JP2007081006A - Case mold type capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize and thin a case mold type capacitor used for a hybrid automobile, or the like, and also to increase its capacity. <P>SOLUTION: In the case mold type capacitor in which a metallized film capacitor element 1 connected by bus bars 2, 3 is stored in a case 4 for molding by resin, the metallized film capacitor element 1 and the case mold type capacitor are realized, where a metallized film in which a metal vapor-deposited electrode is formed on a PP film is wound on a winding core; a flattened element whose section is in an oval shape is formed; the winding core in which the PP film where a/b is equal to 3 or higher, a is equal to 60 mm or higher, and the PP film which is three to ten times thicker than a dielectric film thickness when the long and short diameters of the element section are denoted as a and b, respectively, is used for winding five to ten times; the distance from the winding core to the outer-periphery surface of the element is set to 14 mm or smaller to optimize the strength of the winding core, and volumetric efficiency is improved by increasing capacity and by miniaturization and thinning. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in various electronic devices, electrical devices, industrial devices, automobiles, and the like, and in particular, a case mold using a metallized film capacitor that is most suitable for smoothing, filtering, and snubbing of an inverter circuit for driving a motor of a hybrid vehicle. Type capacitor.

  In recent years, metallized film capacitors used in inverter devices have been actively developed for downsizing, high performance, and low cost. In addition, since metallized film capacitors used in inverter devices are required to have a high operating voltage, large current, large capacity, etc., a plurality of capacitor elements connected in parallel are accommodated in a case. A case mold type capacitor in which a resin is cast in a case has been developed and used.

  FIGS. 7A and 7B are a front sectional view and a side sectional view showing the structure of this type of conventional case mold type capacitor. In FIG. 7, 11 is a capacitor in which a metallized film is wound or laminated. Element 12 is a capacitor case containing the capacitor element 11, 13 is an epoxy resin filled in the capacitor case 12, 14 is a urethane resin filled on the epoxy resin 13, and 15 is connected to the capacitor element 11. A connection terminal for connecting to an external device or the like, 16 is an opening portion of the capacitor case 12 for casting into a resin casting portion, and 17 is a pair of electrodes provided at both ends of the capacitor element 11.

  The capacitor element 11 is formed by winding a metallized film having a metal vapor-deposited electrode on one or both sides so that the pair of metal vapor-deposited electrodes are opposed to each other with a dielectric film therebetween, and the cross section is formed in an oval or oval shape. A pair of electrodes 17 are provided on both end faces, and a plurality of these are arranged. The connection terminal 15 is connected to each electrode 17 of the plurality of capacitor elements 11 so that the capacitor elements 11 can be connected in parallel and further connected to the outside. The capacitor case 12 houses the capacitor element 11 and incorporates a part of the connection terminal 15. A part of the connection terminal 15 protrudes from the capacitor case 12 so that it can be connected to an external device or the like.

  Further, the epoxy resin 13 is cast from the case opening 16 into the capacitor case 12, and after being cured, the urethane resin 14 is cast. As shown in FIG. 7B, the epoxy resin 13 is cast. A two-layer structure of resin 13 and urethane resin 14 was adopted.

  The conventional case mold type capacitor configured as described above has the capacitor element 11 covered with an epoxy resin 13 excellent in heat resistance, moisture resistance, and insulation resistance, and then has elasticity on the epoxy resin 13 layer and cracks. By forming a difficult urethane resin 14 layer, it is possible to obtain a case mold type capacitor that has excellent heat resistance, moisture resistance, and insulation resistance and can improve environmental resistance such as a heat shock test. It was.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2003-338423 A

  However, in the conventional case mold type 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. When trying to improve the volumetric efficiency, further flattening is necessary, and this has many problems.

  That is, in order to fabricate the flat 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 strength of the core is too strong, it is difficult to pull out the core after winding, and it is difficult to process it flat, and bulges occur to return to the original after processing, Conversely, if the strength of the core is too weak, there is a problem that the strength of the capacitor element after flattening becomes weak and the desired shape cannot be maintained.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a case-molded capacitor that solves such conventional problems, improves volume efficiency by reducing the size and thickness, and is excellent in productivity and reliability. It is.

  In order to solve the above-mentioned problems, the present invention connects at least one metallized film capacitor element with a bus bar provided with a terminal portion for external connection at one end, and accommodates this in a case so that at least the terminal of the bus bar. In the case mold type capacitor which is resin-molded except for the part, the metallized film capacitor element includes a metallized film in which a metal vapor-deposited electrode is formed on a dielectric film made of polypropylene, and a pair of metal vapor-deposited electrodes through the dielectric film. The capacitor element is formed by flattening by winding on a winding core so as to face each other, and a pair of extraction electrodes respectively provided on both end faces of the capacitor element. A / b = 3 or more, where a = 60 mm when the major axis of the cross section formed in the oval is a and the minor axis is b, a = 60 mm Using a core in which a polypropylene film having a thickness of 3 to 10 times the dielectric film thickness constituting the metallized film is wound for 5 to 10 turns, the dimension from the core to the outer peripheral surface of the capacitor element is The configuration is 14 mm or less.

  As described above, the case mold type capacitor according to the present invention sets the strength of the core to an optimum value even if the flatness of the capacitor element having a cross section is increased and the capacity is increased. Therefore, it is possible to realize a metallized film capacitor element that has a large capacity, a small size and a thin shape, and has improved volumetric efficiency and heat dissipation, and this metallized film capacitor element can be used to reduce the size and thickness. Therefore, an effect that a case mold type capacitor having excellent reliability can be realized.

(Embodiment)
Hereinafter, the invention described in the entire claims of the present invention will be described using embodiments.

  FIG. 1 is a perspective view showing the configuration of a case mold type capacitor according to an embodiment of the present invention. FIGS. 2 and 3 are perspective views before molding. In FIGS. 1 shows a metallized film capacitor element formed in a metallized film capacitor element 1, in which a metallized film having a metal-deposited electrode formed on one or both sides of a dielectric film made of polypropylene is a pair of metallized films. The P-electrode 1a and the N-electrode 1b are respectively provided by forming metallized electrodes with zinc sprayed on both end faces, and details will be described later.

  Reference numeral 2 denotes a P-pole bus bar made of a tin-plated copper plate to be joined to the P-pole electrode 1 a side of the metallized film capacitor element 1, and 2 a denotes a tongue-like solder that serves as an electrode provided at one end of the P-pole bus bar 2 The part 2b is a P pole terminal for external connection provided so as to be drawn out from the P pole bus bar 2, and the P pole bus bar 2 is configured in a flat plate shape obtained by punching a plate-like base material. Is.

  3 is an N-pole bus bar made of a tin-plated copper plate to be joined to the N-pole electrode 1 b side of the metallized film capacitor element 1, and 3 a is a tongue-like solder that serves as an electrode provided at one end of the N-pole bus bar 3. And 3b are N pole terminals for external connection provided so as to be drawn out from the N pole bus bar 3, and the N pole bus bar 3 is formed into a metallized film capacitor element after punching a plate-like base material. The soldering portion 3a is bent from one end of the main plane portion that is in contact with the peripheral surface of 1 and the N-pole terminal 3b is bent in the opposite direction from the other end.

  Reference numeral 4 denotes a resin case for housing the metallized film capacitor element 1 in which the P-pole bus bar 2 and the N-pole bus bar 3 are joined and connected. In this way, the P-pole bus bar 2 and the N-pole bus bar 3 are joined. The metallized film capacitor element 1 housed in the case 4 is molded by a mold resin (not shown) in a state where the P-pole terminal 2b and the N-pole terminal 3b are adjacently exposed from the same side of the case 4. It is composed.

  4 (a) and 4 (b) are a front view and a perspective view showing the capacitor element constituting the metallized film capacitor element 1. In FIG. 4, 5 is a core, and 6 is a dielectric film made of polypropylene. A metallized film having a metal vapor-deposited electrode formed thereon, and the metallized film 6 is wound around the outer surface of the core 5 in a state where the core 5 is held by a core holding jig (not shown). A capacitor element is formed by extracting a core holding jig (not shown) from the core 5.

  Note that the capacitor element according to the present embodiment is flattened after being wound into a columnar shape as shown in FIG. 4A and then being crushed from the vertical direction in the drawing as shown in FIG. 4B. It has become. Moreover, the symbol t in the figure indicates the dimension from the core 5 to the outer peripheral surface of the capacitor element.

  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. 5A to 5D are cross-sectional views of capacitor elements fabricated according to Example 1, Example 2, Example 4, and Example 6, and FIG. 6 illustrates capacitors obtained according to the above examples. It is the characteristic figure which showed the relationship between the volumetric efficiency of an element, and the ripple heat generation | occurrence | production of a capacitor | condenser element center.

  As apparent from Table 1 and FIG. 6, 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.

  Thus, the metallized film capacitor according to the present embodiment is a capacitor element that maintains high volumetric efficiency when the thickness of the dielectric film is 3.5 μm or less and the flatness ratio a / b is 3.0 or more. Central ripple heat generation can be kept small.

  Next, using the capacitor elements of Example 1, Example 2, and Example 3 above, the characteristics when the specifications of the winding core used in the capacitor element were changed were evaluated.

  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 having 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. Together with each of the examples described below, the 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, along with the specifications of the core 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 3 μm was produced in the same manner as in Example 1-1 except that 30 turns were wound.

(Example 1-6)
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.

  As apparent from (Table 2), in the case of Example 1-5 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.

  On the other hand, in Example 1-6 using a thick polypropylene film constituting the core of 38 μm, the strength of the core is too strong, so that it swells to return to its original state after flattening. Not only causes poor appearance, but also has a large capacity reduction rate. Further, in Examples 2-2 and Example 3-2 in which the thickness of the polypropylene film is increased to 100 μm, this phenomenon occurs. Appears prominently.

  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.

  As described above, the case mold type capacitor according to the present invention can be reduced in size and thickness and increased in capacity at the same time by using a metallized film capacitor element that has a large capacity and is reduced in size and thickness to improve volume efficiency. It will be like that.

  In addition, the reduction in dead space and the effective use of the device can be achieved with the reduction in size and thickness as well as the increase in capacity, thereby making it possible to use different types of metallized film capacitor elements, which were previously impossible. It can also be accommodated in a case. One of the most effective types of metallized film capacitor elements of different types is a combination of a smoothing capacitor and a noise removing capacitor. Furthermore, these types of metallized film capacitor elements can be combined using the same bus bar. By connecting, there is an extraordinary effect that further downsizing and cost reduction can be achieved. The noise removing capacitor means a snubber capacitor that absorbs a surge voltage, a common mode capacitor (Y-type capacitor) that removes noise in a radio frequency band, or the like.

  The case mold type capacitor according to the present invention has an effect that it is possible to simultaneously realize a reduction in size and thickness and an increase in capacity, and is particularly useful for smoothing an inverter circuit for driving a motor of a hybrid vehicle.

The perspective view which showed the structure of the case mold type capacitor by one embodiment of this invention Perspective view before mold Perspective view before mold (A) Front view of capacitor element constituting metallized film capacitor element, (b) Perspective view (A) Cross-sectional view of the capacitor element fabricated according to Example 1, (b) Cross-sectional view of the capacitor element fabricated according to Example 2, (c) Cross-sectional view of the capacitor element fabricated according to Example 4 (D) Sectional drawing of the capacitor | condenser element produced by the Example 6 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) Plan sectional view showing the configuration of a conventional case mold type capacitor, (b) Side sectional view of the same

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metallized film capacitor | condenser element 1a P pole electrode 1b N pole electrode 2 P pole bus bar 2a, 3a Soldering part 2b P pole terminal 3 N pole bus bar 3b N pole terminal 4 Case 5 Core 6 Metallized film

Claims (8)

A case mold type capacitor in which at least one metallized film capacitor element is connected by a bus bar provided with a terminal portion for external connection at one end, is accommodated in a case, and at least the terminal portion of the bus bar is removed and resin molded. The metallized film capacitor element is formed by winding a metallized film, in which a metal vapor-deposited electrode is formed on a dielectric film made of polypropylene, on a core so that the pair of metal vapor-deposited electrodes are opposed to each other through the dielectric film. The capacitor element is formed into an oval cross-sectional shape by flattening and a pair of extraction electrodes provided on both end faces of the capacitor element, and the major axis of the cross-section formed in the oval shape of the capacitor element is defined as a When the minor axis is b, a / b = 3 or more, a = 60 mm or more, and the metallized film is formed. A case mold type using 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, and having a dimension from the core to the outer peripheral surface of the capacitor element of 14 mm or less Capacitor. The case mold type capacitor according to claim 1, wherein the thickness of the dielectric film constituting the metallized film capacitor element is 3.5 μm or less. The case mold type capacitor according to claim 1, wherein the rated capacity of the metallized film capacitor element is 150 μF or more, and the potential gradient at the time of rating is 150 V / μm or more. The case mold type capacitor according to claim 1, wherein the polarity of a pair of extraction electrodes respectively formed on the plurality of metallized film capacitor elements is aligned, and a pair of bus bars are connected to the pair of extraction electrodes. 2. The case mold type capacitor according to claim 1, wherein the external connection terminal portions respectively provided on the pair of bus bars are taken out from the same side. The case mold type capacitor according to claim 1, wherein metallized film capacitor elements of different types are accommodated in the same case. 7. The case mold type capacitor according to claim 6, wherein different types of metallized film capacitor elements are connected using the same bus bar. The case mold type capacitor according to claim 6, wherein a smoothing capacitor and a noise removing capacitor are used as the metallized film capacitor elements of different types.

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