JP4271384B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device for fixing a toner image on a recording material in an image forming apparatus for forming an electrophotographic image such as a copying machine, a printer, or a facsimile.
[0002]
[Prior art]
Conventionally, as a fixing device used in an electrophotographic image forming apparatus, a heat fixing device in which a heater is provided in at least one of a pair of rollers through which a recording material such as paper after the transfer process passes is generally used. Has been. In such a heat-fixing apparatus, particularly when applied to a color image forming apparatus in which a plurality of color toners are transferred to the same portion on the recording material, the thickness of the unfixed toner layer on the recording material is increased. Therefore, an elastic layer is formed on each surface of the pair of rollers constituting the fixing device.
[0003]
One of the pair of rollers constituting the fixing device is a heating roller provided with a heater as described above, and the other is a pressure roller that is pressed against the heating roller with a predetermined pressing force. While the recording material is conveyed while being rotated, the unfixed toner image is pressed against the surface of the recording material while being melted. For this reason, the melted toner is likely to be offset on the surface of the heating roller, and the image quality is deteriorated due to missing or fouling of the toner image on the recording material. Further, the recording material is easily wound around the surface of the heating roller, and the recording material is jammed.
[0004]
Therefore, in the conventional fixing device, not only is a release agent such as silicone oil applied to the surface of the heating roller, or a peeling claw that is in contact with the surface of the roller is provided, but also the hardness of the surface of the heating roller By making the hardness lower than the surface hardness, offset of the toner image with respect to the surface of the heating roller and winding of the recording material are prevented, and deterioration of image quality and occurrence of jamming of the recording material are prevented.
[0005]
[Problems to be solved by the invention]
However, if the hardness of the heating roller is lower than that of the pressure roller, the release of the recording material from the surface of the heating roller is improved, but conversely, the release of the recording material from the surface of the pressure roller is reduced. However, it is easy for the recording material to wrap around the pressure roller, causing jamming, and the pressure contact force of the peeling claw against the roller surface must be increased, causing damage to the roller and streaking of oil on the recording material. There is a problem to do.
[0006]
For this reason, it is conceivable that the surface roughness of the pressure roller is sufficiently roughened compared to the surface roughness of the heating roller to improve the peelability of the recording material from the surface of the pressure roller. Dust easily adheres to the surface of the rough pressure roller, and the surface of the melted toner that is pressed by the pressure roller via the recording material becomes rough, resulting in deterioration of image quality in the recording material. In particular, when an OHP film that requires light transmittance of an image is used as a recording material, there is a problem that sufficient color reproducibility cannot be obtained due to a rough image surface.
[0007]
The object of the present invention is to optimize the surface roughness of the pressure roller mainly when the surface hardness of the heating roller is lower than the surface hardness of the pressure roller. An object of the present invention is to provide a fixing device capable of preventing the occurrence of jamming of a recording material without causing deterioration.
[0008]
[Means for Solving the Problems]
The present invention has the following configuration as means for solving the above problems.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(1) A first roller in which an outer peripheral portion having an elastic layer having heat resistance contacts an unfixed toner image transferred on a recording material, and an outer peripheral portion in pressure contact with the first roller have heat resistance. A second roller provided with an elastic layer, heating means for heating at least the outer periphery of the first roller to a temperature at which the toner image can be melted, and a release agent applied to at least the outer periphery of the first roller Coating means, and upper and lower peeling claws for peeling the recording material from each of the surface of the first roller and the surface of the second roller, and the hardness of the elastic body layer of the second roller is the first In the fixing device that is higher than the hardness of the elastic layer of the roller,
When the Asker C hardness of the elastic layer of the first roller is in the range of 62 to 68 degrees, the Asker C hardness of the elastic layer of the second roller is more than the Asker C hardness of the elastic layer of the first roller. 8-10 degrees higher,
The ten-point average roughness of the surface of the first roller is 0.6 to 1.0 μmRz, and the ten-point average roughness of the surface of the second roller is 1.0 to 3.0 μmRz. To do.
[0010]
In this configuration, the first roller and the second roller are configured to press and fix the unfixed toner image on the recording material while being heated and melted while the recording material after the transfer process is nipped and conveyed. Each of which includes an elastic layer having heat resistance at each outer peripheral portion, and a release agent is applied to at least the outer peripheral surface of the first roller. The hardness of the elastic body layer of the second roller is increased, the surface roughness of the first roller is 0.6 to 1.0 μmRz, and the surface roughness of the second roller is 1.0 to 3.0 μmRz. The Therefore, the first roller on which the recording material is more easily wound than the second roller when the unfixed toner image comes into contact with the second roller because the release agent is applied and the second roller has a lower hardness. The releasability of the second roller is improved by improving the releasability as compared with the roller and making the surface roughness of the second roller rougher than the surface roughness of the first roller to such an extent that the image quality does not deteriorate. Will improve. Accordingly, the recording material that has passed through the contact portion between the first roller and the second roller is conveyed without being wound around any one of the rollers.
[0012]
The surface hardness of the first roller is a 6 2-68 degrees (Asker C hardness) The surface hardness of the first roller in the range of 8 to 10 degrees relative to the surface hardness of the second roller By lowering the recording material, the peelability of the recording material with respect to the first roller and the peelability of the recording material with respect to the second roller are made more uniform. As a result, the recording material that has passed through the contact portion between the first roller and the second roller is more reliably restricted from being wound around one of the rollers.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a fixing device according to an embodiment of the present invention. The fixing device 100 includes a heating roller (first roller of the present invention) 1 and a pressure roller (first roller of the present invention) that are arranged with their rotation axes parallel to each other with a part of their peripheral surfaces being in pressure contact with each other. 2 rollers) 2 are rotatably provided. Each of the heating roller 1 and the pressure roller 2 includes, for example, an elastic body layer made of silicone rubber on the outer periphery of a cylindrical core metal made of aluminum, and a heater (such as a halogen lamp) inside the core metal ( The heating means) 3 and 4 of the present invention are provided. Note that it is sufficient that the heater 3 is provided at least in the heating roller 1, and the heater 4 is not necessarily provided in the pressure roller 2.
[0014]
Around the heating roller 1, an upper roller temperature detector 5, an oil application roller 7, an upper cleaning roller 9, and an upper peeling claw 11 are disposed. A lower roller temperature detector 6, a lower cleaning roller 10, and a lower peeling claw 12 are disposed around the pressure roller 2.
[0015]
The upper and lower roller temperature detectors 5 and 6 are thermistors, and detect the surface temperatures of the heating roller 1 and the pressure roller 2 that are in contact with each other. The upper and lower cleaning rollers 9, 10 are made of felt on the surface, and offset toner adhering to the surfaces of the heating roller 1 and the pressure roller 2 in sliding contact with the surfaces of the heating roller 1 and the pressure roller 2 is removed. to recover. The upper and lower peeling claws 11 and 12 peel off the recording material P to be wound around the surfaces of the heating roller 1 and the pressure roller 2 from these surfaces. The oil application roller 7 contacts the surface of the heating roller 1 and applies silicone oil as a release agent.
[0016]
It should be noted that at least the upper roller temperature detector 5 for detecting the surface temperature of the heating roller 1 may be provided, and the lower roller temperature detector 6 is not necessarily provided. The detection signals of the roller temperature detectors 5 and 6 are output to a fixing control unit (not shown), and the fixing control unit controls the operation of the power supply unit based on the input detection signal and turns on the heaters 3 and 4. / Turn off and adjust the temperature of the heating roller 1 and the pressure roller 2 to a predetermined temperature.
[0017]
Furthermore, the fixing device 100 includes an oil supply device. This oil supply device has an oil tank 20 disposed at the lower part of the fixing device 100, and the silicone oil in the oil tank 20 is positioned above the oil application roller 7 via a piezoelectric or electromagnetic pump 21. Is supplied to the pipe 28 through the tube 22. Silicone oil is supplied dropwise to the felt 23 from a plurality of holes provided in the pipe 28, and further supplied from the felt 23 to the surface of the heating roller 1 through the surface of the oil supply roller 7. At this time, the adhesion amount of the silicone oil on the surface of the oil application roller 7 is adjusted by the blade 24 so that the silicone oil is uniformly supplied in the axial direction of the surface of the heating roller 1.
[0018]
Silicone oil that has not adhered to the oil application roller 7 is returned to the oil tank 20 through the tube 26 from the oil pan 25 disposed below the felt 23. The amount of silicone oil stored in the oil tank 20 is detected by the sensor 27, and when the amount detected by the sensor 27 falls below a predetermined amount, replenishment of silicone oil from the supply port 20a is prompted.
[0019]
FIG. 2 is a diagram showing in detail the configuration of the heating roller and the pressure roller of the fixing device. As described above, both the heating roller 1 and the pressure roller 2 include elastic layers 1b and 2b made of silicone rubber or the like on the outer periphery of cylindrical core bars 1a and 2a made of aluminum or the like. The outer diameter is generally 40 to 50 mm. For example, fluororesin such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene), polyol vulcanized fluororubber or polyamine is provided on the surface of the elastic layers 1b and 2b. A vulcanized fluororubber layer can also be provided.
[0020]
Note that the outer diameters of the heating roller 1 and the pressure roller 2 are not necessarily the same.
[0021]
3 and 4 are diagrams showing experimental results of the surface roughness of the heating roller and the pressure roller in the fixing device, and the peelability of the recording material and the image quality when the surface hardness is variously changed.
[0022]
3 shows that the external environment during image formation is a high-temperature and high-humidity state (temperature 35 ° C., humidity 85%) in which the recording material P easily wraps around the pressure roller 2 in the fixing device 100, and the recording material P is A4. Using normal size paper (moisture absorption 8-10%) and OHP film, the surface roughness of the heating roller 1 is 0.6 μm Rz, the surface hardness of the heating roller 1 is 66 degrees (Asker C hardness), and the pressure roller 2 The surface hardness of the paper is 76 degrees (Asker C hardness), and the peelability of plain paper and the image quality on the OHP film when the surface roughness of the pressure roller 2 is variously changed are shown.
[0023]
As shown in the figure, when the surface roughness of the pressure roller 2 is 0.6 μm Rz, which is the same as the surface roughness of the heating roller 1, it is possible to prevent the recording material P (plain paper) from being wrapped around the pressure roller 2. could not. On the other hand, the peelability of the recording material P (plain paper) from the pressure roller 2 improves as the surface roughness of the pressure roller 2 increases, but recording occurs when the surface roughness of the pressure roller 2 reaches 4.0 μmRz. The image quality of the material P (OHP film) is deteriorated. Further, the amount of dust attached to the surface of the pressure roller 2 increases. Therefore, under the above-mentioned conditions, the surface roughness of the pressure roller 2 should be 1.0 to 3.0 μm Rz.
[0024]
FIG. 4 shows that the heating roller 1 has a surface roughness of 0.6 μm Rz, the pressure roller 2 has a surface roughness of 2.0 μm Rz, A4 size plain paper (moisture absorption 8-10%) and OHP film as the recording material P. The results of determining the peelability of plain paper and the image quality in the OHP film when the surface hardness of the heating roller 1 and the pressure roller 2 are variously changed are shown. As in the experiment of FIG. 3, the peelability of the recording material P was determined using plain paper, and the image quality for the recording material P was determined using an OHP film.
[0025]
As shown in the figure, the lower the surface hardness of the heating roller 1 and the pressure roller 2, the better the peelability of the recording material P from the roller. However, if the surface hardness of the heating roller 1 is lowered to 60 degrees (Asker C hardness) or less, the amount of deformation increases and the life of the heating roller 1 decreases. When the surface hardness of the heating roller 1 is higher than the surface hardness of the pressure roller 2, the recording material P is wound around the peripheral surface of the heating roller 1 as shown in FIG. On the other hand, when the surface hardness of the pressure roller 2 is excessively higher than the surface hardness of the heating roller 1, the recording material P is wound around the circumferential surface of the pressure roller 2 as shown in FIG. Decreases.
[0026]
Accordingly, the hardness difference between the surface of the heating roller 1 and the surface of the pressure roller 2 is preferably about 10 degrees (Asker C hardness), and the surface hardness of the heating roller 1 is 62 to 68 degrees (Asker C hardness). More preferably, it should be 64 to 68 degrees (Asker C hardness), and the surface hardness of the pressure roller 2 is 72 to 78 degrees (Asker C hardness), more preferably 74 to 78 degrees (Asker C hardness). Should.
[0027]
By setting the surface roughness and surface hardness of the heating roller 1 and the pressure roller 2 as described above, the recording material P with respect to the heating roller 1 and the pressure roller 2 does not deteriorate image quality in the recording material P. It is not necessary to excessively increase the pressure contact force of the peeling claws 11 and 12 against the surface of the heating roller 1 and the surface of the pressure roller 2, and the heating roller 1 and the pressure roller 2 are damaged. In addition, it is possible to reliably prevent streaky oil from adhering to the recording material P.
[0028]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0029]
(1) A release agent is applied to at least the surface of the first roller, the hardness of the elastic body layer of the second roller is made higher than the hardness of the elastic body layer of the first roller, and the first roller The surface roughness of the second roller is 0.6 to 1.0 μm Rz, and the surface roughness of the second roller is 1.0 to 3.0 μm Rz. About the 1st roller which is easy to wind rather than a roller, since a mold release agent is apply | coated and it is lower hardness, a releasability can be improved rather than a 2nd roller. In addition, it is possible to improve the releasability of the second roller by making the surface roughness of the second roller rougher than the surface roughness of the first roller to such an extent that the image quality does not deteriorate. Therefore, the recording material that has passed through the contact portion between the first roller and the second roller can be transported without being wound around any one of the rollers, and the pressure roller surface is stained or damaged, and the image quality is increased. It is possible to prevent jamming of the recording material without causing deterioration of the recording material.
[0030]
(2) The surface hardness of the first roller is 66 to 68 degrees (Asker C hardness), and the surface hardness of the second roller is 72 to 78 degrees (Asker C hardness). Is made lower than the surface hardness of the second roller within a range of 10 degrees or less, and the releasability of the recording material to the first roller and the releasability of the recording material to the second roller can be made more uniform. it can. As a result, the recording material that has passed through the contact portion between the first roller and the second roller can be more reliably restricted from being wound around one of the rollers, and the pressure roller surface can be stained or damaged. Further, it is possible to more reliably prevent the occurrence of jamming of the recording material without causing deterioration of the image quality.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a fixing device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating in detail a configuration of a heating roller and a pressure roller of the fixing device.
FIG. 3 is a diagram showing experimental results of peelability and image quality of a recording material when the surface roughness and surface hardness of a pressure roller in the fixing device are variously changed.
FIG. 4 is a diagram showing experimental results of peelability and image quality of a recording material when various surface hardnesses of a heating roller and a pressure roller in the fixing device are changed.
FIG. 5 is a diagram illustrating a state where a recording material is wound around a heating roller in the fixing device.
FIG. 6 is a diagram illustrating a state where a recording material is wound around a pressure roller in the fixing device.
[Explanation of symbols]
1-heating roller (first roller)
2-Pressure roller (second roller)
1b, 2b-elastic layer 3,4-heater (heating means)
7-Oil application roller (application means)
P-recording material

Claims (1)

A first roller in which an outer peripheral portion having an elastic layer having heat resistance contacts an unfixed toner image transferred onto a recording material, and an elastic layer having heat resistance in an outer peripheral portion in pressure contact with the first roller A heating unit that heats at least the outer periphery of the first roller to a temperature at which the toner image can be melted, and an application unit that applies a release agent to at least the outer periphery of the first roller. And upper and lower peeling claws for peeling the recording material from the surface of the first roller and the surface of the second roller, respectively, and the hardness of the elastic layer of the second roller is the elasticity of the first roller. In the fixing device that is higher than the hardness of the body layer,
When the Asker C hardness of the elastic layer of the first roller is in the range of 62 to 68 degrees, the Asker C hardness of the elastic layer of the second roller is more than the Asker C hardness of the elastic layer of the first roller. 8-10 degrees higher,
The ten-point average roughness of the surface of the first roller is 0.6 to 1.0 μmRz, and the ten-point average roughness of the surface of the second roller is 1.0 to 3.0 μmRz. Fixing device to do.

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