JP6096091B2 - Capacitor element - Google Patents

Description

  The present invention relates to a capacitor element that is a raw material for producing a metallized film capacitor, and relates to a capacitor element whose flatness should be 0.6 or more in order to obtain a volume efficiency of a certain level or more. The present invention relates to a technique for improving a pressure resistance characteristic and suppressing an operation sound (squeal) when an alternating current is applied.

  Capacitor elements, which are materials for metallized film capacitors for industrial machinery and vehicles, are generally manufactured through the following steps. That is, a cylindrical metallized film winding body is formed by winding a metallized film composed of a dielectric film and a metal vapor deposition electrode. Next, an exterior film is further wound around the outer periphery of the metallized film wound body and wound and fixed by heat welding (heat sealing) to obtain a composite film wound body. Next, this composite film wound body is pressed in the diameter direction to form an oblong flat columnar body. Next, metal electrodes are formed by thermal spraying of metal fine particles at both axial ends of the flat columnar body to obtain a capacitor element. Here, the exterior film is wound around the metallized film wound body for the purpose of insulating protection of the capacitor element and preventing moisture from entering. The reason why the exterior film is wound and fixed by heat welding is to prevent winding looseness.

  Conventionally, with regard to the winding and fixing of the exterior film, it has been common to perform heat welding over the entire outer peripheral surface of the exterior film. The reason is as follows. Metal particles are sprayed on both ends of the flat columnar body in the axial direction to form metal electrodes. At this time, the sprayed metal particles are between the film layers (between the dielectric film and the exterior film, between the wound films of the exterior film). Intrusion may cause troubles such as insulation deterioration and short circuit failure. In order to avoid such inconvenience, conventionally, in order to make the overlapping portions of the films strongly adhere to each other so that no gap (air gap) is generated between the film layers, the exterior film is fixed by winding the exterior film as described above. It was thermal welding over the entire outer peripheral surface of the film. When heat welding over the entire periphery, the overlapping portions of the film are strongly adhered by the heat shrink of the exterior film, the generation of gaps between each film layer is prevented, and the entry of metal fine particles between each film layer is reliably prevented, Therefore, troubles such as capacitor insulation deterioration and short circuit failure can be avoided.

JP 2007-81007 A Japanese Patent Laid-Open No. 7-161573 JP 2003-59753 A JP 2007-220720 A

  Recently, there is a strong demand for increasing the flatness of capacitor elements from the viewpoint of space saving. The level of flatness affects volumetric efficiency. Increasing volume efficiency by reducing dead space as much as possible is important for increasing the capacity and reducing the thickness and thickness of capacitors (see, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-81007)).

  However, when winding fixing by heat welding of the outer film is performed on the entire outer peripheral surface, when the composite film winding body composed of the metallized film winding body and the outer film is flattened, the overlapping portions of the films are overlapped. The relative slip of the capacitor becomes difficult to perform smoothly, and the oblate shape of the capacitor element is adversely affected. When producing a capacitor element with an aspect ratio of less than 0.6, it is relatively easy to secure a good oblate shape, but the production of a capacitor element with an oblateness of 0.6 or more, which has recently been strongly demanded. In this case, it is very difficult to secure good oblate shape.

  That is, when winding fixing by heat welding of the exterior film is performed on the entire outer peripheral surface, excessive shrinkage of the exterior film is caused when the capacitor element is thermally contracted by heating due to heat welding. Excessive heat shrinkage constrains the vicinity of the exterior of the dielectric film, so that the rectangular shape of the capacitor element tends to deteriorate. When the deterioration occurs, problems such as voids, wrinkles and distortion occur inside the capacitor element.

  This point will be described with reference to FIG. FIG. 9 is a front view of the flat columnar body 9 in the capacitor element. When the capacitor film is flattened by pressing or after the flattening, if the exterior film 5 causes excessive thermal shrinkage, the intermediate portion of the metallized film wound inside the exterior film 5 and making up most of the capacitor element In the portion 6, small voids 11 are generated, wrinkles and strains 12 are generated in each winding layer of the metallized film winding body 6, or thin flat winding by a flattened leading film Refraction / bending 13 occurs in the core portion 2a, obstructing oblateness. If the oblateness is obstructed in this way, the withstand voltage characteristic of the capacitor is lowered (the capacitance changes when a voltage is applied). In addition, there is a problem that when the AC voltage is applied (particularly at high frequency), the capacitor itself vibrates due to the generation of ripple current (pulsating flow), and the operation sound (beat) called “squeal” increases. These problems become increasingly severe as the flatness of the capacitor element increases in order to improve volumetric efficiency. This is because as the flatness ratio increases, resistance to relative slip at the overlapping portion of the film increases, and oblateness tends to occur.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 7-161573) describes a metallized film capacitor using an exterior film having a linear expansion coefficient and a thermal contraction rate larger than those of the metallized film. According to this, since the linear expansion coefficient of an exterior film is larger than a metallized film at the time of temperature rising of a heat aging process, an exterior film clamps a metallized film and suppresses winding looseness of the outer peripheral part of a metallized film. In the process of returning the temperature to room temperature, the outer film has a larger thermal shrinkage than the metallized film, so that the outer air gap is suppressed and the decrease in capacitance is reduced (see paragraphs [0009] and [0010]). ).

  However, in Patent Document 2, although there is a reference to the linear expansion coefficient and the thermal contraction rate, what is the relationship between the flattening rate and the area ratio of the heat-welded area of the exterior film to the total outer peripheral area of the composite film wound body? Also not mentioned.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2003-59753) describes a metallized film capacitor in which when a film wound body is pressure-molded, a winding weld portion having irregularities is formed on the surface of the winding end portion. ing. According to this, the adhesive force between the films in the recesses is strengthened, and variations in the thermal adhesive force at the winding end portion can be absorbed (see paragraphs [0006] and [0007]).

  However, nothing is mentioned about the interrelationship between the heat-welded area area ratio and the flatness ratio in the above-described exterior film.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2007-81007), a / b = 3 or more (flatness 0.67 or less) and a = 60 mm or more, where the major axis of the oval capacitor element is a and the minor axis is b. In addition, a metallized film capacitor is described in which a polypropylene film having a thickness of 3 to 10 times the dielectric film thickness is wound as a winding core for 5 to 10 turns, and the dimension from the winding core to the outer peripheral surface of the capacitor element is 14 mm or less. Yes. Secondary, it is disclosed that at least a part of the end of the core is welded by heat sealing, and a plurality of recesses are provided in the heat sealing portion. According to this, even if the flatness of the capacitor element is increased, the core strength is set to an optimum value, so that the volume efficiency is improved by reducing the size and thickness with a large capacity, and the reliability is excellent. (See paragraphs [0013] and [0014]).

  However, the above is not about the exterior film in the capacitor element, but an improvement on the core in the center, and there is nothing to mention about the interrelationship between the area ratio and the flatness of the heat-welded area in the exterior film described above. Not done.

  In Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-220720 (Patent No. 4733533)), a metallized film is lap-wrapped, heat-sealed as a winding stop, and a capacitor element is pressed to be curved and flat. In the flattened metallized film capacitor, a configuration is described in which the position of the film winding stop portion is set to a curved portion avoiding the press surface. According to this, the winding end portion of the film with uneven marks by the heat seal head is positioned at the curved portion, and the element can be flattened in a state where the winding end portion of the film is removed from the press surface. Therefore, the uneven part of the heat seal head does not spill over to the inner laminate, so that the laminate can be prevented from being distorted or wrinkled, and an increase in roaring sound and a decrease in pressure resistance can be avoided (paragraph [0005] [0006]).

  However, this is only related to the suppression of distortion and wrinkle generation only within the thickness of the exterior film, and distortion and wrinkle generation in the intermediate metallized film winding body that makes up most of the capacitor element. It is not a problem to suppress this.

  The present invention was created in view of such circumstances, and for capacitor elements having a flatness ratio of 0.6 or more from the viewpoint of increasing volume efficiency, obstruction of oblateness, deterioration of withstand voltage characteristics, ripple current In order to cope with the problem of the operation noise of the metallized film, so as not to generate voids, wrinkles, and distortion in the portion of the metallized film wound body that is covered with the exterior film and exists inside the capacitor element. The purpose is to do.

  The present invention solves the above problems by taking the following measures.

  In the capacitor element according to the present invention, an outer film is further wound around the outer peripheral portion of the metallized film wound body, and the composite film wound body is configured by winding and fixing by thermal welding. In the capacitor element in which a flat columnar body is formed, metal electrodes are formed on both ends in the axial direction of the flat columnar body, and the flatness ratio is 0.6 or more, the following configuration is further provided. That is, the winding fixing of the exterior film in the composite film wound body is performed by heat welding between self-overlapping portions and dispersedly arranged in the circumferential direction, and the composite film An area ratio occupied by the total area of the plurality of heat-welded regions in the entire outer periphery area of the wound body is set to 30% or less.

  In the capacitor element of the present invention, the winding fixing of the exterior film in the composite film winding body is heat welding between the overlapping portions of the self, but as a major premise that the flatness is 0.6 or more It is prescribed. In addition, the winding of the outer film is fixed by thermal welding at a plurality of locations dispersed in the circumferential direction, and the total area of the thermal welding regions at the plurality of locations is the total outer circumference of the composite film winding body. The area ratio is set to 30% or less.

  That is, since the heat-welded portion of the exterior film is divided into a plurality of portions and the total area of the heat-welded region is 30% or less, the relative portions of the overlapping portions of the film when the composite film roll is flattened are compared. Sliding is smooth over the entire area of the metallized film roll.

  The heat-welded location is the starting point for resistance when the exterior film is thermally contracted. If the resistance action starting point for this heat shrinkage is only one heat welding place in the circumferential direction, the resistance action against heat shrinkage is concentrated in the vicinity of the one heat welding place, and the resistance coefficient (unit circumference length) The frictional force) is excessive and uneven in the circumferential direction. Also, the resistance coefficient becomes excessive when the total area ratio of the plurality of heat welding regions exceeds 30%. As a result, when the composite film roll is flattened, smooth relative sliding between the overlapping portions of the films is prevented.

  On the other hand, when the heat welding locations are dispersedly arranged at a plurality of locations as in the present invention, and the total area ratio of the plurality of heat welding regions is set to 30% or less, the flatness ratio is 0.6 or more. In the capacitor element to be used, the relative slip between the overlapping portions of the film when the composite film roll is flattened becomes smooth, and the oblong shape is good. As a result, in all regions of the metallized film wound body that is covered with the exterior film and exists in a wound state inside the capacitor element, generation of soot, wrinkles, and distortion is suppressed.

  The area ratio of the total area of the heat-welded area on the exterior film is set to 30% or less, based on the experimental results. When the area ratio exceeds 30%, the generation of soot, wrinkles and distortion Against this backdrop, the deterioration of the breakdown voltage characteristics and the decrease in the capacitance were recognized.

  The flattening is expressed as f = (ab) / a = 1- (b / a) where f is the flatness ratio, a is the dimension in the major axis direction, and b is the dimension in the minor axis direction. (Refer to FIG. 1 for a and b).

  According to the present invention, from the viewpoint of increasing the volumetric efficiency, for the capacitor element that should have an aspect ratio of 0.6 or more, the heat-welded portions are dispersedly arranged at a plurality of locations, and the total area ratio of the plurality of heat-welded regions is 30%. Since it set below, the relative slip of the overlapping part of the film at the time of flattening a composite film winding body will become smooth in the whole area | region of a metallized film winding body. As a result, the oblong shape of the capacitor element has been improved, and it is possible to reliably prevent the occurrence of voids, wrinkles and distortion at the portion of the metallized film wound body inside the capacitor element, and at the same time improve the withstand voltage characteristics. Therefore, it is possible to prevent a decrease in capacitance, and further, it is possible to prevent generation of an operation sound at a ripple current.

The front view (a) of the flat columnar body in the capacitor | condenser element of the Example of this invention and the front view (b) of a thin flat winding core part The perspective view of the capacitor | condenser element of the Example of this invention The front view which shows the manufacturing process of the capacitor | condenser element of the Example of this invention. The front view which shows the manufacturing process of the capacitor | condenser element of the Example of this invention (continuation of the process of FIG. 3) The chart showing the experimental result of pass / fail determination of oblateness for the capacitor element of the embodiment of the present invention The chart showing the experimental result of pass / fail judgment of the withstand voltage characteristic for the capacitor element of the embodiment of the present invention Schematic front view showing variations in the number and position of heat-welded locations for the capacitor element of the embodiment of the present invention Chart showing results of evaluating capacitor elements illustrated in Patent Document 3 Front view of a flat columnar body in a capacitor element for pointing out the soot, wrinkles / strain, and bending of a thin flat winding core, which are problems in the prior art

  The capacitor element of the present invention having the above configuration has several preferred modes as follows.

  About the said several heat welding location, what is equally arrange | positioned at equal intervals in the circumferential direction of the said flat columnar body is preferable. If the heat-welded locations that are the starting point of the resistance action when the exterior film is thermally shrunk are evenly arranged in the circumferential direction, the resistance to heat shrinkage is also equalized in each section (region between the starting point and the starting point) The As a result, the relative slip between the overlapping portions of the film when flattening the composite film roll is smoothed over the entire region of the metallized film roll. Therefore, the suppression effect with respect to the voids, wrinkles and strains in the entire region of the metallized film winding body is sufficient.

  In addition, the plurality of heat welding locations are preferably arranged at positions that are axisymmetric with respect to the central axis of the flat columnar body. By arranging a plurality of heat welding locations in an axisymmetric manner, it becomes possible to make the oblate shape more accurate than in the case of an asymmetrical arrangement (including the arrangement of only one location). Since the flat columnar body itself has an axisymmetric shape, it is reasonable to make the plurality of heat welding locations also axisymmetric.

  In addition, it is a preferable aspect that the plurality of axisymmetric heat welding locations are two locations at the center in the major axis direction in the flat surface portion along the major axis direction of the flat columnar body.

  In addition, it is a preferable aspect that the plurality of axisymmetric heat-welded portions are two central positions in the arc direction in the arcuate curved surface portions at both ends in the major axis direction of the flat columnar body.

  As for the plurality of axisymmetric heat welding locations, in the flat surface portion along the major axis direction of the flat columnar body, two locations at the central position in the major axis direction and the circles at both ends in the major axis direction of the flat columnar body. In the arc-shaped curved surface portion, it is one preferable mode to have a total of four places including two places at the center position in the arc direction.

  Moreover, about the said flat columnar body, what has the thin flat flat core part extended in the said major axis direction through the center axis | shaft in the internal center of the said metallized film winding body is preferable. As described in the section of [Problems to be Solved by the Invention], the thin flat coiled core portion is bent and bent, which is one of the causes of the deterioration of the oblate shape. It is very significant to apply the present invention to such a composite film wound body having a thin-walled core portion that is flattened.

  Embodiments of a capacitor element according to the present invention will be described below with reference to the drawings. 1A is a front view of a flat columnar body 9, FIG. 1B is a front view of a thin flat core portion 2a, FIG. 2 is a perspective view of a capacitor element A, FIG. 3A, FIG. FIGS. 4C, 4A, 4B, and 4C are front views showing the manufacturing process of the capacitor element A. FIG. In these drawings, 1 is a pre-winding film, 2 is a winding core, 2a is a thin flat winding core portion, 3 is a metallized film, 4 is a metallized film wound body, 5 is an exterior film, and 6 is a composite film winding. Rotating body, 7 is a heat welding location, 8 is a seal heater, 9 is a flat columnar body, 9a is a flat surface portion along the major axis direction of the flat columnar body 9, and 9b is an arcuate curved surface portion on both sides in the width direction of the flat columnar body 9. 10 is a metal electrode, and A is a capacitor element.

  The thin flat core 2a shown in FIGS. 1 and 2 was originally the cylindrical core 2 shown in FIG. 3 (a), but in the process of FIGS. 4 (a), (b) and (c). It is flattened, and as shown in FIG. 1 (b), it is a thin flat body of plastic film overwrapping. The metallized film 3 shown in FIG. 3 (b) is obtained by forming a metal vapor deposition electrode on one or both sides of a dielectric film, and this is wound multiple times around the outer periphery of the core 2 to form a metallized film roll 4 Is configured. The metallized film winding body 4 shown in FIG. 1 and FIG. 2 is formed into an elongated oblong flat body, but originally has a cylindrical core 2 as shown in FIGS. 3 (b) and 3 (c). The metallized film 3 is wound around the outer periphery of the film and is flattened in the process of FIGS. 4 (a), 4 (b), and 4 (c). The exterior film 5 is wound around the outer periphery of the metallized film wound body 4 in a multiple manner. In the state of FIGS. A composite film winding body 6 is composed of the winding core 2 (thin flattened winding core portion 2a), the metallized film winding body 4 on the outer periphery thereof, and the exterior film 5 on the outer periphery thereof. In the composite film wound body 6, a plurality of locations at the end of winding of the exterior film 5 are thermally welded by the seal heater 8 in the process of FIG. In this thermal welding, the exterior film 5 is wound and fixed between overlapping portions of itself. In FIG. 1 and FIG. 2, there are two heat welding locations 7, which are dispersedly arranged in the circumferential direction of the elongated oval composite film winding body 6, that is, the flat columnar body 9. Specifically, the two heat welding locations 7 and 7 are equally arranged at equal intervals in the circumferential direction of the flat columnar body 9. Alternatively, the two heat welding locations 7 and 7 are arranged at positions symmetrical with respect to the center axis of the flat columnar body 9. The oblong oblong flat columnar body 9 is composed of flat surface portions 9a, 9a along the long-diameter direction facing in the vertical direction and two arcuate curved surface portions 9b, 9b on both sides in the width direction. The places 7 and 7 are two places of the center position of the long diameter direction in the flat surface parts 9a and 9a along the long diameter direction which oppose the flat columnar body 9 in the up-down direction. In other words, in the present embodiment, the two heat welding locations 7 and 7 are distributed in the circumferential direction, are evenly spaced in the circumferential direction, and are positioned symmetrically with respect to the central axis of the flat columnar body 9. It arrange | positions and is arrange | positioned in the center position of the up-and-down flat surface parts 9a and 9a of the flat columnar body 9. FIG.

  The elongated oblong flat columnar body 9 is flattened by pressing the composite film wound body 6 in the process of FIGS. 4 (a), 4 (b) and 4 (c). Prior to this flattening process, as shown in FIG. 3C, heat sealing is performed in advance at two locations 7 and 7 in the circumferential direction by the seal heater 8. The flat columnar body 9 is flattened under a condition that the flatness ratio is 0.6 or more, and in order to conform to the condition, the heat welded region of the two heat welded portions 7 and 7 The area ratio which the total area occupies in the outer peripheral total area of the composite film winding body 6 is set to 30% or less. Therefore, the flat columnar body 9 that has been flattened into an elongated oval shape through the processes of FIGS. 4A, 4B, and 4C is formed inside the metallized film wound body 4 as the flattening progresses. Relative sliding of the film overlap portion in the film becomes smooth, and defects such as soot, wrinkles, distortion and refraction / bending of the thin flat winding core portion 2a occur in the metallized film wound body 4 inside. I do not.

  As shown in FIG. 2, the oblong oblong flat columnar body 9 obtained under the highly favorable oblate shape as described above has metal electrodes 10 formed at both ends in the axial direction. Capacitor element A having excellent oblate shape, high withstand voltage performance, no change in capacitance upon application of voltage, and suppression of operation noise at the time of ripple current is obtained.

  Next, the manufacturing process will be described with reference to FIGS. 3 (a) to 3 (c) and FIGS. 4 (a) to 4 (c) show a series of manufacturing steps.

  As shown to Fig.3 (a), the thin-walled cylindrical core 2 is produced by winding the film 1 for front windings, such as a polyethylene terephthalate film with a thickness of 6-25 micrometers, in multiple times. Next, as shown in FIG. 3 (b), the metallized film 3 having a thickness of 1 to 10 [mu] m is wound around the outer periphery of the core 2 in multiple layers, thereby winding the thick cylindrical metallized film. The body 4 is produced. The metallized film 3 is obtained by forming a metal vapor deposition electrode on at least one surface of a dielectric film such as a polypropylene film. The metallized film winding body 4 forms the main part of the capacitor element A.

  Next, as shown in FIG.3 (c), by winding the exterior films 5, such as a polypropylene film which is a film for back rolls of 10-25 micrometers, around the metallized film wound body 4 in multiple times. Then, a thick cylindrical composite film winding body 6 is produced. The exterior film 5 has an insulation protection function for the capacitor element A. The composite film winding body 6 is a composite body of the winding core 2, the metallized film winding body 4, and the exterior film 5.

  In the composite film winding body 6, the exterior film 5 performs heat welding (heat sealing) as a winding stop near the end of winding. The thermal welding is performed at a plurality of locations that are uniformly distributed in the circumferential direction of the exterior film 5. In the case of the illustrated example, heat welding locations 7 and 7 are defined at two locations in the circumferential direction, that is, two locations facing each other in the diameter direction (see FIG. 4). As shown in FIG. 3C, the heat welding is performed by abutting the tip of the heated seal heater 8 against the outer packaging film 5 being rotated. In the case of the illustrated example, the seal heater 8 is once abutted and the first heat welding is performed, the seal heater 8 is withdrawn, and the seal heater 8 is abutted again at the timing when the composite film winding body 6 is rotated half a circle. The second heat welding is performed, and the seal heater 8 is retracted again. About this heat welding, winding fixing of the exterior film 5 is made into the heat welding of the overlapping parts of exterior film 5 itself. In addition, the number of the heat welding locations 7 can be arbitrarily set, and the operation timing, cycle (number of times), and abutting time of the seal heater 8 are adjusted according to the number.

In this thermal welding, the area ratio α of the total area Sa of the thermal welding regions at a plurality of locations (two locations in the illustrated example) in the total outer peripheral area So of the composite film wound body 6 is set to 30% or less. That is,
α = (Sa / So) × 100 ≦ 30 [percent]
It is. It is preferable that the heat-welding region areas of the plurality of heat-welding locations 7 are equal to each other.

  In the composite film wound body 6, winding is performed at a plurality of locations (two locations in the illustrated example) in the circumferential direction of the exterior film 5. This is shown in FIG. These two heat welding locations 7 and 7 are equally arranged at equal intervals in the circumferential direction of the composite film winding body 6. In other words, the thick cylindrical composite film winding body 6 is disposed at positions symmetrical with respect to the center axis with respect to the central axis.

  Next, as shown in FIGS. 4 (a), 4 (b), and 4 (c), pressing forces F1 and F2 are applied to the composite film winding body 6 from the both sides in the diameter direction toward the central axis by pressing. Then, the composite film roll 6 is flattened. At this time, it is desirable to perform pressing (pressure forming) so that the two heat welding locations 7 and 7 become the application points of the pressing forces F1 and F2. In pressing, parallel flat press plates (not shown) are brought close to each other. As shown in FIG. 4 (a) → FIG. 4 (b) → FIG. 4 (c), the flatness of the composite film wound body 6 gradually increases as the press molding progresses, and the oblong oblong flat columnar body 9 is increased. Is obtained (see FIG. 4C). It can be said that the flat columnar body 9 is a pressure-molded wound body.

  The pressure forming by pressing is performed so that the flatness of the finished flat columnar body 9 is 0.6 or more. In the production of the flat columnar body 9 in anticipation of the flatness ratio of 0.6 or more, as a measure for preventing deterioration of the oblate shape, as described above, for the winding fixing of the outer film 5 in advance, It is assumed that heat welding is performed at a plurality of locations (two locations) dispersedly arranged in the circumferential direction, and the total area Sa of the heat welding regions at the plurality of locations is the area ratio α that occupies in the total outer area So of the composite film wound body 6. It is set to 30% or less. If the area ratio α of the total area Sa of the heat-welded region is not less than 30% but exceeds 30%, the metallized film that is covered with the exterior film 5 and exists inside the capacitor element A in a wound state This is because it has been confirmed through experiments that spoil, wrinkles / strain, and refraction / bending of the thin flat core portion 2a occur in the wound body 4.

  The experiment will be described next with reference to FIGS. For the flatness of the capacitor element A, that is, the flatness of the flat columnar body 9, four-point sample values of 0.50, 0.60, 0.76, and 0.85 were set. In addition, regarding the area ratio α (= (Sa / So) × 100) of the total area Sa of the heat-welded area in the exterior film 5 with respect to the entire outer peripheral area So of the composite film roll 6, the sample values 20 and 30 of 5 points 40, 50 and 100 (unit: [percent]) were set. The total number of specimens (samples) is 20. The experimental results are shown in FIGS. The column of the area ratio α = 30% substantially represents the range of the area ratio α [more than 20 to 30 or less], and the column of the area ratio α = 40% is substantially the range of the area ratio α [more than 30. ~ 40 or less]. The same applies to other percentages. The column of the flat rate f = 0.60 substantially represents the range of the flat rate f [0.60 to less than 0.76], and the column of the flat rate f = 0.50 is substantially It represents the range of the flatness f (over 0.00 to less than 0.60). The same applies to other flatness ratios.

  FIG. 5 shows an experimental result regarding the pass / fail determination of the oblate shape, and FIG. 6 shows an experimental result regarding the pass / fail determination of the withstand voltage characteristic. In these figures, the flatness and pressure resistance characteristics are all good (◯) regardless of the area ratio α in the column of the flatness ratio 0.50. This is because when the flatness is 0.50, more specifically, when the flatness is less than 0.60, the above-mentioned gaps, wrinkles / strains and thin flat windings in the portion of the metallized film wound body 4 of the flat columnar body 9 are obtained. Problems such as refraction and bending of the core portion 2a do not occur in the first place, and can be manufactured without any problem even by a conventional manufacturing method without special measures. The reason why the flatness ratio 0.50 is provided in FIGS. 5 and 6 is to clearly show this.

  The problem is that, as explained in the section [Problems to be Solved by the Invention], the flatness ratio is 0.6 or more in order to improve the volume efficiency in order to increase the capacity and size of the capacitor. In case of high flatness, there are unavoidable problems such as spurs, wrinkles / strains and refraction / bending of the thin flat core 2a. This is why we are pursuing whether to take measures. The area to be problematic is the range surrounded by a thick frame in FIGS.

  Now, in the experiment about the quality determination of oblateness in FIG. 5, the quality determination is based on visual confirmation of the appearance of the capacitor element A. In the judgment condition of good flatness (○), the metalized film wound body 4 in the flat columnar body 9 is free from creases, wrinkles, distortion, and refraction / bending of the thin flat core 2a. is there.

  When the flatness ratio f is 0.60 or more, the flatness is good (◯) in the correlation with the area ratio α when the area ratio α is 30% or less. When the flatness ratio f is just 0.60, the result of good oblateness (○) is obtained even when the area ratio α is 40%, but when the area ratio α is 40%, the flatness ratio f = 0. .76, flat rate f = 0.85, there is an inappropriate (×) result for flatness, and area ratio is required to obtain good flatness in a high flat area where flatness f is 0.6 or more. It can be concluded that α should be 30% or less.

  Next, the withstand voltage characteristic test of FIG. 6 applies an electric field having an electric field strength of 400 [V / μm] for 1 minute at room temperature (RT), and looks at the change in capacitance of the capacitor at that time. FIG. 6 (b) quantitatively represents the capacitance change as a numerical value (percent), and FIG. 6 (a) is obtained by adding pass / fail judgment to the numerical value of FIG. 6 (b). The determination condition of good withstand voltage characteristics (◯) is that the capacitance does not decrease.

  When the flatness ratio f is 0.60 or more, the pressure resistance is good (◯) in the correlation with the area ratio α when the area ratio α is 30% or less. When the flatness ratio f is just 0.60, even if the area ratio α is 40%, the capacitance change is positive, a good result of 0.08%, but the area ratio α is 40%. In the case of the flatness ratio f = 0.76 and the flatness ratio f = 0.85, there is a result of inappropriate (×) with respect to the withstand voltage characteristics, and good withstand voltage characteristics in a high flat area where the flatness ratio f is 0.6 or more. In order to obtain the above, it can be concluded that the area ratio α should be 30% or less.

  When the evaluation of the oblateness of FIG. 5 and the evaluation of the withstand voltage characteristics of FIG. 6 are combined, when the capacitor element A having an aspect ratio f of 0.6 or more is manufactured, a double-line rectangular frame surrounds the points. It is a requirement to set so as to enter the filled area Q. That is, it is a requirement to set the total area ratio α of the plurality of heat welding regions to 30% or less.

Incidentally, FIG. 8 shows the result of evaluating the capacitor element shown in Patent Document 3 (Japanese Patent Laid-Open No. 2003-59753). In the capacitor element shown in Patent Document 3, a horizontal line-like or grid-like convex portion is formed on the pressure surfaces of a pair of upper and lower press plates, and the film wound body is pressure-molded over the entire pressure surface. Therefore, it is recognized that the entire flat surface portion is the heat welding region. When the total area Sa of the heat-welded region is calculated, the following is obtained. For example, when the major axis dimension a of the capacitor element shown in FIG. The ratio of the major axis a to the minor axis b is a: b = 16: 6, the flattening ratio f is f = 0.625, and Sa = 10 × 2 = 20 (assuming the axial length is 1). ). The outer peripheral total area So of the flat columnar body is So = 20 + π · 6≈38.84, and the area ratio α is α = (20 / 38.84) × 100≈51.2 [percent]. In the same manner as this calculation, the result of obtaining several combinations of the flatness ratio f and the area ratio α on the condition that the heat welding region is the entire upper and lower flat surface portions of the flat columnar body is shown in FIG. 8 (a) and (b). The calculation formula used here is
α = 2 [(ab) / {2 (ab) + πb}] × 100
b = (1-f) a
From these, the relationship between the area ratio α and the flattening ratio f is obtained as follows:
f = πα / {(π−2) α + 200}
It becomes. Based on this, the data values of FIG. 8 are plotted.

  Referring to FIG. 8, the capacitor element of Patent Document 3 excludes the region Q in which the flatness ratio f is 0.6 or more and the area ratio α is 30 percent or less with respect to the correlation between the flatness ratio f and the area ratio α. It turns out that it is. That is, Patent Document 3 does not contain the technical idea of the present invention.

  In the description of the above embodiment of the present invention, the number of the heat-welded locations 7 is two, but the number of the heat-welded locations 7 is arbitrarily three or more. Several examples will be described below. That is, as shown in FIG. 7 (a), in the arcuate curved surface portions 9b, 9b at both ends in the major axis direction of the flat columnar body 9, two heat welded portions 7, 7 are provided at two central positions in the arc direction. You may arrange.

  Further, as shown in FIG. 7B, on the upper and lower flat surface portions 9a, 9a along the major axis direction of the flat columnar body 9, heat welding spots 7, 7 are arranged at two central positions in the major axis direction. In the arcuate curved surface portions 9b and 9b at both ends in the major axis direction of the flat columnar body 9, two heat welding locations 7 and 7 may be arranged at two locations at the center in the arc direction. These four heat welding locations 7 are evenly arranged in the circumferential direction.

  Moreover, as shown in FIG.7 (c), in each of the up-and-down flat surface part 9a and 9a along the major axis direction of the flat columnar body 9, it is a total of four places of two places spaced equally from the center position of the major axis direction. The heat welding locations 7 are arranged, and the two heat welding locations 7 and 7 are arranged at two central positions in the arc direction on the arcuate curved surface portions 9b and 9b at both ends in the major axis direction of the flat columnar body 9. It's okay. These six heat welding locations 7 are evenly arranged in the circumferential direction.

  Moreover, as shown in FIG.7 (d), in each of the up-and-down flat surface part 9a and 9a along the major axis direction of the flat columnar body 9, the center position of the major axis direction and the total of three places equidistantly spaced from the center position The heat welding locations 7 are arranged at six locations, and two heat welding locations 7 and 7 are provided at two central positions in the arc direction on the arcuate curved surface portions 9b and 9b at both ends in the major axis direction of the flat columnar body 9. May be arranged. These eight heat welding locations 7 are evenly arranged in the circumferential direction.

  Further, as shown in FIG. 7 (e), the two heat welding locations 7 and 7 at the arcuate curved surface portions 9b and 9b at both ends in the major axis direction in the case of FIG. 7 (c) are omitted, and the upper and lower flat surface portions 9a are omitted. , 9a, the heat-welded locations 7 may be arranged at a total of four locations, two locations spaced equidistantly from the central position in the major axis direction. These four heat welding locations 7 are evenly arranged in the circumferential direction.

  Further, as shown in FIG. 7 (f), the two heat welding locations 7, 7 at the arcuate curved surface portions 9b, 9b at both ends in the major axis direction in the case of FIG. 7 (d) are omitted, and the upper and lower flat surface portions 9a are omitted. , 9a, the heat welding locations 7 may be arranged at a total of 6 locations, that is, a central location in the major axis direction and 3 locations spaced equidistant from the central location. These six heat welding locations 7 are evenly arranged in the circumferential direction.

  In any of the above-described FIGS. 7A to 7F, the plurality of heat welding locations 7 are evenly arranged at equal intervals in the circumferential direction, and are symmetrical with respect to the central axis of the flat columnar body 9. It is arranged at the position.

  Further, as shown in FIG. 7 (g), on the upper flat surface portion 9a along the major axis direction of the flat columnar body 9, the heat welding spots 7, 7 are arranged at two locations that are equidistant from the center position in the major axis direction. In addition, in the lower flat surface portion 9a, the heat welding location 7 may be arranged at one location in the central position in the major axis direction.

  Alternatively, as shown in FIG. 7 (h), on the upper flat surface portion 9a along the major axis direction of the flat columnar body 9, the heat welding spots 7, 7 are arranged at two positions that are equidistant from the center position in the major axis direction. In addition, in the lower flat surface portion 9a, the heat-welded locations 7 may be arranged at a total of three locations including the center position in the major axis direction and two locations spaced equidistantly from the center position.

  7 (g) and 7 (h), the plurality of heat welding locations 7 are evenly spaced at equal intervals in the circumferential direction.

  In the above-described embodiment, the thin flat core portion 2a is arranged at the central portion of the composite film wound body 6. However, a capacitor element in which the thin flat core portion 2a is omitted may be used.

  The present invention improves the flatness of a capacitor element having a flatness ratio of 0.6 or more from the viewpoint of increasing the volume efficiency and prevents the generation of soot, wrinkles, and distortion inside the element, and has a withstand voltage characteristic. This is useful as a technique for preventing the lowering of noise and the operation noise at the time of ripple current.

DESCRIPTION OF SYMBOLS 1 Film for pre-winding 2 Winding core 2a Thin flat winding core part 3 Metallized film 4 Metallized film winding body 5 Exterior film 6 Composite film winding body 7 Heat welding location 8 Seal heater 9 Flat columnar body 9a Flat surface part 9b Circle Arc-shaped curved surface part 10 Metal electrode A Capacitor element 11 Su
12 Wrinkles / Strain 13 Refraction / bending of thin flat core

Claims (7)

An outer film is further wound around the outer peripheral portion of the metallized film wound body and fixed by heat welding to form a composite film wound body, and a flat columnar body is formed by pressure forming on this composite film wound body. In the capacitor element in which metal electrodes are formed at both axial ends of the flat columnar body and the flatness ratio is 0.6 or more,
The winding fixing of the exterior film in the composite film winding body is performed by heat welding between self-overlapping portions and dispersedly arranged in the circumferential direction, and the composite film winding is performed. The capacitor | condenser element characterized by the area ratio which the total area which the total area of the said several heat welding area | region occupies is set to 30% or less in the outer periphery whole area of a body.   2. The capacitor element according to claim 1, wherein the plurality of heat-welded locations are equally arranged at equal intervals in a circumferential direction of the flat columnar body.   3. The capacitor element according to claim 1, wherein the plurality of heat welding locations are arranged at positions symmetrical with respect to a center axis of the flat columnar body.   4. The capacitor element according to claim 3, wherein the plurality of axisymmetric heat welding locations are two locations at a central position in the major axis direction on a flat surface portion along the major axis direction of the flat columnar body.   4. The capacitor element according to claim 3, wherein the plurality of axisymmetric heat welding locations are two locations at the center in the arc direction in the arcuate curved surface portions at both ends in the major axis direction of the flat columnar body.   The plurality of axisymmetric heat welding locations are two flat central portions along the major axis direction of the flat columnar body, and two arcuate curved surface portions at both ends in the major axis direction of the flat columnar body. 4. The capacitor element according to claim 3, wherein there are a total of four locations, including two central locations in the arc direction.   The flat columnar body has a thin flat winding core portion extending in the major axis direction through a central axis at an inner center of the metallized film winding body. Capacitor element given in any 1 paragraph

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