Conventionally, as a technique for resolving the problem caused by a peeling unit that peels paper from an image holding unit such as a photoreceptor, the techniques described in the following Japanese Patent No. 4687642 and Japanese Patent Application Laid-Open No. 11-219035 are known.

[0003] Japanese Patent Gazette No. 4687642 describes an image forming device including a peeling unit for peeling a recording medium from the surface of a photosensitive drum and guiding it in a conveying direction, wherein the peeling unit is composed of a peeling claw in contact with the photosensitive drum and auxiliary claws arranged on both sides of the peeling claw and not in contact with the photosensitive drum, the auxiliary claws being configured to guide the conveyed recording medium in such a manner that the recording medium peeled by the peeling claw does not come into contact with the back of the peeling claw, and being engaged from above the peeling claw after the peeling claw is assembled to the installation position.

[0004] Japanese Patent Application Laid-Open No. 11-219035 describes a peeling device for an image forming apparatus that transfers a toner image formed on the surface of an image carrier onto a sheet of paper. The peeling device is configured to peel off the sheet of paper adhering to the surface of the image carrier by bringing a portion of a claw-shaped peeling member into contact with the surface of the image carrier. The peeling device is configured to allow the claw-shaped peeling member to contact the image carrier through a portion of the contact portion. Patent Document 2 also describes a method in which a portion of the claw-shaped peeling member is brought into contact with the surface of the image carrier over a wide area in the axial direction. A guide surface is formed on the peeling member closer to the end of the portion contacting the image carrier. This guide surface guides residual toner adhering to the image carrier so that it can pass through without being blocked by the contact portion. Summary of the Invention

[0005] The present invention provides an image forming device that can suppress a portion of the colorant in the non-transfer colorant image formed in the image holding unit from adhering to the portion of the peeling unit that peels the paper from the image holding unit, where the paper passes, compared to a case where a non-transfer colorant image is also formed within the range where a peeling unit exists in the image holding unit.

[0006] According to the first embodiment of the present invention, an image forming device is provided, which comprises: an image holding unit that holds a colorant image transferred to a paper, the paper contacts and passes through the image holding unit; a peeling unit that peels the paper from the image holding unit; and a removal unit that contacts the image holding unit and removes the colorant that remains after passing through the peeling unit, the image forming device forms a non-transferred colorant image that is not transferred to the paper in the image holding unit within a range where the peeling unit is not present.

[0007] According to the second aspect of the present invention, a low-density non-transfer colorant image having a lower density than a normal non-transfer colorant image formed as the non-transfer colorant image in a range where the stripping unit does not exist is formed in the image holding unit in a range where at least the stripping unit exists.

[0008] According to the third aspect of the present invention, the low-density non-transferred toner image is formed at a different timing from that of the normal non-transferred toner image.

[0009] According to the fourth aspect of the present invention, the low-density non-transferred toner image is formed in the range where the peeling unit is present at the same time as the normal non-transferred toner image.

[0010] According to the fifth aspect of the present invention, the low-density non-transferred toner image is formed at a low density of 50% or less of the density of the normal non-transferred toner image.

[0011] According to the sixth aspect of the present invention, the peeling unit includes a peeling claw that peels off the paper and a covering member that is arranged to cover a portion of the peeling claw on a side where the peeled paper passes.

[0012] (Effect)

[0013] According to the first scheme, compared with the case where a non-transfer colorant image is also formed within the range where the peeling unit exists in the image holding unit, it is possible to suppress a portion of the colorant in the non-transfer colorant image formed in the image holding unit from adhering to the portion of the peeling unit that peels the paper from the image holding unit on the side where the paper passes.

[0014] According to the second scheme, compared with the case where a low-concentration non-transferred colorant image is formed in a range where the stripping unit is not present in the image holding unit, it is possible to suppress the occurrence of defects in the portion of the removal unit corresponding to the portion of the image holding unit corresponding to the range where at least the stripping unit is present.

[0015] According to the third aspect, compared to forming a low-density non-transferred toner image at the same time as a normal non-transferred toner image, it is possible to cope with the situation by forming a low-density non-transferred toner image only when necessary.

[0016] According to the fourth scheme, compared with the case where a low-density non-transfer colorant image is formed at a different time from the normal non-transfer colorant image, a low-density non-transfer colorant image can be reliably formed and the number of operations for forming the non-transfer colorant image alone can be reduced.

[0017] According to the fifth scheme, compared with the case where a low-concentration non-transfer colorant image is not formed at a low concentration of less than 50% of the concentration of a normal non-transfer colorant image, it is possible to reliably suppress the occurrence of malfunctions in the portion of the removal unit corresponding to the portion of the image holding unit corresponding to the range where the peeling unit is located, and to suppress the adhesion of colorant to the portion of the peeling unit on the side where the peeled paper passes.

[0018] According to the sixth aspect, compared with a case where the peeling unit is not composed of the peeling claw and the covering member, it is possible to suppress the adhesion of colorant to the portion of the peeling claw on the side where the peeled paper passes, and to suppress the occurrence of contamination of the rear end of the paper, in which a portion of colorant adheres to and contaminates the rear end of the paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram showing the entire image forming apparatus according to Embodiment 1 and the like.

[0020] Figure 2 It shows Figure 1 A schematic diagram of a portion of an image forming apparatus.

[0021] Figure 3 It shows Figure 1 A schematic perspective view of another portion of the image forming apparatus.

[0022] Figure 4 It shows Figure 1 A block diagram showing a structure of a control unit in an image forming apparatus.

[0023] Figure 5 It is a schematic diagram showing the structure of each area of the outer peripheral surface of the intermediate transfer belt.

[0024] Figure 6 This is a conceptual diagram showing the structure of a range where no peeling unit exists in the intermediate transfer belt.

[0025] Figure 7 It is a schematic diagram showing a range in which a non-transferred toner image is formed.

[0026] Figure 8It is a schematic diagram showing the state of the rear end of the paper and the peeling unit.

[0027] Figure 9 This is a schematic diagram showing a portion of the image forming apparatus according to the second embodiment.

[0028] Figure 10 It is shown in Figure 9 Schematic diagram of another configuration example of a period during which a low-density non-transferred toner image is formed in an image forming apparatus.

[0029] Figure 11 This is a graph showing the results of an experiment investigating the relationship between the density of a low-density non-transferred toner image and the occurrence of contamination on the trailing end of paper.

[0030] Figure 12 This is a schematic diagram showing a portion of the image forming apparatus according to the third embodiment.

[0031] Figure 13 (A) shows Figure 12 A perspective view of a peeling device in an image forming apparatus, Figure 13 (B) shows that Figure 13 (A) is a perspective view of the peeling device in an exploded state.

[0032] Figure 14 It shows Figure 13 Schematic diagram of the state of the peeling device and the rear end of the paper.

[0033] Figure 15 It is a schematic diagram showing a comparative example regarding the range in which a non-transferred toner image is formed.

[0034] Figure 16 (A) shows the formation of Figure 15 The schematic diagram of an example of a state in which a non-transferred toner image is shown. Figure 16 (B) is shown in Figure 16 A schematic diagram showing an example of a state in which the rear end of the paper contacts the peeling device in the case of (A).

[0035] Figure 17 This is a schematic diagram showing an example of a state where the trailing end of the paper is noticeably contaminated. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0037] [Implementation Method 1]

[0038] Figure 1 and Figure 2 This is a diagram showing the image forming apparatus 1 according to the first embodiment. Figure 1The overall structure of the image forming apparatus 1 is shown. Figure 2 The structure of a portion of the image forming apparatus 1 (mainly a secondary transfer device and its surroundings) is shown.

[0039] exist Figure 1 、 Figure 2 In the drawings, arrows designated by the symbols X, Y, and Z indicate the directions of width, height, and depth of the three-dimensional space assumed in the drawings. Furthermore, in the drawings, the circular mark at the intersection of the arrows in the X and Y directions indicates that the Z direction is vertically downward in the drawings.

[0040] Image forming apparatus 1 is an apparatus that forms an image composed of toner as a developer on paper 9 as an example of a recording medium. Image forming apparatus 1 in Embodiment 1 is configured as, for example, a printer that forms an image corresponding to image information input from an external device such as a data terminal.

[0041] like Figure 1 As shown, the image forming apparatus 1 includes the following devices, etc.: an image forming device 2, which forms a colorant image based on image information in the internal space of a housing 10; an intermediate transfer device 3, which temporarily holds the toner image formed by the image forming device 2 and then transfers the toner image to a sheet of paper 9 for a second time; a paper feeding device 4, which stores and feeds the sheet of paper 9 to a position where the secondary transfer is to be performed by the intermediate transfer device 3; a fixing device 5, which fixes the toner image secondarily transferred by the intermediate transfer device 3 on the sheet of paper 9; and a control unit 15, which performs control related to the operation of each of the above devices.

[0042] Image information refers to information related to images such as text, graphics, photographs, and patterns. The housing 10 is a structure formed into a desired shape using various supporting components and exterior materials. A discharge receiving portion 12 and a discharge outlet 13 are formed on a portion of the upper surface of the housing 10. The discharge receiving portion 12 receives the paper sheets 9 having images formed thereon in an overlapping state, and the discharge outlet 13 discharges the paper sheets 9 toward the discharge receiving portion 12. Figure 1 The one-dot chain line in FIG. 1 shows a main conveyance path when the paper 9 is conveyed in the housing 10 .

[0043] The image forming device 2 is composed of four image forming devices 2Y, 2M, 2C, and 2K, each of which is dedicated to forming a toner image of four colors: yellow (Y), magenta (M), cyan (C), and black (K).

[0044] Each of the four image forming devices 2 (Y, M, C, K) includes a photosensitive drum 21 as an example of an image holding unit that rotates in the direction indicated by arrow A. Around the photosensitive drum 21, there are arranged a charging device 22, an exposure device 23, a developing device 24 (Y, M, C, K), a primary transfer device 25, a drum cleaning device 26, and other devices. Figure 1 In FIG. 1 , all reference numerals 21 to 26 are described only in the image forming apparatus 2K for black (K), and only some reference numerals are described in the image forming apparatuses 2 for other colors (Y, M, C).

[0045] Among them, the charging device 22 is a device that makes the outer peripheral surface of the photosensitive drum 21 (the surface that can form an image) have a desired surface potential. The exposure device 23 is a device that forms an electrostatic latent image of the desired color component (Y, M, C, K) by exposing the outer peripheral surface of the photosensitive drum 21 based on the image information. In addition, the developing device 24 (Y, M, C, K) is a device that uses the developer (toner) of the corresponding desired color (Y, M, C, K) to develop the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 21 to form a toner image. The primary transfer device 25 is a device that electrostatically transfers the toner images of various colors to the intermediate transfer device 3 (intermediate transfer belt 31). The drum cleaning device 26 is an example of a removal unit that cleans the outer peripheral surface of the photosensitive drum 21 by scraping away unnecessary toner, paper dust and other unnecessary substances attached to the outer peripheral surface of the photosensitive drum 21.

[0046] In these image forming devices 2 (Y, M, C, K), each portion where the photosensitive drum 21 faces the primary transfer device 25 serves as a primary transfer position where a toner image is primarily transferred.

[0047] The intermediate transfer device 3 is a device configured to, after primary transfer and holding the toner images of the respective colors formed by the image forming devices 2 (Y, M, C, K), convey the toner images to a position for secondary transfer onto the paper 9. The intermediate transfer device 3 is disposed above the image forming devices 2 (Y, M, C, K) within the housing 10. Specifically, it includes an intermediate transfer belt 31, another example of an image holding unit that primarily transfers and holds the toner images from the photosensitive drums 21 in the image forming devices 2 (Y, M, C, K). The following components are disposed around the intermediate transfer belt 31.

[0048] The intermediate transfer belt 31 is supported by a plurality of support rollers 32 a to 32 e disposed inside the intermediate transfer belt 31 so as to rotate (orbit) in the direction indicated by arrow B while sequentially passing through the primary transfer positions of the image forming devices 2 (Y, M, C, K).

[0049] Among the plurality of support rollers 32a to 32e, support roller 32a serves as a driving roller and a secondary transfer support roller, while support roller 32b serves as a tension roller. Furthermore, support rollers 32c and 32d serve as reverse rollers for maintaining the position (surface) of the intermediate transfer belt 31 when the belt passes through the primary transfer position, and support roller 32e serves as a cleaning support roller for a belt cleaning device (36) described later. Support roller 32e serves as a cleaning support roller for the belt cleaning device 36 described later.

[0050] The support rollers 32 a to 32 e are rotatably provided on a support frame (not shown) of the intermediate transfer device 3 .

[0051] Furthermore, the primary transfer devices 25 of the respective image forming devices 2 (Y, M, C, K) are arranged inside the intermediate transfer belt 31. The primary transfer devices 25 constitute a part of the intermediate transfer device 3 and are configured to press the intermediate transfer belt 31 against the photosensitive drum 21 using a primary transfer member such as a roller to which a primary transfer current is supplied.

[0052] Furthermore, a secondary transfer device 35 is disposed on the outer peripheral portion of the intermediate transfer belt 31 supported by the support roller 32a. This secondary transfer device 35 allows the paper 9 to pass through and secondarily transfers the toner image on the intermediate transfer belt 31 onto the paper 9. The secondary transfer device 35 is configured such that the paper 9 contacts and passes through the secondary transfer device 35 by using a secondary transfer member, such as a roller, to which a secondary transfer current is supplied, so as to press the paper 9 against the outer peripheral portion of the intermediate transfer belt 31 supported by the support roller 32a.

[0053] In the intermediate transfer device 3 , a portion where the secondary transfer device 35 contacts the outer peripheral surface of the intermediate transfer belt 31 serves as a secondary transfer position TP2 where the toner image is secondary transferred.

[0054] In addition, a belt cleaning device 36 as another example of a removal unit is arranged around the outer side of the intermediate transfer belt 31. The belt cleaning device 36 removes unnecessary substances such as unnecessary colorant remaining on the outer peripheral surface of the intermediate transfer belt 31 after the secondary transfer, thereby cleaning the outer peripheral surface of the intermediate transfer belt 31.

[0055] The belt cleaning device 36 is composed of a plate-shaped cleaning member 36b and a recovery member 36c arranged inside a housing 36a. The cleaning member 36b contacts the outer peripheral surface of the portion of the intermediate transfer belt 31 supported by the support roller 32e to remove unnecessary substances, and the recovery member 36c rotates to recover the unnecessary substances removed by the cleaning member 36b. Figure 1 and Figure 5As shown, the cleaning component 36b of the belt cleaning device 36 is configured to contact the intermediate transfer belt 31 in a state along the width direction (or axial direction) J that is approximately perpendicular to the rotation direction B of the intermediate transfer belt 31 at a position halfway from the support roller 32a to the support roller 32b along the rotation direction B of the intermediate transfer belt 31.

[0056] Furthermore, a peeling device 37 as an example of a peeling unit is arranged around the outer side of the intermediate transfer belt 31 . The peeling device 37 peels the paper 9 after the secondary transfer from the outer peripheral surface of the intermediate transfer belt 31 .

[0057] like Figure 3 As shown, the peeling device 37 is configured as two peeling devices 37A and 37B at a desired interval in the width direction J of the intermediate transfer belt 31. Figure 3 As shown, the peeling devices 37A and 37B are each composed of a peeling claw 371 with a tapered tip and an elastic member 373 such as a coil spring. The peeling claw 371 is mounted on a fixed frame 370 as a support unit so as to be able to swing in the directions indicated by arrows D1 and D2 with a support shaft 372 as a fulcrum. The elastic member 373 applies a force in the direction indicated by arrow D1 so that the tip 371a of the peeling claw 371 elastically contacts the outer peripheral surface of the intermediate transfer belt 31. Figure 3 As shown, the two peeling devices 37A and 37B are mounted so as to be arranged at predetermined positions on a mounting plate 38. The mounting plate 38 is fixed to, for example, a support frame (not shown) of the intermediate transfer device 3.

[0058] The paper feed device 4 is configured to store and feed paper 9 to be fed to the secondary transfer position TP2 of the intermediate transfer device 3. The paper feed device 4 is arranged within the housing 10 below the image forming devices 2 (Y, M, C, K). Specifically, it is configured with a paper storage body 41 and a feeding device 43.

[0059] The storage unit 41 is a storage component that includes a loading plate 42 for loading and storing multiple sheets of paper 9 in a desired orientation. It is mounted so that it can be withdrawn from the housing 10 for operations such as replenishing the sheets of paper 9. The feeding device 43 uses a plurality of rollers or other paper feeding devices to feed the sheets of paper 9 loaded on the loading plate 42 of the storage unit 41 one by one, starting from the upper sheet. The paper 9 can be any recording medium, such as plain paper, coated paper, or thick paper, that can be transported within the housing 10 of the image forming apparatus 1 and to which a toner image can be transferred and fixed. There are no particular limitations on its material or form.

[0060] The fixing device 5 is configured to fix the toner image secondary-transferred by the intermediate transfer device 3 onto the paper 9. The fixing device 5 is disposed within the housing 10 above the secondary transfer position TP2 of the intermediate transfer device 3. Specifically, the fixing device 5 comprises a heating rotator 51, a pressurizing rotator 52, and other components disposed within the interior space of the housing 50, which is provided with an inlet and an outlet for the paper 9.

[0061] The heating rotator 51 is a rotating body composed of a roller, a belt pad, or the like that rotates in the direction indicated by the arrow. It is heated by a heating unit (not shown) to maintain its outer surface at a desired temperature. The pressurizing rotator 52 is a rotating body composed of a roller, a belt pad, or the like that contacts and rotates under a desired pressure in response to the heating rotator 51. The pressurizing rotator 52 may also be heated by a heating unit.

[0062] In the fixing device 5 , the contact area between the heating rotator 51 and the pressing rotator 52 constitutes a nip portion (fixing processing portion) FN that performs heating, pressing, and other processes for fixing the unfixed toner image on the paper 9 .

[0063] In the image forming apparatus 1, as Figure 1 As shown, a paper feeding and transporting path Rt1 is provided between the paper feeding device 4 and the secondary transfer position TP2 of the intermediate transfer device 3 for transporting the paper 9 on the paper feeding device 4 to the secondary transfer position TP2. Figure 1 and Figure 2 As shown, the paper feed transport path Rt1 is configured with a pair of transport rollers 44 that sandwich and transport the paper 9, and a plurality of guide members 45a, 45b that ensure a transport space for the paper 9 and guide the transport of the paper 9. The transport rollers 44 are so-called registration rollers that correct the skew of the paper 9 and feed the paper 9 at the desired timing in conjunction with the secondary transfer.

[0064] Furthermore, in the image forming apparatus 1, as shown in FIG. Figure 1 and Figure 2 As shown, a guide transport path Rt2 is provided between the secondary transfer position TP2 of the intermediate transfer device 3 and the nip portion FN of the fixing device 5. The guide transport path Rt2 guides the paper 9 after the secondary transfer to the nip portion FN. Figure 2 As shown, the guide transport path Rt2 is configured by disposing a plurality of guide members 46a, 46b, 56, etc. These guide members 46a, 46b, 56, etc. ensure a transport space for the paper 9 and guide the transport of the paper 9. Among them, the guide member 56 is an introduction guide member provided at the introduction port of the housing 50 of the fixing device 5.

[0065] Figure 2The dashed line VL shown in FIG. 1 shows an ideal conveyance path for the paper 9 in the guide conveyance path Rt2. The dashed line VL is a virtual straight line obtained by connecting the intersection point CP1, where a straight line connecting the rotation center C1 of the support roller 32a of the intermediate transfer belt 31 and the rotation center C2 of the roller-shaped secondary transfer member of the secondary transfer device 35 intersects the nip portion at the secondary transfer position TP2, and the intersection point CP2, where a straight line connecting the rotation center C3 of the heating rotator 51 and the rotation center C4 of the pressurizing rotator 52 in the fixing device 5 intersects the nip portion FN.

[0066] Furthermore, in the image forming apparatus 1, as shown in FIG. Figure 1 As shown, a discharge transport path Rt3 is provided between the fixing device 5 and the discharge port 13. The discharge transport path Rt3 is used to transport the paper 9 after fixing to the discharge port 13 and discharge it into the discharge storage unit 12. The discharge transport path Rt3 is composed of a pair of discharge rollers 47 arranged near the discharge port 13, and a guide member (not shown) that ensures a transport space for the paper 9 and guides the transport of the paper 9.

[0067] The control unit 15 is composed of, for example, a processing unit, a storage element and device, an input / output device, and a control device for these devices.

[0068] In addition, if Figure 4 As shown, the control unit 15 includes, in addition to a central control unit 151 that comprehensively controls the overall operation of the image forming apparatus 1, image formation control units 153Y, 153M, 153C, and 153K that respectively control the operations of the four-color (Y, M, C, and K) image forming devices 2 (Y, M, C, and K); an intermediate transfer control unit 154 that controls the operations of the intermediate transfer device 3; a paper transport control unit 155 that controls the operations of the paper feed device 4, the paper feed path Rt1, and the paper discharge path Rt3; and a fixing control unit 156 that controls the operations of the fixing device 5. The central control unit 151 includes a storage unit 152 comprised of the aforementioned storage elements and devices that store information such as control programs related to the overall control of the image forming apparatus 1 and data required for such control. Each of the other control units 153 to 156 also includes a storage unit (not shown) that stores necessary control programs and data.

[0069] In addition, if Figure 4As shown, the control unit 15 is configured to be connected to the following parts, etc.: a communication unit 16, which uses the communication unit required by the image forming device 1 to exchange information with external connection equipment, etc.; an image processing unit 17, which performs the required processing of image information input from external connection equipment, etc. to the image forming device 1; and a detection unit 18, which detects the actions, states, etc. within the image forming device 1. The control unit 15 inputs and outputs the required information (signals) between these connection objects.

[0070] Furthermore, the image forming apparatus 1 is configured such that the image forming device 2 forms a non-transferred toner image NT that is not transferred onto the paper 9 .

[0071] After the non-transferred toner image NT is formed as a toner image of a predetermined pattern on the photosensitive drum 21 by the desired image forming device 2 (Y, M, C, K), it is primarily transferred to the intermediate transfer belt 31 of the intermediate transfer device 3 under normal transfer conditions. It then passes through the secondary transfer position TP2 without any transfer action by the secondary transfer device 35. Therefore, the non-transferred toner image NT is not secondary transferred onto the sheet 9 that passes through the intermediate transfer belt 31 in contact with the secondary transfer position TP2. Furthermore, the non-transferred toner image NT that has passed the secondary transfer position TP2 is finally removed from the outer peripheral surface of the intermediate transfer belt 31 by the belt cleaning device 36 of the intermediate transfer device 3.

[0072] Examples of such non-transferred toner images NT include the following.

[0073] Specifically, as the non-transferred toner image NT, there are a process control color patch image NT1 formed when adjusting image forming conditions (conditions required for image forming such as density and registration), an alignment control pattern image NT2 formed when confirming and eliminating the deviation of the toner image formation position, and the like (see FIG. Figure 7 ). For the process control color mark image NT1 and alignment control pattern image NT2 formed in order to obtain the control information, as shown in FIG. Figure 2 and Figure 3 As shown, image reading sensors 18A and 18B, as an example of a detection unit 18 for reading the process control color patch image NT1 and the registration control pattern image NT2, are arranged at predetermined positions on the intermediate transfer belt 31. In the first embodiment, image reading sensors 18A and 18B are arranged just before the intermediate transfer belt 31 is supported by the support roller 32d.

[0074] In addition, as non-transferred toner images NT, there is a toner belt image NT3 formed to suppress problems such as whirring noise and warping of the plate-shaped cleaning member 36b in the belt cleaning device 36. Furthermore, there is a released toner image NT4 formed to forcibly release a specified amount of deteriorated toner within the developing device 24 (Y, M, C, K) of the image forming device 2 that has formed the low-density toner image, when an image composed of a low-density toner image is formed (continuously) in a specified amount.

[0075] And, as Figure 5 As shown, the image forming apparatus 1 is configured to form a non-transferred toner image NT in the ranges Ha, Hb, and Hc of the intermediate transfer belt 31 where the peeling device 37 ( 37A, 37B) is not present.

[0076] In other words, this configuration does not form the non-transferred toner image NT in the range Hd and He (see FIG. 1 ) where the peeling device 37 ( 37A, 37B) exists on the intermediate transfer belt 31. Figure 5 、 Figure 7 ) structure within.

[0077] like Figure 5 As shown, the range Ha is a range located inside between the two peeling devices 37A and 37B when viewed along the width direction J of the intermediate transfer belt 31 .

[0078] On the other hand, the range Hb is the range on the one end side (near front side) between the peeling device 37A on one side (near front side) and the side end 31a of the intermediate transfer belt 31. Furthermore, the range Hc is the range on the other end side (near back side) between the peeling device 37B on the other side (near back side) and the side end 31b of the intermediate transfer belt 31.

[0079] Figure 5 Reference symbol Hd in FIG. 8 indicates a range in which the peeling device 37A is present in the intermediate transfer belt 31 , and reference symbol He indicates a range in which the peeling device 37B is present in the intermediate transfer belt 31 .

[0080] The ranges Ha, Hb, and Hc of the intermediate transfer belt 31 where the peeling device 37 ( 37A, 37B) does not exist are set as follows, for example.

[0081] That is, Figure 6Conceptually, the ranges Ha, Hb, and Hc are demarcated by imaginary boundary lines (two-dot chain lines in the figure). For example, these imaginary boundary lines, for example, pass along the rotational direction B, passing through the positions of the end portions 371a of the stripping claws 371 of the stripping device 37A, which are in contact with the outer peripheral surface of the intermediate transfer belt 31, separated by predetermined distances L1 and L2 relative to the width direction J. The predetermined distances L1 and L2 are effective for preventing a portion of the non-transferred toner image NT from adhering to the stripping claws 371, and are, for example, 1 cm to 3 cm. Distances L1 and L2 may be the same or different. The aforementioned distances L1 and L2 are also set in the stripping device 37B based on the same principle.

[0082] In addition, regarding the above ranges Ha, Hb, and Hc, if there is a fixed frame 370 as a reference indicating one range of the peeling device 37A as in the peeling device 37A in the first embodiment, then Figure 6 As shown, the range can also be set to be divided by imaginary boundary lines (two-dot chain lines in the figure) that pass through positions at predetermined distances L3 and L4 from the fixed frame 370 in the width direction J along the rotation direction B. Distances L3 and L4 in this case can also be arbitrarily set based on the same concept as the above-mentioned distances L1 and L2. Furthermore, the above-mentioned distances L3 and L4 are also set based on the same concept in the other peeling device 37B.

[0083] The desired image forming devices 2 (Y, M, C, K) start forming the non-transferred toner image NT in the areas Ha, Hb, and Hc of the intermediate transfer belt 31 where the peeling device 37 (37A, 37B) is not located, at the desired timing, based on image information previously patterned and stored in the desired section associated with the control unit 15. The desired section mentioned above includes, for example, the storage unit 152 in the central control unit 151, the storage units in the four-color image formation control unit 153, and the storage unit of the image processing unit 17.

[0084] Furthermore, the non-transferred toner image NT has no particular restrictions other than the range within which it is formed. Therefore, there is no need to make any special changes to the conditions for the non-transferred toner image NT, such as its concentration and formation timing; conventional conditions can be used. However, since the non-transferred toner image NT is not formed within the ranges Hd and He of the intermediate transfer belt 31 where the peeling devices 37 (37A and 37B) are located, the toner image formation pattern or toner amount can be adjusted to compensate for these areas.

[0085] Figure 7 Specific examples of the non-transferred toner images NT formed in the ranges Ha, Hb, and Hc of the intermediate transfer belt 31 where the peeling devices 37 ( 37A, 37B) are not present are shown.

[0086] For example, when it is time to perform control to adjust process conditions, the process control color patch image NT1 as the non-transferred toner image NT is formed in a predetermined pattern in the area Hc of the intermediate transfer belt 31 .

[0087] When the time comes to perform control for correcting positional deviation, the registration control pattern image NT2 is formed as a non-transferred toner image NT in a predetermined pattern within the range Hb of the intermediate transfer belt 31 .

[0088] Furthermore, when a predetermined time arrives, the toner band image NT3 is formed as a non-transferred toner image NT using a pattern divided into three parts according to the ranges Ha, Hb, and Hc assigned to the intermediate transfer belt 31. From the perspective of supplying toner to the entire area of the distal end portion 36be of the plate-shaped cleaning member 36b in the belt cleaning device 36 to eliminate malfunctions in the belt cleaning device 36, it is preferable to form the toner band image NT3 over the entire ranges Ha, Hb, and Hc.

[0089] At a desired time after a low-density image has been formed at a predetermined density, the released toner image NT4 is formed as a non-transferred toner image NT in a predetermined pattern, for example, in the area Ha of the intermediate transfer belt 31. Specifically, the released toner image NT4 may be formed not only in the area Ha of the intermediate transfer belt 31 but also in one or both of the areas Hb and Hc.

[0090] Moreover, regardless of the type of non-transfer colorant image NT, the formation of the non-transfer colorant image NT begins by forming an electrostatic latent image for the non-transfer colorant image NT in a desired pattern on the photosensitive drum 21 through the exposure action of the exposure device 23 in the desired image forming device 2 (Y, M, C, K), and then forming the electrostatic latent image into a colorant image of a specified concentration through the developing action of the developing device 24 (Y, M, C, K).

[0091] At this time, an electrostatic latent image for the non-transferred toner image NT is formed on the photosensitive drum 21 in a range corresponding to the ranges Ha, Hb, and Hc of the intermediate transfer belt (see FIG. Figure 6 ).

[0092] Next, the non-transfer colorant image NT formed on the photosensitive drum 21 in the image forming device 2 (Y, M, C, K) is transferred to the range Ha, Hb, Hc of the intermediate transfer belt 31 of the intermediate transfer device 3 through the primary transfer process of the primary transfer device 25, and is then transported by the intermediate transfer belt 31 rotating in the direction indicated by the arrow B, but is not transferred to the paper 9 or the like at the secondary transfer position TP2 for the secondary transfer but passes directly.

[0093] At this time, the secondary transfer device 35 is switched to a condition in which the non-transferred toner image NT on the intermediate transfer belt 31 is not transferred toward the secondary transfer device 35. Specifically, the image reading sensors 18A and 18B read the state of formation of the process control patch image NT1 and the registration control pattern image NT2 in the non-transferred toner image NT. Furthermore, the information (signals) read by the image reading sensors 18A and 18B is transmitted to the central control unit 151 and other components of the control unit 15 and used as control information.

[0094] Next, the non-transferred colorant image NT that has passed the secondary transfer position TP2 of the intermediate transfer device 3 passes through the portion (range Ha, Hb, Hc) of the outer peripheral surface of the intermediate transfer belt 31 where the stripping device 37 arranged immediately after the secondary transfer position TP2 does not exist, and finally, is removed and recovered from the outer peripheral surface of the intermediate transfer belt 31 by the belt cleaning device 36.

[0095] At this time, the non-transferred toner image NT on the outer peripheral surface of the intermediate transfer belt 31 does not contact the distal end 371a of the peeling claw 371 in the peeling device 37 and passes through a position at least a distance L1 or L2 away from the distal end 371a of the peeling claw 371.

[0096] Therefore, in the image forming apparatus 1, even if a non-transferred toner image NT is formed, compared to the case where the non-transferred toner image NT is also formed in the ranges Hd and He where the peeling device 37 (37A and 37B) is present in the intermediate transfer belt 31, it is possible to suppress and prevent a portion of the non-transferred toner image NT formed in the ranges Ha, Hb, and Hc of the intermediate transfer belt 31 from coming into contact with and adhering to the distal end portion 371a of the peeling claw 371, and from floating, scattering, adhering to, or accumulating on the portion 371c of the peeling claw 371 on the side where the peeled paper 9 passes (see FIG. 1 ). Figure 8 ).

[0097] Therefore, in the image forming apparatus 1, when forming an image using a type of paper 9 represented by thick paper or paper with a relatively high hardness, for example, Figure 8As illustrated, even if the rear end 9b of the paper 9 in the conveying direction sometimes approaches and contacts the rear end portion 371a of the stripping claw 371 after passing through the secondary transfer position TP2 (after the clamping state at the secondary transfer position TP2 is released), there is no concern that the colorant attached to or accumulated on the rear end portion 371a of the stripping claw 371 or the portion 371c on the side where the paper 9 passes will be transferred to the rear end 9b of the paper and contaminate the paper. Figure 8 Reference numeral 9a in FIG. 8 denotes the end of the paper 9 in the conveying direction.

[0098] In contrast, as a non-transfer toner image NT, such as Figure 15 When the ranges Hd and He where the peeling device 37 (37A, 37B) is present are formed in the intermediate transfer belt 31 as exemplified by the toner belt image NTx3 and the released toner image NTx4, the following inconvenience may occur due to the peeling device 37. Here, "formed in the same manner" means, for example, that the non-transferred toner image NT is formed under the same formation conditions, such as concentration, as those used for the non-transferred toner image NT formed in the ranges Ha, Hb, and Hc.

[0099] That is, in this case, if Figure 16 As illustrated in (A), the toner belt image NTx3 and a portion of the toner of the released toner image NTx4 come into contact with the end portion 371a of the stripping claw 371 in the stripping device 37, and are attached as attached toner Tx to the end portion 371a of the stripping claw 371 and the portion 371c on the side where the paper 9 passes.

[0100] Therefore, if Figure 16 As shown in the example of (B) of FIG. 1 , when the trailing edge 9b of the paper 9 passes through the secondary transfer position TP2 during image formation and approaches and contacts the trailing edge 371a of the peeling claw 371, some or all of the attached toner Tx adhering to or accumulated on the trailing edge 371a of the peeling claw 371 may transfer to and contaminate the trailing edge 9b of the paper 9. Furthermore, some or all of the adhering toner Tx adhering to or accumulated on the trailing edge 9b of the paper 9 may float or scatter and transfer to the printing surface (front or back) of the paper 9, contaminating it.

[0101] That is, Figure 17 As shown in the example of the oval dotted frame, the contamination of the rear edge of the paper becomes noticeable when a plurality of paper sheets 9 are stacked. Figure 17 As exemplified by the trapezoidal dotted frame in the figure, regardless of the overlapping state of the paper 9 , contamination of one of the printed surfaces of the paper can be visually confirmed.

[0102] In this regard, the image forming apparatus 1 according to the first embodiment can suppress the occurrence of the aforementioned problems (contamination of the paper trailing edge and contamination of the paper printing surface) caused by the peeling device 37 even when forming a non-transferred toner image NT.

[0103] That is, in the image forming apparatus 1 , even when the position of the peeling device 37 ( 37A, 37B) is difficult to change, the formation of the non-transferred toner image NT can suppress the occurrence of the above-mentioned inconvenience caused by the peeling device 37 .

[0104] [Implementation Method 2]

[0105] Figure 9 and Figure 10 Part of an image forming apparatus according to Embodiment 2 of the present invention is shown.

[0106] The image forming apparatus of embodiment 2 is composed of the same structure as the image forming apparatus 1 of embodiment 1 except that the following structure is added. In the added structure, a low-concentration non-transfer colorant image LNT having a lower concentration than the usual non-transfer colorant image NT formed in the range Ha, Hb, Hc where the stripping device 37 (37A, 37B) does not exist is formed as the non-transfer colorant image LNT in the intermediate transfer belt 31 in at least the range Hd, He where the stripping device 37 exists.

[0107] First, in the image forming apparatus according to the first embodiment, a normal non-transferred toner image NT is not formed in the ranges Hd and He where the peeling device 37 is present on the intermediate transfer belt 31 .

[0108] Therefore, compared to the portions corresponding to the aforementioned ranges Ha, Hb, and Hc, the normal non-transferred toner image NT does not reach the portions corresponding to the aforementioned ranges Hd and He of the distal end portion 36be of the plate-shaped cleaning member 36b of the belt cleaning device 36. Consequently, the toner supply amount decreases accordingly. As a result, there is a concern that problems (such as humming noises and rolling over of the cleaning member 36b) may occur in the portions corresponding to the aforementioned ranges Hd and He in the belt cleaning device 36 (or the cleaning member 36b thereof).

[0109] In this regard, in the image forming device of embodiment 2, in addition to the usual non-transfer colorant image NT, a low-concentration non-transfer colorant image LNT is also formed in at least the range Hd, He of the intermediate transfer belt 31 where the stripping device 37 exists. Therefore, compared with the case where the low-concentration non-transfer colorant image LNT is not formed, the above-mentioned adverse condition can be suppressed from occurring in the portion of the belt cleaning device 36 corresponding to at least the portion of the intermediate transfer belt 31 corresponding to the above-mentioned range Hd, He.

[0110] At this time, for the concentration of the low-concentration non-transfer colorant image LNT, since the non-transfer colorant image LNT contacts and passes through the stripping claw 371 of the stripping device 37 (37A, 37B), it is necessary to set the concentration to a level that does not cause part of the colorant of the non-transfer colorant image LNT to adhere to the stripping claw 371.

[0111] In addition, for the low-concentration non-transfer colorant image LNT, as in the case of the non-transfer colorant image NT, the required image forming device 2 (Y, M, C, K) begins to form it at the required time based on the image information that has been patterned and stored in the required part related to the control unit 15 in advance.

[0112] Next, if Figure 9 As conceptually illustrated in FIG. 1 , the image forming apparatus of the second embodiment is configured to form a low-density non-transferred toner image LNT at a different time from that of a normal non-transferred toner image NT. Figure 9 , two structural examples in which a low-density non-transferred toner image LNT is formed at different times are representatively shown.

[0113] One structural example is a structure in which, when forming a toner band image NT3 as a normal non-transferred toner image NT, it is formed at a different timing from a low-density toner band image LNT3 having a lower density than the normal toner band image NT3.

[0114] exist Figure 9 For convenience, the low-density toner band image LNT3 is shown as being formed immediately after the normal toner band image NT3 is formed. However, the term "formed at a different time" here includes the case where the low-density toner band image LNT3 is formed independently at a time completely different from the time when the normal toner band image NT3 is formed.

[0115] Another configuration example is a configuration in which, when forming a normal non-transferred toner image NT, a released toner image NT4 is formed at a different time from a low-density released toner image LNT4 having a lower density than the normal released toner image NT4. The normal non-transferred toner image NT is a pattern formed only in the aforementioned range Ha of the intermediate transfer belt 31. Given this relationship, the low-density released toner image LNT4 is formed not only in the aforementioned ranges Hd and He but also in a range including the aforementioned ranges Hb and Hc.

[0116] exist Figure 9In the figure, as in the case of the low-density toner band image LNT3 described above, for convenience, the low-density released toner image LNT4 is depicted as being formed immediately after the normal released toner image NT4 is formed. However, in this case as well, "formed at a different time" includes forming the low-density released toner image LNT4 independently at a time completely different from the time when the normal released toner image NT4 is formed.

[0117] In a case where a low-concentration non-transfer colorant image LNT is formed at a different time from the usual non-transfer colorant image NT, compared to a case where a low-concentration non-transfer colorant image LNT is formed at the same time as the usual non-transfer colorant image NT, the time for forming the low-concentration non-transfer colorant image LNT can be set regardless of the time for forming the usual non-transfer colorant image NT, thereby being able to cope with the situation in a manner where the low-concentration non-transfer colorant image LNT is formed only when necessary.

[0118] Thus, in the belt cleaning device 36, the above-mentioned inconvenience can be reliably suppressed from occurring in the portion of the cleaning member 36b corresponding to the aforementioned ranges Hd and He of the intermediate transfer belt 31. Furthermore, the low-density non-transferred toner image LNT formed at these different times is not limited to the aforementioned ranges Hd and He, but may be formed within at least one of the aforementioned ranges Ha, Hb, and Hc.

[0119] Furthermore, in the image forming apparatus of embodiment 2, as Figure 10 As conceptually shown in FIG, a low-density non-transferred toner image LNT may be formed at the same time as a normal non-transferred toner image NT. Figure 10 , two structural examples formed at the same time are representatively shown.

[0120] This configuration example is a configuration in which, when forming a toner band image NT3 as a normal non-transferred toner image NT, a low-density toner band image LNT3 is formed at the same time as the formation of the normal toner band image NT3. "Formed at the same time" here means that at least the start time of the formation of the normal toner band image NT3 is the same.

[0121] Another configuration example is a configuration in which, when forming a released toner image NT4 as a normal non-transferred toner image NT, a low-density released toner image NT4 is formed at the same time as the normal released toner image NT4 is formed. Similar to the formation timing of the low-density toner band image LNT3 described above, formation at the same time in this case means that at least the start time of forming the normal released toner image NT4 is the same.

[0122] Figure 10 The normal released toner image NT4 shown is formed in the range Ha, excluding the ranges Hb and Hc, of the intermediate transfer belt 31. In this relationship, the low-density released toner image LNT4 is formed not only in the ranges Hd and He of the intermediate transfer belt 31, but also in the ranges Hb and Hc.

[0123] In the case where a low-concentration non-transfer colorant image LNT is formed at the same time as the normal non-transfer colorant image NT, compared with a case where a low-concentration non-transfer colorant image LNT is formed at a different time from the normal non-transfer colorant image NT, the low-concentration non-transfer colorant image LNT can be reliably formed in accordance with the time of the normal non-transfer colorant image NT, and the number of actions of forming the low-concentration non-transfer colorant image LNT separately from the formation of the normal non-transfer colorant image NT can be reduced.

[0124] In this case, the belt cleaning device 36 can also reliably suppress the occurrence of the above-mentioned malfunction in the portion of the cleaning member 36b corresponding to the above-mentioned ranges Hd and He of the intermediate transfer belt 31. Figure 10 The low-density released toner image LNT4 shown is also formed in the above-mentioned ranges Hb and Hc of the intermediate transfer belt 31. Therefore, in the belt cleaning device 36, the above-mentioned inconvenience can be suppressed from occurring in the portion of the cleaning member 36b corresponding to the above-mentioned ranges Hb and Hc.

[0125] In addition, in the image forming device of embodiment 2, a structure for forming a low-concentration non-transfer colorant image LNT at a time different from the normal non-transfer colorant image NT and a structure for forming a low-concentration non-transfer colorant image LNT at the same time as the normal non-transfer colorant image NT can also be combined.

[0126] In addition, regarding low-concentration non-transfer toner like LNT, as Figure 9 and Figure 10 As illustrated, the length of the low-density non-transferred toner image LNT in the rotational direction B of the intermediate transfer belt 31 is formed to be longer than that of a normal non-transferred toner image NT. Thus, by forming the low-density non-transferred toner image LNT, the total amount of toner supplied to the cleaning member 36b of the belt cleaning device 36, at least in the portion corresponding to the aforementioned ranges Hb and Hc, can be adjusted.

[0127] However, regarding the above-mentioned length of the low-concentration non-transfer colorant image LNT, if it is important to avoid the colorant adhering to the stripping claw 371 of the stripping device 37, etc., it is also effective to set it to a length that is the same as or shorter than the length of the normal non-transfer colorant image NT.

[0128] Figure 11 The following is an experimental result obtained when the image forming apparatus was used to investigate the relationship between the density of the low-density non-transferred toner image LNT and the contamination of the trailing end of the paper 9 .

[0129] This test is based on the premise that a black toner image of 600 mm in length is formed as a normal non-transfer toner image NT. At the same time as the normal non-transfer toner image NT, a corresponding image is formed once in the above range Hd and He. Figure 11 The non-transferred toner image LNT composed of various test densities is plotted in FIG. 1 , and then when the paper 9 passes through the secondary transfer position TP2 , it is checked whether toner adheres to the trailing end 9 b of the paper 9 and causes trailing end edge contamination.

[0130] At this time, the density of the low-density non-transferred toner image LNT was measured using a measuring instrument (spectrometer: X-Rite 962). Based on the density information measured by the measuring instrument, non-transferred toner images LNT having various test densities were prepared.

[0131] In addition, the occurrence of rear edge contamination was evaluated based on the following criteria, and the results were used as evaluation levels. Figure 11 The tolerance level is G1 or less.

[0132] Level G0: Not occurred.

[0133] · Level G1: The adhesion occurs in an extremely slight amount that is difficult to visually confirm even when multiple sheets are stacked.

[0134] Level G2: A slight amount of adhesion occurs that can be visually observed when a plurality of sheets are stacked.

[0135] Level G3: Occurs at a level that is easily visually recognized with the naked eye.

[0136] according to Figure 11 The results show that, as a low-density non-transferred toner image LNT, when formed at a density of 0.4 or less, no trailing edge contamination occurs, or the density reaches an acceptable level, compared to when formed at a density of 0.8 or greater. In other words, the density of the normal non-transferred toner image NT is formed within the range of 0.8 to 1.3.

[0137] Furthermore, from the perspective of suppressing or preventing the occurrence of trailing edge contamination, it is understood that the low-density non-transferred toner image LNT is preferably formed at a low density of 50% or less relative to the density of a normal non-transferred toner image NT. Furthermore, from the perspective of reliably preventing the occurrence of trailing edge contamination, the low-density non-transferred toner image LNT is more preferably formed at a density of 0.2 or less, and may be formed at a low density of 25% or less relative to the density of a normal non-transferred toner image NT.

[0138] [Implementation Method 3]

[0139] Figure 12 This is a diagram showing a portion of an image forming apparatus according to a third embodiment of the present invention.

[0140] The image forming apparatus of embodiment 3 has the same configuration as the image forming apparatus of embodiments 1 and 2 except that the peeling devices 37 ( 37A, 37B) are replaced with peeling devices 37 ( 37C, 37D) having a different configuration.

[0141] like Figure 12 、 Figure 13 As shown in the figures, the peeling device 37 (37C, 37D) is composed of the peeling claw 371 of the peeling device 37A, 37B in embodiments 1 and 2; and a covering member 375, which is configured to cover a portion 371c of the peeling claw 371 on the side where the peeled paper 9 passes. Figure 13 Reference numeral 370a is a bearing provided on the fixed frame 370 for rotatably supporting the support shaft 372 of the peeling claw 371. Reference numeral 38b is a mounting notch provided on the mounting plate 38 for fitting the bearing 370a of the fixed frame 370.

[0142] like Figure 13 As shown in (B) and the like, the covering member 375 is composed of a plate-shaped main body portion 376 that actually covers a portion 371 c of the peeling claw 371 on the side where the paper 9 passes, and a mounting portion 377 that combines the main body portion 376 with the peeling claw 371 and mounts them on the fixed frame 370.

[0143] The main body 376 is a substantially rectangular plate-shaped portion having a size that covers the entire portion 371c of the peeling claw 371. Figure 14 As shown in FIG. 1 and FIG. 2 , the main body 376 is formed in a shape in which a terminal end 376 a close to the outer peripheral surface of the intermediate transfer belt 31 is bent upward so as to float a required distance away from the outer peripheral surface of the intermediate transfer belt 31 .

[0144] The mounting portion 377 is a portion extending downward from the rear end and one side end of the main body 376. The mounting portion 377 is provided with a bearing hole 377a into which the support shaft 372 of the peeling claw 371 is inserted.

[0145] The peeling device 37 (37C, 37D) is assembled as follows: after the support shaft 372 of one side of the peeling claw 371 is inserted into and penetrates the bearing hole 377a of the mounting portion 377, the covering member 375 and the peeling claw 371 are integrated. The support shaft 372 of the peeling claw 371 is then mounted on the bearing portion 370a of the fixed frame 370, and an elastic member 373 such as a coil spring is mounted on the peeling claw 371. Furthermore, the peeling device 37 (37C, 37D) is mounted on the mounting plate 38 via the fixed frame 370.

[0146] Furthermore, in the image forming apparatus of embodiment 3, a peeling device 37 (37C, 37D) having a covering member 375 is applied to the intermediate transfer device 3. Thus, even if there is transfer residual toner remaining on the intermediate transfer belt 31 without secondary transfer during the operation of forming a normal image consisting of a colorant image transferred to the paper 9 and passes through the peeling devices 37C, 37D, or a low-concentration non-transfer colorant image LNT is formed and passes through the peeling devices 37C, 37D, the peeling claw 371 is covered by the covering member 375, and therefore the toner is difficult to adhere to the portion 371c of the peeling claw 371 on the side where the peeled paper 9 passes.

[0147] Furthermore, in the image forming apparatus, as Figure 14 As shown, even if the rear end 9b of the paper 9 that has passed the secondary transfer position TP2 of the intermediate transfer device 3 passes through the state close to and contacts the peeling devices 37C and 37D, even if the rear end 9b of the paper 9 contacts the covering member 375, it will not directly contact the end portion 371a of the peeling claw 371.

[0148] In addition, assuming that colorant is attached to and accumulated on the end portion 371a of the stripping claw 371, even if the rear end 9b of the paper 9 passes through in contact with the stripping devices 37C and 37D, in addition to being able to prevent the rear end 9b of the paper 9 from directly contacting the end portion 371a of the stripping claw 371, even if the colorant accumulated on the portion 371c of the stripping claw 371 is scattered due to the impact of the contact, the covering member 375 can prevent the toner from moving and preventing it from being transferred to the rear end printing surface of the paper 9.

[0149] Therefore, in this image forming apparatus, contamination of the trailing end of the paper 9 is unlikely to occur.

[0150] Therefore, according to this image forming apparatus, compared with a case where the peeling device 37 is not composed of the peeling claw 371 and the covering member 375, it is possible to suppress the adhesion of colorant to the portion 371c of the peeling claw 371 on the side where the peeled paper 9 passes, and to suppress the occurrence of contamination of the rear end of the paper 9.

[0151] [Other Modifications]

[0152] The present invention is not limited in any way to the contents illustrated in Embodiments 1 to 3, and includes, for example, the following modified examples.

[0153] The number of the peeling devices 37 is not limited to two, and may be three or more or one.

[0154] In addition, the image forming apparatus 1 is not limited to an image forming apparatus of an intermediate transfer method including an intermediate transfer device 3 as exemplified in embodiments 1-3, but may also be an image forming apparatus of a direct transfer method in which a colorant image formed on a photosensitive body such as a photosensitive drum is directly transferred onto paper.

[0155] In this direct transfer image forming apparatus, for example, a contact-type peeling device for peeling off the paper 9 may be provided on the photosensitive drum 21, which serves as an example of image holding means. When forming a non-transfer toner image NT on the photosensitive drum 21, the non-transfer toner image NT is formed in an area of the photosensitive drum 21 where the peeling device is not present. Furthermore, the image forming apparatus may be configured to form a low-density non-transfer toner image LNT in at least the area of the photosensitive drum 21 where the peeling device is present.

[0156] Furthermore, the present invention is also applicable to a direct transfer image forming apparatus in which a transfer belt device is used to convey a sheet of paper to a transfer position of a photoreceptor for transfer.

Claims

1. An image forming apparatus, wherein: The image forming apparatus comprises: an image holding unit that holds the toner image transferred to the paper, the paper contacting and passing through the image holding unit; a peeling unit that peels the paper from the image holding unit; and a removal unit that contacts the image holding unit and removes the toner that has passed through the peeling unit; The image forming device forms a normal non-transfer colorant image as a non-transfer colorant image that is not transferred onto paper within a range in the image holding unit where the stripping unit does not exist, and forms a low-concentration non-transfer colorant image having a lower concentration than the normal non-transfer colorant image as the non-transfer colorant image within a range in the image holding unit where at least the stripping unit exists.

2. The image forming apparatus according to claim 1, wherein The low-density non-transferred toner image is formed at a different timing from that of the normal non-transferred toner image.

3. The image forming apparatus according to claim 1, wherein The low-density non-transferred toner image is formed in the range where the peeling unit is present at the same time as the normal non-transferred toner image.

4. The image forming apparatus according to any one of claims 1 to 3, wherein: The low-density non-transferred toner image is formed at a low density of 50% or less of the density of the normal non-transferred toner image.

5. The image forming apparatus according to any one of claims 1 to 3, wherein The peeling unit includes a peeling claw that peels off the paper and a covering member that is arranged to cover a portion of the peeling claw on a side through which the peeled paper passes.

Images