Image forming apparatus

Abstract

To provide an image forming apparatus that can prevent the occurrence of trouble when passing a recording medium with low rigidity, and can prevent toner from being scraped when passing an envelope as a recording medium.SOLUTION: An image forming apparatus comprises a fixing device that has an outlet for ejecting a recording medium in a first direction 91, and the fixing device includes a fixing unit and a conveyance guide 3. The conveyance guide 3 includes a plate-like main body part 31 that has a recording medium width direction 92 as a longitudinal direction, a flat part 32 that is provided to project toward a passage of the recording medium from the main body part 31 in a central section B with respect to the recording medium width direction 92 of the main body part 31, and ribs 33 that project toward the passage from the main body part 31 and extend in a direction parallel to the first direction 91 in parts of a section other than the central section B. With reference to the main body part 31, the flat part 32 projects more toward the passage than the ribs 33.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Image forming apparatuses equipped with a fixing device are known. The fixing device is a device for fixing a toner image transferred onto the surface of a recording medium such as paper onto the recording medium. A typical fixing device includes a heating roller, a fixing member, a fixing belt, and a pressure roller. A heater is disposed inside the heating roller. The fixing belt is an endless belt disposed so as to surround the heating roller and the fixing member, and circulates by the rotation of the heating roller. The pressure roller is in pressure contact with the fixing member via the fixing belt. The location where the pressure roller and the fixing belt are in pressure contact with each other is called a fixing nip portion.

[0003] In order to guide the recording medium that has passed through the fixing nip portion further downstream, the fixing device is provided with a member called a conveying guide. An example of the conveying guide is described in JP 2017-72798 A (Patent Document 1). In the conveying guide, a plurality of ribs are formed parallel to the conveying direction of the recording medium in order to reduce the load when the recording medium is conveyed. If such a plurality of ribs are not provided, when the recording medium passes through, the surface of the conveying guide may condense due to evaporation of moisture contained in the recording medium, and the resistance when the recording medium passes through may increase. When a recording medium with low stiffness such as thin paper is passed through, there is a risk of causing jams or problems such as poor images. In order to prevent such a situation from occurring, the conveying guide is provided with the above-mentioned ribs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-72798 A Summary of the Invention [Problem to be solved by the invention]

[0005] If the transport guide has ribs parallel to the transport direction, the following problem occurs when an envelope is passed through as a recording medium. An envelope is not a single piece of paper but at least two pieces of paper, one on the front and one on the back, and the two pieces are not necessarily in close contact with each other and may bulge. Meanwhile, the toner fixed in the fixing nip adheres to the surface of the envelope facing the transport guide. If the envelope bulges, the toner-adhering surface of the envelope comes into contact with the ribs provided on the transport guide. At that time, a phenomenon may occur in which the toner on the envelope surface is scraped off by the ribs. If the toner already fixed to the envelope surface is scraped off by the ribs, it may result in a defective image.

[0006] Therefore, the present invention aims to provide an image forming device that can suppress problems such as jams and poor images caused by condensation when a recording medium with low stiffness is passed through, while also suppressing poor images caused by toner abrasion when an envelope is passed through as a recording medium. [Means for solving the problem]

[0007] In order to achieve the above object, an image forming apparatus according to the present invention includes a fixing device having an outlet for discharging a recording medium in a first direction. The fixing device includes a fixing section for fixing a toner image formed on the surface of the recording medium to the recording medium, and a transport guide arranged to guide the recording medium that has passed through the fixing section to the outlet. The transport guide includes a plate-shaped main body section having a longitudinal direction in a recording medium width direction perpendicular to the first direction, a flat section provided to protrude from the main body section toward the passage of the recording medium in a central section of the main body section in the recording medium width direction, and a rib extending in a direction parallel to the first direction while protruding from the main body section toward the passage in a part of a section of the main body section other than the central section in the recording medium width direction. When the main body section is used as a reference, the flat section protrudes toward the passage more than the rib. Effect of the Invention

[0008] According to the present invention, the recording medium can be guided by the ribs, thereby preventing problems such as jams caused by condensation and poor images when a recording medium with low stiffness is passed through, and further, since the flat portion protrudes toward the passage more than the ribs, poor images caused by toner scraping when an envelope is passed through as a recording medium can also be prevented. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a conceptual diagram of an image forming apparatus in a first embodiment according to the present invention. [Diagram 2] 1 is a cross-sectional view of a fixing device provided in an image forming apparatus in a first embodiment according to the present invention. [Diagram 3] 2 is a perspective view of a conveyance guide which is a part of a fixing device provided in the image forming apparatus in the first embodiment according to the present invention. FIG. [Figure 4] 2 is a front view of a conveyance guide which is a part of a fixing device provided in the image forming apparatus in the first embodiment according to the present invention. FIG. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] 11 is a front view of a conveyance guide which is a part of a fixing device provided in an image forming apparatus in accordance with a second embodiment of the present invention. FIG. [Figure 7] 7 is a cross-sectional view taken along line VII-VII in FIG. 6. [Figure 8] FIG. 11 is a perspective view of a sliding sheet included in a transport guide which is a part of a fixing device provided in an image forming apparatus in a second embodiment according to the present invention. [Figure 9] FIG. 11 is a partial perspective view of a conveyance guide which is a part of a fixing device provided in an image forming apparatus in accordance with a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) (composition) An image forming apparatus in a first embodiment according to the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0011] First, a conceptual diagram of an example of an image forming apparatus 501 is shown in Fig. 1. The image forming apparatus 501 includes a toner bottle 51, an intermediate transfer belt 52, an image forming section 53, a secondary transfer roller 54, a fixing device 55, a paper feed tray 56, and a discharge section 58. A recording medium is supplied from the paper feed tray 56, passes through the image forming section 53, and is transported to the discharge section 58 via the fixing device 55. The recording medium is, for example, paper. The fixing device 55 is detachable from the other sections.

[0012] FIG. 2 shows a cross-sectional view of the fixing device 55 with the fixing device 55 removed by itself. The fixing device 55 has an entrance 1 and an exit 2. The fixing device 55 has a housing 10, a fixing belt 4, a fixing member 8, a pressure roller 5, and a conveying guide 3. The fixing belt 4 circulates around the outside of the fixing member 8. The pressure roller 5 presses against the fixing member 8 so as to sandwich the fixing belt 4. The location where the fixing belt 4 and the pressure roller 5 come into contact with each other is the fixing nip portion 6, which serves as a fixing section. The recording medium that has passed through the fixing nip portion 6 enters the inside of the fixing device 55 from the entrance 1, passes through the fixing nip portion 6, and is then discharged from the exit 2 via a passage 7.

[0013] Fig. 3 shows the transport guide 3 taken out by itself. Fig. 4 shows the transport guide 3 as seen from the front. In Fig. 4, the direction in which the recording medium is transported is shown as a first direction 91. Fig. 4 also shows the recording medium width direction 92. Fig. 5 shows a cross-sectional view taken along line VV in Fig. 4.

[0014] Image forming apparatus 501 in this embodiment can be expressed as follows. Image forming apparatus 501 includes a fixing device 55 having an outlet 2 for discharging a recording medium in a first direction 91. Fixing device 55 includes a fixing section that fixes a toner image formed on the surface of the recording medium to the recording medium, and a transport guide 3 that is arranged to guide the recording medium that has passed through the fixing section to the outlet 2. In this example, fixing nip section 6 is the fixing section.

[0015] The conveying guide 3 includes a plate-shaped main body 31 having a longitudinal direction in a recording medium width direction 92 perpendicular to a first direction 91, a flat portion 32 provided so as to protrude from the main body 31 toward a passage 7 of the recording medium in a central section B of the main body 31 in the recording medium width direction 92, and a rib 33 extending in a direction parallel to the first direction 91 while protruding from the main body 31 toward the passage 7 in a part of sections A and C other than the central section B of the main body 31 in the recording medium width direction 92. When the main body 31 is used as a reference, the flat portion 32 protrudes toward the passage 7 more than the rib 33. The passage 7 shown in FIG. 2 is the right side of the conveying guide 3 in FIG. 5. FIG. 5 shows that the flat portion 32 protrudes more than the rib 33. As shown in FIGS. 3 and 4, an inclined portion 35 is provided on both sides of the flat portion 32. The flat portion 32 and the main body 31 are smoothly connected by the inclined portion 35. The flat portion 32 is provided so as to occupy a part of the central section B.

[0016] (Action and effect) Since the image forming apparatus 501 in this embodiment has the above-mentioned configuration, when a recording medium with low stiffness such as thin paper is passed through, the resistance does not increase because the recording medium is guided by the ribs 33 provided in the entire longitudinal area, i.e., the entire areas of sections A and C, in the conveying guide 3 of the fixing device 55. By guiding the recording medium by the ribs 33, it is possible to suppress the occurrence of problems such as jams and poor images caused by condensation when a recording medium with low stiffness is passed through.

[0017] In this embodiment, when an envelope is passed as a recording medium, the center of the envelope, which is most likely to expand, comes into contact with the flat portion 32 first, not with the ribs 33, so that the envelope does not come into contact with the ribs 33, and toner is prevented from being scraped off by the ribs 33. This makes it possible to suppress the occurrence of image defects.

[0018] (Embodiment 2) (composition) An image forming apparatus in a second embodiment according to the present invention will be described with reference to Figures 6 to 8. The overall configuration of the image forming apparatus is roughly the same as that of the first embodiment, so description of the common parts will not be repeated.

[0019] The fixing device provided in the image forming apparatus in this embodiment includes a conveying guide 3i. The conveying guide 3i is taken out alone and viewed from the front in Fig. 6. A cross-sectional view taken along line VII-VII in Fig. 6 is shown in Fig. 7.

[0020] In this embodiment, at least a part of the surface of the flat portion 32 facing the passage 7 is covered by the sliding sheet 34, and the friction coefficient of the sliding sheet 34 with respect to the recording medium is smaller than the friction coefficient of the flat portion 32 with respect to the recording medium. As shown in FIG. 6, the sliding sheet 34 covers most of the flat portion 32. The sliding sheet 34 may protrude from the flat portion 32. At least a part of the inclined portion 35 may also be covered by the sliding sheet 34. FIG. 8 shows the sliding sheet 34 taken out alone in FIG. 6. The sliding sheet 34 may be in a flat state before being attached to the flat portion 32, but by attaching the sliding sheet 34 so as to straddle the flat portion 32 and the inclined portions 35 on both sides thereof, the sliding sheet 34 may have a shape that is bent midway as shown in FIG. 8.

[0021] (Action and effect) In this embodiment, the sliding sheet 34 is attached so as to cover at least a part of the flat portion 32, so that the resistance when the recording medium passes through can be reduced.

[0022] In order to prevent the recording medium from getting caught on the end of the sliding sheet 34 in the recording medium width direction 92, as shown in this embodiment, it is preferable that the end of the sliding sheet 34 in the recording medium width direction 92 is located not in the flat portion 32 but in the adjacent inclined portion 35. This also applies to the conveying direction. That is, it is preferable that a slope is provided at the boundary between the flat portion 32 and other portions, and it is preferable that the end of the sliding sheet 34 in the conveying direction is located halfway down the slope. In this way, it is preferable to avoid contact between the end of the sliding sheet 34 and the recording medium.

[0023] As shown in this embodiment, a separation section 36 is provided at the end of the conveying guide 3i close to the fixing section, extending to guide the recording medium to the exit 2, and the area covered by the sliding sheet 34 is recessed compared to the surface of the separation section 36 facing the passage 7. In other words, a step 38 is formed. By adopting this configuration, the recording medium can be smoothly guided to the exit 2. In addition, since the area covered by the sliding sheet 34 is recessed to form the step 38, it is possible to prevent the recording medium from getting caught on the edge of the sliding sheet 34.

[0024] (Embodiment 3) (composition) An image forming apparatus according to a third embodiment of the present invention will now be described with reference to Fig. 9. The overall configuration of the image forming apparatus is generally the same as that of the second embodiment, so description of the common parts will not be repeated.

[0025] The fixing device provided in the image forming apparatus in this embodiment includes a transport guide. Fig. 9 shows an enlarged view of a part of this transport guide. A sliding sheet is attached to the flat portion 32 of this transport guide as described in the second embodiment. Fig. 9 shows the state before the sliding sheet is attached. Although Fig. 9 does not show the sliding sheet, the same reference numerals as those used in Fig. 7 for the second embodiment are used for the sliding sheet.

[0026] The sliding sheet 34 is attached to the flat portion 32 with double-sided tape. Through holes are provided in a portion of the area of ​​the flat portion 32 that is covered by the sliding sheet 34. In this embodiment, slits 37 are provided as an example of through holes. A plurality of slits 37 are provided parallel to the first direction 91. The sliding sheet 34 is attached so as to cover almost all of these through holes. The state after the sliding sheet 34 is attached is the same as that shown in FIG. 6. Note that a portion of the slits 37 may be seen protruding from the sliding sheet 34.

[0027] (Action and effect) In this embodiment, the through holes are provided in the area where the sliding sheet 34 is attached to the flat portion 32 with double-sided tape. Therefore, even if volatile substances are generated from the sliding sheet 34 or the double-sided tape, the volatile substances can be released to the rear side through the through holes, and the floating of the sliding sheet 34 can be prevented. The same applies when volatile substances are generated from the member of the conveying guide itself. The through holes may have other shapes, but as shown in this embodiment, by providing multiple slits 37 arranged in parallel, it is possible to obtain the effect of releasing volatile substances over a wide range. If the multiple slits 37 are provided parallel to the first direction 91, which is the direction in which the recording medium travels, it is possible to prevent the recording medium from getting caught in the step even if the slits 37 cause a step on the surface of the sliding sheet 34.

[0028] In addition, two or more of the above-described embodiments may be appropriately combined and adopted.

[0029] The above-described embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0030] REFERENCE SIGNS LIST 1 entrance, 2 exit, 3,3i conveying guide, 4 fixing belt, 5 pressure roller, 6 fixing nip portion, 7 passage, 8 fixing member, 10 housing, 31 main body portion, 32 flat portion, 33 rib, 34 sliding sheet, 35 inclined portion, 36 separation portion, 37 slit, 38 step, 51 toner bottle, 52 intermediate transfer belt, 53 image forming portion, 54 secondary transfer roller, 55 fixing device, 56 paper feed tray, 58 discharge portion, 91 first orientation, 92 recording medium width direction, 501 image forming device.

Claims

1. a fixing device having an outlet for discharging the recording medium in a first direction; The fixing device is a fixing section for fixing the toner image formed on the surface of the recording medium onto the recording medium; a conveying guide arranged to guide the recording medium that has passed through the fixing unit to the outlet, The conveying guide is a plate-shaped main body portion having a longitudinal direction in a width direction of the recording medium perpendicular to the first direction; a flat portion provided in a central section of the main body portion in the recording medium width direction so as to protrude from the main body portion toward the passage of the recording medium; a rib extending in a direction parallel to the first direction and protruding from the main body portion toward the passage in a portion of a section of the main body portion other than the central section in the recording medium width direction, In an image forming apparatus, when the main body portion is used as a reference, the flat portion protrudes toward the passage more than the rib does.

2. 2. The image forming apparatus according to claim 1, wherein at least a portion of a surface of the flat portion facing the passage is covered by a sliding sheet, and a friction coefficient of the sliding sheet with respect to the recording medium is smaller than a friction coefficient of the flat portion with respect to the recording medium.

3. 3. The image forming apparatus according to claim 2, wherein the sliding sheet is attached to the flat portion with a double-sided tape, and a through hole is provided in a part of the area of ​​the flat portion that is covered by the sliding sheet.

4. a separation portion is provided at an end of the conveying guide that is closer to the fixing portion, the separation portion extending to guide the recording medium to the outlet, 4. The image forming apparatus according to claim 2, wherein an area of ​​said separation section covered by said sliding sheet is recessed from a surface of said separation section facing said passage.

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