Image forming device

Abstract

To provide an image forming apparatus that can quickly and efficiently cool a recording medium after fixing processing without damaging an image.SOLUTION: An image forming apparatus comprises: an image forming unit that forms an image on a recording medium S; a fixing device 200 that thermally fixes an unfixed image carried on a recording medium S; and a cooling device 100 that cools the recording medium S passing through the fixing device 200 on a conveyance path. The cooling device 100 includes a conveying roller member 80 that is in contact with the recording medium S sent out from the fixing device 200 without sandwiching by pressure, a conveyance guide member 90 that is arranged opposite to the conveying roller member 80 with the conveyance path of the recording medium S therebetween, and blowing means 95 that sends air toward the conveying roller member 80.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In image forming devices such as copiers, printers, and facsimiles, images are formed by image forming processes such as electrophotographic recording, electrostatic recording, and magnetic recording, and an unfixed toner image is formed on a recording medium (such as paper) by an image transfer method or a direct method. As a fixing device for fixing the unfixed toner image, a fixing process is known in which the toner image formed on the recording medium is heated and pressed in a nip portion between a fixing member and a pressure member, thereby performing the fixing process.

[0003] After fusing, the paper is ejected from the ejection roller and stacked on the ejection tray. If the heat from the fusing process is stored in the stacked paper, the toner on the paper may melt, causing adjacent sheets of paper to stick together through the molten toner, resulting in a blocking phenomenon (paper ejection adhesion).

[0004] To address this problem, a configuration has been proposed for cooling the paper being conveyed (see, for example, Patent Document 1). Patent document 1 discloses an image forming device in which a cooling roller, which serves as a cooling section for cooling a fixing sheet on which a toner image has been fixed, includes a main body section and a surface section formed by coating, and the heat capacity of the surface section is lower than the heat capacity of the main body section. Summary of the Invention [Problem to be solved by the invention]

[0005] In the device of Patent Document 1, the surface of the cooling roller is pressed against the paper to cool the paper, but there is a risk that the image will become rough when the cooling roller presses against the molten toner on the paper.

[0006] In addition, the contact area between the cooling roller and the paper is small, which can make it difficult to achieve sufficient cooling. In particular, when the production speed increases or the number of consecutive prints increases, it is not possible to ensure a sufficient temperature reduction for the paper, which results in the problem of being unable to effectively prevent the blocking phenomenon.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that can quickly and efficiently cool a recording medium after fixing processing without damaging the image. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the image forming apparatus of the present invention is an image forming apparatus including an image forming unit that forms an image on a recording medium, a fixing device that heats and fixes an unfixed image carried on the recording medium, and a cooling device that cools the recording medium that has passed through the fixing device on a conveying path, wherein the cooling device includes a conveying roller member that contacts the recording medium sent out from the fixing device without clamping it with pressure, a conveying guide member that is arranged opposite the conveying roller member across the conveying path of the recording medium, and an air blowing unit that blows air toward the conveying roller member. The conveying roller member is a brush roller in which brush fibers are implanted on the outer peripheral surface of a core metal serving as a shaft, the core metal of the brush roller is hollow inside, the outer peripheral surface of the core metal has a plurality of ventilation holes communicating with the inside, and a restricting member is in sliding contact with the inner peripheral surface of the core metal of the brush roller and closes some of the ventilation holes to restrict the ventilation range. It is characterized by: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an image forming apparatus that can quickly and efficiently cool a recording medium after fixing processing without damaging the image. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 1 is a schematic cross-sectional view illustrating an example of the configuration of a fixing device according to the present embodiment. [Figure 3] 1 is a schematic cross-sectional view of a main part of an image forming apparatus according to a first embodiment. [Figure 4]FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to a second embodiment. [Figure 5] FIG. 5 is a horizontal cross-sectional view of the configuration shown in FIG. 4. [Figure 6] FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to a third embodiment. [Figure 7] FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to a fourth embodiment. [Figure 8] FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to a fifth embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view of a main part of an image forming apparatus according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The image forming apparatus according to the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any modification that achieves the functions and effects of the present invention is included in the scope of the present invention.

[0012] [Image forming equipment] FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 shown in Figure 1 is a tandem color printer in which image forming units that form multiple color images are arranged side by side along the direction in which the belt is stretched. However, the present invention is not limited to this type, and can also be applied to not only printers but also copiers, facsimile machines, etc.

[0013] The image forming apparatus 1 employs a tandem structure in which photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged side by side as image carriers capable of forming images corresponding to the colors separated into yellow, cyan, magenta, and black.

[0014] In the image forming apparatus 1, the visible images formed on the photosensitive drums 20Y, 20C, 20M, and 20Bk are primarily transferred to an intermediate transfer member (hereinafter referred to as a "transfer belt") 11, which is an endless belt that can move in the direction of arrow A1 while facing the photosensitive drums. By performing this primary transfer process, the images of each color are superimposed and transferred, and then, by performing a secondary transfer process, they are transferred all at once to a recording medium (hereinafter simply referred to as "paper") S.

[0015] Around each photosensitive drum, devices for performing image forming processing in accordance with the rotation of the photosensitive drum are arranged. Taking the photosensitive drum 20Bk that forms a black image as a representative, the following devices are arranged around the photosensitive drum 20Bk: a charging device 30Bk that performs image forming processing in the direction of rotation of the photosensitive drum 20Bk; The photosensitive drum 1 includes a device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk. An optical writing device 8 is used for writing using the writing light Lb after charging.

[0016] In the superimposed transfer onto the transfer belt 11, as the transfer belt 11 moves in the A1 direction, the visible images formed on the photosensitive drums 20Y, 20C, 20M, and 20Bk are transferred and superimposed onto the same position on the transfer belt 11. For this reason, the transfer is performed with staggered timing from the upstream side to the downstream side in the A1 direction by applying a voltage to primary transfer rollers 12Y, 12C, 12M, and 12Bk disposed opposite the photosensitive drums 20Y, 20C, 20M, and 20Bk across the transfer belt 11.

[0017] The photoconductor drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the A1 direction. The photoconductor drums 20Y, 20C, 20M, and 20Bk are provided in image stations for forming yellow, cyan, magenta, and black images, respectively.

[0018] The image forming device 1 has four image stations that perform image formation processing for each color, a transfer belt unit 10 that is arranged above and opposite each photosensitive drum 20Y, 20C, 20M, and 20Bk and is equipped with a transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12Bk, a secondary transfer roller 5 that is arranged opposite the transfer belt 11 and rotates in response to and following the transfer belt 11, a belt cleaning device 13 that is arranged opposite the transfer belt 11 and cleans the transfer belt 11, and an optical writing device 8 that is arranged below and opposite these four image stations.

[0019] The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, and a rotating polygonal mirror as a deflection means. The optical writing device 8 is configured to emit writing light Lb corresponding to each color to each of the photoconductor drums 20Y, 20C, 20M, and 20Bk, forming electrostatic latent images on the photoconductor drums 20Y, 20C, 20M, and 20Bk. For convenience, in FIG. 1, the writing light Lb is labeled only for the image station for black images, but the same applies to the other image stations.

[0020] The image forming apparatus 1 is provided with a sheet feeding device 61 serving as a paper feed cassette that holds recording media S to be transported between the photosensitive drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11. Also provided is a pair of registration rollers 4 that feeds the recording media S transported from the sheet feeding device 61 toward a transfer section between each photosensitive drum and the transfer belt 11 at a predetermined timing that matches the timing of toner image formation by the image station. Also provided is a sensor that detects when the leading edge of the recording media S reaches the pair of registration rollers 4.

[0021] The image forming apparatus 1 is equipped with a fixing device 200 for fixing the toner image onto the recording medium S onto which the toner image has been transferred, a cooling device 100 for cooling the recording medium S on the conveying path after it has passed through the fixing device, a pair of conveying rollers 6 arranged downstream of the fixing device 200, and a pair of discharge rollers 7 for discharging the recording medium S outside the main body of the image forming apparatus 1.

[0022] In addition, an output tray 17 is provided at the top of the main body of the image forming apparatus 1 to hold the recording medium S that has been discharged to the outside of the main body of the image forming apparatus 1 by the pair of discharge rollers 7. In addition, toner bottles 9Y, 9C, 9M, and 9Bk filled with toner of each color, yellow, cyan, magenta, and black, are provided below the output tray 17.

[0023] The transfer belt unit 10 includes a transfer belt 11, primary transfer rollers 12Y, 12C, 12M, and 12Bk, as well as a drive roller 72 and a driven roller 73 around which the transfer belt 11 is wound. The driven roller 73 also functions as a tension applying means for the transfer belt 11, and for this reason, a spring or other such applying means is provided on the driven roller 73. The transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, and 12Bk, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

[0024] The sheet feeding device 61 is disposed at the bottom of the main body of the image forming apparatus 1, and has a feeding roller 3 that contacts the upper surface of the uppermost recording medium S. The feeding roller 3 is driven to rotate counterclockwise in the drawing, thereby feeding the uppermost recording medium S toward the pair of registration rollers 4.

[0025] Although not shown in detail, the cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade disposed to face and contact the transfer belt 11. The cleaning device 13 cleans the transfer belt 11 by scraping off and removing foreign matter such as residual toner on the transfer belt 11 with the cleaning brush and cleaning blade. The cleaning device 13 also has a discharge means for carrying out and discarding the residual toner removed from the transfer belt 11.

[0026] [Fixing device] FIG. 2 is a schematic diagram showing an example of a fixing device mounted in the image forming apparatus of the present invention. The fixing device mounted on the image forming apparatus of this embodiment is not limited to the belt fixing type described below, but may be a roller fixing type. The fixing device 200 shown in Figure 2 includes a rotatable endless belt-like fixing member (hereinafter also referred to as "fixing belt") 201, a heat source 202 that heats the fixing member 201, a non-rotating nip forming member 206 arranged inside the fixing member 201, a heat transfer assisting member 216 that assists the heat transfer of the fixing member 201, and a pressure member (pressure roller) 203 arranged outside the fixing member 201 opposite the nip forming member 206 and forming a nip portion N between the fixing member 201 and the pressing member (pressure roller), and a recording medium S carrying an unfixed image is passed through the nip portion N to perform fixing.

[0027] Fixing belt 201 is directly heated by radiant heat from a plurality of heat sources (halogen heaters) 202A and 202B from the inner circumferential side. Furthermore, temperature sensors 230A and 230B are attached to detect the temperature of fixing belt 201, and detect the temperature of fixing belt 201 in a non-contact manner. The lighting rates of heat sources 202A and 202B are controlled based on the detected temperatures, thereby controlling the temperature of fixing belt 201 to a desired temperature. In other words, control means controls the heat generation (power supply to the heat sources) of heat sources 202A and 202B so that the temperatures detected by temperature sensors 230A and 230B reach predetermined detection target temperatures. Hereinafter, when there is no need to distinguish between multiple heat sources, they will simply be referred to as "heat source 202."

[0028] The inside of the fixing belt 201 in Figure 2 is provided with a nip forming member 206 arranged opposite the pressure roller 203, a heat transfer assisting member 216 covering the surface of the nip forming member 206 facing the inner surface of the fixing belt 201, and a stay member 207 that holds the nip forming member 206 against the pressure from the pressure roller 203. Nip forming member 206 forms a nip N between itself and pressure roller 203 via fixing belt 201, and is configured to slide indirectly against the inner surface of the fixing belt via heat transfer assist member 216. By passing recording medium S carrying a toner image through nip N, the toner on the recording medium is melted by heat and fixed to the recording medium by pressure.

[0029] A sliding coating with a low coefficient of friction is applied to the contact surface of heat transfer assist member 216 with fixing belt 201. Examples of the sliding coating include a fluorine coating and a glass coating such as DLC (diamond-like carbon) that has high abrasion resistance.

[0030] Furthermore, a lubricant is applied to the contact surface of heat transfer assisting member 216 with fixing belt 201. Suitable lubricants are fluorine grease or silicone oil, which have a high heat resistance temperature. Fluorine grease is a gel-like lubricant made by dispersing a thickener in fluorine oil, which serves as a base oil, and because it has a higher viscosity than oil, it is effective as a countermeasure against leakage from sliding parts.

[0031] The heat transfer assisting member 216 is provided to prevent heat from being accumulated locally and to actively transfer heat in the longitudinal direction, thereby reducing temperature non-uniformity in the longitudinal direction. For this reason, a material that allows heat transfer in a short time is preferred as the material for the heat transfer assistance member 216, and examples thereof include copper, aluminum, silver, etc., which have high thermal conductivity. Among these, copper is most preferred when cost, availability, thermal conductivity characteristics, and workability are all taken into consideration. In this embodiment, the surface of the heat transfer assistance member 216 that comes into direct contact with the fixing belt 201 serves as the nip forming surface.

[0032] The fixing belt 201 is composed of a metal belt such as nickel or SUS, or an endless belt or film made of a resin material such as polyimide. The belt's surface has a release layer such as a PFA or PTFE layer to prevent toner from adhering. An elastic layer formed of a silicone rubber layer or other material may be placed between the belt substrate and the PFA or PTFE layer. Without a silicone rubber layer, the heat capacity is reduced and fixing performance is improved. However, when an unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, resulting in a problem of citrus peel-like uneven gloss (citrus peel image) in solid areas of the image. To improve this, a silicone rubber layer of 100 μm or more is required. The deformation of the silicone rubber layer absorbs the minute irregularities, improving the citrus peel image.

[0033] As described above, a sliding coating can be applied to the surface of the fixing belt 201 that slides against the heat transfer assisting member 216, and in this case, a material such as polyimide or polyamideimide can be selected taking into consideration heat resistance and abrasion resistance.

[0034] The stay member 207 has a shape with an upright portion on the nip portion N side and the opposite side, and heat sources 202A and 202B are arranged across the upright portion, and the fixing belt 201 is directly heated by radiant heat from the inner surface side by the heat source 202 in areas other than the nip portion.

[0035] Inside fixing belt 201, stay members 207 are provided as support members for supporting nip forming member 206 and nip portion N, preventing bending of nip forming member 206 that receives pressure from pressure roller 203 and ensuring a uniform nip width in the axial direction. Stay members 207 are held and fixed at their ends by flanges that serve as holding members and are positioned accordingly.

[0036] Furthermore, a reflecting member 209 is provided between the heat source 202 and the stay member 207, thereby suppressing unnecessary energy consumption caused by the stay member 207 being heated by radiant heat from the heat source 202, etc.

[0037] Furthermore, by providing the reflecting member 209, the heaters are prevented from heating each other's glass tubes, thereby enabling efficient heating of the fixing belt 201. The reflecting member 209 is made of a material with low emissivity so as not to absorb the heat from the heat source 202. Instead of providing the reflecting member 209, the same effect can be obtained by subjecting the surface of the stay member 207 to heat insulation or mirror finishing.

[0038] The pressure roller 203 has an elastic rubber layer 204 on a core metal 205, and a release layer (PFA or PTFE layer) on its surface to provide release properties. The pressure roller 203 rotates by receiving a driving force from a drive source such as a motor provided in the image forming apparatus via a gear. The pressure roller 203 is pressed against the fixing belt 201 by a spring or the like, and the elastic rubber layer 204 is compressed and deformed to provide a predetermined nip width. The pressure roller 203 may be a hollow roller, or may have a heating source such as a halogen heater. The elastic rubber layer 204 may be solid rubber, but if the pressure roller 203 does not have an internal heater, sponge rubber may be used. Sponge rubber is more preferable because it has better heat insulation and is less likely to lose heat from the fixing belt.

[0039] The fixing belt 201 rotates together with the pressure roller 203. In the case of Figure 2, the pressure roller 203 is rotated by a drive source, and the driving force is transmitted to the belt at the nip N, causing the fixing belt 201 to rotate. The fixing belt 201 rotates while being sandwiched at the nip N, and is guided by flanges at both ends and runs outside the nip. With the above-described configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up time.

[0040] [Cooling device] The image forming apparatus 1 of the present invention comprises an image forming section that forms an image on a recording medium S, a fixing device 200 that heats and fixes an unfixed image carried on the recording medium S, and a cooling device 100 that cools the recording medium S that has passed through the fixing device 200 on the transport path. The cooling device 100 includes a conveying roller member 80 that contacts the recording medium S sent out from the fixing device 200 without clamping it under pressure, a conveying guide member 90 that is arranged opposite the conveying roller member 80 via the conveying path of the recording medium S, and an air blowing means 95 that blows air toward the conveying roller member 80.

[0041] The cooling device 100 is disposed between the fixing device 200 and the pair of conveying rollers 6 disposed downstream, and is capable of immediately cooling the recording medium S sent out from the fixing device 200. Because cooling can be performed before the heat from the fixing process is transferred in the thickness direction of the recording medium S, i.e., before heat is accumulated inside, it is possible to efficiently cool recording media S that are conveyed at high speed and in large quantities, and to prevent adhesion of the discharged recording media S (blocking phenomenon). It is also possible to prevent temperature rises in peripheral components due to the conveyance of heated recording media S, and any resulting malfunctions.

[0042] The conveying roller member 80 is not pressed against the recording medium S, and the recording medium S is not sandwiched between the conveying roller member 80 and an opposing member due to pressure contact of the conveying roller member 80, so the soft toner immediately after the fixing process is not roughened by pressure contact. It is also suitable for conveying thin recording media S with low stiffness. Furthermore, since a mechanism for pressing the conveying roller member 80 against the recording medium S (for example, a pressing member such as a spring) is not required, space can be saved and the conveying roller member 80 can be held with a simple configuration.

[0043] The cooling device 100 preferably includes a driving means for rotationally driving the transport roller member 80, and the transport roller member 80 preferably rotates at a speed equal to or higher than the transport speed of the recording medium S. This prevents the transport roller member 80 from becoming a transport load, and allows the recording medium S to be transported efficiently.

[0044] First Embodiment 3 is a cross-sectional view showing a main part of the image forming apparatus 1 according to the first embodiment, and shows the cooling device 100, the conveying roller pair 6, and the discharging roller pair 7, which are disposed downstream of the fixing device 200. The conveying direction of the recording medium S is indicated by an arrow D. In this embodiment, a transport roller member 80 constituting the cooling device is a brush roller in which brush fibers 81 are implanted on the outer peripheral surface of a core metal 82 serving as a shaft. Hereinafter, the transport roller member will be referred to as a "brush roller."

[0045] The brush roller 80 can be constructed by directly implanting brush fibers 81 on a core metal 82. The implantation density, implantation area, diameter, type, and penetration amount of the brush fibers 81 are not particularly limited and can be selected as appropriate. The brush roller 80 may also be configured by connecting a plurality of rollers in the form of conveying rollers to which the brush fibers 81 are attached.

[0046] The type of fiber used for the brush fibers 81 includes, but is not limited to, nylon, acrylic, polyester, etc. It is also possible to use heat-resistant polyimide resin, aramid resin, etc. as the brush fibers 81. The brush roller 80 can also be configured by spirally winding a brush cloth or the like made of bristles such as polyimide fibers or aramid fibers on a core metal 82. The width and shape of the wound brush cloth are not particularly limited, and the brush fibers 81 may be configured to spread across the entire width of the roller.

[0047] The brush roller 80 is driven to rotate in the direction indicated by R in the figure at a speed equal to or faster than the transport speed of the recording medium S. The brush fibers 81 can be made of the aforementioned polyimide resin, aramid resin, etc., or, for example, low-wear fluororesin. Alternatively, the main body of the brush fibers 81 can be made of heat-resistant resin or metal, and the surface of the resin or metal that comes into contact with the recording medium S can be coated with a low-wear material such as fluororesin, to achieve the same low-wear effect.

[0048] The brush fibers 81 implanted on the brush roller 80 may or may not be deformed (curved) by contact with the transported recording medium S. The rigidity of the brush fibers 81 is preferably selected so that the width in the transport direction when the brush roller 80 and the recording medium S come into contact (nip width) is 3 mm or less. This makes it possible to minimize the contact width between the brush fibers 81 and the recording medium S within a range that still provides a cooling effect, and to prevent image degradation due to contact.

[0049] The brush roller 80 is preferably rotated at the same speed as the conveying speed or slightly faster than the conveying speed (for example, 1 to 10% faster) so as not to impose a conveying load on the recording medium S.

[0050] The inside of the core metal 82 of the brush roller 80 is hollow, and a plurality of ventilation holes 83 that communicate with the interior are formed on the outer circumferential surface of the core metal 82. The brush fibers 81 are planted at positions that avoid the ventilation holes 83. Heat can be released through the vent holes 83, and the areas where the vent holes 83 are formed become gaps between the brush fibers, improving the cooling effect.

[0051] The transport guide member 90 can be a plate-shaped guide plate 90a arranged on either side of the transported recording medium S (the image side having toner T, or the non-image side on which no image is formed). In the configuration of this embodiment shown in FIG. 3, the transport guide member 90 is a guide plate 90a disposed on the non-image side of the recording medium S on which no image is formed.

[0052] The guide plate 90a can be made of a thermally conductive metal with a large heat capacity to enhance the cooling effect of the recording medium S. For example, the guide plate 90a can be made of SECC (bonded steel plate), aluminum, or stainless steel.

[0053] The guide plate 90a has an opening 91 that allows ventilation toward the transport path of the recording medium S. The opening 91 may be a louver window.

[0054] The image forming apparatus of this embodiment does not have a mechanism for pressing the brush roller 80 against the recording medium S, so space can be saved even if a blower 95 such as a blower fan is provided. In Figure 3, the direction of air blown by the blower 95 is schematically indicated by an arrow 96. By providing the air blowing means 95, the guide plate 90a that has become hot due to heat accumulation can be quickly cooled, thereby enabling the recording medium S to be cooled efficiently and continuously.

[0055] With the above-described configuration, the image forming apparatus of this embodiment can quickly and efficiently cool the recording medium S after the fixing process without damaging the image. Furthermore, since the brush roller 80 does not pressurize and pinch the recording medium S, and therefore does not become a transport load, even if the recording medium S is a thin paper sheet with weak stiffness, it can be transported smoothly while being cooled.

[0056] <Second embodiment> Fig. 4 is a schematic cross-sectional view of the main parts of the image forming apparatus 1 according to the second embodiment, showing the cooling device 100 disposed downstream of the fixing device 200 and the conveying roller pair 6. Fig. 5 is a cross-sectional view of the main parts taken along the horizontal direction of Fig. 4. Note that Fig. 5 shows only the core metal 82 portion of the brush roller 80, and omits the brush fibers 81. In the configuration of this embodiment, the air blowing means 95 constituting the cooling device is disposed outside the transport area W of the recording medium S, and blows air from the axial end side of the brush roller 80 toward the inside of the core metal 82. The air blowing means 95 may be, for example, an air blowing fan.

[0057] In this embodiment, the hollow portion of the core metal 82 of the brush roller 80 serves as an air passage. Air sent by the air blowing means 95 from the axial end side of the core metal 82 toward the inside of the core metal 82 (arrow 96) is blown out from the ventilation holes 83 communicating with the hollow air passage toward the recording medium S (arrow 96a) to cool the recording medium S.

[0058] In this embodiment, the brush roller 80 has a regulating member 84 that comes into sliding contact with the inner circumferential surface of the core metal 82 and restricts the ventilation range by closing some of the ventilation holes 83. The regulating member 84 is, for example, a member with a U-shaped or horseshoe-shaped cross section, and comes into sliding contact with an area of ​​the inner circumferential surface of the core metal 82 that is away from the transport path of the recording medium S. Of the multiple ventilation holes 83, those that overlap with the regulating member 84 and are closed stop blowing air. As the core metal 82 rotates, the ventilation holes 83 that are opened and separated from the regulating member 84 resume blowing air. In this way, by preventing air from being blown into areas that do not face the transport path of the recording medium S, the cooling effect can be enhanced.

[0059] This configuration allows for rapid cooling of the surface (image surface side) of the recording medium S on which an image having toner T is formed. In addition, since the difference in moisture content between the surface (non-image surface side) of the recording medium S on which no image is formed can be reduced, the effect of reducing curling of the recording medium S can also be obtained.

[0060] <Third embodiment> FIG. 6 is a schematic cross-sectional view of a main part of an image forming apparatus 1 according to a third embodiment, showing a cooling device 100 disposed downstream of a fixing device 200 and a pair of conveying rollers 6. As shown in FIG. In this embodiment, a plurality of brush rollers 80, which are transport roller members, are arranged along the transport path of the recording medium S. It is preferable that each of the plurality of brush rollers 80 is rotated at the same speed as the conveying speed of the recording medium S or at a higher speed so as not to impose a conveying load.

[0061] The configuration of this embodiment makes it possible to lengthen the period in which the recording medium S is cooled. This allows the recording medium S, which has become hot after the fixing process, to be cooled quickly, improving cooling efficiency. Since the heat of the toner T on the recording medium S is dissipated before being transmitted in the thickness direction, effective cooling is possible, particularly in situations in which the recording medium S is transported at high speed.

[0062] <Fourth embodiment> FIG. 7 is a schematic cross-sectional view of a main part of an image forming apparatus 1 according to a fourth embodiment, showing a cooling device 100 disposed downstream of a fixing device 200 and a pair of conveying rollers 6. As shown in FIG. In this embodiment, the brush roller 80, which is a transport roller member, the guide plate 90a, which is a transport guide member, and the air blowing means 95 are arranged on opposite sides of the transport path of the recording medium S. That is, the guide plate 90a and the air blowing means 95 are arranged on the image side of the recording medium S, and the brush roller 80 is arranged on the non-image side.

[0063] By arranging the air blowing means 95 on the image surface side of the recording medium S and blowing air toward the image surface side, it is possible to prevent the image surface having the toner T on the recording medium S from being pressed against the guide plate 90a and causing the image to be rubbed. As in the other embodiments described above, the brush roller 80 is rotated in the direction indicated by R in the drawing at a speed equal to or higher than the transport speed of the recording medium S so as not to impose a transport load. This configuration allows the recording medium S to be cooled quickly after the fixing process.

[0064] <Fifth embodiment> FIG. 8 is a schematic cross-sectional view of a main part of an image forming apparatus 1 according to a fifth embodiment, showing a cooling device 100 disposed downstream of a fixing device 200 and a pair of conveying rollers 6. As shown in FIG. In this embodiment shown in FIG. 8A, the transport guide member 90 is a rotatable guide roller 90b disposed on the non-image side of the recording medium S on which no image is formed. The guide roller 90b forms a roller pair with the brush roller 80, which is a conveying roller member, and therefore the conveying efficiency of the recording medium S is improved.

[0065] The outer diameter of the guide roller 90b is preferably smaller than the outer diameter of the brush roller 80. By using a roller member with a small diameter, space saving can be achieved. The guide roller 90b may be configured by dividing a plurality of roller-shaped members into pieces and connecting them together by a rotation shaft.

[0066] Like the brush roller 80, the guide roller 90b is driven to rotate in the direction indicated by R in the drawing at a speed equal to or higher than the conveying speed of the recording medium S so as not to impose a conveying load. Because the brush roller 80 and the guide roller 90b are not in pressure contact, they cannot be configured to rotate together due to pressure. Therefore, the guide roller 90b can be configured to be drivingly connected to the brush roller 80 via a drive transmission member outside the transport area of ​​the recording medium S. For example, the rotating shaft of the brush roller 80 and the rotating shaft of the brush roller 80 can be connected and driven via a gear or the like.

[0067] The guide roller 90b may be disposed so as to come into contact with the brush fibers 81 of the brush roller 80 with a contact width (nip width) shorter than 5 mm. The guide roller 90b can be configured to be pressurized by a spring or the like in order to maintain the above-mentioned nip width, but this pressure does not cause it to come into pressure contact with the brush roller 80. The contact between the guide roller 90b and the brush roller 80 is different from the pressure contact that clamps the recording medium S under pressure, so the image on the recording medium S does not become rough when it passes through the nip portion. Furthermore, as mentioned above, the guide roller 90b and the brush roller 80 are each driven to rotate, so even if they are arranged to abut at the above-mentioned nip width, this does not interfere with the transport of the recording medium S passing through the nip portion.

[0068] The guide roller 90b may be disposed at a distance from the brush roller 80. It is preferable that the distance be very small. The guide roller 90b does not come into contact with the brush fibers 81 of the brush roller 80, and therefore the image on the recording medium S passing through the opposing area is not roughened. Furthermore, as described above, the guide roller 90b and the brush roller 80 are each rotationally driven, and therefore do not interfere with the conveyance of the recording medium S passing through the nip portion.

[0069] 8(B), a guide plate 90a similar to that of the first embodiment may be provided on the upstream side and / or downstream side of the guide roller 90b in the conveying path as the conveying guide member 90. For example, by providing the guide plate 90a on the upstream side of the guide roller 90b in the conveying path, it is possible to easily guide the leading edge of the recording medium S to the guide roller 90b.

[0070] Sixth Embodiment FIG. 9 is a schematic cross-sectional view of a main part of an image forming apparatus 1 according to a sixth embodiment, showing a cooling device 100 disposed downstream of a fixing device 200 and a pair of conveying rollers 6. As shown in FIG. The present embodiment shown in FIG. 9(A) has a configuration including a guide roller 90b as the transport guide member 90, similar to the fifth embodiment described above. As in the second embodiment (FIGS. 4 and 5), the air blowing means 95 constituting the cooling device is configured to blow air from the axial end side of the brush roller 80 toward the inside of the core metal 82. The brush roller 80 has a regulating member 84 that comes into sliding contact with the inner circumferential surface of the core metal 82.

[0071] The provision of the guide roller 90b improves the efficiency of conveying the recording medium S and also saves space. Furthermore, the recording medium S after the fixing process can be cooled quickly and efficiently without damaging the image.

[0072] 9(B), a guide plate 90a similar to that of the second embodiment may be provided on the upstream side and / or downstream side of the guide roller 90b in the conveying path as the conveying guide member 90. For example, by providing the guide plate 90a on the upstream side of the guide roller 90b in the conveying path, it is possible to easily guide the leading edge of the recording medium S to the guide roller 90b. [Explanation of symbols]

[0073] 1. Image forming device 6 Transport roller pair 7 Paper ejection roller pair 80 Conveying roller member (brush roller) 81 Brush Fiber 82 Core 83 Ventilation hole 84 Regulatory member 90 Conveyor guide member 90a Guide plate 90b Guide roller 95 Ventilation means (blower fan) 100 Cooling device 200 Fixing device 201 Fixing belt 203 Pressure roller S Recording media [Prior art documents] [Patent documents]

[0074] [Patent Document 1] Japanese Patent Application Publication No. 2019-101360

Claims

1. An image forming apparatus including an image forming unit that forms an image on a recording medium, a fixing device that heats and fixes an unfixed image carried on the recording medium, and a cooling device that cools the recording medium on a conveyance path after the recording medium has passed through the fixing device, The cooling device is a conveying roller member that contacts the recording medium sent out from the fixing device without pressing and sandwiching the recording medium; a transport guide member disposed opposite the transport roller member across a transport path of the recording medium; a blowing means for blowing air toward the conveying roller member, The conveying roller member is a brush roller having brush fibers planted on the outer peripheral surface of a core metal serving as a shaft, The core metal of the brush roller is hollow inside, and has a plurality of ventilation holes on the outer circumferential surface of the core metal that communicate with the inside, an image forming apparatus comprising: a restricting member that slides against the inner peripheral surface of the core metal of the brush roller and closes a part of the ventilation holes to restrict the ventilation range;

2. 2. The image forming apparatus according to claim 1, wherein the air blowing means blows air from an axial end side of the brush roller toward the inside of the core metal.

3. 3. The image forming apparatus according to claim 1, wherein the transport guide member is a rotatable guide roller disposed on a non-image side of the recording medium on which no image is formed.

4. An image forming apparatus comprising: an image forming section that forms an image on a recording medium; a fixing device that heats and fixes an unfixed image carried on the recording medium; and a cooling device that cools the recording medium on a transport path that has passed through the fixing device, The cooling device is a conveying roller member that contacts the recording medium sent out from the fixing device without pressing and sandwiching the recording medium; a transport guide member disposed opposite the transport roller member across a transport path of the recording medium; a blowing means for blowing air toward the conveying roller member, The conveying roller member is a brush roller having brush fibers planted on the outer peripheral surface of a core metal serving as a shaft, The image forming apparatus is characterized in that the transport guide member is a rotatable guide roller disposed on a non-image side of the recording medium on which no image is formed.

5. 5. The image forming apparatus according to claim 4, wherein the core of the brush roller is hollow, and the outer circumferential surface of the core has a plurality of vent holes communicating with the interior of the core.

6. 6. The image forming apparatus according to claim 5, wherein the air blowing means blows air from an axial end side of the brush roller toward the inside of the core metal.

7. 7. The image forming apparatus according to claim 5, further comprising a restricting member that slides against the inner peripheral surface of the core of the brush roller and closes a part of the ventilation holes to restrict the ventilation range.

8. The outer diameter of the guide roller is smaller than the outer diameter of the brush roller, 8. The image forming apparatus according to claim 3, wherein the brush roller is drivingly connected to the brush roller via a drive transmission member outside a transport area of ​​the recording medium.

9. 9. The image forming apparatus according to claim 3, wherein the guide roller is disposed so as to come into contact with the brush fibers of the brush roller with a contact width shorter than 5 mm.

10. 9. The image forming apparatus according to claim 3, wherein the guide roller is disposed apart from the brush roller.

11. a driving means for driving the conveying roller member to rotate; 11. The image forming apparatus according to claim 1, wherein the transport roller member rotates at a speed equal to or higher than the transport speed of the recording medium.

12. 12. The image forming apparatus according to claim 1, wherein a plurality of the transport roller members are arranged along a transport path of the recording medium.

13. 3. The image forming apparatus according to claim 1, wherein the transport guide member is a plate-like guide plate disposed on either side of the recording medium being transported.

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