JP2014187278A - Aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polar aluminum electrolytic capacitor of automotive electrical apparatus, in which abnormal characteristic change and appearance abnormality do not occur, even if a voltage is applied in the reverse direction.SOLUTION: A capacitor element 1 manufactured by winding an anode foil 2 having a voltage-withstanding film formed thereon and a cathode foil 3 not having the voltage-withstanding film, with a separator 4 interposed therebetween, is impregnated with a nonaqueous electrolyte and housed in a bottomed cylindrical outer case 5, and then the opening of the outer case is sealed with a sealing member 6, and the anode lead terminal 2a of the anode foil and the cathode lead terminal 3a of the cathode foil are led out while penetrating the sealing member 6. In such an aluminum electrolytic capacitor, moisture contained in the electrolyte in the outer case 5 is in a range of 0.05-0.5%.

Description

  The present invention relates to an aluminum electrolytic capacitor. More specifically, the present invention relates to a polar aluminum electrolytic capacitor that does not cause a large characteristic change and appearance abnormality even when a reverse voltage of 14 V DC is applied at room temperature, and that is particularly suitable for automotive use. It is.

  In producing an aluminum electrolytic capacitor, first, as shown in FIG. 2A, an anode foil 2 made of an aluminum material on which a pressure-resistant film (oxide film) is formed, and an aluminum material as a counter electrode having no pressure-resistant film. A capacitor foil 1 is obtained by winding a cathode foil 3 made of

  Then, the capacitor element 1 is impregnated with an electrolytic solution, and the capacitor element 1 is accommodated in a bottomed cylindrical outer case (aluminum case) 5 as shown in FIG. Sealed with a sealing member 6 made of a rubber material or the like, and the anode lead terminal 2a connected to the anode foil 2 and the cathode lead terminal 3a connected to the cathode foil 3 penetrate the sealing member 6 to the outside. Then, the outer case 5 is covered with an insulating sleeve 7 to obtain an aluminum electrolytic capacitor as a final product (see, for example, Patent Documents 1 and 2).

  Such an aluminum electrolytic capacitor is polar because the pressure-resistant film formed on the anode foil 2 by chemical conversion has a rectifying property, and the cathode foil 3 is not subjected to chemical conversion treatment to give a pressure resistance. The cathode foil 3 has essentially no breakdown voltage.

  By the way, among the in-vehicle batteries, for example, in the R type and the L type, the positions of the positive (+) terminal and the negative (-) terminal are reversed, and the positive / negative polarity is confused. A reverse voltage may be applied to the aluminum electrolytic capacitor for in-vehicle use due to a connection error of the operator (reverse connection of (+) and (−)).

  This reverse connection causes an important problem for aluminum electrolytic capacitors for in-vehicle use. For example, when a DC voltage of 14 V is applied to an aluminum electrolytic capacitor in the reverse direction, moisture present in the capacitor is electrolyzed, and oxygen generated thereby reacts with the cathode foil to form an oxide film on the surface of the cathode foil. The characteristics (capacitance and tan δ) of the capacitor deteriorate.

  In addition, when the capacitor characteristics are severely deteriorated, the capacitor runs out of heat due to heat generation due to reverse current, and the gas generated inside the capacitor bursts, causing the in-vehicle electrical circuit to malfunction. Things will happen.

  If it is a bipolar (bipolar) aluminum electrolytic capacitor having a pressure-resistant film (oxide film) on both the anode foil and the cathode foil, the problems caused by the reverse connection as described above hardly occur.

  However, bipolar aluminum electrolytic capacitors are larger in size than current polar aluminum electrolytic capacitors, and the characteristics of the capacitors are also different, so they can be applied directly to existing in-vehicle electrical circuits as a substitute for polar capacitors. I can't. In addition, the cost is greatly increased.

Japanese Patent Laid-Open No. 10-32146 (see paragraph 0002) Japanese Patent Laid-Open No. 11-26317 (see paragraph 0002)

  Accordingly, an object of the present invention is to provide an aluminum electrolytic capacitor for in-vehicle use that is polar but does not cause an abnormal characteristic change or appearance abnormality even when a reverse voltage of -14 VDC is applied. is there.

  In order to solve the above-described problems, the present invention provides a capacitor element in which an anode foil made of an aluminum material having a pressure-resistant film and a cathode foil made of an aluminum material having no pressure-resistant film are wound through a separator. An aqueous lead electrolyte is impregnated and accommodated in a bottomed cylindrical outer case, the opening of the outer case is sealed with a sealing member, an anode lead terminal connected to the anode foil, and the cathode In an aluminum electrolytic capacitor that has been commercialized by pulling out the cathode lead terminal connected to the foil through the sealing member, in order to withstand reverse voltage application up to DC 14V, The present invention is characterized in that it is used in an in-vehicle electrical circuit that uses a battery of an automobile as a power source, in which the moisture contained in the electrolytic solution is in a range of 0.05 to 0.5 wt%. To have.

  After commercialization, in order to further reduce moisture contained in the electrolyte solution, an aging treatment is performed by applying a predetermined DC voltage to the capacitor element in the positive direction for a predetermined time via the anode lead terminal and the cathode lead terminal. It is preferable to apply.

  More preferably, the DC voltage applied during the aging process after commercialization is 5 to 9 V higher than the rated voltage of the aluminum electrolytic capacitor, and the application time is at least 40 minutes.

  Moreover, it is preferable that the said electrolyte solution is a phthalic acid amidine salt type electrolyte solution which uses (gamma) -butyrolactone as a main solvent.

  The aluminum electrolytic capacitor according to the present invention has a characteristic that the rate of change in capacitance after applying a reverse voltage of 14 V DC for 10 minutes after standing at room temperature for 300 hours is −0.42% or less.

  In addition, the aluminum electrolytic capacitor according to the present invention has a characteristic that the capacity change rate after applying a reverse voltage of 14 V DC for 10 minutes after standing at room temperature for 3000 hours is −0.60% or less.

  Moreover, the aluminum electrolytic capacitor by this invention is rated 35V1000microF, and the said electrolyte solution is an electrolyte solution for 125 degreeC high temperature long life low impedance.

  In a polar aluminum electrolytic capacitor, when a reverse voltage is applied, electrolysis of moisture present in the electrolyte causes an electrode reaction, a film formation reaction on the cathode foil side, and a hydrogen gas generation reaction on the anode side. According to the present invention, the moisture contained in the electrolytic solution in the product is reduced to the range of 0.05 to 0.5 wt%, so that the electrode reaction at the time of reverse voltage application is rate-controlled, and the reaction current (reverse) Therefore, an aluminum electrolytic capacitor can be obtained in which the capacitance change of the capacitor is small, no heat is generated, gas generation is reduced, the internal pressure of the capacitor does not increase, and no appearance abnormality occurs.

  In addition, the aluminum electrolytic capacitor according to the present invention is the same size as the current product, and has a specification capable of withstanding a reverse voltage of −14 V particularly for in-vehicle use while maintaining the same characteristics and reliability as the current product. Therefore, it is possible to mount an existing in-vehicle electrical circuit without changing the design, and it has extremely high industrial value.

The graph which shows the reverse voltage application test result of a prototype product. (A) The typical perspective view which decomposes | disassembles and shows a part of foil wound type capacitor | condenser element, (b) Sectional drawing which shows the aluminum electrolytic capacitor as a final product.

  Next, an embodiment of the present invention will be described, but the present invention is not limited to this embodiment. In addition, about the reference code of the component of an aluminum electrolytic capacitor, the reference code of FIG. 2 is used.

  Although the aluminum electrolytic capacitor of the present invention is used for in-vehicle use, as explained in FIG. 2, the basic configuration is as follows: anode foil 2, cathode foil 3, separator 4, outer case (aluminum case) 5, sealing A member 6 and a driving electrolyte are provided.

For the anode foil 2, for example, an aluminum material having a pressure-resistant film (oxide film) on the surface thereof with a foil capacity in the range of 16.0 to 18.6 μF / cm ² is used. In this embodiment, the formation voltage for forming the pressure-resistant film is set to 65.5 V or more.

  For the cathode foil 3, an aluminum material having a purity of 99.8% in which almost no foreign metal is present on the foil surface is preferably employed. In addition, when copper alloy aluminum foil in which copper is present on the foil surface is used, if the activation energy of the copper dissolution reaction is low among the copper dissolution reaction and the aluminum foil film formation reaction, the reverse current response current is A copper alloy aluminum foil is not preferable because it is assumed to flow easily.

  An anode lead terminal 2a and a cathode lead terminal 3a are attached to the anode foil 2 and the cathode foil 3 by caulking or the like, and these lead terminals 2a and 3a are tab terminals made of aluminum material formed in a feather plate shape. What a CP wire (copper covering steel wire) was welded to a round bar portion may be used.

A material similar to the conventional material may be used for the separator 4, but the density is 0.3 g / cm ³ and the thickness is 50 μm in consideration of the impedance characteristics of the product and the operating voltage with a rating of 35 V in this embodiment. It is preferable to use a high strength and low density double separator.

  Also in this embodiment, as shown in FIG. 2 (a), the anode foil 2 and the cathode foil 3 are driven by a capacitor element 1 formed by spirally winding a separator 4 between them. In this embodiment, a non-aqueous 125 ° C. high-temperature long-life low-impedance electrolyte solution containing an organic solvent of γ-butyrolactone, sulfolane, and ethylene glycol and an amidine phthalate salt added thereto is impregnated in this embodiment. Is used.

  In order to guarantee the high temperature of 125 ° C. required for in-vehicle use, the acid is most preferably phthalic acid, which is an aromatic carboxylic acid with high thermal stability. Benzoic acid also has high heat resistance, but the desired conductivity cannot be obtained. The most suitable base is tetramethylimidazolium, which has the highest solubility among amidines.

  In addition, in an ammonium adipate salt electrolyte solution of ethylene glycol solvent containing 50% moisture, a current of 100 mA or more may flow immediately after applying a reverse voltage to generate heat. In this way, when moisture is present in abundance, the cathodic conversion current flows greatly. On the other hand, the non-aqueous amine phthalate salt has a reverse voltage characteristic equivalent to that of the amidine salt. Therefore, in the present invention, the use of an aqueous electrolyte solution is excluded.

  Also in this embodiment, the capacitor element 1 impregnated with the electrolytic solution is housed in a bottomed cylindrical outer case (aluminum case) 5 as shown in FIG. Sealed with a sealing member 6 made of a rubber material or the like, and the anode lead terminal 2a connected to the anode foil 2 and the cathode lead terminal 3a connected to the cathode foil 3 penetrate the sealing member 6 to the outside. An aluminum electrolytic capacitor as a finished product (final product) is obtained by preferably covering the outer casing 5 with the insulating sleeve 7.

  The capacitor element 1 may be impregnated with the electrolytic solution after being accommodated in the outer case 5. Further, the sealing member 6 has a pair of lead terminal insertion holes, is arranged in the opening of the outer case 5 in a state where the lead terminals 2a and 3a are inserted, and is firmly attached by caulking or the like.

  In the present invention, in order to be able to withstand reverse voltage application up to DC 14V due to reverse connection of the on-vehicle battery, the moisture contained in the electrolyte in the finished product state is in the range of 0.05 to 0.5 wt%. .

  The electrolyte is an important factor that affects the characteristics of the capacitor, but if it does not contain any moisture, it will not be used for the slit surface of the anode foil or the lead terminal crimped portion of the anode foil in the aging process performed in the manufacturing process. An oxide film cannot be formed on the chemical conversion part. The aging in this manufacturing process is usually performed by applying a voltage in the positive direction at a temperature of 85 ° C. or higher after impregnation with the electrolytic solution in order to form an oxide film on the unformed part. The voltage is applied for at least 40 minutes until the current is reduced within the leakage current.

  Therefore, although some amount of moisture is contained in the electrolytic solution, the amount of water necessary for forming the oxide film is, for example, 1 mg or less for a product having a rating of 35 V 1000 μF, an outer diameter of 12.5 mm, and an axial length of 25 mm. It is only a small amount of about 5 wt% of the water content in it. Therefore, there is no problem even if the moisture contained in the electrolytic solution is 0.05 to 0.5 wt%.

  Analyzing the electrolyte in the current product (for example, the RKD series aluminum electrolytic capacitor rated at 35V1000μF manufactured by the applicant), the moisture composition is 0.5wt% of the moisture contained in the electrolyte itself from the beginning. It was found that the moisture content possessed by the capacitor element was 1.0 wt%, the process moisture absorption absorbed during the process from the electrolyte impregnation to the sealing was 1.1 wt%, and the total was 2.6 wt%.

  Among these, moisture in the process can be reduced by performing the steps from the electrolytic solution impregnation to the sealing in a dry box having a low humidity, for example, a dew point of −30 to −55 degrees. The separator contains about 7% of its weight by weight, but the moisture in the separator can be almost removed by the capacitor element drying step (for example, hot air drying at 85 ° C. for 1 hour).

  Also, as described above, the aging process is performed in the manufacturing process. After the product is commercialized, if the aging process is performed by applying a positive voltage, moisture is used to repair the oxide film and to form the oxide film in the unformed part. Therefore, the water in the electrolyte can be further reduced accordingly. Therefore, it is preferable to perform aging treatment even after commercialization.

  In order to reduce the characteristic change after application of reverse voltage, it is preferable that the aging voltage after commercialization is high. However, if the voltage is too high, there is a risk of short-circuiting. Is good. The aging time is also long, for example, preferably about 1 hour, but at least 40 minutes are required.

  As a countermeasure for applying a reverse voltage of DC 14V, the moisture in the electrolytic solution may be lower than 0.05 wt%. However, in that case, the formation or repair of an oxide film by aging treatment, the oxide film formation reaction of an unformed part It takes a long time and becomes the rate-limiting (bottleneck) of the manufacturing process, which is not preferable in terms of productivity.

  Phthalic acid amidine salt electrolyte using γ-butyrolactone as a solvent with a moisture content (all wt%) of 0.20%, 0.50%, 1.00%, 1.50%, 3.0% Hereinafter, five types of “electrolyte solutions” were prepared.

  Capacitor elements (5 pieces) rated at 35V1000μF (outer diameter 12.5mm, shaft length 25mm) were left in a hot air dryer at 85 ° C for 1 hour to remove moisture, and then humidity controlled glove box (dew point- 30 to -55 degrees dry box), each capacitor element was impregnated with the above-mentioned electrolytes having different moisture contents, assembled and sealed, and then taken out from the glove box, and as an aging process for commercialization, 85 A positive voltage of 40 V DC was applied for 1 hour in an atmosphere at 0 ° C. to prepare five samples (aluminum electrolytic capacitors).

  Each sample was allowed to stand at room temperature for 300 hours, and then a reverse voltage of DC 14V (−14V) was applied for 10 cycles (1 minute as one minute) for a total of 10 minutes, and the reverse current flowing through the sample was measured. Table 1 in the following table shows the reverse current value (mA) measured for each cycle, the presence or absence of heat generation, and the capacity change rate after 10 cycles. Moreover, the transition of the reverse current flowing through each sample is shown in FIG.

  According to this, when the water content of the electrolytic solution is 3%, the reverse current greatly increases from 20.5 to 90 (mA), there is also heat generation, and the capacity change rate is -4.2. % And big.

  When the water content of the electrolytic solution was 1.00% and 1.50%, although the increase rate of the reverse current was lower than that of 3%, both generated heat, and the rate of change in capacity was also that of the electrolytic solution. With a water content of 1.00%, a capacity change rate of -1.20%, a water content of the electrolyte of 1.50%, a capacity change rate of -1.80%, and a DC 14V reverse voltage application measure It is insufficient as a product.

  In contrast, when the water content of the electrolyte is 0.50%, the reverse current decreases from 11.1 to 8.6 (mA), there is no heat generation, and the capacity change rate is − It is suppressed to a small value of 0.42%, and it can be used as a countermeasure against DC 14V reverse voltage application.

  Similarly, in the case of 0.20% where the water content of the electrolytic solution is further reduced, the reverse current is decreased from 8.4 to 6.8 (mA), there is no heat generation, and the capacity change rate. Was 0.00%, that is, the capacity did not change, and a very good result was obtained as a countermeasure against reverse voltage application of DC 14V.

  Thus, since the moisture content of the electrolytic solution is 0.20% and the capacity change rate is 0.00% without heat generation, it is possible to further reduce the moisture content of the electrolytic solution to less than 0.20%. Although there is not much meaning, if it is less than 0.05%, as described above, it takes a long time for the aging treatment, so the lower limit of the moisture content is preferably 0.05%.

  Next, as another test, five samples of the same electrolyte solution having a water content of 0.20% to 3.0% were prepared and allowed to stand for 3000 hours (125 days) at room temperature. A reverse voltage was applied for 10 cycles (total 10 minutes) with 1 cycle as 1 minute, the capacity change rate after 10 cycles was calculated, and an appearance inspection was performed. The results are shown in Table 2 below.

  In another test, when the water content of the electrolytic solution is 1.50% and 3.00%, both ruptures occur, which is the worst result. Moreover, when the water content of the electrolyte is 1.00%, it does not lead to rupture, but the sealing rubber swells and the capacity change rate is -6%, so that it cannot be used as a product. became.

  On the other hand, when the water content of the electrolytic solution is 0.50%, the capacity change rate is -0.60%, which is slightly larger than the capacity change rate in the 300 hour test -0.42%. However, there is no abnormality in the external appearance, and it can be used as a DC 14 V reverse voltage application countermeasure product.

  Further, in the case of 0.20% where the water content of the electrolytic solution is further reduced, the capacity change rate is 0.00%, that is, the capacity does not change, there is no abnormality in the appearance, and a reverse voltage of 14V DC is applied. A very good result was obtained as a countermeasure product.

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode foil 2a Anode lead terminal 3 Cathode foil 3a Cathode lead terminal 4 Separator 5 Exterior case (aluminum case)
6 Sealing material (sealing rubber)

Claims (7)

A bottomed cylinder is formed by impregnating a non-aqueous electrolyte into a capacitor element formed by winding an anode foil made of an aluminum material with a pressure-resistant film and a cathode foil made of an aluminum material without a pressure-resistant film through a separator. An exterior lead case connected to the anode foil, and a cathode lead terminal connected to the cathode foil. In the aluminum electrolytic capacitor that has been commercialized by penetrating the sealing member,
In order to be able to withstand reverse voltage application up to a direct current of 14 V, a battery of an automobile in which the moisture contained in the electrolytic solution in the outer case is in a range of 0.05 to 0.5 wt% is used as a power source. An aluminum electrolytic capacitor characterized by being used in an on-vehicle electrical circuit.   2. The product according to claim 1, wherein after the commercialization, an aging treatment is performed by applying a predetermined DC voltage to the capacitor element in a positive direction for a predetermined time through the anode lead terminal and the cathode lead terminal. Aluminum electrolytic capacitor.   The DC voltage applied at the time of the aging process after commercialization is 5 to 9 V higher than the rated voltage of the aluminum electrolytic capacitor, and the application time is at least 40 minutes. Aluminum electrolytic capacitor.   The aluminum electrolytic capacitor according to any one of claims 1 to 3, wherein the electrolytic solution is a phthalic acid amidine salt electrolytic solution containing γ-butyrolactone as a main solvent.   The aluminum electrolysis according to any one of claims 1 to 4, wherein a capacity change rate after applying a reverse voltage of 14V DC for 10 minutes after standing at room temperature for 300 hours is -0.42% or less. Capacitor.   6. The aluminum electrolysis according to claim 1, wherein a capacity change rate after applying a reverse voltage of 14 V DC for 10 minutes after standing at room temperature for 3000 hours is −0.60% or less. Capacitor.   The aluminum electrolytic capacitor according to any one of claims 1 to 6, wherein the electrolytic solution has a rating of 35 V and 1000 µF, and the electrolytic solution is a 125 ° C high-temperature long-life low-impedance electrolytic solution.