Automation field device

Abstract

The invention relates to an automation field device comprising: - a housing (2) which forms an interior (2.8) having, with respect to a longitudinal axis of the housing (2), at least a first rotationally symmetrical inner region (2.21) with a first internal diameter (D1) and a second rotationally symmetrical inner region (2.22) with a second internal diameter (D2); - an electronic unit (7) which is arranged in the interior and has at least a printed circuit board (7.1), an electronic component (7.3) to which a specified maximum potting height (7.31) is assigned, up to which the component can be potted with a potting compound (13) without impairing the functionality of the electronic component, and a pin projection (7.2), wherein the first and second diameters (D1, D2) of the rotationally symmetrical regions (2.21, 2.22) are coordinated with one another in such a way that, even in the case of a volume tolerance of the total volume of the potting compound in the interior, the printed circuit board (7.1) and the pin projection (7.2) are completely potted and the electronic component (7.3) is not potted beyond the specified maximum potting height (7.31).

Description

[0001] Field device of automation technology

[0002] The invention relates to a field device for automation technology and a method for manufacturing a field device for automation technology.

[0003] Field devices are known from the state of the art and are used in industrial plants. They are widely employed in process automation as well as in manufacturing automation. In principle, field devices are defined as all devices used close to the process that provide or process process-relevant information. Thus, field devices are used to acquire and / or influence process variables. Measuring devices, or sensors, are used to acquire process variables. These are used, for example, for pressure and temperature measurement, conductivity measurement, flow measurement, etc., and acquire the corresponding process variables such as pressure, temperature, conductivity, pH value, fill level, flow rate, etc. Actuators are used to influence process variables. These include, for example, pumps or valves that can influence the flow of a liquid in a pipe or the fill level in a container.In addition to the aforementioned measuring instruments and actuators, field devices also include remote I / Os, radio adapters, or generally devices that are located at the field level.

[0004] A large number of such field devices are produced and distributed by the Endress+Hauser Group.

[0005] Field devices are usually designed by field device manufacturers in such a way that they are built up during production from various individual components (housing, sensor and / or actuator element, various electronic units, etc.) which are then mechanically and / or electrically connected to each other.

[0006] For example, two electronic units are electrically connected to each other by means of an electrical connector, i.e. a plug with cable and a corresponding mating plug.

[0007] To enable the operation of such field devices in potentially explosive atmospheres, at least parts of the electronic units must be potted with a potting compound. In particular, any protruding pins or wires used for electrical contact must be potted. During the potting process, the electronic unit is first placed in the housing and then encased in the potting compound. The potting is carried out in such a way that not only are any protruding pins completely potted, but also the connector and cable, so that only the cable for electrical contact with the electronic unit protrudes from the potting compound.

[0008] However, the cable protruding from the potting compound is detrimental to the further manufacturing process. For example, the cable can kink or become pinched during the production of the field device.

[0009] The invention is based on the objective of demonstrating a way to manufacture a field device for automation technology more easily.

[0010] The problem is solved according to the invention by the device according to claim 1 and the method according to claim 6.

[0011] The field device for automation technology according to the invention comprises:

[0012] a preferably metallic housing which forms an interior which, with respect to a longitudinal axis of the housing, has at least a first rotationally symmetrical interior area formed at least partially with a first inner diameter and a second rotationally symmetrical interior area formed at least partially with a second inner diameter, wherein the second inner diameter is preferably larger than the first inner diameter;

[0013] An electronic unit arranged in the interior, comprising at least one printed circuit board, wherein the printed circuit board is arranged in the interior such that a plane in which the printed circuit board is formed is oriented orthogonally to the longitudinal axis, wherein at least one electronic component is formed on the printed circuit board, to which a specified maximum potting height is assigned, up to which the component can be potted with a potting compound without impairing the functionality of the electronic component, wherein a pin protrusion of a pin or wire is further formed on the printed circuit board, wherein the interior is at least partially potted with a potting compound up to a potting level, wherein the first and second diameters of the rotationally symmetrical areas are matched to each other in such a way thatthat even with a volume tolerance of the total volume of the potting compound in the interior, the circuit board with the pin protrusion is completely potted and the electronic component is not potted beyond the specified maximum potting height. An advantageous embodiment of the field device according to the invention can provide that the electronic component is a circuit board terminal or a circuit board connector.

[0014] A further advantageous embodiment of the field device according to the invention can provide that the second rotationally symmetrical inner region, formed at least in sections, is realized with the second inner diameter by means of a free rotation.

[0015] An alternative advantageous embodiment of the field device according to the invention can provide that the second rotationally symmetrical inner region, at least partially formed, is realized with the second inner diameter by means of a groove.

[0016] A further advantageous embodiment of the field device according to the invention can provide that the pin protrusion is covered with the potting compound by at least 1 mm, preferably at least 1.25 mm, particularly preferably at least 1.5 mm.

[0017] The invention further relates to a method for manufacturing a field device for automation technology, in particular according to one of the previously described embodiments, comprising the steps:

[0018] Providing a housing, preferably metallic, which forms an interior space which, with respect to a longitudinal axis of the housing, has at least a first rotationally symmetrical interior space formed at least partially, with a first inner diameter and a second rotationally symmetrical interior space formed at least partially, with a second inner diameter;

[0019] Providing an electronic unit comprising at least one printed circuit board on which at least one pin protrusion of a pin or wire and an electronic component are formed, wherein the electronic component is assigned a specified maximum potting height up to which the component can be potted with a potting compound without impairing the functionality of the electronic component;

[0020] Preparing the first and second rotationally symmetrical areas of the interior in such a way that the first inner diameter and the second inner diameter are matched to each other so that, even with a volume tolerance of a total volume of potting compound that can be dispensed into the interior by a potting machine, the circuit board with the pin protrusion can be completely potted and the electronic component cannot be potted beyond the specified maximum potting height;

[0021] Inserting the electronic unit into the interior in such a way that a plane in which the circuit board is formed is aligned and / or positioned orthogonally to the longitudinal axis of the housing;

[0022] At least partial potting of the interior by the potting machine, such that the potting compound is introduced into the interior with the total volume specified by the potting machine, so that despite the volume tolerance caused by the potting machine, the circuit board with the pin protrusion is completely potted and the electronic component is not potted above the specified maximum potting height.

[0023] A further advantageous embodiment of the field device according to the invention or an advantageous embodiment of the method according to the invention may provide that the volume tolerance is in the range of ± 3% to ± 7%, preferably in the range of ± 4% to ± 6%, particularly preferably in the range of about ± 5%.

[0024] A further advantageous embodiment of the method according to the invention can provide that the rotationally symmetrical areas are prepared in such a way that the second inner diameter is larger than the first inner diameter.

[0025] The invention is explained in more detail with reference to the following drawings. They show:

[0026] Fig. 1: a sectional view through a first embodiment of a field device for automation technology in the form of a pressure sensor for determining the pressure of a process medium, and

[0027] Fig. 2: a sectional view through a second embodiment of a field device for automation technology in the form of a pressure sensor for determining the pressure of a process medium.

[0028] Figures 1 and 2 each show a sectional view through a field device for automation technology in the form of a pressure sensor for determining the pressure of a process medium. The invention is not limited to field devices for automation technology in the form of pressure sensors, but can also be applied to field devices for acquiring and / or influencing other process variables, in particular the process variables mentioned above.

[0029] In the embodiments shown in Figures 1 and 2, the pressure sensor 1 is designed as a differential pressure sensor for determining a differential pressure between a first and a second media pressure p1, p2. However, the invention is not limited to differential pressure sensors, but can also be applied to relative and / or absolute pressure sensors.

[0030] The pressure sensor 1 comprises a metallic housing 2 with a glass-metal feedthrough 2.1 arranged therein (to be described in more detail below) and an essentially cylindrical outer housing component 2.2 surrounding the glass-metal feedthrough 2.1, as well as a base body component 5.1, 5.2 formed from two halves.

[0031] The glass-to-metal feedthrough 2.1 forms a first interior space 2.7 in which a pressure measuring cell 3 with a base body 3.1 and a pressure-sensitive element 3.2 is arranged. The pressure-sensitive element 3.2 is preferably a silicon chip. The pressure measuring cell 3 with the pressure-sensitive element 3.2, which is oriented in the direction of the process, is positioned in the first interior space 2.7.

[0032] Several metallic contact pins 2.3 are encased in the glass-to-metal feedthrough 2.1 via a glass body 2.2 (not shown separately in Fig. 1), so that they are hermetically sealed within a metal body 2.4 and electrically insulated from it. The metallic contact pins 2.3 are positioned along a portion of their length such that they protrude from the metal body 2.4 at least at a first end face 2.5 and / or project into the interior 2.7 at a second end face 2.6. The contact pins 2.3 serve to electrically connect the pressure sensor to an electronic unit 7, which will be described in more detail later.

[0033] For hydraulic pressure transmission, a first part 11.1 of a first hydraulic pressure transmission channel 11 and a first part 12.1 of a second hydraulic pressure transmission channel 12 are formed in the glass-metal feedthrough 2.1.

[0034] While the surface of the pressure-sensitive element 3.2 facing the base body component 5.1, 5.2 is subjected to a first media pressure p1 of the process medium via the first hydraulic pressure transmission channel 11, a second pressure p2 is present on the surface of the pressure-sensitive element 3.2 facing away from the base body component. In the case of a differential pressure sensor, a media pressure is also present on the surface of the pressure-sensitive element 3.2 facing away from the base body component 5.1, 5.2. In the case of a relative or absolute pressure sensor, atmospheric pressure from the environment of the pressure sensor or a vacuum is present.

[0035] The base body component 5.1, 5.2 includes an overload chamber 6, which is divided into two separate sub-chambers 6.1, 6.2 by a substantially disc-shaped overload membrane 8. The first half of the base body component 5.1 can, for example, be manufactured as a casting, in particular as a precision casting or as a forging. The second half of the base body component 5.2 can, for example, be made of steel, in particular bar steel.

[0036] For this purpose, the pressure sensor 1 comprises two separating membranes 9.1, 9.2 which can be externally subjected to the respective pressure p1 , p2, of which a first separating membrane 9.1 is attached externally to the first half of the base body component 5.1 in such a way that a first pressure receiving chamber 10.1 is formed and of which a second separating membrane 9.2 is attached externally to the second half of the base body component 5.2 in such a way that a second pressure receiving chamber 10.2 is formed.

[0037] In addition, the base body component 5.1, 5.2 each comprises a first pressure transmitter, which can be subjected to the first pressure p1, and through which the surface of the pressure-sensitive element 3.2 facing the base body component 5.1, 5.2 can be subjected to the first pressure p1 via the first hydraulic pressure transmission channel 11, and a second pressure transmitter, which can be subjected to the second pressure p2, and through which the surface of the pressure-sensitive element 3.2 facing away from the base body component 5.1, 5.2 can be subjected to the second pressure p2 via the second hydraulic pressure transmission channel 12. The two pressure transmission channels 11, 12 are each formed from several parts, which are implemented in different components, in particular the base body component 12.2 and the glass-to-metal feedthrough.

[0038] Both pressure transmission channels 11, 12 are each filled with a pressure-transmitting fluid, e.g. a silicone oil, via which the pressure p1 , p2 acting on the respective pressure transmitter is transmitted to the pressure-sensitive element 3.2.

[0039] The electronic unit 7 is responsible for detecting the deflection of the pressure-sensitive element 3.2 and / or generating a measurement signal representing the differential pressure. In this embodiment, the electronic unit 7 comprises a printed circuit board with a PCB connector via which the electronic unit 7 can be connected to another electronic unit 7, not shown separately in Fig. 1. The PCB connector 7.3 has a maximum potting height 7.31, up to which the component can be potted with a potting compound 13 without impairing its functionality. The maximum potting height can be obtained, for example, from a data sheet of the PCB connector manufacturer or determined experimentally. Furthermore, the printed circuit board 7.1 has a pin protrusion 7.2 on the side where the PCB connector 7.3 is located. The pin protrusion 7.2 is caused in this case by passing the metallic contact pins 2.3 of the pressure measuring cell through a hole in the circuit board 7.1 and soldering the contact pins 2.3.

[0040] Surrounding the glass-to-metal feedthrough 2.1, the pressure sensor has an outer housing component 2.2, which is essentially cylindrical and forms a second interior space 2.8 in which the glass-to-metal feedthrough 2.1 is located. The outer housing component 2.2 sits on the first half of the base body component 5.1 and is radially joined to it, for example by welding. With respect to a longitudinal axis through the housing of the pressure sensor, the outer housing component has at least a first rotationally symmetrical interior space 2.21 with a first inner diameter D1 and a second rotationally symmetrical interior space 2.22 with a second inner diameter D2. The second interior space 2.8 is encapsulated up to a potting level with a potting compound 13. A Silgel, for example, can be used as the potting compound.

[0041] The first and second diameters of the rotationally symmetrical areas D1 and D2 are matched such that, even with a volume tolerance of the total volume of the potting compound 13 in the second interior space, the circuit board with the pin protrusion is completely potted and the electronic component is not potted beyond the specified maximum potting height. In particular, the rotationally symmetrical areas 2.21 and 2.22 are matched and prepared such that the second inner diameter D2 is larger than the first inner diameter D1.

[0042] This can be achieved, as shown in Figure 1, for example by a free rotation or

[0043] The relief groove is realized on the second rotationally symmetrical inner region with the second inner diameter. In this context, the relief groove is understood as the removal of material from the rotationally symmetrical inner region of the cylindrically shaped outer housing component 2.2.

[0044] Alternatively, as shown in Figure 2, this can be achieved by a recess in the second rotationally symmetrical inner region 2.22 with the second inner diameter D2. In this context, a recess is understood to be at least a partial depression of the second rotationally symmetrical inner region 2.22 with the second inner diameter D2.

[0045] A potting machine is used to encapsulate the second interior space 2.8 with the potting compound 13. This machine may pre-prepare the potting compound and dispense it in the appropriately measured amount into the interior space. Such potting machines exhibit a volume tolerance of the total volume dispensed. By adjusting and preparing the two rotationally symmetrical areas 2.21 and 2.22, it can be ensured during the manufacture of the field device that, even when the potting compound is dispensed by the potting machine with a volume tolerance in the range of ±3% to ±7%, preferably in the range of ±4% to ±6%, and particularly preferably in the range of approximately ±5%, the pin protrusion is always completely encapsulated and the specified maximum potting height for the electronic component is not exceeded. (Reference numeral list)

[0046] 1 pressure sensor

[0047] 2 cases

[0048] 2.1 Glass-to-metal feedthrough

[0049] 2.2 Outer housing component

[0050] 2.21 First rotationally symmetrical interior

[0051] 2.22 Second rotationally symmetrical interior

[0052] 2.3 Metallic contact pins

[0053] 2.4 Metal body

[0054] 2.5 First end face of the cup-shaped housing component facing away from the base body component

[0055] 2.6 Second end face of the cup-shaped housing component facing the base body component

[0056] 2.7 First interior

[0057] 2.8 Second interior

[0058] 3 pressure measuring cells

[0059] 3.1 Basic body

[0060] 3.2 pressure-sensitive element

[0061] 5.1 First half of the base body component

[0062] 5.2 Second half of the base body component

[0063] 6 Overload chamber

[0064] 6.1. 6.2 Sub-chambers

[0065] 7 Electronic unit, in particular measuring circuit

[0066] 7.1 Printed circuit board

[0067] 7.2 Pin protrusion

[0068] 7.3 Electronic component, in particular PCB terminal block or PCB connector

[0069] 7.31 Specified maximum potting height

[0070] 8 Overload membrane

[0071] 9.1. 9.2 Separation membranes

[0072] 10.1. 10.2 Pressure receiving chambers

[0073] 11 First pressure transmission channel

[0074] 11.1 First part of the first pressure transmission channel

[0075] 12 Second pressure transmission channel

[0076] 12.1 First part of the second pressure transmission channel

[0077] 12.2 Second part of the second pressure transmission channel

[0078] 13 Potting compound

[0079] D1, D2 First and second diameters of the first and second rotationally symmetrical inner region, respectively

Claims

Patent claims 1. Field device of automation technology, comprising: a preferably metallic housing (2) which forms an interior (2.8) which, with respect to a longitudinal axis of the housing (2), has at least a first rotationally symmetrical interior region (2.21) formed at least partially with a first inner diameter (D1) and a second rotationally symmetrical interior region (2.22) formed at least partially with a second inner diameter (D2), wherein the second inner diameter (D2) is preferably larger than the first inner diameter (D1); an electronic unit (7) arranged in the interior space with at least one printed circuit board (7.1), wherein the printed circuit board (7.1) is arranged in the interior space (2.8) such that a plane in which the printed circuit board (7.1) is formed is oriented orthogonally to the longitudinal axis, wherein at least one electronic component (7.3) is formed on the printed circuit board (7.1) to which a specified maximum potting height (7.31) is assigned, up to which the component can be potted with a potting compound (13) without impairing the functionality of the electronic component, wherein a pin projection (7.2) of a pin or wire (2.3) is further formed on the printed circuit board (7.1), wherein the interior space (2.8) is at least partially encapsulated up to a potting level with a potting compound (13), wherein the first and second diameters of the rotationally symmetric areas (D1, D2) are matched to each other in such a way that even with a volume tolerance of a total volume of the potting compound (13) in the interior (2.8) the circuit board with the pin protrusion (7.2) is completely encapsulated and the electronic component (7.3) is not encapsulated above the specified maximum potting height (7.31).

2. Field device of automation technology according to claim 1, wherein the electronic component (7.3) is a printed circuit board terminal or a printed circuit board connector.

3. Field device of automation technology according to one or more of the preceding claims, wherein the second rotationally symmetrical inner region (2.22) formed at least partially with the second inner diameter (D2) is realized by a free rotation.

4. Field device of automation technology according to one of claims 1 or 2, wherein the second rotationally symmetrical inner region (2.22) formed at least partially is realized with the second inner diameter (D2) by a groove.

5. Field device for automation technology according to one or more of the preceding claims, wherein the pin protrusion (7.2) is coated with the potting compound (13) by at least 1 mm, preferably at least 1.25 mm, particularly preferably at least 1.5 mm.

6. Method for manufacturing a field device for automation technology, in particular according to claim 1, comprising the steps: Providing a preferably metallic housing (2) which forms an interior (2.8) which, with respect to a longitudinal axis of the housing, has at least a first rotationally symmetrical interior area (2.21) formed at least partially with a first inner diameter (D1) and a second rotationally symmetrical interior area (2.22) formed at least partially with a second inner diameter (D2); Providing an electronic unit (7) with at least one printed circuit board (7.1) on which at least one pin protrusion (7.2) of a pin or a wire (2.3) and an electronic component (7.3) are formed, wherein the electronic component (7.3) is assigned a specified maximum potting height (7.31) up to which the component can be potted with a potting compound (13) without impairing the functionality of the electronic component; preparing the first and second rotationally symmetrical regions (2.21, 2.22) of the interior such that the first inner diameter (D1) and the second inner diameter (D2) are matched to each other so that even with a volume tolerance of a total volume of the potting compound (13) that can be dispensed by the potting machine into the interior (2.8) caused by a potting machine, the printed circuit board (7.1) with the pin protrusion (7.2) is completely and the electronic component (7.3) is fully encapsulated.3) cannot be poured above the specified maximum pouring height (7.31); Inserting the electronic unit (7) into the interior (2.8) such that a plane in which the circuit board (7.1) is formed is aligned and / or positioned orthogonally to the longitudinal axis of the housing (2); At least partial potting of the interior (2.8) by the potting machine, such that the potting compound (13) is introduced into the interior (2.8) with the total volume specified by the potting machine, so that despite the volume tolerance caused by the potting machine the circuit board (7.1) with the pin protrusion (7.2) is completely potted and the electronic component is not potted above the specified maximum potting height (7.31).

7. Field device of automation technology according to one of claims 1 to 5 and / or method according to the preceding claim, wherein the volume tolerance is in the range of ± 3% to ± 7%, preferably in the range of ± 4% to ± 6%, particularly preferably in the range of about ± 5%.

8. Method according to one of claims 6 or 7, wherein the rotationally symmetric regions (2.21, 2.22) are prepared such that the second inner diameter (D2) is larger than the first inner diameter (D1).

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