Calender rolls for a calender roll press for manufacturing dry electrodes

Abstract

In this invention, a calendering roll for manufacturing dry electrodes is provided, the calendering rolls being arranged in pairs to press and stretch electrode sheets on both sides. The calendering roll includes: a cylindrical roll body mounted to extend in the width direction of the electrode sheet; a roll drive shaft mounted to pass through the central portion of the cylindrical roll body in the longitudinal direction; and a plurality of oil passages formed outside the roll drive shaft to form a flow path for oil flow, and formed to pass through the cylindrical roll body in the longitudinal direction, wherein the interval between the oil passages and the roll drive shaft is formed to be the largest at both sides of the cylindrical roll body in the longitudinal direction, and the smallest at the central portion of the cylindrical roll body.

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0172114, filed on December 3, 2021, the entire contents of which are incorporated herein by reference.

[0002] This invention relates to a calendering roll for a calendering roll press used to manufacture dry electrodes.

[0003] More specifically, the present invention relates to calendering rolls for calendering roll presses used to manufacture dry electrodes, which can increase bending stiffness by improving the oil passages in the calendering rolls, thereby reducing deformation deviations of the calendering rolls.

[0004] Furthermore, the present invention relates to calendering rolls of a calendering roll press for manufacturing dry electrodes, which can minimize the deformation of the dry electrode sheet. Background Technology

[0005] In recent years, rechargeable batteries have been widely used as a power source for wireless mobile devices.

[0006] In addition, secondary batteries have attracted attention not only as a power source for portable devices such as mobile phones, laptops, and cameras, but also as a power source for electric vehicles and hybrid vehicles, which have been proposed to address the air pollution problems caused by the use of fossil fuels in existing gasoline and diesel vehicles.

[0007] Therefore, due to the advantages of rechargeable batteries, the types of applications using rechargeable batteries have become very diverse. In the future, it is expected that rechargeable batteries will be used in more fields and products than they are now.

[0008] These secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries based on the composition of their electrodes and electrolytes. The use of lithium-ion polymer batteries, which have a low risk of leakage and are easy to manufacture, is increasing.

[0009] Generally, based on the shape of the battery casing, secondary batteries are generally divided into cylindrical batteries, in which the electrode components are housed in cylindrical metal cans and prismatic metal cans, and pouch batteries, in which the electrode components are housed in pouch-type casings made of aluminum laminate.

[0010] In addition, the electrode assembly housed in the battery casing is a power generation element. Each of them is formed in a structure having a positive electrode, a negative electrode and a separator placed between the positive electrode and the negative electrode, so that it can be charged and discharged. They are divided into a jelly roll type in which the separator is placed between long sheet-shaped positive and negative electrodes coated with active material and rolled up, and a stack type in which multiple positive and negative electrodes formed according to a predetermined size are stacked in sequence and a separator is placed between the positive and negative electrodes.

[0011] Here, because electric vehicles and other devices use high-output electrical energy, multiple battery modules are required, in which multiple battery cells are connected in series or parallel.

[0012] Meanwhile, in electrode manufacturing, electrodes are typically manufactured using a wet electrode process, which involves applying a slurry, including electrode active materials, binders, and conductive materials, onto the current collector, followed by a drying process to remove the solvent from the slurry.

[0013] In the aforementioned wet electrode process, the high manufacturing cost due to the energy required to remove the solvent from the slurry applied to the current collector makes it difficult to improve productivity.

[0014] Therefore, a method for manufacturing electrodes using a dry electrode process is proposed, which does not involve applying slurry to the current collector.

[0015] Dry electrode manufacturing is a method of manufacturing electrodes in the absence of liquid media such as solvents or dispersion media. It involves mixing electrode active materials, binders, conductive materials, etc. to prepare a powder mixture, manufacturing the powder mixture into a dry electrode sheet through a calendering process, and then laminating the manufactured dry electrode sheet onto a current collector.

[0016] In this dry electrode process, the energy density is increased and the charge-discharge characteristics are improved compared with the existing wet electrode process. The lifespan is at least twice that of the existing wet electrode process. Furthermore, it does not require the drying process required by the existing wet electrode process. Its advantage is that it does not require the drying chamber, space and drying energy costs required by the drying process.

[0017] Here, in the dry electrode process, the calendering process for manufacturing dry electrode sheets refers to the process of calendering dry electrode sheets using a calendering roll press.

[0018] That is, Figure 1 As shown, the calendering rolls 101 of the calendering roll press 100 are formed into cylindrical bodies. In the calendering process, the dry electrode sheet 108 is pushed between a pair of upper and lower calendering rolls 101 to be stretched.

[0019] In this case, the calendering roll 101 is rotated to form, and drive shafts 103a and 103b are respectively provided at the center of both sides.

[0020] Here, the problem arises when static pressure is applied to each drive shaft of the calender rolls, causing the central portion of the calender rolls to bend.

[0021] As described above, the static pressure applied to each drive shaft causes the central portion of the calender roll to bend. Compared to the central portion, the static pressure acts strongly on both sides of the dry electrode, thereby hindering the uniform deformation of the dry electrode sheet.

[0022] Another problem is that due to the repeated application of static pressure to the drive shaft of the calender roll, buckling occurs on both sides of the calender roll, which leads to defects in the dry electrode sheet to be manufactured.

[0023] As mentioned above, in order to suppress defects in dry electrode sheets, a method has been proposed to apply additional back pressure to counteract the static pressure applied to the calender rolls. However, since a back pressure device that generates the back pressure to counteract the static pressure needs to be installed separately, in addition to incurring additional costs, there is a problem that the entire structure of the calender roll press becomes complicated when the back pressure device is installed.

[0024] In addition, a method has been proposed to replace the existing cylindrical calender rolls with a crown-shaped calender roll. The crown-shaped calender roll is formed into a gentle convex curve shape in the longitudinal direction by forming a larger diameter at the center portion than at the sides of the roll, in order to suppress buckling caused by static pressure. However, this also has the problem that buckling is caused at the center portion of the dry electrode.

[0025] At the same time, such as Figure 2 As shown, in the calendering roll 101 having drive shafts 103a and 103b formed on both sides, multiple oil passages 105 are formed for oil flow and temperature control, and the oil passages 105 are formed in a straight line from one side of the calendering roll 101 to the other side in the longitudinal direction.

[0026] However, due to the formation of multiple oil passages in the longitudinal direction within the calender roll, the bending stiffness of the central part of the calender roll deteriorates when static pressure is applied to the two drive shafts.

[0027] Therefore, in order to improve the production quality of dry electrode sheets and suppress defects in dry electrode sheets, it is necessary to minimize the roll deformation caused by the static pressure applied to both ends of the calendering roll within the width of the dry electrode sheet.

[0028] [Related Technical Documents]

[0029] [Patent Documents]

[0030] (Patent Document 1) Korean Patent Registration No. 10-2028611 Summary of the Invention

[0031] [Technical Issues]

[0032] The present invention aims to solve the above-mentioned problems and provides a calendering roll for a calendering mill for manufacturing dry electrodes, which increases bending stiffness by improving the shape of the oil path through which the oil flows in the calendering roll, thereby reducing the deformation deviation of the calendering roll.

[0033] Furthermore, the present invention aims to provide a calendering roll for a calendering roll press for manufacturing dry electrodes, which can minimize the deformation of the dry electrode sheet.

[0034] [Technical Solution]

[0035] To accomplish the above-mentioned task, the present invention includes a calendering roll for a calendering roll press for manufacturing dry electrodes. The calendering rolls are arranged in pairs to press and stretch electrode sheets on both sides. The calendering rolls include: a cylindrical roll body mounted to extend in the width direction of the electrode sheet; a roll drive shaft mounted to pass through the central portion of the cylindrical roll body in the longitudinal direction; and a plurality of oil passages formed outside the roll drive shaft to form a flow path for oil flow, and passing through the cylindrical roll body in the longitudinal direction. The interval between the oil passages and the roll drive shaft is formed to be maximum at both sides of the cylindrical roll body in the longitudinal direction and minimum at the central portion of the cylindrical roll body.

[0036] As an example, the oil passage can be configured such that the interval can vary linearly from one side of the cylindrical roller body in the longitudinal direction toward the center.

[0037] Specifically, the oil passage can be curved from one side of the cylindrical roller body in the longitudinal direction toward the center.

[0038] More specifically, the oil passage can form a parabolic shape along the longitudinal direction of the cylindrical roller body.

[0039] As another example, the oil passage can be formed in a shape that bends from one side of the cylindrical roller body to the other in the longitudinal direction.

[0040] Specifically, the oil passages can be linearly formed at constant intervals from both sides of the cylindrical roller body in the longitudinal direction in the direction facing each other to a predetermined position, and then formed so that each interval can be linearly varied toward the center portion.

[0041] More specifically, the oil passages can be linearly formed at constant intervals from both sides of the cylindrical roller body in the longitudinal direction in the direction facing each other to a predetermined position, and then each oil passage forms a curved shape towards the center.

[0042] More specifically, the curved shape can be a parabolic shape.

[0043] As another example, the oil passages can be linearly formed at constant intervals from both sides of the cylindrical roller body in the longitudinal direction in directions opposite to each other to a predetermined position and bend toward the roller drive shaft, and then each oil passage can be formed in which each interval maintains a uniform shape toward the central portion.

[0044] As another example, the oil passages can bend longitudinally from both sides of the cylindrical roller body toward the roller drive shaft to a predetermined position, and then each oil passage can be formed in which each interval maintains a uniform shape toward the central portion.

[0045] As another example, the oil passages can be inclined at a predetermined angle from both sides of the cylindrical roller body toward the roller drive shaft in the longitudinal direction, and then they can meet each other to form a curved boundary in the central part.

[0046] [Beneficial Effects]

[0047] According to the present invention, bending stiffness can be sufficiently improved simply by improving the shape of the oil path through which the oil flows in the calender roll, thereby reducing the deformation deviation of the calender roll.

[0048] Furthermore, because the deformation deviation of the calender rolls is improved, the production quality of the dry electrode sheets can be improved and defects can be suppressed by minimizing the deformation of the dry electrode sheets.

[0049] In addition, when the calender roll is pressed by static pressure, it can also prevent buckling at both ends of the calender roll and at the center of the dry electrode sheet. Attached Figure Description

[0050] Figure 1 This is a schematic view illustrating the calendering process of the calendering rolls of a calendering roll press for manufacturing dry electrodes, according to related technologies.

[0051] Figure 2 (a)-(c) are schematic side cross-sectional views of the calendering rolls of a calendering roll press for manufacturing dry electrodes according to the related art.

[0052] Figure 3 (a)-(c) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a first embodiment of the present invention.

[0053] Figure 4 This is a schematic view showing a calendering process performed by calendering rolls according to this embodiment.

[0054] Figure 5 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a second embodiment of the present invention.

[0055] Figure 6 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a third embodiment of the present invention.

[0056] Figure 7 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a fourth embodiment of the present invention.

[0057] Figure 8 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a fifth embodiment of the present invention. Detailed Implementation

[0059] [Reference Figures]

[0060] 10a, 10b, 10c, 10d, 10e: Calendering rolls

[0061] 11: Roller body

[0062] 13: Roller drive shaft

[0063] 13a, 13b: Parts of the roller drive shaft

[0064] 15a, 15b, 15c, 15d, 15e: Oil circuit

[0065] 21: Dry electrode sheet Detailed Implementation

[0066] The present invention provides a calendering roll for a calendering roll press for manufacturing dry electrodes. The calendering rolls are arranged in pairs to press and stretch electrode sheets on both sides. The rolls include: a cylindrical roll body mounted to extend in the width direction of the electrode sheet; a roll drive shaft mounted to pass through the central portion of the roll body in the longitudinal direction; and a plurality of oil passages formed on the outside of the roll drive shaft to form a flow path through which oil flows and passes through the roll body in the longitudinal direction. The spacing between the oil passages and the roll drive shaft is maximized on both sides of the roll body in the longitudinal direction and minimized in the central portion of the roll body.

[0067] [Invention Model]

[0068] The present invention will now be described in detail. Prior to this, the terms and words used in this specification and claims should not be construed as limited to common or dictionary terms, but rather as meanings and concepts consistent with the essence of the invention or the proposed technology, based on the principle that the inventor can appropriately define the concepts of the terms to best describe his invention.

[0069] It should be understood that terms such as “comprising” and “having” used throughout the specification are intended to indicate the presence of features, figures, steps, operations, components, parts or combinations thereof described in the specification, but do not preclude the possibility of the existence or addition of one or more other features, figures, steps, operations, components or combinations thereof.

[0070] Furthermore, when a portion such as a layer, film, region, plate, etc., is referred to as "on" another portion, this includes not only the case where the portion is "directly on" the other portion, but also the case where there is another portion in between. On the other hand, when a portion such as a layer, film, region, plate, etc., is referred to as "below" another portion, this includes not only the case where the portion is "directly below" the other portion, but also the case where there is another portion in between. Additionally, the use of "on" in the specification of this invention can mean that something is placed on a lower or upper part.

[0071] Furthermore, when a portion such as a layer, film, region, plate, etc., is referred to as "on" another portion, this includes not only the case where the portion is "directly on" the other portion, but also the case where there is another portion in between. Similarly, when a portion such as a layer, film, region, plate, etc., is referred to as "below" another portion, this includes not only the case where the portion is "directly below" the other portion, but also the case where there is another portion in between. Moreover, the use of "on" in the description of this invention can mean that something is placed on a lower or upper part.

[0072] (First Implementation)

[0073] Figure 3 (a)-(c) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a first embodiment of the present invention. Figure 4 This is a schematic view showing a calendering process performed by calendering rolls according to this embodiment.

[0074] like Figure 3 As shown in (a)-(c), the calendering roll 10a of the calendering roll press for manufacturing dry electrodes includes a pair of cylindrical roll bodies 11, a roll drive shaft 13 formed at each of the central portions of the roll bodies 11, and an oil passage 15a forming an oil flow path in the roll bodies 11.

[0075] like Figure 4 As shown, the roller bodies 11 are rotatably arranged in pairs and formed into a cylindrical shape extending in the width direction of the dry electrode sheet 21.

[0076] According to the above structure, the dry electrode sheet 21 inserted between the roll bodies 11 of a pair of calendering rolls 10a is stretched when passing between the roll bodies 11.

[0077] The roller drive shaft 13 is shaped as a shaft and mounted to pass through the central portion of the roller body 11 in the longitudinal direction, and the roller drive shaft 13 is arranged to protrude from the central portions of the two sides of the roller body 11 respectively.

[0078] The oil passage 15a is configured to allow the oil used for temperature control of the calender roll 10a to flow, so that the oil passage 15a is formed in the roll body 11, the oil passage 15a forms a flow path for the oil to flow on the outside of the roll drive shaft 13, and is formed to pass through the roll body 11 in the longitudinal direction.

[0079] In this case, multiple oil passages 15a are radially formed on the outside of the roller drive shaft 13.

[0080] Here, according to the first embodiment of the present invention, the interval between the oil passage 15a and the roller drive shaft 13 is formed to be the largest at both sides of the roller body 11 in the longitudinal direction, and to be the smallest at the center portion of the roller body 11.

[0081] The shape of each oil passage 15a is configured to increase the bending stiffness of the roller body 11 against the static pressure applied to the portions 13a and 13b of each roller drive shaft 13. Therefore, a large gap is formed between the oil passages 15a and the roller drive shaft 13 on both sides of the roller body 11, so that they are set away from the roller drive shaft 13, and a small gap is formed between the oil passages 15a and the roller drive shaft 13 in the central portion of the roller body 11, and they are set close to the roller drive shaft 13.

[0082] Therefore, the gap between the oil passage 15a and the roller drive shaft 13 is formed to be the largest on both sides of the roller body 11 in the longitudinal direction, and the smallest at the center of the roller body 11.

[0083] In this way, by maximizing the spacing between the oil passages 15a on both sides of the roller body 11 in the longitudinal direction and the roller drive shaft 13, the bending stiffness against the static pressure applied to each of the portions 13a and 13b of the roller drive shaft 13 is improved.

[0084] In the first embodiment, the oil passage 15a is configured such that the distance between it and the roller drive shaft 13 changes linearly from one side of the roller body 11 in the longitudinal direction toward the center. That is, the oil passage 15a is configured such that the distance between the oil passage 15a and the roller drive shaft 13 changes linearly from one side of the roller body 11 in the longitudinal direction toward the center.

[0085] According to the embodiment shown, the oil passage 15a is curved from one side of the roller body 11 in the longitudinal direction toward the center.

[0086] More specifically, the oil passage 15a is parabolic in shape along the longitudinal direction of the roller body 11.

[0087] In the first embodiment of the invention shown, the curved shape of the oil passage 15a is formed in a parabolic shape, but it can also be formed in an arc shape or an ellipse shape, and can be changed to various other curved shapes.

[0088] According to the above structure, when static pressure is applied to each of the portions 13a and 13b of the roll drive shaft 13 protruding from both sides of the calender roll 10a, the central portion of the roll body 11 of the calender roll 10a, which has the main deformation problem due to static pressure, is significantly enlarged by a distance proportional to the amount of deformation occurring on both sides of the roll body 11. Furthermore, since the spacing of the oil passages 15a on both sides of the roll body 11 is larger, the stiffness against static pressure bending is also greater, thereby solving conventional problems such as bending of the central portion of the calender roll 10a and the strong static pressure on both sides of the roll body 11.

[0089] In this way, because the gap between the oil passage 15 and the roller drive shaft 13 is configured to be smaller toward the center of the roller body 11, the bending stiffness of the calendering roller 10a can be increased. Therefore, the deformation of the center of the roller body 11 in contact with the dry electrode sheet 21 can be reduced, and the deformation deviation of the dry electrode sheet 21 from the center to the end can be minimized.

[0090] Meanwhile, in this invention, although a structure is described to increase the bending stiffness against the static pressure applied to each of the portions 13a and 13b of the roll drive shaft 13 formed on both sides of the calender roll 10a by improving the oil passage 15a applied to the calender roll 10a in the calendering process, the bending stiffness of the roll against the static pressure can also be improved by applying the above structure to the rolls of the pressing and laminating processes used in the secondary battery manufacturing process.

[0091] (Second Implementation)

[0092] Figure 5 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a second embodiment of the present invention.

[0093] like Figure 5 As shown in (a)-(d), the shape of the calendering roll 10b according to this embodiment is such that the oil passage 15b formed in the roll body 11 bends from one side to the other in the longitudinal direction of the roll body 11.

[0094] Here, the oil passage 15b is linearly formed inward from both sides of the roller body 11 in the longitudinal direction to a predetermined position, and then formed such that the interval to the roller drive shaft 13 changes linearly towards the center.

[0095] That is, in the second embodiment, each oil passage 15b is formed in a straight line from both sides of the roller body 11 in the longitudinal direction to a predetermined position, with a constant interval from the roller drive shaft 13, and then formed into a shape that changes linearly from the end of the oil passage 15b to the center.

[0096] Furthermore, after the oil passage 15b is linearly formed to a predetermined position on the roller body 11, it can be formed into a curved shape toward the center.

[0097] For example, the shape of a linear curve can be a parabola.

[0098] In this embodiment, the curved shape of the oil passage 15b is described as forming a parabolic shape, but the oil passage 15b can also be formed into an arc shape or an ellipse, and can be changed to various other shapes.

[0099] (Third Implementation)

[0100] Figure 6 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a third embodiment of the present invention.

[0101] like Figure 6 As shown in (a)-(d), the oil passages 15c formed in the roll body 11 of the calendering roll according to this embodiment are linearly formed from both sides of the roll body 11 in the longitudinal direction in a direction facing each other to a predetermined position and bent toward the roll drive shaft 13, and after bending, each oil passage 15c has a shape in which each interval is uniformly maintained toward the central portion.

[0102] In other words, the structure of the oil passage 15c of the calender roll 10c in the third embodiment, which is linearly formed from both sides of the roll body 11 in the longitudinal direction to a predetermined position, is similar to that of the second embodiment. However, the difference is that the portion of the oil passage 15c that is linearly formed in the oil passage 15c is then formed to bend toward the roll drive shaft 13, and then the oil passage 15c is formed in a straight line from the portion to be bent in the structure toward the center portion.

[0103] According to the above structure, the oil passage 15c in this embodiment is formed such that the remaining portion, except for the portion to be bent, maintains the same distance from the roller drive shaft 13.

[0104] Here, in the oil passage 15c, it is preferable to tilt the portion that bends toward the roller drive shaft 13 so that it bends diagonally to supply oil flow, and this can be changed in various other ways.

[0105] (Fourth Implementation)

[0106] Figure 7 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a fourth embodiment of the present invention.

[0107] like Figure 7 As shown in (a)-(d), the oil passages 15d formed in the roll body 11 of the calendering roll according to this embodiment are bent inward from both sides of the roll body 11 to a predetermined position in the longitudinal direction, and each oil passage has a shape that uniformly maintains each interval.

[0108] That is, in the fourth embodiment, the oil passage 15d of the calender roll 10d bends from both sides of the roll body 11 in the longitudinal direction toward a predetermined position facing each other, and then forms a straight line from the bent portion of the oil passage 15d toward the center portion.

[0109] According to the above structure, the oil passage 15d in this embodiment is formed such that the remaining portion, except for the bent portions on both sides of the roller body 11, maintains the same distance from the roller drive shaft 13.

[0110] (Fifth Implementation)

[0111] Figure 8 (a)-(d) are schematic views illustrating the calendering rolls of a calendering roll press for manufacturing dry electrodes according to a fifth embodiment of the present invention.

[0112] like Figure 8 As shown in (a)-(d), the oil passage 15e formed in the roll body 11 of the calendering roll 10e according to this embodiment is formed to be inclined at a predetermined angle from both sides of the roll body 11 in the longitudinal direction in a direction facing each other, and then connected to the center portion in a curved shape.

[0113] In other words, the oil passage 15e of the calender roll 10e in the fifth embodiment is formed to be inclined at a predetermined angle to a predetermined position in the longitudinal direction from both sides of the roll body 11 in the direction facing each other, thereby forming an approximate "V" shape, and since the central part of the oil passage 15e forms a curved shape, the oil passages 15e extending obliquely from both sides of the roll body 11 are smoothly connected to each other.

[0114] According to the above structure, as described in the first embodiment, since the oil passage 15e of this embodiment is provided on both sides of the roller body 11 away from the roller drive shaft 13, and on the other hand, the oil passage 15e is provided in the central part of the roller body 11 close to the roller drive shaft 13, the bending stiffness of the roller body 11 when subjected to static pressure applied to each of the portions 13a and 13b of the roller drive shaft 13 can be improved.

[0115] While the present invention has been described and illustrated below with reference to specific embodiments, those skilled in the art will readily understand that various modifications and alterations can be made without departing from the spirit and scope of the invention as shown in the appended claims.

Claims

1. A calendering roll for a calendering roll press for manufacturing dry electrodes, the calendering rolls being arranged in pairs to press and stretch electrode sheets on both sides, the calendering rolls comprising: A cylindrical roller body mounted to extend in the width direction of the electrode sheet; A roller drive shaft is mounted to pass through the central portion of the cylindrical roller body in the longitudinal direction; Multiple oil passages are arranged outside the roller drive shaft, with oil flow paths that pass through the cylindrical roller body in the longitudinal direction. in, The interval between the oil passage and the roller drive shaft is greatest at both sides of the cylindrical roller body in the longitudinal direction and smallest at the center of the cylindrical roller body.

2. The calendering roll according to claim 1, wherein the interval changes linearly from one side of the cylindrical roll body in the longitudinal direction toward the center portion.

3. The calendering roll according to claim 2, wherein the oil passage has a curved shape from one side of the cylindrical roll body in the longitudinal direction toward the center portion.

4. The calendering roll according to claim 3, wherein the oil passage has a parabolic shape along the longitudinal direction of the cylindrical roll body.

5. The calendering roll according to claim 1, wherein the oil passage has a shape that bends from one side to the other in the longitudinal direction of the cylindrical roll body.

6. The calendering roll according to claim 5, wherein the oil passages are linearly formed in the longitudinal direction from both sides of the cylindrical roll body at constant intervals to predetermined positions in a direction facing each other, and then each of the intervals is linearly varied toward the center portion.

7. The calendering roll according to claim 6, wherein the oil passages are linearly formed in the longitudinal direction from both sides of the cylindrical roll body at constant intervals to predetermined positions in a direction facing each other, and each oil passage has a shape that curves toward the central portion.

8. The calendering roll according to claim 7, wherein the curved shape is parabolic.

9. The calendering roll according to claim 5, wherein the oil passages are linearly formed at constant intervals from both sides of the cylindrical roll body in the longitudinal direction in a direction facing each other to predetermined positions and are bent toward the roll drive shaft, and each of the oil passages has a shape that uniformly maintains each of the intervals toward the center portion.

10. The calendering roll of claim 5, wherein the oil passages are bent in the longitudinal direction from both sides of the cylindrical roll body toward the roll drive shaft to a predetermined position, and each of the oil passages has a shape that uniformly maintains each of the intervals toward the central portion.

11. The calendering roll according to claim 5, wherein the oil passages must be inclined at a predetermined angle from both sides of the cylindrical roll body toward the roll drive shaft in the longitudinal direction, and then meet each other to have a curved boundary in the central portion.

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