JP2007328109A - Fixing apparatus and image forming apparatus provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus with a pressurizing roller which can be warmed up in short time without occurrence of paper wrinkling in a recording medium and an image forming apparatus provided with it. <P>SOLUTION: A sponge rubber layer 23 in the pressurizing roller 21 is provided with a sponge rubber layer 23-1 with a specified expansion ratio in its central part and sponge rubber layers 23-2, 23-3 and 23-4 with different expansion ratios (density) lined up next to it with expansion ratios sequentially made lower toward shaft end parts, that is the density is made higher toward the shaft end parts. The sponge rubber layers 23-4 on the shaft end parts are solid state rubber layers. By continuously varying the expansion ratio in the sponge rubber layers, the pressurizing roller which can be warmed up in short time is provided without any occurrence of the paper wrinkling in the recording medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device used in an electronic copying machine, a printer, a facsimile machine, a multifunction machine thereof, and the like, and an image forming apparatus including the same.

  In an electrophotographic image forming apparatus, an image latent image formed on an image carrier (photosensitive member) is developed with toner, and the formed toner image is transferred to an intermediate transfer member such as an intermediate transfer belt. A step of forming an image by transferring the recording medium onto the recording medium or directly onto the recording medium and fixing the recording medium onto which the toner image has been transferred with a fixing device is performed.

  FIG. 8 is a diagram illustrating an example of the configuration of a conventionally known image forming apparatus. The image forming apparatus 100 includes a charging device 102, an exposure device 103, a developing device 104, a transfer device 105, and a cleaning device around the photosensitive member 101. 106 is arranged.

  A paper feeding cassette 107 that stores the recording medium P is disposed below the main body of the image forming apparatus 100, and a conveyance path 108 that conveys the recording medium P toward the transfer apparatus 105 is formed. A fixing device 120 described later is disposed on the downstream side in the transport direction of the recording medium P 105.

  The operation of the image forming apparatus 100 will be briefly described. When the photoconductor 101 starts rotating at a constant speed in the direction of arrow a by turning on the power, the surface of the photoconductor 101 is uniformly charged by the charging device 102, and an image signal is output from the exposure device 103 to the charged surface of the photoconductor 101. The laser beam modulated in step (1) is projected to form an image latent image.

  The latent image on the surface of the photoreceptor 101 is developed with toner loaded in the developing device 104. The recording medium P is fed from the paper feed cassette 107 at the timing when the toner image formed on the surface of the photoconductor 101 reaches the transfer position, and the toner image is transferred to the recording medium P by the action of the transfer device 105 at the transfer position. Is done.

  The recording medium P onto which the toner image has been transferred is conveyed to the fixing device 120 and subjected to a fixing process, and the recording medium P subjected to the fixing process is discharged to the discharge unit 109. Thereafter, the residual toner on the surface of the photoreceptor 101 is cleaned by the cleaning device 106, and the image forming operation ends.

  FIG. 9 is a cross-sectional view for explaining an example of the configuration of a conventionally known fixing device 120. A heat source such as a halogen lamp is provided inside the cored bar, a heat-resistant rubber layer 123 is provided on the outer side of the cored bar 122, and a surface layer thereof is provided. A heating roller 121 provided with a release layer 124 and a pressure roller 131 provided with a heat-resistant rubber layer 132 on the outer side of the core metal and provided with a release layer 134 on its surface are arranged in pressure contact with each other, and a nip portion therebetween And a heat roller type in which a recording medium having a toner image transferred thereon is passed through and fixed.

  In addition, in the fixing device, a heating body having a flexible sleeve disposed outside the ceramic heater and a pressure roller having a heat-resistant rubber layer disposed on the outside of the metal core are disposed in pressure contact with each other, and a nip portion between the two. In addition, an on-demand type in which a fixing process is performed by passing a recording medium on which a toner image is transferred, and the like are used.

  The pressure roller used in the fixing device has a structure in which a sponge rubber layer made of heat-resistant rubber is provided on the outside of the metal core. In this case, the central portion is sponge rubber and both ends in the axial direction are solid rubber. (Refer to Patent Document 1 and Patent Document 3).

Also known are those in which the hardness of the central portion of the pressure roller is lower than the hardness of both end portions in the axial direction, and in which the pressure roller is made of sponge rubber (see Patent Document 2).
JP-A-6-67560. Japanese Patent Laid-Open No. 7-219374. JP 2002-258651 A.

  In the fixing device, the heating roller and the pressure roller are pressed against each other to form a fixing nip portion. However, since the pressing force acts on the heating roller shaft and the pressure roller shaft outside the fixing nip portion, the roller shaft Is curved, and the width of the fixing nip portion is narrowed. Even if an attempt is made to increase the width of the fixing nip portion by increasing the pressure contact force, the curvature of the roller shaft becomes large and cannot be sufficiently expanded. Further, when the hardness of the heat-resistant rubber layer disposed on the outer side of the core metal is lowered, there is a disadvantage that the recording medium is curled.

  As a countermeasure against this, as described above, a heat-resistant rubber layer disposed on the outer side of the cored bar has been proposed as a sponge rubber layer. However, if the rubber layer of the pressure roller is made of sponge rubber, the bubble portion of the sponge rubber is crushed at the fixing nip portion, resulting in a volume change. Therefore, the recording medium is conveyed between the central portion of the pressure roller and both ends in the axial direction. There is a disadvantage in that a difference occurs in speed and paper wrinkles occur on the fixed recording medium.

  As a countermeasure, if the rubber layers at both ends in the axial direction of the pressure roller are made of solid rubber, there is a disadvantage that the heat capacity is increased and the warm-up time for raising the temperature to a predetermined fixing temperature is increased.

  The present invention solves the above-described disadvantages by gradually changing the foaming rate of the rubber layer of the pressure roller without affecting the warm-up time.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. The invention of claim 1 is a heat-fixing type fixing device using a pair of fixing rollers, wherein one of the fixing rollers is a heat-resistant sponge rubber around a core metal. The fixing device is characterized in that a foaming ratio is set to be smaller toward the shaft end of the roller.

  In the sponge rubber layer of the fixing roller, the shaft end of the roller is formed of a solid rubber layer.

  The rubber hardness of the sponge rubber layer of the fixing roller may be substantially equal from the center of the roller to the shaft end.

  The fixing roller may have at least one roller having an outer diameter that is different between the central portion and the shaft end portion.

  One of the fixing rollers is a heating roller provided with a heat source inside the cored bar, and the other is provided with a heat-resistant sponge rubber layer around the cored bar, and the foaming ratio is set smaller toward the roller shaft end. Pressure roller.

  According to a sixth aspect of the present invention, in the heat fixing type fixing device using a fixing belt and a pressure roller, the pressure roller has a heat-resistant sponge rubber layer disposed around a core metal, and the sponge rubber layer is The fixing device is characterized in that the foaming ratio is set to be smaller toward the shaft end of the roller.

  The sponge rubber layer of the pressure roller is configured such that the shaft end of the roller is a solid rubber layer.

  The rubber hardness of the sponge rubber layer of the pressure roller may be substantially equal from the center of the roller to the shaft end.

  The pressure roller may have at least one roller having an outer diameter that is different between the central portion and the shaft end portion.

  According to a tenth aspect of the present invention, in the heat fixing type fixing device using a pressure belt and a heat roller, the heat roller is provided with a heat-resistant sponge rubber layer around the core metal, and the sponge rubber layer is a roller. The fixing device is characterized in that the foaming ratio is set to be smaller toward the shaft end portion.

  A tenth aspect of the present invention is an image forming apparatus including the fixing device according to any one of the first to tenth aspects.

  As described above, according to the present invention, the roller has the heat-resistant sponge rubber layer disposed around the core metal, and the sponge rubber layer is set so that the foaming ratio decreases toward the shaft end of the roller. A fixing device capable of raising the temperature to a predetermined fixing temperature in a short time without increasing the heat capacity and generating paper wrinkles unlike a conventional roller, and an image forming apparatus including the fixing device Can be provided.

  The configuration of the fixing device according to the embodiment of the present invention will be described below.

  FIG. 1 is a cross-sectional view illustrating the configuration of a fixing device 10 according to an embodiment of the present invention. The fixing device 10 is a heat roller type fixing device in which a heating roller 11 and a pressure roller 21 are arranged in pressure contact with each other, and a recording medium P on which a toner image is transferred is passed through a nip portion between them to perform fixing processing. .

  The heating roller 11 includes a heat source such as a halogen lamp 15 inside the core metal 12, a heat-resistant rubber layer 13 is provided outside the core metal 12, and a release layer 14 is provided on the surface layer thereof. Although the outer diameter is arbitrary, for example, the outer diameter is about 20 to 50 mm.

  The cored bar 12 is made of a metal such as aluminum or iron, and the outer diameter and thickness are arbitrary. For example, the outer diameter is about 20 to 45 mm and the thickness is about 0.1 to 5 mm. The outer diameter is at both ends in the axial direction. An appropriate shape such as a constant shape toward the end, a large reverse crown shape toward both ends in the axial direction, and a crown shape in which the outer diameter of the central portion is large and gradually decreases toward both ends in the axial direction. The difference between the maximum value and the minimum value of the outer diameter is preferably about 0.001 to 3 mm. The cross-sectional shape of the cored bar may be irregular, such as a triangular shape as well as a cylindrical shape.

  The heat-resistant rubber layer 13 is made of an elastic material having high heat resistance such as silicone rubber and fluorine rubber, and the thickness thereof is preferably about 0.05 to 5 mm. Further, the release layer 14 is formed by covering a fluorine tube or by fluorine coating, and the thickness thereof is preferably 5 to 100 μm, for example.

  The pressure roller 21 is provided with a heat-resistant rubber sponge rubber layer 23 on the outer side of the cored bar 22 and a release layer 24 on the surface layer. The outer diameter of the pressure roller 21 is arbitrary. The diameter is about 20 to 50 mm.

  The cored bar 22 is made of a metal such as aluminum or iron, and the outer diameter and thickness are arbitrary. For example, the outer diameter is about 20 to 45 mm and the thickness is about 0.1 to 5 mm. A suitable shape such as a constant shape toward the end, a large reverse crown shape toward both ends in the axial direction, and a crown shape in which the outer diameter of the central portion is large and gradually decreases toward both ends in the axial direction. The difference between the maximum value and the minimum value of the outer diameter is preferably about 0.001 to 3 mm.

  The release layer 24 is formed by covering a fluorine tube or by fluorine coating, and its thickness is preferably 5 to 100 μm, for example. In some cases, conductivity is imparted.

  When the core bar 22 has a crown shape in which the outer diameter of the central portion is large and gradually decreases toward both ends in the axial direction, or the reverse crown shape, the outer diameter of the pressure roller 21 provided with the heat-resistant rubber layer 13 and the release layer 24. Is different from the central portion toward the shaft end portion.

  The configuration of the sponge rubber layer 23 of the pressure roller 21 includes a plurality of first embodiments. Hereinafter, description will be made sequentially.

[First embodiment]
FIG. 2 is a diagram for explaining the configuration of the sponge rubber layer 23 of the pressure roller 21 of the first embodiment and the change in the expansion ratio (density), and FIG. 2A is a diagram for explaining the configuration of the sponge rubber layer 23. FIG. 2B is a diagram for explaining the relationship between the axial position of the pressure roller 21 and the expansion ratio (density).

  A first embodiment of the configuration of the sponge rubber layer 23 of the pressure roller 21 will be described with reference to FIGS. 2 (a) and 2 (b). The sponge rubber layer 23 is a sponge rubber layer 23-1 having a predetermined foaming ratio at the center, and the foaming ratio gradually decreases from the adjacent side toward the shaft end toward the shaft end. Sponge rubber layers 23-2, 23-3, and 23-4 having different foaming ratios (densitys) that increase toward the end portions are arranged. The sponge rubber layer 23-4 at the shaft end is a solid rubber layer. The thickness of the sponge rubber layer is preferably about 1 to 20 mm.

The foaming ratio of the sponge rubber layer is a value indicating the degree of foaming of the rubber. When the density of the solid rubber layer is Xg / cm ² and the apparent density of the sponge is Yg / cm ² , the foaming ratio is Expressed as Y / X. The apparent density is a value (JIS-K6900) obtained by dividing the mass by the volume of the material including both air-permeable and air-impermeable voids normally existing in the material. For example, in the case of a silicone rubber having a specific gravity of 1.5 g / cm ² in a solid state, the center portion has a foaming ratio of 3 times, that is, an apparent density of 0.5 g / cm ^2, and the foaming ratio is gradually reduced toward the shaft end. The shaft end portion can be in a solid state, that is, the foaming magnification can be 1 time.

  Although the expansion ratio can be arbitrarily determined, it is in the range of 1 to 5 times, and when considering the durability, a certain degree of strength is required, so the range of 1 to 3 times is desirable. Further, the expansion ratio may be expressed by the number of foam cells. That is, the center portion may be a sponge having a large number of foam cells, and the shaft end portion may be a sponge having a small number of foam cells. The numerical range such as the above-described expansion ratio may be changed as appropriate according to the fixing device.

  As the material of the sponge rubber, an elastic material having high heat resistance such as silicone rubber and fluorine rubber may be used, and an additive may be added. The shape of the foam cell may be either closed cells or open cells, or both may be mixed. Although the foaming method is arbitrary, there are a method using a foaming agent, a method of making mechanically, and the like. The size of the bubbles is arbitrary, and the size of the bubbles may be changed between the central portion and the shaft end portion.

  The hardness of the sponge rubber layer is also arbitrary, but the rubber material may be changed between the center portion and the shaft end portion. For example, by using a base rubber material having a hardness higher than that of the shaft end portion in the central portion, the hardness of the sponge rubber layer can be increased even if the expansion ratio is higher than that of the shaft end portion. In addition, the hardness of the sponge rubber layer can be adjusted to the optimum hardness by adding a filler. Further, the hardness of the rubber layer may be substantially equal from the center portion to the shaft end portion.

[Second Embodiment]
FIG. 3 is a diagram for explaining the configuration of the sponge rubber layer 23 of the pressure roller 21 of the second embodiment and the change in the expansion ratio (density). FIG. 3A is a diagram for explaining the configuration of the sponge rubber layer 23. FIG. 3B is a diagram for explaining the relationship between the axial position of the pressure roller 21 and the expansion ratio (density).

  A second embodiment of the configuration of the sponge rubber layer 23 of the pressure roller 21 will be described with reference to FIGS. 3 (a) and 3 (b). The sponge rubber layer 23 is the sponge rubber layer 23-N0 having a predetermined expansion ratio at the center, and the expansion ratio gradually decreases toward the shaft end, that is, the density continues toward the shaft end. It is composed of a sponge rubber layer 23-N that increases in size, and the sponge rubber layer 23-Nn at the end of the shaft is a solid rubber layer. The thickness of the sponge rubber layer is preferably about 1 to 20 mm. In the second embodiment, when the expansion ratio (density) changes continuously, a curve is drawn to change continuously.

  The foaming ratio of the sponge rubber layer, the foaming method, the material of the sponge rubber, the hardness of the sponge rubber layer, etc. are not different from those of the first embodiment, so that the description is omitted.

[Third embodiment]
FIG. 4 is a diagram for explaining the configuration of the sponge rubber layer 23 of the pressure roller 21 of the third embodiment and the change in the expansion ratio (density), and FIG. 4A is a diagram for explaining the configuration of the sponge rubber layer 23. FIG. 4B is a diagram for explaining the relationship between the axial position of the pressure roller 21 and the expansion ratio (density).

    A second embodiment of the configuration of the sponge rubber layer 23 of the pressure roller 21 will be described with reference to FIGS. 4 (a) and 4 (b). The sponge rubber layer 23 is a sponge rubber layer 23-M0 having a predetermined expansion ratio at the center, and the expansion ratio gradually decreases toward the shaft end, that is, the density continues toward the shaft end. The sponge rubber layer 23-M is enlarged, and the sponge rubber layer 23-Mn at the end of the shaft is a solid rubber layer. The thickness of the sponge rubber layer is preferably about 1 to 20 mm. In the third embodiment, when the expansion ratio (density) changes continuously, a straight line is drawn and changes continuously.

  The foaming ratio of the sponge rubber layer, the foaming method, the material of the sponge rubber, the hardness of the sponge rubber layer, etc. are not different from those of the first embodiment, so that the description is omitted.

  Although the pressure roller of the present invention has been described above, the configuration described here is not limited to the pressure roller, but can be applied to a heating roller.

  The above-described pressure roller has been described above as the pressure roller of the fixing device shown in FIG. 1, but the above-described pressure roller can also be applied to fixing devices having other configurations. This will be described below.

  FIG. 5 is a cross-sectional view illustrating the configuration of the belt fixing device 30. A fixing belt 33 is installed between the heating roller 31 and the fixing roller 32, and a pressure roller 34 is disposed in pressure contact with the fixing belt 33 at a position facing the fixing roller 32. The fixing belt 33 is heated to a predetermined fixing temperature by contacting the surface of the heating roller 31.

  The recording medium P on which the toner image is formed is conveyed to a nip portion formed between the fixing belt 33 and the pressure roller 34, and is fixed by passing through the nip portion.

  As the pressure roller 34, the pressure roller 21 described in the first to third embodiments is used. The fixing belt 33 is made of a metal material such as nickel or stainless steel, or a heat resistant synthetic resin such as PA, PI, or PPS. A release layer is preferably formed on the surface of the pressure roller 34 by fluorine coating or the like.

  The heating roller 31 may be provided with a sliding property by covering the surface of a cylindrical cored bar with a fluorine tube or coating with fluorine to form a release layer, or by performing nickel plating or the like. The heating roller 31 is provided with a halogen lamp or the like inside the core as a heat source.

  As the fixing roller 32, the pressure roller 21 described in the first to third embodiments can be used.

  FIG. 6 is also a cross-sectional view illustrating the configuration of the belt fixing device 40. In this configuration, a fixing belt 43 is installed between the heating roller 41 and the pad 42, and the fixing belt 43 is sandwiched between the heating roller 41 and the pad 42. The pressure roller 44 is disposed in pressure contact. The fixing belt 43 is heated to a predetermined fixing temperature by contacting the surface of the heating roller 41.

  The recording medium P on which the toner image is formed is conveyed to a nip portion formed between the fixing belt 43 and the pressure roller 44, and is fixed by passing through the nip portion.

  As the pressure roller 44, the pressure roller 21 described in the first to third embodiments is used. The fixing belt 43 is made of a metal material such as nickel or stainless steel, or a heat resistant synthetic resin such as PA, PI, or PPS. A release layer may be formed on the surface of the pressure roller 44 by fluorine coating or the like.

  FIG. 7 is also a cross-sectional view illustrating the configuration of the belt fixing device 50. In this configuration, the belt fixing device 50 includes a heating roller 51 and a pressure belt 53 fitted on the outer periphery of the support member 52. Are pressed.

  The heating roller 51 is configured by disposing a heat source inside the pressure roller 21 described in the first to third embodiments.

  The pressure belt 53 is made of a metal material such as nickel or stainless steel, and a heat-resistant synthetic resin such as PA, PI, or PPS. A release layer may be formed on the surface of the pressure belt 53 by fluorine coating or the like.

  The recording medium P on which the toner image is formed is conveyed to a nip portion formed between the heating roller 51 and the pressure belt 53, and is fixed by passing through the nip portion.

  Next, the image forming apparatus provided with the fixing device 10 using the pressure roller of the first to third embodiments, or the fixing devices 30 to 50 using the pressure roller of the first to third embodiments. The provided image forming apparatus will be described. The configuration of the image forming apparatus is the same as that of the image forming apparatus 100 described above with reference to FIG. 8, and the fixing device 120 is the fixing device 10 or the fixing devices 30 to 50. Is in the pressure roller of the fixing device described above. Therefore, detailed description is omitted here.

  In the roller, a heat-resistant sponge rubber layer is disposed around the core metal, and the sponge rubber layer is set so that the expansion ratio decreases toward the shaft end of the roller. Provided are a fixing device capable of raising a paper to a predetermined fixing temperature in a short time without generating paper wrinkles, and an image forming apparatus including the fixing device.

FIG. 3 is a cross-sectional view illustrating the configuration of the fixing device according to the embodiment of the invention. The figure explaining the structure of the sponge rubber layer of the pressure roller of 1st Example, and the change of a foaming magnification (density). The figure explaining the structure of the sponge rubber layer of the pressure roller of 2nd Example, and the change of foaming magnification (density). The figure explaining the structure of the sponge rubber layer of the pressure roller of 3rd Example, and the change of foaming magnification (density). Sectional drawing explaining the structure of a belt fixing apparatus (the 1). Sectional drawing explaining the structure of a belt fixing apparatus (the 2). Sectional drawing explaining the structure of a belt fixing apparatus (the 3). FIG. 3 is a diagram illustrating an example of a configuration of a conventionally known image forming apparatus. Sectional drawing explaining an example of a conventionally well-known fixing device structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixing device 11 Heating roller 12 Core metal 13 Heat resistant rubber layer 14 Release layer 15 Halogen lamp 21 Pressure roller 22 Core metal 23 Sponge rubber layer 24 Release layer 30 Belt fixing device 31 Heating roller 32 Fixing roller 33 Fixing belt 34 Addition Pressure roller 40 Belt fixing device 41 Heating roller 42 Pad 43 Fixing belt 44 Pressure roller 50 Belt fixing device 51 Heating roller 52 Support member 53 Pressure belt

Claims (11)

In a heat fixing type fixing device using a pair of fixing rollers, one of the fixing rollers has a heat-resistant sponge rubber layer disposed around a cored bar, and the sponge rubber layer is disposed at a shaft end portion of the roller. A fixing device in which a foaming ratio is set to be smaller toward the head. The fixing device according to claim 1, wherein the sponge rubber layer of the fixing roller is a solid rubber layer at a shaft end portion of the roller. The fixing device according to claim 1, wherein the rubber hardness of the sponge rubber layer of the fixing roller is substantially equal from a center portion of the roller to a shaft end portion. The fixing device according to claim 1, wherein at least one of the fixing rollers has an outer diameter that is different between a central portion and a shaft end portion. One of the fixing rollers is a heating roller provided with a heat source inside a cored bar, and the other is provided with a heat-resistant sponge rubber layer around the cored bar, and the foaming ratio is set smaller toward the roller shaft end. The fixing device according to claim 1, wherein the fixing device is a pressure roller. In a heat-fixing type fixing device using a fixing belt and a pressure roller, the pressure roller has a heat-resistant sponge rubber layer disposed around a cored bar, and the sponge rubber layer is directed toward the shaft end of the roller. A fixing device in which the expansion ratio is set to be smaller. The fixing device according to claim 6, wherein the sponge rubber layer of the pressure roller is a solid rubber layer at a shaft end portion of the roller. 8. The fixing device according to claim 6, wherein the rubber hardness of the sponge rubber layer of the pressure roller is substantially equal from a central portion of the roller to a shaft end portion. 9. The fixing device according to claim 6, wherein at least one of the pressure rollers has an outer diameter that is different between a central portion and a shaft end portion. In a heat fixing type fixing device using a pressure belt and a heat roller, the heat roller has a heat-resistant sponge rubber layer disposed around the core metal, and the sponge rubber layer is directed toward the end of the roller shaft. A fixing device having a low expansion ratio. An image forming apparatus comprising the fixing device according to claim 1.

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