JP2014232287A - Method for manufacturing elastic roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an elastic roller which manufactures an inverted crown-shaped elastic roller capable of suppressing generation of wrinkles in a recording body.SOLUTION: A method for manufacturing an inverted crown-shaped elastic roller which is provided with a fluororesin tube arranged on the outer periphery of a foam elastic layer, and has such an outer diameter that the outer diameter gradually increase and is 20-40 mm at a maximum so that an outer diameter increase rate varies in one displacement point existing in a region of 50-180 nm between ends in an axial direction and the side of a center therein from the center toward each of the ends. The method for manufacturing the elastic roller includes the steps of: polishing a foam cured body arranged on the outer peripheral surface of a shaft body so that the outer diameter increases from the center in the axial direction to the displacement point, and decreases from the displacement point to the end; and covering the foam elastic layer manufactured in the polishing step with a fluororesin tube with a thickness of 20-100 μm.

Description

  The present invention relates to a method for manufacturing an elastic roller, and more particularly to a method for manufacturing an elastic roller for manufacturing an inverted crown-shaped elastic roller capable of suppressing the occurrence of wrinkles on a recording medium.

In an image forming apparatus employing an electrophotographic system such as a copying machine, when an image formed on the surface of an image carrier, such as a toner image, is transferred onto the surface of a recording medium such as transfer paper, the recording medium is fixed. An elastic roller that is sent to the apparatus and rotates while being pressed against each other in the fixing device, for example, is conveyed while being sandwiched between a fixing roller and a pressure roller, and the toner image is fixed to the surface of the recording medium by the fixing roller and the pressure roller. Fixed as an image.
In such a fixing device, at least one of the elastic roller, specifically, the fixing roller and the pressure roller has a so-called “reverse crown shape” having a small outer diameter at the center and a large outer diameter at the end. In this case, it is known that wrinkles can be prevented from occurring in the recording medium that passes through the pressure contact portion between the fixing roller and the pressure roller.

For example, the cited document 1 “provides a fixing device that has the effect of spreading the transfer paper, prevents the transfer paper from wavy, and can maintain the life of the fixing and pressure rollers for a long time”. The roller has a fixing roller and a pressure roller that rotate in pressure contact with each other. One of the rollers is cut into a predetermined amount on the outer periphery of both ends of the roller shaped in an inverted crown shape, and the maximum diameter portion of the roller is set at the end of the roller. The fixing device is characterized in that it is formed at a predetermined distance from the part ”(the second page, upper right column, lines 5 to 9 and claims, etc.).
Further, cited document 1 describes “a pressure roller 120 formed in an inverted crown shape with a central portion having a minimum diameter and both end portions having a maximum diameter” (first page, right column, line 13 to line 13). 18th line and FIG. 6). Note that the reverse crown-shaped pressure roller 120 shown in FIG. 6 and the fixing roller and pressure roller of Patent Document 1 do not include a fluororesin tube.

  Cited Document 2 states that “in order to prevent the transfer material P from being wrinkled, the outer diameter of the central portion in the longitudinal direction is smaller than the maximum outer diameter portion, and the maximum outer diameter is There is described a fixing roller 10 ”in which the diameter portion is located inside the both ends in the longitudinal direction (paragraph number 0024 column and FIG. 3 and the like). Cited Document 2 describes a roller that is “configured in a so-called inverted crown shape in which the outer diameter at both ends in the longitudinal direction is the maximum and the outer diameter at the center is the minimum” (column 0002 and FIG. 7, etc.). .

  By the way, the cited document 1 also includes a description of a specific manufacturing method of the reverse crown-shaped pressure roller 120 shown in FIG. No manufacturing method other than the method of “cutting” is described. Also, in the cited document 2, there is no description regarding the “fixing roller 10” and the manufacturing method of the reverse crown-shaped roller shown in FIG.

  Of the elastic roller for fixing device, a reverse crown-shaped roller having a surface layer such as a fluororesin tube is usually manufactured by covering the elastic layer having a shape corresponding to a desired reverse crown shape with a fluororesin tube or the like. .

JP-A-2-262684 Japanese Patent Laid-Open No. 7-121045

  However, reverse crown-shaped rollers having a surface layer generally cover the elastic layer with a fluororesin tube having an outer diameter smaller than that of the elastic layer in consideration of adhesion between the elastic layer and the fluororesin tube. It is. However, a roller obtained by coating a fluororesin tube on an elastic layer formed to have a desired reverse crown shape sometimes deviates from the desired reverse crown shape and cannot suppress the occurrence of wrinkles on the recording medium. .

  Accordingly, an object of the present invention is to provide an elastic roller manufacturing method for manufacturing an inverted crown-shaped elastic roller capable of suppressing the occurrence of wrinkles on a recording medium.

Means for solving the problems are as follows:
(1) A fluororesin tube disposed on the outer periphery of the foamed elastic layer, and having one displacement point existing in a region of 50 to 180 mm from the end to the center from the center to the end in the axial direction. A method for producing an inverted crown-shaped elastic roller having a maximum outer diameter of 20 to 40 mm so that the outer diameter increase rate changes gradually,
Polishing the foam cured body disposed on the outer peripheral surface of the shaft body so that the outer diameter increases from the center in the axial direction to the displacement point and decreases from the displacement point to the end;
Covering the foamed elastic layer produced in the polishing step with a fluororesin tube having a thickness of 20 to 100 μm.
(2) In the polishing step, the outer diameter difference between the central portion and the displacement point is 0.01 to 0.3 mm, and the outer diameter difference between the displacement point and the end portion is 0.01 to 0.3 mm. And polishing the foamed cured body so that the maximum outer diameter is 20 to 40 mm, and the outer diameter difference between the central portion and the displacement point is 0.10 to 0.20 mm, and the displacement point and the end. The outer diameter difference from the part is more than 0.00 mm and 0.10 mm or less, and the method for producing an elastic roller according to (1),
(3) The foamed cured product has an Asker C hardness (load 1.0 kg) of 20 to 60, an average cell diameter of 50 to 400 μm, and a density of 0.395 to 0.7 g / cm ³ . It is a manufacturing method of the elastic roller of Claim 1 or 2.

  In the elastic roller manufacturing method according to the present invention, the outer diameter of the foamed cured body disposed on the outer peripheral surface of the shaft body increases from the center in the axial direction to the displacement point, and decreases from the displacement point to the end. And the step of covering the foamed elastic layer produced in the step of polishing with a fluororesin tube having a thickness of 20 to 100 μm. A fluororesin tube is provided, and the outer diameter is changed so that the outer diameter increase rate changes at one displacement point existing in the region of 50 to 180 mm from the end portion toward the center side from the center to the end portion in the axial direction. An inverse crown-shaped elastic roller having a maximum diameter of 20 to 40 mm can be produced. The inventors of the present invention have confirmed that when the elastic roller has such an inverted crown shape, wrinkles on the recording medium can be suppressed when the elastic roller is mounted on the fixing device as an elastic roller for the fixing device. Yes. Therefore, according to the present invention, it is possible to provide an elastic roller manufacturing method for manufacturing an inverted crown-shaped elastic roller capable of suppressing the occurrence of wrinkles on the recording medium.

FIG. 1 is a schematic front view showing an example of an elastic roller manufactured by the elastic roller manufacturing method according to the present invention. FIG. 2 is a schematic sectional view showing an example of an elastic roller manufactured by the elastic roller manufacturing method according to the present invention. FIG. 3 is a schematic sectional view showing a roller base used in the method for manufacturing an elastic roller according to the present invention. FIG. 4 is a schematic explanatory view showing a fixing device and an image forming apparatus provided with an elastic roller manufactured by the elastic roller manufacturing method according to the present invention.

  First, an elastic roller manufactured by the elastic roller manufacturing method according to the present invention (hereinafter sometimes referred to as an elastic roller according to the present invention) will be described. The elastic roller according to the present invention is an elastic roller for a fixing device mounted on a fixing device of an image forming apparatus, and specifically, along an axial direction with each other via another member, for example, an endless belt, if desired. These are so-called “pressure rollers” or so-called “heating rollers” arranged so as to be in pressure contact with each other. The elastic roller according to the present invention includes a foamed elastic layer disposed on the outer peripheral surface of the shaft body and a fluororesin tube disposed on the outer peripheral surface of the foamed elastic layer. The elastic roller according to the present invention only needs to have the above-described configuration, and may include an adhesive layer, a surface layer, and the like in addition to the foamed elastic layer and the fluororesin tube.

  The elastic roller according to the present invention has a maximum outer diameter of 20 to 40 mm, preferably 25 to 35 mm, in view of being made more compact and lighter than at present.

  In the elastic roller according to the present invention, the axial length of the foamed elastic layer is usually 300 to 360 mm. The elastic roller according to the present invention has an outer diameter from the center in the axial direction, that is, from the middle point on the axis of the elastic roller to the end, so that wrinkles can be prevented from occurring in the recording medium when mounted on the fixing device. In addition, it has an inverted crown shape that gradually increases toward the center, and further has an inverted crown shape in which the outer diameter increase rate changes at one displacement point located in the region of 50 to 180 mm from the end to the center. doing. That is, the elastic roller according to the present invention has a first increasing portion in which the outer diameter increases from the center portion to the displacement point at the first outer diameter increasing rate, and the outer diameter from the displacement point to the end portion is the first outer diameter increasing rate A second increasing portion that increases at a larger second outer diameter increasing rate, and a sectional shape that appears when the elastic roller is cut along a plane passing through the axis is substantially in the axial direction centering on the midpoint. Is symmetrical. As described above, the elastic roller according to the present invention has a structure in which the frustoconical first increasing portion and the frustoconical second increasing portion are connected. Here, “substantially symmetric” does not mean that it is geometrically exactly symmetric, but may be symmetric within a range in which the object of the present invention can be achieved. It may be within 1 mm. This displacement point is a circumference in which the first increasing portion and the second increasing portion are connected, that is, a displacement periphery, and is capable of suppressing the occurrence of wrinkles on the recording medium when mounted on the fixing device. It is preferable that it exists in the area | region of 30-60 mm toward the center side.

  In the elastic roller according to the present invention, the outer diameter difference between the outer diameter of the central portion and the outer diameter of the displacement point, that is, the outer diameter difference of the first increasing portion is 0.10 to 0.20 mm. The outer diameter difference between the outer diameter of the displacement point and the outer diameter of the end portion, that is, the outer diameter difference of the second increasing portion is more than 0.00 mm and not more than 0.10 mm, and is preferably 0.01 to 0.00 mm. It is preferably 05 mm. When the outer diameter difference of the first increasing portion and the outer diameter difference of the second increasing portion are within the above ranges, the occurrence of wrinkles on the recording medium can be suppressed.

  The elastic roller according to the present invention having such a reverse crown shape is mounted as a pressure roller or a fixing roller on a fixing device of an image forming apparatus. In particular, the recording medium is suitably mounted on a fixing device of a high-definition high-speed image forming apparatus in that wrinkles can be suppressed.

  The elastic roller according to the present invention preferably has an Asker C hardness (load 1.0 kg) of 40 to 60. When the Asker C hardness (load 1.0 kg) of the pressure roller 1A is less than 40, there is a problem that the developer cannot be crushed and not fixed well, and the hardness balance with the fixing roller is poor. When mounted on the fixing device, a sufficient nip pressure with the fixing roller cannot be ensured, and the developer may not be fixed on the recording member as desired. The Asker C hardness (load 1.0 kg) of the pressure roller is preferably 45 to 60, and particularly preferably 50 to 55, from the viewpoint of ensuring a sufficient nip pressure with the fixing roller. Asker C hardness (1.0 kg load) is a state in which a load of 1.0 kg is applied in accordance with JIS K6253 with the outer peripheral surface of the fluororesin tube disposed on the outer peripheral surface of the central portion of the foamed elastic layer as a measurement point. It is a measured value. The Asker C hardness of the pressure roller can be selected, for example, by selecting the type of rubber, foaming agent and / or additive contained in the foamed rubber composition forming the foamed elastic layer, and / or the blending amount thereof. By changing, it can be further adjusted according to the molding conditions of the foamed elastic layer.

The elastic roller according to the present invention will be specifically described. As shown in FIGS. 1 and 2, an elastic roller 1 as an example of the elastic roller according to the present invention includes a shaft body 2, a foamed elastic layer 3 disposed on the outer peripheral surface of the shaft body 2, and FIG. 2. As shown, a fluororesin tube 4 arranged on the outer peripheral surface of the foamed elastic layer 3 is provided.
The shaft body 2 only needs to have good conductive properties, and is usually a so-called “core metal” composed of iron, aluminum, stainless steel, brass, or the like. Further, the shaft body 2 may be a shaft body that is made conductive by plating an insulating core body such as a thermoplastic resin or a thermosetting resin. Furthermore, the shaft body 2 may be a thermoplastic resin or a thermosetting resin. The shaft body may be formed of a conductive resin in which carbon black or metal powder is blended as a conductivity imparting agent.

  The foamed elastic layer 3 has cells inside and / or on the outer peripheral surface (the cells opened on the outer peripheral surface of the foamed elastic layer 3 are not shown in FIGS. 1 and 2). Here, the cell which the foaming elastic layer 3 has refers to the hollow area | region produced by foaming or decomposition | disassembly of the foaming agent contained in a foamed rubber composition. The plurality of cells included in the foamed elastic layer 3 are in a state where they do not contact or communicate with other cells (referred to as independent cell states) and are connected to other cells (referred to as connected cell states). .), Or the independent cell state and the communication cell state may coexist. The communication cell is superior in avoiding bubble breakage, and the independent cell is excellent in terms of good resilience. In this invention, the cell of the foamed elastic layer can be a continuous cell as long as a specific impact resilience is obtained, but is preferably in an independent cell state.

  The foam elastic layer 3 has an Asker C hardness (load 1.0 kg) of preferably 20 to 60, particularly preferably 25 to 45. When the Asker C hardness of the foamed elastic layer 3 is within the above range, the nip width is appropriately maintained, and an effect that the optimum value can be maintained in the torque can be obtained. The Asker C hardness (1.0 kg load) is a value obtained by measuring a plurality of locations in accordance with JIS K6253 and arithmetically averaging the measured values.

The foamed elastic layer 3 preferably has an average cell diameter of 50 to 400 μm, particularly preferably 70 to 200 μm. When the foamed elastic layer 3 has an average cell diameter within the above range, the elastic roller can be adjusted to a desired reverse crown shape in cooperation with the fluororesin tube, and the effect that the image quality is kept optimal is obtained. It is done. For example, when the average cell diameter is increased, the reverse crown shape of the elastic roller tends to become unstable due to the fluffing and unstable.
The average cell diameter is the surface of the foamed elastic layer or an area of about 20 mm ^{2 on} the cut surface when cut by an arbitrary surface, and the maximum length of the opening in each cell existing in the observation field is observed with an electron microscope or the like. It can be determined as an average length obtained by arithmetic averaging of the measured maximum length.

The foamed elastic layer 3 preferably has an expansion ratio of 105 to 400%, particularly preferably 200 to 300%. When the foamed elastic layer 3 has a foaming ratio within the above range, an effect is obtained that the elastic roller can be adjusted to a desired inverted crown shape in cooperation with the fluororesin tube. For example, when the expansion ratio is increased, the reverse crown shape of the elastic roller has a low hardness, and therefore tends to be easily affected by the shrinkage of the fluororesin tube.
The expansion ratio can be calculated from the volume and mass of the foamed elastic layer measured by a conventional method.

The foamed elastic layer 3 preferably has a density of 0.395 to 0.7 (g / cm ³ ), particularly preferably 0.42 to 0.6 (g / cm ³ ). When the foamed elastic layer 3 has a density within the above range, the elastic roller can be adjusted to a desired inverted crown shape in cooperation with the fluororesin tube, the thermal conductivity can be lowered, and the heat capacity of the roll can be reduced. The effect that it can raise is acquired. For example, when the density is increased, the inverse crown shape of the elastic roller increases the hardness of the foamed elastic layer and tends to be less susceptible to shrinkage.
In the foamed elastic layer, the average cell diameter, the expansion ratio and the density can be adjusted by the foaming agent contained in the foamed rubber composition forming the foamed elastic layer or the curing conditions of the foamed rubber composition.

  The fluororesin tube has a thickness of 20 to 150 [mu] m, preferably 30 to 100 [mu] m in that the effect that the elastic roller can be adjusted to a desired inverted crown shape in cooperation with the foamed elastic layer 3 is obtained. .

  The fluororesin tube has an inner diameter that is constant in the axial direction and has a difference from the outer diameter of the end portion of the foamed elastic layer 3 of preferably 0.1 to 2 mm, particularly preferably 0.5 to 1.5 mm. ing. When the fluororesin tube has an inner diameter in the above range, the elastic roller can be adjusted to a desired reverse crown shape in cooperation with the foamed elastic layer 3, and the effect that wrinkles are hardly generated on the surface of the fluororesin tube is obtained. can get. For example, when the inner diameter is increased, the reverse crown shape of the elastic roller tends not to be achieved. The outer diameter of the fluororesin tube is appropriately determined depending on the thickness and inner diameter.

  When the fluororesin tube has contractibility, the elastic roller can be adjusted to a desired reverse crown shape in cooperation with the foamed elastic layer 3, and the effect that wrinkles are hardly generated on the surface of the fluororesin tube is obtained. It is preferable that it is +3 to -3% in the longitudinal direction and +5 to -5% in the circumferential direction, +2 to -2% in the longitudinal direction, and +3 to -3% in the circumferential direction in that it is obtained. .

  Further, the elongation at break of the fluororesin tube is preferably from 150 to 500%, particularly preferably from 200 to 350%. The elongation at break is the same as the dumbbell-shaped No. 3 test piece (JIS K6251) defined in JIS K6891 cut out from the fluororesin tube. It is a value measured under the conditions of a tensile speed of 200 mm / min and a measurement temperature of 25 ± 2 ° C. based on JIS K6891.

  Further, the breaking strength of the fluororesin tube is preferably 3 to 150 MPa. This breaking strength is in accordance with JIS K6891 dumbbell-shaped No. 3 test piece cut out from the fluororesin tube (in accordance with JIS K6251. However, the dumbbell-shaped No. 3 test piece has its longitudinal direction in the axial direction of the resin tube, that is, the longitudinal direction. It is a value measured under the conditions of a tensile speed of 200 mm / min and a measurement temperature of 25 ± 2 ° C. based on JIS K6891. Thus, the said breaking strength and the said breaking elongation are the breaking strength and breaking elongation in the axial direction of a resin tube, ie, a longitudinal direction.

  The fluororesin tube only needs to be formed of fluororesin, for example, PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene-hexafluoropropylene resin), PTFE (polytetrafluoroethylene resin), PVdF (polyfluoride). Vinylidene resin) and the like, and PFA (perfluoroalkoxy resin) is particularly preferable.

  A method for manufacturing the elastic roller according to the present invention will be described. The elastic roller manufacturing method according to the present invention can manufacture the elastic roller according to the present invention, that is, the inverted crown-shaped elastic roller.

  In the elastic roller manufacturing method according to the present invention, the foamed and hardened body disposed on the outer peripheral surface of the shaft body increases in outer diameter from the center in the axial direction to the displacement point, and decreases from the displacement point to the end. Thus, it has the process of grind | polishing, and the process of coat | covering the foaming elastic layer produced by the said grind | polishing process with the fluororesin tube whose thickness is 20-100 micrometers.

  As an example of the method for manufacturing the elastic roller according to the present invention, a method for manufacturing the elastic roller 1 (hereinafter sometimes referred to as one manufacturing method) will be described.

  In this manufacturing method, first, an original roller body having a foamed cured body disposed on the outer peripheral surface of the shaft body 2 is produced. This roller base is produced in a process in which a foamed rubber composition is formed by foaming and curing the foamed rubber composition on the outer peripheral surface of the shaft body.

  In one manufacturing method, after preparing the shaft body 2, the foamed rubber composition is heat-molded on the outer peripheral surface of the shaft body 2 by continuous heat molding by extrusion molding, pressing, mold molding by injection, or the like.

  In the thermoforming of the foamed rubber composition, first, the foamed rubber composition is disposed on the outer peripheral surface of the shaft body 2. As a method of disposing the foamed rubber composition on the outer peripheral surface of the shaft body 2, for example, the shaft body 2 and the foamed rubber composition are integrally extracted by an extruder or the like, and the foamed rubber composition is formed on the outer peripheral surface of the shaft body 2. And a method of injecting the foamed rubber composition into a mold for housing the shaft body 2 and disposing the foamed rubber composition on the outer peripheral surface of the shaft body 2. Among these, the method of integrally dispensing the shaft body 2 and the foamed rubber composition with an extruder or the like is preferable because the operation is easy and can be performed continuously.

  The foamed rubber composition is preferably a composition containing rubber, a foaming agent, and various additives as required. Various rubbers can be adopted as the rubber, and among these, silicone rubber is preferable. As a foamed rubber composition containing silicone rubber, it contains a vinyl group-containing silicone raw rubber, a silica-based filler, a foaming agent, an addition reaction crosslinking agent, an addition reaction catalyst, and a reaction control agent. Furthermore, an addition reaction type foamed silicone rubber composition containing an organic peroxide crosslinking agent, a heat resistance improver, and various additives is preferable. Examples of such an addition reaction type foamed silicone rubber composition include an addition reaction type foamed silicone rubber composition described in JP-A-2008-076751.

  After disposing the foamed rubber composition on the outer peripheral surface of the shaft body 2 in this manner, the foamed rubber composition is heated together with the shaft body 2 while maintaining this state. Heating of the foamed rubber composition may be performed under conditions sufficient for the rubber contained in the foamed rubber composition, for example, a vinyl group-containing silicone raw rubber to crosslink and contain a foaming agent, to decompose or foam. For example, the addition reaction type foamed silicone rubber composition is usually heated to about 170 to 500 ° C., particularly 200 to 400 ° C. by a heating furnace such as an infrared heating furnace or a hot air furnace, a heating machine such as a dryer, and the like, for several minutes. It is heated for 1 hour or less, particularly 5 to 30 minutes. The foamed rubber composition may be further subjected to secondary heating as desired. The physical properties of the foamed elastic layer 3 are stabilized by the secondary heating. In the secondary heating, for example, the foamed rubber composition cross-linked under the above-described conditions is further extruded, for example, at 180 to 250 ° C., preferably 190 to 230 ° C., for 1 to 24 hours. , Preferably for 3 to 10 hours, or using a mold, for example, 130 to 200 ° C., preferably 150 to 180 ° C., for 5 minutes to 24 hours, preferably 10 minutes to 10 hours again This is done by heating.

  Thus, the foaming hardening body arrange | positioned at the outer peripheral surface of the shaft body 2 has the same Asker C hardness (load 1.0kg), average cell diameter, foaming magnification, and density as the foaming elastic layer 3. Yes.

  Next, in the manufacturing method, a step of polishing the foam cured body of the roller original is performed. The polishing step is performed so that the outer diameter after polishing increases from the center in the axial direction to a displacement point corresponding to the displacement point of the elastic roller to be manufactured and decreases from this displacement point to the end. Is made into a foamed elastic layer. That is, as shown in FIG. 3, the foamed elastic layer 3 is composed of a frustoconical outer diameter increasing layer in which the outer diameter gradually increases from the center in the axial direction toward the end of the foam elastic layer 3 and the displacement point. An outer frustoconical shape having an inverted frustoconical shape whose outer diameter gradually decreases to the end. The foamed elastic layer 3 has a maximum outer diameter in the range of 20 to 40 mm, and an outer diameter difference between the central portion and the displacement point, that is, an outer diameter difference of the outer diameter increasing layer is 0.01 to 0.70 mm. The outer diameter difference between the displacement point and the end, that is, the outer diameter difference of the outer diameter reducing layer is 0.01 to 0.10 mm. When the foamed cured body is polished in such a shape and size, an elastic roller having a desired reverse crown shape can be manufactured in cooperation with the foamed elastic layer 3. Here, the maximum outer diameter is preferably 25 to 36 mm, the outer diameter difference of the outer diameter increasing layer is preferably 0.05 to 0.5 mm, and the outer diameter difference of the outer diameter decreasing layer is 0.02. It is preferably ~ 0.05 mm. Polishing of the foamed cured product is performed dry or wet using a polishing machine, a grinding machine or the like, and the conditions are not particularly limited.

  In this one manufacturing method, a fluororesin tube is prepared. The fluororesin tube is as described above.

  In this manufacturing method, the prepared fluororesin tube is then placed on the foamed elastic layer 3 of the roller base. At this time, an adhesive may or may not be applied to the outer peripheral surface of the foamed elastic layer and the inner peripheral surface of the fluororesin tube.

  The arrangement of the fluororesin tube is, for example, a pressure insertion method in which the foamed elastic layer is compressed and inserted into the fluororesin tube under pressure, a vacuum insertion method in which the foamed elastic layer is compressed and inserted into the fluororesin tube under reduced pressure, It can be carried out by a reduced-pressure expanding method or the like in which the fluororesin tube is radially expanded under reduced pressure and a foamed elastic layer is inserted therein. In addition, when the hardness of the foamed elastic layer is high, the reduced pressure insertion method or the reduced pressure diameter expansion method is more preferable than the pressure insertion method in that the foamed elastic layer can be quickly inserted into the fluororesin tube. The pressure environment in the pressure insertion method can be set to, for example, 0.15 to 0.48 MPa, and the pressure reduction environment in the pressure insertion method can be set to, for example, 3 hPa. Further, in the reduced pressure expanding method, a reduced pressure environment for expanding the diameter of the fluororesin tube includes, for example, a reduced pressure environment of 0.3 to 1.0 MPa. After inserting the foamed elastic layer into the expanded diameter fluororesin tube, the reduced pressure environment When is released, the fluororesin tube is placed in close contact with the outer peripheral surface of the foamed elastic layer. In this arranging step, when the adhesive is not applied to the foamed elastic layer, it is not necessary to stretch the fluororesin tube more than necessary, and the problem of durability deterioration due to the thinning of the fluororesin tube described above is a problem. It can be prevented beforehand. Examples of the pressure device in the pressure insertion method include “pressure device 10” shown in FIGS. 4 and 5 of JP-A-2008-299185, and the pressure reduction device in the pressure insertion method includes, for example, Examples thereof include “decompression device 30” shown in FIGS. 6 and 7 of JP-A-2008-299185.

  When the foamed elastic layer 3 is covered with the fluororesin tube in this manner, the foamed elastic layer 3 having the outer diameter increasing layer and the outer diameter decreasing layer is compressed by the fluororesin tube, and the outer diameter increasing layer and the outer diameter decreasing layer are compressed. The joint portion, that is, the displacement point, contracts until it becomes smaller than the maximum outer diameter, that is, the end outer diameter of the outer diameter-reducing layer. The foamed elastic layer 3 thus contracted has the same reverse crown shape and dimensions as the elastic roller 1.

  When the foamed hardened body of the roller original is polished to a predetermined shape and dimensions in this way, the foamed elastic layer 3 is contracted and deformed into a desired inverse crown shape only by being coated with a fluororesin tube having a thickness of 20 to 100 μm. . In this way, the elastic roller 1 can be manufactured.

Since the elastic roller according to the present invention has a desired reverse crown shape and dimensions, the object of the present invention can be well achieved.
The method of manufacturing the elastic roller according to the present invention is not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved.

Next, a fixing device (hereinafter sometimes referred to as a fixing device according to the present invention) including an elastic roller according to the present invention and an image forming device (hereinafter referred to as an image forming device according to the present invention) may be referred to. ) Will be described with reference to FIG.
As shown in FIG. 4, an image forming apparatus 30 according to the present invention includes a rotatable image carrier 31 on which an electrostatic latent image is formed, for example, a photoconductor, and a periphery of the image carrier 31. The charging unit 32 includes a charging roller, an exposure unit 33, a developing unit 40, a transfer unit 34 such as a transfer roller and a cleaning unit 37, and a fixing device 35 on the downstream side in the conveyance direction of the recording medium. The developing means 40 is formed basically in the same manner as the conventional developing means. Specifically, as shown in FIG. 2, the developer accommodating portion 41 and the developer 42 are supplied to the image carrier 31. A developer carrier 44, a developer supply unit 43 that supplies the developer 42 to the developer carrier 44, and a developer regulating member 45 that charges the developer 42 are provided.
A conventional fixing device in an image forming apparatus usually has a fixing roller having a low hardness and a pressure roller having a high hardness to ensure a nip width and a nip pressure. As described above, the heating having the low hardness fixing roller 53 having an Asker C hardness (load 1.0 kg) in the range of 20 to 35 and the low hardness pressure roller 56 which is an example of the pressure roller according to the present invention. It is a fixing device. That is, the fixing device 35 has a fixing roller 53 and an endless arrangement disposed in the vicinity of the fixing roller 53 in a casing 50 having an opening 52 through which the recording medium 36 passes, as shown in a cross section in FIG. A belt support roller 54, an endless belt 55 wound around the fixing roller 53 and the endless belt support roller 54, a pressure roller 56 that presses the fixing roller 53 via the endless belt 55, and a contactless contact with the endless belt 55. And a heating unit 57 that heats the fixing roller 53 from the outside via the endless belt 55, so that the fixing roller 53 and the pressure roller 56 are in contact with or pressed against each other via the endless belt 55. It is a pressure heat fixing device which is supported in a freely rotatable manner.
The endless belt support roller 54 may be a roller that is normally used in an image forming apparatus. For example, an elastic roller or the like is used. The endless belt 55 may be an endless belt made of, for example, a resin such as polyamide or polyamideimide, and the thickness and the like of the endless belt 55 can be appropriately adjusted to match the fixing device 35. The pressure roller 56 is in pressure contact with the fixing roller 53 via an endless belt 55 by an urging means (not shown) such as a spring. In the fixing device 35, the pressure roller according to the present invention is mounted as the pressure roller 56. The heating means 57 employs a radiant heating method using a halogen heater, a reflector, or the like, a direct contact heating method in which a heater or the like is directly contacted to heat, an induction heating method, or the like. The heating means 57 is a member having a length substantially the same as the length of the fixing roller 53 in the axial direction, and may be disposed in any of the fixing devices 35. However, as shown in FIG. It is preferable that the fixing roller 53 is arranged substantially in parallel with a certain distance from the surface. In the induction heating method, a heating coil is used, and this heating coil is usually a ferromagnetic material such as ferrite, and is a typical shape used for a switching power source. It is formed into a mold or the like, and is formed by winding a conducting wire. By passing the recording medium 36 between the endless belt 55 and the pressure roller 56, the recording medium 36 is heated simultaneously with the pressurization, and the developer 42 (electrostatic latent image) transferred to the recording medium 36 is fixed. be able to.
The image forming apparatus 30 according to the present invention operates as follows. First, in the image forming apparatus 30, the image carrier 31 is uniformly charged by the charging unit 32, and an electrostatic latent image is formed on the surface of the image carrier 31 by the exposure unit 33. Next, the developer 42 is supplied from the developing unit 40 to the image carrier 31 to develop the electrostatic latent image, and the developer image is conveyed between the image carrier 31 and the transfer unit 34 on the recording member 36. Is transcribed. The recording body 36 is conveyed to the fixing device 35 and the developer image is fixed on the recording body 36 as a permanent image. In this way, an image can be formed on the recording body 36.
Since the pressure roller according to the present invention is employed as the pressure roller 56 in the fixing device 35 and the image forming apparatus 30 according to the present invention, the fixing device 35 and the image forming apparatus 30 are excellent in fixing property for fixing the developer on the recording medium and consume less power. .
The pressure roller, the fixing device, and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved.
For example, in the pressure roller 1, the foamed elastic layer 3 has a single layer structure, but in the present invention, it may have a multilayer structure of two or more layers.
The image forming apparatus 30 is an electrophotographic image forming apparatus. However, in the present invention, the image forming apparatus is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Good. Further, the image forming apparatus 30 is a monochrome image forming apparatus in which the developing unit 40 contains only a single color developer 42. However, in this invention, the image forming apparatus is not limited to a monochrome image forming apparatus. It may be an image forming apparatus. As the color image forming apparatus, for example, a four-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier to an intermediate transfer body, and a plurality of image carriers provided with developing means for each color And a tandem type color image forming apparatus in which the toner is disposed in series on an intermediate transfer member or a transfer conveyance belt. The image forming apparatus 30 is an image forming apparatus such as a copying machine, a facsimile machine, or a printer.
In the fixing device 35 and the image forming apparatus 30, the developer 42 is advantageously a one-component developer, but a two-component developer containing a toner and a carrier such as iron or nickel is also used. can do.

Example 1
A shaft body (diameter 17 mm × length 370 mm, SUM22) subjected to electroless nickel plating was washed with toluene, and a primer “No. 101A / B” (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name) was applied. The primer-treated shaft body was baked at a temperature of 180 ° C. for 30 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer.

  100 parts by weight of a mixture of a vinyl group-containing silicone raw rubber and a silica-based filler (silicone rubber composition “KE-904FU” manufactured by Shin-Etsu Chemical Co., Ltd.), an addition reaction crosslinking agent “C-153A” (Shin-Etsu Chemical Co., Ltd.) Manufactured by: product name) 2.0 parts by weight, an appropriate amount of platinum catalyst as an addition reaction catalyst, 1.0 part by weight of an organic foaming agent “azobis-isobutyronitrile”, and a reaction control agent “R-153A” ( Shin-Etsu Chemical Co., Ltd .: trade name) 0.5 parts by mass and organic peroxide cross-linking agent “C-3” (Shin-Etsu Chemical Co., Ltd .: trade name) 3 parts by mass with two appropriate amounts The addition reaction type non-foamed silicone rubber composition was prepared by sufficiently kneading with a roll.

  Subsequently, the shaft body 2 on which the primer layer is formed and the prepared addition reaction type foamed silicone rubber composition are integrally extracted by an extrusion molding machine, and the addition reaction type foamed silicone rubber composition using an infrared heating furnace (IR furnace). Was foamed and crosslinked at 250 ° C. for 10 minutes. Thereafter, the addition reaction type foamed silicone rubber composition after foaming and crosslinking was further heated at 200 ° C. for 7 hours using a gear oven, and left at room temperature for 1 hour or more to prepare a roller base. . The roller cured body of this roller base had a straight shape with an outer diameter of 30 mm and an axial length of 340 mm.

Next, this foamed cured body was ground with a cylindrical grinder so as to become an outer diameter increasing portion and an outer diameter decreasing portion having the following dimensions to obtain a substantially plane-symmetric foamed elastic layer.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the outer diameter increased portion: 25.07 mm
Maximum outer diameter of the outer diameter increasing portion and maximum outer diameter of the outer diameter decreasing portion (outer diameter of the displacement point): 25.21 mm
Minimum outer diameter of outer diameter reduced portion (end outer diameter): 25.19 mm
Difference in outer diameter between the center and the displacement point: 0.14 mm
Difference in outer diameter between the displacement point and the end: 0.019 mm

The cured foam and the foamed elastic layer had an Asker C hardness (load 1.0 kg) of 36, an average cell diameter of 150 μm, an expansion ratio of 290%, and a density of 0.5 g / cm ³ .

  Next, a PFA tube having contractility was prepared. This PFA tube has an axial length of 312 mm, an inner diameter of 24 mm, and a thickness of 30 μm. The difference between the inner diameter and the outer diameter of the end portion of the foamed elastic layer 3 is 0.5 to 1.5 mm, and the degree of shrinkage is −1.8. %Met.

Next, this PFA tube was placed on the outer peripheral surface of the foamed elastic layer 3 as described above to produce an elastic roller. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions, and the Asker C hardness (load 1.0 kg) was 49.
Length of elastic roller in axial direction: 340mm
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increasing portion: 24.88 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 25.00 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 25.05 mm
Difference in outer diameter between the center and the displacement point: 0.12 mm
Difference in outer diameter between the displacement point and the end: 0.05 mm

(Example 2)
An elastic roller was manufactured basically in the same manner as in Example 1 except that the thickness of the PFA tube was 50 μm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increased portion: 24.83 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 24.98 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 25.05 mm
Difference in outer diameter between the center and the displacement point: 0.15 mm
Difference in outer diameter between the displacement point and the end: 0.07 mm

Example 3
An elastic roller was manufactured basically in the same manner as in Example 1 except that the thickness of the PFA tube was changed to 100 μm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increased portion: 24.78 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 24.95 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 25.04 mm
Difference in outer diameter between the center and the displacement point: 0.17 mm
Difference in outer diameter between the displacement point and the end: 0.09 mm

Example 4
An elastic roller was manufactured basically in the same manner as in Example 1 except that the displacement point was changed from the end to the center side of 80 mm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 80mm from the end to the center
Minimum outer diameter (center outer diameter) of the first increased portion: 24.86 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 25.03 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 25.05 mm
Difference in outer diameter between the center and the displacement point: 0.17 mm
Difference in outer diameter between the displacement point and the end: 0.02 mm

(Example 5)
An elastic roller was manufactured basically in the same manner as in Example 1 except that the maximum outer diameter was changed to 32 mm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increasing portion: 31.89 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 32.01 mm
Maximum outer diameter of second increasing portion (end outer diameter and maximum outer diameter): 32.05 mm
Difference in outer diameter between the center and the displacement point: 0.12 mm
Difference in outer diameter between the displacement point and the end: 0.04 mm

(Example 6)
An elastic roller was manufactured basically in the same manner as in Example 1 except that a non-shrinkable PFA tube was used. This PFA tube had an axial length of 312 mm, an inner diameter of 24 mm, and a thickness of 30 μm, and the difference between the inner diameter and the outer diameter of the end portion of the foamed elastic layer 3 was 0.5 to 1.5 mm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increasing portion: 24.93 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 25.01 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 25.06 mm
The outer diameter difference between the center and the displacement point: 0.08mm
Difference in outer diameter between the displacement point and the end: 0.05 mm

(Comparative example 1: outer diameter less than 20 mm)
An elastic roller was manufactured basically in the same manner as in Example 1 except that the maximum outer diameter was changed to 18 mm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increased portion: 17.88 mm
Maximum outer diameter of the first increase portion and minimum outer diameter (displacement point outer diameter) of the second increase portion: 18.00 mm
Maximum outer diameter (end outer diameter and maximum outer diameter) of the second increased portion: 18.05 mm
Difference in outer diameter between the center and the displacement point: 0.12 mm
Difference in outer diameter between the displacement point and the end: 0.05 mm

(Comparative Example 2)
An elastic roller was produced basically in the same manner as in Example 1 except that the foamed cured product was polished into a straight shape having an outer diameter of 25 mm. The obtained elastic roller had a plane-symmetric inverted crown shape having a first increasing portion and a second increasing portion having the following dimensions.
Displacement point: 51.5mm from end to center
Minimum outer diameter (center outer diameter) of the first increasing portion: 24.65 mm
Maximum outer diameter of the first increasing portion and minimum outer diameter (displacement point outer diameter) of the second increasing portion: 25.00 mm
Maximum outer diameter of second increasing portion (end outer diameter and maximum outer diameter): 25.12 mm
Difference in outer diameter between the center and the displacement point: 0.35 mm
Difference in outer diameter between the displacement point and the end: 0.12 mm

(Wrinkle generation)
The pressure rollers manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 were pressed against the heating roller set at a surface temperature of 185 ° C. (the sum of the radius of the pressure roller and the radius of the heating roller and the pressure contact). A pressure difference was applied in parallel along the axial direction so that the difference with the distance between the subsequent axes was 1.065 mm (compression ratio with respect to the thickness of the end portion 11A of the foamed elastic layer 3 was 30%). The state of the fluororesin tube 4 in each pressure roller was evaluated after rotating the fixing roller at a rotation speed of 180 rpm for 24 hours while maintaining this pressure contact state. Specifically, while the pressure roller after being rotated is at a temperature of 60 ° C. or higher, the surface is checked for the presence of wrinkles, cracks, etc. (in Table 1, “evaluation of occurrence of wrinkles”) To do.) The evaluation criteria are “」 ”when the fluororesin tube 4 cannot visually confirm any wrinkles, cell patterns, or cracks, and the fluororesin tube 4 is glossy. “◯” when visually confirmed, “△” when only wrinkles that are practically acceptable for the fluororesin tube 4 are visually confirmed, “cell” when the fluororesin tube 4 is not acceptable for practical use. In addition to the wrinkles, cracks can be visually confirmed, and the case where the fluororesin tube 4 does not have gloss is defined as “x”. When this evaluation is “Δ” or more, the state of the fluororesin tube is acceptable in practice even in an actual machine test.

30 Image forming apparatus 31 Image bearing member 32 Charging unit 33 Exposure unit 34 Transfer unit 35 Fixing unit 36 Transfer target member 37 Cleaning unit 40 Developing unit 41 Developer storage unit 42 Developer 43 Developer supply unit 44 Developer carrier 45 Development Agent regulating member 50 Housing 52 Opening 53 Fixing roller 54 Endless belt support roller 55 Endless belt 56 Pressure roller 57 Heating means 70 Testing machine 71 Heating roller 72 Internal heater 73 External heater 74 Test roller mounting portion 75 Pressure adjusting means

Claims (4)

Equipped with a fluororesin tube disposed on the outer periphery of the foamed elastic layer, the outer diameter increases at one displacement point located in the region from 50 to 180 mm from the end to the center from the center to the end in the axial direction. A method of manufacturing an inverted crown-shaped elastic roller having a maximum outer diameter of 20 to 40 mm so that the rate changes gradually,
Polishing the foam cured body disposed on the outer peripheral surface of the shaft body so that the outer diameter increases from the center in the axial direction to the displacement point and decreases from the displacement point to the end;
And a step of coating the foamed elastic layer produced in the polishing step with a fluororesin tube having a thickness of 20 to 100 μm.   The polishing step includes a maximum outer diameter difference between an outer diameter difference of 0.01 to 0.3 mm between the central portion and the displacement point and an outer diameter difference between the displacement point and the end portion of 0.01 to 0.3 mm. It is a step of polishing the foam cured body so that the diameter becomes 20 to 40 mm, the outer diameter difference between the central portion and the displacement point is 0.10 to 0.20 mm, the displacement point and the end portion The elastic roller manufacturing method according to claim 1, wherein the outer diameter difference is more than 0.00 mm and 0.10 mm or less. The foamed cured product has an Asker C hardness (load 1.0 kg) of 20 to 60, an average cell diameter of 50 to 400 μm, and a density of 0.395 to 0.7 g / cm ³ . The manufacturing method of the elastic roller of Claim 1 or 2.   The fluororesin tube has a constant inner diameter whose difference from the outer diameter of the end portion of the foamed elastic layer is 0.1 to 2 mm, and when the fluororesin tube contracts, the contraction degree is +3 in the longitudinal direction. The method for producing an elastic roller according to any one of claims 1 to 3, wherein the elastic roller is made of PFA resin having a characteristic of -3% and + 5-5% in the circumferential direction.

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