JP2005157179A - Fixing device and image forming device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming device which can obtain a fixed image of a stabilized quality by stabilizing the peeling when fixing a toner image on a recording medium which is hard to peel and removing the factor causing uneven gross on a fixed image. <P>SOLUTION: This fixing device has a heater roller 1 and a pressure roller 6 in contact with each other to form a nip N, and fixes the image by inserting the recording medium P having an unfixed toner image T into the nip N. It has a peeling means consisting of a peeling guide plate 7 and a gas nozzle 10 to jet out the pulsing compressed gas towards the gap between the heater roller 1 and the closer side of the guide plate to peel the recording medium P passing the nip N from the roller 1. Further, it has a gas heater 9 to heat the compressed gas to be jetted or already jetted from the above nozzle. The image forming device uses this fixing device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image recording apparatus, and more particularly to a fixing apparatus used in an electrophotographic image recording apparatus such as an electronic copying machine and a facsimile, and an image forming apparatus using the same.

  2. Description of the Related Art Conventionally, in an electrophotographic image recording apparatus such as an electrophotographic copying machine or a facsimile, as a fixing device for fixing a toner image transferred on a sheet surface, a toner is provided at a nip portion of a pair of rolls including a fixing roll and a pressure roll. 2. Description of the Related Art A fixing device (two-roll type fixing device) is widely used that passes a sheet on which an image has been transferred and fuses a toner image to the sheet by heating with a fixing roll and pressing with a pair of rolls.

  In this fixing method, the toner image fused to the paper comes into contact with the fixing roll. For example, as the fixing roll, a roll whose surface is coated with a fluorine-based resin having good releasability is used. However, even when such a fixing roll is used, the melted toner is soft and highly viscous, so that it easily adheres to the surface of the fixing roll, and the paper may be wound around the fixing roll. Therefore, normally, a peeling claw as shown in FIG. 1 of Patent Document 1, a forced peeling device using a plastic release sheet (plastic sheet) as shown in FIG. A method is employed in which the paper is peeled off by being provided in a non-contact manner and the paper is prevented from being wound around the fixing roll.

  However, in a fixing device provided with such a peeling claw or a peeling sheet, for example, when the thickness of a toner image immediately after fixing is relatively thin and the viscosity thereof is large, it can be peeled off without any problem. In the case of the toner image mounted on the toner image, or when the toner image is relatively thick immediately after fixing and the toner image is heated to a high temperature by the fixing roll, as in the case of forming a color image, and the adhesive force is increased. A large amount of toner adheres to the fluororesin layer on the surface of the fixing roll, and an excessive peeling force acts on a peeling member such as a peeling claw or a peeling sheet. At this time, since the toner image immediately after passing through the nip portion is rubbed and conveyed by the guide portion of the peeling member, the toner image is easily damaged by the peeling member. In particular, when fixing color images, it is necessary to sufficiently develop the toner, so the toner must be heated and melted sufficiently. Image defects are likely to occur.

  Under such circumstances, a self-stripping method is adopted as a method for solving this problem. The self-stripping method is often used especially for color fixing. The self-stripping method is a peeling method in which the paper is naturally peeled from the fixing roll by the strength of the paper and the elasticity of the fixing roll without using a forced peeling device such as a peeling claw or a peeling sheet. . As a means for establishing this self-stripping method, in the case of color image fixing, a fixing roll in which an elastic layer using silicone rubber, which is superior to fluororesin on the surface of a roll core, is usually used. Furthermore, a method of constantly supplying a relatively large amount (10 mg / A4 size paper or more) of oil to the surface of the elastic layer is widely adopted (see, for example, Patent Document 2).

However, the conventional fixing device that achieves self-stripping has the following various problems.
(1) The reliability of the fixing roll is increased due to the wear of the elastic layer of silicone rubber on the surface of the fixing roll, the deterioration of the releasability, and the deterioration of the elastic layer by the oil soaking into the fixing roll. May decrease.
(2) Oil must be replenished regularly, resulting in inferior maintenance, image defects due to excessive oil and oil streaks, and lowering the reliability of copiers and printers.
(3) Oil tends to remain on the surface of the paper after fixing, and the writing property with a ballpoint pen or ink is likely to be lowered.

  Furthermore, in recent years, there are more opportunities to use coated paper with a small basis weight, and to output images that use a large amount of toner from the leading edge of the paper, such as photographic images, when the margin at the leading edge of the paper is less than conventional paper. Therefore, there is a need for a peeling technique that can reliably peel off paper even under such circumstances.

  There is a technology that uses compressed air for paper peeling. Specifically, as described in Patent Document 3, for example, there is a configuration in which an air passage is provided inside the peeling claw and compressed air is supplied from the air passage corresponding to the tip position of the printing paper. In this document, the compressed air is blown onto the leading edge of the printing paper to peel off the leading edge of the printing paper, so that the peeling layer on the fixing roller surface deteriorates when the peeling nail hits the fixing roller surface, or the peeling nail is printed. It is described that it has become possible to greatly improve image quality degradation due to damage to the toner image on the paper. However, it is a condition that a plurality of cut grooves are formed at positions corresponding to the peeling claws on the heat roller fixing surface (fixing roller surface), and since the flatness of the fixing roller surface cannot be secured, the texture of the fixed image is improved. It will have an effect. Moreover, the amount of compressed air necessary to peel off the paper is enormous, resulting in an increase in the size and cost of the device, and further problems such as scatter of the supplied compressed air in the device, such as toner scattering There is also concern and practical application is difficult.

  There are other technologies that use compressed air for paper separation, but none of them is a technology that cuts the groove on the surface of the fixing roller and therefore requires a larger amount of compressed air for paper separation. Thus, practical application is difficult (for example, Patent Document 4).

  The problems related to sheet peeling described above are basically the same in the roll-belt nip fixing device and the belt-belt nip fixing device as well as the two-roll fixing device.

  Incidentally, the fixing device is required to stabilize the temperature of the fixing roller surface (fixing temperature). The image quality of the obtained image is affected, for example, the gloss (image gloss) of the fixed image changes depending on the fixing temperature. Due to the recent demand for higher speeds, factors that lower the fixing temperature of the fixing device are increasing, and it is desirable to eliminate factors that lower the fixing temperature as much as possible.

  In addition, the toner image that is at a high temperature immediately after fixing is still in a fluid state, and if the speed of temperature variation varies depending on the part, the glossiness of the fixed image may be affected, thereby affecting the image quality of the obtained image. There is a case. Therefore, it is desirable to eliminate as much as possible the factors that cause a temperature drop in the toner image immediately after fixing depending on the part.

JP 59-188681 A Japanese Patent No. 3322095 JP 2000-250351 A JP-A-61-59468

  In view of the above circumstances, the present invention is difficult to peel off without damaging the image, the recording medium, and the fixing roll (for example, an oilless, toner image having a large amount of toner, close to the front end of the recording medium. Factors that can cause stable peeling and lead to uneven gloss of the fixed image even if the recording medium has a small basis weight, or the recording medium is thin coated paper, etc. It is an object of the present invention to provide a fixing device capable of obtaining a fixed image with stable image quality, and an image forming apparatus including the same. In particular, a technology that uses a compressed gas for paper separation is employed to achieve the above-mentioned purpose, and without affecting the image quality, a highly practical peeling device, and a fixing device and an image forming apparatus having the same The purpose is to provide.

The present inventors have developed an APS (Air Pulse Stripping) technique as a technique for realizing stable peeling in a fixing unit when forming an image on a recording medium that is difficult to peel.
Here, the peeling device (peeling means) by the APS technique is a peeling device for peeling a sheet-like recording medium conveyed in a state of being attached to the surface of a rotating rotating body from the rotating body, From the region where the surface of the rotating body advances in a curved line in the circumferential direction, or the separation guide plate arranged downstream thereof, and the region sandwiched between the surface of the rotating body and the surface of the separation guide plate facing it, It is the peeling apparatus comprised from the gas discharge mechanism which discharges pulse-like compressed gas toward the clearance gap between the said rotary body surface and the one side of the said peeling guide plate adjacent to it.

  Explaining the operation and effect of the peeling device by the APS technique, first, the surface of the rotating body is transported in a state where it is attached to the surface of the rotating body in a region where the surface of the rotating body advances in a curved direction or downstream thereof When the recording medium follows the rotating body, a force for peeling from the surface of the rotating body is exerted by the stiffness of the recording medium itself. However, it is difficult to remove the recording medium (for example, the toner amount of the toner image is large, the toner image is close to the tip of the recording medium, the basis weight of the recording medium is small, the recording medium is thin coated paper, etc.) In some cases, the force to peel off is weak and the peelability is not sufficient.

  Conventionally, in order to compensate for this peeling force, a peeling claw or a peeling sheet was brought into contact with the above-mentioned area or the like, or a self-stripping method was used. It was not satisfactory enough, such as the effect on the surface of the film and the insufficient peelability. Therefore, in the APS technique, the influence on the image quality is suppressed by using a compressed gas for sheet peeling. That is, since the peeling guide plate is separated from the surface of the rotating body, there is no fear of damaging the rotating body, and the recording medium is not mechanically and forcibly separated from the rotating body. No damage. In this case, similarly, the image is not damaged, and the image remains in contact with the peeling guide plate even after peeling, so that the image quality is not deteriorated.

  Furthermore, as a configuration in which a compressed gas is discharged from a region sandwiched between the surface of the rotating body and the surface of the peeling guide plate opposed thereto toward a gap between the surface of the rotating body and one side of the peeling guide plate adjacent thereto. Therefore, the discharged compressed gas is curtained in the slit-shaped gap, proceeds so as to wrap around the surface of the rotating body that is curved, and is the most distal portion in the conveyance direction of the recording medium It hits. At this time, since the air flow of the compressed gas discharged is rectified in the gap and is applied to the recording medium in an expanded state, the compressed gas utilization efficiency is extremely high. Therefore, it is not necessary to make the discharge of the compressed gas continuous, it can be made into a pulse shape, and the amount of the compressed gas can be extremely reduced as a whole. Therefore, the apparatus does not increase in size and cost, and there is almost no concern that the supplied compressed gas convects in the apparatus, and the APS technique is extremely practical.

  Although the APS technique has extremely high peelability and practicality as described above, it is divided into at least a heating rotating body (so-called “fixing roll”) whose surface is heated and rotated, and the heating rotation. A pressure rotating body that contacts the surface of the body and forms a nip portion, and a sheet-like recording medium having a toner image made of unfixed toner formed on the surface, the surface on which the toner image is formed When applied to a fixing device that fixes the toner image by passing through the nip portion so as to abut the surface of the heating rotator, the compressed gas stream contributing to the peeling exerts an effect other than the peeling function. An adverse effect is possible.

  That is, the compressed gas discharged to peel the recording medium conveyed in a state of being attached to the surface of the heating rotator from the heating rotator is a gap between the surface of the heating rotator and the peeling guide plate. The air flows out as an air stream and acts on the leading edge of the recording medium, hits the surface of the heating rotator before transmission through the gap, and after transmission passes through an unfixed toner image (particularly formed on the surface of the recording medium). In some cases, it also hits a portion near the tip of the recording medium. Therefore, these may be cooled. If the heating rotator is exposed to an air flow and the temperature of the surface thereof decreases, gloss unevenness and poor fixing may be caused on the entire surface of the obtained fixed image. Further, if an unfixed toner image is exposed to an air current and the temperature thereof decreases, gloss unevenness may occur in an image near the leading end of the recording medium.

Therefore, the present invention intends to solve these problems by raising the temperature of the air flow by increasing the temperature of the compressed gas discharged in the APS technique. In other words, the fixing device of the present invention includes at least a heating rotator whose surface is heated to rotate, and a pressure rotator that abuts on the surface of the heating rotator to form a nip portion. A sheet-like recording medium on which a toner image made of toner is formed is inserted into the nip portion so that the surface on which the toner image is formed is in contact with the surface of the heating rotator. A fixing device for fixing;
Separating means for separating the recording medium transported in a state of being attached to the surface of the heating rotator by the molten toner constituting the toner image after passing through the nip portion from the heating rotator. Prepared,
The peeling means is located in a region where the surface of the heating rotator progresses in a curved direction in the circumferential direction, or downstream thereof, with one side close to the surface of the heating rotator, and in the circumferential direction of the heating rotator. One side of the peeling guide plate adjacent to the surface of the heating rotator and from the region sandwiched between the peeling guide plate arranged in a laid state and the surface of the heating rotator and the surface of the peeling guide plate facing the heating guide A gas discharge mechanism that discharges a pulsed compressed gas with a nozzle comprising a pipe-shaped conduction path and a discharge port provided at the tip of the pipe-shaped conduction path, and
Furthermore, it includes a gas heating mechanism for heating the compressed gas discharged from the nozzle and / or discharged.

  According to the present invention, first, very good peelability by the APS technique can be obtained. Further, by including a gas heating mechanism that heats the compressed gas discharged from the nozzle and / or the discharged compressed gas, it hits an unfixed toner image formed on the surface of the heating rotator or the surface of the recording medium. The compressed gas is in a heated state. That is, according to the present invention, it is possible to suppress a temperature drop due to a compressed gas stream, a fixing temperature drop that may cause a fixing failure or gloss unevenness, or a sudden temperature of a partial temperature of an unfixed toner image. The problem of change (decrease) can be solved and the reliability of the technology can be improved. Therefore, according to the present invention, it is possible to achieve the stabilization and homogenization of the recorded image while maintaining the extremely good peelability by the APS technique, suppressing the problem of fixing failure, and not damaging the image. Can do.

As the gas heating mechanism, there are two types: (1) an aspect in which some kind of heating member is newly provided, and (2) an aspect in which radiant heat from the heating rotator included in the fixing device is used. Of course, it is possible to incorporate both aspects.
(1) As a mode in which a heating member is newly provided separately,
(1-a) an aspect of an external heating member disposed outside the nozzle conduction path;
(1-b) the gas heating mechanism is an internal heating member provided in the conduction path of the nozzle;
Is mentioned.

  As an aspect of the above (1-a), in addition to the external heating member being an independent heating member, the configuration in which the external heating member also functions to heat the peeling guide plate, or the external heating member, The structure which heats the conduction path of the said nozzle through the said peeling guide plate can be mentioned.

(2) As an aspect using radiant heat from the heating rotator,
(2-a) The gas heating mechanism changes the outer periphery of the conduction path of the nozzle and / or the surface on the heating rotator side of the peeling guide plate to a color that absorbs radiant heat from the surface of the heating rotator. Configuration
(2-b) The gas heating mechanism is arranged so that the outer periphery of the conduction path of the nozzle does not contact the surface of the heating rotator, and at least a part of the gas heating mechanism is close to the surface of the heating rotator. Configuration,
Is mentioned.

  In the present invention, for the APS technology portion, that is, the peeling means, the most distal portion in the transport direction of the recording medium that has been transported along with the circumferential movement of the heating rotator approaches the position where the peel guide plate is disposed. It is preferable that the compressed gas is discharged by the gas discharge mechanism so that the compressed gas hits the foremost part when it is done. At this time, the recording medium conveyance direction most distal portion peeled off from the surface of the heating rotator by the compressed gas is sufficiently large to be in a state of being on one side of the peeling guide plate close to the surface of the heating rotator. According to the image information and / or information on the recording medium so that only compressed gas is discharged, the operating conditions of the gas discharge mechanism are controlled, and the portion following the most distal portion in the transport direction in the recording medium is: Accompanying the conveyance by the circumferential movement of the heating rotator, the peeling guide plate gradually climbs on one side close to the surface of the heating rotator, and the back surface of the peeling guide plate facing the surface of the heating rotator is recorded. It is preferable that the medium surface is configured to be rubbed and gradually peeled off from the surface of the heating rotator and finally peeled off from the entire surface of the recording medium.

  Further, as the gas discharge mechanism, a nozzle that discharges a compressed gas can be arranged in a region sandwiched between the surface of the heating rotator and the surface of the peeling guide plate facing the surface. In this case, a plurality of the nozzles may be arranged in a direction perpendicular to the circumferential direction of the heating rotator. Further, a portion of the side of the peeling guide plate that is close to the surface of the heating rotator that faces the center of the direction of travel of each compressed gas discharged by the nozzle or the vicinity thereof protrudes toward the surface of the heating rotator. It preferably has a shape.

  By adopting the configuration as described above, the portion where the compressed gas from the nozzle hits is peeled and lifted out of the recording medium conveyance direction most distal portion, but it corresponds to the portion, One side of the peeling guide plate adjacent to the surface of the heating rotator is a protruding part. Accordingly, the foremost portion of the recording medium that is well lifted by the compressed gas is guided to the protruding portion of the peeling guide plate, and the entire surface of the recording medium is gradually peeled off. Therefore, the image, the recording medium, and the heating rotator are not damaged, and extremely high releasability is ensured, and the image quality is not affected and is highly practical.

  In the fixing device of the present invention, the heating rotator may have a roll shape or an endless belt shape. Similarly, the pressure rotator may be in the form of a roll or an endless belt. That is, the fixing device of the present invention can be any of a two-roll fixing device, a roll-belt nip fixing device, and a belt-belt nip fixing device. Of course, in the case of the roll-belt nip method, either the heating rotator or the pressure rotator may be a roll or a belt. Any of the above belts may be in a state of being stretched by a plurality of rolls or in a free state of being not stretched (free belt nip method).

In addition, the image forming apparatus of the present invention heats at least a toner image forming unit that forms an unfixed toner image on the surface of a sheet-like recording medium by an electrophotographic method, and a toner image held on the surface of the recording medium. And an image forming apparatus comprising: a fixing unit that fixes by pressing.
The fixing unit is the fixing device of the present invention.

  According to the present invention, even when the recording medium is difficult to peel without damaging the image, the recording medium, and the heating rotator such as the fixing roll, the technique using the compressed gas for paper peeling (APS technique) Can be used to perform stable peeling, and includes a gas heating mechanism that heats the compressed gas discharged from the nozzle and / or discharged, thereby reducing the temperature of the compressed gas that contributes to peeling. Can be raised. Therefore, it is possible to eliminate the influence of the heated rotating body, toner image, and the like due to cooling by the action of the compressed gas, and the occurrence of gloss unevenness can be suppressed, and a fixed image with stable image quality can be formed. A fixing device and an image forming apparatus including the same can be provided.

Hereinafter, the present invention will be described with reference to preferred embodiments.
<First Embodiment>
FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment of the present invention. The fixing device of this embodiment is of a two-roll type.

  The fixing device shown in FIG. 1 includes a fixing roll (heating rotator) 1 that rotates in the direction of arrow A, and a rotary that is driven to rotate in the direction of arrow B opposite to the direction of rotation A of the fixing roll 1 while in contact with the fixing roll 1. A pressure roll (pressure rotator) 6 is provided. A sheet (recording medium) P carrying a toner image T made of unfixed toner on the surface is conveyed in the direction of arrow C, and is inserted into a nip portion N formed between the fixing roll 1 and the pressure roll 6. The toner image T is fixed on the surface of the paper P by being heated and pressed by the pair of rolls 1 and 6 and the toner of the toner image T being fused.

  One side of the fixing roll 1 is close to the surface of the fixing roll 1 on the downstream side in the rotation (circulation) direction A of the fixing roll 1 from the nip portion N, and the fixing roll 1 is laid in the rotation direction A of the fixing roll 1. The peeling guide plate 7 is arranged in the state where it has been. When the paper P carrying the toner image T in which the toner is melted is conveyed in the direction of the arrow C through the nip portion N, the paper P is peeled from the fixing roll 1 by the peeling guide plate 7. A gas discharge device (gas discharge mechanism) 10 is disposed in a region sandwiched between the surface of the fixing roll 1 and the surface of the peeling guide plate 7 facing the surface of the fixing roll 1. Furthermore, an external heater (external heating member) 9 as a gas heating mechanism according to the present invention is provided at the tip of the nozzle in the gas discharge device 10.

  The peeling member is provided for peeling the paper P as a recording medium from the fixing roll 1. In the present embodiment, the sheet P is fixed to the fixing roll by utilizing micro-strain generated by elastic deformation of the fixing roll 1 due to the pressing of the pressure roll 6 at the interface between the sheet P and the fixing roll 1. The self-stripping system configuration is employed in which the film is naturally peeled from 1. By adopting a self-stripping configuration, the image can be sufficiently peeled only under general fixing conditions, such as when fixing a character image on plain paper, but in this embodiment, it will be described in detail later. By providing the peeling device of the present invention including the peeling guide plate 7 and the gas discharge device 10, stable peelability is realized even under even more severe conditions.

  The fixing roll 1 is made of aluminum, the surface of a core 5 having a thickness of 2 to 3 mm is covered with an elastic layer 3 having a thickness of 0.5 to 3 mm, and further the surface layer 4 having a thickness of 20 to 50 μm is further coated thereon. The heater 2 is arranged as a heat source inside. In the present embodiment, a silicone LSR (Liquid Silicone Rubber) rubber having a rubber hardness of 25 to 45 ° is used as the elastic layer 3. As the surface layer 4, a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube is used. In this embodiment, the outer diameter of the fixing roll 1 is 65 mmφ.

The material of the elastic layer 3 is not limited to silicone rubber, and various conventionally known materials can be used. For example, fluorine rubber can be used, and a plurality of layers made of silicone rubber and fluorine rubber can be used. A laminated elastic layer may be used.
As the fixing roll, a so-called hard roll without an elastic layer may be used.

FIG. 2 shows an enlarged plan view of the peeling device in this embodiment, that is, the peeling guide plate 7, the gas discharge device 10, and the external heater 9 as viewed from the surface side of the fixing roll 1. As shown in FIG. 2, three gas ejection devices 10 are provided in the longitudinal direction of the peeling guide plate 7 in this embodiment. However, in the present invention, the number of gas discharge devices is not limited, and at least one gas discharge device may be provided. In the present embodiment, the gas discharge device 10 includes air nozzles 10a-1, 10a-2, 10a-3 having an inner diameter of about 0.5 to 4 mm, electromagnetic valves 10b-1, 10b-2, 10b-3, 2 includes a gas supply device (not shown), and is configured to discharge compressed airflow (compressed gas) in a pulse form from the air nozzles 10a-1, 10a-2, and 10a-3. Here, “pulsed” means not a continuous air flow, but a short time (for example, 0.01 to 0.1 sec), or a intermittent flow at a certain time interval. .
In addition, external heaters 9-1, 9-2, and 9-3 are provided at the tip portions of the air nozzles 10a-1, 10a-2, and 10a-3, respectively.

  FIG. 3 is a schematic configuration diagram schematically illustrating the overall configuration of the gas ejection device 10. In FIG. 3, the gas supply apparatus omitted in FIG. 2 is schematically shown, and is denoted by reference numerals 10c to 10g. That is, the gas supply device which constitutes a part of the gas discharge device 10 generates a gas reservoir (ACCUMULATOR) 10c for storing gas to be sent to each of the air nozzles 10a-1, 10a-2, 10a-3, and compressed gas. The air pump 10d for pressure feeding, the connecting pipe 10e for connecting them as shown in the figure, and the air pulse controllers 10f-1, 10f for controlling the opening and closing of the electromagnetic valves 10b-1, 10b-2, 10b-3. -2, 10f-3, and a regulator 10g for adjusting the pressure of the compressed gas pumped from the air pump 10d.

  Air nozzles 10a-1, 10a-2, and 10a-3 are connected to solenoid valves 10b-1, 10b-2, and 10b-3, respectively, and are supplied from air pulse controllers 10f-1, 10f-2, and 10f-3. The discharge time and discharge timing are controlled by turning on and off the valve opening / closing signal of the solenoid valve. Further, the solenoid valves 10b-1, 10b-2, 10b-3 are connected to the air pump 10d via the gas reservoir 10c by a connecting pipe 10e, and the gas pumped from the air pump 10d is the gas reservoir 10c. Once trapped, it is sent to each of the air nozzles 10a-1, 10a-2, 10a-3, and the compressed gas is discharged from the opening provided at the tip, that is, the discharge port, through the internal conduction path. The In the gas reservoir 10c, the gas supplied from the air pump 10d is stored until a predetermined pressure is reached. At this time, the pressure in the gas reservoir 10c is monitored by a pressure gauge (not shown) provided near the gas reservoir 10c in the path of the connecting pipe 10e.

FIG. 4A is an enlarged plan view of the peeling guide plate 7 in the peeling device as seen from the opposite direction to FIG. 2 (that is, as seen from the side opposite to the surface side of the fixing roll 1). FIG. 4B shows sectional views obtained by further enlarging the AA section of FIG. As shown in FIG. 4B, the cross-sectional shape of the peeling guide plate 7 is a wedge-shaped triangle having 8a, 8b and 8c as sides as a whole, and the apex portion having the sharpest acute angle is the fixing roll. Close to one surface. Since FIG. 4B is a cross-sectional view, in the peeling guide plate 7, 8 a, 8 b, and 8 c are actually all flat, and specifically, 8 b is a surface facing the surface of the fixing roll 1 (“ 8a is a back surface (referred to as "front surface"), and 8c is an end surface (referred to as "end edge surface") that is one side facing one side close to the surface of the fixing roll 1.
In addition, the peeling guide plate in the present invention includes, in the same way as the peeling guide plate 7 in the present embodiment, a cross-sectional shape that is not completely rectangular, but strictly not in a flat plate shape.

  In the present embodiment, one side of the peeling guide plate 7 that is close to the surface of the fixing roll 1 corresponding to the apex portion is not in a straight line, and is directed toward the surface of the fixing roll 1 as shown in FIG. It has a protruding shape (hereinafter, a shape having one or more portions protruding toward the surface of the rotating body in this way may be referred to as “an unusual tip shape”). As shown in FIG. 4A, the deformed tip shape in the present embodiment is composed of a convex portion 7a and a concave portion 7b (note that both end portions are in a protruding state equivalent to the convex portion 7a. In the present embodiment, the part is a part that does not contribute to the paper peeling, and is not included in the convex part 7a.Of course, when the part contributes to the paper peeling, the part is considered as a convex part. .)

  The protrusions 7 a protrude so that their tips are in a straight line, and are provided at three locations in the longitudinal direction of the peeling guide plate 7. On the other hand, the concave portions 7b are provided between and at both ends of the convex portions 7a, and recede in an arc shape. Further, in the concave portion 7b, the degree of retreat differs on the front and back surfaces of the peeling guide plate 7, and the front surface 8a, which is the back surface, retreats from the back surface 8b, and in the center of the arc of the concave portion 7b, A surface inclined with respect to the surface 8a (7c in FIG. 4B) is formed.

  The most distal portion in the conveyance direction C of the paper P peeled off by the compressed gas discharged from the gas discharge device 10 rides on the surface 8a side of the peeling guide plate 7, and thereafter accompanying the conveyance by the circumferential movement of the fixing roll 1. As the sheet P slides and moves on the surface 8a, the sheet P is gradually peeled off from the surface of the fixing roll 1 and finally the entire sheet P is peeled off. That is, only the leading edge of the paper P is peeled off by the compressed gas by the gas discharge device 10, and the peeling guide plate 7 is responsible for peeling the portion up to the rear end.

This effect will be described in detail. 5 and 6 are explanatory views for explaining the operation of the peeling device of the present invention step by step, taking the fixing device of the present embodiment as an example. Steps 1 and 2 are shown in FIG. And 4 are shown in FIG. 6, respectively. Further, in each process, the left figure is a schematic cross-sectional view seen from the same direction as FIG. 1, and the right figure is seen from the opposite direction to FIG. 2 (that is, the fixing roll 1 surface side). FIG. 5 is an enlarged plan view of only the peeling device and the sheet, as viewed from the opposite surface. In FIG. 5 and FIG. 6, “ON” and “OFF” are on / off of the operation of the electromagnetic valves (10b-1, 10b-2, 10b-3 in FIG. 3) in the gas discharge device 10.
In addition, the following processes are shown as typical examples to the last, and the present invention is not limited to the processes of the present embodiment.

  The paper (recording medium) P conveyed in the direction of arrow C and inserted into the nip N between the fixing roll (heating rotator) 1 and the pressure roll (pressure rotator) serves as a heating rotator to be peeled off. It comes out from the exit of the nip portion N in close contact with the surface of the fixing roll 1 (in a state of being stuck). From the exit of the nip portion N, the sheet (recording medium) P travels along the curved surface in the circumferential direction (arrow A direction) along the surface of the fixing roll 1 and is discharged from the air nozzle of the gas discharge device 10. The air nozzle and the vicinity of the air nozzle of the leading edge in the conveyance direction C of the paper P (hereinafter sometimes simply referred to as “paper front end”) are peeled off from the surface of the fixing roll 1 and are conveyed while floating. (See step 1 in FIG. 5).

  Since the compressed gas discharged from the air nozzle is sufficient to instantaneously peel off the leading edge of the paper coming out of the nip portion N, the pulse width (discharge time) does not need to be so long. When the leading edge of the sheet is peeled off and floated, one side (hereinafter referred to as “leading edge”) of the peeling guide plate 7 provided with a slight gap from the surface of the fixing roll 1 close to the surface of the fixing roll 1 may be referred to. ) Enters, and the leading edge of the sheet rides on the leading edge of the peeling guide plate 7. Before and after that stage, the discharge of the compressed gas is completed (see step 2 in FIG. 5).

  Thereafter, the portion of the paper P following the leading edge in the conveyance direction C gradually climbs on the tip of the peeling guide plate 7 as the fixing roll 1 is moved by the circumferential movement of the fixing roll 1 and slidably moves on the surface of the peeling guide plate 7. Then, the sheet is gradually peeled off from the surface of the heating rotator, and finally the entire surface of the paper P is peeled off (see steps 3 and 4 in FIG. 6). Then, the paper P is guided by the discharge guide 11 and discharged from the apparatus by the discharge roll 12.

The surface of the peeling guide plate 7 is preferably formed of a release layer on the surface of a flat plate having a smooth flat surface or a slight curvature, and the toner image T in a molten state immediately after the exit of the nip portion N is obtained. Even if the surface is rubbed slightly, it is supported by the entire surface of the smooth peeling guide plate 7, so that the image is not damaged.
The peeling apparatus of the present invention exhibits extremely good peeling performance due to the above action.

  In this embodiment, the tip of the peeling guide plate 7 has an irregular tip shape as described above, and only the portion corresponding to the portion that is instantaneously peeled off by the compressed gas (the convex portion 7a in FIG. 4) is fixed. Projecting toward the surface of the roll 1. In other words, the peeling guide plate 7 has a shape that protrudes toward the surface of the fixing roll 1 only at a portion or its vicinity facing the center in the traveling direction of each compressed gas discharged from the air nozzle.

  Therefore, only this convex portion 7 a is provided so as to form a slight gap with respect to the surface of the fixing roll 1, and this portion of the paper P first runs on the tip of the peeling guide plate 7. At this time, a portion that is away from the air nozzle in a direction perpendicular to the conveyance direction C at the forefront of the paper P (where the compressed gas does not hit) remains in close contact with the fixing roll 1 because the compressed gas does not act. However, since the tip of the peeling guide plate 7 has entered between the paper P and the fixing roll 1 in the part peeled off by the compressed gas, the base part is already peeled off as the paper P is transported thereafter. Is gradually peeled off by the peeling guide plate 7 (the state of step 2 in FIG. 5). That is, the part where the compressed gas at the leading edge of the paper P does not hit much is peeled off by the peeling guide plate 7 later than the part where the compressed gas hits directly.

  As described above, the peeling apparatus according to the present embodiment first peels off the leading edge of the paper P coming out of the nip portion N in close contact with the fixing roll 1 with compressed gas, and the peeling guide plate 7 is peeled off. When the leading edge of the paper enters, the entire surface of the paper is finally peeled off.

  In the present invention, it is desirable that the tip of the peeling guide plate has an irregular tip shape, and this shape is also adopted for the peeling guide plate 7 in the present embodiment. That is, in the present invention, the shape of the tip portion of the peeling guide plate is such that the portion facing the center of the direction of travel of each compressed gas discharged by the nozzle or the vicinity thereof is close to the surface of the heating rotator to be peeled. It is preferable to form a slight gap, and it is more preferable that the gap is linear. On the other hand (the place away from the nozzle), the recording medium is peeled off with a delay. It is preferable that the position is away from the surface of the heating rotator. Therefore, in the present embodiment, the tip portion of the peeling guide plate 7 is linear in the portion facing the air nozzle (10a-1, 10a-2, 10a-3 in FIG. 3) in the gas discharge device 10 and its vicinity. It protrudes closest to the fixing roll 1, and is gradually cut away in an arc shape so as to gradually move away from the surface of the fixing roll 1 as it moves away from the portion facing the air nozzle.

  Of course, in the present invention, it is not essential that the tip of the peeling guide plate has such a deformed tip shape, for example, it may be a straight shape, but by having a deformed tip shape as in this embodiment, The pressure of the compressed gas to be discharged from the nozzle, the discharge time (pulse width), and the number of nozzles to be provided can be suppressed, which is preferable from the viewpoints of downsizing and cost reduction of the apparatus.

  Air nozzles (10a-1, 10a-2, 10a-3 in FIG. 3) in the gas discharge device 10 are provided in a region sandwiched between the surface of the fixing roll 1 and the surface of the peeling guide plate 7 facing the surface. Is provided downstream of the fixing roll 1 in the circumferential direction A with respect to the gap formed between the leading end of the peeling guide plate 7 and the fixing roll 1.

  In FIG. 7, the model enlarged view for demonstrating the flow of the compressed gas discharged from the air nozzle is shown (in this figure, 10a-1 is represented as a representative among the three air nozzles). As shown in FIG. 7, a linear airflow (initial airflow X) discharged from the air nozzle 10 a-1 and containing a slightly radial component is formed between the tip of the peeling guide plate 7 and the fixing roll 1. When passing through the slit-shaped gap, the shape is changed to become a planar (curtain-shaped) airflow (gap passing airflow Y). Since the planar (curtain-like) airflow hits the leading edge of the paper P in a state close to a linear shape, it is the most efficient when compared with other airflows with the same amount of gas, and the leading edge of the paper P Can be peeled off satisfactorily. In other words, the recording medium can be peeled off with a smaller amount of gas and a smaller number of nozzles by arranging the heating rotating body, the peeling guide plate, and the gas discharge means to be peeled so as to have the positional relationship defined in the present invention. can do.

  In the present embodiment, the peeling guide plate 7 uses a stainless steel (SUS430) material as a base material, and has a surface 8a, a back surface 8b, and an edge surface 8c covered with a fluorine resin layer having a thickness of 30 μm. . Of course, in this invention, it is not limited to using a stainless steel material as a base material of a peeling guide plate, For example, you may use a heat resistant plastic material and another metal.

  In the present embodiment, the tip of the peeling guide plate 7 (specifically, the convex portion 7a) is disposed in close contact with the surface of the fixing roll 1 in a non-contact manner. At this time, the gap (gap) between the tip of the peeling guide plate 7 (specifically, the convex portion 7a) and the surface of the fixing roll 1 is preferably 0.05 to 1 mm, more preferably 0.1 to 1 mm. Selected from. If this gap is too large, the direction of the paper P can be greatly changed by the peeling guide plate 7, and it becomes difficult to smoothly slide on the front end of the peeling guide plate 7 and the surface 8 a, and the paper P becomes a stress of the paper guide and peels off. May cause problems. If the gap is too large, the leading edge of the sheet must be floated so that the leading edge of the sheet is placed on the leading edge of the peeling guide plate 7, and the gap passing airflow Y in FIG. There is also a concern that the pressure and the pulse width of the compressed gas required will increase due to the difficulty of becoming an airflow. On the other hand, if the gap is too small, the compressed gas becomes a resistance when passing through the gap, and there is a concern that the discharge force of the converted planar (curtain-like) airflow may be reduced. The gap adjustment may be appropriately set in accordance with the pressure of the compressed gas discharged from the air nozzle 10a-1, the discharge timing, and the discharge time (pulse width) within the above range.

  The air nozzles 10 a-1, 10 a-2, and 10 a-3 are sandwiched in a non-contact manner between the peeling guide plate 7 and the surface of the fixing roll 1, particularly at the tips of the convex portions 7 a of the peeling guide plate 7. It is arranged at the position where the discharge nozzle tip of the air nozzle approaches. When this position is away, the discharge force of the compressed gas that acts on the most advanced portion of the paper P is weakened, and the effectiveness may be suppressed. Therefore, it is desirable that the discharge nozzle tip of the air nozzle is disposed as close as possible to the tip of each convex portion 7a of the peeling guide plate 7 within a range that does not interfere with the surface of the fixing roll 1 and the peeling guide plate 7.

  The peeling guide plate 7 is arranged in a state of being laid in the circumferential movement direction A of the fixing roll 1. Here, “the state laid down in the circumferential direction” refers to the normal from the heating rotator passing through one side (tip) of the peeling guide plate (7) close to the heating rotator (fixing roll 1). This means that the entire peeling guide plate is tilted in the circumferential direction. The degree of tilting is preferably such that the traveling direction of the recording medium peeled off from the surface of the heating rotator is not changed as much as possible, and the tangent of the heating rotator at the point (peeling point) at which peeling of the recording medium from the surface of the heating rotator starts. It is desirable that the back surface (surface 8a) of the peeling guide plate facing the surface of the heating rotator is nearly parallel (the angle between them is small).

  The arrangement of the peeling guide plate will be described with reference to the drawings. FIG. 8 is a partially enlarged cross-sectional view for explaining the positional relationship between the fixing roll, which is a heating rotator, and the peeling guide plate. In FIG. 8, the periphery of the part where the paper P peels from the surface of the fixing roll 1 is shown in an enlarged manner, and the configuration other than the paper P, the fixing roll 1 and the peeling guide plate 7 is not shown.

In FIG. 8, the paper P transported in a state of being stuck to the surface of the fixing roll 1 is peeled off from the surface of the fixing roll 1 at a peeling point S with a compressed gas by a gas discharge device 10 (not shown).
The leading edge of the paper P peeled off at the peeling point S rides on the tip G of the peeling guide plate 7. FIG. 8 shows this state. The vicinity of the leading edge of the paper P is conveyed along a locus substantially the same as the tangent line E at the peeling point S on the surface of the fixing roll 1. The closer the tangent line E and the trajectory of the paper P are, the more the stiffness of the paper P can be utilized for peeling the paper P. Therefore, the pressure and pulse width of the compressed gas can be suppressed. It can be smoothly peeled off.

  Accordingly, the position of the tip G of the peeling guide plate 7 is preferably a gap range as described above, but besides that requirement, it is on the tangent line E or on the surface of the fixing roll 1 from the tangent line E. Preferably, the closer to the tangent line E, the better.

Further, a straight line connecting the peeling point S and the leading end G of the peeling guide plate 7 (in FIG. 8, since the straight line is the same as the tangent line E, it is indicated as a straight line E), a surface 8a of the peeling guide plate 7, Is preferably −35 ° or more and + 20 ° or less, and is preferably closer to 0 °. If this angle becomes too large on the minus side (the surface 8a of the peeling guide plate 7 is further away from the surface of the fixing roll 1 than the straight line E), the direction of the paper P can be greatly changed by the peeling guide plate 7. It may be difficult to smoothly slide on the tip of the peeling guide plate 7 or the surface 8a, which may cause stress on the paper guide and interfere with the peeling. On the other hand, if this angle becomes too large on the plus side, it will be difficult to arrange the gas ejection device 10 at an appropriate position.
Therefore, the best mode is a state in which the tangent E and the surface 8a of the peeling guide plate 7 are overlapped, in which the sheet P is transported along substantially the same locus as the tangent E.

  The separation position (peeling point S) of the paper P on the fixing roll 1 works more effectively for the separation of the leading edge of the paper P by the compressed gas as the distance from the nip N exit is longer. For example, when the discharge force F (N) of the compressed gas is applied to the leading edge of the paper P in the state where the leading edge of the paper P is k (mm) from the nip portion N outlet, the paper P Since the N exit is fixed as a fulcrum, a moment of approximately F × k acts on the most distal portion of the paper P. In order to overcome the stiffness of the sheet P with the force of the sheet P adhering to the fixing roll 1 and the nip portion N exit as a fulcrum, and to guide the leading edge of the sheet P to the tip of the peeling guide plate 7, The value of k should be larger. However, if k is too large, it takes a long time for the paper P to be carried around the fixing roll 1, and the toner image T carried on the surface of the paper P is heated. There may be uneven gloss in the image. Therefore, the peeling point S at which the discharge force of the compressed gas effectively acts on the outermost end portion of the paper tip P while considering the image quality.

  The position of the peeling point S is appropriately adjusted according to conditions such as the direction, pressure, and pulse width of the compressed gas by the gas discharge device 10, and conditions such as the thickness of the paper P to be used, stiffness, and the toner amount of the toner image to be formed. That's fine. Generally, it adjusts so that the said compressed gas may become a position which hits first.

In the present embodiment, the convex portion 7 a in the peeling guide plate 7 has a width substantially parallel to the axial direction of the fixing roll 1. The preferable range of the width cannot be generally specified, but is preferably selected from about 5 to 80 mm.
In the present embodiment, the air nozzles 10a-1, 10a-2, 10a-3 are provided independently between the peeling guide plate 7 and the fixing roll 1, but in the present invention, the heating rotator is provided. With a configuration capable of discharging a pulsed compressed gas from a region sandwiched between the surface and the peeling guide plate surface facing the surface toward the gap between the surface of the heating rotator and one side of the peeling guide plate adjacent thereto. As long as it is sufficient, the position where it is arranged is not limited (for example, a mode in which the air nozzles 10a-1, 10a-2, and 10a-3 are further retracted), and the peeling guide plate has the nozzle. Even if it is the structure which serves also, it does not interfere in one direction (for example, the aspect which the nozzle to which the opening part was directed protruded from the back surface 8b of the peeling guide plate 7 so that the clearance gap between the surface of the fixing roll 1 and the front-end | tip of the peeling guide plate 7 might be aimed at Raised It is.).

The discharge time (pulse width) of the compressed gas discharged from the air nozzles 10a-1, 10a-2, 10a-3 varies depending on various conditions. About 1 sec is desirable.
When the discharge time exceeds 0.1 sec, a very large amount of gas is released by one discharge, which makes it difficult to cope with high-speed continuous paper feeding and lacks versatility. In addition, a large pump having a large gas supply capability is required as the air pump 10d, and a large-capacity ACCUMULATOR is required as the gas reservoir 10c. As a result, an increase in the size of the apparatus becomes obvious and costs increase, making it impractical. there is a possibility.
On the other hand, if the discharge time is less than 0.01 sec, the open / close response of the solenoid valves 10b-1, 10b-2, and 10b-3 is deteriorated, and variation in valve open / close timing is increased, so that there is a possibility that the reliability is lacking. is there.

  The discharge time may be set appropriately according to the conveyance speed (process speed) of the paper P, but may be variable according to the conveyance speed. In addition to this, it is possible to make the discharge time of the compressed gas variable according to the length (blank part) from the leading edge of the paper P to the image portion where the toner image T exists. It is possible to apply the compressed gas only to the margin at the tip, and consideration can be given so that the compressed gas does not act on the toner image T. Further, the compressed gas can be wedged between the roll and the paper and peeled off even if there is almost no margin at the front end of the paper. Of course, the discharge amount of the compressed gas is considerably small as a whole. Therefore, even if the compressed gas hits the toner image T, the image quality is usually not greatly affected.

  The pressure of the compressed gas discharged from the air nozzles 10a-1, 10a-2, 10a-3 is desirably in the range of 0.05 to 0.5 MPa. If the pressure exceeds 0.5 MPa, a large pump having a large gas supply capability is required as the air pump 10d, leading to an increase in the size of the device, and measures for air leakage are required, leading to an increase in the cost of the device. In order to reduce the size of the apparatus and achieve good sheet tip separation at low cost, it is desirable to reduce the pressure and to reduce the amount of compressed air discharged at one time. By selecting the minimum pressure and the shortest discharge time required for peeling the leading edge of the paper P as the compressed gas discharged from the air nozzles 10a-1, 10a-2, 10a-3, a high-speed copying machine It is also applicable to printers and printers.

  The pressure of the compressed gas may be variable according to conditions such as the type of paper P to be inserted and the conveyance speed. For example, when the paper P is a solid paper and the toner image T has a large amount of toner up to the vicinity of the leading edge of the conveyance direction C on the paper P, the toner having a strong adhesive force is close to the front end of the paper P. For this reason, it is difficult to peel the paper P from the fixing roll 1. Therefore, if the pressure of the gas to be discharged is set high in order to peel off the leading edge of the paper P with a strong compressed gas, the paper P can be reliably peeled off. The pressure of the air pump 10d is adjusted by a regulator 10g disposed between the gas reservoir 10c and the air pump 10d.

The amount of compressed gas is mainly determined by the pressure of the gas, the orifice diameter of the solenoid valve, the number of nozzles (three in this embodiment), and the open time of each solenoid valve.
The gas used as the compressed gas is not particularly limited, but generally air in the atmosphere is used as it is.

  In the present embodiment, the convex portion 8a of the peeling guide plate 7 and the air nozzles 10a-1, 10a-2, 10a-3 corresponding to the convex portion 8a are respectively given as an example, but the first book In the invention, of course, the number is not limited to three. For example, the peeling guide plate may be provided with convex portions of about 1 to 10, and air nozzles may be provided on all the convex portions, or the convex portions. Of these, an air nozzle may be provided only at any one of a plurality of locations.

  Here, the high practicality of the APS technology is proved by verifying specific device configurations of the fixing device and the peeling device of the present embodiment. Some of the air nozzles specified in the present embodiment, such as the number of air nozzles, are considered as some variables.

  The process speed of the paper P conveyed to the nip portion N is v (mm / sec), the length of the conveyed paper P is L (mm), and the interimage between the continuously conveyed paper P is α ( mm), conditions under which compressed air (compressed gas) can be discharged stably are shown. Various conditions are described by the following symbols.

・ Air supply capacity of air pump 10d: S (ml / sec)
-Capacity of the gas reservoir (ACCUMULATOR) 10c: T (ml)
-Set air pressure of gas reservoir 10c: P ₁ (MPa)
・ Atmospheric pressure: P ₀ (MPa)
-Orifice diameter of solenoid valves 10b-1, 10b-2, 10b-3: a (mm)
・ Compressed air discharge time (solenoid valve opening time): t (sec)
・ Number of air nozzles: n (pieces)
・ Total amount of discharged compressed air: A (cc)

When the pressure that decreases when the solenoid valves 10b-1, 10b-2, and 10b-3 are opened by t (sec) is Δp (MPa), the total discharge amount A per air pulse is expressed by the following equation (i ).
A = Δp × T / P ₀ (ml) (i)
A / n (ml) is discharged per air nozzle.

  Air that is a predetermined set pressure is supplied to the gas reservoir 10c during the time from when the paper is conveyed and the compressed air is discharged and then the next paper is conveyed and the compressed air is discharged again. Therefore, the total discharge amount A per air pulse should satisfy the following formula (ii).

A ≦ (L + α) × S / v (ii)
In the above formula (ii), the left side is the maximum air that can be supplied from the air pump 10d to the gas reservoir 10c while the compressed air is not discharged between the first sheet and the next sheet. Amount.

For example, a small pump having an air supply capacity S = 8 liter / min (≈130 ml / sec) is used as the air pump 10d, and an ACCUMULATOR having a capacity T = 200 ml is used as the gas reservoir 10c at a set air pressure P ₁ = 0.3 MPa. From the number of air nozzles n = 3 and the orifice diameters a = 1.5 mm of the solenoid valves 10b-1, 10b-2, 10b-3 (air nozzle inner diameter 2 mm), the compressed air discharge time t = 0. When the compressed air was discharged under the condition of 025 sec, ΔP was approximately 0.04 MPa. Therefore, if the total air discharge amount A is set to atmospheric pressure P ₀ = 0.101 MPa,
A = 0.04 × 200 / 0.101
Approximately 79 ml, which is approximately 26 ml per nozzle.

Here, when A4 size paper is used as a paper P in a lateral feed (ie, the length L of the paper P is 210 mm), the image P is conveyed at an inter image α = 30 mm, and a process speed v = 350 mm / sec. In addition, the maximum amount of air (L + α) × S that can be supplied from the air pump 10d to the gas reservoir 10c within the required time during which compressed air is not discharged between one sheet and the next sheet / V is
(L + α) × S / v = (210 + 30) × 130/350
Approximately 89 ml, which satisfies the above formula (ii).

  Therefore, it can be said that the air supply capacity of the air pump 10d and the capacity of the gas reservoir (ACCUMULATOR) 10c in this case are within an appropriate range, and the same discharge force can be stably obtained even under a high-speed continuous paper feeding condition of 350 mm / sec. The compressed air can be applied to the leading edge of the paper P.

  While the compressed air is discharged (t (sec)), the conveyance distance Δm (mm) of the paper is Δm = v × t, which is 8.75 mm in the case described above. While the compressed air is being discharged, the paper P is still being transported. When the leading edge of the paper P that has exited the nip N reaches a predetermined position, the compressed air begins to be discharged, and then the top of the paper P is discharged. Since the air flow continues to act on the leading edge, the leading edge of the paper P is conveyed while moving in a direction away from the fixing roll 1, and is guided by the convex portion 7a of the peeling guide plate 7 to finish the discharge. Since the air flow of the paper P and the compressed air is in a relative movement relationship with each other, the leading edge of the paper P can be appropriately guided to the convex portion 7a of the peeling guide plate 7 according to the conveyance speed of the paper P. What is necessary is just to select the discharge timing and discharge time of compressed air.

Here, since air of A / n (ml = cm ³ ) is discharged from the orifices having a diameter a (mm) of the respective solenoid valves 10b-1, 10b-2, and 10b-3, in the vicinity of the orifices of the respective solenoid valves. The average flow velocity k (m / sec) of air can be represented by the following formula (iii) when simply calculated while ignoring the loss.
k = (A / n) / {(πa ² ) · t / 4} = 4A / (nπa ² t) (iii)
In the above example,
k = 4 × (79 × 10 ⁻⁶ ) / {3 × π × (1.5 × 10 ⁻³ ) ² × 0.025} ≈600
Thus, the average flow velocity k reaches about 600 m / sec.

  By the way, in this embodiment, in order to raise the temperature of the compressed gas discharged from the air nozzles 10a-1, 10a-2, 10a-3 to a predetermined temperature, a gas heating mechanism according to the present invention is provided at the tip of the nozzle. External heaters (external heating members) 9-1, 9-2, 9-3 (in this specification, these may be collectively referred to as “9” in some cases). This external heater 9 is attached to the vicinity of each air nozzle tip so that the compressed gas discharged from the tip of each air nozzle 10a-1, 10a-2, 10a-3 surrounds a conduction path through which it passes before discharge. Yes. The compressed gas heated by the external heater 9 is discharged from each air nozzle. As a result, the compressed gas that hits the toner image T on the surface of the fixing roll 1 and the paper P after being discharged is preheated, and thus a malfunction caused by lowering the temperature of the surface of the fixing roll 1 and the toner image T, particularly glossy. Problems in image quality such as unevenness are alleviated.

  In order to realize high image quality with little image quality unevenness, the temperature of the compressed gas to be discharged is preferably set higher than room temperature. If the temperature difference between the temperature of the compressed gas and the toner temperature in the toner image T on the surface of the paper P immediately after passing through the nip portion N is large, image quality unevenness may occur. In addition, since the toner that is still in a high temperature state may be rapidly cooled, it is desirable that the temperature of the compressed gas is higher than room temperature.

  Further, the temperature of the compressed gas is preferably close to the temperature near the softening point of the toner, the temperature immediately after the exit of the nip portion N of the toner image T, that is, the sheet P is separated from the fixing roll 1 and the supply of heat is finished. It is more preferable that the temperature be close to the toner temperature immediately after the natural cooling by heat dissipation has started. Specifically, it is preferably higher than the softening point of the toner, and is preferably in the range of −5 ° C. to −80 ° C. with respect to the surface temperature of the fixing roll 1.

  The form of the compressed gas flow changes in the process until it reaches the leading edge of the paper P. FIG. 9 shows a schematic enlarged view for explaining the flow of the compressed gas before and after being discharged from the air nozzle (in this figure as well, FIG. 7 represents 10a-1 among the three air nozzles. Is shown.) FIG. 9 is drawn from the same viewpoint as FIG. 7 and shows the air nozzle 10a-1 in a cross-sectional view for explaining the airflow.

  “Nozzle airflow V” passing through the conduction path of the air nozzle 10a-1 when the electromagnetic valve 10b-1 is released, “Initial airflow X” spreading around the fixing roll 1 and the peeling guide plate 7 after discharging from the nozzle, fixing The form changes in the process of “gap passing airflow Y” converted into a planar (curtain-like) airflow in the gap between the roll 1 and the peeling guide plate 7. For example, in order not to lower the surface temperature of the fixing roll 1, it is better that the temperature of the “air flow V in the nozzle” is closer to the temperature of the fixing roll 1, In order not to affect the toner image T formed on the leading edge of the paper P, the temperatures of the “nozzle airflow V” and “initial airflow X” are adjusted, and the “gap-passing airflow Y” is adjusted. Is set to a temperature at which the toner image T is not rapidly cooled.

  In the present embodiment, an external heater 9 that functions as an external heating member is attached outside the conduction path near the tip of the air nozzle 10a-1 so as to surround the conduction path. Therefore, the compressed gas is warmed at the stage of “air flow in nozzle V”, and “initial air flow X” hitting the fixing roll 1 and “gap passing air flow Y” acting on the leading edge of the paper P and hitting the toner image T may also be used. Both are in a warmed state.

  In the present embodiment, an external heater 9 as an external heating member disposed outside the conduction path of the nozzle is employed for the method of heating the compressed gas (that is, the “gas heating mechanism” referred to in the present invention). However, in the present invention, the gas heating mechanism is not limited to this. The gas heating mechanism is largely divided into two types: (1) a mode in which a certain heating member is newly provided, and (2) a mode in which radiant heat from the heating rotating body (fixing roll 1) included in the fixing device is used. Is mentioned. Of course, it is possible to incorporate both aspects. Each will be described with reference to a modification of the present embodiment.

(1) Aspect in which a heating member is newly provided As this aspect, first, the aspect of this embodiment is applicable. (1-a) External heating in which the gas heating mechanism is arranged outside the conduction path of the nozzle The aspect which is a member is mentioned. By providing the heating member independently, it becomes easy to design to a desired heating temperature, and it is not necessary to change the shape of the nozzle conduction path or to provide an obstacle for heating, and it is a straight tube. Since the compressed gas can pass straight through the conduction path, there is an advantage that there is little pressure loss.

  You may control the temperature of the peeling guide plate 7 as needed. After the compressed gas is discharged, the toner image T surface of the paper P is led out to the discharge guide 11 while rubbing the surface 8a of the release guide plate 7, so that it is discharged from the outlet of the nip portion N, and the release guide plate 7 If the temperature difference between the toner image T on the surface of the paper P when reaching the surface 8a and the surface 8a of the peeling guide plate 7 is large, the image quality may be affected during rubbing. Therefore, it is preferable to control the temperature of the peeling guide plate 7 so that the two temperatures are not separated (the temperature difference is preferably within 80 ° C., more preferably within 60 ° C.).

  As another aspect of the above (1-a) that can realize this, there can be mentioned a configuration in which the conduction path of the nozzle is heated via the peeling guide plate. By heating the peeling guide plate 7, the air nozzle 10 located between the fixing roll 1 and the peeling guide plate 7 is heated by heat transfer (excluding heat conduction). At this time, it is more preferable to bring the air nozzle 10 and the peeling guide plate 7 into contact with each other because it is effective for increasing the amount of heat transfer by heat conduction. Of course, integrating the peeling guide plate and the nozzle is also included in this embodiment, which is preferable.

Examples of the means for heating the peeling guide plate 7 include a method of installing a planar heating element (for example, a ceramic heater) on the surface of the peeling guide plate 7 on the fixing roll 1 side.
The heating of the peeling guide plate 7 also has an effect of increasing the temperature of the compressed gas, and the proper temperature for heating the air nozzle on the peeling guide plate 7 fixing roll 1 side and the proper not affecting the fixed image after peeling. It is desirable to set the temperature to be compatible.

  Moreover, when providing an external heating member, it can also be set as the structure which serves as the function which heats the said peeling guide plate with the nozzle which discharges compressed gas. FIG. 10 shows a schematic enlarged view of the vicinity of the peeling guide plate in the case where such a configuration is adopted in this embodiment. (In this figure as well, FIG. Is shown.) FIG. 10 is drawn from the same viewpoint as FIG.

In the example of FIG. 10, a dual-purpose heater (external heating member, gas heating mechanism) 29 is disposed in the gap between the air nozzle 10 a-1 and the peeling guide plate 7 to contact and heat both. The peeling guide plate 7 is heated by the combined heater 29 together with the compressed gas passing through the conduction path in the air nozzle 10a-1.
In addition, the method for controlling the temperature of the peeling guide plate 7 is not particularly limited. For example, a heater for heating the peeling guide plate 7 is disposed separately from the heater for heating the compressed gas, or the remaining heat of the fixing roll 1 is used. Or the like.

  On the other hand, as another aspect which provides a heating member, (1-b) the aspect whose said gas heating mechanism is an internal heating member provided in the conduction path of the said nozzle is mentioned. FIG. 11 shows a schematic enlarged view of the vicinity of the peeling guide plate when such a configuration is adopted in the present embodiment (in this figure as well, FIG. 11 represents 10a-1 out of the three air nozzles. Is shown.) FIG. 11 is drawn from the same viewpoint as FIG. 7, and shows the air nozzle 10a-1 in a sectional view in order to clarify the internal structure.

  In the example of FIG. 11, an internal heater (internal heating member, gas heating mechanism) 49 is arranged in the conduction path at the tip of the air nozzle 10 a-1. The compressed gas passing through the conduction path in the air nozzle 10a-1 is directly heated by the internal heater 49. In the said structure, since the compressed gas which passes a conduction path directly hits the internal heater 49 as a heating member, although heat efficiency is favorable, compared with the aspect by (1-a) external heating member, a pressure loss is. Since there is an inferior defect, it is desirable to configure so as not to reduce the hole cross-sectional area of the conduction path as much as possible.

  In a mode in which a heating member is newly provided regardless of whether inside or outside, the heating member may be a small nichrome wire heater or a cylindrical ceramic heater, or by electromagnetic induction heating. Also good. Any conventionally known heating member may be used as long as the desired heating performance can be satisfied.

  In order to heat the discharged compressed gas so as to have a higher temperature, it is only necessary to increase the energy for heating in the heating member and / or lengthen the region heated by the heating member. Since the airflow in the conduction path is as high as several hundred m / s, the time for transferring heat to this airflow is very short. Since it is practically difficult to directly measure the temperature of this fast-flowing airflow, fixing failure or the like due to a decrease in the temperature of the fixing roll 1 will not occur, and the fixed image near the leading end of the paper P will be affected. The degree of heating should be controlled so that there is no such thing.

(2) Aspect of Utilizing Thermal Radiation (Radiation Heat) from Heating Rotating Body As this aspect, first, (2-a) the outer periphery of the conduction path of the nozzle and / or the peeling guide plate on the heating rotator side The structure which makes a surface the color with the high absorptivity of the radiant heat from the said heating rotary body surface is mentioned. Specifically, it is preferable to use a dark color system, more preferably black.

  That is, as in the former case, if the outer periphery of the conduction path of the nozzle is colored with high radiant heat absorption, in addition to heat transfer from the heating rotator, the radiant heat is directly absorbed by the outer periphery of the nozzle. The gas can be heated. Further, as in the latter case, if the surface of the peeling guide plate on the side of the heating rotator is colored with high heat absorption, the peeling guide plate once absorbs the heat. It may be simply referred to as “radiation.”) And is absorbed by the outer periphery of the nozzle to heat the compressed gas.

  By effectively using the radiant heat transfer from the surface of the heating rotator by setting the outer periphery of the conduction path of the nozzle and / or the surface of the peeling guide plate on the heating rotator side in such a color. This is preferable in that it does not require a special heating member. However, as described above, since the air flow in the conduction path is extremely fast and the time for transferring heat to the air flow is very short, it is relatively difficult to heat the compressed gas to a desired temperature only by the correspondence. Have difficulty. Therefore, it is preferable to combine with other aspects and configurations.

  In order to change the color of the radiant heat from the surface of the heating rotator to a high absorbability, the nozzle or the peeling guide plate itself uses such a color material or a heat resistant paint of a color having a high radiant heat absorbability such as black. Just paint. For nozzles and peeling guide plates, metal such as aluminum and stainless steel is often used from the viewpoint of heat resistance and durability. In that case, if the latter “painting” method is adopted, Good.

  A simple verification test was conducted on this colored embodiment. In the configuration of the present embodiment, the base material of the air nozzles 10a-1, 10a-2, 10a-3 and the peeling guide plate 7 is stainless steel with metallic luster. The air nozzles 10a-1, 10a-2, and 10a-3 were not attached with the external heater 9 for this verification test, and the stainless steel was exposed. The effect of coloring was confirmed between the stainless steel-derived metallic luster and the nozzle substrate surface coated with a heat-resistant black paint to make it black.

  In order to confirm the difference in effect due to radiation heat absorption, the fixing roll 1 is heated to a predetermined temperature (160 ° C.) and the surfaces of the air nozzles 10a-1, 10a-2, 10a-3 are blackened as they are. The difference of the surface temperature in the case of this state was compared. Compared with the state after the same time (3 minutes) has passed (the temperature of the fixing roll 1 is in an equilibrium state), since the temperature gradient of the temperature increase on the nozzle outer peripheral surface is large, the outer peripheral surface temperature is not colored. It was confirmed that the temperature was higher by about 3 to 5% with coloring compared to.

  Similarly, the same verification test was performed on the peeling guide plate 7. As for the peeling guide plate 7, the state in which the stainless steel is exposed and the metallic gloss is left, and the case where the heat-resistant black paint is applied to the surface of the peeling guide plate 7 facing the fixing roll 1 to make it black. And the effect by coloring was confirmed. As a result of comparison in the same manner as in the case of the nozzle, it was confirmed that the temperature rise temperature on the outer peripheral surface of the nozzle was higher by about 5 to 8% with coloring as compared with without coloring.

  On the other hand, as another aspect of using radiant heat from the heating rotator, (2-b) the gas heating mechanism is arranged so that the outer periphery of the conduction path of the nozzle does not contact the surface of the heating rotator, and A configuration in which at least a part of the route is arranged so as to be close to the surface of the heating rotator is mentioned. FIG. 12 shows a schematic enlarged view of the vicinity of the peeling guide plate when such a configuration is adopted in the present embodiment (in this figure, as well as FIG. 7, one of the three air nozzles is represented. However, since the nozzle shape is different, the reference numeral of the air nozzle is 10'a-1.) FIG. 12 is drawn from the same viewpoint as FIG.

In the example of FIG. 12, the air nozzle 10 a-1 is not a straight tube, and the internal conduction path snakes and is close to the surface of the fixing roll 1. Of course, the outer periphery of the air nozzle 10a-1 and the surface of the fixing roll 1 are not in contact with each other. Thus, since the conduction path in the air nozzle 10a-1 is close to the surface of the fixing roll 1, the compressed gas passing through the conduction path in the air nozzle 10a-1 is heated.
By adopting this mode, it is possible to effectively use the radiant heat from the surface of the heating rotator, which is preferable in that it is not necessary to provide a special heating member.

  The shape of the air nozzle 10 a-1 is not particularly limited to the example of FIG. 12. For example, the shape along the phase shape of the surface of the fixing roll 1 so as to absorb more radiant heat from the fixing roll 1. For example, various shapes can be selected. However, it is desirable to consider that the more complicated the shape of the conduction path, the greater the pressure loss when the compressed gas passes. Therefore, in order to absorb higher radiant heat from the fixing roll 1 while forming a conductive path shape with as little pressure loss as possible, it is preferable to combine with the aspect (2-a).

<Second Embodiment>
FIG. 13 is a schematic cross-sectional view of a fixing device according to the second embodiment of the present invention. The fixing device of this embodiment is of a roll-belt nip type. This embodiment has the same configuration as the first embodiment except that the configuration of the fixing device is different from that of the first embodiment. Therefore, in FIG. 13, a member having the same function as that of the first embodiment. Are denoted by the same reference numerals as those in FIG. 1 and detailed description thereof will be omitted.

In the fixing device of the present embodiment, the fixing roller 1, the pressure rotator 16, and the peeling devices 7 and 10 constitute main parts.
The pressure rotator 16 includes an endless belt 21 stretched by three rolls of a lead roll 18, a pressure roll 19 and a stretch roll 20, and a pressure pad (pressure member) pressed against the fixing roll 1 via the endless belt 21. ) And 17 constitute the main part.

  The endless belt 21 is in contact with the fixing roll 1 so as to be wound at a predetermined angle, thereby forming a nip portion N ′. Inside the endless belt 21, the pressure pad 17 is disposed in a state of being pressed against the fixing roll 1 via the endless belt 21.

  The winding angle of the endless belt 21 around the fixing roll 1 is preferably about 20 to 45 ° so as to ensure a sufficiently wide nip portion N ′, although it depends on the rotation speed of the fixing roll 1. Further, it is preferable that the winding angle is such that the duel time (insertion time of the paper P) of the nip portion is 30 msec or more, particularly about 50 to 70 msec.

  The endless belt 21 is preferably composed of a base layer and a release layer coated on the surface thereof (the surface in contact with the fixing roll 1 or both surfaces). The base layer is selected from polyimide, polyamide, polyamideimide and the like, and the thickness thereof is preferably about 50 to 125 μm, more preferably about 75 to 100 μm. The release layer formed on the surface of the base layer is preferably a layer coated with a fluororesin such as PFA having a thickness of 5 to 20 μm as described above.

  The pressure pad 17 is provided with, for example, an elastic member for securing a wide nip portion N ′, and a low friction layer on the surface of the elastic member that contacts the inner peripheral surface of the endless belt 21. It is held by a holder made of steel. The elastic member having a low friction layer on the surface has a concave shape that substantially follows the outer peripheral surface of the fixing roll 1 and is pressed against the fixing roll 1 to form a nip portion N ′. The downstream pressure roll 19 is strongly pressed against the fixing roll 1 via the endless belt 21, and a certain amount of distortion is generated at the portion of the fixing roll 1.

  As the elastic body member in the pressure pad 17, an elastic body having high heat resistance such as silicone rubber or fluoro rubber, a leaf spring, or the like can be used. The low friction layer formed on the elastic member is preferably provided to reduce the sliding resistance between the inner peripheral surface of the endless belt 21 and the pressure pad 17 and has a small friction coefficient and wear resistance. Specifically, a glass fiber sheet impregnated with Teflon (R), a fluororesin sheet, a fluororesin coating film, or the like can be used.

The endless belt 21 is driven to rotate in the direction of arrow B by the rotation of the fixing roll 1 in the direction of arrow A.
The sheet P on which the toner image T is formed is conveyed from the left side in FIG. 9 toward the nip portion (in the direction of arrow C). The toner image T on the surface of the paper P inserted through the nip portion is fixed by the pressure acting on the nip portion and the heat applied through the fixing roll 1 by the heater 2. If fixing is performed by the fixing device of the present embodiment, a wide nip portion can be taken, and stable fixing performance can be ensured.

  As described above, the pressure roll 19 is pressed against the fixing roll 1 at the exit of the nip portion N ′, and the elastic layer 3 of the fixing roll 1 is distorted. With such a configuration, the nip portion N ′ is secured, and the distortion of the fixing roll 1 is locally increased near the exit of the nip portion N ′.

  According to the fixing device of the present embodiment, the amount of distortion of the fixing roll 1 in the vicinity of the exit of the nip portion N ′ can be relatively large. Thus, if the amount of distortion is large, self-stripping becomes possible, and high mold release performance can be obtained without using a mold release agent (oil). Of course, oil may be used in order to obtain higher releasability. When oil is used, the material of the surface layer of the fixing roll and belt may be changed as appropriate.

However, as described above, the toner image T has a large amount of toner, the toner image T is close to the tip of the paper P, the basis weight of the paper P is small, the paper P is thin coated paper, and the like is difficult to peel off. In order to enable more stable peeling even under the conditions, it is extremely effective to have the peeling device of the present invention. In this embodiment, extremely high peeling performance is realized by employing the same peeling devices 7 and 10 as those in the first embodiment.
Since the specific configuration, preferable mode, modification, and the like of the peeling devices 7 and 10 are the same as those in the first embodiment, detailed description thereof is omitted.

In the fixing device of this embodiment, an external heater (external heating member) 9 as a gas heating mechanism according to the present invention is further provided at the tip of the nozzle in the gas discharge device 10. The compressed gas heated by the external heater 9 is discharged from each air nozzle. As a result, the compressed gas that hits the toner image T on the surface of the fixing roll 1 and the paper P after being discharged is preheated, and thus a malfunction caused by lowering the temperature of the surface of the fixing roll 1 and the toner image T, particularly glossy. Problems in image quality such as unevenness are alleviated.
Since the function, configuration, action, and preferred mode of the external heater 9 and other modes that can be adopted as the gas heating mechanism are the same as those in the first embodiment, the detailed description thereof is omitted.

As described above, according to this embodiment, even if the paper P is difficult to be peeled without damaging the image, the paper P, and the fixing roll 1, high paper peelability can be realized without any problem. The compressed gas contributes to peeling by including an external heater (gas heating mechanism) 9 that can enjoy the benefits of the APS technology and that is discharged from the air nozzle 10a and / or that heats the discharged compressed gas. The temperature can be kept high. Therefore, it is possible to eliminate the influence of the fixing roll 1 and the toner image T that are cooled by the action of the compressed gas, the occurrence of gloss unevenness is suppressed, and a fixed image with stable image quality can be formed. it can.
That is, according to this embodiment, it can be seen that the present invention can be suitably applied to a roll-belt nip type fixing device.

As described above, the fixing device of the present invention has been described with reference to the two aspects of the first embodiment and the second embodiment, but the present invention is not limited to the above example.
Further, as the fixing device, a two-roll type fixing device and a belt-roll nip type fixing device in which the belt is stretched by a plurality of rolls have been described as examples. The present invention can also be suitably applied to a belt-belt nip type fixing device, both of which constitute the fixing device of the present invention. However, when the heating rotator to be peeled is belt-shaped, the mounting position of the peeling guide plate is set to a region where the surface of the heating rotator advances in a curved direction in the circumferential direction or downstream thereof. Is required.

  FIG. 14 is an enlarged cross-sectional view for explaining a contact state between the belt-like heating rotator to be peeled and the paper for considering the attachment position of the peeling guide plate. In FIG. 14, reference numeral 25 denotes a belt-like heating rotator, which is stretched by a roll 26 and other rolls (not shown), and moves in the direction of arrow Q.

The recording medium to be peeled is transported in the direction of the arrow Q along with the circumferential movement of the heating rotator 25 in a state in which the recording medium to be peeled adheres (sticks) to the surface of the heating rotator 25 to be peeled. Figure 14 is a case where the recording medium is assumed to remain in intimate contact, shows only leading end of the recording medium P _a to P _e which moves together with the conveying by a dotted line.
Recording medium P _a which is conveyed in the arrow Q direction in close contact with the heating rotating body 25 surface, since the heating rotating body 25 is proceeding linearly in Shudo direction, the leading end of the recording medium P _a The peeling force due to its own stiffness does not act.

  Since the heating rotator 25 is stretched around the roll 26, the heating rotator 25 advances in a curved direction in the circumferential direction at a point where the roll 26 is wound around and the traveling direction is switched. Specifically, in the region partitioned from the straight line L by the straight line M, the heating rotator 25 advances while drawing a curve in the circumferential direction.

Therefore, the leading end of the recording medium P _b that approaching this region beyond the boundaries of the linear L, the peel force begins to act. The action of the peeling force is surely generated while the leading end portion of the recording medium is between the areas partitioned by the straight line L and the straight line M. In other words, the above-described action naturally occurs in the recording medium P _c in which the most advanced portion is located between the areas.

Furthermore, if the entire recording medium draws a curve for a while after finishing this region, the peeling force still acts due to its own stiffness. In other words, the above-described operation occurs also for the recording medium P _{d in} which the most advanced portion is located downstream of this region beyond the boundary of the straight line M.
Thereafter, ready to proceed again heating rotating body 25 linearly in Shudo direction, the recording medium P _e in a state of close contact with the heating rotating body 25 in the position, occurs by the peeling force due its stiffness Disappear.

In the recording medium shown in FIG. 14, the recording medium between P _{b and} P _d can be peeled off, and these effectively utilize the peeling force due to their own stiffness or compensate for this peeling force. The point of the present invention is that the entire surface of the recording medium is peeled off by peeling off only the tip, and considering this point, the recording medium between P _{b and} P _d , in other words, the surface of the heating rotator is surrounded. It is required to peel off when the most advanced portion of the recording medium is located in the region from the straight line L to the straight line M that travels in a curved line in the moving direction or downstream thereof.

  Of course, if the distance between the one side (tip) of the peeling guide plate close to the surface of the heating rotator and the surface of the heating rotator is reduced, the tip of the peeling guide plate can be arranged almost on the straight line L. When this is separated, the tip of the peeling guide plate can be arranged at a position considerably downstream from the straight line M. Therefore, as described above, the attachment position of the peeling guide plate needs to be a region where the surface of the heating rotator advances in a curved direction in the circumferential direction, or downstream thereof. Here, the specific range of “downstream” cannot be generally described because it changes depending on the thickness and material of the recording medium, the area of the toner image, the toner amount of the toner image, and the like.

  The above example is a problem only when the heating rotator to be peeled is a belt, and when this is a cylinder as in each of the above embodiments, the surface is always curved in the circumferential direction, Since the peeling force acts at any position, the requirement regarding the installation position of the peeling guide plate is not a problem. The concept regarding the position of the peeling guide plate is not limited to the case where the peeling device of the present invention is applied to a fixing device, but is the same when applied to any part of the image forming device, for example, an image forming device described later. It is.

  The fixing device having the above configuration can be used in a conventionally known electrophotographic image forming apparatus. That is, a toner image forming unit that forms an unfixed toner image on the surface of a sheet-like recording medium by electrophotography, and a fixing unit that fixes the toner image held on the surface of the recording medium by heating and pressing. By using the fixing device having the above-described configuration as a fixing unit, an image forming apparatus that is excellent in peelability and can satisfy high image quality and high speed can be provided.

As the toner image forming means, for example, an electrostatic latent image forming means for forming an electrostatic latent image on an electrostatic latent image carrier and a developing means for developing the electrostatic latent image with toner were obtained. And a transfer unit that transfers the toner image to a sheet-like recording medium.
Any configuration other than the fixing device known in the art can be used as long as it is not contrary to the object of the present invention.

  The fixing device and the image forming apparatus of the present invention have been described above with some examples, but the present invention is not limited to these configurations. The present invention has no problem as long as it has essential constituent requirements, and those skilled in the art can make various modifications based on known knowledge.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
<Examples and Comparative Examples>
An image quality evaluation test was performed using the fixing device having the configuration of the first embodiment. Evaluation was performed under the condition that the molten toner on the surface of the paper P after passing through the nip portion N adheres to the fixing roll 1 and a large peeling force is required to peel the paper P from that state.
Specific specifications are shown below.

(Specifications of fixing unit)
Fixer roll 1 configuration: black and white fixing hard roll (fluorine resin-coated hard roll having a 40 mm diameter aluminum core covered with a 20 μm thick PFA tube) and color fixing soft roll (outer diameter 62 mm, inner diameter) An aluminum core formed in a cylindrical shape having a length of 55 mm and a length of 350 mm is covered with silicone LSR (Liquid Silicone Rubber) rubber (JIS-A rubber hardness: 35 degrees) to a thickness of 2 mm, and an elastic layer. 2 types of rolls in which a PFA tube is formed as a surface layer with a thickness of 30 μm on the surface of

-Rotation speed of fixing roll 1 (process speed): 250 mm / s
・ Surface temperature of fixing roll 1: Control to 150 to 160 ° C. ・ Nip pressure between fixing roll 1 and pressure roll 6: 490 to 686 N (50 to 70 kgf))
Paper P (recording medium): A4 size S paper made by Fuji Xerox (basis weight 56 g / m ² , typical plain paper) and Fuji Xerox OK top coat paper (basis weight 64 g / m ² , basis weight) Paper having a small waist), and the transport direction was set to be a lateral feed as shown in FIG.

-Toner: Color polymerization toner for oilless fuser (Fuji Xerox oilless color polymerization toner, EA toner: Pigment and wax particles, and emulsion polymerization resin particles that combine them are chemically reacted in aqueous solution and heat-molded)
Unfixed toner image T: a solid image of process black consisting of three colors of yellow, magenta, and cyan electrostatically transferred over substantially the entire width of the paper P. Twenty sheets with a toner amount of 20 g / m ² were prepared and all were fixed. The margin at the leading edge of the paper was 3 mm as shown in FIG. The unfixed black and white toner image is electrostatically transferred with a solid black image of 0.7 g / m ² .

(Specifications of the gas discharge device 10)
・ Air pump 10d: Commercially available air supply capacity 8 liter / min pump ・ Gas reservoir 10c: ACCUMULATOR with a tank capacity of 200 cc
-Number of air nozzles: 3 (10a-1, 10a-2, 10a-3)
・ Orifice diameter of solenoid valve: 1.5mm
-Compressed gas: Air was used, the pressure was 0.2 MPa (the atmospheric pressure was 0), and the discharge time was 0.025 sec.
・ Compressed gas discharge timing: Perform a compressed gas discharge experiment in advance and set it to an appropriate state

(Aspects and specifications of the gas heating mechanism)
-Mode of the gas heating mechanism: The mode of the external heater 9-1 shown in FIG. 7 is used as in the first embodiment.
・ Type of external heater 9: Nichrome wire heater (150W each)

(Specifications of peeling guide plate 7)
As the peeling guide plate 7, as shown in FIG. 4, the one having a deformed tip shape adapted to the length of the A4 width of the shape having three convex portions was adopted. The specific dimensions are a length of 392 mm in the longitudinal direction, a length of 32 mm of sides 8a and 8b in FIG. 4B and a length of 8 mm of 8c, a width of 36 mm of the convex portion 7a, and a radius of curvature on the surface 8a side of the concave portion 7b. The curvature radius is about 50 mm and the curvature radius on the back surface 8b side is 60 mm.
-Material of the peeling guide plate 7: Stainless steel-Angle θ formed by the surface 8a with respect to the tangent line E of the peeling point S on the surface of the fixing roll 1 (see Fig. 8): -5 °
・ Gap between the leading edge of the peeling guide plate 7 and the surface of the fixing roll 1: 0.2 to 0.5 mm
・ Installation position of peeling guide plate 7: Adjust appropriately (4-15mm from nip N outlet)

  Using the fixing device (including the peeling device) under the above conditions, two types of paper P, two types of fixing roll 1, and the external heater 8 are turned on (Example) -OFF (Comparative Example) in both states. A total of 8 levels were established and an image quality evaluation test was conducted. In the evaluation test, 20 sheets P of paper P on which the unfixed toner image T is electrostatically transferred are continuously passed through the nip portion of the fixing device, and the image quality of the obtained image is sensed as a difference in gloss (gloss difference). Evaluation was made according to the following criteria. The results are summarized in Table 1 below.

(Glossiness difference)
The glossiness of the image at the front end of the paper P and the entire surface of the image surface was measured at 20 points, and the difference in glossiness was compared. Evaluation was made according to the following criteria depending on the range of the measured values distributed with respect to the central value of the glossiness.
○: ± 5.
Δ: More than ± 5 and less than ± 10.
X: ± 10 or more.

(Image quality sensory evaluation)
○: No defects are found even when staring.
(Triangle | delta): If it stares, there will be a micro defect.
X: Defects that can be visually observed may occur.

<Consideration of Examples and Comparative Examples>
As shown in Table 1 above, it can be seen that with the fixing device of the example having the configuration of the present invention, a recorded image with good image quality could be obtained. The effect is particularly significant in color images than in black and white images. On the other hand, in the comparative example, although the peelability was good, there was a condition that the image quality was slightly lowered in part.
Therefore, it can be seen from the results of this example that the fixing device having the configuration of the present invention can obtain a recorded image with good image quality while ensuring high sheet peelability.

1 is a schematic cross-sectional view of a fixing device according to a first embodiment. It is the enlarged plan view of the peeling apparatus in FIG. 1 seen from the fixing roll surface side. It is a schematic block diagram which represents typically the whole structure of the gas discharge apparatus in the peeling apparatus in FIG. It is a figure which shows the peeling guide plate in the peeling apparatus in FIG. 1, (a) is an enlarged plan view seen from the surface on the opposite side to the fixing roll surface side, (b) is A- of (a). It is sectional drawing which expanded the A section further. FIG. 4 is an explanatory diagram for explaining the operation of the APS technique in the fixing device of the present invention step by step, and shows steps 1 and 2; It is explanatory drawing for demonstrating later on about the effect | action of the APS technique in the peeling apparatus of this invention, and the process 3 and 4 are shown. It is a model enlarged view for demonstrating the flow of the compressed gas discharged from the air nozzle. It is a partial expanded sectional view for demonstrating the arrangement | positioning relationship between the fixing roll which is a heating rotary body, and the peeling guide plate. It is a model enlarged view for demonstrating the flow of the compressed gas before and behind discharged from an air nozzle in 1st Embodiment. It is a model enlarged view of the air nozzle periphery at the time of changing the gas heating mechanism in 1st Embodiment to another modification with an external heating member. It is a model enlarged view of the air nozzle periphery at the time of changing the gas heating mechanism in 1st Embodiment into the modification of an internal heating member. It is a model enlarged view of the air nozzle periphery at the time of changing the gas heating mechanism in 1st Embodiment into the other modification which does not use a heating member. FIG. 5 is a schematic cross-sectional view of a fixing device that employs a peeling device according to a second embodiment. It is an expanded sectional view explaining the adhesion state of the belt-shaped heating rotator used as a peeling object, and a paper for considering the attachment position of a peeling guide plate. FIG. 6 is a plan view of a sheet for explaining a state of an unfixed toner image formed in an evaluation test of an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Fixing roll (heating rotary body), 2: Heater, 3: Elastic layer, 4: Surface layer, 5: Core, 6: Pressurizing roll (pressing rotary body), 7: Peeling guide plate, 7a: Convex part 7b: recess, 8a: front surface, 8b: back surface, 8c: edge surface, 9: external heater (external heating member, gas heating mechanism), 10: gas discharge device, 10a, 10'a: air nozzle, 10b : Solenoid valve, 10c: Gas reservoir, 10d: Air pump, 10e: Connection piping, 10f: Air pulse controller, 10g: Regulator, 11: Discharge guide, 12: Discharge roll, 16: Pressure rotating body, 17: Pressure pad , 18: lead roll, 19: pressure roll, 20: tension roll, 21: endless belt, 25: heating rotor, 26: roll, 29: combined heater (external heating member, gas heater) ), 30: Rotary developer, 31: Photoconductor, 32: Cleaning device, 33: Charger, 34: Exposure device, 35: Transfer drum, 36: Feeding guide, 37: Charger, 38: Stripping static eliminator, 39: fixing device, 40: transfer device, 41: transport guide, 42: static eliminator, 49: internal heater (internal heating member, gas heating mechanism), E: tangential line (straight line), G: tip, N: nip portion , P: sheet (recording medium), P _a ~P _e: recording medium, S: peeling point, T: toner image, X: initial stream, Y: gap passing airflow

Claims (15)

At least, a heating rotator whose surface is heated to rotate and a pressure rotator that abuts on the surface of the heating rotator to form a nip portion, and a toner image made of unfixed toner is formed on the surface. A fixing device that fixes the toner image by inserting the sheet-like recording medium into the nip portion so that a surface on which the toner image is formed contacts the surface of the heating rotator,
Separating means for separating the recording medium transported in a state of being attached to the surface of the heating rotator by the molten toner constituting the toner image after passing through the nip portion from the heating rotator. Prepared,
The peeling means is located in a region where the surface of the heating rotator progresses in a curved direction in the circumferential direction, or downstream thereof, with one side close to the surface of the heating rotator, and in the circumferential direction of the heating rotator. One side of the peeling guide plate adjacent to the surface of the heating rotator and from the region sandwiched between the peeling guide plate arranged in a laid state and the surface of the heating rotator and the surface of the peeling guide plate facing the heating guide A gas discharge mechanism that discharges a pulsed compressed gas with a nozzle comprising a pipe-shaped conduction path and a discharge port provided at the tip of the pipe-shaped conduction path, and
The fixing device further includes a gas heating mechanism that heats the compressed gas discharged from the nozzle and / or discharged. The fixing device according to claim 1, wherein the gas heating mechanism is an external heating member disposed outside a conduction path of the nozzle. The fixing device according to claim 2, wherein the external heating member also has a function of heating the peeling guide plate. The fixing device according to claim 3, wherein the external heating member is configured to heat a conduction path of the nozzle through the peeling guide plate. The fixing device according to claim 1, wherein the gas heating mechanism is an internal heating member provided in a conduction path of the nozzle. The gas heating mechanism has a configuration in which the outer periphery of the conduction path of the nozzle and / or the surface of the peeling guide plate on the side of the heating rotator is colored with a high absorbability of radiant heat from the surface of the heating rotator. The fixing device according to claim 1. The gas heating mechanism is arranged so that the outer periphery of the conduction path of the nozzle does not come into contact with the surface of the heating rotator, and at least a part of the middle is close to the surface of the heating rotator. The fixing device according to claim 1. When the most distal portion in the conveyance direction of the recording medium that has been conveyed along with the circumferential movement of the heating rotator approaches the position where the peeling guide plate is disposed, the compressed gas strikes the most distal portion, The fixing device according to claim 1, wherein compressed gas is discharged by the gas discharge mechanism. Only the compressed gas of a degree sufficient for the state in the conveyance direction of the recording medium peeled from the surface of the heating rotator by the compressed gas to be on the side of the peeling guide plate that is close to the surface of the heating rotator. The gas discharge mechanism is controlled so as to discharge, and the portion following the most distal portion in the transport direction in the recording medium is the heating rotation of the peeling guide plate accompanying the transport by the circumferential movement of the heating rotator. Gradually ride on one side close to the surface of the body, and the recording medium surface is rubbed and moved on the back surface of the peeling guide plate facing the surface of the heating rotator. The fixing device according to claim 1, wherein the entire surface of the recording medium is peeled off. The fixing device according to claim 1, wherein the gas discharge mechanism is configured to arrange the nozzle in a region sandwiched between the surface of the heating rotator and the surface of the peeling guide plate facing the surface. The fixing device according to claim 10, wherein a plurality of the nozzles are arranged in a direction perpendicular to a circumferential movement direction of the heating rotator. On one side of the peeling guide plate that is close to the surface of the heating rotator, a portion facing the center of the direction of travel of each compressed gas discharged by the nozzle or its vicinity protrudes toward the surface of the heating rotator. The fixing device according to claim 4, further comprising: a fixing device; The fixing device according to claim 1, wherein the heating rotator has a roll shape or an endless belt shape. The fixing device according to claim 1, wherein the pressure rotating body has a roll shape or an endless belt shape. At least toner image forming means for forming an unfixed toner image on the surface of a sheet-like recording medium by electrophotography, and fixing means for fixing the toner image held on the surface of the recording medium by heating and pressing. An image forming apparatus comprising:
The image forming apparatus according to claim 1, wherein the fixing unit is the fixing device according to claim 1.

Images