JP2009205017A - Fixing unit and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing unit which can secure a desired fixing strength and durability even under a severe condition of high speed fixation. <P>SOLUTION: In the fixing unit, the thickness Tg of a fluororesin layer 13c and the thickness Tj of a rubber layer 13b in a heating roller 13 are defined as 100≤Tg≤180 μm and 50≤Tj≤150 μm, and the thermal conductivity of the rubber layer 13b is defined as 0.6-1.5 W/mK. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes a toner image transferred to a recording material using an electrophotographic method onto the recording material, and an image forming apparatus using the same.

  In the fixing roller of the fixing device for fixing the toner image on the recording material, the outermost layer is made of a silicone rubber, the outermost layer is made of fluororesin (for example, PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), PTFE). (Polytetrafluoroethylene) and FEP (tetrafluoroethylene / hexafluoropropylene copolymer, etc.).

  In the former case, since the rubber layer is in contact with the toner image transferred to the recording material and the rubber layer is heated while elastically deforming following the unevenness of the toner image, the toner image is not crushed too much. Although it is thought that it is more advantageous than the latter in terms of improving image quality, the former has the disadvantage that it is inferior in terms of durability, heat resistance and oil resistance compared to the latter.

  Therefore, in a low-speed printer that outputs about several tens of pages per minute and a medium-speed printer that outputs about 100 pages per minute, a fluororesin layer is provided on the silicone rubber layer. A fixing roller having an advantage has been put into practical use (see, for example, Patent Document 1).

JP 2006-18075 A

  However, in a high-speed or ultrahigh-speed image forming apparatus that outputs 200 pages or more per minute, even if a fixing roller having a fluororesin layer on the silicone rubber layer is used, The fluororesin layer is worn out at an early stage, and has not reached the level of practical use. In addition, the fixing roller used in low- and medium-speed image forming apparatuses has a diameter that is too small in the first place, and the nip width between the heating roller and the pressure roller cannot be taken sufficiently, so that it cannot be used as it is. is doing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus capable of eliminating the above-described drawbacks of the prior art and ensuring desired fixing strength and durability even under severe conditions of high-speed fixing. There is.

  In order to achieve the above object, the present invention comprises a heating roller having a heat source and a pressure roller in pressure contact with the heating roller. The recording material holding the toner image is heated by the heating roller and the pressure roller. In the fixing device that nips and conveys the toner image while pressing and fixing the toner image on the recording material, the heating roller is provided on a hollow cylindrical core material, the core material, and includes a core material and an adhesive function. A rubber layer and a fluororesin layer provided on the rubber layer. When the thickness of the fluororesin layer is Tg and the thickness Tj of the rubber layer including the adhesive function is 100 μm ≦ Tg ≦ 180 μm and 50 μm ≦ Tj ≦ 150 μm are satisfied.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus that can ensure desired fixing strength and durability even under severe conditions of high-speed fixing.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, an overall configuration of a laser beam printer using an electrophotographic system to which the present invention is applied will be described with reference to FIG.

  In FIG. 1, the photosensitive drum 1 of the laser beam printer P starts to rotate in the direction of the arrow based on the printing operation start signal from the controller C. The photosensitive drum 1 rotates at a speed corresponding to the printing speed of the printer P and continues to rotate until the printing operation is completed. When the photosensitive drum 1 starts to rotate, a high voltage is applied to the corona charger 2 and, for example, a positive charge is uniformly charged on the surface of the photosensitive drum 1.

  The photosensitive region charged by the corona charger 2 is image-exposed with a beam from the exposure device 3, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. When the photosensitive region holding the electrostatic latent image reaches a position facing the developing device 4, toner is supplied to the electrostatic latent image, and for example, a positive portion is removed from the portion on the photosensitive drum 1 where the charge is lost by beam irradiation. The charged toner is attracted by electrostatic force to form a toner image on the photosensitive drum 1.

  The web paper W set on the paper hopper 5 is synchronized with the timing at which the toner image formed on the photoconductive drum 1 reaches the transfer position by the web conveying roller 6. It is conveyed toward the middle.

  The toner image formed on the photosensitive drum 1 is transferred onto the web paper W by the action of the transfer unit 7 that applies a charge having a polarity opposite to that of the toner image to the back side of the web paper W.

  In this way, the web paper W set in the paper hopper 5 is transported to the fixing device 10 via the web transport roller 6, the transfer device 7, the web transport suction belt 8 and the buffer plate 9. The web paper W reaching the fixing device 10 is preheated from the back side by a preheating plate 11 incorporating a heater (not shown), and then formed by a heating roller 13 and a pressure roller 14 incorporating a heater lamp 12. The toner image is nipped and conveyed while being heated and pressurized at the nip portion, and the toner image is melted and fixed on the web paper W.

  The web paper W sent out by the heating roller 13 and the pressure roller 14 is sent out of the machine by the web paper feed roller 15 and subjected to processing such as cutting by a post-processing device (not shown).

  On the other hand, the photoreceptor area that has passed the transfer position is prepared for the next printing operation through the static eliminator 16, the static eliminator lamp 17, the cleaning device 18, the precharger 19, and the static eliminator lamp 20. Here, the static eliminator 16 is used to pull back a portion where the surface potential polarity of the photoconductor has been reversed from positive to negative by the action of the transfer device 7, and the photoconductor pulled back to the positive polarity is The electricity is once removed by the electricity removing lamp 17 and cleaned by the cleaning device 18.

  Prior to the charging step in the corona charger 2, the photosensitive region that has passed the cleaning device 18 is charged and discharged again by the pre-charger 19 and the charge-removing lamp 20, and the condition of the surface of the photosensitive member is adjusted.

  In FIG. 1, reference numeral 21 denotes an operation panel for displaying information based on the state of the printer P during a printing operation and for setting printing conditions. Further, the buffer plate 9 described above absorbs the slack and tension generated on the web paper W when a web paper W has a transport speed difference between the web transport suction belt 8 and the fixing rollers 13 and 14. belongs to. Reference numeral 22 denotes a cleaning web provided so as to be able to come into contact with the surface of the heating roller 13 and to be wound up, and for cleaning the surface of the heating roller 13 and applying a release agent to the surface of the heating roller 13. Is.

  Next, the configuration of the heating roller used in the fixing device of the present invention will be described with reference to FIGS.

  In FIG. 2, reference numeral 13a denotes a metal roller serving as a core material. In this embodiment, a hollow cylindrical aluminum roller having a thickness of 4 mm to 8 mm is used. 13b is a rubber layer having an adhesive function provided on the core material 13a, 13c is a fluororesin layer provided on the rubber layer 13b, and the heater lamp 12 shown in FIG. The heating roller 13 is configured by being inserted. The rubber layer 13b is formed on the core material 13a with a thickness of 50 μm to 150 μm.

  Further, as shown in FIG. 3, the rubber layer is divided into a high thermal conductive material portion 13b1 and a liquid dimethyl adhesive portion 13b2, and the high thermal conductive material portion is a thermal conductive agent (alumina fine powder, (Silica, metallic silicon, etc.) 100 to 500 parts by weight are added, and a thermally conductive silicone rubber composition in which the thermal conductivity of the silicone rubber is increased to 2 to 4 times with a catalyst such as platinum is used. Moreover, this structure may be only the high heat conductive material part 13b which has the function of the adhesive agent, as shown in FIG. The fluororesin layer 13c is formed on the rubber layer 13b with a thickness of 100 μm to 150 μm. In this embodiment, the resin layer 13c is composed of a fluororesin tube that covers the rubber layer 13b.

  In the present invention, the thickness of the core member 13a is set in consideration of not only the conductivity but also the strength of the heating roller with a large diameter. To achieve printing in a high speed range where the printing speed exceeds 200 pages / minute, the temperature of the heating roll is increased compared to fixing in low speed printing, and the total amount of heat supplied to the toner image per unit time is secured. Must.

  When securing the amount of heat by increasing the temperature of the heating roll in the roller fixing method, the surface layer of the heating roll should be made as thin as possible to improve the thermal response, and select a material with high heat resistance and high durability. Conceivable.

  Therefore, in the present invention, the fixing roller is a large-diameter roller having a diameter of 70 mm or more, preferably 100 mm or more, and a wide nip width is obtained by reducing the curvature of the roller outer periphery. The reason why the thickness of the core member 13a is set to 4 mm to 8 mm is that if the thickness is less than 4 mm, it cannot withstand high-speed continuous rotation in a state where the pressure roller is in pressure contact, resulting in a problem in durability. On the other hand, when the thickness exceeds 8 mm, heat transfer is poor, and problems such as a long waiting time until the start of printing occur. As described above, the thickness of the core material 13a is set to 4 mm to 8 mm, preferably 5 mm to 7 mm.

  Moreover, about the reason why the thickness of the rubber layer 13b is 50 μm to 150 μm and is divided into the high heat conductive material part and the liquid dimethyl adhesive part, or only the high heat conductive material part, the heating roll is in a high temperature environment of about 200 ° C. Because it is used, if the adhesive strength between the core material and the fluororesin layer is insufficient, peeling becomes a problem, and in order to ensure adhesion without air being included in the bonding process, the thickness is less than 50 μm Then, it is too thin to secure the adhesive strength between the core material and the fluororesin layer. On the other hand, if the thickness exceeds 150 μm, the heat capacity increases, making it difficult to respond at high speed, resulting in insufficient fixing strength at the start of printing. Further, from the viewpoint of heat resistance of the silicone rubber, the interface temperature between the core material 13a and the rubber layer 13b needs to be suppressed to 200 ° C. or lower. As described above, the thickness of the rubber layer 13b is set to 50 μm to 150 μm, preferably about 80 μm to 100 μm.

  As described above, a heat-conductive silicone rubber composition in which the thermal conductivity of silicone rubber is increased 2 to 4 times from a catalyst such as platinum is used for the rubber layer 13b.

  Here, if the amount of increase in the thermal conductivity is less than twice, the amount of heat is insufficient, the desired fixing strength cannot be obtained, and if the thermal conductivity is increased to nearly five times, the adhesion function of the rubber layer 13b is lost. The problem of peeling off of the adhesive occurs.

  The thermal conductivity of the rubber layer 13b in the state containing the thermal good conductivity agent is defined to be in the range of 0.6 W / m · K to 1.5 W / m · K, and is 0.6 W / m · K. If it is less than 1, the desired fixing strength cannot be obtained due to insufficient heat amount, and if it exceeds 1.5 W / m · K, the amount of the heat conducting agent in the rubber layer 13b becomes excessive, resulting in molding problems.

  Next, regarding the reason for setting the thickness of the resin layer 13c to 100 μm to 180 μm, if the thickness is less than 100 μm, the durability sufficient to cope with the high-speed fixing environment used by rotating at high speed continuously cannot be obtained. If it exceeds the upper limit, the heat resistance temperature of the underlying rubber layer exceeds the limit temperature, so that it cannot be set to a predetermined heating roll temperature necessary for fixing, and securing of fixing strength cannot be realized. The resin layer 13c is preferably PFA from the viewpoint of durability.

  From the above, the thickness (Tg) of the resin layer is 100 μm to 180 μm, the thickness (Tj) of the rubber layer including the rubber layer including the adhesive function is 50 μm to 150 μm, and the thermal conductivity of the rubber layer is 0.1. As for the rubber layer, the thickness of the high thermal conductive material (Tk) is 50 μm to 150 μm, and the thickness of the high thermal conductive material rubber layer (Tk) is 6 W / m · K to 1.5 W / m · K. ) As a result of evaluating two types of heating rolls of 50 μm to 150 μm and a rubber layer thickness (Tl) of 20 μm to 60 μm including a dimethyl-based adhesive function, 5 million pages even in a printer having a printing speed exceeding 200 pages / minute In the above continuous printing, a high quality image was obtained with no problem in both fixing strength and durability.

  In the above embodiment, the heating roller using silicone rubber as the rubber layer and PFA tube as the resin layer is exemplified. However, the rubber layer is made of highly heat-resistant fluoro rubber, and the resin layer is made of FEP or PTFE. Also good.

1 is an overall configuration diagram of a laser beam printer using an electrophotographic system to which the present invention is applied. It is sectional drawing of the heating roller used for the fixing apparatus of this invention. It is sectional drawing of the heating roller used for the fixing apparatus of this invention.

Explanation of symbols

  13 is a heating roller, 13a is a core material, 13b is a heat conductive rubber layer, and 13c is a fluororesin layer.

Claims (4)

A heating roller having a heat source; and a pressure roller in pressure contact with the heating roller. The recording material holding the toner image by the heating roller and the pressure roller is nipped and conveyed while being heated and pressed. In a fixing device for fixing to a recording material,
The heating roller includes a hollow cylindrical core material, a rubber layer provided on the core material, and a fluororesin layer provided on the rubber layer, and the thickness of the fluororesin layer is Tg, A fixing device characterized by satisfying a relationship of 100 μm ≦ Tg ≦ 180 μm and 50 μm ≦ Tj ≦ 150 μm when the thickness of the rubber layer is Tj.   2. The fixing according to claim 1, wherein the heating roller has an outer diameter of 70 mm or more, and a thermal conductivity of the rubber layer is 0.6 W / m · K to 1.5 W / m · K. apparatus.   The rubber layer is divided into a thickness Tk of the rubber layer containing the heat conducting agent and a thickness Tl of the rubber layer containing the dimethyl adhesive function, and 50 μm ≦ Tk ≦ 150 μm, 20 μm ≦ Tl ≦ 60 μm. The fixing device according to claim 1, wherein the relationship is satisfied.   An image forming apparatus comprising the fixing device according to claim 1.

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