EP2018520A2

EP2018520A2 - Sensor housing

Info

Publication number: EP2018520A2
Application number: EP07720121A
Authority: EP
Inventors: Bernd Jenne; Burkhard Reetmeyer
Original assignee: Baumer Electric AG
Current assignee: Baumer Electric AG
Priority date: 2006-05-12
Filing date: 2007-05-04
Publication date: 2009-01-28
Also published as: WO2007131372A3; WO2007131372A2

Abstract

The invention relates to a proximity sensor (1) comprising a sensor housing with an outer housing shell (3) and an inner housing shell (15) that is moulded onto the inner wall (7) of the outer shell by injection moulding. A moulded base (17) divides the housing interior into two sub-chambers (19a, 19b). Contact elements (21), which can be used to establish solder-free connections to contact surfaces on a PCB (10), are sunk into said base (7). The front end of the sensor housing is sealed by a welded plastic cap (35). Potting of the sensor housing with a curing casting resin is not required.

Description

sensor housing

The invention relates to a sensor housing for inductive proximity sensors, a corresponding

Proximity sensor and a method for producing the sensor housing and the proximity sensor according to the features of patent claims 1, 10, 11 and 12.

Proximity sensors and distance sensors, which detect the distance of objects by means of different physical principles and generate a digital or analog electrical output signal as a function of the object distance, often comprise a cylindrical or a cuboid metal or metal housing

Plastic. In cylindrical housings, a thread for attaching the sensor to a machine part is usually formed on the outer lateral surface. Inductive proximity switches and position sensors usually comprise an oscillator with a coil inserted into a ferrite core, an evaluation stage and an output amplifier. In the case of cylindrical sensors, the coil is arranged in the region of the one sleeve end, wherein the coil unit is usually covered by means of a plastic or ceramic cap arranged flush with the sleeve or projecting beyond the sleeve. Inside the housing is a print or a printed circuit board with the Control of the oscillator and arranged to evaluate the sensor measurement required components. The printed circuit board may be fastened to the pot core, for example, by means of mechanical connecting means. The ends of the coil wire are electrically connected in such known sensors by soldering with contact surfaces on the print. At the opposite end of the print further contact surfaces for soldering a connection plug or a cable are formed. These form the interface of the sensor to the outside.

In the manufacture of conventional sensors, the interior of the housing is e.g. Poured from the connection side with a hardening casting resin, after the print and the coil unit has been inserted into the sleeve and the end cap has been placed on the front side. Subsequently, the rear end plug is placed with the outwardly guided contacts on the sleeve. Of course, slightly different methods for assembling such sensors are also known.

The manufacture or assembly of such conventional sensors is relatively complex and expensive.

It is therefore an object of the present invention, a sensor housing for a simple and inexpensive to produce inductive sensor and such Sensor and to provide a method for their production.

This object is achieved by a sensor housing and by a proximity sensor and by a method for their production according to the features of patent claims 1, 10, 11 and 12. Advantageous embodiments are described in the subclaims.

The inventive sensor housing comprises an outer, usually metallic housing shell with an inner shell molded on the inside of plastic. The housing is preferably cylindrical or cylinder-like with a round housing cross-section and with or alternatively without external thread on the outer sleeve. Alternatively, the housing may also have a square, a rectangular or any other cross-sectional shape. In particular, the housing may differ in different directions in the axial direction predetermined by the housing jacket

Have cross-sectional areas. The injection molded plastic inner sheath acts as an electrical insulator between the arranged on a printed circuit board inside the housing sensor electronics and the outer housing shell. Guides formed on the inside of the inner shell allow easy and guided insertion of electronic components equipped PCB in the housing and then keep this in the space provided. Longitudinal or transverse grooves, bores or other formed on the inside of the outer housing shell structures ensure that the inner housing shell and the outer housing shell can not move relative to each other, even if the bonding between the injected plastic shell and the outer sleeve or should solve the outer housing shell. In particular, this can be ensured in cylindrical housings an anti-rotation and a displacement protection of the two housing shells. In an advantageous embodiment, a partition wall or a bottom can be formed on the inner shell, which divides the interior of the housing into a front part space and a rear part space. The front subspace is intended for receiving the electronics with the sensor element (s). The rear, usually much shorter subspace is as a connector receptacle for connecting a connecting cable means

Formed connectors. In the manufacturing process, so when injecting the plastic in the designated injection mold, contact elements are poured into the ground or partially encapsulated in plastic. The contact elements project beyond the ground on both sides.

Preferably, the contact elements are all the same and shaped as cranked stampings. To connect a Plug contact pins of the contact elements protrude backwards out of the ground. The positions of the contact pins correspond to the positions of the corresponding contact springs of the desired connector. The back part of the inner

Housing jacket is designed such that it corresponds with the provided connector plugs. In particular, for example, in the rear region on the inside of the inner shell projecting ribs may be provided, which serve as reverse polarity protection when connecting a plug with corresponding grooves. The projecting into the housing part of the contact elements is fork-shaped with contact springs or contact cutting. The contact elements are arranged such that axially projecting into the housing interior contact forks are in a row. When inserting a populated printed circuit board it is clamped between the fork arms, wherein the contact springs or -schneiden produce solderless electrical connections with corresponding pads or pads on the circuit board. The manufacture of a sensor with a housing according to the present invention is very simple. The electronic print is inserted along the guides on the inner wall of the housing into the housing until its rear end is clamped between the contact forks and the electrical connection of the contact elements is made with the pads on the circuit board. Around At the front edge of the print, a plastic end cap is connected to the print or attached to it. The end cap is preferably designed so that it can be used as a support for the sensor element or elements - for example, a coil with a ferrite core - so that they are arranged as close as possible to the front end of the sensor housing. Alternatively, the end cap and coil support may also be designed as separate parts and otherwise secured to the print or to the housing. if the

Sensor elements are not arranged directly on the print, the electrical connection of the sensor elements with the print, for example by soldering or bonding of leads or alternatively by means of connectors. After inserting the print into the housing, the end cap or the end cap is connected in the edge region, for example by laser welding, ultrasonic welding or gluing with the front end of the inner shell. As a result, the front compartment of the housing is sealed tight. The ends of the inner shell may be formed, for example, flange-like and slightly beyond the front edge of the outer jacket sleeve. In alternative embodiments, the frontal edge of the outer jacket sleeve may also project beyond the end of the inner jacket sleeve or be arranged flush therewith. This is especially beneficial when finishing caps be fused by means of ultrasound with the inner jacket sleeve.

In contrast to conventionally manufactured sensors, encapsulation of the interior of the housing with a hardening potting compound is not required, but nevertheless possible if required. Of course, in this case, other embodiments of the sensor housing according to the invention may be used, e.g. Fill and vent openings and ev. Otherwise formed Kontaktelerαente include.

Based on some figures, the invention will be described below on

Example of cylindrical inductive proximity switch described in more detail. Show

1 shows a longitudinal section of a first inductive proximity switch,

FIG. 2 shows two views of a contact element,

3 shows a perspective view of a cover,

FIG. 4 shows a longitudinal section of a further inductive proximity holder,

FIG. 5 shows a detailed view of the proximity switch from FIG. 4.

Figure 1 shows a longitudinal section through a first inductive proximity switch 1 with a metal manufactured cylindrical outer casing 3, also called metal sleeve or sleeve. The housing axis a is shown by a dot-dash line. The front region of the metal sleeve comprises an external thread 5 for mounting the sensor at its destination, for example on a machine part. On the inner wall 7 of the outer housing shell 3 radially extending notches or grooves 9 and paragraphs 11 are formed, so that the sleeve has different cross sections or inner diameter di depending on the axial position. Furthermore, a bore 13 or another recess which penetrates the outer housing jacket 3 is formed in the rear region. On the inner wall 7 of the outer housing shell 3, an inner housing shell 15 is injection molded from plastic. The plastic preferably completely fills the bore 13 and closes flush with the outside of the outer housing jacket 3. The structures on the inner wall 7 of the outer casing jacket prevent a relative movement between the two Gehäusemänteln 3, 15 even if the adhesive bond produced by the injection molding process between the shells 3, 15 should solve. When using a transparent plastic for the inner housing jacket 15 or at least for the part of the housing jacket 15 in the region of holes 13, a light-emitting diode or another optical display means and / or elements of an infrared Communication interface are arranged inside the housing so that it is visible from the outside. On the inside of the inner housing shell 15 are preferably two diametrically opposite, extending in the direction of the housing axis a guide grooves 8 for guided insertion and holding a circuit board or a populated with electronic components 10 prints excluded. Alternatively, guide ribs or other guide elements projecting into the interior of the housing may also be formed on the inner housing shell 15. Preferably, the inner side of the inner casing shell 15 is slightly conical or formed with a light suit at least in the front region of the housing in the direction of the housing axis a such that the inner diameter Ä. ₂ slightly increases towards the front housing end. As a result, a corresponding insert of the injection mold can be more easily pulled out of the sleeve after the injection of the inner housing shell 15. The front end of the inner housing shell 15 is thin-walled with a shoulder or shoulder 16 with a larger inner diameter d ₃ for receiving a shell core 45 is formed. An intermediate wall or a floor 17 separates the space enclosed by the inner housing jacket 15 into a front partial space 19a and a rear partial space 19b. A plurality of contact elements 21 are injected into the bottom 17 or partially encapsulated by the plastic of the bottom 17, such that contact pins 23 for connecting a cable connector protrude back into the rear compartment 19b. The protruding into the front part of the space 19a part of each of the contact elements 21 comprises two opposing, arranged on two fork arms 25 spring contacts or

Contact Cutting 27. In the example of the proximity switch 1 shown in Figure 1 four identical, manufactured as bent punched parts contact elements 21 are arranged in a row, wherein in the illustrated longitudinal section only two of the contact pins 23 and only the two fork arms 25 of the contact elements 21 are visible.

FIG. 2 shows such a contact element in a top view (top) and in a side view (bottom). The pin axis s of the contact pins 23 is below the fork arms 25 and - due to the crank in the central region 29 of the stamped part - laterally offset to these fork arms 25. Four identical stampings of this type can in the front part 19a as a print recording with four adjacently arranged fork arms 25 and in the rear subspace 19b be arranged as corner points of a square or rectangle arranged contact pins 23 for connecting a connector plug. A recess 31 in the central region 29 of the contact elements 21 is filled during encapsulation with the plastic compound of this and is used for Stabilization and absorption of forces when contacting or disconnecting a connector. In the region of the rear partial space 19b, a guide rib 33 projecting inwards in the direction of the housing axis a is formed on the inner housing jacket 15. It serves as Verpolschütz and as a guide when connecting a provided with a corresponding groove connector. FIG. 3 shows a cover lid or a cap 35 made of plastic in a first embodiment. It comprises a round front plate 37, a flange-shaped coil carrier 39 integrally formed thereon, and a cylindrical centrally arranged retaining pin 41 with a forked end 43 for receiving and clamping a print 10. The cap 35 is designed so that a pot-like ferrite pot core 45 with E-shaped cross-section and a central bore can be pushed or plugged onto the retaining pin 41 such that it surrounds a coil wound on the coil support 39 (not shown) on three sides in the manner of a channel or torus (FIG. 1). Here, the rear end 43 of the central retaining pin 41 projects beyond the bottom surface 40 of the shell core 45. The front end of the rectangular print 10 is clamped in the fork-like recess on the retaining pin 41. The free ends of the wound on the bobbin 39 coil wire are directly with corresponding pads 46 on the print 10, for example connected by soldering. Alternatively, the ends of the coil wire may also be connected indirectly to pads on the print 10. For example, they can be electrically conductively connected by laser soldering or bonding to metallizations 47 (FIG. 3) formed on the cap 35. These metallizations 47, in turn, are connected to further contact elements, for example by means of connecting wires or printed conductors 49 introduced or injected into the coil carrier 39, for example further metallizations 51 formed on the inner sides of the fork-like end 43 of the holding pin 41. The contact points 46 on the print 10 are arranged in this way in that, when the cap 35 is pushed onto the print 10, an electrical connection is made between the metallizations 51 on the retaining pin 41 or the coil and the contact points 46 on the print 10. The coil or generally the sensor element is thus electrically connected to the sensor electronics. In a further alternative embodiment, instead of the metallizations 51, other contact elements, such as contact pins or contact springs or contact blades projecting rearwardly on the coil carrier 39, are formed with corresponding contact elements on the print 10, for example with connection surfaces or contact points 46 or with sockets on the print 10 are connected (no representation). After the connection between the spool and the print 10 has been made, the print 10 together with cap 35 is inserted from the front along the guides 8 in the housing until it is clamped in the region of its rear end between the fork arms 25 of the contact elements 21 and the contact blades 27 have contacted one or both sides on the print 10 formed corresponding pads or contact surfaces 53. In the first embodiment of the sensor according to Figure 1, the shell core 45 comes when inserting the print 10 into contact with the shoulder 16 and the shoulder of the front thin-walled inner housing shell 15. In this position, the front end of the inner housing shell 15 and the edge the front panel 37 tightly connected to each other, for example by laser welding or gluing.

In a further embodiment of the proximity switch 1, as shown in Figure 4, the bobbin 39 and the cap 35 are formed as separate parts. The coil unit with the shell core 45, the coil support 39 and the coil wound thereon (not shown) can be connected to the print 10, for example, only by soldering the ends of the coil wires to the intended contact points 46. In addition, further attachment means (not shown) may be provided to secure the spool assembly to the print 10. The print 10 is inserted along the guides 8 in the housing and held in its end position between the fork arms 25 of the contact elements 21. The contact blades 27 in turn contact the contact surfaces 53 provided on the print 10. The coil unit is inserted into the foremost housing region with the thin-walled inner housing jacket 15. Subsequently, the cap 35 is placed on the front of the housing, centered by means of the conical, engaging in the central bore 44 of the pot-like shell core 45 retaining pin 41 and welded by ultrasonic energy to the front edge of the inner housing shell 15. FIG. 5 shows a detail of this proximity switch 1 in the area of connection of the cap 35 and the inner housing shell 15. The cap 35 comprises a peripheral edge 55 with a knife-like shaped

Welding edge 57. This is brought into abutment with the front edge of the inner housing shell 15 and welded by applying the cap 35 with ultrasonic energy with this.

Claims

claims

1. Sensor housing, comprising a metallic outer

Housing jacket (3) with a front-side first opening and a rear-side second opening, characterized in that on the inner wall (7) of the outer housing shell (3), an inner housing shell (15) is molded from plastic.

2. Sensor housing according to claim 1, characterized in that on the inner wall (7) of the outer jacket (3) structures are formed, which make a relative movement between the outer housing shell (3) and the inner housing shell (15) impossible even if the connection between the outer housing shell (3) and the inner housing shell (15) should solve.

3. Sensor housing according to claim 2, characterized in that in the outer housing shell (3) one or more holes (13) are excluded, and that the inner housing shell (15) has pins which at least partially protrude into the bores (13) or the Completely fill holes (13) or protrude through the holes (13).

4. Sensor housing according to one of claims 1 to 3, characterized in that the inner housing shell (15) is at least partially made of transparent plastic.

5. Sensor housing according to one of claims 1 to 4, characterized in that the inner housing shell (15) projects beyond the outer housing shell (3) front and / or rear flange.

6. Sensor housing according to one of claims 1 to 5, characterized in that formed on the inner wall of the inner housing shell (15) in the axial direction of the sensor housing extending guides for guided insertion of a print (10) with the sensor electronics and / or reverse polarity plugging a contact plug are.

7. Sensor housing according to one of claims 1 to 6, characterized in that on the inner housing shell (15) between the front opening and the rear opening a plug-like bottom (17) is formed, the sensor housing in a front part space (19 a) and a divided subspace (19b).

8. Sensor housing according to claim 7, characterized in that a plurality of contact elements (21) penetrate the bottom (17) and project beyond the bottom (17) on both sides.

9. sensor housing according to claim 8, characterized in that the contact elements (21) are formed as cranked punched parts with two opposite, on two fork arms (25) arranged contact cutting edges (27).

10. Proximity sensor (1) with a sensor housing according to one of claims 1 to 9, characterized in that a print (10) is encased with the sensor electronics from the sensor housing, and that a cap (35) made of plastic in the region of the front end of the sensor housing with the inner housing shell (15) is sealingly connected.

11. A method for producing a sensor housing, characterized in that on the inside (7) of an outer housing shell (3), an inner housing shell (15) is molded from plastic, and in that case a bottom (17) with partially molded contact elements (21) is formed, wherein the contact elements (21) overhang the bottom (17) on both sides.

12. A method for producing a proximity sensor (1) with a manufactured according to claim 11 sensor housing, characterized in that a sensor electronics comprehensive and connected to a sensor element print (10) is inserted at the front into the opening on the sensor housing, so that the print ( 10) attached contact surfaces (53) contact the bottom (17) projecting into the interior of the sensor housing contact elements (21), and that then front side a cap (35) or a cover made of plastic with the inner housing shell (15) welded or glued ,