Heating device and imaging apparatus

Abstract

A heating device and an image forming apparatus. The heating device has a second rotary member and a first rotary member heated by a heat source, the second rotary member forming a nip portion with the first rotary member so that a recording material is heated at the nip portion. The heating device also has a first cover provided along an outer peripheral surface of the first rotary member so as to surround the first rotary member, and a second cover provided between the first cover and the first rotary member and having a protruding portion protruding toward the first rotary member. In a longitudinal direction of the first rotary member, a length of the first rotary member is a first length, and a length of the protruding portion is a second length smaller than the first length.

Description

TECHNICAL FIELD

[0001] The present invention relates to an image forming apparatus, such as a laser printer, a copier, or a facsimile, which transfers a toner image formed on an image bearing member using an electrophotographic system or an electrostatic recording system to a transfer material. In addition, the present invention relates to a heating device, such as a fixing unit mounted on the image forming apparatus or a gloss imparting device for increasing a gloss value of a toner image by re-heating the toner image fixed to a recording material. BACKGROUND

[0002] As an example of such an electrophotographic image forming apparatus, a common configuration involves transferring a toner image onto a recording material by heating in an image forming section. Japanese Patent Application Publication No. 2017-3873 discloses such an apparatus having a configuration in which a cover is provided which covers an entire surface of a heating section in a longitudinal direction so as to prevent a product generated due to the influence of heat in the heating section from being discharged from the heating device. SUMMARY

[0003] In the configuration provided with the cover, such as described in the above Japanese Patent Application Publication No. 2017-3873, water vapor is generated when the recording material is heated, and then the water vapor flows to the image forming section and adheres to a print surface of a photosensitive member or the like, which can cause image defects.

[0004] Accordingly, the object of the present invention obtained in view of the above problems is to suppress the influence of water vapor generated by heating the recording material.

[0005] The heating device of the present invention which heats a recording material at a nip portion includes:

[0006] a first rotating member which is heated by a heat source; and

[0007] a second rotating member which forms the nip portion with the first rotating member,

[0008] wherein the heating device further includes:

[0009] a first cover which is provided along an outer peripheral surface of the first rotating member so as to surround the first rotating member; and

[0010] a second cover which is provided between the first cover and the first rotating member; the second cover has a protruding portion which protrudes toward the first rotating member; and

[0011] wherein a length of the first rotary member in a longitudinal direction thereof is a first length, and a length of the protruding portion is a second length, the second length being smaller than the first length.

[0012] An image forming apparatus according to the present application forms an image on a recording material, and includes:

[0013] a transfer mechanism having a photosensitive drum that supports a toner image, a charging unit that charges the photosensitive drum, and a transfer roller that forms a transfer nip portion with the photosensitive drum, such that the transfer mechanism transfers the toner image onto the recording material; and

[0014] a heating mechanism having a first rotary member that is heated by a heat source, and a second rotary member that forms a nip portion with the first rotary member, such that the heating mechanism fixes the toner image onto the recording material;

[0015] wherein the heating mechanism has:

[0016] a first cover that is disposed along an outer peripheral surface of the first rotary member so as to surround the first rotary member; and

[0017] a second cover that is disposed between the first cover and the first rotary member, the second cover having a protruding portion that protrudes toward the first rotary member; and

[0018] wherein a length of the first rotary member in a longitudinal direction thereof is a first length, and a length of the protruding portion is a second length, the second length being smaller than the first length.

[0019] The present application allows the influence of water vapor generated by heating a recording material to be suppressed.

[0020] Other features of the present application will become apparent from the following description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic view showing a configuration of an image forming apparatus according to a first embodiment;

[0022] Figure 2A and Figure 2B is a set of schematic views showing a configuration of a fixing apparatus according to the first embodiment;

[0023] Figure 3 is a schematic view showing a configuration of a cover according to the first embodiment;

[0024] Figure 4A andFigure 4B is a set of schematic diagrams showing a resin member according to the first embodiment;

[0025] Figure 5A and Figure 5B is a set of schematic diagrams showing air flow near a protruding portion according to the first embodiment;

[0026] Figure 6 is a table with estimation results according to the first embodiment;

[0027] Figures 7A to 7G is a set of schematic diagrams showing air flow near a protruding portion in a paper passing estimation;

[0028] Figure 8 is a table with estimation results according to the second embodiment;

[0029] Figure 9A and Figure 9B is a set of schematic diagrams showing a moving direction of air flow toward a photosensitive drum;

[0030] Figure 10 is a schematic diagram showing air flow from a resin member to a fixing film;

[0031] Figure 11 is a table showing occurrence positions of image defects in a comparative example according to the second embodiment; and

[0032] Figure 12 is a graph showing a relationship between an air flow moving distance and a longitudinal length of a resin member. DETAILED DESCRIPTION

[0033] Hereinafter, a description will be given of embodiments (examples) of the present application with reference to the accompanying drawings. However, the size, material, shape, relative arrangement, and the like of the components described in the embodiments can be appropriately changed according to the configuration of an apparatus to which the present application is applied, various conditions, and the like. Therefore, the size, material, shape, relative arrangement, and the like of the components described in the embodiments are not intended to limit the scope of the present application to the following embodiments.

[0034] First Embodiment

[0035] Figure 1is a schematic view showing the configuration of an image forming apparatus 1 according to the first embodiment. Examples of the image forming apparatus to which the present application is applicable include printers and copiers relying on an electrophotographic system or an electrostatic recording system; in this document, an example in which the present application is applied to a monochrome printer that forms an image on a recording material based on image information input from an external device will be explained. The recording material includes paper such as plain paper and thick paper, plastic film such as a sheet for an overhead projector, a sheet of a special shape such as an envelope and an index sheet, and various sheets made of different materials such as cloth. The maximum width of the recording material P used in the image forming apparatus 1 of the present embodiment is an LTR width, and the print surface width is 206 mm.

[0036] Configuration of image forming apparatus

[0037] The image forming apparatus 1 has an image forming portion 10 that forms a toner image on a recording material P, a feeding portion 60 that feeds the recording material P to the image forming portion 10, a fixing device 70 that is a heating mechanism that fixes the toner image to the recording material P, and a discharge roller pair 80 that discharges the recording material P onto a discharge portion. The recording material P is fed from the feeding portion 60 to the image forming portion 10 by a registration roller pair 15. In addition, the image forming apparatus 1 has a control portion (not shown) for controlling the image forming operation performed on the recording material P in the image forming portion 10.

[0038] The image forming portion 10 is a transfer mechanism having a scanner unit 360, a photosensitive drum 21 that supports a toner image, and a transfer roller 12 that transfers the toner image formed on the photosensitive drum 21 to a recording material. The transfer roller 12 that forms a transfer nip Ntr as a transfer nip portion together with the photosensitive drum 21 transfers the toner image to the recording material P while nipping and conveying the recording material. A charging roller 22, a pre-exposure device 23, and a developing device 30 including a developing roller 31 are disposed around the photosensitive drum 21. The rotation axes of the developing roller 31, the discharge roller pair 80, and the registration roller pair 15 are parallel to the rotation axis of the photosensitive drum 21. The photosensitive drum 21, the charging roller 22, the developing roller 31, and the like are rotatable members that are elongated in a longitudinal direction perpendicular to the conveying direction of the recording material P.

[0039] The photosensitive drum 21 is a photosensitive member shaped as a cylinder. The photosensitive drum 21 of the present embodiment has a photosensitive layer formed of a negatively chargeable organic photosensitive member on a drum-shaped base formed of aluminum. In addition, the photosensitive drum 21 as an image bearer is rotationally driven in the arrow direction by a motor. The process speed in the present embodiment is 130 mm / sec.

[0040] The charging roller 22 as a charging unit contacts the photosensitive drum 21 with a predetermined contact force of pressure to form a charged portion. The charging roller 22 applies a desired charging voltage by means of a charging high voltage source, thereby uniformly charging the surface of the photosensitive drum 21 to a predetermined potential. In the present embodiment, the photosensitive drum 21 is negatively charged by the charging roller 22.

[0041] For the purpose of generating stable discharges at the charged portion, the pre-exposure device 23 eliminates static electricity from the surface potential of the photosensitive drum 21 before entering the charged portion.

[0042] The scanner unit 360 as an exposure unit performs scanning exposure of the surface of the photosensitive drum 21 by irradiating the photosensitive drum 21 with a laser beam 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 surface of the exposed photosensitive drum 21. The scanner unit 360 is not limited to a laser scanner device, and, for example, an LED exposure device having an LED array in which a plurality of LEDs are arranged in the longitudinal direction of the photosensitive drum 21 can be used herein.

[0043] The developing apparatus 30 of the present embodiment relies on a contact developing scheme as a developing scheme. Specifically, a toner layer supported on a developing roller 31 as a developing unit is brought into contact with the photosensitive drum 21 in a developing portion (developing zone) in which the photosensitive drum 21 and the developing roller 31 face each other. A developing voltage is applied to the developing roller 31 by a developing high voltage source. Under the developing voltage, the toner carried on the developing roller 31 is transferred from the developing roller 31 to the drum surface in accordance with the potential distribution on the surface of the photosensitive drum 21; thus, the electrostatic latent image on the photosensitive drum is developed into a toner image. In the present embodiment, a reverse developing method is employed. That is, after being charged in the charging step, the toner adheres to the surface region of the photosensitive drum 21, the charge amount of which is attenuated by exposure in the exposure step, and thus a toner image is formed thereby.

[0044] The conventional charging polarity of the toner of the present embodiment, which has a specific gravity of 1.1, is negative. The toner particle diameter is 6 μm. A polymerized toner produced according to a polymerization method is used herein as the toner of the present embodiment. The toner of the present embodiment is a non-magnetic monocomponent developer not containing a magnetic component, and is mainly applied to the developing roller 31 due to intramolecular forces or electrostatic forces (image forces). However, a monocomponent developer containing a magnetic component can also be used. In addition to toner particles, the monocomponent developer can contain additives (e.g., wax or fine particles of silica) to adjust the flowability and charging properties of the toner. A two-component developer composed of a non-magnetic toner and a magnetic carrier can be used as the developer. In the case of using a magnetic developer, for example, a cylindrical developing sleeve having a magnet provided inside thereof is used as the developer carrier.

[0045] As the transfer roller 12, a roller having an outer diameter of 14 mm was used, and the roller was obtained by covering a nickel-plated steel rod having an outer diameter of 8 mm with a 3 mm-thick foamed sponge body containing NBR and a chloro-ether rubber as main components. The volume resistance of the foamed sponge was about 10 8 Ω-cm. The transfer roller 12 was brought into contact with the photosensitive drum 21 under a pressure of 1 kg, and rotated with the rotation of the photosensitive drum 21. In order to transfer the toner image from the photosensitive drum 21 to the recording material P, a voltage was applied to the transfer roller 12 from a voltage source not shown.

[0046] In the present embodiment, a drumless cleaner system was utilized, so that toner remaining on the photosensitive drum 21 without being transferred was negatively charged by the charging roller 22 and returned to the developing device 30. Since the drumless cleaner system does not require a waste toner container, the size of the image forming apparatus can be reduced. The distance between the photosensitive drum 21 and the fixing nip Nf of the present embodiment was 45 mm.

[0047] Next, the fixing device 70 of the present embodiment will be described. The fixing device 70 of the present embodiment is a film heating type image heating apparatus, and aims at shortening the start-up time and reducing the power consumption, as described above. Figure 2A A cross-sectional view depicting an outline of the fixing device 70 of the present embodiment is shown, and Figure 2B A schematic view of the fixing device 70 in the longitudinal direction as viewed from the upstream side in the conveying direction is shown. Figure 2B Only the outer shape of the fixing film 112 and the heater holder 130 is depicted in dotted lines, so as to more easily understand the pattern of the heater 113.

[0048] The fixing device 70 of the present embodiment has a configuration in which the heater 113 as a heat source is held by the heater holder 130, and the fixing film 112 as a loop-shaped belt is disposed around the heater. The heater holder 130 is preferably made of a material having a low heat capacity, so as to prevent heat from being taken away from the heater 113 as much as possible; in the present embodiment, a liquid crystal polymer (LCP) which is a heat-resistant resin is used. The heater holder 130 is supported by the iron holder 120 from the side opposite to the side on which the heater 113 is disposed, for the purpose of increasing the strength. The heater holder 130 is in contact with the inner peripheral surface of the fixing film 112, so as to guide the rotation of the fixing film 112.

[0049] The holder 120 is pressurized from both end portions in the longitudinal direction toward the pressure roller 110 by a compression spring not shown. As Figure 2AAs shown, the heater 113 is in contact with the inner peripheral surface of the fixing film 112 and heats the fixing film 112 from the inside. Due to the pressure applied to the holder 120, a fixing nip Nf as a clamping portion for heating and fixing is formed by the heater 113 together with the opposing pressure roller 110 in such a manner as to clamp the fixing film 112. Specifically, the fixing nip Nf is formed by contact between the fixing film 112 as a first rotating member provided with the heater 113 in the inner space and the pressure roller 110 as a second rotating member. Like the fixing film 112, the pressure roller 110, and the heater holder 130, the holder 120 is also an elongated member in a longitudinal direction perpendicular to the conveyance direction of the recording material P and parallel to the rotational axis direction of the pressure roller 110.

[0050] The pressure roller 110 receives the force of the compression spring via an unshown bearing provided at both end portions of the core metal 117 and is driven by a drive gear 131 provided at the end portions of the core metal 117 by an unshown drive source. As the pressure roller 110 is driven, the fixing film 112 is rotationally driven so as to slide on the pressure roller 110 at the fixing nip Nf. As shown in FIG. 2, the fixing film 112 is in contact with the pressure roller 110 at the fixing nip Nf. The fixing film 112 is in contact with the heater 113 at the fixing nip Nf. Figure 2B As shown, for the purpose of preventing the fixing film 112 from deviating to the left or right in the longitudinal direction, fixing flanges 150 that restrict lateral deviation are provided at both end portions of the fixing film 112. The fixing flanges 150 are fitted and fixed to the holder 120. The fixing film 112 is rotated while being supported from the inner surface thereof by the fixing flanges 150 provided at both end portions.

[0051] The fixing film 112 of the present embodiment has an outer diameter of 20 mm in an undeformed cylindrical state and has a multilayer structure in the thickness direction. The longitudinal length (length in the longitudinal direction) of the fixing film 112 is 230 mm. The fixing film 112 has a base layer 126 for maintaining the strength of the film, a conductive primer layer 127, and a release layer 128 for reducing dirt adhesion to the surface.

[0052] The base layer 126 receives heat from the heater 113, and thus needs to be heat resistant; in addition, the base layer 126 slides on the heater 113, and thus also needs to be strong. Therefore, a metal such as stainless steel (SUS) or nickel, or a heat resistant resin such as polyimide can be used as the material of the base layer 126. Metal is stronger than resin, and thus can be made thinner; metal also has high thermal conductivity, and thus easily transfers heat from the heater 113 to the surface of the fixing film 112. On the other hand, resin has a lower specific gravity than metal, and thus has advantages in terms of low heat capacity, easy heatability. In addition, resin can be molded into a thin film by coating molding, and thus can be inexpensively molded. In the present embodiment, a polyimide resin is used as the material of the base layer 126 of the fixing film 112, with a carbon-based filler added to improve thermal conductivity and strength. The thinner the base layer 126, the easier heat from the heater 113 is transferred to the surface of the fixing film 112, but when the base layer 126 is too thin, the strength instead decreases; therefore, the thickness of the base layer 126 is preferably set to about 15 μm to 100 μm, with a value of 60 μm set in the present embodiment.

[0053] The conductive primer layer 127 is made of a polyimide resin or a fluororesin, and for example, carbon or the like is added to reduce the resistance. The fixing film 112 is stabilized in the electric potential at the time of paper passage by grounding the exposed portion of the conductive layer.

[0054] Preferably, a fluororesin such as a perfluoroalkoxy resin (PFA), a polytetrafluoroethylene resin (PTFE), or a tetrafluoroethylene-hexafluoropropylene resin (FEP) is used as the material of the release layer 128. In the present embodiment, PFA, which is excellent in mold releasability and heat resistance, is used in the fluororesin; here, a conductive material is dispersed therein to impart moderate resistance. The release layer 128 can be obtained by tube covering or by coating the surface with a coating material; in the present embodiment, the release layer 128 is formed using coating, which is excellent in thin wall molding. The thinner the release layer 128, the easier heat from the heater 113 is transferred to the surface of the fixing film 112, but if the release layer 128 is too thin, the durability instead deteriorates; therefore, the thickness of the release layer 128 is preferably set to about 5 μm to 30 μm, with a value of 10 μm set in the present embodiment.

[0055] The pressure roller 110 of the present embodiment has an outer diameter of 14 mm, and has a 2.5 mm thick silicone rubber elastic layer 116 formed on the surface of an iron core metal 117 having an outer diameter of 9 mm.

[0056] Heat-resistant silicone rubber or fluororubber is used in the elastic layer 116; in this embodiment, silicone rubber is used. The outer diameter of the pressure roller 110 is preferably about 10 mm to 50 mm. When the outer diameter of the pressure roller 110 is small, the heat capacity remains low; however, an excessively small outer diameter results in a narrower fixing clamping portion Nf; therefore, it is necessary to select an appropriate diameter. In this embodiment, the outer diameter is set to 14 mm. When the thickness of the elastic layer 116 is too small, heat dissipates to the metal core metal, and therefore the thickness must be appropriate; in this embodiment, the thickness is set to 2.5 mm. A release layer 118 made of perfluoroalkoxy resin (PFA) is formed on the elastic layer 116 as a toner release layer. Similar to the release layer 128 of the fixing film 112, the release layer 118 can be obtained by covering the surface with a tube or by coating the surface with a coating material; in this embodiment, the release layer 118 is a tube with excellent durability and a thickness of 20 μm. Besides PFA, fluoropolymers such as PTFE or FEP, or fluorocarbon rubbers or silicone rubbers with good release properties can also be used as materials for the release layer 118. The lower the surface hardness of the pressure roller 110, the less pressure is required to obtain the width of the fixing clamping portion Nf; however, excessively low surface hardness leads to poor durability; therefore, in this embodiment, the Asker-C hardness (600g load) of the pressure roller 110 is set to 40°. When actuated by a rotating device (not shown), the pressure roller 110 rotates at a surface movement speed of 130 mm / s.

[0057] The heater 113 in this embodiment is a general heater used in a film heating type heating device in which a resistance heating element is connected in series on a ceramic substrate. As the heater 113, a component is obtained by screen printing an Ag / Pd (silver-palladium) resistance heating element at a height of 10 μm onto the surface of an alumina substrate with a width of 6 mm and a thickness of 1 mm, and by covering the applied resistance heating element with a 50 μm thick glass as a protective layer for the heating element.

[0058] like Figure 2A As shown, a temperature sensing element 115 for detecting the temperature of the ceramic substrate is disposed on the back surface of the heater 113. Based on the signal from the temperature sensing element 115, the temperature of the heater 113 is adjusted by appropriately controlling the current flowing through the resistance heating element. The higher the temperature of the heater 113, the greater the power consumption, and therefore the temperature needs to be set appropriately. In this embodiment, the control temperature for ordinary paper operation is set to 180°C.

[0059] For the purpose of ensuring safety by breaking the circuit in the case of abnormal overheating of the heater 113, a thermal fuse (not shown) as a safety element is provided on the back surface of the heater 113. The heater 113 is connected to a commercial power source via the thermal fuse. When the temperature rises abnormally, the thermal fuse is blown, and the supply of power from the commercial power source to the heater 113 is cut off. In the present embodiment, a film heating type fixing unit is used, but the present application is not limited to this, and for example, a hot roller scheme relying on a halogen heater can be adopted instead.

[0060] Imaging operation

[0061] Next, the imaging operation in the image forming apparatus 1 will be described. When an imaging command is input to the image forming apparatus 1, the imaging process of the image forming section 10 is started based on image information input from an external computer connected to the image forming apparatus 1. The scanner unit 360 projects laser light toward the photosensitive drum 21 based on the input image information. At this time, the photosensitive drum 21 is pre-charged by the charging roller 22 and is irradiated with laser light, whereby an electrostatic latent image is formed on the photosensitive drum 21. Thereafter, the electrostatic latent image is developed by the developing roller 31, and a toner image is formed on the photosensitive drum 21.

[0062] In parallel with the above-described imaging process, the recording material P is fed by the feeding section 60 to the registration roller pair 15, and skew is corrected by the collision of the recording material P with the nip of the registration roller pair 15. Then, the registration roller pair 15, which is driven in accordance with the transfer timing of the toner image, conveys the recording material P toward the transfer nip Ntr formed by the transfer roller 12 and the photosensitive drum 21.

[0063] A transfer voltage is applied from a transfer high voltage source to the transfer roller 12 as a transfer device, whereby the toner image supported on the photosensitive drum 21 at the transfer nip Ntr is transferred to the recording material P. The recording material P on which the toner image has been transferred is conveyed to the fixing device 70, where the toner image is heated and pressed while being conveyed and nipped between the fixing film 112 and the pressure roller 110 of the fixing device 70. As a result, the toner particles melt and then fix, whereby the toner image is fixed to the recording material P. The recording material P that has passed through the fixing device 70 is ejected by the ejection roller pair 80 as an ejection device.

[0064] Features of the present embodiment

[0065] The cover structure 50 of the fixing device 70 as a feature of the present embodiment will be described with reference to Figure 3 The cover structure 50 is composed of a metal member 51 as a first cover and a resin member 52 as a second cover. In the present embodiment, the cover structure 50 is a constituent element of the fixing device 70, but the cover structure 50 can also be conceived as a member independent of the fixing device 70.

[0066] The metal member 51 is mounted on the outer peripheral surface of the fixing film 112 in the longitudinal direction of the entire fixing film 112 as a cover portion. The metal member 51 is preferably a metal material for the purpose of forming with good precision; in the present embodiment, an electrogalvanized steel sheet is used as the metal member 51. An airflow guide space S for guiding the airflow in the rotation direction of the fixing film 112 is formed between the outer peripheral surface of the fixing film 112 and the metal member 51.

[0067] The resin member 52 is mounted at the end portion of the metal member 51 upstream of the fixing nip Nf in the conveying direction of the recording material. The resin member 52 is provided with a gap from the fixing film 112; in this context, for the purpose of excluding image defects resulting from damage to the fixing film 112 in the hypothetical case where the resin member 52 comes into contact with the fixing film 112 during rotation, a resin that is a soft material is used in the resin member 52. In the present embodiment, PBT is used as the material of the resin member 52.

[0068] The resin member 52 has a protruding portion 521 that protrudes toward the fixing film 112 (toward the heating rotating member) and a contact surface 522 that is connected to the metal member 51. The contact surface 522 is mounted so as to be a mirror image of the metal member 51, thereby making the space between the fixing film 112 and the protruding portion 521 narrower. The shortest distance between the fixing film 112 and the cover structure 50 is herein the distance A from the fixing film 112 to the protruding portion 521. Preferably, the distance between the fixing film 112 and the resin member 52 is short; in the present embodiment, the distance A from the outer peripheral surface of the fixing film 112 to the protruding portion 521 of the resin member 52 is set to 2.5 mm.

[0069] Figure 4A is a perspective view of the resin member 52, and Figure 4B is a sectional view of the resin member 52. For the purpose of controlling the airflow around the fixing film 112, the longitudinal length L of the protruding portion 521 is smaller than the longitudinal length of the fixing film 112. In the present embodiment, the value of the longitudinal length of the protruding portion 521 is the same as the value of the longitudinal length L of the resin member 52; however, it is sufficient that the longitudinal length of the protruding portion 521 be smaller than the longitudinal length of the fixing film 112 regardless of the longitudinal length of the resin member 52. In the present embodiment, the longitudinal length L of the resin member 52 (the second length of the second cover) is 215 mm, and the longitudinal length of the fixing film 112 (the first length of the first cover) is 230 mm. The mechanism for controlling the airflow around the fixing film 112 is described in detail below.

[0070] As Figure 4BAs shown, the resin member 52 has a protruding portion 521 and a contact surface 522 that contacts the metal member 51. The protruding portion 521 protrudes from a surface on the side opposite the contact surface 522. The resin member 52 is formed so that in a direction perpendicular to the longitudinal direction and a distance C from the contact surface 522 to the metal member 51 on which the contact surface 522 contacts is greater than a distance B from the contact surface 522 to the end of the protruding portion 521. By making the distance C greater, the resin-specific flexing is curtailed, and due to the fact that the resin member 52 is installed in mirror image to the metal member 51, the protruding portion 521 is accurately positioned with respect to the fixing film 112.

[0071] airflow direction

[0072] When the recording material P runs through the fixing nip Nf, due to the rotation of the fixing film 112, an airflow is generated between the fixing film 112 and the cover structure 50 in the arrow direction along the direction of rotation of the fixing film 112, as shown by the arrows in Figure 5A . That is, the metal member 51 of the cover structure 50 guides the airflow around the fixing film 112 along the outer peripheral surface of the fixing film 112. In the case where the recording material P acquires a significant moisture content due to being allowed to be left in a high-temperature, high-humidity environment, then, at the time the recording material P passes through the fixing device 70, water vapor is generated around X in the vicinity of the fixing nip exit. This water vapor moves through the airflow guide space S in the direction of rotation of the fixing film 112 and flows in the conveyance direction from the downstream side to the upstream side toward the fixing nip Nf.

[0073] Figure 5B is a view of the cover structure 50 as viewed from the fixing film 112 side. In Figure 5B , the airflow direction in the vicinity of the protruding portion 521 of the resin member 52 is indicated by the arrows. The airflow from the fixing nip exit vicinity X toward the protruding portion 521 of the resin member 52 in the direction of rotation of the fixing film 112 collides with the protruding portion 521 and flows outward in the longitudinal direction along the protruding portion 521. Openings E are provided in the longitudinal direction at both end portions of the protruding portion 521 through which the airflow in the airflow guide space S is discharged from the fixing device. That is, the airflow that is guided outward in the longitudinal direction within the airflow guide space is discharged from the fixing device through the openings E. The direction of the airflow discharged from the fixing device is controlled by thus providing the resin member 52 of smaller longitudinal length than the longitudinal length of the fixing film 112 at the end portions of the metal member 51 upstream of the fixing nip Nf in the conveyance direction.

[0074] When a large amount of water vapor flows onto the print surface of the photosensitive drum 21, the photosensitive drum 21 can be overcharged by the charging roller 22, and image defects such as white spots can occur. The occurrence of image defects increases particularly in a cleanerless system configuration like the present embodiment that does not have a shield such as a cleaning blade or a toner recovery container. However, in the case where the longitudinal length L of the resin member 52 of the cover structure 50 in the longitudinal direction is sufficiently large with respect to the print surface width W of the photosensitive drum 21, the water vapor flows to the outside of the print surface width W, and thus the inflow of water vapor onto the print surface of the photosensitive drum 21 can be suppressed. In the present embodiment, specifically, the airflow is controlled by the protruding portion 521 of the resin member 52 that protrudes toward the fixing film 112; by this, image defects caused by water vapor generated in the vicinity of the downstream side of the fixing nip Nf in the conveyance direction are suppressed.

[0075] On the other hand, in the case where the longitudinal length L of the resin member 52 is excessively large, it is difficult to direct the airflow to the outside in the longitudinal direction of the resin member 52. The both end portions of the fixing film 112 are supported on the respective side plates via flanges or the like. In the case where there is a sufficient gap between the side plates and the resin member 52, the airflow is directed outward in the longitudinal direction of the resin member 52. However, in the case where the resin member 52 is long and the width of the opening portion E that is the gap between the resin member 52 and the side plate is small, then the amount of air that escapes from the opening portion E decreases, so that by this, air does not flow out but is discharged along the rotation direction of the fixing film 112 from the fixing device.

[0076] Effects of the Invention

[0077] To confirm the effects of the present invention, a paper pass estimation was performed to check the occurrence of image defects originating from water vapor. The configuration of the cover structure 50 that does not have the resin member 52 was estimated similarly to the conventional example 1. As comparative examples, various configurations that modify the longitudinal length L of the resin member 52 from the present embodiment were estimated. The longitudinal length L of the resin member 52 in the comparative examples was 230 mm in comparative example 1, the same as the longitudinal length of the fixing film 112, and 200 mm in comparative example 2, 180 mm in comparative example 3, 166 mm in comparative example 4, and 150 mm in comparative example 5. The estimation was performed in a high-temperature, high-humidity environment (temperature 30°C, humidity 80%). The estimation paper used was Xerox Vitality multipurpose paper (letter size, 20 lb) that had been allowed to stand in this high-temperature, high-humidity environment for 2 days. As described above, the print surface width W of the estimation paper was 206 mm. The estimation image was a halftone print pattern, and 50 sheets were continuously output. A case where the estimation image did not exhibit image defects such as white spots when 50 printed sheets were output was rated as good, and a case where even one printed sheet exhibited image defects such as white spots was rated as poor. The estimation results are summarized in Table 1.Figure 6 In addition, Figures 7A to 7G The air flow directions at the end portions of the metal member 51 provided with the resin member 52 in the present embodiment, in the conventional example, and in the comparative examples are shown.

[0078] In the present embodiment, no image defects occurred.

[0079] As Figure 7A shown, in the present embodiment, the air flow is guided outward in the longitudinal direction by the resin member 52. That is, by modifying the direction of the air flow containing water vapor, the flow of water vapor onto the print surface of the photosensitive drum 21 can be reduced, thereby preventing the occurrence of image defects.

[0080] In the conventional example 1, image defects occurred. As Figure 7B shown, in the conventional example 1, there is no shield such as a protruding portion, and therefore, air flows in the rotation direction of the fixing film 112. Water vapor flowing out from the vicinity of the fixing nip Nf of the fixing device 70 flows in the conveying direction from the downstream side toward the upstream side, and then toward the print surface of the photosensitive drum 21. Due to the water vapor flowing onto the print surface of the photosensitive drum 21, in the conventional example 1, image defects occurred.

[0081] In the comparative example 1, image defects occurred. In the comparative example 1, the longitudinal length L of the resin member 52 is large, and there is substantially no gap for water vapor to pass through. That is, although the resin member 52 has an effect of suppressing the flow of water vapor, there is no position outside in the longitudinal direction of the resin member 52 where water vapor can flow, and therefore water vapor flows through the resin member 52 in the rotation direction of the fixing film 112, as Figure 7C shown. Specifically, in the comparative example 1, the effect of controlling the air flow direction by the resin member 52 cannot be achieved, and water vapor flows onto the print surface of the photosensitive drum 21, which causes image defects.

[0082] In the comparative examples 2, 3, and 4, although the longitudinal length L of the resin member 52 is smaller than the print surface width W, no image defects occurred. Therefore, it is considered that the comparative examples 2, 3, and 4 are also embodiments in which image defects are prevented by using the present application. This is because in the comparative examples 2, 3, and 4, the air flow is made to pass through the opening portion E by the resin member 52 and flow outward in the longitudinal direction, as Figure 7D , Figure 7E , and Figure 7F shown. In addition, the smaller the longitudinal length of the resin member 52, the greater the amount of air that flows out through the opening portion E in the rotation direction of the fixing film 112 without hitting the resin member 52, compared to the amount of air that hits the resin member 52 and is then guided outward in the longitudinal direction. The orientation of the air flow discharged from the fixing device 70 turns from outward in the longitudinal direction to a direction toward the vicinity of the center of the photosensitive drum 21.

[0083] An image defect occurred in Comparative Example 5. The longitudinal length L of the resin member 52 is small, and therefore a large amount of water vapor flows out of the fixing device 70 along the rotation direction of the fixing film 112 through the opening portion E without hitting the resin member 52, as shown. This affects water vapor flowing outward in the longitudinal direction at the protruding portion 521, which then flows in the direction along the rotation direction of the fixing film 112; therefore, water vapor does not easily flow outward in the longitudinal direction. That is, the insufficient longitudinal length L of the resin member 52 causes water vapor to flow onto the print surface of the photosensitive drum 21, which causes an image defect in Comparative Example 5. Figure 7G

[0084] In the present embodiment, the processing speed is set to 130 mm / sec; however, even if the processing speed increases, the length of the resin member 52 required to suppress an image defect does not change. This is because the rotation of the fixing film 112 generates an air current, and the processing speed has little effect on the direction of the air current. In the case of a fast processing side, the amount of air leaking from the resin member 52 tends to increase; however, the speed of the rotation of the photosensitive drum 21 is likewise high in this context, and therefore no significant difference is caused in the amount of water vapor flowing in each unit area of the photosensitive drum 21.

[0085] The device in the present embodiment is a drumless cleaner system, but a similar result can be achieved even if a cleaning blade for toner cleaning or a brush for recovering paper dust is installed on the drum with the aid of the resin member 52.

[0086] It is important to provide the resin member 52 at the end portion of the metal member 51 upstream of the fixing nip Nf in the conveying direction for the purpose of controlling the direction of the air current. In addition, the resin member 52 also has the effect of reducing the possibility of contact with the fixing film 112 in the case where the fixing device is a film heating type. This is because, although the trajectory of the fixing film 112 can vary depending on the conveying state of the recording material, the trajectory of the fixing film 112 along the heater holder 130 is more stable near the upstream side of the fixing nip Nf in the conveying direction than near the downstream side in the conveying direction.

[0087] ​In the paper-passing estimation, the fixing film 112 and the resin member 52 are not in contact with each other. However, even in the configuration in which the pressure of the fixing film 112 and the pressure roller 110 is not released and the pinch portion forming state is maintained without paper passing, the fixing film 112 can be deformed according to the shape of the pinch portion. In this case, the deformation is gradually reduced due to the rotation of the fixing film 112, whereby the fixing film returns to its original shape. In contrast, the fixing film 112 rotates in the deformed state immediately after the rotation, and thus can come into contact with the members in the vicinity. In the present embodiment, the resin member 52 provided in the vicinity of the fixing film 112 is formed of resin, and thus the possibility of the surface of the fixing film 112 being scratched is reduced even when the fixing film comes into contact with the resin member 52.

[0088] As described above, the resin member 52 having an appropriate longitudinal length and protruding from the fixing film 112 side is installed on the cover structure 50 that covers the entire outer peripheral surface of the fixing film 112 in the longitudinal direction; thereby, the airflow directed outward from the print surface of the photosensitive drum 21 can be formed. This configuration allows the inflow of water vapor onto the print surface of the photosensitive drum 21 to be suppressed, and prevents the occurrence of image defects even when water vapor is generated in the fixing nip Nf.

[0089] It is also conceivable that water vapor stagnates and liquefies in the airflow guide space S in a state in which the imaging operation is stopped and the fixing film 112 is not fixed. In the present embodiment, the fixing film 112 is positioned above the photosensitive drum 21 in the vertical direction, with the cover structure 50 being provided in the space between the fixing film 112 and the photosensitive drum 21. Therefore, the cover structure 50 receives the liquefied water vapor, if any, and thus it is possible to expect an effect of preventing water vapor from adhering to the photosensitive drum 21 even in a state in which the image forming apparatus 1 is not driven.

[0090] A monochrome laser printer using a single color of monochrome toner is described as a typical example of an image forming apparatus provided with a transfer mechanism and a heating mechanism and performing paper-passing estimation; however, the use of the present application is not limited to such an image forming apparatus. For example, the present application is also applicable to an image forming apparatus that forms an image by transferring two or more colors of toner onto a recording material via an intermediate transfer belt, such as a tandem type color laser printer, and the like. Even in an image forming apparatus having a transfer belt, the present application is able to prevent water vapor generated in a fixing device from adhering to the transfer belt or the print surface of the photosensitive drum, and thus is able to prevent the occurrence of image defects.

[0091] Second Embodiment

[0092] As a second embodiment, a configuration in which the distance between the photosensitive drum 21 and the fixing nip Nf is set shorter than in the first embodiment will be described next. In this embodiment, the distance between the photosensitive drum 21 and the fixing nip Nf is 35 mm, so that the size of the image forming apparatus is further reduced. The description of features of the image forming apparatus that are similar to those of the first embodiment will be omitted here.

[0093] Effects of the Invention

[0094] To confirm the effects of the present invention, a paper passing estimation was performed to check the occurrence of image defects originating from water vapor. The configuration in which the cover structure 50 did not have the resin member 52 was estimated similarly to that of the conventional example 2. As comparative examples, various configurations in which the longitudinal length L of the resin member 52 was changed from 215 mm of the present embodiment were estimated. The longitudinal length L of the resin member 52 in the comparative examples was 230 mm in comparative example 6, which was the same as the longitudinal length of the fixing film 112, and 200 mm in comparative example 7, 180 mm in comparative example 8, 166 mm in comparative example 9, and 150 mm in comparative example 10. The estimation was performed in a high-temperature, high-humidity environment (temperature 30°C, humidity 80%). The estimation paper used was Xerox Vitality multipurpose paper (letter size, 20 lb) that had been allowed to stand in this high-temperature, high-humidity environment for 2 days. As described above, the print surface width of the estimation paper was 206 mm. The estimation image was a halftone print pattern, and 50 sheets were continuously output. Figure 8 The following estimation results were set forth in tabular form: a case where the estimation image did not exhibit image defects such as white spots when 50 printed sheets were output was rated as good, and a case where image defects such as white spots occurred even in one printed sheet was rated as poor.

[0095] In the present embodiment, no image defects occurred. As in the first embodiment, in the present embodiment, the airflow is guided outward in the longitudinal direction by the resin member 52, and the water vapor generated in the fixing apparatus 70 can be reduced from flowing onto the print surface of the photosensitive drum 21.

[0096] Image defects occurred in the conventional example 2. This is because the water vapor flowed in the rotation direction of the fixing film 112, and flowed onto the print surface of the photosensitive drum 21, similarly to the conventional example 1.

[0097] Image defects occurred in comparative example 6. This is because, similarly to comparative example 1, the water vapor leaked out from between the resin member 52 and the fixing film 112 in the rotation direction of the fixing film 112, and flowed into the photosensitive drum 21.

[0098] In Comparative Examples 7 and 8, the longitudinal length L of the resin member 52 is smaller than the print surface width W, but no image defects occur. This is because, similarly to Comparative Examples 2, 3, and 4, the air flow is guided outward in the longitudinal direction by the resin member 52. That is, it is considered that Comparative Examples 7 and 8 are also embodiments in which image defects are prevented by using the present application.

[0099] In Comparative Examples 9 and 10, image defects occur. This is because the length of the resin member 52 is insufficient, and, as in Comparative Example 5, water vapor flows onto the print surface of the photosensitive drum 21. In the present embodiment, since the distance between the fixing nip Nf and the photosensitive drum 21 is shorter than in the first embodiment, air easily flows onto the print surface of the photosensitive drum 21. Therefore, no image defects occur in Comparative Example 4, but image defects do occur in Comparative Example 9 in which the longitudinal length L of the resin member 52 is the same as in Comparative Example 4. When the distance between the fixing nip Nf and the photosensitive drum 21 is short, the longitudinal length L of the resin member 52 required to suppress image defects is large. This is because, even if the direction of the air flowing out from the fixing device 70 is the same, due to the proximity of the photosensitive drum 21 to the fixing device 70, water vapor cannot flow outward from the print surface, but easily flows onto the print surface of the photosensitive drum 21.

[0100] Therefore, it is found that, even in the present embodiment in which the distance between the fixing nip Nf and the photosensitive drum 21 is short, image defects can be prevented from occurring by installing a resin member 52 having an appropriate longitudinal length. That is, by installing a resin member 52 having an appropriate longitudinal length and projecting toward the fixing film 112 on the metal member 51 covering the periphery of the fixing film 112, an air flow outward from the print surface of the photosensitive drum 21 can be formed. This configuration allows water vapor to be suppressed from flowing onto the print surface of the photosensitive drum 21, and prevents image defects from occurring, even in a case where water vapor is generated at the fixing nip Nf.

[0101] Relationship Expression

[0102] A relationship expression for preventing image defects from occurring is derived herein, where L denotes the longitudinal length of the resin member 52, W denotes the print surface width of the photosensitive drum 21, N denotes the distance between the fixing nip Nf and the photosensitive drum 21, and O denotes the longitudinal length of the fixing film 112. Figure 9A is a schematic view showing the longitudinal length O of the fixing film 112, the longitudinal length L of the resin member 52, and the print surface width W of the photosensitive drum 21, and Figure 9B is a schematic view of the image forming apparatus showing the distance N between the fixing nip Nf and the photosensitive drum 21. In this context, the distance between the fixing nip Nf and the transfer nip Ntr is calculated as the distance N between the fixing nip Nf and the photosensitive drum 21. In addition, Figure 9AThe printing surface on the photosensitive drum 21 is depicted as a double-dot chain line.

[0103] The results of the paper passage estimation performed in the first and second embodiments indicate that, in the case where the longitudinal length L of the resin member 52 is excessively large, as in Comparative Examples 1 and 6, air flowing through the resin member 52 does not flow outward in the longitudinal direction, and water vapor flows onto the printing surface of the photosensitive drum 21. The paper passage estimation also indicates that, if the longitudinal length L of the resin member 52 is equal to or greater than the length in Embodiments 1 and 2 with respect to the longitudinal length O of the fixing film 112, air flows through the opening portion E on the side of both longitudinal end portions of the resin member 52, and water vapor does not flow onto the printing surface of the photosensitive drum 21. The greater the difference O-L between the longitudinal lengths of the fixing film 112 and the resin member 52, and the smaller the longitudinal length L of the resin member 52, the better the air flow around the fixing film 112 is directed outward in the longitudinal direction. Therefore, a value obtained by dividing the difference O-L between the longitudinal lengths of the fixing film 112 and the resin member 52 by the longitudinal length L of the resin member 52 is used herein as a reference. In Embodiments 1 and 2, the value obtained by dividing the difference O-L between the longitudinal lengths of the fixing film 112 and the resin member 52 by the longitudinal length L of the resin member 52 is 0.0698. In this case, it is sufficient to satisfy the following Expression 1 in order to prevent water vapor from flowing onto the printing surface of the photosensitive drum 21.

[0104] Expression 1

[0105] (O-L) / L≥0.069

[0106] On the other hand, the results of Comparative Examples 5, 9, and 10 indicate that, in the case where the longitudinal length L of the resin member 52 is excessively small, the outward air flow is insufficient, and water vapor flows onto the printing surface of the photosensitive drum 21. Therefore, in order to prevent image defects from occurring, a relational expression for determining a minimum value of the longitudinal length L of the resin member 52 will be formulated next.

[0107] The minimum longitudinal length L of the resin member 52 required to prevent water vapor from flowing onto the printing surface of the photosensitive drum 21 depends on the air flow direction from the side through which the resin member 52, as Figure 10 indicated. When the air flow hits the inner side of the printing surface of the photosensitive drum 21, water vapor flows onto the printing surface, and image defects occur. That is, the air flow direction can be determined based on the position at which the air flow collides with the fixing film 112, that is, the position at which image defects occur. Therefore, an additional paper passage estimation was performed on the case where the longitudinal length L of the resin member 52 was 100 mm, as in Comparative Example 11. The estimation conditions were the same as those of the paper passage estimation performed in the first and second embodiments. Figure 11A table summarizing the results is shown, where the water vapor adhesion distance D is the distance from the longitudinal center to the point where the airflow collides with the photosensitive drum 21. It is assumed that in Comparative Examples 9, 10, and 11, image defects occurred because the water vapor adhesion distance D was less than half the width of the printed surface (W / 2). That is, when the water vapor adhesion distance D is less than half the width of the printed surface (W / 2), the water vapor adhesion distance D creates the longitudinal position where the image defect appears, starting from the center of the fixing film 112.

[0108] In this embodiment, the longitudinal centers of the fixing film 112, the resin component 52, and the photosensitive drum 21 are positioned on the same plane perpendicular to the longitudinal direction, and their centers coincide with each other. Figure 11 As shown, the location of the image defect on the fixing film 112 is located on the outer side of the resin member 52 in the longitudinal direction. From this result, it can be concluded that the airflow is guided outward by the resin member 52. Furthermore, the longitudinal distance DL / 2 from the longitudinal location of the image defect on the fixing film 112 to each end of the resin member 52 increases with the increase of the longitudinal length L of the resin member 52. That is, it has been found that, given a sufficient gap on the side of the longitudinal end of the resin member 52, the larger the longitudinal length L of the resin member 52, the more significant the outward guiding effect on the airflow.

[0109] Besides the longitudinal length L and the printing surface width W of the resin component 52, the presence or absence of image defects on the fixing film 112 also affects the distance N between the fixing clamping part Nf and the photosensitive drum 21. This is because for airflow passing through the longitudinal end of the resin component 52 in the same direction, the greater the distance N between the fixing clamping part Nf and the photosensitive drum 21, the greater the extent to which water vapor flows outward before reaching the photosensitive drum 21. Therefore, in addition to the longitudinal length L and the printing surface width W of the resin component 52, the relationship involving the distance N between the fixing clamping part Nf and the photosensitive drum 21 will now be discussed.

[0110] When the fixing clamp Nf moves 1 mm toward the photosensitive drum 21, the range reached by the outward airflow in the longitudinal direction can be expressed in this paper as {D-(L / 2)} / N, which is the longitudinal movement distance of the airflow per mm. Figure 12The results of the values of the longitudinal length L of the resin member 52 and half of the value of the longitudinal length in Comparative Examples 9, 10, and 11 are shown in a graph. In the graph, the y-axis represents the longitudinal moving distance of the air current per mm {D-(L / 2)} / N, and the x-axis represents the half of the value of the longitudinal length of the resin member 52, L / 2. It is apparent from the graph that the greater the longitudinal length L of the resin member 52, the greater the outward air current. The relationship y=0.0001x2-0.002x is obtained as an approximate expression of the results of Comparative Examples 9, 10, and 11. In addition, in order to prevent the water vapor from hitting the print surface of the photosensitive drum 21, it is enough that the water vapor adhesion distance D is greater than half of the print surface of the photosensitive drum 21, W / 2, and satisfies W / 2≤D. For the configuration in which the air current does not hit the print surface of the photosensitive drum 21, the above expression can be rearranged to produce the following expression 2.

[0111] Expression 2

[0112] W≤2x(0.0001xL / 2xL / 2-0.002xL / 2)xN+L

[0113] Therefore, by satisfying the expression 1 and the expression 2, the configuration in which the water vapor does not flow onto the print surface of the photosensitive drum 21 is achieved. That is, the appropriate range of the longitudinal length L of the resin member 52 can be determined based on the longitudinal length O of the fixing film 112, the print surface width W of the photosensitive drum 21, and the distance N between the fixing nip Nf and the photosensitive drum 21.

[0114] While the present application has been described with reference to exemplary embodiments, it is to be understood that the application 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 imaging apparatus in which an image is formed on a recording material, the imaging apparatus comprising: A heating device in which recording material is heated in a clamping portion, the heating device comprising: - A first rotating component, which is heated by a heat source; - A second rotating member, which together with the first rotating member forms the clamping portion; - A first covering, the first covering being disposed along the outer peripheral surface of the first rotating member so as to surround the first rotating member; and - A second cover, disposed between the first cover and the first rotating member; the second cover having a protruding portion projecting toward the first rotating member; and A transfer mechanism comprising a photosensitive drum supporting a toner image, a charging unit for charging the photosensitive drum, and a transfer roller forming a transfer clamping portion with the photosensitive drum, wherein the transfer mechanism transfers the toner image onto the recording material; and In the longitudinal direction of the first rotating member, the length of the first rotating member is a first length, and the length of the protruding portion is a second length, the second length being less than the first length. The following expressions (1) and (2) are satisfied, where L is the longitudinal length of the protruding portion, W is the width of the printing surface on the photosensitive drum, N is the distance between the clamping portion and the photosensitive drum, and O is the longitudinal length of the first rotating member. (OL) / L≥0.069 …(1) W≤2×(0.0001×L / 2×L / 2-0.002×L / 2)×N+L…(2).

2. The imaging device according to claim 1, An airflow guiding space is formed between the first covering and the outer peripheral surface; and The protruding portion protrudes to block the airflow in the airflow guide space within the rotational direction of the first rotating member.

3. The imaging device according to claim 1, The first covering is disposed over the entire first rotating member in the longitudinal direction.

4. The imaging device according to claim 1, In the direction of conveying the recording material, the protruding portion is located upstream of the clamping portion.

5. The imaging device according to claim 4, The protruding portion is located at the end portion of the first cover on the side near the clamping portion.

6. The imaging device according to claim 1, Wherein, as observed in the longitudinal direction of the first rotating member, the shortest distance from the second cover to the first rotating member is shorter than the shortest distance from the first cover to the first rotating member.

7. The imaging device according to any one of claims 1 to 6, The material of the first covering is metal; and The material of the second covering is resin.

8. The imaging device according to claim 7, The second covering also has a contact surface that contacts the first covering; The protruding portion protrudes from a surface on the opposite side to the contact surface; and The length of the contact surface in the direction perpendicular to the longitudinal direction is greater than the length from the contact surface to the end of the protrusion.

9. The imaging device according to claim 1, The heat source is a heater disposed in the internal space of the first rotating component; The first rotating component is a tubular membrane; The second rotating component is a pressure roller with an elastic layer; and The tubular membrane is held between the heater and the pressure roller, and the image on the recording material is heated via the tubular membrane at the holding portion formed between the tubular membrane and the pressure roller.

10. The imaging apparatus according to any one of claims 1 to 6, The first cover is positioned in the space between the photosensitive drum and the first rotating member.

11. The imaging device according to claim 10, The first rotating member is positioned vertically above the photosensitive drum; and When viewed vertically, the first cover overlaps with the photosensitive drum.

12. The imaging device according to any one of claims 1 to 6, The transfer mechanism further includes an exposure unit for forming an electrostatic latent image on the photosensitive drum and a development unit for developing the electrostatic latent image on the photosensitive drum.

Images