ES2206093T3 - ANTENNA COIL MADE IN MINIATURE FOR ELECTRONIC VEHICLE CLOSURE SYSTEMS. - Google Patents

Abstract

Antenna coil made in miniature for electronic vehicle closing systems, composed of a prismatic ferrite core (2), placed on a plastic body (1), in which the plastic body (1) carries ends metal contacts (5) for surface mounting (SMD) of the antenna coil, characterized in that the plastic body (1) is not in the area of the longitudinal expansion of ferrite core (2), greater that this and is wound with it along with the bobbin thread (3).

Description

Antenna coil made in miniature for electronic vehicle closing systems.

The invention relates to an antenna coil miniature for electronic locking systems, Wireless vehicles. Such antenna coil is placed together with the respective control electronics in the vehicle key and must therefore be of very small external dimensions, so that the tendency to miniaturize it still does not cease. To that end certain high frequency characteristic values must be respected such as sensitivity and alignment characteristic. The Reliability properties must meet the high demands of car construction

Various embodiments of such miniature coils, in which the problems of air core coils, and in which they carry cores magnetic as in the present case are similar and to then the potential for the miniaturization regardless of constructive size Used in reality.

A chip inductivity is known, especially an HF shock coil with a winding space relatively large, in which the magnetic function and the carrier they are performed by a ferrite core of rectangular section, the which presents in the vicinity of its extremes widening in which plugged metal parts are placed that are at the same time support and contact elements (DE 43 32 638). Here is you can place the high winding volume necessary for the shock coils without wasting space. But miniaturization it has limits due altogether to the complicated shape of the core and to the problematic form of the support and contact elements with its rectangular luminaries that adapt perfectly to the core.

It has a great potential for miniaturization a rod core shock coil, with a ferrite core, in whose ends plug square caps, preferably of metal, and with the continuation of the winding they are wound on the ferrite core. The winding on the caps is tinned and at the same time forms the SMD contact (DE 195 20 858 A1). But the narrow passage between the winding here constitutes a disadvantage with HF function and that of the contact function, so you have to count here, due to a possible extension of the welding of tin outside the hoods, with a strong dispersion unit of the characteristic electrical values.

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In a known antenna coil it is placed in a tub-shaped plastic housing, and the winding ends made are wound around T-shaped contact appendages, which extend parallel to the mounting surface, whereby the lower wire winding forms the SMD contact around these appendages

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. En ambas soluciones técnicas el núcleo bobinado está rodeado circunferencialmente hasta 3/4 partes por la carcasa en forma de tina, lo que proporciona una buena protección y buenas propiedades de resistencia. La miniaturización tiene aquí también límites, ya que la pared de la "tina", no puede hacerse todo lo delgada que se quiere. Además, los contactos SMD necesitan en el primer caso mencionado mucho sitio en la placa de circuito impreso en su dirección lateral y en el segundo caso citado, en dirección axial.In an equally tub-shaped arrangement, U-shaped sheet strips are used, open frontally outwards, one of whose branches protrudes axially outside the plastic part, is wound with the winding ends and formed by consequently an SMD contact

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. In both technical solutions the winding core is circumferentially surrounded up to 3/4 parts by the tub-shaped housing, which provides good protection and good resistance properties. Miniaturization also has limits here, since the wall of the "tub" cannot be as thin as you want. In addition, in the first mentioned case, the SMD contacts need a lot of room on the printed circuit board in their lateral direction and in the second case mentioned, in the axial direction.

The invention therefore aims to create an antenna coil with greater miniaturization potential and at at the same time greater reliability, in which you can also avoid the other disadvantages cited of the current state of the art.

This objective is achieved by the invention. described in the patent claims.

The solution according to the invention is characterized For high HF sensitivity and good alignment characteristic. It is compact, very resistant to shocks and shocks and suitable for direct welding on both flexible printed circuit boards as not flexible. The construction of the antenna coil is Appropriate for automated production.

In 5-m drop tests the coil antenna according to the invention, due to its overall construction, presented an unexpected resistance to the ferrite piece in miniature used.

The following will describe in more detail the invention in an exemplary embodiment. The attached drawings represent:

Figure 1: A side view of a coil of partially rolled antenna on a circuit board printed;

Figure 2: a top view of a coil of uncoiled antenna;

Figure 3: a cross section noticeably through the center of the unwound antenna coil, Y

Figure 4: a cross section of the strip of metal that forms the contact system.

Figures 1 and 2 show an antenna coil real, executed according to the invention, with an increase of about 10 times while the renderings sections of figures 3 and 4 are enlarged about 20 times. A plastic body 1, for example of an LCP "Vectra E 130 ", supports a ferrite core 2 based on manganese-zinc-ferrite. How I know you can see in figure 2, this body of plastic material 1, which supports in the middle zone the winding 3 indicated in its middle in Figure 1 is not larger than the ferrite core 2, remaining by both covered by the latter, which contributes along with the lack of a tub-shaped inlay known to the current state of the technique, mainly to the saving of space and also to the possibility of miniaturization. At the ends of the core of ferrite 2 has enlarged the body of plastic material 1 in the area 4 and laterally surrounds the ferrite core 2 and forms together with the metal strips 5 a winding space 6 that reaches the support on a printed circuit board 7.

The winding 3 represented only partially in figure 1 it contains, for example 333 turns of a copper wire enameled 0.071 mm, so, for example at a frequency of 125 kHz test at 50 mV, gives an inductivity of 1,056 mH and a Q quality better than 30 for a temperature range of -40ºC up to + 85 ° C.

In a special embodiment of the coil antenna according to the invention, the cross section of the core of ferrite 2 is T-shaped (figure 3), sticking the branch perpendicular 8 of the "T", for example by glue silicone, in a corresponding cavity of the body of matter plastic 1, which with the simultaneous positive union and the closure of matter contributes very importantly to the aforementioned resistance in the drop test. As you can see in figure 3, branch 8 has a slightly trapecial section. To avoid the called overdetermination, the ferrite core 2 is placed with the lower side of its branch 8 on the plastic body 1, while its other faces turned towards the body of matter plastic 1 have such dimensional tolerances that occurs eventually a slit that is filled with the glue of silicone.

Finally it is essential for the invention that the antenna coil contact is fixed by a strip of metal 5 that is inserted into a peripheral groove 9 (figure 4) around the widened end 4 of the plastic body 1, and preferably by pressure exerted on a depression 10 in V shape of this peripheral groove 9. The ends of thread 11 (figure 1) of the winding 3 are joined by thermal compression with the metal strip 5. The contact of the antenna coil on the Printed circuit board 7 runs by soft welding. East contact is also solid and reliable, since the thread of the winding 3 is only free in a minimum section, in which Noxious accelerations could act on it in case of loading.

Claims (4)

1. Miniature antenna coil for electronic vehicle closing systems, composed of a prismatic ferrite core (2), placed on a plastic body (1), in which the plastic body (1) carries at its ends metal contacts (5) for surface mounting (SMD) of the antenna coil, characterized in that the plastic body (1) is not in the area of the longitudinal expansion of ferrite core (2) , greater than this and is wound with it along with the bobbin thread (3). 2. Antenna coil according to claim 1, characterized in that the ends (4) of the plastic material body (1), enlarged relative to the ferrite core (2), surround it until the beginning of the winding and its height together with the metal contacts (5) determine the winding space (6) for the subsequent assembly of the antenna coil on a printed circuit board (7). 3. An antenna coil according to one of the preceding claims, characterized in that the metal contacts are each composed of a metal strip (5) that is inserted in a peripheral groove (9) around the enlarged end (4) of the body of plastic material (1), to which end both ends of the metal strip (5) are compressed in a V-shape in a depression (10) of the peripheral groove (9). 4. An antenna coil according to one of the preceding claims, characterized in that the ferrite core (2) has a T-shaped cross section and the perpendicular branch (8) of the "T" is glued in a cavity of the material body plastic (1).