EP0609109A1 - Bobbin for secondary winding of ignition coil for internal combustion engine - Google Patents

Abstract

Bobbin for secondary winding of ignition coil for internal combustion engine, of the type comprising a tubular winding core (2) and a plurality of fins (5) which are substantially perpendicular to the axis (3) of the core, the fins defining annular winding compartments (6) between them, of which the core forms the bottom (8) and each including a passage (9) in order to allow the wire of the secondary winding to pass, in the direction of the winding, from the compartment situated upstream of this fin to the compartment situated downstream, characterised in that the said core has a shape such that the said passage opens out into the compartment upstream at a certain distance (e) from the said core and into the compartment downstream at the level of the said core. <IMAGE>

Description

The present invention relates to a secondary winding coil of an ignition coil for an internal combustion engine, and more particularly such a coil of the type comprising a tubular winding core and a plurality of fins substantially perpendicular to the axis of the core. , the fins delimiting between them annular winding compartments whose core forms the bottom, and each comprising a passage to allow the wire of the secondary winding to pass, in the winding direction, from the compartment located upstream of this fin to the compartment located downstream.

Such secondary coils are known, for example from document EP-A-0 375 502.

In spark ignition internal combustion engines, the combustion of the gas mixture in the cylinder is caused by the spark that occurs between the electrodes of a spark plug.

In order to produce this spark, the terminals of the spark plug are connected to the ends of the secondary winding (high-voltage) of a transformer such as an ignition coil, the primary winding of which is connected to a voltage source. via a switch such as a transistor.

With this switch closed, an electric current flows through the primary winding. If at a given instant the switch is then open, a sudden overvoltage occurs in the primary winding which, by induction, generates a voltage spike in the secondary winding. When this voltage reaches a sufficient value, the spark occurs causing the ignition of the fuel mixture.

The voltage across the secondary can reach several tens of thousands of volts. The aforementioned fins, by delimiting separate winding compartments, make it possible to limit the risks of the formation of a spark between two turns of this winding. Indeed, the voltage between the input coil and the output coil of the same compartment is limited to a few thousand volts in the usual case where the number of compartments is of the order of ten.

However, the entry and exit of a compartment being effected by a slot in each of the fins delimiting this compartment, the tension between two turns located opposite each other of this slot in two compartments adjacent therefore remains of the order of a few thousand volts, so that the risks of forming a spark are nevertheless not completely ruled out.

The aforementioned document proposes to remedy this drawback by providing isolation compartments between the winding compartments so as to increase the distance between the turns of two successive winding compartments.

Such an arrangement nevertheless has the drawback of increasing the axial dimension of the secondary coil, and consequently of the ignition coil which comprises it.

The present invention aims to overcome this drawback.

To this end, the subject of the invention is a secondary winding coil of an ignition coil for an internal combustion engine, of the type comprising a tubular winding core and a plurality of fins substantially perpendicular to the axis of the core. , the fins delimiting between them annular winding compartments whose core forms the bottom, and each comprising a passage to allow the wire of the secondary winding to pass, in the winding direction, from the compartment located upstream of this fin in the downstream compartment, characterized in that said core has a shape such that said passage opens into the upstream compartment at a certain distance from said core and into the downstream compartment at said core.

Thus, at the level of the passage, the windings of two adjacent compartments are offset, so that it is possible to limit the tension between two turns arranged opposite.

The passage may in particular be constituted by the bottom of a slot extending from the edge of the fin.

More particularly, the bottoms of two adjacent compartments can be offset radially at the level of said passage, by a distance equal to a thickness of winding.

In other words, the wire of the secondary winding is brought back, during the passage from the upstream compartment to the downstream compartment, from the upper level of the winding to a lower level.

In this case, only the last winding turns of the upstream compartment are opposite the first turns of the downstream compartment, so that practically no difference in potential exists at the level of the passage slot.

In a particular embodiment of the invention, the core has a generally rectangular section, said passage being formed in an angle of the core, and the corresponding angle of the upstream compartment being cut.

Other geometries are possible, the essential being that the bottoms of two adjacent compartments are not, in projection one on the other, completely superimposed, so as to allow the passage of the wire of a certain level of the compartment upstream at the bottom of the downstream compartment. The funds of the compartments can in particular be identical and, in projection, between two adjacent compartments, be offset in their plane, or angularly about their axis.

Thus the bottoms of two adjacent compartments can be circular eccentric, or elliptical with large axes angularly offset, or rectangular offset in their plane parallel to one of their side or their diagonal, or even rectangular with their diagonals angularly offset.

It is also possible to angularly offset the inlet passage in a compartment from its outlet passage.

Said inlet and outlet passages may in particular be diametrically opposite.

• la figure 1 est une vue de côté d'un bobinot secondaire selon l'invention,
• la figure 2 est une superposition destinée à mieux faire comprendre l'invention des vues en coupe selon les lignes IIa-IIa et IIb-IIb des figures 1 et 3,
• la figure 3 est une vue en coupe axiale selon la ligne III-III de la figure 2,
• la figure 4 est un schéma en vue axiale de l'enroulement dans un compartiment d'enroulement,
• les figures 5a à 5d illustrent le passage du fil dans des compartiments d'enroulement successifs, et
• les figures 6 à 10 sont des figures similaires à la figure 2, illustrant des variantes de réalisation.

A particular embodiment of the invention will now be described by way of nonlimiting example, with reference to the appended drawings in which:

• FIG. 1 is a side view of a secondary bobbin according to the invention,
• FIG. 2 is a superposition intended to better understand the invention of the sectional views along lines IIa-IIa and IIb-IIb of FIGS. 1 and 3,
• FIG. 3 is a view in axial section along the line III-III of FIG. 2,
• FIG. 4 is a diagram in axial view of the winding in a winding compartment,
• FIGS. 5a to 5d illustrate the passage of the wire through successive winding compartments, and
• Figures 6 to 10 are figures similar to Figure 2, illustrating alternative embodiments.

We see in Figure 1 the secondary coil 1 of an internal combustion engine ignition coil, formed of a tubular core 2 of axis 3, and made in known manner of insulating plastic. The bodies 4 for mounting and connecting the bobbin are made in one piece with the core 2.

Furthermore, fins 5 perpendicular to the axis 3, delimit between them winding compartments 6. Each compartment 6 therefore forms a groove, the side walls 7 of which are formed by the two fins which delimit this compartment, and the bottom 8 of which is formed by the core 2.

The winding is carried out compartment by compartment, from right to left in FIG. 1. Consequently, the fin 5b of FIG. 1 separates its upstream compartment 6a situated on its right from its downstream compartment 6b situated on its left.

As can be seen in FIG. 2, the bobbin 1, and in particular its core 2, has a substantially rectangular shape.

We also see in this figure how the passage of the winding wire from one compartment to the other is effected by slots 9 extending from the edge of the fins and substantially tangent to the core. More particularly, we see in this figure the slot 9a formed in the fin 5a, to allow entry into the compartment 6a, and the slot 9b formed in the fin 5b, to allow the passage of the wire from compartment 6a to the compartment 6b. The slot 9a is tangent to the bottom 8a of the compartment 6a and arrives at this bottom, just as the slot 9b is tangent to the bottom 8b of the compartment 6b and also arrives at this bottom.

We also see in Figure 2 that at the slot 9b for passage from compartment 6a to compartment 6b, the bottom 8a of the compartment 6a has its angle 10 cut, so that at this angle 10 the bottom of the slot 9b extends at a certain distance e from the bottom 8a of the compartment 6a.

FIG. 4 only shows the bottoms 8a and 8b of the compartments 6a and 6b, the slots 9a and 9b, the winding 11a in the compartment 6a and the first coil 12 of winding in the compartment 6b. It can also be seen in this figure that the distance e is equal to the thickness of the winding 11a. Consequently, the first turn 12 of the winding in the compartment 6b is, at the level of the slot 9b, facing the last winding layer in the compartment 6a, so that it is not located no difference in potential between the windings in the two compartments at this slot.

Figures 5a to 5d which show, simplified, sections along a line such as VV of Figure 2, illustrate the winding of a wire 20 whose diameter would be equal to the thickness of a compartment 6, and which schematically so in fact several layers of winding.

We see in Figure 5a the wire 20 filling a compartment 6 _n and entering the compartment 6 _{n + 1} through the slot 9 _n formed in the fin 5 _n .

The filling of the compartment 6 _{n + 1} by the wire 20 is carried out as shown in FIG. 5b. It can be seen in this figure that no potential difference exists at the level of the slot 9 _n between the winding in the compartment 6 _n and the winding in the compartment 6 _{n + 1} .

When the winding in this compartment 6 _{n + 1} arrives, in the angular zone of the slot 9 _{n + 1} of the fin 5 _{n + 1} , at the bottom 8 _{n + 2} of the compartment 6 _{n + 2} , the wire 20 passes through this slot and the winding in the compartment n + 2 is started, as shown in FIG. 5c.

The winding thus continues compartment by compartment, FIG. 5d representing the winding in the following compartment 6 _{n + 3} .

Figures 6 to 10 showing other embodiments, are similar to Figure 2, but only the funds of the compartments have been shown, the passages from one compartment to the other being illustrated by arrows.

In FIG. 6, the bottoms of the compartments are circular, the bottoms 61 and 62 of the upstream and downstream compartments respectively being offset in their plane. The passage from the upstream compartment to the downstream compartment takes place at the arrow 63, and the passage to the following compartment is diametrically opposite.

In FIG. 7, the bottoms 71 and 72 of the upstream and downstream compartments form ellipses whose major axes are perpendicular, the passage from the upstream compartment to the downstream compartment taking place at one of the arrows 73 or 73 '. The passage to the next compartment is here offset by 90 degrees compared to the previous one.

In the case of FIG. 8, the bottoms 81 and 82 of the upstream and downstream compartments are square and offset in their plane parallel to one on their side. The passage from the upstream compartment to the downstream compartment takes place at the arrow 83, in the zone of the middle of the sides 84 offset. The passage to the next compartment is carried out in the area on side 85 opposite side 84.

FIG. 9 also illustrates an embodiment where the bottoms 91 and 92 of the upstream and downstream compartments are square, but here they are angularly offset by rotation in their plane around their axis. The passage from the upstream compartment to the downstream compartment takes place at one of the arrows 93, 93 ', 93'',93''' and the passage to the next following compartment at one of the arrows 94, 94 ', 94'',94'''.

Finally, in the embodiment of FIG. 10, the bottoms 101 and 102 of the upstream and downstream compartments respectively are always square, but they are offset in their plane parallel to one of their diagonals. The passage from the upstream compartment to the downstream compartment takes place at the arrow 103 and the passage to the following compartment is offset by 180 degrees.

Claims (10)

Ignition coil secondary winding coil for an internal combustion engine, of the type comprising a tubular winding core (2) and a plurality of fins (5) substantially perpendicular to the axis (3) of the core, the fins delimiting between them annular winding compartments (6) the core of which forms the bottom (8), and each comprising a passage (9) to allow the wire of the secondary winding to pass, in the direction of winding , from the compartment located upstream of this fin to the compartment located downstream, characterized in that said core has a shape such that said passage opens into the upstream compartment at a certain distance (e) from said core and into the downstream compartment at of said nucleus. Bobbin according to claim 1, wherein said passage is constituted by the bottom of a slot extending from the edge of the fin. Bobbin according to any one of claims 1 and 2, wherein the bottoms of two adjacent compartments are offset radially at said passage, by a distance (e) equal to a winding thickness. Bobbin according to any one of claims 1 to 3, wherein said core has a generally rectangular section, said passage being formed in an angle of the core, and the corresponding angle (10) of the upstream compartment being cut. Bobbin according to any one of claims 1 to 3, in which the bottoms of two adjacent compartments form non-concentric circles, notably substantially identical. Bobbin according to any one of claims 1 to 3, in which the bottoms of two adjacent compartments form ellipses, in particular substantially identical, whose major axes are angularly offset. Bobbin according to any one of claims 1 to 3, in which the bottoms of two adjacent compartments form two rectangles, in particular substantially identical, offset in their plane. Bobbin according to any one of claims 1 to 3, in which the bottoms of two adjacent compartments form rectangles, in particular substantially identical, whose diagonals are angularly offset. Bobbin according to any one of claims 1 to 8, in which the inlet passage in a compartment is angularly offset from its outlet passage. The bobbin of claim 9, wherein said inlet and outlet passages are diametrically opposed.

Images