Method for joining a differential pressure measuring cell and differential pressure measuring cell

Abstract

Method for joining a differential pressure measuring cell (1), which differential pressure measuring cell (1) comprises: a measuring diaphragm (2); a transducer, a first and a second counterbody (41, 42), and a first and a second support body (51, 52), - wherein the measuring membrane (2) is arranged between the first counterbody (41) and the second counterbody (42) and is pressure-tightly connected to both counterbodies (41,42), - wherein a first measuring chamber (61) is formed between the measuring membrane (2) and the first counterbody (41) and a second measuring chamber (62) is formed between the measuring membrane (2) and the second counterbody (42), - wherein the first counterbody (41) and first support body (51) as well as the second counterbody (42) and second support body (52) each have a pressure channel (7) through which the first measuring chamber (61) can be subjected to a first pressure (p1) and the second measuring chamber (62) to a second pressure (p2) and - wherein the transducer is designed to generate an electrical measurement signal from a deformation of the measuring membrane (2) caused by the difference between the first pressure (p1) and the second pressure (p2), wherein the joining process is divided into the following process steps: - Prefabrication of the two counter bodies (41,42) and pressure-tight connection of the measuring membrane (2) to the two counter bodies (41,42), - Applying a joining material (FM) to the end face (13a) of the first support body (51) facing the measuring membrane (2) or to the end face (12a) of the first counter body (41) facing away from the measuring membrane (2) and to the end face (13b) of the second support body (52) facing the measuring membrane (2) or to the end face (12b) of the second counter body (42) facing away from the measuring membrane (2), wherein on at least one of the end faces (12a, 12b, 13a, 13b) the joining material (FM) is structured during application such that • the end face (12a; 12b; 13a; 13b) has a continuous, internal area (31) without joining material (FM), • the end face (12a; 12b; 13a; 13b) has a continuous outer area (32) surrounding the inner area (31) with joining material (FM), - Pressure-tight connection of the end face (12a, 12b) of the counter body (41,42) facing away from the measuring membrane (2) with the end face (13a,13b) of the support body (51,52) facing the measuring membrane (2), wherein, in the connection of at least one of the counter bodies (41;42) with the adjacent support body (51;52) through the connected inner area (31) without joining material (FM) a hydraulic chamber (8) is formed between the counter body (41;42) and the support body (51;52), wherein the hydraulic chamber (8) formed by the continuous inner area (31) without joining material (FM) has a maximum diameter (dS) which deviates by no more than 20% from the diameter (dM) of the measuring diaphragm (2), and wherein the hydraulic chamber (8) communicates with the measuring chamber (61;62) via the pressure channel (7).

Description

[0001] The invention relates to a method for joining a differential pressure measuring cell and to a differential pressure measuring cell produced by the method.

[0002] Differential pressure measuring cells use a measuring diaphragm to measure the difference between two static pressures, p1 and p2. This diaphragm is positioned between two counter bodies, forming two hermetically sealed measuring chambers. The measuring chambers are pressurized to the pressures p1 and p2 via pressure channels integrated into the counter bodies. The deflection of the measuring diaphragm thus represents the pressure difference |p1-p2|, and this deflection is converted into an electronic measurement signal by a transducer. For example, in capacitive differential pressure measuring cells, the measuring diaphragm, together with a conductive plane of the counter body facing the measuring diaphragm and parallel to it, forms a capacitor. Therefore, the deflection of the measuring diaphragm determines the capacitor spacing, allowing the differential pressure acting on the measuring diaphragm to be converted into a measurement signal via capacitance measurements.Such a differential pressure measuring cell is described, for example, in patent DE 103 93 943 B3. Differential pressure measuring cells, which are used in the process and / or automation technology of industrial plants for monitoring process pressures, are manufactured and distributed by the E+H Group in a wide variety of configurations.

[0003] Since differential pressure sensors are designed to measure small pressure differences |p1-p2| at simultaneously high static pressures p1, p2, the correct balance between sensitivity and overload resistance is of central importance. For example, the following relationship can apply to the measuring range of the pressure difference |p1-p2|: |p1-p2| / p1 < 1%. If one of the two pressures (e.g., p2) is absent in a process plant, |p1-p2| / p1 reaches almost 100%. In this case, the differential pressure sensor is thus subjected to more than 100 times its measuring range, which corresponds to a very high one-sided pressure load. For differential pressure sensors with a very fine measuring range of |p1-p2| ∼ 10 mbar, the one-sided pressure load is correspondingly higher relative to the measuring range at a typical process pressure of 160 bar.

[0004] The prior art discloses various designs for overload protection of differential pressure measuring cells at high static pressures p1, p2, including, for example, overload membranes (EP 1 299 701 B1, DE 10 2006 040 325 A1 or DE 10 2006 057 828 A1) or membrane beds (US 4 458 537 or DE 10 2009 046 229 A1).

[0005] To protect against overload and to support the counterbody, the two counterbodies, which are connected to each other in a pressure-tight manner, are usually enclosed between two support bodies.

[0006] It has been shown that at high pressures, a residual notch stress in the area of ​​the connection or joining point between the measuring diaphragm and the counterbody is problematic. To minimize this notch stress, DE 10 2014 109 491 A1 proposes the formation of an additional hydraulic chamber at the connection between the counterbody and the support body, which communicates with the measuring chamber via a compensating channel. The hydraulic chamber extends in a plane parallel to the plane of the measuring diaphragm and ensures that the respective process pressure acts not only on the counterbody from the measuring chamber but also on the counterbody from the rear, namely from the hydraulic chambers. Since the same pressure prevails in both the measuring chamber and the hydraulic chamber, the same pressure acts on the counterbody from both the end face facing away from and the end face facing the measuring diaphragm.

[0007] This means that the forces acting on the counterbody from the end face facing the measuring diaphragm are essentially equal to the forces acting on the counterbody from the end face facing away from the measuring diaphragm. Thus, there are essentially no net forces acting on the counterbody, which significantly reduces pressure-dependent deflection of the counterbody. The isobaric mounting of the counterbody achieved by the hydraulic chambers therefore leads to an increase in compressive strength.

[0008] Furthermore, isobaric mounting of the counterbody reduces systematic errors in the measurement signal caused by high static pressures p1 and p2. A systematic error could, for example in the case of a capacitive differential pressure sensor, be caused by a pressure-induced increase in the electrode-measuring membrane distance and a resulting shift in the zero point and / or a change in sensitivity.

[0009] A similar embodiment is disclosed in US patent 9,274,061 B2. However, the arrangements disclosed therein are—unlike those disclosed in DE 10 2014 109 491 A1—all asymmetrical. Due to this asymmetry, the embodiments disclosed in the US patent are unsuitable for reducing the influence of the static pressure p1, p2 on the measurement signal of the differential pressure sensor.

[0010] To create such a hydraulic chamber between the counterbody and the support body, an additional process step is usually necessary. For example, the end face of the support body and / or counterbody must be specially machined to achieve the desired hydraulic chamber. Depending on the type and material of the counterbody and / or support body, such machining can be complex and requires at least one additional process step.

[0011] Furthermore, differential pressure measuring cells have become known, among other things, from DE 10 2011 006 517 A1, DE 10 2014 109 491 A1, DE 102 28 618 B4 and DE 10 2010 043 043 A1.

[0012] The invention is based on the objective of providing a simple method for obtaining a hydraulic chamber in the connection between conventional counter bodies and support bodies.

[0013] The problem is solved by a method for joining a differential pressure measuring cell, which differential pressure measuring cell comprises: a measuring diaphragm; a transducer, a first and a second counterbody, as well as a first and a second support body, - wherein the measuring membrane is arranged between the first counterbody and the second counterbody and is pressure-tightly connected to both counterbodies, - wherein a first measuring chamber is formed between the measuring membrane and the first counterbody and a second measuring chamber is formed between the measuring membrane and the second counterbody, - wherein the first counterbody and first support body as well as the second counterbody and second support body each have a pressure channel through which the first measuring chamber can be subjected to a first pressure (p1) and the second measuring chamber to a second pressure (p2) and - wherein the transducer is designed to generate an electrical measurement signal from a deformation of the measuring diaphragm caused by the difference between the first pressure (p1) and the second pressure (p2), the joining process is divided into the following steps: - Prefabrication of the two counter bodies and pressure-tight connection of the measuring membrane to the two counter bodies, - Applying a bonding material to the end face of the first support body facing the measuring membrane or to the end face of the first counter body facing away from the measuring membrane and to the end face of the second support body facing the measuring membrane or to the end face of the second counter body facing away from the measuring membrane, wherein on at least one of the end faces the joining material is structured during application in such a way that • the end face has a continuous, internal area without joining material, • the end face has a continuous outer area surrounding the inner area with joining material, - Pressure-tight connection of the end face of the counter body facing away from the measuring membrane with the end face of the support body facing the measuring membrane, wherein, in the connection of at least one of the counter bodies with the adjacent support body through the connected internal area without joining material, a hydraulic chamber is formed between the counter body and the support body, wherein the hydraulic chamber formed by the continuous inner area without joining material has a maximum diameter that deviates by no more than 20% from the diameter of the measuring diaphragm, and the hydraulic chamber communicates with the measuring chamber via the pressure channel.

[0014] In the first step of the inventive process, the two counterbodies are prefabricated. During the pressure-tight joining of the measuring membrane to the two counterbodies, the measuring membrane is positioned between the two counterbodies, and the measuring chambers are formed. The prefabrication in the first process step also includes the arrangement between the counterbodies of all those components required for generating or converting the measurement signal, such as the membrane electrodes and the transducer.

[0015] In the second step of the inventive method, the joining material is applied in a structured manner to the end face of a counterbody and / or support body. The structuring is carried out such that an inner area without joining material, communicating with the measuring chamber, is provided on the end face. The joining material is therefore applied only to the outer area of ​​the end face surrounding the inner area. This outer area extends to the edge regions of the end face. The end face on which the joining material is applied in a structured manner is one of the two end faces in the plane of connection between the first and / or second counterbody and the adjacent support body. The end faces of the counterbody and support body are essentially in a plane parallel to the plane of the measuring membrane.

[0016] In the inventive method, if the joining material is applied to the end face of the support body, the pressure-tight connection of the support body to the adjacent counter body is carried out in a subsequent process step. This step precedes the pressure-tight joining process step. Within the scope of this application, "the end face of the support body facing the measuring membrane" is the end face intended for connection with the end face of the counter body facing away from the measuring membrane. The end face of the support body facing the measuring membrane is therefore the one that is to be combined with the end face of the counter body facing away from the measuring membrane when the counter body and support body are positioned.

[0017] In the third step of the inventive method, a hydraulic chamber is formed between the support body and the counter body by means of the pressure-tight connection of the support body and the counter body, using the inner area without joining material. The pressure channel, which communicates with the measuring chamber, must be located in this area without joining material.

[0018] The advantage of the method according to the invention is that the hydraulic chamber is formed solely by the structured application of the joining material and the pressure-tight connection of the support body and counter body. The hydraulic chamber corresponds to the inner area without joining material. Since the application of the joining material is a standard process step in known methods for joining conventional differential pressure measuring cells, no additional process step is required.

[0019] This also eliminates the need for specific structuring of the counterbody and / or support body itself, so that standardized counterbodies and support bodies with essentially flat or planar end faces can be used. In contrast to known methods, the joining material is applied in a structured manner, thereby creating the hydraulic chamber between the counterbody and the support body. With the method according to the invention, a differential pressure measuring cell with a hydraulic chamber between the counterbody and the support body can therefore be obtained in a simple and cost-effective manner.

[0020] In one embodiment of the inventive method, the joining material is applied using a screen printing process. Since the dosage and / or structuring of the joining material is very precisely adjustable and controllable in screen printing processes, these are particularly well suited to the inventive method. For example, in the screen printing process, it is possible to produce screen printing matrices automatically using computer-aided methods. Thus, very precisely defined patterns of joining material can be applied to the end face, and a high degree of automation can be achieved in the production of differential pressure measuring cells with a hydraulic chamber using the inventive method.

[0021] In one embodiment of the inventive method, a glass solder, adhesive or metallic solder is used as the joining material.

[0022] In a further embodiment of the method according to the invention, the joining material is applied with an approximately constant layer thickness. This approximately constant layer thickness is between 5 and 50 micrometers. The glass solder is used particularly in the joining of differential pressure measuring cells based on microelectromechanical systems (MEMS). In the case of a differential pressure measuring cell based on a MEMS sensor and a glass solder, the layer thickness of the joining material is essentially between 10 and 20 micrometers.

[0023] In a further embodiment of the method according to the invention, the first and second counter bodies are each connected to the adjacent support body with a homogeneous contact pressure distribution in a pressure-tight manner. The contact pressure reduces the size of the joining material in the direction perpendicular to the end face and increases it in a plane parallel to the end face. The joining material should therefore be applied in such a structured manner that the increase in the plane parallel to the end face is taken into account, so that the hydraulic chamber is not completely filled with joining material during the joining process. To achieve this, the contact pressure must be adjustable, and the expansion of the joining material under the influence of the contact pressure must be known or calculable. If the contact pressure distribution is essentially homogeneous, a substantially constant layer thickness of the joining material is achieved after the pressure-tight connection.

[0024] In a particularly advantageous embodiment of the inventive method, the joining material is structured on two end faces so that the first and second counter bodies are each pressure-tightly connected to the adjacent support body, forming a hydraulic chamber. In this particularly preferred embodiment, for the typical application where both process pressures are very high, the inventive joining method can provide a differential pressure measuring cell with particularly high compressive strength, overload protection, and accuracy under high pressure loads on both sides.

[0025] In a further development of this design, the joining material is structured identically on both end faces.

[0026] Typically, the counterbody and / or the support body have at least one axis of symmetry, wherein the counterbody and / or the support body is symmetrical with respect to the axis of symmetry. The axis of symmetry can, for example, be the mirror axis of a mirror symmetry or the rotation axis of a rotational symmetry. The axis of symmetry can lie in the plane of the end face or be perpendicular to the end face. In an advantageous embodiment of the method, the joining material on at least one of the end faces is structured such that the inner area without joining material is arranged symmetrically about at least one axis of symmetry. The axis of symmetry is thus a common axis of symmetry of the support body and / or counterbody and the inner area without joining material.

[0027] In a further embodiment of the method according to the invention, the joining material on at least one of the end faces is structured such that the area without joining material has a cross-shaped surface, and the pressure channel communicating with the measuring chamber is arranged in the center of the cross-shaped surface. The area without joining material of the cross-shaped surface is formed by two intersecting and mutually perpendicular struts without joining material. The struts do not necessarily have to be of the same length and / or width.

[0028] A natural further development of this embodiment of the inventive method involves structuring multiple struts without joining material. For example, any even number of struts without joining material can be provided, which intersect at a point of intersection and extend radially away from the point of intersection.

[0029] In this embodiment, the method yields a differential pressure measuring cell with a hydraulic chamber, wherein radial sections of the hydraulic chamber are arranged distributed over a circular area. The radius of the circular area is defined as the maximum length of the radial struts. The pressure channel is located at the center of the circular area. The hydraulic sections, in the form of radial struts, are distributed over the entire circular area. Simultaneously, intermediate sections exist between the radial struts, in which the counterbody is fully joined to the adjacent support body. Thus, a rigid connection between the counterbody and the support body exists in these intermediate sections via the joining material. This rigid connection in the intermediate sections ensures that the counterbody is fully supported by the support body.The joining process thus makes it possible to distribute hydraulic and support components evenly in the connection plane between the counter body and the support body, and therefore to combine them advantageously.

[0030] In this way, a differential pressure measuring cell is obtained in which both supporting and hydraulic components are distributed over an essentially circular area. The differential pressure measuring cell obtained in this way is therefore highly stable under high unilateral pressure loads and simultaneously exhibits high stability and accuracy under high bilateral pressure loads.

[0031] It is advantageous if the area without joining material is at least partially round. This creates a partially round hydraulic chamber, which helps to reduce stress peaks and discontinuities in the stress distribution.

[0032] In a further embodiment of the method according to the invention, the structuring of the joining material therefore provides a substantially circular area without joining material. The joining material is structured on at least one of the end faces such that the area without joining material has an elliptical or circular shape, and the pressure channel communicating with the measuring chamber is arranged in the center of the elliptical or circular shape.

[0033] The invention includes a differential pressure measuring cell, wherein the differential pressure measuring cell was obtained from the inventive method, comprising; a measuring membrane; a transducer, a first and a second counterbody, as well as a first and a second support body, - wherein the measuring membrane is arranged between the first counterbody and the second counterbody and is pressure-tightly connected to both counterbodies, - wherein a first measuring chamber is formed between the measuring membrane and the first counterbody and a second measuring chamber is formed between the measuring membrane and the second counterbody, - wherein the first counterbody and support body and the second counterbody and support body each have a pressure channel through which the first measuring chamber can be subjected to a first pressure (p1) and the second measuring chamber to a second pressure (p2) and - wherein the transducer is designed to generate an electrical measurement signal from a deformation of the measuring diaphragm caused by the difference between the first pressure (p1) and the second pressure (p2); wherein the end face of the counter body facing away from the measuring membrane is pressure-tightly connected to the end face of the support body facing the measuring membrane, and wherein at least one of the two counter bodies is connected to the adjacent support body to form a hydraulic chamber.

[0034] According to the invention, the diameter of the hydraulic chamber deviates from the diameter of the measuring diaphragm by at most 20% (i.e., the diameter of the measuring diaphragm in the region of the measuring chamber). Preferably, the diameter of the hydraulic chamber is equal to the diameter of the measuring diaphragm. If the cross-sectional area of ​​the hydraulic chamber is adapted to the diameter of the measuring diaphragm (i.e., deviates from it by no more than 20%), the uniform pressure distribution translates into a force equilibrium. This means that the forces acting on the counterbody from the end face facing the measuring diaphragm are essentially equal to the forces acting on the counterbody from the end face facing away from the measuring diaphragm. Thus, there are essentially no net forces acting on the counterbody.

[0035] In one embodiment of the invention, the support body and / or the counter body consists of a ceramic material.

[0036] In a further embodiment, the support body and / or the counterbody consists essentially of silicon (Si), an amorphous or crystalline oxide (SiO2), carbide (SiC), and / or nitride (Si3N4) of silicon, and / or an amorphous or crystalline oxide (Al2O3) and / or nitride of aluminum (AlN). Silicon carbide, which can exist in many energetically almost equivalent polytopes, is suitable due to its high hardness. In contrast, silicon nitride exhibits slightly lower hardness but high fracture toughness combined with a low coefficient of thermal expansion and a relatively small modulus of elasticity.

[0037] The elastic modulus of the components of the differential pressure measuring cell can also be adjusted by selecting the combination of materials. In a further development of the invention, the elastic modulus of the support body is adapted so that it is equal to or greater than the elastic modulus of the counter body. As an upper limit, the elastic modulus of the support body in this further development should be a maximum of three times the elastic modulus of the counter body. In this embodiment, the support body is therefore at least as stable as the counter body.

[0038] The invention is explained in more detail with reference to the following figures. They show: Fig. 1a,b: An embodiment of the method according to the invention and the differential pressure measuring cell obtained with the method according to the invention. Fig. 2a,b: A further embodiment of the method according to the invention and the differential pressure measuring cell obtained with the method according to the invention.

[0039] Fig. Figure 1a shows a top view of the end face 12a of the first counterbody 41 (left), facing away from the measuring membrane 2, and the end face 13a of the first support body 51 (right), facing the measuring membrane 2. The process step shown here is the application of the structured joining material FM to the end face 13a of the first support body 51, facing the measuring membrane 2. The first process step of the process according to the invention (the prefabrication of the two counterbodies 41, 42 and the pressure-tight joining of the measuring membrane 2 to the two counterbodies 41, 42) precedes the process step of applying the joining material FM. The measuring membrane plane ME thus lies in the connection plane of the two counterbodies 41, 42. The side surfaces of the counterbodies 41, 42, perpendicular to the end faces 12a, 12b, are shown as hatched areas.The pressure channel 7 is arranged in the center of the end face 13a of the first support body 51 facing the measuring membrane 2, through which the measuring chamber 61 can be pressurized with the pressure p1.

[0040] The joining material FM is applied in a structured manner to the end face 13a of the support body 51 facing the measuring membrane 2, so that an inner region 31 without joining material FM is formed. This inner region 31 has a cruciform shape. The pressure channel 7, which communicates with the measuring chamber 61, is arranged in the center of the radial struts of the cruciform surface. The outer region 32, which substantially surrounds the inner region 31 and is also without joining material FM, is shown here as a dotted area. During the pressure-tight connection of the end face 13a of the support body 51 facing the measuring membrane 2 with the end face 12a of the counter body 41 facing away from the measuring membrane 2, the hydraulic chamber 8 is formed in the areas without joining material FM due to the structuring of the joining material FM according to the invention. The process of pressure-tight joining is shown by the dashed arrows in Fig. 1a indicated.

[0041] Fig. 1b is a schematic side view of a cross-section of the differential pressure measuring cell 1 according to the invention, which is produced using the inventive method from Fig. 1a was received. For orientation purposes, in Fig. 1a,b the straight line AB (dashed) is drawn into the hydraulic chamber 8 obtained during pressure-tight connection.

[0042] In this embodiment, the joining material FM was structured only on one end face 13a. Therefore, there is only one hydraulic chamber 8 with a diameter dS between the first counterbody 41 and the first support body 51. Nevertheless, the components described below can also be part of a differential pressure measuring cell 1 according to the invention with two hydraulic chambers 8 between counterbodies 41, 42 and support bodies 51, 52. It should be noted that the schematic representation shown here is not to scale.

[0043] The measuring diaphragm 2, which has a diameter dM, is arranged between the two counter bodies 41, 42. The counter bodies 41, 42 are pressure-tightly connected to the measuring diaphragm 2, forming the measuring chambers 61, 62. The two measuring chambers 61, 62 can each be pressurized with pressures p1 and p2 via a pressure channel 7.

[0044] The differential pressure measuring cell 1 further comprises a capacitive transducer (not shown here) which converts a deflection of the measuring membrane 2, dependent on a difference between the two pressures |p1-p2|, into an electrical signal. For this purpose, the two counter bodies 41, 42 each have, for example, at least one measuring electrode 10a, 10b on their membrane-side end faces 11a, 11b, wherein the measuring membrane 2 has a membrane electrode 14a, 14b on each side, which faces a measuring electrode 10a, 10b. In a simple embodiment of the capacitive transducer, the pressure difference to be measured |p1-p2| results from the difference of the reciprocals of the capacitances between each measuring electrode 10a, 10b and the opposite membrane electrode 14a, 14b. The sum of the capacity reciprocals can be used to determine the static pressure p1, p2, to which the pressure difference to be measured |p1-p2| is superimposed.To increase measurement accuracy, the end faces of the counter bodies 41, 42 can each have a circular disk-shaped central electrode and a surrounding ring electrode, in particular one with the same capacitance. Details of the circuitry of such a capacitive transducer are known and disclosed, for example, in EP 1 883 797 B1.

[0045] To detect the static pressure p1, p2, at least one further capacitive transducer can be provided, each having an electrode on the end face 12a, 12b of the counterbody 41, 42 facing away from the measuring membrane 2, or on the end face 13a, 13b of the support body 51, 52 facing the measuring membrane 2. Likewise, a resistive transducer can be provided to detect the static pressure p1, p2, wherein the support body 51, 52 or counterbody 41, 42 in this case has deformation-dependent resistance elements. The latter can, for example, comprise strain gauges, whereby piezoresistive resistance elements are preferable in the case of a differential pressure measuring cell 1 that has a semiconductor material.

[0046] Fig. 2a shows essentially the same thing as we Fig. 1a, namely the structuring of the joining material FM in the end face 13a of the support body 51 facing the measuring membrane 2. In contrast to Fig. In Figure 1a, the joining material FM is structured such that the inner area 31 without joining material FM has a circular surface. A symmetry axis SA is also shown, around which the inner area 31 without joining material FM is arranged essentially symmetrically. In the case of a circular inner area 31, there are further symmetry axes SA, which are not shown here.

[0047] Fig. 2b is (analogous to Fig. 1b) a schematic side view of a cross-section of the differential pressure measuring cell 1 according to the invention, which is produced using the method according to the invention. Fig. 1a was obtained. In this embodiment, two hydraulic chambers 8 are obtained by structuring the joining material FM in two end faces 13a, 13b. Reference symbol list 1 differential pressure measuring cell 2 measuring membranes 31 internal area without joining material 32 external area with bonding material 41 first counterpart 42 second counterpart 51 first support body 52 second support body 61 first measuring chamber 62 second measuring chamber 7 Pressure channel 8 hydraulic chambers 10a Measuring electrode 10b Measuring electrode 11a end face of the first counterbody facing the measuring membrane 11b end face of the second counterbody facing the measuring membrane 12a End face of the first counterbody facing away from the measuring membrane 12b end face of the second counterbody facing away from the measuring membrane 13a end face of the first support body facing the measuring membrane 13b end face of the second support body facing the measuring membrane 14a Membrane electrode 14b Membrane electrode p1 first print p2 second pressure FM joining material dS maximum diameter of the hydraulic chamber dM diameter of the measuring membrane ME measuring membrane level SA axis of symmetry It is the elastic modulus of the supporting body Eg. Elastic modulus of the counterbody

Claims

[1] Method for joining a differential pressure measuring cell (1), which differential pressure measuring cell (1) comprises: a measuring diaphragm (2); a transducer, a first and a second counter body (41, 42), and a first and a second support body (51, 52), - wherein the measuring membrane (2) is arranged between the first counterbody (41) and the second counterbody (42) and is pressure-tightly connected to both counterbodies (41,42), - wherein a first measuring chamber (61) is formed between the measuring membrane (2) and the first counterbody (41) and a second measuring chamber (62) is formed between the measuring membrane (2) and the second counterbody (42), - wherein the first counterbody (41) and first support body (51) as well as the second counterbody (42) and second support body (52) each have a pressure channel (7) through which the first measuring chamber (61) can be subjected to a first pressure (p1) and the second measuring chamber (62) to a second pressure (p2) and - wherein the transducer is designed to generate an electrical measurement signal from a deformation of the measuring membrane (2) caused by the difference between the first pressure (p1) and the second pressure (p2), wherein the joining process is divided into the following process steps: - Prefabrication of the two counter bodies (41,42) and pressure-tight connection of the measuring membrane (2) to the two counter bodies (41,42), - Applying a joining material (FM) to the end face (13a) of the first support body (51) facing the measuring membrane (2) or to the end face (12a) of the first counter body (41) facing away from the measuring membrane (2) and to the end face (13b) of the second support body (52) facing the measuring membrane (2) or to the end face (12b) of the second counter body (42) facing away from the measuring membrane (2), wherein on at least one of the end faces (12a, 12b, 13a, 13b) the joining material (FM) is structured during application such that • the end face (12a; 12b; 13a; 13b) has a continuous, internal area (31) without joining material (FM), • the end face (12a; 12b; 13a; 13b) has a continuous outer area (32) surrounding the inner area (31) with joining material (FM), - Pressure-tight connection of the end face (12a, 12b) of the counter body (41,42) facing away from the measuring membrane (2) with the end face (13a,13b) of the support body (51,52) facing the measuring membrane (2), wherein, in the connection of at least one of the counter bodies (41;42) with the adjacent support body (51;52) through the connected inner area (31) without joining material (FM) a hydraulic chamber (8) is formed between the counter body (41;42) and the support body (51;52), wherein the hydraulic chamber (8) formed by the continuous inner area (31) without joining material (FM) has a maximum diameter (dS) which deviates by no more than 20% from the diameter (dM) of the measuring diaphragm (2), and wherein the hydraulic chamber (8) communicates with the measuring chamber (61;62) via the pressure channel (7). [2] Method according to claim 1, wherein the joining material (FM) is applied using a screen printing process. [3] Method according to claim 1 or 2, wherein the joining material (FM) is a glass solder, adhesive or metallic solder. [4] Method according to at least one of the preceding claims, wherein the joining material (FM) is applied with an approximately constant layer thickness between 5-50 micrometers. [5] Method according to at least one of the preceding claims, wherein the first counterbody (41) and the second counterbody (42) are each connected to the adjacent support body (51, 52) with a homogeneous contact pressure distribution in a pressure-tight manner. [6] Method according to at least one of the preceding claims, wherein the joining material (FM) is structured on two end faces (12a;12b;13a;13b), so that the first counterbody (41) and the second counterbody (42) are each connected to the adjacent support body (51,52) in a pressure-tight manner, forming a hydraulic chamber (8). [7] Method according to claim 6, wherein the joining material (FM) is structured identically on both end faces (12a; 12b; 13a; 13b). [8] Method according to at least one of the preceding claims, wherein the counterbody (41,42) and / or support body (51;52) have at least one axis of symmetry (SA), and wherein the joining material (FM) on at least one of the end faces (12a; 12b; 13a; 13b) is structured such that the inner area (31) without joining material (FM) is arranged symmetrically around the axis of symmetry (SA). [9] Method according to at least one of the preceding claims, wherein the joining material (FM) is structured on at least one of the end faces (12a; 12b; 13a; 13b) such that that the area (31) without joining material (FM) is of a cross-shaped surface, and wherein the pressure channel (7) communicating with the measuring chamber (61;62) is located in the center of the cross-shaped surface. [10] Method according to at least one of the preceding claims, wherein the joining material (FM) is structured on at least one of the end faces (12a; 12b; 13a; 13b) such that that the area (31) without joining material (FM) is of an elliptical or circular shape, and wherein the pressure channel (7) communicating with the measuring chamber (61;62) is located in the center of the elliptical or circular area. [11] Differential pressure measuring cell (1) obtained from a method according to at least one of the preceding claims 1-10 comprising; a measuring membrane (2); a transducer, a first and a second counterbody (41,42), and a first and a second support body (51,52), - wherein the measuring membrane (2) is arranged between the first counterbody (41) and the second counterbody (42) and is pressure-tightly connected to both counterbodies (41,42), - wherein a first measuring chamber (61) is formed between the measuring membrane (2) and the first counter body (41) and a second measuring chamber (62) is formed between the measuring membrane (2) and the second counter body (42), - wherein the first counterbody (41) and first support body (51) and the second counterbody (42) and second support body (52) each have a pressure channel (7) through which the first measuring chamber (61) can be subjected to a first pressure (p1) and the second measuring chamber (62) to a second pressure (p2) and - wherein the transducer is designed to generate an electrical measurement signal from a deformation of the measuring diaphragm caused by the difference between the first pressure (p1) and the second pressure (p2); wherein the end face (12a, 12b) of the counter body (41,42) facing away from the measuring membrane (2) is connected pressure-tight to the end face (13a, 13b) of the support body (51,52) facing the measuring membrane (2), and wherein at least one of the two counter bodies (41;42) is connected to the adjacent support body (51;52) to form a hydraulic chamber (8). [12] Differential pressure measuring cell (1) according to claim 11, wherein the diameter (dS) of the hydraulic chamber (8) is equal to the diameter (dM) of the measuring diaphragm (2). [13] Differential pressure measuring cell (1) according to claim 11 or 12, wherein the counter body (41;42) and / or the support body (51;52) is made of a ceramic material. [14] Differential pressure measuring cell (1) according to at least one of the preceding claims 11-13, wherein the counter body (41;42) and / or the support body (51;52) - made of silicon (Si), - from an amorphous or crystalline oxide of silicon (SiO2), amorphous or crystalline carbide of silicon (SiC) and / or amorphous or crystalline nitride of silicon (SiN), - and / or consists of an amorphous or crystalline oxide of aluminum (Al2O3) and / or aluminum nitride (AlN). [15] Differential pressure measuring cell (1) according to at least one of the preceding claims 11-14, where the modulus of elasticity (Es) of the supporting body (51;52) is equal to or greater than the modulus of elasticity (Eg) of the counterbody (41;42), where the modulus of elasticity (Es) of the supporting body (51;52) is at most three times as large as the modulus of elasticity (Eg) of the counterbody (41;42).

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