JPH0120745B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber roller used in a roller-type heating or pressure fixing device, a paper feed roller, a conveyance roller, etc. in an electrophotographic copying machine, an offset printing machine, etc. For example, in the above-mentioned roller type heat fixing device, at least one of the rollers is an elastic roller, that is, a rubber roller, and this roller is pressed against a heating roller, which is an opposing roller, at a predetermined pressure to form a nip, and a rotating roller pair is formed. The toner image is heated and fixed by passing the unfixed toner image between the supports. Since the above-mentioned rubber rollers are required to have stable physical strength at high temperatures, silicone rubber is generally used, and is simultaneously heat-cured and molded onto the circumferential surface of a rigid body, that is, a metal-core roller, to a predetermined thickness. It is glued together. However, the above rubber rollers generally have JIS hardness.
Since the rubber roller is rotated in pressure contact with the opposing roller, both end surfaces of the rubber roller swell and deform due to the pressure, and the rubber layer near the end surface and the rubber layer around the center roller. There is a problem with it peeling off from the surface. Also, as copying processes become faster, silicone oil is applied to the circumferential surface of rubber rollers to prevent paper from wrapping around the rollers and from sticking to each other.
Silicone rubber originally has low oil resistance to silicone oil, and therefore has the disadvantage of significantly deteriorating the physical strength of the rubber roller. Therefore, conventionally, when molding a rubber roller, a member such as strong and elongated thick rubber or fluorosilicone is vulcanized and molded at both ends to prevent the above-mentioned bulging deformation and act as an oil-resistant seal. The resulting rubber roller surface has oil resistance and
A heat-shrinkable tube coated with a copolymer of tetrafluoroethylene, hexafluoroethylene, perfluoroalkyl vinyl ether, etc., which is suitable in terms of heat resistance and mold releasability, has been developed. However, the above-mentioned rubber roller uses a large amount of expensive soft rubber, has a complicated manufacturing process, and is not perfect in terms of adhesive peeling of the end seal and has many drawbacks. The present invention was proposed in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a rubber roller in which the rubber layer does not peel off from the peripheral surface of the core roller. Another object of the present invention is to provide a rubber roller in which oil-resistant seals are easily formed on both end faces of the rubber roller when oil-resistant is imparted to the peripheral surface of the rubber roller body. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 partially shows a first embodiment of the present invention, in which reference numeral 1 denotes a metal core roller, on the circumferential surface of which a rubber layer 2 made of silicone rubber is formed by heat vulcanization. Also, from the vicinity of both ends of the rubber layer 2, each end face 3
The diameter of the rubber layer 2 is gradually decreased toward each end face 3, and the diameter of the rubber layer 2 is made smaller than that of other parts, that is, the parts that rub against the support. Δr indicates the difference between the diameter of the end face 3 and that of other parts. As a result, in the distance l section, the circumferential surface of the rubber layer 2 either does not come into contact with the opposing roller, or is pressed against it more lightly than the pressure further inside the distance l in the longitudinal direction of the roller, causing a bulge that acts on both end surfaces. Deformation pressure is reduced. The value of l that is effective for edge adhesion peeling can be expressed as a function of the peripheral surface hardness H of the rubber layer 2, the pressure P per unit length of the peripheral surface of the rubber layer 2, and the thickness t of the rubber layer. can be written as l=f(C・Pt/H). Also, the amount of deformation of the rubber layer 2 when pressure P is applied is calculated from the calculation method of G.J. Parish.

It can be expressed as [Formula]. Here, h is the nip width and E is Young's modulus. Furthermore, experiments have shown that in a JIS hardness range of 20 to 80 degrees, which is an appropriate hardness range for a rubber roller, the rubber hardness H and Young's modulus E are in a substantially proportional relationship. Also, if h∝l, then the effective l for edge adhesive peeling is approximately

It can be expressed as [Formula]. Here, C is a constant, and the units of P, t, and H are g/mm, mm, and degrees, respectively. Based on the above function, we prepared rubber rollers with rubber layers of various hardnesses and wall thicknesses and conducted experiments to find appropriate values for l at various pressures.We found that when the constant C is 2/3 or more, , that is, It has been found that this method is effective in preventing peeling between the core roller and the rubber layer. Furthermore, when the various rubber rollers mentioned above are coated with the oil-resistant heat-shrinkable tube, small-diameter portions are formed at both ends of the laminated portion of the rubber layer and the oil-resistant coating layer based on the above experimental formula. Since the bulging deformation of is suppressed, peeling between both layers is prevented,
Moreover, the oil-proof sealing of the end face of the rubber layer becomes simple and reliable. In this case, P is the pressure per 1 mm in the longitudinal direction of the roller on the circumferential surface of the oil-resistant coating layer (g/mm),
H is the JIS hardness (degrees) of the peripheral surface of the oil-resistant coating layer. When forming the above-mentioned oil-resistant coating layer, the hardness of the circumferential surface of the rubber layer should be approximately 18 to 25 degrees, and after forming the oil-resistant coating layer, the hardness of the circumferential surface of the coating layer, that is, the relative hardness of the circumferential surface of the rubber layer, The temperature should be between 50 and 80 degrees. 2 to 5 show a method for covering the circumferential surface of a rubber layer with the heat-shrinkable tube, which will be explained in the order of the steps below. (a) Heat-vulcanized silicone rubber with low hardness (JIS hardness 18 to 25 degrees) is press-vulcanized to a specified thickness on a metal core roller 1, cut to a specified length, and cut to a specified length from the end. The rubber layer 2 has a tapered shape with a small diameter.
form. Next, while rotating the rubber layer 2, the primer 4 is applied to the circumferential surface of the rubber layer 2 to a predetermined thickness using a coating blade. Then rubber layer 2
The heat-shrinkable tube 6 has a diameter larger than the diameter of the rubber layer 2 by a predetermined amount.
is placed over the entire length of the rubber layer 2, both ends of which protrude from both end surfaces 3 of the rubber layer 2, and tube holders 7 are fitted into both openings to reduce the distance between the tube 6 and the circumferential surface of the rubber layer 2. Hold constant. Next, while moving the hot air gun from one end of the tube 6 to the other end, the rubber layer 2 and the tube 6 are rotated together. As a result, the tube 6 is thermally shrunk and comes into close contact with the circumferential surface of the rubber layer 2. At this time, the primer 4 penetrates into the fine recesses on the circumferential surface of the rubber layer 2 due to the adhesive force of the tube 6, thereby ensuring adhesion between the tube and the rubber layer. In addition, the excess primer advances while forming a reservoir 4a near just before the tube 6 contracts, so that air bubbles are prevented from being drawn in (FIG. 2). (b) Cut both ends of the heat-shrinked tube 6 to match the outer end surface of each ring 5 (Fig. 3). (c) When each ring 5 is removed, a recess 8 is formed in front of each end surface 3 of the rubber layer 2 by each protruding heat-shrinkable portion 6a of the tube 6. Next, when the protruding heat-shrinkable portion 6a is further heated and contracted, the portion further contracts as if it had been squeezed. (d) Apply a soft rubber paint or sealant to both end surfaces of the rubber layer 2 in the recesses 8 at both ends of the tube 6, and dry to seal both end surfaces of the rubber layer against oil. In this case, the recess 8 prevents paint etc. from dripping to the outside. In addition to the above-mentioned seals, as a sealing member for both end faces of the rubber layer 2, an oil-resistant plastic plate, a sheet thereof, or a metal plate is attached to both end faces of the rubber layer before the heat shrinking part 6a of the tube is heat-shrinked again. An oil-resistant seal is formed by bonding a rigid sealing member such as, applying an adhesive to the circumferential surface of the member and then heat shrinking it, and bonding the circumferential surface of the member and the inner surface of the protruding heat-shrinkable portion of the tube 6. It's okay. In this case, primer treatment is applied to both end surfaces of the rubber layer, if necessary. Experimental examples regarding various rubber rollers according to the present invention will be explained below. Experimental Example 1 A rubber roller having a silicone rubber layer with a hardness of 40 degrees and a thickness of 8 mm on the outer peripheral surface of a metal core roller was prepared. Both ends of this rubber roller are
= 6 mm, △γ = 3 mm to form a small diameter part, and when it was passed through the support by sliding and rotating under a pressure of 400 g/mm with an opposing roller, the center of the rubber layer remained unchanged even in a 300,000-sheet durability test. No peeling from the roller was observed. When l is calculated using the above-mentioned empirical formula (1), l≧5.9
It was found that the above rubber roller satisfied the experimental formula. When a rubber roller with l=2 mm and Δγ=3 mm was tested under the same conditions, peeling of the rubber layer was observed after 100,000 sheets. Experimental Example 2 A silicone rubber layer with a hardness of 18 degrees and a thickness of 10 mm was formed on the outer circumferential surface of a metal core roller, and the heat-shrinkable tube was coated on the circumferential surface of the rubber layer by the method described above, and both ends of the rubber layer were coated with the heat-shrinkable tube. A rubber roller was created by forming an oil-resistant seal on the surface. This rubber roller has l=3.5
Δγ=3, and the surface hardness was 75 degrees. When the rubber roller was subjected to the same durability test as in Experimental Example 1 while supplying silicone oil under a pressure of 200 g/mm, no abnormality was observed in the oil-resistant seals at both ends of the rubber roller even after 500,000 sheets were printed. When l was calculated from the above-mentioned experimental formula (1), it was found that l=3.4, and it was found that the above rubber roller satisfied the experimental formula. In addition, the rubber roller with both ends of the tube cut in the same manner as both end faces of the rubber layer and oil-resistant seals formed on both end faces of the rubber layer developed a crack in the oil-resistant seal during a 20,000-sheet durability test, and the silicone rubber leaked into silicone oil from that part. It was recognized that the product had swelled and reached the end of its life. Experimental Example 3 When the rubber roller of Experimental Example 2 with l = 3.5 and △γ = 3 was subjected to a durability test at a pressure of 500g/mm, the oil-resistant seal cracked after 100,000 sheets, and the silicone rubber leaked from the silicone oil in that area. It was confirmed that the product had swelled due to water and had reached the end of its life. Here, when an appropriate l is determined from the above-mentioned empirical formula (1), it is found that l=5.4, and the above-mentioned l=3.5 is found to be short. Therefore, l = 6 mm, △γ = 3 mm at both ends of the rubber layer.
A small diameter portion was formed in accordance with the above relationship, its circumferential surface was covered with a heat-shrinkable tube in the same manner as described above, and oil-resistant seals were formed on both end surfaces of the rubber layer using fluorosilicone RTV to obtain a rubber roller. When the above rubber roller was subjected to a durability test under the same pressure as above, no abnormality was observed in the oil-resistant seal even after 100,000 sheets. In place of the above-mentioned oil-resistant seal, good results were also obtained with a rubber roller in which a primer was applied to both end faces of the rubber roller body, and a disk-shaped tetrafluoroethylene having a thickness of 100 μm was adhered to form an oil-resistant seal. The shape of the small diameter portions at both ends of the rubber layer may be tapered as in the above embodiment, or may be stepped to form small diameter portions having the same diameter. Also, the value of △γ does not need to be determined as strictly as the value of l; △γ≧1/3
It is sufficient if it is about l. As described above, in the present invention, at both ends of the rubber roller circumferential surface, the specific distance l is formed to have a smaller diameter than the other parts, so that the pressing force of the opposing roller is not applied to the small diameter part, or is extremely small. Therefore, bulging deformation of both ends of the rubber roller can be slightly suppressed, and peeling of the rubber layer from the core roller can be prevented. In addition, even in the case of a rubber roller with an oil-resistant coating applied to its circumferential surface, the bulging deformation of both end surfaces of the rubber roller is minimal as described above, so a sealing member with high strength, high elongation, and large adhesive force is required unlike the conventional one. There is no need to use
A sufficient oil-resistant seal can be formed using inexpensive paints, flexible synthetic resin materials, metal plates, etc., and peeling between the rubber layer and the coating layer can be prevented. In addition, since the small-diameter portion can be held in a non-contact state with the heated opposing roller or in a state close to it, the temperature of this portion can be kept low, preventing thermal deterioration of the adhesive and creating an oil-resistant seal. It is effective in improving the durability of

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a first embodiment of the present invention, and FIGS. 2 to 5 are explanatory diagrams of manufacturing steps of a second embodiment of the present invention. 1 is a core roller, 2 is a rubber layer, and 6 is a heat-shrinkable tube as an oil-resistant coating layer.

Claims (1)

[Claims] 1. A rubber roller used in a copying machine, etc., which has at least a rubber layer on the circumferential surface of the rigid center roller,
A distance lmm from both ends of the rubber layer inward in the longitudinal direction of the roller. However, [Formula] [Here, P is the pressure per 1 mm of the rubber layer circumferential surface (g/mm), and t is the thickness of the rubber layer. (mm), H is the JIS hardness (degrees) of the circumferential surface of the rubber layer.A rubber roller whose diameter is smaller than the diameter of other parts. 2. The rubber roller according to claim 1, wherein an oil-resistant sealing layer is provided on both end surfaces of the rubber layer. 3. The rubber roller according to claim 2, wherein the outer peripheral surface of the rubber roller is coated with an oil-resistant coating. 4. The oil-resistant coating layer is composed of a heat-shrinkable tube, and the heat-shrinkable tube is heat-shrinked with both ends protruding from both end faces of the rubber layer, and the end faces of the rubber layer are coated within each protruding heat-shrinkable part. The rubber roller according to claim 3, further comprising an oil-resistant seal layer.