JP2008213047A - Manufacturing method of rubber roll and rubber roll for use in electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a rubber roll, which is easy to grind an outline of a rubber layer in a crown shape and reduces degradation in grinding performance of a wide abrasive stone used for grinding. <P>SOLUTION: In forming an unvulcanized rubber layer on a core bar shaft by a cross head die, feeding speed of the core bar shaft is varied to form the rubber layer in a crown shape, and the rubber layer after hardening is plunge-ground by an inverted-crown-shaped wide abrasive stone. A ratio (A/B) of a crown quantity A of the rubber roll to be ground to an inverted crown quantity B of the wide abrasive stone is preferably in the range of 2.5 to 5.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a rubber roll useful for a charging roll, a developing roll, and other various rolls used in electrophotographic apparatuses such as copying machines, laser beam printers and facsimiles.

  In recent years, the electrophotographic apparatus has been colorized, and there has been a demand for higher-definition and higher-level image uniformity (halftone uniformity). Therefore, the outer diameter shape of the rubber roll used in the electrophotographic apparatus is required to have high dimensional accuracy in both the longitudinal direction and the circumferential direction.

  For example, a charging roll used in an electrophotographic apparatus has a constant width (nip width) in contact with the photosensitive drum in the longitudinal direction, so that the outer diameter of both ends is larger than the outer diameter of the central portion. Usually in small crown shape. If there is variation in the nip width in the longitudinal direction, the amount of charge that the charging roll charges the photosensitive drum becomes uneven in the longitudinal direction, and an image that is uneven in the longitudinal direction occurs in the image that is initially printed. . In addition, when the number of durable images is increased, there is a difference in the degree of contamination on the surface of the charging roll, which also affects the charging of the photosensitive drum, and causes unevenness in the image in the longitudinal direction of the charging roll. There is also a case. By controlling the rubber hardness of the charging roll and the strength of the spring that presses the charging roll against the photosensitive drum, the size of the crown shape (crown amount) is made appropriate to suppress the occurrence of these image defects. Is possible. Therefore, in the technology for manufacturing a rubber roll used in an electrophotographic apparatus, it is necessary to make the outer diameter of the rubber roll into a crown shape with high accuracy.

  In addition, if there is a shake when the charging roll is rotated, the nip width between the charging roll and the photosensitive drum will be shaken, the charge amount of the photosensitive drum will be uneven, and the image to be initially printed will be in the circumferential direction. An image defect such as uneven shading occurs. In addition, when the number of durable images increases, the difference in the degree of dirt on the surface of the charging roll increases in the circumferential direction, causing circumferential charging unevenness in the charging of the photosensitive drum, and uneven density in the circumferential direction. An image defect may occur. In the following, the deflection of the charging roll when the charging roll is rotated is referred to as the “outer diameter deflection of the charging roll”, and the magnitude thereof is referred to as the “outer diameter deflection dimension of the charging roll. Making a state with almost no run-out is called “improving dimensional accuracy”. That is, by improving the dimensional accuracy of the outer diameter fluctuation of the charging roll, it is possible to suppress the occurrence of these image defects. For this reason, in a technique for manufacturing a rubber roll used in an electrophotographic apparatus, it is necessary to control the outer diameter runout dimension of the rubber roll with high accuracy, that is, as small as possible.

  As a conventional method for producing a crown-shaped rubber roll, a core metal shaft is loaded into a hollow mold having an inverted crown shape, and an unvulcanized rubber material is poured and filled. There is a way. According to this method, it is possible to obtain a rubber roll having a proper outer crown shape and high outer diameter runout dimensional accuracy. However, since a highly accurate mold is required, there is a problem that the mold cost becomes expensive and the manufacturing cost becomes very high. Also, because the outer shape is crown-shaped, when taking out the rubber roll from the mold after vulcanization is completed, depending on the amount of crown, it becomes difficult to take out or the rubber layer is distorted even if it is taken out. In some cases, the outer diameter deflection dimensional accuracy may be problematic.

  Recently, a technology has been developed in which the outer shape of the rubber roll is changed to a crown shape by changing the feed speed of the core metal shaft by cross-head extrusion in which a rubber roll is manufactured by co-extrusion of unvulcanized rubber and the core metal shaft ( For example, see Patent Document 1). In this method, a rubber roll whose outer shape is a crown shape can be manufactured only by the extrusion process, so that the manufacturing process can be simplified and an expensive mold is not required. However, in the manufacturing method using only the crosshead extrusion, there is a problem that the accuracy of the crown shape and the outer diameter run-out dimension is inferior as compared with the case of using a mold or the case of processing with a grinding apparatus.

  As another method for producing a rubber roll having a crown-shaped outer shape, there is a method in which a straight-shaped rubber roll is produced and then a wide grinding stone having a reverse crown shape is pressed against the rubber roll for grinding. In this method, it is possible to manufacture a rubber roll having a proper crown shape and a high accuracy in outer diameter runout by using a high-precision grinding technique. However, this manufacturing method also has the following problems.

  In the method of grinding by pressing a wide whetstone formed in a reverse crown shape against a straight rubber roll, the pressure to press the wide whetstone against the rubber roll increases as the grinding time is shortened, and the rubber roll pushes against the wide whetstone. The amount to be increased. In such a case, the grinding process ends with the wide grindstone and the rubber roll being pressed, and the surface roughness of the rubber roll after the grinding process becomes large. Moreover, the rubber roll after the grinding process has a crown amount larger than the reverse crown amount of the wide whetstone. Further, the grinding powder is easily clogged in the pores of the wide grindstone of the grinding apparatus, and the grindability of the grindstone is drastically lowered. In this case, it is necessary to perform a dressing process with a diamond dresser in order to restore the grindability of the grindstone, and the operation of the grinding apparatus must be frequently stopped, which greatly reduces productivity. For this reason, in the method of grinding a rubber roll manufactured in a straight shape by crosshead extrusion with a wide grindstone with an inverted crown shape, it is important to achieve both shortening of the grinding time and suppression of grindability degradation of the grindstone. ing.

In order to improve image quality, electrophotography is required to have a high function by a rubber roll, and rubber materials used in recent rubber rolls are also diversified. Solid color rubber rolls tend to be used more often than sponge type rubber rolls for color high-quality electrophotography. Many of the solid type rubber rolls are made of a rubber material having low grindability, such as silicone rubber and urethane rubber, which generates heat due to friction with a grindstone during grinding. In particular, when the rubber hardness is increased with a solid type rubber roll, the grindability is remarkably lowered. When grinding rubber rolls made of rubber materials with poor grindability, it is very difficult to reduce grinding time and suppress grindability degradation of the grindstone. It was.
Japanese Patent Laid-Open No. 2003-300279

  That is, the subject of this invention is providing the manufacturing method of the rubber roll by which the above subjects were solved and grindability was improved.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and in the formation of the rubber layer on the core metal shaft using a cross die type extruder, the extrusion speed of the core metal shaft and the grindstone used for grinding the rubber layer It was found that the adjustment of the reverse crown was important, and finally the present invention was achieved.

  That is, the present invention relates to a method for producing a rubber roll, comprising at least a step of extruding a core metal shaft together with unvulcanized rubber to form a rubber roll, a step of vulcanizing the rubber roll, and a step of plunge grinding the rubber roll. In the process of molding the unvulcanized rubber, the speed at which the core metal shaft is extruded at the exit of the cross die is changed to be the slowest at the center of the core metal shaft while keeping the unvulcanized rubber extrusion amount constant. A rubber roll characterized by using a wide whetstone formed in a reverse crown shape opposite to the crown shape of the rubber roll to be ground in the step of forming the layer into a crown shape and plunge grinding of the rubber roll after vulcanization It is a manufacturing method.

  Further, the present invention is characterized in that the ratio (A / B) of the crown amount A (mm) of the rubber roll to be ground and the reverse crown amount B (mm) of the wide grindstone is 2.5 or more and 5.0 or less. This is a method for producing the rubber roll.

  Further, according to the present invention, the ratio (B / C) between the reverse crown amount B (mm) of the wide whetstone and the crown amount C (mm) of the rubber roll after grinding is 0.6 to 0.9. It is the manufacturing method of the said rubber roll characterized.

  In addition, the present invention is a rubber roll for an electrophotographic apparatus, which is a rubber roll manufactured by the above-described method for manufacturing a rubber roll.

  According to the method for producing a rubber roll of the present invention, the wide whetstone at the time of grinding has little influence of pushing and bending the rubber roll, and the crown shape is stable and stable while the grinding time is short, and the outer diameter runout is highly accurate. A rubber roll can be obtained. Further, since it is possible to suppress the grindability of the grindstone from being lowered, it is possible to make the interval of the grindstone dressing process very long, thereby improving the productivity of the rubber roll and reducing the manufacturing cost. In addition, the manufacturing method of the rubber roll of this invention has a big effect, and is preferable for manufacturing the rubber roll which has a vulcanized rubber layer (elastic layer) which has rubbers, such as NBR, hydrin rubber, and EPDM, as a main component.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The rubber roll manufactured in the present invention is provided with a cylindrical elastic layer made of vulcanized rubber fixed around the axis of the core metal shaft, and the core metal shaft protrudes from both axial ends of the rubber roll. ing.

  FIG. 1 is a cross-sectional view schematically showing an apparatus for extruding unvulcanized rubber together with a core metal shaft in the method for producing a rubber roll of the present invention.

  Unvulcanized rubber 5 is fed into a rubber inlet (not shown) of the extruder 1 in the form of a strip or ribbon. As the screw 3 rotates in the cylinder 2 of the extruder 1, the unvulcanized rubber 5 is gradually extruded toward the crosshead die 13 connected to the tip of the extruder 1. In order to keep the temperature constant in the cylinder 2 and the screw 3, temperature control is performed by circulating hot water. The temperature of the hot water is determined by the type and composition of the rubber material to be extruded, but is generally in the range of 30 ° C to 100 ° C. The unvulcanized rubber 5 extruded by the screw 3 is rectified in flow through the breaker plate 4 installed at the tip of the screw 3 and supplied to the crosshead die 13. A mesh (not shown) is attached to the breaker plate 4 and also serves to remove foreign matters and the like in the unvulcanized rubber 5. Thereafter, the flow of the unvulcanized rubber 5 is changed by 90 ° in the crosshead die 13 and is developed on the outer periphery of the mandrel 11 in the circumferential direction. The shape of the mandrel 11 is a heart type or a spiral type depending on how the unvulcanized rubber 5 is developed. Warm water is also circulated through the crosshead die 13 for temperature control. The unvulcanized rubber 5 developed by the mandrel 11 moves toward the nipple 14 at the tip of the mandrel 11 while the outer diameter is reduced.

  On the other hand, the core metal shaft 6 is fed into the cross head die 13 from the core metal shaft supply port 10 at the rear end of the cross head die 13 by the core metal shaft feed roll 9 of the core metal shaft supply device 8. Usually, an adhesive 7 is applied to a portion of the core metal shaft 6 where a rubber layer of a rubber roll is formed. A core metal shaft guide 12 having an inner diameter that is 0.01 mm to 0.02 mm larger than the outer diameter of the core metal shaft 6 is provided before the core metal shaft supply port 10, and the center of the mandrel 11 is a nipple 14 at the tip. The cored bar 6 is continuously fed toward The unvulcanized rubber 5 developed by the mandrel 11 is attached to the outer periphery of the core metal shaft 6 coming out from the hole at the tip of the nipple 14, and both the core metal shaft 6 and the unvulcanized rubber 5 are dies. 15 is extruded in the form of a rubber roll while its outer diameter is regulated. The outer diameter of the rubber roll 17 to be extruded is determined by the inner diameter of the die 15 and the supply speed of the core metal shaft 6 when the amount of unvulcanized rubber 5 to be extruded is constant. In the present invention, the outer diameter of the rubber roll 17 is controlled by changing the supply speed of the cored bar 6 while keeping the inner diameter of the die 15 constant.

  In order to change the supply speed of the core metal shaft 6, the core metal shaft supply device 8 changes the rotation speed of the core metal shaft feed roll 9 and is connected to a servo motor (not shown). )) Is controlled. A trigger is set at a position that is an integral multiple of the total length of the core metal shaft 6 from the position at the tip of the crosshead die 13 in the core metal shaft supply device 8. Then, deceleration of the supply speed starts just from the tip position of the cored bar 6 and the deceleration of the supply speed ends at the center position. After that, acceleration of the supply speed starts from the center position and acceleration of the supply speed just at the rear end position. Ends. At the rear end position, the feed speed of the subsequent cored bar 6 is switched to the start speed. The core metal shaft feed roll 9 has a specification that can arbitrarily set the supply speed of the core metal shaft 6. In addition, when the supply speed is changed step by step, the number of divisions can be arbitrarily set. In the above description, the case where the maximum outer diameter of the crown shape comes to the longitudinal center of the cored bar shaft has been described. However, when the stripped lengths of the cored bar shafts at both ends are provided differently, It is preferable to control so that the supply speed of the cored bar is minimized at the position where the diameter comes.

  Cutting is performed by inserting a cutting blade 16 between the rear end of the core metal shaft 6 of the rubber roll 17 in which both the core metal shaft 6 and the unvulcanized rubber 5 are extruded from the die 15 and the subsequent tip of the core metal shaft 6. Then, the rubber rolls 17 are obtained one by one by being taken up by a take-up machine (not shown).

  In the rubber roll manufacturing method of the present invention, a change curve is set by providing a plurality of dividing points for the core metal shaft supply speed in the longitudinal direction of the core metal shaft and connecting them with a curve. There is no particular limitation on the number of divisions. Further, it is most desirable to make the change between the dividing points of the core shaft supply speed curved, but even if it is changed linearly, the same effect can be obtained if the number of divisions is increased.

  It is common to set the metal bar shaft supply speed from the front end to the center of the metal core axis to be decelerated and the speed of the core bar shaft supply speed from the center to the rear end to be the same speed change and symmetrical. It is. However, in some cases, the curvature of the speed change is set asymmetrically due to the influence of the extrudability of the rubber material and the length of the extrusion time.

  When the supply speed of the core metal shaft is gradually reduced from the tip to the center in a curvilinear manner, the amount of the unvulcanized rubber 5 deposited on the outer periphery of the core metal shaft 6 gradually increases, and the outside of the rubber roll 17 The diameter gradually increases. Conversely, when the core metal shaft supply speed is gradually accelerated from the center to the rear end, the amount of unvulcanized rubber 5 deposited on the outer periphery of the core metal shaft 6 gradually decreases. The outer diameter of the rubber roll 17 is gradually reduced. Therefore, the outer shape of the manufactured rubber roll has a crown shape. Basically, when the die diameter of the extruder is made constant by crosshead extrusion, and the extrusion amount of unvulcanized rubber is made constant, the outer diameter of the rubber roll after extrusion is determined by the feed rate of the core metal shaft. By. In the rubber roll manufacturing method of the present invention, it is possible to manufacture a rubber roll having an arbitrary crown amount by controlling the core metal shaft supply speed.

  FIG. 2 is a view for explaining an apparatus for grinding a rubber roll in the rubber roll manufacturing method of the present invention. More specifically, FIG. 2 is an explanatory view of an apparatus for rotating by gripping both sides of a cored bar shaft protruding from both ends of a rubber roll, and plunge a wide grindstone rotated at a high speed to grind it. Details will be described below.

  The rubber roll grinding apparatus includes a grinding wheel 21, a grinding wheel drive mechanism 31 that rotates the grinding wheel 21 against the rubber roll 17, chucks 28 and 29 that hold the rubber roll 17 at both ends of the core metal shaft 6, and the chucks 28 and 29. Motors 22 and 30 that rotate in synchronization are provided. The grindstone 21 is formed wider than the length of the rubber roll 17 in the axial direction, and has a predetermined reverse crown shape. In this apparatus, the chucks 28 and 29 for gripping both end portions of the core metal shaft 6 of the rubber roll 17 are of a diaphragm type.

  The grindstone drive mechanism 31 is disposed in parallel with the axial direction of the rubber roll 17 whose surface is ground in the axial direction of the grindstone 21 that is rotationally driven. Although not shown, the grindstone driving mechanism 31 includes a motor that rotationally drives the cylindrical grindstone 21 and a moving mechanism that presses the peripheral surface of the grindstone 21 against the outer peripheral surface of the rubber roll 17.

  In the rubber roll 17, one end side of the cored bar shaft 6 is clamped by the chuck 28, and the other end side is similarly clamped by the chuck 29. The chuck 28 and the chuck 29 facing each other are arranged so that both ends of the cored bar shaft 6 can be gripped and fixed on a coaxial core with the shaft cores aligned.

  In this gripping state, the chuck 28 is configured to be rotationally driven at a predetermined rotational speed by the motor 22, and the chuck 29 is similarly configured to be rotated at a predetermined rotational speed by the motor 30. The motor 22 and the motor 30 are controlled by a control circuit unit (not shown) so as to be rotationally driven in synchronization with each other so that a twisting force does not act around the axis of the cored bar shaft 6. . Then, in a state where the rubber roll 17 is rotated, a grinding stone 21 having a width wider than the entire length of the rubber roll 17 is rotated at a high speed, and is pressed against the outer peripheral surface of the rubber roll 17 to perform grinding.

  A mechanism in which the diaphragm chucks 28 and 29 grip and fix the end portion of the core metal shaft 6 will be described.

  The chuck 28 (29) is attached to the chuck adapter 25 in a state where the chuck claw 27 is attached to the tip of the nose 26. The chuck claw 27 is divided into a plurality of slits (generally divided into 6 to 8) by forming a plurality of slits to the vicinity of the base attached to the noose 26, and the nose 26 is circumferentially arranged at equal intervals. Arranged and mounted along the top.

  An air supply tube (not shown) is provided through the stock table 23 (24) and the chuck adapter 25. The air supply tube feeds the pressure-feed air, and the center of a diaphragm (not shown) provided inside the nose 26 is pressed and deformed by the pressure of the air. Thus, the chuck pawl 27 is opened and closed to grip and fix the outer peripheral surface of the cored bar shaft 6. It should be noted that another configuration may be adopted in which the chuck pawl is opened and closed by joining the piston to the diaphragm and pressing and deforming the central portion of the diaphragm with the piston.

  Normally, the chuck claw of a diaphragm chuck has a gripping part that grips and fixes the core metal shaft in a slightly gentler arc than the arc formed by the outer diameter of the core metal shaft. The holding force for holding the metal shaft is accurately transmitted. As a result, a holding force is uniformly applied at each contact point, and the accuracy of gripping and fixing the outer peripheral surface of the cored bar shaft is extremely high.

  The diaphragm chucks 28 and 29 for gripping and fixing the outer peripheral surfaces of both ends of the cored bar 6 are provided with a discharge hole for discharging air at the center of the chuck claw 27 (not shown). Yes. Diaphragm chucks 28 and 29 are fed with pressure from a pipe passing through the inside of chuck adapter 25 and nose 26, and are fed by a discharge hole from the inside of the core metal shaft insertion hole toward the grip portion of core metal shaft 6. The structure which discharge | releases is taken. This prevents grinding rubber powder, dust, etc. generated during grinding from entering between the chuck claw 27 and the cored bar shaft 6 and lowering the gripping accuracy.

  Further, since the chuck claw 27 can attach a cemented carbide chip (not shown) to the gripping portion, even if the gripping operation of the cored bar 6 is repeated, the gripping portion is hardly damaged and the gripping accuracy can be secured.

  In the rubber roll manufacturing method of the present invention, the rubber roll 17 is gripped and fixed at the same gripping amount by the chucks 28 and 29 at both ends of the cored bar shaft 6. The inner diameters of the chucks 28 and 29 are the same at both ends of the core metal shaft 6, and the rigidity of the rubber roll 17 becomes very high with the core metal shaft 6 held. No difference occurs. For this reason, when the grindstone 21 is pressed against the outer peripheral surface of the rubber roll 17, the left and right stiffnesses are the same, so the crown amount after grinding can accurately reflect the reverse crown shape of the grindstone 21. An appropriate crown shape can be obtained with the same left-right difference.

  In the method for producing a rubber roll according to the present invention, the wide grindstone of the grinding device is formed in an inverted crown shape. The formation can be performed by cutting the diamond dresser 32 over the longitudinal direction of the grindstone surface, and the crown amount is controlled by a dressing operation. In this example, the diamond dresser 32 is a single stone dresser type to which one diamond is attached.

  An inverted crown shape is formed by allowing the diamond dresser 32 to be cut in the inner diameter direction of the grindstone 21 from both ends toward the center in the longitudinal direction of the grindstone 21 with respect to the positional relationship between the surface of the grindstone 21 and the diamond dresser 32. Is done. This cutting operation amount is calculated from the arcuate shape of a circumscribed circle of a triangle connecting the three ends of the grindstone 21 and the center, and has an appropriate inverted crown shape. Since the cutting operation amount of the diamond dresser 32 is controlled in units of 1 / 10,000 mm, it is possible to form a precise arc shape. In addition, by setting the margin for the dressing operation in a plurality of stages, in particular, by setting the margin for the final stage to zero, minute irregularities on the surface of the grindstone are smoothed to further increase the accuracy of the inverted crown shape. In the rubber roll manufacturing method of the present invention, a grindstone having an arbitrary reverse crown amount can be obtained by setting the dressing operation.

  In the rubber roll manufacturing method of the present invention, first, a crown-shaped rubber roll is manufactured by changing the supply speed of the cored bar shaft using the rubber roll extrusion apparatus shown in FIG. The extruded rubber roll is heated and subjected to a vulcanization reaction, and then the rubber at both ends is cut off and the cored bar shaft is exposed. Thereafter, using a rubber roll grinding apparatus shown in FIG. 2, a wide grindstone formed in an inverted crown shape is plungeed and ground to produce a crown-shaped rubber roll.

  In the rubber roll manufacturing method of the present invention, the crown amount A (mm) of the rubber roll to be ground extruded and cured from the cross head, the reverse crown amount B (mm) formed on the wide grindstone, the crown amount of the rubber roll after grinding The relationship with C (mm) is preferably as follows. That is, A / B is in the range of 2.5 to 5.0, and B / C is in the range of 0.6 to 0.9. When in this range, the grindability of the rubber roll to be manufactured becomes extremely good.

  Since the rubber roll manufactured by the method for manufacturing a rubber roll of the present invention has a crown shape with high accuracy, it is useful as various rolls of an electrophotographic apparatus. By making the rubber layer conductive, it is useful as a charging roll, a developing roll or a transfer roll. Further, it is also useful as a feed roll and a take-up roll for a recording medium, and as a pair of fixing rolls.

  Hereinafter, specific examples of the present invention will be described.

The following rubber materials were used.
NBR: manufactured by Nippon Zeon Co., Ltd., trade name: Nipol DN219, base rubber stearic acid: manufactured by Nippon Oil & Fats Co., Ltd., processing aid zinc white: manufactured by Haku Suitec Co., Ltd., vulcanization acceleration aid carbon black: manufactured by Asahi Carbon Co., Ltd. Product name: Asahi # 70
Calcium carbonate: manufactured by Maruo Calcium Co., Ltd., trade name: Super SS
Sulfur: manufactured by Tsurumi Chemical Co., Ltd., trade name: Sulfax PMC, vulcanizing agent MBTS: manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: Noxeller DM, vulcanization accelerator TMTM: manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Product name: Noxeller TS, vulcanization accelerator

Examples 1 and 2 and Comparative Example 1
-Preparation of unvulcanized rubber composition NBR 100 parts by mass, stearic acid 1 part by mass, zinc white 5 parts by mass, carbon black 30 parts by mass, calcium carbonate 30 parts by mass, sulfur 1 part by mass, MBTS 2 parts by mass and TMTM 1 The mass parts were kneaded using a closed kneader and a roll machine to obtain an unvulcanized rubber composition.

-Manufacture of unvulcanized rubber roll As the cored bar shaft, an SUS rod having a diameter of 6 mm and a length of 252 mm coated with a hot melt adhesive with a thickness of 10 μm was prepared except for 10 mm at each end. The above-mentioned unvulcanized rubber composition is extruded with an extruder equipped with a cross die head as shown in FIG. 2, and at the same time, the core metal shaft is continuously passed through the cross head die of the extruder, An unvulcanized rubber roll having a vulcanized rubber layer formed thereon was obtained. Since the unvulcanized rubber layer of the unvulcanized rubber roll extruded from the cross head is continuous, a cutting blade was inserted at a position corresponding to the core metal shaft to obtain individual unvulcanized rubber rolls. In Examples 1 and 2, the speed of the core metal shaft to the cross die is changed, and gradually decreases from the front end to the middle where the rubber layer is formed on the core metal shaft, and then increases faster toward the rear end portion. I changed it. Further, in Comparative Example 1, the speed at which the cored bar shaft was passed through the crosshead die was not changed.
Extruder: φ70mm, L / D20, manufactured by Mitsuba Corporation

-Manufacture of rubber roll to be ground The above-mentioned unvulcanized rubber roll was put into a hot air oven at 180 ° C for 30 minutes for vulcanization to obtain a rubber roll having a vulcanized rubber layer formed on a core metal shaft. Then, both ends 10 mm of the rubber roll were cut off to expose the cored bar shaft to obtain a rubber roll to be ground. In this state, the outer diameter of the center part and both ends of the rubber roll was measured. The results are shown in Table 1.

-Manufacture of a product rubber roll The above-mentioned rubber roll to be ground was ground with the following contents to obtain rubber rolls having the shapes of Examples 1-2 and Comparative Example 1 shown in Table 1 below.
Grinding device: Plunge grinding device manufactured by Tsugami Corporation Grinding wheel: Grinding wheel diameter 305mm, grinding wheel width 235mm
Whetstone GC80, reverse crown 0.1mm
Grinding time: 8 sec

  The relationship among the crown amount A of the rubber roll to be ground manufactured above, the reverse crown amount B of the wide grinding wheel, and the crown amount C of the product rubber roll was as shown in Table 1 below.

  The outer diameter of the rubber roll is obtained by measuring both end portions and the maximum bulge portion (center portion) with a fully automatic roller measuring device RSV-860PC (trade name) manufactured by Tokyo Optoelectronic Co., Ltd. In addition, the measurement of each point measured the roll after rotating 90 degree | times again, and measured again, and made those average values the outer diameter of each measurement point. Further, the outer diameter of the end portion was defined as the end outer diameter, which is the average of the measured values at both ends.

  The crown amount of the rubber roll is obtained by subtracting the outer diameter value of the end portion from the outer diameter value of the central portion of the rubber layer of the rubber roll.

  Further, the reverse crown amount of the wide whetstone is obtained by subtracting the outer diameter value of the central portion from the outer diameter value of the wide whetstone at both ends of the rubber layer width of the rubber roll. However, for the sake of simplicity, the width of the wide whetstone is only slightly larger than the rubber layer width of the rubber roll in the embodiment, so that the reverse crown is obtained by subtracting the median value from the outer diameter value at both ends of the wide whetstone used. The amount was determined.

  In addition, when the surface roughness Rzjis (ten-point average roughness) of the central part was measured with a product rubber roll after grinding with a surface roughness measuring instrument “Surfcoder SE3500” (trade name) manufactured by Kosaka Laboratory Ltd., In Examples 1 and 2, it was about 4 μm, and in Comparative Example 1, it was as large as 6 μm.

  Further, when the decrease in grindability when the rubber roll was continuously ground after dressing the wide whetstone was examined, in both Examples 1 and 2, no decrease in grindability was observed at the time of 30000 pieces. In Comparative Example 1, about 5000 were finally found.

  In Examples 1 and 2, the crown amount A of the rubber roll to be ground is larger than the reverse crown amount B of the wide grindstone, the wide grindstone first contacts the center of the rubber roll to be ground, and grinding is performed with a small amount of pressing and bending the rubber roll. The grinding process is completed in a state where the load of the grinding process is small. On the other hand, in Comparative Example 1, the rubber roll to be ground is a straight outer shape, and the wide grindstone is first brought into contact with both ends of the rubber roll and ground while largely pushing and bending the rubber layer. finish.

  As a result, in Examples 1 and 2, the transfer ratios B / C of the reverse crown shape of the wide whetstone to the crown shape of the rubber roll were good at 0.83 and 0.67, respectively, but in Comparative Example 1, 0.5% Met. This also appears in the Rzjis and the number of continuous grinding.

It is sectional explanatory drawing of the manufacturing apparatus of an unvulcanized rubber roll. It is a schematic explanatory drawing of the apparatus which grinds a rubber roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Cylinder 3 Screw 4 Breaker plate 5 Unvulcanized rubber 6 Core metal shaft 7 Adhesive 8 Core metal shaft supply device 9 Core metal shaft feed roll 10 Core metal shaft supply port 11 Mandrel 12 Core metal shaft guide 13 Crosshead Die 14 Nipple 15 Die 16 Cutting blade 17 Rubber roll 21 Wide grinding wheel 22, 30 Motor 23, 24 Stock base 25 Chuck adapter 26 Noose 27 Chuck claw 28, 29 Chuck 31 Grinding wheel drive mechanism 32 Diamond dresser

Claims (4)

In a method for producing a rubber roll, comprising at least extruding a core metal shaft together with unvulcanized rubber, forming a rubber roll, vulcanizing the rubber roll, and plunge grinding the rubber roll.
In the process of forming the rubber roll, while keeping the extrusion amount of unvulcanized rubber constant, the speed at which the core metal shaft is pushed out at the outlet of the cross die is changed so as to be the slowest at the center of the core metal shaft. Forming a vulcanized rubber layer into a crown shape; and
A method for producing a rubber roll, characterized in that a wide whetstone formed in an inverted crown shape opposite to the crown shape of a rubber roll to be ground is used in a plunge grinding process of the rubber roll after vulcanization.   The ratio (A / B) of the crown amount A (mm) of the rubber roll to be ground and the reverse crown amount B (mm) of the wide grindstone is 2.5 or more and 5.0 or less. Manufacturing method of rubber roll.   The ratio (B / C) of the reverse crown amount B (mm) of the wide grindstone to the crown amount C (mm) of the rubber roll after grinding is 0.6 or more and 0.9 or less. Of producing rubber rolls.   A rubber roll for an electrophotographic apparatus, which is a rubber roll manufactured by the method for manufacturing a rubber roll according to any one of claims 1 to 3.

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