EP0072451B1 - 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 method for assembling and adjusting a transformer, in particular for ballasts for gas discharge lamps or the like, with a divided core and a coil former, the core halves joined to the coil former being clamped between resilient profile legs by brackets extending in the direction of the coil axis, wherein the spring force of the profile legs is perpendicular to the coil axis.

Such transformers, which are also known as stray field transformers, are known (DE-C-959 033). in ballasts of 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 tube. 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 inaccurately, because the core halves themselves have very considerable manufacturing tolerances that affect the inductance, and the inductance is also influenced very significantly by very small changes in the spacing of 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, whose operating parameters can be set mechanically, e.g. 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 of the order of 1-2 cm or less, such devices can no longer be accommodated. The object of the invention is to provide a method of the type described in the introduction with which the characteristics of transformers, in particular also of transformers with small dimensions and with sintered cores, can be set reliably and permanently.

This object is achieved in that the core halves lie at a mutual distance between the resilient profile legs, that the core halves are then moved towards one another in the direction of the coil axis while overcoming the spring-force-related frictional forces acting on them and under the control of a measuring device connected to the coil former, until the measuring device indicates the desired value, and that the core halves are then cold welded or glued to the brackets.

With this method, the core halves can only move against one another during the adjustment under the action of external, defined forces and can not carry out any undesired return movements. Even after completion of the adjustment process in the relative position reached, no restoring forces are effective and the core halves can be fixed. This is only possible because the core halves are not clamped between resilient profile legs, the spring force of which is directed perpendicular to the coil axis. In other words, this spring force is directed perpendicular to the external displacement force. Therefore, it cannot lead to a subsequent, undesirable displacement of the two core halves. However, the spring force directed perpendicular to the coil axis and thus to the displacement force also enables the core halves to be displaced in the direction of the coil axis without a reset or when the displacement force decreases Springback occurs, which would distort the adjustment.

The brackets or their profile legs are also used for fixing, i.e. each core half is attached independently of the other to the brackets by gluing or cold welding, with the result that the brackets in the finished transformer also function as a spacer between the two core halves.

Surprisingly, the remainder values of very wine transformers, the dimensions of which are in the order of magnitude of 1-2 cm and below, can be set with extreme accuracy. H. with deviations that are below 1% of the desired value. This applies to transformers with E or M cores as well as for transformers with shell cores, regardless of whether the cores are so-called sintered cores or made 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 each other. If it is, for example, a transformer with E- or M-Rers, the legs of which have essentially rectangular cross-sections, then the brackets can have a U-shaped profile which covers the one or more legs, the spring forces of the U-legs toward one another are directed. For 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 structures, the spring forces of the brackets being 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 create defined ratios for the introduction of the Rlebstoffes, a proposal of the invention is that the profiles of the bracket on their sides facing the core halves have projections 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, not be resilient tabs bent from the profile or from 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 weaver, both a one-component adhesive and a two-component weaver. 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 Trafo nach Fig. 1,
• Fig. 3 die Ansicht eines Bügels,
• Fig. 4 einen Schnitt in Richtung IV - IV durch den Bügel nach Fig. 3,
• Fig. 5 eine Stirnansicht des Bügels nach Fig. 3,
• Fig. 6 eine andere Ausfünrungsform des Bügels nach Fig. 3,
• Fig. 7 einen Schnitt in Richtung VII - VII durch den Bügel nach Fig. 6,
• Fig. 8 eine Stirnansicht des Bügels nach Fig. 6,
• Fig. 9 eine andere Ausführungsform des Bügels nach Fig. 3,
• Fig. 10 eine Draufsicht auf den Bügel nach Fig. 9,
• Fig. 11 eine abgewandelte Ausführungsform des Bügels nach Fig. 9
• Fig. 12 eine Draufsicht auf den Bügel nach Fig. 11
• Fig. 13 eine abgeänderte Ausfünrungsform des Bügels nach Fig. 6,
• Fig. 14 einen Schnitt in Richtung XIV - XIV durch den Bügel nach Fig. 13,
• Fig. 15 eine Stirnansicht des Bügles 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 transformer of FIG. 1,
• 3 is a view of a bracket,
• 4 shows a section in the direction IV-IV through the bracket according to FIG. 3,
• 5 is an end view of the bracket of FIG. 3,
• 6 shows another embodiment of the bracket according to FIG. 3,
• 7 shows a section in the direction VII - VII through the bracket according to FIG. 6,
• 8 is an end view of the bracket of FIG. 6,
• 9 shows another embodiment of the bracket according to FIG. 3,
• 10 is a plan view of the bracket of FIG. 9,
• 11 shows a modified embodiment of the bracket according to FIG. 9
• 12 is a plan view of the bracket of FIG. 11th
• 13 shows a modified embodiment of the bracket according to FIG. 6,
• 14 shows a section in the direction XIV-XIV through the bracket according to FIG. 13,
• 15 is an end view of the bracket of FIG. 13,
• Fig. 16 shows a transformer with brackets according to Fig. 12 -15 on a circuit board.

The transformer shown has two core halves 1, 2, which are sintered E-codes, and a coil former 3 with connecting pins 4. The respective outer, opposite Rernschenkei 5, 6 and 7, 8 of the two Rern halves 1, 2nd 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 Rern 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 Rern legs 5-8. In the illustrated embodiment, the ribs 13 are arranged so that each Rern leg 5-8 on two ribs 13 of each U-leg 11, 12th is supported.

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, e.g. its inductance, the core halves 1, 2 and the bobbin 3 are first loosely preassembled and then the brackets 9, 10 are pushed onto the mutually associated Rern legs 5, 6 and 7, 8 so that a relatively large distance 15 between the associated ends the core leg 5, 6 or 7, 8 remains. 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 Rern halves 1, 2 are moved towards one another 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 directed perpendicular to the coil axis. When the desired measurement value and thus the desired distance 15 has been reached, a possibly metered, small amount of adhesive is introduced into the gap 14, which adhesive is distributed therein under the action of Rapillary 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 (s) 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 are held with the frame-like stirrup according to FIGS. 9 and 10 , then the spring forces of the brackets 9, 10 also act perpendicular to the coil axis, so that a set distance 15 of the core halves 1, 2 is not affected by these spring forces.

The embodiment shown in FIGS. 11 and 12 is particularly suitable for transformers with shell names. 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 code 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, brackets 9 and 10 are clamped onto the two opposite sides of the lower core half 2 and the coil former (not shown) is placed on the core half 2. This unit is 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, respectively, pass through 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 above 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 (11)

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).

2. A method according to claim 1, characterized by the use of section stirrups (9, lo) with essentially U-shaped section flanges (11, 12) the spring resistances of which are directed to each other or away from each other.

3. A method according to claim 1 or 2, characterized by the use of stirrups (9, lo) which are connected with each other at one end by means of a stirrup support (17).

4. A method according to one of the claims 1 - 3, characterized by the use of stirrups (9, 10) which are provided with projections or ribs (13) arranged in transverse direction to the core axis on their sides facing the core halves (1, 2).

5. A method according to claim 4, characterized by the use of stirrups (9, 10) with which at least one rib (13) is formed by springable shackles (16) which are bent off from the section or the section flanges (11, 12), respectively.

6. A method according to one of the claims 1 - 5, characterized in that the space (14) existing between the open end of the stirrups (9, lo) and the projections or ribs (13) is filled up with a bonding agent.

7. A method according to one of the claims 1 - 6, characterized by the use of stirrups (9, 10) consisting of a non-magnetizable material.

8. A method according to claim 7, characterized by the use of stirrups (9, 10) consisting of aluminum, copper, spring bronze or brass.

9. A method according to claim 7, characterized by the use of stirrups (9, 10) consisting of plastic.

10. A method according to one of the claims 1 - 9, characterized by the use of an electrical neutral adhesive acting as bonding agent.

11. A method according to one of the claims 1 - 9 by the use of stirrups which at least on one side are provided with a center spigot characterized in that the bobbin (3) with one of the core halves (2) and the clamp connected stirrups (9, 10) thereon is placed on a printed circuit board (19), that the connecting pins (4) of the bobbin (3) and the center spigots (18) of the stirrups (£1, 10) will be soldered to the printed circuit board (19), and that after this the other core half (1) will be introduced into the stirrups (9, 10) until the transformer is adjusted.

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