JP6158370B2 - Film winding body and manufacturing method thereof - Google Patents

Description

The present invention is wound by winding a film on a predetermined member Kaitai and relates to its production how.

  Patent Document 1 refers to a wound product (hereinafter referred to as “rolled body”) in which a polyolefin microporous film (hereinafter referred to as “microporous film”) is wound around a winding core (hereinafter referred to as “core”). ). In the technique disclosed in Patent Document 1, the film thickness of the microporous film calculated from the outer diameter of the wound body, the outer diameter of the core, and the length of the microporous film wound around the core, and the actual microporous film The microporous film is wound around the core so that the absolute value of the difference from the film thickness is equal to or less than a predetermined value. Accordingly, the microporous film is not loosened and does not excessively tighten in the wound body.

International Publication No. WO2008 / 013114 (Published January 31, 2008)

  The microporous film as described above is generally formed by preparing a wide original film and slitting it in the longitudinal direction to obtain a plurality of slit films having a predetermined width. And the said original fabric film may have the film thickness distribution in the width direction. The “width direction” means a direction perpendicular to the longitudinal direction and the thickness direction of the slit film.

  A part of the film thickness distribution of the original film is reflected in each slit film formed by slitting the original film having a film thickness distribution in the width direction. Even if the film thickness distribution in the width direction of the original film has waviness, if the width of the slit film is sufficiently small with respect to the waviness, the film thickness in the width direction is monotonous within the range of one slit film. Change, that is, monotonically increase or decrease monotonously from one side of the width direction to the other.

  The outer peripheral surface of the wound body obtained by winding such a slit film on the core is compared from the one end side in the width direction toward the other end side with respect to the central axis of the core by accumulating the film thickness distribution. Will be greatly inclined.

  In such a wound body having an inclined outer peripheral surface, not only the appearance as a product is deteriorated, but also the thick film side may be plastically deformed, which may cause meandering in the battery assembly process. Quality can be adversely affected.

In view of the above problems, and an object thereof is to provide a film winding body and a manufacturing how to suppress the inclination in the width direction of the outer peripheral surface of the film winding body.

  In order to solve the above-described problem, a film winding body according to one embodiment of the present invention is wound on a cylindrical member whose one end side is thinner than the other end side and an outer peripheral surface of the cylindrical member, and in the width direction. The one end side is provided with a film having a larger thickness than the other end side.

  The cylindrical member is elastically bent inward when the film is wound.

  According to the said structure, since the one end side of a cylindrical member is thinner than the other end side, rigidity is low. The cylindrical member bends more inwardly at one end side where the rigidity is lower than at the other end side. And since the thick site | part of a film is wound by the one end side which bend | curves largely inside, the inclination of the width direction in an outer peripheral surface is suppressed.

  The “one end” and the “other end” refer to one end and the other end in the central axis direction of the cylindrical member.

  The material of the cylindrical member may include any of ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, and vinyl chloride resin.

  The cylindrical member can be manufactured by resin molding using a mold. At this time, by adopting a shape in which one end side is thinner than the other end side in the mold, one end side of the cylindrical member can be resin-molded thinner than the other end side.

  The film may be a porous film stretched in a direction in which the central axis of the cylindrical member extends.

  A general film has a film thickness distribution that is not flat in the width direction. Especially, the film thickness distribution of a porous film is large compared with a nonporous film, and especially the film thickness distribution of the porous film manufactured by extending | stretching to the width direction is large in the width direction.

  According to the said structure, since the film is extended | stretched, the film thickness distribution of a film is biased to the one side of the cylinder wound. By utilizing this uneven thickness distribution, the thickness of the cylindrical member and the thickness of the film can be reliably associated with each other, and the film can be wound around the cylindrical member.

  Moreover, the film winding body which concerns on 1 aspect of this invention may further be provided with the several support member arranged at intervals mutually which supports the outer peripheral surface of the said cylindrical member from the inner side.

  According to the said structure, a film can be wound around an outer peripheral surface strongly compared with the case where there is no supporting member. In addition, at one portion of the outer peripheral surface between the support members, one end side of the cylindrical member bends inward more greatly than the other end side. Therefore, winding deviation of the film can be suppressed, and inclination in the width direction on the outer peripheral surface can be suppressed.

  In addition, the film winding body according to one embodiment of the present invention has a cylindrical outer peripheral surface, and when a force in a direction to reduce the peripheral length is applied to the outer peripheral surface, the peripheral length on one end side is A core that is shorter than the peripheral length on the other end side, and a film wound around the outer peripheral surface of the core and having one end side in the width direction thicker than the other end side are provided.

  Moreover, the film winding body which concerns on 1 aspect of this invention is wound by the outer periphery of the core for winding a film on an outer peripheral surface, and the one end side of the width direction is film thickness rather than the other end side. The outer peripheral surface of the core has a peripheral length on one end side shorter than a peripheral length on the other end side.

  According to the said structure, the film thickness of the film wound by the said one end side is thick with respect to the other end side, and the perimeter of the outer peripheral surface of a core is short. Therefore, as a result of these canceling out, the inclination of the outer peripheral surface of the wound body caused by the film thickness difference is suppressed.

  Moreover, the film winding body which concerns on 1 aspect of this invention sets the outer diameter of the said one end side of the said film wound as D1, The outer diameter of the said other end side of the said film wound as D2, When the width of the film is W, it is preferable to satisfy | D1-D2 | / W ≦ 6.

  According to said structure, the bending amount of the film by a film deforming plastically can be made small.

  Moreover, the manufacturing method of the film winding body which concerns on 1 aspect of this invention WHEREIN: The process of specifying the direction of the cylindrical member whose one end side is thinner than the other end side, and the outer peripheral surface of the said cylindrical member, Winding the film having a thickness greater than that of the other end.

  The film wound on the film winding body is unwound from the film winding body and then processed into a secondary product. At this time, it is preferable that the amount of bending of the film unwound from the film winding body is small.

  The inventors have found that the inclination in the direction in which the central axis of the cylindrical member extends on the outer peripheral surface of the film winding body correlates with the amount of bending of the film unwound from the film winding body.

  According to the said structure, based on this inclination, the quality of a film winding body can be test | inspected, without unwinding a film from a film winding body.

  Moreover, it is often complicated to unwind the slit separator from the film winding body and measure the amount of bending with respect to the unwound direction. Furthermore, since the unwinding condition of the slit separator and the measurement condition of the bending amount are easily changed, the measured bending amount often varies. However, by specifying the inclination described above, it is possible to easily test the quality of the film winding body without measuring the amount of bending.

  If based on each aspect of this invention, the inclination of the width direction in the outer peripheral surface of a film winding body will be suppressed. Moreover, this film winding body can be manufactured. Also, the quality of the film roll can be tested.

It is a schematic diagram which shows the cross-sectional structure of a lithium ion secondary battery. It is a schematic diagram which shows the detailed structure of the lithium ion secondary battery shown by FIG. It is a schematic diagram which shows the other structure of the lithium ion secondary battery shown by FIG. It is a schematic diagram which shows the structure of the slit apparatus which slits a separator. It is a side view and a front view which show the structure of the cutting device of the slit apparatus shown by FIG. FIG. 2 is a front view / sectional view showing a configuration of a core of a wound body according to the first embodiment. It is a front view and a schematic diagram for demonstrating the measuring method of the outer diameter of the core shown by FIG. It is sectional drawing which shows the structure of the winding body which wound the slit separator on the core shown by FIG. It is a top view which shows the state of a slit separator when unwinding a slit separator from the winding body shown by FIG. FIG. 6 is a schematic diagram for explaining a method for testing a wound body according to a second embodiment. It is a graph which shows the correlation with the inclination and bending amount in the test | inspection method demonstrated by FIG. It is a flowchart which shows the test method of the winding body based on the correlation shown by FIG. 6 is a flowchart illustrating a method for manufacturing a wound body according to a third embodiment. It is a figure showing the structure of the core used in Embodiment 4. It is sectional drawing which shows the structure of the winding body which wound the slit separator on the core of Embodiment 4. It is a graph showing the relationship between the amount of bending and the inclination index.

  Below, the winding body of the present invention will be explained assuming that a separator for a lithium ion secondary battery is wound around the core. Therefore, first, a lithium ion secondary battery, a separator, a heat-resistant separator, a heat-resistant separator manufacturing method, a slit device, and a cutting device will be described in order.

(Lithium ion secondary battery)
Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries have high energy density, and are therefore currently used for mobile devices such as personal computers, mobile phones, personal digital assistants, automobiles, airplanes, etc. As a battery, it is widely used as a stationary battery that contributes to the stable supply of electric power.

  FIG. 1 is a schematic diagram showing a cross-sectional configuration of a lithium ion secondary battery 1.

  As shown in FIG. 1, the lithium ion secondary battery 1 includes a cathode 11, a separator 12 (film), and an anode 13. An external device 2 is connected between the cathode 11 and the anode 13 outside the lithium ion secondary battery 1. Then, electrons move in the direction A when the lithium ion secondary battery 1 is charged, and in the direction B when the lithium ion secondary battery 1 is discharged.

(Separator)
The separator 12 is disposed between the cathode 11 that is the positive electrode of the lithium ion secondary battery 1 and the anode 13 that is the negative electrode thereof so as to be sandwiched between them. The separator 12 is a porous film that allows lithium ions to move between the cathode 11 and the anode 13 while separating them. The separator 12 includes, for example, polyolefin such as polyethylene and polypropylene as its material.

  FIG. 2 is a schematic diagram showing a detailed configuration of the lithium ion secondary battery 1 shown in FIG. 1, where (a) shows a normal configuration, and (b) shows a temperature rise of the lithium ion secondary battery 1. (C) shows a state when the temperature of the lithium ion secondary battery 1 is rapidly increased.

  As shown in FIG. 2A, the separator 12 is provided with a number of holes P. Usually, the lithium ions 3 of the lithium ion secondary battery 1 can come and go through the holes P.

  Here, for example, the lithium ion secondary battery 1 may be heated due to overcharge of the lithium ion secondary battery 1 or a large current caused by a short circuit of an external device. In this case, as shown in FIG. 2B, the separator 12 is melted or softened, and the hole P is closed. Then, the separator 12 contracts. Thereby, since the traffic of the lithium ion 3 stops, the above-mentioned temperature rise is also stopped.

  However, when the lithium ion secondary battery 1 is rapidly heated, the separator 12 is rapidly contracted. In this case, as shown in FIG. 2C, the separator 12 may be broken. And since the lithium ion 3 leaks from the destroyed separator 12, the traffic of the lithium ion 3 does not stop. Therefore, the temperature rise continues.

(Heat-resistant separator)
FIG. 3 is a schematic diagram showing another configuration of the lithium ion secondary battery 1 shown in FIG. 1, where (a) shows a normal configuration, and (b) shows that the lithium ion secondary battery 1 is abruptly changed. The state when the temperature is raised is shown.

  As shown in FIG. 3A, the separator 12 may be a heat-resistant separator including a porous film 5 and a heat-resistant layer 4. The heat-resistant layer 4 is laminated on one surface of the porous film 5 on the cathode 11 side. The heat-resistant layer 4 may be laminated on one surface of the porous film 5 on the anode 13 side, or may be laminated on both surfaces of the porous film 5. The heat-resistant layer 4 is also provided with holes similar to the holes P. Usually, the lithium ions 3 come and go through the holes P and the holes of the heat-resistant layer 4. The heat resistant layer 4 includes, for example, wholly aromatic polyamide (aramid resin) as a material thereof.

  As shown in FIG. 3B, even when the lithium ion secondary battery 1 is rapidly heated and the porous film 5 is melted or softened, the heat resistant layer 4 assists the porous film 5. Therefore, the shape of the porous film 5 is maintained. Therefore, the porous film 5 is melted or softened, and the holes P are only blocked. Thereby, since the traffic of the lithium ion 3 stops, the above-mentioned overdischarge or overcharge is also stopped. Thus, destruction of the separator 12 is suppressed.

(Separator / heat-resistant separator manufacturing process)
The production of the separator and the heat-resistant separator of the lithium ion secondary battery 1 is not particularly limited, and can be performed using a known method. Below, the case where the porous film 5 mainly contains polyethylene as the material is assumed and demonstrated. However, even when the porous film 5 contains other materials, the separator 12 (heat resistant separator) can be manufactured by the same manufacturing process.

  For example, after adding an inorganic filler or a plasticizer to a thermoplastic resin to form a film, the inorganic filler and the plasticizer are washed and removed with an appropriate solvent. For example, when the porous film 5 is a polyolefin separator formed from a polyethylene resin containing ultra-high molecular weight polyethylene, it can be produced by the following method.

  This method is (1) kneading to obtain a polyethylene resin composition by kneading ultrahigh molecular weight polyethylene and an inorganic filler (for example, calcium carbonate, silica) or a plasticizer (for example, low molecular weight polyolefin, liquid paraffin). A step, (2) a rolling step of forming a film using the polyethylene resin composition, (3) a removal step of removing the inorganic filler or plasticizer from the film obtained in step (2), and (4) It includes a stretching step of stretching the film obtained in the step (3) to obtain the porous film 5. In addition, the said process (4) can also be performed between the said processes (2) and (3).

  The removal step provides a large number of micropores in the film. The micropores of the film stretched by the stretching process become the above-described holes P. Thereby, the porous film 5 (separator 12 which does not have a heat-resistant layer) which is a polyethylene microporous film having a predetermined thickness and air permeability is obtained.

  In the kneading step, 100 parts by weight of ultra high molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler may be kneaded.

  Thereafter, the heat-resistant layer 4 is formed on the surface of the porous film 5 in the coating process. For example, an aramid / NMP (N-methyl-pyrrolidone) solution (coating solution) is applied to the porous film 5 to form the heat-resistant layer 4 that is an aramid heat-resistant layer. The heat-resistant layer 4 may be provided only on one side of the porous film 5 or on both sides. Moreover, you may apply the liquid mixture containing fillers, such as an alumina / carboxymethylcellulose, as the heat-resistant layer 4. FIG.

  In the coating process, the surface of the porous film 5 is coated with a polyvinylidene fluoride / dimethylacetamide solution (coating liquid) (coating process) and solidified (coagulating process) to thereby form the porous film 5. An adhesive layer can also be formed on the surface. The adhesive layer may be provided only on one side of the porous film 5 or may be provided on both sides.

  The method for applying the coating liquid to the porous film 5 is not particularly limited as long as it is a method that enables uniform wet coating, and a conventionally known method can be employed. For example, a capillary coating method, a spin coating method, a slit die coating method, a spray coating method, a dip coating method, a roll coating method, a screen printing method, a flexographic printing method, a bar coater method, a gravure coater method, a die coater method, etc. Can do. The thickness of the heat-resistant layer 4 can be controlled by the thickness of the coating wet film and the solid content concentration in the coating solution.

  A resin film, a metal belt, a drum, or the like can be used as a support for fixing or conveying the polyolefin-based porous film during coating.

  As described above, the separator 12 (heat resistant separator) in which the heat resistant layer 4 is laminated on the porous film 5 can be manufactured. The manufactured separator is wound around a cylindrical core. In addition, the object manufactured with the above manufacturing method is not limited to a heat-resistant separator. This manufacturing method does not need to include a coating process. In this case, the object to be manufactured is a separator having no heat-resistant layer.

  The thickness in the width direction of the manufactured pre-slit separator (raw film) can be measured by a known method of contact type or non-contact type. A non-contact type film thickness measuring method that does not damage the product is preferable. As a method for continuously measuring the thickness in the separator width direction, either a traverse method in which the measuring device reciprocates or a method in which the inspection devices are arranged on the entire width surface may be used. Based on the measurement result of the thickness of the raw film in the width direction, the inclination of the thickness of the separator after being slit can be predicted.

(Slit device)
The heat-resistant separator or the separator having no heat-resistant layer (hereinafter referred to as “separator”) preferably has a width (hereinafter referred to as “product width”) suitable for application products such as the lithium ion secondary battery 1. However, in order to increase productivity, the separator is manufactured such that its width is equal to or greater than the product width. Once manufactured, the separator is cut (slit) to the product width.

  The “separator width” means the length of the separator in the direction parallel to the plane in which the separator extends and perpendicular to the longitudinal direction of the separator. Hereinafter, the wide separator before being slit is referred to as “original fabric”, and the slit separator is particularly referred to as “slit separator”. The slit means that the separator is cut along the longitudinal direction (film flow direction in manufacturing, MD: Machine direction), and the cut means that the separator is cut along the transverse direction (TD). Means to cut. The transverse direction (TD) means a direction parallel to the plane in which the separator extends and substantially perpendicular to the longitudinal direction (MD) of the separator.

  4A and 4B are schematic views showing the configuration of the slit device 6 that slits the separator. FIG. 4A shows the overall configuration, and FIG. 4B shows the configuration before and after slitting the original fabric.

  As shown in FIG. 4A, the slit device 6 includes a cylindrically-shaped unwinding roller 61, rollers 62 to 69, and a plurality of winding rollers 70U and 70L that are rotatably supported. . The slit device 6 is further provided with a cutting device 7 to be described later.

(Before slit)
In the slit device 6, a cylindrical core c around which an original fabric is wound is fitted on the unwinding roller 61. As shown in FIG. 4B, the original fabric is unwound from the core c to the path U or L. The unwound original fabric is conveyed to the roller 68 via the rollers 63 to 67. In the transporting process, the original fabric is slit into a plurality of separators. In addition, in order to convey an original fabric by a desired track | orbit, you may change the number and arrangement | positioning of the rollers 62-69.

(After slitting)
As shown in FIG. 4B, a part of the plurality of slit separators is wound around each cylindrical core u (bobbin) fitted to the winding roller 70U. Further, the other part of the plurality of slit separators is wound around each cylindrical core l (bobbin) fitted to the winding roller 70L. Note that an integrated body of the slit separator and the core u · l wound up in a roll shape is referred to as a “rolled body”.

(Cutting device)
FIG. 5 is a diagram illustrating a configuration of the cutting device 7 of the slit device 6 illustrated in FIG. 4A, where FIG. 5A is a side view of the cutting device 7, and FIG. It is a front view.

  As shown in FIGS. 5A and 5B, the cutting device 7 includes a holder 71 and a blade 72. The holder 71 is fixed to a housing or the like provided in the slit device 6. The holder 71 holds the blade 72 so that the positional relationship between the blade 72 and the conveyed separator raw material is fixed. The blade 72 slits the raw material of the separator with a sharp edge.

Embodiment 1
A first embodiment of the present invention will be described with reference to FIGS.

≪Composition of wound body≫
The wound body is obtained by winding a slit separator (film) obtained by cutting an original fabric in the longitudinal direction around a core. The surface of the wound body 10 (FIG. 8) of the present embodiment to be described later is slit by winding the slit separator 9 around the core 8 in consideration of the deformation of the core 8 and the thickness of the slit separator 9 (film). The inclination in the width direction on the outer peripheral surface t of the separator 9 can be suppressed. Below, the structure of the winding body 10 is demonstrated in order.

(core)
6A and 6B are diagrams illustrating the configuration of the core 8 of the wound body 10 according to the present embodiment, in which FIG. 6A is a front view and FIG. 6B is a cross-sectional view taken along the line AA in FIG. (C) is a cross-sectional view corresponding to (b) showing the manufacturing method of the core 8, and (d) to (e) are cross-sectional views showing other structures in the range E of (b). Note that the XYZ axes shown in FIG. 6A correspond to the XYZ axes shown in the drawings other than FIG.

  As shown in FIG. 6A, the core 8 includes an outer cylindrical portion 81 (cylindrical member), an inner cylindrical portion 82, and ribs 831 to 838.

  The outer cylindrical portion 81 is a cylindrical member having rigidity and elasticity for winding the slit separator around the outer peripheral surface s. The inner cylindrical portion 82 is a cylindrical member for fitting a winding roller on the inner peripheral surface thereof. The ribs 831 to 838 (support members) extend between the inner peripheral surface of the outer cylindrical portion 81 and the outer peripheral surface of the inner cylindrical portion 82, and are spaced apart from each other to support the outer cylindrical portion 81 from the inner side. It is a member.

  As shown in FIG. 6B, the thickness (wall thickness) of the outer cylindrical portion 81 on the Y axis negative direction side (one end side) is smaller than the thickness on the Y axis positive direction side (the other end side).

  Note that the central axis CA of the outer cylindrical portion 81 extends in the Y-axis direction. Further, the central axis CA of the outer cylindrical portion 81 and the central axis of the inner cylindrical portion 82 coincide with each other.

(Core molding method)
As shown in FIG. 6C, the core 8 is manufactured by resin molding using the molds Da and Db. On the surface of the mold Da facing the mold Db, the outer cylindrical portion 81, the inner cylindrical portion 82, and the groove portions de corresponding to the ribs 831 to 838 are provided. In this resin molding, a resin including any one of ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, and vinyl chloride resin is used as the material of the outer cylindrical portion 81 and the inner cylindrical portion 82.

  The groove part d · e is thinner toward the deeper part. By adopting such a shape, the thickness of the outer cylindrical portion 81 of the core 8 to be molded is reduced on the Y-axis negative direction side (the side on which the mold Da is disposed) and the Y-axis positive direction side (the mold Db is It can be enlarged on the arranged side). That is, the thickness distribution of the outer cylindrical portion 81 can be monotonously inclined in the Y-axis direction. At this time, the rigidity can be increased at a portion where the thickness of the outer cylindrical portion 81 is large, and the rigidity can be relatively decreased at a portion where the thickness of the outer cylindrical portion 81 is small.

  The outer peripheral surface s of the outer cylindrical portion 81 after being extracted from the groove portion d is processed so as to be parallel to the central axis CA. The same applies to the inner peripheral surface of the inner cylindrical portion 82 extracted from the groove portion e.

  As shown in FIG. 6D, the thickness distribution of the outer cylindrical portion 81 may not be inclined in the Y-axis direction. Further, as shown in FIG. 6E, the thickness distribution may not be monotonously inclined in the Y-axis direction.

(Outer diameter of core)
FIG. 7 is a view for explaining a method of measuring the outer diameter of the core 8 shown in FIG. 6A, and FIG. 7A is a front view showing a range C in FIG. (B) is a schematic diagram which shows a mode that this outer diameter is measured.

  As shown in (a) of FIG. 7, a mark S is given to one surface of the outer cylindrical portion 81. The mark S is a trace of a jig (for example, a guide pin for positioning the mold) used together with the mold when the core 8 is resin-molded using the mold. Has been granted. The mark S may be a display for identifying a core such as a production lot. When the difference in the thickness of the outer cylindrical portion 81 is slight, it is difficult to visually determine the thicker side, but it can be determined by the presence or absence of the mark S.

  Hereinafter, one surface of the outer cylindrical portion 81 on the Y axis positive direction side is referred to as a “reference surface”. Further, one surface of the outer cylindrical portion 81 on the Y axis negative direction side is referred to as a “back surface”.

  As shown in FIG. 7B, for example, a caliper M is brought into contact with one side of the outer cylindrical portion 81, and the diameter of the outer cylindrical portion 81 (hereinafter referred to as “outer diameter”) is measured.

  Table 1 shows the outer diameter of the core 8 measured by the measurement method described above. As shown in Table 1, the outer diameters of samples 1 to 3 of the three cores 8 were measured. Samples 1 to 3 are common to Tables 2 to 4 described later. Moreover, the outer diameter was measured about the reference surface and the back surface of each sample. The item “difference” is a value obtained by subtracting the outer diameter of the back surface from the outer diameter of the reference surface (hereinafter, “outer diameter difference”). Moreover, the outer diameter was measured about 8 points | pieces of each surface.

  “831” of the item “measurement point” indicates a value related to the outer diameter at the position of the rib 831 shown in FIG. “831a” in this item indicates a value relating to the outer diameter at a position equidistant from the rib 831 and the rib 832. The same applies to other items of “measurement point”. The average value of the outer diameter difference for the eight measurement points is about −0.02 mm or more and −0.01 mm or less.

  Moreover, this outer diameter difference is included in a range of −0.04 mm or more and 0.03 mm or less. That is, the absolute value of the outer diameter difference is 0.04 mm or less. Here, when the film thickness of the slit separator is, for example, 16 μm, the absolute value of the outer diameter difference is less than three in terms of the slit separator. Since the slit separator is wound several hundred to several tens of thousands of times on the core 8, if it is converted into a slit separator and the difference is about 3 sheets, it can be handled that there is no difference in outer diameter.

(Core thickness)
Similar to the measurement method described above, for example, the caliper M is brought into contact with one side of the core 8 so as to sandwich the outer cylindrical portion 81 in the thickness direction, and the thickness of the outer cylindrical portion 81 (hereinafter “thickness”) is measured.

  Table 2 shows the wall thickness measured by the same method as the measuring method shown in FIG. As shown in Table 2, the wall thickness was measured for samples 1 to 3 of the three cores 8. Moreover, the thickness was measured about the reference surface and the back surface of each sample. The item “difference” is a value obtained by subtracting the thickness of the back surface from the thickness of the reference surface (hereinafter “thickness difference”). Further, the wall thickness was measured at 8 points on each surface.

  “831a” in the item “measurement point” indicates a value related to the thickness at a position equidistant from the rib 831 and the rib 832 illustrated in FIG. The same applies to other items of “measurement point”. “838a” indicates a value related to the thickness at a position equidistant from the rib 838 and the rib 831.

  The average value of the difference in thickness at the eight measurement points is about 0.12 mm or more and 0.18 mm or less. That is, the thickness of the reference surface is larger than the thickness of the back surface. Moreover, the thickness difference is more conspicuous than the above-described outer diameter difference. This thickness difference is included in the range of 0.02 mm to 0.34 mm.

(Outer diameter of wound body)
The slit separator 9 is wound around the core 8 by, for example, several hundred to several tens of thousands of times. If the thickness of the slit separator 9 is uniformly 16 μm, the outer diameter of the wound body 10 increases by 32 μm every time the slit separator 9 is wound around the core 8. For this reason, the slit separator 9 is uniformly increased by about 3.2 mm to 320 mm from the start to the end of winding.

  However, the film thickness of the slit separator 9 is inclined in the width direction. For this reason, the actual outer diameter of the wound body does not increase uniformly.

  FIG. 8 is a cross-sectional view showing a configuration of a wound body 10 in which the slit separator 9 is wound around the core 8 shown in FIG. 6B, and FIG. 8A is a case where the outer cylindrical portion 81 does not elastically deform. (B) shows the configuration when the outer cylindrical portion 81 is elastically deformed, and (c) shows the configuration of Reference Example 1 in which the direction of the slit separator 9 is reversed in the Y-axis direction in (b). (D) shows the configuration of Reference Example 2 in which the thickness distribution of the outer cylindrical portion 81 is not inclined in (b).

  As shown in FIG. 8A, if the outer cylindrical portion 81 is not elastically deformed, the surface of the wound body 10 does not tilt and rises at the portion a on the Y axis negative direction side.

  A part of the film thickness distribution of the original fabric is reflected in the film thickness distribution of the slit separator 9. In this part, the film thickness distribution often changes monotonously. At this time, the thickness of the slit separator 9 increases on one side in the width direction. When the slit separator 9 is wound around the core 8 several times, the thick part of the slit separator 9 overlaps many times. For this reason, the one side (for example, site | part a) of the winding body 10 rises.

  The fact that the part a is raised means that the slit separator 9 in the part a is stretched by the winding tension as compared with the other end. Since the slit separator 9 has plasticity, when it is held in a stretched state for a long time, it is plastically deformed into a stretched shape. As a result, the slit separator 9 unwound from the core 8 is bent greatly as shown in FIG. 9C, although the original fabric is cut out linearly at the time of slitting.

  The “width direction” means a direction substantially perpendicular to the longitudinal direction and the thickness direction of the slit separator 9. Further, the “width direction” coincides with the Y-axis direction.

(Deformation of outer cylindrical part)
As shown in FIG. 8B, in practice, the outer cylindrical portion 81 wound with the slit separator 9 is elastically deformed inward. At this time, the part β having a small thickness of the outer cylindrical portion 81 is elastically deformed inward larger than the part α having a large thickness. Since the portion where the thickness of the slit separator 9 is large is wound around the portion β side where the outer cylindrical portion 81 is bent inwardly, the swell of the slit separator 9 which may occur when the outer cylindrical portion 81 is not elastically deformed, The elastic deformation of the cylindrical portion 81 cancels out. As described above, in the case of FIG. 8B, the inclination of the outer peripheral surface t of the slit separator 9 is suppressed as compared with the case of FIG. The principle of this inclination suppression can be explained as follows.

  When the slit separator 9 is wound around the outer cylindrical portion 81, a portion where the thickness of the slit separator 9 is large rises relatively large like a portion a shown in FIG. It is greatly extended by taking tension. For this reason, the force which tries to return to the shape before being extended acts on the slit separator 9. As a result, a force for tightening inward acts on the portion of the outer cylindrical portion 81 corresponding to the side where the thickness of the slit separator 9 is large. The core 8 is elastically deformed, so that the amount of deformation when the slit separator 9 is originally stretched is absorbed, and plastic deformation of the slit separator 9 is less likely to occur.

  This elastic deformation is cylindrical, and when a force is applied to the outer peripheral surface s of the outer cylindrical portion 81 of the core 8 in a direction to reduce the peripheral length, the peripheral length on one end side is the other end side. In other words, it is smaller than the perimeter of.

  The core 8 is repeatedly used for winding the slit separator 9. The deformation amount of the outer cylindrical portion 81 can change between the new core 8 immediately after being manufactured and the old core 8 after being repeatedly used. However, if the core 8 is used in the range where the outer cylindrical portion 81 is elastically deformed, this change may be regarded as small.

  Further, the measured values of the outer diameter and thickness of the outer cylindrical portion 81 are different between the above-described reference surface and the back surface, and also on the same surface of the outer cylindrical portion 81 (either the reference surface or the back surface), Different for each measurement point. The cause is considered to be the fixing method and / or processing method of the outer cylindrical portion 81 in the manufacturing process of the core 8. However, since the slit separator 9 is wound around the entire circumference of the outer cylindrical portion 81, the average value of the plurality of measured values at different positions on the same surface is the core 8 shown in FIG. It may be handled if it reflects the shape.

(Reference Example 1)
In the configuration of FIG. 8C, the direction of the slit separator 9 is opposite in the Y-axis direction with respect to the configuration of FIG. And the site | part with the large thickness of the slit separator 9 is wound by the site | part (alpha) side with the large thickness of the outer side cylindrical part 81. As shown in FIG. As described above, a force of tightening to the inside acts on the portion of the outer cylindrical portion 81 corresponding to the side where the thickness of the slit separator 9 is large. However, since the elastic deformation of the portion α side where the outer cylindrical portion 81 is large is smaller than that of the portion β side where the thickness is small, the slit separator 9 must be plastically deformed. That is, since the core 8 is not elastically deformed and the deformation amount when the slit separator 9 is extended is not absorbed, the slit separator 9 is plastically deformed. Therefore, the slit separator 9 unwound from the core 8 is bent as shown in FIG.

  The part where the thickness of the slit separator 9 is large is tightened more strongly than the part where the thickness is small. For this reason, the deformation amount in the part α of the outer cylindrical portion 81 is larger than the deformation amount in the part β. And the inclination of the outer peripheral surface t of the slit separator 9 is suppressed. The degree of this suppression is smaller than that in the case of FIG.

(Reference Example 2)
In the configuration of FIG. 8D, the thickness distribution of the outer cylindrical portion 81 is not inclined with respect to the configuration of FIG. The thickness of the outer cylindrical portion 81 is uniform from the part α side to the part β side. Therefore, the rigidity of the outer cylindrical portion 81 is also uniform from the part α side to the part β side.

  Also at this time, the portion where the thickness of the slit separator 9 is large is tightened more strongly than the portion where the thickness is small. For this reason, the deformation amount in the part β of the outer cylindrical portion 81 is larger than the deformation amount in the part α. And the inclination of the outer peripheral surface t of the slit separator 9 is suppressed. The degree of this suppression can vary depending on the strength of the outer cylindrical portion 81. The strength can vary depending on the thickness or material of the outer cylindrical portion 81.

  (Outer diameter of core after deformation)

  Table 3 shows the outer diameter of the core 8 measured after the slit separator 9 was wound and deformed. As shown in Table 3, the outer diameters of samples 1 to 3 of the three cores 8 were measured. The items and numerical values in Table 3 correspond to Table 1. Samples 1 and 2 correspond to the core 8 of the wound body 10 shown in FIG. Sample 3 corresponds to the core 8 of the wound body 10 shown in FIG.

  As shown in Table 3, the average value of the outer diameter difference of Sample 1 is 0.08 mm. This average value means that, on average, the outer diameter of the reference surface is larger than the outer diameter of the back surface. And the average value of the outer diameter difference of the sample 1 shown in Table 1 is -0.01 mm. This average value means that, on average, the outer diameter of the reference surface is smaller than the outer diameter of the back surface.

  As described above, the magnitude relationship between the outer diameters of the reference surface and the back surface is reversed before and after the deformation of the core 8. In Sample 2, as in Sample 1, the relationship between the outer diameters of the reference surface and the back surface is reversed before and after the deformation of the core 8. On the other hand, for sample 3, the relationship between the outer diameters of the reference surface and the back surface does not change before and after the deformation of the core 8.

  (Core circumference)

  Table 4 shows the circumference of the core 8 and the like measured before winding the slit separator 9 and after winding the slit separator 9. As shown in Table 4, the circumference and the like of the samples 1 to 3 of the three cores 8 were measured. Moreover, the circumference etc. were measured about the reference surface and the back surface of each sample.

  The item “average thickness” indicates the average thickness of the slit separator 9. The item “core circumferential length (before winding)” indicates the circumferential length of the core 8 (the circumferential length of the outer cylindrical portion 81) before winding the slit separator 9. The item “average thickness” indicates an average thickness of the outer cylindrical portion 81 of the core 8. The item “core circumferential length (after winding)” indicates the circumferential length of the core 8 (the circumferential length of the outer cylindrical portion 81) after winding the slit separator 9. The item “winding body diameter” indicates the diameter of the winding body 10 after the slit separator 9 is wound around the core 8. The item “cumulative thickness” indicates a length between the outer peripheral surface s of the outer cylindrical portion 81 and the outer peripheral surface t of the slit separator 9 after the slit separator 9 is wound around the core 8. That is, this length is a thickness obtained by accumulating the thickness of the slit separator 9 by the number of times of wrinkles. In addition, the value of “average thickness” was measured using “high-precision digital length measuring instrument Lightmatic 50A (manufactured by Mitutoyo Corporation)”. The item “peripheral length change amount” is a value obtained by subtracting the circumference of the core 8 after winding the slit separator 9 from the circumference of the core 8 before winding the slit separator 9.

  As shown in Table 4, the “average thickness” value of Sample 1 is larger on the back surface than on the reference surface. The value of “core circumference (after winding)” of sample 1 is smaller on the back surface than on the reference surface. The same applies to Sample 2. The value of “average thickness” of sample 3 is larger on the reference surface than on the back surface. The value of “core circumference (after winding)” of sample 3 is smaller on the reference surface than on the back surface. The wound body 10 shown in (b) and (c) of FIG. 8 can be specified using the relationship between the values of the above “average thickness” and “core circumference (after winding)”.

  Specifically, the core 8 for winding the slit separator 9 on the outer peripheral surface s of the outer cylindrical portion 81 and the outer peripheral surface s of the outer cylindrical portion 81 of the core 8 are wound, and one end side is more than the other end side. As a film winding body comprising a thick slit separator 9, the outer peripheral surface s of the outer cylindrical portion 81 of the core 8 is characterized in that the peripheral length on one end side is shorter than the peripheral length on the other end side, The wound body 10 can be specified. Thereby, as shown in FIG. 6B, not only the wound body 10 in which the thickness distribution of the outer cylindrical portion 81 is monotonously inclined in the Y-axis direction but also as shown in FIG. 6D. In addition, the wound body 10 in which the thickness distribution of the outer cylindrical portion 81 is not inclined in the Y-axis direction, or the thickness distribution is not inclined monotonously in the Y-axis direction as shown in FIG. The circular body 10 can be specified. The wound body 10 shown in FIG. 8D can be identified in the same manner.

<< Effects of this embodiment >>
9 is a top view showing a state of the slit separator 9 when the slit separator 9 is unwound from the wound body 10 shown in FIGS. 8B to 8D and the wound body of the comparative example. (A) shows the state when the slit separator 9 is unwound from the wound body 10 shown in (b) of FIG. 8, and (b) shows in (c) to (d) of FIG. The state when the slit separator 9 is unwound from the wound body 10 shown is shown, and (c) shows a comparative example described later of (a) to (b).

  As shown in FIG. 9 (a), it was confirmed that the slit separator 9 unwound from the wound body 10 shown in FIG. 8 (b) extends almost straight. Further, as shown in FIG. 9 (b), the slit separator 9 unwound from the wound body 10 shown in FIGS. 8 (c) to 8 (d) is shown in FIG. 9 (a). Although it bends rather than the slit separator 9 (broken line), it was confirmed that it extends substantially straight.

  The degree to which the slit separator 9 is bent can be quantified by the distance h (FIG. 10) described later. The distances h between the samples 1 and 2 corresponding to the wound body 10 shown in FIG. 8B are 1.8 mm and 2.3 mm, respectively. Further, the distance h of the sample 3 corresponding to the wound body 10 shown in FIG. 8C is 4.8 mm. These values of distance h are acceptable as a separator for a lithium ion secondary battery.

(Comparative example)
As shown in FIG. 9 (c), there is also a wound body in which the unwound slit separator 9 bends greatly on its thin side. In this wound body, the thick part of the slit separator 9 is stretched and deformed. The slit separator 9 has a tendency to be largely deformed as the winding body has a higher rigidity of the outer cylindrical portion of the core. If this rigidity is high, the outer cylindrical portion 81 does not substantially change from the state shown in FIG. 8A even when the slit separator 9 is wound.

(Use for lithium ion secondary batteries)
In the lithium ion secondary battery 1 shown in FIGS. 1 to 3, the slit separator 9 is processed so as to be accommodated therein and used as the separator 12. In this processing, the slit separator 9 shown in FIGS. 9A to 9B is more preferable than the slit separator 9 shown in FIG. Moreover, the slit separator 9 shown to (a) of FIG. 9 is still more suitable than the slit separator 9 shown to (b) of FIG.

(Other configurations and effects)
The film is inspected by a film thickness inspection machine provided in the process of manufacturing the film wound around the core c shown in FIG. 4A (that is, the previous process of the process shown in FIG. 4A). Can be measured. The slit separator 9 reflects the film thickness distribution of the original fabric. Therefore, by using this measurement result, the thickness of the outer cylindrical portion 81 and the thickness of the slit separator 9 can be reliably associated with each other, and the slit separator 9 can be wound around the outer cylindrical portion 81.

  The slit separator 9 may be a porous film that is stretched in the direction in which the central axis CA of the outer cylindrical portion 81 extends. That is, the central axis CA extends to the above-described TD. If the slit separator 9 is stretched, the film thickness distribution of the slit separator 9 can be biased in this stretching direction. By utilizing this uneven thickness distribution, the thickness of the outer cylindrical portion 81 and the thickness of the slit separator 9 can be reliably associated with each other, and the slit separator 9 can be wound around the outer cylindrical portion 81.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIGS. For convenience of explanation, members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted. The same applies to the embodiments described later.

≪Method of testing wounds≫
As described above, the slit separator wound out from the wound body having the inclined outer peripheral surface bends to the thin side of the slit separator. The inventors have found that the inclination of the outer peripheral surface of the wound body correlates with the amount of bending of the slit separator unwound from the wound body. By utilizing this correlation, it is possible to test a wound body as described below.

  FIG. 10 is a schematic diagram for explaining the test method of the wound body 10 of the present embodiment, wherein (a) is a front view for explaining the inclination of the outer peripheral surface t of the slit separator 9; b) is a top view for explaining the bending amount of the slit separator 9 unwound from the wound body 10.

(Inclination of the outer peripheral surface of the wound body)
The inclination of the outer peripheral surface t of the slit separator 9 is shown in FIG. 10A. The outer diameter ODa of the wound body 10 on the Y axis positive direction side, the outer diameter ODb on the Y axis negative direction side, and the slit separator 9 The product width W and the end widths wa and wb can be expressed as the following formula (1).
| ODb-ODa | / (W-wa-wb) (1)
The outer diameter Oda is the diameter of the outer peripheral surface t of the slit separator 9 at a position away from the end of the slit separator 9 on the Y axis positive direction side by the end width wa on the Y axis negative direction side. The outer diameter ODb is the diameter of the outer peripheral surface t of the slit separator 9 at a position away from the end of the slit separator 9 on the Y axis negative direction side by the end width wb on the Y axis positive direction side. For these measurements, a known measurement method such as a non-contact method using a laser beam can be used in addition to the above-described measurement method using the caliper M.

  The product width W is the length of the slit separator 9 in the Y-axis direction. The end width wa is the end length of the slit separator 9 in the Y-axis direction, which is defined in order to correctly measure the outer diameter Oda. The end width wb is the end length in the Y-axis direction of the slit separator 9 that is defined in order to correctly measure the outer diameter ODb.

  The outer diameter Oda may not be measured correctly when the end width wa is small. Further, the outer diameter ODb may not be measured correctly when the end width wb is small. This is because the position of the edge of the slit separator 9 in the Y-axis direction varies. The end widths wa and wb are defined so as to exceed the maximum of such fluctuation ranges (for example, 3 mm).

(Bending amount of slit separator unwound from the wound body)
The amount of bending of the slit separator 9 unwound from the wound body 10 is quantified by the distance h shown in FIG. The slit separator 9 unwound in the X-axis positive direction bends to the Y-axis positive direction side like the slit separator 9a when the tension applied during unwinding is lost. The distance h is the maximum distance between the end side La of the slit separator 9a on the Y axis positive direction side and the line segment connecting the apex p and the apex q of the end side La.

  This bending amount tends to increase as the length L of the slit separator 9 unwound from the wound body 10 increases.

(Correlation between tilt and bending amount)
FIG. 11 is a graph showing the correlation between the slope and the amount of bending in the test method described by (a) to (b) of FIG. This amount of bending is the amount of bending per unit length (1000 mm) (when the length L of the slit separator 9 is 1000 mm). The horizontal axis in FIG. 11 is the inclination described above, and the vertical axis is the amount of bending (distance h).

  The data indicated by the rhombuses are obtained by measuring the inclination and the bending amount of 67 wound bodies 10 obtained by winding the slit separator 9 having an average thickness of 16 μm. The data indicated by the squares are obtained by measuring the inclination and the bending amount of five wound bodies 10 obtained by winding the slit separator 9 having an average thickness of 20 μm.

As shown in FIG. 11, if the slope of the data indicated by the rhombus is represented by x and the amount of bending is represented by y, the relationship between x and y approximated by the least square method is the first order of the following equation (2). It is expressed by the formula. Thus, the inclination and the amount of bending have a positive correlation.
y = 0.479x + 0.0864 Expression (2)
That is, it can be seen that the greater the inclination, the greater the amount of bending. That is, a wound body obtained by winding a slit separator 9 having a large difference in average thickness between the reference surface side and the back surface side, or many slit separators 9 having different average thicknesses on the reference surface side and the back surface side are wound and accumulated. There is a tendency for the amount of bending to increase in a wound body having a large difference in thickness.

(Check of wound body)
As shown in FIG. 11, the relationship between the slope of the data indicated by the square and the amount of bending also shows the same positive correlation. For this reason, it is possible to test the wound body 10 without unwinding the slit separator 9 as to whether or not the bending amount is less than a predetermined threshold.

  For example, when the bending amount is 6 mm, the slope is 12.346 according to the linear expression of Expression (2). Therefore, if the inclination calculated | required by Formula (1) is less than 12 about a certain winding body, it can test | inspect that the bending amount of this winding body will be less than 6 mm.

  However, if the average thickness (design thickness) of the slit separator 9 is different, the amount of swell of the outer peripheral surface of the wound body 10 when the slit separator 9 is wound around the core 8 many times also differs. For this reason, when the populations of the inclination and the bending amount are different, the straight line parameter represented by the above equation (2) changes.

(Measurement example of tilt and bending amount)
As described above, the distances h between the samples 1 to 3 are 1.8 mm, 2.3 mm, and 4.8 mm, respectively. The slopes of samples 1 to 3 are 0.91, 3.27, and 6.92, respectively.

(Details of the method for testing wounds)
FIG. 12 is a flowchart showing a test method for the wound body 10 based on the correlation shown in FIG.

  As shown in FIG. 12, this verification method includes step S101, which is a step of specifying an inclination, step S102, which is a step of specifying a bending amount, and a step of determining whether or not the bending amount is less than a threshold value. Step S103 (step of determining whether or not the film winding body is a non-defective product).

(Step S101)
The inclination is specified based on the above equation (1). Specifically, the outer diameter ODb of the wound body 10 on the Y-axis negative direction side (that is, one side in the direction in which the central axis CA of the outer cylindrical portion 81 extends) per unit width of the slit separator 9 and the other The inclination which is a value proportional to the absolute value (| Db-Da |) of the difference with the outer diameter Oda on the side is specified.

  The process for obtaining the value per unit width of the slit separator 9 corresponds to the process of dividing by “W−wa−wb” in the equation (1).

(Step S102)
The amount of bending is specified based on the above equation (2). Specifically, the bending amount is specified from the inclination specified in step S101 based on the correlation between the inclination and the bending amount.

(Step S103)
It is determined whether or not the bending amount specified in step S102 is less than a threshold value (for example, 6 mm). If the decision result in the step S103 is YES, it is verified that the wound body 10 is a non-defective product. If the determination result in step S103 is NO, it is verified that the wound body 10 is defective. Note that an inclination corresponding to the bending amount threshold value is obtained in advance, and the inclination specified in step S101 is compared with the previously obtained inclination to determine whether or not the wound body 10 is a non-defective product. it can. At this time, step S102 may not be executed.

<< Effects of this embodiment >>
The slit separator 9 wound around the wound body 10 is unwound from the wound body 10 and then processed into a secondary product (such as a lithium ion secondary battery). At this time, it is preferable that the slit separator 9 unwound from the wound body 10 is not bent with respect to the unwound direction.

  According to the present embodiment, the amount of bending can be specified based on the correlation between the inclination found by the inventors (see equation (1)) and the amount of bending (see equation (2) in FIG. 11). Accordingly, it is possible to determine whether the winding amount is less than the threshold without unwinding the slit separator 9 from the wound body 10 and to test the quality of the wound body 10.

  It is often complicated to unwind the slit separator 9 from the wound body 10 and measure the amount of bending in the unwound direction. Furthermore, since the unwinding condition of the slit separator 9 and the measurement condition of the bending amount are easily changed, the measured bending amount often varies. By specifying the inclination, it is possible to easily test the quality of the wound body 10 without measuring the amount of bending.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG.

≪Method of manufacturing wound body≫
FIG. 13 is a flowchart showing a method for manufacturing the wound body 10 of the present embodiment.

  As shown in FIG. 13, this manufacturing method includes step S201, which is a step of specifying the orientation of the outer cylindrical portion 81, and step S202, which is a step of winding a film on the outer peripheral surface s of the outer cylindrical portion 81. Including.

(Step S201)
As shown in FIG. 6B, the thickness of the outer cylindrical portion 81 is thinner at one end side on the Y axis negative direction side than at the other end side on the Y axis positive direction side. In this step, the direction of the outer cylindrical portion 81 is specified by specifying which side of the both ends of the outer cylindrical portion 81 is thin.

  The direction of the outer cylindrical portion 81 can be specified by the presence or absence of the mark S shown in FIG. In the above example, the thickness of the outer cylindrical portion 81 is thin on the Y axis negative direction side of the outer cylindrical portion 81 to which the mark S is given. Further, the outer diameter of the outer cylindrical portion 81 can be measured by the caliper M shown in FIG. 7B, and the orientation of the outer cylindrical portion 81 can be specified.

(Step S202)
In step S201, since the direction of the outer cylindrical portion 81 is specified, it is known which side of the both ends of the outer cylindrical portion 81 is thinner. Based on this knowledge, the slit separator 9 is wound around the outer peripheral surface s of the outer cylindrical portion 81 so that the side where the outer cylindrical portion 81 is thin and the side where the slit separator 9 is thicker correspond. The direction of the core 8 may be made to correspond at the time of slitting, and the direction of the core may be made to correspond in the step of winding the wire once to another core after winding.

<< Effects of this embodiment >>
In the wound body 10 manufactured as described above, one end side of the outer cylindrical portion 81 is thinner than the other end side, so that the rigidity is low. The outer cylindrical portion 81 bends more inwardly at one end side where the rigidity is lower than at the other end side. And since the thick site | part of the slit separator 9 is wound by the one end side which bend | curves this inside greatly, the inclination of the width direction in the outer peripheral surface t is suppressed.

[Modification]
The number of ribs 831 to 838 shown in FIG. 6A is not limited to eight. For example, a wound body having an odd number of ribs is also included in the present invention.

[Embodiment 4]
A fourth embodiment of the present invention will be described with reference to FIGS.

≪Composition of wound body≫
FIG. 14 is a diagram illustrating the configuration of the core 108 used in the present embodiment. The XYZ axes shown in (a) of FIG. 14 correspond to the XYZ axes shown in the (b) diagram of FIG.

  FIG. 14A is a front view of the core 108. The core 108 has the outer cylindrical portion 181 as compared with the core 8 of the first embodiment, but does not have the rib and the inner cylindrical portion. That is, it has a single tube structure formed only by the outer cylindrical portion 181.

  FIG.14 (b) is sectional drawing which shows the BB cross section of Fig.14 (a). As can be seen from FIG. 14B, the outer cylindrical portion 181 has a uniform and flat thickness. Therefore, the core 101 has no difference in structure and strength (rigidity) at both ends, or is small enough to ignore the difference in structure and strength (rigidity).

  FIG. 15 is a cross-sectional view illustrating a configuration of a wound body 110 in which the slit separator 9 is wound around the core 108 of the present embodiment, and (a) illustrates a configuration when the outer cylindrical portion 181 is not elastically deformed. (B) shows a configuration when the outer cylindrical portion 181 is elastically deformed.

  As shown in FIG. 15A, when the thickness of the slit separator 9 is large on the Y-axis negative direction side, the surface of the wound body 110 is inclined unless the outer cylindrical portion 181 is elastically deformed. It rises at the part a on the Y axis negative direction side.

  As shown in FIG. 15B, the outer cylindrical portion 181 wound with the slit separator 9 is actually deformed inward by elasticity. Thereby, in the case of (b) in FIG. 15, the inclination of the outer peripheral surface t of the slit separator 9 is suppressed as compared with the case of (a). The principle of this inclination suppression is the same as that in the first embodiment.

  Table 5 shows the circumference of the core 108 measured before winding the slit separator 9 and after winding the slit separator 9. As shown in Table 5, the circumference and the like of the samples 4 to 5 of the two cores 108 were measured. Moreover, the circumference etc. were measured about the reference surface and the back surface of each sample. Each item in Table 5 is the same as each item in Table 4.

  As shown in Table 5, the samples 4 and 5 have different average thicknesses of the outer cylindrical portion 181, and the sample 4 has a structure in which the average thickness of the outer cylindrical portion 181 is about 2 mm thinner than the sample 5. Therefore, the sample 4 is relatively weaker than the sample 5 and the elastic change amount when the slit separator 9 is wound is large. In particular, the amount of elastic deformation is larger on the reference surface side of the sample 4 than on the sample 5.

  As a result, as can be seen from Table 5, sample 4 has a larger amount of change in the difference between the circumference of the reference surface and the circumference of the back surface of core 108 before and after winding.

  Table 6 shows the inclination index and the bending of the core 8 of the samples 1 to 3 used in the first embodiment and the core 108 of the samples 4 to 5 used in the fourth embodiment, which were measured after winding the slit separator 9. .

The “inclination index” in Table 6 means that the outer diameter of one end of the slit separator 9 wound around the core 108 is D1, the outer diameter of the other end is D2, and the product width of the slit separator 9 is W. It is an index represented by the following formula (3), and indicates the inclination of the outer peripheral surface of the slit separator 9.
| D1-D2 | / W Formula (3)
For convenience, the outer diameter Oda at a position separated from the end side on one end side of the slit separator 9 by the end width wa and the outer diameter at a position separated from the end side on the other end side of the slit separator 9 by the end width wb. The value obtained by measuring ODb and using the above-described equation (1) may be used as the slope index.

  In addition, “the amount of bending per unit length” in Table 6 means “the length of the slit separator 9 per unit length (1000 mm) of the slit separator 9 at the distance h shown in FIG. Indicates the length (when L is 1000 mm).

  As shown in Table 6, the inclination index of sample 4 is smaller than that of sample 5, and the bending of slit separator 9 is suppressed. As described above, this is considered to be caused by the fact that the outer cylindrical portion 181 is elastically changed to absorb the thickness difference of the slit separator 9.

  Further, as shown in Table 5, the value of “average thickness” of samples 4 and 5 is larger on the reference surface than on the back surface. The values of “core circumference (after winding)” of samples 4 and 5 are smaller on the reference surface than on the back surface. Using the relationship between the values of the above “average thickness” and “core circumference (after winding)”, the sample shown in FIG. 15B is similar to the sample 1 and 2 described in the first embodiment. The circular body 110 can be specified.

  Specifically, the core 108 for winding the slit separator 9 on the outer peripheral surface s of the outer cylindrical portion 181 and the outer peripheral surface of the outer cylindrical portion 181 of the core 108 are wound, and one end side is more membrane than the other end side. The outer cylindrical portion 181 of the core 108 has a circumferential length on one end side shorter than that on the other end side when the slit separator 9 is wound. The wound body 110 can be specified as the characteristic film winding body.

  Thus, the wound body 110 of the present embodiment having the single-tube structure and the core 108 like the samples 4 and 5 in which the thickness distribution of the outer cylindrical portion 181 is not inclined in the Y-axis direction is as follows. Like Samples 1 and 2, which have a double tube structure including an outer cylindrical portion 81, an inner cylindrical portion 82, and ribs 831 to 838, and the thickness distribution of the outer cylindrical portion 81 is inclined in the Y-axis direction. It can specify like the winding body 10 of Embodiment 1 provided with the core 8. FIG.

<< Effects of this embodiment >>
The bending of the slit separator 9 wound around the sample 4 is suppressed to the same extent as that of the slit separator 9 wound around the sample 2 in Table 6, and when used as a separator for a lithium ion secondary battery. Can be suppressed to the extent that there is no problem.

  Thus, even in the case of a core having a uniform structure with a uniform thickness of the outer cylindrical portion and a single tube structure having no rib and inner cylindrical portion, the slit separator is similar to the first embodiment. The effect that the plastic change can be suppressed and the bending can be suppressed is obtained.

  FIG. 16 is a graph showing the relationship between the amount of bending and the inclination index. In FIG. 16, the horizontal axis represents the amount of bending per unit length (1000 mm) (when the length L of the slit separator 9 is 1000 mm), and the vertical axis represents the inclination index.

  From FIG. 16, it can be seen that, as in FIG. 11, there is a correlation between the inclination index and the amount of bending, and the bending of the slit separator 9 is suppressed as the inclination index (inclination) is smaller. When samples 1-2 and 4 and samples 3 and 5 are compared, it can be seen that the bending of the slit separator 9 wound around each sample is greatly different.

  In view of using the slit separator 9 as a lithium ion secondary battery separator, the amount of bending per unit length of the slit separator 9 is preferably 3 mm or less. Therefore, it is preferable that an inclination index, which is an inclination on the outer peripheral surface of the slit separator 9, with respect to the direction in which the central axis of the cores 8 and 108 extends is 6 or less.

  Therefore, when the non-defective product test of the slit separator 9 is performed using an inclination index, it is preferable to perform the test by setting the threshold value to 6.

  In addition, as above-mentioned, even if the curvature (distance h) of the slit separator 9 is 4.8 mm, it is accept | permitted as a separator for lithium ion secondary batteries.

  However, if the separator drawn out in the battery assembling process meanders, a deviation occurs when the separator is arranged between the positive electrode and the negative electrode, which may cause a short circuit between the positive electrode and the negative electrode.

  When the battery is assembled manually or when the separator is transported at a low speed, the distance h may be a somewhat high value, and 4.8 mm is allowed. When the separator is disposed between the positive electrode and the negative electrode while conveying the separator at a high speed in order to increase productivity, the above-mentioned distance h is preferably 3 mm or less because the separator is more likely to meander.

  In the present embodiment, the wound body 110 having the flat core 108 with the uniform thickness of the outer cylindrical portion 181 has been described. However, the core 108 is the core 8 shown in FIG. Similarly, the thickness of the outer cylindrical portion 181 may be inclined on the reference surface side and the back surface side, and monotonously in the Y-axis direction as shown in FIG. May have a non-inclined thickness distribution.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a battery used for a mobile device such as a personal computer, a mobile phone, a portable information terminal, an automobile, an aircraft, or a stationary battery that contributes to a stable power supply. Moreover, this invention can be utilized also for these manufacturing methods.

4 Heat-resistant layer
5 Porous film (film)
6 Slit device 8.108 Core 9.9a Slit separator (film)
10.110 Winding body
12 Separator (film)
81 ・ 181 Outer cylindrical part (cylindrical member)
82 Inner cylindrical part 831-838 Rib (supporting member)
CA Center axis Da / Db Mold Oda / ODb Outer diameter
S mark S101 step (step of specifying the inclination)
S103 step (step of determining whether or not the film winding body is a non-defective product)
S201 step (step of identifying the orientation of the cylindrical member)
S202 step (step of winding a film on the outer peripheral surface of the cylindrical member)
s Outer peripheral surface (outer peripheral surface of cylindrical member, outer peripheral surface of core)
t outer peripheral surface

Claims (8)

One end wall thickness than the average 0.12mm than the other end side rather thin, thin one side of the wall thickness, and less rigid cylindrical member than the other end,
The cylindrical member is wound on the outer peripheral surface around the film wound body that is the other end side than the one end side in the width direction, characterized in that it comprises a thin have film having a thickness of more than 0.0006Mm.   2. The film winding body according to claim 1, wherein the material of the cylindrical member includes any of ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, and vinyl chloride resin.   The film roll according to claim 1 or 2, wherein the film is a porous film stretched in a direction in which a central axis of the cylindrical member extends.   The film winding body according to any one of claims 1 to 3, further comprising a plurality of support members spaced from each other for supporting the outer peripheral surface of the cylindrical member from the inside thereof. While having a cylindrical outer peripheral surface, one end side has lower rigidity than the other end side , and when a force in a direction to reduce the peripheral length is applied to the outer peripheral surface, the peripheral length on one end side is the other end side. A core that is shorter than the circumference of the side by 0.15 mm or more ,
A film winding body comprising: a film wound around an outer peripheral surface of the core, wherein the one end side in the width direction is thicker than the other end side. A core for winding the film on the outer peripheral surface, the rigidity on one end side being lower than that on the other end side ;
The core is wound around the outer peripheral surface, and one end side in the width direction is provided with a film having a thickness greater than that of the other end side,
When the film is wound on the outer peripheral surface of the core, the outer peripheral surface of the core has a peripheral length on the one end side shorter than the peripheral length on the other end side by 0.15 mm or more. Round body. The outer diameter of the one end of the wound film is D1 (mm) , the outer diameter of the other end of the wound film is D2 (mm), and the width of the film is W (m). When
| D1-D2 | / W ≦ 6
The film winding body according to any one of claims 1 to 6, wherein the film winding body is satisfied. One end wall thickness than the average 0.12mm than the other end side rather thin, thin one side of the wall thickness, the steps of rigidity than the other end to identify the orientation of the lower cylindrical member,
The outer peripheral surface of the cylindrical member, the film winding body manufacturing method of the other end side than the one end side in the width direction, characterized in that it comprises a step of winding the thin have film having a thickness of more than 0.0006mm .

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