EP0102261B1 - Method of obtaining a coil with a closed magnetic circuit and a permanent magnet for the ignition of combustion engines - Google Patents

Description

The invention relates to a method for obtaining a coil with a closed magnetic circuit and a permanent magnet for the ignition of internal combustion engines, in particular of motor vehicles, coil comprising a primary winding and a secondary winding housed in an insulating housing. which surrounds one of the branches of the magnetic circuit.

This circuit consists of strips of sheet metal, of different lengths, stacked on each other and bent at right angles so as to form a closed magnetic circuit which is maintained on the active surfaces 51 and 51 'of the permanent magnet.

A magnetic circuit of the aforementioned type is known, in particular from the Swiss documents CH -A-416817 andUS-A-2878855.

Such a circuit associated with a permanent magnet placed therein as described in document EP - A - 072 266 document referred to in Article 54 (3) of the EPC brings a significant improvement compared to an ignition coil. the magnetic circuit does not have a magnet, due to the fact of the use of a large part of the hysteresis cycle, due to the presence of the permanent magnet.

Although having certain technological advantages compared to the circuit described in FR - 2 484 160, there is a loss of 20% in the use of possible active surfaces in contact with the magnet in a design similar to that described in EP - A - 072 266.

This loss of 20%, which adversely affects the performance of the ignition coil, is due to the fact that the closing of the magnetic circuit is effected by folding the strips according to radii which increase from the inside perimeter to the outside perimeter . The object of the invention is to remedy this drawback and to this end relates to a method for obtaining an ignition coil with a closed magnetic circuit and with a permanent magnet, for ignition of internal combustion engines, coil comprising primary and secondary windings housed in an insulating housing surrounding a branch of the magnetic circuit, consisting of strips, of sheet metal, of width E, stacked on each other, method characterized in that in order to increase the surface of the magnetic circuit in contact with the active surfaces S1, S1 'of the permanent magnet, the strips are pre-bent individually, at right angles, to a radius R1 and at an unequal distance from their ends so that after stacking in a bundle L-shaped, the transverse edges of the ends of the strips are respectively situated on planes corresponding to the planes of the active surfaces S1, S1 ′ of the permanent magnet so that after the insulating housing has been placed on a bronchus of the strip pack, said pack being shaped, by folding, according to increasing radii R2, for its closure on the active surfaces S1, S1 ′ of the permanent magnet, on which the strip pack is held by a device clamping.

The branch on which the insulating housing is placed is previously narrowed, to a width E ', by a stamping in an approximately semi-circular shape, over a length 11, which branch is then brought back to its original width E on a length 12, after installation of the insulating housing.

According to a first embodiment, the clamping device consists of a flange obtained by cutting a side from a sheet, of mild steel, which flange has wings whose internal faces come to bear on the external face of insulating plates inserted between the lateral faces of the strip pack and of the permanent magnet and the internal faces of the flange.

Maintaining the packet of strips and the permanent magnet inside the flange is obtained by prior formation of a hinge which is closed by pressing a tool.

The flange has lugs for fixing the ignition coil to the vehicle, which lugs are formed by successive operations of folding down portions of the flange so that after folding, the portions are presented parallel to an external face so that notches and a side edge formed in the flange portions form openings perpendicular to each other.

According to a variant of this embodiment, the flange has protuberances obtained during the cutting of its side, which protrusions respectively comprise a smooth hole and a threaded hole in which is screwed a screw which reinforces the retention of the packet of strips and the permanent magnet inside the flange.

According to a second embodiment, the clamping device consists of half-flanges comprising a lug for fixing the ignition coil, on the motor vehicle, which half-flanges comprise wings which enclose the pack of strips and the permanent magnet by means of insulating plates. The half-flanges are secured to each other by screws.

In a variant of this second embodiment, the permanent magnet consists of two parts between which a space is formed in which the fixing screw penetrates.

The advantage obtained by the method of the invention consists essentially in that, using a simple shearing tool, strips, at predetermined lengths, and a simple bending tool, at a right angle and at a radius R1 from the sheet metal strips, the surface of the magnetic circuit in contact with the active surfaces S1, S1 'of the permanent magnet is identical to the surface of the magnetic circuit described in the French patent application publication no. 2,486,160, as a result of which, the performance of the ignition coils is identical.

The description which follows with reference to the appended drawings will make it easier to understand how the invention can be implemented.

Figure 1 is a longitudinal sectional view of a magnetic circuit whose strips, of sheet metal, are folded for closure on the permanent magnet, without being carried out, beforehand, a unitary bending of the strips to a radius R1 .

Figure 2 is a longitudinal sectional view of a magnetic circuit whose strips, of sheet metal, are according to the method of the invention, individually bent at a radius R1.

Figure 3 is a longitudinal view of the sheet metal strips, previously arched unitarily at right angles, to a radius R1 and stacked on each other so as to constitute an L-shaped package.

FIG. 4 is a sectional view, along the line AA, of strips, of sheet metal, constituting the package represented by FIG. 3.

FIG. 5 is a longitudinal view of the packet of strips, of sheet metal, in the shape of an L, one of the branches of which is narrowed in width by a stamping in an approximately semicircular shape, over a length 11.

FIG. 6 is a sectional view, along line BB, of the pack of strips, of sheet metal, represented by FIG. 5.

Figure 7 is a longitudinal view of the strip package, sheet, reduced to its original width, over a length 12, after installation of the insulating housing containing the primary and secondary windings.

FIG. 8 is a longitudinal view, in partial section of a first embodiment according to the invention of the device for clamping the pack of bungs, of sheet metal, on the permanent magnet.

FIG. 9 is a sectional view, along the line CC, of the clamping device represented by FIG. 8.

FIG. 10 is the representation of the side of the metal part constituting a part of the first embodiment of the clamping device represented by FIGS. 8 and 9.

FIG. 11 is a representation, in partial perspective and on a reduced scale, of the clamping device corresponding to FIGS. 8, 9 and 10.

Figure 12 is a representation, in partial perspective and on a reduced scale, of a variant of the first embodiment of the clamping device.

Figure 13 is a representation, in partial perspective and on a reduced scale, of a second embodiment of the clamping device.

Figure 14 is a partial longitudinal view on a reduced scale of a variant of the second embodiment of the clamping device.

If, for cost reasons, sheet-cutting tools, in the form of E, L and U, constituting a magnetic circuit such as that described in French patent application publication no: 2486 160, we wish to replace this circuit by a circuit 1 obtained, simply, from strips 2 sheared to different lengths and stacked one on the other, circuit 1 of which one of the branches, FIG. 1, is surrounded by an insulating housing 3 in which are housed primary 4 and secondary 5 windings, it can be seen that the closing of the circuit 1 on the active surfaces 51, Sl'de the magnet losing 20 -% of the surface of the circuit in contact with the active surfaces S1, S1 'relative to the cut sheet circuit whose perimeter and permanent magnet are shown in broken lines, Figure 1. This loss which adversely affects the performance of the ignition coil is due to the fact that the closure of circuit 1 on the active surfaces S1 , S1 'of Aiman t permanent 5, is carried out by folding along increasing R2 radii from the inside perimeter to the outside perimeter.

According to the present invention, the ignition coil shown in Figure 2, comprises a magnetic circuit 1, consisting of strips 2, of sheet metal, one of the branches of which is surrounded by an insulating housing 3 in which are housed windings primary 4 and secondary 5.

According to the method of the invention, and in order to increase the surface of the magnetic circuit 1 in contact with the active surfaces S1, S1 ′ of the permanent magnet 6, the strips 2 sheared to different lengths are previously individually united, at a right angle, to a radius R1, of value 0.5 mm in this exemplary embodiment, and at an unequal distance from their ends in FIG. 3, so that after stacking, one on top of the other, in a bundle 2a, L-shaped, the transverse edges 2b and 2c of the strips 2 are respectively located on planes P and P 'corresponding to the planes of the active surfaces S1 and 51' of the permanent magnet 6. According to a preferred embodiment, 10 branch 2d, Figure 5, of the package 2a, is narrowed to a width E ', over a length 11, by a stamping in an approximately semi-circular shape 2f, Figure 6, before installation of the insulating housing 3, which branch 2d is then brought back to its original width E, over a length 12, f igure 7, after installation, on the portion 2e, of the insulating housing 3, in which are housed the primary 4 and secondary 5 windings.

After which the package 2a is shaped, by folding, along radii R2, of value approximately 2 mm for the internal perimeter of circuit 1 and for this exemplary embodiment, which radii grow from this internal perimeter to the external perimeter, FIG. 2, for 10 closing of the circuit 1 on the active surfaces S1 and S1 'of the permanent magnet 6.

According to a first embodiment, the clamping device 100, of the package 2a on the permanent magnet 6 consists of a flange 101, FIGS. 8 and 9, which flange 101 is obtained by cutting a sidewall 101 a from a sheet of mild steel, FIG. 10 .:

The flange 101 has wings 101 b, FIG. 9, which come to bear on the wings 104a of insulating plates 104 interposed between the lateral jibs of the package 2a and of the permanent magnet 6, the holding of which inside the flange 101 is obtained by the prior formation of a hinge 101c which is closed by pressure in the direction of the arrows F, using any known means. The flange 101 comprises lugs 101d and 101e, obtained during the cutting of the flange 101a, FIG. 10, which lugs, after successive folding operations are presented parallel to the external face 101f of the flange 101, FIGS. 8 and 9, so that notches 101g and 101h and a side edge 101j formed in the legs 101d and 101e, Figure 10, form openings 101k and 1011 perpendicular to each other, Figures 11, for fixing the ignition coil on the vehicle automobile.

According to a variant of the first embodiment of the clamping device 100, the flange 101, has protuberances 101m and 101n shown in FIG. 10 in broken lines, the protrusion 101m has a smooth hole 101p in which engages a screw 110, FIG. 12, the protrusion 101 comprising a threaded hole 101 q, FIG. 10, into which the screw 110, FIG. 12 is screwed, so as to reinforce the retention of the package 2a and of the permanent magnet 6 to 1 inside the flange 101.

According to a second embodiment, the clamping device 100 is made up of half-flanges 120 which include tabs 120a, for fixing the ignition coil to the motor vehicle.

The half-flanges 120 have wings 120b and 120c which enclose the package 2a and the permanent magnet 6, by means of insulating plates 121, arranged identically to the insulating plates 104 of the first embodiment of the clamping device.

The half-flanges 120 are secured to each other using screws 122, one of the half-flanges having smooth holes the other having threaded holes.

According to a variant of the second embodiment of the clamping device, the permanent magnet 6 consists of two parts 6a, 6b, between which a space is formed in which a screw 130 penetrates which secures the half-flanges 120.

The metal flanges 101 and 120, as well as the insulating plates 104 and 121, of the present invention advantageously constitute a circuit for bypassing the magnetic flux created by the primary winding 4, bypass circuit described in the French patent application no. publication 2,486,160.

Claims (7)

1. Process for obtaining a coil with a closed magnetic circuit and with a permanent magnet for the ignition of internal-combustion engines, the coil comprising: a permanent magnet (6) for the primary winding (4) and secondary winding (5) which are accommodated in an insulating housing (3) surrounding a branch of the closed magnetic circuit (1) consisting of sheet-metal strips (2) stacked on top of one another, the process being characterised in that, in order to increase the surface of the closed magnetic circuit (1) in contact with the active surfaces (S1, S1') of the permanent magnet (6), the strips (2) of width E are previously bent as a single unit at right angles to a radius R1 and at an unequal distance from their ends, in such a way that, after stacking in the form of an L-shaped pack (2a), the transverse edges (2b and 2c) of the strips (2) are respectively located on planes P and P' corresponding to the planes of the active surfaces S1, S1 ' of the permanent magnet (6), so that, after the insulating housing (3), in which the primary winding (4) and secondary winding (5) are accommodated, has been fitted over a portion (2e) of the pack (2a), the latter is shaped by means of bending according to radii R2 increasing from the inner perimeter of the magnetic circuit (1) to its outer perimeter, for closing the said circuit (1) on the active surfaces S1, S1 ' of the permanent magnet (G), on which surfaces the pack (2a) is retained by means of a clamping device (100).

2. Process according to Claim 1, characterised in that one branch (2d) of the pack (2a) is narrowed to a width E ' over a length L1 by means of stamping in an approximately semicircular form (2f), before the insulating housing (3) i s fitted, the said branch (2d) is subsequently returned to its original width E over a length L2 after the insul ating housing (3), in which the primary winding (4) and secondary winding (5) are accommodated, has been fitted.

3. Process according to Claim 1, characterised in that the clamping device (100) consists of a clamp (101) obtained by cutting out a blank (101 a) from a sheet of mild steel, the said clamp (101) having wings (101 b), the inner face of which comes up against the outer face (104a) of insulating plates (104) inserted between the side faces of the pack (2a) and of the permanent magnet (6) and the inner faces of the clamp (101), and the pack (2a) and pemanent magnet (6) being obtained as a result of the previous formation of a hinge (101 c) which is closed by means of pressure.

4. Process according to Claim 3, characterised in that the clamp (101) has lugs (101 d and 101e) for fastening the ignition coil to a vehicle, the said lugs (101 d and 101 e) after successive folding-back operations being parallel to the outer face (101f) of the clamp (101), so that notches (101g and 101h) and a lateral edge (101j) made in the lugs (101 d and 101e) form orifices (101 and 1011) perpendicul ar to one another.

5. A process according to either one of Claims 3 and 4, characterised in that the clamp (101) has protuberances (101m and 101 n) which are obtained when the blank (101 a) is cut out and which possess respectively a smooth hole (101 p), which a screw (1101 engages, and a threaded hole (101q), into which the screw (110) is screwed.

6. Process according to Claim 1, characterised in that the clamping device (100) consists of half-clamps (120) having a lug (I20a) for fastening the ignition coil to the vehicle, the said half-clamps (120) having wings (120b and 120c) which grip the pack (2a) and the permanent magnet (61) by means of insulating plates (121), the half-clamps (120) being fixed to one another by means of screws (122).

7. Process according to Claim G, characterised in that the permanent magnet (6G) consists of two parts (6a and 6b), between which there is a space, into which penetrates a screw (130) ensuring that the half-clamps (120) are fixed to one another.

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