Powder-compact sheet conveyance device

Abstract

A powder-compact sheet conveyance device 1 comprises: conveyance rolls 2 for supporting a powder-compact sheet S on a peripheral surface and conveying said sheet which is obtained by compressing a powder P into a sheet shape; and a wall member 14 that is disposed at a prescribed distance from at least a portion of a section of the peripheral surface which supports the powder-compact sheet S and that extends along the at least a portion. The powder-compact sheet S is conveyed inside a conveyance path 16 demarcated by the peripheral surface and the wall member 14.

Description

Powder sheet conveying device

[0001] The present disclosure relates to a powder sheet conveying device.

[0002] Patent Document 1 describes a multi-roll system used for manufacturing dry electrodes. This system includes multiple rolls arranged in a row, and a dry electrode mixture is supplied from a powder hopper to the gap between a pair of rolls to form a mixture sheet, which is then conveyed while being supported by the peripheral surfaces of the rolls.

[0003] US Patent Application Publication No. 2020 / 0227722

[0004] When a powder sheet, not limited to a mixture sheet, in which powder is compressed, is supported on the peripheral surface of a roll and transported, the powder sheet may peel off from the peripheral surface of the roll. The leading edge of the sheet is particularly prone to peeling off from the peripheral surface. If the leading edge of the powder sheet peels off from the peripheral surface of the roll, the powder sheet may enter the gap between a pair of rolls with the leading edge bent. In this case, a powder sheet thicker than expected may enter the gap between the rolls, potentially placing an excessive load on the rolls.

[0005] The present disclosure has been made in view of these circumstances, and its purpose is to provide a technique for suppressing bending of a powder sheet during transport.

[0006] One aspect of the present disclosure is a powder sheet conveying device that includes a conveying roll that supports and conveys a powder sheet formed by compressing powder into a sheet shape on a peripheral surface thereof, and a wall member that extends along at least a portion of the portion of the peripheral surface that supports the powder sheet at a predetermined interval from said portion, and that conveys the powder sheet within a conveying path defined by the peripheral surface and the wall member.

[0007] Any combination of the above components, and conversion of the expression of the present disclosure into a method, device, system, etc., are also valid aspects of the present disclosure.

[0008] According to the present disclosure, bending of the powder sheet during transport can be suppressed.

[0009] 2A and 2B are schematic diagrams illustrating a state in which a powder sheet has been peeled off from the circumferential surface of a transport roll of a powder sheet transporting device according to an embodiment of the present invention.

[0010] The present disclosure will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the present disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the present disclosure. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not represent any order or importance, but are intended to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted from each drawing.

[0011] FIG. 1 is a schematic diagram of a powder sheet conveying device 1 according to an embodiment. The powder sheet conveying device 1 includes a conveying roll 2, a wall member 14, a storage section 10, and a forming roll 12. As an example, the powder sheet conveying device 1 of this embodiment has a plurality of conveying rolls 2 arranged horizontally. FIG. 1 illustrates two adjacent conveying rolls 2. Hereinafter, the conveying roll 2 on the upstream side in the conveying direction of the powder sheet S will be referred to as the first conveying roll 2a, and the conveying roll 2 on the downstream side will be referred to as the second conveying roll 2b. The number of conveying rolls 2 is not limited.

[0012] The storage unit 10 has a known structure, such as a combination of a hopper and a feeder, and stores powder P, which is the raw material for the pressed powder sheet S. The powder P contains predetermined particles and a binder component that binds the particles together. The binder component includes at least one of a known binding agent (also known as a binder) and a solvent. In addition, as an example, the powder P has a binder component content, i.e., the sum of the binder content and the solvent content, of 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.1% by mass or less, or substantially 0% by mass, based on the total mass of the powder P. In other words, as an example, the powder P is a dry powder. However, the powder P may also be a wet powder in which the binder component content exceeds 10% by mass based on the total mass of the powder P.

[0013] As an example, the powder P is an electrode mixture, and the pressed powder sheet S is a mixture sheet. In this case, the powder P contains an electrode active material as a predetermined particle, and, if necessary, a conductive agent. In the case of a typical lithium-ion secondary battery, the electrode active material is lithium cobalt oxide or lithium iron phosphate for the positive electrode, and graphite for the negative electrode. The conductive agent is graphite, carbon black, acetylene black, or the like. The binder is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or the like. When the electrode mixture is used for the negative electrode, examples of the solvent include water; alcohols such as ethanol; N-methylpyrrolidone (NMP); toluene; dimethyl carbonate (DMC); ethyl methyl carbonate (EMC); and the like. When the electrode mixture is used for a positive electrode, examples of the solvent include amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine, ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone, ester solvents such as methyl acetate, and amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Note that the powder P and the pressed powder sheet S may be used for purposes other than electrodes.

[0014] A forming roll 12 and a first conveying roll 2a are disposed at the powder outlet of the storage unit 10. The forming roll 12 and the first conveying roll 2a are positioned so that their respective rotation axes are parallel to each other and are adjacent to each other with a predetermined gap between them. The first conveying roll 2a is disposed downstream of the forming roll 12 in the conveying direction of the pressed powder sheet S. Powder P is supplied from the storage unit 10 to the gap between the forming roll 12 and the first conveying roll 2a. In this embodiment, the forming roll 12 and the first conveying roll 2a also function as feed rolls, and the powder P in the storage unit 10 is placed on their respective peripheral surfaces and supplied to the gap between the two rolls.

[0015] The forming roll 12 and the first conveyor roll 2a rotate in opposite directions to each other, compressing the powder P supplied into the gap into a sheet. This forms a pressed powder sheet S. Therefore, the first conveyor roll 2a in this embodiment also serves as a forming roll. The pressed powder sheet S is continuously fed out from the gap between the forming roll 12 and the first conveyor roll 2a. Therefore, the pressed powder sheet S is in the form of a long strip extending in the conveyance direction. The pressed powder sheet S is conveyed downstream while being supported by the circumferential surface of the first conveyor roll 2a.

[0016] The second conveying roll 2b is disposed downstream of the first conveying roll 2a. The first conveying roll 2a and the second conveying roll 2b are positioned so that their rotation axes are parallel to each other and are adjacent to each other with a predetermined gap between them. The pressed powder sheet S is supported on the circumferential surface of the first conveying roll 2a and conveyed through the gap between the first conveying roll 2a and the second conveying roll 2b. The first conveying roll 2a and the second conveying roll 2b rotate in opposite directions with the pressed powder sheet S sandwiched between them, thereby sending the pressed powder sheet S downstream. The pressed powder sheet S is delivered to the second conveying roll 2b at a position where the first conveying roll 2a and the second conveying roll 2b face each other. The pressed powder sheet S is then supported on the circumferential surface of the second conveying roll 2b and conveyed downstream.

[0017] The transport roll 2 in this embodiment also functions as a stretching roll. That is, for example, the first transport roll 2a and the second transport roll 2b rotate at different peripheral speeds. Specifically, the rotation speed of the second transport roll 2b is faster than the rotation speed of the first transport roll 2a. This allows the compressed powder sheet S to be transported and stretched due to the difference in peripheral speed between the two. Therefore, the thickness of the compressed powder sheet S located on the peripheral surface of the second transport roll 2b is smaller than the thickness of the compressed powder sheet S located on the peripheral surface of the first transport roll 2a.

[0018] Alternatively, instead of or in addition to the difference in peripheral speed between the first transport roll 2a and the second transport roll 2b, the surface roughness of the peripheral surface of the second transport roll 2b may be made greater than the surface roughness of the peripheral surface of the first transport roll 2a, thereby enabling the stretching of the pressed powder sheet S. In the present embodiment, the "surface roughness" refers to the arithmetic mean roughness Ra defined in JIS B 0601 2001. However, the surface roughness is not limited to Ra and may be other known indices such as the maximum height roughness Rz. The pressed powder sheet S can also be stretched by narrowing the gap between the first transport roll 2a and the second transport roll 2b to a value smaller than the thickness of the incoming pressed powder sheet S.

[0019] 2(A) and 2(B) are schematic diagrams showing a state in which the compressed powder sheet S has peeled off from the peripheral surface of the transport roll 2. The first transport roll 2a supports and transports the compressed powder sheet S on a portion of its peripheral surface facing vertically downward. On the peripheral surface facing vertically downward, the compressed powder sheet S is pulled downward by its own weight. For this reason, the compressed powder sheet S is easily peeled off from the first transport roll 2a. In particular, as shown in FIG. 2(A), the leading edge of the compressed powder sheet S is easily peeled off from the peripheral surface.

[0020] Furthermore, when the supply of powder P begins to enter the gap between the forming roll 12 and the first conveyor roll 2a and the powder P reaches the gap, a large load is likely to be applied to the forming roll 12 and the first conveyor roll 2a. The force applied to each roll when the powder P enters the gap between the two rolls is often greater than the force applied when the pressed powder sheet S enters the gap between the two rolls. If a large load is applied to the forming roll 12 and the first conveyor roll 2a, the resulting impact may hinder adhesion of the pressed powder sheet S to the circumferential surface of the first conveyor roll 2a. For this reason, the leading edge of the pressed powder sheet S is particularly likely to peel off from the first conveyor roll 2a, which also serves as a forming roll.

[0021] When the powder sheet S, whose leading edge has peeled off from the circumferential surface of the first conveyor roll 2a, is conveyed to the gap between the first conveyor roll 2a and the second conveyor roll 2b, the powder sheet S may enter the gap in a bent state, as shown in FIG. 2B. In this case, the powder sheet S may be thicker than expected and may place excessive load on the first conveyor roll 2a and the second conveyor roll 2b. As a result, the powder sheet conveying device 1 and the powder sheet S may be damaged.

[0022] Therefore, in the powder sheet transport device 1 according to this embodiment, as shown in FIG. 1 , a wall member 14 is provided relative to the first transport roll 2a. The wall member 14 extends along at least a portion of the circumferential surface of the first transport roll 2a, with a predetermined distance therebetween, that supports the powder sheet S. In this embodiment, the wall member 14 extends over the entire area of ​​the circumferential surface of the first transport roll 2a that is visible when the first transport roll 2a is viewed from below in the vertical direction. Therefore, the wall member 14 has an arc-shaped portion that extends parallel to the circumferential surface of the first transport roll 2a when viewed axially of the first transport roll 2a. The wall member 14 may also have a mechanism for moving the arc-shaped portion toward and away from the first transport roll 2a. The powder sheet S is transported downstream through a transport path 16 defined by the circumferential surface of the first transport roll 2a and the wall member 14.

[0023] By dividing the transport path 16 for the pressed powder sheet S between the circumferential surface of the first transport roll 2a and the wall member 14, even if the leading edge of the pressed powder sheet S peels off from the circumferential surface of the first transport roll 2a, the pressed powder sheet S can be transported downstream with the leading edge of the pressed powder sheet S oriented approximately parallel to the circumferential surface. In other words, the wall member 14 can guide the leading edge of the pressed powder sheet S into the gap between the first transport roll 2a and the second transport roll 2b. This makes it possible to prevent the pressed powder sheet S from entering the gap between the first transport roll 2a and the second transport roll 2b in a bent state.

[0024] The distance between the peripheral surface of the first transport roll 2a and the wall member 14 is preferably equal to or less than twice the expected thickness of the compressed powder sheet S at the installation position of the wall member 14. This makes it easier to prevent the compressed powder sheet S from bending.

[0025] Preferably, the end of the wall member 14 contacts the peripheral surface of at least one roll adjacent to the first transport roll 2a, i.e., the peripheral surface of one or both of the forming roll 12 and the second transport roll 2b. In this embodiment, the upstream end of the wall member 14 in the transport direction of the pressed powder sheet S contacts the peripheral surface of the forming roll 12, and the downstream end of the wall member 14 in the transport direction of the pressed powder sheet S contacts the peripheral surface of the second transport roll 2b. The end of the wall member 14 slides against the portion of the peripheral surface of the roll that does not support the pressed powder sheet S. This allows the wall member 14 to scrape off powder P and foreign matter remaining on the peripheral surface of the forming roll 12 and the peripheral surface of the second transport roll 2b.

[0026] The wall member 14 may be provided for transport rolls 2 other than the first transport roll 2 a. In this case, it is preferable that the wall member 14 be provided for the transport roll 2 that supports the pressed powder sheet S at a portion of the circumferential surface that faces vertically downward, but the wall member 14 may also be provided for the transport roll 2 that supports the pressed powder sheet S at a portion that faces vertically upward, such as the second transport roll 2 b.

[0027] The configuration of the powder sheet conveying device 1 can be modified as appropriate. For example, the powder sheet conveying device 1 may include a thickness sensor that measures the thickness of the powder sheet S on the circumferential surface of the first conveying roll 2a and a displacement mechanism that changes the gap between the first conveying roll 2a and the second conveying roll 2b. When the detection result of the thickness sensor indicates that the thickness of the powder sheet S exceeds an expected value, the displacement mechanism is controlled to widen the gap between the first conveying roll 2a and the second conveying roll 2b. This prevents excessive load from being applied to the first conveying roll 2a and the second conveying roll 2b when the powder sheet S enters the gap.

[0028] Furthermore, when the thickness of the compressed powder sheet S exceeds the expected value, the rotation of the second conveying roll 2b may be controlled so that the circumferential speed of the second conveying roll 2b increases. This allows a stronger shear force to be applied to the compressed powder sheet S that has entered the gap, and prevents excessive load from being applied to the first conveying roll 2a and the second conveying roll 2b. Furthermore, the compressed powder sheet S can be further stretched, and the thickness of the compressed powder sheet S can be brought closer to the expected value. Note that the thickness sensor and the displacement mechanism may be provided for the other conveying rolls 2. The roll whose circumferential speed is adjusted is not limited to the second conveying roll 2b.

[0029] The arrangement direction of the transport rolls 2 is not particularly limited. For example, the first transport roll 2a and the second transport roll 2b may be arranged vertically or obliquely. One or more transport rolls 2 may be arranged downstream of the second transport roll 2b. A stacking roll may be arranged adjacent to the most downstream transport roll 2. In this case, the pressed powder sheet S can be stacked on a sheet material such as a current collector plate transported by the stacking rolls.

[0030] As described above, the powder sheet conveying device 1 according to this embodiment includes a conveying roll 2 that supports and conveys the powder sheet S on its circumferential surface, and a wall member 14 that extends along at least a portion of the circumferential surface at a predetermined distance from the supporting portion of the powder sheet S. The powder sheet S is conveyed through a conveying path 16 defined by the circumferential surface and the wall member 14. This prevents the powder sheet S from bending during conveyance. This prevents a powder sheet S with a thickness greater than expected from entering the gap between the rolls and placing an excessive load on the rolls. In particular, when the powder P is a dry powder, the powder sheet S is likely to peel off from the circumferential surface of the conveying roll 2. Therefore, the powder sheet conveying device 1 according to this embodiment can function particularly effectively when the powder P is a dry powder.

[0031] The powder sheet transport device 1 also includes one or more rolls adjacent to the first transport roll 2a, which defines the transport path 16 together with the wall member 14. In this embodiment, the forming roll 12 and the second transport roll 2b are adjacent to the first transport roll 2a. The end of the wall member 14 is in sliding contact with at least one of the forming roll 12 and the second transport roll 2b. This allows the powder P and foreign matter remaining on the circumferential surface of the roll to be removed from the circumferential surface. This improves the quality of the powder sheet S.

[0032] The wall member 14 is disposed opposite the first transport roll 2a, which also serves as a forming roll. The wall member 14 is disposed opposite the first transport roll 2a, which supports the compressed powder sheet S at a portion of its circumferential surface facing downward in the vertical direction. This makes it possible to more reliably prevent the compressed powder sheet S from bending.

[0033] The embodiments of the present disclosure have been described in detail above. The above-described embodiments merely illustrate specific examples of implementing the present disclosure. The content of the embodiments does not limit the technical scope of the present disclosure, and many design modifications, such as changing, adding, or deleting components, are possible within the scope of the concept of the present disclosure defined in the claims. A new embodiment with design modifications will combine the effects of the combined embodiments and modifications. In the above-described embodiments, the content that allows such design modifications is emphasized by using notations such as "in this embodiment" or "in this embodiment," but design modifications are also permitted even in content without such notation. Any combination of the components included in each embodiment is also valid as an aspect of the present disclosure. Hatching on cross sections in the drawings does not limit the material of the hatched object.

[0034] Embodiments may be specified by the following items. [Item 1] A compacted powder sheet transport device (1) comprising: a transport roll (2) that supports and transports a compacted powder sheet (S) formed by compressing powder (P) into a sheet shape on its peripheral surface; and a wall member (14) that extends along at least a portion of the portion of the peripheral surface that supports the compacted powder sheet (S) at a predetermined interval from said at least a portion, and transports the compacted powder sheet (S) within a transport path (16) defined by the peripheral surface and the wall member (14). [Item 2] The compacted powder sheet transport device (1) according to item 1 further comprises one or more rolls (12, 2b) adjacent to the transport roll (2a), and an end of the wall member (14) contacts the peripheral surface of at least one of the rolls (12, 2b). [Item 3] The compressed powder sheet transport device (1) according to item 1 or 2, wherein the transport roll (2 a) also serves as a forming roll that compresses the powder (P) to form the compressed powder sheet (S). [Item 4] The compressed powder sheet transport device (1) according to any one of items 1 to 3, wherein the transport roll (2 a) supports the compressed powder sheet (S) at a portion of its circumferential surface that faces downward in the vertical direction.

[0035] The present disclosure can be used in a powder sheet conveying device.

[0036] REFERENCE SIGNS LIST 1 Compacted powder sheet transport device, 2 Transport roll, 2a First transport roll, 2b Second transport roll, 12 Forming roll, 14 Wall member, 16 Transport path.

Claims

1. A powder sheet conveying device comprising: a conveying roll that supports and conveys a powder sheet formed by compressing powder into a sheet shape on its peripheral surface; and a wall member that extends along at least a portion of the portion of the peripheral surface that supports the powder sheet, at a predetermined interval from said portion; and conveys the powder sheet within a conveying path partitioned by said peripheral surface and said wall member.

2. The powder sheet transport device according to claim 1, further comprising one or more rolls adjacent to the transport roll, and an end of the wall member contacts the peripheral surface of at least one of the rolls.

3. A powder sheet conveying device according to claim 1 or 2, wherein the conveying roll also serves as a forming roll for compressing the powder to form the powder sheet.

4. A powder sheet conveying device according to claim 1 or 2, wherein the conveying roll supports the powder sheet at a portion of the peripheral surface facing vertically downward.

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