DE10355003A1 - Inductive sensor for producing switching signal when electromagnetic radiation damping material approaches has flat circuit board with at least one through opening through which coil core is passed - Google Patents

Abstract

The inductive sensor has at least one conducting track (14) on a circuit carrier (16) that forms at least one coil (12) and a coil core (18) associated with the coil. The circuit carrier is a flat circuit board and has at least one through opening (28) through which the coil core is passed. The coil core is U-shaped or semi-toroidal in shape. An independent claim is also included for a method of manufacturing an inventive device.

Description

The The invention relates to an inductive sensor according to the preamble of the claim 1.

One such inductive proximity sensor has usually an LC resonant circuit, a signal evaluator and a switching amplifier on. The coil of this resonant circuit generates a high-frequency, electromagnetic alternating field. This field occurs at the active area of the sensor. approaches a dampening one Material of the active surface, Thus, eddy currents are generated in non-ferrous metals. For ferromagnetic In addition, metals are created Hysteresis losses. These losses escape the resonant circuit Energy and steam the vibration. The damping of the resonant circuit causes a change in the oscillator current. The signal evaluator recognizes this change and puts this into action Switching signal to.

From the DE 200 01 648 U1 Such an inductive sensor is known in which the coil consists of a conductor printed on a three-dimensional circuit carrier and the three-dimensional circuit carrier has a recess in which a coil core is held, so that the coil core is positioned defined relative to the coil. The three-dimensional circuit carrier simultaneously forms part of the sensor housing.

outgoing From this prior art, it is an object of the invention to provide a To provide sensor of the type mentioned, in particular easier, in fewer steps and thus more cost-effective is to produce and allows a smaller design.

These Task is solved by a sensor having the features of claim 1 and a manufacturing method with the features of claims 10 or 11.

According to the invention the inductive sensor at least one arranged on a circuit carrier Track on which forms at least one coil and one of the coil associated coil core, wherein the circuit carrier as a flat circuit board is formed and has at least one breakthrough of the spool core is interspersed.

In This new arrangement can be applied to a three-dimensional training of the circuit board omitted become, whereby considerable space is gained. Besides that is a planar circuit carrier, So a printed circuit board, a standard commodity and therefore inexpensive in the acquisition and handling.

Around Assigning the bobbin to the bobbin is a breakthrough provided in the circuit carrier, which is interspersed by the coil core. This is a very simple one and cost-effective Allocation created and the previous separation of coil core and the other arranged on the circuit board electronics lifted, allowing an automated, cost-effective production of the complete Sensors possible is.

Around the coil core can easily bring in the breakthrough and to be able to direct the magnetic field of the sensor to the outside, has the coil core on a U-shape or a Halbtoroidform.

In order to the bobbin firm and immovable in the breakthrough is in development of the invention provided that the coil core over a Clamping is held, including the breakthrough prefers clamping lugs or the like.

ever according to which application the sensor should be used, it may be desirable to obtain a specially shaped magnetic field of the sensor, so that the spool core can be designed multi-legged to a desired Course of the magnetic field to achieve. About the course of the magnetic field let yourself For example, affect the switching distance of the sensor.

If the spool core is formed mehrschenklig, can advantageously in the circuit carrier several breakthroughs be provided.

To the Protection of circuit carriers and spool core should preferably be provided a housing in which these are held.

For a cost-effective mass production is the case produced by injection molding.

In Further development of the invention, the spool core made of a plastic exist, which has soft magnetic properties. That would result the particularly advantageous possibility also to produce the coil core in injection molding and in the Breakthrough breakthrough, resulting in mass production further cost savings results.

In terms of process technology, the object is achieved by a method for producing such a sensor in which, in a first method step, a planar circuit carrier is provided with a coil consisting of a conductor and with an opening and then introduced and fixed in the opening of the coil core and finally the complete Circuit carrier in a housing is arranged.

In an alternative method is used in a first method step first in turn, the planar circuit carrier provided with a conductor track coil and breakthrough and then, however, the spool core in injection molding from a first Plastic having soft magnetic properties produced and in the same injection process, the housing of a second plastic will be produced. It is therefore a known per se Two-component injection technique, whereby the production costs continue can be reduced, as for the production of the sensor only the circuit carrier to equip is and then in just one injection process of the bobbin and the casing can be produced.

in the The invention will be described below with reference to exemplary embodiments explained in detail on the drawing. In the drawing show:

1 a schematic representation of a sensor according to the invention in cross section;

2 a schematic representation of the sensor 1 in the plan view;

3 a schematic representation of another embodiment of the sensor in plan view;

4 an end view of the sensor 3 ,

A first embodiment of an in 1 and 2 illustrated inductive sensor 10 has at least one magnetic field generating coil 12 on, its windings through a on a circuit carrier 16 arranged conductor track 14 are formed. The circuit carrier 16 is designed as a printed circuit board.

The sink 12 generated at current flow through the conductor track 14 a magnetic field that by means of a coil core 18 such that it is in a desired range 20 generates a corresponding field strength.

Furthermore, the sensor has 10 on the circuit carrier 16 an evaluation circuit 21 on, in the one of the inductance of the coil 12 dependent sensor signal can be generated. About leads 22 the sensor can be supplied with electrical energy and / or are the signals of the evaluation circuit 21 dispensable.

All components of the sensor 10 , in particular the circuit carrier 16 and the coil core 18 , are preferred in a housing 24 held. Not shown in the drawing display elements, controls and / or connection components, such as cables or connectors, can also in the housing 24 be arranged.

In the first embodiment ( 1 and 2 ) is just a circuit carrier 16 intended. The circuit carrier 16 , also referred to as PCB (printed circuit board), carries all electronic components 26 the sensor, in particular the evaluation circuit 21 and the coil 12 forming conductor track 14 , Furthermore, the PCB has 16 a breakthrough 28 on top of that from the spool core 18 is interspersed and from the conductor track 14 spiral ( 2 ) is surrounded.

The coil core 18 is in the illustrated ( 1 and 2 ) Embodiment U-shaped to the through the coil 12 generated magnetic field in the effective range 20 respectively. Other training, such as halftone, are conceivable. The coil core 18 may consist of a soft magnetic material of high permeability in a known manner. About clamping noses 30 is the spool core 18 in the breakthrough 28 kept clamped. It is also conceivable that the PCB 16 and the one through the PCB 16 inserted coil core 18 each in corresponding holders, not shown, of the housing 24 are held. The in the breakthrough 28 used spool core 18 can also be cast when inserted.

In a second embodiment 110 of the invention, in 3 and 4 is shown, is the bobbin 118 multi-legged - in the example shown with three legs 118.1 . 118.2 and 118.3 - educated. In this way, in the effective range 120 of the sensor 110 a different magnetic field and thus obtained a different switching characteristic than in the first embodiment. 3 shows a schematic side view and 4 an end view of the magnetic field-side end of the sensor 110 ,

For the arrangement of such a coil core 118 in a housing 124 here is a circuit carrier 116 with three breakthroughs 128.1 . 128.2 . 128.3 for receiving the three legs 118.1 . 118.2 and 118.3 intended. For reasons of space carries the circuit carrier 116 essentially only the tracks for three coils 112.1 . 112.2 and 112.3 holding the individual legs of the spool core 118 Surrounded to generate the magnetic field. The spools 112.1 . 112.2 and 112.3 are in the 3 and 4 shown in simplified form as thick lines, without the individual conductors forming the windings are shown.

The remaining electronics, so in particular the evaluation circuit 121 of the sensor 110 , is on another circuit carrier 117 arranged by lines 119 with the first circuit carrier 116 is in electrical connection. For power supply and Signalausleitung are again lines 122 intended.

All elements of the sensor 110 are in a housing 124 arranged.

Further embodiments with other arrangements of coil cores, tracks, coils and breakthroughs are possible within the scope of the invention.

The sensor according to the invention can be produced according to the invention as follows:
In a first production variant, a PCB is initially provided on which the necessary electronic components and in particular the conductor track forming the coil or coils as well as the opening (s) are provided. In a further step, the spool core is inserted into the opening and optionally mechanically fixed, for example by means of the clamping noses described above. Finally, the PCB with all electronic components and the coil core is inserted into a housing. The housing can also be injected around the mentioned sensor elements. Then the injection molding compound could fix the spool core in the opening. A separate mechanical fixation via clamping lugs or the like would not be necessary.
In a second production variant, first the PCB is also equipped with the electronic components and provided with the coil or coils forming conductor track or conductor tracks and provided. Then, in a first injection molding step, the spool core is injection molded from a soft magnetic plastic. A soft magnetic plastic can be formed, for example, by a plastic interspersed with a magnetizable material, for example a ferrite powder. The breakthrough could then be kept relatively small, for example, slightly smaller than the cross-sectional dimensions of the bobbin, so that the finished sprayed bobbin is held automatically in the breakthrough. In a second injection molding step, the housing is injection molded from another, ie not soft-magnetic plastic. Such an injection molding technique is also known as a two-component injection molding technique.

Claims (11)

Inductive sensor with at least one on a circuit carrier ( 16 ; 116 ) arranged conductor track ( 14 ), the at least one coil ( 12 ; 112 ) as well as with one of the coil ( 12 ; 112 ) associated coil core ( 18 ; 118 ), characterized in that the circuit carrier ( 16 ; 116 ) as a flat printed circuit board ( 16 ; 116 ) and at least one breakthrough ( 28 ; 128.1 . 128.2 . 128.3 ), which from the bobbin ( 18 ; 118 ) is interspersed. Sensor according to claim 1, characterized in that the coil core ( 18 ) has a U-shape or a half-toroidal shape. Sensor according to one of the preceding claims, characterized in that the coil core ( 18 ) via a press fit in the breakthrough ( 28 ) is held. Sensor according to one of the preceding claims, characterized in that the coil core ( 118 ) is designed multi-legged. Sensor according to one of the preceding claims, characterized in that a plurality of openings ( 128.1 . 128.2 . 128.3 ) are provided. Sensor according to one of the preceding claims, characterized by a housing ( 24 ; 124 ), in which the circuit carrier ( 16 ; 116 ) and the coil core ( 18 ; 118 ) are held. Sensor according to one of the preceding claims, characterized in that the housing ( 24 ; 124 ) is produced by injection molding. Sensor according to one of the preceding claims, characterized characterized in that the coil core of a soft magnetic Plastic exists. Sensor according to claim 8, characterized in that the spool core is manufactured by injection molding and in the breakthrough injected. Method for producing a sensor according to a of the preceding claims, characterized by the method steps: - Provide a circuit carrier with a coil consisting of a track and with a breakthrough; - bring in and fixing a spool core in the breakthrough; - Deploy the arrangement in a housing. Method for producing a sensor according to one of the preceding claims 1 to 9, characterized by the method steps: - providing the circuit carrier with a coil consisting of a conductor track and with an opening; - Spraying a bobbin with a first soft magnetic plastic; - spraying a Ge housing with a second plastic.