EP0072451A1 - Methode of mounting and adjusting a transformer - Google Patents

Abstract

1. A method for assembly and adjustment of a transformer, in particular for ballasts of gas discharge lamps or suchlike, with a divided core and a bobbin (3), the halves of the core (1, 2) joined with the bobbin being clamped between the springable section flanges (11, 12) of the stirrups (9, 10) extending into the direction of the coil axis, the spring resistance of the section flanges being directed vertically to the core axis, characterized in, that the core halves (1, 2) are arranged with mutual distance between the springable section flanges (11, 12), that the core halves (1, 2) by overcoming the frictional forces conditional on the spring resistance acting upon them as well as by checking by means of a measuring device connected to the bobbin (3) will then be moved in direction of the core axis against each other until the measuring instrument indicates the desired value, and that subsequently to this the core halves (1, 2) will be cold welded or cemented on the stirrups (9, 10).

Description

The invention relates to a transformer, in particular for ballasts for gas discharge lamps or the like, with a split core and a coil former, the core halves being held together with springs and brackets while leaving a distance between the mutually associated ends of the core halves and which extend in the direction of the coil axis Brackets have a profile which is essentially adapted to the profile of the parts of the core halves projecting beyond the coil former.

Such transformers, which are also called stray field transformers, are used e.g. in ballasts for fluorescent tubes used in the leisure sector, e.g. on boats and in caravans. With these transformers, the existing low voltage is transformed up to a voltage suitable for the fluorescent tubes. At the same time, such a transformer functions as an ignition device for the fluorescent tube because it first supplies the tube with a higher voltage, which breaks down to the so-called burning voltage when the tube is in nominal operation.

A major problem with such transformers is the adaptation of the operating parameters to the respective fluorescent tube, in particular the adaptation of the inductance of the transformer. Transformers are known in which the distance between the core halves is set by a so-called air gap insert. The two core halves are then held in a bracket system and are pressed together in the direction of the coil axis by means of a spring. This means that the inductance of such a transformer can only be set very imprecisely, because the core halves themselves have considerable manufacturing tolerances that relate to the inductor Effectiveness affect and also the inductance is very significantly affected by very small changes in the distance between the core halves. This influence increases with decreasing size of the transformers, so that their inductance can deviate up to 25% from the desired value.

From practice, a method for adjusting the inductance of transformers is known, the dimensions of which are of the order of magnitude of 1-2 cm, in which the core halves and the coil former are first joined together and then the coil former is connected to a measuring device. Then the two core halves are brought together under observation of the measuring device until the desired measured value (inductance) is reached.

An adhesive is then injected into the gap between the mutually assigned ends of the core halves, which hardens. The core halves are then held together only by the adhesive. Temples are superfluous. Apart from the fact that with this method the amount of adhesive has to be overdosed and therefore large parts of the transformer are covered with adhesive, one does not achieve any significant improvement with regard to the setting of the characteristic values of the transformer, because each adhesive shrinks after hardening, as a result of which the distance between the core halves is in turn changed. The deviations of the inductance from the desired value are still approx. 10%.

There are also transformers, in particular transformers with a shell core, the operating parameters of which can be set mechanically, for example with an adjustable thread core. Other transformers have adjustable yokes or the like. Such a mechanical adjustment is only possible with transformers that have sufficiently large dimensions. If the dimensions of the transformer are on the order of 1 - 2 cm or less, such facilities can no longer be accommodated.

The object of the invention is therefore to provide a transformer of the type described above, the parameters of which can be set reliably and permanently in a simple manner.

This object is achieved with a transformer of the type described in the introduction in that the spring force of the springs is directed perpendicular to the coil axis and in that the brackets are at least partially glued or cold-welded to the core halves.

In the transformer according to the invention, no forces act on the core halves which can change the mutual distance. Since the spring forces on the brackets are directed perpendicular to the coil axis, the core halves are held on and by the brackets, but they cannot move relative to them, especially not because the brackets (after adjustment and adjustment of the transformer) with the Core halves are glued at least in regions. Also due to the gluing, no forces directed in the coil axis can arise, so that the set distance of the core halves cannot change.

The invention also relates to a method for adjusting such a transformer, in which the core halves joined with the coil former are clamped to the brackets and adjusted to the desired distance. This is done by connecting the bobbin to a measuring device before setting the distance and then moving the two core halves against each other, overcoming the spring-force-related frictional forces, until the measuring device displays the desired value, and that the core halves then subsequently with the Ironing can be glued or cold welded.

In practice, one will proceed in such a way that in the course of a pre-assembly the core halves and the bobbin are put together and then the clamps are pushed onto the core halves in such a way that the core halves have an arbitrary distance. After connecting the bobbin to the measuring device, the core halves are then slowly pushed together until the desired measured value is reached. The adhesive is then applied in an area that is distant from the mutually associated ends of the core halves, so that the shrinkage of the adhesive cannot influence the distance between these ends.

Surprisingly, the characteristic values of very small transformers, the dimensions of which are in the order of magnitude of 1-2 cm and below, can be set with extreme accuracy, i.e. with deviations that are below 1% of the desired value. This applies both to transformers with E or M cores and to transformers with shell cores, regardless of whether the cores are so-called sintered cores or made up of laminated cores.

According to a preferred embodiment of the invention, the springs are to be formed by profile legs of the bracket profiles, the spring forces of profile legs assigned to one another being directed towards or away from one another. If it is, for example, a transformer with an E or M core, the legs of which have essentially rectangular cross sections, then the brackets can have a U-shaped profile which covers the leg or legs, the spring forces of the U legs toward one another are directed. With slotted shell cores, bracket profiles will be used, the profile legs of which engage in the slot and spring apart.

However, it is within the scope of the invention to design the brackets themselves as springs and to connect them to one another at one end via a bracket support. This version is particularly suitable for transformers with unslit shell cores, whereby the spring forces of the brackets are directed towards the coil axis.

In all cases, the spring forces are sufficient to maintain the set distance between the two core halves until the adhesive introduced between the bracket and the core halves has hardened. In order to also create defined conditions for the introduction of the adhesive, one proposal of the invention is that the profiles of the stirrups have projections on their sides facing the core halves or ribs directed transversely to the coil axis. The profiles of the stirrups consequently lie with the projections or ribs on the core halves and, moreover, form a narrow gap into which the adhesive can be introduced from the end of the stirrups. The gaps are preferably dimensioned such that the adhesive flows into the gap under the action of capillary forces. The amount of adhesive can then be measured accordingly. The ribs can, for example, be resilient tabs bent out of the profile or out of the profile legs.

It is useful to use brackets made of a non-magnetizable material, in particular aluminum or brass or also plastic, because otherwise the brackets themselves will additionally change the characteristic values of the transformer. The adhesive can be a plastic adhesive, both a one-component adhesive and a two-component adhesive. This does not exclude that magnetizable materials can also be used.

• Fig. 1 in schematischer Darstellung und vergrößert die Seitenansicht eines Transformators für ein Vorschaltgerät einer Leuchtstofflampe,
• Fig. 2 eine Draufsicht auf den Gegenstand nach Fig. 1,
• Fig. 3 die Ansicht eines Bügels,
• Fig. 4 einen Schnitt in Richtung IV - IV durch den Gegenstand nach Fig. 3,
• Fig. 5 eine Stirnansicht des Gegenstandes nach Fig. 3,
• Fig. 6 eine andere Ausführungsform des Gegenstandes nach Fig. 3,
• Fig. 7 einen Schnitt in Richtung VII - VII durch den Gegenstand nach Fig. 6,
• Fig. 8 eine Stirnansicht des Gegenstandes nach Fig. 6,
• Fig. 9 eine andere Ausführungsform des Gegenstandes nach Fig. 3,
• Fig. 10 eine Draufsicht auf den Gegenstand nach Fig. 9,
• Fig. 11 eine abgewandelte Ausführungsform des Gegenstandes nach Fig. 9,
• Fig. 12 eine Draufsicht auf den Gegenstand nach Fig. 11,
• Fig. 13 eine abgeänderte Ausführungsform des Gegenstandes nach Fig. 6,
• Fig. 14 einen Schnitt in Richtung XIV - XIV durch den Gegenstand nach Fig. 13,
• Fig. 15 eine Stirnansicht des Gegenstandes nach Fig. 13,
• Fig. 16 einen Transformator mit Bügeln nach Fig. 12 - 15 auf einer Leiterplatte.

Exemplary embodiments of the invention illustrated in the drawing are explained below; show it:

• 1 in a schematic representation and enlarged the side view of a transformer for a ballast of a fluorescent lamp,
• 2 is a plan view of the object of FIG. 1,
• 3 is a view of a bracket,
• 4 shows a section in the direction IV-IV through the object according to FIG. 3,
• 5 is an end view of the object of FIG. 3,
• 6 shows another embodiment of the object according to FIG. 3,
• 7 shows a section in the direction VII - VII through the object according to FIG. 6,
• 8 is an end view of the object of FIG. 6,
• 9 shows another embodiment of the object according to FIG. 3,
• 10 is a plan view of the object of FIG. 9,
• 11 shows a modified embodiment of the object according to FIG. 9,
• 12 is a plan view of the object of FIG. 11,
• 13 shows a modified embodiment of the object according to FIG. 6,
• 14 shows a section in the direction XIV-XIV through the object according to FIG. 13,
• 15 is an end view of the article of FIG. 13,
• 16 shows a transformer with brackets according to FIGS. 12-15 on a printed circuit board.

The transformer shown has two core halves 1, 2, which are sintered E cores, and a coil former 3 with connecting pins 4. The respective outer, opposite core legs 5, 6 and 7, 8 of the two core halves 1, 2 are held clamped in U-shaped brackets 9 and 10 respectively. The U-legs 11, 12 of each bracket 9 and 10 are set so that they can be pushed onto the core legs 5, 6 and 7, 8, the respective spring forces acting perpendicular to the coil axis. Embossed ribs 13 are located on the inside of the U-legs 11, 12, so that a gap 14 remains between the inside of each U-leg 11 and 12 and the associated outside of the core legs 5-8. In the illustrated embodiment, the ribs 13 are arranged so that each core leg 5-8 is supported on two ribs 13 of each U-leg 11, 12.

To set the distance 15 between the mutually assigned ends of the core legs 5, 6 or 7, 8 and thus the characteristic values of the transformer, for example its inductance, the core halves 1, 2 and the coil former 3 are first loosely preassembled and then the brackets 9 , 10 pushed onto the mutually assigned core legs 5, 6 or 7, 8 in such a way that a relatively large distance 15 remains between the assigned ends of the core legs 5, 6 or 7, 8. Then the transformer prepared in this way is connected via connection pins 4 to a suitable measuring device with which, for example, the inductance can be measured. Then the two core halves 1, 2 are moved towards each other in the direction of the coil axis until the measuring device displays the desired value. The movement of the core halves 1, 2 takes place against the action of the frictional forces acting on them, generated by the spring force of the profile legs 11, 12, which, however, cannot influence a set distance 15, since they are perpendicular to the coils axis are directed. When the desired measured value and thus the desired distance 15 has been reached, a possibly metered, small amount of adhesive is introduced into the gap 14, which is distributed therein under the action of capillary forces. It is sufficient if the gap is filled with adhesive up to approximately the next rib 13. The adhesive can be a one-component adhesive or a two-component adhesive. If the adhesive shrinks during curing, the set distance 15 is not influenced or changed because the shrinkage stresses of the adhesive also act perpendicular to the coil axis.

The characteristic value or values of the transformer set in this way can consequently no longer change.

Figures 3-5 show the bracket 9 with further details.

Another embodiment of a bracket 9 is shown in FIGS. 6-8, in which the ribs 13 are formed by angled tabs 16, which are produced by partially separating the U-legs 11, 12 from the associated 'U-web of the bracket 9.

In the embodiment shown in FIGS. 9 and 10, the brackets 9, 10 are connected to one another at one end via a bracket support 17. The bracket support 17 also has a U-profile. The brackets 9, 10 are resiliently connected to the bracket support 17 in such a way that their resilient forces are directed towards one another. In addition, the U-legs of the stirrups 9, 10 can develop their own spring forces, as in the embodiment according to FIGS. 3-5. However, the core halves 1, 2 of the transformer shown in FIG. 1 with the frame-like stirrup 9 and 10 held clamped, then the spring forces of the bracket 9, 10 also act perpendicular to the coil axis, so that a set distance 15 of the core halves 1, 2 is not influenced by these spring forces.

The embodiment shown in FIGS. 11 and 12 is particularly suitable for transformers with shell cores. The brackets 9, 10 each have a circular section-shaped profile, the radius of which is adapted to the radius of the shell core. Via the bracket support 17, the two brackets 9, 10 are resiliently connected to one another in such a way that their spring forces act radially on the shell core. A transformer with a shell core is set as described above.

It goes without saying that in the embodiments according to FIGS. 9-12, the inner sides of the stirrups 9, 10 can also be provided with ribs, not shown, in order to form defined gaps between the inner sides of the stirrups 9, 10 and the associated outer sides of the core halves.

In the embodiment shown in FIGS. 13-15, only the profile legs 12 are formed by cut-out and angled tabs, while the profile legs 11 are smooth. This has the advantage that the core halves 1 and 2 are pressed by the resilient profile legs 12 against the smooth profile legs 11 and are therefore better guided during adjustment. In addition, the brackets 9 shown in FIGS. 13-15 have a protruding plug pin 18 on one side.

The function of this plug pin results from Fig. 16, which shows that the transformer shown is immediately mounted and adjusted on a circuit board 19. For this purpose, two brackets 9 and 10 are clamped onto the two opposite sides of the lower core half and the bobbin, not shown, is placed on the core half 2. This assembly is then placed on the circuit board 19 in such a way that both the connecting pins 4 of the coil former and the plug pins 18 of the brackets 9 and 10 are associated with openings in the circuit board 19. Pins 4 and plug 18 are then fixed to the circuit board 19 by soldering. So that the lower core half 2, the bobbin and the bracket 9 and 10 are attached to the circuit board 19. Additional gluing or cold welding is not necessary. Now the upper core half 1 is inserted into the bracket and, as described above, the transformer is adjusted. The circuit still present on the printed circuit board 19 can also be included.

Claims (13)

1. Transformer, in particular for ballasts for gas discharge lamps or the like with a divided core and a coil former, the core halves being held together with springs and brackets while leaving a distance between the mutually assigned ends of the core halves and the brackets extending in the direction of the coil axis forming a profile have, which is essentially adapted to the profile of the parts of the core halves projecting beyond the coil body, characterized in that the spring force of the springs (11, 12; 9, 10) is directed perpendicular to the coil axis and that the brackets (9, 10) with the core halves (1, 2) are at least partially glued or cold welded. 2. Transformer according to claim 1, characterized in that the springs of profile legs (11, 12) of the bracket profiles are formed, wherein the spring forces of mutually associated profile legs (11, 12) are directed towards or away from each other. 3. Transformer according to claim 1 or 2, characterized in that the brackets (9, 10) are designed as springs and are connected to one another at one end via a bracket support (17). 4. Transformer according to one of claims 1-3, characterized in that the profiles of the brackets (9, 10) on their sides facing the core halves (1, 2) have projections or ribs (13) directed transversely to the coil axis. 5. Transformer according to one or more of claims 1-4, characterized in that at least one rib (13) from the profile or from the profile legs (11, 12) bent resilient tabs (16) is formed. 6. Transformer according to one or more of claims 1-5, characterized in that the space (14) between the open end of the bracket (9, 10) and the projections or ribs (13) is filled with the adhesive. 7. Transformer according to one or more of claims 1-6, characterized in that the brackets (9, 10) consist of a non-magnetizable material. 8. Transformer according to claim 7, characterized in that the brackets (9, 10) consist of aluminum, copper, spring bronze or brass. 9. Transformer according to claim 7, characterized in that the brackets (9, 10) consist of plastic. 10. Transformer according to one or more of claims 1-9, characterized in that the adhesive is an electrically neutral adhesion promoter. 11. A method for adjusting a transformer according to one or more of claims 1-10, in which the core halves joined together with the bobbin are clamped with the brackets and adjusted to the desired distance, characterized in that the bobbin (3) before adjusting the Distance (15) is connected to a measuring device and then the two core halves (1, 2) are moved against each other, overcoming the spring force-induced frictional forces, until the measuring device displays the desired value and that the core halves (1, 2) then with the Brackets (9, 10) can be glued or cold welded. 12. The method according to claim 11, characterized in that the core halves (1, 2) are moved towards each other in the direction of the coil axis. 13. The method according to claim 11 or 12, using brackets which have a projecting pin at least on one side, characterized in that the coil former (3) with a core half (2) and brackets (9, 10) clamped thereon on a printed circuit board ( 19) is set so that the connecting pins (4) of the coil former (3) and the plug pins (18) of the brackets (9, 10) are soldered to the printed circuit board (19) and then the second core half (1) so far into the Bracket (9, 10) is inserted until the transformer is adjusted.

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