US3209295A

US3209295A - Ignition coil with permanent magnets in core

Info

Publication number: US3209295A
Application number: US354501A
Authority: US
Inventors: Baermann Max
Original assignee: Max Baermann GmbH
Current assignee: Max Baermann GmbH
Priority date: 1959-03-13
Filing date: 1964-03-20
Publication date: 1965-09-28
Anticipated expiration: 1982-09-28
Also published as: DE1255990B; GB914371A

Description

Sept. 28, 1965 M- BAERMANN 3,209,295

IGNITION COIL WITH PERMANENT MAGNETS IN CORE Filed March 20, 1964 -2 Sheets-Sheet l INVENTOR. MAX BAffiMAA/A/ Lymw P 1965 M. BAERMANN 3,209,295

IGNITION COIL WITH PERMANENT MAGNETS IN CORE Filed March 20, l964 2 Sheets sheet 2 113 7151 Fig.4

p m y 122 w in 221 i D 115 I04 123 Fig. 5

INVENTOR. MAX BAL-W/VA/V/V United States Patent "ice IGNITION COIL WITH PERMANENT MAGNETS IN CORE Max Baermann, Benshergwulfshof, Bezirk Cologne, Germany Filed Mar. 20, 1964, Ser. No. 354,501 Claims priority, application Germany, Mar. 13, 1959, B 52,473 8 Claims. '(Cl. 336-155) This application is a continuationin-part application of my copending application Serial No. 14,094, filed March 10, 1960, now abandoned.

The invention pertains to ignition coils for generating sparks for igniting combustible gas mixtures. Such ignition coils have found their best known use for gasoline motors in motor vehicles, but they can also be used for gas burners and oil heaters.

Most of the best known ignition coils are cylindrical and consist of a laminated core fitted with a high tension and low tension winding. A hollow cylinder of laminated sheet metal is slipped over the low tension winding for better conduction of the magnetic field. The magnetic iron circuit is not completely closed at the ignition coil, but has an air gap in order to enable a quick breakdown of the magnetic field. The time of buildup of the magnetic field generated by the direct current is determined from the ratio of the electric resistance to the inductance of the winding multiplied by a time constant. If such an ignition coil is used for the ignition of gasoline motors, then the time between two firings is greater with a low r.p.m., while at high r.p.m.s the time is less, so that the magnetic field cannot completely build itself up as necessary. At high speeds of rotation this results in the ignition spark lacking the power necessary for firing and the firing therefore misses.

French Reissue Patent No. 66,586 described an ignition coil in which the laminations of the magnetic circuit consist of U-shaped, ferromagnetic sheets made from Ferrocube material which has a low coercivity. The high and low tension windings are placed on one leg, while the other leg has an air gap in which a permanent magnet of low permeability and high coercivity is located. This permanent magnet is magnetized in the direction of its smallest dimension, i.e., toward the ends of the legs forming the gap, and the magnet is so placed in the air gap that its direction of magnetization is opposite to the direction of the magnetic field generated by the low tension winding. The magnetic material provides an ignition coil improved over those used heretofore. However, it is not yet possible with this ignition coil to achieve the short firing times required by fast-running motors with the desired power in the ignition spark.

The present invention contemplates an ignition coil which overcomes all of the objections heretofore known and others, and provides a coil which is relatively small in physical size while still having the required power output to supply the desired power of ignition spark at all motor speeds.

In accordance with the present invention there is provided an ignition coil for generating electric sparks especially for firing of combustible gas mixtures in internal combustion engines comprised of a closed loop of ferromagnetic material, a low coercivity, ferro-magnetic core having high and low tension windings in overlapping relationship thereon, the core extending across and within the loop with the ends of the core spaced from the inner sides of the loop, a pair of permanent magnets one within the space between each end of the core and the inside of the loop, the permanent magnets having a permeability 3,209,295 Patented Sept. 28, 1965 of approximately one and the permanent magnets being in magnetic series with respect to each other.

In accordance with a further aspect of the present invention, the ends of the core facing the permanent magnets are fanned out to provide a magnet contacting area larger than the cross-sectional area of the core body. By this construction, a large number of flux lines from the magnets can be funneled into the core for the purpose of saturating the same as will be hereinafter described in detail.

Also in accordance with the invention, the core has a cross-sectional area such that it will be magnetically saturated by the magnetic flux from the permanent magnets and will also be magnetically saturated by the current flowing in the low tension or energizing coil around the core.

Further in accordance with the invention, pole shoes preferably of two layers, each of a plurality of ferromagnetic strips are placed between the core ends and the permanent magnets with the strips of each layer crossing at right angles relative to the other layer to lessen eddy current loses at the ends of the core.

As a result of the invention, the high tension connection may be placed on a long side of the ignition coil, while the connections for the low tension winding may be on the same or on the opposite side. The connections for the low tension winding can be developed as contact pins. This makes it possible to provide a simply and easily replaceable ignition coil, in that a base plate may be provided on the motor distributor with two plug sockets to receive pins mounted in the base of the ignition coil.

As a further result of the invention, the high tension connection may be placed on the top of the ignition coil, while the low tension connections are put on the same side. These ignition coils can advantageously be set directly on the cover cap of the distributor. Special wiring connections are no longer necessary.

The principal object of the invention is the provision of a new and improved ignition coil which is simple in constructon, small in physical size and yet which is capable of supplying a powerful ignition spark at all motor speeds.

Another object of the invention is the provision of a new and improved ignition coil wherein the parts of the coil may be so arranged that improved arrangements of the terminals may be obtained and in particular, ignition coils may be obtained which can be plugged into and removed from terminal sockets for ease of replacement.

A further object of the invention is the provision of a new and improved ignition coil wherein the coil around which the windings are placed when the windings are unenergized, is completely saturated by permanent magnets having a high electrical resistance whereby when the low tension coil has been energized and is de-energized, a rapid reversal of the flux lines in the core will result.

The invention may take physical form in certain parts and arrangements of parts, the preferred embodiments of which will be described in this specification and illustrated in the accompanying drawing which forms a part hereof and wherein:

FIGURE 1 is a side cross-sectional view of an ignition coil and its\ associated energizing circuit illustrating a preferred embodiment of the invention;

FIGURE 2 is an elevational perspective view of an ignition coil shown in FIGURE 1;

FIGURE 3 is a view somewhat similar to FIGURE 2, but showing a slightly alternative construction;

FIGURE 4 is a cross-sectional view of an ignition coil illustrating another form which the present invention may take; and,

FIGURE 5 is a side elevational view of the coil of FIGURE 4.

manent magnets.

Referring now to the drawings wherein the showings are for the purposes of illustrating preferred embodiments of the invention only and not for the purposes of limiting same, FIGURE 1 shows an ignition coil as well as the details to understand its operation. The ignition coil consists of an elongated ferro-magnetic core 6, at whose ends

permanent magnets

5 and 7 are placed, having the magnetic polarity given in FIGURE 1, i.e., in series. In accordance with the present invention these magnets are formed from a low permeability, high coercivity magnetic material such as iron-barium-oxide and bismuth-manganese. Generally such magnets are formed by bonding small particles of iron-bari-um-oxide within a plastic binder which may be rigid or flexible. The high coercivity of such a magnet, i.e., in the range of 1,600-2,400 oersteds or at least greater than 1,000 oersteds, makes it extremely 'diificult to demagnetize the permanent magnets after they have been magnetized to saturation. The low permeability of these magnets, i.e. 1.02.0 and preferably nearer 1.0, enables these magnets to act as an air gap to the flow of magnetic flux lines. These characteristics of the permanent magnets greatly improve the electrical operation of an ignition coil if they are positioned in the magnetic circuit of the coil as taught by this invention. A bonded magnet of the type contemplated by the present invention has a high electrical resistivity because the magnetic particles are separated by the binder which is non-conductive. Accordingly, no substantial eddy currents can flow in the magnets themselves. Such eddy currents in the magnets would tend to impede the flux change in the magnets and, thus, slow the response of the core to a change in flux.

These

permanent magnets

5, 7 lie directly against the inner surface of the sides 1, 3 of a rectangular ferromagnetic short circuit body consisting of

sides

1, 2, 3, 4. The high tension winding 8 is put on the core, and the low tension winding 9 upon this. One end of the high tension winding leads over a wire 10 to a spark plug 11 (here only symbolically indicated), while the other end 13 of the high tension winding with one end of the low tension win-ding 9 is connected to the positive pole of a battery 16 over the wire 15. The second end of the low tension winding is carried to the contact 18 over the wire 12. This contact 18 isactuated by a cam placed on the axle 20. When the contact 18 is closed, a current flows from the battery 16 over the wire 12, the low tension winding 9 and over the wires 14, back to the battery 16. The winding direction of the coil is so chosen that a magnetic field is generated by the direct current flowing in the coil, which field is opposed to the magnetic field generated by the

permanent magnets

5, 7. If the contact 18 is opened by turning the cam 19, the direct current is interrupted, the'field generated by it collapses, and is immediately built up in the opposite direction because of the arrangement of the

permanent magnets

5 and 7. This rapid change of flux induces a high tension in the high tension winding 8, which is suflicient to create an ignition spark in the spark plug 11. The condenser 17 prevents the formation of a spark across the contacts 18 when they are opened.

FIGURE 2 show-s a perspective view of the ignition coil shown in FIGURE 1 by the windings 28. As may be seen from this figure, the core 26 has ends which are fanned out to fit the shape of the permanent magnets and 27 on the ends which are turned toward them. The

fanned out ends of core 26 enables the magnetic flux lines generated by

magnets

25, 27 to be funneled into the body of core 26. Thus, a large number of flux lines are directed through the core by the serially arranged

magnets

25, 27 and the core is saturated by these flux lines in one magnetic direction determined by the polarity of the per- It is also possible instead of connecting the core through the

permanent magnets

25 and 27 to the

sides

29 and 23 of the short circuit body, as shown in this drawing, to provide an air gap at both ends of the iron core 26.

Preferably, and in accordance with the invention, in all of the embodiments described, the core, for example, core 6 in FIGURE 1, should have a cross-sectional area such that, for the material employed in the core, the core is magnetically saturated by the magnetic flux generated by the permanent magnets in one direction. Also and preferably in accordance with the invention, the core 6 will be saturated in the opposite direction by the magnetic flux generated by the current in the low tension winding 9.

With the arrangement shown, it will be appreciated that the core 6 and its associated windings will have a minimum of inductance so that the time required for the build up of magnetic flux in the core 6 as the low tension coil 9 is magnetized will be a minimum. Furthermore, when the coil 9 is de-energized, the flux of the permanent magnets causes a very rapid decay of flux in the core 6 and a build up of the magnetic flux in the opposite direction resulting in the generation of a pulse of electrical energy in the high tension winding 8 of the maximum possible voltage and energy content.

Attention must also be called to the fact that the dimensions of the

permanent magnets

25 and 27 are such that no de-magnetizing of these permanent magnets results from the magnetic field generated by direct current in the low tension winding. The high coercivity of these magnets assures that they are not dc-magnetized when they are subjected to magnetic flux in the direction opposite to their magnetization. Electrically non-conducting permanent magnets with a coercive force of H 750 oe. should preferably be used. These magnets in accordance with the invention should have a specific resistivity in excess of 1012 ohm mm.

and a permeability approaching unity, i.e. 1.0.

FIGURE 3 shows another development of the invention. The magnetic short circuit body 46 is cylindrical and preferably consists of a rolled strip of sheet metal. The axis of the core 42 is perpendicular to the cylinder axis. The ends of the core 42 are rounded, and

permanent magnets

41 and 43 having the given magnetic polarity and fitted to the cylinder, are slipped between the core and the short circuit body. However, it may be advantageous for manufacturing reasons as shown in dotted lines, to press the permanent magnetic bodies in cylindrical form, and to magnetize them only on the arc adjacent the ends of core 42. The windings are only indicated by the coils 45 with the wires 44. It is also possible to close the cylinder openings with covers, which however, must be electrically insulated from the short circuit body to prevent eddy currents.

The core 42 can also be so placed that its axis coincides with the cylinder axis. In this case both bases of the cylinder can be closed by plates. With such an arrangement however, the development of eddy currents must be prevented by slitting the cylinder and the two covers.

The core and the magnetic short circuit body should preferably be made in the known manner of a material preventing the formation of eddy currents, for example, a laminated sheet metal.

FIGURE 4 shows an ignition coil according to the invention. The high tension winding 102 is placed on the laminated core 101, and the low tension winding 103 placed upon this. At the ends of the core 101 are the pole shoes consisting of two

layers

104 and 105, each of which are made of parallel ferro-magnetic strips in sideby-side relationship. Strips of one layer cross at a right angle relative to the strips of the other layer.

The strips of one layer are insulated from each other and from the adjacent layer. Eddy currents are thus held down and improved operation results. Eddy currents could also be prevented by making each layer from a single plate having a slit therein extending to the center of the plate, the slits of the separate layers of course being spaced 180 from each other.

The permanent magnets 106 with the given magnetic polarity are placed between the part 105 with a ferromagnetic short circuit 107 which is in the form of a rectangular loop surrounding the coil in a horizontal plane as viewed in FIGURE 4. This loop is opened at the top and bottom and is closed at the bottom by the insulating plate 109 and the base plate 110 and at the top by an insulating plate 111 and a cover plate 112. This base plate 110 and the cover plate 112 are held in place by the flanged housing 108. The end 119 of the high tension winding 104 is fastened to a contact piece 118 mounted in plate 111. This contact piece is connected with the contact nipple 117 which is connected by the spring 116 with the connection coupling 115 for a high tension cable. A spark-over from the high tension to the low tension connections is prevented by the insulating bushing 123. The second end 122 of the high tension winding is fastened with the terminal 113, to which also an end 121 of the low tension winding is carried. The other end 120 of the low tension winding is fastened with the terminal screw 114. The core arrangement in accordance with the invention thus enables a very meritorious terminal arrangement for an ignition coil.

FIGURE 5 shows another development of the invention. The

pins

132 and 133 are provided instead of the

terminal screws

113 and 114. As an example, the pin 132 is connected with the circuit 120 and the pin 133 with the

circuits

121 and 122. The angle guides 130 are placed on both faces of the ignition coil for fastening it to a base plate.

The invention is not limited to the examples shown, but can also be used for other developments in which high power with small construction is needed.

Having thus described my invention, I claim:

1. In an ignition coil for generating electric sparks especially for the firing of combustible gas mixtures in internal combustion engines comprised of a closed loop of ferro-magnetic material, a low coercivity, ferro-magnetic core having high and low voltage windings in overlapping relationship thereon, said core extending across and within said loop with the ends of said core spaced from the inner sides of said loop, a pair of permanent magnets within the space between said core ends and the inside of said loop, said permanent magnets having a permeability of approximately one and said permanent magnets being in magnetic series with respect to each other.

2. The combination of claim 1 wherein the cross sec tional area of said core and the magnetic flux generated by said two permanent magnets is such that said core is magnetically saturated in a first direction when there is no appreciable winding created flux in said core.

3. The combination of claim 2 wherein the cross sectional area of said core is such that it will be magnetically saturated in a second direction opposite from said first direction by the magnetic flux generated by the current in the low voltage winding.

4. In an ignition coil for generating electric sparks especially for the firing of combustible gas mixtures in internal combustion engines, comprised of a closed generally rectangular loop of ferro-magnetic material and having inwardly facing sides defining a coil core recess, a low coercivity, magnetically high permeable magnetic core having high and low voltage windings in overlapping relationship there-around, said core being located Within said recess with the ends of said core spaced from said sides, a pair of permanent magnets, one placed at each core end between said core end and said side, said permanent magnets having a low permeability and a pair of pole shoes between said magnets and the ends of said core, said pole shoes being comprised of two layers of laminated ferro-magnetic material, said laminations of each layer crossing at right-angles to the laminations of the other layer.

5. An ignition coil for generating electric spark, especially for an ignition circuit of an internal combustion engine comprised of a closed loop of ferro-magnetic material, a ferro-magnetic core having high and low voltage windings thereon extending across and within said loop with the ends of said core spaced from the inner sides of said loop, a permanent magnet having low permeability placed between each end of said core and the inner side of said loop, said permanent magnets generating a permanent magnetic flux in said core sufiicient to substantially saturate said core, and said low voltage winding, when energized, generating magnetic flux in said core substantially larger than and in opposition to said permanent magnetic flux and connecting means on said core to connect said winding into said ignition circuit.

6. The ignition coil defined in claim 5 wherein a ferromagnetic eddy current preventing member is positioned between said magnets and each end of said ferro-magnetic core, said member being comprised of two layers of laminated ferro-magnetic material, said laminations of each layer crossing at right angles to the laminations of the other layer.

7. The ignition coil as defined in claim 5 wherein each of said core ends are provided with a pole shoe between said core and one of said magnets, said shoes adjacent said magnet having .a substantially greater cross-sectional area than said core.

8. In an ignition coil for generating electric sparks es pecially for the firing of combustible gas mixtures in internal combustion engines comprised of a closed loop of ferro-magnetic material, a low coercivity, ferro-magnetic core having high and low voltage windings in overlapping relationship thereon, said core extending across and within said loop with the ends of said core spaced from the inner sides of said loop, a pair of permanent magnets within the space between said core ends and the inside of said loop, said permanent magnets having a permeability in the order of substantially 1.0, a coercivity greater than ap proximately 1,000 oersteds and a high electrical resistivity.

References Cited by the Examiner UNITED STATES PATENTS 2,218,711 10/40 Hubbard 336l10 X 2,699,530 1/55 Latimer 336 X 2,730,681 1/56 Went et al 336'110 3,060,394 10/62 Maeda 336136 JOHN F. BURNS, Primary Examiner.

Claims

1. IN AN IGNITION COIL FOR GENERATING ELECTRIC SPARKS ESPECIALLY FOR THE FIRING OF COMBUSTIBLE GAS MIXTURES IN INTERNAL COMBUSTION ENGINES COMPRISED OF A CLOSED LOOP OF FERRO-MAGNETIC MATERIAL, A LOW COERCIVITY, FERRO-MAGNETIC CORE HAVING HIGH AND LOW VOLTAGE WINDINGS IN OVERLAPPING RELATIONSHIP THEREON, SAID CORE EXTENDING ACROSS AND WITHIN SAID LOOP WITH THE ENDS OF SAID CORE SPACED FROM THE INNER SIDES OF SAID LOOP, A PAIR OF PERMANENT MAGNETS WITHIN THE SPACE BETWEEN SAID CORE ENDS AND THE INSIDE OF SAID LOOP, SAID PERMANENT MAGNETS HAVING A PERMEABILITY OF APPROXIMATELY ONE AND SAID PERMANENT MAGNETS BEING MAGNETIC SERIES WITH RESPECT TO EACH OTHER.