JP4930099B2 - Case mold type capacitor - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used in various electronic equipment, electrical equipment, industrial equipment, automobiles, and the like. The present invention relates to a 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.

  However, in such a metallized film capacitor, the metallized film capacitor itself vibrates due to an alternating current (ripple) current, and noise generated due to this vibration may be a problem. In particular, when such a metallized film capacitor is used for smoothing an inverter circuit for HEV, since the switching frequency is an audible frequency of several kHz to 15 kHz, it is used for automobiles that require high quietness. When doing so, it is necessary to reduce the noise as much as possible.

  Until now, various proposals have been made to reduce the noise caused by the ripple current of the film capacitor.

For example, as a means for reducing the noise by the capacitor itself, a liquid insulator such as 25 mm ² / s at 25 ° C. is formed on a capacitor element formed by laminating and winding a metallized plastic film having an electrode film on the surface of a dielectric film. By impregnating methyl hydrogen silicone oil, which is a low-viscosity crosslinking reactive monomer, and then heating to 130 ° C. for 15 minutes or 100 ° C. for 60 minutes to polymerize methyl hydrogen silicone oil to increase the viscosity. A capacitor manufacturing method has been proposed that can suppress the vibration of the capacitor that occurs when an AC voltage is applied (Patent Document 1).

  In addition, as a means for reducing noise in a metallized film capacitor of a type in which a metallized film capacitor is placed in a resin case and molded with resin, the present applicant shows the following FIGS. 11A and 11B. I have a proposal like this.

  11 (a) and 11 (b) are a front sectional view and a side sectional view showing the structure of the metallized film capacitor, in which 11 is a wound capacitor element composed of a metallized film, Reference numeral 12 denotes a resin case, 13 denotes a connection terminal, 13a denotes a bus bar for connecting the electrode portions of the capacitor element 11, 14 denotes a filling resin, and 15 denotes a sound absorbing and soundproofing material.

The conventional metallized film capacitor configured as described above has a configuration in which a sound absorbing and soundproof material 15 made of urethane foam is disposed between the outer surface of the capacitor element 11 and the inner surface of the resin case 12. 11 was able to suppress the propagation of 11 vibrations to the outside, enhance the sound insulation effect, and reduce the noise to the outside (Patent Document 2).
JP 2004-303934 A JP 2005-93515 A

  However, in the above conventional metallized film capacitor (Patent Document 1) or in a resin-molded state placed in a resin case (Patent Document 2), vibration is suppressed and noise is reduced. However, it has been a problem to suppress the vibration of the film capacitor element from being transmitted to the case, and the vibration from being transmitted through the member that is in contact with or fastened to the case to generate noise. In particular, when used for hybrid vehicles, high quietness is required, so it has been important to solve this problem.

  For example, for the purpose of assembling to a metal inverter box mounted on a vehicle, a metallized film capacitor placed in a resin case and resin molded as described in Patent Document 2 is further replaced with a metal case (such as an aluminum die-cast case). When housed inside, the vibration may be propagated through the joint between the metal case and the resin case, and the noise will be reduced as much as possible by further suppressing vibration. There was a problem that it was necessary.

  Also, film capacitors tend to increase vibration due to ripple current when the temperature is raised, which is also a problem.

  An object of the present invention is to solve such a conventional problem and to provide a case mold type capacitor capable of reducing the generation of noise by suppressing the vibration generated in the metallized film capacitor. It is.

In order to achieve the above object, the present invention eliminates the terminal portion provided on the bus bar by housing the metallized film capacitor to which the bus bar having the terminal portion for external connection at one end is connected in a resin case. In the case mold type capacitor molded by resin, the resin case is formed of polyphenylene sulfide mixed with an elastomer, and the blending amount of the elastomer with respect to the polyphenylene sulfide is 1 wt% or more and 10 wt% or less. It is.

  As described above, the case mold type capacitor according to the present invention blends an elastic elastomer into the case material polyphenylene sulfide so that even if the metallized film capacitor vibrates due to the ripple current, the vibration is made of resin. Since it can be mitigated by the case, the vibration propagated through the resin case is greatly reduced, and as a result, the effect that noise generation can be reduced can be obtained. is there.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing the configuration of a case mold type capacitor according to Embodiment 1 of the present invention (in order to make the configuration easy to understand, the mold resin described later is omitted), and FIG. 2 is the case mold type. FIG. 1 is a cross-sectional view showing a configuration of a capacitor. In FIGS. 1 and 2, reference numeral 1 denotes a metallized film capacitor. A metallized film is formed by winding a metallized film electrode so that the metal vapor-deposited electrode faces the dielectric film, and a pair of metallicon electrodes are formed by metal spraying on both ends of the element. It is.

  2 and 3 are a pair of bus bars, 2a and 3a are external connection terminal portions provided at one ends of the bus bars 2 and 3, respectively. In the embodiment, 5 pieces) are soldered to the pair of metallicon electrodes formed on both end faces of the metallized film capacitor 1 in an aligned state via soldering portions 2b and 3b as shown in FIG. Thus, a plurality of metallized film capacitors 1 are connected in parallel. The capacitance is 1000 μF because one element is 200 μF.

  Reference numeral 4 denotes a resin case in which a plurality of metallized film capacitors 1 connected in parallel by the bus bars 2 and 3 are housed. In the present embodiment, the material of the resin case 4 is PPS ( A material obtained by adding an elastomer as an elastic body to (polyphenylene sulfide) was used. At this time, the compounding amount of the elastomer was adjusted so that the flexural modulus of the resin case 4 was 15000 MPa or less. In this embodiment, a PPS material blended with 3% by weight elastomer was used. The thickness of the resin case 4 was 2 mm.

  In FIG. 2, 5 is a mold resin cast in the resin case 4, and the mold resin 5 is made up of external connection terminal portions 2 a and 3 a provided at one end of the bus bars 2 and 3. A plurality of metallized film capacitors 1 and bus bars 2 and 3 are covered in a state where they are exposed from a case 4 made of epoxy. In this embodiment, an epoxy resin is used.

  In the present embodiment, a PPS material in which 3% by weight of an elastomer is blended is used. However, the effect of reducing vibration is exhibited at 1% by weight to 10% by weight.

  (Table 1) shows the blending amount of elastomer, (1) vibration acceleration when a ripple current of 100 kHz of 10 kHz flows, (2) audibility test, (3) elastic modulus of case material, (4) 2 kHz of case material, 25 The result of investigating the relationship of the loss coefficient in ° C., (5) high temperature and high humidity bias test, and (6) cold shock test results is shown.

  In (1), the vibration amount was measured by attaching an acceleration pickup for vibration level measurement to the side of the case. In (2), it was confirmed whether it can be heard by the human ear from a distance of 5 m under the current condition of (1). (3) and (4) are the results of measuring physical property values of the case material. (5) shows the results of a high-temperature and high-humidity test under conditions in which a temperature of 85 ° C., a relative humidity of 85%, and a bias voltage of 600 V are continuously applied. In (6), a pass / fail judgment was made based on whether cracks occurred in the case at −40 ° C. to 120 ° C. and 3000 cycles.

  From Table 1, it was found that when the amount of the elastomer is 1% by weight or more, vibration is reduced, that is, noise is reduced, and when it exceeds 10% by weight, there is a problem in moisture resistance. In order to reduce vibration, the loss factor of the case material is important. By increasing the blending amount of the elastomer, the loss factor increases and there is a vibration damping effect due to ripple current. Since the amount of elastomer blended was 1% by weight or more, the level was inaudible in the audibility test.

  In addition, in the bias test at high temperature and high humidity, when the elastomer exceeded 10% by weight, the capacity reduction was 5% or more, which was rejected. In the thermal shock test, when the elastomer was 0.5% by weight or less, a case crack was generated, but when it was 1% by weight or more, the toughness was increased and no crack was generated.

  3 and 4 show frequency characteristics of the loss factor of the case material at 25 ° C and 80 ° C. In the first embodiment, the amount of elastomer is 3% by weight in the present embodiment, and Comparative Example 1 shows a case where there is no elastomer in the same configuration.

  The first embodiment has a high loss coefficient in a wide frequency range (10 Hz to 10 kHz), and can be expected to be effective in attenuating vibration caused by a ripple current. Further, it was confirmed that the same effect was obtained even at 80 ° C., and that the material exhibited the effect even at a high temperature.

  FIG. 5 shows a result of comparison between the vibration acceleration due to the ripple current of the capacitor in the cases of the first embodiment and the comparative example 1 at 25 ° C. and 80 ° C. The ripple current is the result when 100 Arms is passed with a sine wave of 10 kHz. The capacitor of Comparative Example 1 has the same structure except that only the case material uses PPS that does not contain an elastomer.

  When Embodiment 1 and Comparative Example 1 are compared, the amount of vibration in Embodiment 1 is reduced and the increase in vibration at high temperature is reduced due to the effect of elastomer blending. As a problem of the film capacitor, there is a case where vibration increases at a high temperature, but the increase width can be reduced by using the technique of the first embodiment.

  According to the case mold type capacitor configured in this way, the resin case 4 is blended with an elastomer, which is an elastic body, so that the flexural modulus is 15000 MPa or less. It is possible to suppress vibrations generated by current or the like.

  This is because, conventionally, a case material made of PPS as a main component is used for the resin case 4, and the reason is that metalized film capacitors used for automobiles have surroundings such as temperature and humidity. This is because PPS was a material having excellent heat resistance, moisture resistance, and strength under severe environmental conditions.

  Thus, it is useful to use a strong material, that is, a material having a high elastic modulus, for the resin case 4 in order to secure heat resistance, moisture resistance, and strength of the fixing portion.

  However, since the elastic modulus of the material constituting the resin case 4 is high, vibration generated from components in the resin case 4 is easily propagated. In the first place, when it is used for smoothing an inverter circuit for HEV, since the switching frequency is an audible frequency in a high frequency region of several kHz to 15 kHz, it is difficult to suppress the vibration.

  Furthermore, PPS has low toughness and is fragile, so it is easily broken by impact, and cracks are likely to occur when the wall thickness is reduced.

  On the other hand, according to the embodiment of the present invention, the bending elastic modulus of a general PPS is about 17000 MPa, but the bending elastic modulus of the resin case 4 is 15000 MPa or less. Propagation can be suppressed, absorbency against impact can be increased, and cold shock resistance can also be improved. Further, since the occurrence of cracks can be suppressed as compared with PPS not containing an elastomer, the resin thickness of the case can be further reduced.

  Here, in order to reduce the loss factor and the flexural modulus of the resin case 4, an elastomer is added to the PPS as the material of the case 4 in the present embodiment, but the elastomer is a glass transition temperature below room temperature. It is a resin material with In particular, by blending at 1% to 10% by weight with respect to PPS, it has the characteristics of having heat resistance, moisture resistance, and thermal shock resistance as well as vibration suppression.

  In particular, when used in automobile applications, the product size increases, and the amount of mold resin 5 filled in the resin case 4 often increases, and the product is subjected to a thermal shock called a heat cycle. In addition, the thermal stress of expansion and contraction of the mold resin 5 is increased, and by using the resin case 4 as in the present embodiment, it is possible to withstand this thermal stress.

  The elastomer of the present invention has heat resistance such as silicone and urethane, and any effect can be expected as long as it has a glass transition temperature below room temperature.

(Embodiment 2)
6 is an exploded perspective view showing the configuration of a case mold type capacitor according to an embodiment of the present invention (in order to make the configuration easy to understand, the mold resin described later is omitted), and FIG. 7 is the case mold type. It is sectional drawing which showed the structure of the capacitor | condenser.

  Reference numeral 4a denotes a fixing portion provided on the outer surface of the resin case 4 shown in the first embodiment, and reference numeral 6 denotes a plurality of metallized film capacitors 1 connected in parallel by the bus bars 2 and 3. A metal outer case 6a that accommodates a resin case 4 that is accommodated and molded with resin, 6a is a fixing portion provided in the outer case 6. In the present embodiment, aluminum is used as the material of the outer case 6. The exterior case 6 and the resin case 4 are fixed to each other by fixing the fixing portions 6a and 4a provided on both sides through bolts or the like (not shown).

  (Table 2) shows the results of examining whether the fixing portion 6a is broken by a torque of 13 N · m with M6 bolts by changing the elastomer content.

  When the elastomer exceeded 10% by weight, the torque resistance strength was lowered, and the fixing portion 6a was broken. From this result, it was found that, if the elastomer is increased too much, the strength is lowered, so that it is necessary to make the fixing portion at most 10% by weight or less.

  FIG. 8 shows the vibration acceleration by the ripple current of the second embodiment. The acceleration pickup, which is a measuring element for measuring the vibration acceleration, was attached to the fastening portion between the resin case 4 and the metal outer case 6 for measurement. For Comparative Example 2, the same capacitor was used except that a PPS case containing no elastomer was used.

  Similar to the first embodiment, the vibration damping effect of the resin case 4 was smaller than that of the comparative example 2 even when the vibration was measured with the outer case 6. Moreover, the increase width of the vibration accompanying the temperature rise could be reduced.

(Embodiment 3)
FIG. 9 shows the configuration of the third embodiment. The third embodiment is the same as the second embodiment except that the seventh cushioning material layer is disposed between the resin case 4 and the outer case 6 in the second embodiment.

  The buffer material layer 7 is provided in a gap provided between the resin case 4 and the exterior case 6 except for the fixing portions 4a and 6a. In the present embodiment, the buffer layer 7 A urethane resin is used as the material layer 7.

  In the case mold type capacitor according to the present embodiment, the flexural modulus of the resin case 4 is set to 8000 MPa or more and 15000 MPa or less, and the resin case 4 and the outer case 6 are fixed by the fixing portions 4a and 6a. A ripple current is generated by applying an AC voltage to the metallized film capacitor 1 with a configuration in which a buffer material layer 7 made of urethane resin is provided in a gap provided between the resin case 4 and the outer case 6. Thus, even if the capacitor itself vibrates, this vibration can be mitigated by the resin case 4 and the buffer material layer 7, so that the vibration acceleration transmitted to the outer case 6 can be reduced. As a result, it is possible to obtain a special effect that noise generation can be greatly reduced.

  FIG. 10 shows the vibration acceleration due to the ripple current of the capacitor of the third embodiment. Due to the effect of the PPS case containing the elastomer and the buffer material layer 7, the vibration levels at 25 ° C. and 80 ° C. were almost the same, and the result of suppressing the increase in vibration accompanying the temperature rise was obtained.

  The bending elastic modulus of the resin case 4 is set to 8000 MPa or more. However, if the bending elastic modulus is smaller than 8000 MPa, the torque strength of the fixing portion 4a is weak as shown in (Table 2).

  In the present embodiment, the example in which urethane resin is used as the buffer layer 7 provided in the gap provided between the resin case 4 and the exterior case 6 has been described. It is not limited to the above, and any material that can be disposed in the gap between the resin case 4 and the outer case 6 and that functions as a cushioning material is preferable. Those having an elastic modulus of are effective.

  Further, a material having a large loss factor may be properly used depending on the frequency and temperature of noise to be reduced. For example, other than urethane, an effect similar to that of the present embodiment could be confirmed with epoxy, silicone resin, and the like that are often used as potting resins.

  The case mold type capacitor according to the present invention has an effect that the generation of noise can be greatly reduced by suppressing the vibration generated in the metallized film capacitor, such as a hybrid vehicle that requires particularly high silence. Useful for automobiles.

1 is an exploded perspective view showing a configuration of a case mold type capacitor according to an embodiment of the present invention. Sectional view showing the configuration of the same case mold type capacitor Frequency characteristics graph of loss factor of case material at 25 ° C of the same case mold type capacitor Frequency characteristic graph of loss factor of case material at 80 ℃ of the same case mold type capacitor Graph comparing vibration acceleration due to ripple current of the case mold type capacitor at 25 ℃ and 80 ℃ The disassembled perspective view which showed the structure of the case mold type capacitor | condenser by Embodiment 2 of this invention Sectional view showing the configuration of the same case mold type capacitor Graph comparing vibration acceleration due to ripple current of the case mold type capacitor at 25 ℃ and 80 ℃ The top view which showed the structure of the case mold type capacitor | condenser by Embodiment 3 of this invention Graph comparing vibration acceleration due to ripple current of the case mold type capacitor at 25 ℃ and 80 ℃ (A) Front sectional view showing the configuration of a conventional case mold type capacitor, (b) Side sectional view

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metallized film capacitor 2, 3 Bus bar 2a, 3a Terminal part 2b for external connection 2b, 3b Soldering part 4 Resin case 4a, 6a Fixing part 5 Mold resin 6 Exterior case 7 Buffer material layer

Claims (6)

In a case mold type capacitor in which a metallized film capacitor element to which a bus bar provided at one end with a terminal part for external connection is connected is accommodated in a resin case and resin molded except for the terminal part provided on the bus bar, The resin case is formed of polyphenylene sulfide in which an elastomer is blended, and the blending amount of the elastomer with respect to the polyphenylene sulfide is 1 wt% or more and 10 wt% or less . 2. The case mold type capacitor according to claim 1, wherein the resin case has a flexural modulus of 8000 MPa to 15000 MPa, and the resin case includes a fixing portion. The case mold type capacitor according to claim 1, wherein the case mold type capacitor is coupled into a metal outer case by a fixing portion provided in the resin case. The fixing portion provided in the resin case is coupled to the inside of the metal outer case, and a gap is provided in at least a part between the resin case and the fixing portion of the metal outer case. The case mold type capacitor according to claim 3 , wherein a buffer material layer is provided therein. The case mold type capacitor according to claim 4 , wherein urethane resin is used as the buffer material layer. The case mold type capacitor according to claim 4 , wherein aluminum is used as the metal outer case.

Images