DE647242C - Electrolytic capacitor with one or more top layer electrodes immersed in an electrolyte - Google Patents

Description

Electrolytic capacitor with one or more in an electrolyte Immersed Cover Electrodes The invention relates to electrolytic capacitors with one or more top layer electrodes immersed in an electrolyte.

While with the known capacitors the electrolytes predominantly Consists of aqueous solutions of ionogens, the electrolytic one is characterized Capacitor according to the invention by an electrolyte, which in terms of electrolytic effect essential constituents an alcohol and a dissolved in it Are ionic.

A preferred alcohol for the purpose of the invention is a polyhydric one like glycerin. Although it is already known to use electrolytes in electrolytic capacitors to use that from a solution of the ionogen in water with the addition of a certain amount Amount of glycerin exist, however, such an electrolyte still has the characteristics an aqueous electrolyte as different from the electrolyte of the invention on. According to the invention, the electrolyte consists of an alcohol and one in this dissolved ionogen, and is the ionogen and the alcohol and therefore also the one from it The electrolyte formed is anhydrous or has a maximum water content of Der electrolytic capacitor according to the invention has the following advantages: The Electrolyte does not evaporate or creep, leaving the capacitor indefinitely can be in service for a long time without maintenance.

The top layer is against regression when it is not in use protected, d. H. a non-aqueous solution does not dissolve the top layer, so that the Capacitor can be out of service for a long time without having to be reformatted.

The stability of the cell over long periods is increased.

The leakage flow during the opposite half cycle is reduced.

The freezing point is lowered.

The electrolyte can absorb a large volume of gases, so that the effect of the condenser is not disturbed by the development of gas.

The invention also consists in a method for forming the Cover electrodes for the capacitor. While earlier the top layer electrodes have been formed in aqueous electrolytes, the formation according to the invention the electrode acts in an electrolyte like it does in the finished capacitor is used. The formation of the top layer can, however, also be carried out in an aqueous manner Electrolytes are started. Furthermore, the formation is preferably carried out in such a way that that the electrode and the electrolyte in which it is formed are first one For a while with the poles of an AC power source and then with the poles of a DC power source connects. This procedure can be repeated once or several times. By the new formation process becomes a very strong and durable dielectric Cover layer formed on the electrode. Another benefit of forming the Electrode in an electrolyte of the same quality as that used in the capacitor is that especially with viscous electrolytes, e.g. B. a ..- solution of the ionogen in glycerine, the shaped electrode after removal; _ from the forming bath without removing the adhering forming bath layer can be used in the electrolyte in the capacitor. If the electrode were in to form an electrolyte, which is essentially different from that in the capacitor is used, and it would be immersed in the electrolyte directly from the formation bath placed in the condenser, an adhering coating of the forming bath could be considerable Cause disturbances in the form of high undiclite currents. Would the adhesive coating removed from the forming bath, there would be a great risk of air bubbles between remain seated on the electrode plates.

The term ionogen is intended here to generally include acids, bases, salts and denote other chemical compounds in certain solutions and / or ionize fluid states and form electrically conductive media.

The new capacitor has many new features: features in training and Assemble so that it is stronger, simpler and cheaper Manufacture and assembly enables.

In the drawing are exemplary embodiments of an electrolytic Capacitor according to the invention shown schematically.

Fig. I is a vertical section of a capacitor, Fig. 2 is a plan view Another embodiment, Fig.3 a vertical section according to 3-3 of Fig. 2, Fig..I a horizontal cut after 4-d. Fig. 3, Fig.5 an elevation of the top layer electrode according to fig. i.

The housing io is z. B. made of drawn steel, against rusting outside is plated with cadmium. The housing could of course also be made of other conductive material Material.

The housing contains an electrolyte i i, which is produced thereby is that you get essentially dry, chemically pure glycerine (specific weight not below 1.252 at 20 ° C) heated to about 89 ° C and 31/2 percent by weight sodium bicarbonate Na HCO3, stir in. About 20 minutes are usually enough to completely dissolve whereupon the glycerin is allowed to cool to room temperature. Of course, you can have different ones Use amounts of glycerin and sodium bicarbonate and / or other acids, bases or salts instead of sodium bicarbonate.

. The electrolyte can also be made in a non-liquid form. You can z. B. <free parts by weight of gelatin in one part of glycerine on the steam bath Dissolve and saturate the hot solution with sodium bicarbonate. Other ionogens can can also be used for the non-liquid electrolyte form. By adding a few drops Formaldehyde hardens the jelly quickly and becomes non-liquefiable when it is heated later.

The cover layer electrode 12 is spaced from the housing by a Lid 13, held from an insulating material that is chemically inert, such as. B. a Phenol condensation product.

The top layer electrode consists of several stamped aluminum disks 14 of essentially conical shape or cup shape (Fig. I), the side surfaces protrude upwards so that any air bubbles can escape. These aluminum discs are held at a distance by spacers 15. The discs are on one Aluminum rod 16 lined up and held in position by a washer 17, which is retained on the rod by the head 18. The upper disc is against a bunch of the rod.

A lower sleeve 22 of the cover 13 surrounds the upper part of the rod 16. To prevent chemical or electrolytic effects where the aluminum touches the lid below the surface of the electrolyte (e.g. at 20) a mica disk 2i is provided. This is for successful operation at high levels Tensions are extremely important. The aluminum electrode comes with a phenolic condensate at 2o in contact, a chemical change seems to take place in this, which carbonizes its surface and makes it conductive, so that a leakage current occurs 2o occurs. This causes sparks, which further destroy the skin there and ultimately renders the capacitor unusable. Has the experience of the inventor shown that, if not a disk of mica, celluloid, or other inert Isolation compound separates the skin-clad surface from the phenol condensate, the capacitors at this point will inevitably fail if they are high voltages get abandoned. The importance of sticking the sleeve under the mirror of the electrolyte is known insofar as it results in surface effect through the combined Influence of the air, the spark formation, the electrolyte and the electrolytic Gases at this point is prevented.

The housing io has an annular recess 24 at the top, so that a round seat 25 is formed for the outwardly protruding annular flange 26 of the cover 1,3. The latter is centered by upstanding walls 27 and carries a sealing ring 28 over the the walls 2,7 at 29 are folded over to hold the parts firmly together and the To cover sealing ring. The wall 29 is advantageously against the vertical wall 3o of the lid 13. The sealing ring 28 is preferably made of asbestos with about 100% rubber or other inert insulating material.

At the top, the cover has several ribs 3i, 31 'and annular grooves in between 32, 32 'to complicate the surface conduction and short-circuit the condensate by preventing the electrolyte from creeping over the top of the capacitor. So should liquid flow through the joints around the mica disk 21 or the ring 28 penetrate through it, it would collect in the grooves 32, 32 'before it is removed from the housing part 29 can crawl to the aluminum rod 16, so that electrical leakage is avoided will.

The lid preferably has a small bore 33 under the ring 28 (Fig. I) so that any gases diffuse through the sealing ring or can escape under and around him. This makes the occurrence excessive Pressure in the capacitor and also the outflow of electrolyte when reversing the Condenser prevented.

A clamping post 34 with a perforated horizontal part 35 is on the Aluminum rod preferably attached by dumping the latter (Fig. I) and is preferably made of aluminum in order to have an electrolytic effect in the event of leakage of electrolyte to prevent. Different metals would make a galvanic element and then cause corrosion. To make the soldering of wires easier, a tin-plated brass thimble 3.7 is attached in the hole 38 of the clamp 34.

In the embodiment according to FIGS. 2 to 4, three smaller electrodes are used in a capacitor instead of the cover layer electrode 12 in FIG. They consist of turned aluminum rods 16 'with a shoulder ig' and several disks i4 'arranged at a distance and forming a piece with the rod (Fig. 5). This electrode can be made very cheaply on a lathe or automatic screw cutting machine. The cover 13 'of this embodiment has three downwardly projecting sockets 22, each of which surrounds an aluminum rod and is held at a distance therefrom by mica washer 2i'. The assembly of the wall 29 'and clamp 34' etc. corresponds to Fig. I.

The top layer electrode, which is made up of alternately on the rod after Fig. I arranged punched discs and spacers or the turned aluminum body according to Fig.5, it is first cleaned with an alkali solution and then in an acidic one Solution treated. The electrodes are placed in a 5 percent solution of sodium carbonate immersed at about 70 ° C. The electrodes are moved back and forth in order to achieve the Remove air from between the plates and apply the sodium carbonate solution well to all Allow surfaces to act. All traces of fat are removed in a few seconds, and the surface of the aluminum shows a lightly etched or matt appearance, a foaming gas evolution occurs. The work is done preferentially in iron vessels and requires io or i-5 seconds. This step can be practical omitted as the acid treatment is usually sufficient to remove all impurities to remove and to prepare the surface for effective topcoat formation.

The electrodes are then removed from the soda solution and placed in pure Rinsed with water.

The last cleaning solution is made by mixing z. B. i part by volume concentrated nitric acid with 3 parts of water. The rinsed plates are Immersed in this cold solution for 2 or 3 hours. The main purpose here is Removing metallic surface contaminants from aluminum. ' The chemical However, the effect is usually very small.

The electrodes are then rinsed in pure water and then in Rinsed with distilled water as it is absolutely essential that all traces of acid be removed removed before further treatment. The remaining water is preferably used for this purpose blown out by compressed air. The plates should be at this stage of the procedure show a uniform silver-gray color. Too long immersion creates irregularities Appearance.

After the disk unit has been cleaned, the cover 13 and the aluminum lug 34 butted to the other end of the disk 16; being for that care is taken to rule out contamination of the unit.

The next step is the alternating current formation, in which the Plates completely in a solution of by means of a clamp chemically pure: @atriuiiicarbonates submerged in distilled water «-erden. The concentration this solution can vary depending on the forming voltage. The diluted solutions are used for higher voltages. All metals that are not aluminum must be kept away from the panels during formation, and especially must to keep away the corrosion products of copper and brass with regard to the Pay attention to plates and the bath. The bath is preferably in a steel vessel, and the plates are divided into two groups, each of which has one pole of the alternating current source forms. The electrolyte is about 3 inches above the top disk.

The alternate supply is regulated so that about 1/2 ampere the large disk structure (about 38 disks with a diameter of 25.4 mm) is omitted and a corresponding current for electrodes of other sizes. The initial potential is about 50 volts and is increased to 29o volts over about 5 minutes. During this During this period, the current falls to a substantially constant value. The progression The formation can be through resistance or reactance in series with the power source regulated «earth. Preferably, the 29o volts are reached in about 4 minutes and pause until the current is constant, which is usually r or 2 minutes longer will take. The initial formation with alternating current is important because it forms a more robust membrane that is less prone to imperfections or weak points tends.

The groups of panels formed with alternating current then receive a direct current formation, preferably using the steel tank as negative Pole and all aluminum plates used as positive pole. This formation happens without disturbing the plates in the same vessel by switching from alternating current to direct current switches. The direct current treatment requires 21 /, to 3 hours in the 2 percent aqueous solution of sodium carbonate. The temperature should be kept below 40 ° C otherwise streaking can easily occur on the panels.

Instead of the Wecliselstroinformierung before the beginning of the DC waveform formation To finish, one can alternate the two by progressively reducing the tension for alternating current and direct current in the treatment increases and the current significantly holds constant until the voltage has reached a maximum value, whereupon the current is applied drops to a minimum value. Achieved by this alternating treatment you have a very robust and resistant skin covering on the aluminum electrode.

The electrodes are then carefully removed from the formation container and dried thoroughly with a jet of compressed air. There and with all later It is very important that the electrode aggregates with as little as possible treatments mechanical friction are treated. A break in the membrane does that Capacitor unusable or it increases the time for the last necessary one Formation.

This takes place in a substantially dry solution of 3,1201 sodium bicarbonate in glycerine. Usually it is necessary to warm the glycerin a little to cause it to dissolve. Usually a temperature of 80 ° C is necessary for about 20 minutes. Great care should be taken to keep the glycerin away from the surface of the lid 13 as it is very difficult to remove and can short-circuit and spoil the capacitor. The dried electrodes are immersed in this glycerol-sodium bicarbonate solution and left to stand for several hours in order to allow the air to escape from the spaces between the plates. The DC voltage is then applied and the electrodes are exposed to 250 volts until the leakage reaches the desired linear value.

The formed electrodes are then carefully lifted out of the bath, without removing the electrolyte held by the panes, and «-grounding then put into the housing ro, which was previously so high with the same glycerine solution was filled so that the electrolyte level was finally about 3 mm above the top Plate of the unit is in place. You have to be particularly careful with the electrode prevent contact with the side of the housing or other objects.

After inserting the disk units into the housing ro, the Sealing ring 28 inserted, and the housing is closed by inan the upper Edge 29 folds over the sealing ring. The capacitors are then connected to 25o volts DC connected and should have a leak of less than r milliamps per unit demonstrate. The voltage of 2.50 volts is maintained until the current drops to less drops than 0.2 milliamps. Defective capacitors can be found by their high Leak out.

Capacitor plates that are formed in aqueous solutions and then introduced into glycerin electrolvten can cause interference due to stray current. Through this, that the top layer is formed in the glycerine solution, this difficulty is avoided. The thin, the plate when removed from the Forming glycerin adhering glycerin layer also serves to better contact to ensure with the electrolyte in the capacitor cell, d. H. it is then there is less tendency to form air sacs.

The capacitor made in this way is about 50 mm high and 32 mm in diameter, has a capacity of ro microfarads, a leak of 0.2 milliamps at 25o Volts DC, is substantially stable; H. does not require any reforming a period of non-use, does not suffer unduly through age or use and is cheap to manufacture.

It was indeed a capacitor with an aluminum electrode in one Sodium bicarbonate electrolytes in glycerin are described above, but could also be any other suitable cover layer electrodes, such as tantalum or the like, instead of aluminum be used. You could also use other alcohols, especially polyhydric alcohols like ethylene glycol and the like use instead of glycerine. each essentially dry Ionic, such as B. essentially dry sulfuric acid can be used instead of sodium bicarbonate can be used, and gelatin or other substances can be used in the context of the invention add to the electrolyte.

A very important feature of the capacitor according to the invention is its current leakage at high voltages. It is well known that ordinary paper capacitors the leakage current directly proportional to the applied voltage, d. H. the graphic Representation is a straight line. In the case of the electrolytic capacitor according to the Invention, however, the top layer allows a rapid increase in the leakage flow, if the applied voltage increases above a certain value, and the voltage across the capacitor is prevented from rising significantly beyond the given value. With others Words, while a paper capacitor is generally speaking the properties of a has pure capacitance, to which a solid resistance of high value in shunt is, the capacitor according to the invention generally has the properties of a pure capacitance, to which a resistor is shunted, which after rise the applied voltage over a certain point is opposite in high Relation to the applied voltage changes. To use an analogy, the capacitor according to the invention acts very similar to a pressure safety valve. Because of these Characteristic, the capacitor according to the invention finds an important application in filter circuits for rectifiers.

Very often the voltage wave of the outgoing circuit is characterized of the rectifier by one or more sharp slopes or high, narrow peaks in each half cycle wave of the rectified voltage. These tips will due to the magnetic and electrical properties of the supply transformer and rectifier caused. In the case of a filter circuit that only uses paper capacitors these peaks or rises disturbances in the choke coils belonging to the filter, and can cause unsatisfactory filtering, i. H. there can be too much restlessness prevail in the outgoing stream of the filter. But if the capacitor after the Invention used as the first element of the filter circuit, it effectively prevents that fluctuations in the rectifier output voltage exceeding a certain value can be transferred to the following elements in the filter circuit. As a result, will therefore a very evenly filtered flow from the filter is achieved.

The fluctuations in the rectifier output voltage are each for of a short duration compared to the entire half-period wave or the impulse of the rectified voltage. In graphical representation they are sharp points, which are quite high, but relatively narrow, so that the area under the stress curve the rectifier output current is only slightly larger than the area under a rectified one Is sine wave that is drawn entirely under this voltage curve. Therefore removing these spikes or bumps makes only a small sacrifice in performance and a relatively negligible decrease in efficiency.

By choosing the metal for the top layer electrode, that in the electrolyte The used ionogen and the ionogen concentration in the electrolyte can be found in the capacitor cell according to the invention the desired characteristics for critical stress and leakage give within certain limits to meet the requirement that the peaks be stamped out from the outgoing voltage wave of a particular rectifier.

Claims (3)

PATENT CLAIMS: I. One or more electrolytic capacitor Cover_layer electrodes immersed in an electrolyte. through this characterized, (1ass the electrolyte from an alcohol and a dissolved in diesels Ionic exists, and that Ionic and alcohol and therefore also the one formed from them The electrolyte is anhydrous or has a maximum water age of 5 ° jo. 2. Elel; trolvtiscller capacitor according to claim i, characterized in that a Polyhydric alcohol such as glycerine is dispersed. 3. Electrolytic capacitor according to claim i, characterized in that the cover layer electrode consists of a Rod of a metal forming a barrier membrane, which is a number at a distance held, made of the same metal, carries disks on the rod be held by a part that forms one piece, and that the electrode iin condenser is held by a capped end of the rod, which too is used to attach an end clamp to the rod. q .. Electrolytic capacitor according to claim 3, characterized in that the rod has an intermediate collar, between your end and one of the ends of the rod are the spaced-apart disks are fixed by crimping one end of the rod while the other end the rod in a supporting and protective socket by overcumming the other The end of the rod is attached to this socket between the collar and the crinkled End too small. An electrolytic capacitor according to claim i, the electrodes thereof are held by a support that protrudes below the surface of the electrolyte, characterized in that an inert spacer between the electrode and the prop is switched on to prevent chemical action between the two. 6. Electrolytic capacitor according to claim 5, characterized in that the Support for each electrode is a socket made of a phenol condensate. «-Moose surrounds the electrode and protrudes under the level of the electrolyte, and that the inert Isolator, e.g. B. a Glininierscheibe, between the socket and the electrode there is appropriate where their union is exposed to the electrolyte. . Electrolytic Capacitor according to Claim 5 or 6, characterized in that the electrode support or supports through the cover or as part of a 1> cover for las F_lektrolygefäl @ formed «-erden, (read preferably from a metal that does not form a cover layer ordered, and that the lid is attached to the container in a liquid-tight manner. B. Electric capacitor according to Claim 7, characterized in that the container Has an annular flange to support the lid, and folded over the lid at the top is to ensure a tight seal between the lid and the container. 9. Electrolytic Capacitor according to Allspring 8, characterized in that the - \. B (lichtuilg -between the housing and a cover for it is formed by an asbestos rubber washer, which is clamped between the housing and the cover. 10. Electrolytic capacitor according to claims 7, 8 or 9, characterized in that its cover is made of insulating compound and a number of distributed ridges and grooves to reduce surface conduction and / or electrolyte creep. ii. Electrolytic capacitor after Claim i or 6, characterized in that the one made of aluminum Electrode an existing aluminum connection arm is attached to which an eyelet made of a metal that can be easily soldered with cables. 12. Method of manufacture a cover layer on an electrode for electrolytic capacitors, thereby characterized, (let the electrode in an electrolyte according to claim i and 2 immersed and the electrode and the solution corresponding to the poles of a power source connects. 13. The method according to claim 12, characterized in that the electrode first immersed in an aqueous solution of an ionogen and the electrode and the solution can be connected to the poles of a power source. i.I. procedure according to claim 13, characterized in that the electrode and the aqueous electrolyte, In which she is first immersed, first for a while with the poles of one AC power source and then for a while with the poles of a DC power source get connected. 15. Process for the production of a cover layer on electrodes of electrolytic capacitors, characterized (let the process according to claim 15 repeated one or more times before the one according to claim 1 = applies. i <. Procedure laughs: Proverb 12 for Manufacturing a cover layer to an electrode for electrolytic capacitors, the one Use relatively viscous electrolytes, characterized in that the formation the top layer in an electrolyte causes or terminates that in the capacitor The electrolyte used is the same, and that the electrode is removed from the formulation bath transferred to the condenser without removing the adhering forming solution. z7. The use of an electrolytic capacitor according to claim r and following in a filter circuit for rectified alternating current to avoid excessive increases To prevent potential in the circuit to which the capacitor is shunted lies.