Electrolytic capacitors

Abstract

To provide an electrolytic capacitor that can suppress the deterioration of the separator. [Solution] The electrolytic capacitor 1 comprises a capacitor element 11 formed by overlapping and winding an anode foil 14a and a cathode foil 15a, to which lead tabs 14 and 15 for drawing out electrodes are connected, via a separator 16. The electrolytic capacitor 1 has a protective material 30. The protective material 30 is provided so as to overlap in the overlapping direction Y of the connection portions 140 and 150 to which the lead tabs 14 and 15 are overlapped and connected on one side of the anode foil 14a and cathode foil 15a. The protective material 30 is provided on the opposing surface 16c of the separator 16 that faces the anode foil 14a and cathode foil 15a to which the lead tabs 14 and 15 are connected. The protective material 30 covers at least a portion of the end face 16a of the separator 16 on the side opposite to the side from which the lead tabs 14 and 15 are drawn out.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor in which a lead tab is connected to an electrode foil.

Background Art

[0002] Conventionally, an electrolytic capacitor has a capacitor element in which an anode foil and a cathode foil, which are electrode foils, are wound through a separator. The capacitor element impregnated with an electrolytic solution is housed in a bottomed cylindrical exterior case, and the open end side of the exterior case is sealed with a sealing body. Further, a lead tab for leading out the electrode to the outside is connected to the electrode foil of the capacitor element. Generally, one end portion of the lead tab flattened is connected to the electrode foil, and the other end portion of the lead tab is inserted through the sealing body and led out to the outside.

[0003] In order to prevent a short circuit (internal short) between the anode foil and the cathode foil, a structure in which a connection portion where the lead tab and the electrode foil are connected is covered with a protective material is known. For example, in Patent Document 1, it is described that insulating paper is adhered as a protective material so as to cover a tab for electrode extraction (lead tab) fixed to an electrode foil.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] At the connection point between the electrode foil and the lead tab, the lead tab is flattened, but this connection point is thicker than other parts of the capacitor element, creating a gap where it overlaps with the separator when wound. When aging treatment is performed to repair the oxide film of the electrode foil in this state, the gas generated from the electrolyte bubbles in this gap, causing the fibers of the electrolytic paper (separator) to unravel and deteriorate, potentially leading to an internal short circuit between the electrodes. In experiments conducted by the inventors of the present invention, it was found that the separator deteriorates particularly rapidly and is prone to internal short circuits near the connection point between the lead tab and the electrode foil of the capacitor element, and at the end face of the separator in a direction perpendicular to the winding direction of the capacitor element.

[0006] Therefore, the object of the present invention is to provide an electrolytic capacitor that can suppress the deterioration of the separator. [Means for solving the problem]

[0007] The electrolytic capacitor of the present invention comprises a capacitor element formed by overlapping and winding electrode foils, each connected to a lead tab for drawing out electrodes, via a separator, wherein the capacitor element has a first protective material provided on the opposing surface of the separator facing one or the other surface of the electrode foil, such that the connection portion to which the lead tab is overlapped and connected on one side of the electrode foil overlaps in the overlapping direction, and the first protective material covers at least a portion of the end face of the separator on the side from which the lead tab is drawn out. [Effects of the Invention]

[0008] According to the present invention, the deterioration of the separator can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing the configuration of electrolytic capacitor 1. [Figure 2] This is a perspective view showing the capacitor element 11 of the electrolytic capacitor 1. [Figure 3] This is a side view showing the capacitor element 11 of the electrolytic capacitor 1 before winding. [Figure 4] This is a view from the F4-F4 arrow in Figure 3. [Figure 5] This is a modified example of the arrangement of the protective material 30. [Figure 6] This is a modified example of the arrangement of the protective material 30. [Modes for carrying out the invention]

[0010] The electrolytic capacitor 1 according to this embodiment will be described below with reference to the attached drawings.

[0011] As shown in Figure 1, the electrolytic capacitor 1 includes a capacitor element 11, an outer casing 12, a sealing body 13, and lead tabs 14 and 15.

[0012] As shown in Figure 2, the capacitor element 11 consists of an anode foil (anodic aluminum foil) 14a and a cathode foil (cathode aluminum foil) 15a, which have been etched and subjected to dielectric oxide film formation treatment. These are superimposed on a separator (electrolytic paper) 16, wound into a cylindrical shape, and secured with element fixing tape 21 (see Figure 1). This capacitor element 11 is housed in an outer case 12 (see Figure 1).

[0013] The outer case 12 is a bottomed cylindrical case. A sealing body 13 is fitted to the opening of the outer case 12, and the opening has a structure that is sealed by drawing. In this way, the sealing body 13 seals the opening of the outer case 12. For example, the sealing body 13 is an elastic material. More specifically, for example, the sealing body 13 is a rubber elastic material. For example, the sealing body 13 may be natural rubber or synthetic rubber.

[0014] Lead tabs 14 and 15 are drawn out from the capacitor element 11. Lead wires 14b and 15b are welded to lead tabs 14 and 15, respectively. Lead wires 14b and 15b are formed to be smaller in diameter than lead tabs 14 and 15. Lead wires 14b and 15b are drawn out to the outside through the sealing body 13. At this time, lead tabs 14 and 15 are inserted through the sealing body 13. The outer case 12 is covered by a sleeve 22 (see Figure 1).

[0015] Lead tab 14 is an anode-side lead tab connected to the anode foil 14a by methods such as crimping or welding. Lead tab 15 is a cathode-side lead tab connected to the cathode foil 15a by methods such as crimping or welding.

[0016] As shown in Figure 3, the anode-side lead tab 14 has a round bar portion 141 and a flattened portion 142 that protrude from the end face of the capacitor element 11 (see Figure 2) on the sealing body 13 side. The flattened portion 142 is formed at one end of the round bar portion 141, and the anode foil 14a is connected to it. For example, the lead tab 14 may be formed by pressing one end of a round bar-shaped member made of aluminum to a predetermined length to form the flattened portion 142, and making the remaining portion the round bar portion 141. The lead wire 14b is connected to the tip of the round bar portion 141 (the end opposite to the flattened portion 142). In this way, a connection portion 140 is formed to which the lead tab 14 and the anode foil 14a are connected.

[0017] Furthermore, the cathode-side lead tab 15, like the anode-side lead tab 14, has a round bar portion 151 protruding from the end face of the capacitor element 11 and a flat portion 152. The flat portion 152 is formed at one end of the round bar portion 151, to which the cathode foil 15a is connected. The lead wire 15b is connected to the tip of the round bar portion 151 (the end opposite to the flat portion 152). In this way, a connection portion 150 is formed to which the lead tab 15 and the cathode foil 15a are connected. Note that in Figure 3, the cathode-side configuration is indicated by the symbols in parentheses.

[0018] (direction) Here, the direction in which the anode foil 14a (cathode foil 15a) extends is defined as the left - right direction X. Also, the direction in which the separator 16 is overlapped with the anode foil 14a (cathode foil 15a) is defined as the overlapping direction Y. Further, the direction in which the lead tab 14 (lead tab 15) is pulled out is defined as the up - down direction Z. In the up - down direction Z, the side (direction) from which the lead tab 14 is pulled out is defined as the lower side Z2, and the opposite side (direction) of the lower side Z2 is defined as the upper side Z1. The longitudinal direction (left - right direction X), the overlapping direction Y, and the up - down direction Z are perpendicular to each other.

[0019] As described above, the anode foil 14a and the cathode foil 15a are overlapped via the separator 16. The separator 16 is provided so that the anode foil 14a and the cathode foil 15a do not contact each other. Also, the separator 16 has a function of holding the electrolytic solution. The separator 16 is formed such that the length in the up - down direction Z is longer than that of the anode foil 14a and the cathode foil 15a.

[0020] A protective material 30 is provided on the separator 16. When the electrode foils (anode foil 14a and cathode foil 15a) and the separator 16 are overlapped, the protective material 30 is provided between the connection portions 140 and 150 and the separator 16. That is, the protective material 30 is provided on the opposing surface 16c (see FIG. 4) of the separator 16 that opposes the other surface of the electrode foils (anode foil 14a and cathode foil 15a) so as to overlap in the overlapping direction Y with the connection portions 140 and 150 where the lead tabs 14 and 15 are overlapped and connected to one surface 14a1 (15a1) of the electrode foils (anode foil 14a and cathode foil 15a). The protective material 30 covers at least a part of the end face 16a of the separator 16 on the side opposite to the side from which the lead tabs 14 and 15 are drawn out. The protective material 30 is a paper sheet made by individually or mixedly papermaking Manila paper, kraft paper, esparto paper, regenerated cellulose, etc. The protective material 30 may be a resin film, but preferably one that can hold an electrolytic solution. The protective material 30 may be made of the same material as the separator 16 or a different material. The protective material 30 may be provided so as to cover either one of the connection portion 140 and the connection portion 150, or may be provided so as to cover both the connection portion 140 and the connection portion 150. The protective material 30 is attached to the separator 16 with an adhesive. For example, an acrylic adhesive is used as the adhesive. FIG. 3 shows a state in which the capacitor element 11 before winding of the electrolytic capacitor 1 is arranged in the order of the protective material 30, the electrode foils (anode foil 14a and cathode foil 15a), and the separator 16 as seen from the side.

[0021] As shown in Figure 4, the protective material 30 is provided on the anode foil 14a (cathode foil 15a) side of the connection portion 140-150. That is, the protective material 30 is provided on the separator 16 facing the non-connected surface 14a2 (non-connected surface 15a2) of the electrode foil (anode foil 14a, cathode foil 15a) to which the lead tabs 14-15 are connected, where the lead tabs 14-15 are not connected. The protective material 30 is provided between the separator 16, which is superimposed in the overlapping direction Y, and the anode foil 14a (cathode foil 15a). The end portion 30a of the protective material 30 on the connection portion 140-150 side reaches the lower end surface 16b of the separator 16 Z2. The protective material 30 is then folded back at the upper end surface 16a of the separator 16 Z1 to the side opposite to the connection portion 140-150. As a result, the upper end face 16a of the separator 16 at Z1 is covered by the protective material 30. The folded end 30b of the protective material 30 reaches the lower end face 16b of the separator 16 at Z2. In this way, the protective material 30 is folded back to sandwich the separator 16. Specifically, the protective material 30 is folded back at the end face 16a of the separator 16 on the side from which the lead tabs 14 and 15 are pulled out, and is also provided on the non-opposing surface 16d on the side opposite to the opposing surface 16c that faces the connection surface of the electrode foils (anode foil 14a, cathode foil 15a) to which the lead tabs 14 and 15 are connected. Thus, the protective material 30 is folded back at the end face 16a of the separator 16 on the side opposite to (upper Z1) from which the lead tabs 14 and 15 are pulled out (lower Z2), and extends to the back side of the opposing surface 16c of the separator 16. Furthermore, the protective material 30 is provided to cover the entire length of the separator 16 in the vertical direction Z. That is, the protective material 30 provided on the non-opposing surface 16d covers the non-opposing surface 16d up to the end surface 16b on the side from which the lead tabs 14 and 15 of the separator 16 are pulled out. In this way, the protective material 30 extends from the back side of the opposing surface 16c of the separator 16 to the end on the side (lower Z2) from which the lead tabs 14 and 15 are pulled out.

[0022] The protective material 30 is not limited to the above configuration, and only needs to cover the connection portions 140 and 150 and the end face 16a of the upper Z1 of the separator 16. The protective material 30 only needs to cover at least the end face 16a of the connection portions 140 and 150 in the left-right direction X. For example, the length of the protective material 30 in the left-right direction X is preferably longer than the length of the lead tab 14 (lead tab 15) in the left-right direction X. For example, the length of the protective material 30 in the left-right direction X is preferably 1.0 mm or more longer on each side than the length of the lead tab 14 (lead tab 15) in the left-right direction X. Also, the length of the protective material 30 in the left-right direction X may be determined based on the diameter of the placement position of the lead tab 14 (lead tab 15) in the capacitor element 11. For example, the length of the protective material 30 in the left-right direction X may be the length obtained by adding 1 / 3 of the diameter up to the lead tab 14 (lead tab 15) to each side of the length of the lead tab 14 (lead tab 15) in the left-right direction X.

[0023] Furthermore, the positions of ends 30a and 30b do not have to be the same as the position of the lower end face 16b of the separator 16 Z2. The ends 30a and 30b of the protective material 30 may be located below (towards Z2) the lower end face 16b of the separator 16 Z2. The length of the protective material 30 in the left-right direction X may be the same as the length of the connecting portion 140-150 in the left-right direction X. Also, the length of the protective material 30 in the left-right direction X may be determined based on the gap when it is wound around the capacitor element 11.

[0024] Furthermore, as shown in Figure 5, the protective material 30 may also be provided on the lead tab 14 (lead tab 15) side of the connection portion 140-150. That is, the protective material 30 is provided on the separator 16 facing the connection surface 14a1 (connection surface 15a1) of the electrode foil (anode foil 14a, cathode foil 15a) to which the lead tabs 14-15 are connected. In this way, the protective material 30 is provided on the opposing surface 16c of the separator 16 facing the connection surface 14a1 (connection surface 15a1), which is one side to which the lead tabs 14-15 of the electrode foil (anode foil 14a, cathode foil 15a) are overlapped. Also, as shown in Figure 6, the protective material 30 may be provided on both the lead tab 14 (lead tab 15) side of the connection portion 140-150 and the anode foil 14a (cathode foil 15a) side of the connection portion 140-150. In other words, the protective material 30 may have a first protective material 30A and a second protective material 30B. The first protective material 30A may be provided on the opposing surface 16Ac of the separator 16A on the connection surface 14a1 (connection surface 15a1) side of the electrode foil (anode foil 14a, cathode foil 15a), and the second protective material 30B may be provided on both the opposing surface 16Bc of the separator 16B on the non-connection surface 14a2 (non-connection surface 15a2) side of the electrode foil (anode foil 14a, cathode foil 15a).

[0025] The protective material 30 can be attached to the separator 16 in the following manner, for example. First, a predetermined amount of the protective material 30 is fed from the upper side Z1 to the lower side Z2 of the separator 16. For example, it is fed until the end 30a of the protective material 30 reaches the end face 16b of the lower side Z2 of the separator 16. Then, the protective material 30 is folded back at the end face 16a of the upper side Z1 of the separator 16 to the opposite side (back side) from which it was fed. The folded protective material 30 is then attached to the back side of the separator 16. For example, it is attached so that the end 30b of the protective material 30 aligns with the end face 16b of the lower side Z2 of the separator 16. The adhesive may be applied to the separator 16 side or to the protective material 30 side beforehand.

[0026] (Configuration of electrolytic capacitor 1) As shown in Figure 3, the electrolytic capacitor 1 has a capacitor element 11 formed by overlapping and winding electrode foils (anode foil 14a, cathode foil 15a), to which lead tabs 14 and 15 for drawing out electrodes are connected, via a separator 16. The capacitor element 11 has a protective material 30 (first protective material 30A or second protective material 30B) provided on the opposing surface 16c of the separator 16 that faces the connection surface 14a1 (connection surface 15a1) or non-connection surface 14a2 (non-connection surface 15a2) of the electrode foils (anode foil 14a, cathode foil 15a), so as to overlap in the overlapping direction Y with the connection portions 140 and 150 to which the lead tabs 14 and 15 are overlapped with the connection surface 14a1 (connection surface 15a1) or non-connection surface 14a2 (non-connection surface 15a2) of the electrode foils (anode foil 14a, cathode foil 15a). The protective material 30 covers at least a portion of the end face 16a of the separator 16 on the side opposite to the side from which the lead tabs 14 and 15 are pulled out.

[0027] According to the above configuration, the connection points 140 and 150 between the lead tabs 14 and 15 and the electrode foils (anode foil 14a, cathode foil 15a), and the end face 16a of the separator 16 are covered with the protective material 30. This reinforces the stressed areas of the lead tabs 14 and 15 with the protective material 30, thereby suppressing deterioration of the separator 16. Furthermore, the separator 16 in the gap of the capacitor element 11 is reinforced with the protective material 30, thereby suppressing deterioration of the separator 16 due to gas bubbling that occurs in this gap.

[0028] The protective material 30 is folded back at the end face 16a of the separator 16 on the side from which the lead tabs 14 and 15 are pulled out, and extends to the back side of the opposing surface 16c of the separator 16. This ensures that the protective material 30 reliably covers the end face 16a of the separator 16 on the side from which the lead tabs 14 and 15 are pulled out.

[0029] The protective material 30 extends from the back side of the opposing surface 16c of the separator 16 to the end on which the lead tabs 14 and 15 are pulled out. This allows the protective material 30 to cover the separator 16 that contacts the connection parts 140 and 150 on both sides, and further reinforces the protective material 30.

[0030] As shown in Figure 6, in addition to the first protective material 30A provided on the opposing surface 16c of the separator 16 facing the connection surface 14a1 (connection surface 15a1) of the electrode foils (anode foil 14a, cathode foil 15a), a second protective material 30B is provided on the opposing surface 16c of the separator 16 facing the non-connection surface 14a2 (non-connection surface 15a2) of the electrode foils (anode foil 14a, cathode foil 15a) so as to overlap with the connection portion 140 and 150 in the overlapping direction Y. By providing the protective material 30 on both sides of the electrode foils 14a (15a), the deterioration of the separator 16 can be further suppressed.

[0031] Although embodiments of the present invention have been described above, these are merely illustrative examples and do not particularly limit the present invention. Specific configurations and other aspects can be modified as appropriate. Furthermore, the actions and effects described in the embodiments of the invention are merely a list of the most preferred actions and effects resulting from the present invention, and the actions and effects according to the present invention are not limited to those described in the embodiments.

[0032] (Examples) Next, electrolytic capacitors for comparative examples (Comparative Examples 1-3) and examples (Examples 1-3) were fabricated, and each electrolytic capacitor was evaluated. The electrolytic capacitors used in the comparative examples and examples below have a rated voltage of 400V, a rated capacitance of 180μF, and a product size of φ18 × 46L (mm). In the comparative examples and examples, protective material was provided only on the anode side. Also, the length of the lead tabs on the anode side in the left-right direction X (see Figure 3) was 2.2 mm for all of them. Furthermore, 40 μm thick kraft paper was used as the protective material and was attached to the separator (electrolytic paper) with an acrylic adhesive.

[0033] Comparative Examples 1-3 used separators in which the protective material did not cover the end face. The lengths of the protective material in the vertical Z direction (see Figure 3) for Comparative Examples 1-3 were 24 mm, 34 mm, and 40 mm, respectively. The length of the separators in the vertical Z direction for Comparative Examples 1-3 was 40 mm for all of them. The length of the protective material in the horizontal X direction (see Figure 3) was 10.8 mm for all of them. The protective material was provided only on the separator on the electrode foil side of the connection.

[0034] Furthermore, in Examples 1 to 3, the protective material was folded back to cover both sides of the separator up to the lead tab end. Therefore, the vertical Z length of the separators in Examples 1 to 3 is approximately 80 mm in all cases. Also, the horizontal X length of the protective material (see Figure 3) is 10.8 mm in all cases. In Example 1, the protective material was provided only on the separator facing the non-connected side of the electrode foil where the lead tabs are not connected. Example 1 has the same configuration as the example shown in Figure 4. Furthermore, in Example 2, the protective material was provided only on the separator facing the connected side of the electrode foil where the lead tabs are connected. Example 2 has the same configuration as the example shown in Figure 5. In Example 3, the protective material was provided on both the separator facing the non-connected side of the electrode foil and the separator facing the connected side of the electrode foil. Example 3 has the same configuration as the example shown in Figure 6.

[0035] (Evaluation method) For the electrolytic capacitors of the comparative examples (Comparative Examples 1-3) and examples (Examples 1-3) configured as described above, overvoltage aging was performed by applying a voltage exceeding the rated voltage, and then the internal short circuit rate was measured.

[0036] [Table 1]

[0037] According to Table 1, the internal short-circuit rate in Examples 1 to 3 was lower than in Comparative Examples 1 to 3. Specifically, in Example 1, where the protective material covering the end face of the separator was placed on the non-connecting side of the electrode foil, as shown in Figure 4, the internal short-circuit rate was 0.06%. In Example 2, where the protective material covering the end face of the separator was placed on the connecting side of the electrode foil, as shown in Figure 5, the internal short-circuit rate was 0.02%. Furthermore, in Example 3, where the protective material covering the end face of the separator was placed on both sides of the electrode foil, as shown in Figure 6, no internal short-circuit occurred. These Examples 1 to 3 demonstrate the effectiveness of covering the end face of the separator with protective paper. [Explanation of Symbols]

[0038] 1: Electrolytic capacitor 11: Capacitor element 12: Outer case 13: Sealing body 14: Lead Tab 14a: Anode foil 14a1: Connection surface 14a2: Non-connected surface 14b: Lead wire 15: Lead Tab 15a: Cathode foil 15a1: Connection surface 15a2: Non-connected surface 15b: Lead wire 16: Separator 16a: End face 16b: End face 16c: Opposite surface 16d: Non-opposing surface 21: Element fixing tape 22: Sleeves 30: Protective material 30A: 1st protection material 30B:Second protective material 30a: End 30b: End 140: Connection part 141: Round bar section 142: Flat part 150: Connection part 151: Round bar section 152: Flat part X: Left / right direction Y: Overlap direction Z: Vertical direction Z1: Upper side Z2: Lower side

Claims

1. An electrolytic capacitor comprising a capacitor element formed by overlapping and winding electrode foils, each connected to lead tabs for drawing out electrodes, via a separator, The aforementioned capacitor element is The separator has a first protective material provided on the opposing surface of the separator that faces one or the other surface of the electrode foil, such that the lead tab overlaps in the overlapping direction with the connecting portion to which the lead tab is superimposed and connected to one side of the electrode foil, The first protective material covers at least a portion of the end face of the separator on the side opposite to the side from which the lead tab is pulled out. Electrolytic capacitor.

2. The electrolytic capacitor according to claim 1, wherein the first protective material is folded back at the end face of the separator on the side opposite to the side from which the lead tab is pulled out, and extends to the back side of the opposing surface of the separator.

3. The electrolytic capacitor according to claim 2, wherein the first protective material extends from the back side of the opposing surface of the separator to the end on which the lead tab is pulled out.

4. The electrolytic capacitor according to any one of claims 1 to 3, wherein the first protective material is provided on the surface of the separator facing one side of the electrode foil to which the lead tab is connected, An electrolytic capacitor in which a second protective material is provided on the opposite surface of the separator that faces the other surface of the electrode foil, such that it overlaps with the connection portion in an overlapping direction.

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