DE102004032258A1 - Inductive proximity sensor adjusts effect of metallic device on reference and sensor coils to provide same sensitivity for ferro and non-ferromagnetic materials - Google Patents

Abstract

Inductive proximity sensor has a reference coil (24) and a sensor coil (14) designed so that a defined difference of the damping effect of a metallic neighboring device (32) on the reference and sensor coils is adjusted so that the influence of the neighboring device (32) on a sensor output signal is eliminated. INDEPENDENT CLAIM is also included for compensation method.

Description

The The invention relates to an inductive proximity sensor comprising a Sensor coil device for detecting a metallic target and a reference coil device with at least one coil.

The The invention further relates to a method for balancing an inductive Proximity sensor, which a reference coil device and a sensor coil device comprises being facing this a metallic environmental device are not shielded.

From the DE 196 11 810 C2 is a contactlessly operating proximity switch with a influenced by externally guided objects resonant circuit and with an evaluation device for obtaining a switching signal from a change in the oscillation state of the resonant circuit descriptive output, the resonant circuit a resonant circuit bridge with at least two capacitors and at least two by the from outside zoom guided objects is different influenced coils. In the evaluation device, the bridge transfer function is formed from the bridge diagonal voltage and the input voltage of the oscillating circuit bridge, the real part of which serves independently of the imaginary part for obtaining the switching signal.

By the differently influenced coils is a sensor coil device and a reference coil device educated.

at inductive proximity sensors is the influence of the resonant circuit dependent on electromagnetic Properties of the metallic target to be detected. For example, dampen ferromagnetic metals, the resonant circuit stronger because additional Energy losses caused by the reversal of the remanent magnetic field. In paramagnetic metals, the resonant circuit is less strong attenuated However, the resonant circuit inductance is much more changed (in particular reduced) than in ferromagnetic metals.

By the provision of a sensor coil device and a reference coil device let yourself a proximity sensor realize which at least with respect to a switching distance or a switching distance range the same sensitivity to a Object made of a ferromagnetic material and non-ferromagnetic Material has ("factor 1 "-Näherungssensor).

Of the Invention is based on the object, an inductive proximity sensor to improve the type mentioned so that it can be used universally is.

These Task is in the aforementioned inductive proximity sensor according to the invention thereby solved, that the Reference coil means and the sensor coil means arranged and are designed so that a defined difference of the damping effect a metallic environmental device on the sensor coil means and the reference coil device is set, at least when the Sensor coil device and the reference coil device in one certain position to the environmental device, and that the influence of the environmental device to a sensor output is eliminated.

A metallic environment affects the sensor coil means and the reference coil means, if not shielded. For example, the environment device may be part of an application or itself part of the proximity sensor be. When the damping influence difference (relative to the sensor coil device and the reference coil device) is defined and the corresponding difference value known is, then lets itself the damping effect of the metallic Environment device hardware and / or eliminate by software, so that one Sensor output signal from the metallic environmental device not affected becomes.

The Sensor output signal is a signal which from an evaluation is delivered. The evaluation device can be located internally in a housing of the inductive proximity sensor be arranged or external. The sensor output signal is for example a switching signal or an analog (distance) signal.

For example can by appropriate arrangement and design of the reference coil means the damping influence difference be set to substantially zero, so that the damping effect of the environmental device to the sensor coil means and the reference coil means is compensated. For such a proximity sensor is then the metallic environment "invisible", so that this is the detection result for the actual measurement object, namely that metallic target, essentially unaffected.

At defined damping Einflußeinflußdifferenzwert it is also possible in principle, that in an evaluation of the approx sensors, for example, a software compensation takes place, so as to eliminate the influence of the metallic environmental device.

According to the invention is a Proximity sensor provided, which is based on a sensor signal to be detected metallic Target "sees" while a metallic environmental device is "invisible".

Especially are the sensor coil device and the reference coil device arranged and designed so that the environmental device a defined signal change difference between the sensor coil device and the reference coil device causes. The metallic target affects the sensor coil means and the reference coil means and there are corresponding signals generated. The environmental device affects the sensor coil device and the reference coil device as well. When the signal change difference due to the influence of the sensor coil means and the reference coil device is known, then can be thereby the influence due to the metallic target (as actual measurement object) determine. In particular, it is provided that the signal change difference is set to substantially zero, so that changes in the sensor signal of Proximity sensor solely due to distance changes of the metallic target to an active sensor surface are and the distance changes can be determined.

Especially are the sensor coil device and the reference coil device arranged and designed so that the environmental device a defined inductance change difference between the sensor coil device and the reference coil device causes. The essential damping effect of the metallic Ambient device is an inductance change at the sensor coil device and an inductance change the reference coil device. The damping effect also leads to a (direct) quality change, where the inductance change another (usually larger) contribution in the quality change represents. When set the difference of these inductance changes defined and in particular is set to substantially zero, then you can the influence of eliminate metallic environmental device to the sensor signal. (For a difference value, which is not equal to zero, but the known is, basically for example, software and / or circuitry the influence be eliminated from the sensor signal.)

If the setting is such that the Bedämpfungsänderungen not equal or approximate are the same (i.e., the damping change difference between sensor coil device and reference coil device not disappears), then it is convenient an evaluation device is provided, which is a sensor output signal generated in which the different damping effect on the Sensor coil device and the reference coil device through consideration the known attenuation influence difference is calculated out. By specifying the defined attenuation influence difference can the evaluation of the signals it receives, the calculate out different damping effects and generate a sensor output signal which varies by the different Damping influence is "cleaned up", that is, it can be a software compensation carry out. When the damping influence difference Zero, such compensation is not necessary.

The Bedämpfungseinflußdifferenz can be over the Arrangement of the reference coil device in a housing and / or the area the at least one coil of the reference coil device and / or the number of turns of the at least one coil of the reference coil device to adjust. Also other settings can be provided be.

About distance and / or angular position of the at least one coil of the reference coil device a housing side let yourself the damping effect of the environmental device adjust to the reference coil device and thereby turn the Bedämpfungseinflußdifferenz set defined.

It For example, it can also be provided that around the at least one coil the reference coil device at least one conductor loop is arranged. This can form a short circuit turn over the an inductance setting for the reference coil device possible is.

It is advantageous if a balancing resistor in series with the at least one conductor loop is connected. Thereby results in a further setting possibility. It can also be provided be that the Balancing resistance can be influenced externally, so externally, for example via a Teach-in process, the inductance adjust the reference coil device and thus turn the inductance due to the environment setting. Thereby again it is possible set the damping influence difference.

It can also be provided that the at least one coil of the reference coil device is partially covered and / or shielded and is shielded in particular to an environmental device out. For example, the corre sponding Covering device or shielding arranged towards a mounting side of the proximity sensor. As a result, in turn, the inductance of the reference coil means can be set defined, so as to be able to adjust the inductance change again and the Einämpfungseinflußdifferenz.

For example is on a carrier for the least a coil of the reference coil device a metal layer arranged, so for to provide a cover or shielding.

It can also be provided that a Cover or shield is movable. In particular, this is Cover or shield from outside of a housing of the inductive proximity sensor lockable positionable. This can be, depending on the positioning the cover or shielding, the damping effect of the environmental device adjust and thus the damping effect difference to adjust. The setting may be, for example, during a Teach-in process done.

All It is particularly advantageous if the sensor coil device and the reference coil means are arranged in a differential circuit and / or a differential evaluation of signals of the reference coil device and the sensor coil device takes place. This can be done just use the reference coil device as a reference, for example a factor 1 proximity switch too realize.

The Sensor coil means and the reference coil means can do so in a bridge circuit be arranged such as an L-C bridge circuit or in a L-R-bridge circuit, as stated in the unpublished German Patent Application No. 10 2004 020 978.2 of April 22, 2004 is.

It is possible, that the metallic environmental device is part of the proximity sensor and in the process in particular a non-shielding part of a housing of the Proximity sensor forms.

It can also be provided that the metallic environment means a mounting base for the proximity sensor forms. The metallic environment is then part of a Application, such as a machine part, where the proximity sensor to assemble.

Around a different influence on the sensor coil device and the reference coil means through the metallic target (as actual measurement object) to achieve, they are preferably spaced from each other.

It can be provided that the Sensor coil device and the reference coil device in parallel are spaced. It can be then a flat proximity sensor realize.

It is possible, too, that the Sensor coil device and the reference coil device or a or a plurality of coils of the reference coil means at an angle are arranged to each other. This can be advantageous for certain applications be. For example, can be thereby a proximity sensor realize, which has more than one mounting side.

It is then cheap, if the at least one coil of the reference coil device in is arranged at an angle to a mounting side of the proximity sensor. Depending on the mounting side can then be the reference coil device the environmental device are influenced, the defined Difference value is set.

universal applications arise if at least two mounting sides are provided.

conveniently, is the reference coil device with respect to an active sensor surface behind the Sensor coil device arranged. The sensor coil device serves to detect the metallic target, for example to provide a switching function. So here is a great sensitivity present, she should be near be arranged an active sensor end.

Out for the same reason it is favorable when the sensor coil device with respect to a mounting side of the Proximity sensor (in the direction from the mounting side to the sensor coil device) the reference coil device is arranged.

It can also be provided that the Sensor coil device laterally to the reference coil means is arranged.

at an embodiment it is envisaged that the Reference coil device at least partially between a circuit carrier and the sensor coil device is arranged. This results an easy manufacturability. For example, it is the same possible, change the relative position of the reference coil device in a housing to so also externally change the damping effect can.

It is also possible for the reference coil device to be arranged at least partially on a circuit carrier. As a result, the assembly, since the reference coil means integrally on the circuit carrier (which the wide ren components of a resonant circuit and an evaluation device carries) can produce.

Further settings arise when the reference coil means a plurality of Coils included. This results in setting options for the total coil area, the Windungszahlen, the geometric arrangement, etc. Further, a Adaptation to specific applications possible.

It can while several coils are arranged in a plane or different Coils may also be arranged in different planes.

Especially then coils of the reference coil device are connected in series, as a total inductance for the To provide reference coil device. Also at least partial Parallel connection is basically possible.

It is possible, too, that coils the reference coil means to different union sides of the proximity sensor are aligned. This can be for certain applications, for example for applications, where the proximity sensor flush is installed in a recess or the like.

For certain Applications, it is advantageous if the at least one coil of the Reference coil device with its winding axis substantially is arranged parallel to a sensor axis; especially then, when the sensor coil means and the reference coil means are aligned parallel to each other and a mounting side of a active sensor surface parallel opposite.

One Proximity sensor with small dimensions can be realize when the at least one coil of the reference coil device a flat coil is. The same applies in principle even if the coil or coils of the sensor coil means are flat coils.

By the solution according to the invention can be a proximity sensor realize with a cuboid housing.

Especially is the case non-shielding trained. It can be, for example, out produce a plastic material. This, in turn, is the production simplified and the production costs are reduced.

It can be provided that the Bedämpfungsbeeinflussung the reference coil device is externally adjustable. A user then can the proximity sensor adapt to an application so that the metallic environmental device for the proximity sensor is "invisible" relative to a sensor signal. This can be, for example as part of a teach-in process.

It is possible, for example, to set the position of the reference coil device in a housing, to allow an external adjustment of the damping effect.

It is also conceivable that the magnetic properties of the at least one coil of the reference coil device via the Setting a position of a bobbin are adjustable. For example the coil core is formed as a ferrite core pin-shaped and his Position can be determined variably. Depending on the position again result in different inductance values for the coil or coils. It then in turn the damping effect is adjustable and thereby the damping influence difference.

Especially is the proximity sensor designed as a factor 1 switch, d. H. as a switch, where the Detection result at least related to a specific operating distance and a certain switching distance range regardless of the material of the metallic Targets is.

Of the The proximity sensor according to the invention comprises at least a resonant circuit which can be influenced by approaching the target; the at least one resonant circuit is by means of the sensor coil device and the reference coil means. For example, includes a resonant circuit the sensor coil device and the reference coil device or they are two separate but coupled oscillating circuits provided, one of which comprises the sensor coil means and the others, the reference coil device.

conveniently, the reference coil device has a smaller coil area as the sensor coil means. This results in a good signal.

Of the Invention is also based on the object, a method of the initially to provide a sensor output signal, which is substantially unaffected by the metallic environment is.

This becomes according to the invention by the method mentioned in the introduction solved, that the Reference coil device is modified or a signal evaluation is adjusted by an evaluation that a different Damping influence of the environmental device to the sensor coil means and the reference coil means substantially eliminated based on a sensor output is.

It is then the different damping effect substantially compensated, so that for a difference signal the sensor coil means and the reference coil means the metallic environmental device is essentially "invisible". The compensation can take place directly at the influence of damping, so that signals the sensor coil means and reference coil means substantially influenced the same are, or the compensation can be calculated by the evaluation respectively.

Of the Adjustment is carried out in particular when the sensor coil device in a certain position to the metallic environment is. For example, the inductive proximity sensor to be adjusted is mounted on the metallic environmental device.

The Modification of the damping effect can by positioning the reference coil means on a casing and / or adjustment of the inductance of the reference coil device and / or Adjusting the cover or shielding one or more coils the reference coil device take place. It can be, for example, in a Teach-in process affect the reference coil device so the existence certain damping effect of the metallic Environment is set, in such a way that this Damping influence with the damping effect on the Sensor coil device compensated. The reference coil device is preferably from the outside modifiable by, for example, their position within a housing is detectably adjustable and / or the inductance adjustable is and / or the cover or shield is adjustable. The corresponding Setting parameters are then modified until a compensation of the Damping influences receives.

The The following description of preferred embodiments is used in conjunction with the drawing of the closer explanation the invention. Show it:

1 a schematic representation of a first embodiment of a proximity sensor, which is mounted on a metal plate;

2 A second embodiment of a proximity sensor according to the invention;

3 a third embodiment of a proximity sensor according to the invention;

4 A fourth embodiment of a proximity sensor according to the invention;

5 an embodiment of a conductor loop (short-circuit coil), which is arranged around a coil of a reference coil device and

6 a side sectional view of a bobbin.

A first embodiment of a proximity sensor according to the invention, which in 1 shown schematically and there as a whole with 10 is designated, comprises a housing 12 , In this case 12 is a sensor coil device 14 arranged. This sensor coil device 14 has at least one coil, which is formed for example as a flat coil, which on a support 16 is arranged. The sensor coil device 14 serves to detect a metallic target 18 , For example, the proximity sensor 10 designed as a proximity switch which provides a switching signal when the target 18 a certain switching distance (distance between an active sensor surface 20 and the target 18 ) has reached.

The proximity sensor 10 is an inductive proximity sensor. Its function is based on the interaction of the metallic target 18 with the electromagnetic alternating field of the proximity sensor 10 , In the target 18 , which is a metallic damping material, eddy currents are induced by the electromagnetic alternating field, which withdraw energy from the alternating field. As a result, among other things, the height of the vibration amplitude in an oscillator of the proximity sensor 10 reduced. This change in turn can be evaluated.

The housing 12 is formed nichtabschirmend. For example, the housing 12 made of a plastic material. It is also possible in principle that the housing 12 has metallic parts which are not closed, so that the sensor coil means 14 is not shielded and in particular not backwards with respect to a housing side 22 is shielded which of the active sensor surface 20 opposite.

The housing 12 is formed, for example, cuboid with a rectangular cross-section.

In the case 12 is spaced from the sensor coil means 14 a reference coil device 24 arranged. The reference coil device 24 is parallel to the sensor coil device 14 aligned and has, for example, a (reference) coil. The coil axes of the sensor coil device 14 and the reference coil device 24 are aligned in parallel and are substantially parallel to a sensor axis 26 ,

The sensor axis 26 stands substantially perpendicular to the active sensor surface 20 and the distance direction between the target 18 and the proximity sensor 10 is parallel to the sensor axis 26 ,

The reference coil device 24 lies relative to the active sensor surface 20 behind the sensor coil device 14 ,

The area of the coil of the reference coil device 24 is smaller than the area of the coil of the sensor coil device 14 ,

The reference coil device 24 has a different distance to the target 18 as the sensor coil means 14 on. By means of the reference coil device 24 can be a proximity sensor or proximity switch realize, which has the same sensitivity to an object made of a ferromagnetic and non-ferromagnetic material ("factor 1" proximity sensor). The sensor coil device 14 and the reference coil device 24 are connected in a differential circuit and / or a differential evaluation of corresponding coil signals is made.

Other circuit components of the proximity sensor 10 and in particular an evaluation device are on a circuit carrier 28 arranged, which in the housing 12 sitting. In the embodiment shown, the circuit carrier sits 28 the housing side 22 facing. The proximity sensor 10 provides an output signal which is provided by the evaluation device. This is in particular a switching signal or an analog (distance) signal.

The coil of the sensor coil device 14 (Sensor coil) and the coil of the reference coil device 24 (Reference coil) form part of a resonant circuit, the rest of the resonant circuit on the circuit carrier 28 is arranged.

The sensor coil device 14 and the reference coil device 24 For example, they may be arranged in a bridge circuit. German Patent Application No. 10 2004 020 978 dated April 22, 2004, assigned to the same Applicant, describes an LR bridge circuit in which the coil of the sensor coil device (sensor coil) and the coil of the reference coil device (reference coil) are provided with resistance elements in an LR circuit. Bridge circuit are arranged, wherein a voltage tap is provided in each case in the coil branch and in the resistance branch of the LR bridge circuit. This application is expressly incorporated by reference.

For example it is also possible to gain a signal that in a resonant circuit with a sensor coil and a reference coil an oscillating circuit voltage signal and a coil voltage signal is supplied to a subtracting amplifier. This is also described in the aforementioned non-prepublished application.

For example, it is also possible to use the resonant circuit as a resonant circuit bridge with at least two capacitors and at least two objects brought from the outside (target 18 ) form different influenceable coils, namely the coils of the sensor coil means 14 and the reference coil device 24 , In an evaluation device (which in particular on the circuit carrier 28 is arranged) can be formed from a bridge diagonal voltage and the input voltage of the resonant circuit bridge, the bridge transfer function whose real part is independent of the imaginary part for obtaining a switching signal. Such a non-contact proximity switch with a by an externally introduced target 18 influenced resonant circuit and having an evaluation device for obtaining a switching signal from a change of the oscillatory state of the resonant circuit descriptive output signal is from DE 196 11 810 C2 known, to which reference is expressly made.

It can be provided that the proximity sensor 10 itself has metallic parts such as a metallic housing part or on a metal part such as a metal plate 30 should be mounted. Such metallic parts form a metallic environmental device 32 , which due to the non-shielding design of the housing 12 the sensor coil device 14 and the reference coil device 24 influence and in particular exercise a damping effect.

At the in 1 the embodiment shown is the proximity sensor 10 on the metallic environmental device with the housing side 22 (Mounting side) mounted. The environment 32 is for example a machine part of an application.

Since the sensor coil device 14 and the reference coil device 24 in the direction of the sensor axis 26 are spaced, is the distance between the sensor coil means 14 to the environment facility 32 and the reference coil device 24 to the environment facility 32 differently. The damping effect of the environmental device 32 on coils is location dependent.

According to the invention it is provided that in relation to the sensor coil means 14 the re Conference coil device 24 is arranged and designed so that the difference in variation in the attenuation between the sensor coil means 14 and the reference coil device 24 due to the metallic environment 32 when the proximity sensor 10 is mounted on this, defined is set. The metallic environment 32 applies to the sensor coil device 14 a certain damping effect and in particular changes the inductance of the sensor coil device 14 , Further, it applies to the reference coil means 24 a certain - but compared to the sensor coil device 14 different - damping effect on the reference coil device 24 and generates an inductance change there. These damping influences in turn lead to signal changes of the sensor coil device 14 and the reference coil device 24 for the detection of the metallic target 18 , relative to the case when the environmental device 32 not available.

According to the invention the damping effect is adjusted so that at least when the proximity sensor 10 at the environmental facility 32 is positioned, ie the sensor coil means 14 and the reference coil device 24 each at a defined distance from the environmental device 32 lie, there is a known Schwämpfungseinflußdifferenz and in particular a known inductance change difference exists. The difference of the inductance changes on the sensor coil device 14 and the reference coil device 24 is therefore known and is adjusted in particular, by arrangement and design of the reference coil device 24 in relation to the sensor coil means 14 , As a result, the signal difference is known and can be taken into account, for example by the evaluation and in particular compensated. It is therefore possible to influence the environment 32 out, so that the target detection function of the proximity sensor 10 through the environment 32 is not affected and in particular the switching function of the proximity sensor 10 is not affected.

In particular, it is provided according to the invention that the sensor coil device 14 and the reference coil device 24 are arranged and designed so that when the proximity sensor 10 over its housing side 22 (Mounting side) at the environmental facility 32 is mounted, the difference of the damping influences on the sensor coil means 14 and the reference coil device 24 is substantially zero, ie the environmental device 32 at the sensor coil device 14 and the reference coil device 24 generates the same inductance change, so that the difference of the inductance changes to the sensor coil means 14 and the reference coil device 24 essentially disappears. This then means that the proximity sensor with the sensor coil means 14 and the reference coil device 24 "backwards" to the environment 32 the environmental device "does not see" because their influence on the resonant circuit of the proximity sensor on the arrangement and design of the sensor coil means 14 and the reference coil device 24 is compensated. After "front", ie at the active sensor surface 20 , is the influence of the metallic target 18 on the sensor coil device 14 and the reference coil device 24 However, different, so that in particular a proximity sensor or a proximity switch can be realized, which has the same sensitivity to an object made of a ferromagnetic material and non-ferromagnetic material, at least based on a specific switching distance or switching distance range of the target 18 to the active sensor surface 20 ,

The setting of a defined attenuation influence difference for the sensor coil device 14 and the reference coil device 24 (and thus for a resonant circuit of the proximity sensor 10 ) can be performed when the environmental device is part of the proximity sensor 10 is (in this case, the metallic environmental device exerts a pre-damping) or if the environmental device 32 is arranged externally, at least when the sensor coil means 14 and the reference coil device 24 at a certain distance from the environment 32 are positioned.

The adjustment of the damping influence difference when from a given sensor coil means 14 is assumed, for example, on the arrangement of the reference coil means 24 in the case 12 and / or the surface of the coil or coils of the reference coil device 24 and / or the number of turns of this coil or coils of the reference coil device 24 respectively. The arrangement of the reference coil device 24 Can over the distance to the housing side 22 or to the environmental device, if this is an integral part of the proximity sensor 10 is, and / or the angular position of the coil of the coils of the reference coil means 24 related to the active sensor surface 20 be set.

It is also possible that the reference coil device 24 comprises a plurality of (partial) coils, which at different distances and / or angular positions, for example, to the housing side 22 are arranged. This will be explained in more detail below.

A dampening effect (to Ein adjustment of the damping influence difference) is also possible, as shown schematically in FIG 5 shown when around a coil and in particular a (reference) coil 34 the reference coil device 24 one or more trace loops 36 are arranged as short circuit windings. Such a strip conductor loop can, for example, also in series with a balancing resistor 38 be switched. It can thereby exert a damping effect and the balance resistance 38 also adjust and in particular, the inductance can be adjusted, so that in turn the Schwämpfungseinflußdifferenz between the sensor coil means 14 and the reference coil device 24 is adjustable and in particular is adjustable so that it is substantially zero.

Another setting possibility is one or more coils of the reference coil device 24 partially cover and / or shield, with respect to the environmental facility 32 ; This means a cover or shielding to "back", ie to the housing side 22 to. This shield is then based on the damping effect of the target 18 to the reference coil device 24 not effective.

Such a shielding possibility is schematically shown in FIG 6 shown. There is a carrier 40 for a reference coil 42 shown in a schematic sectional view. The carrier 40 is multi-layered with a first layer 44a , a second layer 44b and a third layer 44c , The layers 44a . 44b For example, carry the reference coil 42 , The layer 44c has one to the reference coil 42 electrically insulated metal layer arranged 46 on, which is made for example of copper. This covers the reference coil 42 to the "back", ie to the housing side 22 out, and thus affects the damping effect of the environmental device 32 , This in turn allows the attenuation influence difference in particular in connection with the further arrangement and design of the reference coil device 24 set and in particular set to zero.

It can be a sliding cover or shield 47 be provided. The position of this cover or shield is externally detectable adjustable, so that on the positioning of the cover or shield of the damping effect of the environmental device 32 is adjustable. A set position is fixed, so that the damping effect is fixed. The setting can be made in a teach-in process.

It is in principle possible that the defined setting of the damping influence difference in the resonant circuit, based on the sensor coil means 14 and the reference coil device 24 takes place during manufacture and then is firm. This is advantageous if the environmental device is part of the proximity sensor or if the external environmental device 32 is known and the positioning is known.

In principle, it can also be provided that the damping influence difference can be set from the outside. Such influence is, for example, via adjustment of the resistance value of the balancing resistor 38 (please refer 5 ) possible. For example, the resistance value of the balancing resistor 38 via an external access to the proximity sensor 10 adjustable. It is possible to provide a teach-in function.

It is also alternatively or additionally possible to adjust the damping influence difference by changing the mechanical position of the reference coil device 24 perform. This is in 1 shown schematically. The proximity sensor 10 has an adjustment 48 which is externally accessible. For example, the adjusting element 48 designed as a screw. A carrier 50 the reference coil device 24 is parallel to the sensor axis 26 lockable in the housing 12 arranged, wherein the displacement movement through the adjusting element 48 is operable.

For example, the adjusting element 48 accessible from a lateral side and via a corresponding conversion instinct 52 can the carrier 50 at the lead 54 be moved.

For example, adjustability is also possible in that the (at least one) reference coil of the reference coil device 24 a coil core such as a ferrite core and the position of the bobbin in the reference coil is adjustable. For this purpose, an adjusting element can be provided, via which this coil core can be pushed further into the reference coil or pushed out of it. Depending on the position of such, for example, pin-shaped or mushroom-shaped or shell-shaped coil core, the inductance of the reference coil changes, so that the influence of damping is different depending on the position of the bobbin and thus in turn the Bedämpfungseinflußdifferenz is adjustable.

Also on the positioning of the cover or shield 47 an adjustment is possible.

For example, it is also possible to influence the damping effect on the reference coil device 24 - And thus the Bedämpfungseinflußdifferenz on the resonant circuit, which with the sensor coil means 14 and the reference coil device 24 is formed - set by that more number of coils for the reference coil means 24 is provided, that is, that the reference coil means 24 has a plurality of partial coils.

In 2 is a second embodiment of a proximity sensor, which as a whole with 56 is indicated, shown schematically, wherein this has a plurality of coils. Same parts as in the first embodiment according to 1 are provided with the same reference numerals.

It is a reference coil device 58 provided, which on a circuit carrier 60 is arranged for the other parts of the resonant circuit and for an evaluation device. The reference coil device 58 includes a plurality of (sub) coils 62a . 62b . 62c , This allows the number of turns and the coil area for the reference coil device 58 set specifically, so in turn the damping effect of the environment 32 to the reference coil device 58 to be able to set specifically and as a result of the Einämpfungseinflußdifferenz between the sensor coil means 14 and the reference coil device 58 to be able to set specifically to a defined value and in particular to be able to set the value to zero.

This adjustment takes place in particular during the production of the proximity sensor 56 , But it is also conceivable that partial coils there on the circuit board 60 are formed so that they from the reference coil means 58 can be decoupled, this decoupling via an external switching operation such as a teach-in process may be possible. As a result, the influence of damping on the reference coil device can be externally determined 58 to adjust.

At the in 2 The embodiment shown partial coils are 62a . 62b . 62c in a plane, namely in the plane of the circuit carrier 60 , However, it may also be possible in principle that different partial coils of the reference coil device lie in different planes. This will be explained below.

Furthermore, according to the exemplary embodiments 1 and 2 the winding axes of coils of the reference coil device 24 respectively. 58 essentially parallel to the sensor axis 26 , It may also be provided that these at an angle to the sensor axis 26 lie.

In a third embodiment, which is in 3 shown schematically and there as a whole with 64 is designated, is a housing 66 intended. The proximity sensor 64 has an active sensor area 68 and a sensor axis 70 on, with the sensor axis 70 substantially perpendicular to the active sensor surface 68 lies.

The proximity sensor 64 has a first mounting page 72 and a second mounting side 74 on. Depending on the application, one of the active sensor surface 68 for example, opposite side of the housing 76 (which the mounting side 72 forms) to be positioned on an application or a housing side 78 which the second mounting side 74 forms, be positioned on an application. The housing side 78 is for example parallel to the sensor axis 70 especially if the case 66 is formed cuboid. The application may be a metallic environmental device 80a respectively. 80b act.

In the case 66 is a sensor coil device 82 for the detection of a metallic target 84 arranged. This is basically the same design as described above. A winding axis of the sensor coil of the sensor coil device 82 is substantially parallel to the sensor axis 70 aligned. The sensor coil is preferably designed as a flat coil.

In the case 66 is also a reference coil device 86 arranged, which comprises one or more (reference) coils on a support 88 are arranged. The carrier is at an angle of, for example, 45 ° to the sensor axis 70 , A winding axis of (reference) coils of the reference coil device 86 then lies in a corresponding angle to the sensor axis 70 ,

The reference coil device 86 is arranged and designed so that, depending on the arrangement of the proximity sensor 64 at an application, a defined attenuation influence difference between the sensor coil means 82 and the reference coil device 86 is set, the environmental device 80a and or 80b a Bedämpfungsbeeinflussung for the sensor coil device 82 and the reference coil device 86 represents.

The reference coil device 86 may be arranged and configured such that the defined attenuation influence difference (for example, zero) is set when the proximity sensor 64 with its mounting side 72 at the environmental facility 80a is mounted or with its mounting side 74 at the environmental facility 80b is mounted. Preferably, the setting is such that in both cases, a defined difference (and in particular the difference zero) is set, so that a user can choose both mounting options.

It may also be provided that a defined damping Einflußdifferenz is set when both the environmental device 80a and the surrounding means 80b are present and each have a damping effect on the sensor coil means 82 and the reference coil device 86 exercise.

Another embodiment of a proximity sensor, which in 4 shown schematically and there as a whole with 90 is designated, has a housing 92 on. A sensor coil device 94 defines an active sensor area 96 , A metallic target 98 is via the sensor coil device 94 detectable. In particular, a switching distance can be specified.

The sensor coil device 94 includes, for example, a (sensor) coil whose winding axis is parallel to a sensor axis 100 is aligned. The sensor axis 100 is substantially perpendicular to the active sensor surface 96 ,

It is a reference coil device 102 provided, which, for example, a first part coil 104 , a second partial coil 106 and a third sub-coil 107 includes. The two partial coils 104 and 106 are aligned in parallel and have winding axes, which substantially coincide. The winding axes of the two partial coils 104 . 106 lie at the in 4 embodiment shown substantially perpendicular to the sensor axis 100 , The partial coil 107 is oriented transversely thereto and has a winding axis which is perpendicular to the other winding axes.

The partial coil 104 is adjacent to a housing side 108 and the partial coil 106 is adjacent to a housing side 110 , where the two sides of the housing 108 . 110 opposite and transverse to the active sensor surface 96 lie. The partial coil 107 is adjacent to a housing side 111 , which the two sides of the housing 108 and 110 combines.

The sensor coil device 94 lies laterally to the sub-coils 104 . 106 . 107 and thus laterally to the reference coil device 102 ,

The proximity sensor 90 can be in an application 112 install, the application a metallic environment 114 which has a first metal plate 116 and a second metal plate 118 includes. The metal plates 116 and 118 lie opposite. These influence the reference coil device 102 and the sensor coil means 94 ,

The reference coil device 102 is arranged and designed, and in particular, the partial coils 104 . 106 and 107 arranged and formed so that the damping influence difference of the environmental device 114 to the reference coil device 102 and the sensor coil means 94 is set to a defined value. This defined value can be, for example, the value zero, so that the damping influence is compensated.

Otherwise, the proximity sensor works 90 as described above with reference to the other embodiments.

It is according to the invention provided that related to a given sensor coil means the reference coil means defined and formed to a certain attenuation influence difference to adjust to the sensor coil device. Preferably, this will Difference set to the value zero. As a result, the proximity sensor "sees" the metallic environmental device while it is a metallic target to be detected sees. After "forward", d. H. to the active one sensor surface down, lets go So perform a detection process. After "back", d. H. to the metallic environment out, a compensation is performed.

These Compensation can also, if a known, defined value the damping influence difference is set, over the evaluation device, for example, software and / or circuit technology respectively.

It is thereby possible Proximity sensors according to the invention partially flush Screw on a metal plate without a shield of the proximity sensor necessary is.

It is possible, the setting of the defined value of the damping influence difference to carry out during manufacture. But it is also possible, one external adjustment for one prepared proximity sensor provide, for example, about a teach-in process the overall influence (i.e., the combined influence on the Sensor coil device and the reference coil means) to "eliminate". It can be then influencing the coils of the proximity sensor (i.e., sensor coils and Reference coils) through metal parts of an application or the sensor eliminate yourself.

Especially Is it possible, a proximity sensor according to the invention via a the active sensor surface opposing Mounting side to a metallic application.

Claims (46)

Inductive proximity sensor comprising a sensor coil device ( 14 ; 82 ; 94 ) for the detection of a metallic target ( 18 ; 84 ; 98 ) and a reference coil device ( 24 ; 58 ; 86 ; 102 ) with at least one coil, characterized in that the reference coil device ( 24 ; 58 ; 86 ; 102 ) and the sensor coil device ( 14 ; 82 ; 94 ) are arranged and designed so that a defined difference of the damping effect of a metallic environmental device ( 32 ; 80a . 80b ; 114 ) on the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) is set, at least when the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) in a certain position to the environmental device ( 32 ; 80a . 80b ; 114 ), and that the influence of the environmental device ( 32 ; 80a . 80b ; 114 ) is eliminated to a sensor output. Inductive proximity sensor according to Claim 1, characterized in that the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) are arranged and designed such that the environmental device ( 32 ; 80a . 80b ; 114 ) a defined signal change difference between the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) causes. Inductive proximity sensor according to Claim 1 or 2, characterized in that the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) are arranged and designed such that the environmental device ( 32 ; 80a . 80b ; 114 ) a defined inductance change difference between the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 . 86 ; 102 ) causes. Inductive proximity sensor according to one of the preceding claims, characterized in that the attenuation changes at the sensor coil device ( 14 ; 82 ; 94 ) and at the reference coil device ( 24 ; 58 ; 86 ; 102 ) due to the environment ( 32 ; 80a . 80b ; 114 ) are equal or approximately the same. Inductive proximity sensor according to one of the claims 1 to 4, characterized in that an evaluation device is provided, which generates a sensor output signal in which the different damping effect on the Sensor coil device and the reference coil device through consideration the known attenuation influence difference is calculated out. Inductive proximity sensor according to one of the preceding claims, characterized in that the damping influence difference across the arrangement of the reference coil device ( 24 ; 58 ; 8b ; 102 ) in a housing ( 12 ; 66 ; 92 ) and / or the surface of the at least one coil of the reference coil device ( 14 ; 82 ; 94 ) and / or the number of turns of the at least one coil of the reference coil device ( 24 ; 58 ; 86 ; 102 ) is set. Inductive proximity sensor according to claim 6, characterized in that the distance and / or the angular position of the at least one coil of the reference coil device ( 24 ; 58 ; 86 ; 102 ) to one or more housing sides ( 22 . 76 . 78 ; 108 ; 110 ) is set. Inductive proximity sensor according to one of the preceding claims, characterized in that around the at least one coil ( 34 ) of the reference coil device ( 24 ; 58 ; 86 ; 102 ) at least one track loop ( 36 ) is arranged. Inductive proximity sensor according to claim 8, characterized in that a balancing resistor ( 38 ) in series with the at least one track loop ( 36 ) is switched. Inductive proximity sensor according to one of the preceding claims, characterized in that the at least one coil ( 42 ) of the reference coil device ( 24 ; 58 ; 86 ; 102 ) is partially covered and / or shielded. Inductive proximity sensor according to claim 10, characterized in that on a support ( 40 ) for the at least one coil ( 42 ) a metal layer ( 46 ) is arranged. Inductive proximity sensor according to claim 10 or 11, characterized in that a cover ( 47 ) or shielding ( 47 ) is displaceable. Inductive proximity sensor according to one of the preceding claims, characterized in that the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) are arranged in a differential circuit and / or a differential evaluation of signals of the reference coil device ( 24 ; 58 ; 86 ; 102 ) and the sensor coil device ( 14 ; 82 ; 94 ) he follows. Inductive proximity sensor according to Claim 13, characterized in that the sensor coil device ( 14 . 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) are arranged in a bridge circuit. Inductive proximity sensor according to one of the preceding claims, characterized that the metallic environmental device is part of the proximity sensor. Inductive proximity sensor according to claim 15, characterized in that the environmental device on a housing is arranged or forms part of the housing. Inductive proximity sensor according to one of the preceding claims, characterized in that the metallic environmental device ( 32 ; 80a . 80b ; 114 ) forms a mounting base for the proximity sensor. Inductive proximity sensor according to one of the preceding claims, characterized in that the sensor coil device ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) are spaced from each other. Inductive proximity sensor according to Claim 18, characterized in that the sensor coil device ( 14 ) and the reference coil device ( 24 ; 58 ) are spaced parallel. Inductive proximity sensor according to one of the preceding claims, characterized in that the sensor coil device ( 82 ; 94 ) and the reference coil device ( 86 ) or one or more coils ( 104 . 106 . 107 ) of the reference coil device ( 102 ) are arranged at an angle to each other. Inductive proximity sensor according to one of the preceding claims, characterized in that the at least one coil of the reference coil device ( 86 ) at an angle to a mounting side ( 72 ; 74 ) of the proximity sensor is arranged. Inductive proximity sensor according to claim 20 or 21, characterized by at least two mounting sides ( 72 . 74 ). Inductive proximity sensor according to one of the preceding claims, characterized in that the reference coil device ( 24 ; 58 ; 86 ; 102 ) relative to an active sensor surface ( 20 ; 68 ; 96 ) behind the sensor coil device ( 14 ; 82 ) is arranged. Inductive proximity sensor according to one of the preceding claims, characterized in that the sensor coil device ( 14 ; 82 ) relative to a mounting side ( 22 ; 72 ; 74 ; 108 ; 110 ; 111 ) of the proximity sensor in front of the reference coil device ( 24 ; 58 ; 86 ; 102 ) is arranged. Inductive proximity sensor according to one of Claims 1 to 24, characterized in that the sensor coil device ( 94 ) laterally to the reference coil device ( 102 ) is arranged. Inductive proximity sensor according to one of the preceding claims, characterized in that the reference coil device ( 24 ) at least partially between a circuit carrier ( 28 ) and the sensor coil device ( 14 ) is arranged. Inductive proximity sensor according to one of the preceding claims, characterized in that the reference coil device ( 58 ) at least partially on a circuit carrier ( 60 ) is arranged. Inductive proximity sensor according to one of the preceding claims, characterized in that the reference coil device ( 58 ; 102 ) a plurality of coils ( 62a . 62b . 62c ; 104 . 106 . 107 ). Inductive proximity sensor according to Claim 28, characterized in that a plurality of coils ( 62a . 62b . 62c ) are arranged in a plane. Inductive proximity sensor according to claim 28 or 29, characterized in that coils ( 104 . 106 . 107 ) are arranged in different levels. Inductive proximity sensor according to one of Claims 28 to 30, characterized in that coils ( 62a . 62b . 62c ; 104 . 106 ) of the reference coil device are connected in series. Inductive proximity sensor according to one of Claims 27 to 31, characterized in that coils ( 104 ; 106 ; 107 ) of the reference coil device ( 102 ) to different pages ( 108 ; 110 ; 111 ) of the proximity sensor are aligned. Inductive proximity sensor according to one of the preceding claims, characterized in that the at least one coil of the reference coil device ( 24 ) with its winding axis substantially parallel to a sensor axis ( 26 ) is arranged. Inductive proximity sensor according to one of the preceding claims, characterized in that the at least one coil of the reference coil device ( 24 ; 58 ; 86 ; 102 ) is a flat coil. Inductive proximity sensor according to one of the preceding claims, characterized in that a housing ( 12 ) is cuboid. Inductive proximity sensor according to one of the preceding claims, characterized in that a housing ( 12 ) is formed nichtabschirmend. Inductive proximity sensor according to claim 36, characterized in that the housing ( 12 ) is made of a plastic material. Inductive proximity sensor according to one of the preceding claims, characterized in that the damping influence of the reference coil device ( 24 ; 58 ; 86 ; 102 ) is externally adjustable. Inductive proximity sensor according to one of the preceding claims, characterized in that the position of the reference coil device ( 24 ; 58 ; 86 ; 102 ) in a housing ( 12 ) is adjustable. Inductive proximity sensor according to one of the preceding claims, characterized in that the magnetic properties of the at least one coil of the reference coil device ( 24 ; 58 ; 86 ; 102 ) are adjustable over the adjustment of a position of a spool core. Inductive proximity sensor according to one of the preceding claims, characterized by a Training in which the detection result at least based on a certain switching distance or a certain switching distance range independent of Material of the metallic target is. Inductive proximity sensor according to one of the preceding claims, characterized in that at least one resonant circuit, which by approaching the target ( 18 ; 84 ; 98 ) is influenced, by means of the sensor coil means ( 14 ; 82 ; 94 ) and the reference coil device ( 24 ; 58 ; 86 ; 102 ) is formed. Inductive proximity sensor according to one of the preceding claims, characterized in that the reference coil device ( 24 ; 58 ; 86 ; 102 ) has a smaller coil area than the sensor coil device ( 14 ; 82 ; 94 ). Method for adjusting an inductive proximity sensor, which is a reference coil device and a sensor coil device comprises being facing this a metallic environment are not shielded, wherein the reference coil means is modified or one Signal evaluation is set by an evaluation device so the existence different damping effect of the environmental device to the sensor coil means and the reference coil means substantially eliminated based on a sensor output is. Method according to claim 44, characterized in that that the Adjustment performed when the sensor coil device is in a certain position to the metallic environmental device. A method according to claim 44 or 45, characterized that the Damping effect on the Reference coil device by positioning the reference coil device in a housing and / or adjustment of the inductance of the reference coil device and / or adjustment of the cover or shielding of one or more Coils of the reference coil device takes place.