JP5865800B2 - Pressure roller, fixing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a pressure roller, a fixing device, and an image forming apparatus. More specifically, the present invention relates to a pressure roller that exhibits high durability and easily follows the fixing roller, and a highly durable fixing device and image forming apparatus.

  Various image forming apparatuses using an electrophotographic system are employed in printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof. An image forming apparatus using an electrophotographic system generally includes a fixing device including a fixing roller and a pressure roller that are in pressure contact with each other along an axial direction via another member, such as an endless belt, if desired. The fixing roller and the pressure roller usually include a shaft body, an elastic layer disposed on the outer peripheral surface thereof, and a fluororesin tube disposed on the outer peripheral surface of the elastic layer as required.

  In the fixing device, it is excellent to fix the developer on the recording medium as desired by increasing the pressure contact width (also referred to as nip width) of the pressure contact portion formed by pressure contact between the fixing roller and the pressure roller. For the purpose of contributing to power saving as a fixing device due to the heat insulation, a foamed elastic layer in which a pressure roller is also formed of a foam may be employed in addition to a fixing roller.

  By the way, when the pressure roller is pivotally supported so as to be driven and rotated by the fixing roller that is in contact with the pressure roller, the end of the foamed elastic layer in the pressure roller is used for the purpose of ensuring the followability to the fixing roller. A technique for exposing a portion without covering with a fluororesin tube is known. For example, Patent Document 1 discloses that in a pressure roller having a metal shaft, an elastic rubber layer formed on the outer periphery thereof, and a fluororesin tube mounted on the outer periphery of the elastic rubber layer, the elastic rubber layer is provided with a plurality of elastic rubber layers. It is composed of an elastic rubber layer containing bubbles or holes, the inner diameter of the fluororesin tube is smaller than the outer diameter of the elastic rubber layer, and the length of the elastic rubber layer in the roller axial direction is the fluororesin layer. The pressure is set so as to be longer than the length of the tube in the axial direction of the roller, and a part of the outer peripheral surface of the elastic rubber layer is exposed at both ends in the axial direction of the pressure roller. "Roller" is described.

JP 2006-208659 A

In such a pressure roller, if an adhesive layer is provided between the outer peripheral surface of the elastic rubber layer and the inner peripheral surface of the fluororesin tube, the elastic rubber layer and the fluororesin tube are in close contact with each other. The fluororesin tube stretched when placed on the outer peripheral surface of the rubber layer relaxes without being completely restored, or changes in rotational torque of the pressure roller or fixing roller, changes in hardness of the elastic rubber layer over time There is no escape from stress due to stress, distortion occurs in the thin fluororesin tube, and wrinkles extending in the axial direction occur to an unacceptable level for practical use. In the worst case, the fluororesin tube is damaged particularly at its end. Sometimes. Here, “practically unacceptable” means that “wrinkles” generated on the surface of the fluororesin tube (pressure roller) are heated to 60 ° C. or more to expand the foamed elastic layer. Means a state that remains to the extent that it can be visually confirmed.
Also, if an adhesive layer is provided between the outer peripheral surface of the elastic rubber layer and the inner peripheral surface of the fluororesin tube, it is applied to the outer peripheral surface of the elastic rubber layer when the fluororesin tube is disposed on the outer peripheral surface of the elastic rubber layer. It is necessary to extend the fluororesin tube greatly in the radial direction so that the fluororesin tube does not contact the adhesive. As described above, if the fluororesin tube is stretched more than necessary, the thickness of the fluororesin tube becomes thin and may not exhibit sufficient mechanical strength to ensure the durability required for the pressure roller. .

  Incidentally, the column 0019 of Patent Document 1 states that “the inner diameter of the fluororesin tube is smaller than the outer diameter of the silicon rubber layer, so that it can be used without interposing an adhesive between the elastic rubber layer and the fluororesin tube”. Is described. In this way, if the adhesive is not present, the stress is relatively easy to escape, and it is not necessary to stretch the fluororesin tube more than necessary, so that it is possible to prevent wrinkles and the like that are unacceptable in practice and damage. On the other hand, when the fluororesin tube is fixed by such a pressing force of the silicon rubber layer, the characteristics of the fixing device to which the pressure roller is attached so that the fluororesin tube is not displaced with respect to the elastic rubber layer. For example, it is necessary to adjust the inner diameter of the fluororesin tube and the outer diameter of the silicone rubber layer in consideration of the pressure contact force of both rollers, the rotational torque, the thickness of the fluororesin tube, the change in hardness of the silicone rubber layer over time, etc. There is. If the adjustment of the diameter is neglected, the fluororesin tube cannot actually be firmly fixed to the silicon rubber layer to withstand actual use, and the fluororesin tube may be displaced over time and have poor durability. .

  As described above, in the pressure roller in which the end of the foamed elastic layer is not covered with the fluororesin tube, it is possible to achieve both prevention of wrinkles and breakage that are unacceptable for the fluororesin tube and prevention of displacement. In some cases, high durability was not exhibited.

  An object of the present invention is to provide a pressure roller that exhibits high durability and is easily driven by a fixing roller.

  An object of the present invention is to provide a fixing device and an image forming apparatus having high durability.

As means for solving the problems,
[Claim 1] A foamed elastic layer having tubular end portions and a central portion disposed therebetween, and an annular slit having an incision angle? When,
A pressure roller that is disposed at least on the outer peripheral surface of the central portion and includes a fluororesin tube having both open ends sandwiched in the annular slit;
According to a second aspect of the present invention, the central portion has an outer diameter that is equal to or less than the outer diameter of the both end portions, and a reduction rate of 0.05 to 0.2% from the connecting portion with the both end portions to the center in the axial direction of the central portion. The pressure roller according to claim 1, wherein the pressure roller has an inverted crown shape having a diameter.
A third aspect of the present invention is the pressure roller according to the first or second aspect, wherein the both end portions are located outside a sheet passing area when the pressure roller is mounted on the fixing device.
Claim 4 is the pressure roller according to any one of claims 1 to 3, wherein the both end portions have an axial length of 5 to 30 mm from an edge.
According to a fifth aspect of the present invention, there is provided a fixing device comprising: a fixing roller; and the pressure roller according to any one of the first to fourth aspects disposed so as to be in pressure contact with the fixing roller along an axial direction. Yes,
A sixth aspect of the present invention is an image forming apparatus including the fixing device according to the fifth aspect.

  The pressure roller according to the present invention has tubular end portions and a central portion disposed between them, and an annular slit that opens on the outer peripheral surface at a cut angle θ of 90 to 150 ° on the end side. A foamed elastic layer and a fluororesin tube disposed at least on the outer peripheral surface of the central portion and having both open ends sandwiched in the annular slit. It is difficult to be displaced, and it is easy to follow the fixing roller by both end portions where the outer peripheral surface is exposed. The fixing device and the image forming apparatus according to the present invention include the pressure roller according to the present invention. Therefore, according to the present invention, it is possible to provide a pressure roller that exhibits high durability and easily follows the fixing roller, and a highly durable fixing device and image forming apparatus.

FIG. 1 is a schematic view showing a pressure roller which is an example of a pressure roller according to the present invention, and FIG. 1A is a schematic front view showing a pressure roller which is an example of a pressure roller according to the present invention. FIG. 1B is a schematic sectional view showing a pressure roller which is an example of the pressure roller according to the present invention. FIG. 2 is a schematic sectional view showing a pressure roller as another example of the pressure roller according to the present invention. FIG. 3 is a schematic explanatory view showing the fixing device according to the present invention and the image forming apparatus according to the present invention.

  A pressure roller according to the present invention includes a foamed elastic layer and a fluororesin tube disposed on a part of the outer peripheral surface of the foamed elastic layer. Therefore, the pressure roller according to the present invention is only required to include the foamed elastic layer and the fluororesin tube. In addition to these, the shaft body supporting the foamed elastic layer, and other layers on the outer peripheral surface of the fluororesin tube Etc. may be provided.

  The pressure roller according to the present invention will be specifically described below. As shown in FIG. 1, a pressure roller 1A, which is an example of a pressure roller according to the present invention, includes a shaft body 2, a foamed elastic layer 3A disposed on the outer peripheral surface of the shaft body 2, and a foamed elastic layer 3A. And a fluororesin tube 4 disposed without interposing an adhesive layer on a part of the outer peripheral surface.

  The pressure roller 1A 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 1A is preferably 45 to 60, and particularly preferably 50 to 55, from the viewpoint that a sufficient nip pressure with the fixing roller can be secured. Asker C hardness (1.0 kg load) was measured by applying a load of 1.0 kg in accordance with JIS K6253 using the outer peripheral surface of the fluororesin tube 4 disposed on the outer peripheral surface of the central portion 12A of the foamed elastic layer 3A as a measurement point. It is a value measured in the state. The Asker C hardness of the pressure roller 1A is selected, for example, from the types of rubbers, foaming agents and / or additives contained in the foamed rubber composition forming the foamed elastic layer 3A, and / or their blending amounts. Can be adjusted by changing the molding conditions of the foamed elastic layer 3A.

  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 3A has cells inside and / or on the outer peripheral surface (cells opened on the outer peripheral surface and end surface of the foamed elastic layer 3A are not shown in FIG. 1). Here, the cell included in the foamed elastic layer 3A refers to a hollow region generated by foaming or decomposition of a foaming agent contained in the foamed rubber composition. The plurality of cells in the foamed elastic layer 3A are in a state where they do not contact or communicate with other cells (referred to as independent cell states), a state where they contact or communicate with other cells (communication cell state) 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 may be a continuous cell, but is preferably in an independent cell state.

In the foamed elastic layer 3A, the average cell diameter of the cells formed in the foamed elastic layer 3A, the foaming magnification, the specific gravity and the like of the foamed elastic layer 3 are adjusted, and the effect of the present invention can be further enhanced. It is preferable. For example, the average cell diameter is preferably 60 to 800 μm, particularly preferably 100 to 400 μm, and the expansion ratio is preferably 1.8 to 4.2 times, and preferably 2 to 3.5 times. The specific gravity is preferably 0.395 to 0.7 (g / cm ³ ), and more preferably 0.42 to 0.6 (g / cm ³ ). In the foamed elastic layer 3A, the average cell diameter, expansion ratio, and specific gravity can be adjusted by the foaming agent contained in the foamed rubber composition forming the foamed elastic layer 3A or the curing conditions of the foamed rubber composition. The foaming ratio can be calculated from the volume and mass of the foamed elastic layer 3A measured by a conventional method. The average cell diameter is about 20 mm ^{2 on} the surface of the foamed elastic layer 3A or the cut surface when cut with an arbitrary surface, and is observed with an electron microscope or the like, and the maximum opening in each cell existing in the observation field of view. It is possible to obtain the average length obtained by measuring the length and arithmetically averaging the measured maximum length. The specific gravity can be measured by an electron density meter (in-water replacement method water temperature 23 ° C.).

  The Asker C hardness of the foamed elastic layer 3A (load 1.0 kg) is appropriately adjusted according to the thickness of the fluororesin tube so that the Asker C hardness of the pressure roller according to the present invention is within the above range. For example, it is preferable that it is 40-60.

  As shown in FIG. 1B, the foamed elastic layer 3A having such cells has tubular end portions 11 (each end portion is collectively referred to as both end portions) disposed at both ends in the axial direction. And a tubular central portion 12 </ b> A that is arranged continuously at both end portions 11 so as to be sandwiched between both end portions 11. Here, although both the end portions 11 and the central portion 12A are connected, the central portion 12A may be disposed between the end portion 11 via a cylindrical intermediate portion or the like. Each of the end portions 11 has a tubular shape having a constant outer diameter in the axial direction, and most of the outer peripheral surface, in this example, the entire outer peripheral surface is exposed. The central portion 12A has an outer diameter equal to or less than the outer diameter of the end portion 11, and the reduction rate is 0.05 to from the connecting portion (one-dot chain line in FIG. 1B) to each end portion 11 to the center in the axial direction of the central portion 12A. It has a so-called “reverse crown shape” having an outer diameter of 0.2%, and is covered with a fluororesin tube 4 described later. Here, the reduction rate of the central portion 12A is a value calculated by [(maximum outer diameter−minimum outer diameter) / (axis length / 2)] / 2.

  Each of the end portions 11 is formed so as to be positioned outside the sheet passing area when the pressure roller 1A is mounted on the fixing device. For example, the axial length from each end edge of the foamed elastic layer 3A toward the central portion 12A Is set to 5 to 30 mm. The central portion 12A only needs to have an axial length slightly longer than the sheet passing area, and is appropriately set according to the fixing device and the sheet passing area.

  The outer diameter and thickness of the foamed elastic layer 3A are determined as appropriate, and the outer diameter is determined so as to have an appropriate thickness according to the dimensions of the shaft body 2 and the like. In general, the thickness of the end portion 11 is preferably 3 to 12 mm, particularly preferably 3 to 6 mm, and the maximum thickness of the central portion 12A (in the foamed elastic layer 3A, the connecting portion with the end portion 11). The (thickness) is preferably equal to or less than the thickness of the end 11, and particularly preferably the same as the thickness of the end 11. Further, the minimum thickness of the central portion 12A (the thickness in the axial center in the foamed elastic layer 3A) is less than the thickness of the end portion 11, and is preferably 1.5 to 10 mm, preferably 2.5 to Particularly preferred is 5 mm.

  As shown in FIG. 1B, the foamed elastic layer 3A has an outer peripheral surface thereof, for example, in the vicinity of a connecting portion between each of the end portions 11 and the central portion 12A. An annular slit 13A that opens to a connecting portion located outside the sheet passing area is provided. The annular slit 13A is a slit cut in a circumferential direction of the foamed elastic layer 3A and inclined from the end 11 side to the central portion 12A side, and the opening may be blocked. . Such an annular slit 13 </ b> A has a cut angle θ (see FIG. 1B) on the end portion 11 side in a cut angle of 90 to 150 °. This cutting angle θ can also be referred to as an angle with respect to the foamed elastic layer 3A in the cross section including the axis of the foamed elastic layer 3A, particularly the outer peripheral surface contour line of the end 11 as shown in FIG. Moreover, it can also be called the crossing angle by the side of the edge part 11 among the crossing angles of this outer peripheral surface outline and notch | incision or a depth direction. When the cutting angle θ is 90 to 150 °, the fluororesin tube 4 can be disposed at a predetermined position for a long period of time without causing wrinkles and breakage. One reason for this is that the inventors of the present invention contract the fluororesin tube 4 when the fluororesin tube 4 having an inner diameter smaller than the outer diameter of the central portion 12A is disposed on the outer peripheral surface of the foamed elastic layer 3A. Thus, it is assumed that the holding pressure of the annular slit 13A sandwiching the opening end 4a of the fluororesin tube 4 is to be reinforced. That is, when the cutting angle θ is less than 90 °, the opening end 4a may be pulled out of the annular slit 13A due to the displacement of the fluororesin tube 4 in the axial direction of the pressure roller 1A, and the fluororesin tube 4 May cause wrinkles and eventually damage. On the other hand, when the cutting angle θ exceeds 150 °, the fluororesin tube 4 is likely to be displaced in the axial direction, the strength in the vicinity of the annular slit 13A may be lowered, and workability is also lowered. The cut angle θ of the annular slit 13A is preferably 120 to 150 °, and specifically 150 °.

  The depth of the annular slit 13A, that is, the depth of cut, is not particularly limited, but the fluororesin tube 4 can be disposed at a predetermined position for a long period of time without causing wrinkles and breakage in the fluororesin tube 4, It is preferably 1 to 3.5 mm, particularly preferably 2 to 3 mm. The width of the annular slit 13A is equal to or greater than the thickness of the fluororesin tube 4 and is preferably 0.01 to 2 mm, and particularly preferably 0.01 to 1 mm. The annular slit 13A is formed as a slit having a substantially constant width and opening width in that the opening end 4a exhibits a high clamping pressure. For example, the annular slit 13A is a V-shaped slit or U-shaped section having a V-shaped cross section. It may be a U-shaped slit or the like.

  The fluororesin tube 4 has a tube shape in which both end edges are open and the axial length is shorter than that of the foamed elastic layer 3A. The axial length of the fluororesin tube only needs to cover at least the paper passing area of the pressure roller 1A, that is, the center portion 12A and can be narrowly inserted into the annular slit 13A, and is appropriately set according to the fixing device to be mounted. Is done. For example, the axial length of the fluororesin tube 4 is preferably longer than the axial length of the central portion 12A and shorter than the sum of the axial length of the central portion 12A and the depth of the two annular slits 13A. The fluororesin tube 4 is disposed at the central portion 12A of the foamed elastic layer 3A, that is, at least at the outer peripheral surface of the entire area of the paper passing region without interposing an adhesive layer between the outer peripheral surface of the foamed elastic layer 3A and the central portion 12A. The outer peripheral surfaces of both end portions 11 are exposed. As described above, when both end portions 11 of the foamed elastic layer 3A are exposed and the outer peripheral surface of the center portion 12A is covered with the fluororesin tube 4, both end portions are mounted when the pressure roller 1A is attached to the fixing device. 11 is pressed against the fixing roller and is driven by the fixing roller, and the developer is transferred from the pressure roller even if the developer before being transferred to the recording medium and fixed is in contact with the pressure roller 1A. It is possible to prevent contamination of the recording medium which is easily separated and conveyed later. Further, when the fluororesin tube 3 is disposed without interposing an adhesive layer between the outer peripheral surface of the central portion 12A, the foamed elastic layer 3A is made to have a low hardness in which the Asker C hardness is within the above range. The problems due to the adhesive layer described above can be avoided. In the present invention, the fluororesin tube 4 is sandwiched by the tubular slit 13 as will be described later without providing an adhesive layer. Can be arranged.

  As shown in FIG. 1B in particular, the fluororesin tube 4 has its entire opening end 4a sandwiched in the annular slit 13A, and the entire circumference in the circumferential direction of the opening end 4a is fixed. Thus, since both the opening ends 4a of the fluororesin tube 4 are fixed, no wrinkles or breakage occurs, and the fluororesin tube 4 is difficult to be displaced.

  The fluororesin tube 4 has an inner diameter set to be smaller than the minimum outer diameter of the foamed elastic layer 3A and the minimum outer diameter of the central portion 12A in the foamed elastic layer 3A having an inverted crown shape. When pressed, the foamed elastic layer 3A is pressed in the axial direction to slightly reduce it. When the inner diameter of the fluororesin tube 4 is smaller than the outer diameter of the foamed elastic layer 3A in this way, the fluororesin tube 4 is brought into close contact with the foamed elastic layer 3A by the pressing force applied to the foamed elastic layer 3A and is displaced by itself. As described above, the open end 4a can be firmly held. The inner diameter of the fluororesin tube 4 only needs to be smaller than the outer diameter of the foamed elastic layer 3A. However, if it is too small, it is difficult to dispose the fluororesin tube 4 on the outer peripheral surface of the foamed elastic layer 3A. Thus, for example, the outer diameter of the foamed elastic layer 3A is preferably about 0.5 to 1.5 mm smaller.

  The fluororesin tube 4 is preferably thinned so that the pressure roller 1A has an Asker C hardness in the above range and can retain the inverse crown shape of the foamed elastic layer 3A. The thickness is preferably 20 to 100 μm, particularly preferably 30 to 50 μm. Therefore, the fluororesin tube 4 can also be called a thin-walled tube. The fluororesin tube 4 preferably has a shrinkage rate of +3 to -3% in the longitudinal direction and +5 to -5% in the circumferential direction, +2 to -2% in the longitudinal direction, and 0 to 0 in the circumferential direction. Particularly preferred is a shrinkage of -4%. This shrinkage ratio is calculated by measuring the inner diameters by measuring the inner diameter difference between the inner diameter at normal temperature and the inner diameter after heating at 150 ° C. for 20 minutes.

  Thus, even if the fluororesin tube 4 is thin or no adhesive layer is provided between the outer peripheral surface of the foamed elastic layer 3A, the pressure roller 1A including the foamed elastic layer 3A and the fluororesin tube 4 is provided. The surface unevenness due to the cells opening in the outer peripheral surface of the foamed elastic layer 3A is offset, and the surface of the fluororesin tube 4 becomes flat.

  The fluororesin tube 4 may be insulative or conductive, and is appropriately selected according to the use of the pressure roller 1A. In order to make the fluororesin tube 4 conductive, a method of adding a conductivity imparting agent such as carbon black can be used. The fluororesin tube 4 preferably has high mechanical strength in terms of ensuring high durability of the pressure roller 1A. For example, when the thickness is 20 to 60 μm, it preferably has a breaking strength of 30 to 70 MPa, and preferably has a breaking elongation of 150 to 500%. The breaking strength is in accordance with JIS K6881 dumbbell-shaped No. 3 test piece cut out from the fluororesin tube 4 (according to JIS K6251. However, the dumbbell-shaped No. 3 test piece has its longitudinal direction in the axial direction of the fluororesin tube 4, that is, the longitudinal direction. And is measured under conditions of a tensile speed of 200 mm / min and a measurement temperature of 25 ± 2 ° C., and the elongation at break is cut out from the fluororesin tube 4. A dumbbell-shaped No. 3 test piece (according to JIS K6251) defined in JIS K6891. However, the dumbbell-shaped No. 3 test piece is cut out so that its longitudinal direction is along the axial direction of the fluororesin tube 4, that is, the longitudinal direction. Used, based on JIS K6891, tensile speed 200mm / min, measuring temperature 25 ± 2 ° C It is a value measured under the conditions of Thus, the breaking strength and the breaking elongation are the breaking strength and breaking elongation in the axial direction, that is, the longitudinal direction of the resin tube 4.

  The fluororesin tube is made of fluororesin and may be formed in a so-called “straight shape” having a constant inner diameter and outer diameter before being disposed on the outer peripheral surface of the foamed elastic layer 3A. Alkoxy resin), FEP (tetrafluoroethylene-hexafluoropropylene resin), PTFE (polytetrafluoroethylene resin), PVdF (polyvinylidene fluoride resin) and the like.

  In this manner, the foamed elastic layer 3A having an annular slit 13A that opens at both ends 11 when the cut angle θ on the end 11 side is 150 °, and at least the outer peripheral surface of the central portion 12A are disposed without an adhesive layer interposed therebetween. The pressure roller 1A provided with the fluororesin tube 4 having both open ends 4a sandwiched between the annular slits 13A is less susceptible to wrinkling and breakage of the fluororesin tube 4, and the fluororesin tube 4 is also difficult to displace. When mounted on the fixing device, the both ends 11 follow the fixing roller and rotate.

  As shown in FIG. 2, a pressure roller 1B, which is another example of the pressure roller according to the present invention, includes a shaft body 2, a foam elastic layer 3B disposed on the outer peripheral surface of the shaft body 2, and a foam elasticity. And a fluororesin tube 4 arranged without interposing an adhesive layer on a part of the outer peripheral surface of the layer 3B.

  The pressure roller 1B is basically the same as the pressure roller 1A except that the central portion 12B of the foamed elastic layer 3B and the annular slit 13B are different. That is, the central portion 12B is formed in a tubular body having a constant outer diameter, and the center portion 12A and the foamed elastic layer 3A have a so-called “straight shape” in which the entire foamed elastic layer 3B has a constant outer diameter. Basically the same. The annular slit 13B is basically the same as the annular slit 13A except that the cutting angle θ is 90 °.

  Accordingly, in this way, the foamed elastic layer 3B having the annular slit 13B opened at both end portions 11 with the cut angle θ on the end portion 11 side of 90 °, and at least the outer peripheral surface of the central portion 12B without an adhesive layer interposed The pressure roller 1B provided with the fluororesin tube 4 disposed and having both open ends 4a sandwiched between the annular slits 13B is less susceptible to wrinkling and breakage of the fluororesin tube 4, and the fluororesin tube 4 is displaced. If it is difficult, it is driven by the fixing roller by the both end portions 11 when it is mounted on the fixing device, and rotates.

  The pressure roller according to the present invention includes a step of foaming and curing a foamed rubber composition on the outer peripheral surface of the shaft body to form a foamed elastic layer, a step of disposing a fluororesin tube on the outer peripheral surface of the foamed elastic layer, It can manufacture by the manufacturing method which has the process of fixing a resin tube.

  The shaft body 2 is made of, for example, a metal such as iron, aluminum, stainless steel, brass or an alloy thereof, a resin such as a thermoplastic resin or a thermosetting resin, and carbon black or metal powder as a conductivity-imparting agent for the resin. It is prepared in a desired shape by a known method using a material such as a conductive resin blended with a body. When the shaft body 2 is required to have conductivity, in addition to the metal and the conductive resin, the surface of the insulating core body formed of the resin or the like is plated by a regular method to thereby form the shaft body 2. Can be formed. Among the above materials, a metal is preferable and aluminum or stainless steel is particularly preferable from the viewpoint that conductivity can be easily imparted. The shaft body 2 may be coated with a primer layer on the outer peripheral surface as desired.

  In this manufacturing method, after preparing the shaft body, the foamed rubber composition is heat-molded on the outer peripheral surface of the shaft body 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.

  The foamed elastic layer 3 thus molded is subjected to a grinding step, a polishing step and / or a cutting step for adjusting it to a desired size and shape.

  In this manufacturing method, an annular slit is then formed in the molded foamed elastic layer. Specifically, a cutter such as a cutter is inserted into the foamed elastic layer at a predetermined cutting angle from the vicinity of the outer peripheral surface, for example, the connecting portion between the end and the center. Thus, an annular slit that makes a round in the circumferential direction is formed. When the blade does not have an annular blade, the blade that has entered at a predetermined cutting angle can be moved in the circumferential direction to form an annular slit.

  In this 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 outer peripheral surface of the molded foamed elastic layer. At this time, it is preferable that the adhesive is not applied to the outer peripheral surface of the foamed elastic layer and the inner peripheral surface of the fluororesin tube because the problems due to the adhesive layer described above can be avoided. 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.

  In this manufacturing method, the open end of the disposed fluororesin tube is then narrowly inserted into the annular slit. At this time, for example, an instrument having a flat or slightly curved tip, for example, a flat-blade screwdriver or an instrument having an annular tip is disposed on the annular slit via the fluororesin tube, and the tip is attached to the fluororesin tube. Enter the annular slit. If it does so, the opening end of a fluororesin tube will be pinched | interposed in an annular slit, and will be clamped by an annular slit.

  In this manufacturing method, if desired, an adhesive may be applied to the inner peripheral surface of the opening of the fluororesin tube or the inside of the annular slit and cured.

  In this manner, the pressure roller according to the present invention including the fluororesin tube having both open ends sandwiched between the annular slits can be manufactured.

  The pressure roller according to the present invention is not limited to the above-described example, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, a foamed elastic layer having a so-called “crown shape” having an outer diameter with an increasing rate of 0.05 to 0.2% from the connecting portion to each end portion to the center in the axial direction of the central portion may be provided. . Here, the increasing rate is a value calculated by [(maximum outer diameter of the central portion−minimum outer diameter of the central portion) / (axis length / 2)] / 2.

  Next, a fixing device provided with a pressure roller according to the present invention (hereinafter sometimes referred to as a fixing device according to the present invention) and an image forming device (hereinafter referred to as an image forming device according to the present invention). .) Will be described with reference to FIG.

  Since the pressure roller according to the present invention has the above characteristics and effects, it is preferably used as a pressure roller mounted on a fixing device provided in the image forming apparatus.

  As shown in FIG. 3, the 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. 3, the developer 42 is supplied to the developer accommodating portion 41 and 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.

  3, the fixing device 35 includes a fixing roller 53 and an endless belt support roller disposed in the vicinity of the fixing roller 53 in a housing 50 having an opening 52 through which the recording medium 36 passes. 54, an endless belt 55 wound around the fixing roller 53 and the endless belt support roller 54, a pressure roller 56 pressed against the fixing roller 53 via the endless belt 55, and the endless belt 55 in a non-contact manner. And a heating means 57 that heats the fixing roller 53 from the outside via the endless belt 55, and is rotatable so that the fixing roller 53 and the pressure roller 56 are in contact with or in pressure contact with each other via the endless belt 55. The pressure heat fixing device is supported by the above.

  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 substantially the same length as that 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.

  In the fixing device 35 according to the present invention, the pressure roller according to the present invention is arranged as the pressure roller 56 so that the end portion 11 is in pressure contact with the fixing roller 53 so as to be located outside the sheet passing area. Therefore, the fixing roller 53 is easy to follow, and is provided with a fluororesin tube that is less likely to cause wrinkles and breakage that is unacceptable for practical use and that is difficult to displace. Therefore, since the pressure roller according to the present invention is employed as the pressure roller 56, the fixing device 35 and the image forming apparatus 30 according to the present invention exhibit high durability.

  The pressure roller, the fixing device, and the image forming apparatus according to the present invention are not limited to the above-described examples, 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 rollers 1A and 1B, the foamed elastic layers 3A and 3B have a single-layer structure, but in the present invention, they 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 18 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.

An addition reaction type foamed silicone rubber composition having the following composition was prepared.
・ 100 parts by mass of a rubber composition “KE-551U” (manufactured by Shin-Etsu Chemical Co., Ltd.) containing a vinyl group-containing silicone raw rubber and a silica-based filler having the above-mentioned content. ・ Organic foaming agent “azobis-isobutyronitrile” 2.0 parts by mass of addition reaction crosslinking agent “C-153A” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) 2.0 parts by mass of platinum catalyst as an addition reaction catalyst / reaction control agent “R-153A” ( Shin-Etsu Chemical Co., Ltd .: trade name) 0.5 parts by mass. Organic peroxide crosslinking agent “C-3” (Shin-Etsu Chemical Co., Ltd .: trade name) 3 parts by mass.

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 is further heated at 200 ° C. for 7 hours using a gear oven, and left at room temperature for 1 hour or more. The so-called “crown-shaped” foamed elastic layer 3 </ b> A having the following dimensions was formed on the outer peripheral surface of the shaft body 2. Each connecting portion of the foamed elastic layer 3A thus molded was cut with a cutter to form an annular slit 13 having the following dimensions and a cutting angle θ. The Asker C hardness (load 1.0 kg) of the foamed elastic layer 3 was 43, the average cell diameter was 150 μm, the foaming ratio was 2.2 times, and the specific gravity was 0.6.
・ Axis length (full length): 340mm
・ Axis length of end 11: 20.5 mm
・ Axis length of central part 12A: 299mm
-The outer diameter of the end portion 11 and the maximum outer diameter of the central portion 12A: 25.1 mm (thickness: 3.55 mm)
・ Minimum outer diameter of the central portion 12A (the outer diameter at the center in the axial direction): 24.8 mm (thickness: 3.4 mm)
-Decrease rate of central part 12A: 0.1%
・ Cutting angle θ: 150 °
Depth (cut amount): 2.4 mm (68% of the thickness of the end portion 11)
・ Width: 30μm

  Next, the prepared fluororesin tube 4 (made of PFA resin, axial length 304 mm, outer diameter 24.0 mm, thickness 30 μm, circumferential shrinkage -1.0%, longitudinal shrinkage -1.4%, A surface resistance value of 1.91E + 05 to 3.24E + 05Ω / □, manufactured by Gunze Co., Ltd.) was disposed on the outer peripheral surface of the foamed elastic layer 3A. Specifically, the shaft body 2 having the foamed elastic layer 3A formed on the outer peripheral surface and the fluororesin tube 4 are arranged in series in the “pressure reducing device 30” shown in FIG. 6 of Japanese Patent Application Laid-Open No. 2008-299185. The pressure inside the pressure reducing device 30 was reduced. After maintaining the decompression state for a while, the decompression of the decompression device 30 is released, and the foamed elastic layer 3A whose outer diameter is smaller than the inner diameter of the fluororesin tube 4 is inserted into the fluororesin tube 4, and the foamed elastic layer 3A The sample was allowed to stand under normal pressure until it expanded in diameter and in close contact with the fluororesin tube 4. In this way, the fluororesin tube 4 was disposed on the outer peripheral surface of the foamed elastic layer 3A.

  Next, a flat-blade screwdriver is placed on the annular slit 13A via the fluororesin tube 4, the tip thereof is made to enter the annular slit 13A together with the fluororesin tube 4, and both open ends 4a are inserted into the annular slit 13A. .

  In this way, the pressure roller 1A shown in FIG. 1 was manufactured. The Asker C hardness (1.0 kg load) of the pressure roller 1A was 54.

(Examples 2 to 5)
A pressure roller 1A was produced in the same manner as in Example 1 except that the cutting angle θ or depth of the annular slit 13A was changed to the value shown in Table 1.

(Example 6)
Pressure is applied basically in the same manner as in Example 1 except that a so-called “straight-shaped” foamed elastic layer 3B is formed by grinding to a central portion 12B having a constant outer diameter of 25.1 mm instead of the central portion 12A. A roller 1A was produced.

(Comparative Example 1)
The process is basically the same as in Example 1 except that the fluororesin tube 4 having an axial length of 342 mm is disposed in a state where the opening end protrudes from the foamed elastic layer 3A without forming an annular slit in the foamed elastic layer. A pressure roller was produced.

(Evaluation of fluororesin tube condition)
Each pressure roller manufactured in Examples 1 to 6 and Comparative Example 1 was 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 roller after pressing). Pressure contact was made in parallel along the axial direction so that the difference from the distance between the 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.

  While the pressure roller after being rotated as described above was at a temperature of 60 ° C. or higher, the presence or absence of wrinkles, cracks, etc. was confirmed on the surface (indicated as “evaluation of occurrence of wrinkles” in Table 1). 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 wrinkles, cracks could be visually confirmed, and the case where the fluororesin tube 4 did not have a gloss was designated as “x”. When this evaluation was “Δ” or more, the state of the fluororesin tube was practically acceptable even in the actual machine test.

  Next, the displacement of the fluororesin tube 4 was confirmed (denoted as “displacement evaluation” in Table 1). The evaluation criteria were “」 ”when the fluororesin tube 4 was not displaced,“ ◯ ”when the fluororesin tube 4 was displaced but the displacement was 0.5 mm or less, and the fluororesin tube 4 The case where the amount of displacement was 0.5 mm and 1.0 mm or less was “Δ”, and the case where the fluororesin tube 4 was displaced exceeding 1.0 mm was “x”. When this evaluation was “Δ” or more, the fluororesin tube 4 was hardly displaced even in an actual machine test, and was acceptable in practice.

  Each pressure roller manufactured in Examples 1 to 6 and Comparative Example 1 is attached to the fixing device when it is confirmed that the pressure roller is rotated by following the heating roller in the “evaluation of the state of the fluororesin tube”. As a result, it can be estimated that the roller rotates following the fixing roller.

DESCRIPTION OF SYMBOLS 1, 1A, 1B Pressure roller 2 Shaft body 3A, 3B Foaming elastic layer 4 Fluororesin tube 4a Open end 11 End part 12A, 12B Central part 13A, 13B Annular slit 30 Image forming apparatus 31 Image carrier 32 Charging means 33 Exposure Means 34 Transfer means 35 Fixing device 36 Transferred body 37 Cleaning means 40 Developing means 41 Developer storing section 42 Developer 43 Developer supplying means 44 Developer carrier 45 Developer regulating member 50 Housing 52 Opening 53 Fixing roller 54 Endless Belt support roller 55 Endless belt 56 Pressure roller 57 Heating means

Claims (6)

A foamed elastic layer having tubular end portions and a central portion disposed between them, and having an annular slit that opens on the outer peripheral surface at a cut angle θ of 90 to 150 ° on the end side;
A pressure roller comprising: a fluororesin tube disposed at least on the outer peripheral surface of the central portion and having both open ends sandwiched between the annular slits.   The center portion has an outer diameter that is equal to or less than the outer diameter of the both end portions and has an outer diameter that decreases from 0.05 to 0.2% from the connecting portion with the both end portions to the center in the axial direction of the center portion. The pressure roller according to claim 1, which has a shape.   3. The pressure roller according to claim 1, wherein the both end portions are positioned outside a sheet passing area when the pressure roller is mounted on a fixing device.   The pressure roller according to any one of claims 1 to 3, wherein the both end portions have an axial length of 5 to 30 mm from an end edge.   A fixing device comprising: a fixing roller; and the pressure roller according to claim 1 disposed so as to be in pressure contact with the fixing roller along an axial direction.   An image forming apparatus comprising the fixing device according to claim 5.

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