Image forming apparatus

Abstract

An image forming apparatus is disclosed. An image forming apparatus includes an image forming portion, a fixing portion, a housing configured to accommodate the image forming portion and the fixing portion and having an opening portion through which an exterior of the housing and an interior of the housing communicate with each other. The photosensitive member includes a conductive substrate and a surface layer portion formed on an outer periphery of the substrate. In a case where a thickness of the surface layer portion is a distance from an outer peripheral surface of the base to a surface of the photosensitive member, a maximum particle size of particles capable of passing through the filter is smaller than the thickness of the surface layer portion.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus for forming an image on a recording material. Background Art

[0002] Japanese Patent Application Laid-Open No. H9-281825 discloses that an opening portion (discharge port) for discharging water vapor generated in a fixing portion to the outside of the apparatus is provided in a top cover of an image forming apparatus.

[0003] There is a possibility that dust entering the inside of the apparatus through an opening portion provided in a housing of the image forming apparatus causes problems such as image defects or breakage of a film of a fixing portion or an intermediate transfer belt. Summary of the invention

[0004] The present invention provides an image forming apparatus which can reduce problems caused by dust.

[0005] According to one aspect of the present invention, an image forming device includes: an image forming part, which includes a photosensitive member and is configured to form a colorant image on a recording material by using the photosensitive member; a fixing part, which is configured to form a clamping part that clamps the recording material, and is configured to fix the colorant image to the recording material by heating the colorant image while conveying the recording material by using the clamping part; a shell, which is configured to accommodate the image forming part and the fixing part, and has an opening part, the outside of the shell and the inside of the shell are connected to each other through the opening part, and the opening part is positioned above the clamping part in the vertical direction; and a filter, which covers the opening part, wherein the photosensitive member includes a conductive substrate and a surface layer part formed on the periphery of the substrate, and wherein when the thickness of the surface layer part is the distance from the peripheral surface of the substrate to the surface of the photosensitive member, the maximum particle size of particles that can pass through the filter is smaller than the thickness of the surface layer part.

[0006] According to another aspect of the present invention, an image forming device includes: an image forming part, which is configured to form a colorant image on a recording material; a fixing part, which includes a tubular film and a heating part configured to heat the film, the fixing part is configured to form a clamping part for clamping the recording material, and the fixing part is configured to fix the colorant image to the recording material by heating the colorant image using the film; a shell, which is configured to accommodate the image forming part and the fixing part and has an opening part, the outside of the shell and the inside of the shell are connected to each other through the opening part, and the opening part is positioned above the clamping part in the vertical direction; and a filter, which covers the opening part, wherein the maximum particle size of particles that can pass through the filter is smaller than the thickness of the film.

[0007] According to another aspect of the present invention, an image forming device includes: an image forming part, which includes a photosensitive member and an intermediate transfer belt, and is configured to transfer a colorant image formed on the photosensitive member to the intermediate transfer belt by primary transfer and then transfer the colorant image from the intermediate transfer belt to a recording material by secondary transfer; a fixing part, which is configured to form a clamping part that clamps the recording material, and is configured to fix the colorant image to the recording material by heating the colorant image while conveying the recording material using the clamping part; a shell, which is configured to accommodate the image forming part and the fixing part, and has an opening part, the outside of the shell and the inside of the shell are connected to each other through the opening part, and the opening part is positioned above the clamping part in the vertical direction; and a filter, which covers the opening part, wherein the intermediate transfer belt includes a base layer and a surface layer formed on the periphery of the base layer, the surface layer is configured to carry the colorant image, and wherein the maximum particle size of particles that can pass through the filter is smaller than the thickness of the surface layer.

[0008] According to another aspect of the present invention, an image forming device includes: an image forming portion, the image forming portion including a photosensitive member and configured to form a toner image on a recording material by using the photosensitive member; a fixing portion, the fixing portion configured to form a clamping portion for clamping the recording material, and configured to fix the toner image to the recording material by heating the toner image while conveying the recording material using the clamping portion; a housing, the housing configured to accommodate the image forming portion and the fixing portion, and having an opening portion, the outside of the housing and the inside of the housing being connected to each other through the opening portion, the opening portion being positioned in the vertical direction above the clamping portion; and a filter covering the opening portion, wherein the photosensitive member includes a conductive substrate and a surface layer portion formed on the periphery of the substrate, and wherein the filter is formed of an open-cell plastic foam, and wherein α (μm) represents the average value of the cell diameter of the plastic foam in a plane orthogonal to the thickness direction of the filter, β (μm) represents the thickness of the filter, γ (μm) represents the average value of the cell diameter of the plastic foam in the thickness direction of the filter, and δ (μm) represents the distance from the peripheral surface of the substrate to the surface of the photosensitive member, α / (β / γ)<δ is satisfied.

[0009] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a schematic diagram of an image forming apparatus according to an example.

[0011] Figure 1B is an explanatory diagram of a photosensitive drum according to an example.

[0012] Figure 2 is a schematic diagram of an image forming apparatus according to an example.

[0013] Figure 3A is a schematic diagram of an image forming apparatus according to an example.

[0014] Figure 3B is a detailed view of an image forming apparatus according to an example.

[0015] Figure 4A and Figure 4B is a diagram illustrating a discharge port according to an example.

[0016] Figure 5 is a diagram illustrating a ventilation portion and a filter according to an embodiment.

[0017] Figure 6 is a perspective view of a rear door according to an example.

[0018] Figure 7 is a diagram illustrating an example of an image defect caused by dust particles.

[0019] Fig. 8A and Figure 8B is an explanatory diagram of a filter according to an example.

[0020] Fig.9A and Fig. 9B It is an explanatory diagram of a dust-proof performance test of a filter according to an example.

[0021] Fig.10 This is a diagram showing traces of water drops.

[0022] Fig.11 is an explanatory diagram of a dust resistance evaluation test of an image forming apparatus according to an example. DETAILED DESCRIPTION

[0023] Embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0024] Example 1

[0025] In this example, Figure 1A An example of the configuration of an image forming apparatus is described by taking the image forming apparatus 100 shown in FIG. 1 as an example. The image forming apparatus 100 is a monochrome laser printer that forms a monochrome image by an electrophotographic system and forms an image (toner image) on a recording material P by using a toner as a developer according to image information transmitted thereto from an external device such as a personal computer. As the recording material P (recording medium), various sheet materials of different materials can be used. Examples of the various sheet materials include paper sheets such as plain paper and cardboard, irregularly shaped sheets such as envelopes and index paper sheets, and cloth.

[0026] In the following description, the up-down direction (vertical direction, direction along the direction of gravity) of the image forming device 100 when the image forming device 100 is deployed on a horizontal surface will be referred to as the Z-axis direction. The direction of the rotation axis of the photosensitive drum 1 will be referred to as the X-axis direction. The direction intersecting both the X-axis direction and the Z-axis direction will be referred to as the Y-axis direction. The X-axis direction, the Y-axis direction and the Z-axis direction are preferably orthogonal to each other. In the X-axis direction, the positive side (+X side) is referred to as the right side, and the negative side (-X side) is referred to as the left side. In the Y-axis direction, the positive side (+Y side) is referred to as the front side or the front surface side, and the negative side (-Y side) is referred to as the rear side or the rear surface side. In the Z-axis direction, the positive side (+Z side) is referred to as the upper side, and the negative side (-Z side) is referred to as the lower side.

[0027] In this example, the X-axis direction is the width direction of the recording material P which is orthogonal to both the vertical direction and the discharge direction Dc of the recording material P.

[0028] Image forming device

[0029] Figure 1A and Figure 2 is a schematic diagram illustrating a cross section of an image forming apparatus 100 according to Example 1.

[0030] like Figure 1A and Figure 2 As shown in FIG. 1 , the image forming apparatus 100 includes a feeding portion 6, a registration roller pair 8, an image forming portion 10, a fixing portion 9, and a discharge portion 16. In addition, the image forming apparatus 100 includes a housing 101 that accommodates the feeding portion 6, the registration roller pair 8, the image forming portion 10, the fixing portion 9, and the discharge portion 16.

[0031] The feeding section 6 includes a stacking section (box, tray) which is attachable to and detachable from the housing 101 and on which recording materials P are stacked, and a pair of rollers 41 which feed the recording materials P one by one from the stacking section. The registration roller pair 8 conveys the recording material P fed by the feeding section 6 to the transfer nip Ntr at a timing matching the toner image formation in the image forming section 10. The image forming section 10 forms a toner image by performing an electrophotographic process, transfers the toner image to the recording material P in the transfer nip Ntr, and thus forms an image on the recording material P. The fixing section 9 forms a fixing nip Nf serving as a nip section for clamping the recording material P, and fixes the toner image to the recording material P by heating the toner image in the fixing nip Nf while conveying the recording material P. The discharge portion 16 discharges the recording material P on which the image has been formed to the outside of the image forming apparatus 100 (outside of the housing 101 , housing exterior) in a discharge direction Dc intersecting the vertical direction (Z-axis direction).

[0032] Figure 1A The arrow P1 indicates a conveyance path of the recording material P in the case of performing single-sided printing (single-sided image formation) in which the image forming apparatus 100 forms an image only on one surface (first surface) of the recording material P. Note that when an image is formed on the first surface in the case where the image forming apparatus 100 performs double-sided printing (double-sided image formation) in which an image is formed on each of the first surface and the second surface opposite thereto of the recording material P, the recording material P is also conveyed along the path of the arrow P1. Figure 2 An arrow P2 indicates a transport path for transporting the recording material P on the first surface on which image formation has been completed again toward the image forming portion 10 in a case where the image forming apparatus 100 performs double-sided printing.

[0033] A series of operations in which the image forming apparatus 100 performs single-sided printing or double-sided printing while conveying one recording material P and discharges the recording material P to the outside of the image forming apparatus 100 will be referred to as an image forming operation or a sheet transfer operation. An operation in which the image forming apparatus 100 continuously performs an image forming operation on a plurality of recording materials P (sheet transfer operation) will be referred to as continuous sheet transfer. The cumulative sheet number of recording materials P indicating the number of recording materials P on which the image forming apparatus 100 has performed an image forming operation since the image forming apparatus 100 was shipped from a factory or since the image forming apparatus 100 was initialized after shipment will be referred to as a cumulative sheet transfer number.

[0034] In this example, among the recording materials on which the image forming device 100 can form images, the recording material (recording material of the largest size) having the largest width in the X-axis direction (width direction) is a recording material of LTR (letter) size (width: 215.9 mm). In addition, the maximum printing width, which is the width of the area (effective printing area) on which the image forming part 10 can form an image on the LTR size recording material, is 206 mm. Among the recording materials on which the image forming device 100 can form images in this example, the recording material (recording material of the smallest size) having the smallest width in the X-axis direction (width direction) is a recording material of 98.4 mm in width. In other words, in this example, the maximum sheet passing width of the image forming device 100 is 215.9 mm, and the minimum sheet passing width is 98.4 mm.

[0035] That is, in this example, in the width direction orthogonal to both the vertical direction and the discharge direction, the passage area of ​​the recording material with the largest size having the maximum length in the X-axis direction (width direction) among the recording materials on which the image forming device can form an image is an area with a width of 215.9 mm. Furthermore, in this example, the passage area of ​​the recording material with the smallest size in the width direction is an area with a width of 98.4 mm. In this example, the passage area of ​​the recording material extends symmetrically with respect to the center of the conveying path CP in the X-axis direction (width direction). The center of the conveying path CP refers to the center of the space through which the recording material P can pass, and can be Figure 4A The center position in the X-axis direction between the two rubber roller portions 81a positioned at both ends of the discharge drive roller 81 shown in FIG. In addition, in the case where a positioning portion for positioning both ends of the recording material P in the X-axis direction is provided on the stacking portion of the feeding portion 6, the center of the conveying path CP may be the center position between the positioning portions at both ends in the X-axis direction.

[0036] The housing 101 includes a frame of the image forming apparatus 100 and an external member (cover member or door member) serving as an external surface of the image forming apparatus 100. A rear door 14 and an ejection tray 17, which will be described later, are each an example of an external member. A space located outside relative to the external surface of the housing 101 will be referred to as the outside of the image forming apparatus 100 or the outside of the apparatus, and a space located inside relative to the external surface of the housing 101 will be referred to as the inside of the image forming apparatus 100 or the inside of the apparatus. In the interior of the image forming apparatus 100, a conveying path CP serving as a passing space through which a recording material P passes is provided.

[0037] The housing 101 of this example is provided with an inlet port 6s, an outlet port 16s, and a ventilation portion 51. The inlet port 6s, the outlet port 16s, and the ventilation portion 51 are each an opening portion including an opening that communicates the interior of the image forming device 100 with the exterior of the image forming device 100. More specifically, the inlet port 6s, the outlet port 16s, and the ventilation portion 51 are each an opening portion that communicates the conveying path CP with the exterior of the image forming device 100. The inlet port 6s is an opening portion (feeding port) that receives the recording material P fed by the feeding portion 6. The outlet port 16s is an opening portion through which the recording material P discharged by the discharge portion 16 passes. The ventilation portion 51 will be described later.

[0038] In this example, the inlet 6s and the outlet 16s are each one opening, and the ventilation portion 51 includes a plurality of openings (a plurality of ventilation holes 51a to be described later). A plurality of inlet 6s and / or a plurality of outlets 16s may be provided. The ventilation portion 51 may be configured to include only one opening. In addition, the housing 101 may have an opening different from the above-mentioned openings.

[0039] The conveying path Cp includes a main conveying path CP1 and a double-sided conveying path CP2. The main conveying path CP1 is a conveying path extending from the entrance 6s via the transfer nip Ntr and the fixing nip Nf to the discharge port 16s. The double-sided conveying path CP2 is a conveying path that branches from the main conveying path CP1 at a position between the fixing section 9 and the discharge port 16 in the recording material conveying direction in the main conveying path CP1 and merges with the main conveying path CP1 at a position between the roller pair 41 of the feeding section 6 and the registration roller pair 8.

[0040] In other words, the conveying path CP includes a main conveying path CP1 serving as a first conveying path through which the recording material P passes when the image forming section 10 forms an image thereon. Further, the conveying path CP includes a duplex conveying path CP2 serving as a second conveying path that branches from the first conveying path and, in the case where an image is formed on a second surface of the recording material opposite to the first surface, the recording material on the first surface of which a toner image has been formed by the image forming section 10 is conveyed toward the image forming section 10 again through the duplex conveying path CP2.

[0041] The image forming section 10 includes a photosensitive drum 1 serving as an image bearing member, a charging roller 2 serving as a charging section, a scanner unit 4 serving as an exposure section, a developing unit 3 serving as a developing section, a transfer roller 5 serving as a transfer unit, and a pre-exposure unit 23. The developing unit 3 includes a toner container 32 containing a toner T serving as a developer, and a developing roller 31 that carries the toner in the toner container 32 and thereby supplies the toner to the photosensitive drum 1. A transfer nip Ntr serving as a transfer section that performs transfer of an image is formed between the photosensitive drum 1 and the transfer roller 5.

[0042] A part or all of the image forming portion 10 may be a cartridge that is attachable to and detachable from the housing 101. In this case, for example, the housing 101 may include a cover member openably and closably provided on the front surface or upper surface of the housing 101, and attachment and detachment of the cartridge may be allowed by opening the cover member.

[0043] The photosensitive drum 1 is a photosensitive body formed in a cylindrical shape (drum shape). The layer configuration of the photosensitive drum 1 of this example will be described below.

[0044] The photosensitive drum 1 is rotationally driven by a driving source (not shown) at a predetermined circumferential speed about its rotation axis in the direction of arrow R1. The circumferential speed of the photosensitive drum 1 defines the speed of image formation of the image forming apparatus 100 and is also referred to as the process speed. The process speed of this example is, for example, 140 mm / sec.

[0045] The charging roller 2 contacts the photosensitive drum 1 with a predetermined contact pressure, thereby forming a charging portion. In this example, the contact portion (nipping portion) between the charging roller 2 and the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 is about 1 mm. The charging roller 2 includes a conductive substrate. As a result of applying a predetermined charging voltage to the conductive substrate by a charging power source, the charging roller 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential. In this example, the photosensitive drum 1 is negatively charged by the charging roller 2.

[0046] The charging roller 2 used in this example includes a core metal having a diameter of 5 mm as a conductive substrate, a base layer formed of polyepichlorohydrin rubber, and a surface layer formed of polyurethane, and is formed to have an outer diameter of 9.7 mm. In addition, the resistance of the charging roller 2 is 1×10 6 Ω or less, and its hardness as measured by an MD-1 rubber hardness meter is 70°. Note that, although a DC voltage is used as a charging voltage in this example, the configuration is not limited thereto, and the charging voltage may be a voltage in which an AC voltage is superimposed on a DC voltage.

[0047] The core metal is provided with a gear, and as a result of the meshing of the gear with the gear of the photosensitive drum 1, the charging roller 2 rotates at a constant speed relative to the photosensitive drum 1. In this example, the gear ratio and the like are set so that the peripheral speed ratio between the charging roller 2 and the photosensitive drum 1 is about 107% when the image is formed. The peripheral speed ratio between the charging roller 2 and the photosensitive drum 1 is the ratio of the surface speed of the charging roller 2 to the surface speed of the photosensitive drum 1. In the charging portion, as a result of the speed difference between the charging roller 2 and the photosensitive drum 1, the toner attached to the charging roller 2 may be returned to the photosensitive drum 1 by frictional charging.

[0048] In this example, a pressurizing spring is used which presses the charging roller 2 against the photosensitive drum 1. The pressurizing spring presses the bearings of the core metal portion supporting the charging roller 2 at both ends in the charging portion in a direction perpendicular to the surface of the photosensitive drum 1. In the direction of the rotation axis of the photosensitive drum 1 (X-axis direction), the pressing force of the side where the gear of the charging roller 2 is disposed, that is, the driving side, is 7.5N, and the pressing force of the opposite side of the gear, that is, the non-driving side, is 5.6N.

[0049] In order to generate stable discharge at the charged portion, the pre-exposure unit 23 irradiates the region of the surface of the photosensitive drum 1 after passing through the transfer nip Ntr and before reaching the charged portion with light to remove residual charge.

[0050] The scanner unit 4 exposes the surface of the photosensitive drum 1 in a scanning manner by irradiating the photosensitive drum with laser light corresponding to image information input from an external device using a polygon mirror. An electrostatic latent image corresponding to the image information is formed on the exposed surface of the photosensitive drum 1.

[0051] The developing unit 3 supplies toner T to the photosensitive drum 1, thereby developing the electrostatic latent image into a toner image. In this example, a contact developing method is adopted as a developing method, and the toner layer carried on the developing roller 31 contacts the photosensitive drum 1 at a developing portion where the photosensitive drum 1 and the developing roller 31 are opposite to each other. A developing voltage is applied to the developing roller 31 by a developing power source. As a result of the electric field being formed at the developing roller 31 by the developing voltage, the toner carried on the developing roller 31 is transferred from the developing roller 31 to the drum surface according to the potential distribution on the surface of the photosensitive drum 1. Therefore, the electrostatic latent image on the photosensitive drum 1 is visualized as a toner image.

[0052] A polymer toner formed by a polymerization method can be used as the toner T of this example. The normal charging polarity (standard polarity) of the toner T is negative. In addition, the toner particle diameter is 6 μm.

[0053] The transfer roller 5 abuts against the photosensitive drum 1 with a predetermined pressing force, thereby forming a transfer nip Ntr. The transfer roller 5 rotates by following the rotating photosensitive drum 1 or following the recording material P passing through the transfer nip Ntr. A voltage of positive polarity is applied from a transfer power source (not shown) to the core metal of the transfer roller 5. According to the electric field generated by the voltage application, the toner image carried on the photosensitive drum 1 is transferred to the recording material P at the transfer nip Ntr.

[0054] The transfer roller 5 used in this example includes a core metal of a nickel-plated steel rod, and a foam sponge layer mainly formed of nitrile rubber (NBR) and epichlorohydrin rubber on the outer peripheral surface of the core metal. The diameter of the core metal is 8 mm, and the thickness of the foam sponge layer is 3 mm. In addition, as a result of the bearings holding both ends of the core metal being pushed by the spring member, the transfer roller 5 is in pressure contact with the photosensitive drum 1 with a pressing force of 1 kgf (9.8 N).

[0055] In this example, a cleaner-less system (drum cleaner-less system, simultaneous development-cleaning system) is adopted, in which the toner (transfer residual toner) remaining on the photosensitive drum 1 without being transferred to the recording material P at the transfer nip Ntr is collected by the developing unit 3. The transfer residual toner is charged to a negative polarity by the charging roller 2 at the charging portion. The developing voltage is set so that the surface potential of the developing roller 31 relative to the non-image portion of the photosensitive drum 1 is at a positive polarity. Therefore, the transfer residual toner attached to the non-image portion is transferred from the photosensitive drum 1 to the developing roller 31 in the developing portion and is collected by the developing unit 3. The collected transfer residual toner is stirred with the toner T contained in the toner container 32 and used again for development.

[0056] In the drum-less cleaner system, a cleaning member for removing transfer residual toner from the photosensitive drum 1 and a waste toner container for accommodating the removed transfer residual toner can be omitted. Therefore, the image forming apparatus can be miniaturized. It should be noted that, in addition to the configuration of this example, the image forming apparatus 100 may include a cleaning member and a waste toner container instead of the drum-less cleaner system.

[0057] The fixing section 9 is a unit (image heating unit) of a heat fixing system that fixes the toner image to the recording material P by heating the toner image. More specifically, the fixing section 9 heats and presses the toner image on the recording material P while the recording material P to which the toner image has been transferred in the transfer nip Ntr is nipped and conveyed in the fixing nip Nf. As a result, the toner particles are melted and then adhered, thereby fixing the toner image to the recording material P.

[0058] The fixing part 9 of this example is a unit of a film heating system that is excellent in shortening activation time and reducing power consumption. The fixing part 9 includes a fixing film 112 used as a heating member (fixing member), a heater 113 used as a heating part, a heater holder 130 that holds the heater 113, and a pressure roller 110 used as a pressure member. The fixing film 112 is a tubular (ring-shaped) film with flexibility. The heater 113 is held by the heater holder 130 and is disposed in the internal space of the fixing film 112 together with the heater holder 130. The pressure roller 110 is disposed so that the fixing film 112 is inserted between the pressure roller 110 and the heater 113. The fixing clamping portion Nf is formed as a contact portion (clamping portion) between the fixing film 112 and the pressure roller 110.

[0059] The pressure roller 110 is an elastic roller (rubber roller) including a core metal and an elastic layer. As a result of bearings provided at both ends of the core metal being pushed by a pressure spring, the pressure roller 110 is in pressure contact with the heater 113 with the fixing film 112 therebetween. It is to be noted that a configuration may be adopted in which the heater holder 130 (or a supporting member such as a metal bracket supporting the heater holder 130) is pushed toward the pressure roller 110 by a pressure spring.

[0060] A driving force is input from a driving source to a driving gear provided at an end of the core metal, thereby rotating the pressure roller 110. The fixing film 112 rotates by following the rotation of the pressure roller 110 or following the recording material P passing through the fixing nip Nf.

[0061] A typical heater used in a heating unit of a film heating system may be used as the heater 113. For example, the heater 113 is a ceramic heater including a ceramic substrate and a heating resistor disposed on a series circuit on the substrate. Specifically, the heater 113 includes an alumina substrate having a width of 6 mm and a thickness of 1 mm, an Ag / Pd (silver palladium) heating resistor having a height of 10 μm applied on the surface of the substrate by screen printing, and a glass layer having a thickness of 50 μm formed to cover the heating resistor and used as a protective layer.

[0062] As the fixing film 112, a film having a multilayer structure in which different material layers are laminated in the thickness direction can be used. The multilayer structure includes, for example, a base layer sliding on the heater 113, a surface layer in contact with the recording material P, and a conductive primer layer joining the base layer and the surface layer together. The outermost layer in the surface layer is a release layer for suppressing surface contamination. The fixing film 112 of this example has a circumference of 20 mm in outer diameter when the fixing film 112 is formed into a cylindrical shape.

[0063] The base layer requires heat resistance to receive the heat of the heater 113, and also requires strength to slide on the heater 113. As the material of the base layer, metals such as stainless steel (SUS) or nickel, or heat-resistant resins such as polyimide can be used. Metals are stronger than resins, so they can be made thinner, and in addition, they have higher thermal conductivity, so it is more likely to transfer the heat of the heater 113 to the surface layer. In contrast, the specific gravity of the resin is smaller than that of the metal, so it has a smaller heat capacity and is easier to heat. In addition, a thin film of the resin can be formed by coating, so it can be formed at a lower cost. In this example, polyimide resin is used as the material of the base layer of the fixing film 112. In addition, a carbon-based filler is added to the polyimide resin to improve thermal conductivity and strength. The thinner the base layer, the higher the heat transfer efficiency of the fixing film 112, but if the base layer is too thin, sufficient strength may not be obtained. The thickness of the base layer is preferably about 15μm to about 100μm, and is set to 60μm in this example.

[0064] The conductive primer layer is formed of polyimide resin, fluororesin, etc., and its resistance is reduced by adding carbon, etc. The potential of the fixing film 112 during image formation is preferably stabilized by electrically connecting (grounding) the exposed portion of the conductive layer to ground potential.

[0065] As the material of the outermost layer (release layer), fluororesin, such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE) or tetrafluoroethylene-hexafluoropropylene resin (FEP) is preferably used. In this example, PFA, which is excellent in demoulding property and heat resistance among fluororesins, is used, and the resistance value of PFA is adjusted (to medium resistance) by dispersing a conductive agent in the substrate of PFA. The release layer can be formed by covering the peripheral surface of the base layer and the conductive primer layer by a tube, or can be formed by coating the surface of the conductive primer layer with a coating. In this example, the release layer is formed by a coating method that can form the release layer to be thin. The thinner the release layer, the higher the heat transfer efficiency of the fixing film 112, but if the release layer is too thin, the durability of the fixing film 112 may be low. The thickness of the release layer is preferably about 5 μm to about 30 μm, and is set to 10 μm in this example.

[0066] The pressure roller 110 of this example includes, for example, a core metal having an outer diameter of 9 mm and formed of iron and an elastic layer having a thickness of 2.5 mm and formed of silicone rubber on the outer peripheral side of the core metal. The elastic layer is formed of silicone rubber or fluororubber having heat resistance. The outer diameter of the pressure roller 110 is preferably about 10 mm to about 50 mm. The smaller the outer diameter of the pressure roller 110, the smaller the heat capacity, but if the outer diameter is too small, the width of the fixing nip Nf is small, so there is a possibility that the toner image is not sufficiently heated and the fixing of the toner image is degraded. In this example, the outer diameter of the pressure roller 110 is set to 14 mm. The heat capacity can also be suppressed when the elastic layer is thin, but if the elastic layer is too thin, the heat is easily dissipated to the core metal formed of metal, thereby degrading the total thermal efficiency of the fixing part 9, so an appropriate thickness is required.

[0067] A release layer that enhances the demoulding property of the toner can be provided on the outer peripheral surface of the elastic layer of the pressure roller 110. In this example, a release layer formed of a perfluoroalkoxy resin (PFA) is provided. Similar to the release layer of the fixing film 112, the release layer can be formed by covering the surface with a tube or coating the surface with a coating, and in this example, a release layer formed of a tube with a thickness of 20 μm and excellent in durability is used. As the material of the release layer, fluororesins such as PTFE or FEP, fluororubbers with high demoulding properties, silicone rubbers, etc. can be used instead of PFA. When the surface hardness of the pressure roller 110 is low, a larger width of the fixing nip Nf can be obtained at a lower pressure, but if the surface hardness is too low, the durability is degraded. In terms of Asker-C hardness (load: 600g), the surface hardness of the pressure roller 110 of this example is set to 40°.

[0068] A temperature detection element 115 (such as a thermistor) for detecting the temperature of the heater 113 is disposed on the back side of the heater 113. The controller of the image forming apparatus 100 controls the power supply to the heating resistor according to the output signal of the temperature detection element 115, thereby controlling the heating amount of the heater 113 so that the heater 113 is at a predetermined target temperature (adjusted temperature). The controller controls the heating amount of the heater 113 so that the surface temperature of the fixing film 112 at the fixing nip Nf is maintained at a temperature suitable for fixing the toner image. The adjusted temperature of the fixing portion 9 in the case of using a plain paper sheet as the recording material P is, for example, 180°C.

[0069] The discharge portion 16 is a conveying unit (discharge unit) that discharges the recording material P on which the image formation has been completed to the outside of the housing 101. The discharge portion 16 includes a discharge roller pair consisting of a discharge drive roller 81 and a discharge driven roller 82. The discharge drive roller 81 is a drive roller that rotates by receiving a driving force from a driving source, and the discharge driven roller 82 is a driven roller that forms a nip portion with the discharge drive roller 81 and rotates by following the discharge drive roller 81.

[0070] The discharge portion 16 is disposed inside or near the discharge port 16s of the housing 101. The discharge portion 16 clamps and conveys the recording material P in the discharge direction Dc by the discharge drive roller 81 and the discharge driven roller 82, thereby discharging the recording material P from the inside to the outside of the housing 101 through the discharge port 16s. A discharge tray 17 on which the recording material P discharged by the discharge portion 16 is stacked is provided on the upper surface of the housing 101.

[0071] In the case of single-sided printing, Figure 1A As shown in FIG. 1 , the recording material P having passed through the fixing nip Nf is discharged as it is by the discharge portion 16 through the discharge port 16s. In the case of double-sided printing, as shown in FIG. Figure 2As shown in , after the trailing end of the recording material P in the discharge direction Dc has passed through the fixing nip Nf, the discharge drive roller 81 is rotationally driven in the direction opposite to the rotation direction following the discharge direction Dc, and the conveying direction of the recording material P is reversed. That is, the recording material P on which an image has been formed on the first surface while the recording material P is conveyed in the main conveying path CP1 is switched back at the discharge portion 16, and is conveyed to the double-sided conveying path CP2. In other words, in this example, the discharge portion 16 serves as a reverse conveying portion for reversing the recording material P in the case of double-sided printing. It is to be noted that, in addition to the discharge portion 16, a reverse conveying roller pair serving as a reverse conveying portion for reversing the recording material P may be provided. The recording material P conveyed along the double-sided conveying path CP2 is conveyed again to the main conveying path CP1 in a state where its first surface and second surface are switched. Then, an image is formed on the second surface of the recording material P while the recording material P is conveyed again in the main conveying path CP1, and the recording material P is discharged by the discharge portion 16 through the discharge port 16s.

[0072] Duplex transmission path

[0073] The double-sided conveying path CP2 will be described. Figure 2 As shown in FIG. 1 , the double-sided conveying path CP2 is defined by the double-sided guide 13, the double-sided rib 42, the U-shaped guide 43, etc. In other words, the housing 101 includes the double-sided guide 13, the double-sided rib 42, and the U-shaped guide 43. The double-sided guide 13, the double-sided rib 42, and the U-shaped guide 43 are each an example of a guide member that defines a portion of the conveying path CP (a portion of the double-sided conveying path CP2).

[0074] In this example, the main conveying path CP1 extends from the feeding portion 6 approximately in the vertical direction toward the discharge portion 16. The double-sided conveying path CP2 extends from a branch portion of the main conveying path CP1 in the direction opposite to the discharge direction Dc in the Y-axis direction (toward the -Y side), and extends downward in the vertical direction (toward the -Z side). The double-sided conveying path CP2 merges with the main conveying path CP1 via a U-shaped curved portion that is curved so that the double-sided conveying path CP2 curves upward in the vertical direction (toward the +Z side) while extending in the Y-axis direction toward the same side (+Y side) as the discharge direction Dc.

[0075] The double-sided guide 13 defines a portion of the double-sided transport path CP2 (an upstream portion of the double-sided transport path CP2). The double-sided guide 13 is an example of a guide member (a second guide portion) that defines a second transport path. The double-sided guide 13 guides the first surface of the recording material P.

[0076] The double-sided guide 13 has a curved shape to have a convex shape convex upward when viewed in the direction of the rotation axis (X-axis direction) of the photosensitive drum 1. In other words, the upper surface of the double-sided guide 13 (second guide portion) is curved to have a convex shape convex upward when viewed in the width direction (X-axis direction) orthogonal to both the vertical direction and the discharge direction Dc. When viewed in the X-axis direction (width direction), the double-sided guide 13 (second guide portion) is positioned between the discharge port 16s of the housing 101 and the ventilation portion 51 (opening portion) in the direction (Y-axis direction) orthogonal to the vertical direction.

[0077] The double-sided rib 42 is the rear door 14 ( Figure 6 ) part. The double-sided rib 42, together with the guide portion 15a (Figure 3) of the transfer guide unit 15, defines a part of the double-sided conveying path CP2 (a part extending downward in the vertical direction). That is, the guide portion 15a of the transfer guide unit 15 is an example of a relative portion that is opposite to the inner surface 14b of the external member (the rear door 14) and has a gap therebetween. In addition, the guide portion 15a is an example of a guide portion that is opposite to the inner surface 14b of the external member (the rear door 14) and defines a part of the conveying path CP together with the external member (the rear door 14). In other words, the gap (space) provided between the inner surface 14b and the guide portion 15a is a part of the conveying path CP through which the recording material P passes (a part of the double-sided conveying path CP2). It can be said that the space continuous with the gap provided between the inner surface 14b and the guide portion 15a is connected to the outside of the housing 101 through the ventilation portion 51. It is to be noted that the upper end portion of the double-sided rib 42 in this example is opposed to the double-sided guide 13 , and is curved in accordance with the curved shape of the double-sided guide 13 when viewed in the X-axis direction.

[0078] The double-sided rib 42 includes a plurality of rib shapes 42a ( Figure 6 ). The rib shapes 42a each protrude inwardly of the housing 101 (toward the +Y side) relative to the inner surface 14b of the rear door 14, and extend substantially in the Z-axis direction. That is, the rear door 14 has a rib shape that protrudes from the inner surface 14b in a direction approaching the guide portion 15a of the transfer guide unit 15 and extends in the recording material conveying direction in the conveying path. The double-sided rib 42 contacts the recording material P on the ridge line portion (end surface on the +Y side) of the rib shape 42a, and guides the second surface of the recording material P.

[0079] The U-shaped guide 43 defines a curved portion of the double-sided transport path CP2. The U-shaped guide 43 guides the first surface of the recording material P.

[0080] Jam removal

[0081] In the event of a jam that occurs in which a recording material P remains in the image forming apparatus 100 during printing, the user may perform so-called jam removal in which the remaining recording material P is removed from the inside of the image forming apparatus 100 .

[0082] like Figure 3A and Figure 3B As shown in FIG. 1 , a housing 101 of the image forming apparatus 100 includes a rear door 14 and a transfer guide unit 15. The rear door 14 and the transfer guide unit 15 are each an opening / closing member provided to be openable and closable relative to other parts of the housing 101. In the case where a user performs jam removal, the rear door 14 and the transfer guide unit 15 are opened and closed.

[0083] The housing 101 of the image forming apparatus 100 includes a rear door 14 and a transfer guide unit 15. The rear door 14 is an exterior member (rear cover) having an outer surface 14a serving as an exterior surface (second exterior surface) of the rear side (-Y side) of the housing 101.

[0084] The rear door 14 can be moved to an open position ( Figure 3A and Figure 3B ), and the closed position where the main body opening 101a is closed ( Figure 1A ). The rear door 14 of the present example pivots about a hinge portion 141 provided at a lower end portion of the rear door 14 positioned at the closed position, about an axis extending in the X-axis direction. When the rear door 14 is in the closed position, the recording material P can pass through the double-sided conveying path CP2. That is, the closed position of the rear door 14 is a position when the image forming device 100 can perform an image forming operation. When the rear door 14 is in the open position, at least a portion of the double-sided conveying path CP2 is opened, so that the recording material P retained in the double-sided conveying path CP2 can be accessed from the outside of the housing 101. In other words, in a state where the rear door 14 serving as an external member is positioned in the open position, it is allowed to remove the recording material P from a portion of the conveying path CP (double-sided conveying path CP2) through the main body opening 101a.

[0085] The transfer guide unit 15 includes a guide portion 15a that defines a portion of the double-sided transport path CP2 together with the double-sided ribs 42 of the rear door 14, and the above-mentioned transfer roller 5. The transfer guide unit 15 is disposed between the rear door 14 and the photosensitive drum 1. More specifically, the transfer guide unit 15 is disposed between the photosensitive drum 1 and the gap (space) provided between the inner surface 14b and the guide portion 15a. In the vertical direction, the transfer guide unit 15 is positioned below the ventilation portion 51, and the upper end of the transfer guide unit 15 is positioned above the photosensitive drum 1.

[0086] The transfer guide unit 15 can be moved to a closed position (blocking position, Figure 1A ) and the open position (exposed position, Figure 3A and Figure 3B ). The transfer guide unit 15 of this example pivots around a hinge portion 151 provided at a lower end portion of the transfer guide unit 15 positioned at the closed position, around an axis extending in the X-axis direction. The position of the hinge portion 151 may be referred to as the position of the rotation axis of the transfer guide unit 15. In the vertical direction, the position of the rotation axis of the transfer guide unit 15 is positioned above the ventilation portion 51 and the photosensitive drum 1.

[0087] When the transfer guide unit 15 is in the closed position, the recording material P can pass through the main transport path CP1. That is, the closed position of the transfer guide unit 15 is a position when the image forming apparatus 100 can perform an image forming operation. When the rear door 14 is in the open position and the transfer guide unit 15 is in the open position, at least a portion of the main transport path CP1 is opened, so that the recording material P retained in the main transport path CP1 can be accessed from the outside of the housing 101.

[0088] The transfer guide unit 15 of this example is urged by a spring member in a direction from an open position toward a closed position. By urging the transfer guide unit 15 by a spring member, the contact pressure between the transfer roller 5 and the photosensitive drum 1 can be made more stable.

[0089] In the case where the recording material P is retained in the main conveying path CP1, as shown in FIG. Figure 3A and Figure 3B As shown in FIG. 1 , the user opens both the rear door 14 and the transfer guide unit 15 . Figure 3A and Figure 3B 1 is a schematic diagram and a detailed diagram illustrating jam removal in a case where the recording material P fails to pass through the fixing portion 9 and remains in the main transport path CP1. The user can grab and remove the recording material P remaining in the main transport path CP1 by opening both the rear door 14 and the transfer guide unit 15. Then, the user closes the rear door 14 and the transfer guide unit 15 again, and thus the image forming apparatus 100 returns to a state where an image forming operation can be performed.

[0090] like Figure 2 As shown in FIG. 1 , in duplex printing, when the recording material P passes through the duplex transport path CP2, a paper jam may occur. In this case, it is sufficient for the user to open only the rear door 14. By opening the rear door 14, the user can grab and remove the recording material P stuck in the duplex transport path CP2. Then, the user closes the rear door 14 again, and thus the image forming apparatus 100 returns to a state where an image forming operation can be performed.

[0091] Layer configuration of the photosensitive drum

[0092] Will refer to Figure 1B The layer configuration of the photosensitive drum 1 is described. Figure 1B The layer configuration of the photosensitive drum 1 is schematically illustrated. The photosensitive drum 1 includes a conductive substrate (hereinafter simply referred to as substrate 1a) and a surface layer portion 1b formed on the periphery of the substrate 1a. The surface layer portion 1b of the present embodiment includes an undercoat layer 1b1, a charge generating layer 1b2, and a charge transporting layer 1b3.

[0093] The charge generation layer 1b2 and the charge transport layer 1b3 function as a photosensitive layer (photoconductive layer) that attenuates the potential of the surface 1s in response to light irradiation. The charge generation layer 1b2 absorbs light radiated from the scanner unit 4, thereby generating charges. The charge transport layer 1b3 has a function as an insulating layer that retains the surface charge imparted to the surface 1s in the charging step, and has a function of transporting the charges generated in the charge generation layer 1b2 to the surface 1s.

[0094] The photosensitive layer of this example is an organic photoconductor (OPC) that can be negatively charged. That is, when a pair of charges is generated in the charge generation layer 1b2 in response to light irradiation, the charge transport layer 1b3 transports positive charges toward the surface 1s of the photosensitive drum 1, thereby neutralizing the negative surface charge imparted to the surface 1s in the charging step. Therefore, the surface potential of the irradiated area irradiated with light from the scanner unit 4 is attenuated, thereby forming an electrostatic latent image on the surface 1s of the photosensitive drum 1.

[0095] The photosensitive drum 1 rotates around a rotation axis Ax. In this example, the direction of the rotation axis Ax is parallel to the X-axis direction. The direction orthogonal to the rotation axis Ax of the photosensitive drum 1 will be referred to as the radial direction Dr of the photosensitive drum 1. The radial direction Dr is the radial direction of a virtual circle centered on the rotation axis Ax when viewed in the X-axis direction.

[0096] The distance from the outer peripheral surface of the substrate 1a to the surface 1s of the photosensitive drum 1 in the radial direction Dr will be referred to as the thickness δ (μm) of the surface layer portion 1b. In the present embodiment, the film thickness of the undercoat layer 1b1 is 25 μm, the film thickness of the charge generating layer 1b2 is 1 μm, and the film thickness of the charge transporting layer 1b3 is 22 μm. Therefore, the thickness δ of the surface layer portion 1b of the photosensitive drum 1 is 25+1+22=48 (μm). It should be noted that the film thickness of each layer constituting the surface layer portion 1b is not limited to this, and the total thickness of the surface layer portion 1b is not limited to this.

[0097] The layer configuration of the surface layer portion 1b is not limited to the above configuration. For example, the surface layer portion 1b may include a release layer (protective layer) for improving the releasability of the toner on the peripheral surface of the charge transport layer 1b3. In this case, the film thickness of the release layer (protective layer) is included in the thickness of the surface layer portion 1b. In addition, a photosensitive layer having a single-layer structure including a charge generating material and a charge transporting material may be used instead of the charge generating layer 1b2 and the charge transporting layer 1b3.

[0098] The surface layer portion 1b of the photosensitive drum 1 gradually wears as the cumulative sheet passing number of the image forming apparatus 100 increases. Unless otherwise described, the thickness of the surface layer portion 1b in this embodiment is based on the state just after shipment (the state where the cumulative sheet passing number is substantially 0).

[0099] A more specific configuration example of the photosensitive drum 1 will be described below. The base 1a is a drum-shaped (cylindrical) member (aluminum cylinder) formed of aluminum and having a diameter of 24 mm. The surface layer portion 1b is formed by sequentially coating an undercoat layer 1b1, a charge generating layer 1b2, and a charge transporting layer 1b3 on the outer peripheral surface of the base 1a by dip coating. The photosensitive drum 1 is a cylindrical member having a relatively high rigidity as a whole.

[0100] Examples of the undercoat layer 1b1 include a layer mainly formed by a resin, a layer mainly formed by a white pigment and a resin, and a metal oxide film obtained by chemically or electrochemically oxidizing the surface of the substrate 1a. Examples of the resin used for the undercoat layer 1b1 include thermoplastic resins such as polyamide resins, polyvinyl alcohol resins, casein resins and methylcellulose resins, and thermosetting resins such as acrylic resins, phenolic resins, melamine resins, alkyd resins, unsaturated polyester resins and epoxy resins. Examples of white pigments include metal oxides such as titanium oxide, aluminum oxide, zirconium oxide and zinc oxide. Among these, titanium oxide having excellent resistance to charge injection from the substrate 1a is a preferred white pigment. In the white pigment in the undercoat layer 1b1, the use amount of titanium oxide is 60% to 100% by weight, preferably 70% to 100% by weight, and more preferably 80% to 100% by weight. When the use amount of titanium oxide is less than 60%, the characteristics of the undercoat layer may change according to environmental changes, and the effect of blocking charge injection from the conductive support becomes unstable, which may be undesirable.

[0101] The undercoat layer 1 b 1 is formed between the substrate 1 a and the photosensitive layer (charge generating layer 1 b 2 and charge transporting layer 1 b 3 ), and functions as an intermediate layer for limiting charge injection from the substrate 1 a to the photosensitive layer.

[0102] As the material of the photosensitive layer (charge generating layer 1 b 2 and charge transporting layer 1 b 3 ), known organic materials and inorganic materials can be used, and as a method for forming the photosensitive layer, a known method can be used.

[0103] Examples of the charge generating material used for the charge generating layer 1b2 include organic pigments and dyes such as monoazo pigments, disazo pigments, triazo pigments, tetrazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine colorants, styryl colorants, pyran dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indanthrone pigments, squaric acid pigments, and phthalocyanine pigments, and inorganic materials such as selenium, selenium-arsenic, selenium-tellurium, cadmium sulfide, zinc oxide, titanium oxide, and amorphous silicon. These charge generating materials may be used alone or as a mixture.

[0104] Examples of the charge transport material used for the charge transport layer 1b3 include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styrylhydrazone compounds, enamine compounds, butadiene compounds, distyryl compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, and triphenylmethane derivatives. These charge transport materials may be used alone or as a mixture.

[0105] In addition, examples of binder resins that can be used to form the photosensitive layer include known thermoplastic resins, thermosetting resins, photocurable resins, and photoconductive resins. Examples of suitable binder resins include thermoplastic resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, ethylene-vinyl acetate copolymers, polyvinyl butyral, polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, polyether sulfone, and ABS resin, thermosetting resins such as phenolic resins, epoxy resins, polyurethane resins, melamine resins, isocyanate resins, alkyd resins, silicone resins, and thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene. These resins can be used alone or as a mixture.

[0106] Exhaust

[0107] Will refer to Figure 4A and Figure 4B The configuration of the discharge port 16s of the present example will be described. Figure 4A is a schematic diagram illustrating the discharge port 16 of the present example when viewed from the front side (+Y side) of the image forming apparatus 100, and Figure 4B yes Figure 4BDetailed diagram of.

[0108] In this example, the discharge port 16s is formed on the wall surface 101f ( Figure 1A ) and is an opening through which the recording material P discharged by the discharge portion 16 passes. In other words, the housing 101 includes the wall surface 101f serving as a first outer surface facing the discharge direction Dc and provided with the discharge port 16s through which the recording material P discharged by the discharge portion 16 passes. It is to be noted that the wall surface 101f extends upward from the upstream end of the discharge tray 17 in the discharge direction Dc, and serves as a standard surface for aligning the recording material P by abutting against the trailing end of the recording material P stacked on the discharge tray 17.

[0109] More specifically, in this example, the discharge port 16s is an opening defined in the wall surface 101f of the housing 101 when the image forming apparatus 100 is viewed from the front side (+Y side) and extending to the inside of the image forming apparatus 100. In this example, the conveying path CP, which is the space inside the image forming apparatus 100, and the space outside the image forming apparatus 100 are connected to each other through the discharge port 16s.

[0110] Here, the configuration of the discharge portion 16 will be described. Preferably, at least one of the rollers in the roller pair for clamping and conveying a sheet material such as a recording material P is a split roller including a plurality of rotating members (a driving roller portion and a driven roller portion), each of which is in contact with the recording material P. The split roller is a roller including a plurality of rotating members, each of which has a width smaller than a maximum width of the recording material P serving as a conveying target in a width direction of the recording material P orthogonal to a discharge direction Dc of the recording material P, and the plurality of rotating members are arranged in the width direction. As a result of using the split roller, a situation in which the contact pressure becomes insufficient in a partial region in the width direction due to warping of the roller or the rollers in the roller pair do not contact each other is less likely to occur, and thus the recording material P can be conveyed more stably.

[0111] Each roller of the roller pair for pinching and conveying the sheet material may be a split roller. The discharge portion 16 of the present example is a roller pair including a discharge drive roller 81 and a discharge driven roller 82 each serving as a split roller.

[0112] The discharge drive roller 81 includes a shaft 81b extending in the width direction and a plurality of rubber roller parts 81a used as a plurality of rotating members. In this example, four rubber roller parts 81a are attached to one shaft 81b. A drive gear is provided at the end of the shaft 81b, and a driving force is inputted therein from a driving source via the drive gear. As a result of the driving force being inputted to the shaft 81b, the shaft 81b and the four rubber roller parts 81a rotate integrally.

[0113] The discharge driven roller 82 includes a plurality of roller parts 82a used as a plurality of rotating members, a plurality of roller retainers 82b that keep the roller parts 82a, and a plurality of springs 82c that push the roller retainers 82b. The discharge driven roller 82 of this example includes four roller parts 82a used as a plurality of rotating members, four roller retainers 82b that keep the roller parts 82a, and four springs 82c corresponding to the four rubber roller units 81a of the discharge drive roller 81. The roller parts 82a are each rotatably supported by a corresponding roller retainer 82b. In addition, as a result of each roller retainer 82b being pushed by a corresponding spring 82c, the roller parts 82a corresponding thereto are in pressure contact with a corresponding rubber roller part 81a. Each roller part 82a rotates by following a corresponding rubber roller part 81a.

[0114] In four areas separated from each other in the width direction, nip portions are formed where the rubber roller portion 81a of the discharge drive roller 81 contacts the roller portion 82a of the discharge driven roller 82. The discharge portion 16 nip the recording material P in the above-mentioned nip portions and conveys the recording material P in the discharge direction Dc by the rotational drive of the discharge drive roller 81.

[0115] Since the discharge portion 16 has the above-described configuration, a region serving as a rotating member where no split roller exists is defined inside the opening 101h defined in the wall surface 101f of the housing 101 ( Figure 4A That is, in this example, the “discharge port 16s” is an area obtained by excluding portions such as the rubber roller portion 81a of the discharge drive roller 81 and the roller portion 82a of the discharge driven roller 82 (i.e., portions through which the recording material P cannot pass) from the area inside the opening 101h provided in the wall surface 101f of the housing 101 when the image forming apparatus 100 is viewed from the front side (+Y side).

[0116] Ventilation area near the fixing section

[0117] The ventilation portion 51 serving as an opening portion provided near the fixing portion 9 of the image forming apparatus 100 will be described below. Figure 5 1 is a schematic diagram illustrating the ventilation portion 51 , and illustrates a cross section of the rear door 14 orthogonal to the X-axis direction provided with the ventilation portion 51 . Figure 6 is a perspective view of the rear door 14. It should be noted that Figure 5 The diagram shows the Figure 6 In addition, as will be described later, since the filter 50 covering the ventilation portion 51 is provided, the position of each ventilation hole 51a of the ventilation portion 51 is Figure 6 Indicated by dotted lines.

[0118] like Figure 5As shown in FIG. 1 , the ventilation portion 51 includes at least one ventilation hole 51 a serving as an opening for communicating the outside and the inside of the image forming apparatus 100. More specifically, the outside of the image forming apparatus 100 communicates with the conveying path CP (particularly, the double-sided conveying path CP2 in this example) which is a space inside the image forming apparatus 100 through the ventilation hole 51 a. The ventilation portion 51 of this example includes a plurality of ventilation holes 51 a.

[0119] The ventilation hole 51a is opened toward the outside of the image forming apparatus 100 in the outer surface 14a, which is a surface facing the direction (-Y direction) opposite to the discharge direction Dc of the rear door 14. In other words, the housing 101 includes the outer surface 14a, which serves as a second outer surface facing the direction opposite to the discharge direction Dc of the recording material P and provided with an opening portion (ventilation portion 51) through which the outside of the housing 101 and the conveying path CP through which the recording material P passes in the housing 101 communicate with each other.

[0120] In the image forming apparatus 100, heat is generated in the fixing portion 9 as a heat fixing system. When heat is accumulated in the image forming apparatus 100, for example, there is a possibility that the temperature of the toner rises and thus the properties of the toner change or the aging of parts of the image forming apparatus 100 is accelerated. The ventilation portion 51 suppresses these problems by discharging the heat generated in the fixing portion 9 to the outside of the image forming apparatus 100.

[0121] Furthermore, in the fixing portion 9, water vapor is generated from the recording material P heated when passing through the fixing nip Nf. When the water vapor is accumulated in the image forming apparatus 100, for example, there is a possibility that water condensation occurs in the conveying path CP and thus water droplets adhere to the recording material P to cause image defects or accelerate aging of parts of the image forming apparatus 100 (rusting of metal members, etc.). The water vapor generated in the fixing portion 9 is discharged to the outside of the image forming apparatus 100 through the ventilation portion 51, thereby suppressing these problems. In the Z-axis direction, the ventilation portion 51 is positioned above the photosensitive drum 1.

[0122] Heat and water vapor tend to move upward. Therefore, at least a portion of the ventilation portion 51 is positioned above the upper end position of the fixing nip Nf in the Z-axis direction ( Figure 1A ). In addition, at least a portion of the discharge port 16s is positioned above the upper end position of the fixing nip portion Nf in the Z-axis direction ( Figure 1A ). In other words, at least a portion of the discharge port 16s and at least a portion of the opening portion (ventilation portion 51) are positioned above the upper end position of the nip portion (fixing nip Nf) in the vertical direction.

[0123] The ventilation portion 51 of this example is disposed at the upper end portion of the outer surface 14a of the rear door 14 constituting the outer surface (second outer surface) of the rear side of the image forming device 100. In this example, the lower end position of the ventilation portion 51 is positioned above the upper end position of the fixing clamp Nf in the Z-axis direction. In addition, in this example, the lower end position of the discharge port 16s is positioned above the upper end position of the fixing clamp Nf in the Z-axis direction. It should be noted that the ventilation portion 51 may also be provided in the top surface of the housing 101.

[0124] Hereinafter, the range in which the ventilation portion 51 is provided in the X-axis direction (width direction) will be referred to as the installation range of the ventilation portion 51. In the case where the ventilation portion 51 includes a plurality of ventilation holes 51a (a plurality of openings) provided at different positions in the X-axis direction as in the present example, the installation range of the ventilation portion 51 can be defined as follows. That is, the range in the X-axis direction from the farthest ventilation hole 51a1 (first opening) on ​​one side (+X side) in the X-axis direction among the plurality of ventilation holes 51a to the farthest ventilation hole 51a2 (second opening) on ​​the other side (-X side) in the X-axis direction is defined as the installation range of the ventilation portion 51. As Figure 6 As shown in , in the X-axis direction, the installation range of the ventilation portion 51 overlaps with the position of the dotted line L. In other words, the dotted line L is positioned between one end (the position of the ventilation hole 51a1) and the other end (the position of the ventilation hole 51a2) of the installation range of the ventilation portion 51 in the X-axis direction. It is to be noted that the position of the dotted line L in the X-axis direction coincides with the position of the center of the transport path CP in the X-axis direction and the position of the center of the passing area of ​​the recording material P in the X-axis direction.

[0125] In the fixing portion 9, heat for fixing the toner image is mainly generated in the passage area of ​​the recording material P in the X-axis direction (width direction). In addition, water vapor is generated from the recording material P by heating the recording material P in the fixing nip Nf, and thus water vapor is generated in the passage area of ​​the recording material P in the X-axis direction (width direction). Here, among the recording materials P on which the image forming operation can be performed by the image forming apparatus 100, the recording material P having the largest size in the X-axis direction (width direction) will be referred to as the recording material P of the largest size. Therefore, the installation range of the ventilation portion 51 preferably overlaps with the passage area of ​​the recording material P of the largest size in the X-axis direction (width direction). In this example, the installation range of the ventilation portion 51 overlaps with the passage area of ​​the recording material P of the LTR size which is the maximum sheet passing width of the image forming apparatus 100, whereby the heat and water vapor generated in the fixing portion 9 can be efficiently discharged to the outside of the image forming apparatus 100.

[0126] In the X-axis direction (width direction), the length of the installation range of the ventilation portion 51 (the length from one end to the other end of the installation range of the ventilation portion 51) is preferably 50% or more of the length of the conveying path CP, and more preferably 70% or more. In addition, in the X-axis direction, the length of the installation range of the ventilation portion 51 is preferably 50% or more of the length of the maximum size of the recording material P, and more preferably 70% or more. In addition, in the X-axis direction, it is preferred that the installation range of the ventilation portion 51 includes the range of the maximum width (effective printing area) in which the image forming portion 10 can form an image. In this example, in the X-axis direction (width direction), the length of the installation range of the ventilation portion 51 is 90% or more of the maximum size of the recording material P. For the above reasons, in the fixing portion 9, heat and water vapor are mainly generated in the passage area of ​​the recording material P of the maximum size (more specifically, in the passage area of ​​the recording material P of the maximum size) (more specifically, in the effective printing area of ​​the recording material P of the maximum size). Therefore, as a result of the ventilation portion 51 being provided within a range having a predetermined ratio or greater relative to the maximum size of the recording material P and including an effective printing area for the maximum size of the recording material P, heat and water vapor generated in the fixing portion 9 can be efficiently discharged to the outside of the image forming device 100.

[0127] Here, among the recording materials P on which the image forming apparatus 100 can perform an image forming operation, the recording material P having the smallest size in the X-axis direction (width direction) will be referred to as the smallest-sized recording material P. The installation range of the ventilation portion 51 preferably includes at least the passage area of ​​the smallest-sized recording material P. That is, the length of the installation range of the ventilation portion 51 in the X-axis direction (width direction) is greater than the length of the smallest-sized recording material P. This is because, regardless of the size of the recording material P, at least a portion of the recording material P on which an image is formed by the image forming apparatus 100 always passes through the passage area of ​​the smallest-sized recording material P, and thus water vapor is likely to be generated in the passage area of ​​the smallest-sized recording material P.

[0128] In the case where the air permeability of the ventilation portion 51 is higher, the amount of heat and water vapor that can be discharged through the ventilation portion 51 is larger, and thus the problem caused by the accumulation of heat and water vapor can be more reliably suppressed. However, if the air permeability of the ventilation portion 51 is too high, then in the case where wind blows in from the front side (+Y side) of the image forming device 100, the wind speed from the discharge port 16s through the conveying path CP and then through the ventilation portion 51 becomes higher, and dust becomes more likely to enter. Therefore, the air permeability of the ventilation portion 51 can be set in consideration of the balance between the amount of heat and water vapor that can be discharged from the ventilation portion 51 and the suppression of dust from entering through the discharge port 16s. Specifically, the number of ventilation holes 51a of the ventilation portion 51, the opening area of ​​each individual ventilation hole 51a, the total opening area of ​​all ventilation holes 51a included in the ventilation portion 51, etc. can be set in consideration of the above-mentioned balance.

[0129] like Figure 6 As shown in , in this example, each ventilation hole 51a has a circular shape, and its diameter is, for example, 5 mm. It is to be noted that the shape and size of the ventilation hole 51a may be changed.

[0130] The ventilation portion 51 of this example is arranged so that three rows of ventilation holes 51a are arranged in the Z-axis direction, and nineteen ventilation holes 51a are arranged in the X-axis direction (width direction) in each row of ventilation holes 51a. That is, the ventilation portion 51 includes a total of fifty-seven ventilation holes 51a. The width of the range in which the ventilation portion 51 is provided in the X-axis direction (width direction) is 209 mm, which is larger than the width (206 mm) of the effective printing area for the recording material P of the maximum size (LTR size).

[0131] Furthermore, the ventilation holes 51a are disposed in the region between the plurality of rib shapes 42a of the double-sided rib 42 included in the rear door 14 in the X-axis direction (width direction). The ventilation holes 51a penetrate from the outer surface 14a to the inner surface 14b ( Figure 5 ).

[0132] Filters

[0133] The filter 50 included in the image forming apparatus 100 of this example will be described. Figure 5 and Figure 6 As shown in FIG. 1 , the image forming apparatus 100 includes a filter 50 disposed to cover a ventilation portion 51. More specifically, at least one filter 50 covering each ventilation hole 51a of the ventilation portion 51 is attached to the inner surface 14b of the rear door 14. By providing the filter 50 covering the ventilation portion 51, as will be described later, the occurrence of image defects caused by dust entering the interior of the image forming apparatus 100 through the ventilation hole 51a can be suppressed.

[0134] It is to be noted that in the present disclosure, foreign matter that can be blown into the interior of the image forming apparatus 100 by the airflow flowing from the exterior to the interior of the image forming apparatus 100 will be collectively referred to as “dust.” Therefore, “dust” may be particles other than sand (e.g., particles derived from plastic or wood), or may include a plurality of particles.

[0135] In the case where the filter 50 is not provided on the ventilation portion 51, dust having entered the inside of the image forming apparatus 100 through the ventilation hole 51a is likely to move in the image forming apparatus 100 and adhere to the photosensitive drum 1. In particular, when dust greater than the thickness of the surface layer portion 1b of the photosensitive drum 1 (48 μm in this example) adheres to the photosensitive drum 1, the dust is likely to form a scratch that penetrates the surface layer portion 1b when passing through the contact portion of the photosensitive drum 1 with another member.

[0136] For example, dust may be strongly pushed into the surface layer portion 1b of the photosensitive drum 1 at the contact portion (charging nip) between the charging roller 2 and the photosensitive drum 1, thereby forming a scratch on the surface layer portion 1b. Therefore, in the image formed on the recording material P, an image defect in the shape of a black dot (referred to as a black dot image) occurs at a position corresponding to the scratch in the surface layer portion 1b of the photosensitive drum 1.

[0137] More specifically, when a scratch penetrating the surface layer portion 1b is formed by dust, the function of the charge transport layer 1b3 to maintain the surface charge imparted to the surface 1s in the charging step and the function of the undercoat layer 1b1 (intermediate layer) to restrict the charge injection from the substrate 1a to the photosensitive layer may be degraded. In this case, at the portion where the scratch is formed, the photosensitive drum 1 cannot maintain the surface charge imparted in the charging step, and due to the charge injection from the substrate 1a, the surface potential of the photosensitive drum 1 becomes closer to the potential (ground potential) of the substrate 1a. In addition, regardless of whether the portion has been exposed, the toner image is developed at the portion where the scratch is formed, so that a black dot image appears.

[0138] Figure 7 An example of a black dot image is shown in the figure. Figure 7 As shown in FIG. 1 , black dots appear periodically at intervals corresponding to the peripheral length of the photosensitive drum 1 according to the positions of the scratches on the surface layer portion 1b of the photosensitive drum 1. For each scratch formed on the photosensitive drum 1, a black dot image appears repeatedly in the conveying direction of the recording material P at a period corresponding to the peripheral length of the photosensitive drum 1. A line of black dot images that appear periodically as described above will be defined as a stripe of a black dot image. In addition, as the number of scratches on the surface layer portion 1b of the photosensitive drum 1 increases, the number of stripes of the black dot image increases.

[0139] The filter 50 is formed of a material having air permeability, moisture permeability, and high heat and moisture resistance. In this example, a sheet material of moltopren (registered trademark) SM-55, which is a polyurethane foam manufactured by INOAC CORPORATION, is used as the filter 50 .

[0140] Furthermore, in this example, a sheet obtained by heating and pressurizing a sheet material (raw sheet) of the above-mentioned polyurethane foam to compress the sheet material in the thickness direction is used as the filter 50. The thickness of the raw sheet is 2 mm, and the thickness of the filter 50 is 1 mm.

[0141] The thickness of the filter 50 of this example is set so that the filter 50 does not come into contact with the recording material P conveyed in the double-sided conveying path CP2. Figure 5 As shown in , at each position within the range in which the filter 50 is provided in the Z-axis direction, the thickness of the filter 50 is smaller than the protrusion amount of the rib shape 42a of the double-sided rib 42 relative to the inner surface 14b of the rear door 14. In other words, the thickness of the filter 50 is smaller than the minimum value H1 of the protrusion height of the double-sided rib 42 relative to the inner surface 14b of the rear door 14. The minimum value H1 of the protrusion amount of the rib shape 42a is, for example, 3.5 mm, and the thickness of the filter 50 is 1 mm.

[0142] When the filter 50 contacts the recording material P conveyed in the double-sided conveying path CP2, skew or jam of the recording material P may occur, or the recording material P may be contaminated by water droplets or foreign matter attached to the filter 50. By setting the thickness of the filter 50 to be smaller than the protruding height of the double-sided ribs 42, the possibility of such problems can be reduced.

[0143] For example, the filter 50 is attached to the inner surface 14b of the rear door 14 using a double-sided tape or adhesive. In the case where the filter 50 is attached to the inner surface 14b using a double-sided tape, it is preferred that the holes defined in the double-sided tape overlap with the ventilation portion 51 so as to suppress the clogging of the ventilation portion 51 by the double-sided tape. Figure 6As shown in , the central filter 50 among the nine filters 50 covers more ventilation holes 51a than the other eight filters 50, and is wider than the other eight filters 50 in the X-axis direction. Therefore, for the central filter 50, by setting the length of the central filter 50 in the Z-axis direction to be greater than the length of the other eight filters 50, it is possible to suppress the central filter 50 from being attached to the wrong position (misassembly). That is, in the case where a plurality of filters 50 are provided and the length of a portion of the filter 50 in a predetermined direction is different from the length of the other filters 50, misassembly can be reduced by making the length of the portion of the filter 50 in a direction orthogonal to the predetermined direction different from the length of the other filters 50. As described above, the plurality of filters 50 may include a filter 50 having a first shape and a filter 50 having a second shape different from the first shape.

[0144] Fig. 8A and Figure 8B is a conceptual diagram of the filter 50 of this example. Fig. 8A is a diagram showing a raw material sheet 50S (moltopren SM-55) before pressing, and Figure 8B is a diagram illustrating the filter 50 obtained by pressing. Fig. 8A and Figure 8B , the shaded area indicates the polyurethane matrix, and the solid white circles indicate the cells CL (bubbles). It should be noted that, although the cells CL are illustrated as circles independent of each other for the purpose of description, the actual filter 50 has a continuous cell structure (open cell structure). The thickness direction TD of the filter 50 is a direction orthogonal to the surface of the filter 50 adhered to the inner surface 14b of the rear door 14.

[0145] like Fig. 8A As shown in , the raw material sheet 50S of the filter 50 has an average cell diameter D of 200 μm. That is, when the diameter of each cell CL in the raw material sheet 50S is defined as the cell diameter, the average value of the cell diameter is 200 μm. In addition, the thickness of the raw material sheet 50S will be represented by 2t.

[0146] like Figure 8BAs shown in , the filter 50 is formed by pressing the raw material sheet 50S to reduce the thickness by half (2t→t). By pressing, the structure of the polyurethane foam shrinks approximately uniformly in the thickness direction TD. Therefore, the average value of the pore diameter in the thickness direction TD of the filter 50 is 100μm, which is half (1 / 2·D) of the raw material sheet 50S. In this example, the thickness t is 1mm. Therefore, in the filter 50, approximately 1mm / 100μm=10 pores CL are arranged in the thickness direction TD. In the following description, the ratio (β / γ) of the thickness (β) of the filter 50 to the average value (γ) of the pore diameter in the thickness direction TD of the filter 50 will be referred to as "the number of pores in the thickness direction TD of the filter 50".

[0147] When the raw material sheet 50S is pressed, no shrinkage or expansion occurs in the direction orthogonal to the thickness direction TD (hereinafter referred to as the horizontal direction), or the shrinkage or expansion is almost negligible. Therefore, the average value of the cell diameter D in the horizontal direction of the filter 50 is 200 μm, which is the same as the raw material sheet 50S.

[0148] It is to be noted that the above-mentioned cell diameter is obtained as follows. The filter 50 or the raw material sheet 50S is observed by using an optical microscope (VHX-5000 manufactured by Keyence). In the case of obtaining the cell diameter in the horizontal direction, as Figure 8B As shown in FIG. 1 , the surface of the filter 50 or the raw material sheet 50S is observed in the thickness direction TD. A circle overlapping each cell is drawn by using image processing software, and the diameter of the circle (so-called equivalent circle diameter) is used as the cell diameter of the cell. 2 ) is observed at five positions in a field of view of the filter 50 or the raw material sheet 50S, and the average value of the cell diameters of all cells in the observation area is used as the average value of the cell diameters in the horizontal direction of the filter 50 or the raw material sheet 50S.

[0149] The cell diameter in the thickness direction TD of the raw material sheet 50S is obtained by cutting the raw material sheet 50S in the thickness direction TD using a razor and observing the cross section. A circle overlapping each cell is drawn using image processing software, and the diameter of the circle is used as the cell diameter of the cell. 2 ) is performed at five positions in a field of view of the raw material sheet 50S, and the average value of the cell diameters of all cells in the observation area is used as the average value of the cell diameters in the thickness direction TD of the raw material sheet 50S.

[0150] In the case of the filter 50 obtained by pressing the raw material sheet 50S, the cell diameter in the thickness direction TD of the filter 50 can be obtained by multiplying the cell diameter in the thickness direction TD of the raw material sheet 50S by the pressing ratio. The pressing ratio mentioned herein is the ratio (t2 / t1) of the thickness (t2) of the filter 50 after pressing to the thickness (t1) of the raw material sheet 50S before pressing. The pressing ratio in this example is 1 / 2.

[0151] The relationship between the cell diameter of the filter 50 and the particle size of particles that can pass through the filter 50 will be described. When the cell straight holes in the horizontal direction of the filter 50 are smaller, it is more difficult for large particles to pass through the filter 50. In addition, the greater the number of cells in the thickness direction TD of the filter 50, the greater the number of cells that the particles need to pass through in order to pass through the filter 50, and thus it is more difficult for large particles to pass through the filter 50.

[0152] Therefore, it can be considered that the maximum particle size of particles that can pass through the filter 50 is proportional to the average value (α) of the cell diameters in the horizontal direction of the filter 50, and is inversely proportional to the number of cells (β / γ) in the thickness direction TD of the filter 50. That is, the maximum particle size of particles that can pass through the filter 50 can be roughly estimated by the following equation (1).

[0153] Maximum particle size = α / (β / γ)...(1)

[0154] In this example, the maximum particle size is approximated as (average value of cell diameters in the horizontal direction of the filter 50) / (number of cells in the thickness direction TD of the filter 50)=200 μm / 10=20 μm. That is, it can be estimated that particles approximately larger than 20 μm cannot pass through the filter 50. The maximum particle size of particles that can pass through the filter 50 estimated by using equation (1) as described above is preferably smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1.

[0155] In other words, in the case of using a plastic foam such as polyurethane foam as the filter 50, preferably, where α (μm) represents the average value of the cell diameters in the plastic foam in a plane orthogonal to the thickness direction TD of the filter 50, β (μm) represents the thickness of the filter 50, γ (μm) represents the average value of the cell diameters in the plastic foam in the thickness direction TD of the filter 50, and δ (μm) represents the thickness from the peripheral surface of the base 1a of the photosensitive drum 1 to the surface 1s of the photosensitive drum 1, α / (β / γ)<δ is satisfied.

[0156] There is a case where an airflow flowing through the space where the discharge port 16s and the ventilation portion 51 communicate with each other is generated by air conditioning equipment or air supply equipment in the room where the image forming apparatus 100 is installed. In the case where the image forming apparatus 100 is used in an environment where a lot of dust exists in the air and the airflow flowing through the space where the discharge port 16s and the ventilation portion 51 communicate with each other is strong, the dust may enter the image forming apparatus 100 together with the outside air. In addition, when scratches are formed on the photosensitive drum 1 by the dust that has entered the image forming apparatus 100 and image defects occur, the photosensitive drum 1 needs to be replaced.

[0157] In this example, a filter 50 having a maximum particle size of particles that can pass through the filter 50 that is smaller than the thickness δ of the surface layer portion 1b of the photosensitive drum 1 is provided on the ventilation portion 51. Thus, the possibility that large dust particles that may cause black dot images enter the interior of the image forming apparatus 100 and adhere to the photosensitive drum 1 can be reduced.

[0158] Dust-proof performance of filters

[0159] As described above, in the case where the maximum particle size of particles that can pass through the filter 50 is smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1, the possibility of generating a black dot image can be reduced. Fig.9A and Fig. 9B A method of inspecting the dust-proof performance of the filter 50 according to the present example is described.

[0160] like Fig.9A As shown in , the filter 50 is placed on the acrylic resin flat plate 400, and 0.1 g of quartz powder Q is sprinkled from above. As the quartz powder Q, a 1:1 mixed crystal powder #7 and crystal powder #8 manufactured by NAKAGAWA GOFUN ENOGU Co., Ltd. are used. "#7" and "#8" are grades indicating the fineness of the particles, and the larger the number, the finer the particles. The particle size distribution of the quartz powder Q used in the experiment is about several tens of μm to 150 μm. That is, the quartz powder Q includes both particles having a particle size greater than the thickness of the surface layer portion 1b of the photosensitive drum 1 and particles having a particle size equal to or less than the thickness of the surface layer portion 1b of the photosensitive drum 1.

[0161] After the quartz powder Q is sprinkled, vibration is applied by tapping the acrylic plate 400 with fingers 20 to 30 times, and then the filter 50 is carefully removed from the acrylic plate 4000. Fig. 9B As shown in FIG. 5 , the portion of the acrylic resin flat plate 400 where the filter 50 exists is observed with an optical microscope, and the size of the particles that have passed through the filter 50 is observed. VHX-5000 manufactured by Keyence Corporation is used as an optical microscope, and the image is obtained at a magnification of 300 times on a 1 mm square (1 mm 2) at five locations (i.e., a total of 5 mm 2 Observation is performed at the observation area).

[0162] The equivalent circle diameter Xq (μm) of the measured particles is mostly less than 20 μm, and its maximum value is about 20 μm. That is, the maximum particle size (about 20 μm) of the quartz powder Q passing through the filter 50 of this example is sufficiently smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1. In addition, the result that the maximum particle size is about 20 μm matches the estimated result obtained by using the above equation (1).

[0163] In this disclosure, "the maximum particle size of particles that can pass through the filter" means the maximum particle size of particles that can pass through the filter by the above-mentioned inspection method within a total of 5 mm. 2 The maximum value of the equivalent circle diameter Xq of the quartz powder Q observed in the observation area.

[0164] It is to be noted that, although it is considered that all particles that have passed through the filter are subjected to the particle size distribution analyzer, in the process of preparing and measuring the measurement sample, the size of foreign matter that is different from the intended measurement target (particles that have passed through the filter) may be erroneously detected as the maximum particle size. Examples of foreign matter include fragments that are different from the quartz powder Q, and bubbles in the case of a particle size distribution analyzer using a wet system. Therefore, in the present disclosure, the maximum particle size is defined as described above.

[0165] A description will be given of a test method and results for evaluating water drop resistance and dust resistance performed on the above-described image forming apparatus 100 .

[0166] Water drop resistance test

[0167] As an accelerated test for evaluating the water drop resistance of the image forming apparatus 100, a sheet placed in an environment of room temperature 32.5°C and humidity 80% for 48 hours is set in the feeding section 6, and double-sided printing is performed on ten sheets, and it is checked whether water drop traces can be observed on the image. It is to be noted that this test is started after the internal temperature of the image forming apparatus 100 becomes substantially equal to room temperature after a sufficient time has passed since the last image forming operation was completed. This is because condensation is more likely to occur after the internal temperature returns to room temperature compared to the internal hot state of the image forming apparatus 100. The sheet used for the test is CS-680 manufactured by Canon Inc. A halftone image with an image coverage of 25% is formed on the entire effective printing area of ​​each surface of each sheet.

[0168] During the duplex printing process, when water droplets are accumulated somewhere in the duplex transport path CP2, the sheet passing through the duplex transport path CP2 comes into contact with the water droplets and becomes wet. Then, when the image is transferred from the photosensitive drum 1 to the second surface of the sheet, moisture is adsorbed onto the surface area of ​​the photosensitive drum 1 that has been in contact with the wet portion of the sheet. The surface area of ​​the photosensitive drum 1 adsorbed with moisture is more strongly charged than the charged portion of its surrounding area. In the surface area where the charged portion is strongly charged, the concentration of the colorant image formed by the exposure and development steps is lower than that of its surrounding area. Therefore, in the halftone image transferred to the sheet, the following image defect (called a water drop mark or a white spot image) occurs: a white spot appears at a position in the image corresponding to the surface area of ​​the photosensitive drum 1 that has been in contact with the wet portion of the sheet.

[0169] Fig.10 An example of a water drop mark is illustrated. The water drop mark is an image defect that appears periodically at a pitch corresponding to the peripheral length of the photosensitive drum 1. If water vapor generated in the fixing portion 9 is efficiently discharged to the outside of the image forming apparatus 100, the water drop mark is less likely to occur.

[0170] Dust resistance test

[0171] The method of the dust resistance test will be described. First, Fig.11 As shown in , quartz powder Q used as dust is supplied while blowing air from the rear side (-Y side) of the image forming device 100 by the fan 300. The wind speed is set so that wind with a wind speed of 1 m / s is blown onto the outer surface 14a of the rear door 14 at the position of the ventilation part 51. A particle mixture of crystal powders #7 and #8 manufactured by NAKAGAWA GOFUN ENOGU Co., Ltd. is used as quartz powder Q. 1g of quartz powder Q is placed on a weighing paper and supplied little by little within 30 seconds. Then, the image forming device 100 is moved to an environment with a room temperature of 32.5°C and a humidity of 80%, and a durability test is started. In the durability test, 10,000 A4 sheets are passed. Then, the number of stripes of black dot images appearing on the output sheet is checked. The results are shown in Table 1.

[0172] Table 1

[0173]

[0174] In Example 1, although slight water drop marks were observed on the second surfaces of two of the ten sheets, no water drop marks were observed on the other sheets. This indicates sufficient water drop resistance for practical use. That is, according to this example, even in the case where the filter 50 is provided on the ventilation part 51, the function of the ventilation part 51 of discharging heat and water vapor generated in the fixing part 9 to the outside of the image forming device 100 can be maintained. That is, by providing the filter 50 on the ventilation part 51, it is possible to suppress dust from entering the image forming device 100 through the discharge port 16s and the ventilation part 51, while maintaining the function of the ventilation part 51 of discharging heat and water vapor to the outside of the image forming device 100.

[0175] Furthermore, in Example 1, no black dot image was observed in the dust resistance test. In this example, the maximum particle size of particles that can pass through the filter 50 is about 20 μm, which is smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1. Therefore, by providing the filter 50 on the ventilation portion 51, it is possible to suppress the quartz powder Q having a particle size larger than the thickness of the surface layer portion 1b of the photosensitive drum 1 from entering the image forming apparatus 100 through the ventilation portion 51. It is considered that the occurrence of black dot images caused by large quartz powder Q is thereby suppressed.

[0176] Comparative Example 1

[0177] As Comparative Example 1, an image forming apparatus was prepared in which the filter 50 was not provided on the ventilation portion 51. The image forming apparatus of Comparative Example 1 had the same configuration as the image forming apparatus 100 of Example 1 except that the filter 50 was not provided.

[0178] As shown in Table 1, in Comparative Example 1, the same result as that of Example 1 was obtained for the water drop resistance, but in the dust resistance test, eight streaks of black dot images were observed. In Comparative Example 1, since the filter 50 was not provided on the ventilation portion 51, the quartz powder Q having a particle diameter larger than the thickness of the surface layer portion 1b of the photosensitive drum 1 could enter the interior of the image forming apparatus 100 through the ventilation portion 51. It is considered that the black dot images caused by the large quartz powder Q appeared as a result.

[0179] Comparative Example 2

[0180] As Comparative Example 2, an image forming apparatus was prepared in which the ventilation portion 51 was sealed with tape. The image forming apparatus of Comparative Example 2 had the same configuration as the image forming apparatus 100 of Example 1 except that the ventilation portion 51 was sealed with tape. A heat-resistant polyimide tape manufactured by 3M was used as the tape.

[0181] As shown in Table 1, in Comparative Example 2, in the water drop resistance test, obvious water drop traces were observed on the second surface of six of the ten sheets. In contrast, in the dust resistance test, no black spot images were observed. It can be considered that the reason why the water drop resistance is worse than that of Example 1 is that, as a result of the ventilation part 51 being blocked by the tape, the water vapor generated in the fixing part 9 is accumulated in the image forming device, and thus a large amount of condensation occurs in the double-sided conveying path CP2. In contrast, it can be considered that, as a result of the ventilation part 51 being sealed by the tape, the entry of the quartz powder Q through the ventilation part 51 is almost completely suppressed, and therefore no black spot images caused by the quartz powder Q appear.

[0182] Comparative Example 3

[0183] As Comparative Example 3, an image forming apparatus using moltopren which was not pressed and had a thickness of 1 mm as filter 50 was prepared. The image forming apparatus of Comparative Example 3 had the same configuration as the image forming apparatus 100 of Example 1 except for the filter 50 .

[0184] As a test of the dustproof performance of the filter 50 used in Comparative Example 3 ( Fig.9A and Fig. 9B ), the particles having a maximum particle size of 110 μm passed through the filter 50. That is, in Comparative Example 3, the maximum particle size of the particles that can pass through the filter 50 is larger than the thickness of the surface layer portion 1 b of the photosensitive drum 1 .

[0185] The cell diameter of moltopren used in Comparative Example 3 is 300 μm. Therefore, the number of cells in the thickness direction TD of the filter 50 is 1 mm / 300 μm=3.3. In addition, the estimated value of the maximum particle size of particles that can pass through the filter 50 obtained by using the above equation (1) is (cell diameter in the horizontal direction of the filter 50) / (number of cells in the thickness direction TD of the filter 50)=300 μm / 3.3≈100 μm. This estimated value is close to the result of the dustproof performance test (110 μm).

[0186] As shown in Table 1, in Comparative Example 3, the same result as that of Example 1 was obtained for the water drop resistance. It can be considered that there is no problem with the air permeability and moisture permeability of the filter 50 of Comparative Example 3. In contrast, in the dust resistance test, five stripes of black dot images were observed. In Comparative Example 3, although the filter 50 is provided on the ventilation portion 51, the dustproof performance is worse than that of Example 1, so that the large quartz powder Q is more likely to enter the inside of the image forming device 100 than in the case of the filter 50 of Example 1. It can be considered that, as a result, the quartz powder Q having a particle size larger than the thickness of the surface layer portion 1b of the photosensitive drum 1 enters the inside of the image forming device 100 through the ventilation portion 51, so that the black dot image caused by the large quartz powder Q appears.

[0187] Example 2

[0188] As Example 2, an image forming apparatus using moltopren which was not pressed and had a thickness of 2 mm as the filter 50 was prepared. The image forming apparatus of Example 2 had the same configuration as the image forming apparatus 100 of Example 1 except for the filter 50 .

[0189] As a result of the above-mentioned dustproof performance test of the filter 50 used in Example 2, particles with a maximum particle size of 20 μm passed through the filter 50. That is, the dustproof performance of the filter 50 of Example 2 was equivalent to that of the filter 50 of Example 1.

[0190] The cell diameter of moltopren used in Example 2 is 200 μm. Therefore, the number of cells in the thickness direction TD of the filter 50 is 2 mm / 200 μm=10. In addition, the estimated value of the maximum particle size of particles that can pass through the filter 50 obtained by using the above equation (1) is (cell diameter in the horizontal direction of the filter 50) / (number of cells in the thickness direction TD of the filter 50)=200 μm / 10≈20 μm. This estimated value is close to the result of the dustproof performance test (20 μm).

[0191] As shown in Table 1, in Example 2, results equivalent to those of Example 1 were obtained for both water drop resistance and dust resistance. That is, the filter 50 of Example 2 had good air permeability and moisture permeability, and suppressed the large quartz powder Q from entering the image forming apparatus 100 through the ventilation portion 51. In other words, whether the filter 50 is pressed does not directly affect the performance regarding water drop resistance and dust resistance.

[0192] Example 3

[0193] As Example 3, an image forming apparatus using a plain woven mesh formed of stainless steel as the filter 50 was prepared. The image forming apparatus of Example 3 had the same configuration as the image forming apparatus 100 of Example 1 except for the filter 50 .

[0194] The fineness of the net is 200 mesh, the wire thickness is 50 μm, and the mesh opening (interval between wires) is 77 μm. As a result of the dustproof performance test, the maximum particle size of the particles that can pass through the filter 50 of Example 3 is about 40 μm. This is smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1. The maximum particle size is smaller than the mesh opening of the net, because the particles collide with each other when passing through the net and are captured by the net or attached to the wire, so particles slightly smaller than the mesh opening also have difficulty passing through the gap.

[0195] As shown in Table 1, in Example 3, the same results as those of Example 1 were obtained for both water droplet resistance and dust resistance. That is, the mesh filter 50 of Example 3 had good air permeability and moisture permeability, and suppressed the large quartz powder Q from entering the image forming apparatus 100 through the ventilation portion 51.

[0196] Summarize

[0197] As described above, in the dust resistance test, in the case of using the filter 50 in which the maximum particle size of particles that can pass through the filter 50 is smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1, good results were obtained for dust resistance. That is, it can be seen that by adopting a configuration in which the maximum particle size of particles that can pass through the filter 50 is smaller than the thickness of the surface layer portion of the photosensitive member, problems caused by dust can be suppressed.

[0198] Furthermore, in the configuration other than Comparative Example 2 in which the ventilation portion 51 was sealed with tape, good results were obtained for water drop resistance. Therefore, it can be seen that by using a filter 50 having a maximum particle size of particles that can pass through the filter 50 that is smaller than the thickness of the surface layer portion 1b of the photosensitive drum 1 and disposing the filter 50 on the ventilation portion 51, image defects caused by dust can be suppressed while suppressing the occurrence of condensation.

[0199] It is to be noted that, although no difference was observed between Examples 1 and 2 in terms of water drop resistance and dust resistance, the filter 50 of Example 1 is thinner than the filter 50 of Example 2. Therefore, the filter 50 of Example 1 is advantageous in that the filter 50 is less likely to come into contact with the recording material P conveyed in the conveying path CP (double-sided conveying path CP2), and more stable recording material conveyance can be achieved. It is to be noted that whether or not to perform pressing can be selected in consideration of the ease with which the filter 50 is attached, the cost of pressing, and the like.

[0200] Modifications

[0201] The material of the filter 50 is not limited to the polyurethane foam and the plain woven mesh made of stainless steel described in the examples. The material of the filter 50 can be selected from foam sponge materials, olefin sponge materials, melamine sponge materials and other foam sponge materials formed by ester or ether polyurethane materials other than moltopren. That is, the material of the filter 50 can be an open-cell plastic foam (synthetic resin foam). In addition, the material of the filter 50 can be a non-woven fabric formed by cotton fiber, polyethersulfone (PES), polyethylene terephthalate (PET), glass, etc. In addition, the material of the filter 50 can be filter paper (paper filter), or a metal mesh with a honeycomb structure. Regardless of the material of the filter 50, by using a filter 50 whose maximum particle size of particles that can pass through the filter 50 is less than the thickness of the surface layer portion 1b of the photosensitive drum 1, advantages similar to the above examples can be obtained.

[0202] In addition, the ventilation portion 51 in the above example is an example of an opening portion that the housing 101 of the image forming apparatus 100 has. The position of the opening portion (ventilation portion 51) and the shape, size, number, and arrangement of the openings (ventilation holes 51a) in the opening portion may be appropriately changed according to the specific configuration of the image forming apparatus 100. For example, the ventilation holes 51a may be narrow and long holes extending in the X-axis direction (the width direction of the recording material P) in the range of the effective printing area including the maximum size of the recording material.

[0203] Furthermore, although the filter 50 is pasted on the inner surface 14b of the surface of the rear door 14 which is the inner side of the housing 101 in the above example, the filter 50 may be pasted on the outer surface 14a of the rear door 14. Also in this case, the filter 50 can suppress dust from entering the image forming apparatus 100 through the ventilation portion 51.

[0204] Furthermore, although image defects (black dot images) caused by scratches on the surface layer portion 1b of the photosensitive drum 1 have been described as an example of problems caused by dust particles entering the interior of the image forming apparatus 100, dust particles may cause other problems.

[0205] For example, in the case where the image forming apparatus 100 includes the fixing portion 9 of a film heating system using a tubular film (fixing film 112) as a heating member (fixing member), dust may form scratches on the fixing film 112. That is, when dust particles having a large particle size reach the fixing portion 9, scratches may be formed on the fixing film 112.

[0206] Therefore, it is preferable to use a filter 50 whose maximum particle size of particles that can pass through the filter 50 is smaller than the thickness of the fixing film 112. In the above-mentioned Example 1, the thickness of the fixing film 112 is at least 70 μm (thickness of the base layer + thickness of the release layer = 60 μm + 10 μm), so the filter 50 described in Examples 1 to 3 can be appropriately used. Therefore, the possibility that dust having a large particle size scratches the fixing film 112 can be reduced.

[0207] Furthermore, in the case of using a plastic foam such as polyurethane foam as the filter 50, it is preferable to satisfy the relationship of α / (β / γ)<δ according to the above-mentioned definitions of α, β, and γ, where δ (μm) represents the thickness of the fixing film 112. Thus, the possibility of accelerated tearing of the fixing film 112 due to dust having a large particle size can be reduced.

[0208] As another problem caused by dust particles, there is a case where dust causes image defects in an image forming apparatus including an intermediate transfer belt. An image forming apparatus including an intermediate transfer belt is an image forming apparatus of a system (intermediate transfer system) in which a toner image is transferred from a photosensitive drum 1 to an intermediate transfer belt by primary transfer and an image is formed on a recording material P by secondary transfer from the intermediate transfer belt to the recording material P at a secondary transfer portion.

[0209] The intermediate transfer belt includes a base layer responsible for mechanical strength and a surface layer serving as a toner image bearing surface. An elastic layer may be provided between the base layer and the surface layer.

[0210] When dust particles enter the interior of an image forming apparatus including an intermediate transfer belt, there is a possibility that the dust particles are strongly pressed against the intermediate transfer belt at a contact portion between the intermediate transfer belt and another member, and the dust particles form scratches that penetrate the surface layer of the intermediate transfer belt. For example, the "other member" is a cleaning blade that is in pressure contact with the surface (peripheral surface) of the intermediate transfer belt to remove transfer residual toner that is not transferred to the recording material P at the secondary transfer portion from the intermediate transfer belt. When scratches are formed on the surface layer of the intermediate transfer belt, the surface of the intermediate transfer belt may become uneven, and thus a toner image formed on the surface thereof may be disturbed, or the efficiency of primary transfer and secondary transfer may be reduced, which may cause image defects.

[0211] Therefore, it is preferable to use a filter 50 whose maximum particle size that can pass through the filter 50 is smaller than the thickness of the surface layer of the intermediate transfer belt. Thus, it is possible to suppress the occurrence of image defects caused by scratches formed on the surface layer of the intermediate transfer belt by dust having a large particle size.

[0212] Furthermore, in the case of using a plastic foam such as polyurethane foam as the filter 50, it is preferable to satisfy the relationship of α / (β / γ)<δ according to the above-mentioned definitions of α, β, and γ, where δ (μm) represents the thickness of the surface layer of the intermediate transfer belt. Thus, the possibility of occurrence of image defects caused by scratches formed on the surface layer of the intermediate transfer belt by dust having a large particle size can be suppressed.

[0213] In the above example, the space inside the housing 101 communicating with the ventilation portion 51 functions as a conveying path for the recording material P. However, in the case where the technology of the present disclosure is applied to an image forming apparatus, the space inside the housing 101 communicating with the ventilation portion 51 does not need to function as a conveying path.

[0214] Other embodiments

[0215] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming device, comprising: an image forming section including a photosensitive member and configured to form a toner image on a recording material by using the photosensitive member; a fixing section configured to form a nip portion that clamps the recording material and configured to fix the toner image to the recording material by heating the toner image while conveying the recording material using the nip portion; a housing configured to accommodate the image forming portion and the fixing portion and having an opening portion through which the outside of the housing and the inside of the housing communicate with each other, the opening portion being positioned above the clamping portion in the vertical direction; as well as a filter, the filter covering the opening portion, wherein the photosensitive member includes a conductive substrate and a surface layer portion formed on the outer periphery of the substrate, and In the case where the thickness of the surface layer portion is the distance from the outer peripheral surface of the substrate to the surface of the photosensitive member, the maximum particle size of particles that can pass through the filter is smaller than the thickness of the surface layer portion.

2. The image forming apparatus according to claim 1, The filter is made of open-pore plastic foam.

3. The image forming apparatus according to claim 2, in, When α (μm) represents the average value of the pore diameter of the plastic foam in a plane orthogonal to the thickness direction of the filter, β (μm) represents the thickness of the filter, γ (μm) represents the average value of the pore diameter of the plastic foam in the thickness direction of the filter, and δ (μm) represents the thickness of the surface layer part, α / (β / γ)<δ is satisfied.

4. The image forming apparatus according to claim 1, The filter is a metal mesh.

5. The image forming apparatus according to any one of claims 1 to 4, The surface layer portion includes a photosensitive layer and an intermediate layer, wherein the photosensitive layer is configured to generate charge in response to light irradiation and attenuate the potential of the surface of the photosensitive member, and the intermediate layer is provided between the substrate and the photosensitive layer and limits charge injection from the substrate to the photosensitive layer.

6. The image forming apparatus according to any one of claims 1 to 4, wherein the housing includes an outer member including an outer surface constituting an outer surface of the housing and an inner surface provided on an opposite side to the outer surface, and an opposing portion opposing the inner surface with a gap therebetween, and wherein the opening portion is provided in the exterior member, and a space continuous with the gap and the outside of the housing communicate with each other through the opening portion.

7. The image forming apparatus according to claim 6, Wherein the filter is attached to the inner surface of the outer member.

8. The image forming apparatus according to claim 7, wherein the outer member includes a rib shape protruding in a direction from the inner surface toward the opposing portion, wherein the filter is attached to the inner surface at a location different from the shape of the ribs, and wherein at each position in a range in which the filter is provided in the vertical direction, a thickness of the filter is smaller than a protrusion amount of the rib shape relative to the inner surface.

9. An image forming device, comprising: an image forming section configured to form a toner image on a recording material; a fixing section including a tubular film and a heating section configured to heat the film, the fixing section being configured to form a nip section that nipped the recording material, and the fixing section being configured to fix the toner image to the recording material by heating the toner image using the film; a housing configured to accommodate the image forming portion and the fixing portion and having an opening portion through which the outside of the housing and the inside of the housing communicate with each other, the opening portion being positioned above the clamping portion in the vertical direction; as well as a filter, the filter covering the opening portion, The maximum particle size of particles that can pass through the filter is smaller than the thickness of the membrane.

10. An image forming device, comprising: an image forming section including a photosensitive member and an intermediate transfer belt and configured to transfer a toner image formed on the photosensitive member to the intermediate transfer belt by primary transfer and then transfer the toner image from the intermediate transfer belt to a recording material by secondary transfer; a fixing section configured to form a nip portion that clamps the recording material and configured to fix the toner image to the recording material by heating the toner image while conveying the recording material using the nip portion; a housing configured to accommodate the image forming portion and the fixing portion and having an opening portion through which the outside of the housing and the inside of the housing communicate with each other, the opening portion being positioned above the clamping portion in the vertical direction; as well as a filter, the filter covering the opening portion, wherein the intermediate transfer belt includes a base layer and a surface layer formed on an outer periphery of the base layer, the surface layer being configured to carry a toner image, and The maximum particle size of particles that can pass through the filter is smaller than the thickness of the surface layer.

11. An image forming device, comprising: an image forming section including a photosensitive member and configured to form a toner image on a recording material by using the photosensitive member; a fixing section configured to form a nip portion that clamps the recording material and configured to fix the toner image to the recording material by heating the toner image while conveying the recording material using the nip portion; a housing configured to accommodate the image forming portion and the fixing portion and having an opening portion through which the outside of the housing and the inside of the housing communicate with each other, the opening portion being positioned above the clamping portion in the vertical direction; as well as a filter, the filter covering the opening portion, wherein the photosensitive member includes a conductive substrate and a surface layer portion formed on the outer periphery of the substrate, and wherein the filter is formed of open-cell plastic foam, and Wherein α (μm) represents the average value of the cell diameter of the plastic foam in a plane orthogonal to the thickness direction of the filter, β (μm) represents the thickness of the filter, γ (μm) represents the average value of the cell diameter of the plastic foam in the thickness direction of the filter, and δ (μm) represents the distance from the peripheral surface of the substrate to the surface of the photosensitive member, α / (β / γ)<δ is satisfied.

Images