JP3979128B2 - Fixing device for image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device of an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly to a fixing rotating body used in the fixing device.
[0002]
[Prior art]
Conventional electrophotographic image forming apparatuses such as copying machines and printers are known. In such an image forming apparatus, the latent image formed on the photosensitive member is developed with toner, and the developed toner image is transferred to a recording medium. Then, the recording medium to which the toner image is transferred is fixed by the fixing device to fix the image on the recording medium, and the image recording is completed.
[0003]
Some fixing devices include a fixing roller having a heat source therein and a pressure roller, and others using a fixing belt. In the configuration using the fixing belt, there is a configuration in which an endless belt or an endless film serving as a fixing belt is wound around a fixing roller provided with a single composition / single layer silicone sponge layer. A pressure roller is pressed against the fixing roller from above. As the pressure roller, a single composition / single layer silicone rubber roller whose surface is covered with a synthetic resin tube such as PFA is used.
[0004]
In a fixing device using a fixing belt, the advantages of using a sponge roller as the fixing roller are high heat insulation, less heat loss to the core, less energy loss, and lower hardness compared to solid rubber. When the fixing belt and the pressure roller are brought into contact with each other, a wide nip width (contact width when two rollers are in contact) can be obtained with a low contact pressure.
[0005]
However, the sponge roller has low mechanical strength due to its structure, and is not suitable for use under high pressure conditions or high speed conditions.
[0006]
[Problems to be solved by the invention]
In a fixing device using a fixing belt, it is required to increase the amount of heat transfer in the fixing unit in order to enable use under high speed conditions. In order to achieve this, the pressure applied to the fixing roller around which the fixing belt is wound is increased, the deformation rate of the elastic layer of the fixing roller is increased, and a wide nip is formed, so that the time for passing through the nip portion is reached. It can be solved by lengthening.
[0007]
However, when the pressure applied to the fixing roller is increased, the sponge layer constituting the fixing roller is deformed by pressurization, and bubbles are broken by the distortion stress at the time of driving. The outer diameter of the roller is reduced. For this reason, the conveyance speed of the recording medium is lowered by the rotation of the fixing roller, and inconveniences such as the core metal and the sponge layer peeling off finally occur.
[0008]
The bubble breaking phenomenon described above is preferentially generated inside the sponge layer slightly behind the adhesion boundary surface, not the adhesion boundary surface between the core metal and the sponge layer.
[0009]
In addition, foaming can be made into multiple layers by foaming with a mold instead of foaming by extrusion molding. However, foaming with a molding die causes a delay in temperature rise near the interface between the core metal and the sponge layer. The diameter of the foam cell becomes larger, the strength is weakened, and the inconvenience is likely to occur. The present invention aims to solve the above problems.
[0010]
[Means for Solving the Problems]
The present invention solves the above problems, and the invention of claim 1 includes a fixing belt provided between a fixing roller and a heating roller having a heating source therein, and the fixing roller is interposed via the fixing belt. the fixing device pressed pressure roller and the heating pressurizing fixing process to that images forming apparatus unfixed toner image formed on a recording medium by passing between the fixing belt, the fixing The roller is provided with a plurality of elastic layers made of silicone rubber having different physical properties formed on a core metal that is driven to rotate, and the elastic layer has a higher hardness in the lower silicone rubber layer than in the upper layer. And an upper layer is a silicone sponge rubber layer.
[0012]
The lower silicone rubber layer on the core is preferably made of low-temperature vulcanized silicone solid rubber.
[0013]
Furthermore, a silicone rubber layer having a JIS-A material hardness of 10 degrees or less may be used for the lower silicone rubber layer on the core metal.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. Since the image forming apparatus itself has a known configuration, a description thereof will be omitted. First, an outline of the configuration of a fixing device using a fixing belt suitable for applying the fixing roller of the present invention will be described.
[0016]
FIG. 1 is a diagram for explaining an outline of the configuration of the fixing device 10. The fixing device 10 includes a heating roller 11 having a heater lamp 11a therein and two silicone rubber layers having different physical characteristics on the surface. The fixing roller 13, the fixing belt 12 installed between the heating roller 11 and the fixing roller 13, and a heater lamp 14 a that is pressed against the fixing roller 13 from above the fixing belt 12 are provided. And a pressure roller 14.
[0017]
FIG. 2 is a cross-sectional view for explaining the structure of the fixing roller 13 constituting the fixing rotating body. In the fixing roller 13, a silicone rubber layer is formed in a two-layer structure on a core metal 13a. That is, the lower layer is formed of a silicone solid rubber layer 13b, and a silicone sponge rubber layer 13c is formed thereon as a surface layer.
[0018]
The lower solid rubber layer 13b is made of a silicone rubber having different physical characteristics from the surface silicone sponge rubber layer 13c, such as low temperature vulcanization (LTV) silicone rubber, and the lower silicone solid rubber layer 13b is a surface silicone sponge rubber. The strength is higher than that of the layer 13c. The lower silicone solid rubber layer 13b has a JIS-A material hardness of 10 degrees or less.
[0019]
Further, the lower silicone solid rubber layer 13b can be made of silicone sponge rubber instead of silicone solid rubber. In this case, the lower silicone sponge rubber layer 13b has a higher hardness than the surface silicone sponge rubber layer 13c. And The pressure roller 14 is configured by forming a solid rubber layer on a cored bar.
[0020]
As described above, the fixing roller 13 has a two-layer structure of the silicone rubber layer on the cored bar 13a. At this time, a silicone sponge rubber cylindrical body serving as a surface layer is formed by extrusion molding and is molded in advance. In addition, a surface layer silicone sponge rubber cylindrical body formed on the lower layer silicone solid rubber roller is covered. This is because it is possible to obtain a silicone sponge rubber roller having higher strength, better durability, and less change in physical properties when the sponge is formed by extrusion molding than when the sponge is formed by foaming with a mold.
[0021]
The silicone rubber layer is composed of two layers, and the silicone solid rubber layer is provided between the core metal and the surface silicone sponge rubber layer, so that the distortion generated between the core metal and the surface silicone sponge rubber layer is reduced to the lower silicone. It can be buffered by the solid rubber layer, and distortion of the surface layer can be reduced by increasing the adhesion area between the surface silicone rubber layer and the lower silicone rubber layer.
[0022]
Next, the physical characteristics of the fixing roller having a two-layer structure according to the embodiment of the present invention will be described in comparison with a conventional fixing roller having a single-layer structure. In this comparative experiment, the fixing roller according to the embodiment of the present invention has a two-layer structure in which the surface layer is composed of silicone sponge rubber and the lower layer is composed of silicone solid rubber.
[0023]
FIG. 3 is a graph showing experimental results of the change in hardness of the fixing roller. The horizontal axis indicates the number of recording media subjected to fixing processing (unit: 1000 sheets), and the vertical axis indicates the hardness of the fixing roller (Asker C2: 4.9 N load). And shows the change in hardness according to the number of recording media subjected to fixing processing. As is apparent from the figure, the two-layer fixing roller of this embodiment has a small change in hardness even when the number of fixed recording media increases, whereas the single-layer fixing roller has a large hardness. It turns out that it falls.
[0024]
FIG. 4 is a diagram showing an experimental result of a reduction change in the outer diameter of the fixing roller. The horizontal axis indicates the number of recording media subjected to fixing processing (unit: 1000 sheets), and the vertical axis indicates a reduction change amount in the outer diameter of the fixing roller (in FIG. (Unit: mm), and the amount of change in reduction of the outer diameter according to the number of fixed recording media. As is clear from the figure, the fixing roller having the two-layer configuration of this embodiment has a small change in outer diameter even when the number of fixed recording media increases, whereas the fixing roller has a single-layer configuration. It can be seen that the outer diameter of the roller is greatly reduced.
[0025]
FIG. 5 is a graph showing experimental results of the durability change rate of the conveyance speed of the fixing roller. The horizontal axis indicates the number of recording media subjected to fixing processing (unit: 1000 sheets), and the vertical axis indicates the change rate of the conveyance speed of the fixing roller (unit: 1000). %), And the rate of change in the conveyance speed according to the number of recording media subjected to the fixing process. As is apparent from the figure, in the two-layer fixing roller of this embodiment, the rate of change in the conveyance speed is small even when the number of fixed recording media increases, whereas in the single-layer fixing roller, It can be seen that the conveyance speed is greatly reduced.
[0026]
FIG. 6 is a diagram showing experimental results of the amount of change in the nip width of the fixing roller. The horizontal axis represents the number of recording media (1000 units) subjected to the fixing process, and the vertical axis represents the amount of change in the nip width of the fixing roller (unit). mm), and the amount of change in the nip width corresponding to the number of recording media subjected to fixing processing is shown. As is apparent from the figure, in the two-layer fixing roller of this embodiment, the amount of change in the nip width is small even when the number of fixed recording media increases, whereas in the single-layer fixing roller, It can be seen that the nip width is greatly reduced.
[0027]
FIG. 7 is a diagram showing experimental results of changes in the pressure contact force between the fixing roller and the pressure roller. The horizontal axis represents the number of recording media subjected to fixing processing (1000 units), and the vertical axis represents the addition to the fixing roller. The amount of change in pressing force with the pressure roller (unit Newton (N)) is taken to indicate the amount of change in pressing force according to the number of fixed recording media. As is apparent from the figure, in the two-layer fixing roller of this embodiment, the amount of change in the pressure contact force is small even when the number of fixed recording media increases, whereas in the single-layer fixing roller, It can be seen that the pressure contact force decreases greatly.
[0028]
The embodiments described above include the inventions described below. That is, in the invention according to claim 1, the plurality of silicone sponge layers formed on the core metal are formed by laminating a plurality of cylindrical bodies made of extruded silicone sponges having different physical properties in a plurality of layers. The fixing device for an image forming apparatus according to claim 1, wherein the fixing device is configured.
[0029]
【The invention's effect】
As described above, the fixing device of the image forming apparatus according to the present invention includes the fixing belt that is installed between the fixing roller and the heating roller having a heating source therein, and presses the fixing roller via the fixing belt. In a fixing device of an image forming apparatus that heats and presses an unfixed toner image formed on a recording medium by passing between a pressure roller and a fixing belt, the fixing roller rotates. A plurality of elastic layers made of silicone rubber having different physical properties formed on a driven metal core are provided, and the elastic layer has higher hardness in the lower silicone rubber layer than in the upper layer, and the upper layer Is composed of a silicone sponge rubber layer.
[0030]
With this configuration, the deformation rate of the elastic layer of the fixing roller is increased, and the time for passing through the nip portion can be increased by forming a wide nip portion. Therefore, the heat transfer amount to the recording medium is increased at the fixing portion. And fixing processing at high speed becomes possible.
[0031]
Further, an elastic layer made of silicone rubber constitute a plurality of layers, by increasing the lower hardness than the upper layer, there is no fear that bubbles inside the sponge is broken even by increasing the pressure applied to the fixing roller, long-term use However, there is no reduction in the hardness of the fixing roller , reduction in outer diameter, reduction in the conveyance speed of the recording medium, change in the nip width, change in pressure contact force, etc., and physical characteristics differ between the core metal and the surface layer. Since the silicone rubber layer is interposed, there is no possibility that the core metal and the surface silicone sponge rubber layer are peeled off.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an outline of a configuration of a fixing device.
FIG. 2 is a cross-sectional view illustrating a configuration of a fixing roller.
FIG. 3 is a diagram showing an experimental result of a change in hardness of the fixing roller.
FIG. 4 is a diagram illustrating an experimental result of a reduction change in the outer diameter of the fixing roller.
FIG. 5 is a diagram illustrating an experimental result of a durability change rate of a conveyance speed of a fixing roller.
FIG. 6 is a diagram illustrating an experimental result of the amount of change in the nip width of the fixing roller.
FIG. 7 is a diagram illustrating experimental results of changes in pressure contact force between a fixing roller and a pressure roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fixing device 11 Heating roller 11a Heater lamp 12 Fixing belt 13 Fixing roller (rotating body for fixing)
13a Metal core 13b Silicone solid rubber layer 13c Silicone sponge rubber layer 14 Pressure roller 14a Heater lamp

Claims (3)

A fixing belt is provided between the fixing roller and a heating roller having a heating source therein, and is passed between the pressure roller and the fixing belt pressed against the fixing roller via the fixing belt. in the fixing device of the heating pressurizing fixing process to that images forming apparatus unfixed toner image formed on the recording medium,
The fixing roller includes a plurality of elastic layers formed of silicone rubber having different physical characteristics formed on a core metal that is driven to rotate, and the elastic layer is a lower silicone rubber layer than an upper layer. A fixing device for an image forming apparatus, characterized by having a high hardness and an upper layer being a silicone sponge rubber layer. The fixing device for an image forming apparatus according to claim 1, wherein the lower silicone rubber layer on the core metal is made of a low-temperature vulcanized silicone solid rubber. Lower silicone rubber layer on said metal core is a fixing device of an image forming apparatus according to claim 1 or 2, characterized in that it consists of JIS-A material hardness of 10 degrees or less of the silicone solid rubber.

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