EP0173100B1 - High power ignition transformer - Google Patents

Abstract

A high-power ignition coil for internal-combustion engines has a soft-magnetic layered core (8) of grain-oriented lamination and an air gap ( DELTA ) and a primary and secondary winding (2, 3) surrounding the main core (4). In order to achieve an unchanged energy storage capability and unchanged performance data for the ignition coil, without having to provide a permanent magnet, the core (8) is designed and constructed such that the main flux (0H) in the main core (4) generated by the primary winding (2) runs in the preferred direction of the grain-oriented lamination and such that the magnetic induction in the yoke parts (9, 10) of the core (8) is reduced such that an approximately equally large magnetisation requirement results in all the partial sections (4, 9, 10, 11, 12) of the magnetic circuit. <IMAGE>

Description

The invention relates to a high-performance ignition coil for internal combustion engines with a soft magnetic layered core made of grain-oriented sheet and air gap and a primary and secondary winding surrounding the main core, in which the main flow generated by the primary winding in the main core runs in the preferred direction of the grain-oriented sheet.

Such an ignition coil is known from DE-U-79 24 989. There, an obliquely arranged air gap in the main core with permanent magnets attached therein is mandatory, while the course of the main flow in the main core has not been explicitly discussed. The dimensioning of the remaining sections of the magnetic circuit was not discussed in any way there.

CH-A-342 282 discloses a core for magnetic circuits, in particular for magnetic amplifiers, which is constructed from U-plates which are layered without overlapping layers and in which the height of the yokes lying transverse to the preferred magnetic direction increases by the ratio of an induction along the rolling direction an induction transverse to the rolling direction at the same field strength is greater than twice the leg width in order to make the yokes and legs magnetically equivalent.

It is known to increase the storage capacity of magnetic energy stores for pulsating direct current, in particular ignition coils, in that the magnetic material in the magnetic circuit is premagnetized in the magnetic direction by a permanent magnet in the opposite direction to the main flow of the pulsating direct current and is therefore no longer subjected to pulsating direct current on one side becomes. This means that with the same amount of active material - magnetic circuit and winding - either almost twice as much electrical energy can be stored, or the active part can be dimensioned correspondingly smaller with the same stored magnetic energy. The field line density, i.e. Magnetic induction can be increased by up to 35% compared to conventional dimensioning in such magnetically pre-stressed circles, whereby a proportionality between the impressed current and the magnetic flux is nevertheless achieved. In the magnetic induction of 1.0 ... 1.4 T of such pre-stressed magnetic circuits used in practice, the magnetic field in the air gap where the magnetic energy is concentrated already has such a high magnetic field strength that the permanent magnets in their coercive force are overridden.

In order to avoid such overdriving, the air gap is arranged, for example, obliquely in the magnetic circuit (DE-U-79 24 989), or else the air gap is arranged on one or both end faces of the main core which carries the exciting primary winding (DE-B - 12 55 990) and / or the air gap area is increased. As a result of the arrangement of the permanent magnets on one or both end faces of the main core carrying the primary winding, an undesirable magnetic scattering occurs because the main flux leaves the paths predetermined in the magnetic circuit due to the lower magnetic resistance outside the exciting primary winding. The main magnetic flux is thus no longer completely linked to the individual turns of the primary winding, the yoke legs of the magnetic circuit are no longer fully utilized; the magnetic circuit is locally supersaturated with this arrangement of the air gaps.

The permanent magnets are expensive and the arrangement in the magnetic circuit during manufacture requires great care. Permanent magnet materials made of cobalt and rare earths, especially cobalt samarium, are characterized by a particularly large coercive field strength with high saturation and good temperature resistance. However, there are limits to the thermal stress, the exceeding of which leads to a drop in the coercive field strength and thus the storage capacity of an ignition coil can be significantly impaired.

In known magnetic circuits of ignition coils, core sheets in E, I, U, I or M shape, such as are standardized in DIN 41302, for example, are used when using soft magnetic material. A common feature of these core sheets is that the magnetic induction is practically the same size over the entire magnetic circuit. When using grain-oriented electrical steel (according to DIN 46400), core plates for ignition coils according to DIN 41302 or similar symmetrical dimensions are used.

Grain-oriented electrical sheet is distinguished from the other soft magnetic materials by a pronounced magnetic preferred direction in the rolling direction (longitudinal direction) and has about ten times better magnetizability in this longitudinal direction than conventional non-grain-oriented electrical sheets. Across the direction of rolling, grain-oriented electrical steel has about the same magnetic properties as non-grain-oriented electrical steel.

The invention has for its object to design and build the soft magnetic core of a high-performance ignition coil of the type described in such a way that with unchanged primary and secondary winding and thus unchanged magnetic induction in the main core and An unchanged large magnetic energy can be stored without arrangement of a permanent magnet and accordingly unchanged performance data of the ignition coil can be obtained.

This object is achieved according to the invention with a high-performance ignition coil of the type described at the outset in that the core is layered as a core of the core type with abutting core parts and without a permanent magnet in the air gap, and that with the same core layer height, the height of the yokes magnetized transversely to the preferred direction is approximately 1.5 times to 1.8 times the width of the main core magnetized in the preferred direction.

Another solution to the problem is that the core is layered as a jacket-type core with abutting core parts and without a permanent magnet in the air gap, and that with the same core layer height, the height of the yokes magnetized transversely to the preferred direction is approximately 0.75 to 0.9 times the width of the main core magnetized in the preferred direction.

Another solution to the problem is that the core is made of EI sheets with abutting core parts and without a permanent magnet in the air gap, and that with the same core layer height, the height of the yoke magnetized transversely to the preferred direction is approximately 0.75 to 0.9 times and the height of the I-shaped yoke magnetized in the preferred direction is approximately 0.5 times the width of the main core magnetized in the preferred direction.

The yoke parts of the core are expediently dimensioned transversely to the preferred direction of the grain-oriented sheet in magnetic induction in accordance with the assigned greatest possible permeability.

With the configuration of the core according to the invention, it is possible, while maintaining the number of turns of the primary and secondary windings and the cross-sectional area of the in the preferred direction, i.e. Rolling direction of the magnetized parts of the core, to achieve the same properties and performance data of the ignition coil, as can be achieved with the attachment of a permanent magnet for magnetic bias, only by slightly more material expenditure while increasing the cross-sectional area of the parts of the core magnetized transverse to the preferred direction.

With slightly more material for the magnetic circuit, an expensive permanent magnet can thus be saved in the construction according to the invention and, moreover, the production can be simplified considerably, since no increased care and attention has to be paid to the correct installation and correct polarization of the brittle permanent magnet.

In addition, ignition coils with a core designed and constructed in accordance with the invention, which have practically half the power-to-weight ratio compared to pencil ignition coils, can now be subjected to a short-term thermal load of up to 150 C without permanent magnet, without the magnetic properties and thus the performance data of the ignition coil being influenced.

The height of the yokes magnetized transversely to the preferred direction is 1.7 times that of the core type cores or 0.85 times the width of the main core magnetized in the preferred direction for cores of the cladding type.

The air gap is expediently arranged in the main core in the middle of the primary winding. In particular, this has the advantage of optimally dissipating the heat generated over the main core and the entire core.

According to further preferred embodiments of the invention, the core consists of two identical U parts in a core layered from UU sheet metal or two identical E parts in the case of a core layered from EE sheet metal.

Furthermore, the core can advantageously be constructed from UU sheets and an I-shaped main core magnetized in the preferred direction, which is connected to the UU sheets with four wedge surfaces by an oblique fermentation cut, the air gap being arranged symmetrically on at least one end face of the main core.

Finally, to improve the magnetic properties, the punched core sheets can advantageously be after-annealed.

• Fig. 1 einen erfindungsgemäßen Kernaufbau für einen Kern vom Kerntyp in Seitenschnittansicht,
• Fig. 2 einen Kernaufbau wie in Fig. 1 in Stirnschnittansicht,
• Fig. 3 einen Kernaufbau wie in Fig. 1 in Querschnittsansicht,
• Fig. 4 einen erfindungsgemäßen Kernaufbau mit einem Kern vom Manteltyp in Seitenschnittansicht,
• Fig. 5 einen Kernaufbau wie in Fig. 4 in Stirnschnittansicht,
• Fig. 6 einen Kernaufbau wie in Fig. 4 in Querschnittsansicht,
• Fig. 7 eine Darstellung eines erfindungsgemäßen Kernaufbaus aus EI-Blechen,
• Fig. 8 eine Darstellung eines erfindungsgemäßen Kernaufbaus aus UU-Blechen und I-förmigem Hauptkern mit Schrägschnitt an den Stirnseiten,
• Fig. 9 eine Darstellung der Gleichfeld-Kommutierungskurve (Permeabilitätskurve), und
• Fig. 10 eine Darstellung der Kennlinie Hauptfluß über Erregerstrom.

The invention is explained below using exemplary embodiments and with reference to the drawings. Show in the drawings

• 1 shows a core structure according to the invention for a core of the core type in a side sectional view,
• 2 shows a core structure as in FIG. 1 in an end sectional view,
• 3 shows a core structure as in FIG. 1 in a cross-sectional view,
• 4 shows a core structure according to the invention with a core of the shell type in a side sectional view,
• 5 shows a core structure as in FIG. 4 in an end sectional view,
• 6 shows a core structure as in FIG. 4 in a cross-sectional view,
• 7 shows an illustration of a core structure according to the invention made of EI sheets,
• 8 is an illustration of a core structure according to the invention made of UU sheets and an I-shaped main core with an oblique cut on the end faces,
• 9 shows a representation of the constant field commutation curve (permeability curve), and
• Fig. 10 shows the characteristic of the main flow versus excitation current.

1 to 3 show a core structure with a soft magnetic layered core 1 of the core type, layered from UU sheets of the same shape. A primary winding 2 with the number of turns wi and a secondary winding 3 with the number of turns _W2 surround the main core 4. The core sheets are stamped in such a way that both the main lerm 4 and the yoke leg 5 are magnetized in the magnetic preferred direction (rolling direction) of the grain-oriented sheet, while Yokes 6 and 7 are magnetized transversely to the magnetic preferred direction. An air gap A is arranged in the main core 4 approximately in the middle of the primary winding 2.

The winding window has a width b and a height e. The core layer height is d, the width of the main core 4 is a, the width of the yoke leg 5 is approximately a. The height of yokes 6 and 7 is c. The direction of rolling of the sheets is indicated by arrows. F _EL denotes the cross-sectional area of the main core 4 magnetized in the preferred direction, and F _EQ denotes the cross-sectional area of the yokes 6, 7 magnetized transverse to the preferred direction.

The core 1 is designed and constructed such that the ratio of yoke height c to core width a is 1.5 to 1.8, preferably 1.7.

4 to 6, a preferred core structure of the jacket type with a core 8 is shown. Yokes 9 and 10 have a height ci2 here, while yoke legs 11 and 12 have a width of approximately a / 2. Here, the ratio of the height c / 2 of the yokes 9, 10 to the width a of the main core 4 is 0.75 to 0.9, preferably 0.85.

FIG. 7 shows a further example of a core structure of the jacket type according to the invention with a core 13 which is layered from E and I sheets. The ratio of the height c / 2 of the one yoke 10 to the width a of the main core 4 is again 0.75 to 0.9, preferably 0.85, while the height a / 2 of the yoke 9 is approximately half the width a of the main core 4 is. The yoke 9 is layered from 1-sheet metal, which are magnetized in the preferred direction.

The heights and widths of the embodiment shown in FIG. 8 of a core type core structure according to the invention with core 14 are the same as in the preferred embodiment of FIGS. 4 to 6.

The core sheets of both the core 6 of the core type and the cores 8, 13, 14 of the sheath type are punched in such a way that the main magnetic flux 0 _{H is} built up in the rolling direction of the magnetic preferred direction of the grain-oriented sheet when it is acted upon by the current I of the primary winding 2. The magnetic circuit is preferably interrupted approximately in the middle of the primary winding 2 by the air gap A, the main seat of the magnetic field.

The magnetic field is an energy store. According to the theory, the total energy present in the magnetic field is a coil through which current I flows

In this equation it is assumed that the inductance L is constant and that the coil fluxes are proportional to the exciting currents, that is, there is no iron or at least the iron is unsaturated. In a coil with an iron core, the magnetic flux is a function of the current itself, so that when the iron core is saturated, the magnetic flux 0 increases with the current I; the coil inductance L decreases, and thus the storage capacity for magnetic energy.

It is known that the magnetization requirement of grain-oriented electrical sheets in the rolling direction, the magnetic preferred direction, is only about 1/10 of that required to magnetize the electrical sheets transverse to the rolling direction. Cold and hot rolled, non-grain oriented electrical sheets and strips have approximately the same magnetization requirement as grain oriented sheets across the rolling direction. In the rolling direction, the grain-oriented sheet can be specifically loaded with magnetic induction of 1.5 ... 1.7 T without requiring a greater magnetization than the conventional electrical sheets.

The core sheets of conventional and commercial type are dimensioned so that the cross section of the return flow is approximately the same size as the cross section of the main flow. If this type of electrical sheet is used, magnetic material with a pronounced preferred direction, e.g. Grain-oriented sheet with the preferred direction in the rolling direction applied, so that the part of the magnetic circuit leading the main magnetic flux can be subjected to a specific high load, those parts of the core sheet in which the magnetic flux must be driven transversely to the rolling direction, however, require a corresponding high need for magnetization.

In FIG. 9, the magnetization requirement H (A / cm) for a commercially available grain-oriented sheet according to DIN 40600 is assigned to the specific material stress, the magnetic induction B (T). Curve a) shows the magnetization requirement in the rolling direction, curve b) transverse to Rolling direction. The magnetization requirement and the saturation properties of this material both in the rolling direction and transverse to the rolling direction are illustrated by the curves a) and b) of the relative permeability ur: In the rolling direction, the relative permeability is about ten times greater than in the transverse direction.

In Fig. 10, curve I shows the known shear when the magnetic circuit is oversaturated. In designs of ignition coils which have become known and have core sheets of DIN-sized design, the shear of the characteristic curve I, for example in the induction of 1.0 ... 1.2 T, is solely due to the increased magnetization requirement transverse to the rolling direction of the parts of the magnetic circuit . The attachment of a permanent magnet in the air gap of the magnetic circuit avoids this disadvantage of the deflection and thus the storage capacity of the inductance, because, as is well known, the induction stroke is increased by the DC bias against the direction of flow of the ignition coil and the storage capacity increases quadratically with the current applied.

According to the configuration of the core sheets for core materials with a magnetic preferred direction according to the invention, those parts of the magnetic circuit which are magnetized transverse to the rolling direction are dimensioned up to at most the induction which corresponds approximately to the maximum relative permeability. In FIG. 9, a specific material stress of approximately 1.0 T can be seen from a design example for the core sheet from the relative permeability curve b) at the maximum permeability (point A). In order to drive the main magnetic flux 0H through these sections transversely to the rolling direction, about 1.8 A / cm is required (point B). In the core structure according to the invention, the entire magnetic circuit is approximately balanced with respect to the magnetization if the parts of the magnetic circuit which are magnetized in the rolling direction are used until about the same magnetization requirement for these parts. In this exemplary embodiment for the dimensioning, this is approximately the case in the magnetization curve a) for the sheet in the rolling direction when the magnetic sections in the rolling direction are specifically stressed with approximately 1.7 T induction (point C). In the exemplary embodiments according to FIGS. 1 to 6, the sections of the longitudinal and transverse magnetization are approximately of the same length.

Für die bisher bekannt gewordenen Kernmaterialien mit magnetischerVorzugsrichtung ergibt sich je nach Einsatz der Sorte für die Vergrößerung des Querschnitts in Querrichtung etwa der Faktor 1,5 ... 1,8. Versuche haben bestätigt, daß beispielsweise beim Einsatz der Sorte VM 111-35 gemäß DIN 40600 mit einer Vergrößerung des Joches bei einem EE-Blech auf das 1,7-fache des Querschnittes des Hauptflusses ein Optimum hinsichtlich der magnetischen Speicherfähigkeit erzielt worden ist.In this exemplary embodiment, this means that in order to drive the main magnetic flux through the entire magnetic circuit, the following applies approximately:

For the previously known core materials with magnetic preferential direction, depending on the use of the grade for the enlargement of the cross-section in the transverse direction, the factor is approximately 1.5 ... 1.8. Experiments have confirmed that, for example, when using VM 111-35 in accordance with DIN 40600, the yoke of an EE plate was enlarged to 1.7 times the cross-section of the main flow, and an optimum in terms of magnetic storage capacity was achieved.

Fig. 10 also illustrates the invention. In one exemplary embodiment, given a primary winding with the number of turns wi and the iron cross section F _EL, this diagram shows the magnetic flux 0 as a function of the magnetic flux, the impressed current I. Induction B 1 is shown in the coordinate, that is, based on the specific stress in the rolling direction; this is directly proportional to the main magnetic flux 0 _H. Curve II applies to a core sheet of conventional type, without cross-sectional reinforcement transverse to the rolling direction. First, the flux 0 increases proportionally with the current I applied, until saturation is reached in the magnetic sections with the magnetization transverse to the rolling direction. As the current continues to increase, the magnetic flux hardly increases; the characteristic curve is strongly curved. According to the embodiment of the magnetic circuit according to the invention, however, there is still a directly proportional relationship at the maximum coil current to be applied, so that the maximum magnetic energy can be stored at this current of the ignition coil (permanent magnet).

With the design and construction of the core according to the invention, it is possible, while maintaining the same number of turns and the same cross-section F _E in the rolling direction, to achieve the same properties and performance data of the ignition coil as with a coil with only a little more material expenditure by reinforcing the area transverse to the rolling direction the attachment of a permanent magnet for magnetic bias.

The design of the core according to the invention thus has the advantage that an expensive permanent magnet can be saved with slightly more material expenditure of the magnetic circuit and, moreover, the production is simplified considerably because no increased care and attention to the correct installation and the rich term polarization of the brittle permanent magnet must be dedicated. In addition, ignition coils of this type with a practically half power-to-weight ratio can be subjected to thermal loads of up to 150 ° C. for a short time compared to pencil ignition coils without permanent magnets, without negatively influencing the magnetic properties and thus the performance data of the ignition coil.

The structure of the core according to the invention can be used not only for ignition coils, but also generally for magnetic energy stores, for example for switching power supplies, chokes in DC dividers in power electronics, etc.

Claims (11)

1. High energy ignition coil for internal combustion engines with a soft magnetic laminated core (1) of grain oriented metal laminates and air gap (A) and a primary and secondary winding (2, 3) surrounding the main core (4), in which the main flux (0H) produced by the primary winding (2) flows in the main core (4) in the preferred direction of the grain oriented metal laminate,
characterised
in that the core as core (1) of the core type is laminated with parts of the core abutting against each other and without a permanent magnet in the air gap (A), and that with same core layer height (d) the height (c) of the yokes (6, 7) magnetised transversely to the preferred direction is approximately 1,5 to 1,8 times the width (a) of the main core (4) magnetised in the preferred direction.

2. High energy ignition coil for internal combustion engines with a soft magnetic laminated core (8, 14) of grain oriented metal laminates and air gap (A) and a primary and secondary winding (2, 3) surrounding the main core (4), in which the main flux (0_H) produced by the primary winding (2) in the main core (4) flows in the preferred direction of the grain oriented metal laminate,
characterised
in that the core as the core (8, 14) of the shell- type is laminated with parts of the core abutting against each other and without a permanent magnet in the air gap (A), and that with the same core layer height (d) the height (c/2) of the yokes (9, 10) magnetised transversely to the preferred direction is approximately 0,75 to 0,9 times the width (a) of the main core (4) magnetised in the preferred direction.

3. High energy ignition coil for internal combustion engines with a soft magnetic core (13) of grain oriented metal laminates and air gap (A) and a primary and secondary winding (2, 3) surrounding the main core (4), in which the main flux (O_H) produced by the primary winding (2) flows in the main core (4) in the preferred direction of the grain oriented metal laminates,
characterised
in that the core (13) is laminated with El- shaped metal laminates with parts of the core abutting against each other and without a permanent magnet in the air gap (A), and that with the same core layer height (d) the height (c/2) of the yoke (10) magnetised transversely to the preferred direction is approximately 0,75 to 0,9 times the width (a) of the main core (4) magnetised in the preferred direction and the height (a/2) of the I-shaped yoke (9) magnetised in the preferred direction is approximately 0,5 times the width (a) of the main core (4) magnetised in the preferred direction.

4. High energy ignition coil according to claim 1, 2 or 3,
characterised
in that the yoke parts (6, 7, 9, 10) of the core (1, 8, 13, 14) transversely to the preferred direction of the grain oriented metal laminates are dimensioned for magnetic induction according to the relevant greatest possible permeability.

5. High energy ignition coil according to claim 1, characterised
in that the height (c) of the yokes (6, 7) magnetised transversely to the preferred direction is 1,7 times the width (a) of the main core (4).

6. High energy ignition coil according to claim 2 or 3,
characterised
in that the height (c/2) of the yokes (9, 10) magnetised transversely to the preferred direction is 0,85 times the width (a) of the main core (4).

7. High energy ignition coil according to claim 1 or 2,
characterised
in that the air gap (A) in the main core (4) is arranged centrally to the primary winding (2).

8. High energy ignition coil according to claim 1,
characterised
in that in a core (1) laminated with UU-shaped metal laminates the core consists of two identical U-shaped parts.

9. High energy ignition coil according to claim 2,
characterised
in that in a core (8) laminated with EE-shaped metal laminates the core consists of two identical E-shaped parts.

10. High energy ignition coil according to claim 2,
characterised
in that the core (14) is constructed of UU-shaped metal laminates and an I-shaped main core (4), magnetised in the preferred direction, which through four wedge surfaces forms mitred joints with the UU-shaped metal laminates, and that the air gap (A) is symmetrically arranged on at least one of the end faces of the main core (4).

11. High energy ignition coil according to one of the preceding claims,
characterised
in that the core laminates are annealed after stamping.

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