JP2020166078A - Preheating apparatus before ultraviolet irradiation - Google Patents

Abstract

To provide a fixation device that can physically prevent a heater tube from being contacted by providing a shield between the heater tube and a sheet conveyance surface, inhibit the shield from interfering with heating of the sheet conveyance surface, and further ensure the safety for a human.SOLUTION: A mesh member satisfying the following conditions (1)-(4) is disposed between a heater tube and a conveyance sheet. The conditions are as follows: (1) heat transfer coefficient is small, or (and) calorific capacity is small; (2) the shape is maintained even when exposed to the heater (melting point=600°C or higher); (3) the mesh member is composed of a fine wire material (φ2 or less) having enough strength as to expel a hand or a conveyance sheet even if the hand or the conveyance sheet comes into touch with it and not interfering with heat ray irradiation; (4) the mesh member has coarse satisfying the conditions of "Safety of machinery-Safety distances to prevent hazard zones being reached by upper and lower limbs" stipulated by JISB9718 and ISO13857.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heating device that heats a paper image surface in a non-contact manner using a heater in a fixing device of an electrophotographic image forming apparatus.

Usually, fixing an image in an electrophotographic image forming apparatus means melting toner with heat and applying pressure to bring the toner image into close contact with paper. Conventionally, in a fixing device of an electrophotographic image forming apparatus, it is common to apply heat and pressure to a toner image formed on paper by using a heat roll or the like. On the other hand, in high-speed printers, there is a flash fixing technology in which the toner absorbs light energy by momentarily irradiating the toner image formed on the paper with strong light, and the toner is instantly melted and fixed. Some are used. This fixing method is non-contact with the toner image, and a xenon tube or the like is used as a light source.

As another non-contact fixing method, Patent Document 1 proposes a technique in which ultraviolet irradiation energy is used to cure a developer and infrared rays are irradiated to heat the developer before it is irradiated. Further, Patent Document 2 discloses that a quartz tube heater that emits far infrared rays having a peak wavelength of 3 nm is used for heating before irradiation with ultraviolet rays from the viewpoint of heating efficiency of organic substances.

JP-A-2017-187739 Japanese Unexamined Patent Publication No. 2016-224438

In general, in a far-infrared heater, a heat generating configuration (nichrome wire or the like) is arranged in a quartz tube, and the quartz tube is heated by the heat generating configuration to emit far infrared rays in a specific frequency band. The surface temperature of the quartz tube in the fixing portion of the image forming apparatus is 600 to 900 ° C., and it takes several minutes for the surface of the quartz tube to warm from room temperature to the fixing operating temperature. On the contrary, it takes several tens of minutes to cool the quartz tube surface from the fixing operating temperature to a temperature at which there is no problem even if the surface of the quartz tube is touched by hand, and the device stops and the power supply is cut off. However, the quartz tube does not cool immediately. Further, the far infrared rays emitted from the quartz tube are characterized in that they have a large wavelength dependence and a small distance dependence when heating paper, which is an organic substance.

In the image forming apparatus, the far-infrared heater is arranged with a Gap of 25 to 100 mm from the conveying surface due to the limitation of the arrangement space in the apparatus. If the transport paper on which the unfixed image is placed curls and reaches the fixing paper transport section for some reason, the unfixed transport paper is not transported well by the transport belt, but curls into a cylindrical shape and stays in the heating section. It can come into contact with the heater. From the viewpoint of device miniaturization, it is better for the far-infrared heater to be as close to the paper transport surface as possible. Is more likely to come into contact with.

When the unfixed transport paper touches the heater tube, stains such as paper, toner, and developer adhere to the surface of the heater tube, and when they accumulate, the surface temperature variation of the heater tube increases and the image fixing uniformity is improved. It becomes a factor to hinder. Further, if the temperature variation on the surface of the heater tube is large, the heater tube may be cracked or damaged. Furthermore, when the transport paper comes into contact with the heater tube, the transport paper may be carbonized or burned. Further, the dirt accumulated on the surface of the heater tube is carbonized and falls on the paper transport portion, which causes image defects and paper stains.

On the other hand, if the image forming machine suddenly stops during the printing job for some reason such as an error or jam, the paper in the middle of the job will be stuck in the paper circulation section of the machine, so the paper will first stay in the machine to restart the job. It is necessary to remove all the paper. Paper may remain in the heating section upstream of the ultraviolet irradiation device, and the far-infrared heater does not cool instantly even when the power is turned off, so various measures have been required. In particular, the paper in front of the ultraviolet irradiation device is in a state where the image is unfixed and the image forming material (toner or developer) is easily peeled off. Therefore, when the stagnant paper is removed, the stagnant paper is mistakenly removed. If the paper shakes on the heater tube, the toner and developer of the unfixed image tend to adhere to the surface of the heater tube and accumulate.

As described above, the surface of the quartz tube of the far-infrared heater should not be touched not only by the hand but also by the carrier paper / retention paper on which the unfixed image is transferred.

Therefore, an object of the present invention is to provide a shield between the heater tube and the paper transport surface to physically prevent contact with the heater tube, and the shield heats the paper transport surface. The purpose of the present invention is to provide a fixing device that does not hinder and ensures safety for humans.

In order to achieve the above object, the image forming apparatus according to the present invention is
In the fixing device of the electrophotographic image forming apparatus, the image surface of the conveyed paper is heated non-contactly by using a heater that emits infrared rays or far infrared rays and reaches a temperature (70 ° C. or higher) where the surface of the heater tube cannot be touched with bare hands. And between the transport paper
(1) The thermal conductivity is small, or (and) the heat capacity is small.
(2) Maintains its shape even when exposed to a heater (melting point = 600 ° C or higher).
(3) A thin wire diameter material (φ2 or less) that has sufficient strength to repel the hand or the transport paper even if it touches the hand or the transport paper, and does not hinder the heat ray irradiation.
(4) Roughness that satisfies the condition of "safety of machinery-safe distance to prevent upper limbs from reaching dangerous areas" defined by JIS B9718 and ISO 13857. Specifically, the crease is square (rectangle has a disadvantage in safety distance / round hole has a smaller opening area), one side is 10 mm or less, and the dangerous area (high temperature part) has a gap of 25 mm or more.
It is characterized in that a mesh member satisfying the above conditions (1) to (4) is arranged.

According to the present invention, by arranging the mesh member between the heater tube and the transfer paper, the transfer paper / retention paper cannot physically contact the heater tube, and the shielding area of the mesh member is small, so that heating is performed. It is hardly affected by performance, and since the heat capacity of the mesh member is small and the surface area relative to the volume is large, the mesh member is instantly invaded by outside air when the door of the device is opened for the purpose of removing stagnant paper. It is possible to provide a heating device that does not affect the human body even if the worker's hand is shaken by the mesh member.

Schematic cross-sectional perspective view illustrating the configuration of the fixing device according to the first embodiment of the present invention. Schematic cross-sectional perspective view illustrating the configuration of the mesh material of Example 1 of the present invention in detail. Maker lineup diagram of the mesh material adopted in Example 1 of the present invention Schematic diagram explaining the safety standards defined by JIS B9718 and ISO 13857 Schematic overall cross-sectional view of the image forming apparatus according to the embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, taking as an example an image forming apparatus that cures and fixes by ultraviolet rays using a liquid developer. However, the components described in this embodiment are merely examples, and not only an image forming apparatus using a liquid developer, but also an image forming apparatus using flash fixing technology, an electrophotographic method using a dry toner, and the like. It is applied to all image forming apparatus such as an electrostatic recording type copier and a laser beam printer, or an inkjet printer, and is not limited to those described in the embodiment of the present invention.

(Image forming device)
FIG. 5 is a schematic view showing an example of the configuration of an image forming apparatus that is cured and fixed by ultraviolet rays using a liquid developer. The image forming apparatus 100 includes an image forming unit 10 that forms an image on the recording medium 16, and a fixing unit 11 that fixes the image 15 formed on the recording medium 16 to the recording medium 16. Here, the recording medium 16 is one in which a toner image is formed by the image forming apparatus 100, and includes, for example, plain paper, coated paper, and paper such as postcards and envelopes. Further, for example, the recording medium 16 may be an OHP sheet or a film.

The cassette 25 is an accommodating portion for accommodating the recording medium 16 used for image formation. The recording medium 16 housed in the cassette 25 is fed to the image forming unit 10 by the feeding mechanism 2. The feed mechanism 2 is, for example, a paper feed roller, and feeds the recording medium 16 in the cassette 25 to the transport path 26. The accommodating portion may have a configuration having a plurality of cassettes, or may have a tray shape (for example, a manual feed tray).

The recording medium 16 supplied from the cassette 25 by the feed mechanism 2 is supplied to the contact portion between the image holding member 1 and the transfer means 4 through the transport path 26. The recording medium 16 is transferred to the fixing portion 11 through the transport path after the image on the outer peripheral surface of the image holding member 1 is transferred by the transfer means 4 at the contact portion between the image holding member 1 and the transfer means 4. Be transported.

The image forming unit 10 forms an image 15 on the recording medium 16 using a liquid developer. The liquid developer is a developer containing an ultraviolet curing agent (curing agent) and a toner (coloring material) that are cured by ultraviolet rays. The image forming unit 10 includes a cylindrical image holding member 1 and a transfer means 4. The electrophotographic image forming means (not shown) develops a latent image using a charged portion that charges the image holding member 1 to a uniform surface potential, an exposed portion that forms a latent image by exposure, and a liquid developer. It includes a developing unit and forms an image on the outer peripheral surface of the image holding member 1. The image 15 formed on the image holding member 1 is transferred onto the recording medium 16 supplied to the contact portion between the image holding member 1 and the transfer means 4 by the transfer roller as the transfer means 4. That is, the image forming unit 10 forms an unfixed image 15 on the recording medium 16.

The image holding member 1 in this embodiment has an organic photoconductor surface layer on the surface of an aluminum cylinder (photosensitive drum) having a thickness of 3 mm and an outer diameter of 84 mm, and has a long side width (a direction substantially orthogonal to the transport direction of the recording medium). Length) is 370 mm. The image holding member 1 is rotationally driven in the direction of arrow R1 in FIG. 7 around a central support shaft by a drive motor as a driving means (not shown) of the image holding member 1.

In this example, the image forming unit 10 is configured by an electrophotographic direct transfer method, but the image forming method on the recording medium 16 is not limited to this. For example, an intermediate transfer method may be configured in which the image holding member 1 is used as an intermediate transfer belt. Specifically, the primary transfer roller primary transfers the image 15 formed on the photosensitive drum by the image forming means (not shown) using a liquid developer, and the transfer means 4 primary transfers the image 15 to the intermediate transfer body. The image 15 on the intermediate transfer body is transferred to the recording medium 16.

The recording medium 16 on which the image 15 is formed by the image forming unit 10 is conveyed to the fixing unit 11 through the conveying path 27. The fixing unit 11 includes an infrared irradiation device (infrared irradiation unit) 13, an ultraviolet irradiation device (ultraviolet irradiation unit) 12, and a paper transport device 30. The paper transport device 30 includes an endless transport belt 31 provided with a large number of holes, a drive roller 35 for tensioning the transport belt 31, and driven rollers 36 and 37. The paper transport unit 30 includes a drive motor (not shown) that rotates the transport belt 31 via a drive roller 35. The transport belt 31 rotates in the direction of arrow R2 in the drawing by being driven by a drive motor. The paper transport unit 30 supports the recording medium 16 on which the image 15 is formed by the image forming unit 10 on the transport belt 31, so that the recording medium 16 passes under the infrared irradiation device 13 and the ultraviolet irradiation device 12. The recording medium 16 is conveyed. The transport belt 31 in this embodiment has a width of 350 mm and a peripheral length of 900 mm.

Inside the transport belt 31, a suction fan (suction device) as a suction device that sucks the recording medium 16 transported by the transport belt 31 onto the peripheral surface of the transport belt 31 through a large number of holes formed in the transport belt 31. (Not shown) is arranged. That is, the suction fan sucks air from the upper surface side of the transfer belt 31 and attracts the transferred recording medium 16 to the upper surface of the transfer belt 31.

The infrared irradiation device 13 heats the liquid developer by irradiating the image 15 of the liquid developer on the recording medium 16 with infrared rays. The ultraviolet irradiation device 12 fixes the image 15 of the liquid developer on the recording medium 16 on the recording medium 16 by irradiating the recording medium 16 with ultraviolet rays.

The recording medium 16 that has been fixed by the fixing unit 11 passes through the discharge transport path 28 and is discharged to the outside of the machine.

(Fixing device)
As described above, the fixing unit 11 includes an infrared irradiation device (infrared irradiation unit) 13, an ultraviolet irradiation device (ultraviolet irradiation unit) 12, and a paper transport device 30. The paper transport device 30 is arranged directly under the infrared irradiation device (infrared irradiation unit) 13 and the ultraviolet irradiation device (ultraviolet irradiation unit) 12 arranged adjacent to each other in the transport direction of the recording medium 16, and one transport belt is an infrared irradiation device. It is configured to continuously pass through both the (infrared irradiation unit) 13 and the ultraviolet irradiation device (ultraviolet irradiation unit) 12.

The fixing of the image 15 of the liquid developer on the recording medium 16 is excited by ultraviolet rays by irradiating the recording medium 16 with ultraviolet rays by the ultraviolet irradiation device 12, for example, in the case of cationic polymerization, the ultraviolet rays hit the ultraviolet curing liquid. The photopolymerization initiator generates an acid, and as a result of the polymerization reaction between the generated acid and the monomer, the ultraviolet curing liquid is cured. In order to improve the efficiency of the polymerization reaction at this time, the liquid developer is preheated by irradiating the image 15 of the liquid developer on the recording medium 16 with infrared rays before the ultraviolet irradiation by the infrared irradiation device 13.

(Structure of infrared irradiation device)
The configuration of the infrared irradiation device 13 in the fixing portion 11 will be described in detail with reference to FIG. FIG. 1 is a cross-sectional perspective view of the fixing portion 11.

As shown in FIG. 1, the fixing unit 11 includes a paper transport device 30, an ultraviolet irradiation device 12, and an infrared irradiation device (infrared irradiation unit) 13, and the infrared irradiation device (infrared irradiation unit) 13 includes an infrared irradiation device (infrared irradiation unit) 13.
A heater unit 20 composed of a quartz tube 21 that emits far infrared rays having a peak wavelength of 3 nm, a reflecting unit 22 that radiates the heat generated by the quartz tube 21 to the paper transport surface, a heater unit 20, and a paper transport device 30. It is composed of a mesh member 23 arranged between the two. By arranging the mesh member 23 between the quartz tube 21 and the paper transport surface, the quartz tube 21 or the paper is shielded from contacting the quartz tube 21 or the reflective portion 22 and the quartz is shielded by the mesh. Most of the infrared rays emitted by the tube irradiate the paper transport surface.

More specifically, the quartz tube 21 and the reflecting portion 22 are arranged with a gap of 25 to 100 mm from the paper transport surface, and the gap between the mesh member 23 and the quartz tube 21 or the reflecting portion 22 in close proximity is 27 mm. The Gap of the paper transport surface and the mesh member 23 is 20 mm. At the time of Jam processing, for example, the paper transport device 30 retracts downward to form a Jam processing work space, and the accumulated paper stuck on the paper transport surface of the paper transport device 30 is removed. At that time, the paper transport device 30 may remain in the machine, but better, it is easier to remove the stagnant paper when the paper transport device 30 is retracted downward and then pulled out from the inside of the main body. Further, an example was given in which the paper transport device 30 retracts downward in order to form a Jam processing work space, but the ultraviolet irradiation device 12 and the infrared irradiation device (infrared irradiation unit) 13 located above the paper transport device 30 You may evacuate upward.

(Required characteristics of mesh material)
As described above, the mesh member 23 is a member that may come into contact with curled paper or a worker's hand during Jam processing. In order to prevent the problem from occurring even if the worker's hands come into contact with each other, the amount of heat transferred to the non-contact object should be reduced. In general, heat conduction is Q = kA (ΔT / d)
Q = heat flow rate (W)
k = thermal conductivity (W / m-K)
It is expressed as A = contact area d = heat flow distance ΔT = temperature difference. Here, since d is approximated to zero because it is intended for contact, and assuming that the temperature difference is not control symmetric because the primary purpose is to heat, to reduce the amount of heat transfer Q It can be seen that using a material having a small k (thermal conductivity) or reducing the contact area A is an effective means.

Generally speaking, "net / mesh" is made of resin, fiber, metal, or the like. Of these, it is desirable to use non-metallic materials such as resins and fibers from the viewpoint of thermal conductivity, but since the surface temperature of the adjacent quartz tube 21 is as high as 600 to 900 ° C, it is exposed to the heater. It is optimal to select a metal material from the viewpoint of having the property of maintaining the shape (= high melting point) and the balance of cost. From the viewpoint of material strength, if a metal material is used, it is possible to reduce the wire diameter and coarsen the mesh. This has the effect of reducing the contact area A and the heat capacity (fast cooling = reducing ΔT). As described above, it is appropriate to select a metal material as the material of the mesh member.
To reorganize the required characteristics of the mesh member,
Material ・ Heat-resistant temperature 600 ℃ or higher (Since there is an air layer between the heater tube, melting point 600 ℃ or higher is required. 900 ℃ or higher is desirable)
-Strength that does not break even if paper or hand comes into contact (contact pressure strength 1 kg / m2 or more)
・ Thin wire diameter material (preferably φ2 or less)
(= Reduce the contact area / reduce the heat capacity / reduce the shielding effect / do not interfere with heat ray irradiation)
Reliably captures mesh roughness, mesh shape, paper, and hands (does not slip through)
・ Shape that is as coarse as possible and minimizes the shielding area = square mesh (= reduces the contact area / reduces the shielding effect / does not interfere with heat ray irradiation)
Therefore, in the first embodiment, the mesh material was selected from the existing commercially available products (lineup table of a certain manufacturer: Fig. 3) from the viewpoint of cost on the premise that the metal (= rigid body) is used. In addition, the arrangement of the mesh members and the mesh roughness must comply with "JIS B9718: Safety of machinery-safe distance to prevent the upper limbs from reaching the dangerous area" (Fig. 4) from the viewpoint of safety. is there.

From the above viewpoint, the mesh material should be SUS304 (melting point 1400 ° C.), wire diameter φ0.8, mesh roughness (opening) 10 mm □ or less (thick frame in FIG. 3), and from the heat source of the heater tube or reflector. The distance was set to 25 mm or more (thick frame portion in FIG. 4).

(Heat capacity limit of mesh material)
As another means for reducing the amount of heat transfer, in addition to using the above-mentioned material having a small k (thermal conductivity) and reducing the contact area A, a method of reducing the heat capacity is also effective. This is because if the heat capacity is small, the amount of heat transferred to the non-contact object will be small even if they come into contact with each other. Generally, the heat capacity is C = m × c
C = heat capacity (J / K)
m = mass (g)
c = specific heat (J / g · K)
It is represented by "Since the heat capacity of the mesh member is small and the surface area relative to the volume is large, the mesh member is instantly cooled by the intrusion of outside air when the door of the device is opened for the purpose of jam processing, and the worker is allowed to mesh. In order to satisfy the condition of "being in a state of touching", it is necessary to suppress the heat capacity to about C = 420 J / ° C (a calorific value of spreading 100 g of water thinly over a target area range and changing it by 1 ° C.).

(Concavo-convex direction of mesh material)
The mesh material of the mesh member 23 will be described with reference to FIG. FIG. 2 is a cross-sectional perspective view of the mesh material, in which the A direction in the drawing represents the paper passing surface side, the B direction in the drawing represents the heater side, and the C direction in the drawing represents the paper transporting direction.

As shown in FIG. 2, the mesh material adopted this time is obtained by arranging wire-shaped SUS wires vertically and horizontally and performing electric resistance welding at all intersections. When the vertical wire and the horizontal wire are layered to form a mesh in this way, the orientation of the wire on the paper transport surface side is ± 45 ° with respect to the paper transport direction from the viewpoint of paper transportability. It is desirable to set it in the range. Better yet, the orientation of the wire on the paper transport surface side is ideally the same as the paper transport direction.

In the first embodiment, the mesh material is selected from the existing commercially available products from the viewpoint of cost. However, the material does not have to be SUS304 as in Example 1, as long as the above-mentioned required characteristics of the mesh material are satisfied, for example, a material in which the mesh is formed of carbon fiber, ceramic, copper or other alloy, or a composite material. It may be.

100 image forming device, 10 image forming part, 1 image holding member, 4 transfer means,
11 Fixing part, 12 Ultraviolet irradiation device, 13 Infrared irradiation device, 30 Paper transport part,
31 Conveyance belt, 35 Drive roller, 36 Driven roller,
15 Image consisting of liquid developer, 16 Recording medium, Conveyed paper, Paper,
20 Heater section, 21 Quartz tube, 22 Reflective umbrella, 23 Mesh member

Claims (6)

An electrophotographic image having an image forming section for forming an image with a developer containing toner, a transfer section for transferring the image to paper, and a UV irradiation section for fixing an unfixed image on paper using ultraviolet irradiation energy. In the fixing part of the forming device
A heating means that heats toner and developer in a non-contact manner,
A transporting means for transporting paper in the vicinity of the heating means and
Have,
A mesh-like member is provided between the heating means and the paper transport portion so that the test fingers defined by JIS B 9718 (2013) and ISO 13857 (2008) cannot access the heating means and the high temperature danger region in the vicinity thereof. An image forming apparatus characterized in that it is arranged. The image forming apparatus according to claim 1, wherein the mesh-like member arranged between the heating means and the paper transport portion is made of a metal material. The image forming apparatus according to claim 1 or 2, wherein the wire diameter of the metal material of the mesh-like member is in the range of φ0.2 to φ2. The invention according to any one of claims 1 to 3, wherein the metal mesh member covers at least the width of the conveyed paper in a direction perpendicular to the paper conveying direction, and the heat capacity of the metal mesh member is 420 J / K or less. Image forming device. The material forming the mesh member has vertical lines and horizontal lines in layers to form a mesh, and the orientation of the wire on the paper transport surface side is within ± 45 ° with respect to the paper transport direction. The image forming apparatus according to claim 2 or 3. An ultraviolet curable electrophotographic image forming apparatus having the characteristics of any one of claims 1 to 5.