JPH0430592B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to an electrophotographic copying machine, a facsimile machine,
This invention relates to a fixing device used in devices that use electrophotographic processes, such as printers. [Prior Art] In conventional copying machines and the like that use electrophotographic processes, it is necessary to fix the unfixed toner image formed on the copy paper to make a permanent image, and the fixing methods include solvent fixing and pressure fixing. method, heat fixing method, etc. are known. The above-mentioned solvent fixing method uses a vapor or liquid solvent to dissolve the toner and infiltrate it into the fibers of the copy paper. Although it is more efficient than other fixing methods, the solvent vapor scatters and creates an odor. It is not widely used due to many hygiene problems. In addition, the pressure fixing method is a method of applying mechanical force to the toner to adhere the toner to the copy paper, and it has the advantage of being able to fix with less energy, and also allows for quick start and high speed. However, the fixing properties are worse than those of other fixing methods, and pressure-sensitive toner has the disadvantage that its manufacturing method is complicated and expensive, so it has not been widely put into practical use. It is. Therefore, for fixing unfixed toner images, a heat fixing method is generally employed in which the toner is melted by heating and adhered to the copy paper. For this heat fixing, a pair of rolls (fixing roll and pressure roll), at least one of which is heated, are used.
A heat roll method has long been known, which performs fusing by applying constant pressure between copy sheets and passing the unfixed toner image on the copy paper. It is the most widely used because it has advantages such as less risk of fire due to blockage. This heat fixing roll may be one whose surface is coated with a heat-resistant resin such as polytetrafluoroethylene (PTFE), or
HTV silicone rubber (High Temperature)
Vulcanization Silicone Rubber), RTV Silicone Rubber (Room Temperature Vulcanization
One of the pressure rolls is coated with a heat-resistant elastic material such as silicone rubber), and when it comes into pressure contact with the heat-fixing roll, the surface of the cylindrical core metal is coated with a certain width of contact. HTV silicone rubber, LTV silicone rubber (Low
Temperature Vulcanization Silicone
Rubber), RTV silicone rubber, fluoro rubber,
EPDA rubber (Ethy-lene Propylene Diene
A material coated with a heat-resistant elastic material such as Acryl Rubber is used. However, the biggest drawback of this heat roll method is that the toner side of the copy paper comes into direct contact with the surface of the heating and fixing roll, so some of the unfixed toner on the copy paper is transferred to the heating and fixing roll, and that toner is transferred to the copy paper. A so-called offset phenomenon occurs in which the toner is retransferred to the trailing edge of the paper or to the next copy paper, staining the copy paper. In order to prevent this phenomenon, a method of applying a release agent such as silicone oil to the surface of the heat fixing roll has been adopted, but this requires an oil storage tank and a device for coating, making the device complicated and Not only does this lead to an increase in size, but there is a risk that the copy paper may be stained by the oil, and in fact, problems caused by oil account for approximately 30% of all problems with fixing devices. Therefore, recently, instead of applying a release agent, a roll impregnated with a release agent such as silicone oil is pressed into contact with a heat fixing roll, and the silicone oil oozes out from the surface of the roll and is applied to the heat fixation roll. A method of applying a treatment substance such as low molecular weight polyethylene or low molecular weight polypropylene that improves release properties to the toner in advance, or a method of attaching a cleaning roll to the surface of a heating fixing roll and toner adhering to the surface of the roll. A method for cleaning the water has been put into practical use. [Problems to be Solved by the Invention] However, with the method of pressing a roll impregnated with silicone oil against a heat fixing roll, the silicone oil quickly runs out and the offset phenomenon cannot be prevented for a long period of time. On the other hand, the method of incorporating a treatment substance into the toner that improves release properties is incomplete in preventing the offset phenomenon. When the number of copies exceeds 100,000, or when the number of copies exceeds 50,000 for heat-fixing rolls coated with a heat-resistant elastic material such as silicone rubber, the surface of the fixing roll becomes rough due to wear and an offset phenomenon occurs. This has the disadvantage that toner is deposited on the surface of the fixing roll. In addition, the method of attaching a cleaning roll also has the disadvantage that toner accumulates and solidifies on the surface of the cleaning roll, so the solidified toner may damage the surface of the heat-fixing roll or cause fusing failure. A similar problem occurred when a cleaning device using heat-resistant felt or the like was used instead of the roll. The present invention eliminates and improves the above-mentioned drawbacks of the prior art, and provides a fixing device that prevents offset phenomena and poor fixing, thereby providing stable toner fixing performance over a long period of time. be. [Means for Solving the Problems] That is, the present invention includes a heat fixing roll and a pressure roll that rotate while being pressed against each other, and a sheet on which an unfixed toner image is formed is inserted between these rolls to fix an unfixed toner image. Assuming a fixing device that fixes toner images, the surface of the cylindrical core metal is coated with silicone-modified rubber, which is a heat-resistant elastic material with a siloxane addition rate of 30 to 70% and which has inferior release properties than a heated fixing roll. In addition to using a pressure roll with layers formed,
This pressure roll is characterized in that it is provided with an abrasive member that comes into contact with the coating layer and polishes the surface thereof. [Function] According to the above-mentioned technical means, the pressure roll has a siloxane addition rate of 30% on the surface of the cylindrical core metal.
A coating layer made of silicone-modified rubber, which is a heat-resistant elastic material with ~70% release properties inferior to that of a heat-fixing roll, is formed. Unfixed toner on the fixing roll is reliably transferred to the pressure roll side. At this time, since an abrasive member for surface polishing is placed in contact with the pressure roll, the unfixed toner transferred onto the pressure roll is removed by the abrasive member. [Examples] Examples of the present invention will be described below with reference to the drawings. Incidentally, FIG. 1 shows an explanatory sectional view of the fixing device of the present invention. That is, the fixing device of the present invention is composed of a heat fixing roll 1, a pressure roll 2, and an abrasive member 3, as shown in FIG. First, the heat fixing roll 1 is made up of a cylindrical core bar 4 rotatably supported in the direction of arrow A, and a heat-resistant elastic layer 5 such as RTV silicone that covers the surface of the core bar 4. A heater 6 for heating the fixing roll is disposed within the metal 4. On the other hand, the pressure roll 2 is provided below the heat fixing roll 1, and like the fixing roll, it has a cylindrical core bar 7 and a heat resistant material that covers the surface of the core bar 7 and has inferior mold releasability than the heat fixing roll 1. Elastic material, such as silicone-modified EPDM rubber (trade name: SEP rubber, manufactured by Shin-Etsu Chemical Co., Ltd., Ethylene Propylene)
Heat-resistant elastic material layer 8 such as Diene Methacryl Rubber)
The core metal 7 is the heat fixing roll 1.
It is supported on a bearing so that it can rotate in the direction of arrow B as the roller 1 rotates, and an appropriate pressure is applied between the heat fixing roll 1 and the pressure roll 2 by a mechanism not shown. Note that silicone-modified EPDM rubber refers to EPDM rubber mixed with siloxane, and is a rubber in which siloxane is mixed into EPDM rubber, which has poor toner releasability, to adjust the toner releasability as appropriate. Further, the pressure roll 2 is provided with a plate-shaped polishing member 3 that is in contact with the heat-resistant elastic layer 8 and polishes its surface.
are disposed along the length of the pressure roll 2, and this polishing member 3 removes toner adhering to the surface of the pressure roll 2. In FIG. 1, reference numeral 9 denotes a copy paper separation claw provided on the heat fixing roll 1, 10 a paper guide for inserting the copy paper between the rolls, and 11 a paper guide on which an unfixed toner image is formed. Shows copy paper. To fix the toner using the fixing device of the present invention, as shown in FIG. The toner is melted by heat transfer from the heat fixing roll 1, poured into the fibers of the copy paper 11, cooled, and fixed. At this time, even if some of the unfixed toner on the copy paper 11 adheres to the surface of the heat fixing roll 1, this roll 2 is transferred when this toner comes into contact with the pressure roll 2, which has poor release properties. The heat fixing roll 1 is not soiled with toner, and therefore offset phenomena and the like can be prevented.
Note that since the toner transferred to the pressure roll 2 is removed by the polishing member 3, no toner is deposited on the pressure roll 2. Here, by using the fixing device of the present invention and a conventional fixing device that uses a heat fixing roll and a pressure roll that have approximately the same toner release properties, heat fixing based on the occurrence of offset phenomenon, fixing failure, etc. A comparative experiment was conducted to compare the replacement life of the rolls. The fixing device of the present invention uses RTV60 (manufactured by General Electric Company) as a heating fixing roll.
RTV silicone rubber) coated with 90% siloxane, and as a pressure roll,
Silicone modified by adding 70%, 50%, 30%
A material coated with EPDM rubber was used, and an aluminum plate was used as the polishing member. On the other hand, as a conventional fixing device, both a heat fixing roll and a pressure roll were coated with RTV60, and no abrasive member was attached. The temperature setting of the heating fixing roll for both devices is 160.
℃, the load between both rolls was 60 kg, and the copying speed was 12 sheets/min. As a result, the measurement results shown in Table 1 below were obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the releasability balance between the heat fixing roll and the pressure roll is finely adjusted, unfixed toner is reliably transferred from the heat fixation roll to the pressure roll side, and the toner is polished. Since the unfixed toner transferred to the pressure roll side is removed by the member, even if some of the unfixed toner adheres to the surface of the heat fixing roll, the unfixed toner on the heat fixing roll can be removed by pressure. It is now possible to remove everything through the roll and abrasive member, and accordingly,
There is no risk of unfixed toner accumulating on the heat fixing roll or pressure roll and staining the sheet. Therefore, unlike conventional toner offset phenomena and poor fixing, stable toner fixing performance can be obtained, and the replacement life of the heat fixing roll can be significantly extended.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an explanatory sectional view of the fixing device of the present invention, and FIG.
5 to 5 show other embodiments of the present invention,
FIG. 7 is an explanatory cross-sectional view of a fixing device in which the abrasive member is changed. Description of symbols, 1... Heat fixing roll, 2... Pressure roll, 3... Polishing member, 4, 7... Core bar, 5,
8...Heat-resistant elastic layer, 6...Heater, 9...Copy paper separation claw, 10...Paper guide, 11
... Copy paper, 12 ... Polishing roll, 13,1
5... Brush roll, 14, 16... Case.

Claims (1)

[Claims] 1. In a fixing device that includes a heat fixing roll and a pressure roll that rotate while being pressed against each other, a sheet on which an unfixed toner image is formed is inserted between these rolls to fix the unfixed toner image. A pressure roll with a coating layer made of silicone-modified rubber, a heat-resistant elastic material with a siloxane addition rate of 30 to 70% and inferior release properties than a heat-fixing roll, is used on the surface of the gold. A fixing device characterized in that the roll is provided with an abrasive member that comes into contact with the coating layer and polishes the surface of the roll.