US2327784A - Ignition coil - Google Patents

Description

Aug. 24, 1943. H, 1 HARTzl-:LL

IGNITION COIL Filed Sept. 28. 1959 INVENTOR /y/ma Patented Aug. 24, 1943 IGNITION COIL Herman L. Hartzell, Anderson, lnd., assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application September 28, 1939, Serial No. 296,904

(Cl. 17E-961) 4 Claims.

This invention relates to ignition coils for automotive engines and is directed particularly to ignition coils whose winding assemblies are enclosed in fluid tight casings and impregnated with an oil or wax.

An ignition coil for internal combustion engines is required, considering its size, to carry current of relatively great magnitude while the engine is in operation for a substantial proportion of the engine operating time. The current ow may be regarded as practically continuous so far as concerns the heating eiects upon the coil. A considerable portion of the current impressed upon the windings of the coil results in the heating of the component parts, including the windings which may alter the electrical resistance of the unit as a whole, and may also amount to destructive influences upon the parts of the coil. It is therefore necessary for efficient operation to maintain the temperature of the coil below a certain maximum. It has been customary to depend upon the use of thin walled metal casing members closely arranged about the windings for conducting the heat developed by the windings to the exterior of the casing, where cooling would be effected by a draft of air owing about the casing. Due to the increased speed tendency of the present day automotive engine, that method of cooling is not satisfactory, and therefore applicant has devised an ignition coil constructionv of smaller mass in which there is a direct liquid communication between the windings of the ignition coil and its enclosing casing by which the unit as a wholel can be more adequately controlled and effectively cooled.

With thel foregoing in mind it is an object of this invention to improve the efficiency of an ignition coil by filling all of the voids of the enclosure with an impregnating medium so that the working temperatures of the coil are better controlled, and so that heat developed during its operation is more readily dissipated for cooling.

Another object of the invention is to provide a method of impregnating ignition coils with oil, wax or like substances.

Still another object of the invention is to provide an ignition coil with a housing having a fluid seal at the juncture of housing members and terminal supports, so that an ignition coil may be impregnated with a fluid medium and mainf' tained in sealed condition.

Still another object of the invention is to providea terminal connection for a housing member that will be proc-f against leakage in an oil impregnated construction.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the' present invention is clearly shown.

In the drawing:

Fig. 1 is a longitudinal sectional view of an oil impregnated ignition coil for relatively moderate service, the section being substantially as indicated by the line and arrows i-I of Fig. 2.

Fig. 2 is a transverse sectional View through the ignition coil, substantially as indicated by ie line and arrows 2-2 of Fig. l.

Fig. 3 is an enlarged detail in section illustrating one step in the method of assembling the coil casing and end members.

Fig. 4 is an enlarged detail in section illustrating the juncture of the casing and end member a .1er the assembly has been completed.

Fig. 5 is a plan view of the top end of the coil with the terminal enclosing cup having een removed.

Fig. 6 is a view in elevation of a lock plate for the terminal cover, it being a view substantially as indicated by the line and arrows C-S of Fig. 5.

Fig. 7 is a bottom plan view of the terminal enclosing cap after removal from the lock plate as shown in Fig. l.

Fig. 8 is a longitudinal sectional view of a heavy Aduty ignition coil illustrating certain modifications of construction.

With specific reference to the drawing, an ignition coil comprises an assembly of coil windings IS, mounted upon a bunch of core wires l2 which are enclosed within a casing I4 (Fig. l) or casing I6 (Fig. 8). Particularly with respect to the model illustrated in Fig. l and shown in inverted position, the winding assembly I0 consists of a paper tube I8 upon which there is a secondary winding 20 covered by a layer of insulation 22 around which is a primary winding 24. At the inside end of the secondary there is a lead 2S that is tucked inside of the end of the tube i8 where it is electrically engaged by the core wires l2 when they are nally packed within the tube I8. The outside secondary lead and the inside primary lead are twisted together and joined to a conductor 28 by means of a clip and solder connection 3U. The outside primary winding is joined to a conductor 32 in a similar manner as at 34.

The winding assembly thus constructed is adapted for mounting within a housing member which in the moderate service model comprises suitable clamp devices.

a sheet metal can 4|) of tubular construction having'sealed seams fitted with end members 42 and 44 secured thereto in double crimpedand sealed relation. The end member 42 (bottom member when the coil is installed), is preferably secured to the can 4|) iirst, the details of which procedure are illustrated in Figs. 3 and 4. Each end of the can 40 terminates in a diverging iiange 46 and each of the end members 42 and 44 has a right angular wall portion 48 which transforms theend member into a shallow cup, at the top of which is a planar flange 55 terminating in a roll 52. The cylindrical Wall 48 of the end member snugly fits within the end of the can 40, and the diverging ange 46 of the can passes within the roll 52, where it is adapted to encounter the planar portion U, a compressible gasket 54 of oil and heat resisting material, such as rubber latex bonded cork, being disposed therebetween. That loose assembly of housingparts is illustrated in Fig. 3 which is a relation preparatory to rolling down and sealing in the form illustrated in Fig. 4, wherein the diverging ange 46 is folded back along the can 40, and the rolled edge 52 is compressed and attened downto compress the gasket 54 between the successive layers of casing material. That relation is accomplished by forcing the end member and the can together endwise of the can While the folding, seaming or crimping of the can end and rolled edge vis accomplished. The completely fluid-sealed juncture is indicated at 56, and both end members are sealed to the can 4G in the same manner and by the same means.

A high tension terminal is provided by the bottom end member, which in the instance of the moderate service coil embraces a porcelain insulator 58 having a i'lange 60 forming a shoulder at one end of a cylindrical portion 62 adapted to project through an aperture centrally of a depression 64 of the head member 42. For reinforcing the end member and forming a secure abutment for the insulator, there is provided a dished washer 66 attached to the inside of the end member. A gasket 68 of oil and heat resisting material rests in the depression of the end member and engages the face or shoulder of the insulator flange 60, and a second dished washer or flanged ring lll, closely surrounds the iiange 60 and is secured to the end member 42. The peripheral flanges of the discs or washers 66 and 1|) may be secured to the end member 42 by spot welding or otherwise. With the insulator 58 disposed within the cylindrical portion of the washer 1|), and against the gasket 68, the upper edge of the disc 1Q is crimped over against the outer surface of the flange 6F), while the parts are held together under a pressure of something like 400 pounds. As a result, a fluid tight seal around the flange of the insulator is eiTected, the seal 'being maintained by the crimped edge 'I2 of the iianged ring 76. The insulator 58 is further characterized in that it has a longitudinal bore 14, reduced at its outer end to incorporate an internally threaded portion 16 adapted to receive a high tension terminal member 18 having, a threaded stem 86. 'In the iinal assembly a gasket 82 of heat and oil resisting material is dis- .posed between the end of the insulator and a shoulder of the terminal 16.

For mountingv upon the engine block, bulk head or other support, the can 40 is tted with a bracket 84 apertured at 86 for reception of At a short distance from lthe upper end of the vcan an inwardly rolled rib 68 is provided that forms a seating portion for locating an assembly of magnetic strips forming the outside iron Si] of the ignition coil. As in the usual practice, this assembly of outside iron constitutes a metallic sheet transverse `oi which there are several slits. The mutilated or slitted sheet of iron is then rolled into cylindrical form and inserted within the can 4Q, where it expands to engage the side walls substantially as shown with one inner end portion engaging the shoulder or abutment formed by the rib 8S. Extending throughout substantially the entire length of the casing 45 there is a tubular insulator 92 which in eiect forms a liner within the assembly of outside iron 96. One end of this insulator engages the head member 42, while the other end of the tubular insulator is in close proximity to the head member 44, an end insulator 95| being disposed therebetween.

For closing the opposite end oi the can 4|?, the top end member 44 is fashioned similarly to the end member 42 insofar as the juncture between the head member and can 46 are concerned for eiiecting the sealed connection terminating in the double rolled rim 56, described with respect to Figs. 3 and 4. The end member 44 is further fashioned to support a pair of terminal members such as a distributor terminal 96 and a battery terminal 58 to which a lock switch unit may be attached. The construction Vof the terminal members 26 and 58 is identical, in that each comprises a conductive element |66 having a ange or head |52 and a terminal attaching portion |64, the shank portion |06 being recessed and tapped at |96 to receive a terminal screw. The tapped recess |66 does not extend all the way through the element Ilm, but leaves a portion of solid metal so that there will be no fluid leak through the element.

At appropriate points the head member 44 is formed with rectangular depressions |08 that receive a `similarly shaped insulator HQ on each side of which is disposed a gasket ||2 of oil and heat resisting material. These elements having been passed over the shank of the conductive element |66, they are thence disposed between the iiange |02 and the inside bottom of the depression |58 after the shank of the conductive element |63 has been passed through the aperture of the depression |66. Element |00 receives an insulator H6 and a metal washer ||3 against which the recessed end of the element |00 is peened over, similar to a tubular rivet, as indicated at H4 in Fig. 1.

With respect to the terminal S8, its element |86 receives an insulator |253 and metal washer |22. In the instance of the terminal 96, the square embossment |68 through which the element extends is surrounded by a spacing washer |24 and a larger diameter lock plate |26 which are secured to the end member 44 by spot welding, or otherwise, such as indicated at |28 in Fig. 5. The insulating washer |26 extends over the inner edge of the lock plate |26 as shown in Fig. 1v. The lock plate |26 is extended peripherally over the spacer |24 and is provided with a cut-away portion |36 and with notches |32 for receiving inwardly extending radial lugs |34 'of a terminal cover member |36 '(Fig. 7). The cutaway portion |50 and notches |32 extend inwardly to the periphery of the lock plate |26. The internal diameter of the cap |36 is slightly greater in diameter than the lock plate |26. Portions of plate |26 between the cut-away portion |38 and the notches |32 provide iianges overhanging the spacer |24. Portions |38 of these flanges are struck inwardly toward the head member 44 to provide rotation stopsy and other portions of the flanges intervening are provided with corrugations or cross ribs |40 extending also toward the head member 44 to provide detents. Looking upon Fig. 5, the terminal cover |36 is assembled with respect to the coil and member 44 by passing the lugs |34 through the cut-away portion and the notches |32, and then rotating the cap |36 in a clockwise direction until the lugs |34 engage beneath the flanges of the lock plate and pass beneath the corrugated portions |40 to rest between one of them and the near edge of a deflected portion |38. Thus the cover is coupled to the head member 44 since its lugs |34 are confined between the flanges of plate |26 and outside wall of member 44. In certain aspects, this form of coupling resembles a bayonet slot connection. The terminal cover |36` usually incorporates a hub portion |42 secured to the cover in any desired manner, as by spot welding, and is usually rigidly assembled with an armor |44 by spot welding, staking or the like. The armor encloses an insulated conductor |46 ending with a terminal clip |48 adapted to be secured to the terminal 98.

These several sub-assemblies of the ignition coil are assembled in their final relation in the following manner. The can is so positioned that the high tension terminal 18 is lowermost. A tubular insulator |41 forming an inner iron support tube is passed over the inner end 62 of the high tension insulator so that it rests against the inner periphery of the flange ring 6B. spacing tube |49 of insulating material is then disposed against the inner surface of head member 42 so that it embraces the outer periphery of the ring member 65. A coil spring |5| is then placed in the bore 14 of the insulator 58, .i

to act as a connector between the terminal 18 and the coil core when assembled. The winding assembly I8, including the centrally disposed core wires |2 is then tted at each end with a winding locator |50, the winding locator being generally rectangular in plan such as to provide the Iiat edges |52 with rounded corners |54, so as to just iit within the tubular insulator or outer iron liner 92. The winding assembly so fitted is inserted in the housing assembly so that the winding locators move along inside of the insulator 92 and until the winding assembly is supported at the lower end by the end 62 of the insulator 53 and `spacing tubes |41 and |49. The ends of the core wires I2 will then have engaged the exposed end of the spring conductor |5| and compressed it toward the reduced end of the insulator 58. The conductors 28 and 32 of the windings passing between the dats |52 of the winding locato-r and the inner wall of the insulator S2 are secured at their ends to the `lugs |64 of terminal elements |00 by crimping and soldering or as may be desired. Then a spring washer |56 is placed against the exposed end of the core wires I2, and a core cup |58 which is usually of porcelain, is inverted over the washer |56 and about the end of the core. The leads having been fixed to the terminals 96 and 98 with the end insulator 9.4 between the core cup |58 and head member 44, the end assembly 44 is then assembled upon the open end of the casing 40 as illustrated in Fig. 3, and is secured in its sealing relation as illustrated in Fig. 4, and as has herein been described.

From the foregoing description, it is apparent that the coil includes a sealed casing enclosing a winding assembly that is rigidly and centrally spaced therein so as to present the end spaces |51 and |59 between the ends of the winding assembly and the end members 42 and 44, respectively, that are connected by the cylindrical space |6| between the casing insulator 92 and the outside of the primary winding 24. It is these spaces, and the voids of the assembly that communicate with the spaces that are subsequently filled with the impregnating mediums.

With respect to the heavy duty type of ignition coil, illustrated in Fig. 8 the essential features of the invention are the same, though the construction by which the improvements are achieved differ somewhat. The winding assembly is essentially the same except for proportions, but provides the leads or conductors 28 and 32 which are adapted to be secured to outside terminals provided by the casing. In this instance the casing comprises a deep cup-like member l5 having, an integrally formed bottom wall |52 with an inwardly projecting central boss |54 and inner peripheral shoulders |66 or ledges. The exterior cylindrical portion may be iiuted, finned or otherwise provided for rapid cooling. The case i6 is provided with integral, threaded, bosses |68 for receiving screws by which the coil is mounted on a support. The open end of the casing or cup is reduced in form to provide a peripheral groove |10 adjacent a narrow terminating iiange |72, adapted to provide a. ledge behind which a crimp ring |14 is bent to retain in sealing relation a nonconducting head member |76 that compresses a gasket |18 of oil and heat resisting material. The .head member |16` supports terminals |80 and |82 having electrical engagement with the leads 28 and 32 respectively. Oil and heat resisting gaskets |84 provide for the sealing of the terminals in the insulator. The inner side of the insulator provides a tubular boss |86 serving as a cup for one end of the core wires I2, the tubular portion of said boss having an extension for reception of va conductor assembly comprising a coil spring |90 resting against the core wires i2, and supporting a spring cup |92 somewhat of inverted conical form the apex of which extends within the spring and toward the ends ci the cere wires l2. The spring cup is apertured at |93 and is engaged by a contact pin |84 extending through a small bore |95 of the insulator |16. An outwardly extending tubular extension |96 of the insulator |16 carries a threaded sleeve insert |98 adapted to receive a screw plug 200 for clamping a compressible lead washer 7.02 against the insulator |16 to seal the hole |95 therein which receives the pin |94 and thereby to prevent the escape oi oil from the coil case I5 while Aalso completing he electrical connection between the core wires I2 (electrically connected to i secondary coil lead 26) and the insert |98.

In this embodiment, a core cup 204 which may be of porcelain is disposed in the casing i6 against the bottom wall |62, there being a central depression in the insulator for piloting over the bess |54-, and the insulator having a socket 28B for reception at the lower end of the core wires I2. On the upper surface of the core cup 204, there one or more cross channels 250 indicated by clash lines in Fig. 8, providing for fluid communication between the socket 268 and the pee riphery of the insulator.

In assembling the coil parts the core cup or insulator 204 is disposed against the bottom wall |62, and the outside iron 90 and the tubular insulator 92 are disposed withinthe casingso as to `restI ,at one end against the ledge 56. Electrical Connections having been completed between the windings and terminals i8@ and 182, the winding assembly is thence'passed withinthe tubular insulator 92 where it is substantially centrally positioned by the core cup 204i. The gasket Hi8 being in place the insulating head member il@ is then adjusted in position until an inner edge 2 l2 engages the upper end of the insulating tube 32 and presses it against the shoulder 56. The tubular boss H3G will then engage the winding locator |50 and the windings' and press them against the bottom wall of the casing. While the end member is held against the hanged end of the casing under something like 400 lbs. pressure so as to compress the gasket l'l into sealing relation, the clamp ring llt is then crimped into place, which seals the casing and cover member proof against uid leakage. The resulting assembly is shown by Fig. 8, where the winding assembly is firmly held centrally of a sealed-en-V closure so that there are cavities or spaces such as Elli, 2133 at the ends of the winding assembly, `and spaces such as 2ll5 between it and the casing assembly.

Either of the coil constructions thus described is now ready for the final step in completion, which comprises impregnating the construction, or in other words filling all of the spaces, cavities and voids of the assembly within the casing and about the windings with an impregnating medium. While it is proposed to make the assemblies as thus described complete before impregnation, it

may be desirable to impregnato the winding assemblies separately before they are assembled within the casing, and then ll the assembly with the impregnating medium after the housing has been closed, after which the sealing plugs may be secured in place.

One satisfactory method for impregnating the completed construction is to assemble the units on a tray within a tank with the high tension terminal insulator kfree of its sealing means. That is to say, as respects the coil of Fig. 1, the terminal 'I8 with its gasket 82 will not be in place, but there will be a single free passage from the exterior of the casingr to the interior thereof through the threaded bore l5, the enlarged portion Til, and around the springs l5l, and thence through the spacing between the core wires l2 and other passages to the spaced p0rtions ol the assembly. As respects the form shown in Fig. 8, the screw plug 2&0, the lead washer 2&2 and the conducting pin |94 will not be in place, thus allowing free passage into the interior of the assembly, through the insert |98 the bore E95 of the insulator, the apertures |93 rof the spring cup and thence in a manner similar to that just described to all the spaces of the assembly. In other words, both of the coil constructions, though the casing members are sealed in fluid tight relation, will be open to the atmosphere of the impregnating kettle through passages extending through the high tension terminal insulator.

With the coil constructions loaded in a tank tted with a cover capable of hermetic seal, and so that the passages into the interior of the coil constructions are uppermost, the tank is evacuated for something like two hours and while the load is maintained substantially cold, so that a pressure of some four mm. or less of mercury is accomplished. It is preferable that this step be accomplished slowly particularly at rst. The

tank and its loaded coils `is then heated and the evacuation continued for something like ten hours or more under temperatures of about 210 F. for the rst rive hours, which may be increased to 225 for the remainder of the period, the pressure reduction being accomplished to something like 6 mm. or less. By that time, substantially all of the air and moisture will have been removed from all of the voids and spaces of the coil assembly. When this has been accomplished, sufiicient impregnating compound is drawn into the evacuated tank to cover the coils to be impregnated, under which condition they are left to stand for a period of one half hour vor more vunder a temperature of 210 to 225 F. That the vacuum may be relieved by admitting dry airv followed by heating to a temperature of 225 to 265, after which the impregnating compound may be returned to the storage tank, though the impregnating tank Yand its charge of coils is kept at a temperature of about 255 F. or more until the coil units are removed for sealing. The coil units, then will have been completely lilled with the impregnating oil or wax, sincerevacuation of their interiors followed by the introduction of hot impregnating material, fills all of the voids between the core wires l2, and between the turns of` the primary and secondary windings, as well as the spaces itil', 159, itl or 29E, 233 and 265; and the like, with the introduced material. The impregnating material iinds its way into the .coil cavities through the passages in the terminal insulators and thence flows into all of the evacuated voids and spaces to ll thesame. Each of the coils is linally sealed with the terminal members and gaskets, while the impregnated coil is stillhot from the impregnating cycle, which is at a temperature that is somewhat higher than that that will be experienced bythe ignition coil under operative conditions in an ignition circuit of an auto-motive engine.

In sealing the coil of Fig. l, the sealing gasket 32 is placed on the threaded end 86 of the terminal lll, and the stem Bil is then coated with 'a cement so that when the terminal i8 is threaded into the end of the insulator and the cement hardens, the coil casing will be completely sealed against the passage of any fluid either into or out of the casing. In the instance of Fig. 8, the casing is finally sealed by inserting the contact pin or plug lllll, until it engages the spring cap |32 and depresses it to compress the spring Il. The soit lead washer 2M is then placed over the end of the pin lf'l and is forced into place by the screw plug 2li@ that is threaded into the insert 198, thereby finally sealing the casing against fluid flow therethrough. l

It has been found that ignition coils constructed and impregnated according to the instant disclosure have a longer lifethan heretofore attained. The impregnating medium which lls all the voids and spaces or the coil. construction facilitates cooling of the coil since it providesY aperture therethrough for the location and support of an electric terminal, a recessed rivet having a flange and whose shank is ldisposed in the aperture of said end member socket, a gasket of rubber bonded cork engaging the bottom of said end member socket for sealing the juncture against fluid flow, an insulating disc disposed between the gasket and rivet flange and commensurate in area with that of the socket, said rivet being peened over against a metallic washer on the opposite side of the said member for effecting seal and insulation of the rivet relative to the head member.

2. An ignition coil comprising in combination, a coil body, a tubular metallic case surrounding the coil body, metallic end members joined to the case by lock seams and situated one at the top and one at the bottom thereof, terminals insulatingly supported by each end member of the case, a lock plate secured about one of the terminals and having bayonet ways between the edge of the lock plate and the end member, and a conductor armor having tongues adapted to traverse the bayonet ways.

3. An oil or wax impregnated ignition coil, comprising in combination, a coil body, a sealed casing enclosing the coil body, winding locators at each end of the coil body centralizing the coil body with respect to the casing, said locators being spaced from the end closures thereof, and supporting the body from the sides of the casing, and means at each end of the coil body and engaged by the casing end members for positioning the coil body longitudinally of the casing.

4. An ignition coil comprising in combination, a coil body, a tubular metallic case surrounding the coil body, metallic end members joined to the case by lock seams and situated one at the top and one at the bottom thereof, a circuit terminal supported by one of the end members, a lock plate secured to the end member about the circuit terminal and providing bayonet Ways between the lock plate and the end member, a ter* minal cover adapted to enclose one of the circuit terminals and having radially extending tongues cooperable with the bayonet ways, said terminal cover being coupled with the lock plate by substantial `relative rotation to engage stops, said stops being located at the ends of the bayonet ways.

HERMAN L. HARTZELL.

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