DE102004048444A1 - Inductive sensor for detecting presence of contact less metallic article, has coils and capacitance that are connected to LC-circuit, where coils are arranged in window wall, and capacitance and coils are adjacent to each other - Google Patents

Abstract

The sensor has a housing, which consists of a circumferential wall and a window wall, where a rear wall lies opposite to the window wall. Coils (48, 50) and a capacitance are connected to a LC-circuit. The coils are arranged in the window wall, and the capacitance and the coils are adjacent to each other. One of the coils is designed as a conductive strip of a printed circuit. Inner surface of the housing are connected with grooves.

Description

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

inductive Sensors are known from the market. Their function is to the approach or Detect presence of a metallic object without contact and then to give a signal. This signal is on the one hand as electrical Signal for forwarding and further processing before and can on the other hand, locally also for generating an optical functional or error signals are used, which during installation, commissioning, Maintenance and troubleshooting is beneficial.

The Operation of inductive sensors is based on the effect that one with high-frequency alternating current charged coil high-frequency magnetic field generated, its field strength in the nearer Surround the coil one for the detection of metallic objects reaches usable size. If electrically conductive Penetrate materials into this environment induces the high-frequency magnetic field in them high-frequency electric currents, something to an increased Power loss in the coil and a significant change the inductance the coil leads. At least one of these changes is evaluated in a downstream circuit.

The However, known inductive sensors do not provide for all applications with respect to their response satisfied.

By The present invention is an inductive sensor according to the preamble of claim 1 be further developed such that its response (such as its sensitivity) is improved.

These The object is achieved by an inductive sensor having the features specified in claim 1.

at the sensor according to the invention Both the coil and the capacity cooperating with it are immediate at (in, in or in particular behind) one of the boundary surfaces of the sensor housing arranged (so-called "active Area "). The corresponding housing wall preferably has as possible low wall thickness.

Kitchen sink and capacity are also closely adjacent to each other.

These Arrangement is in terms of generating a far-reaching Feldes advantageous, but is also preferred because coil and capacity the same environmental influences are exposed, in particular are at the same temperature.

advantageous Further development of the invention are specified in subclaims.

The Development of the invention according to claim 2 is, however, in terms of inexpensive manufacture of the coil also with regard to interest, the coil as possible close to the active area of the sensor housing provided.

The Development of the invention according to claim 3 ge equips the realization of a coil with high quality in a compact Dimensions and continue to be cheaper Production.

One Sensor as stated in claim 4 claims based Its compact dimensions only a small installation space, creating a size Number of applications possible becomes.

The Development of the invention according to claim 5 allows the working state of an inductive sensor easily visually check.

With the development of the invention according to claim 5, the commissioning, maintenance and troubleshooting for an inductive sensor is simplified. To indicate the correct function of such sensors signal lights used previously in a housing wall were used (see DE 195 10 470 A1 ). These have the disadvantage that their observability is possible only in a limited viewing angle and / or from a short distance. According to the invention, an observability of the signal light is obtained under a virtually arbitrary observation angle.

you receives therefore further savings in commissioning and time the troubleshooting or maintenance, as a result of the diffuser invention the signal light can be seen in a very wide angle range can.

there is the specified in claim 6 point of attachment of the visualization the working state used scattered light disc particularly advantageous, because so the stray light itself from different directions is seen. The scattered light can thus also be used e.g. during assembly or Commissioning or inspection are particularly well

The developments of the invention according to claim 7 and claim 8 allows a simple and precise positioning of the signal light on the sensor housing.

The Development of the invention according to claim 9 allows using largely the same basic components a sensor also sensors with different characteristics to realize. One only needs different carrier elements, which coil and capacity wear, use. As far as a complete pouring of the sensor housing with Plastic material is not or only partially made, can one with such sensors even at the place of use, the working characteristics of the considered sensor, be it through exchange be it by appropriate control devices on the components.

The Development of the invention according to claim 10 is advantageous in terms of manipulation of the sensor to prevent and arranged inside the sensor housing components against environmental influences to protect. Through the potting compound gets over it In addition, a homogeneous temperature distribution inside the sensor promoted. The sealing compound also serves as a heat storage, the temperature changes, especially suddenly occurring temperature changes, balances.

forms one is a carrier element for the Coil-forming window wall with its active surface according to claim 11, so shows such a support element high wear resistance and resistance to aggressive environmental conditions with good permeability for the alternating magnetic field.

The Development of the invention according to claim 12 brings the advantage that the casing high wear resistance having. About that In addition, it is resistant to welding spatters in plant construction Construction and / or repair work are difficult to prevent and when installing a sensor on or in the vicinity of a welding robot constantly hit the sensor.

Also the development of the invention according to claim 13 is in view on good wear resistance of the sensor housing and insensitivity of the sensor against welding spatter beneficial.

One Inductive sensor according to claim 14 can be under easily adjustable setting of its connector, the to the connection one Supply line (with conductors for data transmission and possibly also to the power supply), at the most diverse Install locations, always ensuring that on the Connecting cables no torsional moments are exercised.

The Development of the invention according to claim 15 allows a locking of the connector of the inductive Sensors in a selected angular position, guaranteed but at the same time a simple adjustment of the desired Connector angular position. This is for easy accessibility the sensor during installation and a low installation cost.

Under Receives working conditions one with inductive sensors an increased power loss, if stationary at the installation location of the sensor metallic bodies because also induced in these high-frequency electrical currents become (parasitic Ring currents).

At the The state of the art is disturbing that the Sensitivity related technical data of the inductive sensor depend on what electrical properties the environment of - before generally not known - installation locations has. Are z. B. only electrically insulating plastics at the installation site, there is virtually no interaction with this the magnetic high frequency field, the sensor sensitivity is relatively high. Is the inductive sensor at the installation against it surrounded by metal (eg within a machine or device), this reduces sensor sensitivity. By adjustment works During installation, this deficiency can only be remedied inadequately become.

With the development of the invention according to claim 16 is achieved that the Sensitivity of the inductive sensor less of the installation environment dependent is.

It it was recognized that the electrically conductive Peripheral wall of the housing has a shielding effect in such a way that the radially outward located Installation environment then only a weakened magnetic high frequency field "sees", so that it approximately indifferent is whether this installation environment has electrical conductivity or not.

at an electrically conductive Peripheral wall is expected to be in this comes to the formation of parasitic ring currents. To avoid such becomes the electrical conductivity interrupted in at least one point in the peripheral wall. This can be done by mechanical slots, the z. B. parallel to Axis of the coil in the electric peripheral wall are working, or in that one electrically insulating peripheral wall provided with an electrically conductive layer is provided and in these interruptions in the form of slits are.

As a result, the sensitivity of the inductive sensor is largely independent of the electrical properties of the installation environment, thereby Adjustment work in connection with assembly, commissioning, maintenance and repair can be saved.

Especially robust and very good dimensional stability are sensors according to the claims 17 and 18, because metallic perimeter walls particularly good strength have and can be produced very accurately, for example. In die casting.

On the other hand are housings according to the claims 19 and 20 in big numbers produce particularly inexpensive, with their peripheral walls largely electrically behave as if they were made of metal.

further developments according to claim 21 are for it provided, installed in rectangular cutouts or installation spaces to become while Further developments according to claim 22 find installation space for round cutouts. there If necessary, the circumferential wall interrupting slots ensure an interruption of eddy currents in the circumferential direction.

cost savings in the manufacturing offers the development according to claim 23, by the number of production steps is reduced.

The Continuing education according to claims 24 and 25 leads while on the other hand increased Number of manufacturing steps, but allows easier and thus cheaper tools for the sensor housing (Making the peripheral wall as extruded profile material), which especially for small series can be beneficial.

One Sensor according to claim 26 is characterized by high resistance against adverse environmental conditions and security against manipulation out.

The Training according to claim 27 is particularly advantageous if the electrical shield not only in the peripheral wall of the sensor, but in addition also in the radially outer area the front wall of the inductive sensor to achieve the desired sensitivity is required.

The Training according to claim 28 is also in terms of tightness of the housing and protection the components arranged in it against environmental influences of Advantage.

The Training according to claim 29 facilitates the installation and retrieval of the sensors provided with a housing according to the invention and her situation control.

below the invention with reference to embodiments with reference closer to the drawing explained.

In show this:

1 a sensor housing of a first embodiment with the front wall removed in a perspective view;

2 : the case of 1 with a view of the back wall;

3 : a housing similar 1 , but with front wall and with indicated on the back electrical feedthrough and mechanical attachment;

4 : a cross section through the sensor housing of 3 along the line IV-IV with indicated functional elements;

5 a sensor housing of a second embodiment in a plan view;

6 an axial section through the sensor housing of 5 along the line VI-VI with indicated functional elements;

7 : a similar view as 4 in which, however, a modified sensor is shown;

8th : a top view of the sensor after 7 ;

9 and 10 : similar views as 8th in which, however, further sensor variants are shown;

11 to 13 : similar views as 7 in which further sensor variants are shown;

14 : An exploded view of an adjustable lockable pivot bearing for a connector of the sensor according to 13 ;

15 : A perspective view of a locking disk of the adjustable pivot bearing according to 14 ;

16 : A perspective view of another inductive sensor compared to the embodiments of FIGS 1 up to 15 large sensor surface;

17 : an axial section through the sensor after 16 ;

18 a side view of a further modified inductive sensor with a large sensor area;

19 and 20 : similar views as the 16 and 17 in which a further modified sensor is shown;

21 : A perspective view of a lens of the sensor after the 19 and 20 ; and

22 : a similar view as 21 , wherein now a display board is shown inserted into a recess of the lens.

1 shows a perspective view of an empty housing 10 for a substantially cubic inductive sensor without front wall. From the four peripheral walls 12 . 14 . 16 . 18 are the upper wall in the picture 12 and the right wall 14 seen from the outside, while the bottom wall in the picture 16 as well as the left wall 18 can be seen from the inside. At the back is the case 10 from a back wall 20 limited, which with two circular openings 22 . 24 is provided (see. 2 ). In 1 it is only the lower opening 22 to see.

The front, the back wall 20 opposite wall is in 1 away.

The four peripheral walls 12 . 14 . 16 . 18 each have flat outer surfaces, whereby the approximately cubic housing 10 simply in appropriate, usually a grid of z. B. 40 mm recesses in devices, machines or tools can be installed.

The back wall 20 (please refer 2 ) has a non-planar outer surface, which is composed of several partial surfaces. In the bottom, the bottom wall 16 adjacent area includes the back wall 20 a substantially planar partial surface 26 , which in the transition area to the side walls 14 and 18 rounded down.

Parallel to the partial surface 26 and set off a little further to the front is another surface 28 arranged, in which the two kreiförmigen openings 22 . 24 are located. The subarea 26 So is stepwise something forward over. A deck surface 34 The step thus formed in turn comprises mutually offset in height subareas 36 . 38 and 40 ,

On both sides of the subarea 28 are concave arc-shaped towards the inside of the housing and to the two side walls 14 . 18 towards extending surfaces 30 . 32 arranged such that the space above the faces 36 . 40 becomes accessible to a tool, in particular a screwing tool. Within the subareas 36 . 40 are given from top to bottom through accesses, to carry out fixing screws 42 serve (cf. 3 ).

The perimeter walls 12 . 14 . 16 . 18 are at least partially made of electrically conductive material. Such electrically conductive material may be a metal or a metal alloy, e.g. As aluminum, magnesium, zinc, or an alloy with these metals. With sufficient electrical conductivity come with conductive material filled plastics or conductive coated plastics in question.

The Shape of the housing may change somewhat due to the manufacturing process, e.g. in terms of radii on edges and grooves. The same applies to the angles, under which the housing walls hired are (e.g., draft angles).

Further changes relate to the dimensions and the basic geometry, according to the respective in the case be accommodated sensor and the site can be modified. Also the materials of the case can depending on the one to be fulfilled Requirements are modified; In particular, parts of the housing may be transparent.

The back wall 20 Can be integral with the peripheral walls 12 to 18 connected and in this case made of the same material. However, it is also conceivable, the rear wall 20 made separately and then mittles a suitable joining method (gluing, friction welding o. Ä.) With the peripheral walls 12 to 18 connect to. In 3 is at 44 indicated such a joint.

In the 1 to 3 is always at the middle of the perimeter walls 12 to 18 one axial slot each 64 drawn, which is from a front wall 46 towards the back wall 20 extends over a length that is slightly less than half the distance between the two walls 46 . 20 equivalent. The slot 64 interrupts each at one of the peripheral surfaces 12 to 18 in the circumferential direction, the electrical conductivity and thus prevents the formation of induced ring currents.

As a result, the attenuation of the magnetic RF field is reduced, which favorably influences the sensitivity of the inductive sensor. It is sufficient, the length of the slots 64 to set up so that in the extension of the slots 64 towards the back wall 20 no significant magnetic RF fields are present.

When sizing the length of the slots 64 Care is taken to ensure that an impermissibly large mechanical weakening of the housing 10 is avoided. In the example shown, each of the walls has 12 to 18 an edge length of 40 mm, each slot 64 has a length of 15 mm.

In modified embodiments, the slot 64 also fall away.

4 shows a section through the housing along the line IV-IV of 3 , where in 4 Also functional components of an inductive sensor (in part schematically) are shown.

The front wall 46 is at the same time a carrier for two high frequency coils 48 . 50 trained, and carries on a rear approach 52 one only schematically 54 indicated supply and evaluation, the internal structure is not interested here.

A five-pole electrical feedthrough 56 is in the circular opening 22 arranged; their electrical contacts are inside the housing 10 in a manner not shown with the supply and evaluation electronics 54 connected. The outer contacts of the bushing 56 are connected in a manner not shown also via cable in a known manner with a jumper or the like.

Above the passage 56 is an LED 66 recognizable, which with its front area through the recess 24 led to the outside and there by a lens 68 is taken. The diffuser 68 lies close to the surface 28 on and is with this z. B. by an adhesive layer (not shown) connected.

At the point where the LED 66 with their front part in the lens 68 protrudes, the latter has a blind hole-like recess 76 , The diffuser 68 gets its scattering properties z. B. in that its rear surface 78 is frosted. This frosting causes on the one hand an apparent increase in the light source and on the other hand, a light emission in a very large angular range, so that the lighting of the LED 66 can be observed particularly well by the maintenance or commissioning staff.

The diffuser 68 at the same time seals the opening 24 against ingress of dust, etc.

Another help with commissioning and adjustment is a on the outside of the front wall 46 applied mark 70 , This is used for optical and / or tactile detection of the inductive sensor and its orientation by the commissioning or maintenance personnel. The mark 70 may have mechanical stiffening function and is formed, for example, by its symmetrical structure so that the central axis of the coils 48 . 50 is recognizable from the outside.

The design of the housing of the inductive sensor is not limited to the previously described, substantially cubic shape. 5 and 6 show a different shape, in which a peripheral wall 74 having circular cross-section. Corresponding elements are again provided with the same reference numerals, even if they differ in detail. A detailed description of these elements can therefore be dispensed with.

Based on this embodiment, but not limited to this, show the 5 and 6 in that the electrical feedthrough 56 and the LED 66 also on the peripheral wall 74 can be arranged. In addition, these figures show that the overall height, that is substantially the width of the peripheral wall 74 , Also significantly lower than the coil diameter can be.

In the 4 and 6 are at 82 and 84 Two capacitors are shown connected to the ends of the coil 48 or the coil 50 are connected and each form an LC resonant circuit with the associated coil.

The resonant circuit 48 . 52 is connected to an excitation circuit, not shown in the drawing, which acts on this resonant circuit with a high-frequency voltage. The coil builds accordingly 48 a high-frequency magnetic field. This is done by the metal banner 60 differently influenced in their different positions, and accordingly one also obtains a different induction voltage in the coil 50 and the capacitor 84 formed LC resonant circuit. The latter is connected to an evaluation circuit, which provides different output signals, depending on whether the metal flag 60 the sensor front wall 46 faces or not.

Based on 4 Let's briefly describe the operation of an inductive sensor with a housing according to the invention.

From the coil 48 an electromagnetic field is generated, the strength of which through the coil 50 is determined. This field strength depends on whether and to what extent the HF field is disturbed by the presence of electrically conductive bodies in the influence of the RF field. The passing of a metal banner 60 in the direction of the arrow 62 leads to a field change coming from the coil 50 detected and from the circuit 54 is evaluated. The presence of the metal banner 60 is lit by the LED 66 signaled locally; elec trical signals can be carried through the electrical contacts 56 be tapped.

For reliable operation of the inductive sensor with the coil axis perpendicular movement of the object to be detected, the maintenance of a distance between the outer surface of the front wall 46 and the metal banner 60 required within a permissible bandwidth. If the distance were too small, there would be the possibility of mechanical contact between the metal lug 60 and front wall 46 with the risk of jamming or destruction of a component; if the distance became too large, so could the approach of the metal flag 60 no longer be reliably detected.

The use of a housing 10 with electrically conductive peripheral wall 12 to 18 has the advantage that the propagation of the magnetic RF field perpendicular to the axial direction of the coils 48 . 50 is limited, in which there is a field line compression. As a result, the function of the inductive sensor becomes essentially independent of whether and how many other metallic bodies are in its vicinity.

The slots 64 in the metallic peripheral walls 12 to 18 . 74 can be poured in the manufacture of the inductive sensor when casting the sensor components with each other and with the housing with suitable casting material with, so you get an additional mechanical stability and tightness of the housing.

In the embodiment according to 5 and 6 is another slot 80 in the front wall 46 to recognize ( 5 ). This slot 80 is in the outer section of the front wall 46 arranged and extends radially inward to about the wires of the coils 48 . 50 , This slot 80 prevents in the front wall 46 if it is electrically conductive, parasitic ring currents are induced and thus have the same function as the slots 64 in the perimeter walls 12 to 18 . 74 ,

In the other embodiments according to the 7 to 18 are components that functionally correspond to such components as described with reference to FIGS 1 to 6 have already been described above, again provided with the same reference numerals. These components will not be described again in detail below.

In the embodiment of the 7 and 8th is the coil 48 as a spiral-shaped printed conductor layer on the front wall forming the sensor window 46 appropriate. This can be done with the known etching techniques, as it is also used for the production of normal printed circuit boards.

On the inner surface of the front window plate 46 and in the middle of the coil 48 lying is also a capacitor 82 attached, by three interconnected capacitor components 82a . 82b and 82c is formed.

At the sensor after 7 is only a single coil 48 provided with a single capacitor 82 forms an LC circuit. The sensor after 7 works so that one with the coil 48 and capacitor 82 formed LC circuit connected operation / evaluation circuit, the damping of the LC circuit by the metal flag 60 Measures, for example, by the phase position of the current in the resonant circuit and / or the amount of the resonant circuit nachgespeisten energy.

It can be seen that in this embodiment, the coil 48 has only a very small distance to the outer surface of the sensor and that the capacitor 82 the coil 48 is closely adjacent. In this way, coil and capacitor are at the same temperature, and the alternating current between capacitor and coil is limited to a spatially narrow area, which is advantageous for a good directional characteristic of the sensor.

The embodiment according to 9 differs from the one after 8th in that in one of the window plate 46 axially adjacent area again slots 64 are provided to ring currents at the free end of the housing 10 to prevent.

According to the embodiment 10 is in the open end of the case 10 instead of a window plate 46 a window cap 86 used. This consists of a permeable to the electromagnetic field plastic material. On the inside of the cap floor is again the coil 48 imprinted, in the middle again the capacitor 82 sits, as in the embodiment according to 7 ,

In the 10 shown variant allows using the same housing 10 the location of the coil 48 concerning the holes 43 to change.

You can do this by a dashed ring 88 From electrically conductive material again achieve that located in the vicinity of the installation site electrical materials do not affect the operation of the sensor.

For other applications in which one desires a transverse field component in the vicinity of the sensor, one can use the ring 88 omit or only over part of the axial dimension of the window cap 86 provide.

In the modified embodiment according to 11 are on the inside of the circumferentially extending housing walls 12 . 14 . 16 . 18 triangular cross-section grooves 90 stabbed. These serve as anchors for a casting resin, with which the interior of the housing 10 is filled in, as in 92 indicated.

In 11 is also a parallel to the window plate 46 running circuit board 94 which carries various components, including integrated circuits, which together supply the RF through the coil 48 and capacitor 82 accomplish LC circuit formed and its damping according to the position of the metal flag 60 measure up.

The embodiment according to 12 is similar to the one after 11 , only the circuit board is 94 perpendicular to the window plate 46 ,

At the sensor after 13 is the connector 56 Lockable in different angular positions on the housing 10 appropriate.

How out 13 can be seen, includes the connector 56 an insulating plate 96 and worn by this pins 98 ,

The insulating plate 96 is in a threaded sleeve 100 firmly inserted, eg glued.

The threaded sleeve 100 has a flange at its inner end 102 , the two radial locking lugs on its inner end face 104 . 106 having. On its outwardly facing end face is the flange 102 with a stop nose 108 Mistake.

Radial from the edge of the opening 22 offset to the outside is from the rear wall 20 a cylindrical bearing wall 110 to the housing interior. In between the inner surface of the bearing wall 110 and the outer surface of the threaded sleeve 100 lying annulus is a coil spring 112 arranged, which the flange 102 towards a latching ring 114 biased firmly in the end of the camp wall 110 pressed or glued.

How out 15 can be seen, the locking ring has a plurality of circumferentially equally distributed locking recesses 116 , which are each shaped so that they one of the locking lugs 104 . 106 be able to record.

It can be seen that in the sensor after the 13 to 15 in that one the threaded sleeve 100 moved in the drawing to the left, the locking lugs 104 . 106 out of engagement with the locking ring 114 can bring. You can then the threaded sleeve 100 rotate freely. If you leave the threaded sleeve in the desired angular position 100 go again, so the locking noses return 104 . 106 again in locking recesses 116 of the detention ring 114 back (possibly with a slight additional turning of the threaded sleeve). The threaded sleeve 100 and with it the contact pins 98 are now locked in the desired angular position.

In the embodiment of the 13 to 15 you can see the angular position of the threaded sleeve 100 in increments of 45 °. By closer arrangement of the locking recesses 116 even smaller angle increments can be realized.

The stop nose 108 of the flange 102 runs in a not shown in the drawing circumferential groove of the bearing wall 110 having at one point a stop lug, also not shown in the drawing. In this way it is prevented that the threaded sleeve 100 is rotated by more than 360 °, resulting in undesirable mechanical stresses of the contact pins 98 connected wires (not shown) could result. About the angular extent of the bearing wall 110 carried stop lug can be the available angle of rotation for the threaded sleeve 100 reduce, eg to 300 ° or less.

The embodiment of the 16 and 17 is similar in principle to the one after 9 , only has the case 10 the basic shape of a short cylinder.

The embodiment according to 18 is similar in principle to that 10 , only the case again has the shape of a short cylinder.

In 17 is further shown that the housing 10 a coating 118 wearing. The coating 118 is adhesion-inhibiting and high temperature resistant. It may for example consist of Teflon or ceramic and be applied in a manner customary for these materials (eg by spraying, brushing or spraying in an arc or the like.

The coating 118 causes spatter that occurs during assembly or repair work in the vicinity of the sensor at the site, do not cause damage to the housing outer surface.

Similar is the window cap 86 with an adhesion-inhibiting and high-temperature resistant coating 120 provided (see. 20 ), which serves the same purpose as the coating 118 ,

Is the housing 10 made of a plastic, so you can also make the crosslinking of the plastic using high-energy rays, such as electron beams. The plastic housing is then very hard and its surfaces are similar insensitive to spatter, as by a coating 118 or 120 would receive.

The Ausführugnsbeispiel after the 19 to 22 is similar to the one after the 16 to 18 , only the outside of his case 10 prismatic with a qudratischem cross-section and without slots 64 executed. A cubic outer shape is also possible.

The LED 66 is from a circuit board 122 carried, which with an outer end portion in a recess 124 the diffuser 68 led is inserted and in this section the LED 66 wearing. The board 122 intersperses a window 126 in the implementation 56 carrying housing wall under play. Furthermore, the lens is 68 with the housing 10 through a pen 128 accurately connected.

In the 21 and 22 is at 130 an opening is shown which is performing 56 can accommodate 132 a hole through which the pin 128 can extend.

The above-described protection against welding spatter can also be found in the window plates 46 provide that in the embodiments of the 1 to 6 were used.

You can see the windowsills 46 (and also the window caps 86 ) also made of a ceramic material or single or multi-layer coated GS.

The Sensors described above build in at least one of their dimensional directions compact, have a dimension of about 55 mm in this direction Or less.

So has the square cross section of the housing of the sensors after the 1 to 4 and 7 to 15 in a practical embodiment, an edge length of about 40 mm.

In a practical embodiment of the sensor according to the 5 and 6 respectively. 16 to 18 the axial dimension of the sensor housing is about 40 mm. This is in view of a simple mounting of the sensor, even if its connector is not rotatable, an advantage.

at the LEDs used to indicate the working condition of the inductive sensor can be used, single-color or multi-colored LEDs act. The distinction of the different working conditions can then over a particular flashing pattern and / or the colors of the LED take place.

In the above-described inductive sensors can be that portion of the housing 10 , which is opposite to a coil, equipped with a metal lining, such as a copper ring to obtain a defined pre-damping. such allows a flush and a non-flush mounting of the sensor without significant influence on the operating characteristics. In the above-described concrete embodiments with a square housing cross section with an edge length of 40 mm, the width of such a metallic lining may be between 5 and 15 mm. In the above-mentioned practical embodiments for a cylindrical housing having an axial dimension of 40 mm, the diameter of the housing is about 80 mm. In such a housing then the width or the axial dimension of the metallic lining is between 5 and 20 mm. The just mentioned linings fulfill the same function as that associated with the window cap 86 above-mentioned metallic ring 88 ,

For small series it is preferred that the walls forming a peripheral wall 12 . 14 . 16 . 18 are formed by a cut-to-length section of an extruded profile material, which is already provided with extrusions during drilling with holes, grooves, etc., which serve for attaching components of the sensor or fasteners. The back wall 20 and the front wall permeable to alternating magnetic fields 46 are then separate parts that are placed in positive engagement on the cut profile piece. Here is the back wall 20 usually a metal part, the front wall 46 a plastic part.

Where this with regard to manipulation security and / or protection the electrical and / or electronic components of the sensor is required, the sensor housing is poured with synthetic resin.

Claims (29)

Inductive sensor with a housing ( 10 ), which has a window wall ( 46 ; 86 ), one of these opposite back wall ( 20 ) and a peripheral wall ( 12 . 14 . 16 . 18 ; 74 ), with at least one coil ( 48 . 50 ) and with at least one capacity ( 82 . 84 ), wherein at least one coil and at least one capacitor are connected to form an LC circuit, characterized in that the coils ( 48 . 50 ) at the window wall ( 46 ; 86 ) and the capacities ( 82 . 84 ) and the coils ( 48 . 50 ) are adjacent to each other. Sensor according to claim 1, characterized in that at least one of the coils ( 48 . 50 ) is formed as a conductor of a printed circuit. Sensor according to claim 2, characterized in that at least one of the coils ( 48 . 50 ) is formed by printed conductors of a printed multilayer printed circuit board which are interconnected by means of through-connection. Sensor according to one of claims 1 to 3, characterized in that its housing ( 10 ) has compact dimensions, preferably in at least one extension direction has a dimension of less than 55 mm. Sensor according to one of claims 1 to 4, characterized by a housing ( 10 ) carried lens ( 68 ) illuminated by at least one signal lamp ( 66 ) is exposed to light and is visible from the outside of the housing, wherein the signal light ( 66 ) is preferably an LED. Sensor according to claim 5, characterized in that the diffuser ( 68 ) in the vicinity of a connector part ( 56 ) is arranged, which from the housing ( 10 ), wherein the material from which the lens ( 68 ), preferably the same material as the material of a rear wall ( 20 ) of the housing, and wherein again preferably diffuser ( 68 ) and back wall 20 ) are integrally connected. Sensor according to claim 5 or 6, characterized in that the lens ( 68 ) a recess ( 124 ), in which a signal light ( 66 ) carrying end portion of a board ( 122 ) Recording finds. Sensor according to one of claims 5 to 7, characterized in that the lens ( 68 ) with the housing ( 10 ) ( 128 ). Sensor according to one of claims 1 to 8, characterized in that a wall ( 46 ) of the housing ( 10 ) is formed as a separate carrier element and at least the coils ( 48 . 50 ) of the LC circuit carries. Sensor according to one of claims 1 to 9, characterized in that the inner surface of the housing with grooves ( 90 ) and the interior of the housing with a casting resin ( 92 ) is poured into the grooves ( 90 ) intervenes. Sensor according to one of claims 1 to 10, characterized in that the window wall ( 46 ; 86 ) made of ceramic or GS. Sensor according to one of claims 1 to 11, characterized in that the housing ( 10 ) and / or the window wall ( 46 ; 86 ) at least partially a coating ( 118 ; 120 ), which is resistant to welding spatter. Sensor according to one of Claims 1 to 12, characterized in that the housing ( 10 ) and / or the window wall ( 46 ; 86 ) consists at least partially of irradiated plastic. Sensor according to one of claims 1 to 13, characterized in that the housing ( 10 ) a connector part ( 56 ), which is rotatable about its axis. Sensor according to claim 14, characterized in that the connector part ( 56 ) via a detachable in the angular direction in a plurality of positions lockable storage ( 104 to 116 ) on the housing ( 10 ) is attached. Sensor according to one of claims 1 to 15, characterized in that a peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) is electrically conductive and the electrically conductive peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) on at least one of the window walls ( 46 ) is interrupted so that the induction of parasitic ring currents in the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) is kept small. Sensor according to claim 1 to 16, characterized in that the material of the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) comprises a metallic material. Sensor according to claim 17, characterized that the metallic material is selected from the following group: Light metals, light metal alloys, zinc, zinc alloys, stainless steel. Sensor according to claim 1 to 16, characterized in that the material of the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) comprises an electrically conductive plastic. Sensor according to claim 1 to 16, characterized in that a non-electrically conductive peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) a surface coating or lining ( 88 ) carries an electrically conductive metal. Sensor according to one of the preceding claims, characterized in that the peripheral wall ( 12 . 14 . 16 . 18 ) has an outer rectangular cross-section and preferably in each of four walls ( 12 . 14 . 16 . 18 ) at least one slot ( 64 ) is provided with axial extension component. Sensor according to one of claims 1 to 20, characterized in that the peripheral wall ( 74 ) has a substantially circular cross-section on the outside, and preferably at least one slot (at least two preferably uniformly distributed over the circumference) 64 ) having. Sensor according to one of the preceding claims, characterized in that the rear wall ( 20 ) with the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) is integrally formed. Sensor according to one of claims 1 to 22, characterized in that the window wall ( 46 ; 86 ) and / or the rear wall ( 20 ) with the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) via a joint ( 44 ) connected is. Sensor according to one of the preceding claims, characterized in that the window wall ( 46 ; 86 ) and / or the rear wall ( 20 ) is made of a different material than the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ). Sensor according to one of the preceding claims, characterized in that the window wall ( 46 ; 86 ) and / or the rear wall ( 20 ) with the peripheral wall ( 12 . 14 . 16 . 18 ; 74 ) is shed. Sensor according to one of the preceding claims, characterized in that the window wall ( 46 ) has in its radially outer portion of electrical conductivity and by at least one, extending in the radial direction electrically insulating slot ( 80 ) is interrupted. Sensor according to one of claims 16, 21, 22, 27, characterized in that the slots ( 64 ; 80 ) are densely filled with an electrically insulating material. Sensor according to one of the preceding claims, characterized in that the outer surface of the window wall ( 20 ) visible and / or tactile marks ( 70 ).