Fixing device and image forming apparatus

Abstract

The invention relates to a fixing device and an image forming apparatus capable of sufficiently removing electricity from the surface of a pressure roller. A conductive surface layer (34) having conductivity of the pressure roller (31) is formed on a roller main body portion (31a) so as to be in contact with the surface of the fixing belt (21) at a nip portion, and an annular member (65) having conductivity and grounding is provided on a core shaft (32) of the pressure roller (31) so as to face an end face of the roller main body portion (31a). Furthermore, the end surface of the roller body (31a) is inclined so as to approach the annular member (65) from the roller surface side toward the roller center axis side when viewed from a cross-section including the roller center axis (W) of the pressure roller (31). In addition, the conductive surface layer (34) is provided with a folded-in part (34a) at the end part in the width direction of the side provided with the annular component (65), and the folded-in part (34a) is folded in from the roller surface side to the roller center shaft side in a manner of inclining along the end surface of the roller main body part (31a). The folded portion (34a) is in contact with an end surface of the annular member (65).

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing an image of toner carried on the surface of a sheet by heating it, and an image forming apparatus such as a copier, printer, fax machine or multifunction printer having the fixing device. Background Technology

[0002] In the past, in the fixing device of image forming apparatus such as copiers and printers, in order to prevent the generation of abnormal images such as electrostatic drift, there are known techniques for removing static electricity from the pressure roller (for example, see Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technique of providing an annular conductive elastic member for de-energizing the fixing belt and the pressure roller at the shaft portion at the end in the width direction of the pressure roller.

[0004] Existing fixing devices do not sufficiently remove static electricity from the surface of the pressure roller, which cannot adequately mitigate the occurrence of abnormal images such as electrostatic drift.

[0005] The present invention was proposed to solve the above-mentioned problems, and its purpose is to provide a fixing device and an image forming device that can effectively remove static electricity from the surface of the pressure roller.

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-13613 Summary of the Invention

[0007] The fixing device of the present invention includes: a fixing rotating body heated by a heat source, and a pressure roller forming a clamping portion for conveying sheet by pressing against the fixing rotating body. The pressure roller includes: a conductive surface layer having conductivity formed on a roller body in such a way that it contacts the surface of the clamping portion and the fixing rotating body; and an annular member disposed on the shaft portion of the pressure roller facing the end face of the roller body, having conductivity and being grounded. When viewed in cross-section of the roller central axis including the pressure roller, the end face of the roller body is inclined from the roller surface side toward the roller central axis side towards the annular member. The conductive surface layer has a folded-in portion at its width-direction end on the side where the annular member is disposed. The folded-in portion is folded in from the roller surface side toward the roller central axis side in such an inclined manner along the end face of the roller body, and the folded-in portion contacts the end face of the annular member.

[0008] According to the present invention, a fixing apparatus and an image forming apparatus are provided that can sufficiently remove static electricity from the surface of a pressure roller. Attached Figure Description

[0009] Figure 1The diagram shown is an overall configuration diagram of the image forming apparatus in an embodiment of the invention.

[0010] Figure 2 The diagram shown is a configuration diagram of the fixing device.

[0011] Figure 3 The image shown is a top view of the fixing device as seen from the width direction.

[0012] Figure 4 The image shown is a schematic side view of the fixing belt and guide components as seen in the width direction.

[0013] Figure 5 The image shown is a cross-sectional view of the fixing device connected to the grounding path.

[0014] Figure 6 The image shown is a cross-sectional view of the width end of the main part of the fixing device.

[0015] Figure 7 The image shown is a cross-sectional view of the main part of the fixing device as a comparative example, taken in the width direction.

[0016] Figure 8 The figure shown is a diagram showing the relationship between the knurling diameter of the annular component, which is a variation of Example 1, and the outer diameter of the end of the pressure roller.

[0017] Figure 9 The figure shown is a cross-sectional view of the width end of the main part of the fixing device in Modification Example 2.

[0018] Figure 10 The figure shown is a cross-sectional view of the width end of the main part of the fixing device in Modification Example 3.

[0019] Figure 11 The image shown is a cross-sectional view of the main part of the fixing device as a comparative example, taken in the width direction. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent parts are given the same reference numerals, and detailed descriptions thereof are omitted where appropriate.

[0021] First, through Figure 1 The overall structure and operation of the image forming apparatus 100 will be explained.

[0022] exist Figure 1In this text, 100 represents a small printer that serves as an image forming apparatus, 1 represents a photosensitive drum that forms a toner image on its surface, 6 represents a processing cartridge that integrates the photosensitive drum 1, the charged roller 4, the developing device 5, and the cleaning device 2, and 7 represents an exposure device (writing unit) that irradiates the photosensitive drum 1 with exposure light L based on image information input from an input device such as a personal computer.

[0023] Additionally, 9 represents a transfer roller that transfers the toner image carried on the surface of the photosensitive drum 1 to the sheet P that is conveyed to the transfer clamping part (transfer position); 12 represents a paper feeding device (paper feeding cassette) that houses the sheet P such as paper; 16 represents a registration roller (timing roller) that conveys the sheet P toward the transfer clamping part that abuts against the photosensitive drum 1 and the transfer roller 9; and 20 represents a fixing device that fixes the unfixed image on the sheet P.

[0024] Here, a charging roller 4, a developing unit 5, and a cleaning unit 2 are arranged around the photoreceptor drum 1. These components (photoreceptor drum 1, charging roller 4, developing unit 5, and cleaning unit 2) are then integrated as a processing cartridge 6 and are configured to be detachable (replaceable) relative to the image forming apparatus main body 100 (apparatus main body). The processing cartridge 6 is removed by the user from the image forming apparatus main body 100 and replaced with a new one when a predetermined replacement cycle is reached.

[0025] Reference Figure 1 The operation of the image forming apparatus 100 during normal image forming will be explained.

[0026] First, when image information is sent from an input device such as a personal computer to the exposure device 7 of the image forming apparatus 100, an exposure beam (laser) based on the image information is emitted from the exposure device 7 toward the surface of the photosensitive drum 1.

[0027] On the other hand, the photoreceptor drum 1 is driven by a drive motor mounted on the image forming apparatus main body 100 and rotates in the direction of the arrow (clockwise). Then, the surface of the photoreceptor drum 1 is uniformly charged at a position opposite to the charging roller 4 (charging process). This creates a charged potential (approximately -900V) on the photoreceptor drum 1. Then, the charged surface of the photoreceptor drum 1 reaches the irradiation position of the exposure beam L. The potential of the portion irradiated by the exposure beam L then becomes a latent image potential (within the range of 0 to -100V), forming an electrostatic latent image on the surface of the photoreceptor drum 1 (exposure process).

[0028] Subsequently, the surface of the photosensitive drum 1, on which the electrostatic latent image is formed, reaches the position opposite to the developing apparatus 5. Then, toner is supplied from the developing apparatus 5 to the photosensitive drum 1, and the latent image on the photosensitive drum 1 is developed to form a toner image (developing process).

[0029] After this, the surface of the photosensitive drum 1, after the developing process, reaches the transfer clamping part (transfer position) with the transfer roller 9. Then, in the transfer clamping part with the transfer roller 9, by applying a transfer bias voltage (a bias voltage of different polarity from the toner) to the transfer roller 9 from the power supply unit, the toner image formed on the photosensitive drum 1 is transferred onto the sheet P conveyed by the registration roller 16 (transfer process).

[0030] Then, the surface of the photosensitive drum 1 after the transfer process reaches a position facing the cleaning device 2. At this position, the untransferred toner remaining on the photosensitive drum 1 is mechanically removed by a cleaning scraper and recycled into the cleaning device 2 (cleaning process).

[0031] This completes the series of imaging processes performed on the photosensitive drum 1.

[0032] On the other hand, the sheet P, which is conveyed to the transfer clamping section between the photosensitive drum 1 and the transfer roller 9, performs the following operation.

[0033] First, the topmost sheet of paper P stored in the paper feeding device 12 will be fed along the conveying path via the paper feeding roller 15.

[0034] Subsequently, the sheet P reaches the position of the alignment roller 16. Then, the sheet P, which has reached the position of the alignment roller 16, is transported toward the transfer clamp (the contact position between the transfer roller 9 and the photosensitive drum 1) in a timely manner so as to correspond with the position of the image formed on the photosensitive drum 1.

[0035] Next, after the transfer process, the sheet P passes through the transfer clamping part (transfer roller 9) and then travels along the conveying path to the fixing unit 20. The sheet P arriving at the fixing unit 20 is fed between the fixing belt 21 and the pressure roller 31, and the image is fixed by heat from the fixing roller 21 and pressure from the components 21 and 31 on both sides (fixing process). After the sheet P with the fixed image is conveyed out from between the fixing belt 21 and the pressure roller 31 (fixing clamping part), it is discharged from the image forming apparatus main body 100 and carried onto the paper output tray.

[0036] This completes the series of image formation processes.

[0037] Next, use Figures 2-6 The structure and operation of the fixing device 20 will be explained.

[0038] The fixing unit 20 is a device that heats and conveys a sheet P (a sheet carrying toner in an unfixed state) while simultaneously heating it.

[0039] Reference Figure 2The fixing device 20 comprises a fixing belt 21 as a fixing rotating body, a surface heater 24 as a heat source (heating unit), a holding member 23, a support bar 30, a thermistor 40, a pressure roller 31 as a pressure rotating body, and an annular component 65 (see reference). Figure 3 , Figure 5 , Figure 6 It consists of (etc.).

[0040] Here, the fixing belt 21 is an annular belt component externally connected to the pressure roller 31 and rotating consequently with the rotation of the pressure roller 31. The fixing belt 21 is a thin, flexible annular belt. Figure 2 Rotate (driven rotation) in the direction of the arrow (clockwise). (See reference) Figure 5 (Not to scale) etc., the fixing tape 21 has a substrate layer 21a as a conductive layer and an insulating (or medium resistance) surface layer 21b (surface layer) stacked from the inner peripheral surface (sliding contact surface with the planar heater 24) side, and the overall thickness is set to less than 1 mm.

[0041] The substrate layer 21a of the fixing tape 21 has a thickness of 30 to 50 μm and is formed of a material containing carbon dispersed in a metal material such as nickel or stainless steel, or a resin material such as polyimide. It functions as a conductive layer with conductivity.

[0042] The fixing tape 21 has a layer thickness of 5μm to 50μm and is formed from insulating materials such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkoxy vinyl acid), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, and PES (polyethersulfone). By providing an insulating tape surface layer 21b, the release properties (peelability) of the toner (toner like T) are ensured.

[0043] In addition, in this embodiment, the surface layer 21b is formed of an insulating material, but it can also be formed of a medium-resistance material by dispersing a relatively small amount of carbon in the insulating material.

[0044] A surface heater 24, a holder 23, a support 30, a thermistor 40, etc. are provided on the inner side (inner circumferential side) of the fixing belt 21.

[0045] Here, the planar heater 24 is positioned in the width direction ( Figure 2 The vertical direction of the paper surface, Figures 3-6The surface heater 24 is arranged to extend in the left-right direction (synonymous with "axial direction"). Furthermore, the surface heater 24 is pressed onto the pressure roller 31 via the fixing belt 21 on the inner side (inner circumferential surface side) of the fixing belt 21, forming a clamping portion (fixing clamping portion) for conveying the sheet P. That is, the surface heater 24 is configured to slide in contact with the inner circumferential surface of the fixing belt 21. Furthermore, the surface heater 24 is pressed onto the pressure roller 31 via the fixing belt 21 to form the clamping portion of the sheet P. Thus, the surface heater 24 functions as a component forming the clamping portion (fixing clamping portion) (clamping portion forming component).

[0046] Furthermore, the planar heater 24 has an impedance pattern (heating resistor) formed on the portion that slides in contact with the inner circumferential surface of the fixing belt 21. Then, power is supplied to the impedance pattern 26 (heating resistor) from the unlabeled power supply section, and the impedance pattern heats up through its resistance, thereby heating the fixing belt 21. In this way, the planar heater 24 also functions as a heat source (heating means) for heating the fixing belt 21.

[0047] In addition, in this embodiment, in order to reduce the sliding resistance between the planar heater 24 and the inner circumferential surface of the fixing belt 21, a lubricant such as silicone oil or fluorinated grease is directly applied to the inner circumferential surface of the fixing belt 21.

[0048] In addition, in this embodiment, the lubricant is directly applied to the inner peripheral surface of the fixing belt 21, but the lubricant can also be applied to the sliding contact surface of the surface heater 24, or indirectly applied to the inner peripheral surface of the fixing belt 21.

[0049] In addition to applying lubricant to the inner circumferential surface of the fixing belt 21, a sheet-like component made of a low-friction material such as PTFE can be covered or a surface layer can be provided on the surface of the planar heater 24.

[0050] In this embodiment, the planar heater 24 is held on the retainer 23 (retaining member).

[0051] The retainer 23 has a recess, in which the planar heater 24 is embedded to retain the planar heater 24 in the entire width direction.

[0052] Furthermore, the retainer 23 is held on the support 30 while holding the planar heater 24. Then, the two ends of the support 30 holding the planar heater 24 and the retainer 23 in the width direction are respectively held on the frame 60 of the fixing device 20 by flange members 42 (see reference). Figure 3 wait).

[0053] In this way, the fixing belt 21 is directly heated by the planar heater 24 (impedance pattern) disposed therein. Then, heat is applied from the surface of the heated fixing belt 21 to the toner image on the sheet P.

[0054] Here, the output control of the surface heater 24 is based on the temperature detection result of the thermistor 40, which is in direct contact with the surface heater 24 (or indirectly via other components). In this embodiment, a temperature sensor that directly detects the surface temperature of the fixing belt 21 is not provided. Instead, the surface temperature (fixing temperature) of the fixing belt 21 is indirectly controlled by controlling the temperature of the surface heater 24 through the thermistor 40, so that it reaches the desired temperature.

[0055] Reference Figure 4 A pair of flange members 42 guide the two ends of the fixing belt 21 in the width direction from the inner peripheral surface side to maintain the fixing belt 21 in a generally cylindrical posture.

[0056] In detail, the two flange members 42 are formed of heat-resistant resin material or the like, and are respectively located at both ends of the frame 60 of the fixing device 20 in the width direction, and are held so as to be able to slide in the direction of forming the clamping part (fixing clamp). The flange members 42 are provided with a guide part 42a for holding the fixing belt 21 while maintaining the generally cylindrical posture of the fixing belt 21, and a limiting part for limiting the movement (belt bias) of the fixing belt 21 in the width direction.

[0057] In addition, in this embodiment, such as Figure 3 As shown, the fixing belt 21 (and the surface heater 24 and the holder 23) is configured such that it is pressed onto the pressure roller 31 by the pressure rod 52 (pressure mechanism 51) through the flange member 42.

[0058] In addition, the flange members 42 are arranged at both ends in the width direction, excluding the circumferential direction of the fixing clamping part, so as not to interfere with the formation of the fixing clamping part by the planar heater 24.

[0059] In addition, in this embodiment, the only components that come into contact with the inner peripheral surface of the fixing belt 21 are the flange component 42 and the planar heater 24, which are loosely in contact at both ends in the width direction. Apart from these, there are no other components (with guide portions) that come into contact with the inner peripheral surface to guide the rotation of the fixing belt 21.

[0060] In this embodiment, the support member 30 is disposed inside the fixing belt 21 so as to abut against the pressure roller 31 via the surface heater 24 (and the holder 23) and the fixing belt 21. The support member 30 is used to strengthen the surface heater 24 (and the holder 23) that forms the fixing clamping part, and is mounted on the frame 60 (or the holder 23) by means of screws or the like.

[0061] Furthermore, by having the support member 30 abut against the pressure roller 31 via the surface heater 24 (and the holder 23) and the fixing belt 21, the undesirable situation of excessive deformation of the surface heater 24 (and the holder 23) under the pressure of the pressure roller 31 in the fixing clamping section is suppressed. To achieve the above functions, the support member 30 is preferably made of a metal material with high mechanical strength such as stainless steel or iron.

[0062] Furthermore, as the material forming the retainer 23, resin or metal materials can be used. Preferably, a resin material (e.g., liquid crystal polymer (LCP), polyamide-imide (PAI), polyethersulfone (PES), polyphenylene sulfide (PPS), polyether nitrile (PEN), polyether ether ketone (PEEK), etc.) is preferred, as it possesses rigidity that does not produce significant deflection even when subjected to pressure from the pressure roller 31. In this embodiment, liquid crystal polymer (LCP) is used as the material for the retainer 23.

[0063] Reference Figure 2 The pressure roller 31, which serves as a pressure rotating body, is formed by sequentially layering an elastic layer 33 and a conductive surface layer 34 on a spindle 32, which serves as a shaft. It is driven by a motor 95 in a predetermined direction. Figure 2 Rotation drive (in the counterclockwise direction).

[0064] The spindle 32 (shaft portion) of the pressure roller 31 is a hollow structure made of a metallic material (conductive material). The elastic layer 33 of the pressure roller 31 is formed of an insulating material such as silicone rubber, foamed silicone rubber, or fluororubber.

[0065] The conductive surface layer 34 of the pressure roller 31 is a thin surface layer (release layer) formed by dispersing carbon or the like in PFA, PTFE, etc., and is conductive. In this embodiment, the conductive surface layer 34 is tubular and can be formed by covering the elastic layer 33 with a tube and performing heat processing or the like. Furthermore, the conductive surface layer 34 will be used later. Figure 6 Further details will follow.

[0066] The pressure roller 31 presses against the fixing belt 21, forming the required clamping part (fixing clamp) between the components of both. Additionally, refer to... Figure 3 The pressure roller 31 is provided with a gear 45 that meshes with the drive gear of the drive motor. Figure 2 The roller is driven to rotate in the direction of the arrow (counterclockwise). Furthermore, the two ends of the pressure roller 31 in the width direction are supported by bearings within the frame 60 of the fixing device 20, allowing it to rotate.

[0067] In addition, the fixing device 20 of this embodiment is also provided with an annular component 65, but these will be described in detail later.

[0068] The following is a brief explanation of the normal operation of the fixing device 20 configured as described above.

[0069] When a printing command is input into the main body 100 of the device, power is supplied to the surface heater 24, and the pressure roller 31 is started to move via the drive motor 95. Figure 2 The rotation is driven in the direction of the arrow. Therefore, through the friction between the fixing belt 21 and the pressure roller 31 in the fixing clamp, the fixing belt 21 also rotates... Figure 2 The arrow in the middle rotates in the direction of the passive rotation (driving the rotation).

[0070] Then, sheet P is supplied from paper feeding device 12, and an unfixed image is carried (transferred) onto sheet P at the position of transfer roller 9. The sheet P, carrying the unfixed image (toner image), is guided by an inlet guide plate (not shown) while... Figure 2 It is conveyed in the direction of arrow Y10 and fed into the clamping part (fixing clamping part) of the fixing belt 21 and the pressure roller 31, which are in a pressing state.

[0071] Then, the toner image is fixed onto the surface of the sheet P by the heating of the fixing belt 21 heated by the surface heater 24 and the pressing pressure of the surface heater 24 (and the holder 23) reinforced by the support member 30 and the pressure roller 31. Afterwards, the sheet P delivered from the fixing clamp is guided by the exit guide plate (not shown) and conveyed in the direction of arrow Y11.

[0072] Hereinafter, the configuration and operation of the characteristic fixing device 20 in the image forming apparatus 100 of this embodiment will be described in detail.

[0073] As previously used Figure 2 , Figure 5 As explained above, a substrate layer 21a, which is a conductive layer, is provided on the fixing tape 21. In addition, in the fixing tape 21, an insulating surface layer 21b (or a surface layer with medium resistance) is directly laminated on the substrate layer 21a (conductive layer).

[0074] That is, the fixing tape 21 in this embodiment is a double-layer structure in which a conductive tape with a conductive layer as a substrate layer 21a is used as a substrate layer 21a, and an insulating or medium-resistance tape surface layer 21b is stacked on the substrate layer 21a.

[0075] In particular, in this embodiment, one end of the substrate layer 21a (with a conductive layer) in the width direction (the side where the conductive annular member 65 described later is disposed) Figure 5The left side of the substrate layer 21a (with a conductive strip) is formed in such a way that it protrudes further into the width direction than the surface layer 21b. That is, the substrate layer 21a (with a conductive strip) is formed with a portion exposed at the width direction end on the side where the annular member 65 is provided.

[0076] Furthermore, the substrate layer 21a (with a conductive layer) protruding to one end in the width direction directly contacts the annular component 65 described later (forming a contact portion).

[0077] Therefore, the surface layer 21b extends in the width direction other than the contact portion between the substrate layer 21a and the annular component 65 described later. Figure 5 , Figure 6 The surface layer 21b is stacked on the substrate layer 21a (with a conductive layer) within a range in the left-right direction and axial direction. In other words, the surface layer 21b is directly stacked on the substrate layer 21a within the width direction excluding the exposed portion of the substrate layer 21a.

[0078] On the other hand, a conductive surface layer 34 (which is conductive) is provided on the pressure roller 31, which serves as a pressure rotating body, to form a clamping portion (fixing clamping portion) by contacting the belt surface layer 21b of the fixing belt 21 (fixing rotating body). The conductive surface layer 34 is formed on the roller body portion 31a (the portion where the elastic layer 33 and the conductive surface layer 34 are stacked) in such a way that it contacts the surface of the clamping portion and the fixing belt 21.

[0079] Here, as Figure 5 , Figure 6 As shown, in the fixing apparatus 20 of this embodiment, the pressure roller 31 (pressure rotating body) has a conductive and grounded annular member 65 disposed on the spindle 32, which serves as the shaft of the pressure roller 31, with its end face facing the roller body 31a (the part on which the elastic layer 33 and the conductive surface layer 34 are formed, except for the part at both ends of the spindle 32 which are exposed). Furthermore, in this embodiment, the annular member 65 contacts and conducts with the exposed portion of the substrate layer 21a (with the conductive layer) (the portion exposed at one end in the width direction where the surface layer 21b is not laminated). Therefore, the annular member 65 contacts and conducts with both the substrate layer 21a (with the conductive layer) and the conductive surface layer 34 of the fixing belt 21.

[0080] In detail, such as Figure 5 , Figure 6 As shown, the annular component 65 is an annular (donut-shaped) component formed of a conductive material.

[0081] In particular, the annular component 65 in this embodiment has knurling (multiple protrusions and recesses) on its outer peripheral surface, and its outer peripheral surface is in contact with the exposed portion of the substrate layer 21a (with conductive layer).

[0082] The annular component 65, as the annular component, functions as a conductive component for grounding the substrate layer 21a (with a conductive layer) and the conductive surface layer 34 of the fixing tape 21, respectively.

[0083] Furthermore, the annular member 65 is inserted (set) into the spindle 32 of the pressure roller 31 (which functions as an end shaft portion) in a manner that contacts the end face of the substrate layer 21a (with a conductive layer) of the fixing belt 21 or the roller body portion 31a of the pressure roller 31. The annular member 65 and the pressure roller 31 move together in a predetermined direction ( Figure 2 Rotate in the counterclockwise direction.

[0084] Furthermore, in this embodiment, the outer diameter (knurled outer diameter) of the annular component 65 is approximately equal to or slightly larger than the outer diameter of the roller body portion 31a of the pressure roller 31 (the portion where the elastic layer 33 and the conductive surface layer 34 are formed). Also, the knurled protrusions of the annular component 65 contact the substrate layer 21a of the fixing belt 21 (the exposed portion within the conductive layer).

[0085] At this time, even if the outer diameter (knurled outer diameter) of the annular component 65 is the same as the outer diameter of the roller body 31a, since the surface layer 21b is extremely thin and the pressure roller 31 presses against the fixing belt 21 in a way that bites into it, the annular component 65 (protrusion) contacts the substrate layer 21a (with conductive layer) and becomes conductive.

[0086] In this embodiment, an annular component that contacts the substrate layer 21a (with a conductive layer) of the fixing belt 21 is used. This annular component has multiple knurled protrusions on its outer peripheral surface (in this embodiment, it is a spur gear-shaped annular component). Therefore, compared to the case where the annular component is completely in contact with the substrate layer 21a, the multiple protrusions arranged in a circumferential and width direction alternately contact the substrate layer 21a, reducing poor contact such as one-end contact. As a result, good and stable relatively large contact pressure can ensure conductivity with the substrate layer 21a.

[0087] Furthermore, in this embodiment, the annular member 65 is pressed into the mandrel 32 to improve its conductivity (electrical connection) with the mandrel 32, which serves as the shaft portion. In addition, to prevent the annular member 65 in the mandrel 32 from shifting in the width direction (axial direction), the annular member 65 may be bonded and fixed to the mandrel 32 by a conductive adhesive.

[0088] In addition, such as Figure 5 As shown, in this embodiment, the annular component 65 is grounded via the spindle 32.

[0089] Specifically, the spindle 32 is connected to a grounding wire (connected to the grounded frame 60), and a resistor 68 (resistor component) is provided in the grounding wire. Thus, the annular component 65 is properly grounded.

[0090] Furthermore, the annular component 65 is positioned outside the area of ​​the maximum paper-passing region M (the width direction through which the largest sheet P that can be transported passes) in the fixing device 20 (the non-paper-passing region). Therefore, the effect of the annular component 65 contacting the fixing image is avoided.

[0091] Thus, the fixing apparatus 20 of this embodiment is provided with an annular member 65 that functions as a conductive component, thereby ensuring good conductivity between the substrate layer 21a (with a conductive layer) of the fixing belt 21, the conductive surface layer 34 of the pressure roller 31, and the grounded annular member 65. Therefore, it is difficult for charge to accumulate on the fixing belt 21 and the pressure roller 31, reducing abnormal images such as electrostatic drift caused by charge accumulation.

[0092] In addition, "electrostatic shift" refers to the phenomenon in which, during the fixing process, the toner carried on the sheet P being fed into the clamping part (fixing clamping part) is electrostatically transferred and adheres to the surface of the fixing belt 21 (fixing rotating body), and the adhered toner is re-adhered to the sheet P as the fixing belt 21 rotates once.

[0093] This transfer of toner to the fixing belt 21 is caused by the fact that the surfaces of the fixing belt 21 and the pressure roller 31 are respectively charged. In particular, the toner used in this embodiment is negatively polarized. Since the fixing belt 21 carries a positive charge and the pressure roller 31 carries a negative charge, the toner, which is subjected to electrostatic repulsion from the pressure roller 31 side and electrostatic attraction from the fixing belt 21 side, adheres to the fixing belt 21.

[0094] In this embodiment, as described above, the fixing apparatus 20 actively removes static electricity from the substrate layer 21a (with a conductive layer) of the fixing belt 21 and the conductive surface layer 34 of the pressure roller 31, making it difficult for the surfaces of the fixing belt 21 and the pressure roller 31 to become charged. Therefore, electrostatic displacement is unlikely to occur.

[0095] Here, refer to Figure 6 When viewed from a section containing the roller body 31a of the pressure roller 31 (the end face on the side of the annular member 65), the end face of the roller body 31a of the pressure roller 31 is inclined (formed as a cone) in a manner that approaches the annular member 65 from the roller surface side toward the roller center axis side.

[0096] That is, the outer diameter of one end of the roller body portion 31a in the width direction is smaller than the outer diameter of the rest (appropriately referred to as the "outer diameter of the pressure roller"). In other words, the end of one end of the roller body portion 31a in the width direction is formed into a generally frustum conical shape.

[0097] In addition, the shape of these roller body parts 31a is not the shape of the roller body part 31 under thermal expansion, but the shape of the roller body part 31 at room temperature.

[0098] Moreover, refer to Figure 6 In the pressure roller 31 of this embodiment, the conductive surface layer 34 is located at the width-direction end (width-direction end side) of the side where the annular member 65 is provided. Figure 5 , Figure 6 A fold-in portion 34a is formed at the left end of the pressure roller 31. This fold-in portion 34a is a portion folded in from the roller surface side (outer diameter (outer peripheral surface) side of the pressure roller 31) toward the roller center axis side (roller center axis W side) in an inclined manner along the end face of the roller body portion 31a (the portion where the elastic layer 33 or the conductive surface layer 34 is formed). (It also includes cases where it is not actually folded in during the manufacturing process, but is formed in an appearance of being folded in.) In particular, the conductive surface layer 34 in this embodiment is tubular and is formed in such a way that it covers approximately the entire area of ​​the outer peripheral surface and end face of the elastic layer 33.

[0099] Furthermore, it is formed such that the folded-in portion 34a contacts the end face of the annular member 65. That is, the width direction end (axial end) of the conductive surface layer 34 is folded in obliquely along the inclined end face of the elastic layer 33, and its front end portion 34a1 (the small diameter portion near the mandrel 32) contacts the end face of the annular member 65.

[0100] In this way, by making the front end 34a1 (small diameter portion) of the folded-in portion 34a formed on the conductive surface layer 34 in an inclined (conical shape) manner along the width direction of the roller body portion 31a (elastic layer 33) contact the end face of the annular member 65, even if the pressure roller 31 deforms due to thermal expansion during the fixing process (in actual use), it is difficult to produce poor contact (poor conductivity) between the folded-in portion 34a and the end face of the annular member 65.

[0101] That is, such as Figure 7As shown in the comparative example, the pressure roller 131 has an end face of the roller body (elastic layer 133) that is a plane substantially perpendicular to the roller's central axis W. A folded-in portion 134a of the conductive surface layer 134 is formed along this substantially perpendicular end face. During the fixing process (in actual use), the pressure roller 31 undergoes thermal expansion, causing deformation at the end face. This easily leads to poor contact (poor conductivity) between the folded-in portion 34a and the end face of the annular component 65. In particular, the inner diameter portion of the pressure roller 31 (roller body 31a) that is bonded (joined) to the mandrel 32 is difficult to thermally expand, while the outer diameter portion, lacking the constraint created by such bonding, is prone to thermal expansion. Figure 7 Thermal expansion occurs in the direction indicated by the white arrow. Furthermore, if such thermal expansion occurs, the annular component 65 will be deformed by the pressure of the roller body 31a, which can easily lead to poor contact (poor conductivity) between the folded-in portion 34a and the end face of the annular component 65.

[0102] In contrast, in this embodiment, the use of Figure 7 During the fixing process (in actual use), the thermal expansion of the pressure roller 31 (roller body 31a) causes the end of the pressure roller 31 (roller body 31a) in the width direction to be formed into a roughly frustum-shaped cone, with a folded-in portion 34a formed along its end face shape. Therefore, poor contact (poor conductivity) between the folded-in portion 34a and the end face of the annular member 65 is less likely to occur. Conversely, when the roller body 31a expands thermally during the fixing process (in actual use), the outer diameter portion of the folded-in portion 34a can easily contact the end face of the annular member 65, in addition to the inner diameter portion, thereby ensuring sufficient contact area between the conductive surface layer 34 and the annular member 65.

[0103] Therefore, the surface of the pressure roller 31 (conductive surface layer 34) is sufficiently de-electrolyzed, effectively mitigating the generation of abnormal images such as electrostatic offset.

[0104] <Variation Example 1>

[0105] Reference Figure 8 The annular component 65 provided in the fixing device 20 of modified example 1 is also related to Figure 6 As shown, a knurled surface is formed on its outer peripheral surface, which becomes conductive after contacting the exposed portion of the substrate layer 21a (with conductive layer) of the fixing tape 21.

[0106] Here, Figure 8 (A) shows the configuration of the fixing device 20, which consists of a roller body 31a (see reference). Figure 5 The outer diameter D (outer diameter of the front end 34a1 (small diameter portion)) of the width direction end of the annular component 65 is smaller than the knurled inner diameter B1 (diameter of the bottom of the knurled recess) of the annular component 65. <B1)。

[0107] With this configuration, the front end 34a1 (small diameter portion) of the conductive surface layer 34 (roller body portion 31a) abuts against the end face inside the knurled inner diameter B1 of the annular member 65, thus ensuring sufficient contact area between the conductive surface layer 34 and the annular member 65.

[0108] In contrast, Figure 8 (B) The fixing device 20 shown is configured such that the outer diameter D (outer diameter of the front end 34a1 (small diameter portion)) of the side of the roller body 31a where the annular member 65 is located is greater than the knurling inner diameter B1 (diameter of the bottom of the knurling recess) of the annular member 65, and smaller than the knurling outer diameter B2 (diameter of the bottom of the knurling recess) of the annular member 65. <D<B2)。

[0109] In this configuration, the front end 34a1 (small diameter portion) of the conductive surface layer 34 (roller body portion 31a) abuts against the sides of the multiple knurled protrusions of the annular member 65. Therefore, the multiple protrusions arranged in a circumferentially spaced manner alternately contact the substrate layer 21a, reducing poor contact due to one-end contact, and as a result, good and stable relatively large contact pressure can ensure conductivity with the substrate layer 21a.

[0110] Furthermore, in the fixing device 20 of Modified Example 1, the surface of the pressure roller 31 can also be sufficiently de-electrified.

[0111] <Variation Example 2>

[0112] like Figure 9 As shown, in the fixing device 20 of Modified Example 2, the annular component 65 is located at the junction of the roller body 31a (see reference). Figure 5 The opposite end faces are knurled.

[0113] Furthermore, the fixing device 20 in Modification Example 2 is also similar to... Figure 6 Similarly, in the fixing device, the end of the pressure roller 31 (roller body 31a) in the width direction is formed into a generally frustum-shaped shape, and the fold-in portion 34a is formed in such a way as to follow the shape of its end face.

[0114] In this way, by forming the end face of the annular member 65 into a knurled shape, and having multiple protrusions arranged in sections on the end face contact the folded-in portion 34a, poor contact at one end is reduced, and as a result, good and stable large contact pressure can be used to ensure conduction with the folded-in portion 34a (conductive surface layer 34).

[0115] Furthermore, in the fixing device 20 of Modified Example 2, the surface of the pressure roller 31 can also be sufficiently de-electrified.

[0116] <Variation Example 3>

[0117] like Figure 10 As shown in (A), in the fixing device 20 of Modified Example 3, the annular member 65 has a plurality of protrusions 65s (or, one protrusion 65s is formed in a circumferential shape) on the end face opposite to the roller body 31a.

[0118] In contrast, Figure 10 (B) The annular component 65 shown in the figure is connected to the roller body 31a (see reference). Figure 5 On the opposite end face, multiple recesses 65t are formed in the entire circumferential direction on the inner circumferential side (or, one recess 65t is formed in a circumferential shape).

[0119] and, Figure 10 (A) shows the annular component 65 and Figure 10 (B) The outer peripheral surface of the annular component 65 is in contact with the folded-in portion 34a, which is folded in at an incline along the end face of the roller body portion 31a.

[0120] This configuration reduces poor contact (poor conductivity) between the folded-in portion 34a and the end face of the annular component 65.

[0121] That is, such as Figure 11 As a comparative example, when no protrusion 65s or recess 65t is formed on the end face of the annular member 65, the clamping part (fixing clamping part) is compressed. Due to Poisson's ratio, the elastic layer 33 of the pressure roller 31 expands in the axial direction. When the annular member 65 is deformed (tilted) by the expansion, poor contact (poor conduction) between the folded-in part 34a and the end face of the annular member 65 is likely to occur.

[0122] In contrast, in variation 3, it was anticipated that Figure 11 The annular component 65 shown is deformed (tilted) so that it maintains contact with the folded-in portion 34a even when such deformation occurs. Therefore, the annular component 65 has a protrusion 65s and a recess 65t formed on its end face, so that the aforementioned defect is less likely to occur.

[0123] Furthermore, in the fixing device 20 of Modified Example 3, the surface of the pressure roller 31 can also be sufficiently de-electrified.

[0124] As described above, the fixing apparatus 20 in this embodiment includes a fixing belt 21 (fixing rotor) heated by a surface heater 24 (heat source), and a pressure roller 31 that forms a clamping portion for conveying sheet P by pressing against the fixing belt 21. Furthermore, a conductive surface layer 34 of the pressure roller 31 is formed on the roller body 31a in such a way that it contacts the surface of the clamping portion and the fixing belt 21. A conductive and grounded annular member 65 is disposed on the spindle 32 (shaft portion) of the pressure roller 31, facing the end face of the roller body 31a. Moreover, when viewed from a cross-section containing the roller center axis W, the end face of the roller body 31a is inclined from the roller surface side toward the roller center axis side towards the annular member 65. Furthermore, the conductive surface layer 34 has a folded-in portion 34a formed at the width-direction end of the side where the annular member 65 is provided. This folded-in portion 34a is folded in from the roller surface side toward the roller center axis side in an inclined manner along the end face of the roller body portion 31a. Moreover, the folded-in portion 34a contacts the end face of the annular member 65.

[0125] Therefore, the surface of the pressure roller 31 can be effectively de-electrified.

[0126] Furthermore, in this embodiment, the present invention is applied to a fixing device 20 that uses a planar heater 24 as a heat source, but the fixing device to which the present invention is applied is not limited to this. For example, the present invention can also be applied to fixing devices that use a heater or an electromagnetic induction coil as a heat source.

[0127] Furthermore, in this embodiment, the present invention is applied to a fixing device 20 that uses a fixing belt 21 as a fixing rotating body, but the fixing device to which the present invention is applied is not limited to this. For example, the present invention can also be applied to fixing devices that use a fixing roller or a fixing belt (a component mounted on multiple roller components) as a fixing rotating body.

[0128] In addition, in this embodiment, a substrate layer 21a is used as a conductive layer formed on the fixing belt 21, but a conductive elastic layer and a surface layer 21b can also be sequentially stacked on the substrate layer 21a in the fixing belt 21 (as a three-layer structure), and a conductive elastic layer can be used as a conductive layer.

[0129] In addition, in this embodiment, an annular component 65 with knurled outer surface is used, but the outer surface of the annular component does not have to be knurled. For example, a gear-shaped component can also be used as an annular component.

[0130] In addition, in this embodiment, the planar heater 24, which serves as a heat source, is used as a clamping forming member and is pressed onto the pressure roller 31 via the fixing belt 21 to form a clamping part (fixing clamp). However, the clamping forming member does not necessarily have to be a heat source.

[0131] In addition, in this embodiment, the annular component 65 is made to contact the fold-in portion 34a (pressure roller 31) and the substrate layer 21a (fixing belt 21) to form a grounding path. However, the annular component 65 may only contact the fold-in portion 34a (pressure roller 31) to form a grounding path, and other grounding paths may be formed relative to the substrate layer 21a (fixing belt 21).

[0132] Then, even in that case, the same effect as in this embodiment can be obtained.

[0133] Furthermore, this invention is not limited to this embodiment. Within the scope of the technical concept of this invention, it is obvious that appropriate modifications can be made to this embodiment beyond what is taught in this embodiment. In addition, the number, position, shape, etc., of the constituent components are not limited to this embodiment, and suitable numbers, positions, shapes, etc., can be selected when implementing this invention.

[0134] Furthermore, in this specification, etc., "sheet" is defined as all conveying materials that are sheet-shaped recording media, such as coated paper, label paper, OHP sheets, and film sheets, in addition to paper, and which are the objects of conveying.

[0135] In addition, the methods in this invention can be combined, for example, as described in 1-8 below.

[0136] <Postscript 1>

[0137] A fixing device, characterized in that it comprises:

[0138] The fixing rotating body is heated by a heat source, and

[0139] The pressure roller forms a clamping portion for conveying the sheet by pressing against the fixing rotor.

[0140] The pressure roller has:

[0141] A conductive surface layer, having electrical conductivity, is formed on the roller body in such a manner that it contacts the surface of the clamping portion and the fixing rotor.

[0142] A ring-shaped component is disposed on the shaft portion of the pressure roller, facing the end face of the roller body, and is conductive and grounded.

[0143] Viewed in cross-section from the central axis of the roller containing the pressure roller, the end face of the roller body is inclined toward the annular member from the roller surface side toward the central axis side.

[0144] The conductive surface layer has a folded-in portion at the width end of the side on which the annular member is provided. This folded-in portion is folded in from the roller surface side toward the roller central axis side in an inclined manner along the end face of the roller body.

[0145] The folded-in portion contacts the end face of the annular component.

[0146] <Appendix 2>

[0147] The fixing device according to Appendix 1 is characterized in that:

[0148] The fixing rotating body is a fixing belt, which includes:

[0149] A conductive layer is formed, having a portion exposed at the width-direction end on the side where the annular component is disposed, and

[0150] An insulating or medium-resistance surface layer is laminated directly or indirectly on the conductive strip in the width direction, excluding the exposed portion.

[0151] The annular component contacts and conducts electricity with the exposed portion of the conductive layer.

[0152] <Appendix 3>

[0153] The fixing device according to Appendix 2 is characterized in that:

[0154] The annular component has knurling formed on its outer peripheral surface, which is in contact with the exposed portion in the conductive layer.

[0155] <Appendix 4>

[0156] The fixing device according to Appendix 3 is characterized in that:

[0157] The outer diameter of the width-direction end of the side of the roller body where the annular component is located is smaller than the knurled inner diameter of the annular component.

[0158] <Appendix 5>

[0159] The fixing device according to Appendix 3 is characterized in that:

[0160] The outer diameter of the width-direction end of the side of the roller body where the annular component is located is greater than the knurled inner diameter of the annular component and smaller than the knurled outer diameter of the annular component.

[0161] <Appendix 6>

[0162] The fixing device according to any one of Appendices 1 to 5 is characterized in that:

[0163] The annular component has knurling formed on its end face opposite to the main body of the roller.

[0164] <Appendix 7>

[0165] The fixing device according to any one of Appendices 1 to 6 is characterized in that:

[0166] The annular component has a protrusion on its end face opposite to the roller body, either on its outer circumferential surface or on its inner circumferential surface.

[0167] The outer peripheral surface of the annular component contacts the folded portion, which is folded in at an incline along the end face of the roller body.

[0168] <Appendix 8>

[0169] An image forming apparatus, characterized in that:

[0170] It is equipped with the fixing device described in any one of Appendix 1 to 7.

Claims

1. A fixing device, characterized in that... include: The fixing rotating body is heated by a heat source, and The pressure roller forms a clamping portion for conveying the sheet by pressing against the fixing rotor. The pressure roller has: A conductive surface layer, having electrical conductivity, is formed on the roller body in such a manner that it contacts the surface of the clamping portion and the fixing rotor. A ring-shaped component is disposed on the shaft portion of the pressure roller, facing the end face of the roller body, and is conductive and grounded. Viewed in cross-section from the central axis of the roller containing the pressure roller, the end face of the roller body is inclined toward the annular component from the roller surface side toward the central axis side. The conductive surface layer has a folded-in portion at the width end of the side on which the annular member is provided. This folded-in portion is folded in from the roller surface side toward the roller central axis side in an inclined manner along the end face of the roller body. The folded-in portion contacts the end face of the annular component.

2. The fixing device according to claim 1, characterized in that: The fixing rotating body is a fixing belt, which includes: A conductive layer is formed, having a portion exposed at the width-direction end on the side where the annular component is disposed, and An insulating or medium-resistance surface layer is laminated directly or indirectly on the conductive strip in the width direction, excluding the exposed portion. The annular component contacts and conducts electricity with the exposed portion of the conductive layer.

3. The fixing device according to claim 2, characterized in that: The annular component has knurling formed on its outer peripheral surface, which is in contact with the exposed portion in the conductive layer.

4. The fixing device according to claim 3, characterized in that: The outer diameter of the width-direction end of the side of the roller body where the annular component is located is smaller than the knurled inner diameter of the annular component.

5. The fixing device according to claim 3, characterized in that: The outer diameter of the width-direction end of the side of the roller body where the annular component is located is greater than the knurled inner diameter of the annular component and smaller than the knurled outer diameter of the annular component.

6. The fixing device according to claim 1 or 2, characterized in that: The annular component has knurling formed on its end face opposite to the main body of the roller.

7. The fixing device according to claim 1 or 2, characterized in that: The annular component has a protrusion on its end face opposite to the roller body, either on its outer circumferential surface or on its inner circumferential surface. The outer peripheral surface of the annular component contacts the folded portion, which is folded in at an incline along the end face of the roller body.

8. An image forming apparatus, characterized in that: It has the fixing device as described in claim 1 or 2.

Images