JP2013218130A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance heating type fixation device capable of preventing generation of image noise caused by abrasion powder of a power feeding member while maintaining durability of a fixing belt, and an image forming apparatus comprising the fixation device.SOLUTION: A resistance heating type fixation device 100 allows a recording sheet to pass through a fixing nip formed by pressure-contacting a pressure roller 220 to a fixing belt 200 loosely fit to a pressing roller 210, and thereby thermally fixes a toner image. Both end parts of the fixing belt 200 in the rotation shaft direction are electrode parts 201, and a power feeding member 231 contacts therewith to allow an AC current to be conducted from an AC power supply 230. A v-shaped cross-section groove part 224 is provided on the outer peripheral surface of the pressure roller 220 in such a manner as to straddle the electrode part 201 and a release layer of the fixing belt 200 at the nip, and extend annularly over a whole periphery of the pressure roller 220.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly, to a technique for improving image noise caused by foreign matter in a resistance heating element type fixing device.

  In the field of image forming apparatuses, various fixing methods have been proposed in order to thermally fix a toner image onto a recording sheet on which the toner image has been electrostatically transferred. For example, a resistance heating type fixing device is applied to a fixing belt while causing current to flow through a power supply member such as a carbon brush to an electrode portion provided at both ends in the axial direction of a fixing belt having a resistance heating layer to generate Joule heat. The toner image is fixed by passing a recording sheet through a fixing nip formed by pressing a pressure roller.

  The resistance heating element method has an advantage that the warm-up time can be shortened with a simple device configuration. In order to shorten the warm-up time, it is desirable to use a thin fixing belt with a small heat capacity. However, if the fixing belt is thin, it is likely to be damaged by an external force. ing. For example, it is desirable to balance the external force applied in the radial direction of the fixing belt between the outer peripheral surface side and the inner peripheral surface side.

For this reason, the pressing member is brought into contact with a position corresponding to the fixing nip on the inner peripheral surface of the fixing belt. However, when the axial length of the pressure roller is shorter than the length of the fixing belt, the external force applied to the fixing belt suddenly changes between the fixing nip position and other positions, causing the fixing belt to be broken. Durability may be deteriorated.
In order to deal with such a problem, a measure for bringing the pressure roller into contact with the pressing member over the entire axial length of the fixing belt can be considered. With this configuration, the pressure applied to the fixing belt can be made uniform over the entire length in the axial direction, so that the durability of the fixing belt can be improved.

JP 2005-189484 A JP-A-2-63083

  However, carbon brushes as power supply members are in contact with both ends of the fixing belt in the axial direction, and the carbon brushes are worn by friction with the fixing belt that is rotationally driven during fixing, so that wear powder accumulates at the electrodes. To do. For this reason, if the pressure roller is in contact with the fixing belt over the entire length in the axial direction, the wear powder moves to the pressure roller or the fixing belt meanders. Spread. As a result, when the abrasion powder reaches the sheet passing area of the fixing belt or the pressure roller, it may be transferred to the recording sheet being fixed and image noise may be generated.

  The present invention has been made in view of the above-described problems, and is a resistance heating element system capable of preventing the occurrence of image noise due to abrasion powder of the power supply member while maintaining the durability of the fixing belt. It is an object of the present invention to provide a fixing device and an image forming apparatus.

  In order to achieve the above object, a fixing device according to the present invention includes a pair of electrode portions provided at both ends in the rotation axis direction, a resistance heating element layer that generates Joule heat by energization through the pair of electrode portions, An endless fixing belt, a pressure roller that forms a fixing nip by being pressed against the fixing belt over the entire length of the fixing belt in the rotation axis direction, and a lower hardness than the pair of electrode portions. A pair of power supply members for supplying power to the pair of electrode portions, and the pressure roller is configured such that the wear powder generated by the power supply member slidingly slid on the electrode portions A movement suppressing unit that suppresses movement into the sheet passing region, and the movement suppressing unit is provided on the entire circumference when viewed from the rotation axis direction of the pressure roller; Axis of rotation In direction, the position of the inner end of the shift suppressing portion is located inward from the position of the inner end of the feeding member, and is characterized in that is outside the paper feed area.

In this way, since the fixing nip is formed by pressing the pressure roller against the fixing belt over the entire length of the fixing belt in the rotation axis direction, durability of the fixing belt can be maintained. In addition, since the movement suppression unit is provided to prevent the abrasion powder from moving into the sheet passing area of the fixing belt, it is possible to prevent the occurrence of image noise.
In this case, the movement suppressing unit may be a groove formed by reducing the diameter of the pressure roller. In addition, in the said groove part, if the outer diameter of the said pressure roller is continuously diameter-reduced toward the center part from the both ends of the said groove part in the rotating shaft direction of the said pressure roller, it is still more suitable. . In this way, since a sudden change in external force applied to the fixing belt in the vicinity of the groove can be mitigated, the durability of the fixing belt can be improved.

Moreover, the said movement suppression part is good also as a friction coefficient being higher than parts other than the said movement suppression part among the outer peripheral surfaces of the said pressure roller. Specifically, the movement suppressing part may be a part where the outer peripheral surface of the pressure roller is made of silicone rubber or fluorine rubber. The movement suppression unit may adhere the wear powder.
In addition, the said movement suppression part may consist of two or more parts in a mutually different position in the rotating shaft direction of the said pressure roller, and may be spiral shape. Even in this case, the movement of the wear powder can be suppressed.

In addition, a cooling unit that cools at least a part of the outer peripheral surface of at least one of the fixing belt or the pressure roller by blowing air, the cooling unit from the movement suppressing unit in the rotation axis direction of the fixing belt. It is characterized in that the air is blown so that the wind does not flow to the central portion of the fixing belt.
An image forming apparatus according to the present invention includes the fixing device according to the present invention. If it does in this way, there can exist the above effects of the fixing device concerning the present invention.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a partially cutaway perspective view showing a main configuration of the fixing device 100. FIG. 2 is a cross-sectional view showing a laminated structure of a fixing belt 200. FIG. FIG. 6 is a diagram showing the relationship between the length of the pressure roller 220 in the rotation axis direction and the pressure applied to the fixing belt 200 at the fixing nip, where (a) is a center of the pressure roller 220 from the electrode portion 201 of the fixing belt 200. FIG. 4B shows a case where the pressure roller 220 is pressed over the entire length of the fixing belt 200. FIG. 6 is a diagram illustrating a relationship between a cross-sectional shape of a groove provided on the outer peripheral surface of the pressure roller 220 and a pressure applied to the fixing belt 200, where (a) illustrates a case where the bottom surface of the groove is flat; Shows a case of the groove 224 according to the present embodiment. 2 is a schematic diagram illustrating a main configuration of a fixing device 100. FIG. It is the model which illustrates the adhesion state of the abrasion powder in the case where a groove part is not provided in the pressure roller 220, (a) shows the initial state before abrasion powder adheres, (b) shows the pressure roller 220. The adhesion state of the abrasion powder by rotating is shown, and (c) further shows the adhesion state after diffusion due to meandering of the fixing belt. It is a schematic diagram which illustrates the adhesion state of the abrasion powder in the case where the groove portion 224 is provided in the pressure roller 220, and (a) shows the adhesion state of the abrasion powder by rotating the pressure roller 220, and (b ) Further shows the adhesion state after diffusion due to the fixing belt meandering. FIG. 9 is a schematic view illustrating an attached state of wear powder in a fixing device according to a modification of the present invention, where (a) shows an initial state before the wear powder diffuses, and (b) shows the fixing belt meandering. (C) shows the adhesion state when the fixing belt meanders. FIG. 9 is a schematic diagram illustrating a main configuration of a fixing device according to a modification of the present invention, in which (a) shows a fixing device in which a spiral groove is provided on the outer peripheral surface of the pressure roller 220; ) Shows a fixing device in which a spiral high friction portion is provided on the outer peripheral surface of the pressure roller 220. FIG. 10 is an external view showing a main configuration of a fixing device according to a modification of the present invention. FIG. 6 is a cross-sectional view showing a laminated structure of a fixing belt 200 according to a modification of the present invention. FIG. 6 is a diagram illustrating the state of attachment of wear powder on the power supply member 231 for each positional relationship between the groove portion 224 and the fixing belt 200, and (a) and (b) are both groove portions in the direction of the rotation axis of the pressure roller 220. 224 shows the state of attachment of the wear powder when disposed at a position corresponding to the power supply member 231. (c) and (d) both show wear when the groove portion 224 is disposed within the maximum sheet passing range. The adhesion state of the powder is shown. 3 is a diagram illustrating a positional relationship between a groove portion 224 and a fixing belt 200 that can suppress image noise. FIG.

Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. The image forming apparatus 1 is a so-called intermediate transfer type color image forming apparatus, and as shown in FIG. 1, toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors. The image forming units 101Y to 101K are formed. Since the image forming units 101Y to 101K have the same configuration, the description of the image forming unit 101Y will be replaced with the description of the image forming units 101M to 101K. At the time of image formation, the image forming unit 101Y uniformly charges the outer peripheral surface of the cylindrical photosensitive drum 102 to a predetermined potential by the charging device 103. Next, the exposure device 104 exposes the outer peripheral surface of the uniformly charged photosensitive drum in accordance with an image signal corresponding to the document image, thereby forming an electrostatic latent image.

  The developing device 105 develops the electrostatic latent image by supplying each color toner of YMCK supplied from the toner cartridges 108Y to 108K onto the outer peripheral surface of the photosensitive drum 102 by the developing roller 105a to which a developing bias is applied. A visible toner image is obtained. A primary transfer bias is applied to the primary transfer rollers 106 </ b> Y to 106 </ b> K, and a visible toner image is primarily transferred from the outer peripheral surface of the photosensitive drum 102 onto the intermediate transfer belt 110 by electrostatically adsorbing toner. To do. After the primary transfer of the visible toner image onto the intermediate transfer belt 110, the toner remaining on the outer peripheral surface of the photosensitive drum 102 is removed by the cleaning device 107.

  The intermediate transfer belt 110 is stretched around a secondary transfer counter roller 111 and a driven roller 112. The secondary transfer counter roller 111 is rotationally driven by a main motor described later, and the intermediate transfer belt 110 is driven to rotate by a frictional force with the secondary transfer counter roller 111. While the intermediate transfer belt 110 rotates in the direction of arrow A, the toner images of each color of YMCK are sequentially primary-transferred, thereby forming a color image. The driven roller 112 is driven to rotate by a frictional force with the intermediate transfer belt 110 that rotates.

  In parallel with the above, in the paper feeding cassette 120 containing the recording sheet S, the recording sheet S is sent out one by one by the pickup roller 121 and passes through the timing roller 115 and the secondary transfer counter roller 111 and the secondary transfer. It is conveyed to the secondary transfer nip formed by the transfer roller 113. The secondary transfer roller 113 is pressed against the secondary transfer counter roller 111 via the intermediate transfer belt 110, and a secondary transfer bias is applied thereto. When the recording sheet S passes through the secondary transfer nip, the toner image (color image) carried on the intermediate transfer belt 110 is electrostatically transferred (secondary transfer).

  Note that the rotational driving force is transmitted to the timing roller 115 via a timing clutch (not shown). When the timing clutch is turned on and off, the toner image carried on the intermediate transfer belt 110 is recorded on the recording sheet S. The timing at which the recording sheet S is conveyed is adjusted so that the recording sheet S is transferred to the upper desired position. A pre-timing sensor 114 is disposed on the conveyance path of the recording sheet S from the pickup roller 121 to the timing roller 115 and detects the passage of the recording sheet S.

The recording sheet S carrying the toner image is detected by the fixing loop sensor 116 and then conveyed to the fixing device 100.
The fixing device 100 is a resistance heating element type fixing device, and includes a fixing belt that heats a toner image and a pressure roller that presses against the fixing belt to form a fixing nip, as will be described later. By passing the recording sheet S through the fixing nip, the toner image is melted and pressed onto the recording sheet S. Thereafter, the recording sheet S is detected as being discharged from the fixing device 100 by the paper discharge sensor 117, and is discharged onto the paper discharge tray 131 by the paper discharge roller 130. On the other hand, the toner remaining on the intermediate transfer belt 110 after the secondary transfer is conveyed in the direction of arrow A and then removed by the cleaning device 109.

[2] Configuration of Fixing Device 100 Next, the configuration of the fixing device 100 according to the present embodiment will be described.
FIG. 2 is a partially cutaway perspective view showing the main configuration of the fixing device 100. As shown in FIG. 2, the fixing device 100 is pressed against the pressing roller 210 via the fixing belt 200, an endless fixing belt 200 that can be elastically deformed, a pressing roller 210 in which the fixing belt 200 is loosely fitted, and the fixing belt 200. The pressure roller 220 and an AC power source 230 that supplies AC power for Joule heat generation to the fixing belt 200 are provided. A fixing nip is formed by pressing the fixing belt 200 and the pressure roller 220, and the toner image is thermally fixed by passing the recording sheet S through the fixing nip. In order to increase the thermal efficiency, the recording sheet S is passed through the fixing nip so that the surface carrying the unfixed toner image comes into contact with the fixing belt 200.

  Further, both end portions in the rotation axis direction of the fixing belt 200 are electrode portions 201, and the power supply member 231 connected to the AC power supply 230 via the conductive wire (harness) 232 comes into contact with the fixing belt 200. An alternating current is applied to the resistance heating element layer (not shown). The fixing device 100 also includes a meandering restricting plate that restricts the meandering of the fixing belt 200. However, in FIG. 2, the meandering restricting plate is not shown to make the device configuration easy to see.

The fixing belt 200 is an endless belt and has a cylindrical shape before assembling. On the other hand, the fixing belt 200 is elastically deformed when a certain amount of external force is applied in the radial direction. A self-holding shape that returns to its original state by a restoring force is used. The dimension of the fixing belt 200 in the radial direction is, for example, an inner diameter of 30 [mm].
The fixing belt 200 has a multilayer structure including the resistance heating element layer. FIG. 3 is a cross-sectional view showing a laminated structure of the fixing belt 200. As shown in FIG. 3, the fixing belt 200 has a structure in which a reinforcing layer 302, an elastic layer 303, and a release layer 304 are sequentially laminated on a resistance heating element layer 301, and electrodes provided at both ends in the rotation axis direction. The unit 201 is electrically connected to the resistance heating element layer 301. An alternating current is applied to the resistance heating element layer 301 from the power supply member 231 via the electrode portion 201, and the resistance heating element layer 301 generates Joule heat.

  The resistance heating element layer 301 is adjusted to a predetermined electrical resistivity by dispersing a conductive filler in resin. As the resin material, it is preferable to use heat-resistant resin materials such as polyimide (PI), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK). Among materials, PI has the highest heat resistance.

  Conductive fillers include metal powders such as silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), graphite, carbon black, carbon nanotubes, carbon nanofibers, carbon Carbon-based compound powders such as microcoils, high ionic conductor powders such as silver iodide (AgI) and copper iodide (CuI) may be used, and two or more of these may be mixed and dispersed. As the shape of the conductive filler, a fibrous shape is desirable in order to increase the probability of contact between the fillers with the same content and facilitate percolation.

  Carbon compounds and high ionic conductors have a negative temperature coefficient (NTC) in which the volume resistivity decreases as the temperature rises, and are used to impart NTC characteristics to the resistance heating element layer 301. be able to. Further, the high ion conductor is effective because it does not lower the mechanical strength of the resistance heating element layer 301. However, it is difficult to adjust the electrical resistivity of the resistance heating element layer 301 to a calorific value suitable for a fixing device of about 500 [W] to 1500 [W] with a commercial power source using only a carbon compound or a high ion conductor. Therefore, it is desirable to adjust the electrical resistivity of the resistance heating element layer 301 by using metal powder together.

  As the metal powder, needle-like or flaky silver or nickel is preferable, and the particle size is preferably in the range of 0.01 [μm] to 10 [μm]. In this way, since the carbon compound and the high ionic conductor are intertwined linearly, the resistance heating element layer 301 having a uniform volume resistivity can be formed. The conductive filler dispersed in the heat resistant resin is within the range of 50 [wt%] to 300 [wt%] of the metal powder and 5 [wt%] to 100 of the carbon compound and high ion conductor with respect to the weight of the heat resistant resin. It is preferable to be within the range up to [% by weight]. If there is too much metal powder, the electrical resistivity of the resistance heating element layer 301 will be too low to use. On the other hand, if the amount is too small, the electric resistance of the resistance heating element layer 301 becomes too large to be used.

The thickness of the resistance heating element layer 301 is preferably in the range of about 5 [μm] to about 150 [μm]. Needless to say, the electrical resistivity should be determined in accordance with the voltage to be applied, the power, the thickness of the resistance heating element layer 301, the diameter and length of the fixing belt 200, and the like. It may be in the range of × 10 ⁻⁶ [Ω · m] to 1.0 × 10 ⁻² [Ω · m], and 1.0 × 10 ⁻⁵ [Ω · m] to 5.0 × 10 ^−. It is more preferable if it is within the range up to ³ [Ω · m]. In order to adjust the electrical resistivity of the resistance heating element layer 301, conductive particles such as a metal alloy or a metal compound may be added. In order to improve the mechanical strength, glass fiber, whisker, titanium oxide (TiO ₂ ), potassium titanate (K ₄ O ₄ Ti), or the like may be added. Furthermore, aluminum nitride (AlN), alumina (Al ₂ O ₃ ) or the like may be added to improve thermal conductivity.

The resistance heating element layer 301 is manufactured by uniformly dispersing a conductive filler in a polyimide varnish obtained by polymerizing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent, and then applying it to a mold to convert it into an imide. To do. Considering the production stability of the resistance heating element layer 301, it is effective to add an imidizing agent, a coupling agent, a surfactant, and an antifoaming agent.
The reinforcing layer 302 is made of a resin such as polyimide or polyphenylene sulfide. The elastic layer 303 is made of a material having high heat resistance such as silicone rubber or fluorine rubber.

  The release layer 304 is disposed on the outermost periphery of the fixing belt 200 and is made of perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), or the like. It is desirable to provide a release property such as a fluorine tube and a fluorine coating, and a conductive material may be used. As the fluorine-based tube, for example, products such as PFA350-J, 451HP-J, and 951HP Plus manufactured by Mitsui DuPont Fluorochemical Co., Ltd. can be used. The contact angle between the release layer 304 and water may be 90 ° or more, and more preferably 110 ° or more.

The surface roughness of the release layer 304 is preferably such that the center line average roughness (Ra) is in the range of 0.01 [μm] to 50 [μm]. The thickness of the release layer 304 is preferably in the range of 5 [μm] to 100 [μm], for example.
The electrode portion 201 is laminated over the entire circumference of the fixing belt 200 at both ends in the rotation axis direction of the fixing belt 200. By adopting such a shape, a uniform current distribution can be realized in the entire resistance heating element layer 301 when the electrode portion 201 is energized, so that uniform heat generation can be obtained.

  The material of the electrode part 201 is preferably a metal having a low electrical resistivity. Gold (Au), silver, copper, aluminum, zinc (Zn), tungsten (W), nickel, brass, phosphor bronze, stainless steel (SUS: Stainless Use Steel) or the like may be used. In laminating the electrode part 201 on the resistance heating element layer 301, it is desirable to use a method such as chemical plating or electroplating. When the electrode is directly formed on the resistance heating element layer 301, it is preferable to perform electroplating after performing chemical plating. Of these, copper and nickel are preferable, and it is better to perform nickel plating on copper chemical plating or electroplating. Further, copper foil or nickel foil may be adhered with a conductive adhesive, or conductive ink or paste may be applied. A ring-shaped metal member may be insert-molded.

Now, referring back to FIG. 2, the pressing roller 210 is formed by laminating an elastic layer 211 on the outer peripheral surface of the long cored bar 212, and the rotation path of the fixing belt 200 (when the fixing belt 200 travels in a circular manner). Traveling path (hereinafter referred to as “belt loop path”).
The cored bar 212 as the shaft part is made of, for example, aluminum or stainless steel having a shaft diameter of 18 [mm]. For the cored bar 212, a pipe-shaped member having a thickness in the range of 0.1 [mm] to 10 [mm] may be used, or a solid member may be used. Moreover, you may use an atypical member, such as a cross-shaped cross-section. The cored bar 212 is rotatably supported by a housing (not shown) of the fixing device 100 at both axial ends, for example, via a bearing.

  For the elastic layer 211, it is desirable to use a heat-resistant material such as silicone rubber or fluorine rubber. In addition, the elastic layer 211 may be a solid material, but if a sponge-like foam material is used, the heat insulation can be enhanced, so that the thermal efficiency of the fixing device 100 can be enhanced. Further, if a two-layer structure in which a solid material is laminated on a sponge material, durability can be enhanced. The thickness of the elastic layer 211 is preferably in the range of 1 [mm] to 20 [mm].

  The outer diameter of the pressing roller 210 is smaller than the inner diameter of the fixing belt 200, and is preferably in the range from 20 [mm] to 100 [mm], for example. In addition, the pressing roller 210 and the fixing belt 200 are in contact with each other at a portion corresponding to the fixing nip on the inner peripheral surface of the fixing belt, and a gap (space) is provided between the two at portions other than the portion corresponding to the fixing nip. It is supposed to be.

  With such a configuration, the area of heat transfer from the fixing belt 200 to the pressing roller 210 is smaller than when the fixing belt 200 is in close contact with the pressing roller 210, and one of the heat generated from the fixing belt 200 is reduced. The heat transfer loss is reduced such that the portion escapes from the both ends of the core metal 212 to the housing of the fixing device 100 via the bearing member via the core metal 212 of the pressing roller 210 to achieve high thermal efficiency. Can do.

  The pressure roller 220 is formed by laminating a release layer 221 around an elongated cored bar 223 via an elastic layer 222, and is disposed outside the belt circulation path of the fixing belt 200. The pressure roller 220 has both ends of the cored bar 223 in the axial direction rotatably supported by an urging mechanism (not shown) via a bearing or the like, and is urged by the urging mechanism to be fixed to the fixing belt. A pressing roller 210 is pressed from the outside of the fixing belt 200 through the fixing belt 200 to secure a fixing nip N between the surface of the fixing belt 200. A groove portion 224 having a V-shaped cross section is provided on the outer peripheral surface of the pressure roller 220 in an annular shape over the entire circumference of the pressure roller 220. Details of the groove 224 will be described later.

  The pressure roller 220 is rotationally driven in the direction of arrow B by transmission of a driving force from a driving motor (not shown). Following the rotation of the pressure roller 220, the fixing belt 200 runs around in the direction of arrow C, and the pressing roller 210 is driven to rotate in the direction of arrow D. The pressing roller 210 may be the driving side, and the fixing belt 200 and the pressure roller 220 may be the driven side. The outer diameter of the pressure roller 220 is preferably in the range of 20 [mm] to 100 [mm].

  The cored bar 223 has a hollow pipe shape made of, for example, aluminum or iron (Fe), and has an outer diameter of, for example, 30 [mm]. The thickness is preferably within a range of 0.1 [mm] to 10 [mm]. A solid cylindrical shape or a cross-sectional shape having a three-pointed shape may be used. The elastic layer 222 is made of, for example, rubber having high heat resistance such as silicone rubber or fluorine rubber, foamed materials thereof, or the like, and the thickness is desirably in the range of 1 [mm] to 20 [mm]. The release layer 221 may be made of a fluororesin tube such as PFA or PFTE, a fluororesin coating, or the like, and may be provided with conductivity in order to prevent toner offset due to charging. The thickness of the release layer 221 is preferably in the range of 5 [μm] to 100 [μm].

  The power supply member 231 is a rectangular parallelepiped block having a size of, for example, 10 [mm] in length, 5 [mm] in width, and 7 [mm] in height, and is made of copper graphite or carbon having slidability and conductivity. This is a so-called carbon brush made of a material such as graphite. Each of the power supply members 231 receives an urging force in a direction from the outer peripheral side to the inner peripheral side of the fixing belt 200 by an elastic member such as a spring and is pressed against the electrode unit 201. The power supply member 231 desirably has a lower hardness than the electrode unit 201. This is because the abrasion powder scraped from the power supply member 231 by sliding forms a thin film on the outer peripheral surface of the electrode portion 201, so that a more stable power supply state can be obtained.

  In general, in a fixing device using a belt such as a fixing belt, when an external force is applied by bringing a pressing member into contact with the belt, in order to prevent the belt from being cracked, a rapid change in the rotation axis direction of the belt is required. It is desirable to adopt a configuration that does not cause a change in external force (pressure). For example, in the rotation axis direction of the fixing belt, it is desirable that both the pressure roller and the pressure roller have a length longer than that of the fixing belt. In the present embodiment, the fixing belt 200, the pressing roller 210, and the pressure roller 220 are almost the same length in the rotation direction of the fixing belt 200.

  FIG. 4 is a diagram showing the relationship between the length of the pressure roller 220 in the direction of the rotation axis and the pressure applied to the fixing belt 200 at the fixing nip. FIG. 5B shows a case where the pressure roller 220 is in pressure contact with the center of the fixing belt 200, and FIG. 5B shows a case where the pressure roller 220 is pressed over the entire length of the fixing belt 200. A graph showing is shown. In addition, when there exists a corresponding member in FIG.2, 3, the same code | symbol is provided.

As shown in FIG. 4A, when the pressure roller 220 is in pressure contact with the center side of the electrode portion 201 of the fixing belt 200, as shown in the graph, the pressure roller 220 in the rotation axis direction. The pressure applied to the fixing belt 200 changes rapidly in the vicinity of both ends.
On the other hand, as shown in FIG. 4B, when the pressure roller 220 is in pressure contact over the entire length of the fixing belt 200, the pressure applied to the fixing belt 200 is somewhat depending on the pressure contact position of the pressure roller 220. Although it changes, the change is very gentle. Therefore, in order to prevent the fixing belt from cracking and increase its durability, it is preferable to press the pressure roller 220 over the entire length of the fixing belt 200.

  FIG. 5 is a view showing the relationship between the cross-sectional shape of the groove provided on the outer peripheral surface of the pressure roller 220 and the pressure applied to the fixing belt 200, and FIG. 5A shows the case where the bottom of the groove is flat. (B) has shown the case of the groove part 224 which concerns on this Embodiment. 5A and 5B, a schematic diagram showing the device configuration and a graph showing the belt pressure distribution are shown. In addition, when there are corresponding members in FIGS.

  As shown in FIG. 5A, when the bottom surface of the groove portion 501 is flat and the side surface 501 of the groove portion is perpendicular to the outer peripheral surface of the pressure roller 220, the pressure distribution applied to the fixing belt 200. As shown in the graph, a portion 502 where the pressure applied to the fixing belt 200 abruptly changes appears at the end of the groove 501 in the rotation axis direction of the fixing belt 200. On the other hand, as shown in FIG. 5B, in the groove 224 according to the present embodiment, as shown in the pressure distribution graph, the pressure applied to the fixing belt 200 is higher than that in the case of the groove 501. It changes slowly. For this reason, if the depth of the groove portion is gradually increased from both ends of the groove portion in the rotation axis direction of the pressure roller 220 as in the groove portion 224 according to the present embodiment, the groove portion is pressed against the end portion of the groove portion. A sudden change in pressure applied to the fixing belt 200 at a certain position can be mitigated.

Note that meandering restricting plates are attached to the shaft portion 211 at both ends of the fixing roller 210 in the rotation axis direction. The meandering restriction plate rotates together with the fixing belt 200 and restricts the meandering of the fixing belt 200.
[3] Prevention of Wear Powder Diffusion Next, a configuration for preventing the diffusion of wear powder generated by cutting the power supply member 231 will be described.

  FIG. 6 is a schematic diagram illustrating a main configuration of the fixing device 100. As shown in FIG. 6, the pressure roller 220 is provided with a groove portion 224 having a V-shaped cross section, and the groove portion 224 straddles the electrode portion 201 of the fixing belt 200 and the release layer 304 in the fixing nip. Yes. Considering that the fixing belt 200 meanders, the width of the groove 224 in the rotation axis direction of the pressure roller 220 is preferably in the range of 2 [mm] to 5 [mm], and the depth of the groove 224 The length is preferably in the range of 1 [mm] to 5 [mm].

  A portion (hereinafter simply referred to as “end portion”) 220 a outside the groove portion 224 in the rotation axis direction of the pressure roller 220 is in pressure contact with the electrode portion 201 of the fixing belt 200. The end portion 220a is wider than a range where the power supply member 231 of the electrode portion 201 contacts, and includes the contact range. Further, a portion on the center side of the groove portion 224 (hereinafter simply referred to as “central portion”) 220b is wider than the maximum sheet passing range through which the recording sheet S passes during fixing, and includes the maximum sheet passing range. doing.

  7A and 7B are schematic views illustrating the state of attachment of wear powder when no groove is provided in the pressure roller 220. FIG. 7A shows an initial state before the wear powder diffuses, and FIG. The adhesion state of the abrasion powder by rotating the pressure roller 220 is shown, and (c) further shows the adhesion state after the fixing belt meanders. As shown in FIG. 7A, in the initial state, no abrasion powder adheres to the outer peripheral surface of either the electrode portion 201 or the pressure roller 220 of the fixing belt 200.

  On the other hand, when the pressure roller 220 is driven to rotate, as shown in FIG. 7B, the power supply member 231 is worn by friction with the electrode portion 201 of the fixing belt 200, and wear powder is generated. The fixing belt 200 also rotates following the rotation of the pressure roller 220, so that the wear powder adhesion region 701 extends over the entire circumference of the electrode unit 201. Further, the abrasion powder adhering to the electrode part 201 is transferred to the pressure roller 220 side when the electrode part 201 and the pressure roller 220 are pressed in the fixing nip. For this reason, an abrasion powder adhesion region 702 is also formed on the outer peripheral surface of the pressure roller 220 at a position corresponding to the adhesion region 701 of the electrode part 201.

  Further, when the fixing belt 200 meanders while the pressure roller 220 is rotationally driven, the fixing belt 200 reciprocates in the direction of the rotation axis, and the relative positional relationship between the fixing belt 200 and the pressure roller 220 is reached. Changes in the direction of the rotation axis. Then, due to the change in the relative position, the wear powder is also conveyed in the direction of the rotation axis by the frictional force, and as shown in FIG. 7C, the area where the wear powder adheres expands in the direction of the rotation axis.

  That is, the adhesion region 701 (FIG. 7B) when the fixing belt 200 does not meander is expanded beyond the boundary between the electrode part 201 and the release layer 304 due to the meandering of the fixing belt 200, and reaches the adhesion region 711. spread. In accordance with this, also on the outer peripheral surface of the pressure roller 220, the wear powder adhesion area expands from the adhesion area 702 to the adhesion area 712 in FIG. When the adhesion area 711 on the outer peripheral surface of the fixing belt 200 reaches the sheet passing area of the recording sheet S, wear powder adhering to the area (image noise generation area) 713 reaching the sheet passing area is recorded. As a result of the transfer to the sheet S, image noise is generated.

On the other hand, in the fixing device 100 provided with the groove 224, the state of attachment of the wear powder differs. FIG. 8 is a schematic view illustrating the state of attachment of wear powder when the groove portion 224 is provided in the pressure roller 220, and (a) shows the state of wear powder attachment by rotating the pressure roller 220. (B) shows the adhesion state due to meandering of the fixing belt.
Even when the groove portion 224 is provided, if the fixing belt 200 does not meander while the pressure roller 220 is rotationally driven, the electrode portion 201 of the fixing belt 200 is shown in FIG. 8A. The wear powder adheres to the adhesion region 801 over the entire circumference of the pressure roller and the adhesion region 802 over the entire circumference of the pressure roller 220.

Further, when the fixing belt 200 meanders, the wear powder diffuses in the direction of the rotation axis of the fixing belt 200, and the adhesion areas 801 and 802 expand to the adhesion areas 803 and 804. However, since the pressure roller 220 and the fixing belt 200 are not in pressure contact with each other in the groove portion 224, the driving force does not act on the wear powder, and the expansion of the wear powder adhesion region is limited.
Returning to FIG. 6, the fixing device 100 is provided with a cooling device 601, and the fixing device 100 is a non-printing sheet when a small size recording sheet is passed among the recording sheets on which the toner image is thermally fixed. Blowing and cooling the paper passing area. This is because if the temperature adjustment control is performed in order to maintain the temperature of the sheet passing area where heat is removed by the sheet passing of the recording sheet S at a predetermined fixing temperature, the temperature rises in the non-sheet passing area where such cooling is not performed. This is because there is a risk of overheating. The cooling device 601 includes a fan portion 601a and a duct portion 601b. The air is taken in by the fan portion 601a from a location where the temperature is relatively low even outside or inside the image forming apparatus 1, and the air is sent by the duct portion 601b. Then, the non-sheet passing area is cooled by blowing.

The downstream end portion of the duct portion 601b in the air feeding direction has a ventilation path 601c on the end side so that air is blown to the end portion side in the rotation axis direction of the fixing belt 200. By blowing air toward the end in the rotation axis direction of the fixing belt 200 via the air blowing path 601c, the abrasion powder is prevented from diffusing into the maximum sheet passing range.
[4] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .

(1) In the above embodiment, the case where the groove portion 224 is provided on the outer peripheral surface of the pressure roller 220 to suppress the movement of the wear powder has been described. Needless to say, the present invention is not limited to this. Instead of this, the following may be used.
That is, instead of the groove portion 224, a high friction portion having a higher friction coefficient than the other outer peripheral surfaces of the electrode portion 201, the release layer 304, and the pressure roller 220 of the fixing belt 200 may be provided. FIGS. 9A and 9B are schematic views illustrating the state of attachment of wear powder in the fixing device according to this modification, where FIG. 9A shows the initial state before the wear powder diffuses, and FIG. 9B shows the fixing belt meandering. FIG. 4C shows the adhesion state when the fixing belt meanders. As shown in FIG. 9A, in the initial state, no abrasion powder adheres to the outer peripheral surface of either the electrode portion 201 or the pressure roller 220 of the fixing belt 200.

  In the initial state before the pressure roller 220 is rotated, as shown in FIG. 9A, the high friction portion 901 has the pressure roller so as to straddle the electrode portion 201 and the release layer 304 of the fixing belt 200. 220. In the state where the pressure roller 220 is rotated, if the fixing belt 200 is not meandering, as shown in FIG. 9B, the adhesion region 902 over the entire circumference of the electrode portion 201 of the fixing belt 200, Wear powder adheres to the adhesion region 903 over the entire circumference of the pressure roller 220.

  When the fixing belt 200 meanders, the wear powder diffuses in the direction of the rotation axis of the fixing belt 200, and the adhesion areas 902 and 903 expand to the adhesion areas 904 and 905. However, in the high friction part 901, since the abrasion powder cannot move against the frictional force, the expansion of the adhesion area of the abrasion powder is limited. In particular, when the high friction portion 901 has adhesiveness, the wear powder adheres to the high friction portion 901, so that the adhesion area is prevented from expanding.

  In order to increase the friction coefficient in the high friction part 901, for example, a method of exposing the elastic layer 222 by removing the release layer 221 constituting the pressure roller 220 only in the high friction part 901 can be mentioned. As described above, the elastic layer 222 is made of a rubber having high heat resistance such as silicone rubber or fluorine rubber, or a foamed material thereof, and thus has a high coefficient of friction. Note that the elastic layer 222 may be formed so as to be thicker than other portions of the pressure roller 220 in the high friction portion 901.

  Further, a member having a high friction coefficient may be laminated on the release layer 221. For example, a heat-resistant double-sided tape may be applied on the release layer 221 to form the high friction portion 901. Needless to say, the double-sided tape has a high coefficient of friction because it has adhesiveness. Examples of the heat-resistant double-sided tape include a polyimide film-based silicon double-sided adhesive tape 4390 manufactured by Sumitomo 3M Limited.

Also with the configuration described in this modification, it is possible to suppress the abrasion powder from diffusing into the paper passing area, and thus it is possible to prevent the occurrence of image noise due to the diffusion of the abrasion powder.
(2) In the above embodiment, the case where the annular groove portion 224 is provided on the outer peripheral surface of the pressure roller 220 has been described. Needless to say, the present invention is not limited to this. You may do as follows.

  FIG. 10 is a schematic diagram showing the main configuration of the fixing device according to this modification. FIG. 10A shows a fixing device in which a spiral groove is provided on the outer peripheral surface of the pressure roller 220. FIG. 5B shows a fixing device in which a spiral high friction portion is provided on the outer peripheral surface of the pressure roller 220. As shown in FIG. 10A, the groove 1001 is provided in a spiral shape on the outer peripheral surface of the pressure roller 220 and is not annular.

  However, when viewed from the rotation axis direction of the pressure roller 220, the pressure roller 220 is provided over the entire circumference on the outer peripheral surface side of the pressure roller 220. For this reason, the abrasion powder that moves from the end of the pressure roller toward the center in the direction of the rotation axis always reaches the groove 1001, and further movement is suppressed. Further, as shown in FIG. 10B, the movement of the wear powder can be similarly suppressed when the high friction portion 1002 is provided in a spiral shape on the outer peripheral surface of the pressure roller 220.

In addition, even when the groove part and the high friction part are divided into a plurality of parts, they are provided over the entire circumference on the outer peripheral surface side of the pressure roller 220 when viewed from the rotation axis direction of the pressure roller. If so, the movement of the wear powder can be suppressed.
(3) In the above embodiment, the case where the pressing roller 210 is brought into contact with the inner peripheral surface of the fixing belt 200 has been described, but it goes without saying that the present invention is not limited to this configuration. It may be as follows.

  FIG. 11 is an external view showing the main configuration of the fixing device according to this modification, and the same reference numerals are given when there are members corresponding to FIG. As shown in FIG. 11, the fixing device 100 according to this modification is provided with a non-rotating pressing member 1101 instead of the pressing roller 210. As a material for the pressing member 1101, a resin having high heat resistance such as polyphenylene sulfide, polyimide, or a liquid crystal polymer, a metal such as aluminum or iron, a ceramic, or the like may be used. It is good also as 2 components structure with components which consist of silicone rubber, fluororubber, etc.

  Further, a sliding member may be interposed between the pressing member 1101 and the fixing belt 200 in order to reduce friction between the pressing member 1101 and the fixing belt 200. The sliding member generally has a configuration in which a glass cloth is used as a base material and the sliding surface is covered with a heat resistant resin. It is preferable that the surface of the pressing member 1101 that is in pressure contact with the pressure roller 220 via the fixing belt 200 is a smooth flat surface or a curved surface so that the fixing nip has a desired shape. Further, it is desirable that the portion not facing the fixing nip is located inside the belt rotation path of the fixing belt 200 so as not to prevent the rotation of the fixing belt 200.

  (4) The laminated structure of the fixing belt 200 shown in the above embodiment is merely an example, and the effects of the present invention can be obtained even if other laminated structures are employed. FIG. 12 is a cross-sectional view showing a laminated structure of the fixing belt 200 according to this modification. As shown in FIG. 12, the fixing belt 200 according to this modification has a structure in which a resistance heating element layer 301, an elastic layer 303, and a release layer 304 are sequentially laminated on the outer peripheral surface of a cylindrical reinforcing layer 302. I'm taking it. Further, the electrode layer 201 is laminated on the resistance heating element layer 301, and the power feeding member 231 is in pressure contact therewith.

  With such a laminated structure, the adhesion area between the electrode layer 201 and the resistance heating element layer 301 can be increased, so that the electrode layer 201 is resisted by the frictional force between the electrode layer 201 and the power feeding member 231. The problem of peeling from the heating element layer 301 can be reduced. Note that the resistance heating element layer 301, the reinforcing layer 302, the elastic layer 303, and the release layer 304 are all preferably formed using the materials described in the above embodiment modes.

(5) In the above embodiment, the outer end of the groove portion 224 is in pressure contact with the electrode portion 201 of the fixing belt 200 and the inner end of the groove portion 224 is the release layer of the fixing belt 200 in the rotation axis direction of the pressure roller 220. Although the case of pressing to 304 has been described as an example, it goes without saying that the present invention is not limited to this, and the following may be used instead.
FIG. 13 is a diagram illustrating the state of attachment of the wear powder of the power supply member 231 for each positional relationship between the groove 224 and the fixing belt 200, and (a) and (b) in the rotation axis direction of the pressure roller 220. Shows the state of adhesion of wear powder when the groove portion 224 is disposed at a position corresponding to the power supply member 231, and (c) and (d) both indicate that the groove portion 224 is disposed within the maximum sheet passing range. Shows the state of wear powder adhesion. Note that (a) and (c) both show the adhesion state of the abrasion powder due to the rotation of the pressure roller 220, and (b) and (d) both after the abrasion powder is diffused due to the meandering of the fixing belt 200. The adhesion state of is shown.

  As shown in FIG. 13A, when the groove 224 is disposed at a position corresponding to the power supply member 231, the abrasion powder of the power supply member 231 is generated in the region 1302 outside the outer end Go of the groove 224. In addition to adhering, wear powder also adheres to a region 1303 inside the inner end Gi of the groove 224. When the fixing belt 200 meanders in this state, the abrasion powder diffuses inward in the rotation axis direction while repeating transfer between the outer peripheral surface of the fixing belt 200 and the outer peripheral surface of the pressure roller 220 in the fixing nip. As shown in FIG. 13B, the wear powder adhesion regions 1301 and 1303 eventually reach the maximum sheet passing range, and image noise may occur in the entire sheet passing range.

  Further, as shown in FIG. 13C, when the groove 224 is within the maximum sheet passing range in the rotation axis direction of the pressure roller 220, the outer end Bo of the power supply member 231 is moved to the outer end Go of the groove. Since there is nothing that hinders the movement of the wear powder in the meantime, the wear powder can reach the maximum paper passing range. However, as shown in FIG. 13B, the wear powder cannot diffuse beyond the groove portion 224 to the inside of the groove portion 224 in the rotation axis direction of the pressure roller 220. It is limited to a region outside the outer end Go of the groove 224.

  If the positional relationship between the groove portion 224 and the fixing belt 200 is set as follows with respect to the image noise generated as described above, the image noise can be suppressed. FIG. 14 is a diagram illustrating a positional relationship that can suppress image noise. As shown in FIG. 14A, when the inner end Gi of the groove 224 is disposed outside the inner end Bi of the power supply member 231 in the rotation axis direction of the pressure roller 220, Since the abrasion powder of the member 231 cannot be diffused inward beyond the groove portion 224, image noise can be suppressed.

Further, as shown in FIG. 14B, if the groove portion 224 is disposed so that the outer end Go of the groove portion 224 is outside the maximum sheet passing range, the abrasion powder of the power supply member 231 exceeds the groove portion 224. Therefore, it is not possible to diffuse inward in the rotation axis direction, so that it is possible to suppress the abrasion powder from diffusing into the maximum sheet passing range.
Therefore, in order to suppress image noise due to abrasion powder of the power supply member 231, the position of the inner end Gi of the groove portion 224 is on the inner side of the position of the inner end Bi of the power supply member 224 and the outer end of the groove portion 224. The groove 224 may be disposed so that the Go position is outside the maximum sheet passing range. However, if the groove 224 overlaps within the maximum sheet passing range, it is difficult to secure a sufficient fixing pressure in the groove 224. In this sense, it is more preferable to dispose the groove 224 so that the position of the inner end Gi of the groove 224 is outside the maximum sheet passing range.

  (6) In the above-described embodiment, the case where the present invention is applied to a color printer apparatus has been described as an example. However, it goes without saying that the present invention is not limited to this. The present invention may be applied to a single function machine such as a device, or a multi-function machine (MFP) having these functions. The same effect can be obtained by applying the present invention to a monochrome machine instead of a color machine.

  INDUSTRIAL APPLICABILITY The fixing device and the image forming apparatus according to the present invention are useful as a technique for improving image noise caused by foreign matters in a resistance heating element type fixing device.

1 …………………………………………………… Image forming apparatus 100 …………………………………………… Fixing device 200 …………… …………………………… Fixing belt 201 …………………………………………… Electrode unit 210 ………………………………………… ... Pressing roller 220 ....................................... …………………… Pressure roller 224 …………………………………………… V-shaped groove 231 ... ………………………………………… Power supply member 501 ……………………………………………… Groove 502 with a flat bottom surface …………………… ……………………… Pressure change part 220a ………………………………………… End 220b ………………………………………… Center 601... ...... Cooling devices 701, 702, 11, 712 ... Wear powder adhesion area 801 to 804, 902 to 905 ... ... Wear powder adhesion area 901 ... High friction Part 1001 ………………………………………… Spiral groove 1002 ………………………………………… Spiral high friction part 1101 ……… ……………………………… Pressing members 1301 to 1303, 1311, 1312 ... Wear powder adhesion region Bi ……………………………………………… Inside of the feeding member End Bo ……………………………………………… The outer end Gi of the power feeding member ……………………………………………… The inner end Go of the groove portion ... …………………………………………… Outer edge of groove

Claims (8)

An endless fixing belt having a pair of electrode portions provided at both ends in the rotation axis direction, and a resistance heating element layer that generates Joule heat by energization through the pair of electrode portions;
A pressure roller that forms a fixing nip by being pressed against the fixing belt over the entire length of the fixing belt in the rotation axis direction;
Made of a carbon material having a lower hardness than the pair of electrode parts, and a pair of power supply members for supplying power to the pair of electrode parts,
The pressure roller has a movement suppressing portion that suppresses movement of wear powder generated by the power feeding member sliding on the electrode portion into a sheet passing area of the fixing belt,
The movement suppression unit is provided on the entire circumference when viewed from the rotation axis direction of the pressure roller,
In the rotation axis direction of the pressure roller, the position of the inner end of the movement suppressing unit is inside the position of the inner end of the power supply member and is outside the sheet passing area. apparatus. The fixing device according to claim 1, wherein the movement suppressing unit is a groove formed by reducing the diameter of the pressure roller. The outer diameter of the pressure roller is continuously reduced in diameter from the both end portions of the groove portion in the rotation axis direction of the pressure roller toward the center portion. The fixing device according to 1. The fixing device according to claim 1, wherein the movement suppression unit has a higher coefficient of friction than a portion other than the movement suppression unit on an outer peripheral surface of the pressure roller. The fixing device according to claim 4, wherein the movement suppressing unit is a portion in which an outer peripheral surface of the pressure roller is made of silicone rubber or fluorine rubber. The fixing device according to claim 1, wherein the movement suppressing unit includes two or more portions that are located at different positions in the rotation axis direction of the pressure roller. A cooling means for cooling at least a part of the outer peripheral surface of at least one of the fixing belt or the pressure roller by blowing air;
7. The cooling device according to claim 1, wherein the cooling unit blows air so that air does not flow from the movement suppressing unit to a central portion of the fixing belt in a rotation axis direction of the fixing belt. Fixing device. An image forming apparatus comprising the fixing device according to claim 1.

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