JP4720390B2 - Metallized film capacitors - Google Patents

Description

  The present invention relates to a metallized film capacitor which is used in various electronic devices, electrical devices, industrial devices, automobiles, etc., and is particularly suitable for smoothing, filtering, and snubbing of motor drive inverter circuits of hybrid vehicles.

  In recent years, from the viewpoint of environmental protection, all electric devices are controlled by inverter circuits, and energy saving and high efficiency are being promoted. In particular, in the automobile industry, hybrid vehicles (hereinafter referred to as HEVs) that run on electric motors and engines have been introduced into the market, and the development of technologies relating to energy saving and high efficiency has been activated.

  Since such a HEV electric motor has a high operating voltage range of several hundred volts, a metallized film capacitor having high withstand voltage and low loss electric characteristics is used as a capacitor used in connection with such an electric motor. In addition, due to the demand for maintenance-free in the market, the tendency to adopt metallized film capacitors with a very long life is conspicuous.

  And this kind of metallized film capacitor is squeezed into an oval by crushing a cylindrical capacitor element made of a wound film due to the size of equipment used or the power supply section and restrictions such as mounting area on the printed circuit board. A flat shape is used.

  5 (a) and 5 (b) are a plan sectional view and a front sectional view showing the structure of such a conventional metalized film capacitor. In FIG. 5, 11 is a winding core of the capacitor element, and 12 is this winding. A bent portion provided on the core 11, 13 is a metallized film obtained by depositing a metal film electrode on a resin film, and 14 is an exterior film for insulating and protecting the capacitor element. 15 is a capacitor element comprising the metallized film 13, the core 11 and the exterior film 14, 16 is a metal layer provided on the end face of the capacitor element 15, 17 is a terminal for drawing out an electrode, 18 is a capacitor element 15. An exterior case 19 is a filling resin. The capacitor element 15 is flattened after being wound in a cylindrical shape.

  The conventional metallized film capacitor configured as described above suppresses the variation in characteristics of the capacitor element having a large aspect ratio, and the winding core can be rounded to increase the winding speed, thereby reducing the number of production steps. It was something that could be done.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2005-93761 A

  However, in the above conventional metallized film capacitor, in order to meet the market demand for further increase in capacity and reduction in size and thickness, the capacity of the capacitor element is realized and the shape of the capacitor element accommodated in the limited space is changed. In order to improve the volume efficiency by devising, further flattening is necessary, and this has many problems.

  That is, as shown in FIG. 6, when calculating the volume efficiency in the case where the capacitor elements having the same capacity are accommodated in the case having the same height and depth, a plurality of capacitor elements having a round cross-sectional shape, Multiple of the same oval, the same large oval (the oval is further enlarged and flattened into a single piece), and the stacked type (the one wound around the large diameter is cut into two) In this case, it can be seen that the large oval is the most efficient. Considering only the volumetric efficiency, a multilayer capacitor with a rectangular film laminated can achieve volume efficiency close to 100%. However, a large-sized multilayer capacitor is produced by laminating a thin film and cutting it. It is difficult to do this, and it has been found that there is a problem with the breakdown voltage and a high potential gradient cannot be obtained.

  However, in order to fabricate the large-sized oval capacitor element, a method of fabricating a large circular capacitor element and processing it into a flat shape is the most suitable method for mass production. The strength of the core becomes a big problem, and if the core material is too thick and too strong, it is difficult to remove the core holding jig (not shown) after winding. Further, as shown in FIG. In addition, there is a problem that the capacitor element is swollen as the core is returned to the original state after the processing, and the capacitor element is swollen after the processing.

  On the other hand, if the material of the core is too thin and the strength is too weak, a part of the core moves together with the core holding jig when the core holding jig (not shown) is pulled out after winding. As shown in FIG. 9, the strength of the capacitor element after flattening, such as protruding from the end face of the capacitor element, or wrinkles in the core as shown in FIG. 9 as the capacitor element tries to return to the original state after processing. There was a problem that the desired shape could not be maintained due to weakening.

  An object of the present invention is to solve such a conventional problem and to provide a metallized film capacitor which has a large capacity, is reduced in size and thickness to improve volumetric efficiency, and is excellent in productivity and reliability. It is.

In order to solve the above problems, the present invention provides a metallized film in which a metal vapor-deposited electrode is formed on a dielectric film made of polypropylene. In a metallized film capacitor consisting of a capacitor element formed in a cross-sectional oblong shape by turning and flattened, and a pair of extraction electrodes provided on both end faces of the capacitor element, the capacitor element is formed in an oblong shape. When the major axis of the cross section is a and the minor axis is b, a / b = 3 or more, a = 60 mm or more, and a polypropylene film having a thickness of 3 to 10 times the thickness of the dielectric film constituting the metallized film using a winding core wound 5-10 turns, and the dimension from the core to the outer peripheral surface of the capacitor element and 14mm below the end of the core less Together also welded part by heat sealing, it is of structure in which a plurality of recesses in the heat-sealed portion.

  As described above, the metallized film capacitor according to the present invention sets the strength of the core to an optimum value even when the flatness of the capacitor element having a cross section is increased and the capacity is increased. Therefore, it is possible to achieve a metalized film capacitor that has a large capacity, is small and thin, improves volumetric efficiency, and is excellent in productivity, heat dissipation, and reliability. It is.

(Embodiment 1)
Hereinafter, the first and third aspects of the present invention will be described with reference to the first embodiment.

  1A and 1B are a front view and a perspective view showing a capacitor element constituting a metallized film capacitor according to Embodiment 1 of the present invention. In FIG. 1, 1 is a core and 2 is polypropylene. A metallized film having a metal vapor-deposited electrode formed on a dielectric film made of a metal film, and the metallized film 2 is wound around the outer surface of the core 1 while the core 1 is held by a core holding jig (not shown). The capacitor element 3 is configured by rotating and winding the winding core holding jig (not shown) from the winding core 1 after winding.

  The metal vapor-deposited electrode is divided by an oil margin, and each divided electrode is connected in parallel by a fuse of the vapor-deposited electrode and has a self-security mechanism.

  In addition, the capacitor element 3 according to the present embodiment is wound in a columnar shape as shown in FIG. 1A, and then crushed from the vertical direction in the drawing as shown in FIG. 1B. It is flattened, and a symbol t in the figure indicates a dimension from the core 1 to the outer peripheral surface of the capacitor element 3.

  Specific examples will be described below.

Example 1
A metallized film composed of a dielectric film made of polypropylene having a thickness of 3 μm and a width of 80 mm is used and wound on the core so that the dimension from the core to the outer peripheral surface of the capacitor element is 7.8 mm. A capacitor element having a capacitance of 150 μF was produced. Subsequently, this is flattened so that the major axis a of the capacitor element cross section is 78.4 mm, the minor axis b is 15.6 mm, a / b is about 5.0, and the volume efficiency of the capacitor element is 95. It was set to 7%. The result of measuring the ripple heat generation ΔT (K) at the center of the capacitor element is shown in Table 1 together with the specifications of the capacitor element together with each example described below.

(Example 2)
By setting the dimension from the winding core to the outer peripheral surface of the capacitor element to 9.4 mm, the major axis a of the capacitor element cross section to 65.9 mm, and the minor axis b to 18.8 mm, a / b is about 3.5, The device was fabricated in the same manner as in Example 1 except that the volume efficiency of the device was 93.3%.

(Example 3)
When the dimension from the winding core to the outer peripheral surface of the capacitor element is 10.2 mm, the major axis a of the capacitor element cross section is 61.2 mm, and the minor axis b is 20.4 mm, a / b is 3.0, and the capacitor element This was produced in the same manner as in Example 1 except that the volumetric efficiency of was 91.8%.

Example 4
By setting the dimension from the winding core to the outer peripheral surface of the capacitor element to 11.3 mm, the major axis a of the capacitor element cross section to 55.6 mm, and the minor axis b to 22.6 mm, a / b is about 2.5, The device was manufactured in the same manner as in Example 1 except that the volume efficiency of the device was 90.7%.

(Example 5)
By setting the dimension from the winding core to the outer peripheral surface of the capacitor element to 14.0 mm, the major axis a of the capacitor element cross section to 46.8 mm, and the minor axis b to 28.0 mm, a / b is about 1.7. The device was manufactured in the same manner as in Example 1 except that the volume efficiency of the device was 83.4%.

(Example 6)
By setting the dimension from the winding core to the outer peripheral surface of the capacitor element to 15.1 mm, the major axis a of the capacitor element cross section to 44.3 mm, and the minor axis b to 30.2 mm, a / b is about 1.5, The device was manufactured in the same manner as in Example 1 except that the volume efficiency of the device was 80.0%.

(Example 7)
By setting the thickness of the dielectric film to 3.5 μm, the dimension from the core to the outer peripheral surface of the capacitor element to 10.0 mm, the major axis a of the capacitor element cross section to 82.7 mm, and the minor axis b to 20.0 mm, It was fabricated in the same manner as in Example 1 except that a / b was about 4.2 and the volume efficiency of the capacitor element was 52.3%.

(Example 8)
By setting the thickness of the dielectric film to 4 μm, the dimension from the core to the outer peripheral surface of the capacitor element to 13.4 mm, the major axis a of the capacitor element cross section to 80.2 mm, and the minor axis b to 26.8 mm, It was fabricated in the same manner as in Example 1 except that b was about 3.0 and the volume efficiency of the capacitor element was 31.0%.

  In addition, the calculation of the volumetric efficiency in (Table 1) is obtained by the following (Equation 1).

  FIGS. 2A to 2D are cross-sectional views of capacitor elements fabricated according to Example 1, Example 2, Example 4, and Example 6, and FIG. 3 illustrates capacitors obtained according to the above examples. It is the characteristic figure which showed the relationship between the volume efficiency of an element, and the ripple heat_generation | fever of the capacitor | condenser element center.

  As apparent from Table 1 and FIG. 3, the ripple heat generation at the center of the capacitor element decreases as the flatness ratio a / b, which is the ratio of the major axis a to the minor axis b of the flattened capacitor element, increases. I understand that. It can also be seen that the smaller the dimension from the winding core to the outer peripheral surface of the capacitor element, the smaller the ripple heat generation at the center of the capacitor element. This means that since the heat generation is highest in the center of the capacitor element, the heat generation can be suppressed by reducing the total thickness of the wound dielectric film.

  Further, in Examples 7 and 8, the volume efficiency is lowered due to the increase in the thickness of the dielectric film. In particular, in Example 8, the volume efficiency is significantly lowered.

  As described above, the metallized film capacitor according to this embodiment suppresses the ripple heat generation at the center of the capacitor element to be small when the thickness of the dielectric film is 3.5 μm or less and the aspect ratio a / b is 3.0 or more. It is something that can be done.

(Embodiment 2)
Hereinafter, the invention according to the fourth aspect of the present invention will be described with reference to the second embodiment.

  In the metallized film capacitors of Example 1, Example 2, and Example 3 manufactured in the first embodiment, evaluation was performed by changing the specifications of the core used for the capacitor.

  4 (a) and 4 (b) are perspective views showing the configuration of the core used in the metallized film capacitor according to the second embodiment of the present invention, and FIG. 4 (a) shows the core without heat sealing. FIG. 4 (b) shows a core with heat seal.

  In FIG. 4, 4 and 5 indicate cores, and the cores 4 and 5 are made of a polypropylene film which is the same material as the dielectric film forming the metallized film, and the thickness thereof is 3 to 10 of the dielectric film. The thickness is doubled and wound by 5 to 10 turns. In FIG. 4B, a heat seal portion 5a formed by welding the terminal portion is provided.

  Specific examples will be described below.

(Example 1-1)
A polypropylene film having a thickness of 10.5 μm was wound for 10 turns, and a winding core provided with a heat seal portion was prepared by welding the terminal portion, and a capacitor element similar to that of Example 1 was manufactured using this winding core. The external appearance of this capacitor element and the results of measuring and evaluating the time to reach a capacity reduction of 5% in a life test at 90 ° C., 600 V, 30 Arms, together with the specifications of the core, together with each example described below Shown in (Table 2).

(Example 1-2)
A polypropylene film having a thickness of 12 μm was produced in the same manner as in Example 1-1 except that the film was wound for 8 turns.

(Example 1-3)
A polypropylene film having a thickness of 18 μm was prepared in the same manner as in Example 1-1 except that the film was wound 8 turns.

(Example 1-4)
A polypropylene film having a thickness of 35 μm was produced in the same manner as in Example 1-1 except that it was wound for 5 turns.

(Example 1-5)
A polypropylene film having a thickness of 18 μm was wound for 8 turns and produced in the same manner as in Example 1-1 except that the heat seal part was not provided.

(Example 1-6)
A polypropylene film having a thickness of 3 μm was produced in the same manner as in Example 1-1 except that 30 turns were wound.

(Example 1-7)
A polypropylene film having a thickness of 38 μm was produced in the same manner as in Example 1-1 except that it was wound for 5 turns.

(Example 2-1)
A polypropylene film having a thickness of 18 μm was wound for 8 turns, and a winding core having a heat seal portion was prepared by welding the terminal portion, and a capacitor element similar to that of Example 2 was manufactured using this winding core.

(Example 2-2)
A polypropylene film having a thickness of 100 μm was produced in the same manner as in Example 2-1, except that it was wound for one turn.

(Example 3-1)
A polypropylene film having a thickness of 18 μm was wound for 8 turns, and a winding core having a heat seal portion was prepared by welding the terminal portion, and a capacitor element similar to that of Example 3 was manufactured using this winding core.

(Example 3-2)
A polypropylene film having a thickness of 100 μm was produced in the same manner as in Example 3-1, except that it was wound for one turn.

(Example 3-3)
A polypropylene film having a thickness of 250 μm was wound for one turn and produced in the same manner as in Example 3-1, except that the heat seal portion was not provided.

  As apparent from (Table 2), in the case of Example 1-6 in which the polypropylene film constituting the core has a thin thickness of 3 μm, the strength of the core is too weak, so When the tool is removed, a part of the core moves together with the core holding jig and protrudes, causing not only a poor appearance but also a large capacity reduction rate.

  Even in Example 1-5 in which the polypropylene film constituting the core has a thickness of 18 μm, the strength of the core is low when the terminal portion is not welded (the heat seal portion is not provided). For this reason, wrinkles are generated in the winding core to cause poor appearance, and the capacity reduction rate is also increased.

  On the other hand, in Example 1-7 in which the polypropylene film constituting the core has a thickness as thick as 38 μm, the core is too strong, so that it swells to return to its original state after flattening. Example 2-2, Example 3-2, and Example in which the thickness of the polypropylene film was increased to 100 μm and 250 μm. In the case of 3-3, this phenomenon appears remarkably.

  From the above results, the core used for the metallized film capacitor according to the present embodiment is configured by winding 5 to 10 turns of a polypropylene film having a thickness of 3 to 10 times the dielectric film thickness constituting the metallized film. Is most preferable.

  In addition, it is preferable to improve the strength of the core by welding the terminal end of the core configured in this way to provide a heat seal portion, and further to provide a plurality of recesses in the heat seal portion. Is more preferable because a more stable strength can be obtained.

  In addition, a metallized film capacitor that achieves higher performance by providing a split electrode on a metal vapor-deposited electrode formed on a dielectric film and providing a self-safety function that is formed by connecting the split electrode in parallel with a fuse. Can be realized.

  As described above, the metallized film capacitor according to the present invention has a large capacity, a small size and a thin shape, improves volumetric efficiency, and has an excellent effect of being excellent in productivity and reliability. Not only can the number of capacitor elements be reduced to reduce the dead space, but also the number of soldering points can be reduced, so it is possible to reduce the man-hours and reduce costs. is there.

  The metallized film capacitor according to the present invention has an effect that the volume efficiency can be improved by reducing the size and thickness, and the capacity can be increased, and is particularly useful for smoothing an inverter circuit for driving a motor of a hybrid vehicle. It is.

(A) The front view which showed the capacitor | condenser element which comprises the metallized film capacitor by Embodiment 1 of this invention, (b) The perspective view (A) Cross-sectional view of capacitor element according to Example 1, (b) Cross-sectional view of capacitor element according to Example 2, (c) Cross-sectional view of capacitor element according to Example 4, (d) According to Example 6 Cross section of capacitor element Characteristic diagram showing the relationship between the volumetric efficiency of the capacitor element and ripple heat generation at the element center obtained by the same embodiment (A), (b) The perspective view which showed the structure of the core used for the metallized film capacitor by Embodiment 2 of this invention (A) Plan sectional view showing the structure of a conventional metallized film capacitor, (b) Front sectional view of the same Conceptual diagram for estimating volumetric efficiency due to the shape of the capacitor element Front view showing the swelling phenomenon of the capacitor element Plan view showing the core protrusion phenomenon of the capacitor element Front view showing wrinkles generated on the core of the capacitor element

Explanation of symbols

1, 4, 5 Core 2 Metallized film 3 Capacitor element 5a Heat seal part

Claims (2)

A metallized film in which a metal-deposited electrode is formed on a dielectric film made of polypropylene is wound on a winding core so that the pair of metal-deposited electrodes are opposed to each other with the dielectric film interposed therebetween, and is flattened. In the metallized film capacitor composed of the capacitor element formed in the above and a pair of extraction electrodes provided on both end faces of the capacitor element, the major axis of the cross section formed in the oval shape of the capacitor element is a, A core obtained by winding 5 to 10 turns of a polypropylene film having a thickness of 3 to 10 times the thickness of the dielectric film constituting the metallized film. the use, the dimension from the core to the outer peripheral surface of the capacitor element and 14mm below the welding by heat sealing at least a portion of the end of the winding core Rutotomoni, metalized film capacitor having a plurality of recesses in the heat-sealed portion. The metallized film capacitor according to claim 1, wherein the dielectric film constituting the capacitor element has a thickness of 3.5 μm or less.

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