SWITCH WITH INDUCTOR FUNCTION

Abstract: The invention relates to an inductive component having a relay and inductor function. According to the invention, one and the same magnetic circuit is used for both the relay and the inductor function. The inductive component includes a fixed part (22, 32, 52) and a movable part (21, 31, 51) with an air gap (24, 44, 53) therebetween, and further includes a coil having two windings. The first winding is adapted to receive a strong current and therewith attract the movable part towards the fixed part, therewith providing the relay function, whereas the other winding is adapted to receive a weak current that will not influence the position of the movable part, such as to provide the inductor function.

Description: SWITCH WITH INDUCTOR FUNCTION FIELD OF INVENTION The present invention relates to a component that has a combined relay function and inductor function in one and the same magnetic circuit . DESCRIPTION OF THE BACKGROUND ART The line circuits of telecommunications networks often include both relays and inductors. The relay works at the beginning and at the end of a call set-up procedure and is at rest therebetween, when the inductor instead comes into operation. Many variants of both relays and inductors are known to the art. One inductor variant, such as the variant taught by U.S. Patent Specification 4,635,018 is fabricated by winding a strip of non-amorphous material into a rectangular shape, and thereafter winding a strip of amorphous material around the non-amorphous strip through a number of turns. SUMMARY OF THE INVENTION The invention is based on the realisation that relay and inductor need never operate simultaneously in a line circuit, and that component use can therefore be rationalised by using a common component for both relay and inductor functions. More specifically, the object of the present invention is to provide an inductive component whose magnetic circuit is adapted to function both as a relay and as an inductor. This affords the advantage of reduced component costs and reduced assembly costs . A saving in board space is also achieved and because the invention contributes towards enabling more lines to be placed on a circuit board, the common mechanical part of the total line cost is also reduced. The invention includes a coil having two windings arranged on a magnet core which comprises a fixed part and a movable part that are separated mutually by an air gap. When the invention is to be used as an inductor, a weak current is passed through one winding, wherewith the movable part remains unaffected and the air gap unchanged. When the invention is to be used as a relay instead, a strong current is passed through the other winding, wherewith the movable part is drawn or attracted to the fixed part and the air gap is reduced to zero. The area of the air gap can be increased conveniently by giving the air gap a V-shape, therewith decreasing its reluctance and increasing the attractive force. The term "V-shaped" is not to be interpreted strictly, but shall be understood to include all V- like shapes, including conical shapes. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a principle diagrammatic illustration of a present- day relay and inductor in a line circuit. Figures 2a and b illustrate the magnetic flux in air gaps of different angles. Figures 3a and b are respective side views of one embodiment of the invention. Figure 3c illustrates part of one variant of Figure 3b. Figures 4a and b are respectively a perspective view and a sectional view of another embodiment of the invention. Figures 5a and b illustrate a further embodiment of the invention from above. All illustrated air gaps have been exaggerated for the sake of clarity. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a principle diagram illustrating part of a present- day line circuit construction. The relay 1 works at the beginning and at the end of a call set-up procedure and is at rest therebetween. The inductor 2, on the other hand, operates between the call set-up and call release procedures, i.e. during the time at which the relay 1 is at rest. According to the present invention, the relay function and inductor functions are combined in one and the same component and in one and the same magnetic circuit. This is made possible mainly by the use of strips of ferromagnetic, amorphous material. These strips have very good magnetic properties and result in low losses. They are best suited for winding. Among other things, the combined relay and inductor component includes a coil 20, 30, 50 having two windings. A weak current is caused to flow in one winding when wishing to use the component as an inductor, whereas a strong current is caused to flow in the other winding when wishing to use the component as a relay. The component also includes a fixed part 22, 32, 52 and a movable part 21, 31, 51 with an air gap 24, 44, 53 therebetween for the relay function. The force required to draw the parts together is proportional to the reluctance, and hence the reluctance will preferably be as small as possible. The reluctance in an air gap is proportional to the thickness of the air gap divided with the area. Consequently, it is best to have as wide an area as possible in the air gap of a relay. Trials have shown that in practice, a V-shaped air gap 10 (see Figure 2a) which is inclined at about 45° to the flux direction 12 will function best. The symmetry thus achieved will result in the parts 15, 16 being drawn straight together. Normally, the magnetic flux 12 crosses the air gap 10 at right angles to the edge 11 of the air gap, although when attempting to obtain an excessively acute angle, such as that in Figure 2b, it is necessary in theory for the magnetic flux 12 to make an abrupt swing (the dotted line 14) . This will not occur in practice, and the air gap 10 is instead passed at an angle of close to 45° to the earlier flux direction 12 in all instances (the full line 13) and hence the air gap 10 is experienced as being wider than it actually is and the attractive force thus becomes smaller. In one embodiment shown in Figures 3a and b, a ferromagnetic, amorphous strip 27 of thickness 10-40 μm and width 5 mm is wound to provide a rectangular magnetic core 23 having a thickness of 8 mm. The core 23 is cut with the aid of a laser to provide two air gaps 24, 25. A laser is used in this respect because the two strip windings are then fused together. It would otherwise be necessary to affix the strip windings with some sort of fixative in the air gaps 24, 25. One air gap, 24, is V-shaped with an angle of about 45° to the main flux direction 29, and it is here that the relay function is achieved. The other air gap, 25, is cut straight. Because the area of the air gap 25 is smaller than the area of the V- shaped air gap 24, the air gap 25 will move to a far lesser extent during a switching process than the V-shaped air gap 24 and therefore functions in the manner of a hinge. This "hinge" function can be improved, by giving the air gap 24 the shape of a thin wedge with the apex facing inwards, as illustrated in Figure 3c. Finally, a coil 20 having two windings is provided at some location around the magnet core 23, as illustrated schematically in Figure 3b. Figures 4a and b illustrate another embodiment of the invention. In this case, the V-shaped air gap has been widened to three dimensions and has a conical shape, which provides a larger air-gap area. The increase in symmetry by one dimension also provides improved stability properties. The fixed part 32 is fabricated from three ferromagnetic, amorphous strips 35, 36, 37. Two of the strips 35, 36 have generally equal widths, whereas the third strip 37 is substantially narrower than the other two strips 35, 36. The two wider strips 35, 36 are wound around a support pin 46a and also around one another to form a cylinder 34 that has a planar outer end 38 and a stepped inner end 67. The broader of the bands 36 is wound outermost. The narrow band 37 is then wound edge-to-edge with the planar end 38 to form a flange 37. The movable part 31 is produced from four ferromagnetic, amorphous strips 39, 40, 41, 42. Two of the strips 39, 40 are almost of equal width and the third strip 41 is substantially narrower than the two first strips 39, 40. The fourth strip 42 will be described below. The two wide strips 39, 40 are wound around a support pin 46b and around each other to form a cylinder 33 having a planar outer end 43 and a stepped inner end 66. The narrower strip 40 is wound outermost. The narrow strip 41 is then wound edge-to-edge with the planar end 43, to form a flange 41. A casing 42 is finally wound edge-to-edge with the planar end 43. The casing 42 is fabricated from the fourth strip 42, whose width is essentially equal to the combined width of the two cylinders 33, 34. The cylinder 34 in the fixed part 32 and the cylinder 33 in the movable part 31 are complementary to one another with respect to their stepped inner ends 66, 67, and a cone-like stepped air gap 44 is thus formed between said inner ends 66, 67 when the movable part 31 is disposed around the fixed part 32. A true cone 49 will be obtained when lines are drawn along the edges of the steps in the air gap 44. The resultant cone 49 considered in the plane through the centre line 47 of the cylinders will suitably define an angle of about 45° with the main flux direction 48. The diameter of the flange 37 on the fixed part is almost as large as the inner diameter of the casing 43 on the movable part, so as to form a narrow air gap therebetween. Finally, a coil 30 having two windings is disposed around the two cylinders 33, 34, as shown schematically in Figure 4b. The connection wires to the coil 30 pass through a hole or aperture (not shown) provided somewhere in the fixed part 31. The hole will not disturb the magnetic flux to any appreciable extent, provided that the hole is not too large. When a monostable relay is required, a spring 45 which strives to separate the two parts 31, 32 is provided in one end of the coil. Although not shown, a plastic casing or the like is applied around the parts 31, 32, for the purpose of guiding and holding the parts 31, 32 in place. The support pins 46a, 46b may be made of plastic or copper for instance, the only criterion being that the material used in this respect is non-magnetic. Instead of winding the strips around a support pin, the strips may be wound around air, which is, after all, a non-magnetic material. It will also readily be understood that the number of strips/steps in the cylinders can be increased. Figures 5a and b illustrate another embodiment of the invention. Ferromagnetic, amorphous material is best suited for the windings, because of its hardness. The windings may also be punched for instance, although the tools used herefor will become quickly worn, which is not particularly economical. When the demands placed on the magnetic properties of the material are not particularly high, and particularly when the inductor part is not required to handle high frequencies, the material used may be punched metal sheet for instance . This provides greater flexibility with regard to design. The aforementioned V-shaped air gap need not be strictly V-shaped. The apex of the V may be displaced plane-parallel outwardly along the main flux direction. This divides the air gap into three parts with narrow cracks therebetween. This construction provides a stronger attractive force in respect of large air gaps. Alternatively, the apex of the V may be displaced plane-parallel inwardly, so that the air gap obtains a more W-like shape instead. In the Figure 5a embodiment, the fixed part 52 has an E-shape with three legs 54, 55, 56. The outer legs 54, 56 are straight while the outer end 57 of the centre leg 55 is V-shaped with the apex of the V pointing outwards. The apex portion 57b of the V is displaced outwards in plane-parallel along the main flux direction 63. The movable part 51 includes a leg 60 and a cross-leg 64. The width of the cross-leg 64 is almost equal to the distance between the outer legs 54, 56 of the fixed part, so as to form narrow air gaps between the cross-leg 64 and respective outer legs 54, 56 of the fixed part. The leg 60 of the movable part is shaped complementary to the centre leg 55 of the fixed part and forms together therewith a straight centre leg 62 (see Figure 5b) . Those sides of the centre leg 55 of the fixed part and those sides of the leg 60 of the movable part that are not parallel with the main flux direction 63 define an angle of about 45° with said main flux direction 63. An air gap 53abc is formed between the fixed part 52 and the movable part 51. Finally, a coil 50 having two windings is disposed around the resultant straight centre leg 62, as shown schematically in the Figure. By way of variation, the outer end 57 of the centre leg of the fixed part may be V-shaped with the apex of the V pointing inwards. The apex portion 57b of the V-shape may be displaced plane-parallel both inwardly and outwardly in both cases. The drawings do not show the necessary outer guide mechanics in the form of plastic rings, for instance.

Claims: CLAIMS 1. An inductive component that has both relay and inductor functions, characterized by a magnet core which comprises a fixed part (22, 32, 52) and a movable part (21, 31, 51) and an air gap (24, 44, 53) therebetween, and by a coil (20, 30, 50) having two windings disposed around the core; wherein the first winding is adapted to attract the movable part towards the fixed part when a strong current is passed through the first winding, such as to provide the relay function; and wherein the other winding is adapted to receive a weak current that will not influence the position of the movable part and therewith provide the inductor function. 2. An inductive component according to Claim 1, characterized in that the magnet core (23) comprises a strip of material (27) wound to a rectangular shape, wherein the core (23) is cut to form an air gap (24, 25) at two locations. 3. An inductive component according to Claim 2, characterized in that one air gap (24) is V-shaped, when seen from one side, and is formed in one side (26) of the rectangular magnet core (23) ; and in that the other air gap (25) is generally straight and is formed in an opposite side (28) perpendicular to said opposite side (28) . 4. An inductive component according to Claim 3, characterized in that the V-shaped air gap (24) defines an angle of about 45° with the main flux direction (29) . 5. An inductive component according to any one of Claims 2-4, characterized in that the straight air gap (25) has the shape of a thin wedge with the apex of the wedge pointing towards the interior of the rectangular core (23) . 6. An inductive component according to any one of Claims 2-5, characterized in that the air gaps (24, 25) have been cut with the aid of a laser. 7. An inductive component according to Claim 1, characterized in that the fixed part (32) includes a cylinder (34) having a planar outer end (38) and a stepped inner end (67) , wherein the cylinder (34) has been formed by winding at least two strips (35, 36) of mutually different widths around a non-magnetic material (46a) and around each other, and further comprises a flange (37) which has been formed by winding a narrower band (37) around the cylinder (34) edge-to-edge with the planar outer end (38) ; in that the movable part (31) comprises a cylinder (33) having a planar outer end (43) and a stepped inner end (66) , wherein the cylinder (33) has been formed by winding at least two strips (39, 40) of mutually different widths around a non-magnetic material (46b) and around each other, and further comprises a flange (41) formed by winding a narrow band (41) around the cylinder (33) edge-to-edge with the planar outer end (43) , and further comprises a casing (42) which includes a strip (42) whose width is generally equal to the combined width of the two cylinders (33, 34) , wherein said casing strip (42) has been wound around the flange (41) edge- to-edge with the planar outer end (43) ; in that the cylinders (33, 34) are complementary at their stepped inner ends (66, 67) ; in that the casing (42) of the movable part is disposed around the fixed part (32) with the cylinders (33, 34) positioned along a common centre line (47) , wherein the air gap (44) is formed between the complementary stepped inner ends (66, 67) of the cylinders; in that the diameter of the flange (37) on the fixed part is substantially equal to the inner diameter of the casing (43) of said movable part, wherein the movable part (31) is able to move along the centre line (47) of respective cylinders freely in relation to the fixed part (32) ; and in that the coil (32) is disposed around the cylinders (33, 34) inwardly of the casing (42) , wherein the casing (42) includes a hole or aperture through which the coil connecting wires are passed. 8. An inductive component according to Claim 7, characterized in that when the air gap (44) is viewed in a plane through the centre line (47) of the cylinders, those angles that are defined between the main flux direction (48) and alluded lines (49) between the steps in the air gap (44) are about 45°. 9. An inductive component according to any one of Claims 7-8, characterized in that the coil (30) includes a spring (45) at one end, said spring functioning to forcibly separate the fixed part (32) and the movable part (31) . 10. An inductive component according to any one of Claims 7-9, characterized in that the non-magnetic material (46a, 46b) is air. 11. An inductive component according to any one of Claims 7-9, characterized in that the non-magnetic material (46a, 46b) is plastic or copper. 12. An inductive component according to any one of Claims 2- 11, characterized in that the strip (27) or the strips (35, 36, 37, 39, 40, 41, 42) is/are comprised of ferromagnetic, amorphous material. 13. An inductive component according to Claim 1, characterized in that the fixed part (52) is E-shaped and has two outer, straight legs (54, 56) and a centre leg (55) whose outer end (57) is V-shaped with the apex portion (57b) of the V-shape displaced plane-parallel along the main flux direction (63) ; and in that the movable part (51) includes a cross-leg (64) whose length is almost equal to the distance between the outer legs (54, 56) of the fixed part, and further includes a leg (60) whose shape is complementary to the shape of the centre leg (55) of the fixed part and which together with said centre leg (55) forms a straight centre leg (62) with the air gap (53) for the relay function, wherein the coil (50) is disposed around the straight centre leg (62) . 14. An inductive component according to Claim 13, characterized in that those sides of the centre leg (55) of the fixed part and those sides of the leg (60) of the movable part which is not parallel with the main flux direction (63) define an angle of about 45° with said main flux direction (63) . 15. An inductive component according to any one of Claims 13- 14, characterized in that the core material is punched metal sheet . 16. An inductive component according to any one of Claims 13- 14, characterized in that the core material is punched ferromagnetic, amorphous material.

Inventors: LINDQVIST BENGT ARNE YNGVE, LINDQVIST, BENGT, ARNE, YNGVE
Applicants: ERICSSON TELEFON AB L M, LINDQVIST BENGT ARNE YNGVE, LINDQVIST, BENGT, ARNE, YNGVE, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1996
Main classification: H01F7
IPC codes: H01F7, H01F17, H01H50, H04M19