Image forming apparatus

Abstract

To simply perform positioning of a transfer unit holding a transfer member with respect to an image forming apparatus body, and power supply to the transfer member.SOLUTION: An image forming apparatus is provided with a secondary transfer roller 89 (transfer member) for transferring an image to a sheet P (transfer target body), and a secondary transfer unit 60 (transfer unit) that is supported on an image forming apparatus body 1 rotatably about a support shaft 50a and holds the secondary transfer roller 89. The image forming apparatus is further provided with a power supply part 110 that can output a secondary transfer bias (transfer bias) to be applied to the secondary transfer roller 89, and a compression spring 93 (urging member) that urges the secondary transfer unit 60 to bring the secondary transfer unit 60 into contact with a positioning part 23a of the image forming apparatus body 1. The compression spring 93 functions as part or all of a power supply path of the secondary transfer bias from the power supply part 110 to the secondary transfer roller 89.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a combination machine thereof or a printing machine, in which a transfer member such as a secondary transfer roller is installed. [Background technology]

[0002] Conventionally, in image forming devices such as copiers and printers, a technology has been known in which a transfer unit holding a secondary transfer roller (transfer member) is urged by a urging member to abut against a positioning portion of the image forming device main body, thereby positioning the transfer unit relative to the image forming device main body (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 2 discloses a technology in which a power supply terminal provided on the main body cover is brought into contact with a power-receiving member such as a secondary transfer roller in conjunction with the action of closing the main body cover, thereby enabling power to be supplied from a power supply unit to the power-receiving member. Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional image forming devices had separate components for positioning the transfer unit holding the transfer member in the image forming device body and for supplying power to the transfer member, which made the device complicated and expensive.

[0005] This invention has been made to solve the above-mentioned problems, and aims to provide an image forming apparatus that can easily position a transfer unit holding a transfer member relative to the image forming apparatus main body and supply power to the transfer member. [Means for solving the problem]

[0006] The image forming apparatus of the present invention comprises a transfer member for transferring an image onto a receiving material, a transfer unit supported rotatably about a support axis relative to the image forming apparatus main body and holding the transfer member, a power supply unit capable of outputting a transfer bias to be applied to the transfer member, and a biasing member for biasing the transfer unit so that the transfer unit abuts against a positioning portion of the image forming apparatus main body, the biasing member functioning as part or all of the power supply path for the transfer bias from the power supply unit to the transfer member. Effect of the Invention

[0007] According to the present invention, it is possible to provide an image forming apparatus in which it is possible to easily position the transfer unit holding the transfer member relative to the image forming apparatus main body and to easily supply power to the transfer member. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 11A to 11C are schematic diagrams illustrating an operation of opening the opening / closing cover. [Diagram 3] FIG. 2 is a diagram illustrating the vicinity of a secondary transfer unit. [Figure 4] 13 is a diagram showing the vicinity of a secondary transfer unit as a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. 1, the image forming apparatus 1 in this embodiment is a tandem type color printer. In the bottle storage section 101 located at the top of the image forming apparatus main body 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceably) installed. An intermediate transfer unit 85 is disposed below the bottle storage unit 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side so as to face an intermediate transfer belt 78 (intermediate transfer body) of the intermediate transfer unit 85. Below the image forming apparatus main body 1, there is provided a paper feed section 12 (paper feed cassette) in which a plurality of sheets P such as paper are stored in a stack. Further, on the left side of the image forming apparatus 1, an opening / closing cover 50 for exposing the inside of the image forming apparatus 1 (transport paths K0 and K1 of the sheet P, fixing device 20, etc.) is provided so as to be openable and closable.

[0011] Photoconductor drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. A charging unit 75, a developing device 76, a cleaning device 77, a charge removing unit, and the like are disposed around each of the photoconductor drums 5Y, 5M, 5C, and 5K. An image forming process (charging process, exposure process, developing process, transfer process, and cleaning process) is performed on each of the photoconductor drums 5Y, 5M, 5C, and 5K, and an image of each color is formed on the surface of each of the photoconductor drums 5Y, 5M, 5C, and 5K.

[0012] The photoconductor drums 5Y, 5M, 5C, and 5K are rotated by a main motor in the counterclockwise direction in Fig. 1. Then, at the position of the charging unit 75, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K are uniformly charged (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light emitted from the exposure section 3 (writing section), and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position (this is the exposure process).

[0013] Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach positions facing the developing devices 76, where the electrostatic latent images are developed to form toner images of the respective colors (developing process). Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions the toner images on the photoconductor drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is the first transfer step). At this time, a small amount of untransferred toner remains on the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K.

[0014] Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning device 77, at which point the untransferred toner remaining on the photoconductor drums 5Y, 5M, 5C, and 5K is mechanically collected by the cleaning blade of the cleaning device 77 (this is the cleaning process). Finally, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach a position facing a charge removing unit, where the residual potential on the photoconductor drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes carried out on the photoconductor drums 5Y, 5M, 5C, and 5K is completed.

[0015] Thereafter, the toner images of each color formed on the surface of each photosensitive drum through a developing process are transferred and superimposed on the surface of an intermediate transfer belt 78 (intermediate transfer body), thus forming a color image on the surface of the intermediate transfer belt 78. Here, the intermediate transfer unit 85 is composed of an intermediate transfer belt 78 as an intermediate transfer body, four primary transfer bias rollers 79Y, 79M, 79C, 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, an intermediate transfer cleaning device 80, etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is moved endlessly in the direction of the arrow in FIG. 1 by the rotational drive of one roller 82 connected to a main motor.

[0016] The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 between the photoconductor drums 5Y, 5M, 5C, and 5K, respectively, to form primary transfer nips. A primary transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. Then, the intermediate transfer belt 78 travels in the direction of the arrow and passes sequentially through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of each color on the photoconductor drums 5Y, 5M, 5C, and 5K are primarily transferred onto the surface of the intermediate transfer belt 78 in a superimposed manner (this is the primary transfer process).

[0017] Thereafter, the intermediate transfer belt 78, onto which the toner images of each color are superimposed and primarily transferred, reaches a position facing a secondary transfer roller 89 serving as a transfer member. At this position, a secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between itself and the secondary transfer roller 89 (transfer member) to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 78 are then transferred (secondary transfer) onto a sheet P conveyed to the position of this secondary transfer nip (secondary transfer process). At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning device 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes carried out on the intermediate transfer belt 78 is completed.

[0018] Here, the sheet P conveyed to the position of the secondary transfer nip is conveyed from a paper feed unit 12 disposed below the apparatus main body 1 via a conveying path K0. More specifically, a plurality of sheets P (transfer receiving bodies) such as paper are stored in a stack in the paper feed section 12. When the paper feed roller 31 is rotated counterclockwise in FIG. 1, the topmost sheet P sandwiched between the paper feed roller 31 and the friction pad 32 is fed toward between the rollers of the registration roller pair 33 (timing roller pair) while being guided by a guide plate that forms the transport path K0.

[0019] The sheet P conveyed to the registration roller pair 33 (timing roller pair) is temporarily stopped at the roller nip (nip portion) of the registration roller pair 33 that has stopped rotating. Then, the registration roller pair 33 is rotated in synchronization with the color image on the intermediate transfer belt 78, and the sheet P as the transfer object is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0020] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip is conveyed via a conveying path to the position of the fixing device 20. Then, at this position (the fixing nip portion formed by the pressure contact between the fixing belt 21 and the pressure roller 22), the toner image carried on the surface is fixed onto the sheet P by heat and pressure (the fixing process).

[0021] Then, the sheet P after the fixing process passes through the conveying path K1 and is discharged to the outside of the apparatus by the discharge roller pair 40. The sheets P discharged to the outside of the apparatus by the discharge roller pair 40 are sequentially stacked on the stack unit 100 as output images. In this manner, a series of image forming processes in the image forming apparatus is completed.

[0022] Hereinafter, the characteristic configuration and operation of image forming apparatus 1 in this embodiment will be described in detail with reference to FIG. 2, FIG. 3, etc. As previously described with reference to FIG. 1, an opening / closing cover 50 for opening and closing the inside of image forming apparatus 1 is provided on the left side of image forming apparatus 1 in this embodiment. 2A and 2B, the opening / closing cover 50 is configured to be rotatable about a support shaft 50a in order to open and close the inside of the image forming apparatus 1. The opening / closing cover 50 holds a secondary transfer unit 60 (which holds a secondary transfer roller 89 and the like), which will be described later. Therefore, the secondary transfer unit 60 rotates about the support shaft 50a together with the opening / closing cover 50 in conjunction with the opening and closing operation of the opening / closing cover 50.

[0023] Specifically, when the opening / closing cover 50 in the closed state as shown in FIG. 2(A) (and FIG. 1) is rotated counterclockwise (in the direction of the arrow) around the support shaft 50a as shown in FIG. 2(B) together with the secondary transfer unit 60, a part of the interior of the image forming apparatus 1 (such as the conveying paths K0, K1, the secondary transfer unit 60, and the fixing device 20) is opened (exposed), making it possible to remove a sheet P that has jammed in the conveying paths K0, K1 or the fixing device 20, or to detach and attach the secondary transfer unit 60 or the fixing device 20 for maintenance. In addition, when the opening / closing cover 50, which is in the open state as shown in FIG. 2(B), is rotated clockwise in FIG. 2 around the support shaft 50a together with the secondary transfer unit 60, the opening / closing cover 50 becomes in the closed state as shown in FIG. 2(A) and FIG. 3, and the secondary transfer roller 89 comes into contact with the intermediate transfer belt 78 to form a secondary transfer nip.

[0024] As described above with reference to FIG. 1, the image forming apparatus 1 in this embodiment is provided with a secondary transfer roller 89 as a transfer member for transferring an image onto a sheet P as a receiving body. The secondary transfer roller 89 as a transfer member is a roller member that abuts against the intermediate transfer belt 78 as an intermediate transfer body to form a secondary transfer nip and secondarily transfers the image primarily transferred to the intermediate transfer belt 78 onto the sheet P as a transfer body that is transported to the secondary transfer nip. The secondary transfer roller 89 has an elastic layer formed (coated) on a shaft portion 89a (see FIG. 3) made of a conductive material such as stainless steel. The elastic layer of the secondary transfer roller 89 can be formed in a solid or foam sponge shape by dispersing a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, or silicone, or by incorporating an ionic conductive material.

[0025] Furthermore, referring to FIG. 3, image forming apparatus 1 in the present embodiment is provided with a power supply unit 110 capable of outputting a transfer bias (secondary transfer bias) to be applied to secondary transfer roller 89 (transfer member). This power supply unit 110 forms a secondary transfer electric field at the position of the secondary transfer nip by applying a secondary transfer bias of a polarity different from the polarity of the toner to the secondary transfer roller 89, and electrostatically moves the toner carried on the outer belt surface (toner carrying surface) of the intermediate transfer belt 78 toward the secondary transfer roller 89. The secondary transfer bias may be a DC voltage or a DC current superimposed with an AC current.

[0026] Furthermore, with reference to FIG. 3 (and FIG. 2), image forming apparatus 1 in the present embodiment is provided with secondary transfer unit 60 as a transfer unit that holds secondary transfer roller 89 (transfer member). This secondary transfer unit 60 (transfer unit) is supported rotatably about a support shaft 50a with respect to the image forming apparatus main body 1. Specifically, as described above with reference to FIG. 2 etc., the secondary transfer unit 60 is held by an opening / closing cover 50 that is rotatable (openable and closable) about the support shaft 50a. Further, the secondary transfer unit 60 is provided with a holding portion 61 that rotatably holds the secondary transfer roller 89, as well as a conveying guide member 62 that guides the sheet P sent out from the secondary transfer nip.

[0027] The transport guide member 62 of the secondary transfer unit 60 is located downstream in the sheet transport direction from the secondary transfer nip and upstream in the sheet transport direction from the fixing entrance guide member 23 of the fixing device 20, and is a member for guiding the sheet P after the secondary transfer process that is sent out from the secondary transfer nip toward the fixing device 20 (fixing entrance guide member 23).

[0028] The holding portion 61 of the secondary transfer unit 60 holds a bearing (not shown) that rotatably holds the shaft portion 89a of the secondary transfer roller 89 so that part of the secondary transfer roller 89 fits into its recess (a portion recessed in the direction away from the secondary transfer nip). The secondary transfer unit 60 (holding portion 61) is provided with a fitting member 90 that fits onto the shaft portion 89a of the secondary transfer roller 89, and a second compression spring 91 as a second biasing member that biases the fitting member 90 so that the secondary transfer roller 89 abuts against the intermediate transfer belt 78 (intermediate transfer body). The fitting member 90 fits into a groove portion (in which the second compression spring 91 is provided) formed in the holding portion 61, and is configured to be slidable in the left-right direction of FIG. 3 (the direction in which the groove portion extends, which is the direction in which the secondary transfer roller 89 approaches and moves away from the intermediate transfer belt 78).

[0029] Now, referring to FIG. 3, the image forming apparatus 1 in this embodiment is provided with a compression spring 93 (first compression spring) as a biasing member that biases the secondary transfer unit 60 (transfer unit) so that the secondary transfer unit 60 abuts against the positioning portion 23a of the image forming apparatus main body 1. Specifically, the positioning portion 23a is a portion formed at an end portion of the fixing inlet guide member 23 of the fixing device 20 in the width direction (the direction perpendicular to the paper surface of FIG. 3) so as to protrude downward. On the other hand, the transport guide member 62 of the secondary transfer unit 60 is formed at its widthwise end with a contact portion 62a (a portion that protrudes in the widthwise direction like a boss) that contacts the positioning portion 23a. 3 by the compression spring 93 installed at the widthwise end, the secondary transfer unit 60 is biased diagonally to the upper right in FIG. 3, so that the abutting portion 62a of the secondary transfer unit 60 abuts against the positioning portion 23a, and the position of the secondary transfer unit 80 in the image forming apparatus 1 is determined with high precision. Therefore, the position of the secondary transfer nip is determined with high precision, and a good secondary transfer process is performed. Furthermore, the position of the transport guide member 62 in the image forming apparatus 1 is also determined with high precision, and the transportability of the sheet P from the secondary transfer nip to the fixing nip is improved. The members (such as the compression spring 93, the contact portion 62a, and the positioning portion 23a) related to the positioning of the secondary transfer unit 60 are provided at both ends in the width direction. In order to efficiently perform the positioning described above, it is preferable to configure the direction of the force exerted by the compression spring 93 to coincide with the direction in which the contact portion 62a contacts the positioning portion 23a.

[0030] In this embodiment, the secondary transfer unit 60 is held in the opening / closing cover 50 so as to be movable in a direction toward and away from the intermediate transfer belt 78. The compression spring 93 is installed in the main body of the opening / closing cover 50 (indirectly installed in the image forming apparatus main body 1) and is installed in the opening / closing cover 50 so as to urge the secondary transfer unit 60 in the above-mentioned direction. Alternatively, the secondary transfer unit 60 may be fixed to the opening / closing cover 50, and the compression spring 93 may be directly installed in the image forming apparatus main body 1 without using the opening / closing cover 50. In this case, the overall positioning of the opening / closing cover 50 is determined by the contact between the contact portion 62a of the secondary transfer unit 60 and the positioning portion 23a. In addition, in this embodiment, the positioning portion 23a against which the abutment portion 62a of the secondary transfer unit 60 abuts is provided on the fixing inlet guide member 23 of the fixing device 20, but the position (member) at which the positioning portion is provided is not limited to this.

[0031] Here, the compression spring 93 (first compression spring) as the biasing member in this embodiment is configured to function as a part of a power supply path for a secondary transfer bias from the power source unit 110 to the secondary transfer roller 89 (transfer member). Specifically, the compression spring 93 is made of a conductive material such as metal, and one end side of the compression spring 93 is connected to the power supply unit 110 via a first power supply path 94 (for example, configured by a harness or the like). The fitting member 90 and the second compression spring 91 of the secondary transfer unit 60 (holding portion 61) described above are made of a conductive material such as metal or conductive resin. Furthermore, a conductive plate 92 is provided on the secondary transfer unit 60 (holding portion 61). One end side of the conductive plate 92 is connected to the second compression spring 91 (first biasing member), and the other end side is connected to a contact portion 93a (which is conductive and has a certain degree of rigidity) formed on the other end side of the first compression spring 93. With this configuration, the secondary transfer bias (transfer bias) output from the power supply unit 110 (first power supply path 94) is applied to the shaft portion 89a of the secondary transfer roller 89 via the compression spring 93, the conductive plate 92, the second compression spring 91 (second biasing member), and the engaging member 90. In addition, components that function only as power supply paths and are not involved in the positioning of the secondary transfer unit 60 (mainly the conductive plate 92 and the first power supply path 94) are not provided at both ends in the width direction, but are only provided at one end in the width direction.

[0032] Thus, in this embodiment, the compression spring 93 (urging member) having the function of positioning the secondary transfer unit 60 on the image forming apparatus main body 1 also functions as a power supply path for applying a secondary transfer bias from the power supply section 110 to the secondary transfer roller 89, resulting in a simpler and less expensive image forming apparatus 1 compared to a case in which a member having a positioning function and a member having a power supply function are provided separately. In this embodiment, the compression spring 93 (spring member) is configured to function as part of the power supply path for the secondary transfer bias from the power source unit 110 to the secondary transfer roller 89, but the compression spring can also be configured to function as the entire power supply path by, for example, connecting it directly to the secondary transfer roller.

[0033] <Modification> As shown in FIG. 4, in the modified secondary transfer unit 60 (transfer unit), a de-electrifying member 70 for de-electrifying the sheet P sent out from the secondary transfer nip is provided between a transport guide member 62 and a holding portion 61 for rotatably holding the secondary transfer roller 89. The charge removal member 70 has a needle-shaped charge removal plate 70a at its tip, which removes the charge accumulated on the sheet P after the secondary transfer process, thereby reducing the problem of the sheet P being electrostatically attracted to the transport guide member 62. In the modified example, the compression spring 93 having the function of positioning the secondary transfer unit 60 also has the function of determining the position of the charge removing member 70 in the image forming apparatus 1. Therefore, the charge removing function of the charge removing member 70 described above is satisfactorily exhibited.

[0034] As described above, the image forming apparatus 1 in this embodiment is provided with a secondary transfer roller 89 (transfer member) for transferring an image to a sheet P (transfer receiving body), and a secondary transfer unit 60 (transfer unit) that is supported rotatably about a support shaft 50a relative to the image forming apparatus main body 1 and holds the secondary transfer roller 89. Also provided are a power supply unit 110 capable of outputting a secondary transfer bias (transfer bias) to be applied to the secondary transfer roller 89, and a compression spring 93 (urging member) that urges the secondary transfer unit 60 so that the secondary transfer unit 60 abuts against a positioning portion 23a of the image forming apparatus main body 1. The compression spring 93 functions as a part or the whole of a power supply path for the secondary transfer bias from the power supply unit 110 to the secondary transfer roller 89. This makes it possible to easily position the secondary transfer unit 60, which holds the secondary transfer roller 89 (transfer member), relative to the image forming apparatus main body 1 and to easily supply power to the secondary transfer roller 89.

[0035] In this embodiment, the present invention is applied to a color image forming apparatus 1, but the present invention can also be applied to a monochrome image forming apparatus. In this case, the transfer member to which the present invention is applied is a transfer roller that comes into contact with a photosensitive body such as a photosensitive drum and forms a transfer nip through which a sheet as a transfer target is transported. In addition, in the present embodiment, the secondary transfer roller 89 is used as the transfer member to which the present invention is applied, but the primary transfer rollers 79Y, 79M, 79C, and 79K can also be used as the transfer member to which the present invention is applied. In that case, the intermediate transfer belt 78 is used as the transfer medium to which the image is transferred by the transfer member. In addition, in this embodiment, a secondary transfer roller 89 that contacts the intermediate transfer belt 78 to form a transfer nip is used as the transfer member to which the present invention is applied, but a secondary transfer charger that faces the intermediate transfer belt 78 without contacting it can also be used. In the present embodiment, the compression spring 93 is used as the biasing member having both a positioning function and a power supply function, but the biasing member is not limited to this, and for example, a leaf spring or the like can also be used. Even in such cases, the same effects as those of this embodiment can be obtained.

[0036] It is clear that the present invention is not limited to the present embodiment, and that the present embodiment may be modified as appropriate within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention. [Explanation of symbols]

[0037] 1 Image forming apparatus (image forming apparatus main body), 20 Fixing device, 23 Fixing entrance guide member, 23a positioning portion, 50 Opening and closing cover (opening and closing unit), 50a spindle, 60 Secondary transfer unit (transfer unit), 61 Holding part, 62 conveying guide member, 62a Contact part, 70 Static electricity removing member, 70a Antistatic brush, 78 Intermediate transfer belt (intermediate transfer body), 89 Secondary transfer roller (transfer member), 89a shaft, 90 Fitting member, 91 second compression spring (second biasing member), 92 Conductive plate, 93 compression spring (biasing member, first biasing member), 93a contact part, 94 first power supply path, 110 Power supply section, P sheet (receiving material).

[0038] The present invention can also be embodied in the following combinations of Supplementary Notes 1 to 5, for example. (Appendix 1) A transfer member for transferring an image to a receiving material; a transfer unit that is supported rotatably about a support shaft with respect to a main body of the image forming apparatus and that holds the transfer member; a power supply unit capable of outputting a transfer bias to be applied to the transfer member; a biasing member that biases the transfer unit so that the transfer unit abuts against a positioning portion of the image forming apparatus main body; Equipped with The image forming apparatus according to claim 1, wherein the biasing member functions as a part or an entirety of a power supply path for the transfer bias from the power supply unit to the transfer member. (Appendix 2) The transfer member is a secondary transfer roller that contacts an intermediate transfer body to form a secondary transfer nip and performs secondary transfer of an image that has been primarily transferred onto the intermediate transfer body onto a sheet that is the transfer target body and is conveyed to the secondary transfer nip, 2. The image forming apparatus according to claim 1, wherein the biasing member is a compression spring made of a conductive material. (Appendix 3) The transcription unit comprises: a fitting member that fits onto a shaft portion of the secondary transfer roller; a second biasing member that biases the fitting member so that the secondary transfer roller abuts against the intermediate transfer body; a conductive plate having one end connected to the second biasing member and the other end connected to the compression spring; Equipped with The image forming apparatus described in Appendix 2, characterized in that the transfer bias output from the power supply unit is applied to the secondary transfer roller via the compression spring, the conductive plate, the second biasing member, and the engaging member. (Appendix 4) the transfer unit includes a transport guide member that guides the sheet sent out from the secondary transfer nip; 4. The image forming apparatus according to claim 2, wherein the transport guide member is formed with a contact portion that contacts the positioning portion. (Appendix 5) The image forming apparatus described in Appendix 4, characterized in that the transfer unit includes a charge-removing member that removes charge from the sheet sent out from the secondary transfer nip, the charge-removing member being provided between the transport guide member and a holding portion that rotatably holds the secondary transfer roller. [Prior art documents] [Patent documents]

[0039] [Patent Document 1] JP 2019-133008 A [Patent Document 2] Patent No. 4368663

Claims

1. A transfer member for transferring an image to a receiving material; a transfer unit supported rotatably about a support shaft with respect to a main body of the image forming apparatus and holding the transfer member; a power supply unit capable of outputting a transfer bias to be applied to the transfer member; a biasing member that biases the transfer unit so that the transfer unit abuts against a positioning portion of the image forming apparatus main body; Equipped with The image forming apparatus according to claim 1, wherein the biasing member functions as a part or an entirety of a power supply path for the transfer bias from the power supply unit to the transfer member.

2. the transfer member is a secondary transfer roller that contacts an intermediate transfer body to form a secondary transfer nip and performs secondary transfer of an image that has been primarily transferred onto the intermediate transfer body onto a sheet that is the transfer target body and that is transported to the secondary transfer nip; 2. The image forming apparatus according to claim 1, wherein the biasing member is a compression spring made of a conductive material.

3. The transcription unit comprises: a fitting member that fits onto a shaft portion of the secondary transfer roller; a second biasing member that biases the fitting member so that the secondary transfer roller abuts against the intermediate transfer body; a conductive plate having one end connected to the second biasing member and the other end connected to the compression spring; Equipped with 3. The image forming apparatus according to claim 2, wherein the transfer bias output from the power supply unit is applied to the secondary transfer roller via the compression spring, the conductive plate, the second biasing member, and the engaging member.

4. the transfer unit includes a transport guide member that guides the sheet sent out from the secondary transfer nip; 3. The image forming apparatus according to claim 2, wherein the transport guide member is formed with a contact portion that contacts the positioning portion.

5. 5. The image forming apparatus according to claim 4, wherein the transfer unit includes a discharge member for discharging the sheet sent out from the secondary transfer nip, the discharge member being provided between the transport guide member and a holding portion for rotatably holding the secondary transfer roller.

Images