Rolling and folding integrated equipment

Abstract

The utility model relates to the technical field of battery core pole group forming, and provides rolling and stacking integrated equipment. The winding and stacking integrated equipment comprises a winding needle and two diaphragms wound on the winding needle, the two diaphragms comprise the first diaphragm and the second diaphragm, and the second diaphragm is stacked on the side, away from the winding needle, of the first diaphragm; first pole pieces are arranged on the first diaphragm, second pole pieces are arranged on the second diaphragm, the number of the second pole pieces is one more than that of the first pole pieces, one of the second pole pieces forms a coating pole piece, the other second pole pieces are arranged in one-to-one correspondence with the first pole pieces, and the coating pole piece is arranged on one side, far away from the fixed end, of the other second pole pieces. According to the rolling and stacking integrated equipment provided by the invention, the stacking of the first pole piece and the second pole piece can be directly realized in the diaphragm rolling process, so that a pole group meeting requirements is formed, rolling and stacking are integrated, and the forming efficiency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode group forming, and particularly relates to a winding and stacking integrated device. BACKGROUND

[0002] At present, electrode group forming is mostly in the Z-shaped stacking forming mode, the cutting and stacking integrated forming mode or the hot-composite stacking forming mode. However, in the Z-shaped stacking forming mode, the device is prone to sucking and stacking multiple pieces of the electrode sheet at one time, and the stacking efficiency is not high. Meanwhile, the diaphragm is deformed during the electrode group forming, and the tension is uneven, and the performance of the battery is low.

[0003] Although the cutting and stacking integrated forming mode integrates the processes of die cutting, stacking and hot pressing, reduces the feeding and transferring processes, and is similar in essence to the Z-shaped stacking technology, the diaphragm is still deformed and the tension is uneven. The hot-composite stacking continuously transports in a single direction during the production process, the speed and tension are stable, and the problem of diaphragm deformation in the Z-shaped stacking can be avoided. However, the hot-composite stacking introduces multiple hot-composite and roller pressing processes, and the forming processes are more, and the liquid injection in the later stage is more difficult. CONTENT OF THE UTILITY MODEL

[0004] In order to solve the above technical problems or at least partially solve the above technical problems, the present application provides a winding and stacking integrated device.

[0005] The present application provides a winding and stacking integrated device, which comprises a winding needle and two diaphragms wound on the winding needle, and one end of each of the two diaphragms is formed with a fixed end, and the fixed end is arranged on the winding needle.

[0006] The two diaphragms comprise a first diaphragm and a second diaphragm, and the second diaphragm is arranged on the side of the first diaphragm away from the winding needle.

[0007] A plurality of first electrode sheets are arranged on the first diaphragm at intervals, a plurality of second electrode sheets are arranged on the second diaphragm at intervals, and the number of the second electrode sheets is one more than the number of the first electrode sheets. One of the second electrode sheets is formed as a cladding electrode sheet, and the rest of the second electrode sheets are arranged one by one corresponding to the first electrode sheets, and the cladding electrode sheet is arranged on the side of the rest of the second electrode sheets away from the fixed end.

[0008] Optionally, the winding needle comprises a first arc surface and a second arc surface arranged oppositely, and the first arc surface and the second arc surface are smoothly connected, and the first electrode sheet and the second electrode sheet are both within the range of the first arc surface and the second arc surface.

[0009] Optionally, a gap is formed on the first arc surface and the second arc surface, and the fixed end is inserted into the gap.

[0010] Optionally, a pre-rolling area is formed on the first and second diaphragms corresponding to the region between the connecting position of the first and second curved surfaces and the gap.

[0011] The first pole piece is arranged on the side of the pre-rolling area of the first diaphragm away from the fixed end, and the second pole piece is arranged on the side of the pre-rolling area of the second diaphragm away from the fixed end.

[0012] Optionally, a first pole lug is arranged on the first pole piece, and a second pole lug is arranged on the second pole piece, and the second pole lug is arranged at a position different from the first pole lug on the first pole piece.

[0013] Optionally, the first pole lug is arranged close to one side of the first pole piece, and the arrangement positions of the first pole lugs on adjacent first pole pieces are opposite.

[0014] The second pole lug is arranged close to one side of the second pole piece, and the arrangement positions of the second pole lugs on adjacent second pole pieces are opposite.

[0015] Optionally, in the direction from the fixed end to the other end of the first diaphragm, the distance between adjacent first pole pieces gradually increases.

[0016] In the direction from the fixed end to the other end of the second diaphragm, the distance between adjacent second pole pieces gradually increases.

[0017] Compared with the prior art, the technical scheme provided by the embodiments of the present application has the following advantages:

[0018] The application provides a winding and folding integrated device, which comprises a winding needle and two diaphragms wound on the winding needle, one end of the two diaphragms is formed with a fixed end, the fixed end is arranged on the winding needle, the two diaphragms comprise a first diaphragm and a second diaphragm, the second diaphragm is arranged on the side, away from the winding needle, of the first diaphragm, that is, the fixed ends of the first diaphragm and the second diaphragm can be arranged on the winding needle after the first diaphragm and the second diaphragm are laminated, and the innermost circle of the first diaphragm can be arranged in close contact with the winding needle after the first diaphragm and the second diaphragm are wound, a plurality of first pole pieces are arranged on the first diaphragm at intervals, a plurality of second pole pieces are arranged on the second diaphragm at intervals, the first pole pieces and the second pole pieces can be wound and folded when the first diaphragm and the second diaphragm are wound, the number of the second pole pieces is one more than the number of the first pole pieces, one of the second pole pieces is formed into a cladding pole piece, the rest of the second pole pieces are arranged one by one in correspondence with the first pole pieces, and the cladding pole piece is arranged on the side, away from the fixed end, of the rest of the second pole pieces, the first pole pieces and the second pole pieces successively surround the winding needle and are stacked on the winding needle along with the winding of the first diaphragm and the second diaphragm, the tension of the diaphragm is constant during winding, and the influence of periodic changes and swings of tension on the mechanical properties, porosity and other properties of the diaphragm during Z-shaped stacking of pole pieces can be avoided; compared with hot-combined pole pieces, the winding and folding integrated device does not need to increase redundant processes, is simple in form, can directly realize the stacking of the first pole pieces and the second pole pieces during the winding of the diaphragm, and further forms a pole group meeting the requirements, and the winding and folding are integrated, and the forming efficiency is high. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings incorporated into the specification and constituting a part of the specification show embodiments consistent with the application and, together with the specification, serve to explain the principles of the application.

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0021] Figure 1 The structure diagram of the diaphragm of an embodiment of the application;

[0022] Figure 2 The structure diagram of the diaphragm of another embodiment of the application;

[0023] Figure 3 The structure diagram of the winding and folding integrated device of an embodiment of the application;

[0024] Figure 4 The structure diagram of the pole group of an embodiment of the application.

[0025] As shown in the figure, 1, winding needle; 11, first arc surface; 12, second arc surface; 13, clamping gap; 2, diaphragm; 21, first diaphragm; 211, blank area; 22, second diaphragm; 23, fixed end; 24, pre-winding area; 3, first pole piece; 31, first pole lug; 4, second pole piece; 41, second pole lug. DETAILED DESCRIPTION

[0026] In order to enable one skilled in the art to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0027] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some of the embodiments of the present application, not all the embodiments.

[0028] The winding and folding integrated device will be described in detail below through specific embodiments:

[0029] Referring to Figures 1 to 4 The winding and folding integrated device provided by some embodiments of the present application includes a winding needle 1 and two diaphragms 2 wound on the winding needle 1. One end of each of the two diaphragms 2 is formed with a fixed end 23, and the fixed end 23 is arranged on the winding needle 1. The two diaphragms 2 include a first diaphragm 21 and a second diaphragm 22. The second diaphragm 22 is arranged on the side of the first diaphragm 21 away from the winding needle 1, that is, after the first diaphragm 21 and the second diaphragm 22 are stacked, the fixed ends 23 of both can be arranged on the winding needle 1, and after the first diaphragm 21 and the second diaphragm 22 are wound, the innermost circle of the first diaphragm 21 can be arranged to adhere to the winding needle 1.

[0030] A plurality of first pole pieces 3 are arranged on the first diaphragm 21, and a plurality of second pole pieces 4 are arranged on the second diaphragm 22. When the first diaphragm 21 and the second diaphragm 22 are wound, the first pole pieces 3 and the second pole pieces 4 can be driven to be wound and folded. The number of second pole pieces 4 is one more than the number of first pole pieces 3. One of the second pole pieces 4 is formed as a cladding pole piece, and the rest of the second pole pieces 4 are arranged one by one corresponding to the first pole pieces 3, and the cladding pole piece is arranged on the side of the rest of the second pole pieces 4 away from the fixed end 23.

[0031] It can be understood that, with the winding of the first diaphragm 21 and the second diaphragm 22, the first pole piece 3 and the second pole piece 4 are sequentially wrapped around the winding needle 1 and stacked on the winding needle 1, and the diaphragm 2 is constant in tension during winding, which can avoid the influence of the periodic change and swing of the pulling force on the mechanical properties, porosity and other properties of the diaphragm 2 during Z-shaped stacking; compared with hot composite stacking, no additional process is needed, the form is simple, and the winding and stacking integrated equipment of the present application can directly realize the stacking of the first pole piece 3 and the second pole piece 4 during the winding process of the diaphragm 2, and then form a pole group meeting the requirements, the winding and stacking are integrated, the efficiency is high, the stacking and winding are communicated, and the practicality is high.

[0032] In specific implementation, the position corresponding to the coated pole piece on the first diaphragm 21 is formed as a blank area 211, one of the first pole piece 3 and the second pole piece 4 is a positive pole piece, and the other is a negative pole piece, when the first pole piece 3 is a positive pole piece and the second pole piece 4 is a negative pole piece, the coated pole piece is a negative pole piece and is coated in the outermost layer, and the battery cell is in the form of negative coating positive, when the first pole piece 3 is a negative pole piece and the second pole piece 4 is a positive pole piece, the coated pole piece is a positive pole piece and is coated in the outermost layer, and the battery cell is in the form of positive coating negative, which can be specifically set according to actual requirements, and the present application does not limit this.

[0033] Referring to Figure 3 As shown in the figure, the first pole piece 3 is arranged on the side of the first diaphragm 21 away from the winding needle 1, and the second pole piece 4 is arranged on the side of the second diaphragm 22 away from the winding needle 1, so as to avoid the direct contact of the first pole piece 3 or the second pole piece 4 with the surface of the winding needle 1, which may cause damage or pollution and lead to the performance degradation of the battery cell.

[0034] In some embodiments, the winding needle 1 includes oppositely arranged first and second arc surfaces 11 and 12, and the first pole piece 3 and the second pole piece 4 are both within the range of the first and second arc surfaces 11 and 12. That is, during the winding process of the diaphragm 2, after passing through the first or second arc surface 11 or 12 once, a group of pole pieces (a group of pole pieces includes the first pole piece 3 and the second pole piece 4, and the first pole piece 3 is closer to the winding needle 1 than the second pole piece 4) is stacked on the first or second arc surface 11 or 12. By such arrangement, after one winding of the diaphragm 2, a group of pole pieces can be stacked on the first and second arc surfaces 11 and 12 respectively, until a pole group meeting the requirements is formed. Specifically, the first and second arc surfaces 11 and 12 are smoothly connected, avoiding damage to the first and second diaphragms 21 and 22 by the winding needle 1, ensuring the service life of the diaphragm 2 and further ensuring the performance of the battery cell.

[0035] In specific implementation, the first arc surface 11 and the second arc surface 12 are provided with a gap 13, and the fixed end 23 is inserted into the gap 13 to fix the fixed end 23 relative to the winding needle 1, so as to facilitate the winding of the first diaphragm 21 and the second diaphragm 22. It should be noted that the fixed end 23 can also be separated from the gap 13, so as to take out the winding needle 1 from the first diaphragm 21 and the second diaphragm 22 after the winding is completed, to form the final pole group.

[0036] Further, the first diaphragm 21 and the second diaphragm 22 are formed with a pre-winding area 24 between the connection of the first arc surface 11 and the second arc surface 12 and the gap 13, and after the fixed end 23 is inserted into the gap 13, the pre-winding area 24 is first wound on the winding needle 1, so as to ensure the tightness of the winding and avoid misalignment to affect the stacking performance between the first pole piece 3 and the second pole piece 4.

[0037] The first pole piece 3 is arranged on the side of the pre-winding area 24 of the first diaphragm 21 away from the fixed end 23, and the second pole piece 4 is arranged on the side of the pre-winding area 24 of the second diaphragm 22 away from the fixed end 23. That is, after the pre-winding area 24 is wound on the winding needle 1, the first pole piece 3 and the second pole piece 4 are correspondingly wound, and then the coated pole piece and the blank area 211 are wound and formed on the outermost layer, until the pole group meeting the requirements is formed.

[0038] In some embodiments, referring to Figure 1 , the first pole piece 3 is provided with a first lug 31, and the second pole piece 4 is provided with a second lug 41, and the second lug 41 is arranged at a position offset from the first lug 31 of the corresponding first pole piece 3. In this way, after the first pole piece 3 and the second pole piece 4 are wound and stacked, the first lug 31 and the second lug 41 on the final pole group can be arranged offset, avoiding the short circuit phenomenon caused by the contact between the first lug 31 and the second lug 41, and ensuring the service life of the battery cell.

[0039] In specific implementation, referring to Figure 1 , the first lug 31 is arranged on the side close to the first pole piece 3, that is, the first lug 31 is not arranged at the center of the first pole piece 3, and the arrangement positions of the first lugs 31 on the adjacent first pole pieces 3 are opposite. It can be understood that after the diaphragm 2 is wound for one turn, the adjacent first pole pieces 3 are located on the first arc surface 11 and the second arc surface 12 of the winding needle 1 respectively, and since the arrangement positions of the first lugs 31 on the adjacent first pole pieces 3 are opposite, the positions of the first lugs 31 on the adjacent first pole pieces 3 correspond after winding and stacking, so that the positions of the first lugs 31 on the final pole group are correspondingly arranged.

[0040] Further, continuing to refer to Figure 1As shown, the second lug 41 is arranged close to one side of the second pole piece 4, that is, the second lug 41 is not arranged at the middle of the second pole piece 4, and the arrangement positions of the second lug 41 on the adjacent second pole pieces 4 are opposite. It can be understood that after the diaphragm 2 is wound for one turn, the adjacent second pole pieces 4 are located on the first arc surface 11 and the second arc surface 12 of the winding needle 1 respectively, and since the arrangement positions of the second lug 41 on the adjacent second pole pieces 4 are opposite, the positions of the second lug 41 on the adjacent second pole pieces 4 correspond after being wound and folded, thereby making the positions of the second lug 41 of the final pole group correspondingly arranged.

[0041] Of course, it needs to be explained that, with reference to the above description of the first lug 31 and the second lug 41, the first lug 31 and the second lug 41 can be arranged at the middle of the first pole piece 3 and the second pole piece 4 respectively, as long as the first lug 31 and the second lug 41 are arranged on different sides of the first pole piece 3 and the second pole piece 4 respectively to stagger the arrangement and avoid the contact between the first lug 31 and the second lug 41. Figure 2 As shown, the first lug 31 can also be arranged at the middle of the first pole piece 3, and the second lug 41 can also be arranged at the middle of the second pole piece 4, as long as the first lug 31 and the second lug 41 are arranged on different sides of the first pole piece 3 and the second pole piece 4 respectively to stagger the arrangement and avoid the contact between the first lug 31 and the second lug 41.

[0042] In some embodiments, in the direction from the fixed end 23 to the other end of the first diaphragm 21, the distance between the adjacent first pole pieces 3 gradually increases; in the direction from the fixed end 23 to the other end of the second diaphragm 22, the distance between the adjacent second pole pieces 4 gradually increases.

[0043] It can be understood that the first diaphragm 21 between the adjacent first pole pieces 3, the second diaphragm 22 between the adjacent second pole pieces 4 are arranged around the transition zone between the first arc surface 11 and the second arc surface 12, and as the number of winding turns increases, by increasing the distance between the adjacent first pole pieces 3 and the distance between the adjacent second pole pieces 4, a high alignment degree between the first pole piece 3 and the second pole piece 4 after being wound and folded can be ensured, and the winding efficiency is improved.

[0044] The winding integrated device of the present application can be used to first die-cut the first pole piece 3 and the second pole piece 4 of a predetermined size, arrange the first pole piece 3 on the first diaphragm 21 and the second pole piece 4 on the second diaphragm 22; then stack the first diaphragm 21 and the second diaphragm 22, and arrange the fixed end 23 of the first diaphragm 21 and the second diaphragm 22 on the winding needle 1; then wind and arrange the first diaphragm 21 and the second diaphragm 22 around the winding needle 1, and take out the winding needle 1 after winding is completed to form a pole group; finally, the pole group is subjected to heat pressing treatment to be shaped, and the excess first diaphragm 21 and second diaphragm 22 on both sides of the pole group are cut.

[0045] In a specific implementation, the first and second pole pieces 3 and 4 (i.e., positive and negative pole pieces) are die-cut to form the size required by the pole group of the battery cell. Specifically, the first and second tabs 31 and 41 are formed on the same side of the pole group or on different sides of the pole group, respectively, and are arranged staggeredly to avoid the phenomenon of positive and negative contact short circuit.

[0046] Referring to FIGS. 1 to 4, the first and second pole pieces 3 and 4 are arranged on the first and second separators 21 and 22, respectively, and are wound around the winding needle 1. Figure 1 and Figure 2 As shown in FIGS. 1 to 4, the die-cut first and second pole pieces 3 and 4 are arranged on the first and second separators 21 and 22, respectively, and are arranged with a placement interval between the different pole pieces to ensure that the first and second pole pieces 3 and 4 can be arranged in alignment during winding. Specifically, when the pole pieces are attached, the front ends of the first and second separators 21 and 22 are left with a certain blank area to form a fixed end 23, and a pre-winding area 24 is formed at the rear end of the fixed end 23 for clamping and pre-winding of the winding needle 1, so as to avoid direct contact between the first or second pole piece 3 or 4 and the surface of the winding needle 1, which may cause damage or contamination and result in performance degradation of the battery cell.

[0047] The first and second separators 21 and 22 are wound around the winding needle 1, and the winding needle 1 is placed on a winding device to wind the first and second separators 21 and 22. Since the winding device has a constant tension control of the separator 2, the tension of the separator 2 during winding is constant, the forming efficiency is higher, the intercommunication between the lamination and the winding is realized, and the practicability of the device is improved.

[0048] After winding is completed, the winding needle 1 is taken out, and the wound first and second pole pieces 3 and 4 can form a pole group meeting the requirements. The wound pole group is formed by hot pressing, and after hot pressing, the pole group is pressed by a pressing plate, and the excess separator 2 on both sides of the pole group is cut by a cutter. Cutting the excess separator 2 is conducive to reducing the space occupancy of the pole group in the battery cell and facilitating subsequent cell casing.

[0049] In a specific implementation, the first pole pieces 3 are sequentially arranged on the first separator 21 in a direction away from the fixed end 23, and the second pole pieces 4 are correspondingly arranged on the second separator 22 in a one-to-one manner with the first pole pieces 3. The cladding pole piece is arranged at a position corresponding to the position of the first pole piece 3 beyond the first pole piece 3 in a direction away from the fixed end 23.

[0050] Specifically, when the first pole piece 3 is a positive pole piece and the second pole piece 4 is a negative pole piece, i.e., there is one more negative pole piece than positive pole piece, and the extra negative pole piece forms a cladding pole piece, the battery cell is in a negative cladding positive form. When the first pole piece 3 is a negative pole piece and the second pole piece 4 is a positive pole piece, i.e., there is one more positive pole piece than negative pole piece, and the extra positive pole piece forms a cladding pole piece, the battery cell is in a positive cladding negative form.

[0051] In specific implementation, the sizes of the fixed end 23, the pre-rolling area 24, the blank area 211 and the distance between adjacent pole pieces can be set according to actual conditions, and the present application does not limit this, as long as the positive and negative pole pieces can be aligned during rolling, and the phenomenon of abnormal battery capacity or short circuit caused by insufficient alignment can be avoided.

[0052] In some embodiments, the outer periphery of the pole group is also wrapped with a fixing tape to fix the first pole piece 3 and the second pole piece 4, which can avoid the problem that the first pole piece 3 and the second pole piece 4 are separated after the excess separator 2 is cut, and the layer spacing between the first pole piece 3 and the second pole piece 4 is increased, and can also avoid the problem that the separator 2 shrinks due to reduced tension during cutting, and the first pole piece 3 and the second pole piece 4 are short-circuited, thereby ensuring the performance of the battery cell.

[0053] It should be noted that in this document, relational terms such as“first” and“second”, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms“comprises”,“comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by“comprises a” does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0054] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A roll folding integrated apparatus characterized by comprising: The application relates to a winding needle (1) and two diaphragms (2) wound on the winding needle (1), one end of the two diaphragms (2) is formed with a fixed end (23), and the fixed end (23) is arranged on the winding needle (1). The two diaphragms (2) comprise a first diaphragm (21) and a second diaphragm (22), the second diaphragm (22) is arranged on the side, away from the winding needle (1), of the first diaphragm (21). A plurality of first pole pieces (3) are arranged on the first diaphragm (21) at intervals, a plurality of second pole pieces (4) are arranged on the second diaphragm (22) at intervals, the number of the second pole pieces (4) is one more than the number of the first pole pieces (3), one of the second pole pieces (4) is formed as a cladding pole piece, the rest of the second pole pieces (4) are arranged one by one in correspondence with the first pole pieces (3), and the cladding pole piece is arranged on the side, away from the fixed end (23), of the rest of the second pole pieces (4).

2. The folding unit of claim 1, wherein The winding needle (1) comprises oppositely arranged first and second arc surfaces (11) and (12), and the first and second arc surfaces (11) and (12) are smoothly connected, the first and second pole pieces (3) and (4) are arranged within the range of the first and second arc surfaces (11) and (12).

3. The folding unit of claim 2, wherein A clamping gap (13) is formed on the first and second arc surfaces (11) and (12), and the fixed end (23) is arranged in the clamping gap (13).

4. The folding unit of claim 3, wherein A pre-winding area (24) is formed on the first and second diaphragms (21) and (22) between the connecting part of the first and second arc surfaces (11) and (12) and the clamping gap (13). The first pole pieces (3) are arranged on the side, away from the fixed end (23), of the pre-winding area (24) of the first diaphragm (21), and the second pole pieces (4) are arranged on the side, away from the fixed end (23), of the pre-winding area (24) of the second diaphragm (22).

5. The folding unit of any one of claims 1 to 4, wherein, A first lug (31) is arranged on the first pole piece (3), and a second lug (41) is arranged on the second pole piece (4), and the second lug (41) is arranged in a staggered manner with the first lug (31) of the first pole piece (3) at the corresponding position.

6. The folding unit of claim 5, wherein The first lug (31) is arranged on the side, close to the first pole piece (3), of the first pole piece (3), and the arrangement positions of the first lugs (31) on the adjacent first pole pieces (3) are opposite to each other. The second lug (41) is arranged on the side, close to the second pole piece (4), of the second pole piece (4), and the arrangement positions of the second lugs (41) on the adjacent second pole pieces (4) are opposite to each other.

7. The folding unit of any one of claims 1 to 4, wherein In the direction from the fixed end (23) to the other end of the first diaphragm (21), the distance between the adjacent first pole pieces (3) gradually increases. In the direction from the fixed end (23) to the other end of the second diaphragm (22), the distance between the adjacent second pole pieces (4) gradually increases.

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