JP5945684B2 - Case mold type capacitor - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used in various electronic equipment, electrical equipment, industrial equipment, automobiles, etc., and in particular, a metallized film capacitor that is optimal for smoothing, filtering, and snubbing of a motor drive inverter circuit of a hybrid car is accommodated in a case. And a resin-molded case mold type capacitor.

  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, which is friendly to the global environment.

  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 as a capacitor used in connection with such an electric motor. In addition, the trend of adopting metalized film capacitors with a very long life is conspicuous due to the demand for maintenance-free in the market.

  Such metallized film capacitors are roughly classified into those generally using a metal foil as an electrode and those using a deposited metal provided on a dielectric film as an electrode. Among these, metallized film capacitors that use vapor-deposited metal as an electrode (hereinafter referred to as metal vapor-deposited electrode) have a smaller volume occupied by the electrode compared to that of metal foil and can be reduced in size and weight. High reliability in dielectric breakdown due to recovery function (capacity of metal evaporated electrode around the defective part evaporates and scatters and insulates when the short-circuit occurs in the defective part) Therefore, it has been widely used conventionally.

  In addition, when the metallized film capacitor configured as described above is used for HEV, it is strongly required to increase the withstand voltage, increase the current, increase the capacity, etc. of the operating voltage. A case mold type capacitor in which a metallized film capacitor is housed in a case and a mold resin is cast in the case has been developed and put into practical use.

  The configuration of a conventional case mold type capacitor is shown in FIG. In FIG. 6, reference numeral 10 denotes a capacitor element. The capacitor element 10 is a metallized film in which a metal vapor-deposited electrode is formed on one or both sides of a dielectric film made of polypropylene, and a pair of metal vapor-deposited electrodes are opposed to each other through the dielectric film. The positive electrode and the negative electrode are respectively provided by forming a metallicon electrode which is wound as described above and sprayed with zinc on both end faces.

  11 is a positive bus bar, 11a is a positive terminal for external connection provided at one end of the positive bus bar 11, and this positive bus bar 11 is made of a metal plate, and a plurality of the capacitor elements 10 are arranged in close contact with each other. Each of the capacitor elements 10 is joined to a positive electrode formed on one end face thereof, and the positive electrode terminal 11a is pulled out above the capacitor element 10 and exposed from a case 13 described later. .

  Reference numeral 12 denotes a negative electrode bus bar, and 12a denotes a negative electrode terminal for external connection provided at one end of the negative electrode bus bar 12. The negative electrode bus bar 12 is also made of a metal plate, and, like the positive electrode bus bar 11, a plurality of the capacitor elements 10 are provided. In a state of being in close contact with each other, the negative electrode formed on the other end face of each capacitor element 10 is joined to each other, and the negative electrode terminal 12a is pulled out above the capacitor element 10 and is exposed from a case 13 described later. Thus, a plurality of capacitor elements 10 are connected.

  13 is a case made of polyphenylene sulfide (hereinafter referred to as PPS) resin, 14 is a mold resin filled in the case 13, and the mold resin 14 includes a plurality of pieces connected by the positive electrode bus bar 11 and the negative electrode bus bar 12. The capacitor element 10 is resin-molded in a case 13.

  The conventional case mold type capacitor configured as described above is obtained by molding the capacitor element 10 in the case 13 with the mold resin 14 having excellent heat resistance, moisture resistance, and insulation resistance. By using PPS which is excellent in mechanical strength, heat resistance and water resistance and can withstand harsh use conditions, it is possible to provide a case mold type capacitor with higher reliability than before.

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

JP 2006-319300 A

  However, since the above conventional case mold type capacitor is used in applications other than the conventional in-vehicle use, for example, in a severe condition where a large current of 50 to 100 A is input at a high frequency. The positive electrode terminal 11a and the negative electrode terminal 12a generate heat, heat is propagated together with the current applied from the input side, and the positive electrode bus bar 11 and the negative electrode bus bar 12 generate heat.

  When the positive electrode bus bar 11 and the negative electrode bus bar 12 generate heat, heat is sequentially propagated from the capacitor element 10 closest to the positive electrode terminal 11a and the negative electrode terminal 12a to the adjacent capacitor element 10, and the temperature of all the capacitor elements 10 is increased. As a result, the characteristics of the case mold type capacitor deteriorate.

  This is because the current flowing through the metal plate, which is a bus bar, is concentrated on the surface of the metal plate due to the skin effect, and the current does not flow through the center of the plate thickness.

  To solve this, it can be solved by increasing the surface area of the metal plate, but if the surface area of the metal plate is increased, the case also becomes larger, creating a useless space in the case, and filling the space with the mold resin 14 Therefore, there is a problem that the weight of the case mold type capacitor is increased and the cost is increased.

  The present invention solves such a conventional problem, is small and lightweight, efficiently suppresses heat generation by efficiently flowing the current flowing through the bus bar, makes it difficult to propagate heat to the capacitor element, and has a long life with excellent heat resistance. An object of the present invention is to provide a case mold type capacitor.

In order to achieve the above object, the present invention provides a case-molded capacitor comprising a capacitor element, a pair of bus bars connected to a pair of electrodes of the capacitor element, and a resin-molded case containing the capacitor element. The bus bar includes a resin-molded conductor, an external connection terminal provided at an end of the conductor, and an electrode connection portion that protrudes from the side of the conductor and is connected to the electrode of the capacitor element. a, conductive body, have a hollow and through hole penetrating from the outside into the hollow portion, and the said hollow portion, characterized in that the resin is composed of flat tube filled.

  In the present invention, by making the conductor of the bus bar into a hollow flat tube, the current flowing from the terminal portion for external connection to the conductor flows uniformly to the thickness of the flat tube due to the skin effect of the conductor. If the surface area is the same as when using a conventional metal plate, the current flows efficiently and the heat dissipation effect is excellent even when the flat tube is thinned and the cross-sectional area of the bus bar is reduced. Thus, the case mold type capacitor can have a long life. In this case, the material cost of the bus bar can be reduced.

  Also, if the cross-sectional area when using a conventional metal plate is the same, even if the current flowing through the bus bar is increased, the conductor is hollow, so the heat capacity is small and the heat dissipation efficiency is good. A case mold type capacitor can be provided.

The perspective view of the case mold type capacitor in this Embodiment 1 The perspective view showing the structure of the conductor of the bus bar Perspective view of the case mold type capacitor of the comparative example The perspective view of the case mold type capacitor in this Embodiment 2 The perspective view of the case mold type capacitor in this Embodiment 3 Perspective view of a conventional case mold type capacitor

(Embodiment 1)
FIG. 1 is a perspective view of a case mold type capacitor according to the present embodiment. In FIG. 1, a capacitor element 21 has a pair of metallized films (not shown) in which a metal such as aluminum is vapor-deposited on one or both sides of a dielectric film such as polypropylene, and the metallized film is interposed through the dielectric film. The electrodes 21a are formed by thermal spraying zinc or the like on both end faces of the capacitor element 21.

  The bus bar 22 includes a long conductor 22a, a terminal portion 22b for external connection provided at an end of the conductor 22a in the longitudinal direction, and an electrode connection portion 22c connected to each electrode 21a of the capacitor element 21. Is provided. The electrode connection part 22c of the bus bar 22 is connected to each electrode of the plurality of capacitor elements 21 and connected in parallel. The terminal portion 22 b for external connection is disposed so as to be exposed from the opening of the case 24.

  The conductor 22a of the bus bar 22 is formed of a hollow flat tube. By making the inside of the flat tube hollow, even if a high-frequency large current flows, it flows through the entire thickness of the flat tube due to the skin effect, resulting in excellent current efficiency.

  The structure of the flat tube 22a is shown in FIG. As the flat tube 22a, for example, a copper tube that has been crushed, a copper plate that is bent into a cylindrical shape, and the cylindrical shape that has been crushed can be used. By making the hollow thickness c thinner than the wall thickness b of the flat tube 22a, it is possible to reduce the height of the case mold type capacitor. Further, since the thickness of the flat tube can be made thinner than that of the conventional metal plate, a heat dissipation effect can be expected, and the material cost can be reduced.

  Even if a large current is input from the outside, the terminal portion 22b for external connection has a structure in which one end of the conductor 22a is crushed and bent at a predetermined length a to be overlapped. Heat generation of the terminal portion 22b can be suppressed, and a current can be efficiently passed through the conductor 22a.

  The electrode connecting portion 22c has a configuration in which a plate piece such as copper is attached to each side of the conductor 22a for each electrode of the capacitor element 21.

  The bus bar 23 has the same configuration as the bus bar 22 and is connected to the other electrode of the capacitor element 21.

  The case 24 needs to be made of a material having good affinity with the filling resin in order to stably hold the filling resin (not shown). Polyphenylene sulfide is preferred as satisfying this requirement. Moreover, when giving priority to heat dissipation, metal cases, such as aluminum, can also be used.

  Thermosetting epoxy resin or the like is used as the filling resin. However, in order to withstand rapid temperature changes and cooling cycles, the thermal expansion coefficient of the case 24 and the filling resin are made close to prevent cracks in the filling resin and the case 24. Therefore, it is preferable to contain an inorganic filler. The inorganic filler may be mainly composed of an inorganic material such as alumina or silica, and the content is preferably about 30 to 80 parts by weight with respect to 100 parts by weight of the filled resin.

  In the case mold type capacitor according to the first embodiment configured as described above, when the conductor 22a of the bus bar 22 is formed into a hollow flat tube, the surface area when the conventional metal plate is used is the same. Since the cross-sectional area of the bus bar 22 can be reduced by reducing the thickness of the flat tube, the current flows efficiently and the heat dissipation effect is excellent, so the temperature of the bus bar 22 does not increase, and the length of the case mold type capacitor Lifespan can be improved.

  Also, if the cross-sectional area when using a conventional metal plate is the same, even if the current flowing through the bus bar 22 is increased, the conductor 22a is hollow, so the heat capacity is small and the heat dissipation efficiency is good. A case mold type capacitor for large current can be provided.

  Here, regarding the case mold type capacitor of the first embodiment and the case mold type capacitor when the metal plate (copper plate) is used for the bus bars 32 and 33 shown in FIG. The results of the life test are shown in (Table 1).

  The bus bar of the first embodiment is a flat tube (a = 20, b = 1.0, c = 0.2) shown in FIG. 2 by pressing a copper tube (φ13 mm, wall thickness 0.4 mm). Was used. The bus bars 32 and 33 of Comparative Example 1 were 20 mm wide and 1.0 mm thick.

  The conditions of the life test are as follows: when the temperature is 100 ° C., the load voltage is 750 V, the ripple current is 50 Arms (frequency: 100 kHz), the time when the capacity change rate reaches −5% is calculated, and the comparative example 1 is 100 The index of.

  The exothermic temperature of the bus bar is the highest temperature of the bus bar when the life test is performed, and is a value increased from a temperature of 100 ° C.

  As apparent from (Table 1), with the ripple current applied even in the bus bar having the same outer dimensions, in the first embodiment, the temperature rise can be suppressed to about 0.52 times that of Comparative Example 1, It was confirmed that the lifetime of the capacitor was extended 1.45 times by reducing the influence of the temperature rise of the bus bar on the capacitor element.

(Embodiment 2)
FIG. 4 is a perspective view of the case mold type capacitor of the second embodiment. In FIG. 4, the bus bars 43 and 44 are made up of conductors 43a and 44a, external connection terminal portions 43b and 44b, and electrode connection portions (not numbered).

  Here, the conductors 43a and 44a and the electrode connecting portion are the same as those in the first embodiment. The terminal portions 43b and 44b for external connection are configured in a cylindrical shape.

  By using the terminal portions 43b and 44b for external connection as described above, the external connection portion can be formed into a simple bar shape. Further, the connection method is a simple method in which a rod-like shape is inserted and crimped or welded, so that the connection current loss can be reduced, and the heat generation of the bus bars 43 and 44 can be reduced.

(Embodiment 3)
FIG. 5 is a perspective view of the case mold type capacitor of the third embodiment. In FIG. 5, the same as the first embodiment, except that the conductor of the bus bar has several through holes.

  By providing through holes 55 at predetermined intervals in the bus bars 53 and 54, when the capacitor element connected to the bus bars 53 and 54 is inserted into the case and filled resin is injected, the hollow shape of the flat tube which is a conductor is formed. Since the resin is filled in, the skin effect can be secured by maintaining the insulating property without contact in the flat tube even when a large current is passed, so that a case mold type capacitor suitable for a large current can be provided. .

  The case mold type capacitor according to the present invention is excellent in the current efficiency of the bus bar and can be designed at a low cost, a small size and a light weight when a plurality of capacitors are accommodated in one case and resin molded. This is useful for smoothing an inverter circuit for driving a motor of an automobile.

21 Capacitor element 21a Electrode 22, 23 Bus bar 22a Conductor 22b Terminal portion for external connection 22c Electrode connection portion 24 Case

Claims (3)

A capacitor element;
A pair of bus bars connected to a pair of electrodes of the capacitor element;
In a case mold type capacitor having a capacitor element and a resin molded case,
The bus bar is
A resin-molded conductor;
A terminal portion for external connection provided at the end of the conductor;
An electrode connecting portion that protrudes from the side of the conductor and connects to the electrode of the capacitor element
Conductive body, hollow and have a through hole penetrating from the outside into the hollow portion, and the case mold type capacitor, characterized in that the said hollow portion is configured from flat pipe resin is filled. The case mold type capacitor according to claim 1, wherein the flat tube has a plurality of the through holes. The case mold type capacitor according to claim 1 , wherein the through holes are provided in the flat tube at a predetermined interval.

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