FR2591024A1 - MAGNETIC CIRCUIT WITH LOW MAGNETIC FIELD RAYS, ESPECIALLY FOR A HIGH VOLTAGE TRANSFORMER SUPPLYING A CATHODE TUBE - Google Patents

Abstract

To reduce the magnetic field radiated by a high voltage transformer, the air gap is placed inside the coil 9, a shim 8 ensuring the mechanical rigidity of the magnetic circuit 2, 3 which is assembled by cold bonding. Application: televisions. (CF DRAWING IN BOPI)

Description

2 5 9 1 0 2 4

I

  MAGNETIC CIRCUIT WITH LOW MAGNETIC FIELD

  RADIATES, ESPECIALLY FOR A TRANSFORMER

  HIGH VOLTAGE FEEDING A CATHODIC TUBE

  The present invention relates to a magnetic circuit to

  radiated magnetic field, in particular for a transfor-

  high voltage generator feeding a cathode ray tube.

  High voltage transformers such as those used to power cathode ray tubes generally include a well-defined value of their ferrite magnetic circuit. This gap radiates a magnetic field producing harmful effects on the cathode ray tube, and even on other circuits

  can capture them by antenna effect.

  The subject of the present invention is a magnetic circuit for a high-voltage transformer whose radiations produced by the air gap are reduced to a minimum value and whose effects on the surrounding components or circuits are negligible, this magnetic circuit being easy and inexpensive to produce , especially for mass production, the value of

  inductance, and in particular the primary inductance of the transformer

  The meter is easy to adjust with low tolerances.

  The magnetic circuit according to the invention, of the type with two half-circuits in "U", comprises an air gap housed inside a

  winding, the thickness of this gap being determined by the manufacturer

  cation of the magnetic circuit by grinding the ends of the legs of the two half-circuits, which are then glued together, the

  side of the gap with the interposition of a shim

  equal to the desired air gap thickness, made of

  tick, and the opposite side directly to each other.

  The present invention will be better understood on reading the

  detailed description of an embodiment taken as an example

  non-limiting and illustrated by the accompanying drawing, the single figure is a simplified sectional view of a magnetic circuit according to

the invention.

  The magnetic circuit described below is intended for a high voltage transformer supplying a cathode ray tube, but it is understood that the invention is not limited to such an application, and can be used both when it is desired to reduce the magnetic radiation of a transformer or inductor, when it is desired to set the

  inductance value of a winding arranged on a magnetic circuit

  tick. The magnetic circuit I shown in the drawing comprises two half-circuits 2, 3, ferrite, shaped "U". The ends of the legs of the half-circuits 2 and 3 are referenced 4, 5 and 6, 7 respectively. The ends 4 and 6 of the legs of the half-circuits 2, 3 must come into close contact with one another to leave only a very small air gap, the residual air gap having

  less than 0.1 mm thick after bonding.

  Between the ends 5, 7, the necessary gap is created by shortening, preferably of the same value, that is to say the value of half the thickness of the air gap, the lengths of the legs having for ends 5 and 7 (it is assumed that initially the two legs of each "U" have the same length). The front faces of the ends 4 to 7 are ground so that on the one hand the ends 4 and 6 allow to susbsister a regular minimal residual gap, and that we obtain between the ends 5 and 7

the gap of desired value.

  To obtain a solid assembly, we stick between the

  5 and 7 a wedge 8 of non-magnetic material, whose thickness is substantially equal to that of the desired gap, given the

  glue joint, this wedge playing only a mechanical role.

  According to a variant of the invention, the shim 8 is made of magnetic material, of magnetic characteristics different from those of the half-circuits 2 and 3 and / or of section different from that of the legs of these circuits, in order to obtain other possibilities for adjusting the inductance values of the windings arranged on this circuit

  magnetic. A winding 9 with one or more windings (transforming

2 5 9 1 0 2 4

  meter or inductance) surrounds the ends 5 and 7 and the shim 8.

  Preferably, the assembly of the parts 2 and 3 and the shim 8 is made using glue type quick-setting cold gluing, to obtain joints with a thickness of less than 0.1 mm. It is also possible to fix with the same glue the carcass of the winding on

the ends 5 and 7.

  In the case of the realization of a high-voltage transformer

  supplying a cathode ray tube, it has been found that the inductive

  the primary winding of such a transformer was critical, the tolerance to be less than or equal to 8%, which

  could be difficult to obtain with the processes of the prior art.

  to adjust the thickness of the air gap individually

for each transformer.

  By cons, according to the present invention, it is sufficient, for the same series of transformers or inductors, to machine the legs

  half circuits 2 and 3 always at the same lengths, these half

  circuits being assembled automatically with the shim 8 and the winding 9, to no longer have to adjust after assembly the gap thickness, easily respecting the tolerances set for the

inductance value.

  Moreover, there has been a sharp decrease in the field radiated by the circuit of the invention. For example, this field may be measured at a point 10 located at a distance d (for example 1 cm) from the circuit, on the joint plane of the ends 4 and 6. This

  decrease can be in a ratio of about 3. -

Claims (6)

  1. Magnetic circuit with a low magnetic field radiated, in particular for a high-voltage transformer supplying a cathode-ray tube, of the type with two half-circuits in "U" (2, 3), characterized in that it comprises an air gap ( 5, 7) housed inside a winding (9), the thickness of this air gap being determined during manufacture of the magnetic circuit by rectification of the ends (4).   to 7) legs of the two half-circuits.   2. Magnetic circuit according to claim 1, characterized in that the ends of the legs of the two magnetic half-circuits are, together, glued together on the side of the air gap with the interposition of a shim (8) d thickness substantially equal to the desired gap thickness, and the opposite side (4, 6) directly on one another.   Magnetic circuit according to claim 2, characterized by   the fact that the wedge is made of non-magnetic material.   4. Magnetic circuit according to claim 2, characterized in that the wedge is a magnetic material, characteristics   different from that of the magnetic circuit material. tick.   Magnetic circuit according to one of Claims 2 to 4,   characterized by the fact that the section of the hold is different from   that of the legs of the magnetic circuit.   Magnetic circuit according to one of Claims 2 to 5,   characterized in that a glue of the   cold-setting type with fast setting.