Method for producing an electrolytic capacitor

Abstract: In a method for producing an electrolytic capacitor, a pair of lead wires (13) extend from a case (12) through holes (16a) in an insulation board (16) and are bent to fit in grooves (16b) formed in the bottom surface of the insulation board (16). Portions (13b) of the pair of lead wires (13) projecting from the edge of the insulation board (16) are cut off after the completion of the bending operation. Prior to bending, intermediate portions (13a) of the lead wires (13) are flattened to improve the accuracy of the bending operation and the fit in the grooves (16b).

Description: The present invention relates to a method for producing an electrolytic capacitor for use in various electronic apparatuses. A conventional chip type aluminum electrolytic capacitor (approximately 3 to 10 mm in diameter) is structured as shown in FIG.11 (sectional view) and FIG.12 (perspective view). A capacitor element 1 of the conventional aluminum electrolytic capacitor comprises an anode foil which is made by electrochemically roughening the surface of a high-purity aluminum foil and then subjecting the aluminum foil to anodic oxidation so as to form an oxidized dielectric film, and a cathode foil which is made by roughening the surface of an aluminum foil. The capacitor element 1 has such a configuration that the anode foil and the cathode foil are wound with an electrolytic paper intervening between the two foils. After the capacitor element 1 is impregnated with electrolytic liquid, the capacitor element 1 is housed in a case 2 in the form of cylinder with an open bottom. A pair of lead wires 3 are connected to the anode foil and the cathode foil of the capacitor element 1. A sealing member 4 made of rubber is inserted in the open end of the case 2. By subjecting the case 2 to a drawing step, the open end of the case 2 is sealed by the sealing member 4. The capacitor body 5 of the conventional aluminum electrolytic capacitor is structured as described above. The pair of lead wires 3 connected to the anode foil and the cathode foil of the capacitor element 1 pass through the sealing member 4 made of rubber and extend externally from the outer end surface of the sealing member 4. The outer end surface, from which the pair of lead wires 3 of the capacitor body 5 extend, is provided with an insulation board 6. The insulation board 6 has through holes 6a through which the pair of lead wires 3 pass. Concave portions 6b connecting with the through holes 6a are formed on the bottom surface of the insulation board 6. The tip parts of the pair of lead wires 3 passing through the through holes 6a are bent so as to fit in the concave portions 6b. The insulation board 6 is mounted on the capacitor body 5 by using the steps shown at PART A to PART G in FIG.13. As shown at PART A in FIG.13, a pair of lead wires 3 of different lengths extend from the outer end surface of the capacitor body 5 so as to give identification of polarities. As shown at PART B in FIG.13, the pair of lead wires 3 having different lengths are first cut to have the same length. As shown at PART C and PART D in FIG.13, the pair of lead wires 3 are then inserted into the insulation board 6 so that the lead wires 3 pass through the through holes 6a of the insulation board 6. As shown at PART E in FIG.13, the tip parts of the pair of lead wires 3 are then pulled slightly outwards so as to hold the insertion condition of the pair of lead wires 3 in the insulation board 6. The pair of lead wires 3 are then cut to a predetermined length as shown at PART F in FIG.13. Finally, as shown at PART G in FIG.13, the pair of lead wires 3 cut to the predetermined length are bent into the concave portions 6b of the insulation board 6. By using the above-mentioned processes, the insulation board 6 is mounted on the capacitor body 5. In the conventional method for producing the chip type aluminum electrolytic capacitor as described above, the pair of lead wires 3 were inserted in the through holes 6a of the insulation board 6 and pass through the insulation board 6. The pair of lead wires 3 were then bent slightly outwards thereby to hold the inserted state of the pair of lead wires 3. In this position, the pair of lead wires 3 were cut to predetermined length. Therefore, in the conventional method, the cut lengths of the pair of lead wires 3 were apt to have various values. As a result, the lengths of the pair of lead wires 3 projecting radially outward from the brim face of the insulation board 6 had various values, after the pair of lead wires 3 were bent so as to fit the lead wires 3 in the concave portions 6b of the insulation board 6. According to the present invention, there is provided a method for producing an electrolytic capacitor, comprising the steps of: inserting a capacitor element into a cylindrical case through an opening of said cylindrical case; producing a capacitor body by sealing said opening with a sealing member so as to leave a pair of lead wires projecting through said sealing member; cutting so as to leave said pair of lead wires having predetermined lengths extending from said case; forming flat portions by pressing intermediate portions of said pair of cut lead wires; and using unflattened tip parts of said pair of lead wires to guide said lead wires through holes in an insulation board. A non-limiting embodiment of the present invention will now be described with reference to the accompanying drawings, in which:- FIG. 1 is a sectional side view of a chip type aluminum electrolytic capacitor capable of being manufactured using the present invention; FIG. 2 is a perspective view of the chip type aluminum electrolytic capacitor shown in FIG. 1; FIG. 3 is process chart showing steps for producing the aluminum electrolytic capacitor shown in FIG.1; FIG.4 is an enlarged front view showing an inserting step of the process of FIG.3; FIG.5A is a front view of pressing apparatus for pressing intermediate portions of lead wires of the aluminum electrolytic capacitor shown in FIG.1 to form flat sections of the lead wires; FIG.5B is a side sectional view of the pressing apparatus shown in FIG.5A; FIG.6 is a front view showing an initial state of the pressing apparatus shown in FIG.5A; FIG.7 is a plan view showing a pressing state of the pressing apparatus shown in FIG.5A; FIG.8 is an enlarged front view showing a cutting step of the process of FIG.3; FIG.9 is a side view showing a cutting apparatus used in the production process for the aluminum electrolytic capacitor shown in FIG.1; FIG.10 is a side view showing a cutting condition of the cutting apparatus of FIG.9; FIG.11 is the sectional view showing the conventional chip type aluminum electrolytic capacitor; FIG.12 is the perspective view showing the aluminum electrolytic capacitor shown in FIG.11; and FIG.13 is the process chart showing steps for producing the aluminum electrolytic capacitor shown in FIG.11. It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. FIGs. 1 and 2 show a chip type aluminum electrolytic capacitor suitable of being produced with help of the present invention. FIG.1 is a sectional view of the aluminum electrolytic capacitor of the embodiment, and FIG.2 is a perspective view of the aluminum electrolytic capacitor shown in FIG.1. In FIGs. 1 and 2, the aluminum electrolytic capacitor comprises a capacitor element 11 configured by cylindrically winding an aluminum anode foil, an aluminum cathode foil and an electrolytic paper. The anode foil and the cathode foil are convolutely wound so as to face each other through the electrolytic paper intervening between the anode foil and the cathode foil. The anode foil is made by electrochemically roughening the surface of a high-purity aluminum foil and then subjecting the aluminum foil to anodic oxidation to form an oxidized dielectric film. The cathode foil is made by roughening the surface of an aluminum foil. After impregnating the capacitor element 11 with electrolytic liquid, the capacitor element 11 is encapsulated in a case 12 made of aluminum. The case 12 is a cylinder with an open bottom. A pair of lead wires 13 are connected to the anode foil and the cathode foil of the capacitor element 11. A sealing member 14 made of elastic material such as natural rubber or synthetic rubber is inserted in the open end of the case 12. By subjecting the external circumference of the case 12 to a drawing step, the open end of the case 12 is sealed by the sealing member 14. The pair of lead wires 13 connected to the anode foil and the cathode foil of the capacitor element 11 pass through the sealing member 14 and extend externally from the outer end surface of the sealing member 14. An insulation board 16 is disposed tightly against the end surface of a capacitor body 15 from which the pair of lead wires 13 extend. The insulation board 16 has a rectangle shape and is made of resin having heat resistance, such as polyphenylene sulfide. The insulation board 16 has through holes 16a through which the pair of lead wires 13 pass. Flat grooves 16b connecting with the through holes 16a are formed on the bottom surface of the insulation board 6 so as to receive flattened parts of the lead wires 13. The portions of the pair of lead wires 13, which have passed through the through holes 16a, are bent outward so as to fit in the grooves 16b. FIG.3 is a process chart illustrating steps for mounting the insulation board 16 on the capacitor body 15 in the production process in accordance with the preferred embodiment of the present invention (steps A to E) and further steps to achieve a surface mountable capacitor. The pair of lead wires 13 extending through the outer end surface of the capacitor body 15 shown at PART A in FIG.3 and having different lengths are cut so as to have the same projecting lengths as shown at PART B in FIG.3. The intermediate portions of the pair of lead wires 13 are then pressed as shown at PART C in FIG.3, thereby forming flat portions 13a. The pair of lead wires 13 are then inserted and passed through the through holes 16a of the insulation board 16 as shown at PART D and PART E in FIG.3. FIG.4 is an enlarged front view showing the inserting step shown at PART D in FIG.3. As shown in FIG.4, the tip parts of the pair of lead wires 13 have round rod portions and are inserted into the through holes 16a of the insulation board 16. A core mold 17 is then inserted between the pair of lead wires 13 as shown at PART F in FIG.3 and the pair of lead wires 13 are pushed slightly outward, thereby to keep the insertion condition of the pair of lead wires 13 into the insulation board 16. The flat portions 13a of the lead wires 13 are then bent by a lead bending plate mold 18 so as to fit in the flat grooves 16b provided on the bottom surface of the insulation board 16 as shown at PART G in FIG.3. A lower cutter 19 makes contact with the bottom surface of the insulation board 16 as shown at PART H in FIG.3. In this condition, the projecting portions 13b of the pair of lead wires 13, which are shown at PART G in FIG.3 and project from the brim face of the insulation board 16, are cut with upper cutters 20a, 20b. The bent portions of the pair of lead wires 13 slightly stick out from the grooves 16b in the bottom surface of the insulation board 16 due to stress or burrs, which may be generated at the time of cutting shown at PART H in FIG.3. The bent portions of the pair of lead wires 13 are bent again by using a lead holding plate 21 as shown at PART I in FIG.3, so as to fit in the grooves 16b. The chip type aluminum electrolytic capacitor shown at PART J in FIG.3 is completed by the above-mentioned steps. In the process for mounting the insulation board 16 of the chip type aluminum electrolytic capacitor, shown as the embodiment of the present invention, the mechanism of the pressing apparatus used to form the flat portions 13a by pressing the intermediate portions of the pair of lead wires 13 shown at PART C in FIG.3 is shown together with the capacitor body 15 in FIGs. 5A, 5B, 6 and 7. FIG.5A is a front view of the pressing apparatus. FIG.5B is a side sectional view of the pressing apparatus shown in FIG.5A. FIG.6 is a front view showing the initial condition of a pressing process wherein the capacitor body 15 is set in the pressing apparatus. FIG.7 is a segmentary view showing the relationship between a pressing mold core 22 of the pressing apparatus and the capacitor body 15. As shown in FIGs. 5A and 6, in this pressing step, the pressing mold core 22 is inserted between the pair of lead wires 13 extending from the outer end surface of the capacitor body 15 to support the pair of lead wires 13. One end of the pressing mold core 22 is rotatably supported by a fulcrum pin 23. Therefore, the tip of the pressing mold core 22 is rotatable around the fulcrum pin 23. As shown in FIGs. 5A and 6, a pair of chucks 24a, 24b are provided in the pressing apparatus and the chucks 24a, 24b are rotatably supported by the fulcrum pin 23 at the substantial center of the chucks 24a, 24b. At the upper ends of the chucks 24a, 24b, pressing members 25a, 25b are provided, which are used to form the flat portions 13a by pressing the intermediate portions of the pair of lead wires 13. The other ends (lower ends) of the chucks 24a, 24b are connected to a connecting rod 27 via chuck open/close levers 26a, 26b. The lower ends of the chucks 24a, 24b are rotatably connected to first ends of the chuck open/close levers 26a, 26b by support pins 28a, 28b. In addition, the other ends of the chuck open/close levers 26a, 26b and the upper end of the connecting rod 27 are rotatably connected by a support pin 29. When forming the flat portions 13a by pressing the intermediate portions of the pair of lead wires 13 by using the above-mentioned pressing apparatus, the capacitor body 15 is placed at a predetermined position by contacting the capacitor body 15 against a positioning pin 40. As shown in FIG.6, the tip of the pressing mold core 22 is then inserted between the lead wires 13 of the capacitor body 15. By driving the connecting rod 27 downward in this insertion condition, the pair of pressing members 25a, 25b provided on the chucks 24a, 24b are driven via the chuck open/close levers 26a, 26b, and moved in the direction indicated by arrow A in FIG.6. By this pressing operation, the intermediate portions of the pair of lead wires 13 are pressed, thereby forming the flat portions 13a. In this pressing step, when the capacitor body 15 is placed at the predetermined position as shown at PART A in FIG.7, the positioning is correct. However, in the case that the center axis of the capacitor body 15 is not aligned with the center axis of the pressing mold core 22 as shown at PART B in FIG.7, it becomes very difficult to insert the tip of the pressing mold core 22 between the pair of lead wires 13. In order to solve this problem, the lower end of the pressing mold core 22 is rotatably supported by the fulcrum pin 23 in the embodiment of the present invention so that the tip of the pressing mold core 22 can move loosely to some extent. According to the above-mentioned configuration of the pressing apparatus, even when the center axis of the capacitor body 15 is out of alignment with the center axis of the pressing mold core 22 as shown at PART B in FIG.7, the tip of the pressing mold core 22 can be inserted easily between the pair of lead wires 13 without applying any excessive load to each of the pair of lead wires 13. Furthermore, the flat portions 13a having a uniform thickness can be formed in the intermediate portions of the pair of lead wires 13, by means of the pressing members 25a, 25b mounted on the upper ends of the chucks 24a, 24b. In the embodiment of the present invention, by the pressing step shown at PART C in FIG.3 in the mounting process of the insulation board 16 shown in FIG.3 as described above, the intermediate portions of the pair of lead wires 13 are pressed so as to form the flat portions 13a, and tip parts of the pair of lead wires 13 are still kept as round rod portions. Therefore, when inserting the pair of lead wires 13 into the insulation board 16, the tip parts of the pair of lead wires 13 hardly bend and hence can be inserted easily into the through holes 16a of the insulation board 16. Preferably, the pair of lead wires 13 are bent by the lead-bending plate mold 18 so as to fit in the grooves 16b provided on the bottom surface of the insulation board 16 as shown at PART G in FIG.3. FIG.8 is an enlarged front view showing the cutting step shown at PART H in FIG.3. As shown in FIG.8, the lower cutter 19 makes contact with the bottom surface of the insulation board 16 as shown at PART H in FIG.3. In this state, the portions 13b of the pair of lead wires 13 projecting from the brim face of the insulation board 16 are cut or scissored off by the pull-down operation of the upper cutters 20a, 20b. FIGs.9 and 10 are diagrammatic side views showing the mechanism of the cutting apparatus used at PART H in FIG.3. FIG.9 is a diagrammatic view showing a condition when the capacitor body 15 is placed in the cutting apparatus. FIG.10 is a diagrammatic view showing a cutting condition of the cutting apparatus. As shown in FIGs. 9 and 10, the lower cutter 19 is moved vertically by the rotation of a lower cutter-up/down cam 32a. The upper cutter 20a is moved vertically by the rotation of the upper cutter-up/down cam 32b. In addition, the upper cutter 20a is moved vertically via an upper cutter rocking lever 31. The upper cutter rocking lever 31 is actuated to be rotated on a circle segment in a counterclockwise direction (FIG.9) by an actuating means, such as a spring. The upper cutting rocking lever 31 engages an upper cutter-rocking cam 30, which is linked with the upper cutter-up/down cam 32b. When the upper cutter 20a is moved upwardly, the upper cutter-rocking cam 30 is slid in a leftward direction by a predetermined distance as shown in FIG.9. When the upper cutter 20a is moved downwardly, when the lead wires 13 are cut, the upper cutter-rocking cam 30 is slid in a rightward direction by a predetermined distance as shown in FIG.10. Therefore, in the above-mentioned cutting apparatus, when the upper cutter 20a moves upward, the upper cutter 20a evades the projecting portions 13b of the lead wires 13. In the cutting step shown in FIG.9, when the capacitor body 15 is placed at the predetermined position by a positioning pin 50, the lower cutter 19 is pressed against the lower surface of the insulation board 16. The pull-down operation of the upper cutter 20a is then performed as shown in FIG.10, and the projecting portions 13b of the lead wires 13 are cut off. By conducting the cutting step by using the above-mentioned cutting apparatus, the lengths of the portions of the lead wires 13 projecting from the brim face of the insulation board 16 can be made uniform. This enables prevention of the variations in the projecting lengths of the pair of lead wires 13, which are observed in the conventional production method. Preferably, the lead holding plate 21 is used as shown at PART I in FIG.3. In the cutting process shown at PART H in FIG.3, the bent portions of the pair of lead wires 13 slightly stick out from inside the grooves 16b in the bottom surface of the insulation board 16. They are bent again so that the bent portions can fit in the grooves 16b. Since the bent portions of the lead wires 13 can fit uniformly in the grooves 16b of the insulation board 16 in this way, the chip type aluminum electrolytic capacitor produced by the method of the present invention can be mounted uniformly and properly when the aluminum electrolytic capacitor is mounted on a PC board by soldering. Moreover, since the bent portions of the lead wires 13 of the aluminum electrolytic capacitor produced by the above-mentioned production method are placed securely in the grooves 16b, it is possible to prevent the capacitor from inclined fixing during soldering.

Claims: A method for producing an electrolytic capacitor, comprising the steps of: inserting a capacitor element (11) into a cylindrical case (12) through an opening of said cylindrical case; producing a capacitor body (15) by sealing said opening with a sealing member (14) so as to leave a pair of lead wires (13) projecting through said sealing member (14); cutting so as to leave said pair of lead wires (13) having predetermined lengths extending from said case (12); forming flat portions (13a) by pressing intermediate portions of said pair of cut lead wires (13); and using unflattened tip parts of said pair of lead wires (13) to guide said lead wires (13) through holes (16a) in an insulation board (16). A method in accordance with claim 1, wherein said flat portions (13a) are formed by pressing said intermediate portions of said pair of lead wires (13) by using a pressing apparatus comprising a pressing mold core (22) which is inserted between said pair of lead wires (13) of said capacitor body (15) to support said pair of lead wires (13) and pressing members (25a, 25b) which press said pair of lead wires (13) against said pressing mold core (22) to form said flat portions (13a). A method in accordance with claim 1 or 2, wherein: said insulation board (16) has grooves (16b) which connect with said holes (16a); and during said step of using said unflattened tip parts of said pair of lead wires (13) to guide said lead wires (13) through said holes (16a) in said insulation board (16), said insulation board (16) is brought into abutment against said capacitor body (15), after which said method continues with the steps of: bending said flat portions (13a) of said pair of lead wires (13) so as to fit in said grooves (16b); and cutting off projecting portions (13b) of said pair of lead wires (13), at the parts projecting past the edge of said insulation board (16). A method in accordance with claim 3, further comprising the step of: after said cutting-off step, bending again the bent portions of said pair of lead wires (13) which slightly stick out from said grooves (16b) of said insulation board (16) due to said cutting-off step so that said bent portions better fit in said grooves (16b). A method in accordance with any one of claims 1 to 4, wherein said capacitor is an aluminum electrolytic capacitor.

Inventors: FUKUDA MORIHIRO, KURASAKI YASUSHI, YAMASHITA ICHIROU, FUKUDA, MORIHIRO, KURASAKI, YASUSHI, YAMASHITA, ICHIROU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1995
Main classification: H01G9
IPC codes: H01G9