EP1671338B1 - Ignition coil for a spark ignition engine - Google Patents

Description

State of the art

The invention relates to an ignition coil for a gasoline engine according to the closer defined in the preamble of claim 1. Art.

Such an ignition coil is an energy-transmitting high-voltage source and is used in the gasoline engine to control a spark plug, which in turn ignites the fuel mixture in the combustion chamber of the engine and thus initiates the movement of the piston and thus the crankshaft.

The operating principle of such an ignition coil is also known under the name "inductive ignition" or "battery ignition" and is found today in almost all spark-ignited fuel engines.

The storable magnetic energy is essential for the ignition coil and depends on the structure of its magnetic circuit and its material properties. The magnetic circuit is usually made of a ferromagnetic material and is commonly referred to as an "iron circle". Usually this is composed of a laminated core or is designed as a metal powder core. Since the iron circuit in certain embodiments does not consistently wrap around the winding but has gaps, also referred to as air gaps, it is also referred to as a "sheared" iron circle.

When the ignition coil is driven by an engine control unit, magnetic energy is stored in the ignition coil due to the rising primary current. The increase in energy does not continue indefinitely with the current increase, but is limited by the saturation flux density of the iron circuit. This means that with increasing current the material of the iron circle can not be further magnetized. The material is magnetically saturated. This connection is also expressed by the so-called hysteresis curve of the iron circle.

To counteract these physical conditions, it is known from practice as a usual measure to introduce a permanent magnet in the iron cycle. Such a permanent magnet or a plurality of such permanent magnets are integrated into the magnetic circuit in such a way that the direction of the flux density is directed counter to the excitation field of the current-carrying winding. This is also referred to as a "premagnetization", since in the passive state, in which no electric current flows, there is already a magnetic flux in the iron circuit.

This biasing makes it possible to shift the magnetic saturation of the iron circuit, based on the magnitude of the primary current, so that more total magnetic energy can be stored in the ignition coil. This is in practice a common measure of energy optimization of ignition coils.

In the case of the so-called compact coils, for this purpose usually a single permanent magnet is introduced into the iron circle, whereas in the case of the so-called bar coils preferably two permanent magnets are introduced at the respective end of the bar core into the iron circle.

However, in the case of conventional ignition coils, it is disadvantageous that the permanent magnets or the permanent magnets must be installed in the iron circuit with considerable manufacturing outlay. Especially with rod coils, it is important that the edges of the magnets are rounded off prior to installation in order to counteract the risk of electrical breakdown. In addition, care must be taken to the polarity of the magnet or the magnet, as an incorrect polarity counteracts the desired effect of energy storage.

Furthermore, permanent magnets are temperature-dependent, so that it can come at high flow and high temperatures at the same time for demagnetization of a permanent magnet. Such demagnetization is an irreversible process.

The properties of a permanent magnet are mainly determined by its material and the geometry of the structure. If a permanent magnet is installed in a conventional ignition coil, its properties can no longer be modified in a targeted manner. For example, if the same ignition coil is to be used in another engine that requires other characteristics of the ignition coil, the energy optimization of the ignition coil may need to be changed. The energy optimization of the ignition coil is adjusted by means of the bias. For this purpose, the permanent magnet must be replaced and replaced by a magnet with possibly modified geometry.

The latter, however, disadvantageously requires a constructive modification of the ignition coil.

The document US Pat. No. 6,188,304 B1 discloses an ignition coil according to the preamble of claim 1.

The invention has for its object to provide an ignition coil for a gasoline engine, in which the energy optimization by adjusting the bias of the iron circuit without simultaneous structural modification is possible.

In addition, in the ignition coil according to the invention, no permanent magnets for biasing the iron circuit must be used, the manufacturing cost is reduced by cumbersome handling of such permanent magnets.

Advantages of the invention

When an ignition coil for a gasoline engine of the type mentioned, ie with a coil core, in which by means of a current-carrying, substantially coil-shaped primary winding, a primary magnetic field is inducible, and a substantially coil-shaped secondary winding, in which by the primary magnetic field, at least one spark plug-driving energy field can be built, wherein on the coil core a biasing device for forming a primary magnetic field of the opposite bias field is effective, the biasing a current-carrying, essentially Having coil-shaped bias winding, can be achieved by the bias winding by means of a corresponding electric current advantageously a bias.

In the constructive design of the iron circuit accordingly no permanent magnet must be taken into account or in other applications of the ignition coil and no different magnet geometries.

Due to the omission of the permanent magnets, the rod core can be correspondingly extended, in particular in the case of rod coils, which brings about further advantages in energy optimization. In this case, advantageously, the winding length may increase accordingly, especially as turns, which are located on permanent magnets, are physically hardly effective.

Conversely, the Vormagnetisierungswicklung represent the only way to optimize energy, since in the case of a required maximum length of the rod core under certain circumstances no space for a permanent magnet is available.

The bias by means of additional winding is also flexible, d. H. In addition to the field direction and the magnetic field strength can be freely selected via an appropriate control with optimal utilization of the core material.

By introducing the bias winding, which has no limiting properties such as a permanent magnet, the bias flux density can be increased up to the saturation polarization of the core material.

This advantage also applies to a so-called compact coil, since conventionally the core material can be optimally utilized only if a permanent magnet of large area is inserted into the magnetic circuit. In addition to high costs, this also requires a great deal of space.

Due to the bias winding, the ignition coil according to the invention is very flexible in terms of energy yield, with no structural changes must be made. Especially in space problems in the axial direction therefore provides the invention Embodiment of an ignition coil is an advantageous alternative to permanent magnets.

Depending on the possibility of execution of the bias winding, it can thereby also have a price advantage over the use of permanent magnets.

In order to achieve the best possible bias effect, the primary winding and the bias winding are wound substantially parallel to each other around the spool core. In this case, the current flow directions of the electric current should be aligned in antiparallel in adjacent turns of the primary winding and the Vormagnetisierungswicklung.

In order to achieve the least possible control of the bias winding, the power supply terminals of the primary winding and the bias winding can be formed separately from each other.

Alternatively, however, the primary winding and the bias winding may also be jointly controlled and have a common power supply connection. It may be advantageous if a series resistor is connected between the power supply terminal and the bias winding.

Depending on the embodiment of the drive, the bias winding can be actuated either permanently or temporarily, and thereby generates a magnetic field which counteracts the field of excitation of the primary winding and thereby causes the effect of premagnetization.

With a suitable current control, the bias by means of additional winding according to the invention is temperature independent.

The opposite end of the power supply terminal of the bias winding can be connected in a particularly simple embodiment of an ignition coil according to the invention with ground.

A manufacturing technology particularly advantageous structure can be achieved in that the primary winding and the Vormagnetisierungswicklung is wound as a single multi-layer winding on the spool core, wherein the multi-layer winding is separated to separate primary and Vormagnetisierungswicklung at least one point and contacted the free ends for connection purposes are. This has manufacturing technology the advantage that an additional operation is saved.

drawing

• Figur 1 in vereinfachter schematischer Seitenansicht eine erfindungsgemäß ausgestaltete Zündspule, bei der eine Primärwicklung und eine Vormagnetisierungswicklung dargestellt sind;
• Figur 2 eine schematische Schaltbilddarstellung eines Zündsystems mit einer separaten Ansteuerung der Vormagnetisierungswicklung einer Zündspule gemäß Figur 1; und
• Figur 3 eine schematische Schaltbilddarstellung eines Zündsystems mit einer gemeinsamen Ansteuerung der Primärwicklung und der Vormagnetisierungswicklung einer Zündspule gemäß Figur 1.

An embodiment of the invention is illustrated in the drawing and will be explained in the following description. Show it

• Figure 1 in a simplified schematic side view of an inventively designed ignition coil, in which a primary winding and a bias winding are shown;
• Figure 2 is a schematic diagram of an ignition system with a separate control of the bias winding of an ignition coil according to Figure 1; and
• 3 shows a schematic diagram of an ignition system with a common control of the primary winding and the bias winding of an ignition coil according to FIG. 1.

Description of the embodiment

1 shows a simplified schematic side view of an ignition coil 10 for a gasoline engine of a motor vehicle, in which a primary winding 14 and a bias winding 20 are shown. An existing secondary winding is performed in a known manner and not shown in detail in Figure 1.

The primary winding 14 consists of an electrically conductive, insulated wire, which is wound on a rod core 12, wherein the wire is wound from a left in Figure 1 end of the rod core 12 in the direction of a in Figure 1 right end of the rod core 12.

The secondary winding, not shown in greater detail, of the ignition coil 10, in which an energy field is induced by a magnetic field Hp generated on the primary side, is mounted adjacent to the primary winding 14 of this electrically insulated.

In the embodiment shown, the bias winding 20 shown in dashed lines in FIG. 1 represents a completely independent winding. In this case, the electrically conductive, insulated wire of the bias winding 20 is of a left end of the rod core 12 in FIG. 1 in the direction of a right end in FIG wound around the rod core 12, wherein the wire of the bias winding 20 is inserted into the space between the individual turns of the primary winding 14 almost over the entire extent range of the windings. The bias winding 20 and the primary winding 14 are thus wound in parallel over most of the length of the rod core 12.

The current flow I _V in one winding of the Vormagnetisierungswicklung 20 and the current flow I _P in an adjacent winding of the primary winding 14 is anti-parallel, so that the magnetic fields forming a Vormagnetisierungsfeld H _V and the primary-side magnetic field Hp, have an antiparallel orientation. This alignment provides the desired "bias effect"

In the embodiment according to FIG. 1, a connection 24 for supplying an electrical current I _P to the primary winding 14 is arranged separately from a connection 22 for supplying an electrical current I _V to the bias winding 20. In this case, both terminals 22 and 24 can be performed separately via a common connector 28 on a wiring harness of a motor vehicle.

In an alternative embodiment, the bias winding 20 may also be integrated into the primary winding 14. In the manufacture of such an "integrated" bias winding 20, more primary turns than necessary are wound onto the bar core 12 in a single winding operation. Subsequently, both the primary winding 14 and the bias winding 20 are separated by appropriately separating and contacting the respective wire ends of the co-applied winding. In this case, in turn, the terminals 22 and 24 of the primary winding 14 and the bias winding 20 can be performed separately via a common connector 28 on the wiring harness of the motor vehicle.

2 shows a schematic diagram of an ignition system 1 with a separate control of the bias winding 20 of an ignition coil 10 according to the invention for a gasoline engine, wherein the ignition coil 10 - as shown in Figure 1 - a coil core 12, to which the primary winding 14 and the bias winding 20th are wound up.

Here, a separate bias winding drive line 30 is led from the power connector 22 presently connected to the wiring harness of the motor vehicle (not shown) to one end of the bias winding 20 of the ignition coil 10. The other winding end of the bias winding 20 is connected to ground GND.

In a control circuit representing primary circuit 2 of the ignition system 1 is a separate primary winding drive line 32, which may be connected to the primary-side power connector 24, for example, also with the (not shown) harness of the motor vehicle, led to one end of the primary winding 14 of the ignition coil 10. The other end of the primary winding 14 is connected to a transistor 34. This is driven at the base via an engine control 36 of the gasoline engine.

The also surrounding the coil core 12 secondary winding 16 of the ignition coil 10 is part of an ignition circuit forming a secondary circuit 3, in which it contacted in a known manner with one end connected to a ground GND spark plug 18 of a gasoline engine.

In particular, the fact that the bias field H _V does not have to be permanently present, such a separate control of the bias winding 20 of the ignition coil 10 is practicable.

FIG. 3 shows a schematic diagram of an ignition system 1 'with a common control of the primary winding 14 and the bias winding 20.

In this embodiment, as in the ignition system 1 of Figure 2 in the primary circuit leads the primary winding drive line 32 from a power connector 26 on a (not shown) wiring harness of the motor vehicle to one end of the primary winding 14 of the ignition coil 10. The other end of the primary winding 14 is connected to a transistor 34, which is driven at the base via the engine control 36 of the gasoline engine.

A bias winding drive line 30 is here connected to the current terminal 26 of the primary winding drive line 32, the bias winding drive line 30 branching off from the primary winding drive line 32 at a junction 29 and via a bias resistor Rv to one end of the bias winding wound on the coil core 12 20 of the ignition coil 10 is guided. The other winding end of the bias winding 20 is connected to ground GND.

The arrangement of the secondary winding 14 of the ignition coil 10 and the configuration of the secondary circuit 3 with a spark plug 18 of a gasoline engine otherwise corresponds to the embodiment of FIG. 2.

Alternatively, other variants of the control are conceivable. It is important in each case that an anti-parallel to the primary field H _P bias field H _{V is} built to achieve energy optimization by adjusting the bias of the iron orbit.

Claims (8)

1. Ignition coil (10) for a spark-ignition engine, comprising a coil core (12), in which a primary magnetic field (H_P) can be induced by means of a substantially coil-like primary winding (14) through which current flows (I_P), and a substantially coil-like secondary winding (16) in which an energy field which activates at least one spark plug (18) can be built up by the primary magnetic field (H_P), with a premagnetization device for forming a premagnetization field (H_V) which opposes the primary magnetic field (H_P) being active on the coil core (12), characterized in that the premagnetization device has a substantially coil-like premagnetization winding (20) through which current flows (I_V).
2. Ignition coil according to Claim 1, characterized in that the primary winding (14) and the premagnetization winding (20) are wound around the coil core (12) substantially parallel to one another.
3. Ignition coil according to Claim 1 or 2, characterized in that the directions in which the electrical current (I_P and, respectively, I_V) flows are oriented back-to-back in parallel in adjacent turns of the primary winding (14) and of the premagnetization winding (20).
4. Ignition coil according to one of Claims 1 to 3, characterized in that the current-supply connections (22, 24) of the primary winding (14) and of the premagnetization winding (20) are formed separately from one another.
5. Ignition coil according to one of Claims 1 to 3, characterized in that the primary winding (14) and the premagnetization winding (20) have a common current-supply connection (26).
6. Ignition coil according to Claim 5, characterized in that a series resistor (R_V) is connected between the current-supply connection (26) and the premagnetization winding (20).
7. Ignition coil according to one of Claims 4 to 6, characterized in that an end of the premagnetization winding (20), which end is opposite the current-supply connection (22, 24; 26), is connected to earth (GND).
8. Ignition coil according to one of Claims 1 to 7, characterized in that the primary winding (14) and the premagnetization winding (20) are wound onto the coil core (12) as a single multi-layer winding, with the multi-layer winding being split at at least one point in order to separate the primary winding (14) and the premagnetization winding (20) and contact being made with the free ends for connection purposes.

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