JP2009063735A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which prevents the occurrence of a slipping-through phenomenon of waste toner due to a level difference in toner adhered to its cleaning roller of the fixing device to reliably prevent the surface and backside of a recording sheet from becoming soiled. <P>SOLUTION: In the cleaning roller 30', which press contacts with the heating roller or pressure roller of the fixing device, the outer diameters Φ2 of parts 32a, 32b, 32c, 32d and 32e, which correspond to positions in the axis width direction at which peripheral members such as a peeling pawl and a temperature-detecting means are provided, are larger than those Φ1 of other parts 31 at which such peripheral members are not provided. By this arrangement, even if the cleaning roller is used at least for a certain period of time, level differences between large adhesion amount areas (a) (the parts corresponding to the positions at which no peripheral members exist) and small adhesion amount areas (b) (the parts corresponding to the positions at which the peripheral members exist) in the toner D adhered to the cleaning roller are not made, and consequently the slipping-through phenomenon of the waste toner is not caused. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device provided in an image forming apparatus, and more particularly to a fixing device provided with a cleaning roller.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as an electrophotographic copying machine or a printer includes a fixing device. The fixing device includes a heating roller that is heated by a heating unit and a fixing roller that is in pressure contact with the heating roller with a predetermined contact pressure. A recording paper on which unheated developer (for example, toner) is transferred is passed between a heating roller and a pressure roller to fix the unheated developer onto the recording paper. It has been.

  An electrophotographic image forming apparatus includes a color image forming apparatus that uses a plurality of color developers. However, in the case of an electrophotographic color image forming apparatus, developers of a plurality of colors are transferred to recording paper, and the layer thickness of the unheated developer is increased. Therefore, the conventional fixing device as described above has a problem that a part of the melted developer (or foreign matter such as paper dust from the recording paper) adheres to the heating roller or the pressure roller. It was.

In order to solve such problems, a cleaning member having a roller shape or a scraper (blade) shape is disposed so as to be in pressure contact with the heating roller or pressure roller, and an unnecessary developer adhered to the heating roller or pressure roller. For example, Patent Document 1 proposes a cleaning device that removes foreign matter.
JP 2003-162171 A

  The heating roller of the fixing device is temperature-controlled so that the surface temperature becomes a predetermined set temperature in order to heat the unheated developer. For example, when the developer used has a softening point of 60 to 80 ° C. and a melting point of 130 to 180 ° C., the set temperature of the heating roller surface temperature is 180 to 210 ° C. In a fixing device using a cleaning roller as a cleaning member, the cleaning roller is in direct contact with the surface of such a high-temperature heating roller, and the surface temperature of the cleaning roller is almost the same as the set temperature of the surface of the heating roller. . Accordingly, the surface temperature of the cleaning roller becomes equal to or higher than the melting point of the developer, and unnecessary developer on the heating roller collected by the cleaning roller is in a molten state and remains on the surface of the cleaning roller as it is. For this reason, after the cleaning roller collects the predetermined saturation amount of developer, the unnecessary developer on the heating roller cannot be collected on the cleaning roller, and the unnecessary developer remains on the heating roller. This causes the heating roller and the pressure roller to become dirty.

  FIG. 3 shows how waste toner adheres to a conventional cleaning roller. In the case of a metal cleaning roller having a uniform outer diameter in the axial width direction as shown in FIG. As the temperature detection means such as the thermistor provided on the outer peripheral portion of the pressure roller and the portion corresponding to the position where the peeling claw is present are not easily contaminated, as shown in FIG. After the lapse of time, a level difference occurs between the area c where the adhesion amount is large and the area d where the adhesion amount is small in the adhesion toner D on the cleaning roller. This step makes it impossible to remove the waste toner remaining on the overheating roller or the pressure roller facing the region d, and a so-called waste toner slipping phenomenon occurs.

  The present invention has been made in view of such a problem, and prevents the waste toner from slipping through the cleaning roller due to the level difference of the adhered toner, thereby reliably preventing the surface contamination and the back surface contamination of the recording sheet. It is an object of the present invention to provide a fixing device that can perform the above operation.

  In order to solve the above-mentioned problem, the first technical means of the present invention is to contact a heating roller having a heating means, a fixing roller having a pressure roller in pressure contact with the heating roller, and an outer peripheral surface of the fixing roller. And a cleaning roller that presses against the fixing roller. The cleaning roller has an outer diameter (diameter) dimension of a portion corresponding to a position where the peripheral member is present. It is characterized in that it is larger by a predetermined dimension than the outer diameter (diameter) dimension of the other part corresponding to the position where no exists.

  According to a second technical means, in the first technical means, the predetermined dimension has a diameter of 0.9 to 1.5 mm.

  According to a third technical means, in the first or second technical means, a concave portion having a predetermined depth is formed over the entire surface of the cleaning roller.

  According to a fourth technical means, in the third technical means, the depth of the concave portion is 0.1 to 0.2 mm.

  According to a fifth technical means, in any one of the first to fourth technical means, an axial width of the cleaning roller is set to be equal to or larger than a maximum sheet width that can be processed by the fixing device. Is.

  According to a sixth technical means, in any one of the first to fifth technical means, the cleaning roller is formed of a metal shaft.

  A seventh technical means according to any one of the first to sixth technical means is characterized in that the peripheral member includes a peeling claw.

  According to an eighth technical means, in any one of the first to seventh technical means, the peripheral member includes a temperature detecting means.

  A ninth technical means is an image forming apparatus including any one of the first to eighth technical means.

  According to the present invention, even if the usage time elapses to some extent, a step cannot be formed on the toner adhering to the cleaning roller, so that the waste toner can be prevented from slipping through. Accordingly, it is possible to appropriately collect unnecessary toner from the fixing roller, and it is possible to reliably eliminate the surface contamination and the back surface contamination of the recording sheet.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing a configuration of a fixing device targeted by the present invention. The fixing device 1 heats an image of toner T, which is a developer transferred onto the recording sheet P, by heat and pressure. A heating roller 10 and a pressure roller 20 that constitute a fixing roller, Cleaning rollers 30 and 30 for removing adhering foreign matters, upper peeling claw 41 for mechanically peeling the recording sheet attached to the heating roller 10, and lower peeling for mechanically peeling the recording sheet attached to the pressure roller 20. A claw 42, a thermistor 43 which is a temperature detecting element for detecting the surface temperature of the heating roller, a thermostat 44 as an excessive temperature rise preventing means, and the like are provided. The temperature detection element may also be provided on the pressure roller.

  The metal core 11 of the heating roller 10 is formed by, for example, drawing an iron-based cold-rolled carbon steel pipe into a desired outer diameter and thickness by drawing or the like, and then polishing to obtain an outer diameter of 40 mm and a thickness of 1.3 mm. Both ends are drawn to an outer diameter of 30 mm and a wall thickness of 1.5 mm, and a load applied to the heating roller is supported by a ball bearing (a type of rolling bearing) that is a shaft support member. Furthermore, the cored bar 11 is subjected to parkerizing treatment (phosphate coating treatment) on the material surface for the purpose of preventing rust, thereby suppressing the occurrence of rust.

  For the central sleeve portion of the heating roller 10 that has not been drawn, a fluorine-based resin that can maintain the release performance even when in contact with the heated and melted toner is generally used. Examples of the fluororesin include PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), or a mixture thereof. An intermediate layer 12 is formed on a conductive core 11. It is coated as a surface insulating layer 13.

  As the surface insulating layer 13, from the viewpoint of heat resistance and releasability, other examples include tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), and polychloro. A material containing fluororesin such as trifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), or fluororubber latex is used alone or in combination of two or more. It can also be used. These can be formed by coating and baking, or can be formed by tube coating.

  The intermediate layer 12 enhances the adhesion between the fluororesin as the surface insulating layer 13 and the surface of the carbon steel pipe subjected to the parkerizing treatment. In the present embodiment, an insulating primer such as a rubber-based or resin-based adhesive is used. In addition to the insulating primer described above, a conductive primer can be used as the intermediate layer 12.

  Further, a heat resistant and heat absorbing layer is formed on the inner surface of the heating roller 10. This heat-resistant and heat-absorbing layer efficiently absorbs radiation energy such as infrared light and converts it into heat when the halogen lamp 14, which is a heating element contained in the heating roller 10, emits radiant energy such as infrared light to the inner peripheral surface of the heating roller. To do. The heat-resistant endothermic layer is formed by applying and drying a mixture of a modified silicone resin, an inorganic heat-resistant black pigment, a hydrocarbon (solvent), and the like, and is formed to have a film thickness of 20 to 30 μm. Generally, heat resistant paints such as Okitsumo (trade name), Tetzol (trade name), and Serumo black (trade name) are used.

  Further, a bias voltage is applied to the heating roller 10 by a bias power source (not shown) for the purpose of giving a potential difference in the direction in which the reverse polarity toner adhering to the back surface of the recording sheet P is retained on the recording sheet P.

  The pressure roller 20 forms an insulating elastic layer 22 having heat resistance such as silicone rubber on a conductive core 21 made of iron or stainless steel, and forms an intermediate layer 23 on the outer periphery thereof. On the outer periphery of the intermediate layer 23, a surface resistance layer 24 for improving the surface release performance is formed. The intermediate layer 23 enhances the adhesion between the insulating elastic layer 22 and the surface resistance layer 24, and for example, an insulating primer is used.

The surface resistance layer 24 of the pressure roller 20 uses 10 ¹⁰ Ω as the surface resistivity. A surface resistivity of 10 ⁷ Ω to 10 ¹⁸ Ω or more is preferable, although 10 ⁵ Ω can be used. The volume resistivity is 10 ⁷ Ω · cm or more, more preferably 10 ¹⁰ Ω · cm or more.
As the insulating elastic layer 22, if it is the above-mentioned silicone rubber type, high temperature vulcanization type silicone rubber (HTV), addition reaction curable type silicone rubber (LTV), condensation reaction curable type silicone rubber (RTV), and also fluorine. Examples thereof include rubber or a mixture thereof. Specific examples include silicone rubbers such as dimethyl silicone rubber, fluorosilicone rubber, methylphenyl silicone rubber, vinyl silicone rubber, vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, tetrafluoroethylene-perfluoromethyl vinyl ether rubber. Fluorine rubber such as phosphazene-based fluororubber and fluoropolyether can be used. These rubbers can be used alone or in combination of two or more, and are molded by casting, vulcanization, polishing or the like.

  The cleaning rollers 30 and 30 are made of a metal shaft made of aluminum, iron, or an alloy thereof (including stainless steel), and are processed into a hollow roller or a solid roller to have a slide bearing or a rolling bearing at both ends. They are fitted and pressed against the heating roller 10 and the pressure roller 20 by a load spring or the like while holding a nip in a predetermined range. The surfaces of the cleaning rollers 30 and 30 are provided with a predetermined surface roughness by forming concave portions having a predetermined depth in order to clean a small amount of toner remaining on the surfaces of the heating roller 10 and the pressure roller 20. Unnecessary toner is collected in the recesses on the surface. By selecting the depth of the concave portion to be about 0.1 to 0.2 mm, the toner recovery performance is optimized.

  The axial width of the cleaning rollers 30 is set to be equal to or greater than the maximum sheet width that can be processed by the fixing device. As a result, unnecessary developer does not remain in the portion of the fixing roller corresponding to the maximum sheet width that can be processed by the heating device.

  Next, the cleaning roller improved by the present invention will be described. The toner adhering to the cleaning roller provided in pressure contact with the heating roller or the pressure roller is always provided by the peripheral members such as the peeling claw and temperature detecting means in contact with the outer peripheral surface of the fixing roller. The portion corresponding to the position where the amount is attached has a small amount of adhesion, and if the usage time elapses to some extent, a step is formed between the portion where the amount of adhesion is large and the waste toner slips through as described above.

  Therefore, in the present invention, the outer diameter (diameter) of the cleaning roller is set such that the outer diameter of the portion corresponding to the position in the axial width direction where the peripheral members such as the peeling claw and the temperature detecting means are provided is made larger than other portions in advance. This prevents the adhesion toner from being stepped.

  The improved cleaning roller will be described below with reference to FIG. FIG. 2A is an external view showing the entire cleaning roller. The cleaning roller 30 ′ includes parts 32 a, 32 b, 32 b, 32 b, 32 b, 32 b, 32 b, 32 b, 32 b, The outer diameter Φ2 at 32c, 32d, and 32e is made larger than the outer diameter Φ1 of the other portion 31 where the peripheral member is not provided. Specifically, for example, in the case of the cleaning roller on the pressure roller side, it is appropriate to select the difference between the diameters of Φ1 and Φ2 in the range of 0.9 to 1.2 mm. However, since the surface of the pressure roller is usually an elastic member with a rubber layer, the cleaning roller is normally pressed against the surface of the pressure roller even if the difference in diameter between Φ1 and Φ2 is about Φ1.5 mm. Can be made.

  FIG. 2B shows a state in which waste toner adheres to the cleaning roller 30 ′. As described above, the outer diameter of the portion corresponding to the axial position where the peripheral member such as the peeling claw or the temperature detecting means is provided is larger than the outer diameter of the other portion where the peripheral member is not provided. As shown in FIG. 2B, the adhesion toner D on the roller has a region a where the adhesion amount is large (a portion corresponding to a position where no peripheral member is present) and a region b where the adhesion amount is small (a position where the peripheral member exists). The step (see FIG. 3B) cannot be made as in the prior art. As a result, the waste toner does not slip through, and unnecessary toner can be properly collected from the heating roller or the pressure roller, and the surface contamination and the back surface contamination of the recording sheet can be reliably prevented. it can.

1 is a schematic longitudinal sectional view illustrating a configuration of a fixing device targeted by the present invention. It is explanatory drawing about the cleaning roller used for the fixing apparatus of this invention. It is explanatory drawing about the conventional cleaning roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixing device, 10 ... Heating roller, 11 ... Core metal, 12 ... Intermediate layer, 13 ... Surface insulating layer, 14 ... Halogen lamp (heating means), 20 ... Pressure roller, 21 ... Core metal, 22 ... Insulating property Elastic layer, 23 ... intermediate layer, 24 ... surface resistance layer, 30, 30 '... cleaning roller, 41,42 ... peeling claw, 43 ... thermistor (temperature detection means), 44 ... thermostat (over temperature rise prevention means), P ... recording sheet, T ... unfixed toner.

Claims (9)

A fixing roller having a heating roller incorporating a heating unit, a pressure roller in pressure contact with the heating roller, a peripheral member provided in contact with the outer peripheral surface of the fixing roller, and a cleaning roller in pressure contact with the fixing roller. In the fixing device
The cleaning roller has an outer diameter (diameter) dimension of a portion corresponding to a position where the peripheral member is present larger by a predetermined dimension than an outer diameter (diameter) dimension of another portion corresponding to a position where the peripheral member is not present. A fixing device.   The fixing device according to claim 1, wherein the predetermined dimension has a diameter of 0.9 to 1.5 mm.   The fixing device according to claim 1, wherein a recess having a predetermined depth is formed over the entire surface of the cleaning roller.   The fixing device according to claim 3, wherein a depth of the concave portion is 0.1 to 0.2 mm.   The fixing device according to claim 1, wherein a width of the cleaning roller in an axial direction is set to be equal to or greater than a maximum sheet width that can be processed by the fixing device.   The fixing device according to claim 1, wherein the cleaning roller is formed of a metal shaft.   The fixing device according to claim 1, wherein the peripheral member includes a peeling claw.   The fixing device according to claim 1, wherein the peripheral member includes a temperature detection unit.   An image forming apparatus comprising the fixing device according to claim 1.

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