Unit positioning mechanism and image forming apparatus

Abstract

To prevent positional deviation of a unit, while preventing a reduction in the resolvability of a positioning member and the periphery thereof.SOLUTION: A unit positioning mechanism comprises a first unit, a second unit, and a positioning member. The positioning member has a cylindrical part, a hook part, and a part to be regulated. The second unit has a unit side part, a support shaft, and a regulating part. The hook part is engaged with a boss part to regulate the rotation of the second unit. The regulating part overlaps the part to be regulated from the outside in a predetermined direction in a state where the hook part is engaged with the boss part, and includes a twisted coil spring having a coil spring part arranged on the cylindrical part, a first arm part, and a second arm part. The twisted coil spring is engaged with the positioning member at the first arm part, and engaged with the unit side part at the second arm part, to urge the positioning member in a direction in which the hook part is engaged with the boss part.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a unit positioning mechanism and an image forming apparatus. [Background technology]

[0002] A conventional image forming apparatus includes a unit that is rotatable around one edge of the apparatus as a fulcrum. For example, in Patent Document 1, the unit is a cover member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 201982 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, for example, the hook portion of the positioning member engages with the unit to restrict the rotation of the unit. In other words, the unit is positioned. In this configuration, if the positioning member becomes misaligned (for example, the positioning member falls off), the unit also becomes misaligned. However, if the positioning member is fixed so that it does not become misaligned, the disassembly of the positioning member and its surroundings becomes difficult.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a unit positioning mechanism and an image forming apparatus that can suppress misalignment of the unit while preventing a decrease in disassembly of the positioning member and its surroundings in a configuration in which the rotation of the unit is regulated by a positioning member. [Means for solving the problem]

[0006] In order to achieve the above object, a unit positioning mechanism according to a first aspect of the present invention includes a first unit having a boss portion, a second unit that is displaceable between a first position, which is positioned relative to the first unit, and a second position other than the first position, by rotating about an axis extending in a predetermined direction, and a positioning member that holds the second unit at the first position. The positioning member has a cylindrical portion having a cylindrical axis direction in the predetermined direction, a hook portion that is arranged radially outward of the cylindrical portion as viewed from the predetermined direction and engages with the boss portion so as to embrace the boss portion from one side in the circumferential direction centered on the cylindrical axis of the cylindrical portion, and a regulated portion that is arranged radially outward of the cylindrical portion as viewed from the predetermined direction and at a different position in the circumferential direction from the hook portion as viewed from the predetermined direction. The second unit has a unit side portion, a support shaft that protrudes outward in the predetermined direction from the unit side portion, into which the cylindrical portion is fitted from the outside in the predetermined direction, and supports the positioning member so as to be displaceable in the circumferential direction, and a regulating portion that is arranged on a rotation locus of the regulated portion that rotates around the cylindrical axis of the cylindrical portion as viewed from the predetermined direction. The hook portion engages with the boss portion when the second unit is in the first position, thereby restricting the rotation of the second unit from the first position to the second position. When the hook portion is engaged with the boss portion, the restricting portion overlaps with the regulated portion from the outside in the predetermined direction, thereby restricting the outward movement of the positioning member in the predetermined direction. The torsion coil spring includes a wound spring portion disposed in the cylindrical portion, a first arm portion extending from one end of the wound spring portion, and a second arm portion extending from the other end of the wound spring portion. The torsion coil spring biases the positioning member in the direction in which the hook portion engages with the boss portion, by engaging the first arm portion with the positioning member and the second arm portion with the unit side portion.

[0007] An image forming apparatus according to a second aspect of the present invention includes the above-mentioned unit positioning mechanism. The first unit is a unit having an image carrier that carries an image. The second unit is a unit having a transfer roller that is in pressure contact with the image carrier. The image forming apparatus conveys a sheet to a transfer nip formed between the image carrier and the transfer roller, and transfers the image onto the sheet. Effect of the Invention

[0008] In the present invention, in a configuration in which the rotation of the unit is restricted by the positioning member, it is possible to suppress a decrease in the disassembly ability of the positioning member and its surroundings, while suppressing misalignment of the unit. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of an image forming apparatus according to an embodiment. [Diagram 2] 2 is a perspective view of the image forming apparatus shown in FIG. 1 with a rear cover removed. [Diagram 3] 1 is a schematic diagram illustrating an internal configuration of an image forming apparatus according to an embodiment. [Figure 4] 1 is a schematic diagram illustrating a configuration of an image forming unit of an image forming apparatus according to an embodiment. [Diagram 5] 1 is a side view of an image forming apparatus according to an embodiment in a state where a transport unit is separated from a main unit. [Figure 6] 2 is a side view of a transport unit and a positioning member attached to the transport unit of the image forming apparatus according to the embodiment. FIG. [Figure 7] 1 is a front perspective view of a transport unit and a positioning member attached to the transport unit of an image forming apparatus according to an embodiment; [Figure 8] 2 is a rear perspective view of a transport unit and a positioning member attached to the transport unit of the image forming apparatus according to the embodiment; FIG. [Figure 9] FIG. 2 is an enlarged perspective view of the periphery of a side portion of a transport unit of the image forming apparatus according to the embodiment. [Figure 10] 4 is a side view of a positioning member of the image forming apparatus according to the embodiment and a torsion coil spring temporarily fixed thereto. FIG. [Figure 11] 11A and 11B are perspective views for explaining a mounting step of the positioning member according to the embodiment. [Figure 12] 12 is a perspective view of the positioning member shown in FIG. 11 in a state where it has been rotated to one side in the circumferential direction. [Figure 13] 13A to 13C are schematic diagrams for explaining a mounting step of a positioning member according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An image forming apparatus 100 according to one embodiment of the present invention and its modified examples will be described below with reference to Figures 1 to 13. In the following description, a color laser printer capable of executing a print job to print an image on a sheet S is taken as an example, but the present invention is not limited to printers and can also be applied to multifunction machines having functions such as a copy machine.

[0011] In the following description, a direction perpendicular to a flat floor surface on which the image forming apparatus 100 is installed is defined as an up-down direction and is denoted by the symbol D. In addition, of horizontal directions perpendicular to the up-down direction D, one direction is denoted by the symbol D1, and the other direction perpendicular to the direction D1 is denoted by the symbol D2.

[0012] For example, one direction D1 is the width direction (left-right direction) of image forming apparatus 100. In the following description, one direction D1 is referred to as width direction D1. Width direction D1 corresponds to a "predetermined direction." The other direction D2 is the front-rear direction of image forming apparatus 100. In the following description, the other direction D2 is referred to as front-rear direction D2.

[0013] <Overall configuration of image forming apparatus> Image forming apparatus 100 of this embodiment has an external appearance as shown in Figures 1 and 2. Image forming apparatus 100 includes a main body frame (reference numeral omitted). Image forming apparatus 100 also includes a rear cover CV. The main body frame is covered with an exterior cover including the rear cover CV (reference numerals of other covers are omitted). In Figure 2, the rear cover CV is omitted and only a part of the inside of the apparatus is illustrated.

[0014] The main body frame supports the exterior cover. The main body frame supports the rear cover CV rotatably around an axis extending in the width direction D1. For example, the main body frame has a rotation axis RA1 (see FIG. 5) extending in the width direction D1. The rotation axis RA1 supports a lower end of the rear cover CV. The rear cover CV rotates around the rotation axis RA1 as a fulcrum so as to swing an end (i.e., an upper end) opposite to the side supported by the rotation axis RA1. In other words, the rear cover CV is supported so as to be openable and closable relative to the main body frame.

[0015] When the rear cover CV is opened, the inside of the image forming apparatus 100 is exposed to one side (rear side) in the front-rear direction D2. When the rear cover CV is closed, the inside of the image forming apparatus 100 is covered from one side in the front-rear direction D2. For example, when a sheet S jams in the image forming apparatus 100, the rear cover CV is opened to remove the sheet S.

[0016] As shown in Fig. 3, the image forming apparatus 100 includes a main transport path MP. The main transport path MP passes through a transfer nip, which will be described later. In Fig. 3, the main transport path MP is shown typically with a solid arrow. A double-sided printing transport path DP, which will be described later, is shown typically with a dashed arrow.

[0017] The image forming apparatus 100 also includes a sheet cassette CA. The sheet cassette CA stores sheets S to be used in a print job. The type of the sheets S is not particularly limited.

[0018] In a print job, the image forming apparatus 100 supplies a sheet S in a sheet cassette CA to a main transport path MP and transports the sheet S along the main transport path MP. Then, the image forming apparatus 100 prints an image on the sheet S being transported. In other words, the image forming apparatus 100 includes a printing unit 1000 that prints an image on the sheet S being transported.

[0019] The printing unit 1000 includes image forming units 110 for four colors: cyan, magenta, yellow, and black. Each image forming unit 110 forms a toner image of the corresponding color. The configuration of one image forming unit 110 will be described below. The basic configuration of each image forming unit 110 is the same. Therefore, the description of the configuration of the other image forming units 110 will be omitted, as the following description will be used as an example.

[0020] As shown in Fig. 4, the image forming unit 110 includes a developing cartridge 200. The developing cartridge 200 contains toner of a corresponding color and executes a developing process using the toner. The image forming unit 110 also includes a photoconductor drum 111 and a charging device 112. The image forming apparatus 100 also includes one exposure unit 113 for each of the image forming units 110 for four colors. The image forming unit 110 also includes a cleaning device 114.

[0021] When the image forming unit 110 forms an image, the photosensitive drum 111 rotates. The charging device 112 charges the outer peripheral surface of the photosensitive drum 111. The exposure unit 113 exposes the outer peripheral surface of the photosensitive drum 111 to light, and forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum 111. The developing cartridge 200 then supplies toner to the outer peripheral surface of the photosensitive drum 111 as a developing process, and executes a process of developing the electrostatic latent image into a toner image. The toner image on the outer peripheral surface of the photosensitive drum 111 is primarily transferred to an intermediate transfer belt 121, which will be described later. The cleaning device 114 removes toner that has not been transferred to the intermediate transfer belt 121 and remains on the outer peripheral surface of the photosensitive drum 111.

[0022] 3, the printing section 1000 includes a transfer belt unit 120. The printing section 1000 also includes a secondary transfer roller .

[0023] The transfer belt unit 120 is disposed below each image forming unit 110. The transfer belt unit 120 includes an intermediate transfer belt 121. The intermediate transfer belt 121 is an endless belt.

[0024] The intermediate transfer belt 121 is stretched and rotatably supported by multiple rollers including a drive roller 122 (reference numbers for the other rollers are omitted). The intermediate transfer belt 121 contacts the outer circumferential surface of the photoconductor drum 111 and rotates in this state. The drive roller 122 rotates by power transmitted from a belt motor (not shown). The intermediate transfer belt 121 rotates in response to the rotation of the drive roller 122. The intermediate transfer belt 121 corresponds to an "image carrier."

[0025] The transfer belt unit 120 includes primary transfer rollers 123. One primary transfer roller 123 is assigned to each of the colors cyan, magenta, yellow, and black. Each primary transfer roller 123 is disposed on the inner circumferential side of the intermediate transfer belt 121. Each primary transfer roller 123 is disposed opposite a photoconductor drum 111 carrying a toner image of the corresponding color, with the intermediate transfer belt 121 sandwiched therebetween.

[0026] The secondary transfer roller 130 is disposed to face the drive roller 122 with the intermediate transfer belt 121 in between. The secondary transfer roller 130 is in pressure contact with the intermediate transfer belt 121. The secondary transfer roller 130 forms a transfer nip between itself and the intermediate transfer belt 121. The secondary transfer roller 130 corresponds to a "transfer roller."

[0027] Each image forming unit 110 forms a toner image of a corresponding color. Then, each primary transfer roller 123 primarily transfers the toner image onto the outer circumferential surface of the intermediate transfer belt 121. The intermediate transfer belt 121 rotates while carrying the toner image primarily transferred from each photoconductor drum 111 on its outer circumferential surface. While the sheet S is passing through the transfer nip, the sheet S comes into contact with the outer circumferential surface of the intermediate transfer belt 121. The secondary transfer roller 130 forms a transfer electric field between itself and the intermediate transfer belt 121, thereby secondary transferring the toner image onto the sheet S passing through the transfer nip.

[0028] The printing unit 1000 includes a fixing roller pair 140. The fixing roller pair 140 includes a heating roller and a pressure roller. The heating roller has a built-in heater. The pressure roller is in pressure contact with the heating roller to form a fixing nip between the heating roller and the fixing roller pair 140. The fixing roller pair 140 nips the sheet S conveyed from the transfer nip and rotates. That is, the fixing roller pair 140 applies heat and pressure to the sheet S passing through the fixing nip. As a result, the fixing roller pair 140 fixes the toner image transferred to the sheet S to the sheet S. The sheet S is then discharged to the discharge tray ET.

[0029] The image forming apparatus 100 is capable of executing, as a print job, a single-sided print job in which a toner image is printed on only one side of a sheet S, as well as a double-sided print job in which a toner image is printed on both sides of a sheet S. To execute a double-sided print job, the image forming apparatus 100 is provided with a double-sided printing transport path DP.

[0030] The double-sided printing transport path DP branches off from the main transport path MP downstream of the fixing nip in the sheet transport direction, and merges with the main transport path MP upstream of the transfer nip in the sheet transport direction.

[0031] When the job to be executed is a single-sided print job, the sheet S passes through the transfer nip only once, and a single transfer process is performed on the sheet S while it is passing through the transfer nip. After the first transfer process, the sheet S is discharged directly onto the discharge tray ET.

[0032] When the job to be executed is a double-sided printing job, the sheet S passes through the transfer nip twice in order to perform the transfer process once on each of the front and back sides of the sheet S. Specifically, when the sheet S passes through the transfer nip for the first time, the transfer process is performed on one side of the sheet S. After the first transfer process, the sheet S is switched back after the rear end of the sheet S has passed through the fixing nip and before the sheet S is completely discharged onto the discharge tray ET. As a result, the rear end of the sheet S is drawn into the double-sided printing transport path DP.

[0033] Thereafter, the sheet S is transported along the double-sided printing transport path DP. The sheet S is then returned to the main transport path MP from the upstream side of the transfer nip in the sheet transport direction. The sheet S returned to the main transport path MP passes through the transfer nip again. At this time, the orientation of the front and back surfaces of the sheet S is inverted to the opposite orientation from when it passed through the transfer nip the previous time. As a result, when the sheet S passes through the transfer nip for the second time, a transfer process is performed on the other side of the sheet S that is opposite to the one side.

[0034] <Units inside the device> The image forming apparatus 100 includes a plurality of units. Some of the units will be described below.

[0035] As shown in Fig. 5, the image forming apparatus 100 includes a main body unit 1 and a transport unit 2. The main body unit 1 corresponds to a "first unit," and the transport unit 2 corresponds to a "second unit." Fig. 5 illustrates a state in which the rear cover CV is slightly open (a state in which the transport unit 2 is separated from the main body unit 1).

[0036] The main body side unit 1 is a unit that includes a transfer belt unit 120. That is, the main body side unit 1 includes an intermediate transfer belt 121.

[0037] The transport unit 2 is a unit that is mainly responsible for transporting the sheet S. Hereinafter, the transport unit 2 will be described with reference to FIGS.

[0038] The conveying unit 2 has unit side portions 20. The unit side portions 20 are disposed on one side and the other side in the width direction D1. The pair of unit side portions 20 face each other in the width direction D1.

[0039] The transport unit 2 has a transport guide G1 that defines a part of the main transport path MP. The transport guide G1 is located between the pair of unit side portions 20 in the width direction D1. The transport guide G1 defines a part of the main transport path MP together with a transport guide (not shown) of another unit.

[0040] The transport unit 2 also has a transport guide G2 that defines a portion of the double-sided printing transport path DP. The transport guide G2 is located between the pair of unit side parts 20 in the width direction D1. The transport guide G2 defines a portion of the double-sided printing transport path DP together with a transport guide (reference number omitted) provided on the rear cover CV.

[0041] Here, the transport unit 2 has a secondary transfer roller 130. However, the transport unit 2 is a separate unit from the main body side unit 1. In this configuration, the transport unit 2 is positioned relative to the main body side unit 1 in order to form a transfer nip between the intermediate transfer belt 121 and the secondary transfer roller 130.

[0042] The transport unit 2 is rotatable about an axis extending in the width direction D1. For example, the main body frame has a rotation axis RA2 extending in the width direction D1. The rotation axis RA2 supports a lower end of the transport unit 2. The transport unit 2 rotates about the rotation axis RA2 as a fulcrum so as to swing an end opposite to the side supported by the rotation axis RA2 (i.e., the upper end). The transport unit 2 is displaceable between a first position and a second position by rotating about the axis of the rotation axis RA2.

[0043] The first position is a position where the transport unit 2 is positioned relative to the main body side unit 1. The position of the transport unit 2 shown in FIG. 6 is the first position. By holding the transport unit 2 at the first position (i.e., by positioning the transport unit 2 relative to the main body side unit 1), the secondary transfer roller 130 is pressed against the intermediate transfer belt 121. As a result, a transfer nip is formed between the intermediate transfer belt 121 and the secondary transfer roller 130.

[0044] The second position is a position other than the first position, and is a position where the transport unit 2 is not positioned relative to the body side unit 1. When the transport unit 2 is in the second position, it is not possible to position the transport unit 2 relative to the body side unit 1. The position of the transport unit 2 shown in Fig. 5 is the second position.

[0045] When the transport unit 2 is held in the first position, a part of the main transport path MP is formed by the transport guide G1 of the transport unit 2 and the transport guides of the other units. When the transport unit 2 is held in the first position and the rear cover CV is closed, a part of the double-sided printing transport path DP is formed by the transport guide G2 of the transport unit 2 and a transport guide (reference number omitted) of the rear cover CV.

[0046] For example, when a jam occurs during execution of a print job, the rear cover CV is opened and the transport unit 2 is rotated to the second position to clear the jam. By opening the rear cover CV, the double-sided printing transport path DP is exposed, making it possible to remove the jammed sheet S on the double-sided printing transport path DP. By rotating the transport unit 2 to the second position, the main transport path MP is exposed, making it possible to remove the jammed sheet S on the main transport path MP.

[0047] After the jam clearing operation, the rear cover CV is closed. For example, the rear cover CV is rotated in the closing direction, whereby the rear cover CV pushes the transport unit 2. As a result, the transport unit 2 is returned to the first position in synchronization with the closing of the rear cover CV.

[0048] In this configuration, it is necessary to reliably hold the transport unit 2 at the first position during normal times (such as while a print job is being executed). If the transport unit 2 is displaced from the first position while a print job is being executed, the image quality may deteriorate or a jam may occur.

[0049] Therefore, the image forming apparatus 100 includes a positioning member 3. The positioning member 3 positions the transport unit 2 with respect to the main body unit 1. In other words, the positioning member 3 holds the transport unit 2 at a first position. In further other words, the positioning member 3 restricts the rotation of the transport unit 2 from the first position to the second position.

[0050] <Unit positioning> Hereinafter, the structure of the positioning member 3 and the structure for attaching it to the transport unit 2 will be described with reference to FIGS.

[0051] The positioning members 3 are attached to each of a pair of unit side portions 20 of the transport unit 2. The structure of the positioning members 3 and the structure of attaching them to the transport unit 2 are the same on both sides. For this reason, only one of the positioning members will be described below, and the other will be omitted as the following description is incorporated herein by reference.

[0052] The positioning member 3 is disposed outward in the width direction D1 of the unit side part 20. The secondary transfer roller 130 and the like are disposed inward in the width direction D1 of the unit side part 20. Note that the outward direction in the width direction D1 refers to a direction from the center of the width direction D1 of the transport unit 2 toward one side or the other side in the width direction D1. The inward direction in the width direction D1 refers to a direction from one side or the other side in the width direction D1 of the transport unit 2 toward the center in the width direction D1.

[0053] The unit side part 20 has a support shaft 21 that supports the positioning member 3 outward in the width direction D1. The support shaft 21 protrudes outward from the unit side part 20 in a columnar or cylindrical shape. The support shaft 21 has a circular outer shape when viewed in the width direction D1. For example, the unit side part 20 is made of resin. The support shaft 21 is molded integrally with the unit side part 20.

[0054] The positioning member 3 has a cylindrical portion 30. When the positioning member 3 is attached to the unit side portion 20, the width direction D1 corresponds to the cylindrical axis direction of the cylindrical portion 30. The positioning member 3 is attached to the unit side portion 20 by inserting the support shaft 21 into the cylindrical portion 30. The cylindrical portion 30 is fitted into the support shaft 21 from the outside in the width direction D1. In the following description, the circumferential direction centered on the cylindrical axis of the cylindrical portion 30 fitted into the support shaft 21 (i.e., the support shaft 21) as viewed from the width direction D1 will be simply referred to as the circumferential direction.

[0055] The cylindrical portion 30 is slidable in the circumferential direction relative to the outer circumferential surface of the support shaft 21. That is, the support shaft 21 supports the positioning member 3 so as to be displaceable in the circumferential direction. Note that the cylindrical portion 30 is also slidable in the width direction D1 relative to the outer circumferential surface of the support shaft 21.

[0056] The positioning member 3 has a hook portion 31. The hook portion 31 is disposed radially outward of the cylindrical portion 30 as viewed in the width direction D1. The hook portion 31 is a portion that extends radially outward (i.e., in a direction away from the cylindrical portion 30) as viewed in the width direction D1 from the cylindrical portion 30, and is a hook-shaped portion that can engage with a boss portion 10 (described later) from one side in the circumferential direction. The hook portion 31 rotates about the cylinder axis of the cylindrical portion 30 as a result of the cylindrical portion 30 being displaced in the circumferential direction.

[0057] In order to hold the conveying unit 2 at the first position using the positioning member 3, the main body side unit 1 has a boss portion 10 (see Figs. 5 and 6) that protrudes in the width direction D1. When viewed from the width direction D1, the boss portion 10 is disposed on a rotation trajectory of the hook portion 31 when the hook portion 31 is rotated around the cylindrical axis of the cylindrical portion 30 (i.e., when the hook portion 31 is rotated in the circumferential direction).

[0058] When the transport unit 2 is in the first position, the hook portion 31 engages with the boss portion 10 so as to embrace the boss portion 10 from one side in the circumferential direction. This causes the hook portion 31 to restrict the rotation of the transport unit 2 from the first position to the second position. As a result, the transport unit 2 is held in the first position. In other words, the transport unit 2 is positioned relative to the main body side unit 1.

[0059] However, the positioning member 3 is not fixed to the unit side part 20 (i.e., the transport unit 2). That is, the positioning member 3 is detachable from the unit side part 20. In this configuration, unless some measure is taken, the cylindrical part 30 may come off the support shaft 21, causing the positioning member 3 to fall off from the unit side part 20.

[0060] If the positioning member 3 falls off from the unit side portion 20, the hook portion 31 is disengaged from the boss portion 10, causing the transport unit 2 to rotate from the first position to the second position. In other words, the transport unit 2 is displaced relative to the main body side unit 1.

[0061] In order to prevent such inconvenience, the unit side portion 20 has a restricting portion 23. The positioning member 3 also has a restricted portion 32.

[0062] The regulated portion 32 is disposed radially outward from the cylindrical portion 30 and at a different position in the circumferential direction from the hook portion 31, as viewed in the width direction D1. For example, the positioning member 3 has a portion 32a extending radially outward from the cylindrical portion 30, as viewed in the width direction D1, and has a protruding piece protruding from the portion 32a to one side in the circumferential direction as the regulated portion 32. Note that the cylindrical portion 30 is displaceable in the circumferential direction. Therefore, the regulated portion 32 disposed radially outward from the cylindrical portion 30 is rotatable around the cylinder axis of the cylindrical portion 30.

[0063] When viewed from the width direction D1, the restricting portion 23 is disposed at a predetermined position (hereinafter, the predetermined position is referred to as the restricting position) on a rotation trajectory of the restricted portion 32 that rotates around the cylinder axis of the cylindrical portion 30. The restricted portion 32 is disposed at the restricting position by engaging the hook portion 31 with the boss portion 10 from one side in the circumferential direction. As a result, in a state in which the hook portion 31 is engaged with the boss portion 10 from one side in the circumferential direction, the restricting portion 23 overlaps the restricted portion 32 from the outside in the width direction D1.

[0064] In a state in which the restricting portion 23 overlaps the restricted portion 32 from the outside in the width direction D1, even if the restricted portion 32 (i.e., the positioning member 3) tries to move outward in the width direction D1, the restricted portion 32 collides with the restricting portion 23. That is, the restricting portion 23 restricts the outward movement of the positioning member 3 in the width direction D1. As a result, it is possible to prevent the positioning member 3 from falling off the unit side portion 20.

[0065] However, when the positioning member 3 is displaced to the other side in the circumferential direction, the restricting portion 23 and the restricted portion 32 do not overlap in the width direction D1. In this case, the positioning member 3 may fall off the unit side portion 20.

[0066] Therefore, image forming apparatus 100 further includes a torsion coil spring 4. Torsion coil spring 4 is attached to positioning member 3. Torsion coil spring 4 restricts, by its biasing force, displacement of positioning member 3 to the other side in the circumferential direction.

[0067] The torsion coil spring 4 has a wound spring portion 40 (in other words, a coil-shaped portion). The wound spring portion 40 is fitted into the cylindrical portion 30, and thereby disposed on the outer periphery of the cylindrical portion 30. In other words, the cylindrical portion 30 is inserted into the wound spring portion 40. The wound spring portion 40 is fitted into the cylindrical portion 30, and thereby the torsion coil spring 4 is attached to the positioning member 3.

[0068] The torsion coil spring 4 has a first arm 41 extending from one end of the wound spring portion 40 and a second arm 42 extending from the other end of the wound spring portion 40. The first arm 41 and the second arm 42 each extend in a tangential direction of the wound spring portion 40 when viewed from the width direction D1.

[0069] The first arm portion 41 engages with the positioning member 3. Specifically, the positioning member 3 has a first engagement portion 33. The first engagement portion 33 is disposed radially outward of the cylindrical portion 30 when viewed from the width direction D1. The first arm portion 41 engages with the first engagement portion 33.

[0070] The second arm portion 42 engages with the transport unit 2. Specifically, a second engagement portion 22 is provided on the unit side portion 20. An edge portion of an opening 20a penetrating the unit side portion 20 in the width direction D1 functions as the second engagement portion 22. The second arm portion 42 engages with the second engagement portion 22.

[0071] The torsion coil spring 4 generates a force that biases the positioning member 3 to one side in the circumferential direction by engaging the first arm portion 41 with the first engagement portion 33 (i.e., the positioning member 3) and the second arm portion 42 with the second engagement portion 22 (i.e., the unit side portion 20). In other words, the torsion coil spring 4 biases the positioning member 3 in a direction in which the hook portion 31 engages with the boss portion 10 (i.e., to one side in the circumferential direction). In yet other words, the torsion coil spring 4 restricts the displacement of the positioning member 3 to the other side in the circumferential direction.

[0072] In this embodiment, it is possible to prevent the positioning member 3 from being displaced to the other side in the circumferential direction. If the positioning member 3 does not displace to the other side in the circumferential direction, the overlap between the regulating portion 23 and the regulated portion 32 in the width direction D1 is maintained, thereby preventing the positioning member 3 from falling off from the unit side portion 20. This makes it possible to prevent the transport unit 2 from rotating from the first position to the second position. In other words, it is possible to prevent the transport unit 2 from being misaligned with respect to the main body side unit 1.

[0073] In this embodiment, a torsion coil spring 4 is used to suppress rotation of the transport unit 2 from the first position to the second position. By using the torsion coil spring 4, the rotation of the transport unit 2 (i.e., positional deviation of the transport unit 2) can be reliably restricted by the positioning member 3 even if the positioning member 3 is not fixed to the unit side part 20. In other words, even if the positioning member 3 is not fixed to the unit side part 20, it is possible to suppress the positioning member 3 from falling off from the unit side part 20 due to the positioning member 3 being displaced in the circumferential direction. When the positioning member 3 is not fixed to the unit side part 20, disassembly of the positioning member 3 and its surroundings (for example, removal of the positioning member 3 from the unit side part 20) becomes easier.

[0074] In this embodiment, in a configuration in which the rotation (i.e., positional displacement) of the transport unit 2 is restricted by the positioning member 3, it is possible to suppress a decrease in the disassembly ability of the positioning member 3 and its surroundings while suppressing positional displacement of the transport unit 2. When removing the positioning member 3 from the transport unit 2, it is only necessary to release the engagement between the second arm portion 42 of the torsion coil spring 4 and the second engagement portion 22 of the unit side portion 20 and rotate the positioning member 3 to the other side in the circumferential direction.

[0075] <Installation of positioning member> The positioning member 3 has a temporary fastening portion 34. The temporary fastening portion 34 is engageable with the second arm portion 42 of the torsion coil spring 4. The temporary fastening portion 34 is used when attaching the positioning member 3 to the unit side portion 20 (i.e., the transport unit 2).

[0076] Hereinafter, the process of attaching the positioning member 3 to the unit side portion 20 will be described with reference to FIGS.

[0077] First, before the positioning member 3 is attached to the unit side portion 20, the torsion coil spring 4 is attached to the positioning member 3. At this time, the coil spring portion 40 is fitted into the cylindrical portion 30, and the first arm portion 41 is engaged with the first engagement portion 33. Furthermore, the second arm portion 42 is engaged with the temporary fastening portion 34. That is, the torsion coil spring 4 is temporarily fastened to the positioning member 3.

[0078] Next, the cylindrical portion 30 is fitted into the support shaft 21. At this time, the regulated portion 32 is held so as not to overlap with the regulating portion 23 in the width direction D1, and in this state, the fitting of the cylindrical portion 30 into the support shaft 21 is advanced. This results in the state shown in Fig. 11. The engagement of the second arm portion 42 with the temporary fixing portion 34 is maintained until the fitting of the cylindrical portion 30 into the support shaft 21 is completed.

[0079] After the cylindrical portion 30 is fitted onto the support shaft 21, the second arm portion 42 is shifted from the temporary fastening portion 34 to the second engagement portion 22 (i.e., the unit side portion 20). At this time, the worker grasps the second arm portion 42, removes the second arm portion 42 from the temporary fastening portion 34, and engages the second arm portion 42 with the second engagement portion 22.

[0080] When the coil spring portion 40 is fitted into the cylindrical portion 30 and the first arm portion 41 is engaged with the first engagement portion 33, the second arm portion 42 is engaged with the second engagement portion 22, whereby a force that biases the positioning member 3 to one side in the circumferential direction is generated in the torsion coil spring 4. As a result, the positioning member 3 is held in the state shown in Fig. 12, that is, in a state in which the regulated portion 32 and the regulating portion 23 overlap in the width direction D1.

[0081] In this embodiment, the temporary fastening portion 34 is provided on the positioning member 3, thereby improving the workability when attaching the positioning member 3 to the unit side portion 20. Specifically, the coil spring portion 40 is fitted into the cylindrical portion 30, the first arm portion 41 is engaged with the first engagement portion 33, and the second arm portion 42 is engaged with the temporary fastening portion 34, so that the torsion coil spring 4 is held in a state in which it is biased in the torsional direction. This makes it possible to prevent the torsion coil spring 4 from falling off the positioning member 3 during the attachment work of the positioning member 3 to the unit side portion 20 (specifically, before the cylindrical portion 30 is fitted into the support shaft 21). This is convenient for the worker because there is no need to pay attention to the torsion coil spring 4 falling off during the attachment work of the positioning member 3 to the unit side portion 20.

[0082] As a modified example, the following configuration may be used: The modified example will be described below with reference to FIG.

[0083] In the modified example, the transport unit 2 has a guide portion 24. The guide portion 24 is disposed on the inside in the width direction D1 of the unit side portion 20. The guide portion 24 also has an inclined surface 240 that slopes upward from the outside to the inside in the width direction D1.

[0084] The inclined surface 240 is disposed on a moving path of the tip of the second arm 42 (specifically, the tip of the second arm 42 on the opposite side to the connection side with the coil spring 40) when the cylindrical portion 30 is fitted into the support shaft 21. Specifically, when the cylindrical portion 30 is fitted into the support shaft 21 with the second arm 42 engaged with the temporary fastening portion 34, the tip of the second arm 42 reaches the inclined surface 240 of the guide portion 24 disposed on the inside of the width direction D1 of the unit side portion 20 from the outside of the width direction D1 of the unit side portion 20 through the second engagement portion 22 (i.e., the opening 20a penetrating the unit side portion 20 in the width direction D1). In other words, the second arm 42 comes into contact with the inclined surface 240. After that, the second arm 42 moves along the inclined surface 240.

[0085] As the second arm 42 moves along the inclined surface 240, the vertical position of the tip of the second arm 42 is displaced upward. In other words, the second arm 42 is displaced upward from the position where it can engage with the temporary fastening portion 34. This releases the engagement between the second arm 42 and the temporary fastening portion 34. Then, the second arm 42, having come off the temporary fastening portion 34, engages with the second engagement portion 22 (i.e., the edge of the opening 20a of the unit side portion 20).

[0086] In the modified example, by fitting the cylindrical portion 30 onto the support shaft 21, the second arm portion 42 can be switched from the temporary fastening portion 34 to the second engaging portion 22 without the need to perform a separate operation to switch the second arm portion 42 from the temporary fastening portion 34 to the second engaging portion 22. Since there is no need to perform a separate operation to switch the second arm portion 42 from the temporary fastening portion 34 to the second engaging portion 22, convenience for the worker is improved.

[0087] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0088] 1 Main unit (first unit) 2 Transport unit (second unit) 3 Positioning member 10 Boss 20 Unit side 20a opening 21 Support shaft 23 Regulatory Department 24 Guide section 30 Cylindrical section 31 Hook part 32 Regulated part 34 Temporary fastening 40 Coil spring section 41 1st arm 42 Second arm 100 Image forming apparatus (sheet conveying apparatus) 121 Intermediate transfer belt (image carrier) 130 Secondary transfer roller (transfer roller) 240 Slope 1000 printing department S Seat

Claims

1. A first unit having a boss portion; a second unit that is displaceable between a first position that is positioned relative to the first unit and a second position other than the first position by rotating about an axis that extends in a predetermined direction; a positioning member that holds the second unit at the first position, The positioning member is a cylindrical portion having a cylindrical axis aligned in the predetermined direction; a hook portion that is disposed radially outward of the cylindrical portion when viewed from the predetermined direction and engages with the boss portion so as to embrace the boss portion from one side in a circumferential direction about a cylindrical axis of the cylindrical portion; a restricted portion that is disposed radially outward of the cylindrical portion and at a different position in the circumferential direction from the hook portion when viewed from the predetermined direction, The second unit is A side of the unit; a support shaft that protrudes outward in the predetermined direction from a side portion of the unit, into which the cylindrical portion is fitted from the outside in the predetermined direction, and that supports the positioning member so as to be displaceable in the circumferential direction; a restricting portion that is disposed on a rotation trajectory of the restricted portion that rotates about a cylindrical axis of the cylindrical portion when viewed from the predetermined direction, the hook portion engages with the boss portion when the second unit is in the first position to restrict rotation of the second unit from the first position to the second position, the restricting portion overlaps the restricted portion from the outside in the predetermined direction when the hook portion is engaged with the boss portion, thereby restricting outward movement of the positioning member in the predetermined direction, a torsion coil spring including a coil spring portion disposed in the cylindrical portion, a first arm portion extending from one end of the coil spring portion, and a second arm portion extending from the other end of the coil spring portion, A unit positioning mechanism in which the torsion coil spring urges the positioning member in a direction in which the hook portion engages with the boss portion by engaging the first arm portion with the positioning member and the second arm portion with the unit side portion.

2. The unit positioning mechanism according to claim 1 , wherein the positioning member has a temporary fastening portion engageable with the second arm portion.

3. the unit side portion has an edge portion of an opening penetrating in the predetermined direction as an engagement portion with which the second arm portion engages, the second unit is disposed on the inside of the unit side portion in the predetermined direction and has an inclined surface that slopes upward from the outside to the inside in the predetermined direction, 3. The unit positioning mechanism according to claim 2, wherein when the cylindrical portion is fitted onto the support shaft with the second arm portion engaged with the temporary fastening portion, the second arm portion reaches the inclined surface through the opening, and the second arm portion moves along the inclined surface, thereby releasing the engagement between the second arm portion and the temporary fastening portion and engaging with the edge of the opening.

4. A unit positioning mechanism according to any one of claims 1 to 3, the first unit is a unit having an image carrier that carries an image, the second unit is a unit having a transfer roller that is in pressure contact with the image carrier, an image forming apparatus that conveys a sheet to a transfer nip formed between the image carrier and the transfer roller, and transfers the image onto the sheet;

Images