Image forming device

Abstract

To reduce an amount of water vapor flowing into a second conveyance path from a fixing unit.SOLUTION: An image forming apparatus comprises a fixing device 3 having a fixing roller pair 31 that heat a sheet to fix an image and a case 30. The image forming apparatus comprises a conveyance guide G3 that is supported by an exterior cover and forms a re-conveyance path 4b. The image forming apparatus comprises a conveyance guide G2 that is supported by the exterior cover, forms an opening into which the case 30 is inserted and forms a conveyance path 4a and the re-conveyance path 4b, and allows visual recognition of the re-conveyance path 4b through the opening while the exterior cover is at an open position. The image forming apparatus further comprises an elastic plate 50 that partitions a gap da which is formed between the case 30 inserted into the opening and the conveyance guide G2 while the exterior cover is at a closed position.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus including a fixing section that heats a sheet to fix an image thereon, and a transport path that guides an inverted sheet to a transfer section. [Background technology]

[0002] For example, in a laser beam type image forming apparatus such as a printer, a facsimile, or a multifunction machine, a toner image is transferred onto a sheet, and then the image is fixed onto the sheet by applying heat and pressure using a fixing device. For example, when performing double-sided printing, the sheet with the image fixed onto the front side is transported to a reversing roller, the sheet transport direction of the sheet is reversed, and the sheet is transported again to a transfer section via a re-transport path, where an image is formed on the back side. In other words, such an image forming apparatus has a main transport path that discharges the sheet from the transfer section through the fixing device to the outside of the apparatus, and a re-transport path that re-transports the sheet from the reversing roller to the transfer section.

[0003] However, a sheet may get stuck in the main transport path or the re-transport path, which is called a jam. To address this issue, there is a device that supports two guide members on a cover that can be opened and closed relative to the device body, and allows the main transport path and the re-transport path to be opened by opening the cover (see Patent Document 1). Patent Document 1 proposes that the outer guide member in the opening direction has a recess into which a part of the fixing device is inserted when the cover is closed, and an opening hole is formed in the recess, making it possible to visually check whether a sheet is present in the re-transport path when the two guide members are open. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-359441 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, a sheet made of paper or the like contains moisture, and when the sheet is heated by the fixing device, water vapor is released from the sheet, so a lot of water vapor is released inside the fixing device and in the conveying path downstream of the fixing device in the sheet conveying direction. When such water vapor flows into the re-conveying path, condensation is likely to occur, especially since the guide member forming the re-conveying path is close to the outside of the device and has a low temperature. Then, when a sheet is conveyed to the re-conveying path where condensation has occurred, the sheet is likely to jam, or water droplets attached to the sheet may cause transfer failure and generate image unevenness. Therefore, although it is particularly undesirable to let water vapor flow into the re-conveying path, if the device is configured to be able to visually check the presence or absence of a sheet in the re-conveying path with the cover open as in Patent Document 1, there is a problem that water vapor is likely to flow into the re-conveying path because the fixing device and the re-conveying path are connected to each other.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide an image forming apparatus capable of reducing the amount of water vapor that flows into the second transport path from the fixing unit. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a fixing unit including a transfer unit that transfers an image onto a sheet, a pair of fixing rotors that heat the sheet to fix the image transferred by the transfer unit, and a case that contains the pair of fixing rotors; and a fixing device disposed downstream of the fixing unit in a sheet conveying direction. , Sa pair of inverting rotors capable of inverting and transporting a sheet, a first transport path that guides a sheet from the fixing unit to the pair of inverting rotors, a second transport path that guides the sheet inverted by the pair of inverting rotors to the transfer unit, an opening / closing member rotatably supported at a closed position in which it is closed with respect to a main body of the apparatus and at an open position in which the first transport path is opened, a first guide member supported by the opening / closing member and forming one guide surface of the second transport path, a second guide member supported by the opening / closing member and forming an inserted portion into which the case is inserted and forming the other guide surface of the second transport path, forming one guide surface of the first transport path when the opening / closing member is at the closed position, and making the second transport path visible through the inserted portion when the opening / closing member is at the open position, 、 A gap is formed between the case inserted into the insertion portion and the second guide member. From the second conveying path and a partition member for separating the image forming apparatus. Effect of the Invention

[0008] According to the present invention, the gap between the case of the fixing unit and the second guide member can be partitioned by the partition member, and the amount of water vapor flowing from the fixing unit into the second transport path can be reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an entire image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing the fixing device according to the embodiment. [Diagram 3] FIG. 2 is a cross-sectional view showing the fixing device according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the cover unit and the fixing device in the open position according to the embodiment. [Diagram 5] FIG. 4 is a cross-sectional view showing the cover unit and the fixing device in the closed position according to the embodiment. [Figure 6] 2 is a schematic cross-sectional view showing the fixing device and each conveying guide according to the embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings. The image forming apparatus includes a printer, a copier, a facsimile, and a multifunction machine, and forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from an original. The sheets used as recording media include paper such as plain paper and cardboard, plastic films such as sheets for overhead projectors, sheets of special shapes such as envelopes and index paper, and cloth.

[0011] <Configuration of Image Forming Apparatus> 1 is a schematic cross-sectional view showing the entire image forming apparatus 1 according to the present embodiment. The image forming apparatus 1, which is a full-color laser printer, is configured to include an image forming section 150, a sheet feeding section 2, a fixing device 3 which is a fixing section, a toner storage section T (TY, TM, TC, TK), and a reversing and discharging section 4 inside a device main body 1A. The image forming apparatus 1 is also configured to include a sheet stacking section 5 on the upper surface of the device main body 1A. Note that a document reading device may be disposed on the upper part of the device main body 1A to configure it as a multifunction machine.

[0012] The image forming apparatus 1 is equipped with an electrophotographic image forming section 150. The image forming section 150 forms toner images of four colors, yellow (Y), magenta (M), cyan (C) and black (Bk). That is, the image forming section 150 is a so-called intermediate transfer tandem type electrophotographic unit in which four photosensitive drums 11 (11Y, 11M, 11C, 11K) are arranged along an intermediate transfer belt 13a of an intermediate transfer unit 13. The toner storage sections T (TY, TM, TC, TK) store toners of yellow (Y), magenta (M), cyan (C) and black (K), respectively.

[0013] The image forming section 150 includes photosensitive drums 11 (11Y, 11M, 11C, 11K) as photosensitive members, an intermediate transfer unit 13, primary transfer rollers 14 (14Y, 14M, 14C, 14K), and a secondary transfer roller 24 as a transfer section. Around each of the photosensitive drums 11 (11Y, 11M, 11C, 11K), a developing unit 10 (10Y, 10M, 10C, 10K) that develops a toner image is disposed.

[0014] Each photosensitive drum 11 is configured to be irradiated with laser light from an exposure device 12 provided below it. When the image formation process is started, the photosensitive drum 11, the surface of which has been uniformly charged in advance by a charger (not shown), is irradiated with laser light from the exposure device 12 to expose the photosensitive drum 11. At this time, the exposure device 12 receives a signal (video signal) corresponding to the image data to be printed, and irradiates the photosensitive drum 11 with laser light modulated in accordance with the video signal via a scanning optical system including a polygon mirror. As a result, an electrostatic latent image corresponding to the image data is formed on the drum surface.

[0015] A developing unit (not shown) supplies toner to the electrostatic latent image formed on the photosensitive drum 11 to visualize (develop) the latent image into a toner image. Thereafter, a primary transfer roller 14 (not shown) applies a predetermined pressure force and an electrostatic load bias, thereby performing primary transfer of the toner image from the photosensitive drum 11 to the intermediate transfer belt 13a. Residual toner remaining on the photosensitive drum 11 after primary transfer is collected by a cleaning device (not shown), and the drum surface of the photosensitive drum 110 is cleaned.

[0016] The above-mentioned toner image forming operation is performed in parallel on each photosensitive drum 11. In addition, primary transfer is performed by the primary transfer roller 14 on the rotating intermediate transfer belt 13a so that the toner image formed on the upstream photosensitive drum 11 is superimposed on the toner image formed on the downstream photosensitive drum 11. As a result, a full-color toner image is finally formed on the intermediate transfer belt 13a, and is carried by the intermediate transfer belt 13a and conveyed to the secondary transfer roller 24 for transfer. The secondary transfer roller 24 transfers the toner image from the intermediate transfer belt 13a to the sheet S while nipping and conveying the sheet S. Note that the residual toner remaining on the intermediate transfer belt 13a after the secondary transfer is collected by a cleaning device 15, and the surface of the intermediate transfer belt 13a is cleaned.

[0017] Thereafter, the sheet S is conveyed to a fixing device 3 as a fixing section that applies heat and pressure to the toner image to fix it. The fixing device 3 has a pair of fixing rollers 31 as a pair of fixing rotors. The pair of fixing rollers 31 is composed of a fixing film 31a as a heating rotor with a built-in heater (not shown), and a pressure roller 31b that applies pressure to the fixing film 31a (see FIG. 3). The fixing film 31a and the pressure roller 31b apply heat and pressure to the toner image while sandwiching and conveying the sheet S. This melts the toner, which then solidifies and adheres to the sheet S, thereby fixing the image on the sheet S.

[0018] Meanwhile, a sheet S used as a recording medium is supplied to the image forming unit 150 by a sheet feeding unit 2. The sheet feeding unit 2 includes a cassette 21 having a lift-up device that moves up and down with the sheets S stacked thereon, and the sheets S are sent out one by one from the cassette 21. The sheet S fed from the cassette 21 is conveyed to a registration roller pair 23 via a conveying path 2a. The registration roller pair 23 corrects skew of the sheet S, and conveys the sheet S to a secondary transfer roller 24 via a conveying path 2b at a timing determined in accordance with the formation of a toner image by the image forming unit 150.

[0019] The sheet S on which the toner image is transferred by the secondary transfer roller 24 is conveyed to the fixing device 3 via the conveying path 2c. The sheet S on which the fixed image is fixed by the fixing device 3 is conveyed by the fixing discharge roller pair 42, which is a conveying rotary body pair, through the conveying path 3a, and the sheet S is guided to the conveying path 4a toward the reverse discharge roller pair 45, which is a reverse rotary body pair. The sheet S that has reached the reverse discharge roller pair 45 is directly discharged to the sheet stacking unit 5 by the reverse discharge roller pair 45, or, in the case of double-sided printing, the sheet conveying direction is reversed by the reverse operation of the reverse discharge roller pair 45 and conveyed. In the case of double-sided printing, the reversed sheet S is guided to the re-conveying path 4b by the switching flap FL (see FIG. 6). The sheet S guided to the re-conveying path 4b is reversed and conveyed to the double-sided joining conveying path 4c by the double-sided conveying roller pairs 46 and 47, and re-conveyed to the registration roller pair 23. The sheet S that has reached the pair of registration rollers 23 has an image formed on its second side in a process similar to that for the first side on which the image has already been formed, and then is discharged to the sheet stacking unit 5.

[0020] [Configuration of the fixing device] Next, the configuration of the fixing device 3 will be described with reference to Figures 2 and 3. As shown in Figures 2 and 3, the fixing device 3 has a case 30 as a housing, and the internal space of the case 30 contains the fixing roller pair 31 consisting of the fixing film 31a and the pressure roller 31b. The fixing film 31a and the pressure roller 31b are in contact with each other over a width greater than the width of the sheet conveying path in the width direction perpendicular to the sheet conveying direction. In other words, the fixing roller pair 31 is configured to be in contact with each other over the entire width, which is greater than the width of the maximum size sheet that can be conveyed by the image forming apparatus 1. Therefore, the nip formed by the contact between the fixing film 31a and the pressure roller 31b blocks the air flow in the sheet conveying direction.

[0021] When the sheet S is conveyed by the pair of fixing rollers 31, heat is applied to the sheet S by being sandwiched between the fixing film 31a and the pressure roller 31b. Generally, the sheet S, such as paper, used in the image forming apparatus 1 often stores moisture by absorbing moisture in the air. In particular, the amount of moisture stored in the sheet S tends to increase when the sheet S is used in a high-humidity environment. For this reason, when heat is applied to the sheet S, the moisture stored in the sheet S evaporates and remains in the internal space of the case 30, and water droplets may adhere to the inner surface of the case 30 due to continuous contact of the steam. If the amount of water droplets exceeds a certain amount, the water droplets may drip or leak out of the case 30, which may induce problems such as a breakdown in the electrical system of the image forming apparatus 1 or poor image quality.

[0022] In order to prevent such a problem, in the case 30 of the fixing device 3 in this embodiment, a plurality of through holes 30a penetrating the internal space of the case 30 and the outside are formed in parallel in the width direction so that air does not stagnate in the internal space of the case 30, as shown in FIG. 2. That is, these through holes 30a have end through holes 30ab arranged at both ends in the width direction, and a plurality of intermediate through holes 30aa arranged between the end through holes 30ab in the width direction. In general, when a toner image is fixed on a sheet S by a fixing roller pair 31, moisture inside the sheet S is moved to the pressure roller 31b side by a heater inside the fixing film 31a as shown in FIG. 3 and is released as water vapor. The water vapor is generated on the pressure roller 31b side and moves upward, so the plurality of through holes 30a are arranged above the pressure roller 31b in the case 30.

[0023] [Configuration of the transport path, transport guides, and exterior cover unit] Next, the sheet transport path, the layout of each transport guide, and the configuration of the exterior cover unit in the image forming apparatus 1 according to the present embodiment will be described with reference to FIGS.

[0024] 6, a conveying path 3a as a third conveying path, a pair of fixing discharge rollers 42 as a conveying rotator pair, a conveying path 4a as a first conveying path, and a pair of reversing discharge rollers 45 as a reversing rotator pair are arranged downstream in the sheet conveying direction from the fixing device 3. In addition, a re-conveying path 4b as a second conveying path is arranged from the pair of reversing discharge rollers 45 to the secondary transfer roller 24.

[0025] The fixing discharge roller pair 42 includes a driving roller 42a and a driven roller 42b. The driving roller 42a and the driven roller 42b are each formed of, for example, a rubber cylinder, and are arranged so that both ends are located outside both ends of the conveying path 182 in the width direction. That is, the driving roller 42a and the driven roller 42b are in contact with each other over a width larger than the width of the sheet conveying path in the width direction perpendicular to the sheet conveying direction. That is, these rollers are also configured to be in contact with each other over a full width that is larger than the width of the maximum size sheet that can be conveyed by the image forming apparatus 1. Therefore, the nip formed by the contact between the driving roller 42a and the driven roller 42b blocks the air flow in the sheet conveying direction.

[0026] As shown in FIGS. 4 to 6, between the transport path 3a and the transport path 4a and the re-transport path 4b, 2 Conveying guides G1 and G2 are arranged as guide members. The lower guide member, conveying guide G1, is arranged below the fixing device 3 so as to have a clearance. The upper guide member, conveying guide G2, is arranged above the fixing device 3 so as to have a gap da as a clearance between them. Meanwhile, at a position facing the conveying guides G1 and G2 across the re-conveying path 4b and inside the exterior cover 49 which is an opening / closing member, a first 1A transport guide G3 is disposed as a guide member. These transport guides G1, G2, and G3 are supported by an exterior cover 49 as an opening / closing member, and constitute an exterior cover unit 60. The exterior cover unit 60 is configured to be rotatable relative to the exterior case 1C of the apparatus main body 1A by a support shaft 48 that rotatably supports the exterior cover 49, that is, the exterior cover 49 is configured to be openable and closable relative to the exterior case 1C of the apparatus main body 1A.

[0027] 6, a conveying guide G4 is disposed on the sheet stacking unit 5 side of the conveying guide G2 in the horizontal direction across the conveying paths 3a and 4a. Furthermore, a conveying guide G5 is disposed on the sheet stacking unit 5 side of the conveying guide G3 in the horizontal direction above the conveying guide G4 across the conveying path 4a.

[0028] As shown in FIG. 5, the guide surface G1a, which is the surface on the sheet stacking unit 5 side at one side of the conveying guide G1, forms one guide surface of the conveying path 2b (see FIG. 1) on the upstream side of the fixing device 3 in the sheet conveying direction. Also, as shown in FIG. 6, the guide surface G2a, which is the surface on the sheet stacking unit 5 side at one side of the conveying guide G2, forms one guide surface of the conveying path 3a on the downstream side of the fixing device 3 in the sheet conveying direction and on the upstream side of the fixing discharge roller pair 42 in the sheet conveying direction. Furthermore, the guide surface G2a forms one guide surface of the conveying path 4a on the downstream side of the fixing discharge roller pair 42 in the sheet conveying direction. And the guide surface G4a, which is the surface from the upper side of the conveying guide G4 to the exterior cover 49 side, forms one guide surface of the conveying path 3a and the conveying path 4a. Also, the guide surface G5a, which is the surface on the lower side of the conveying guide G5, forms the other guide surface of the conveying path 4a.

[0029] Furthermore, a guide surface G3a, which is a surface on one side of the conveying guide G3 from the lower side to the sheet stacking unit 5 side, forms one guide surface of the re-conveying path 4b. A guide surface G2b, which is a surface on the other side of the conveying guide G2 facing the exterior cover 49, forms the other guide surface of the re-conveying path 4b. Furthermore, as shown in FIG. 5, a guide surface G1b, which is a surface on the other side of the conveying guide G1 facing the exterior cover 49, forms the other guide surface of the re-conveying path 4b. Note that the guide surfaces forming each of the conveying paths of the conveying guides G1 to G5 described above are not necessarily formed in a surface shape without irregularities, but refer to a surface that the sheet S comes into contact with and is guided by, such as a surface connecting the apexes of a plurality of ribs.

[0030] [Layout of the fixing device and the exterior cover unit] Next, a description will be given of the positional relationship between the fixing device 3 and the exterior cover unit 60, and the formation of the re-conveying path 4b by a part of the case 30 of the fixing device 3. As described above, the exterior cover unit 60 is configured to be freely opened and closed with respect to the exterior case 1C of the apparatus main body 1A. As shown in Fig. 4, the exterior cover unit 60 rotates between an open position where it opens with respect to the exterior case 1C to open the conveying paths 2a and 3a, and a closed position where it is closed with respect to the exterior case 1C, as shown in Fig. 5.

[0031] As shown in Fig. 4, in the exterior cover unit 60, a transport guide G3 is disposed on the inside of the opening and closing direction of the exterior cover 49 (closing direction), and transport guides G1 and G2 are disposed inside the transport guide G3 with a gap therebetween in the vertical direction. For this reason, an opening H, which is concave in cross-sectional view in Fig. 4 and opens to the re-conveying path 4b, is formed between the transport guide G1 and the transport guide G2 as an insertion portion into which a part of the fixing device 3 is inserted. By opening the exterior cover unit 60 to the open position, the re-conveying path 4b is exposed through this opening H, and when a jam occurs in the re-conveying path 4b and a sheet S is present, the sheet S can be visually confirmed and removed.

[0032] Then, as shown in FIG. 5, when the exterior cover unit 60 is closed to the closed position, a part of the fixing device 3 fixed and supported by the apparatus main body 1A is inserted into the opening H. As a result, the side of the fixing device 3 on the exterior cover 49 side, which is a part of the case 30, forms a part of the re-conveying path 4b. When the exterior cover unit 60 is opened and closed in this manner, the fixing device 3 is inserted and removed from the opening H, so that in the closed position, gaps are required as clearances between the fixing device 3 and the conveying guide G1 and between the fixing device 3 and the conveying guide G2. However, the gap da (see FIG. 6) between the fixing device 3 and the conveying guide G2 communicates with the re-conveying path 4b as it is, so that water vapor discharged from the through hole 30a of the fixing device 3 may enter the re-conveying path 4b and cause condensation. Therefore, in this embodiment, the following configuration is used.

[0033] [Configuration of partition members] Next, the configuration of the partition member according to this embodiment will be described with reference to FIG. 6. As described above, a gap da is formed between the fixing device 3 and the conveying guide G2. An elastic plate 50 is attached to the lower portion of the conveying guide G2 on the re-conveying path 4b side as a partition member or plate-like member that separates the gap da from the re-conveying path 4b. Note that this elastic plate 50 does not need to be positioned strictly at the boundary between the gap da and the re-conveying path 4b, and it is preferable that the elastic plate 50 is located within the gap da so as not to obstruct the conveyance of the sheet S in the re-conveying path 4b.

[0034] The elastic plate 50 is made of an elastic member such as rubber, and is disposed so that its upper end abuts against the transport guide G2 and its lower end abuts against the case 30 of the fixing device 3 in the closed position. As described above, the fixing device 3 has a plurality of through holes 30a arranged in parallel in the width direction, and the elastic plate 50 is disposed on the re-transport path 4b side of the through holes 30a. The elastic plate 50 is formed wide so that it is disposed outward in the width direction from the end through holes ab (see FIG. 2) of the through holes 30a. That is, the elastic plate 50 covers and closes substantially the entire width of the gap da, and separates the gap da from the re-transport path 4b to block the air flow.

[0035] As described above, in this embodiment, the elastic plate 50 is an elastic sheet member. This allows the elastic plate 50 to be strongly pressed against the case 30 of the fixing device 3 when it is brought into contact with the case 30 of the fixing device 3. In other words, if a member having no elasticity is used instead of the elastic plate 50, there is a risk that the case 30 of the fixing device 3 may be damaged if it is brought into strong contact, but in this embodiment, there is no such risk.

[0036] In this embodiment, the elastic plate 50 is attached so as to be supported by the conveying guide G2, but may be attached to the case 30 of the fixing device 3. The partition member may be supported by the conveying guide G2 or the fixing device 3 so as to be movable in the rotation direction. In this case, the partition member may be made of an elastic member or a non-elastic member. When a non-elastic member is used as the partition member, it is possible to rotatably support the partition member on one side of the conveying guide G2 or the fixing device 3, and to press the partition member against the other side of the conveying guide G2 or the fixing device 3 by biasing the partition member in the rotation direction with a spring or the like. In this way, by closely contacting the partition member, the flow of air from the gap da to the re-conveying path 4b can be suppressed.

[0037] [Air flow in image forming equipment] Next, the air flow in the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. 6. As shown in FIG. 6, below the transport guide G2, an opening D1 is formed, which faces the case 30 of the fixing device 3 and communicates with the gap da. Furthermore, above the opening D1 of the transport guide G2, an opening D2 is formed, which faces the transport guide G3 and communicates with the re-transport path 4b. The inside of the transport guide G2 is formed to have a ventilation section GW2 that communicates from the opening D1 to the opening D2 to ventilate.

[0038] An opening E1 is formed below the transport guide G3, facing the opening D2 of the transport guide G2 and communicating with the re-transport path 4b. An opening E2 and an opening E3 are formed in the upper part of the transport guide G3, and the inside of the transport guide G3 is formed to have a ventilation section GW3 that ventilates the opening E1 through the openings E2 and E3.

[0039] In the image forming apparatus 1 according to the present embodiment configured as described above, when a toner image is fixed to a sheet S by the fixing device 3, a large amount of water vapor is released from the sheet S into the inside of the case 30 of the fixing device 3 and into the conveying path 3a. Since the fixing roller pair 31 is a so-called through roller that is in close contact with the sheet S over its entire width, air containing water vapor does not almost reach the upstream side of the fixing roller pair 31 in the sheet conveying direction. In addition, since the fixing discharge roller pair 42 is also a so-called through roller that is in close contact with the sheet S over its entire width, air containing water vapor does not almost reach the conveying path 4a downstream in the sheet conveying direction from the conveying path 3a.

[0040] Air containing water vapor flows from inside the case 30 of the fixing device 3 through the through hole 30a into the gap da, and also flows from the transport path 3a into the gap da. The air containing water vapor that has flowed into the gap da is blocked by the elastic plate 50 and flows from the opening D1 into the transport guide G1. Most of the air containing water vapor that has flowed into the transport guide G1 passes through the opening D2 and the opening E1, flows into the transport guide G3, and is released to the outside of the image forming apparatus 1 through the openings E2 and E3.

[0041] As described above, in the image forming apparatus 1 according to the present embodiment, the gap da formed between the case 30 of the fixing device 3 inserted into the opening H with the exterior cover 49 in the closed position and the transport guide G2 can be partitioned by the elastic plate 50. This prevents air from entering the re-transport path 4b from the fixing device 3, and reduces the amount of water vapor that flows in. It is obvious that the elastic plate 50 is most effective when it is completely in contact with the case 30 of the fixing device 3 and the transport guide G2, but a small gap may be allowed within an effective range. This is because the amount of water vapor that flows into a larger space is greater than the amount that passes through a small gap.

[0042] Furthermore, in the image forming apparatus 1 according to the present embodiment, the case 30 of the fixing device 3 is inserted into the opening H with the exterior cover 49 in the closed position, thereby forming a part of the guide surface of the re-conveying path 4b. As a result, when the sheet S jams in the re-conveying path 4b, not only can the re-conveying path be visually recognized from the opening hole as in, for example, JP-A-2004-359441, but also the sheet S can be removed simply by setting the exterior cover 49 to the open position.

[0043] Furthermore, in this embodiment, the elastic plate 50 is arranged with a width longer than the width of the multiple through holes 30a arranged in parallel in the width direction of the fixing device 3, so that most of the water vapor discharged from those through holes 30a can be blocked from reaching the re-transport path 4b.

[0044] In this embodiment, the opening D1 of the transport guide G2 opens to the gap da, and the air blocked from the re-transport path 4b by the elastic plate 50 is ventilated to the transport guide G3 via the ventilation section GW2 and discharged to the outside of the device. This reduces the amount of water vapor that flows into the re-transport path 4b.

[0045] [Possibility of other embodiments] In the above-described embodiment, each of the transport guides G1 to G5 is constituted by a single transport guide, but the transport guide member may be divided into a plurality of transport guides.

[0046] In the present embodiment, the rollers for discharging the sheet are only the pair of reverse discharge rollers 45. However, it is also possible to have another pair of discharge rollers, that is, to discharge the sheet from two positions, or to have a plurality of discharge rollers, to discharge the sheet from three or more positions. In these cases, the structure of the conveying path downstream of the pair of fixing discharge rollers 42 in the sheet conveying direction is different, and therefore the number and arrangement of the conveying guides will change accordingly.

[0047] In the present embodiment, the air flows from inside the fixing device 3, but this means that the air is sucked in from any gap in the case 30 of the fixing device 3. In addition, the air may not simply rise due to heat, but may be actively sucked in or blown out. In this case, for example, it may be possible to provide a blower fan that blows air toward the transport path 3a, or a suction fan that sucks in and exhausts the air inside the transport guide G3 to the outside of the device.

[0048] In the present embodiment, the fixing device 3 has a plurality of through holes 30a arranged in parallel in the width direction, but the present invention is not limited to this, and may have, for example, a single slit-shaped through hole or a plurality of through holes arranged in a staggered pattern. Furthermore, the openings D1, D2, E1, E2, and E3 may be formed by a single opening or may have a plurality of openings arranged in parallel in a slit shape, that is, may have any shape. [Explanation of symbols]

[0049] 1...image forming apparatus / 1A...apparatus main body / 3...fixing device (fixing section) / 3a...conveying path (third conveying path) / 4a...conveying path (first conveying path) / 4b...re-conveying path (second conveying path) / 24...secondary transfer roller (transfer section) / 30...case / 30a...through hole / 31...pair of fixing rollers (pair of fixing rotors) / 42...pair of fixing discharge rollers (pair of conveying rotors) / 45...pair of reversing discharge rollers (pair of reversing rotors) / 49...outer cover (opening / closing member) / 50...elastic plate (partition member, plate-shaped member) / D1...opening / G1...conveying guide (second 2 Guide member, lower guide) / G2...Transport guide (first 2 Guide material, upper guide) / GW2...Ventilation section / G3...Transport guide (third 1 Guide member) / H…Opening (inserted part) / S…Sheet / da…Gap

Claims

1. A transfer unit that transfers an image onto a sheet; a fixing unit including a pair of fixing rotors that heats a sheet to fix an image transferred by the transfer unit, and a case that contains the pair of fixing rotors; a pair of reversing rotors arranged downstream of the fixing unit in a sheet conveying direction and capable of reversing and conveying a sheet; a first conveying path that guides a sheet from the fixing unit to the pair of reversing rotors; a second conveying path that guides the sheet inverted by the pair of inverting rotors to the transfer unit; an opening / closing member rotatably supported at a closed position where the opening / closing member is closed relative to a main body of the apparatus and at an open position where the opening / closing member opens the first transport path; a first guide member supported by the opening / closing member and forming one guide surface of the second transport path; a second guide member supported by the opening / closing member, forming an inserted portion into which the case is inserted and forming the other guide surface of the second transport path, forming one guide surface of the first transport path when the opening / closing member is in the closed position, and making the second transport path visible via the inserted portion when the opening / closing member is in the open position; a partition member that separates a gap formed between the case inserted into the insertion portion and the second guide member from the second transport path when the opening / closing member is in the closed position, 1. An image forming apparatus comprising:

2. the case forms a part of the other guide surface of the second transport path by being inserted into the insertion portion when the opening / closing member is in the closed position.

2. The image forming apparatus according to claim 1,

3. a third conveying path that guides the sheet from the transfer unit to the fixing unit; the second guide member has an upper guide that forms one guide surface of the first transport path when the opening / closing member is in the closed position, and a lower guide that is disposed below the upper guide and forms one guide surface of the third transport path when the opening / closing member is in the closed position, and the inserted portion is formed between the upper guide and the lower guide.

3. The image forming apparatus according to claim 2,

4. the case has a through hole passing through the case so as to communicate an internal space of the case with the gap when the opening / closing member is in the closed position, the partition member partitions the gap between the through hole in the gap and the second transport path; 4. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises a first fixing unit.

5. The through hole is a first through hole, the case has a second through hole penetrating the case so as to communicate an internal space of the case with the gap when the opening / closing member is in the closed position, the first through hole and the second through hole are arranged such that a longitudinal direction of the first through hole is aligned with the sheet conveying direction, and are arranged in parallel with each other in a width direction perpendicular to the sheet conveying direction, The partition member has a width greater than a width in the width direction in which the first through hole and the second through hole are arranged side by side.

5. The image forming apparatus according to claim 4.

6. The through hole is provided above the pair of fixing rotors.

6. The image forming apparatus according to claim 4, wherein the image forming apparatus is a multi-color image forming apparatus.

7. the partition member is supported by one of the case and the second guide member, and is in contact with the other of the case and the second guide member when the opening / closing member is in the closed position.

6. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:

8. The partition member is a plate-like member having elasticity.

8. The image forming apparatus according to claim 7,

9. The partition member is movably supported on one of the case and the second guide member.

9. The image forming apparatus according to claim 7, wherein the image forming apparatus is a multi-color image forming apparatus.

10. A biasing member is provided which biases the partition member toward the other of the case and the second guide member when the opening / closing member is in the closed position.

10. The image forming apparatus according to claim 9,

11. The partition member is provided at the boundary between the gap and the second conveying path.

7. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: a first fixing member;

12. The second guide member has a first opening that opens into the gap, and a first ventilation section that communicates with the first opening and ventilates air flowing from the gap to the outside of the second guide member.

12. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:

13. The second guide member has a second opening that opens into the second conveying path and communicates with the first ventilation section, the first guide member has a third opening facing the second opening and opening into the second transport path, a second ventilation section communicating with the third opening, and a fourth opening communicating with the second ventilation section to ventilate air flowing through the second ventilation section toward the outside of the first guide member.

13. The image forming apparatus according to claim 12.

14. A pair of conveying rotors is disposed on the first conveying path and capable of conveying a sheet toward the pair of inverting rotors, and is in contact over the entire width in a width direction perpendicular to the sheet conveying direction when the sheet is not being conveyed.

14. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:

Images