Image forming device

Abstract

To provide an image forming apparatus that can suppress vapor generated by heating a sheet in a fixing device from being exhausted as stream from a paper ejection port.SOLUTION: An image forming apparatus comprises: a guide member 30 that has a guide surface guiding a sheet ejected from a fixing device 5 to an ejection rotating body 17; an opposite member 21 that is provided opposite to a surface of the guide member 30 on an opposite side of the guide surface and forms, with the opposite side surface, an air passage A communicating at one end with an outer space on an outside of a paper ejection port and communicating at the other end with a predetermined space B on the fixing device 5 side in an image forming apparatus main body 2; and an interception part 24 that is located on a downstream side in a sheet conveyance direction of the ejection rotating body 17 and intercepts air exhausted together with a sheet from the ejection rotating body 17 and guides the air to one end side of the air passage A.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] In general, an electrophotographic image forming apparatus has a fixing device for fixing a toner image transferred onto a sheet of paper to the sheet of paper. The fixing device includes a heating roller having a heat source such as a heater, and a pressure roller that rotates while being pressed against the heating roller. When the sheet of paper onto which the toner image has been transferred passes through a nip between the heating roller and the pressure roller, the toner image is heated and pressurized to be fixed onto the sheet of paper.

[0003] In this type of image forming device, the fixing device is operated when performing the image forming operation. As a result, the moisture contained in the paper is heated by the heating roller and evaporates, generating water vapor inside the device. Some of this water vapor is cooled by the surrounding air and turns into a fine mist (steam). If this steam sprays out from the paper outlet, it is undesirable because the user may mistake it for smoke.

[0004] In view of this, a configuration has been proposed for discharging water vapor generated within the device to the outside without passing through the paper discharge port.

[0005] In the image forming apparatus described in Patent Document 1, a guide member for guiding paper, which is provided downstream of the fixing device in the paper transport direction, has multiple holes formed therein. In addition, in this image forming apparatus, a suction fan is provided within the apparatus, and an exhaust port for discharging air is separately formed. In this image forming apparatus, the suction fan is driven during image formation. Then, an air flow is generated within the image forming apparatus, in which the air inside is discharged from the exhaust port. As a result, water vapor generated from the paper passes through the holes in the guide member, is carried by the air flow generated within the apparatus, and is discharged from the exhaust port. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-206611 A Summary of the Invention [Problem to be solved by the invention]

[0007] Recently, there is a demand for image forming apparatuses with lower costs. As a result, there is a demand for image forming apparatuses that are not provided with fans. In the image forming apparatus of Patent Document 1, if a suction fan is not provided, the water vapor generated from the paper will pass through the holes in the guide member and accumulate inside the apparatus. If the image forming operation is continued, a lot of water vapor will accumulate inside the apparatus, and as a result, the water vapor will overflow and be discharged from the paper discharge port. Some of the water vapor will turn into steam, which a user may mistake for smoke.

[0008] The present invention has been made in consideration of the above points, and its purpose is to provide an image forming device that can prevent steam generated when paper is heated in the fixing device from being discharged as vapor from the paper outlet. [Means for solving the problem]

[0009] The image forming apparatus of the present invention comprises a fixing device that is housed within the image forming apparatus main body and has a heating rotor and a pressure rotor, and fixes a toner image to the paper by passing the paper through a nip portion formed between the two rotors, a discharge rotor that discharges the paper after fixing processing by the fixing device from a paper discharge outlet formed in the image forming apparatus main body to the external space on the top surface of the image forming apparatus main body, and a guide member having a guide surface that guides the paper discharged from the fixing device to the discharge rotor.

[0010] The guide member is provided with an opposing member that is disposed opposite the guide surface side of the guide member and that forms an air passage between the opposing surface and the opposing surface, the air passage having one end that communicates with the external space and the other end that communicates with a predetermined space on the fixing device side within the image forming device main body, and a dam portion that is located downstream of the discharge rotor in the paper transport direction and that blocks the air discharged together with the paper by the discharge rotor and guides it to the one end of the air passage. Effect of the Invention

[0011] According to the present invention, it is possible to prevent steam generated when the paper is heated in the fixing device from being discharged as steam from the paper discharge port. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing the appearance of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the internal configuration of the image forming apparatus. [Diagram 3] FIG. 3 is an enlarged cross-sectional view showing a portion extending from the fixing device to the pair of discharge rollers. [Figure 4] FIG. 4 is a perspective view showing the fixing device. [Diagram 5] FIG. 5 is a perspective view showing the upper exterior cover as viewed from the back side. [Figure 6] FIG. 6 is a perspective view showing the ejection guide as viewed from the front side. [Figure 7] FIG. 7 is a perspective view showing the ejection guide as viewed from the back side. [Figure 8] FIG. 8 is a perspective view showing the upper exterior cover to which the ejection guide is attached, as viewed from the back side. [Figure 9] FIG. 9 is a view corresponding to FIG. 3 and showing the first modified example. [Figure 10] FIG. 10 is a view equivalent to FIG. 3 and showing a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment.

[0014] <<Embodiment>>

[0015] [Image forming equipment] Fig. 1 is a perspective view showing the external appearance of image forming apparatus 1. Fig. 2 is a schematic diagram showing the internal configuration of image forming apparatus 1. In the following description, the front side and the rear side refer to the front side and the rear side of image forming apparatus 1 (the near side and the far side perpendicular to the paper surface of Fig. 2), and the left side and the right side refer to the left side and the right side when image forming apparatus 1 is viewed from the front side.

[0016] The image forming device 1 is, for example, a monochrome laser printer. The image forming device 1 includes an image forming device main body 2, a paper feed section 3, an image forming section 4, a fixing device 5, and a paper discharge tray 6. The image forming device main body 2 incorporates various devices necessary for operating the image forming device 1, such as an operation panel and a control board. Each side of the image forming device main body 2 is covered with a resin exterior cover. FIG. 1 shows an upper exterior cover 21 and a left exterior cover 22. The upper exterior cover 21 is formed with the paper discharge tray 6, and the left exterior cover 22 is formed with an exhaust port 28, which will be described later.

[0017] The image forming apparatus 1 is configured to form an image on a sheet based on image data transmitted from a terminal (not shown) while transporting the sheet along a sheet transport path C in the image forming apparatus main body 2.

[0018] The paper feed unit 3 is provided at the bottom of the image forming apparatus main body 2. The paper feed unit 3 includes a paper feed cassette 7 that stores multiple sheets of paper stacked on top of each other, and a pick roller 8 that picks up the sheets of paper in the paper feed cassette 7 one by one.

[0019] The image forming unit 4 is provided above the paper feed unit 3 in the image forming apparatus main body 2. The image forming unit 4 includes a photoconductor drum 10 which is an image carrier rotatably provided in the image forming apparatus main body 2, a charger 11 arranged around the photoconductor drum 10, a developing unit 13, a transfer roller 14, and an optical scanning device 12 arranged to the right of the photoconductor drum 10. Thus, the image forming unit 4 forms an image on the paper supplied from the paper feed unit 3.

[0020] The fixing device 5 is a device for fixing a toner image formed on a sheet by the image forming unit 4 to the sheet. The fixing device 5 is disposed above 10 in the image forming unit 4. The fixing device 5 includes a heating roller 15 and a pressure roller 16 which rotate while being pressed against each other. The heating roller 15 is heated by a halogen heater 18 (see FIG. 3 described later) disposed inside the heating roller 15. A nip portion N through which the sheet supplied from the image forming unit 4 passes is formed between the heating roller 15 and the pressure roller 16. The heating roller 15 corresponds to a heating rotator, and the pressure roller 16 corresponds to a pressure rotator. The heating rotator is not limited to the heating roller 15, and may be, for example, a fixing belt or the like.

[0021] The paper discharge tray 6 is formed by recessing the right side portion of the upper surface of the image forming apparatus main body 2. The paper discharge tray 6 is inclined upward toward the downstream side (right side) in the paper transport direction.

[0022] Next, a description will be given of an image forming operation by the image forming apparatus 1. When the image forming apparatus 1 receives image data, in the image forming section 4, the photoconductor drum 10 is rotationally driven, and the charger 11 charges the surface of the photoconductor drum 10.

[0023] Then, based on the image data, a laser beam is emitted from the optical scanning device 12 to the photoconductor drum 10. An electrostatic latent image is formed on the surface of the photoconductor drum 10 by irradiating the surface with the laser beam. The electrostatic latent image formed on the photoconductor drum 10 is developed by the developing unit 13 into a visible toner image.

[0024] The paper then passes between the transfer roller 14 and the photoconductor drum 10. At this time, the toner image on the surface of the photoconductor drum 10 is moved and transferred to the paper by the transfer bias applied to the transfer roller 14. The paper onto which the toner image has been transferred is heated and pressurized when passing through the nip portion N between the heating roller 15 and the pressure roller 16 in the fixing device 5. As a result, the toner image is fixed to the paper.

[0025] The paper on which the toner image has been fixed by the fixing device 5 is sent further downstream in the paper transport direction by the rotation of the heating roller 15 and the pressure roller 16, and is discharged from the paper discharge outlet 2a to the paper discharge tray 6 by the discharge roller 17. The direction in which the paper is discharged by the discharge roller 17 may be horizontal, or may be inclined at a predetermined small angle above or below the horizontal. Here, the predetermined small angle is, for example, between 0° and 10°.

[0026] [Cross-sectional configuration from the fixing device to the pair of ejection rollers] FIG. 3 is an enlarged cross-sectional view showing a portion from the fixing device 5 to the discharge roller 17 in the image forming apparatus main body 2. As shown in FIG.

[0027] The fixing device 5 has a fixing housing 40 in addition to the heating roller 15 and the pressure roller 16. The heating roller 15 and the pressure roller 16 are housed in the fixing housing 40 with their axes extending in the front-rear direction. The fixing housing 40 is formed in the shape of a hollow box having a substantially rectangular parallelepiped shape that is long in the front-rear direction.

[0028] The fixing housing 40 is disposed below a predetermined space B that extends in the front-rear direction along a corner formed by the left exterior cover 22 and the upper exterior cover 21. The fixing housing 40 is disposed on the inner wall surface of the upper end portion of the left exterior cover 22 with a small gap therebetween. A plurality of exhaust ports 28 that communicate with the predetermined space B are formed in the upper end portion of the left exterior cover 22. As shown in FIG. 1, the plurality of exhaust ports 28 are made up of a front exhaust port group and a rear exhaust port group, and each exhaust port group is made up of four pairs of exhaust ports 28 arranged in the front-rear direction.

[0029] A paper receiving opening 40a is formed on the bottom surface of the fixing housing 40 to receive paper supplied from the image forming unit 4 toward the nip portion N. A paper sending opening 40b is formed on the top surface of the fixing housing 40 to send out the paper that has passed through the nip portion N toward the downstream side in the paper transport direction.

[0030] 3 and 4, a pair of guide rollers 19 spaced apart in the front-to-rear direction are rotatably attached to the right edge of the paper outlet 40b on the top surface of the fixing housing 40. Also, a discharge roller 17 is rotatably supported on the right end of the top surface of the fixing housing 40. Note that this discharge roller 17 may be supported by, for example, a support wall formed inside the housing.

[0031] A plurality of guide ribs 43 are arranged at intervals in the front-rear direction and protrude from the upper surface of the fixing housing 40 between the guide roller 19 and the discharge roller 17, and the lower surface of the paper is guided by the upper end surface of each guide rib 43. The upper surface of the paper is guided by a discharge guide 30 (an example of a guide member) described later.

[0032] An inclined plate portion 42 extending to the left at a slight upward incline from the horizontal direction is formed on the left edge portion of the paper feed opening 40b on the top surface of the fixing housing 40. This inclined plate portion 42 protrudes into a predetermined space B extending in the front-rear direction along the upper left corner of the image forming apparatus main body 2.

[0033] As shown in FIG. 3, a housing wall 46 is formed below the inclined plate 42. The housing wall 46 has a U-shaped cross section that opens to the right and surrounds the left side and both the top and bottom sides of the pressure roller 16. The upper wall of the housing wall 46 and the inclined plate 42 are continuously connected via a connecting wall 47. The upper wall and the inclined plate 42 are connected by a plurality of ribs 48 (see FIG. 4) that are spaced apart in the front-rear direction. The connecting wall 47 that connects the upper wall and the inclined plate 42 has a plurality of openings 41 formed between the plurality of ribs 48 and communicating the inside and outside of the housing. The plurality of openings 41 are located to the right of the exhaust port 28 formed in the left exterior cover 22 of the image forming apparatus main body 2. The plurality of openings 41 are also located directly above the pressure roller 16.

[0034] The discharge guide 30 forms a paper transport path C between itself and the upper surface of the fixing housing 40. The downstream end of this paper transport path C in the paper transport direction is located at the nip position of the discharge roller 17 and forms the paper discharge port 2a. The discharge guide 30 is attached to the lower surface of the upper exterior cover 21. An air passage A is formed between the upper exterior cover 21 and the discharge guide 30, which guides the air discharged from the paper discharge port 2a together with the paper to the fixing device 5. A damming plate 24 (an example of a damming portion) is formed at the right end of the upper exterior cover 21, which blocks the air discharged from the paper discharge port 2a together with the paper by the discharge roller 17 and guides it to the air passage A.

[0035] Next, the upper exterior cover 21 and the ejection guide 30 will be described in detail with reference to the drawings.

[0036] [Upper exterior cover configuration] FIG. 5 is a perspective view showing the upper exterior cover 21 as viewed from the back side (lower side).

[0037] The upper exterior cover 21 is made of resin or metal. The upper exterior cover 21 includes a base plate 23 and the above-mentioned paper discharge tray 6. The upper exterior cover 21 is an example of a facing member.

[0038] The base plate 23 is formed in a U-shape when viewed from the top-bottom direction (front-back direction). That is, the left half of the base plate 23 is formed of a rectangular plate extending in the front-rear direction, and the right half is composed of two rectangular plate parts arranged at a distance in the front-rear direction, and a vertical plate part 62 protruding from the back side is connected to the inner edge of each of the two rectangular plate parts, and the paper discharge tray 6 is supported by the base plate 23 via the vertical plate part 62. As shown in FIG. 1 and FIG. 4, the paper discharge tray 6 is provided on the right side of the base plate 23 and is formed so as to be recessed downward (back side). An opening 61 for paper discharge is formed at the left end of the paper discharge tray 6. The opening 61 is closed by a vertical wall (not shown) extending in the front-rear direction so that only the paper discharge port 2a facing the discharge roller 17 is exposed.

[0039] As shown in FIG. 2, the paper discharge tray 6 is gently inclined so that it is positioned higher on the right side.

[0040] As shown in FIG. 5, a blocking plate 24, a pair of reinforcing ribs 25, a pair of engaging projections 26, and a pair of guide support portions 27 are provided on the rear surface (lower surface) of the base plate 23.

[0041] The damming plate 24 is formed in a long plate shape and protrudes backward (downward) from the rear surface of the base plate 23. The damming plate 24 extends in the front-rear direction in the left-right central portion of the rear surface of the base plate 23. The damming plate 24 is provided on the left side of the opening 61. In other words, the damming plate 24 is provided upstream of the opening 61 in the paper transport direction.

[0042] The left side surface of the blocking plate 24 functions as an air blocking surface 24a that blocks air. The blocking surface 24a is inclined downward and to the right. In other words, the blocking plate 24 is inclined downward toward the downstream side in the paper transport direction.

[0043] 5, two reinforcing ribs 25 are provided on the back surface (lower surface) of base plate 23 on the left side (upstream side in the paper transport direction) of dam plate 24. The two reinforcing ribs 25 protrude from the back surface (lower surface) of base plate 23 toward the back side (lower side) and are arranged at an interval in the front-rear direction.

[0044] Two engagement protrusions 26 are provided on the back surface (lower surface) of base plate 23 on the left side (upstream side in the paper transport direction) of dam plate 24. The engagement protrusions 26 protrude in an L-shape from the back surface (lower surface) of base plate 23 to the rear side (lower side). The two engagement protrusions 26 are arranged at a distance in the left-right direction.

[0045] The guide support portion 27 is provided on the rear surface (lower surface) of the base plate 23, on the left side (upstream side in the paper transport direction) of each reinforcing rib 25. That is, two guide support portions 27 are provided on the rear surface (lower surface) of the base plate 23. The two guide support portions 27 are arranged with a gap in between in the front-rear direction. Each guide support portion 27 is formed in a U-shape when viewed from the front-rear direction, and a rectangular assembly hole 27a is formed between the guide support portion 27 and the base plate 23. The assembly hole 27a is used to assemble the discharge guide 30, which will be described later, to the upper exterior cover 21.

[0046] The base plate 23 of the upper exterior cover 21 is formed with only an opening required for mounting the discharge guide 30, and no openings for other purposes are formed. This ensures air circulation in the air passage A between the upper exterior cover 21 and the discharge guide 30.

[0047] [Ejection guide configuration] Fig. 6 is a perspective view showing the ejection guide 30 as viewed from the front side, and Fig. 7 is a perspective view showing the ejection guide 30 as viewed from the back side.

[0048] The discharge guide 30 has a guide main body 30A including a guide surface 35a that guides the paper on which the toner image has been fixed (paper after fixing process) to the discharge roller 17 (an example of a discharge rotator), and an extension portion 30B that is connected to the downstream end of the guide main body 30A in the paper transport direction and extends downstream in the paper transport direction beyond the discharge roller 17. The discharge guide 30 is an elongated member that extends in the front-rear direction, and is made of, for example, resin or metal.

[0049] Specifically, the guide main body 30A has a main body base plate 31a, an attachment plate 32, an upper surface rib 33, a protrusion 34, and a guide rib 35 (see FIG. 7). The extension 30B has an extension base plate 31b and a restriction rib 39.

[0050] The main substrate portion 31a and the extending substrate portion 31b are both rectangular plates extending in the front-rear direction.

[0051] The main body base plate portion 31a and the extending base plate portion 31b each have one mounting opening 36 formed therein. The two mounting openings 36 are located in the center of the discharge guide 30 in the front-rear direction and are formed with a gap in the left-right direction. Each mounting opening 36 penetrates the main body base plate portion 31a and the extending base plate portion 31b in the up-down direction. The two mounting openings 36 are located at positions corresponding to the engagement protrusions 26 of the upper exterior cover 21.

[0052] The cutouts 37 are formed at intervals in the front-rear direction at the left end of the main substrate 31a. In other words, the cutouts 37 are formed at the upstream end of the main substrate 31a in the paper transport direction. The cutouts 37 are formed at intervals in the front-rear direction. The cutouts 37 penetrate the left end of the main substrate 31a in the up-down direction and open to the left. As a result, the left end of the main substrate 31a is formed in a comb shape when viewed from the front-rear direction.

[0053] The mounting plate parts 32 are provided at both ends of the main body substrate part 31a in the front-rear direction. Each mounting plate part 32 is formed in a rectangular flat plate shape and protrudes outward in the front-rear direction from both ends in the front end direction of the main body substrate part 31a.

[0054] 6, the top surface ribs 33 are formed on the top surface (front surface) of the main body substrate part 31a and protrude upward from the main body substrate part 31a (the top surface of the main body substrate part 31a). The top surface ribs 33 include a plurality of ribs extending in the front-rear direction and a plurality of ribs extending in the left-right direction.

[0055] A plurality of protrusions 34 are formed on the upper end surface of the upper surface rib 33. The protrusions 34 protrude upward from the upper end surface of the upper surface rib 33. In other words, the protrusions 34 are convex portions formed in plurality on the upper end surface of the upper surface rib 33. The protrusions 34 are an example of a first protrusion.

[0056] As shown in Fig. 7, a plurality of guide ribs 35 are formed on the lower surface (rear surface) of the main body substrate portion 31a, and protrude downward from the main body substrate portion 31a (the lower surface of the main body substrate portion 31a). The plurality of guide ribs 35 are trapezoidal vertical ribs extending in the left-right direction, and are arranged at intervals in the front-rear direction. The protruding end surface of each guide rib 35 is formed in a substantially V-shape with the left-right central portion recessed upward compared to both ends when viewed from the front-rear direction. The protruding end surface of each guide rib 35 functions as a guide surface 35a that guides the paper to the discharge roller 17.

[0057] The extending substrate portion 31b is connected to the right edge of the main substrate portion 31a. The extending substrate portion 31b is formed so that its length in the front-rear direction is shorter than that of the main substrate portion 31a. The plurality of regulating ribs 39 are vertical ribs in the shape of right-angled triangles extending in the left-right direction, and are arranged at intervals in the front-rear direction. The end surface on the protruding side of each regulating rib 39 is an inclined surface that becomes lower toward the right side when viewed from the front-rear direction. Each regulating rib 39 protrudes downward from the lower surface of the extending substrate portion 31b. The end surface on the protruding side of each regulating rib 39 has the function of regulating the upward bulge of the paper discharged from the discharge roller 17 and guiding the paper to the paper discharge tray 6.

[0058] Incidentally, the discharge guide 30 has a plurality of openings, but these openings are configured only as openings for attaching the discharge guide 30 to the upper exterior cover 21. This improves the flow of air toward the fixing device 5 in the air passage A between the discharge guide 30 and the upper exterior cover 21.

[0059] [Assembly of the ejection guide to the upper exterior cover] FIG. 8 is a perspective view showing a state in which the ejection guide 30 is attached to the upper exterior cover 21, as viewed from the back side.

[0060] When assembling the discharge guide 30 to the upper exterior cover 21, first, the front surface (upper surface) of the discharge guide 30 (see FIG. 6) is opposed to the back surface (lower surface) of the upper exterior cover 21 (see FIG. 5). Then, the engagement protrusions 26 of the upper exterior cover 21 are inserted into the mounting openings 36 of the discharge guide 30, and the mounting plate portions 32 of the discharge guide 30 are inserted into the mounting holes 27a of the guide support portions 27 of the upper exterior cover 21.

[0061] As a result, the engagement protrusions 26 of the upper exterior cover 21 engage with the edges of the mounting openings 36 on the underside of the discharge guide 30, and the mounting plate portions 32 of the discharge guide 30 are supported by the guide support portions 27 of the upper exterior cover 21. In this manner, the discharge guide 30 is attached to (supported by) the upper exterior cover 21.

[0062] As shown in FIG. 3, when the discharge guide 30 is attached to the upper exterior cover 21, the protrusion 34 of the discharge guide 30 abuts against the base plate 23 of the upper exterior cover 21. As a result, an air passage A is secured between the base plate 23 of the upper exterior cover 21 and the base plate 31 of the discharge guide 30 .

[0063] In this state, the discharge guide 30 is located above the fixing device 5, and the roller sliding part 38 protruding from the center in the width direction of the discharge guide 30 and the discharge roller 17 are in contact with each other in the vertical direction. In addition, the predetermined space B is formed in the area above the fixing device 5 and on the left side of the discharge guide 30.

[0064] The left side of the air passage A communicates with the predetermined space B, and the right side of the air passage A communicates with the external space outside the paper discharge port. The air passage A is formed over the entire paper transport path C in the front-rear direction (the direction perpendicular to the paper surface in FIG. 9 ) (the transport path width direction).

[0065] 3, the upper exterior cover 21 has an overhang portion 121a that extends downstream in the paper transport direction from the discharge guide 30. The overhang portion 121a is formed so as to cover the upper side of the paper discharge path by the discharge rollers 17.

[0066] The blocking plate 24 protrudes from the leading edge of the overhanging portion 121a (an example of a predetermined portion) toward the paper discharge path. The air blocking surface 24a of the blocking plate 24 is inclined to the right (downstream in the paper direction) toward the lower side in the vertical direction.

[0067] The blocking plate 24 is located above the discharge roller 17 and to the right of the discharge roller 17 (downstream in the paper transport direction). The blocking plate 24 is also located to the right of the right end face (downstream end face in the paper transport direction) of the extension portion 30B of the discharge guide 30. The distance L between the blocking plate 24 and the discharge roller 17 in the left-right direction is preferably 3 mm to 60 mm, and more preferably 20 mm to 35 mm. An air introduction space I is formed between the right end face (downstream end face in the paper transport direction) of the extension portion 30B of the discharge guide 30 and the blocking plate 24 to introduce the air blocked by the blocking plate 24 toward the air passage A.

[0068] [Air flow inside the device] In the image forming apparatus 1, when an image forming operation starts, the heating roller 15 is heated, and the temperature of the air around the heating roller 15, i.e., the temperature around the fixing device 5, rises. The air with the increased temperature moves upward (see FIG. 3). Then, the air with the increased temperature passes through the paper outlet 40b of the fixing housing 40, the multiple openings 41, and the notch 37 of the discharge guide 30, and gathers in the predetermined space B. In this way, high-temperature air is gathered in the predetermined space B.

[0069] On the other hand, when the paper conveyed from the image forming unit 4 to the fixing device 5 passes through the nip portion N between the heating roller 15 and the pressure roller 16, the moisture contained in the paper is heated by the heating roller 15, generating water vapor. The air containing this water vapor moves together with the paper and travels along the underside of the discharge guide 30 to the discharge roller 17.

[0070] Then, as shown by arrow F1, the air containing water vapor moves downstream in the paper transport direction and slightly upward from the discharge roller 17. Then, as shown by arrow F2, the air containing water vapor hits the damming plate 24 of the upper exterior cover 21, and then proceeds in the opposite direction (upstream in the paper transport direction) along the underside of the overhang portion 121a of the upper exterior cover 21 in the air introduction space I.

[0071] As a result, the air containing water vapor moves toward the left side (upstream in the paper transport direction) through the air passage A between the upper exterior cover 21 and the discharge guide 30 as shown by the arrow F3, and reaches the specified space B. As described above, high-temperature air is collected in the specified space B. Therefore, the water vapor that reaches the specified space B is warmed by the high-temperature air. As a result, even if some of the water vapor has turned into steam, the steam is heated and evaporates again. Then, as shown by the arrow F4, the water vapor that has passed through the specified space B passes through the exhaust port 28 of the left exterior cover 22 and is discharged to the outside.

[0072] [Effects] As described above, the image forming apparatus 1 of this embodiment is provided with an upper exterior cover 21 that is disposed opposite the guide surface side of the discharge guide 30 and forms an air passage A between the upper exterior cover 21 and the opposite surface. The right end of the air passage A communicates with the external space outside the paper discharge port 2a, and the left end of the air passage A communicates with a predetermined space B on the fixing device 5 side inside the image forming apparatus main body 2. The image forming apparatus 1 further includes a blocking plate 24 that is located downstream of the discharge roller 17 in the paper transport direction and blocks the air discharged together with the paper by the discharge roller 17 and guides it to the opening at the right end of the air passage A.

[0073] According to this configuration, when water vapor (air containing a lot of moisture) generated by heating the paper in the fixing device 5 is discharged together with the paper, the water vapor can be made to flow back toward the air passage A by the blocking plate 24 before it turns into steam. Therefore, it is possible to prevent the steam generated by heating the paper in the fixing device 5 from being discharged as steam from the paper discharge port 2a with a simple configuration. Moreover, this backflowing water vapor is guided through the air passage A to the predetermined space B on the fixing device 5 side, which is a high-temperature space. Since the water vapor evaporates by being heated in this high-temperature space (predetermined space B), the problem of water vapor turning into steam can be reliably avoided. Therefore, water vapor does not remain in the space above the fixing device 5 and turn into water droplets as in the conventional case.

[0074] Further, an exhaust port 28 for discharging air within the predetermined space B to the outside is formed in a wall portion (the upper end portion of the left exterior cover 22) adjacent to the predetermined space B in the image forming apparatus main body 2.

[0075] If the amount of water vapor in the specified space B becomes excessive, there is a risk that the water vapor will turn into steam, but by providing the exhaust port 28 as described above, the water vapor can be released outside the apparatus through the exhaust port 28 before it turns into steam.

[0076] In this embodiment, the discharge guide 30 has a guide body 30A including a guide surface that guides the paper on which the toner image has been fixed (paper after the fixing process) to the discharge roller 17, and an extension 30B that is connected to the downstream end of the guide body 30A in the paper transport direction and extends downstream in the paper transport direction beyond the discharge roller 17. The upper exterior cover 21 has an overhang 121a that extends downstream in the paper transport direction beyond the extension 30B of the discharge guide 30. The dam plate 24 protrudes from the overhang 121a toward the paper discharge path, and is configured to form an air introduction space I that communicates with the air passage A between the overhang 121a and the tip of the extension 30B of the discharge guide 30.

[0077] According to this configuration, the air discharged together with the paper by the discharge roller 17 can be firmly captured in the air introduction space I on the left side of the blocking plate 24 and caused to flow back.

[0078] In this embodiment, the discharge roller 17 is configured to discharge paper horizontally or in a direction inclined at a predetermined small angle upward or downward from the horizontal, and the overhang portion 121a of the upper exterior cover 21 is formed so as to cover the discharge path from above, downstream of the discharge roller 17 in the paper transport direction.

[0079] According to this configuration, the air discharged together with the paper by the discharge roller 17 tends to rise due to the temperature difference with the surroundings, but this can be reliably captured by the overhanging portion 121a and guided to the air passage A.

[0080] In this embodiment, the predetermined space B within the image forming apparatus main body 2 is adjacent to a paper feed opening 40b formed in the fixing housing 40, and communicates with the space within the fixing housing 40 via the paper feed opening 40b.

[0081] According to this configuration, the air with an increased temperature around the heating roller 15 can be collected in the predetermined space B through the paper delivery opening 40b of the fixing housing 40. The predetermined space B also serves as an area through which air containing water vapor can pass. Therefore, even if some of the water vapor has turned into steam, the steam can be heated and evaporated again before being discharged to the outside.

[0082] In this embodiment, the fixing housing 40 further has an opening 41 formed in a wall portion of the fixing housing 40 facing the exhaust port 28 to allow communication between the inside and the outside of the fixing housing 40 .

[0083] According to this configuration, the air with an increased temperature around the heating roller 15 can be collected near the exhaust port 28 of the predetermined space B through the opening 41 of the fixing housing 40. This ensures that the air is heated immediately before it is exhausted to the outside from the exhaust port 28, and prevents water vapor from turning into steam immediately before it is exhausted from the exhaust port 28.

[0084] In this embodiment, the discharge guide 30 is disposed such that its upstream end in the paper transport direction is located above the fixing device 5. The upstream end of the discharge guide 30 in the paper transport direction is formed with a plurality of notches 37 (an example of a through-hole) that are aligned in the transport path width direction and penetrate vertically.

[0085] According to this configuration, the air with an increased temperature around the heating roller 15 can pass through the cutout portion 37 and be collected in the specified space B. In addition, the specified space B is a passage area for water vapor. Therefore, even if some of the water vapor has turned into steam, the steam can be heated and evaporated again before being discharged to the outside.

[0086] In this embodiment, a protrusion 34 is formed on the surface of the discharge guide 30 facing the upper outer cover 21, which abuts against the upper outer cover 21 to ensure an air passage A between the discharge guide 30 and the upper outer cover 21.

[0087] According to this configuration, when assembling the discharge guide 30 to the upper exterior cover 21, the discharge guide 30 is brought into contact with the protrusion 34, thereby reliably securing the air passage A between the upper exterior cover 21 and the discharge guide 30. Furthermore, if the protrusion 34 is not provided, the air passage A may be blocked by the application of an external force or thermal deformation, but by providing the protrusion 34, such a situation can be avoided.

[0088] In this embodiment, the air blocking surface 24a of the blocking plate 24 is inclined downward from the right end of the overhang portion 121a of the upper exterior cover 21 toward the downstream side in the paper transport direction.

[0089] According to this configuration, the air blocked by the air blocking surface 24 can be smoothly redirected (returned) and guided to the air passage A.

[0090] In this embodiment, the upper exterior cover 21 constituting the exterior wall of the image forming apparatus main body 2 is used as an opposing member that faces the surface of the discharge guide 30 opposite to the guide surface side.

[0091] According to this configuration, compared to a case in which a separate opposing member is provided in addition to the upper exterior cover 21, it is possible to reduce the number of parts and reduce costs.

[0092] In this embodiment, the dam plate 24 is integrally formed with the upper exterior cover 21 .

[0093] This allows the number of parts to be reduced, thereby reducing costs.

[0094] <<Variation 1>>

[0095] Fig. 9 shows a first modified example of the embodiment. In this modified example, the ejection guide 30 does not have the protruding portion 34, but instead the upper exterior cover 21 has a protruding portion 45. The protruding portion 45 is an example of a second protruding portion. In the following modified examples, the same components as those in Fig. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0096] A plurality of protrusions 45 are provided on the base plate 23 of the upper exterior cover 21. The protrusions 45 protrude downward from the lower surface (the surface facing the discharge guide 30) of the base plate 23. That is, the protrusions 45 protrude toward the discharge guide 30. When the discharge guide 30 is attached to the upper exterior cover 21, the base plate 31 of the discharge guide 30 abuts against the protrusions 45 of the upper exterior cover 21, and an air passage A is formed between the base plate 23 of the upper exterior cover 21 and the base plate 31 of the discharge guide 30.

[0097] According to this modification, similarly to the above embodiment, the air passage A can be reliably secured between the upper exterior cover 21 and the discharge guide 30 via the protrusion 45. Therefore, the same effects as those of the embodiment can be obtained.

[0098] Variation 2 10 shows a second modified example of the embodiment. In this modified example, the configuration of the damming portion is different from that of the above-described embodiment.

[0099] That is, the damming plate 29 (damming portion) of this example has an air damming surface 29a that is inclined downward from the right end of the upper exterior cover 21 toward the upstream side (left side) in the paper transport direction.

[0100] According to this, the air blocked by the blocking plate 29 can be redirected at an acute angle along the air blocking surface 24a and the lower surface of the overhanging portion 121a of the upper exterior cover 21. Therefore, it is possible to prevent the blocked air from overflowing to the right side due to inertial force.

[0101] As shown by the dotted line in the figure, the air blocking surface 29a of the blocking plate 29 may extend straight downward. This makes it relatively easy to remove the mold during molding, and therefore makes it possible to achieve both moldability and the ability to guide air in the reverse direction.

[0102] In this way, in the second modification, the blocking plate 29 can reliably cause the air to flow backward and be guided to the air passage A. Therefore, the same effects as those of the embodiment can be more reliably obtained. [Industrial Applicability]

[0103] INDUSTRIAL APPLICABILITY As described above, the present invention is useful for image forming apparatuses, and is particularly useful when applied to printers, facsimiles, copiers, multi-function peripherals (MFPs), and the like. [Explanation of symbols]

[0104] A: Air passage B: Predetermined space C: Paper transport path I: Air intake space N: Nip part 1: Image forming device 2: Image forming device main body 5: Fixing device 15: Heating roller (heating rotor) 16: Pressure roller (pressure rotating body) 18: Halogen heater 21: Upper exterior cover (opposing member) 24: Dam plate (dam section) 24a: Air barrier surface 28: Exhaust port 29: Dam plate (dam section) 29a: Air barrier surface 30A: Guide body 30B: Extension part 34:Protrusion 40: Fixed housing 40a: Paper receiving port 40b:Paper outlet 45:Protrusion 121a: Overhang section

Claims

1. An image forming apparatus including: a fixing device that is housed within an image forming apparatus main body, the fixing device having a heating rotator and a pressure rotator and fixing a toner image onto a sheet of paper by passing the sheet of paper through a nip portion formed between the two rotators; a discharge rotator that discharges the sheet of paper after the fixing process by the fixing device from a paper discharge port formed in the image forming apparatus main body into an external space on an upper surface of the image forming apparatus main body; and a guide member having a guide surface that guides the sheet of paper discharged from the fixing device to the discharge rotator, an opposing member that is provided opposite to the guide surface side of the guide member and forms an air passage between the opposing surface and the opposing surface, the air passage having one end communicating with the external space and the other end communicating with a predetermined space in which high-temperature air, the temperature of which increases as a result of the heating of the heating rotator on the fixing device side in the image forming apparatus main body, gathers; a blocking portion that is located downstream of the discharge rotor in the paper transport direction and blocks air discharged together with the paper by the discharge rotor and guides the air to the one end of the air passage. An image forming apparatus.

2. 2. The image forming apparatus according to claim 1, an exhaust port for discharging air within the predetermined space to the outside, the exhaust port being formed in a wall portion of the image forming apparatus body adjacent to the predetermined space.

3. 3. The image forming apparatus according to claim 1, the guide member has a guide body portion including the guide surface, and an extension portion connected to a downstream end portion of the guide body portion in the paper transport direction, extending downstream in the paper transport direction beyond the discharge rotor, and forming one end side of the air passage between the guide body portion and the opposing member; the opposing member has an overhang portion that extends downstream in a paper transport direction beyond the extending portion of the guide member, An image forming apparatus, wherein the damming portion protrudes from the overhang portion toward the discharge path from which the paper is discharged, and is configured to form an air introduction space communicating with the air passage between the damming portion and the tip of the extension portion of the guide member.

4. 4. The image forming apparatus according to claim 3, the discharge rotor is configured to discharge paper in a horizontal direction or in a direction inclined at a predetermined small angle upward or downward from the horizontal direction; The overhang portion is formed so as to cover the discharge path from above on a downstream side of the discharge rotor in a paper transport direction.

5. 5. The image forming apparatus according to claim 1, the fixing device has a fixing housing that has a paper receiving inlet for receiving paper heading toward the nip portion and a paper delivery outlet for delivering paper that has passed through the nip portion, and that houses the pressure rotating body and the heating rotating body therein; an image forming apparatus, wherein the predetermined space within the image forming apparatus main body is adjacent to the paper feed outlet formed in the fixing housing, and communicates with the space within the fixing housing via the paper feed outlet.

6. 6. The image forming apparatus according to claim 5, an exhaust port for exhausting air from within the predetermined space to the outside is formed in a wall portion of the image forming apparatus body adjacent to the predetermined space; In the image forming apparatus, the fixing housing further has a communication port that faces the exhaust port and communicates between the inside and the outside of the housing, in addition to the paper receiving inlet and the paper sending out outlet.

7. 7. The image forming apparatus according to claim 2, the guide member is disposed such that an end portion on an upstream side in a paper transport direction is located above the fixing device, an upstream end of the guide member in the paper transport direction, the guide member having a plurality of through-holes aligned in a width direction of the transport path and vertically penetrating the guide member;

8. 8. The image forming apparatus according to claim 1, an air passage provided between the guide member and the opposing member by contacting the opposing member, the air passage being provided between the guide member and the opposing member;

9. 9. The image forming apparatus according to claim 1, an air passage provided between the opposing member and the guide member by contacting the guide member, the air passage being provided between the opposing member and the guide member;

10. 5. The image forming apparatus according to claim 3, an air blocking surface of the blocking portion inclines downward from a predetermined point of the overhang portion toward a downstream side in a paper transport direction.

11. 5. The image forming apparatus according to claim 3, An image forming apparatus, wherein an air blocking surface of the blocking portion extends vertically downward from a predetermined position of the overhang portion, or is inclined downward from the predetermined position toward the upstream side in a paper transport direction.

12. 12. The image forming apparatus according to claim 1, The facing member constitutes a part of an exterior wall of the main body of the image forming apparatus.

13. 13. The image forming apparatus according to claim 1, The damming portion is integrally formed with the facing member.

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