JP2010181879A - Heat roller and heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat roller capable of uniforming the hardness of the heat roller in a longitudinal direction upon fixing, thereby improving a fixing performance, and having an enough heat capacity to prevent fixing failure even in a high-speed driving process by configuring the roller optimally adjustable of the heat capacity, and to provide a heating device. <P>SOLUTION: The heat roller 22 includes a layered structure between the core bar 22a of the roller 22 and a metal conductive layer 22d, the layered structure composed of a foamed rubber layer 22b-1 having a small heat capacity per unit volume and a silicon rubber layer 22b-2 having a larger heat capacity per unit volume compared to the foamed rubber layer 22b-1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heating roller used for heating a toner image formed on a sheet and a heating device using the heating roller.

  2. Description of the Related Art Conventionally, a general electrophotographic image forming apparatus is equipped with a heating device that heats and pressurizes a toner image formed on a sheet in an image forming unit to melt and fix the toner image on the sheet. This heating device is provided with a heating source for heating one or both of the heat roller and the press roller. As this heating source, a halogen lamp or an induction heating type coil is widely used.

  The points required for these heating devices are to increase energy efficiency and increase the number of sheets heated per unit time (high speed).

  In order to satisfy these requirements, various improvements have been made to the structure of the heat roller that heats the paper. For example, an elastic body layer is provided on a heat roller, and the surface is covered with a metal conductive layer. This type of heat roller absorbs the expansion of the elastic layer by providing a space between the elastic layer and the metal conductive layer because the air in the elastic layer expands due to heat. By comprising in this way, the required heat roller hardness is maintained, reducing the heat capacity of a heat roller (for example, patent document 1).

  However, by providing the elastic layer as described above, the heat capacity of the heat roller is lowered, and as a result, the energy efficiency is raised, but there is a problem that it is not possible to cope with the high speed. That is, when the speed increases exceed a certain level, the amount of heat taken away by the sheet becomes larger than the amount of heat that the heat roller has, and as a result, fixing failure occurs.

  As a means for solving the above problems, the present invention provides a core member, a first elastic body disposed on the outer periphery of the core member, and a heat capacity per unit volume larger than that of the first elastic body, A heating roller comprising: a second elastic body disposed on the outer periphery of the first elastic body; and a conductive metal layer disposed on the outer periphery of the second elastic body, and the heating roller It consists of a heating device using.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the heating roller which can adjust a heat capacity, and the heating apparatus using this heating roller, maintaining required hardness. This makes it possible to increase the speed without significantly reducing energy efficiency.

1 is a schematic configuration diagram illustrating an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating a fixing device according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Schematic explanatory drawing which shows the induced current generation coil of the embodiment of this invention. The longitudinal direction sectional view of the heat roller of the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing an image forming apparatus 1 equipped with a fixing device 11 which is an induction heating fixing device according to an embodiment of the present invention. On the upper surface of the image forming apparatus 1, a scanner unit 6 that reads a document supplied by an automatic document feeder 4 is provided. The image forming apparatus 1 includes a cassette mechanism 3 that supplies a sheet paper P, which is a fixing medium, to the image forming unit 10.

  The cassette mechanism 3 includes first and second paper feed cassettes 3a and 3b. Pickup rollers 7a and 7b for taking out sheet paper from the paper feed cassettes 3a and 3b, separation and conveyance rollers 7c and 7d, a conveyance roller 7e, and a resist are provided on the conveyance path 7 from the paper supply cassettes 3a and 3b to the image forming unit 10. A roller 8 is provided. A fixing device 11 that fixes a toner image formed on the sheet paper P by the image forming unit 10 is provided downstream of the image forming unit 10. A paper discharge roller 40 is provided downstream of the fixing device 11, and a paper discharge conveyance path 41 for conveying the fixed sheet paper P to the paper discharge unit 1 b is provided.

  The image forming unit 10 includes image forming stations 18Y, 18M, 18C, and 18K for respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming stations 18Y, 18M, 18C, and 18K are arranged in tandem along the transfer belt 10a that is rotated in the direction of the arrow q.

  The yellow (Y) image forming station 18Y has a charger 13Y as a process member, a developing device 14Y, a transfer roller 15Y, a cleaner 16Y, a removal member around a photosensitive drum 12Y that is an image carrier that rotates in the direction of arrow r. Electric appliance 17Y is arranged. A laser exposure device 19 for irradiating the photosensitive drum 12Y with a laser beam is provided above the yellow (Y) image forming station 18Y.

  The magenta (M), cyan (C), and black (K) image forming stations 18M, 18C, and 18K have the same configuration as the yellow (Y) image forming station 18Y.

  In the image forming unit 10, at the start of the printing operation, in the yellow (Y) image forming station 18Y, the photosensitive drum 12Y rotates in the direction of the arrow r and is uniformly charged by the charger 13Y. Next, the photosensitive drum 12Y is irradiated with exposure corresponding to the image information read by the scanner unit 6 by the laser exposure device 19 to form an electrostatic latent image. Thereafter, a toner image is formed on the photosensitive drum 12Y by the developing device 14Y, and the toner image is transferred onto the sheet paper P conveyed in the direction of the arrow q on the transfer belt 10a at the position of the transfer roller 15Y. After the transfer is completed, the photosensitive drum 12Y is cleaned of residual toner by the cleaner 16Y, the surface of the photosensitive drum 12Y is discharged by the charge eliminator 17Y, and the next printing is possible.

  The image forming stations 18M, 18C, and 18K for each color of magenta (M), cyan (C), and black (K) perform the image forming operation for yellow (Y) in the same manner as the image forming station 18Y. A toner image is formed. Thereafter, the sheet paper P is heated and pressure-fixed by the fixing device 11 which is an induction heating fixing device, and a printed image is completed and discharged to the paper discharge unit 1b.

  Next, the fixing device 11 will be described. FIG. 2 is a schematic configuration diagram showing the fixing device 11. The fixing device 11 includes a heat roller 22 that is an endless member to be heated and a press roller 23 that is a pressure member. The heat roller 22 is driven in the arrow s direction by the drive motor 25. The press roller 23 is brought into pressure contact with the heat roller 22 by a compression spring 24a. As a result, a nip 26 having a constant width is formed between the heat roller 22 and the press roller 23. The press roller 23 follows the heat roller 22 and rotates in the arrow t direction.

  Further, an induction current generating coil 27 that heats the heat roller 22 is disposed opposite to the outside of the heat roller 22 of the fixing device 11 via a gap. Further, on the outer periphery of the heat roller 22, a peeling claw 31 for preventing the sheet paper P after fixing from being wound, a first thermistor 33a for detecting the surface temperature of the heat roller 22, a second thermistor 33b, and a third thermistor. 33c and a thermostat 34 for detecting an abnormality in the surface temperature of the heat roller 22 and shutting off the heating. In addition, when there is no fear that the sheet paper P is wound around the heat roller, the peeling claw 31 may not be provided. A cleaning roller 24 b is provided on the outer periphery of the press roller 23.

  The heat roller 22 includes an elastic body (rubber) layer 22b having a thickness of 5 to 12 mm, a metal conductive layer 22d having a thickness of 40 μm made of nickel (Ni), a solid rubber layer 22e having a thickness of 200 μm, and a thickness. The release layer 22f has a thickness of 30 μm. The metal conductive layer 2c is not limited to nickel, and may be stainless steel, aluminum, a composite material of stainless steel and aluminum, or the like.

  The press roller 23 has a metal core 23a and a silicon rubber layer 23b around the core metal 23a. The press roller 23 further has a release layer 23c. Note that a fluorine rubber layer may be used in place of the silicon rubber layer 23b. Both the heat roller 22 and the press roller 23 are formed to have a diameter of 40 mm. The sheet paper P passes through the nip 26 between the heat roller 22 and the press roller 23 as described above, whereby the toner image on the sheet paper P is heated and pressed and fixed.

  Note that the press roller 23 may have a metal conductive layer heated by an induction current generating coil, or may incorporate a halogen lamp heater, if necessary.

  Next, the induction current generating coil 27 will be described. The induced current generating coil 27 includes first to third induced current generating coils 27a, 27b, and 27c. The magnetic cores 28a, 28b, 28c of the first to third induced current generating coils 27a, 27b, 27c are substantially coaxial with the heat roller 22. The magnetic core 28 concentrates the magnetic flux generated by the induction current generating coil 27 on the heat roller 22. The magnetic cores 28a, 28b, and 28c have magnetic shielding materials 30a, 30b, and 30c projecting on both sides, so that the magnetic flux can be further concentrated on the heat roller 22.

  As shown in FIG. 3, the first induced current generating coil 27 a has a length of 200 mm and heats the central region of the heat roller 22. The second and third induced current generating coils 27b and 27c are disposed on both sides of the first induced current generating coil 27a. The second and third induced current generating coils 27b and 27c are connected in series and driven by the same control. The first to third induced current generating coils 27a, 27b, and 27c heat the entire length 320mm of the heat roller 22. The first induced current generating coil 27a and the second and third induced current generating coils 27b and 27c are alternately switched and output. The outputs of the first induced current generating coil 27a and the second and third induced current generating coils 27b and 27c may be simultaneous.

  The induction current generating coil 27 generates a magnetic flux by applying a high frequency current. Due to this magnetic flux, an eddy current is generated in the heat roller 22 so as to prevent a change in the magnetic field. Due to this eddy current and the resistance of the heat roller 22, Joule heat is generated in the metal conductive layer 22d, and the heat roller 22 is heated.

  The induced current generating coil 27 uses, for example, a litz wire having a wire diameter of 3 mm obtained by twisting a plurality of copper wires. A heat-resistant polyamideimide is used as the copper wire insulating material. The electric wire and the insulating material are not limited to this, and the wire diameter is also arbitrary. Further, when a litz wire is used, its structure is also arbitrary, and it may be simply a bundle of a plurality of insulated copper wires, and the number and thickness of the copper wires are not limited. The induction current generating coil 27 is formed by winding a litz wire around the magnetic cores 28a, 28b, 28c.

  In the present embodiment, the configuration in which the metal layer is induction-heated using the induction current generating coil is disclosed. However, the present invention is not limited to this. For example, the present invention can be applied to a type in which heating is performed by a halogen lamp.

  FIG. 4 is a cross-sectional view of the heat roller 22 taken along a plane parallel to the rotation axis. The heat roller 22 has a metal core 22a made of a metal such as iron. Both ends of the metal core 22a are supported by bearings (not shown), and a rotational force is transmitted by the drive motor 25.

  An elastic body layer 22b is disposed on the outer periphery of the cored bar 22a by an adhesive. The elastic body layer 22b includes a foamed rubber layer 22b-1 and a silicon rubber layer 22b-2. The foamed rubber layer 22b-1 is formed by adding a foaming agent to silicon rubber or the like, and is bonded to the cored bar 22a.

  The silicon rubber layer 22b-2 is silicon rubber, and is bonded to the outer periphery of the foam rubber layer 22b-1. Silicon rubber has a larger heat capacity per unit volume and higher hardness than the foamed foam rubber layer 22b-1.

  As a method of increasing the heat capacity, it is possible to prevent the foaming from occurring as described above, or to set the foaming rate lower than the foaming rate (foaming ratio) of the foamed rubber layer 22b-1. By setting the low foaming rate in this way, the density of the silicon rubber of the foamed rubber layer 22b-2 is higher than the density of the silicon rubber of the foamed rubber layer 22b-1, so that the heat capacity is increased and the thermal conductivity is high. Become.

Further, a rubber material having a higher heat capacity than the silicon rubber used for the silicon rubber layer 22b-2 may be used, or the heat capacity may be increased by adding a conductive filler or the like to the same material. That is, when compared with the same volume, it is only necessary to have a heat capacity higher than that of the foamed rubber layer 22b-1, and the method is not limited to the present embodiment.

  However, when the heat capacity of the silicon rubber layer 22b-2 becomes too large, energy is accumulated excessively, which is not practical. In this embodiment, the thickness of the silicon rubber layer 22-2 is 1.5 mm.

  The silicon rubber layer 22b-2 has a cylindrical shape, and is processed with a step so that the outer diameter of the central portion of the outer periphery of the silicon rubber layer 22b-2 is smaller than the outer diameter of the end portion in the longitudinal direction of the heat roller. ing. The depth of this step is about 1 mm. The length of the step in the longitudinal direction of the roller is set to be slightly longer than the maximum size of the paper to be used. For example, when the width of A4 (297 mm) is the maximum sheet passing size, the length may be slightly longer 320 mm.

  A metal conductive layer 22d is disposed on the outer periphery of the silicon rubber layer 22b-2. The metal conductive layer 22d is bonded at both ends of the silicon rubber layer 22b-2. As a result, when the internal temperature of the heat roller is about room temperature (about 25 degrees), a gap 29 is formed between the silicon rubber layer 22b-2 and the metal conductive layer 22d in the center of the heat roller. Become.

  On the outside of the metal conductive layer 22d, a solid rubber layer 22e made of silicon rubber is formed with a thickness of about 200 μm. On the outside of the solid rubber layer 22e, a release layer 22f made of a fluorine-based resin is formed with a thickness of 30 μm.

  For example, when the hardness of the silicon rubber layer 22b-2 is increased by using the heat roller having the multilayer structure as described above, the heat roller is desired by adjusting the hardness of the foamed rubber layer 22b-1 or the like. It is possible to obtain the hardness of the heat roller.

  According to this embodiment, the heat capacity of the heat roller can be increased as necessary while maintaining the hardness of the heat roller.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  In this embodiment, the fixing device of the image forming apparatus has been described as an example, but the present invention is not limited to this. For example, the present invention can be applied to a erasing apparatus that erases the color of a toner image fixed on a sheet.

  DESCRIPTION OF SYMBOLS 11 ... Fixing device, 22 ... Heat roller, 22a ... Core metal, 22b ... Elastic body layer, 22b-1 ... Foam rubber layer, 22b-2 ... Silicon rubber layer, 22d ... Metal conductive layer, 22e ... Solid rubber layer, 22f ... release layer

JP 2008-209946 A

Claims (10)

A core member;
A first elastic body disposed on the outer periphery of the core member;
A second elastic body having a larger heat capacity per unit volume than the first elastic body and disposed on the outer periphery of the first elastic body;
A conductive metal layer disposed on the outer periphery of the second elastic body;
A heating roller comprising:   The heating roller according to claim 1, wherein a density of the first elastic body is lower than a density of the second elastic body.   The heating roller according to claim 1, wherein the hardness of the first elastic body is lower than the hardness of the second elastic body.   The heating roller according to claim 2, wherein the first elastic body is silicon foam rubber obtained by foaming silicon rubber by adding a foaming agent.   In the longitudinal direction of the heating roller, the outer diameter of the second elastic body is smaller than the outer diameter of both ends, and the metal layer is bonded only at the both ends of the second elastic body. The heating roller according to claim 1, wherein the heating roller is provided. A core member, a first elastic body disposed on the outer periphery of the core member, and a second heat element having a larger heat capacity per unit volume than the first elastic body and disposed on the outer periphery of the first elastic body A heating roller having an elastic body and a conductive metal layer disposed on the outer periphery of the second elastic body,
A pressure roller that is disposed opposite to the heating roller and applies pressure to the medium with the heating roller;
A heating source disposed in the vicinity of the outer periphery of the heating roller for heating the metal layer;
A heating device comprising:   The heating apparatus according to claim 6, wherein the density of the first elastic body is lower than the density of the second elastic body.   The heating device according to claim 6, wherein the hardness of the first elastic body is lower than the hardness of the second elastic body.   8. The heating apparatus according to claim 7, wherein the first elastic body is silicon foam rubber obtained by foaming silicon rubber by adding a foaming agent.   In the longitudinal direction of the heating roller, the outer diameter of the second elastic body is smaller than the outer diameter of both ends, and the metal layer is bonded only at the both ends of the second elastic body. The heating apparatus according to claim 6, wherein the heating apparatus is provided.

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