JP7670733B2 - Film Capacitors - Google Patents

Description

The present invention relates to a film capacitor.

One type of capacitor is a film capacitor, which uses a flexible resin film as a dielectric and has a first metal layer and a second metal layer facing each other with the resin film in between. Such a film capacitor is produced, for example, by winding a first dielectric film on which a first metal layer made of aluminum or the like is formed, and a second dielectric film on which a second metal layer made of aluminum or the like is formed.

Capacitors made in this way are usually cylindrical, but they may be deformed to have a flattened cross-sectional shape to improve volumetric efficiency.

Patent document 1 discloses a capacitor element having an oval cross section formed by flattening a metallized film, in which metal vapor deposition electrodes are formed on a dielectric film made of polypropylene, by winding the metallized film around a core so that a pair of metal vapor deposition electrodes face each other via the dielectric film.

Patent document 2 discloses a capacitor element in which a composite film roll is formed by wrapping an outer casing film around the outer periphery of a metallized film roll and fixing the roll by thermal welding, and then press-molding the composite film roll to an aspect ratio of 0.6 or less.

JP 2007-81007 A JP 2015-70125 A

However, when flattening, excessive force can be applied to the metallized film, which can reduce the reliability of the capacitor, such as causing the capacitor to lose its self-healing function in the event of a short circuit.

The aim of Patent Document 1 is to increase volumetric efficiency by making the capacitor smaller and thinner, but it does not mention the relationship between the detailed shape of the flat body and the reliability of the capacitor.

Patent document 2 describes the relationship between the thermal welding method of the exterior film and the flatness of the element, but does not describe the relationship between the detailed shape of the flat body and the reliability of the capacitor.

The present invention has been made to solve the above problems and aims to provide a film capacitor that has high volumetric efficiency and is less likely to short circuit.

The film capacitor of the present invention comprises a laminate formed by laminating a metallized film having a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin, the laminate being a flat columnar shape formed by deforming a wound body formed by winding the metallized film in a stacked state, the cross-sectional shape of the laminate in a plane parallel to the stacking direction of the metallized film is a flat shape having a major axis and a minor axis, the flat shape having a straight line portion that is located approximately in the center in the direction in which the major axis extends and includes a straight line that is approximately parallel to the major axis, and curved portions that are located at both ends of the straight line portion in the direction in which the major axis extends and include a curve, and the flat shape is a shape that satisfies the following formula (1).
0≦f≦0.3 (1)
[wherein f is a number expressed by f=1-(a/b), a is a number expressed by a=[(L ₁ -L ₂ )/2] when the length of the major axis is L ₁ and the length of the straight portion is L ₂ , and b is a number expressed by b=L ₃ /2 when the length of the minor axis is L _3. ]

The present invention makes it possible to provide a film capacitor that has high volumetric efficiency and is less likely to short circuit.

FIG. 1 is a perspective view illustrating an example of a film capacitor according to the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a perspective view that shows a schematic diagram of a roll formed by rolling up a metallized film. FIG. 4 is a perspective view that illustrates an example of a laminate that constitutes the film capacitor of the present invention. FIG. 5 is a diagram for explaining a method for determining the boundaries of straight line portions and curved line portions. FIG. 6 is a diagram showing a schematic cross-sectional shape of the laminate shown in FIG. 1 when the laminate is cut along the line VI-VI.

The film capacitor of the present invention will be described below.
However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual preferable configurations of the present invention described below.

The embodiments shown below are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, a description of matters common to the first embodiment will be omitted, and only the differences will be explained. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

The drawings shown below are schematic and the dimensions and aspect ratios may differ from those of the actual product.

The film capacitor of the present invention comprises a laminate formed by laminating a metallized film having a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin, the laminate being a flat columnar shape formed by deforming a wound body formed by winding the metallized film in a stacked state, the cross-sectional shape of the laminate in a plane parallel to the stacking direction of the metallized film is a flat shape having a major axis and a minor axis, the flat shape having a straight line portion that is located approximately in the center in the direction in which the major axis extends and includes a straight line that is approximately parallel to the major axis, and curved portions that are located at both ends of the straight line portion in the direction in which the major axis extends and include a curve, and the flat shape is a shape that satisfies the following formula (1).
0≦f≦0.3 (1)
[wherein f is a number expressed by f=1-(a/b), a is a number expressed by a=[(L ₁ -L ₂ )/2] when the length of the major axis is L ₁ and the length of the straight portion is L ₂ , and b is a number expressed by b=L ₃ /2 when the length of the minor axis is L _3. ]

FIG. 1 is a perspective view illustrating an example of a film capacitor of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.
The film capacitor 10 shown in FIG. 1 includes a laminate 40 , and a first external electrode 41 and a second external electrode 42 connected to both end faces of the laminate 40 .
As shown in FIG. 2, laminate 40 is formed by winding first metallized film 11 and second metallized film 12 in a laminated state.
First metallized film 11 comprises a first dielectric resin film 13 and a first metal layer (counter electrode) 15 provided on the surface of first dielectric resin film 13 .
Second metallized film 12 comprises a second dielectric resin film 14 and a second metal layer (counter electrode) 16 provided on the surface of second dielectric resin film 14 .

2, the first metal layer 15 and the second metal layer 16 face each other with the first dielectric resin film 13 or the second dielectric resin film 14 sandwiched therebetween. Furthermore, the first metal layer 15 is electrically connected to the first external electrode 41, and the second metal layer 16 is electrically connected to the second external electrode 42.

The first dielectric resin film 13 and the second dielectric resin film 14 may have different configurations, but it is preferable that they have the same configuration.

The first metal layer 15 is formed on one surface of the first dielectric resin film 13 so as to reach one edge, but not to reach the other edge. On the other hand, the second metal layer 16 is formed on one surface of the second dielectric resin film 14 so as not to reach one edge, but to reach the other edge. The first metal layer 15 and the second metal layer 16 are composed of, for example, an aluminum layer.

FIG. 3 is a perspective view that shows a schematic diagram of a roll formed by rolling up a metallized film.
As shown in Figures 2 and 3, the first dielectric resin film 13 and the second dielectric resin film 14 are wound in a stacked state so that the end of the first metal layer 15 that reaches the side edge of the first dielectric resin film 13 and the end of the second metal layer 16 that reaches the side edge of the second dielectric resin film 14 are both exposed from the stacked films, thereby forming a wound body 40a, and the first metal layer 15 and the second metal layer 16 are kept exposed at their ends and are in a stacked state.

In the wound body 40a, the second dielectric resin film 14 is wound so that it is on the outside of the first dielectric resin film 13, and the first metal layer 15 and the second metal layer 16 of each of the first dielectric resin film 13 and the second dielectric resin film 14 face inward.
A cavity 50a is provided in the center of the wound body 40a.

FIG. 4 is a perspective view that illustrates an example of a laminate that constitutes the film capacitor of the present invention.
The laminate 40 shown in Fig. 4 can be obtained, for example, by pressing the wound body 40a shown in Fig. 3. At this time, the cavity 50a is also deformed to become the cavity 50. The cross-sectional shape of the laminate 40 in a plane parallel to the lamination direction of the metallized films is a flat shape having a major axis and a minor axis.
By pressing the wound body 40a, the volume efficiency can be improved.
In addition, the surface parallel to the stacking direction of the metallized film of the laminate 40 corresponds to a surface perpendicular to the axial direction of the flat column (the direction in which the column extends) and a surface perpendicular to the winding axis of the wound body 40a used when producing the laminate 40.

Here, the larger the size of the cavity 50a provided in the center of the wound body 40a, the more flat the cross-sectional shape of the laminate 40 can be. In other words, by adjusting the size of the cavity 50a in the wound body 40a, the cross-sectional shapes of the laminate 40 and the cavity 50 can be adjusted.

[Laminate]
The film capacitor of the present invention includes a laminate in which a metallized film having a metal layer provided on the surface of a dielectric resin film containing a thermosetting urethane resin is laminated.
The laminate has a flat shape obtained by deforming a roll in which metallized films are laminated and wound.

Metallized films are made by providing a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin.

In the film capacitor of the present invention, the dielectric resin film contains, for example, a thermosetting urethane resin which is a cured product of a first organic material having a hydroxyl group (OH group) and a second organic material having an isocyanate group (NCO group).
Specifically, the thermosetting urethane resin is a cured product obtained by reacting a hydroxyl group contained in the first organic material with an isocyanate group contained in the second organic material.

The first organic material may be an organic polymer having a hydroxyl group and a benzene ring in the repeating unit, such as a phenoxy resin.
As the phenoxy resin, for example, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, etc. are preferable.

The second organic material may be diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), etc. Among these compounds, MDI or TDI is preferred. These may contain modified polyisocyanates, or may be used in combination.

In the film capacitor of the present invention, the dielectric resin film may also contain additives for imparting other functions. For example, smoothness can be imparted by adding a leveling agent. The additive may be a material that has a functional group that reacts with a hydroxyl group and/or an isocyanate group and forms part of the crosslinked structure of the cured product. Examples of such materials include resins having at least one functional group selected from the group consisting of an epoxy group, a silanol group, and a carboxyl group.

In the film capacitor of the present invention, the CR value, which is the product of the capacitance value of the film capacitor and the insulation resistance value measured after leaving it to stand in an atmosphere at a temperature of 125° C. for 1 hour and then applying a voltage of 150 V/μm for 1 minute, is preferably 250 Ω·F or more, and more preferably 500 Ω·F or more.
A capacitor having a CR value of 250 Ω·F or more under the above conditions can be said to have high resistance to high temperatures.

Thermosetting urethane resin means a urethane resin that can be cured by heat, and does not limit the curing method. Therefore, as long as it is a urethane resin that can be cured by heat, urethane resin that has been cured by a method other than heat (for example, light, electron beam, etc.) is also included in thermosetting urethane resin. Also, depending on the material, the reaction may start due to the reactivity of the material itself, and even those that cure without necessarily being exposed to heat or light from the outside are considered to be thermosetting urethane resins.

The dielectric resin film may contain a thermoplastic resin or a silicone resin in addition to the thermosetting urethane.
Examples of the thermoplastic resin include polypropylene, polyethersulfone, polyetherimide, and polyarylate.

The metal layer is provided on the surface of the dielectric resin film.
The thickness of the metal layer is not particularly limited, but is preferably 5 nm or more and 40 nm or less.

The thickness of the metal layer can be determined by observing a cut surface of the metallized film in the thickness direction using a transmission electron microscope (TEM).

Materials that can be used to form the metal layer include, for example, metals such as aluminum, zinc, titanium, magnesium, tin, and nickel.

The metal layer may be provided on both sides of the dielectric resin film, or on only one side.
When the metal layer is provided on both sides of the dielectric resin film, a dielectric resin film having no metal layer on either side (non-metallized film) and a dielectric resin film having metal layers on both sides (double-sided metallized film) may be laminated and wound to obtain a roll. On the other hand, when the metal layer is provided on only one surface of the dielectric film, two dielectric resin films having a metal layer on one side (single-sided metallized film) may be laminated and wound so that the metal layers do not come into contact with each other to obtain a roll.

The metal layer may have a fuse portion.

The metal layer may be provided over the entire surface of one of the dielectric resin films, or may be provided over only a portion of the surface.

The coefficient of static friction between the surface of the metallized film on which the metal layer is provided and the surface of the metallized film on which the metal layer is not provided is preferably 0.3 or more and 1.5 or less.
The static friction coefficient is measured in accordance with JIS K 7125-1999.
When the static friction coefficient is within this range, the metallized film has favorable slip properties and is smoothly flattened, making it easy to adjust the flat shape, which is the cross-sectional shape of the laminate, to a shape that satisfies formula (1).

The laminate has a flattened columnar shape obtained by deforming a roll in which metallized films are laminated and wound.
The cross-sectional shape of the laminate in a plane parallel to the lamination direction of the metallized films is a flat shape having a major axis and a minor axis.

The flat shape has straight lines and curved lines.
The straight line portion is a portion that is disposed approximately in the center in the direction in which the major axis extends and that includes a straight line that is approximately parallel to the major axis.
The curved portions are portions that are disposed on both ends of the straight portion in the direction in which the major axis extends, and are configured to include curves.

The straight and curved portions are identified by the following procedure.
First, two straight lines that are approximately parallel to the long axis are identified from the flat shape, and the portion surrounded by the two straight lines is defined as a straight line portion. The straight line portion is an approximately rectangular shape formed by the two straight lines and the line segments connecting the ends of the two straight lines.
Next, the portion of the flat shape excluding the straight line portion is defined as the curved line portion. Therefore, the boundary between the straight line portion and the curved line portion is a straight line.

If the boundary between the straight line and curved section is unclear, the boundary will be the point where the angle between the tangent at each point constituting the outer shape of the curved section and the straight line constituting the straight line section is 10°. In other words, starting from the point closest to the straight line section, the angle between the tangent at each point of the curved section and the straight line constituting the straight line section is calculated. The point where the angle between the tangent and the straight line is 10° will be the starting point of the curved section.

FIG. 5 is a diagram for explaining a method for determining the boundaries of straight line portions and curved line portions.
In the cross-sectional shape of the laminate shown in FIG. 5, the boundary between the straight line portion L and the curved line portion _C2 is assumed to be unclear, and the boundary between the straight line portion and the curved line portion is determined.
FIG. 5 shows an extension line _X0 extending the straight line portion L toward the curved portion _C2 , and tangent lines _X1 , _X2 , and _X3 at arbitrary points _P1 , _P2 , and _P3 on the curve Cb.
Here, the angle between the tangent _X1 and the extension _X0 at the point _P1 is 5°. The angle between the tangent _X2 and the extension X0 at the point _P2 is 10°. The angle between the tangent _X3 and _the extension _X0 at the point _P3 is 15°.
Therefore, the point _P2 where the tangent _X2 , which makes an angle of 10° with the straight line constituting the straight line portion, touches the curved portion Cb, is the starting point of the curved portion _C2 .

The flat shape is a shape that satisfies the following formula (1).
0≦f≦0.3 (1)
f is a number expressed as f=1-(a/b).
The number a is expressed by a=[(L ₁ -L ₂ )/2], where L ₁ is the length of the major axis and L ₂ is the length of the straight portion.
b is a number expressed by b=L ₃ /2.

When the cross-sectional shape of the laminate satisfies the above formula (1), it can be said that uneven force is unlikely to be applied to the metallized films at the curved portion, so that even if dielectric breakdown occurs in the film capacitor, a short circuit does not occur and the insulation can be restored.
When the cross-sectional shape of the laminate has an f-value exceeding 0.3, the laminate is not smoothly flattened, and an abnormal force is applied to the metallized film at the straight line portion. If a dielectric breakdown occurs at the portion where the abnormal force is applied to the metallized film, the dielectric breakdown cannot be restored and a short circuit occurs.
On the other hand, in the cross-sectional shape of the laminate, when the f value is less than 0, the distance between the metallized films is increased in the curved portion, resulting in a decrease in capacitance and a decrease in dielectric breakdown strength. Furthermore, when dielectric breakdown occurs, it becomes difficult to restore the insulation.

Fig. 6 is a diagram showing a cross-sectional shape of the laminate when the laminate shown in Fig. 1 is cut along line VI-VI. Therefore, Fig. 6 omits the state in which the metallized films constituting the laminate are wound, and the external electrodes formed on the end faces of the laminate.
The cross-sectional shape of the laminate 40 shown in Fig. 6 is a flat shape having a major axis x and a minor axis y. The cross-sectional shape of the laminate 40 also has a straight line portion L and curved lines _C1 and _C2 . The straight line portion L is configured to include straight lines La and Lb parallel to the major axis x. The curved lines _C1 and _C2 are disposed at both ends of the straight line portion L in the direction in which the major axis x extends, and are configured to include curved lines Ca and Cb, respectively.
The length of the curved portions C ₁ and C ₂ in a direction substantially parallel to the major axis x is given by [(length L ₁ of the major axis x)−(length L ₂ of the straight portion L)]/2=a.

In the cross-sectional shape of the laminate 40 shown in FIG. 6, the length of the major axis x, the length of the straight line portion L, and the length of the minor axis y are L ₁ , L ₂ , and L ₃ , respectively.
6, when the length L1 of the major axis x is ₁ , the length L2 of the straight line portion L is 0.648, and the length _L3 of the minor axis _y is 0.365. Therefore, f is 1-[(1-0.648)/0.365]≈0.036.

In the film capacitor of the present invention, a cavity or a winding core may be arranged in the center of the laminate.

In the film capacitor of the present invention, the ratio [XL/YL] of the interlayer distance XL between the metallized films in the curved portions to the interlayer distance YL between the metallized films in the straight portions is preferably 0 or more and 1 or less, and more preferably 0.45 or more and 1.0 or less.

The interlayer distance YL between the metallized films in the straight portion can be determined from the thickness of the straight portion from the center of the laminate, the average thickness of the metallized films that make up the straight portion, and the number of turns (number of layers) of the metallized films that make up the straight portion.
First, the thickness _tL of the straight portion from the center of the laminate is expressed by the following formula (2) using the interlayer distance YL between the metallized films in the straight portion, the average thickness _tFL of the metallized films constituting the straight portion, and the number of turns (number of layers) n of the metallized films constituting the straight portion.
t _L = (YL+t _FL )×(n-1)+t _FL (2)
The interlayer distance YL between the metallized films in the straight line portion is expressed by the following formula (3), which is a modification of the above formula (2).
YL=(t _L -t _FL )/(n-1) - t _FL (3)
Moreover, by modifying the above formula (3), it can also be expressed as the following formula (4).
YL=[(t _L )-(t _FL ×n)]/(n-1) (4)

On the other hand, the interlayer distance XL between the metallized films in the curved portion can be calculated from the thickness from the center of the laminate in the curved portion, the average thickness of the metallized films constituting the straight portions, and the number of turns (number of layers) of the metallized films constituting the curved portion.
First, the thickness _tC of the curved portion from the center of the laminate is expressed by the following formula (5) using the interlayer distance XL between the metallized films in the curved portion, the average thickness _tFL of the metallized films constituting the straight portion, and the number of turns (number of layers) n of the metallized film constituting the curved portion.
t _C = (XL+t _FL )×(n-1)+t _FL (5)
The interlayer distance XL between the metallized films in the curved portion is expressed by the following formula (6), which is a modification of the above formula (5).
XL=(t _C -t _FL )/(n-1) - t _FL (6)
Moreover, by modifying the above formula (6), it can also be expressed as the following formula (7).
XL=[(t _C )-(t _FL ×n)]/(n-1) (7)
Here, the reason for using the average thickness _tFL of the metallized films constituting the straight line portions when determining the interlayer distance XL between the metallized films in the curved line portions will be described.
The interlayer distance XL between metallized films in the curved portion in this specification is not the interlayer distance between metallized films in the curved portion of an actual film capacitor, but the distance between the metallized films calculated under the assumption that the thickness of the metallized film does not change due to the flattening process.
Since the thickness of the metallized film in the straight line portions does not change due to the flattening process, and furthermore, the thickness of the metallized film before the flattening process does not change between the straight line portions and the curved line portions, the thickness of the metallized film in the curved line portions before the flattening process is considered to be equal to the thickness of the metallized film in the straight line portions after the flattening process. For the above reasons, in determining the interlayer distance XL between the metallized films in the curved line portions, the average thickness _tFL of the metallized film constituting the straight line portions is used.
Therefore, when the thickness of the metallized film is reduced by the flattening process, the interlayer distance XL between the metallized films may become a negative value.

The thickness from the center of the laminate at the straight and curved sections, the average thickness of the metallized film, and the number of layers of the metallized film can be measured by observing the cut surface of the film capacitor cut in a direction perpendicular to the lamination direction of the metallized film with a scanning electron microscope or the like. The average thickness of the metallized film is the average value of the thicknesses of all the metallized films present on the minor axis of the flat shape that is the cross-sectional shape of the laminate at the cut surface, in the case of straight sections, and the average value of the thicknesses of all the metallized films present on the major axis of the flat shape that is the cross-sectional shape of the laminate at the cut surface, in the case of curved sections.

The interlayer distance YL between the metallized films in the straight line portion is, for example, the distance between the second metal layer 16 constituting the second metallized film 12 and the first dielectric resin film 13 constituting the first metallized film 11 in Figure 2. However, Figure 2 shows an example in which the interlayer distance YL between the metallized films in the straight line portion is zero.

On the other hand, in curved sections, the interlayer distance between metallized films may shrink or expand depending on how easily the metallized films slide against each other.
When the ratio [XL/YL] is 0 or more and 1 or less, the interlayer distance between the metallized films constituting the curved portion is within an appropriate range, so that the metallized films constituting the curved portion are not subjected to abnormal forces, and therefore the insulation recovery function can be fully exhibited.

If the above ratio [XL/YL] exceeds 1, the metallized film at the curved portion slides too much or is pulled during the process of deforming the laminate, causing the interlayer distance between the metallized films at the curved portion to become too long. In such a case, if dielectric breakdown occurs at the curved portion, the dielectric recovery function of the metallized film is not exerted, which is thought to lead to a short circuit. Furthermore, a decrease in capacitance and a decrease in dielectric breakdown strength are likely to occur.

On the other hand, when the ratio [XL/YL] is less than 0, it is considered that abnormal force is applied to the metallized film in a state where the distance between the metallized films is almost not large at the curved portion, and the thickness of the metallized film is thinned or deformed. In such a case, if dielectric breakdown occurs at the curved portion, the dielectric recovery function of the metallized film is not exerted, and a short circuit occurs. Furthermore, a decrease in capacitance and a decrease in dielectric breakdown strength are likely to occur.
The ratio [XL/YL] is less than 0 when the interlayer distance XL of the metallized film constituting the curved portion has a negative value.
Note that the negative value of the film interlayer distance XL is a calculated value and is not related to the actual distance between the metallized films. A state in which the film interlayer distance XL is a negative value actually means that there is almost no film interlayer distance and the metallized film constituting the curved portion is excessively pressed or stretched during the flattening process, making the film thickness of the curved portion thinner than the average film thickness.

A cavity 50 is provided in the center of the laminate 40 shown in FIG.
The thickness of the straight line portion L from the center of the laminate 40 is the length indicated by the double-headed arrow _tL . The thickness of the curved line portion _C2 from the center of the laminate 40 is the length indicated by the double-headed arrow _tC .
In the laminate 40 shown in FIG. 6, the thickness t _C of the curved portion C ₂ from the center side of the laminate 40 is equal to a=(L ₁ -L ₂ )/2.
When a winding core is provided in the center of the laminate instead of a cavity, the interlayer distance between the metallized films can be determined by replacing the cavity in the above procedure with the winding core.

6, the cavity 50 has a predetermined thickness tv, so the thickness _tL of the straight portion L from the center of the laminate 40 does not match b= _L3 /2. On the other hand, if the laminate 40 does not have a cavity 50 or a winding core, the thickness _tL of the straight portion L from the center of the laminate 40 matches b= _L3 /2.

In determining the straight and curved portions in the cross-sectional shape of the laminate, the thickness of one or two metallized films is to be ignored, i.e., the step that occurs at the end of the winding of the metallized film is not to be taken into consideration.
Similarly, in determining the shape of the cavity present inside the laminate, the step that occurs at the point where the winding of the metallized film begins is not taken into consideration.

It is preferable that the curved portion has an outer shape that is composed only of curves.
When the outer shape of the curved portion is formed only from curves, it becomes easier to distribute the force applied to the metallized films that make up the laminate.

In the film capacitor of the present invention, when a boundary line between the curved portion and the straight portion is assumed, it is preferable that the difference between the maximum and minimum distances from the center point of the boundary line in the short axis direction to the outer edge of the curved portion is 35% or less of the value represented by [(a+b)/2].
When the difference between the maximum and minimum values is 35% or less of the value represented by [(a+b)/2], the outer shape of the curved portion becomes close to an arc that constitutes a perfect circle, making it easier to distribute the force applied to the metallized film.
When the curve that constitutes the curved portion is a semicircle of a perfect circle, the distance from the center point in the minor axis direction of the boundary line between the curved portion and the straight portion to the outer edge of the curved portion at every point is the same as a and b. Therefore, the difference between the maximum and minimum distances from the center point to the outer edge of the curved portion is zero, and the ratio of the difference to the value represented by [(a+b)/2] is zero%.

In the laminate 40 shown in FIG. 6, the distance Ln from the center point p in the minor axis y direction of the boundary line between the curved portion _C2 and the straight portion L to an arbitrary point on the outer edge portion (curve Cb) of the curved portion _C2 is equal to a and b.
Here, when the difference between the maximum and minimum values of the distance Ln is 35% or less of the value represented by [(a+b)/2], the value of the distance Ln is close to a and b, and the shape of the curved portion is close to an arc that constitutes a perfect circle, which makes it easier to distribute the force applied to the metallized film, and makes it difficult for abnormal forces to be applied to the metallized film.

[External electrode]
The film capacitor of the present invention may include external electrodes.
The external electrodes are provided on end faces of the laminate in a direction perpendicular to the lamination direction of the metallized films so as to be in contact with the metal layers.

The external electrodes are preferably made of zinc, aluminum, tin, alloys thereof, etc.

Methods for forming external electrodes include, for example, thermal spraying.

The thickness of the external electrode is not particularly limited, but may be 0.5 mm or more and 5 mm or less.

The film capacitor of the present invention may include lead terminals connected to external electrodes and a housing case.
When the film capacitor of the present invention is provided with a housing case, it is preferable that the film capacitor is housed in the housing case with lead terminals connected to the external electrodes, and that the film capacitor housed in the housing case is sealed with a sealing resin.

The film capacitor of the present invention can be used in known applications, but is particularly suitable for use in environments with large temperature changes, particularly at high temperatures. As it extends the life of the equipment, it is suitable for use in power electronics equipment such as electric compressors/pumps, chargers, DC-DC converters, and drive inverters that are installed in automobiles and industrial equipment.

[Method of manufacturing film capacitor]
Next, an example of a method for producing the film capacitor of the present invention will be described.
The dielectric resin film constituting the film capacitor of the present invention can be produced by forming a resin solution containing a first organic material having a hydroxyl group and a second organic material having an isocyanate group into a film, and then heat-treating it to harden it.

Next, a metal layer is formed on one surface of the dielectric resin film thus prepared to obtain a metallized film. The metal layer can be formed by a method such as vapor deposition.
At this time, the metal layer is formed so that a strip-shaped insulating portion is formed on one side edge of one surface of the dielectric resin film.

Next, prepare two metallized films, each of which has a metal layer formed on one side of a dielectric resin film. One of the two metallized films is rotated 180 degrees around the lamination direction as an axis so that the positions of the insulating parts are staggered, and the two films are stacked with a predetermined distance shifted in the width direction, and then wound to obtain a wound body.

Next, the obtained wound body is sandwiched in a direction perpendicular to the width direction and pressed into a flat shape to obtain a flat columnar laminate.
At this time, by adjusting various conditions such as the thickness of the metallized film, the number of turns, the volume of the cavity in the center of the wound body, and the pressing pressure, the cross-sectional shape of the laminate is adjusted to satisfy the following formula (1).
0≦f≦0.3 (1)

Next, external electrodes are formed on the end faces of the laminate to obtain a film capacitor as shown in Figure 1. One method for forming external electrodes on the end faces of the laminate is thermal spraying.

If necessary, the resulting film capacitor may be connected to lead terminals, housed in an outer case, and sealed with sealing resin.

Below, we will present examples that more specifically disclose the film capacitor of the present invention. Note that the present invention is not limited to these examples.

Example 1
First, a mixed solution of phenoxy resin and 4,4-phenylmethane diisocyanate was molded into a film and heat-cured to obtain a dielectric resin film having a thickness of 2.89 μm. A metallized film was prepared by forming an aluminum layer having a thickness of 10 nm on one surface of the obtained dielectric resin film by vapor deposition.

Next, two of these metallized films were stacked together and wound to obtain a wound body. The cross-sectional shape of the wound body was a doughnut shape with a roughly circular cavity in the center.

The wound body was then pressed to obtain a laminate. The cross-sectional shape of the laminate was a flat shape having a major axis, a minor axis, and straight and curved portions, as shown in Figure 6. The dimensions of the flat shape were as follows:
Length of major axis x _L1 : 25.1 mm
Length L2 of straight portion _L : 18.0 mm
Length of minor axis y _L3 : 9.4 mm
Thickness _tL of the straight portion from the center of the laminate: 4.70 mm
Thickness _tC of the curved portion from the center of the laminate: 3.55 mm
Average thickness _tFL of the metallized film constituting the straight line portion: 2.9 μm
The number of layers of the metallized film: 1220. From these dimensions, the f value and XL/YL were calculated. The results are shown in Table 1.

Zinc was sprayed onto the end faces of the laminate to form external electrodes, and the film capacitor of Example 1 was produced.

(Examples 2 to 5, Comparative Examples 1 to 5)
External electrodes were produced in the same manner as in Example 1, except that the f value of the dielectric resin film was changed as shown in Table 1.

[Load test]
A voltage of 100 V/μm was applied to the film capacitors of each Example and Comparative Example in an atmosphere of 125° C. The voltage was increased by 100 V/μm every hour, and then a load was applied in which the voltage was maintained for one hour. This load application operation was repeated until the film capacitor underwent dielectric breakdown and the capacitance became 0, or until the film capacitor was shorted.
The film capacitor was evaluated as ◯ when dielectric breakdown occurred and the capacitance became 0, and as × when the film capacitor was shorted. The results are shown in Table 1.

The results in Table 1 show that the film capacitors according to the examples were able to restore insulation without short-circuiting until the capacitance reached zero.
From the above, it was found that the film capacitor of the present invention is less likely to cause a short circuit.

REFERENCE SIGNS LIST 10 film capacitor 11 first metallized film 12 second metallized film 13 first dielectric resin film 14 second dielectric resin film 15 first metal layer 16 second metal layer 40 laminate 40a wound body 41 first external electrode 42 second external electrode 50a, 50 cavity _C1 , _C2 curved portion Ca, Cb curve L straight portion _L1 length of major axis _L2 length of straight portion _L3 length of minor axis La, Lb straight lines _P1 , _P2 , _P3 any point on the curve _tV thickness of cavity x major axis _X0 extension line of straight portion towards the curved portion _X1 , _X2 , _X3 tangent at any point on the curve _tC thickness of curved portion from center of laminate y minor axis _tL thickness of straight portion from center of laminate

Claims (3)

The laminate includes a metallized film having a metal layer provided on a surface of a dielectric resin film containing a thermosetting urethane resin,
the laminate has a flattened columnar shape obtained by deforming a roll obtained by rolling the metallized film in a stacked state,
a cross-sectional shape of the laminate in a plane parallel to a lamination direction of the metallized film is a flat shape having a major axis and a minor axis,
A winding core is not disposed in the center of the laminate,
the flat shape has a straight line portion disposed at a substantially center in a direction in which the long axis extends and including a straight line substantially parallel to the long axis, and curved lines disposed at both ends of the straight line portion in a direction in which the long axis extends and including a curved line,
The flat shape satisfies the following formula (1) ,
a ratio [XL/YL] of an interlayer distance XL between the metallized films constituting the curved portion to an interlayer distance YL between the metallized films constituting the straight portion in a cross section of the laminate in a plane parallel to the stacking direction of the metallized film is 0 or more and 1 or less .
0≦f≦0.3 (1)
[wherein f is a number expressed by f=1-(a/b), a is a number expressed by a=[(L ₁ -L ₂ )/2] when the length of the major axis is L ₁ and the length of the straight portion is L ₂ , and b is a number expressed by b=L ₃ /2 when the length of the minor axis is L _3. ] The film capacitor of claim 1, wherein the outer shape of each of the curved portions is composed only of curves. 3. The film capacitor according to claim 1, wherein, when a boundary line between the curved portion and the straight portion is assumed, the difference between the maximum and minimum distances from the center point of the boundary line in the short axis direction to the outer edge of the curved portion is 35% or less of the value represented by [(a + b)/2].

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