Pressure transducer for transmitting the pressure of a process medium

Abstract

The invention relates to a pressure transducer (1) for transmitting the pressure of a process medium, comprising: a metal main body (2), a pressure sensor module (5) comprising a ceramic insulation body (6) and a pressure sensor (7), a separating membrane (8) to which the process medium can be applied from a first separating membrane side (8.1); wherein at least one electrically conductive contact pin (6.2) is introduced into the ceramic insulation body (6) such that the contact pin (6.4) extends through the ceramic insulation body (6) at least from the first end face (6.1) to a second end face (6.2) opposite the first end face, wherein the at least one contact pin (6.4) is also arranged or positioned in the ceramic insulation body (6) such that a distance (d) between the contact pin (6.4) and another electrically conductive component of the pressure transducer at the second end face is not less than a value specified in standard DIN EN 60079-11 (2011 edition) for a clearance and / or creepage distance in air.

Description

[0001] Pressure transducer for transmitting the pressure of a process medium

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

[0003] Pressure transducers for measuring pressure are regularly used in industrial pressure measurement technology for absolute, gauge, or differential pressure measurements. Typically, the initial pressure of the medium acts on a separating diaphragm and is transmitted to a pressure sensor via a first hydraulic pressure transmission path. The hydraulic pressure transmission path is usually filled with a diaphragm seal fluid to transmit the pressure to the pressure sensor. To be able to transmit a sensor signal from the pressure sensor out of the pressurized area, a so-called glass-to-metal feedthrough is usually used. The pressure sensor is attached to one side of the glass-to-metal feedthrough, and the sensor signal is transmitted out of the pressurized area through glazed contact pins.

[0004] Particularly in the process industry, but also in automation technology, such pressure transducers are often used in areas with a potential explosion hazard, so-called potentially explosive atmospheres. For use in potentially explosive atmospheres, minimum values ​​for clearance and / or creepage distances between intrinsically safe circuits and grounded metal parts are required for device protection through intrinsic safety, such as a metal base body of the pressure transducer, which is grounded via a container in which the pressure of the medium is to be determined.

[0005] When using the aforementioned glass-to-metal bushings in pressure sensors designed for potentially explosive atmospheres, achieving the required clearance and / or creepage distances is relatively complex. For example, an additional electrically non-conductive body is placed between the glass-to-metal bushing and the pressure sensor to meet the required clearance and / or creepage distances.

[0006] The disadvantage of this is that the additional non-conductive bodies must be manufactured separately and installed in the pressure sensor.

[0007] The invention is therefore based on the object of proposing a pressure transducer which can be used in particular in potentially explosive atmospheres and which is easier to manufacture.

[0008] The object is achieved according to the invention by the pressure measuring sensor according to patent claim 1.

[0009] The pressure transducer according to the invention for transmitting the pressure of a process medium comprises: a metallic base body having a surface and a receiving space for receiving a pressure sensor module; the pressure sensor module comprising a ceramic insulating body, in particular one having a substantially cylindrical or conical outer contour, and a pressure sensor mounted on a first end face of the ceramic insulating body, wherein the pressure sensor module is inserted into the metallic base body such that the pressure sensor is directed toward the separating membrane and points into the receiving space, wherein the ceramic insulating body is further joined to the metallic base body at a lateral surface; a separating membrane attached to the surface, wherein a pressure chamber is formed between the separating membrane and the surface, which communicates with a hydraulic path via an opening in the surface,the separating membrane can be pressurized with the process medium from a first separating membrane side, the pressure chamber, the hydraulic path, and the receiving space are filled with a transmission fluid to transmit the pressure of the process medium to the pressure sensor; wherein at least one electrically conductive contact pin is inserted into the ceramic insulating body such that the contact pin extends through the ceramic insulating body at least from the first end face to a second end face opposite the first end face, wherein the at least one contact pin is further arranged or positioned in the ceramic insulating body such that a distance between the contact pin and another electrically conductive component of the pressure sensor on the second end face is not less than a value specified in the standard DIN EN 60079-11 (2011 edition) for a clearance and / or creepage distance in air.

[0010] An advantageous embodiment of the pressure transducer according to the invention can provide that at least part of a reference pressure path is formed in the ceramic insulation body, via which a reference pressure can be supplied to the pressure sensor, and wherein the at least part of the reference pressure path formed in the ceramic insulation body is designed such that the path has a minimum length which is not less than a value specified in the standard DIN EN 60079-11 (2011 edition) for an air gap and / or creepage distance in air.

[0011] A further advantageous embodiment of the pressure sensor according to the invention can provide that the minimum length and / or distance is not less than a value specified for a voltage of 30 V and a protection level ia, ib for the clearance and / or creepage distance in air according to Table 5 of the standard DIN EN 60079-11, edition 2022.

[0012] A further advantageous embodiment of the pressure measuring sensor according to the invention can provide that the minimum length and / or the distance is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm.

[0013] A further advantageous embodiment of the pressure sensor according to the invention can provide that the other electrically conductive component of the pressure sensor comprises an edge of the metallic base body, to which the ceramic insulation body is joined with its lateral surface to the metallic base body.

[0014] A further advantageous embodiment of the pressure measuring transducer according to the invention can provide that the ceramic insulating body has a recess on the first end face into which the pressure sensor is introduced, wherein the recess is preferably designed such that the pressure sensor is introduced into the recess up to a maximum height of approximately half the actual height of the pressure sensor.

[0015] The invention is explained in more detail with reference to the following drawing. It shows:

[0016] Fig. 1 : a sectional view through a pressure sensor.

[0017] Figure 1 shows a sectional view through a pressure transducer 1. The pressure transducer 1 comprises a metallic base body 2, in particular made of steel or stainless steel, with a surface 3 to which a disc-shaped separating membrane 8 is attached with a circumferential weld seam on a circumferential outer edge, thereby forming a pressure chamber 9 between the base body 2 and the separating membrane 8. The separating membrane 8 can, as shown, have a plurality of beads 8.3.

[0018] In the illustrated embodiment, the base body 2 is constructed in two parts; however, the invention is not limited to a two-part base body, but is also transferable to a one-part or more than two-part construction. A first part of the base body 2.1 has a disk-like shape with a stepped recess 2.11 on the end facing the separating membrane 8, or a substantially hollow-cylindrical shape. A second part of the base body 2.2 also has a disk-like shape and is designed with its outer contour such that the second part can be inserted into the stepped recess 2.11. On one of the end faces facing away from the separating membrane 8, the second part of the base body 2.2 has a recess 2.21, so that in the installed state, in which the second part is inserted into the first part of the base body, a receiving space 4 is formed in the base body 2 for receiving a pressure sensor 7, which will be described in more detail later. The first and second parts of the base body 2.1, 2.2 are joined together, in particular in a pressure-tight manner.

[0019] A bore 10 extends from the pressure chamber 9 through the base body, in the present embodiment, through the second part of the base body, to form a hydraulic path and transmit the first process pressure applied to the separating membrane to the pressure sensor module 5, which will be described in more detail below. To ensure that the first process pressure can be transmitted accordingly, the pressure chamber and the bore or the hydraulic path 10 are filled with a transmission fluid. The transmission fluid can be, for example, an oil, in particular a silicone oil.

[0020] The first part of the base body 2.1 has a preferably central bore 2.12 adjacent to the stepped recess 2.11, which extends through the base body to a rear side, i.e., the side facing away from the process. A central bore 2.12 here means a bore that extends along a rotational axis relative to an outer contour of the base body.

[0021] The pressure sensor module 5 is inserted into the central bore 2.12. The pressure sensor module 5 comprises a ceramic insulator body 6 according to the invention, in particular comprising aluminum and / or zirconium oxide, and a pressure sensor 7 to be described in more detail below. The ceramic insulator body 6 has a substantially cylindrical or conical outer contour with a diameter of a few millimeters, for example in the range of 5-15 mm, preferably in the range of 7.5-12.5 mm. Furthermore, the ceramic insulator body 6 can have a recess 6.5 on one end face for receiving the pressure sensor 7. The recess 6.5 can be designed such that the pressure sensor 7 can be inserted into the recess up to a maximum height of approximately half the actual height of the pressure sensor 7. Several metallic contact pins 6 are inserted into the ceramic insulator body 6.4, which serve to electrically contact the pressure sensor 7, are inserted over part of their length in such a way that they are essentially flush with the ceramic insulator body 6 on the end face of the recess or the end face where the pressure sensor 7 is located, and protrude from the ceramic insulator body 6 on a rear side opposite the end face. Alternatively, the metallic contact pins may not be flush with the ceramic insulator body 6, but may protrude slightly. The contact pins.

[0022] 6.4 are connected in a pressure-tight manner to the ceramic insulator body 6. This can be achieved, for example, by the contact pins 6.4 being connected to the ceramic insulator body 6 by gluing, soldering, or by glazing. Preferably, the contact pins 6.4 and the ceramic insulator body 6 can be designed such that the contact pins

[0023] 6.4 on the front side, where the pressure sensor 7 is located, have a deformation 6.41, in particular a conical one, so that the contact pins 6.4 are supported on the ceramic insulator body 6 under pressure load.

[0024] Furthermore, the contact pins 6.4 are arranged or positioned in the ceramic insulator body 6 in such a way that a distance d between the contact pins

[0025] 6.4 and an edge of the metallic base body 2 or the circumferential edge of the bore made in the base body, at which the ceramic insulating body 6 is joined to the metallic base body 2, is not smaller than a value specified in the standard DIN EN 60079-11 (2011 edition) for a clearance and / or creepage distance in air. In particular, the distance is not smaller than a value specified for the clearance and / or creepage distance in air for a voltage of 30 V and a protection level ia, ib in accordance with Table 5 of the standard DIN EN 60079-11 (2011 edition). For example, the distance d can be selected such that it is not smaller than 1.5 mm, preferably not smaller than 1.75 mm, particularly preferably not smaller than 2 mm. This clearance and creepage distance is required to meet the insulation distance requirements according to IEC 60079-11.

[0026] The electrical signal of the pressure sensor representing the pressure measurement value can first be pre-processed by an electrical sensor circuit located on a circuit board on the rear, before it is further processed and prepared for communication via the common protocols, for example 4-20mA or digital fieldbus protocols.

[0027] The ceramic insulator body 6 is joined to the base body 2 of the pressure sensor 1 along a circumferential surface, particularly in a pressure-tight manner. This can be achieved, for example, by soldering, by applying a metallization to the insulator body 6 and then brazing. Furthermore, the joining can also be achieved by active brazing or diffusion soldering. Alternatively, the joining can also be achieved by adhesive bonding.

[0028] Furthermore, a reference pressure path 11 can be formed in the ceramic insulator body 6 in order to guide a reference pressure to the pressure sensor 7, which will be described in more detail later. The reference path 11 can be formed by corresponding channels introduced into the insulator body 6, for example by pressing or channels produced with the aid of a ceramic powder injection molding process (“ceramic injection molding”). In the present exemplary embodiment, the reference pressure path 11 has a bore extending parallel to the central axis of the ceramic insulator body 6 and a transverse bore adjoining or connected thereto. If the pressure sensor 1 is designed as a reference pressure sensor, an atmospheric air pressure is supplied as the reference pressure via the reference path 11. If the pressure sensor is designed as an absolute pressure sensor, a defined pressure, in particulara vacuum is applied. In both cases, the reference pressure path 11 cannot be filled with a pressure-transmitting fluid.

[0029] In the reference pressure sensor, the reference path 11 formed in the ceramic insulator body 6 can be continued in the metallic base body and led to an outer surface of the base body. A filter element 12 can also be provided upstream of the reference pressure path on this outer surface. Advantageously, the reference pressure path 11 is designed such that the specifications regarding a clearance and / or creepage distance according to the standard DIN EN 60079-11 (2011 edition) are met by the part of the reference path 11 formed in the ceramic and thus electrically non-conductive insulator body 6. This means that the part of the reference pressure path formed in the ceramic insulator body has a minimum length that corresponds to the specified value for the clearance and / or creepage distance according to the standard DIN EN 60079-11 (2011 edition).In the exemplary embodiment shown in the figures, the minimum length is made up of the two lengths L1 and L2 added together. In particular, the minimum length L1 + L2 is not less than a value specified for a voltage of 30 V and a protection level ia, ib for the clearance and / or creepage distance in air according to Table 5 of the standard DIN EN 60079-11 (2011 edition). For example, the part of the reference pressure path 11 formed in the ceramic insulation body 6 can be designed such that the minimum length L1 + L2 is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm. The insulation distances according to IEC 60079-11 are met by the minimum length L1 + L2 and the minimum distance to an electrically conductive component, e.g. the metallic base body, achieved by the minimum length.

[0030] If the pressure sensor is designed as a differential pressure sensor, a second process pressure is supplied to the pressure sensor via the reference pressure path. In this case, the reference pressure path 11 can also be filled with a pressure-transmitting fluid.

[0031] The pressure sensor 7, for example a silicon chip, has a measuring diaphragm 7.3, which is subjected to the first process pressure on the first end face 7.1 facing the separation diaphragm and to the reference pressure on the second end face 7.2 facing away from the separation diaphragm. As a result, the measuring diaphragm 7.3 experiences a pressure-dependent deflection, which in turn can be detected, e.g., capacitively or resistively, and converted into the corresponding electrical signal.

[0032] To keep the volume of the transmission fluid in the receiving chamber 4 as low as possible, the pressure sensor 1 further comprises a filler body 13 introduced into the receiving chamber. The filler body 13 is designed such that cavities between the walls of the receiving chamber 4 and the pressure sensor 7 are filled as completely as possible. The filler body 12 can be formed in one piece or in multiple pieces, in particular in two pieces. Furthermore, the filler body 13 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.

[0033] List of reference symbols

[0034] 1 pressure sensor

[0035] 2 metallic base bodies

[0036] 2.1 First part of the basic body

[0037] 2.11 Stepped recess

[0038] 2.12 Central bore

[0039] 2.2 Second part of the main body

[0040] 2.21 Recess

[0041] 3 Surface

[0042] 4 Recording room

[0043] 4.1 Opening

[0044] 5 Pressure sensor module

[0045] 6 Ceramic insulation body

[0046] 6.1 First end face of the insulation body

[0047] 6.2 Second end face of the insulation body

[0048] 6.3 Surface of the insulation body

[0049] 6.4 Electrically conductive contact pins

[0050] 6.41 Conical deformation

[0051] 6.5 Deepening

[0052] 7 Pressure sensor

[0053] 7.1 First face of the pressure sensor

[0054] 7.2 Second front side of

[0055] 7.3 Measuring membrane

[0056] 8 Separation membrane

[0057] 8.1 First separation membrane side

[0058] 8.2 Second separation membrane side

[0059] 8.3 Beading of the separation membrane

[0060] 9 Pressure chamber

[0061] 10 Hydraulic path, e.g. in the form of a bore

[0062] 11 Reference pressure path

[0063] 12 filter element

[0064] 13 Filling body d distance

[0065] L1 +L2 minimum length

Claims

Patent claims 1 . Pressure transducer (1) for transmitting the pressure of a process medium, comprising: a metallic base body (2) having a surface (3) and a receiving space (4) for receiving a pressure sensor module (5); the pressure sensor module (5) comprising a ceramic, in particular an insulating body (6) having a substantially cylindrical or conical outer contour, and a pressure sensor (7) which is attached to a first end face of the ceramic insulating body (6.1), wherein the pressure sensor module (5) is introduced into the metallic base body (2) in such a way that the pressure sensor (7) is directed towards a separating membrane (8) and points into the receiving space (4), wherein the ceramic insulating body (6) is further joined to the metallic base body at a lateral surface (6.3), the separating membrane (8) which is fastened to the surface (2), wherein a pressure chamber (4) is formed between the separating membrane and the surface, which pressure chamber (4) has an opening (4.1 ) communicates in the surface with a hydraulic path (10), the separating membrane (8) can be pressurised with the process medium from a first separating membrane side (8.1 ), the pressure chamber (9), the hydraulic path (10) and the receiving space (4) are filled with a transmission fluid in order to transmit the pressure of the process medium to the pressure sensor; wherein at least one electrically conductive contact pin (6.2) is introduced into the ceramic insulating body (6) in such a way that the contact pin (6.4) extends through the ceramic insulating body (6) at least from the first to a second end face (6.2) opposite the first end face (6.1 ), wherein the at least one contact pin (6.4) is further arranged or positioned in the ceramic insulating body (6) in such a way that a distance (d) between the contact pin (6.4) and another electrically conductive component of the pressure measuring sensor on the second. front side is not smaller than a value specified in the standard DIN EN 60079-11 (edition 2011) for a clearance and / or creepage distance in air.

2. Pressure measuring sensor according to the preceding claim, wherein at least part of a reference pressure path (11) is formed in the ceramic insulation body (6), via which reference pressure can be supplied to the pressure sensor (7), and wherein the at least part of the reference pressure path (11) formed in the ceramic insulation body (6) is designed such that the path has a minimum length (L1 + L2) which is not less than a value specified in the standard DIN EN 60079-11 (2011 edition) for an air gap and / or creepage distance in air.

3. Pressure sensor according to one or more of the preceding claims, wherein the minimum length (L1 + L2) and / or distance (d) is not less than a value specified for a voltage of 30 V and a protection level ia, ib for the clearance and / or creepage distance in air according to Table 5 of the standard DIN EN 60079-11, edition 2022.

4. Pressure measuring sensor according to one or more of the preceding claims, wherein the minimum length (L1 + L2) and / or the distance (d) is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm.

5. Pressure sensor according to one or more of the preceding claims, wherein the other electrically conductive component of the pressure sensor (1) comprises an edge of the metallic base body (2), to which the ceramic insulating body (6) is joined with its outer surface (6.3) to the metallic base body (2).

6. Pressure measuring sensor according to one or more of the preceding claims, wherein the ceramic insulating body (6) has a recess (6.5) on the first end face (6.1) into which the pressure sensor (7) is introduced, wherein the recess (6.5) is preferably designed such that the pressure sensor (7) is introduced into the recess up to a maximum height of approximately half the actual height of the pressure sensor (7).

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