DE102007028909A1 - Safety inductive sensor unit for e.g. position detection of article i.e. door, has measuring region, which is arranged outside housing that forms explosion safe inductive sensor unit in pressure-resistant manner - Google Patents

Abstract

The unit (1) has a housing (2) defining an inner space (4), and an inductive sensor arranged at the inner space. The inductive sensor detects change of position of an article in a measuring region relative to the sensor unit by detecting change of inductivity by the sensor. The measuring region is arranged outside the housing that forms an explosion safe inductive sensor unit in a pressure-resistant manner. A wall region of the housing comprises plastic e.g. plastic polyetheretherketone, and the housing is formed as a metallic housing. An independent claim is also included for an arrangement comprising an inductive sensor unit and a support.

Description

TECHNICAL AREA

The The invention relates to an inductive sensor unit for position detection an article comprising: a housing defining an interior space; at least one inductive sensor arranged in the interior of the housing to record a change the position of the article in a arranged outside of the housing Measuring range relative to the inductive sensor unit by means of detection the change a detectable by the inductive sensor inductance. It also concerns the invention an arrangement comprising an inductive sensor unit and a carrier for arranging the inductive sensor unit on the carrier.

STATE OF THE ART

at Technical applications for position detection of objects can be known various Types of sensors are used. Depending on the purpose for the investigation the relative position of two objects, for example in the Detecting if a gate opened or closed, optical sensors such as light barriers or Inductive sensors used.

The Functioning of inductive sensors is based on the physical Effect, that the inductance a sensor coil through which, at least temporarily, in particular high-frequency alternating current flows when approaching a electrically conductive Object changed in the effective or measuring range of the coil. Especially occur at approach of the electrically conductive Subject eddy current effects on the inductance of the sensor coil change significantly. The change of inductance can by means of an electronic evaluation circuit in electrical Signals are converted.

One special application for Inductive sensors is the position detection of electrically conductive objects in environments, in which more and more or explosion hazard prevails. In such environments where For example, gases such as methane, propane, etc. may occur and may only so-called safety inductive sensors for accident and explosion protection be used. These safety inductive sensors are in the Generally intrinsically safe, d. H. they have means for limiting the current. Thus, a maximum allowable Input voltage not exceeded become. Although safety can be increased in this way, for environments with highest Danger levels, however, they are not suitable or permissible.

OBJECT OF THE INVENTION

outgoing It is the object of the present invention is a Inductive sensor unit to provide the highest safety requirements in terms of explosion protection, without the response of the sensor impaired becomes.

TECHNICAL SOLUTION

These Task is solved by providing an inductive sensor unit according to the claim 1 and an arrangement according to claim 9. Advantageous embodiments result from the features of the dependent claims.

The Inductive sensor unit according to the invention for Position detection of an article includes: a housing that an interior limited; at least one arranged in the interior of the housing Inductive sensor for detecting a change in the position of the object in an outside of the housing arranged measuring range relative to the inductive sensor unit means the recording of the change a detectable by the inductive sensor inductance. The case is to form an explosion-proof inductive sensor unit flameproof educated.

The Inductive sensor unit, for example, as an inductive proximity switch is used, in particular, as a safety-inductive sensor unit for accident and explosion protection used.

Of the electrically conductive Subject changed when entering the measuring range arranged in the inductive sensor Inductance. The inductance can for example, one or more sensor coils, toroidal coils, one Arrangement of at least one planar sensor coil, etc. include.

The Sensor coil with an alternating voltage, in particular with a high-frequency alternating voltage, at least briefly applied to the inductance change capture. The inductance change is received by an evaluation circuit and in an electrical Signal converted.

In order to detect a change in position of the object by the inductive sensor in the interior, the housing must be designed accordingly. Otherwise, the field lines resulting from the alternating voltage are shielded from the wall so that no or no sufficiently large measuring range can be achieved outside the housing. Conversely, the influence of the conductive object outside the housing on the inductive sensor, which is located inside space is to be ensured. Eddy current effects which can significantly influence the inductance of the sensor coil must occur in the electrically conductive object located in the measuring region.

The casing becomes according to the invention either partly or completely from one for the electromagnetic radiation (the frequency used) is sufficient permeable Material formed. In particular, the housing may have at least one window, the influence of the object to be detected on the inductance of the inductive sensor does not shield significantly. This requires the window from a wall area be covered for the electromagnetic radiation in the frequency range of the AC voltage, with the inductance is largely permeable, d. H. the wall area may not be made of any conductor material or other materials with lower Transmission for the radiation (eg bulletproof glass) be made. When using conductive Materials would the sensor on the housing when using materials with insufficient transmission would the Impact or measuring range of the sensor unit are limited to unacceptable levels. The radiolucent Wall area corresponds to the sensor area. The wall area can be, for example as a cover of the window opening a basic housing made of metal may be formed.

Around one for to ensure explosion protection sufficient compressive strength, must (at a multi-part design of the housing) also the Connections between the individual housing components be designed in such a way that even in an explosion, for example, within the cavity of the housing does not release the cover from the other housing parts. All in all must be fulfilled highest Safety requirements a very flameproof Encapsulation are provided around the inductive sensor around. Thereby prevents an explosion taking place inside the device outward penetrates.

According to the invention, at least The window is made of a material that, if sufficient Compressive strength is a big one Active or measuring range is maintained to the response of the Sensor unit while meeting the highest safety requirements not to interfere. The flameproof enclosure, which was an explosion inside the housing keeps leading that the inductive sensor unit in different explosion environments, For example, gas (zone 1) or dust (zone 21), but also in so-called "Ex" zones (zones 1, 2, 21, 22) can be used.

The Inductive sensor unit may further include a power supply. The power supply for For example, the inductive sensor unit may be a 24 VDC power source.

Preferably can the case so explosion proof is formed, that the housing a inside the case to withstand the explosion that is taking place. One inside the case The explosion is said to have no effect on the environment remain the sensor unit. By a sufficiently pressure-resistant training of the housing The inductive sensor unit ensures that the through a Explosion released energy is insufficient to the housing wall to blow up or damage like that, that an impairment the environment of the sensor unit, such as a fire or the release an explosion, be triggered in a corresponding atmosphere outside the housing can.

At least a wall portion of the housing comprises preferably at least one plastic, in particular the plastic PEEK (polyetheretherketone).

It it was recognized that plastic, especially high performance plastic as PEEK, for the production of the wall area or the window in the Unlike metal or glass is very suitable. For one thing that fulfills Plastic material meets the high safety requirements with regard to ignition protection, Explosion protection and accident prevention, on the other hand, the material as window material sufficient permeability to the relevant electromagnetic Radiation on. This ensures that the induction sensor unit a sufficiently large one Measuring range in the vicinity of the sensor surface has. In the implementation For example, the invention has a secured switching distance realized in a range between 2 mm and 8 mm.

In a preferred embodiment is the case formed at least in two parts, and comprises a basic housing with a window and a wall area that closes the window. The wall area As a closure element forms the sensor surface and seals the housing. The measuring range extends away from the sensor surface to the outside.

The Headers is as a pressure-resistant, in particular metallic housing part educated. In particular, the housing made of nickel-plated brass consist.

Of the Wall area can be a plastic, especially the plastic PEEK (Polyetheretherketone), comprise or consist of the plastic.

The inductive sensor unit has vorzugswei a visual display, in particular a light diode (LED), which indicates the positioning of an object in the measuring range of the inductive sensor unit. For example, the LED by its color or by turning on or off the LED indicate whether the object to be detected by the inductive sensor is detected within the measuring range of the sensor unit or not In addition to the inductive sensor, other sensors, such as Hall, reed or capacitive sensors ,

A inventive arrangement comprises an inductive sensor unit as described above, and a carrier for arranging the inductive sensor unit on the carrier.

At least as a sensor surface provided wall portion of the housing can be flush either or not flush with a surface a carrier on the carrier be attached.

at not flush Arrangement may be at a lateral distance or in at least one Peripheral area with a lateral distance from the sensor unit a demarcation element for forming a free space between the Sensor unit and the demarcation element to be formed.

BRIEF DESCRIPTION OF THE FIGURES

Further Features and advantages of the invention will become apparent from the description special embodiments in connection with the figures. It show the

1 a safety inductive sensor unit according to the invention;

2 the inductive sensor unit off 1 at the approach of an object;

3 a first embodiment of the inductive sensor unit according to the invention; and

4 a second mounting form of the inductive sensor unit according to the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The 1 shows a safety inductive sensor unit according to the invention 1 , The unit 1 has a metallic housing part 2 , for example, made of brass, nickel-plated, on. The sensor surface 3 , is designed as a plastic cover, for example made of PEEK mod.

The housing part 2 and the cover 3 are joined together in such a way that an airtight protected pressure-resistant interior 4 inside the case 2 . 3 provided. In particular, the interior is 4 from the walls of the housing part 2 and the cover 3 sealed to the environment so that one in the cavity 4 taking place explosion from the housing 2 and the cover 3 effectively shielded from the environment. This means that the housing part 2 and the cover 3 the cavity 4 encapsulate so firmly that one in the interior 4 taking place explosion in the area 5 of the sensor 1 without appreciable effects on the environment. Thus, the device meets the safety and health requirements for the design and construction of equipment and protective systems intended for use in potentially explosive atmospheres. The housing 2 . 3 with a plastic finish 3 complies with the pressure-resistance requirements necessary for explosion protection.

Inside the cavity 4 In particular, there is a sensor coil (not shown). Further electronic components, in particular an evaluation circuit for detecting an inductance change in the sensor coil, can also be found in the interior 4 be arranged.

In the 1 is in the active or measuring range of the sensor unit 1 which is schematically indicated by the field lines 6 implied, no object detected. A display LED 7 In this case, for example, it lights up red.

In the 2 is the sensor 1 out 1 represented, in this illustration, an electrically conductive object 8th in the measuring range of the sensor unit 1 , indicated by the field lines 6 ' , has been brought.

The influence of the field lines 6 ' through the object 8th is reflected in an inductance change of the sensor coil (not shown), so that the display LED 7 For example, green is lit.

The 3 shows a first, non-flush installation option of the sensor unit 1 , The sensor surface 3 protrudes in this embodiment by a distance s over the surface of a metal wall of a carrier 9 out. Non-flush built-in inductive sensor units 1 Although they have a large switching distance. However, since a part of the electromagnetic field is emitted laterally, the sensors could already be damped by the environment. To avoid this, we laterally at a distance A by means of the cover 10 a free space at the side of the sensor 1 shielded.

The in the 4 shown, flush in the metal wall 9 built-in inductive sensor unit 1 can be used without space. Beside egg A better mechanical protection is the sensor 1 in this type of installation less sensitive to incorrect influences. On the other hand, the switching distance compared to the non-flush mounted sensor 1 reduced.

Claims (11)

Inductive sensor unit ( 1 ) for detecting the position of an object ( 8th ) comprising: a housing ( 2 . 3 ), which has an interior ( 4 ) limited; at least one in the interior ( 4 ) of the housing ( 2 . 3 ) arranged inductive sensor for detecting a change in the position of the object ( 8th ) in one outside the housing ( 2 . 3 ) arranged measuring range relative to the inductive sensor unit ( 1 ) by detecting the change of a detectable by the inductive sensor inductance, characterized in that the housing ( 2 . 3 ) for forming an explosion-proof inductive sensor unit ( 1 ) is pressure-resistant. Inductive sensor unit ( 1 ) according to claim 1, characterized in that the housing ( 2 . 3 ) is designed explosion-proof that the housing ( 2 . 3 ) one within the housing ( 2 . 3 ) sustains the explosion. Inductive sensor unit ( 1 ) according to one of the preceding claims, characterized in that at least one wall region of the housing ( 2 . 3 ) comprises at least one plastic, in particular the plastic PEEK (polyetheretherketone). Inductive sensor unit ( 1 ) according to one of the preceding claims, characterized in that the housing ( 2 . 3 ) is formed at least in two parts and a basic housing ( 2 ) with a window and a wall area ( 3 ) closing the window. Inductive sensor unit ( 1 ) according to claim 4, characterized in that the basic housing ( 2 ) as pressure-resistant, in particular metallic housing part ( 2 ) is trained. Inductive sensor unit ( 1 ) according to claim 4 or 5, characterized in that the wall area ( 3 ) comprises a plastic, in particular the plastic PEEK (polyetheretherketone). Inductive sensor unit ( 1 ) according to one of the preceding claims, characterized in that the inductive sensor unit ( 1 ) an optical display ( 7 ), in particular a light diode (LED), having the positioning of an object in the measuring range of the inductive sensor unit ( 1 ). Arrangement comprising an inductive sensor unit ( 1 ) according to one of the preceding claims, and a carrier ( 9 ) for the arrangement of the inductive sensor unit ( 1 ) on the carrier ( 9 ). Arrangement according to claim 8, characterized in that at least one wall surface provided as a sensor surface ( 3 ) of the housing ( 2 . 3 ) flush with a surface of a carrier ( 9 ) on the carrier ( 9 ) is attached. Arrangement according to claim 8, characterized in that at least one wall surface provided as a sensor surface ( 3 ) of the housing ( 2 . 3 ) not flush with a surface of a carrier ( 9 ) on the carrier ( 9 ) is attached. Arrangement according to claim 10, characterized in that in a lateral distance (A) or in at least one peripheral region with a lateral distance (A) from the sensor unit ( 1 ) a demarcation element ( 10 ) to form a free space between the sensor unit ( 1 ) and the demarcation element ( 10 ) is trained.