Pressure sensor for determining the pressure of a process medium

Abstract

The invention relates to a pressure sensor (1) for determining the pressure of a process medium, comprising a cup-shaped housing component (2), in which a pressure measuring cell (3) with a pressure-sensitive element (4) is arranged, and a main part component (5.1, 5.2), to which at least one separating membrane (9.1, 9.2) is secured, thereby forming a pressure chamber (10.1, 10.2), wherein the cup-shaped housing component (2) and the main part component (5.1, 5. 2) are arranged relative to each other such that a first and second joint surface (13.1, 13.2) adjoin each other, and a first and second part of a hydraulic channel (12.1, 12.2) lie opposite each other in a flush manner. The cup-shaped housing component (2) and the main part component (5.1, 5.2) are welded together such that a welding seam (15) is formed on the first or second joint surface (13.1, 13.2), said welding seam surrounding the hydraulic channel at said location, without having to close the channel.

Description

[0001] Pressure sensor for determining the pressure of a process medium

[0002] The invention relates to a pressure sensor for determining the pressure of a process medium.

[0003] Pressure sensors are used to measure pressure and / or to control, regulate, and / or automate a process occurring within a plant. Pressure sensors are used in automation technology in a wide variety of industries, such as the chemical and food industries, to name just a few important applications.

[0004] A pressure sensor typically comprises a pressure measuring cell and sensor electronics connected to the pressure measuring cell. The pressure measuring cell includes an electromechanical transducer that converts the response of a pressure-sensitive element into an electrical signal, which is recorded by the sensor electronics and accessible for further evaluation and / or processing.

[0005] The pressure sensor can be designed as an absolute pressure sensor, a relative pressure sensor, or a differential pressure sensor. While an absolute pressure sensor measures the pressure to be measured in absolute terms, i.e., as a pressure difference relative to the vacuum, a relative pressure sensor measures the pressure of a process medium relative to a reference pressure. The reference pressure is usually the atmospheric pressure prevailing at the installation location of the pressure sensor.

[0006] A differential pressure sensor, on the other hand, measures the difference between two measuring pressures of the process medium. Differential pressure sensors are used, for example, in tanks for level measurement or in pipelines for flow measurement.

[0007] While the measuring pressure of the process medium is applied via the separating diaphragm to the surface of the pressure-sensitive element facing the process, the surface of the pressure-sensitive element facing away from the process is subjected to vacuum, the atmospheric relative pressure or, in the case of a differential pressure sensor, to another measuring pressure.

[0008] To transmit the measured pressure(s) of the process medium to the pressure-sensitive element, hydraulic channels filled with a pressure transmission fluid are implemented in the pressure sensor. The pressure transmission fluid typically comprises an oil, such as silicone oil. Due to manufacturing constraints, the hydraulic channels cannot be implemented in a single component of the pressure sensor; therefore, a hydraulic channel can consist of multiple channel sections or parts, with each part of the channel being implemented in a different component of the pressure sensor. Joining the two components then creates the entire hydraulic channel or pressure sensor. Welding is typically used as the joining process.

[0009] The disadvantage of this is that joining the two components can lead to the hydraulic channel becoming blocked.

[0010] The invention is therefore based on the object of showing a possibility of how two components of a pressure sensor, in each of which a part of a hydraulic channel is realized, can be joined without the hydraulic channel being closed.

[0011] The object is achieved according to the invention by the pressure sensor according to patent claim 1.

[0012] The pressure sensor according to the invention for determining the pressure of a process medium comprises at least one cup-shaped housing component in which a pressure measuring cell with a pressure-sensitive element is arranged, and a base body component to which at least one separating membrane is attached to form a pressure chamber, wherein at least one hydraulic channel filled with a transmission fluid is provided, via which the pressure chamber is connected to the pressure-sensitive element in order to transmit a medium pressure applied to the separating membrane, wherein the cup-shaped housing component has a metallic base body designed in the form of a cup and at least one metallic contact pin, which is glazed into the metallic base body over part of its length for electrical insulation such that the contact pin protrudes from the base body at a first end face,wherein the metallic base body has, on a second end face opposite the first end face, a preferably step-shaped outer contour, which is realized by a pipe extension formed on the second end face of the metallic base body, wherein the hydraulic channel has a first part that extends in the axial direction at least through the part of the metallic base body forming the pipe extension and ends at the second end face of the cup-shaped housing component, wherein a wall of the pipe extension formed on the second end face of the metallic base body is designed in the region of the first part of the channel in such a way that - viewed in cross section - a wall reinforcement, in particular in the form of a nose, is formed around the first part of the channel, wherein the wall forms a first joining surface with the wall reinforcement on the second end face of the metallic base body,wherein the base body component has a second joining surface corresponding to the first joining surface formed by the wall with the wall reinforcement, wherein the hydraulic channel further has a second part which is formed in the base body component and ends at the second joining surface of the base body component, wherein the cup-shaped housing component and the base body component are arranged relative to one another such that the first and second joining surfaces adjoin one another and the first and second parts of the channel are flush with one another, wherein the cup-shaped housing component and the base body component are welded to one another such that a weld seam is formed on the first or second joining surface, which weld seam surrounds the hydraulic channel at this point without closing it.

[0013] According to the invention, it is proposed to adapt the wall around the hydraulic channel at the joint to the welded joint or the welding process by means of a wall reinforcement or to optimize it accordingly, so that the welding of the cup-shaped housing component and the base body component can take place without closing the hydraulic channel.

[0014] An advantageous embodiment of the pressure sensor according to the invention can provide that the wall of the tube extension formed on the second end face of the metallic base body is designed such that the wall reinforcement - seen in cross section - is formed in the direction of a central axis of the cup-shaped housing component.

[0015] An alternative embodiment of the pressure sensor according to the invention can provide that the wall of the tube extension formed on the second end face of the metallic base body is designed such that the wall reinforcement - seen in cross section - is formed in the opposite direction to a central axis of the cup-shaped housing component.

[0016] A further advantageous embodiment of the pressure sensor according to the invention can provide that the wall reinforcement and the first part of the channel extending in the axial direction through the tube extension of the metallic base body are designed and matched to one another in such a way that - seen in cross section - a first wall thickness extending radially outward from the first channel is greater than a second wall thickness extending radially inward from the first channel.

[0017] Yet another advantageous embodiment of the pressure sensor according to the invention can provide that at least the first part of the channel has a round cross-sectional opening on the second end face and wherein a diameter of the round cross-sectional opening is greater than a first wall thickness extending radially outward from the first channel as seen in cross section and / or greater than a second wall thickness extending radially inward from the first channel as seen in cross section.

[0018] A further advantageous embodiment of the pressure sensor according to the invention can provide that a preferably cylindrical filling body is provided, which is also arranged in the cup-shaped housing component and is designed such that it has a receptacle that encloses the pressure measuring cell.In particular, the design can provide that a lateral surface of the filler body and a corresponding inner surface of the tube extension of the cup-shaped housing component are designed and matched to one another in such a way that the filler body can be inserted into an interior space of the cup-shaped housing component defined by the tube extension and / or that the lateral surface of the filler body has a recess corresponding to the wall reinforcement formed in the direction of the central axis of the cup-shaped housing component, so that the filler body can not only be inserted / inserted into the interior space, but is also oriented or positioned via the wall reinforcement in combination with the recess.

[0019] The invention is explained in more detail with reference to the following drawings. It shows:

[0020] Fig. 1 : a sectional view through a pressure sensor for determining the pressure of a process medium with a hydraulic pressure transmission channel,

[0021] Fig. 2: a sectional view through an embodiment of the cup-shaped housing component,

[0022] Fig. 3: a perspective view of a first embodiment of the cup-shaped housing component,

[0023] Fig. 4: a perspective view of a second embodiment of the cup-shaped housing component, and Fig. 5: a perspective view of the first half of the base body component.

[0024] Fig. 1 shows a sectional view through a pressure sensor for determining the pressure of a process medium. In the present embodiment, the pressure sensor 1 is designed as a differential pressure sensor for determining a differential pressure between a first and a second medium pressure p1, p2. Nevertheless, the invention is not limited to differential pressure sensors, but can also be applied to relative and / or absolute pressure sensors.

[0025] The pressure sensor 1 comprises a cup-shaped housing component 2, which will be described in more detail later, which forms an interior space 2.8 in which a pressure measuring cell 3 with a pressure-sensitive element 4 is arranged, and a base body component 5.1, 5.2 formed from two halves.

[0026] The pressure measuring cell 3 with the pressure-sensitive element 4 arranged in the direction of the process is positioned in the cup-shaped housing component 2, which will be described in more detail below. While the surface of the pressure-sensitive element 4 facing the base body component 5.1, 5.2 is subjected to a first media pressure of the process medium p1, a second pressure p2 is applied to the surface of the pressure-sensitive element 4 facing away from the base body component. In the case of a differential pressure sensor, a media pressure is also applied to the surface of the pressure-sensitive element 4 facing away from the base body component 5.1, 5.2. In the case of a relative or absolute pressure sensor, an atmospheric pressure from the environment of the pressure sensor or a vacuum is present. The detection of the deflection of the pressure-sensitive element 4, which is preferably a silicon chip, is carried out via a measuring circuit 7.

[0027] The base body component 5.1, 5.2 encloses an overload chamber 6, which is divided into two separate sub-chambers 6.1, 6.2 by a substantially disc-shaped overload diaphragm 8. The first half of the base body component 5.1 can be manufactured, for example, as a cast part, in particular as an investment casting. The second half of the base body component 5.2 can be manufactured, for example, from a steel, in particular a steel bar.

[0028] Furthermore, the pressure sensor 1 comprises two separating membranes 9.1, 9.2 which can be acted upon from the outside with the respective pressure p1, p2, of which a first separating membrane 9.1 is fastened on the outside 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 fastened on the outside 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. 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 via which the surface of the pressure-sensitive element facing the base body component 5.1, 5.2 can be subjected to the first pressure p1 via a first hydraulic pressure transmission channel 11, and a second pressure transmitter which can be subjected to the second pressure p2 and via which the pressure generated by the base body component 5.1, 5.2, the surface of the pressure-sensitive element 4 facing away from the first surface can be subjected to the second pressure p2 via a 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 and the cup-shaped housing component.

[0029] Both pressure transmission channels 11, 12 are further each filled with a pressure-transmitting liquid, e.g. a silicone oil, via which the pressure p1, p2 acting on the respective pressure transmitter is transmitted to the pressure-sensitive element 4.

[0030] Fig. 2 shows a cross-section of the cup-shaped housing component 2, which is essentially rotationally symmetrical with respect to its outer contour. The cup-shaped housing component 2 is a so-called glass-metal feedthrough. It comprises a metallic, in particular stainless steel, base body 2.4, a plurality of metallic contact pins 2.1 glazed into the metallic base body 2.4 for electrically contacting the pressure measuring cell 3, and furthermore two filling tubes 2.2 for filling the pressure transmission channels 11, 12. The metallic contact pins 2.1 and filling tubes 2.2 are inserted over part of their length in such a way that they protrude from the base body 2.4 at a first end face 2.5. The metallic base body 2.4 can have a stepped outer contour 2.7 on a second end face 2.6 opposite the first end face 2.5. The stepped outer contour 2.7 is realized by a tubular extension formed on the second end face 2.6 of the metallic base body 2.4. This can be produced, for example, by a machining process, in particular turning and / or milling. The tubular extension formed on the second end face 2.6 of the metallic base body 2.4 defines at least part of the aforementioned interior space 2.8, into which the pressure measuring cell and, if appropriate, a particularly cylindrical filler body 14 to be described in more detail are introduced. A first part of the second hydraulic pressure transmission channel 12.1 is formed in the metallic base body 2.4 such that the part 12.1 extends axially through the tubular extension formed on the second end face 2.6 of the metallic base body 2.4, i.e., along or parallel to the central axis 13 shown in Fig. 2. This part of the second hydraulic pressure transmission channel 12.1 can be realized, for example, by a bore.The first part of the second hydraulic pressure transmission channel 12.1 ends at an opening formed on the second end face 2.6.

[0031] According to the invention, a wall of the pipe extension formed on the second end face 2.6 of the metallic base body 2.4 has a reinforcement 2.10 in the area where the first part of the second hydraulic pressure transmission channel 12.1 ends, as viewed in cross section. The reinforcement 2.10 can, in particular, be designed in the form of a nose. This means that, as viewed in cross section, the wall around the first part of the channel 12.1 has a nose-shaped configuration.

[0032] The wall reinforcement 2.10 can in particular be designed such that it is formed in the direction of the central axis 13, i.e. the wall reinforcement 2.10 extends inwards towards the central axis 13, so that an inner surface 2.9 of the interior 2.8 of the cup-shaped housing component 2 has a circular arc-shaped, convex contour. Fig. 3 shows such a design of the wall reinforcement 2.10. This variant offers the advantage that the wall reinforcement 2.10, particularly in the case that it is designed in the form of a nose, in combination with a correspondingly adapted outer surface of the filler body 14, which will be described in more detail below, can provide a positioning aid for the introduction of the filler body.

[0033] Alternatively, the wall reinforcement 2.10 can also be designed in such a way that it is formed in the opposite direction to the central axis 13, i.e., the wall reinforcement 2.10 extends outwardly, so that a lateral surface of the cup-shaped housing component 2 has a circular-arc-shaped, convex contour. Fig. 4 shows such a design of the wall reinforcement 2.10.

[0034] In both possible designs, the reinforcement and the first part of the channel can be designed and matched to one another in such a way that - seen in cross section - a first wall thickness W1 extending radially outwards from the first channel, ie towards the outer surface, is greater than a second wall thickness W2 extending radially inwards from the first channel 12.1 to an inner surface 2.9 of the interior 2.8 of the cup-shaped housing component 2.

[0035] Additionally or alternatively, in the event that the first part of the second hydraulic pressure transmission channel 12.1 ending at the second end face 2.6 has a round cross-sectional opening, the reinforcement 2.10 and the first part of the channel 12.1 can be designed and coordinated with one another such that - seen in cross-section - a diameter D of the round cross-sectional opening is greater than at least one of the two wall thicknesses W1, W2, preferably greater than both wall thicknesses W1, W2. An end face of the wall (with the wall reinforcement) on the second end face of the metallic base body 2.4 forms a first, in particular substantially hollow-cylindrical joining surface 13.1, at which the cup-shaped housing component 2 is joined to the base body component 5.1, 5.2. In the exemplary embodiment shown in Fig. 2, the cup-shaped housing component 2 is joined to the first half of the base body component 5.1.Accordingly, the second part of the hydraulic pressure transmission channel 12.2 ends at a second joining surface 13.2 of the first half of the base body component 5.1. Fig. 5 shows a perspective view of the first half of the base body component from above. The second part of the hydraulic pressure transmission channel 12.2 can be arranged in the first half of the base body component 5.1 in such a way that it also extends parallel to the central axis 13. The second part of the hydraulic pressure transmission channel 12.2 can also be produced by a corresponding bore in the first half of the base body component 5.1. The second joining surface 13.2 of the first half of the base body component 5.1 is designed such that it has a surface corresponding to the first joining surface 13.1, i.e. the second joining surface 13.2 has a joining surface that matches the wall (with the wall reinforcement).For example, the first half of the base body component 5.1, at the end directed towards the first end face, can have a particularly cylindrical, step-like shape 5.11. The step-like shape 5.11 is preferably designed such that a central plateau 5.111 is formed, which is surrounded by a deeper annular surface that represents the second joining surface 13.2. The central plateau 5.111 can further be adapted to the interior 2.8 of the cup-shaped housing component 2 and the annular surface to the first joining surface 13.1 of the cup-shaped housing component 2, so that the cup-shaped housing component 2 can be plugged with the tube attachment onto the step-like shape 5.11 of the first housing component 5.1 in order to weld the two components together at the first and second joining surfaces 13.1, 13.2.

[0036] The cup-shaped housing component 2 and the first half of the base body component 5.1 are welded together in such a way that a weld seam 15 is formed on the first and second joining surfaces 13.1, 13.2, respectively, which weld seam extends from the outer surface in the radial direction to the central axis 13 through the hydraulic pressure transmission channel without closing it.

[0037] For welding, for example, a beam welding process can be used. In particular, a laser beam welding process in a vacuum or an electron beam welding process can be used. Preferably, the two components 2, 5.1 are welded radially circumferentially using a welding beam, which is preferably guided within a range of approximately ± 45° to a normal vector of the outer surface.

[0038] In the manufacture of pressure sensors 1 according to the invention,

[0039] Wall reinforcement must be carried out in such a way that the welding can be carried out over the entire circumference at an essentially constant welding speed and / or welding power.

[0040] In order to minimize the volume available to the pressure-transmitting fluid, as already mentioned, a particularly cylindrical filler body 14 can be arranged in the interior of the cup-shaped housing component 2. The filler body 14 or oil displacement body can be made of a non-conductive material and can preferably be made of a temperature-resistant plastic that is chemically inert to the transmission fluid.

[0041] The filler body 14 has an opening in the end face facing the base body component 5.1, 5.2, through which opening the pressure of the process medium is guided to the pressure-sensitive element 4 via the first hydraulic pressure transmission channel 11. The interior of the filler body 14 is structured such that it encloses the pressure measuring cell 3. The outer surface of the filler body 14 and the corresponding inner surface 2.9 of the cup-shaped housing component 2 are designed such that the filler body 14 can be inserted or introduced into the interior 2.8 of the cup-shaped housing component 2.

[0042] In the case that the wall reinforcement 2.10 extends inwards, the outer surface of the filling body 14 has a corresponding recess for the wall reinforcement, so that the filling body can not only be inserted into the interior, but can also be centered or aligned via it.

[0043] List of reference symbols

[0044] 1 pressure sensor

[0045] 2 cup-shaped housing components

[0046] 2.1 Contact pins

[0047] 2.2 Filling tubes

[0048] 2.4 Metallic base body

[0049] 2.5 First end face of the cup-shaped housing component

[0050] 2.6 Second end face of the cup-shaped housing component

[0051] 2.7 Stepped outer contour

[0052] 2.8 Interior

[0053] 2.9 Interior surface of the interior

[0054] 2.10 Wall reinforcement

[0055] 3 pressure measuring cell

[0056] 4 pressure-sensitive element

[0057] 5.1 First half of the basic body component

[0058] 5.11 step-like shape of the first half of the basic body component

[0059] 5.111 middle plateau of the step-like form

[0060] 5.2 Second half of the basic body component

[0061] 6 Overload chamber

[0062] 6.1 , 6.2 Subchambers

[0063] 7 Measuring circuit

[0064] 8 Overload diaphragm

[0065] 9.1 , 9.2 Separation membrane

[0066] 10.1 , 10.2 Pressure receiving chambers

[0067] 11 First pressure transmission channel

[0068] 12 Second pressure transmission channel

[0069] 12.1 First part of the second pressure transmission channel

[0070] 12.2 Second part of the second pressure transmission channel

[0071] 13 Central axis

[0072] 13.1 First joining surface of the cup-shaped housing component

[0073] 13.2 Second joining surface of the first half of the base body component

[0074] 14 packing

[0075] 14.1 Shell surface of the packing

[0076] 15 Weld seam

[0077] D Diameter of the cross-sectional opening of the hydraulic channel at the first or second joining surface

Claims

Patent claims 1 . Pressure sensor (1) for determining the pressure of a process medium, comprising a cup-shaped housing component (2) in which a pressure measuring cell (3) with a pressure-sensitive element (4) is arranged, and a base body component (5.1, 5.2) to which at least one separating membrane (9.1, 9.2) is fastened to form a pressure chamber (10.1, 10.2), wherein at least one hydraulic channel (11, 12) filled with a transmission fluid is provided, via which the pressure chamber (10.1, 10.2) is connected to the pressure-sensitive element (4) in order to transmit a medium pressure (p1, p2) applied to the separating membrane (9.1, 9.2), wherein the cup-shaped housing component (2) has a metallic base body (2.4) designed in the form of a cup and at least one metallic contact pin (2.1) which is embedded in the base body over part of its length for electrical insulation in such a way that metallic base body is glazed in such a way that the contact pin (2.1) is on a first end face (2.5) protrudes from the base body (2.4), wherein the metallic base body (2.4) has, on a second end face (2.6) opposite the first end face (2.5), a preferably stepped outer contour (2.7), which is realized by a pipe extension formed on the second end face (2.6) of the metallic base body (2.4), wherein the hydraulic channel has a first part (12.1) which extends at least through the part of the metallic base body (2.4) forming the pipe extension in the axial direction and ends at the second end face (2.6) of the cup-shaped housing component (2), wherein a wall of the pipe extension formed on the second end face (2.6) of the metallic base body (2.4) is designed in the region of the first part of the channel (12.1) in such a way that - viewed in cross section - a wall reinforcement (2.10), in particular in the form of a nose, surrounds the first part of the channel (12.1), wherein the wall is connected to the wall reinforcement (2.10) forms a first joining surface (13.1) on the second end face (2.6) of the metallic base body, wherein the base body component (5.1, 5.2) has a second joining surface (13.2) corresponding to the first joining surface (13.1) formed by the wall with the wall reinforcement (2.10). wherein the hydraulic channel further comprises a second part (12.2) which is formed in the base body component (5.1, 5.2) and ends at the second joining surface (13.2) of the base body component, wherein the cup-shaped housing component (2) and the base body component (5.1, 5.2) are arranged relative to one another in such a way that the first and second joining surfaces (13.1, 13.2) are adjacent to one another and the first and second parts of the channel (12.1, 12.2) are aligned opposite one another, wherein the cup-shaped housing component (2) and the base body component (5.1, 5.2) are welded together in such a way that a weld seam (15) is formed on the first or second joining surface (13.1, 13.2), which surrounds the hydraulic channel at this point without closing it.

2. Pressure sensor according to the preceding claim, wherein the wall of the tube extension formed on the second end face (2.6) of the metallic base body (2.4) is designed such that the wall reinforcement (2.10) - seen in cross section - is formed in the direction of a central axis (13) of the cup-shaped housing component (2).

3. Pressure sensor according to claim 1, wherein the wall of the tube extension formed on the second end face (2.6) of the metallic base body (2.4) is designed such that the wall reinforcement (2.10) - seen in cross section - is formed in the opposite direction to a central axis (13) of the cup-shaped housing component (2).

4. Pressure sensor according to one or more of the preceding claims, wherein the wall reinforcement (2.10) and the first part of the channel (12.1) extending in the axial direction through the tube extension of the metallic base body (2.4) are designed and matched to one another in such a way that - seen in cross section - a first wall thickness (W1) extending radially outward from the first channel (12.1) is greater than a second wall thickness (W2) extending radially inward from the first channel.

5. Pressure sensor according to one or more of the preceding claims, wherein at least the first part of the channel (12.1) has a round cross-sectional opening on the second end face (2.6) and wherein a diameter of the round cross-sectional opening is greater than a first wall thickness (W1) extending radially outwards from the first channel as seen in cross section and / or greater than a second wall thickness (W2) extending radially inwards from the first channel as seen in cross section.

6. Pressure sensor according to one or more of the preceding claims, wherein a preferably cylindrical filling body (14) is provided, which is also arranged in the cup-shaped housing component (2) and is designed such that it has a receptacle which encloses the pressure measuring cell (3).

7. Pressure sensor according to the preceding claim, wherein a lateral surface (14.1) of the filling body (14) and a corresponding inner surface of the tube extension of the cup-shaped housing component are designed and matched to one another in such a way that the filling body can be introduced into an interior space of the cup-shaped housing component (2) defined by the tube extension.

8. Pressure sensor according to claim 2 and 7, wherein the outer surface (14.1) of the filling body (14) has a recess corresponding to the wall reinforcement (2.10) formed in the direction of the central axis (13) of the cup-shaped housing component (2), so that the filling body (14) is not only insertable / introducible into the interior, but is also oriented or positioned via the wall reinforcement (2.10) in combination with the recess.

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